• information theory
• wireless communications
• optimization
• signal processing
More specifically, my recent research has focussed on the fundamental limits (information theoretic) of communication in wireless and cognitive networks, such as:
• The cognitive radio channel with P. Mitran and V. Tarokh
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A primary link and a secondary link wish to share the wireless spectrum. The secondary transmitter is cognitive and knows the primary's message. We introduced this channel and derived achievable rate regions which benefit both users and outperform orthogonal (or traditional spectral gap filling) transmission strategies. |
• Asymmetric transmitter cooperation with N.B. Mehta and A.F. Molisch
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We considered a 2 phase downlink cellular transmission scheme with relays. Relays cooperate using linear precoding to transmit the messages which they received from the base station. We introdcued the notion of asymmetric relay cooperation, and showed that it may be optimal, from a throughput perspective, to cooperate asymmetrically! |
• Scaling laws of wireless/cognitive networks with M. Vu and V. Tarokh
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Consider a network in which a primary transmitter and receiver lie within a primary exclusive region. The secondary users outside of the primary exclusive region transmit subject to a soft outage constraint for the primary user. We determine the primary exclusive region radius and sum- throughput scaling law for the cognitive network. |
• Multiplexing gains of wireless networks with M. Sharif
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The multiplexing gain is a measure of how many streams of information a MIMO channel can sustain at high SNR. It is unclear whether self-interference may be reduced when asymmetric transmitter cooperation is used. We determined the multiplexing gains of cognitive and cognitive X channels. |