Interference Cancellation Scheme Research Articles

X-Secure T-Private Information Retrieval From MDS Coded Storage With Byzantine and Unresponsive Servers

The problem of $X$-secure $T$-private information retrieval from MDS coded storage is studied in this paper, where the user wishes to privately retrieve one out of $K$ independent messages that are distributed over $N$ servers according to an MDS code. It is guaranteed that any group of up to $X$ colluding servers learn nothing about the messages and that any group of up to $T$ colluding servers learn nothing about the identity of desired message. A lower bound of achievable rates is proved by presenting a novel scheme based on \emph{cross-subspace alignment} and a successive decoding with interference cancellation strategy. For large number of messages $(K\rightarrow\infty)$ the achieved rate, which we conjecture to be optimal, improves upon the best known rates previously reported in the literature by Raviv and Karpuk, and generalizes an achievable rate for MDS-TPIR previously found by Freij-Hollanti et al. that is also conjectured to be asymptotically optimal. The setting is then expanded to allow unresponsive and Byzantine servers. Finally, the scheme is applied to find a new lower convex hull of (download, upload) pairs of secure and private distributed matrix multiplication that generalizes, and in certain asymptotic settings strictly improves upon the best known previous results.

Iterative multipacket detection with FDE based MAC protocol in vehicular ad hoc networks

Wireless access in vehicular environments (WAVE), is especially designed to support vehicular ad hoc networks (VANETs) requirements, where rapidly changing channel conditions introduces unsynchronized transmissions. In such networks, instead of dealing with interferences in medium access control (MAC) layer or physical layer alone, both layers should be considered to cooperate and complement each other. In this paper, multipacket detection (MPD) technique with frequency domain equalization (FDE) is proposed for VANETs, with cyclically shifted different interleavers for different nodes, to remove interference and reducing the information exchange between nodes. These promising multi-hop wireless networks are used in situations, where temporary network connectivity is needed. Therefore, to improve the communication between vehicles (V2V) and from vehicles to roadside infrastructure (V2I), MPD-FDE with interference cancellation (IC) schemes can be used iteratively to successfully decode and receive even colliding packets. For designing such a protocol, different key aspects are discussed with an emphasis on iterative MPD-FDE. Numerical results with different network nodes, show the MPD-FDE performances for coded and uncoded transmissions with different IC schemes, where successive IC (SIC) is much better than parallel IC (PIC) schemes. It is also shown that the proposed protocol provide reliable detection and excellent throughput improvements, with much less resource consumption compared to multiple random interleavers.

SLLR‐MDIC: Spatial log‐likelihood multiuser detection and interference cancelation scheme for OFDM‐IDMA

SummaryWireless communication systems have gained huge attraction from research community, industrial, and academic field due to their significant impact on improving the communication efficiency, ease of deployment, and cost‐effective solution for real‐time communication. In this field of wireless communication, cellular communications have grown rapidly due to their daily usages and advantages. This increased demand of cellular communication systems has led to the evolution of 3G, 4G, and 5G communication systems, which in turn demands for higher efficiency and better bandwidth utilization. Due to heavy usage of network communication, multiple users may cause interference which subsequently may lead to the performance degradation which could be addressed using multiuser detection scheme. However, several schemes have been introduced for improving the system performance, but multiple access (MA) still remains a challenging task. Hence, in this work, we present a novel approach called Spatial Log‐Likelihood Multiuser Detection and Interference Cancelation (SLLR‐MDIC) that uses interleaving division multiple access (IDMA) to improve the communication and developed a multiuser detection approach using spatial log‐likelihood ratios. Further, we have developed orthogonal frequency‐division multiple access (OFDM)–IDMA‐based interference cancelation scheme in multiple access to improve the performance using rake receiver based approach. The performance of SLLR‐MDIC scheme is compared with existing techniques of multiuser detection in terms of bit‐error rate (BER) and symbol error rate (SER). The experimental analysis shows that proposed approach achieves improved performance when compared with existing techniques.

