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  • 301.
    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.
    Slimane, Ben
    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.
    Cooperative Device-to-Device Communications in the Downlink of Cellular Networks2014In: Proceedings of the IEEE Wireless Communications and Networking Conference (WCNC), 2014, p. 2265-2270Conference paper (Refereed)
    Abstract [en]

    We propose a cooperative device-to-device (D2D) communications framework in order to combat the problem of congestion in crowded communication environments. The idea is to allow a D2D transmitter to act as an in-band relay for a cellular link and at the same time transmit its own data by employing superposition coding in the downlink. Cooperation between the cellular link and D2D transmitter eases down the requirement on the interference. The main benefit of the proposed method is in increasing the number of connections per unit area with the same spectrum usage. It could also be beneficial to offload over-loaded cells. We formulate our problem to minimize the assigned power for cooperation while making sure the cellular user’s performance does not degrade. Our results show that cooperation possibilities and improvement in overall cell capacity increase with the number of cellular users within the cell as well as the cell size.

    Download full text (pdf)
    wcnc2014a
  • 302.
    Shalmashi, Serveh
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Slimane, Ben
    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 Secondary User Transmission Schemes in Relay-Assisted Cognitive Radio Networks2013In: 2013 IEEE 77th Vehicular Technology Conference (VTC Spring), IEEE , 2013, p. 6692665-Conference paper (Refereed)
    Abstract [en]

    We consider a cooperative cognitive radio network with one primary user and many secondary users. In each transmission frame, one secondary user is selected to act as a relay for the primary user and also transmits its own data. Three different schemes for the secondary user's transmission is studied, namely, time-splitting, superposition coding, and a combined scheme that takes advantages of both time-splitting and superposition coding schemes. We formulate the relay selection problem for each scheme with the objective of maximizing the secondary user's data rate while satisfying a pre-defined gain threshold for the primary user. This constraint provides an incentive for the primary user when allowing the secondary user access its licensed band. We obtain the optimal solution for this problem in each scheme, on which the relay selection is based on. Finally, we compare the performance of different schemes using Monte-Carlo simulations.

    Download full text (pdf)
    vtc2013
  • 303.
    Shalmashi, Serveh
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Slimane, Ben
    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.
    Performance analysis of relay-assisted cognitive radio systems with superposition coding2012In: Proceedings of the IEEE 23rd International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), IEEE , 2012, p. 1226-1231Conference paper (Refereed)
    Abstract [en]

    We study the problem of relay selection in a cooperative cognitive radio system in which a secondary transmitter can act as a relay for the primary transmitter in order to maximize the primary user's gain. Moreover, we take into account that the secondary users may have certain quality-of-service (QoS) requirements which need to be satisfied. In the cooperative scenario of a cognitive radio system, the primary user should have an incentive to allow the secondary user to transmit in its licensed band. At the same time, the secondary user should be able to transmit its own data with the required QoS in order to be willing to help the primary user's performance by relaying its data. Hence, we take into account both primary and secondary users' objectives. We use numerical methods in order to study how different parameters, such as assigned powers in the coding scheme, direct link reliability, and the number of secondary users affect the overall system performance. Our results show that the gain, which the primary user can achieve by cooperation, highly depends on the quality of its direct link as well as the secondary users' QoS requirements. Furthermore, the percentage of cooperation instances between secondary users and the primary user is dependent on the amount of power the secondary users allocate for relaying the primary's signal based on the direct link quality.

    Download full text (pdf)
    pimrc2012
  • 304.
    Shi, Lei
    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 for Secondary Access in TV White Space2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In recent years, the rapid growth in wireless data traffic has posed not only unique opportunities but also great challenges for the wireless industry. In order to meet the growing demand without excessive cost or energy consumption, one feasible option for the operators is to acquire more spectrum for wireless communication. Unlike the lengthy allocation process for exclusive spectrum licenses, secondary spectrum access is deemed as a flexible alternative to obtain additional spectrum at low cost. In particular, the VHF/UHF TV band, so called ’TV White Space’, is considered as the most promising candidate for secondary access thanks to its well defined primary usage and favorable propagation characteristic for building penetration and wide area coverage.

    Therefore, secondary access in the TV band has been extensively studied by both academic and industry. Most of the research have focused on the detection of ’spectrum holes’ with sensing technologies, while a few others have provided high level analysis of the potential of TV white space with simplistic secondary interference model for single secondary user. Only A limited number of studies have investigated aggregate interference from multiple secondary users, but even these studies have ignored the adjacent channel interference from secondary users close to the TV receivers.

    Thus, in this thesis we first concentrate on examining the effect of harmful interference on TV reception from short range devices transmitting on adjacent channels, and model the accumulative effect of multi-channel interferences observed in the measurement. Then the basic methodology for evaluating the potential of TV white space is developed in the second part of the thesis, where we propose a new analytical approach for regulating the secondary transmit power that significantly outperforms the existing method in the regulatory framework. Finally, we combine the aggregate interference model and the basic regulation methodology to extend the analysis from single user to multiple user case, first with only users transmitting on different adjacent TV channels and later also including users transmitting on co-channels.

    Our performance evaluation have shown that the effect of adjacent channel interference at close distance is far from negligible and the accumulative effect of multi-channel interferences has substantial impact on the scalability of a secondary system. In fact, the adjacent channel interference proves to be the primary limiting factor of the TV white space availability for low power short range systems. Nonetheless, because the proposed approach can adapt to varying environmental conditions and consequently utilize the spectrum reuse opportunity more efficiently than existing frameworks, we can still note considerable amount of TV white space available for short range secondary devices.

