Parallel Interference Cancellation Research Articles

Off-grid compressed channel estimation with parallel interference cancellation for millimeter wave massive MIMO

Off-grid compressed channel estimation with parallel interference cancellation for millimeter wave massive MIMO

A novel iterative detection method based on a lattice reduction-aided algorithm for MIMO OFDM systems

The lattice reduction-aided algorithm has received broad attention from researchers since it operates as a maximum likelihood receiver with better system performance for multiple-input multiple-output orthogonal frequency division multiplexing systems and contains a full diversity. A novel iterative detection algorithm canceling parallel iterations that employ the lattice reduction-aided approach is proposed. Soft information is exchanged through the detector itself. Its iteration occurs inside the detector, which reduces much of the exchange cost between the multiple-input multiple-output orthogonal frequency division multiplexing detector and the turbo decoder. Since the parallel interference cancellation algorithm is constrained by the accuracy of the initial value of the detection, it is easy to form error propagation after several iterations. Due to the lattice reduction-aided algorithm, its performance is approximated with the maximum likelihood algorithm. Therefore, the lattice reduction-aided algorithm is introduced into the parallel interference cancellation algorithm to make its detection algorithm more accurate and overcome the effect of error propagation in the manuscript. Simulation results indicate that the proposed algorithm leads to an improvement of 0.8–2 dB when the bit error rate is set to 10–4 when compared to other algorithms.

Analysis of Multiuser Detectors and Performance improvement in DS-CDMA system using Multistage Multiuser Detection Techniques

The Direct Sequence Code Division Multiple Access (DS-CDMA) system faces several disruptions, this is most crucial of which is the Multi Access Interference (MAI) caused by its users. The efficiency of the system gradually declines as every quantity rises, and the MAI rises, especially in faded environments. This work proposes a multiple-phase multiuser identification approach called Differencing Partial Parallel Interference Cancellation (DPPIC), which improves the overall efficiency. The methods known as Differencing Parallel Interference Cancellation (DPIC) and Partial Parallel Interference Cancellation (PPIC) are combined in this methodology. Current solutions for Parallel Interference Cancellation (PIC) and PPIC have enhanced overall effectiveness; however, this has come at the expense of increasing the complexity of computation. As the variety of consecutive stages grows, the MAI falls. Using the DPIC approach may reduce the computational burden without improving system functionality. The use of the Partial Differencing Parallel Interference Cancellation (PDPIC) technique can enhance system performance while lowering the level of complexity. According to the simulation findings, Bit Error Rate (BER) vs normalized signal strength (i.e., Eb / N0) performs more effectively for the suggested DPPIC approach than for PIC, the PPIC, and PDPIC.

Accumulation and Elimination: A Hard Decision-Based Multi-User Interference Cancellation Method in Satellite Communication System

With the increasing number of users in the Medium-Orbit (MEO) satellite communication system, multi-access interference (MAI) has become an important factor that restricts the reliability and capacity of the system. Additionally, the low carrier-power-to-noise-density ratio (C/N0) resulting from long-distance transmission poses a significant concern. The parallel interference cancellation (PIC) algorithm, utilized within the paradigm of multi-user detection (MUD), exhibits the capability to effectively mitigate the impact of MAI within the same system. Simultaneously, coherent accumulation serves as a means to substantially enhance the correct detection probability (Pcd) at low C/N0. In this study, a signal acquisition method for multi-user spread spectrum satellite receivers is proposed, which employs interference cancellation and coherent accumulation as its core mechanisms. Furthermore, we introduce a power estimation method based on the outcomes of signal acquisition, which can be integrated into the signal reconstruction module of PIC. Finally, we implement the aforementioned algorithms in both simulation and hardware platforms. Remarkably, we observe that when the interference-to-signal ratio (ISR) caused by MAI equals 20 dB, the improved algorithm attains a maximum Pcd of 0.95 within the high signal-to-noise ratio (SNR) region, closely approaching the theoretical limit for the bit error rate (BER). The experimental results prove the effectiveness and feasibility of the acquisition algorithm. In summary, the enhanced algorithm holds vast potential for widespread implementation in multi-user spread spectrum communication systems.