Low-Complexity Massive MIMO Detectors Under Spatial Correlation and Channel Error Estimates

The performance, complexity and effectiveness of various massive MIMO (M-MIMO) detectors are analyzed operating under highly spatial correlated uniform planar arrays (UPA) channels. In such context, M-MIMO systems present a considerable performance degradation and also, in some cases, an increased complexity. Considering this challenging, but realistic practical scenario, various sub-optimal M-MIMO detection structures are evaluated in terms of complexity and bit error rate (BER) performance trade-off. Specifically, the successive interference cancellation, lattice reduction (LR) and likelihood ascent search (LAS) schemes, as well as a hybrid version combining such structures with conventional linear MIMO detection techniques are comparatively investigated, aiming to improve performance. Hence, to provide a comprehensive analysis, we consider the number of antennas varying in a wide range (from conventional to massive MIMO condition), as well as low and high modulation orders, aiming to verify the potential of each MIMO detection technique according to its performance–complexity trade-off. We have also studied the correlation effect when both transmit and receiver sides are equipped with UPA antenna configurations. The BER performance is verified under different conditions, varying the array configurations, combining the detection techniques, increasing the number of antennas and/or the modulation order, especially aiming a near M-MIMO condition, i.e. up to $$64\times 64$$ and $$121\times 121$$ antennas has been considered. The aggregated LAS technique has demonstrated good performance in scenarios with high number of antennas, while LR and OSIC operates better in high correlated arrangements.

Energy-Efficient and Secure Resource Allocation for Multiple-Antenna NOMA With Wireless Power Transfer

Non-orthogonal multiple access (NOMA) is considered as one of the promising techniques for providing high data rates in the fifth generation mobile communication. By applying successive interference cancellation schemes and superposition coding at the NOMA receiver, multiple users can be multiplexed on the same subchannel. In this paper, we investigate resource allocation algorithm design for an OFDM-based NOMA system empowered by wireless power transfer (WPT). In the considered system, users who need to transmit data can only be powered by the WPT. With the consideration of an existing eavesdropper, the objective is to obtain secure and energy efficient transmission among multiple users by optimizing time, power and subchannel allocation. Moreover, we also take into consideration for the practical case that the statistics of the channel state information of the eavesdropper is not available. In order to address the optimization problem and its high computational complexity, we propose an iterative algorithm with guaranteed convergence to deliver an upper bound and a suboptimal solution in more general cases. For some special cases, we identify the optimality condition that ensures the global optimum in our algorithm. Extensive simulation studies demonstrate the competitiveness and effectiveness of the proposed algorithmic solution over conventional OFDMA systems as well as over other existing NOMA resource allocation schemes.

Spatial Throughput Analysis and Transmission Strategy Design in Energy Harvesting Cognitive Radio Networks

In this paper, we consider an energy harvesting cognitive radio network where each secondary transmitter (ST) harvests radio frequency energy from ambient primary transmitters (PTs), and communicates with its secondary receiver (SR) which suffers co-channel interference from PTs. A positive correlation is observed between the harvested energy at the ST and the aggregate interference at the SR, which illustrates that an ST will have a higher probability to harvest enough energy if there is strong interference at the SR. To exploit the positive correlation, we propose an interference threshold-based transmission strategy for STs, so as to protect secondary transmissions as well as increase the amount of harvested energy. We model the battery level of each ST as a finite state discrete-time Markov chain and derive the expression of the secondary spatial throughput as a function of the transmission probability and coverage probability. We investigate the impact of interference threshold and density of PTs on the secondary spatial throughput, and provide guidelines in the optimal design of these two factors to maximize the spatial throughput. To further improve the spatial throughput of a secondary network, we consider the successive interference cancellation strategy at SRs, and reveal its superiority in the high density regime of PTs.

Generalized Interlaced Magnetic Recording With Flexible Inter-Track Interference Cancellation

In this paper, interlaced magnetic recording (IMR) is generalized with a flexible inter-track interference cancellation (F-ITIC) scheme to enhance the overall areal density capability (ADC) by balancing and mitigating the mutual ITI between neighboring tracks. The IMR showed ADC gain by interlaced recording of aggressive bit density (BD) top and relaxed BD bottom tracks, where asynchronous ITI mitigation was applied to the bottom ones. On the other hand, IMR configuration can be generalized by the selective write width control, such that narrower relaxed BD top tracks are recorded over wider aggressive BD bottom tracks. In this generalized IMR (G-IMR), balanced ITI between interlaced tracks can provide ADC gain over legacy IMR (L-IMR) and customized F-ITIC for both tracks can further increase the gain. Note that the ITI processing scheme for G-IMR should be flexible in order to manage the ITI signals from high BD affecting low BD tracks, or vice versa. To evaluate the performance of G-IMR with the F-ITIC, numerical evaluations are conducted with the micro-pixelated magnetic channel model. The results show that G-IMR provides a favorable tradeoff between both tracks’ BDs and track density associated mutual ITIs, which offers a tangible ADC gain with the ITI cancellation over the L-IMR.

