eBook: Site Solutions for techies · 2020. 11. 10. · 8 Site solutions for techies | Chapter 1:...

Site solutions for techies

The wireless industry continues to be driven by the increased demand for capacity and bandwidth, as well as the constant need to decrease costs and time to market. Meanwhile, new and emerging technologies like 5G and IoT present additional network opportunities and challenges. Those who design, engineer and deploy network sites, in all their forms, are on the front lines of these changes.

CommScope is your eyes and ears in the field. We see the changes before they affect you and are constantly working to keep you better equipped, better informed and one step ahead. Our technical insight and long-range perspective are the result of more than 40 years of proven experience.

This book reflects a small part of that experience. Each chapter looks at a specific issue affecting the performance and efficiency of your network sites. Together, they present a best-practice approach to deploying a network that is efficient, reliable and future-ready—hallmarks of our innovation and passion for progress. At CommScope, we never stop working to help you realize your full potential.

I N T R O D U C T I O N

CHAPTER 1High capacity solutions . . . . . . . . . . . . . . . . . . . . . 4

CHAPTER 2Site sharing on leased towers . . . . . . . . . . . . . . . 17

CHAPTER 3Operational challenges and solutions . . . . . . . . 31

CHAPTER 4Small Cell solutions. . . . . . . . . . . . . . . . . . . . . . . . . . 43

Site solutions for techies

C H A P T E R 1

Site solutions for techies | Chapter 1: High capacity site solutions 5

A

· Dimensioning challenges and the capacity crunch

· Cell densification with multibeam antennas and combiners

· Improving spectral efficiency with high-performance BSAs and 4x4 MIMO

· Supporting new spectrum with ultra wide-band antennas

High capacity site solutions

A

B

C

A

B C

HIGHLIGHTS

6 Site solutions for techies | Chapter 1: High capacity site solutions


IntroductionWhen it comes to the major challenges facing wireless network planners, accurately forecasting and designing for future capacity needs ranks at or near the top. At CommScope, it’s our job to know what’s next and to make sure you have the insight and solutions to be prepared.

In this chapter, we discuss selecting and utilizing the right RF components to optimize your network capacity in order to meet current and future needs. We’ve provided performance data from actual installations as well as the part numbers for each component. Using the CommScope web portal you can enter the part number to see the most current performance data.

The dimensioning challengeThe demands for data capacity are exploding as the number of people, devices and data-hungry applications accessing the network rise. Accurately predicting how much capacity you’ll need in two years is difficult. Industry reports, such as the Cisco Visual Network Index and Ericsson’s Mobility reports, can offer guidance on telecom trends and future expectations. The picture they paint is not for the faint of heart.

By 2022, mobile traffic will represent nearly 20 percent of all global online traffic and reach 930 exabytes annually—113 times more than the global mobile traffic generated in 2012. Much of the increase will be driven by video consumption and 4G adoption. All the while, widespread 5G deployments are waiting in the wings.

Figure 1.1: Cisco VIN report—February 2019

Figure 1.2: Ericsson mobility report—June 2018

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By 2022, 60 percent of the world’s population will be online. Each user will consume 85 Gb of data per month and the average broadband speed will be 54 Mbps.

Source: 2018 Cisco Visual Networking Index

Now that we’ve identified the magnitude of the problem, the

question becomes: How do we prepare for it? At CommScope,

we’ve been focused on this question for over 40 years. We can

help you answer it.

of the world’s poplulationwill be online

of data per month per user

85Gbis the averagebroadbandspeed

54Mbs60%

By 2022…


The three capacity domainsBefore we get into the specific equipment and strategies needed to meet the coming capacity challenge, let’s step back and review some basics about capacity. To understand the variables that dictate a cell site’s capacity, consider the famous Shannon-Hartley equation.

The equation indicates three main strategies for expanding cell site capacity:

· Higher cell densification: Increasing the number of cells per square kilometer creates more channels and improves capacity.

· Increased spectral efficiency: Reducing signal interference means a higher signal-interference-to-noise ratio (SINR) for improved spectral efficiency (bps/Hz).

· More available bandwidth: This includes adding new spectrum as well as offloading existing traffic onto non-licensed bands.

Let’s take a closer look at each of these strategies and how the right RF equipment can translate to more capacity.

Cell densificationDensification is about adding more cells for expansion. Traditionally, this is accomplished by adding new macro sites between existing ones. But this solution has limitations. As the distance between macro sites is reduced, the risk of signal overlap and interference increases. Today, site-to-site distances in most networks are very short. In these cases, increasing cell density by adding more macro

sites is not an option. Fortunately, there are other practical solutions:

· High-order sectorization (HoS) using multibeam antennas

and/or combiners

· Heterogeneous networks featuring small cells and

in-building solutions

High-order sectorization (HoS) using multibeam antennas and combinersHigher-order sectorization uses multiple antenna arrays to split a traditional three-sector site into six sectors—enabling twice the frequency reuse. It improves cell densification without having to add more macro sites.

Channel Capacity(bps) = Log2 (1+S/N) • BW(Hz)

More channels Less interference More spectrum

There are two main challenges involved in implementing an

HoS solution:

· Excessive tower wind loading

· Sector overlap

In addressing each of these challenges, CommScope engineers have developed a single narrow-width panel antenna capable of radiating two beams with minimal overlap. Figure 1.3 shows how the pattern of CommScope’s 33-degree twin-beam antenna compares to the traditional HoS solution: two 65-degree single-beam antennas.

Figure 1.3: Twin-beam antenna patterns

Twin beam (33°)

Two single beam (65°)



Figure 1.4: Butler Matrix

Phase shifter

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rejected users

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users because of HSDPA resource

saturation

Single Beam 181,395 128,224 53,171.32 1,710 113 509 169 248 671

Twin Beam 300,399 232,036 68,363.24 1,720 189 509 170 134 717

To achieve such narrow-width form factors, the antenna uses a network of phase shifters and hybrid combiners—also known as a Butler Matrix. Both beams radiate from a single column, so the tower wind load of the twin-beam antenna is similar to that of the single-beam model.

To measure how this design translates into capacity performance, CommScope conducted RF simulations involving the twin-beam and single-beam solutions. When factoring in tilt optimization, impacts on coverage and throughput are very promising. The results are shown in Figure 1.5.


Innovation at work: Spectrum re-farmingAmong its many applications, twin-beam antennas can be used to free up UMTS spectrum for LTE use. Consider an operator with four UMTS carriers—F1, F2, F3 and F4—running on a three-sector site, for a total of 12 cells per site. By upgrading to twin-beam antennas, the three-sector site could support the same 12 cells while using only two carriers (F1 and F2). This frees up two carriers, F3 and F4, for LTE re-farming while maintaining the same number of cells per site.

4 carriers x 3 sectors 2 carriers x 6 sectors

Capacity = 12 cells F3 and F4 freed

Capacity = 12 cells Resources = 4 carriers

Figure 1.6: Spectrum re-farming using twin-beam antennas

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Multibeam antenna configurationsDue to their growing popularity, multibeam antennas are available in a wide variety of beams, bands and gains. Following are a few specifications from CommScope’s multibeam portfolio.

· Twin beam (low band) Dual beam 4x 790–960 MHz, HPBW 37°

· Twin beam (high band) Dual beam 4x 1695–2400 MHz, HPBW 33°

· Hybrid multibeam (single+twin beams in one box)

Single beam 2x 694–960 MHz, HPBW 65°

+Single beam 4x 1695–2690 MHz, HPBW 65°

+Dual beam 4x 1695–2180 MHz, HPBW 33°

· Twin beam (multiband) 4x698–894 and 4x1710–2180 MHz, HPBW 35°

· Twin beam with 4x4 MIMO 8x1695–2200 MHz, HPBW 38°

· Five beams (high band) H-HPBW 10–14°, V-HPBW 11°

· Five beams (low band) H-HPBW 13.5°. V-HPBW 13.6°

· 2x9 beams (high band) H-HPBW 6.3°–5.1°. V-HPBW 7.2°–5.8°

Figure 1.7: A hybrid multibeam



CombinersA second technique for implementing HoS is by using RF combiners. This enables cells of different frequencies, bands or technologies to share the same RF path (coaxial cables and antennas). It also provides several other key benefits:

· Facilitates initiatives such as modernizing networks, introducing new technologies on an existing site, and adding capacity without adding feeders or antenna ports

· Supports the addition of LTE 4x4 MIMO at existing sites without having to make changes in the base station antenna or add extra feeder cables

· Simplifies site configuration by reducing the number of feeder cables and overcoming issues created by limited working space

· Minimizes insertion loss to as low as 0.2-0.3 dB without affecting coverage or key performance indicators (KPIs)

· Reduces cost across the board, including the cost of deployment, CapEx, OpEx and tower leasing

· Accelerates the rollout of new LTE services

Combiners can be classified into the following categories.

Multiband combiners (x-plexers)Some operators believe that all combiners create high power losses. While standard hybrid RF combiners do suffer 3 dB of power loss, multiband combiners have insertion losses that are typically in the range of 0.1–0.3 dB. Additionally, dissimilar bands are easier to combine as they have the luxury of large guard bands in between. This makes filter design significantly easier and less expensive. The variety of multiband combiners includes diplexers, triplexers, quadplexers and even pentaplexers. They are designed for combining standard bands and are usually not customized over-the-shelf products. Examples of a diplexer, triplexer and quadplexer from the CommScope portfolio are shown in Figure 1.8.

A common challenge when adding combiners between the BTS and antenna line devices (ALD) is blocking the dc power and AISG signaling path. Operators used to specify fixed bypass ports on the combiners, which made them difficult to reconfigure or move between sites. A recent evolution was adding the so-called “dc smart bypass” functionality. Its primary function is to provide “automatic” internal routing of dc/AISG between “input/output” ports without the

Figure 1.9: A CommScope multiband combiner with dc smart bypass—block diagram

Combiner Mode Splitter Mode

Port 1

Dc Auto Switch

COM COM

Dc Auto Switch

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Port 4

Port 1

Port 2

Port 3

Port 4

800BTS

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2600BTS

800TMA

900TMA

1800TMA

2600TMA

Figure 1.8: Diplexer (E14F05P16), triplexer (E12F01P81) and quadplexer (E16V90P34)

requirement for external dc stops or specific “fixed” bypass model(s). This enables “fail-safe” field configuration/installation where dc/AISG is required to ALDs such as TMAs, smart bias tees, etc. On-board (optional) LEDs provide real-time visual indication to field engineers of the “condition” of each of the ports and the presence of dc voltage within the system.


Same-band combinersWith the spread of software-defined radios (SDRs), it has become common to use existing antenna technologies in support of new bands—so long as the handsets support it. For example, many operators are using their existing GSM 900 MHz antennas to support the new UMTS 900 MHz band. This requires the use of same-band combiners. When there are no defined guard bands between the signals to be combined, standard hybrid combiners can be used. But the tradeoff in performance (about 3 dB of insertion loss) is a steep price to pay.

Alternatively, low-loss same-band combiners—which can be thought of as customized diplexers—can be designed and built to the exact start and stop frequencies for the operator’s intended sub-band combinations. Their insertion losses are typically in the 0.5 dB range. As the available guard band gets smaller, however, the complexity, size and cost of the filters increase. Therefore, achieving the same insertion loss comes at a higher price.

adjusted separately. As shown in Figures 1.11 and 1.12, each input port is specific to certain bands, and the internal combiners must be tuned for specific frequencies within those bands with allowances made for the guard bands in between. Other potential challenges, not present with side-by-side arrays, are the possible limitations in 4x4MIMO activation for the filtered low bands. This is one more thing to consider when choosing a solution.

