AP Roaming Context Transfer for Sequence-Safe Data Handover

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Solution Overview

Problem

Existing wireless communication systems face challenges in efficiently handling uplink and downlink data during context transfer and data flushing for seamless roaming, which can lead to data loss or duplication during roaming, particularly in wireless networks.

Innovation Solution

Implement context transfer mechanisms for both uplink and downlink data transfer, including options for sequence number coordination and buffer management between serving and target APs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If context information is coordinated between serving and target APs during roaming, then data continuity is maintained, but system complexity increases

Engineering Contradiction:

Improvedata continuityVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent performs context transfer from serving AP to target AP before the actual roaming occurs. This preliminary action includes transferring sequence number states, buffer information, and delivery progress of MPDUs, so that when roaming happens, data continuity is already established without requiring complex real-time coordination during the transition.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces a context transfer mechanism that acts as an intermediary between serving and target APs. This mechanism systematically transfers and coordinates context information including sequence numbers, buffer states, and delivery progress, simplifying the interaction between APs while maintaining data continuity during roaming.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If sequence number coordination is implemented during context transfer, then data loss and duplication are prevented, but processing overhead increases

Engineering Contradiction:

Improvedata integrityVSAvoidprocessing overhead

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent transfers sequence number states and buffer information in advance during the context transfer phase, before roaming occurs. This preliminary coordination of sequence numbers ensures that when data transmission resumes at the target AP, there is no data loss or duplication, while avoiding the need for complex real-time sequence number management during the actual roaming event.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20250392899A1Uplink and downlink data and context handling for roaming

Publication Date: 2025.12.25 CISCO TECHNOLOGY INC

AI summary

The present disclosure provides techniques for seamless roaming with uplink/downlink context transfer. A serving AP transmits a sequence of downlink data units for a TID to a client device, the sequence of downlink data units having sequence numbers falling within a transmit window for the TID. The serving AP receives, from the client device, a roaming request identifying a target AP. In response, the serving AP sends a roaming context message to the target AP, comprising at least one of a SSN of the transmit window corresponding to the TID, or a NSN for the TID, where the NSN is a first sequence number to be assigned for downlink data units of the TID transmitted by the target AP to the client device.