Ultra-wideband (UWB) communications exhibit many special characteristics, one of which is the random clustering phenomenon in the resolved channel multipaths. The randomness in path arrivals will, however, make exact performance analysis quite challenging. In this thesis, an analytical framework for precise characterization of a unified UWB channel structure is developed. The channel structure under consideration can comprise both the IEEE 802.15.3a and IEEE 802.15.4a channel models of great practical interests. The key idea is to capture the average eRect of the cluster and ray arrival processes through the extended density functions. The density functions are verified to be useful in deriving exact channel statistical quantities of interests, including the second-order and fourth-order joint moments. Precise performance analysis for UWB systems regarding practical channel and interference scenarios can therefore be carried out based on the exact channel analytical results.

Specifically, the performance analysis and optimization for direct-sequence UWB (DS- UWB) and multi-band orthogonal frequency-division multiplexing (MB-OFDM) systems are investigated. For the DS-UWB systems, improved analysis that do not rely on simplified interference assumption and random spreading as in the previous related works is conducted. For the MB-OFDM systems, the discrete-time receiver operation, the pulse-shaping function, and the practical cyclic addition scheme that can achieve a significant performance gain are all included in the analysis. Numerical results are also provided to verify the precise performance evaluation and the practical value of system optimization by our analytical results.

It is noticed that, due to the lack of good analytical results for the special channel characteristics, previous methodology for estimation of the channel parameters can cause inconvenience and ambiguity. As a novel application of our analytical results, a system- atic approach for estimating the UWB channel parameters is also developed in the thesis. The estimation is formulated as an optimization problem with an explicit analytical metric function that can be systematically solved. A limited set of good candidate parameters can rapidly be obtained, and further statistical tests with moderate eRorts can give the best estimation. The eRectiveness of the proposed method will be demonstrated by showing the achieved good agreements under the considered statistical profiles.

With the unified analytical framework and the practical applications in the thesis, it is expected that our work can provide fundamental contributions to the research field of UWB communications.

[1] “Revision of part 15 of the commission's rules regarding ultra-wideband transmission systems,” FCC First Report and Order, ET-Docket 98-153, Feb. 2002.
[2] M. Z. Win and R. A. Scholtz, “Ultra-wide bandwidth time-hopping spread-spectrum impulse radio for wireless multiple access communications,” IEEE Trans. Commun., vol. 48, pp. 679-689, Apr. 2000.
[3] M. Z. Win and R. A. Scholtz, “Characterization of ultra-wide bandwidth wireless indoor channels: a communication-theoretic view,” IEEE J. Select. Areas Commun., vol. 20, pp. 1613-1627, Dec. 2002.
[4] M. Ghavami, L. B. Michael, and R. Kohno, Ultra Wideband Signals and Systems in Communication Engineering. New York: Wiley, 2004.
[5] L. Yang and G. B. Giannakis, “Ultra-wideband communications: an idea whose time has come,” IEEE Signal Processing Mag., vol. 21, pp. 26-54, Nov. 2004.
[6] R. C. Qiu, H. Liu, and X. Shen, “Ultra-wideband for multiple access communications,” IEEE Commun. Mag., vol. 43, pp. 80-87, Feb. 2005.
[7] A. F. Molisch, “Ultrawideband propagation channels-theory, measurement, and modeling,” IEEE Trans. Veh. Technol., vol. 54, pp. 1528-1545, Sept. 2005.
[8] A. Saleh and R. Valenzuela, “A statistical model for indoor multipath propagation,” IEEE J. Select. Areas Commun., vol. 5, pp. 128-137, Feb. 1987.
[9] J. Foerster, et al., “Channel modeling sub-committe report final,” IEEE doc.: IEEE P802.15-02/490r1-SG3a, Feb. 2003.
[10] A. F. Molisch, J. R. Foerster, and M. Pendergrass, “Channel models for ultrawideband personal area networks,” IEEE Wireless Commun., vol. 10, pp. 14-21, Dec. 2003.
[11] A. F. Molisch, et al., “IEEE 802.15.4a channel model - final report,” IEEE doc.: IEEE 802.15-04-0662-02-004a, 2005.
[12] A. F. Molisch, D. Cassioli, C.-C. Chong, S. Emami, A. Fort, B. Kannan, J. Karedal, J. Kunisch, H. G. Schantz, K. Siwiak, and M. Z. Win, “A comprehensive standardized model for ultrawideband propagation channels,” IEEE Trans. Antennas Propagat., vol. 54, pp. 3151-3166, Nov. 2006.