Heterogeneous networksUsing outdoor small cells is another sensible densification approach. Small cells’ ability to address capacity issues within a very precise area can make them a key part of an effective capacity strategy. Due to their importance, we’ve dedicated an entire upcoming chapter to them: Creating an effective small cell strategy.

Figure 1.10: CommScope LLC900 E15Z55P02 family, LLC1800 E11F01P38 family and LLC2100 E15S09P39 family

Figure 1.11: Side-by-side twin low-band arrays (left) versus filtered antenna construction (right)

700-900 700-900 700-800 900

DPX

DPX

DPX

DPX

Figure 1.12: CommScope filtered antenna

Filtered antennasAs more digital dividends in the low bands become available—like band 28 (700 MHz) and band 20 (800 MHz)—the demand for antennas with more low-band ports increases. The challenge of adding more low-band side-by-side arrays to the antenna, however, is the larger size and wind loading, due to the relatively bigger wavelengths. Filtered antennas allow sharing a single physical array among several bands while maintaining independent tilt control for each band.

Figure 1.11 shows a construction comparison between an antenna with side-by-side twin low-band arrays and a filtered antenna. The filtered antenna uses filters (diplexers) on the internal elements just before the radiating elements. This reduces the number of arrays and allows the electrical tilts for each individual input band to be



Spectral efficiencyOur second available strategy for increasing capacity is improving spectral efficiency. Spectral efficiency is usually expressed in Mbps per hertz—in other words, how much throughput we can get out of each available hertz of spectrum. Figure 1.13 illustrates how evolving technology has enabled spectral efficiency to steadily increase over the years.

This trend reflects successful attempts by network operators to continually modernize and upgrade to the latest technologies—a practice that must continue if wireless networks are to maximize their capacities and meet future demand. At the same time, there are other components and technologies in the RF path that can make a significant and immediate impact on capacity. These include the use of high-performance base station antennas (BSAs) and 4X4 MIMO.

High-performance base station antennas (BSAs)The concept of high-performance antennas is relatively new. As late as the 1990s, the number of cellular bands was few and their bandwidths were small. The GSM 900 MHz band had just 80 MHz of bandwidth. Today, it is very common to see antennas spanning the 1400 to 2600 MHz bands—15 times wider.

However, the increase in bandwidth creates challenges. Panel antennas have radiating elements whose dimensions and separations are designed for specific wavelengths. As frequency span increases, the radiating patterns typically become more irregular—in some cases, the actual patterns are not even close to what’s specified in datasheets.

Consider one of the most important antenna parameters: the horizontal half-power beamwidth (H-HPBW). Most deployments are planned for 65-degree HPBW, and that specification is commonly listed on the datasheets. But is that really how the pattern looks across all supported bands? It depends on the manufacturer.

Figure 1.13: Evolution of spectral efficiencyiv

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Figure 1.14 plots H-HPBW versus frequency for three antenna manufacturers. Each curve on the chart, shown in a different color, represents an e-tilt setting. We can see that the intended 65-degree H-HPBW changes with frequency and e-tilt. In the case of Supplier A, it ranges from 50 degrees to 75 degrees. This poses a serious problem for the operator and can result in coverage gaps or overlap interferences. For your fellow optimizers, this unexpected and extreme variance can mean a subsequent loss in their capacity as well.

By selecting high-performance BSAs that are supported by BASTA-certified datasheets, operators can avoid such problems. High-performance BSAs exhibit far less variance and, when viewed together with BASTA-certified datasheets, it is easier to see the difference.

Adopted by the Next Generation Mobile Networking (NGMN) Alliance in 2013, the Base Station Antenna Standards (BASTA) provide an expanded list of antenna parameters across a range of predefined sub-bands and e-tilt settings. They enable network engineers to accurately compare selected antennas based on detailed performance specifications as well as environmental and reliability parameters and other pre-purchase considerations.

4x4 MIMO solutionsAs can be seen in Figure 1.14 above, MIMO plays an important role in improving spectral efficiencies. In fact, 4x4 MIMO is a main building block for achieving Gigabit LTE speeds. When implementing their 4x4 MIMO strategy, most operators start by activating the technology on the high bands, above 1 GHz. Two distinct approaches can be taken here.

The first approach involves upgrading your existing antennas to those with higher port counts. In cases where the existing antennas do not support the full band, or where combined bands on a shared RF path may create unacceptable PIM, this approach is the only way to achieve 4x4 MIMO on the high band. When planning for this strategy, be sure to factor in the extra time and costs involved with replacing or adding feeder cables as well as the new antennas.

An alternative approach for activating 4x4 MIMO on the high band uses combiners such as duplexers and triplexers. There is less cost involved and it enables you to use your existing antennas to support 4x4 MIMO. Before taking this approach, ensure the existing antennas will support the combined bands and will not pose the risk of unacceptable PIM levels. Also, keep in mind that there will be an added group delay (timing alignment error). This delay should be within the 3GPP TS 36.104 specifications. To facilitate 4x4 MIMO introduction, CommScope recommends using 4x4 MIMO-ready multiband combiners—a specific family of combiners designed for this application.

Supplier A

Frequency FrequencyFrequency

Ho

rizo

nta

l BW

Supplier B

Figure 1.14: H-HPBW comparison



700–900 MHz

E14F05P89 E14F05P66 E14F05P99

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THZR

Figure 1.16: 4x4 MIMO plumbing diagram

Figure 1.17: Ultra Compact Diplexer 7000-800/900 E14F05P89, Twin Diplexer 1400/1800-2600 E14F05P66, Ultra Compact Quad Diplexer 1800/2100 E1405P99

Figure 1.15: 4x4 MIMO-ready diplexer 1800-2100/2300-2600 E14F55P17

X

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Twin Module Diplexer

Quad Module Diplexer


Available spectrumSpectrum is the scarcest and most valuable resource in the wireless

industry. When it comes to your mobile network, you need every

single hertz you can get. In looking at this last strategy for improving

capacity, we’ll take a deeper dive into the following areas:

· Mobile bands and spectrum allocation regulations

· IMF filters

· Passive intermodulation

How mobile bands and spectrum are regulatedThe International Telecommunications Union (ITU) is the United

Nations specialized agency for information and communication

technologies. As described in their mission statement, the ITU’s job

is to “allocate global radio spectrum and satellite orbits, develop

the technical standards that ensure networks and technologies

seamlessly interconnect, and strive to improve access to ICTs to

underserved communities worldwide.”

To accomplish this, the ITU divides the globe into three regions, as

shown in Figure 1.18. ITU regional offices are located in Addis Ababa

(Africa), Bangkok (Asia/Pacific), Brasilia (Americas), Cairo (Arab

States), and Moscow (Commonwealth of Independent States).

There is also a Europe Coordination Office located at ITU

headquarters in Geneva.

Additionally, many countries maintain their own telecom regulatory

authorities, such as the FCC in the United States, the CEPT in Europe,

ATU in Africa, ASMG in the Middle East, CITEL in the Americas, and

APT in Asia. These bodies are largely responsible for managing their

unique regional spectral needs.

Allocating and re-allocating the world’s mobile spectrumEvery three to four years, ITU arranges a World Radio Conference

(WRC) where much of the world’s spectrum available for mobile

use is allocated to wireless networks. During WRC, industry leaders

come together to review and revise radio regulations, international

treaties governing the use of the radio-frequency spectrum, and

geostationary-satellite and non-geostationary-satellite orbits. At

WRC-15 (November 2015), a number of new bands were

re-allocated to the mobile industry:

· C-band (3.4–3.6 GHz)

· L-band (1427–1518 MHz)

· 700-band (694–790 MHz)

At WRC-19 (Nov. 2019, Sharm-el-Sheikh, Egypt), planned discussions

included allocating spectrum above 24 GHz for 5G.

Figure 1.18: ITU regions

Region 1

Region 2

Region 3



Ultra-wideband antennasThe re-allocated spectrum (WRC-15) and spectrum planned for allocation (WRC-19) includes bands up to 200 MHz wide. To support these new wider bands, CommScope has taken the lead in developing ultra-wideband antennas. These ultra-wideband antennas enable operators to take advantage of large blocks of spectrum—more than 266 MHz on the low band and 1263 MHz on the high band. By supporting all four major air-interfaces and operates in 694–960 MHz and 1695–2690 MHz ranges, our ultra-wideband antennas enable operators to reduce their antenna counts while adding more available spectrum. Figure 1.19 shows two of CommScope’s ultra-wideband antenna solutions.

EGVV65D-FL-C3-4XR

Low band arrays are diplexed at the element level.

• 2 x 65°, 694-862 MHz

• 2 x 65°, 880-960 MHz

• 2 x 65°, 1695-2690 MHz

• Gain: 16.7/18.4 dBi

• E-tilt: 2-12°/2-12°

• Size: 2690 x 350 x 208 mm

RRZZHHTT-65D-R6

High band arrays are diplexed at the element level.

• 4 x 65°, 694-960 MHz

• 4 x 65°, 1427-2690 MHz

• 4 x 65°, 1695-2180 MHz

• 4 x 65°, 2490-2690 MHz

• Gain: 16.5/17 dBi

• E-tilt: 2-12°/2-12°

• Size: 2688 x 498 x 197 mm

Figure 1.19: Ultra-wideband antenna examples

Capacity meets confidenceFueled by an explosion in cellular data consumption, today’s capacity demands are skyrocketing. Operators must prepare and respond. But knowing which technologies, strategies and solutions are best for your specific sites is difficult and complex. Rely on CommScope to make it simple. We don’t just see the future of wireless infrastructure—we’re shaping it, with game-changing innovations based on more than 40 years of experience. That’s CommScope: where capacity meets confidence.

i VNI Global Fixed and Mobile Internet Traffic Forecasts; Cisco Systems; updated February 2019

ii The Ericsson Mobility Report; Ericsson; June 2019; https://www.ericsson.com/49d1d9/assets/local/mobility-report/documents/2019/ericsson-mobility-report-june-2019.pdf

iii Cisco Visual Networking Index: 2018; Cisco Systems; February 2019;

iv Economics of the Thousand Times Challenge: Spectrum, Efficiency and Small Cells; Techneconomy; November 2012

https://www.ericsson.com/49d1d9/assets/local/mobility-report/documents/2019/ericsson-mobility-report-june-2019.pdf

https://www.ericsson.com/49d1d9/assets/local/mobility-report/documents/2019/ericsson-mobility-report-june-2019.pdf

C H A P T E R 2

Site sharing on leased towers

18 Site solutions for techies | Chapter 2: Site sharing on leased towers

· Realities of co-siting

· Overview of network sharing models

· Passive sharing using RF combiners A

· Combiners or multiport antennas B

· Independent remote electrical tilt (RET) C

· Space-saving low-width filtered antennas D

· Active sharing

· Accelerating deployment


A

C D

B

HIGHLIGHTS

Site solutions for techies | Chapter 2: Site sharing on leased towers 19

Carpooling neighborhood kids to school is a great cost-saving scheme that comes with its own limitations. If I drive your kids (along with mine) to school in the morning and you bring them home in the afternoon, we could save on gas and the wear and tear on both of our cars. Of course, that may not be an optimal situation for either of us. My kids stay after school on Tuesdays and your kid’s tuba may make for a cramped car.

Driven in part (no pun intended) by a rise in the number tower

company-owned cell sites, more wireless operators are choosing

to “carpool” by sharing RF resources at the same cell site. So, too,

they’re facing the challenges of getting the system performance

they need.

The rise and realities of co-sitingTechnology isn’t the only thing rapidly reshaping the wireless market.

The business models and relationships between the players are

changing as well. Traditionally, service providers contracted with

third-party design/build companies to acquire the land and construct

the cell sites. Today the role of the tower company is shifting from

contractor to owner.

