Multi-user detection method for low-earth orbit satellite random access system based on CRDSA protocol

Abstract

The invention belongs to the technical field of satellite communication, and discloses a multi-user detection method for a low-earth orbit satellite random access system based on a CRDSA protocol. Themulti-user detection method comprises the steps that multiple access users transmit user groups to a satellite according to the CRDSA protocol; a satellite receiving terminal sequentially processes aplurality of superimposed user groups on each time slot in a frame according to the CRDSA protocol; the satellite receiving terminal performs modeling on a channel of each user on the time slot by adopting a basis expansion model when processing K superimposed user groups on a certain time slot; solving a base coefficient of each user in a joint manner according to a maximum likelihood method; fitting each user channel by using the solved base coefficients; reconstructing all interference user groups and performing interference elimination by using the top (K-1) pieces of user data which aredetected and decoded when processing other time slots and the top (K-1) fit user channels; detecting and decoding the residual signals after interference elimination; and performing iterative channelestimation and interference elimination by using decoding bits. The multi-user detection method is high in channel estimation accuracy, accurate in interference elimination and low in packet error rate.

Description

technical field [0001] The invention belongs to the technical field of satellite communication, in particular to a multi-user detection method of a low-orbit satellite random access system based on a CRDSA protocol. Background technique [0002] At present, the existing technologies commonly used in the industry are as follows: Since the Internet of Things was put forward, it has gradually become one of the key research issues at home and abroad. The Internet of Things is widely used in environmental monitoring, disaster prediction and oil and gas exploration. In such scenarios, IoT devices are usually distributed in vast or remote areas, and it is difficult for the ground network to provide data collection and transmission services for such a large or specific area, while the satellite network can well make up for the coverage of the ground network. Defects. In the satellite Internet of Things, the random access method can avoid excessive access delay and improve through...

AI Technical Summary

Problems solved by technology

However, due to the extremely high angular velocity of LEO satellites flying near the earth, the maximum Doppler frequency shift brought by high-speed movement can reach tens to hundreds of KHz, which will lead to the rapid time-varying problem of the channel, while the quasi-static channel in the above literature The model is not capable of describing such a channel

Using the above method in the LEO satellite scenario will lead to an increase in the system's packet error rate

[0003] In summary, the problems in the prior art are: Due to the extremely high angular velocity of LEO satellites flying near the earth, the maximum Doppler frequency shift brought by high-speed movement can reach tens to hundreds of KHz, resulting in the rapid time-varying problem of the channel

It is difficult to obtain accurate channel estimation accuracy for fast time-varying channel estimation in the presence of multi-user interference and noise

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