RNN-driven joint channel estimation and interference cancellation in FBMC: a breakthrough for 5G and beyond

FBMC is a pivotal system in 5G, serving as a cornerstone for efficient use of available bandwidth while simultaneously meeting stringent requirements for high spectral efficiency. Notably, FBMC harnesses the power of multicarrier modulation (MC), a good alternative to orthogonal frequency division multiplexing (OFDM) technology that supports fourth-generation (4G) systems. The wireless communications field is full of challenges, the most important of which are channel estimation and interference cancellation, both of which deserve comprehensive study to increase the efficiency of data transmission. In this paper, our investigation takes a deliberate step towards the convergence of two prominent modulation models: OFDM and FBMC. We specifically contrast these modulation techniques with the intricate field of joint channel estimation and interference cancellation (JCEIC). In this research study, we take advantage of recurrent neural networks' (RNNs') efficiency as a vehicular channel to perform precise channel estimation and recovery of uncorrupted transmitted signals, thereby lowering the bit error rate (BER). Our channel estimation for a dual selective channel is based on the thoughtful placement of pilots scattered over the temporal and frequency dimensions, and is further improved by the interference cancellation method of low complexity that was selected. Our JCEIC proposal aims to integrate RNNs carefully, using the output sequences of JCEIC algorithms as useful inputs to this neural architecture. By clearly demonstrating a decrease in BER as compared to traditional approaches, it is evident that the performance of the novel approach is near to that of a perfect channel. Additionally, a comparison of the performance of FBMC and OFDM systems at various signal-to-noise ratios reveals a clear performance divide that favors the former in terms of system efficiency. The BER is restricted by FBMC to a commendable threshold of less than 0.1 at a modest 5 dB, continuing the higher trend started by its improved RNN-based channel estimate. The accuracy of channel estimation is clearly improved by this paradigm shift, and the computing complexity typical of 5G networks is also clearly reduced.

Multicarrier code division multiple access (MC-CDMA) systems has arrested a lot of attention, owing to the simple implementation and powerful resistance to frequency-selective channels and the CDMA with the suitability for multiuser systems. This paper considers the joint channel estimation and interference cancellation for uplink MC-CDMA communication systems in frequency-selective multipath fading channel. The proposed algorithm consists of three parts: Expectation step, Maximization step and Initialization. Expectation step performs channel estimation and interference cancellation. Maximization step performs data detection. The proposed interference cancellation scheme not only performs multiple access interference (MAI) cancellation but also performs inter-carrier interference (ICI) cancellation. Some simulation examples are given to show the effectiveness and comparisons of the proposed receiver.

In this paper, a joint channel estimation and interference cancellation scheme for space-time coded multiuser systems is presented. We consider M synchronous co-channel users, each equipped with N/sub t/ transmitting antennas. The receiver is equipped with N/sub r/ (/spl ges/ M) receive antennas. It is shown that the proposed scheme estimates the channel and suppresses the interference without any explicit knowledge of the channel and the interference. In addition, this interference cancellation scheme has less complexity than the minimum mean squared error (MMSE) scheme, while maintaining the same decoding complexity with acceptable performance degradation due to channel estimation errors.

We treat the problem of channel estimation and interference cancellation in multiuser ultra-wide-band (UWB) communication systems over multipath fading channels. The UWB system under consideration employs a random time-hopping impulse radio format. We develop a channel estimation method based on linear weighted algorithm. An iterative channel estimation and interference cancellation scheme is proposed to successively improve the receiver performance. We also consider systems employing multiple transmit and/or receive antennas. For systems with multiple receive antennas, we develop a diversity receiver for the well-separated antennas. For systems with multiple transmit antennas, we propose to make use of Alamouti's space-time transmission scheme, and develop the corresponding channel estimation and interference cancellation receiver techniques. Simulation results are provided to demonstrate the performance of various UWB receiver techniques developed in this paper.

This paper studies a direct-sequence spread-spectrum communication system with a small spreading factor (e.g., a single digit) in underwater acoustic multipath channels. Exploiting the channel characteristics that the propagation paths can be grouped into distinct clusters, a receiver with a set of parallel branches is proposed, where per-survivor processing (PSP) is applied on each branch to deal with the signal from one cluster while explicitly treating the signals from other clusters as structured interference. As such, it overcomes a major limitation of an existing PSP based receiver [Zhou, Morozov, and Preisig, J. Acoust. Soc. Am. 133, 2746-2754 (2013)], avoiding exponential complexity increase when the spreading factor decreases. On the first branch, joint channel estimation and interference cancellation are performed based solely on the survivor paths. On the other branches, joint channel estimation and interference cancellation are carried out based on the survivor paths and the tentatively decoded data. The bit log-likelihood ratios from different branches are combined for channel decoding. Performance results based on simulations and collected data sets validate the superior performance of the proposed receiver over the conventional RAKE receiver, which is effective only when the spreading factor is large.

