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We design a low-complexity minimum mean square error (MMSE) receiver for a practical rectangular pulse-shaped orthogonal time frequency space (OTFS) massive multiple-input multiple-output (mMIMO) system. The proposed receiver is designed by exploiting the OTFS channel sparsity, and the structure of matrices involved in the MMSE receiver. We show that the sparse OTFS channel matrix is multi-banded, and has a high bandwidth. This is because its non-zero elements, which occur in multiple bands, are scattered throughout the matrix. We reduce its bandwidth by using the Reverse Cuthill-Mckee algorithm. The proposed MMSE receiver does not use any approximation, and thus has the same bit error rate (BER) as that of its conventional counterpart. We show that the proposed receiver, without any BER loss, achieves significantly lower complexity than the existing state-of-the-art receivers. [ABSTRACT FROM AUTHOR]

In this letter, we propose a novel inter-symbol interference (ISI) mitigation scheme for molecular communication via diffusion (MCvD) systems with the optimal detection interval. Its rationale is to exploit the discarded duration (i.e., the symbol duration outside this optimal interval) to relieve ISI in the target system. Following this idea, we formulate an objective function to quantify the impact of the discarded time on bit error rate (BER) performance. Besides, an optimally reusable interval within the discarded duration is derived in closed form, which applies to both the absorbing and passive receivers. Finally, numerical results validate our analysis and show that for the considered MCvD system, significant BER improvements can be achieved by using the derived reusable duration. [ABSTRACT FROM AUTHOR]

Pre-trained Models (PTMs) have reached the state-of-the-art (SOTA) on many Natural Language Processing (NLP) tasks and Computer Vision (CV) tasks, and are called the foundation models of artificial intelligence (AI) systems. In this letter, we introduce PTMs into communication receiver design, which is the first attempt to apply PTMs to the communications field. The powerful capability of PTMs to capture knowledge from massive data enables the PTMs-based receivers to utilize the natural redundancy (NR) that widely exists in the transmitted sources to obtain high performance gains. Intended for uncompressed Chinese text sources, we design a high-performance receiver based on the Bidirectional Encoder Representation from Transformers (BERT) model in the NLP field. We achieve an approximate maximum of posterior marginals (MPM) estimation by obtaining the conditional distribution of the input data from the pre-trained BERT model, and the performance of the approximate MPM estimation can be improved by fine-tuning the BERT model with self-supervised learning. Simulation results demonstrate that the performance of our designed PTMs-based receiver significantly outperforms the classical receiver. [ABSTRACT FROM AUTHOR]

In this letter, an effective divide-and-conquer noise decontamination strategy is proposed to reduce the noise corrupting the reference signals of Hilbert-transform-based $M$ -ary differential chaos shift keying ($M$ -ary DCSK), thereby enhancing the system robustness. An $M$ -ary DCSK with discrete Hartley transform (MDCSK-DHT) is first proposed, which is taken as an example to show the effectiveness of the proposed noise decontamination strategy. Then, a noise-decontamination-driven MDCSK-DHT (ND-MDCSK-DHT) scheme is presented. In this design, the discrete Hartley transform enables the reference and $M$ -ary information-bearing signals to be transmitted in the same time slot, which improves the spectral efficiency and peak to average power ratio (PAPR) performance. Computer simulations show that the bit error rate (BER) performance of MDCSK-DHT can be significantly enhanced by the proposed noise decontamination strategy, and ND-MDCSK-DHT can achieve better BER performance than its competitors. [ABSTRACT FROM AUTHOR]

Radio frequency fingerprint (RFF) is an intrinsic physical characteristic of the device caused by hardware imperfection. It can be extracted from wireless signals and has been widely applied for device identification. However, the improving precision of electronic components reduces the distinguishability of RFF, which makes it difficult to identify large amount of devices that are of the same model, especially in a low signal-to-noise ratio (SNR) scenario. In this letter, we propose an artificial radio frequency fingerprint (ARFF) embedding scheme for device identification, which greatly increases the distinguishability of fingerprints and minimally affects the performance of communication. The scheme includes an adaptive filter based RFF extraction method, a principal component analysis (PCA) based ARFF generation algorithm and a proposed ARFF embedding algorithm that eliminates the influence of the device’s original RFF to form a preset ARFF pattern. Experimental results on ZigBee devices demonstrate that our ARFF based scheme achieves 99.91% identification accuracy and simultaneously has little impact on bit error rate. [ABSTRACT FROM AUTHOR]

