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This paper studies the design of signaling waveforms for time-hopping impulse radio (TH-IR) with limits on the power spectral density. Such restrictions are imposed by the spectral mask prescribed by frequency regulators for ultrawideband (UWB) signals. The "conventional" TH-IR system with pulse-position modulation and time-hopping multiple access gives rise to spectral lines that either violate the regulations, or require a significant power back-off. To remedy this situation, we propose the use of polarity randomization, which eliminates the spectral lines and also leads to a smoothing of the continuous part of the spectrum. We analyze different variants of the polarity randomization, considering short and long randomization sequences, as well as symbol-based or pulse-based randomization. We analyze the effect of this technique on both PPM and BPSK modulation. IEEE Journal on Selected Areas in CommunicationsThis work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part without payment of fee is granted for nonprofit educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of Mitsubishi Electric Research Laboratories, Inc.; an acknowledgment of the authors and individual contributions to the work; and all applicable portions of the copyright notice. Copying, reproduction, or republishing for any other purpose shall require a license with payment of fee to Mitsubishi Electric Research Laboratories, Inc. All rights reserved.

We present an efficient, low-cost implementation of time-hopping impulse radio that fulfills the spectral mask mandated by the FCC and is suitable for high-data-rate, short-range communications. Key features are (i) all-baseband implementation that obviates the need for passband components, (ii) symbol-rate (not chip rate) sampling, A/D conversion, and digital signal processing, (iii) fast acquisition due to novel search algorithms, and (iv) spectral shaping that can be adapted to accommodate different spectrum regulations and interference environments. Computer simulations show that this system can provide 110 Mbps at 7–10 m distance, as well as higher data rates at shorter distances under FCC emissions limits. Due to the spreading concept of time-hopping impulse radio, the system can sustain multiple simultaneous users, and can suppress narrowband interference effectively

Ultra Wide Band technology has attracted a lot of attention recently as a viable solution for high data rate, low power, short-range wireless link. The growing multi-media home networking is demanding more bandwidth and wireless throughput has become a bottleneck for high quality multi-media services. With the maximum data rate above 100 Mbps, UWB is a perfect solution for such applications.This paper describe such a system that takes advantage of the high data rate offered by UWB. We first implemented the complete MB-OFDM PHY layer using multi-FPGA hardware and discrete RF design. Out implementation is fully compliant to the WiMedia/MBOA PHY specifications and the FCC power regulations. The system achieved 110Mbps maximum data rate with a BER better than 10-6 over a range of 4 meters.Subsequently, we developed a testbed that demonstrates simultaneous transmission of multiple High Definition video streams over the MB-OFDM link. The use-case scenario is a Multimedia Client-Server application where we have one Media Server (transmitter) and several Media Players (receivers). IEEE Consumer Communications and NetworkingThis work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part without payment of fee is granted for nonprofit educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of Mitsubishi Electric Research Laboratories, Inc.; an acknowledgment of the authors and individual contributions to the work; and all applicable portions of the copyright notice. Copying, reproduction, or republishing for any other purpose shall require a license with payment of fee to Mitsubishi Electric Research Laboratories, Inc. All rights reserved.

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