83 results about "Companding" patented technology

The invention discloses a method for suppressing the peak-to-average ratio of orthogonal frequency division multiplexing (OFDM) signals. The method includes the following steps that: (1) inputted serial data signals are converted into parallel signals at a signal transmitting end, so that a parallel signal sequence can be obtained; (2) the obtained parallel signal sequence is multiplied by a constructed precoding matrix, so that a peak-to-average ratio-suppressed precoded signals can be obtained; (3) a cyclic prefix is added to the precoded signals, companding processing is performed through using a segmented exponential companding function, so that the peak-to-average ratio of the companded signals can be further suppressed; and (4) parallel-to-serial conversion is performed on the companded signal sequence at the signal transmitting end, so that orthogonal frequency division multiplexing (OFDM) transmission signals can be obtained. The method of the invention is low in complexity, can significantly reduce the signal-to-average ratio of the signals without decreasing the bit error rate of the received signals, and can improve the performance of a communication system.

A method and system for improving buffer compression in automatic retransmission request (ARQ) systems includes both a compander and decompander for further processing data. A received data string k bits in length is first companded according to a predetermined companding scheme. The companded data string is reduced to a length of k−1 bits for more efficient storage. Upon receipt of a request for retransmission, the stored companded data string is loaded and decompanded back to a length of k bits. Once decompanded, the data string is combined with a retransmitted data string to produce a single data string with an increased likelihood of being correct. By companding the data string before storage, a smaller memory block can be used for the storage of the data string.

The invention discloses a companding method for reducing OFDM (orthogonal frequency division multiplexing) system peak-to-average ratio. By researching the relation between reduced PARP (peak-to-average power ratio) in signals and bit error ratio (BER) in the OFDM system to compromise the same, the novel companding method is provided. The companding algorithm is a method capable of reducing the PAPR of the OFDM system effectively, and the maximum PAPR of output signals can be set so as to meet the requirements of different systems. Further, according to different signal noise ratio (SNR), standard for inverse companding transformer is provided, and a better BER performance receiver can be obtained. Indicated by a simulation result, the companding method can remarkably reduce the PAPR of the OFDM system and has better spectrum characteristics and bit error ratio performance as compared with conventional methods.

A wireless microphone having a split-band audio frequency companding system is disclosed. The companding system includes a compression circuit in which one amplification element is utilized in connection with a number of frequency bands. Each frequency band has a rectifier and filter element associated therewith. High-pass filter elements are utilized in the higher frequency bands of the compression and expander circuits to reduce the transfer of low-frequency signals to the rectifier elements that process the low-frequency signals, thereby reducing undesirable modulations of a variable resistance element associated therewith.

The invention discloses a multifunctional hydraulic companding wheel which comprises a rotation shaft, a hub and an outer wheel. The multifunctional hydraulic companding wheel is characterized in that a hydraulic device capable of companding is connected between a shaft hole of the hub and the outer wheel, the hydraulic device comprises a hydraulic driving piece and a hydraulic support piece, the hydraulic driving piece comprises a hydraulic ring and a hydraulic mouth, the hydraulic ring is arranged on the outside of the shaft hole, and the hydraulic mouth is fixed on the hydraulic ring. The hydraulic support piece comprises a hydraulic cylinder, a hydraulic rod and a support fork, one end of the hydraulic cylinder is arranged on an excircle lateral side of the hydraulic ring and communicated with a hydraulic hole on the hydraulic ring, the other end of the hydraulic cylinder is sleeved with the hydraulic rod, one end of the support fork is connected with one end of the hydraulic rod, and the other end of the support fork is connected with an inside of the outer wheel. The excircle lateral side of the hub is fixed on the hydraulic cylinder, the outer wheel is in a same-arc-multiple-joint mode, and a high-strength arc metal piece is arranged on one side of the outer wheel connected with the support fork. The multifunctional hydraulic companding wheel is exquisite in design technique structure, various in function, convenient to operate, energy-saving, environment-friendly, durable and obvious in economic benefit and social benefit.

