Adel Omar Dahmane

FPGA implementation of floating-point complex matrix inversion based on GAUSS-JORDAN elimination

This work presents the architecture of an optimized complex matrix inversion using GAUSS-JORDAN elimination (GJ-elimination) on FPGA with single precision floating-point representation to be used in MIMO-OFDM receiver. This module consists of single precision floating point arithmetic components and control unit which perform the GJ-elimination algorithm. The proposed architecture performs the GJ-elimination for complex matrix element by element. Only critical arithmetic operations are calculated to get the needed values without performing all the arithmetic operations of the GJ-elimination algorithm. This results in a reduced hardware resources and execution time.

Automatic emotion recognition using auditory and prosodic indicative features

In this paper, a new framework for the automatic recognition of human emotions from speech was proposed. Besides auditory indicative features, selected prosodic and voice quality parameters were optimally combined with Mel frequency coefficients to perform an automatic emotion classification. For this purpose, the Emotion Prosody Speech and Transcript database, a certified speech corpus, was used throughout this study. An extensive set of experiments have been carried out in order to assess the effectiveness of this original mixture of prosodic, perceptual and auditory features to perform the emotion recognition task. These features were selected by using Linear Discriminant Analysis (LDA) and Principal Component Analysis (PCA) on the basis of their ability of discrimination. The selected features were used by the front-end processing stage of a hybrid Gaussian Mixture Model and Support Vector Machines (GSVMs) to perform the emotion classification. The results showed the effectiveness of the proposed feature extraction framework to discriminate between different human emotions when the LDA-PCA-GSVM classifier was used.

Bit Error Rate Performance of a MIMO-CDMA System Employing Parity-Bit-Selected Spreading in Frequency Nonselective Rayleigh Fading

We analytically derive the upper bound for the bit error rate (BER) performance of a single user multiple input multiple output code division multiple access (MIMO-CDMA) system employing parity-bit-selected spreading in slowly varying, flat Rayleigh fading. The analysis is done for spatially uncorrelated links. The analysis presented demonstrates that parity-bit-selected spreading provides an asymptotic gain of dB over conventional MIMO-CDMA when the receiver has perfect channel estimates. This analytical result concurs with previous works where the (BER) is determined by simulation methods and provides insight into why the different techniques provide improvement over conventional MIMO-CDMA systems.

Spreading Strategies for MIMO-CDMA in Presence of Channel Estimation Errors and Spatial Correlation

Parity bit selected spreading and permutation spreading have been proposed as alternative techniques for assigning spreading codes to different users in a multiple input multiple output Direct-Sequence Code Division multiple Access (MIMO-CDMA). In frequency selective fading with perfect channel estimates and in the absence of spatial correlation, the two techniques have similar performance in terms of quality of service and capacity. In this paper, channel estimation errors and spatial correlation effects are considered to study the robustness of these two spreading strategies. Simulation results show that both spreading strategies outperform the conventional system. Moreover, permutation spreading system is much more robust when compared to parity bit selected spreading system in the presence of spatial correlation and channel estimation errors.

Spreading code assignment strategies for MIMO-CDMA systems operating in frequency-selective channels

Code Division Multiple Access (CDMA) and multiple input multiple output- (MIMO-) CDMA systems suffer from multiple access interference (MAI) which limits the spectral efficiency of these systems. By making these systems more power efficient, we can increase the overall spectral efficiency. This can be achieved through the use of improved modulation and coding techniques. Conventional MIMO-CDMA systems use fixed spreading code assignments. By strategically selecting the spreading codes as a function of the data to be transmitted, we can achieve coding gain and introduce additional degrees of freedom in the decision variables at the output of the matched filters. In this paper, we examine the bit error rate performance of parity bit-selected spreading and permutation spreading under different wireless channel conditions. A suboptimal detection technique based on maximum likelihood detection is proposed for these systems operating in frequency selective channels. Simulation results demonstrate that these code assignment techniques provide an improvement in performance in terms of bit error rate (BER) while providing increased spectral efficiency compared to the conventional system. Moreover, the proposed strategies are more robust to channel estimation errors as well as spatial correlation.

