Wireless LAN Professional 2015 Conference - Designing For Voice 10-Talk

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@MikeLeibovitz
Designing For Voice
Wireless LAN Pro Conference 2015
10 Talk

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Emergence of Voice over Wi-Fi
In 2015

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Market Disruption
City-Wide Wi-Fi Services

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Voice Over X, Where X = Data

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Every WLAN We Design Must Support
Real-Time Applications

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VoWLAN Design Considerations
1. Device capabilities (clients)
– Constraints = certifications, drivers/software, power, durability, size
– Understand protocols/standards and channels supported
– Take measurements with device, understand Rx sensitivities
2. Coverage
– How much? 2.4GHz or 5GHz? Choose one!
– Recommended target -65dBm to -67dBm
 802.11ac designs likely incorporate stronger signal
– Always consider environmental elements, SNR & retries
– Match AP and Client Tx power; target symmetrical speeds

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VoWLAN Design Considerations
3. Interference
– Channel reuse and cell dimension critical – 20MHz for high-density
– Static channel assignment to avoid CCI
– More power ≠ better Wi-Fi
4. Roaming
– How many channels in use? Fewer are better for roaming – less scans
 Active vs. passive client scanning – both consume airtime
– WPA2-PSK vs. WPA2-ENT? 802.11r/802.11k?
– Target below 50ms
– Consider wired network and traffic forwarding (L2/L3, local/centralized)

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VoWLAN Design Considerations
5 Quality of Service (QoS)
– Does the client/application support marking?
 If not, consider how you will classify the traffic
– Consider both voice signaling and encoding
– Never forget end-to-end QoS
 Wireless QoS (WMM/802.11e) + Wired QoS (802.1D/Diffserv)
 Use OKC if 802.11r/802.11k not available

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Voice Is Dead… Long Live Voice

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