Advanced carrier sensing to resolve local channel congestion
VANET '11 Proceedings of the Eighth ACM international workshop on Vehicular inter-networking
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Recently, tuning the physical carrier sensing threshold (CSth) has been proposed as an efficient mechanism to enhance the network throughput in an IEEE 802.11-based multihop ad hoc networks. The physical carrier sensing method reduces the likelihood of collision by preventing nodes in the vicinity of each other from transmitting simultaneously, while allowing nodes that are separated by a safe margin to engage in concurrent transmission. In this paper, we propose a distributed adaptive scheme through which nodes dynamically adjust their CSth to eliminate the likelihood of collisions from hidden terminals and in turn enhances spatial reuse by reducing the number of exposed terminals. Specifically, a node adjusts its CSth based on both its success/ failure history attempts and the information it receives from neighboring nodes through CTS packets. Moreover, to reduce the effect of exposed terminals, the proposed scheme employs the RTS/CTS exchange only for the purpose of informing neighboring nodes of their CSth but not to silence them. The proposed scheme adaptively performs a dynamic switch between the RTS/CTS access scheme and the basic scheme based on a predefined policy in order to avoid the additional overhead caused by the RTS/CTS exchange. Simulations results have demonstrated the significant throughput gains that can be achieved by the proposed scheme, compared with other methods in recent literature.