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On the feasibility of blind dynamic TDD in ultra-dense wireless networks
KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.ORCID iD: 0000-0003-2948-1082
KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.ORCID iD: 0000-0001-7642-3067
2015 (English)In: IEEE Vehicular Technology Conference, IEEE , 2015Conference paper, Published paper (Refereed)
Abstract [en]

Abstract-Dynamic configuring of uplink and downlink switching point in time division duplex (TDD) systems is considered a promising solution to cope with the traffic variations caused by the burstiness of mobile broadband data. However, such dynamic TDD (D-TDD) requires fast inter-cell coordination which may be difficult to implement in ultra-densely deployed networks (UDNs). In order to explore the possibility of designing simplified UDN, we investigate the feasibility of uncoordinated and greedy TDD operation, namely blind D-TDD. It exploits the characteristics of UDN such as low average network utilization and similar transmit power for base stations (BS) and user equipment (UE). To reduce the impact of co- channel interference (CCI), the effect of beamsteering is also evaluated. Our results indicate that blind D-TDD outperforms traditional static TDD (S-TDD) when instantaneous traffic demands for uplink and downlink are highly asymmetric. Also, beamsteering exerts a significant influence on the feasibility of blind D-TDD.

Place, publisher, year, edition, pages
IEEE , 2015.
Keyword [en]
Blind, Dynamic TDD, Throughput, Ultra-dense network, Interference suppression, Mobile telecommunication systems, Cochannel interference (CCI), Dense network, Dense wireless networks, Inter-cell coordinations, Net work utilization, Switching points, Time-division duplex systems, Cochannel interference
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-175070DOI: 10.1109/VTCSpring.2015.7145967ISI: 000371404700381Scopus ID: 2-s2.0-84940434725ISBN: 9781479980888 (print)OAI: oai:DiVA.org:kth-175070DiVA: diva2:881410
Conference
81st IEEE Vehicular Technology Conference, VTC Spring 2015, 11 May 2015 through 14 May 2015
Note

QC 20151210

Available from: 2015-12-10 Created: 2015-10-09 Last updated: 2017-09-20Bibliographically approved
In thesis
1. On the Performance of Dynamic TDD in Ultra-Dense Wireless Access Networks
Open this publication in new window or tab >>On the Performance of Dynamic TDD in Ultra-Dense Wireless Access Networks
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The appetite for wireless high-data rate services is expected to continue for many years to come and drive the need for more capacity. Ultra-dense networks (UDNs) represent a paradigm shift where each base station (BS) serves only a few user equipments (UEs). By most accounts, most of the traffic will be generated indoor and operate in time-division duplex (TDD). This thesis considers dynamic TDD which has shown to perform well indoor for fluctuating traffic where the shorter communication range enables similar transmit powers to be used in uplink and downlink, but also generates potentially more harmful same-entity interference. Because of the sheer number of cells in UDN, the interference management needs to be both effective and scalable.

 

In the first part of the thesis, we compare static TDD with non-cooperative dynamic TDD and show that flexible time resource allocation is preferred for indoor UDNs. However, since it only provides a lower bound on performance, additional interference coordination is required. Unfortunately, existing schemes often consider either too few, too many, or simply the wrong interferers. We introduce a scheduling model that relates BS-to-BS interferences measured offline to individual BS activation probability taking into account traffic and propagation environment. Results show that the proposed scheme performs well when interference is high, and optimally when interference is low.

 

In the second part, we introduce cooperation to utilize the otherwise idle BSs and mitigate same- and other entity interference. Zero forcing (ZF) is employed in the downlink where not only downlink UEs but also uplink BSs are included in the precoding. Since downlink BSs do not know the information to be sent by uplink UEs beforehand, dummy symbols with zero power are transmitted. It shown that both uplink and downlink performance improves at low and medium load. Furthermore, it is possible to trade performance in the two directions at high load.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. 44 p.
Series
TRITA-ICT, 2017:22
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Information and Communication Technology
Identifiers
urn:nbn:se:kth:diva-214775 (URN)978-91-7729-522-8 (ISBN)
Presentation
2017-10-26, Ka-Sal C, Electrum, KTH Royal Institute of Technology, Kistagången 16, Kista, 13:00 (English)
Opponent
Supervisors
Note

QC 20170922

Available from: 2017-09-22 Created: 2017-09-20 Last updated: 2017-09-28Bibliographically approved

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