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A quantitative analysis of the throughput gains and the energy efficiency of multi-radio transmission diversity in dense access networks
KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.ORCID iD: 0000-0002-3704-1338
2015 (English)In: Telecommunications Systems, ISSN 1018-4864, E-ISSN 1572-9451, Vol. 59, no 1, 145-168 p.Article in journal (Refereed) Published
Abstract [en]

Densification of mobile network infrastructure and integration of multiple radio access technologies are important approaches to support the increasing demand for mobile data traffic and to reduce energy consumption in future 5G networks. In this paper, the benefits of multi-radio transmission diversity (MRTD) are investigated by modelling the radio access link throughputs as uniform- and Rayleigh-distributed random variables and evaluating different user schedulers and resource allocation strategies. We examine different strategies for the allocation of radio accesses to individual users ranging from independent utilisation of the radio accesses to MRTD-enabled schemes. The schemes are compared by considering the statistics of the system throughput and energy consumption of the mobile devices. It is shown that MRTD can increase the throughput significantly through two types of diversity gain: Firstly by having multiple radio accesses to choose from for each user and secondly by having more available users to choose from for each radio access. The increased throughput also helps to reduce the energy consumption per bit, but this comes at a cost of increased energy consumption for channel measurement and reporting.

Place, publisher, year, edition, pages
Springer, 2015. Vol. 59, no 1, 145-168 p.
Keyword [en]
Multi-radio access, Multi-radio transmit diversity, Dense radio access networks, Multi-radio access infrastructure, Multi-radio energy consumption
National Category
Telecommunications
Identifiers
URN: urn:nbn:se:kth:diva-165192DOI: 10.1007/s11235-014-9889-0ISI: 000351695800011Scopus ID: 2-s2.0-84919934490OAI: oai:DiVA.org:kth-165192DiVA: diva2:810964
Note

QC 20150508

Available from: 2015-05-08 Created: 2015-04-24 Last updated: 2017-12-04Bibliographically approved
In thesis
1. 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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