Multitap RF Canceller with Single LMS Loop for Adaptive Co-Site Broadband Interference Cancellation

With the development of wireless communication technology,an urgent problem to be solved is co-site broadband interference on independent communication platforms such as satellites,space stations,aircrafts and ships.Also,the problem of strong selfinterference rejection should be solved in the co-time co-frequency full duplex mode which realizes spectrum multiplication in 5G communication technology.In the research of such interference rejection,interference cancellation technology has been applied.In order to reject multipath interference,multitap double LMS(Least Mean Square)loop interference cancellation system is often used for cancelling RF(Radio Frequency)domain interference cancelling.However,more taps will lead to a more complex structure of the cancellation system.A novel tap single LMS loop adaptive interference cancellation system was proposed to improve the system compactness and reduce the cost.In addition,a mathematical model was built for the proposed cancellation system,the correlation function of CP2FSK(Continuous Phase Binary Frequency Shift Keying)signal was derived,and the quantitative relationship was established between the correlation function and the interference signal bandwidth and tap delay differential.The steadystate weights and the expression of the average interference cancellation ratio(ICR)were deduced in the scenes of LOS(Line of Sight)interference with antenna swaying on an independent communication platform and indoor multipath interference.The quantitative relationship was deeply analyzed between the interference cancellation performance and the parameters such as antenna swing,LMS loop gain,and interference signal bandwidth,which was verified by simulation experiment.And the performance of the proposed interference cancellation system was compared with that of the traditional double LMS loop cancellation system.The results showed that the compact single LMS loop cancellation system can achieve an average interference rejection capability comparable to the double LMS loop cancellation system.

Off-Grid Compressed Channel Estimation with Parallel Interference Cancellation for Millimeter Wave Massive MIMO

Millimeter wave(mmWave)massive multiple-input multiple-output(MIMO)plays an important role in the fifth-generation(5G)mobile communications and beyond wireless communication systems owing to its potential of high capacity.However,channel estimation has become very challenging due to the use of massive MIMO antenna array.Fortunately,the mmWave channel has strong sparsity in the spatial angle domain,and the compressed sensing technology can be used to convert the original channel matrix into the sparse matrix of discrete angle grid.Thus the high-dimensional channel matrix estimation is transformed into a sparse recovery problem with greatly reduced computational complexity.However,the path angle in the actual scene appears randomly and is unlikely to be completely located on the quantization angle grid,thus leading to the problem of power leakage.Moreover,multiple paths with the random distribution of angles will bring about serious interpath interference and further deteriorate the performance of channel estimation.To address these off-grid issues,we propose a parallel interference cancellation assisted multi-grid matching pursuit(PIC-MGMP)algorithm in this paper.The proposed algorithm consists of three stages,including coarse estimation,refined estimation,and inter-path cyclic iterative inter-ference cancellation.More specifically,the angular resolution can be improved by locally refining the grid to reduce power leakage,while the inter-path interference is eliminated by parallel interference cancellation(PIC),and the two together improve the estimation accuracy.Simulation results show that compared with the traditional orthogonal matching pursuit(OMP)algorithm,the normalized mean square error(NMSE)of the proposed algorithm decreases by over 14dB in the case of 2 paths.

Iterative Signal Detection Based Soft Interference Cancellation for Satellite-Terrestrial Downlink NOMA Systems

To improve the bit error rate(BER)performance of multi-user signal detection in satelliteterrestrial downlink non-orthogonal multiple access(NOMA)systems,an iterative signal detection algorithm based on soft interference cancellation with optimal power allocation is proposed.Given that power allocation has a significant impact on BER performance,the optimal power allocation is obtained by minimizing the average BER of NOMA users.According to the allocated powers,successive interference cancellation(SIC)between NOMA users is performed in descending power order.For each user,an iterative soft interference cancellation is performed,and soft symbol probabilities are calculated for soft decision.To improve detection accuracy and without increasing the complexity,the aforementioned algorithm is optimized by adding minimum mean square error(MMSE)signal estimation before detection,and in each iteration soft symbol probabilities are utilized for soft-decision of the current user and also for the update of soft interference of the previous user.Simulation results illustrate that the optimized algorithm i.e.MMSE-IDBSIC significantly outperforms joint multi-user detection and SIC detection by 7.57dB and 8.03dB in terms of BER performance.

