Narrowband communication system frequency offset correction method suitable for multi-level train mixed running

Abstract

The invention discloses a narrowband communication system frequency offset correction method suitable for multi-level train mixed running. The correction method comprises the following steps: adding alinear frequency modulation synchronization sequence into a physical layer burst preamble signal; performing time coarse synchronization by using the linear frequency modulation synchronization sequence; carrying out frequency offset coarse correction on the basis of time coarse synchronization; adding a PN sequence in a time slot in the physical layer burst preamble signal; intercepting a PN sequence to perform time fine synchronization; and carrying out frequency offset fine correction on the basis of time fine synchronization. The linear frequency modulation signal sequence and the data signal can be completely distinguished, the distance resolution is high, the method is not sensitive to Doppler frequency shift, and frequency offset coarse correction can be effectively achieved. Aiming at the characteristic of bandwidth limitation of a narrowband communication system, the selected PN sequence length can realize the most effective frequency offset fine correction on the premise ofensuring the transmission efficiency of the system.

Description

technical field [0001] The invention belongs to the field of data transmission, and in particular relates to a method for correcting a frequency offset of a narrowband communication system suitable for mixed running of multi-level trains. Background technique [0002] Most of the existing frequency offset correction algorithms are concentrated in common scenarios, and the frequency offset correction algorithms for high-speed scenarios are also concentrated in broadband systems such as LTE. For narrowband communication systems, due to bandwidth limitations, especially when trains are running at high speed, Doppler frequency offset will seriously affect the performance of the communication system, so higher requirements are put forward for the error correction capability and reliability of the system frequency offset. [0003] There are two main reasons for the frequency offset. One is that the oscillators of the transmitter and receiver are not synchronized, and the other is ...

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Problems solved by technology

[0006] The frequency offset estimation range of the fractional carrier frequency offset estimation part is [-1 / T, 1 / T], and the relative frequency offset estimation range obtained from the sampling interval is [-1, 1], which is a subcarrier interval. The integer multiple carrier frequency offset estimation part expands the estimation range of the algorithm to the entire frequency spectrum, but since the integer part needs to be searched one-dimensionally, the computational complexity is greatly increased, and the PN sequence and INFO signal do not have high distance resolution. Poor performance at low SNR conditions

[0007] Therefore, the present invention provides a narrowband communication system physical layer frequency deviation correction algorithm suitable for mixed running of multi-level trains to solve the frequency deviation problem of narrowband communication systems in high-speed scenarios

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