Parallel Interference Cancellation Detector Research Articles

Hybrid MAP and PIC Detection for OTFS Modulation

Orthogonal time frequency space (OTFS) modulation has attracted substantial attention recently due to its great potential of providing reliable communications in high-mobility scenarios. In this article, we propose a novel hybrid signal detection algorithm for OTFS modulation. Based on the system model, we first derive the near-optimal <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">symbol-wise</i> maximum <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a posteriori</i> (MAP) detection algorithm for OTFS modulation. Then, in order to reduce the detection complexity, we propose a partitioning rule that separates the related received symbols into two subsets for detecting each transmitted symbol, according to the corresponding path gains. According to the partitioning rule, we design the hybrid detection algorithm to exploit the power discrepancy of each subset, where the MAP detection is applied to the subset with larger channel gains, while the parallel interference cancellation (PIC) detection is applied to the subset with smaller channel gains. We also provide the error performance analysis of the proposed hybrid detection algorithm. Simulation results show that the proposed hybrid detection algorithm can not only approach the performance of the near-optimal <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">symbol-wise</i> MAP algorithms, but also offer a substantial performance gain compared with existing algorithms.

Domain decomposition based SIC detectors for massive MIMO

Recently, domain decomposition techniques were used for the first time to develop a novel block-wise parallel Interference Cancellation (PIC) detector for communication systems (Bentrcia, 2017). The author simulated and tested a novel block-wise PIC detector to cancel Inter-Antenna-Interference (IAI) in a massive Multiple Input Multiple Output (MIMO) uplink system. In this work, we complement the work in Bentrcia (2017) by developing the serial version of the proposed block-wise PIC detector; specifically, we devise a new block-wise successive interference cancellation (SIC) detector using Multiplicative Schwarz (MS) method. As far as we know, no such work has been proposed before. Compared to the block-wise PIC detector of Bentrcia (2017), the proposed block-wise SIC detector exhibits several advantages such as lower computational complexity, lower detection delay and faster convergence. After deriving the update equation of the new block-wise SIC detector, we study its conditions of convergence and the impact of some design parameters on the performance of the novel block-wise SIC detector. Finally, extensive numerical simulations are conducted to validate our theoretical findings.

Knowledge‐aided iterative detection and decoding for multiuser multiple‐antenna systems

In this work, the authors assess the performance and latency of a receiver design for multiuser multiple-antenna systems using low-density parity-check (LDPC) codes with iterative detection and decoding (IDD). The proposed knowledge-aided IDD (KA-IDD) receiver employs a parallel interference cancellation detector with refined iterative processing and a reweighted belief propagation (BP) decoder. Additionally, two BP-based decoding algorithms are proposed for improved performance of the decoder. The first cycle knowledge-aided reweighted-BP decoder takes advantage of the information about the distribution of cycles in the Tanner graph and the second expansion knowledge-aided reweighted-BP decoder expands the original graph into a set of subgraphs, then locally optimises the reweighting parameters of each subgraph. Novel reweighting parameter optimisation strategies are developed for decoding regular or irregular LDPC codes. The developed schemes optimise the parameters off-line and neither of these proposed algorithms imposes extra computational complexity to the on-line decoding procedure. Furthermore, the proposed schemes reduce the decoding latency. Simulation results show that the proposed KA-IDD scheme and algorithms outperform prior art and require a reduced number of decoding iterations.

Multi-Stage Partial Parallel Interference Cancellation Algorithm for MUSA Systems

Multi-User Shared Access is a non-orthogonal multiple access scheme of 5G,which has a high computational complexity and a large time delay due to the usage of successive interference cancellation detection algorithm. This paper proposes a multi-stage partial parallel interference cancellation detection algorithm, which does not require repeated ordering and repeated matrix inversion. In the first stage of detection, the bits of these users with good channel conditions will be outputted, and the influence of multiple access interference on users with bad channel conditions in the second stage will be decreased. Theoretical analysis and simulation results show that the symbol error rate of the proposed algorithm is slightly better than that of the two-stage MMSE-PIC, and the complexity is reduced. In the meanwhile, the computational complexity is significantly reduced without SER performance degradation when compared with MMSE-SIC algorithm.

