Wireless four-way relaying using physical layer network coding with nested lattices

Abstract

Two-way relaying in wireless systems has initiated a large research effort during the past few years. In particular, structured codes and lattices are instrumental for achieving high rates when using Physical Layer Network Coding (PLNC). In an attempt to bring the gains of PLNC beyond the classical traffic pattern of two-way relaying, in this paper we consider a scenario with four-way relaying, where each of the two Mobile Stations (MSs) has a two-way connection to the same Base Station (BS), while each connection is through a dedicated Relay Station (RS). The two RSs are in the range of the BS, but they are at antipodal positions within the cell and do not interfere with each other, i. e. achieve a perfect spatial reuse. We introduce communication schemes for serving the four communication flows in two transmission phases. Each phase consists of combined broadcast and multiple access. The main design ingredients are dirty paper coding nested lattice code codes. We compare the performance with a reference scheme that utilizes Decode-and-Forward (DF). The results show that the usage of structured codes in the four-way relaying scenario can significantly increase the achievable rate region.