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  • 1.
    Agnihotri, Mohit
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Chirikov, R.
    Militano, F.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Topology formation in mesh networks considering role suitability2016In: IEEE Wireless Communications and Networking Conference, WCNC, IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    The paper studies various mesh topology formation techniques that can be used to aid the development of large-scale capillary networks. The work focuses on how mesh networks can be established using Bluetooth Low Energy exploiting the heterogeneous characteristics of the devices in the network. A novel algorithm called Topology Formation considering Role Suitability (TFRS) is proposed aiming to maximize the network lifetime. The algorithm employs a newly introduced metric called role suitability metric (RSM) to assign the best role among master, relay and slave to a participating device. The RSM metric is computed from device characteristics including, but not limited to, energy, mobility and computational capability. We use systemlevel simulation to evaluate the performance of the proposed algorithm against a reference under a homogeneous deployment scenario consisting of heterogeneous devices. Results show that the network lifetime can be improved significantly when the topology is formed considering the device characteristics for both master role selection and relay selection. TFRS can achieve 20% to 40% higher network lifetime depending on the deployment characteristics over the reference algorithm.

  • 2.
    Alabbasi, Abdulrahman
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Shihada, Basem
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    On Energy Efficiency of Prioritized IoT Systems2017In: Globecom 2017 - 2017 IEEE Global Communications Conference, IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    The inevitable deployment of 5G and the Internet of Things (IoT) sheds the light on the importance of the energy efficiency (EE) performance of Device-to- Device (DD) communication systems. In this work, we address a potential IoT application, where different prioritized DD system, i.e., Low-Priority (LP) and High-Priority (HP) systems, co-exist and share the spectrum. We maximize the EE of each system by proposing two schemes. The first scheme optimizes the individual transmission power and the spatial density of each system. The second scheme optimizes the transmission power ratio of both systems and the spatial density of each one. We also construct and analytically solve a multi- objective optimization problem that combines and jointly maximizes both HP and LP EE performance. Unique structures of the addressed problems are verified. Via numerical results we show that the system which dominates the overall EE (combined EEs of both HP and LP) is the system corresponding to the lowest power for low/high power ratio (between HP and LP systems). However, if the power ratio is close to one, the dominating EE corresponds to the system with higher weight.

  • 3. Ansari, A.
    et al.
    Jaumard, B.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Energy optimization of a cellular network with minimum bit-rate guarantee2017In: 2017 15th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks, WiOpt 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7959933Conference paper (Refereed)
    Abstract [en]

    Energy optimization in cellular networks has been studied using different perspectives in the literature: sleep patterns, network interference, association of users and base stations, resource allocation of resources (bandwidth and power), etc. All these means have been discussed individually in previous works. However, none of the existing works has succeeded in proposing an exact mathematical model that takes into account several of these parameters simultaneously. In this article, we propose a first exact modelling of several network parameters and their interaction in order to minimize the energy consumption in a LTE cellular network. The optimization model guarantees to satisfy all the users with a minimum quality of service (data rate). Its exact solution allows energy savings of up to 50% in a moderately loaded network, which leads to energy savings up to twice that of the heuristic proposed by Piunti et al., (2015). Various numerical results are presented on hexagonal and randomly generated cellular networks.

  • 4.
    Azari, Amin
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Cavdar, Cicek
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Performance Evaluation and Optimization of LPWAIoT Networks: A Stochastic Geometry Approach2018Conference paper (Refereed)
    Abstract [en]

    Leveraging grant-free radio access for enabling lowpowerwide-area (LPWA) Internet of Things (IoT) connectivityhas attracted lots of attention in recent years. Regarding lack ofresearch on LPWA IoT networks, this work is devoted to reliabilitymodeling, battery-lifetime analysis, and operation-controlof such networks. We derive the interplay amongst density ofthe access points, communication bandwidth, volume of trafficfrom heterogeneous sources, and quality of service (QoS) incommunications. The presented analytical framework comprisesmodeling of interference from heterogeneous sources with correlateddeployment locations and time-frequency asynchronousradio-resource usage patterns. The derived expressions representthe operation regions and rates in which, energy and costresources of devices and the access network, respectively, couldbe traded to achieve a given level of QoS in communications. Forexample, our expressions indicate the expected increase in QoSby increasing number of transmitted replicas, transmit power,density of the access points, and communication bandwidth.Our results further shed light on scalability of such networksand figure out the bounds up to which, scaling resources cancompensate the increase in traffic volume and QoS demand.Finally, we present an energy-optimized operation control policyfor IoT devices. The simulation results confirm tightness of thederived analytical expressions, and indicate usefulness of themin planning and operation control of IoT networks.