    Download full text (pdf)
    fulltext
  • 305.
    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.

  • 306.
    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.

    Download full text (pdf)
    fulltext
  • 307.
    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.

    Download full text (pdf)
    fulltext
  • 308.
    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.

  • 309.
    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.

  • 310.
    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)
  • 311.
    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.

    Download full text (pdf)
    fulltext
  • 312.
    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.

    Download full text (pdf)
    fulltext
  • 313.
    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.

  • 314. Shibata, Naotaka
    et al.
    Yamamoto, Koji
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Murata, Hidekazu
    Yoshida, Susumu
    Channel-Gain-Based Transmission Scheduling for Cooperative Relaying2010In: IEICE transactions on communications, ISSN 0916-8516, E-ISSN 1745-1345, Vol. E93B, no 3, p. 776-779Article in journal (Refereed)
    Abstract [en]

    A cooperative relaying. system with transmission scheduling is investigated Cooperative relaying, is composed of multiple links because the source;ends the data to more than one receiver, and the destination receive; multiple data transmitted by more than one transmitter Therefore. tithe source can transmit the data when the channel gains of the links are high, it is not clear which channel gains should he high in order to achieve high spectral efficiency In the present letter. the spectral efficiency of a cooperative relay me system is theoretically derived under the assumption that the source transmits the data only when the channel gains of links are above certain threshold values Numerical results reveal that a high spectral efficiency can be achieved by assuring a high channel gain for the link with the highest average received power among links to the destination.

  • 315.
    Smith, Mark
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Markendahl, Jan
    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.
    Andersson, Per
    Handelshögskolan, Stockholm School of Economics.
    Analysis of roles and position of mobile network operators in mobile payment infrastructure2010Conference paper (Refereed)
    Abstract [en]

    A number of different mobile payment solutions have been presented the last decade. The phone subscription with its security mechanisms are used for user identification and payments. This is the case for SMS based payment and ticketing systems that are getting more and more popular. However, there are other ways to implement a Trusted Element (TE) , where a SIM card architecture is only one. It can be in the mobile phone, as a separate integrated circuit, as an optional customer deployed plug-in device (e.g., microSD) or be running as an application on a server existing entirely as software.

    In this paper we analyze what roles and responsibilities different actors have in different types of mobile payments solutions. The main focus is on the implications for the mobile operator business. It turns out that new types of intermediary actors in most cases play an important role. Sometimes mobile operators are not even involved. The emergence of new payment together with other non-SIM card based TE solutions opens up for many different market scenarios for mobile payment services.

  • 316.
    Stabellini, Luca
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Energy-aware channel selection for cognitive wireless sensor networks2010In: Proceedings of the 2010 7th International Symposium on Wireless Communication Systems, ISWCS'10, 2010, p. 892-896Conference paper (Refereed)
    Abstract [en]

    Wireless sensor nodes operating in unlicensed bands can exploit frequency agility in order to mitigate, through dynamic spectrum access, the effects of interference induced by collocated networks. With this respect sensor devices can select the frequency band used for their communications in an opportunistic manner: this however requires spectrum sensing and consumes precious energy when more and more channels are sensed. In this paper we propose an algorithm allowing to limit the overhead introduced by spectrum sensing. We formulate a stochastic control problem which solution allows sensor nodes to decide whether it is better to stop the sensing procedure and transmit on a sensed channel or check a new frequency band hoping to find better interfering conditions. Simulation and experimental results show significant energy gains with respect to previously proposed channel selection algorithms that sense all the available channels.

  • 317.
    Stabellini, Luca
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Energy-aware exploitation of white spaces in the time domain for wireless sensor networks2010In: Proceedings of the 2010 7th International Symposium on Wireless Communication Systems, ISWCS'10, 2010, p. 981-985Conference paper (Refereed)
    Abstract [en]

    Low power communications of sensor nodes operating in unlicensed bands are easily corrupted by transmissions of collocated wireless terminals whose interference can induce packet losses and consequently increase energy consumption of sensor devices. Dynamic spectrum access mechanisms can mitigate these problems however the energy aware design of these access schemes is a challenging task. In this paper we consider an energy constrained system comprising two sensor nodes that avoid interference by exploiting spectrum opportunities in the time domain. Using the distributions of idle period duration obtained during a measurement campaign we show how it is possible to design the access scheme deployed by sensors in an energy efficient manner. We compare different spectrum sensing strategies, showing that per-packet sensing results in significant energy overhead. We further provide a way for dimensioning the size of transmitted packets. Simulation results show that our approach outperforms other access strategies and allows to reduce energy consumption of 20 to 90 percent depending on channel conditions.

  • 318.
    Stabellini, Luca
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Shi, Lei
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Al Rifai, Ahmad
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Espino, Juan
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Magoula, Veatriki
    KTH, School of Electrical Engineering (EES), Communication Theory.
    A New Probabilistic Approach for Adaptive Frequency Hopping2009In: 2009 IEEE 20th International Symposium on Personal, Indoor and Mobile Radio Communications, NEW YORK: IEEE , 2009, p. 2147-2151Conference paper (Other academic)
    Abstract [en]

    This paper proposes Utility Based Adaptive Frequency Hopping (UBAFH), an adaptive hopping technique implementing a new paradigm for frequency hopping systems. Traditional adaptive algorithms aim at identifying bad channels that are consequently removed from the hopset. UBAFH instead utilizes all the available frequencies but assigns different usage probabilities to different channels according to the experienced channel conditions. Opportune upper and lower limits are used in order to bound these usage probabilities and achieve a desired level of frequency diversity. We simulate the behavior of UBAFH over frequency selective fading channels and compare the achieved packet error rate and throughput with the ones of IEEE 802.15.1 and with the adaptive frequency hopping implementation proposed by IEEE 802.15.2 showing that UBAFH outperforms both approaches.

