112 research outputs found
IST-2000-30148 I-METRA: D3.1 Design, analysis and selection of suitable algorithms
This deliverable contains a description of the space-time coding algorithms to be simulated within the I-METRA project. Different families of algorithms have been selected and described in this document with the objective of evaluating their performance. One of the main objectives of the I-METRA project is to impact into the current standardisation efforts related to the introduction of Multiple Input Multiple Output (MIMO) configurations into the High Speed Downlink and Uplink Packet Access concepts of UMTS (HSDPA and HSUPA). This required a review of the current specifications for these systems and the analysis of the impact of the potential incorporation of the selected MIMO schemes.Preprin
IST-2000-30148 I-METRA: D4 Performance evaluation
This document considers the performance of multiantenna transmit/receive techniques in high-speed downlink and uplink packet access. The evaluation is done using both link and system level simulations by taking into account link adaptation and packet retransmissions. The document is based on the initial studies carried out in deliverables D3.1 and D3.2.Preprin
Link-to-System Interfaces for System Level Simulations Featuring Hybrid ARQ
Projecte de final de carrera fet en col.laboració amb Technische Universität München. Lehrstuhl für KommunikationsnetzeWithin the continuous evolution of wireless communications, new and ambitious
requirements are planned to be met by next generation of mobile communications. In
order to achieve those requirements, new technologies and mechanisms that work
well over broadband frequency, like OFDM and OFDMA, need to be investigated,
developed and tested in simulators.
New cellular systems designs are based on exploiting instantaneous channel
conditions, improving the system performance. Due to this, system level simulations
must support a Physical Layer (PHY) abstraction which accurately predicts the
instantaneous performance of the link layer.
In order to accomplish this, a new link-to-system (L2S) interface has been developed
and implemented in OpenWNS, a system level simulator for evaluation of OFDM
systems developed at RWTH, Aachen. This interface is mainly realized through a set
of mapping mechanisms, used to provide a BLER given a received coded block SINR.
Together with the theoretical study and evaluation of these mappings mechanisms,
this thesis will analyze and evaluate Hybrid Automatic Repeat Request mechanisms
(H-ARQ), and how these protocols can be implemented in system level simulators
working together with the L2S interface.
This thesis shows how the new L2S interface is more accurate than past approaches,
providing a gain of around 3 dB. Concerning H-ARQ protocols, the results show how
the use of these new techniques provides a considerable gain with respect to normal
ARQ or not using any such techniqu
Quality of service optimization of multimedia traffic in mobile networks
Mobile communication systems have continued to evolve beyond the currently deployed Third
Generation (3G) systems with the main goal of providing higher capacity. Systems beyond 3G
are expected to cater for a wide variety of services such as speech, data, image transmission,
video, as well as multimedia services consisting of a combination of these. With the air interface
being the bottleneck in mobile networks, recent enhancing technologies such as the High Speed
Downlink Packet Access (HSDPA), incorporate major changes to the radio access segment of
3G Universal Mobile Telecommunications System (UMTS). HSDPA introduces new features
such as fast link adaptation mechanisms, fast packet scheduling, and physical layer retransmissions
in the base stations, necessitating buffering of data at the air interface which presents a
bottleneck to end-to-end communication. Hence, in order to provide end-to-end Quality of
Service (QoS) guarantees to multimedia services in wireless networks such as HSDPA, efficient
buffer management schemes are required at the air interface.