  • 5.
    Azari, Amin
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Cavdar, Cicek
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Self-organized Low-power IoT Networks: ADistributed Learning Approach2018Conference paper (Refereed)
    Abstract [en]

    Enabling large-scale energy-efficient Internet-ofthings(IoT) connectivity is an essential step towards realizationof networked society. While legacy wide-area wireless systemsare highly dependent on network-side coordination, the level ofconsumed energy in signaling, as well as the expected increase inthe number of IoT devices, makes such centralized approachesinfeasible in future. Here, we address this problem by selfcoordinationfor IoT networks through learning from pastcommunications. To this end, we first study low-complexity distributedlearning approaches applicable in IoT communications.Then, we present a learning solution to adapt communicationparameters of devices to the environment for maximizing energyefficiency and reliability in data transmissions. Furthermore,leveraging tools from stochastic geometry, we evaluate theperformance of proposed distributed learning solution againstthe centralized coordination. Finally, we analyze the interplayamongst energy efficiency, reliability of communications againstnoise and interference over data channel, and reliability againstadversarial interference over data and feedback channels. Thesimulation results indicate that compared to the state of the artapproaches, both energy efficiency and reliability in IoT communicationscould be significantly improved using the proposedlearning approach. These promising results, which are achievedusing lightweight learning, make our solution favorable in manylow-cost low-power IoT applications.

  • 6.
    Dinc, Ergin
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Vondra, Michal
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Multi-user Beamforming and Ground Station Deployment for 5G Direct Air-to-Ground Communication2017In: Globecom 2017 - 2017 IEEE Global Communications Conference, Institute of Electrical and Electronics Engineers (IEEE), 2017Conference paper (Refereed)
    Abstract [en]

    On-board of aircraft is one of the last venues without high-speed connectivity, which makes it an important problem to address for both industry and academia. To this end, direct air-to-ground communications (DA2GC), where communication link is provided via direct link between aircraft and ground station, is a promising solution to provide high capacity and low latency backhaul capacity for aircraft. In this paper, we investigate the ground station deployment problem to provide 1.2 Gbps average backhaul capacity for each aircraft. The feasible operation points for the key network parameters: the number of ground stations, antenna array size, transmit power and bandwidth, are calculated. In addition, we propose a multi-user beamforming algorithm for dual-polarized hybrid DA2GC antenna arrays, and derive a tractable expression for the DA2GC cell throughput.

  • 7.
    Dinc, Ergin
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Vondra, Michal
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Seamless Gate-to-Gate Connectivity Concept: Onboard LTE, Wi-Fi and LAA2017In: 2017 IEEE 86th Vehicular Technology Conference  (VTC-FALL), Institute of Electrical and Electronics Engineers (IEEE), 2017Conference paper (Refereed)
    Abstract [en]

    Aircraft is one of the last venues with no highspeed connectivity, which makes it an important research issue to address for both industry and academia. This paper introduces seamless gate-to-gate connectivity concept so that passengers can stay connected in all phases of the flight. The backhaul capacity is provided via direct air-to-ground communications links. Passengers can utilize both LTE andWi-Fi access technologies on-board. In order to avoid interference with licensed ground LTE network, in-cabin LTE users will be served in the unlicensed spectrum via license assisted access (LAA) functionality when the aircraft is close to the ground. In this paper, we determine the altitude threshold for switching to LAA in order to provide seamless LTE connectivity. According to our analysis the myth about the 3 km threshold for the interference with the terrestrial network is not anymore valid. In addition, throughput and user data rates for LTE and Wi-Fi networks are investigated in different flight phases. We have found out that in-cabin LTE network can serve 80-240 users between 5-15 Mbps data rates, and Wi-Fi network can provide peak data rates of 14 Mbps in the worst-case scenario.

