TCP-aware bidirectional bandwidth allocation in IEEE 802.16 networks |
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Authors: | Eun-Chan Park Hwangnam Kim |
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Affiliation: | (1) Department of Information and Communications Engineering, Dongguk University-Seoul, Seoul, Korea;(2) School of Electrical Engineering, Korea University, Seoul, Korea |
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Abstract: | 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. |
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