Simplified Maximum Likelihood Detection Research Articles

Low-complexity equalizer with a hybrid decision scheme for 50 Gb/s/λ PAM4-PON using a low-cost 10 G receiver.

In this Letter, we experimentally demonstrate a 50Gb/s/λ four-level pulse amplitude modulation-based passive optical network system with a 10 G class receiver. A memory polynomial equalizer (MPE) combined with a decision feedback equalizer (DFE) is applied to eliminate channel distortions in the system. To further improve the performance of the MPE-DFE, for the first time, to the best of our knowledge, a low-complexity hybrid decision scheme (HDS) is proposed, which consists of single-symbol decision (SSD) and multi-symbol decision (MSD). The SSD is exactly the conventional hard decision based on minimum Euclidean distance, whereas MSD is based on a simplified maximum likelihood detection principle with M-algorithm. In terms of complexity, MSD requires 19.1% more multiplications than SSD, but the symbol number of MSD only accounts for less than 20% of the total signal frame when the received optical power is greater than -27dBm. Experimental results show that the proposed MPE-DFE with HDS achieves a 0.7 dB and 1.3 dB sensitivity gain compared with conventional SSD, and up to 35.4 dB and 31.4 dB link power budget, regarding the forward error correction threshold of 10-2 and 10-3, respectively.

Simplified Maximum Likelihood Detection for FTN Non-Orthogonal FDM System

In this letter, we first apply simplified maximum likelihood detection (MLD) with QR decomposition and M-algorithm (QRM-MLD) to reduce inter-carrier interference (ICI) in a faster-than-Nyquist non-orthogonal frequency division multiplexing (FTN-NOFDM) system. A QRM-MLD algorithm has lower computational complexity than an MLD algorithm owing to the decrease of searched path number. In the experiment, 10-Gb/s FTN-NOFDM with the QRM-MLD algorithm was transmitted over 25-km standard single mode fiber. For 20% bandwidth saving, FTN-NOFDM with the QRM-MLD algorithm can achieve almost the same performance as FTN-NOFDM with the MLD algorithm when the path with minimal metric is not discarded before detecting the last subcarrier, meanwhile the bit error rate of FTN-NOFDM with the QRM-MLD algorithm or the MLD algorithm can achieve 7% forward error correction (FEC) limit, but that with an iterative detection (ID) algorithm only can achieve 20% FEC limit. For reducing ICI, the QRM-MLD algorithm has lower computational complexity but can obtain almost the same performance as the MLD algorithm, and the QRM-MLD algorithm also has much better performance than the ID algorithm.

Simplified Maximum Likelihood Detection with Unitary Precoding for XOR Physical Layer Network Coding

Simplified Maximum Likelihood Detection with Unitary Precoding for XOR Physical Layer Network Coding

Super-orthogonal trellis-coded spatial modulation

Spatial modulation (SM), which employs the indices of multiple transmit antennas to transmit information in addition to the conventional M-ary signal constellations, is a novel transmission technique that has been proposed for multiple-input multiple-output systems. In this study, a new class of space-time trellis codes, called ‘super-orthogonal trellis-coded SM’ (SOTC-SM), is proposed. These codes combine set partitioning and a super set of space-time block coded SM (STBC-SM) codewords to achieve maximal diversity and coding gains by exploiting both SM and space-time block codes. Unlike super-orthogonal space-time trellis codes (SOSTTCs), which parametrise the orthogonal STBCs, these new codes expand the antenna constellation using the principle of SM. Systematic construction methods are presented for the SOTC-SM scheme and design examples are given for 2, 4 and 8 trellis states, at 2, 3 and 4 bits/s/Hz spectral efficiencies. The approximate bit-error probability performance of SOTC-SM is derived and shown to match computer simulation results. A simplified maximum likelihood detection method for the proposed scheme is given. It is shown through computer simulations that the proposed SOTC-SM schemes achieve significantly better error performance than SOSTTCs with comparable complexity.

A Simplified Maximum Likelihood Detector with the Aid of Reduced-Size Searching Set for MIMO Systems

In this paper, a simplified maximum likelihood (ML) detector is proposed for multi-input multi-output (MIMO) systems over the Rayleigh flat-fading channels. The main idea of the proposed method is to pre-construct a reduced-size searching set for the optimal ML detection to reduce its computational load without significant performance loss. This can be done by a two-stage searching algorithm combined with the ordered successive interference cancellation scheme. Computer simulations show that with an adequate size of searching set, the proposed simplified ML detection can outperform the conventional MIMO detectors and achieve the same performance as that of the optimal ML detection.

Analysis of Single-Symbol Detectable Space-Time Block Codes With COD and GCIOD

In this paper, we present a simplified maximum likelihood detection metric for the newly emerging space-time block codes (STBCs) with generalized coordinate interleaved orthogonal design (GCIOD). We also derive the symbol pairwise error probability (PEP) and the union bound on symbol error rate (SER) for a space-time block coded (STBCed) system with single-symbol detection and rotated QAM scheme over flat Rayleigh fading channels. In particular, linear STBCs with complex orthogonal design (COD) and GCIOD are considered. Based on the theoretical analysis, the symbol PEP of the GCIOD codes is related to the transmit power, signal-to-noise ratio, and the rotated angle of the rotated QAM scheme. However, the symbol PEP of the COD code is irrelevant to the rotated angle. It is shown that simulation results match well with our analysis. Thus, the union bounds on SER can be applied to predict the performance of a STBCed system with adaptive code selection between the full-rate COD and GCIOD codes.

SMLD: Enhanced MIMO-Signal Detection for Wireless MIMO Communication Receivers

This letter proposes a simplified maximum likelihood detection (SMLD) scheme to improve the detection performance of multiple-input multiple-output receivers. The SMLD detects V streams according to the first detected V sub-streams. Through an ML test, the most probable stream is selected. Moreover, to detect the layer with the worst post-detection SNR accurately, reverse ordering is applied to the SMLD. Simulation results show that the performance of the Vertical Bell Laboratories layered space-time (V-BLAST) system can be improved by adopting the SMLD technique. In the case of reverse ordering, the SMLD can achieve a similar ML performance with significant reduction in computational complexity.