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.     

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.     

Performance evaluation of (D)APSK modulated coherent optical OFDM system

Performance of amplitude and phase shift keying (APSK) modulated coherent optical orthogonal frequency division multiplexing (CO-OFDM) with and without differential encoding is investigated. Numerical simulations based on 40 Gbit/s single-channel and 5 ^* 40 Gbit/s wavelength division multiplexing transmission are performed, and the impacts of amplified spontaneous emission noise, laser linewidth, chromatic dispersion, and fiber nonlinearity on the system performance are analyzed. The results show that compared with conventional 16 quadrature amplitude modulation (QAM) modulated optical OFDM signal, although 16(D)APSK modulated optical OFDM signal has a lower tolerance towards amplified spontaneous emission (ASE) noise, it has a higher tolerance towards fiber nonlinearity such as self-phase modulation (SPM) and cross-phase modulation (XPM): the optimal launch power and the corresponding Q² factor of 16(D)APSK modulated OFDM signal are respectively 2 dB and 0.5 dB higher than 16QAM modulated optical OFDM signal after 640 km transmission, both in single-channel and WDM CO-OFDM systems. Although the accumulated CD decreases the peak-to-average power ratio (PAPR) during transmission, 16(D)APSK modulated OFDM signal will still remain an advantage compared with 16QAM modulated OFDM signal up to 1000 km single-channel transmission, meanwhile relaxing the needs for training symbols and pilot subcarriers and consequently increase the spectral efficiency.     

Media‐based single‐symbol generalized spatial modulation

Single‐symbol generalized spatial modulation (GSM) improves upon the limitation of spatial modulation (SM) by reducing the number of required transmit antennas to achieve high data rates. In this paper, we investigate the application of media‐based modulation (MBM) based on radio frequency mirrors to single‐symbol GSM, with the aim of improving error performance. The theoretical average bit error probability of the proposed scheme is derived, employing a lower bound approach and used to validate the Monte Carlo simulation results. Finally, the effect of optimal and suboptimal mirror activation pattern selection employing Euclidean distance and channel amplitude coupled with antenna correlation is investigated for the proposed media‐based single‐symbol GSM system. The Monte Carlo simulation results obtained demonstrate a significant improvement over the conventional SM, GSM, and media‐based SM (MB‐SM) schemes in terms of error performance and spectral efficiency.     

Dual-mode SM/STBC system with antenna subset selection employing ML detection

Multiple input multiple output (MIMO) antenna system is a promising candidate to meet the demands of 4th Generation (4G) cellular communication systems by offering increased spectral efficiency through the spatial multiplexing (SM) gain, and improved link reliability through the space–time block coding (STBC) diversity gain. This paper presents a new scheme that combines the dual-mode SM/STBC and the antenna subset selection (AnSS) schemes. In the proposed scheme, the combination of the SM/STBC switching and the full antenna subset selection (AnSS) at both the transmitter (Tx) and the receiver (Rx) ends of the communication channel are adaptively selected through a simple algorithm based on the singular values of the channel matrix at the Rx side. Thus, the new scheme achieves the best BER performance over the previous works regardless of the data rate. The simulation results show that the proposed scheme with the full AnSS outperforms the previous works, by up to the 12.5 dB at the bit error rate (BER) of 10^‐5${10}^{‐5}$. Further, a partial AnSS is also proposed which dramatically reduces both the computational complexity (by 31%) and the hardware (by 50%), cost, without any appreciable loss in the BER performance, when compared with the full AnSS.     

Performance analysis of hybrid transmit antenna selection/maximal‐ratio transmission in Nakagami‐m fading channels

Hybrid diversity systems have been of great importance because they provide better diversity orders and robustness to the fading effects of wireless communication systems. This paper focuses on the performance analysis of multiple‐input gle‐output systems that employ combined transmit antenna selection (TAS)/maximal‐ratio transmission (MRT) techniques (i.e., hybrid TAS/MRT). The probability density function, the moment generating function and the n ^th order moments of the output signal‐to‐noise ratio of the investigated diversity scheme are derived for independent identically distributed flat Nakagami‐m fading channels. The system capacity of the hybrid TAS/MRT scheme is examined from the outage probability perspective. Exact bit/symbol error rate (BER/SER) expressions for binary frequency shift keying, M‐ary phase shift keying and square M‐ary quadrature amplitude modulation signals are derived by using the moment generating function‐based analysis method. By deriving the upper bounds for BER/SER expressions, it is also shown that the investigated systems achieve full diversity orders at high signal‐to‐noise ratios. Also, by Monte Carlo simulations, analytical performance results are validated and the effect of feedback delay, channel estimation error and feedback quantization error on BER/SER performances are examined. Copyright © 2011 John Wiley & Sons, Ltd.     