  • 8.
    Dinc, Ergin
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Vondra, Michal
    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.
    Hofmann, Sandra
    Schupke, Dominic
    Prytz, Mikael
    Bovelli, Sergio
    Frodigh, Magnus
    Zander, Jens
    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.
    In-Flight Broadband Connectivity: Architectures and Business Models for High Capacity Air-to-Ground Communications2017In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 55, no 9, p. 142-149Article in journal (Refereed)
    Abstract [en]

    In-Flight Broadband Connectivity (IFBC) is a significant open market for mobile network operators, considering that more than 3.3 billion passengers were served by airlines in 2015. On-board broadband services are provided via air-to-ground (A2G) connectivity through direct A2G communication (DA2GC) and satellite A2G communication (SA2GC). Available on-board connectivity systems have significant limitations: high latency in SA2GC and low capacity in DA2GC. The customer expectancy is multi-Mb/s connections in every seat, which leads to capacity requirements of Gb/s to the aircraft. Creation of high capacity IFBC requires a collaborative interaction between different industry partners. For this reason, we investigate A2G architectures in terms of economic and technical perspectives, and propose business models by identifying new roles and positioning them in the A2G business ecosystem. In addition, we provide an extensive summary of the state-of-the-art and future improvements for A2G communications.

  • 9. Dolfi, M.
    et al.
    Morosi, S.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Del Re, E.
    Energy efficient optimization of a sleep mode strategy in heterogeneous cellular networks2017In: EuCNC 2017 - European Conference on Networks and Communications, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7980740Conference paper (Refereed)
    Abstract [en]

    As base stations (BS) are responsible for the large amount of energy consumed in cellular networks, energy efficient BS sleep mode techniques have the potential to save a significant amount of energy. However, assuming that BSs are able to alternate between sleeping and active states as frequently as possible may have a negative impact on network reliability, shortening BS lifetime. In this paper we propose a multiobjective optimization framework aimed at minimizing the power consumption and number of BS sleep mode switchings in heterogeneous cellular networks (HetNet), by jointly considering Quality of Service (QoS) requirements. We focus on the HetNet scenario in which macro and micro cells coexist. The Mixed Integer Quadratic Programming (MIQP) optimization technique is used to minimize the power consumption together with the number of BS sleep mode operations of both macro and micro cells. The trade-off between power consumption, sleep mode switchings and performance of the network is shown for different energy saving solutions. Results show that the proposed optimization can guarantee QoS target throughput for users and significant reduction of 50% for macro and 73% for micro BS respectively daily number of switchings, while still achieving 8% savings in terms of daily energy consumption.

  • 10.
    Hossain, M. M. A.
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    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.
    Jantti, R.
    Traffic offloading based energy saving market for cellular operators2017In: 2017 IEEE International Conference on Communications Workshops, ICC Workshops 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 97-102, article id 7962640Conference paper (Refereed)
    Abstract [en]

    Larger share of total energy consumed by mobile network operators (MNOs) is wasted to ensure seamless coverage. Three to six MNOs covering the same geographical area results in even more energy waste. Division of scarce resource, i.e., spectrum into small chunks also deteriorates the overall performance. With exponential growth of the traffic and insignificant marginal revenue, it is time for the regulators and MNOs to resort to new ideas in order to reduce operational cost and devise appropriate mechanisms to ensure business as well as environmental sustainability. In this paper, we propose a double auction based energy saving market where MNOs share coverage and spectrum to save energy. In this market each MNO submits bid and asks to an independent auctioneer simultaneously. The bid is the offer to offload its total traffic to some other MNO along with releasing its own spectrum to be used by the latter. Similarly, the ask is the offer by a MNO to accept excess load along with the spectrum. The auctioneer matches the bids and asks, determines the trading price and makes the offloading decisions to minimize the total energy consumption. We show that even though the information is hidden among the MNOs, this mechanism allows the MNOs to save significant percentage of energy.