In this letter, we present a reconfigurable intelligent surface (RIS)-assisted space shift keying (SSK) modulation and reflection phase modulation (RPM) scheme, where RIS embeds its own information in the reflection phase shift of the reflected radio frequency (RF) signal. More specifically, the RIS simultaneously performs two tasks: i) reflecting the impinging RF signal with a discrete phase shift and ii) embedding the information bits in the phase shift. We perform joint detection for the RPM and SSK symbols using a maximum likelihood detector, and a unified analytical framework is presented for theoretical analysis of the average bit error rate (ABER) and ergodic capacity of the proposed scheme. All numerical results are thoroughly verified through Monte Carlo simulation. Numerical results reveal that the proposed scheme outperforms the conventional SSK scheme. [ABSTRACT FROM AUTHOR]

Quadrature Amplitude Modulation based Filter-Bank Multi-Carrier (QAM-FBMC) is a promising technology to replace Orthogonal Frequency Division Multiplexing (OFDM) in future radio access systems. In this letter, we derive a bit error probability expression of QAM-FBMC systems over AWGN channels and over Rayleigh fading channels. We model the intrinsic interference related to the prototype filter through the interference table and consider the interference distribution to derive the bit error probability in QAM-FBMC systems. Numerical results reveal that the proposed expressions pair perfectly with the simulation results. [ABSTRACT FROM AUTHOR]

Long-Range (LoRa) is one of the emerging technologies in low-power wide-area networks (LPWANs). In this letter, we proposed a Time Domain Multiplexed LoRa (TDM-LoRa) modulation to improve the throughput of conventional LoRa by using up-chirp and down-chirp simultaneously. A low complexity non-coherent algorithm for the TDM-LoRa modulation is also presented. We then derive an analytical expression for the bit error rate (BER) of non-coherent demodulation in the additive white Gaussian noise (AWGN) channel. In addition, a scheme that encodes information bits on both in-phase and quadrature components of the TDM-LoRa symbol is presented to further improve the system data rate. Performance analysis and simulation show that our proposed schemes can achieve better spectral efficiency (SE) and throughput without obvious bit error rate (BER) degradation compared to the LoRa Physical Layer (PHY) scheme. [ABSTRACT FROM AUTHOR]

In this letter, a joint position and constellation mapping (JPCM) assisted differential chaos shift keying (JPCM-DCSK) scheme is proposed to address the problem of unreliable data transmission in the power line communication (PLC) channel subjected to Laplacian impulsive noise. The constellation states and time slot position patterns are integrated cooperatively, which enables JPCM-DCSK to transmit more information bits. An effective JPCM detection algorithm is proposed to recover the information bits. Moreover, the bit error rate (BER) expression of JPCM-DCSK is derived over a multipath PLC channel, which is verified by computer simulations. Comparisons of BER performances demonstrate that JPCM-DCSK outperforms its competitors by 2 dB to 6 dB gains. [ABSTRACT FROM AUTHOR]

Ambient backscatter communication (AmBc) is a modern communication technique that permits smart devices to transfer data with the aid of ambient radio frequency (RF) radiation. This letter investigates the issue of eavesdropper (ED) attacks on multi-tag AmBc systems. In particular, we explore a realistic scenario in which both the reader and the ED are in motion and analyze the influence of their motion on the AmBc system’s secrecy performance when channel estimation is imperfect. Specifically, an analytical expression of secrecy outage probability (SOP) and an asymptotic SOP is derived. Also, the simulation results are shown to confirm the analytical expressions. [ABSTRACT FROM AUTHOR]

Reconfigurable intelligent surface (RIS) and spatial scattering modulation (SSM) are promising candidates for future generations of wireless communication. The former provides an enhanced transmission environment by providing an alternative communication path, while the latter boosts spectral efficiency. In this letter, we firstly propose a novel uplink millimeter-wave (mmWave) communication system that utilizes both RIS and SSM to support data transmission over wireless channels. Specifically, we design the reflecting phase shifters at the RIS to support the two-hop communications. Moreover, a maximum likelihood detector is adopted to a new system with RIS-SSM and a new analytical expression for a tight union upper bound on the bit error rate (BER) is derived. Monte Carlo simulation results are provided to verify the accuracy of the derived analytical expression. Numerical results reveal that the proposed RIS-SSM scheme has a significantly lower BER than the traditional SSM. [ABSTRACT FROM AUTHOR]

In this letter, we investigate the performance of reconfigurable intelligent surface (RIS)-aided networks in the presence of non-identically distributed interferers at the destination. A mathematical framework is proposed to statistically characterize the cascaded channels and to evaluate the performance in terms of outage probability (OP) and average bit error rate (BER). The high signal-to-interference-plus-noise ratio (SINR) analysis reduces to easy-to-compute expressions for the outage probability and BER, which reveals inside information for the system design. We also extend the analysis to study multi-RIS networks with two schemes. Representative results show that the RIS element number and interference setting have a significant impact on the overall system performance. [ABSTRACT FROM AUTHOR]

