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  • 1.
    Ahmed, Ashraf
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Yang, Yanpeng
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Won Sung, Ki
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Markendahl, Jan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    On the Engineering Value of Spectrum in Dense Mobile Network Deployment Scenarios2015Conference paper (Refereed)
    Abstract [en]

    the continuing growth in the mobile data traffic magnifies the challenges for the design and deployment of scalable high-capacity mobile networks that can meet the future demand at reasonable cost levels. In order to meet the future traffic demand, an operator should invest on both infrastructure, i.e. densification of base stations, and more radio spectrum. Knowing the effectiveness of each element is thus of utmost importance for minimizing the investment cost. In this paper, we study the economic substitutability between spectrum and densification. For this, we measure the engineering value of spectrum, which refers to the potential saving in the total cost of ownership (TCO) as result of acquiring additional spectrum resources. Two countries are considered to represent different market situations: India with dense population and high spectrum price and Sweden with moderate population density and low spectrum fee. Numerical results indicate that additional amount of spectrum substantially relieves the need for densifying radio base stations, particularly for providing high user data rate in dense India. Nonetheless, the engineering value of spectrum is low in India (i.e. spectrum acquisition has less cost benefit) under the high spectrum price of today, whereas spectrum is instrumental in lowering the total cost of ownership in Sweden. Our finding highlights the importance of affordable and sufficient spectrum resources for future mobile broadband provisioning.

  • 2. Al-Saadeh, Osama
    et al.
    Sung, Ki Won
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    A performance comparison of in-band full duplex and dynamic TDD for 5G indoor wireless networks2017In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, article id 50Article in journal (Refereed)
    Abstract [en]

    In-band full duplex has emerged as a solution for high data rate and low access delay for 5G wireless networks after its feasibility has been demonstrated. However, the impact of the in-band full duplex on the system-level performance of multi-cell wireless networks has not been investigated thoroughly. In this paper, we conduct an extensive simulation study to investigate the performance of in-band full duplex for indoor 5G small cell wireless networks. Particularly, we compare the in-band full duplex with static and dynamic time division duplexing schemes which require much less hardware complexity. We examine the effects of beamforming and interference cancellation under various traffic demands and asymmetry situations in the performance comparison. Our objective is to identify under which condition and with which technology support the in-band full duplex becomes advantageous over the simpler duplexing schemes. Numerical results indicate that for highly utilized wireless networks, in-band full duplex should be combined with interference cancellation and beamforming in order to achieve a performance gain over traditional duplexing schemes. Only then in-band full duplex is considered to be advantageous at any number of active mobile stations in the network and any downlink to uplink traffic proportion. Our results also suggest that in order to achieve a performance gain with the in-band full duplex in both links, the transmit power of the access points and the mobile stations should be comparable.

  • 3.
    Celik, Haris
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Sung, Ki Won
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Efficacy of Successive Interference Cancellation in Dynamic TDD Cellular NetworksManuscript (preprint) (Other academic)
  • 4.
    Celik, Haris
    et al.
    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.
    Sung, Ki Won
    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.
    On the feasibility of blind dynamic TDD in ultra-dense wireless networks2015In: IEEE Vehicular Technology Conference, IEEE , 2015Conference 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.

  • 5.
    Celik, Haris
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Sung, Ki Won
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Success Probability of Successive Interference Cancellation in Random Wireless NetworksManuscript (preprint) (Other academic)
  • 6.
    Dahlberg, Christian
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Liu, Zhicheng
    KTH, School of Electrical Engineering (EES). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Pradini, Aidilla
    KTH, School of Electrical Engineering (EES). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Sung, Ki Won
    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.
    A Techno-Economic Framework of Spectrum Combining for Indoor Capacity Provisioning2013In: 2013 IEEE 24th International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), IEEE conference proceedings, 2013, p. 2759-2763Conference paper (Refereed)
    Abstract [en]

    Spectrum combining refers to utilizing multiple types of spectrum authorization options for a wireless network. The approach is considered as an essential ingredient of high-capacity provision in the coming years. This paper presents a techno-economic framework to analyze capacity and cost of different spectrum combining options. We focus on indoor environments where the traffic demand is expected to be extremely demanding. We describe various spectrum options such as licence-exempt, light licensing, and licensed shared access (LSA). Then, we compare various combinations of these options with increasing traffic demand over time. In terms of capacity provisioning, this framework is based on the idea that spectrum combining must be done at the right time, that is when the existing deployment can no longer satisfy capacity demand. For the cost analysis, most relevant cost drivers are included in a cost structure which becomes the backbone of this framework. The proposed framework can help network providers determine the most cost-effective spectrum acquisition strategy which can meet capacity demand in indoor environments.

  • 7.
    Gimenez, Jordi Joan
    et al.
    Univ Politecn Valencia, iTEAM Res Inst, E-46022 Valencia, Spain..
    Sung, Ki Won
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS.
    Gomez-Barquero, David
    Univ Politecn Valencia, iTEAM Res Inst, E-46022 Valencia, Spain..
    Semianalytical Approach to the PDF of SINR in HPHT and LPLT Single-Frequency Networks2018In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 67, no 5, p. 4173-4181Article in journal (Refereed)
    Abstract [en]

    Single-frequency networks (SFN) are widely adopted in terrestrial broadcast networks based on high-power high-tower (HPHT) deployments. The mobile broadcasting standard Evolved Multimedia Broadcast Multicast Service (eMBMS) has been enhanced in Release 14 to enable SFN operation with larger CP duration which may allow for the deployment of large area SFNs and even the combined operation between HPHT and low-power low-tower (LPLT) cellular stations. The knowledge of the signal-to-interference-plus-noise ratio (SINR) distribution over an SFN area may facilitate the selection of transmission parameters according to the network topology. This paper presents a semianalytical method for the calculation of the SINR distribution in SFNs with low computational complexity compared to Monte Carlo simulations. The method, which builds on previous work developed for cellular communications, is applied to HPHT+LPLT SFNs and evaluated against different transmission and network parameters.