One result of this shift is the presence of multiple operators having to

share the same tower. Of course, the emergence of tower companies

as owners didn’t create the phenomenon of tower sharing—outside

the U.S., many countries have long required co-location as a way

to conserve resources—but it has forced operators to address the

unique challenges of sharing a common site. For example, the

technology and practices that enable the sharing of cellular base

stations, radios and antennas involve trade-offs.

One way to think about the various models of co-siting is to use

the analogy of a carpool involving multiple families. For example,

multiple families might split the cost of one vehicle and recruit a

shared driver. Or they may even sell their vehicle and hire a taxi

company to drive their kids for a monthly fee. In co-siting, as in

carpooling, there are always tradeoffs. In either case, the goal is to

balance the cooperative advantages with the need for participants to

maintain some degree of individual flexibility.

With tower space at a premium, there are real incentives to

reducing your equipment footprint for less sharing cost—but every

square foot saved places new constraints on the way that base

station operates. Since every site has unique limitations, it can be a

challenge to identify and implement the best co-siting solutions.

Whatever the specifics of a given cellular installation, CommScope

offers a wide range of solutions that meet virtually any installation

requirement. It takes a combination of technology and insight to

make the best of every situation. Let’s have a deeper look.

Dealing with the realitiesJust as it would be supremely convenient to have your own vehicle

and driver, it would be ideal for cellular base stations to be equipped

with their own dedicated towers, antennas and feeders at every cell

site (Figure 2.1). Consider the benefits:

· Individually optimized antenna pattern, azimuth direction and downtilt angle

· Minimal RF path loss and signal mismatch

· Reduced interference and intermodulation between systems

· The ability to perform maintenance on one system without impacting the others

Figure 2.1: Multiband sector with separate feeders

X

X

X900

XXXXX

1700-2100

XXXXX

1700-2100

GSM 900 LTE1800 UMTS2100



Sadly, this arrangement isn’t a practical option for most real-world

designs. When a cellular base station moves from the drawing board

concept to the actual tower installation, the design becomes

subject to an incredible number of variables and limiting factors.

These include:

· Local zoning ordinances that restrict antenna quantity, size and location

· The tower’s structural weight and wind load restrictions

· Budget constraints that limit both the initial CapEx costs and ongoing OpEx costs

· Scheduling demands that require accelerated service rollouts

Network sharing modelsNetwork sharing has been in use since the early 2000s, when

it was used to mitigate the onerous costs of deploying new 3G

infrastructure in Europe. It gained additional importance when

4G/LTE deployments began to heat up there in 2015—again in

response to costs.

In general, network sharing is a cooperative agreement between

two or more wireless operators to use common infrastructure,

including antennas, backhaul capabilities, base stations and even

core networks themselves. The major driver of network sharing

continues to be the potential for cost savings. It’s estimated that

these arrangements can reduce CapEx and OpEx spending by

10 to 40 percent for each participating operator.i

The amount of savings depends upon the depth of the sharing

arrangement. Sharing models range from real estate and

infrastructure sharing to more active models involving the sharing

of a common RAN network, spectrum resources and core networks

among different MNOs. As the potential cost savings and benefits

increase, so do the risks. An overview of the most common network

sharing models is illustrated in Table 2.1.

Despite some 3GPP efforts, there are no standard sharing

terminologies, architectures or classifications in the industry.

Encountering different names for the same sharing type is very

likely. Even the term “sharing” itself is referred to as “colocation”

in some markets. However, all terminologies involve three main

sharing categories:

· Site sharing. Shared assets may include the physical real estate for the site, space on a tower, cabinets or enclosure spaces, and any utility connections supporting the site. This has become an extremely common practice and is even mandatory in some markets.

· Passive sharing. This is the sharing of passive (or non-electronic) components needed to support a macro cell site, such as antennas and transmission lines, tower-mounted amplifiers, and other RF conditioning equipment.

· Active sharing. This refers to the sharing of active electronic infrastructure and radio spectrum used in the RF path, such as base station radios and controllers, as well as operational services like maintenance, radio design and planning. Operators can also share resources such as the core network, infrastructure management systems, content platforms, and administrative resources like billing systems and customer service platforms. While active sharing is less common than passive sharing, it is becoming more widespread as operators look to offset the cost of their 4G/LTE rollouts. More on this in a minute.

· National roaming. This is the practice of sharing responsibility for coverage and capacity by dividing costs between participating operators based on geography. It’s similar to how separate railway lines share coverage of specific routes and areas with each other in a mutually beneficial way. This practice also gives entrée to new operators who do not own a physical network. They can contract to use another operator’s infrastructure to ensure consistent QoS and equitable pricing.

Site SharingCivil infrastructure

Backhaul

Passive SharingRF path

Antennas

Active sharing, MOCN, MORAN

Base station

Controllers

Spectrum

GWCN Core network

Table 2.1: Popular network sharing models

3rd Generation Partnership Project (3GPP)

A collaborative coalition of telecom associations originally

formed to create global 3G specifications, 3GPP has since added

standards for 4G/LTE and other technologies.


A closer look at passive sharingUsing RF combinersBy combining multiple RF signals on the same RF path, operators can

make better use of limited tower space and increase their savings.

RF combiners enable operators to reduce the total number of

feeder runs. This helps decrease tower loading, which drives down

tower leasing costs. It also enables operators to take advantage of

monopoles or concealed small cells where space is limited and tight.

RF combiners also reduce the total number of antennas needed, as

well as the number of ports. So, it not only lowers CapEx and OpEx

costs but also decreases wind loading.

To visualize the use of RF combiners, think of multiple computer

cables bundled with a single plastic cable wrap. At one end the

cables separate into various ports on the back of your computer.

On the other end the cables separate into your keyboard, mouse,

network and printer connections. In between they are combined into

one slim run that reduces space requirements and complexity.

A common myth about combiners is that they always add 3 decibels

of loss. Fact is, this is true only for certain types of combiners. As

we’ll see in a minute, there are low-loss options available to help

you maintain more signal power.

Multiband combiningAs its name implies, a multiband combiner is used to combine two

or more frequency bands. Multiband combiners (MBCs) are often

added to a system as separate components, but they can also be

built directly into other components such as antennas.

As a group, MBCs are also commonly referred to as crossband

couplers. When referencing specific types we often use names

that are based on the number of frequency paths being combined:

diplexers (two frequencies), triplexers (three frequencies), etc. (See

Figures 2.2 and 2.3).

Figure 2.2: Diplexer 380-960/18-26 E15V95P36 Figure 2.3: Triplexer 800-900/1800/2100 E11F05P85

X

X

X900

XXXXX

1700-2100

380-900 18-26 360-900 18-26

TWIN DIPLEXER COM COM

COM COM

TWIN DIPLEXER380-900 18-26 360-900 18-26

GSM 900 DSC1800

X

X

X900

XXXXX

1800-2100

380-900 18-26 360-900 18-26

TWIN DIPLEXER COM COM

COM COM

TWIN TRIPLEXER900 1800 2100 900 1800 2100

GSM 900 LTE1800 UMTS2100

Diplexer380-900/1800-2600

E15V95P36

Diplexer380-900/1800-2600

E15V95P36

Diplexer380-900/1800-2600

E15V95P36

Triplexer800-900/1800/2100

E11F05P85

Multiband combining (MBC)

A configuration that connects multiple base station services

that operate in separate bands to multiple antennas via a single

feeder cable and its associated couplers.



The kind of MBC required for a particular application is determined

largely by the frequencies the system uses and, more specifically,

how far apart from each other those frequencies are. In systems

with wide frequency separation—such as 700-1000 MHz, 1700-

2200 MHz, and 2400-2700 MHz—the needed MBCs are likely to

be low-cost, compact devices that introduce virtually no loss

or mismatch.

However, when dealing with frequencies that are relatively close

to one another—such as 800 MHz and 900 MHz—the appropriate

MBC tends to become larger and more complex, as seen in

Figure 2.4.

Figure 2.4: Diplexer 380-960/18-26 E15V95P36 (left) and Diplexer 700-800/900 E11F02P72 (right)

Innovation at workLike many other decisions involved in planning an efficient and compliant base station site, antenna selection plays a large part in how a particular co-siting solution comes together. It must support the base station’s assigned frequencies. Beyond that, selecting broadband antennas that can also accept more than one frequency through a single port enables you to operate across a range of bands with a single feeder cable.

Same-band combiningIn some instances, you may need to combine different services

or technologies within the same frequency band. When this

happens, multiband combiners—which are designed to support

specific frequency separation—don’t provide the solution we

need. Instead, we can use a variety of same-band combining (SBC)

options, allowing different services to share the same space on the

electromagnetic spectrum.

In some applications, same-band combining is even used for single-

service systems—not to enable additional services but to increase

the channels available to the one operating service. In all cases,

the idea is to combine transmit signals (TX) and divide receive

signals (RX). The best way to achieve this depends on the specifics

of the application. Let’s look at some of the more commonly

used techniques.

Hybrid combining Hybrid combiners offer a low-cost means of combining TX

signals and dividing RX signals (Figure 2.5), but this advantage

comes at the cost of other operational restrictions inherent

in its design.

The main disadvantage of this technique is the high rate of loss,

usually in the range of 3 dB, experienced in both directions. This loss

increases with the number of ports involved, so hybrid combiners are

generally used only in two-port applications. This disadvantage can

be mitigated using TMA in order to boost the uplink thanks to

12 dB gain.

Another consideration is the significant heat generated, which

must be dissipated. CommScope has designed a hybrid combiner,

shown in Figure 2.5, that distributes the load to offset the additional

heat. This hybrid combiner is also extremally flexible. Its wideband

range—694 to 2700 MHz—makes it suitable for a variety of

different applications.

Same-band combining (SBC)

A base station configuration that allows multiple services to

share the same bands.


Figure 2.5: Hybrid Combiner 694-2700 MHz D15T01P38

Low loss combiner-multiplexers (LLCs) LLCs offer a different way to combine base station transmitters.

Integrated duplexers allow combining of TX signals and distribution

of RX signals as well (Figure 2.6).

Like the multiband combiners discussed earlier, the LLC is a filtered

multiplexer. However, unlike an MBC that requires separation

between bands, the LLC handles frequencies inside the same

band. It has an increased number of cavities to sharpen the filters’

abilities to accommodate and enable the shorter guard bands. This

heightened ability is due, in part, to the use of ceramic resonators

in place of coaxial resonators in the filters.

Guard bands help reduce in-band interference, but they also

occupy valuable bandwidth. CommScope offers LLCs designed to

handle extremely narrow guard bands, measuring just a few

hundred MHz. It should be noted that designing any LLC to work

with smaller guard bands involves greater cost, size and complexity.

Another drawback of an LLC is its reliance on filtered multiplexing,

which significantly restricts scalability. As technology develops,

networks require constant upgrading, adjusting and scaling—which

often entail replacing or re-tuning the LLC components should its

spectrum configuration change.

Examples of LLC configurations are shown in Figure 2.6.

Figure 2.6: LLC with integrated diplexer, RX distribution from GSM BTS

X

X

X900

COM

LLC900 GSM900 UMTS900

COM

LLC900 GSM900 UMTS900

GSM900 UMTS900

Low Loss Combiner900MHz

E15Z55P02

Hybrid combinerD15T01P38

X

X

X1800

COM

HYBRID -3dBBTS1 BTS2

COM

HYBRID -3dBBTS1 BTS2

DCS1800 LTE1800



Overcoming challenges in antenna sharing and co-siting As mentioned earlier, the challenge in antenna sharing between

multiple operators is providing each operator the ability to optimize

their individual coverages. Oftentimes, it can seem easier and more

economical to simply add unshared antennas.

