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Practical acquisition of compressed sensing measurements involves a finite-range finite-precision quantisation step. To solve the sparse recovery problem and handle the quantisation distortion, this Letter proposes a non-smooth graduated-non-convexity approach that follows a path of gradually improved solutions along a sequence of non-smooth non-convex optimisation problems that progressively promote...
In this paper, we consider a bit interleaved coded modulation (BICM) scheme over a frequency selective channel. At the receiver, a turbo-equalizer composed of a maximum a posteriori (MAP) equalizer and a MAP decoder is used. We derive an upper bound of the bit error probability (BEP) at the output of the equalizer. We give an analytical approximate expression of this BEP when the a priori information...
In this paper, an efficient procedure for collision resolution in slotted ALOHA MIMO systems is proposed. We have proved in a previous work that packet collision resolution with spatial successive interference cancellation (SSIC) is a promising approach to improve the performance of slotted ALOHA protocol, when the colliding users' powers are different. However, it is not efficient for very close...
In cooperative networks, different single-antenna terminals cooperate in order to provide better signal quality over Rayleigh fading channels. The main drawback of cooperative diversity is the throughput loss due to the extra resources needed for relaying. Therefore, we propose to use adaptive modulation in cooperative networks in order to compensate the throughput loss due to the relaying. In this...
Packet collision resolution is proved to be a promising approach to improve the performance of slotted ALOHA protocol with TDMA technique. In the present paper, we propose a random access protocol that utilizes an efficient Spatial Successive Interference Canceller (SSIC) to separate collided packets for users that share the same time slot and that utilizes the benefits of retransmitted packets combining...
In this paper, we propose an improvement of truncated ARQ protocol throughput through the optimization of the distribution of the average energy cost per packet (or, equivalently, per symbol) among all packet transmission attempts. We consider exclusively BPSK-modulated ARQ transmission over an AWGN channel, with and without packet combining using the selective repeat as a transmission protocol. Our...
In this paper, we propose an efficient scheme using a new single-symbol preamble structure for OFDM data-aided synchronization. The preamble symbol is constituted of two successive equal-duration sub-symbols, the second one of which is a differentially encoded version of the first one, using an adequately designed precoding sequence. This structure leads to almost perfect channel autocorrelation profile...
In this paper, we propose a novel optimization approach for Amplify-and-Forward (AF) relaying schemes. In previous works, we have optimized the AF relaying scheme carried on a symbol-by-symbol basis. Here, we focus on AF and Incremental AF (IAF) schemes, operating on a packet-by-packet basis. The optimization is carried out while keeping the additional multiple access interference cost, inherent to...
In this contribution, we propose a novel scheme for time and frequency synchronization in OFDM systems. A differential modulation is indeed used to design two training symbols with appropriate properties used as a preamble for the detection of the frame start and for the recovery of the integral carrier frequency offset. The new scheme is compared to the well known algorithm of Cox and Schmidl, also...
Signal transmission over mobile channels undergoes interferences coming from neighboring symbols in time and frequency. In this paper, we consider a mobile transmission by the OFDM/BFDM technique. Single pulse modulation (SPM) or multi pulse modulation (MPM) combined with a partial equalization of few neighboring pulses (for SPM) or co-located pulses (for MPM) at the receiver can be suited efficiently...
In radio mobile cellular networks, the users located at the cell border are suffering from a bad quality of service (QoS). Cooperative communications is a promising technique that can overcome this weakness by allowing the users to profit from powerful benefits of the spatial diversity. Nevertheless, abstraction is usually made on the impact of the additional multiple access interference inherent...
In this paper, we evaluate the throughput performance of Hybrid Automatic Repeat reQuest (HARQ) protocols using Adaptive Modulation and Coding (AMC) based on either the instantaneous Signal to Noise Ratio (SNR) or the average SNR. We also propose a cross layer optimization algorithm in order to offer the highest throughput at the physical (PHY) layer and verify some Quality Of Service (QOS) constraints...
In radio mobile cellular networks, the users located at the cell border suffer from a bad quality of service (QoS). Cooperative communication is a promising technique that can overcome this weakness by allowing these users to profit from powerful benefits of spatial diversity. Nevertheless, abstraction is usually made on the impact of the additional multiple access interference inherent to relaying...
In this paper, we consider joint iterative equalization and channel estimation for TDMA systems over a frequency selective, quasi-static fading channel. We assume a slowly varying channel impulse response from one burst to the following one. We modify the maximum a posteriori (MAP) criterion by taking into account an a priori channel estimate obtained from the burst preceding the one processed. Assuming...
Pedestrian detection in a real scene is an interesting application for video surveillance systems. This paper presents our contribution to improve the work of Viola and Jones, originally designed to detect faces. This work uses a cascade of classifiers based on Adaboost using Haar features. It improves the learning step by including a decision tree presenting the different poses and possible occlusions...
In this paper, we study the throughput enhancement in a wireless slotted ALOHA system, where all users transmit space-time coded information sequences and the destination is able to separate a given number of collided packets. These users operate with the slotted ALOHA protocol to access to the wireless channel resulting in a high probability of collision. To increase the packet throughput of such...
In this paper, we evaluate the root mean square error (RMSE) performance of MUSIC ("Multiple Signal Classification") and COMET ("COvariance Matching EsTimator") algorithms in the presence of dispersion in azimuth and elevation. We use a 3D hemishperoid scattering model to describe angle of arrival in azimuth and elevation. We derive a closed- form expression for the joint and marginal...
In order to enhance soft-handover performance in the downlink of DS-CDMA systems, we propose to use different codes at the base stations in the active set to encode the information sequence targeted to a mobile station. For reliable information recovery, in case all links except one happen to be simultaneously in deep fade, self-decodable complementary punctured convolution codes, inspired from Hybrid...
The planning of the second generation mobile network can be carried out in two distinct stages. The first stage sets out to determine the position of the base stations so as to ensure a total coverage. The second step aims to attribute frequency bands to the base stations in a view to responding to a given traffic requirement. Such a method is no longer adequate for the planning of the base stations...
This paper derives explicit closed-form expressions for the joint/marginal probability density functions of the uplink/downlink multipathspsila time-of-arrival (TOA) and azimuth angle-of-arrival (AOA) in a wireless-communication fading channel. These models assume that the scatterers lie within a hollow-disc and an elliptical space, respectively. These probability density functions (pdf) provide insight...
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