  • 8.
    Hwang, Youngju
    et al.
    Yonsei University.
    Kim, Seong-Lyun
    Yonsei University.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Scenario making for assessment of secondary spectrum access2012In: IEEE wireless communications, ISSN 1536-1284, E-ISSN 1558-0687, Vol. 19, no 4, p. 25-31Article in journal (Refereed)
    Abstract [en]

    Secondary spectrum access, through which secondary users opportunistically access the underutilized radio spectrum, has emerged as a solution to cope with the perceived spectrum scarcity. The potential of secondary spectrum has therefore attracted industry players and regulators worldwide. To assess the real-life benefits of the secondary spectrum, it is crucial to estimate the amount of spectrum available for secondary use. This estimation requires a well defined set of models and parameters, which are collectively termed a scenario. In this article, we demonstrate the importance of scenario making in the quantitative assessment of secondary spectrum access. We first describe the elements that constitute a comprehensive secondary access scenario: a primary system and spectrum, a secondary system and usage, and the methods and context of spectrum sharing. Then we demonstrate how the assessment results of the spectrum availability differ depending on the scenario elements. We also illustrate the crucial aspects of a scenario in the business analysis, which, together with the technical assessment, is the input for the regulatory decision.

  • 9.
    Hwang, YoungJu
    et al.
    Yonsei University.
    Park, JiHong
    Yonsei University.
    Sung, Ki Won
    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.
    Kim, Seong-Lyun
    Yonsei University.
    On the throughput gain of device-to-device communications2015In: ICT Express, ISSN 2405-9595, Vol. 1, no 2, p. 67-70Article in journal (Refereed)
    Abstract [en]

    In an uplink underlaid device-to-device (D2D) cellular network, this paper considers its two aspects of throughput improvement. The two-fold gain comprises the throughput increase by offloading downlink cellular traffic to D2D communications, duplexing gain, and the increase by reusing uplink resources of D2D transmissions, capacity gain. Both impacts are investigated by exploiting stochastic geometry. On the basis of the analysis, a throughput optimal D2D operation guideline is provided for different network congestion environments.

  • 10.
    Kang, Du Ho
    et al.
    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.
    Han, Sang-Wook
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Sung, Ki Won
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Zander, Jens
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Competitive Network Power Control between Operators in Shared SpectrumManuscript (preprint) (Other academic)
  • 11.
    Kang, Du Ho
    et al.
    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.
    Sung, Ki Won
    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.
    Jens, Zander
    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.
    The Validity of Unlicensed Spectrum for Future Local Highcapacity Services2013Conference 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.

  • 12.
    Kang, Du Ho
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Attainable User Throughput by Dense Wi-FiDeployment at 5 GHz2013In: 2013 IEEE 24th International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), IEEE conference proceedings, 2013, p. 3418-3422Conference 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.

  • 13.
    Kang, Du Ho
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Cooperation and Competition between Wireless Networks in Shared Spectrum2011In: 2011 IEEE 22nd International Symposium On Personal Indoor And Mobile Radio Communications (PIMRC), New York: IEEE , 2011, p. 284-288Conference 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.

  • 14.
    Kang, Du Ho
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Cost and Feasibility Analysis of Self-deployed Cellular Networks2011In: 2011 IEEE 22nd International Symposium On Personal Indoor And Mobile Radio Communications (PIMRC), New York: IEEE , 2011, p. 248-252Conference paper (Refereed)
    Abstract [en]

    A self-deployed network is considered to be one of cost-efficient deployment solutions by skipping an expensive network planning process. However, it may result in the serious degradation of capacity or the infeasibility of coverage constraint due to the rise of interference although radio adaptation techniques are employed. Therefore, deployment decision makers, e.g., operators, need to identify when and where the self-deployed network is feasible and economical compared with the planned network. For this, we estimate the average network throughput of the self-deployed network subject to a coverage constraint and compare it with the planned network. Three distinct regions of self-deployment are identified where different deployment strategies are required: infeasible, cost-effective, and uneconomical. We evaluate how the regions alter according to different channel environments and make suggestions for economical deployment.

  • 15.
    Kang, Du Ho
    et al.
    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.
    Sung, Ki Won
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Zander, Jens
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Cost saving of DynamicCoordination using Best-effortBackhaulManuscript (preprint) (Other academic)
  • 16.
    Kang, Du Ho
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Economic Hotspot Deployment Strategy: Denser Wi-Fior Coordinated Pico-cellular?Article in journal (Other academic)
    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.

  • 17.
    Kang, Du Ho
    et al.
    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.
    Sung, Ki Won
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Zander, Jens
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Economic Spectrum Reuse between Inbuilding Wireless Access NetworksManuscript (preprint) (Other academic)
  • 18.
    Kang, Du Ho
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    High capacity indoor and hotspot wireless systems in shared spectrum: A techno-economic analysis2013In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 51, no 12, p. 102-109Article in journal (Refereed)
    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.

  • 19.
    Kang, Du Ho
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Is Multicell Interference Coordination Worthwhile in Indoor Wireless Broadband Systems?2012In: 2012 IEEE Global Communications Conference (GLOBECOM), IEEE , 2012, p. 4255-4260Conference 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.

  • 20.
    Kang, Du Ho
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Operator competition with asymmetric strategies in shared spectrum2012In: 2012 IEEE Wireless Communications and Networking Conference, WCNC, IEEE Communications Society, 2012, p. 3183-3187Conference 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.

