Reachability and Goodput Enhancement via Fragmentation in Public IEEE 802.11b WLAN

In wireless packet networks, such as IEEE 802.11 wireless LAN, users can suffer from bad channel quality at cell boundaries, and wireless stations may not overcome the bad communication condition, in spite of using the lowest transmission rate via link adaptation. Unless handoff is considered due to the deployment of APs, the case of initial access to a WLAN network, and so on in such an area, fragmentation can be a unique and compatible solution for coping with the channel limitation. We have evaluated a public WLAN service network, called NESPOT, which is operated by Korea Telecom, especially the case of initial access. We evaluate delay and error performances of NESPOT initial access procedure via both mathematical analysis and simulations. From the results, we conclude that WLAN user can experience enhanced goodput, enlarged reachability, and shortened delay via fragmentation. We also propose a practical method, TCP maximum segment size spoofing to get the same effect as fragmentation. Finally, we propose a policy, called cut-off delay, for WLAN users not to wait too long time to get an IP address without severe performance degradation