Channel Hopping Multiple Access with Packet Trains for Ad Hoc Networks

We present a new medium-access control protocol for ad hoc networks that does not require carrier sensing or the preassignment of unique codes to nodes to ensure that intended receivers receive unicast, or multicast, or broadcast data packets without interference from hidden sources. We call this new protocol channel hopping access with trains (CHAT). CHAT combines the notion of packet trains with synchronous channel hopping to improve channel utilization. We compare CHAT against two of the most efficient protocols proposed to date based on the preassignment of codes (MACA-CT), or channel hopping with no predefined code assignment (CHMA) via simulations. The results show that CHAT provides considerable improvement in the throughput of an ad hoc network for unicast traffic, broadcast traffic and mixed traffic consisting of both unicast and broadcast transmissions. CHAT is applicable to ad hoc networks based on commercial offthe-shelf spread spectrum radios operating in unlicensed frequency bands. Keywords— Medium Access Protocols, ad-hoc networks, packet train, multichannel radio, frequency hopping spread spectrum