A Differentiated Distributed Coordination Function (DDCF) MAC Protocol for Cluster-based Wireless Ad Hoc Networks

Wireless Mobile Ad Hoc Networks (MANETs) have been defined as infrastructure-less networks, including mobile and fixed nodes relying on peer-to-peer protocols and management. To support more reliable communications, efficient network management and high resources' utilization, distributed clustering protocols have been considered as a solution to introduce some kind of hierarchy in MANETs by means of dynamic and adaptive virtual infrastructures. In clustering schemes, the different node-roles, and respective management tasks, could take advantage by Medium Access Control (MAC) protocols able to differentiate distributed nodes' accesses. To cope with the system dynamics, the MAC itself is required to exploit existing clustering schemes, and to be adaptive to load and clustering variations, with no static access schemes. In this paper we propose and analyze a possible solution for the mutual support of distributed MAC and clustering schemes, named Differentiated Distributed Coordination Function (DDCF). The DDCF scheme is based on the IEEE 802.11 DCF access scheme, and inspired to the IEEE 802.11e design. Unlike IEEE802.11e, whose focus is to support Quality of Service (QoS) on the prioritized frame-flows basis, the focus of the DDCF is to implement nodes differentiation based on the node roles, which have been assigned by the upper-layer clustering scheme. Extensive, still preliminary, performance evaluation shown that the proposed DDCF access scheme can adaptively exploit the roles of cluster nodes, to support heterogeneous and differentiated MAC access needs