ZigBee Frequency Hopping Retransmission Mechanism
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Solution Overview
Problem
ZigBee communication systems face interference issues with WiFi and Bluetooth, particularly at the 2.4 GHz frequency band, leading to poor penetration, sensitivity, and transmission distance, and in dense meter deployment scenarios, channel quality changes rapidly, making data interaction unreliable due to lack of adaptive frequency-hopping mechanisms.
Innovation Solution
A data transmission method that selects two channels as a prescribed and spare channel, divides the contention-free period into three sub-periods for re-transmission, and broadcasts a beacon frame with channel and timeslot information to enable flexible channel switching based on quality, ensuring timely response to interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If ZigBee operates at 2.4 GHz frequency band, then data transmission speed is maintained, but penetration and transmission distance deteriorate due to co-channel interference with WiFi and Bluetooth
Solution Approach 1:
The patent changes the operating frequency parameter from 2.4 GHz to low frequency bands (433 MHz or 470-510 MHz) to avoid co-channel interference with WiFi and Bluetooth, thereby improving penetration and transmission distance while maintaining data transmission capability
Solution Approach 2:
The patent introduces an adaptive frequency-hopping mechanism as an intermediary layer that dynamically selects optimal channels based on real-time channel quality detection, mediating between the need for stable transmission and avoidance of interference
2Measurement precision
If channel scanning is performed according to GB/T15629.15-2010 standard, then channel quality is determined, but it cannot keep up with rapid changes in complex indoor electromagnetic environment
Solution Approach 1:
The patent performs preliminary channel quality detection during the beacon period before the contention-free period begins, so that channel selection is already determined before data transmission starts, enabling rapid response to channel changes without delaying data collection
Solution Approach 2:
The patent segments the superframe into distinct functional periods (beacon period for channel detection, contention-free period for data transmission) to allow simultaneous channel quality monitoring and data collection without mutual interference
3Reliability
If adaptive frequency-hopping with retransmission is implemented, then data transmission reliability is improved, but system complexity increases due to multiple channels and timeslot management
Solution Approach 1:
The patent divides the contention-free period into multiple sub-contention-free periods (SCFPs), each dedicated to specific retransmission functions, thereby organizing complex retransmission management into manageable segments with clear purposes
Solution Approach 2:
The patent implements dynamic channel selection where the coordinator and nodes adaptively switch between prescribed and spare channels based on real-time channel quality, allowing the system to dynamically respond to interference while maintaining organized timeslot structures
4Use of energy by moving object
If beacon interval is set to be relatively long with small duty cycle, then power consumption is reduced, but channel quality determination cannot keep up with rapid environmental changes
Solution Approach 1:
The patent performs channel quality detection in advance during the beacon period, so that channel selection is determined before the contention-free period begins, enabling the system to maintain long beacon intervals for power savings while still tracking channel changes effectively
Data Source
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AI summary
The disclosed is a data transmission method and apparatus configured to establish a frequency hopping-retransmission mechanism in a CPF of a superframe and switch a channel accordingly, which shortens a switching period and improves reliability of data interaction. The method provided by an embodiment of the present invention includes: selecting two channels as a prescribed channel and a spare channel; dividing a CFP of a superframe into three SCFPs, where a second SCFP is used to re-transmit data that a node fails to transmit in a first SCFP, a third SCFP is used to re-transmit data that the node fails to transmit in the second SCFP, and a timeslot position of each node in the first SCFP is the same as in the second SCFP; broadcasting a beacon frame on the prescribed channel in a beacon period of the superframe, where the beacon frame includes channel selection information and timeslot division information; receiving data from the node; and transmitting an acknowledgement frame.