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  • 101. G, Fodor
    et al.
    E, Nordstrom
    S, Blaabjerg
    Revenue optimization and fairness control of priced guaranteed and best effort services on an ATM transmission link1998In: ICC 98 - 1998 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS VOLS 1-3 / [ed] anon, New York: IEEE , 1998, p. 1696-1705Chapter in book (Other academic)
    Abstract [en]

    This paper is the sequel of two previous papers describing and analyzing partially blocking-queueing systems. In [1, 2] we proposed the extension of the classical multirate circuit switched loss model [11] in order to model and analyze on the call level ATM systems supporting best effort type service classes, such as the ABR or UBR service classes. After a brief review of the basic modelling concepts, in this paper we are concerned with optimal Call Admission Control, (CAC) of CBR/VBR and ABR/UBR calls in the sense that we want to maximize the revenue on a single ATM link when both QoS guaranteed and best effort service classes are present. We formulate the problem as a Markov Decision Problem [3, 4, 5, 11, 13, 15, 16] and find that the concept of intelligent blocking is useful in this context. We solve this optimization task by policy iteration to find the blocking states of the link. This modelling framework (in its present form and by extensions) allows to study the impact of pricing policies on CAC and fairness.

  • 102. G, Fodor
    et al.
    G, Leijonhufvud
    S, Malomsoky
    A, Racz
    Comparison of call admission control algorithms in ATM/AAL2 based 3/sup rd/ generation mobile access networks1999In: 1999 IEEE Wireless Communications and Networking Conference (WCNC) / [ed] IEEE, New York: IEEE , 1999, p. 1508-1512Chapter in book (Other academic)
  • 103. G, Fodor
    et al.
    G, Malicsko
    S, Malomsoky
    A joint radio-IP resource reservation scheme in All-IP 3rd generation networks2000In: Proceedings of the IEEE Wireless Communications and Networking Conference (WCNC) / [ed] IEEE, New York: IEEE , 2000, p. 1286-1290Chapter in book (Other academic)
  • 104. G, Fodor
    et al.
    K, El-Malki
    D, Partain
    Closing the gap between industry, academia and users: Is there a need for QoS in wireless systems?2005In: Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349, Vol. 3552, p. 375-378Article in journal (Refereed)
    Abstract [en]

    In this short paper we make the point that although there may be a gap between academic and industrial research in the area of quality of service (QoS), this gap can be narrowed. In order for this to happen, it is important that the academic and industrial players jointly make an effort to better understand business drivers and end user needs and analyze how networks are used and how they are likely to evolve. That is, understanding the key drivers (the "why"-s) in the QoS area is the key in bringing academic and industrial research (that aims to answer the "how"-s) closer to each other.

  • 105. G, Fodor
    et al.
    M, Lindström
    On multi-cell admission control in CDMA networks2008In: International Journal of Communication Systems, ISSN 1074-5351, E-ISSN 1099-1131, Vol. 21, no 1, p. 25-50Article in journal (Refereed)
    Abstract [en]

    We consider a multi-cell (MC) code division multiple access (CDMA) system that supports multiple service classes, including peak rate allocated and elastic ones. Peak rate allocated sessions—when admitted into the system—transmit at a constant bit rate, while elastic sessions can be slowed down at the expense of increasing their residency time. Admitted sessions cause an instantaneous bit rate-dependent interference in neighbour cells. In this rather general setting, we propose a method to calculate the class-wise blocking probabilities as the functions of the estimated so-called inter-cell coupling factors. In the paper this coupling factor is the ratio between the uplink path gains to different Node-B:s (that can be easily obtained in a CDMA system from pilot measurement reports), but our model could include other coupling measures as well. We find that when these coupling factors are underestimated, the system may get into false states (FSs) or false rate states(FRSs) that lead to violating the noise rise threshold. As traffic becomes increasingly elastic, the probability of FSs decreases, but the probability of FRSs increases. Based on numerical results, we make the point that as the traffic becomes more elastic, avoiding the underestimation of these coupling factors as well as exercising MC admission control plays an increasingly important role in guaranteeing proper service quality.

  • 106. G, Fodor
    et al.
    P, Skillermark
    Performance analysis of a reuse partitioning technique for multi-channel cellular systems supporting elastic services2009In: International Journal of Communication Systems, ISSN 1074-5351, E-ISSN 1099-1131, Vol. 22, no 3, p. 307-342Article in journal (Refereed)
    Abstract [en]

    For multi-cell systems employing intra-cell orthogonal communication channels, inter-cell interference mitigation techniques are expected to be one of the key radio resource management functions. In this paper we propose and analyze a simple reuse partitioning technique (with random and coordinated resource block allocation in neighbor cells) that is able to reduce inter-cell interference. We propose a model that is able to take into account that sessions dynamically enter and leave the system. Rigid sessions require a class-specific fixed number of resource blocks, while elastic sessions can enter the system if a minimum number of resources are allocated to them. In this rather general setting (and using the example of a system employing frequency division for multiple access) we analyze the system performance in terms of the expected number of channel collisions, the session-blocking probabilities, the signal-to-interference-and-noise ratio (SINR) and packet error rate performance. We present numerical results on the various trade-offs between these measures (including the trade-off between the reuse factor and the SINR performance) that provide insight into the behavior of multi-channel cellular systems and help dimensionalize the parameters of a reuse partitioned system.

  • 107. G, Fodor
    et al.
    S, Sorrentino
    S, Sultana
    Network assisted device-to-device communications: Use cases, design approaches, and performance aspects2014In: Smart Device to Smart Device Communication / [ed] Mumtaz, Shahid; Rodriguez, Jonathan, Cham (Svájc): Springer, 2014, p. 135-163Chapter in book (Other academic)
    Abstract [en]

    Network assisted device-to-device (D2D) communications have emerged as a means of increasing spectral and energy efficiency, reducing latency and creating a platform for proximity-based services. Application areas of D2D communications include cellular network offloading and coverage extension, proximity-based social networking, and providing national security and public safety (NSPS) in infrastructure-less situations. This broad range of applications has led to a large set of technical requirements that must be taken into account when designing physical layer algorithms, user and control plane protocols, and network architecture. In this chapter we review the key requirements and current approaches to network assisted service and device discovery, radio resource management and tuning the performance of integrated D2D, and cellular networks.

