Abstract
It is well known that transmission control protocol (TCP) performance degrades severely in IEEE 802.11-based wireless ad hoc networks. We first identify two critical issues leading to the TCP performance degradation: (1) unreliable broadcast, since broadcast frames are transmitted without the request-to-send and clear-to-send (RTS/CTS) dialog and Data/ACK handshake, so they are vulnerable to the hidden terminal problem; and (2) false link failure which occurs when a node cannot successfully transmit data temporarily due to medium contention. We then propose a scheme to use a narrow-bandwidth, out-of-band busy tone channel to make reservation for broadcast and link error detection frames only. The proposed scheme is simple and power efficient, because only the sender needs to transmit two short messages in the busy tone channel before sending broadcast or link error detection frames in the data channel. Analytical results show that the proposed scheme can dramatically reduce the collision probability of broadcast and link error detection frames. Extensive simulations with different network topologies further demonstrate that the proposed scheme can improve TCP throughput by 23% to 150%, depending on user mobility, and effectively enhance both short-term and long-term fairness among coexisting TCP flows in multihop wireless ad hoc networks.
Highlights
It is well known that transmission control protocol (TCP) performance degrades significantly in IEEE 802.11-based multihop wireless ad hoc networks [1,2,3,4,5] due to the TCP instability problem and the unfairness problem
Extensive simulation results with different network topologies demonstrate that the proposed scheme can improve TCP throughput by 23% to 150%, for both high-mobility and low-mobility cases, and enhance both short-term and longterm fairness among coexisting TCP flows in multihop wireless ad hoc networks
In the IEEE 802.11 standard, a wireless ad hoc network is defined as an independent basic service set (IBSS) deploying the distributed-coordination-function-(DCF-) based carrier sense multiple access with collision avoidance (CSMA/CA) medium access mechanism
Summary
It is well known that TCP performance degrades significantly in IEEE 802.11-based multihop wireless ad hoc networks [1,2,3,4,5] due to the TCP instability problem and the unfairness problem. A dual busy tone scheme was proposed in [7], which uses two busy tone channels together with the RTS/CTS scheme to solve the hidden terminal and exposed terminal problems for unicast transmissions This scheme requires both the sender and the receiver transmitting in two busy tone channels to protect RTS and data packets, and it is not suitable to protect the broadcast frame and the link error detection frame. We propose a busy tone assisted broadcast and link error detection scheme with low overhead and good energyefficiency, where only the sender needs to transmit two short messages in the busy tone channel before sending broadcast or link error detection frames in the data channel.
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