Ambient IoT Retransmission Scheduling for Collision and Energy Limits
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Solution Overview
Problem
Ambient IoT systems face challenges with power saving and collision reduction due to the large number of low-end devices performing D2R transmissions, which can lead to interference and deteriorate system performance, especially when repetitions are consecutive or closely timed, and energy harvesting is limited.
Innovation Solution
Implementing frequency diversity techniques, resource scheduling, and relaying methods to control the number of re-transmissions, utilize CW energy harvesting, and separate transmissions in time to avoid collisions and improve link reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple repetitions/re-transmissions are performed for D2R transmissions to improve link reliability, then transmission reliability is improved, but interference levels increase and system performance deteriorates
Solution Approach 1:
The patent segments the large number of ambient IoT devices into different groups, each assigned to different time-frequency resources for D2R transmissions. This segmentation reduces the number of simultaneous transmissions on any single resource, thereby reducing interference levels while maintaining link reliability through multiple repetitions across different resource groups.
Solution Approach 2:
The patent implements dynamic resource allocation where the reader dynamically assigns time-frequency resources to different device groups based on current system conditions, traffic load, and channel states. This dynamic approach allows the system to adaptively manage interference levels while ensuring reliable transmissions by allocating sufficient repetitions when needed.
2Productivity
If a large number of ambient IoT devices perform D2R transmissions simultaneously, then system throughput increases, but collision probability increases and reduces transmission success rate
Solution Approach 1:
The patent divides the system into multiple resource pools (time slots, frequency resources) and assigns different device groups to different pools. This segmentation allows many devices to transmit simultaneously across the system (maintaining high throughput) while ensuring that each individual resource experiences reduced collision probability, thereby improving transmission success rate.
Solution Approach 2:
The patent extends the resource allocation from a single dimension to multiple dimensions by utilizing both time and frequency domains. Devices are allocated resources across different time slots and frequency subcarriers, creating a two-dimensional resource space that increases system capacity while reducing collisions in any single dimension.
3Loss of time
If consecutive or closely timed re-transmissions are performed, then transmission latency is reduced, but energy harvesting capability is compromised and power consumption increases
Solution Approach 1:
The patent implements periodic transmission patterns where devices perform D2R transmissions at scheduled intervals rather than continuously. The reader assigns periodic resource allocations that provide sufficient time gaps between transmissions, allowing energy harvesting devices to recharge while maintaining acceptable latency through optimized periodic scheduling.
Solution Approach 2:
The patent dynamically adjusts the timing and spacing of re-transmissions based on device energy status, device type, and channel conditions. For energy harvesting devices, the system dynamically extends transmission intervals to coincide with energy availability windows, while for devices with sufficient energy, tighter scheduling is applied to minimize latency.
4Length of stationary object
If more re-transmissions are performed to reach distant IoT devices, then coverage range is extended, but interference levels increase and system resources are consumed
Solution Approach 1:
The patent utilizes both time and frequency dimensions to extend coverage. Distant devices are allocated resources across multiple time slots and frequency subcarriers, allowing the system to reach farther devices through repeated transmissions on diverse resources while distributing interference across the time-frequency space rather than concentrating it.
Solution Approach 2:
The patent applies different transmission parameters and resource allocation strategies tailored to local conditions of distant devices. The reader identifies devices at the coverage edge and allocates them specific resource patterns with appropriate repetition counts and time-frequency spacing, optimizing for their specific channel conditions while minimizing overall system interference.
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
Enhances system performance by reducing interference and improving the ability to reach distant IoT devices through optimized resource allocation and transmission strategies.
Implementation Method 1
The device's UL transmission is backscattered on a carrier wave (CW) provided externally
Implementation Method 2
separate base retransmissions from each other by a time domain interval based on a carrier wave (CW) energy harvesting ability of the ambient IoT device
Data Source
AI summary
Apparatus and methods are disclosed for performing D2R and R2D transmission in an ambient IoT system. A method performed by an ambient IoT device includes receiving, from a reader, a control indication to trigger a D2R transmission; identifying a number of base retransmissions to perform for the D2R transmission; performing an initial transmission of the D2R transmission; and performing base retransmissions of the D2R transmission based on the number of base retransmissions. Consecutive base retransmissions among the base retransmissions of the D2R transmission are separated from each other by a time domain interval based on a CW energy harvesting ability of the ambient IoT device.