Low-complexity Detection Scheme Research Articles

Detection and performance analysis for MIMO visible light communication system using joint optical spatial and pulse amplitude width modulation

Conventional optical spatial modulation (SM) scheme activates one of the light-emitting diodes (LEDs) to transmit an intensity-modulated optical signal, in which the index of the activated LED is determined by spatial symbol and the emitted intensity is controlled by temporal symbol. In order to enhance the spectral efficiency (bits per channel use), we propose a joint SM and pulse amplitude width modulation (PAWM) as a novel optical spatial–temporal signaling scheme. In this paper, the proposed SM-PAWM optical signaling scheme is applied in a multi-input multi-output (MIMO) visible light communication (VLC) system. Employing optimal maximum likelihood (ML) algorithm to extract the spatial and temporal symbols is computationally prohibitive; hence, we develop a novel low-complexity detection scheme that converts the joint optimization problem separately to decode the spatial and temporal symbols. Moreover, theoretical results in terms of the successful identification probability of activated LED as well as the overall symbol error rate are derived. Extensive computer simulations are performed to validate the analytical results. It is shown that the proposed detection scheme is a feasible alternative to the ML detector in the VLC-MIMO system employing SM-PAWM.

Deployment of Energy-Efficient Aerial Communication Platforms With Low-Complexity Detection

Due to their flexibility, mobility and autonomy, unmanned aerial vehicles (UAVs) are considered as a potential candidate to operate as flying base stations to provide a specific geographical area with air-to-ground wireless communications services. Besides, the limitation of the on-board energy motivates the design of a more energy-efficient way to transmit information. Moreover, the deployment of multiple UAVs can affect the quality of experience (QoE) of users. In this paper, we propose a method that combines the concept of index modulation (IM) with the UAV communications systems, which we refer to as IM-UAV, to attain an improved energy-efficiency (EE). Furthermore, based on the proposed IM-UAV communication system, a gradient descent based UAV deployment scheme is designed to maximize the downlink average rate of the ground users (GUs) in the target area. On the other hand, the maximum likelihood (ML) detection for the IM-UAV requires a high computational complexity for detection at the GUs, while providing the best possible performance. Hence, we propose a low-complexity detection scheme that can separately detect the index symbols and data symbols to reduce the computational complexity at the receiver side. The simulation results demonstrate that the proposed deployment method is capable of attaining the appropriate positions to deploy the UAVs, while the EE is also improved by combining IM with UAV communication system. In addition, the proposed low-complexity detection scheme reduces the computation complexity by slightly sacrificing the bit error rate (BER) performance.

Permutation Matrix Modulation

We propose a novel scheme that allows MIMO system to modulate a set of permutation matrices to send more information bits, extending our initial work on the topic. This system is called Permutation Matrix Modulation (PMM). The basic idea is to employ a permutation matrix as a precoder and treat it as a modulated symbol. We continue the evolution of index modulation in MIMO by adopting all-antenna activation and obtaining a set of unique symbols from altering the positions of the antenna transmit power. We provide the analysis of the achievable rate of PMM under Gaussian Mixture Model (GMM) distribution \revv{and finite cardinality input (FCI). Numerical results are evaluated by comparing PMM with the other existing systems.} We also present a way to attain the optimal achievable rate of PMM by solving a maximization problem via interior-point method. A low complexity detection scheme based on zero-forcing (ZF) is proposed, and maximum likelihood (ML) detection is discussed. We demonstrate the trade-off between simulation of the symbol error rate (SER) and the computational complexity where ZF performs worse in the SER simulation but requires much less computational complexity than ML.

Evaluation of Non-Coherent Signal Detection Techniques for Mobile Molecular Communication.

In recent years, there have been more and more research on molecular communication (MC). Because the deployment of mobile nanomachines may be required in some applications of MC, research on mobile MC has become a trend. The signal detection schemes for static MC are no longer applicable due to the time varying channel impulse response (IR), which is caused by the mobile characteristics of nanomachines. In this paper, a low complexity and non-coherent detection scheme is proposed for mobile scenario, which is based on the energy difference between two adjacent symbols. Most of the existing signal detection methods do not consider inter-symbol interference (ISI). Compared with those methods, the proposed scheme can achieve signal detection utilizing ISI without knowing channel state information (CSI). The bit error rate (BER) performance of the proposed method is investigated under different conditions through simulations. Besides, the influence of mobility features of nanomachines on the signal detection accuracy is also investigated in detail. The simulation results demonstrate that the BER performance of the proposed scheme outperforms the latest signal detection scheme for short-distance mobile MC system with high velocity. Consequently, the detection scheme proposed in this paper can reduce the influence of nanomachines' mobility and has the potential to be used in mobile MC systems.

