Improved error performance of a 3/4‐Sezginer space‐time block codes

The Alamouti space‐time block code (STBC) achieves full diversity gain at a rate of 1/2. However, the Alamouti scheme does not provide multiplexing gain. The Silver code offers both diversity and multiplexing gain. It has a minimum normalization determinant of . The Golden code is another STBC that offers both diversity and multiplexing gain. The Golden code is ranked higher than the Silver code because of its lower minimum normalization determinant of , however, the golden code suffers from a high detection complexity in the modulation order of M⁴. The 3/4‐Sezginer code is another STBC, which compromises between the Alamouti scheme and the Golden code in terms of diversity gain and multiplexing gain. The 3/4‐Sezginer code achieves full diversity and half of multiplexing gain. The uncoded space‐time labeling diversity (USTLD) is a recent scheme that improves the error performance when applied to the STBC in multiple‐input multiple‐output (MIMO) systems and will be applied to the 3/4‐Sezginer STBC to improve the error performance in this paper. The theoretical error probability for both the 3/4‐Sezginer STBC and the improved system is formulated using the union bound in this paper. The theoretical error probabilities of both 16‐QAM and 64‐QAM are validated through Monte Carlo simulation. The simulation and theoretical results show that the proposed system with 4 N_R can achieve an SNR gain of 1 dB for 16‐QAM and 1.2 dB 64‐QAM at a bit error rate (BER) of 10^?6.     

Trellis code‐aided high‐rate M‐QAM space‐time labeling diversity using a unitary expansion

In this paper, we present a high‐rate M‐ary quadrature amplitude modulation (M‐QAM) space‐time labeling diversity (STLD) system that retains the robust error performance of the conventional STLD system. The high‐rate STLD is realised by expanding the conventional STLD via a unitary matrix transformation. Robust error performance of the high‐rate STLD is achieved by incorporating trellis coding into the mapping of additional bits to high‐rate codes. The comparison of spectral efficiency between the proposed trellis code‐aided high‐rate STLD (TC‐STLD) and the conventional STLD shows that TC‐STLD with 16‐QAM and 64‐QAM respectively achieves a 12.5% and 8.3% increase in spectral efficiency for each additional bit sent with the transmitted high‐rate codeword. Moreover, we derive an analytical bound to predict the average bit error probability performance of TC‐STLD over Rayleigh frequency‐flat fading channels. The analytical results are verified by Monte Carlo simulation results, which show that the derived analytical bounds closely predict the average bit error probability performance at high signal‐to‐noise ratios (SNR). Simulation results also show that TC‐STLD with 1 additional bit achieves an insignificant SNR gain of approximately 0.05 dB over the conventional STLD, while TC‐STLD with 2 additional bits achieves an SNR gain of approximately 0.12 dB.     

SSD‐enhanced uncoded space‐time labeling diversity

Space‐time labeling diversity (STLD) has been shown to be an efficient technique for improving the bit error rate (BER) performance of an uncoded space‐time coded modulation system. In this paper, signal space diversity (SSD) is incorporated into the uncoded STLD system to further enhance the system BER performance. A tight closed‐form union bound on the BER of the proposed system is derived and is used to optimize the rotation angle of the SSD scheme. Simulation results are used to confirm the theoretical bound derived for the system. The results also show performance gains of approximately 2.0 dB at a BER of 10^?6 and 1.6 dB at a BER 10^?4 from incorporating SSD into the uncoded STLD system using 16QAM and 64QAM, respectively. Furthermore, a low complexity detection scheme based on orthogonal projection is formulated for the proposed scheme and, in comparison with the optimal maximum‐likelihood detector, is shown to result in a 56% and 95% reduction in computation complexity for the 16QAM and 64QAM versions of the proposed system, respectively.     

BER performance of MQAM with L‐branch MRC diversity reception over correlated Nakagami‐m fading channels

Exact and closed form generalized expressions for bit error rate (BER) of M‐ary quadrature amplitude modulation (MQAM) with L‐branch maximal ratio combining (MRC) space diversity reception in fading channels are derived and analyzed. The fading channels are modeled as identical but correlated frequency‐nonselective slow Nakagami‐m fading channels corrupted by additive white Gaussian noise (AWGN). Analytical results obtained are in terms of few finite range integrals with an integrand composed of elementary functions. Because of their simple form, these analytical results readily allow numerical evaluation in cases of practical interest. The results are also general enough to include Nakagami‐m fading channels with and without correlation, no diversity system, Rayleigh fading channels with and without correlation, and AWGN as special cases. The numerical results for the case of 16QAM are shown graphically and also in tabular form in order to examine the effects of fading severity, order of diversity, and branch correlation on the BER performance. The two correlation models considered are constant correlation model and exponential correlation model. One may be interested to know how the BER of MQAM is related to symbol error rate (SER) of MQAM. Therefore, the BER results obtained in this paper are also compared with that obtained directly from the SER. It is expected that the analytical results presented in this paper will provide a convenient tool for design and analysis of a radio communication system with space diversity reception in uncorrelated and correlated fading environment. Copyright © 2002 John Wiley & Sons, Ltd.     

