Modeling TCP throughput: a simple model and its empirical validation
Proceedings of the ACM SIGCOMM '98 conference on Applications, technologies, architectures, and protocols for computer communication
Radio Propagation in Cellular Networks
Radio Propagation in Cellular Networks
DCF+: an enhancement for reliable transport protocol over WLAN
Journal of Computer Science and Technology
Ensuring the QoS requirements in 802.16 scheduling
Proceedings of the 9th ACM international symposium on Modeling analysis and simulation of wireless and mobile systems
Quality of service support in IEEE 802.16 networks
IEEE Network: The Magazine of Global Internetworking
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In this paper, we propose a bidirectional bandwidth-allocation mechanism to improve TCP performance in the IEEE 802.16 broadband wireless access networks. By coupling the bandwidth allocation for uplink and downlink connections, the proposed mechanism increases the throughput of the downlink TCP flow and it enhances the efficiency of uplink bandwidth allocation for the TCP acknowledgment (ACK). According to the IEEE 802.16 standard, when serving a downlink TCP flow, the transmission of the uplink ACK, which is performed over a separate unidirectional connection, incurs additional bandwidth-request/allocation delay. Thus, it increases the round trip time of the downlink TCP flow and results in the decrease of throughput accordingly. First, we derive an analytical model to investigate the effect of the uplink bandwidth-request/allocation delay on the downlink TCP throughput. Second, we propose a simple, yet effective, bidirectional bandwidth-allocation scheme that combines proactive bandwidth allocation with piggyback bandwidth request. The proposed scheme reduces unnecessary bandwidth-request delay and the relevant signaling overhead due to proactive allocation; meanwhile, it maintains high efficiency of uplink bandwidth usage by using piggyback request. Moreover, our proposed scheme is quite simple and practical; it can be simply implemented in the base station without requiring any modification in the subscriber stations or resorting to any cross-layer signaling mechanisms. The simulation results ascertain that the proposed approach significantly increases the downlink TCP throughput and the uplink bandwidth efficiency.