Experimental Evaluation of Application Performance with 802.11 PHY Rate Adaptation Mechanisms in Diverse Environments

We examine the impact of physical layer rate adaptation mechanisms on the performance of real applications over 802.11 wireless links in diverse channel environments. Our evaluations are based on a testbed with real wireless devices equipped with commodity 802.11 hardware and a hardware channel emulator. We consider two different and well-known 802.11 rate adaptation mechanisms (Onoe and SampleRate) and study their performance under several realistic workloads, including multimedia streaming and web browsing. We observe that the application performance with different rate adaptation mechanisms is dependent on the specific tradeoffs these mechanisms make at the link layer in an application-oblivious manner between improving throughput and limiting frame loss. More importantly, their relative performance for a given workload is quite sensitive to the channel quality and environment. These observations highlight the importance of choosing the rate selection strategy adaptively in an application and channel aware manner.