  • 319. Strandberg, Ove
    et al.
    Markendahl, Jan
    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.
    Pöyhönen, Petteri
    Connectivity and access provisioning with Ambient Networks2007In: 2007 IEEE 18TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOLS 1-9, 2007, p. 3903-3907Conference paper (Refereed)
    Abstract [en]

    In future wireless systems using Ambient Networks technology the users will be able to use a multitude of networks. Frequent roaming between networks will be key characteristic of mobile services and the terms “home” and “visited” networks will be common also at local and national level. The user will be able to access any network. Besides business agreements/roaming there are several functions that need coordination to provide connectivity and access everywhere and any time. The attachment of a user with an access link is one such key consideration. The actual access link attachment includes several steps including access advertisement, evaluation, selection and activation.

    In this paper the Ambient Networks concepts are briefly introduced. Business relations, business agreements and value networks are described for different scenarios. Selected results of performance evaluation illustrate how operators and users can exploit the flexibility and benefits in selection among different access options and especially look at access evaluation and selection decision effects.

  • 320. Sundström, P.
    et al.
    Taylor, A. S.
    Grufberg, K.
    Wirström, N.
    Solsona, Jordi
    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.
    Lundén, Marcus
    Inspirational bits: Towards a shared understanding of the digital material2011In: Conference on Human Factors in Computing Systems, 2011, p. 1561-1570Conference paper (Refereed)
    Abstract [en]

    In any design process, a medium's properties need to be considered. This is nothing new in design. Still we find that in HCI and interactive systems design the properties of a technology are often glossed over. That is, technologies are black-boxed without much thought given to how their distinctive properties open up design possibilities. In this paper we describe what we call inspirational bits as a way to become more familiar with the design material in HCI, the digital material. We describe inspirational bits as quick and dirty but fully working systems in both hardware and software built with the aim of exposing one or several of the dynamic properties of a digital material. We also show how they provide a means of sharing design knowledge across the members of a multi-disciplined design team.

  • 321. Sundström, P.
    et al.
    Vaara, E.
    Solsona, Jordi
    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.
    Wirström, N.
    Lundén, M.
    Laaksolhati, J.
    Waern, A.
    Höök, K.
    Experiential artifacts as a design method for somaesthetic service development2011In: RDURP'11 - Proceedings of the 2011 ACM Symposium on the Role of Design in UbiComp Research and Practice, 2011, p. 33-36Conference paper (Refereed)
    Abstract [en]

    How can deep understandings of material properties, limitations and possibilities be used concretely as a resource in the design of embodied experiences? How can material explorations spur and potentially direct, inspire, open up for new technologies and innovations? How can we identify, develop, and polish desirable core mechanics for embodied experiences and what kind of mobile services can be built with these experiences? In this position paper we describe our idea of experiential artifacts, and how we think these can help us open up the design space of the next generation of physically engaging mobile technologies.

  • 322.
    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.
    Apparatus and Method for Operating Broadcast Message in Broadband Wireless Communication System2006Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    Provided is an apparatus and method for transmitting neighbor base station information in a broadband wireless communication system. In the method, the priorities of subcells included in neighbor base stations that use at least one frequency allocation are determined. Subcells are selected among the subcells according to the determined priorities, information about which is to be transmitted to mobile stations located in a coverage area. Information about the selected subcells is transmitted to the mobile stations. Thus, the amount of resource for transmission of the neighbor base station information can be reduced. Therefore, the available resource of the downlink can be increased and the amount of a scan operation of the mobile station can be reduced.

  • 323.
    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.
    Method and apparatus for scanning signals of neighboring base station in broadband wireless communication system2006Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    An apparatus and method for scanning signals of a neighboring Base Station (BS) in a broadband wireless communication system is provided. In the broadband wireless communication system, a scanning method of a serving base station includes: receiving information on a frequency use status of a neighboring base station from an upper network entity; and after determining a recommended scan frequency by using the received information, transmitting a scanning response message including the recommended scan frequency.

  • 324.
    Sung, Ki Won
    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.
    Haas, Harald
    The University of Edinburgh.
    McLaughlin, Stephen
    The University of Edinburgh.
    A Semianalytical PDF of Downlink SINR for Femtocell Networks2010In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, p. 256370-Article in journal (Refereed)
    Abstract [en]

    This paper presents a derivation of the probability density function (PDF) of the signal-to-interference and noise ratio (SINR) for the downlink of a cell in multicellular networks. The mathematical model considers uncoordinated locations and transmission powers of base stations (BSs) which reflect accurately the deployment of randomly located femtocells in an indoor environment. The derivation is semianalytical, in that the PDF is obtained by analysis and can be easily calculated by employing standard numerical methods. Thus, it obviates the need for time-consuming simulation efforts. The derivation of the PDF takes into account practical propagation models including shadow fading. The effect of background noise is also considered. Numerical experiments are performed assuming various environments and deployment scenarios to examine the performance of femtocell networks. The results are compared with Monte Carlo simulations for verification purposes and show good agreement.

