Characterization and Estimation of High Frequency Channel with Multiple Antenna System

  • Kumaresh Krishnan


This thesis presents the development of an efficient and adaptable simulation model for
characterization and estimation of MIMO-HF channel subjected to impairments, such as
multipath fading, system non-linearity and non-Gaussian noise. Under channel
characterization and modelling, this thesis proposes the extension of conventional
Watterson model for SISO to MIMO-HF channel incorporating the associated spatial
correlation and the non-linearity of the system. The novelty of the developed model lies
in the capability of its impulse response to emulate nearly the practical HF channel by
incorporating the cited adverse channel impairments. This thesis proposes the modelling
of MIMO-HF channel through the computationally efficient IIR /AR filter approach
instead of conventional FIR filter. The generic and the versatile features of IIR filterbased
approach for modelling the HF channel impairments have been demonstrated by its
application to both SISO and MIMO-HF systems.
Within the purview of channel estimation for improved reliability and enhanced data rate
of the MIMO-HF communication link, this thesis proposes a novel PF based channel
estimation technique for HF communication links subjected to multipath fading and
system non-linearity. The PF based channel estimation algorithm proposed in thesis for
MIMO-HF is shown to closely approximate the impulse response of the channel induced
by the channel impairments. The improved channel estimation facilitates the effective
utilization of system resources to ensure enhanced capacity and reliability of HF links.
Although one can conceive an idea of invoking the PF concept devoid of EKF, this thesis
attempts to adopt a unified approach wherein PF and EKF schemes are combined to
realize better posterior density functions, thereby improving the accuracy in channel
estimation. The advantageous and desirable features derived by invoking the proposed PF
formulation over the conventional RLS have also been addressed. This thesis also
addresses the effects of spatial correlation, system non-linearity and the non-Gaussian
noise on the proposed PF based channel estimation algorithm. The expected improvement
in the receiver performance in lieu of improved channel estimation algorithms, as well as
replacement of conventional SISO with MIMO, is validated through the performance
parameters such as capacity and reliability.

The contributions of this thesis to the broad topic of modelling, characterization and
estimation of HF channel can be summarized as follows:
  • A generic framework to extend the concept of HF channel modelling characterization and estimation techniques applicable to conventional SISO has been proposed for the emerging MIMO technology.
  • The computational complexity and accuracy in the simulation of AR/IIR based HF channel model have been compared with the FIR based model.
  • Methods of modelling HF channel to characterize the effects of system nonlinearity with channel impairments and non-Gaussian noise have been proposed and validated. 
  • The channel estimation algorithms which can mitigate the effects of the multipath fading non-Gaussian noise the system induced non-linearity with channel impairments have been proposed and analysed for their functionality.
  • The relative improvement in the overall performance of the HF communication system in lieu of adaptation of MIMO over SISO has been investigated through numerous analytical and simulation studies.