Distributed Power Control Mechanisms for HSDPA Femtocells Report

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Wireless Mobile Communication Lab

Study of Research Paper:

Distributed Power Control Mechanisms for HSDPA Femtocells

By:

Usman M. Nooruddin

Roll Number: 07-0039

Section A

Department of Electrical Engineering

National University of Computers & Emerging Sciences

FASTKarachi Campus


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Table of Contents:

1. Introduction 3

2. Background 3

3. Description of technical words 4

4. Summary

Fixed Transmit Power for Femtocells Calibration Techniques Adaptive Transmit Power Control

45

5

5

5. Conclusion 6

6. List of References 6


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Introduction:

This research paper investigates power control algorithms for femtocells that can be

performed locally with minimal network intervention.

In the Calibration Techniques, the transmitted power in the femtocell is adjusted so they donot change their transmitting power frequently. In Adaptive Power Control Scheme, the

transmitted power of the femtocells is adjusted as to achieve the minimal target data rates.

Background:

Operators, due to decreasing number of Average Revenue per User (ARPU), are now

introducing more bundled home services such as voice, data and television as triple play and

mobile access which adds another dimension to this scenario. But since the spectrum is

scarce, the technologies of 3G and above have to operate at 2 GHz and higher, which causes

spotty mobile coverage indoors because of the phenomenon of increased signal deterioration

/degradation at higher frequencies.

One of the solutions to this problem is using Femtocells. In combination with a macrocell

network, femtocells can significantly reduce the network costs.

Figure 1: Femtocell Deployment

Femtocells are low-power wireless access points that operate in licensed spectrum to connect

standard mobile devices to a mobile operators network using residential DSL or cablebroadband connections.

Femtocells deliver significantly improved coverage inside homes, small and large offices,

and outdoor public spaces (metro hotspots and rural). This means a stronger signal and better

voice quality, plus improved data download and upload speeds. Femtocells also facilitate a

new breed of mobile service that exploits the technologys ability to detect presence, and

connect and interact with home networks.


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Some applications of Femtocell communication include:

Virtual home number, allowing families to keep a home number even if they canceltheir fixed line.

SMS alerts when kids arrive or depart the home, providing reassurance for workingparents.

Automatic Im at home profile / presence update on social networking websites. Automatic back-up of photos and videos from the phone to the web and / or the PC

when one arrives at home.

Description of technical words:

Femtocells Femtocells are small, user-installed base stations that enhance coverage for in-

building cellular services. Also known as 3G Microcell by some companies.

Macrocells A macrocell provides the largest area of coverage within a mobile network. Theantennas for macrocells can be mounted on ground-based masts, rooftops or

other existing structures. Macrocell base stations have a typical power output in

tens of watts.

3G 3G is the third-generation of mobile phone technology standards. The typical

services associated with 3G include wireless voice telephony and broadband

wireless data, all in a mobile environment.

HSDPA HSDPA, short for High-Speed Downlink Packet Access, is a new protocol for

mobile telephone data transmission. It is known as a 3.5G technology.

4G 4G is the fourth generation of cellular wireless standards and a successor to 3G

technology. A 4G system provides ultra-broadband Internet access, IP

telephony, gaming services, and streamed multimedia.

FTP File Transfer Protocol (FTP) is a standard network protocol used to transfer files

from one host to another host over a TCP-based network, such as the Internet.

CPICH Stands for Common Pilot Indicator Channel in UMTS and some other CDMA

communications.

Summary of the research paper:

The core of the research paper is divided into three sections:

1. Fixed Transmit Power for Femtocellsa. Impact on Macrocell Capacityb. Impact on Macrocell Coverage

2. Calibration Techniquesa. Femtocells with Varying Data/Control Power Ratiosb. Geo-static Transmit Power

3. Adaptive Transmit Power Control


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Fixed Transmit Power for Femtocells:

If the transmitted powers of femtocells are fixed, they would have catastrophic effects on the

macrocells that are serving the users.

Here a scenario is considered in which, a HSDPA system is considered which is deployed ina suburban environment. The macrocell users are all assumed to be outdoors while the

femtocell users are located indoors.

With regards to Impact on Macrocell Capacity, it is observed that the macrocell throughput

suffers significantly for even moderate femtocells transmit powers. On the other hand,

femtocell throughputs are reasonably large even when their transmit powers are low.

With regards to Impact on Macrocell Coverage, the Common Pilot Indicator/Control Channel

(CPICH) indicates the extent of a macrocells coverage. The macrocells coverage further

deteriorates and is almost independent of the activity factor. The results show that the

number of active femtocells and the control channel of femtocells have a strong negativeimpact on the macrocell performance.

Calibration Techniques:

In this section, the writers have proposed power control schemes that do not require the

femtocells to change their transmit powers at a fast time scale.

With regards to Femtocells with Varying Data/Control Power Ratios, instead of scaling down

the control and data channel powers by the same factor, the control channel power is fixed

and the power of the data channel is reduced.

With regards to Geo-Static Transmit Power, the network can set the transmit power of the

femtocells according to the location they lie in.

Adaptive Transmit Power Control

In this approach, the network provides each femtocell with a target bit-rate. The femtocells

collect the SINR measurements from the MSs and schedule transmission opportunities. The

femtocells can determine the appropriate data rates and regulate their transmit powers so that

the data rates is justmet.


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Conclusion:

The above discussed techniques ensure optimum coverage for femto users and minimizes the

effect on macro users. According to needs, the power control mechanism has to be chosen for

the best application and best arrange-able cost

Both the Calibration Techniques and the Adaptive Transmit Power Control have efficient

tradeoffs between femtocell and macrocell performances. The only major difference between

both power control techniques is the implementation intricacy which needs to be evaluated

beforehand implementation.

List of References:

[1] Naveen Arulselvan, Vinod Ramachandran, Suresh Kalyanasundaram, DistributedPower Control Mechanisms for HSDPA Femtocells, IEEE Transactions, 2009.

[2] NEC, Femtocell Whitepaper, 2009.[3] Theodore S. Rappaport, Wireless Communications: Principles and Practice,

January 10, 2002, ISBN: 0-130-42232-0.

[4] Bernard Sklar, Digital Communication: Fundamentals and Applications, January2001, ISBN: 0-130-84788-7.

[5] Femto Forum [6] Alcatel-Lucent [7] LTE World [8] Think Femtocell [9] IP Access [10] Airvana Solutions [11] Wikipedia.org

Distributed Power Control Mechanisms for HSDPA Femtocells Report

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