19 research outputs found
Indoor Radio Measurement and Planning for UMTS/HSPDA with Antennas
Over the last decade, mobile communication networks have evolved tremendously with a key focus on providing high speed data services in addition to voice. The third generation of mobile networks in the form of Universal Mobile Telecommunications System (UMTS) is already offering revolutionary mobile broadband experience to its users by deploying High Speed Downlink Packet Access (HSDPA) as its packet-data technology. With data speeds up to 14.4 Mbps and ubiquitous mobility, HSDPA is anticipated to become a preferred broadband access medium for end-users via mobile phones, laptops etc. While majority of these end-users are located indoors most of the time, approximately 70-80% of the HSDPA traffic is estimated to originate from inside buildings. Thus for network operators, indoor coverage has become a necessity for technical and business reasons.
Macro-cellular (outdoor) to indoor coverage is a natural inexpensive way of providing network coverage inside the buildings. However, it does not guarantee sufficient link quality required for optimal HSDPA operation. On the contrary, deploying a dedicated indoor system may be far too expensive from an operator\u27s point of view. In this thesis, the concept is laid for the understanding of indoor radio wave propagation in a campus building environment which could be used to plan and improve outdoor-to-indoor UMTS/HSDPA radio propagation performance. It will be shown that indoor range performance depends not only on the transmit power of an indoor antenna, but also on the product\u27s response to multipath and obstructions in the environment along the radio propagation path.
An extensive measurement campaign will be executed in different indoor environments analogous to easy, medium and hard radio conditions. The effects of walls, ceilings, doors and other obstacles on measurement results would be observed.
Chapter one gives a brief introduction to the evolution of UMTS and HSDPA. It goes on to talk about radio wave propagation and some important properties of antennas which must be considered when choosing an antenna for indoor radio propagation. The challenges of in-building network coverage and also the objectives of this thesis are also mentioned in this chapter.
The evolution and standardization, network architecture, radio features and most importantly, the radio resource management features of UMTS/HSDPA are given in chapter two. In this chapter, the reason why Wideband Code Division Multiple Access (WCDMA) was specified and selected for 3G (UMTS) systems would be seen. The architecture of the radio access network, interfaces with the radio access network between base stations and radio network controllers (RNC), and the interface between the radio access network and the core network are also described in this chapter. The main features of HSDPA are mentioned at the end of the chapter.
In chapter three the principles of the WCDMA air interface, including spreading, Rake reception, signal fading, power control and handovers are introduced. The different types and characteristics of the propagation environments and how they influence radio wave propagation are mentioned. UMTS transport, logical and physical channels are also mentioned, highlighting their significance and relationship in and with the network.
Radio network planning for UMTS is discussed in chapter four. The outdoor planning process which includes dimensioning, detailed planning, optimization and monitoring is outlined. Indoor radio planning with distributed antenna systems (DAS), which is the idea and motivation behind this thesis work, is also discussed.
The various antennas considered and the antenna that was selected for this thesis experiment was discussed in chapter five. The antenna radiation pattern, directivity, gain and input impedance were the properties of the antenna that were taken into consideration. The importance of the choice of the antenna for any particular type of indoor environment is also mentioned.
In chapter six, the design and fabrication of the monopole antennas used for the experimental measurement is mentioned. The procedure for measurement and the equipment used are also discussed. The results gotten from the experiment are finally analyzed and discussed. In this chapter the effect of walls, floors, doors, ceilings and other obstacles on radio wave propagation will be seen.
Finally, chapter seven concludes this thesis work and gives some directions for future work
Performance analysis of multi-antenna and multi-user methods for 3G and beyond
Performance of cellular networks has become an issue with forecasted growing public demand for medium and high data rate services. Motivated by these expectations multi-antenna techniques such as transmit diversity (TD), channel-aware scheduling and multiple-input multiple-output (MIMO) transceivers have received a lot of enthusiasm within wireless communications community.
We first focus on closed-loop (CL) TD and introduce extended mode 1 and 2 (e-mode 1 and 2) algorithms that are designed based on universal terrestrial radio access (UTRA) frequency division duplex (FDD) CL mode 1 and 2. We derive analytical performance results for e-mode 1 and 2 in terms of signal to noise ratio (SNR) gain, link capacity and bit error probability (BEP). We also consider the effect of feedback errors to the performance of closed-loop system.
