Cell-free Massive MIMO in Realistic LoS/NLoS Channel

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In cellular communication systems, it is conventional to assume the absence of any line-of-sight (LoS) path between the users and their associated access nodes (ANs). However, in the context of the recent developments in the direction of distributed large-scale antenna systems, such as the cell-free (CF) massive MIMO systems, such a simplistic assumption becomes questionable in terms of performance analysis. In the CF massive MIMO systems, where the AN density is comparable to the user density, the probability of the existence of an LoS link between any user and its associated ANs is significantly high, and therefore the performance analysis carried out using the conventional extremes of channel modeling (i.e., all NLoS or all LoS channels) may not depict the entire picture. To understand the implications of the random existence of LoS/NLoS channels, we adopt a probabilistic LoS channel model and analyze the uplink performance of a CF massive MIMO system. Here, we first derive the effective channel statistics and argue that their behavior is fundamentally different from that of the conventional rich scattering channels. Utilizing these statistics, we also compare the performance for stream-wise and joint decoding at the CF massive MIMO systems. Following this, we also explore the performance of the centralized MMSE-based data detection in CF massive MIMO systems.

Sudarshan Mukherjee, IIT Guwahati

Dr. Sudarshan Mukherjee received the B.Tech. degree in electronics and communication engineering from the National Institute of Technology, Durgapur (NIT Durgapur), India, in 2011, the M.Tech. degree in electronics and communication engineering from the Indian Institute of Technology Roorkee (IIT Roorkee), India, in 2013, and the Ph.D. degree in electrical engineering from the Indian Institute of Technology Delhi (IIT Delhi), India, in 2017. From 2017 to 2019, he was a Post-Doctoral Researcher with the Department of Information and Communication Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Republic of Korea. Since January 2020, he has been an Assistant Professor with the Electronics and Electrical Engineering Department, Indian Institute of Technology Guwahati (IIT Guwahati), India. His research interests include communication and signal processing using large-scale antenna systems, mobile-edge computing, and ultra-dense networks.