MW Links Planning With Pathloss IV

Imran Siddiqui copy right reserved 1

Microwave Engineering with Pathloss IV

Imran Siddiqui

Email :[email protected]


Microwave Communication

A communication system that utilizes the radio frequency band spanning 2 to 60 GHz. As per IEEE, electromagnetic waves between 30 and 300 GHz are called millimeter waves (MMW) instead of microwaves as their wavelengths are about 1 to 10mm.

Small capacity systems generally employ the frequencies less than 3 GHz while medium and large capacity systems utilize frequencies ranging from 3 to 15 GHz. Frequencies > 15 GHz are essentially used for short-haul transmission.

Microwave radio communication requires a clear line-of-sight (LOS) condition.

Radio LOS takes into account the concept of Fresnel ellipsoids and their clearance criteria.


Available RF Spectrum

Band2-4 GHz

6-8 GHz

10 GHz

11 GHz

13-18 GHz

23-38 GHz

AdvantageBest propagation - no power fading (decoupling, ducting).Effective space diversity.

Lowest outage in non-ducting areas. Best high capacity, long-haul performance Very effective space diversity. Good discrimination to interference and long-delayed reflections.

Good longer path performance .Effective space diversity. Low rain outage in thunderstorm areas.

Wide spectrum (1000 MHz) available Many high capacity channels available

Narrow and wideband channels availableUncrowded bands (2000 MHz @ 18 GHz).

Few bandwidth constrictions .Uncrowded bands (e.g. 2400 MHz wide band at 23 GHz)

AdvantageBest propagation - no power fading (decoupling, ducting).Effective space diversity.

Lowest outage in non-ducting areas. Best high capacity, long-haul performance Very effective space diversity. Good discrimination to interference and long-delayed reflections.

Good longer path performance .Effective space diversity. Low rain outage in thunderstorm areas.

Wide spectrum (1000 MHz) available Many high capacity channels available

Narrow and wideband channels availableUncrowded bands (2000 MHz @ 18 GHz).

Few bandwidth constrictions .Uncrowded bands (e.g. 2400 MHz wide band at 23 GHz)

DisadvantageWideband links are vulnerable to dispersive fading. Reduced fade margins due to lower antenna gains. Higher interference levels. 2 GHz impacted by UMTS, FWA. High clearance paths are vulnerable to reflections. 4 GHz shared with satellites.

Longer paths are vulnerable to power fades due to ducting and decoupling in an adverse climate, requiring higher path clearances in some areas. Bands are crowded in some areas.

Limited bandwidth (4-16 T1/E1) RF channels.

Rain outage is a major factor in some areas. Shared with satellite services 10.9-12.75 GHz.

Outages are dominated by rain in thunderstorm areas, so path lengths are limited.

Very rain sensitive - e.g. needs 12-16 dB more fade margin (or 50% shorter paths) at 23 GHz than 18 GHz for equal outage in rain areas.


TDM and PCM

The Bi-Polar PCM Digital Signal

(50% duty cycle)

11111111 12710100000 3210010000 1610001000 810000010 210000001 100000000 000000001 -100000010 -200001000 -800010000 -1600100000 -3201000000 -6401111111 -127

10011000* (Amplitude = 24)

Ch. 2 Analog Signal (VF)

µ-law (DS1)

1 1 1 0 0 0 1 1* 1 0 0 1 1 0 0 0* 1 0 1 0 0 1 1 1*

8-bit code of DS0 Ch. 1



DS1 Frame = 24 x 8-bit Bytes + 1 Framing Pulse = 193 bits193 bits x 8000 samples/sec = 1.544 Mbit/s

*DS0 VF Supervisory Signalson the

Least Significant Bit (LSB)

0 772 1544 3000 kHzNote the negligible energy

below 10 kHz and above 1.544 MHz

En

erg

y

Am

pli

tud

e

PC

M Q

uan

tizi

ng

Co

de

*Bi-Polar Violation (Alarm)

*


Microwave Link Design Methodology

Microwave Link Design is a methodical, systematic and sometimes lengthy process that includes :

Loss/attenuation calculations.

Fading and fade margins calculations.

Frequency planning and interference calculations.

Quality and availability calculations.


Micrwave Link Design

Microwave Link Design Process

The whole process is iterative and may go through many redesign phases before the required quality and availability are achieved.

Frequency Planning

Frequency Planning

Link BudgetLink Budget

Qualityand

AvailabilityCalculations

FadingPredictions

Interferenceanalysis

Propagation losses

Branching losses

Other Losses

Rainattenuation

Diffraction-refraction losses

Multipathpropagation


Radio Path Link Budget

Transmitter 1

Receiver 1

Splitter Splitter

Transmitter 2

Receiver 2

OutputPower (Tx)

Branching Losses

waveguide

Pro

paga

tion

Los

ses

Ant

enna

G

ain

Ant

enna

G

ain

Branching Losses Received

Power (Rx)

Receiver threshold Value

Fade Margin


Hierarchy in Multiple Access Networks

Analog FDM Hierarchy:FDM Subgroup: 3 Channels, 4-16 kHz, 4 kHz per channel Basic FDM Multiplex Group: 12 Channels, 12-60/60-108 kHz (2x48 kHz)2-nd order Multiplex Group: 60 Channels, 2x240 kHz3-rd order Multiplex Group: 300 Channels, 2x1.2 MHz4-th order Multiplex Group: 960 Channels, 2x4 MHzPlesiochronous Digital Hierarchy:Europe-ETSI: E1 (2048 kb/s, 30-31 channels 64 kb/s each), E2 (8448 kb/s, 4E1s, 120-124 channels) E3 (34.368 Mb/s, 16E1s, 480-496 channels E4 (139.264 Mb/s, 64E1s, 1920-1984 channels)USA-FCC: DS1 (1544 kb/s, 24 channels), DS2 (6312 kb/s, 4DS1, 96 channels) DS3 (44.736 Mb/s, 28DS1, 672 channels)Synchronous Digital Hierarchy: STM-1 (155.520 Mb/s, 63 E1s or 1 E4) STM-4 (622.08 Mb/s, 252 E1s) STM-16 (2488.32 Mb/s, 1088 E1s) STM-64 (9953.28 Mb/s, 4032 E1s)


SDH Capacities

Line Rate(Mbit/s)

SDH Signal PDH Signal# E1 (2048 kbit/s)

Channel Transport

2.048 VC - 12 1 30

34.368 VC - 3 16 480

51.84 Sub-STM-1* 21 630

139.264 VC - 4 64 1,920

155.52 STM - 1 63 1,890

622.08 STM - 4 252 7,560

2488.32 STM - 16 1,008 30,240

9953.28 STM - 64 4,032 120,960

Reference: ITU-R Rec. F.750-3 (1997)

Radio or Fiber

Fiber

1:N Radio or Fiber


SDH Frame Structure

Frame Length: 125RSOH : Regenerator Section OverheadMSOH: Multiplexer Section OverheadBit rate: 155.520 Mbps

sec


SDH Frame Overhead

X … Bytes reserved fornational usage

M … Bytes reserved for media specific usage

(empty) … Bytes reserved for future standardization


Typical Service Requirements

Bandwidth requirements for the applications listed are considered sufficient to provide adequate user experience on a single workstation.


Transmission Media

Copper or Fiberoptics Cable - Leased Services Monthly fee…operator never owns the network Often long repair times ... customers are out of service Limited availability...e.g. ~99.8% (~17 hr/yr traffic loss)

Fiberoptics Cable - Purchase High installing cost ($30k-300k per km) favors very high capacity (2.5-10 Gb/s, per

“colour” with WDM) data transport Vulnerable to route damage with long service interruptions

Wireless Optical (Infrared, Laser, etc.) - Purchase Very short range - affected by optical visibility (300 m – 3 km) Low to high capacity, now to ~10 Gbit/s (OC-192/STM-64)

Microwave Radio - Purchase Low life cycle cost Rapid deployment, responsive service implementation, and under full user control (sites

and routes are secure)


Terrestrial Radio-relay links

Terminal “A”

RadioMultiplex

Tx

Rx

RadioMultiplex

Tx

Rx

Terminal “B”

Antenna

Path

Feeder

Interference

Data Data

Antenna

Feeder

Radio meets superior reliability, higher security, and more demanding performance and quality standards.

Radio user has total control over site access and restore time.Radio grows with the network: Easily expandable and accommodates future relocation.Radio has an operational life long after the leased-line payback has passed (~2 yrs).Radio provides clear channel and protection capabilities.


Advantages of MW wireless solution

Advantages of MW wireless solution

Disadvantages of MW wireless solution

Disadvantages of MW wireless solution

Low fixed costs Fast implementation (days) Focus deployment on best opportunities Winning cost profile in urban and rural markets Speed allows entry into new markets Unregulated at local levels 80% of cost is electronics (not labor and structures)

Line of sight (LOS) propagation Weather affects availability Aesthetics problems of customer antenna, community base stations and towers MMW technology is relatively new to commercial applications (55 GHz)

Advantages and Disadvantages


Radio Wave Propagation

GEO, MEO, and LEO Satellites

Sky Wave(HF only)

REFRACTED WAVE

NON-REFRACTED (k=1) WAVE

REFLECTED WAVE

TransmittingAntenna

ReceivingAntenna

Troposphere

Ionosphere

Ground Wave(LF/MF only)

True Earth’s Curvature

MULTIPATH RAYS


MW versus Optic Fibre

Favors Microwave

Microwave or fiber

FavorsFiber

Required Transport Capacity

Favors: Radio Fiber

Availability/security Payload (transport) Cost effectiveness Implementation time

Terrain considerations

Transport ChoicesShort

Tu

rn-U

p T

ime

Graph shows typical installation and commissioning time vs. transmission capacity.

Microwave is favored for short installation times and low-to-medium transport capacities.

Lightwave is obviously favored for its high to very high transport capacities.

Radio generally has a lower fixed cost/unit capacity and thus is less expensive for medium capacities.


MW Radio in Cellular Networks


2.5G GSM Network

Intranet

MSC

Server

Router

Intranet

Serving GPRSSupport Node(SGSN)

BSCBTS

Um

Gateway GPRSSupport Node(GGSN)

Server

Router

PSTNNetwork

GPRSbackbonenetwork

Internet LAN

Frame Relay Network (New)

Options: IP over FR: IP over ATM over SDH : IP over DWDM: IP over FWA

Leased lines

Fibre, Microwave


MW radio-relay point-to-point wireless transmission is applicable to all communication networks.

MW applied for Mobile, Broadcast and Backhauling

2G

3G

WiMAX

3G LTE

WiFi

xDSL

FTTN

FTTU

GPON

WiMAX

BTS

Microwave for metro

Microwave for backboneBSC

Regional TV Studio

Microwave

Microwave

WiMAXWiMAX

Microwave

WAC

Mobile 2G and 3GMobile 2G and 3G

TV BroadcastingTV Broadcasting

MicrowavesBackhaulingMicrowavesBackhauling

MicrowavesBackbone

MicrowavesBackbone

OMSN


Broadband Services in TDM Transmission Solution

The Broadband effect:

Traffic

Revenues

Data Era

Voice Era

Cost

TDM Backhaul ModelTDM Backhaul Model

TDM solution loose its effectiveness as data traffic becomes predominant, since it is bursty in nature,Improved versions of TDM platforms are available to mitigate this effect in its early phase (Nodal Solutions; Higher spectral efficiency using SW configured modulation schemes 16- QAM, 64-QAM, 128-QAM, 256-QAM; Super-PDH platforms).


Exercise

Task: Convert to logarithmic dB units:Task: Convert to logarithmic dB units:

Power Amplification:• Twice• 20 times• 400 times• 500 000 times

Power Attenuation:• One half• 1/20•1/400•1/500 000

Use calculator and round the values to integer number of deci-bells.


Logarithmic Units

1pW = -90 dBm1nW = -60 dBm1 W = -30 dBm1mW = 0 dBm1W = 1000 mW = 30 dBm2W = 2000 mW = 33 dBm4W = 4000 mW = 36 dBm10W = 40 dBm40W = 46 dBm

mW

PdBmP

1log10][

V

UVdBU

1log20][

Power expressed in dBm:Power expressed in dBm: Voltage expressed in dBuV:Voltage expressed in dBuV:


Synchronization

Slip Rate: f x frames/s x 86400 s/daySlip Rate: f x frames/s x 86400 s/day

Type of Service EffectVoice Clicks

Video Frozen frames or missing lines

Modem Outage

Encryption Slow throughput

Fax Missing lines


Antenna Center-line Determination

The antenna height should be chosen in such a way that obstruction losses during adverse propagation conditions are acceptable.

Also, designer must consider the increased risk for ground reflections if too large a clearance is used.