In this letter, a novel transmission scheme for spatial modulation (SM) is proposed to enhance the security of wiretap channel. In this scheme, partial channel state information (CSI) of the legitimate channel is exploited by the transmitter (Tx) to dynamically adapt the spatial and signal constellations mapping patterns that are unknown to Eve. Thus, Eve cannot successfully decode the confidential information over the wiretap channel. Further, an important virtue of the proposed transmission scheme, Tx does not need to know the full CSI of Eve and legitimate channels. To demonstrate the security guaranteed by the proposed scheme, bit error rate, secrecy rate, and secrecy outage probability are evaluated. [ABSTRACT FROM AUTHOR]

In visible light communications (VLC), the bulbs are used to provide communication and illumination simultaneously. Therefore, it is important to design modulation schemes, which are capable of adjusting the illumination level. The simplest approach to achieve this is compensating an all-one or an all-zero sequence, which however is spectrally inefficient. In this letter, we propose to use the constant sum codes to construct spectral-efficient dimmable pulse amplitude modulation (PAM) for VLC. We also present an efficient algorithm based on graph expanding to design the mapping for the proposed dimmable PAM. Numerical results show that the spectral efficiencies of the proposed dimmable PAM are higher than those of the state-of-the-arts. Numerical results also show that the proposed dimmable PAM performs better than the state-of-the-arts in coded VLC. These results show the potential advantages of the proposed dimmable PAM. [ABSTRACT FROM AUTHOR]

Filter bank orthogonal frequency division multiplexing(FB-OFDM) is a promising multicarrier technique due to its ability to significantly reduce out-of–band (OOB) emission. In this letter, a combined application of FB-OFDM and index modulation (IM) (FB-OFDM-IM) is proposed to improve bit error rate (BER) performance. Firstly, the average bit error probability (ABEP) upper bound is derived over multipath fading channel. Then, a low-complexity maximum likelihood (ML) detection method is designed at receiver. Simulation results verify the superiority of FB-OFDM-IM system in terms of BER performance. Furthermore, the proposed detection scheme is proven to be ML-optimal with much lower complexity. [ABSTRACT FROM AUTHOR]

In this letter, a non-coherent discrete W transform based index-keying $M$ -ary differential chaos shift keying (DWT-IK-MDCSK) system is proposed to tackle the high peak to average power ratio (PAPR) in the code-shifted DCSK systems and meet the demand of high-data-rate transmissions. In such system, multiple chaotic signals and their Hilbert transforms are cooperated closely to convey the $M$ -ary information-bearing signals, and the resultant signals are extended by the index-keying discrete W vectors prior to being added up and transmitted over the channel. Since the index keying technique is used to select the specific discrete W vectors, extra information bits are conveyed by the indices of these vectors, thereby improving the data rate. Then, the analytical bit error rate (BER) expressions of DWT-IK-MDCSK are derived over additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels. Finally, simulation results show the DWT-IK-MDCSK system has a lower PAPR and better BER performance compared to its competitors. [ABSTRACT FROM AUTHOR]

In this work, a particle-based simulation of two differential detectors for a reactive receiver in mobile molecular communication (MMC) is presented. The received signal is filtered and used for detection. On-off keying (OOK) is used as the modulation in both schemes. The detector in first scheme finds two-time instants in the filtered signal to maximize absolute concentration difference within the same bit duration. Then the concentration difference is used as the decision metric. The second scheme uses Manchester coding at the transmitter where the bit-0 and bit-1 are represented as the symbol [0 1] and symbol [1 0] respectively. The difference between the peak values of filtered signals in successive bit durations is used as the decision metric. Correlation between the analytical signal and particle-based signal is also found. Further, the bit error rate (BER) of the proposed detection schemes is calculated using the analytical signal and validated using the particle-based signal. Simulation results show a good agreement between the BER obtained using the analytical signal and the particle-based signal. [ABSTRACT FROM AUTHOR]

We propose an adaptive reinforcement learning (A-RL) framework to maximize the sum-rate for non-orthogonal multiple access-unmanned aerial vehicle (NOMA-UAV) network. In this framework, Mamdani fuzzy inference system (MFIS) supervises a reinforcement learning (RL) policy based on multi-armed bandits (MAB). UAV as learning agent serves an internet of things (IoT) region. It manages an interference affected, channel block for NOMA uplink. Sum-rate, rate outage probability and average bit error rate (BER) for far-user are compared. Simulations reveal superior performance of A-RL, compared to non-adaptive RL counterpart. Joint maximum likelihood detection (JMLD) and successive interference cancellation (SIC) are also compared for BER performance and implementation complexity. [ABSTRACT FROM AUTHOR]

