Hybrid channel access with CSMA/CA and SOTDMA to improve the performance of MANET

MANET (Mobile Ad-hoc Network) has great potential applications in emergency communications since it is a flexible and infrastructure-less network. Currently, the radio access technologies supporting Ad-hoc network mainly employ CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance based MAC protocol, which cannot guarantee a prompt channel access for those commanders in emergency communication due to the access collisions. Moreover, although SOTDMA (CSMA and Self-Organized Time Division Multiple Access) is proposed to maintain a stable transmission for MANET, the network throughput rate of SOTDMA is less than CSMA/CA with small nodes. In this paper, according to the network throughput rate, a hybrid channel access strategy is proposed and implemented, which can combine the advantages of CSMA\CA and SOTDMA to maintain high and stable network throughput rate automatically or manually. To further improve the performance of hybrid channel access, a new time synchronization scheme with NMEA data and PPS (Pulse Per Second) is proposed in this paper since clock synchronization is a key factor affecting throughput rate of SOTDMA. Considering the network switching process consuming large energy, the paper presents a new parameter called residual energy number, which considers the energy consumption rate and the energy remaining amount as a parameter of power control to increase the stability of hybrid channel access.