Iterative Interference Cancellation Scheme Research Articles

Enabling User Relaying in MCM-NOMA Under Doubly Selective Channels Using Iterative Interference Cancellation Schemes for Wireless IoT Networks

Cell-edge users of future cellular Internet of Things (IoT) sensor networks can suffer from extremely severe channel conditions, especially under mobility with high speeds, i.e., doubly selective channels. This letter presents a performance improvement method for IoT cell-edge users’ downlink transmission under doubly selective channels. To this end, we consider the implementation of multicarrier modulation-based cooperative user relaying nonorthogonal multiple access combined with two interference cancellation schemes and derive the lower-bound of the E2E-BER of the proposed scheme. The obtained results showed that the proposed scheme requires a low computational complexity and significantly improves the system’s performance even if the channel state information is imperfect.

Maximum likelihood detection for coded combinerless LINC-OFDM systems

Owning to the high peak-to-average power ratio problem, the power efficiency of orthogonal-frequency-division-multiplexing (OFDM) systems is usually low. It deteriorates in millimeter wave systems in which the design of an efficient linear power amplifier is much more challenging. The linear-amplification-with-nonlinear-component (LINC) technique can serve as a remedy, decomposing the input signal into two constant-envelop component signals followed by high-efficient nonlinear amplifiers. However, the power combiner, a key component used to combine the amplified signals, is difficult to implement. Combinerless LINC systems employ two transmit antennas such that two component signals can be naturally combined at the receiver. Unfortunately, the performance of combinerless LINC-OFDM systems is seriously degraded if difference, even small, exists between the two channels. The maximum likelihood (ML) receiver can effectively solve the problem; however, its computational complexity is prohibitedly high. We propose a coded combinerless LINC-OFDM system, including a convolutional encoder and a list Viterbi algorithm (LVA) decoder, to solve the problem. The LVA can provide a small number of candidates for the ML detector, dramatically reducing the required computational complexity. We also utilize an enhanced zero-forcing equalizer such that the soft-demapping operation can be effectively conducted. Finally, we propose a simple iterative interference cancellation scheme to further enhance the performance. Simulations show that the proposed combinerless LINC-OFDM system can outperform the conventional OFDM while the consumed power is much lower.

Low‐complexity iteration‐based interference cancellation in asynchronous physical‐layer network coding

When two terminals exchange information through an intermediate relay, physical-layer network coding (PLNC) improves the spectrum efficiency by allowing cocurrent packet transmission. Synchronisation is one of the most important issues in distributed wireless communications systems. In time-domain (TD)-based PLNC, signals transmitted from user terminals may arrive the relay at different time. The fractional symbol level delay will introduces inter-symbol interference because of the use of practical pulse-shaping and matched-filter. Orthogonal-frequency division-multiplexing (OFDM) can be used to deal with time asynchrony. However, OFDM systems are very sensitive to carrier frequency offsets, which will introduce inter-carrier interference. In this study, a novel low-complexity symbol-based decoding iterative interference cancellation schemes are proposed for TD-based and OFDM-based PLNC. Signals from two sources are separately decoded, and interference is reconstructed and eliminated. Monte Carlo simulations show that the proposed scheme with over just one iteration can significantly improve the bit error rate performance.

Distributed Iterative Interference Cancellation and MapReduce Paradigm for Cooperative Network

In this paper, we propose an iterative interference cancellation scheme based on nested lattice to combat the inter-cell interference for cooperative cellular networks. The achievable rate region of the proposed scheme under a two-cell and two-user model is obtained. In this simplified model, each decoder separately decodes its corresponding user message, and sends the result to the other decoder for interference cancellation. The interference can be mitigated gradually by the step-by-step iterative decoding. Once the message from one user is successively decoded, the interference to the other receiver can be totally canceled. For more general multi-cell and multi-user networks, a sufficient condition of convergence of the proposed scheme is derived. In addition, we find that the modern cloud computing paradigm, MapReduce, is very suitable for our distributed scheme. This means that the proposed scheme can be utilized as joint decoder in Cloud Ratio Access Network (CRAN).

