49 research outputs found
Inter-micro-operator interference protection in dynamic TDD system
Abstract. This thesis considers the problem of weighted sum-rate maximization (WSRM) for a system of micro-operators subject to inter-micro-operator interference constraints with dynamic time division duplexing. The WSRM problem is non-convex and non-deterministic polynomial hard. Furthermore, micro-operators require minimum coordination among themselves making the inter-micro-operator interference management very challenging. In this regard, we propose two decentralized precoder design algorithm based on over-the-air bi-directional signalling strategy. We first propose a precoder design algorithm by considering the equivalent weighted minimum mean-squared error minimization reformulation of the WSRM problem. Later we propose precoder design algorithm by considering the weighted sum mean-squared error reformulation. In both approaches, to reduce the huge signalling requirements in centralized design, we use alternating direction method of multipliers technique, wherein each downlink-operator base station and uplink-operator user determines only the relevant set of transmit precoders by exchanging minimal information among the coordinating base stations and user equipments. To minimize the coordination between the uplink-opeator users, we propose interference budget allocation scheme based on reference signal measurements from downlink-operator users. Numerical simulations are provided to compare the performance of proposed algorithms with and without the inter-micro-operator interference constraints
D 3. 3 Final performance results and consolidated view on the most promising multi -node/multi -antenna transmission technologies
This document provides the most recent updates on the technical contributions and research
challenges focused in WP3. Each Technology Component (TeC) has been evaluated
under possible uniform assessment framework of WP3 which is based on the simulation guidelines
of WP6. The performance assessment is supported by the simulation results which are in their
mature and stable state. An update on the Most Promising Technology Approaches (MPTAs)
and their associated TeCs is the main focus of this document. Based on the input of all the TeCs in WP3, a consolidated view of WP3 on the role of multinode/multi-antenna transmission
technologies in 5G systems has also been provided. This consolidated view is further
supported in this document by the presentation of the impact of MPTAs on METIS scenarios
and the addressed METIS goals.Aziz, D.; Baracca, P.; De Carvalho, E.; Fantini, R.; Rajatheva, N.; Popovski, P.; Sørensen, JH.... (2015). D 3. 3 Final performance results and consolidated view on the most promising multi -node/multi -antenna transmission technologies. http://hdl.handle.net/10251/7675
Wireless transmission protocols using relays for broadcast and information exchange channels
Relays have been used to overcome existing network performance bottlenecks in meeting the growing
demand for large bandwidth and high quality of service (QoS) in wireless networks. This thesis
proposes several wireless transmission protocols using relays in practical multi-user broadcast and
information exchange channels. The main theme is to demonstrate that efficient use of relays provides
an additional dimension to improve reliability, throughput, power efficiency and secrecy. First,
a spectrally efficient cooperative transmission protocol is proposed for the multiple-input and singleoutput
(MISO) broadcast channel to improve the reliability of wireless transmission. The proposed
protocol mitigates co-channel interference and provides another dimension to improve the diversity
gain. Analytical and simulation results show that outage probability and the diversity and multiplexing
tradeoff of the proposed cooperative protocol outperforms the non-cooperative scheme. Second,
a two-way relaying protocol is proposed for the multi-pair, two-way relaying channel to improve the
throughput and reliability. The proposed protocol enables both the users and the relay to participate
in interference cancellation. Several beamforming schemes are proposed for the multi-antenna
relay. Analytical and simulation results reveal that the proposed protocol delivers significant improvements
in ergodic capacity, outage probability and the diversity and multiplexing tradeoff if compared
to existing schemes. Third, a joint beamforming and power management scheme is proposed for
multiple-input and multiple-output (MIMO) two-way relaying channel to improve the sum-rate. Network
power allocation and power control optimisation problems are formulated and solved using
convex optimisation techniques. Simulation results verify that the proposed scheme delivers better
sum-rate or consumes lower power when compared to existing schemes. Fourth, two-way secrecy
schemes which combine one-time pad and wiretap coding are proposed for the scalar broadcast channel
to improve secrecy rate. The proposed schemes utilise the channel reciprocity and employ relays
to forward secret messages. Analytical and simulation results reveal that the proposed schemes are
able to achieve positive secrecy rates even when the number of users is large. All of these new wireless
transmission protocols help to realise better throughput, reliability, power efficiency and secrecy
for wireless broadcast and information exchange channels through the efficient use of relays
Advanced Signal Processing Techniques for Two-Way Relaying Networks and Full-Duplex Communication Systems
Sehr hohe Datenraten und ständig verfügbare Netzabdeckung in
zukĂĽnftigen drahtlosen Netzwerken erfordern neue Algorithmen auf der
physischen Schicht. Die Nutzung von Relais stellt ein vielversprechendes
Verfahren dar, da die Netzabdeckung gesteigert werden kann. Zusätzlich
steht hierdurch im Vergleich zu Kupfer- oder Glasfaserleitungen eine
preiswerte Lösung zur Anbindung an die Netzinfrastruktur zur Verfügung.