  • 108.
    Gabor, Fodor
    et al.
    Ericsson Research.
    Miklos, Telek
    On the Tradeoff Between Blocking and Dropping Probabilities in Multi-cell Cdma Networks2007In: Journal of Communications, ISSN 1796-2021, E-ISSN 1796-2021, Vol. 2, no 1, p. 22-33Article in journal (Refereed)
    Abstract [en]

    This paper is a sequel of previous work, in which we proposed a model and computational technique to calculate the Erlang capacity of a single CDMA cell that supports elastic services. The present paper extends that base model by taking into account two important aspects of CDMA. First, we describe a simple and a refined multicell CDMA model that are able to capture the impact of the neighbor cells on important performance measures of the cell under study. These performance measures include the class-wise blocking probabilities and the mean time that elastic sessions spend in the system. Secondly, we model the impact of the outage by taking into account that in-progress sessions can be dropped with a probability that depends on the current load in the serving and neighbor cells. We then consider a system with elastic and rigid service classes and analyze the trade-off between the total (soft and hard) blocking probabilities on the one hand and the throughput and the session drop probabilities on the other.

  • 109.
    Guimaraes, Francisco R. V.
    et al.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, CP 6005, BR-60440970 Fortaleza, Ceara, Brazil..
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. Ericsson Res, S-16483 Stockholm, Sweden.
    Freitas, Walter C., Jr.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, CP 6005, BR-60440970 Fortaleza, Ceara, Brazil..
    Silva, Yuri C. B.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, CP 6005, BR-60440970 Fortaleza, Ceara, Brazil..
    Pricing-Based Distributed Beamforming for Dynamic Time Division Duplexing Systems2018In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 67, no 4, p. 3145-3157Article in journal (Refereed)
    Abstract [en]

    Multicell dynamic time division duplexing (TDD) systems make it possible to adapt the number of uplink and downlink time slots in each cell to the prevailing cell-wide traffic demand. Although dynamic TDD systems can be advantageously deployed in scenarios in which the uplink and downlink traffic demands are asymmetric and time varying, dynamic TDD systems give rise to base station to base station (BS-to-BS) interference and user equipment to user equipment (UE-to-UE) interference that negatively impact the system performance. In this paper, we propose employing a distributed beamforming scheme to mitigate the BS-to-BS interference and thereby to improve the uplink performance. Specifically, the proposed scheme uses interference pricing to find the appropriate precoder vectors at the BSs, which also improves the signal-to-interference-plus-noise ratio (SINR) performance in the downlink. We compare the performance of the pricing-based (PB) beamforming scheme with that of zero-forcing beamforming in an outdoor picocell environment specified by the 3rd Generation Partnership Project using a realistic system simulator. We find that the proposed PB scheme boosts the SINR in the uplink at the expense of a small degradation of the downlink SINR compared with the zero-forcing scheme. On the other hand, the PB beamforming approach can significantly reduce the downlink transmit power levels and thereby improve the overall energy efficiency of the system.

  • 110. Guo, K.
    et al.
    Dai, S.
    Zhang, C.
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control. Ericsson Research, Sweden.
    Ascheid, G.
    Massive MIMO aided multi-pair relaying with underlaid D2D communications2017In: European Wireless 2017 - 23rd European Wireless Conference, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 8011348Conference paper (Refereed)
    Abstract [en]

    Device-to-device (D2D) communication underlaying a cellular infrastructure is an important technique, e.g. to offload traffic, but has a limit of short range, which can be overcome via relaying. In such context, the coexistence of D2D and multi-pair communications in massive MIMO aided relaying is considered in this paper. The direct D2D transmission reuses the source-torelay spectrum in the first hop, which leads to a rate loss at the destination users, due to the amplify-and-forward relaying. To evaluate this loss, a closed-form deterministic equivalent of the end-to-end (e2e) signal to interference-plus-noise ratio (SINR) is derived. Moreover, in case of failed direct transmissions, D2D receivers can perform the detection in the second hop, based on the signal forwarded by the relay. The associated deterministic D2D SINR equivalent is also derived. The asymptotic analysis indicates that the transmit power of source users can be made inversely proportional to the number of relay antennas, such that non-vanishing e2e rate at the destination users and relay assisted D2D rate exist. Simulations validate the analytical results and the feasibility of supporting underlaid D2D transmissions when deploying multi-pair relaying with massive MIMO.

  • 111. Guo, Kaifeng
    et al.
    Guo, Yan
    Fodor, Gabor
    Ascheid, Gerd
    Uplink power control with MMSE receiver in multi-cell MU-massive-MIMO systems2014In: 2014 IEEE International Conference on Communications (ICC), New York: IEEE conference proceedings, 2014, p. 5184-5190Conference paper (Other academic)
    Abstract [en]

    In the current literature considering multi-cell multi-user massive multiple-input multiple-output (MU-Massive-MIMO) systems, equal uplink power allocation among users is typically assumed, which does not exploit the potential of peruser power control. By contrast, in this paper we apply multi-cell uplink power control, assuming the minimum mean-square-error receiver based on the pilot contaminated channel estimation and a very large but finite number of antennas at the base station. We derive the lower bound on the average post-processing uplink signal to interference-plus-noise ratio (SINR) with individual power assignment between pilot and data transmissions for each user, which facilitates a joint iterative uplink pilot and data power control strategy that minimizes the sum transmit power of all users subject to the per-user SINR and per-user power constraints. The convergence of the proposed algorithm to a unique fixed point optimal solution is discussed for both single- and multi-user scenarios. Numerical results indicate the significance of uplink power control which further improves the energy efficiency in MU-Massive-MIMO systems.

