Showing papers on "Constellation diagram published in 2016"
TL;DR: A novel and robust DM synthesis method based on conditional minimum mean square error that is capable of substantially improving the bit error rate performance compared with the state-of-the-art methods.
Abstract: Directional modulation (DM) is a secure transmission technology that is able to retain the original constellation of transmitted signals along the desired direction, while distort the constellation in the undesired directions at the same time. In this letter, we develop novel and robust DM synthesis methods for enhancing the transmission performance. Specifically, we first propose a low-complexity dynamic DM synthesis method. In this method, we derive a closed-form expression for the null space of conjugate transpose of the steering vector in the desired direction. Based on the expression derived, we construct a projection matrix in order to form artificial noises to those undesired directions. Then, we focus our attention on more practical scenarios, where there is uncertainty in the estimated direction angle. This uncertainty will cause estimation errors and seriously jeopardize the receiving performance in the desired direction. To mitigate the uncertainty effect, we further propose a robust DM synthesis method based on conditional minimum mean square error. The proposed method aims to minimize the distortion of the constellation points along the desired direction. Simulation results show that our proposed robust DM method is capable of substantially improving the bit error rate performance compared with the state-of-the-art methods.
139 citations
15 May 2016
TL;DR: A multi-dimensional SCMA (MD-SCMA) codebook design based on constellation rotation and interleaving method is proposed for downlink SCMA systems, which outperforms that of the existing SCMA codebooks and low density signature (LDS) in downlink Rayleigh fading channels.
Abstract: Sparse code multiple access (SCMA) is a new non- orthogonal multiple access scheme, which effectively exploits the shaping gain of multi-dimensional codebook. In this paper, a multi-dimensional SCMA (MD-SCMA) codebook design based on constellation rotation and interleaving method is proposed for downlink SCMA systems. In particular, the first dimension of mother constellation is constructed by subset of lattice $\mathbf{Z}^2$. Then the other dimensions are obtained by rotating the first dimension. Further, the interleaving is used for even dimensions to improve the performance in fading channels. In this way, we can design different codebooks for the aim of spectral efficiency or power efficiency. And the simulation results show that the bit error rate (BER) performance of MD-SCMA codebooks outperforms that of the existing SCMA codebooks and low density signature (LDS) in downlink Rayleigh fading channels.
112 citations
TL;DR: The results show that SPA, and its variants AST and SAH, are simple and very efficient solutions to improve the physical layer security of mm-wave communication.
Abstract: In this paper, we propose a new wireless communication transmission architecture called switched phased-array (SPA), to enhance physical layer security. SPA works as a platform for three different transmission techniques: 1) conventional phased-array transmission; 2) antenna subset transmission (AST) technique; and 3) silent antenna hopping (SAH) transmission technique. SPA consists of a conventional phased-array blacktransmitter followed by antennas with an on–off switching circuit. The proposed solution maintains the objective of scrambling the constellation points in both amplitude and phase in undesired directions, while preserving a clear constellation in the target direction. The proposed solution—SPA—is different from previously used methods in the following ways: 1) SPA is not restricted to the use of phase modulation, and can accept any modulation type including QAM; 2) it does not need to modulate the signal in the radio frequency (RF) domain, where the conventional phased-array transmitter circuits remain unchanged; 3) in the far field, SPA scrambles the signal constellation by randomly switching- off some of the transmitting antennas (AST), or only one of them (SAH); 4) SPA can be easily integrated with the current infrastructure of phased-array transmitters; 5) SPA breaks up the correlation between the data rates and the switching speed; and 6) SPA performs a variety of DM transmission techniques. We present the potential transmission techniques including PA, AST, and SAH. We analyze the performance for all cases and derive an exact expression of the bit error probability, and also we analyze the secrecy capacity. The results show that SPA, and its variants AST and SAH, are simple and very efficient solutions to improve the physical layer security of mm-wave communication.
87 citations
TL;DR: A new precoding design is proposed that minimizes the transmit power while guaranteeing the quality of service (QoS) and energy harvesting constraints for generic phase shift keying modulated signals and shows significant power savings.