Quasi-Orthogonal Space-Time Block Coded Spatial Modulation

The introduction of space-time block code (STBC) can efficiently increase the diversity of original spatial modulation (SM). However, the spectral efficiency of STBC will be reduced gradually with the increase of the transmit antennas. In this contribution, we conceive a novel quasi-orthogonal space-time block coded spatial modulation (QOSTBC-SM) design for multiple-input and multiple-out (MIMO) transmission by reaping their respective benefits, while improving the spectral efficiency compared to conventional space-time block coded spatial modulation (STBC-SM). More specifically, in the proposed QOSTBC-SM structure, the information bits are conveyed via the active antenna index, as well as the QOSTBC blocks at the transmitter, while at the receiver, a low-complexity detection scheme is proposed. Furthermore, a closed-form union bound of the bit error rate (BER) is also quantified by theoretical derivation. Finally, our simulation results demonstrate that QOSTBC-SM is capable of outperforming the conventional counterpart as STBC-SM with higher spectral efficiency.

Enabling joint transmitter-receiver spatial modulation with RF mirrors: A low-cost and highly-flexible perspective

Joint transmitter and receiver modulation (JSM) is a promising spatial-domain modulation scheme, which is capable of enhancing the spatial diversity, as well as the spatial multiplexing gain for the modulated multiple-input multiple-output (MIMO) systems. In this piece of paper, in order to generalize the JSM for arbitrary size MIMOs, we propose and investigate a novel joint transmit and receive spatial pattern grouping based JSM (SPG-JSM), which is enabled by RF mirrors configured around transmit antennas. To provide the proposed SPG-JSM with further enhanced spatial diversity, a SPG associated alternative null-space beamforming (ANB) strategy is introduced for accomplishing the transmitter preprocessing. In addition to the classical maximum-likelihood detection (MLD), we design a ratio sorting assisted low-complexity detection (RS-LCD) scheme to decrease the implementation cost at the receiver. Furthermore, we analyze the capacity, error performance, and the spatial diversity achievable by the proposed SPG-JSM, provided that the MLD is exploited at the receiver. Simulation outcomes are characterized to demonstrate the advantages of our novel SPG-JSM, and to validate the analytical performance derivations.

On the Error Analysis of Hexagonal-QAM Constellations

Future communication systems are envisioned to support applications that require very high data rates in an energy efficient manner. To this direction, the use of hexagonal quadrature amplitude modulation (HQAM) provides high data rates and power efficiency, due to its compact allocation of symbols on the 2D plane. However, because of its hexagonal lattice, it is difficult, if not impossible, to evaluate exactly the error probability. In this letter, we propose a tight upper bound as well as a closed-form approximation for the symbol error probability of HQAM, which are validated from numerical and simulation results. Finally, exploiting the analytical results a novel low complexity detection scheme is presented.

Low Complexity Optimal and Suboptimal Detection at Spatial Modulation MIMO Receivers

This paper develops three low-complexity detection schemes for the spatial modulation (SM) Multiple Input Multiple Output (MIMO) systems. We first propose a reduced complexity maximum likelihood (RC-ML) detection scheme. For the practical values of the modulation index, the proposed RC-ML method is simpler than the existing hard-limiting-based ML schemes. The two other proposals are based on a suboptimal Maximum Ratio Combining (MRC) detection method. We present a new analysis of the MRC detector in the uncorrelated Rayleigh fading channel and identify the system operational scenarios for which the MRC performance is nearly identical to the ML performance. Our proposals — a hybrid MRC-ML method and an MRC scheme with rank reduction — are inspired by this analysis. The analytical and simulation results show that the proposed MRC-based schemes can attain a near-optimal performance while reducing the complexity of the ML-based SM receiver.

