Frequency-Hopping IoT Network Collision Mitigation
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Solution Overview
Problem
Existing low-power wireless networks for IoT applications face challenges such as high interference resistance, regulatory compliance, and limited system load due to frequency and power collisions, especially in unlicensed bands, which restricts the capacity and efficiency of sensor node communications.
Innovation Solution
A wireless transmitter device and network utilizing modified ultra-narrowband modulation with coherent phase modulation, error-correction codes, and frequency hopping spread spectrum, along with adaptive sub-band management and implicit signalling of hopping sequences, to enhance robustness and mitigate collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If random medium access like ALOHA is used for sensor nodes, then power efficiency is improved, but collision rate increases significantly
Solution Approach 1:
The frequency band is segmented into multiple sub-bands, and each sensor node is assigned to a specific sub-band. This segmentation reduces the probability of frequency collisions while maintaining random medium access for power efficiency. Nodes within the same sub-band can communicate without interfering with nodes in other sub-bands.
Solution Approach 2:
The invention introduces frequency sub-band assignment as an additional dimension for collision avoidance. By organizing nodes into different frequency sub-bands, the system adds a frequency-dimensional separation layer to the time-random access mechanism, effectively reducing collisions in the time-frequency space.
2Adaptability or versatility
If there is no frequency grid in ultra-narrowband network, then frequency flexibility is improved, but frequency collisions double the collision rate
Solution Approach 1:
Different sub-bands are assigned to different groups of sensor nodes based on their local requirements and characteristics. Each sub-band operates with its own frequency characteristics, allowing local optimization for specific node groups while maintaining overall system flexibility.
Solution Approach 2:
The system changes the frequency parameter by introducing a structured sub-band organization within the ultra-narrowband framework. This parameter change allows the system to maintain frequency flexibility while reducing random frequency collisions through organized sub-band allocation.
3Area of stationary object
If marginal sensor nodes or weak nodes participate in collisions, then network coverage is improved, but they always lose in any collision
Solution Approach 1:
Frequency sub-band assignment acts as an intermediary mechanism that protects weak nodes from direct competition with strong nodes. By assigning weak nodes to dedicated sub-bands with reduced load, the system mediates the collision environment to favor weaker participants while maintaining overall network coverage.
Solution Approach 2:
Different sub-bands are optimized for different node types, with certain sub-bands specifically allocated for weak or marginal nodes. This local quality differentiation ensures that weak nodes have dedicated resources where they can succeed, improving their performance while maintaining their contribution to network coverage.
4Device complexity
If phase noise of the transmitter is present, then hardware simplicity is improved, but adjacent user rejection level is limited
Solution Approach 1:
The frequency spectrum is segmented into multiple sub-bands separated by guard bands. This segmentation isolates adjacent users in frequency space, allowing transmitters with high phase noise to operate without interfering with adjacent users, thereby maintaining hardware simplicity while improving rejection levels.
Solution Approach 2:
The invention converts the harmful effect of phase noise into a benefit by using wider sub-band allocations that can tolerate higher phase noise. Transmitters with poor frequency stability are assigned to sub-bands where their phase noise does not affect adjacent users due to the frequency separation, effectively utilizing low-cost hardware.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution significantly improves the robustness and capacity of low-power wireless networks by reducing interference and collisions, allowing for higher system load and efficient data transmission even with low-quality oscillators in IoT sensor nodes.
Implementation Method 1
The uplink communication from a sensor node to a gateway uses frequency hopping spread spectrum
Implementation Method 2
modified ultra-narrowband modulation with coherent phase modulation
Data Source
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AI summary
A hopping spread-spectrum wireless network for loT applications operating in a predetermined frequency band, with mobile device that have unsynchronized local frequency references and receiving gateways that are capable of detecting whether modulated radio signals will collide in frequency in a collision time interval, and blanking the signals in the collision time. Preferably, the frequency band is subdivided into a sub-bands, and the mobile devices adapt the width of the sub-bands used for transmission based on a synchronization status indicative of the frequency error of the local frequency reference.