Pulse or digital communications – Pulse code modulation
Patent
1994-08-01
1996-04-02
Tse, Young T.
Pulse or digital communications
Pulse code modulation
375241, 341173, 371 492, 342189, H04B 1404, H04B 1500, H04L 2700
Patent
active
055047815
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a process for recovering, at a reception end of a transmission path for digital data streams, data transmitted over the transmission path from a transmission end to the reception end.
In the present invention, various data are coded at the transmission end of the transmission path by means of a binary code word. The binary code word is generated by a code-word generator. The auto-correlation of the binary code word produces a Dirac Pulse. The various data at the transmission end of the transmission path are also coded with further binary code words produced by cyclically shifting the code word and by inverting the code word and further code words.
Further, in the present invention, the code word received is cross-correlated at the reception end of the transmission path by means of a cross-correlator to decode the code word. The relative position and the sign of the main maximum of the corresponding cross-correlation function is used to recover the data sent over the transmission path.
In a known process of this type ("telcom report" 14 (1991), No. 2, pages 104 to 107), a 2.sup.5 -m sequence is used as binary code word. This 2.sup.5 -m sequence has the property that the auto-correlation of this 2.sup.5 -m sequence produces an ideal Dirac impulse. From the 2.sup.5 -m sequence, further binary code words are produced by cyclically shifting the binary code word. These further binary code words are characterized by phases which differ from each other. In this way, 31 different data words can be coded on the transmission end, and thus 4-bit data words can be coded. 5-bit data words cannot be coded since only 31 code words are available. One embodiment of the known process, which constitutes an improvement with respect to the number of codable data words, uses inverted binary 2.sup.5 -m sequences on the transmission end in addition to the coding. In this way, coding a maximum of an additional 31 different data words is possible. As a whole, 5-bit data words can thus be transmitted and recovered on the reception end of a transmission path by cross-correlation, despite disturbances on the transmission path, if not more than 7 bit errors occur upon the transmission.
The object of the present invention is to develop the above process so that a comparatively large number of data present on the transmission end can be reliably recovered on the reception end.
SUMMARY OF THE INVENTION
To achieve the above mentioned object, the present invention provides that a second supply of code words is used on the transmission end of the transmnission path, a second code word being generated by a second code-word generator. The auto-correlation of the second code word produces a Dirac pulse. Further second binary code words are produced by cyclically shifting the second code word and by inverting the second code word and further second code words to produce second inverse code words.
The second code-word generator can be defined by a generator polynomial of the same degree as the code-word generator.
The present invention further provides that a number of data are coded with data polynomials of the seventh order such that the code words of the two code-word generators are associated with data polynomials formed therefrom having, in each case, the five lowest binary places of tile seven order data polynomial as a function of two combinations of values of the two highest binary places of the seven data polynomial.
A further number of data are coded with data polynomials of the seventh order such that the inverse code words of the two code-word generators are associated with data polynomials formed therefrom having the five lowest binary places of the seven order data polynomial as a function of two further combinations of values of the two highest binary places of the seven order data polynomial. Further, an additional number of data are coded with data polynomials of the seventh degree such that code words of an additional code-word supply are associated with data polyno
REFERENCES:
patent: 4833470 (1989-05-01), Iketani
patent: 5025455 (1991-06-01), Nguyen
H. W. Atweiler, et al., "Bitfehler-Strukturanalyse in der Breitband-ISDN- Messtechnik," Messtechnik, vol. 44, No. 8, pp. 548-557 (1991).
A. Wolf, "Messprazision auf breitem Band," Telecom Report, vol. 14, No. 2, pp. 104-107 (Mar./Apr. 1991).
Luther William
Siemens Aktiengesellschaft
Tse Young T.
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