Enhanced fading and random pattern error protection for dynamic bit allocation sub-band coding

A method for communicating signals using sub-band coding, comprising the steps of:

• a. generating for signal samples from plural frequency bands, a band energy bit sequence representing an individual band energy value for each of the plural frequency bands;
• b. protecting one of the significant bits in some or all of the band energy bit sequences;
• c. transmitting and receiving protected bit sequences with corresponding sub-band coded signal samples;
• d. determining for a received speech frame, a number of bit errors in the protected bits;
• and
• e. replacing the energy values for a current speech free if the number of bit errors exceeds a preset number for less than a predetermined number of speech frames including replacing an individual band energy value with a previous corresponding band energy value if the previous corresponding band energy value is less than a threshold energy value, and replacing an individual band energy value with an average band energy value if the previous corresponding band energy value exceeds the threshold energy value.

A method for communicating signals using sub-band coding, comprising the steps of:

• a. generating for signal samples from plural frequency bands, a band energy bit sequence representing an individual band energy value for each of the plural frequency bands;
• b. protecting one of the significant bits in some or all of the band energy bit sequences;
• c. transmitting and receiving protected bit sequences with corresponding sub-band coded signal samples;
• d. determining a bit error in protected bits of a received bit sequence;
• e. for each band, developing a confidence score that represents a likelihood that the received protected bits actually represent a corresponding transmitted protected bit;
• f. examining individual confidence scores for each band energy;
• g. determining if a first condition of an individual confidence score exceeding a first preset value or a second condition of an individual band energy exceeding a second preset value exists;
• h. calculating a replacement energy value if either the first or the second condition exists;
• and
• i. substituting the replacement energy value for the band energy.

In a sub-band coded speech communications system where bits corresponding to sub-band energy levels are protected before transmission, a method for compensating for random and fading errors corrupting the protected bits, comprising the steps of:

• determining if a protected bit error rate for a first received speech frame exceeds a threshold;
• determining if a protected bit error rate for a second received speech frame exceeds the threshold;
• zeroing speech samples for the second or a subsequent received speech frame if the protected bit error rates determined for the first and second received speech frames exceed the threshold:
• and
• if the protected bit error rates for the first and second received speech frames do not both exceed the threshold, replacing band energies for the second speech frame with corresponding band energies of a previous speech frame if the previous band energies are below a preset value.

In a sub-band coded speech communications system where bits corresponding to sub-band energy levels are protected before transmission, a method for compensating for random and fading errors corrupting the protected bits, comprising the steps of:

• determining if a protected bit error rate for a first received speech frame exceeds a threshold:
• determining if a protected bit error rate for a second received speech frame exceeds the threshold:
• zeroing speech samples for the second or a subsequent received speech frame if the protected bit error rates determined for the first and second received speech frames exceed the threshold;
• and
• if the protected bit error rates for the first and second received speech frames do not both exceed the threshold, replacing individual band energies for the second or a subsequent speech frame which are corrupted or other wise unreliable with replacement energy values below a preset value.