TCP-ACK triggered bandwidth request in mobile WiMAX/WiBro (IEEE 802.16e) networks

Abstract

In IEEE 802.16 networks, the bandwidth request-grant process introduced by this standard is required whenever a Subscriber Station (SS) has data packets to transmit in the uplink. Since IEEE 802.16 standard is an IP-based network, Transmission Control Protocol (TCP) is the most widely used protocol within it for a reliable data transmission. The robustness of TCP is the primary reason of its widespread usage in a wide variety of networking environments, especially asymmetric networks such as Mobile WiMAX/WiBro network. However, many researchers [1], [2], [3] have shown that the network asymmetry affects the performance of TCP because TCP protocol relies on feedback in the form of acknowledgments from the receiver to ensure reliability. In addition, the aforementioned bandwidth request-grant mechanism is not optimized for TCP protocol, since the uplink data packets stream can be disrupted due to the several stages of the process which introduces transmission delay and overheads of TCP data packets [4]. In this thesis, we propose a new mechanism, called TCP-ACK Triggered Bandwidth Request, for uplink TCP data transmission, where the Base Station (BS) can predict in advance TCP data packets, based on downlink TCP-ACK packets, and allocate the uplink bandwidth for the next TCP data transmission without using the original bandwidth request-grant process. The simulation results with NS-2 showed that the proposed scheme increases significantly the uplink throughput and reduces the transmission delay of TCP data packets.