1. A Novel Idle Mode Operation in IEEE 802.11 WLANs
January 2006
A Novel Idle Mode Operation in IEEE WLANs
Date:
Authors: Sunggeun Jin, Sunghyun Choi, Youngsoo Kim, Kyunghun Jang
Notice: This document has been prepared to assist IEEE 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
Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures < 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 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 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

2. A Novel Idle Mode Operation in IEEE 802.11 WLANs
January 2006
A Novel Idle Mode Operation in IEEE WLANs
January 2006
Sunggeun Jin, Sunghyun Choi
(Seoul National University)
Youngsoo Kim, Kyunghun Jang
(Samsung Advanced Institute of Technology)
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

3. Outline Need for idle mode operation
January 2006
Outline
Need for idle mode operation
Limitations of the current alternative
“Idle Mode (IM)” in IEEE WLANs
Introduction of new concepts for the “Idle Mode”
Performance evaluation
Summary
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

4. Recent Enhancement of Mobility and Power Saving Support
January 2006
Recent Enhancement of Mobility and Power Saving Support
Mobility support of current/emerging standards
Focused on reducing handoff delay for fast roaming
802.11k, r
No consideration for the mobile hosts without active traffic
Even without traffic, mobiles hosts must perform handoff operation
Power saving schemes in current/emerging standards
Focused on reducing power consumption without QoS compromise
PSM, e APSD, n Multi-Phase PSMP
Need further consideration for the mobile hosts without active traffic
Current PSM is not efficient enough as will see later!
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

5. Needs for Idle Mode (IM)
January 2006
Needs for Idle Mode (IM)
What is Idle Mode operation?
Operation to efficiently support idle mobile hosts without active traffic
No association while no active traffic, and then the station is paged (i.e., broadcast/multicast across multiple BSSs within a given paging area) once a frame arrives
In addition to active mode (AM) and power save mode (PSM)
What is it for?
Reducing power consumption of idle mobile hosts, thus increasing the “standby” time
Reducing signaling cost for networks when supporting idle mobile hosts
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

6. Available Alternative to Idle Mode
January 2006
Available Alternative to Idle Mode
PSM + IP Paging [4,5,6]
Utilization of PSM and IP paging is widely accepted scheme for the alternative to Idle Mode
Mobile hosts in PSM can be paged via IP paging protocol
IP paging is a functional extension of IP mobility protocol such as MIP and HAWAII [2,3]
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

7. January 2006
IP Paging
Paging scheme to support IP mobility when no active IP session.
Two or more routers are grouped into a paging area.
There is no handoff within a paging area.
Page an idle mobile host using multicast when a packet destined to the mobile host exists.
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

8. Limitations of Current Alternative (1)
January 2006
Limitations of Current Alternative (1)
Limitations of PSM
Always associated
“Association” should keep maintained
Handoff failures would cause waste of power consumption
Long handoff duration
L3 handoff takes several seconds
Inefficient power consumption
Frequent handoffs need more power consumption
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

9. Limitations of Current Alternative (2)
January 2006
Limitations of Current Alternative (2)
Limitations of IP paging
Redundant operation if MAC level paging is supported
Naturally weak in IEEE WLANs
IP paging relies on multicast frames
Broadcast/multicast frames make mobile hosts in IM wake up frequently
Since mobile cannot differentiate between IP-paging and other broadcast/multicast frames until it receive them
0~10ms
10~100ms
100ms~1s
≥ 1s
67%
27% 6% 0%
< Multicast and broadcast packet inter-arrival time in NESPOT, a commercial WLAN service in Korea>
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

10. Proposed Idle Mode (IM) Operation [1]
January 2006
Proposed Idle Mode (IM) Operation [1]
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

11. Idle Mode Operation in IEEE 802.11 WLANs
January 2006
Idle Mode Operation in IEEE WLANs
Requirements
Backward compatibility
Efficient power consumption
Location tracking
Paging
 We developed new protocol to meet the requirements
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

12. Idle Mode Operation in IEEE 802.11 WLANs
January 2006
Idle Mode Operation in IEEE WLANs
Major components
Paging
Idle handoff
Delayed handoff
New concepts and terms
layer-3 handoff should be deferred until a successful paging
AP reselection
in order to receive beacon including paging information, new AP should be selected while a mobile host moves around
Home-Node
A node which a mobile host signals to in order to enter the idle mode
Most Recently Associated Node (MRA-Node)
A node (in a different paging area), which a mobile host in the idle mode has most recently associated with
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