  • 11.
    Hossain, M. M. Aftab
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Cavdar, Cicek
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Bjornson, Emil
    Linkoping Univ, Dept Elect Engn, S-58183 Linkoping, Sweden..
    Jantti, Riku
    Aalto Univ, Sch Elect Engn, Espoo 02150, Finland..
    Energy Saving Game for Massive MIMO: Coping With Daily Load Variation2018In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 67, no 3, p. 2301-2313Article in journal (Refereed)
    Abstract [en]

    Massive MIMO (MM) is one of the leading technologies that can cater for very high capacity demand. However, energy consumption of MM systems needs to be load adaptive in order to cope with the significant temporal load variations (TLV) over a day. In this paper, we propose a game-theoretic model for studying load adaptive multicell massive MIMO system where each base station (BS) adapts the number of antennas to the TLV in order to maximize the downlink energy efficiency (EE). The utility function considered here is defined as the number of bits transferred per Joule of energy. In order to incorporate the TLV, the load at each BS is modeled as an M/G/m/m state dependent queue under the assumption that the network is dimensioned to serve a maximum number of users at the peak load. The EE maximization problem is formulated in a game theoretic framework where the number of antennas to be used by a BS is determined through the best response iteration. This load adaptive system achieves around 24% higher EE and saves around 40% energy compared to a baseline system where the BSs always run with the fixed number of antennas that is most energy efficient at the peak load and that can be switched OFF when there is no traffic.

  • 12.
    Hossain, M. M. Aftab
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Jantti, Riku
    Aalto Univ, Sch Elect Engn, Espoo, Finland..
    Dynamic capacity sharing based energy saving market for MNOs2017In: Globecom 2017 - 2017 IEEE Global Communications Conference, Institute of Electrical and Electronics Engineers (IEEE), 2017Conference paper (Refereed)
    Abstract [en]

    As the larger share of total energy consumed by mobile network operators (MNOs) is wasted in order to ensure coverage, three to five MNOs covering the same geographical area results in enormous energy waste. In order to cater for the data tsunami with almost zero marginal revenue, required densification of cells are not sustainable from both Capex and Opex perspective. Even with densification of networks, it is hard to satisfy the performance requirement of the cell edge users due to interference. However, the performance can be upgraded as well as energy can be saved by the offloading of the cell edge users to other MNOs if regulator and MNOs resort to appropriate mechanism. In our previous work, we proposed a double auction based energy saving market mechanism where MNOs participate in bidding to share coverage and capacity in order to save energy, especially during low to medium load. Unlike previous work, in this paper we use this mechanism that involve cell level bidding, i.e., cells bid for each user which not only allows total offloading of the cells at the low load but also offloading of cell edge users among the MNOs during high load. As a result, the energy saving potential becomes very high also at high load conditions along with improvement in performance of cell edge users.

  • 13.
    Hossain, M. M. Aftab
    et al.
    AALTO.
    Jantti, Riku
    AALTO.
    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.
    Dimensioning of PA for massive MIMO system with load adaptive number of antennas2014In: Globecom Workshops (GC Wkshps), 2014, 2014, p. 1102-1108Conference paper (Refereed)
    Abstract [en]

    This paper takes into consideration the non-ideal efficiency characteristics of realistic power amplifiers (PAs) along with the daily traffic profile in order to investigate the impact of power amplifier dimensioning on the energy efficiency of load adaptive massive MIMO system. A multicellular system has been considered where each base station (BS) is equipped with large number of antennas to serve many single antenna users. For a given number of users in a cell, the optimum number of active antennas maximizing energy efficiency (EE) has been derived where total BS downlink power is assumed to be fixed. Under the same assumption, the power amplifiers have been dimensioned in a way that maximize network energy efficiency not only for a for a single time snapshot but over twenty four hours of operation while considering dynamic efficiency characteristics of the PAs. In order to incorporate this daily load profile, each BS has been modeled as an M/G/c/c state dependent queue under the assumption that the network is dimensioned to serve a maximum number of users at a time corresponding to 100% cell traffic load. This load adaptive system along with the optimized PA dimensioning achieves 30% higher energy efficinecy compared to a base line system where the BSs always run with a fixed number of active antennas which are most energy efficient while serving 100% traffic load.