Traditionelle Einwege-Relais-Techniken (One-Way Relaying [OWR]) nutzen
Halbduplex-Verfahren (HD-Verfahren), welche das Ăśbertragungssystem
ausbremst und zu spektralen Verlusten fĂĽhrt. Einerseits erlauben es
Zweiwege-Relais-Techniken (Two-Way Relaying [TWR]), simultan sowohl an das
Relais zu senden als auch von diesem zu empfangen, wodurch im Vergleich zu
OWR das Spektrum effizienter genutzt wird. Aus diesem Grunde untersuchen
wir Zweiwege-Relais und im Speziellen TWR-Systeme fĂĽr den
Mehrpaar-/Mehrnutzer-Betrieb unter Nutzung von Amplify-and-forward-Relais
(AF-Relais). Derartige Szenarien leiden unter Interferenzen zwischen Paaren
bzw. zwischen Nutzern. Um diesen Interferenzen Herr zu werden, werden
hochentwickelte Signalverarbeitungsalgorithmen – oder in anderen Worten
räumliche Mehrfachzugriffsverfahren (Spatial Division Multiple Access
[SDMA]) – benötigt. Andererseits kann der spektrale Verlust durch den
HD-Betrieb auch kompensiert werden, wenn das Relais im Vollduplexbetrieb
arbeitet. Nichtsdestotrotz ist ein FD-Gerät in der Praxis aufgrund starker
interner Selbstinterferenz (SI) und begrenztem Dynamikumfang des
Tranceivers schwer zu realisieren. Aus diesem Grunde sollten
fortschrittliche Verfahren zur SI-ĂśnterdrĂĽckung entwickelt werden. Diese
Dissertation trägt diesen beiden Zielen Rechnung, indem optimale und/oder
effiziente algebraische Lösungen entwickelt werden, welche verschiedenen
Nutzenfunktionen, wie Summenrate und minimale Sendeleistung, maximieren.Im
ersten Teil studieren wir zunächst Mehrpaar-TWR-Netzwerke mit einem
einzelnen Mehrantennen-AF-Relais. Dieser Anwendungsfall kann auch so
betrachtet werden, dass sich mehrere verschiedene Dienstoperatoren Relais
und Spektrum teilen, wobei verschiedene Nutzerpaare zu verschiedenen
Dienstoperatoren gehören. Aktuelle Ansätzen zielen auf
InterferenzunterdrĂĽckung ab. Wir schlagen ein auf Projektion basiertes
Verfahren zur Trennung mehrerer Dienstoperatoren (projection based
separation of multiple operators [ProBaSeMO]) vor. ProBaSeMO ist leicht
anpassbar fĂĽr den Fall, dass jeder Nutzer mehrere Antennen besitzt oder
unterschiedliche Systemdesignkriterien angewendet werden mĂĽssen. Als
BewertungsmaĂźstab fĂĽr ProBaSeMO entwickeln wir optimale Algorithmen zur
Maximierung der Summenrate, zur Minimierung der Sendeleistung am Relais
oder zur Maximierung des minimalen
Signal-zu-Interferenz-und-Rausch-Verhältnisses (Signal to Interference and
Noise Ratio [SINR]) am Nutzer. Zur Maximierung der Summenrate wurden
spezifische gradientenbasierte Methoden entwickelt, die unabhängig davon
sind, ob ein Nutzer mit einer oder mehr Antennen ausgestattet ist. Um im
Falle eines „Worst-Case“ immer noch eine polynomielle Laufzeit zu
garantieren, entwickelten wir einen Algorithmus mit polynomieller Laufzeit.
