Idle period shortening for TDD communications in large cells,”

Abstract-Time division duplex (TDD) technologies are necessary to deal with unpaired frequency bands and to allow low-complexity user equipments (UE) without duplexer in paired frequency bands. In TDD communications, a frame is divided into several sub-frames, each sub-frame being allocated to either uplink (UL) or downlink (DL). An idle period (IP) is required at a DL/UL switching point. It is usually dimensioned according to the cell radius and is identical for all UEs of the cell. In this paper, we propose a UE-specific IP duration, which increases the overall data rate of TDD communications for large cells. Numerical results show the potentially large benefit of the proposed dimensioning in term of spectral efficiency, which can be obtained without any specific signaling

Enabling Technologies for Ultra-Reliable and Low Latency Communications: From PHY and MAC Layer Perspectives

© 1998-2012 IEEE. Future 5th generation networks are expected to enable three key services-enhanced mobile broadband, massive machine type communications and ultra-reliable and low latency communications (URLLC). As per the 3rd generation partnership project URLLC requirements, it is expected that the reliability of one transmission of a 32 byte packet will be at least 99.999% and the latency will be at most 1 ms. This unprecedented level of reliability and latency will yield various new applications, such as smart grids, industrial automation and intelligent transport systems. In this survey we present potential future URLLC applications, and summarize the corresponding reliability and latency requirements. We provide a comprehensive discussion on physical (PHY) and medium access control (MAC) layer techniques that enable URLLC, addressing both licensed and unlicensed bands. This paper evaluates the relevant PHY and MAC techniques for their ability to improve the reliability and reduce the latency. We identify that enabling long-term evolution to coexist in the unlicensed spectrum is also a potential enabler of URLLC in the unlicensed band, and provide numerical evaluations. Lastly, this paper discusses the potential future research directions and challenges in achieving the URLLC requirements

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

4G Technology Features and Evolution towards IMT-Advanced

Kiinteiden- ja mobiilipalveluiden kysyntä kasvaa nopeasti ympäri maailmaa. Älykkäiden päätelaitteiden, kuten iPhone:n ja Nokia N900:n markkinoilletulo yhdistettynä näiden korkeaan markkinapenetraatioon ja korkealuokkaiseen käyttäjäkokemukseen lisäävät entisestään palveluiden kysyntää ja luovat tarpeen jatkuvalle innovoinnille langattomien teknologioiden alalla tavoitteena lisäkapasiteetin ja paremman palvelunlaadun tarjoaminen. Termi 4G (4th Generation) viittaa tuleviin neljännen sukupolven mobiileihin langattomiin palveluihin, jotka International Telecommunications Union:in Radiocommunication Sector (ITU-R) on määritellyt ja nimennyt International Mobile Telecommunications-Advanced (IMT-Advanced). Nämä ovat järjestelmiä, jotka pitävät sisällään IMT:n ne uudet ominaisuudet, jotka ylittävät IMT-2000:n vaatimukset. Long Term Evolution-Advanced (LTE-Advanced) ja IEEE 802.16m ovat IMT-A sertifiointiin lähetetyt kaksi pääasiallista kandidaattiteknologiaa. Tässä diplomityössä esitellään kolmannen sukupolven järjestelmien kehityspolku LTE:hen ja IEEE 802.16e-2005 asti. Lisäksi työssä esitetään LTE-Advanced:n ja IEEE 802.16m:n uudet vaatimukset ja ominaisuudet sekä vertaillaan näiden lähestymistapoja IMT-A vaatimusten täyttämiseksi. Lopuksi työssä luodaan katsaus LTE ja IEEE 802.16e-2005 (markkinointinimeltään Mobile WiMAX) -järjestelmien markkinatilanteeseen.The demand for affordable bandwidth in fixed and mobile services is growing rapidly around the world. The emergence of smart devices like the iPhone and Nokia N900, coupled with their high market penetration and superior user experience is behind this increased demand, inevitably driving the need for continued innovations in the wireless data technologies industry to provide more capacity and higher quality of service. The term "4G" meaning the 4th Generation of wireless technology describes mobile wireless services which have been defined by the ITU's Radiocommunication Sector (ITU-R) and titled International Mobile Telecommunications-Advanced (IMT-Advanced). These are mobile systems that include the new capabilities of IMT that go beyond those of IMT-2000. Long Term Evolution-Advanced (LTE-Advanced) and IEEE 802.16m are the two main candidate technologies submitted for IMT-Advanced certification. This thesis reviews the technology roadmap up to and including current 3G systems LTE from the 3rd Generation Partnership Project (3GPP) and IEEE 802.16e-2005 from the Institute of Electrical and Electronics Engineers (IEEE). Furthermore, new requirements and features for LTE-Advanced and IEEE 802.16m as well as a comparative approach towards IMT-Advanced certification are presented. Finally, the thesis concludes with a discussion on the market status and deployment strategies of LTE and IEEE 802.16e-2005, or Mobile WiMAX as it is being marketed