  • 14.
    Jalalinia, Shabnam S.
    et al.
    KTH, School of Information and Communication Technology (ICT).
    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.
    Green and resilient design of telecom networks with shared backup resources2017In: OPTICAL SWITCHING AND NETWORKING, ISSN 1573-4277, Vol. 23, p. 97-107Article in journal (Refereed)
    Abstract [en]

    Backbone telecommunication network infrastructures are deployed with redundant resources taking into account the backup capacity for protection in order to be resilient against link failures, and serving extremely large amount of data transmission resulting in increasing power consumption. In this study, the interplay between green and resilient network design, and flow routing mechanisms is analyzed. We propose Mixed Integer Linear Programming (MILP) models to obtain optimum solutions under various objectives: Minimizing consumption of (I) Capacity, (II) Capacity+ Power, and (III) Power. Two different shared backup protection (SBP) schemes (1) SBP-ind (failure independent) and (2) SBP-dep (failure dependent) are compared with dedicated path protection (DPP). It is assumed that network links utilized by only backup paths can be put into sleep mode. It is observed that when power consumption is minimized, the backup sharing decreases in SBP and, in the extreme case, it behaves similar to DPP. The models are generalized and valid for both IP traffic flow routing and lightpath routing. It is shown that for a sample network topology, to save e.g., 32.33% power, capacity consumption increases significantly, e.g., in SBP-ind up to 127.53%. In order to achieve a compromise between power and capacity consumption, we propose a multi-objective approach. All the MILP models are run and results are presented for a small scale European network topology as well as a larger scale sample US network topology. For larger problem instances ILP solutions are not scalable. Therefore, a novel energy efficient and survivable routing and network design algorithm, called energy-aware shared path protection (EASPP), addressing the trade-off caused by conflicting objectives of green and resilient network planning is proposed. Moreover this study presents a complete picture of various survivability mechanisms when power consumption is minimized together with the capacity consumption.

  • 15.
    Masoudi, Meysam
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Azari, Amin
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Yavuz, Emre Altug
    Ericsson AB, Stockholm, Sweden.
    Cavdar, Cicek
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Grant-free Radio Access IoT Networks:Scalability Analysis in Coexistence Scenarios2018Conference paper (Refereed)
    Abstract [en]

    IoT networks with grant-free radio access, likeSigFox and LoRa, offer low-cost durable communications overunlicensed band. These networks are becoming more and morepopular due to the ever-increasing need for ultra durable, interms of battery lifetime, IoT networks. Most studies evaluatethe system performance assuming single radio access technologydeployment. In this paper, we study the impact of coexistingcompeting radio access technologies on the system performance.Considering K technologies, defined by time and frequencyactivity factors, bandwidth, and power, which share a set of radioresources, we derive closed-form expressions for the successfultransmission probability, expected battery lifetime, and experienceddelay as a function of distance to the serving access point.Our analytical model, which is validated by simulation results,provides a tool to evaluate the coexistence scenarios and analyzehow introduction of a new coexisting technology may degrade thesystem performance in terms of success probability and batterylifetime. We further investigate solutions in which this destructiveeffect could be compensated, e.g., by densifying the network toa certain extent and utilizing joint reception.

  • 16.
    Masoudi, Meysam
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Khamidehi, Behzad
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Green Cloud Computing for Multi Cell Networks2017In: 2017 IEEE Wireless Communications and Networking Conference, WCNC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7925672Conference paper (Refereed)
    Abstract [en]

    This paper investigates the power minimization problem for the user terminals by application offloading in multi-cell multi-user OFDMA mobile cloud computing networks where some practical constraints such as backhaul capacity limitation, interference level on each channel and maximum tolerable delay as user's quality of service is taken into account. Furthermore, the mixed integer nonlinear problem is converted into a convex form using D.C. approximation. Moreover, to solve the optimization problem, we have proposed joint power allocation and decision making (J-PAD) algorithm which can make offloading decision and allocate power at the same time. Simulation results illustrate that by utilizing the J-PAD algorithm, in comparison with baselines, considerable power saving could be achieved e.g. about 30% for delays more than 100 ms.