A Unified Framework for Non-Orthogonal Multiple Access

This paper proposes a unified framework of non-orthogonal multiple access (NOMA) networks. Stochastic geometry is employed to model the locations of spatially NOMA users. The proposed unified NOMA framework is capable of being applied to both code-domain NOMA (CD-NOMA) and power-domain NOMA (PD-NOMA). Since the detection of NOMA users mainly depend on efficient successive interference cancellation (SIC) schemes, both imperfect SIC (ipSIC) and perfect SIC (pSIC) are taken into account. To characterize the performance of the proposed unified NOMA framework, the exact and asymptotic expressions of outage probabilities as well as delay-limited throughput for CD/PD-NOMA with ipSIC/pSIC are derived. In order to obtain more insights, the diversity analysis of a pair of NOMA users (i.e., the $n$-th user and $m$-th user) are provided. Our analytical results reveal that: i) The diversity orders of the $m$-th and $n$-th user with pSIC for CD-NOMA are $mK$ and $nK$, respectively; ii) Due to the influence of residual interference (RI), the $n$-th user with ipSIC obtains a zero diversity order; and iii) The diversity order is determined by the user who has the poorer channel conditions out of the pair. Finally, Monte Carlo simulations are presented to verify the analytical results: i) When the number of subcarriers becomes lager, the NOMA users are capable of achieving more steep slope in terms of outage probability; and ii) The outage behavior of CD-NOMA is superior to that of PD-NOMA.

Performance Enhancement of Optical PPM-CDMA Using Successive Interference Cancellation Scheme

A comprehensive mathematical model of Successive Interference Cancellation (SIC) using Direct Sequence (DS) and Spectral Amplitude Coding (SAC), which is employed in incoherent optical CDMA using On-Off Keying (OOK) Pulse Position Modulation (PPM) and On-Off Keying (OOK) considering the presence of Phase–Induced Intensity Noise (PIIN), shot noise and thermal noise is presented in this work. SIC scheme has the potential to suppress Multiple Access Interference (MAI). The concept of SIC is the following: detection is taken place in successive stages where the most reliable symbols are chosen at each stage. Where the interference contributed by the already detected symbols will be removed. It has been found out that, theoretically, the size of M-ary on optical CDMA system limits the MAI effect. Thus, the system performance improves with the increasing of M-ary PPM. Hence, the system using PPM has better performances if compared to the one using OOK, due to a lower average number of interfering optical pulses. In addition, a lot of users can be accommodated with SIC/SAC-optical CDMA based PPM signaling system instead of the SIC/SAC-optical CDMA based OOK one.

Balanced Detection of 100-Gb/s Optical OFDM Signals With SSBI Cancellation Based on Fused-Type Fiber Mode-Selective Coupler

We propose a signal-to-signal beating interference (SSBI) cancellation scheme in two-mode fiber (TMF) transmission system based on balanced detection without requirement of a guard band. The SSBI can be eliminated based on the mode selectivity characteristic of mode coupler. The mode selectivity in mode coupler relies on the coupling behavior between the fundamental mode LP01 and the first-order mode LP11, which is highly dependent on the spatial orientation of the fiber modes. We design and fabricate a fused-type fiber mode coupler (FFMC) based on circular-core TMF. Based on the fabricated FFMC, we experimentally demonstrate a multi-band 100-Gb/s optical orthogonal frequency division multiplexing signal transmission over 10-m TMF with SSBI cancellation. Significant performance improvement is observed when compared with conventional direct detection scheme under the condition of insufficient bandwidth of a guard band.

Joint Power Allocation for OFDM-Based Non-Concurrent Two-Way AF Relaying

We consider an amplify-and-forward non-con-current two-way relaying for an orthogonal frequency division multiplexing (OFDM) system, where the base station (BS) serves a transmit-only user (TU) and a receive-only (RU) user, whose receive signal is interfered by the TU transmit signal. We design an overhearing-based interference cancellation scheme wherein the RU collects side-information by overhearing the TU transmit signal, and uses that to cancel its interference. We then jointly allocate power at the TU, BS, and the relay nodes across OFDM subbands to optimize the sum-rate, which is a non-convex problem. We solve it using successive convex approximation (SCA), which approximates the non-convex sum-rate optimization as a sequence of convex programs. The SCA approach is shown to converge within few iterations. Numerical results demonstrate the improved performance of the proposed algorithm over other state-of-the-art algorithms.