  • 21.
    Kim, Donggu
    et al.
    Korea Adv Inst Sci & Technol, Sch Elect Engn, Daejeon 34141, South Korea..
    Yang, Yanpeng
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Sung, Ki Won
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Kang, Joonhyuk
    Korea Adv Inst Sci & Technol, Sch Elect Engn, Daejeon 34141, South Korea..
    Cooperation Strategies for Partly Wireless C-RAN2018In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 22, no 6, p. 1248-1251Article in journal (Refereed)
    Abstract [en]

    This letter presents a variant of cloud radio access network (C-RAN) architecture, which we term partly wireless C-RAN (PW-CRAN). It is characterized by extra radio nodes connected through the existing remote radio heads. Because of the newly connected nodes and the consequent additional delay, the operation of PW-CRAN requires different approaches compared with that of the typical C-RAN. Specifically, the effect of delayed channel state information on the suitability of network cooperation should be identified. To tackle this problem, we introduce two representative cooperation strategies and evaluate the performance with regard to the delay via simulations. Numerical results suggest that it is better to exclude the extra nodes from cooperation if they incur excess delay. Furthermore, whether the delay is deemed excessive depends on the interference environment. Hence, we provide quantified guidelines on the cooperation strategy of PW-CRAN.

  • 22.
    Kim, Jeemin
    et al.
    Yonsei Univ, Sch Elect & Elect Engn, Seoul 03722, South Korea..
    Park, Jihong
    Univ Oulu, Ctr Wireless Commun, Oulu 90014, Finland..
    Kim, Seunghwan
    Yonsei Univ, Sch Elect & Elect Engn, Seoul 03722, South Korea..
    Kim, Seong-Lyun
    Yonsei Univ, Sch Elect & Elect Engn, Seoul 03722, South Korea..
    Sung, Ki Won
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Center for Wireless Systems, Wireless@kth.
    Kim, Kwang Soon
    Yonsei Univ, Sch Elect & Elect Engn, Seoul 03722, South Korea..
    Millimeter-Wave Interference Avoidance via Building-Aware Associations2018In: IEEE Access, E-ISSN 2169-3536, Vol. 6, p. 10618-10634Article in journal (Refereed)
    Abstract [en]

    Signal occlusion by building blockages is a double-edged sword for the performance of millimeter-wave (mmW) communication networks. Buildings may dominantly attenuate the useful signals, especially when mmW base stations (BSs) are sparsely deployed compared with the building density. In the opposite BS deployment, buildings can block the undesired interference. To enjoy only the benefit, we propose a building-aware association scheme that adjusts the directional BS association bias of the user equipments (UEs), based on a given building density and the concentration of UE locations around the buildings. The association of each BS can thereby be biased: 1) toward the UEs located against buildings for avoiding interference to other UEs or 2) toward the UEs providing their maximum reference signal received powers. The proposed association scheme is optimized to maximize the downlink average data rate derived by stochastic geometry. Its effectiveness is validated by simulation using real building statistics.

  • 23.
    Lee, Chae Y.
    et al.
    Korea Advanced Institute of Science and Technology (KAIST).
    Sung, Ki Won
    Korea Advanced Institute of Science and Technology (KAIST).
    Call admission control for real time multimedia services with variable bit rate in WCDMA systems2004In: VTC2004-FALL: 2004 IEEE 60TH VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-7: WIRELESS TECHNOLOGIES FOR GLOBAL SECURITY, IEEE , 2004, Vol. 4, p. 2559-2563Conference paper (Refereed)
    Abstract [en]

    Call admission control for real time multimedia services with variable bit rate (VBR) is considered in this paper. In the WCDMA system, one of the most prevailing services will be real time multimedia in which the data rate changes dynamically. In this paper, we propose two call admission schemes that effectively reflect features of VBR multimedia services and well satisfy the objectives. The proposed schemes are based on the signal to interference ratio (SIR) of the system. Especially, they anticipate the fluctuation of SIR due to the data rate change of each multimedia service and make an admission decision based on prediction of future SIR rather than the current SIR value. The proposed schemes are compared with an admission policy whose admission decision depends only on the current SIR value.

  • 24. Lee, Chae Y.
    et al.
    Sung, Ki Won
    Dynamic Resource Allocation for CDMA-TDD Indoor Wireless Systems2003In: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677, Vol. 3, p. 921-931Article in journal (Refereed)
    Abstract [en]

    Future wireless communication systems are expected to provide a broad range of multimedia services that have a significant traffic asymmetry between uplink and downlink. The code division multiple access-time division duplex (CDMA-TDD) system is a promising solution to cope with the problem of traffic asymmetry. However, the TDD system is subject to inter-cell interference compared to frequency division duplex (FDD) system. Since both uplink and downlink share the same frequency in TDD, uplink and downlink may interfere each other especially when neighboring cells require different rates of traffic load. Thus, the resource allocation among cells is an important issue in TDD. In this paper, the resource allocation in the CDMA-TDD is formulated as a mixed integer programming (MIP) problem. A dynamic resource allocation algorithm (DRAA) is provided that effectively solves the traffic asymmetry problem. The MIP problem is also solved by a well-known branch and bound procedure. Both the crossed slot and non-crossed slot allocation are examined and compared to the DRAA. Computational result shows that proposed DRAA gives a good performance as the traffic asymmetry increases between the uplink and downlink. Copyright © 2003 John Wiley & Sons, Ltd.

