A New Multi-channel MAC Based On The Low Control Overheads For Ad Hoc Networks

Ad hoc network is wireless self-organizing network with non-central control node,to ensure non-conflict communication for nodes, MAC (Medium Access Control) playsan important role. According to the number of available channels, MAC protocol can bedivided into two types, one is single-channel MAC (SC-MAC), and another ismulti-channel MAC (MC-MAC). For SC-MAC, all the control/data packets are sharingthe same channel, which will result in lots of packets confliction when the network loadis heavy, thus degrades network throughput. In MC-MAC, by dividing the channelbandwidth into multiple sub-channels, multiple nodes can transfer data in parallel ondifferent channels at the same time, which reduces confliction and network delay, thusimproves network throughput. Considering above advantages, more and more scholarsfocus on MC-MAC.Aiming at solving multi-channel hidden terminal problem and control channelbottleneck problem for MC-MAC, after doing research of channel allocationmechanism for channel table-based and non-channel table, two improved MC-MACprotocols are proposed as follows:Firstly, referring to allocation mechanism of non-channel table class, a low controloverhead of MC-MAC protocol-LCO-MAC (Low Control Overheads-MAC,LCO-MAC) is proposed. In the LCO-MAC, each available channel (including thecontrol channel) is corresponded to one slot of the time frame, the node transmits anRTS during the control period to apply for a channel, and then select the channel fordata transmission, which corresponding to the slot when the destination node begins toreply the CTS frame.Then, although LCO-MAC only demands nodes equip with one half-duplextransceiver, there is the listening deafness problem when nodes operating in the datachannel. To solve this problem, an improved LCO-MAC is proposed, it requires nodesto fix two transceivers for nodes receiving control packets correctly in one transceiver,and RES-frame added to provide nodes with updating neighbors’ communication status.Lastly, the simulation results indicate that LCO-MAC protocol is of low control overheads due to the simple and efficient channel allocation algorithmis, and improvesthe network throughput, average packet delay and the ability to solve the controlchannel bottleneck relative to DCA, MMAC, and TSMD-MAC in the case of moreavailable channels; when less channels, although LCO-MAC has little disadvantages inthe throughput and average delay compared to DCA and MMAC, the control overheadsis decreased significantly.