In this letter, a new channel coding technique is proposed for optical spatial shift keying (SSK)-based visible light communications (VLC) systems by introducing redundancy in the spatial domain. The information is encoded by the redundant indices of the light emitting diodes (LEDs), assuming full channel state information (CSI) at the transmitter. The efficient construction of index-coding (IC) is presented with low computational complexity. Depending on the number of LEDs and the PDs as well as the amount of redundancy, it is concluded that IC/SSK achieves excellent coding gains at full rate and given target bit error rate (BER), as contrasted to the conventional channel coding in bit-domain, and yields superior BER performance in the presence of the VLC blockage channels as compared to the uncoded SSK systems. [ABSTRACT FROM AUTHOR]

Reconfigurable intelligent surface (RIS) has been proved effective in improving the performance of communications. In this letter, the effect of RIS on individual links in ambient backscatter communications is examined. The average bit error rate is derived for the cases when the source-to-reader (S-R) link, the source-to-tag (S-T) link, or both S-R and S-T links use RIS to enhance their links. Numerical results show that generally speaking the performance of ambient backscatter communications degrades when the number of RIS elements in the S-R link increases, while improves when the number of RIS elements in the S-T link increases, when RIS is used to enhance the relevant link. Also, the two effects cancel out but in general the performance improves when both links are enhanced by RIS. [ABSTRACT FROM AUTHOR]

Uplink power domain non-orthogonal multiple access (PD-NOMA) allows multiple users to simultaneously transmit their data over the same resource block by using different power levels, which are exploited by the base station (BS) for multi-user detection (MUD). Conventional PD-NOMA receivers can perform MUD when the data streams from all the multiplexed users are continuous, and the received signal is always a superposition of symbols from each user. However, the data received from each user may not always be continuous due to sporadic activity, and may contain missed packets or moments of silence. In such scenarios, the BS needs to precisely identify the users whose data packets are received at a particular time to successfully recover their messages. In this context, this letter proposes multiple detectors to efficiently detect user activity and perform MUD in such situations. It is shown through simulations that the proposed detectors significantly outperform conventional PD-NOMA receivers in terms of the bit error rate. [ABSTRACT FROM AUTHOR]

In this letter, the impact of residual hardware impairment (RHI) on the performance of non-orthogonal multiple access (NOMA) is investigated by taking into account the effect of imperfect successive interference cancellation (ipSIC). The new exact and asymptotic pairwise error probability (PEP) expressions with RHI under ipSIC are derived over Rayleigh fading channels. The asymptotic PEP expression is subsequently utilized to quantify the diversity orders achieved by NOMA users in the presence of RHI. In particular, we show that the effective diversity order of each NOMA user equals to user’s order for both ideal and non-ideal (RHI) scenarios. Leveraging the derived PEP, the union bound on the bit error rate of NOMA users are further evaluated. We demonstrate that the impact of RHI with ipSIC on each user’s error rate performance is negligible. In contrast, when perfect SIC is considered, such effects are significant. Numerical and Monte Carlo simulation results are presented to corroborate the analysis. [ABSTRACT FROM AUTHOR]

The generalized integrated interleaved (GII) codes nest BCH sub-codewords to form codewords of more powerful BCH codes. They can achieve hyper-throughput decoding with excellent error-correcting performance and are among the most suitable codes for next-generation memories. However, the new storage class memories require high code rate and short codeword length. In this case, the sub-codewords have small correction capability. The miscorrections of the sub-codewords lead to much more severe degradation on the GII error-correcting performance compared to the miscorrections of classic BCH codes. This letter investigates the miscorrections in GII decoding. Three low-complexity methods are developed to identify and mitigate the miscorrections by utilizing the nested syndromes, adding one single parity to each sub-codeword, and keeping track of the error locator polynomial degree. Besides, formulas for estimating the miscorrection rates are given. Using the proposed mitigation methods, the actual GII decoding performance becomes very close to that of the case without any miscorrections. [ABSTRACT FROM AUTHOR]

In this letter, we study the performance of wireless communications empowered by Reconfigurable Intelligent Surface (RISs) over Nakagami- $m$ fading channels. We consider two phase configuration designs for the RIS, one random and another one based on coherent phase shifting. For both phase configuration cases, we present single-integral expressions for the outage probability and the bit error rate of binary modulation schemes, which can be efficiently evaluated numerically. In addition, we propose accurate closed-form approximations for the ergodic capacity of the considered system. For all considered metrics, we have also derived simple analytical expressions that become tight for large numbers of RIS reflecting elements. Numerically evaluated results compared with Monte Carlo simulations are presented in order to verify the correctness of the proposed analysis and showcase the impact of various system settings. [ABSTRACT FROM AUTHOR]