  • 17.
    Ok, Dudu
    et al.
    KTH.
    Ahmed, Furqan
    KTH.
    Agnihotri, Mohit
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Self-organizing mesh topology formation in Internet of things with heterogeneous devices2017In: EuCNC 2017 - European Conference on Networks and Communications, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7980779Conference paper (Refereed)
    Abstract [en]

    This paper focuses on the design of self-organizing algorithms for mesh topology formation between low-power short-range heterogeneous devices. To this end, we consider randomly deployed devices that are heterogeneous in terms of characteristics such as energy source (e.g. mains, rechargeable battery, and coin-cell), computational resources, and communication capabilities. Resilient topology formation is considered in a Bluetooth based setting, where devices communicate locally to form pico-nets comprising of devices in master and slave roles. These pico-nets are connected via primary and secondary bridges that forward the traffic between the pico-nets. A role suitability metric based on the device characteristics (e.g. energy source and number of neighbors) is used to assign appropriate roles to devices. By energy aware RSM based topology formation, more than 100% increase in network lifetime over the baseline approach is achieved. And by adding secondary bridges between piconets ≈ 35% further increase in network lifetime is shown.

  • 18.
    Ok, Dudu
    et al.
    KTH.
    Ahmed, Furqan
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS.
    Di Marco, Piergiuseppe
    Ericsson Res, S-16440 Stockholm, Sweden..
    Chirikov, Roman
    Ericsson Res, S-16440 Stockholm, Sweden..
    Cavdar, Cicek
    KTH Royal Inst Technol, S-16440 Stockholm, Sweden..
    Energy Aware Routing for Internet of Things with Heterogeneous Devices2017In: 2017 IEEE 28TH ANNUAL INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR, AND MOBILE RADIO COMMUNICATIONS (PIMRC), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    This paper focuses on the impact of intelligent topology formation and routing on resilient mesh topologies consisting of heterogeneous devices in Internet of Things (IoT) networks. We consider a Bluetooth network comprising of low-power short-range devices that are heterogeneous in terms of energy source (e.g. the mains or coin-cell). In the first step, a resilient mesh topology is created by taking into account device characteristics such as energy sources and parameters related to neighbors. The Bluetooth devices negotiate master and slave roles, and form piconets which are then connected through multiple bridge nodes thus forming a scatternet. An energy aware algorithm is proposed to select the routing paths for packet forwarding between connected devices. The performance of topology and routing is evaluated through simulations in a large indoor office scenario based on realistic channel models and propagation characteristics. Results show that intelligent topology formation, in conjunction with the proposed energy aware routing algorithm leads to a significant gain (more than 100%) in terms of network lifetime, when compared to the baseline approaches.

  • 19. Pourvali, M.
    et al.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Shaban, K.
    Crichigno, J.
    Ghani, N.
    Post-failure repair for cloud-based infrastructure services after disasters2017In: Computer Communications, ISSN 0140-3664, E-ISSN 1873-703X, Vol. 111, p. 29-40Article in journal (Refereed)
  • 20. Rocha, H.
    et al.
    Delsart, G.
    Andersson, A.
    Bousselmi, A.
    Conte, A.
    Gati, A.
    Masucci, A. M.
    Grangeat, C.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Marquet, D.
    Alexandri, E.
    Akpoli-Johnson, G.
    Scheck, H. -O
    Gascon, J.
    Nuaymi, L.
    Salahaldin, L.
    Tabach, M. E.
    Hossain, M. M. A.
    Elayoubi, S. E.
    Imadali, S.
    Chahed, T.
    Jonsson, V.
    Yoro, W.
    Campderros, X.
    SooGREEN: Service-oriented optimization of green mobile networks2017In: 2017 15th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks, WiOpt 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7959935Conference paper (Refereed)
    Abstract [en]

    Today, mobile networks are witnessing an exponential growth of traffic volumes, linked to new services, especially for smart cities and smart-grid. The European Celtic-Plus SooGREEN project, started mid 2015, is targeting to reduce the energy consumption of the services in different mobile architectures in interaction with smart-grid. So GREEN is focused on the services energy consumption modelling and measurement, the dynamic optimization of the mobile access network and of the content delivery, the design of an Energy Efficient Virtualized and Centralized Radio Access Network (RAN), and the bi-directional interaction of the mobile network with the smart-grid. This paper presents insight into the project after its first year, and discusses research trends in green communication networks for the future.

