| The background of the work presented in this thesis is the project of "Research on the Unmanned Aerial System Tactic Network Architecture (UAS-TNA)". UAS-TN is a special type of MANET (Mobile Ad hoc NETwork) except that it works in a hostile space and its nodes (UAV, Unmanned Aerial Vehicle) move faster than ground vehicles. Therefore, the techniques developed in this project are generally applicable to other types of MANET.This dissertation is dedicated to improving channel access control (or Medidium Access Control, MAC) protocol, with an emphasis on multi-channel communication environment. A brief survey of existing MAC protocols is provided and issues faced with channel access control protocols are analyzed in some details. After that, this thesis provides a comprehensive study on typical MAC protocols for single channel such as IEEE 802.11 DCF, as well as for those with multiple channels.To solve hidden-terminal and exposed-terminal problems and to improve the efficiency, the author introduced an Improved Multi-Channel MAC Protocol (IMCMP) based on the existing Multi-Channel MAC Protocol(MCMP) proposed by Nakjung Choi. The author has simulated, with NS2 (Network Simulator 2), single-channel and multi-channel MAC protocols. Comparison of simulation results have showen that multi-channel MAC protocols are superior over single-channel MAC protocols and that IMCMP has better performance than that of MCMP in throughput, successful sending rate, and mean transity delay. These are gained from the following technical tactics:a) Extension of control fields in channel table,b) Applicable channel numbering scheme,c) Neighbor communication queue mechanism, andd) Acknowledgement in data channel to reduce data re-transmission. |
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