Antenna heights for a path can be obtained:

Graphically from path profiles By using mathematical formulae Using Link planning software tools (e.g. Pathloss v.4.0,

Enterprise Connect, TEMS Link Planner, Ellipse, Harris Magic)


Path Calculations

270

330

390

440

500

Ele

vati

on

, m

A

MS

L

300

360

410

470

270

330

390

440

500

300

360

410

470

k = 4/3F = 0.6

Site: Yates CenterLat.: 37-51-02.NLong.: 095-43-53. W

Marmaton37-49-40. N

095-09-44. W

____

__ __ __ __ ____

__ __ __ __ ____

__ __ __ __ ____

__ __ __ __ ____

__ __ __ __ ____

__ __ __ __ ____

__

0 5 10 15 20 25 30

Distance, km

k=4/3

0.6F1

1.9 GHz

k=4/3


Frequency Spectrum Allocation

Radio signals have to be frequency-separated if neither antenna discrimination nor topographical shielding provides the necessary suppression of interfering

signals.Distinct segments of MW frequency spectrum exhibits different propagation

characteristics (mutli-path effects, rain attenuation, absorption). Particular frequency bands differ by their spectral width hence can support

different link capacities (channel separations range between 1.75 to 56 MHz).All frequencies used in a radio-relay network should normally be selected from

an established frequency plan, generated either by international or nationalorganization.


Receiver Sensitivity

Receiver sensitivity of a digital radio, is a minimum signal level on thereceiver’s input terminals, that secures specified maximum allowable BER behind receivers detector (typically 10-3 or 10-6 ), including FEC.

Receiver sensitivity is affected by:

Type of modulation method employed Type of carrier and clock recovery circuits Noise figure of the receiver path Phase noise level of the local oscillator Type of FEC and soft-detection employed


Receiver Sensitivity and C/N

Sensitivity (minimum required Rx power) can be also expressed in terms of minimum required Carrier-to-Noise Ratio (C/N).Sensitivity (minimum required Rx power) can be also expressed in terms of minimum required Carrier-to-Noise Ratio (C/N).

NCNP Th /min [dBm; dBm, dB]

Where thermal noise:

dBTh NFkTBN 30)log(10

k… Boltzman’s constant = 1.38 x 10-23 J/KT… Absolute temperature of the receiver in K (0 oC = 273.15 K)B … Noise bandwidth in HzNF … Noise Figure of the receiver in dB

E.g. for BPSK minimum required C/N= 6 dB, for QPSK minimumRequired C/N=10 dB, for 16-QAM minimum required C/N= 17 dB@10-3

[dBm; dBW, dB]


Receiver Thresholds

The 10-6 BER (or other BER<10-6) Static Threshold is for factory and in-service field verification of receiver noise and interference levels, measured manually with attenuators

The 10-3 BER Dynamic Threshold is for outage calculations and “hands-off” field measurements in a normal fading environment with BER network management, following ITU-T G.821 performance definitions.

The BER-SES Dynamic Threshold is the same as the above dynamic threshold, but is used for outage calculations following ITU-T G. 826 performance definitions. Usual range of BER-SES is 10-3 – 10-4.

Three Digital Radio Thresholds: One for factory and field in-service testing, and two for outage calculations, performance measurements, etc.

Three Digital Radio Thresholds: One for factory and field in-service testing, and two for outage calculations, performance measurements, etc.


Comparison of Modulation Methods

Receiver sensitivities for BER = 10-6 (3.5, 10.5 GHz)Receiver sensitivities for BER = 10-6 (3.5, 10.5 GHz)

For the same input data rate, more crowded M-QAM constellations use channel frequency band more effectively, but require higher C/I

Higher level M-QAM are susceptible to selective fading and other types of linear distortion.

M-QAM schemes require linear RF power amplification. Spectrum is expensive => Spectrum efficiency wins the battle


Free Space Loss and Absorption

2

4

DAFS

DAFSdB

4

log20

A free space equation simply assumes that radio waves are transmitted equally in all directions. Hence the power density is equal in every point of a sphere having transmitter in its center. Receiver captures only small part of the power, which is proportional to the effective area of receiving antenna – isotropic radiator.

In decibels:

Where D… distance between transmitter and receiver … wavelength


Atmospheric Absorption Curves

Significant for frequency bands above 15 GHz.

Significant for frequency bands above 15 GHz.

Absorption on water vapor H2O Absorption on oxygen molecules O2

Absorption on other gasses: smog, exhaustions, etc.


Terrain Related Effects

Specular Reflection: For MW hops routed across large or medium sized bodies of water (see, lakes, rivers), part of the energy radiated by the transmitter can be almost totally reflected from the water level, then reach the receiver and add destructively with a direct signal. This causes a power fade, the depth of which changes nocturnally (K-variation).

Diffraction effects: MW energy reaching an obstacle, the longitudinal dimension of which is comparable to the wavelength, is bent behind the obstacle. This bending is called diffraction. The rays behind the obstacle, that are bent under different angles, add up in a complex manner and cause cross-sectional variation in power density. Common manifestation of such varying power density is an attenuation on the direct path between Tx and Rx. This attenuation is subjected to K-variation and is closely coupled to Fresnel zones clearance.


Long High Hop

K = 4/3

0.25° Discriminationto the

Reflection

1500

500

0

1000

0 20 40 60 80 100(161 km)

0.249°Grazing Angle

5 ns

Multi

path D

elay

K = 0.543°

DecouplingAngle

Distance,Mi

2000

2400(731m)

1150 ft(350 m)

Ele

vati

on

AM

SL

, Ft

Short delays (up to 5 nsec) must be tolerable if radio DFM is high enough (>50dB), since there is very little antenna discrimination on long paths. Coupling of the reflected ray can be sometimes controlled by up-tilting the antennae (0-0.5 deg.)


Short High Hop

1150 ft (351m)

K = 4/31.25O Discriminationto the

Reflection

1200(365m)

750

500

250

0

1000

0 4 8 12 16 20(32 km)

1.248O

Grazing Angle

25 n

s

Multi

path D

elay

K =0.109O Decoupling

Angle

Distance,Mi

Ele

vati

on

AM

SL

, Ft

For high grazing angles (1-5 deg.), vertical polarization shall be preferred. Decoupling of the reflected ray is difficult to control and delays can be high (up to 25 ns).


Basic of Fresnel Zone

Fresnel Zone - Areas of constructive and destructive interference created when electromagnetic wave propagation in free space is reflected (multipath) or diffracted as the wave intersects obstacles. Fresnel zones are specified employing ordinal numbers that correspond to the number of half wavelength multiples that represent the difference in radio wave propagation path from the direct path.

The Fresnel Zone must be clear of all obstructions.

Typically the first Fresnel zone (N=1) is used to determine obstruction loss.

The direct path between the transmitter and the receiver needs a clearance above ground of at least 60% of the radius of the first Fresnel zone to achieve free space propagation conditions.

Earth-radius factor k compensates the refraction in the atmosphere.

Clearance is described as any criterion to ensure sufficient antenna heights so that, in the worst case of refraction the receiver antenna is not placed in the diffraction region.


Fresnel Zones Concept

Radius of the n-th Fresnel zone:

21

21

dd

ddnr

Where … wavelength

Electromagnetic energy directed by the transmitting antenna needs 3D unobstructed space to travel to the particular receiver. More then 90% of the energy radiated in particular direction is concentrated in so called 1-st Fresnel zone. 1-st Fresnel zone must remain unobstructed to avoid diffraction losses. Even Fresnel zone are important to judge upon reflection points.


Fade Margin

–10-2 —----

–10-3 —----

–10-4 —----

–10-5 —----

–10-6 —----

–10-7 —----

–10-8 —----

–10-9 —----

–10-10 —----

–10-11 —----

–10-12 —5 10 15 20 25 30 35 40

C/N or C/I Ratio, dB

— - - - - — - - - - — - - - - — - - - - — - - - - — - - - - — - - - - —

BE

R

—----—----—----—----—----—----—----—

(OUTAGE)

BPSK

4PSK4QAMQPSK

9QPR

8PSK 16QAM 32QAM

49QPR 64QAM

225QPR 128QAM32PSK

256QAM

Excludes FEC Coding Gains

(STATIC)

512QAM25QPR

Fade Margin is a difference between median received signal level, calculated from Power Budget equation, and BER=10-3 threshold of the receiver system.This difference has to account for stochastic propagation phenomena, that can compromise system reliability.

These phenomena are: Attenuation due to rain. Intersystem interference. Multipath fading. K-factor variation. Ducting.


Table of Contents – Pathloss v.4.0

Introduction to Pathloss v.4.0

Hop Definition

Terrain Profiling & Clearance Criteria

Microwave Worksheet

Applying Diversity and Protection

Diffraction Module Overview

Reflection Analysis

Multipath Operation

Network Description

Intra-system Interference

Design with Passive Repeater

Map Grid Module

Radio and Antenna Data Files

Case Studies

Introduction to Pathloss v.4.0

Hop Definition

Terrain Profiling & Clearance Criteria

Microwave Worksheet

Applying Diversity and Protection

Diffraction Module Overview

Reflection Analysis

Multipath Operation

Network Description

Intra-system Interference

Design with Passive Repeater

Map Grid Module

Radio and Antenna Data Files

Case Studies


Pathloss v.4.0 is Developed by


Pathloss Web Sites

Pathloss Forum (Questions and Answers about the planning with Pathloss v.4.0)

Regular Maintenance Updates

Radio and Antenna Description files for new products on the market

Documentation on new Pathloss v.4.0 features (e.g. on GIS formats) and appendix to the User Manual

Ordering Information and Part Number List


Introduction of Pathloss

The Pathloss program is a comprehensive path design tool for radio links operating in the frequency range from 30 MHz to 100 GHz.

The program is organized into eight path design modules, an area signal coverage module and a network module which integrates the radio paths.Coverage module and a network module which integrates the radio paths and area coverage analysis. Switching between modules is accomplished by selecting the module from the menu bar.


Cont… Introduction of Pathloss

Pathloss 4.0 (PL4B)Basic Pathloss program. Contains all of the necessary tools to carry out point to point radio system design.

Pathloss 4.0 (PL4C)As above, but with the additional power of a full featured radiocoverage prediction module.

Pathloss 4.0 (PL4I)Basic Pathloss program with complete Microwave network interference capabilities.

Pathloss 4.0 (PL4CI)Basic Pathloss program with both the coverage prediction and the Microwave interference modules.


Prerequisites

Following prerequisites imply successful participation in the Pathloss course:

Knowledge of basic principles of MW Transmission Engineering and Link planning Laptop/desktop computer with installation of Pathloss v.4.0 planning software : For your country or region of interest:• NED (SRTM 3”) Data http://srtm.usgs.gov/geodata/• Void Killer SW allows to correct raw STRM 3” with GTOPO 30”• Or any other DTM compatible with Pathloss v.4.0.


Cont…Introduction of Pathloss


Planning Concept

Planning modules contained in Pathloss:

Summary Module Terrain Data Generation Antenna Height Calculation Worksheet Module (Reliability Calculation) Diffraction Module Reflection Module Multipath Module Network Module (Frequency Planning) Map Grid Coverage Module (only for PtMP systems)

Pathloss v.4.0 is an advanced planning software for design of microwave radio-relay links and networks. It allows a qualified user to perform step by step analysis of all important propagation related phenomena, needed to generate a planning report containing all the data necessary for correct and reliable implementation of MW radio-relay hop.


Pathloss Basic Parameters

Adjusting the display options availableIn Configure Selection:

Antenna Configuration:

1. TR-Transmit/Receive Antenna2. Tx-Transmitting Antenna3. Rx-Receiving Antenna4. DR-Diversity Receiving Antenna5. TH- Transmitting/Hybrid Diversity


Coordinate Systems

• The user can choose most suitable local geodetic datum (e.g. in Nigeria it is Minna Nigeria), Singapore use South Asia datum and Ellipsoid is Modified Fischer 1960.For East Malaysia use Timbalai 1948 datum and Everest (Sabah Sarawak) Ellipsoid and Pakistan use WGS84 datum and WGS84 Ellipsoid.

Typical choice for world-wide datum is WGS 84 (World Geographic System 1984)

If special maps have to be handled, ellipsoid can be defined independently from datum (e.g. GRS80)

Note: WGS 84datum uses WGS84 ellipsoid.

Grid coordinate system can be chosen to define planar projection from geodetic

systems defined on ellipsoid

Most common: UTM-Universal Transverse Mercator.


Summary Module

Data entered into Summary Module, Option in Module-Summary


Radio Lookup Tables

Defining look-up table from Equipment option with Radio Code Index table andModule-Worksheet-Double click on Antenna-Lookup.


