Statistical scaling of soft decisions before decoding
View Patent ↗A wireless-communications unit has a receiver chain including a codec decoding the output of a rake receiver. Soft decisions passing from the rake receiver to the codec are scaled. The scaling factor can be tuned by monitoring a function based on the cumulative probability distribution function of the scaled soft decisions.
1. A method of conditioning signal values being conveyed to a decoder in a wireless-communications network receiver, the method comprising steps of:
(a) scaling the signal values, outputted by a rake receiver, by a scaling factor;
(b) monitoring the probability distribution of the amplitudes of the scaled signal values including generating a parameter based on the probability distribution that is not grossly effected by amplitude saturation of the signal values; and
(c) adjusting the scaling factor according to the parameter obtained in step (b).
2. The method according to claim 1 , wherein the step (b) comprises calculating a complementary cumulative probability density function for a signal value magnitude.
3. The method according to claim 1 , wherein the step (b) comprises determining the fraction of a group of the scaled signal values that exceed a certain magnitude.
4. The method according to claim 1 , wherein the decoder is a 3G telecommunications bit-rate signal decoder.
5. A wireless-communications network receiver, comprising:
a scaling means for scaling signal values, outputted by a rake receiver, by a scaling factor so as to output scaled signal values to a decoder; and
a monitoring means for monitoring the probability distribution of amplitudes of the scaled signal values and for generating a parameter based on the probability distribution that is not grossly effected by amplitude saturation of the signal values;
wherein the scaling means adjusts the scaling factor according to the parameter generated by the monitoring means.
6. The wireless-communications network receiver according to claim 5 , wherein the monitoring means is adapted to calculate a complimentary cumulative probability density function for a signal value magnitude.
7. The wireless-communications network receiver according to claim 5 , wherein the monitoring means is adapted to determine fraction of a group of signal values the exceed a certain magnitude.
8. The wireless-communications network receiver according to claim 5 , wherein the decoder is a 3G telecommunications bit-rate signal decoder.