Chaos-based multi-user time division multiplexing communication system

Throughput improvement of STS-based MC DS-CDMA system with adaptive modulation

This paper investigates the impact of multiple narrow-band interference (NBI) signals or jamming signals on the signal reception of multi-carrier code-division multiple-access (MC-CDMA) systems in single path Rayleigh fading channels. Different blind adaptive algorithms are proposed which determine a weight vector that optimally combines the desired signal contributions from different carriers while suppressing noise and interference. A performance comparison among these algorithms is provided via extensive simulations. No knowledge of the channel conditions (fading coefficients, signature sequences and timing of interferers, statistics of other noises, etc.) nor any training sequence is required. Performance results show that the proposed algorithms perform well and are robust against jamming or NBI.

In this paper, we investigate the bit error rate (BER) performance of the joint space-time coding and massive multiple-input multiple-output (MIMO) technologies known as STCM-MIMO. We derive closed-form mathematical expressions to predict the BER of such systems in Rayleigh fading channels.

Since the accuracy of channel prediction influences the performance of adaptive multiple-input-multiple-output (MIMO) systems in Rayleigh fading channels, we analyze the performance of adaptive V-BLAST systems with a minimum-mean-square-error (MMSE) channel predictor in this paper. Considering the channel prediction error, we obtain the closed-form expressions for the bit-error-rate (BER) and throughput of adaptive V-BLAST systems, and maximize system transmission rate by choosing optimum block length under BER constraint. The numerical results reveal the critical value of channel prediction error below which systems can match the transmission rate of the systems with perfect channel prediction.

The performance of a multi-user chaos-based direct sequence code division multiple access (DS-CDMA) communication system with a sequence synchronisation unit incorporated is examined. Synchronisation is achieved through code acquisition and maintained through the code tracking phase. The performance of the proposed system is evaluated in a Rayleigh fading channel with additive white Gaussian noise and interuser interference. Results are compared to a fade-free channel. It is shown that, although the system is robust to the influence of noise and interuser interferences, it fails to satisfy the maximum allowable bit error rate limit of 10−3 in the Rayleigh fading channel.

We investigate the systematic convolutional low density generator matrix (SC-LDGM) codes over Rayleigh fading channels with symmetric alpha-stable (S\(\alpha \)S) impulsive noise. The performance is analyzed by deriving a lower bound based on an equivalent genie-aided (GA) system. Numerical simulations show that the SC-LDGM codes can achieve a significant gain compared to the convolutional codes over Rayleigh fading channels with impulsive noise. Numerical results also show that the performance of the SC-LDGM codes can be around one dB away from Shannon limits at the bit-error rate (BER) of \(10^{-5}\) and matches well with the GA lower bound in the low BER region.

For channel estimation in the relay-assisted multiple-input multiple-output and orthogonal frequency division multiplexing indoor visible light communication (VLC) system affected by light source, there is a problem that the received signal cannot be separated by simple filtering. To solve this problem, a channel estimation by PARATUCK2-PARAFAC-based noise compensation which introduces tensors to construct the suitable model of VLC is proposed. First, the transmitting pilots for channel estimation and noise estimation are constructed separately with the Hermitian symmetry structure. Then the tensor-based transmission model of the indoor VLC system is established, and the signals for channel and noise estimations are received. Finally, an asymptotic estimation for separating signals from different sources and noise is proposed by PARATUCK2-PARAFAC. Simulation results show that the proposed algorithm provides a more effective scheme for channel estimation comparing with the state-of-the-art algorithms.

Transmit diversity is one of the best approaches to combat the fading channels in high data rate wireless systems. We present a new transmit diversity scheme for MC-CDMA systems. It is composed of multiple transmission branches. Each branch transmits the same data symbol synchronously with the same spread code but with different delay. A RAKE receiver is employed in the frequency domain to obtain space diversity gains. Analysis and simulation results show that performance benefits can be achieved compared to conventional MC-CDMA systems in Rayleigh fading channels.