Radio Specifications

Radio parameters: This table is not editable Radio specification has defined via converting a radio data file. only few of the entries in the table are mandatory. Pathloss can use rough calculation of certain missing parameters likeRx-selectivity curve or T/I curves. There are minimum 5 parameters to define a radio .Option is on Module-Summary-Double click on Code-View.


Antenna Lookup Tables

Defining look-up table from Antenna Code Index table


Antenna Radiation Pattern

Co-polar and Cross-polar patterns


Active & Passive Antenna

Antenna types

Pasive Active


Polarization

Polarization

The electric and magnetic fields of electromagnetic wave are perpendicular to each other. Their intensities rise and fall together, reaching their maximums 90 degrees apart (Fig. 5-1). The direction of wave’s polarization is determined by electric field i.e. in a vertically polarized wave, the electric lines of force lie in a vertical direction and in a horizontally polarized wave, the electric lines of force lie in a horizontal direction. When a single-wire antenna is used to extract energy from a passing radio wave, maximum pickup will result when the antenna is oriented in the same direction as the electric field. Hence, a vertical antenna is used for the efficient reception of vertically polarized waves, and a horizontal antenna is used for the reception of horizontally polarized waves.


Antenna Beamwidth

Antenna beam width

In a radiation patter due to antenna directivity the points, in which power comparing to the maximum power is decreased by – 3 dB may be noticed. The angle between these points is called a beam width. In other words the beam width is an opening angle between the points where the radiated power is 3 dB lower than in the main direction


Graphical Representation of Antenna Beam width Beam width definition

GSM Cell PlanningFigure 5-2Page X

Main directionBeam width

3 dBAntenna lobe


Types of Antenna in MW

Antenna Gain Side lobe levels and front-to-back ratio Beam width Voltage Standing-wave Ratio (VSWR) Cross-polarization discrimination Mechanical stability

The most common type of antenna used on MW links is a parabolic dish. For higher frequency bands (15-38 GHz) parabolic dish can be substituted by microstrip patch-array antennae (flat antennae).

The antenna parameters are very important for the system performance.

The most important antenna parameters from propagation point of view are:


VSWR, Cross-polarization Discrimination

Voltage Standing-wave Ration (VSWR) is important parameter for high Speed communication systems with stringent linearity objectives. To avoid inter-modulation distortion, VSWR should be minimized by proper antenna selection and cable length adjustment. Standard antennae in MW bands have VSWR within a range of 1.06 – 1.15 typically.

Another important parameter for MW frequency planning is a discrimination between co-polar and cross-polar signal by the antenna. A good cross-polarization discrimination enables full utilization of the frequency band in both the vertical and horizontal polarization planes. Typical values are within range of 20–30 dB for standard antennae. Cross-polarization discrimination reaches its largest value in direction of the main lobe.


Beam-width & Radiation Pattern

… angle in horizontal or vertical plane

The half power beam width of antenna is defines as the angular width of the main beam at the –3 dB point, relative to the bore-sight. For parabolic antennae:

The half power beam width of antenna is defines as the angular width of the main beam at the –3 dB point, relative to the bore-sight. For parabolic antennae:

DdB

353

where D… diameter of antenna [m]

[degrees]

Side and back-lobe levels are importantparameters in frequency planning andinterference calculations. Low side lobesallow for more efficient use of the fre-quency spectrum. A front-to-back ratioindicates the levels for angles within aRange of 90-180 degrees.


Antenna Alignment

0dB

0 dB

A. Poor Alignment (One Antenna Peaked on a Side Lobe)

-10 to -20dB(First Side Lobe) High

Antenna

-1dB

B. Optimum Antenna Alignment (Best compromise between path and propagation)

0dB

Desired Path

-10dB

Low Antenna

Reflected Path

Attain free-space or optimum Received Signal Levels

Discriminate against ground reflections which cause fading and may reduce link Dispersive Fade Margins,

Accommodate, by size and/or up-tilt, K-factor angle-of-arrival variations which may cause antenna decoupling and severe fading.


Antenna Gain

Antenna gain evaluates antenna’s capability to focus electromagnetic energyto preferred direction (bore-sight). For parabolic antennae used on MW bands,gain can be expressed as :

2

4

SA [dBi]

Where S… aperture area … wavelength … aperture efficiency (0.55-0.70)

f

c c = 3x10 8


Exercise

Task: Calculate the theoretical gain and beam-width for the following types of parabolic antenna:

1. Antenna 1.2 m in diameter (0.75) for 15 GHz band 2. Antenna 0.3 m in diameter (0.7) for 38 GHz band 3. Antenna 0.6 m in diameter (0.7) for 38 GHz band 4. Antenna 3.0 m in diameter (0.8) for 7 GHz band

Hint: Figures in parenthesis indicate the aperture efficiency.


Typical antenna characteristics (standard, X-polar)


Antenna Mounting – Full Indoor & Split Systems

Split SystemFull Indoor System


Frequency Planning Rules

Radio signals have to be frequency-separated if neither antenna discrimination nor topographical shielding provides the necessary suppression of interfering signals.

The degree of separation depends on the transmitted bandwidth - the spectrum bandwidth in MHz. Raster: 1.75;3.5;7;14;28;56 MHz.

This separation – called adjacent-channel separation - should be as small as possible to give a frequency economic solution. This requires some kind of standardization, a frequency plan.

Certain basic rules should be followed setting up the frequency plan. All frequencies used in a radio-relay network should normally be selected from an established frequency plan, approved either by an international or national standardization body.


Frequency Planning

The objective of frequency planning is to assign frequencies to a network using as few frequencies as possible and in a manner such that the quality and availability of the radio link path is minimally affected by interference. The following aspects are the basic considerations involved in the assignment of radio frequencies.

Determining a frequency band that is suitable for the specific link (path length, site location, terrain topography and atmospheric effects)

Prevention of mutual interference such as interference among radio frequency channels in the actual path, interference to and from other radio paths, interference to and from satellite communication systems

Correct selection of a frequency band allows the required transmission capacity while efficiently utilizing the available radio frequency spectrum


Frequency Planning

Assignment of a radio frequency or radio frequency channel is the authorization given by an administration for a radio station to use a radio frequency or radio frequency channel under specified conditions. It is created in accordance with the Series-F recommendations given by the ITU-R.

Frequency Channel Arrangements

The available frequency band is subdivided into two halves, a lower (go) and an upper (return) duplex half. The duplex spacing is always sufficiently large so that the radio equipment can operate interference free under duplex operation. The width of each channel depends on the capacity of the radio link and the type of modulation used


Frequency Planning

The most important goal of frequency planning is to allocate available channels to the different links in the network without exceeding the quality and availability objectives of the individual links because of radio interference.

Frequency planning of a few paths can be carried out manually but, for larger networks, it is highly recommended to employ a software transmission design tool. One such vendor independent tool is Pathloss 4.0. This tool is probably one of the best tools for complex microwave design. It includes North American and ITU standards, different diversity schemes, diffraction and reflection (multipath) analysis, rain effects, interference analysis etc.


Frequency Planning for Different Network Topologies

Chain/cascade configuration is used for horizontal and vertical Polarization

LU Uf1 HP f1 VP f1 HP


Ring Configuration

If the ring consisted of an odd number of sites there would be a conflict of duplex halves and changing the frequency band would be a reliable alternative.

UU

L

UU

L

L

UUf1 HP

f1 VP

f1 VP f1 VP

f1 HP

f1 VP


Star Configuration

The link carrying the traffic out of the hub should use a frequency band other than the one employed inside the cluster.

L

UU UU

UU UU

UUf1 HP

f2 VP

f1 HP

f1 HP

f2 VP


Frequency Channel Tables

Frequency channels are chosen from predefined raster which follows ITU-R Recs. or local regulations,Polarization is defined independently.Option available in Summary- Equipment-TX - Channel-Lookup.


Map Study and Path Profile Preparation

Preliminary map studies help in determining the actual topography of the terrain, the height, and obstacles along the desired path.

Soon after, tentative antenna sites have been selected, and the relative elevations of the terrain between these sites has been determined, preparation of path profiles can begin.


Field Survey and Site Determination

Confirmation of LOS

Check-up of suspected reflection points, vegetation, water, buildings and other man-made obstacles

Determination of height of, and distance to critical obstacles

Determination and confirmation of the path profile

Determination of site co-ordinates and altitudes

Site survey


Purpose of Terrain Profiling

Location of the reflection zone (dish heights).Calculating dish discriminations to the reflection (dish sizes)Determining Fresnel clearance at the reflection (diversity, spacing).Calculating Path inclination angle. Calculating Reflection grazing angle (V- or H-pol assignment)Finding Ray height at the reflection or obstruction areaCalculating Reflected ray time delay (nsec). Choosing Optimum diversity dish separations to specular reflections.Calculating Arrival angle with K-factor variations.Calculating diffraction Obstruction loss vs. terrain type.


Generated Profile in Terrain Data Module

Representation of Terrain Data


Types of Digital Terrain Models (DTM)

Window for choosing source directory with GTOPO 30 DTM data Window for choosing type of DTM

(Digital Terrain Model) to be used for planning and LOS analysis.Option is in Configure-Terrain

Database.

Window with adjustable parameters for UTM DTM data. UTM zone used by the data file Index file describing the UTM data


UTM Database

Index File for UTM Data


SRTM Database

Importing BIL, HDR, BLW files from USGS DVD


Clutter Insertion

Clutter inserted in Terrain Data module, Double click on Structure option.


Propagation Losses

Obstacle Loss –also called Diffraction Loss or Diffraction Attenuation. One method of calculation is based on Knife edge approximation.

Having an obstacle free 60% of the Fresnel zone gives 0 dB loss.

0 dB20dB16dB6dB0 dB

First Fresnel Zone


Earth Radius Factor K - Values Variations


Radio Refractivity

K = Effective Earth’s Radius

6378 km

Ray day-to-night arrival angle change could approach 1o on long paths traversing humid areas

Sea LevelTrue Earth Radius (6378 km)

k = 0.33

k = 0.5

k = 1 (Dry, Elevated)

k = (follows Earth’s curvature)

k = -1

Subrefractive - Earth Bulge

Superrefractive - Ducting

“Earth’s Bulge”Obstruction

Duct Entrapment

8

Obstruction

k = 4/3rds Average Refractivity in Temperate Areas


Earth Curvature

h =2x6.378 K

d1 d2

The K factor in the above equation is a constant whose value depends upon the actual propagation conditions of the microwave energy along the path (gradient of refractive index).

Various values of the K are used to describe radio ray trajectories that differ from a straight line.

Where:

h represents Earth bulge height relative to he terminal stations [m]

d1 and d2 are distances from terminal stations [km]

Where:

h represents Earth bulge height relative to he terminal stations [m]

d1 and d2 are distances from terminal stations [km]

Parabolic transformation of Earth’s bulge:


Bending in the Atmosphere

Snell's law indicates that the rays bend towards the denser of the two media. In the atmosphere the index of refraction is varying continuously with gradient of dN/dh= – 40 ppm/km. Normal n=1.000320 Consequently no distinctive boundary will be found as in figure below.

Ray bending in the atmosphere may be considered as a large number of boundaries with a small variation n.


Bending cont.

During normal conditions, temperature, humidity and pressure in the lower atmosphere decrease almost linearly with increased altitude.

The above corresponds to a linear decrease in the refractive index of the atmosphere and the velocity of microwaves traveling through the atmosphere increases as the refractive index decreases

As the wave front passes through a normal atmosphere, the increased phase velocities at the top of the wave front cause microwave to bend slightly downward in relatively uniform curve.


Gradient of Refraction

1

1571

h

N

K

ii n

cv

251073.36.77

T

eH

T

pN

610).1( inN

h

N

is gradient of refractive index ni

expressed in N units (std. –40 N/km)

ni is atmospheric refractive index (standard value 1.000320 near sea level)

p is atmospheric pressure (std. value 1013 hPa)

T is atmospheric temperature (std. value 288 K)

e is saturation pressure due to the water vapor (10 hPa)

H is relative atmospheric humidity (std. value 50%)

c is velocity of light (299 798 km/s)

h represents height in kilometers


Refractive Ray Bending

G = 0, K = 1 (No refraction)

G = > 0, K = 2/3

G = - 157 K approaches infinity

Moderate Negative Gradient: Flat Earth

G < - 157, K < 0

DUCTING

G = - 79 , K =2

G = - 40 , K =4/3 ( Mean)STANDARD

EARTH

SUPERREFRACTIVE

SUBREFRACTIVE

G = - 314 K = -1

Steep Gradient: Possible Blackout

G = - 470 K = -0.5

Extreme Gradient: Blackout

G = 80 K = 2/3 Slightly Sub refractive

G = 157 K = ½ Moderately Sub refractive

G = 220 K = 5/12

Humidity Inversion: Extreme Earths Bulge: Diffraction Fade


Gradient of Refractive Index

Also the negative values are more extreme than the positive values,

NOTE: Positive gradient cause diffraction loss (substandard bending) or sub-refraction,

NOTE: When the gradient becomes more negative than dN/dh = -100 N Units/km (super-refractive) and leads to multipath fading,

When the gradient becomes more negative than dN/dh = - 157, ducting conditions occur resulting in severe mutipath fading, beam spreading and even blackout conditions,

ITU in recommendation P.453 provides a series of curves that give the percentage of time, dN/dh is less than – 100 N-unit/km. This gives the probability of multipath being a problem. It is the PL chart.


