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A study on the deployment and cooperative operation of ultra-dense networks
KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).ORCID iD: 0000-0002-7559-8911
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The traffic volume in wireless communication has grown dramatically in the last decade and is predicted to keep increasing in the future. In this thesis, we focus on the densification dimension for capacity improvement, which has been proved to be the most effective in the past. The current gain of network densification mainly comes from cell splitting, thereby serving more user equipments (UEs) simultaneously. This trend will decelerate as base station (BS) density gets closer to or even surpass UE density which forms an ultra-dense network (UDN). Thus, it is crucial to understand the behavior of ultra-densification for future network provisioning.

 

We start from comparing the effectiveness of densification with spectrum expansion and multi-antenna systems. Our findings show that deploying more BSs provides a substantial gain in sparse network but the gain decreases progressively in a UDN. The diminishing gain appears in a UDN make us curious to know if there exists a terminal on the way of densification. Such uncertainty leads to the study on the asymptotic behavior of densification. We incorporate a sophisticated bounded dual-slope path loss model and practical UE densities in our analysis. By using stochastic geometry, we derive the expressions and prove the convergence of the coverage probability of a typical UE and network area spectral efficiency (ASE). Considering the large portion of dormant BSs in a UDN, it is an interesting question whether we can utilize these dormant BSs to improve system performance is an interesting question. To this end, we employ joint transmission (JT) techniques into a UDN. Two types of cooperation schemes are investigated: non-coherent JT and coherent JT depending on the availability of channel state information (CSI). Our results reveal that non-coherent JT is not beneficial in a UDN while coherent JT are able to increase UE spectral efficiency (SE) depending on the environmental parameters.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. , p. 41
Series
TRITA-ICT ; 03
National Category
Communication Systems
Research subject
Information and Communication Technology
Identifiers
URN: urn:nbn:se:kth:diva-199892ISBN: 978-91-7729-260-9 (print)OAI: oai:DiVA.org:kth-199892DiVA, id: diva2:1065947
Presentation
2017-02-17, Sal B, Electrum, Isafjordsgatan 26, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20170117

Available from: 2017-01-17 Created: 2017-01-17 Last updated: 2017-01-20Bibliographically approved
List of papers
1. Tradeoff between spectrum and densification for achieving target user throughput
Open this publication in new window or tab >>Tradeoff between spectrum and densification for achieving target user throughput
2015 (English)In: IEEE Vehicular Technology Conference, IEEE , 2015Conference paper, Published paper (Refereed)
Abstract [en]

Dense deployment which brings small base stations (BS) closer to mobile devices is considered as a promising solution to the booming traffic demand. Meanwhile, the utilization of new frequency bands and spectrum aggregation techniques provide more options for spectrum choice.Whether to increase BS density or to acquire more spectrum is a key strategic question for mobile operators. In this paper, we investigate the relationship between BS density and spectrum with regard to individual user throughput target. Our work takes into account load-dependent interference model and various traffic demands. Numerical results show that densification is more effective in sparse networks than in already dense networks. In sparse networks, doubling BS density results in almost twofold throughput increase. However, in dense networks where BSs outnumber users, more than 10 times of BS density is needed to double user throughput. Meanwhile, spectrum has a linear relationship with user throughput for a given BS density. The impact of traffic types is also discussed. Even with the same area throughput requirement, different combination of user density and individual traffic amount leads to different needs for BS density and spectrum.

Place, publisher, year, edition, pages
IEEE, 2015
Keyword
Densification, Individual user throughput, Spectrum, Frequency bands, Mobile devices, Individual traffic, Interference modeling, Linear relationships, Mobile operators, Numerical results, Spectrum Aggregation, Traffic demands, Throughput
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-175100 (URN)10.1109/VTCSpring.2015.7146138 (DOI)000371404700552 ()2-s2.0-84940399382 (Scopus ID)9781479980888 (ISBN)
Conference
81st IEEE Vehicular Technology Conference, VTC Spring 2015, 11 May 2015 through 14 May 2015
Note

QC 20151211

Available from: 2015-12-11 Created: 2015-10-09 Last updated: 2017-01-17Bibliographically approved
2. Technical rate of substitution of spectrum in future mobile broadband provisioning
Open this publication in new window or tab >>Technical rate of substitution of spectrum in future mobile broadband provisioning
2015 (English)In: 2015 IEEE International Symposium on Dynamic Spectrum Access Networks, DySPAN 2015, IEEE conference proceedings, 2015, p. 297-300Conference paper, Published paper (Refereed)
Abstract [en]

Dense deployment of base stations (BSs) and multi-antenna techniques are considered as key enablers for future mobile networks. Meanwhile, spectrum sharing techniques and utilization of higher frequency bands make more bandwidth available. An important question for future system design is which element is more effective than others. In this paper, we introduce the concept of technical rate of substitution (TRS) from microeconomics and study the TRS of spectrum in terms of BS density and antenna number per BS. Numerical results show that TRS becomes higher with increasing user data rate requirement, suggesting that spectrum is the most effective means of provisioning extremely fast mobile broadband.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2015
Keyword
densification, multi-antenna, Spectum, stochastic geometry
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-185918 (URN)10.1109/DySPAN.2015.7343923 (DOI)000380544200043 ()2-s2.0-84960327036 (Scopus ID)978-147997452-8 (ISBN)
Conference
IEEE International Symposium on Dynamic Spectrum Access Networks (DySPAN),Stockholm,Sept.29-Oct.2, 2015
Note

