Ultra-wideband Radio Signals Research Articles

Performance Degradation Due to OFDM-UWB Radio Signal Transmission Along Dispersive Single-Mode Fiber

The performance degradation of orthogonal frequency-division multiplexing (OFDM) ultra-wideband (UWB) radio signals caused by transmission along dispersive single-mode fiber is assessed theoretically and by numerical simulation. It is shown that the performance degradation of OFDM-UWB signals caused by fiber dispersion is due to the power fading induced on the subcarrier showing stronger fading. Results show that the power fading description based on a small signal analysis provides good estimates of the optical signal-to-noise ratio degradation for OFDM-UWB signals with modulation index (defined as the ratio between the root-mean-square voltage of the OFDM-UWB signal and the bias voltage of the Mach-Zehnder modulator) values up to 18%. This is a pessimistic value for some OFDM-UWB carrier frequencies.

An IR-UWB Photonic Distribution System

Experimental results are presented for a novel distribution system for an impulse radio ultra-wideband (UWB) radio signals employing a gain-switched laser. The pulse position modulated short optical pulses with a bit rate of 1.25 Gb/s are transmitted over fiber to a remote antenna unit, where the signal is converted to the electrical domain and undergoes spectral shaping to remove unwanted components according to UWB requirements. An experimental radio terminal has also been constructed to enable bit-error-rate measurements to be carried out. These experiments show that the optical distribution system will be capable of supporting the radio part of the system.

UWB and MEMS Based Indoor Navigation

Thanks to its physical characteristics, Ultra-wideband (UWB) is one of the most promising technologies for indoor pedestrian navigation. UWB radio localisation systems however experience multipath phenomena that decrease the precision and the reliability of the user's location. To cope with complex indoor environments, UWB radio signals are coupled with inertial measurements from Micro Electro Mechanical Sensors (MEMS) in an extended Kalman filter. Improved performances of the filter are presented and compared with reference trajectories and with pure inertial solutions. Only specific selection methods enable this improvement by detecting and removing outliers in the raw localisation data.

Ultra-Wideband Radio Signals Distribution in FTTH Networks

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The use of an ultra-wideband (UWB) radio technique is proposed as a viable solution for the distribution of high-definition audio/video content in fiber-to-the-home (FTTH) networks. The approach suitability is demonstrated by the transmission of standards-based UWB signals at 1.25 Gb/s along different FTTH fiber links with 25 km up to 60 km of standard single-mode fiber length in a laboratory experiment. Experimental results suggest that orthogonal frequency-division-multiplexed UWB signals exhibit better transmission performance in FFTH networks than impulse radio UWB signals. </para>

Multiuser Interference Mitigation in Noncoherent UWB Ranging via Nonlinear Filtering

Ranging with energy detectors enables low-cost implementation. However, any interference can be quite detrimental to range accuracy. We develop a method that performs nonlinear filtering on the received signal energy to mitigate multiuser interference (MUI), and we test it over time hopping and direct sequence impulse radio ultra-wideband signals. Simulations conducted over IEEE 802.15.4a residential line of sight ultrawideband multipath channels indicate that nonlinear filtering helps sustain range estimation accuracy in the presence of strong MUI.