Simulation code for "Wideband MIMO Channel Diagonalization in the Time Domain" (IEEE PIMRC'11).
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README.md

README.md

pimrc2011_polynomial_svd

pimrc2011_polynomial_svd is the simulation environment for

R. Brandt and M. Bengtsson, "Wideband MIMO Channel Diagonalization in the Time Domain", in Proc. IEEE Int. Symp. Indoor, Mobile Radio Commun. (PIMRC'11), 2011, pp. 1958-1962.

Note that this code was written a couple of years ago, for now defunct versions of Matlab. This code comes with ABSOLUTELY NO WARRANTY.

DOI

Abstract

Methods for spatially diagonalizing wideband multiple-input multiple-output channels using linear finite impulse response (FIR) filters are investigated. The PSVD approach by applying the PQRD-BC algorithm for approximate singular value decomposition (SVD) of polynomial matrices is compared to the approach of performing a set of conventional SVDs in the Discrete Fourier Transform (DFT) domain, in terms of complexity and approximation error. Reduced order filters, based on the DFT-SVDs, are then obtained by optimizing the phases of the filters. Applying the phase optimized filters as linear filters then forms a benchmark on the accuracy attainable for any PSVD factorization, for the given filter length.

Simulations show that the DFT-SVD method has significantly lower complexity than the PSVD by PQRD-BC, but results in higher order filters. On the other hand, the PSVD by PQRD-BC yields filters which are close to being perfectly unitary for all frequencies. To achieve good performance, the reduced order filters are around one order of magnitude longer than the channel impulse response length. Therefore there is no gain in performing time domain diagonalization using a polynomial SVD, compared to using a multicarrier solution.

Simulation code features

  • Matlab implementation of PSVD and PQRD algorithms as proposed in [2] and as used in [1] and [3].
  • pmatlib with PMatrix Matlab class, for easy manipulation of polynomial matrices in Matlab.
  • Matlab implementation of the phase optimization technique proposed in [4].

Running the simulations

  1. Ensure that you are able to build MEX files in Matlab. See guide here.
  2. For improved performance, build the MEX files:
  • cd pmatlib and then convmat_build The MEX implementation of convmat is a direct convolution of the two polynomial matrices. If the MEX implementation is not available, for example due to not being compiled, a frequency domain Matlab implementation is used for the convolution.
  • There is also a MEX file implementing the subproblems of [4]. This MEX file however segfaults on the author's new computer, at the time of this writing (Nov. 2014). If you are feeling lucky, you may try using this MEX file by cd palomar and then palomar_am_loop_build. If this crashes your Matlab, just remove the palomar_am_loop MEX file.
  1. matlabpool X where X is the number of cores available
  2. Run any _run scripts to run the simulation, and the corresponding _plot to plot the results.

pmatlib

As part of this package is the pmatlib library, which is a Matlab library for handling polynomial matrices. By using the provided Matlab class PMatrix, it becomes easy to apply polynomial matrix operations. The pmatlib also contains implementations of the polynomial matrix algorithms in [1], [2], and [3].

License and referencing

This source code is licensed under the GPLv2 license. If you in any way use this code for research that results in publications, please cite our original article. The following Bibtex entry can be used.

@inproceedings{Brandt2011,
  Title                    = {Wideband {MIMO} Channel Diagonalization in the Time Domain},
  Author                   = {R. Brandt and M. Bengtsson},
  Booktitle                = {Proc. IEEE Int. Symp. Indoor, Mobile Radio Commun. (PIMRC'11)},
  Year                     = {2011},
  Pages                    = {1958--1962}
}

References

  1. R. Brandt and M. Bengtsson, "Wideband MIMO Channel Diagonalization in the Time Domain," in Proc. IEEE Int. Symp. Indoor, Mobile Radio Commun. (PIMRC'11), 2011, pp. 1958-1962.
  2. J.A Foster, J.G. McWhirter, M.R. Davies, and J.A. Chambers, "An Algorithm for Calculating the QR and Singular Value Decompositions of Polynomial Matrices," in IEEE Trans. Signal Process., vol.58, no.3, pp. 1263-1274, 2010
  3. R. Brandt, "Polynomial matrix decompositions: Evaluation of algorithms with an application to wideband MIMO communications," M.Sc. thesis, Uppsala University, Dec. 2010.
  4. D. P. Palomar, M. A. Lagunas, A. Pascual, and A. P. Neira, "Practical implementation of jointly designed transmit receive space-time IIR filters,” in Proc. Int. Symp. Signal Processing and its Applications, 2001, pp. 521-524.