This letter investigates the error probability of reconfigurable intelligent surfaces (RIS)-enabled communication systems with quantized channel phase compensation. Exact and asymptotic bit error rate (BER) expressions are derived assuming different practical channel environments and the presence of the direct link. The theoretical frameworks and findings are validated with the aid of Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

Reconfigurable intelligent surface (RIS) is an emerging technology that can achieve reconfigurable radio propagation environments for beyond 5G/6G wireless systems by smartly tuning the signal reflection via a large number of low-cost passive reflecting elements. In this letter, we investigate the effect of co-channel interference (CCI) on RIS-based dual-hop mixed free-space optical (FSO)-radio frequency (RF) communication systems. The source node, equipped with multiple FSO apertures, transmits subcarrier intensity modulated symbols on the FSO link subjected to Gamma-Gamma (GG) distributed atmospheric turbulence with pointing errors (PEs). It is assumed that the relay-RIS and RIS-destination links follow Rayleigh distribution. The destination node is corrupted by multiple CCI (each following Rayleigh distribution). The performance of the considered system is evaluated by deriving novel closed-form expressions for the outage probability (OP) and bit error rate (BER). It is shown through numerical results that RIS-based dual-hop mixed FSO-RF system provide a significant performance enhancement in comparison to a traditional dual-hop mixed FSO-RF system even in presence of CCI. [ABSTRACT FROM AUTHOR]

In this letter, the design of a low-complexity receiver which is robust to orthogonal frequency division multiplex (OFDM) signals with nonlinear clipping distortion is investigated. An approximation of the probability density function (PDF) of the received signals with nonlinear distortion is derived. Based on iteration-dependent approximation of the mean and variance of the clipped signal, a fast generalized approximate message passing (F-GAMP) algorithm is proposed. The proposed F-GAMP achieves bit error rate (BER) performance gain over the conventional OFDM receiver due to the F-GAMP’s ability to recover inter-carrier interference (ICI) and exploit frequency diversity induced by the spectral growth of a clipped signal. With almost the same BER performance as the conventional GAMP algorithm, the proposed F-GAMP reduces the computational complexity by a factor of about 3000! [ABSTRACT FROM AUTHOR]

Simultaneous wireless information and power transfer can be realized by means of an integrated receiver, where both the energy harvester and the information decoder operate on the rectified received signal. We investigate the effect of the non-linearity of the rectifier on the error performance of the information decoder when transmitting over a Nakagami- $m$ fading channel. Through analysis and simulation, we demonstrate that the low-noise error performance strongly depends on the small-signal behavior of the rectifier, even when the average operating point is outside the small-signal area. Approximating for analysis purposes the rectifier by a quadratic detector yields accurate bit error rate results for the fading channel in the low-noise regime, whereas an over-optimistic error performance is obtained when applying the envelope detector approximation. [ABSTRACT FROM AUTHOR]

A novel low-complexity transmit antenna selection (TAS) scheme is proposed for spatial modulation (SM) multiple-input multiple-output (MIMO) systems towards large-scale antennas. In contrast to the conventional optimized Euclidean distance antenna selection (EDAS) scheme, the proposed scheme is capable of reducing the search complexity by efficiently searching the candidate antenna subsets assisted by depth-first search. Our performance results demonstrate that the developed scheme can substantially reduce the search complexity in the context of large-scale SM-MIMO configuration, while achieving comparable bit error rate (BER) performance to the optimal EDAS scheme. [ABSTRACT FROM AUTHOR]

Recently, the Fisher-Snedecor F distribution was proposed to model the turbulence in free-space optical (FSO) communications. However, the existing model does not consider pointing error impairment. To fill this gap, in this letter, we derive novel closed-form expressions for the probability density function (PDF) and cumulative distribution function (CDF) for irradiance fluctuations in the presence of pointing error impairments. Subsequently, the PDF and CDF of the received signal-to-noise ratio (SNR) are derived and employed to obtain novel closed-form expressions for the outage probability, average bit error rate, and average ergodic capacity. To gain more insight into the impact of system and turbulence channel parameters, simple and accurate asymptotic expressions are further derived. Our analytical results are supported by Monte-Carlo simulations to validate the analysis. [ABSTRACT FROM AUTHOR]

In this letter, we propose a novel modulation concept which we call index and composition modulation (ICM). In the proposed concept, we use indices of active/deactive codeword elements and compositions of an integer to encode information. In this regard, we first determine the activated codeword elements, then we exploit energy levels of these elements to identify the compositions. We depict a practical scheme for using ICM with orthogonal frequency division multiplexing (OFDM) and show that OFDM with ICM (OFDM-ICM) can enhance the spectral efficiency (SE) and error performance of OFDM-IM. We design an efficient low-complexity detector for the proposed technique. Moreover, we analyze the error and SE performance of the OFDM-ICM technique and show that it is capable of outperforming existing OFDM benchmarks in terms of error and SE performance. [ABSTRACT FROM AUTHOR]