Abstract: In this paper, we propose a power-efficient approach for information and energy transfer in multiple-input single-output downlink systems. By means of data-aided precoding, we exploit the constructive part of interference for both information decoding and wireless power transfer. Rather than suppressing interference as in conventional schemes, we take advantage of constructive interference among users, inherent in the downlink, as a source of both useful information signal energy and electrical wireless energy . Specifically, we propose a new precoding design that minimizes the transmit power while guaranteeing the quality of service (QoS) and energy harvesting constraints for generic phase shift keying modulated signals. The QoS constraints are modified to accommodate constructive interference, based on the constructive regions in the signal constellation. Although the resulting problem is nonconvex, several methods are developed for its solution. First, we derive necessary and sufficient conditions for the feasibility of the considered problem. Then we propose second-order cone programming and semi-definite programming algorithms with polynomial complexity that provide upper and lower bounds to the optimal solution and establish the asymptotic optimality of these algorithms when the modulation order and SINR threshold tend to infinity. A practical iterative algorithm is also proposed based on successive linear approximation of the nonconvex terms yielding excellent results. More complex algorithms are also proposed to provide tight upper and lower bounds for benchmarking purposes. Simulation results show significant power savings with the proposed data-aided precoding approach compared to the conventional precoding scheme.
77 citations
TL;DR: It is demonstrated that some recently proposed attractive LDPC codes could in fact be represented as special instances of irregular quasi cyclic (QC)-LDPC codes from pairwise balanced designs (PBDs), and an optimized signal constellation design approach as well as an optimized mapping rule has been discussed.
Abstract: This tutorial paper presents an overview of advanced FEC and coded modulation (CM) for optical communications. It describes the following ultra-high-speed optical transport enabling techniques: codes on graphs (turbo-product and LDPC codes), rate-adaptive CM, and turbo equalization. Given the high potential of LDPC codes, several binary and nonbinary LDPC decoding algorithms are described and FPGA implementation is also discussed. We then demonstrate that some recently proposed attractive LDPC codes could in fact be represented as special instances of irregular quasi cyclic (QC)-LDPC codes from pairwise balanced designs (PBDs). In addition, we describe several LDPC-coded modulation schemes, including hybrid multidimensional CM, block-interleaved CM, multilevel coding, nonbinary (NB) LDPC-CM, and multilevel NB-LDPC-CM. We also demonstrate the application of turbo equalization and rate-adaptive coding in high-speed optical transmission to deal with fiber nonlinearities. Finally, an optimized signal constellation design approach as well as an optimized mapping rule has been discussed.
59 citations
TL;DR: The simulation results show that the proposed schemes can be adapted to multiple-input multiple-output systems with an arbitrary number of transmit antennas and offer better ABEP performance than those existing schemes.
Abstract: This letter proposes a jointly mapped spatial modulation (JM-SM) scheme to break through the constraint on the number of transmit antennas in traditional SM systems. It is realized via jointly mapping the transmit information bits to 3-D constellation points. A 3-D constellation design scheme for a JM-SM is analyzed and established by minimizing the system average bit error probability (ABEP). In addition, the extension of the joint 3-D mapping to generalized spatial modulation is discussed. The simulation results show that the proposed schemes can be adapted to multiple-input multiple-output systems with an arbitrary number of transmit antennas and offer better ABEP performance than those existing schemes.
41 citations
TL;DR: Simulation results show that the proposed scheme can prevent the exchanging signal from eavesdroppers' classification or inception and can guarantee the BER performance at a tolerate increasing in computational complexity for the legitimate receivers.
Abstract: In this paper, a multiple parameters weighted fractional Fourier transform (MP-WFRFT) and constellation scrambling (CS) method based physical layer (PHY) security system is proposed. The proposed scheme is executed by two steps. In the first step, MP-WFRFT, implemented as the constellation beguiling (CB) method, is applied to change the signal's identity. In the second step the additional pseudo random phase information, regarded as the encryption key, is attached to the original signal to enhance the security. Typically, the pseudo random phase information can be removed effectively by the legitimate receiver. In contrast to the cryptography based encryption algorithms and the conventional PHY secrecy techniques, the main contribution of the proposed scheme is concentrated on the variation in signal's characteristics. Simulation results show that the proposed scheme can prevent the exchanging signal from eavesdroppers' classification or inception. Moreover, the proposed scheme can guarantee the BER performance at a tolerate increasing in computational complexity for the legitimate receivers.
40 citations
TL;DR: A demapping algorithm is proposed that reduces from 69% to 93% the number of required distances when using 2D-NUCs, and discards or replicates those constellation symbols that provide scarce information, with a performance degradation lower to 0.1 dB compared to the optimal maximum likelihood demapper.
