Decoding Receiver Research Articles

5G‐coded fluid antenna multiple access over block fading channels

AbstractFluid antenna multiple access (FAMA) is a concept capable of massive connectivity on the same physical channel without the need of precoding or interference cancellation, by exploiting a super‐high dimensional received signal in the spatial domain from fluid antenna system (FAS). This letter investigates the use of 5G New Radio (NR) Modulation Coding Scheme (MCS) for FAMA systems to improve its connectivity over block fading channels. In particular, an iterative decoding receiver with iterative interference covariance estimation is proposed, designed explicitly for slow fading channels. Extrinsic information transfer (EXIT) chart is used to analyze the performance of the proposed iterative receiver. Both EXIT chart analysis and numerical results indicate that the proposed receiver outperforms the existing approach that uses fixed covariance in block fading channels. Also, the results indicate that coded FAMA can serve 100 user terminals (UTs) at the rate of 0.5 bit/s/Hz under rich scattering.

Emoji as gesture in digital communication: Emoji improve comprehension of indirect speech.

As reliance on digital communication grows, so does the importance of communicating effectively with text. Yet when communicating with text, benefits from other channels, such as hand gesture, are diminished. Hand gestures support comprehension and disambiguate characteristics of the spoken message by providing information in a visual channel supporting speech. Can emoji (pictures used to supplement text communication) perform similar functions? Here, we ask whether emoji improve comprehension of indirect speech. Indirect speech is ambiguous, and appropriate comprehension depends on the receiver decoding context cues, such as hand gesture. We adapted gesture conditions from prior research (Kelly et al.,1999, Experiment 2) to a digital, text-based format, using emoji rather than gestures. Participants interpreted 12 hypothetical text-message exchanges that ended with indirect speech, communicated via text only, text+emoji, or emoji only, in a between-subjects design. Like that previously seen for hand gesture, emoji improved comprehension. Participants were more likely to correctly interpret indirect speech in the emoji-only condition compared with the text+emoji and the text-only conditions, and more likely in the text+emoji condition compared to the text-only condition. Thus, emoji are not mere decoration, but rather are integrated with text to communicate and disambiguate complex messages. Similar to gesture in face-to-face communication, emoji improve comprehension during text-based communication.

Asynchronous Pattern-Designed Channel Access Protocol in Underwater Acoustic Wireless Sensor Networks

Due to the significant propagation delay in underwater sensor networks, conflict retransmission in channel access protocols comes at a high cost. This poses a challenge in scenarios where multiple sensor nodes generate data frames with strong temporal correlations, such as in disaster warning applications. Traditional channel allocation and timeout-based retransmission mechanisms lead to considerable access delays, making it difficult to meet the requirements. To tackle this issue, we propose the asynchronous pattern-designed random access (APDRA) protocol. This protocol enhances the access probability by designing retransmission time intervals for data frames based on pattern design. Additionally, we introduce a successive interference cancellation (SIC) mechanism at the receiver for decoding. This mechanism facilitates the transformation of the conventional method of discarding conflicted data frames into iterative decoding, thereby enhancing transmission efficiency. Via the utilization of simulations, we compare the APDRA protocol conventional underwater medium access control (MAC) protocols and existing retransmission mechanisms. The results demonstrate that the APDRA protocol has the ability to improve both the transmission success ratio (TSR) and reduces the access delay to some extent.

Electro‐optical spiking neural networks using an enhanced optical axon with pulse amplitude modulation and automatic gain controller

AbstractVisible light communication can be leveraged to establish a wireless link between neurons in spiking networks even when neural areas are in relative motions. In electro‐optical spiking neural networks (SNN), parallel transmission is often achieved through wavelength division multiplexing (WDM). However, WDM can be prohibitive in certain applications due to the need for multiple narrow‐band transmitters and receivers with optical bandpass filters. Instead of WDM, an alternative approach of using non‐orthogonal multiple access is explored (NOMA) with a pulse amplitude modulation (PAM) scheme in optical axons to enable parallel neural paths in an SNN. To evaluate NOMA with PAM, the authors implement an electro‐optical SNN that controls the force of two anthropomorphic fingers actuated by the shape memory alloy‐based actuators. An optical reference channel is used to dynamically adjust the optical receiver's gain to improve the receiver's decoding performance. Experimental results demonstrate that the electro‐optical SNN can maintain control over the fingers and hold an object under varying channel conditions. Hence, the proposed system offers robustness against dynamic optical channels induced by the relative motion of neurons.

