On the performance of interference cancelation in D2D‐enabled cellular networks

Device‐to‐device (D2D) communication underlaying cellular networks is a promising technology to improve network resource utilization. In D2D‐enabled cellular networks, interference among spectrum‐sharing links is severer than that in traditional cellular networks, which motivates the adoption of interference cancelation (IC) techniques at the receivers. However, to date, how IC can affect the performance of D2D‐enabled cellular networks is still unknown. In this paper, we present an analytical framework for studying the performance of two IC methods, that is, unconditional IC and successive IC, in large‐scale D2D‐enabled cellular networks using the tools from stochastic geometry. To facilitate the interference analysis, we propose an approach of stochastic equivalence of the interference, which converts the two‐tier interference (interference from the cellular tier and D2D tier) to an equivalent single‐tier interference. Based on the proposed stochastic equivalence models, we derive the general expressions for the successful transmission probabilities of both cellular uplinks and D2D links in the networks where unconditional IC and successive IC are respectively applied. We demonstrate how these IC methods affect the network performance using both analytical and numerical results. Copyright © 2016 John Wiley & Sons, Ltd.     

Co‐channel interference cancelation at the user terminal in multibeam satellite systems

We study the applicability of soft interference cancelation in the forward link of multibeam satellite systems with focus on mobile terminals. We adopt a standard currently used in commercial satellite systems as a reference. The multibeam satellite antenna radiation diagram has been generated using a physical optics reflector model while a widely adopted channel model has been used for the land mobile satellite channel. The interference pattern has been derived using a system simulator developed by the European Space Agency. Starting from the analysis of the interference pattern, we study the application of a low‐complexity soft interference cancelation scheme for commercial applications. Our results show that, under realistic conditions, a two‐colors frequency reuse scheme can be employed while guaranteeing service availability across the coverage and keeping the complexity at the user terminals relatively low. Copyright © 2015 John Wiley & Sons, Ltd.     

A network coding based interference cancelation scheme for wireless ad hoc networks

The performance of wireless networks is limited by multiple access interference (MAI) in the traditional communication approach where the interfered signals of the concurrent transmissions are treated as noise. In this paper, we treat the interfered signals from a new perspective on the basis of additive electromagnetic (EM) waves and propose a network coding based interference cancelation (NCIC) scheme. In the proposed scheme, adjacent nodes can transmit simultaneously with careful scheduling; therefore, network performance will not be limited by the MAI. Additionally we design a space segmentation method for general wireless ad hoc networks, which organizes network into clusters with regular shapes (e.g., square and hexagon) to reduce the number of relay nodes. The segmentation method works with the scheduling scheme and can help achieve better scalability and reduced complexity. We derive accurate analytic models for the probability of connectivity between two adjacent cluster heads which is important for successful information relay. We proved that with the proposed NCIC scheme, the transmission efficiency can be improved by at least 50% for general wireless networks as compared to the traditional interference avoidance schemes. Numeric results also show the space segmentation is feasible and effective. Finally we propose and discuss a method to implement the NCIC scheme in a practical orthogonal frequency division multiplexing (OFDM) communications networks. Copyright © 2009 John Wiley & Sons, Ltd.     

Throughput and cost‐efficient interference cancelation strategies for the downlink of spectrum‐sharing Long Term Evolution heterogeneous networks

In a heterogeneous network (HetNet), small cells such as femtocells considered in this work are deployed jointly with macrocells. This new cells' layer, when added to the network, generates interference, which could hamper neighboring macro‐user equipment (MUE) and femto‐user equipment (FUE) transmissions. In fact, this interference results in degradation of the network performance. In this paper, we propose a downlink interference cancelation (DL‐IC) strategy for spectrum‐sharing Long Term Evolution (LTE) HetNet. This DL‐IC strategy aims to reduce the interference impact on users by optimizing their received signal to interference plus noise ratio (SINR) using new utility functions for both FUEs and MUEs. These utility functions allow relaxation of the cancelation ratios in order to reduce implementation complexity while maximizing SINR, QoS, and throughput. We support by different system‐level simulations that both global network performance and user experience in terms of total throughput and received SNR or link‐level throughput, respectively, are significantly enhanced. Throughput gains achievable by the new DL‐IC strategy can reach as much as 200% against a homogeneous LTE network without IC along with an extra 48% per additional femtocell base station against a basic spectrum‐sharing LTE HetNet without IC. These performance figures are shown to surpass those achieved by interference avoidance techniques using either power or frequency resource allocation. Copyright © 2014 John Wiley & Sons, Ltd.     

