Dynamics of contention free period reservation in IEEE 1901 networks

Power line communications (PLC) technology has become a competitor in the home networking arena. In an inter-networked home, PLC promises to provide an inexpensive, high throughput, and easy-to-install means of extending connectivity to areas of the home or small office that have poor wireless coverage. A key enabling technology within the IEEE 1901 PLC standard is that of the contention free period (CFP). Following a successful reservation, a station allocated to the CFP will not suffer any form of contention-based packet loss. The IEEE 1901 standard presents this as a way of accommodating flows with well-defined delay, jitter and bandwidth requirements. However, to date there has been little research done on the dynamics of the CFP reservation procedure and its scalability. Since the procedure inherently relies on the collision-prone contention access period for reservations, a successful reservation bid is not guaranteed on the first attempt. Our work looks at the resulting delay characteristics of the IEEE 1901 reservation procedure. We present details for 1-persistent and VoIP traffic. Using a simplified simulation model, we give best practice suggestions on operation of the CFP mechanism.