Non-coherent hierarchical cooperation

Abstract

Hierarchical cooperation is a communication strategy introduced recently byÖzgür et al., where it was shown to significantly outperform standard multi-hop communication in some wireless scenarios. To achieve this gain over multi-hop communication, full availability of channel state information at all the nodes in the network is required. In this paper, we investigate the impact of absence of channel state information on the performance of hierarchical cooperation. If the product of coherence time and coherence bandwidth of the wireless channel is on the order of the number of nodes in the network, we show that non-coherent hierarchical cooperation achieves the same order rate as the coherent version. If the product is smaller than the number of nodes, we show that non-coherent hierarchical cooperation can still yield sizable gains over multihop communication, but may not achieve the same order rate as the coherent version.

Generalized Degrees of Freedom of Noncoherent Diamond Networks

“…3) We demonstrate the tradeoff between network learning and utilization, by showing that there are certain regimes 5 where a simple relay selection is gDoF-optimal and that there are other regimes where we need both the relays. Even in the regimes where both the relays are used, we do not necessarily learn the channel values, as seen in the TS-QMF scheme.…”

“…Exceptions include[4],[5],[6] 2. Throughout this paper, we assume that the net channel strength includes the transmit power absorbed in it and the noise at receivers are of unit variance.…”