The impact of impulse postfix length on the BER performance of IP‐OFDM systems

The impulse postfix OFDM (IP‐OFDM) system exploits the IP, which consists of a high power impulse sample and several zero samples at the end of a zero padded‐OFDM symbol block, to estimate channel impulse response (CIR) in time domain. In this paper, the impact of IP length on the BER performance of the IP‐OFDM system is analyzed. According to the analytic results, the BER performance can be significantly degraded with both a shorter length of IP as well as a longer length of IP than that of the CIR. Thus, an adaptive IP scheme, which adjusts the length of IP adaptively depending on the length of CIR, is proposed to enhance the BER performance of IP‐OFDM systems and its effectiveness is demonstrated by computer simulations. The BER performance of the IP‐OFDM systems with the proposed adaptive scheme is compared with that of the conventional IP‐OFDM system over various modulation schemes. Simulation results show that the IP‐OFDM with the proposed scheme can achieve about 2 dB performance enhancement compared with that of conventional systems at BER=10^?2. Copyright © 2010 John Wiley & Sons, Ltd.     

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.     

Turbo‐coded APSK modulations design for satellite broadband communications

This paper investigates the design of power and spectrally efficient coded modulations based on amplitude phase shift keying (APSK) modulation with application to satellite broadband communications. APSK represents an attractive modulation format for digital transmission over nonlinear satellite channels due to its power and spectral efficiency combined with its inherent robustness against nonlinear distortion. For these reasons APSK has been very recently introduced in the new standard for satellite Digital Video Broadcasting named DVB‐S2. Assuming an ideal rectangular transmission pulse, for which no nonlinear inter‐symbol interference is present and perfect pre‐compensation of the nonlinearity, we optimize the APSK constellation. In addition to the minimum distance criterion, we introduce a new optimization based on the mutual information; this new method generates an optimum constellation for each spectral efficiency. To achieve power efficiency jointly with low bit error rate (BER) floor we adopt a powerful binary serially concatenated turbo‐code coupled with optimal APSK modulations through bit‐interleaved coded modulation. We derive tight approximations on the maximum‐likelihood decoding error probability, and results are compared with computer simulations. The proposed coded modulation scheme is shown to provide a considerable performance advantage compared to current standards for satellite multimedia and broadcasting systems. Copyright © 2006 John Wiley & Sons, Ltd.     

Constellation design and performance analysis of the parallel spatial modulation

Spatial modulation (SM) is a relatively recent multiple‐input multiple‐output (MIMO) system in which information is carried by the index of the antenna used for transmission as well as by the conventional signal symbols. Several systems that build upon SM have since been proposed including the generalized SM (GSM), a variant of GSM with multiple active antennas (MA‐SM), quadrature SM (QSM), and parallel SM (PSM), among others. The PSM system can increase the spectral efficiency by splitting the antenna set into groups and applying SM independently in each group using the same signal symbol. In this paper, we first derive the upper bound on the error probability of the PSM. The search of the optimal constellation set is then formulated as a multi‐objective optimization problem, where the obtained constellation minimizes the asymptotic error probability. We conclude that as the number of antenna groups increases, the proposed constellation converges to the conventional phase‐shift keying at relatively low number of transmit antennas. The simulation results show that the proposed constellation outperforms conventional constellations by as much as 5 dB, for high‐modulation orders. Since the multi‐objective optimization is independent of the channel matrix, it can be easily done off‐line. This implies that these gains come at no complexity or delay cost.     

