Adaptive Downlink/Uplink Bandwidth Allocation in IEEE 802.16 (WiMAX) Wireless Networks: A Cross-Layer Approach

In this paper, we study adaptive bandwidth allocation for uplink and downlink channels in time division duplex (TDD)-based IEEE 802.16 (WiMAX) wireless networks. In a TDD system, uplink and downlink transmissions share the same frequency at different time intervals. The TDD framing can be adaptive in the sense that the downlink to uplink bandwidth ratio can vary with time. For WiMAX channels, we consider the impact of improper bandwidth ratio on the performance of TCP and propose an adaptive bandwidth allocation scheme (ABAS) which adjusts the bandwidth ratio according to the current traffic profile. Our scheme also cooperates with the scheduler to throttle the TCP source when acknowledgements are infrequent. The performance of our mechanism is validated via ns-2 simulations. The results show that our scheme outperforms static allocation in terms of higher aggregate throughput.