Signal decoding systems

摘要

We describe an ultra wideband (UWB) orthogonal frequency division multiplexed (OFDM) modified dual carrier modulation (MDCM) decoder comprising: first and second inputs to input first and second signals for first and second OFDM carriers; third and fourth inputs for respective third and fourth signals comprising channel quality estimates for the OFDM carriers; a set of integer arithmetic units coupled to said first, second, third and fourth inputs to form a set of intermediate terms; a first set of adders to form first and second sets of combinations of said intermediate terms, one for each MDCM coded bit value; a compare-select stage to select a first and second minimum valued said combination of said intermediate terms from said first and second set; and a subtracter to determine a log likelihood ratio (LLR) value for said bit from said first and second minimum valued combinations.

主权项

1. A modified dual carrier modulation (MDCM) decoder for MDCM decoding of an orthogonal frequency division multiplexed (OFDM) signal, the decoder comprising:
first and second inputs to input first and second signals dependent on signals from respective first and second carriers of said OFDM signal; third and fourth inputs for respective third and fourth signals responsive to respective first and second channel quality estimates for said first and second carriers; a set of arithmetic units coupled to said first, second, third and fourth inputs to form a set of intermediate terms comprising integer multiples of signals derived from said first, second, third and fourth signals; a first set of adders coupled to said set of arithmetic units to form first and second sets of combinations of said intermediate terms, one set for each binary value of a bit of MDCM coded data encoded on said first and second carriers; at least one compare-select stage coupled to said first set of adders to select a first minimum valued said combination of said intermediate terms from said first set of combination of said intermediate terms and to select a second minimum valued said combination of said intermediate terms from said second set of combination of said intermediate terms, wherein said first and second sets of combinations of said intermediate terms each define a set of distances from a set of constellation points in which said bit has a respective first and second said binary value; a subtractor to determine a log likelihood ratio (LLR) value for said bit from said first and second minimum valued combinations; and a multiply unit to rotate said first and second signals by a factor, and wherein said constellation points comprise points rotated by substantially the same factor; wherein said first and second signals are dependent on a product of signals from said respective first and second carriers and squared said respective first and second channel quality estimates, and wherein said third and fourth signals are derived from squared said respective first and second channel quality estimates.