Method and apparatus for multiple access between transceivers in wireless communications using OFDM spread spectrum
DC CAFCFirst Claim
1. A transceiver including a transmitter for transmitting electromagnetic signals and a receiver for receiving electromagnetic signals having amplitude and phase differential characteristics, the transmitter comprising:
- an encoder for encoding information;
a wideband frequency division multiplexer or multiplexing the information onto wideband frequency channels;
a low pass filter;
a local oscillator for upconverting the multiplexed information for transmission;
a processor for applying a fourier transform to the multiplexed information to bring the information into the time domain for transmission;
further including, in the receiver of the transceiver;
a bandpass filter for filtering the received electromagnetic signals;
a local oscillator for downconverting the received electromagnetic signals to produce output;
a sampler for sampling the output of the local oscillator to produce sampled signals to the channel estimator;
a channel estimator for estimating one or both of the amplitude and the phase differential of the received signals to produce as output one or both of an estimated amplitude and an estimated phase differential respectively; and
a decoder for producing signals from the sampled signals and the output from the channel estimator.
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Abstract
A method for allowing a number of wireless transceivers to exchange information (data, voice or video) with each other. A first frame of information is multiplexed over a number of wideband frequency bands at a first transceiver, and the information transmitted to a second transceiver. The information is received and processed at the second transceiver. The information is differentially encoded using phase shift keying. In addition, after a pre-selected time interval, the first transceiver may transmit again. During the preselected time interval, the second transceiver may exchange information with another transceiver in a time duplex fashion. The processing of the signal at the second transceiver may include estimating the phase differential of the transmitted signal and pre-distorting the transmitted signal. A transceiver includes an encoder for encoding information, a wideband frequency division multiplexer for multiplexing the information onto wideband frequency voice channels, and a local oscillator for upconverting the multiplexed information. The apparatus may include a processor for applying a Fourier transform to the multiplexed information to bring the information into the time domain for transmission.
1016 Citations
12 Claims
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1. A transceiver including a transmitter for transmitting electromagnetic signals and a receiver for receiving electromagnetic signals having amplitude and phase differential characteristics, the transmitter comprising:
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an encoder for encoding information; a wideband frequency division multiplexer or multiplexing the information onto wideband frequency channels; a low pass filter; a local oscillator for upconverting the multiplexed information for transmission; a processor for applying a fourier transform to the multiplexed information to bring the information into the time domain for transmission; further including, in the receiver of the transceiver; a bandpass filter for filtering the received electromagnetic signals; a local oscillator for downconverting the received electromagnetic signals to produce output; a sampler for sampling the output of the local oscillator to produce sampled signals to the channel estimator; a channel estimator for estimating one or both of the amplitude and the phase differential of the received signals to produce as output one or both of an estimated amplitude and an estimated phase differential respectively; and a decoder for producing signals from the sampled signals and the output from the channel estimator. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for allowing a number of wireless transceiver to exchange frames of information, the method comprising the steps of:
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multiplexing a first frame of information over a number of frequencies within a frequency band at a first transceiver to produce multiplexed information; processing the multiplexed information at the first transceiver, transmitting the processed information to a second transceiver using a carrier frequency fc; receiving the processed information at the second transceiver; and processing the processed information at the second transceiver during a first time interval; in which the frequency band is formed from a first set of K1 points and a pair of tall slots each having K2 points, each of the points being separated by a frequency range of Δ
f, the second transceiver has a maximum expected clock error χ
T, where T is the duration of one time domain sample, the information is multiplexed over a number M of levels, and K1 selected such that 2π
χ
/K1<
π
/M, whereby the width of the frequency band is chosen so that neither carrier nor clock recovery is required at the second transceiver. - View Dependent Claims (8, 9, 10, 11, 12)
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Specification