Power Aware Link Metric Month Year doc.: IEEE 802.11-yy/xxxxr0 September 2008 Power Aware Link Metric Date: 2008-09-03 Authors: Liwen Chu, STMicroelectronics John Doe, Some Company

Month Year doc.: IEEE 802.11-yy/xxxxr0 September 2008 Abstract The current 802.11s airtime link metric does not include or take into account a power saving factor. As consequence a power saving MP with the same metrics than non-power saving MP have the same chance to become a forwarding node. This may increase end-to-end delay and the power consumption of the battery powered MPs. This presentation describes how link metric should take power save into account. Normative text for the presentation is given in document 11-08-1015r0-Forwarding-MPs-in-Power-Save.doc Liwen Chu, STMicroelectronics John Doe, Some Company

Approach for the power save Month Year doc.: IEEE 802.11-yy/xxxxr0 September 2008 Approach for the power save Power save should not have impact to the QoS of forwarded traffic For instance VoIP traffic in AC3 is less tolerant to delay and delay variation than best effort traffic in AC1 If the QoS is violated, the whole traffic may be useless The power saving MPs should consider also traffic type and traffic load when selecting power mode 11-08-578r0 discusses on different traffic types and how power saving MPs should forward Liwen Chu, STMicroelectronics John Doe, Some Company

Month Year doc.: IEEE 802.11-yy/xxxxr0 September 2008 Power save use in MPs The power saving MPs may be divided into two category: Battery powered MPs that desire to minimize the power consumption at all times Mains powered MPs that desire to minimize the stand-by power consumption and maximize the throughput Mesh networks should Try to avoid battery powered MPs use in frames forwarding Not force mains powered MPs to operate only in active mode Liwen Chu, STMicroelectronics John Doe, Some Company

O: varies depending on PHY Month Year doc.: IEEE 802.11-yy/xxxxr0 September 2008 Issue: Link Metric The power saving feature is not considered in calculating airtime link metric A battery powered MP has the same chance as mains powered MP to be selected as a forwarding MP May cause a power consumption problem for battery powered MPs May cause problems with maintaining end-to-end QOS Equation in Draft: r: Transmission rate O: varies depending on PHY Bt: 8192 bits ef: frame error rate Liwen Chu, STMicroelectronics John Doe, Some Company

Solution: Power Save Aware Link Metric Month Year doc.: IEEE 802.11-yy/xxxxr0 September 2008 Solution: Power Save Aware Link Metric 5000 is half of the default Mesh beacon period and corresponds to an average buffered traffic indication delay to a power saving MP (5000 = 50TUs) K is power save factor K is set to 1, if forwarding MP may apply all power modes for the links in the forwarding path K is set to 0, if the forwarding MP operates in active mode and may signal to transition to power save only, if no frame from the path is received in Inactivity Timeout (10 secs) The battery powered MPs should set K to 1, mains powered MPs should set K to 0 When the path expires also the MP that set K=0 may apply any power modes for the links in the path The new airtime link metric makes it less likely that a forwarding power saving MP to be selected as a forwarding node Proposed Equation: Liwen Chu, STMicroelectronics John Doe, Some Company

Summary of the Power Save Aware Link Metric Month Year doc.: IEEE 802.11-yy/xxxxr0 September 2008 Summary of the Power Save Aware Link Metric The QoS violations due to operation in power save are reduced Power save aware link metric avoids battery powered MPs use in forwarding The power save aware link metric solves as an example the comments with CIDs: 25, 337, 725, 947, 951, and 1164. Liwen Chu, STMicroelectronics John Doe, Some Company