Buffer management for rate-varying 3G wireless links supporting TCP traffic

Radio resource management functions in third generation cellular systems allocate capacity based on both demand and available capacity. A 3G wireless link may therefore be subject to considerable rate variations. These rate variations impose particular challenges on the buffer design. A well performing buffer should secure a high degree of link utilization without introducing excessive buffering delays. Meeting both objectives under highly varying link conditions is not possible with a conventional, fixed-size buffer. In this work, we evaluate a novel active queue management scheme tailored to the specific characteristics of 3G links. The method uses a simple algorithm to achieve favorable interaction with TCP. At the same time, the link state is reflected in the buffer control parameters. Based on an analysis of the pipe capacity of wireless links, we evaluate the required buffer size for different link rates. The analysis is verified using simulations. We show that the proposed method of using adaptive buffer sizes is a feasible approach resulting in adequate performance at different link conditions.