On the DoF of two‐way 2×2×2 relay networks with or without relay caching

• Published in: IET communications Vol. 11; no. 13; pp. 2089 - 2094
• Main Authors: Ashraphijuo, Mehdi, Aggarwal, Vaneet, Wang, Xiaodong
• Format: Journal Article
• Language: English
• Published: The Institution of Engineering and Technology 07.09.2017
• Subjects: bidirectional links; bidirectional transmissions; channel gain symmetric configuration; degrees of freedom; DoF; four‐unicast networks; generic channel gains; radio spectrum management; relay caching; relay networks (telecommunication); source‐destination nodes; source‐destinations pairs; spectrum sharing; two relay nodes; two‐way relay networks
• ISSN: 1751-8628; 1751-8636
• DOI: 10.1049/iet-com.2017.0252

Two‐way relay is potentially an effective approach to spectrum sharing and aggregation by allowing simultaneous bidirectional transmissions between source–destinations pairs. In this study, the two‐way 2×2×2 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, is studied. They 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 2×2×2 relay network is 2). Further, they show that the DoF of 8/3 is achievable for the two‐way 2×2×2 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.