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Switched Multi-Radio Transmission Diversity for Non-Collocated Radio Accesses
2006 (English)In: 2006 IEEE 63RD VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-6, 2006, 167-171 p.Conference paper, Published paper (Refereed)
Abstract [en]

We evaluate the spectral efficiency gains observed through multi-radio transmission diversity (MRTD), whereby packets of data are jointly scheduled for downlink transmission over multiple independent radio accesses. We specifically address downlink switched MRTD employed across macro- and pico-cellular radio accesses with non-collocated base stations in a hierarchical cell structure. It is shown that while significant gains can be achieved via MRTD among collocated macro-cell (or pico-cell) base stations, tight cooperation across non-collocated macro- and pico-cell base stations is only beneficial for a small subset of possible geometries. The impact of CQI reporting delays is also investigated.

Place, publisher, year, edition, pages
2006. 167-171 p.
Series
IEEE VTS Vehicular Technology Conference Proceedings, ISSN 1090-3038
Keyword [en]
multi-radio transmission diversity, joint scheduling, radio access allocation, networks beyond 3G, Ambient Networks, generic link layer, multi-radio access
National Category
Telecommunications
Identifiers
URN: urn:nbn:se:kth:diva-123048ISI: 000259580100034ISBN: 978-0-7803-9391-2 (print)OAI: oai:DiVA.org:kth-123048DiVA: diva2:624347
Conference
63rd IEEE Vehicular Technology Conference, MAY 07-10, 2006, Melbourne, AUSTRALIA
Note

QC 20130531

Available from: 2013-05-31 Created: 2013-05-31 Last updated: 2016-04-05Bibliographically approved
In thesis
1. Study of Multi-Radio Transmission Diversity in Heterogeneous Access Networks
Open this publication in new window or tab >>Study of Multi-Radio Transmission Diversity in Heterogeneous Access Networks
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

With the advent of multi-radio access (MRA), an integration of differentradio access technologies (RATs) into a heterogeneous radio access network(RAN) becomes feasible. Such integration allows a user to be at any instantof time served by one or multiple radio accesses (RAs) concurrently, where anRA constitutes an independent radio resource, such as a carrier or a channel,implemented by a single RAT. It also allows a user´s service demands to bemapped onto the aggregated network resources in a transparent and efficientway. An approach for the realization of such multi-radio integrated environmentsis through a unifying generic link layer (GLL) that provides joint radiolink processing and enables communication between nodes and devices acrossdifferent radio accesses.Based on the requirements on multi-access, an architecture that supportsMRA is suggested and the functions of GLL that aims at integrating andutilising multiple RATs are defined. We explore the potential for performanceimprovements through novel extensions of the transmission diversityparadigm which builds on GLL functions that enable multi-radio access selection.Multi-radio transmission diversity (MRTD) is defined as the dynamicselection of radio access for the transmission of a user´s data and it can bethought of as consisting of a packet scheduler operating across multiple radiointerfaces. Different MRTD schemes may be envisaged through combinationsof access re-selection rate, transmission parallelism and transmission redundancy.The re-selection rate refers to the rate at which radio access selectionis performed. It may range from multiple IP packets to one single MACframe. Switched MRTD corresponds to an access selection scheme where auser transmits via one RA at a time, while parallel MRTD corresponds to ascheme where simultaneous transmissions over multiple RAs are scheduled.Finally, redundancy refers to the transmission of copies of the same data overmultiple RAs to increase the possibility of correct reception.The benefits of MRTD are investigated by simulation studies on two multiradiocase scenarios, based on generic RATs and on specific RATs respectively.In the RAT generic scenario, switched MRTD has been evaluated for networktopologies of collocated and non-collocated RAs consisting of macroand pico-cells. In the case of collocated RAs, spectral efficiency is increasedby exploiting diversity in multi-path fading while in non-collocated RAs, thespectral efficiency increase is due to diversity exploitation in both shadowingand multi-path fading. Simulation results show that switched MRTD is mostadvantageous when the RAs provide comparable throughputs. Furthermore,when combined with multi-radio ARQ, MRTD significantly reduces packetloss and packet transmission delays. This is also shown in the specific radioaccesssimulation scenario where a delay sensitive voice service is studied. Inaddition, switched MRTD provides comparable gains to parallel MRTD interms of average packet transmission delay and packet loss, while using lessradio resources. In all cases, it is concluded that maximum performance isconditioned on the reporting delays of the channel quality indicator (CQI).Reporting delays of CQI that are half the channel coherence time render sucha complex MRTD mechanism less effective.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. viii, 84 p.
Series
Trita-EE, ISSN 1653-5146 ; 2013:027
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-122723 (URN)978-91-7501-793-8 (ISBN)
Presentation
2013-06-11, Q17, Osquldasväg 6, KTH, Stockholm, 15:00 (English)
Opponent
Supervisors
Note

QC 20130531

Available from: 2013-05-31 Created: 2013-05-28 Last updated: 2013-09-09Bibliographically approved
2. Radio Resource Allocation and Utilization in Multiple Radio Access Networks
Open this publication in new window or tab >>Radio Resource Allocation and Utilization in Multiple Radio Access Networks
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Meeting in a sustainable way the demands of an unprecedented explosive growth in the number of connected devices and mobile data traffic, next-generation mobile networks are expected to make flexible use of spectrum and provide higher capacity by a denser deployment of radio access network infrastructure. In addition, the allocation and the utilisation of radio access resources should improve spectrum usage efficiency and keep energy consumption low, implying the capability to effectively exploit the denser deployment of radio accesses and the co-existence of radio accesses belonging to one or multiple radio access technologies. The term radio access (RA) is used to denote the radio resources associated with a frequency carrier that can be allocated to one or multiple users for their data transmissions.

