Coherent Multiuser Relaying with Partial Relay Cooperation


Armin Wittneben


IEEE Wireless Communication and Networking Conference, Las Vegas, NV, USA, Apr. 2006.

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We consider a heterogeneous wireless ad hoc network. All nodes are within radio range and may employ an arbitrary number of antennas. Our goal is to achieve a distributed spatial multiplexing gain in this scenario without introducing additional delay. To this end we let 2N of the nodes form N source/destination pairs, that concurrently communicate on the same physical channel. Other nodes in the network act as coherent amplify&forward relays. We use relaying to minimize the cochannel interference between different links (coherent multiuser relaying) and to achieve diversity. Some of the relays may be able to exchange received signal information e.g. by utilizing a suitable short range wireless technology such as Bluetooth (partial cooperation). The main contributions of this paper are (i) a unified derivation of coherent multiuser relaying with an arbitrary number of relays and an arbitrary cooperation pattern and (ii) a novel block zero forcing relay gain allocation for this setting. The derivation naturally includes any combination of multi-antenna (MIMO) nodes. The gain allocation is based on a subspace approach and the complexity is essentially independent of the number of relays. Performance results show, that it achieves the full spatial multiplexing gain N. If the number of relays and/or cooperations exceeds a minimum value, we additionally obtain a distributed diversity gain and array gain for each source/destination link.


relay; gain allocation; spatial multiplexing; diversity; ad hoc network

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