POWER OPTIMIZATION OF MULTIUSER CDMA BASED TACTICAL NETWORKS

Abstract

Power Optimization of Multiuser CDMA based Tactical Networks Wireless communication systems which employ multiple access techniques require very sensitive management of the sources. This is the key requirement because of random and frequent movement of mobile users and rapid variations in the channel. In Code Division Multiple Access (CDMA) based wireless communication systems, the most important issue on transmitter side is the power management. Intelligently controlled power heavily improves the systems performance and capacity. The requirement of power control becomes more important in tactical network which is a type of self organizing and self operating systems. The topic of this thesis is to optimize the transmitted powers of mobile users in a multiuser CDMA based tactical networks. The proposed power optimization method for tactical networks is of valuable importance because it can be extended to other types of networks which are self organizing and infrastructureless. This thesis deals with the power optimization of multiple users of CDMA system where only peer-topeer communication can take place due to the absence of any central unit or base station. Firstly, the simplified CDMA system is simulated under different power profiles and a pair of multiuser detection techniques to ensure elimination of Multiple Access Interference (MAI). Performance comparison has been made between conventional detector and multiuser detector on the basis of bit error rate and capacity. Secondly, taking Stanford University Interim (SUI) channel as the approximation to tactical networks, the system is simulated in SUI channels where the equalization is done using Maximal Ratio Combining (MRC) based Rake receiver. Finally, a power optimization algorithm is proposed which is based on Distance Based Power Allocation (DBPA) scheme. This simplified algorithm is selected due to the location awareness characteristic of tactical networks. The proposed algorithm is applied to both the stationary and moving users’ environment. Due to the presence of Near-far effect and Multiple Access Interference in all practical systems, only power control is not enough to yield best results, rather best performance has been obtained when power control is used along with Multiuser Detection techniques. It is observed that in SUI channels, when delay spread increases, the power control performance decreases but still it is much better than that of uncontrolled power.