Turbo Message Passing Based Burst Interference Cancellation for Data Detection in Massive MIMO-OFDM Systems

This paper investigates the fundamental data detection problem with burst interference in massive multiple-input multiple-output orthogonal frequency division multiplexing(MIMO-OFDM) systems. In particular, burst interference may occur only on data symbols but not on pilot symbols, which means that interference information cannot be premeasured. To cancel the burst interference, we first revisit the uplink multi-user system and develop a matrixform system model, where the covariance pattern and the low-rank property of the interference matrix is discussed. Then, we propose a turbo message passing based burst interference cancellation(TMP-BIC) algorithm to solve the data detection problem, where the constellation information of target data is fully exploited to refine its estimate. Furthermore, in the TMP-BIC algorithm, we design one module to cope with the interference matrix by exploiting its lowrank property. Numerical results demonstrate that the proposed algorithm can effectively mitigate the adverse effects of burst interference and approach the interference-free bound.

On Normalized Least Mean Square Based Interference Cancellation Algorithm for Integrated Sensing and Communication Systems

Integrated sensing and communication(ISAC)technology is a promising candidate for next-generation communication systems.However,severe co-site interference in existing ISAC systems limits the communication and sensing performance,posing significant challenges for ISAC interference management.In this work,we propose a novel interference management scheme based on the normalized least mean square(NLMS)algorithm,which mitigates the impact of co-site interference by reconstructing the interference from the local transmitter and canceling it from the received signal.Simulation results demonstrate that,compared to typical adaptive interference management schemes based on recursive least square(RLS)and stochastic gradient descent(SGD)algorithms,the proposed NLMS algorithm effectively cancels co-site interference and achieves a good balance between computational complexity and convergence performance.

Group-Based Successive Interference Cancellation for Multi-Antenna NOMA System with Error Propagation

Non-orthogonal multiple access(NOMA)is viewed as a key technique to improve the spectrum efficiency and solve the issue of massive connectivity.However,for power domain NOMA,the required overall transmit power should be increased rapidly with the increasing number of users in order to ensure that the signal-to-interference-plus-noise ratio reaches a predefined threshold.In addition,since the successive interference cancellation(SIC)is adopted,the error propagation would become more serious as the order of SIC increases.Aiming at minimizing the total transmit power and satisfying each user’s service requirement,this paper proposes a novel framework with group-based SIC for the deep integration between power domain NOMA and multi-antenna technology.Based on the proposed framework,a joint optimization of power control and equalizer design is investigated to minimize transmit power consumption for uplink multi-antenna NOMA system with error propagations.Based on the relationship between the equalizer and the transmit power coefficients,the original problem is transformed to a transmit power optimization problem,which is further addressed by a parallel iteration algorithm.It is shown by simulations that,in terms of the total power consumption,the proposed scheme outperforms the conventional OMA and the existing cluster-based NOMA schemes.

Digital Cancellation Scheme and Hardware Implementation for High-Order Passive Intermodulation Interference Based on Hammerstein Model

Passive intermodulation(PIM)interference urgently needs to be solved in the satellite communication system,owing to degrading the whole performance.Mainstream research contributions to the cancellation method for PIM were focused on the analog domain,however,the PIM distortion cannot be eliminated completely with the approaches.Meanwhile,some researchers attempt to tackle the problem through digital signal processing,nevertheless,the proposed methods were not suitable for the practical satellite communication scenario.In this paper,we present a general scheme for the adaptive feedforward PIM cancellation.High-order PIM signals at baseband are estimated by modeling the PIM distortion with Hammerstein model in the digital domain.Based on the reconstructed PIM signal,we adopt the least mean square algorithm to adaptively mitigate the PIM interference for tracking the variation of PIM.The time and frequency synchronization of PIM are based on the correlation of the peak of received signals with the corresponding reconstructed PIM signal.Practical experimental results show that the scheme can effectively cancel the PIM interference,and achieve an interference suppression gain more than 20dB.

