466 research outputs found
Solunvaihdon suorituskyvyn arviointi 450 MHz ja 2600 MHz LTE-verkkojen välillä
This thesis evaluates handover performance between two different LTE frequency bands, band 31 and band 38, which are operated on 450 MHz and 2600 MHz frequencies, respectively. Mobile network operators are deploying multiple LTE frequency bands within same geographical areas in order to meet demand created by continuously growing mobile data usage. This creates additional challenges to network design, performance optimization and mobility management. Studied bands 31 and 38 differ on their propagation characteristics, as well as on their specified transmission capabilities. Bands also utilize different duplex methods, Frequency Division Duplex and Time Division Duplex. Performance evaluation was conducted in order to allow efficient usage of both bands.
Evaluation is based on information obtained from 3GPP specifications and laboratory measurements conducted with commercially available equipment. Current handover parameters of the studied network have been optimized for 450 MHz cells only, and utilize mostly default configurations introduced by device manufacturer. This configuration is evaluated and more suitable handover strategy is proposed. The proposed strategy is then compared with the default strategy through measurements conducted in laboratory environment.
Conducted measurements confirm that with proper handover parameter optimization, 2600 MHz frequency band can be prioritized over less capable 450 MHz band, which is likely to improve user perceived service quality. By utilizing collected results, associated network operator could improve offered services and gain savings in network equipment costs.Tässä diplomityössä tutkitaan solunvaihdon suorituskykyä kahden LTE-taajuuskaistan, 31 ja 38, välillä. Taajuuskaistaa 31 operoidaan 450 MHz taajuudella ja taajuuskaistaa 38 2600 MHz taajuudella. Vastatakseen jatkuvaan mobiilidatan käytön kasvuun, verkko-operaattorit ottavat käyttöön useita LTE-taajuuksia saman maantieteellisen alueen sisällä. Tämä luo ylimääräisiä haasteita verkkosuunniteluun, verkon suorituskyvyn optimointiin ja mobiliteetin hallintaan. Tutkitut taajuuskaistat eroavat niin etenemis- kuin tiedonsiirtokyvyiltään. Lisäksi taajuuskaistat käyttävät erilaisia duplex-muotoja.
Suorituskyvyn arvioinnin tarkoitus on mahdollistaa molempien taajuuskaistojen tehokas käyttö. Suorituskyvyn arviointi perustuu 3GPP:n spesifikaatioihin ja kaupallisella laitteistolla suoritettuihin laboratoriomittauksiin. Nykyisin käytössä olevat verkkoparametrit on optimoitu vain 450 MHz solujen käyttöön, jonka lisäksi suuri osa verkon konfiguraatioista hyödyntää valmistan käyttämiä oletusarvoja. Työssä verkon konfiguraatiolla suoritetaan arviointi, jonka perusteella esitetään suositeltu solunvaihdon strategia. Suositeltua strategiaa verrataan oletus-strategiaan laboratoriomittausten avulla.
Mittaustulokset näyttävät toteen, että oikeanlaisilla solunvaihdon parametreilla 2600 MHz taajuuskaistaa voidaan priorisoida heikomman 450 MHz taajuuskaistan yli. Monissa tilanteissa tämä parantaa käyttäjien verkosta saamaa palvelukokemusta. Hyödyntämällä tämän työn tuottamia tuloksia, verkko-operaattori voi parantaa tarjoamaansa palvelua ja saavuttaa säästöjä laitehankinnoissa
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Radio network management in cognitive LTE-Femtocell Systems
This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London.There is a strong uptake of femtocell deployment as small cell application
platforms in the upcoming LTE networks. In such two-tier networks of LTEfemtocell
base stations, a large portion of the assigned spectrum is used
sporadically leading to underutilisation of valuable frequency resources.
Novel spectrum access techniques are necessary to solve these current spectrum
inefficiency problems. Therefore, spectrum management solutions should have
the features to improve spectrum access in both temporal and spatial manner.
Cognitive Radio (CR) with the Dynamic Spectrum Access (DSA) is considered
to be the key technology in this research in order to increase the spectrum
efficiency. This is an effective solution to allow a group of Secondary Users
(SUs) to share the radio spectrum initially allocated to the Primary User (PUs) at
no interference.
The core aim of this thesis is to develop new cognitive LTE-femtocell systems
that offer a 4G vision, to facilitate the radio network management in order to
increase the network capacity and further improve spectrum access probabilities.
In this thesis, a new spectrum management model for cognitive radio networks is
considered to enable a seamless integration of multi-access technology with
existing networks. This involves the design of efficient resource allocation
algorithms that are able to respond to the rapid changes in the dynamic wireless
environment and primary users activities. Throughout this thesis a variety of
network upgraded functions are developed using application simulation
scenarios. Therefore, the proposed algorithms, mechanisms, methods, and system
models are not restricted in the considered networks, but rather have a wider
applicability to be used in other technologies.
This thesis mainly investigates three aspects of research issues relating to the
efficient management of cognitive networks: First, novel spectrum resource
management modules are proposed to maximise the spectrum access by rapidly
detecting the available transmission opportunities. Secondly, a developed pilot
power controlling algorithm is introduced to minimise the power consumption by
considering mobile position and application requirements. Also, there is
investigation on the impact of deploying different numbers of femtocell base
stations in LTE domain to identify the optimum cell size for future networks.
Finally, a novel call admission control mechanism for mobility management is
proposed to support seamless handover between LTE and femtocell domains.
This is performed by assigning high speed mobile users to the LTE system to
avoid unnecessary handovers.
The proposed solutions were examined by simulation and numerical analysis to
show the strength of cognitive femtocell deployment for the required
applications. The results show that the new system design based on cognitive
radio configuration enable an efficient resource management in terms of
spectrum allocation, adaptive pilot power control, and mobile handover. The
proposed framework and algorithms offer a novel spectrum management for self organised LTE-femtocell architecture.
Eventually, this research shows that certain architectures fulfilling spectrum
management requirements are implementable in practice and display good
performance in dynamic wireless environments which recommends the
consideration of CR systems in LTE and femtocell networks
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