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  • 1. Abrardo, A
    et al.
    Fodor, G
    Tola, B
    Network coding schemes for D2D communications based relaying for cellular coverage extension2015Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. -Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Although network-assisted device-to-device (D2D) communications are known to improve the spectral and energy efficiency of proximal communications, the performance of cooperative D2D schemes in licenced spectrum is less understood when employed to extend the coverage of cellular networks. In this paper, we study the performance of D2D-based range extension in terms of sum rate and power efficiency when a relaying user equipment (UE) helps to improve the coverage for cell edge UEs. In our design, the relaying UE may have own traffic to transmit and receive to/from the cellular base station (BS) and can operate either in amplify-and-forward (AF) or decode-and-forward (DF) modes and can make use of either digital or analogue physical (PHY) layer network coding. In this rather general setting, we propose mode selection, resource allocation and power control schemes and study their performance by means of system simulations. We find that the performance of the DF scheme with network coding is superior both to the traditional cellular and the AF-based relaying schemes, including AF with two-slot or three-slot PHY layer network coding.

  • 2.
    Athanasiou, George
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Tassiulas, Leandros
    Design and implementation of distributed load balancing and fast handoff for wireless mesh networks2015Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 26, nr 4, s. 630-649Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The association/handoff procedures are very important towards achieving a balanced operation in 802.11-based wireless mesh networks. In this paper, we design and implement a cooperative association/handoff scheme, where stations share useful information, and handoff is executed in a seamless manner. Furthermore, we introduce a cross-layer load balancing mechanism that takes into account uplink and downlink channel conditions, routing performance and congestion control. The proposed heuristic algorithms are inspired by the rapidly designed cooperative protocols and control the communication load of each mesh access point in a distributed manner. We evaluate the performance of our mechanisms through OPNET () simulations and testbed experiments. Copyright (c) 2013 John Wiley & Sons, Ltd.

  • 3.
    Athanasiou, George
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Tassiulas, Leandros
    Dynamic Frequency Management in 802.11-based Multi-Radio Wireless Networks2014Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 25, nr 7, s. 752-768Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Efficient channel selection is essential in 802.11 mesh deployments, for minimising contention and interference among co-channel devices and thereby supporting a plurality of quality of service (QoS)-sensitive applications. A few protocols have been proposed for frequency allocation in such networks; however, they do not address the problem end-to-end. In this paper, we present a general formulation of the channel selection problem, taking into account the performance of both mesh access and mesh backhaul. Moreover, we propose a routing-aware channel selection protocol for wireless mesh networks (ARACHNE). ARACHNE is distributed in nature and motivated by our measurements on a wireless testbed. The main novelty of our protocol comes from adopting a metric that captures the end-to-end link loads across different routes in the network. ARACHNE prioritises the assignment of low-interference channels to links that (i) need to serve high-load aggregate traffic and/or (ii) already suffer significant levels of contention and interference. Our protocol takes into account the number of potential interfaces (radios) per device and allocates these interfaces in a manner that efficiently utilises the available channel capacity. We evaluate ARACHNE through extensive, trace-driven simulations, and we show the approaches to the optimal channel selection. We observe that our protocol improves the total network throughput, as compared to three other representative channel allocation approaches in literature.

  • 4.
    Ben Slimane, Slimane
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    MC-CDMA with Quadrature Spreading for Wireless Communication Systems1998Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 9, nr 4, s. 371-378Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Multi­Carrier CDMA (MC­CDMA) systems using the Orthogonal Frequency  Division Division Multiple Access (OFDM) technique resolve the frequency se­  lectivity in multipath fading channels and have good spectral properties. The  addition of a spread spectrum component to the OFDM introduces a frequency  diversity gain that can combat deep multipath fading situations.  In this paper a MC­CDMA system operating over frequency selective, slowly  fading channels is considered and its performance is studied analytically and by  computer simulations. We consider the downlink of a cellular radio system where  for each user a BPSK modulation and a quadrature (complex) spreading code is  used. The spreading codes are arranged in a way that reduces the effect of the  multipath fading channel and restores some of the orthogonality losses between  users. The obtained results show considerable performance improvement compared  to conventional OFDM and to MC­CDMA that uses single spreading codes. The  effect of frequency offsets on the system performance is also addressed in this  paper.  Its superior performance and low complexity receiver make MC­CDMA with  quadrature spreading codes suitable for future wireless communication systems to  achieve the requirements of high quality services, high speed, and low cost­receiver.

