Periodic Contention Free Multiple Access (PCFMA)
A Protocol to Enhance Multimedia Traffic over Power Lines

Applications running over PLC networks draw a lot of interest in the academy and industry, not only because of the convenience (connecting PLC capable devices requires no new wires), but also because all devices have to connect to a power outlet eventually. This technology makes implementing digital home entertainment centers more realistic than ever – HDTVs in different rooms will be able to share digital information from one set top box to another without rewiring, or through wireless access points. MP3 players can access music data through PLC networks from different rooms where different music is played. PLC networks make the concept of the smart home a reality.

However, PLC technology is still in the evolving stage so a lot of issues remain unsolved. The hostile environment of the PLC channel makes reliable data transmission difficult. A lot of research has to be done to ensure that data transmission is correct and efficient.

To accomplish the above mentioned purposes, researchers at the LIST lab have developed a new protocol – Periodic Contention Free Multiple Access (PCFMA). PCFMA is an explicit R-Aloha like protocol specifically designed for the PLC network. In this protocol, we propose a RTS/CTS like scheme in the reservation stage to prevent hidden node problems, and a delayed NACK mechanism to conquer the near-far effect. We also propose a one time reservation scheme to reduce competition in the reservation stage. Performances of the proposed protocol are evaluated by event driven computer simulation and mathematical analysis. The simulation results show that 80Mbps MAC throughput with 100Mbps channel data rate can be obtained from the PCFMA protocol, even if there are hidden nodes in the network.