In the analysis of channel-aware scheduling we focus on on-off scheduling (OOS) where user's feedback consists of only a single bit. Performance results in both downlink and uplink clearly indicate that most of the achievable gain from channel-aware scheduling can be obtained with very scarce channel state information (CSI). Results also show that the design of feedback channel is of great importance because feedback errors may seriously degrade the system performance.
The third topic of the thesis concentrates on MIMO techniques that can be implemented in UTRA FDD uplink without major revisions to the current air interface. We show that the UTRA FDD uplink coverage and capacity performance can be boosted by single-input multiple-output (SIMO) and MIMO transceivers. The information MIMO employing parallel multiplexing instead of transmit diversity shows its potential when extremely high user data rates are needed.Solukkoverkkojen suorituskyky on noussut tärkeään rooliin nopeiden datapalveluiden kasvuennusteiden myötä. Näiden kasvuodotusten perusteella moniantennitekniikat kuten lähetysdiversiteetti, kanavan huomioon ottava lähetyksen aikataulutus sekä useaa samanaikaista datavirtaa tukevat lähetinvastaanotinmenetelmät ovat saaneet osakseen paljon kiinnostusta langattoman tietoliikenteen tutkijayhteisössä.
Tutkimuksessa keskitytään aluksi suljettua säätöä käyttäviin lähetysdiversiteettimenetelmiin, missä yhteydessä esitellään laajennetut moodien 1 ja 2 algoritmit, jotka on aiemmin kehitetty kolmannen sukupolven WCDMA järjestelmän suljetun säädön moodien 1 ja 2 pohjalta. Laajennetuille moodien 1 ja 2 algoritmeille johdetaan analyyttisiä suorituskykytuloksia käyttäen mittarina signaali-kohinasuhteen parannusta, linkin kapasiteettia sekä bittivirheiden todennäköisyyttä. Myös säätövirheiden vaikutusta järjestelmän suorituskykyyn tarkastellaan.
Lähetyksen aikataulutuksen analyysi painottuu kytkettyyn aikataulutukseen, missä käyttäjän säätöinformaatio sisältyy yhteen bittiin. Sekä ylä- että alalinkin suorituskykytulokset osoittavat selvästi, että suurin osa mahdollisesta parannuksesta voidaan saavuttaa hyvin karkeaan kanavatilan informaatioon perustuen. Tulokset osoittavat myös, että säätökanavan suunnittelu on tärkeää, koska säätövirheet voivat vakavasti heikentää järjestelmän suorituskykyä.
Kolmannessa aihealueessa keskitytään moniantennitekniikoihin, jotka voidaan toteuttaa WCDMA järjestelmän ylälinkissä ilman perustavanlaatuisia muutoksia nykyiseen ilmarajapintaan. Tutkimuksessa osoitetaan, että ylälinkin peittoa ja kapasiteettia voidaan parantaa tutkituilla moniantennitekniikoilla olipa lähettimessä yksi tai useampia antenneja. Menetelmä, jossa informaatio jaetaan useisiin rinnakkaisiin datavirtoihin sen sijaan että käytettäisiin vain yhtä datavirtaa, osoittautuu erityisen lupaavaksi kun tarvitaan hyvin nopeita tiedonsiirtoyhteyksiä.reviewe
Aspects of capacity enhancement techniques in cellular networks
Frequency spectrum is the scarce resource. From mobile operator’s point of view, efficient utilization of the radio resources is needed while providing maximum coverage, and ensuring good quality of service with minimal infrastructure. In high capacity demanding areas, multilayer networks with multiband and multi radio access technologies are deployed, in order to meet the capacity requirements. In his doctoral thesis, Usman Sheikh has proposed a “Smart Traffic Handling” strategy, which is based on user’s required service type and location. Smart traffic handling scheme efficiently utilizes the different layers of the network, balances the load among them, and improves the system capacity. Power resources at base station are also limited. Usman Sheikh’s proposed “Power Control Scheme for High Speed Downlink Packet Access (HSDPA) network” improves the cell edge user experience, while maintaining the fairness among the other users in a cell. With the help of a proposed power control scheme, a user far from the base station can also enjoy the better quality of service.
