Method and device for calculating bit error rate of received signal
View Patent ↗System and method of estimating radio channel bit error rate (BER) in a digital radio telecommunications system wherein the soft output of the turbo decoder is used as pointer or index to look-up-tables containing the bit-wise BER of a certain bit in the data field of the received frame. A quantizer quantizes the received data frame and the quantized bit operates on a switch which selects the appropriate look-up-table. By means of accumulation and scaling the average BER of a certain amount of bits are calculated. Decoding bit-errors may occur but as they are submitted to posterior probability estimation, systematic errors which normally happen at low SNR are avoided.
1. A system for determining a bit error rate in a digital communication system, comprising:
a transmitting station;
a receiving station having a decoder;
the transmitting station arranged for transmitting a bit sequence to a receiving station;
the receiving station arranged for receiving the bit sequence;
the decoder arranged for decoding one or more bits out of the received bit sequence;
a plurality of look-up tables arranged for containing predetermined bit error rates related to ranges of soft output values;
a quantizer being arranged for quantizing the received bit;
a switch being arranged for selecting an output, representing a Bit error Rate contribution, of one of the look up tables out of the plurality of look up tables, the selection being based on the quantized bit;
a soft-output of the decoder being arranged as an index to the plurality of look up tables for retrieving a bit-wise bit error rate contribution to the bit error rate of a received bit sequence; and
a summing and scaling device being arranged for accumulating and averaging the bit-wise BER.
2. The system as claimed in claim 1 , wherein the lookup tables are replaced by one or more processing devices, arranged for providing accompanying values for the Bit Error Rate contribution on input of the value of the soft output.
3. The system as claimed in claim 2 , wherein the processing device is a floating point processor.
4. The system as claimed in claim 1 , wherein the decoder is a turbo-decoder.
5. The system as claimed in claim 1 , wherein the decoding algorithm is the Maximum A Posteriori algorithm (MAP).
6. The system as claimed in claim 1 , wherein the decoding algorithm is the Logarithmic Maximum A Posteriori algorithm (LOG-MAP).
7. The system as claimed in claim 1 , wherein the decoding algorithm is the Maximum-Logarithmic-Maximum A Posteriori algorithm (MAX-LOG-MAP).
8. The system as claimed in claim 1 , wherein the decoding algorithm is the Soft Output Viterbi Algorithm (SOVA).
9. A receiving station system arranged for determining a bit error rate in transmitted bit sequence, comprising:
a decoder arranged for decoding one or more bits out of the received bit sequence;
a plurality of look-up tables arranged for containing predetermined bit error rates related to ranges of soft output values;
a quantizer being arranged for quantizing the received bit;
a switch being arranged for selecting an output representing a Bit Error Rate contribution, of one of the plurality of look up tables, the selection being based on the quantized bit;
a soft-output of the decoder being arranged as an index to the plurality of look up tables for retrieving a bit-wise bit error rate contribution to the bit error rate of a received bit sequence;
a summing and scaling device being arranged for accumulating and averaging the bit-wise BER.
10. The receiving station system as claimed in claim 9 , wherein the receiving station system is a mobile unit within a wireless communication system.
11. The receiving station system as claimed in claim 9 , wherein the receiving station is a radio base station within a CDMA communication system.
12. The receiving station system as claimed in claim 9 , wherein the receiving station system operates in a wireless communication network according to a GSM, Bluetooth, or Code Division Multiple Access (CDMA) standard.
13. A method for determining a bit error rate in a digital communication system comprising a transmitting station and a receiving station having a decoder comprising the steps of:
transmitting a bit sequence to the receiving station by the transmitting station;
receiving the bit sequence by the receiving station;
decoding a bit out of the received bit sequence by the decoder;
quantizing the received bit by a quantizer;
selecting an output of a look up table, the look up table being one of a plurality of look up tables, the selection being based on the quantized bit;
indexing the selected look up table, for obtaining a bit-wise bit error rate of the received bit sequence, by the soft-output of the decoder;
accumulating and averaging the bit-wise BER of the received bit sequence by a summing and scaling device, resulting in the estimated average BER.
14. The method as claimed in claim 13 , wherein the decoding method is turbo-decoding.
15. The method as claimed in claim 13 , wherein the decoding algorithm is the Maximum A Posteriori algorithm (MAP).
16. The method as claimed in claim 13 , wherein the decoding algorithm is the Logarithmic Maximum A Posteriori algorithm (LOG-MAP).
17. The method as claimed in claim 13 , wherein the decoding algorithm is the Maximum-Logarithmic-Maximum A Posteriori algorithm (MAX-LOG-MAP).
18. The method as claimed in claim 13 , wherein the decoding algorithm is the Soft Output Viterbi Algorithm (SOVA).