In fact, a 2015 regional market survey conducted by CommScope

showed that the practice of antenna sharing in North America and

Europe was virtually unheard of, while co-siting individual antennas

is common. One reason for this may be the cost of the continued

rollout of 4G/LTE. Yet cost savings is not the only issue. In some

countries—such as Brazil, Canada, Jordan, and Egypt—aesthetic,

environmental, health or safety regulations require antenna sharing

as a condition of operators who want to expand their networks.

Whether forced or voluntary, the question remains: “How can

two or more operators share the same antenna without sacrificing

pattern performance?”

Using multiport antennas or combinersThere are two basic solutions to antenna sharing: using

multiport antennas or deploying combiners.

Today’s modern, slim multiport antennas provide an excellent

opportunity for mobile network operators (MNOs) to take

advantage of antenna sharing while retaining control of their

individual antenna elements and coverage patterns. Current

multiport antennas, such as the one shown in Figure 2.8, can

support multiple RET controllers, feature low-loss RF performance,

and enable mobile operators to change their frequency band

allocation without physically modifying the antenna.

Figure 2.7: Low loss combiners 900 MHz E15Z55P02 family and E15Z89P52 family

Figure 2.8: A multiport antenna panel

CommScope low-loss combiners deliver network modernization solutions to UAE’s top wireless carrier.

· Minimal insertion loss (compared to traditional hybrid units)

· Customized low-loss combiners (LLC) enable sharing of existing sites with other carriers

and generate new revenue—without a major CapEx investment.

Case study


As illustrated in Figure 2.9, the biggest challenge when deploying

multiport antennas in support of a shared network is the larger

physical size of the antenna and the resulting increase in tower

loading. This is especially problematic across multiport antennas in

the lower frequency bands where the array is larger to begin with.

As an alternative to multiport antennas, MNOs can deploy multiband

or same-band combiners. As we’ve already seen, this approach

reduces the number of antenna arrays required and enables the

Figure 2.9: Multiport antennas and MBCs/SBCs allow for antenna sharing when required

Multiport antennas Low loss combiners

X X X X X X X

X X X X X X X

Operator A Operator B

X X X X X X X

Operator A Operator B

Multiport antenna sharing Combiner sharing

PROS

• Multi BTS RET control after mods• Normal PIM and VSWR risk• Lower RF path losses• Can re-allocate bands in future

Normal antenna size and tower load for all bands

CONS Increased antenna size and tower loading for low bands

• Higher PIM and VSWR risk• Increased RF path losses • Does not support multi BTS RET control • LLC fixed for existing bands

operator to minimize the antenna size and tower loading. This

type of solution is often used to deploy a newer technology overlay

(e.g., LTE) onto a network’s legacy services.

However, this approach has drawbacks as well. Operators give up

independent RET control, and, should frequency bands change,

low-loss combiners may need to be re-tuned or replaced.

Innovation at work: Pairing multiport antennas with combiners While either multiport antennas or combiners can be used to enable antenna sharing, the best solution may be a combination of both. Using a combiner for the low bands and a multiport antenna for the high bands takes advantage of the strengths of both technologies while minimizing the weaknesses. Certain antennas are available with factory-integrated combiners—reducing interconnections and saving space on the tower but also offering less flexibility as to the bands that can be combined.



Case study

CommScope’s combiner solutions reduce Orange Tunisia’s deployment time and costs.

The Middle East – Africa (MEA) region is among the fastest growing wireless markets in the world. But with explosive growth comes significant challenges, including overloaded towers and rooftops, and few available options for new sites. With minimal insertion loss compared to traditional hybrid units, CommScope’s customized low-loss combiners (LLC) enable Orange Tunisia to share existing sites with two other carriers and generate new revenue without a major CapEx investment.

CommScope low-loss combiners deliver site sharing solutions to Tunisia’s largest wireless carrier.

· Minimal insertion loss (compared to traditional hybrid units)

· Customized low-loss combiners (LLC) enable sharing of existing sites with other carriers and generate new revenue—without a major CapEx investment

· and generate new revenue—without a major CapEx investment.

Case study

Multiport antenna sharing using independent RETSo how can an operator ensure they maintain control of their

own traffic on a shared antenna? Through independent remote

electrical tilt (RET) control for each operator. RET uses actuators

built into the antenna to adjust the beam up or down relative to

the horizon. So, each operator can remotely adjust the aim of their

antenna beam for optimal efficiency and radiation pattern. Many

(but not all) multiport antennas will provide independent RET. If

this feature is not available, operators must either purchase new

multiport antennas equipped with independent RET control or, in

some cases, implement using external hardware.

RET uses an open platform developed by the Antenna Interface

Standards Group (AISG), a body composed of representatives from

the world’s leading wireless equipment manufacturers and service

providers, including CommScope.

AISG standards have led to improvements in RET control and

monitoring, as well as reporting alarms and other important

advances in remote management. One of these developments is

a standardized AISG input available on sharing-capable antennas.

Using separate AISG inputs, shown in Figure 2.10, operators can

independently control their RETs and successfully share antennas.


For non-sharing applications, antennas may be shipped with all RETs

assigned to AISG input port 1, as shown in Figure 2.10. These same

antennas can be reconfigured to enable future sharing by assigning

specific RETs to AISG input port 2. This separate connection allows a

second AISG controller to have independent control.

After configuring an antenna for sharing, a specific RET can be

controlled only through the AISG input port to which it is assigned.

The diagrams shown in the middle and on the right show example

configurations, with the AISG input ports shaded the same color as

the RETs that will be controlled.

AISG in

Non-sharing (default) configuration

AISG in

R1 R2 R3 R4

AISG in

Antenna sharing example configuration 1

AISG in

R1 R2 R3 R4

AISG in

Antenna sharing example configuration 2

AISG in

R1 R2 R3 R4

Figure 2.10: Various independent RET configurations

Innovation at workFor more than two operators or technologies sharing a group of antennas, CommScope has recently introduced an antenna sharing hub. Using this, operators can map up to six AISG input signals in order to control different RET motors, as shown in Figure 2.11.

Figure 2.11: CommScope’s antenna sharing hub can map up to six AISG signal for sharing

R1.1

Antenna 1EGYHHTT-65B-R6

R1.2

B1.1 B1.2

G1.1 G1.2

R2.1

B2.1

Y1.1

Antenna 2EGYHHTT-65B-R6

X X X X X

X X X X X

X X X X X

X X X X X

X X X X X

X X X X X

X X X X X

X X X X X

X X X X X

X X X X X

X X X X X

X X X X X

A

B

C

D

E

F

R1.1 R1.2 (SRET)

R2.1 R2.2 (MRET)

B1.1 B1.2 (SRET)

B2.1 B2.2 (MRET)

G1.1 G1.2 (SRET)

Y1.1 Y1.2 (MRET)

CommScope Antenna Share

Hub



Low-width filtered antennasInternally combined (filtered) antennas feature multiple RF ports

that feed a single antenna array. [For more on filtered antennas, see

the chapter on high-capacity site solutions.] These antennas allow

operators to increase the port count for sharing while maintaining

independent tilt control and a more narrow physical footprint—a

very useful feature when it comes to minimizing tower rental costs

and wind loading.

Figure 2.12 shows how a 16-port antenna can fit in an antenna

that is 400 mm wide. A single large, low-band array is shared

between two pairs of cross-polarized ports (694-862 MHz and

880-960 MHz) with independent tilt control, while the smaller

high-band arrays are designed into a compact arrangement of

three columns and two rows.

Active sharing overviewActive sharing is drawing a great deal of interest as a means of

dealing with the high rollout costs of new and overlaid networks

(such as 4G/LTE and 5G), as well as the constant need to conserve

available spectrum. Operators are currently experimenting with

several different active sharing arrangements involving various RF

path components, spectrum assets and core network components.

Multi-operator RAN (MORAN)Here, only the RAN components of the RF path are shared;

specifically, the base transceiver station (BTS), base station

controller (BSC), node B, and radio network controller (RNC) are

split into multiple virtual radio access networks—each connected

to the core network of the respective operator. Operators continue

to use their own dedicated frequency bands.

Multi-operator core network (MOCN) As with MORAN, RAN components in an MOCN are shared

while core networks remain separate. The difference here is the

addition of spectrum pooling to the mix. It allows each cell in

the shared RAN to broadcast all sharing operators’ identities

and other relevant information, including their NMO (network

mode of operation) and common T3212 (location update timer).

Participating operators in this arrangement tend to be similar in

terms of market presence and spectrum assets in order to create

an equitable arrangement.

Gateway core network (GWCN) This goes even further, sharing infrastructure, frequencies, AND

core network elements such as the mobile switching center (MSC),

serving GPRS support node (SGSN) and—in some cases—the

mobility management entity (MME). This configuration enables

the operators to realize additional cost savings compared to the

MOCN model. However, it is a little less flexible and regulators

may be concerned that it reduces the level of differentiation

between operators.

These three active sharing arrangements can be viewed as a

continuum of complexity involving clear tradeoffs between

efficiency and flexibility. Figure 2.13 illustrates where each

arrangement falls in the continuum.

Figure 2.12: 16 port slim antenna

EGZV-65D-R6

2 x 694-862 MHz2 x 880-960 MHz2 x 1427-2690 MHz10 x 1695-2690 MHz


Figure 2.13: Active sharing models applicable to co-siting and their various degrees of sharing

Figure 2.14: CommScope SiteRise

BTS/Node B

BSC/RNC

MSC/SGSN

HLR

Serviceplatforms

MSC/SGSN

First stage of active RAN sharing where spectrum is not shared

Backhaul

HLR

Serviceplatforms

BTS/Node B

BSC/RNC

MSC/SGSN

HLR

Serviceplatforms

MSC/SGSN

Second stage of active RAN sharing where spectrum is also shared

Backhaul

HLR

Serviceplatforms

BTS/Node B

BSC/RNC

MSC/SGSN

HLR

Serviceplatforms

Third stage of active RAN sharing where CS and PS core elements

are also shared

Backhaul

HLR

Serviceplatforms

MORAN MOCN MORAN

MOCN

Key

■ Operator A

■ Operator B

■ Shared element

HLR = Home location register

MSC = Mobile switching center

SGSN = Serving GPRS support mode

GPRS = General packet radio service

BSC = Base station controller

RNC = Radio network controller

BTS = Base station

Deployment efficiencyPre-assembled tower topsRemote radio units (RRU) have enabled operators to successfully

eliminate RF losses due to long cable runs and reduce the need

for TMAs. These benefits, however, come at a price. Deploying

top-of-tower solutions requires specialized personnel, such as field

technicians and antenna riggers, who must spend considerable

time connecting, testing and securing RRUs and antennas while

suspended hundreds of feet off the ground.

To minimize the physical risks, CommScope has developed SiteRise™,

which integrates all major tower-top components into one factory-

assembled, factory-tested unit that can be quickly hoisted and

attached to the tower. The SiteRise portfolio offers different

configurations, as shown in Figure 2.14. Each assembly undergoes

rigorous testing, including PIM tests, before being shipped to the

site. It installs quickly on towers, monopoles and rooftops, enabling

crews to reduce installation times by up to 50 percent.

HFF cablesA second problem we face with RRU deployments is their

complicated optical fiber and power cabling. Figure 2.15 shows how

messy some installations can get. This undoubtedly increases failure

rates and makes it harder to troubleshoot problems. CommScope’s

hybrid fiber feed (HFF) is designed to solve such challenges.

HFF combines copper power wires and optical fibers inside a single

armored cable. The configuration can be customized and the armor

ensures reliability—especially over shared or rented infrastructures.