Generally, mobile operators use macro cells with wide beam antennas for wider coverage in the cell, but future capacity demands cannot be achieved by using only them. “Higher Order Sectorization” is one possible way to increase the system capacity. Usman Sheikh proposed new network layouts called “Snowflake” and “Flower” tessellations, for 6-sector and 12-sector sites, respectively. These tessellations can be used as a basis for making a nominal network plan for sites with higher order sectorization. These tessellations would be helpful for simulation purposes. Through his work, he has also tried to highlight the importance of deploying “Adaptive MIMO Switching” in Long Term Evolution (LTE) system, the fourth generation of wireless networks.
In future, the fifth generation of wireless networks is expected to offer thousand times more capacity compared to LTE. The novel concept of “Single Path Multiple Access (SPMA)” given by Usman Sheikh is a revolutionary idea, and gives a possibility to increase the system capacity by a giant margin. SPMA can be considered as a right step towards 5G technology.
Usman Sheikh’s work is of high importance not only from mobile operator’s point of view; rather his contributions to the scientific community will also lead to better user (customer) experience. His work will definitely benefit the mankind in utilizing the limited resources in an optimum and efficient way
Assessment of Frequency Selective Surface for Improving Indoor Cellular Coverage
Modern houses use energy efficient building materials like metal shielding and energy saving windows to improve the thermal efficiency. Such energy efficient building mate-rials creates the barrier for outdoor-to-indoor RF signals propagation which is one of the challenging problems in the field of cellular communication. In order to solve such problem of outdoor-to-indoor propagation, an effective and efficient solution is very essential. Some existing techniques to solve the indoor coverage problem are the use of outdoor to indoor repeaters, pico-cell or dedicated indoor systems like distributed an-tenna system and radiating cables. However, such techniques are operator oriented; ex-pensive for single residential houses; possess additional network architecture design and maintenance complexity. One of the newer passive techniques which is operator inde-pendent and does not have additional network burden, is the use of frequency selective windows. Frequency selective windows consist of Frequency Selective Surface (FSS) etched on the metal coating of the energy saving windows, allowing cellular frequencies to pass through them while blocking the thermal radiation. FSS is the combination of either conducting patches or apertures in a thin conducting sheet arranged periodically in one or two dimensional array. FSS possess frequency selective behavior based on the element geometry. Patch type of FSS exhibits total reflection around resonant frequency whereas aperture type exhibits total transmission.
This thesis presents the modelling, simulation, fabrication and test measurements of the FSS that is transparent to GSM and UMTS frequency band. FSS with a double square loop aperture as a unit cell is selected for the analysis. The modelling and simu-lation of the FSS are carried out in the Computer Simulation Technology (CST) micro-wave studio, 2012 version. FSS prototype is fabricated using the commercial available aluminum foil. Furthermore, the FSS prototype is tested in the laboratory as well as in real-time networks. The real-time or field measurement is conducted in the real networks for all three operators of Finland, namely DNA, Elisa and TeliaSonera. The laboratory result shows the resonant frequency shift downwards by a factor of 1.22 comparing to the simulation results of freestanding FSS. The reason behind such frequency shift is well explained by the presence of a dielectric substrate in FSS prototype. On average, for all operators the field measurement result shows the transmission improvement of around 10 dB and 4.5 dB in GSM and UMTS band respectively over the plain aluminum foil. Although the field measurement result does not show much improvement compared to the laboratory measurement result, it still prevails the possibility of using FSS for indoor coverage improvement
Assessment of Frequency Selective Surface for Improving Indoor Cellular Coverage
Modern houses use energy efficient building materials like metal shielding and energy saving windows to improve the thermal efficiency. Such energy efficient building mate-rials creates the barrier for outdoor-to-indoor RF signals propagation which is one of the challenging problems in the field of cellular communication. In order to solve such problem of outdoor-to-indoor propagation, an effective and efficient solution is very essential. Some existing techniques to solve the indoor coverage problem are the use of outdoor to indoor repeaters, pico-cell or dedicated indoor systems like distributed an-tenna system and radiating cables. However, such techniques are operator oriented; ex-pensive for single residential houses; possess additional network architecture design and maintenance complexity. One of the newer passive techniques which is operator inde-pendent and does not have additional network burden, is the use of frequency selective windows. Frequency selective windows consist of Frequency Selective Surface (FSS) etched on the metal coating of the energy saving windows, allowing cellular frequencies to pass through them while blocking the thermal radiation. FSS is the combination of either conducting patches or apertures in a thin conducting sheet arranged periodically in one or two dimensional array. FSS possess frequency selective behavior based on the element geometry. Patch type of FSS exhibits total reflection around resonant frequency whereas aperture type exhibits total transmission.
