为解决水下无线传感器网络中由于水声信号传播的时-空不确定性引起的空间公平性问题,并有效实现多信道通信,提出了一种基于单收发器的水下多信道MAC协议,即SFM-MAC. 该协议利用水下定位信息进行时空信息转换,避免全网同步;通过RTS/CA/CL/CTS握手机制避免多信道隐蔽终端问题,并实现公平接入. 采用马尔科夫链构建了控制信道的预约模型,理论分析并计算了考虑预约碰撞条件下的多信道MAC协议的理论吞吐量. 仿真实验表明:SFM-MAC的网络公平性指数较传统RTS/CTS类协议提高15%;在2个业务场景下,网络有效吞吐量较单信道水下MAC协议SFAMA和多信道水下MAC协议UMMAC分别提高60%~70%及12%~15%,证明SFM-MAC可以有效提高网络公平性与网络吞吐量.%This paper proposes a multi-channel medium access control ( MAC) protocol named SFM-MAC to tackle the spatial fairness problem that results from the spatial-temporal uncertainty in underwater sensor networks ( UWSNs) and to realize multi-channel communication. SFM-MAC enables hosts to utilize multiple channels via on-ly one transducer. The proposed protocol, combining with the location information, fairly accesses channels and a-voids the multi-channel hidden terminal problem by a RTS/CA/CL/CTS handshaking scheme. The Markov chain was used to build the reservation model of the control channel, and the theoretical throughput of the multi-channel MAC protocol under the reservation collision condition was analyzed and computed. The simulation results show that comparing with the traditional RTS/CTS protocol, SFM-MAC achieves a better fairness index that increases by 15%. Additionally, the results showed that SFM-MAC outperforms slotted FAMA and UMMAC in terms of network throughput by 60%~70% and 12%~15% in two representative network scenarios, respectively, proving that SFM-MAC can effectively improve network fairness and throughput.
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