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  • 251.
    Björsell, Niclas
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics..
    Bengtsson, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap.
    Large Antenna Array for Low-Latency and Ultra-Reliable Communication2017Konferensbidrag (Övrigt vetenskapligt)
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  • 252.
    Blasco-Serrano, Ricardo
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Coding Strategies for Compress-and-Forward Relaying2010Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    The deployment of large communication networks with many autonomous devices has opened new possibilities for transmission. In particular cooperation among the different nodes has been identified as an enabling technology to satisfy the increasing demand of resources. This thesis studies different coding strategies for cooperation in relay channels in the form of compress-and-forward.

    In the first part of this thesis we consider the application of the newly introduced polar codes for compress-and-forward relaying in relay channels with orthogonal receivers. First we construct polar codes for compress-and-forward relaying based on Slepian-Wolf coding for the scenario where the capacity of the relay-destination channel is large enough. We then consider the more general picture where the capacity of the relay-destination channel is arbitrary. As for Wyner-Ziv coding, we employ nested polar codes for source and channel coding that allow for compression at any desired distortion and exploit the correlation between the observations of the source transmission to minimize the transmission rate over the relay-destination channel. This construction allows for transmission at the prominent compress-and-forward rate under some additional constraints.

    In the second part of this thesis we propose a new coding strategy for compress-and-forward relaying for half-duplex Gaussian channels. Our code construction is based on simple code concatenation for joint source-channel coding at the relay and iterative decoding at the destination. Finally, we propose several realizations of the structure at the relay and different iterative decoding algorithms in order to adapt the construction to different scenarios. Our simulation results show remarkable performance gains over other cooperation strategies such as decode-and-forward and amplify-and-forward in the scenarios where both source-relay and relay-destination links have low signal-to-noise ratios.

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  • 253.
    Blasco-Serrano, Ricardo
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    On Compression and Coordination in Networks2013Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    The current trends in communications suggest that the transfer of information between machines will soon predominate over the traditional human-oriented exchange. The new applications in machine-to-machine communications demand for a new type of networks that are much larger and, especially, much denser. However, there are currently many challenges that hinder an efficient deployment of such networks. In this thesis, we study some fundamental and practical aspects of two of these challenges: coordination and compression.

    The problem of coordination in a network is that of organizing the nodes to make them work together. The information-theoretic abstraction of this corresponds to generating actions with a desired empirical distribution. In this thesis, we construct polar codes for coordination for a variety of topologies. These codes combine elements of source coding, used to produce the actions, with elements of channel coding, used to obtain efficient descriptions. We show that our constructions achieve several fundamental coordination limits in a structured manner and with affordable complexity.

    Then, we consider the problem of coordinating communications to control the interference created to an external observer, measured in terms of its empirical distribution.

    To study the relationship between communication and interference, we introduce the notion of communication-interference capacity region. We obtain a complete characterization of this region for the single user scenario and a partial solution for a multiple user case. Our results reveal a fundamental tradeoff between communication, coordination, and interference in this type of networks.

    The second problem considered in this thesis, compression, involves capturing the essence of data and discarding the irrelevant aspects to obtain compact representations. This takes on a new dimension in networks, where the importance of data is no longer a local matter. In this thesis, we show that polar codes are also suitable for achieving information-theoretic bounds that involve compression in networks. More precisely, we extend our coordination constructions to realize compress-and-forward relaying with affordable complexity.

    In the last part of the thesis, we take a network approach to the problem of compressive sensing and develop methods for partial support set recovery. We use these methods to characterize the tradeoff between the measurement rate and the mean square error. Finally, we show that partial support recovery is instrumental in minimizing measurement outages when estimating random sparse signals. 

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  • 254.
    Blasco-Serrano, Ricardo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Lv, Jing
    Dresden University of Technology.
    Thobaben, Ragnar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jorswieck, Eduard
    Dresden University of Technology.
    Kliks, Adrian
    Poznan University of Technology.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Comparison of Underlay and Overlay Spectrum Sharing Strategies in MISO Cognitive Channels2012Ingår i: 2012 7th International ICST Conference on Cognitive Radio Oriented Wireless Networks and Communications (CROWNCOM), IEEE Computer Society, 2012, s. 224-229Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider an extension of the cognitive radio channel model in which the secondary transmitter has to obtain (“learn”) the primary message in a first phase rather than having non-causal knowledge of it. We propose an achievable rate region that combines elements of decode-and-forward relaying with coding for the pure cognitive radio channel model. Moreover, we find the choice of parameters that maximize the secondary rate under a primary rate constraint. Finally, we compare numerically the performance of our system to that of an underlay scheme that combines beamforming, rate splitting, and successive decoding. We observe that although the overlay design provides higher rates, the losses due to the first phase are quite severe. In fact, for the considered scenarios, cleverly designed underlay schemes can provide comparable performance.

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  • 255.
    Blasco-Serrano, Ricardo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Lv, Jing
    Dresden University of Technology.
    Thobaben, Ragnar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jorswieck, Eduard
    Dresden University of Technology.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Multi-antenna transmission for underlay and overlay cognitive radio with explicit message-learning phase2013Ingår i: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499Artikel i tidskrift (Refereegranskat)
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  • 256.
    Blasco-Serrano, Ricardo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Andersson, Mattias
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Rathi, Vishwambhar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Polar Codes for Cooperative Relaying2012Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 60, nr 11, s. 3263-3273Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We consider the symmetric discrete memoryless relay channel with orthogonal receiver components and show that polar codes are suitable for decode-and-forward and compress-and-forward relaying. In the first case we prove that polar codes are capacity achieving for the physically degraded relay channel; for stochastically degraded relay channels our construction provides an achievable rate. In the second case we construct sequences of polar codes that achieve the compress-and-forward rate by nesting polar codes for source compression into polar codes for channel coding. In both cases our constructions inherit most of the properties of polar codes. In particular, the encoding and decoding algorithms and the bound on the block error probability O(2 (N beta)) which holds for any 0 < beta < 1/2.