[13] C.-C. Chong and S. K. Yong, “A generic statistical-based UWB channel model for high-rise apartments,” IEEE Trans. Antennas Propagat., vol. 53, pp. 2389-2399, Aug. 2005.
[14] Y. Na and M. Saquib, “Analysis of the channel energy capture in ultra-wideband transmitted reference systems,” IEEE Trans. Commun., vol. 55, pp. 262-265, Feb. 2007.
[15] T. Jia and D. I. Kim, “Analysis of average signal-to-interference-noise ratio for indoor UWB Rake receiving system,” in Proc. IEEE Veh. Tech. Conf., Stockholm, Sweden, May 2005, pp. 1396-1400.
[16] T. Jia and D. I. Kim, “Analysis of channel-averaged SINR for indoor UWB Rake and transmitted reference systems,” IEEE Trans. Commun., vol. 55, pp. 2022-2032, Oct. 2007.
[17] C.-C. Lee, W.-D. Wu, and C.-C. Chao, “Signal-to-interference-plus-noise ratio analysis for direct-sequence ultra-wideband systems,” in Proc. IEEE Wireless Commun. Network Conf., Hong Kong, Mar. 2007, pp. 1763-1767.
[18] W. P. Siriwongpairat, W. Su, and K. J. R. Liu, “Performance characterization of multi-band UWB communication systems using poisson cluster arriving fading paths,” IEEE J. Select. Areas Commun., vol. 24, pp. 745-751, Apr. 2006.
[19] H.-Q. Lai, W.-P. Siriwongpairat, and K. J. R. Liu, “Performance analysis of multiband OFDM UWB systems with imperfect synchronization and intersymbol interference,” IEEE J. Selected Topics Signal Processing, vol. 1, pp. 521-534, Oct. 2007.
[20] J. A. Gubner and K. Hao, “A computable formula for the average bit error probability as a function of window size for the IEEE 802.15.3a UWB channel model,” IEEE Trans. Microwave Theory Tech., vol. 54, pp. 1762-1768, June 2006.
[21] K. Hao and J. A. Gubner, “Performance measures and statistical quantities of Rake receivers using maximal-ratio combining on the IEEE 802.15.3a UWB channel model,” IEEE Trans. Wireless Commun., submitted for publication. Available: http://eceserv0.ece.wisc.edu/sgubner/research.html.
[22] J. A. Gubner and K. Hao, “The IEEE 802.15.3a UWB channel model as a two-dimensional augmented cluster process,” IEEE Trans. Inform. Theory, submitted for publication. Available: http://eceserv0.ece.wisc.edu/sgubner/research.html.
[23] W.-C. Liu and L.-C. Wang, “Performance analysis of pulse based ultra-wideband systems in the highly frequency selective fading channel with cluster property,” in Proc. IEEE Veh. Tech. Conf., Melbourne, Australia, May 2006, pp. 1459-1463.
[24] W.-C. Liu and L.-C. Wang, “BER analysis of the IEEE 802.15.4a channel model with Rake receiver,” in Proc. IEEE Veh. Tech. Conf., Montreal, Canada, Sept. 2006, pp. 1-5.
[25] W.-C. Liu and L.-C. Wang, “BER analysis in a generalized UWB frequency selective fading channel with randomly arriving clusters and rays,” in Proc. IEEE Int. Conf. Commun., Glasgow, Scotland, June 2007, pp. 4281-4286.
[26] W.-D. Wu, C.-C. Lee, C.-H. Wang, and C.-C. Chao, “Signal-to-interference-plus-noise ratio analysis for direct-sequence ultra-wideband systems in generalized Saleh-Valenzuela channels,” IEEE J. Selected Topics Signal Processing, vol. 1, pp. 483-497, Oct. 2007.
[27] J.-Y. Chang, W.-D. Wu, and C.-C. Chao, “An analytical framework for ultra-wideband communications over IEEE 802.15.4a channels,” in Proc. IEEE Int. Symp. Inform. Theory, Toronto, Canada, July 2008, pp. 2757-2761.
[28] C. Unger and G. P. Fettweis, “Analysis of the Rake receiver performance in low spreading gain DS/SS systems,” in Proc. IEEE Global Telecommun. Conf., Taipei, Taiwan, Nov. 2002, pp. 830-834.
[29] K. Huang, F. Adachi, and Y. H. Chew, “A more accurate analysis of interference for Rake combining on DS-CDMA forward link in mobile radio,” IEICE Trans. Commun., vol. E88-B, pp. 654-663, Feb. 2005.
[30] M. Suzuki, C. Fujita, M. Yotsuya, K. Takamura, and T. Usui, “Techniques for MB-OFDM improvement,” IEEE doc.: IEEE P802.15-03/0337r1, Sept. 2003.
