OFDM-MAC algorithms and their impact on TCP performance in next generation mobile networks

With the increasing adoption of wireless technology, it is reasonable to expect an increase in the demand for supporting both real-time multimedia and high rate reliable data services. Next generation wireless systems employ Orthogonal Frequency Division Multiplexing (OFDM) based physical layer owing to the high data rate transmissions that are possible without increase in bandwidth. Towards improving the performance of these systems, we look at the design of resource allocation algorithms at medium-access layer, and their impact on higher layers. While TCP performance has been extensively studied for interaction with link layer ARQ, little attention has been given to the interaction of TCP with MAC layer. In this work, we explore cross-layer interactions in an OFDM based wireless system, specifically focusing on channel-aware resource allocation strategies at the MAC layer and its impact on TCP congestion control. Both efficiency and fairness oriented MAC resource allocation strategies were designed for evaluating the performance of TCP. The former schemes try to exploit the channel diversity to maximize the system throughput, while the latter schemes try to provide a fair resource allocation over sufficiently long time duration. First, we evaluate the resource allocation schemes from a TCP goodput standpoint and show that the class of MAC algorithms that incorporate a fairness metric and consider the backlog outperform the channel diversity exploiting schemes. Second, we introduce a cross layer strategy of using congestion window instead of the backlog at the base-station resource scheduler. We compare the schemes previously designed with and