Dieser ist inspiriert von der „Polynomial Time Difference of Convex
Functions“-Methode (POTDC-Methode). Bezüglich der Summenrate des Systems
untersuchen wir zuletzt, welche Bedingungen erfĂĽllt sein mĂĽssen, um einen
Gewinn durch gemeinsames Nutzen zu erhalten. Hiernach untersuchen wir die
Maximierung der Summenrate eines Mehrpaar-TWR-Netzwerkes mit mehreren
Einantennen-AF-Relais und Einantennen-Nutzern. Das daraus resultierende
Problem der Summenraten-Maximierung, gebunden an eine bestimmte
Gesamtsendeleistung aller Relais im Netzwerk, ist ähnlich dem des
vorangegangenen Szenarios. Dementsprechend kann eine optimale Lösung für
das eine Szenario auch fĂĽr das jeweils andere Szenario genutzt werden.
Weiterhin werden basierend auf dem Polynomialzeitalgorithmus global
optimale Lösungen entwickelt. Diese Lösungen sind entweder an eine
maximale Gesamtsendeleistung aller Relais oder an eine maximale
Sendeleistung jedes einzelnen Relais gebunden. Zusätzlich entwickeln wir
suboptimale Lösungen, die effizient in ihrer Laufzeit sind und eine
Approximation der optimalen Lösung darstellen. Hiernach verlegen wir unser
Augenmerk auf ein Mehrpaar-TWR-Netzwerk mit mehreren Mehrantennen-AF-Relais
und mehreren Repeatern. Solch ein Szenario ist allgemeiner, da die
vorherigen beiden Szenarien als spezielle Realisierungen dieses Szenarios
aufgefasst werden können. Das Interferenz-Management in diesem Szenario
ist herausfordernder aufgrund der vorhandenen Repeater.
Interferenzneutralisierung (IN) stellt eine Lösung dar, um diese Art
Interferenz zu handhaben. Im Zuge dessen werden notwendige und ausreichende
Bedingungen zur Aufhebung der Interferenz hergeleitet. Weiterhin wird ein
Framework entwickelt, dass verschiedene Systemnutzenfunktionen optimiert,
wobei IN im jeweiligen Netzwerk vorhanden sein kann oder auch nicht. Dies
ist unabhängig davon, ob die Relais einer maximalen Gesamtsendeleistung
oder einer individuellen maximalen Sendeleistung unterliegen. Letztendlich
entwickeln wir ein Ăśbertragungsverfahren sowie ein Vorkodier- und
Dekodierverfahren fĂĽr Basisstationen (BS) in einem TWR-assistierten
Mehrbenutzer-MIMO-Downlink-Kanal. Im Vergleich mit dem
Mehrpaar-TWR-Netzwerk leidet dieses Szenario unter Interferenzen zwischen
den Kanälen. Wir entwickeln drei suboptimale Algorithmen, welche auf
Kanalinversion basieren. ProBaSeMO und „Zero-Forcing Dirty Paper
Coding“ (ZFDPC), welche eine geringe Zeitkomplexität aufweisen, schaffen
eine Balance zwischen Leistungsfähigkeit und Komplexität. Zusätzlich
gibt es jeweils nur geringe EinbrĂĽche in stark beanspruchten
Kommunikationssystemen.Im zweiten Teil untersuchen wir Techniken zur
SI-UnterdrĂĽckung, um den FD-Gewinn in einem Punkt-zu-Punkt-System
auszunutzen. Zunächst entwickeln wir ein Übertragungsverfahren, dass auf
SI RĂĽcksicht nimmt und die SI-UnterdrĂĽckung gegen den Multiplexgewinn
abwägt. Die besten Ergebnisse werden durch die perfekte Kenntnis des
Kanals erzielt, was praktisch nicht genau der Fall ist. Aus diesem Grund
werden Übertragungstechniken für den „Worst Case“ entwickelt, die den
Kanalschätzfehlern Rechnung tragen. Diese Fehler werden deterministisch
modelliert und durch Ellipsoide beschränkt. In praktischen Szenarien ist
der HF-Schaltkreise nicht perfekt. Dies hat Einfluss auf die Verfahren zur
SI-UnterdrĂĽckung und fĂĽhrt zu einer Restselbstinterferenz. Wir entwickeln
effiziente Ăśbertragungstechniken mittels Beamforming, welche auf dem
Signal-zu-Verlust-und-Rausch-Verhältnis (signal to leakage plus noise
ratio [SLNR]) aufbauen, um Unvollkommenheiten der HF-Schaltkreise
auszugleichen. Zusätzlich können alle Designkonzepte auf FD-OWR-Systeme
erweitert werden.To enable ultra-high data rate and ubiquitous coverage in future wireless
networks, new physical layer techniques are desired. Relaying is a
promising technique for future wireless networks since it can boost the
coverage and can provide low cost wireless backhauling solutions, as
compared to traditional wired backhauling solutions via fiber and copper.