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  • 257.
    Blasco-Serrano, Ricardo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Rathi, Vishwambhar
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Polar codes for compress-and-forward in binary relay channels2010Ingår i: 44th Asilomar Conference on Signals, Systems and Computers, Asilomar 2010, IEEE conference proceedings, 2010, s. 1743-1747Konferensbidrag (Refereegranskat)
    Abstract [en]

    We construct polar codes for binary relay channels with orthogonal receiver components. We show that polar codes achieve the cut-set bound when the channels are symmetric and the relay-destination link supports compress-and-forward relaying based on Slepian-Wolf coding. More generally, we show that a particular version of the compress-and-forward rate is achievable using polar codes for Wyner-Ziv coding. In both cases the block error probability can be bounded as O(2-Nβ) for 0 < β < 1/2 and sufficiently large block length N.

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  • 258.
    Blasco-Serrano, Ricardo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Bandwidth efficient compress-and-forward relaying based on joint source-channel coding2011Ingår i: 2011 IEEE Wireless Communications and Networking Conference, WCNC 2011, IEEE conference proceedings, 2011, s. 1800-1804Konferensbidrag (Refereegranskat)
    Abstract [en]

    We propose a new code design for compress-and-forward relaying over bandlimited relay-to-destination channels. The main contribution of this paper is a code design based on joint (source-channel) coding and modulation that uses the correlation between the observations at the relay and the destination as protection against channel errors. This allows for relay nodes with reduced complexity, shifting most of the processing requirements to the destination node. Moreover, by using scalar quantizers with an entropy constraint our system provides remarkable performance in channel conditions where neither amplify-and-forward nor compress-and-forward efficiently exploit the presence of a relay node. Simulation results confirm the benefits of our proposed system.

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  • 259.
    Blasco-Serrano, Ricardo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Communication and interference coordination2014Ingår i: 2014 Information Theory and Applications Workshop, ITA 2014 - Conference Proceedings, IEEE conference proceedings, 2014, s. 6804218-Konferensbidrag (Refereegranskat)
    Abstract [en]

    We study the problem of controlling the interference created to an external observer by a communication processes. We model the interference in terms of its type (empirical distribution), and we analyze the consequences of placing constraints on the admissible type. Considering a single interfering link, we characterize the communication-interference capacity region. Then, we look at a scenario where the interference is jointly created by two users allowed to coordinate their actions prior to transmission. In this case, the tradeoff involves communication and interference as well as coordination. We establish an achievable communication-interference region and show that efficiency is significantly improved by coordination.

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  • 260.
    Blasco-Serrano, Ricardo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Compress-and-forward relaying based on symbol-wise joint source-channel coding2010Ingår i: IEEE International Conference on Communications, IEEE conference proceedings, 2010, s. 1-5Konferensbidrag (Refereegranskat)
    Abstract [en]

    We propose a new compress-and-forward implementation for the relay channel based on joint source-channel coding techniques. The relay performs scalar quantization of its observation in combination with a redundant index mapping. Our system utilizes the correlation between the quantized signal and the direct-link observation of the transmitted symbols as redundancy for error protection on the relay-to-destination link. In order to fully exploit this correlation the destination requires iterative decoding to recover the quantized observation sent by the relay. Once regenerated, this quantized signal is optimally combined with the direct-link observation to decode the message conveyed by the source. By quantizing the observed signal itself rather than a measure on the reliability of the information bits (e.g. a posteriori probabilities from a decoder), and by using digital communication methods on the relay-to-destination link our system yields superior performance to that of amplify-and-forward, decode-and-forward and previous implementations of compress-and-forward based on soft decoding.

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  • 261.
    Blasco-Serrano, Ricardo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Polar Codes for Coordination in Cascade Networks2012Ingår i: International Zurich Seminar on Communications: February 29-March 2, 2012, Sorell Hotel Zürichberg, Zurich, Switzerland proceedings, Zürich: Eidgenössische Technische Hochschule Zürich , 2012, s. 55-58Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider coordination in cascade networks and construct sequences of polar codes that achieve any point in a special region of the empirical coordination capacity region. Our design combines elements of source coding to generate actions with the desired type with elements of channel coding to minimize the communication rate. Moreover, we bound the probability of malfunction of a polar code for empirical coordination. Possible generalizations and open problems are discussed.

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  • 262.
    Blasco-Serrano, Ricardo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. Ericsson Research.
    Zachariah, Dave
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. Division of Systems and Control. Division of Systems and Control. Uppsala University.
    Sundman, Dennis
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    A Measurement Rate-MSE Tradeoff for Compressive Sensing Through Partial Support Recovery2014Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 62, nr 18, s. 4643-4658Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the fundamental relationship between two relevant quantities in compressive sensing: the measurement rate, which characterizes the asymptotic behavior of the dimensions of the measurement matrix in terms of the ratio m/ log n (m being the number of measurements and n the dimension of the sparse signal), and the mean square estimation error. First, we use an information-theoretic approach to derive sufficient conditions on the measurement rate to reliably recover a part of the support set that represents a certain fraction of the total signal power when the sparsity level is fixed. Second, we characterize the mean square error of an estimator that uses partial support set information. Using these two parts, we derive a tradeoff between the measurement rate and the mean square error. This tradeoff is achievable using a two-step approach: first support set recovery, then estimation of the active components. Finally, for both deterministic and random signals, we perform a numerical evaluation to verify the advantages of the methods based on partial support set recovery.

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  • 263.
    Blasco-Serrano, Ricardo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Zachariah, Dave
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Sundman, Dennis
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    An Achievable Measurement Rate-MSE Tradeoff in Compressive Sensing Through Partial Support Recovery2013Ingår i: 2013 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), New York: IEEE , 2013, s. 6426-6430Konferensbidrag (Refereegranskat)
    Abstract [en]

    For compressive sensing, we derive achievable performance guarantees for recovering partial support sets of sparse vectors. The guarantees are determined in terms of the fraction of signal power to be detected and the measurement rate, defined as a relation between the dimensions of the measurement matrix. Based on this result we derive a tradeoff between the measurement rate and the mean square error, and illustrate it by a numerical example.