  • 325.
    Sung, Ki Won
    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.
    Kim, Seong-Lyun
    Yonsei University.
    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.
    Temporal Spectrum Sharing Based on Primary User Activity Prediction2010In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 9, no 12, p. 3848-3855Article in journal (Refereed)
    Abstract [en]

    In this paper we investigate the opportunistic spectrum access in temporal domain where a secondary user shares a radio channel with a primary user during the OFF period of the primary user. We consider practical ON/OFF traffic models whose bursty natures are not properly described by a Markovian assumption. An optimal strategy to determine the transmission power of the secondary user is proposed, which can be adapted to any source traffic model of the primary user. This strategy will maximize the spectrum utilization of the secondary user while keeping interference violations to the primary user below a threshold. Numerical results show that the transmission power of the secondary user depends on the probability distribution of the primary traffic as well as the elapsed time of the OFF period.

  • 326.
    Sung, Ki Won
    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.
    Lee, Chae-Young
    Korea Advanced Institute of Science and Technology.
    Ham, Seung-Yong
    Samsung Electronics.
    Kim, Ho-Dong
    Korea Advanced Institute of Science and Technology.
    Oh, Sang-Min
    Korea Advanced Institute of Science and Technology.
    Apparatus and Method for Allocating Segments in Broadband Wireless communication System2012Patent (Other (popular science, discussion, etc.))
  • 327.
    Sung, Ki Won
    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.
    Lee, Chae-Young
    Korea Advanced Institute of Science and Technology.
    Ham, Seung-Yong
    Samsung Electronics.
    Kim, Ho-Dong
    Korea Advanced Institute of Science and Technology.
    Oh, Sang-Min
    Korea Advanced Institute of Science and Technology.
    Apparatus and Method for IDcell Allocation in a Broadband Wireless Communication System2011Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    An apparatus and a method for allocating IDcells in a wireless communication system are provided, in which an initial IDcell allocation is performed by allocating entire sectors to elements of an N×M IDcell matrix, a sector pair with the highest proximity is selected for each IDcell in the initial allocation, an IDcell with a sector pair having the highest of the proximities of the selected sector pairs is determined as a target IDcell, one sector of the sector pair with the highest proximity for the target IDcell is selected as a target sector, a predetermined number of sectors are selected for each of the other IDcells except for the target IDcell, from among sectors to which the each of the other IDcells is allocated, and the IDcell of the target sector is swapped with the IDcell of a sector satisfying a first condition among the selected sectors.

  • 328.
    Sung, Ki Won
    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.
    Lee, Chae-Young
    Korea Advanced Institute of Science and Technology.
    Kim, Ho-Dong
    Korea Advanced Institute of Science and Technology.
    Oh, Sang-Min
    Korea Advanced Institute of Science and Technology.
    Apparatus and Method for Reallocating Segments in Broadband Wireless Communication System2006Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    An apparatus and a method for reallocating segments in a broadband wireless communication system are provided. An average density for all cells in system and an average minimal inter-cell distance R are computed. A circle is determined having a radius kR and a center at a corresponding cell by increasing a constant k until a density of the circle becomes less than or equal to the average density. A cluster is generated for each cell, which is composed of cells included in the determined circle. Accordingly, segment allocation capability can be improved while minimizing a width of segment reallocation.

  • 329.
    Sung, Ki Won
    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.
    Obregon, Evanny
    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 requirements of secondary access to 960-1215 MHz aeronautical spectrum2011In: 2011 IEEE International Symposium on Dynamic Spectrum Access Networks, DySPAN 2011, IEEE, 2011, p. 371-379Conference paper (Refereed)
    Abstract [en]

    In this paper, we investigate the spectrum sharing requirements of secondary access to 960-1215 MHz band which is primarily allocated to aeronautical usage. Primary system of interest is distance measuring equipments (DME) aiding navigation of airplanes. We consider a scenario where indoor femtocells share the spectrum as secondary users. For the protection of the primary system, each secondary user decides whether to transmit or not depending on an interference threshold established by a central network. We provide a simple mathematical framework for analyzing the aggregate interference generated by multiple secondary users spreading in a large area. Requirement for the secondary access is established in terms of the size of exclusion region depending on the density of secondary users. Numerical results suggest the use of adjacent DME channel is required for a dense deployment of the secondary users. We discuss the challenges and implementation issues of practical secondary access, and suggest the directions of further research.

  • 330.
    Sung, Ki Won
    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.
    Oh, Soo-Yeul
    Samsung Electronics.
    Apparatus and Method for Preamble Pseudo Noise Code Allocation in Broadband Wireless Communication System2007Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    An apparatus and a method for preamble pseudo noise code allocation in a broadband wireless communication system are provided. The method includes defining an inherent index for each FA, allocating a preamble PN index to base stations using a reference FA index, defining an inherent offset by each FA for remaining FA indexes, and shifting the preamble PN index allocated to the base stations using the reference FA index by the defined offset, and allocating the preamble PN index to base stations using the remaining FA indexes. The price of a system can thus be lowered by reducing a Peak-to-Average Power Ratio (PAPR) of a preamble, increase the number of FAs that a specific amplifier can amplify, and immediately allocate a preamble PN index when adding a new FA during an operation of a system.

  • 331.
    Sung, Ki Won
    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.
    Shi, Lei
    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.
    Coexistence of LTE femtocells with GSM cellular network2010In: 2010 IEEE 21st International Symposium on Personal Indoor and Mobile Radio Communications, PIMRC 2010, IEEE , 2010, p. 1556-1560Conference paper (Refereed)
    Abstract [en]

    In this paper we investigate the deployment of LTE indoor femtocells on the frequency band currently used by GSM cellular network. We consider a scenario where the LTE femtocells share GSM uplink spectrum provided that the legacy GSM users are not harmed by interference from the femtocells. Difference in the characteristics of GSM and LTE technologies is exploited to enable the spectrum sharing. The performance of both systems is analyzed mathematically in terms of average SINR. Simulation is employed to support the analysis. Numerical results show that the availability of the spectrum sharing depends on the number of femtocells in each GSM cell and the locations of femtocells.

