113 research outputs found
Cognitive Blind Interference Alignment for Macro-Femto Cellular Networks
The proceeding at: 2014 IEEE Global Communications Conference took place 8-12 December 2014 in Austin, TX, USA.A cognitive Blind Interference Alignment scheme is devised for use in macro-femto cellular networks. The proposed scheme does not require any channel state information at the transmitter or data sharing among the Macro Base Station and the Femto Access Points. It achieves transmission to femto cell users without affecting the rates of the Macro users. This is achieved by appropriately combining the supersymbols of the Macro Base Stations and the Femto Access Points. It is shown that in some scenarios the use of this scheme results to considerable rates for Femto users.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.Publicad
Energy-Efficient NOMA Enabled Heterogeneous Cloud Radio Access Networks
Heterogeneous cloud radio access networks (H-CRANs) are envisioned to be
promising in the fifth generation (5G) wireless networks. H-CRANs enable users
to enjoy diverse services with high energy efficiency, high spectral
efficiency, and low-cost operation, which are achieved by using cloud computing
and virtualization techniques. However, H-CRANs face many technical challenges
due to massive user connectivity, increasingly severe spectrum scarcity and
energy-constrained devices. These challenges may significantly decrease the
quality of service of users if not properly tackled. Non-orthogonal multiple
access (NOMA) schemes exploit non-orthogonal resources to provide services for
multiple users and are receiving increasing attention for their potential of
improving spectral and energy efficiency in 5G networks. In this article a
framework for energy-efficient NOMA H-CRANs is presented. The enabling
technologies for NOMA H-CRANs are surveyed. Challenges to implement these
technologies and open issues are discussed. This article also presents the
performance evaluation on energy efficiency of H-CRANs with NOMA.Comment: This work has been accepted by IEEE Network. Pages 18, Figure
Blind interference alignment for cellular networks
Mención Internacional en el título de doctorManaging the interference is the main challenge in cellular networks. Multiple-Input
Multiple-Output (MIMO) schemes have emerged as a means of achieving high-capacity
in wireless communications. The most efficient MIMO techniques are based on managing
the interference instead of avoiding it by employing orthogonal resource allocation
schemes. These transmission schemes require the knowledge of the Channel State Information at the Transmitter (CSIT) to achieve the optimal Degrees of Freedom (DoF),
also known as multiplexing gain. Providing an accurate CSIT in cellular environments
involves high-capacity backhaul links and accurate synchronization, which imply the use
of a large amount of network resources. Recently, a Blind Interference Alignment (BIA)
scheme was devised as a means of achieving a growth in DoF regarding the amount of
users served without the need for CSIT in the Multiple-Input Single-Output (MISO)
Broadcast Channel (BC). It is demonstrated that BIA achieves the optimal DoF in
the BC without CSIT. However, the implementation of BIA in cellular networks is not
straightforward. This dissertation investigates the DoF and the corresponding sum-rate
of cellular networks in absence of CSIT and their achievability by using BIA schemes.
First, this dissertation derives the DoF-region of homogenous cellular networks with
partial connectivity. Assuming that all the Base Stations (BSs) cooperate in order to
transmit to all users in the network, we proposed an extension of the BIA scheme for the
MISO BC where the set of BSs transmits as in a network MIMO. It is shown that the
cooperation between BSs results futile because of the lack of full connectivity in cellular
networks. After that, this dissertation presents several transmission schemes based on
the network topology. By differentiating between users that can treat this interference
optimally as noise and those who need to manage the interference from neighbouring
BSs, a network BIA scheme is devised to achieve the optimal DoF in homogeneous
cellular networks. Second, the use of BIA schemes is analyzed for heterogeneous cellular networks. It is demonstrated that the previous BIA schemes based on the network topology result nonoptimal in DoF because of the particular features of the heterogenous cellular networks. More specifically, assuming a macro-femto network, cooperation between both tiers leads to a penalty for macro users while femto users do not exploit the particular topology of this kind of network. In this dissertation, the optimal linear DoF (lDoF) in a two-tier network are derived subject to optimality in DoF for the upper tier. It is demonstrated
that, without CSIT or any cooperation between tiers, the lower tier can achieve nonzero
DoF while the upper tier attains the optimal DoF by transmitting independently of
the lower tier deployment. After that, a cognitive BIA scheme that achieves this outer
bound is devised for macro-femto cellular networks.