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  • 264.
    Blomgren, Mats
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Hultell, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Decentralized market-based radio resource management in multi-network environments2007Ingår i: IEEE VTS VEH TECHNOL CONF, 2007, s. 2884-2889Konferensbidrag (Refereegranskat)
    Abstract [en]

    For voice, an efficient radio resource management (RRM) essentially boils down to providing a predefined signal to interference ratio (SIR) at lowest cost possible and centralized schemes has, evidently, been an effective approach to address these problems. Delay-elastic data services, however, introduce both heterogeneous user requirements and possibilities for opportunistic RRM. One way, among others,to handle this would be to let autonomous trade-agents, acting on behalf of users, manage the radio resources, and this is our point of departure. We propose a market-based framework for decentralized RRM in environments populated by multiple, possibly heterogeneous, "access points" (APs), and the provided service for the users consists of file transfers. Resources (transmission time) are partitioned between users through a proportionally fair divisible auction. The problem at hand for the user (trade-agent), is then to determine how much resources it should purchase from the different APs in order to maximize its utility ("value for money"). Our results indicate that decentralized selfish bidding strategies are able to capitalize on temporary beneficial conditions and offer comparable performance with a centralized scheme (based on the 'mu C-rule') that requires knowledge about peak data-rates, queue lengths, and preferences for all users in the system.

  • 265.
    Blomgren, Mats
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Hultell, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Demand-responsive pricing in open wireless access markets2007Ingår i: IEEE VTS VEH TECHNOL CONF, 2007, s. 2990-2995Konferensbidrag (Refereegranskat)
    Abstract [en]

    Radio resource management (RRM) across operator boundaries is emerging as a salient feature for wireless systems beyond 3G. Until recently, research has been confined to solutions where cooperating networks enter explicit sharing agreements that define how responsibilities and revenues should be divided. An alternative would be to share the infrastructure implicitly by establishing an open wireless access market wherein networks not only compete for users on a long-term time-scale, but also on a much shorter time-base. This could be realized with an architecture where autonomous trade-agents, that reside in terminals and access points (APs), manage the resources through negotiations. In this paper we develop a framework for studying demand-responsive pricing in contexts where APs with overlapping coverage compete for users. Resources are partitioned through a proportional fair divisible auction and our aim is to establish if, and when, an open market for wireless access can be se sustained. Compared to a scenario where APs cooperate, our results show that, an open access market results in better services at lower price which in the prolonging also yields more satisfied customers. As an effect demand will increase and, from the perspective of the APs, act as a counterbalance to the reduced prices. Thus, the revenue earned by the AN will be comparable to the one in which obtained through AP cooperation and monopoly (cartel) pricing. Generally speaking, the difference between the cooperative and noncooperative RRM is small when the demand is concave and increases with the convexity of demand.

  • 266.
    Blomgren, Mats
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Hultell, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Cai, Rui
    Cai, Tao
    Distributed demand-aware access selection in wireless multi-cell data networks2007Ingår i: 2007 IEEE 18th International Symposium On Personal, Indoor And Mobile Radio Communications: Vols 1-9, 2007, s. 2888-2892Konferensbidrag (Refereegranskat)
    Abstract [en]

    Regardless of advances in transmission technology, wireless broadband access will result in that fewer active users can be supported in a given cell. This may, due to lower levels of statistical multiplexing, yield in an unbalanced network. For such contexts load aware access point (AP) selection (load balancing) has been proposed as a means to increase network performance. This paper evaluates the downlink capacity (maximum number of users that can be admitted given a throughput requirement) of distributed load aware AP selection criteria for a well planned network, where the expected number of users per cell coincide. We propose a market based algorithm in which AP selection is aided by market mechanisms. In contrast to most of the existing research, we account for that interference levels generated in different cells depend on user assignment, and therefore varies as terminals perform handoff. Compared to single-frequency systems where users base their selection on the received signal strength our results show that the downlink capacity can be increased with around 25 percent by introducing a channel plan in combination with demand, or load, aware AP selection criteria. This gain is fairly insensitive to the throughput requirement and does not come at the expense of uplink performance. To benefit from demand metrics it is, however, of paramount importance that the entire system bandwidth is not reused in all cells.

  • 267. Boccardi, Federico
    et al.
    Shokri-Ghadikolaei, Hossein
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Fodor, Gabor
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. Ericsson Research, United States.
    Erkip, Elza
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Kountouris, Marios
    Popovski, Petar
    Zorzi, Michele
    Spectrum Pooling in MmWave Networks: Opportunities, Challenges, and Enablers2016Ingår i: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 54, nr 11, s. 33-39Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Motivated by the specific characteristics of mmWave technologies, we discuss the possibility of an authorization regime that allows spectrum sharing between multiple operators, also referred to as spectrum pooling. In particular, considering user rate as the performance measure, we assess the benefit of coordination among networks of different operators, study the impact of beamforming at both base stations and user terminals, and analyze the pooling performance at different frequency carriers. We also discuss the enabling spectrum mechanisms, architectures, and protocols required to make spectrum pooling work in real networks. Our initial results show that, from a technical perspective, spectrum pooling at mmWave has the potential to use the resources more efficiently than traditional exclusive spectrum allocation to a single operator. However, further studies are needed in order to reach a thorough understanding of this matter, and we hope that this article will help stimulate further research in this area.