  • 5.
    Ben Slimane, Slimane
    et al.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Cai, Meng
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Zhang, Xi
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Zhou, Ning
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    On the Capacity of CDMA with Linear Successive Interference Cancellation2003Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 14, nr 6, s. 501-513Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Combined power control and interference cancellation in CDMA systems can be a very efficient resourcemanagement tool. While conventional power control tries to maintain equal received power or balancedsignal-to-interference ratio (SIR), successive interference cancellation (SIC) in multi-user detection (MUD)relies more on the disparities between the powers of the different users. The combination can save morepower into the system and thus a room for a better capacity.

    This paper investigates the interaction between power control and linear SIC in a single-rate CDMAsystem and its impact on the system capacity. The obtained results show that interference cancellation canimprove the capacity of CDMA and relax power control requirements. The full integration of power controland linear SIC detection is shown to provide excellent resource management in CDMA systems. Limitedinterference cancellation can be a good solution for CDMA systems as it provides considerable capacitygain with reduced complexity. An upper bound on the system capacity as a function of the cancellationparameters used along the different stages of the SIC detector is derived. Investigation of the optimumdecoding order is also provided in this paper.

  • 6.
    Bergfeldt, Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Ericsson, Research Area Packet Technologies, Stockholm, Sweden .
    Ekelin, Svante
    Ericsson, Research Area Packet Technologies, Stockholm, Sweden .
    Karlsson, Johan M
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    Real-time bandwidth measurements over mobile connections2011Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 22, nr 6, s. 255-267Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The first study that investigates the characteristics of received probe packets and the reliability of bandwidth estimates when actively measuring the available bandwidth over radio interfaces in mobile communication networks is presented. Knowledge of available bandwidth is very useful in various contexts, e. g. in network management and adaptive streaming applications. Bandwidth measuring tools have so far primarily been designed for and evaluated in wired networks. However, such tools should also be examined in wireless networks since the use of, e. g., mobile broadband is rapidly increasing. The properties of wired and wireless links differ substantially, which affect the performance of the tools. We have made active-probing experiments over a high-speed downlink shared channel, which is used for High-Speed Downlink Packet Access (HSDPA) in the mobile communication technology UMTS, and over a forward traffic channel in CDMA2000 1xEV-DO. Both experiments were performed over commercial networks. They show that one cannot always expect uniform per-packet processing over the radio channel in mobile networks, which is expected by many probing tools. This reduces the reliability of the available-bandwidth estimates, however we suggest how this can be handled. Finally, the mobile-network measurements are compared to experiments performed in an IEEE 802.11 wireless LAN, where the radio channel does not create the same packet-processing behaviour. We also discuss the possibility of using the probe traffic for the purpose of identifying the communication technology at the bottleneck of the network path, assumed this is a wireless broadband link, by mapping specifications of standardised communication technologies to observed probe-traffic characteristics.

  • 7.
    Berggren, Fredrik
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    An error bound for moment matching methods of lognormal sum distributions2005Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 6, nr 6, s. 573-577Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To evaluate the distribution function of a sum of lognormal random variables. it is common to use approximation methods based on moment matching.  These include the classical and simple Fenton-Wilkinson method, which approximates the sum with a single lognormal variable, having the first two moments matched.  In this letter, we give a closed-form bound for the error of the distribution function, resulting from moment matching methods.  Numerical evaluation for a typical CDMA case, shows that the bound becomes tight for large processing gains.  The error bound can also be used to find bounds on the outage probability.

