A Polite Cross-Layer Protocol for Contention-Based Home Power-Line Communications

In typical home power-line communication (PLC) networks using contention-based access methods, providing quality-of-service (QoS) to high-priority users often comes at the expense of reducing the throughput of low-priority users. This paper proposes a cross-layer protocol which involves interaction between the physical (PHY) and the medium-access-control (MAC) layers, for ensuring politeness of the high-priority users toward the low-priority users for uplink transmission in home PLC networks. This protocol modifies the contention-based CSMA protocol of the MAC layer to exploit the cyclostationarity of the noise in home PLC networks. The PLC noise spectrum has been shown in literature to be periodic with the period of AC line cycle. Using this periodicity, the proposed protocol allows longer medium-access times for low-priority users in every AC line cycle, while meeting the high throughput requirements of the high-priority users. The proposed cross-layer protocol, termed opportunistic CSMA, improves the throughput of the low-priority users by as much as 300% compared to the current CSMA protocols in home PLC networks.