  • 112. I, Cananéa
    et al.
    D, Mariz
    J, Kelner
    D, Sadok
    G, Fodor
    An on-line access selection algorithm for ABC networks supporting elastic services2008In: Wireless Communications and Networking Conference, 2008. WCNC 2008. IEEE, New York: IEEE conference proceedings, 2008, p. 2033-2038Conference paper (Refereed)
    Abstract [en]

    The problem of access selection (AS) for multi-access networks has for long been addressed by both the standardization and research communities. As a result, a number of papers have proposed efficient AS algorithms that can take into account radio resource efficiency, overall capacity and quality of service (QoS) requirements in a multi-service environment. However, only a few works have developed on-line AS algorithms that do not require a priori knowledge of the traffic mix when delay sensitive (e.g. voice) and best effort (data) applications are supported. In this work, we present an online AS algorithm that performs well in a multiaccess network supporting two service classes and specifically takes into account the elastic nature of data applications. We model AS as a binpacking problem and realize that the problem is NP-complete. Therefore, we develop a heuristic algorithm called LessDamage that calculates a damage parameter and uses it as a metric for the allocation strategy. Simulation results show that LessDamage performs better in terms of blocking probability and elastic data throughput than available online binpacking heuristics, independently of the number of the available access technologies.

  • 113. JMB, Da Silva
    et al.
    G, Fodor
    TF, Maciel
    Performance analysis of network-assisted two-hop D2D communications2014In: 2014 IEEE Globecom Workshops (GC Wkshps), New York: IEEE conference proceedings, 2014, p. 1050-1056Conference paper (Other academic)
    Abstract [en]

    Network-assisted single-hop device-to-device (D2D) communication can increase the spectral and energy efficiency of cellular networks by taking advantage of the proximity, reuse, and hop gains. In this paper we argue that D2D technology can be used to further increase the spectral and energy efficiency if the key D2D radio resource management algorithms are suitably extended to support network assisted multi-hop D2D communications. Specifically we propose a novel, distributed utility maximizing D2D power control (PC) scheme that is able to balance spectral and energy efficiency while taking into account mode selection and resource allocation constraints that are important in the integrated cellular-D2D environment. Our analysis and numerical results indicate that multi-hop D2D communications combined with the proposed PC scheme can be useful not only for harvesting the potential gains previously identified in the literature, but also for extending the coverage of cellular networks.

  • 114.
    Kant, Shashi
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering. Ericsson AB.
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. Ericsson AB.
    Bengtsson, Mats
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Göransson, Bo
    Ericsson AB.
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering.
    Low-Complexity OFDM Spectral Precoding2019In: 20th IEEE International Workshop on Signal Processing Advances in Wireless Communications (SPAWC) 2019, 2019, article id 8815554Conference paper (Refereed)
    Abstract [en]

    This paper proposes a new large-scale mask compliant spectral precoder (LS-MSP) for orthogonal frequency division multiplexing systems. In this paper, we first consider a previously proposed mask-compliant spectral precoding scheme that utilizes a generic convex optimization solver which suffers from high computational complexity, notably in large-scale systems. To mitigate the complexity of computing the LS-MSP, we propose a divide-and-conquer approach that breaks the original problem into smaller rank 1 quadratic-constraint problems and each small problem yields closed-form solution. Based on these solutions, we develop three specialized first-order low-complexity algorithms, based on 1) projection on convex sets and 2) the alternating direction method of multipliers. We also develop an algorithm that capitalizes on the closed-form solutions for the rank 1 quadratic constraints, which is referred to as 3) semianalytical spectral precoding. Numerical results show that the proposed LS-MSP techniques outperform previously proposed techniques in terms of the computational burden while complying with the spectrum mask. The results also indicate that 3) typically needs 3 iterations to achieve similar results as 1) and 2) at the expense of a slightly increased computational complexity.

  • 115. Kazmi, Muhammad Ali
    et al.
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Method for generating a congestion flag based on measured system load2014Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A radio base station generates a congestion status flag, based on measured resource usage in its cell, and based on performance of sessions in the cell. The flag may be a one bit, or a small number of bits, indicating whether the base station is congested. The flag can be sent to neighboring radio base stations, for use in determining whether to perform handovers to that radio base station. The flag generated in a radio base station, and the flags generated in neighboring radio base stations, can also be sent to user equipment in a cell.

  • 116. Kazmi, Muhammad Ali
    et al.
    Fodor, Gabor
    Methods and arrangements for ad-hoc wireless networks2010Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A method, User Equipment (UE), and network node in an ad-hoc network. The UE determines a node in the ad-hoc network that is able to provide a reference signal comprising a pattern that can be used for synchronization purposes when the UE is in DRX mode in the ad-hoc network. The node is determined by requesting the node to indicate whether the node is able to provide the reference signal, and receiving an accept signal or message from the node. The UE then receives the reference signal from the determined node, enters DRX mode, and uses the received reference signal to maintain synchronization while in the DRX mode.

  • 117. Kazmi, Muhammad
    et al.
    Fodor, Gabor
    Ericsson Research.
    A Method for Controlling Uplink Transmissions, an Access Point, a Controller, and a Wireless Telecommunications System2005Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A method for controlling uplink transmissions from a user device (3) to an access point (5) in a wireless telecommunications system is described. Each access point defines a communications cell, and the method comprises monitoring interference in an uplink channel at an access point (5), performing interference control actions at the access point when monitored interference exceeds a first predetermined level, monitoring occurrences of such control actions at the access point (5), and if a number of such occurrences exceeds a predetermined level, performing interference control actions with reference to a plurality of cells at a central controller (11) of the telecommunications system, which central controller is operable to control a plurality of access points (5).

  • 118. Kazmi, Muhammad
    et al.
    Fodor, Gabor
    Method for load balancing of devices in idle mode2007Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    The invention discloses a method for a cellular communications system, in which there is a first plurality of cells and a second plurality of base stations, each base station controlling the traffic to and from user terminals in a cell. User terminals can assume an idle mode, where a user terminal when in an idle mode performs cell reselection, comprising an evaluation of the cells which are available to the user terminal. The base stations of a number of cells in the system transmit a set of reselection probabilities, each probability in said set being the probability with which a terminal when in idle mode may carry out a reselection from its present cell to the cell to which the probability refers.

  • 119. Kazmi, Muhammad
    et al.
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Selecting a cell associated with a radio access technology2012Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    Embodiments herein include a method in a base station serving a cell for assisting a user equipment to select a cell. The method comprises the step of sending a message comprising a reference to a service class and a priority level associated with a radio access technology used by the cell that the base station serves. Embodiments herein also include a corresponding arrangement in a base station. Embodiments herein further include a method in a core network node for configuring service classes in a network. The method comprises associating a radio access technology with a service class and a priority level. The method further comprises sending to a base station a reference to the service class and the priority level associated with the radio access technology used by the base station. Embodiments herein finally include a corresponding arrangement in a core network node.

