In order to treat a wide scope of news sentences, the system is provided with more than I00,000 lexical entries as well as about 3,000 grammatical rules which can robustly analyze various types of undefined words. It is also effective in translation of news sentences to preprocess proper nouns, to resolve structural ambiguities by weighting grammatical rules, and to select appropriate words usi...

Practical realizations of the optimum closed loop structure for coherent demodulation of QPSK signals demands the approximation of the hyperbolic tangent nonlinearity (Tanh) with simpler and more easily implementable functions. This paper compares the commonly considered approximations to this nonlinearity and the practical structures which result, with an alternative in which the hyperbolic ta...

Geostationary satellites are an efficient way to provide a large scale multipoint communication service. In the context of reliable multicast communications, a new hybrid satellite/terrestrial approach is proposed. It aims at reducing the overall communication cost using satellite broadcasting only when enough receivers are present, and terrestrial transmissions otherwise. This approach has bee...

We consider the problem of data dissemination in a satellite network. In contrast to previously studied models, broadcasting is among peers, rather than client server. We introduce a cost model for data dissemination in peer to peer satellite networks. The model quantifies the tradeoff between the inconsistency of the data, and its transmission cost; the transmission cost may be given in terms ...

This paper summarizes the main results of an early investigation on desirable signal structures for the European &Galileo' civil satellite navigation system. Stemming from the requirements for increased accuracy, reduced time-to-"rst-"x and integrity information provision, the report describes the logical steps and the related numerical results leading to a novel &Galileo' signal de"nition. Alt...

Digital Video Broadcasting (DVB) provides the opportunity for high-speed Internet delivery direct to user’s homes and offices. Most applications require full duplex communication, and the return path from the user to the Internet will be provided using lower speed terrestrial connections. Two challenges are presented when using DVB for high-speed Internet access: the poor performance of TCP ove...

The introduction of digital video broadcasting (DVB) satellite systems has become an important tool for future mobile communication and is currently a focus in several research areas such as the integration of DVB satellite systems with different wireless technologies. This tutorial consists of two parts, Enabling technologies and Future service scenarios, which aims to provide an introduction ...

This chapter is dedicated to the application of cooperative relaying in heterogeneous land mobile satellite (LMS) systems. The aim of cooperation in this context is to help providing the missing coverage in harsh propagation environments characterized by a high node density such as urban areas. We study benefits and limits of the cooperative approach adopting a network model that is at the same...

Ki-Dong Lee et al. 251 ABSTRACT We developed a method for optimal superframe design in the multi-frequency time division multiple access (MF-TDMA) return-link of a satellite multimedia interactive network called a digital video broadcasting return channel over satellite (DVB-RCS) sub-network. To find the optimal superframe pattern with the maximum data throughput, we formulated the design prob...