Frequency Hopping Transceiver for IoT Synchronization
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Solution Overview
Problem
Low-power IoT devices face challenges in transmitting data without synchronization overhead, maintaining compliance with regulatory channel occupation rules, and minimizing collisions in unlicensed radio bands, especially in low-rate wide-area networks.
Innovation Solution
A radio transmitter using frequency hopping spread-spectrum modulation generates unique hopping sequences for each packet through a binary XOR mask applied to a maximal-length linear feedback shift register, ensuring good cross-correlation properties and compliance with regulatory requirements, allowing for efficient data transmission without synchronization and minimizing collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency hopping is used to spread spectrum and increase system capacity, then resistance to interference improves, but device complexity increases due to need for precise clock synchronization and hopping sequence coordination
Solution Approach 1:
The transmitter generates and transmits its own hopping sequence information within the packet header, making the receiver self-sufficient to synchronize without external coordination. The system serves itself by embedding the synchronization information in the data stream rather than requiring separate synchronization protocols.
Solution Approach 2:
The hopping sequence information is prepared and included in the packet header before the actual data transmission begins. This preliminary inclusion of synchronization information allows the receiver to prepare for frequency hopping in advance, eliminating the need for complex real-time synchronization mechanisms.
2Reliability
If transmitters wake up frequently to maintain time synchronization, then hopping sequence coordination improves, but power consumption increases
Solution Approach 1:
The patent extracts the time synchronization function from the frequent wake-up requirement by using packet arrival time as the synchronization reference. Instead of maintaining continuous time synchronization through frequent wake-ups, the system only needs to synchronize at packet boundaries, removing the continuous synchronization overhead.
Solution Approach 2:
Synchronization occurs periodically at packet boundaries rather than continuously. The receiver synchronizes its hopping sequence at the start of each packet and maintains this synchronization for subsequent packets, converting continuous synchronization requirements into periodic updates that consume less power.
3Measurement precision
If detection sequences are made longer to improve reliable detection, then detection accuracy improves, but transmission time increases
Solution Approach 1:
The hopping sequence information is prepared and embedded in the packet header before transmission begins. This preliminary preparation allows the receiver to have detection sequences ready in advance, matched to the incoming packet's hopping pattern, improving detection accuracy without requiring extended detection periods.
Solution Approach 2:
The system changes the parameter of detection sequence length dynamically based on the packet structure and hopping sequence. Rather than using fixed long detection sequences, the detection sequence adapts to the specific packet characteristics, maintaining adequate detection accuracy while minimizing transmission time overhead.
Data Source
AI summary
A radio transmitting device configured to transmit a spread-spectrum radio signal wherein a carrier frequency changes in a predetermined set of radio channels according to a hopping sequence, the radio signal being organized in packets having each a header transmitted at a first channel in the hopping sequence comprising a detection sequence, and payload data encoding a message transmitted at following channels in the hopping sequence.