Improving VoIP Capacity in Multi-Rate IEEE 802.11e WLANs via Relay

In order to improve the Voice over IP (VoIP) capacity of a Wireless Local Area Network (WLAN), we develop a relay-aided solution, which includes a relay-aided admission control scheme, a packet aggregation scheme, and a protocol for packet relay without sacrificing the voice quality. Basically, our admission control scheme utilizes relay stations to admit as many VoIP sessions as possible. When a new VoIP session requests admission, the admission controller checks whether it can be admitted by either using relay or communicating with the AP directly. Moreover, to overcome the overhead increased due to relaying small-size VoIP packets, we employ a packet aggregation scheme for VoIP packet transmissions between the AP and relay stations. Simulation results demonstrate that the proposed relay-aided VoIP provisioning scheme can significantly improve the VoIP capacity without compromising the service quality of the admitted VoIP sessions.