Figure 2.15: Optical and power cabling at the tower top, before (left) and after (right) CommScope’s hybrid fiber feed.

Figure 2.16: HFF building blocks

While HFF was originally introduced in 2013, CommScope has

continued to expand the HFF portfolio. The latest addition (see

Figure 2.16) further illustrates the most recent hybrid pendant

solution, which allows direct RRU fiber and power connectivity

from standard sockets.

In 2018, an independent engineering firm undertook a time study

to measure the installation efficiency of the HFF solution. Using

HFF, installers needed just one hour and 49 minutes to fully deploy

a six-RRU configuration on a 30-meter tower. Installing the same

components with a traditional discrete cabling approach took four

hours and 46 minutes.

· Network sharing includes passive and active sharing, national roaming and antenna sharing practices

· Co-siting allows more performance in less space

· Co-siting strategy is driven by limits on amount, weight and cost of base equipment and antenna-mounted equipment

· Multiband combining leverages the feeder cable’s capacity for multiple frequencies—with guard bands

· Same-band combining includes hybrid combining (inexpensive but lossy) and low-loss combiners (efficient but with limited frequencies)

· Independent RET control makes antenna sharing more practical

CommScope helps you realize more potential in every opportunity The design of a cellular communications system reflects many choices

and compromises. The result is that no two deployments are exactly

alike, and that every decision is based on a unique balance of benefit

and cost.

Co-siting is an advantage to many and a necessity for some; as

global demand rises and available spaces disappear, co-siting will

become more common all over the world. With the right strategy and

solutions, the opportunity can outweigh the costs—ensuring better

service for users and better efficiency for operators.

CommScope ensures you have the right strategy and RF solutions

to make the most of every site, every opportunity. Our 40+ years of

experience as a global leader in wired and wireless infrastructure design

gives you a unique long-range perspective and a powerful competitive

edge. Together we can build a smarter, more connected world.

i Coleago Consulting, February 2015

Antennas

Radio matching RF jumpers

RRUs

Fiber/power or hybrid tails

Junction box

Fiber/power or hybrid trunk cableBaseband

Chapter 2 Summary

HFF Cable Pendant Junction box

C H A P T E R 3

32 Site solutions for techies | Chapter 3: Operational challenges and solutions

· Controlling interference with IMF filters A

· Understanding and minimizing PIM

· Tower-top power B

· Links imbalance

Operational challenges and solutions

B

HIGHLIGHTSA

A

Site solutions for techies | Chapter 3: Operational challenges and solutions 33

As with any large-scale engineering project, when it comes to designing and deploying a wireless site solution the devil is, as they say, so often in the details. From site considerations and performance requirements to the exact technical solutions needed in the RF path, there are enough moving parts to make your head spin. Each is important—some more so than others.

Several issues are playing an increased role in engineering a

tower solution that is both efficient and effective from day one,

and beyond:

1. Recognizing the causes of interference, including RF leakage and passive intermodulation (PIM), and understanding the tools and strategies available to minimize it.

2. Getting power to the increasing number of remote radio units being deployed at the top of the tower while ensuring accurately proportioned power and minimizing tower loading.

3. Identifying and ameliorating performance-draining link imbalances that often appear after start-up.

IMF filtersThe leakage problem While capacity-enhancing solutions such as re-farming of existing frequencies and releasing new spectrum help meet the increasing data demand, they have created new challenges as well. To make the most of the available bandwidth, the space between frequency blocks is growing smaller. If your local regulator isn’t careful with spectrum allocation planning, your uplink (UL) channels can end up adjacent to another high-power downlink (DL) transmission source. The result is in-band interference that must be controlled.

Figure 3.1 illustrates what happens when a CDMA DL channel is adjacent to a victim WCDMA UL channel. Due to cost and size restrictions, the filters in the base station transmitters and receivers are not sharp enough to remove the interference. The overlapping area shown in Figure 1 indicates the amount of co-channel interference that is passed to the receiver, saturating its reception.

The resulting adjacent channel interference ratio (ACIR) is a measure of the total power transmitted from a source compared to the total interference power affecting a victim receiver. ACIR is the result of imperfections in both the transmitter and receiver. As such, it is the product of two main contributing factors:

The IMF solutionIn most cases, the offenders fail to clean up their own mess, leaving the victims—which might be you—looking for solutions. One of the most effective solutions is the IMF. IMF solutions include both fully customized designs as well as a complete line of existing solutions that can be adapted for specific needs. IMF technology can be incorporated into a variety of filter types and designs, including ceramic, cavity, stripline, crystal, surface acoustic wave (SAW), tubular and adjustable filters. The resulting solutions can be deployed as standalone filters or integrated into tower-mounted amplifiers (TMAs) and combiners.

By comparing Figure 3.1 with Figure 3.2, we can see the degree to which the IMF filter (blue line) reduces the amount of overlapping interference.

Figure 3.2: IMF effect

0

-0.3

-0.6

-0.9

-1.2

-1.5

-1.8

-2.1

-2.4

-2.7

-3

5MH

1958 1961.5 1965 198.5 1972

5MH

IMF

Remainingoverlapping area

Figure 3.1: Adjacent interference

5MH

1960 MHz 1965 MHz 1970 MHz

5MH

InterferingCDMA DL Band

· Transmitter out of band emission (OOBE), or adjacent channel (power) leakage ratio (ACLR)

· Receiver selectivity or adjacent channel selectivity (ACS)

ACIR can be expressed by the following equation: ACIR=1/(1/ACLR + 1/ACS)



Figure 3.3: A CommScope IMF

Passive intermodulation—PIMLinearity and non-linearityLinear systems exhibit linear relations between their input and output signals. When it comes to active devices like amplifiers, nonlinearity is expected and measured as part of its frequency response curves. On the other hand, passive devices like connectors and cables are assumed to behave linearly, showing a uniform response across supported bands. But passive RF components can also unexpectedly produce non-linear distortion, mainly due toi:

· Improper connector attachment

· Poorly torqued connections with incorrect contact pressure

· Contamination or corrosion of conducting surfaces

· Inadequate plating on rust-prone ferromagnetic components

· Poor connections due to cold solder joints

IMD and THDPIM’s non-linear distortion can be expressed in terms of a Fourier series. It shows how signals in the time domain can be decomposed to combinations of pure sine and cosine waves in the frequency domain. Figure 4 shows a pure sine wave that deforms after passing through a non-linear system. The deformation results in additional “harmonics” being added to the output signal—integer multiplications of the input carrier. Their effect is referred to as total harmonic distortion (THD).

The passing of two or more carriers results in intermodulation distortion (IMD). It is a result of adding and subtracting input carriers with different weights. The IMD order is the modulus sum of these weights.

Figure 3.4: Harmonic Distortionii

Device under test

Equivalentline space

Frequency

Sine-wave input signal Distorted output signal

Am

plitu

de

Frequency

Odd and evenharmonic distortion

Original component

Am

plitu

de

Diffusing interference in Northern Iraq Use QR code to download case study

A proactive approach to potential interference in Europe Use QR code to download case study

Keeping success on schedule in Asia Use QR code to download case study

Developing a coordinated interference solution in Paraguay Use QR code to download case study

Creating a unique interference solution in Jamaica Use QR code to download case study

Case studies

Learn how CommScope is helping network operators around the world improve coverage and capacity by minimizing interference.


For example, let’s assume three input carriers F1, F2 and F3. Third-order IMD can be any combination of the following carriers and multiplied weights that add up to 3.

1F1 - 2F2, or 2F1 - 1F2, or 1F1 + 1F2 - 1F3, or 1F1 + 1F2 + 1F3, ...etc.

Fifth- and seventh-order IMD can be calculated similarly.

So, the term passive intermodulation (PIM) describes any instance in which the passing of two or more carriers along a passive nonlinear RF path results in intermodulation (IMD).

The PIM riskSo why are we so concerned with PIM? Because the resulting combinations of downlink IMD frequencies might fall into one of the operational uplink bands. This will raise the UL noise floor and might even saturate the receiver, causing significant losses in UL throughput and performance. Further, it has been shown that the higher the IMD order, the lower the amplitude—and the wider the effect across the bandwidth. For this reason, we are mostly concerned with IMD3.

It is also worth mentioning that, with LTE operating on resource block subcarriers (180 KHz bandwidths)—plus LTE’s wide support of various spectral bands—the possibility of PIM hits is expanding more than ever.

Figure 3.5: IMD and PIM orderiii

7th7th

5th 5th

F1

2F 1-F 2

2F 2-F 1

3F 2-2F 1

3F 1-2F 2

4F 1-3F 2

4F 2-3F 1

F2

3rd 3rddBc value

PIM standards and measurementsIEC 62037 is the international standard for measuring PIM in passive RF and microwave devices. The standard specifies injecting two continuous-wave test signals to the device under test (DUT). As PIM is generated from the DUT, the resulting IMD propagates and can be measured in both the reverse and forward directions. This is shown in Figure 3.6. The diagram on the left shows a reverse test scenario for a BSA, which is the most common type in field measurements.

Figure 3.6: IEC 62037 reverse and forward PIM measuringiv

Amplifiers

Transmit Filters

Diplexer

Test Chamber

AUT

Receive Filter

Receiver Low Noise Amplifier

Amplifiersf1

f2

Transmit Filters

Transmit Filters

Diplexer

Load

Test Chamber

AUT Receive Antenna

Receive Filter

Receiver Low Noise Amplifier

PIM test precautions Because PIM levels are extremely sensitive to test equipment and the surrounding environment, the antenna (DUT) should ideally be placed in a test chamber away from external affecting objects or signals. However, this is not possible in the field, so special precautions are needed to improve testing accuracy. Field testing should be conducted on a clear day, away from other equipment. Forklifts, people with cell phones, metal objects, fences, site equipment—even the weather— can impact the test results.v

Innovation at workFor a complete guide to measuring PIM, we invite you to download CommScope’s Discrete Frequency PIM Calculator. It enables you to check for third-, fifth- and/or seventh-order PIM for up to 12 discrete TX and RX frequencies. Download calculator >

https://www.commscope.com/calculators/qimdcalculator.aspx





Figure 3.7: IEC 62037 internal PIM effect

Measuring units and acceptable limitsPIM is expressed in decibels relative to the carrier, or dBc. This is the measured PIM level relative to the injected signal power as shown in Figure 3.7. The industry standard is <-150 dBc with 20-watt input test signals, but this value differs slightly between operators.

Measured dBm can be easily converted to dBc and vice versa using the following formula:

For example, a measured -120 dBm PIM level from 2x20-watt (43 dBm) test signals equals -163 dBc.

Test signal powerAlthough the IEC standard recommends 20 watts for the input test signals, there has been a debate in the industry as to whether that level should be increased to reflect the higher power of today’s radios. Increasing the test signal power, however, means larger, bulkier equipment with shorter battery life. Given that the test equipment is used in the field, the preference is to keep it smaller and lighter with longer-lasting batteries. Like everything else, this is a tradeoff.

In theory, the third-order PIM product should increase 3 dB for every 1 dB change in test power. Assuming linearity, we can extrapolate values for higher radio powers. So 20-watt or lower test signals should be fine so long as the cable attenuation does not violate the receiver’s sensitivity levels.

On the other hand, each test device has its own internal PIM that is added or subtracted to the DUT readings (blue and red curves, respectively, in Figure 3.7). The IEC standard specifies that such “self-PIM” is to be at least 10 dB lower than the measured DUT readings. By looking at Figure 3.7, we can see that, as this difference increases to 20 dB (X-axis), the error margin decreases to ±1 dB (Y-axis).

