Spread-Spectrum Frequency Hopping for IoT Interference Reduction
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Solution Overview
Problem
Existing wireless networks for the Internet of Things (IoT) devices face challenges at intermediate ranges, particularly in populated areas, due to interference and reliability issues, which are unsuitable for applications requiring interactivity and real-time communication, and are not conducive for battery-powered devices.
Innovation Solution
A hub-based wireless network system using digital spread-spectrum frequency hopping with a spectrum-impact-smoothed channel set, where packets include a preamble and data payload, and end-devices can operate at intermediate ranges of thousands of meters, distributing radio-frequency emissions over a set of frequencies to reduce interference and improve reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If intermediate-range wireless communication is used for IoT devices in populated areas, then communication range is extended to thousands of meters, but interference from other devices operating on the same radio bands increases significantly
Solution Approach 1:
The communication channel is segmented into multiple frequency bands or channels. The system divides the available spectrum into discrete segments that can be selectively used, allowing devices to hop between segments to avoid interference. This is achieved through frequency hopping spread spectrum (FHSS) where the carrier frequency changes periodically according to a pseudorandom sequence.
Solution Approach 2:
The system employs dynamic frequency selection and hopping mechanisms where the operating frequency is not fixed but changes over time according to a predetermined sequence. This dynamic behavior allows the communication system to adapt to changing interference conditions and avoid persistent interference from other devices.
2Reliability
If spread-spectrum techniques with multiple frequencies are used to reduce interference, then interference resistance is improved, but data throughput is reduced such that audio and video data cannot be streamed in real-time
Solution Approach 1:
The system applies spread-spectrum techniques selectively rather than continuously. During periods of high interference, the full spread-spectrum capability is activated to ensure reliable communication. During periods of low interference, the system can operate at higher data rates using narrower bandwidth, thus achieving partial use of the spread-spectrum capability only when necessary.
3Reliability
If battery-powered end devices operate at intermediate ranges with continuous reception to ensure real-time responsiveness, then interactivity is improved, but power consumption increases
Solution Approach 1:
The receiving device operates in periodic cycles, alternating between sleep mode and active reception mode. The device wakes up at predetermined intervals to check for incoming communications, then returns to sleep mode. This periodic operation significantly reduces average power consumption while maintaining the ability to respond to time-critical communications within each active window.
Data Source
AI summary
Disclosed herein are hub-based wireless networks employing end-devices at intermediate wireless at ranges of thousands of meters, utilizing packets that include a preamble and a data payload. End-devices may be such things as keypads, door latches, occupancy monitors, sprinkler controllers and other devices controlled or monitored in a campus or a collection of buildings. A digital spread-spectrum frequency hopping rotation is used, wherein packet transmissions rotate through frequency sequences to spread radio-frequency emissions impact over a set of frequencies. A spectrum-impact-smoothed channel set is fashioned using sequences that each specify a unique preamble frequency relative to the other sequences and channels. The set is traversed as packets are transmitted, thereby distributing the focused radio-frequency emission impact of packets having long preambles over time. Detailed information on various example embodiments of the inventions are provided in the Detailed Description below, and the inventions are defined by the appended claims.