The Ultra Wide-Band (UWB) Radio Propagation Channel

The Ultra Wide-Band (UWB) radio communications can be viewed as an extreme form of spread spectrum communication systems. UWB radios are generally defined to have a -3dB fractional bandwidth which is at least 25% of the centre frequency used. The UWB signals generation methods can be groupped in two major categories: Single-Band (SB) based, employing one single transmision frequency band, and Multi-Band (MB) based, employing two or more frequency bands, each with at least 500MHz bandwidth. In the SB solution, the UWB signal is generated using very short, low duty-cycle, baseband electrical pulses with appropiate shape and duration. Due to the carrier-less characteristics - no sinusoidal carrier to raise the signal to a certain frequency band - these UWB systems are also referred to as carrier-free or impulse radio (IR-UWB) communication systems. The MB UWB systems can be implemented carrier less (different pulse shapes/lengths are used according to the frequency band)or carrier based (multi-carrier like). In the view of WLAN/ WPAN applications of the UWB technology and analysing the results from previously conducted studies, the following main topics have been identified for further research on the UWB radio propagation aspects: 1) Characterisation of the small-size antenna on the radio propagation channel (body worn devices, etc.) 2) Characterisation of the user body proximity environment on the radio propagation channel 3) Practical limits for ?traditional? wideband antenna diversity, including a diversity propagation model if relevant 4) MIMO potential for parallel communication channels and possible capacity or throughput gain, including a UWB MIMO propagation model if relevant 5) Implementation issues and specifications for a practical HW UWB radio test bed Read more about this project at http://kom.auc.dk/antprop/uwb