Steps in Handoffs and Use Cases

1
Steps in Handoffs and Use Cases

• Vivek Gupta
• Intel Corporation
• vivek.g.gupta_at_intel.com
• May 2004

2
Background.

• IEEE 802.21from PAR and 5 Criteria
• Media Access Independent mechanisms to facilitate
  optimization of L3 handoffs (e.g. Mobile IP
  sessions) between homogeneous or heterogeneous
  media types
• Optimize Detection and Selection of Network
  attachment points
• Ensure compatibility with the 802 architectural
  model and security mechanisms
• No new security algorithms or protocols

3
BackgroundScope of 802.21
802.X
802.X
802.Y
zG (WWAN)

• Intra 802 Handoffs (802.x ? 802.x)
• Covered by respective 802 working groups
• These 802 WGs will also deliver fast intra 802
  handoff solutions that address 30 msec or less
  handoff latency
• Through proactive pre-authentication, soft
  handoffs, and/or fast reconnections between nodes
  (TGr, TGi, etc. for 802.11)
• Inter 802 Handoffs (802.x ?802.y) and extension
  to more general case of inter network handoff
  across cellular systems (802 ?zG)
• Within scope of 802.21
• Intra 802 Handoffs across Administrative domains
  also within scope
• Handoffs across 802.11a, 802.11b, 802.11g,
  802.11n in scope?

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Customers of 802.21

• Layer 3 and above applications
• Mobile IP for data transfers
• Voice based applications
• Network Selection Service
• Select best radio
• Others?

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Steps in Handoff Process

• Scenario
• Multi radio mobile handset roaming in
  heterogeneous wireless network environment.
• Steps in Handover
• Detect Changes in Link Availability
• L2 Connection and Network Provider Selection
• Link Selection and Configuration
• Connection Handover

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Steps in Handoff Process

• Detect Changes in Link Availability
• Availability of New Links
• Through Native radios
• Media Sense and Link Quality Estimation
• Through non-Native radios
• E.g.Using 802.11 radio, find out about all other
  radios in vicinity
• Site Report for all radios (Global Network
  Neighborhood)
• GPS assisted
• Degradation and Loss of Existing links
• Link Quality estimation and comparison
• Signal Strength, Signal to Noise Ratio, Bit Error
  Rate
• gt Link layer Triggers to notify higher layers

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Steps in Handoff Process

• L2 Connection and Network Provider Selection
• Establish L2 connection with Available Links
• Need Radio specific MAC level parameters
• SSID, BSSID, Channel, etc.
• Network Provider Selection
• Based on preferred operator and available
  services
• Provisioning utilities like Microsoft WPS may do
  most of the work here
• There may be other cases where WPS may not be
  applicable, (Low power mode of operation)
• gtExtended Site Report (Global Network
  Neighborhood) can help with Link discovery and
  selection
• Link layer parameters for existing radios (no
  probes, beacons, scans, etc.)
• Service provider information

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Steps in Handoff Process

• Link Selection and Configuration
• Link selection
• Input from user policies, available links and
  services, etc.
• Mostly an OS function
• Link Configuration
• IP connectivity

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Steps in Handoff Process

• Connection Handover
• Decision to switch Connections or Maintain
  simultaneous connections etc.
• Make before Break
• Break before Make
• Context Transfer
• Application specific

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Use Case 1
Steps in Handover Wired ? Wireless (Email) Comments
Changes in Link Availability Abrupt! Link_down
L2 Connection and Network Provider Selection WLAN, BT, WWAN (Global Site Report) 802.21 can help with Network Discovery and Selection
Link Selection and Configuration Select WLAN and get IP connectivity Based on policy, cost, bandwidth, etc.
Connection Handover Break before Make. Email app reconnects No need for MobileIP!
For other Wired ? Wireless transitions, for
time/latency critical applications user may want
to use wireless even when device is NOT mobile.
E.g. VoIP Phone
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Use Case 2
Mobile user using VoIP over WLAN in office walks
out, gets into car, and drives out of town!
Steps in Handover 802.11 ? 802.16 ? Cellular (Voice/Video) Comments
Changes in Link Availability Gradual decay. Link_Going_Down Link_Up 802.21 can specify Predictive Triggers.
L2 Connection and Network Provider Selection Get network and provider preferences. Get provider specific access info. 802.21 can help with Provider Selection and Access info
Link Selection and Configuration Select network and get connectivity Notify TCP appropriately when going across networks with big difference in bandwidth
Connection Handover Make before Break. Seamless handover
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Use Case 3
User roaming in an airport across domains and
Service Providers. 802.21 facilitates handover
to preferred Network Service Provider
Steps in Handover Connected to 802.11 (User roaming in an airport) Comments
Changes in Link Availability Link_Available! Better service provider available, based on Global Site Report
L2 Connection and Network Provider Selection Select the new/preferred service provider
Link Selection and Configuration
Connection Handover Break before Make
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802.21 Work Items

• Things to do in 802.21
• Use cases
• Find compelling user scenarios to solve
• Global Network Neighborhood
• Discover about other radios through current radio
• Neighbor graphs of all radios
• Media Independent Triggers
• Notifications about changes in link availability
• Things NOT to do in 802.21
• Link Quality Comparison
• Link Selection
• Policy decision (Mostly an OS function.)
• Connection handovers
• Make before break etc. (Application specific)

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IEEE 802.21 Specification

• General organization of 802.21 specification
• Type of Spec
• More general and abstract in nature than other
  802 specs
• Customers of spec
• Other 802 WGs and other Standard bodies
• Normative vs Informative
• How will compatibility with 802.21
  enforced/measured
• Mapping to other technology

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Conclusion

• Key areas of contribution for 802.21
• Media Independent Triggers
• Global Network Neighborhood