36 results about "Carrier interferometry" patented technology

Carrier Interferometry (CI) provides wideband transmission protocols with frequency-band selectivity to improve interference rejection, reduce multipath fading, and enable operation across non-continuous frequency bands. Direct-sequence protocols, such as DS-CDMA, are provided with CI to greatly improve performance and reduce transceiver complexity. CI introduces families of orthogonal polyphase codes that can be used for channel coding, spreading, and/or multiple access. Unlike conventional DS-CDMA, CI coding is not necessary for energy spreading because a set of CI carriers has an inherently wide aggregate bandwidth. Instead, CI codes are used for channelization, energy smoothing in the frequency domain, and interference suppression. CI-based ultra-wideband protocols are implemented via frequency-domain processing to reduce synchronization problems, transceiver complexity, and poor multipath performance of conventional ultra-wideband systems. CI allows wideband protocols to be implemented with space-frequency processing and other array-processing techniques to provide either or both diversity combining and sub-space processing. CI also enables spatial processing without antenna arrays. Even the bandwidth efficiency of multicarrier protocols is greatly enhanced with CI. CI-based wavelets avoid time and frequency resolution trade-offs associated with conventional wavelet processing. CI-based Fourier transforms eliminate all multiplications, which greatly simplifies multi-frequency processing. The quantum-wave principles of CI improve all types of baseband and radio processing.

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.

Techniques for reducing peak-to-average power in multicarrier transmitters employ peak cancellation with subcarriers that are impaired by existing channel conditions. The use of Carrier Interferometry (CI) coding further improves the effectiveness of peak reduction. CI coding can also be impressed onto pulse sequences in the time domain, which enhances spectral selection and facilitates peak-power control.

A wireless communication system transmits data on multiple carriers simultaneously to provide frequency diversity. Orthogonality is provided by carrier interference, which causes a narrow pulse in the time domain corresponding to each transmitted data symbol. Selection of the frequency separation and phases of the carriers controls the timing of the pulses. Equivalently, pulse waveforms may be generated from an appropriate selection of polyphase sub-carrier codes. Time division of the pulses and frequency division of the carriers may be employed for multiple access. Received signals are processed by combining frequency-domain components corresponding to a desired user's allocated carriers. Individual data symbols are processed by providing polyphase decoding, matched filtering, or time-domain shifting the received carriers. Carrier Interferometry components may be used to build various signals corresponding to other transmission protocols.

An adaptation to Carrier Interferometry synthesis and analysis provides for frequency-varying subcarriers. Coding and decoding functionality can be extended to orthogonal chirped and frequency-hopped waveforms. Poly-amplitude codes permit successive interference cancellation in spatial and frequency-domain processing. Dynamic re-sectorization and bandwidth exchange are facilitated by subcarrier allocation.

The invention discloses a visible light communication system and a visible light communication method thereof, which relate to the technical field of wireless optical communication. The system comprises a transmitter and a receiver. An input signal is converted into an optical signal by the transmitter, the optical signal is transmitted to the receiver by a wireless optical channel, and the receiver converts the optical signal into an electrical signal and outputs the electrical signal. The transmitter comprises a carrier interferometry orthogonal frequency division multiplexing (CI-OFDM) modulation circuit and a white light-emitting diode (LED) drive circuit which are connected, wherein the CI-OFDM modulation circuit is used for performing CI-OFDM modulation on data input by a user; and the white LED drive circuit is used for converting the electrical signal generated by the CI-OFDM modulation circuit into the optical signal. The receiver comprises a PD photoelectric detector and a CI-OFDM demodulation circuit which are connected, wherein the PD photoelectric detector is used for performing P/D conversion on the received optical signal to convert the optical signal into the electrical signal; and the CI-OFDM demodulation circuit is used for performing CI-OFDM demodulation on the received data. By the system and the method, the transmission quality of the visible light communication system can be effectively improved, and the peak-to-average power ratio of an OFDM transmitted signal can be reduced.

