Jean-François Diouris

Optimal JPWL forward error correction rate allocation for robust JPEG 2000 images and video streaming over mobile ad hoc networks

Based on the analysis of real mobile ad hoc network (MANET) traces, we derive in this paper an optimal wireless JPEG 2000 compliant forward error correction (FEC) rate allocation scheme for a robust streaming of images and videos over MANET. The packet-based proposed scheme has a low complexity and is compliant to JPWL, the 11th part of the JPEG 2000 standard. The effectiveness of the proposed method is evaluated using a wireless Motion JPEG 2000 client/server application; and the ability of the optimal scheme to guarantee quality of service (QoS) to wireless clients is demonstrated.

Energy Detection Approach for Spectrum Sensing in Cognitive Radio Systems with the Use of Random Sampling

In radiomobile contexte, radio frequency spectrum is a ressource that needs to be used with appropriate efficiency. This can be achieved by the mean of spectrum sensing operation. This function consists to analyze the occupancy of the radio frequency spectrum in order to detect which bands are unused. This concept is largely appreciated in cognitive radio where more flexibility is required to adapt to the communication environment. Different techniques are presented in the literature. In this paper, we are interested by the application of the energy detector method for spectrum sensing. This application is performed in cognitive radio systems with the use of random sampling. The performance of this approach is evaluated in term of its receiver operating characteristic curve and compared to the uniform sampling case.

Robust threshold compressed sensing based sparse multipath channel estimation in OFDM system

In this paper, the Compressed Sensing (CS) based channel estimation scheme for the sparse multipath channel in OFDM system is considered. The CS based multipath delay channel model is investigated by using only a small amount of pilots to get the measurement matrix and the orthogonal matching pursuit (OMP) is adopted to reconstruct the channel impulse response. In order to overcome the drawback of not knowing the optimal number of iterations for OMP which reflects the number of optimal significant taps of a sparse multipath channel, this paper proposes a robust threshold CS-OMP based sparse channel estimation scheme, which uses noise coefficients among the detail wavelet coefficients to get a robust threshold, and achieves an effective channel estimation performance. Simulations show that the proposed method can significantly improve the performance which approximates closely the performance of optimal iteration number for CS-OMP based channel estimation.

Dynamic channel coding for efficient motion JPEG2000 video streaming over mobile ad-hoc networks

In this work, we present a dynamic channel coding scheme for robust transmission of JPEG2000 codestreams over Mobile Ad-hoc Networks (MANET). The proposed system, based on dynamic Forward Error Correction (FEC) rate allocation allied to layered Unequal Error Protection (UEP), is implemented according to the main recommendations of Wireless JPEG2000 standard final draft. We demonstrate that dynamic FEC rate allocation outperforms a priori FEC rate allocation. Going straightforward we validate the proposed scheme by deriving interesting results from Motion JPEG2000 video streaming over real MANET data traces. This application, developed within the European IST WCAM project, validates wireless JPEG2000 standards recommendations and is a step toward guaranteeing Quality of Service (QoS) in wireless JPEG2000 based data streaming systems.

Spectrum sensing operation based on a real signal of FM radio: Feasibility study using a random sampling mode

In this paper, we are interested to the implementation of the spectrum sensing (SS) operation based on a real signal of the FM radio and using a random sampling mode. This application consists on the realization of the spectrum sensing operation based on the energy detector (ED) method combined with random sampling. The analyzed real signal is an FM radio signal captured under GNU-Radio. This application is performed in cognitive radio (CR) systems in order to analyze the occupancy of the radio frequency spectrum. The performance of this approach is evaluated in terms of its receiver operating characteristic curves (ROC curves) and in terms of the false alarm probability.

Power amplifier design challenges in UHF and VHF transmitters

UHF (225 MHz-400 MHz) and VHF (118 MHz-144 MHz) transmitters in aeronautical domain are among the most strict telecommunication equipments. ICAO (International Civil Aviation Organization) forcasts 4% traffic growth over the coming 15 years. Due to this evolution, the data exchange between the planes and the infrastructure increases more and more resulting in a saturation of the frequency bands allocated to this service. The main purpose of this paper is to describe Power Amplifier (PA) conception challenges. Distant noise (to carrier) issue is resolved by the right PAs structure choice. Reliable and well-chosen linearization method is necessary in close noise (to carrier) significant reduction.

