VoIP in WLAN

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VoIP in WLANs

• QoS and mobile devices

David Jackisch
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Outline

• Quality of Service
• CISCO Solution
• Mobil Devices
• Scenarios

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David Jackisch
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Quality of Service

• WLAN is shared medium
• QoS is important for wireless mobile IP phone
  calls
• Delay up to 150ms acceptable for most user
  applications, above 400ms unacceptable
• Jitter (75ms), delay, packet loss (3)
• Optimising the path of a voice packet
• Technique buffers, admission ctrl,
• Security issues WPA

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David Jackisch
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Quality of Service (2)

• Reliability
• Availability (data networks 94 22 days/year)
• Real-time
• DiffServ priority in data traffic, service
  classes
• Echo cancellation
• Some proprietary standards
• -gt 802.11e

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David Jackisch
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IEEE 802.11e

• Defines QoS for 802.11 wireless networks
• Due packet delay/loss and jitter QoS is needed
• Mechanism for prior data streams
• EDCF defines 8 traffic categories, software
  update
• HCF allocates timeslots, hardware upgrade
  necessary
• Implemented 2004

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David Jackisch
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CISCO Implementations

• Skinny client control protocol (SCCP) for
  communicating with Call Manager IP PBX
• CISCO Aironet WLAN infrastructure is expensive
• In future push to talk, WPA, layer-3 roaming,
  SIP, voice dial

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David Jackisch
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A A A

• Authentification, Authorization, Accounting
• Possibilities use of SIM cards, electronic keys
• Different invoices from service provider,
  internet provider

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David Jackisch
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Mobile Devices

• Notebook or PDA with soft phone
• Inexpensive, effective
• Not comfortable in use
• UMA (unlicensed mobile access) seamless to WLAN,
  GSM/GPRS, Bluetooth

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David Jackisch
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Mobile Devices (2)

• WiFi phones
• ZyXEL P2000W
• 802.11b WLAN Standard
• SIP v2
• G.711 G.729a voice coding
• 802.11 Ad hoc modus
• Range 300m/75m
• 64/128bit WEP encryption
• QoS TOS/DiffServ

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David Jackisch
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Mobile Devices (3)

• Dual mode phones
• MOTOROLA CN620
• GSM and WLAN support
• MS Windows CE
• T-Mobile MDA3
• PDA with GSM
• NOKIA Communicator 9500

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David Jackisch
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Scenarios

• Last mile for telecommunication service providers
• Connecting new infrastructure with the core
  network
• Backup for cellular phone in emergency situations
• Company telecommunication network, intranet
• Access from all over the world to corporate
  network

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David Jackisch
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Summary

• Cheaper to operate, maintain and upgrade
• More powerful, flexible and feature-rich than
  conventional devices currently in the market
• One telephone number in every location
• New markets for hardware producers, service
  providers and network providers

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David Jackisch
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Sources

• 1 www.google.de
• 2 www.networkcomputing.de/cms/fileadmin/
  nwc/downloads/pdf/itwissen_ebook_voip.pdf
• 3 www.motorola.com
• 4 www.siemens.de
• 5 www.zdnet.com
• 6 www.ivs.tu-berlin.de/Lehre/WS0304/TIA/Material
  /09-QoS-Teil2.pdf
• 7 www.cisco.com

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David Jackisch
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• Thank you. Questions?

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David Jackisch