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  • 1. Alinia, Bahram
    et al.
    Yousefi, Hamed
    Talebi Mazraeh Shahi, Mohammad Sadegh
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Khonsari, Ahmad
    Maximizing Quality of Aggregation in Delay-Constrained Wireless Sensor Networks2013In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, no 11, p. 2084-2087Article in journal (Refereed)
    Abstract [en]

    In this letter, both the number of participating nodes and spatial dispersion are incorporated to establish a bi-objective optimization problem for maximizing the quality of aggregation under interference and delay constraints in tree-based wireless sensor networks (WSNs). The formulated problem is proved to be NP-hard with respect to Weighted-sum scalarization and a distributed heuristic aggregation scheduling algorithm, named SDMAX, is proposed. Simulation results show that SDMAX not only gives a close approximation of the Pareto-optimal solution, but also outperforms the best, to our knowledge, existing alternative proposed so far in the literature.

  • 2.
    Anderlind, Erik
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Zander, Jens
    KTH, Superseded Departments, Signals, Sensors and Systems.
    A Traffic Model for Non-Real-Time Data Users in Wireless Radio Networks1997In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 1, no 2, p. 37-39Article in journal (Refereed)
    Abstract [en]

    Based on an analysis of Internet protocols for data communication, we propose a simple model for future data traffic in wireless radio networks. Model parameters are selected so as to resemble traffic from the Worldwide Web (WWW) access and from distributed file systems. By changing a single parameter, the model can be switched between resembling up- or down-link traffic. The model is intended for design and performance analysis of radio resource allocation algorithms in future wireless systems.

  • 3.
    Andersson, Mattias
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Theory.
    Rathi, Vishwambhar
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Kliewer, Jorg
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Theory.
    Nested Polar Codes for Wiretap and Relay Channels2010In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 14, no 8, p. 752-754Article in journal (Refereed)
    Abstract [en]

    We show that polar codes asymptotically achieve the whole capacity-equivocation region for the wiretap channel when the wiretapper's channel is degraded with respect to the main channel, and the weak secrecy notion is used. Our coding scheme also achieves the capacity of the physically degraded receiver-orthogonal relay channel. We show simulation results for moderate block length for the binary erasure wiretap channel, comparing polar codes and two edge type LDPC codes.

  • 4.
    Athanasiou, George
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Tsagkaris, Kostas
    Vlacheas, Panagiotis
    Karvounas, Dimitrios
    Demestichas, Panagiotis
    Multi-Objective Traffic Engineering for Future Networks2012In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 16, no 1, p. 101-103Article in journal (Refereed)
    Abstract [en]

    An important goal towards the design of Future Networks is to achieve the best ratio of performance to energy consumption and at the same time assure manageability. This paper presents a general problem formulation for Energy-Aware Traffic Engineering and proposes a distributed, heuristic Energy-Aware Traffic Engineering scheme (ETE) that provides load balancing and energy-awareness in accordance with the operator's needs. Simulation results of ETE compared to the optimal network performance confirm the capability of ETE to meeting the needs of Future Networks.

  • 5.
    Athanasiou, Georgios
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Weeraddana, Pradeep Chathuranga
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Auction-Based Resource Allocation in MillimeterWave Wireless Access Networks2013In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, no 11, p. 2108-2111Article in journal (Refereed)
    Abstract [en]

    The resource allocation problem of optimal assignment of the stations to the available access points in 60 GHz millimeterWave wireless access networks is investigated. The problem is posed as a multi-assignment optimization problem. The proposed solution method converts the initial problem to a minimum cost flow problem and allows to design an efficient algorithm by a combination of auction algorithms. The solution algorithm exploits the network optimization structure of the problem, and thus is much more powerful than computationally intensive general-purpose solvers. Theoretical and numerical results evince numerous properties, such as optimality, convergence, and scalability in comparison to existing approaches.

  • 6.
    Ben Slimane, Slimane
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Approximation to the Symmetric Capacity of Rayleigh Fading Channels with Multi-Level Signals2006In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 0, no 3, p. 129-131Article in journal (Refereed)
    Abstract [en]

    A simple approximation for the symmetric capacity of Rayleigh fading channels with finite input alphabet and ideal channel state information is proposed in this letter. This approximation is quite tight over all SNR ranges and can be considered as a good alternative for estimating the symmetric channel capacity for both AWGN and Rayleigh fading channels.

  • 7. Berggren, F.
    et al.
    Zander, Jens
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Throughput and energy consumption tradeoffs in pathgain-based constrained power control in ALOHA networks2000In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 4, no 9, p. 283-285Article in journal (Refereed)
    Abstract [en]

    Power control has been proposed as a tool to improve the performance of packet radio systems in terms of increased throughput and battery lifetime for mobile terminals. In this paper we study the tradeoff between transmitter dynamic range, average energy consumption and the achievable throughput for a simple pathgain based power control algorithm in a slotted ALOHA radio system. The results show that increasing the throughput significantly by means of transmitter power control requires only a very moderate increase in energy consumption and transmitter dynamic range.

