New frame-based network allocation vector for 802.11b multirate wireless LANs

To enhance the system capacity of the IEEE 802.11 wireless local area networks (WLANs), a frame-based adaptive multirate transmission scheme is envisaged. The medium access control (MAC) operation and the selection of parameters, such as the thresholds of request to send (RTS) and fragmentation, are discussed. The original virtual carrier sense mechanism in the IEEE 802.11 WLAN standard is no longer suitable because the transmission rate is adaptively selected such that it is prone to allocate a wrong network allocation vector (NAV) to jam or inhibit the radio transmission that degrades the performance. A modification of the NAV reservation scheme must be made to adopt this change. The authors have performed simulations to illustrate the performance improvement to the modification of the NAV reservation scheme. Simulations are based on a time-correlated multipath fading channel model and a movable mobile station assumption, where the station may be out of range from certain mobile stations