Energy efficient SQRD processor for LTE-A using a group-sort update scheme

This paper presents an energy-efficient sorted QR-decomposition (SQRD) processor for 3GPP LTE-Advanced (LTE-A) systems. The processor adopts a hybrid decomposition scheme to reduce computational complexity and provides a wide-range of performance-complexity trade-offs. Based on the energy distribution of spatial channels, it switches between the brute-force SQRD and a low-complexity group-sort QR-update strategy, which is proposed in this work to effectively utilize the LTE-A pilot pattern. As a proof of concept, a run-time reconfigurable vector processor is developed to efficiently implement this adaptive-switching QR decomposition algorithm. In a 65 nm CMOS technology, the proposed SQRD processor occupies 0.71mm² core area and has a throughput of up to 100MQRD/s. Compared to the brute-force approach, an energy reduction of 5 ~ 33% is achieved.