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Parallel triple-layer wireless sensor network (WSN) assisted by frequency-hopping (FH) and M-ary frequency-shift keying (MFSK) modulation, abbreviated FH/MFSK WSN, is proposed to monitor multiple source events (SEs) each having multiple states. The SEs are simultaneously observed by a few local sensor nodes (LSNs), which convey their decisions to a fusion center (FC) where the SEs? states are classified (detected) based on noncoherent fusion rules. In this paper, four low-complexity noncoherent fusion rules are studied. They are the conventional benchmark of equal-gain combining (EGC) and three proposed noncoherent fusion rules, namely erasure-supported EGC (ES-EGC), EGC-assisted N-order iterative interference cancellation (IIC), and ES-EGC-assisted N-order IIC. The complexity of these fusion rules is analyzed and the performance of the FH/MFSK WSN employing these fusion rules is investigated and compared when wireless channels from LSNs to the FC experience Rayleigh fading. [ABSTRACT FROM AUTHOR]

In this paper, we analyze in a unified way the achievable rate and spectral efficiency of multicarrier and multiantenna two-hop relay systems with an interference-free linear transceiver. We consider two kinds of decode-and-forward (DF) relay systems with three nodes. In the first kind of relay systems where only the relay node employs the full channel state information (CSI) of both the source–relay (S–R) link (first hop) and the relay–destination (R–D) link (second hop), the relay eliminates the interference of these links. In the second kind of systems, where the source node employs the CSI of the first hop, the destination node employs the CSI of the second hop, whereas the relay node employs the full CSI of both the hops; these nodes can jointly eliminate the interference. For the multicarrier relay or multiantenna relay systems supporting different diversity and multiplexing gains and under the aforementioned assumptions for the CSI, we find that the achievable rate of each hop or its lower bound can be unified in the generalized mean of the eigenvalues of an equivalent channel correlation matrix. Furthermore, by using the properties of generalized mean and by resorting to the random matrix theory, we derive the asymptotic spectral efficiency of the multicarrier or multiantenna systems with different CSI assumptions. Finally, we provide simulation results to validate our analytical results. Our studies show that the multicarrier systems using code-division multiplexing (CDM) or the multiantenna systems can benefit more from exploiting the CSI at all the three nodes than the multicarrier systems using frequency-division multiplexing (FDM), particularly, in the case of a high load factor. [ABSTRACT FROM AUTHOR]

The performance of multihop links is studied in this contribution by both analysis and simulations when communicating over generalized-K (KG) fading channels. The performance metrics considered include symbol error rate (SER), outage probability, level crossing rate (LCR), and average outage duration (AOD). First, the expressions for both the SER and outage probability are derived by approximating the probability density function (pdf) of the end-to-end signal-to-noise ratio (SNR) using an equivalent end-to-end pdf. We show that this equivalent end-to-end pdf is accurate for analyzing the outage probability. Then, the second-order statistics of LCR and AOD of multihop links are analyzed. Finally, the performance of multihop links is investigated by either simulations or evaluation of the expressions derived. Our performance results show that the analytical expressions obtained can be well justified by the simulation results. The studies show that the KG channel model and the expressions derived in this paper are highly efficient for the prediction of the performance metrics and statistics for the design of multihop communication links. [ABSTRACT FROM PUBLISHER]

Iterative decoding of an irregular variable-length coding (IrVLC) scheme concatenated with precoded fast frequency-hopping (FFH) M-ary frequency-shift keying (MFSK) is considered. We employ EXtrinsic Information Transfer (EXIT) charts to investigate the three- stage concatenation of the FFH-MFSK demodulator, the rate-i decoder, and the outer IrVLC decoder. The proposed joint source and channel coding scheme is capable of operating at low signal-to-noise ratios (SNRs) in Rayleigh fading channels contaminated by partial-band noise jamming (PBNJ). The IrVLC scheme is composed of a number of component variable-length coding (VLC) codebooks employing different coding rates that encode particular fractions of the input source symbol stream. These fractions may be chosen with the aid of EXIT charts to shape the inverted EXIT curve of the IrVLC codec so that it can be matched with the EXIT curve of the inner decoder. We demonstrate that using the proposed scheme, an infinitesimally low bit error ratio (BER) may be achieved at low SNR values. [ABSTRACT FROM AUTHOR]

Proposes a broadband multiple access scheme which combines frequency hopping with multicarrier direct sequence-code division multiple access (FH/MC DS-CDMA). Characteristics of the FH/MC DS-CDMA; Implementation of MC modulation; Factors influencing the application of adaptive rate transmission (ART) in the broadband wireless communication system; ART schemes in FH/MC DS-CDMA systems.

