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Interference Coordination for Low-cost Indoor Wireless Systems 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.
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: urn:nbn:se:kth:diva-144195OAI: oai:DiVA.org:kth-144195DiVA: diva2:712210
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
List of papers
1. High capacity indoor and hotspot wireless systems in shared spectrum: A techno-economic analysis
Open this publication in new window or tab >>High capacity indoor and hotspot wireless systems in shared spectrum: A techno-economic analysis
2013 (English)In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 51, no 12, 102-109 p.Article in journal (Refereed) Published
Abstract [en]

Predictions for wireless and mobile Internet access suggest an exponential traffic increase, particularly in in-building environments. Non-traditional actors such as facility owners have a growing interest in deploying and operating their own indoor networks to fulfill the capacity demand. Such local operators will need spectrum sharing with neighboring networks because they are not likely to have their own dedicated spectrum. Management of internetwork interference then becomes a key issue for high capacity provision. Tight operator-wise cooperation provides superior performance, but at the expense of high infrastructure cost and business-related impairments. Limited coordination, on the other hand, causes harmful interference between operators, which in turn will require even denser networks. In this article, we propose a techno-economic analysis framework for investigating and comparing indoor operator strategies. We refine a traditional network cost model by introducing new inter-operator cost factors. Then we present a numerical example to demonstrate how the proposed framework can help us to compare different operator strategies. Finally, we suggest areas for future research.

Keyword
Operator strategy, Techno-Economic analysis framework, Shared spectrum, Indoor and hotspot deployment
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-104175 (URN)10.1109/MCOM.2013.6685764 (DOI)000328984300013 ()2-s2.0-84891621985 (Scopus ID)
Projects
The Mobile Broadband Project Phase 3: “More for less” (MBB++)
Funder
Wireless@kth
Note

QC 20140130. Updated from submitted to published.

Available from: 2012-10-29 Created: 2012-10-29 Last updated: 2017-12-07Bibliographically approved
2. Is Multicell Interference Coordination Worthwhile in Indoor Wireless Broadband Systems?
Open this publication in new window or tab >>Is Multicell Interference Coordination Worthwhile in Indoor Wireless Broadband Systems?
2012 (English)In: 2012 IEEE Global Communications Conference (GLOBECOM), IEEE , 2012, 4255-4260 p.Conference paper, Published paper (Refereed)
Abstract [en]

The rapid growth in demand for mobile and nomadic wireless access forces the use of more and more base stations (BSs). In such dense networks, various techniques for multicell interference coordination have been investigated. However, whether or not the interference coordination provides cost benefit compared with a loosely coordinated system is not obvious because the tight coordination at PHY-layer is likely to need an expensive high-speed backbone infrastructure. In this paper, we assess the worthiness of the tight interference coordination, referred to as coordination gain, in various indoor environments. We compare a hypothetical interference-free system as an upper bound with a simple interference-limited system opportunistically avoiding interference. The range of possible coordination gain is examined for various wall losses, path loss exponents, building shapes, and deployment density. Results show that substantial gain can be achieved in dense deployment at open areas with low path loss exponent, e.g., lightly furnished offices partitioned with soft walls. Nevertheless, the coordination gain significantly drops in the presence of marginal wall loss regardless of the other environmental factors.

Place, publisher, year, edition, pages
IEEE, 2012
Series
IEEE Global Telecommunications Conference (Globecom), ISSN 1930-529X
Keyword
Coordinated system, Environmental factors, Interference co-ordination, Interference-limited systems, Multi-cell interferences, Path loss exponent, Tight coordination, Wireless broadband
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-104179 (URN)10.1109/GLOCOM.2012.6503786 (DOI)000322375104104 ()2-s2.0-84877644166 (Scopus ID)978-146730921-9 (ISBN)
Conference
2012 IEEE Global Communications Conference, GLOBECOM 2012; Anaheim, CA; United States; 3 December 2012 through 7 December 2012
Projects
The Mobile Broadband Project Phase 3: “More for less” (MBB++)
Funder
ICT - The Next GenerationWireless@kth
Note

QC 20121029

Available from: 2012-10-29 Created: 2012-10-29 Last updated: 2014-04-16Bibliographically approved
3. Economic Hotspot Deployment Strategy: Denser Wi-Fior Coordinated Pico-cellular?
Open this publication in new window or tab >>Economic Hotspot Deployment Strategy: Denser Wi-Fior Coordinated Pico-cellular?
(English)Article in journal (Other academic) Submitted
Abstract [en]

