Abstract
The Medium Access Control (MAC) protocol of the IEEE 802.11 standard is based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). The basic retransmission mechanism, binary exponential backoff, may cause large packet delay and packet delay jitter that are not suitable for real-time traffic. In this thesis, we will first investigate some MAC enhancement mechanisms discussed in the IEEE 802.11 task group E, which was formed for enhancing the current 802.11 MAC protocol to support for applications with Quality of Service (QoS) requirements. Then, we will propose a jamming-based retransmission mechanism that is compatible with the 802.11 standard and could reduce the packet delay for real-time traffic. Besides, this mechanism performs stably when the traffic load is heavy. The optimal setting of our proposed mechanism is discussed analytically. We perform simulated experiments by comparing our proposed retransmission mechanism with the other two mechanisms discussed in the 802.11 task group E. We show that the jamming-based retransmission mechanism can reduce the packet delay and the packet dropping rate.