3 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 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.

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.