Summary of this paper are presented in this Chapter.
Conclusions
UWB/wideband-MIMO is the major technology for B3G wireless communication systems. In this research, the bandwidth-space-polarization characterizations of UWB/wideband MIMO channels are investigated. By understanding the channel characteristics, we developed novel methods for UWB/wideband MIMO channel modeling.
In Chapter 3, a novel method for wideband model parameters estimation is developed.
Through this method, the model parameters of a wideband signal can be determined from those of a narrowband signal. This method is validated by the measurement results of 1.95 GHz and 2.44 GHz broadband signals in metropolitan and suburban areas, and by the results of 3-5 GHz UWB signals in indoors. Here, with the help of ∆-K model that is used for multipath time-of-arrival modeling, the effect of signal bandwidth on observable multipath-clustering is investigated by exploring the relationship between ∆, signal bin width, and K , an index to quantify the multipath-clustering phenomenon. It is found that the signal with larger bandwidth yields finer time resolution and observes more multipath components, which leads stronger multipath-clustering. Furthermore, a stochastic model is applied to characterize the averaged power delay profile with two coefficients, the power ratio and decay constant. In addition, the amplitude fading is described by a Rician
distribution function. It is found that (1) the power ratio is decreased when the signal bandwidth is increased; (2) the decay constant is independent of signal bandwidth; and (3) the Rician factor is increased as the signal bandwidth is increased.
In Chapter 4, a wideband hybrid spatial channel model, which combines the site-specific specular rays with a newly 3D GBSBM for scattering rays, is presented. Here, the 3D GBSBM is extended from a 2D model, which combines the concept of the GBSBCM and the GBSBEM. The GBSBEM is used to determine the region of scatterers for different delay-taps, and then the effective scatters located near the transmitting and receiving antennas are modeled by the GBSBCM. In the 3D GBSBM, the effect of 3D multipath on sub-channel correlation of the spatial/polar arrays is taken into account. It is noted that 3D propagations is significant to the receiving power and sub-channel correlations especially for indoor environments. From the comparisons between measured and simulated space correlation, it is found that the 3D GBSBM gives more reasonable results compared to the 2D GBSBM for both the co-polarized and the cross-polarized antenna cases.
In Chapter 5, performance of UWB-MIMO in BANs is investigated through measurements for both spatial and polar antenna arrays. In our experiments, channel frequency responses were measured in the frequency ranges of 3-10 GHz that covers the whole UWB band. The key finding here is to that in BAN the MIMO channel capacity is
mainly determined by the power imbalance between sub-channels compared to the sub-channel correlation. For spatial array, the measured results show that the MIMO channel capacity is decreased when the array spacing is increased, despite the spatial correlation coefficient is decreased. This phenomenon is different from that in WAN and WLAN. It is because that power difference among elements of the spatial array is significant in BAN short-range communications compared to that in WAN and WLAN. For polar array, the achievable channel capacity is lower than that of the spatial array in LOS conditions, which is due to high cross-polarization discrimination. However, the device compactness is achieved by using polar array without sacrifice of channel capacity compared to spatial array in NLOS conditions. Furthermore, the MIMO channel capacity is slightly dependent on the environments due to dominance of human body effect. It is also found that the MIMO channel capacity decreased with frequency or bandwidth.
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Author’s Publications (2003~2008)
A. Journal
1. Wei-Ju Chang and Jenn-Hwan Tarng, “Effects of Bandwidth on Observable Multipath Clustering in Outdoor/Indoor Environments for Broadband and Ultra-Wideband Wireless Systems,” IEEE Transactions on Vehicular Technology, vol. 56, no.4, pp. 1913-1923, July 2007.
2. Wei-Ju Chang and Jenn-Hwan Tarng, “Bandwidth Effects – A Validation Study of the Spatial Channel Model Extension (SCME) for 3GPP Long-Term Evolution and IEEE 802.16e Technologies,” International Journal of Electrical Engineering, vol.
15, no. 1, pp. 9-15, February 2008.
3. Wei-Ju Chang, Jenn-Hwan Tarng and Szu-Yun Peng, “Frequency-Space- Polarization on UWB MIMO Performance for Body Area Network Applications,”
IEEE Antenna and Wireless Propagation Letters (to be published)
4. Wei-Ju Chang, Jenn-Hwan Tarng and Ming-Jiun Shen, “Recursive Determination of the Bandwidth Dependent Parameters of a Modified Cassioli-Win-Molisch Ultra-Wideband Indoor Radio Channel Model,” IEEE Transactions on Wireless
Communications (in revise)
B. Conference
5. Wei-Ju Chang and Jenn-Hwan Tarng, “Effect of radio bandwidth on multipath clustering,” IEEE Vehicular Technology Conference 2003-Sprint, March 2003.
6. Wei-Ju Chang and Jenn-Hwan Tarng, “A Novel Method to Estimate Time-of- Arrival of Broadband Signal Propagation in Outdoor Environment,” presented in
COST273, Czech, September 2003.
7. Wei-Ju Chang and Jenn-Hwan Tarng, “A Novel TOA Estimation Method of Broadband Signal Propagation in Outdoor Environment, ＂ IEEE Vehicular
Technology Conference 2004-Spring, March 2004.
8. Wei-Ju Chang and Jenn-Hwan Tarng, “Investigation on Radio Bandwidth Dependency of UWB Indoor Channels,” presented in COST273, Sweden, June 2004.
9. Jenn-Hwan Tarng, Wei-Ju Chang and Ming-Jiun Shen, “Radio Bandwidth on Indoor UWB Channel Response”, 2004 International Conference on
Electromagnetic Applications and Compatibility, October 2004.
10. Jenn-Hwan Tarng, Wei-Ju Chang and Ming-Jiun Shen, “Bandwidth Dependency of Ultra-Widenbande Indoor Radio Channel Parameters,” Asia Pacific Symposium of
EMC Taipei 2005, December 2005.
11. Wei-Ju Chang and Jenn-Hwan Tarng, “Characterization of Wideband Spatio- Temporal Radio Channels for Beyond-3G Systems,” 2006 Cross strait Tri-regional