This paper presents pilot symbol aided channel estimation in Filter Bank Multicarrier (FBMC). FBMC has been employed widespread in communication applications because of its good spectral behaviors. Unlike Orthogonal Frequency Division Multiplexing, FBMC structure avoids imaginary interference. So that auxiliary symbols are employed and decrease peak to power ratio and improve achievable capacity. OFDM and FBMC are compared about achievable of channel estimation with pilot symbols. The achievable capacity is increased with linear precoding by interference cancellation. Using two or three auxiliary pilot symbols instead of one is purposed and achievable capacity via Signal to Noise Ratio (SNR) is compared. OFDM and FBMC with coding and auxiliary symbols are discussed about capacity and numerical results are realized in Matlab.

An iterative joint channel estimation, symbol detection, phase recovery and interference cancellation structure is proposed for asynchronous code-division multiple-access systems over frequency-selective fading channels. Based on the expectation maximization (EM) algorithm, a recursive channel estimator is developed for blind channel tracking, using a novel stochastic signal processing technique. To perform symbol detection given the phase ambiguities of the resultant EM channel estimates, a noncoherent scheme is developed to compute the a posteriori probabilities (APPs) of data symbols. Moreover, by incorporating the APPs into the proposed recursive channel estimator, phase ambiguity due to the EM channel estimation can be resolved, which enables soft multiple access interference cancellation for multiuser detection. Based on these new signal processing schemes, an iterative structure is proposed for joint channel estimation and multiuser detection over fast fading channels.

Filter bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) has been studied as an alternative waveform for post-orthogonal frequency division multiplexing (OFDM) wireless communications. However, due to the intrinsic imaginary inter-carrier/inter-symbol interference of FBMC/OQAM signals, accurate channel estimation and equalization remain open issues for FBMC/OQAM systems in dispersive channels. In this article, two new signal models of the analysis filter bank (AFB) output are first derived in the absence of any channel assumption and in the presence of a relaxed channel assumption, respectively. Based on the new-built models, initial channel estimation with least squares (LS) (IniCE-LS) is presented and its output is used as the initial condition of recursive weighted LS (RWLS) estimation; moreover, non-iterative and iterative channel equalization combined with RWLS channel estimation (i.e., N-ICE-RWLS and ICE-RWLS) are proposed by using the real-time reconstructed FBMC/OQAM data symbols as pilots. The proposed N-ICE-RWLS and ICE-RWLS schemes not only allow to improve channel estimation and equalization performance, but also achieve high transmission efficiency. Considering the requirements of practical application, we further develop the low-complexity implementation methods of N-ICE-RWLS and ICE-RWLS. All these schemes are validated by analyzing the channel estimation accuracy and bit error rate (BER) over various frequency selective channels.

In this paper, we propose a method that joints channel estimation and interference cancellation for direct-sequence ultra-wideband (DS-UWB) systems. For the channel estimation, we apply an expectation-maximization algorithm which adopts an iterative computation of maximum-likelihood parameter estimates, with a few number of iterations, the channel coefficient in each finger of Rake receiver can be efficiently estimated. A fuzzy step size LMS algorithm that adopts a variable step size for the interference cancellation is proposed in the multiuser transmission environment. To achieve a better performance, the joint of expectation-maximization (EM) algorithm and fuzzy adaptive filter is presented for the DS-UWB systems and the simulation result is investigated as well.

In this paper, channel estimation and interference cancellation techniques are presented jointly for multipath DS-CDMA systems employing long spreading codes. The linear prediction (LP) approach is applied to estimate the channel response of the desired user, which is based on interference cancellation. The minimum-mean-square-error (MMSE) criterion is used to make the final statistical decision based on the estimated parameters. It is shown that the proposed receiver performs well in the presence of frequency-selective multipath fading.