  • 8.
    Berggren, Fredrik
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Ben Slimane, Slimane
    KTH, Superseded Departments, Signals, Sensors and Systems.
    A simple bound on the outage probability with lognormal interferers2004In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 8, no 5, p. 271-273Article in journal (Refereed)
    Abstract [en]

    We consider the problem of determining the outage probability in a cellular radio system, where the interference is modeled by a sum of lognormal random variables. As no closed form expression is known, bounds can serve as a quick way of evaluating performance. By applying the arithmeticgeometric mean inequality, we give a lower bound, computationally simple as it is expressed by a single Q-function. The bound includes the case of correlated interferers and background noise. Numerical evaluation for a range of parameters valid for practical applications, shows good accuracy for moderate variances and improvement over a previously suggested bound. This is especially emphasized when the number of interferers is large.<

  • 9.
    Björnson, Emil
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Capacity Limits and Multiplexing Gains of MIMO Channels with Transceiver Impairments2013In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, no 1, p. 91-94Article in journal (Refereed)
    Abstract [en]

    The capacity of ideal MIMO channels has a high-SNR slope that equals the minimum of the number of transmit and receive antennas. This letter analyzes if this result holds when there are distortions from physical transceiver impairments. We prove analytically that such physical MIMO channels have a finite upper capacity limit, for any channel distribution and SNR. The high-SNR slope thus collapses to zero. This appears discouraging, but we prove the encouraging result that the relative capacity gain of employing MIMO is at least as large as with ideal transceivers.

  • 10.
    Brännström, Fredrik
    et al.
    Chalmers University of Technology.
    Graell i Amat, Alexandre
    Telecom Bretagne, France.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    A general structure for rate-compatible concatenated codes2007In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 11, no 5, p. 437-439Article in journal (Refereed)
    Abstract [en]

    In this letter, a general concatenated code structure is presented, encompassing both parallel and serially concatenated codes as special cases. The structure provides a unifying framework for the analysis of concatenated codes and offers new degrees of freedom for code design. Performance analysis based on error bounds in the error floor region and suggestions for suitable design criteria are provided, together with a design approach for the waterfall region. The proposed structure allows for constructing very high-rate codes with no penalty in the error floor region and good performance in the waterfall region.

  • 11.
    Cao, Phuong
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Oechtering, Tobias
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES).
    Transmit Beamforming for Single-user Large-Scale MISO Systems with Sub-connected Architecture and Power Constraints2018In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558Article in journal (Refereed)
  • 12.
    Charalambous, Themistoklis
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Nomikos, Nikolaos
    Krikidis, Ioannis
    Vouyioukas, Demosthenes
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Modeling Buffer-Aided Relay Selection in Networks With Direct Transmission Capability2015In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, no 4, p. 649-652Article in journal (Refereed)
    Abstract [en]

    We consider a wireless relay network that consists of a source, half-duplex decode-and-forward buffer-aided relays and a destination. While the majority of previous works on relay selection assume no direct transmission between source and destination in such a setting, we lift this assumption and propose a link selection policy that exploits both the buffering ability and the opportunity for successful reception of a packet directly from the source. The proposed relay selection scheme incorporates the instantaneous strength of the wireless links and adapts the relay selection decision based on the strongest available link. The evolution of the network as a whole is modeled by means of a Markov chain and thus, the outage probability is associated with the steady state of the Markov chain. It is deduced that even if the link between the source and the destination is in principle a very unreliable link, it is always beneficial for the source to multicast a packet to both the relay with the strongest available link and the destination.

  • 13.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101), Photonics (Closed 20120101).
    Chen, Biao
    He, Sailing
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    A novel algorithm for intra-ONU bandwidth allocation in ethernet passive optical networks2005In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 9, no 9, p. 850-852Article in journal (Refereed)
    Abstract [en]

    A novel decentralized algorithm is introduced for the intra-ONU bandwidth allocation in an Ethernet Passive Optical Network (EPON). The algorithm is of low computational complexity, and can guarantee both the priority and fairness of the differentiated services. Simulation results are presented and compared with those of two existing bandwidth allocation algorithms.

  • 14.
    Cheng, Yuxin
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Fiorani, Matteo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Reliable and Cost Efficient Passive Optical Interconnects for Data Centers2015In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, no 11, p. 1913-1916Article in journal (Refereed)
    Abstract [en]

    To address the sustainability, scalability, and reliability problems that data centers are currently facing, we propose three passive optical interconnect (POI) architectures on top of the rack. The evaluation results show that all three architectures offer high reliability performance (connection availability for intra-rack interconnections higher than 99.999%) in a cost-efficient way.