Analysis of suppression of high-power narrow-band interference in radiometric receivers

The subject of this article is analytical analysis of the method and scheme of high-power narrow-band interference suppression in the vicinity of the local oscillator frequency. The used method is based on the automatic detection of interference combined with the local oscillator frequency and maintaining constancy of its signal. Interference cancellation scheme is based on the principle of operation of the modulation radiometer, in which the "meander" voltage switching unit controls the operation of the microwave key, the voltage adders and the phase detector. The circuits of automatic frequency tuning and adjustment of the amplitude of the local oscillator are independent and act continuously.

Modeling and Analysis of Two-Way Relay Non-Orthogonal Multiple Access Systems

A two-way relay non-orthogonal multiple access (TWR-NOMA) system is investigated, where two groups of NOMA users exchange messages with the aid of one half-duplex (HD) decode-and-forward (DF) relay. Since the signal-plus-interference-to-noise ratios (SINRs) of NOMA signals mainly depend on effective successive interference cancellation (SIC) schemes, imperfect SIC (ipSIC) and perfect SIC (pSIC) are taken into account. In order to characterize the performance of TWR-NOMA systems, we first derive closed-form expressions for both exact and asymptotic outage probabilities of NOMA users' signals with ipSIC/pSIC. Based on the derived results, the diversity order and throughput of the system are examined. Then we study the ergodic rates of users' signals by providing the asymptotic analysis in high SNR regimes. Lastly, numerical simulations are provided to verify the analytical results and show that: 1) TWR-NOMA is superior to TWR-OMA in terms of outage probability in low SNR regimes; 2) Due to the impact of interference signal (IS) at the relay, error floors and throughput ceilings exist in outage probabilities and ergodic rates for TWR-NOMA, respectively; and 3) In delay-limited transmission mode, TWR-NOMA with ipSIC and pSIC have almost the same energy efficiency. However, in delay-tolerant transmission mode, TWR-NOMA with pSIC is capable of achieving larger energy efficiency compared to TWR-NOMA with ipSIC.

Cooperative spectrum sharing in cognitive radio networks with energy accumulation: design and analysis

The authors propose an efficient spectrum sharing scheme in cooperative cognitive radio networks, where an energy-constrained secondary transmitter (ST) first scavenges radio frequency (RF) energy from the received primary signals, and then the ST assists the primary transmission to obtain the opportunity of spectrum access. Specifically, the ST can forward the primary signal with its own signal by adopting both the Alamouti coding technique and superposition scheme only if the harvested energy is sufficient while the primary data is decoded correctly by the ST. Otherwise, the ST will continue to harvest RF energy. The authors use the discrete Markov chain to model the processes of charging and discharging of the battery. Moreover, two different joint decoding and interference cancellation schemes are employed at the receivers to restore the desired data. Closed-form expressions of outage probabilities for both the primary and secondary systems are derived. Aiming to minimise the outage probability of the secondary system with guaranteeing the primary transmission, an optimal power allocation factor for the ST is determined by Monte-Carlo simulation. Numerical results demonstrate that the proposed scheme can effectively improve the transfer performance of the secondary system while realising the transfer requirement of the primary system.

Dynamic Clustering and Coordinated User Scheduling for Cooperative Interference Cancellation on Ultra-High Density Distributed Antenna Systems.

This paper proposes dynamic clustering and user scheduling for previously conceived inter-cluster interference cancellation scheme on ultra-high density distributed antenna system (UHD-DAS). UHD-DAS is composed of one central unit (CU) and densely deployed remote radio units (RUs) serving as small cell access points. It can enhance spatial spectral efficiency by alleviating traffic load imposed per radio unit; however, intenser small cell deployment revives the inter-cell interference (ICI) problem. Cell clustering, cooperation of multiple RUs, can mitigate ICI partially, whereas inter-cluster interference (ICLI) still limits its possible capacity. Simplified ICLI cancellation based on localized RU cooperation was previously proposed to mitigate interference globally. The resolved issue is that it required frequency reuse distance to fully obtain its interference cancellation ability. This paper introduces dynamic clustering with coordinated user scheduling to ensure reuse distance without extra frequency reuse. Joint dynamic clustering and ICLI cancellation can effectively work and almost reaches ideal performance as full cooperative spatial multiplexing transmission.