K-factor Fading

Density profiles in Subrefractive, Standard, and Superrefractive Atmospheric Boundary Layers (ABL)

Refractivity Terms

S

Top of LayerDenver: NS = 301 - (1.6km x 40 ppm/km) = 239

Standard Atmosphere

Density Lapse Rate

dN/dh = +157 N-units/km (k=1/2)+7

5 (k

=2/

3)h, km

dN/dh = -314 N-units/km (k=-1)-157 (k = )-100 (k = 3)

-58 (k = 1.6)

-40 (k = 4/3)

0 (

k =

1)

NS = 239N0 = 301 370 469 548

Inland CoastalMedian

N = Atmospheric density (refractive index)N0 = N at sea levelNs = N at ground surface level

Normal Propagation90-95%

(Wave refracted downwards)

N-units(Radio Refractive Index

at Sea Level)

Subrefractive1-5% of the time(Wave refracted

upwards)

SuperRefractiveTrapping0-1% (severeducting orblackout)

Super Refractive 1-5 % Ducting(Horizon extended)


Ducting and Blackout Fade

Ducting: The atmosphere has a very dense layer at the ground (or at certain height above) with a thin layer on the top of it. For such layer configuration, there will be almost total reflection present on this layer boundary.

Effect of ducting results in considerable higher signal levels then those calculated from standard propagation models.

Danger: Interference from remote sources!Difficult to predict quantitatively.


Super-refraction (black out)

Anomalous propagation occurs outside the normal range of K from 1 to infinity. This catastrophic phenomenon is known as Blackout fading.

K becomes negative

K = - 1/2

When an extreme drop in atmospheric density with height (a negative refractive index) occurs, or when the gradient is positive, climatic conditions are conducive to anomalous

propagation.


Concept of Clearance

Fresnel Zone Boundaries

+10 0 -10 -20 -30 -40

A

A

OBSTRUCTION ZONE(Obstructed path)

CLEARANCE OR

INTERFERENCE ZONE(Reflective path)

GRAZING

0.6 1 2 3 4 5

Site A 64km path, k=1 (on true earth’s radius profile) Site B

FRESNEL ZONE NUMBERS RSL, dB FROM FREE SPACE

Ray F1 = 56m DIAMETER

GRAZING PATH(6-20 dB LOSS)

0.6F1@k=1 PATH

Knife E

dge

Smooth Earth

AverageTerrain

0.6F1 PATHCLEARANCE

= FREE SPACE(NO LOSS)

CROSS-SECTION A-A

5 4 3 2 1 0.6

0

0.6 1 2 3 45


Choosing Clearance Criteria

Clearance criteria are chosen separately for Main and Diversity Antenna, Two values of K-factor are involved (K for normal conditions [median value

K=4/3] and minimum K [0.60-0.80]), Fixed provision for vegetation growth can be entered as well.Option available in Configure - Antenna height - Operation — Set Clearance Criteria.


Typical antenna characteristics (standard, X-polar)


Towers and Masts

Poles for rooftop installations Self-supported Lattice towers (20 – 150 m) Tube towers (10 – 40 m) Guyed Masts (10 – 100 m) up to 300 m for TV transmitters

Accessories: Leaders, Platforms, Mounting Brackets,Obstruction Lights, Aircraft Warning Lights

Soil bearing shall be measured during comprehensive site survey and test drilling shall be performed to determine optimum size of the tower base.


Microwave Installation – Ground Based Tower


Microwave Installation – Rooftop Structures


Shelters and Containers

Bricked technology houses – expensive but provides most suitable environment for technology

Shelters – cost-effective, less esthetic, requires air-conditioning Containers - for sites with limited technology requirements (e.g. remote BTS)

Chosen technology housing shall reflect the radio type, requirements for expansion and power back-up times.

Accessories: Heating and Air-conditioning Cable trays and inlets Burglary Alarm Mains Power Board Grounding system

Accessories: Heating and Air-conditioning Cable trays and inlets Burglary Alarm Mains Power Board Grounding system


Shelter for Full Indoor Equipment

Branching Connection

Pressure Windows

Waveguide Connector

Wall/Roof Feed-Thru or Plate/Boot

Grounding Kit

Dehydrator

Clamps

Waveguide

Cable / Waveguide Bridge

Grounding Bar


Outdoor Container for Split System

Standard Shelter BS Integration


Auxiliary Equipment

Dehydrator


Antenna Center-line Calculation

Option in Module – Antenna Height


Path Calculations

270

330

390

440

500

Ele

vati

on

, m

A

MS

L

300

360

410

470

270

330

390

440

500

300

360

410

470

k = 4/3F = 0.6

Site: Yates CenterLat.: 37-51-02.NLong.: 095-43-53. W

Marmaton37-49-40. N

095-09-44. W

____

__ __ __ __ ____

__ __ __ __ ____

__ __ __ __ ____

__ __ __ __ ____

__ __ __ __ ____

__ __ __ __ ____

__

0 5 10 15 20 25 30

Distance, km

k=4/3

0.6F1

1.9 GHz

k=4/3


Path Clearance Criteria

“HEAVY” ROUTEAbout 6 GHz and above in

moderate to heavy fade areas

“LIGHT” ROUTEAbout 2 GHz and below in all areas, and all paths in good to average fade areas

0.6 F1 @ K = 4/30.6 F1 @ K = 2/3 (Kmin)

andF1 @ K = 4/3

MAIN PATH(Top Dishes)

0.6 F1 @ K = 4/3+3m Close-In

For tree growth, etc.typically 10-12mbelow main dish

DIVERSITY PATH(Top-To-Bottom Dishes)

No Special AllowanceOver a 50m

Surface Ducting Layer,grazing @ K = 1/2

DUCTINGMain path clearance with known surface duct entrapment (paths 30 kilometers)

See the next page for minimum K (Kmin) concept.

0.3 F1 @ K = 4/3or grazing @ K = 4/3,

typically 10-20mbelow main dish


Survey Equipment

The Survey Report contains System Description Site Description and Layout Antenna and Tower Heights Path Profile Fresnel Zone Drawing and Diffraction Calculation Photographs of the site Panorama photographs

List of Survey Equipment: Maps in scale 1:50 000 or better Digital camera Binocular Compass Barometric altimeters (pair) Signaling mirrors, He-filled balloon Flash light Tape measure Hand-held radio or Cell phone Hand-held GPS receiver DGPS set (2 receivers) Theodolite with tripod Laptop with DTM and planning SW Spectrum analyzer with accessories Test antennae Test transmitter


Site Selection Considerations

System Related: Distance to the customer (BTS search ring) LOS to the existing and possible future neighbors Local climatic conditionsVegetation, clutter (buildings, chimneys) in the vicinity Currently installed technology in the vicinity

Construction Related: Site accessibility (distance to the roads) Available electric power source (PUC, Sunny Days) Soil bearing Underground water level

Other: Type of land ownership Security (guard needed) Military area considerations


Map Study

The purpose of the preliminary map study is to familiarize with the overall system layout and to assemble information including, but not limited to, the best available topographic mapping for the area under consideration, site addresses, site names or designations, site coordinates and elevations.

Establishing of site coordinates

Generation of Path profile

Identification of Reflective surfaces

Identification of Critical points


Digitized Maps


Generating Profile Report

Print Profile Report in Module option for LOS Verification


Microwave Worksheet

Net Pathloss Components

Free Space Loss and Absorption

Multipath Propagation Reliability Prediction Models

Vigants-Barnet Model

K.Q Factor

ITU-R P.530-6

ITU-R P.530-7

ITU-R P.530-9/10

Rain Attenuation Models

Crane Model

ITU-R P.530-7

Rain and Co-channel Operation

Section Performance Calculation

Loss / Attenuation Calculation.


Net Path Loss Components

Calculated net path loss components in Module option – Microwave worksheet


Loss / Attenuation Calculations

The loss/attenuation calculations are composed of three main contributions :

Propagation losses

(Due to Earth’s atmosphere and terrain).

Branching losses

(Comes from the hardware used to deliver the transmitter/receiver output to/from the antenna).

Miscellaneous (other) losses

(unpredictable and sporadic in character like fog, moving objects crossing the path, poor equipment installation and less than perfect antenna alignment etc).

This contribution is not calculated but is considered in the planning process as an additional loss.


Link Budget Calculation

Path-loss equation used for MW (3 - 38 GHz)Path-loss equation used for MW (3 - 38 GHz)

aDDfdBA log20log2045.92

Where f … RF frequency in GHz D… Propagation distance in km a … Attenuation due to the air and water vapor in dB/km (Typically 0.1 – 0.4)

MiscRxTxTLTxTLRxTot AGGAAAA

Where ATL… Transmission line losses and branching circuit losses on Rx and Tx side G … Antenna gain on Rx and Tx side AMisc … Miscellaneous losses (e.g. antenna misalignment, Tx power variations)


Fade Margin

–10-2 —----

–10-3 —----

–10-4 —----

–10-5 —----

–10-6 —----

–10-7 —----

–10-8 —----

–10-9 —----

–10-10 —----

–10-11 —----

–10-12 —5 10 15 20 25 30 35 40

C/N or C/I Ratio, dB

— - - - - — - - - - — - - - - — - - - - — - - - - — - - - - — - - - - —

BE

R

—----—----—----—----—----—----—----—

(OUTAGE)

BPSK

4PSK4QAMQPSK

9QPR

8PSK 16QAM 32QAM

49QPR 64QAM

225QPR 128QAM32PSK

256QAM

Excludes FEC Coding Gains

(STATIC)

512QAM25QPR

Fade Margin is a difference between median received signal level, calculated from Power Budget equation, and BER=10-3 threshold of the receiver system.This difference has to account for stochastic propagation phenomena, that can compromise system reliability.

These phenomena are: Attenuation due to rain. Intersystem interference. Multipath fading. K-factor variation. Ducting.


Fading and Fade Margins

Rain Fading

Rain attenuates the signal caused by the scattering and absorption of electromagnetic waves by rain drops.

It is significant for long paths (>10Km)

It starts increasing at about 10GHz and for frequencies above 15 GHz, rain fading is the dominant fading mechanism.

Rain outage increases dramatically with frequency and then with path length.

The specific attenuation of rain is dependent on many parameters such as the form and size of distribution of the raindrops, polarization, rain intensity and frequency.


Recommendation for Rain Fading

Microwave path lengths must be reduced in areas where rain outages are severe.

The available rainfall data is usually in the form of a statistical description of the amount of rain that falls at a given measurement point over a period of time. The total annual rainfall in an area has little relation to the rain attenuation for the area.

Hence a margin is included to compensate for the effects of rain at a given level of availability. Increased fade margin (margins as high as 45 to 60dB) is of some help in rainfall attenuation fading.


How Reducing the Effects of Rain

Multipath fading is at its minimum during periods of heavy rainfall with well aligned dishes, so entire path fade margin is available to combat the rain attenuation (wet-radome loss effects are minimum with shrouded antennas)

Route diversity with paths separated by more than about 8 Km can be used successfully.Radios with Automatic Transmitter Power Control have been used in some highly vulnerable links.Vertical polarization is far less susceptible to rainfall attenuation (40 to 60%) than are horizontal polarization frequencies.


Refraction – Diffraction Fading

Also known as K-type fading

For low k values, the Earth’s surface becomes curved and terrain irregularities, man-made structures and other objects may intercept the Fresnel Zone.

For high k values, the Earth’s surface gets close to a plane surface and better LOS (lower antenna height) is obtained.

The probability of refraction-diffraction fading is therefore indirectly connected to obstruction attenuation for a given value of Earth –radius factor.

Since the Earth-radius factor is not constant, the probability of refraction-diffraction fading is calculated based on cumulative distributions of the Earth-radius factor.


Ground Reflection

Reflection on the Earth’s surface may give rise to multipath propagation.

The direct ray at the receiver may interfered with by the ground-reflected ray and the reflection loss can be significant.

