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arXiv · 1611.08660

On the DoF of Two-way $2\times2\times2$ Relay Networks with or without Relay Caching

Mehdi Ashraphijuo·Vaneet Aggarwal·Xiaodong Wang
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Abstract

Two-way relay is potentially an effective approach to spectrum sharing and aggregation by allowing simultaneous bidirectional transmissions between source-destinations pairs. This paper studies the two-way $2\times2\times2$ relay network, a class of four-unicast networks, where there are four source/destination nodes and two relay nodes, with each source sending a message to its destination. We show that without relay caching the total degrees of freedom (DoF) is bounded from above by $8/3$, indicating that bidirectional links do not double the DoF (It is known that the total DoF of one-way $2\times2\times2$ relay network is $2$.). Further, we show that the DoF of $8/3$ is achievable for the two-way $2\times2\times2$ relay network with relay caching. Finally, even though the DoF of this network is no more than $8/3$ for generic channel gains, DoF of $4$ can be achieved for a symmetric configuration of channel gains.

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Mehdi Ashraphijuo, Vaneet Aggarwal, Xiaodong Wang. 2016-11-26. On the DoF of Two-way $2\times2\times2$ Relay Networks with or without Relay Caching. https://doi.org/10.1049/iet-com.2017.0252

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