MIMO-HSDPA : An approach to enhance the performance of wireless networks

摘要

The thesis focuses on improving the performance of wireless networks including energy efficiency and the maximum capacity of the network. In wireless networks such as ad hoc networks, they have been observed that the physical transmission rate is a vital parameter. For slow data rate networks, not only the end-to-end throughput is poor, the energy efficiency is also not good, because the transmission energy cannot be consumed effectively. In order to improve both performance matrices, this thesis proposes the use of MIMO-HSDPA techniques collaborating with an optimal resource allocation technique. When using the MIMO-HSDPA approach, it will be demonstrated in the thesis that the total physical data rate increases significantly, which render the improvement in both energy efficiency and the end-to-end throughput.ududIn chapter 2, the performance of stationary ad hoc networks has been examined. The network uses the HSDPA technique to improve the physical data rate whilst a multipath routing communication with the load balancing algorithm is also employed to maximize energy efficiency. The focus of the chapter is on optimizing a packet size in order to achieve the target end-to-end throughput required by a user. The packet length optimization involves the analysis and modification of the MAC service time model, which will be used to determine the optimum packet size.udud In chapter 3, for further improvement of the physical data rate, the MIMO transmission technique is employed in collaboration with the HSDPA approach. However, when increasing the data rate, fading in the communication channel fluctuates and has effects on the received signal. The fading causes the communication channel to be a frequency selective channel, which renders an Inter-Symbol-Interference (ISI) in the received signal and the subsequent reducing in the performance of the receiver. The chapter shows how to allocate energy in the MIMO-HSDPA communication system where a channel is considered as a frequency selective channel. In order to mitigate the effect of the ISI the successive interference cancellation (SIC) technique is also used at the receiver. By using the energy allocation and the SIC technique, the maximum capacity of the system is greatly enhanced and is close to the upper bound capacity achieved by the water-filling algorithm.ududThe communication channels being examined in the thesis mainly are type of pedestrian A channels. The channels are assumed to represent Wireless LAN systems, which are used only for short distance communications. Once MIMO techniques are applied, antenna configurations might produce spatial correlations on the pedestrian A channels, which causes reduction in the capacity given by a spatial multiplexing gain of the MIMO systems. In chapter 4 chapter, the capacity of the MIMO-HSDPA systems over correlated channels is identified and, in order to improve the performance, MIMO pre-coding techniques such as an Eigen value and a channel inverse pre-coding approach are proposed to deal with the correlated channel problem.