Abstract: Non-uniform constellations (NUCs) have been recently introduced in digital broadcasting systems to close the remaining gap to the unconstrained Shannon theoretical limit. Compared to uniform quadrature amplitude modulation (QAM) constellations, NUCs provide a signal-to-noise ratio (SNR) gain (i.e., a reduction in the required SNR), especially for high-order constellations. One-dimensional NUCs (1D-NUC) have a squared shape with non-uniform distance between the constellation symbols. Since the ${I}$ and ${Q}$ components remain as two independent signals, a 1D-demapper as for uniform QAM constellations is feasible. Two-dimensional NUCs (2D-NUC) provide a better performance than 1D-NUCs, since they are designed by relaxing the square shape constraint, with arbitrary shape along the complex plane. However, the main drawback of 2D-NUCs is the higher complexity at the receiver, since a 2D-demapper is needed. In this paper, we propose a demapping algorithm that reduces from 69% to 93% the number of required distances when using 2D-NUCs. The algorithm discards or replicates those constellation symbols that provide scarce information, with a performance degradation lower to 0.1 dB compared to the optimal maximum likelihood demapper.
34 citations
01 Sep 2016
TL;DR: A method of NOMA constellation rotation is proposed where the constellations are respectively rotated before superposition so as to exploit signal space diversity and there is performance gain for one user while almost no negative impact on the other user.
Abstract: The non-orthogonal multiple access (NOMA) technique or more generally the non-orthogonal principle is a crucial component for the next generation cellular system. For two-user downlink NOMA, the constellations of near and far users are superposed for transmission, and maximum likelihood (ML) or successive interference cancellation (SIC) receiver is used for reception. In this paper, we aim to further enhance the linklevel performance for NOMA with ML receiver. A method of NOMA constellation rotation is proposed where the constellations are respectively rotated before superposition so as to exploit signal space diversity. The symbol error rate (SER) upper bounds for both near and far users are derived and used for rotation angle optimization. Within this framework, we show the best we can do in terms of enhancing the performance for a particular user (either near or far). Simulation results have verified the effectiveness of our proposed method. It can be observed that there is performance gain for one user while almost no negative impact on the other user.
31 citations
TL;DR: This letter proposes a novel ACE scheme, along with a low-complexity implementation, for orthogonal frequency division multiplexing (OFDM) systems, where the subcarrier grouping technique is adopted to increase the degrees of freedom in the optimization process.
Abstract: The active constellation extension (ACE) scheme provides an effective means of reducing the peak-to-average power ratio (PAPR) without the need for side information. However, traditional ACE schemes involve a time-consuming iteration process. This letter proposes a novel ACE scheme, along with a low-complexity implementation, for orthogonal frequency division multiplexing (OFDM) systems, where the subcarrier grouping technique is adopted to increase the degrees of freedom in the optimization process. The simulation results show that for an OFDM system with 256 subcarriers and 16-ary quadrature amplitude modulation, the proposed scheme achieves a maximum performance gain of 4.3 dB compared with the original OFDM signal given that $\mathrm { Prob}(\mathrm {PAPR}(\mathbf {x})>\gamma )=10^{-3}$ .
31 citations
TL;DR: In this paper, three new signal designs for enhanced spatial modulation (ESM) are presented for multi-stream MIMO systems with four transmit antennas out of which two are active, but also briefly present extensions to higher numbers of antennas.
Abstract: In this paper, we present three new signal designs for enhanced spatial modulation (ESM), which was recently introduced by the present authors. The basic idea of ESM is to convey information bits not only by the index(es) of the active transmit antenna(s) as in conventional SM, but also by the types of the signal constellations used. The original ESM schemes were designed with reference to single-stream SM and involved one or more secondary modulations in addition to the primary modulation. Compared with single-stream SM, they provided either higher throughput or improved signal-to-noise ratio (SNR). In this paper, we focus on multi-stream SM (MSM) and present three new ESM designs leading to increasing SNR gains when they are operated at the same spectral efficiency. The secondary signal constellations used in the first two designs are derived through a single geometric interpolation step in the signal constellation plane, while the third design also makes use of additional constellations derived through a second interpolation step. The new ESM signal designs are described for MIMO systems with four transmit antennas out of which two are active, but we also briefly present extensions to higher numbers of antennas. Theoretical analysis and simulation results indicate that the proposed designs provide a significant SNR gain over MSM.