  • 268. Boche, H.
    et al.
    Jorswieck, Eduard Axel
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Sezgin, A.
    Calculus for multiuser MIMO performance measures2006Ingår i: Conf. Rec. Asilomar Conf. Signals Syst. Comput., 2006, s. 369-373Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we review and combine recent results from multiuser MIMO MSE-based performance optimization and from concave and convex interference function calculus. First, a generalized MIMO MAC weighted MSE-based performance measure is developed using matrix-monotone functions. Next, the connection to interference functions is established. The representation of convex and concave interference functions are reviewed. Finally, the transition of a multiuser MIMO performance measure to the interference functions in terms of weighted sum optimization is shown.

  • 269.
    Bodriagov, Oleksandr
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Teoretisk datalogi, TCS.
    Kreitz, Gunnar
    KTH, Skolan för datavetenskap och kommunikation (CSC), Teoretisk datalogi, TCS.
    Buchegger, Sonja
    KTH, Skolan för datavetenskap och kommunikation (CSC), Teoretisk datalogi, TCS.
    Access Control in Decentralized Online Social Networks: Applying a Policy-Hiding Cryptographic Scheme and Evaluating Its Performance2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Privacy concerns in online social networking services have prompted a number of proposals for decentralized online social networks (DOSN) that remove the central provider and aim at giving the users control over their data and who can access it. This is usually done by cryptographic means. Existing DOSNs use cryptographic primitives that hide the data but reveal the access policies. At the same time, there are privacy-preserving variants of these cryptographic primitives that do not reveal access policies. They are, however, not suitable for usage in the DOSN context because of performance or storage constraints. A DOSN needs to achieve both privacy and performance to be useful. We analyze predicate encryption (PE) and adapt it to the DOSN context. We propose a univariate polynomial construction for access policies in PE that drastically increases performance of the scheme but leaks some part of the access policy to users with access rights. We utilize Bloom filters as a means of decreasing decryption time and indicate objects that can be decrypted by a particular user. We evaluate the performance of the adapted scheme in the concrete scenario of a news feed. Our PE scheme is best suited for encrypting for groups or small sets of separate identities.

  • 270.
    Bogodorova, Tetiana
    et al.
    KTH.
    Vanfretti, Luigi
    Peric, Vedran S.
    Turitsyn, Konstantin
    Identifying Uncertainty Distributions and Confidence Regions of Power Plant Parameters2017Ingår i: IEEE Access, E-ISSN 2169-3536, Vol. 5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Power system operators, when obtaining a model's parameter estimates; require additional information to guide their decision on a model's acceptance. This information has to establish a relationship between the estimates and the chosen model in the parameter space. For this purpose, this paper proposes to extend the usage of the particle filter (PF) as a method for the identification of power plant parameters; and the parameters' confidence intervals, using measurements. Taking into consideration that the PF is based on the Bayesian filtering concept, the results returned by the filter contain more information about the model and its parameters than usually considered by power system operators. In this paper the samples from the multi-modal posterior distribution of the estimate are used to identify the distribution shape and associated confidence intervals of estimated parameters. Three methods [rule of thumb, least-squares cross validation, plug-in method (HSJM)] for standard deviation (bandwidth) selection of the Gaussian mixture distribution are compared with the uni-modal Gaussian distribution of the parameter estimate. The applicability of the proposed method is demonstrated using field measurements and synthetic data from simulations of a Greek power plant model. The distributions are observed for different system operation conditions that consider different types of noise. The method's applicability for model validation is also discussed.

  • 271.
    Bohge, Mathias
    et al.
    TU Berlin.
    Gross, James
    Telecommunication Networks Group (Fachgebiet TKN), TU Berlin.
    Meyer, Michael
    Ericsson Research.
    Wolisz, Adam
    TU Berlin.
    A New Optimization Model for Dynamic Power and Sub-Carrier Allocations in Packet-Centric OFDMA Cells2007Ingår i: Frequenz, ISSN 0016-1136, E-ISSN 2191-6349, Vol. 61, nr 1-2, s. 35-38Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is well known that applying dynamic resource allocation to down-link transmissions of OFDMAsystems provides a significant performance increase, by taking advantage of diversity effects. In order toquantify the maximum possible gain achievable by applying dynamic mechanisms, several optimizationproblems have been suggested for studying a dynamic system's optimal behaviour. However, so far theseoptimization approaches do not take sophisticated system requirements into account, as there are differentpacket-arrival processes, buffering constraints, scheduling policies, as well as QoS requirements per serviceclass. In this paper we present a new optimization model that is based on a packet-centric system view andincludes the system requirements mentioned above. We compare the performance results of the conventionaland the new approach and study the impact of dynamic power allocation in both cases.

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    fulltext
  • 272.
    Bohge, Mathias
    et al.
    TU Berlin.
    Gross, James
    Telecommunications Networks Group (TKN), Technical University Berlin.
    Meyer, Michael
    Ericsson Research.
    Wolisz, Adam
    TU Berlin.
    Dynamic Resource Allocation in OFDM Systems: An Overview of Cross-Layer Optimization Principles and Techniques2007Ingår i: IEEE Network, ISSN 0890-8044, E-ISSN 1558-156X, Vol. 21, nr 1, s. 53-59Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recently, a lot of research effort has been spent on cross-layer system design. It has been shown that cross-layer mechanisms (i.e., policies) potentially provide significant performance gains for various systems. In this article we review several aspects of cross-layer system optimization regarding wireless OFDM systems. We discuss basic optimization models and present selected heuristic approaches realizing cross-layer policies by means of dynamic resource allocation. Two specific areas are treated separately: models and dynamic approaches for single transmitter/receiver pairs (i.e., a point-to-point communication scenario) as well as models and approaches for point-to-multipoint communication scenarios (e.g., the downlink of a wireless cell). This article provides basic knowledge in order to investigate future OFDM cross-layer-optimization issues.

    Ladda ner fulltext (pdf)
    fulltext
  • 273.
    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.