频率复用DS/CDMA系统中自适应盲多用户检测的一种方法

该文给出一种工作于强窄带干扰(NBI)多径衰落信道中DS/CDMA系统盲多用户检测接收机模型。它具有RAKE接收机的基本结构,在每一条并行支路中利用MMSE准则跟踪各路径信号。因此具有抗多径衰落,同时抑制NBI和多址接入干扰(MAI)的能力。模拟结果证明,它的性能优于未考虑NBI抑制的多用户检测接收机。     

Low complexity ordered successive interference cancelation detection algorithm for uplink MIMO SC-FDMA system

In mobile communication, the most exploratory technology of fifth generation is massive multiple input multiple output (MIMO). The minimum mean square error and zero forcing based linear detectors are used in multiuser detection for MIMO single-carrier frequency division multiple access (SC-FDMA). When the received signal is detected and regularization sequence is joined in the equalization of spectral null amplification, these schemes experience an error performance and the signal detection assesses an inversion of a matrix computation that grows into complexity. Ordered successive interference cancelation (OSIC) detection is considered for MIMO SC-FDMA, which uses a posteriori information to eradicate these problems in a realistic environment. To cancel the interference, sorting is preferred based on signal-to-noise ratio and log-likelihood ratio. The distinctiveness of the methodology is to predict the symbol with the lowest error probability. The proposed work is compared with the existing methods, and simulation results prove that the defined algorithm outperforms conventional detection methods and accomplishes better performance with lower complication.     

A HYBRID INTERFERENCE CANCELLATION SCHEME FOR BLIND MULTIUSER DETECTION IN MULTIPATH FADING CHANNELS

This paper introduces and analyzes a detection scheme for adaptive suppression of Multiuser Access Interference(MAI) and Multipath Distortion(MPD) for mobile station of DS/CDMA system.The proposed detection scheme may amount to a RAKE receiver structure, wherein each branch is considered as a linear multiuser filter designed under a Linear Constrained Minimum Variance(LCMV) optimization strategy to suppress MAI, followed by a proper combin-ing rule to suppress MPD.The adaptive blind multiuser detecting and optimum combining of the proposed receiver are realized, based on the Least-Mean-Square(LMS) algorithm and an adap-tive vector tracking algorithm respectively.Finally,the feasibility of the above two algorithms is proved by the numerical results provided by computer simulation.     

EM‐based noise plus interference estimation for OFDM‐based cognitive radio systems

In this paper, we consider the narrowband interference problem for orthogonal frequency division multiplexing (OFDM)‐based cognitive radio (CR) systems, in which parts of the OFDM subcarriers and parts of the data frame can be seriously interfered, resulting in significant performance degradation. We propose a scheme of iterative noise plus interference estimation and decoding (IED) to mitigate the performance degradation caused by the narrowband interference, which is based on expectation maximization (EM) algorithm. To reduce the number of OFDM symbols for time domain averaging required in the proposed scheme, and adapt the proposed scheme to rapid changing narrowband interference conditions, we also propose an IED scheme with frequency domain partial averaging (IED‐FPA). Moreover, we derive the Cramér‐Rao lower bounds for unbiased noise plus interference variance estimations, and they can be achieved via the proposed IED schemes. Simulation results show that the proposed IED‐FPA scheme can effectively achieve the same performance as that of the optimal maximum likelihood decoder with full knowledge of the power plus interference variances, and the proposed IED‐FPA scheme is very robust with respect to the number of the interfered subcarriers and positive errors of the knowledge of the interfered subcarriers' number. Copyright © 2010 John Wiley & Sons, Ltd.     

New detection algorithms based on the jointly Gaussian approach and successive interference cancelation for iterative MIMO systems

A new detection algorithm based on the jointly Gaussian approach (JGA) and successive interference cancelation (SIC), named the SIC‐JGA algorithm, is proposed for iterative MIMO systems. Both the a priori symbol estimates of the undetected layers and the a posteriori symbol estimates of the previously detected layers are used in the SIC process. To reduce the complexity of covariance matrix inversion in the proposed algorithm, simplified algorithms named S‐SIC‐JGA are investigated for both the single path and multipath block fading channels under M Phase Shift Keying modulations. A detailed complexity analysis is presented for both the SIC‐JGA and S‐SIC‐JGA algorithms. Numerical results exhibit that the system using the SIC‐JGA algorithm outperforms the JGA algorithm, with an additional complexity for determining the detection order of SIC. The S‐SIC‐JGA algorithm has a much lower complexity compared with the SIC‐JGA algorithm while experiencing an acceptable system performance degradation. Proper detection algorithms can be chosen in different iterations to balance the system performance and the detection complexity. Copyright © 2012 John Wiley & Sons, Ltd.     