Since the refraction properties of the atmosphere are constantly changing the reflection loss varies.

The loss due to reflection on the ground is dependent on the total reflection coefficient of the ground and the phase shift.

The highest value of signal strength is obtained for a phase angle of 0o and the lowest value is for a phase angle of 180o.


Ground Reflection

The reflection coefficient is dependent on the frequency, grazing angle (angle between the ray beam and the horizontal plane), polarization and ground properties.

The grazing angle of radio-relay paths is very small – usually less than 1o

It is recommended to avoid ground reflection by shielding the path against the indirect ray.

The contribution resulting from reflection loss is not automatically included in the link budget. When reflection cannot be avoided, the fade margin may be adjusted by including this contribution as “additional loss” in the link budget.


Fade Margin vs Unavailability


Causes of Unavailability

Predictable rain outage in local-grade links above about 10-12 GHz, especially in tropical equatorial areas and costal regions,

Dual equipment failure within the MTTR period,

Maintenance error or manual intervention (e.g. failure of a locked-on module or path and error in switching the module),

Infrastructure failure (e.g. antenna, batteries),

Low fade margin in non-diversity links,

Power fade (long-term loss of fade margin) in lower clearance paths above about 6 GHz in some difficult areas, or with antenna misalignment,

Ducting (subrefractive, superrefractive) and black-out fading.


Multipath Propagation Reliability Prediction Models

Multipath fading algorithm embedded in Pathloss: Vigants-Barnet ITU-R P.530-6 Recs. ITU-R P.530-7 Rec. (Normally used) . ITU-R P.530-9 Recs. K.Q Factor. K.Q Factor with Terrain Roughness.

Results presentation: Total annual time bellow level SESR, Availability as per G.821 definition

(Bit Error Rate) SESR, Availability as per G.826 definition

(Block Error Rate)


Multipath Fading Mechanism

Unfortunately, normal atmospheric conditions do not always prevail.

Irregularities in the atmosphere cause energy components of a microwave beam to be reflected or refracted upwards or downwards instead of following normal slightly curved path to the receiving antenna.

As a result, two or more separate wave components may travel to the receiver over slightly different paths.

These components will be somewhat out of phase with each other because of the difference in the length of path each has traveled.

Also at each point of reflection approximately 180 degree phase shift normally occurs.

If two signal components travel paths are different by a wavelength, one signal component has been reflected, they will arrive 180 deg out of phase at the receiver and their vector sum will be zero.


Vector Sums

Signal envelope variations:

Constructive sum:Destructive sum:


Availability and Performance Recs

Performance Recommendations derived from ITU-T G.821: ITU-R F. 594 (Parameters and definitions) ITU-R F. 634 (Application to High Grade portion –below PRI rate) ITU-R F. 696 (Application to Medium Grade portion –below PRI rate) ITU-R F. 697 (Application to Local Grade portion –below PRI rate)Performance Recommendations derived from ITU-T G.826/828: ITU–R F.1092 Quality Rec. for the “International” Reference circuit - obsolete ITU–R F.1189 Quality Rec. for the “National” Reference circuit - obsolete ITU–R F.1397 Quality Rec. for the “International” Reference circuit – real hop. ITU–R F.1491 Quality Rec. for the “National” Reference circuit – real hop. ITU-R F. 1668 Quality Objectives for real digital fixed wireless linksAvailability Recommendations: ITU-R F.557 Availability Objective for Radio Relay Systems ITU-R F.695 Availability Objective for Real Radio Relay SystemsAvailability Recommendations derived from ITU-T G.827: ITU–R F. 1492 Application of G 827 to the “international” portion ITU–R F. 1493 Application of G 827 to the“national” portion ITU-R F.1703 Availability Objectives for real digital fixed wireless links

Performance Recommendations derived from ITU-T G.821: ITU-R F. 594 (Parameters and definitions) ITU-R F. 634 (Application to High Grade portion –below PRI rate) ITU-R F. 696 (Application to Medium Grade portion –below PRI rate) ITU-R F. 697 (Application to Local Grade portion –below PRI rate)Performance Recommendations derived from ITU-T G.826/828: ITU–R F.1092 Quality Rec. for the “International” Reference circuit - obsolete ITU–R F.1189 Quality Rec. for the “National” Reference circuit - obsolete ITU–R F.1397 Quality Rec. for the “International” Reference circuit – real hop. ITU–R F.1491 Quality Rec. for the “National” Reference circuit – real hop. ITU-R F. 1668 Quality Objectives for real digital fixed wireless linksAvailability Recommendations: ITU-R F.557 Availability Objective for Radio Relay Systems ITU-R F.695 Availability Objective for Real Radio Relay SystemsAvailability Recommendations derived from ITU-T G.827: ITU–R F. 1492 Application of G 827 to the “international” portion ITU–R F. 1493 Application of G 827 to the“national” portion ITU-R F.1703 Availability Objectives for real digital fixed wireless links


Vigants-Barnet Model

Where: x =a - climatic factor.f – frequency [GHz]d – path length [km]b – Roughness factorCFM- Composite Fade Margin

In Vigants-Barnet model the fading occurrence factor P0 is a function of the Path length and location, the terrain roughness and frequency band used.

S is the standard deviation (RMS) of the terrain elevations, measured with 1 km step along the path, excluding the radio sites. The value is limited within 6 m < S < 42 m.

3.12.15

Sb

1010.CFM

oPP

Annual outage probability:Annual outage probability:

3

0 5043.0

dfbxP


V-B Climatic Regions


Example Vigants – Barnett

PND = SESR = 6x10-7 c f D3 10-CFM/10

= 0.0001042

Where:PND - Non-diversity probability of outage (SESR)c - NA climate-terrain factor

c = 1 (from c map bellow), or x(S/15.2)-1.3

x - NA climate factor, 1 (from x map bellow)S - Terrain roughness, 15.2 m (from profile)f - frequency 6.7 GHzD - Path length, 40 kmCFM - Composite Fade Margin, 34 dB

For Terrain Roughness Module-Worksheet-Operation-Reliability – Select Vigants – Barnett or KQ Factor.


NA Climate Terrain Factor c

Caribbean, c = 4

Hawaii, c = 4

Alaska coast, c = 0.25Alaska interior, c = 1


NA Climate Factor x

*Flat terrain (w = 20', c =6) in this climate area.

Hawaii, x = 2

Alaska, x = 1 (inland)x=0.5 (coastal)

Caribbean, x = 2

southern Yukon, British Columbia,x = 0.5 Other Canadian Provinces, x = 1


K.Q Factor

PND = KŸQ f D3 10-CFM/10

= 0.0001042

Where (similar to NA path):

PND - Non-diversity probability of outage (SESR)KŸQ - ITU-R climate-terrain factorKŸQ = x(S)-1.3

x - Climate factor, 2.1x10-5 (see table in Pathloss manual-Worksheet)

S - Terrain roughness, 15.2 m (from profile)f - 6.7 GHzD - Path length, 40 kmCFM - Composite Fade Margin, 34 dB


ITU-R P.530-6

Where: K – a geo-climatic factor (Worksheet-Path profile-Geoclim)f – frequency [GHz]d – path length [km]Ep – path inclination [m rad]theta - average grazing angle corresponding to K=4/3 [mrad]h1, h2 – antenna heights above mean sea level [m]

d

hharctgE p 1000

1000 21

The ITU-R P.530-6 model is applicable from fmin = 15/d [GHz]. The fading occurrence factor P0 is a function of Geo-climatic factor K (i.e. path location), path length and inclination, grazing angle as well as frequency band used.

Worst month outage probability:Worst month outage probability:1010.

CFM

oPP

1.12.193.03.30 1

pEfdKP


ITU-R P.530-7

The ITU-R P.530-7 model is applicable from fmin = 15/d [GHz].The fading occurrence factor P0 is a function of Geo-climatic factor K (i.e. path location), path length and inclination, as well as frequency band used.

1010.CFM

oPP

Worst month outage probability:

Where: K – a geo-climatic factor from tables belowf – frequency [GHz]d – path length [km]Ep – path inclination [mrad]h1, h2 – antenna heights above mean sea level [m]

4.189.06.30 1

pEfdKP

d

hharctgE p 1000

1000 21


Geo-climatic Factor ITU-R P.530-7

PL is the percentage of time for which the average refractivity gradient in the lowest100 m of the atmosphere is lower than –100 N-units/km.

5.11.07 01010.5 LCCC PK LonLat 5.11.07 01010.5 L

CCC PK LonLat


Cont…Geo-climatic Factor


ITU-R P.530-9/10

For detailed link design using ITU-R P.530-9, fading occurrence factor P0:

Lhfpd

KP 00085.0032.097.02.3 10)|ε|1(

1000

Then the outage probability:Then the outage probability:

0log2.125 PAt Calculate a transition (deep to shallow fading distribution) depth:

[dB]

1010.tA

oPP

ITU-R P.530-9 terrain factor K:

1003.09.342.0 10 dNasK


ITU-R P.530-9 New Parameters

Where dN1 - the point refractivity gradient in the lowest 65 m of the atmosphere not exceeded for 1% of an average year,Sa - the area terrain roughness.

d1N is provided on a 1.5° grid in latitude and longitude in Recommendation ITU-R P.453. The correct value for the latitude and longitude at path centre should be obtained from the values for the four closest grid points by bilinear interpolation.

Sa is defined as the standard deviation of terrain heights (m) within a 110 km x 110 km area with a 30” resolution (e.g. the Globe GTOPO 30 data). The area should be aligned with the longitude, such that the two equal halves of the area are on each side of the longitude that goes through the path center.


Rain Attenuation Models


Crane Model

A B C D1 D2 D3 E F

0.1 6.5 6.8 7.2 11.0 15.0 22.0 35.0 5.5

0.05 8.0 9.5 11.0 16.0 22.0 31.0 52.0 8.0

0.01 15.0 19.0 28.0 37.0 49.0 63.0 98.0 23.0

0.005 19.0 26.0 41.0 50.0 64.0 81.0 117.0 34.0

0.001 28.0 54.0 80.0 90.0 102.0 127.0 164.0 66.0

CRANE NORTH AMERICAN RAIN REGIONCRANE NORTH AMERICAN RAIN REGION% of Time

Rain Rate

Exceeded

bc

eg

bc

eg

b

eaRA

cbDbcbdbbdbpp ..

.

.

1

b

eaRA

bDbpp .

1

d

eg cd.ln

17.03.2 pRg pRc ln03.0026.0 pRd ln6.08.3

for d <= D <= 22.5 km

for d > D

Where:Rp is rain rate (mm/hr) calculate by Crane table


Rain Rate Values

Drizzle = 0.25 mm/hour

Light rain = 1.0 mm/hour

Moderate rain = 4.0 mm/hour

Heavy rain = 16.0 mm/hour

Thunderstorm = 35.0 mm/hour

Intense thunderstorm = 100.0 mm/hour

Region B = Polar taiga (moderate)

Region C = Moderate maritime

Region D1 = Moderate continental (dry)

Region D2 = Moderate continental (mid)

Region D3 = Moderate continental (wet)

Region E = Sub-tropical (wet)

Region F = Sub-tropical (arid)


Cont…Crane Model

C (Alaska, Pacific Coast)

E (Hawaii)E (Caribbean)


Rain Attenuation ITU-R P.530-7

A0.01%=aR0.01%b D [1/(1 + D/d)] [dB]

Where: A0.01% - Rain attenuation exceeded <0.01% of the time, dB

R0.01% - Rain rate <0.01% of the time, mm/hr, from table

a - Multiplier, f (frequency/polarization), from table bellow

b - Exponent, f (frequency/polarization), from table bellow

D - Path length, km

d - Effective path length, km

d = 35 exp (-0.015R0.01%) Rain Outage:


Coefficients for Estimating Attenuation due to the Rain

h subscript stands for horizontal polarizationv subscript stands for vertical polarization


Rain Availability Example

A0.01% = aR0.01%b D [1/(1 + D/d)], dB

- Rain attenuation exceeded <0.01% of the time, dB

- Required path fade margin, dB

R0.01% - Rain rate exceeded <0.01% of the time (145 mm/hr, P region)

Pakistan in K-Region (42 mm/hr).

