Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1997-03-10
2001-07-03
Maung, Nay (Department: 2681)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S012100, C455S430000
Reexamination Certificate
active
06256496
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns an apparatus and method for improved digital radio communication in a satellite supported VSAT network consisting of a plurality of VSAT member stations and at least one central station (hub).
BACKGROUND INFORMATION
Digital data, voice and video communication within closed user groups with a central structure (companies with subsidiaries, retail chains with many affiliates, mainframe systems with several user levels) can be advantageously operated using radio communication via satellites. The switching and organization functions in these networks are carried out by a central station (hub). The antenna size and transmission power of the hub are considerably greater than those of the other member stations. Since member stations' satellite dishes usually have a very small diameter (Very Small Aperture Terminal, VSAT), such a satellite network is usually referred to as a VSAT network. A description of a typical VSAT network is given in Supplement 3, “Handbook on Satellite Communication: VSAT Systems and Earth Stations,” ITU-R, Geneva 1994, which is hereby incorporated by reference herein.
The data flow from the hub to the VSATs (outroute) is received by all the members in the network; the signals sent by the individual VSATs (inroute) are usually of a lower speed and can only be correctly received by the hub due to the limited size of the VSAT stations. Communication between VSAT stations usually takes place via the central station (hub), referred to as a double hop, which causes an additional up to half-second delay in the signal transmission time due to the great distance to the satellites.
A specific advantage of such VSAT networks includes the fact that messages destined for a plurality of members need to be sent only once and can be received by all destinations simultaneously. By installing the communication equipment in the immediate proximity of the user, complex routing over several switching stations can be avoided, which can be considerable especially for international terrestrial communications.
Due to the signal attenuation caused by atmospheric effects, typical for radio frequencies higher than 10 GHz, a certain power margin must be provided when operating such systems, so communications do not immediately break down when attenuation occurs. In order to guarantee 99.5% availability over a year, this margin must be approximately 2-3 dB for the currently common “Ku band” transmission frequencies of 12-14 GHz. This margin is permanently built in through the dimensioning of the satellite network and therefore cannot be used for other transmission purposes in today's systems during the greater part of the year, when atmospheric path attenuation is much lower than the margin provided.
By providing a satellite link within a satellite-supported network with an inflexible fixed attenuation margin, a certain degree of reliability (availability) is achieved at the expense of system economy.
SUMMARY OF THE INVENTION
A basic object of an exemplary embodiment of the present invention is to provide an apparatus and method for improved digital radio communication in a satellite-supported VSAT network between members of a closed group, wherein the existing margins can be put to additional use in the case when path attenuation is lower than the margin provided, in order to operate more economically and to achieve more efficient utilization of the equipment required for operating the central station.
This can be achieved by an exemplary embodiment of the present invention through an apparatus of a VSAT network comprising at least one central station (hub), a plurality of VSAT stations, and a satellite, where the central station (hub) further comprises a plurality of earth stations arranged clearly separated from one another, each having an antenna and transmission equipment in the radio frequency range, and having a terrestrial line link existing between the earth stations and a central station (hub) control unit (computer).
This can also be achieved by an exemplary method of the present invention comprising a plurality of VSAT member stations with at least one central station (hub) for voice, video, and data communication, wherein individual members or user groups can request telecommunication services, wherein in the exemplary method the member traffic is classified as time-critical traffic (ZKV) or non-time-critical traffic (ZUV) and where the transmission parameters of the satellite links are determined as a function of the propagation conditions on the individual communication paths by the central station (hub).
An advantage of an exemplary embodiment of the present invention includes the fact that the available reserves can be used for other purposes when path attenuation is lower than the reserve provided, which allows for more economical operation. For this purpose, the proposed improved VSAT system uses different transmission methods allowing maximum utilization of the available satellite capacity, depending on the propagation conditions at the time. This is achieved through special measures for compensating atmospheric attenuation (Fade Counter Measures, FCM), some of which are known in principle, but not yet proposed in this combination for use in satellite networks. The prerequisites for the effective use of some of these measures include the physical separation of the individual VSAT stations of the network, so that simultaneous rain-induced attenuation at different locations is unlikely due to the limited area affected by strong rain events.
The concept of the novel VSAT system proposed here (apparatus and method) also provides more effective utilization of the equipment needed for the central station (hub), since a single central station (hub) is jointly used by a plurality of user groups, for example, by accessing different separate and independent signals from the central station (hub). Furthermore, replacing a known complex earth-based station having a large antenna at the central station (hub) with two or more simpler earth-based sub-stations having smaller antennas provides greater security and availability of the networks.
The use of the apparatus and method of the present invention allows the current quality standard to be met using less expensive equipment with less reserve capacity or more members to be served by the same satellite and equipment resources, or the quality standard to be raised with an unchanged number of members and equipment characteristics. In addition, the normally strict technical requirements for a single VSAT network central station (hub) can be considerably reduced by using two or more physically separated earth-based sub-stations linked by a terrestrial line.
REFERENCES:
patent: 4639937 (1987-01-01), McRae et al.
patent: 4731866 (1988-03-01), Muratani et al.
patent: 4941199 (1990-07-01), Saam
patent: 5128942 (1992-07-01), Kojima
patent: 5161194 (1992-11-01), Ujiie
patent: 5204981 (1993-04-01), Karasawa et al.
patent: 5295138 (1994-03-01), Greenberg et al.
patent: 5303286 (1994-04-01), Wiedeman
patent: 5404375 (1995-04-01), Kroeger et al.
patent: 5625624 (1997-04-01), Resen et al.
patent: 5659487 (1997-08-01), Cho et al.
patent: 5758261 (1998-05-01), Wiedeman
patent: 5887257 (1999-03-01), Olds
patent: 3210298 (1990-11-01), None
patent: 0 346 868 (1989-12-01), None
patent: 0 411 538 (1991-02-01), None
patent: 6-53878 (1994-02-01), None
patent: 96/04718 (1996-02-01), None
patent: 96/15601 (1996-05-01), None
J. Posecker, “Der Telekom-VSAT-Service-Eine Bilanz ein Jahr danach”, ntz. Bd. 44,1991.
G. Mocker, “VSAT-Pilotsystem fur Satellitengestutzte Datenubertragung” ntz. Bd. 43, 1990.
G. Mocker, “VSAT-Pilotsystem für satellitengestützte Datenübertragung.” In: ntz, Bd. 43, 1990, H.2, S.68-72.* Sited in the attached search report.
J. Posecker, “Der Telekom-VSAT-Service—Eine Bilanz ein Jahr danach., ” In: ntz, Bd. 44, 1991, H. 4, S.246, 248-250, 252-255.
Dintelmann Friedrich
Ortgies Gerd
Ruecker Friedrich
von Hugo Dirk
Deutsche Telekom AG
Kenyon & Kenyon
Maung Nay
LandOfFree
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