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Impact of asymmetric transmission power on operator competition in shared spectrum
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.
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.
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2012 (English)In: Communication Technologies Workshop (Swe-CTW), 2012 Swedish, IEEE , 2012, 25-29 p.Conference paper, Published paper (Refereed)
Abstract [en]

To maintain affordable access for the rapidly increasing mobile traffic, base station deployment has to be tailored to hot-spot areas and primarily indoors where facility owners, e.g., shopping malls or hotels, mostly provide wireless service. Since such local access providers (LAPs) do not have access to exclusive spectrum, one proposed option is sharing spectrum with other nearby LAPs, e.g. unlicensed or secondary spectrum. Due to limited or no coordination between the LAPs, they selfishly access the spectrum, causing harmful interference to the neighboring networks. Especially by increasing transmission power, one operator may attempt to improve its own throughput at the expense of its neighbors. In this paper, we explore the impact of power asymmetry on competition between LAPs. We model the competition between two networks with different maximum power constraints as a network-wide power control game. By analyzing the pure Nash equilibria, we find that a lower power (LP) network becomes more aggressive to overcome the inter-network interference. Due to the aggressive behavior, sharing spectrum can out-perform fixed spectrum split even for the LP network, provided that the power asymmetry is below a certain limit. On the other hand, a higher power (HP) network is mainly affected by its own 'self-interference' so that it has little incentive to employ complicated inter-operator interference management schemes. In addition, we demonstrate that the power asymmetry limit strongly depends on the inter-network propagation conditions, e.g., inter-building distance or building penetration loss.

Place, publisher, year, edition, pages
IEEE , 2012. 25-29 p.
National Category
Communication Systems
Identifiers
URN: urn:nbn:se:kth:diva-104194DOI: 10.1109/Swe-CTW.2012.6376283Scopus ID: 2-s2.0-84871901073ISBN: 978-146734763-1 (print)OAI: oai:DiVA.org:kth-104194DiVA: diva2:563375
Conference
2012 Swedish Communication Technologies Workshop, Swe-CTW 2012; Lund; 24 October 2012 through 26 October 2012
Projects
The Mobile Broadband Project Phase 3: “More for less” (MBB++)
Funder
ICT - The Next GenerationWireless@kth
Note

QC 20121030

Available from: 2012-10-30 Created: 2012-10-30 Last updated: 2016-04-21Bibliographically approved
In thesis
1. Cost Effective Interference Management in Ultra-dense Hotspot Mobile Broadband Systems
Open this publication in new window or tab >>Cost Effective Interference Management in Ultra-dense Hotspot Mobile Broadband Systems
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Rapid mobile data traffic growth is becoming in a reality and several forecasts expect that it will be continued in upcoming years. It is expected that significant indoor investment will be made not only by traditional operators but also by facility owners for their own purposes. A key challenge to such local network providers is provisioning ever-increasing mobile traffic demand at the current level of production cost per bit. A popular deployment strategy so far is deploying WLAN networks. While denser indoor deployment is foreseen, the interference from inside of a network as well as other neighboring operators can be a limiting factor for higher capacity. Tighter interference management will certainly provide higher efficiency in network and spectrum usage. Nevertheless, costs to allow fast information sharing among access points are necessary for advanced interference coordination. Moreover, managing interference across networks owned by different operators raises not only infrastructure cost but also the network interrelatedness which operators are typically reluctant for business independency. When taking into account the cost and barriers for interference coordination, it is still not so obvious that coordination in wireless broadband systems will be advantageous to operators.

In this thesis, we address the operator benefit of downlink interference coordination in two aspects: 1) multi-cell coordination with no interference from neighboring operators, and 2) inter-operator coordination in shared spectrum. In order to deal with interference and cost tradeoff analysis, we explicitly develop a techno-economic analysis framework and reform a traditional cost model. Numerical results indicate that the economic benefit of the multi-cell coordination significantly depends on propagation conditions and average user demand level. A self-deployed WLAN network can be the cheapest deployment option in closed areas up to certain average demand level. Over the demand level or in open areas, advanced joint processing schemes in a cellular domain may be a viable solution. The drawback is that it requires extremely accurate channel state information at transmitters for practical usage. When inter-operator interferences is present, asymmetric cellular networks will be likely to appear due to business independency and selfishly compete to access spectrum with no or little network-level coordination. A network designed for more fairness with higher transmission power will have more benefit against the other counterpart. Although asymmetric competition lets operators unfairly utilize spectrum, sharing spectrum with reasonable geographical separation can outperform over static coordination, i.e., traditional spectrum split. Tight cooperation to maximize a common objective can further offer the performance benefit to both involved partners. However, the cooperation gain quickly diminishes as network separation and size increases because self-interference becomes more dominant.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. viii, 55 p.
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-104100 (URN)
Presentation
2012-11-27, C1, Electrum 229, Isafjordsgatan 26, Kista, 15:00 (English)
Opponent
Supervisors
Projects
The Mobile Broadband Project Phase 3: “More for less” (MBB++)
Funder
ICT - The Next GenerationWireless@kth
Note

QC 20121031

Available from: 2012-10-31 Created: 2012-10-29 Last updated: 2013-11-28Bibliographically approved
2. 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.
Series
TRITA-ICT-COS, ISSN 1653-6347 ; 1401
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-144195 (URN)
Public defence
2014-05-09, Sal/Hall D, KTH-ICT, Isafjordsgatan 39, Kista, 14:00 (English)
Opponent
Supervisors
Note

QC 20140416

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

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