  • 120. Kazmi, Muhammad
    et al.
    Fodor, Gabor
    Ericsson Research.
    Muller, Walter
    Semi-Distributed, Quality-of-Service-Based Scheduling Protocols, with Minimum Control Plane Signaling2008Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    Methods and apparatus for scheduling link resources in a wireless communication system (100) are disclosed. In an exemplary method, a first scheduling policy vector (210), or SPV (210), is generated, the SPV (210) including scheduling elements (220) that prescribe a probability of use for each of several corresponding quantities of link resources. In some embodiments the link resources are LTE resource blocks. The SPV (210) is transmitted to a mobile terminal (150) for use in determining a quantity of link resource units to be scheduled in at least a first transmission time interval. The SPV (210) may be transmitted along with a scheduling window parameter that specifies a period of applicability for SPV (210).

  • 121. Kazmi, Muhammad
    et al.
    Fodor, Gabor
    Müller, Walter
    Semi-distributed, quality-of-service-based scheduling protocols, with minimum control plane signaling2008Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    The present invention generally relates to wireless communication systems, and particularly relates to scheduling of resources in such systems.

  • 122. Klang, Göran N.
    et al.
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Interference management for D2D system2012Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    User equipment, UEs, (306 a,d) being interfered by direct D2D traffic, and UEs (306 b,c) involved in D2D communication being interfered by a UE (306 a,d), instead of passively reporting that they are interfered to their serving base station (305), intervene and communicate directly with the pair of D2D communicating UEs or the UE that are causing the interference without involving any of the serving base stations.

  • 123. Koutsimanis, C
    et al.
    Fodor, G
    A dynamic resource allocation scheme for guaranteed bit rate services in OFDMA networks2008In: 2008 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, PROCEEDINGS, VOLS 1-13, New York: IEEE conference proceedings, 2008, p. 2524-2530Conference paper (Other academic)
    Abstract [en]

    While several previous works have considered the problem of resource (including subcarrier and power) allocation in multicell orthogonal frequency division multiple access networks, only a few contributions have explicitly taken into account the elastic nature of data applications. In this work, each user is associated with a minimum and maximum resource block requirement and the resource allocation problem consists of maximizing the overall throughput such that these requirements are met. We propose a hybrid method that partitions this problem into a centralized and a distributed algorithm that balances between maximizing the overall throughput and being feasible in real systems. By means of simulations we compare four resource allocation strategies that represent various degrees of multi- cell coordination and taking advantage of multi-user diversity. We find that a feasible dynamic coordination combined with intra-cell multi-user diversity provides large throughput gains compared with non-coordinated schemes or schemes that would limit the degree of freedom of multi-user diversity.

  • 124. Li, Zexian
    et al.
    Moya, Fernando Sanchez
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control.
    B. da Silva Jr., Jose Mairton
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Koufos, Konstantinos
    Device-to-device (D2D) communications2016In: 5G Mobile and Wireless Communications Technology / [ed] Osseiran, A; Marsch, P; Monserrat, J F, Cambridge: Cambridge U Press , 2016, p. 107-136Chapter in book (Other academic)
  • 125. Lu, Qianxi
    et al.
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES). Ericsson Research.
    Miao, Qingyu
    Method and Arrangement for D2D Discovery2012Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    According to a first aspect of embodiments herein, the object is achieved by a method in a base station for handling a process of discovering a candidate user equipment for Device to Device, D2D, communication in a cell. The cell is served by the base station. The base station divides (200) the cell into a number of regions. The base station then assigns (201) to each one out of the number of regions, a channel resource for use in the region. The channel resource is for sending beacon signals in the process of discovering the D2D candidate user equipment.

  • 126. M, Telek
    et al.
    A, Pfening
    Fodor, Gabor
    Department of Telecommunications and Telematics Technical University of Budapest, 1521 Budapest, Hungary.
    An effective numerical method to compute the moments of the completion time of Markov reward models1998In: Computers and Mathematics with Applications, ISSN 0898-1221, E-ISSN 1873-7668, Vol. 36, no 8, p. 59-65Article in journal (Refereed)
    Abstract [en]

    Analysis of Markov Reward Models (MRM) with preemptive resume (prs) policy results in a double transform expression, whose solution is based on the inverse transformations both in time and reward variable domain. We present a symbolic expression of moments of the completion time, from which a computationally effective recursive numerical method can be obtained. (C) 1998 Elsevier Science Ltd. All rights reserved.

  • 127. MGDS, Rêgo
    et al.
    TF, Maciel
    HDHM, Barros
    FRP, Cavalcanti
    Fodor, Gabor
    Ericsson Research, SE-164 80, Stockholm, Sweden.
    Performance analysis of power control for device-to-device communication in cellular MIMO systems2012In: 2012 International Symposium on Wireless Communication Systems (ISWCS) / [ed] IEEE, New York: IEEE Press, 2012, p. 336-340Chapter in book (Other academic)
  • 128. Mikael, Fallgren
    et al.
    Fodor, Gabor
    Forsgren, Anders
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Optimization approach to joint cell, channel and power allocation in wireless communication networks2012In: 2012 Proceedings of the 20th European Signal Processing Conference (EUSIPCO), New York: IEEE conference proceedings, 2012, p. 829-833Conference paper (Other academic)
    Abstract [en]

    In multicell wireless networks the resource allocation task includes the selection of the serving cell and the allocation of channels and transmission powers. While all of these tasks have been studied in the past, all three jointly are seldom addressed. In this paper we formulate the joint cell, channel and power allocation problem as an optimization task, whose purpose is to maximize the total user throughput. The joint problem is decomposed into separate subproblems of cell, channel and power allocation. We propose heuristic and optimization based algorithms to solve each of these tasks and present numerical results that give new and valuable insights into a sum throughput optimal joint resource allocation strategy.

