1996-09-27
1999-08-17
Beausoliel, Jr., Robert W.
Excavating
370241, G06F 1110
Patent
active
059404124
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/F195/00164, filed Mar. 27, 1995.
BACKGROUND OF THE INVENTION
This invention relates to a decoding method of a telecommunication network, in which method: information frames are received and data contained in them is buffered until the amount of the buffered data corresponds to a predetermined amount, the buffered data is decoded, a parity check is made for the buffered data, and the buffered data is transmitted further in the telecommunication network.
This invention is specifically connected to the GSM mobile telephone system (Groupe Special Mobile), and more precisely to a method by which the quality of the connection between the mobile, that is, the subscriber unit, and the mobile services switching center can be improved.
In situations in which there is an active traffic channel in a base station but the mobile does not transmit radio signals to the base station on the connection continuously, the base station has no way of detecting from a received signal whether the subscriber unit has transmitted the frame or not. Therefore, the base station constantly receives noise from the radio path, detects and decodes it, and sends speech blocks further in TRAU-frames to a transcoder.
The above-mentioned situation occurs in the GSM system at least in connection with a handover when the handover is made between two base stations, or when a subscriber unit uses discontinuous transmission, that is, is in a DTX state. In the DTX state the-subscriber unit sends one speech frame of 20 ms in length in accordance with the GSM specifications, after which it has a pause of 460 ms in length before transmitting the next speech frame.
According to the GSM specifications, the base station has to be able to detect 99,8% of all defective speech blocks sent via the base station. This detection is based on a parity check made in connection with the decoding of speech blocks. Because in the above mentioned special situations all the speech blocks received from the radio path by the base station are defective, a defective speech block passes through the base station in compliance with the GSM specifications every tenth second on the average without the decoding of the base station detecting the error.
SUMMARY OF THE INVENTION
The object of this invention is to eliminate the above-mentioned drawback and to improve the quality of the connection between the subscriber unit and the mobile services switching center. This object is achieved with the method of the invention that is characterized in that the accuracy of the buffered data is resolved by a parity check and an additional check, the additional check taking into account results obtained in connection with the processing of data received earlier in time.
The invention is based on the idea that the number of forwarded defective speech blocks marked as faultless will decrease significantly when an additional check based on information obtained in the processing of previous speech blocks is made in addition to a parity check to ascertain the accuracy of the buffered speech block. Thus, the most important advantage of the method of the invention is that the connection between the subscriber unit and the mobile services switching. center can be significantly improved by very simple procedures. For example, in channel decoding of a GSM base station the utilization of the invention can be carried out as a whole by means of a software change, whereby the hardware costs of the base station will not rise.
A first preferred embodiment of the method of the invention is characterized in that in the additional check the number of successive parity checks showing error is checked, and if the number exceeds a predetermined limit value, the buffered data is found to be defective. In this embodiment of the invention, the first faultless speech block following a long string of defective speech blocks is rejected. As regards a base station according to the GSM specifications, the probability of a defective speech block being i
REFERENCES:
patent: 4546474 (1985-10-01), Sako et al.
patent: 5214687 (1993-05-01), Kansakoski et al.
patent: 5327574 (1994-07-01), Monma et al.
patent: 5357513 (1994-10-01), Kay et al.
patent: 5432778 (1995-07-01), Minde et al.
patent: 5432800 (1995-07-01), Kuroda et al.
patent: 5491719 (1996-02-01), Sellin et al.
patent: 5502713 (1996-03-01), Lagerqvist et al.
patent: 5563895 (1996-10-01), Malkamaki et al.
patent: 5574983 (1996-11-01), Douzono et al.
patent: 5612992 (1997-03-01), Dupuy et al.
Inspec Abstract No. B9407-6250F-014 "New Base For GSM".
Inspec Abstract No. B9303-6120B-004 "A Survey of Array Error Control Codes".
Inspec Abstract No. : B91051248 "Introduction to Coding Theory V.".
Inspec Abstract No.: B9307-6120B-053, C9307-6130S-065 "Convergence of a Bayesian Iterative Error-Correction Procedure on a Noisy Shift".
Beausoliel, Jr. Robert W.
Iqbal Nadeem
Nokia Telecommunications Oy
LandOfFree
Decoding method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Decoding method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Decoding method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-322077