6

5

4

3

2

1

0

-1

-2

-3

-4

-5

-6

-7

-8

-9

-10

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Erro

r (d

B)

(True PIM)–(System PIM) (dB)

Measurement error (dB) when PIMs add Measurement error (dB) when PIMs subtract Zero error line

< 2 dB error

< 3 dB error

PIM (dBm) – Test Signal (dBm) = PIM (dBc)


Fixed or sweeping test signalsThe IEC standard specifies two equal-power, continuous-wave (CW) test signals. But should these test signals sweep the entire frequency band under test or remain fixed? In fact, there are pros and cons to each approach.

One challenge in using fixed test carriers is that, when tested in the field, UL bands are never free from surrounding UE devices’ transmissions. This can impact the PIM readings for the DUT. If we fix the F1 and F2 test carrier frequencies, we can select F1 and F2 such that their third-order IMD (2F1-F2, 2F2-F1) falls within the guard band or duplex gap band, where no UEs are transmitting.

Fixed test carriers also have limitations. Out-of-phase PIM signals can cancel each other out so PIM problems go undetected. Sweeping one of the test signal frequencies will avoid such a problem, enhancing the test’s accuracy.

Practical tips for PIM improvement Clearly, PIM is a serious network problem, but what should be done to avoid it? Remember: PIM is generated when two or more RF signals share a non-linear RF path. There are thus two components that require further investigation: RF signal combinations and RF path linearity.

RF signals and PIM calculatorsCertain RF band combinations are known to result in risky PIM signals; a famous example involves Europe’s Digital Dividend bands 20 and 28. Therefore, before deciding to use combiners or separate RF paths, be sure to check for potential known PIM risks of the bands you are working with. CommScope has developed PIM calculators to help make the evaluation process easier. Figure 3.8 shows the program’s easy-to-use GUI interface. The RF engineer simply clicks on the band combinations they intend to combine and the tool will do all the math. As mentioned earlier, PIM calculators can be downloaded for free from the CommScope website.

RF path linearityTo improve RF path PIM performance, it is advisable to select superior PIM-rated RF components. Here are some examples from CommScope’s portfolio.

Figure 3.8: PIM calculator

The 4.3-10 connectorsThis timeline shows the evolution of high-power RF connectors. Until recently, the 7-16 DIN connector was the most deployed high-power RF connector used in cellular network infrastructure. The name 7-16 refers to the inner and outer diameters of the female connector in millimeters, respectively.

As networks continue to grow more complex—demanding higher frequency bands and tighter PIM tolerances—a new generation of connectors has evolved. The 4.3-10 connectors are characterized by smaller size (4.3 and 10 mm) and better PIM performance. The improved PIM performance is due to the connector being more installer friendly. Here’s why.

As shown in Figure 3.9, the electrical contacts of the 7-16 DIN connector are located at the mechanical stop. Achieving a solid electrical connection requires a high degree of mechanical screwing. Therefore, manufacturers of these connectors recommend the use of a torque wrench, typically set at 30 Nm.

Type N

1940s

BNC

1950s

SMA

1960s

7-16 DIN

1990s

4.1-9.5 DIN 4.3-10

NOW



Electrical contact

Cross section of 7-16 Cross section of 4.3-10

Mechanical stop

Figure 3.9: Cross sections of 7-16 connector (left) and 4.3-10 connector (right)1

Today, however, most RF network installations are performed without torque wrenches. The result is poor or incomplete electrical contact and a higher degree of PIM. As you can see in Figure 27, the 4.3-10 connector separates the mechanical locking mechanism from the electrical contact, reducing the required torque to around 5 Nm. The less mechanical screwing, the greater the chances of a good electrical connection—and the lower the risk of PIM. The 4.3-10 connector comes in three different versions: traditional screw-on, hand screw and push-pull (quick lock).

D-Class jumpersTower vibration, varying component installation techniques, and changing weather can all cause PIM in your site’s RF components, even if they have already passed static PIM tests. The International Electrotechnical Commission (IEC) developed a series of five tests to measure PIM caused by dynamic factors. The tests involve placing the RF components under physical stress—flexing, tapping, pulling—to duplicate the adverse effects of weather and other environmental conditions at the top of a tower.

Hammer testing for multiband combiners and tower-mounted amplifiersMBCs and TMAs are designed to respond to the PIM excellence standards being driven by the market. To help ensure they do, manufacturers perform dynamic PIM testing using a hammering table. This test helps guarantee that the component meets the more stringent PIM performance levels for both static as well as dynamic operating conditions.

Innovation at workCommScope SureFlexTM D-CLASS jumpers are individually tested under the same type of difficult conditions specified by the IEC’s PIM tests for dynamic factors. Test results are accessible online over the CommScope WebTrak® and C-Trak® smart phone apps.

Use QR code to play video or download PIM Calculator

Technician uses hammering table to perform dynamic PIM testing

https://www.commscope.com/Docs/CaseStudy/Etisalat_UAE_LLC_Success_Story_CU-109834.pdf


Tower-top power solutionsAs the industry evolves to LTE-Advanced, with more bands and higher MIMO schemes, it has become common to add more remote radio units (RRUs) to working sites. This, however, has created additional challenges, including the need to run power from the base of the tower to the additional RRUs at the top. Often, in these cases, the dc power cables are not thick enough to support the extra current load. Until recently, the only real option was to pull extra power cables—either up the tower or to wherever they may be needed for an in-building system.

Another option is to lower the current in order to step down to a smaller diameter power cable. You’ll remember from the basics of electrical engineering:

Power (W) = Voltage (V) x Current (I).

Based on this equation, we know that, if voltage increases, the current must decrease if we are to maintain the same power output. This simple theory holds a key to powering additional RRUs in the network. Why? Because a lower current enables use of a smaller diameter power cable. Taking advantage of this fundamental relationship between current, voltage and power, CommScope has developed an innovative solution to power more RRUs without having to pull an excess number of oversized cables.

PowerShift® works by maintaining the optimum voltage at the RRU, compensating for the voltage drop in copper power lines. The solution consists of a base unit and capacitive jumpers installed across the target RRU power terminals. The base unit is used in conjunction with the existing dc power plant at the installation site.

How it works

The operating concept of PowerShift is simple and brilliant. It takes advantage of the fact that dc currents can’t pass through capacitors. A small initial ac current is injected into the power line and returns through the capacitive jumper. By measuring the voltage drop in the jumper, PowerShift dynamically adjusts the power output to compensate for the drop while using dc voltage to power the RRU.

A single 19-inch 1RU base unit has up to four plug-and-play modules. Each module provides enough dc input and output to support three RRUs, with a maximum 1200 watts of power.

RRU

Capacitive jumper

AC current

Figure 3.11: PowerShift diagram

Figure 3.10: The PowerShift base unit is deployed at the bottom of the tower, in conjunction with the existing dc power plant.

Key benefits

The PowerShift system enables network operators to re-use existing

copper supply lines and reliably power higher wattage radios without

having to install larger or additional copper conductors. By eliminating

the dc voltage drop in the power supply cable, it also conserves total

battery backup time.



Figure 3.12: Link imbalance and different coverage footprint without TMA and with TMA

Overcoming link imbalance

Handheld devices typically have much lower transmit power

(usually <1 watt) than base stations. As towers become more

overloaded, operators are moving the RRUs down the tower.

This increases the length of the feeder cables between the BTS

cabinet and antennas, further attenuating the UE signal. Often,

the signal strength falls below the receiver’s sensitivity and is

ignored. Subscribers on the cell edge may see sufficient coverage

bars on their handsets but be unable to make or receive calls.

The problem is generally described as an imbalance between the

uplink and downlink signals. A tower-mounted amplifier (TMA)

is designed to overcome such problems by lowering the overall

noise factor and improving gain.

Cable loss (dB) Receiver NF: No TMA (dB)

Receiver NF: With TMA (dB) Difference

0 4.5 1.84 2.66

1 5.5 1.97 3.53

2 6.6 2.13 4.37

3 7.5 2.32 5.18

4 8.5 2.54 5.96

5 9.5 2.81 6.69

6 10.5 3.13 7.37

Table 3.1: TMA and noise figures

Noise figure

A receiver’s noise factor—the noise added by the receiver itself—

is the ratio of its input SNR to output SNR. In the UL path, a TMA

amplifier followed by a BTS amplifier creates a cascaded receiver

noise factor. This can be expressed by the following simplified Friis

formula, where F is the noise factor and G is the amplifier’s gain:

FReceiver = FTMA + F BTS / GTMA

The noise factor of the first amplification stage FTMA has the biggest

weight. The higher the TMA’s gain, the lower the effect of the BTS

noise. Consequently, adding a TMA with low noise factor and higher

gain improves the overall noise figures.

Table 3.1 shows the extent to which a TMA improves the receiver’s

overall noise figure (NF). Note that NF is the noise factor expressed

in decibels. What does not appear in the table is the fact that, the

longer the cable, the larger the positive impact of the TMA.

TMA impact on uplink throughputAs mobile traffic continues to grow, network operators attempt to

meet capacity demands with strategies such as spectrum overlays,

sector splitting and active beamforming antennas. While locating

additional equipment at the top of the tower is preferred, space

and weight constraints frequently require some radios to be placed

on the ground. Connecting the radios using feeder cables results in

signal loss and uplink (UL) degradation.

UL/DL imbalance

https://www.commscope.com/Docs/Multiband_Tower_Mounted_Amplifiers_BR-111906-EN.pdf

https://www.commscope.com/Docs/Multiband_Tower_Mounted_Amplifiers_BR-111906-EN.pdf


Using TMAs along with ground-mounted RRUs allows operators to

fully compensate for UL degradation and improve UL performance

compared to using tower-mounted RRUs only. The TMAs can also

improve UL throughput in a major part of the area served by a cell

and help improve in-building UL performance.

Innovation at work

Take a deeper dive into how TMAs benefit uplink performanceCommScope has been a leader in the development and use of tower-mounted amplifiers for improving cell coverage. For a more in-depth look at the use of TMAs to address the issue of signal imbalance, we recommend reading our tower-mounted amplifiers white paper—TMA impact on uplink throughput.

TMA portfolioRecently, the industry has seen greater diversity in the available

TMAs, including those for FDD and TDD applications. As more

frequency bands have become available and the use of 4x2 and

4x4 MIMO has increased, CommScope’s suite of multiband TMAs

has also expanded. This has led to network operators being able to

reduce the number of boxes on towers as well as their total tower

loads. In general, TMAs can be classified as single-band, dual-band,

tri-band, quad-band and penta-band.

Single-band TMAs: Among the most common and widely used

TMAs are single-band TMAs. These support different standard 3GPP

bands or customized sub-bands, including RF bypass. CommScope

offers single-band TMAs for use with the following bands: 700 MHz,

800 MHz, 850 MHz, 900 MHz, 1800 MHz, 2100 MHz, 2300 MHz

(TDD) and 2600 MHz.

Dual-band TMAs: Dual-band TMAs cover all commercial 3GPP

bands: 700/850 MHz, 700/900 MHz, 850/900 MHz, 800/900

MHz, 1800/2100 MHz, 1800/2600 MHz and 2100/2600 MHz,

among others. Different versions are available with 7/16 or 4.3-10

connectors. For instance, there is a twin-dual-band TMA (1800/2100

MHz) designed to reduce feeder runs. It has two ports toward the

BTS and four ports toward the antenna with a built-in 1800/2100

diplexer. Typically, an external diplexer is used at the tower’s bottom,

enabling the operator to combine 1800 MHz and 2100 MHz signals

on a single feeder. The TMA then separates these to the respective

antenna ports.