  • 129. Mildh, Gunnar
    et al.
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control. Ericsson Research.
    Hedberg, Tomas
    Vikberg, Jari
    Methods and User Equipments for Providing Information about a Connection State2016Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A method in a first user equipment (110) and a first user equipment (110) for providing information about at least one of a first and a second connection state are provided. Moreover, a corresponding method in a second user equipment (120) and a second user equipment (120) are provided. The first connection state is related to a first connection between the first user equipment (110) and a radio network node (140). The second connection state is related to a second connection between the first user equipment (110) and the second user equipment (120). The first user equipment (110) encodes (220) information about at least one of the first and second connection states into a synchronization signal for synchronizing the second user equipment (120) to the first user equipment (110). The first user equipment (110) sends (230) the synchronization signal to at least the second user equipment (120), thereby providing information about at least one of the first and second connection states. The second user equipment (120) decodes (250) the synchronization signal.

  • 130. Mildh, Gunnar
    et al.
    Fodor, Gabor
    Ericsson Research.
    Hedberg, Tomas
    Vikberg, Jari
    Multiple Gateway Handling for Supporting Network Sharing for Home Base Stations2011Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A home base station receives from a wireless user equipment an identification of a selected Public Land Mobile Network, PLMN, among multiple available PLMNs to which the wireless user equipment is to be connected. The home base station identifies a communication path to a home base station gateway is associated with the selected PLMN and communicates with the selected PLMN that was identified over the communication path that was identified. The home base station may thereby be shared among multiple PLMNs. Related networks, methods and home base stations are described.

  • 131. Mildh, Gunnar
    et al.
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control. Ericsson Research.
    Parkvall, Stefan
    Dahlman, Erik
    A Method and a User Equipment for Peer-to-Peer Communication2017Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    The exemplary embodiments relate to a method for use in a user equipment (UE), and a cellular infrastructure, for achieving synchronization between UEs for a peer-to-peer or device-to-device (D2D) communication. The method comprising: receiving at a UE a synchronization message from a cell or a RAT or a source of the cellular infrastructure; assembling a message including a list comprising information on the source or cell or RAT, sending the assembled message to a another UE and initiate synchronization between involved UEs based on the information in the assembled message.

  • 132. Mildh, Gunnar
    et al.
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES).
    Vikberg, Jari
    Hedberg, Tomas
    Radio base stations and methods therein for handling interference and scheduling radio resources accordingly2011Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    Embodiments herein relate to a first radio base station (12) for handling radio interference in a radio communications network, which first radio base station (12) provides radio coverage over a geographical area forming a first cell (14). In the first cell (14) a first user equipment (10) and a second user equipment (11) are served, which first radio base station (12), the first user equipment (10) and the second user equipment (11) are comprised in the radio communications network. The first radio base station (12) determines that a first radio resource is allocated to the first user equipment (10) for communicating over a device-to-device, D2D, connection with the second user equipment (11) within the first cell (14), The first radio base station then transfers information to an arrangement serving a second cell (15), which information identifies the first radio resource and indicates that the first radio resource is allocated to the first user equipment (10) for communicating over the D2D connection with the second user equipment (11) within the first cell (14). The information is to be taken into account by the arrangement serving the second cell (15) for scheduling a second radio resource to a third user equipment (16) in the second cell.

  • 133.
    Moghadam, Nima N.
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Bengtsson, Mats
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Love, David J.
    Purdue Univ, Sch Elect & Comp Engn, W Lafayette, IN 47906 USA..
    On the Energy Efficiency of MIMO Hybrid Beamforming for Millimeter-Wave Systems With Nonlinear Power Amplifiers2018In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, no 11, p. 7208-7221Article in journal (Refereed)
    Abstract [en]

    Multiple-input multiple-output (MIMO) millimeter-wave (mm-wave) systems are vulnerable to hardware impairments due to operating at high frequencies and employing a large number of radio-frequency hardware components. In particular, nonlinear power amplifiers (PAs) employed at the transmitter distort the signal when operated close to saturation due to energy efficiency considerations. In this paper, we study the performance of an MIMO mm-wave hybrid beamforming scheme in the presence of nonlinear PAs. First, we develop a statistical model for the transmitted signal in such systems and show that the spatial direction of the inband distortion is shaped by the beamforming filter. This suggests that even in the large antenna regime, where narrow beams can be steered toward the receiver, the impact of nonlinear PAs should not be ignored. Then, by employing a realistic power consumption model for the PAs, we investigate the tradeoff between spectral and energy efficiency in such systems. Our results show that increasing the transmit power level when the number of transmit antennas grows large can be counter-effective in terms of energy efficiency. Furthermore, using numerical simulation, we show that when the transmit power is large, analog beamforming leads to higher spectral and energy efficiency compared to digital and hybrid beamforming schemes.

  • 134.
    Moghadam, Nima N.
    et al.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Shokri-Ghadikolaei, Hossein
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Pilot precoding and combining in multiuser MIMO networks2017In: 2017 IEEE International Conference on Acoustics Speech and Signal Processing ICASSP (ICASSP), Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 3544-3548Conference paper (Refereed)
    Abstract [en]

    Although the benefits of precoding and combining of data streams are widely recognized, the potential of precoding the pilot signals at the user equipment (UE) side and combining them at the base station (BS) side has not received adequate attention. This paper considers a multiuser multiple input multiple output (MU-MIMO) cellular system in which the BS acquires channel state information (CSI) by means of uplink pilot signals and proposes pilot precoding and combining to improve the CSI quality. We first evaluate the channel estimation performance of a baseline scenario in which CSI is acquired with no pilot precoding. Next, we characterize the channel estimation error when the pilot signals are precoded by spatial filters that asymptotically maximize the channel estimation quality. Finally, we study the case when, in addition to pilot precoding at the UE side, the BS utilizes the second order statistics of the channels to further improve the channel estimation performance. The analytical and numerical results show that, specially in scenarios with large number of antennas at the BS and UEs, pilot precoding and combining has a great potential to improve the channel estimation quality in MU-MIMO systems.

