w&m 2009 – 4th generation wireless – building for the future
TRANSCRIPT
4th Generation Wireless-Building for the Future
Dave Crowder – Senior Systems Engineer
Agenda
Evolution of Wireless
The Challenges of Ordinary Wireless
Business Benefits and Cost Savings of 4th Generation Architectures
4th Generation Wireless and 802.11n
Evolution of Wireless
First Generation
Second Generation
Third Generation
Fourth Generation
Controller ControllerAP
AP AP AP AP
Pre-standard
AP
AutonomousCentralized
MicrocellCentralizedVirtual Cell
AP
Challenges of Ordinary Wireless
Co-channel interference
Contention for shared medium
Clients control association
Lack of QoS / Fairness
Co-Channel Interference
SignalStrength
Distance
-68dBm
-95dBm
54Mbps
1Mbps
There are 3 non-overlapping channels in 2.4GHz(Ch 1, 6, 11)
x x
x
xx
x
Contention for Shared Medium
Number of Contenders (Devices in interference range)
20
Tota
l Ban
dwid
th a
t Pea
k
3
Baseband + Protocol overhead
Peak Aggregate Throughput in Single Cell Environment
Contention Limits Throughput and User Density in Traditional 802.11 Networks
• Peak aggregate capacity with 3 or fewer contending stations
• Very limited user density– Capacity drops precipitously with ~10
contending stations– Effective lack of connectivity with 20 stations
Standard CSMA Curve
• CSMA (Ethernet and 802.11) designed for low contentionand low load
• Contention penalty in 802.11 is even worse because there is no collision detection; all transmissions must be acknowledged
ContentionLoss
Clients control association
Airtime Fairness and QoS
‘g’ client
‘g’ client
‘g’ client
Airtime Fairness and QoS
‘g’ client‘b’ client
‘g’ client
Challenges of Ordinary Wireless
Co-channel interference
Contention for shared medium
Clients control association
Lack of QoS / Fairness
4th Generation Wireless
4th Generation Wireless
Optimised coverage No co-channel interference Ease of deployment and upgrade
4th Generation Wireless
Number of Contenders (Devices in interference range)
20
Tota
l Ban
dwid
th a
t Pea
k
3
Baseband + Protocol overhead
Peak Aggregate Throughput in Single Cell Environment
Standard CSMA Curve
ContentionLoss
100+ simultaneous connections per access point
4th Generation Wireless
4th Generation Wireless
‘g’ client‘b’ client
‘g’ client
4th Generation Wireless
‘b’ client
‘g’ client
‘g’ client
4th Generation Wireless
‘b’ client
‘n’ clients
4th Generation Wireless- Summary
Ease of deployment, upgrade and maintenance (lowest TCO)
Optimal throughput, even with dense deployments
Seamless roaming Multi-application QoS / Legacy
client support
4th Generation and 802.11n
Benefits of 802.11n : Improved network throughput Improved (but less predictable)
coverageOpportunities from 802.11n : Access layer connection Substitute for desktop cabling?
4th Generation and 802.11n
Available Spectrum
40MHz 802.11n Choices
36, 40 36, 40 44, 48 44, 48
52, 56 52, 56 60, 64 60, 64
149, 153 157, 161 149, 153 157, 161
1, 6* 1, 6* 1, 6* 1, 6*
20MHz 802.11abg Choices
11* 11* 11* 11*
64 64
*2.4 GHz
36 40 44 48 52 56 60 64 165
UNI I UNI II UNI III149 153 157 161Unavailable Frequencies
Channel Selection Options for 802.11abgn
Only 3x40-Mhz channels in 5Ghz range (11a)
Only 1x40-Mhz channel in 2.4 Ghz Range (11 b/g)
4th Generation and 802.11n
X
Office Floor Office Floor
Current Technology
4th Generation
Solution
Initial planning and optimization difficult
Fixing coverage holes requires re-planning and “domino effect” of changing channel plans
Not possible to fix co-channel interference issues in multi-floors
No channel planning needed Deploy APs based on rule-of-thumb
(e.g. 80 feet in office cubes) Any coverage holes easily fixed
without re-planning Packet-access-level coordinated AP
mitigates co-channel interference
Traditional WLANs
Meru Networks
Fastest Growing Wifi Vendor Leading 4th Generation Wifi Vendor Gartner’s “most visionary” Thousands of deployments
worldwide Hundreds of UK deployments
(education, healthcare … )
Thank You
Dave Crowder – Senior Systems Engineer
http://www.merunetworks.com