The third part of this dissertation is focused on the implementation of BIA in practical
scenarios. It is shown that transmission at limited SNR and coherence time are the
main hurdles to overcome for practical implementations of BIA. With aim of managing
both constraints, the use of BIA together with orthogonal approaches is proposed in this
work. An improvement on the inherent noise increase of BIA and the required coherence
time is achieved at expenses of losing DoF. Therefore, there exists a trade-off between
multiplexing gain, sum-rate at finite SNR and coherence time in practical scenarios. The
optimal resource allocation for orthogonal transmission is obtained after solving a very
specific optimization problem. To complete the characterization of the performance of
BIA in realistic scenarios a experimental evaluation based on a hardware implementation
is presented at the end of this work. It is shown that BIA outperforms the sum-rate
of schemes based on CSIT such as LZFB because of the hardware impairments and the
costs of providing CSIT in a realist implementation.Programa Oficial de Doctorado en Multimedia y ComunicacionesPresidente: Luc Vandendorpe.- Secretario: María Julia Fernández-Getino García.- Vocal: Ignacio Santamaría Caballer
Interference Alignment for Cognitive Radio Communications and Networks: A Survey
© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Interference alignment (IA) is an innovative wireless transmission strategy that has shown to be a promising technique for achieving optimal capacity scaling of a multiuser interference channel at asymptotically high-signal-to-noise ratio (SNR). Transmitters exploit the availability of multiple signaling dimensions in order to align their mutual interference at the receivers. Most of the research has focused on developing algorithms for determining alignment solutions as well as proving interference alignment’s theoretical ability to achieve the maximum degrees of freedom in a wireless network. Cognitive radio, on the other hand, is a technique used to improve the utilization of the radio spectrum by opportunistically sensing and accessing unused licensed frequency spectrum, without causing harmful interference to the licensed users. With the increased deployment of wireless services, the possibility of detecting unused frequency spectrum becomes diminished. Thus, the concept of introducing interference alignment in cognitive radio has become a very attractive proposition. This paper provides a survey of the implementation of IA in cognitive radio under the main research paradigms, along with a summary and analysis of results under each system model.Peer reviewe
TeamUp5G: a multidisciplinary approach to training and research on new RAN techniques for 5G ultra-dense mobile networks
Proceeding of: 12th IEEE/IET International Symposium on Communication Systems, Networks and Digital Signal Processing, (CSNDSP), 20-22, July 2020, (online).This paper presents a summary of the main research directions being followed in TeamUp5G European Training Network, teaming up a new generation of researchers and entrepreneurs ready to address complex engineering problems and innovation to work both at university and industry in the 5G field. This project is focused on new radio access network (RAN) techniques for 5G, considering ultradense mobile networks as a key ingredient of the actual mobile networks and their evolution. Research covers a wide spread of topics from physical layer and medium access control to applications, looking at spectrum sharing and energy efficiency as important features.This work has received funding from the European Union (EU) Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie ETN TeamUp5G, grant agreement No. 813391
Control Channel Interference Measurement in LTE-TDD Heterogeneous Network
Deploying low power eNodeBs inside macro-cells is an effective way to enhance indoor coverage. By reusing frequency between macro-cells and indoor femto-cells, the efficiency of expensive licensed spectrum can be further increased. This thesis measured Physical Downlink Control Channel (PDCCH) performance in such a heterogeneous LTE-TDD network. Four USRP software radio terminals and connected Linux workstations were deployed to build a test environment. They acted as eNodeB and UE respectively. During the test, the femto-cell was configured to coordinate its radio frame with the macro-cell. Several criteria including received block error rate, payload bit error rate and symbols signal to interference and noise ratio were used to evaluate the PDCCH performance in macro-cell under heterogeneous environment
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