Uplink Cell Selection for Cooperative Multi-Cell Networks with Hybrid ARQ

In a cooperative multi-cell network we propose to simultaneously demodulate the uplink signal coming from mobile terminals (MTs) with multiple base stations (BSs) for a joint decoding of the data packets. However, limited backhaul capacity and BS demodulation capabilities limits the number of cooperating BSs. In this paper we consider MTs using a hybrid automatic repeat request (HARQ) protocol for error control, as in 3G and 4G cellular systems. In order to limit the exchange of information among BSs we aim at minimizing the number of demodulating BSs at each HARQ retransmission, under a constraint on the outage probability after a pre-set number of retransmissions. A greedy approach is developed for the system using HARQ, which determines at each retransmission which BSs must perform demodulation and share the information in the backhaul. Numerical results compare the performance of the proposed algorithm with existing solutions, showing that backhaul usage can be reduced up to 38% in a usual 3G scenario.