Sum-Capacity of the MIMO Gaussian Many-Access Channel

Providing massive connectivity is one of the key challenges for the next generation of wireless communication networks, and hence the capacity limits of massive connectivity need to be thoroughly studied. The uplink in the regime of massive connectivity is captured by the many-access channel (MnAC) model, assuming the number of users to be extremely large and comparable to the blocklength. This work investigates a generalized MnAC, in which the transmitters and/or the receiver can be equipped with multiple antennas, and the channel gain of each user is allowed to be different. This work characterizes the sum-message-length capacity of the multiple-input and multiple-output Gaussian MnAC in the regime where the number of users increases sub-linearly in the blocklength (i.e., K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> = o(n)).