Harmful Coexistence Between 802.15.4 and 802.11: A Measurement-based Study

Due to recent advances in wireless technology, a broad range of standards catering to a diverse set of users are currently emerging. Interoperability and coexistence between these heterogeneous networks are becoming key issues, and proper mitigation of these issues requires a good understanding of how and why heterogeneous networks may harm each other's p.erformance. In this paper, we focus on the coexistence of 802.11 (wireless LAN) and 802.15.4 (sensor networks) in the ISM band. These networks have very different transmission characteristics that result in asymmetric interaction patterns. Consequently, many studies assume that the impact of 802.15.4 on 802.11 is negligible. In this paper, we examine this assumption in detail and show that, in many cases, 802.15.4 significantly impacts 802.11 performance. Even when 802.15.4 is executing a listen-before-send, which should theoretically prevent interference, a significant 802.11 performance degradation frequently occurs due to disparate slot sizes between the two protocols. This is one of the first papers studying the listen-before-send performance for heterogeneous networks with substantial measured data. The results raise important coexistence issues for 802.15.4 and 802.11 in particular, but even more so for dynamic spectrum sharing between heterogeneous devices in general.