带有块间串扰MC-CDMA的时域信道估计和多用户检测

本文把带有IBI的MC-CDMA系统等效解释为特殊的直接序列码分多址（DS-CDMA）系统，并给出了相应的时域信道估计方法和时域线性最小均方误差（MMSE）多用户检测方法。仿真实验表明了本文方法的性能。     

MC‐CDMA MIMO systems with quasi‐orthogonal space–time block codes: Channel estimation and multiuser detection

This paper investigates blind channel estimation and multiuser detection for quasi‐synchronous multi‐carrier code‐division multiple‐access (MC‐CDMA) multiple‐input multiple‐output (MIMO) systems with quasi‐orthogonal space–time block codes (QO‐STBC). Subspace‐based blind channel estimation is proposed by considering a QO‐STBC scheme that involves four transmit antennas and multiple receive antennas. Based on the first‐order perturbation theory, the mean square error of the channel estimation is derived. With the estimated channel coefficients, we employ minimum output energy and eigenspace receivers for symbol detection. Using the QO‐STBC coding property, the weight analyses are performed to reduce the computational complexity of the system. In addition, the forward–backward averaging technique is presented to enhance the performance of multiuser detection. Numerical simulations are given to demonstrate the superiority of the proposed channel estimation methods and symbol detection techniques. Copyright © 2011 John Wiley & Sons, Ltd.     

Successive interference cancelation for a CDMA system with diversity reception in non‐Gaussian noise

A large class of physical phenomenon observed in practical wireless systems exhibits non‐Gaussian behavior. The performance of many multiuser detectors can degrade substantially in the presence of such impulsive ambient noise. In this paper, multiuser detection of space coded MIMO and code division multiple access (CDMA) signals under impulsive noise with diversity reception are investigated. We analyze and derive the probability of bit error (P_b) performance of a successive interference cancelation (SIC) system under impulsive noise and maximal ratio combining. We use Middleton's class A model for the noise distribution. Furthermore, we employ post detection SIC as the robust multiuser detection technique for combating the impulsive noise at specific noise parameters in a CDMA setting. The performance of the system under power imbalance is also shown. Novel analytical derivations for both combining techniques are presented, and simulations were performed, which confirm the theoretical results. Copyright © 2011 John Wiley & Sons, Ltd.     

Design of near‐optimal local likelihood search‐based detection algorithm for coded large‐scale MU‐MIMO system

Massive multiuser multiple input multiple output (MU‐MIMO) system is aimed to improve throughput and spectral efficiency through a large number of antennas incorporated at the transmitter and/or receiver. However, the MU‐MIMO system usually suffers from interantenna interference (IAI) and multiuser interference (MUI). The IAI imposes due to closely spaced antennas at each user equipment (UE), and MUI is enforced when one user comes under the vicinity of another user in the same cellular network. Most of the previous literatures considered any one of these interferences. However, the present work proposes singular value decomposition (SVD) precoding‐assisted user‐level local likelihood ascent search (LLAS) algorithm to mitigate both IAI and MUI. In the uplink MU‐MIMO, the IAI is cancelled by SVD, and the residual MUI is mitigated by LLAS detection. The LLAS detection balances the trade‐off between the classical suboptimal likelihood ascent search (LAS) and optimal maximum likelihood (ML) detection techniques. The proposed LLAS performs local search among all 2M_T‐dimensional neighborhood vectors at each UE, where M_T represents number of transmitting antennas of each UE. Thus, its performance is near optimal, and its complexity is much lower than ML detector.     

Low‐complexity inter‐carrier interference cancelation scheme for SC‐IFDMA system

After the standardization of SCFDMA as the uplink transmission scheme for LTE, frequency synchronization and resulting interference cancelation received considerable attention. In this paper, mathematical modeling of uplink SCFDMA system with interleaved subcarrier assignment scheme (SC‐IFDMA) is carried out in the presence of carrier frequency offset, and the results were utilized in framing the concept of effective interference matrix, which efficiently represents the interference cancelation problem. We propose two schemes to mitigate the effects of interference and channel based on linear filtering approach, and the typical structure of effective interference and channel matrices in SC‐IFDMA were utilized in formulating a low‐complexity implementation model for the proposed compensation schemes. Even though many works have been reported in the field of interference cancelation of SCFDMA system, majority of them were extension of the interference compensation schemes proposed for OFDMA system, whereas schemes proposed in this paper utilize the typical characteristics of the SC‐IFDMA system. The proposed schemes were simulated using MATLAB, and the performance is compared with existing schemes. Copyright © 2015 John Wiley & Sons, Ltd.     

