A practical approach to rate adaptation for multi-antenna systems

Multi-antenna systems can provide greater throughput and range coverage than traditional single antenna systems. A key aspect of exploiting this new physical layer (PHY) is rate adaptation, which consists of finding the best rate for sending data packets. Unlike rate adaptation in single antenna systems, nodes have many choices apart from adapting different modulation types, and these choices include using spatial multiplexing or transmit diversity, types of guard intervals, and channel width. We present an evaluation and implementation of a new rate adaptation scheme for multi-antenna systems applicable to off-the-shelf wireless cards. Our rate adaptation scheme, rate adaptation for multi-antenna systems (RAMAS), is simple and practical, and eliminates the complexity of the rate adaptation approaches proposed for IEEE 802.11n in the recent past. Extensive experimental evaluation is used to show that RAMAS performs consistently better than many current IEEE 802.11n rate adaptation schemes with much less complexity, and that RAMAS is especially efficient in multi-user and interference-laden environments.