TL;DR: Simulation results show that the performance of the proposed Kolmogorov-Smirnov classifier is close to that of the optimal likelihood-based classifier, while its robustness to noise uncertainty is improved and its computational complexity is reduced compared to that.
Abstract: Modulation classification is crucial in applications such as electronic warfare and interference cancellation. In this letter, a novel feature-based Kolmogorov–Smirnov classifier is proposed for the identification of the modulation formats. The received signal is first preprocessed with a folding operation that helps identify the modulation formats based on their different axes of symmetry. Simulation results show that the performance of the proposed classifier is close to that of the optimal likelihood-based classifier, while its robustness to noise uncertainty is improved and its computational complexity is reduced compared to that of the optimal likelihood-based classifier.
TL;DR: Simulation results demonstrate that the proposed low-complexity TI scheme can achieve significant complexity savings while maintaining a good PAPR performance.
Abstract: Tone injection (TI) can effectively reduce the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals without incurring data rate loss and extra side information. However, the optimal TI scheme requires an exhaustive search over all combinations of the possible perturbations of the expanded constellation over all perturbed subcarriers, which is not suitable for practical applications. To reduce the complexity while still achieving good PAPR performance, a low-complexity TI scheme based on distortion signals is proposed in this paper. Motivated by the goal of mitigating the distortions when OFDM signals pass high power amplifiers, we intuitively get the perturbation information for OFDM signals directly from the distortion signals. By exploiting the distribution of the perturbation vectors depending on the distortion signals, we design a search range limited extended constellation. Then, based on the statistical information of perturbed subcarriers, the number of the subcarriers to be perturbed is restricted. Moreover, to further reduce the complexity, we choose a proper subcarrier perturbation sequence from candidate subcarrier sets according to the mutual information between the peak sample and the distortion signals. With the selected subcarrier perturbation sequence, the original problem is decomposed into a sequential search problem, which provides a dramatic complexity reduction. Simulation results demonstrate that the proposed scheme can achieve significant complexity savings while maintaining a good PAPR performance.
TL;DR: It is shown that an asynchronized PNC system in which the symbol arrival times of the two users at the relay are deliberately made to be asynchronous can remove the sensitivity problem, allowing a robust high-order modulated P NC system to be built.
Abstract: This paper investigates various subtleties of applying linear physical-layer network coding (PNC) with $q$ -level pulse amplitude modulation ( $q$ -PAM) in two-way relay channels. A critical issue is how the PNC system performs when the received powers from the two users at the relay are imbalanced. In particular, how would the PNC system perform under slight power imbalance that is inevitable in practice, even when power control is applied? To answer these questions, this paper presents a comprehensive analysis of $q$ -PAM PNC. Our contributions are as follows. First, we give a systematic way to obtain the analytical relationship between the minimum distance of the signal constellation induced by the superimposed signals of the two users (a key performance determining factor) and the channel-gain ratio of the two users, for all $q$ . In particular, we show how the minimum distance changes in a piecewise linear fashion as the channel-gain ratio varies. Second, we show that the performance of $q$ -PAM PNC is highly sensitive to imbalanced received powers from the two users at the relay, even when the power imbalance is slight (e.g., the residual power imbalance in a power-controlled system). This sensitivity problem is exacerbated as $q$ increases, calling into question the robustness of high-order modulated PNC. Third, we propose an asynchronized PNC system in which the symbol arrival times of the two users at the relay are deliberately made to be asynchronous. We show that such asynchronized PNC, when operated with a belief propagation decoder, can remove the sensitivity problem, allowing a robust high-order modulated PNC system to be built.
01 Sep 2016
TL;DR: The computer simulations show that the proposed double spatial modulation scheme provides considerably better error performance than QSM and ESM schemes for different spectral efficiency values.
Abstract: In this paper, a new multiple-input multiple-output (MIMO) transmission technique, which is called double spatial modulation (DSM), is proposed as a new high-rate generalized spatial modulation (SM) scheme. DSM scheme aims to improve the spectral efficiency of classical SM by increasing the number of active transmit antennas. In the DSM scheme, incoming data bits determine two modulated symbols as well as their corresponding activated transmit antenna indices. One of the modulated symbols is directly transmitted over its corresponding activated transmit antenna, while the other one is transmitted with a rotation angle, which is optimized for M-ary quadrature amplitude modulation (M-QAM) signal constellation, over the second activated transmit antenna. The error performance of the proposed DSM scheme is compared with the recently proposed emerging SM schemes such as quadrature SM (QSM) and enhanced SM (ESM). Our computer simulations show that the DSM scheme provides considerably better error performance than QSM and ESM schemes for different spectral efficiency values. In addition, the pairwise error probability (PEP) of DSM is derived and the average bit error probability (ABEP) over uncorrelated Rayleigh fading channels is obtained for different M-QAM constellations.
