An improved forwarding protocol for updating channel state information in mobile FH wireless networks

The purpose of adaptive forwarding is to provide short-term responses to changes in propagation conditions and network topology in mobile store-and-forward wireless communication networks. The primary need for such short-term responses occurs during the time period between consecutive updates to the routing tables. In this paper a new adaptive-forwarding protocol is described and evaluated for frequency-hop (FH) mobile wireless networks. The forwarding protocol operates in conjunction with adaptive routing and adaptive transmission to provide energy-efficient delivery of packets. Channel state information, which is developed in the receivers of the terminals in the network, is used to estimate the energy requirements of alternative routes for use in the routing protocol. For FH networks the channel state information consists primarily of counts of errors and erasures that are generated in the demodulators and decoders. Since channel state information may become outdated, especially for infrequently used links, it is desirable to provide a mechanism for occasionally testing links that have not handled packets recently. A feature of the new adaptive-transmission protocol is that it employs information packets, rather than control packets, to update the channel state information and thereby benefit the routing protocol without adding overhead traffic to the network load.