A Cross-Layer Study Of MAC Layer And PHY Layer For Broadband Wireless Access System

The modern broadband wireless communication now faces two critical problems: one is the fading of wireless channel and the other is low efficiency of bandwidth usage. The former can be solved mainly by OFDM(Orthogonal Frequency Division Multiplexing), including multi-path fading and frequency selective fading and so forth. The latter can be solved by the cross-layer optimization currently.This thesis is based on the OFDM system of 802.16-2004. After the principle and work flow of AMC(Adaptive Modulation and Coding) is discussed, some disadvantages will be revealed. To get the disadvantages over, the channel prediction should be added in the MAC layer. And the throughput of the system greatly increased with this improvement. The thesis is arranged as follow:First chapter introduces the research background and the concept of Broadband Wireless Communication System and Cross-layer Optimization.Chapter 2 provides an introduction on the simulation platform of 802.16-2004, which is used for the research in the thesis. And detailed description of PHY layer module, channel module and pipeline module will be given.Chapter 3 shows the development of AMC from the Adaptive Transmission Technologies. The necessity of channel prediction will be followed. And the comparison of several classical prediction methods will be presented.Chapter 4 is the core of thesis. It provides the cross-layer optimization scheme between MAC layer and PHY layer, which using the result of channel prediction in MAC layer for controlling the AMC. After AMC process, the result is inputted to scheduler in the purpose of efficient scheduling.Chapter 5 compares two groups of simulations of different scenarios. And provide the result with/without channel prediction. Analysis for the results will be given.Chapter 6 gives the conclusion of the thesis. And it also summarizes the work which has been done and the work will be done in future.