An Iterative Detection and Decoding Receiver for LDPC-Coded MIMO Systems

This paper presents a high-throughput, area-efficient and energy-efficient iterative detection and decoding (IDD) receiver for low-density parity-check (LDPC)-coded multiple-input multiple-output (MIMO) systems. A layered non-resetting IDD technique is used to minimize the number of inner iterations for a required error performance. An area-efficient minimum mean-square error with parallel interference cancellation (MMSE-PIC) detector is devised to simplify matrix inversion. A detector-decoder interface that is used to exchange soft messages efficiently is proposed. Given the throughput specifications, inner and outer loops are optimally combined to maximize the error performance. The design specifications defined in the IEEE 802.11n standard are adopted as the design target. A 4 $\times$ 4 antenna configuration with BPSK, QPSK, 16-QAM modulations are realized in silicon. The designs that support 64-QAM and 256-QAM modulations are also demonstrated for comparison with prior work. Fabricated in 40 nm technology, the chip integrates 998k logic gates in 1.33 ${\rm mm}^{2}$ and achieves a maximum throughput of 794 Mb/s. The chip dissipates 135 mW at 0.9 V, achieving an energy efficiency of 170 pJ/bit.

A Blind Adaptive Kalman-PIC MUD Algorithm for the Multiple Access Communication Network

In the parallel signal processing, the multi-user detection precision of parallel interference cancellation (PIC) detector is always easily affected by the decision error diffusion. Based on the fast convergence and low complexity of blind adaptive Kalman algorithm, a new blind adaptive Kalman-PIC (KPIC) multi-user detection (MUD) algorithm is proposed for the direct sequence spread spectrum code division multiple access (DS-CDMA) system network with strong multiple access interference (MAI). Compared with traditional standard Kalman filter and PIC algorithm, the proposed combined program can totally track the time-varying channel, effectively estimate unknown noise statistics characteristics on-line while conducting state filtering, possibly minimize the detection error diffusion in the interference cancellation processing of single PIC algorithm, thus effectively suppress MAI. Simulation results show that the KPIC algorithm is of better convergence, dynamic tracking ability and precision

Efficient interference cancellation detector for asynchronous upstream optical code division multiple access‐passive optical network with mixed Poisson–Gaussian noise

Optical code division multiple access (OCDMA) is a promising candidate for next generation passive optical networks (NG-PON). OCDMA-PON can potentially provide all customers with a Gb/s-class BW upstream with inherent flexibility. Unfortunately OCDMA suffers from multiple access interference (MAI) and various detection noises. In this study, the authors consider developing efficient interference cancellation detection under mixed Poisson-Gaussian noise. The latter is more realistic than considering Gaussian or Poisson noise alone. The authors first start by developing a maximum likelihood framework of the detection process under Gaussian, Poisson and Poisson-Gaussian noises, respectively. Then, the authors develop the proposed interference cancellation detector for the Poisson-Gaussian noise case after deriving the conventional expectation-maximisation (EM) detector for the Poisson noise case. Finally, the authors simulate the proposed detector and compare it to the projected parallel interference cancellation, EM and other detectors to validate its superiority and enhanced performance.

Interference and Complexity Reduction in Multi-stage Multi-user Detection in DS-CDMA

Multi-stage parallel interference cancellation (PIC) technique gives good performance compared to successive interference cancellation (SIC) method, but biased decision statistic and complexity problems are raised due to imperfect estimation of multiple access interference (MAI) as number of stages increases. partial parallel interference cancellation (PPIC) technique is proposed to cancel the interference partially stage by stage to overcome biased problem. The complexity reduction for PIC detection is based on the convergence nature of interference cancellation which is called the difference PIC (D-PIC) detection technique. In this paper we combine (PPIC and DPIC) these two techniques and propose a multi-stage multi-user (PD-PIC) detector for performance improvement and complexity reduction compared to conventional PIC detector. The performance is degraded as the number of users increases in each technique.

Competitive linear parallel interference cancellation detection based on monotone line‐search techniques

In this study, a competitive linear parallel interference cancellation (LPIC) detector that is memory efficient, enjoys fast convergence and low complexity and can be used to approximate the decorrelator/minimum-mean-square error detector in large-scale communication systems is proposed. Similar to the non-monotone gradient-based LPIC detectors developed recently by Bentrcia and Alshebeili, the proposed detector maintains its efficiency and does not break down quickly if matrix-vector products are not performed accurately. However, unlike the previous detectors, the proposed detector relies on a monotone line-search technique which renders it more attractive because early stopping methods such as the L-curve method can be used to stop the LPIC iterations prior to convergence in order to avoid the noise enhancement effect. Simulation results agree well with the authors theoretical findings.