  • 135. Muppirisetty, L. Srikar
    et al.
    Wymeersch, Henk
    Karout, Johnny
    Fodor, Gabor
    Location-aided pilot contamination elimination for massive MIMO systems2016In: 2015 IEEE Global Communications Conference, GLOBECOM 2015, New York: IEEE conference proceedings, 2016Conference paper (Other academic)
    Abstract [en]

    Massive MIMO systems, while being a promising technology for 5G systems, face a number of practical challenges. Among those, pilot contamination stands out as a key bottleneck to design high-capacity beamforming methods. We propose and analyze a location-aided approach to reduce the pilot contamination effect in uplink channel estimation for massive MIMO systems. The proposed method exploits the location of user terminals, scatterers, and base stations. The approach removes the need for direct estimation of large covariance matrices and provides good channel estimation performance in the large antenna regime.

  • 136.
    Najari Moghadam, Nima
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Fodor, Gabor
    Bengtsson, Mats
    Love, David J.
    On the Energy Efficiency of MIMO Hybrid Beamforming for Millimeter Wave Systems with Nonlinear Power AmplifiersManuscript (preprint) (Other academic)
    Abstract [en]

    Multiple-input multiple-output (MIMO) millimeter wave (mmWave) systems are a promising candidate to support extremely high data rate services in future wireless communication networks. However, operating at high frequencies and employing a large number of radio frequency (RF) hardware components make MIMO mmWave systems vulnerable to hardware impairments. In particular, nonlinear power amplifiers (PAs) employed at the transmitter distort the signal when operated close to their saturation regions due to energy efficiency considerations. In this paper, we study the performance of a MIMO mmWave hybrid beamforming scheme in the presence of nonlinear PAs. First, distortion signal we develop a statistical model for the transmitted signal in such systems and show that the spatial distortion signal is shaped by the beamforming filter. This suggests thateven in the large antenna regime, where narrow beams can begenerated and steered toward the receiver, the impact of thenonlinear PAs should not be ignored. Then, by employing arealistic power consumption model for the PAs, we investigate thetrade-off between spectral and energy efficiency in such systems.For the special case, when the number of transmit RF-chains isone, closed forms for the achievable spectral efficiency as wellas the system energy efficiency is derived. Our results show thatwhen using hybrid beamforming, increasing the transmit powerlevel when the number of transmit antennas grows large can becounter-effective in terms of spectral and energy efficiency. Onthe other hand, with a moderate number of transmit antennas,increasing the transmit power up to a certain threshold isbeneficial for the spectral and energy efficiency of the system.

  • 137.
    Najari Moghadam, Nima
    et al.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Shokri-Ghadikolaei, Hossein
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Pilot Precoding and Combining in Multiuser MIMO Networks2017In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. June, no 6Article in journal (Refereed)
    Abstract [en]

    Although the benefits of precoding and combining data signals are widely recognized, the potential of these techniques for pilot transmission is not fully understood. This is particularly relevant for multiuser multiple-input multiple-output(MU-MIMO) cellular systems using millimeter-wave (mmWave)communications, where multiple antennas have to be used both at the transmitter and the receiver to overcome the severe path loss.In this paper, we characterize the gains of pilot precoding and combining in terms of channel estimation quality and achievable data rate. Specifically, we consider three uplink pilot transmission scenarios in a mmWave MU-MIMO cellular system: 1) non-precoded and uncombined, 2) precoded but uncombined, and3) precoded and combined. We show that a simple precoder that utilizes only the second-order statistics of the channel reduces the variance of the channel estimation error by a factor that is proportional to the number of user equipment (UE) antennas.We also show that using a linear combiner design based on the second-order statistics of the channel significantly reduces multiuser interference and provides the possibility of reusing some pilots. Specifically, in the large antenna regime, pilot preceding and combining help to accommodate a large number ofUEs in one cell, significantly improve channel estimation quality, boost the signal-to-noise ratio of the UEs located close to the cell edges, alleviate pilot contamination, and address the imbalanced coverage of pilot and data signals.

  • 138. Ometov, Aleksandr
    et al.
    Orsino, Antonino
    Militano, Leonardo
    Moltchanov, Dmitri
    Araniti, Giuseppe
    Olshannikova, Ekaterina
    Fodor, Gabor
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. Ericsson Res, Stockholm, Sweden.
    Andreev, Sergey
    Olsson, Thomas
    Iera, Antonio
    Torsner, Johan
    Koucheryavy, Yevgeni
    Mikkonen, Tommi
    TOWARD TRUSTED, SOCIAL-AWARE D2D CONNECTIVITY: BRIDGING ACROSS THE TECHNOLOGY AND SOCIALITY REALMS2016In: IEEE wireless communications, ISSN 1536-1284, E-ISSN 1558-0687, Vol. 23, no 4, p. 103-111Article in journal (Refereed)
    Abstract [en]

    Driven by the unprecedented increase of mobile data traffic, D2D communications technology is rapidly moving into the mainstream of the 5G networking landscape. While D2D connectivity originally emerged as a technology enabler for public safety services, it is likely to remain at the heart of the 5G ecosystem by spawning a wide diversity of proximate applications and services. In this work, we argue that the widespread adoption of the direct communications paradigm is unlikely without embracing the concepts of trust and social-aware cooperation between end users and network operators. However, such adoption remains conditional on identifying adequate incentives that engage humans and their connected devices in a plethora of collective activities. To this end, the mission of our research is to advance the vision of social-aware and trusted D2D connectivity, as well as to facilitate its further adoption. We begin by reviewing the various types of underlying incentives with the emphasis on sociality and trust, discuss these factors specifically for humans and for networked devices (machines), and also propose a novel framework allowing construction of much needed incentive-aware D2D applications. Our supportive system-level performance evaluations suggest that trusted and social-aware direct connectivity has the potential to decisively augment network performance. We conclude by outlining the future perspectives of its development across the research and standardization sectors.

