Soft metrics compressing method

1. A method of processing in a receiver a signal that has been encoded and interleaved in a transmitter comprising:

receiving the signal;

process the signal to obtain a stream of soft metrics representing bit probability of symbols in a predetermined constellation, wherein the stream of the soft metrics are divided into a plurality of groups of the soft metrics;

applying to the groups of the soft metrics a compression operation that preserves a total length of the groups of soft metrics, wherein the groups of the soft metrics are related to a same constellation symbol; and

rearranging the stream of compressed soft metrics so as to inverse the interleaving done in the transmitter,

wherein the compression operation generates a plurality of compressed codes, and the method further comprises a step of substitution of the compressed codes with other codes of shorter length representing a different symbol in the predetermined constellation when the total length of the groups of the soft metrics exceeds a determined value.

2. The method of claim 1 , further comprising

decompressing the compressed soft metrics;

processing the decompressed soft metrics in a decoder to reconstruct a transmitted message.

3. The method of claim 1 , comprising a step of quantizing the soft metrics prior to an application of said compression operation.

4. The method of claim 3 , wherein the compression operation includes the application of an entropy code.

5. The method of claim 3 , wherein the compression operation generates a prefix code.

6. The method of claim 1 , wherein said soft metrics are represented as fixed-point numbers.

7. The method of claim 3 , wherein the quantizing operation generates a constant number of bits for the groups of the soft metrics.

8. The method of claim 3 , where in the quantizing operation generates different number of bits for each soft metric relative to the same constellation symbol.