Coexistence of Wi-Fi and WAVE in the DSRC Spectrum: Impact on WAVE Latency and Throughput 2018-01-1097

In this paper, we study the impact on Wireless Access in a Vehicular Environment (WAVE) using IEEE 802.11p when Wi-Fi, using IEEE 802.11a/n/ac, is deployed in the same spectrum. Recently, there have been proposals to share the Dedicated Short Range Communication (DSRC) spectrum between 5.85 - 5.925GHz, the U-NII-4 band, between the two systems. Though both systems are similar in the PHY and MAC, since neither was designed at the outset to coexist with the other, the mutual interference between the two can cause performance degradations, in both throughput and latency. We develop a comprehensive system level coexistence simulation model in ns-3 that allows us to test interference in realistic environments with dense Wi-Fi and WAVE deployments, which are difficult to perform experimentally at scale. Our extensive simulation results show that while adjusting energy detection (ED) thresholds and inter-frame spacing (AIFSN) can improve the throughput performance of 802.11p, the latency performance remains compromised. Furthermore, we show that the performance of 802.11p deteriorates when Wi-Fi employs rate adaptation instead of using a constant rate. These results indicate that delay-sensitive critical safety messages should not be transmitted by WAVE in spectrum that is shared with Wi-Fi even if the latter modifies its ED threshold and AIFSN.