WLAN Paging and Idle Mode Month Year Sept 2006 Sept 2006 WLAN Paging and Idle Mode Authors: Date:2006-09-8 Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures <http:// ieee802.org/guides/bylaws/sb-bylaws.pdf>, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair <stuart.kerry@philips.com> as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at <patcom@ieee.org>. Emily Qi et al Emily Qi et al

Month Year Sept 2006 Sept 2006 Abstract This document describes WLAN Paging and Idle normative text proposal (doc#06/0943r5) in support of Power Saving objective in accordance with REQ2010. What’s new: Removed Paging Service Protection Use the Paging Virtual Bitmap for Paging Indication Changed the mechanism used to broadcast the Paging Indication from the Action Frame to the Beacon frame Included additional updates to improve the draft Emily Qi et al Emily Qi et al

Agenda Power Saving Goal Power Consumption Issues Month Year Sept 2006 Sept 2006 Agenda Power Saving Goal Power Consumption Issues Idle Mode Concepts and Protocols Power Consumption Comparison Emily Qi et al Emily Qi et al

Month Year Sept 2006 Sept 2006 Power Saving Goal Extend standby hours for handheld and Ultra Mobile Devices to support applications such as VoIP over WLAN Emily Qi et al Emily Qi et al

Power Consumption Issues Month Year Sept 2006 Sept 2006 Power Consumption Issues Awake time at DTIM and Listen interval Overhearing broadcast/unicast messages at Rx Unnecessary BSS transitions while roaming Scanning Overhead OS wakes up to call supplicant Key Derivations: PMKR1 and PTK Exchange of Authentication and Reassociation messages Emily Qi et al Emily Qi et al

Unnecessary BSS Transition Scenario Month Year Sept 2006 Sept 2006 Unnecessary BSS Transition Scenario BSS Transition Data packets Emily Qi et al Emily Qi et al

Introducing Idle Mode and Paging Month Year Sept 2006 Sept 2006 Introducing Idle Mode and Paging Idle Mode : STA enters “deep sleep” if there is no outgoing/incoming traffic STA wakes up at a longer “sleep” interval to check if there is any incoming frame If STA roams out of the coverage area of the last known associated AP, STA doesn’t need to reassociate with a new AP when it is in “idle mode” WLAN Paging: Infrastructure will “page” the client if there is incoming traffic STA will be active when it receives the notification of incoming traffic from the infrastructure Emily Qi et al Emily Qi et al

Idle Mode Operation & Paging Concepts Month Year Sept 2006 Sept 2006 Idle Mode Operation & Paging Concepts Idle Mode Operation Paging Capability Discovery and Advertisment STA Enters Idle Mode APs broadcasts Paging Indications, and STA wakes up to receive paging indication STA Exits Idle Mode Paging concepts and logical entities Paging Domain (PD) - a set of BSSs within the same ESS Paging Server - provides Paging Services Can be in the AP/controller or a separate network entity Paging Group (PG) - a group of APs in which STA can be paged A Paging Domain comprises one or more Paging Groups Emily Qi et al Emily Qi et al

Idle Mode and Paging Protocol Month Year Sept 2006 Sept 2006 Idle Mode and Paging Protocol Paging Capability and Service Discovery (Beacon/Probe Response) Idle Mode Request (STAAP) and Response (APSTA) Enter Idle Mode Exit Idle Mode Idle Mode Update for Paging Group ID and Keep-alive Paging Indication Beacon at Paging Interval Probe Response as STA requests Emily Qi et al Emily Qi et al

Paging Advertising and Discovery Month Year Sept 2006 Sept 2006 Paging Advertising and Discovery Wireless Network Management Capability element AP/ STA exchange Paging capability Paging bit is set to 1 to indicate that Paging service is enabled by AP or STA B0 B1 B2 B3 B4 B5 B15 Multicast Event Log Diagnostics Presence Paging Reserved Bits: 1 11 Paging Information element Advertise Paging Service and Paging Indication delivery information and Present in Beacon and Probe Response Element ID Length Paging Domain ID Paging Service ID Paging Group ID Paging Interval DPIM Count Octets: 1 6 2 Emily Qi et al Emily Qi et al

Paging Indication and Paging Interval Month Year Sept 2006 Sept 2006 Paging Indication and Paging Interval Paging Indication element Element ID Length Page Bitmap Control Partial Virtual Bitmap Octets: 1 1– 251 Bit number N is 0 if there are no paging for the station whose Paging ID is N. If any paging notification for that station arrives at the Paging Server, bit number N in the page-indication virtual bitmap is 1. Frames containing Paging Indication: Beacon only when DPIM count is 0 Probe Response Emily Qi et al Emily Qi et al

