Jonathan Lloyd Cromwell

US Patent:

6484283, Nov 19, 2002

Filed:

Dec 30, 1998

Appl. No.:

09/223473

Inventors:

Karen J. Stephen - Carlsbad CA
Hon W. Lam - Carlsbad CA
Jonathan Cromwell - Solana Beach CA

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

H03M 1303

US Classification:

714786

Abstract:

The present invention is a method and apparatus for encoding and decoding a turbo code. In the encoder, an interleaver interleaves and delays a block of input bits to generate interleaved input bits and delayed input bits. A first encoder generates a first, second, and third encoded bits. A second encoder generates a fourth encoded bit. A symbol generator generates a plurality of symbols which correspond to the input bits. In a decoder, a sync search engine detects a synchronizing pattern and extracts symbols from the encoded bits. An input buffer is coupled to the sync search engine to store the extracted symbols. A first soft-in-soft-out (SISO ) is coupled to the input buffer to generate a first soft decision set based on the extracted symbols. An interleaver is coupled to the SISO to interleave the first soft decision set. A second soft-in-soft-out (SISO ) is coupled to the input buffer and the interleaver to generate a second soft decision set.

US Patent:

60146826, Jan 11, 2000

Filed:

May 30, 1997

Appl. No.:

8/866590

Inventors:

Karen J. Stephen - Carlsbad CA
Alok Gupta - Encinitas CA
Jonathan Cromwell - Cardiff By The Sea CA

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G06F 1710

US Classification:

708313

Abstract:

Methods and apparatus for variable-rate down-sampling filters for discrete-time sampled systems using a fixed sampling rate are disclosed. The Variable Rate Down-Sampling Filter allows a continuous range of sample rates to be derived from input samples at a fixed rate. The output rate does not have to be related to the fixed input rate in any integral or rational way, and in fact, the output rate can vary in time such as will occur when tracking a signal received from a station using a different timebase. A fixed sampling rate at the A/D Converter greatly simplifies the design of the analog front end. A single anti-aliasing filter can be designed and precisely matched to the fixed sampling rate. Used with a frequency-modulated numerically controlled oscillator (NCO), the Down-Sampling Filter keeps the entire frequency-synthesis and time-tracking loop in the digital domain. The need for an analog time-tracking loop to adjust the sampling instant at the A/D converter is eliminated.