213 research outputs found
Blind Interference Alignment in General Heterogeneous Networks
Heterogeneous networks have a key role in the design of future mobile
communication networks, since the employment of small cells around a macrocell
enhances the network's efficiency and decreases complexity and power demand.
Moreover, research on Blind Interference Alignment (BIA) has shown that optimal
Degrees of Freedom (DoF) can be achieved in certain network architectures, with
no requirement of Channel State Information (CSI) at the transmitters. Our
contribution is a generalised model of BIA in a heterogeneous network with one
macrocell with K users and K femtocells each with one user, by using Kronecker
(Tensor) Product representation. We introduce a solution on how to vary
beamforming vectors under power constraints to maximize the sum rate of the
network and how optimal DoF can be achieved over K+1 time slots.Comment: 5 pages, 7 figures, accepted to IEEE PIMRC'1
Blind Interference Alignment for Private Information Retrieval
Blind interference alignment (BIA) refers to interference alignment schemes
that are designed only based on channel coherence pattern knowledge at the
transmitters (the "blind" transmitters do not know the exact channel values).
Private information retrieval (PIR) refers to the problem where a user
retrieves one out of K messages from N non-communicating databases (each holds
all K messages) without revealing anything about the identity of the desired
message index to any individual database. In this paper, we identify an
intriguing connection between PIR and BIA. Inspired by this connection, we
characterize the information theoretic optimal download cost of PIR, when we
have K = 2 messages and the number of databases, N, is arbitrary
Aiming Perfectly in the Dark - Blind Interference Alignment through Staggered Antenna Switching
We propose a blind interference alignment scheme for the vector broadcast
channel where the transmitter is equipped with M antennas and there are K
receivers, each equipped with a reconfigurable antenna capable of switching
among M preset modes. Without any knowledge of the channel coefficient values
at the transmitters and with only mild assumptions on the channel coherence
structure we show that MK/M+K-1 degrees of freedom are achievable. The key to
the blind interference alignment scheme is the ability of the receivers to
switch between reconfigurable antenna modes to create short term channel
fluctuation patterns that are exploited by the transmitter. The achievable
scheme does not require cooperation between transmit antennas and is therefore
applicable to the MxK X network as well. Only finite symbol extensions are
used, and no channel knowledge at the receivers is required to null the
interference.Comment: 27 pages, 15 figure
Elements of Cellular Blind Interference Alignment --- Aligned Frequency Reuse, Wireless Index Coding and Interference Diversity
We explore degrees of freedom (DoF) characterizations of partially connected
wireless networks, especially cellular networks, with no channel state
information at the transmitters. Specifically, we introduce three fundamental
elements --- aligned frequency reuse, wireless index coding and interference
diversity --- through a series of examples, focusing first on infinite regular
arrays, then on finite clusters with arbitrary connectivity and message sets,
and finally on heterogeneous settings with asymmetric multiple antenna
configurations. Aligned frequency reuse refers to the optimality of orthogonal
resource allocations in many cases, but according to unconventional reuse
patterns that are guided by interference alignment principles. Wireless index
coding highlights both the intimate connection between the index coding problem
and cellular blind interference alignment, as well as the added complexity
inherent to wireless settings. Interference diversity refers to the observation
that in a wireless network each receiver experiences a different set of
interferers, and depending on the actions of its own set of interferers, the
interference-free signal space at each receiver fluctuates differently from
other receivers, creating opportunities for robust applications of blind
interference alignment principles
Blind Interference Alignment for Cellular Networks
We propose a blind interference alignment scheme for partially connected cellular networks. The scheme cancels both intracell and intercell interference by relying on receivers with one reconfigurable antenna and by allowing users at the cell edge to be served by all the base stations in their proximity. An outer bound for the degrees of freedom is derived for general partially connected networks with single-antenna receivers when knowledge of the channel state information at the transmitter is not available. It is demonstrated that for symmetric scenarios, this outer bound is achieved by the proposed scheme. On the other hand, for asymmetric scenarios, the achievable degrees of freedom are not always equal to the outer bound. However, the penalty is typically small, and the proposed scheme outperforms other blind interference alignment schemes. Moreover, significant reduction of the supersymbol length is achieved compared with a standard blind interference alignment strategy designed for fully connected networks.This work has been partially funded by research projects COMONSENS
(CSD2008-00010) and GRE3N (TEC2011-29006-C03-02). This research work
was partly carried out at the ESAT Laboratory of KU Leuven in the frame of
the Belgian Programme on Interuniversity Attractive Poles Programme
initiated by the Belgian Science Policy Office: IUAP P7/23 ‘Belgian network
on stochastic modeling analysis design and optimization of communication
systems’ (BESTCOM) 2012–2017. The work of D. Toumpakaris was
supported by the European Union (European Social Fund—ESF) and Greek
national funds through the Operational Program Education and Lifelong
Learning of the National Strategic Reference Framework through the Research
Funding Program Thales—Investing in knowledge society through the
European Social Fund. The work of Syed Jafar was supported in part by
NSFgrants CCF-1319104 and CCF-1317351.Publicad
Experimental Evaluation of Blind Interference Alignment
The proceeding at: 2015 Vehicular Technology Conference (VTC Spring) took place 11-14 May in Glasgow, Ireland.An experimental evaluation of Blind Interference Alignment (BIA) over a hardware platform is presented in this work. In contrast to other transmission techniques such as Linear Zero Forcing Beamforming (LZFB) or Interference Alignment (IA), BIA achieves a growth in Degrees of Freedom (DoF) without channel state information at the transmitter (CSIT). A real implementation based on Orthogonal Frequency Division Multiplexing (OFDM) and LTE parameters is implement on a testbed made up of a transmitter equipped with two antennas and two users equipped with a reconfigurable antenna each. Furthermore, a full CSIT technique such as LZFB is also implemented for comparison purposes. First, the theoretic achievable rates are obtained for both techniques. After that, the bit error rate of both schemes is evaluated regarding the achieved sum-thorughput.This work has been partially funded by research projects COMONSENS (CSD2008-00010), and GRE3N (TEC2011-29006-C03-02)
Grouping Based Blind Interference Alignment for -user MISO Interference Channels
We propose a blind interference alignment (BIA) through staggered antenna
switching scheme with no ideal channel assumption. Contrary to the ideal
assumption that channels remain constant during BIA symbol extension period,
when the coherence time of the channel is relatively short, channel
coefficients may change during a given symbol extension period. To perform BIA
perfectly with realistic channel assumption, we propose a grouping based
supersymbol structure for -user interference channels which can adjust a
supersymbol length to given coherence time. It is proved that the supersymbol
length could be reduced significantly by an appropriate grouping. Furthermore,
it is also shown that the grouping based supersymbol achieves higher degrees of
freedom than the conventional method with given coherence time.Comment: 5 pages, 3 figures, to appear in IEEE ISIT 201
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