Orange S.A.

About: Orange S.A. is a company organization based out in Paris, France. It is known for research contribution in the topics: Terminal (electronics) & Signal. The organization has 6735 authors who have published 9190 publications receiving 156440 citations. The organization is also known as: Orange SA & France Télécom.

MPEG-4's binary format for scene description

Abstract: The new MPEG-4 standard provides a suite of functionalities under one standard: streaming multimedia content, good compression, and user interactivity. This paper provides an introduction to the use and internal mechanisms of these functions.

Cryptanalysis of grain

Abstract: Grain [11] is a lightweight stream cipher proposed by M. Hell, T. Johansson, and W. Meier to the eSTREAM call for stream cipher proposals of the European project ECRYPT [5]. Its 160-bit internal state is divided into a LFSR and an NFSR of length 80 bits each. A filtering boolean function is used to derive each keystream bit from the internal state. By combining linear approximations of the feedback function of the NFSR and of the filtering function, it is possible to derive linear approximation equations involving the keystream and the LFSR initial state. We present a key recovery attack against Grain which requires 243 computations and 238 keystream bits to determine the 80-bit key.

Enhanced multiuser random beamforming: dealing with the not so large number of users case

Abstract: We consider the downlink of a wireless system with an M-antenna base station and K single-antenna users. A limited feedback-based scheduling and precoding scenario is considered that builds on the multiuser random beamforming (RBF). Such a scheme was shown to yield the same capacity scaling, in terms of multiplexing and multiuser diversity gain, as the optimal full CSIT-based (channel state information at transmitter) precoding scheme, in the large number of users K regime. Unfortunately, for more practically relevant (low to moderate) K values, RBF yields degraded performance. In this work, we investigate solutions to this problem. We introduce a two-stage framework that decouples the scheduling and beamforming problems. In our scenario, RBF is exploited to identify good, spatially separable, users in a first stage. In the second stage, the initial random beams are refined based on the available feedback to offer improved performance toward the selected users. Specifically, we propose beam power control techniques that do not change the direction of the second-stage beams, offering feedback reduction and performance tradeoffs. The common feature of these schemes is to restore robustness of RBF with respect to sparse network settings (low K), at the cost of moderate complexity increase.

A mixed ray launching/tracing method for full 3-D UHF propagation modeling and comparison with wide-band measurements

Abstract: The growth of radio communication services has stimulated interest in ray propagation modeling, particularly in urban areas. The main drawback of these methods is lengthy computation time due to three-dimensional (3-D) space analysis. The model geometrical ray implementation for mobile propagation modeling (GRIMM) presented here splits the 3-D ray construction problem into two successive two-dimensional (2-D) stages without loss of generality compared with brute-force 3-D ray methods. The gain in time and simplicity enables consideration of large areas typical of a cellular environment. The reflections and diffractions (vertical or horizontal) are taken in any order, and their number can be taken large enough to meet convergence. After the description of the model, the results of simulation are compared with a set of 1465 mean power-delay profiles measured over a 30-MHz band at 900 MHz in a cellular environment for mobile positions almost uniformly spread within a 3-km radius from the base station. The model is shown to be very accurate for path-loss prediction with a mean error of about 1 dB and a standard deviation lower than 5 dB. The wide-band evaluation was performed on the delay spread (DS). This parameter was correctly predicted in about 75% of cases.

Transmission error concealment in an audio signal

Abstract: A method of concealing transmission error in a digital audio signal in which a signal that has been decoded after transmission is received, the samples decoded while the transmitted data is valid are stored, at least one short-term prediction operator and one long-term prediction operator are estimated as a function of stored valid samples, and any missing or erroneous samples in the decoder signal are generated using the operators estimated in this way, the method being characterized in that the energy of the synthesized signal as generated in this way is controlled by means of a gain that is computed and adapted sample by sample.