Uplink time synchronization method of LTE system of GEO satellite

Abstract

The invention relates to the time synchronization technology of wireless communication systems, in particular to an uplink time synchronization method of an LTE system of a GEO satellite. According to the method, on the premise of being compatible with the conventional LTE air interface standard, a standard frame structure which is 10 ms in length can be used; by performing estimation compensation on synchronization errors, a transmission time on the side of user equipment and a start time of a base receiving window are corrected to realize the protection of the subcarrier orthogonality in the OFDM technology by the uplink synchronization of the GEO satellite; a transformational LMS algorithm is designed according to the characteristics of the system to realize quick estimation of the synchronization errors; user equipment platforms with different moving speeds can be adapted by setting update velocity; the method is high in structural universality, lower in complexity and easy to realize, and can meet a requirement of time synchronization on the LTE system of the GEO satellite, as well as a requirement of standard compatibility on a conventional LTE air interface.

Description

technical field [0001] The invention relates to a time synchronization technology of a wireless communication system, in particular to a method for uplink time synchronization of a GEO satellite LTE system. Background technique [0002] Compared with terrestrial mobile communication systems, satellite mobile communication systems have the advantages of wide coverage, high outdoor channel quality, and strong invulnerability, and are widely used in communication network construction in remote areas, emergency communications for emergency rescue and disaster relief, and military communications. With the further promotion of commercialization of LTE in my country, the terrestrial mobile communication network is gradually completing the evolution from 3G to 4G. The evolution of the new generation satellite mobile communication system based on the LTE technology system has also become an important development of the current satellite mobile communication system. direction. [0003...

AI Technical Summary

Problems solved by technology

At the same time, the large delay characteristics of link transmission in the satellite system (single-hop transmission delay is about 270ms), making it impossible for the base station to feed back the uplink synchronization error of each terminal to the user terminal in real time

When the user terminal does not receive real-time scheduling, the continuous accumulation of uplink synchronization errors will occur. When the accumulation exceeds the length of the cyclic prefix and the guard interval, the uplink signal of this time slot will cause crosstalk to the user's signal in the next time slot, causing the uplink signal Interference problem, which seriously affects system performance

[0004] At present, the LTE standard for TDD full-duplex mode adopts the method of lengthening the cyclic prefix and guard interval. This method extends the guard interval of users under the single beam of GEO satellite to 2.16ms, and extends the length of a complete frame in the original standard to 16ms. , this method of simply extending the data frame length will cause about 60% system capacity loss

Therefore, although this method can avoid most of the uplink signal interference, it also brings new problems of greatly reduced system capacity and poor compatibility with ground systems

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