The present invention discloses a recoverable multi-linear companding method lowering a peak-to-average ratio of an ACO-OFDM system. A recoverable multi-linear companding unit is introduced in a transmit end, a corresponding de-companding module is introduced in a receive end, and a maximum posterior probability (MAP) rule is used for data recovery in the receive end. The method includes a first step that the transmit end performs recoverable multi-linear companding on an ACO-OFDM signal and then sends the signal; and a second step that the receive end uses the maximum posterior probability rule to detect a received signal and performs corresponding de-companding, so as to recover the sent data. According to the method, due to use of a special structure of an ACO-OFDM time domain signal, a problem that signal amplitudes before and after segmented linear change are not in one-to-one correspondence is solved, multi-linear companding is possible, a good PAPR suppression result is achieved with low complexity, and BER performance of a system is ensured.

The invention provides an improved scheme which combines a precoding technology with a companding technology through contrast with an existing peak-to-average ratio reducing technology according to the characteristic that an OFDM system applied to low-voltage power line communication has a high peak-to-average ratio. An OFDM peak-to-average ratio restraining method is provided according to the characteristics of OFDM signals, wherein a linear matrix is used for being multiplied by a transmitted OFDM signal, then, the OFDM signal is subjected to nonlinear companding so that the OFDM signal can be quite suitable for being used in a power line channel, and the effect on OFDM is reduced as much as possible. The implementation method of the OFDM signal is provided in detail, wherein a power line channel simulation platform which is set up through SIMULINK is used for simulation of the OFDM signal, and the simulation result indicates that the OFDM peak-to-average ratio restraining method can improve the peak-to-average ratio of the OFDM signal and reduce the error rate.

The invention discloses a digital frequency shift companding system, which comprises a local machine, a remote machine and an operation maintenance center, wherein the local machine is connected with a base station through a coupler; the local machine and the remote machine are connected with relay antennae and are connected with each other through transmission signals of the relay antennae; the remote machine is also connected with a retransmission antenna; and the local machine and the remote machine are connected with the operation maintenance center. The problems of signal coverage of complex terrains such as remote and mountain areas, hilly grounds, deserts, grasslands, large rivers, railway lines, forests and the like as well as coverage areas with tense urban frequency resources are solved effectively; a high-efficiency compact design is adopted, so that integration degree and overall efficiency are improved in a certain degree and size is further reduced; power capability is enhanced; simultaneously, cost is lowered and reliability is enhanced.

The invention discloses a method and a device for concealing lost packages, belonging to the field of network communication and comprising the following steps: generating a first composite signal according to a first decoded signal; determining the phase difference of the first composite signal and a second decoded signal; determining interpolation time points with gradually changed interpolation intervals according to the phase difference, and carrying out the wave shape companding of the first composite signal to obtain a first reconstruction signal; and reconstructing a lost signal between the first decoded signal and the second decoded signal by the first reconstruction signal. The invention solves the problem of discontinuous fundamental period frequency inside a lost frame and enhances the quality of a recovered audio-frequency signal, thereby solving the distortion problem caused by longer lost signal or longer lost frame.

The invention discloses a blind audio watermark implementing method based on logarithmic quantization index modulation, and belongs to the technical field of audio watermarks. The blind audio watermark implementing method is characterized by including sufficiently utilizing robustness of vector norms and imperceptibility of the logarithmic quantization index modulation based on mu-law companding; improving safety and robustness of a watermark by the aid of a chaos sequence encryption watermark image; converting the sectioned vector norms of wavelet approximate components into a transform domain via the mu-law companding; then embedding an encryption binary watermark image; and extracting the binary watermark image after the watermark is attacked. The audio watermark algorithm has the advantages of high volume, fine tone, imperceptibility and robustness and low complexity, the watermark still can be correctly extracted by the aid of the method under various watermark attack conditions, and accordingly amplitude attack can be effectively resisted by the method.

