Evaluating Spatial Resolution and Channel Capacity of Sparse Cylindrical Arrays for Massive MIMO

How to design antenna arrays plays an important role in wireless communications, especially when there are hundreds of antennas. In massive multiple-input and multiple-output (MIMO), if the number of antennas and RF chains are increasing, the channel capacity and transmission efficiency could be obviously improved as well. Since in massive MIMO, antennas at the base station (BS) usually scale up greater than 100, the complexity and hardware requirement of the system are also increased. Many studies about massive MIMO are focused on the analysis of channel capacity, precoding, and so on, and very few are about the sparse antenna array deployment. Based on the sparse linear array structures as indicated by previous studies, three new arrays, namely co-prime cylindrical array (CCA), nested cylindrical array (NCA), and sparse nested cylindrical array (SNCA), are proposed, which are based on co-prime linear array, nested linear array, and sparse circular array, respectively. Compared with the traditional uniform cylindrical array (UCA), the proposed arrays vastly reduce the number of antennas used at the BS. In addition, the performance of spatial resolution and channel capacity of CCA, NCA, and SNCA are discussed in detail. The results show that our proposed sparse cylindrical arrays can obtain a higher resolution with much fewer antennas. Besides, the uplink channel capacity of all the three sparse cylindrical arrays is larger than the UCA with the same number of antennas at the BS.