Utilization of the IEEE802.11 Power Save Mode with IP Paging

1. Utilization of the IEEE802.11 Power Save Mode with IP Paging Marco Liebsch, Xavier P' erez-Costa NEC Europe Ltd., Network Laboratories, Kurfuersten-Anlage 36, 69115 Heidelberg, Germany {liebsch, perez-costa }@netlab.nec.de ICC 2005

2. Outline • Introduction • Paging architecture • Protocol operation • Address and Identification Scheme • Standard IEEE802.11 Power Save Mode – unicast V.S. multicast • Performance Evaluation • Analytical Evaluation • Conclusion

3. Introduction –Mobile IPv6 Home Network Mov.1 Mobile NodeCare-of Address Mobile NodeHome Address Mov.2 Router Home Agent Trans.2 Trans.3 Trans.1 Trans.4 Binding – The mapping of Home Address and Care-of Address CNc Correspondent Node

4. Introduction –IP Paging Service • Phenomenon • Only a fraction of powered mobile terminals participate in a data session at a time • Wireless bandwidth and the mobile devices' battery energy waste • How to… • Save the battery power • Decrease signaling load both on network and the air

5. Introduction –MN with Paging • Idle & Active Modes Receive Paging Request or Open Connection Update location when PA change Update location on every handoff Idle Active All Connection Closed or Active timeout The operator often arranges several access router as a Paging Area, which is identified by a PA address as well as always a multicast address.

6. Introduction –IP Paging Service • Dormant state • Switch network interface card (NIC) into power save mode (PSM) • Reduce transmit (Tx) and receive (Rx) activity to save energy resources • Dormant Mode Host AlertingRFC 3132 - Dormant Mode Host Alerting ("IP Paging") Problem StatementSeamoby, http://www.ietf.org/html.charters/seamoby-charter.html

7. Introduction –IP Paging Service • The MNs at idle mode could register after a long period or crossing over the customized geographic region, rather than for each hand-off. • To reduce registration cost • The operator often arranges several access router as a Paging Area, which is identified by a PA address as well as always a multicast address. • Home Address – CoA  Home Address – PA Address

8. Introduction –IP Paging Service • Paging • The network locates and wakes up a dormant mobile • How to communicate with a mobile device in Dormant state?

9. Introduction –Paging HA Registration z z z z z z HA Registration Paging

10. Paging architecture • Basic functional entities for paging: • Dormant Monitoring Agent (DMA) : buffer IP data packets addressed to mobile terminals in PSM. • Tracking Agent (TA) : tracks the mobiles' location with the granularity of a paging area • Paging Agent (PA) : coordinates the paging procedure within a registered paging area • Paging Controller : full control the paging procedure and implements the TA and DMA function

11. Paging architecture

12. Protocol operation • Active state • Paging Controller doesn' t maintain the mobile terminal' s registration • Dormant state • Buffer those data packets addresed mobile terminal • Trigger the paging procedure (register first)

13. Protocol operation - Registration , paging , de-registration Associated registration information + paging area' s identifier Change state from Active to Dormant With PID With current location Set state to active

14. Address and Identification Scheme • Address of paged mobile device might obsolete • Paging identifier (PID) • unique identification of mobile terminal in Dormant state • Derivate IPv6 Solicited Node Multicast address Terminal NIC' s MAC address

15. Address and Identification Scheme Least 3 significant byte of MAC address of each NIC NIC type (IEEE802.11 , Bluetooth , CDMA, ...) Actual length if this fraction

16. THE STANDARD IEEE802.11 POWER SAVE MODE • Power save • Switch mobile device' s state from RxTx state to Doze state • Doze state • NIC receive traffic at regular beacon interval (BI) • Authentication & Association • Perform after mobile device select a AP • Mobile device inform AP about Listen Interval parameter • Listen Interval :the amount of beacon interval a NIC remain unreachable before listening to the next beacon

17. THE STANDARD IEEE802.11 POWER SAVE MODE - unicast • Mobile device in the PSM : • AP assign the mobile device’s NIC an Association Identifier (AID) • AP listen to the packets addressed to the mobile device • Packet buffered in AP • Traffic indication bitmap (TIM) inform mobile device about buffer packets • TIM sent with each beacon • Mobile device sent Power Save Poll (PSP) message to poll buffered packets

18. THE STANDARD IEEE802.11 POWER SAVE MODE - multicast Multicast packets buffered at AP and forward mobile device at regular interval (BI) How the mobile device know when to listen multicast packets? And how to delivery? Beacon comprise a Delivery Traffic Indication Map (DTIM) Synchronization : beacon advertise a DTIM Counter Moredata Flag

19. NIC' s MAC address

20. PERFORMANCE EVALUATION • Total cost (Ctotal ) , paging delay cost (Cdelay ) , energy cost (Cerergy) • Ctotal = Cdelay + Cenergy • Paging delay : link delay + queuing delay + wireless delay dd : downlink paging delayy du : uplink paging delay

21. PERFORMANCE EVALUATION • μw: IEEE802.11 specific wireless process rate • dl : link delay between AP and Paging Controller • dw : IEEE802.11 specific wireless delay (dw = 1/μw) • ρ. BI : DTIM period (multiple beacon interval) • Queuing delay (dqueue) : Affected by DTIM period , multicast frame received before paging request , wireless delay

22. PERFORMANCE EVALUATION

23. PERFORMANCE EVALUATION • Downlink delay include delay caused by the transmission of N previously multicast frames.

24. PERFORMANCE EVALUATION • Total paging delay dp = dd + du • Delay cost • β: cost per second delay

25. PERFORMANCE EVALUATION - energy cost • Session duration (SD) : time between two session start • Timeout value (T) : cause the mobile device enter Dormant State and PSM after the end of session • Idle duration (ID) : listen to Paging Request packets every DTIM period • Energy cost : during the inter-session interval , the time a mobile device' s NIC in RxTx state or listen and deliver multicast packets each DTIM perio d. • Energy cost Cenergy = α ‧k The time a NIC consumes energy to receive or send data Unit of cost per second of activity

26. Analytical Evaluation session interval • To estimate the cost efficiency, we evaluate the impact of the session interval (IS ) , multicast traffic load (N ) , DTIM period (ρ ‧BI) to the total cost

27. Analytical Evaluation • Fig. 8 illustrates the total costs for two different DTIM period settings

28. Analytical Evaluation • Environment : • AD : 30 seconds • T : 5 seconds • Cost unit of paging delay β and relative energy consumption α: 1 • IS : between 35 seconds and 200 seconds • Previously buffered data packets at AP : 20 multicast packets • Link delay : 5 ms • Wireless delay : 10 ms • BI : 100 ms

29. Analytical Evaluation • Low multicast traffic , less paging delay cost. • multicast PSM queue does not introduce a major delay

30. Analytical Evaluation • The active period small compare to DTIM period • Energy cost decrease with the increasing session interval

31. Analytical Evaluation • Increase the multicast load on the PSM queue (N)

32. Analytical Evaluation • However , if low load condition ? ?

33. Conclusion • It' s a sub-optimal solution, but it utilized without modify the IEEE802.11 AP • It can support initial integration and migration scenarios toward future mobile communication system.

34. Favorite English sentence • An analytical evaluation of energy and paging delay costs allows estimation of the proposed mechanism’s efficiency, which might be sub-optimal for high load conditions , but appropriate to support migration scenarios towards future heterogeneous access mobile communication networks.

35. Q &A