Multi-channel Mac Protocol For Wireless Sensor Networks

With the development of microelectronic technologies, communication technologies and embedded technologies, wireless sensor networks (WSNs) have been extensively applied and studied in the recent decade. In this thesis, we study into the multi-channel MAC protocol for WSNs. The main contributions of this thesis are as follows.1. Aiming at triple hidden terminal problems in wireless sensor networks, this paper proposed an adaptive duty cycle based multi-channel MAC protocol, called MCR. MCR efficiently handled triple hidden terminal problems with multiple channel reservation. By minimizing the lower bound of average times of channel switching in MCR, this paper obtained the optimal duty cycle in theoretical analysis. To investigate values of multiple channel reservation and dynamic duty cycling in MCR, extensive simulation and real testbed experiments were conducted. The results show that compared with other protocols, when the number of channels is larger or loads are heavy, M-cube improves throughput and energy efficiency significantly.2. In order to solve the problems of multi-channel MAC protocols which require time synchronization and lots orthogonal channels;exist large number of multi-channel hidden terminals and loss of single-hop multi-channel broadcast data, this paper proposes a competition based multi-channel MAC protocol HM-MAC, which works without time synchronization, uses few orthogonal channels and takes advantage of handshake mechanism to reduce the number of multi-channel hidden terminals. Meanwhile, probability based sender Adjustment mechanism reduces the loss of data and improves broadcasting efficiency. By theoretical analysis of the unicast mode, this paper obtains the number of used channel, the number of multi-channel hidden terminals and broadcasting efficiency. The experimental results show that HM-MAC uses less orthogonal channels, reduces the number of multi-channel hidden terminals effectively, and improves broadcasting efficiency and network throughput significantly.3. To tackle control channel saturation and triple hidden terminal problems, this paper proposes RIM, a receiver-initiated multi-channel MAC protocol with duty cycling for WSNs. By adopting a receiver-initiated transmission scheme and probability-based random channel selection, RIM effectively alleviates, if not completely eliminates, control channel saturation and triple hidden terminal problems. In addition, RIM exploits a simple but reliable asynchronous broadcast scheme to solve the problem of broadcast data loss with reliability guarantees for broadcast-intensive applications. More importantly, RIM is fully distributed with no requirements of time synchronization or multi-radio. Therefore, RIM is very easy to be implemented in resource-constrained sensor nodes. Via the theoretical analysis, the optimal duty cycle are obtained, respectively. The simulation and real testbed experimental results show that RIM achieves significant improvement in energy efficiency with increasing benefit when the number of channels and traffic loads increase, while maintaining higher throughput. Moreover, RIM exhibits a prominent ability to enhance its broadcast reliability.