A link adaptation algorithm for IEEE 802.16

Broadband wireless access (BWA) is a promising emerging technology. The IEEE 802.16 task group recently standardized the physical (PHY) and medium access control (MAC) layers for BWA systems. To operate in a wide range of physical channel conditions, the standard defines a robust and flexible PHY. A wide range of modulation and coding schemes are defined. While the standard provides a framework for implementing link adaptation, it does not define how exactly adaptation algorithms should be developed. The paper evaluates the performance of IEEE 802.16 using a few typical PHY burst profiles defined in the standard. Based on these performance results, TCP delay is identified as a suitable metric to serve as the link quality indicator. A simple link adaptation algorithm is developed to minimize the end-to-end (ETE) TCP delay based on the measured signal-to-noise ratio (SNR). The effects of TCP performance enhancements, namely dynamic window scaling and selective acknowledgements, on the adaptation algorithm are also studied.