Rate matching method in mobile communication system
A rate matching method is provided for a mobile communication system that performs an adjustment to a code rate based on an optimal level by puncturing or repetition to respective bit streams of transport channels. The rate matching method is preferably applicable to uplink and downlink rate matching for channel coding including turbo coding, convolutional coding and the like. The rate matching method for uplink can include executing coding for bits of a transport channel, and branching off the bits into a plurality of sequences, constructing a first interleaving pattern for the plurality of sequences, constructing a virtual interleaving pattern for at least one sequence based on a mapping rule with a corresponding first interleaving pattern and calculating different bit shifting values in each column of each virtual interleaving pattern. Then, a bit position to be punctured is determined in each constructed virtual interleaving pattern using the calculated bit shifting values.
1. A method for puncturing of an uplink transmission signal in a mobile communication system, the method comprising:
channel coding input bits using a turbo encoder to output a turbo-coded bit stream;
interleaving the turbo-coded bit stream at an interleaver to generate interleaved turbo-coded bits;
separating the interleaved turbo-coded bit stream into a first sequence, a second sequence and a third sequence;
determining a first number of bits to be punctured for the second sequence, a second number of bits to be punctured for the third sequence, and an average puncturing distance (q);
performing an algorithm for determining a first shifting parameter for the second sequence and a second shifting parameter for the third sequence, wherein the algorithm is performed differently according to whether (q) is greater than 2; and
performing puncturing on each of the second sequence and the third sequence by using the determined first and second shifting parameters,
wherein the first and the second shifting parameters are determined in a unit that corresponds to (q) within a range of a number (K) of columns of the interleaved turbo-coded bits when (q) is an odd number greater than 2,
wherein the first and the second shifting parameters are determined in a unit that corresponds to (q′) within a range of (K) when (q) is an even number greater than 2, with (q′) calculated by subtracting a variable from (q), the variable determined based on a relation between (q) and (K), and
wherein the first and second shifting parameters are determined iteratively as “0” or “1” when (q) is not greater than 2.
2. The method according to claim 1 , wherein (K) is 1, 2, 4 or 8.
3. The method according to claim 2 , wherein (q′) is defined as [(q)-gcd (q, K)/K], wherein “gcd (q, K)” indicates a greatest common divisor of (q) and (K).
4. The method according to claim 1 , wherein the first and the second shifting parameters are determined independently.
5. The method according to claim 1 , wherein the first and the second shifting parameters are determined in consideration of column positions of the second and third sequences before the interleaving.
6. The method according to claim 5 , wherein the first shifting parameter is determined using an index of (3k+1), where 0≦k≦K−1.
7. The method according to claim 5 , wherein the second shifting parameter is determined using an index of (3k+2), where 0≦k≦K−1.
8. The method according to claim 5 , wherein the first sequence comprises a systematic sequence of the turbo-coded bits.
9. The method according to claim 5 , wherein each of the second sequence and the third sequence comprises a first parity sequence and a second parity sequence of the turbo-coded bits.