Improvement on Network Capacity for Voice Services over HCCA

In the 802.11e protocol, voices traffic takes a higher priority than other services. However, there are still some technical problems existing in VoIP services over WLAN: (a) low voice capacity caused by the inherent characteristic of WLAN and heavy packet headers from upper layers and (b) unacceptable voice delay in the presence of coexisting with other applications. To address these problems, in this paper we propose several schemes to better manage the limited network capacity of VoIP network. In the proposed schemes, every voice stream occupies a fixed bandwidth to avoid collision between packets. With the Packet Header Compression technology, the overhead of voice packets is greatly reduced. Under various PHY rates, we investigate the performance of our proposed scheme over various voice codecs. Compared to HCCA, the proposed scheme greatly advances the maximum throughput of voice streams.