TL;DR: A new power-efficient symbol recovery scheme for dc-biased optical OFDM (DCO-OFDM) in an intensity-modulation direct-detection (IM/DD) system is presented and an alternative method for clipping is introduced in order to maintain a nonnegative real-valued signal and still preserve information, which is lost when using clipping.
Abstract: Orthogonal frequency division multiplexing (OFDM) has proven itself as an effective multicarrier digital communication technique. In recent years, the interest in optical OFDM has grown significantly, due to its spectral efficiency and inherent resilience to frequency-selective channels and to narrowband interference. For these reasons, it is currently considered to be one of the leading candidates for deployment in short fiber links such as the ones intended for inter-data-center communications. In this paper, we present a new power-efficient symbol recovery scheme for dc-biased optical OFDM (DCO-OFDM) in an intensity-modulation direct-detection (IM/DD) system. We introduce an alternative method for clipping in order to maintain a nonnegative real-valued signal and still preserve information, which is lost when using clipping, and propose an iterative detection algorithm for this method. A reduction of $\text{50\%}$ in the transmitted optical power along with an increase of signal-independent noise immunity (gaining 3 dB in SNR), compared to traditional DCO-OFDM with a dc bias of $\text{two}$ standard deviations of the OFDM signal, is attained by our new scheme for a symbol error rate of $10^{-3}$ in a QPSK constellation additive white Gaussian noise flat channel model.
TL;DR: In this paper, a cyclic spatially modulated codebook with temporal permutations over four consecutive time slots is proposed to ensure a full transmit diversity order for the designed codebook, assuming that two distinct pairs from the available transmit antennas are activated over two consecutive times slots to construct a $2\times 2$ STBC transmission matrix.
Abstract: In this letter, we propose temporal modulation as a new dimension to enhance the performance of spatially modulated space-time block codes (STBCs). We efficiently integrate a cyclic spatially modulated codebook with temporal permutations over four consecutive time slots. To ensure a full transmit diversity order for the designed codebook, we assume that two distinct pairs from the available transmit antennas are activated over two consecutive time slots to construct a $2\times 2$ STBC transmission matrix. We design a rotated version of the orthogonal full-diversity Alamouti STBC as a building block of our proposed codebook. Our numerical results confirm the reduced error rate of the proposed transmission scheme over the state-of-the-art schemes at the same spectral efficiency.
TL;DR: This paper proposes an additively uniquely decomposable constellation (signal amplitude set) group (AUDCG) group to transmit multilayer data for VLC through constellation cooperation by minimizing the average optical power subject to a fixed minimum Euclidean distance.
Abstract: In visible light communication (VLC) systems for automotive applications, different kinds of traffic data with intended priority are usually demanded for transmission to meet an important requirement for both driving safety and the simplicity of a receiver, mainly due to a time urgency issue. For this need, a concept called an additively uniquely decomposable constellation (signal amplitude set) group (AUDCG) is proposed in this paper to transmit multilayer data for VLC through constellation cooperation. Then, an optimal AUDCG is designed by minimizing the average optical power subject to a fixed minimum Euclidean distance. One of the significant advantages of this optimal design is fast demodulation of the sum signal from a noisy received signal, as well as fast decoding of individual signal from the estimated sum signal. Another important advantage is that this design allows each user constellation to be flexibly assigned to meet different priority requirements. Computer simulations indicate that our proposed design has better error performance than the currently available time-orthogonal transmission scheme for this application.
TL;DR: A hierarchical CSK (HCSK) modulation scheme based on the traditional CSK, which is capable of generating interdependent layers of signals having different error probability, which can be readily reconfigured by changing its parameters is conceived.