Block Decision Feedback Multistage PIC Scheme for DS-CDMA systems

In direct-sequence code division multiple access (DS-CDMA) systems, performances are limited by multiple access interference (MAI). To mitigate these interferences and hence increase the capacity and allow high data rates, multiuser detection (MUD) techniques are used. The main drawback of such receivers is the increase in complexity when compared to the conventional receiver based on the Rake receiver. The multistage parallel interference cancellation (MPIC) receiver is considered a serious candidate for practical implementation showing a good tradeoff between performance and complexity. However, in order to satisfy the performances of the third generation systems, it is important to use MPIC with decision feedback (DF). In the other hand, the parallel implementation of the DF-MPIC has been proven to be strongly compromised. In order to improve the implementation aspects with minimum effect on the algorithm performances, a new block DF-MPIC scheme is proposed in this paper. Simulation results are conducted in different scenarios in order to evaluate the impact of such scheme

A mew MMSE based cascade filter MUD tracking mode in time-varying channels

In direct-sequence code division multiple access (DS-CDMA) systems, performances are limited by multiple access interference (MAI) and intersymbol interference (ISI). To mitigate these interferences and hence increase the capacity and allow high data rates, multiuser detection (MUD) techniques are used. In time varying channels, the MUDs parameters have to be tracked continuously in order to cancel efficiently the different interferences. Motivated by the fact that minimum mean square error (MMSE) based receivers allow significant gain in performances and that decision directed adaptive linear MMSE (DD-AL-MMSE) receivers show poor performances specially in a fast fading environment, a new tracking mode of the two-stage linear cascade filter MUD (CF-MUD) is proposed in this paper offering a good trade-off between performance and complexity. A comparative study analysis of different receivers is conducted, including AL-MMSE and CF-MUD with and without decision directed scheme.

Subspace Decomposition for Channel Estimation in SC-FDE Systems

Single carrier frequency division multiple access (SC-FDMA), a multiple user access scheme based on the single carrier frequency domain equalization (SC-FDE) technique, has been proposed for the uplink in fourth generation (4G) mobile communications. SC- FDE requires reliable channel estimates to maintain an acceptable bit error rate (BER) performance. Much research focuses on the use of pilot symbols which reduces the spectral efficiency of SC-FDE systems. In this paper, we propose a subspace decomposition approach for semi-blind channel estimation in SC-FDE systems as a means to reduce or eliminate the need for pilot symbols and increase their overall spectral efficiency. Simulation results show that, under the conditions presented in this paper, a BER of 10-3 can be achieved with a power loss of roughly 1 dB compared to a system with perfect channel estimates. This result is achieved with channel estimates that have a normalized mean square error (NMSE) less than 1%.

Permutation Spreading for Asynchronous MIMO-CDMA Systems Using Hadamard Codes and Gold Scrambling Sequences

Permutation spreading has been proposed as an alternative technique for assigning spreading codes to the different transmit antennas of a user in a Multiple Input Multiple Output Code Division Multiple Access (MIMO-CDMA) system. In this paper, we propose the use of the permutation spreading technique using Hadamard codes for antenna separation and Gold scrambling codes for user separation. All users are assigned the same set of Hadamard sequences, thus our proposed technique reduces the overall number of spreading sequences required by the system. In the example shown in the paper, the proposed spreading combination allows both an increase in spectral effciency and a four-fold decrease in the number of spreading codes needed by the system. Moreover, permutation spreading shows more than 7dB advantage over conventional MIMO-CDMA system in a heavily loaded environment.

Parity bit selected spreading for MIMO-CDMA using Hadamard codes and Gold scrambling sequences

Parity bit selected spreading has been proposed for use in code division multiple access (CDMA) systems as a means of allowing the spreading to provide an added measure of coding gain. The technique has been extended to CDMA systems operating in multiple input multiple output (MIMO) channels. In previous work, Hadamard codes are used for spreading. In this paper, we propose assigning each user the same set of Hadamard sequences while employing a unique Gold scrambling code. This reduces the overall number of codes required while making the system more robust to frequency selective fading. Compared to a conventional MIMO-CDMA system, the proposed combination of spreading codes allows both increase in data rates and decrease number of needed spreading codes by a factor of 4. Moreover, parity bit selected spreading shows more than 8dB advantage over the conventional MIMO-CDMA system in a loaded frequency selective channels at BER=10−3.