[UCI-Calit2] Upcoming Event: Collaboration, Competition and Cognitive Radio Transmission in Wireless Networks

Anna Lynn Spitzer aspitzer at calit2.uci.edu
Fri Dec 1 09:11:53 PST 2006


Title:                                        Collaboration, Competition
and Cognitive Radio Transmission in Wireless Networks

 

Speaker:                                  Vahid Tarokh, Harvard
University

 

Time:                                       11 a.m. - Noon

 

Date:                                       Friday, Dec. 8, 2006

 

Location:                                 Calit2 Building, Room 3008

 

Abstract:                                  Elements/clusters of a sensor
network operating on the same band can operate using three different
paradigms:

 

Competition - This is information theoretically cased in the framework
of interference channels;

 

Collaboration - Silent transmitters/receivers can help active
transmitters/receivers in the transmission/reception of their messages,
but have to extract this message from the underlying transmission or by
other methods, and;

            

Cognitive Radio Transmission - Some devices extract the message of other
transmitters from their signals or by other methods, and use it to
minimize interference from/to their own transmitted signals.

 

Competition has been well-studied in the literature. Collaboration has
been less studied and Cognitive Radio Transmission has not been much
studied.

 

For the case of collaboration, we demonstrate that most of the MIMO
space-time gain can also be achieved through collaborative
communications with single-antenna/multiple-antenna nodes when there is
one receiving agent. In particular, for the single antenna case, we
consider communication to take place between clusters of nearby nodes.
We show the existence of collaborative codes for communications for
which the intra-cluster negotiation penalty is in principle small and
almost all the diversity gain of traditional space-time codes may be
realized. For example, for a single transmitter node with two
collaborators and one receiver node, if the collaborators have as little
as 10 dB path loss advantage over the receiver, the penalty for
collaboration over traditional space-time systems is negligible.

 

For the cognitive radio transmission, we consider a channel defined as
an n-transmitter, m-receiver interference channel in which sender i
obtains (causally or non-causally) the messages senders 1 through i-1
plan to transmit. The two-sender, two-receiver case is considered. In
this scenario, one user, a cognitive radio, obtains (genie assisted, or
causally) knowledge of the data to be transmitted by the other user. The
cognitive radio may then simultaneously transmit over the same channel,
as opposed to waiting for an idle channel as in a traditional cognitive
radio channel protocol. Dirty-paper coding and ideas from achievable
region constructions for the interference channel are used, and an
achievable region for the cognitive radio channel is computed. It is
shown that in the Gaussian case, the described achievable region
approaches the upper bounds provided by the 2 x 2 Gaussian MIMO
broadcast channel, and an interference-free channel. Finally, we
demonstrate/discuss the implementation of these ideas on an SDR
platform.

 

 

Bio:                                          Vahid Tarokh worked at
AT&T, where he was the head of the Department of Wireless Communications
and Signal Processing Labs-Research, until August 2000.  In September
2000, he joined the Department of Electrical Engineering and Computer
Sciences (EECS) at MIT as an associate professor.

In June 2002, he joined Harvard University as Gordon McKay Professor of
Electrical Engineering. Since July 2005, he has been the Hammond Vinton
Hayes Senior Fellow of Electrical Engineering at Harvard University, and
also holds the Perkins professorship of applied mathematics. His
research is mainly focused in the areas of signal processing,
communications (wireline and wireless) and networking. He has received a
number of awards and holds two honorary degrees.

 

 

Additional Information:             Faculty sponsor is Hamid Jafarkhani

 

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