Rapidly increasing traffic demand has forced indoor operators to deploy more and more Wi-Fi access points (APs). As AP density increases, inter-AP interference rises and may limit the capacity. Alternatively, cellular technologies using centralize dinterference coordination can provide the same capacity with the fewer number of APs at the price of more expensive equipment and installation cost. It is still not obvious at what demand level more sophisticated coordination pays off in terms of total system cost. To make this comparison, we assess the required AP density of three candidate systems for a given average demand: a Wi-Fi network, a conventional pico-cellular network with frequency planning, and an advanced system employing multi-cell joint processing. Numerical results show that dense Wi-Fi is the cheapest solution at a relatively low demand level. However, the AP density grows quickly at a critical demand level regardless of propagation conditions. Beyond this “Wi-Fi network limit”, the conventional pico-cellular network works and is cheaper than the joint processing in obstructed environments, e.g., furnished offices with walls. In line of sight condition such as stadiums, the joint processing becomes the most viable solution. The drawback is that extremely accurate channel state information at transmitters is needed.

Keyword
Wi-Fi densification, Interference coordination, Networked MIMO, Cost-capacity analysis, Network deploymen
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-104193 (URN)
Projects
The Mobile Broadband Project Phase 3: “More for less” (MBB++)
Funder
Wireless@kth
Note

NV 20160427

Available from: 2012-10-30 Created: 2012-10-30 Last updated: 2016-04-27Bibliographically approved
4. Attainable User Throughput by Dense Wi-FiDeployment at 5 GHz
Open this publication in new window or tab >>Attainable User Throughput by Dense Wi-FiDeployment at 5 GHz
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, Published 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
Keyword
Capacity limit, Carrier sensing, Cellular system, Interference mitigation, Propagation environment, Spectrum availability, Wi Fi networks, Wi-Fi deployment
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-133326 (URN)10.1109/PIMRC.2013.6666739 (DOI)000346481203094 ()2-s2.0-84893339325 (Scopus ID)978-146736235-1 (ISBN)
Conference
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
Projects
METIS, Mobile and wireless communications Enablers for Twenty-twenty (2020) Information Society
Funder
Wireless@kthEU, FP7, Seventh Framework Programme
Note

QC 20140205

Available from: 2013-10-30 Created: 2013-10-30 Last updated: 2015-12-03Bibliographically approved
5. The Validity of Unlicensed Spectrum for Future Local Highcapacity Services
Open this publication in new window or tab >>The Validity of Unlicensed Spectrum for Future Local Highcapacity Services
2013 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Unlicensed spectrum indeed initiates high-data rate wireless services with the combination of the great success of Wi-Fi technology. Interestingly, the local high data rate services are deployed and invested by non-traditional local actors, e.g., facility owners who have local fixed line infrastructure. Motivated by the great success of the Wi-Fi eco-system, there are growing interests from various regulatory initiatives on short-range indoor shared spectrum access to continuously foster new business innovations and local investment by new players. Despite of flexible spectrum access and almost no regulatory management overhead, it is still not so clear that the traditional unlicensed approach can work for future high-capacity services where require extremely denser deployment than today. In this paper, we aim to discuss the validity of the traditional unlicensed approach for the new local operators in an economic aspect. We evaluate the required deployment cost of conventional Wi-Fi system and compare it with a hypothetical cellular-like system with marginal regulatory coordination. We found that the traditional node-level etiquettes in unlicensed band work as system design constraints, leading to too conservative full distributed systems. Although the current unlicensed band approach is the lowest cost solution for relatively low-capacity services, it may not be work at future high-capacity provisioning. Thus, regulations need to be designed to allow more coordinated systems such as cellular-like technologies with certain inter-network regulation.

National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-133323 (URN)
Conference
24th European Regional Conference of the International Telecommunications Society, Florence, Italy, 20 - 23 October 2013
Projects
METIS, Mobile and wireless communications Enablers for Twenty-twenty (2020) Information Society
Funder
Wireless@kthEU, FP7, Seventh Framework Programme
Note

QC 20131128

Available from: 2013-10-30 Created: 2013-10-30 Last updated: 2014-04-16Bibliographically approved
6. Cost saving of DynamicCoordination using Best-effortBackhaul
Open this publication in new window or tab >>Cost saving of DynamicCoordination using Best-effortBackhaul
(English)Manuscript (preprint) (Other academic)
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-144194 (URN)
Note

QS 2014

Available from: 2014-04-14 Created: 2014-04-14 Last updated: 2014-04-16Bibliographically approved
7. Impact of asymmetric transmission power on operator competition in shared spectrum
Open this publication in new window or tab >>Impact of asymmetric transmission power on operator competition in shared spectrum
Show others...
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
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-104194 (URN)10.1109/Swe-CTW.2012.6376283 (DOI)2-s2.0-84871901073 (Scopus ID)978-146734763-1 (ISBN)
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
8. Competitive Network Power Control between Operators in Shared Spectrum
Open this publication in new window or tab >>Competitive Network Power Control between Operators in Shared Spectrum
(English)Manuscript (preprint) (Other academic)
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-144193 (URN)
Note

