miscellaneous research

Papers dealing with miscellaneous interesting topic.

Keywords: Digital redesign

R. A. Kennedy and R. J. Evans, "Digital redesign of a continuous controller based on closed loop performance", Proc. IEEE Conf. Decision and Contr., CDC'90, pp. 1898-1901, December 1990.
Abstract BibTeX
Official: Link DOI: 10.1109/CDC.1990.203950 PDF: 00203950.pdf Google-Scholar: [18]
Abstract: The authors present a digital controller redesign philosophy which attempts to match the closed-loop performance of a nominal continuous-time controller using a model-following design setting. The requirement of excessive sampling rates necessary with a number of popular existing techniques (e.g. the prewarped bilinear transform redesign) is largely obviated. Sampling rates close to twice the closed-loop bandwidth (Nyquist rate) give good performance with the proposed technique. It is concluded that the proposed model can be used as is for an analog-to-digital redesign which appears to work favorably at low sampling rates, or it can be used as a starting point for further pole-zero placement.
@inproceedings{KennedyC1990m,
    title = {Digital redesign of a continuous controller based on closed loop performance},
    author = {Kennedy, R. A. and Evans, R. J.},
    booktitle = {Proc. IEEE Conf. Decision and Contr., CDC'90},
    pages = {1898-1901},
    month = {December},
    year = {1990}}
T. S. Pollock, T. D. Abhayapala, and R. A. Kennedy, "Antenna Saturation Effects on MIMO Capacity", Proc. International Conference on Communications, ICC'03, vol. 3, pp. 2301-2305, May 2003.
Abstract BibTeX
Official: Link DOI: 10.1109/ICC.2003.1204285 PDF: 01204285.pdf Google-Scholar: [12]
Abstract: A theoretically derived antenna saturation point is shown to exist for MIMO systems, at which the system suffers a capacity growth decrease from linear to logarithmic with increasing antenna numbers. We show this saturation point increases linearly with the radius of the region containing the receiver antennas and is independent of the number of antennas. Using an alternative formulation of capacity for MIMO systems we derive a closed form capacity expression, which uses the physics of signal propagation combined with statistics of the scattering environment. This expression gives the capacity of a MIMO system in terms of antenna placement and scattering environment and show that the saturation effect is due to spatial correlation between receiver antennas.
@inproceedings{KennedyC2003k,
    title = {Antenna Saturation Effects on {MIMO} Capacity},
    author = {Pollock, T. S. and Abhayapala, T. D. and Kennedy, R. A.},
    booktitle = {Proc. International Conference on Communications, ICC'03},
    volume = {3},
    pages = {2301-2305},
    month = {May},
    year = {2003}}
T. S. Pollock, T. D. Abhayapala, and R. A. Kennedy, "Fundamental Limits of MIMO Capacity for Spatially Constrained Arrays", Proc. 4th Australian Communications Theory Workshop, pp. 7-12, February 2003.
Abstract BibTeX
PDF: KennedyC2003a.pdf Google-Scholar: [11]
Abstract: In this paper we investigate the capacity behavior of spatial constrained multiple-antenna array communications. By increasing the number of antennas within a fixed region of space the antenna array becomes dense and spatial correlation inhibits capacity growth. Using a novel spatial channel model we show that the underlying physics of wave propagation limits the capacity of constrained arrays. A theoretically derived antenna saturation point is shown to exist for dense array MIMO systems, at which there is no capacity growth with increasing antenna numbers. We show this saturation point increases linearly with the radius of the region, and that it naturally lends itself to a definition for the theoretical maximum capacity for a fixed region of space. 
@inproceedings{KennedyC2003a,
    title = {Fundamental Limits of {MIMO} Capacity for Spatially Constrained Arrays},
    author = {Pollock, T. S. and Abhayapala, T. D. and Kennedy, R. A.},
    booktitle = {Proc. 4th Australian Communications Theory Workshop},
    pages = {7-12},
    month = {February},
    year = {2003}}
R. A. Kennedy, T. D. Abhayapala, and T. S. Pollock, "Generalized Herglotz Wave Functions for Modelling Wireless Nearfield Multipath Scattering Environments", Proc. IEEE Int. Conf. Acoust., Speech, Signal Processing, ICASSP'2003, vol. IV, pp. 660-663, April 2003.
Abstract BibTeX
Official: Link PDF: 01202729.pdf Google-Scholar: [3]
Abstract: We develop a general mathematical model for nearfield multipath scattering as a basis for studying the spatial limits imposed on multi-antenna wireless communication systems. This model generalizes the Herglotz Wave Function, which is an important tool in the study of inverse scattering problems, to a form where the scatterers can be nearfield. This permits the development of the most general form of spatial correlation which is known to constrain the capacity of wireless systems.
@inproceedings{KennedyC2003h,
    title = {Generalized {H}erglotz Wave Functions for Modelling Wireless Nearfield Multipath Scattering Environments},
    author = {Kennedy, R. A. and Abhayapala, T. D. and Pollock, T. S.},
    booktitle = {Proc. IEEE Int. Conf. Acoust., Speech, Signal Processing, ICASSP'2003},
    volume = {IV},
    pages = {660-663},
    month = {April},
    year = {2003}}