HIGHLY BANDWIDTH-EFFICIENT COMMUNICATIONS
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Abstract
A discrete multitone stacked-carrier spread spectrum communication method is based on frequency domain spreading including multiplication of a baseband signal by a set of superimposed, or stacked, complex sinusoid carrier waves. In a preferred embodiment, the spreading involves energizing the bins of a large Fast Fourier transform (FFT). This provides a considerable savings in computational complexity for moderate output FFT sizes. Point-to-multipoint and multipoint-to-multipoint (nodeless) network topologies are possible. A code-nulling method is included for interference cancellation and enhanced signal separation by exploiting the spectral diversity of the various sources. The basic method may be extended to include multielement antenna array nulling methods for interference cancellation and enhanced signal separation using spatial separation. Such methods permit directive and retrodirective transmission systems that adapt or can be adapted to the radio environment. Such systems are compatible with bandwidth-on-demand and higher-order modulation formats and use advanced adaptation algorithms. In a specific embodiment the spectral and spatial components of the adaptive weights are calculated in a unified operation based on the mathematical analogy between the spectral and spatial descriptions of the airlink.
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Citations
265 Claims
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1-245. -245. (canceled)
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246. A highly bandwidth-efficient communications method to optimize a multiple cell network for inter-cell interference, comprising:
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receiving at a first base station located in a first cell, a first spread signal comprising a first data signal spread over a plurality of discrete tones received over a first path from a first remote station located in said first cell, said first signal further comprising an interfering signal spread over said plurality of discrete tones received over an interference path from a second remote station located in a second cell;
adaptively despreading the signal received at the first base station by using first despreading codes that are based on the characteristics of the received spread signal over said first path and over said interference path;
spreading a second data signal at the base station with first spreading codes derived from said despreading codes based on a retrodirectivity of said first path and of said interference path, the first spreading codes distributing the second data signal over a plurality of discrete tones, forming a second spread signal that is selectively diminished in said interfering path to said second remote station;
transmitting said second spread signal from the first base station over said first path to said first remote station and transmitting the second signal selectively diminished over said interference path to said second remote station;
receiving at said second remote station said selectively diminished second spread signal;
adaptively despreading the selectively diminished second signal received at the second remote station by using second despreading codes that are based on the characteristics of the received second signal over said interference path;
spreading a third data signal at the second remote station with second spreading codes derived from said second despreading codes based on a retrodirectivity of said interference path, the second spreading codes distributing the third data signal over a plurality of discrete tones, forming a third spread signal that is selectively diminished in said interfering path to said first base station; and
transmitting said selectively diminished third spread signal from the second remote station over said interference path to said first base station. - View Dependent Claims (247, 248, 249, 250, 251, 252, 253, 254, 255)
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256. A highly bandwidth-efficient communications system to optimize a multiple cell network for inter-cell interference, comprising:
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means for receiving at a first base station located in a first cell, a first spread signal comprising a first data signal spread over a plurality of discrete tones received over a first path from a first remote station located in said first cell, said first signal further comprising an interfering signal spread over said plurality of discrete tones received over an interference path from a second remote station located in a second cell;
means for adaptively despreading the signal received at the first base station by using first despreading codes that are based on the characteristics of the received spread signal over said first path and over said interference path;
means for spreading a second data signal at the base station with first spreading codes derived from said despreading codes based on a retrodirectivity of said first path and of said interference path, the first spreading codes distributing the second data signal over a plurality of discrete tones, forming a second spread signal that is selectively diminished in said interfering path to said second remote station;
means for transmitting said second spread signal from the first base station over said first path to said first remote station and transmitting the second signal selectively diminished over said interference path to said second remote station;
means for receiving at said second remote station said selectively diminished second spread signal;
means for adaptively despreading the selectively diminished second signal received at the second remote station by using second despreading codes that are based on the characteristics of the received second signal over said interference path;
means for spreading a third data signal at the second remote station with second spreading codes derived from said second despreading codes based on a retrodirectivity of said interference path, the second spreading codes distributing the third data signal over a plurality of discrete tones, forming a third spread signal that is selectively diminished in said interfering path to said first base station; and
means for transmitting said selectively diminished third spread signal from the second remote station over said interference path to said first base station. - View Dependent Claims (257, 258, 259, 260, 261, 262, 263, 264, 265)
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Specification