Method and device for error correction of data blocks
In a method for error correcting a data signal that is transmitted via a channel and contains data blocks with associated error checking information, the data signal is first equalized, with calculated soft-bit information. In a subsequent step, the error checking information is evaluated with respect to the data block. If the evaluation of the error checking information shows that a single bit error is present in one message bit, the single bit error is corrected only when a condition that is dependent on the soft-bit information is satisfied.
1. A method for error correcting a data signal transmitted via a channel and containing data blocks with associated error checking information, which comprises the steps of:
deciding message bits in a transmitted data block resulting in decided message bits;
calculating soft-bit values relating to the decided message bits in the data block, the soft-bit values being representative of a level of reliability of a message bit decision;
evaluating the associated error checking information with respect to the data block to determine if a single bit error exists and, if the single bit error exists, determining a location of the single bit error resulting in a located single error bit; and
correcting the located single bit error, if:
a first variable, determined on a basis of the soft-bit values and allows an assessment as to whether more than one decided message bit in the data block is incorrect, satisfies a first threshold value condition; and
a second variable, determined on a basis of the soft-bit values and allows an assessment as to whether the decided message bit to be corrected is incorrect, satisfies a second threshold value condition.
2. The method according to claim 1 , which further comprises performing the method for error correcting the data blocks in general packet radio service mobile radio systems.
3. The method according to claim 1 , which further comprises performing the method for error correcting on data blocks which have been error-protection-coded in accordance with coding scheme CS-4.
4. The method according to claim 1 , which further comprises performing the calculating and deciding steps with an equalizer.
5. A device for error correcting a data signal transmitted via a channel and containing data blocks with associated error checking information, the device comprising:
bit decision means for deciding message bits in a transmitted data block resulting in decided message bits;
means for calculating soft-bit values relating to the decided message bits in the data block, the soft-bit values being representative of a level of reliability of a message bit decision;
means for evaluating the associated error checking information with respect to the data block to determine whether a single bit error exits and, if the single bit error exists, determining a location of the single bit error resulting in a located single bit error; and means for error correcting the located single bit error if:
a first variable, determined on a basis of the soft-bit values and allows an assessment as to whether more than one decided message bit in the data block is incorrect, satisfies a first threshold value condition; and
a second variable, determined on a basis of the soft-bit values and allows an assessment as to whether the decided message bit to be corrected is incorrect, satisfies a second threshold value condition.
6. The device according to claim 5 , wherein the device is configured for error correcting data blocks in general packet radio service mobile radio systems.
7. The device according to claim 5 , wherein the device is configured for error correcting the data blocks which have been error-protection-coded in accordance with coding scheme CS-4.
8. The device according to claim 5 , wherein said bit decision means and said means for calculating soft-bit values are performed by a hard and soft output equalizer.
9. A device for error correction of a data signal transmitted via a channel and containing data blocks with associated error checking information, the device comprising:
a hard and soft output equalizer for deciding message bits in a transmitted data block and for calculating soft-bit information relating to decided message bits in the data block, the soft-bit information being representative of a level of reliability of a message bit decision;
an error checking unit for evaluating the associated error checking information with respect to the data block to determine whether a single bit error exits and, if the single bit error exists, determining a location of the single bit error resulting in a located single bit error; and
an error correction unit for correcting the located single bit error if:
a first variable, determined on a basis of the soft-bit information and allows an assessment as to whether more than one decided message bit in the data block is incorrect, satisfies a first threshold value condition; and
a second variable, determined on a basis of the soft-bit information and allows an assessment as to whether the decided message bit to be corrected is incorrect, satisfies a second threshold value condition.