D - Path length, 5 km [mi x 1.6093]

a - Multiplier, f (18 GHz & V-polarization, from table: av= 0.058)

b - Exponent, f (18 GHz & V-polarization, from table: bv = 1.090)

d = 35 exp (-0.015R0.01%) = 3.98 km

A0.01% = 0.058 (145)1.09 5 [1/(1 + 5/3.98)]

= 29 dB (36 dB if horizontally-polarized, ah = 0.060 , bh = 1.127)


Ap = A0.01% 0.12 p-(0.546 + 0.043 log p)

where: Ap = Rain attenuation exceeded p% of the time, dB

A0.01% = Rain attenuation exceeded 0.01% of the time,dB

p = probability of outage, % = 100 - availability, %

For 99.995% availability, p = 0.005% (26 min/yr outage), same path

A0.005% = A0.01% 0.12 (0.005-(0.546 + 0.043 log 0.005) )

= A0.01% 0.12 (0.005-0.45) = A0.01% x 1.28

= 32 x 1.28 = 41 dB (51 dB if H-pol) required fade margin

Multiplier Table (replaces the above multiplier computation)

p = 1% 0.1% 0.05% 0.01% 0.005% 0.001%

Availability = 99% 99.9% 99.95% 99.99% 99.995% 99.999%

Multiplier = 0.12 0.39 0.52 1.00 1.28 2.14

For Required Availabilities other than 99.99%:

Probability Scaling Examples


Rain Rate in ITU-R Rain Regions

A B C D E F G H J K L M N P

0.1 2 3 5 8 6 8 12 10 20 12 15 22 35 65

0.03 5 6 9 13 12 15 20 18 28 23 33 40 65

0.01 8 12 15 19 22 28 30 32 35 42 60 63 95 145

0.003 14 21 26 29 41 54 45 55 45 70 105 95 140 200

0.001 22 32 42 42 70 78 65 83 55 100 150 120 180 250

ITU-R RAIN REGIONITU-R RAIN REGION% of Time

Rain Rate

Exceeded

If reliable local rain rate data are available, they shall be preferred to the world averaged data from ITU-R.

Pakistan in K - Region.By Worst Month Availability Pakistan in Region 3 and Class B


Classification of Countries by Worst Month


Excess Path Attenuation for Rainfall intensity exceeded

ITU-T rain regions (Table 1)

bdB aR

Where: ß dB is the unit excess path attenuation with respectto free-space loss exceeded for the percentage of time [dB/km]a, b are regression coefficients for given polarization ( Table 2)R is rain rate exceeded for specified percentage of time (Table 1)


Coefficients for estimating attenuation due to the rain

h subscript stands for horizontal polarizationv subscript stands for vertical polarization

(Table 2)


Rain Attenuation Curves

20

Frequency, GHz

H POL

V POL

Rain Rate (mm/hr)

Rain Rate (mm/hr)

200

150

100

5075

25

5

10

15

00 10 20 30 40

10

Att

enu

atio

n, d

B/k

m


ITU-R Rain Regions Maps


Map of Average Temperature

0F 0C-50 -46-40 -40-30 -34-20 -29-10 -23 0 -18 10 -12 20 -7

30 -1 40 4 50 10 60 16 70 21 80 27

50

6070

80

70

70

6050

4030

20100

-10

-20 -40 -50

-30

80 70

0F


7.5 GHz Case


Rain and Co-channel Operation

For co-channel operation, rain can also affect Cross-polar discrimination (XPD) and degrade XPD threshold. Severity of such degradation depends on system parameters like:

Antenna XPD and XPIF (Cross-polar Improvement Factor) of XPIC (Cross-polar Interference Canceller).

This option is available in Worksheet-Operation-Co-channel XPD


Table with Results – Full Report

Text Report with Reliability Calculation, Option in Module- Worksheet - report


Diversity Options

Frequency diversity: a single model available in Pathloss v.4.0,

Space Diversity: Baseband Switching,

- Method Nortel,

- Method Alcatel-Richardson,

- Method Harris Farinon

Space Diversity: IF Combining,

Methods are used to combine the improvement factors for flat and selective fading, respectively,

Angle diversity: Derived from SD under assumption of fixed antenna separation s= 9.1m. Improvement factor limited to I=20.

Option is available in Worksheet – Operation - Diversity Calculation


Frequency Diversity

10/10.

80 CMFfd f

f

dfI

Where:f : frequency separation [GHz]f : carrier frequency [GHz], CMF: composite fade margin [dB]. This equation applies only for the following ranges of parameters: 2 f 11 GH 30 d 70 km f / f 5% Boundary value shall be used if boundary limit is exceeded. Ifd is limited to 5.


Space Diversity

Baseband Switching:

IF Combining:

10223 10...102.1A

sd vsd

fI

20

][

10dBv

v

10

4

223 10.

1

.16..102.1

cA

sdv

vs

d

fI

2

1log.206.2

vAA tc

Where: s – Rx antenna separation [m] f – frequency [GHz] d – path length [km] vdB – difference between main and diversity antenna gains [dB] Ac – combined thermal fade margin [dB] At – greater of the main and diversity thermal fade margins [dB]


SD Calculation Example

Outage Time: TSD=TND/ISD

NA Calculation: ISD=7x10-5 f s2 10CFM/10/D= 42 (SD dish separation s = 30 ft / 9.1 meter)

Tnd = U(0.0001042) x SESR (8 x 10e6) x Avg. Temp= 834 SES /yr

TSD = 834/42 = 20 SES/yr ITU-R Calculation: ISD=1.2x10-3 f s2 10CFM/10/D

= 42 (s = 9.1 m), same as NA aboveTnd = U(0.000142) x SESR(2.59 x 10e6) = 270

TSD = 270/42 = 7 SES/any month

Space Diversity Improvement Factor:

Where: Frequency f= 6.7 GHz, Composite fade margin CFM=34 dB and distance D= 40 km.


Frequency Selective Fading

Selective fading or frequency selective fading is a radio propagation anomaly caused by partial cancellation of a radio signal by itself — the signal arrives at the receiver by two different paths and at least one of the paths is changing (lengthening or shortening). The two paths can both be from skyway or one be ground wave.

The Effect can be counteracted by applying some diversity scheme, for example OFDMA or by using two receivers with separate antennas spaced a quarter-wavelength apart, or a specially-designed diversity receivers with two antennas. Such a receiver continuously compares the signals arriving at the two antennas and presents the better signal.


Multipath , Upfade and Downfade

Multipath Fading is the dominant fading mechanism for frequencies lower than 10GHz. A reflected wave causes a multipath, i.e. when a reflected wave reaches the receiver as the direct wave that travels in a straight line from the transmitter

If the two signals reach in phase then the signal amplifies. this is called upfade.

Upfade max=10 log d – 0.03d (dB) : d is path length in Km

If the two waves reach the receiver out of phase they weaken the overall signal. A location where a signal is canceled out by multipath is called null or downfade.

As a thumb rule, multipath fading, for radio links having bandwidths less than 40MHz and path lengths less than 30Km is described as flat instead of frequency selective.


Flat Fading

A fade where all frequencies in the channel are equally affected. There is barely noticeable variation of the amplitude of the signal across the channel bandwidth .

Recommendation for Flat Fading are flat fade margin of a link can be improved by using larger antennas, a higher-power microwave transmitter, lower –loss feed line and splitting a longer path into two shorter hops.

On water paths at frequencies above 3 GHz, it is advantageous to choose vertical polarization.


Calculating Frequency Selective Fading

o

mB

NMo

mB

Msel

NMM

WWP

220

220 101015.2

0

2

43.0

msfPsel

4/3

1002.0exp1 oP

2/3

507.0

dm

BM, BNM – minimum and non-minimum phase signature depth [dB]WM, WNM - minimum and non-minimum phase signature width [GHz]d – path length [km]

In case the signature area sf is not available (more conservative result):

Probability of outage due to the selective fading (ITU-R Rep. 784-3):Probability of outage due to the selective fading (ITU-R Rep. 784-3):

Where fading activity factor: And typical echo delay:


Interference Fade Margin

For each interfering transmitter, the receive power level in dBm is compared to the maximum power level to determine whether the interference is acceptable.

Composite Fade Margin (CFM) is the fade margin applied to multipath fade outage equations for a digital microwave radio.

CFM = TFM + DFM + IFM + AIFM

CFM = -10 log (10-TFM/10 + 10 – DFM/10 + 10-IFM/10 + 10-AIFM/10 ).

Dispersive fade margin is provided by radio's manufacturer, and is determined by the type of modulation, effectiveness of any equalization in the receive path, and the multipath signal's time delay. Dispersive fade margin characterizes the radio's robustness to dispersive (spectrum-distortion) fades.


Cont…Interference Fade Margin

Where

TFM = Flat fade margin (the difference between the normal (unfaded) RSL and the BER=1 x10-3 digital signal loss-of frame point)

DFM = Dispersive fade margin (contribution to outage that accounts for in-band distortion that can at times cause a digital system to fail when the flat fade is less than that required to reach the thermal noise threshold ).

IFM = Interference fade margin .

AIFM =Adjacent-channel interference fade margin (contribution to system outage resulting from the broad transmit spectra of digital systems that have sufficient energy that spills over into adjacent channel digital receivers).


Dispersive Fade Margin

6(2) 12(4) 18(6) 24(8) 30(10) 36(12)

10

30

50

70 72 dB2n

sec

55 dB

50 dB = Minimum link DFM for no ES degradation due to dispersion

30 dB

25n

sec

6.3n

sec

(“R

um

mle

r’s

Mo

del

”)Required antenna

discrimination(A1+A2)

= Multipath Delay, nsec/feet (m)

Link DFM = Radio DFM + Antenna Discriminations to the Multipath Ray = 50 dB min. for Good Error Performance

Dis

pe

rsiv

e F

ad

e M

arg

in @

10

-3 B

ER

, d

B

Radio-only DFM

0 1010.DFS

osel PP

4.158log.106.17

sfDFS


Microwave Link Multipath Outage Models

A major concern for microwave system users is how often and for how long a system might be out of service. An outage in a digital microwave link occurs with a loss of Digital Signal frame sync for more than 10 sec. Digital signal frame loss typically occurs when the BER increases beyond 1 x 10-3.


Outage Availability and Unavailability

Outage (Unavailability) (%) = (SES / t) x 100

Where :

t = time period (expressed in seconds)

SES = severely errored second (Error not exceed 10-3 more then 0.2% of second in any month)

Availability is expressed as a percentage as : -

A = 100 - Outage (Unavailability).

A digital link is unavailable for service or performance prediction/verification after a ten consecutive BER> 1 x 10-3 SES outage period.


SD Effect on Selective Fading

The SD improvement factor, for the dispersive (frequency selective) component of the fade margin, is independent of the vertical antenna separation for values greater then 3m. As the antenna separation is reduced bellow 3m, the improvement factor decreases rapidly:

Combining Method Nortel:

Combining Method Alcatel-Richardson:

sD=8.5m

Where: ISD – SD improvement factor for flat fading (all previous formulae) P – probability of flat fading (also PND) FM – thermal + interference fade margin DFM – dispersive fade margin RD – correlation coefficient

2

1010 1010~

D

DFM

D

FM

SDtotal sR

sP

selSD

sel

SDSDtotal I

P

I

PP

_

10_ 1009.0

DFM

selSD d

fI


Variable Parameters

Parameters controlling space diversity: Diversity antenna diameter and gain Diversity antenna height (AGL) Loss of the transmission line and branching circuitry for diversity antennaOption available in Microwave Worksheet then double click on antenna.


Diffraction Algorithms Overview

Diffraction loss represents the deficiency, with respect to free space loss, in electromagnetic energy of the radio beam that was diffracted (bent) behind the obstacle entering the area around the line of interconnection (line of sight) between receiver and transmitter.

There are two limiting cases that can be easily handled mathematically: Knife-edge like obstacle Earth bulge (ellipsoid like) obstacle Practical case are somewhat “in between” the above two cases and have to be solved numerically:

Pathloss contains following numerical diffraction algorithms:Knife Edge, Isolated Obstacle, Longley and Rice, Pathloss (automatic selection of the calculation algorithm), NSMA, Average, Height Gain, Two ray optics, TIREM.


Diffraction

More complex diffraction algorithms use multiple knife-edges to better fit the shape of terrain and clutter: Bullington model Epstein Peterson model Deygout model Giovanelli model

More complex diffraction algorithms use multiple knife-edges to better fit the shape of terrain and clutter: Bullington model Epstein Peterson model Deygout model Giovanelli model

A wave-front reaching an obstacle, which is comparable in size to the wave-length, is bended around the obstacle in a phenomenon called diffraction. According to Huygen’s theory, each point of original wave-front is a source of elementary spherical wave, which all together form

a new wave-front behind the obstacle. This theory was later formulated mathematically by Fresnel, resulting in integral theory of diffraction. However analytical solution are available for simple cases only (knife-edge, ellipsoid, sphere).


Diffraction Losses Knife-edge Obstacle

Signal level can be obtained by solvingFresnel integral. Approximate solution:

Where:21

21 )(2

dd

ddhv


Bullington Model

Bullington’s model replaces two knife edges with a single equivalent edge to reduce the number of calculations.