Linear IC detectors for low to medium SNR ill-conditioned communication systems with unknown noise variance

In this paper, we introduce two new linear parallel interference cancellation (LPIC) detectors that are suitable for low to medium signal-to-noise ratio ill-conditioned communication systems and do not require knowledge of the noise variance but perform close to the linear minimum mean square error detector, which needs such information. Particularly, we focus in this work on fast linear parallel interference cancellation detectors that are asymptotically equivalent to the steepest descent and conjugate gradient algorithms, respectively, and show that they exhibit a spectral filtering property and semi-convergence behavior. Consequently, a deterministic stopping rule to stop the LPIC iterations that is independent of the noise level (known as the L-curve method) is investigated and tested. Simulation results are presented to support our theoretical findings.

A Projected Parallel Interference Cancellation for Asynchronous Upstream OCDMA-PON

OCDMA is a promising candidate for next generation passive optical networks (NG-PON). OCDMA-PON can potentially provide all customers with a Gb/s-class BW upstream with inherent flexibility. Unfortunately OCDMA suffers from multiple access interference (MAI) and various detection noises. To mitigate MAI, we propose a novel parallel interference cancellation technique for incoherent DS-OCDMA that better exploits the non-negativity of the solution. The proposed PIC scheme incorporates this additional information into its structure. The proposed PIC detector is shown to outperform the conventional correlator detector, the decorrelator detector, the linear parallel interference Cancellation (LPIC) detector and even the linear minimum mean square error (LMMSE) detector.

Regularization property of linear interference cancellation detectors

In this article, we unveil a new property of linear interference cancellation detectors. Particularly, we focus in this study on the linear parallel interference cancellation (LPIC) detector and show that it exhibits a semi-convergence property. The roots of the semi-convergence behavior of the LPIC detector are clarified and the necessary conditions for its occurrence are determined. In addition, we show that the LPIC detector is in fact a regularization scheme and that the stage index and the weighting factor are the regularization parameters. Consequently, a stopping criterion based on the Morozov discrepancy rule is investigated and tested. Simulation results are presented to support our theoretical findings.

New linear PIC detectors based on non-monotone line-search techniques

In this communication, three novel linear parallel interference cancellation (LPIC) detectors that exhibit fast convergence, low complexity, low memory requirements and can be used to efficiently approximate the decorrelator/MMSE detector in large-scale wireless communication systems are proposed. Unlike conjugate gradient based LPIC detectors, the proposed LPIC detectors maintain their efficiency and do not break down quickly if the matrix–vector products are performed only approximately. These detectors employ non-monotone line search techniques and use a pre-conditioner that exploits the structure of the inter-carrier interference (ICI) matrix to speed up the convergence of the conventional LPIC detector. Moreover, the chaotic behavior observed in the convergence of the proposed detector in AWGN channel is greatly reduced, thanks to the time-varying nature of the fading channel. Simulation results support well our theoretical findings.

Photon-counting chip-interleaved iterative PIC detector over atmospheric turbulence channels

A photon-counting-based iterative parallel interference cancellation (PIC) scheme for free-space opticalcommunications in the presence of multiple-access interference, shot noise, background radiation, and turbulence fading is designed. An efficient chip-level iterative equivalent noise estimation algorithm is also derived. Simulation results show that the proposed scheme can achieve a single-user performance,bound with the fast convergence property. More importantly, it can eliminate the bit-error rate floor of the conventional optical code-division multiple-access system with the aid of a relatively short spreading code length.

On the Selection of Partial Cancellation Factors for a Two-Stage Hard-Decision PPIC Scheme in DS-CDMA Systems

In this paper, we present a simple method of selecting the partial cancellation factors (PCFs) for a two-stage, hard-decision, partial parallel interference cancellation (PPIC) detector for direct-sequence code-division multiple access (DS-CDMA) systems. Using Price's theorem, we derive a range of the optimal PCF for each PPIC stage in multipath fading environments, where the lower and upper bounds can be explicitly calculated from the processing gain and the number of active users of the DS-CDMA system considered. Computer simulation results show that, using the average of the lower and upper bounds as the PCF for each PPIC stage, the bit error rate (BER) performance closely approximates that of the real optimal PCFs. Moreover, a multistage PPIC detector using the proposed PCFs in the first two stages achieves its BER performance limit with fewer stages. That is, the proposed PCF selection method reduces the complexity of a PPIC detector and provides the same BER performance. This makes the proposed PCFs attractive for use in PPIC receivers in DS-CDMA systems.

