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A Realistic Reverse Link Capacity A Realistic Reverse Link Capacity Improvement with A Joint Multiple Improvement with A Joint Multiple

Access of CDMA and SDMA Systems Access of CDMA and SDMA Systems using Smart Antennausing Smart Antenna

Ng Chee KyunBorhanuddin Mohd Ali

Sabira Khatun

Sudhanshu Shekhar Jamuar

Mahamod Ismail

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Presentation OutlinePresentation Outline

• Introduction• Cellular System Capacity• CDMA Capacity• SDMA Capacity• Joint Multiple Access (CDMA and SDMA) System• Joint Multiple Access System Reverse Link Capacity• Concluding Remarks

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Digital Radio Communication SystemsDigital Radio Communication Systems

• Frequency Division Multiple Access (FDMA)

~ 1st Generation

• Time Division Multiple Access (TDMA)

~ 2nd Generation

• Code Division Multiple Access (CDMA)

~ 3rd Generation (3G)

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Space Division Multiple Access (SDMA)

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Cellular System Capacity

• Narrowband radio systems (TDMA and FDMA)

- dimension or bandwidth limited.

• Spread spectrum system (CDMA) - interference limited. - Traditional CDMA systems are all self-interference systems.

• Spatial diversity system (SDMA) - interference limited.

Any attempt to reduce interference will convert directly and linearly into increased capacity.

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CDMA Capacity(Source of Interferences)

Intra-cell interference.

Inter-cell interference.

BS0

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Power Control

1

1

)1(

N

SN

S

SIR

• To avoid near far effect - The base station receives all mobile stations at the same power

level, S. Signal to interference ratio (SIR)

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Intra-Cell Interference

0

1IE

RWN

b

W = Spreading rate (chip per second)R = Bit rate (bit per second) W/R = Processing gain (PG)

System Capacity:

Assume that a minimum of 5 (7 dB) is required to achieve bit error rate (BER) of 10-3 [Gilhousen 91]

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Inter-Cell Interference

= power of distance = shadowing loss

1010),( rrPL

Propagation Model:Path-loss, PL

1

1

1

1

1

1

1

Frequency Reuse Pattern in CDMA

K

k

N

i k

km

erkikim

i

i

r

rSI

1

1

0

10)(

4

0int

010

Total inter-cell interference

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SDMA Capacity

• Smart Antenna – Generates high directive narrow beam. • System capacity Number of nulls• Co-channel and side-lobes interferences

4

2

3

7

6

5

1

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Smart Antenna

)2/cossin(

)2/cos(sin1)(

k

kn

nG

Radiation pattern

= Phase shift = Angle of arrivaln = Number of antenna elements

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Smart Antenna Beamwidth Sizes

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Smart Antenna with 8 antenna elements

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Smart Antenna with 32 antenna elements

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Joint Multiple Access (CDMA and SDMA) System

• A.F. Naguib, A. Paulraj and T. Kailath, “Capacity Improvement with Base-Station Antenna Arrays in Cellular CDMA”, IEEE Transactions on Vehicular Technology, vol. 43, no. 3, pp. 691 – 698, Aug. 1994.

• E. Buracchini, F. Muratore, V. Palestini and M. Sinibaldi, “Performance Analysis of A Mobile System Based on Combined SDMA/CDMA Access Technique”, IEEE 4th International Symposium on Spread Spectrum Techniques and Applications Proceedings, vol. 1, pp. 370 – 374, 22-25 Sept. 1996.

• B. Ng and E.S. Sousa, “Performance Enhancement of DS-CDMA System for Wireless Local Loop”, IEEE International Telecommunications Symposium (ITS) Proceedings, vol.1, pp. 78 – 82, 9-13 Aug. 1998. 

• J. Yu, Y.D. Yao and J. Zhang, “Reverse-Link Capacity of Power-Controlled CDMA Systems with Beamforming”, IEEE Transactions on Vehicular Technology, vol. 53, no. 5, pp. 1423 – 1433, Sept. 2004.

Related Works

Motivation

• Non of them have consider the co-channel and side-lobes interferences in their system performance simulations.

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Co-Channel and Side-Lobes Interferences

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Joint Multiple Access System Reverse Link Capacity

C

I

I

I

I

I

I

II

BS0

BS1BS2

r0

rm

1

1

1

1int

)2/)cos(sin(

)2/)cos((sin

)()(

N

i i

i

N

iiCra

k

kn

n

S

GSI

6

1 1

10)(0

4

0int

010)(

)()(

j

N

i m

jim

cerjijim

jiji

ji

G

G

r

rSI

Intra-cell interference

Inter-cell interference

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System Parameters for Capacity Analysis

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System Capacity in Intra-Sector Interference Environment

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System Capacity in Intra-Sector Interference Environment

• For the 0.01 outage probability, the system capacity increases from 45 users per sector in omnidirectional antenna case to about 200 users per sector if smart antenna is exploited.

• This depicts an increase of 344.4 %.

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System Capacity in Inter-Sector Interference Environment

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• When a comparison of system capacity is considered between intra and inter cells interference environment, it depicts a significant decrease.

• For example, the total users that can be accommodated in a cell are 30 users. It shows that the number is dropped from 200 users per cell yield about 85 % decreases.

System Capacity in Inter-Sector Interference Environment

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Smart Antenna Beamwidth Sizes

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System Capacity in Inter-Sector Interference Environment for Smart Antenna with Its Number of

Antenna Elements, n = 8, 16, 32 and 64.

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• For the 0.01 outage probability, the system capacity increases from 8 users per sector for n = 8 elements case to about 40 users per sector if n = 64 elements are used, which depicts an increase of 400 %.

•If 0.1 outage probability is considered, the system capacity is further increase from 25 users per sector for n = 8 elements case to about 170 users per sector if n = 64 elements are used, which give a 580 % increase.

System Capacity in Inter-Sector Interference Environment when the Beamwidth become

Narrower

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Concluding Remarks

• The system capacity will be increased by taking the advantage of both code and spatial signature schemes to distinguish each user. • The most realistic reverse link capacity performance of this joint

system has been depicted by taking into consideration of prevailing co-channel and sides-lobes interferences in both intra-cell and inter-cell environments. • The obtained results have also revealed that the system capacity

is further deteriorated by interfering users from neighbouring cells. • However, this deterioration can be compensated if the

synthesized beams of smart antenna are narrower. • Therefore, the system capacity of this joint multiple access

system will significant increase spatial diversity becomes more dominant by increasing the number of element in smart antenna system.

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Thank YouThank You