Adaptive Decoding Mechanisms for UAV-Enabled Double-Uplink Coordinated NOMA

In this paper, we propose a novel adaptive decoding mechanism (ADM) for the unmanned aerial vehicle (UAV)-enabled uplink (UL) non-orthogonal multiple access (NOMA) communications. Specifically, considering a harsh UAV environment, where ground-to-ground links are regularly unavailable, the proposed ADM overcomes the challenging problem of conventional UL-NOMA systems whose performance is sensitive to the transmitter's statistical channel state information and the receiver's decoding order. To evaluate the performance of the ADM, we derive closed-form expressions for the system outage probability (OP) and system throughput. In the performance analysis section, we provide novel expressions for practical air-to-ground and ground-to-air channels, while taking into account the practical implementation of imperfect successive interference cancellation (SIC) in UL-NOMA. Moreover, the obtained expression can be adopted to characterize the OP of various systems under a Mixture of Gamma (MG) distribution-based fading channels. Next, we propose a sub-optimal Gradient Descent-based algorithm to obtain the power allocation coefficients that result in maximum throughput with respect to each location on UAV's trajectory. To determine the significance of the proposed ADM in nonstationary environments, we consider the ground users and the UAV to move according to the Random Waypoint Mobility (RWM) and Reference Point Group Mobility (RPGM) models, respectively. Accurate formulas for the distance distributions are also provided. Numerical solutions demonstrate that the ADM-enhanced NOMA not only outperforms Orthogonal Multiple Access (OMA), but also improves the performance of UAV-enabled UL-NOMA even in mobile environments.

Beyond Turbo: An Integrated ADMM Receiver for URLLC MIMO Systems

The emergence of ultra-reliable and low-latency communication (URLLC) poses challenges on the receiver design. Classical turbo receivers, which exhibit excellent performance under long data packet transmissions, can suffer from non-negligible error propagation in the context of URLLC due to the use of short error correction codes. To address this issue, we advocate a novel joint detection and decoding (JDD) receiver for URLLC multi-input multi-output (MIMO) systems with short low-density parity-check (LDPC) codes. Specifically, we first establish a maximum likelihood (ML) based JDD problem formulation by incorporating the bit-to-symbol mapping and the LDPC code constraints, which circumvents the error propagation issue in turbo receivers. In order to solve this difficult large-scale non-convex problem, we develop a low-complexity alternating direction method of multipliers (ADMM) algorithm to directly acquire the ultimate decoding results. Simulation results validate the performance advantage of the proposed JDD receiver over the turbo receivers in the URLLC scenario.

ПЕРЕСТАНОВОЧНОЕ ДЕКОДИРОВАНИЕ В МАЛОМОЩНЫХ БЕСПРОВОДНЫХ СЕНСОРНЫХ СЕТЯХ

Wireless sensor networks are currently considered for many subject areas as effective communication systems, including, for example, industrial and agricultural facilities and enterprises, monitoring of sensors of transport security systems, medicine applications, environmental and weather monitoring, etc. In such systems, the correction code (CC) is a classic approach used to increase the reliability of the data transmission channel while simultaneously reducing the required transmitted signal power, called the energy gain code. At the same time, the power of the transmitter is reduced due to additional power consumption in the receiver decoder. Stronger codes provide better performance with lower power requirements, but have more complex decoders with higher power consumption than relatively simple error control systems. If the additional power consumption at the output of the decoder exceeds the savings in transmitted power due to the use of CC, then such a code will not be energy efficient compared to a system with a non-redundant code. Various codes can be used to protect data, while the best codes for which the critical distance turns out to be large according to a number of studies are codes with a low parity check density. The paper proposes an alternative variant based on the synthesis of a permutation decoding system using the method of localization of a limited number of permutations and the organization of additional parity checks exclusively for the verification bits of the CC using the Bayesian approach to iterative transformations of integer soft solutions of symbols.