Traditional one-way relaying (OWR) techniques suffer from the spectral loss
due to the half-duplex (HD) operation at the relay. On one hand, two-way
relaying (TWR) allows the communication partners to transmit to and/or
receive from the relay simultaneously and thus uses the spectrum more
efficiently than OWR. Therefore, we study two-way relays and more
specifically multi-pair/multi-user TWR systems with amplify-and-forward
(AF) relays. These scenarios suffer from inter-pair or inter-user
interference. To deal with the interference, advanced signal processing
algorithms, in other words, spatial division multiple access (SDMA)
techniques, are desired. On the other hand, if the relay is a full-duplex
(FD) relay, the spectral loss due to a HD operation can also be
compensated. However, in practice, a FD device is hard to realize due to
the strong loop-back self-interference and the limited dynamic range at the
transceiver. Thus, advanced self-interference suppression techniques should
be developed. This thesis contributes to the two goals by developing
optimal and/or efficient algebraic solutions for different scenarios
subject to different utility functions of the system, e.g., sum rate
maximization and transmit power minimization. In the first part of this
thesis, we first study a multi-pair TWR network with a multi-antenna AF
relay. This scenario can be also treated as the sharing of the relay and
the spectrum among multiple operators assuming that different pairs of
users belong to different operators. Existing approaches focus on
interference suppression. We propose a projection based separation of
multiple operators (ProBaSeMO) scheme, which can be easily extended when
each user has multiple antennas or when different system design criteria
are applied. To benchmark the ProBaSeMO scheme, we develop optimal relay
transmit strategies to maximize the system sum rate, minimize the required
transmit power at the relay, or maximize the minimum signal to interference
plus noise ratio (SINR) of the users. Specifically for the sum rate
maximization problem, gradient based methods are developed regardless
whether each user has a single antenna or multiple antennas. To guarantee a
worst-case polynomial time solution, we also develop a polynomial time
algorithm which has been inspired by the polynomial time difference of
convex functions (POTDC) method. Finally, we analyze the conditions for
obtaining the sharing gain in terms of the sum rate. Then we study the sum
rate maximization problem of a multi-pair TWR network with multiple single
antenna AF relays and single antenna users. The resulting sum rate
maximization problem, subject to a total transmit power constraint of the
relays in the network, yields a similar problem structure as in the
previous scenario. Therefore the optimal solution for one scenario can be
used for the other. Moreover, a global optimal solution, which is based on
the polyblock approach, and several suboptimal solutions, which are more
computationally efficient and approximate the optimal solution, are
developed when there is a total transmit power constraint of the relays in
the network or each relay has its own transmit power constraint. We then
shift our focus to a multi-pair TWR network with multiple multi-antenna AF
relays and multiple dumb repeaters. This scenario is more general because
the previous two scenarios can be seen as special realizations of this
scenario. The interference management in this scenario is more challenging
due to the existence of the repeaters. Interference neutralization (IN) is
a solution for dealing with this kind of interference. Thereby, necessary
and sufficient conditions for neutralizing the interference are derived.