Low-Complexity Data-Detection Algorithm in Cooperative SFBC-OFDM Systems With Multiple Frequency Offsets

This paper addresses the problem of data detection in cooperative space-frequency block-coding (SFBC) orthogonal frequency-division multiplexing (OFDM) systems in the presence of multiple carrier frequency offsets (CFOs). A new ordered-successive parallel interference cancellation (OSPIC) detector is proposed. This method consists of first carrying out coarse ordered interference cancellation detection, where the interference components are successively eliminated, and then performing fine interference cancellation detection using parallel interference reduction. Simulation results show that the proposed detector significantly outperforms existing detectors and performs close to that of CFO-free systems for practical signal-to-noise ratios (SNRs). To further reduce the computational complexity, a minimum mean-square error (MMSE)-based reduced-complexity OSPIC (RC-OSPIC) detector is proposed. Compared with the MMSE detector, which requires a full-size complex matrix inversion, the proposed RC-OSPIC detector performs better and is computationally much more effective.

Adaptive parallel interference cancellation for CDMA systems—A weight selection and filtering scheme

Parallel interference cancellation (PIC) is a well-known multiuser detection algorithm in direct-sequence code-division multiple-access (DS-CDMA) systems. It is typically implemented with a multi-stage architecture. One problem associated with the PIC is that unreliable interference cancellation may occur in the early stages and the system performance may be degraded. Thus, the partial PIC detector was developed to control the cancellation level by use of interference cancellation factors. Partial PIC can be implemented with an adaptive form, in which optimal weights are derived using the least mean square (LMS) algorithm. In this paper, we propose an algorithm improving the conventional adaptive partial PIC. The main idea is to reduce the number of active weights in the LMS algorithm, and to perform weight post-filtering such that the resultant excess mean square error can be reduced. We also analyze the performance of the proposed algorithm and derive the bit error rate of the second stage output. Simulation results verify that the proposed algorithm outperforms the conventional partial PIC, and derived analytical results are accurate.

GPU detectors for interference cancellation in chaos-based CDMA communications

Multi-user detection is an effective technique to reduce the mutual interference between users in code division multiple access (CDMA) communications at the cost of a larger number of arithmetic operations. It is shown that multi-user detection can be efficiently computed on graphics processors using a GPGPU approach. Specifically, two GPU parallel interference cancellation detectors for chaos-based CDMA communications are presented. The method is general and scalable and exploits the thousands of threads that the GPU can execute in parallel.

Soft Decision Parallel Interference Cancellationfor Scrambled/Unscrambled DS-CDMA System

A soft decision linear parallel interference cancellation for the direct sequence spread spectrum CDMA systems which can accommodate more users (K = N+M >N) than the processing gain of the system is analyzed in this paper. The proposed technique accommodates N users without any mutual interference and a number of additional users at the expense of a small signal-to-noise ratio. Two sets of orthogonal Gold codes are used, one for the first N users and the other for the additional users. Both the N users and additional users are overlaid by a set-specific pseudonoise scrambling sequence. The performance of scrambled and unscrambled system for matched filter and linear parallel interference cancellation is analyzed and the scrambled system is found better than unscrambled system. The allowable load of this scheme is investigated, so that the uncoded performance with linear parallel interference cancellation detector using soft (SDIC) decision functions remains close to the single user bound for N= 64 at 33% overloading.

Interference cancellation technique under imperfect synchronization in cellular systems

In this paper, an asynchronous cooperative cellular system applied with space-time block coding (STBC) is investigated. A signal detector is proposed based on parallel interference cancellation (PIC), to cancel the inter-symbol interference (ISI) caused by the imperfect synchronization. Simulation results show that the proposed PIC detector can effectively suppress the ISI, but there is still a comparatively high error floor, due to the co-channel interference (CCI) of the cellular system.