Massive MIMO relaying with imperfect RF chains and coarse ADC/DAC in beyond 5G networks

Abstract

AbstractMassive connectivity, low cost, and energy saving are key requirements in providing Internet of Things (IoT) services in the beyond 5G (B5G) communication networks. Motivated by these requirements, we investigate a massive multiple‐input multiple‐output (MIMO) relaying system with imperfect radio frequency (RF) chains and coarse analog‐to‐digital converters/digital‐to‐analog converters (ADCs/DACs), where IoT user pairs communicate through the assistance of a relay equipped with transceiver antennas in quantity. First, the accurate and the approximate achievable rate expressions are derived in closed form. Then, we evaluate the impacts of critical design parameters on the rate performance. Moreover, scaling laws for transmit powers and RF hardware impairments are established when the number of antennas, M, at the relay grows infinity. It is revealed that, as M increases, the system can yield a non‐vanishing rate while cutting down the transmit powers of the IoT devices and relay, and/or scaling up the RF impairments of the relay. The power allocation scheme for maximizing the sum rate is proposed. Numerical results are conducted to demonstrate the analysis and show that, in the large scale antennas regime, employing high‐quality RF hardware at the IoT users and high‐resolution DACs at the transmit end of the relay can significantly improve the system's sum rate.