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This paper investigates adaptive Beamforming techniques used in concatenation with a ppSNR-based switching algorithm in multi-user MIMO OFDM systems. The performance's equivalence of SM adaptive beamforming and STBC adaptive one is shown analytically and by simulation, and a complexity study is carried out and allows selecting the beamforming adapted to SM. The effect of the MIMO architecture (with...
Comparer l’efficacité du préremplissage par le HEA 130/0,4 (Voluven ® ) à celle du sérum salé isotonique dans la prévention de l’hypotension après la rachianesthésie pour césarienne programmée.Prospective, randomisée.Soixante patientes ASA I proposées pour une césarienne programmée sous rachianesthésie ont été randomisées en deux groupes pour recevoir un préremplissage soit par 1000mL de sérum...
Smart functions begin to be integrated into some camera acquisition systems for CCTV applications. In this regard, smoke detection based on the compressed video is a highly desirable functionality for the monitoring of forest that present a high risk of fire. In this paper, we propose a fast and early smoke detection method that measures the local fractal feature of smoke areas based on the Discrete...
In this paper, we propose two methods to perform a switching between spatial multiplexing and MIMO diversity in order to improve performances of a 2×2 OFDM-MIMO system. Each method is defined depending on the granularity of the spatial processing. The comparison of BER performances of the two schemes leads to the choice of the sub-carrier based switching processing which gives the most significant...
Performances and capacity of MIMO-OFDM systems are enhanced with adaptive MIMO techniques such as Demmel condition number based switching algorithm. In this paper we show that the complexity of this algorithm can be reduced by using the 2-norm condition number of the channel matrix as the selection metric. Simulation results show that using this selection criterion, the switching algorithm offers...
This paper proposes an advanced OFDM-MIMO reconfigurable architecture that uses an adaptive switching algorithm between diversity and spatial multiplexing. The transmitter blocs' specifications such as the MIMO technique and the modulation scheme are adjusted according to the channel state, which gives a practical cognitive radio strategy. The system cost- efficiency is performed by the application...
This paper presents a study of switching algorithm performances when combined to several beamforming techniques in a multi-user MIMO communication system. The study of three beamforming solutions shows that the beamforming processing has an important influence in the decision criterion of the switching algorithm. The STBC adaptive beamforming, which is better than Zero forcing (ZF) and Singular Value...
This paper presents an extra processing added to conventional LS estimation to improve its performances in OFDM-MIMO systems. The new technique is based on the knowledge of the power delay profile. The application of the improved estimator is useful when employing advanced MIMO adaptation techniques such switching algorithms and leads to significant improvement in decision criterion precision and...
This paper presents a technique for maintaining good broadband transmission quality in the face of impulsive noise in OFDM-PLC systems. The proposed technique is based on adding one zero between two signal samples in order to estimate the noise power in every transmitted signal sample. Simulation results of complete PLC system highlight good improvement in BER and correction ability performances for...
This paper presents a novel coding procedure to correct error bursts generated by impulsive noise corruption in broad-band PLC systems. The coding technique is based on a turbo code structure that uses RS coding and hard decision iterative decoding with erasure process in the decoder. The application of the new coding technique instead of simple RS in the HomePlug 1.0 FEC stage leads to significant...
Low-density parity-check (LDPC) codes deliver very good performance when decoded with the BP algorithm. Unfortunately, this algorithm has the disadvantage to be complex for implementation. In this paper, we investigate the BP algorithm and its simplifications (BP-based, normalized BP-based, offset BP-based). Previous works on normalized and offset BP-based proposed theoretical values for the offset...
We propose in this paper a decision-directed channel estimation technique for OFDM systems operating in time and frequency selective channels. This technique exploits both frequency and time correlation of the channel transfer function. The frequency correlation is achieved by applying a Karhunen-Loeve (KL) expansion which performs the separation of the channel space from the noise space and generates...
This paper proposes an improved decoding technique to remove impulsive noise effects on broadband powerline communication systems. Presented contribution deals with Home Plug 1.0 OFDM-based PLC scheme in presence of impulsive noise modeled by a stochastic distribution approximation. In order to improve receiver BER regarding impulsive noise effect and to reduce the complexity processing, a decoding...
The new H264 video coding standard can achieve considerably higher coding efficiency than previous standards by extending the notion of bidirectional prediction. Unfortunately, this improvement requires heavy computational loads to select the best mode in the sense of rate-distortion tradeoff. In this paper, we propose to apply an accurate estimation of the bit rate in order to accelerate the rate-distortion...
In this paper, we deal with channel estimation for OFDM systems operating in time and frequency selective channels. In order to exploit the frequency correlation of the channel transfer function, we use the Karhunen-Love expansion to separate the signal space from the noise space. Afterwords, we use decision-directed technique for tracking the time varying coefficients of the transfer function in...
The data that is transmitted in PLC systems is subject to corruption by impulsive noise. Many techniques were proposed to correct its effect. In this paper, we propose the use of a modified erasure algorithm to shield PLC system from noise bursts. Apart its performance to correct burst errors, this algorithm presents the advantage of reducing the end- to-end delay of the system.
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