Frequency Hopping in Sensor Networks for FCC Compliance
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Solution Overview
Problem
The existing frequency hopping solutions for sensor networks in the 902-928 MHz band are limited by low permissible radiated power, making it difficult to achieve high communication range while complying with FCC regulations, especially for low-power sensors that require efficient energy management and synchronization.
Innovation Solution
Implementing a frequency hopping scheme where the master terminal specifies and transmits the channel for return messages, using a well-encrypted CRC message to determine the channel number, reducing energy usage and eliminating the need for synchronization and extra data transmission, with optional modifications to CRC processing and message integrity checks to maintain low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If low-power radiated operation is used to comply with FCC regulations, then energy consumption is reduced, but communication range is limited
Solution Approach 1:
The system dynamically switches between fixed-frequency and frequency-hopping modes based on communication requirements. The master terminal can select from multiple frequency channels (64 channels in 902-928 MHz band) and switch frequencies during communication, allowing the sensor network to adapt between low-power operation and extended range communication as needed
Solution Approach 2:
The invention changes the frequency parameter dynamically by implementing frequency hopping across 64 channels. The master terminal determines the next frequency based on pseudo-random sequences or acknowledgment patterns, allowing the system to transition between different frequency states to achieve both energy efficiency and extended communication range
2Length of moving object
If frequency hopping is implemented to achieve high communication range, then communication range is improved, but synchronization complexity increases
Solution Approach 1:
The master terminal autonomously determines the frequency hopping sequence without requiring synchronization from slave terminals. The master uses pseudo-random sequences or acknowledgment-based methods to select frequencies independently, eliminating the need for complex synchronization protocols and reducing overall system complexity
Solution Approach 2:
Instead of having slave terminals synchronize to the master's frequency hopping sequence, the invention inverts the approach by having the master terminal independently select frequencies based on received acknowledgments or pre-shared pseudo-random sequences. This reversal eliminates the synchronization burden on slave terminals
3Length of moving object
If spectrum spreading is used to comply with high-power FCC regulations, then communication range is extended, but energy usage increases
Solution Approach 1:
The system applies spectrum spreading partially by using frequency hopping across 64 channels rather than continuous spreading. The master terminal hops to different frequencies only when needed for extended range communication, allowing low-power sensors to maintain long battery life while achieving high communication range when necessary
Data Source
AI summary
Systems and methods for facilitating compliance with FCC frequency hopping requirements are described. The described innovations may be used to facilitate frequency hopping in a sensor network having a network link with two endpoints, those endpoints comprising a master and a slave, wherein the slave comprises a server and the master comprises a sensor, and wherein the slave transmits one message in response to each master message on the link. All communication over the link may be initiated by the master terminal, requiring only one return message per transmission. A channel to be used for a following reception from the slave terminal is specified at the master, and the specified channel is transmitted from the master to the slave terminal. The slave terminal then uses the specified channel for its next transmission.