Cross-layer energy-throughput evaluation of multi-hop/path communication and link adaptation for IEEE 802.11a

Future wireless communication devices are expected to support a wide range of applications, while coping with stringent energy budget requirements. Delivering at each moment in time the required performance with minimal energy consumption is a promising energy management technique to enable pervasive wireless networking. Considering transmission energy only, the use of multiple small hops results in a decrease of the energy consumption. On the other hand, decreasing the transmission rate of a single hop similarly results in a decrease of the energy needed to deliver a bit. In this paper we compare the use of multiple small hops along different paths with a single large hop in the energy-throughput design space. In contrast with earlier work, realistic transceiver models are used, that cover the complete MAC, transmit and receive chain and support different transmission rates. Results show that, compared to single hop link adaptation, the use of multiple hops in indoor environments is only optimal in the energy-throughput space for distances larger than 30 m or when there are obstacles present that can be avoided in alternative paths. For those larger distances, significant gains are possible though. Hence, to achieve energy optimal operation in 802.11a networks, it is important to adapt jointly the physical layer constellation and network layer path selection.