LTE baseband DSP/FPGA for beamspace MIMO RF antenna

Abstract

As the MIMO processing gets popular in LTE wireless mobile communication, the number of RF chains of eNodeB for MIMO processing gets increased, which results in the increase of cost and the volume of eNodeB base-station. In order to solve this problem, the Beamspace MIMO RF Antenna has been proposed. The advantage of Beam-space MIMO RF Antenna is to reduce the RF chain which results in the cost reduction of LTE RF module. In order to support Beam-space MIMO RF Antenna, the LTE baseband signal from LTE modem should be transformed. This transformation includes the matrix and trigonometric computation which is complex to be performed by FPGA. From this observation, authors have implemented baseband algorithm in DSP processor which enables the complex matrix computation efficiently. The requirement of DSP processing is 300 Mbps in 33MHz band which supports 4 streams. While DSP processor is very efficient for the matrix computation, there should be interface module between baseband DSP and the impedance loading module for Beam-space MIMO RF Antenna. Authors have implemented this interface module with FPGA. The interface between DSP processor and FPGA has been implemented PCIe (PCI Express) to support high-speed serial IO. The integration system has been designed with LTE modem that supports 4×4 MIMO. The testing of full integration system consists of baseband DSP, FPGA, LTE modem and Beam-space MIMO RF Antenna module. Various spectrum analyzers have been used to validate the design of Beamspace MIMO RF baseband system during the test procedure.