Telephonic communications – Special services – Service trigger
Patent
1996-12-23
1999-03-02
Chiang, Jack
Telephonic communications
Special services
Service trigger
379220, H04M 342, H04M 700
Patent
active
058781250
DESCRIPTION:
BRIEF SUMMARY
This application is the national phase of international application PCT/FI95/00361 filed Jun. 21, 1995 which designated the U.S.
BACKGROUND OF THE INVENTION
The invention relates to a method in accordance with the preamble of the attached claim 1 for storing analysis data in a telephone exchange. The method of the invention is intended especially for storing data structures used in the digit analyses of telephone exchanges, but as the following more detailed description will show, the same principle may also be utilized for storing in a telephone exchange data which is intended for carrying out other analyses.
When a subscriber of a telephone network makes a call, the destination (subscriber B) of the call is determined on the basis of the dialled digit combination (i.e. telephone number). Each node of the telephone network finds out the destination of incoming calls by analysing these digits. This procedure, in the following referred to as digit analysis, is a functional part of a telephone exchange, which, in response to a given telephone number, returns the corresponding destination.
Digit analysis is based in a telephone exchange (e.g. in a DX 200 of the applicant) on a data structure in which records form a hierarchical tree structure. Each record contains e.g. 16 fields, each corresponding to a certain button of the telephone (0, 1, 2, . . . 9, *, #, etc.). A single field is either empty (i.e. it is not in use and thus contains nothing), or it contains a pointer. The pointer (which in practice is some binary digit) may point either to the following record or to a destination that is the result of the digit analysis. An empty field means in practice that no digit analysis is carried out for the corresponding button of the telephone.
FIG. 1 illustrates the principle described above. A data structure is composed of several records 11, each containing 16 fields, which are marked with reference symbols 0 . . . 9, a, . . . f. For instance, an analysis carried out for telephone number 408178 returns destination D and an analysis carried out for telephone number 504178 returns destination E. The analysis is carried out by proceeding in the tree structure one dialled digit at a time and examining the content of the field corresponding to the dialled digit, and by proceeding to the record pointed to by the pointer included in said field, in which record the content of the field corresponding to the following digit is examined etc. The field corresponding to the digit to be examined last provides the result of the analysis (destination).
A problem in the present situation is that the size of the data structure to be used for digit analyses tends to grow very large and demands plenty of memory capacity in the exchange. Reasons for this are e.g. the growth of the capacity of the telephone exchanges, new services offered by the telephone exchanges, particularly the willingness of the telephone operators to employ free (i.e. non-hierarchical) numbering.
In prior art, a hierarchical structure has been used in numbering, whereby in each node of the telephone network the destination may be determined by using only a part of the whole telephone number. This prior art way of numbering and the problem arising from free numbering are illustrated in FIGS. 2 . . . 4. FIG. 2 shows a transit exchange 21, which is connected via interconnecting lines to local exchanges 22 and 23, to which subscriber devices SD are connected via subscriber lines. This example contains a total number of 1000 subscriber lines. Let us assume that the telephone numbers of the subscribers located within the area of the transit exchange 21 are in the range 0. . . 999 and that the subscribers whose telephone numbers are within the range 000 . . . 199 are connected to local exchange 22, and the subscribers whose telephone numbers are within the range 200 . . . 999 are connected to local exchange 23. Thus, the data structure to be used for digit analyses in the transit exchange 21 is similar to that shown in FIG. 3, comprising one record 31, the first
REFERENCES:
patent: 4442321 (1984-04-01), Stehman
patent: 5375167 (1994-12-01), Bales et al.
Chiang Jack
Nokia Telecommunications Oy
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