Bit error rate for rectangular QAM with arbitrary constellation mapping in Nakagami‐m channels

We present closed‐form expressions for the bit error rate (BER) of rectangular quadrature amplitude modulation (QAM) in Nakagami‐m fading channels. The presented formulas, which are valid for arbitrary bits‐to‐symbols mapping, thus may be used when non‐Gray mapping is employed, are particularly useful in the low signal‐to‐noise ratio (SNR) range and/or for small values of the parameter m. The advantage of the proposed expressions over the known bounding techniques is illustrated through numerical simulations. Copyright © 2006 John Wiley & Sons, Ltd.     

16‐QAM OFDM‐Based W‐Band Polarization‐Division Duplex Communication System with Multi‐gigabit Performance

This paper presents a novel 90 GHz band 16‐quadrature amplitude modulation (16‐QAM) orthogonal frequency‐division multiplexing (OFDM) communication system. The system can deliver 6 Gbps through six channels with a bandwidth of 3 GHz. Each channel occupies 500 MHz and delivers 1 Gbps using 16‐QAM OFDM. To implement the system, a low‐noise amplifier and an RF up/down conversion fourth‐harmonically pumped mixer are implemented using a 0.1‐μm gallium arsenide pseudomorphic high‐electron‐mobility transistor process. A polarization‐division duplex architecture is used for full‐duplex communication. In a digital modem, OFDM with 256‐point fast Fourier transform and (255, 239) Reed‐Solomon forward error correction codecs are used. The modem can compensate for a carrier‐frequency offset of up to 50 ppm and a symbol rate offset of up to 1 ppm. Experiment results show that the system can achieve a bit error rate of 10^–5 at a signal‐to‐noise ratio of about 19.8 dB.     

Exact closed‐form symbol error rate of arbitrary rectangular M‐QAM over Rayleigh fading for two‐branch transmit diversity

By using a ‘pre‐averaging method’, we successfully derive an exact closed‐form symbol error rate (SER) expression for the particular case of two transmit‐one receive antenna diversity system employing arbitrary rectangular M‐QAM signalling over flat Rayleigh fading. Fading between branches are assumed independent. Both identical and distinct branch powers are considered. The closed‐form SER obtained is in terms of elemental functions containing no unevaluated integrals nor lengthy and complicated transcendental functions. Simulation results show that square M‐QAM outperforms rectangular M‐QAM for a given size M. Monte Carlo simulation results are found in excellent agreements with theoretical results. Copyright © 2006 John Wiley & Sons, Ltd.     

Bit error probability of the M‐QAM scheme under η‐μ fading and impulsive noise in a communication system using spatial diversity

This paper presents a new and exact expression for the bit error probability (BEP) of the square M‐ary quadrature amplitude modulation (M‐QAM) scheme, with the channel under double gated additive white Gaussian noise (G²AWGN) and η‐μ fading in a communication system using the spatial diversity technique. The expression for the BEP is written in terms of the Appell function. The BEP curves are presented under different values of the number of branches of the maximum ratio combining (MRC) receiver, order of the constellation M, and parameters that characterize mathematically the channel, corroborated by simulations performed with Monte Carlo method.     

Variable antenna‐space shift keying for high spectral efficiency in exponentially correlated channels

In space shift keying (SSK), all information bits are transmitted by antenna indices rather than transmitting symbols. To obtain high spectral efficiency, exponentially increasing number of antennas is used, which is generally not practical. Less number of antennas can only be possible by using more than one active antenna, such as generalized SSK, but this type of solutions result in excessive degradation in bit error ratio in correlated channels. In this study, variable number of active antennas for each codeword is proposed and called variable antenna‐SSK. First of all, pairwise error probability is obtained for variable number of antennas in the case of correlated channels. Then, to reduce the correlation effect, a novel antenna codeword construction method that minimizes the pairwise error probability is introduced for exponentially correlated channels. Codeword sets are obtained for k = 3 and 8 bits/s/Hz for 7 and 13 transmit antennas. Simulation results show that variable antenna‐SSK gets better performance according to its counterparts with increasing effect of correlation. Copyright © 2014 John Wiley & Sons, Ltd.     