Sample, Quantize, and Encode: Timely Estimation Over Noisy Channels

The effects of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">quantization</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">coding</i> on the estimation quality of Gauss-Markov processes are considered, with a special attention to the Ornstein-Uhlenbeck process. Samples are acquired from the process, quantized, and then encoded for transmission using either <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">infinite incremental redundancy</i> (IIR) or <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">fixed redundancy</i> (FR) coding schemes. A fixed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">processing</i> time is consumed at the receiver for decoding and sending feedback to the transmitter. Decoded messages are used to construct a minimum mean square error (MMSE) estimate of the process as a function of time. This is shown to be an increasing functional of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">age-of-information</i> (AoI), defined as the time elapsed since the sampling time pertaining to the latest successfully decoded message. Such functional depends on the quantization bits, codewords lengths and receiver processing time. The goal, for each coding scheme, is to optimize sampling times such that the long-term average MMSE is minimized. This is then characterized in the setting of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">general increasing functionals of AoI,</i> not necessarily corresponding to MMSE, which may be of independent interest in other contexts. We first show that the optimal sampling policy for IIR is such that a new sample is generated only if the AoI exceeds a certain <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">threshold,</i> while for FR it is such that a new sample is delivered <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">just-in-time</i> as the receiver finishes processing the previous one. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Enhanced</i> transmissions schemes are then developed in order to exploit the processing times to make new data available at the receiver sooner. For both IIR and FR, it is shown that there exists an optimal number of quantization bits that balances AoI and quantization errors, and hence minimizes the MMSE. It is also shown that for longer receiver processing times, the relatively simpler FR scheme outperforms IIR.

Performance of Uplink NOMA with User Mobility Under Short Packet Transmission

The scenario of an uplink two-user non-orthogonal multiple access (NOMA) communication system is analytically studied when it operates in the short packet transmission regime. The considered users support mobility and each is equipped with a single antenna, while they directly communicate with a multi-antenna base station. Power-domain NOMA is adopted for the signal transmission as well as the successive interference cancellation approach is performed at the receiver for decoding. The packet error rate (PER) is obtained in simple closed formulae under independent Rayleigh faded channels and for arbitrary user mobility profiles. The practical time variation and correlation of the channels is also considered. Moreover, useful engineering insights are manifested in short transmission time intervals, which define a suitable setup for the forthcoming ultra-reliable and low latency communication systems. Finally, it turns out that the optimal NOMA power allocation can be computed in a straightforward cost-effective basis, capitalizing on the derived PER expressions.

WIDE: Physical-Level CTC via Digital Emulation

Cross-Technology Communication (CTC) is an emerging technique that enables direct communication across different wireless technologies. Recent works achieve physical-level CTC by emulating the standard time-domain waveform of the receiver. This method faces the challenges of inherent unreliability due to the imperfect emulation. Different from analog emulation, we propose a novel concept named digital emulation, which stems from the following insight: The receiver relies on phase shift rather than the phase itself to decode signals. Instead of emulating the original time-domain waveform, the sender emulates the phase shift associated with the desired signals. Clearly there are multiple different phase sequences that correspond to the same signs of phase shifts. Digital emulation has flexibility in setting the phase values in the emulated signals, which is effective in reducing emulation errors and enhancing the reliability of CTC. The key point of digital emulation is generic and applicable to a set of CTCs, where the transmitter has a wider bandwidth for emulation and the receiver decoding is based on the phase shift. In this paper, we implement our proposal as WIDE, a physical-level CTC via digital emulation from WiFi to ZigBee. We conduct extensive experiments to evaluate the performance of WIDE. The results show that WIDE significantly improves the Packet Reception Ratio (PRR) from 41.7% to 86.2%, which is 2× of WEBee's, an existing representative physical-level CTC.

Likelihood ascent search augmented sphere decoding receiver for MIMO systems using M‐QAM constellations

MIMO systems employing sphere decoding (SD) algorithm are known to achieve near maximum likelihood (ML) performance at a reduced complexity by restricting the candidate search space to a sphere of a certain radius. The performance of SD depends on the precise estimation of its soft output. In this paper, a low complexity modified Likelihood Ascent Search (LAS) algorithm is proposed to be used within a SD receiver in order to precisely estimate the counter-hypothesis for its winner candidates. The LAS algorithm is modified to search for the best counter-hypothesis in only one-half of the signal lattice thereby improving the performance of MIMO receiver. Our results challenge the popular perception that for a SD receiver a large number of candidates within the search sphere is essential for good performance. Instead, it is shown that accurate estimation of the counter-hypothesis is equally important and in fact, the performance of the proposed augmented SD receiver with only single candidate approaches that of a classical SD with multiple candidates. Bit error rate performance of the proposed method when compared with the existing research works on soft output generation for the same number of candidates shows that our proposed method outperforms them by upto 3 dB.

