TY - JOUR

T1 - Optimization of CDMA systems with respect to transmission probability, part II

T2 - Signal to noise plus interference ratio optimization

AU - Bergel, Itsik

AU - Messer, Hagit

PY - 2008/6

Y1 - 2008/6

N2 - Code division multiple access (CDMA) systems commonly use power control mechanism to reduce the amount of interference between the users. In part I of this paper, we introduced the concept of probability control that optimizes system performance with respect to the users' transmission probabilities. The importance of probability control was demonstrated by proving that probability control alone optimizes the mutual information rates over a frequency-flat slow-fading multiple access channel. In this part we extend this result to the optimization of the average signal-to-noise plus interference ratio (SIR) in a CDMA system over a frequency-selective slow-fading channel model and any network topology. We prove that there is a group of CDMA receivers, in which the average SIR (ASIR) of all users is maximized using probability control (while all users transmit their maximal allowed power). This receivers group includes, among others, the common matched filter (MF) RAKE receiver, as well as the sophisticated minimal mean square error (MMSE) RAKE receiver. Simulations demonstrate for a 2-users scenario that both users achieve significantly higher ASIR using probability-control instead of power-control. Results are applicable both for CDMA and impulse radio (IR) systems.

AB - Code division multiple access (CDMA) systems commonly use power control mechanism to reduce the amount of interference between the users. In part I of this paper, we introduced the concept of probability control that optimizes system performance with respect to the users' transmission probabilities. The importance of probability control was demonstrated by proving that probability control alone optimizes the mutual information rates over a frequency-flat slow-fading multiple access channel. In this part we extend this result to the optimization of the average signal-to-noise plus interference ratio (SIR) in a CDMA system over a frequency-selective slow-fading channel model and any network topology. We prove that there is a group of CDMA receivers, in which the average SIR (ASIR) of all users is maximized using probability control (while all users transmit their maximal allowed power). This receivers group includes, among others, the common matched filter (MF) RAKE receiver, as well as the sophisticated minimal mean square error (MMSE) RAKE receiver. Simulations demonstrate for a 2-users scenario that both users achieve significantly higher ASIR using probability-control instead of power-control. Results are applicable both for CDMA and impulse radio (IR) systems.

KW - CDMA

KW - IR

KW - Power control

KW - Probability control

KW - UWB

UR - http://www.scopus.com/inward/record.url?scp=45849135662&partnerID=8YFLogxK

U2 - 10.1109/TWC.2008.05946

DO - 10.1109/TWC.2008.05946

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AN - SCOPUS:45849135662

SN - 1536-1276

VL - 7

SP - 2084

EP - 2093

JO - IEEE Transactions on Wireless Communications

JF - IEEE Transactions on Wireless Communications

IS - 6

M1 - 4543061

ER -