  • 21.
    Ruiz, Alberto Camacho
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Cavdar, Cicek
    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.
    Beckman, Claes
    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 Base Station Antenna Vertical Beam Width and Tilt on the Performance of LTE Networks2016In: 2016 IEEE ANTENNAS AND PROPAGATION SOCIETY INTERNATIONAL SYMPOSIUM, IEEE, 2016, p. 907-908Conference paper (Refereed)
    Abstract [en]

    In this study, system level simulations are performed using two different vertical antenna radiation patterns from two real base station antennas with otherwise similar characteristics. The vertical half power beam widths of the two antennas in the investigation were 4 and 8 degrees respectively. In addition the two antennas are compared with the ideal antenna model proposed by 3GPP. The results show that the choice of vertical beam width and electrical tilt setting may improve both the coverage and capacity of up to 50% in an LTE network. However, the optimum vertical beam width and tilt differs for different network sizes and propagation environment.

  • 22. Sabella, D.
    et al.
    Rapone, D.
    Fodrini, M.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Olsson, M.
    Frenger, P.
    Tombaz, S.
    Energy management in mobile networks towards 5G2016In: Studies in Systems, Decision and Control, Springer International Publishing , 2016, p. 397-427Conference paper (Refereed)
    Abstract [en]

    The evolution of mobile networks from the introduction of the first generation systems until today, and the forecasts for the next decade [1], clearly indicate a growth of both the network itself in terms of installed equipment and carried traffic in terms of transmitted bits. The deployment of new generation systems upon existing ones unavoidably increases the energy consumption, even if new systems are more efficient than the older ones. More consumption means more costs, i.e., less margins for the operators, and greater carbon footprint from the entire Planet. On the other hand, for operators, it would not be possible to dismiss old generation systems in lieu of the new ones, due to the presence of legacy terminals in the network. For these reasons operators need to perform accurate assessment of the energy performance of 2G, 3G and 4G networks by looking in perspective at the evolution of the network in terms of traffic growth, change of paradigms/business models, introduction of next generation networks (i.e. 5G) and so on. This book chapter focuses on the energy efficiency aspects relevant for a sustainable evolution of mobile networks towards 5G from an operator perspective. The conducted analysis will cover both network deployment aspects, equipment evolution, introduction of energy efficiency features, cost analysis, network-level energy efficiency assessment and related standardization initiatives. 

  • 23.
    Thießen, Christian
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Fragmentation-aware survivable Routing and Spectrum Assignment in elastic optical networks2014In: Proceedings of 2014 6th International Workshop on Reliable Networks Design and Modeling, RNDM 2014, IEEE , 2014, p. 97-101Conference paper (Refereed)
    Abstract [en]

    Transparent elastic optical networks (EON) allow provisioning connections with different bandwidth requirements in an efficient way. To achieve the high spectrum efficiency under dynamic traffic scenario, fragmentation-aware Routing, Modulation and Spectrum Assignment (RMSA) decisions is essential. Since fiber cuts are common, resiliency against single-link failures is another important topic. This can be provided efficiently through shared-path protection, which in turn complicates the connection provisioning problem. Unlike existing algorithms that decide first the primary and then the backup path, we introduce an algorithm in this paper that considers pairs of primary and backup paths. To select a candidate pair, we use a hybrid cost function that combines three different objectives: (1) the separation of primary and backup connections to different ends of the spectrum; (2) fragmentation-awareness as a pro-active provisioning objective trying to avoid fragmentation especially among primary resources and (3) maximization of shareability of backup resources among primary paths of link-disjoint connections. Using network level simulations in a scaled-down sample US network with load values of 190-240 Erlang, and bandwidth requests corresponding to 1% blocking probability, an average improvement of 79% compared to a recently presented reference algorithm is shown.

  • 24. Wang, X.
    et al.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Wang, L.
    Tornatore, M.
    Zhao, Y.
    Chung, H. S.
    Lee, H. H.
    Park, S.
    Mukherjee, B.
    Joint allocation of radio and optical resources in virtualized cloud RAN with CoMP2017In: 2016 IEEE Global Communications Conference, GLOBECOM 2016 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7841923Conference paper (Refereed)
    Abstract [en]

