A new achievable sum DoF result in multi-user half-duplex relay networks

This paper investigates the achievable sum degrees of freedom (DoF) in a wireless single-antenna multi-user relay network, which consists of multiple sources, multiple destinations, and multiple layers of half-duplex relays in between. A cluster successive relaying (CSR) transmission scheme is applied to efficiently deliver information in this network. Different from existing works on the CSR scheme which normally divide each layer of relays into two alternatively activated equal-size clusters, we allow the clusters to contain different numbers of terminals in order to properly involve all available relays into the transmission process. Using the channel-extension based interference alignment technique, it is shown that the asymptotically achievable sum DoF can be larger than the previously known results and hence can serve as a new lower bound to the optimally achievable sum DoF in the considered relay network.