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Deployment Challenges of Wi-Fi Telephony

Deployment Challenges of Wi-Fi Telephony. John DiGiovanni Director of Marketing Staff Technologist john.digiovanni@xirrus.com. Voice over Wi-Fi – It’s Coming!. 802.11 Standards Review. 802.11b Ratified 1999 – Up to 11Mbps in the 2.4GHz Band 802.11a

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Deployment Challenges of Wi-Fi Telephony

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  1. Deployment Challenges of Wi-Fi Telephony John DiGiovanni Director of Marketing Staff Technologist john.digiovanni@xirrus.com

  2. Voice over Wi-Fi – It’s Coming!

  3. 802.11 Standards Review • 802.11b • Ratified 1999 – Up to 11Mbps in the 2.4GHz Band • 802.11a • Ratified 1999 – Up to 54Mbps in the 5GHz Band • Not backward compatible to 802.11b • 802.11g – Backward Compatible to 802.11b • Ratified 2001 – Up to 54Mbps in the 2.4GHz Band • Backward compatible to 802.11b • 802.11n – Ratified Standard Expected 2008

  4. Voice over Wi-Fi Challenges • Shared Medium, Collision Avoidance & Limited Bandwidth • Channel Allocation, Planning & Usage • Quality of Service • 802.11e available for voice • Mapping QoS priorities through the wired network • Wi-Fi Architecture Choices

  5. Ch# 1 2 3 4 5 6 7 8 9 10 11 2.4GHz ISM Band Ch# 1 6 11 Channels & Capacity – 802.11b/g Only 3 Channels are Non-overlapping 33Mbps in 802.11b of Total Capacity 162Mbps in 802.11g of Total Capacity Voice Calls Proportional to Channel Usage

  6. Ch# 36 40 44 48 52 56 60 64 149 153 157 161 Ch# 100 104 108 116 120 112 124 128 132 136 140 Channels & Capacity – 802.11a • 12 channels for 802.11a • Use as many Channels as possible • Reuse them as often as possible 5GHz UNI Band FCC has approved 11 more channels Up to 1.24Gbps of Total Capacity

  7. Quality of Service • 802.11e (Over the Air) • Packet prioritization for downstream traffic • Wired Class of Service is mapped to wireless TCID settings

  8. Architecture Choices 1st Generation: Independent APs • 108Mbps per Cell (2 channels) • Individually Managed 2nd Generation: Controller + APs • 108Mbps per Cell (2 channels) • Centrally Managed 3rd Generation: Controller + Ultra Thin APs • 108Mbps per Area (2 channels) • Good for Roaming

  9. Architecture Choices Wi-Fi Array • Up to 864Mbps of Bandwidth per cell • Up to 16 channels per cell • Sector Antenna System • Long Range • Very high client capacity • Very high voice capacity

  10. Take Aways • Design for Performance – Not Just Coverage • Over provision for wireless (same as for wired) • Use all available 802.11a/b/g channels simultaneously • Reuse channels as often as possible • Designed for Voice • More users at higher data rates = less contention/latency • Insist on standards-based QoS (802.11e / scheduled access) • Map QoS through the wired network

  11. Thank You John DiGiovanni Director of Marketing Staff Technologist john.digiovanni@xirrus.com

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