An adaptive multiuser detector for DS‐CDMA systems in multipath fading channels

In this paper, we investigate the performance of an adaptive multistage detection scheme for direct‐sequence code‐division multiple‐access (DS‐CDMA) systems. The first stage consists of an adaptive multiuser detector which is based on the linear constrained minimum variance (LCMV) criterion. The interference cancellation (IC) occurs in the second stage. The performance of the iterative receiver over both flat and frequency‐selective fading channels is investigated and compared to the single‐user bound. In all cases, and under heavy system loads with near‐far problems, the iterative receiver is shown to offer substantial performance improvement and large gain in user‐capacity relative to the standard LCMV. In flat‐fading channels, our results show that the performance of the iterative detector is very close to the single‐user bound. For the frequency‐selective channel, this performance is noted to be in the order of 1 dB far from the single‐user bound. Copyright © 2007 John Wiley & Sons, Ltd.     

Pilot Symbol Assisted Hybrid Detection for OFDM‐Based Spatial Multiplexing Systems

In this paper, we provide a new detection scheme for a pilot symbol assisted interference nulling and cancellation operation to reduce unexpected effects owing to parallel transmission in orthogonal frequency division multiplexing (OFDM)‐based spatial multiplexing systems. We have shown that the investigated OFDM vertical Bell laboratories layered space time (VBLAST) detection based on hybrid processing performs better than ordinary OFDM‐VBLAST detections based on serial processing and parallel processing, respectively.     

CDMA系统中联合功率控制、波束赋形与多用户检测

应用功率控制、波束赋形和多用户检测可以有效地消除和减少CDMA系统中的干扰。本文结合波束赋形和多用户检测的特性，提出一种应用波束赋形增益和多用户相关矩阵的解相关算法。基于算法的复杂性，提出一种区分聚集用户进行多用户检测的的算法。由于波束赋形能够消减主瓣波束之外的多用户干扰，对聚集移动台采用解相关检测达到减少运算量和消除多用户干扰的目的。对算法进行了仿真分析，证明了本算法的优越性。     

Minimum symbol error rate multiuser detection using an effective invasive weed optimization for MIMO/SDMA–OFDM system

Space division multiple access–orthogonal frequency division multiplexing system has become a potential wireless communication system by offering high spectral efficiency, performance and capacity. This article deals with minimum symbol error rate (MSER)‐based multiuser detection (MUD) technique for the space division multiple access–orthogonal frequency division multiplexing system using an efficient invasive weed optimization (IWO) algorithm. The IWO algorithm is used for finding optimal weights such that the probability of error is directly minimized rather than minimizing the mean square error. Because of this, the MSER MUD is able to detect users even in overload scenario, where the number of users is more than the number of receiving antennas, unlike several classical detection techniques. The IWO is inspired from the nature of invasive colonization of weeds and relatively simple compared with other optimization techniques. The bit error rate performance of the proposed IWO‐aided MSER MUD is found to be better than minimum means square error and differential evolution algorithm‐aided MSER MUDs. Simulation results show that the proposed IWO MSER achieves faster convergence and lower complexity compared with the differential evolution MSER MUD. Copyright © 2013 John Wiley & Sons, Ltd.     

A new hybrid heuristic multiuser detector for DS‐CDMA communication systems

In this work, we present a new multiuser detection (MUD) structure which results from incorporating the tabu search (TS) heuristic algorithm with the local search (LS) heuristic algorithm. The new proposed structure brings much improvement when compared to both the conventional (matched filter) detector and the decorrelating detector. Moreover, the new TS‐LS‐detector proposed here approximates well the performance of the optimal MUD detector but with a very low computational complexity. Copyright © 2008 John Wiley & Sons, Ltd.     

Adaptive joint beamforming and B‐MMSE detection for CDMA signal reception under multipath interference

The combination of antenna array beamforming with multiuser detection can effectively improve the detection efficiency of a wireless system under multipath interference, especially in a fast‐fading channel. This paper studies the performance of an adaptive beamformer incorporated with a block‐wise minimum mean square error(B‐MMSE) detector, which works on a unique signal frame characterized by training sequence preamble and data blocks segmented by zero‐bits. Both beam‐former weights updating and B‐MMSE detection are carried out by either least mean square (LMS) or recursive least square (RLS) algorithm. The comparison of the two adaptive algorithms applied to both beamformer and B‐MMSE detector will be made in terms of convergence behaviour and estimation mean square error. Various multipath patterns are considered to test the receiver's responding rapidity to changing multipath interference. The performance of the adaptive B‐MMSE detector is also compared with that of non‐adaptive version (i.e. through direct matrix inversion). The final performance in error probability simulation reveals that the RLS/B‐MMSE scheme outperforms non‐adaptive B‐MMSE by 1–5 dB, depending on the multipath channel delay profiles of concern. The obtained results also suggest that adaptive beamformer should use RLS algorithm for its fast and robust convergence property; while the B‐MMSE filter can choose either LMS or RLS algorithm depending on antenna array size, multipath severity and implementation complexity. Copyright © 2004 John Wiley & Sons, Ltd.