Orthogonal superposition coding for direct-sequence communications
View Patent ↗An adaptation to Carrier Interferometry synthesis and analysis provides for complex coding and decoding in a sliding window transform. Coding and decoding functionality can be extended to spatial processing in systems employing multiple transceiver elements. Poly-amplitude codes permit successive interference cancellation in spatial and frequency-domain processing. Handoffs in cellular systems are facilitated by selecting spectral/base station combinations that optimize link performance.
1. A multi-carrier communications transmitter including:
a sub-carrier allocator adapted to allocate at least one set of subcarriers for communication,
a pulse generator to be coupled to the sub-carrier allocator, the pulse generator adapted to generate a plurality of pulses having spectral components corresponding to the at least one set of subcarriers, wherein the pulse generator comprises:
a subcarrier weighting module to impress at least one set of complex weights generated from at least one carrier interferometry code onto the at least one set of subcarriers to generate a plurality of weighted subcarriers; and
a sub-carrier combiner adapted to combine the weighted subcarriers to produce the plurality of pulses;
a modulator to be coupled to at least one of the sub-carrier allocator and the pulse generator, the modulator adapted to impress at least one data symbol onto the plurality of pulses, and
a sequential pulse positioner to be coupled to at least one of the sub-carrier allocator, the pulse generator, and the modulator, the sequential pulse positioner to sequentially position the plurality of pulses.
2. The multi-carrier transmitter recited in claim 1 , further including a coder to be coupled to the modulator, the coder adapted to encode the at least one data symbol with at least one code selected from a set of codes consisting of a spread-spectrum code, a multiple-access code, a spectrum-shaping code, a channel code, and an encryption code.
3. The multi-carrier transmitter recited in claim 1 , further including a cyclic-prefix prepender to be coupled to the pulse generator or the sequential pulse positioner, the cyclic-prefix prepender adapted to provide the plurality of pulses with at least one of a set of guard intervals, the set consisting of a cyclic prefix, a cyclic postfix, and a sequence of zeros.
4. The multi-carrier transmitter recited in claim 1 , wherein the pulse generator is adapted to combine the at least one set of subcarriers to generate the plurality of pulses.
5. The multi-carrier transmitter recited in claim 1 , wherein at least one of the sub-carrier allocator, the pulse generator, the modulator, or the sequential pulse positioner is adapted to provide for multiple access with respect to at least one multiple-access technique.
6. The multi-carrier transmitter recited in claim 1 , wherein the sub-carrier allocator is configured to allocate the at least one set of subcarriers with respect to at least one of a set of conditions consisting of availability of spectrum, multipath fading, interference, quality of service, link priority, throughput requirements of at least one user, network load, and geographical location of at least one user.
7. The multi-carrier transmitter recited in claim 1 , wherein the sequential pulse positioner is configured to position the plurality of pulses to provide at least one of a set of pulse sequences, the set of pulse sequences consisting of an orthogonally positioned sequence of modulated pulses and a pseudo-orthogonally positioned sequence of modulated pulses.
8. The multi-carrier transmitter recited in claim 1 wherein the pulse generator is adapted to shape the plurality of pulses.
9. The multi-carrier transmitter recited in claim 1 , wherein the pulse generator is adapted to perform at least one spectrum-shaping function selected from the group consisting of weighting the at least one set of subcarriers and selecting a subset of the at least one set of subcarriers.
10. A method of transmitting data symbols, comprising:
generating at least one set of weighted, orthogonal sub-carriers spaced apart in frequency, said generating including weighting the sub-carriers using complex sub-carrier weights generated from one or more carrier interferometry (CI) codes; and
modulating the sub-carriers by sequential, overlapping data symbols to obtain modulated sub-carriers,
wherein the data symbols are mapped to a plurality of pulse positions within a sequence of modulated pulses with spectral components characterized by the sub-carriers.
11. The method of claim 10 , wherein said generating comprises:
generating time-domain values corresponding to said sub-carriers; and
converting the time-domain values into frequency-domain values.
12. The method of claim 11 , wherein said converting comprises performing a fast Fourier transform (FFT).
13. The method of claim 11 , wherein said generating further comprises:
selecting a subset of a set of possible sub-carriers.
14. The method of claim 11 , wherein said generating further comprises:
performing a frequency-domain to time-domain conversion of weighted frequency-domain values.