Idle Mode Request/Response Month Year Sept 2006 Sept 2006 Idle Mode Request/Response Idle Mode Request element Element ID Length Request Type STA Address Paging Domain ID Server Group Octets: 1 6 Request Type: Enter Idle Mode, Update Idle Mode, and Exit Idle Mode Idle Mode Response element Element ID Length Response Type Status STA Address Paging Server Group Keep-alive Timer Octets: 1 6 2 Request Type: Enter Idle Mode and Update Idle Mode Emily Qi et al Emily Qi et al

Message Flow Sept 2006 Month Year Sept 2006 Emily Qi et al

Example: Roaming with Idle Mode Scenario Month Year Sept 2006 Sept 2006 Example: Roaming with Idle Mode Scenario Paging Group 1 Paging Group 2 Paging Exit Idle Mode Paging Server Idle Mode Update (Paging Group update) BSS transition Enter Idle Mode Data packets Idle Mode messages Emily Qi et al Emily Qi et al

Feature Summary Idle mode operation extends a STA standby time Month Year Sept 2006 Sept 2006 Feature Summary Idle mode operation extends a STA standby time WLAN paging wakes up the STA to receive incoming traffic The Paging Group provides bandwidth efficiency and scalability A Paging Server can be used for deployment flexibility and scalability Emily Qi et al Emily Qi et al

Power Consumption Comparison Month Year Sept 2006 Sept 2006 Power Consumption Comparison Emily Qi et al Emily Qi et al

Scanning Comparison while STA roaming Month Year Sept 2006 Sept 2006 Scanning Comparison while STA roaming Legacy STA Idle Mode STA Goals of Scanning Scanning for BSS Transition: Find the best AP to associate with Scanning to receive Paging Indication: Receive a beacon from any AP that belongs to the same paging domain Possible Actions 1.Scan all or many channels and measure the RSSI of Beacon or other parameters of each channel 2. Select the best AP 1. Stay with the same channel, and then switch to a valid channel, if required 2. STA will stop trying other channels once STA hears a beacon in the same PG Optimization Use .11k “Neighbor Report” to narrow down number of channels Use .11k “AP Channel Report” for the next channel scanning Average number of channels scanned ~2 for 2.4Ghz ~6 for 5.0Ghz 0~3 Scanning time Assume a minimum wait of 10ms in the same channel, if no beacon, do active probing on a channel, average of 30ms. 10ms (wait) + 30ms * (2~6) = 70ms ~190ms 10ms +30ms *(0~3)= 10ms ~100ms Emily Qi et al Emily Qi et al

Awake Time Comparison Sept 2006 Legacy STA Idle Mode STA Month Year Sept 2006 Sept 2006 Awake Time Comparison Legacy STA Idle Mode STA WNIC periodically wakes up at DTIM and Listen Interval at Paging interval NIC Wake up time for Roaming time Scanning + authentication/association = (70ms ~190ms) + (30ms ~210ms) = 100ms ~ 400ms Scanning + Sync = (10ms ~100ms) + 0 ~ 50 = 10ms ~150ms NIC Total wake up time (per minute) =WT Assumption: Beacon interval = 100 TUs, DTIM = 2, Listen Interval = Paging Interval = 20 (2.048s); STA stays awake on average for 2 ms to receive and process a beacon (DTIM, Paging, TIM) from the home AP. Average background scans per hour = 60; n = # of roaming per hours, WT= [#of DTIMs *2ms OR #of Listen Intervals *2ms] + n*(100ms ~ 400ms) +periodic background scanning ((50ms~500ms) * 60) WT= [#of DTIMs *2ms OR #of Listen Intervals *2ms] + n*(10ms ~150ms) OS awake time - calling supplicant, key derivation, and initiate/maintain network connection - depending on device type: handheld, PDA UMPC, Laptop 0 – potentially Emily Qi et al Emily Qi et al

WNIC Awake Time Comparison Month Year Sept 2006 Sept 2006 WNIC Awake Time Comparison Periodic background scanning overhead added to legacy power-save Average minimum overhead per scan = 50 ms Average maximum overhead per scan = 500 ms Average scans per hour = 60 Emily Qi et al Emily Qi et al

Month Year Sept 2006 Sept 2006 Conclusions The “Awake Time” in legacy power-save is compared with that of idle mode The actual power consumption may vary depending on whether the STA is transmitting or receiving or idle when awake Awake-time in idle-mode 2 – 10 times better than legacy depending on how frequently STAs roam The actual power-consumption benefits may be much higher as idle mode operations may be implemented without OS intervention Reduce OS Power Consumption will be significant Detail is not considered in the analysis. Emily Qi et al Emily Qi et al

Thank You! Sept 2006 Month Year Sept 2006 Emily Qi et al