  • 25.
    Lee, Chae Young
    et al.
    Korea Advanced Institute of Science and Technology (KAIST).
    Sung, Ki Won
    Korea Advanced Institute of Science and Technology (KAIST).
    Cell based QoS provisioning scheme for indoor wireless network2001In: IEEE 53rd Vehicular Technology Conference, VTC2001-Spring, 2001, Vol. 2, p. 1154-1158Conference paper (Refereed)
    Abstract [en]

    The rapid growth in the demand for wireless multimedia services makes the provision of quality of service (QoS) an important issue. It is more important in an indoor environment. One of the key requirements of QoS is to reduce the dropping probability of handoff calls. It can be reduced by a proper call admission control (CAC) algorithm. In this paper, we propose a call admission control scheme that is adequate to an indoor environment to resolve the requirement of the dropping probability. Simulation experiments are used to evaluate the performance of the proposed scheme

  • 26.
    Miao, Guowang
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Zander, Jens
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Sung, Ki Won
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Slimane, Slimane Ben
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Fundamentals of Mobile Data Networks2016Book (Other academic)
    Abstract [en]

    This unique text provides a comprehensive and systematic introduction to the theory and practice of mobile data networks. Covering basic design principles as well as analytical tools for network performance evaluation, and with a focus on system-level resource management, you will learn how state-of-the-art network design can enable you flexibly and efficiently to manage and trade-off various resources such as spectrum, energy, and infrastructure investments. Topics covered range from traditional elements such as medium access, cell deployment, capacity, handover, and interference management, to more recent cutting-edge topics such as heterogeneous networks, energy and cost-efficient network design, and a detailed introduction to LTE (4G). Numerous worked examples and exercises illustrate the key theoretical concepts and help you put your knowledge into practice, making this an essential resource whether you are a student, researcher, or practicing engineer.

  • 27.
    Mudesir, Abdurazak
    et al.
    Jacobs University Bremen.
    Bode, Mathias
    Jacobs University Bremen.
    Sung, Ki Won
    The University of Edinburgh.
    Haas, Harald
    The University of Edinburgh.
    Analytical SIR for Self-Organizing Wireless Networks2009In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499Article in journal (Refereed)
    Abstract [en]

    The signal to interference ratio (SIR) in the presence of multipath fading, shadowing and path loss is a valuable parameter for studying the capacity of a wireless system. This paper presents a new generalized path loss equation that takes into account the large-scale path loss as well as the small-scale multipath fading. The probability density function (pdf) of the SIR for self-organising wireless networks with Nakagami-mchannel model is analytically derived using the new path loss equation. We chose the Nakagami-mchannel fading model because it encompasses a large class of fading channels. The results presented show good agreement between the analytical and Monte Carlo- based methods. Furthermore, the pdf of the signal to interference plus noise ratio (SINR) is provided as an extension to the SIR derivation. The analytical derivation of the pdf for a single interferer in this paper lays a solid foundation to calculate the statistics for multiple interferers.

  • 28.
    Obregon, Evanny Carol
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Sung, Ki Won
    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.
    Zander, Jens
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Is spectrum sharing in the radar bands commercially attractive?: -a regulatory and business overview2016In: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 27, no 3, p. 428-438Article in journal (Refereed)
    Abstract [en]

    The need to meet users' expectations in the 'mobile data avalanche' represents a significant challenge for mobile network operators. More spectrum is a natural way to meet these requirements in a cost and time-efficient way, but new, exclusively licenced spectrum is increasingly hard to come by. Instead, vertical spectrum sharing has been discussed as a potential solution for finding additional spectrum. In this paper, we focus on vertical spectrum sharing in the radar bands for providing short-range wireless access, for example, indoors and in hotspots that 'offload' traffic demand. We propose a methodology for analysing the technical, regulatory and business aspects of deploying large-scale wireless networks. Then, we identify the following criteria for achieving business success: spectrum availability, availability of low-cost end-user devices, system scalability in terms of number of concurrently used devices and finally the ability to guarantee a quality of service for the users. Our technical availability assessment has identified geo-location database as the necessary technical enabler and detect-and-avoid mechanism as an auxiliary enabler for improving sharing conditions. Moreover, licenced shared access was found to be the suitable regulatory framework to support the proposed sharing mechanism and regulatory policies in real-life implementation. Our business feasibility assessment concludes that there is enough spectrum available for indoor and hotspots communication in urban areas in the radar bands to make a large-scale system commercially viable. Service quality can be guaranteed, and there is a strong potential to construct low-cost devices. Uncertainties do, however, remain regarding the spectrum access cost.

  • 29.
    Obregon, Evanny
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Availability Assessment of Secondary Usage in Aeronautical Spectrum2013In: 2013 IEEE Wireless Communications and Networking Conference (WCNC), IEEE Communications Society, 2013, p. 4510-4515Conference paper (Refereed)
    Abstract [en]

    In this paper, we provide a quantitative assessment of the available spectrum for massive indoor broadband secondary access in the 960-1215 MHz band, primarily allocated to the distance measuring equipment (DME) systems. We employ a practical sharing scheme where the secondary users share the DME spectrum via geo-location database and spectrum sensing. Since the DME system performs a safety-of-life functionality, protection from harmful interference becomes extremely critical. A DME channel is considered available in a certain time and location if the secondary users, under the applied sharing scheme, are able to successfully access the channel without violating the primary protection criteria. We analyze the impact of the secondary system parameters and the potential uncertainties in the applied sharing mechanism on the availability in the DME band. Numerical results show that at least 30% of the total DME band (57 MHz out of 190 MHz) can be available for a dense low-power indoor secondary network, even if conservative primary system protection criteria and high levels of uncertainty are considered.

  • 30.
    Obregon, Evanny
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Is Spectrum Sharing in the Radar Bands Commercially Attractive?: A Regulatory and Business OverviewIn: Telecommunications Policy, ISSN 0308-5961, E-ISSN 1879-3258Article in journal (Other academic)
    Abstract [en]

    The need to meet users’ expectations in the ”mobile data avalanche” represents a significant challenge for mobile networks operators (MNOs). More spectrum is a natural way to meet these requirements in a cost and time-efficient way; but new, exclusively licensed, spectrum is increasingly hard to come by. Instead, vertical spectrum sharing has been discussed as a potential solution for finding additional spectrum for mobile communications. In this paper, we focus on vertical spectrum sharing in the radar bands for providing short-range wireless access, e.g. indoors and in ”hotspots” that ”offload” mobile traffic demand. We propose a methodology for dealing with the technical, regulatory and business aspects of deploying large-scale wireless networks. Moreover, we identify the following criteria for achieving business success: spectrum availability, availability of low-cost end user devices, system scalability in terms of number of concurrently used devices and finally, the ability to guarantee a quality of service for the users.

