T. Aaron Gulliver
Project Topics
- 1.
- Turbo Codes
Description:
Turbo codes provide a means of achieving near Shannon capacity
performance with a reasonable amount of decoding complexity.
The key to this performance is an iterative soft output decoding algorithm.
To date, turbo codes are not well understood, particularly the role of the
random interleaver and the structures of the component codes.
This project will explore this class of codes (as well as classes
of random-like codes) with the aim of
developing decoding algorithms and codes with
good performance/complexity tradeoffs.
In particular, simple low complexity codes will be considered as
component codes because of their simple structures.
The graph structure of these codes is also of interest.
The graph structure of these codes is also of interest.
- 2.
- Neural Network Diversity Combining for
Fast Frequency Hopped Communications
Description:
Symbol repetition is used in frequency hopped
spread spectrum communication systems as a simple means of providing
protection against interference and fading.
Many of the techniques used for combining these symbols
have limitations which can cause system failures in certain types
of channel conditions.
This project will consider the development of new combining techniques
based on a neural network.
The goal is to provide robustness to changing interference patterns to ensure
the greatest system reliability and performance.
- 3.
- Trellis Structures for Linear Block Codes
Description:
Convolutional codes have traditionally been favored over
block codes for communication systems because
soft decision decoding is possible using a
trellis (Viterbi) decoder.
As well, trellis coded modulation has successfully combined convolutional
coding and modulation.
However, convolutional codes are not well suited to packet type
communication systems, among others.
The soft decision decoding of block codes
has recently been characterized, but suffers from the
structure of existing block codes which were not developed
for trellis decoding.
This project considers the design of block codes specifically
for decoding using trellis decoders.
The theory will be developed to systematically construct
codes which have simple trellis structures.
Block trellis coded modulation
is a related problem which can also be investigated.
Bounds can also be examined to determine the achievable coding gains.
- 4.
- Spread Spectrum Multimedia Communications
Description:
The tremendous increases in demand for personal and mobile communications
has created a requirement for integrated services such as voice, data, images
and video (often using ATM).
Since different users require different quality of service (QOS),
the channel resources should not be shared equally among the various
classes of users.
The multiple access capability of the CDMA channel can be used to
accommodate voice calls (and other real-time services),
while the data users follow the ALOHA protocol.
One means of achieving control over the QOS is through the error control
coding mechanisms that are employed.
This project will consider adaptive coding techniques as a means of improving
capacity while maintaining QOS.
- 5.
- Design of Good Linear Error Correcting Codes
Description:
One of the fundamental problems in algebraic coding theory is
the determination of bounds on the maximum achievable
distance between codewords for a given code size.
Lower bounds are usually devised through construction techniques
which provide a code with the required parameters.
A good code is defined as one which achieves the largest
known minimum distance.
This project will investigate the
development of techniques and/or application of existing techniques
for constructing good codes which improve these bounds.
In particular, combinatorial heuristics will be considered.
- 6.
- Multiuser Communications with Nonorthogonal Signalling
Description:
A large number of multiuser communications systems rely on
orthogonal signalling.
Although this is effective, it is not a criterion of optimality.
This project will consider signal design based on maximizing the minimum
Euclidean distance in the overall summed set of signals.
- 7.
- Coding for Error Control in Computer Memory Systems
Description:
The density of modern computer memory components makes them
susceptible to interference and failure.
Single event upsets are soft errors (and sometimes hard)
caused by atomic particles travelling through the device,
and normally appear as random bit errors.
Component failures and damage to bus lines lead to hard
byte type errors, depending on the memory configuration.
As well, adjacent errors commonly occur due to the device structure.
Majority logic decodable codes which can correct random and adjacent errors
are currently being considered because of the ease and speed of decoding.
Future research will consider the design of
codes which can correct both bit errors
and byte errors/erasures
to overcome both random bit errors and block (byte) memory failures.
In addition, error detection in conjunction with error correction
will be investigated.
- 8.
- Self-Dual Codes and Weighing Matrices
Description:
Weighing matrices provide a rich source of constructions for
self-dual or orthogonal codes.
However, few constructions are known to provide extremal, or optimal codes.
This project will investigate the theory of weighing matrices
with the goal of defining extremal self-dual codes.
- 9.
- Design of Fast and Secure Software Cryptographic Systems
Cryptography has become an important part of many digital
communications systems.
Because of the ever increasing use of the internet for
commerce, improved techniques for the electronic transfer of
funds is required.
The algorithms and their implementations must be simple and fast.
This project will look at developing new
software based cryptographic systems that will achieve these goals.
- 10.
- Chaotic Cryptographic Systems
Chaotic systems show great promise for use in cryptographic
systems.
The problems left to be solved are how to integrate these
systems with digital data, and also the reproducibility of
the system outputs.
This project will explore these issues as well as the
cryptographic strength of such systems.
- 11.
- Coding for Frequency-Hopped MFSK
Error control coding is an essential part of every
spread spectrum communication system.
This project will consider the use of Reed-Solomon and
related burst error correcting codes in a frequency
hopped system.
The goal is to obtain a robust and efficient
solution in fading and multiple-access interference.
- 12.
- Digital Watermarking
In the manufacturer of paper, wet fiber is subjected to high
pressure to expel the moisture. If the mold has a
slight pattern, this pattern leaves an imprint in the paper,
called a watermark.
Digital watermarks are imperceptible, or barely perceptible,
transformations of digital data; often the digital data set
is a digital multimedia object.
Watermarks can be applied to almost any form of digital
data, for example, videos and music.
This project will consider the development of a digital
watermarking system for a particular class of media.
Aaron Gulliver
2000-02-21