  • 8.
    Bohge, Mathias
    et al.
    TU Berlin.
    Gross, James
    RWTH Aachen University, UMIC Research Centre,.
    Wolisz, Adam
    TU Berlin.
    Optimal Soft Frequency Reuse and Dynamic Sub-carrier Assignments in Cellular OFDMA Networks2010Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 21, nr 8, s. 704-713Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Soft frequency reuse (SFR) is a common technique for co-channel interference (CCI) mitigation in cellular OFDMA networks. The performance of such networks significantly depends on the configuration of the power profiles that implement the soft frequency reuse patterns. In this paper, we investigate the performance of static soft frequency reuse by comparing it against the optimal case, in which a central entity optimally distributes power among the users of the network. It is shown that there is a significant performance gap between both approaches, which needs to be filled by adaptive SFR mechanisms. Moreover, we show that the achievable gain of static SFR is small in a system that is able to optimally decide on terminal/sub-carrier assignments.

  • 9.
    Charalambous, Themistoklis
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Klerides, Evelina
    Imperial College London.
    Wiesemann, Wolfram
    Imperial College London.
    Vassiliou, Angelos
    University of Cyprus.
    Hadjitheophanous, Stavros
    Deliparaschos, Kyriakos
    Cyprus University of Technology.
    On the Minimum Latency Transmission Scheduling in Wireless Networks with Power Control under SINR Constraints2013Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 26, nr 3, s. 367--379Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to alleviate interference and contention in a wireless network, we may exploit the existence of multiple orthogonal channels or time slots, thus achieving a substantial improvement in performance. In this paper, we study a joint transmission scheduling and power control problem that arises in wireless networks. The goal is to assign channels (or time slots) and transmitting powers to communication links such that all communication requests are processed correctly, specified quality-of-service requirements are met, and the number of required time slots is minimised. First, we formulate the problem as a mixed-integer linear programming. Then, we show that the problem considered is non-deterministic polynomial-time hard, and subsequently, we propose non-trivial bounding techniques to solve it. Optimisation methods are also discussed, including a column generation approach, specifically designed to find bounds for the transmission scheduling problem. Moreover, we develop optimisation techniques in which the bounding techniques are integrated in order to derive the optimal solution to the problem faster. We close with an extensive computational study, which shows that despite the complexity of the problem, the proposed methodology scales to problems of non-trivial size. Our algorithms can therefore be used for static wireless networks where propagation conditions are almost constant and a centralised agent is available (e.g. cellular networks where the base station can act as a centralised agent or wireless mesh networks), and they can also serve as a benchmark for the performance evaluation of heuristic, approximation or distributed algorithms that aim to find near-optimal solutions without information about the whole network. 

  • 10.
    Graell i Amat, Alexandre
    et al.
    Telecom Bretagne, France.
    Brännström, Fredrik
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    On the design of rate-compatible serially concatenated convolutional codes2007Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 18, nr 5, s. 519-527Artikel i tidskrift (Refereegranskat)
  • 11.
    Gross, James
    et al.
    TU Berlin.
    Valentin, Stefan
    Bell Labs.
    Karl, Holger
    Universitaet Paderborn.
    Wolisz, Adam
    TU Berlin.
    A Study of Impact of Inband Signalling and Realistic Channel Knowledge for an Example Dynamic OFDM-FDMA System2005Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 16, nr 1, s. 37-49Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dynamically assigning sub-carriers of orthogonal frequency division multiplexing (OFDM) systems to multiple different terminals in a cell has been shown to be beneficial in terms of different transmission metrics. The success of such a scheme, however depends on the ability of the access point to inform terminals of their newest sub-carrier assignments as well as on the accuracy of the channel state information used to generate new assignments. It is not clear whether the overhead required to implement these two functions consumes all of the potential performance increase possible by dynamically assigning subcarriers. In this paper, a specific MAC structure is selected enabling the operation of a dynamic OFDM system, incorporating a signalling scheme for dynamically assigned sub-carriers. Based on this structure, we study the overhead required for a dynamic sub-carrier scheme; a static variant that serves as a comparison case. We investigate the performance difference of these two schemes for various scenarios where at first signalling and then realistic channel knowledge is added to the system model. Average throughput and goodput per terminal serve as figures of merit; the number of terminals in the cell, the transmission power per sub-carrier, the delay spread and the movement speed of the terminals are varied. We find that a realistic overhead model decreases the performance of both static and dynamic schemes such that the overall ratio favours in all cases except for higher speeds the dynamic rather than the static scheme especially in realistic system environments.

