Abstract
The development of ultra-wideband (UWB) communications is impeded by the drastic transmitted power limitations imposed by regulation authorities due to the "polluting" character of these radio emissions with respect to existing services. Technical solutions must be researched in order either to limit the level of spectral pollution by UWB devices or to increase their reception sensitivity. In the present work, we consider pulse-based modulations and investigate time-domain multiple-input multiple-output (MIMO) diversity as one such possible solution. The basic principles of time-domain diversity in the extreme (low multipath density) or intermediate (dense multipath) UWB regimes are addressed, which predict the possibility of a MIMO gain equal to the product of the numbers of transmit/receive antenna elements when the channel is not too severe. This analysis is confirmed by simulations using a parametric empirical stochastic double-directional channel model. They confirm the potential interest of MIMO approaches solutions in order to bring a valuable performance gain in UWB communications.
Highlights
Ultra-wideband (UWB) technologies are among the “hot topics” in the present days as their specificities are promising for future communications or positioning applications
The signal-to-noise ratio (SNR) gain is computed on the basis of the correlation magnitude squared, divided by the integrated noise power over the duration of the correlation signal acquisition
We have investigated and evaluated by simulations a few SIMO and multiple-input multiple-output (MIMO) diversity schemes which can improve the performance of a UWB radio link, in the hope to surmount the heavy constraints imposed by stringent regulations
Summary
Ultra-wideband (UWB) technologies are among the “hot topics” in the present days as their specificities are promising for future communications or positioning applications. Cautious regulations are expected due to the wide emitted radiation spectra which ignore the numerous protected bands. The latter exist for a great variety of scientific, public, or commercial services, and sensitive to electromagnetic pollution are those requiring very low noise levels (spatial scientific services, fixed wireless access, GPS, etc.). The Federal Communications Commission (FCC), for instance, imposes to indoor communications a maximum emitted isotropic radiated power (EIRP) of −41.3 dBm/MHz between 3.1 and 10.6 GHz, and much less outside this band. This is still a subject of debate, European authorities will probably adopt conditions at least as stringent as the FCC. It is crucial to develop solutions that make the best possible use of the radiated and received power, for the feasibility and the future commercial success of UWB communications systems
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