Inter-cell relay cooperation in heterogeneous cellular uplink systems

Consider a multi-cell relay-assisted time-division uplink system, i.e. one active user per time slot per cell with a relay serving that user. In this paper, we are concerned with heterogeneous networks (networks with unbalanced spatial loads) and we are interested in techniques for increasing the data rate in a congested cell. We propose inter-cell relay cooperation with single-cell decoding as one such solution. In this technique, relays of different cells cooperate to determine optimum precoding weights, but the base stations do not communicate. We compare this strategy to another technique of current interest: base station cooperation through multi-cell decoding, where each cell has a single relay that amplifies and forwards the desired transmission to the base station, and all the base stations cooperatively decode the signals received at each. There will be distinct architectural and implementation consequences for each approach, and inter-cell relay cooperation with single-cell decoding may require less overhead and expense than base station cooperation through multi-cell decoding. Despite this, we see that in some likely channel and interference scenarios, the former actually outperforms the latter. The key contribution of this paper is to propose inter-cell relay cooperation as a promising technology for increasing data rates in heterogeneous cellular uplink networks.