Proposes a multiple access scheme based on slow frequency hopping multicarrier direct-sequence code division multiple access (SFH/MC DS-CDMA). Discussion on the transmitted signal and the channel and receiver models of the SFH/MC DS-CDMA system; Average error bit probability; Overview of the numerical results.

This paper investigates the first resource management problem for vehicular-to-infrastructure (V2I) networks under the in-band full-duplex (IBFD) backhauling scheme with guaranteed ultra-reliable and low-latency (URLLC) service. The considered networks suffers from interference caused by three node transmission in IBFD scheme and the mobility of vehicular user equipments (VUEs). The resource allocation problem is formulated to jointly optimize VUE association, resource block assignment (RA) and power allocation (PA), while satisfying the reliability and latency constraints at the same time. The formulated problem is a mixed integer non-linear problem with non-convex objective function and constraints. Finding globally optimal solution for this type of problem is still an open problem. To develop tractable solutions, the original problem is firstly simplified using derived equivalent expression for the objective function. The proposed method then decomposed it into RA and PA sub-problems. In each iteration, the PA sub-problem is solved for a set of given PA solution; while the solution for PA sub-problem is searched under determined RA results. The RA and PA sub-problems are solved iteratively until the converging condition is achieved. Theoretical analysis proves that the proposed method achieves Nash-stable equilibrium and local optimality for RA and PA sub-problems respectively. Simulation results verify the effectiveness of the derived performance analysis and demonstrate that the proposed algorithm outperforms the state-of-the-art algorithms in the literatures. [ABSTRACT FROM AUTHOR]

Low-complexity detectors are conceivedfor the spatial modulation-aided sparse code-division multiple-access (SM-SCDMA). Firstly, the approximate message passing (AMP) algorithm is adapted for the detection of SM-SCDMA, which has less than 1% detection complexity of the state-of-the-art message passing-aided (MPA) detection albeit at a bit error ratio (BER) degradation. Therefore, inspired by the benefits of interference cancellation (IC) and the unique characteristics of SM, an enhanced AMP (EAMP) detector is proposed for mitigating BER degradation without increasing the detection complexity. Finally, the classic expectation propagation (EP) is intrinsically amalgamated with our EAMP detector, leading to a novel EAMP-EP detector, which further reduces the detection complexity of the EAMP algorithm. The three detectors are compared both in terms of their coded and uncoded BER, as well as complexity. [ABSTRACT FROM AUTHOR]

Message passing (MP) aided detectors are designed for orthogonal time frequency space (OTFS) modulated system. We first characterize the transmit-receive relationship of our OTFS-modulated system in the delay-Doppler (DD) domain by designing a joint factor graph. Based on this joint factor graph, we then conceive a joint message passing aided (JMPA) detector. Furthermore, a novel low-complexity Gaussian approximate MP (GA-MP) detector is also conceived, which models the a posteriori probabilities propagated through the proposed joint factor graph by Gaussian distributions. Finally, we demonstrate that the proposed GA-MP detector outperforms the state-of-the-art MP detector by at least 1.5 dB at a bit error ratio (BER) of $10^{-4}$ , while keeping the same complexity order. [ABSTRACT FROM AUTHOR]