QC 20160429

Available from: 2016-04-28 Created: 2016-04-28 Last updated: 2017-01-17Bibliographically approved
3. On the Engineering Value of Spectrum in Dense Mobile Network Deployment Scenarios
Open this publication in new window or tab >>On the Engineering Value of Spectrum in Dense Mobile Network Deployment Scenarios
2015 (English)Conference paper, Published paper (Refereed)
Abstract [en]

the continuing growth in the mobile data traffic magnifies the challenges for the design and deployment of scalable high-capacity mobile networks that can meet the future demand at reasonable cost levels. In order to meet the future traffic demand, an operator should invest on both infrastructure, i.e. densification of base stations, and more radio spectrum. Knowing the effectiveness of each element is thus of utmost importance for minimizing the investment cost. In this paper, we study the economic substitutability between spectrum and densification. For this, we measure the engineering value of spectrum, which refers to the potential saving in the total cost of ownership (TCO) as result of acquiring additional spectrum resources. Two countries are considered to represent different market situations: India with dense population and high spectrum price and Sweden with moderate population density and low spectrum fee. Numerical results indicate that additional amount of spectrum substantially relieves the need for densifying radio base stations, particularly for providing high user data rate in dense India. Nonetheless, the engineering value of spectrum is low in India (i.e. spectrum acquisition has less cost benefit) under the high spectrum price of today, whereas spectrum is instrumental in lowering the total cost of ownership in Sweden. Our finding highlights the importance of affordable and sufficient spectrum resources for future mobile broadband provisioning.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2015
Series
IEEE International Symposium on Dynamic Spectrum Access Networks (DySPAN)
Keyword
economic value of spectrum, mobile broadband, MNO, Total Cost of ownership (TCO)
National Category
Telecommunications
Research subject
Information and Communication Technology
Identifiers
urn:nbn:se:kth:diva-185912 (URN)10.1109/DySPAN.2015.7343922 (DOI)000380544200042 ()2-s2.0-84960403130 (Scopus ID)
Conference
2015 IEEE International Symposium on Dynamic Spectrum Access Networks (DySPAN),29 Sep - 02 Oct 2015,Stockholm, Sweden
Projects
METIS-II project
Funder
Wireless@kth
Note

QC 20160429

Available from: 2016-04-28 Created: 2016-04-28 Last updated: 2017-05-10Bibliographically approved
4. On the Asymptotic Behavior of Ultra-Densificationunder a Bounded Dual-Slope Path Loss Model
Open this publication in new window or tab >>On the Asymptotic Behavior of Ultra-Densificationunder a Bounded Dual-Slope Path Loss Model
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this paper, we investigate the impact of networkdensification on the performance in terms of downlink signal-tointerference(SIR) coverage probability and network area spectralefficiency (ASE). A sophisticated bounded dual-slope path lossmodel and practical UE densities are incorporated in the analysis.By using stochastic geometry, we derive an integral expressionalong with closed-form bounds of the coverage probability andASE, validated by simulation results. Through these, we providethe asymptotic behavior of ultra-densification. The coverageprobability and ASE have non-zero convergence in asymptoticregions unless UE density goes to infinity (full load). Meanwhile,the effect of UE density on the coverage probability is analyzed.The coverage probability will suffer from decreasing with largeUE densities due to interference fall into the near-field, but it willkeep increasing with lower UE densites. Furthermore, we showthe performance is overestimated without applying the boundeddual-slope path loss model. Our study can give insights on efficientnetwork provisioning in the future.

Keyword
Network densification, bounded path loss model, dual-slope path loss model, stochastic geometry
National Category
Communication Systems
Research subject
Information and Communication Technology
Identifiers
urn:nbn:se:kth:diva-199887 (URN)
Note

QC 20170117

Available from: 2017-01-17 Created: 2017-01-17 Last updated: 2017-01-23Bibliographically approved
5. Cooperative Transmissions in Ultra-Dense Networks under a Bounded Dual-Slope Path Loss Model
Open this publication in new window or tab >>Cooperative Transmissions in Ultra-Dense Networks under a Bounded Dual-Slope Path Loss Model
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In an Ultra-dense network (UDN) where there aremore base stations (BSs) than active users, it is possible thatmany BSs are instantaneously left idle. Thus, how to utilizethese dormant BSs by means of cooperative transmission is aninteresting question. In this paper, we investigate the performanceof a UDN with two types of cooperation schemes: non-coherentjoint transmission (JT) without channel state information (CSI)and coherent JT with full CSI knowledge. We consider a boundeddual-slope path loss model to describe UDN environments wherea user has several BSs in the near-field and the rest in thefar-field. Numerical results show that non-coherent JT cannotimprove the user spectral efficiency (SE) due to the simultaneousincrement in signal and interference powers. For coherent JT, theachievable SE gain depends on the range of near-field, the relativedensities of BSs and users, and the CSI accuracy. Finally, weassess the energy efficiency (EE) of cooperation in UDN. Despitecosting extra energy consumption, cooperation can still improveEE under certain conditions.

Keyword
Ultra-dense networks, cooperative transmissions, bounded path loss model, multi-slope path loss model
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-199890 (URN)
Note

QC 20170117

Available from: 2017-01-17 Created: 2017-01-17 Last updated: 2017-01-23Bibliographically approved

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