Low complexity joint time offset and frequency offset estimations for LTE uplink system

The orthogonal frequency division multiplexing（OFDM） is currently used in long term evolution（LTE） system. The time offset estimation（TOE） and frequency offset estimation（FOE） of OFDM is essential in mobile communication base. According to the conventional cross correlation TOE and FOE algorithms, a new cross correlation computation was proposed to estimate the time offset and frequency offset for LTE uplink system, so that the time offset and frequency offset can be estimated simultaneously with low complexity. Compared with the conventional TOE and FOE algorithms, the simulation show that the proposed can reduce complexity and improve performance for FOE with good performance for TOE in additive white Gaussian noise（AWGN） and multipath channel.

Frequency offset estimation based on peak power ratio in LTE system

Orthogonal frequency division multiplexing （OFDM） is one of the key techniques for long term evolution （LTE） system. Frequency offset estimation of OFDM is an essential issue. Especially in the high-speed environment, the frequency offset will become large. Based on the features of LTE uplink physical random access channel （PRACH）, this paper proposes a new frequency offset algorithm by using peak power ratio to enlarge the range of frequency offset estimation. According to the relation between frequency offset and the power delay profile （PDP）, the ratio of the peak power of the PDP at the main window to that at the negative window or positive window is utilized to estimate frequency offset. Simulation results show that the new proposed algorithm extends the estimation range of frequency offset from 1 000 Hz to 1 250 Hz. Meanwhile the accuracy of frequency offset estimation is almost not lost. Particularly in low signal noise ratio （SNR）, the new algorithm has lower mean square error （MSE） compared with traditional phase differential algorithm.