A Hybrid UWB Modulation Design Compatible for both Coherent and Transmit-Reference Receivers

Abstract

In a pulsed UWB system, either coherent receivers or transmit-reference (TR) receivers can be used to demodulate the signals. For coherent receivers, which are typically based on a Rake Structure, the large number of resolvable multipaths is a major challenge for channel estimation and receiver complexity. TR receivers can effectively collect energy from all the received multipath components with much smaller complexity, but show reduced performance. Current modulation formats are tuned to either coherent or TR receivers, but cannot interoperate with both of them. In this paper, we propose an innovative modulation scheme that enables the useage of TR and coherent recievers in the same wireless network. The modulation allows demodulation by TR receivers, while at the same time enabling a coherent receiver to fully exploit all available signal energy, and actually to perform slightly better (by 1.8 dB) than a coherent receiver working with conventional BPSK modulation; this additional gain can be interpreted as a coding gain of a trellis-coded modulation scheme. The scheme thus allows the network designers to trade off performance vs. complexity in the receivers, while allowing a uniform signaling (modulation) scheme for all transmitters. ICC 2006This 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. Abstract-In a pulsed UWB system, either coherent receivers or transmit-reference (TR) receivers can be used to demodulate the signals. For coherent receivers, which are typically based on a Rake structure, the large number of resolvable multipaths is a major challenge for channel estimation and receiver complexity. TR receivers can effectively collect energy from all the received multipath components with much smaller complexity, but show reduced performance. Current modulation formats are tuned to either coherent or TR receivers, but cannot interoperate with both of them at the maximum performance possible for each of them. In this paper, we propose an innovative modulation scheme that enables the use of TR and coherent receivers in the same wireless network. The modulation allows demodulation by TR receivers, while at the same time enabling a coherent receiver to fully exploit all available signal energy, and actually to perform slightly better (by 1.8 dB) than a coherent receiver working with conventional BPSK modulation; this additional gain can be interpreted as a coding gain of a trellis-c...

Hybrid Ultrawideband Modulations Compatible for Both Coherent and Transmit-Reference Receivers

“…In the proposed scheme, whose basic idea can be found in [23], each bit or symbol is represented by N f pulse pairs, where N f is a positive integer. The two pulses in each pair are separated by a fixed time T d .…”

A Non-Coherent 802.15.4a UWB Impulse Radio

“…Therefore, multipath components in the arriving signal can be easily identified. Assume that φ(t) is the transmitted UWB pulse waveform with unit energy, T sym denotes the symbol duration, N sym is the 0101-10101000-1110-11-1-1-10010011000 S 3 -11011000-11-11100110100-10000-1010-1 S 4 00001-100-100-1111101-1100010-10110-1 S 5 -101-100111-11000-1101110-1010000-00 S 6 1100100-1-1-11-1011-10001010-11010000 S 7 100001-101010010001011-1-1-10-1100-11 S 8 0100-10-10110000-1-1100-11011-1110100 number of symbol repetitions within the preamble, T pri is the pulse repetition interval, N s the total number of pulses per symbol and E s denotes the symbol energy. Then, for the ith basis symbol S i , the preamble symbol waveform w i (t) and the resulting preamble waveform P i (t) can be written as…”