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?

Edge-user effect (example):

CCI

CCI

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 (cont)Example of the Co-Channel Interference Measured

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

Thank You

Questions?

Cameron Lau – Clau@globalskm.com

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