Increasing high data rate coverage in cellular systems using relaying

In a conventional cellular system, base stations (BSs) and mobile stations (MSs) communicate directly. However, in a multihop system, the BS-MS link can be divided into two or more smaller hops by using relays. This can allow the BS to communicate with previously inaccessible MSs and can also improve the quality of existing links. We investigate the improvement in high data rate downlink coverage of a cellular system which can be achieved when randomly positioned MSs are used as relays. Results are given showing the effect of MS density on coverage for both a path loss only channel model, and a channel model which includes both path loss and lognormal shadowing. These demonstrate that, although there are improvements in coverage for both models, the improvements are considerably greater if shadowing is included. In particular, even with low densities of potential relays, considerable increases in coverage are possible. The results therefore suggest that a path loss only channel model can give pessimistic results for coverage.