Table 3.2: Throughput (UL) with and without TMA

Allocated BW Throughput (UL)

kbps

% o

f Fo

cus

zon

e ar

ea

RRU @ top w/o TMA RRU @ ground w/o TMA RRU @ ground w/TMA

Figure 3.13: CommScope TMA1800 E14R00P02, TMA2100 E14R00P07, TMA2300 TDD E15S07P13

https://www.commscope.com/Docs/TMA_Impact_on_Uplink_Throughput_WP-113171-EN.pdf





i CommScope e-book, Understanding the RF path; https://www.commscope.com/Docs/RF_Path_eBook_EB-112900-EN.pdf

ii Francis Rumsey; Tim McCormick. Sound and Recording: An Introduction (6th ed.). Focal Press

iii Passive Intermodulation (PIM); Anritsu; https://www.anritsu.com/en-IN/test-measurement/technologies/pim

iv IEC 62037, Passive RF and Microwave Devices, Intermodulation Level Measurement.

v Ray Butler, PIM Testing, white paper CommScope, PIM testing; http://www.commscope.com/Docs/PIM_Testing_WP-107482.pdf

Quad- and penta-band TMAs: The world’s first quad-

band and penta-band TMAs enable integrating four or five

TMAs in one device—for example, 850/900/1800/2100,

1800/2100/2300TDD/2600 or 700/850/900/1800/2100—aiming for

further reductions in wind loading and occupied space on the tower.

Different versions are available with 7/16 and 4.3-10 connectors, as

well as various antenna port configurations, including two input/two

output ports or two input/four output ports with low-band bypass.

Tri-band TMA: CommScope has been a pioneer in the

development of tri-band TMAs—especially for high bands. A single

device can cover 1800/2100/2600 MHz or 1800/2100/2300 MHz

for TDD as well as FDD. This allows networks to reduce tower

loading, wind loading, and leasing cost. Different versions are

available with 7/16 and 4.3-10 connectors, as well as different

antenna port configurations.

A tri-band TMA can have two input ports through the BTS and

two output ports through the antenna, accommodating all three

bands—1800, 2100 and 2600 MHz.

Recently, CommScope has also introduced new tri-band TMAs

that greatly expand the operator’s ability to adapt their RF path

configurations to their specific needs. The TMAs, shown in

Figure 3.15, feature two input/four output ports, two input/six

output ports, and two input/eight output ports, including

low-band bypass.

Figure 3.16: CommScope quadband TMA 850/900/1800/2100 E15Z01P37, TMA1800/2100/2300TDD/2600 2in:2out E16Z01P74,

TMA1800/2100/2300TDD/2600 2in:4out LB bypass E16Z01P82 and penta-band TMA 700/850/900/1800/2100 2in:4out E16Z01P68 and

TMA 700/850/900/1800/2100 2in:6out E16Z01P63

Figure 3.14: A CommScope TMA1800/2100 7/16 E15S02P59 and 4.3-10 E16S02P59

Figure 3.15: CommScope tri-band TMA1800/2100/2300 TDD E16Z01P71, TMA1800/2100/2600 E14R00P29, TMA1800/2100/2600 2in:4out E16Z01P86, TMA 1800/2100/2600 2in:6out E16Z01P88 and

TMA1800/2100/2600 2in:8out E16Z01P90

Solving operational challenges, realizing greater potentialFrom smarter ways to power your top-of-the-tower equipment to

innovative solutions for addressing link imbalances, CommScope is

helping network operators create more opportunity and realize more

network potential. As technologies and challenges evolve, look to us

to keep you informed and prepared to meet tomorrow head-on.

The ability to anticipate what’s next—it’s not just our strength,

it’s our job.

https://www.commscope.com/Docs/RF_Path_eBook_EB-112900-EN.pdf

https://www.commscope.com/Docs/RF_Path_eBook_EB-112900-EN.pdf

https://www.anritsu.com/en-IN/test-measurement/technologies/pim

https://www.anritsu.com/en-IN/test-measurement/technologies/pim

https://www.commscope.com/Docs/PIM_Testing_WP-107482.pdf

https://www.commscope.com/Docs/PIM_Testing_WP-107482.pdf

C H A P T E R 4

44 Site solutions for techies | Chapter 4: Small Cell solutions

· Small cells for capacity problems

· Small cells for coverage problems

· Small cells for latency improvement

· Small cells for spectrum offloading

· Concealment and installation solutions

Small Cell solutions

HIGHLIGHTS

A

A

A

Site solutions for techies | Chapter 4: Small Cell solutions 45

Efficiently meeting subscribers’ traffic demands has been a never-ending major challenge for cellular operators. Network congestion not only reduces revenue, it frustrates customers and leads to costly churn. To meet the increasing demand for data, many networks are turning to site densification, boosting the number of cells per square kilometer. But, as the distance between macro sites decreases, the amount of signal overlap and interference increases.

One very attractive solution is small cells. Small cells allow operators

to address issues—such as capacity, coverage, latency and spectrum

availability—at the precise location the problems exist. True to

their name, small cells are compact, low-profile units with a lower

equivalent isotropically radiated power (EIRP). This enables operators

to reuse precious spectrum with greater efficiency and a minimum of

interference. In other words, small cells are well suited to help

operators solve many of their densification problems. Recent market

forecasts indicate that operators are re-thinking their small cells

strategy to do just that.

The 2018 Small Cell Market Status Update Report shows that, in

2015, 43 percent of the world’s small cells were used in non-dense

environments to plug coverage or capacity gaps; only 23 percent

were deployed to create dense or hyperdense environments.

By 2025, however, 78 percent of all small cells are expected to be

used for densification. The total market for small cells is growing

just as dramatically.

By 2025, the report forecasts a reverse in the trend, with 78 percent

of new deployments in dense or hyperdense environments, and

only 4 percent in non-dense, with an overall installed base reaching

70.2 million cells.

Ann

ual D

eplo

ymen

t (‘0

00 c

ells

)

5G Small cells deployment and Installed base

Inst

alle

d Ba

se (‘

000

cells

)

Figure 4.1: Small Cell Forum, Dec. 2018

cells

‘000

Small cells deployed by environment

Figure 4.2: Small Cell Forum, Dec. 2018



Small cell hardwareWhen speaking about small cells, one of the basic challenges is

how to define them. How small is a small cell? The hardware is

usually classified by its baseband processing capacity, transmit

power and antenna type. Table 4.1 shows some further

classifications and common terminologies in the industry.

Small cell use casesSmall cells can locally address capacity needs for both

outdoor and indoor hotspots. Metro or micro types are

typically found outdoors, while femtos and picos are mostly

used indoors.

In some high-traffic indoor venues, like large shopping

malls, operators deploy a second layer of small cells on top

of an existing passive distributed antenna system (DAS). This

enables them to support higher MIMO schemes without

increasing the amount of DAS infrastructure required.

In outdoor environments, small cells play a critical role

as networks continue to progress toward a more fully

realized vision of 5G. Gigabit LTE is an important milestone

along the way. As the name implies, Gigabit LTE enables

peak throughput speeds exceeding 1 Gbps. Supporting it

Class Capacity (users) TX Power Antenna

Femto <32 20–24 dBm Internal

Pico 32–128 24–30 dBm Mostly internal

Micro/metro 128–256 30–37 dBm Internal or small external

Table 4:1: Small cell classes

Figure 4.3: Ericsson and Huawei small cells examples

Figure 4.4: OneCell network architecture

Devicemanagement system (DMS)

Core

Ethernet LAN

Radio pointsRadio points

User-centric network:

single PCI, no borders

or handovers

Ethernet fonthaul

Baseband controller

Edge intelligence for cell

virtualization, location awareness.

Innovation at work

OneCell®

CommScope’s OneCell® illustrates how small cells are evolving to help operators better support wireless users indoors. Using a unique C-RAN architecture, OneCell connects multiple distributed radio points via standard Ethernet cabling to a centralized baseband controller. LTE scheduling takes place in the baseband controller, creating a single physical cell ID across all radio points. This eliminates border interference and the need for handovers within the coverage area. OneCell also employs sophisticated coordination across radio points, enabling simultaneous re-use of physical resource blocks (PRB) in different parts of the building. This increases spectral efficiency and system capacity.

requires 4x4 MIMO, three- component carrier aggregation,

and 256 QAM performance. This means small cells deployed

for capacity must support multi bands, higher MIMO schemes

and, in some cases, resource sharing. CommScope’s small cell

antennas portfolio enables operators to check all three boxes.


Enhancing coverageBesides capacity, small cells are also useful for improving coverage.

For instance, in remote, low-traffic regions or null areas between

macros sectors, outdoor metro cells deploy quickly and deliver

excellent results. When deployed in higher traffic urban areas, these

same solutions also help boost indoor coverage—especially when

equipped with omni antennas.

Due to their small size and weight, metro cells are also being used

for more specialized applications. For example, when installed in

mid-sized vehicles and backhauled using automatic tracking satellite

dishes, metro cells can be used for military applications.

Femto cells have also been extensively used to address indoor

coverage issues by many operators around the globe. A typical

femto cell is usually backhauled over the user’s internet connection

and looks similar to a Wi-Fi access point. This also makes it a very

cost-efficient solution in some markets.

Another practical strategy for solving outdoor coverage and capacity

challenges involves an outdoor DAS such as CommScope’s outdoor

DAS, shown in Figure 4.5. Remote radios are distributed over a fiber

network and connected to a centralized base station. Each remote

radio provides multiband, multi technology and multi operator

support. The compact size and simplified deployment make this

solution well suited for installations inside street furniture or other

space-constrained structures.

CentralizedRAN Master Unit

600-800 mcoverage

Camouflageantenna

Fiber-opticnetwork

Up to 40-kilometer radius from BTS hotel location

Remote unit

Figure 4.5: Outdoor DAS architecture



Improved latencyIt is no secret that low latency and edge computing applications are

increasing in importance. The ITU has set a stringent target of 1 ms

latency for its 5G IMT2020 requirements.

Two of the most common approaches for improving latency are:

1) extending fiber to the edge or 2) bringing the radios as close

to the user as possible. One of the major challenges in moving

the radios closer to users is ensuring reliability of the physical

connections while accelerating speed and ease of installation.

Widely driven by CommScope, recent developments in hardened

multi-fiber connectivity are making it easier and less costly to

reduce network latency.

For example, CommScope has designed hardened, pre-

connectorized, multiple fiber drops from the fiber network

demarcation point to the metro cell. As shown in Figure 4.6,

the fiber backbone terminates inside the handhole (demarcation

point) into a connectorized flexible service terminal (FST)

or multiport HMFOC terminal (MHT). Hardened, multi-fiber

connectors inside the terminals eliminate splicing and enable

plug-and-play connectivity.

Drop cables equipped with HFMOC or Optitap™ compatible

connectors can be quickly connected between the FST or MHT and

the fiber termination point on the metro cell. The example (shaded

gray) in Figure 4.6 is an HMFOC-to-LC duplex drop cable, which is

available with armoring.

Figure 4.6: CommScope fiber connectivity solutions

Fiber OpticNetwork

Handhole

Equipment enclosures

FST: Pole or buried

MHT: Aerial or buried

HMFOC Terminal Options (CCS)

HMFOC to LC duplex drop cable


Spectrum offloadingAs previously noted, one of the biggest advantages of small cells is

tighter frequency re-use and the resulting increase in capacity. Bands

above 1 GHz make better candidates for such deployments as they

fade faster, provide a more controlled coverage pattern, and create

less interference for neighboring cells. This capacity-generating

ability enables operators to offload traffic from more congested

areas of their network and improve quality of service and spectral

efficiency. The question then becomes, which networks can be used

to carry the offloaded traffic? Two good alternatives have emerged.

