Effect of Pilot Overhead on Spectral Efficiency in Massive MIMO V2I Networks

Massive multiple-input multiple-output (MIMO) networks are considered to be one of the key technologies of next-generation wireless communication systems because of their ultra-high spectral efficiency (SE), and are expected to be used in machine-type communication fields that require large throughput, such as vehicle-to-infrastructure (V2I) communication. The prerequisite for achieving the claimed performance of massive MIMO is to obtain accurate channel state information. A common approach is to use mutually orthogonal uplink pilots to estimate the channel, thereby reducing pilot contamination. However, in a V2I network, when a large number of vehicle users appear, orthogonal pilots often bring greater pilot overhead and reduce system performance. Based on the highway scenario, this paper simulates the influence of pilot overhead on network SE under different uplink combining strategies. Our numerical results reveal the relationship between the SE metric and the major performance-impacting parameters, which has a certain guidance for designing massive MIMO V2I networks.