Carrier interferometry coding and multicarrier processing
View Patent ↗Carrier Interferometry (CI) codes include families of orthogonal polyphase codes that have no length restrictions and can be used for direct-sequence and multicarrier coding. Quasi-orthogonal CI channel codes simultaneously improve probability-of-error performance and increase throughput. CI filtering, which is based on CI codes, enables filtering and correlation operations via sampling and adding. CI codes simplify transform operations, such as Fourier transforms, by reducing or eliminating complex multiplications. CI filtering may be used to simplify synthesis and analysis functions and allow all physical-layer processing operations to be consolidated into simple sub-carrier selection and weighting operations. Thus, CI processing enables a software-defined baseband processor.
1. A CI filter adapted to separate at least one symbol impressed on at least one CI carrier of a plurality of CI carriers having a frequency spacing of f s , the filter including:
a sampler adapted to sample the CI signals at a sampling frequency including at least one frequency of a set, the set including a frequency f n of a desired CI carrier, a harmonic of f n , and a sub-harmonic of f n , the sampler generating a plurality of sample values and
a combiner coupled to the sampler, the combiner adapted to combine the samples, the combiner including a time base adapted to direct the combiner to combine at least one set of the samples collected over a symbol period of T s =1/f s to recover at least one received data symbol on the desired CI carrier.
2. The CI filter recited in claim 1 wherein the combiner includes a weighting system adapted to provide weights to the samples.
3. The CI filter recited in claim 1 wherein the combiner includes an optimal combiner.
4. The CI filter recited in claim 1 wherein at least one of the sampler and the combiner includes an in-phase and a quadrature-phase processor.
5. The CI filter recited in claim 1 further comprising a processor coupled to the combiner, the processor including at least one of a set of signal processors, the set including a channel decoder, a demodulator, a trellis decoder, an encryption decoder, a filter, a correlator, a multi-user detector, a decision system, a deinterleaver, a multi-user detector, a combiner, and an A/D converter.
6. The CI filter recited in claim 1 further comprising an anti-aliasing filter coupled to the sampler, the anti-aliasing filter adapted to pass a predetermined set of CI carriers.
7. The CI filter recited in claim 1 further comprising a frequency converter adapted to adjust a carrier offset frequency f o of the CI carriers.
8. A CI filter adapted to separate at least one symbol impressed on at least one CI carrier of a plurality of CI carriers having a frequency spacing of f s , the filter including:
a sampler adapted to sample the CI signals at a sampling frequency including at least one frequency of a set, the set including a frequency f n of a desired CI carrier, a harmonic of f n , and a sub-harmonic of f n , the sampler generating a plurality of sample values,
a storage device coupled to the sampler, the storage device adapted to collect the samples,
a sample selector coupled to the storage device, the sample selector adapted to select and combine one or more groups of samples, and
a symbol-interval selector coupled to the sample selector, the symbol-interval selector adapted to control the symbol interval over which the sample selector combines samples.
9. A digital CI filter adapted to separate at least one symbol impressed on at least one carrier of a multicarrier signal characterized by a frequency spacing of f s , the filter including:
a sampler adapted to collect a plurality of time-domain samples x k of the multicarrier signal, and
a combiner coupled to the sampler, the combiner adapted to combine the samples x k with respect to the equation
X
(
f
n
)
=
∑
k
=
0
K
-
1
x
k
Γ
(
t
,
f
n
)
over a period of T s =1/f s wherein Γ(t,f n ) expresses a step function having at least one predetermined frequency f n and X(f n ) represents a value associated with an information signal modulated onto carrier frequency f n resulting from a summation of the samples x k , over the period T s .