Cooperative retransmission in heterogeneous cellular networks

This paper studies spatiotemporal cooperation between base stations in the presence of interference in a heterogeneous cellular network. The focus of the paper is the cooperative retransmission scenario, where a set of randomly located base stations that are selected based on their average received powers, possibly belonging to different network tiers, jointly transmit data in each transmission. If a decoding error occurs in the first transmission, data is cooperatively retransmitted by a possibly different set of BSs, such that the receiver can benefit from spatiotemporal BS cooperation. Using tools from stochastic geometry, the coverage probability at the typical user is characterized as an integral function of the network parameters and the sets of cooperating BSs. An integral expression for the coverage probability is also derived for the case when the typical user is able to perform maximum ratio combining (MRC) of the received copies in two transmissions. Numerical evaluation shows that in the high coverage regime spatiotemporal cooperation outperforms joint transmission with no retransmissions and that the gains extend to all regimes if the user has MRC capability.