GF(q)‐based precoding: information theoretical analysis and performance evaluation

In this paper, a new precoding scheme that is based on the operations in Galois field of size q = 2^m(GF(q)) is proposed. Generally, precoding is a processing technique at transmitters to match the input signal to the channel in order to achieve optimal channel capacity through fully utilizing space, time, and frequency diversity. Precoding schemes can be divided into two main categories: linear precoding and nonlinear precoding. It has been shown from an information theoretical aspect that both the linear and nonlinear precoding schemes can achieve the optimal channel capacity. Our proposed GF(q)‐based precoding scheme is a nonlinear precoding technique, and the idea originates from finite inputs of the modulated symbols. When representing the modulated symbols and the elements in precoding matrix with the finite elements in Galois field of size q, and applying the operations defined in GF(q), we can obtain the precoded symbols that contains information of the original symbols. Starting from binary symmetry channel to additive Gaussian white noise channels, we have demonstrated that the proposed GF(q)‐based precoding schemes can enhance the system mutual information when the original finite inputs are not uniformly distributed. In addition, inspired by the mutual information analysis in binary symmetry channel, we investigated the selection of the precoding matrix in GF(q)‐based precoding schemes. As mutual information indicates the information about the source carried by the symbols of the channel output, greater mutual information enables the receivers to recover more information about the original source. To further utilize the greater mutual information brought by the proposed GF(q)‐based precoding schemes, we proposed a novel‐receiving structure by exchanging soft information between the GF(q) decoding block and channel decoding block. Simulation results show that the proposed iterative receiver improves the system bit error rate performance by 1 and 2 dB at the bit error rate level of 10 ^− 6 with binary phase shift keying and quadrature phase shift keying modulations, respectively. Inspired by the encouraging results of greater mutual information and better bit error rate performance, we are convinced that the proposed GF(q)‐based precoding schemes can be extended to fading channels and multiple input–multiple output systems to further approach channel capacity. Copyright © 2016 John Wiley & Sons, Ltd.     

Spectral efficiency improvement with SISO and SIMO in M‐QAM over millimeter‐wave links

This paper proposes a spectral efficiency improvement technique for millimeter wave (mmWave) links. The proposed technique provides an efficient utilization of the mmWave link capacity. This technique is applied in three cases the single‐input single‐output (SISO), single‐input multiple‐output (SIMO) with the maximal ratio combining and with the equal gain combining. The M‐ary quadrature amplitude modulation scheme is used in our work. The power series expansion is used for deriving closed‐form expressions for bit error rate (BER) performances in all studied cases. The BER closed‐form expressions are confirmed by the numerical solution of the integral equations. The simulation results show that a high spectral efficiency can be accomplished by the proposed technique. As well as the derived expressions closely match with the numerical solution of integration expressions at different values of modulations order the Rician factor. For instance, the spectral efficiency gain achievement is 8 at signal‐to‐noise ratio (SNR) equals 34 dB in the case of SISO system whereas in the case of SIMO system, the same gain is achieved at SNR equals 24 dB. As well as the BER performance is enhanced from 1.188 × 10^?4, 7.112 × 10^?4, 4.164 × 10^?3, and 3.286 × 10^?2 to 8.717 × 10^?16, 1.119 × 10^?12, 1.308 × 10^?9, and 4.905 × 10^?6 for M = 4, 16, 64, and 256, respectively, at SNR equals 30 dB.     

Error performance of Uncoded Space Time Labelling Diversity in spatially correlated Nakagami‐q channels

Greater spectral efficiency has recently been achieved for Uncoded Space Time Labelling Diversity (USTLD) systems by increasing the number of antennas in the transmit antenna array. However, due to constrained physical space in hardware, the use of more antennas can lead to degradation in error performance due to correlation. Thus, this paper studies the effects of spatial correlation on the error performance of USTLD systems. The union bound approach, along with the Kronecker correlation model, is used to derive an analytical expression for the average bit error probability (ABEP) in the presence of Nakagami‐q fading. This expression is validated by the results of Monte Carlo simulations, which shows a tight fit in the high signal‐to‐noise ratio (SNR) region. The degradation in error performance due to transmit and receive antenna correlation is investigated independently. Results indicate that transmit antenna correlation in the USTLD systems investigated (3 × 3 8PSK, 2 × 4 16PSK, 2 × 4 16QAM, and 2 × 4 64QAM) causes a greater degradation in error performance than receive antenna correlation. It is also shown that 2 × 4 USTLD systems are more susceptible to correlation than comparable space‐time block coded systems for 8PSK, 16PSK, 16QAM, and 64QAM.     