Multiple Knife-Edges Methods

Model Epstein-Peterson, Deygout

This model is used in most planning tools, including Pathloss algorithms. It resembles reality closely enough, but has a limited accuracy. E.g. oval shaped hills are not well modeled by multiple knife edges. Deygout method is limited to two knife-edges.


Diffraction Loss Concept

Diffraction loss over “knife-edge like” obstacle, option available on Module - Diffraction - Average


Diffraction Parameters

Diffraction loss can also be calculated as a function of frequency, K-factor and

antenna height.

All parameters used in these variable calculations are local, except polarization. Option is available in Module-Reflection-

Variables.


Refractive Ray Bending

K = 1 (No refraction)

K = 2/3

K approaches infinity

Moderate Negative Gradient: Flat Earth

K < 0

DUCTING

K =2

K =4/3 ( Mean)STANDARD

EARTH

SUPERREFRACTIVE

SUBREFRACTIVE

K = -1

Steep Gradient: Possible Blackout

K = -0.5

Extreme Gradient: Blackout

K = 2/3 Slightly Sub refractive

K = ½ Moderately Sub refractive

K = 5/12

Humidity Inversion: Extreme Earths Bulge: Diffraction Fade


Antenna Height Variation

Choosing antenna heights – 4 degrees of freedom. Option is available in Module-Reflection


K –variation in Pathloss

Option available in Module-Reflection-Variable-Earth Radius Factor


Two Ray Optics

Reflection analysis is based on two-ray optics and is limited to a single specular reflection. The received signal is a vector addition of the direct signal and the reflected signal. The amplitude of the reflected signal depends on:

Theoretical reflection coefficient Terrain roughness ray divergence ground cover over reflection surface antenna discrimination additional loss due to the lack of clearanceReceived signal amplitude:

Where: R – reflection coefficient amplitude (R=0 to R= -0.1)l - wavelength [m]Δr – difference in path-length between the direct and reflected signal path [m]

φv,h – phase shift which occurs on reflection (close to 180 deg.), polarization dependant

hv

rRRA ,

2 2cos21log10


Dispersion Analysis

During dispersion analysis, Pathloss user can calculate: Location of the reflection point on the path, Delay of the reflected ray relative to direct ray, Reflection loss relative to the FSL of a direct ray.Option available Module-Reflection-Dispersion


Modifying Reflection Parameters

Terrain roughness with reduce theoretical reflection coefficient. The higher the roughness, the lower the magnitude of reflection coefficient,Any ground cover will contribute by additional loss to the specular reflection

(water, desert: 0-1 dB; fields with grass: 1-3 dB; sage brush and high grass: 3-6 dB; trees and forests: 8-15 dB), Antenna discrimination (which depends on the main-lobe beamwidth) helps to discriminate the reflected signal. Ray divergence takes into account the scattering effects cause by Earth curvature.Option available Module-Reflection-Modify-Parameters.


Constant Gradient Trace

Rays are straight.

Constant gradient ray trace used to determine reflective characteristics. Angle between rays determined by program. Option is available in Module-Multipath


Variable Gradient Trace

Rays are curved.Atmospheric Duct

Variable gradient ray trace used to determine ducting & atmospheric anomalies. Angle between rays determined by program. Option is available in Module-Multipath


Network Overview

Option available in Module-Network


Network Background

Background is generated from the DTM installed, option available Module-Network-Site Data-Show background


Site List

Can be printed out as a special report, option available Module-Network-Site Data-Site List


Link List

Review of the incorporated xxx.pl4, option available Module-Network-Site Data-Site List


Importing Sites into Pathloss

Sites can be imported into site list: by importing xxx.pl4 files by importing xxx.txt file by importing xxx.csv file transformed into text file by importing Mapinfo xxx.mif files

Links can be imported into site list: by importing xxx.txt file by importing xxx.csv file transformed into text file by importing Mapinfo xxx.mif files

Pathloss v.4.0 exports into xxx.csv filewhich can be converted into MS Excel xxx.xls file.

Option available in Module-Map grid-Site data- Site List-Import-Site Text File & Link file


Interference Calculation Procedure

Interference analysis calculates threshold degradations of all the receivers in a specified network, using

frequency plan defined by the Pathloss user,

Digital Interference Objective is maximum allowable Rx threshold degradation, Coordination Distance specifies the

maximum length of interfering path, Maximum Frequency Separation excludes all the interferers that fall outside of it, Default Minimum Interference Level is

used if T/I data are not available for the Radio in its radio data file,

Calculation Margin sets the limit for reported interference cases.

Option in Module-Network-Interference-Calc Intra


Interference Reports

Shows threshold degradation for each interferer-victim pair. Option is on Module-Network-Interference-Reports.


Repeated Analysis Method

Error log indicating missing data in hop description file xxxx.pl4, which prevented a successful calculation of Rx threshold degradation during interference analysis. Option is on Module-Network-Interference-View Error Log.

A Transmission Planner repeatedly uses interference analysis to calculate threshold degradations, and manually modifies the frequency plan to ensure, the threshold degradations fall bellow tolerable level (1 dB intrasystem, 3 dB intersystem).


Cross-reference Report

Highlighted case show the threshold degradation exceeding preset tolerable value. Option is on Module-Network-Interference-Reports.


Passive Repeaters

WHY TO USE THEM:• When a microwave hop is required in a place which has some

unavoidable physical obstacles.

• Where a mountain peak has to be surmounted which may be so inaccessible that power cannot be provided for a usual active repeater.


Configuration of Passive Link

View from reflector site

View from terminal site


Double Plane Repeater

Bird-view


Plane Reflector Passive Repeater

Option is available in Module-Worksheet-Operations-Create Passive Repeater


Passive Repeater Data Plane Reflector

Option is available in Module-Worksheet-Report- Passive


Back-to-back Antenna Passive Repeater

Option is available in Module-Worksheet-Operations-Create Passive Repeater


Passive Repeater Data Back-to-back

Option is available in Module-Worksheet-Report- Passive


Network Snapshot

Possibility of backdrop file insertion, option in module-network


Backdrop Image in Pathloss v.4.0

Option is available in Module-Map grid-Site Data- Backdrop


Elevation View

Option is available in Module-Map grid-Site Data- Elevation View


Backdrop Configuration

Directory and Index File has to be configured for:

1. Backdrop Image2. Terrain Elevation Data3. Clutter Height Data

Backdrop Image must be in .TIF format

Datum or Ellipsoid as wellAs UTM Zone must correspondto that of the GIS source

Option is available in Module-Map grid-Site Data- Backdrop


Microwave Wave Radio File Definition

Files for well known radio manufacturers are available on Pathloss CD-ROM, in Equipment/mrs directory.


Microwave Wave Antenna File Definition

Files for well known antenna manufacturers are available on Pathloss CD-ROM, in Equipment /mas directory.


Step by Step Procedure on MW RR Hop Design

1. Perform sites selection (map study, finding of coordinates)2. Choose transmission capacity and HW protection (as per customer, # of

BTS, etc.)3. Choose frequency band (based on distance and TRM capacity)4. Generate profile (DTM, map, determine HASL)5. Suggest preliminary antenna heights (use clearance criteria)6. Perform site survey, path survey (verify HASL, find CP, clutter)7. LOS OK/not OK! (for realistic minimum antenna height)8. Perform diffraction analysis (if needed in exceptional cases)9. Perform reflection analysis (if needed for specular reflections)10. SD for reflection mitigation needed/not needed??11. Determine precise minimum main (and SD) antenna heights12. Determine radio and feeder type


Step by Step Procedure on MW RR Hop Design (cont.)

• Determine preliminary Tx power and Antenna Size/Type (based on frequency band, TRM capacity and distance of the hop)

• Apply SD if needed of FD/HD if applicable (2nd run)• Check clearance criteria for SD antenna (2nd run)• Calculate the link budget and fade margin• Calculate the percentages of outage due to the rain and multipath fading

(SES, ES, BBER, UAT)• Compare with performance allocations from the ITU standard (Rule of

thumb, scalable G.821 – green table)• Complies with standard? (If not, change antenna and/or Tx power, add SD

and repeat 13-19)• Perform End-to-end performance calculation for the complete link (standard

G. 826)• Complies with standard? (If not, change antenna and/or Tx power, add SD

and repeat 13-21)


Step by Step Procedure on MW RR Hop Design (cont.2)

1. Allocate a frequency channel and choose polarization2. Decide upon co-channel operation (if needed)3. Decide upon ATPC range4. Perform intra-system interference analysis5. Threshold degradations less then 3 dB? (If not, repeat 22-26 with different

frequency channel and/or polarization)6. Print the performance calculation report and profile7. Allocate [IP] address for network management (if applicable)8. END

Note: The above is a generic procedure. Some steps can be cancelled in particular cases. For example, designing 30 hops in 23, 26 GHz band in the city, that

are just 1-2 km long, doesn’t require comprehensive performance analysis, since there will be no fading. Designing just one MW hop in the middle of a desert, obviously doesn’t require intra-system interference analysis.


Process Flowchart: MW Link Design

Receive Customer Input• RPF• Budgetary Quote

Review Input• Understand• Clarify• Recommend

Obtain Min. Information•Protection Scheme•Coordinates or Path Length•Capacity

Min.InformationObtained?

Perform Preliminary Analysis and Design• Path Calculations• Routing• Equipment Determination• System Layout

ProfilesAvailable

?

Perform Field Survey• Verify Sites• Path Clearance• Antenna Centerlines• Mounting Conditions • Storage Capability

NO YESNO

AYES


Cont…Process Flowchart

B

MeetClearance

Criteria?

MeetSES/any month

Objective?

Modify Design• Wave guide Type• Dish Size• Tx Output Power• Diversity Scheme

Modify Design• Change Centerline

Begin Frequency Interference Study• Intra-System• Inter-System

YES

YES

YES

NO

NOA


Cont…Process Flowchart

Begin Frequency Interface Study• Intra-System• Inter-System

Frequency PairsAssigned?

Determine Pairs• ITU-T Channel Plans• Minimum T/R Spacing

Perform FrequencyInterference Study• T/I Curves• Antenna Type/Size and patterns• Tx Output Power• Polarization• Radio Capacities• Coordinates (or Azmuth’s and Distance)

NO

YES

B HL-LowViolations

?

NO

YES Modify Design• Move Frequency pairs

Intra-System Interference

Modify Design• Move Frequency pairs• Obtain Additional Pairs• Change Polarization• Upgrade Antennas

DONE

NO

YES


Difficult Areas for Microwave Links

In areas with lots of rain, use the lowest frequency band allowed for the project.

Microwave hops over or in the vicinity of the large water surfaces and flat land areas can cause severe multipath fading. Reflections may be avoided by selecting sites that are shielded from the reflected rays.

Hot and humid coastal areas.


Troubleshooting Procedure

Isolate the problem to the specific link with BER test, internal network management system reports, etc.

Isolate modules by switching off-line (substitution) by local or remote command.

Is the ES impairment two-way?

Does it correlate with nighttime power fade activity?

If the ES events are daytime occurrences with no fade activity, do open door alarms or other reports suggest “manual intervention”?

Are the ES events seen in both diversity receivers? Simultaneously?

If so, does a far-end transmit chain switch correct the problem?

If not, does it follow an antenna feeder system (Receiver, Demodulator, Decoder, Multiplexer)?

Are the ES Continuous or Random, Recurring or Periodic?

Are there events like Unavailability (>10 CSES), Outage (SES), Burst ES, Dribbling ES (excessive RBER)? What is their statistical distribution?


Important Recommendations

Use higher frequency bands for shorter hops and lower frequency bands for longer hops.

Avoid lower frequency bands in urban areas.

Use star and hub configurations for smaller networks and ring configuration for larger networks.

In areas with heavy precipitation , if possible, use frequency bands below 10 GHz.

Use protected systems (1+1) for all important and/or high-capacity links.

Leave enough spare capacity for future expansion of the system.



Space diversity is a very expensive way of improving the performance of the microwave link and it should be used carefully and as a last resort.

The activities of microwave path planning and frequency planning preferably should be performed in parallel with line of sight activities and other network design activities for best efficiency.

Use updated maps that are not more than a year old. The terrain itself can change drastically in a very short time period. Make sure everyone on the project is using the same maps, datums and coordinate systems.



Perform detailed path surveys on ALL microwave hops. Maps are used only for initial planning, as a first approximation.

Below 10 GHz , multipath outage increases rapidly with path length. It also increases with frequency , climatic factors and average annual temperature. Multipath effect can be reduced with higher fade margin. If the path has excessive path outage the performance can be improved by using one of the diversity methods.