In the differential chaos shift keying (DCSK) system, half of the symbol period is used to transmit the reference signal, resulting in the poor energy efficiency. The existing DCSK-based systems also inherit this disadvantage, restricting the development of DCSK-based systems significantly. To tackle this issue completely, we propose a trinal-code shifted differential chaos shift keying (TCS-DCSK) system, where information bits are sorely transmitted by specific indices of Walsh codes and thus this system removes the reference signal. Comparison results of energy efficiency show that the TCS-DCSK system achieves higher energy efficiency in contrast to its competitors. In addition, we derive the bit error rate (BER) expressions of the TCS-DCSK system over additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels. Finally, the BER performance of the TCS-DCSK system is compared to that of other systems. It is shown that the TCS-DCSK system can obtain considerable performance gain compared to other state-of-the-art chaotic communication systems. [ABSTRACT FROM AUTHOR]

Two-user non-orthogonal multiple access systems with quadrature phase-shift keying modulation are studied. A time asynchronous scheme for successive interference cancellation receivers that maximally suppresses the inter-user interference compared to any other time asynchronous schemes is proposed. Exact bit error rate (BER) solutions for the two users operating in the additive white Gaussian noise channel using the proposed scheme are derived. A simpler closed-form BER approximation for the weaker user is also presented. Compared to the symbol-synchronous scheme, numerical results show the proposed asynchronous scheme reduces the BER for the stronger signal by a factor of one-half. [ABSTRACT FROM AUTHOR]

In this letter, we investigate the downlink hybrid precoding design for time-division duplexing (TDD) millimeter wave (mmWave) massive multiuser MIMO (MU-MIMO) systems, aiming to enhance both the sum spectral efficiency (SSE) and the bit error rate (BER) performance. First, we propose a joint analog precoding and combining design via Gram-Schmidt orthogonalization to maximize the beamforming gain while mitigating the inter-user interference. Then, by exploiting the uplink-downlink duality, we propose a block diagonal uniform channel decomposition (BD-UCD) based digital precoding and combining scheme to further improve the SSE and BER performance. Furthermore, Tomlinson–Harashima precoding (THP) is utilized to eliminate both the inter-user interference and the inter-stream interference. Simulation results demonstrate that the proposed BD-UCD-based nonlinear hybrid precoding scheme performs close to the fully-digital BD-UCD scheme and outperforms the other existing hybrid precoding schemes in terms of SSE and BER performance. [ABSTRACT FROM AUTHOR]

In mobile molecular communication (MC), inter-symbol interference (ISI) can be mitigated by power control, requiring accurate estimates of the distance from transmitter to receiver. We present two power control strategies based on binary concentration shift keying (BCSK), namely BCSK with power control based on distance (BCSK-d), and BCSK with power control jointly considering distance and residual molecules in the channel (BCSK-d-RM). Performance of BCSK-d and BCSK-d-RM are analyzed in terms of the bit error rate (BER), the average energy consumption per bit, and the optimal detection threshold. Simulation results show that BCSK-d-RM and BCSK-d outperform BCSK in BER with the varying distance and the number of transmitted molecules. As BCSK-d-RM has higher performance, while BCSK-d has lower complexity, these schemes present a useful design tradeoff for mobile MC. [ABSTRACT FROM AUTHOR]

We suggest a new protocol for the information reconciliation stage of quantum key distribution based on polar codes. The suggested approach is based on the blind technique, which is proved to be useful for low-density parity-check (LDPC) codes. We show that the suggested protocol outperforms the blind reconciliation with LDPC codes, especially when there are high fluctuations in quantum bit error rate (QBER). [ABSTRACT FROM AUTHOR]

This letter considers the exact bit error rate (BER) analysis of a two-user non-orthogonal multiple access (NOMA) system using square quadrature amplitude modulation (QAM). Unlike existing work, no constraints are imposed on the modulation order of the QAM symbols for any user. Closed-form expressions are derived for the BER of the successive interference cancellation (SIC) receiver in Raleigh fading channels. The analytical BER results corroborated by Mote Carlo simulation show that the power control becomes challenging for high order QAM. Moreover, the BER of each user is approximately independent of the modulation scheme used by the other user for certain power settings. [ABSTRACT FROM AUTHOR]

