An analytic model for infrastructure WLAN capacity with bidirectional frame aggregation

The paper presents an analytic model for computing the capacity of an infrastructure IEEE 802.11 WLAN enhanced with the support of bidirectional MAC frame aggregation, which fits specifically well to TCP by allowing a TCP link to "piggyback" TCP ACK collection onto TCP data transmission and is being considered by the IEEE 802.11n task group as a standard MAC feature. The proposed analysis applies to the RTS/CTS-based contention access mechanism. The mechanism is to be used for the closed-loop link adaptation considered for 802.11n as well as to help reduce the aggregated packet collision cost that is usually large. Simulations with ns2 are performed and the simulation results show that the analytic model provides an adequate approximation to the capacity of the considered WLAN. The analytic model helps us to understand the performance gain of bidirectional aggregation, suggests guidelines on when and how to adjust aggregation parameters, and thus to serve as the foundation for future aggregation scheduler development.