Multihop relay-aided multicast scheduling for cellular wireless networks

Efficient multicasting of critical messages is of essential importance in public safety and commercial multimedia cellular networks. We study the effectiveness of using relay stations to enhance the spectral efficiency of multicast distribution in a mobile wireless networks. Coloring oriented adaptive rate scheduling algorithms are considered, including such that temporally employ TDMA schedules with reuse levels of 1, 3, 4 and 7 over a cellular arrangement. These schemes are used to regulate multicast transmissions executed by base station and (when employed) relay station nodes. We examine the utility of using in each cell single and double levels of placed relay stations. When the latter are employed, 2-hop and 3-hop relaying paths are considered. We also examine a cellular system that has experienced the failure of base stations, and identify the adaptive rate coloring-based scheduling mechanism that should be used when a failover operation is pursued. For both pre-failure and post-failure scenarios, we show that when the inter site distance (ISD), identifying the range between macro base stations, is lower than certain threshold levels, it is most effective to employ schedules that are based on direct (1-hop) multicast transmissions by base stations (BSs) to associated mobile station (MS) clients. In turn, under longer ISD ranges (e.g., as employed in less dense cellular layouts), the spectral efficiency of the system can be significantly enhanced by using a joint scheduling and routing scheme that makes use of multihop relaying.