Achievable Rate of Beamforming Dual-Hop Relay Network With a Jammer and EH Constraint

This paper studies a wireless sensor relay network consist of a source, a jammer, some distribution helping relays, a information decoding (ID) receiver and a Energy harvesting (EH) receiver. In the first time-slot, the source transmits the legitimate signal to the helping relays equipped a single antenna. Meanwhile, the jammer transmits the jamming signal to the relays in order to disturb the communication between the source and the ID receiver. In the second time-slot, the relays forward the sum signal from the source and jammer to the ID receiver employing beamforming. Meanwhile, the EH receiver need to receive the sufficient energy radiated from the relays satisfying the EH constraint to prolong the service life. With the linear beamforming scheme at the relays, this network can be modeled as an equivalent Gaussian arbitrarily varying channel (GAVC). The purpose is to seek the maximal transmission rate under the EH constraint. Since this problem is nonconvex and hard to tackle, we present a second order cone programming (SOCP)-based algorithm to obtain the optimal beamforming vector so as to maximize the transmission rate between the source and ID receiver when perfect channel state information (CSI) is available. In addition, the two important points of the Rate-Energy Region is identified by (SOCP)-based algorithm. Finally, simulations are used to validate the proposed scheme.

Trainable Communication Systems: Concepts and Prototype

We consider a trainable point-to-point communication system, where both transmitter and receiver are implemented as neural networks (NNs), and demonstrate that training on the bit-wise mutual information (BMI) allows seamless integration with practical bit-metric decoding (BMD) receivers, as well as joint optimization of constellation shaping and labeling. Moreover, we present a fully differentiable neural iterative demapping and decoding (IDD) structure which achieves significant gains on additive white Gaussian noise (AWGN) channels using a standard 802.11n low-density parity-check (LDPC) code. The strength of this approach is that it can be applied to arbitrary channels without any modifications. Going one step further, we show that careful code design can lead to further performance improvements. Lastly, we show the viability of the proposed system through implementation on software-defined radios (SDRs) and training of the end-to-end system on the actual wireless channel. Experimental results reveal that the proposed method enables significant gains compared to conventional techniques.

Programmable Radio Environments with Large Arrays of Inexpensive Antennas

Conventional wireless network designs to date target endpoint designs that view the channel as a given. Examples include rate and power control at the transmitter, sophisticated receiver decoder designs, and high-performance forward error correction for the data itself. We instead explore whether it is possible to reconfigure the environment itself to facilitate wireless communication. In this work, we instrument the environment with a large array of inexpensive antenna (LAIA) elements, and design algorithms to configure LAIA elements in real time. Our system achieves a high level of programmability through rapid adjustments of an on-board phase shifter in each LAIA element. We design a channel decomposition algorithm to quickly estimate the wireless channel due to the environment alone, which leads us to a process to align the phases of the LAIA elements. We implement and deploy a 36-element LAIA array in a real indoor home environment. Experiments in this setting show that, by reconfiguring the wireless environment, we can achieve a 24% TCP throughput improvement on average and a median improvement of 51.4% in Shannon capacity over baseline single-antenna links.

Low-Complexity CRC Aided Joint Iterative Detection and SCL Decoding Receiver of Polar Coded SCMA System

As the fifth-generation (5G) wireless networks’ key technology, the joint design of SCMA and polar code is concerned by the future communication system. In this paper, a CRC aided joint iterative detection and successive cancellation list (SCL) decoding (CAJIDS) receiver is proposed for the polar coded SCMA (PC-SCMA) system. For the receiver, the SCL decoder’s extrinsic messages construction algorithm is designed by using Bayes rule and soft cancellation algorithm. Additionally, the distributed CRC aided polar (DCA-polar) code and variable list size are used to reduce the receiver’s decoding latency and complexity. Simulation results demonstrate that the CAJIDS receiver has better error rate performance than the joint iterative detection and decoding (JIDD) receiver. It also outperforms the LDPC coded SCMA (LDPC-SCMA) system. Specifically, when code length $N=256$ and code rate $R = 1/3$ , the CAJIDS outperforms the JIDD and LDPC-SCMA 1.2 dB and 1.9 dB over the Rayleigh fading channel, respectively. It also shows that, compared with the fixed-list-size receiver, with a similar error rate performance, the CAJIDS receiver has lower decoding latency and complexity.

