Title page for ETD etd-08282012-193626

Type of Document Master's Thesis
Author Gonzalez Fitch, David E
Author's Email Address davidgf@vt.edu
URN etd-08282012-193626
Title A novel OFDM Blind Equalizer: Analysis and Implementation
Degree Master of Science
Department Electrical and Computer Engineering
Advisory Committee
Advisor Name Title
Bose, Tamal Committee Chair
Amanna, Ashwin E. Committee Member
Pratt, Timothy J. Committee Member
  • estimation
  • cognitive
  • blind equalizer
  • OFDM
Date of Defense 2012-07-13
Availability unrestricted
Link adaptation is important to guarantee robust and reliable wireless communications with-

out wasting valuable radio resources. This technique has become more feasible with the

recent appearance of Software Defined Radios (SDRs), which allow easy reconfiguration of

their parameters via software. As the environment changes over time, the transmitter needs

to be able to effectively estimate its performance under different radio input parameters to

be able to find a close to optimal solution. In most wireless communications, an equalizer

is implemented at the receiver to estimate the channel impulse response. This estimate can

be fed back to the transmitter via a feedback channel, which can in turn help generate a

sub-optimal transmission solution for the current situation.

In this thesis, a link adaptation method is proposed that uses Orthogonal Frequency-Division

Multiplexing (OFDM) in conjunction with blind channel estimation. With the use of OFDM,

it can be assumed that the frequency fading at each subcarrier is approximately flat. In

addition, under the assumption that the channel is quasi-stationary, the Bit Error Rate

(BER) at each subcarrier can be estimated by using the well-known BER formulas for an

Additive White Gaussian Noise (AWGN) channel. However, the effect of imperfect channel

estimation must also be taken into account.

A novel OFDM blind channel estimator is developed. Finally, both simulations and real

over-the-air results are presented.

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