    Ladda ner fulltext (pdf)
    fulltext
  • 274.
    Bohge, Mathias
    et al.
    Telecommunication Networks Group, TU Berlin.
    Gross, James
    Telecommunication Networks Group, TU Berlin.
    Wolisz, Adam
    Telecommunication Networks Group, TU Berlin.
    The Potential of Dynamic Power and Sub-carrier Assignments in Multi-User OFDM-FDMA Cell2005Ingår i: Global Telecommunications Conference, 2005. GLOBECOM '05. IEEE (Volume 5 ), IEEE conference proceedings, 2005, s. 2932-2936Konferensbidrag (Refereegranskat)
    Abstract [en]

    OFDM systems are known to overcome the impairment of the wireless channel by splitting the given system bandwidth into parallel sub-carriers, on which data symbols can be transmitted simultaneously. This enables the possibility of enhancing the system's performance by deploying adaptive (dynamic) mechanisms, namely power and modulation adaption and dynamic sub-carrier assignments. In multi-user communication systems (OFDM-FDMA), these mechanisms can be used to achieve a level of system fairness ensuring that each terminal receives at least an environment-specific minimum amount of data per down-link phase. However, it has been doubted by multiple previous investigations that dynamic power adaption provides enough performance gain in order to be applied in such systems, as it increases the computational load significantly. In this study we discuss the performance gain due to the different approaches and show that in specific communication scenarios enabling a dynamic power distribution provides a significant performance increase compared to dynamic schemes without power adaption.

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    fulltext
  • 275. Bohge, Mathias
    et al.
    Gross, James
    Wolisz, Mathias
    Optimal Power Masking in Soft Frequency Reuse based OFDMA Networks2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    Soft frequency reuse is a strong tool for co-channel interference mitigation in cellular OFDMAILTE networks. The performance of such networks significantly depends on the configuration of the power masks that implement the soft frequency reuse patterns. In this paper, we investigate the performance of different power mask configurations against the optimal case, in which a central entity optimally distributes power and resource blocks among the users of the network. It is shown that large differences exist between the performance of different mask types and the optimal case in both, the overall cell throughput, as well as the cell-edge user performance.

    Ladda ner fulltext (pdf)
    fulltext
  • 276.
    Bohge, Mathias
    et al.
    TU Berlin.
    Naghibi, Farshad
    TU Berlin.
    Wolisz, Adam
    TU Berlin.
    The use of guard bands to mitigate multiple access interference in the OFDMA uplink2008Ingår i: Proceedings of the 13th International OFDM-Workshop (InOWo),, 2008, s. 75-79Konferensbidrag (Refereegranskat)
    Abstract [en]

    The usual approach to mitigate multiple access interference (MAI) in the uplink of cellular OFDMA based systems is to use relatively large cyclic prefixes as time domain guard periods. In this paper, we suggest to use a combination of short time domain guard periods and frequency domain guard bands to protect against MAI instead. Guard bands can be added and removed as necessary and, thus, increase the MAI protection flexibility. We show that, if optimally applied, the use of guard bands can significantly increase the system’s uplink capacity or minimum capacity per user.

  • 277.
    Boongerd, Sanhawad
    et al.
    KTH, Skolan för teknik och hälsa (STH), Data- och elektroteknik.
    Lindstein, Fredrik
    KTH, Skolan för teknik och hälsa (STH), Data- och elektroteknik.
    Analys av datakommunikationssäkerhet för VoIP-protokoll2012Självständigt arbete på grundnivå (högskoleexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Voice over IP (VoIP) är en datakommunkationsteknik som möjliggör röstsamtal överdatanätverk. Med VoIP är det möjligt att sänka kostnader, utöka funktionalitet och flexibilitet.Från Försvarsmaktens perspektiv är säkerhetsfrågan med VoIP av stor vikt, därför läggs speciellfokus för denna rapport på säkerhetsaspekten av de två största öppna VoIP-protokollen H.323och SIP, några av de vanligaste attackerna, och åtgärder mot dessa attacker.

    Eftersom uppbyggnaden av ett H.323- eller SIP-baserat nätverk är komplext och inte allsbeprövat i samma utsträckning som traditionell telefoni, innehåller det många kända säkerhetshåloch förmodligen för närvarande många okända säkerhetsbrister.

    Slutsatsen är att det krävs mycket stor kunskap och insikt hur ett VoIP-nätverk baserat på H.323eller SIP fungerar för att göra nätverket tillräckligt säkert i nuläget, vilket gör det till en tveksamttillfredställande lösning för Försvarsmakten idag för deras kommunikation av känsligare slag.

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  • 278. Bosiljevac, M.
    et al.
    Persson, Patrik
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Sipus, Z.
    Hybrid spectral domain - UTD method applied to conformal antenna analysis2006Ingår i: Eur Space Agency Spec Publ ESA SP, 2006Konferensbidrag (Refereegranskat)
    Abstract [en]

    A hybrid spectral domain - UTD method (Uniform Theory of Diffraction) developed for the analysis of conformal antennas is presented in this paper. The basic idea behind the hybrid method is to combine different analysis methods for conformal antennas and, at the same time, preserve the advantages of the considered methods. More specifically, the considered hybrid SD - UTD method joins the possibility of analyzing multilayer structures (spectral domain method) and the possibility of analyzing electrically large structures (UTD method). Hence, using the developed method it is possible to analyze large multilayered conformal antennas with high accuracy and speed. This work has been made possible by the ACE program for structuring the research on conformal antennas in Europe. The developed method is a result of joining research activities of University of Zagreb, Croatia and the Royal Institute of Technology, Sweden.

