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Satellite Internet of Things large-scale access design method based on OFDM

A design method and technology of the Internet of Things, applied in the field of satellite communication, to achieve the effect of improving performance, better distinguishing effect, and reducing mismatch

Active Publication Date: 2022-03-18
UNIV OF ELECTRONICS SCI & TECH OF CHINA
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

In this case, the channel estimation problem is more challenging

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  • Satellite Internet of Things large-scale access design method based on OFDM
  • Satellite Internet of Things large-scale access design method based on OFDM
  • Satellite Internet of Things large-scale access design method based on OFDM

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Embodiment Construction

[0120] The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

[0121] Figure 4 Is the flow chart of the algorithm, including the repeated symbols at the sending end, the introduction of multipath channels, and the message passing algorithm at the receiving end.

[0122] Provide a specific implementation method of the present invention based on above-mentioned algorithm below, the parameter setting of this specific method is as follows:

[0123] At the sending end, the number of repeated OFDM symbols in repeated symbols is N=2, U=6 repeated symbols in one transmission frame, the number of subcarriers is M=16, and the interval between subcarriers is 15kHz. The total number of users served by the system is K=100, and the channel grid size of each user is 4×10. The maximum Doppler frequency shift of the actual physical channel is 15kHz, and the maximum delay is 1.675×...

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Abstract

The invention belongs to the technical field of satellite communication, and relates to an OFDM (Orthogonal Frequency Division Multiplexing)-based satellite Internet of Things large-scale access design method. In order to solve the problem of large-scale access of the satellite Internet of Things, the invention provides an unlicensed random access method which comprises the following steps: carrying out joint active user detection and channel estimation at a sending end by repeatedly sending OFDM symbols and using a message passing algorithm based on variance state propagation at a receiving end; on one hand, the effect of improving the frequency domain resolution of a receiving end is achieved by repeatedly sending OFDM symbols, and on the other hand, a prior probability model is established at the receiving end by fully utilizing the sparsity of a channel in a time delay-Doppler-user domain to improve the performance of active user detection and channel estimation. And an error between the model and an actual channel is reduced through an expectation maximization frame parameter.

Description

technical field [0001] The invention belongs to the technical field of satellite communication, and relates to an OFDM-based large-scale access design method of satellite internet of things. Background technique [0002] The commonly used user access method in the communication system is authorization-based random access. The user first randomly selects an orthogonal preamble or pilot sequence for access. Collisions will occur between users who select the same pilot. The user will be authorized by the base station and allocated physical resources for subsequent data transmission. For the satellite Internet of Things communication system, the number of users served by satellites has greatly increased. Due to the limited orthogonal pilot resources, the authorization-based random access method will generate serious user conflicts in the face of large-scale access, resulting in huge access problems. input delay. [0003] Aiming at this problem, authorization-free random access...

Claims

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Application Information

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IPC IPC(8): H04L27/26H04L5/00
CPCH04L27/2695H04L27/2666H04L5/0048H04L5/0008Y02D30/70
Inventor 袁晓军岳明扬李思贤
Owner UNIV OF ELECTRONICS SCI & TECH OF CHINA