Abstract: Colour-shift keying (CSK) constitutes an important modulation scheme conceived for the visible light communications (VLC). The signal constellation of CSK relies on three different-color light sources invoked for information transmission. The CSK constellation has been optimized for minimizing the bit error rate, but no effort has been invested in investigating the feasibility of CSK aided unequal error protection (UEP) schemes conceived for video sources. Hence, in this treatise, we conceive a hierarchical CSK (HCSK) modulation scheme based on the traditional CSK, which is capable of generating interdependent layers of signals having different error probability, which can be readily reconfigured by changing its parameters. Furthermore, we conceived an HCSK design example for transmitting scalable video sources with the aid of a recursive systematic convolutional (RSC) code. An optimization method is conceived for enhancing the UEP and for improving the quality of the received video. Our simulation results show that the proposed optimized-UEP 16-HCSK-RSC system outperforms the traditional equal error protection scheme by $\sim 1.7$ dB of optical SNR at a peak signal-to-noise ratio of 37 dB, while optical SNR savings of up to 6.5 dB are attained at a lower PSNR of 36 dB.
TL;DR: This paper builds a FSO communication system with 16-ary phase shift key-orthogonal frequency division multiplexing (16PSK-OFDM) downstream signals, and analyzes the transmission performance of 16PSK -OFDM optical signals under five different weather conditions.
Abstract: Free Space Optical (FSO) communication is one of the most promising access methods. But, the different weather conditions will affect the transceiver performance. In this paper, we build a FSO communication system with 16-ary phase shift key-orthogonal frequency division multiplexing (16PSK-OFDM) downstream signals. We analyze the transmission performance of 16PSK-OFDM optical signals under five different weather conditions (sunny, light rain, moderate rain, snow, and fog). The optical spectral diagrams, constellation diagrams, and bit error rate (BER) of the received signals are simulation measured and analyzed. The results show that the constellation diagram under sunny condition is clear, and the value of BER is about 10?4.2 after 16PSK-OFDM optical signals pass through 500 m FSO link. Note that, the constellation points are dispersed under the other weather conditions.
Patent•
15 Apr 2016
TL;DR: In this paper, an integrated circuit includes an analog front-end that converts an analog signal vector representing an optical signal into digital signal vector, and a digital signal processing circuit that processes the digital signal vectors to recover data from the optical signal.
Abstract: Apparatus and method for digital signal constellation transformation are provided herein. In certain configurations, an integrated circuit includes an analog front-end that converts an analog signal vector representing an optical signal into a digital signal vector, and a digital signal processing circuit that processes the digital signal vector to recover data from the optical signal. The digital signal processing circuit generates signal data representing a signal constellation of the digital signal vector. The digital signal processing circuit includes an adaptive gain equalizer that compensates the signal data for distortion of the signal constellation arising from biasing errors of optical modulators used to transmit the optical signal.
TL;DR: An algorithm is introduced to determine the optimal signal constellation sets for the proposed non-uniform scheme with the criterion of maximizing constellation figure of merit (CFM) with the same spectral efficiency as the conventional 8-QAM.
Abstract: In this paper, we first describe a 9-symbol non-uniform signaling scheme based on Huffman code, in which different symbols are transmitted with different probabilities. By using the Huffman procedure, prefix code is designed to approach the optimal performance. Then, we introduce an algorithm to determine the optimal signal constellation sets for our proposed non-uniform scheme with the criterion of maximizing constellation figure of merit (CFM). The proposed nonuniform polarization multiplexed signaling 9-QAM scheme has the same spectral efficiency as the conventional 8-QAM. Additionally, we propose a specially designed GF(32) nonbinary quasi-cyclic LDPC code for the coded modulation system based on the 9-QAM non-uniform scheme. Further, we study the efficiency of our proposed non-uniform 9-QAM, combined with nonbinary LDPC coding, and demonstrate by Monte Carlo simulation that the proposed GF(23) nonbinary LDPC coded 9-QAM scheme outperforms nonbinary LDPC coded uniform 8-QAM by at least 0.8dB.
TL;DR: A SM-MISO system relying on a single radio-frequency chain equipped with a finite-rate feedback channel to provide quantized channel state information (CSI) to the transmitter and a novel feedback scheme, which requires (nt - 1) log2(M) fewer bits of feedback with any performance erosion, where nt is the number of TAs.