Filter Bank Multi-Carrier (FBMC) modulation has been recognized as a consistent contender and a possible successor for Orthogonal Frequency Division Multiplexing (OFDM) in 5G and beyond because of its outstanding spectral properties. The channel is assessed in FBMC using pilot-symbol aided channel estimation that provides robust estimates even for severe channel conditions. In the present work, neutraliz ing the imaginary interference at the pilot positions is focused while estimating the channel. To neutralize the imaginary in terference, multiple auxiliary symbols have been proposed to enhance the throughput and channel capacity. The Iterative Minimum Mean Squared Error (IMMSE) cancellation scheme has been proposed to reduce the interference at the pilot and data positions. Transmission power, Bit Error Rate (BER) and throughput are computed for Filter Bank Multi Carrier (FBMC), OFDM and proven that better system performance is obtained for FBMC. The performance of channel estimation is evaluated through 5G standards and indicates that the usage of multiple auxiliary symbols per pilot leads to better throughput and low Bit Error Rate at low power transmission.

The employment of MIMO OFDM technique constitutes a cost effective approach to high throughput wireless communications. The system performance is sensitive to frequency offset which increases with the doppler spread and causes Intercarrier interference (ICI). ICI is a major concern in the design as it can potentially cause a severe deterioration of quality of service (QoS) which necessitates the need for a high speed data detection and decoding with ICI cancellation along with the intersymbol interference (ISI) cancellation in MIMO OFDM communication systems. Iterative parallel interference canceller (PIC) with joint detection and decoding is a promising approach which is used in this work. The receiver consists of a two stage interference canceller. The co channel interference cancellation is performed based on Zero Forcing (ZF) Detection method used to suppress the effect of ISI in the first stage. The latter stage consists of a simplified PIC scheme. High bit error rates of wireless communication system require employing forward error correction (FEC) methods on the data transferred in order to avoid burst errors that occur in physical channel. To achieve high capacity with minimum error rate Low Density Parity Check (LDPC) codes which have recently drawn much attention because of their error correction performance is used in this system. The system performance is analyzed for two different values of normalized doppler shift for varying speeds. The bit error rate (BER) is shown to improve in every iteration due to the ICI cancellation. The interference analysis with the use of ICI cancellation is examined for a range of normalized doppler shift which corresponds to mobile speeds varying from 5Km/hr to 250Km/hr.

The Filter Bank Multi Carrier (FBMC) has been studied as replacement for Orthogonal Frequency Division Multiplexing (OFDM) on the physical layer of the telecommunication systems. FBMC presents improvements on the spectrum utilization, bit rate and robustness to interference, without the need for inclusion of a Cyclic Prefix (CP). Since the orthogonality among symbols on FBMC is accomplished by means of using Offset QAM (OQAM), channel estimation becomes a challenge. This work presents a scattered pilot frame proposed for digital TV and a cubic spline interpolation combined with DFT-based iterative channel estimation method with statistical limit. The system was developed and tested on GNU Radio Companion (GRC) environment and its performance was analyzed on noise and multipath scenarios. The Bit Error Rate (BER) curves shows the better performance of proposed model.

A downlink interleave division multiple access (IDMA) receiver, employing sparse channel estimation and interference canceller (IC), is proposed for multi-user underwater communications. To eliminate inter-symbol interference (ISI) and multiple access interference (MAI), an equalizer, a decoder, and an interference canceller are implemented in the receiver. The equalizer is used to eliminate ISI. The channel parameters used in the equalizer are estimated by a modified OMP sparse channel estimation algorithm. The performance of channel estimation is further improve ed using the decoder soft output information during the receiver iteration. MAI, reconstructed by the decoder output and channel parameters, can be eliminated in IC section of other users. The receiver’s performance is verified in shallow water acoustic channels during a sea-trail in the South China Sea. Three different ranges between the transmitter and the receiver, i.e., 4.5 km,6 km, and 7 km, were investigated with a maximum of four users at the data rate of 500 bps per user. The results demonstrated that the proposed IDMA receiver provides good performance with low bit error rate (BER). Furthermore, the receiver has been applied in a real-time underwater communication network.

Filter bank multicarrier (FBMC) modulation is a promising candidate modulation method in future communication systems. Aiming at the problems of imaginary part interference, channel estimation and symbol detection in multi-carrier (FBMC) systems, a detection method for FBMC systems based on gated cyclic units is proposed. A simulation system based on the combination of the GRU(Gated Recurrent Unit) model and the offset quadrature amplitude modulation (OQAM)-FBMC system is completely built to optimize the preprocessing of the FBMC demodulation data. The NN-GRU joint signal detection system and the CNN-GRU joint signal detection system are used for integrated modeling of channel estimation, symbol detection, OQAM demodulation and other modules. This method not only improves the structure of the traditional FBMC model, but also optimizes the reception of the traditional model. The parameters of the module. Compared with traditional classifiers, the accuracy of symbol detection is improved. Theoretical analysis and simulation results show that the bit error rate (BER) performance of the new method is significantly improved compared to the performance of the pilot estimated FBMC system.