Spatial modulation (SM) conveys additional information bits via the index of an activated transmit antenna. When the number of antennas is not an integer power of two, the antenna activation becomes challenging. In such a case, only a subset of the available transmit antennas whose cardinality is an integer power of two is used. This leads to antenna activation with unequal probability, which causes high error rates and losses in the spectral efficiency. The same limitations and performance losses equally exist in quadrature spatial modulation (QSM) and generalized spatial modulation (GSM), the two prominent variants of SM. In this contribution, in contrast to the conventional approach of antenna activation within each symbol period, a space-time bit-mapping method in which the antenna selection procedure is extended to multiple symbol periods is proposed. Use of the proposed method in SM, QSM, and GSM techniques, is shown to achieve performances close to their full potential for any given number of transmit antennas, with only a marginal increment in detection complexity. [ABSTRACT FROM AUTHOR]

In this letter, a new amplitude phase shift keying (APSK) based ${M}$ -ary differential chaos shift keying (A- ${M}$ -DCSK) system is proposed. The theoretical symbol error rate (SER) and bit error rate (BER) expressions of A- ${M}$ -DCSK system for two constellations are derived and verified for both AWGN and multipath Rayleigh fading channels. Numerical results reveal that A- ${M}$ -DCSK system provides near or better BER with much lower peak-to-average power ratio (PAPR) as compared to quadrature amplitude modulation (QAM) based ${M}$ -DCSK (Q- ${M}$ -DCSK) system. Furthermore, A- ${M}$ -DCSK system shows better robustness against channel estimation error than Q- ${M}$ -DCSK system. At last, with APSK constellation rotation, the BER of A- ${M}$ -DCSK system is enhanced with a slightly increased PAPR. [ABSTRACT FROM AUTHOR]

In this letter, a Cloud Radio Access Network-type cluster-head-driven uplink model for multiple-antenna Unmanned Aerial Vehicles (UAV) relaying schemes is presented, which enables joint Maximum Likelihood symbol detection in the UAV cluster-head and the selection of UAV sources to communicate with each other aided by UAV-based relays. A relay selection technique, named Cluster-Head-Driven Best-Link (CHD-Best-Link), which employs cluster-head buffers and physical-layer network coding, is devised. A recursive maximum minimum distance relay selection strategy that exploits time-correlated channels and equips the CHD-Best-Link scheme is also developed. Simulations illustrate that CHD-Best-Link has superior average delay and bit error rate performances to that of previous schemes. [ABSTRACT FROM AUTHOR]

In this letter, we propose a new convert information embedded spatial modulation (SM) system for secure communications, in which the transmitter tries to send covert information to the specific receiver while keeping the unintended receiver unaware of the transmission. In the proposed system, the covert information bits are conveyed via the activated antenna index while the common information bits are via the modulation symbols. Specifically, the convert information modulation is achieved by carefully designing the space-time mapping principle so that it is disguised as a conventional SM antenna index. Furthermore, an efficient detection scheme is designed for the proposed system. The simulation results show that the proposed scheme with the developed receiver can offer nearly the same performance gain as conventional SM, whereas the unintended receiver can hardly detect the information correctly. Moreover, the average bit error rate (BER) is analyzed, which also validates our simulation results. [ABSTRACT FROM AUTHOR]

A new Time Interleaved Block Windowed Burst OFDM (TIBWB-OFDM) transceiver scheme is studied in this paper, where adjacent OFDM sub-blocks are allowed to overlap in time. This leads to a smaller overall block, increasing the spectral efficiency and decreasing the peak-to-average power ratio (PAPR) of the transmitted signals, when compared with standard TIBWB-OFDM. These efficiency gains are obtained at the expense of interference between sub-blocks, which deteriorates the performance. Thus, we propose several receiver embodiments that include frequency domain equalizers and time domain interference cancellation algorithms to cope with channel effects and interference introduced by the overlapping operation. [ABSTRACT FROM AUTHOR]

This letter investigates the effect of compactness of a pulse shaping filter on the inter-symbol interference (ISI) by presenting a theoretical equation which directly expresses the bit error rate (BER) in terms of quantified compactness of the pulse. We numerically compute time-bandwidth product (TBP) of the considered pulses as the measure of compactness. To compute the TBP, we use four definitions of pulse width (i.e., time duration in time domain and bandwidth in frequency domain) including root mean square (RMS), full width at half maximum (FWHM), 99% energy concentration and – 40 dB bounded energy duration. We show that the standard pulses poses different compactness properties based on the defined TBP and the – 40 dB definition is the most effective definition to study ISI versus TBP. We also propose a new pulse which offers the least TBP based on – 40 dB definition among all standard pulses and show that this pulse outperforms these well-known pulses in terms of BER and bandwidth efficiency. [ABSTRACT FROM AUTHOR]

