01-06-2012, 01:19 PM
Ultra-Wide Band Communication for the Internet of Things
[attachment=23851]
Ultra Wide Band (UWB) Communication
Use a very large spectrum
up to Several GHzs
Very low power
Below level of unintentional emission
Unlicensed
Co-exists with other technologies
Power Limits
FCC (2002) limits
peak power (0dBm per 50MHz)
mean power (-41.3dBm per MHz)
Europe (and CH-Ofcom, 2007) put more stringent limits
Various Uses of UWB Signals Radar and Ranging
Radar
A very old UWB application, used for maritime or air navigation, and as remote speedometer
New apps: automotive security, rescue operation
One active device analyzes echo Target is passive and unaware of signal
Not always low power
Ranging
From device to device
Device is active sender
Base station is receiver /transmitter
E.g Ubisense, Cambridge UK
Low power
Impulse Radio UWB Uses Time Hopping
Time Hopping Sequence: […, 2, 5, 4, 7 …]
Pulses appear random unless you know THS
THS is predictible to user who knows the key ; e.g.: MAC address
Transforms packet collision into symbol collision
Increaed bit error rate instead of packet loss
Software-like flexibility in hardware
When a pulse is sent can easily be changed by modifying a few values in the system
Change the time hopping sequence
Change the modulation rate
[attachment=23851]
Ultra Wide Band (UWB) Communication
Use a very large spectrum
up to Several GHzs
Very low power
Below level of unintentional emission
Unlicensed
Co-exists with other technologies
Power Limits
FCC (2002) limits
peak power (0dBm per 50MHz)
mean power (-41.3dBm per MHz)
Europe (and CH-Ofcom, 2007) put more stringent limits
Various Uses of UWB Signals Radar and Ranging
Radar
A very old UWB application, used for maritime or air navigation, and as remote speedometer
New apps: automotive security, rescue operation
One active device analyzes echo Target is passive and unaware of signal
Not always low power
Ranging
From device to device
Device is active sender
Base station is receiver /transmitter
E.g Ubisense, Cambridge UK
Low power
Impulse Radio UWB Uses Time Hopping
Time Hopping Sequence: […, 2, 5, 4, 7 …]
Pulses appear random unless you know THS
THS is predictible to user who knows the key ; e.g.: MAC address
Transforms packet collision into symbol collision
Increaed bit error rate instead of packet loss
Software-like flexibility in hardware
When a pulse is sent can easily be changed by modifying a few values in the system
Change the time hopping sequence
Change the modulation rate