Frequency-dependent cancellation separates a plurality of interfering signals received by a plurality of receivers. Received wideband single-carrier signals or multicarrier signals are separated into a plurality of narrowband subcarriers. Sub-carrier frequencies and frequency-band characteristics may be selected with respect to channel characteristics (e.g., coherence bandwidth, interference, etc.). A cancellation circuit provides complex weights to the sub-carrier components. Weighted components associated with each sub-carrier frequency are combined to separate a plurality of interfering signals. Optionally, a plurality of the separated subcarriers may be combined to reconstruct at least one transmitted single-carrier signal from a plurality of frequency components. Combining may include decoding, such as to reconstruct a coded sequence of data symbols transmitted via direct-sequence coding, code division multiple access (CDMA), multicarrier CDMA, carrier interferometry (CI), CI coding, or coded orthogonal frequency division multiplexing.

Transmission waveforms are synthesized from orthogonal subcarriers using appropriate combinations of complex sub-carrier codes. This allows conventional single-carrier signaling (such as GSM and CDMA transmission protocols) to be generated and received using a multicarrier platform that is similar to OFDM. Carrier interferometry provides unprecedented bandwidth efficiency and enables substantial improvements in interference rejection, power efficiency, and system versatility.

Carrier Interferometry (CI) provides wideband transmission protocols with frequency-band selectivity to improve interference rejection, reduce multipath fading, and enable operation across non-continuous frequency bands. Direct-sequence protocols, such as DS-CDMA, are provided with CI to greatly improve performance and reduce transceiver complexity. CI introduces families of orthogonal polyphase codes that can be used for channel coding, spreading, and/or multiple access. Unlike conventional DS-CDMA, CI coding is not necessary for energy spreading because a set of CI carriers has an inherently wide aggregate bandwidth. Instead, CI codes are used for channelization, energy smoothing in the frequency domain, and interference suppression. CI-based ultra-wideband protocols are implemented via frequency-domain processing to reduce synchronization problems, transceiver complexity, and poor multipath performance of conventional ultra-wideband systems. CI allows wideband protocols to be implemented with space-frequency processing and other array-processing techniques to provide either or both diversity combining and sub-space processing. CI also enables spatial processing without antenna arrays. Even the bandwidth efficiency of multicarrier protocols is greatly enhanced with CI. CI-based wavelets avoid time and frequency resolution trade-offs associated with conventional wavelet processing. CI-based Fourier transforms eliminate all multiplications, which greatly simplifies multi-frequency processing. The quantum-wave principles of CI improve all types of baseband and radio processing.

The invention discloses a zero padding mode-based carrier interferometry orthogonal frequency division multiplexing (CI-OFDM) communication method, and belongs to the field of communication technology. The conventional CI-OFDM system eliminates intersymbol interference by using a cyclic prefix (CP) mode when adding a guard interval so as to remove the data of the cyclic prefix at a receiving end; but the processing method causes loss of part of received information so as to reduce the bit error rate of the system. The zero padding mode is adopted as the guard interval during the data transmission and detection is performed by combining the data symbol of the guard interval in the data receiving process, so the frequency diversity gain is fully utilized and the bit error rate of the system is improved.

The invention discloses an interference processing method based on a carrier interferometry orthogonal frequency division multiplexing (CI-OFDM) system. The method is characterized in that a transceiver structure of the CI-OFDM system carries out OFDM receipt after a transceiver receives data so as to obtain frequency domain data after the OFDM receipt; and an interference detection result, the ratio that interference bandwidth accounts for total communication channel bandwidth as well as interference power are utilized to process the frequency domain data. By adopting the characteristic thatthe CI-OFDM is utilized to expand each path of low-speed parallel data to all sub-carries via using orthogonal CI codes, according to performance differences exerted by resisting different interferences via using the CI-OFDM under minimum mean squared error (MMSE) equilibrium, a traditional CI-OFDM is introduced under the MMSE equilibrium; the CI-OFDM performing zero setting on interfered sub-carriers at a receiving end and the CI-OFDM with consideration of the interference power of the MMSE equalizer carry out self-adaptive processing on power and bandwidth of different interference signals,thus effectively eliminating the interferences.