Analyses on Achievable Data Rate for Single-User Decoding(SUD) Receiver: with Application to CIS NOMA Strong Channel User

Analyses on Achievable Data Rate for Single-User Decoding(SUD) Receiver: with Application to CIS NOMA Strong Channel User

Average PER Performance Metrics of Iterative Successive Interference Cancellation

The average packet error rate (PER) and user-PER profiles of iterative successive interference cancellation (I-SIC) are analyzed for a proof-of-concept scenario where asymptotically many code-division-multiple-access users share the same channel encoder. To characterize the iterative decoding receiver, we propose a novel multivariate PER function evaluated over the consecutive signal-to-interference-plus-noise ratios (SINRs) experienced by each undecoded user. Analytic expressions for the user-energy and user-SINR profiles at every iteration are derived via warping operators on the user ordering that relate the asymptotic distribution of undecoded users at different iterations. Monte Carlo simulations using a chip-level I-SIC implementation assess the accuracy of the proposed user-limit analysis.

Low-Routing-Complexity Convolutional/Turbo Decoder Design for Iterative Detection and Decoding Receivers

A highly hardware-shared convolutional/turbo decoder for iterative detection and decoding (IDD) receivers is presented here. Furthermore, parallel dual-mode decoding kernels are proposed to alternatively decode the long-term evolution (LTE)-compatible convolutional codes (CCs) and turbo codes (TCs) using a parity-enhanced soft-input soft-output maximum a-posteriori algorithm. However, decoding the high-constraint-length CC results in complicated interconnections among the parallel decoding kernels and unroutable back-end chip implementation. Therefore, a minimized global route (MGR) design is proposed for the dual-mode decoder to further simplify the global data transfers and reduce the routing complexity. Using a 40-nm CMOS process, the proposed dual-mode decoder achieves a 48% area reduction compared with the individual single-mode TC and single-mode CC decoders. The global routing length of the proposed decoding kernels is reduced by 32% using the MGR design. Because of the feasible placements and routing, the proposed dual-mode decoder is implemented in an application-specific integrated circuit of 2.88-mm2 core area at the maximum operating frequency of 364 MHz. For the LTE-based IDD receiver, the proposed dual-mode decoder achieves high area efficiencies of 0.21 and 0.35 bits/mm2 for the TC and CC decoding, respectively.

Ultra-Reliable Energy-Efficient Cooperative Scheme in Asynchronous NOMA With Correlated Sources

Massive Internet-of-Things is proposed in fifth generation networks to serve the sporadic traffic generated by devices operating under tight resource constraints. In these applications the overhead for synchronization and control functions is comparable to the data size, hence the control/data ratio is very unfavorable. The proposed techniques in this paper take advantage of the fact that transmitters are privy to whole data in order to boost the spectral and power efficiency, while increasing the reliability. We propose identical content transmission over identical content transmission over NOMA (ICToNOMA) for transmitters with correlated sources, who cooperatively combine and transmit identical messages over consecutive data packets. Our proposed redundant transmission of data is not as straightforward as it seems, considering the asynchronous reception of the data streams at the receiver. Traditionally, it is believed that the substantial spectral efficiency (SE) achievements in nonorthogonal multiple access (NOMA) could be jeopardized in the asynchronous channels. We investigate the potency of successive interference cancellation (SIC), as the main block in current NOMA receivers, in asynchronous channels. By applying water-filling and geometric power allocation, we show that the SE degradation is caused by the nature of SIC. Moreover, we demonstrate that the SE is improved in asynchronous NOMA and ICToNOMA, by managing the channel’s memory and correlation instead of canceling it. In addition, we propose our iterative joint detection and decoding (IJDD) receiver to outperform SIC in asynchronous NOMA receivers. Our extensive simulations show that ICToNOMA can outperform NOMA by providing a considerable boost in the channel reliability while increasing the spectral and power efficiency.

Network Coverage in Interference Limited Wireless Sensor Networks

The performance of a wireless sensor network is limited by the available bandwidth of the shared wireless channel. For the need to share the available bandwidth sensors contend for concurrent transmissions. The simultaneous transmissions by the neighbouring nodes are the main source of interference at the intended receiver sensor. In this paper, we derive the successful decoding probability of receiver sensor in presence of interference and Rayleigh fading channel. We introduce the concept of circular influence zone, to impose a restriction on the aggregated interference from the distant neighbours at an intended receiver sensor. We provide an insight about the critical sensor density which yields an optimal trade-off between the achievable coverage and receiver decoding probability in presence of co-channel interference.