  • 332.
    Sung, Ki Won
    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.
    Tercero Vargas, Miurel
    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.
    Aggregate Interference in Secondary Access with Interference Protection2011In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 15, no 6, p. 629-631Article in journal (Refereed)
    Abstract [en]

    This paper presents a derivation of the probability distribution function (pdf) of the aggregate interference in a secondary access network where multiple secondary users cause interference to a single primary user. The derivation considers a practical interference protection mechanism that the transmission of each secondary user is regulated by an interference threshold. Analytic pdf of the interference from a secondary user is obtained. Then, the distribution of the aggregate interference is approximated based on its cumulants. The derived pdf shows a good agreement with Monte Carlo simulation.

  • 333.
    Sung, Ki Won
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, 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: Services and Infrastucture, Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Aeronautical Communication Systems as Potential Primary Users in Secondary Spectrum Access2011In: 10th Scandinavian Workshop on Wireless Ad-hoc Networks (ADHOC 11), Stockholm, Sweden, May 2011, 2011Conference paper (Refereed)
    Abstract [en]

    Secondary spectrum access emerges as a meansto increase spectrum utilization significantly in a near future.However, the technical availability and the economic value of thesecondary access have not been fully investigated. Particularly,the impact of the secondary access on the real-life primary systemsremains mostly unaddressed. Among the primary systemsof interest are aeronautical communication systems operating inthe radio frequencies under 6 GHz. In this paper, we presentan overview of various aeronautical communication systems asthe potential primary users. We describe the purposes, characteristics,and operational facts of not only existing but alsofuture aeronautical systems. We also discuss the opportunitiesand challenges of secondary access to aeronautical spectrumand suggest a secondary use case suitable for the aeronautical spectrum.

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  • 334.
    Sung, Ki Won
    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.
    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.
    Coordination of Clusters for Inter-Cell Scheduling2011In: 2011 IEEE 73RD VEHICULAR TECHNOLOGY CONFERENCE (VTC SPRING), IEEE , 2011, p. 1-5Conference paper (Refereed)
    Abstract [en]

    Coordination of base stations is essential in the mitigation of inter-cell interference in cellular communication systems. One of practical solutions is a cluster-based inter-cell scheduling where base stations in each cluster determine their transmissions in cooperative fashion. In spite of potential performance improvement, the inter-cell scheduling may result in conflict between clusters. However, a dynamic coordination in the cluster level is difficult due to the prohibitive burden of inter-cluster communication. In this paper, we address the coordination of clusters in the downlink of cellular networks. We propose a rule of inter-cluster coordination, namely nominal scheduling order with penalty (NSOP) which does not require communication between the clusters. Dynamic system level simulations are performed to examine the performance of the NSOP in various interference scenarios. It is observed that the proposed NSOP effectively strikes a balance between the inter-cluster interference avoidance and the intra-cluster multi-user diversity by means of a simple penalty factor.

  • 335.
    Sánchez Pardo, Ignacio
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Spatial Audio for the Mobile User2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Voice over the Internet Protocol (VoIP) is one of the latest and most successful Internet services. It takes advantage of Wireless Local Area Networks (WLANs) and broadband connections to provide high quality and low cost telephony over the Internet or an intranet. This project exploits features of VoIP to create a communication scenario where various conversations can be held at the same time, and each of these conversations can be located at a virtual location in space. The report includes theoretical analysis of psychoacoustic parameters and their experimental implementation together with the design of a spatial audio module for the Session Initiation Protocol (SIP) User Agent “minisip”. Besides the 3D sound environment this project introduces multitasking as an integrative feature for “minisip”, gathering various sound inputs connected by a SIP session to the “minisip” interface, and combining them altogether into a unique output. This later feature is achieved with the use of resampling as a core technology. The effects of traffic increment to and from the user due to the support of multiple streams are also introduced.

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    fulltext
  • 336.
    Tarhan, Aras
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Cavdar, Cicek
    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.
    Shared path protection for distance adaptive elastic Optical Networks under dynamic traffic2013In: 2013 5th International Congress on Ultra Modern Telecommunications and Control Systems and Workshops (ICUMT), IEEE Computer Society, 2013, p. 62-67Conference paper (Refereed)
    Abstract [en]

    Elastic Optical Networks (EONs), evolved as a scalable infrastructure to provide optical connectivity for large variety of bandwidth requests ranging from 1Gbps to 1Tbps. Thanks to the enabling technologies such as bandwidth variable transponders and flexible switches, bandwidth adaptive spectrum allocation became possible. EONs can carry large optical channels with higher spectrum efficiency with the recent changes in the standard fixed division of optical spectrum. In this study we propose a distance adaptive, dynamic shared path protection scheme for EONs. In conventional WDM networks, sharability used to be one of the prime objectives to maximize the backup resource efficiency. In EONs, spectrum resources can be shared partially between connections and different parts of the allocated spectrum may be shared by different connections at the same time. Not only the routing but also spectrum allocation of backup resources has a big impact on the sharability in EONs. Taking this into account, we developed a novel RSA (Routing and Spectrum Allocation) algorithm applying different strategies for primary and backup resources called Primary First-Fit Modified Backup Last-Fit (PF-MBL) aiming to reduce the fragmentation and to increase the sharability. As a result overall bandwidth blocking probability is significantly reduced in the network. Results show that PF-MBL can improve the performance in terms of bandwidth blocking probability by 24% up to 59% compared to the current outperforming algorithm when the bandwidth acceptance ratio of the system varies from 90% to 99.9% in different loads.

