Generation of fixed-point VHDL MIMO-OFDM QR pre-processor for Spherical Detectors

This paper presents an automatic VHDL generator for a modified fixed-point interpolation QR decomposition algorithm for Spherical Detector (SD) based Multiple-Input Multiple-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) systems. A modified algorithm is proposed that moves the bulk of the complex domain calculations to the real domain, by leveraging Givens rotations requiring only additions, multiplications, and inverse square root operations. An efficient inverse square root algorithm is presented along with fixed-point analysis of a typical MIMO-OFDM system in various noisy wireless channels. Autogeneration of VHDL modules is described with results of 2 × 2 and 4 × 4 QR-based SD MIMO detection in terms of FPGA slice registers and slice LUTs.