Ball-Tree-Based Signal Detection for LMA MIMO Systems

In this letter, we consider the uplink multiuser load-modulated array (LMA) multiple-input multiple-output (MIMO) communication system, where multiple users transmit the phase modulation on hypersphere (PMH) signals to a base station (BS). To reduce the detection complexity, we propose a low-complexity detection scheme based on a ball-tree (BT) structure. The received codewords are stored in a space BT data structure and the detection process can be regarded as a nearest neighbor point search operation. Two partition rules are proposed in the BT codebook construction. Simulation results show that the proposed BT based signal detection achieves about the same bit error rate (BER) performance as the ML detection while the detection complexity is significantly reduced.

Rotated Golden Codewords Based Space-Time Line Code Systems

The space-time line code (STLC) has been recently proposed in the literature. In STLC systems, the channel state information is assumed to be known at the transmitter, but not at the receiver. In the conventional STLC systems, the inputs of the STLC encoder are either M-ary phase shift keying symbols or M-ary quadrature amplitude modulation symbols and can achieve diversity order with very low detection complexity. In order to further improve the error performance of the STLC systems, in this paper, rotated Golden codewords based STLC (RGC-STLC) systems are proposed.We extend the 1×2 and 2 × 2 transmit-receive antenna structure in the conventional STLC into 1 × 4 and 2 × 4 transmit-receive antenna structures in the proposed RGC-STLC system. The inputs of the proposed RGC-STLC encoder are the rotated Golden codewords. Compared to the conventional 1 × 2 and 2 × 2 STLC systems, the 1 × 4 and 2 × 4 RGC-STLC systems achieve a higher diversity order. Based on the feature of the rotated Golden codewords, low complexity detection schemes for the 1 × 4 and 2 × 4 RGC-STLC systems are further proposed. Finally, the union bounds on the average symbol error probability for the 1 × 4 and 2 × 4 RGC-STLC systems are derived and shown to match the simulation results very well at high signal-to-noise ratios.

An Alternative Encoding of the Golden Code and its Low Complexity Detection

The Golden code is a full-rate full-diversity (FRFD) space-time block code. The encoder of the Golden code takes four complex symbols and generates two pairs of Golden codewords. The encoding of each Golden codeword can be regarded as superposition coding with “complex” power allocation. In this paper, we propose an alternative encoding of the Golden code which can be regarded as superposition coding with “real” power allocation. The Golden code with “complex” power allocation or “real” power allocation is hereinafter referred to as the C-Golden code or R-Golden code, respectively. The R-Golden code also preserves the FRFD property. The R-Golden code can be easily implemented in passband modulation using in-phase and quadrature components compared to the C-Golden code. An equivalent received signal model of the R-Golden code system is constructed, then used to derive a closed-form on the lower bound of the average bit error probability. We further propose a low complexity detection scheme, the fast essentially maximum-likelihood detection with adaptive signal detection subset (FE-ML-ASDS) for the R-Golden code. Both simulation and theoretical results show that both the C-Golden code and the R-Golden code achieve the same error performance. Compared to the fast essentially ML detection with signal detection subset (FE-ML-SDS), at high signal-to-noise ratios, the proposed FE-ML-ASDS further reduces detection complexity by at least 68% for the 16QAM or 64QAM R-Golden code with three receive antennas.

Equal-gain combining with interference mitigation for molecular type hopping assisted molecular shift keying systems

In multiple access molecular diffusive communications, many nano-machines exchange information and fuse data through a common Diffusive Molecular Communication (DMC) channel. Hence, there is Multiple-Access Interference (MAI), which should be sufficiently mitigated so as to achieve reliable communications. In this paper, we propose a novel low-complexity detection scheme, namely Equal-Gain Combining with Interference Mitigation (EGC-IM), for signal detection in the Molecular Type Hopping assisted Molecular Shift Keying (MTH-MoSK) DMC systems. By removing a number of entries from each row of the detection matrix formed during detection, the EGC-IM scheme shows its potential to significantly mitigate MAI and hence, outperform the conventional EGC scheme. Furthermore, the EGC-IM scheme has lower complexity than the conventional EGC scheme and therefore, it is beneficial for practical implementation.

