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Attainable User Throughput by Dense Wi-FiDeployment at 5 GHz
KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.ORCID iD: 0000-0001-7642-3067
KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.ORCID iD: 0000-0003-4986-6123
2013 (English)In: 2013 IEEE 24th International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), IEEE conference proceedings, 2013, 3418-3422 p.Conference paper (Refereed)
Abstract [en]

Most of currently deployed Wi-Fi networks use the IEEE 802.11b/g standard and operate in 2.4 GHz ISMband. As mobile traffic demand rapidly increases, significant Wi-Fi deployment in the still very lightly used 5 GHz band is anticipated. In combination with the recent PHY amendments, e.g., 802.11ac, such Wi-Fi in many settings emerges as a strong competitor to small cellular deployment. In this paper, we aim to quantify what total capacity and which data rates per user can be supported by high-density, the state-of-the-art 5 GHz Wi-Fi deployment. Unlike previous studies, we consider the effect of densification by explicitly modeling the different level of interference among access points for office-type scenarios with various internal wall losses. Although abundant spectrum availability at 5 GHz may compensate for system inefficiency caused by carrier sensing and contention, we find that there is a capacity limit. This capacity limit depends on propagation environments and is especially low in 'open' environments or environments with low wall losses. To operate at capacities above this limit, cellular systems with their more advanced interference mitigation techniques are required.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2013. 3418-3422 p.
Keyword [en]
Capacity limit, Carrier sensing, Cellular system, Interference mitigation, Propagation environment, Spectrum availability, Wi Fi networks, Wi-Fi deployment
National Category
Communication Systems
URN: urn:nbn:se:kth:diva-133326DOI: 10.1109/PIMRC.2013.6666739ISI: 000346481203094ScopusID: 2-s2.0-84893339325ISBN: 978-146736235-1OAI: diva2:660529
2013 IEEE 24th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications, PIMRC 2013; London; United Kingdom; 8 September 2013 through 11 September 2013
METIS, Mobile and wireless communications Enablers for Twenty-twenty (2020) Information Society
Wireless@kthEU, FP7, Seventh Framework Programme

QC 20140205

Available from: 2013-10-30 Created: 2013-10-30 Last updated: 2015-12-03Bibliographically approved
In thesis
1. Interference Coordination for Low-cost Indoor Wireless Systems in Shared Spectrum
Open this publication in new window or tab >>Interference Coordination for Low-cost Indoor Wireless Systems in Shared Spectrum
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Mobile broadband services have become a big success over the last several years. Innovative, smart handsets have caused explosive traffic growth which has led to a severe capacity shortage. Since the majority of traffic originates from indoor locations or hotspots, significant invest- ment in indoor wireless infrastructure is predicted in order to resolve the capacity problem. While existing public operators mainly focus on high-mobility wide-area services, non-traditional local access providers (LAPs) such as facility owners are more and more interested in high data rate indoor services for their employees or customers. An obstacle is that they do not have access to dedicated spectrum. One proposal is spectrum sharing between LAPs. In shared spectrum, interference management emerges as a key technical challenge, and this becomes more critical as indoor systems become increasingly dense.

This thesis concentrates on the interference management problem when spectrum is shared between high-density indoor wireless systems. There are two different design directions which require different system architectures. A Wi-Fi or femtocell system works in a fully uncoordinated manner without any inter-cell signaling. This allows high network scalability with cheap devices but leads to poor performance. Alter- natively, advanced interference coordination can be used. It certainly improves the performance; however, it usually requires expensive infras- tructure for real-time information exchange. A key question asked in this thesis is if the interference coordination gives sufficient economic gain to a LAP in terms of a total deployment cost. In order to answer this question, we first develop a conceptual framework to define and compare various levels of coordination. Then, we measure the re- quired number of access points (APs) at a given area capacity demand to estimate the economic gain.

The coordination decision problem for a LAP is divided into two. Firstly, the LAP needs to choose the right level of coordination within its own network. Secondly, it determines whether or not to cooperate with neighboring LAPs for coordinating interference across the net- works. Regarding the intra-network decision, the comparison ranges from uncoordinated CSMA/CA to ideal interference cancellation. We find the total deployment cost of the uncoordinated CSMA/CA network soars when an area capacity requirement exceeds a certain threshold. The performance gain of the ideal coordination does not pay off the cost of high-speed backhaul because walls effectively suppress interference. Therefore, the most viable approach in a typical indoor environment is using dynamic coordination schemes via existing backhauls, for example Ethernet or xDSL. As for the cooperation decision, our major finding is that non-cooperative spectrum sharing is feasible provided that the transmit power of the APs is properly regulated. Although cooperation with advanced inter-network coordination schemes brings about cost savings, it is not sufficient to overcome practical barriers to a cooperation agreement especially when the capacity demand is high.



Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. ix, 55 p.
TRITA-ICT-COS, ISSN 1653-6347 ; 1401
National Category
urn:nbn:se:kth:diva-144195 (URN)
Public defence
2014-05-09, Sal/Hall D, KTH-ICT, Isafjordsgatan 39, Kista, 14:00 (English)

QC 20140416

Available from: 2014-04-16 Created: 2014-04-14 Last updated: 2014-04-16Bibliographically approved

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Kang, Du HoSung, Ki WonZander, Jens
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