    Our technical availability assessment has identified geo-location database support as necessary technical enabler and detect-and-avoid mechanism as a beneficial technical enabler for improving sharing conditions. Therefore, we propose a sharing mechanism based on three components: a central spectrum manager witha geo-location database controlling the aggregate interference, a spectrum sensing mechanism and a fast feedback between the radars and the central spectrum manager. Moreover, Licensed Shared Access (LSA) was found to be the suitable regulatory framework to support the proposed sharing mechanism and regulatory policies in real-life implementation. Our business feasibility assessment concludes that there is enough spectrum available for indoor and hotspots communication in urban areas in the radar bandsto make a large scale system commercially viable. Service quality can be guaranteedand there is a strong potential to construct low-cost devices. Uncertainties do, however, remain regarding the spectrum access cost.

  • 31.
    Obregon, Evanny
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    On the Feasibility of Indoor BroadbandSecondary Access to the 960-1215 MHz Aeronautical Spectrum2013In: Transactions on Emerging Telecommunications Technologies, ISSN 2161-3915, Vol. 24, no 7-8, p. 724-733Article in journal (Refereed)
    Abstract [en]

    In this paper, we analyse the feasibility of indoor broadband service provisioning using secondary spectrum access to the 960–1215 MHz band, primarily allocated to the distance measuring equipment (DME) system for aeronautical navigation. We propose a practical secondary sharing scheme customised to the characteristics of the DME. Because the primary system performs a safety-of-life functionality, protection from harmful interference becomes extremely critical. The proposed scheme controls aggregate interference by imposing an individual interference threshold on the secondary users. We examine the feasibility of large scale secondary access in terms of the transmission probability of the secondary users that keeps the probability of harmful interference below a given limit. Uncertainties in the estimation of propagation loss and DME location affect the feasibility of the secondary access. Numerical results show that a large number of secondary users are able to operate in adjacent DME channels without harming the primary system even with limited accuracy on the estimation of the propagation loss.

  • 32.
    Obregon, Evanny
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    On the Sharing Opportunities for Ultra-Dense Networks in the Radar Bands2014In: 2014 IEEE International Symposium on Dynamic Spectrum Access Networks, DYSPAN 2014, IEEE Computer Society, 2014, p. 215-223Conference paper (Refereed)
    Abstract [en]

    Finding additional spectrum for indoor networks with very high capacity (ultra-dense networks, UDN) is a prime concern on the road to 5G wireless systems. Spectrum below or around 10 GHz has attractive propagation properties and previous work has indicated that vertical spectrum sharing between indoor users and outdoor wide-area services is feasible. In this paper, we focus on spectrum sharing between UDNs and radar systems. We propose and evaluate regulatory policies that improve sharing conditions/opportunities in areas with large demand (i.e. hot-spots and urban areas). We consider three regulatory policies: area power regulation, deployment location regulation and the combination of these. We address the scenario where secondary users can reliably exploit time and space domain sharing opportunities in the S- and Ku-Bands by means of geo-location databases and spectrum sensing. We evaluate these opportunities in terms of the required time-averaged separation distance between the radar system and the UDN that both protects the radar system as well as guarantees a minimum secondary transmission probability. Our results show that there are ample adjacent channel sharing opportunities for indoor usage in both the S- and Ku-Bands. In the Ku-Band, even outdoor hot-spot use is feasible with very relaxed restrictions. Co-channel usage in the S-band requires large separation distances that makes it practically unfeasible in cities with nearby radar sites. Overall, deployment location regulation seems to be the most effective means to limit interference to the radar system and improve sharing opportunities. 

  • 33.
    Obregon, Evanny
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Secondary Access to the Radar Spectrum Bands: Regulatory and Business Implications2013Conference paper (Refereed)
    Abstract [en]

    The large expected increase in the capacity requirements raises not only technical issues but also regulatory and business challenges. One of the key methods to increase the capacity of mobile networks in a cost efficient way is to find additional frequency spectrum. However, it is a difficult task since most of the spectrum is already allocated in long-term basis. Therefore, innovation in the technical and regulatory domain is needed to make additional spectrum available for mobile communications that not only improve spectrum utilization but also to make long-term investments feasible. Secondary spectrum access was proposed as a technical solution to improve spectrum utilization. However, uncertainties on the regulatory regime have been the main “show-stopper” for long-term investments.  This paper has devised techno-regulatory conditions for making large-scale secondary access to the "radar bands" an attractive business scenario from the MNO's perspective. Our numerical results showed that applying regulation on the deployment of secondary users can significantly improve sharing opportunities, especially in lower frequency bands (S-band) where the impact of interference aggregation is higher. We also identified Licensed Shared Access (LSA) as suitable authorization model for secondary access to the "radar bands" since it provides the level of reliability on the protection against harmful interference and it could also motivate long-term investments. Finally, establishing the right spectrum access cost or license fee for secondary access to the "radar bands" is crucial for achieving competitive edge over alternatives indoor solutions.

  • 34.
    Ozyagci, Ali
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    An empirical aggregate throughput model for dense WLANsManuscript (preprint) (Other academic)
    Abstract [en]

    Due to the popularity of WLANs based on the IEEE 802.11 standard, these WLANs are being deployed in close proximity of each other in urban office and residential environments. This dense deployment of WLANs, in combination with the complex indoor propagation environment created by walls, make the performance analysis of such a system of WLANs difficult. Existing WLAN throughput models cannot accurately represent the aggregate throughput performance of these systems. Performing a packet-level analysis of each system of WLANs would be accurate but costly in time and computational resources. In this work, we propose an empirical aggregate throughput model for a system of densely deployed WLANs based on a comprehensive simulation analysis of such WLANs using OPNET. Our proposed model can estimate the throughput performance of a system of WLANs with fairly good accuracy in a range of propagation environments, deployment densities, deployment and association types.

