Performance Evaluation, Improvement and Channel Adaptive Strategy for IEEE 802.11 Fragmentation Mechanism

We first examine the impact of channel errors and collisions on the performance of legacy IEEE 802.11 fragmentation, and find the optimal fragment size depends on both channel condition and network size. Then, we present an improved contention-free fragmentation burst (CFF) scheme, by which the source immediately retransmits the failed fragment without backoff procedure except for the first one. Finally, a channel adaptive fragmentation (ADF) scheme based on CFF is proposed to combat both channel errors and collisions. ADF can distinguish frame transmission failure caused by collision from that by channel error in moderate noisy channel. Simulations show our CFF and ADF have distinct performance improvements in noisy channel and large size networks.