Isabelle Buret

A carrier phase estimator for multimedia satellite payloads suited to RSC coding schemes

Most of GEO satellite telecommunication systems today aim at providing multimedia access services to low cost and power-limited user terminals by implementing performant regenerative onboard processing techniques (demodulation, routing). In order to meet high QoS performance at low SNR, especially on the satellite uplink, performant coding schemes such as turbo codes are necessary. We focus on the critical point of the on-board demodulator: the carrier phase recovery performed in presence of powerful turbo decoding. Non-data aided (NDA) and TD estimators are presented and analysed in terms of characteristics for transmissions using recursive systematic convolutional (RSC) codes that can be used for turbo codes. We show that TD estimation can operate down to E/sub c//N/sub 0/=0 dB with frequency offset up to 10/sup -3/.

Low-complexity carrier-phase estimator suited to on-board implementation

In this paper, we describe and analyze a new feedforward carrier-phase algorithm suited to on-board digital implementation. The algorithm studied here (for phase recovery of M-ary phase-shift keying signals) has the particularity to perform all calculations in polar coordinates in order to reduce the implementation complexity. The defined phase estimator is operating at very low signal-to-noise ratio with small frequency offsets. Its performance is close to those of the Viterbi and Viterbi algorithm.

A mobile ad-hoc satellite and wireless Mesh networking approach for Public Safety communications

It is widely recognized that emergency management and disaster recovery systems are an issue of paramount importance in communities through the world. The definition of a public safety communications infrastructure is a high-priority task due to the lack of interoperability between emergency response departments, the reduced mobility during coordinated operations on a broad scale and the need for access to critical data in real-time. This work proposes an ldquoad-hoc networkingrdquo approach for emergency mobile communications in a satellite and wireless mesh scenario, in which ad hoc and IPv6 mobility mechanisms are combined together. First we analyze mobility management aspects and IP layer protocols and then we focus on proxy mobile IPv6, a network-based mobility management protocol which represents the more suitable micro-mobility solution for the proposed scenario with heterogeneous networks and unmodified mobile terminals.

Combining mobility and heterogeneous networking for emergency management: a PMIPv6 and HIP-based approach

Emergency Management is an important topic for research community worldwide, especially after recent major disasters. The problem of supporting mobility at the disaster site to rescue teams equipped with different heterogeneous access technologies and providing interoperability between different agencies and jurisdictions is still under investigation. In this work we propose to merge the advantages of IPv6 micro-mobility management of Proxy Mobile IPv6 (PMIPv6) with macro-mobility management, security, inter-technology handover and multi-homing features of Host Identity Protocol (HIP). This new approach applied to our proposed ad-hoc satellite and wireless mesh system architecture for emergency mobile communications can improve mobility, security, reliability and interoperability in Emergency Management domain.

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.

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.

Cross-layer enhancement of error control techniques for adaptation layers of DVB satellites

This paper assesses the way error control is managed jointly by Forward Error Codes (FEC) and Cyclic Redundancy Checks (CRC) in the lower layers of today’s Digital Video Broadcasting (DVB) satellites. Mathematical and simulation results clearly show that the outer block codes of the coding schemes used in DVB-S and DVB-S2 (Reed-Solomon and Bose-Chaudhuri-Hocquenghem, respectively) can provide very accurate error-detection information to the receiver in addition to their basic correction task at virtually no cost, making an uncorrected error after decoding an extremely improbable event. For this reason, the workload of CRCs can be ensured safely by the FEC subsystem if a dedicated function allowing the physical layer to share its decoding information with the adaptation layer is set. This particular crosslayer mechanism would allow freeing up the bandwidth currently used by CRCs -which adds up to 10 % for more than 35 % of the total number of IP packets- and pave the way for an enhanced transport of IP over DVB-S2.

Design Issues for the Generic Stream Encapsulation (GSE) of IP Datagrams over DVB-S2

The DVB-S2 standard has brought an unprecedented degree of novelty and flexibility in the way IP datagrams or other network level packets can be transmitted over DVB satellite links, with the introduction of an IP-friendly link layer -the continuous Generic Streams- and the adaptive combination of advanced error coding, modulation and spectrum management techniques. Recently approved by the DVB, the Generic Stream Encapsulation (GSE) used for carrying IP datagrams over DVB- S2 implements solutions stemmed from a design rationale quite different from the one behind IP encapsulation schemes over its predecessor DVB-S. This paper highlights GSEs original design choices under the perspective of DVB-S2s innovative features and possibilities.

Carrier recovery scheme for on-board demodulation suited to low E/sub b//N/sub 0/

In this paper we describe and analyse new feedforward synchronization algorithms suited to on-board digital implementation. Both algorithms studied here (for phase and frequency recovery) have the particularity to perform all calculations in polar coordinates and so to reduce complexity of implementation. A phase estimator operating at very low SNR with no frequency offset is defined. Its performances are close to the Viterbi and Viterbi algorithm. A frequency estimator based on the previous phase estimator is also presented and analysed.