Wireless Internet Telephony

1
Wireless Internet Telephony

• Tom La Porta
• Director, Networking Techniques Research
  Department
• Bell Labs, Lucent Technologies

2
Outline

• Background and Overview
• Transport
• mobility management and QoS
• wireless specific services
• Signaling and Control
• mobility management
• call control and interworking

3
Mobile Internet Telephony - All IP

• Goal migrate wireless mobile access networks to
  IP
• Support the anticipated explosive growth of the
  wireless Internet
• merging of services for wireline and wireless
  networks
• merging of wireless voice and data networks
• Reduced product and operational costs of IP
  infrastructure
• increased efficiency of packet-based networks for
  combining voice and data
• Technical Challenges
• Transport
• quality of service
• real-time mobility management
• wireless specific services
• Signaling and Control
• personal and device mobility
• call control
• interworking with existing telephony systems

4
Current Cellular Networks Circuit Switched
BS base station BSC BS controller MSC Mobile
Switching Center VLR Visitor Location
Register HLR Home Location Register
1. Air
2. Backhaul
3. Full Rate
4. Full Rate

• Link 1 Air Interface
• compressed voice (8Kbps) on dedicated channel
• Link 2 Backhaul
• compressed voice multiplexed on sub-rate
  circuits
• BSC performs voice coding to 64 Kbps (one
  option)
• BSC performs soft handoff or frame selection
  function (one option)
• Link 3-4 Full rate
• full rate voice switched at MSC to the PSTN
• MSC may perform voice coding and soft handoff

5
Migration to All-IP Packet Core
Software Controller
Intranet
BS base station PVG Packet-Voice Gateway HLR
Home Location Register
4. Full Rate
3. Packet Voice
1. Air
2. Backhaul

• Link 1 Air Interface
• compressed voice (8Kbps) on dedicated channel
• Link 2 Backhaul
• compressed voice multiplexed on sub-rate
  circuits
• Access PVG performs soft handoff or frame
  selection function
• Access PVG may perform voice coding
• Link 3 Packet Voice
• RTP session between Access and Egress PVGs
• Egress PVG may perform voice coding
• Link 4
• full rate voice switched at Egress PVG to the
  PSTN

6
All-IP
Software Controller
Intranet
Internet
5. Packet Voice
4. Full Rate
3. Packet Voice
1. Air
2. Backhaul

• Link 1 Air Interface
• compressed voice (8Kbps) on dedicated channel
• Link 2 Backhaul
• aggregated, compressed IP voice
• IP-BSC performs soft handoff or frame selection
  function
• Link 3 Packet Voice
• RTP session between Access and Egress PVGs
• Egress PVC performs voice coding
• Link 4
• full rate voice switched at Egress PVG to the
  PSTN
• Link 5 Packet voice to Internet

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Outline

• Background and Overview
• Transport
• mobility management and QoS
• wireless specific services Soft Handoff and
  Paging
• Signaling and Control
• mobility management
• call control and interworking

8
Current Telecom-Based Mobile Packet Networks
GPRSGeneral Packet Radio Service
Regular routing
Tunneled packets using special methods
GGSN
Host
Intranet

• Compatible with cellular telecom networks
• may be deployed using existing infrastructure
• requires separate advances from the Internet
• Specialized nodes manage mobility and forward
  packets
• requires no changes to fixed hosts or
  intermediate routers
• results in triangular routing
• special failure recovery mechanisms needed
• Packets are tunneled through the Intranet
• intermediate routers are not mobile-aware
• difficult to perform QoS
• Inter-SGSN handoffs always managed by GGSN
• high update overhead
• slow handoffs

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Current Internet-Based Mobile Packet Networks
Mobile IP
Tunneled packets using IP
HA
Regular routing
Radio Access Networks
MD
Host
Internet

• Compatible with regular IP networks and hosts
• most Internet advances apply
• Specialized agents manage mobility and forward
  packets
• requires no changes to fixed hosts or routers
• results in triangular routing
• special failure recovery mechanisms needed
• Packets are tunneled through the Internet
• Internet routers are not mobile-aware
• difficult to perform QoS
• Handoffs always managed by Home Agent
• high update overhead
• slow handoffs
• No paging
• high update overhead

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HAWAII A Domain Based Approach to IP Mobility

• Distributed control Enhanced reliability
• host-based routing entries in routers on path to
  mobile
• Localized mobility management Lower overhead,
  fast handoffs
• updates only reach routers affected by a
  movement
• Minimized or Eliminated Tunneling no triangular
  routing, easy QoS
• dynamic, public address assignment to mobile
  devices
• Supports paging
• Compatible with Mobile IP

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HAWAII Local Mobility

• Initial host-based routing entries in routers
  shaded in yellow (DR, R1, R2)
• minimizes number of host-based entries
• Update host-based routing entries in routers
  shaded in green (R3, R1)
• minimizes number of routers processing updates
• reduces handoff time
• Address of mobile device remains constant
• allows uninterrupted communication
• allows QoS entries in unaffected routers
  (yellow) to remain unchanged

