136results about How to "Frequency synchronization" patented technology

The invention relates to an IEEE 1588 based accurate clock synchronization protocol system and a synchronization method thereof, belonging to the technical field of network information transmission. By adopting the invention, a main clock carries an accurate timestamp while sending a synchronization message, and a follow message is not required to be sent, thus greatly reducing communication bandwidth required for realizing clock synchronization. Meanwhile a frequency adjustable clock counter is constructed, and clock synchronization algorithm is combined, so as to realize frequency compensation function and achieve high accuracy clock synchronization requirement.

The present invention discloses a method for modulating digital television ground broadcasting transmitter based on insertion training sequence and LDPC code, wherein the method comprises the following steps: 1) forming an FFT coded data block with the input bit flow through LDPC coding; 2) switching the FFT coded data block to a time domain discrete coded data sample block through IFFT; 3) forming a complex training sequence discrete sample block with a mode that a training sequence is used as a real part sequence and an operational indicator sequence is used as an imaginary part sequence; 4) continuously repeating the complex training sequence for four times to form a time domain insertion training sequence discrete sample block; 5) directly overlapping the time domain discrete coded data sample block with the time domain insertion training sequence discrete sample block for forming a time domain insertion training sequence coded data block; 6) inserting a circulating prefix into the time domain insertion training sequence coded data block for forming a signal frame; 7) forming a signal frame pulse with a square-root raised cosine roll-off filter; and 8) upconverting the baseband signal to the carrier.

The invention relates to a method for synchronizing the time and the frequency of a motor-driven configured bistatic radar. The frequency and the time between a receiving station and a transmitting station of the bistatic radar can be realized by utilizing the characteristics of long-term stability, low phase noise and low stray; when the receiving station and the transmitting station are deployed separately, the real-time statistics of time synchronization errors of the receiving station and the transmitting station are completed on the basis of pulses per second of a navigation satellite; when the time synchronization errors exceed a limit value and the state of the pulses per second of the navigation satellite is normal, time resynchronization between the receiving station and the transmitting station is completed in a navigation satellite time service synchronization mode; the receiving station and the transmitting station enter a timekeeping synchronization state again. The method is applicable to synchronizing the time and the frequency of the motor-driven configured bistatic radar, and has the advantages of short erecting and withdrawing time, high maneuverability, high working stability and the like. Before the receiving station and the transmitting station are deployed separately, the modes of direct time contrast synchronization and long-time autonomous timekeeping maintenance are adopted, and have the advantages of being not limited by the navigation satellite and not impacted by electromagnetic environment in wartime.

The invention discloses a device and a method for synchronizing system frequency in a packet transport network, and relates to a packet transport network in optical communication. The system frequency synchronizing device comprises a microcomputer processor, a field programmable gate array (FPGA) processing module, a clock integrated circuit, a packet transport network service disk, a synchronous state byte extracting module, a synchronous state byte generating module, a phase locked loop circuit, an external clock input circuit, a high stable crystal oscillator, a clock distributing circuit, a HDB3 coding module and an external clock output circuit, wherein the FPGA processing module comprises a preceding stage preselector, a priority level control module, a first selector, a second selector and a third selector. By the device and method, the system frequency in the whole packet transport network can be synchronized rapidly, data business package transmission and smooth transition can be carried out rapidly and hierarchically, and the device is flexible and has high reliability.

The invention discloses a space frequency modulation method for digital TV terrestrial broadcasting transmitter based on embedding training sequence and LDPC coding comprising: 1) coding input bit stream by LDPC and forming coding data block on frequency domain; 2) then demodulating by space-frequency coder and regulating time for synchronization; 3) converting data block after space-frequency modulation to time domain discrete data sample value block via IFFT; 4) training sequence serving as real part, service index sequence serving as imaginary part sequence, constituting discrete sample value block of plural training sequence; 5) repeating continuously the plural training sequence four times to form discrete sample value block of time domain embedded training sequence; 6) superposing the space-frequency modulated time domain discrete data sample value block and time domain embedding training sequence discrete sample value block to form space-frequency modulated time domain embedded training sequence data block; 7) inserting cyclic prefix as protective interval and forming signal frame; 8) pulse shaping to signal frame using square root raised consine roll-off filter; 9) up-converting base band to carrier.