Enhancing Multi-User Detection in Multicarrier 5G and Beyond: A Space-Time Spreading Approach with Parallel Interference Cancellation

Enhancing Multi-User Detection in Multicarrier 5G and Beyond: A Space-Time Spreading Approach with Parallel Interference Cancellation

Performance of Iterative Coded CDMA Receivers with APP Feedback: A Use of a Weighted Delay Filter

The prohibitive computational complexity of optimal coded multiuser detection necessitates using suboptimal detectors in practical implementations. The filter is very computationally simple and is also demonstrated to provide faster convergence and superior bit error rate (BER) performance. Further investigation of the weighted delay filter concept produces a second filter—derived via the joint likelihood function. It is analytically demonstrated that extrinsic feedback systems will not benefit from weighted delay filtering. A system model is provided that introduces the notion of feedback ‘residue’, which is shown to be the key difference between a-posterior probability (APP) and extrinsic systems when determining the parallel interference cancellation (PIC) output statistics. It is analytically shown that the weighted delay filter derived via a maximum signal-to-noise ratio (SNR) approach is identical to a weighted delay filter derived via the joint likelihood function. It is analytically shown that when extrinsic feedback is used in a coded-code division multiple access (C-CDMA) system, no benefit will be realised by weighted delay filtering, as soft outputs from previous cycles are a merely scaled, noisy version of the most recent data. The notion of a ‘feedback residue’ for systems with APP feedback is introduced, and it is empirically shown that this residue term is a key consideration when determining the PIC output statistics. Using the ‘residual feedback’ model, it is shown that when APP feedback is utilised, data from previous cycles is not simply “a scaled, noisy version” of the current data. For this reason, benefits may be realised by APP feedback use. The simulation results shows that the residue may be trivial at small loads, the residue builds to the substantial value of nearly 0.4 at a reasonably modest load of K/N=15/10, and continues to grow as the load increases.

Residual Transceiver Impairments Aware Expectation Propagation Algorithm Receiver for PDMA Systems

Pattern division multiple access (PDMA) is a promising non-orthogonal multiple access technology for the next generation wireless communication systems. In PDMA systems, the inherent residual transceiver impairments introduced by nonideal hardwares incur significant performance degradation. In this paper, we propose a residual-transceiver-impairments-aware (RTIA) expectation propagation algorithm (EPA) receiver to mitigate the detrimental influences of the nonideal hardware imperfections for uplink PDMA systems. The user-specific transmitter distortion powers are considered in the message passing procedure of the EPA detection. The parallel interference cancellation (PIC) scheme is incorporated into the proposed RTIA-EPA receiver to further improve the system performance and reduce the computational complexity. Simulation results illustrate that the proposed RTIA-EPA and RTIA-EPA-PIC receivers achieve significant performance gains over the conventional residual-transceiver-impairments-agnostic counterparts with negligible computational complexity overhead.

Ordering parallel successive interference cancellation mechanism to mitigate ICI interference at downlink of the LTE-A HetNet

Ordering parallel successive interference cancellation mechanism to mitigate ICI interference at downlink of the LTE-A HetNet

Ordering parallel successive interference cancellation mechanism to mitigate ICI interference at downlink of the LTE-A HetNet

Ordering parallel successive interference cancellation mechanism to mitigate ICI interference at downlink of the LTE-A HetNet

Research on improved multiple users detection algorithm in pattern division multiple access system

Receiver detection algorithm has always been a research hotspot in communication system and the key point to determine the performance of 5G system. Both industry and academia have been committed to finding detection algorithms with lower complexity and higher detection performance. This paper will study how to solve the problems of low detection performance and high complexity of classical algorithms. Taking Pattern Division Multiple Access (PDMA) as an example, this paper improves the existing receiver detection algorithms such as Minimum Mean Square Error-Serial Interference Cancellation (MMSE-SIC), Message Passing Algorithm (MPA) and Expectation Propagation Algorithm (EPA), and puts forward corresponding improved algorithms with specific formulas, i.e. Enhanced-MMSE-SIC, Turbo-like MPA (MPA-Turbo) and Turbo-like EPA with hybrid parallel interference cancellation (EPA-Turbo-PIC). Link-level simulation results and analysis show that the proposed improved algorithms have performance advantages over the corresponding traditional algorithms.

