Low-Complexity Radio Frontends and Noncoherent Detection for Massive MIMO

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Multi-user communication systems with a central base station equipped with a very large number of receive antennas, so-called massive MIMO, are attaining more and more attention. The main challenges in such systems are the acquisition of accurate channel state information as well as the effort for realizing such systems, e.g., the distribuation of a high-quality LO-signal to the RF frontends. These problems can be overcome by applying noncoherent transmission schemes in particular, if low-complexity frontends may be used.Consequently, this proposal addresses the design and assessment of multi-user massive MIMO uplink systems. In particular, the interaction between the analog radio frontend and the employed joint detection algorithms has to be studied in detail. New insights, new results, and novel methods are expected, when treating these areas jointly. On the one hand, enhanced noncoherent detection schemes based on subspace methods have to be developed. Since, as preliminary work shows, the influence of the antenna characteristics like pattern is much more pronounced in the noncoherent case compared to the coherent one, this influence has to be assessed in detail. On the other hand, the use of low-linearity/low-complexity (roughly quantizing) receiver frontends has to be studied in the context of massive MIMO. The philosophy of Sigma-Delta conversion, i.e., resolution is exchanged by speed, will be carried over to the situation at hand of spatially sampling the field in the channel. The potential of such a spatial Sigma-Delta sampling approach aiming at enabling low-complexity frontends in a still high-performing scheme will be assessed.