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    RNDM2013
  • 337.
    Tecsor, Irina
    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.
    Isaksson, Gunnar
    Luleå tekniska universitet.
    Borg, Johan
    Luleå tekniska universitet.
    Beckman, Claes
    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. Luleå University of Technology, Sweden.
    Initial Investigations into the Effects of Mutual Coupling and Architecture of the EISCAT3D array2013Conference paper (Other academic)
    Abstract [en]

    To study the layers of the ionosphere and also the interactions between Earth and Sun, the EISCAT association will build a three dimensional imaging radar: EISCAT3D. The infra­structure of the radar system will include 5 sites with ~10000 antenna elements each.

    For such arrays, the electromagnetic interaction between radiating elements (coupling effects) and the influence of the ground plane cannot be neglected. In addition, for array applications requiring a large number of elements, a process called thinning is most often applied to remove elements while maintaining much of the same characteristics for the antenna. When the density of components decreases, the coupling in the array will decrease as well.

    The relative position of elements doesn’t have a great influence on the performance of main beam. It has, however, on the mutual coupling that changes the input impedance of the radiators and the characteristics of the radiation pattern. The challenge is to find a layout where radiating elements will be separated enough for them not to couple but close enough to not disturb the performance of the array antenna.

    For the purpose of analyzing the performance of the EISCAT3D array, a simulation tool has been developed in Matlab/ Mathematica. In this initial study, thinned arrays with three types of elements: isotropic, half wavelength dipoles and an antenna element designed and simulated at Luleå Technical University are investigated. The latter element was designed with the ambition to meet the rigorous requirements put on the EISCAT3D array when deployed in the Northern part of Scandinavia in order to withstand the harsh environment. The radiation pattern of the single radiator is provided by an EM simulation tool (NEC2) and

    includes the mutual coupling to identical elements. Thus, analyzing the radiation pattern of the array with Luleå elements, the mutual coupling effects are taken into consideration.

    In the simulations an attempt is made to, in a realistic manner and for different scanning angles, calculate per­formance indicators such as Directivity and Sidelobe level. When the main beam is directed towards the zenith, it was found that between the three elements analyzed, dipoles will result in the lowest directivity and the smallest side lobe level. The directivity of the array with isotropic elements and Luleå elements increases with a regular pattern with increasing number of elements. Between the three types of radiators, Luleå elements will results in the highest average side lobe level and the peak side lobe level gets better than isotropic elements when more than 60% of elements are active.

  • 338.
    Tercero, Miurel
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. Ericsson Research, Sweden.
    Sharma, Sachin
    Coldrey, Mikael
    Kronander, Jonas
    Coexistence between 5G and Fixed Services2016In: 2016 IEEE 83RD VEHICULAR TECHNOLOGY CONFERENCE (VTC SPRING), IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    This study focuses on the coexistence between 5G networks and Fixed Services (FS), where fixed links (FL) is one application. 5G is expected to require spectrum in high frequency ranges and fixed services is a highly probable candidate to share spectrum with. Most of the spectrum is co-primary allocated to both mobile and fixed. This study gives assessment on the inference to/from the fixed link, and identifies areas for further study. The results indicate that the interference that 5G radiates to the fixed link is higher than the requirement in the co-channel case. However a low traffic load at 5G together with beamforming is the best scenario with a 30% probability of interference. One possibility to reduce the probability of interference to 6% is to increase antenna directivity of the fixed links. This can be a valid solution to be applied for operators owning both fixed and 5G networks. The interference from fixed link to 5G downlink is below the allowed limit and it is found that at 5G downlink the main contributor to the aggregated interference is the intra network interference. The interference scenario can be improved by utilizing coordination protocols with beam-steering, and advanced antennas. Operators can also consider to deploy in a coordinated manner, or even using other deployments type like micro or indoor.

  • 339.
    Tercero, Miurel
    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.
    Aggregate Interference from Secondary Users with Heterogeneous Density2011In: 2011 IEEE 22nd International Symposium On Personal Indoor And Mobile Radio Communications (PIMRC), IEEE , 2011, p. 428-432Conference paper (Refereed)
    Abstract [en]

    This paper presents an analytical model to approximate the probability distribution function of the aggregate interference that a primary user receives from multiple secondary transmitters. In particular, we consider heterogeneity in spatial distribution of secondary users such that there are several sites with densely populated secondary users in the whole area. The concentration of secondary users is modeled as an annulus sector with higher user density, which is termed hot zone. The mathematical framework presented in this paper can readily be adapted to various existing interference models. It is observed that the heterogenous user distribution has a considerable impact on the aggregate interference if the hot zone is near the primary receiver, while hot zones over a certain distance is well approximated by a homogeneous secondary user distribution. The aggregate interference also depends on the shape of the hot zone and the interference threshold imposed on the secondary users.

  • 340.
    Tercero, Miurel
    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.
    Exploiting Temporal Secondary Access Opportunities in Radar Spectrum2013In: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. 72, no 3, p. 1663-1674Article in journal (Refereed)
    Abstract [en]

    In this paper, we quantify the temporal opportunities for secondary access to radar spectrum. Secondary users are assumed to be WLANs which opportunistically share the radar frequency band under the constraint that the aggregate interference does not harm radar operation. Each WLAN device employs dynamic frequency selection (DFS) as a mechanism to protect the radar from the interference. We also consider an advanced interference protection mechanism, which is termed temporal DFS. It exploits the temporal variation of interference power due to the periodic rotation of radar antenna. It is observed that the probability of accessing the radar spectrum is significantly higher when the temporal DFS is used compared to the conventional DFS. As a consequence, more WLANs can utilize the radar spectrum when the temporal DFS mechanism is considered. This shows that having better knowledge of the primary user activity can bring about the increased opportunity of secondary spectrum access to radar band, and thus improve the spectrum utilization.