Generalized Quadrature Spatial Modulation and its Application to Vehicular Networks With NOMA

Quadrature spatial modulation (QSM) is recently proposed to increase the spectral efficiency (SE) of SM, which extends the transmitted symbols into in-phase and quadrature domains. In this paper, we propose a generalized QSM (GQSM) scheme to further increase the SE of QSM by activating more than one transmit antenna in in-phase or quadrature domain. A low-complexity detection scheme for GQSM is provided to mitigate the detection burden of the optimal maximum-likelihood (ML) detection method. An upper bounded bit error rate is analyzed to discover the system performance of GQSM. Moreover, by collaborating with the non-orthogonal multiple access (NOMA) technique, we investigate the practical application of GQSM to cooperative vehicular networks and propose the cooperative GQSM with OMA (C-OMA-GQSM) and cooperative GQSM with NOMA (C-NOMA-GQSM) schemes. Computer simulation results verify the reliability of the proposed low-complexity detection as well as the theoretical analysis, and show that GQSM outperforms QSM in the entire SNR region. The superior BER performance of the proposed C-NOMA-GQSM scheme make it a promising modulation candidate for next generation vehicular networks.

Joint-Mapping Orthogonal Frequency Division Multiplexing With Subcarrier Number Modulation

Orthogonal frequency division multiplexing with subcarrier number modulation (OFDM-SNM) has been recently proposed to improve the spectral efficiency (SE) of the traditional OFDM system. In this paper, we propose a joint-mapping OFDM-SNM (JM-OFDM-SNM) scheme to transmit the signal vector with a constant length of information bits by jointly considering the subcarrier activation patterns and constellation symbols. A low-complexity detection scheme based on log-likelihood ratio criterion is proposed to relieve the high computational complexity of the maximum-likelihood detection at the cost of a negligible performance loss. Upper-bounded bit error rate (BER) and lower-bounded achievable rate are both derived in closed-form to evaluate the performance of JM-OFDM-SNM. To suit different application scenarios, we further propose two enhanced schemes, named adaptive JM-OFDM-SNM (AJM-OFDM-SNM) and JM-OFDM with in-phase/quadrature SNM (JM-OFDM-IQ-SNM), where the former adjusts the constellation orders for different numbers of active subcarriers, and the latter extends the indexing to in-phase and quadrature domains. Simulation results corroborate the tightness of the derived BER expression in the high signal-to-noise ratio region and show that (A)JM-OFDM-SNM improves the performance of OFDM-SNM, while both AJM-OFDM-SNM and JM-OFDM-IQ-SNM schemes perform better than JM-OFDM-SNM at the same SE.

저복잡도 LoRa 심볼 검파 방식

IoT(Internet of Things) 기기를 광범위하게 이용하기 위해서는 통신기술을 저전력/저비용으로 구현하는 것이 중요하다. 이를 달성하기 위해, 본 논문에서는 IoT 분야에서 널리 이용되는 LPWA(low power wide area) 기술인 LoRa를 위한 심볼 검파 문제를 다룬다. 특히 IoT 기기의 저전력/저비용 구현을 위해, 저복잡도 LoRa 심볼 검파 방식을 제안한다. 제안된 방식의 동작을 검증하기 위해 기존 FFT(fast Fourier transform) 기반 심볼 검파 방식과의 성능비교를 수행하였고, 제안된 방식이 최적의 심볼 검파 성능을 보이면서도 계산량을 효과적으로 줄임을 보였다.

A Novel Index Modulation Dimension Based on Filter Domain: Filter Shapes Index Modulation

A novel domain for Index Modulation (IM) named “Filter Domain” is proposed. This new domain generalizes many existing modulations and IM domains. In addition, a novel scheme “Filter Shape Index Modulation” (FSIM) is proposed. This FSIM scheme allows a higher Spectral Efficiency (SE) gain than the time and frequency IM dimensions in Single-Input Single-Output (SISO) systems. In the FSIM system, the bit-stream is mapped using an Amplitude Phase Modulation (APM) as QAM or PSK, and an index of a filter-shape changing at the symbol rate. This filter shape, being changed at each symbol, enables a SE gain in SISO system without sacrificing any time or frequency resources. Compared to an equivalent 8QAM and 16QAM schemes and at the same SE, the FSIM with QPSK using 2 and 4 non-optimal filter shapes achieves a gain of 3.8 dB and 1.7 dB respectively at BER= 10−4, and this superiority is maintained in frequency selective fading channel compared to equivalent SISO-IM schemes. A low complexity detection scheme, approaching the maximum likelihood detector performance, is proposed along with a full performance characterization in terms of theoretical probability of filter index error and BER lower bound. Finally, FSIM can achieve better spectral and energy efficiencies when a filter bank and an ISI cancellation technique are optimally designed.