  • 15.
    Cho, Jeong-woo
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Kim, Seong-Lyun
    Yonsei University.
    Chong, Song
    KAIST (Korea Advanced Institute of Science and Technology).
    Capacity of Interference-Limited Ad Hoc Networks with Infrastructure Support2006In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 10, no 1, p. 16-18Article in journal (Refereed)
    Abstract [en]

    In this letter, we consider the capacity of ad hoc networks with infrastructure support. Although Grossglauser-Tse mobile network model enables Θ(1) per-node throughput scaling, the mobility assumption may be too unrealistic to be accepted in some practical situations. One of the key observations we acquired is that the infrastructure support plays the same role played by the mobility in the Grossglauser-Tse model. We show that nodes can utilize the randomly located infrastructure support instead of mobility when nodes are nearly static. In this case, we show that the per-node throughput of Θ(1) is still achievable when the number of access points grows linearly with respect to the number of nodes.

  • 16. Christopoulos, D.
    et al.
    Arnau, J.
    Chatzinotas, S.
    Mosquera, C.
    Ottersten, Björn
    SnTUniversity of Luxembourg, Luxembourg .
    MMSE Performance Analysis of Generalized Multibeam Satellite Channels2013In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, no 7, p. 1332-1335Article in journal (Refereed)
    Abstract [en]

    Aggressive frequency reuse in the return link (RL) of multibeam satellite communications (SatComs) is crucial towards the implementation of next generation, interactive satellite services. In this direction, multiuser detection has shown great potential in mitigating the increased intrasystem interferences, induced by a tight spectrum reuse. Herein we present an analytic framework to describe the linear Minimum Mean Square Error (MMSE) performance of multiuser channels that exhibit full receive correlation: an inherent attribute of the RL of multibeam SatComs. Analytic, tight approximations on the MMSE performance are proposed for cases where closed form solutions are not available in the existing literature. The proposed framework is generic, thus providing a generalized solution straightforwardly extendable to various fading models over channels that exhibit full receive correlation. Simulation results are provided to show the tightness of the proposed approximation with respect to the available transmit power.

  • 17.
    Dwivedi, Satyam
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Zachariah, Dave
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    De Angelis, Alessio
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Cooperative Decentralized Localization Using Scheduled Wireless Transmissions2013In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, no 6, p. 1240-1243Article in journal (Refereed)
    Abstract [en]

    In this letter we develop a solution for decentralized localization of transceiving nodes in wireless networks. By exploiting a common transmission schedule, this is achieved without any additional communication and dispels the need for synchronized nodes. We derive the Cramer-Rao bounds for the solution and formulate two practical estimators for localization. Finally, the solution and estimators are tested in numerical experiments.

  • 18.
    Fiorani, Matteo
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Aleksic, Slavisa
    Casoni, Maurizio
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Energy-Efficient Elastic Optical Interconnect Architecture for Data Centers2014In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 18, no 9, p. 1531-1534Article in journal (Refereed)
    Abstract [en]

    To address the urgent need for high-capacity, scalable and energy-efficient data center solutions, we propose a novel data center network architecture realized by combining broadcast-and-select approach with elastic channel spacing technology. We demonstrate that the proposed architecture is able to scale efficiently with the number of servers and offers lower energy consumption at a competitive cost compared to the existing solutions.

  • 19.
    Fiorani, Matteo
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Rostami, Ahmad
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Transport Abstraction Models for an SDN-Controlled Centralized RAN2015In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, no 8, p. 1406-1409Article in journal (Refereed)
    Abstract [en]

    In a centralized radio access network (C-RAN) scenario the joint coordination of radio (e.g., remote radio units, baseband units) and transport (e.g., optical cross connects) resources can be achieved via software defined networking (SDN) control plane, where a global orchestrator harmonizes the use of resources across all network segments. The more accurate the information about each domain (i.e., the abstraction of wireless and transport resources) is, the better will be the outcome of the orchestration work. This letter presents three transport resources abstraction models along with their corresponding orchestration policies. Their performance are compared showing that there is not a single best abstraction strategy that fits all the cases. If radio resources are scarce compared to transport resources, complex transport abstraction models are not needed. Contrariwise, if enough radio resources are widely available, more detailed abstraction models are required for achieving good network performance, but at the expense of an increased implementation complexity.