  • 279. Bouman, N.
    et al.
    Borst, S.
    Van Leeuwaarden, J.
    Proutiere, Alexandre
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Backlog-based random access in wireless networks: Fluid limits and delay issues2011Ingår i: Proceedings of the 2011 23rd International Teletraffic Congress, ITC 2011, 2011, s. 39-46Konferensbidrag (Refereegranskat)
    Abstract [en]

    We explore the spatio-temporal congestion dynamics of wireless networks with backlog-based random-access mechanisms. While relatively simple and inherently distributed in nature, suitably designed backlog-based access schemes provide the striking capability to match the optimal throughput performance of centralized scheduling algorithms in a wide range of scenarios. In the present paper, we show that the specific activity functions for which maximum stability has been established, may however yield excessive queue lengths and delays. The results reveal that more aggressive/persistent access schemes can improve the delay performance, while retaining the maximum stability guarantees in a rich set of scenarios. In order to gain qualitative insights and examine stability properties we will investigate fluid limits where the system dynamics are scaled in space and time. As it turns out, several distinct types of fluid limits can arise, exhibiting various degrees of randomness, depending on the structure of the network, in conjunction with the form of the activity functions. We further demonstrate that, counter to intuition, additional interference may improve the delay performance in certain cases. Simulation experiments are conducted to illustrate and validate the analytical findings.

  • 280.
    Bourennane, Mohamed
    et al.
    KTH, Tidigare Institutioner                               , Elektronik.
    Ljunggren, Daniel
    KTH, Tidigare Institutioner                               , Elektronik.
    Karlsson, Anders
    KTH, Tidigare Institutioner                               , Elektronik.
    Jonsson, Per
    KTH, Tidigare Institutioner                               , Elektronik.
    Hening, A.
    KTH, Tidigare Institutioner                               , Elektronik.
    Peña Císcar, J.
    KTH, Tidigare Institutioner                               , Elektronik.
    Experimental long wavelength quantum cryptography: from single-photon transmission to key extraction protocols2000Ingår i: Journal of Modern Optics, ISSN 0950-0340, E-ISSN 1362-3044, Vol. 47, s. 563-579Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present experiments on long wavelength (λ = 1.55 μm) 'plug and play' quantum cryptography systems. We discuss the performance of single-photon detectors at λ = 1.55 μm. Furthermore, we address the full implementation of the quantum cryptography protocol, discussing in detail the implementation of protocols for error correction and privacy amplification needed to get a secure key. We illustrate the theory with examples from a full software simulation to show the performance of the complete protocol in terms of final secure key creation rate

  • 281.
    Brade, Dirk
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    The need for credible Modeling and simulation in the context of the network based defense2006Ingår i: Modeling and Simulation Tools for Emerging Telecommunication Networks: Needs, Trends, Challenges and Solutions / [ed] Ince, AN; Topuz, E, 2006, s. 423-447Konferensbidrag (Refereegranskat)
    Abstract [en]

    In concert with numerous other western world nations, in Sweden military doctrine is changing focus from a platform-oriented towards a network-based approach. Military platforms become participants in "the network", share information, and provide services that allow them to sense, decide, and act beyond their individual capabilities in a cooperative and distributed manner. The information exchange occurs through an information infrastructure, the so called "infostructure" which constitutes a communication network spanned by the participating nodes. Although technologically not far beyond the edge of today's state of the art, are functional and technological requirements on the infostructure high: Mobile units exposed to lethal threats and electronic countermeasures shall connect and disconnect rapidly and reliably to build networks in an adhoc manner, ensuring secure and fault tolerant communication with sufficiently high quality of service. Nodes in the infostructure consist of heterogeneous systems provided by numerous nations, providing various types of end-user and communication services. Various alternative approaches can be taken for the creation of the infostructure, which must be expected to become a highly complex system, challenging to control and administrate. Modeling and Simulation are considered to be the mandatory enablers to optimize its design, maintenance, use, and improvement. This concept paper describes a vision of the infostructure, operational conditions, and desired properties, and identifies challenges which must be met on order to early avoid dead-end roads. Finally, it outlines application areas for communication related Modeling and Simulation to support the transition to and continuous improvement of a Network Based Defense.

  • 282.
    Brandt, Rasmus
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Coordinated Precoding for Multicell MIMO Networks2014Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [sv]

    Genom att låta flera radiobasstationer samarbeta är det möjligt att förbättra spektraleffektiviteten i trådlösa interferensnätverk. Fokus i denna licentiatavhandling ligger på multicellnätverk där både radiobasstationer och mobilenheter har flera antenner. Radiobasstationerna väljer sina spatiella förkodare gemensamt, men skickar data individuellt till sina respektive mobilenheter. För sådana system med koordinerad förkodning ('coordinated precoding') är interferensupprätning ('interference alignment') ett användbart teoretiskt verktyg, eftersom det möjliggör överföring av maximalt antal dataströmmar i nätverket. I avhandlingen studeras tre aspekter av interferensupprätning och koordinerad förkodning.

    Först undersöks interferensupprätning när signalrummet består av en kombination av rymd- och frekvensdimensioner. Ett nödvändigt villkor härleds för existensen av rymd/frekvens-interferensupprätning, och prestandavinsten analyseras i jämförelse med system där enbart rymddimensionerna används för interferensupprätning. Det föreslagna systemet utvärderas med hjälp av numeriska simuleringar och uppmätta inomhus- och utomhuskanaler. Resultaten visar att rymd/frekvens-interferensupprätning ger upphov till ett ökat antal frihetsgrader, men att summadatatakten främst förbättras tack vare en upplevd effektförstärkning.

    Därefter undersöks tekniker för skattning av den nödvändiga kanalkännedom som krävs för att genomföra koordinerad förkodning. Det finns flera sätt att erhålla den nödvändiga informationen, t.ex. genom olika kombinationer av kanalskattning, feedback, signalering och användning av backhaulnätverk. Speciellt söks distribuerade metoder, eftersom dessa är fördelaktiga vid praktisk implementering. Tre metoder för skattning av kanalkännedom föreslås. Dessa motsvarar olika avvägningar mellan kanalskattning och signalering, och en av metoderna är helt distribuerad. När den skattade informationen används med en existerande algoritm för koordinerad förkodning blir prestandan undermålig. Därför föreslås två förändringar av algoritmen, vilka leder till mer robusta prestanda. Förändringarna bygger på den välkända diagonal loading-tekniken. Utvärdering av det föreslagna systemet, som består av distribuerad erhållning av kanalkännedom samt den förbättrade algoritmen för koordinerad förkodning, genomförs med numerisk simulering. Resulterande prestanda är i nivå med ett tidigare föreslaget system, som dock kräver centraliserad tillgång till kanalskattningarna, till skillnad från vår nya lösning.

