TDLS Discovery Frame Scheduling in WLAN Stations

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Solution Overview

Problem

In wireless local-area networks (WLANs), the existing tunneled direct link setup (TDLS) mechanisms result in significant power expenditure for stations (STAs) due to the need for prolonged wakefulness to transmit and receive discovery request frames, especially when the receiving STA may be in sleep mode, leading to inefficient power usage in battery-powered devices.

Innovation Solution

Implementing a controller and transmitter configuration that allows TDLS discovery request frames to be transmitted only within a predetermined interval preceding a delivery traffic indication message (DTIM) from the access point (AP), reducing the minimum awake interval for STAs and enabling quicker response times.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If STAs transmit TDLS discovery request frames immediately upon trigger event, then direct link establishment speed is improved, but power consumption increases due to prolonged awake intervals

Engineering Contradiction:

Improvedirect link establishment speedVSAvoidpower consumption

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The system performs preliminary actions by scheduling TDLS discovery request frames to be transmitted just before DTIM intervals, and by having the AP pre-buffer these frames. This allows STAs to wake up only at DTIM intervals to receive or transmit frames, rather than remaining awake continuously, thus reducing power consumption while maintaining establishment speed.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent utilizes the periodic DTIM (Delivery Traffic Indication Message) intervals as a framework for TDLS frame transmission. By aligning TDLS discovery requests with these periodic DTIM cycles, STAs can enter sleep mode between intervals and only wake periodically to check for buffered frames or send new requests, converting continuous operation into periodic action to save energy.

Inventive Principle:

Principle #19Periodic action

2Reliability

If STAs remain awake to receive TDLS discovery response frames, then link establishment reliability is improved, but awake interval duration increases causing power loss

Engineering Contradiction:

Improvelink establishment reliabilityVSAvoidawake interval duration

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The AP acts as an intermediary by buffering TDLS discovery request frames and managing their transmission timing. The AP receives requests from STAs, stores them until the appropriate DTIM interval, and then transmits them to the destination STA. This intermediary role ensures reliable delivery while allowing original STAs to return to sleep mode immediately after sending requests, without needing to remain awake for responses.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent extracts the frame transmission function from the STA and relocates it to the AP. The AP takes over the responsibility of transmitting buffered TDLS frames at optimal times, separating the request sending function (performed by STA) from the actual transmission timing (controlled by AP). This extraction allows STAs to minimize their awake time while maintaining reliable communication.

Inventive Principle:

Principle #2Taking out (Extraction)

3Use of energy by moving object

If DTIM interval is extended to reduce wake frequency, then power saving is improved, but TDLS frame transmission timing flexibility is reduced

Engineering Contradiction:

Improvepower savingVSAvoidframe transmission timing flexibility

Core Design Contradiction:

Use of energy by moving objectVSAdaptability or versatility

Solution Approach 1:

The system introduces dynamic buffering and scheduling capabilities at the AP, allowing frame transmission timing to be adjusted based on DTIM intervals and network conditions. The AP can hold frames in a buffer and transmit them at dynamically determined optimal times, providing flexibility despite extended DTIM intervals. This dynamic approach maintains adaptability while enabling longer sleep periods for STAs.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS8937893B1Method and apparatus for delaying wireless message transmission for saving power

Publication Date: 2015.01.20 MARVELL ASIA PTE LTD

AI summary

A basic service set includes first and second stations and an access point (AP). An apparatus for the first station includes a controller and a transmitter. The controller is configured to, subsequent to a first delivery traffic indication message (DTIM) being transmitted by the AP, selectively provide a trigger signal that indicates a message should be transmitted by the first station to the second station via the AP. The message requests that the second station transmit a reply to the message directly to the first station. The transmitter is configured to, in response to the trigger signal, (i) enter a sleep mode until less than a predetermined period remains preceding an expected transmission of a second DTIM by the AP and (ii) transmit the message within the predetermined period. The second DTIM is transmitted by the AP subsequently to transmission of the first DTIM by the AP.