The efficiency of link adaptation in wireless communications relies greatly on the accuracy of channel knowledge and transmission mode selection. In this paper, a novel deep learning based link adaptation framework is proposed for the orthogonal frequency-division multiplexing (OFDM) systems with compressed-sensing-assisted index modulation, termed as OFDM-CSIM, communicating over millimeter-wave (mmWave) channels. To achieve link adaptation, a novel multi-layer sparse Bayesian learning (SBL) algorithm is proposed for accurately and instantaneously providing the required channel state information. Meanwhile, a deep neural networks (DNN)-assisted adaptive modulation algorithm is proposed to choose the best possible transmission mode to maximize the achievable throughput. Simulation results show that the proposed multi-layer SBL algorithm enables more accurate channel estimation than the conventional techniques. The DNN-based adaptive modulator is capable of achieving a higher throughput than the learning-assisted solution based on the $k$ nearest neighbor ($k$ -NN) algorithm, and also the classic average signal-to-noise ratio (SNR)-based solutions. Moreover, analysis shows that both the multi-layer SBL algorithm and the DNN-assisted adaptive modulator achieve better performance than their respective conventional counterparts while at a significantly lower computational complexity cost. [ABSTRACT FROM AUTHOR]

This article discusses the self-sustainability of reconfigurable intelligent surface (RIS) in wireless powered Internet of Things (IoT) networks. Our vision is that RIS helps improve energy harvesting and data transmission capabilities simultaneously, without the extra utilization of RF spectrum and energy consumption. The inherent properties of RIS are first discussed to unveil its distinctive features, followed by a broader range of use cases motivated by RIS as their enabling technology. The focus is on the application of RIS in the wireless powered IoT networks, and its potential to interconnect and support these practical use cases. Such an application is then thoroughly evaluated in a case study of an RIS-assisted wireless powered sensor network, with system throughput, energy transmission time consumption, and energy harvesting as the key performance metrics. The comprehensive performance evaluation showcases the self-sustainable property of RIS being unlocked in the considered scenario, identifying a clear pathway toward the future wireless powered IoT networks. We further pave the way by exploring research challenges and open issues related to emerging technological development. [ABSTRACT FROM AUTHOR]

A forward error correction (FEC) and unity-rate coded (URC) autoencoder (AE)-assisted communication system is proposed for the first time, which relies on soft iterative decoding for attaining a vanishingly low error probability. The AE-demapper is specifically designed for directly calculating the extrinsic logarithmic likelihood ratios (LLRs), which can be directly entered into the URC decoder for soft iterative decoding. This avoids the potential degradation due to the conversion of symbol probabilities to bit LLRs. A comprehensive capacity analysis of the AE is performed, which demonstrates the capacity advantage of the AE-aided constellation design over its conventional quadrature amplitude modulation (QAM)/ phase shift keying (PSK) counterpart. Furthermore, we carry out its EXtrinsic Information Transfer (EXIT) chart analysis, which indicates that as a benefit of our URC, the EXIT curve always reaches the [1,1] point of perfect convergence, leading to a vanishingly low error probability. More explicitly, our bit error ratio (BER) and block error ratio (BLER) results demonstrate that the proposed FEC-URC-AE system achieves significant iterative gains both in additive white Gaussian noise (AWGN) and Rayleigh channels, outperforming both its model-based FEC-AE and its conventional coded QAM/QPSK counterparts. [ABSTRACT FROM AUTHOR]

Reconfigurable intelligent surfaces (RIS) constitute a revolutionary technique of beneficially reconfiguring the smart radio environment. However, despite the fact that wireless propagation is of time-varying nature, most of the existing RIS contributions focus on time-invariant scenarios for the following reasons. Firstly, it becomes impractical to instantaneously feed back the control signal based on the doubly selective non-line-of-sight (NLoS) fading scenario. Secondly, channel estimation conceived for the high-mobility and high-dimensional RIS-assisted links has to take into account the spatial-domain (SD), time-domain (TD), and frequency-domain (FD) correlations imposed by the angle-of-arrival/departure (AoA/AoD), the Doppler and the orthogonal frequency-division multiplexing (OFDM) operations, respectively, where none of the existing solutions can be directly applied. Thirdly, it is far from trivial to maximize the NLoS channel powers on all subcarriers by a common set of RIS reflecting coefficients. Fourthly, in the face of double selectivity, it becomes inevitable to encounter either inter-symbol interference (ISI) or inter-channel interference (ICI) during the signal detection in the TD or in the FD, respectively. Against this background, firstly, we focus our attention on line-of-sight (LoS) dominated unmanned aerial vehicle (UAV) scenarios. Secondly, we conceive new minimum mean squared error (MMSE) channel estimation methods for doubly selective fading, which perodically transmit pilot symbols embedded into the TD and FD over the SD in order to beneficially exploit the correlations in the three domains. Thirdly, the RIS coefficients are optimized by a low-complexity algorithm based on the LoS representation of the end-to-end system model. Fourthly, tailor-made interference cancallation techniques are devised for improving the signal detection both in the FD and in the TD. Our simulation results are examined in six frequency bands licensed in 5 G, which confirms that the employment of RIS is capable of achieving substantial performance improvements. [ABSTRACT FROM AUTHOR]