13. New Concepts & New Terms
January 2006
New Concepts & New Terms
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

14. January 2006
Procedures for Idle Mode Operation in IEEE WLANs (from the previous figure)
Beginning of idle mode operation
A mobile host enters idle mode when it is associated with “AP2”
AP reselection
The mobile host in idle mode moves from “AP2” to “AP4”
Mobile host changes AP without handoff
Mobile host continues to listen to the beacons for paging
Idle handoff
The mobile host performs idle handoff from “AP4” to “AP5”
Idle handoff operation is newly defined
The node, which is firstly associated by the mobile host, becomes “MRA-Node”
“AP5” becomes MRA-Node
Paging
The mobile host is paged when it is in the coverage of “AP7”
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

15. Procedure for Beginning of IM and Paging
January 2006
Procedure for Beginning of IM and Paging
* PM: Power Mngt bit in Frame Control field of the MAC header
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

16. Procedure for Idle Handoff
January 2006
Procedure for Idle Handoff
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

17. Delayed Handoff New concept Why is “delayed handoff” needed? Goals
January 2006
Delayed Handoff
New concept
IP related operations are deferred as late as possible
Why is “delayed handoff” needed?
Location tracking in layer 2 comes true
WLAN MAC and network can support the location tracking without IP mobility management schemes when there is no active IP session.
It is possible to replace IP level mobility management with Idle Mode operation.
IP level handoff should be supported
However, IP related operations still remain to support active IP session, and hence, IP level handoff operation is performed at the end of the Idle Mode.
Goals
MH does not perform IP related operations while in IM.
Physical separation between WNIC and MH is possible.
Enhance power saving efficiency
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

18. Information Conveyed over Beacon
January 2006
Information Conveyed over Beacon
Paging Area Identification (PAID)
to indicate the paging area which the corresponding AP belongs to
allows the station in idle mode to learn which paging area it currently resides in
Paging information
to indicate the paging to a particular station in idle mode
the MAC address of the station being paged is included
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

19. Performance Evaluation (numerical analysis [1])
January 2006
Performance Evaluation (numerical analysis [1])
Actual values and gaps will vary depending on devices and environments
(a) Power consumption of WNIC
(b) Remaining energy
In (b), we assume that cell sojourn time is 20 seconds. The standby time is estimated under the consideration of power consumption by both PDA and WNIC
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

20. Prototype Implementation of Idle Mode
January 2006
Prototype Implementation of Idle Mode
Implementation Environment
Mobile Host : LG-IBM X40
WNIC : MW-500CB, MMC Tech.
WNIC chipset : Atheros Communications, Inc. AR5212
Experiments
Capture IEEE frames for idle mode operation
Measure remaining energy while idle mode operation performing
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

21. Captured IEEE 802.11 Frames for the IM
January 2006
Captured IEEE Frames for the IM
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

22. Captured IEEE 802.11 Frames for the IM
January 2006
Captured IEEE Frames for the IM
(1) – (6) : initial association with AP
(7) : beginning of Idle Mode operation
WNIC transmits ‘disassociation’ frame with PM bit set to ‘1’
(8) : paging via beacon
(9)-(10) : re-association
Paging is successfully performed and MH wakes up to begin active IP session.
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

23. Performance Evaluation (measurement result)
January 2006
Performance Evaluation (measurement result)
In this figure, if paging is successfully performed, mobile host changes operation mode into “active mode.” In this period, it consumes more power.
Note: the power consumption difference between active mode and idle mode is not much due to high power consumption at the laptop
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

24. Summary New concepts Performance Idle mode operation
January 2006
Summary
New concepts
Idle mode operation
Paging, Home-Node, and MRA-Node
Delayed handoff and AP reselection
Performance
IM operation outperforms both PSM and IP paging
IM operation extends standby time of a Mobile Host
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.

25. January 2006
References
[1] S. Jin, K. Han, and S. Choi, “A Novel Idle Mode Operation in IEEE WLANs,” to appear in Proc. IEEE ICC’06, June 2006.
[2] R. Ramjee, L. Li, T. L. Porta, and S. Kasera, “IP Paging Service for Mobile Hosts,” in Proc. ACM MobiCom’01, 2001.
[3] X. Zhang, J. Gomez, G. Castellanos, and A. T. Campbell, “P-MIP: Paging Extensions for Mobile IP,” ACM Mobile Networks and Applications, July 2002.
[4] S. Pack and Y. Choi, "An Adaptive Power Saving Mechanism in IEEE Wireless IP Networks," KICS/IEEE Journal of Communications and Networks (JCN), June 2005.
[5] M. Liebsch, X. Perez-Costa, “Utilization of the IEEE Power Save Mode with IP Paging,” in Proc. IEEE ICC’05, 2005.
[6] B. Sarikaya and T. Ozugur, “Tracking Agent Based Paging for Wireless LANs,” in Proc. IEEE CCNC’04, 2004.
Sunggeun Jin, Sunghyun Choi et al., Seoul National U.