Bayesian Neural Network Detector for an Orthogonal Time Frequency Space Modulation

The orthogonal time frequency space (OTFS) modulation is proposed for beyond 5G wireless systems to deal with high mobility communications. The existing low complexity OTFS detectors’ performance is suboptimal in rich scattering environments where there are a large number of moving reflectors that reflect the transmitted signal towards the receiver. In this letter, we propose an OTFS detector, referred to as the BPICNet OTFS detector that integrates NN, Bayesian inference, and parallel interference cancellation concepts. Simulation results show that the proposed detector outperforms the state-of-the-art.

The effect of quantized ETF, grouping, and power allocation on non-orthogonal multiple accesses for wireless communication networks

Nonorthogonal multiple access (NOMA) is a significant technology in radio resource sharing and it has been recognized as a favorable method in fifth-generation (5G) wireless networks to meet the requirements of system capacity, service latency, and user connectivity. Many schemes for NOMA have been proposed in the last few years. such as transmitter linear spreading-based NOMA as a code domain, as well as a linear minimum mean square error (LMMSE), parallel interference cancellation (PIC), and serial interference cancellation (SIC) with power allocation and grouping as a power domain at the receiver side for uplink NOMA. This work aims to evaluate the performance of multiple types of linear spreading-based NOMA schemes. Simulations are achieved for the error-rate performance evaluation of these NOMA schemes, received signal after detection, and received signal and effect of every user on the other. Evaluating the performance of these technologies with comparison is also achieved through using grouping and power allocation. Simulations are achieved for the sum rate and spectral efficiency. For the future, 5G NOMA development, an equiangular tight frame (ETF) is suggested for improving performance and suggests grouping with 64qam-quantized Grassmannian for improving performance favorite about grouping with Generalized welch-bound equality (GWBE)

Spread Unsourced Random Access With an Iterative MIMO Receiver

This work is dedicated to the unsourced random access (URA) with multiple-antenna receiver. We utilize a preamble-payload packet format where the preamble, selected from a pool shared between all active users, serves as a temporary activity detection identifier. The payload carries the main portion of the message data which is encoded for error correction, permuted, and scrambled. The compressed-sensing (CS) preamble receiver that estimates the active preambles and the respective user channels is followed by a payload receiver which performs several iterations of data and channel estimation and parallel interference cancellation. Our numerical and analytic results demonstrate that the presented system outperforms the related work in terms of the achievable numbers of active users and signal-to-noise ratios (SNR)s supported by the system.

Graph Neural Network Aided MU-MIMO Detectors

Multi-user multiple-input multiple-output (MU-MIMO) systems can be used to meet high throughput requirements of 5G and beyond networks. A base station serves many users in an uplink MU-MIMO system, leading to a substantial multi-user interference (MUI). Designing a high-performance detector for dealing with a strong MUI is challenging. This paper analyses the performance degradation caused by the posterior distribution approximation used in the state-of-the-art message passing (MP) detectors in the presence of high MUI. We develop a graph neural network based framework to fine-tune the MP detectors’ cavity distributions and thus improve the posterior distribution approximation in the MP detectors. We then propose two novel neural network based detectors which rely on the expectation propagation (EP) and Bayesian parallel interference cancellation (BPIC), referred to as the GEPNet and GPICNet detectors, respectively. The GEPNet detector maximizes detection performance, while GPICNet detector balances the performance and complexity. We provide proof of the permutation equivariance property, allowing the detectors to be trained only once, even in the systems with dynamic changes of the number of users. The simulation results show that the proposed GEPNet detector performance approaches maximum likelihood performance in various configurations and GPICNet detector doubles the multiplexing gain of BPIC detector.

