Making wireless networks MORAL

Wireless networks which support multiple modulation techniques and data rates suffer from the so-called multi-rate anomaly problem resulting in unfair environments; in which all the users, regardless of their data rate choices, observe the same, low throughput values. This situation violates the baseline fairness principle which states that the desired throughput of a node competing against any nodes running at different speeds is equal to the throughput that the node would achieve in an existing single-rate network in which all the competing nodes were running at its own rate. In our work presented here, we propose a novel algorithm which utilizes the retry limit parameter of the CSMA/CA algorithm in order to differentiate different data rate user groups. Our algorithm, MORAL (Multiuser data Rate Adjustment Algorithm), dynamically adjusts the retry limits of the users according to the channel characteristics observed and the neighbor information gathered from previous communications. MORAL chooses the most appropriate retry limit to use in order to establish a more baseline-fair environment.