Excavating
Patent
1996-09-12
1998-05-12
Baker, Stephen M.
Excavating
371 3706, H03M 1322, H04L 120
Patent
active
057517304
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The field of the invention is that of digital transmission, in particular to mobile stations.
To be more precise, the invention concerns an encoding/interleaving method and a deinterleaving/decoding method to be used in a TDMA (Time-Division Multiple Access) type digital transmission system, for example.
2. Description of the Prior Art
The principle of the TDMA technique is to time-share all of the transmission channel. In other words, to prevent information overlapping only one station sends at a time and when it is sending it occupies all of the transmission channel.
In all digital transmission systems the data symbols to be transmitted are protected by adding to them judiciously determined redundancy symbols. This standard technique is known as error control encoding or channel encoding. The redundancy is used at the receiving end to decode the receive symbols correctly, i.e. to correct any transmission errors.
Interleaving after encoding is used in digital transmission systems. The encoded symbols are then divided up and transmitted at separate times. At the receiver, decoding is preceded by deinterleaving which breaks up the bursts of errors and, ideally, yields isolated errors that are easier to process by means of the codes used subsequently in decoding.
In a TDMA system data is transmitted in the form of blocks of encoded symbols that are divided (i.e. interleaved) into bursts of several consecutive TDMA frames. At the receiver the bursts are first equalized and then deinterleaved in order to form received encoded blocks which are then decoded in order to retrieve the data symbols transmitted.
The quality of a burst after equalization varies after transmission over a radio channel, in particular a mobile radio channel with frequency hopping and a quasi-random distribution of interference signals. The transmission channel may be subject to various kinds of interference, in particular rapid fading and impulsive interference, which cause blocks of errors in the bursts.
The purpose of deinterleaving is to burst these blocks of errors so that the decoder does not have to process excessively long blocks of errors and therefore can operate correctly.
Nevertheless, even after deinterleaving, the blocks of errors may be divided into sub-blocks of errors that are too long for correct decoding. These sub-blocks of errors then affect an even greater number of symbols contained in the bursts.
A prior art solution to the problem of reducing the size of the sub-blocks of errors is to increase the depth of interleaving, i.e. the number of blocks used to construct a burst. However, this prior art solution has the drawback of increasing the transmission time-delay and therefore of reducing transmission quality (especially in the transmission of speech).
One object of the invention is to overcome these various drawbacks of the prior art.
To be more precise, one object of the present invention is to provide an encoding/interleaving method that, for the same encoding power, is less complex than the prior art encoding/interleaving methods.
Another object of the invention is to provide a deinterleaving/decoding method that enables correct decoding even in the presence of blocks of errors of such a size that it is not possible to correct them using the known methods.
Another object of the invention is to provide a deinterleaving/decoding method of this kind that reduces the depth of interleaving and therefore the transmission time-delay.
SUMMARY OF THE INVENTION
These various objects, and others that will emerge hereinafter, are achieved in accordance with the invention by means of a method of encoding/interleaving a source sequence of data symbols to be transmitted to produce at least two bursts to be sent over a transmission channel and made up of said data symbols to be transmitted and redundancy symbols, this method comprising the steps of: row into a base matrix, redundancy symbols which are stored in a second quadrant of said send extended matrix and constitu
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Shenton et al, "Improved Reed-Solomon Decoding Using Multiple-Pass Decoding", Journal of the Audio/Acoustics/Applications, vol. 33, No. 1/2, Jan./Feb. 1985, pp. 878-887.
ALCATEL N.V.
Baker Stephen M.
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