Abstract: In this paper, we consider a spatial modulation (SM)-based multiple-input–single-output (MISO) system relying on a single radio-frequency chain equipped with a finite-rate feedback channel to provide quantized channel state information (CSI) to the transmitter. First, under the assumption of Rayleigh flat-fading channels and perfect CSI at the transmitter (CSIT), we analyze the symbol error probability (SEP) of an SM scheme, which perfectly compensates the channel phase and employs constellation rotation at the different transmit antennas (TAs). Then, we consider a more practical scenario, where scalar quantization of the channel phase angles is employed, and the quantized CSI is made available to the transmitter via a finite-rate feedback channel. We analyze the SEP reduction, i.e., $P_{e_L}$ , relative to perfect CSIT, imposed by the quantized CSIT (Q-CSIT). We show that at a high feedback rate, $P_{e_L}$ varies as $C^{\prime}\mbox{2}^{-2B}$ , where each channel phase angle is quantized to $B$ bits, and $C^{\prime}$ is a constant. Furthermore, based on the rotational symmetry of the $M$ -ary phase-shift keying ( $M$ -PSK) signal constellation, we propose a novel feedback scheme, which requires $(n_t-\mbox{1})\log_2(M)$ fewer bits of feedback with any performance erosion, where $n_t$ is the number of TAs. We characterize the performance of the SM-MISO system with finite-rate feedback and validate our analysis through Monte Carlo simulations.
TL;DR: Results reveal that IQ imbalance can lead to significant performance degradation of QSM system and should be carefully addressed for any future deployment.
Abstract: Quadrature spatial modulation (QSM) is proposed recently as an efficient multiple-input–multiple-output wireless communication technique. In QSM, spatial multiplexing gain is achieved through modulating a two-dimensional spatial constellation diagram in addition to conventional signal modulation. It was demonstrated that QSM can be designed with single in-phase and quadrature (IQ) transmitter. However, the impact of IQ modulator imperfections, which degrade signal fidelity and overall system performance, has not been studied in the literature. In this study, typical IQ modulator/demodulator is considered for QSM system and the performance of the system is analysed and discussed. In particular, IQ imbalance channel modelling, pair-wise error probability, and average bit error ratio are discussed. Results reveal that IQ imbalance can lead to significant performance degradation of QSM system and should be carefully addressed for any future deployment.
Patent•
01 Jun 2016
TL;DR: In this paper, the authors proposed a simple codebook design method under a Gauss channel and belongs to the communication system technical field, which includes the following steps that: the total constellation diagram of all users on each resource block is designed; a subset segmentation method in trellis coded modulation (TCM) is utilized to generate constellations corresponding to the users; a mapping matrix is constructed; the constellation of the users and the mapping matrix are combined to construct a constellation matrix; and a codebook is generated according to the constellation matrix.
Abstract: The invention relates to an SCMA (sparse code multiple access) simple codebook design method under a Gauss channel and belongs to the communication system technical field. The method is mainly applied to conditions under Gaussian channels. The method includes the following steps that: the total constellation diagram of all users on each resource block is designed; a subset segmentation method in trellis coded modulation (TCM) is utilized to generate constellations corresponding to the users; a mapping matrix is constructed; the constellations of the users and the mapping matrix are combined tougher to construct a constellation matrix; and a codebook is generated according to the constellation matrix. With the method of the invention adopted, it can be ensured that the minimum Euclidean distance between constellation points between the users is maximized, and at the same time, it can be ensured that the minimum Euclidean distance between constellation points of the users is maximized; the bit error rate (BER) of a system can be low; and the performance of the system is also favorable under a high overload rate condition.
TL;DR: The concept of adaptive spatial modulation is extended to the parallel Gaussian channel with finite alphabet input and a transmit scheme called adaptive index modulation (AIM) is proposed, which adaptively selects the index modulation pattern according to the criterion of maximizing the minimum squared Euclidean distance.
Abstract: In this paper, we extend the concept of adaptive spatial modulation to the parallel Gaussian channel with finite alphabet input and propose a transmit scheme called adaptive index modulation (AIM). In the proposed scheme, the transmitter adaptively selects the index modulation pattern, consisting of the active channel subset and the associated signal constellations, according to the criterion of maximizing the minimum squared Euclidean distance. To reduce the complexity, first, the number of candidate patterns in the selection procedure is reduced by employing the relation of the normalized signal constellations with different modulation orders. Second, a simple lookup table method is presented. Finally, the performance of the proposed scheme is demonstrated in both the scenarios of multicarrier transmission and multiantenna transmission by computer simulations.
TL;DR: Simulation results show that the proposed WLSD can achieve quasi-optimal bit error rate performance, while the computational complexity is reduced by more than a half compared with the Schnorr-Euchner sphere decoder.