  • 12.
    Li, Di
    et al.
    Rhein Westfal TH Aachen, D-52074 Aachen, Germany..
    Fang, Erwin
    Swisscom Schweiz AG, Zurich, Switzerland..
    Gross, James
    KTH.
    Robust clustering for ad hoc cognitive radio network2018Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 29, nr 5, artikel-id e3285Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cluster structure in cognitive radio (CR) networks facilitates cooperative spectrum sensing, routing, and other functionalities. Unlicensed channels, which are temporally available for a group of CR users in one area, consolidate the group into a cluster. More available unlicensed channels in a cluster make the cluster more likely to uphold against the licensed users' influence, making clusters more robust. This paper analyzes the problem of how to form robust clusters in a CR network such that CR systems benefit from collaboration within clusters despite intense primary user activity. We give a formal description of the robust clustering problem, prove it to be NP-hard, and propose both centralized and distributed solutions. The congestion game model is adopted to analyze the process of cluster formation, which not only contributes to the design of the distributed clustering scheme but also provides a guarantee on the convergence to a Nash equilibrium and the convergence speed. The proposed distributed clustering scheme outperforms state-of-the-art in terms of cluster robustness, convergence speed, and overhead. Extensive simulations are presented supporting the theoretical claims.

  • 13.
    Nomikos, Nikos
    et al.
    University of Aegean.
    Vouyioukas, Demosthenis
    University of Aegean.
    Charalambous, Themistoklis
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Krikidis, Ioannis
    University of Cyprus, Electrical and Computer Engineering Department.
    Skoutas, Dimitrios
    University of Aegean.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Joint relay-pair selection for buffer-aided successive opportunistic relaying2014Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 25, nr 8, s. 823-834Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, we present a buffer-aided successive opportunistic relaying scheme that aims at improving the average capacity of the network when inter-relay interference arises between relays that are selected for simultaneous transmission and reception. We propose a relay selection policy that, by exploiting the benefits of buffering at the relays, decouples the receiving relay at the previous time slot to be the transmitting relay at the next slot. Furthermore, we impose an interference cancellation threshold allowing the relay that is selected for reception to decode and subtract the inter-relay interference. The proposed relaying scheme selects the relaying pair that maximises the average capacity of the relay network. Its performance is evaluated through simulations and comparisons with other state-of-the-art half-duplex and full-duplex relay selection schemes, in terms of outage probability, average capacity and average delay. The results reveal that a trade-off has to be made between improving the outage at the cost of reduced capacity and increased delay and vice versa. Finally, conclusions are drawn and future directions are discussed, including the need for a hybrid scheme incorporating both half-duplex and full-duplex characteristics.