An adaptive algorithm is tailored to fit the local fringe frequency of single-frame spatial-carrier data under analysis. Each set of data points used sequentially by the algorithm is first processed with a Fourier Transform to find the local frequency of the fringes being analyzed. That information is then used to adapt the algorithm to the correct phase step thus calculated, thereby optimizing the efficiency and precision with which the algorithm profiles the local surface area. As a result, defects are identified and measured with precision even when the slope of the surface varies locally to the point where the algorithm without adaptive modification would not be effective to measure them. Once so identified, the defects may be measured again locally with greater accuracy by conventional temporal PSI.

The invention provides a visible light communication (VLC) system optical orthogonal frequency division multiplexing (OOFDM) modulation method based on hadamard matrix amplification, which keeps the orthogonality characteristics of a matrix by utilizing hadamard matrix amplification, and forms an HICI code by performing the hadamard matrix amplification on a carrier interferometry (CI) spread code, so that code element interval of the HICI code and the CI spread code keeps consistent. Compared with the traditional CI spread code, the HICI code does not cause reduction of the code element interval along with the increasing of the number of subcarriers, and simultaneously has the capability of reducing OOFDM-based VLC system signal PAPR and the capability of withstanding PSN. Based on theoretical analysis and simulation results, the HICI code provided by the VLC system OOFDM modulation method based on hadamard matrix amplification, which is provided by the invention, improves the capability of the original CI spread code to withstand the PSN and simultaneously has the capability of reducing the OOFDM communication system PAPR.

The invention discloses an adaptive modulation method for optimizing a peak-to-average power ratio (PAPR). The method provided by the invention is improved on the basis of a traditional Greedy adaptive bit allocation method, and m bits are allocated to a subcarrier every time, thus, the complexity in computing is reduced; meanwhile, the modulation ways of the m number of bits can also be flexibly matched; next, CI-OFDM (Carrier Interferometry-Orthogonal Frequency Division Multiplexing) is regarded as a power linear amplitude limiting way, N subcarriers are divided into subcarriers subjected to CI expansion and subcarriers not subjected to CI expansion through a single-threshold step or a double-threshold step, the PAPR is limited by a power threshold, and respective advantages of OFDM and the CI-OFDM are combined, so that the optimization of transmitting power and the PAPR is realized under the condition that the service quality and the transmission rate are fixed.

The invention provides a carrier interferometry orthogonal frequency division multiplexing (CI-OFDM) communication method based on consideration of inter-carrier interference (ICI) influences under time-varying fading channels, belonging to the technical field of communications. The method comprises the steps as follows: a sender sequentially carries out digital modulation and carrier interference code extension on information source data, then transforms symbols of the extended data to time domains by inverse discrete Fourier transform (IDFT) at an N point, and finally performs OFDM transmission after cyclic prefixes are added; after a receiver receives the data, the receiver gets rid of the cyclic prefixes, and transforms symbols of the received data to frequency domains by discrete Fourier transform (DFT) at the N point; the received OFDM signals are detected, and the influences caused by the ICI are considered in the detection so as to obtain estimated values of data symbols whichare subjected to the digital modulation; and carrier interference code de-extension and the digital modulation are sequentially carried out on the modulated data symbols by the DFT at the N point so as to obtain information sink bit data. In the method, because the ICI influences are considered in the signal detection, and combined noises and the data symbols are taken as receiving signals, thus the minimum mean square error (MMSE) equilibrium can be performed more accurately. Compared with a traditional OFDM communication method, the method provided by the invention has the advantages of thegrains produced by frequency multipath diversity and the improvement of error rate performance gains and channel estimation accuracy due to reduction of the ICI.