  Cell-free Massive MIMO (mMIMO) is envisaged to be a next-generation
technology beyond 5G with its high spectral efficiency and superior spatial
diversity as compared to that of conventional MIMO technology. The main
principle is that many distributed access points (APs) cooperate to
simultaneously serve all the users within the network without creating cell
boundaries. This paper considers the uplink of a cell-free mMIMO system
utilizing the radio stripe network architecture. We propose a novel sequential
processing algorithm with normalized linear minimum mean square error (N-LMMSE)
combining at every. This algorithm enables interference suppression in
cell-free MMO while keeping the cost and front-haul requirements low. The
spectral efficiency of the proposed algorithm is computed and analyzed. We
conclude that it provides an attractive trade-off between low front-haul
requirements and high spectral efficiency.
