Bidirectional Bandwidth Allocation for TCP Performance Enhancement in Mobile WiMAX Networks

We propose a virtual bidirectional connection for efficient bandwidth allocation to downlink TCP data and uplink acknowledgment (ACK) in mobile WiMAX networks based on IEEE 802.16. We observed that, in serving a downlink TCP flow, the standard bandwidth-request/allocation mechanism inevitably results in additional delay to transmit uplink TCP ACK, which increases round trip time of downlink TCP flow and decreases its throughput accordingly. To resolve this problem, we propose a hybrid approach combining proactive bandwidth allocation with piggyback bandwidth request. The proposed framework removes the unnecessary bandwidth-request delay, and also decreases signaling overhead involved in the bandwidth-request. Simulation results show that this approach significantly increases downlink TCP throughput and uplink bandwidth efficiency.