  • 20. Fodor, Gabor
    et al.
    Di Marco, Piergiuseppe
    Telek, Miklós
    On Minimizing the MSE in the Presence of Channel State Information Errors2015In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, no 9, p. 1604-1607Article in journal (Refereed)
    Abstract [en]

    We consider the uplink of a multiuser multiple input multiple output (MU MIMO) system, in which the base station acquires channel state information (CSI) for which the estimation error depends on the resources assigned to the uplink pilot symbols. For this system, we first derive the receiver that minimizes the mean square error (MSE) of the uplink detected data symbols, as opposed to the naïve receiver that does not minimize the MSE in the presence of CSI errors. We then derive a closed form expression for the MSE as a function of the employed pilot-to-data power ratio, number of antennas and the MU MIMO interference power. This expression allows us to gain the insight that the gain of using the actual MMSE receiver as opposed to the naïve receiver becomes particularly important when the number of BS antennas is large.

  • 21.
    Gerami, Majid
    et al.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Two-Layer Coding in Distributed Storage Systems With Partial Node Failure/Repair2017In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 21, no 4, p. 726-729Article in journal (Refereed)
    Abstract [en]

    We a distributed storage system where parts of the stored packets in storage nodes are subject to being lost. In a process, termed as the partial repair, the lost packets in a faulty node are recovered by the transmitted packets from other storage nodes and the available packets in the faulty node. To improve reliability of the stored data, and reduce the transmission costs, we propose a scheme that implements two-layer coding for storing files in the system. We study the minimum possible partial-repair bandwidth, and the codes that achieve the optimal bound.

  • 22. Gharanjik, Ahmad
    et al.
    Rao, Bhavani Shankar Mysore Rama
    Arapoglou, Pantelis-Daniel
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. University of Luxembourg, Luxembourg.
    Gateway Switching in Q/V Band Satellite Feeder Links2013In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, no 7, p. 1384-1387Article in journal (Refereed)
    Abstract [en]

    A main challenge towards realizing the next generation Terabit/s broadband satellite communications (SatCom) is the limited spectrum available in the Ka band. An attractive solution is to move the feeder link to the higher Q/V band, where more spectrum is available. When utilizing the Q/V band, due to heavy rain attenuation, gateway diversity is considered a necessity to ensure the required feeder link availability. Although receive site diversity has been studied in the past for SatCom, there is much less maturity in terms of transmit diversity techniques. In this paper, a modified switch and stay combining scheme is proposed for a Q/V band feeder link, but its performance is also evaluated over an end-to-end satellite link. The proposed scheme is pragmatic and has close to optimal performance with notably lower complexity.

  • 23. Gu, Feng
    et al.
    Xie, Chongyang
    Peng, Min
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Khan, Samee
    Ghani, Nasir
    Virtual Overlay Network Scheduling2011In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 15, no 8, p. 893-895Article in journal (Refereed)
    Abstract [en]

    As applications continue to expand, there is a growing need to provide advance reservation scheduling for higher-end virtual overlay network services. Hence this work presents an optimization formulation for this problem and studies several heuristic solutions using network simulation.

  • 24.
    Hamid, Mohamed
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. Department of Electronics, University of Gävle, Gävle, Sweden .
    Björsell, Niclas
    Academy for Natural Science and Built Environment, University of Gävle.
    Slimane, Ben Slimane
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Signal Bandwidth impact on Maximum-minimum Eigenvalue Detection2015In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, no 3, p. 395-398Article in journal (Refereed)
    Abstract [en]

    The impact of the signal bandwidth and observation bandwidth on the detection performance of the maximum-minimum eigenvalue detector is studied in this letter. The considered signals are the Gaussian signals. The optimum ratio between the signal and the observation bandwidth is analytically proven to be 0.5 when reasonable values of the system dimensionality are used. The analytical proof is verified by simulations.

  • 25.
    Hu, Yulin
    et al.
    RWTH Aachen University.
    Gross, James
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Schmeink, Anke
    RWTH Aachen University.
    On the Performance Advantage of Relaying under the Finite Blocklength Regime2015In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, no 5, p. 779-782Article in journal (Refereed)
    Abstract [en]

    We consider a two-phase relaying system with finite blocklengths. We study the performance difference of relaying under the finite blocklength regime as well as under the Shannon capacity regime. Most importantly, we are interested in the conditions that lead to a higher performance of relaying under the finite blocklength regime. We find that these situations are characterized by error probabilities of relaying, e.g., the overall error probability of relaying and the error probability of the bottleneck link of relaying. We identify scenarios where relaying outperforms direct transmission under the finite blocklength regime even if their performances are similar under the Shannon capacity regime. Moreover, we prove that under these scenarios the performance advantage of relaying is more significant with short blocklengths. Finally, numerical results are provided and discussed.

  • 26. Huang, J.
    et al.
    Fei, Z.
    Cao, C.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Jia, D.
    On-Line Fountain Codes with Unequal Error Protection2017In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 21, no 6, p. 1225-1228, article id 7857018Article in journal (Refereed)
    Abstract [en]

    A new encoding scheme for on-line fountain codes is proposed to provide unequal error protection (UEP) for source symbols. Both the weighted-selection strategy and the expanding-window strategy are used to achieve the UEP property. We analyze the bound of overhead to demonstrate the performance. We also make comparisons with on-line fountain codes that provide equal error protection. Simulation results show that with the proposed scheme, UEP is achieved, where the most important symbols are recovered faster than the least important symbols.

