| Jorge
Arturo Cobb Associate Professor Director of Graduate Studies B.S. 1987 (UT-El Paso), M.A. 1989 and Ph.D. 1996 (UT-Austin) First appointment at UTD: Fall 1998 Contact Information 800 West Campbell Road Richardson, TX 75080-3021 email: cobb@utdallas.edu phone: 972 883 2479 fax: 972 883 2349 office: ECSS 4.208 Office Hours (Fall '23), Mondays and Wednesdays, 3:00 to 5:00 pm |
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Research
Focus: Computer Networking
Quality
of Service in Computer Networks
Most
networks in use today are based on the datagram paradigm, also known as
"best effort service". In a datagram system, the network makes no
guarantees with respect to the delivery of each message. The network
forwards
each message from one computer to the other, but in the process the
message may
be dropped due to congestion or it may be delayed excessively.
Currently,
networks are moving toward the virtual circuit paradigm. In this
paradigm, a
source-destination pair may allocate resources from at each in the
network path
between them. With this reservation of resources, each computer in the
network
can schedule the forwarding of messages such that each virtual-circuit
is
guaranteed an average forwarding rate, a maximum packet delay, and no
message
loss due to congestion.
Protocols
that provide such forwarding rate and delay guarantees are called
rate-reservation protocols. We have developed a nice and simple theory,
called
Flow Theory, for the analysis of message delay and buffer requirements
in
rate-reservation protocols and other real-time protocols. Our main
research
interests include further development of Flow Theory and developing new
rate-reservation protocols. We are in the process of developing
rate-reservation protocols that are more flexible, efficient, and fair.
Our
interests also include the adaptation of rate-reservation protocols for
the
support of particular traffic characteristics of multimedia
applications such
as voice and video.
Mobile
Computing
In
mobile computing, a computer is free to move from one point in the
network to
another. An example of this is a laptop computer that communicates with
the
network via a wireless interface, such as radio or infrared waves.
Networking
issues in mobile computing include network addressing, location
management,
frequency allocation, data compression, hand-off management, and
security.
We
have developed an acknowledgment strategy for the efficient transfer of
data
over transport sessions that involve noisy wireless networks of mobile
computers. With a small additional support from the router of the
wireless
network, the transport source is able to distinguish between losses due
to
congestion and losses due to corruption. With this distinction, the
source can
reduce its throughput (i.e., window size) when congestion occurs, and
quickly
retransmit when corruption occurs. Without this distinction, throughput
over a
path with a large bandwidth-delay product terminating in a noisy
wireless
network is reduced significantly.