Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
1998-12-15
2001-04-24
Nguyen, Lee (Department: 2746)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S450000, C455S422100, C455S451000, C455S452200, C455S454000, C455S464000, C455S509000, C455S517000, C375S132000, C375S133000, C375S135000, C375S136000, C370S330000, C370S436000, C370S478000
Reexamination Certificate
active
06223048
ABSTRACT:
This invention relates to a method of generating a frequency-hopping sequence as set forth in the preamble of claim
1
as well as to a radio facility which communicates with another radio facility in accordance with the frequency-hopping sequence and to a radio communication system comprising such radio facilities as set forth in the preambles of the respective independent claims.
Radio communication systems are known in which radio transmission between radio facilities takes place on several allocated carrier frequencies, with the radio facilities changing between the allocated carrier frequencies. This method of radio transmission is known as “frequency hopping”. A well-known radio communication system using frequency hopping is the GSM system (Global System for Mobile Communications).
In a book by M. Mouly, “The GSM System for Mobile Communications”, published by the author in 1992, Palaiseau, France, the structure and operation of GSM are described in detail. In Chapters 4.2.2.2 and 4.2.2.3, on pages 218 to 224, a method of generating a frequency-hopping sequence is described: The so-called Mobile Allocation Index (MAI), i.e., data on the carrier frequencies to be allocated, is determined. Input data for this determination are, for example, the Mobile Allocation Index Offset (MAIO) and the Hopping Sequence Number (HSN).
From the ETSI Standard GSM 05.02, version 5.1.0, a method of generating a frequency-hopping sequence is known which involves determining the above-mentioned MAI (Mobile Allocation Index), which specifies the carrier frequency to be allocated within a carrier unit. As described in Secton 6.2.3 and shown in FIG. 6 of GSM 05.02, the known method comprises the following steps. First, input data are determined which specify at least the number of available carrier frequencies, N, and a frequency-hopping scheme to be used, HSN. The number N of available carrier frequencies varies between 1 and 64, and the hopping sequence number HSN indicates which of 64 possible frequency-hopping schemes is used. As can be seen in FIG. 6, further input data are: MA (Mobile Allocation) and FN (Frame Number) with the parameters T1 to T3. From these input data, the hopping sequence is generated by calculating the MAI (Mobile Allocation Index) for each time interval using the algorithm shown on page 17 and in FIG. 6 of GSM 05.02. The input data are obtained from a lookup table RNTABLE (see GSM 05.02, page 17). This lookup table contains a pseudorandom association of 114 input values (addresses from 000 to 113) with 128 output values (contents from 0 to 127). The pseudorandom association causes intermediate results produced by the algorithm to be scrambled (see “look-up table” in FIG. 6).
The invention is predicated on recognition that the lookup table, which is known per se, can also serve to identify those radio facilities which are in radio communication with one another, and thus to associate these radio facilites with one another.
According to the invention, therefore, several different lookup tables are created, with those radio facilities which are in radio communication with one another being assigned the same lookup table. This means that the known method of generating a frequency-hopping sequence is improved in that several different lookup tables are accessed to establish a unique association between the intercommunicating radio facilities.
This has the advantage that the association between the radio facilities not only is established on the basis of usual identification codes, such as the subscriber identification IMSI (International Mobile Subscriber Identity) or the device code IMEI (International Mobile Equipment Identity), but is improved by a further criterion, namely by the different lookup tables.
With the measures according to the invention, it is possible not only to improve the unique association between the radio facilities, but also to form a radio communication system which differs from the conventional GSM mobile communications system in that it uses several different lookup tables. The newly formed radio communication system is therefore particularly suited for private radio communication using conventional GSM hardware, with new software (modified algorithm) being used to generate the frequency-hopping sequence.
The radio communication system according to the invention therefore comprises means for calculating the frequency-hopping sequence which access several different lookup tables, and radio facilities comprising storage means in which these lookup tables are stored in such a way that the intercommunicating radio facilities contain the same lookup table. Also proposed is a radio facility for the radio communication system which includes a means suitable for calculating the frequency-hopping sequence and a suitable storage means.
Further advantageous features of the invention are defined in the subclaims.
Advantageously, the different lookup tables are matrices whose input vectors are assigned to one output vector each, with the output vectors of the different matrices being orthogonal to each other. This ensures that interference between the radio facilities, which operate in a frequency-hopping mode, is minimized.
If the radio facilities are represented by at least one base station and at least two mobile stations, each of the mobile stations will advantageously contain a lookup table whose pseudorandom association is dependent on a subscriber identification. This subscriber identification identifies the subscriber who is using the mobile station. This means that each subscriber in the radio communication systems is assigned a separate lookup table.
It is also advantageous to assign to each mobile station a lookup table whose pseudorandom association is dependent on the device code of the mobile station. In this manner, each radio facility is unambiguously assigned a respective one of the lookup tables.
Furthermore, it is advantageous to store all lookup tables of the mobile stations in the base station, so that all mobile stations can communicate with this base station. In this connection it is also conceivable to use several base stations, of which individual ones contain only a limited set of lookup tables. This makes it possible to assign the mobile station to a subset of base stations (“group assignment”).
A further advantage results if the storage means of the mobile station contains not only the lookup table for radio communication with the above base station but also a further lookup table for radio communication with a base station of a second mobile communication system. A radio facility is thus proposed which can communicate both with the first mobile communication system (for example a private radio communication system) and with a second mobile communication system (for example a public radio communication system, such as GSM). The hardware of such a radio facility corresponds essentially to that of a conventional radio facility for the second mobile communication system.
REFERENCES:
patent: 5257398 (1993-10-01), Schaeffer
patent: 5881094 (1999-03-01), Schilling
patent: WO 95/20844 (1995-08-01), None
M. Mouly, “The GSM: System for Mobile Communications”, 1992, pp. 218-224.
ETSI Standard GSM 05.02, Version 5.1.0.
Deissner Jürgen
Noll Barreto André
Alcatel
Ferguson Keith
Nguyen Lee
Sughrue Mion Zinn Macpeak & Seas, PLLC
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