LARGE MIMO DETECTION SCHEMES BASED ON CHANNEL PUNCTURING: PERFORMANCE AND COMPLEXITY ANALYSIS

Abstract

A family of low-complexity detection schemes based on channel matrix puncturing targeted for large multiple-input multiple-output (MIMO) systems is proposed. It is well-known that the computational cost of MIMO detection based on QR decomposition is directly proportional to the number of nonzero entries involved in back-substitution and slicing operations in the triangularized channel matrix, which can be too high for low-latency applications involving large MIMO dimensions. By systematically puncturing the channel to have a specific structure, it is demonstrated that the detection process can be accelerated by employing standard schemes such as chase detection, list detection, nulling-and-cancellation detection, and sub-space detection on the transformed matrix. The performance of these schemes is characterized and analyzed mathematically, and bounds on the achievable diversity gain and probability of bit error are derived. Surprisingly, it is shown that puncturing does not negatively impact the receive diversity gain in hardoutput detectors. The analysis is extended to soft-output detection when computing per-layer bit log-likelihood ratios; it is shown that significant performance gains are attainable by ordering the layer of interest to be at the root when puncturing the channel. Simulations of coded and uncoded scenarios certify that the proposed schemes scale up efficiently both in the number of antennas and constellation size, as well as in the presence of correlated channels. In particular, soft-output per-layer subspace detection is shown to achieve a 2:5 dB SNR gain at 10ô€€€4 bit error rate in 256-QAM 16_16 MIMO, while saving 77% of nulling-and-cancellation computations.

Existing System

Zero forcing (ZF) and minimum mean square error (MMSE)

Proposed System

We present a family of WRD-based detectors that build on popular QRD-based detectors. In particular, we propose a punctured ML (PML) detector, a punctured N/C (PN/C) detector, a punctured CD (PCD), as well as a hard-output sub-space detector. 2) We analyze mathematically the bit error rate (BER) performance of the proposed HO detectors. First, the diversity gain is characterized and used to show that channel matrix puncturing does not negatively affect the diversity gain in HO detection. Second, the performance of these detectors is studied via a probabilistic BER characterization. 3) We extend the study for several variations of SO detection schemes, and show that significant performance gains can be achieved with channel puncturing. 4) We propose efficient architectures and analyze the computational complexity of the proposed detectors. We show that the computational savings are much more pronounced with large MIMO dimensions. 5) We study the performance of the proposed detectors in the context of large MIMO with high order modulation constellations, and in the presence of spatial channel correlation. We show that the performance of these schemes scales up efficiently with high orders, and that they are superior to their QRD-based counterparts in the presence of channel correlation.

Architecture