Period
2025.01-2028.12
Introduction
With the rapid development of the Internet of Things and mobile computing, Bluetooth, as one of the important branches of wireless transmission technology, has been widely used in scenarios such as personal audio-visual, indoor positioning and asset management. Different from active Bluetooth technology, passive Bluetooth technology can achieve wireless transmission with approximate performance with lower power consumption, so it has become an international research hotspot in recent years. This project plans to focus on the research of key technologies of passive Bluetooth Internet of Things for commercial use, study the edge architecture design for multi-node passive Bluetooth transmission, the efficient passive downlink physical layer mechanism based on edge base stations, and the passive network protocol compatible with commercial Bluetooth connection, and solve a series of problems such as low downlink efficiency in the application of passive Bluetooth transmission system, high resource consumption of node decoding and FM signals, and incomplete compatibility between traditional passive nodes and commercial equipment. Explore the design of passive Bluetooth communication architecture based on edge base stations, realize the modulation and demodulation of efficient amplitude modulation links based on commercial WiFi signals, study the design of commercially compatible passive Bluetooth transport layer protocols, and build a passive Bluetooth communication network demonstration system for space capsules, so as to fully verify the effectiveness and practicability of the proposed theory and key technologies.
Target
It solves a series of problems that need to be solved urgently, such as the low efficiency of the downlink, the high resource consumption of node decoding and FM signals, and the incomplete compatibility between traditional passive nodes and commercial equipment in the practical application of passive Bluetooth communication network. A passive Bluetooth communication network system for the application of capsule sensing is constructed to provide a scientific basis for the monitoring of oxygen content in the space capsule and the detection of the tightness of the cabin door. Strive to achieve more than 30 networks in the demonstration application, more than 5 kinds of synchronous passive transmission sensing data, and more than 50 kbps passive transmission rate, so as to provide theoretical and technical support for the innovative development of China's Internet of Things and aerospace sensing applications.
Methodology
I.Passive Bluetooth communication architecture design based on edge base station
In order to solve the problems of high resource consumption of direct demodulation and FM signal of nodes, low transmission efficiency of downlink PLM transmission, and inability of passive nodes to perceive the perceived carrier frequency, the project proposes to adopt a mechanism based on edge base stations to assist downlink communication. First, the edge base station needs to act as a bridge in the downlink communication, responsible for performing complex decoding operations on the downlink, thereby transferring the power consumption from the node to the edge base station. In the link from the receiver to the node, the edge base station converts the BLE signal sent by the commodity device into an ASK signal based on the commercial WiFi simulation. At the same time, the project uses an auxiliary edge base station for frequency identification, in the link from the node to the receiver, the edge base station identifies carrier signals of different frequencies and forwards the frequency information to the node, and the node modulates the data.
Fig1 Edge architecture design
II.Modulation and demodulation of high-efficiency amplitude modulation links based on commercial WiFi signals
One of the core problems of achieving bidirectional communication between a passive node and a receiver is to achieve efficient downlink communication. However, existing PLM coding methods are inefficient and require additional hardware modifications, limiting the status quo of widespread deployment of passive communication. To this end, the project intends to use commercial WiFi to simulate ASK signals for downlink message transmission. First, in the receiver to the edge base station part, the receiver emits a BLE signal, and the edge base station uses the BLE module to receive the signal. The edge base station then converts the message into a WiFi-ASK signal and forwards it to the node, where we plan to design an RC filtering circuit to extract the envelope. Furthermore, the edge base station is used to realize the environmental carrier frequency identification.
III.Commercially compatible passive Bluetooth transport layer design
To get closer to the vision of commercial compatibility, nodes should be able to implement broadband frequency hopping. First, the project proposes to adopt the method of setting a dynamic clock for node modulation, by introducing a hash table for clock switching, and the node can backscatter its excitation signal to the dynamic Bluetooth channel by applying different frequency shifts. This wideband frequency hopping mechanism can support communication with standard equipment. In addition, the establishment of a connection between a passive node and a standard Bluetooth device requires an urgent normalization process.
Fig2 The process of establishing a connection for passive Bluetooth communication
IV.Demonstration application of passive Bluetooth sensor communication network for space capsule
The project plans to build a prototype system and establish a demonstration platform for monitoring the oxygen content of the capsule and detecting and alarming the tightness of the hatch based on the passive Bluetooth communication network, so as to verify, evaluate and improve the reliability of the passive Bluetooth communication network. The indicators measured by the experiment mainly include the accuracy of data transmission, the accuracy of oxygen content monitoring, the accuracy of door airtightness detection and alarm, the throughput of the system, the transmission delay and the communication range. Finally, according to the results of verification and evaluation, the system is improved in time.