UDC 621.3.018.51
USE OF SYMBOLS WITH FREQUENCY MODULATION FOR JOINT ESTIMATION OF TIME AND FREQUENCY OFFSET DURING OFDM SIGNALS RECEPTION
A. V. Bakke, PhD (technical sciences), associate professor of the department of Telecommunication and Radio Engineering foundations, RSREU, This email address is being protected from spambots. You need JavaScript enabled to view it.
I. V. Lukashin, Post graduate student of the department of Radio control and Communication, RSREU, This email address is being protected from spambots. You need JavaScript enabled to view it.
The work purpose is development of a synchronization algorithm of OFDM signals using preamble with frequency modulation. The proposed algorithm provides robust estimates of time and frequency shift through the use of preamble with symmetrical frequency law in the multipath channel and without it. Using these signals provides the possibility of forming a likelihood function based on two different criteria for the estimation of time and frequency offset of OFDM signals. The effect of joint use in the likelihood function of different criteria is most pronounced for multipath channels. The effect is shown in a decrease in the values of the mean square error of time shift estimation compared to using each criterion separately. Research of ways to improve robustness of the proposed algorithm in multipath is made. It is shown that the target selection frequency deviation and the introduction of non-linearity in the frequency law of preamble provides improved time shift estimation accuracy to 8 dB or more at a signal-to-noise ratio of up to 2 dB.
Key words: preamble, OFDM, estimation of time offset, estimation of frequency offset, lfm (chirp), multipath, frequency deviation, COST 259.