Multi-Cell Cooperation Using Subcarrier-Cooperative Two-Way Amplify-and-Forward Relaying

We consider two-way communication between multiple MIMO transceiver pairs that is assisted by non-regenerative half-duplex two-way relays. A generalized system model is formulated in which an arbitrary number of multi-antenna relays can make use of symbol extensions in frequency, e.g. OFDM subcarriers. In contrast to conventional approaches, the relays can forward arbitrary linear combinations of their receive symbols in the spatial as well as frequency domain. We apply a closed form zero-forcing approach to orthogonalize the different transceiver pairs and compare simple heuristic power allocation with numerically optimized relay gain allocation schemes. Based on simulation results, we study the advantages of cooperation between subcarriers to improve the sum rate of two-way relaying. Furthermore, we show how such a two-way relaying scheme can beneficially be implemented in a cellular network.