12
HAWAII Overhead

• Comparison of most heavily loaded entities in
  each network
• HAWAII DR processes 34 number of messages as
  M-IP HA
• HAWAII DR is utilization is 11 of M-IP HA

13
HAWAII Handoff Delay Packet Loss
Audio (160B/20msec)
Video (4KB/33msec)
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HAWAII Performance Handoff Delay

• Voice (or other real-time applications) less
  disruption
• packets dropped due to late arrival

Local Mobile IP
IP network delay
Roaming Mobile IP
HAWAII
Acceptable for voice
15
Wireless Services IP-Paging
Paging entry
Internet
Multicast entries

• Hierarchical scheme
• scaleable
• allows load balancing between levels of routers
• Uses IP Multicast
• no new protocols
• Alternatives
• paging from Home Agent
• paging from Foreign Agent
• Result
• Domain paging supports 10 higher load than
  FA-Paging

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Wireless Services IP Soft Handoff
Internet
IP Soft Handoff

• Goals
• true end-to-end IP networking
• leverage IP protocols (e.g., multicasting)
• support efficient routing
• Challenges
• traffic aggregation
• processing overhead
• QoS

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Outline

• Background and Overview
• Transport
• mobility management and QoS
• wireless specific services
• Signaling and Control
• mobility management
• call control and interworking

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Integrated SIP Registrar and HLR
Provide enhanced HLR functionality for Internet
and wireless network users
Current
HLR
Cellular
VoIP server
Internet (VoIP)
MAP / SS7
User location manager
Cellular

• Integrate 3 key functions of
• HLR IP (VoIP) servers
• mobility management
• security
• profile management
• Support multiple standard interfaces
• Wireless ANSI 41, GSM / UMTS MAP
• Internet VoIP (SIP, H.323), AAA (RADIUS)

Protocol Gateways
Integrated User Profile Database
VoIP / IP AAA / IP
Internet
Security manager
Super HLR
Next-Generation
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Mobility Management Terminal and User Mobility

• Current telephone network
• mobile phone number points to home network of
  device
• home network points to current location based on
  registration information and locally assigned
  temporary phone numbers

• SIP
• personal URL defines a server
• registrars and proxies point to devices
• extra level of indirection of interworking with
  cellular phone

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Mobility Management

• User mobility across networks (wireless,
  Internet) in addition to terminal mobility
• Manage profile information for a user, not a
  wireless terminal
• Call delivery to the current user terminal ?
  Unified user location DB
• Global roaming between network types
• Receive the same service anywhere ? Unified
  service profile

?
Super HLR
SIP user name (URL) Tel 1 (MSISDN)
BS
User location manager
?
?
Internet
SIP terminal
GSM phone
?
PSTN phone
Security manager
User location DB
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Preliminary Analysis Internetworking with Super
HLR

• Call delivery from a SIP terminal to a GSM phone
• No dual registration or routing number lookup
  with super HLR
• 1530 less signaling message load

Modified call setup
Super HLR
MAP mobile registration
Routing info. lookup
?
HLR

PSTN/MAP
Home MSC
SIP proxy
Mobile registration
IP Wireless Access
Serving MSC
Call delivery (SIP )
Call delivery (SIP )
BS
BS
IP stream up to BS
IP up to BS
Serving MSC
Internet
Internet
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Call Control Internetworking among wireless,
VoIP, and PSTN networks

• Develop general internetworking models and
  procedures
• ? To avoid different procedures for each
  internetworking scenario
• Call delivery to home/gateway MSC or SIP proxy
• Location query to super HLR
• Routing information if delivered to wireless
  mobile terminal
• Call delivery to a mobile terminal
• ? Extend the procedures for supplementary
  services

Super HLR
(2) LOCREQ/SRI SIP location lookup
(1) IAM / SIP INVITE
SIP user name DN1 (MSISDN)
(3) Request Location
hMSC /gMSC SIP proxy
PG 1
(10) locreq/SRI Ack SIP loc. Lookup rsp
sHLR User Location Server
(9) Request Location RSP
user profile
(11) IAM / SIP INVITE
(4) DB lookup
(5) Request Route Info
DN2
(6) ROUTEREQ / PRN
Serving MSC SIP UA
PG 2
(7) routereq / PRN Ack
(8) Request Route Info RSP
SIP terminal
GSM phone
PSTN phone
(12) Call delivery
Core s-HLR operations
User location DB
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Super HLR Architecture

• Super HLR core servers
• Common functions across protocols
• Multiple server instances on a cluster of
  processors for system scalability
• Interworking function between protocols O(n)
  versus O(n2) complexity
• Super HLR common operations
• Protocol independent
• Protocol gateways
• Performs protocol specific control
• Facilitates new protocol introduction
• Integrated user profile DB
• Common database for a user

PG MAP
Super HLR
User location manger
PG VoIP
Super HLR Common operations
Integrated user profile Database
PG AAA
? ? ?
? ? ?
s-HLR core servers
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Summary

• Mobile Internet Telephony requires
• Transport advancements
• efficient mobility management
• QoS
• wireless services
• Signaling advancements
• additional levels of mobility
• interworking with cellular telephony
• Other Issues
• efficiency of Internet signaling over the air