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3558 results about "Spread spectrum" patented technology

In telecommunication and radio communication, spread-spectrum techniques are methods by which a signal (e.g., an electrical, electromagnetic, or acoustic signal) generated with a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth. These techniques are used for a variety of reasons, including the establishment of secure communications, increasing resistance to natural interference, noise and jamming, to prevent detection, and to limit power flux density (e.g., in satellite down links).

Narrow-band interference rejecting spread spectrum radio system and method

A spread spectrum receiver and method having narrow-band interference rejection of narrow-band jamming signals using digital signal processing frequency domain techniques. The method performed in the receiver includes transforming the received signal to a frequency domain signal and identifying narrow-band interference components in the frequency domain signal; suppressing the identified narrow-band interference components by excising the identified narrow-band interference components from the frequency domain signal to produce an interference excised signal in the frequency domain, and storing in a memory frequencies corresponding to the identified narrow-band interference components; synchronizing a receiver code to a transmitter code in the frequency domain using the interference excised signal; generating coefficients for a time domain filter that includes notches at the frequencies corresponding to the excised narrow-band interference components and that jointly despreads and rejects narrow-band interference from the excised frequencies; applying the coefficients generated in the preceding step to the time domain filter, and despreading and filtering in real time in the time domain the received signal using the applied coefficients.

Remote radio operating system, and remote operating apparatus, mobile relay station and radio mobile working machine

The present invention relates to remote radio control technology, and a remote radio control system includes a radio movable working machine (1), a remote control apparatus (6A), and a movable repeater station (7). First bidirectional communication means (31, 71) having a high radio wave directionality and first automatic tracking means (32, 71A) are provided between the working machine (1) and the repeater station (7), and second bidirectional communication means (63, 76) having a high radio wave directionality, second automatic tracking means (63A, 76A), and emergency spread spectrum bidirectional communication means (64, 87) for enabling bidirectional communication between the remote control apparatus (6A) and the repeater station (7) when communication by the second bidirectional communication means (63, 76) is impossible are provided between the remote control apparatus (6A) and the repeater station (7). Consequently, even if communication between the working machine (1) and the movable repeater station (7) is disabled, each of the working machine (1) and the repeater station (7) is permitted to perform a minimum necessary operation, and any other person than those skilled in actual controlling operation of the working machine (1) can perform remote control easily.

Emergency location transceivers (ELT)

Emergency Location Transceivers (ELT) and communication transceivers (transmitters and receivers) for reception and demodulation of location finder signals, Global Positioning System (GPS) satellite signals and non GPS satellite location finder and other location finder signals. The received location finder signals are demodulated to location finder baseband signals. Baseband signal processors for processing single or a plurality of input signals for providing Orthogonal Frequency Division Multiplex (OFDM) baseband signals, filtered signals, cross-correlated shaped in-phase and quadrature-phase baseband signals and spread spectrum signals. Signal modulators for modulating the processed signals and for providing the modulated signals to the signal transmitter for transmission of the modulated signals. Emergency receiver systems for reception, demodulation and processing of the modulated transmitted signals. Certain emergency receiver embodiments, such as receivers of calls made to emergency call number 911 contain two or more receive antennas for reception and processing of the transmitted modulated signal. In certain embodiments emergency receiver systems have two or more receive antennas operated in a diversity mode, for reception and processing of the transmitted modulated signal.

Highly bandwidth-efficient communications

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.

Systems and methods for communicating spread spectrum signals using variable signal constellations

According to embodiments of the invention, a communications system includes an error correction encoder that error correction encodes a bitstream according to an error correction code. The system also includes a variable symbol generator that generates a symbol according to a selected one of a plurality of selectable signal constellations from a group of bits of the error correction encoded bitstream. The system further includes a spreader that spreads the symbol according to a spreading code, and a transmitter that transmits the spread symbol in a communications medium. Preferably, the plurality of selectable signal constellations includes at least two signal constellations of different order. In other embodiments, the error correction encoder includes a variable error-correction encoder that encodes the bitstream according to a selected error correction code of a plurality of selectable error correction codes. In still other embodiments, the spreader includes a variable spreader that spreads the symbol according to a selected spreading code of a plurality of selectable orthogonal spreading codes including at least two spreading codes of different lengths. A controller may select the error correction code used by the variable error correction encoder, the signal constellation used by the variable symbol generator, and the spreading code used by the variable spreader to provide a desired information transmission rate for the bitstream. Related methods are also described.
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