  • 14.
    Nordström, Ernst
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    Carlström, Jakob
    Communication networks: a new reward model for MDP state aggregation with application to CAC and routing2005Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 16, nr 6, s. 495-508Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An optimal solution of the call admission control and routing problem in multi-service loss networks, in terms of average reward per time unit, is possible by modeling the network behavior as a Markov decision process (MDP). However, even after applying the standard link independence assumption, the solution of the corresponding set of link problems may involve considerable numerical computation. In this paper, we study an approximate MDP framework on the link level, where vector-valued MDP states are mapped into a set of aggregate scalar MDP states corresponding to link occupancies. In particular, we propose a new model of the expected reward for admitting a call on the network. Compared to Krishnan's and Hübner's method [11], our reward model more accurately reflects the bandwidth occupancy by different call categories. The exact and approximate link MDP frameworks are compared by simulations, and the results show that the proposed link reward model significantly improves the performance of Krishnan's and Hübner's method.

  • 15.
    Nordström, Ernst
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    Dziong, Zbigniew
    CAC and routing for multi-service networks with blocked wide-band calls delayed, part I: exact link MDP framework2006Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 17, nr 1, s. 21-36Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we study the call admission control (CAC) and routing issue in multi-service networks. Two categories of calls are considered: a narrow-band (NB) with blocked calls cleared and a wide-band (WB) with blocked calls delayed. The objective function is formulated as reward maximisation with penalty for delay. The optimisation is subject to quality of service (QoS) constraints and, possibly, grade of service (GoS) constraints. A suboptimal solution is achieved by applying Markov decision process (MDP) theory together with a two-level approximation. First, the network is decomposed into a set of links assumed to have independent Markov and reward processes respectively. Second, the dimensions of the link Markov and reward processes are reduced by aggregation of the call classes into call categories. The CAC and routing policy is computed by the policy iteration algorithm from MDP theory. The numerical results show that the proposed CAC and routing method, based on the exact link MDP framework, is able to find an efficient trade-off between reward loss and average call set-up delay, outperforming conventional methods such as the least loaded routing (LLR).

  • 16.
    Nordström, Ernst
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    Dziong, Zbigniew
    CAC and routing for multi-service networks with blocked wide-band calls delayed, Part II: approximative link MDP framework2007Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 18, nr 1, s. 13-33Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we study the call admission control (CAC) and routing issue in multi-service networks. Two categories of calls are considered: a narrow-band with blocked calls cleared and a wide-band with blocked calls delayed. The optimisation is subject to several quality of service (QoS) constraints, either on the packet or call level. The objective function is formulated as reward maximisation with penalty for delay. A suboptimal solution is achieved by applying Markov decision process (MDP) theory together with a three-level approximation. First, the network is decomposed into a set of links assumed to have independent Markov and reward processes respectively. Second, the dimensions of the link Markov and reward processes are reduced by aggregation of the call classes into call categories. Third, by applying decomposition of the link Markov process, the link MDP tasks are simplified considerably. The CAC and routing policy is computed by the policy iteration algorithm from MDP theory. The numerical results show that the proposed CAC and routing method, based on the approximate link MDP framework, is able to find an efficient trade-off between reward loss and average call set-up delay, outperforming conventional methods such as least loaded routing (LLR).

  • 17.
    Obregon, Evanny Carol
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Sung, Ki Won
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Zander, Jens
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Is spectrum sharing in the radar bands commercially attractive?: -a regulatory and business overview2016Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 27, nr 3, s. 428-438Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 18. Shibli, Muhammad Awais
    et al.
    Masood, Rahat
    Ghazi, Yumna
    Muftic, Sead
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    MagicNET: mobile agents data protection system2015Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 26, nr 5, s. 813-835Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Literature study and analysis on mobile agents reveal many challenging and uncovered aspects that still do not have comprehensive solutions. Despite the fact that significant research has been carried out on mobile agents, it is still not widely adopted by industry and research community because of the immaturity of various technical aspects of agent paradigm. One of the main reasons that limits the scope of the potential applications of mobile agents is the lack of reliable security solutions for mobile agents' code and their baggage. The protection of mobile agents' codes has been solved by the research community to some extent; however, there is not even a single solution that provides complete protection and access control mechanism for agents' code and their baggage (data being accumulated/ carried by agent during execution). Most of the existing solutions such as execution tracing, code obfuscation, encrypted code execution and partial result encapsulation mainly cover security threats of mobile agents' code. In this paper, we present a security solution to overcome the security threats on traditional mobile agents computing paradigm. Our proposed solution is one step ahead of extant solutions in that it provides complete protection and enforces access control on agents' complex baggage structure. We have extended our previous work that was limited to the protection of agents and the agent platforms only. Our approach provides holistic access control mechanism between users and agents, agents and agent platform resources and platform and agents baggage. By adopting the proposed solution in the mobile agent-oriented software engineering, secure and complex mobile agent-based applications can be developed, which will greatly benefit the software industry.

