Method for encoding a user identifier in a communication system
View Patent ↗A method of generating coded user ID information that is combined with CRC codes and the result is appended to signaling information. The CRC codes are generated from the signaling information. The resulting codeword is transmitted over shared signaling channels to various users of a communication system. The resulting codeword is such that the likelihood of users attempting to decode codewords not intended for them is significantly reduced.
1. A method for generating coded user ID information to be transmitted with signaling information to users of a communication system over shared signaling channels, the method comprising the steps of:
applying an (N, K, D MIN ) coding scheme to user ID information having K bits so that a resulting coded user ID block of information has N bits and has a codespace that has a minimum coding distance of D MIN where D MIN is as large as possible for particular values of K and N and where K and N are integers equal to 1 or greater, and K<N;
combining the coded user ID block of information with error detection code information, generated from the signaling information having I bits, to generate coded blocks of information having a pairwise coding distance D xy between arbitrary code blocks x and y, where D xy , D MIN and I are integers equal to 1 or greater and x, y represent arbitrary codewords;
modifying the (N, K, D MIN ) coding scheme to reduce occurrences of D xy <D MIN for the coded blocks; and
transmitting over the shared signaling channels codewords comprising signaling information appended to coded blocks, to users of the communication system thus reducing occurrences of false alarms by users receiving the codewords.
2. The method of claim 1 where the step of combining the coded user ID information with error detection code information comprises modulo 2 adding the coded user information to the error detection code.
3. The method of claim 1 where the step of modifying the (N, K, D MIN ) coding scheme comprises the step of padding the K-bit user ID information with at least one bit and/or rotating the N-bit coded user ID information before it is combined with the error detection code.
4. The method of claim 1 where the communication system complies with the UMTS HSDPA standard and K=1, N=16, I=21 and D MIN =4 and where the user ID coding scheme is a (16, 11, 4) code obtained by bit padding followed by extended Hamming (15, 11, 4) followed by rotation and the error detection code is a CRC code.
5. The method of claim 1 where the communication system complies with the UMTS HSDPA standard (work in progress) and K=1, N=16, I=21 and D MIN =4 and where the user ID coding scheme is a (16, 11, 4) code obtained by a shortened Hamming (15, 10, 4) code followed by a bit padding which is followed by rotation and the error detection code is a CRC code.
6. The method of claim 4 where the 10-bit user ID information is padded with a 1 or 0 bit at a location within the 10-bit block tending to reduce occurrences of overall user specific corresponding coded blocks having coding distance of less than 4.
7. The method of claim 6 where the 15-bit partially coded user ID information is padded with a 1 or 0 bit at a location within the 15-bit block that to reduce occurrences of overall user specific corresponding coded blocks having a coding distance of less than 4.
8. The method of claims 4 - 7 where the resulting 16-bit coded user ID information is rotated by a certain angle before it is combined with the CRC code to reduce occurrences of overall user specific corresponding coded blocks having a coding distance of less than 4.