16‐QAM OFDM‐Based K‐Band LoS MIMO Communication System with Alignment Mismatch Compensation

This paper presents a novel K‐band (18 GHz) 16‐quadrature amplitude modulation (16‐QAM) orthogonal frequency‐division multiplexing (OFDM)‐based 2 × 2 line‐of‐sight multi‐input multi‐output communication system. The system can deliver 356 Mbps on a 56 MHz channel. Alignment mismatches, such as amplitude and/or phase mismatches, between the transmitter and receiver antennas were examined through hardware experiments. Hardware experimental results revealed that amplitude mismatch is related to antenna size, antenna beam width, and link distance. The proposed system employs an alignment mismatch compensation method. The open‐loop architecture of the proposed compensation method is simple and enables facile construction of communication systems. In a digital modem, 16‐QAM OFDM with a 512‐point fast Fourier transform and (255, 239) Reed‐Solomon forward error correction codecs is used. Experimental results show that a bit error rate of 10^?5 is achieved at a signal‐to‐noise ratio of approximately 18.0 dB.     

16‐QAM‐Based Highly Spectral‐Efficient E‐band Communication System with Bit Rate up to 10 Gbps

This paper presents a novel 16‐quadrature‐amplitude‐modulation (QAM) E‐band communication system. The system can deliver 10 Gbps through eight channels with a bandwidth of 5 GHz (71‐76 GHz/81‐86 GHz). Each channel occupies 390 MHz and delivers 1.25 Gbps using a 16‐QAM. Thus, this system can achieve a bandwidth efficiency of 3.2 bit/s/Hz. To implement the system, a driver amplifier and an RF up‐/down‐conversion mixer are implemented using a 0.1 µm gallium arsenide pseudomorphic high‐electron‐mobility transistor (GaAs pHEMT) process. A single‐IF architecture is chosen for the RF receiver. In the digital modem, 24 square root raised cosine filters and four (255, 239) Reed‐Solomon forward error correction codecs are used in parallel. The modem can compensate for a carrier‐frequency offset of up to 50 ppm and a symbol rate offset of up to 1 ppm. Experiment results show that the system can achieve a bit error rate of 10^?5 at a signal‐to‐noise ratio of about 21.5 dB.     

Performance analysis of M‐APSK generalised spatial modulation with constellation reassignment

Generalised spatial modulation (GSM) is a recently developed multiple‐input multiple‐output (MIMO) technique aimed at improving data rates over conventional spatial modulation (SM) systems. However, for identical antenna array size and configurations (AASC), the bit error rate (BER) of GSM systems in comparison with SM systems is degraded. Recently, a GSM system with constellation reassignment (GSM‐CR) was proposed in order to improve the BER of traditional GSM systems. However, this study focused on M‐ary quadrature amplitude modulation (M‐QAM) schemes. The focus of this paper is the application of a circular constellations scheme, in particular, amplitude phase shift keying (APSK) modulation, to GSM and GSM‐CR systems. An analytical bound for the average BER of the proposed M‐APSK GSM and M‐APSK GSM‐CR systems over fading channels is derived. The accuracy of this bound is verified using Monte Carlo simulation results. A 4 × 4 16‐APSK GSM‐CR system achieves a gain of 2.5 dB at BER of 10^?5 over the traditional 16‐APSK GSM system with similar AASC. Similarly, a 6 × 4 32‐APSK GSM‐CR system achieves a gain of 2 dB at BER of 10^?5 over equivalent 32‐APSK GSM system.     

Space‐time block coded spatial modulation with labeling diversity

Space‐time block coded spatial modulation (STBC‐SM) exploits the advantages of both spatial modulation and the Alamouti space‐time block code. Meanwhile, space‐time labeling diversity has demonstrated an improved bit error rate (BER) performance in comparison to the latter. Hence, in this paper, we extend the application of labeling diversity to STBC‐SM, which is termed STBC‐SM‐LD. Under identical channel assumptions, STBC‐SM‐LD exhibits superior BER performance compared to STBC‐SM. For example, with 4 × 4, 64‐quadrature amplitude modulation (64‐QAM), STBC‐SM‐LD has a BER performance gain of approximately 2.6 dB over STBC‐SM. Moreover, an asymptotic bound is presented to quantify the average BER performance of M‐ary QAM STBC‐SM‐LD over independent and identically distributed Rayleigh frequency‐flat fading channels. Monte Carlo simulations for STBC‐SM‐LD agree well with the analytical framework. In addition to the above, low‐complexity (LC) near‐maximum‐likelihood detectors for space‐time labeling diversity and STBC‐SM‐LD are presented. Complexity analysis of the proposed LC detectors shows a substantial reduction in computational complexity compared to their ML detector counterparts. For example, the proposed detector for STBC‐SM‐LD achieves a 91.9% drop in computational complexity for a 4 × 4, 64‐QAM system. The simulations further validate the near‐maximum‐likelihood performance of the LC detectors.     