PAPR Distribution for Single Carrier M-QAM Modulations

Single carrier modulations such as quadrature amplitude modulation (QAM) are recently becoming an attractive and complementary alternative to multiple carrier modulations. High order QAM provides spectral efficiency advantage at the price of larger dynamic range. This characteristic leads to enlarge the peak-to-average power ratio (PAPR) and so, to reduce the energy efficiency. This study provides an analysis of the PAPR distribution for QAM based systems. We focus on the distribution of the PAPR since it is the main evaluation means of PAPR reduction techniques. We present an analytic expression of the probability density function of the PAPR for limited length frames. The analysis shows that the expression of the PAPR usually found in the literature is valid only for long frames and is the asymptotic limit of the formula we propose. According to the simulation results, the distribution we suggest accurately describes the PAPR for long frames and is a good approximation for short frames.

On the Spectral Efficiency of Energy Constrained Short-Range Communicating Systems

Recently the energy efficiency (EE) in wireless communication is becoming one of the key performance metric for wireless communicating systems. For battery driven system like wireless sensor networks and ad-hoc networks, the energy conservation is a critical factor for node life. In addition, the spectral efficiency (SE) has been traditionally used as a performance index for wireless transmission. This paper investigates the optimum spectral to energy efficiency tradeoff especially for short range communications. The analysis starts with the Shannon case in additive white gaussian noise channel where some theoretic results are developed when considering both transmit and circuit energy. Then, point to point communication system with uncoded M-ary quadrature amplitude modulation (MQAM) is considered. At the device layer, a system level power consumption model is proposed. At the physical layer, a novel and accurate approximation of the bit error rate (BER) function of the signal to noise ratio is made. The total energy per bit is formulated and the link between the Shannon limit capacity and MQAM based communication is established. The impact of distance, bandwidth, power consumption and BER as a quality-of-service parameter on EE–SE tradeoff is analyzed. It is shown that, varying distance, bandwidth and circuit power consumption induce more impact in the low SE regime whereas, the BER has more impact on the high SE regime. Moreover, the energy optimal spectral efficiency for MQAM is obtained in closed-form and confirmed by numerical results.

Energy optimisation of an OOK transmitter using high-order orthogonal modulation

ABSTRACT In this paper, we show that high-order orthogonal modulation can be used to optimise the power consumption of an energy-efficient On-Off Keying (OOK) transmitter for short-range wireless sensor applications. Our work is based on the characteristics of a high-performance OOK modulator that completely turns off during the transmission of zeros and provides energies per bit in the picojoule range. We take into account the limitations of the circuit in terms of maximum modulation rate and constant output power. Based on a bit error rate performance analysis and a circuit energy model, we propose an original approach to find the energy optimal modulation order for a given range constraint. When considering only the transmitter power consumption, a large improvement in energy per bit can be obtained by using this optimisation. When considering a residual power consumption during the transmitter off state, an improvement is still obtained but is less important.

A RSSI-based parameter tracking strategy for constrained position localization

In this paper, a received signal strength indicator (RSSI)-based parameter tracking strategy for constrained position localization is proposed. To estimate channel model parameters, least mean squares method (LMS) is associated with the trilateration method. In the context of applications where the positions are constrained on a grid, a novel tracking strategy is proposed to determine the real position and obtain the actual parameters in the monitored region. Based on practical data acquired from a real localization system, an experimental channel model is constructed to provide RSSI values and verify the proposed tracking strategy. Quantitative criteria are given to guarantee the efficiency of the proposed tracking strategy by providing a trade-off between the grid resolution and parameter variation. The simulation results show a good behavior of the proposed tracking strategy in the presence of space-time variation of the propagation channel. Compared with the existing RSSI-based algorithms, the proposed tracking strategy exhibits better localization accuracy but consumes more calculation time. In addition, a tracking test is performed to validate the effectiveness of the proposed tracking strategy.