The main objective of this thesis is to propose and evaluate solutions that will address the
QoS optimization of multimedia traffic at the radio link interface of HSDPA systems. In the
thesis, a novel queuing system known as the Time-Space Priority (TSP) scheme is proposed for
multimedia traffic QoS control. TSP provides customized preferential treatment to the constituent
flows in the multimedia traffic to suit their diverse QoS requirements. With TSP queuing, the
real-time component of the multimedia traffic, being delay sensitive and loss tolerant, is given
transmission priority; while the non-real-time component, being loss sensitive and delay tolerant,
enjoys space priority. Hence, based on the TSP queuing paradigm, new buffer managementalgorithms are designed for joint QoS control of the diverse components in a multimedia session
of the same HSDPA user. In the thesis, a TSP based buffer management algorithm known as the
Enhanced Time Space Priority (E-TSP) is proposed for HSDPA. E-TSP incorporates flow
control mechanisms to mitigate congestion in the air interface buffer of a user with multimedia
session comprising real-time and non-real-time flows. Thus, E-TSP is designed to provide
efficient network and radio resource utilization to improve end-to-end multimedia traffic
performance. In order to allow real-time optimization of the QoS control between the real-time
and non-real-time flows of the HSDPA multimedia session, another TSP based buffer management
algorithm known as the Dynamic Time Space Priority (D-TSP) is proposed. D-TSP
incorporates dynamic priority switching between the real-time and non-real-time flows. D-TSP
is designed to allow optimum QoS trade-off between the flows whilst still guaranteeing the
stringent real-time component’s QoS requirements. The thesis presents results of extensive
performance studies undertaken via analytical modelling and dynamic network-level HSDPA
simulations demonstrating the effectiveness of the proposed TSP queuing system and the TSP
based buffer management schemes
MBMS—IP Multicast/Broadcast in 3G Networks
In this article, the Multimedia Broadcast and Multicast Service (MBMS) as standardized in 3GPP is presented. With MBMS, multicast and broadcast capabilities are introduced into cellular networks. After an introduction into MBMS technology, MBMS radio bearer realizations are presented. Different MBMS bearer services like broadcast mode, enhanced broadcast mode and multicast mode are discussed. Streaming and download services over MBMS are presented and supported media codecs are listed. Service layer components as defined in Open Mobile Alliance (OMA) are introduced. For a Mobile TV use case capacity improvements achieved by MBMS are shown. Finally, evolution of MBMS as part of 3GPP standardization is presented
Estudio y optimización de los procedimientos de adaptación al enlace en HSDPA
[ES] La tecnologÃa HSDPA (High Speed Downlink Packet Access) es una evolución de UMTS creada con el
objetivo de aumentar la capacidad de transmisión en el enlace descendente. Su mejora se basa en la utilización de un
canal compartido de comunicación gestionado de forma eficiente desde la estación base (por medio de un packet
scheduler), la utilización de mecanismos de retransmisión y combinación de información avanzados (hybrid ARQ) y la
posibilidad de emplear modulaciones de alto orden (16QAM y 64QAM).
Las dos últimas caracterÃsticas nombradas serÃan inútiles sin unos buenos procedimientos de adaptación al enlace
(link adaptation) que ajustaran los parámetros de transmisión a la calidad del enlace radio.
La presente tesina aborda el estudio y optimización de los mecanismos de link adaptation en HSDPA. Para tratar el
problema se siguen dos estrategias. Por un lado, se estudia un link adaptation genérico con el fin de obtener conclusiones
fácilmente trasladables a sistemas particulares como HSDPA. Por otro lado, se aportan soluciones a problemas
especÃficos de HSDPA como los fallos del link adaptation con baja carga.[EN] HSDPA (High Speed Downlink Packet Access) technology is an evolved version of UMTS focused on the
improvement of the downlink capacity. HSDPA enhancement is based on the efficient management of a shared channel
done by the Node-B (employing a packet scheduler), the using of advanced retransmission and combination mechanisms
(hybrid ARQ) and the availability of high order modulations (16QAM and 64QAM).
The later characteristics would be worthless without good link adaptation procedures that adjust transmission
parameters according to the radiolink quality.
This thesis deals with the study and optimization of link adaptation mechanisms in HSDPA. Two strategies are
followed herein. First, a generic link adaptation is studied with the aim of reaching some general conclusions and
applying them to real systems as HSDPA. Besides, a more detailed study is done for HSDPA finding solutions for some
specific problems as link adaptation failures with low loadMartÃn-Sacristán GandÃa, D. (2007). Estudio y optimización de los procedimientos de adaptación al enlace en HSDPA. http://hdl.handle.net/10251/12494Archivo delegad
Resource Allocation in Ad Hoc Networks
Unlike the centralized network, the ad hoc network does not have any central administrations and energy is constrained, e.g. battery, so the resource allocation plays a
very important role in efficiently managing the limited energy in ad hoc networks.
