3 research outputs found
Cognitive Interference Alignment for OFDM Two-tiered Networks
In this contribution, we introduce an interference alignment scheme that
allows the coexistence of an orthogonal frequency division multiplexing (OFDM)
macro-cell and a cognitive small-cell, deployed in a two-tiered structure and
transmitting over the same bandwidth. We derive the optimal linear strategy for
the single antenna secondary base station, maximizing the spectral efficiency
of the opportunistic link, accounting for both signal sub-space structure and
power loading strategy. Our analytical and numerical findings prove that the
precoder structure proposed is optimal for the considered scenario in the face
of Rayleigh and exponential decaying channels.Comment: 5 pages, 4 figures. Accepted and presented at the IEEE 13th
International Workshop on Signal Processing Advances in Wireless
Communications (SPAWC), 2012. Authors' final version. Copyright transferred
to IEE
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A composite approach to self-sustainable transmissions : rethinking OFDM
This paper proposes two novel strategies to extend the battery life of an orthogonal frequency division multiplexing (OFDM) receiver, by exploiting the concept of wireless power transfer (WPT). First a new receiver architecture is devised that does not discard the cyclic prefix (CP), but instead, exploits it to extract power from the received signal, realizing a WPT between the transmitter and the receiver. Subsequently, a flexible composite transmit strategy is designed, in which the OFDM transmitter transmits to the receiver two independent signals coexisting in the same band. It is shown that, by means of this approach, the transmitter can arbitrarily increase the power concentrated within the CP at the OFDM receiver, without increasing the redundancy of the transmission. The feasibility conditions for the self-sustainability of the transmission are derived, in terms of power consumption at the receiver, for both legacy and composite transmission. Numerical findings show that, under reasonable conditions, the amount of power carried in the CP could be made sufficient to decode the information symbols, making the transmission fully self-sustainable. The potential of the proposed approach is confirmed by the encouraging results obtained when the full self-sustainability constraint is relaxed, and partially self-sustainable OFDM transmissions are analyzed