Data Link Layer Protocol for a Powerline Local Area Network

The inhospitable powerline environment necessitates data link layer protocols capable of dealing with harsh transients. This paper outlines suitable protocols for the logical link and media access control sublayers. We propose a token bus mechanism for contention, and a hybrid Automatic Repeat reQuest (ARQ) system for error control. The performance of the protocol is evaluated using an Additive White Gaussian Noise (AWGN) channel. Introduction With the advent of multimedia technology, bandwidth has become a sought after resource. Channels previously disregarded as sources of bandwidth due to their poor conditions, are now looked on as potentially favourable. One such candidate is the powerline channel. The powerline environment, however, is associated with various types of interference [l], such as Gaussian, white and impulsive noise. These conditions pose a challenge in the use of the powerline channel as a media for high datarate transfer. Existing protocols for high data-rate transfer can only be used with 'noise-fiee' media. They are not resilient enough to cope with the sources of error associated with the powerline. For such applications, these protocols need to be modified, or new ones adopted to account for the noisy conditions. This paper introduces a unique protocol that caters for long distance, low power digital powerline communications. This protocol offers a media contention mechanism and an error control scheme to .' deal with the problems encountered. Previous investigations by Coffey et a1 [2] have shown that the concept of a token bus network can be applied to the powerline environment. This paper incorporates a hybrid ARQ scheme with the token passing mechanism. Figure 1 shows how the data link layer is subdivided into two sublayers; Logical Link Control (LLC) and Media Access Control (MAC). The LLC sublayer provides error control and flow control techniques and the MAC sublayer provides a suitable media contention technique. Figure 1: Data Link Layer of the OSI Model used for Powerline Protocol