Post on 18-Jan-2017
Introducing Blanket Wireless LAN TechnologiesBICSI Seminar - 14th September 2011
Cameron LauICT Systems Engineer
Agenda
1. Existing 802.11 Micro Cell Based Technology– Architecture– Propagation– Co-Channel Interference– Security
2. Blanket Technology– Architecture– Co-Channel Interference – Mobility– Increased Data Throughput (802.11n)
3. Case Study
Micro Cell Based Technology
• Existing Micro-Cell Typical Architecture:– Multiple APs are used to provide extended coverage to an area.
– Client Network Interface Cards are used to access the network.
6
11
111
11
6
6
Micro Cell Based Technology (cont)
– Each AP is relatively independent, channels are spread apart to minimise interference.
– User portability.
Wave Propagation
• Wave Propagation is analogue.
• AP Signals Propagate longer than expected.
• Average data rates diminish as propagation distance increases.
• Client’s transmission power is usually out of network administrator’s control.
• Propagation property of waves can result in Co-Channel Interference.
@ 5
4 M
bp
s
@ 1
1 M
bp
s
@ 1
Mb
ps
Radio Transmission Still Continues
Co-Channel Interference
• Undesirable effects due to signal propagation.
• Overlapping signals of the same channel.
• Connection disruptions, edge user effect.
• Channel planning is complex.
• Focus on Portability, not mobility.
Sign
al S
tre
ngt
h
A?
Security
Current micro cell WLANs are susceptible to:
• Session Hijacking– Hackers imitate client MAC
addresses/APs and hijack networking sessions.
– Does not require AP to prove it is an AP.
– Half-duplex communication.
• DoS Attacks
• Eavesdropping
6
11
111
11
6
6
Blanket Technology
Architecture:• A ‘channel’ blanket is formed due to an aggregate coverage of all APs.• APs are ‘dumb’ radios, connected to a centralised intelligent switch.• AP devices consist of MIMO radios, allowing for 802.11n standard to be
used.
Architecture (cont).
• Each channel can be separated out for specific end user applications.– Dedicated security layer to scan rogue APs.
– No AP-AP hand off, therefore security session is maintained continuously.
• Blanket removes cell planning complexity.
1
6
11
Co-Channel Interference
• Switch controls which APs to talk to specific client devices, preventing co-channel interference.
Mobility
• Multiple APs can receive data, increases diversity of uplink paths: Improve uplink resilience to disruption due to multiple pathway
options.
Total mobility, and zero latency service.
(1)(2)
Increased Data Throughput• 802.11n standard for MIMO
radios.• Use one dedicated channel
blanket for 802.11n throughout the network.
• 802.11b/g occupies 20MHz. • 802.11n occupies 40MHz (double
bandwidth). • Using MIMO technology to
transfer 4 streams, achieve theoretical 600Mbps throughput!
Ch 1 Ch 6 Ch 11
Ch 2 Ch 7
Ch 3 Ch 8
Ch 4 Ch 9
Ch 5 Ch 10
802.11n 802.11b/g
Today
802.11b/g/n
40MHz 20MHz
Ch 1 Ch 6 Ch 11
Ch 2 Ch 7
Ch 3 Ch 8
Ch 4 Ch 9
Ch 5 Ch 10
802.11n 802.11b/g
Today
802.11b/g/n
40MHz 20MHz
2.4GHz ‘n’
2.4GHz ‘b/g’
5GHz ’n’
5GHz ‘a’ orSecurity Blanket
Data
Voice
Multimedia
Locationing
Any combination of channels, bands, modes, & security
Summary
Blanket Technology Provides:
• No Co-Channel Interference.
• No ‘edge’ users slowing total bandwidth.
• Higher density of AP’s than microcell. – Users are closer to AP’s.
– Get better signal.
– Faster transmit/receive.
• Uplink Diversity and total mobility.
• Can utilise 802.11n effectively: 70% throughput increase!
Case Study School Wireless Survey
SKM was asked to investigate wireless problems:
– MicroCell layout with multiple access points spread throughout the school.
Problems:
– Connection problems when many laptop users try to connect.
– Signal black spot areas.
– Sporadic and intermittent connections.
Case Study Summary
Causes Identified:
– Severe Co-Channel Interference.
– Insufficient Signal Strength.
– Poor AP positioning.
– High noise, low SNR.
Potential Solutions:
– Increase Signal Output Power.
– Increase Channel Diversity, by using 5GHz band.
– Implement blanket technology
References
• Allied Telisis & Extricom - 4th Generation Wireless Presentationhttp://www.youtube.com/watch?v=EY3zpmHqmG0
• SANS Institute InfoSec Reading Room – WLAN Security Issues & Solutions
• Aruba Networks – WLAN Single Channel and Adaptive Multi Channel Models