Decoder and a method for determining a decoding reliability indicator

Abstract

A decoder for use in a wireless communication device, the decoder comprising a correlator for correlating a received data sequence with a set of codewords such that a correlation value is generated for each correlation, wherein the set of codewords correspond to possible codewords that could be generated from encoding bit sequences having a predetermined number of information bits; a selector for selecting a first correlation value and a second correlation value generated by the correlator and for subtracting the second correlation value from the first correlation value to generate a third value; and a comparator for comparing the third value with a predetermined value to generate a decoding reliability indicator.

1. A decoder for use in a wireless communication device, the decoder comprising a correlator for correlating a received data sequence with a set of codewords such that a correlation value is generated for each correlation, wherein the set of codewords correspond to possible codewords that could be generated from encoding bit sequences having a predetermined number of information bits; a selector for selecting a first correlation value and a second correlation value generated by the correlator and for subtracting the second correlation value from the first correlation value to generate a third value; and a comparator for comparing the third value with a predetermined value to generate a decoding reliability indicator; wherein the decoder is arranged to switch, based on a threshold for said number of information bits, between decoding via said correlation of codewords and a Viterbi-based algorithm. 
     
     
       2. A decoder according to  claim 1 , wherein the received data sequence corresponds to a transmitted codeword representing a predetermined number of encoded information bits. 
     
     
       3. A decoder according to  claim 2 , wherein the correlation values are indicative of the likelihood that the respective codeword corresponds to the information bits represented by the transmitted codeword. 
     
     
       4. A decoder according to  claim 1 , wherein the set of codewords corresponds to all possible codewords that could be generated from encoding bit sequences having the predetermined number of information bits. 
     
     
       5. A decoder according to  claim 1 , further comprising a memory for storing the set of codewords. 
     
     
       6. A decoder according to  claim 1 , wherein the first correlation value is the highest determined correlation value for a given set of codewords and the second correlation value is the second highest determined correlation value for the given set of codewords. 
     
     
       7. A decoder according to  claim 1 , wherein the predetermined number of information bits is below a threshold number. 
     
     
       8. A decoder according to  claim 1 , further comprising a receiver arranged to receive a data sequence that corresponds to the first slot of a wideband code division multiple access WCDMA shared control channel transmission time interval TTI. 
     
     
       9. A decoder according to  claim 8 , wherein the WCDMA shared control channel is the high speed shared control channel HS-SCCH, and the first slot contains part  1  of the HS-SCCH. 
     
     
       10. A decoder according to  claim 1 , wherein the received data sequence corresponds to a transmitted forty bit codeword representing eight encoded information bits. 
     
     
       11. A decoder according to  claim 10 , wherein the correlator includes 256 parallel correlators to allow correlation of the received data sequence with 256 codewords. 
     
     
       12. A decoder according to  claim 11 , wherein the memory is arranged to store 256 codewords that correspond to the 256 possible codewords that can represent eight encoded information bits. 
     
     
       13. A decoder according to  claim 1 , wherein if the third value is greater than the predetermined value the reliability indicator is arranged to indicate that the codeword is intended for an apparatus associated with the decoder. 
     
     
       14. A wireless communication device having a decoder according to  claim 1 . 
     
     
       15. A radiotelephone having a decoder according to claims  1 . 
     
     
       16. A method for determining a decoding reliability indicator, the method comprising correlating a received data sequence with a set of codewords, where the set of codewords corresponds to possible codewords that could be generated by encoding a predetermined number of information bits, to generate a correlation value for each correlation; selecting a first generated correlation value and a second generated correlation value and subtracting the second generated correlation value from the first generated correlation value to generate a third value; and comparing the third value with a predetermined value to generate a decoding reliability indicator; wherein the method further comprises switching, based on a threshold for said number of information bits, between decoding via said correlation of codewords and a Viterbi-based algorithm. 
     
     
       17. A user equipment having a decoder according to claim 1, wherein the decoder is arranged in the user equipment to decode a data sequence received on a downlink.  
     
     
       18. A user equipment according to claim 17, wherein the decoder is configured to decode a data sequence received on a downlink shared control channel.  
     
     
       19. A user equipment according to claim 18, wherein the decoder is configured to decode a data sequence received on a high speed shared control channel HS-SCCH.  
     
     
       20. A user equipment according to claim 18, wherein said data sequence is to allow the user equipment to make a determination as to whether data being transmitted on a downlink shared data channel is intended for the user equipment.  
     
     
       21. A user equipment according to claim 20, wherein said data sequence is to allow the user equipment to make a determination as to whether data being transmitted on a high speed downlink shared channel HS-DSCH is intended for the user equipment.