Automatic rate adaptation

Rate adaptation is a fundamental primitive in wireless networks. Since wireless channel strength varies quickly and unpredictably, senders have to constantly measure the channel and correspondingly adapt the bitrate so that the transmitted packet gets correctly decoded. Prior approaches to this problem can be divided into two classes: those that require constant and expensive feedback from the receiver about channel strength, or those that use coarse and often inaccurate inference based on packet losses to measure channel strength and decide what bitrate to use. In this paper we take the opposite approach. Instead of actively adapting the bitrate based on receiver or packet loss feedback, we present a technique where the sender does no measurement or adaptation, yet the receiver manages to receive packets at a bitrate corresponding to whatever channel conditions exist at that point. The technique works with existing coding and modulation techniques (e.g. convolutional codes in WiFi), and requires no changes to them. Our preliminary evaluation shows that our proposed feedback-free technique achieves a performance that is nearly as good as if the sender knew exactly what the channel strength was in advance.