突发自适应调制信号的调制识别算法研究

针对突发自适应调制信号中的PSK和QAM调制方式识别问题,本文提出了一种能够识别BPSK、QPSK、8PSK以及16QAM、32QAM、64QAM、128QAM、256QAM八种信号类型的盲识别算法。该算法首先对信号的循环平稳性进行了分析和讨论,给出了利用循环高阶累积量的特征实现信号识别分类的理论依据。然后,提出了三种基于循环累积量的特征分别实现了QAM和PSK类间识别、MPSK类内识别以及方形QAM与十字形QAM的识别。最后通过对MQAM信号的瞬时幅度分布特性的深入研究和分析,提出了一种基于瞬时包络平方的方差的特征实现了QAM的类内识别。该算法选择了二叉树支持向量机作为识别分类器,并设计了一种新的识别流程完成了对上述信号调制方式的识别。该算法无需精确同步,对载波相位具有较好的鲁棒性,并能够对中频信号进行识别。仿真实验表明,该算法能够实现在较低信噪比条件下突发信号的识别。      

High‐rate uncoded space‐time labelling diversity with low‐complexity detection

Uncoded space‐time labelling diversity (USTLD) is a recent scheme that improved the error performance compared to conventional multiple‐input, multiple‐output systems. Thus far, USTLD has suffered from limited achievable data rates, as the original model uses only two transmit antennas. This motivates for the work in this paper, where the USTLD model is extended to allow for any desired number of transmit antennas. An analytical bound for the average bit error probability of this high‐rate USTLD (HR‐USTLD) system is derived. This expression is verified using the results of Monte Carlo simulations, which show a tight fit in the high signal‐to‐noise ratio region. The increased data rates associated with larger transmit antenna arrays in HR‐USTLD systems come at the cost of increased detection complexity. Therefore, this paper studies the application of low‐complexity detection algorithms based on the popular QR decomposition technique and proposes a new algorithm specifically designed for HR‐USTLD systems. Analysis of this algorithm in terms of accuracy and computational complexity is also provided and benchmarked against maximum‐likelihood detection (MLD). It is shown that the proposed algorithm achieves near‐MLD accuracy, while reducing complexity by 79.75% and 92.53% for the respective 4 × 4 16QAM and 4 × 5 16PSK HR‐USTLD systems investigated.     

Effects of pointing errors and channel fading on the performance of free‐space optically‐preamplified PPM systems

In this paper, we study the impact of pointing errors and channel fading on the performance of free‐space, optically preamplified, M ‐ary PPM systems. We consider two types of free‐space optical links: (i) inter‐satellite links and (ii) inter‐building links. For inter‐satellite links, only pointing error is considered. Starting with a Rayleigh model for the pointing error angle, we derive analytically the PDF for the pointing error parameter and for the signal‐to‐noise ratio (SNR) per bit. For inter‐building links, we derive the density function for the SNR per bit that includes the combined effects of pointing errors and channel fading, assuming Rayleigh‐distributed pointing errors. The channel fading models considered in this study for inter‐buildings links are the log‐normal and gamma–gamma models. We provide the error probability as a function of the average SNR per bit for both types of links. To cover systems with and without forward error correction, we compute the average SNR per bit required to achieve a bit error rate of 10^?4 and 10^?9. The corresponding power penalties are computed for different symbol sizes, scintillation indexes, and pointing jitters. Copyright © 2016 John Wiley & Sons, Ltd.     

Performance of optimum and suboptimum OFDM‐CPM receivers over multipath fading channels

A class of orthogonal frequency division multiplexing‐continuous phase modulation (OFDM‐CPM) signals is introduced in which binary data sequence is mapped to complex symbols using the concept of correlated phase states of a CPM signal. Canonical optimum and suboptimum multiple‐symbol‐observation OFDM‐CPM receivers are derived. Multipath channel with AWGN is assumed. The receivers are analyzed for bit error rate (BER) performance in terms of high‐ and low‐SNR bounds. These bounds are illustrated as a function of parameter h, time delay and attenuation level. It is shown that OFDM‐CPM systems, with h=0.5,0.25 and an observation interval length of two symbols, can outperform conventional OFDM‐PSK system for a two‐ray multipath model. Copyright © 2005 John Wiley & Sons, Ltd.