Student Project

Implementation and Performance Evaluation of an Adaptive Filter for a Low-complexity UWB receiver

Ultra wideband (UWB) communication attracted much interest for the use in wireless sensor and body area networks (BAN) due to low complexity and energy efficient system realizations. In particular noncoherent receivers can be implemented very efficiently and promise low power consumption to meet stringent constraints on battery autonomy.

Recently, we presented an energy detection based ultra-low power UWB system design with an overall estimated current consumption of less than 1 mW [1]. Low duty cycle operation together with a high peak data rate are the key to achieve a medium data rate system with very low current consumption. Using binary pulse position modulation (PPM), data is transmitted at different time-shifts according to the different bit values. Having a delay spread of 10 ns, the minimal PPM frame duration without inter-symbol interference (ISI) is restricted to 20 ns [2], implying a peak data rate of 50 Mbps. Requiring an average data rate of 500 kbps, a duty cycle of 1% can be realized. With respect to streaming applications, the maximum allowed latency time is set to 1 ms. Therefore, a burst of 500 bits and 10 μs duration is sent every millisecond. Besides the low duty cycle operation also the usage of low complexity resonant circuits in the analog part, which requires a moderate relative bandwidth, is important to achieve low power consumption. Hence, the frequency range from 3.5 to 4 GHz has been chosen for the design. The theoretical feasibility of the presented design respecting FCC power limits together with transmission of only one pulse per bit has been shown by means of computer simulation and over the air [3]. However, synchronization is an increasing important component in a UWB system. Due to high data rate and low duty cycle operation, timing estimation is critical to system performance. Moreover, clock accuracy is restricted by the complexity and cost requirements for the desired application in BAN.

In this work, the use of a digital adaptive filter for synchronization shall be investigated. Optimal filter coefficients shall be calculated by minimizing the mean-square error (MMSE), commonly known as the Wiener Filter. Based on the receiver design from [1], the filter shall be implemented and its performance evaluated and compared to perfect synchronization. Finally, complexity of the filter shall be estimated to analyze performance-complexity trade-offs.



UWB-NB comparison





References:

[1] F. Troesch, C. Steiner, T. Zasowski, T. Burger, and A. Wittneben, "Hardware aware optimization of an ultra low power UWB communication system," IEEE International Conference on Ultra-Wideband, ICUWB 2007, pp. 174-179, September 2007.

[2] T. Zasowski, F. Troesch, and A. Wittneben, "Partial channel state information and intersymbol interference in low complexity UWB PPM detection," IEEE International Conference on Ultra-Wideband, ICUWB 2006, pp. 369-374, September 2006.

[3] C. Steiner, H. Luecken, T. Zasowski, F. Troesch, and A. Wittneben, "Ultra low power UWB modem design: Experimental verification and performance evaluation," Union Radio Scientifique Internationale, URSI, August 2008.




Subject area Ultrawideband (UWB) Communications
Type of work 40% Theory, 60% Simulation
Student Hannes Friederich
Supervisor Dr. Heinrich Luecken, Dr. Thomas Zasowski
Professor Prof. Dr. Armin Wittneben