Channel Table 1 (1.4 – 6 GHz)


Channel Table 2 (7-13 GHz)


Case Studies

Design of MW 16E1 PDH Hop in 15 GHz

Diffraction Loss on PDH hop in 8 GHz

Reflection Analysis for Over-water 6 GHz hop

Rain Attenuation for PDH 8E1 hop in 18 GHz

MW PDH Link from BTS to BSC

Design of a MW SDH Transmission Link 4+0

Interference Analysis in Multan City, Pakistan

Backdrop Image of Sana’a, Yemen


Where to find the Case Studies?

Go to the files copied from the CD-ROM you have received from the trainer:

Beside the individual Case Studies, there are some other radio and antenna definition files in this directory.


Acronyms 1

1+1 -Single line protection switching (FD, HS, etc.)1:N, 2:N -Multiline protection switching (N = no. of bearer channels)

ABL -Atmospheric Boundary LayerACO -Alarm CutoffACU -Antenna Coupling UnitA/D -Analog-to-Digital (conversion)ADM -Add/Drop MultiplexerADPCM -Adaptive Differential PCMADSL -Asymmetric Digital Subscriber LineAGC -Automatic Gain ControlAIS -Alarm Indication Signal (“All Ones” at DS1, “Blue” at DS3) AMI -Alternate Mark Inversion (DS1)AMPS -Advanced Mobile Phone System (FDMA -Analog Cellular) ANSI -American National Standards InstituteAPS -Automatic Protection SwitchingASAE/AFDE -Adaptive [Frequency Domain] Slope Amplitude EqualizerASCII -American Standard Code for Information Interchange ATDE -Adaptive Time Domain (transversal) EqualizerATM -Asynchronous Transfer ModeATPC -Automatic Transmitter Power Control (also APC)AU -Administration Unit (SDH)AZD -Ambiguity Zone (error) Detection (QPR Radios)

B3ZS -Bipolar with 3-Zero Substitution (DS3) B6ZS -Bipolar with 6-Zero Substitution (DS2) B8ZS -Bipolar with 8-Zero Substitution (DS1) BBER -Background Block Error Rate (EB/time period) BER -Bit Error Ratio or Rate (Errors/time period) BERTS -BER Test Set (being replaced with internal NMS) BISDN -Broadband ISDNBITS -Building Integrated Timing SupplyBLSR -Bi-directional Line-Switched RingBPV -Bipolar ViolationBWA -Broadband Wireless Access

CAD/CAM -Computer Aided Design/ManufacturingCB - Channel Bank (1st order mux)CBR - Constant Bit Rate (ATM)CCC -Clear Channel CapabilityCCDP -Co-Channel Dual Polarized linkCCIR -International Radio Consultative Committee (now ITU-R)CCITT -International Telephone and Telegraph

Consultative Committee (now ITU-T)CDMA -Code Division Multiple Access (spread spectrum)CDPD -Cellular Digital Packet DataCDV -Cell Delay Variation (ATM)CEPT -Conference of European Postal and

Telecommunications administrationsCFM -Composite Fade MarginCGA -Carrier Group AlarmCIR -Carrier-to-Interference Ratio (also C/I Ratio) CIT -Craft Interface TerminalCLR -Cell Loss Ratio (ATM)CMI -Coded Mark Inversion (E4)CMISE -Common Management Information Service ElementCNR -Carrier-to-Noise Ratio (also C/N Ratio)CO -Central OfficeCODEC -Coder/DecoderCPE -Customer Premises EquipmentCRC -Cyclic Redundancy Check (on ESF T1 trunks)CSMA/CD -Carrier Sense Multiple Access with Collision DetectionCSU/DSU -Channel Service Unit/Data Service UnitCV -Coding Violation

DACS -Digital Access Crossconnect System (© LucentTechnologies ). See DCS.

DADE -Diversity Antenna Differential Equalization orDifferential Absolute Delay Equalization

DCC -Digital Communications Channel (e.g., SONET OAM&P)


Acronyms 2

FM -Frequency ModulationFM-FDM -FM radio with FDM multiplex (also FDMA)FSK -Frequency Shift KeyingFTTC -Fiber To The CurbFTTH -Fiber To The HomeFWL -Fixed Wireless Local Loop (also WLL)FXO, FXS -Foreign eXchange unit at CO, subscriber (VF)

Gbit/s -Gigabits per second (also Gb/s, Gbps)GHz -Gigahertz(109 Hz)GPS -Global Positioning Satellite systemGUI -Graphical User Interface

HD -Hybrid DiversityHDB3 -High Density Bipolar order 3 (E1-E3)HFC -Hybrid Fiber/Coax cable (see FTTH and FTTC)HDSL -High bit-rate Digital Subscriber LineHNM -Harris Network Management SystemHP - High Performance (e.g., shrouded antenna)HS - Monitored Hot Standby (also MHSB)HSSI - High Speed Serial Interface

IEC - International Electrotechnology CommissionIF - Intermediate FrequencyIFM -Interference Fade MarginIP - Internet ProtocolISDN - Integrated Services Digital NetworkISI - Intersymbol InterferenceISO - International Standards OrganizationITU-R - International Telecommunication Union-

Radiocommunications SectorITU-T - International Telecommunication Union-

Telecommunication Standardization Sector

kbit/s -kilobits per second (also kb/s, kbps)kHz -kilohertz (103 Hz)

DCE -Data Circuit-Termination EquipmentDCS -Digital Access Crossconnect System (also DXC, TCS,

DACCS, DACS - Lucent)DLC -Digital Local Loop Carrier (fiber) DFM -Dispersive Fade MarginDRRS -Digital Radio-Relay SystemDS0, 1,2,3 -North American Digital Signals levels 0, 1, 2, 3DSP -Digital Signal ProcessingDS -Direct Sequence (spread spectrum - CDMA) DSX -Digital Cross-Connect panel (-1, -3 for DS1, DS3) DTE -Data Terminating Equipment

E1, E2, E3, E4 -CEPT Digital Trunks or SignalsEB -Errored Block (Sonet and SDH) %EFS -%Error-free seconds (over a measurement period) ESR -Errored Second Ratio (ES/time period)EIRP -ERP ref. to an Isotropic Antenna (= ERP+2.2 dB)EIA -Electronic Industries Association (ass’n w/TIA) EMC -Electromagnetic CompatibilityEMI -Electromagnetic InterferenceEPROM -Erasable Programmable Read-Only MemoryEPO -Error Performance ObjectiveERP -Effective Radiated Power ref. to a Dipole AntennaES -Errored SecondESF -Extended Super FrameESR -Errored Second Ratio (ES/Time Period) ETSI -European Telecommunication Standards

Institute (ANSI equivalent)

FD -Frequency DiversityFDDI -Fiber Distributed Data InterfaceFDM -Frequency Division MultiplexFDMA -Frequency Division Multiple Access (also FM-FDM)FEC -Forward Error CorrectionFH -Frequency Hopping (spread spectrum)FITS -Failures In Time (109 hours)


Acronyms 3

LAN -Local Area NetworkLED -Light Emitting DiodeLNC -Low Noise ConverterLOS -Loss Of Signal, Line Of SightLOF -Loss Of Frame synchronizationLOP -Loss Of Pointer (SONET)LSB -Least Significant Bit

MAN -Metropolitan Area NetworkMbit/s -Megabits per second (also Mb/s, Mbps)MHz -Megahertz (106 Hz)micron -10-6 meter (= 1000 nm - lightwave)MIS -Management Information SystemMODEM -MODulator/DEModulatorMPEG -Motion Picture Experts Groupmrad -milliradian (also mr)msec -millisecond (also ms)MTBF -Mean Time Between FailureMTBMA -Mean Time Between Maintenance ActivitiesMTBO -Mean Time Between OutageMTR -Mean Time to Restore (after failure)MTSO -Mobile Telephone Switching Office (also MSO,

MTX, MSC)MTTR -Mean Time To Repair (at the site)MUX -Multiplexer

ND -Non-DiversityNE -Near-End or transport Network ElementNode -SONET/SDH line terminating devicenm -nanometer (10-9 meter), lightwaveNMS -Network Management SystemNNI -Network Node InterfaceNP -Non-ProtectedNPL -Net Path LossNRZ -Non-Return to Zeronsec -nanosecond (10-9 sec) - also ns

OAM&P -Operations, Administration, Maintenance, and Provisioning functions (usually SONET/SDH)

OC-1,-3 -Optical Carrier Level 1, 3 Signal (51, 155 Mbit/s)OC-3c -OC-3 Concatenated Signal for Broadband/ATMOCUDP -Office Channel Unit Data PortOOF -Out Of FrameOPX -Off-Premises eXtensions (VF)OQPSK -Offset QPSKOSI -Open Systems Interconnection

PA -Power AmplifierPAD -Packet Assembler/DisassemblerPBX -Private Branch eXchange (also PABX)PCM -Pulse Code ModulationPCR -Peak Cell Rate (ATM), Paperless Chart RecorderPCS -Personal Communications Services (also PCN)PDH -Plesiochronous Digital HierarchyPLL -Phased-Locked LoopP-MP -Point-to-Multipoint access radioPN -Psuedo-Noise sequence code (spread spectrum/CDMA)P-P -Point-to-Point radio-relay linkPOH -Path Overhead (SONET/SDH)POTS -Plain Old Telephone ServicePSTN -Public Switched Telephone NetworkPTE -Path Terminating Equipment (SONET)PVC -Permanent Virtual Circuit/Connection (ATM)

QAM -Quadrature Amplitude ModulationQD -Quadruple DiversityQoS -Quality of Service (ATM)QPRS -Quadrature Partial Response Signaling (also QPR)QPSK -Quadrature Phase Shift Keying


Acronyms 4

RBER -Residual (dribbling) BERRing -Circular configuration of nodes RF -Radio FrequencyRR-STM -STM-0 (51 Mbit/s) for Radio Relay. Also sub-STM-1RRRP -Radio-Relay Reference Point (SDH)RSL -Receive Signal LevelRSVP -Resource reSerVation Protocol (ATM)RTU -Remote Terminal UnitRZ -Return to Zero

SCADA -Supervisory Control and Data AcquisitionSCU -Service Channel UnitSDH -Synchronous Digital Hierarchy (ETSI standard))SD -Space DiversitySEP -Severely Errored Period (G.828). See CSESSEPI -SEP IntensitySES -Severely-Errored SecondSESR -Severely-Errored Second Ratio (SES/time period)SF -Super Frame (format for DS1 signal)SMDS -Switched Multi-megabit Data ServiceSNA -Systems Network ArchitectureSNMP -Simple Network Management ProtocolSOH -Section Overhead (SONET/SDH)SONET -Synchronous Optical NETwork (ANSI standard)SPE -Synchronous Payload Envelope (SONET)SPU -Signal Processing UnitST -Split Transmitters (to separate antennas)STE -Section Terminating Equipment (SONET)STM-n -Synchronous Transport Module (SDH transport)STS-n -Synchronous Transport Signal (SONET transport)STS-3c -STS-3 Concatenated Signal (for Broadband/ATM)SVC -Switched Virtual Circuit (ATM)

T1,T3 -North American digital trunks or facilitiesT1M1 & T1X1 -ANSI telecommunications standards committees

TABS -Telemetry Asynchronous Byte Serial (Protocol) TBOS-Telemetry Byte-Oriented Serial (Protocol)

TCM -Trellis Code ModulationTDMA -Time Division Multiple AccessTFM -Thermal (flat) Fade Margin (also FFM)TIA -Telecommunications Industries Association

(ass’n w/EIA)TL1 -Transaction Language 1TMN -Telecommunication Management NetworkTSA -Time Slot AssignmentTSI -Time Slot InterchangeTU -Tributary Unit (SDH)TUG -Tributary Unit Group (SDH)

UAS -UnAvailable (failed) Seconds (also NAS)UBR -Unspecified Bit Rate (ATM)UNI -User-to-Network InterfaceUPSR -Unidirectional Path-Switched Ring

VBR -Variable Bit Rate (ATM)VC -Virtual Container (SDH)VCI -Virtual Channel Indicator (ATM)VDSL -Very high speed Digital Subscriber LineVF -Voice FrequencyVP -Virtual Path (ATM)VSAT -Very Small Aperture Terminal (satellite)VT -Virtual Tributary (SONET)VTG -Virtual Tributary Group (SONET)

WAN -Wide Area NetworkWLL -Wireless Local Loop (also FWL)www -World Wide Web

XPD -Cross-Pol antenna DiscriminationXPIC -Cross-Pol Interference Canceller for CCDP linksXPU -Expansion Unit

MW Links Planning With Pathloss IV

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Transcript of MW Links Planning With Pathloss IV