Analysis And Design On MAC Mechanism Of Wireless Packet Networks

With the rapid development of the wireless communication systems, several networks based on IEEE 802.11 MAC protocol such as Ad Hoc, WLANs have been observed and analyzed. In this thesis, we mainly focus on MAC mechanism of IEEE 802.11-based networks. Several protocols and MAC mechanism are proposed aimed for the Ad Hoc Networks and WLANS. We get the following achievements:1. Focused on the multi-hop Mobile Ad Hoc Networks (MANET), a novel MAC which is joint Rout-layer information designed is proposed. Using sense mechanism of uni-directional antenna, route layer information is tagged by RTS/CTS handshake frames. Then a hybrid MAC is proposed which can switch between the Sender-initiated MAC and Receiver-initiated MAC. This approach reduces the antenna turn-around time and handshake transmission time. Simulation results show that this approach can enhance the throughput performance significantly.2. Emerging Inter-Vehicle Communication (IVC) technique is getting increasing attention. Inspired by cross-layer design, receiver-initiated MAC and fragment burst of IEEE 802.11, a new MAC protocol supporting priority differentiation for IVC based on IEEE 802.11 is proposed. With this approach, top priority applications can be relayed from source car to destination with minimum contentions, redundant overhead such as Require-to-Send (RTS) and Distributed Inter-Fame Space (DIFS) is also retrenched. Another new term named relay-interruption can introduce more contention for lower priority applications and traditional IEEE 802.11 four-way frame exchange is applied for lowest priority traffic. Simulation demonstrates the feasibility of the proposed approach.3. The performance degradation caused by small-size packet and by low rate nodes has been observed and analyzed by researchers. In multi-rate WLANs, dominant small-size packets will cause the inefficient channel utilization, and performance anomaly problem happens for the presence of low rate nodes. In this paper, we proposed a novel algorithm named Dynamic Frame Aggregation (DFA) aimed for performance enhancement in multi-rate WLANs. Several techniques are proposed with DFA. Firstly, we redefine the maximum frame size of once transmission according to the data rate. Secondly, packets on both unidirectional and bidirectional link can be assembled...