School of Telecommunication EngineeringSuranaree University of Technology, Thailand

Investigation into GPRS Transmission Employing Switched Beam Antenna at Mobile Station

by P. Sriploy, M. Uthansakul and R. Wongsan

Page 2School of Telecommunication EngineeringSuranaree University of Technology, Thailand

Outline

Introduction- Background

- GPRS System- Smart Antenna System

- Literature Survey motivation GPRS Transmission Simulation

- Assumption- Results

Conclusion

Page 3School of Telecommunication EngineeringSuranaree University of Technology, Thailand

Introduction

GPRS (General Package Radio Service) is a packet oriented Mobile Data Service available to users of Global System for Mobile Communications (GSM)

Quality of GPRS transmission Coding Scheme (CS)

Smart antenna system is envisaged to improve the quality of GPRS transmission

Coding Scheme C/I Datarate (kbps)

CS -1 less than 7 9.05

CS -2 7 – 12 13.4

CS -3 12 - 17 15.6

CS -4 more than 17 21.4

Page 4School of Telecommunication EngineeringSuranaree University of Technology, Thailand

Introduction

Smart antenna system

= array antenna

+ signal processing unit

Benefits- better range/coverage

- greater battery life

- smaller/lighter handset size

- increased capacity

- multipath rejection

- reduced expense

Signal Processing Unit

Output

. . .

Desire

dSig

nals

Interference

Mul

tipat

h

Antenna Array

Page 5School of Telecommunication EngineeringSuranaree University of Technology, Thailand

Introduction

2 types of smart antenna system: - Switched beam antenna

. . . . . .

BeamformingNetwork

Output

Beam Selector

. . .

- Switched beam antenna performs similarly to adaptive antenna when employing few antenna elements [5]

- Switched beam antenna outperforms adaptive antenna when the desired signal is not sufficiently larger than interferences [5]

. . . . . .

Summing Network

Output

Signal Processing Unit

. . . . . .

- Adaptive antenna

Page 6School of Telecommunication EngineeringSuranaree University of Technology, Thailand

Introduction

Literatures- Concept of smart antenna has been proposed at Base Station to enhance

GPRS transmission [6]

- This results in high cost and complexity

For this paper:- We propose the idea of using switched beam antenna at Mobile Station to

enhance the quality of GPRS transmission

- Effect of array size reduction on the system throughput is also investigated

Page 7School of Telecommunication EngineeringSuranaree University of Technology, Thailand

GPRS Transmission

GPRS Parameter- TDMA/FDD

- Reverse Channel: 890 – 915 MHz

- Forward Channel: 935 – 960 MHz

- Channel Bandwidth: 200 kHz

- Duplex Separation: 45 MHz or 3 Time Slots

- Total Number of RF Duplex Channel: 124 users

Path Loss

2( ) 2 ( ) 2 ( )m dB p m L dB

( ) 32 20log 20logL dB f d

(Fading)

(No Fading)

( )x b uC T G G m dB

received power

transmitted power

antenna gain at BS

antenna gain at user

PL

Page 8School of Telecommunication EngineeringSuranaree University of Technology, Thailand

Computer Simulation

Assumption

1 kmInterference 2

Interference 1

Interference 3

- 100 users uniformly distributed

- Antenna gain:• switched beam; 6.76 dB• omnidirectional; 0 dB• at BS; 14 dB

- Mutual coupling effect between the array elements is included

Page 9School of Telecommunication EngineeringSuranaree University of Technology, Thailand

Simulation Results

-10 -5 0 5 10 15 20 25 30 35 400

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

C/I (dB)

PD

F

Omnidirectional

0.1

0.2

0.3

0.4

0.5

switched beam

- Switched beam antenna provides better performance compared with omni- directional antenna- Best C/I is obtained from the case when the array antenna is spaced by 0.5λ

Average C/I (dB)- Omnidirectional = 7.22 - 0.1λ = 7.45- 0.2λ = 8.25- 0.3λ = 11.10- 0.4λ = 12.95- 0.5λ = 15.23

Page 10School of Telecommunication EngineeringSuranaree University of Technology, Thailand

Simulation Results

9.05 13.4 15.6 21.40

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Throughput (kbps)

PD

F

Omnidirectional

0.1

0.2

0.3

0.4

0.5

switched beam

Switched beam antenna provides better throughput, specially when we utilize the array having inter-element spacing of 0.5λ

Average throughput (dB)- Omnidirectional = 11.22 - 0.1λ = 11.26- 0.2λ = 12.45- 0.3λ = 14.44- 0.4λ = 14.83- 0.5λ = 16.56

Page 11School of Telecommunication EngineeringSuranaree University of Technology, Thailand

Simulation Results

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.565

70

75

80

85

90

95

100

Array Spacing ()

Th

rou

gh

pu

t (%

)

Switched Beam

Omnidirectional(67.75%)

40%

13%

System throughput decreases as the array spacing is reduced

Page 12School of Telecommunication EngineeringSuranaree University of Technology, Thailand

Conclusion

Utilizing switched beam antenna at Mobile Station enhances the performance of GPRS system

Array elements spaced by 0.5λ provides the best performance Array spacing reduction affects the system C/I and throughput Ones can find the provided information useful for designing a switched

beam antenna for GPRS system

Page 13School of Telecommunication EngineeringSuranaree University of Technology, Thailand

End

Thank you for attention!! Question?