January 23-26, 2007• Ft. Lauderdale, Florida

Deployment Challenges of Wi-Fi Telephony

John DiGiovanniDirector of MarketingStaff Technologistjohn.digiovanni@xirrus.com

January 23-26, 2007• Ft. Lauderdale, Florida

Voice over Wi-Fi – It’s Coming!

January 23-26, 2007• Ft. Lauderdale, Florida

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

January 23-26, 2007• Ft. Lauderdale, Florida

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

January 23-26, 2007• Ft. Lauderdale, Florida

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

Ch# 1 2 3 4 5 6 7 8 9 10 11

2.4GHz ISM Band

Ch# 1 6 11

January 23-26, 2007• Ft. Lauderdale, Florida

Channels & Capacity – 802.11a

• 12 channels for 802.11a

• Use as many Channels as possible• Reuse them as often as possible

FCC has approved 11 more channels

Up to 1.24Gbps of Total Capacity

5GHz UNI Band

Ch# 36 40 44 48 52 56 60 64 161149 153 157

Ch# 100 104 108 112116 120 124 128 132 136 140

January 23-26, 2007• Ft. Lauderdale, Florida

Quality of Service

• 802.11e (Over the Air)– Packet prioritization for downstream traffic

• Wired Class of Service is mapped to wireless TCID settings

January 23-26, 2007• Ft. Lauderdale, Florida

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

January 23-26, 2007• Ft. Lauderdale, Florida

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

January 23-26, 2007• Ft. Lauderdale, Florida

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

January 23-26, 2007• Ft. Lauderdale, Florida

Thank YouJohn DiGiovanniDirector of MarketingStaff Technologistjohn.digiovanni@xirrus.com