[31] K. Witrisal, “UWB channel characterization for system studies,” in Proc. COST 2100 Management Committee Meeting, Duisburg, Germany, Sept. 2007.
[32] L. J. Greenstein, S. S. Ghassemzadeh, S.-C. Hong, and V. Tarokh, “Comparison study of UWB indoor channel models,” IEEE Trans. Wireless Commun., vol. 6, pp. 128-135, Jan. 2007.
[33] W.-D. Wu, C.-H. Wang, C.-C. Chao, and K. Witrisal, “On parameter estimation for ultra-wideband channels with clustering phenomenon,” in Proc. IEEE Veh. Tech., Calgary, Canada, Sept. 2008.
[34] R. Fisher, R. Kohno, M. M. Laughlin, and M. Welborn, “DS-UWB physical layer sub- mission to 802.15 task group 3a,” IEEE doc.: IEEE P802.15-04/0137r3, July 2004.
[35] A. B. et al., “Multi-band OFDM physical layer proposal for IEEE 802.15 task group 3a,” IEEE doc.: IEEE P802.15-04/0493r1, Sept. 2004.
[36] A. Batra, J. Balakrishnan, G. R. Aiello, J. R. Foerster, and A. Dabak, “Design of a multiband OFDM system for realistic UWB channel environments,” IEEE Trans. Microwave Theory Tech., vol. 52, pp. 2123-2138, Sept. 2004.
[37] D. J. Daley and D. Vere-Jones, An Introduction to the Theory of Point Processes, Volume I : Elementary Theory and Methods, 2nd ed. New York: Springer, 2003.
[38] S. M. Ross, Stochastic Processes. New York: Wiley, 1996.
[39] E. P. C. Kao, An Introduction to Stochastic Processes. Belmont, CA: Duxbury Press, 1997.
[40] Y.-W. Hong and A. Scaglione, “Time synchronization and reach-back communications with pulse-coupled oscillators for UWB wireless ad hoc networks,” in Proc. IEEE Int. Conf. Ultra-Wideband Systems Tech., Reston, VA, Nov. 2003, pp. 190-194.
[41] X. Luo and G. B. Giannakis, “Raise your voice at a proper pace to synchronize in multiple ad hoc piconets,” IEEE Trans. Signal Processing, vol. 55, pp. 267-278, June 2007.
[42] M. K. Simon and M. Alouini, Digital Communication over Fading Channels: A Unified Approach to Performance Analysis, 2nd ed. New York: Wiley, 2005.
[43] K. Witrisal, M. Pausini, and A. Trindade, “Multiuser interference and inter-frame interference in UWB transmitted reference systems,” in Proc. Int. Workshop Ultra Wideband Sys. Joint Conf. Ultrawideband Sys. Tech., Kyoto, Japan, May 2004, pp. 96-100.
[44] K. Witrisal and M. Pausini, “Impact of multipath propagation on impulse radio UWB autocorrelation receivers,” in Proc. IEEE Int. Conf. Ultra-Wideband, Zurich, Switzer- land, Sept. 2005, pp. 485-490.
[45] K. Witrisal and M. Pausini, “Statistical analysis of UWB channel correlation functions,” IEEE Trans. Veh. Technol., vol. 57, pp. 1359-1373, May 2008.
[46] G. M. Maggio, “TG4a UWB-PHY overview,” IEEE doc.: IEEE P802.15-05/0707r1, Nov. 2005.
[47] J.-Y. Chang, “Performance analysis of multiband OFDM systems over generic ultra-wideband channels,” M.S. thesis, Inst. Commun. Eng., Nat. Tsing Hua Univ., Hsinchu, Taiwan, 2008.
[48] T. Z. F. Althaus, F. Troesch and A. Wittneben, “STS measurements and characterization,” PULSERS Deliverable D3b6a, vol. IST-2001-32710 PULSERS, 2005.
[49] C. Steiner, F. Althaus, F. Troesch, and A. Wittneben, “Ultra-wideband geo-regioning: A novel clustering and localization technique,” EURASIP J. Advances Signal Process- ing, vol. 8, Jan. 2008.
[50] R. Hoctor and H. Tomlinson, “Delay-hopped transmitted-reference RF communica- tions,” in Proc. IEEE Conf. Ultra Wideband Sys. Tech., Baltimore, MD, May 2002, pp. 265-269.
[51] Y.-L. Chao and R. A. Scholtz, “Ultra-wideband transmitted reference systems,” IEEE Trans. Veh. Technol., vol. 54, pp. 1556-1569, Sept. 2005.