This thesis presents the modelling, simulation, fabrication and test measurements of the FSS that is transparent to GSM and UMTS frequency band. FSS with a double square loop aperture as a unit cell is selected for the analysis. The modelling and simu-lation of the FSS are carried out in the Computer Simulation Technology (CST) micro-wave studio, 2012 version. FSS prototype is fabricated using the commercial available aluminum foil. Furthermore, the FSS prototype is tested in the laboratory as well as in real-time networks. The real-time or field measurement is conducted in the real networks for all three operators of Finland, namely DNA, Elisa and TeliaSonera. The laboratory result shows the resonant frequency shift downwards by a factor of 1.22 comparing to the simulation results of freestanding FSS. The reason behind such frequency shift is well explained by the presence of a dielectric substrate in FSS prototype. On average, for all operators the field measurement result shows the transmission improvement of around 10 dB and 4.5 dB in GSM and UMTS band respectively over the plain aluminum foil. Although the field measurement result does not show much improvement compared to the laboratory measurement result, it still prevails the possibility of using FSS for indoor coverage improvement
Linear space-time modulation in multiple-antenna channels
This thesis develops linear space–time modulation techniques for (multi-antenna) multi-input multi-output (MIMO) and multiple-input single-output (MISO) wireless channels. Transmission methods tailored for such channels have recently emerged in a number of current and upcoming standards, in particular in 3G and "beyond 3G" wireless systems. Here, these transmission concepts are approached primarily from a signal processing perspective.
The introduction part of the thesis describes the transmit diversity concepts included in the WCDMA and cdma2000 standards or standard discussions, as well as promising new transmission methods for MIMO and MISO channels, crucial for future high data-rate systems. A number of techniques developed herein have been adopted in the 3G standards, or are currently being proposed for such standards, with the target of improving data rates, signal quality, capacity or system flexibility.
The thesis adopts a model involving matrix-valued modulation alphabets, with different dimensions usually defined over space and time. The symbol matrix is formed as a linear combination of symbols, and the space-dimension is realized by using multiple transmit and receive antennas. Many of the transceiver concepts and modulation methods developed herein provide both spatial multiplexing gain and diversity gain. For example, full-diversity full-rate schemes are proposed where the symbol rate equals the number of transmit antennas. The modulation methods are developed for open-loop transmission. Moreover, the thesis proposes related closed-loop transmission methods, where space–time modulation is combined either with automatic retransmission or multiuser scheduling.reviewe
Self-Organized Coverage and Capacity Optimization for Cellular Mobile Networks
Die zur Erfüllung der zu erwartenden Steigerungen übertragener
Datenmengen notwendige größere Heterogenität und steigende Anzahl von
Zellen werden in der Zukunft zu einer deutlich höheren Komplexität bei
Planung und Optimierung von Funknetzen führen. Zusätzlich erfordern
räumliche und zeitliche Änderungen der Lastverteilung eine dynamische
Anpassung von Funkabdeckung und -kapazität
(Coverage-Capacity-Optimization, CCO). Aktuelle Planungs- und
Optimierungsverfahren sind hochgradig von menschlichem Einfluss abhängig,
was sie zeitaufwändig und teuer macht. Aus diesen Grnden treffen Ansätze
zur besseren Automatisierung des Netzwerkmanagements sowohl in der
Industrie, als auch der Forschung auf groes
Interesse.Selbstorganisationstechniken (SO) haben das Potential, viele der
aktuell durch Menschen gesteuerten Abläufe zu automatisieren. Ihnen wird
daher eine zentrale Rolle bei der Realisierung eines einfachen und
effizienten Netzwerkmanagements zugeschrieben. Die vorliegende Arbeit
befasst sich mit selbstorganisierter Optimierung von Abdeckung und
Übertragungskapazität in Funkzellennetzwerken. Der Parameter der Wahl
hierfür ist die Antennenneigung. Die zahlreichen vorhandenen Ansätze
hierfür befassen sich mit dem Einsatz heuristischer Algorithmen in der
Netzwerkplanung. Im Gegensatz dazu betrachtet diese Arbeit den verteilten
Einsatz entsprechender Optimierungsverfahren in den betreffenden
