256 research outputs found
Semi-blind CFO estimation and ICA based equalization for wireless communication systems
In this thesis, a number of semi-blind structures are proposed for Orthogonal Frequency Division Multiplexing (OFDM) based wireless communication systems, with Carrier Frequency Offset (CFO) estimation and Independent Component Analysis (ICA) based equalization. In the first contribution, a semi-blind non-redundant single-user Multiple-Input Multiple-Output (MIMO) OFDM system is proposed, with a precoding aided CFO estimation approach and an ICA based equalization structure. A number of reference data sequences are carefully designed and selected from a pool of orthogonal sequences, killing two birds with one stone. On the one hand, the precoding based CFO estimation is performed by minimizing the sum cross-correlations between the CFO compensated signals and the rest of the orthogonal sequences in the pool. On the other hand, the same reference data sequences enable the elimination of permutation and quadrant ambiguities in the ICA equalized signals. Simulation results show that the proposed semi-blind MIMO OFDM system can achieve a Bit Error Rate (BER) performance close to the ideal case with perfect Channel State Information (CSI) and no CFO. In the second contribution, a low-complexity semi-blind structure, with a multi-CFO estimation method and an ICA based equalization scheme, is proposed for multiuser Coordinated Multi-Point (CoMP) OFDM systems. A short pilot is carefully designed offline for each user and has a two-fold advantage. On the one hand, using the pilot structure, a complex multi-dimensional search for multiple CFOs is divided into a number of low-complexity mono-dimensional searches. On the other hand, the cross-correlation between the transmitted and received pilots is explored to allow the simultaneous elimination of permutation and quadrant ambiguities in the ICA equalized signals. Simulation results show that the proposed semi-blind CoMP OFDM system can provide a BER performance close to the ideal case with perfect CSI and no CFO. In the third contribution, a semi-blind structure is proposed for Carrier Aggregation (CA) based CoMP Orthogonal Frequency Division Multiple Access (OFDMA) systems, with an ICA based joint Inter-Carrier Interference (ICI) mitigation and equalization scheme. The CFO-induced ICI is mitigated implicitly via ICA based equalization, without introducing feedback overhead for CFO correction. The permutation and quadrant ambiguities in the ICA equalized signals can be eliminated by a small number of pilots. Simulation results show that with a low training overhead, the proposed semi-blind equalization scheme can provide a BER performance close to the ideal case with perfect CSI and no CFO
Abstracts of manuscripts submitted in 1990 for publication
This volume contans the abstracts of manuscripts submitted for publication during calendar year 1990 by the staff and students
of the Woods Hole Oceanographic Institution. We identify the journal of those manuscripts which are in press or have been
published. The volume is intended to be informative, but not a bibliography.
The abstracts are listed by title in the Table of Contents and are grouped into one of our five deparments, Marine Policy
Center, Coastal Research Center, or the student category. An author index is presented in the back to facilitate locating specific papers
A tomographic view of the Gulf Stream southern recirculation gyre at 38°N, 55°W
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 1993Reciprocal acoustic transmissions made in a region just south of the Gulf Stream
are analyzed to determine the structure and variability of temperature, current
velocity, and vorticity fields at the northern extent of the southern recirculation
gyre. For ten months (November, 1988 through August, 1989), a pentagonal array
of tomographic transceivers was situated in a region centered at 38°N, 55°W as
part of the eastern array of the SYNOP (SYNoptic Ocean Prediction) Experiment.
The region of focus is one rich in mesoscale energy, with the influence of local Gulf
Stream meandering and cold-core ring activity strikingly evident. Daily-averaged
acoustic transmissions yielded travel times which were inverted to obtain estimates
of range-averaged temperature and current velocity fields, and area-averaged relative
vorticity fields. The acoustically determined estimates are consistent with
nearby current meter measurements and satellite infrared imagery. The signature
of cold-core rings is clearly evident in the sections. Spectral estimates of the fields
are dominated by motions with periodicities ranging from 32-128 days. Second-order
statistics, such as eddy kinetic energies, and heat and momentum fluxes, are
also estimated. The integrating nature of the tomographic measurement has been
exploited to shed some light on the radiation of eddy energy from the Gulf Stream.
The Eliassen-Palm flux diagnostic has been applied to an investigation of wave
radiation from the Gulf Stream. Results of the diagnosis suggest that the Gulf
Stream itself is the source of wave energy radiating into the far field and found in
the interior of the North Atlantic subtropical gyre.This research was carried out under Office of Naval Research (ONR) University
Research Initiative contract N00014-86-K-0751 and ONR contract N00014-
90-J-1481. Construction of the tomographic instruments was supported by grants
and contracts with MIT: National Science Foundation grant OCE 85-12430 and
by ONR. The field work was supported by ONR under contract N00014-85-G-0241
(Secretary of the Navy Professorship (C. Wunsch))
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