1. Interference Detection and Signature Matching
Month Year
doc.: IEEE yy/xxxxr0
10 Nov 05
Interference Detection and Signature Matching
Authors:
Date:
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Roger Durand, AutoCell Labs
John Doe, Some Company

2. Month Year
doc.: IEEE yy/xxxxr0
10 Nov 05
Abstract
The interference detection techniques require a mechanism for quieting the channel and a mechanism for sampling energy in the channel relative to sample period and measurement duration.
The interference results can be forwarded for signature mapping. The signature mapping techniques require a mechanism for matching the signature results to known sources of interference for identification – or catalogue.
Once a source of interference is characterized and/or matched, appropriate responses or countermeasures may be taken to improve likelihood of successful transmissions.
Roger Durand, AutoCell Labs
John Doe, Some Company

3. Interference Detection
10 Nov 05
Interference Detection
Signal Processor G
BPF G
LPF G
A/D
Valid assumptions, WLAN Radios all are able to…
1.) Sample energy in a short time interval = to determine the noise floor in an IFS (Availability of the channel)
2.) Convert the A/D voltages for time samples to an RF dBm value at the antenna connector (802.11k)
3.) Blocking higher firmware is usually the only concern… you want to do what?
4.) All known modern WLAN radios CAN employ this method without dedicated or additional hardware
Valid Interference Detection Measurement set up…
1.) Quiet the Channel
2.) Sample energy in a repeating 10 microsecond window (or shorter) and repeat 2000 times for 20 milliseconds
3.) Other combinations are valid dependant on resolution results and or types of interference expected.
4.) Read the results, interpret and match the results to signature from catalog or add to catalog…
Roger Durand, AutoCell Labs

4. Interference Detection & Signature Analysis
10 Nov 05
Interference Detection & Signature Analysis
CW Interferer degrades noise floor 8 to 12 dB
Example AP
A/D Output of Interference Detection
CW Interferer
dBm
10 dB Elevated Noise Floor
Time
Roger Durand, AutoCell Labs

5. Interference Detection & Signature Analysis
10 Nov 05
Interference Detection & Signature Analysis
Microwave Interferer degrades noise floor 3 to ~50 dB
Example AP
A/D Output of Interference Detection
16 msec/60Hz
Microwave Interferer
6 msec
dBm
Time
Roger Durand, AutoCell Labs

6. Interference Detection & Signature Analysis
10 Nov 05
Interference Detection & Signature Analysis
FHSS Interferer degrades noise floor 4 to~35 dB
Example AP
A/D Output of Interference Detection
FHSS Interferer
780 µsec
840 µsec
680 µsec
780 µsec
dBm
Time
Roger Durand, AutoCell Labs

7. Why is this Important An important tool for the kit:
10 Nov 05
Why is this Important
An important tool for the kit:
A means to access the channel quality on channel selection
Knowledge of the degradations that are happening in the channel
Explain increasing errors and the dropping data rates
Countermeasures are dependent on type of interference
Increase Transmitter Power
Increase Radio Sensitivity Threshold
Fragment packets
Enables synchronization methods
Change operating channel (variant of channel switch command)
Roger Durand, AutoCell Labs

8. 10 Nov 05
Motion
Motion:“The substantive text IEEE 802/11_05_ 1067r1 Interference Detection addresses objectives: degradations caused by contention or other issues, channel selection and dynamic channel selection, site survey mode, access point coordination, and neighbor learning process is worthy of inclusion in the base draft”
Merge=
No=
Abstain=
Roger Durand, AutoCell Labs