Method and system for judging frequency offset in high-speed rail system

Abstract

The present invention provides a method for judging frequency offset in a high-speed rail system. The method includes: the base station obtains the received energy of the uplink signal according to the uplink signal of the user received by each RRU, and determines the maximum value of the received energy of the uplink signal; The change of the RRU corresponding to the maximum value of the received signal energy determines the positive or negative of the Doppler frequency shift; according to the uplink signal received by the RRU, the phase difference of the OFDM symbol is obtained, and according to the Doppler The phase difference is corrected by the positive or negative of the frequency shift; and the phase of the OFDM symbol is compensated according to the corrected phase difference. The invention provides a frequency offset judgment system in a high-speed rail system. The system includes a setting module, a determination module, a correction module and a compensation module. The invention has a large range of frequency offset estimation and low calculation complexity, and can solve the problem of Doppler frequency shift under high-speed conditions.

Description

technical field [0001] The invention relates to the field of communication technology, in particular to a method and system for judging frequency offset in a high-speed rail system. Background technique [0002] In the communication system, the high-speed movement of the terminal will cause Doppler frequency shift. For example, if the terminal is traveling at a speed of 300km / h and the carrier frequency is 2.6GHz, the maximum Doppler frequency shift generated is about 722Hz. In the uplink, the Doppler frequency shift caused by the movement of the terminal will be at most twice the maximum Doppler frequency deviation, that is, the terminal is traveling at a speed of 300km / h, regardless of the downlink synchronization error condition Down, the uplink frequency deviation can reach up to 1444Hz. Under such frequency deviation conditions, if some measures are not taken, the uplink data cannot be received correctly. [0003] In existing frequency offset estimation algorithms, so...

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Problems solved by technology

Under such frequency deviation conditions, if some measures are not taken, the uplink data cannot be received correctly

[0003] In existing frequency offset estimation algorithms, some use pilots for frequency offset estimation. For example, in LTE, the phase difference between two columns of pilots in a PUSCH subframe is used for frequency offset estimation. This method can estimate The maximum frequency deviation is around 1071Hz. If the uplink frequency deviation exceeds this range, the uplink signal will be unacceptable

In high-speed situations such as high-speed rail, the speed of the terminal may reach or even exceed 300km / h. If the carrier frequency is 2.6GHz, considering that the downlink synchronization error is 0.01ppm, the uplink frequency deviation will reach 1444+260=1704Hz. The maximum frequency offset range that can be estimated by using the pilot is exceeded, and the data will not be received at this time

[0004] Therefore, in the current uplink frequency offset estimation algorithms, some frequency offset estimation ranges are limited, and some cannot solve the Doppler frequency shift problem under high-speed conditions such as high-speed rail, and the signal reception performance is poor.

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