An inter user interference cancellation scheme for two users in full-duplex MIMO system

The inter-user interference is a critical performance degradation factor in a full-duplex multi-user system. However, the conventional pre-processing filters, such as null space projection filter and regularized channel inversion filter, are unsuitable for user pre-processing filter when each user has the same number of transmit and receive antennas. Thus, we propose an inter-user-interference cancellation scheme applicable to the users with the same number of transmit and receive antennas. By summing the received signals for two symbol periods, the proposed scheme can cancel inter-user interference and obtain a twofold diversity order. The simulation results show that the proposed scheme obtains higher spectral efficiency than the half-duplex system.

Full-Duplex Small-Cell Networks: A Physical-Layer Security Perspective

We provide a theoretical study of physical (PHY)-layer security performance in full-duplex (FD) small-cell networks. Here, the multi-antenna base stations (BSs) and user equipments (UEs) follow from the homogeneous Poisson point process-based abstraction model. To facilitate FD communications, we take into account: 1) successive interference cancellation capability at the UE side via guard regions of arbitrary radii and 2) residual self-interference at the BS side using Rician fading distribution with arbitrary statistics. We investigate the small-cell network PHY-layer security performance in the presence of a Poisson field of eavesdroppers, under the different scenarios of passive and colluding eavesdropping. Considering linear zero-forcing beamforming, we characterize the downlink and the uplink ergodic secrecy rates and derive closed-form expressions for the different useful and interference signals statistics. In certain special cases of interest, we apply non-linear curve-fitting techniques to large sets of (exact) theoretical data in order to obtain closed-form approximations for the different ergodic rates and ergodic secrecy rates under consideration. Our findings indicate that the FD functionality, in addition to enhancing the spectral efficiency, can significantly improve the PHY-layer security performance, especially with the aid of multi-antenna communications and interference cancellation schemes.

Interference Cancellation in CDMA Systems Employing Complementary Codes Under Rician Fading Channels

The ideal correlation properties of single user code division multiple access (CDMA) systems with complementary codes (CC) are lost by multiple access interference and near–far effects in downlink frequency selective fading channels. This severity in interference has motivated to develop ways to overcome the threats with suitable suboptimal interference cancellation schemes. In this paper, we propose successive interference cancellation (SIC) for downlink CDMA systems with CC to improve the system capacity and reduce error rate under near–far situations. Theoretical study and extensive simulations were conducted to verify the effectiveness of proposed SIC under frequency selective Rician fading channels in achieving frequency diversity gain, close to theoretical lower bound in complementary coded CDMA (CC-CDMA) systems.

Hybrid SNR-Adaptive Multiuser Detectors for SDMA-OFDM Systems

Multiuser detection (MUD) and channel estimation techniques in space-division multiple-access aided orthogonal frequency-division multiplexing systems recently has received intensive interest in receiver design technologies. The maximum likelihood (ML) MUD that provides optimal performance has the cost of a dramatically increased computational complexity. The minimum mean-squared error (MMSE) MUD exhibits poor performance, although it achieves lower computational complexity. With almost the same complexity, an MMSE with successive interference cancellation (SIC) scheme achieves a better bit error rate performance than a linear MMSE multiuser detector. In this paper, hybrid ML-MMSE with SIC adaptive multiuser detection based on the joint channel estimation method is suggested for signal detection. The simulation results show that the proposed method achieves good performance close to the optimal ML performance at low SNR values and a low computational complexity at high SNR values.

Error-detection-coding-aided iterative hard decision interference cancellation for MIMO systems with HARQ

In this paper, an error-detection-coding-aided iterative hard decision interference cancellation (EDC-IHIC) scheme for multiple-input multiple-output systems employing hybrid automatic repeat request (HARQ) for multi-packet transmission is developed and investigated. In the EDC-IHIC scheme, only packets identified as error-free by the EDC are submitted to the interference cancellation (IC) stage for cancellation from the received signals. Therefore, the possibility of error propagation, including inter-transmission error propagation, can be eliminated using EDC-IHIC. Because EDC must be implemented in systems that employ HARQ to determine packet retransmission, error propagation can be prevented without the need for additional redundancy. The results of simulations conducted herein verify that the EDC-IHIC scheme outperforms conventional hard decision IC schemes in terms of the packet error rate in various environments.