In this contribution, we consider the performance of multiple-input multiple-output (MIMO) code division multiple access (CDMA) system for digital image transmission over correlated Rayleigh fading channel. MIMO system employs multiple antennas both at the transmitter and receiver. In our work, we consider turbo coded system to investigate the performance of MIMO-CDMA system. We realize turbo code using parallel concatenated convolutional encoder and second convolutional encoder is preceded by random interleaver. Further the output of two convolutional encoder are punctured to get rate of ½. At the receiver, we employ iterative decoding algorithm to reduce the effect of multiple access interference (MAI) and Inter-Symbol-Interference (ISI) and median filters to reduce the effect of salt and pepper noise.. In particular, we evaluate the performance of coded MIMO-CDMA system using Zero forcing (ZF) - multi-user detection (MUD) and minimum mean square error (MMSE)-MUD detection technique to mitigate the effects of multi-stream interference (MSI). It is shown through the simulation study that our considered coded MIMO-CDMA system with MMSE algorithm achieves better picture quality with less signal-to-noise ratio (SNR) as compared to ZF MUD.

This work explores the performances of Space-Time and Space Frequency Coded Orthogonal Frequency Division Multiplexing (OFDM) with simple two branches transmit diversity scheme. The combination of multiple-antenna and orthogonal frequency division multiplexing (OFDM) provides reliable communications over frequency selective fading channels. We focus on the application of space-time block codes (STBC) and space-frequency block codes (SFBC) in OFDM systems over time-varying and frequency-selective channels. SFBC transmitter shows superior performance in fast varying channels while STBC shows better performance in frequency selective channels. A switching technique is presented that selects an appropriate transmission scheme between the STBC and SFBC assuming Rayleigh fading model.

Power Control of Turbo Coded System in Rayleigh Fading Channel

This paper indicates the space time block code provides transmit diversity in wireless fading channel during the STBC-OFDM system. OFDM is enforced in broadband wireless access systems as the way to beat wireless channel impairments and to enhance and breadth potency. This research is to analyze the performance of non STBC-OFDM system and STBC-OFDM system. The performance has been evaluated for construction modulation (QAM) technique for orthogonal frequency division multiplexing (OFDM) systems using multiple transmit diversity antenna system in the channel. Conjointly the equation of SNR and BER has been derived for 16-QAM for multiple transmit and receive antenna for STBC-OFDM system by considering the have an effect on of Inter-symbol interference (ISI), phase noise and temporal arrangement noise in Raleigh fading channel.

An exact closed-form expression is derived for the average secrecy capacity of transmit-receive diversity systems in Rayleigh fading channels. Moreover, a simple upper bound on this capacity and its asymptotic approximation are presented. Numerical results corroborating the theoretical analysis are also provided.

We consider multiple-input multiple-output decode-and-forward relay systems in Rayleigh fading channels under the partial channel state information (CSI) that the channel statistics of the source-relay (SR) link and the instantaneous CSI of the source-destination and relay-destination links are known at the destination. In this paper, we propose a new near maximum likelihood (near-ML) decoder with two-level pairwise error probability (near-ML-2PEP) which uses the average PEP instead of the exact PEP. Then, we theoretically prove that the near-ML and near-ML-2PEP decoders achieve the maximum diversity, which is confirmed by Monte Carlo simulations. Moreover, we show that the near-ML-2PEP decoder can also achieve the maximum diversity by substituting the average PEP with the values that represent the error performance of the SR link.

Optimum and suboptimum scheduling schemes are proposed in the uplink of array antenna systems. We assume that once a user is permitted to transmit the data, the user transmits the data using the maximum power and adjusts the transmission bit rate so that the received SINR remains fixed. In this system model, we consider an optimization problem: how many and which users should be selected to transmit their data at a time in order to maximize the throughput? Based on the analysis on the complexity of the optimum scheme, we propose another optimum scheme having reduced complexity. In circular arrays, numerical results suggest that the maximum number of simultaneously transmitting users can be limited at the expense of small throughput penalty. Motivated by this result, we propose a suboptimum scheme to reduce the complexity further. Numerical results show that the suboptimum scheme provides almost the same performance as the optimum scheme with a dramatic decrease in the complexity.