Interference Cancellation in Device-to-Device Communications underlying MU-MIMO Cellular Networks

This paper investigates the device-to-device(D2 D) communication underlaying multi-user multi-input multi-output(MU-MIMO) cellular networks. It is assumed that D2 D users reuse the downlink time-frequency resources of cellular links, and the base station(BS) is assumed to be equipped with multiple antennas. We investigate the ergodic achievable sum rate of the system when the interference cancellation(IC) precoding strategy is employed at the BS. The distributions of the received signal-to-interference-plus-noise ratio(SINR) for each link are firstly analyzed, and an exact ergodic achievable sum rate of the whole system with closedform expressions is then derived. Furthermore, we present novel upper and lower bounds with simpler expressions, which are later verified to be fairly close to the Monte-Carlo simulations. All the expressions we presented are suitable for arbitrary network topology and arbitrary number of antennas at BS. Based on the derived bounds, the influence of the antennas at BS on system performance is then analyzed. We reveal that the system performance increases along with the number of antennas at BS in a logarithmic way. The accuracy of our analytical results is validated via comparisons with Monte-Carlo simulations.

A Linear Interference Cancellation Multi-User Detector for Synchronous CDMA Communications

This paper describes a linear interference cancellation multi user detector for synchronous DS CDMA systems under the condition that all spread spectrum code waveforms have the constant cross correlating coefficients. The basic idea is to get the estimation for total multiple access interference (MAI) of all users using a reference code waveform, then subtract the total MAI from the received signal. The structure of such a detector is nearly similar to the conventional detector. The BER expression obtained in the paper shows significant performance improvement compared to the other detectors.

Successive Interference Cancellation and Alignment in K-User MIMO Interference Channels with Partial Unidirectional Strong Interference

Recently cellular networks have been densely and heterogeneously deployed indoors and outdoors to expand the network capacity,and thus the in-building propagation loss and the transmit power diversity of access points will exacerbate link heterogeneity and result in partial unidirectional strong interference.To make full use of the strong interference feature,we propose the successive interference cancellation and alignment(SICA)scheme in the K-user interference channel with partial unidirectional strong interference.SICA is designed to transmit two kinds of data streams simultaneously,the alignment streams and superposition streams.The alignment streams will follow the interference alignment criterion to maintain the optimal degrees of freedom(DoF)performance;the superposition streams are handled via successive interference cancellation at all the strongly interfered receivers to improve the overall achievable rate.The joint transceiver designs for SICA is modeled as a weighted sum rate(WSR)maximization problem,and then can be alternately solved for a local optimum according to the optimality equivalence between WSR and its corresponding weighted mean square error(WMMSE)problem.Simulation results have confirmed the sum rate improvement and DoF optimality of the proposed SICA scheme.

