Mathieu Dervin

Development and validation of an OFDM/DVB-T sensor for positioning

The use of Global Navigation Satellite System (GNSS) for positioning has grown significantly in recent years thanks in particular to the development of several mass-market applications, such as car navigation or mobile positioning. Unfortunately, in difficult environments such as dense urban or indoor areas, GNSS exhibits degraded performances in terms of precision and availability. The use of signals of opportunity is one of the solutions to replace or assist GNSS in those environments. These signals are communication signals that are usually designed to provide a service in dense environment and can thus be used in location where GNSS is unavailable. Several commercial positioning services based on signals of opportunity already exist such as ROSUM with ATSC digital TV signals, or Skyhook with Wi-Fi signals

PLATINE: DVB-S2/RCS Enhanced Testbed for Next Generation Satellite Networks

Emulation is a cost effective and efficient tool to perform performances evaluation and innovative access and network techniques validation. Its ability to interconnect real equipments with real applications provides excellent demonstrations means. The main problem is to overcome the emulation weakness which is the accuracy of the model reproducing the systems to be evaluated. Owing to its modular design and implementation, the PLATINE satellite emulation platform, presented in this paper, is able to emulate a complete DVB-RCS (Digital Video Broadcasting – Return Channel via Satellite)- DVB-S2 (Digital Video Broadcasting – Second ) system in a realistic and flexible way. It is possible to configure the platform to emulate a transparent DVBRCS system dimensioned around a single Hub, or to emulate a system using a regenerative satellite with an on-board switching matrix. Different DVB-RCS protocol stacks are implemented, and the adaptive physical layer is emulated in real time thanks to pre-calculated DRA schemes and MODCOD files. A DiffServ-like QoS Architecture that couples MAC and IP-Layer QoS mechanisms and Layer 2 security framework are currently under development. At the network side, IPv4 and IPv6 are fully supported as well as IPv6 mobility and dynamic multicast. In this paper, we mainly focus on the emulation platform and the tools developed to help the performance analysis of the emulated system.

Use of OFDM-based digital TV for ranging: Tests and validation on real signals

This article presents results of tests on real signal of a method of positioning using a digital TV DVB-T signal-of-opportunity which is based on an OFDM modulation. OFDM and DVB-T standard are presented and the positioning method using the DVB-T signal is detailed. The result on real signal are analyzed qualitatively and quantitatively in static and dynamic scenarios and indoor and outdoor environments. In static scenarios, the standard deviation of pseudorange error is about 8 cm outdoor and 0.7 m indoor. In dynamic scenarios the pseudorange estimation is considerably disturbed and additional experiments are necessary to quantify the performance in this case.

On linear MMSE based turbo-equalization of nonlinear volterra channels

This article deals with Minimum Mean Square Error (MMSE) turbo equalization of nonlinear interference using a volterra series decomposition of the underlying nonlinear channel. Although it has been often argued that linear MMSE based equalization is unsuited for cancelling nonlinear interference, we show that this common belief is not true in a strict sense. By a proper derivation of the linear based MMSE soft equalizer, we are able to show that the underlying structure of the equalizer is equivalent to a Soft Interference Canceller (SIC) treating both the linear and nonlinear interference. Based on these results, approximations are provided for lowering the computational complexity. Links to previously proposed “nonlinear” SIC are emphasized showing that the previously proposed structures are nothing but approximations of a linear MMSE receiver applied to nonlinear ISI channels. Simulations show that significant improvements can be achieved by using the proposed exact and approximate MMSE based turbo-equalizers.

Easy-to-Deploy Emergency Communication System Based on a Transparent Telecommunication Satellite