  • 27.
    Huang, Jinliang
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Communication Systems, CoS.
    Signell, Svante
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Communication Systems, CoS.
    Asymptotic Performance of MMSE MIMO Systems Using Adaptive ModulationIn: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558Article in journal (Other academic)
    Abstract [en]

    This letter investigates the asymptotic performance of minimum-mean-square error (MMSE) in MIMO systemsusing adaptive modulation. The asymptotic average spectral efficiency and bit-error rate (BER) are derived basedon three approximations of the probability density function (p.d.f.) of effective SNR. Simulations suggest that themost accurate estimation of average spectral efficiency is obtained by using Gamma distribution.

  • 28.
    Hussain, Iqbal
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rasmussen, Lars
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Design of LT Codes with Equal and Unequal Erasure Protection over Binary Erasure Channels2013In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, no 2, p. 261-264Article in journal (Refereed)
    Abstract [en]

    The erasure floor performance of Luby Transform (LT) codes is mainly determined by the minimum variable-node degree. Thus we propose a modified encoding scheme that maximizes the minimum variable-node degree for transmission over binary erasure channels. The proposed scheme leads to an almost-regular variable-node degree distribution. The encoding process is generalized to accommodate arbitrary variable-node degree distributions for additional improved performance. The asymptotic performance is investigated using density evolution and compared with a conventional LT code. The scheme is further extended to enable a higher level of unequal erasure protection.

  • 29. Jang, Han Seung
    et al.
    Kim, Su Min
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Ko, Kab Seok
    Cha, Jiyoung
    Sung, Dan Keun
    Spatial Group Based Random Access for M2M Communications2014In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 18, no 6, p. 961-964Article in journal (Refereed)
    Abstract [en]

    We expect that the number of machine-to-machine (M2M) devices will rapidly increase in the near future due to a growing demand for a wide range of M2M applications such as e-health, public safety, surveillance, remote maintenance and control, and smart metering. Therefore, the future cellular networks should accommodate a large number of M2M devices and their random access (RA) requests at a specific time instant. In this letter, we propose a novel RA scheme to effectively increase the number of available preambles for the future M2M communication environment. The proposed scheme provides additional preambles by spatially partitioning a cell coverage into multiple group regions and reducing cyclic shift size in RA preambles. As a result, the proposed RA scheme can accommodate a significantly larger number of machine nodes with much lower collision probability and shorter random access delay, compared to a conventional RA scheme.

  • 30.
    Jorswieck, Eduard
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Uplink throughput maximization with combined sum and individual power constraints2006In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 10, no 12, p. 816-818Article in journal (Refereed)
    Abstract [en]

    Optimal power allocation in cellular uplink systems is used to maximize the average throughput under individual and sum power constraints. In the uplink, the transmit power of the mobiles is limited leading to individual power constraints. Additionally, in order to reduce the inter-cell interference, the sum power is constraint. First, we approximate the individual and sum power constraints by a combined constraint on a suitable l-norm of the power allocation vector. Then, we derive the optimal power allocation for individual and sum power constraints as well as for the combined constraint for the three CSI scenarios with uninformed transmitter, long-term feedback, and perfect CSI. The results and illustrations show that under combined sum and individual power constraints completely different power allocation strategies are optimal than with pure sum or pure individual power constraints.

  • 31.
    Katselis, Dimitrios
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Some Preamble Design Aspects in CP-OFDM Systems2012In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 16, no 3, p. 356-359Article in journal (Refereed)
    Abstract [en]

    A fundamental problem in training-based channel estimation for various communication systems is the preamble design. Two crucial aspects in such a design are the achievable mean square error (MSE) and the corresponding peak-to-average power ratio (PAPR). In this letter, preamble-based least squares (LS) channel estimation in CP-OFDM systems is considered. Ignoring the PAPR aspect, several MSE-optimal preambles and a necessary condition for their existence are presented. To this end, a training energy constraint, containing also the energy spent to the cyclic prefix (CP), is imposed. This constraint differs from the usual training energy constraints in the existing literature, which ignore the CP energy during training. These preambles contribute in the completion of existing results concerning MSE-optimal preambles in CP-OFDM systems. However, since high PAPR is an issue concerning these optimal designs, we show how these MSE-optimal preambles can be combined with the usual Zadoff-Chu (ZC) sequences to enlarge the class of PAPR-optimal preambles that achieve good MSE performance at the same time.

