A Novel Piggyback Selection Scheme in IEEE 802.11e HCCA

A control frame can be piggybacked in a data frame to increase the channel efficiency in a wireless communication such as IEEE 802.11 WLAN. However, the piggyback scheme may cause the decrease of the channel efficiency and the increase of the frame transmission delay for other stations when any station has the low transmission rate and the control frame has the global control information such as the channel reservation time. It is similar to the anomaly phenomenon in the network which supports the multi-rate transmission. In this paper, we define this phenomenon as "the piggyback problem at low physical transmission rate" and evaluate the effect of this problem with respect to the physical transmission rate and the normalized traffic load. Then, we propose the delay-based piggyback algorithm which decides to use the piggyback scheme for a control frame based on the delay efficiency in IEEE 802.11e HCCA. In the simulation results, the proposed algorithm reduces the average frame transmission delay and the channel utilization about 24% and 25%, respectively if there is one station which has low physical transmission rate.