This document discusses improving battery life for devices with multiple radio interfaces through more efficient idle mode and paging operations. It proposes standardized message primitives to enable: paging elimination by waking one radio to contact another; paging aggregation across radios; location updates over connected radios; aggregated location updates; and coordinated idle mode entry across radios. The presentation argues 802.21 could define such primitives to optimize low power multi-radio operations and improve performance for users and networks.

1. IEEE 802.21 MEDIA INDEPENDENT HANDOVER
DCN: 21-06-0701-00-0000-Media-Independent_IdleMode-andpaging
Title: Media Independent Idle Mode and Paging
Date Submitted: May, 2006
Presented at IEEE 802.21 session #15 San Diego
Authors or Source(s):
Muthiah Venkatachalam
Abstract: This presentation talks about the concept of paging in
multi-radio environment.
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2. IEEE 802.21 presentation release statements
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3. Multi-Radio Networking Evolution
•Multiple Wireless Technologies
•More Capable Devices
•Evolving Usage Models
Multi-radio operation is becoming the Norm…
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4. Overview
•So far the focus of 802.21 has been primarily handovers.
– Vertical handover is something that needs to be addressed in the
context of multi radio networking.
•Multi radio operation does not stop with handovers!
– Host of other issues for multi radio operations exist.
– Many of these could be better solved by means of standardized
primitives.
•We talk about another key multi radio networking issue
– How best to extend the battery life of a multi radio MS
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5. Extending battery life..
•Most radio technologies define low power modes for power
saving and extending the battery life.
– Commonly called “idle mode”
•When the MS does not have any traffic on a radio interface for
a period of time, the interface may switch to “idle mode” from
“connected mode”
– Switch may happen from the MS or from the network.
•Once in idle mode,
– the radio of the MS is typically tracked at a granularity of a
“paging group” or a “tracking area”, comprising of multiple
BS/APs.
– the radio has to listen to Downlink transmissions for a certain
amount of time periodically, so that the network may be able to
contact the MS
•In a multi radio environment, the MS may have multiple radios
– Each radio may be in “connected” or “idle” states
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6. Key operations during idle mode
•Location Update
– When the radio of the MS crosses a paging group, it performs
location update
– Location Updates keep the network updated on the location of the
MS
•Paging
– When there is incoming packets for the MS on its idle radio
interface, the network may choose to “page” the MS.
– Paging is typically initiated by a paging controller that has the
latest location of the MS.
– Paging would involve contacting multiple BS/APs in the paging
group to locate the BS/AP where the MS is currently present.
•Idle mode exit: switch back to connected mode, happens
when
– When the MS wants to transmit data on the uplink on the given
radio,
– or when the MS is paged and wants to get back to connected
mode.
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7. Power saving at the MS
•If the MS is guaranteed that it will be paged on one
(or a subset) of the radios all the time, then
– It can periodically listen to the downlink transmissions only
on this radio.
– It can switch off the other radios.
•May lead to considerable power saving at the MS
•For example: MS has WiMAX and 3G interfaces, and
– the MS knows that it will always be paged on WiMAX
– The MS would not need to listen to the 3G downlink
transmissions periodically.
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8. Paging-elimination
•Scenario
–
–
–
User is browsing on the WiFi
interface
User gets a voip call on the WiMAX
interface.
WiMAX network needs to page the
user
•Instead of paging the user on the
WiMAX airlink and spending
considerable resources, the WiMAX
network:
–
–
Determines if any other radio is
currently on for the user
Eliminates paging by sending a
unicast message on WiFi to turn on
the WiMAX radio.
•Need standard compliant message
primitives to do so.
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9. Paging-aggregation
•Page on a single idle radio to wake up
multiple idle radios.
•Need standard compliant message
primitives to do so.
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10. Location Update via “connected” radio
•User has WiFi connection that is
currently active and WiMAX
connection that is idle.
•WiMAX radio needs to do a
location update
–
Instead of contending on the
WiMAX airlink, it uses the WiFi
radio to perform location update
for its WiMAX radio
•Need standard compliant message
primitives to do so.
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11. Aggregated Location Update
•If the PGs are overlapping,
perform a single LU operation for
multiple radios.
•Minimizes messaging and
processing at the MS
•Need standard compliant message
primitives to do so.
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12. Idle mode entry
•Scenario: Multiple radios are
switched to idle mode
–
For example: when the user
takes a break, his WiMAX,
WiFi and 3G connections may
go into idle mode
•IM Entry for radios i, j , k
happens on radio-i.
•Need standard inter-radio
message primitives to do so.
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13. Summary
•Standards based multi radio primitives for idle mode will help
– Save power at the MS
– Reduce signaling, processing and contentions
– Improve performance for the user and cost savings for the
operator
•802.21 can take a first step here to move the industry toward
an integrated framework for low power mode of multi-radio
operation
– By studying the issues more closely
– By defining the primitives for such a framework
•Vertical radio standard bodies can then use these primitives to
optimize the low power operation in the multi radio scenario.
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