In a network consisting of multiple radio accesses, improvements in spectral and energy efficiency can be achieved when either channel gains are increased or interference is eliminated or both. There are at least three possible approaches to improve performance, namely, (i) by opportunistically utilizing channel conditions of multiple radio accesses, (ii) by mitigating interference across and within radio accesses, and (iii) by redistributing traffic load among radio accesses. In this work, four different technical solutions for downlink transmissions have been studied and evaluated with respect to throughput, spectral efficiency and energy efficiency performance: (a) multi-access transmit diversity, which refers to the dynamic selection of multiple radio accesses for the transmission of a user’s data, (b) inter-cell interference coordination, which mitigates interference by dividing radio access bandwidth among neighbouring nodes, (c) power on/off of access nodes, which mitigates interference by switching off radio accesses of interfering neighbouring nodes, and (d) radio access load balancing, which effectively distributes load by associating users to radio accesses where the expected rate is higher. For the implementation of the technical solutions different algorithms have been devised and their performance have been evaluated for different user distribution scenarios and different heterogeneous multi-radio access networks deployments consisting of at least a tier of macro-cellular and/or a tier of pico-cells of different densities.

The technical solutions are combined into a framework for the allocation and utilisation of radio access resources in heterogeneous multi-radio access dense networks. The framework consists of two subsequent steps: (1) a step solving the multi-radio allocation problem which associates users with a single or multiple radio accesses in the network on the basis of the expected data rates, and (2) a step solving the multi-radio utilisation problem that determines which of the associated radio access(s) should be used at any time for the user data transmissions in the downlink on the basis of the expected instantaneous data rate. To solve the first problem, we employ the flexible spectrum access solution that performs load balancing by associating users to multiple radio accesses while keeping radio accesses without users switched off. For the second problem, we utilise different multi-radio transmit diversity schemes while taking into account different forms of static inter-cell interference coordination. The evaluation of our framework, which is performed by means of simulations, demonstrates significant performance improvements in terms of user throughput, cell-edge throughput, spectral efficiency and energy efficiency.

Abstract [sv]

För att på ett hållbart sätt uppfylla de krav som en explosiv framtida tillväxt i mobildatatrafik medför, förväntas att nästa generations radionät ger en högre nätkapacitet genom en tät utbyggnad av radionätinfrastruktur, och en effektiv användming av radioaccessresurser. Avhandlingen behandlar resursallokering och resursutnyttjande i radionät med flera olika radioaccesser tillhörande en eller flera olika tekniker. Radioaccesserna, som tilldelas radionätets användare kan användas parallellt eller sekvensiellt där bäraren med högst kvalitet används vid varje transmissionstillfälle. Med radioaccess avses här är en frekvensbärare som består av en eller flera radio resurser som kan tilldelas användare för deras dataöverföringar. Fyra olika tekniska lösningar har studerats och utvärderats med avseende på genomströmning, spektrumeffektivitet och energieffektivitet: (a) multi-diversitet, som gäller det dynamiska urvalet av flera radioaccesser för överföring av en användares data, (b) samordning av intercell-interferens, vilket minskar störningar genom att dela upp radiobandbredden bland grannoder, (c) slå på/av transmissionseffekt, vilket minskar störningar genom att stänga av radion i angränsande noder som stör, och (d) lastbalansering mellan radioaccesser, som effektivt fördelar lasten genom att associera användare till radioaccesser där förväntade genomströmningen är högst.

Dessa tekniska lösningar kombineras till ett ramverk för resursallokering och resursutnyttjande i multiradioaccessnät. Ramverket består av en tvåstegslösning till två på varandra följande problem: (i) ett resursallokeringsproblem, där användarna associeras till radioaccesser på grundval av de förväntade genomsnittliga genomströmningarna, och (ii) ett problem för resursutnyttjande, där användarna nyttjar radioaccesserna på grundval av de förväntade momentana genomströmningarna. För att lösa det första problemet, använder vi oss av en teknisk lösning som bygger på lastbalansering, där användare tilldelas en eller flera radioaccesser, samtidigt som radioaccesser utan användare stängs av. Det andra problemet löser vi genom att använda oss av olika former av multi-diversitet, samtidigt som vi tar hänsyn till samordningar av intercellinterferens. För genomförandet av de tekniska lösningarna har olika algoritmer tagits fram och deras prestanda har utvärderats för olika användarscenarier. Vi studerar installationer av heterogena multiradioaccessnät som består av åtminstone en grupp av makroceller och/eller picoceller av olika densitet. Utvärderingen har utförts med simuleringar som visar betydande prestandaförbättringar i form av datagenomströmning, cellkantsgenomströmning, spektrumeffektivitet och energieffektivitet.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. xii, 116 p.
Series
TRITA-EE, ISSN 1653-5146
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-184620 (URN)978-91-7595-874-3 (ISBN)
Public defence
2016-04-25, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 17:39 (English)
Opponent
Supervisors
Note

QC 20160404

Available from: 2016-04-05 Created: 2016-04-01 Last updated: 2016-04-05Bibliographically approved

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