Diploma Thesis

April-October 2005

Synchronization Methods for Simple UWB Receiver Structures

In body area networks (BAN) several wireless nodes are placed directly or very close to the human body, e.g., in every day clothes. A number of different applications can be imagined, such as medical monitoring or wireless multimedia transfer. Due to comfort reasons a node has to be very energy efficient and very small. Moreover, the nodes should be inexpensive, i.e., should have low complexity, due to the required number of nodes.

Ultra Wideband (UWB) communication is one transmission technology promising less complex hardware. There, transmission takes place in baseband, i.e., no hardware is required for mixers, RF oscillators or PLLs, as it would be necessary in narrowband systems. The Federal Communications Commission (FCC) allowed in the USA the frequency range between 3.1 and 10.6GHz for UWB communication purposes, i.e., the maximum allowed bandwidth is 7.5GHz. But the minimum bandwidth used by any UWB system has to be 500MHz. Using such a large bandwidth corresponds to transmission of very short pulses of some hundred pico-seconds.

Transmitted Reference Receiver

Due to the above mentioned complexity reasons, RAKE receivers are not suited for simple BAN nodes. Therefore, two simple receiver structures, the transmitted-reference (TR) receiver and the energy detector (ED), received increasing attention recently. In TR systems, two pulses, a reference and a data pulse, are transmitted and correlated in the receiver. Since both pulses pass the same channel, no explicit channel estimation is needed. Such an explicit channel estimation is not needed in the ED, too. The ED collects the energy from the multipaths. Although, there are some differences between both receivers they are very similar. Therefore, it shall be shown theoretically in this work that performance of TR and ED is almost equal. Based on this result, the receivers shall be optimized, e.g., using a weighting function for the TR receiver.

Due to the short pulse durations in UWB systems, acquisition and synchronization have high impact on the performance. Already, slight variations from the real arrival time of the receive signal can lead to synchronization errors. Therefore, a suited acquisition and synchronization method shall be proposed and the performance investigated.

[1] Thomas Zasowski, Frank Althaus, and Armin Wittneben, "An Energy Efficient Transmitted-Reference Scheme for Ultra Wideband Communications", International Workshop on Ultra Wideband Systems (IWUWBS) Joint with Conference on Ultra Wideband Systems and Technologies (UWBST) 2004, May 2004, Kyoto, Japan

Subject area Ultra Wideband, Body Area Networks, Physical Layer, Synchonization
Type of work 80% Theory, 20% Software
Students Martin Arnold, Cyril Stutz
Advisor Dr. Thomas Zasowski
Professor Prof. Dr. Armin Wittneben