5,864 research outputs found
Interference Cancellation trough Interference Alignment for Downlink of Cognitive Cellular Networks
In this letter, we propose the interference cancellation through interference
alignment at the downlink of cognitive cellular networks. Interference
alignment helps the spatial resources to be shared among primary and secondary
cells and thus, it can provide higher degrees of freedom through interference
cancellation. We derive and depict the achievable degrees of freedom. We also
analyse and calculate the achievable sum rates applying water-filling optimal
power allocation
Demo: Non-classic Interference Alignment for Downlink Cellular Networks
Our demo aims at proving the concept of a recent proposed interference
management scheme that reduces the inter-cell interference in downlink without
complex coordination, known as non-classic interference alignment (IA) scheme.
We assume a case where one main Base Station (BS) needs to serve three users
equipments (UE) while another BS is causing interference. The primary goal is
to construct the alignment scheme ; i.e. each UE estimates the main and
interfered channel coefficients, calculates the optimal interference free
directions dropped by the interfering BS and feeds them back to the main BS
which in turn applies a scheduling to select the best free inter-cell
interference directions. Once the scheme is build, we are able to measure the
total capacity of the downlink interference channel. We run the scheme in
CorteXlab ; a controlled hardware facility located in Lyon, France with
remotely programmable radios and multi-node processing capabilities, and we
illustrate the achievable capacity gain for different channel realizations.Comment: Joint NEWCOM/COST Workshop on Wireless Communications JNCW 2015, Oct
2015, Barcelone, Spain. 201
Degrees of Freedom of Uplink-Downlink Multiantenna Cellular Networks
An uplink-downlink two-cell cellular network is studied in which the first
base station (BS) with antennas receives independent messages from its
serving users, while the second BS with antennas transmits
independent messages to its serving users. That is, the first and second
cells operate as uplink and downlink, respectively. Each user is assumed to
have a single antenna. Under this uplink-downlink setting, the sum degrees of
freedom (DoF) is completely characterized as the minimum of
,
, , and , where denotes
. The result demonstrates that, for a broad class of network
configurations, operating one of the two cells as uplink and the other cell as
downlink can strictly improve the sum DoF compared to the conventional uplink
or downlink operation, in which both cells operate as either uplink or
downlink. The DoF gain from such uplink-downlink operation is further shown to
be achievable for heterogeneous cellular networks having hotspots and with
delayed channel state information.Comment: 22 pages, 11 figures, in revision for IEEE Transactions on
Information Theor
Downlink Cellular Interference Alignment
Cellular networks have been notoriously interference-limited systems in dense urban areas, where base stations are deployed in close proximity to one-another. Recently, a signal processing method called Interference Alignment has emerged, making use of the increasing signal dimensions available in the system through multiple-input multiple output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM) technologies. In this report, we review the state of the art of interference alignment since its foundation, and we detail algorithms and baseline comparisons to make when applying interference alignment schemes to downlink cellular networks. We also propose a number of research directions of interest which are not yet answered in the current literature.Les réseaux cellulaires ont été l'exemple typique de réseaux dont les performances sont limités par les interférences, particulièrement dans les régions urbaines. Récemment, une nouvelle technique de traitement du signal appelée "alignement d'interférences" a été dévelopée, et permet d'utiliser les dimensions du signal reçu à travers les technologies MIMO (multiple input multiple output) et OFDM (orthogonal frequency division multiplexing) pour annuler tout ou partie de l'interférence reçue par les mobiles. Dans ce rapport, nous évaluons la littérature liée à l'alignement d'interférence et nous détaillons les algorithmes existants et leur application aux réseaux cellulaires en voie descendante. Nous proposons ensuite un ensemble de directions de recherche d'intérêt par rapport à l'état de l'art actuel
Exploiting Spatial Interference Alignment and Opportunistic Scheduling in the Downlink of Interference Limited Systems
In this paper we analyze the performance of single stream and multi-stream
spatial multiplexing (SM) systems employing opportunistic scheduling in the
presence of interference. In the proposed downlink framework, every active user
reports the post-processing signal-to-interference-plus-noise-power-ratio
(post-SINR) or the receiver specific mutual information (MI) to its own
transmitter using a feedback channel. The combination of scheduling and
multi-antenna receiver processing leads to substantial interference suppression
gain. Specifically, we show that opportunistic scheduling exploits spatial
interference alignment (SIA) property inherent to a multi-user system for
effective interference mitigation. We obtain bounds for the outage probability
and the sum outage capacity for single stream and multi stream SM employing
real or complex encoding for a symmetric interference channel model.
The techniques considered in this paper are optimal in different operating
regimes. We show that the sum outage capacity can be maximized by reducing the
SM rate to a value less than the maximum allowed value. The optimum SM rate
depends on the number of interferers and the number of available active users.
In particular, we show that the generalized multi-user SM (MU SM) method
employing real-valued encoding provides a performance that is either
comparable, or significantly higher than that of MU SM employing complex
encoding. A combination of analysis and simulation is used to describe the
trade-off between the multiplexing rate and sum outage capacity for different
antenna configurations
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