Voip from kishor ramani

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Voip from kishor ramani

  1. 1. Wireless & VoIP Kishor ramani july 25, 2013
  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 0 200 400 600 value 5 10 20 30 40 60
  7. 7. Bandwidth => Quality Delay => Header/Payload ratio 0 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 Router, Radio Signaling: •Voice Call ? •Quality ? Network Control Authorize Core Network
  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 SIP agent Correspondent DHCP Register InviteDHCP DHCP Register Invite #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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