The invention discloses a multimedia broadcast wireless signal single-frequency network anti-noise transmission method. In the multimedia broadcast wireless signal single-frequency network anti-noise transmission method of the invention, after processing of multimedia data stream by a central data manager on a single-frequency network multimedia broadcast wireless transmitter, network data manager bit stream LDPC coding, code element modulation, constellation rotation, empty frequency code modulation, frame body formation, time domain training sequence insertion framing, pulse shaping, and up-conversion to carrier waves, multimedia broadcast wireless signals form radio-frequency signals which are transmitted to an air wireless channel and received by a receiver terminal for processing signals transmitted by each multimedia broadcast wireless transmitter in a single-frequency network. The multimedia broadcast wireless signal single-frequency network anti-noise transmission method has the advantages of short receiving synchronization time, high transmission efficiency, controllable multiple services and the like.

The invention discloses a method for transmitting a digital mobile broadcast signal, which is a transmission proposal of time domain and frequency domain mixing. The method for transmitting a digital mobile broadcast signal disclosed by the invention has the advantages of low peak-to-average power ratio, short synchronization time, fading noise influence resistance, controllable multi-service etc.

The invention relates to a frequency synchronization method based on joint estimation carrier of frequency offset, belonging to the technical field of wireless mobile communication. The frequency synchronization method comprises the steps of: carrying out coarse frequency synchronization by using a short training field so as to correct integer frequency offset and carrying out frequency offset compensation on the basis of a coarse frequency synchronization result; by using a signal subjected to frequency offset compensation and a long training field, in combination with a segmentation related algorithm, carrying out frequency estimation to obtain a carrier frequency offset 1; obtaining a carrier frequency offset 2 on the basis of an MMSE (Minimum Mean Square Error) criterion; further obtaining a carrier frequency offset 3 on the basis of a mean square error criterion, and giving frequency synchronization results in different wireless channel environments; and finally, on the basis of the frequency synchronization results, carrying out frequency offset correction on a received signal. According to the frequency synchronization method, the synchronization mean square error of a wireless system is greatly lowered and the synchronization precision is effectively improved.

The invention discloses a multiuser OFDM modulation method based on embedded training sequence and LDPC coding, which includes the following steps: 1) each user inserting zero even in its own training sequence to form discrete FFT training sequence block; 2) each user performing LDPC coding to its own input data bit stream to further form an FFT coding data block; 3) directly superimposing the discrete FFT training sequence block and the FFT coding data block to form an FFT embedded training sequence coding data block; 4) adopting IFFT to switch the FFT embedded training sequence coding data block into a time-domain discrete sample block; 5) taking circulating prefix as guard interval to insert into the time-domain discrete sample block to from a signal frame; 6) using a Raised Cosine Roll-off Filter to perform pulse shaping to the signal frame; 7) upconverting the baseband signal to carrier. The method has advantages of short synchronization time, channel dwindle resistance and multiuser disturbance resistance and the like.

The invention discloses a method for unidirectionally synchronizing transmission time frequency. Through utilization of the method, the high-precision time frequency synchronization problem between amaster station and a secondary station can be effectively solved. The method is realized by the following technical scheme that the master station and the secondary station realize inter-station relative distance high-precision measurement through satellite navigation relative positioning; the master station measures surrounding parameters through utilization of a meteorograph, precisely evaluatestransmission path atmosphere delay, takes own rubidium clock as a reference clock, generates a spread spectrum distance measurement signal through a spread spectrum distance measurement signal moduleand transmits the spread spectrum distance measurement signal to the secondary station through a transmitting radio frequency front end and an antenna; and the secondary station captures and tracks the spread spectrum distance measurement signal and sends a code frequency control word output by a code loop filter to a direct digital synthesizer DDS, phase detection is carried out on an output sinusoidal wave signal and a constant temperature crystal oscillator of a phase-lock loop of the secondary station, and frequency synchronization of the constant temperature crystal oscillator of the secondary station and the rubidium clock of the master station is realized through application of a high-precision reference clock output by the constant temperature crystal oscillator.

The invention is suitable for the mobile communication field and especially provides a frequency synchronization method and an apparatus thereof. The method is characterized in that a first base station acquires a first frequency offset and informs a second base station to feed back a second frequency offset to the first base station; the first frequency offset is a frequency difference of the first base station and UE which is served by the first base station; a pilot signal sent by the UE which is served by the first base station is measured and acquired through the first base station; the second frequency offset is a frequency difference of a second base station and UE which is served by the first base station or the second base station; a pilot signal sent by the UE which is served by the first base station or the second base station is measured and acquired through the second base station; the first base station acquires a frequency difference of the first base station and the second base station according to the first frequency offset and the second frequency offset so that the second base station synchronizes a frequency of the second base station to be the same with a frequency of the first base station according to the frequency difference. By using the method and the apparatus of the invention, under the condition that an existing protocol does not need to be changed, a frequency offset estimation process of a cooperation cell is greatly simplified.