  • 32.
    Khormuji, Majid Nasiri
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Larsson, Erik G.
    Rate-optimized constellation rearrangement for the relay channel2008In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 12, no 9, p. 618-620Article in journal (Refereed)
    Abstract [en]

    We study the. instantaneous relay channel where the relay's output only depends on the current received signal at the relay. We propose a novel forwarding strategy for this class of relay channels which can outperform amplify-and-forward, detect-and-forward and estimate-and-forward. The proposed scheme is based on a remapping of the signal constellation at the relay.

  • 33.
    Khormuji, Majid Nasiri
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Capacity of Two Semideterministic Classes of Multiple-Access Relay Channels2012In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 16, no 10, p. 1529-1531Article in journal (Refereed)
    Abstract [en]

    We investigate memoryless multiple-access relay channels (MARCs) and establish the capacity of two semideterministic classes of such channels: MARCs with orthogonal receive components and state-decoupled MARCs. For both cases, the achievability and converse are proved using the noisy network coding lower bound and the cutset upper bound, respectively. Finally, the capacity of a MARC with additive Gaussian interference is quantified.

  • 34.
    Kim, Donggu
    et al.
    Korea Adv Inst Sci & Technol, Sch Elect Engn, Daejeon 34141, South Korea..
    Yang, Yanpeng
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Sung, Ki Won
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Kang, Joonhyuk
    Korea Adv Inst Sci & Technol, Sch Elect Engn, Daejeon 34141, South Korea..
    Cooperation Strategies for Partly Wireless C-RAN2018In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 22, no 6, p. 1248-1251Article in journal (Refereed)
    Abstract [en]

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

  • 35.
    Kim, Jung-Bin
    et al.
    Department of Electrical Engineering and Computer Science, Hanyang University, Ansan, 425-791 Korea.
    Kim, Dongwoo
    Joint Adaptive Modulation and Power Allocation for Variable-Rate Space-Time Block Codes2008In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 12, no 1, p. 26-28Article in journal (Refereed)
    Abstract [en]

    Variable-rate space-time block codes (vr-STBCs) without any feedback can support different transmission rates and unequal error protection (UEP) which are needed for multimedia communications. Assuming necessary feedback, in this letter, we introduce a joint adaptive modulation and power allocation (AMP) for vr-STBCs so as to maximize the total throughput under constraints of transmit power limit and error requirements. Based on a Lagrangian multiplier method, optimum modulation orders and power levels are provided for the transmitter. Numerical results show that the proposed AMP enhances the throughput of existing vr-STBCs up to 20% with very limited feedback, e.g., at most 3-5 bits feedback.

  • 36.
    Koo, Insoo
    et al.
    Dept. of Infor. and Comm., Gwang-Ju Institute of Science and Technology, 1 Oryong-dong, Puk-gu, Gwangju, 500-712, Korea.
    Furuskär, Anders
    KTH, Superseded Departments, Wireless at KTH.
    Zander, Jens
    KTH, Superseded Departments, Wireless at KTH.
    Kim, Kiseon
    Dept. of Infor. and Comm., Gwang-Ju Institute of Science and Technology, 1 Oryong-dong, Puk-gu, Gwangju, 500-712, Korea.
    Erlang Capacity of Multi-Access Systems with Service-based Access Selection2004In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 8, no 11, p. 662-664Article in journal (Refereed)
    Abstract [en]

    In this letter, we provide the lower and upper bounds of Erlang capacity of multi-access systems supporting several different radio access technologies in the multi-service scenario, by considering two extreme operation methods; separate and common operation. In a numerical example with GSM/EDGE-like and WCDMA-like sub-systems, it is shown that the common operation method can provide up to 60% Erlang capacity improvement over the separate operation method when using a near optimum so-called service-based user assignment scheme, with the combined effects of the assignment and the trunking gains. Even in the worst-case, the common operation method still can provide about 15% capacity improvement over the separate operation method, which mainly comes from the trunking gain.

  • 37.
    Kron, Johannes
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Alajaji, Fady
    Queen's University, Kingston, ON, Canada.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Low-Delay Joint Source-Channel Mappings for the Gaussian MAC2014In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 18, no 2, p. 249-252Article in journal (Refereed)
    Abstract [en]

    The bivariate Gaussian multiterminal source coding problem with transmission over the Gaussian multiple-access channel is studied. We propose the use of low-delay joint source-channel mappings and show how performance saturation, which is unavoidable with linear transmission, can be overcome by optimizing the mappings. The optimized mappings are in general nonlinear and perform a combination of hard and soft decision signaling for the error-resilient transmission of analog data.

