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 performing rate matching in a wireless communication terminal, the method comprising:
interleaving a first bit stream to produce an interleaved first bit stream;
interleaving a second bit stream to produce an interleaved second bit stream;
interleaving a third bit stream to produce an interleaved third bit stream;
buffering the interleaved first bit stream, the interleaved second bit stream and the interleaved third bit stream in a virtual buffer; and
performing rate matching on at least one output of the virtual buffer.
2. The method of claim 1 wherein the interleaved first bit stream, the interleaved second bit stream and the interleaved third bit stream are buffered on a condition that the number of bits of the interleaved first bit stream, the interleaved second bit stream and the interleaved third bit stream is not larger than a size of the virtual buffer.
3. The method of claim 2 , further comprising:
buffering a portion of the interleaved first bit stream, the interleaved second bit stream and the interleaved third bit stream in the virtual buffer on a condition that the number of bits of the interleaved first bit stream, the interleaved second bit stream and the interleaved third bit stream is larger than a size of the virtual buffer.
4. The method of claim 3 wherein the buffered portion of the interleaved first bit stream, the interleaved second bit stream and the interleaved third bit stream includes all of the interleaved first bit stream.
5. The method of claim 1 , further comprising:
collecting bits associated with the interleaved first bit stream, the interleaved second bit stream and the interleaved third bit stream.
6. The method of claim 1 performed by a wireless transmit/receive unit (WTRU).
7. The method of claim 1 performed by a node B.
8. An apparatus for performing rate matching, the apparatus comprising:
a first interleaver configured to interleave a first bit stream to produce an interleaved first bit stream;
a second interleaver configured to interleave a second bit stream to produce an interleaved second bit stream;
a third interleaver configured to interleave a third bit stream to produce an interleaved third bit stream;
a virtual buffer configured to buffer the interleaved first bit stream, the interleaved second bit stream and the interleaved third bit stream; and
a rate matching unit configured to perform rate matching on at least one output of the virtual buffer.
9. The apparatus of claim 8 wherein the interleaved first bit stream, the interleaved second bit stream and the interleaved third bit stream are buffered on a condition that the number of bits of the interleaved first bit stream, the interleaved second bit stream and the interleaved third bit stream is not larger than a size of the virtual buffer.
10. The apparatus of claim 9 wherein the virtual buffer is further configured to buffer a portion of the interleaved first bit stream, the interleaved second bit stream and the interleaved third bit stream on a condition that the number of bits of the interleaved first bit stream, the interleaved second bit stream and the interleaved third bit stream is larger than a size of the virtual buffer.
11. The apparatus of claim 10 wherein the buffered a portion of the interleaved first bit stream, the interleaved second bit stream and the interleaved third bit stream includes all of the interleaved first bit stream.
12. The apparatus of claim 8 , further comprising:
a bit collection unit configured to collect bits associated with the interleaved first bit stream, the interleaved second bit stream and the interleaved third bit stream.
13. The apparatus of claim 7 configured as a wireless transmit/receive unit (WTRU).
14. The apparatus of claim 7 configured as a node B.