Ultra Wideband

Overview

Ultra-Wideband (UWB) is an emerging technology for short-range, wireless personal area networks that provides the convenience and mobility of wireless communications to high-speed interconnections in the home and office. Strictly speaking, UWB is defined as any radio technology having a spectrum that occupies a bandwidth greater than 20 percent of the center frequency, or a bandwidth of at least 500 MHz. While several different UWB technologies are under investigation and/or development, TRLabs’ UWB research focuses primarily on impulse radio. Impulse radio offers a practical way of implementing UWB with reasonable tradeoffs between system capacity, complexity and robustness relative to competing UWB technologies. TRLabs is currently exploring several important research issues related to the design and implementation of impulse radio transceivers, including:

  • How to handle multi-path effectively?
  • How to mitigate the effects of narrowband interference?
  • How to synchronize terminals quickly and efficiently?

An underlying theme of this research is the development of practical transceiver architectures that effectively deal with these real-world issues. Work to date includes the development of a uniform sampling rake receiver based on single-bit sampling quantization. This single-bit rake structure significantly reduces the receiver’s complexity and processing requirements. This allows a large number of rake fingers to be implemented in the receiver, with corresponding performance gains. Analysis and simulation results also show that the single-bit rake receiver is resilient to both multi-path spreading and narrowband interference.

Impulse Radio Transceiver

The goal of this project is to design and implement practical impulse radio transceiver architectures under stringent processing power and target cost constraints. Work is currently progressing on: a low-cost transmitter; simplified receiver architectures based on the single-bit rake structure; filter banks; and synchronization and acquisition techniques. Specific research objectives include: Propose various receiver structures and investigate the effects of narrow band interference on the performance of the system.
Investigate the effect of timing jitter and clock phase noise on impulse radio pulses to develop a suitable tracking algorithm for clock synchronization. Blind detection schemes are necessary for locking the receiver synchronization. Propose and analyze techniques for multi-user detection in UWB. Construct a hardware test-bed using the data obtained from the simulations. Investigate the impacts of nonlinear hardware effects and other real-world effects on system performance.

UWB Channel Characterization

This research project involves developing a UWB channel sounder to characterize the impulse response of the indoor radio environment. Because UWB propagation models in multi-path environments are more complex than existing narrowband models, direct extension of narrowband techniques are not possible. Also, low complexity channel estimation methods with explicit consideration of multiple access interference need to be developed. Utilizing direct sequence spread spectrum, the proposed channel sounder will be used to collect a series of impulse response measurements for an indoor radio environment. These measurements will then be used to analyze the performance of different techniques for channel estimation and tracking for UWB receivers.