  • 38.
    Kron, Johannes
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Persson, Daniel
    Linköpings universitet.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Larsson, Erik G.
    Linköpings universitet.
    Closed-form sum-MSE minimization for the two-user Gaussian MIMO broadcast channel2011In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 15, no 9, p. 950-952Article in journal (Refereed)
    Abstract [en]

    We study the Gaussian multiple-input, multiple-output broadcast channel, where a base station with N(T) antennas transmits K independent messages to K users, each having a single receive antenna. The messages consist of independent, identically distributed Gaussian random variables and we study linear transmission with an end-to-end distortion criterion. By using an already established uplink/downlink duality and a recently discovered special relation between beamforming vectors and channel vectors, we present a closed-form expression for the optimal power allocation in the two-user case. We also outline an iterative algorithm that finds the optimal power allocation for an arbitrary number of users.

  • 39.
    Larsson, Erik G.
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Cao, Y
    Collaborative transmit diversity with adaptive radio resource and power allocation2005In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 9, no 6, p. 511-513Article in journal (Refereed)
    Abstract [en]

    We consider optimized collaborative transmit diversity schemes for the situation when the source and the relay know the magnitudes of all channel gains in the system. We demonstrate how one can optimally allocate not only transmit power but also the time and bandwidth used by the different nodes. Numerical examples illustrate the possible performance gain over non-adaptive collaboration.

  • 40. Larsson, Erik G.
    et al.
    Regnoli, Giorgio
    KTH, School of Electrical Engineering (EES).
    Primary system detection for cognitive radio: Does small-scale fading help?2007In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 11, no 10, p. 799-801Article in journal (Refereed)
    Abstract [en]

    We consider the effect of small-scale fading on the detection of weak signals in cognitive radio systems. We formulate a model for the detection problem taking fading into account, and give the associated likelihood ratio tests. Additionally we give an expression for the asymptotic detection performance and use this to consider the tradeoff between the detection performance and the coherence time and bandwidth of the channel.

  • 41.
    Larsson, Erik G.
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Vojcic, Branimir R
    Cooperative transmit diversity based on superposition modulation2005In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 9, no 9, p. 778-780Article in journal (Refereed)
    Abstract [en]

    We propose a new strategy for cooperative transmit diversity based on superposition modulation and multiuser detection. The new scheme can outperform "classical" cooperative diversity based on decode-and-forward by about 1.5-2 dB in the SNR range of interest, and at the same computational complexity.

  • 42.
    Ligeti, Agnes
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Outage Probability in the Presence of Correlated Lognormal Useful and Interfering Components2000In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 4, no 1, p. 15-17Article in journal (Refereed)
    Abstract [en]

    In many modern wireless communications systems (e.g., in OFDM based digital audio broadcasting/digital video broadcasting (DAB/DVB), CDMA) the received signal can be a superposition of multiple useful and interfering lognormal components, and correlation may exist between the components. We propose a simple method for estimating the correlation coefficient between the total useful and total interfering signals as the function of the correlation between the individual components. We show that, by taking into account this correlation factor in the derivation of the distribution of the signal-to-interference ratio, considerable accuracy improvement can be achieved in the outage probability estimation.

  • 43. Liu, Fei
    et al.
    Riihijarvi, Janne
    Petrova, Marina
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). RWTH Aachen University, Germany.
    Analysis of Proportional Fair Scheduling Under Bursty On-Off Traffic2017In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 21, no 5, p. 1175-1178Article in journal (Refereed)
    Abstract [en]

    Proportional fair scheduling (PFS) has been adopted as a standard solution for fair resource allocation in modern wireless cellular networks. With the emergence of heterogeneous networks with widely varying user loads, it is of great importance to characterize the performance of PFS under bursty traffic, which is the case in most wireless streaming and data transfer services. In this letter, we provide the first analytical solution to the performance of PFS under bursty on-off traffic load. We use the Gaussian approximation model to derive a closed-form expression of the achievable user data rates. In order to further improve the accuracy of our baseline analytical solution for multi-cell networks, we design a hybrid approximation by employing multi-interference analysis. The simulation results verify that our model guarantees extremely low data rate estimation error, which is further insensitive to changes in session duration, traffic load and user density.

  • 44. Matthaiou, Michail
    et al.
    Papadogiannis, Agisilaos
    Björnson, Emil
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Debbah, Merouane
    Two-Way Relaying Under the Presence of Relay Transceiver Hardware Impairments2013In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, no 6, p. 1136-1139Article in journal (Refereed)
    Abstract [en]

    Hardware impairments in physical transceivers are known to have a deleterious effect on communication systems; however, very few contributions have investigated their impact on relaying. This paper quantifies the impact of transceiver impairments in a two-way amplify-and-forward configuration. More specifically, the effective signal-to-noise-and-distortion ratios at both transmitter nodes are obtained. These are used to deduce exact and asymptotic closed-form expressions for the outage probabilities (OPs), as well as tractable formulations for the symbol error rates (SERs). It is explicitly shown that non-zero lower bounds on the OP and SER exist in the high-power regime-this stands in contrast to the special case of ideal hardware, where the OP and SER go asymptotically to zero.