  • 139. Orsino, Antonino
    et al.
    Ometov, Aleksandr
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control. Ericsson Research.
    Moltchanov, Dmitri
    Militano, Leonardo
    Andreev, Sergey
    Yilmaz, Osman N. C.
    Tirronen, Tuomas
    Torsner, Johan
    Araniti, Giuseppe
    Iera, Antonio
    Dohler, Mischa
    Koucheryavy, Yevgeni
    Effects of Heterogeneous Mobility on D2D- and Drone-Assisted Mission-Critical MTC in 5G2017In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 55, no 2, p. 79-87Article in journal (Refereed)
    Abstract [en]

    mcMTC is starting to play a central role in the industrial Internet of Things ecosystem and have the potential to create high-revenue businesses, including intelligent transportation systems, energy/ smart grid control, public safety services, and high-end wearable applications. Consequently, in the 5G of wireless networks, mcMTC have imposed a wide range of requirements on the enabling technology, such as low power, high reliability, and low latency connectivity. Recognizing these challenges, the recent and ongoing releases of LTE systems incorporate support for low-cost and enhanced coverage, reduced latency, and high reliability for devices at varying levels of mobility. In this article, we examine the effects of heterogeneous user and device mobility - produced by a mixture of various mobility patterns - on the performance of mcMTC across three representative scenarios within a multi-connectivity 5G network. We establish that the availability of alternative connectivity options, such as D2D links and drone-assisted access, helps meet the requirements of mcMTC applications in a wide range of scenarios, including industrial automation, vehicular connectivity, and urban communications. In particular, we confirm improvements of up to 40 percent in link availability and reliability with the use of proximate connections on top of the cellular-only baseline.

  • 140. Persson, Fredrik
    et al.
    Fodor, Gabor
    A QoS parameters translater2003Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    When UMTS is part of IP end-to-end communication, there must exist means for UMTS to be able to provide the required Quality of Service (QoS) for applications running over IP. Hence there is a need for a translation function for translation between IP QoS parameters and UMTS QoS attributes. This translation is not trivial because of several reasons. First, the number of QoS parameters in the IP level and the UMTS level are different. Second, definitions of parameters at the two levels are different. Keeping these factors in view, the present invention provides for a method for translation of IP QoS parameters to UMTS QoS attributes, and another method for translation of UMTS QoS attributes to IP QoS parameters. This translation will enable spectrum efficient UMTS bearers to be set up for applications running over IP. This will also make negotiation of services possible between an entity at the IP level and the UMTS network. These methods are placed in both the User Equipment as well as the Gateway of the UMTS network.

  • 141.
    Petrov, Vitaly
    et al.
    Tampere Univ Technol, Lab Elect & Commun Engn, Tampere, Finland..
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Kokkoniemi, Joonas
    Univ Oulu, Ctr Wireless Communicat, Oulu, Finland..
    Moltchanov, Dmitri
    Tampere Univ Technol, Lab Elect & Commun Engn, Tampere, Finland..
    Lehtomaki, Janne
    Univ Oulu, Ctr Wireless Communicat, Oulu, Finland..
    Andreev, Sergey
    Tampere Univ Technol, Lab Elect & Commun Engn, Tampere, Finland..
    Koucheryavy, Yevgeni
    Tampere Univ Technol, Lab Elect & Commun Engn, Tampere, Finland..
    Juntti, Markku
    Univ Oulu, Telecommun, Oulu, Finland..
    Valkama, Mikko
    Tampere Univ Technol, Lab Elect & Commun Engn, Tampere, Finland..
    ON UNIFIED VEHICULAR COMMUNICATIONS AND RADAR SENSING IN MILLIMETER-WAVE AND LOW TERAHERTZ BANDS2019In: IEEE wireless communications, ISSN 1536-1284, E-ISSN 1558-0687, Vol. 26, no 3, p. 146-153Article in journal (Refereed)
    Abstract [en]

    Future smart vehicles will incorporate high-data-rate communications and high-resolution radar sensing capabilities operating in the millimeter-wave and higher frequencies. These two systems are preparing to share and reuse many common functionalities, such as steerable millimeter-wave antenna arrays. Motivated by this growing overlap, which is advanced further by space and cost constraints, the vehicular community is pursuing a vision of unified vehicular communications and radar sensing that represents a major paradigm shift for next-generation connected and self-driving cars. This article outlines a path to materialize this decisive transformation. We begin by reviewing the latest developments in hybrid vehicular communications and radar systems, and then propose a concept of unified channel access over millimeter-wave and higher frequencies. Our supporting system-level performance characterization relies upon real-life measurements and extensive ray-based modeling to confirm the significant improvements brought by our proposal to mitigating the interference and deafness effects. Since our results aim to open the door to unified vehicular communications and radar sensing, we conclude by outlining the potential research directions in this rapidly developing field.

  • 142.
    Petrov, Vitaly
    et al.
    Tampere Univ Technol, Lab Elect & Commun Engn, Tampere, Finland..
    Mikhaylov, Konstantin
    Univ Oulu, Ctr Wireless Commun, Oulu, Finland..
    Moltchanov, Dmitri
    Tampere Univ Technol, Tampere, Finland..
    Andreev, Sergey
    Tampere Univ Technol, Lab Elect & Commun Engn, Tampere, Finland..
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Torsner, Johan
    Ericsson Res, Stockholm, Sweden..
    Yanikomeroglu, Halim
    Carleton Univ, Dept Syst & Comp Engn, Ottawa, ON, Canada..
    Juntti, Markku
    Univ Oulu, Telecommun, Oulu, Finland..
    Koucheryavy, Yevgeni
    Tampere Univ Technol, Lab Elect & Commun Engn, Tampere, Finland.;Natl Res Inst, Higher Sch Econ, Moscow, Russia..
    When IoT Keeps People in the Loop: A Path Towards a New Global Utility2019In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 57, no 1, p. 114-121Article in journal (Refereed)
    Abstract [en]

    While the IoT has made significant progress supporting individual machine-type applications, it is only recently that the importance of people as an integral component of the overall IoT infrastructure has started to be fully recognized. Several powerful concepts have emerged to facilitate this vision, whether involving the human context whenever required or directly impacting user behavior and decisions. As these become the stepping stones to develop the IoT into a novel people-centric utility, this article outlines a path to realize this decisive transformation. We begin by reviewing the latest progress in human-aware wireless networking, then classify the attractive human-machine applications and summarize the enabling IoT radio technologies. We continue with a unique system-level performance characterization of a representative urban IoT scenario and quantify the benefits of keeping people in the loop on various levels. Our comprehensive numerical results confirm the significant gains that have been made available with tighter user involvement, and also corroborate the development of efficient incentivization mechanisms, thereby opening the door to future commoditization of the global people-centric IoT utility.

