Designing Heterogeneous MAC Protocols for Single-Channel Ad Hoc Wireless Networks

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My research has focused on finding contention-based MAC protocols in single-channel, single radio ad hoc wireless networks. In particular, given the legacy Government of Canada (GofC) networks we study, we have looked at protocols which allow network nodes to use different rules to access the network. ***That we are aware, most protocols give their base service set (BSS) nodes the same rule. This is to ensure fairness-the requirement that all nodes have the same access to the network. For example, under the p-Persistent CSMA protocol, all nodes use the same probability p in the back-off procedure. We term such protocols homogenous protocols. ***So what does it mean for a protocol to have "different rules"? After all, a protocol is a rule. Here is what we mean. Suppose we consider a protocol where we partition the BSS into classes and then give each class a different rule. Our work has shown that such a protocol can be designed to be fair (each node in the BSS has the same expected access) and if the BSS is sufficiently small, it can also increase channel utilization (Hurley and Brimberg (2011)). We term such protocols heterogeneous protocols and we believe that they are a new general class of MAC protocol.***It is important to point out that "heterogeneous protocols" and "hybrid protocols" are not equivalent terms. Generally, protocols have been classified as either contention-based (e.g. CSMA/CA) or contention-free (e.g. TDMA) and a hybrid protocol is one that employs some mixture (e.g. 802.11 [DCF] which uses a RTS/CTS handshake). But within a hybrid protocol, generally all nodes use the same rule and for that reason they are homogenous protocols. In this research, we are examining hybrid protocols that employ heterogeneous rules.**