Unlicensed bandsData traffic is constantly rising while revenue per MB continues to

fall. The use of unlicensed bands for small cells is emerging as an

attractive and cost-effective solution for offloading traffic. Evolving

standards around this application include Licensed Assisted Access

(LAA), LTE-WLAN aggregation (LWA) and muLTEfire.

5G bandsAs the industry moves toward 5G, channel bandwidths of 100

MHz and more are needed per operator. Traditional spectral bands

cannot accommodate such allocations without carrier aggregation.

One alternative is to move into the higher bands, with the C-band

(3.5 GHz) and mmWave bands being the most likely candidates.

However, attenuation for such bands is much higher. In the existing

macro networks, site-to-site distances will result in inter-cell coverage

gaps. To address this problem, operators are looking at using massive

MIMO at macro sites and/or deploying small cells nearby.

The CommScope small cell antenna portfolio includes a variety of

models, enabling operators to utilize the 5G C-band for offloading.

Figure 4.7 shows the profile and port layout for the CommScope

V4SSPP-360S-F. This 16-port small cell antenna covers the existing

4G bands, new 5G bands, as well as the unlicensed bands. It

features eight ports that support the 1,695–2,690 MHz band,

four ports for the 3,400–3,800 MHz band and four ports for the

5,150–5,925 MHz band. Figure 4.7: CommScope V4SSPP-360S-F 16-port

small cell antenna



Small cell deployment challengesDespite their advantages, small cells present network

operators with significant challenges regarding

deployment. In a 2018 survey by the Small Cells Forum,

78 MNOs were asked to name their top three barriers

to small cell. The results, summarized in Figure 4.8,

show that uncertainty regarding TCO (19 percent), site

acquisition issues (16 percent), and potential interference

with the macro layer (13 percent) as the major obstacles.

However, in developing countries—where stable

commercial utility power and fiber reach for backhaul

are still largely inadequate—the obstacles to small cell

deployment are much higher.

Immature automation/virtualization 6%

Hetnet Interoperability 7%

Equipment Approvals 7%

Site Approvals 8%

Backhaul Cost and Availability 9%

Ability to monetise via new services 12%

Wifi Interworking 3%

TCO uncertainty 19%

Site Cost and Availability 16%

Macro Interworking 13%

Figure 4.8: SCF deployment barriers survey 2018

MNO’s small cell concerns include total cost of ownership, site acquisition issues and potential macro layer interference.


Figure 4.9: Top, middle and bottom pole solutions

Metro cell concealment solutionsThe Small Cells Forum survey makes clear that small cell site

acquisition and equipment approval are primary concerns for

MNOs. These concerns are hardly unfounded. Writing in 2017,

FCC Chairman Ajit Pai said: “We shouldn’t apply burdensome

rules designed for 100-foot towers to small cells the size of

a pizza box.” But changing the zoning regulations to speed

deployment will take time.

Meanwhile, CommScope has been developing a variety of metro

cell concealment solutions to help operators accelerate the site

acquisition and deployment process. Three of these practical

workarounds, shown in Figure 4.9, are designed to integrate the

small cell radios and antennas inside the top, middle or bottom

section of a piece of street furniture such as a streetlamp post.

Such solutions not only make the process of acquisition and

approval much easier; it secures the communications hardware

from vandalism or theft.Well-designed metro cell concealment solutions can accelerate network deployment without intruding on the environment.



Interference controlInterference control is important for maximizing the operational

efficiency of outdoor metro cells. It is also an important requirement

for supporting the 256 QAM functionality necessary for achieving

Gigabit LTE speeds. CommScope’s quasi-omni antennas offer

two key design improvements that enable operators to minimize

interference and enhance small cell performance.

The first design improvement involves the placement of three x-pol

panel antennas with 120-degree azimuth separation under one

radome. All panel antennas are fed from the same RF input ports,

creating quasi-omni patterns (shown in Figure 4.10). The use of

panel antennas allows operators to utilize electrical tilt with an omni-

directional antenna to better control coverage and interference.

to use 4x4 MIMO in the overlapping areas, making it especially

well suited for antenna sharing, 4x4 MIMO and Gigabit LTE

applications.

Enabling RF path sharingAs with macro cells, the number of operators sharing small cell

locations is increasing along with the number of spectrum bands

and air interface technologies. The volume of cabling needed to

support the various RF elements inside the concealment poles

is becoming a growing concern. Using shared feeders that

allow operators to combine radios on thinner, lighter cabling is

emerging as a key tool for operators looking to conserve space

within the poles.

Figure 4.10: Quasi-omni antenna and its horizontal patterns across various e-tilts

Figure 4.11: 4x4 MIMO small cell antenna (showing Port 1 and Port 3 H-patterns at 2,100 MHz)

Antenna ports

Panel direction

The second improvement maximizes the number of input ports

to support licensed and unlicensed bands, while minimizing the

overall antenna diameter. As seen in the V4SSPP-360S-F, the two

orthogonal peanut-shaped patterns (Figure 4.11) allow operators


3/8-in. LSF4 jumpersCommScope’s new thinner and lighter LSF4 coaxial jumpers enable

operators to conserve space while maintaining the insertion loss

performance of the industry standard 1/2-inch jumper. With its

3/8-inch diameter, it is also 40 percent lighter than the 1/2-inch FSJ4,

making it ideal for use in small cells concealment solutions.

Ultra-compact multiband combinersAt the same time, operators must also look to reduce the total

number of feeder cables. Multiband combiners (MBC) provide a

good approach. Using an MBC, the outputs from multiband radios

can be combined over a single feeder cable and the multiple

signals are separated just before the antenna. CommScope

has a wide portfolio of diplexers, triplexers and quadplexers

with extremely low insertion losses.

Among the recent advancements is a new family of ultra-compact

multiband combiners. Extremely lightweight and with a small

footprint, these MBC solutions are ideal for concealed small cell

applications. They can also be used in any situation where space

and tower loading are of concern. As shown in Figure 4.13, these

new ultra-compact MBCs enable operators to reduce weight and

size within the small cell housing structure by about 50 percent. In

addition, they are highly cost effective, can be used in non-TMA

configurations, and offer better lead times for faster ROI.

Figure 4.13: Ultra-compact versus standard diplexer for the 700–800 MHz and 900 MHz bands.

E14F05P89 Ultra Compact

E11F02P72 Standard

Figure 4.12: 3/8” LSF4 Vs 1/2” FSJ4 RF jumpers

380-960/1800-2600 MHz 1800-2100/2600 MHz 1800-2100/2600 MHz 700-800/900 MHz 700-800/900 MHz

1800/2100 MHz

E14F55P08 E14F55P16 E14F55P19 E14F06P05 E14F05P89

E14F05P95

E14F06P03

E14F05P99

1800/2100 MHz

1800/2100 MHz

Ultra Compact Diplexer



698-960/1800/2100/ 2100-2700 MHz

1800-2600/3400-3800/ 5100-5900 MHz

698-960/1800/2100/ 2100-2700 MHz

1800-2600/3400-3800/ 5100-5900 MHz

1800/2100/2300-2700 MHz

700-2600/3400-5900 MHz

1800/2100/2300-2700 MHz

1400-1800/2100/2300-2600/ 3400-3800 MHz

698-960/1800/ 2100/2300-2700 MHz

1400-1800/2100/2300-2600/ 3400-3800 MHz

E14F10P59

E14F60P01

E14F10P47

E14F60P02

E14F10P54

E14F55P89

E14F10P46

E14F15P24

E14F15P19

E14F15P23

E14F15P17

E14F20P05

E14F20P06

698-960/1800/ 2100/2300-2700 MHz

700-900/1400-1800/2100/ 2300-2600/3400-3800 MHz

700-900/1400-1800/2100/ 2300-2600/3400-3800 MHz

ConclusionSmall cells have evolved across different cellular generations.

They present efficient approaches for capacity, coverage and

latency improvements—yet the wide spread of small cells is

usually impaired by tough challenges specific to each market.

Still, innovation is relentless.

Spurred by the efforts of leaders such as CommScope,

the industry is developing new solutions to help operators

realize more potential in their indoor and outdoor small cell

deployments. From antennas that deliver better interference

rejection and pattern performance to the combiners, cabling and

concealment solutions that help speed deployment, CommScope

is pushing the possibilities to enable a more connected future.

i Small Cell Market Status Report; Small Cell Forum; December 3, 2018

For more information on CommScope’s entire portfolio

of ultra-compact combiners, including those featured

above, view product details from our online catalog.

Ultra Compact Triplexer and Quadplexer

Ultra Compact Combiners for 5G introduction

Why Ultra Compact Combiners?

· Much more compact size VS Standard

· 50% Lighter VS Standard Combiners

https://www.commscope.com/search/?searchquery=ultra+compact+multiband&pageNumber=1

CommScope proudly dedicates this guide to our customers—network operators around the globe, working to keep their customers and the world connected.

In partnership with our customers, suppliers and industry stakeholders, we constantly push the boundaries of cell site design, looking to improve every aspect of performance, value and the user experience. Our 40+ years of industry experience and ongoing involvement with global standards bodies give us a unique perspective that informs our vision of what’s next. Where we see opportunity, we challenge ourselves to pioneer the technology that you deserve, rethinking solutions to maximize results.

In doing so, CommScope ensures you are not only prepared for today, you are ready for tomorrow. Let’s go.

CommScope pushes the boundaries of communications technology with game-changing ideas and

ground-breaking discoveries that spark profound human achievement. We collaborate with our customers

and partners to design, create and build the world’s most advanced networks. It is our passion and commitment

to identify the next opportunity and realize a better tomorrow. Discover more at commscope.com

commscope.comVisit our website or contact your local CommScope representative for more information.

© 2020 CommScope, Inc. All rights reserved.

Unless otherwise noted, all trademarks identified by ® or ™ are registered trademarks, respectively, of CommScope, Inc. This document is for planning purposes only and is not intended to modify or supplement any specifications or warranties relating to CommScope products or services. CommScope is committed to the highest standards of business integrity and environmental sustainability with a number of CommScope’s facilities across the globe certified in accordance with international standards, including ISO 9001, TL 9000, and ISO 14001. Further information regarding CommScope’s commitment can be found at www.commscope.com/About-Us/Corporate-Responsibility-and-Sustainability

CO-113629.1-EN (09/20)

Author Biographies

Dr. Mohamed Nadder Hamdy

Dr. Mohamed Nadder Hamdy is CommScope’s director of

mobility network engineering for the Middle East, Africa,

Australia and New Zealand. He provides technical expertise

to operators and OEMs, helping optimize cellular network

strategies for cost and performance. Previously, Mohamed held

senior roles with the Emirates Telecommunications Corporation

(Etisalat), including CTO (Etisalat Nigeria), head of mobile

network capacity planning and mobile technology strategy

(Etisalat UAE), and regional radio planning manager (Etisalat

Egypt). He holds Ph.D., Master of Science, and Bachelor of

Science degrees in electrical communications engineering from

Alexandria University (Egypt).

Paolo di Carne

Paolo di Carne is applications engineering manager for the

Middle East and Africa (MEA) at CommScope—responsible for

enhancing the company’s technical leadership position with

filter and tower-mounted amplifier products in the region,

as well as for base station antennas and Heliax® products in

Africa’s French-speaking countries. Paolo has nearly 20 years’

experience in the telecommunications sector, working as an RF

engineer and in other roles at AdvaComm, Ericsson, Devoteam,

Nokia Siemens Networks, and Telecom Italia. Paolo has a degree

in electronic engineering from the Politecnico di Milano.

https://www.commscope.com

http://www.commscope.com

http://www.commscope.com/About-Us/Corporate-Responsibility-and-Sustainability

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