    5G Radio Access Networks (RANs) are supposed to increase their capacity by 1000x to handle growing number of connected devices and increasing data rates. The concept of cloud-RAN (CRAN) has been recently proposed to decouple digital units (DUs) and radio units (RUs) of base stations (BSs), and centralize DUs into central offices. CRAN can ease the implementation of advanced radio coordination techniques, e.g., Coordinated Multi-Point (CoMP) Transmission/Reception, to enhance its system throughput. However, separating DUs and RUs, and implementing CoMP in CRAN require low-latency and high-bandwidth connectivity links, called "fronthaul". Today, consensus has not yet been achieved on how BSs, fronthaul, and central offices will be orchestrated to enhance the system throughput. In this study, we present a CRAN over Passive Optical Network (PON) architecture called virtualized-CRAN (V-CRAN). V-CRAN leverages the concept of virtualized PON (VPON) that can dynamically associate any RU to any DU so that several RUs can be coordinated by the same DU, and the concept of virtualized BS (V-BS) that can jointly transmit common signals from multiple RUs to a user. We propose a novel mathematical model based on constraint programming for joint allocation of radio, optical network, and baseband processing resources to enhance RAN throughput, and we solve it by optimally forming VPONs and V-BSs. Comprehensive simulations show that V-CRAN can enhance the system throughput and the efficiency of resource utilization.

  • 25. Wang, X.
    et al.
    Wang, L.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Tornatore, M.
    Figueiredo, G. B.
    Chung, H. S.
    Lee, H. H.
    Park, S.
    Mukherjee, B.
    Handover reduction in virtualized cloud radio access networks using TWDM-PON fronthaul2016In: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, Vol. 8, no 12, p. B124-B134Article in journal (Refereed)
    Abstract [en]

    To meet challenging 5G capacity requirements, operators are densifying their cellular networks by deploying additional small cells to cover hot spots, and such an increase in the number and density of cells may result in excessive numbers of handovers. In this study, we propose a handover reduction mechanism implemented in a cloud radio access network (CRAN) by exploiting the high capacity of an optical access network serving as a "fronthaul." CRAN has been proposed as a 5G radio access network architecture, where the digital unit (DU) of a conventional base station (BS) is separated from the radio unit (RU) and moved to the "cloud" (DU-cloud) for better mobility management and cost saving. Separating RUs and DUs requires a low-latency and high-bandwidth 5G transport network to handle "fronthaul" traffic, for which optical access is an excellent choice. Here, we present a new 5G architecture, called virtualized-CRAN (V-CRAN), moving toward a cell-less 5G mobile network architecture. We leverage the concept of a "virtualized-BS" (V-BS) that can be formed by exploiting several enabling technologies such as software-defined radio and coordinated multipoint transmission/reception. A V-BS can be formed on a per-user basis by allocating virtualized resources on demand so that common signals can be jointly transmitted from multiple RUs to the user without triggering handover. We first model the handover reduction optimization problem for a scenario where future mobility information is known, and then propose a suite of algorithms for a scenario where future information is unknown. Simulation results show that V-CRAN can enhance the throughput of users at the cell-edge, as well as significantly reduce the number of handovers, handover delay, and failure rate.

  • 26. Wang, X.
    et al.
    Wang, L.
    Elayoubi, S. E.
    Conte, A.
    Mukherjee, B.
    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.
    Centralize or distribute?: A techno-economic study to design a low-cost cloud radio access network2017In: 2017 IEEE International Conference on Communications, ICC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7996771Conference paper (Refereed)
    Abstract [en]

    Cloud radio access network (CRAN) has been proposed as a promising evolution of mobile network architecture where baseband processing functions of a base station are split/decoupled from the radio unit (RU) and centralized. However, rigid bandwidth and latency requirements are incurred by fronthaul, i.e., transport link, which connects RU to the central cloud. Therefore, new functional splits are discussed for CRAN with dual-site processing, which we call Hybrid-RAN (H-RAN), where some functions remain distributed while others are centralized. In this work, from a perspective of minimizing the total cost of ownership (TCO) for H-RAN, we present a techno-economic study to find the optimal functional splits for a base station (BS), with a given configuration. A configuration of a BS represents frequency layers, carrier bandwidths, and MIMO schemes, associated with different frequency bands. For each functional split, we present a model to calculate the requirement of computational resources and fronthaul bandwidth. We formulate a TCO minimization model using constraint programming. Numerical results show that the optimal functional split depends on BS configuration, fiber ownership, and data transmission direction. H-RAN with optimal functional split can achieve lower TCO than both classical Distributed RAN and CRAN.

1 - 26 of 26
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