Abstract:

Cell-Free (CF) Massive MIMO (mMIMO) is a technology which can potentially augment not only the deployment of 5G, but also the deployment of "beyond 5G'' (B5G) wireless networks. The basic idea behind this “user-centric” arrangement is that many spatially dispersed access points (APs) coherently serve all nearby devices without being confined by cell boundaries. However, the cost for rolling out such systems, at a macro-level, may be significant. Radio stripes form a promising intermediate solution, which offers the potential of scalability at a reduced price. This paper investigates the uplink scenario of a CF massive MIMO (mMIMO) system, implemented with a limited-capacity radio stripe, which integrates a novel AP arrangement that fully exploits macro-diversity benefits. We also analyze a heuristic compare-and-forward (CnF) strategy, which, by comparing normalized minimum mean square error (N-MMSE) soft estimates, enables optimal dynamic cooperation clustering. Aiming at maximizing the spectral efficiency (SE) of a high percentage of users, we ensure that, under finite capacity constraints, our solution can guarantee better performance than existing radio stripe architectures when size of the system scales.