  • 35.
    Ozyagci, Ali
    et al.
    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, Radio Systems Laboratory (RS Lab).
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Association and deployment considerations in dense wireless LANs2014In: Vehicular Technology Conference (VTC Spring), 2014 IEEE 79th, IEEE conference proceedings, 2014Conference paper (Refereed)
    Abstract [en]

    Wireless LANs based on the IEEE 802.11 standard are one of the most commonplace indoor wireless access solutions. As the ever growing demand for data consumption necessitates higher rates and volumes, it is fairly common to observe more and more WLANs being deployed in close proximity to each other. As distances between WLAN installations diminish, the access points (APs) and stations (STAs) in these WLANs create a complex interference environment, which is also compounded by the indoor propagation environment. In this paper, we investigate the impact of two important parameters related to the deployment and operation of densely deployed wireless LANs on the aggregate throughput obtained by all the nodes in these WLANs. The first such operational parameter we investigate is access point and user station association; namely, whether STAs associate with a random ``strong'' AP or the AP from which they obtain the strongest received power. The second operational parameter we consider is the way in which APs are placed in the indoor environment; namely, whether APs are deployed randomly or in a manner to reduce inter-AP interference. In order to account for the complex node interactions in the MAC layer, which is crucial for accurate performance estimation, we perform packet-level simulations using OPNET. Our results show that the type of node association used in densely deployed WLANs has a critical impact on the aggregate throughput. In comparison, the type of AP deployment used is not nearly as significant; varying from moderate to no impact at all.

  • 36.
    Ozyagci, Ali
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Delay bound capacity analysis of dense WLANsManuscript (preprint) (Other academic)
    Abstract [en]

    Indoor WLAN deployments are becoming denser such that it is fairly common to observe several WLANs operating on the same channel. Increasing density creates more congestion and interference on these WLANs, which potentially has a significant impact on the delay and throughput performance of these WLANs. Therefore, we investigate the behavior of MAC layer delay and aggregate throughput in densely deployed WLANs in connection with different traffic arrival rates, propagation environments and deployment choices. The novelty of this work is that such a comprehensive study has not been performed before. We perform an extensive simulation study using OPNET by incorporating in our analysis a realistic MAC model and the impact of indoor propagation environment causing hidden nodes. We identify the relationship between delay and aggregate throughput in a system of densely deployed WLANs and propose guidelines for determining suitable WLAN deployment densities in different propagation environments.

  • 37.
    Shalmashi, Serveh
    et al.
    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.
    Björnson, Emil
    Kountouris, Marios
    Sung, Ki Won
    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, Radio Systems Laboratory (RS Lab).
    Debbah, Mérouane
    Energy Efficiency and Sum Rate Tradeoffs for Massive MIMO Systems with Underlaid Device-to-Device Communications2016In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499Article in journal (Refereed)
    Abstract [en]

    In this paper, we investigate the coexistence of two technologies that have been put forward for the fifth generation (5G) of cellular networks, namely, network-assisted device-to-device (D2D) communications and massive MIMO (multiple-input multiple-output). Potential benefits of both technologies are known individually, but the tradeoffs resulting from their coexistence have not been adequately addressed. To this end, we assume that D2D users reuse the downlink resources of cellular networks in an underlay fashion. In addition, multiple antennas at the BS are used in order to obtain precoding gains and simultaneously support multiple cellular users using multiuser or massive MIMO technique. Two metrics are considered, namely the average sum rate (ASR) and energy efficiency (EE). We derive tractable and directly computable expressions and study the tradeoffs between the ASR and EE as functions of the number of BS antennas, the number of cellular users and the density of D2D users within a given coverage area. Our results show that both the ASR and EE behave differently in scenarios with low and high density of D2D users, and that coexistence of underlay D2D communications and massive MIMO is mainly beneficial in low densities of D2D users.

  • 38.
    Shalmashi, Serveh
    et al.
    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.
    Björnson, Emil
    Linköping University, Linköping, Sweden.
    Kountouris, Marios
    Sung, Ki Won
    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, Radio Systems Laboratory (RS Lab).
    Debbah, Mérouane
    Energy Efficiency and Sum Rate when Massive MIMO meets Device-to-Device Communication2015In: Proc. of the IEEE International Conference on Communications (ICC), 2015, p. 627-632Conference paper (Refereed)
  • 39.
    Shi, Lei
    et al.
    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.
    Obregon, Evanny
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Boström, Jan
    CellTV - On the Benefit of TV Distribution Over Cellular Networks: A Case Study2014In: IEEE transactions on broadcasting, ISSN 0018-9316, E-ISSN 1557-9611, Vol. 60, no 1, p. 73-84Article in journal (Refereed)
    Abstract [en]

    As mobile IP-access is becoming the dominant technology for providing wireless services, the demand for more spectrum for this type of access is increasing rapidly. Since IP-access can be used for all types of services, instead of a plethora of dedicated, single-service systems, there is a significant potential to make spectrum use more efficient. In this paper, the feasibility and potential benefit of replacing the current terrestrial UHF TV broadcasting system with a mobile, cellular data (IP-) network are analyzed. In the cellular network, TV content would be provided as one of the services (CellTV). In the investigation, we consider typical Swedish rural and urban environments. We use different models for TV viewing patterns and cellular technologies as expected in the year 2020. Results of the quantitative analysis indicate that CellTV distribution can be beneficial if the TV consumption trend goes toward more specialized programming, more local contents, and more on-demand requests. Mobile cellular systems, with their flexible unicast capabilities, will be an ideal platform to provide these services. However, the results also demonstrate that CellTV is not a spectrum-efficient replacement for terrestrial TV broadcasting with current viewing patterns (i.e., a moderate number of channels with each a high numbers of viewers). In this case, it is doubtful whether the expected spectrum savings can motivate the necessary investments in upgrading cellular sites and developing advanced TV receiver required for the success of CellTV distribution.