Low complexity approximate message passing (AMP) orthogonal frequency division multiplexing combined with index modulation (OFDM-IM) detection algorithms are proposed, which exploit the sparse structure of the frequency domain (FD) OFDM-IM symbols. To circumvent the high root mean square error (RMSE) in the conventional AMP algorithm, a minimum mean square error (MMSE) denoiser is proposed based on the classic Bayesian approach and on the state evolution of AMP. Our simulation results demonstrate that it is capable of improving both the RMSE as well as the convergence rate. However, in practice, the channel's diagonal FD matrix may be a non-Gaussian sensing matrix, hence a damping strategy is conceived. In conclusion, the proposed MMSE denoiser based damping-assisted AMP-aided detector strikes a compelling bit error ratio vs. complexity trade-off. [ABSTRACT FROM AUTHOR]

An edge-cancellation-aided iterative detection and decoding (EC-IDD) algorithm is proposed for polar-coded sparse code multiple access (SCMA), which jointly performs Gaussian-approximated message passing (GA-MP) detection of SCMA supported by the soft list decoding (SLD) of polar codes. A reduced-edge factor graph is formulated in each consecutive iteration with the aid of the cyclic redundancy check (CRC) and EC. Based on the simplified factor graph, the EC-IDD gradually reduces its complexity in each subsequent iteration, while improving the bit error rate (BER) performance, compared to the state-of-the-art joint detection and decoding (JDD) of polar-coded SCMA. Furthermore, an embedded decision-directed channel estimator (DD-CE) is proposed for our polar-coded SCMA system under realistic imperfect channel state information (CSI). Our simulation results demonstrate that the proposed EC-IDD achieves better BER performance than the state-of-the-art JDD under both perfect and imperfect CSI, despite achieving a complexity reduction of 92%. Finally, the BER of the proposed joint DD-CE and EC-IDD algorithm under imperfect CSI converges to that of EC-IDD operating under perfect CSI. [ABSTRACT FROM AUTHOR]

Polar coding has been ratified for employment in the 3GPP New Radio standard and several soft-decision decoders achieved comparable performance to that of the state-of-the-art successive cancellation list decoder. Aiming for further improving the performance of the soft-decision polar decoders, we propose a soft-output successive cancellation stack (SSCS) polar decoder, which jointly exploits the benefits of the depth-first search of the stack decoder and the soft information output of the belief propagation decoder. This has the substantial benefit of facilitating soft-input soft-output (SISO) decoding and seamless iterative information exchange in turbo-style receivers. As a further contribution, we intrinsically amalgamate our SSCS decoder into polar-coded large-scale multiple-input multiple-output (MIMO) systems and conceive an iterative turbo receiver, operating on the basis of logarithmic likelihood ratios (LLRs). Our simulation results show that the proposed SSCS decoder is capable of outperforming the state-of-the-art SISO polar decoders, despite requiring a lower complexity at moderate to high signal-to-noise ratios (SNRs). Additionally, compared with the non-iterative hard-output SCS decoder, our SSCS scheme attained 1.5 dB SNR gain at a bit error ratio level of 10−5, when decoding the [256,512] polar code of a (64 × 64) MIMO system. [ABSTRACT FROM AUTHOR]