An intelligent reflecting surfaces based iterative PhC‐MIMO system for atmospheric optical channels

AbstractOptical intelligent reflecting surface (IRS) is regarded as a forward‐looking technology to deal with line‐of‐sight limitations in optical wireless communications. This paper proposes an iterative photon counting nonorthogonal multiple access‐multiple‐input–multiple‐output (NOMA‐MIMO) system based on optical IRS. By analyzing the geometric and misalignment losses under turbulence effect in the optical IRS‐based atmospheric channel, we construct the channel fading coefficient matrix of the NOMA‐MIMO system. At the receiver, a novel iterative parallel interference cancellation algorithm based on logarithmic likelihood ratio is developed for signal detection. Through the simulation of bit error rate (BER), the reliability of the proposed system is proved. Quantitatively, the BER performance can achieve at the dBJ per bit for the scenario of MIMO system. Furthermore, the numerical results of the external information transfer process indicated that the proposed system has a rapid convergence performance.

Multipoint Overlapping Optical Networks

Coherent transmission has drastically evolved in the last decade to provide high flexibility to improve spectral efficiency. This yields a point-to-point capacity close to Shannon's limit. In this work, we present the multipoint overlapping optical network architecture in a multi-transmitter to single-receiver context to boost the network capacity. It overlaps two optical signals, partly reusing network resources, here frequency slots of 12.5 GHz width. We show that a joint digital signal processing, based on multi-stage parallel interference cancellation efficiently compensates inter-channel interference up to 39% spectrum overlap with a 1 dB SNR penalty for PDM-QPSK signals. To investigate the impact of the residual interference penalty, we model the proposed solution as an additional power-independent Gaussian-noise term introduced in the transmission. Experiments and simulations have successfully validated the model and the extra penalty is shown to be dependent only on the chosen overlapping given factor. Finally, with such a model, we study the network gains brought by the proposed architecture. We investigate different networking scenarios assuming either 2-slot and 3-slot of overlapping, resulting in ∼20% and ∼40% of overlapping. We demonstrate a network capacity gain of up to 17%.

MIMO Processing With Linear Beat Interference Cancellation for Space Division Multiplexing Self-Homodyne Coherent Transmission

We investigate self-homodyne coherent transmission employing space division multiplexing (SDM), where a continuous wave laser source is divided to produce spatially multiplexed signals and a co-propagating pilot-tone (PT), which serves as a local oscillator for self-homodyne detection at the receiver side. The beat interference caused by the spatial coupling between PT and the signals during propagation is investigated through derivations and numerical modelling. Both conventional multiple-input–multiple-output (MIMO) and unreplicated parallel interference canceler (UPIC)-assisted MIMO suffer from the effects of beat interference and additional mode dependent loss introduced by PT-signal crosstalk, which limits the performance of SDM-based self-homodyne coherent systems. We propose two novel MIMO processing schemes employing digital conjugate input branches to handle the beat interference and demonstrate system performance improvement in both simulations and experiments. For a 240-Gbps self-homodyne coherent system transmitting mode-multiplexed QPSK signals over a 3-mode multimode fiber, after adapting the two enhanced MIMO schemes, simulations show a up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 4 dB improvement in PT-signal crosstalk level tolerance, and experiments show undistorted constellations as well as BER improvements from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim 10^{-2}$</tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim 10^{-5}$</tex-math></inline-formula> with PT-signal delay alignment after the mode demultiplexer.