Moreover, a general framework to optimize different system utility
functions in this network with or without IN is developed regardless
whether the AF relays in the network have a total transmit power limit or
individual transmit power limits. Finally, we develop the relay transmit
strategy as well as base station (BS) precoding and decoding schemes for a
TWR assisted multi-user MIMO (MU-MIMO) downlink channel. Compared to the
multi-pair TWR network, this scenario suffers from the co-channel
interference. We develop three suboptimal algorithms which are based on
channel inversion, ProBaSeMO and zero-forcing dirty paper coding (ZFDPC),
which has a low computational complexity, provides a balance between the
performance and the complexity, and suffers only a little when the system
is heavily loaded, respectively.In the second part of this thesis, we
investigate self-interference (SI) suppression techniques to exploit the FD
gain for a point-to-point MIMO system. We first develop SI aware transmit
strategies, which provide a balance between the SI suppression and the
multiplexing gain of the system. To get the best performance, perfect
channel state information (CSI) is needed, which is imperfect in practice.
Thus, worst case transmit strategies to combat the imperfect CSI are
developed, where the CSI errors are modeled deterministically and bounded
by ellipsoids. In real word applications, the RF chain is imperfect. This
affects the performance of the SI suppression techniques and thus results
in residual SI. We develop efficient transmit beamforming techniques, which
are based on the signal to leakage plus noise ratio (SLNR) criterion, to
deal with the imperfections in the RF chain. All the proposed design
concepts can be extended to FD OWR systems
Spatio-Temporal processing for Optimum Uplink-Downlink WCDMA Systems
The capacity of a cellular system is limited by two different phenomena, namely
multipath fading and multiple access interference (MAl). A Two Dimensional (2-D)
receiver combats both of these by processing the signal both in the spatial and temporal
domain. An ideal 2-D receiver would perform joint space-time processing, but at the
price of high computational complexity. In this research we investigate computationally
simpler technique termed as a Beamfom1er-Rake. In a Beamformer-Rake, the output of a
beamfom1er is fed into a succeeding temporal processor to take advantage of both the
beamformer and Rake receiver. Wireless service providers throughout the world are
working to introduce the third generation (3G) and beyond (3G) cellular service that will
provide higher data rates and better spectral efficiency. Wideband COMA (WCDMA)
has been widely accepted as one of the air interfaces for 3G. A Beamformer-Rake
receiver can be an effective solution to provide the receivers enhanced capabilities
needed to achieve the required performance of a WCDMA system.
We consider three different Pilot Symbol Assisted (PSA) beamforming techniques,
Direct Matrix Inversion (DMI), Least-Mean Square (LMS) and Recursive Least Square
(RLS) adaptive algorithms. Geometrically Based Single Bounce (GBSB) statistical
Circular channel model is considered, which is more suitable for array processing, and
conductive to RAKE combining. The performances of the Beam former-Rake receiver are
evaluated in this channel model as a function of the number of antenna elements and
RAKE fingers, in which are evaluated for the uplink WCDMA system. It is shown that,
the Beamformer-Rake receiver outperforms the conventional RAKE receiver and the
conventional beamformer by a significant margin. Also, we optimize and develop a
mathematical formulation for the output Signal to Interference plus Noise Ratio (SINR)
of a Beam former-Rake receiver.
In this research, also, we develop, simulate and evaluate the SINR and Signal to Noise
Ratio (Et!Nol performances of an adaptive beamforming technique in the WCDMA
system for downlink. The performance is then compared with an omnidirectional antenna
system. Simulation shows that the best perfom1ance can be achieved when all the mobiles
with same Angle-of-Arrival (AOA) and different distance from base station are formed in
one beam
D3.2 First performance results for multi -node/multi -antenna transmission technologies
This deliverable describes the current results of the multi-node/multi-antenna technologies
investigated within METIS and analyses the interactions within and outside Work Package 3.
Furthermore, it identifies the most promising technologies based on the current state of
obtained results. This document provides a brief overview of the results in its first part. The second part, namely the Appendix, further details the results, describes the simulation
alignment efforts conducted in the Work Package and the interaction of the Test Cases. The
results described here show that the investigations conducted in Work Package 3
are maturing resulting in valuable innovative solutions for future 5G systems.Fantini. R.; Santos, A.; De Carvalho, E.; Rajatheva, N.; Popovski, P.; Baracca, P.; Aziz, D.... (2014). D3.2 First performance results for multi -node/multi -antenna transmission technologies. http://hdl.handle.net/10251/7675