New Parallel Interference Cancellation Scheme for DS/CDMA Systems

This paper proposes a new multi-stage parallel interference cancellation scheme by modifying the conventional multi-stage parallel interference canceller (PIC). At each stage, it first converts the interference-cancelled outputs from previous stage into thea prior information, in terms of which the bit mean values are computed and the multi-access interference (MAI) for each user is evaluated, and then an interference cancellation is performed to obtain further interference suppression. To reduce the implementation complexity, we give an approximation expression for bit mean value. The performance over AWGN channel is analyzed and compared to the conventional PIC. The user numberK=7 and spreading factorN=13 are chosen as simulation parameters. The computer simulation results show that the proposed PIC has better performance than the conventional PIC both with 2 interference cancellation (IC) stages, at bit error rate of 10?3, for example, about 3 dB performance gain is obtained by using the proposed PIC. It is also shown that our proposed PIC with 1-stage is superior to the conventional PIC with 2-stage in performance, which is of practical value because PIC with fewer stages can bring about shorter processing delay. Key words CDMA - parallel interference cancellation - multi-access interference CLC number TN 914 Foundation item: Supported by the National Natural Science Foundation of China (69772015)Biography: Xu Guo-xiong (1967-), male, Ph. D candidate, research direction: wireless communication.

Uplink Performance Evaluation of CDMA Communication System with RAKE Receiver and Multiple Access Interference Cancellation

In CDMA communication systems, all the subscribers share the common channel. The limitation factor on the system’s capacity is not the bandwidth, but multiuser interference and the near far problem. This paper models CDMA system from the perspective of mobile radio channels corrupted by additive white noise generated by multipath and multiple access interferences. The system’s receiver is assisted using different combining diversity techniques. Performance analysis of the system with these detection techniques is presented. The paper demonstrates that combining diversity techniques in the system’s receivers markedly improve the performance of CDMA systems.

Research on Interference Cancellation for Switched-on Small Cells in Ultra Dense Network

In ultra-dense heterogeneous networks, the co-channel inter- ference between small cells turns to be the major challenge to cell throughput improvement, especially for cell edge users. In this paper, we propose a distributed frequency resource al- location approach for interference cancellation, which allo- cates appropriate frequency resources when a small cell is switched on to reduce the co-channel interference to its neigh- boring small cells. This frequency resource pre-allocation aims at avoiding co-channel interference between small ceils and improving users ＇ throughput. The simulation results show that our proposed scheme can effectively reduce the co-chan- nel interference and achieve considerable gains in users＇ through put.

On Design of Conjugated Transmission Scheme for FBMC/OQAM Systems with Interference Cancellation

Compared to OFDM systems with cyclic prefi x, fi lterbank multicarrier with offset quadrature amplitude modulation(FBMC/OQAM) system is considered as an alternative technology for next generation wireless communication systems. However, FBMC systems suffer from intrinsic imaginary interference caused by the real-fi eld orthogonality destruction when passing through complex-valued fading channels. By analyzing the transmultiplexer's response of FBMC/OQAM systems, in this paper, a simple conjugated transmission scheme is proposed for FBMC/OQAM systems. Following the specific conjugation design, the intrinsic imaginary interference including the intrinsic inter-symbol and the inter-carrier interference can be eliminated at the receiver side through linear signal processing operation. Meanwhile, the proposed conjugated transmission scheme is able to obtain extra linear combination diversity gains for improving the systematic performance of FBMC/OQAM. Simulation results show that the proposed scheme is more efficient than conventional methods, especially in practical application scenarios with large Doppler spread caused by high-speed movement.

Particle filter based stochastic interference cancellation for frequency-selective MIMO channel equalization

To mitigate the effects of the previous symbol decision errors of a decision-feedback （DF） equalizer on the current decision, a particle filter （PF） based DF equalizer for frequency selective multiple-input-multiple-output （MIMO） channel is proposed. On the basis of the analyses of DF equalization for the MIMO wireless system, it is found that a stochastic interference cancellation （IC） scheme can be employed to prevent the error propagation in a severe space-time interference scenario. This is because the random rather than the deterministic scheme can reduce the probability of an error decision even if an error decision occurs. Besides, the signal-to-interference-plus-noise ratio （SINR） based IC order, which is obtained via pilot, can guarantee the optimality of the cancellation. The bit error rate （BER） performance of the proposed scheme is verified through simulation experiments under different multipath interference environment.