A Poisson-Gaussian Noise Limited Quantum Iterative Multi-User System With Non-Ideal Photon-Counting Receiver

Coherent state quantum communication is attracting extensive attention for its great value in terrestrial and satellite information networks. This paper proposes a new non-orthogonal quantum multi-user (MU) iterative detection scheme. At the receiving end, we develop a composite quantum receiver with multi-stage measurement instrument and soft iterative MU detector. Furthermore, based on a three-dimensional factor graph, a nonlinear Poisson-Gaussian noise limited coherent state iterative MU parallel interference cancellation (PIC) algorithm is derived. Our results demonstrate that this system can well support MU communication and achieve good performance. Quantitatively, for the 8 users scenario, the BER of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$10^{-6}$</tex-math></inline-formula> can be obtained when the photon number is 19. Further numerical results show that the system we designed exhibits superior robustness against imperfections (e.g., quantum mode mismatch and quantum thermal noise).

Unsourced Random Access Over Fading Channels via Data Repetition, Permutation, and Scrambling

We focus on an unsourced random access (URA) system for communication over fading channels where the payload of each packet is encoded for error-correction, repeated, permuted, and scrambled. Each packet is also equipped with a preamble that is used for channel estimation and detection of permutation and scrambling sequences utilized for payload encoding. We propose an algorithm to resolve multiple-access preamble transmission, based on the approximate message-passing (AMP), that is capable to support high numbers of active users and achieve low probabilities of miss-detection. We also develop a parallel interference cancellation technique for payload reception that iteratively refines the channel estimates and attempts to minimize the mean squared error (MSE) of the users’ data via selective error-correction decoding. Finally, we derive a detailed system performance analysis that closely matches the obtained numerical results. We demonstrate that the presented system can more than double the number of active users, supported by the state-of-the-art systems. Large gains in terms of the minimal required signal-to-noise ratios (SNR)s are also demonstrated for a wide range of active user numbers.

M-ARY CDMA SCHEME WITH CCSK MODULATION AND PARALLEL INTERFERENCE CANCELLATION TECHNIQUE

In this paper, we tackle the problem of implementation a parallel interference cancellation scheme for multi-user detection (MUD) in M-ary CCSK-modulated CDMA system. Complexity remains the main obstacle to the practical implementation of MUD and a factor limiting, if not the very possibility, then the feasibility of using high order M-ary modulation formats for applications such as low-probability-of-intercept systems with a large spreading factor or, myriads of small self-powered IoT devices. The design of MUD algorithms for M-ary systems leads to a new round of growth in the receiver complexity comparing with the binary modulation. Demodulator has a major impact on the complexity of CDMA system. Cyclic code-shift keying (CCSK) is a modulation technique which is designed to reduce the complexity of M-ary signaling. In this, each symbol is a circularly shifted version of a single code sequence. Assuming synchronization, the receiver cyclically correlates the input signal plus noise with the base sequence and estimates the position of the correlation peak. The preliminary stage of the proposed scheme is a conventional multi-channel CDMA receiver. The preliminary estimates of the data is multiplied by user codes and amplitude estimates in the spreader, and then fed to the adder to generate the MAI estimates. After the latter are subtracted from the group signal, K-dimensional vector of cleared user signals is passed to the matched filter bank to form the refined estimates of the data. At each subsequent stage, the estimates of the output data of the previous stage are used as input data. The complexity gain is the ratio of the number of computations for finding cyclic convolution and, the amount of computations for finding M linear convolutions, i.e., M/log2M. Since the performance of the algorithm is sensitive to the reliability of the preliminary decisions, there are strict criteria for the selection of spreading codes: the length which must be an integer power of 2, the large family size, good periodic autocorrelation and good cross-correlation properties. To examine the proposed algorithm using computer simulation, we selected minimax periodic and odd-periodic complementary codes, the properties of which are close to the properties of the codes used in the CCSK scheme implemented in Link-16 protocol tactical data networks JTIDS and MIDS. Our study shows that the gain over the conventional receiver increases as the SNR increases, achieving 15 dB for BER 10-5. The system with complementary codes outperform system based on minimax PN-codes, achieving a target bit error rate at a lower SNR.