The invention discloses a multimedia broadcast mobile signal robust framing modulation method, and belongs to a time domain and frequency domain mixed framing modulation scheme. The multimedia broadcast mobile signal robust framing modulation method has the advantages of low peak-to-average power ratio, short synchronous time, robustness, controllable multi-service and the like.

The invention discloses an anti-noise digital broadcast wireless signal transmitting method, and relates to a time domain / frequency domain mixed scheme. The anti-noise digital broadcast wireless signal transmitting method has the advantages of low peak-to-average power ratio, short synchronization time, resistance to channel noise, controllable multiple services and the like.

The invention discloses a method for framing and modulating wireless multimedia broadcast signals, which is a framing and modulating scheme mixing a time domain with a frequency domain. The method for framing and modulating wireless multimedia broadcast signals has a signal generation mode and a signal selection method which are easy to process and recover an original signal obtaining an OFDM (Orthogonal Frequency Division Multiplexing) signal at a receiver end, and has the advantages of being low in peak average power ratio, short in synchronization time, resistant to channel fading, capableof controlling various businesses, etc.

The invention discloses a system for processing an MBMS service by a base station MAC layer in an LTE system. The system is characterized by comprising a multiplexing module (101), an MSI module (102), an MAC PDU module (103), a processing packet losing module (104), a dispatching module (105) and a system clock (106). The byte number calculated by the MSI module needs to be transmitted to the MAC PDU module for use; the numbers of the data volume and transmission blocks (TBs) capable of being borne within each transmission time interval (TTI) and calculated by the MAC PDU module need to be transmitted to the multiplexing module (101); after the multiplexing module (101) detects that packet losing is carried out, processing is carried out through the processing packet losing module (104); the processing packet losing module needs to guide the dispatching module (105) to dispatch the MBMS service according to the type for stopping a PDU. By means of the system, synchronization of contents, time and frequencies of the service transmitted between multiple base stations is guaranteed, and the processing processes of the LTE base station MAC layer and the MBMS service are perfected.

The invention discloses a multimedia broadcasting wireless signal anti-interference framing modulation method which is a time domain and frequency domain mixed framing modulation scheme. The multimedia broadcasting wireless signal anti-interference framing modulation method provided by the invention has the advantages of low peak average power ratio, short synchronizing time, anti-interference, capability of controlling multiple services, and the like.

The invention discloses a micro-grid frequency synchronization anti-attack coordinated control method. The frequency of a micro grid is controlled by using a specially designed control rate, and any constant attack on a controller can be completely eliminated on the premise of ensuring system frequency synchronization. The control rate is obtained by carrying out integral operation on the basis ofa traditional distributed control method and subtracting a corresponding frequency state quantity, and the purpose of eliminating constant value attacks exerted by the controller is achieved. The convergence of the control method is strictly proved through the final value theorem. Compared with an existing constant value attack resisting method, a complex evaluation mechanism does not need to beestablished to evaluate the credibility of neighbor node information, an additional communication network is not needed to assist in attack elimination, and the influence of constant value attacks onthe system can be completely eliminated.

The invention discloses a method for framing and modulating anti-interference wireless multimedia broadcast signals in a single frequency network. The method provides a framing and modulating scheme mixing a space domain, a time domain and a frequency domain. According to a training sequence optimal design, a signal generation pattern and a signal selection method of the method for framing and modulating the anti-interference wireless multimedia broadcast signals in the single frequency network, an original signal of an OFDM signal can be easily obtained through processing and recovery on a receiver terminal. The method for framing and modulating the anti-interference wireless multimedia broadcast signals in the single frequency network has the advantages that the peak-to-average power ratio is low, synchronization time is short, channel fading is prevented, and multiple services can be controlled.

The invention discloses a robust transmission method of digital broadcast mobile signals, which is a mixed transmission scheme of time domain and frequency domain. The method has the advantages of low PAPR (peak-to-average power ratio), short synchronous time, robustness, multiple controllable services and the like.

The invention provides an intelligent two-channel real-time compensation method for electromagnetic radiation testing. Two channels with both time and frequency synchronized are used for simultaneously receiving signals of tested devices and background noise in complex environments, and electromagnetic signals in the two channels are compensated in real time through self-adapting wavelet neural network compensation algorithm to obtain practical and accurate electromagnetic radiation conditions of the tested devices. The method adopts the two-channel real-time compensation technology to solve problems of instantaneity of two-channel signals and processing of same-frequency signals, improves testing accuracy, widens application range and reduces cost of electromagnetic radiation testing.

