7 results about "Integer frequency offset" patented technology

A telecommunications receiver is adapted to communicate with mobile devices that operate according to a protocol where the telecommunications receiver operates outside of expected ranges for the protocol but modifies its communications with mobile devices to appear to those mobile devices as being within the expected ranges. To determine what modifications to make to transmissions, the telecommunication receiver processes signals from mobile devices to determine where a communications channel is relative to the expected ranges and uses that information to modify transmissions to mobile devices. The expected ranges might relate to maximum distance between telecommunications receiver and a mobile device, maximum relative velocity, power etc. Determining a relative velocity, and therefore a Doppler shift, can be done by determining a fractional frequency offset, determining an expected subchannel, and determining an integer frequency offset based on the expected subchannel carrier frequency and the measured carrier frequency.

The present invention provides a time-frequency synchronization method and apparatus applicable to DRM, belonging to the field of communication technologies. The method includes: determining the robust mode and the symbol coarse timing starting point of the received DRM signal; estimating and compensating the fractional frequency offset at the symbol coarse timing starting point; determining the transmission frame coarse starting point according to the time pilot signal; estimating and compensating the integer frequency offset at the transmission frame coarse starting point by using the time pilot; estimating the precise transmission frame starting point by using the gain pilot; and estimating and compensating the precise fractional frequency offset at the precise transmission frame starting point by using the gain pilot. The present invention is applicable to various robust modes and spectrum occupancy situations of DRM. Its synchronization performance is not affected by the initial frequency offset. By continuously tracking the symbol timing offset and carrier frequency offset to reduce ISI and ICI, it has the advantages of high precision, good robustness, simple process, and being suitable for transplantation to a hardware system.

A method for designing a frequency domain ZC sequence synchronization head resistant to ultra-large frequency difference belongs to the technical field of communication, and comprises the following steps: avoiding correlation peak ambiguity caused by overlarge frequency offset through piecewise iterative estimation and compensation of decimal frequency offset; a ZC sequence sideband protection design is adopted, so that a sideband part and a base sequence form a continuous structure, and the time synchronization robustness is improved; in combination with pilot frequency cross-correlation and self-correlation processing, a cross-correlation signal is divided into subsequences for conjugate multiplication and summation, and accurate estimation of integer frequency offset is realized. According to the invention, the synchronization reliability and the system spectrum efficiency can be remarkably improved, high-precision synchronization in an ultra-large frequency difference range is supported, and the synchronization problem in a high-speed mobile communication scene is effectively solved.

The invention provides a half-carrier frequency offset estimation method and system in an OFDM (Orthogonal Frequency Division Multiplexing) system, and the half-carrier frequency offset estimation method comprises the steps of baseband signal acquisition, CP (Cyclic Prefix) phase calculation, ambiguity judgment, phase ambiguity transfer, CP frequency offset estimation, integer frequency offset estimation and final frequency offset estimation, converting the cross-correlation phase deviation value into a single-peak structure to obtain a phase deviation of the single-peak structure, then counting a risk coefficient of the phase deviation falling into a fuzzy region, if the risk coefficient is greater than a set value, performing phase fuzzy transfer, performing phase fuzzy transfer on a scene falling into the fuzzy region to obtain a defuzzification-processed phase deviation, and finally obtaining the defuzzification-processed phase deviation. The invention further provides a system for estimating the frequency offset of the half carrier in the OFDM system. According to the method, a fuzzy region can be converted into superposition of two determined regions, and the problem that CP frequency offset estimation is unstable near the half-carrier frequency offset is well solved.

The invention provides a time frequency offset estimation method and device of an LTE system, and relates to the technical field of communication, and the method comprises the steps: employing a plurality of decimal frequency offsets to carry out the frequency offset compensation of an initial receiving signal, and obtaining a first target signal; performing PSS detection and screening on the first target signal to obtain first m first correlation peak values in descending order and N-ID-2, a first timing position and a first frequency offset value corresponding to the first correlation peak values; presetting a plurality of integer frequency offsets and calculating a second correlation peak value corresponding to each first correlation peak value; positioning the time domain position of each second correlation peak value and performing frequency offset compensation to obtain a second target signal; and performing SSS detection and screening on the second target signal to obtain first n second correlation peak values in descending order as well as N-ID-1, a second timing position and a second frequency offset value corresponding to the second correlation peak values, and combining N-ID-1 and N-ID-2 to obtain a cell ID. According to the method, decimal frequency multiplication estimation and integer frequency offset estimation are separated, and the accuracy is improved through double frequency offset estimation.

This invention discloses a two-level collaborative OFDM frequency offset estimation method using adaptive weighting and multi-candidate search, comprising the following steps: preprocessing the received OFDM signal; calculating the real-time signal-to-noise ratio (SNR) of each received frame in the preprocessed OFDM signal; determining an initial fractional frequency offset estimate using an edge sampling and adaptive weighting method; performing integer frequency offset estimation on the frequency domain signal after fractional frequency offset pre-compensation using an energy window-based multi-candidate mechanism and correcting the window length of the fractional frequency offset estimate to obtain the final window length of the fractional frequency offset estimate; performing fractional and integer frequency offset estimation again using the final window length to obtain the final fractional and integer frequency offset estimates; and obtaining the final joint frequency offset estimate using a weighted fusion strategy. The method of this invention can significantly improve the accuracy of frequency offset estimation.

The embodiment of the invention provides a frequency offset estimation hardware device suitable for a PLC wireless communication chip, and relates to the technical field of power line communication. The device comprises a decimal frequency offset calculation unit used for processing a short training sequence to obtain a decimal frequency offset value; the common phase rotation unit is used for processing the first long training sequence and the second long training sequence by using a decimal frequency offset value to obtain a first compensation long training sequence and a second compensation long training sequence; the long training field fine synchronization unit is used for determining a fine synchronization point and a synchronization point deviation according to the first compensation long training sequence and the protocol definition long training sequence; the long training field averaging unit is used for determining an average long training sequence; the public fast Fourier transform unit is used for obtaining a Fourier transform sequence; the cache SRAM unit is used for storing an average long training sequence and a Fourier transform sequence; the integer frequency offset searching unit is used for obtaining an integer frequency offset value and determining a final frequency offset value. According to the invention, the accuracy of the frequency offset estimation result can be improved.