Antenna Selection Schemes in Quadrature Spatial Modulation Systems

This paper presents antenna selection schemes for recently proposed quadrature spatial modulation (QSM) systems. The antenna selection strategy is based on Euclidean distance optimized antenna selection (EDAS). The symbol error rate (SER) performance of these schemes is compared with that of the corresponding algorithm associated with spatial modulation (SM) systems. It is shown through simulations that QSM systems using EDAS offer significant improvement in terms of SER performance over SM systems with EDAS. Their SER performance gains are seen to be about 2 dB–4 dB in E_s/N₀ values.     

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.     

Cross-correlated correlative encoding: an efficient modulationmethod

A new cross-correlated correlative baseband encoding scheme is presented as a means of doubling the capacity of a mobile communication systems without the cost of complex baseband filtering. System performance is studied in a non-linear amplified channel for 6 to 9 dB improved power efficiency. The system is analyzed for spectrum efficiency, adjacent channel interference (ACI), co-channel interference (CCI) and bit error rate (BER) performance in a Rayleigh faded cellular network. Computer simulated results and hardware experimentation show that modified correlative encoding achieves up to a 70% improvement in spectrum efficiency and double network capacity when compared to constant envelope GMSK modulation used in GSM, DCS1800, PCS1900 and DECT systems     

一种用于BICM-ID系统的新颖8APSK映射方案

为了能够通过高阶调制信号增加信道容量,提高编码增益和频谱效率,对8阶振幅移相键控(APSK)星座映射方案进行优化.基于欧氏距离设计准则提出一种新颖(2,6)-scheme 8APSK映射方案,并应用于联合准循环构造法构造的低密度奇偶校验(LDPC)(4599,4307)码的比特交织编码调制迭代译码(BICM-ID)系统中.信道容量仿真表明,所提方案在高、低信噪比区域都具有非常优越的互信息性能.误码率(BER)性能仿真表明,在BER为10-7时,联合LDPC(4599,4307)码的(2,6)-scheme 8APSK映射方案较(4,4)-scheme 8APSK映射方案、8PSK调制的格雷(Gray)映射、集分割(SP)映射、半集分割(SSP)映射分别提高了约0.45 dB、1.10 dB、1.62 dB、2.13 dB的编码增益.外附信息转移(EXIT)图仿真说明,所提方案能够更早地打开译码通道,从而更早地通过迭代来实现无错译码.     

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.     

A novel artificial bee colony detection algorithm for massive MIMO system

As a hot‐spot of 5G, the research on detection algorithms for massive multiple input multiple output (MIMO) system is significant but difficult. The traditional MIMO detection algorithms or their improvements are not appropriate for large scaled antennas. In this paper, we propose artificial bee colony (ABC) detection algorithm for massive MIMO system. As one advanced technology of swarm intelligence, ABC algorithm is most efficient for large scaled constrained numerical combinatorial optimization problem. Therefore, we employ it to search the optimum solution vector in the modulation alphabet with linear detection result as initial. Simulation and data analysis prove the correctness and efficiency. Versus the scale of massive MIMO systems from 64 × 64 to 1024 × 1024 with uncoded four‐quadrature‐amplitude‐modulation signals, the proposed ABC detection algorithm obtains bit error rate of 10 ^− 5 at low average received signal‐to‐noise‐ratio of 12 dB with rapid convergence rate, which approximates the optimum bit error rate performance of the maximum likelihood and achieves the theoretical optimum spectral efficiency with low required average received signal‐to‐noise‐ratio of 10 dB in similar increasing regularity, over finite time of low polynomial computational complexity of per symbol, where N_T denotes the transmitting antennas' number. The proposed ABC detection algorithm is efficient for massive MIMO system. Copyright © 2016 John Wiley & Sons, Ltd.     