Multiple Complex Symbol Golden Code

The Golden code is a full-rate full-diversity (FRFD) space-time block code (STBC). The conventional Golden code takes four complex symbols and generates two pairs of Golden codewords. Each pair of Golden codewords contains two complex symbols. In this paper, a new type of Golden code is proposed, where we extend the two complex symbols in each pair of Golden codewords into multiple complex symbols. The scheme hereinafter referred to as the multiple complex symbol Golden code (MCS-Golden code) preserves the FRFD property but achieves a diversity order of 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sup> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> compared to the conventional Golden code, where N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> is the number of receive antennas, n, n ≥ 1, is an integer, and 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sup> is the number of multiple complex symbols in the MCS-Golden code system. An equivalent model of the MCS-Golden code is constructed, then used to derive a closed-form bound on the average bit error probability (ABEP) for the MCS-Golden code system. We further propose a low complexity detection scheme, sphere decoding with sorted detection subset (SD-SDS) for the MCS-Golden code. Finally, we discuss the detection complexity for the proposed SD-SDS. Both simulation and theoretical results show that the MCS-Golden code significantly improves error performance compared to the conventional Golden code. For example, at an average bit error rate of 3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> , a four complex symbol Golden code system with three receive antennas achieves approximately 2.5 dB signal-to-noise ratio (SNR) gain compared to the conventional Golden code.

Space-Time Block Coded Rectangular Differential Spatial Modulation: System Design and Performance Analysis

In this paper, a novel scheme dubbed space-time block coded rectangular differential spatial modulation (STBC-RDSM) is proposed for multiple-input and multiple-out (MIMO) systems, which combines space-time block coding (STBC) and rectangular differential spatial modulation (RDSM) to reap their respective benefits while avoiding the drawbacks of conventional differential spatial modulation (DSM) systems. More specifically, in the proposed STBC-RDSM scheme, information bits are conveyed via the rectangular differentially encoded antenna index matrices, as well as the STBC blocks. Furthermore, a low-complexity detection scheme is proposed. Our simulation results demonstrate that STBC-RDSM outperforms its conventional DSM counterparts in various spectral efficiencies. Finally, a closed-form union bound on the bit error rate (BER) is derived and validated by our simulation results.

Golden codeword–based modulation schemes for single‐input multiple‐output systems

SummaryThe Golden code has full rate and full diversity. The Golden codeword matrix contains two pairs of super symbols. Based on one pair of super symbols, two modulation schemes, Golden codeword–based M‐ary quadrature amplitude modulation (GC‐MQAM) and component‐interleaved GC‐MQAM (CI‐GC‐MQAM), are proposed for single‐input multiple‐output (SIMO) systems. Since the complexities of the maximum likelihood detection for the proposed GC‐MQAM and CI‐GC‐MQAM are proportional to O(M2) and O(M4), respectively, low complexity detection schemes for the proposed GC‐MQAM and CI‐GC‐MQAM are further proposed. In addition, the theoretical average bit error probabilities (ABEPs) for the proposed GC‐MQAM and CI‐GC‐MQAM are derived. The derived ABEPs are validated through Monte Carlo simulations. Simulation and theoretical results show that the proposed GC‐MQAM can achieve the error performance of signal space diversity. Simulation and theoretical results further show that the proposed CI‐GC‐16QAM, ‐64QAM, and ‐256QAM with three receive antennas can achieve approximately 2.2, 2.0, and 2.1 dB gain at a bit error rate of 4 × 10−6 compared with GC‐16QAM, ‐64QAM, and ‐256QAM, respectively.

Low complexity and high performance symbol detection scheme for uplink wide‐banded cyclic prefixed filter bank multiple access system without analysis filtering

This Letter proposes a new symbol detection scheme for an uplink wide-banded cyclic prefixed filter bank multiple access system. The feature of the proposed scheme is that it eliminates the analysis filter bank processing that is commonly employed in the existing schemes. By leveraging a particular interleaving structure, the large matrix inversion operation is decomposed into parallel matrices inversions with small sizes. The benefits of the proposed scheme include lower complexity and higher spectral efficiency. In addition, the detection performance is also improved, which is verified by simulations.