Spectrum Sharing Methods in Coexisting Wireless Networks

Radio spectrum, the fundamental basis for wireless communication, is a finite resource. The development of the expanding range of radio based devices and services in recent years makes the spectrum scarce and hence more costly under the paradigm of extensive regulation for licensing. However, with mature technologies and with their continuous improvements it becomes apparent that tight licensing might no longer be required for all wireless services. This is from where the concept of utilizing the unlicensed bands for wireless communication originates. As a promising step to reduce the substantial cost for radio spectrum, different wireless technology based networks are being deployed to operate in the same spectrum bands, particularly in the unlicensed bands, resulting in coexistence. However, uncoordinated coexistence often leads to cases where collocated wireless systems experience heavy mutual interference. Hence, the development of spectrum sharing rules to mitigate the interference among wireless systems is a significant challenge considering the uncoordinated, heterogeneous systems. The requirement of spectrum sharing rules is tremendously increasing on the one hand to fulfill the current and future demand for wireless communication by the users, and on the other hand, to utilize the spectrum efficiently. In this thesis, contributions are provided towards dynamic and cognitive spectrum sharing with focus on the medium access control (MAC) layer, for uncoordinated scenarios of homogeneous and heterogeneous wireless networks, in a micro scale level, highlighting the QoS support for the applications. This thesis proposes a generic and novel spectrum sharing method based on a hypothesis: The regular channel occupation by one system can support other systems to predict the spectrum opportunities reliably. These opportunities then can be utilized efficiently, resulting in a fair spectrum sharing as well as an improving aggregated performance compared to the case without having special treatment. The developed method, denoted as Regular Channel Access (RCA), is modeled for systems specified by the wireless local resp. metropolitan area network standards IEEE 802.11 resp. 802.16. In the modeling, both systems are explored according to their respective centrally controlled channel access mechanisms and the adapted models are evaluated through simulation and results analysis. The conceptual model of spectrum sharing based on the distributed channel access mechanism of the IEEE 802.11 system is provided as well. To make the RCA method adaptive, the following enabling techniques are developed and integrated in the design: a RSS-based (Received Signal Strength based) detection method for measuring the channel occupation, a pattern recognition based algorithm for system identification, statistical knowledge based estimation for traffic demand estimation and an inference engine for reconfiguration of resource allocation as a response to traffic dynamics. The advantage of the RCA method is demonstrated, in which each competing collocated system is configured to have a resource allocation based on the estimated traffic demand of the systems. The simulation and the analysis of the results show a significant improvement in aggregated throughput, mean delay and packet loss ratio, compared to the case where legacy wireless systems coexists. The results from adaptive RCA show its resilience characteristics in case of dynamic traffic. The maximum achievable throughput between collocated IEEE 802.11 systems applying RCA is provided by means of mathematical calculation. The results of this thesis provide the basis for the development of resource allocation methods for future wireless networks particularly emphasized to operate in current unlicensed bands and in future models of the Open Spectrum Alliance

Physical Layer Techniques for High Frequency Wireline Broadband Systems

This thesis collects contributions to wireline and wireless communication systems with an emphasis on multiuser and multicarrier physical layer technology. To deliver increased capacity, modern wireline access systems such as G.fast extend the signal bandwidth up from tens to hundreds of MHz. This ambitious development revealed a number of unforeseen hurdles such as the impact of impedance changes in various forms. Impedance changes have a strong effect on the performance of multi-user crosstalk mitigation techniques such as vectoring. The first part of the thesis presents papers covering the identification of one of these problems, a model describing why it occurs and a method to mitigate its effects, improving line stability for G.fast systems.A second part of the thesis deals with the effects of temperature changes on wireline channels. When a vectored (MIMO) wireline system is initialized, channel estimates need to be obtained. This thesis presents contributions on the feasibility of re-using channel coefficients to speed up the vectoring startup procedures, even after the correct coefficients have changed, e.g., due to temperature changes. We also present extensive measurement results showing the effects of temperature changes on copper channels using a temperature chamber and British cables. The last part of the thesis presents three papers on the convergence of physical layer technologies, more specifically the deployment of OFDM-based radio systems using twisted pairs in different ways. In one proposed scenario, the idea of using the access copper lines to deploy small cells inside users' homes is explored. The feasibility of the concept, the design of radio-heads and a practical scheme for crosstalk mitigation are presented in three contributions