Soft-output (SO) decoding is proposed for the Logarithmic Successive Cancellation List (Log-SCL) polar decoder for the first time, by exploiting the left-to-right propagation of the Belief Propagation (BP) decoder, which opens new avenues for its employment in powerful turbo-receivers. In the case of decoding a half-rate polar code having a block length of 1024 bits, the proposed soft list polar decoder achieves a 1.5 dB Block Error Ratio (BLER) performance gain, 50% latency improvement and 26% complexity reduction, compared to the state-of-the-art SO Soft Cancellation (SCAN) polar decoder in a polar-coded Multiple-Input Multiple-Output (MIMO) system. Furthermore, we conceive a Memory-Efficient (ME) soft list polar decoder, which requires only 16% of the soft list polar decoder's memory, at the cost of slightly increased latency and complexity. [ABSTRACT FROM AUTHOR]

Index modulation (IM) is a recently proposed multi-carrier transmission scheme, which conveys information both by conventional symbols as well as by the specific subcarrier activation patterns conveying them. However, an impediment of IM is that it lacks transmit diversity gain. In this paper, we circumvent this limitation by proposing a limited-feedback assisted IM transmission scheme. Specifically, Euclidean distance based subcarrier subset selection (ED-SSS) is proposed and its attainable transmit diversity order is shown to be $N_c-N_{IM}+1$ , where $N_c$ is the total number of subcarriers in an IM block and $N_{IM}$ is the number of subcarriers used for IM. Furthermore, the ED-SSS is shown to be amenable to low-complexity implementation owing to the orthogonality of its subcarriers. In order to attain the maximum transmit diversity order of $N_c$ , ED-SSS is further extended with the aid of transmit precoding and its transmit diversity order is quantified. The proposed precoding assisted ED-SSS is shown to subsume several of the existing precoding aided IM transmission schemes. Simulation studies are conducted for validating our theoretical claims and also for quantifying the attainable performance gains of the proposed schemes. Specifically, at a BER of $10^{-3}$ an SNR gain as high as 8 dB is observed in case of precoding when compared to its counterpart operating without precoding. [ABSTRACT FROM AUTHOR]

Communication between nanomachines is still an important topic in the construction of the Internet of Bio-Nano Things (IoBNT). Currently, molecular communication (MC) is expected to be a promising technology to realize IoBNT. To effectively serve the IoBNT composed of multiple nanomachine clusters, it is imperative to study multiple-access MC. In this article, based on the molecular division multiple access technology, we propose a novel multiuser MC system, where information molecules with different diffusion coefficients are first employed. Aiming at the user fairness in the considered system, we investigate the optimization of molecular resource allocation, including the assignment of the types of molecules and the number of molecules of a type. Specifically, three performance metrics are considered, namely, min-max fairness for error probability, max-min fairness for achievable rate, and weighted sum-rate maximization. Moreover, we propose two assignment strategies for types of molecules, i.e., best-to-best (BTB) and best-to-worst (BTW). Subsequently, for a two-user scenario, we analytically derive the optimal allocation for the number of molecules when types of molecules are fixed for all users. In contrast, for a three-user scenario, we prove that the BTB and BTW schemes with the optimal allocation for the number of molecules can provide the lower and upper bounds on system performance, respectively. Finally, numerical results show that the combination of BTW and the optimal allocation for the number of molecules yields better performance than the benchmarks.

In this paper, we propose an energy-efficient spatial modulation-based molecular communication (SM-MC) scheme, in which a transmitted symbol is composed of two parts, i.e., a space derived symbol and a concentration derived symbol. The space symbol is transmitted by embedding the information into the index of a single activated transmitter nanomachine. The concentration symbol is drawn according to the conventional concentration shift keying (CSK) constellation. Benefiting from a single active transmitter during each symbol period, SM-MC can avoid the inter-link interference problem existing in the current multiple-input multiple-output (MIMO) based MC schemes, which hence enables low-complexity symbol detection and performance improvement. Correspondingly, we propose a low-complexity scheme, which first detects the space symbol by energy comparison, and then detects the concentration symbol by the maximum ratio combining assisted CSK demodulation. In this paper, we analyze the symbol error rate (SER) of the SM-MC and of its special case, namely the space shift keying-based MC (SSK-MC), where only space symbol is transmitted and no CSK modulation is invoked. Finally, the analytical results are validated by computer simulations. Our studies demonstrate that both the SSK-MC and SM-MC are capable of achieving better SER performance than the conventional MIMO-MC and single-input single-output-based MC, when given the same symbol rate.