PSM Queue Segmentation for Wireless QoS
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Solution Overview
Problem
The integration of IEEE 802.11 Power Save Mode (PSM) and 802.11e Quality of Service (QoS) mechanisms in wireless networks leads to significant degradation of high-priority frame service due to low emptying rates of low-priority frames, causing high-priority frames to be discarded under congestion conditions, which is detrimental for real-time applications like voice over IP.
Innovation Solution
Dividing the PSM queue into sub-queues corresponding to Access Categories (ACs) at the Access Point, allowing incoming frames to be buffered separately based on priority, thereby preventing high-priority frame losses by separating the service rates of different ACs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a common PSM queue is used to buffer frames of all Access Categories, then the device can operate in Power Save Mode with reduced energy consumption, but high-priority frames are discarded when the queue is full due to low emptying rates of low-priority frames
Solution Approach 1:
The common PSM queue is segmented into multiple separate queues, one for each Access Category (AC). This segmentation allows independent management and emptying of frames based on their priority level, ensuring that high-priority frames are not blocked by low-priority frames while still enabling Power Save Mode operation.
2Device complexity
If frames are buffered in a common PSM queue without separation, then the queue management is simple, but the service rates of different ACs cannot be differentiated leading to loss of high-priority frames
Solution Approach 1:
The queue structure is segmented into AC-specific sub-queues within the PSM. Each sub-queue maintains independence while being managed under the unified PSM framework, providing differentiated service rates without excessive complexity.
Solution Approach 2:
Each AC sub-queue within the PSM is given local quality characteristics specific to its priority level. High-priority ACs receive preferential treatment in terms of emptying rates and buffer management, while low-priority ACs operate with standard rates, ensuring quality differentiation where needed.
3Productivity
If the PSM queue is filled with low-priority frames, then the queue utilization is high, but newly arriving high-priority frames are discarded despite their urgent nature
Solution Approach 1:
By segmenting the queue into AC-specific sub-queues, each with its own capacity and emptying rate, the system can maintain high overall utilization while protecting high-priority frame delivery. Low-priority frames fill the low-priority sub-queue without blocking high-priority sub-queue operations.
Solution Approach 2:
The emptying rate parameter is changed dynamically based on the AC priority. High-priority ACs have higher emptying rates that increase when their sub-queue is non-empty, while low-priority ACs have lower rates, allowing the system to adapt to varying traffic conditions and priorities.
Data Source
AI summary
A method to improve the Quality of Service (QoS) in a wireless network, preferably in a WLAN according to the IEEE proposal 802.11e comprising an Access Point (AP) and at least one mobile station (STA) with different Access Categories (ACs) being defined for the transmission of frames depending on their priority, and in which a Power Save Mode (PSM), preferably according to IEEE standard 802.11, is used in the network is characterized in that the PSM queue is separated into several sub-queues at the Base Station.