Two‐step interference cancellation scheme in doubly selective channel estimation using superimposed training

Channel estimation for single-input–multiple-output systems over doubly selective channel using superimposed training and discrete prolate spheroidal basis expansion model is considered. To remove the interference from unknown data, a two-step interference cancellation scheme is proposed, where in the first step, a first-order statistics-based estimator with cyclic mean removal before transmission is proposed. In this step, only interference components corresponding to cyclic mean of data sequence are removed, which avoids the conflict between total interference elimination and symbol recovery. In the second step, a low complexity iterative interference cancellation scheme is proposed to further improve estimation performance with detected symbols at the receiver's end. Simulation results show that the proposed iterative scheme has the symbol error rate (SER) performance slightly inferior to that of the partially-data-dependent approach but with less computational complexity and outperforms the data-dependent scheme in terms of SER as well as mean-square error over doubly selective channels.

Iterative Interference Cancellation for OFDM Signals With Blanking Nonlinearity in Impulsive Noise Channels

A simple iterative interference cancellation scheme for orthogonal frequency division multiplexing (OFDM) signals with blanking nonlinearity in impulsive noise channels is presented. Blanking nonlinearity has been widely used in practical OFDM systems to suppress impulsive noises at the expense of reducing signal power and generating intercarrier interference (ICI). To improve the performance of blanking nonlinearity element, we propose an iterative interference cancellation scheme which can effectively reduce the level of ICI caused by the blanking operation at the OFDM receiver. With adaptive blanking threshold for each iteration, the proposed iterative receiver design can converge to its best performance with only three iterations. Simulation results show significant performance improvement is achieved by the proposed scheme.

On the serial iterative co-channel interference cancellation technique for MFSK/FH-SSMA system

A serial iterative co-channel interference cancellation scheme is proposed for the MFSK/FH-SSMA system. First, a soft-limiter is employed to formulate the received time-frequency matrix with multilevel entry to suppress the residual interference due to the co-channel interference cancellation. Secondly, a serial detection scheme is utilised to solve the ambiguity problem. Both the detection performance and the computation complexity are simulated to validate the applicability of the proposed scheme. It is unveiled that the proposed scheme could be utilised to improve the iterative interference cancellation scheme significantly with negligible increase in computation complexity. Moreover, the proposed scheme is able to achieve the maximum likelihood detection performance with much lower computation complexity.

Blind adaptive and iterative interference cancellation receiver structures based on the constant modulus criterion in multipath channels

Blind adaptive and iterative interference cancellation (IC) receiver structures for direct sequence code division multiple access systems in multipath channels are proposed. A code-constrained constant modulus design criterion based on constrained optimisation techniques and adaptive algorithms for receiver and channel parameter estimation are described for successive IC (SIC) and parallel IC (PIC) detectors and a new hybrid IC (HIC) scheme in scenarios subject to multipath fading. The proposed HIC structure combines the strengths of linear, SIC and PIC receivers and is shown to outperform the conventional linear, SIC and PIC structures. A novel iterative detection approach that generates different cancellation orders and selects the most likely symbol estimate on the basis of the instantaneous minimum constant modulus criterion is also proposed and combined with the new HIC structure to further enhance performance. Simulation results for an uplink scenario assess the algorithms, the proposed blind adaptive IC detectors against existing receivers and evaluate the effects of error propagationof the new cancellation techniques.

Iterative interference cancellation and channel estimation in multibeam satellite systems

AbstractThis paper deals with the use of non‐linear multiuser detection techniques to mitigate co‐channel interference on the reverse link of multibeam satellite systems. These techniques allow more capacity efficient frequency reuse strategies than classical ones, as they make possible to cope with lower C/I. The considered system takes as a starting point the DVB‐RCS standard, with the use of convolutional coding, and the use of the Ka‐band.We propose different iterative interference cancellation schemes, which operate at the beamformer outputs, and which use information from decoders. The proposed receivers assume an initial single‐user synchronization step: frame synchronization and timing recovery, and then perform channel estimation: beamformer coefficients; signal carrier phases and signal amplitudes.In a first step, these receivers are evaluated by simulation in terms of bit error rate and of channel estimation error on two interference configurations. For one of these receivers, sensitivity to imperfect timing recovery and to low‐frequency offsets from user terminals is evaluated.In a second step, since the receiver performances highly depend on the interference configuration, we propose an approach to evaluate performances on a multibeam coverage (by taking into account the variability of interference configurations on the coverage). This method is used to compare different receivers on an example based on a coverage designed on a digital focal array feed reflector antenna. Copyright © 2007 John Wiley & Sons, Ltd.