Abstract: This paper investigates the widely linear processing (WLP) for the detection of circular signals, such as M-ary phase-shift keying (MPSK) signals and M-ary quadrature amplitude modulation (MQAM) signals. First, a unified mathematical model is derived to describe the conjugate symmetry of general MPSK/MQAM signals. In the unified model, a phase-rotation matrix (PRM) is introduced to partition the constellation of multiple-input multiple-output (MIMO) signals into subsets. Signals in a subset share the same PRM. Second, a widely linear receiver is proposed in each subset for MIMO detection. To avoid repetitive WLP in each subset, a widely linear sphere decoder (WLSD) is further proposed for MIMO systems. WLSD transforms the traditional sphere decoder (SD) searching for a true transmitted vector into a shrunk one by searching for the corresponding phase-rotation vector. Finally, the diversity order of WLSD is proven to be more than $N_R-\frac{N_T-1}{2}$ and less than $N_R$ , where $N_T$ (or $N_R$ ) denotes the number of transmitting (or receiving) antennas. Additional performance analysis is also conducted to quantify the signal-to-noise ratio improvement. The complexity analysis reveals that the candidate phase-rotation vectors of WLSD are no more than $(\frac{1}{2})^{N_T}$ of the SD candidates. Simulation results show that the proposed WLSD can achieve quasi-optimal bit error rate performance, while the computational complexity is reduced by more than a half compared with the Schnorr–Euchner sphere decoder.
01 Sep 2016
TL;DR: GSPPM is compared with some of the existing spatial modulation techniques, and results show that GSPPM provides an attractive trade-off between energy and spectral efficiency.
Abstract: In this paper, we investigate the performance of a spatial modulation scheme that combines the energy efficiency of pulse position modulation (PPM) with the spectral efficiency of generalized space shift keying (GSSK) for optical wireless communication system. The combined scheme is called generalized spatial pulse position modulation (GSPPM). We present the error performance analysis and validate the results through simulation. Error performance results show that the upper bound derived in the theoretical analysis is tight for all cases when the symbol error rate is below 0.1. The influence of parameters such as channel path gain and number of PPM slots on GSPPM's performance is illustrated. GSPPM is compared with some of the existing spatial modulation techniques, and results show that GSPPM provides an attractive trade-off between energy and spectral efficiency.
TL;DR: This paper investigates the bit error rate (BER) for multicast multiple-input multiple-output (MIMO) systems, employing spatial modulation and its variants, called multicast SM-type MIMO systems, in Rayleigh fading channels and provides an explicit expression for the SNR degradation caused by the receive correlation through the analysis.
Abstract: In this paper, we investigate the bit error rate (BER) for multicast multiple-input multiple-output (MIMO) systems, employing spatial modulation (SM) and its variants, called multicast SM-type MIMO systems, in Rayleigh fading channels. The system BER, here, is derived by first attaining the BER of the worst receiver of each channel realization set, and then averaging over all possible sets. We first consider the uncorrelated channels. By exploiting the system statistics, a tight BER upper bound is proposed and the diversity is discussed for the systems. We then perform the asymptotic analysis, and show that the BER of the multicast SM-type MIMO system can be alternatively analyzed by analyzing the simple point-to-point SM-type MIMO system with Weibull fading channels. Through this property, a closed-form asymptotic BER upper bound is provided and the impact of the receiver number on BER is analyzed. Subsequently, our investigation is extended to correlated channels where all the receivers share the same correlation statistics. The BER analysis is performed again through the framework similar to the uncorrelated case. In the analysis, the tight upper bound is derived and the effect of correlations is analyzed. Moreover, we provide an explicit expression for the SNR degradation caused by the receive correlation through the analysis. Finally, simulations are exploited to evaluate the BER of the multicast SM-type MIMO systems and validate the analyses.
TL;DR: It is shown that the decision metric for MC is an accumulation of the Euclidean distances used by the ML single-user MIMO detector, and an efficient hardware architecture emerges that exploits this commonality between the classification and detection steps and results in sharing of hardware resources.
Abstract: We consider a multi-user multiple-input multiple-output (MU-MIMO) system that uses orthogonal frequency division multiplexing (OFDM). Several receivers are developed for data detection, where the receivers have partial state information about the MU-MIMO transmission; however, the modulation constellation of the co-scheduled users is unknown. We propose a joint data detection and maximum likelihood (ML) modulation classification (MC) of the co-scheduled user. We show that the decision metric for MC is an accumulation of the Euclidean distances used by the ML single-user MIMO detector. An efficient hardware architecture emerges that exploits this commonality between the classification and detection steps and results in sharing of hardware resources.