ABSTRACT
Contents 4.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 4.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 4.3 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 4.4 Background. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
4.4.1 IEEE 802.11 MAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 4.4.1.1 Distributed Coordination Function (DCF) . . . . . . . . . 118 4.4.1.2 Point Coordination Function (PCF) . . . . . . . . . . . . . . . . 120
4.4.2 Upper-Layer FEC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 4.5 MAC Protocol Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
4.5.1 Reliable Multicast MAC Protocol with Polling-Based Feedback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
4.5.2 Reliable Multicast MAC Protocol with Contention-Based Feedback. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 4.5.2.1 Main Transmission Period. . . . . . . . . . . . . . . . . . . . . . . . . . 127 4.5.2.2 Contention Round . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 4.5.2.3 NAK Transmission Round . . . . . . . . . . . . . . . . . . . . . . . . . . 128 4.5.2.4 Last NAK Transmission Round . . . . . . . . . . . . . . . . . . . . . 128 4.5.2.5 Last Contention Round . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 4.5.2.6 Contention Window Size in RNAK . . . . . . . . . . . . . . . . 129
4.5.3 Discussion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 4.5.3.1 Loss of Control Frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 4.5.3.2 Selective Retransmission . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
4.6 Performance Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 4.6.1 Mathematical Analysis of Idealized Performance . . . . . . . . . . . 133 4.6.2 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
4.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
4.1 Overview Prevailing IEEE 802.11 wireless local area network (WLAN) today does not support any medium access control (MAC) protocol for reliable multicast (RM). It only provides unreliable multicast without any feedback from receivers and reliable unicast with positive acknowledgment (ACK) from the receiver. This chapter delves into parity-based multicast protocols. To support RM over the 802.11 WLAN, two different RM MAC protocols — a polling-based feedback protocol and a contention-based feedback protocol — are developed. Both protocols improve the efficiency of multicast as well as the reliability by supporting the per-group feedback based on negative ACK (NAK). That is, combined with the reliable MAC protocols that support per-group feedback, parity-based loss recovery can improve multicast efficiency. Therefore, we investigate how the proposed RM MAC protocols can be combined with forward error correction (FEC) of the upper layer to achieve reliable and efficient multicast. For the performance evaluation, we consider multicasting scenarios using MAC-level reliable protocols and upper-layer-level FEC. The simulation results demonstrate that our multicast schemes substantially outperform the existing scheme based on per-packet feedback in terms of efficiency, and guarantee the RM, which the 802.11 cannot provide.
