5 research outputs found
Wireless Channel Equalization in Digital Communication Systems
Our modern society has transformed to an information-demanding system, seeking voice, video, and data in quantities that could not be imagined even a decade ago. The mobility of communicators has added more challenges. One of the new challenges is to conceive highly reliable and fast communication system unaffected by the problems caused in the multipath fading wireless channels. Our quest is to remove one of the obstacles in the way of achieving ultimately fast and reliable wireless digital communication, namely Inter-Symbol Interference (ISI), the intensity of which makes the channel noise inconsequential.
The theoretical background for wireless channels modeling and adaptive signal processing are covered in first two chapters of dissertation.
The approach of this thesis is not based on one methodology but several algorithms and configurations that are proposed and examined to fight the ISI problem. There are two main categories of channel equalization techniques, supervised (training) and blind unsupervised (blind) modes. We have studied the application of a new and specially modified neural network requiring very short training period for the proper channel equalization in supervised mode. The promising performance in the graphs for this network is presented in chapter 4.
For blind modes two distinctive methodologies are presented and studied. Chapter 3 covers the concept of multiple cooperative algorithms for the cases of two and three cooperative algorithms. The select absolutely larger equalized signal and majority vote methods have been used in 2-and 3-algoirithm systems respectively. Many of the demonstrated results are encouraging for further research.
Chapter 5 involves the application of general concept of simulated annealing in blind mode equalization. A limited strategy of constant annealing noise is experimented for testing the simple algorithms used in multiple systems. Convergence to local stationary points of the cost function in parameter space is clearly demonstrated and that justifies the use of additional noise. The capability of the adding the random noise to release the algorithm from the local traps is established in several cases
Enhanced coding, clock recovery and detection for a magnetic credit card
Merged with duplicate record 10026.1/2299 on 03.04.2017 by CS (TIS)This thesis describes the background, investigation and construction of a system
for storing data on the magnetic stripe of a standard three-inch plastic credit
in: inch card. Investigation shows that the information storage limit within a 3.375 in
by 0.11 in rectangle of the stripe is bounded to about 20 kBytes. Practical issues
limit the data storage to around 300 Bytes with a low raw error rate: a four-fold
density increase over the standard. Removal of the timing jitter (that is prob-'
ably caused by the magnetic medium particle size) would increase the limit to
1500 Bytes with no other system changes. This is enough capacity for either a
small digital passport photograph or a digitized signature: making it possible
to remove printed versions from the surface of the card.
To achieve even these modest gains has required the development of a new
variable rate code that is more resilient to timing errors than other codes in its
efficiency class. The tabulation of the effects of timing errors required the construction
of a new code metric and self-recovering decoders. In addition, a new
method of timing recovery, based on the signal 'snatches' has been invented to
increase the rapidity with which a Bayesian decoder can track the changing velocity
of a hand-swiped card. The timing recovery and Bayesian detector have
been integrated into one computation (software) unit that is self-contained and
can decode a general class of (d, k) constrained codes. Additionally, the unit has
a signal truncation mechanism to alleviate some of the effects of non-linear distortion
that are present when a magnetic card is read with a magneto-resistive
magnetic sensor that has been driven beyond its bias magnetization.
While the storage density is low and the total storage capacity is meagre in
comparison with contemporary storage devices, the high density card may still
have a niche role to play in society. Nevertheless, in the face of the Smart card its
long term outlook is uncertain. However, several areas of coding and detection
under short-duration extreme conditions have brought new decoding methods
to light. The scope of these methods is not limited just to the credit card
Full Proceedings, 2018
Full conference proceedings for the 2018 International Building Physics Association Conference hosted at Syracuse University