This thesis focuses on the resource allocation in ad hoc networks and aims to develop
novel techniques that will improve the network performance from different network
layers, such as the physical layer, Medium Access Control (MAC) layer and network
layer.
This thesis examines the energy utilization in High Speed Downlink Packet Access (HSDPA) systems at the physical layer. Two resource allocation techniques,
known as channel adaptive HSDPA and two-group HSDPA, are developed to improve the performance of an ad hoc radio system through reducing the residual
energy, which in turn, should improve the data rate in HSDPA systems. The channel adaptive HSDPA removes the constraint on the number of channels used for
transmissions. The two-group allocation minimizes the residual energy in HSDPA
systems and therefore enhances the physical data rates in transmissions due to adaptive modulations. These proposed approaches provide better data rate than rates
achieved with the current HSDPA type of algorithm.
By considering both physical transmission power and data rates for defining the
cost function of the routing scheme, an energy-aware routing scheme is proposed
in order to find the routing path with the least energy consumption. By focusing
on the routing paths with low energy consumption, computational complexity is
significantly reduced. The data rate enhancement achieved by two-group resource
allocation further reduces the required amount of energy per bit for each path. With
a novel load balancing technique, the information bits can be allocated to each path
in such that a way the overall amount of energy consumed is minimized.
After loading bits to multiple routing paths, an end-to-end delay minimization
solution along a routing path is developed through studying MAC distributed coordination function (DCF) service time. Furthermore, the overhead effect and the
related throughput reduction are studied. In order to enhance the network throughput at the MAC layer, two MAC DCF-based adaptive payload allocation approaches
are developed through introducing Lagrange optimization and studying equal data
transmission period
Information Technology
The new millennium has been labeled as the century of the personal communications revolution or more specifically, the digital wireless communications revolution. The introduction of new multimedia services has created higher loads on available radio resources. These services can be presented in different levels of quality of service. Namely, the task of the radio resource manager is to provide these levels. Radio resources are scarce and need to be shared by many users. The sharing has to be carried out in an efficient way avoiding as much as possible any waste of resources.
The main contribution focus of this work is on radio resource management in opportunistic systems. In opportunistic communications dynamic rate and power allocation may be performed over the dimensions of time, frequency and space in a wireless system. In this work a number of these allocation schemes are proposed.
A downlink scheduler is introduced in this work that controls the activity of the users. The scheduler is a simple integral controller that controls the activity of users, increasing or decreasing it depending on the degree of proximity to a requested quality of service level. The scheduler is designed to be a best effort scheduler; that is, in the event the requested quality of service (QoS) cannot be attained, users are always guaranteed the basic QoS level provided by a proportional fair scheduler. In a proportional fair scheduler, the user with the best rate quality factor is selected. The rate quality here is the instantaneous achievable rate divided by the average throughput
Uplink scheduling is more challenging than its downlink counterpart due to signalling restrictions and additional constraints on resource allocations. For instance, in long term evolution systems, single carrier FDMA is to be utilized which requires the frequency domain resource allocation to be done in such a way that a user could only be allocated subsequent bands. We suggest for the uplink a scheduler that follows a heuristic approach in its decision. The scheduler is mainly based on the gradient algorithm that maximizes the gradient of a certain utility. The utility could be a function of any QoS. In addition, an optimal uplink scheduler for the same system is presented. This optimal scheduler is valid in theory only,
nevertheless, it provides a considerable benchmark for evaluation of performance for the heuristic scheduler as well as other algorithms of the same system.
A study is also made for the feedback information in a multi-carrier system. In a multi-carrier system, reporting the channel state information (CSI) of every subcarrier will result in huge overhead and consequent waste in bandwidth. In this work the subcarriers are grouped into subbands which are in turn grouped into blocks and a study is made to find the minimum amount of information for the adaptive modulation and coding (AMC) of the blocks.
The thesis also deals with admission control and proposes an opportunistic admission controller. The controller gradually integrates a new user requesting admission into the system. The system is probed to examine the effect of the new user on existing connections. The user is finally fully admitted if by the end of the probing, the quality of service (QoS) of existing connections did not drop below a certain threshold.
It is imperative to mention that the research work of this thesis is mainly focused on non-real time applications.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format
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