233 research outputs found
Optimal Signaling of MISO Full-Duplex Two-Way Wireless Channel
We model the self-interference in a multiple input single output (MISO)
full-duplex two-way channel and evaluate the achievable rate region. We
formulate the boundary of the achievable rate region termed as the Pareto
boundary by a family of coupled, non-convex optimization problems. Our main
contribution is decoupling and reformulating the original non-convex
optimization problems to a family of convex semidefinite programming problems.
For a MISO full-duplex two-way channel, we prove that beamforming is an optimal
transmission strategy which can achieve any point on the Pareto boundary.
Furthermore, we present a closed-form expression for the optimal beamforming
weights. In our numerical examples we quantify gains in the achievable rates of
the proposed beamforming over the zero-forcing beamforming.Comment: To appear in IEEE ICC 2015, London, U
An Analog Baseband Approach for Designing Full-Duplex Radios
Recent wireless testbed implementations have proven that full-duplex
communication is in fact possible and can outperform half-duplex systems. Many
of these implementations modify existing half-duplex systems to operate in
full-duplex. To realize the full potential of full-duplex, radios need to be
designed with self-interference in mind. In our work, we use an experimental
setup with a patch antenna prototype to characterize the self-interference
channel between two radios. In doing so, we form an analytical model to design
analog baseband cancellation techniques. We show that our cancellation scheme
can provide up to 10 dB improved signal strength, 2.5 bps/Hz increase in rate,
and a 10,000 improvement in BER as compared to the RF only cancellation
provided by the patch antenna.Comment: 5 pages, 8 figures, to appear in 2013 Asilomar Conference proceeding
Cooperative Compute-and-Forward
We examine the benefits of user cooperation under compute-and-forward. Much
like in network coding, receivers in a compute-and-forward network recover
finite-field linear combinations of transmitters' messages. Recovery is enabled
by linear codes: transmitters map messages to a linear codebook, and receivers
attempt to decode the incoming superposition of signals to an integer
combination of codewords. However, the achievable computation rates are low if
channel gains do not correspond to a suitable linear combination. In response
to this challenge, we propose a cooperative approach to compute-and-forward. We
devise a lattice-coding approach to block Markov encoding with which we
construct a decode-and-forward style computation strategy. Transmitters
broadcast lattice codewords, decode each other's messages, and then
cooperatively transmit resolution information to aid receivers in decoding the
integer combinations. Using our strategy, we show that cooperation offers a
significant improvement both in the achievable computation rate and in the
diversity-multiplexing tradeoff.Comment: submitted to IEEE Transactions on Information Theor
Fast Multi-user Detector for a Time-varying CDMA System
This paper investigates methods to reduce the amount of computation needed to detect information bits using a linear detector for a CDMA system. We show windowing technique coupled with pipelining can reduce the amount of computation without significantly sacrificing the performance of linear feedback detector. We also describe efficient techniques to adapt to a dynamic system where the system parameters vary due to the change in delays associated with individual users.Nokia CorporationNational Science FoundationTexas Advanced Technology Progra
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