  • 40.
    Shi, Lei
    et al.
    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.
    Sung, Ki Won
    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.
    Spectrum Requirement for Vehicle-to-Vehicle Communication for Traffic Safety2014In: Vehicular Technology Conference, 2014Conference paper (Refereed)
    Abstract [en]

    We investigate the amount of radio spectrum required for reliable vehicle-to-vehicle (V2V) communication for traffic safety. The basic feature of the traffic safety application is that it uses periodical broadcasts of status messages containing the location and velocity of transmitting vehicles. In our study we consider two dominant technologies for V2V communication, namely IEEE 802.11p and self-organizing time division multiple access (STDMA). We analyze the spectrum demand for a dense highway scenario with a stringent reliability requirement. The results indicate that more than 80 MHz bandwidth is needed to achieve 99% reliability in certain cases. This is in stark contrast to current regulatory decisions that dedicate only 10 MHz bandwidth in 5.9 GHz band for safety purposes in intelligent transportation system (ITS) in Europe and US. Our results suggests that a substantial change would be required in either spectrum allocation or in V2V communication system design to achieve the required traffic safety.

  • 41.
    Shi, Lei
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Controlling Aggregate Interference under Adjacent Channel Interference Constraint in TV White Space2012In: 2012 7th International Conference on Cognitive Radio Oriented Wireless Networks (CROWNCOM), IEEE , 2012, p. 1-6Conference paper (Refereed)
    Abstract [en]

    TV White space, where secondary systems can be deployed inside the TV coverage area and utilize the geographically unoccupied TV channels, is considered as a promising solution to relieve the spectrum shortage. To utilize this spectrum, the secondary users must ensure the protection of TV receptionfrom harmful interference on both co-channel and adjacent channels. In this paper, we propose an analytical approach to determining the permissible transmit power for short-range secondary users under aggregate adjacent channel interferenceconstraint in TV white space. This approach employs statistical interference modeling which considers random deployment of secondary users, antenna gain pattern, shadow fading, and the cumulative effect of interference from multiple adjacent channels. Numerical results show that the proposed scheme permits significantly higher transmit power than the existing deterministic method does, while at the same time, it keeps the required level of TV protection. Therefore, considerable potential for the shortrange secondary access to TV white space is expected with our approach.

  • 42. Shi, Lei
    et al.
    Sung, Ki Won
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Zander, Jens
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Future TV Content Delivery Over Cellular Networks From Urban to Rural Environments2015In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 14, no 11, p. 6177-6187Article in journal (Refereed)
    Abstract [en]

    With the increasing number of TV channels and the growing need for on-demand services, the traditional digital terrestrial television is becoming a less attractive way of distributing TV content. As an alternative, we discuss a converged platform in the UHF band for TV and mobile broadband provisioning based on LTE cellular technology and infrastructure, which is here referred to as CellTV. The requirement for CellTV is to provide seamless TV coverage from urban to rural environments and to minimize the spectrum requirement so that the leftover can be used for mobile services. We formulate an optimal spectrum allocation problem for CellTV to distribute different TV channels with different transmission modes. Each TV channel is delivered via either unicast links or the broadcast over single-frequency networks of different modulation orders according to the location-dependent viewing demand and the cellular infrastructure availability. Based on a case study of the Greater Stockholm region, we identify that CellTV only requires a small portion of the UHF band to deliver the TV content in urban areas, thus releasing a significant amount of spectra for mobile broadband services. Meanwhile, the spectrum requirement for CellTV is considerably higher in suburban and rural areas due to the transitions of transmission modes. We further generalize these findings to provide a guiding principle for CellTV deployment in mixed environments and to demonstrate the flexibility advantage of CellTV in adapting to the growing diversity of TV content.

  • 43.
    Shi, Lei
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    On the Permissible Transmit Power for Secondary User in TV White Spaces2012In: 2012 7th International Conference on Cognitive Radio Oriented Wireless Networks (CROWNCOM), IEEE , 2012, p. 13-17Conference paper (Refereed)
    Abstract [en]

    Secondary spectrum access to TV white spaces is considered as a promising solution to relieve the spectrum shortage. In Europe, SE43 working group in CEPT is leading the discussion on the technical requirements for exploiting TV white spaces through the recent ECC report 159. Its analytical approach for determining the maximum permissible power for the secondary user, however, overestimates the power level, and leads to significant violation of the interference limit for TV reception. In this letter, we address the problem by proposing a new approach for determining the secondary user transmit power based on the framework established in ECC report 159. Monte Carlo simulation shows that our method keeps the interference close to the target.

  • 44.
    Shi, Lei
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Opportunities and challenges for converged platform for audio-visual and data services in 470-790 MHz UHF broadcasting band2013In: 24th European Regional ITS Conference, Florence 2013, 2013Conference paper (Refereed)
    Abstract [en]

    In this paper, we will investigate the potential opportunities and challenges for deploying a converged platform in the UHF Broadcasting band (470-790 MHz) to replace the legacy systems and provide terrestrial audio-visual and dataservice. As recent development shows, both mobile broadband and terrestrial broadcasting (DTT) now overlap to offer audio-visual services to customers. Whereas DTT is designed only for audio-visual content, mobile broadband systems are converged all-IP platforms that may carry a multitude of services in unified and device-agnostic way. DTT used to be highly effective, when the task was to distribute a few TV channels to large audiences. However, for the rapidly increasing long-trail of niche television channels, each with diminishingly few viewers, DTT is no longer an efficient way of using the spectrum. Progressively re-farming of the UHF broadcasting band for more flexible and efficient use, is high on the list of discussion items in the upcoming World Radio Conference 2015, it is highly relevant to evaluate this option with a holistic view. This paper will present findings from the analysis of the inherent strengths and weaknesses of mobile and broadcasting industries in their new roles in the converged ecosystem. Detailed discussions are focused on identifying the possible benefits and threats from the perspectives of the broadcasters, mobile network operators, digital terrestrial network operators and the society as a whole. Overall we consider such a converged platform is a win-win solution for most of the stakeholders thanks to the increase in spectrum and network efficiency and flexibility improvement in the all-IP network. Nevertheless, there are still challenging issues to be addressed, such as the compensation and new business model for the digital terrestrial network operator and ensuring the quality of service for audio-visual content delivery in cellular network.

