The objective of this project is to investigate massive multiple-input multiple-output (MIMO) coding and signal processing techniques for massive machine-type communications, which is an important scenario in the emerging 5G wireless systems. Key features of the massive machine-type communication system include the massive device connectivity and the sporadic device activity pattern. The massive MIMO technique is well suited for accommodating a large number of devices and maintaining a constant level of energy efficiency that is independent of the number of devices. In addition to the potential technical impacts, the investigators plan to incorporate the research into graduate and undergraduate curricula and to also develop summer projects to facilitate K-12 outreach.
This project considers the uplink of a massive machine-type communication system consisting of a base station equipped with a large number of antennas, as well as a large number of potential device nodes, out of which a fraction are active at any given time. On the transmitter side, to address the shortage of orthogonal pilot sequences when the number of devices is large, multi-base codes will be designed that contain a large number of orthogonal subsets of vectors. To address the high-complexity of device activity detection when the number of nodes is large, pilot sequences based on various codes and Grassmannian modulation constellations will be designed that can be decoded efficiently with complexity independent of the number of nodes. On the receiver side, joint device activity detection and channel estimation will be developed by exploiting the sparsity in both device activity and the channel structures. Moreover, when the base station employs a smaller number of radio frequency chains compared with the antenna size, matrix or tensor completion techniques will be developed for channel estimation or data decoding in the presence of missing data, by exploiting the low-rank property of the received signals.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