  • 19.
    Xiao, Ming
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Aulin, Tor
    Chalmers University of Technology.
    Serially concatenated continuous phase modulation with symbol interleavers: Performance, properties and design principles2006Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 17, nr 4, s. 439-449Artikel i tidskrift (Refereegranskat)
  • 20.
    Yao, Yong
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Popescu, Alexandru
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Popescu, Adrian
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    On prioritised opportunistic spectrum access in cognitive radio cellular networks2015Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 27, nr 2, s. 294-310Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cognitive radio (CR) networks allow secondary users (SUs) to opportunistically access licensed spectrum, thus providing efficient use of radio resources. Different studies carried out on CR networks have focused on the procedure of spectrum handoff of SUs such as the data transmission in a communication that can be carried out in different channels. In this paper, we consider cellular networks enhanced with facilities for CR communication where a user with a call in progress moves across neighbouring cells, that is, the so-called inter-cell handoff. Our model assumes that the cell gives priority to inter-cell handoff calls over the calls originating within it. A finite queue is used in every cell for SUs, and a fixed number of buffer slots are reserved for the inter-handoff SU calls. With these considerations, we study the transmission performance of SUs by using Markov chains-based modelling approach. The numerical analysis is validated by simulation experiments. We also suggest a fuzzy logic-based hybrid decision-making algorithm to select the best solution for inter-handoff prioritisation. The goal is to optimise the transmission performance of SUs by leveraging their requirements on service completion throughput and waiting time in each cell. Copyright © 2014 John Wiley & Sons, Ltd.

  • 21.
    You, Lei
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Wu, Ping
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Song, Mei
    PCN CAD Center, Beijing University of Posts and Telecommunications, Beijing, China.
    Song, Junde
    PCN CAD Center, Beijing University of Posts and Telecommunications, Beijing, China.
    Zhang, Yong
    Cross-layer optimisation for uplink transmission in OFDMA cellular networks with fixed relays2011Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 22, nr 6, s. 296-314Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we consider a cross-layer design aimed to enhance performance for uplink transmission in an orthogonal frequency division multiple-access (OFDMA)-based cellular network with fixed relay stations. Because mobile stations (MSs) spend most of the power on the uplink transmission, power efficiency resource allocation becomes very important to MSs. We develop a cross-layer optimisation framework for two types of uplink flows (inelastic and elastic flows) that have different quality-of-service requirements. For inelastic flows with fixed-rate requirement, we formulate the cross-layer optimisation problem as the minimisation of the sum transmission power of MSs under the constraints of flow conservation law, subcarrier assignment, relaying path selection and power allocation. For elastic flows with flexible-service-rate requirement, we consider the cross-layer trade-off between uplink service rate and power consumption of MSs and pose the optimisation problem as the maximisation of a linear combination of utility (of service rates) and power consumption (of MSs). Different trade-offs can be achieved by varying the weighting parameters. Dual decomposition and subgradient methods are used to solve the problems optimally with reduced computational complexity. The simulation results show that, through the proposed cross-layer resource optimisation framework and algorithms, significant benefits of deployment of multiple fixed relays in an OFDMA cellular network can be fully obtained such as reduction in power consumption, increase in service rate and energy savings in the uplink transmission of MSs.

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