Reverse Slot Reservation in Industrial Wireless Networks
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Solution Overview
Problem
The IEEE 802.15.4 TSCH standard lacks a defined method for slot scheduling and reservation, leading to instability and packet loss in congested industrial wireless networks, particularly due to the concentration of 6P packets from multiple child devices in a single autonomous Rx cell of a parent device.
Innovation Solution
A reverse slot reservation method where a parent device initiates a 6P transaction to perform mutual slot reservation, allowing child devices to send slot demands through enhanced beacons and solicitation packets, and the parent device offers available slots to child devices based on priority or round-robin selection, enabling stable slot reservation and reducing packet loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If child devices send slot reservation requests using conventional 6P transactions, then slot reservation can be performed, but packet concentration occurs in a single autonomous Rx cell causing instability and packet loss
Solution Approach 1:
The patent inverts the conventional slot reservation initiation direction. Instead of child devices sending ADD requests to parent devices, the parent device sends OFFER packets containing available slot information to child devices. Child devices then respond with their slot demands, and the parent device performs slot allocation based on these demands. This reversal distributes the control flow and prevents packet concentration in a single autonomous Rx cell.
Solution Approach 2:
The patent introduces an intermediary mechanism where the parent device acts as a mediator that collects slot demands from multiple child devices and performs centralized slot allocation. The parent device uses enhanced beacon frames to gather slot demand information from child devices and then distributes allocated slots through OFFER packets, preventing direct packet concentration between child devices and the autonomous Rx cell.
2Productivity
If multiple child devices transmit 6P packets simultaneously, then slot reservation requests can be processed, but network congestion increases leading to packet loss
Solution Approach 1:
The patent implements preliminary action by having the parent device prepare and transmit OFFER packets containing available slot information before child devices need to make slot reservations. Child devices receive these pre-prepared slot offers and can respond with their demands without needing to initiate complex transaction sequences, reducing simultaneous packet transmissions and network congestion.
Solution Approach 2:
The patent employs periodic action through the use of enhanced beacon frames that are transmitted periodically to collect slot demands from child devices. The parent device periodically sends OFFER packets with available slot information, and child devices periodically report their slot demands, creating a structured periodic communication pattern that prevents random packet bursts and network congestion.
3Device complexity
If slot reservation is performed without reverse slot reservation, then simple transaction flow is maintained, but slot allocation efficiency decreases in congested networks
Solution Approach 1:
The patent applies universality by making the parent device perform multiple functions: it acts as a slot information provider by sending OFFER packets, a slot demand collector through enhanced beacon frames, and a centralized slot allocator. This multi-functional approach consolidates slot management operations in the parent device, improving allocation efficiency without significantly increasing overall system complexity.
Solution Approach 2:
The patent implements self-service by enabling child devices to autonomously determine their slot demands based on their traffic requirements and directly report these demands to the parent device in response to OFFER packets. Child devices self-evaluate their slot needs and participate actively in the slot allocation process, improving efficiency without requiring complex centralized control for every decision.
Data Source
AI summary
Disclosed is a device for reverse slot reservation in an industrial low-power wireless network, which includes: a child device configured to send a slot demand of the child device to a parent device through an information element (IE) and a solicitation (SOLICIT) packet included in an enhanced beacon (EB) and configured to select a required number of slots and respond using a Response packet to reserve the slots when an OFFER is received; and a parent device configured to transmit an OFFER packet to a device with the highest priority or a device selected in round-robin order when there is no priority on the basis of slot demands of child devices to start reverse slot reservation and configured to select some slots from among available slots of the parent device, add the selected slots to CellList, and transmit the OFFER packet to a corresponding child device.