  • 341.
    Tercero, Miurel
    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. National University of Engineering (UNI), Nicaragua.
    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.
    Impact of aggregate interference on meteorological radar from secondary users2011In: IEEE Wireless Communications and Networking Conference (WCNC), IEEE , 2011, p. 2167-2172Conference paper (Refereed)
    Abstract [en]

    In this paper, we investigate the impact of aggregate interference in a secondary spectrum access system. Particularly, meteorological radar operating in 5.6 GHz band is considered to be a primary user. Secondary users are WLAN devices spreading in a large area which induce aggregate interference to the radar. We develop a mathematical model to derive the robability distribution function (PDF) of the aggregate interference. The derivation considers dynamic frequency selection (DFS) mechanism for the protection of the radar such that the transmission of each WLAN is regulated by an interference threshold. Numerical experiments are performed with various propagation environments and densities of WLAN devices. It is observed that the effect of aggregate interference is severe in a rural environment. The interference threshold for individual WLAN should be much lower than the maximum tolerable interference at the radar. Thus, only a limited number of WLANs can transmit at the same time. On the other hand, adverse effect of the aggregate interference is not shown in an urban environment, where up to 10 WLANs per square kilometer can use the radar spectrum without considering the aggregate interference. The framework discussed in this paper can readily be adapted to assess the aggregate interference for other types of radars.

  • 342.
    Tercero, Miurel
    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.
    Temporal secondary access opportuities for WLAN in radar bands2011In: Wireless Personal Multimedia Communications (WPMC), 2011 14th International Symposium on, Elsevier, 2011, p. 6081515-Conference paper (Refereed)
    Abstract [en]

    In this paper we quantify the temporal opportunities for secondary access in radar bands. In our study, WLANs are secondary users homogeneously or heterogeneously distributed, which opportunistically access the radar spectrum. Each WLAN employs dynamic frequency  selection (DFS) as a mechanism to protect the radar from interference. We also consider an interference protection mechanism based on DFS and the prediction of the radar’s antenna pattern, which is termed Temporal DFS. We have the most of the time the probability of accessing the radar band are higher when Temporal DFS is used. As a consequence, there are more active WLANs when Temporal DFS mechanism is considered compare with normal DFS mechanism. This, shows once more that by having knowledge of the primary users activity secondary users can increase the probability of accessing the spectrum and improve spectrum utilization.

  • 343.
    Tercero Vargas, Miurel
    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.
    González Sánchez, Pamela
    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.
    Ileri, Ömer
    The Scientific and Technological Research Council of Turkey.
    Zander, Jens
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Distributed spectrum access with energy constraint for heterogeneous channels2010In: 2010 Proceedings of the 5th International Conference on Cognitive Radio Oriented Wireless Networks and Communications, CROWNCom 2010, Cannes, 2010Conference paper (Refereed)
    Abstract [en]

    The demand for wireless communications services has increased the amount of spectrum resources required, promoting research interest in dynamic spectrum allocation schemes. There exist many promising solutions to allocate spectrum on a dynamic basis in order to get an efficient spectrum usage. One particular form is auction mechanism, tailored for allocating transmission rights on a short term basis to provide efficient allocation of scarce resources. However, most existing approaches are focused on homogeneous settings where all channels are treated as if they have the same propagation characteristics. In this work we consider two distributed auction schemes; sequential and concurrent, based on sequential ascending and combinatorial bidding, respectively, taking into account the propagation conditions of the channels (heterogeneous settings). The performance of these schemes is compared to two reference cases: (i) distributed homogeneous channels allocation (channel-agnostic case), and (ii) the centralized allocation scheme. Experimental results suggest that auction mechanisms which take into account the channel characteristics improve spectrum utilization under energy constraint. For wireless cellular networks with high unit energy cost (low coverage) concurrent access gives a better utilization of the spectrum and energy resources with higher service providers utility.

  • 344. Teshima, Kunihiko
    et al.
    Yamamoto, Koji
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Murata, Hidekazu
    Yoshida, Susumu
    Capacity Analysis of Cooperative Relaying Networks with Adaptive Relaying Scheme Selection2009In: IEICE transactions on communications, ISSN 0916-8516, E-ISSN 1745-1345, Vol. E92B, no 12, p. 3744-3752Article in journal (Refereed)
    Abstract [en]

    In the present paper, the performance of cooperative relaying networks with adaptive relaying scheme selection is analyzed. Cooperative relaying is a new technique to achieve spatial diversity gain by using neighboring stations. However, when multiple stations transmit simultaneously, the number of interference signals increases. Therefore, the introduction of cooperative relaying in radio communication systems does not always increase the network capacity due to the co-channel interference. Therefore, in order to achieve high spectral efficiency, it is necessary to select cooperative relaying or non-cooperative relaying adaptively. Assuming both centralized and decentralized adaptive controls, the spectrum efficiency is evaluated. The performance under decentralized control is evaluated using a game-theoretic approach. Simulation results show that the introduction of cooperative relaying with centralized control always increases the spectral efficiency. On the other hand, Simulation results also show that, when each source selects a relaying scheme independently and selfishly to maximize its own spectral efficiency, the introduction of the co-operative relaying may reduce the spectral efficiency due to the increase in the number of interference signals.