The invention discloses a multimedia broadcast mobile signal anti-interference framing modulation method and in particular relates to a framing modulation scheme with mixing of time domains and frequency domains. The multimedia broadcast mobile signal anti-interference framing modulation method has the advantages that the peak-average power ratio is low, the synchronization time is short, the interference resistance is achieved, and the multiple services can be controlled and the like.

The invention discloses a mobile terminal and a signal processing method, a baseband chip and a radio frequency chip of the mobile terminal. The mobile terminal comprises the baseband chip and the radio frequency chip. In the radio frequency chip, radio frequency modules of all communication modes share oscillator signals generated by a crystal oscillator. In the baseband chip, sampling modules corresponding to the radio frequency modules are used for sampling obtained output signals, so that sampling signals are obtained, and according to the frequency shift between the output signals and corresponding base station signals, compensation modules are used for conducting phase compensation on respective sampling signals to obtain communication signals, so that frequency synchronism of all the communication signals and corresponding base station signals is realized. The mobile terminal and the signal processing method, the baseband chip and the radio frequency chip of the mobile terminal reduce the cost and the power consumption of the radio frequency chip in the multi-mode mobile terminal and the cost and the power consumption of the baseband chip in the multi-mode mobile terminal, and eliminate the complex clock switching process.

The invention discloses an anti-fading framing modulating method for a multimedia broadcast radio signal, and is a time-domain and frequency-domain hybrid framing modulating scheme and has the advantages of low PAPR (Peak to Average Power Ratio), short synchronous time, anti-fading property, capability of controlling multi-service, and the like.

The invention discloses an anti-fading digital broadcast wireless signal transmitting method, and relates to a time domain / frequency domain mixed scheme. The anti-fading digital broadcast wireless signal transmitting method has the advantages of low peak-to-average power ratio, short synchronization time, resistance to fading, controllable multiple services and the like.

The invention discloses an anti-interference transmission method for a digital broadcast wireless signal. The method is a time domain / frequency domain combined transmission scheme. The anti-interference transmission method has the advantages of low peak-to-average power ratio, short synchronization time, anti-interference performance, multi-service controllability and the like.

The invention discloses a multimedia broadcasting wireless signal anti-noise transmission method; in the multimedia broadcasting wireless signal anti-noise transmission method, the multimedia broadcasting wireless signal is at the multimedia broadcasting wireless transmitter terminal, a multimedia data stream is processed by media data processing, bit stream LDPC coding, code element modulation, constellation rotating, frame body formation, time domain training sequence insertion framing, pulse formation and up-conversion to carrier wave to form a radio-frequency signal which is transmitted to an air wireless information channel, and the signal transmitted by the multimedia broadcasting wireless transmitter terminal is received and processed by a receiver terminal; the multimedia broadcasting wireless signal anti-noise transmission method has the advantages of short receiving synchronization time, high transmission efficiency and controllable multi-service and the like.

The invention discloses a multimedia broadcast mobile signal anti-noise framing modulation method, and belongs to a time domain and frequency domain mixed framing modulation scheme. The multimedia broadcast mobile signal anti-noise framing modulation method has the advantages of low peak-to-average power ratio, short synchronous time, noise resistance, controllable multi-service and the like.

The invention discloses a multimedia broadcast mobile signal framing modulation method, and belongs to a time domain and frequency domain mixed framing modulation scheme. The multimedia broadcast mobile signal framing modulation method has the advantages of low peak-to-average power ratio, short synchronous time, channel fading resistance, controllable multi-service and the like.

The invention discloses a robust transmission method for digital broadcasting wireless signals, which is a time domain and frequency domain hybrid transmission scheme. The method has the advantages of low peak-to-average power ratio, short synchronous time, robustness, controllability in multiple services and the like.

The invention discloses a digital radio broadcast signal transmission method which is a transmission scheme of mixing a time domain and a frequency domain. According to the digital radio broadcast signal transmission method disclosed by the invention, a low-complexity peak-to-average power ratio reduction technology, a serially concatenated multi-code rate punctured convolution code modulation technology and a signal frame time-frequency domain combined iteration separation treatment technology are designed aiming at the technical problems of high signal peak-to-average power ratio and channel fading noises of a broadband multi-carrier digital radio broadcast transmission system, which need to be solved, and therefore the broadband multi-carrier digital radio broadcast transmission systemhas the advantages of low peak-to-average power ratio, short synchronization time, fading noise influence resistance, controllable multi-service, and the like.