Coding, Modulation, and Detection in Impulse-Radio Ultra-Wideband Systems


Overview

Project Processing: Andreas Schenk
Project Funding: DFG
Duration: 03/09 -- 03/13
Keywords: UWB, Impulse-Radio Ultra-Wideband, Low Complexity Receivers, Noncoherent Detection

Motivation

Impulse-radio ultra-wideband (IR-UWB) systems are especially well-suited for short-range low-data-rate communications, such as, e.g., in wireless-sensor networks. iruwb_system.jpeg The main advantages of IR-UWB include its robustness to severe multi-path fading even in indoor environments, the potential to provide accurate localization, and, last but not least, its low cost and complexity. Whereas the design of low-complexity low-power-consuming IR-UWB transmitters is well known, in this project the design of low-complexity and power-efficient IR-UWB receivers is addressed. In particular, noncoherent detection schemes, which directly use the receive signal as reference for demodulation, are widely regarded as the key for low-complexity receiver design, since costly channel estimation required for coherent detection is avoided. Moreover, the influence of the low-complexity demand on the design of coded IR-UWB systems is addressed.

Major Goals

  • Low-complexity receiver design for (coded) IR-UWB transmission
    In this project we focus on differential pulse-amplitude-modulated IR-UWB in combination with autocorrelation-based detection as one variant of noncoherent detection schemes. In the course of the project it has been shown, that the inherent loss in performance of traditional noncoherent autocorrelation-based differential detection (DD), as compared to coherent detection based on explicit channel estimation, can be alleviated by advanced autocorrelation-based detection schemes operating on the output of an extended autocorrelation receiver (ACR), which delivers correlation coefficients of symbols separated by several symbol durations. Based on the output of such extended ACRs, block-based detection schemes, which partition the receive symbol stream into (possibly overlapping) blocks and thus process multiple symbols jointly, have proven to enable power-efficient, yet low-complexity detection in both uncoded and coded IR-UWB transmission systems. In the case of coded transmission, such detection schemes can be extended to incorporate computation of reliability information, i.e., so-called soft output, which can be used to improve the decoding performance of the subsequent channel decoder.
  • Design Rules for (coded) IR-UWB systems
    The application of low-complexity receivers has significant consequences on the design of the entire IR-UWB system. We conduct an information theoretic analysis of coded IR-UWB transmission in combination with autocorrelation-based detection, which enables us to deduce design rules for realisitic IR-UWB systems, and to identify optimum rates for the employed channel code. It can be shown that especially if noncoherent receivers are employed, coding, modulation, and detection should be considered jointly to achieve the goal of designing low-complexity, power-efficient IR-UWB systems.

Persons Involved