  • 345.
    Thanos, Anastasios
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Shalmashi, Serveh
    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.
    Miao, Guowang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Network-Assisted Discovery for Device-to-Device Communications2013In: 2013 IEEE Globecom Workshops (GC Wkshps), IEEE Computer Society, 2013, p. 660-664Conference paper (Refereed)
    Abstract [en]

    Network-assisted device-to-device (D2D) communications allow two devices to communicate with each other directly using one bidirectional link. Exchange of signaling messages with the base station allows the establishment of D2D communications. The discovery of D2D pairs of devices is an essential part of D2D communications as it provides the base station with all the information necessary to evaluate the possibility of D2D communication for the pair. This paper proposes two discovery algorithms, the centralized fully network-dependent and the semi centralized semi-network-dependent algorithms to identify D2D pairs through the exchange of a number of signaling messages. A comparison between those algorithms is performed with respect to delay and signaling overhead. Simulation results show that the second discovery algorithm is faster and more efficient than the first one in discovering new D2D pairs.

  • 346.
    Timus, Bogdan
    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.
    Resource Allocation Schemes in Evaluating the Infrastructure Cost of a Wireless Multihop Architecture with Fixed Relays2005Conference paper (Refereed)
    Abstract [en]

    The downlink of a hybrid system with regenerative relaying (cellular extended by means of fixed wireless router) is studied in terms infrastructure costs. Using a static linear cost model, the feasibility of the hybrid system is analyzed by comparing the infrastructure cost of providing a predefined service level with a traditional single hop system and with a hybrid system, respectively. The analysis is performed with two resource allocation schemes: fixed and adaptive link rates. The same centralized STDMA scheme is used in both cases. The usage of adaptive rates reduces significantly the infrastructure cost of both the reference and the hybrid system. However, the hybrid system becomes feasible when the cost of a relay is 6 to 9% the cost of a base station, no matter which of the two resource allocation scheme is used.

  • 347.
    Timus, Bogdan
    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.
    Roll-out Decisions in a Multihop Cellular System with Fixed Relays2005Conference paper (Refereed)
    Abstract [en]

    The infrastructure costs of a hybrid multihop cellular has previously been analyzed by assuming fixed traffic loads. In reality the traffic load in a commercial system gradually increases and therewith the network must be upgraded. The timing and the type of upgrade may have important impact on the overall infrastructure cost. A first step in analyzing the costs of a hybrid network roll-out is taken in this paper. It is assumed that a wireless relay can be turned into an access point by connecting it to a wired transport network. A criterion is introduced for deciding whether to deploy a new relay or turn an old one into an access point, based on the estimated capacity increase and on the present value of the additional costs associated with each upgrade type. The decision is taken as a single-action event at a given time, i.e. ignoring the opportunities created or missed by the decision. It also assumes that the equipment is worth nothing at the end of the operational phase. Numerical examples in a simple deployment scenario show that it is worth deploying relays for up to three hops, at the beginning of the operation period, if the units are of pico-base station type. Relays are always turned into access points toward the end of the operation period.

  • 348.
    Timus, Bogdan
    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.
    Hultell, Johan
    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.
    Nilson, Mats
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Techno-economical viability of deployment strategies for cellular-relaying networks2008In: 2008 IEEE 67TH VEHICULAR TECHNOLOGY CONFERENCE-SPRING: Vols 1-7, 2008, p. 2259-2263Conference paper (Refereed)
    Abstract [en]

    The ability of an operator to respond to changes in demand by incrementally deploying additional network infrastructure is essential. This paper(1) presents a method for evaluating and comparing the economic viability of incremental deployment strategies given a limited initial investment budget. Any strategy is seen as a sequence of deployment decisions. The time-dynamic relation between service quality and demand is taken into account via the limited investment budget (cash How analysis), while the focus is maintained on the technical properties of the network. As an example, the economic viability of a 1D cellular-relaying network is analyzed under greedy deployment strategies. In order for the cellular-relaying solution to be viable, we show that the maximum allowed relay cost decreases with the investment budget.

  • 349.
    Timus, Bogdan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Kim, Dongwoo
    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.
    Cross-Layer Resource Allocation Model for Cellular-Relaying Network Performance Evaluation2011In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 60, no 6, p. 2765-2776Article in journal (Refereed)
    Abstract [en]

    The enhancement of cellular networks with relaying technologies is expected to bring significant technoeconomic benefits at the expense of more complex resource allocation. Suitable models for solving network dimensioning problems in cellular-relaying networks must handle radio resource allocation among hundreds of links and tackle interactions between networking layers. For this purpose, we propose a novel cross-layer resource allocation model based on average interference and ideal rate adaptation for the physical layer (PHY), time shares for the medium access layer, and fluid flows for the transport and network layers. We formulate a centralized social welfare maximization problem. When the routes are selected with an a priori algorithm, we show that the resource allocation problem admits an equivalent convex formulation. We show a numerical example for how to use the proposed framework for configuring the backhaul link in a practical relaying network. The overall problem of selecting routes and allocating time shares and link rates is nonconvex. We propose an iterative suboptimal algorithm to solve the problem based on a novel approximation of PHY. We state and prove several convergence properties of the algorithm and show that it typically outperforms routing based on signal-to-noise ratio only.

  • 350.
    Tollmar, Konrad
    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.
    Design by Use2005In: Lund on Informatics, Liber , 2005Chapter in book (Other academic)
45678 301 - 350 of 396
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