RTT-Aware Downlink Scheduling for LPWAN Energy-Constrained Devices
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Solution Overview
Problem
In Low-Power Wide-Area Networks (LPWAN), energy-constrained devices face challenges in receiving downlink transmissions due to variations in Round Trip Time (RTT) between RF gateways and backend servers, which can result in missed downlink slots and inefficient battery usage.
Innovation Solution
The implementation of adaptive scheduling for downlink transmissions based on RTT measurements between RF gateways and backend servers, where the backend server determines candidate RF gateways, measures RTT, and adjusts the configured time interval between uplink messages and downlink receive time slots to ensure timely delivery of downlink messages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the configured time interval between uplink message transmission and downlink receive time slot is fixed, then device simplicity is maintained, but downlink transmissions may be missed when RTT exceeds the fixed interval
Solution Approach 1:
The patent implements dynamic adjustment of the configured time interval between uplink message transmission and downlink receive time slot based on measured RTT values. The backend server continuously monitors RTT and adapts the time interval parameter to match actual network conditions, transforming a static scheduling approach into a dynamic one that responds to changing network latency
Solution Approach 2:
The system establishes a feedback loop where the backend server measures RTT between RF gateways and backend, uses this measurement to determine whether the current configured time interval is sufficient, and adjusts the interval accordingly. This closed-loop control ensures that downlink scheduling parameters reflect actual network conditions
2Reliability
If the configured time interval is increased to accommodate high RTT, then downlink reception reliability improves, but battery consumption increases due to extended listening periods
Solution Approach 1:
The patent dynamically changes the time interval parameter based on measured RTT conditions. When RTT is high, the interval is extended to ensure reliable downlink reception; when RTT is low, the interval is reduced to minimize battery consumption. This adaptive parameter adjustment optimizes the trade-off between reliability and energy usage
3Reliability
If RTT measurement and adaptive scheduling is implemented, then downlink reception reliability improves, but system complexity increases
Solution Approach 1:
The backend server acts as an intermediary that centralizes the RTT measurement and scheduling decision-making functions. Rather than requiring complex RTT measurement and adaptation logic in each end device, the backend server performs these functions centrally and communicates scheduling parameters to devices, simplifying the overall system architecture while maintaining reliability
Data Source
AI summary
Some implementations of the disclosure relate to a backend server that is configured to perform operations including: determining one or more radio frequency (RF) gateways that are candidates for communicating with an end device over a RF link in a low-power wide-area network (LPWAN); obtaining, for each of the one or more RF gateways, a round trip time (RTT) of communications between the backend server and the RF gateway over a backhaul link; determining whether at least one of the one or more RTTs exceeds a threshold value; and when at least one of the one or more RTTs exceeds the threshold value, increasing a configured time interval between transmission of an uplink message by the end device and a downlink receive time slot in which the end device is configured to listen for a downlink message.