  • 45.
    Molavipour, Sina
    et al.
    Sharif University of Technology.
    Gohari, Amin
    Sharif University of Technology.
    Recovery From Random Samples in a Big Data Set2015In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, no 11, p. 1929-1932Article in journal (Refereed)
    Abstract [en]

    Consider a collection of files, each of which is a sequence of letters. One of these files is randomly chosen and a random subsequence of the file is revealed. This random subsequence can be the result of a random sampling of the file. The goal is to recover the identity of the file, assuming a simple greedy matching algorithm to search the file collection. We study the fundamental limits on the maximum size of the file collection for reliable recovery in terms of the length of the random subsequence. The sequence of each file is assumed to follow a hidden Markov model (HMM), which is a common model for many data structures such as voice or DNA sequences. The connection between this problem and coding over a deletion channel with greedy decoders is discussed.

  • 46.
    Muhammad, Ajmal
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Fiorani, Matteo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Joint Optimization of Resource Allocation for Elastic Optical Intra-Datacenter Network2016In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 20, no 9, p. 1760-1763Article in journal (Refereed)
    Abstract [en]

    The ever-increasing demand for cloud services is posing serious challenges to the scalability of the computing, storing, and networking infrastructure deployed inside the datacenters. To address these challenges, we formulate the integer linear program (ILP) model to minimize the spectrum and the switch port usage by exploiting transparent multi-hop connection capability in elastic optical interconnect architecture for datacenters. The proposed ILP model not only takes into account the networking resources but also the other resources (such as computing and storage) in order to achieve a joint resource optimization in intra-datacenter networks. The optimal results show that substantial savings in both spectrum and switching resources can be achieved by properly tuning the objective function of the proposed optimization strategy.

  • 47.
    Oechtering, Tobias J.
    et al.
    Fraunhofer German-Sino Lab. for Mobile Communications, Berlin, Germany.
    Boche, Holger
    Optimal time-division for bidirectional relaying using superposition encoding2008In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 12, no 4, p. 265-267Article in journal (Refereed)
    Abstract [en]

    Bidirectional wireless communication between two nodes is enabled by a half-duplex relay node using a two-phase decode-and-forward protocol. In the first phase, the messages of two nodes are transmitted to the relay node, which broadcasts a superposition of the re-encoded messages in the succeeding, phase. Individual mean transmit power constraints averaged over both phases are considered so that they are inversely proportional to the time division between the phase. An equivalent characterization of the achievable rate region with optimal time division is presented. Moreover, it is proved that the rate region is convex, which makes efficient algorithmic optimization solutions feasible.

  • 48.
    Palomar, Daniel Perez
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Unified framework for linear MIMO transceivers with shaping constraints2004In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 8, no 12, p. 697-699Article in journal (Refereed)
    Abstract [en]

    This letter considers optimum linear transceivers for MIMO channels under a general framework based on Schur-concave and Schur-convex cost functions, subject to shaping constraints on the transmit covariance matrix. Such constraints may be useful, for example, to impose spectral masks in cable systems, to control the power transmitted along certain directions in wireless systems, or to limit the dynamic range of the power amplifiers at the different transmit dimensions.

  • 49.
    Ruiz, Marc
    et al.
    Universitat Politècnica de Catalunya.
    Velasco, Luis
    Universitat Politècnica de Catalunya.
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    A Linearized Statistical XPM Model for Accurate Q-factor Computation2012In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 16, no 8, p. 1324-1327Article in journal (Refereed)
    Abstract [en]

    Non-linear physical layer impairments make the mathematical programming formulation of off-line impairment-aware (IA) Routing and Wavelength Assignment (RWA) problem to be non-linear. To alleviate that, this paper presents for the first time a statistical linear model to compute the Cross Phase Modulation (XPM) noise variance. Exhaustive evaluation reveals that the proposed linear model provides an accurate Q-factor estimation. An example of Integer Linear Programming (ILP) formulation integrating the XPM model is also given.

  • 50. Sezgin, A.
    et al.
    Jorswieck, Eduard A.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Tight upper bound on the outage probability of QSTBC2006In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 10, no 11, p. 784-786Article in journal (Refereed)
    Abstract [en]

    Recently, the statistical properties of the equivalent channel representation of a multiple-input-multiple output (MIMO) system employing rate one quasi-orthogonal space-time block codes (QSTBC) for nT = 2", n &gt; 2 transmit antennas was characterized. It was shown, that these QSTBC were capable of achieving a significant fraction of the outage mutual information of a MIMO system. In this letter, based on the Minkowski's determinant inequality and the Meijer's G-function we derive an upper bound for the fraction of outage probability achieved with QSTBC for the general case of nT = 2n,n &gt; 2 transmit antennas. Simulations results show that this bound gets tight for all signal-to-noise-ratios (SNR) values by increasing the number of receive antennas.

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