MMSE-Optimal Sequential Processing for Cell-Free Massive MIMO With Radio Stripes

Cell-free massive multiple-input-multiple-output (mMIMO) is an emerging technology for beyond 5G with its promising features such as higher spectral efficiency and superior spatial diversity compared to conventional (MIMO) technology. The main working principle of cell-free mMIMO that many distributed access points (APs) cooperate simultaneously serve all the users within network without creating cell boundaries. This paper considers uplink a system utilizing radio stripe architecture sequential fronthaul between APs. A novel processing algorithm developed, which proved be optimal in both maximum (SE) minimum mean square error (MSE) sense. detailed quantitative analysis requirement or signaling proposed comparison competing sub-optimal algorithms provided. Key conclusions implications are summarized form corollaries. Based on analytical numerical simulation results, we conclude scheme can significantly reduce signaling, compromising communication performance.