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Cooperative Transmissions in Ultra-Dense Networks under a Bounded Dual-Slope Path Loss Model
KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).ORCID iD: 0000-0002-7559-8911
KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).ORCID iD: 0000-0001-7642-3067
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(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.

Keywords [en]
Ultra-dense networks, cooperative transmissions, bounded path loss model, multi-slope path loss model
National Category
Communication Systems
Identifiers
URN: urn:nbn:se:kth:diva-199890OAI: oai:DiVA.org:kth-199890DiVA, id: diva2:1065938
Note

QC 20170117

Available from: 2017-01-17 Created: 2017-01-17 Last updated: 2017-01-23Bibliographically approved
In thesis
1. A study on the deployment and cooperative operation of ultra-dense networks
Open this publication in new window or tab >>A study on the deployment and cooperative operation of ultra-dense networks
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:nbn:se:kth:diva-199892 (URN)978-91-7729-260-9 (ISBN)
Presentation
2017-02-17, Sal B, Electrum, Isafjordsgatan 26, Stockholm, 13:00 (English)
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Note

QC 20170117

Available from: 2017-01-17 Created: 2017-01-17 Last updated: 2017-01-20Bibliographically approved

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