    Slutligen studeras ett system med koordinerad förkodning och icke-perfekt radiohårdvara. En modell för distortionsbruset orsakad av bristerna i radiohårdvaran används, och en iterativ resurstilldelningsteknik föreslås baserad på ett existerande ramverk. Den föreslagna algoritmen kan implementeras distribuerat över mobilenheterna, men kan i allmänhet inte implementeras distribuerat över radiobasstationerna. Den föreslagna algoritmen utvärderas med numeriska simuleringar, och resultaten visar att prestanda är bättre än alla referensmetoder. Detta visar betydelsen av att hantera bristerna i radiohårdvaran i resurstilldelningen.

    Sammantaget visar avhandlingen på möjligheterna att öka spektraleffektiviteten i framtida multicellnätverk med hjälp av koordinerad förkodning.

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    Rasmus_Brandt_licentiate_thesis
  • 283.
    Brandt, Rasmus
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Björnson, Emil
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Bengtsson, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Weighted Sum Rate Optimization for Multicell MIMO Systems with Hardware-Impaired Transceivers2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Physical transceivers exhibit distortions from hardware impairments, of which traces remain even after compensation and calibration. Multicell MIMO coordinated beamforming methods that ignore these residual impairments may suffer from severely degraded performance. In this work, we consider a general model for the aggregate effect of the residual hardware impairments, and propose an iterative algorithm for finding locally optimal points to a weighted sum rate optimization problem. The importance of accounting for the residual hardware impairments is verified by numerical simulation, and a substantial gain over traditional time-division multiple access with impairments-aware resource allocation is observed.

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    icassp2014
  • 284. Braun, Christian
    et al.
    Engblom, Gunnar
    Beckman, Claes
    Allgon System AB, Sweden.
    Evaluation of antenna diversity performance for mobile handsets using 3-D measurement data1999Ingår i: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 47, nr 11, s. 1736-1738Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An evaluation of two-branch antenna diversity on mobile telephones is performed in the presence of head and hand phantoms to model the influence of the user. Two mobile telephone prototypes for the 1800-MHz band are considered. The evaluation is done by measuring the three-dimensional (3-D) complex radiation patterns from each antenna with the prototypes positioned near the phantom head and hand (i.e., in talk position) and calculating the diversity performance for three different scenarios of the incoming field. The two-branch antenna setups on both prototypes produce a calculated diversity gain of about 9 dB for selection diversity at the 99% reliability level.

  • 285.
    Bria, Aurelian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Cost-based resource management in hybrid cellular-broadcasting systems2005Ingår i: VTC2005-SPRING: 2005 IEEE 61ST VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5, PROCEEDINGS  , New York: IEEE , 2005, s. 3183-3187Konferensbidrag (Refereegranskat)
    Abstract [en]

    This article introduces a cost based framework for the resource management in hybrid cellular-broadcasting systems with adaptive data rate. The considered service is delivery of multimedia items to the cache memory of user terminals. The problem investigated here is the minimization of the delivery cost per item, given that we have at our disposal a cellular and a broadcasting system. The proposed solution is to search for optimum set of users that are assigned to the broadcasting radio access and the respective data rate for serving them. The simulations performed on a test bed show that it is possible to achieve even four to five times reduction in cost per item if we employ both infrastructures, compared to a simpler strategy that assumes the transmission to only one of them. This significant gain justify the need for centralized resource management of the cellular and broadcasting systems. We have identified also situations when this gain is not significant, hence centralized management is not needed. Both situations are possible in realistic environments.

  • 286.
    Bria, Aurelian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster, Kommunikationssystem, CoS.
    Hybrid cellular-broadcasting infrastructure systems: radio resource management issues2006Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis addresses the problem of low-cost multicast delivery of multimedia content in future mobile networks. The trend towards reuse of existing infrastructure for cellular and broadcasting for building new systems is challenged, with respect to the opportunities for low cost service provision and scalable deployment of networks.

    The studies outline significant potential of hybrid cellular-broadcasting infrastructure to deliver lower-cost mobile multimedia, compared to conventional telecom or broadcasting systems. Even with simple interworking techniques the achievable cost savings can be significant, at least under some specific settings.

    The work starts with a foresight study shaped around four scenarios of the future, and continues with the introduction of a high-level framework for radio resource management in Ambient Networks. Two approaches on the hybrid system architecture are considered. The first one assumes different degrees of interworking between conventional cellular and broadcasting systems, in single and multi-operator environments. Second, is a broadcast only system where cellular sites are used for synchronized, complementary transmitters for the broadcasting site. In the first approach, the key issue is the multi-radio resource management, which is strongly affected by the degree of integration between the two networks. Two case studies deal with the problem of delivering, for lowest cost, a data item to a certain number of recipient users. A flexible broadcasting air interface, which offers several transmission data rates that can be dynamically changed, is demonstrated to significantly increase cost efficiency under certain conditions. An interesting result is that real-time monitoring of the user reception conditions is not needed, at least when multicast group is large. This indicates a high degree of integration between cellular and broadcasting networks may not by generally justified by visible cost savings.

    Scalability of the hybrid infrastructure deployment is the main topic in the second approach. For a DVB-H type of network, the numerical evaluations show that achievement of economies of scale while increasing network capacity and coverage, by employing higher modulation and coding rate or installing new transmission sites, is difficult. Therefore, a technique based on application-layer forward error correction with Raptor codingA is suggested for enabling a flexible trading between system capacity, perceived coverage and delay, in the case of mobile users.