The invention provides an OFDM communication system and method based on companding. A bit stream input into a transmitting device forms OFDM signals after base band mapping and IFFT, and after companding and transformation are carried out on the OFDM signals, parallel-serial conversion is carried out on the OFDM signals and then the OFDM signals enter a power amplifier, and the amplified signals are mapped to a transmitting unit to be transmitted; a receiving device carries out serial-parallel conversion on received time-domain signals, the first time of FFT is carried out on the time-domain signals, the time-domain signals is transformed into frequency domain signals, channel information is obtained through channel estimation, channel equalization is carried out on the received frequency domain signals, the equalized signals are converted into a time domain through the IFFT, expanding transformation is carried out on the equalized signals, then the equalized signals are sent to an FFT module for demodulation and decoding, and finally the needed bit stream is obtained through the base band mapping. The OFDM communication system based on the companding can effectively solve the problem that constellation diagrams of a traditional companding OFDM communication system are scattered in a multipath channel, can effectively reduce an EVM value, and lowers the error rate.

The invention discloses a method for a hyperbolic tangent companding transform capable of decreasing the peak-to-average power ratio (PAPR) of an OFDM (orthogonal frequency division multiplexing) signal, mainly used for solving the problems of non-constant average power and high error rate in the prior art. The method comprises the following realization steps of: (1) performing a quadrature amplitude modulation on the data bit stream generated by an information source, performing a serial-to-parallel conversion then sampling; (2) performing an inverse fast Fourier transform (IFFT) on an over-sampling signal to obtain an original OFDM signal; (3) establishing a companding function based on a hyperbolic tangent function, performing a companding transform on the original OFDM signal, performing a parallel-to-serial conversion then transmitting the signal; (4) calculating the PAPR of a transmitting signal; (5) performing a serial-to-parallel conversion on a receiving signal, then performing a de-companding transform and a fast Fourier transform (FFT); (6) de-over-sampling a FFT signal to obtain an OFDM demodulation signal; and (7) performing a parallel-to-serial conversion and a quadrature amplitude demodulation on the OFDM demodulation signal, then counting an error rate. The method for a hyperbolic tangent companding transform capable of decreasing the PAPR of an OFDM signal disclosed by the invention can efficiently suppress the PAPR, remarkably decrease the error rate, and keep a constant average power; and the method can be widely applied to a new generation of broadband wireless OFDM communication system.

A method and system processes a speech signal. A fast Fourier transform is performed on a speech signal to produce a speech signal having a plurality of frequency bands in a frequency domain. For each frequency bands, filter the speech signal in the frequency domain with a spatial broadband filter, compress the broadband filtered speech signal, filter the compressed speech signal with a spatial narrowband filter; and, expand the narrowband filtered signal to an expanded signal

The invention discloses a solvent-free companding and forming mold for a porous propellant and a companding process, and mainly solves the existing problem of preparation of a porous modified dual-base propellant. The mold disclosed by the invention is machined by turning tempered steel 45# with the smoothness of 1.6 [mu]m, and the preparation is completed by using the mold, a pre-companding process and a conventional process through a soft material special for companding. The solvent-free companding and forming mold is applicable to porous dual-base and modified dual-base propellant filling.

The invention belongs to the technical field of wireless communication, and provides a method of reducing a PAPR of an OFDM (Orthogonal Frequency Division Multiplexing) system by an adaptive companding technique with a u rate, indexes and k transform combined. The method comprises the following steps: S1, serial-to-parallel conversion is carried out on data, inverse fast fourier transform processing is then carried out, and the optimal companding algorithm is selected; S2, according to the algorithm selected in the first step, a cyclic prefix with a corresponding length is added, and data are transmitted; S3, the type of the cyclic prefix receiving the data is detected, and the cyclic prefix is removed; and S4, according to the type of the cyclic prefix, a corresponding inverse transform algorithm is called to transform signals after the third step, and through fast fourier transform and parallel-to-serial conversion, the signals are demodulated and outputted. The scheme of the invention selects the optimal companding algorithm for each OFDM symbol, the cyclic prefix with a corresponding length is added for marking, and through detecting the length type of the cyclic prefix, a corresponding inverse companding algorithm is called for retrieving the signals. Compared with the traditional method, the method of the scheme of the invention can more effectively reduce the peak-to-average power ratio (PAPR), and larger system bit error rate overhead is not caused.