Energy Efficient Group-Sort QRD Processor With On-Line Update for MIMO Channel Pre-Processing

This paper presents a Sorted QR-Decomposition (SQRD) processor for 3GPP LTE-A system. It achieves energy-efficiency by co-optimizing techniques, such as heterogeneous processing, reconfigurable architecture, and dual-supply voltage operation. At algorithm level, a low-complexity hybrid decomposition scheme is adopted, which switches, depending on the energy distribution of spatial channels, between the traditional brute-force SQRD and a proposed group-sort QR-update strategy. A reconfigurable vector processor is accordingly developed to support the adaptive processing with high hardware efficiency. Furthermore, on-chip power management technique is also integrated to obtain real-time power-saving by adapting the voltage supply based on the instantaneous workload. As a proof-of-concept, we implemented the processor using a 65 nm CMOS technology and conducted post-layout simulation. The proposed SQRD processor occupies 0.71 mm² core area and has a throughput of up to 69 MQRD/s. Compared to the brute-force approach, an energy reduction of 10 ~ 61.8% is achieved.