Accurate method for estimating frequency deviation of inseting constant pilot carrier in orthogonal frequency division multiplex system
A technology of orthogonal frequency division and frequency offset estimation, applied in the direction of multi-frequency code system, etc., can solve problems such as offset, interference, leakage, etc., and achieve the effect of improving system performance and strong use value
Inactive Publication Date: 2009-10-21
TSINGHUA UNIV
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Problems solved by technology
The frequency deviation between the transmitter and the receiver causes the received signal to shift in the frequency domain. If the frequency deviation is n times the subcarrier spacing, the subcarriers are orthogonal, but the frequency sampling values have shifted by n subcarriers. carrier position
If the carrier deviation is not an integer multiple of the subcarriers, there will be energy "leakage" between the subcarriers, resulting in the destruction of the orthogonality between the subcarriers, thus introducing interference between the subcarriers, making the system The bit error rate performance deteriorates,
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[0031] Below in conjunction with accompanying drawing and example, effect of the present invention is described in detail:
[0032] In this embodiment, the MIMO-OFDM system is used for transmitting and receiving, each OFDM symbol has 2048 subcarriers, and the number of transmitting antennas is N t =4, the number of receiving antennas N r =4, the frequency-domain pilot used for precise frequency estimation is inserted at the 768th subcarrier position of each OFDM symbol, its power P is the same as that of other data subcarriers, the OFDM symbol cyclic prefix length is 330 points, and two adjacent OFDM symbols The frequency domain pilots used for fine frequency estimation are separated by 2048+330=2378 sampling points, and the bandwidth of each subcarrier is 11.2 KHz.
[0033] OFDM symbol frequency domain structure such as figure 1 As shown, subcarriers 0-767 and 1280-2047 are used to transmit data or insert ordinary pilots for channel estimation, subcarriers 768 are inserted ...
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The present invention belongs to the technical field of precise frequency offset estimation of OFDM systems, and is characterized in that, for single-transmit and single-receive OFDM systems, or multiple-transmit and multiple-receive OFDM systems, on the premise that rough frequency offset estimation has been completed and the best cyclic prefix interception position has been selected Next, the frequency domain pilot is inserted at a certain subcarrier position of each OFDM symbol, and the time domain waveform c*(n) of the pilot is calculated based on this, so that the waveform is consistent with the arbitrary selected on the i-th receiving antenna The corresponding time-domain value of the jth OFDM symbol is correlated, and the phase angle of the post-correlation value can be obtained, and then the phase angle is combined by receiving antennas to obtain the average phase angle, so that two adjacent OFDM symbols can be obtained The difference between the average phase angles of , and then the estimated value of the instantaneous frequency deviation is obtained, and the accurate estimated value of the frequency deviation can be obtained after smoothing and filtering the instantaneous value. The present invention can estimate the fine frequency offset within one subcarrier offset, and has strong use value.
Description
technical field [0001] The invention relates to a method for estimating the subcarrier frequency deviation of fractional times between sending and receiving in a single sending and receiving or multiple sending and receiving orthogonal frequency division multiplexing system. Background technique [0002] With the increasing bandwidth requirement in wireless communication, Orthogonal Frequency Division Multiplexing (OFDM) multi-carrier transmission system is attracting a lot of attention in recent years. [0003] Since the Orthogonal Frequency Division Multiplexing OFDM system uses technologies such as inverse Fourier transform and cyclic prefix at the transmitting end and uses Fourier transform demodulation after discarding the cyclic prefix at the receiving end, thereby eliminating inter-symbol interference and making frequency selection Therefore, in practical applications, only a simple frequency domain equalization technique is required to allow high-speed data transmiss...
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IPC IPC(8): H04L27/26
Inventor 周世东高群毅许希斌赵明张秀军王京
Owner TSINGHUA UNIV