Enhancing spectral efficiency of FSO system using adaptive SIM/M‐PSK and SIMO in the presence of atmospheric turbulence and pointing errors

This paper proposes an adaptive transmission modulation (ATM) technique for free‐space optical (FSO) links over gamma‐gamma turbulence channels.The ATM technique provides efficient utilization of the FSO channel capacity for improving spectral efficiency, by adapting the order of the phase‐shift keying modulation scheme, according to the channel conditions and the required bit error rate (BER). To overcome the channel degradation resulting from the turbulence effects as well as the pointing errors (PEs), single‐input multiple‐output (SIMO) system with maximal ratio combining (MRC) is proposed. Exact closed‐form expressions of BER and upper bound of the capacity are derived and verified by Monte Carlo simulations. The numerical results show that the proposed adaptive technique improves the spectral efficiency (SE) five times higher than the nonadaptive technique at the same BER threshold (10^?3).This improvement is achieved at signal‐to‐noise ratio (SNR) equals 27 and 42  dB in the case of atmospheric turbulence without and with PE, respectively. Furthermore, this SE could be obtained while the SNR = 30  dB by using ( 1 × 4 ) SIMO scheme with MRC and PE and having the same transmitting optical power.     

Adaptive predistortion of COFDM signals for a mobile satellite channel

In this paper, we consider the optimization of the performance of QPSK and 16‐QAM coded orthogonal frequency division multiplexing (COFDM) signals over the non‐linear and mobile satellite channel. A high power amplifier and Rician flat fading channel produces non‐linear and linear distortions; an adaptive predistortion technique combined with turbo codes will reduce both types of distortion. The predistorter is based on a feedforward neural network, with the coefficients being derived using an extended Kalman filter (EKF). The conventional turbo code is used to mitigate Rician flat fading distortion and Gaussian noise. The performance over a non‐linear satellite channel indicates that QPSK COFDM followed by a predistorter provides a gain of about 1.7 dB at a BER of 3×10^?3 when compared to QPSK COFDM without the predistortion scheme and 16‐QAM COFDM provides a gain of 0.5 dB output back‐off and 1.2 dB signal to noise ratio at a BER of 3×10^?5 when compared with an adaptive predistorter based on the Harmmerstein model. We also investigate the influence of the guard time interval and Doppler frequency effect on the BER performance. When the guard interval increases from 0 to 0.125T samples and the normalized Doppler frequency is 0.001, there is a gain of 0.7 and 1 dB signal to noise ratio at a BER of 6×10^?4 for QPSK and 16‐QAM COFDM, respectively. Copyright © 2003 John Wiley & Sons, Ltd.     

BER minimization for dual‐polarized wireless systems with polarization‐domain rotation

We consider the problem of bit error rate (BER) degradation because of the power gain imbalance between horizontal (H)‐polarization and vertical (V)‐polarization components in an orthogonal dual‐polarization transmission system. To alleviate the aforementioned BER degradation problem, we propose a non‐orthogonal polarization‐domain rotation scheme where the axes of H‐polarization and V‐polarization components are rotated with different angles at the transmitter and de‐rotated at the receiver. In addition, in order to assess the effectiveness of the polarization‐domain rotation scheme, we derive the closed‐form BER expression under a practical dual‐polarized channel model, which is represented by cross‐polarization ratio and co‐polarization ratio (CPR). We also derive the approximated BER expressions for the two asymptotic values of CPR: balanced CPR and infinite CPR. With the derived BER expressions, we find the optimal rotation angles that jointly minimize the BER. According to the numerical results, it is shown that about 3dB E_b/N₀ gain is obtained at the BER of 10^?4 and the CPR of 10dB by the polarization‐domain rotation scheme with optimal rotation angles compared with the conventional orthogonal dual‐polarization transmission. Copyright © 2015 John Wiley & Sons, Ltd.     

Performance improvement of 60‐GHz wireless optical systems with reverse‐parallel hybrid modulation scheme

This paper improves the performance of 60‐GHz wireless optical system including radio over fibre (RoF) and radio over free space optics (RoFSO), based on novel reverse‐parallel (RP) hybrid modulation scheme. This scheme combines the chromatic dispersion compensation technique of parallel modulation with energy efficiency manipulation technique of reverse modulation. Superior functioning of RoFSO is provided with reverse modulation compared with normal modulation. Comparative investigations are performed by loading 60‐GHz RF signal with 2.5 and 10‐Gbps data and modulating it with both reverse and hybrid modulators. Hybrid modulation performed better with improved BER of 10^?23 at distance of 51 km for 2.5‐Gbps data compared with reverse modulation with BER of 10^?7.