D2R Transmission Slot Allocation for Low-SFO IoT Devices
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Solution Overview
Problem
Existing IoT devices face challenges in reducing size, complexity, and power consumption while maintaining accurate timing for D2R transmissions, leading to inter-device interference due to weak timing capabilities and high power consumption, which is not compatible with energy harvesting.
Innovation Solution
A method for IoT devices to determine appropriate time and frequency resources for D2R transmissions based on sampling frequency offset (SFO) capability, using two sets of resources allocated before or after a specified number of slots, depending on the device's SFO threshold, to minimize inter-device interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If AIoT devices use weak timing capability for D2R transmissions, then device complexity and power consumption are reduced, but inter-device interference increases
Solution Approach 1:
The patent segments the transmission time window into multiple slots and divides frequency resources into multiple channels. Devices are scheduled to transmit in different time slots or on different frequency channels, which segments the potential interference and allows devices with weak timing capability to transmit without causing significant inter-device interference.
Solution Approach 2:
The reader performs preliminary actions by transmitting reference signals and control information before the actual D2R transmissions. This preliminary synchronization allows devices to align their transmissions without requiring high timing accuracy, as the reference signals provide the timing reference that compensates for weak device timing capabilities.
2Reliability
If existing cellular devices are used for D2R transmissions, then communication capability is maintained, but power consumption exceeds energy harvesting capability
Solution Approach 1:
The patent employs periodic action by using continuous wave (CW) reference signals transmitted periodically by the reader and having AIoT devices respond periodically. This periodic communication pattern allows devices to transmit in short bursts rather than continuously, significantly reducing power consumption to levels compatible with energy harvesting while maintaining reliable communication.
Solution Approach 2:
The patent replaces the traditional cellular communication mechanism with a backscatter-based AIoT communication mechanism. Instead of active transmission requiring high power, AIoT devices modulate the reference signal by changing their load impedance, which is a passive process that consumes minimal power, thereby enabling communication with energy harvesting capability.
3Productivity
If multiple AIoT devices transmit simultaneously on the same frequency, then spectrum efficiency is improved, but inter-device interference increases
Solution Approach 1:
The patent merges time and frequency dimensions into a two-dimensional resource allocation scheme. Multiple AIoT devices can transmit simultaneously in the time-frequency grid without interfering with each other, as each device is assigned a unique time slot and frequency channel combination. This merging allows high spectrum efficiency while maintaining low inter-device interference.
Solution Approach 2:
The patent adds the time dimension to frequency-based multiplexing by introducing time slots. Instead of only using frequency division, the system uses time-frequency division where devices are scheduled in different time slots or on different frequency channels within a slot. This dimensional expansion allows multiple devices to transmit simultaneously without interference while maintaining efficient spectrum utilization.
Data Source
AI summary
The disclosed process addresses transmission of data from a device to a reader (D2R) in communication systems where devices receive reader-to-device (R2D) transmissions. Methods to determine the appropriate time and frequency resources for the D2R transmission based on the device's sampling frequency offset (SFO) capability is disclosed. The device receives an R2D transmission in a first slot, which specifies two sets of resources for D2R transmission: a first set and a second set. The device compares its SFO capability with a pre-defined threshold. If the device's SFO capability is below the threshold, it uses resources from the first set, which are allocated to time and frequency slots occurring before a specified number of slots (N) from the first slot. Conversely, if the SFO capability exceeds the threshold, the device uses resources from the second set, which are allocated to slots occurring after N slots from the first slot.