Impact of Various VoIP and Video Traffics to Performance of Aggregation with Fragment Retransmission (AFR) in WLAN

Agregation With Fragment Retransmision (AFR) is a frame transmission scheme that can improve the efficiency and the throughput of MAC layer in WLAN 802.11n. In this paper, we studied the performance of AFR scheme when various VoIP and video traffics transmitted over WLAN. The purpose of this work is to know how the number of connections, packet size and fragment size of VoIP and video traffics influence the throughput and the delay performance of frame transmission. We used G.711, G.723a and G.729 format as VoIP traffics and H.264/MPEG-4 AVC format as video traffics which used 768 Kbps, 2 Mbps, 4 Mbps, 10 Mbps and 20 Mbps video bit rate. We used network simulator 2 (NS-2) with AFR module to simulate VoIP and video trafics over WLAN and measured each traffic performance. Simulation results show that throughput of MAC layer with AFR scheme will saturate when 70 connections of G.711 were transmitted. The transmission delay of G.723a and G.729 will be optimum when each traffic aggregated in 512 bytes of frame size. Simulation results also show that the throughput of AFR scheme is 70 Mbps and the delay is 0.025 ms when 30 H.264 video connections with 2 Mbps bit rate were transmiited. We have found the fragment and frame sizes that will give optimum throughput and the delay performance in AFR MAC scheme.