Following the constant increase of the multimedia traffic, it seems necessary to allow transport protocols to be aware of the video quality of the transmitted flows rather than the throughput. This paper proposes a novel transport mechanism adapted to video flows. Our proposal, called QAIMD for video quality AIMD (Additive Increase Multiplicative Decrease), enables fairness in video quality while transmitting multiple video flows. Targeting video quality fairness allows improving the overall video quality for all transmitted flows, especially when the transmitted videos provide various types of content with different spatial resolutions. In addition, QAIMD mitigates the occurrence of network congestion events, and dissolves the congestion whenever it occurs by decreasing the video quality and hence the bitrate. Using different video quality metrics, Q-AIMD is evaluated with different video contents and spatial resolutions. Simulation results show that Q-AIMD allows an improved overall video quality among the multiple transmitted video flows compared to a throughput-based congestion control by decreasing significantly the quality discrepancy between them.

The use of Global Navigation Satellites System, better known by the acronym GNSS, in an urban environment has grown signicantly, especially with the advent of GNSS chips in mobile phones. However, the urban environment introduces many diculties in GNSS signal reception that can lead to position ?s errors of several tens of meters. We chose to answer these problems by using a 3D city model allowing to simulate a realistic propagation of the GNSS signal in urban environment. The rst part of our work regards the Non Line Of Sight problem, where we propose a navigation solution based on a 3D city model to estimate geometrical properties of NLOS measured by the receiver. In a second part, the 3D city model is used to estimate the bias coming from the multipath on the pseudorange measurement. Finally, the last part of our study provides a solution coupling the GNSS signal vectorial tracking method to the information produced from the 3D city model in order to improve the tracking in the context of strong GNSS signal power attenuation.

Satellite navigation signals demodulation performance is historically tested and compared in the Additive White Gaussian Noise propagation channel model which well simulates open areas. Nowadays, the majority of new applications targets dynamic users in urban environments; therefore the implementation of a simulation tool able to provide realistically GNSS signal demodulation performance in obstructed propagation channels has become mandatory. This paper presents the simulator SiGMeP (Simulator for GNSS Message Performance) which is wanted to provide demodulation performance of any GNSS signals in urban environment, as faithfully of reality as possible. The demodulation performance of GPS L1C/A, GPS L2C, GPS L1C and Galileo E1 OS signals simulated with SiGMeP in the AWGN channel model configuration is firstly showed. Then, the demodulation performance of GPS L1C simulated with SiGMeP in urban environments is presented using the Prieto channel model with two signal carrier phase estimation configurations: perfect signal carrier phase estimation and PLL tracking.

The use of Global Navigation Satellites System, better known by the acronym GNSS, in an urban environment has grown signicantly, especially with the advent of GNSS chips in mobile phones. However, the urban environment introduces many diculties in GNSS signal reception that can lead to position ?s errors of several tens of meters. We chose to answer these problems by using a 3D city model allowing to simulate a realistic propagation of the GNSS signal in urban environment. The rst part of our work regards the Non Line Of Sight problem, where we propose a navigation solution based on a 3D city model to estimate geometrical properties of NLOS measured by the receiver. In a second part, the 3D city model is used to estimate the bias coming from the multipath on the pseudorange measurement. Finally, the last part of our study provides a solution coupling the GNSS signal vectorial tracking method to the information produced from the 3D city model in order to improve the tracking in the context of strong GNSS signal power attenuation.

This paper proposes methods designed to optimize and robustify the demodulation of the Time Of Week information contained in the GALILEO navigation message. The TOW is crucial to the determination of user’s Position-Velocity-Time and is broadcasted several times in each message frame. The redundancy and predictability of the successive TOW values can be used to reduce the probability of a demodulation error. Three methods are proposed to take advantage of this, two are empirical methods, the third consists in considering the sequence of TOWs and determining the values which maximize reception probability.

The estimation of the ionospheric delay by a GNSS receiver is quite simple when the receiver has access to signals located at different frequencies. However, when these two frequencies are very close, this estimation process becomes very noisy. The paper presents a technique to overcome this problem in the case of the reception of Galileo signals in the E5 band only. This technique is based on a local ionosphere model and the use of carrier phase dual frequency measurements. This paper also widen this investigation to the case of the reception of two GNSS constellations, GPS and Galileo, broadcasting in the same E5 band. The performance of the estimation process are shown to be very good in Europe with a standard deviation of the estimation error at L1 that is below 30cm for the worst case ionosphere conditions.

Procédé de calibration de linéariseur et composant électronique linéarisé. Le procédé comprend la pré-distorsion, dans un linéariseur par pré-distorsion (20, 34), d'un signal en amont d'un composant électronique (18, 28) pour compenser une distorsion non-linéaire. La détermination des paramètres de réglage de pré-distorsion comprend l'application au composant d'un signal de test bi-fréquence, la mesure d'amplitudes relatives des raies en sortie du composant. Une grandeur indicative du module |Kp| du coefficient de conversion AM/PM du composant est calculée sur la base ce ces mesures. Les paramètres de réglage de pré-distorsion sont ajustés de sorte à minimiser |Kp|. Le procédé peut notamment être mis en oeuvre dans un dispositif amplificateur linéarisé (12) et dans un banc de test d'amplificateurs (24).

This paper presents an analysis on the implementation on a GNSS signal of a Code Shift Keying (CSK) modulation: an orthogonal M-ary modulation specifically designed to increase the bandwidth efficiency of direct-sequence spread spectrum (DS-SS) signals. Two decoding methods are presented as suitable candidates to be implemented by a CSK modulation with a LDPC channel code: classical sequential decoding and Bit-interleaved coded Modulation – Iterative Decoding (BICM-ID). Afterwards, this paper presents the methodology used to construct CSK signals which increase the useful bit rate with respect to a BPSK signal but maintaining the same symbol rate. This methodology includes the calculation and comparison of signal demodulation performances in AWGN and mobile channels, the generation of CSK symbols allowing the desired bit rate and the determination of the codeword durations. Proposals for real signals have been made. Finally, this paper analyses the impact of processing a CSK modulated signal on a GNSS receiver with respect to a BPSK signal. This analysis includes the increase of complexity of the demodulator block and the possible performance degradation of the acquisition and, the carrier and code delay tracking.

Routing in mobile ad hoc networks (MANET) is a complex task due to the mobility of the nodes and the constraints linked to a wireless multihop network (e.g., limited bandwidth, collisions, bit errors). These adverse conditions impair not only data traffic but also routing signaling traffic which feeds route computation. In this contribution, we propose to use satellite communications to help in the distribution of MANET routing signaling. The Optimized Link-State Routing (OLSR) is chosen among several routing protocols to be extended with satellite-based signaling, yielding a version we call OLSR Hybrid signaling (OLSR-H). This new scheme is evaluated through simulations and yields improvements of ca. 10% in the data delivery ratio compared to a regular OLSR. This evaluation is conducted using two different network topology models, one being fit for representing forest firefighting operations.