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 rate matching method for uplink transmission of a mobile telecommunication system, the method comprising:
interleaving turbo-coded bits comprising a first sequence, a second sequence and a third sequence from a turbo encoder at an interleaver;
determining rate matching parameters including a number of bits to be punctured or repeated for the second and the third sequences (Ni), an average puncturing or repetition distance (q), a first shifting parameter for the second sequence and a second shifting parameter for the third sequence, wherein the first and second shifting parameters are determined in consideration of column positions of the second and third sequences before the interleaving; and
performing a rate matching on the second and third sequences by applying the determined rate matching parameters to a rate matching algorithm commonly used for the uplink transmission and a downlink transmission.
2. The rate matching method according to claim 1 , further comprising:
constructing the first sequence, the second sequence and the third sequence separately from the interleaved turbo-coded bits, wherein the first and the second shifting parameters are determined using the separately constructed second and third sequences.
3. The rate matching method according to claim 2 , wherein performing the rate matching is independently performed on the second sequence and the third sequence.
4. The rate matching method according to claim 1 , wherein the first and the second shifting parameters are independently determined.
5. The rate matching method according to claim 4 , wherein the first shifting parameter is determined using an index of (3k+1), where 0≦k≦K−1.
6. The rate matching method according to claim 4 , wherein the second shifting parameter is determined using an index of (3k+2), where 0≦k≦K−1.
7. The rate matching method according to claim 1 , wherein determining the rate matching parameters further determines an initial error offset value (eini) for use in performing the rate matching based on the determined first and second shifting parameters and a predetermined constant (a).
8. The rate matching method according to claim 7 , wherein (eini) is determined differently for the second sequence and the third sequence based on the first and second shifting parameters.
9. The rate matching method according to claim 8 , wherein the rate matching algorithm is a puncturing algorithm and comprises:
setting a current bit index as “1”;
updating an error offset value by subtracting (a)*(Ni) from the error offset value to generate a first updated error offset value;
puncturing a current bit and updating the first updated error offset value by adding (a)*(N) when the first updated error offset value is not greater than 0; and
increasing the current bit index by “1”,
wherein the updating, puncturing and increasing steps are repeated until the current bit index is larger than (N) where (N)=floor (Nc/3), (Nc) is a number of data bits in each column of the interleaver, and “floor (x)” indicates a greatest integer not greater than (x).