POWER CONTROL FOR INDOOR CDMA COMMUNICATION SYSTEMS USING TIME DIVISION DUPLEXING

Abstract

One of the very important problem in wireless spread spectrum that utilizes code division multiple access (CDMA) is transmit power control. In this thesis, this problem for wireless indoor CDMA communication systems using time division duplexing (TDD) is addressed. An architecture for power controlled CDMA using TDD is developed and its per- formance is analyzed. The analysis takes into account a time-variant multipath Rayleigh fading channel which is modelled by two rays. The transmit power control is based on keeping the signal to interference power ratio (SIR) of the RAKE (optimum) receiver de- cision variable constant. The probability density functions (pdf) of the signal power and interference power are derived as is the SIR of the RAKE decision variable. Simulation results verifies the validity of the pdf of the signal power of the RAKE decision variable. It also verifies the shape of the pdf of interference power of the RAKE decision variable. Simulation results show that the SIR does not dip significantly over time. It does have a few positive going peaks when there are more users, however, these peaks 'the favor of the user and do not harm the co-user.