VoIP Applications over WLAN with Multistage Interference Cancellation Smart Antennas

In order to improve the transmission quality of wireless local area network (WLAN), incorporation of emerging technologies is required. Smart antennas, as one of the key technologies in future communications, can significantly improve the Signal-to-Interference-plus-Noise ratio (SINR) and hence reduce the transmission errors. Because WLAN uses the unlicensed industrial, scientific, and medical (ISM) radio bands, strong cochannel interference (CCI) sources from systems other than WLAN can significantly degrade the throughput of WLAN and result in various transmission problems, such as latency, jitter, and packet loss. These problems usually render performance degradation of Voice over IP (VoIP) services. The CCI from uncoordinated sources also lead to slow convergence of smart antennas using data-dependent adaptive algorithms. This work demonstrates that applying low cost Multistage Interference Cancellation Smart Antennas (MICSA) to WLAN conducts superior interference suppression and better performance improvement of VoIP services compared with using conventional single stage smart antennas to WLAN.