  • 45.
    Shi, Lei
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Opportunities and challenges forTV and Mobile broadband in 470-790 MHz (P8)2013Conference paper (Refereed)
  • 46.
    Shi, Lei
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Permissible Transmit Power for Secondary User in TV White Space2012Conference paper (Refereed)
    Abstract [en]

    Secondary spectrum access to TV white spaces is considered as a promising solution to relieve the spectrum shortage. In Europe, SE43 working group in CEPT is leading the discussion on the technical requirements for exploiting TV white spaces through the recent ECC report 159. Its analytical approach for determining the maximum permissible power for the secondary user, however, overestimates the power level, and leads to significant violation of the interference limit for TV reception. In this letter, we address the problem by proposing a new approach for determining the secondary user transmit power based on the framework established in ECC report 159. Monte Carlo simulation shows that our method keeps the interference lose to the target.

  • 47.
    Shi, Lei
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Secondary spectrum access in TV-bands with combined co-channel and adjacent channel interference constraints2012In: 2012 IEEE International Symposium on Dynamic Spectrum Access Networks, DYSPAN 2012, 2012, p. 452-460Conference paper (Refereed)
    Abstract [en]

    The potential of VHF/UHF band as a candidate for secondary spectrum access, so called ”TV white spaces”, has been intensively investigated in recent years. However, the impact of the accumulated interference from multiple secondary users on different adjacent channels has not been well studied thus far, let alone the effect of combined interference from both co-channel and adjacent channels. This paper presents a framework for assessing secondary spectrum reuse opportunities for portable and mobile devices that comply with geo-location database concepts. The opportunity is evaluated in terms of the maximal number of secondary users that can access the ”TV white space” simultaneously. Particular emphasis is given to the protection of TV receiver from harmful aggregate interference originated from not only the secondary users outside the TV coverage on the same channel but also those close to the TV receivers operating on different adjacent TV channels. An optimization problem is solved to maximize the number of secondary users admitted to the available TV channels at different locations. Through in-depth analysis of the interference characteristics of the optimal solution, it is identified that the cumulative effect of adjacent channel interferences has the dominant impact on TV reception, particularly for the case of secondary devices with limited transmit power. This suggests the possibility to achieve near-optimal exploitation of TV-bands for secondary reuse without explicit coordination of co-channel interference from the secondary users deployed over a wide geographical area.

  • 48.
    Shi, Lei
    et al.
    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.
    Sung, Ki Won
    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.
    Zander, Jens
    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.
    Spectrum Requirement for Cellular TV distribution in UHF Band from Urban to Rural Environment2014In: 2014 IEEE International Symposium on Dynamic Spectrum Access Networks (DYSPAN), IEEE Computer Society, 2014, p. 362-365Conference paper (Refereed)
    Abstract [en]

    An the number of TV-channels increase and the number of viewers per channel decreases, Terrestrial Broadcasting is becoming a less attractive way to distribute TV. In addition it does not represent a very efficient use of the UHF band (470790 MHz). In this paper we discuss an alternative, converged platform for TV and mobile broadband provisioning based on LTE cellular technology and infrastructure, here referred to as CelITV. The key feature of Cell-TV is the ability to switch between a unicast mode for small viewer populations and broadcast over LTE single frequency networks (SFN) for popular content. The main advantage is that the spectrum can flexibly be shared with LTE mobile data services, effectively freeing significant parts of the UHF spectrum for these purposes. Based on a case study of the greater Stockholm area, significant potential for spectrum saving is identified in urban areas where the need for spectrum is the largest. Meanwhile, only limited spectrum savings are observed in rural areas due to the large user populations in each cell and the long inter-site distance. As most of the TV channels are broadcasted in urban areas but unicasted in rural areas, this switch of transmission modes causes considerably high spectrum demand in suburban areas.

  • 49.
    Shokri-Ghadikolaei, Hossein
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering.
    Yang, Yanpeng
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Petrova, Marina
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Sung, Ki Won
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering.
    Fast and Reliable Initial Cell-search for mmWave Networks2018Conference paper (Refereed)
    Abstract [en]

    In millimeter-wave wireless networks, the use of narrow beams, required to compensate for the severe path-loss, complicates the cell-discovery and initial access. In this paper, we investigate the feasibility of random beam forming and enhanced exhaustive search for cell-discovery by analyzing the latency and detection failure probability in the control-plane and the user throughput in the data-plane. We show that, under realistic propagation model and antenna patterns, both approaches are suitable for 3GPP New Radio cellular networks. The performance gain, compared to the heavily used exhaustive and iterative search schemes, is more prominent in dense networks and large antenna regimes and can be further improved by optimizing the beam forming code-books.

  • 50. Song, Yujae
    et al.
    Sung, Ki Won
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Han, Youngnam
    Coexistence of Wi-Fi and Cellular With Listen-Before-Talk in Unlicensed Spectrum2016In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 20, no 1, p. 161-164Article in journal (Refereed)
    Abstract [en]

    In this letter, we analyze the coexistence performance of Wi-Fi and cellular networks with different listen-before-talk (LBT) procedures in the unlicensed spectrum. For this analysis, the behavior of a cellular base station is modeled as a Markov chain that is combined with Bianchi's Markov model depicting the behavior of a Wi-Fi access point. The proposed mathematical framework finds the optimal contention window size of cellular base stations, which maximizes the total throughput of both networks while satisfying the required throughput of each network. Numerical results show the validity of adjustment in the parameter of LBT.

12 1 - 50 of 94
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