QS 2014

Available from: 2014-04-14 Created: 2014-04-14 Last updated: 2014-04-16Bibliographically approved
9. Operator competition with asymmetric strategies in shared spectrum
Open this publication in new window or tab >>Operator competition with asymmetric strategies in shared spectrum
2012 (English)In: 2012 IEEE Wireless Communications and Networking Conference, WCNC, IEEE Communications Society, 2012, 3183-3187 p.Conference paper, Published paper (Refereed)
Abstract [en]

As the regulation in wireless communications is moving toward a more flexible and efficient way of managing radio spectrum, it is envisaged that multiple small-sized cellular networks owned by different operators, e.g., facility owners or local operators, will operate in close vicinity on shared spectrum. In this environment, the networks may compete for their own utilities in a selfish manner with giving harmful internetwork interference to competitors. In practice, it is not so unusual that each operator has different fairness criteria or quality of service (QoS) strategies by employing distinct objective functions from competitors. Particularly, we in this paper study power control competition between two networks with the sum of rates (SR) and the minimum rate (MR) as their objective functions, respectively. By exploring Nash equilibria, we identify that the MR network benefits from the objective asymmetry thanks to the adaptability of its competitor, i.e., no constraint in the SR objective. On the other hand, the SR network takes disadvantage due to the fairness requirement reflected in the MR objective of its competitor. However, such asymmetry effects in competition becomes negligible with marginal network separation, e.g., indoor deployment in adjacent buildings. Additionally, we identify cooperation potential with the proper choice of a common objective function although the asymmetric objectives are difficult to be aligned.

Place, publisher, year, edition, pages
IEEE Communications Society, 2012
Series
IEEE Wireless Communications and Networking Conference. Proceedings, ISSN 1525-3511
Keyword
Adjacent buildings, Cellular network, Facility owners, Fairness criteria, Local operators, Nash equilibria, Objective functions, Radio spectra, Wireless communications, Quality of service, Telecommunication networks, Wireless telecommunication systems
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-101553 (URN)10.1109/WCNC.2012.6214355 (DOI)000324580703052 ()2-s2.0-84864349727 (Scopus ID)978-146730437-5 (ISBN)
Conference
IEEE Wireless Communications and Networking Conference, WCNC 2012; Paris; 1 April 2012 through 4 April 2012
Projects
The Mobile Broadband Project Phase 3: “More for less” (MBB++)
Funder
ICT - The Next GenerationWireless@kth
Note

QC 20120905

Available from: 2012-09-05 Created: 2012-08-30 Last updated: 2014-04-16Bibliographically approved
10. Cooperation and Competition between Wireless Networks in Shared Spectrum
Open this publication in new window or tab >>Cooperation and Competition between Wireless Networks in Shared Spectrum
2011 (English)In: 2011 IEEE 22nd International Symposium On Personal Indoor And Mobile Radio Communications (PIMRC), New York: IEEE , 2011, 284-288 p.Conference paper, Published paper (Refereed)
Abstract [en]

As the regulation in wireless communications is moving toward a more flexible and efficient way of managing radio spectrum, it is envisaged that multiple small-sized cellular networks owned by different operators will operate in close vicinity on shared spectrum. This brings a new interference environment where a cell is interfered by not only base stations in own network but also those in other networks. These networks may compete for their own utilities in a selfish manner or cooperate in order to minimize the mutual interference. Since a cooperation between the networks requires a business-wise agreement or extra infrastructure cost, the operators have to identify how much they will benefit from the cooperation. In this paper, we compare the effects of competition and cooperation between the cellular networks. The competition and cooperation are modeled as a transmit power control in downlink. It is observed that the cooperation in an average sense gives better network utility. However, as the network size increases, the cooperation gain diminishes significantly. Furthermore, the marginal separation of network deployments, e.g., indoor deployments in adjacent buildings, can notably shrink the cooperation incentive.

Place, publisher, year, edition, pages
New York: IEEE, 2011
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-70458 (URN)10.1109/PIMRC.2011.6139967 (DOI)000300719700056 ()2-s2.0-84857516681 (Scopus ID)978-1-4577-1348-4 (ISBN)
Conference
22nd IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) Location: Toronto, Canada, Date: SEP 11-14, 2011
Projects
The Mobile Broadband Project Phase 3: “More for less” (MBB++)
Funder
Wireless@kth
Note

QC 20120201

Available from: 2012-01-30 Created: 2012-01-30 Last updated: 2016-04-26Bibliographically approved
11. Economic Spectrum Reuse between Inbuilding Wireless Access Networks
Open this publication in new window or tab >>Economic Spectrum Reuse between Inbuilding Wireless Access Networks
(English)Manuscript (preprint) (Other academic)
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-144192 (URN)
Note

QS 2014

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

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