A CSMA/CA-Based Media Access Protocol Using the Registered Backoff Time Vector (RBTv) Mechanism for M2M Communications

Abstract

This paper proposes an enhanced IEEE 802.11 CSMA/CA media access scheme designated as CSMA/CA-RBTv, in which RBT denotes the Registered Backoff Time and v denotes vector for Machine-to-Machine (M2M) communication. In the proposed CSMA/CA-RBTv, when a mobile node transmits data to the AP, it attaches a random number called the RBT, which denotes the next time slot the mobile node would like to transmit its next data packet, to the packet. Once the AP receives the packet, it extracts the RBT and adds it to a Registered-Time-Slot-List (RTSL) used to conduct channel access scheduling. Before transmitting the ACK packet to the mobile node, the AP (1) selects the node with the smallest RBT from the RTSL list as the next one to access the wireless channel and (2) uses RTSL to make a bit vector marking which time slots have been registered for data transmission, i.e., channel access. Then, the AP appends the aforementioned two pieces of channel access information to the ACK packet. Since the ACK packet is transmitted in a broadcast manner, all of the mobile nodes which overhear the transmission know which node has the next right to access the channel and which time slots are still available for channel access. Consequently, the occurrence of collisions can be reduced, which also results in decreasing power consuming. The simulation results show that CSMA/CA-RBTv has significant improvement in both transmission performance and energy efficiency of the M2M network as the number of mobile nodes increases.