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

Marco Liebsch, Xavier P' erez-Costa NEC Europe Ltd., Network Laboratories, Kurfuer

sten-Anlage 36, 69115 Heidelberg, Germany {liebsch, perez-costa }@netlab.nec.de

ICC 2005

Outline Introduction Paging architecture Protocol operation Address and Identification Scheme Standard IEEE802.11 Power Save Mode – u

nicast V.S. multicast Performance Evaluation Analytical Evaluation Conclusion

Introduction – Mobile IPv6

Home Network

Correspondent Node

CNc

Mobile NodeHome Address

Mobile NodeCare-of Address

Home Agent

Trans.1

Mov.1

Mov.2

Trans.3

Router

Trans.4 Binding – The mapping of Home Address and Care-of Address

Trans.2

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

Introduction – MN with Paging

Idle & Active Modes

Idle Active

Receive Paging Request or Open Connection

All Connection Closed or Active timeout

Update location on every handoff

Update location when PA change

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.

Introduction – IP Paging Service

Dormant state Switch network interface card (NIC) into pow

er save mode (PSM) Reduce transmit (Tx) and receive (Rx) activit

y to save energy resources Dormant Mode Host Alerting

RFC 3132 - Dormant Mode Host Alerting ("IP Paging") Problem StatementSeamoby, http://www.ietf.org/html.charters/seamoby-charter.html

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 r

outer 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

Introduction – IP Paging Service

Paging The network locates and wakes up a dor

mant mobile How to communicate with a mobile devic

e in Dormant state?

Introduction – Paging

HA

Registration

HA

Registration

Paging

z z z z zz

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

Paging architecture

Protocol operation

Active state Paging Controller doesn' t maintain the mo

bile terminal' s registration Dormant state

Buffer those data packets addresed mobile terminal

Trigger the paging procedure (register first)

Protocol operation - Registration , paging , de-registration

Associated registration information + paging area' s identifier

With PID

Change state from Active to Dormant

With current location

Set state to active

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

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

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 parame

ter Listen Interval :the amount of beacon interval a NIC remai

n unreachable before listening to the next beacon

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

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 Count

er Moredata Flag

NIC' s MAC address

PERFORMANCE EVALUATION

Total cost (Ctotal ) , paging delay cost (Cdelay ) , energy cost (Cerergy)

Ctotal = Cdelay + Cenergy Paging delay : link delay + queuing dela

y + wireless delay

dd : downlink paging delayy

du : uplink paging delay

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 fra

me received before paging request , wireless delay

PERFORMANCE EVALUATION

PERFORMANCE EVALUATION

Downlink delay include delay caused by the transmission of N previously multicast frames.

PERFORMANCE EVALUATION Total paging delay dp = dd + du

Delay cost

β: cost per second delay

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

Analytical Evaluation

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 ‧

session interval

Analytical Evaluation Fig. 8 illustrates the total costs for two

different DTIM period settings

Analytical Evaluation Environment : AD : 30 seconds T : 5 seconds Cost unit of paging delay β and relative energy co

nsumption α: 1 IS : between 35 seconds and 200 seconds Previously buffered data packets at AP : 20 multic

ast packets Link delay : 5 ms Wireless delay : 10 ms BI : 100 ms

Analytical Evaluation Low multicast traffic , less paging delay cost.

multicast PSM queue does not introduce a major delay

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

interval

Analytical Evaluation

Increase the multicast load on the PSM queue (N)

Analytical Evaluation

However , if low load condition ? ?

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.

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.

Q &A