Wireless broadcast time service system based on OFDM technology

Abstract

The invention relates to a wireless broadcast time service system based on an OFDM technology. The method comprises an OFOM system design and a time service signal forwarding network. The OFOM systemdesign comprises a basic parameter baseband, a subcarrier, an OFDM data body, an OFDM cyclic prefix, an OFDM symbol, a modulation mode, an FEC code, a synchronization signal, a signal intra-frame OFDMsymbol, a signal frame, an OFDM symbol effective subcarrier and a frequency domain pilot. The method comprises the following processing steps of establishing an OFDM signal frame structure, designinga synchronization signal, designing an OFDM symbol, carrying out FEC spread spectrum processing, and processing by other system sub-modules. The wireless broadcast time service system based on OFDM technology is advantaged in that the system not only can complete a communication network for transmitting time service signals in a common environment and a complex environment, but also has the characteristics of strong signal coverage, high time service precision and good concurrency, and meets the transmission requirements of the time service signals under different conditions.

Description

technical field [0001] The invention belongs to the field of digital information transmission, in particular to a wireless broadcast timing system based on OFDM technology. Background technique [0002] High-precision time information plays an increasingly important role in the technological and economic development of today's society. Industries such as communications, electric power, and finance are inseparable from accurate timing systems to achieve synchronization and high-efficiency operation. With the wide application and development of time service in these fields, the performance, reliability, cost of implementation and maintenance of the time service system used to achieve precise time synchronization have gradually been paid more attention. [0003] Common timing methods on the market include atomic clocks, navigation satellite timing, short-wave timing, long-wave timing, and network timing. Among them, atomic clocks have the highest precision, but are difficult t...

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Problems solved by technology

Among them, the atomic clock has the highest precision, but it is difficult to be widely used due to its high price.

The accuracy of navigation satellite timing can reach 20ns, but the limitation is that the satellite signal is weak and susceptible to interference, especially indoors and other environments without satellite signals cannot work, due to the flexibility of distance, wiring and obstacles and timing network Considering various factors, such as forwarding the receivable satellite timing signal, or transmitting it to the timing target device through a wired network, it is sometimes difficult to operate in practice.

[0004] The short-wave timing signal is transmitted by the reflection of the ionosphere. Because the ionosphere is affected by factors such as sunspot high and low annual changes, seasonal changes and diurnal changes, its reflectivity presents irregular changes, which leads to the stability of time signal transmission. Suffering a lot of impact, the shortwave timing receiver cannot successfully time service for a long time

Moreover, its timing accuracy is only about ±1ms, which cannot be used in some occasions that require high timing accuracy.

[0005] The anti-interference performance of the long-wave timing signal is good, and the timing accuracy can reach ±5us, but the long-wave timing has many limitations such as single timing information and inability to independently time service.

At the same time, if the data repetition period of the long-wave timing station chain is long, it will take a long time for the user to succeed in timing, which is not conducive to accurate measurement and real-time timing

[0006] The network time service technology with Ethernet as the medium has the advantages of convenience, quickness and low cost, but its time service accuracy is low, generally around tens of milliseconds, and changes with the network structure and network load

[0007] In addition, there are also some wireless communication technologies for timing signals, but basically all of them require the slave to initiate a timing application to the host, and then the host sends the timing signal to the slave to transmit timing information through a specific wireless communication system. In this process, there are not only The problem of uncontrollable delay, and it is also difficult to support the sudden timing demand of a large number of slaves

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