Multiplex communications – Wide area network – Packet switching
Patent
1992-05-27
1994-03-22
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
370 70, 370 84, 329327, H04J 400
Patent
active
052971368
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to satellite data communication systems and it is in particular concerned with an apparatus to demodulate simultaneously a great number of data channels having low and medium data rates, that is data rates lower than 4 Mbit/s.
Nowadays the satellite communication networks are experiencing an evolution from the original trunk oriented network configuration in which the data are transmitted at a high data rate (typically 4 Mbit/s) towards user oriented network configurations including small stationnary and mobile earth stations operating at relatively low data rates down to e.g. 64 kbit/s. In such networks, either private or public, the earth stations have different needs in communication capabilities in accordance with the number of users which are to be served. The problem then is to optimize the apportionment of the available communication capability between the different operating systems. Heretofore, sharing the overall communication capacity was made by defining a range of data rates for each system. To cite two examples, the INTELSAT IBS communication system operates at data rates from 64 kbit/s to 4 Mbit/s, while the EUTELSAT SMS communication system operates at data rates from 64 kbit/s to 2 Mbit/s.
In order to process a great number of data channels it is known to use an apparatus called multicarrier demodulator (MCD) that is capable to simultaneously process a great number of carriers modulated each by one data channel. An apparatus of this type is disclosed for instance in U.S. Pat. No. 4,754,449. However, such a known apparatus is designed to process only data channels having a fixed data rate. Now in those new business applications which are anticipated for satellite communication systems an earnest need has arisen for apparatus capable of simultaneously handling data channels having different data rates and more particularly apparatus capable of simultaneously processing various combinations of data channels having various data rates without loss in bandwidth, for instance an apparatus which is capable of demodulating 16 channels transmitting data at a rate of 2 Mbit/s as well as any operating combination up to 512 channels transmitting data at a rate of 64 kbit/s still in the same frequency bandwidth.
A multicarrier demodulator capable of processing data having different data rates is disclosed in the publication Electrical Communication Vol. 62, No. 3/4, 1988. This demodulator implements a signal processing method and comprises for each channel complex filters for translating the channel frequency band to the baseband, a synchronizer and a shaping filter. The method which is carried out in this known demodulator results in an architecture that has the drawback of being complex and bulky, which makes it improper for being used on board a satellite.
The object of this invention is to remedy the above drawback by providing a demodulator apparatus capable of processing data channels having variable data rates, which is simple to construct and less bulky and which can thus be used either on board a satellite or in an earth station.
In accordance with an aspect of the invention there is provided an apparatus for demodulating a multicarrier signal, comprising an input circuit as defined in the claims, by virtue of which a known multicarrier demodulator is made capable of processing data channels having different data rates.
The input circuit according to this invention is based on the implementation of a method of processing a multicarrier signal occupying a predetermined frequency bandwidth, in which, in accordance with a further aspect of the invention, the frequency band of the multicarrier signal to be processed is divided into a predetermined number K of sub-bands in each of which the number of modulated carriers is related to the data rate adopted for the respective sub-band. Then the data contained in each sub-band or group of subbands are sampled at a predetermined rate to generate a plurality of expanded sample sequences. Said expanded sample sequences thus ge
REFERENCES:
patent: 4754449 (1988-06-01), Crookshanks
patent: 4785447 (1989-11-01), Ichiyoshi
patent: 4884265 (1989-11-01), Schroeder et al.
patent: 5038344 (1991-08-01), Kawamura
IEEE Global Telecommunications Conference, Tokyo, Japan, Nov. 15-18, 1987, vol. 1, pp. 8.4.1-8.4.6.
IEEE, New York, U.S., Kohri et al.: "A 400ch SCPC signal demodulator using chirp transform and correlation detection scheme" voir abrege; figure 1,2.
"Onboard Multicarrier Demodulation for Nontransparent Satellite Repeaters", Electrical Communication, vol. 62, No. 3/4, 1988.
Bella Luigi
Soprano Claudio
Agence Spatiale Europeenne
Kizou Hassan
Olms Douglas W.
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