New Parallel Interference Cancellation for Convolutionally Coded CDMA Systems

Based on BCJR algorithm proposed by Bahlet al and linear soft decision feedback, a reduced-complexity parallel interference cancellation (simplified PIC) for convolutionally coded DS CDMA systems is proposed. By computer simulation, we compare the simplified PIC with the exact PIC. It shows that the simplified PIC can achieve the performance close to the exact PIC if the mean values of coded symbols are linearly computed in terms of the sum of initiala prior log-likelihood rate (LLR) and updateda prior LLR, while a significant performance loss will occur if the mean values of coded symbols are linearly computed in terms of the updateda prior LLR only. Meanwhile, we also compare the simplified PIC with MF receiver and conventional PICs. The simulation results show that the simplified PIC dominantly outperforms the MF receiver and conventional PICs, at signal-noise rate (SNR) of 7 dB, for example, the bit error rate is about 10?4 for the simplified PIC, which is far below that of matched-filter receiver and conventional PIC. Key words convolutionally coded CDMA - parallel interference cancellation - BCJR CLC number TN 914 Foundation item: Supported by the National Natural Science Foundation of China (69772015)Biography: Xu Guo-xiong (1967-), male, Ph. D candidate, research direction: wireless communication.

Cochannel interference cancelation for multiple access systems

Many properties of frequency-hopped spread-spectrum multiple access （FH/SSMA）, such as, robustness against frequency selective fading and jamming make it a preferred multiple access communication scheme. But cochannel interference （CCI） can seriously harm the system＇s performance. On the basis of the analysis of the CCI pattern of frequency hopped multiple access signal, a new multiuser detection algorithm for canceling the CCI in frequency hopped multiple access systems is proposed. In the proposed scheme, the CCI is canceled by first detecting the frequency hopping slot, and then classifying and regenerating the candidates of the interference pattern from the time-frequency matrix. Both the theoretical analysis and computer simulation results show that compared to the conventional detector and Mabuchi＇s detector, this new multiuser detector has lower complexity, better convergence stability, and is suitable for both additive white Gaussian noise （AWGN） channels and Rayleigh fading channels.

Interference cancellation scheme for uplink cognitive radio systems

This paper investigates the interference cancellation （IC） scheme for uplink cognitive radio systems, using the spectrum underlay strategy where the primary users （PUs） and the secondary users （SUs） coexist and operate in the same spectrum. Joint MMSE-based parallel interference cancellation （PIC） and Turbo decoding scheme is proposed to reduce the interference to the PUs, as well as to the SUs, in which the minimum mean square estimation （MMSE） filter is only employed in the first iteration, regarded as the ＂weakest link＂ of the whole detection process, to improve the quality of the preliminary detections results before they are fed to the Turbo decoder. Simulation results show that the proposed scheme can efficiently eliminate the interference to the PUs, as well as to the SUs.

A Soft Parallel Interference Cancellation Algorithm in WCDMA

A two-stage soft parallel interference cancellation (SPIC) algorithm in WCDMA system is proposed. The performance of the algorithm is analysed in perfect power control and near-far case, and the influence of the timing error on the system BER is discussed. Analysis and simulation show that the SPIC technique can enhance system capacity, and have a good ability to resist near-far impact. With its simple structure, it has good potential for practical applications.

Research on Downlink Precoding for Interference Cancellation in Massive MIMO Heterogeneous UDN

In order to solve the data surge brought by largescale increasing of mobile de-vices, Massive MIMO ultra dense networking can greatly improve the system spectral efficiency and energy efficiency. It plays an important role in coping with the exponential growth of the business, but also brought big problems and challenges. For heterogeneous ultra dense networks, both macro and femto users are facing with both the cross-layer interference and co-layer in-terference. The precoding technology studied in this paper resolves the cross-layer interference and co-layer interference for macro users and femto users, and lays a theoretical foundation for the deployment of heterogeneous and ultra dense networks.