WLAN Service Interval Timing Synchronization
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Solution Overview
Problem
Current IEEE 802.11E standard for WLANs experiences ambiguity in service interval start and end times, leading to protocol failures, power waste, and inefficient resource utilization due to unclear communication between Hybrid Coordinators (HC) and Quality of Service Stations (QSTA) regarding traffic transmission and reception.
Innovation Solution
Implementing a method that sets a substantially absolute start time for service intervals using a clocking mechanism, synchronizing device clocks via the Timing Synchronization Function (TSF) or absolute offset relative to a target beacon transmission time, and using a schedule frame element (SEF) with a start time frame element to ensure clear communication and power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the service period timing is set relative to the first successful data or QoS CF-Poll transmission by the HC, then the polling sequence efficiency is improved, but ambiguity in start and end times causes protocol failures and resource waste
Solution Approach 1:
The patent introduces a Timing Synchronization Function (TSF) as an intermediary mechanism that provides a common reference time for all devices in the WLAN. The TSF timer generates timing information that is distributed to all stations, serving as a mediator that eliminates the ambiguity in service period timing. Instead of relying on relative timing from Poll transmissions, both HC and QSTA use the absolute TSF time to determine service period start and end times, ensuring consistent understanding of timing parameters.
Solution Approach 2:
The patent implements preliminary timing synchronization by having the HC distribute timing information to QSTA before service periods begin. The TSF timing parameters are established in advance, allowing QSTA to pre-calculate and prepare for service period start times. This preliminary action ensures that when service periods occur, both parties are already synchronized and ready, preventing protocol failures due to timing ambiguity.
2Use of energy by moving object
If QSTA enters power save mode after each service period, then power consumption is reduced, but frequent switching between power save mode and active state wastes energy
Solution Approach 1:
The patent enables multiple transmission opportunities (TXOPs) to occur within a single service period, allowing QSTA to remain in active state continuously serving multiple communication bursts without returning to power save mode. By extending the service period duration and allowing multiple TXOPs, the system maintains continuous useful action during the active period, reducing the frequency of power save mode transitions and the associated energy losses.
3Productivity
If the service period is set to equal the period required to deliver one TXOP, then transmission opportunities are managed, but QSTA must frequently switch to power save mode causing power waste
Solution Approach 1:
The patent merges multiple transmission opportunities into a single extended service period. Instead of having separate service periods for each TXOP, the system combines multiple TXOPs within one service period framework. This allows QSTA to handle multiple transmissions during a single active period, reducing the number of times it needs to switch to power save mode and wake back up, thereby reducing overall power consumption while maintaining effective TXOP management.
Data Source
AI summary
A wireless local area network (WLAN) includes at least one hybrid coordinator (HC) and at least one Quality of Service Station (QSTA). The HC transmits a schedule frame element (SEF). The WLAN also includes a clocking mechanism that sets a substantially absolute start time of a service interval. A method of synchronizing the HC and the QSTA includes transmitting a schedule element frame (SEF), and setting a substantially absolute start-time of a service interval, and a first transmitted frame element.