Effects of radio channel characteristics on IEEE 802.11b QoS performance in an outdoor point-to-multipoint configuration

Achieving and maintaining acceptable quality of service (QoS) is a difficult task in wireless networks due to highly variable transmission channel parameters and the scarce bandwidth available in such networks. Although IEEE 802.11b is traditionally used for indoor wireless local area networks (WLANs), we have experimented using it as a point-to-multipoint (PMP) configuration for an outdoor WLAN environment with extended coverage areas using suitable amplifiers and antennas. This is an emerging alternative to expensive sub-5 GHz PMP networks for providing cost-effective voice, video, and data services to commercial customer premises equipment (CPE) and end users. The paper evaluates the degradation in performance of data (indicated by measured throughput) and degradation in performance of voice over IP (VoIP) (indicated by measured mean opinion score, MOS) due to effects of fading and interference in a PMP configuration. Tests were carried out in a controlled RF environment. Effects of interference, noise power, signal power, and number of CPEs per base transceiver station (BTS) were investigated. The intent was to evaluate the performance at different traffic loads when the signal-to-noise-and-interference ratio (SNIR) was below a certain threshold. The results show important findings that can be used as a guideline in radiofrequency (RF) engineering a service provider access network using WLANs.