Detection, avoidance and/or correction of problematic puncturing patterns in parity bit streams used when implementing turbo codes
Detecting, avoiding and/or correcting problematic puncturing patterns in parity bit streams used when implementing punctured Turbo codes is achieved without having to avoid desirable code rates. This enables identification/avoidance of regions of relatively poor Turbo code performance. Forward error correction comprising Turbo coding and puncturing achieves a smooth functional relationship between any measure of performance and the effective coding rate resulting from combining the lower rate code generated by the Turbo encoder with puncturing of the parity bits. In one embodiment, methods to correct/avoid degradations due to Turbo coding are implemented by puncturing interactions when two or more stages of rate matching are employed.
1. A method of rate matching comprising:
interleaving systematic bits;
interleaving a first parity bit stream;
interleaving a second parity bit stream;
buffering the interleaved systematic bits, the interleaved first parity bit stream and the interleaved second parity bit stream in a virtual buffer when the number of bits of the interleaved systematic bits, the interleaved first parity bit stream and the interleaved second parity bit stream is not larger than the virtual buffer;
buffering a portion of the interleaved systematic bits, the interleaved first parity bit stream and the interleaved second parity bit stream when the number of bits of the interleaved systematic bits, the interleaved first parity bit stream and the interleaved second parity bit stream is larger than the virtual buffer; and
performing rate matching on at least one output of the virtual buffer.
2. The method of claim 1 wherein the buffered portion includes all of the interleaved systematic bits.
3. The method of claim 1 further comprising:
collecting bits associated with the interleaved systematic bits, the interleaved first parity bit stream and the interleaved second parity bit stream.
4. An apparatus for use in wireless communications comprising:
a first interleaver configured to interleave systematic bits;
a second interleaver configured to interleave a first parity bit stream;
a third interleaver configured to interleave a second parity bit stream;
a virtual buffer configured to buffer the interleaved systematic bits, the interleaved first parity bit stream and the interleaved second parity bit stream when the number of bits of the interleaved systematic bits, the interleaved first parity bit stream and the interleaved second parity bit stream is not larger than the virtual buffer and configured to buffer a portion of the interleaved systematic bits, the interleaved first parity bit stream and the interleaved second parity bit stream when the number of bits of the interleaved systematic bits, the interleaved first parity bit stream and the interleaved second parity bit stream is larger than the virtual buffer; and
a rate matching unit configured to perform rate matching on at least one output of the virtual buffer.
5. The apparatus of claim 4 wherein the buffered portion includes all of the interleaved systematic bits.
6. The apparatus of claim 4 further comprising:
a bit collection unit configured to collect bits associated with the interleaved systematic bits, the interleaved first parity bit stream and the interleaved second parity bit stream.
7. The apparatus of claim 4 configured as a wireless transmit/receive unit (WTRU).
8. The apparatus of claim 4 configured as a Node B.