The bit error rate (BER) analysis has been recognized as an effective approach to investigate the problems in non-orthogonal multiple access (NOMA) systems, such as inter-user interference (IUI) and error propagation. However, the impact of asymmetric channels on adaptive modulation and coding (AMC) will bring great challenges to the BER analysis of NOMA systems. In this letter, by exploiting the scaling characteristics of Euclidean distance, we disclose the boundary effect of asymmetric channels and derive the boundary value for paired users. In addition, we provide closed-form BER expressions for uplink NOMA users on both sides of the boundary value. Numerical results verify the existence of the boundary value and conform to our derivations. [ABSTRACT FROM AUTHOR]

A novel concatenated coding scheme is introduced, where the Reed-Solomon (RS) code is concatenated with the spatially coupled low-density parity-check (SC-LDPC) code, namely the RS-SC-LDPC code. We first propose the locally systematic encoding of the inner code and its termination when considering the concatenated code has a finite length. A decoding scheme is then proposed, in which the belief propagation (BP) based sliding window decoding (SWD) decodes the inner code with the assistance of the outer Berlekamp-Massey (BM) decoding feedback. This research shows the RS-SC-LDPC codes can achieve a high decoding performance without yielding an error floor until the bit error rate (BER) of 10−8. They also significantly outperform the incumbent RS-convolutional concatenated (RS-CC) codes, as well as the BCH-SC-LDPC codes. [ABSTRACT FROM AUTHOR]

Visible light communication (VLC) exhibits rapid development tendency in recent years since it has many attractive features such as its low cost, electromagnetic interference-free and license-free spectrum. In this work, we consider the indoor VLC system with single mobile user. Due to mobility, the distance between the activated light-emitting diode (LED) and receive photodiode (PD) is varied. Under the assumption of random direction (RD) mobility model, we derive the probability density function (PDF) and the cumulative distribution function (CDF) of received electrical signal-to-noise ratio (SNR) for the mobile user. The adaptive spatial modulation (ASM) scheme with two adaptive mechanisms is developed where the modulation size can be dynamically changed based on the derived CDF and pre-specified switching threshold. Simulation results demonstrate that the proposed scheme can balance the trade-off in terms of spectral efficiency and link robustness. [ABSTRACT FROM AUTHOR]

The Doppler effect severely degrades the orthogonality of orthogonal frequency division multiplexing (OFDM) systems, and is a severe problem in the underwater acoustic (UWA) communications, leading to nonuniform Doppler shifts for all subcarriers. In order to alleviate Doppler effect, resampling technique by oversized fast Fourier transform (FFT) can achieve fast and accurate resampling in frequency domain. Nevertheless, the accuracy of this conventional FFT based approach depends on the FFT size, which in turn increases receiver complexity. In order to overcome this problem, the Doppler compensation model in frequency domain is simplified by Taylor series expansion in this letter. Based on the simplified model, we propose the Doppler compensation algorithm by using FFT and interpolation to achieve higher compensation accuracy. Simulation results demonstrate that the proposed algorithm shows very similar bit error rate (BER) performance with that of Chirp Z-transform (CZT) based method. However, the complexity of our proposed algorithm is about half of CZT based method. Further, our proposed low-complexity Doppler compensation algorithm can also be applied to the sampling frequency offset (SFO) correction in terrestrial OFDM communication systems. [ABSTRACT FROM AUTHOR]

In this letter, we analyze ergodic capacity (EC) and outage probability (OP) for threshold-based selective cooperative non-orthogonal multiple access (TBS-C-NOMA) which has been proposed as a reliable alternative to conventional C-NOMA networks. We derive exact expressions for EC and OP in closed-forms and the theoretical analyses are validated via computer simulations. The trade-off for TBS-C-NOMA is raised where the data reliability (i.e., error rate) changes reversely with the EC and OP performances. Nevertheless, it is proved that TBS-C-NOMA provides a remarkable gain in data reliability compared to the decay in EC and OP. Finally, the optimization of power allocation (PA) is re-defined considering the trade-off in TBS-C-NOMA and a joint PA-threshold selection (TS) optimization is proposed in terms of capacity maximization under required data reliability. [ABSTRACT FROM AUTHOR]

In this letter, the method to reduce peak-to-average power ratio (PAPR) is studied in the pilot-embedded orthogonal time frequency space modulation where guard symbols with zero padding are introduced to avoid the interference between data and pilot symbols. By permitting the guard symbols to be padded with signals of small magnitudes, an efficient PAPR reduction method based on the iterative clipping and filtering (ICF) framework is proposed. In the proposed method, first, the clipping noise other than the clipped signal is filtered; second, the filtering coefficients for the clipping noises in the data-plus-pilot region and guard region are set to be different values to achieve good tradeoff between PAPR and bit error rate (BER) performance. Simulation results show that the proposed method can reduce the PAPR efficiently with mild BER performance loss. [ABSTRACT FROM AUTHOR]