  • 143. Pioro, M
    et al.
    Nilsson, P
    Kubilinskas, E
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control.
    On efficient max-min fair routing algorithms2003In: Proceedings of the Eighth IEEE Symposium on Computers and Communications (ISCC 2003) / [ed] IEEE, Antalya: IEEE conference proceedings, 2003, p. 365-372Chapter in book (Other academic)
    Abstract [en]

    In the paper, we consider the problem of routing and bandwidth allocation in networks that support elastic traffic. We assume that the bandwidth demand between each source-destination (S-D) pair is specified in terms of a minimum and maximum value, and a set of flows between each S-D pair is allowed to realize these demands. (We say that a set of flows realizes the demand associated with an S-D pair, if the sum of the bandwidths allocated to these flows is greater than the minimum value assumed for the demand of that S-D pair). In this setting, we show that routing and bandwidth allocation can be formulated as an optimization problem, where network utilization is to be maximized under capacity and the widely used max-min fairness constraints. We describe three different algorithms to solve variants of this problem. The most important one, an efficient, original algorithm assuming multipath routing is studied in detail and illustrated with a numerical example.

  • 144.
    Pradini, Aidilla
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control. Ericsson Research, Sweden .
    Miao, Guowang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Belleschi, M.
    Near-optimal practical power control schemes for D2D communications in cellular networks2014In: EuCNC 2014 - European Conference on Networks and Communications, IEEE Computer Society, 2014, p. 6882666-Conference paper (Refereed)
    Abstract [en]

    Device-to-device (D2D) communication has the potential of increasing the system capacity, energy efficiency and achievable peak rates while reducing the end-to-end latency. To realize these gains, recent works have proposed resource allocation (RA) and power control (PC) approaches that show near optimal performance in terms of spectral or energy efficiency. However, the proposed schemes either consider a single cell environment or assume instantaneous channel state information (CSI) and/or rely on iterative algorithms that require excessive inter-node message exchange and suffer from slow convergence time. For D2D user equipment (UE), we propose a distributed utility optimization based PC scheme that relies on locally available measurement data and is made practical by constraining the number of iterations and the interference caused to the cellular receiver, while legacy UEs employ the standard Long Term Evolution (LTE) PC. We investigate the performance of the proposed PC scheme when combined with two RA schemes that differ in terms of the required channel state information. We find that when properly tuned, this practical PC scheme combined with a RA algorithm that requires limited channel knowledge, not only shows near optimal performance, but it also constraints the impact of D2D communications on the cellular layer.

  • 145. Qianxi, Lu
    et al.
    Q, Miao
    Fodor, Gabor
    Ericsson Res., Stockholm, Sweden.
    N, Brahmi
    Clustering schemes for D2D communications under partial/no network coverage2014In: 2014 IEEE 79th Vehicular Technology Conference (VTC Spring) / [ed] IEEE, New York: IEEE Press, 2014Chapter in book (Other academic)
  • 146. Qianxi, Lu
    et al.
    Qingyu, Miao
    Fodor, Gabor
    Brahmi, Nadia
    Radio resource management for network assisted D2D in cellular uplink2013In: 2013 IEEE/CIC International Conference on Communications in China - Workshops, CIC/ICCC 2013, New York: IEEE conference proceedings, 2013, p. 159-164Conference paper (Other academic)
    Abstract [en]

    Cellular network assisted Device-to-Device (D2D) communication has the potential to increase the network capacity, offload access and core network resources and reduce latency. To realize these potential gains and to ensure a win-win type of coexistence between the cellular and the D2D layer, there is a need to carefully design the procedures for radio resource management (RRM). This paper develops and evaluates low complexity radio resource management (RRM) algorithms that are based on practically feasible and well known measurements. These RRM algorithms include mode selection, power control, and resource allocation. First, the network assists D2D users on a coarse time scale to select D2D (direct) mode or cellular mode. Subsequently, the network informs the D2D users of tolerable power levels which cause minimal interference to the base station, and the possible resources that can be used for D2D communications. Based on this information, the D2D users act autonomously for executing the RRM functions. The simulation result shows that our approach to D2D RRM can harvest the offloading/proximity gain to the network.

  • 147. R, Baldemair
    et al.
    E, Dahlman
    S, Parkvall
    Y, Selén
    Fodor, Gabor
    Ericsson Res. Ericsson AB, Stockholm, Sweden.
    H, Tullberg
    K, Balachandran
    T, Irnich
    Future wireless communications2013In: 2013 IEEE 77th Vehicular Technology Conference (VTC Spring) / [ed] IEEE, New York: IEEE Press, 2013Chapter in book (Other academic)
  • 148. Rajatheva, N
    et al.
    Suyama, S
    Zirwas, W
    Thiele, L
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Tölli, A
    Carvalho, E
    Sorensen, J H
    Massive Multiple Input Multiple Output (MIMO) Systems2016In: 5G Mobile and Wireless Communications Technology / [ed] Osseiran, A; Marsch, P; Monserrat, J F, Cambridge: Cambridge University Press, 2016, p. 208-247Chapter in book (Other academic)
  • 149. Reider, Norbert
    et al.
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control.
    A distributed power control and mode selection algorithm for D2D communications2012In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, p. 266-Article in journal (Refereed)
    Abstract [en]

    Device-to-device (D2D) communications underlaying a cellular infrastructure has recently been proposed as a means of increasing the resource utilization, improving the user throughput and extending the battery lifetime of user equipments. In this article we propose a new distributed power control algorithm that iteratively determines the signal-to-noise-and-interference-ratio (SINR) targets in a mixed cellular and D2D environment and allocates transmit powers such that the overall power consumption is minimized subject to a sum-rate constraint. The performance of the distributed power control algorithm is benchmarked with respect to the optimal SINR target setting that we obtain using the Augmented Lagrangian Penalty Function method. The proposed scheme shows consistently near optimum performance both in a single-input-multiple-output and a multiple-input-multiple-output setting. We also propose a joint power control and mode selection algorithm that requires single cell information only and clearly outperforms the classical cellular mode operation.

  • 150. Reider, Norbert
    et al.
    Fodor, Gabor
    Ericsson Research, Stockholm, Sweden.
    On opportunistic power control for Alamouti and SM MIMO systems2012In: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. 67, no 2, p. 335-358Article in journal (Refereed)
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