This paper presents a satellite-based communication system dedicated to disaster recovery. The proposed solution relies on the underlay transmission of low-power emergency signals in the frequency band of a primary transparent satellite telecommunication system. Wideband spreading is used so as to guarantee that the primary system performance is not affected by the inter-system interference. The emergency system capacity is evaluated under realistic assumptions regarding the primary satellite mission. It is shown that depending on the emergency terminal characteristics, various emergency communication services can be envisaged, from simple alert missions to voice communications. As it does not require any specific space segment development nor the full-time reservation of expensive radio resources, the described solution is attractive in terms of deployment cost. Provided an extension of the regulatory framework for exceptional security-oriented missions, it might satisfactorily match a governmental need for reliable, easy-to-deploy emergency communication means.With more and more enterprises and organizations outsourcing their IT services to distributed clouds for cost savings, historical and operational data generated by these services grows exponentially, which usually is stored in the data centers located at different geographic location in the distributed cloud. Such data referred to as big data now becomes an invaluable asset to many businesses or organizations, as it can be used to identify business advantages by helping them make their strategic decisions. Big data analytics thus is emerged as a main research topic in distributed cloud computing. The challenges associated with the query evaluation for big data analytics are that (i) its cloud resource demands are typically beyond the supplies by any single data center and expand to multiple data centers, and (ii) the source data of the query is located at different data centers. This creates heavy data traffic among the data centers in the distributed cloud, thereby resulting in high communication costs. A fundamental question for query evaluation of big data analytics thus is how to admit as many such queries as possible while keeping the accumulative communication cost minimized. In this paper, we investigate this question by formulating an online query evaluation problem for big data analytics in distributed clouds, with an objective to maximize the query acceptance ratio while minimizing the accumulative communication cost of query evaluation, for which we first propose a novel metric model to model different resource utilizations of data centres, by incorporating resource workloads and resource demands of each query. We then devise an efficient online algorithm. We finally conduct extensive experiments by simulations to evaluate the performance of the proposed algorithm. Experimental results demonstrate that the proposed algorithm is promising and outperforms other heuristics.Future processor will not be limited by the transistor resources, but will be mainly constrained by energy efficiency. Reconfigurable architecture offers higher energy efficiency than CPUs through customized hardware and more flexibility than ASICs. FPGAs allow configurability at bit level to keep both efficiency and flexibility. However, in many computation-intensive applications, only word level customizations are necessary, which inspires coarse-grained reconfigurable arrays(CGRAs) to raise configurability to word level and to reduce configuration information, and to enable on-the-fly customization. Traditional CGRAs are designed in the era when transistor resources are scarce. Previous work in CGRAs share hardware resources among different operations via modulo scheduling and time multiplexing processing elements. In the emerging scenario where transistor resources are rich, we develop a novel CGRA architecture that features full pipelining and dynamic composition to improve energy efficiency and implement the prototype on Xilinx Virtex-6 FPGA board. Experiments show that fully pipelined and dynamically composable architecture(FPCA) can exploit the energy benefits of customization for user applications when the transistor resources are rich.

High Throughput Satellite System with Q/V-band gateways and its integration with terrestrial broadband communication networks

Satellite broadband systems will play a key role in reducing the Digital Divide by complementing terrestrial networks in the delivery of superfast broadband in remote and rural areas. We present the system architecture, sizing and performance assessment of a next generation High Throuhgput Satellite system with Q/V-band gateways targeting the 2020 timeframe. In addition, we present a novel optimisation framework for the design of the backbone network interconnecting the satellite gateways with national PoPs in the serviced countries, which takes into account the impact in costs an payload constraints.

Very Wide Band Satellite Transmissions for Emergency Situations

This paper presents an emergency communication system based on a regenerative payload, added as a piggy back onboard a broadband telecommunication satellite. The emergency system does not require the reservation of specific radio resources for the user link, as the signals are spread over a very wide band and superposed to the primary system transmissions using the same frequency band. The emergency system is dimensioned so as to be invisible, from the primary system point of view. The affordable forward- and return-link performances of the emergency system are evaluated, considering man-pack transportable terminals and handset terminals.

A soft decision directed phase detector suited to satellite communications at very low signal to noise ratio

The introduction of data redundancy for the purpose of carrier synchronization over a Gaussian channel may be a profitable operation. We present in this paper the performance of a phase detector suited to 8 PSK receivers, based on the soft decoding of a single parity-check code. It is shown that in presence of phase noise and a quite important frequency error, the proposed synchronization scheme outperforms the classical non-data-aided and decision-directed algorithms, reducing the phase jitter in considerable proportions.

Low complexity block pre-distortion of a multi-carrier non-linear satellite channel

In a multi-carrier non-linear satellite communication channel, inter-symbol interference (ISI) and adjacent channel interference (ACI) occur due to the non-linear power amplifier aboard the satellite. In order to prevent a too high performance degradation, large input back-offs (IBO) are generally considered. However, if all carriers are issued from the same ground station, pre-distortion of the whole transmitted signal can be a better solution to achieve higher power efficiency aboard the satellite and/or spectral efficiency. The relation between the symbols transmitted on the channel and the received symbols is tricky for a multi-carrier system, as it involves several symbol flows. Few approaches have been proposed yet to provide an efficient algorithm with reasonable complexity in such context. In this paper, we will derive a sub-optimum algorithm for the pre-distortion of a multi-carrier non-linear satellite channel which offers a good trade-off between performance and complexity.

Iterative Predistortion of the Nonlinear Satellite Channel

Digital Video Broadcasting-Satellite-Second Generation (DVB-S2) is the current European standard for satellite broadcast and broadband communications. It relies on high-order modulations up to 32 amplitude/phase-shift keying (APSK) in order to increase the system spectral efficiency. Unfortunately, as the modulation order increases, the receiver becomes more sensitive to physical-layer impairments and, notably, to the distortions induced by the power amplifier and the channelizing filters aboard the satellite. The predistortion of a nonlinear satellite channel has been studied for many years. However, the performance of existing predistortion algorithms generally becomes poor when high-order modulations are used on a nonlinear channel with long memory. In this paper, we investigate a new iterative method that predis-torts the blocks of transmitted symbols to minimize the Euclidian distance between the transmitted and received symbols. We also propose approximations to relax the predistorter complexity while keeping its performance acceptable.