Coverage enhancement through two-hop relaying in cellular radio systems

Digital relaying is a technique that uses certain mobile terminals that have good communication links with the base station to act as relay nodes for those that do not have. With this technique, the signal quality at the destination is expected to improve since the signal only goes through favorable links and, at each intermediate node, the signal is decoded and re-encoded (so that no noise is propagated) before forwarding. One of the major costs of relaying is that additional channels are needed. We investigated the effect of using different schemes for selecting channels - among those already used in the adjacent cells - for relaying on performance improvement. Our simulation results show that not only can relaying improve the performance; but also, with power control this improvement is quite insensitive to the channel selection scheme. Furthermore, with small cell radii where there is a potential for high interference level, only a low relay node transmit power is sufficient to improve the system performance significantly.