Bidirectional Sensor Node Frequency Calibration
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Solution Overview
Problem
Existing methods for bidirectional radio transmission of sensor data between battery-operated nodes and base stations face challenges such as interference, poor reception quality due to frequency misalignment, and high power consumption, particularly in downlink transmissions where exact time synchronization is required.
Innovation Solution
Implementing a method that uses a node with both a high-frequency and a low-frequency generator for calibration during data packet transmission, allowing for precise adjustment of the reception window and reducing temperature-related frequency offsets, thereby improving reception quality and conserving energy by minimizing processing power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a simple crystal frequency generator is used in autonomous consumption meters, then power consumption is reduced, but time synchronization accuracy deteriorates due to crystal errors of 10-100 ppm
Solution Approach 1:
The system dynamically switches between two frequency generators based on operational mode: the low-power first frequency generator operates continuously for basic timing, while the high-precision second frequency generator is activated only during communication phases requiring accurate time synchronization. This dynamic adaptation resolves the contradiction by providing high precision only when needed, rather than continuously.
Solution Approach 2:
The second frequency generator is activated in advance before communication events that require precise time synchronization, allowing the system to pre-establish accurate timing references. This preliminary activation ensures that when synchronization is needed, the high-precision generator is already running, eliminating the need for continuous operation while maintaining accuracy.
2Stability of the object's composition
If temperature variations occur, then frequency stability deteriorates due to crystal errors, but using a more stable crystal increases power consumption
Solution Approach 1:
The system employs dynamic frequency generator selection where the high-stability second frequency generator is activated only during temperature-sensitive communication operations, while the low-power first frequency generator handles stable-temperature periods. This resolves the contradiction by applying high stability only when temperature variations threaten frequency accuracy.
Solution Approach 2:
The system changes the operational parameters of frequency generators based on temperature conditions and communication requirements. By adjusting which generator is active based on environmental and operational parameters, the system achieves high frequency stability only when necessary, rather than maintaining it continuously at high power cost.
3Loss of time
If the node opens its reception window at the expected time, then time synchronization is maintained, but frequency misalignment occurs due to temperature-related divergence of the frequency generator
Solution Approach 1:
The second frequency generator is activated in advance before the expected reception time to allow the system to prepare accurate frequency references. This preliminary action ensures that when the reception window opens at the expected time, the high-precision generator is already running and can compensate for temperature-related frequency divergence, preventing both time synchronization loss and frequency misalignment.
Solution Approach 2:
The system uses feedback from time synchronization requirements to control the activation of the second frequency generator. When time synchronization accuracy is needed for opening the reception window, the system activates the high-precision generator to compensate for temperature effects, creating a feedback loop that maintains both time synchronization and frequency alignment.
4Productivity
If data packets are transmitted successively at intervals, then complete data transmission is achieved, but reception quality deteriorates due to accumulated frequency and time misalignment
Solution Approach 1:
The second frequency generator is activated at the beginning of data packet transmission sequences to establish accurate frequency and time references before packets are sent. This preliminary action ensures that throughout the successive packet transmission interval, the system maintains synchronization accuracy, preventing accumulated misalignment from degrading reception quality while still achieving complete data transmission.
Data Source
AI summary
A method for transmitting data or sensor data by radio between a preferably fixed battery-operated node and base station in a communication system with bidirectional radio transmission, includes providing a base station communication module having a first frequency transmitter, and a node communication module having a first frequency transmitter and second frequency transmitter with lower frequency. The node communication module transmits data in the uplink to the base station communication module by splitting a radio telegram into data packets transmitted successively with temporal spacing. The base station communication module transmits data in the downlink to the node communication module by splitting a radio telegram into data packets transmitted successively with temporal spacing. To improve downlink reception quality, two calibrations of first and second node frequency transmitters occur during transmission of the sum of a sequence of uplink data packets and subsequent sequence of downlink data packets including periods therebetween.