The IEEE 802.11 medium-access control (MAC) protocol is usually considered to be a default standard in multihop wireless networks. However, in a multihop network with a large interference range, the request-to-send/clear-to-send (RTS/CTS) handshake and virtual carrier sensing mechanism may not be able to eliminate interference or solve hidden- and exposed-terminal problems. This paper proposes two new MAC protocols, i.e., the power-fixed dual (PFD) and power-aware dual (PAD) busy-tone schemes, both of which are able to effectively prevent collision of data/acknowledgment (ACK) packets and are applicable in various open-space environments with different path-loss characteristics. Analytical models are developed to evaluate their performance in terms of the blocking area, saturation throughput, and capability of mitigating aggregate interference of simultaneous transmissions. Numerical examples are presented to show the effectiveness of the proposed MAC protocols and the interaction between performance metrics and key parameters. Analysis and simulation results indicate that both PFD and PAD schemes can achieve a much higher throughput and a lower packet-collision ratio than IEEE 802.11 distributed coordination function (DCF), conservative CTS reply (CCR), and dual busy-tone multiple-access (DBTMA) schemes.
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