Netzwerkknoten. Durch diesen Ansatz können zentrale Fehlerquellen (Single
Point of Failure) und Skalierbarkeitsprobleme in den kommenden heterogenen
Netzwerken mit hoher Knotendichte vermieden werden.Diese Arbeit stellt
einen "Fuzzy Q-Learning (FQL)"-basierten Ansatz vor, ein einfaches
Maschinenlernverfahren mit einer effektiven Abstraktion kontinuierlicher
Eingabeparameter. Das CCO-Problem wird als Multi-Agenten-Lernproblem
modelliert, in dem jede Zelle versucht, ihre optimale Handlungsstrategie
(d.h. die optimale Anpassung der Antennenneigung) zu lernen. Die
entstehende Dynamik der Interaktion mehrerer Agenten macht die
Fragestellung interessant. Die Arbeit betrachtet verschiedene Aspekte des
Problems, wie beispielsweise den Unterschied zwischen egoistischen und
kooperativen Lernverfahren, verteiltem und zentralisiertem Lernen, sowie
die Auswirkungen einer gleichzeitigen Modifikation der Antennenneigung auf
verschiedenen Knoten und deren Effekt auf die Lerneffizienz.Die
Leistungsfähigkeit der betrachteten Verfahren wird mittels eine
LTE-Systemsimulators evaluiert. Dabei werden sowohl gleichmäßig verteilte
Zellen, als auch Zellen ungleicher Größe betrachtet. Die entwickelten
Ansätze werden mit bekannten Lösungen aus der Literatur verglichen. Die
Ergebnisse zeigen, dass die vorgeschlagenen Lösungen effektiv auf
Änderungen im Netzwerk und der Umgebung reagieren können. Zellen stellen
sich selbsttätig schnell auf Ausfälle und Inbetriebnahmen benachbarter
Systeme ein und passen ihre Antennenneigung geeignet an um die
Gesamtleistung des Netzes zu verbessern. Die vorgestellten Lernverfahren
erreichen eine bis zu 30 Prozent verbesserte Leistung als bereits bekannte
Ansätze. Die Verbesserungen steigen mit der Netzwerkgröße.The challenging task of cellular network planning and optimization will
become more and more complex because of the expected heterogeneity and
enormous number of cells required to meet the traffic demands of coming
years. Moreover, the spatio-temporal variations in the traffic patterns of
cellular networks require their coverage and capacity to be adapted
dynamically. The current network planning and optimization procedures are
highly manual, which makes them very time consuming and resource
inefficient. For these reasons, there is a strong interest in industry and
academics alike to enhance the degree of automation in network management.
Especially, the idea of Self-Organization (SO) is seen as the key to
simplified and efficient cellular network management by automating most of
the current manual procedures. In this thesis, we study the self-organized
coverage and capacity optimization of cellular mobile networks using
antenna tilt adaptations. Although, this problem is widely studied in
literature but most of the present work focuses on heuristic algorithms for
network planning tool automation. In our study we want to minimize this
reliance on these centralized tools and empower the network elements for
their own optimization. This way we can avoid the single point of failure
and scalability issues in the emerging heterogeneous and densely deployed
networks.In this thesis, we focus on Fuzzy Q-Learning (FQL), a machine
learning technique that provides a simple learning mechanism and an
effective abstraction level for continuous domain variables. We model the
coverage-capacity optimization as a multi-agent learning problem where each
cell is trying to learn its optimal action policy i.e. the antenna tilt
adjustments. The network dynamics and the behavior of multiple learning
agents makes it a highly interesting problem. We look into different
aspects of this problem like the effect of selfish learning vs. cooperative
learning, distributed vs. centralized learning as well as the effect of
simultaneous parallel antenna tilt adaptations by multiple agents and its
effect on the learning efficiency.We evaluate the performance of the
proposed learning schemes using a system level LTE simulator. We test our
schemes in regular hexagonal cell deployment as well as in irregular cell
deployment. We also compare our results to a relevant learning scheme from
literature. The results show that the proposed learning schemes can
effectively respond to the network and environmental dynamics in an
autonomous way. The cells can quickly respond to the cell outages and
deployments and can re-adjust their antenna tilts to improve the overall
network performance. Additionally the proposed learning schemes can achieve
up to 30 percent better performance than the available scheme from
literature and these gains increases with the increasing network size