Method and apparatus for soft-in soft-out turbo code decoder
First Claim
1. A method for computing extrinsic likelihood values in a soft in soft out (SISO) decoder the method comprising:
- accepting a block of channel metrics and a priori values;
dividing the block of channel metrics and a priori values into sub blocks accepting an nth channel metric and an nth a priori value into an alpha (α
) computer;
computing an nth α
value from the nth channel metric and the nth a priori value using the nth α
value to compute the (n+1)th a value;
pushing α
values corresponding to the beginning of a sub block on a checkpoint stack until a beginning of the last sub block is reached;
pushing each of the α
values of the final sub block on the checkpoint stack;
popping each of the α
values of the last sub block from the checkpoint stack and combining them with beta (β
) values to form extrinsic likelihood values.
3 Assignments
0 Petitions
Accused Products
Abstract
Method and apparatus for Soft In Soft Out Turbo Code Decoder. Metrics are received by a decoder having SISO unit(s). The SISO unit computes all the alpha values corresponding to a block of data. Of the alpha values computed some alpha values, for example alpha values selected at regular intervals, corresponding to checkpoint values are pushed on a checkpoint stack. Alpha values are computed with some being saved as checkpoint values and some being discarded are computed until the computation reaches a predetermined distance from the end of the block of data. Once the predetermined distance is reached all alpha values are pushed on a computation stack. Once all the values corresponding to the values between the predetermined end of the block and the end of the block have been computed and placed in the computation stack they may be combined with beta values to produce extrinsic values. Once all the values have been used from the computation stack the next checkpoint value can be used to compute another computation stack of alpha values. The alpha values can then be combined with beta values to form extrinsic values and the process continued.
46 Citations
18 Claims
-
1. A method for computing extrinsic likelihood values in a soft in soft out (SISO) decoder the method comprising:
-
accepting a block of channel metrics and a priori values;
dividing the block of channel metrics and a priori values into sub blocks accepting an nth channel metric and an nth a priori value into an alpha (α
) computer;
computing an nth α
value from the nth channel metric and the nth a priori value using the nth α
value to compute the (n+1)th a value;
pushing α
values corresponding to the beginning of a sub block on a checkpoint stack until a beginning of the last sub block is reached;
pushing each of the α
values of the final sub block on the checkpoint stack;
popping each of the α
values of the last sub block from the checkpoint stack and combining them with beta (β
) values to form extrinsic likelihood values. - View Dependent Claims (2, 3)
-
-
4. A method for computing extrinsic likelihood values in a soft in soft out (SISO) decoder the method comprising:
-
accepting a block of channel metrics and a priori values;
dividing the block of channel metrics and a priori values into sub blocks accepting an nth channel metric and an nth a priori value into an alpha (α
) computer;
computing a nth α
value from the nth channel metric and the nth a priori value using the nth α
value to compute the (n+1)th a value;
pushing α
values corresponding to the beginning of a sub block on checkpoint stack until a beginning of the last sub block is reached;
pushing each of the α
values, once the beginning of the last sub block has been reached, on a first computation stack to form a first set of α
values;
popping α
values of the first set of α
values from the first computation stack once the last value of α
of the sub block has been computed and combining α
values from the first set of α
values with beta (β
) values to form extrinsic likelihood values. - View Dependent Claims (5, 6, 7, 8)
-
-
9. An apparatus for computing extrinsic likelihood values in a soft in soft out (SISO) decoder the apparatus comprising:
-
an α
computer that receives a priori values and channel metrics and computes α
values;
a checkpoint stack, for receiving α
checkpoint values from the α
computer;
a β
computer that receives a priori values and channel metrics and computes β
values; and
an extrinsic calculator that accepts the α
values provided by the α
computer and the β
values provided by the β
computer and produces extrinsic likelihood values;
a first computational stack that receives the α
values when a second computational stack is providing computational the α
values; and
the second computational stack that receives the α
values when the first computational stack is providing computational the α
values. - View Dependent Claims (10, 11, 12, 13, 14, 15)
-
-
16. A method of computing extrinsic values for a block of metrics and corresponding a priori values the method comprising:
-
computing α
values for the block of metrics and saving only values corresponding to the beginning of a sub block as checkpoint values on a checkpoint stack;
computing α
values between checkpoint values when such α
values are required wherein computing α
values and saving only checkpoint values on the checkpoint stack comprises;
computing all α
values;
selecting the values corresponding to the beginning of the sub block as the checkpoint values; and
pushing the selected values on the checkpoint stack.
-
-
17. A method of computing extrinsic values for a block of metrics and corresponding a priori values the method comprising:
-
computing α
values for the block of metrics and saving only values corresponding to the beginning of a sub block as checkpoint values on a checkpoint stack;
computing α
values between checkpoint values when such α
values are required, wherein computing α
values between checkpoint values when such α
values are required further comprises computing α
values and pushing them on a first stack such that the first stack is full when a second stack, which is providing α
values, is empty. - View Dependent Claims (18)
-
Specification