Precoder Implementation and Optimization in 5G NR Massive MIMO Radio

The evolution of 5G New Radio (NR) has brought significant improvements in signal strength and service quality for users. By the integration of Multiple Input Multiple Output(MIMO) systems in communications, multiple data streams can be transmitted simultaneously across multiple antennas. Additionally, the incorporation of precoding in MIMO systems enables enhanced data rates and spectral efficiency. In the case of wireless networks, precoders are used to steer high-gain beams that are intended for specific users. The paper focuses on the implementation of 16, 32 and 64 channel linear precoders in the Remote Radio Head (RRH) of the indigenously developed 5G testbed at IIT Madras. These precoders have a memory module which stores the channel matrices and a multiplier module which performs matrix multiplications between the channel matrices and user data within a slot duration of 500 microseconds. The system demonstrates DSP utilization levels of 9.75%, 19.5%, and 39% for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(16 \times 8), (32\times 8)$</tex>, and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(64 \mathrm{x}8)$</tex> antenna-layer configurations respectively, while maintaining the BRAM (Block RAM) usage within 2.28%, 3.91 %, and 7.16%. Additionally, a throughput of 1.2 Gbps with four active layers highlights the system's optimized performance under hardware constraints.