Iab wless-voip

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Iab wless-voip

  1. 1. Wireless & VoIP Christian Huitema February 26, 2000
  2. 2. Wireless Voice over IP: 2 Questions• Can we make it work? – Can we provide decent quality? – Can we support efficient signaling?• Can the telcos accept it? – Loose control of voice? – Loose control on “services” ?
  3. 3. Interactive voice quality, Component #1: delay 0 200 400 600
  4. 4. Components of delay• Network (delay, jitter): – Access Network, Uplink – Core Network, – Access Network, Downlink• Packetization, De-Packetization• Device: – Acquisition, Echo control, Compression, – Jitter, Decompression, Playback
  5. 5. Managing the Uplink: beware of contention• Data Usage emphasizes “load” – Highly variable sources, – Contention access fits best (CSMA, TDMA- DA, slot request, etc.)• Contention access unfit for voice – Generates “large deviation” – Deviation => jitter => delay.• … Unless very low load factor
  6. 6. Packetization frequency: Size => Delay => Quality value 5 10 20 30 40 600 200 400 600
  7. 7. Bandwidth => QualityDelay => Header/Payload ratio0 16 32 48 64 80 96 112 128
  8. 8. Voice Quality: Effects of Packet Losses• Loss effect aggravated by “fractal” distribution.• Moderate losses (1%) can be concealed.• Higher losses require redundancy: (standard in RTP): – Affects bandwidth (split / N packets) – affects delay (N packets) => quality…
  9. 9. Uplink Starvation => Control Bandwidth, Packet Rate Edge Core Network Router, Radio AuthorizeSignaling: •Voice Call ? Network Control •Quality ?
  10. 10. Can we do efficient signaling? Wireless VoIP => Mobility• Classic telephony approach: – HLR (home) /VLR (visitor) – Based on phone number – Number = Transport + User identity.• VoIP separates network, service – Network: IP address – Service: DNS name, e-mail, URL• Need clean architecture
  11. 11. The VoIP Protocol Soup More than one choice…• H.323 – ITU standard, implementations – Complex, heavy, hard to evolve• MGCP – Client server, “telephony device” – Used in Cable networks – Not really adequate for mobility support – MGCP / Megaco / H.248 debacle• SIP – Clean end-to-end architecture
  12. 12. Signaling & Mobility: Combine “Mobile IP”, SIP DHCP Register SIP agent DHCP Invite DHCP Correspondent RegisterInvite #2
  13. 13. Can the telcos accept VoIP? Wireless VoIP?• Special price for voice, data: – Wire line: price of voice is 10 x data bit – Wireless: data is “special service.”• Bundling of services: – Caller-ID, Call-Waiting, – Voice Mail, – 3000 “IN” services – 911, etc.
  14. 14. Wireless VoIP: loosing control of voice?• In the short term, QoS issues – Contention on the uplink, – Telco can control “voice quality IP”, – But “real time” is more than voice (video, games, monitoring.)• The end of uplink starvation? – High speed wireless LAN, 3GIP? – Need adequate “sharing” procedure.
  15. 15. Wireless VoIP: becoming “the” infrastructure• Need to be always on, meet the classic 99.999% requirement,• Deal with societal issues, such as wiretap, in an end-to-end environment,• Provide 911 like services: – Special signaling, no hang-up, – Location services, route to local 911, – “Emergency” level for QoS.
  16. 16. Wireless VoIP: loosing control of services• IP signaling is end to end – SIP agent “outside” the network, – Service independent of transport.• State is kept in the device: – Local implementation of services, – Call waiting, multiparty call in device.• Empower users, unleash creativity
  17. 17. Wireless VoIP Roadmap• Solve the uplink issue: – QoS on “first hop”, not end-to-end, – Independent of payload type (voice, etc.) – Security, authorization (DHCP, QoS).• Encourage competition: – “Secure Wireless DHCP,” Roaming• Concentrate signaling work on SIP: – Forget the ITU!

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