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  • 287.
    Bria, Aurelian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Mobile Multimedia Multicasting in Future Wireless Systems: A Hybrid Cellular-Broadcasting System Approach2008Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    This dissertation addresses the problem of providing a®ordable mobile mul-timedia services in wide area wireless networks. The approach is to con-sider novel system architectures, based on reusing and sharing of the ex-isting network infrastructure for cellular and terrestrial TV broadcastingsystems. The focus has been on the radio resource management techniques,and the evaluation of the potential cost savings, compared to traditionalevolution tracks of the cellular and broadcasting systems.The studies show that deployment cost of a wide area broadcastingnetwork, using DVB-H technology, is very large if high data rate and fullarea coverage is targeted. For this reason we propose to avoid the broad-casting infrastructure dimensioning for full area coverage, and use insteadthe cellular systems to enable error correction for broadcasting transmis-sions. For the special case of mobile users, the chosen approach is to tradesystem's cost and capacity for improved perceived coverage. This trade-o®is enabled by the use of application layer forward error correction, usingRaptor coding.The general purpose Ambient Networks technology was chosen to en-able a platform for inter-operability between cellular and broadcasting sys-tems, especially the necessary interfaces. Under the Ambient Networksframework, we investigate the achievable cost savings o®ered by a hybridcellular-broadcasting system when combinations of broadcast and point-to-point transmissions are jointly utilized to provide ¯le transfers and stream-ing services. Two cases were investigated: one where the cellular systemacts as a replacement and deliver the data in the areas where broadcastingtransmissions cannot reach, and another one where cellular system carriesparity data to users that experience temporary outage in the broadcastingsystem. The results are encouraging, as they show that ¯le transfer costcan be reduced by more than 50%, but only under certain conditions.On a short term, hybrid cellular-broadcasting systems based on 3G andDVB-H, o®er a good platform for testing new and innovative mobile TVservices, enriched with interactivity and content personalization. From atechnical perspective, the outcomes of the presented studies indicate thatfuture systems built on hybrid cellular-broadcasting infrastructures are ableprovide a long term and cost e±cient solution for delivery of a®ordablebroadband multimedia services to mobile users. However, today's cellularand broadcasting systems live in di®erent worlds, are driven by di®erentrevenue models, and they are now starting to compete, instead of cooperate,for controlling the multimedia delivery channels to mobile users.

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  • 288.
    Bria, Aurelian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Performance of Cost-Based Resource Management in Cellular-Broadcasting Systems with Multicast Push Traffic2005Rapport (Övrigt vetenskapligt)
  • 289.
    Bria, Aurelian
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    González Font, Álvaro
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Cost-Based Resource Management for Filecasting Services in Hybrid DVB-H and 3G systems2008Ingår i: 2008 IEEE INTERNATIONAL SYMPOSIUM ON WIRELESS COMMUNICATION SYSTEMS (ISWCS 2008), NEW YORK: IEEE , 2008, s. 159-163Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper describes and evaluates a novel resource management technique for minimizing the file transmission cost in a hybrid cellular-broadcasting system. While DVB-H technology is utilized for wide area broadcasting, the 3G-HSDPA(1) system takes the role of providing not only feedback about reception conditions, but also on-demand repair information to the users that have missed part of the DVB-H transmissions. The Application Layer - Forward Error Correction with Raptor coding is used to generate parity data that is sent to the users through both cellular and broadcasting system. Our results show significant potential for cost reduction under certain settings and scenarios. Overall, we think that the outcomes of this study should encourage the interworking of cellular 3G and DVB-H broadcasting systems, in an effort to achieve cost efficient delivery of multimedia content to mobile users.

  • 290.
    Bria, Aurelian
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Gómez-Barquero, David
    Scalability of DVB-H deployment on existing wireless infrastructure2005Ingår i: IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, IEEE , 2005, s. 716-720Konferensbidrag (Refereegranskat)
    Abstract [en]

    This article investigates the scalability of DVB-H deployment on existing wireless infrastructure for digital broadcasting and cellular networks. Three deployment strategies are investigated: when only the broadcasting and the cellular infrastructure are used separately, and the case when both can be used jointly. The outcomes show that, in general, the investment needed for increasing the service capacity by switching to higher order modulation, or for increasing the coverage level over a given service area, lead to a higher annualized cost per Mb/s.

  • 291.
    Broman, Rickard
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    A Practical Study of Network Coding in Distributed Storage Systems2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Highly increased data traffic over the last few years has led to a need to improve the networkefficiency. One way to achieve this is by network coding. In this thesis two codes, namelyreplication code and regenerating codes, have been examined. Most other works in this area hasbeen theoretical, so we created a testbed to perform practical tests. Then these practical resultsare compared to the theoretical results with varying finite field size. It will be shown that thepractical studies verify the theoretical work. Furthermore, we observe the probability ofsuccessful repair after several stages of repair.

    More so, the achievability of exact repair of a failed node in a tandem network has beenexamined. This has been proven possible, and also the required finite field size is presented.Another issue at focus is the number of transfers required to achieve exact repair in such anetwork. The results show that 2*k transfers is required, which is comparable to functionalrepair.

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  • 292.
    Brännström, Fredrik
    et al.
    Chalmers University of Technology.
    Aulin, Tor M.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    Chalmers University of Technology.
    Capacity considerations for trellis code multiple access systems2001Ingår i: IEEE Information Theory Workshop, 2001, s. 153-155Konferensbidrag (Refereegranskat)
  • 293.
    Brännström, Fredrik
    et al.
    Chalmers University of Technology.
    Aulin, Tor M.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    Chalmers University of Technology.
    Constellation-constrained capacity for trellis code multiple access systems2001Ingår i: IEEE Global Telecommunications Conference, 2001, s. 791-795Konferensbidrag (Refereegranskat)
  • 294.
    Brännström, Fredrik
    et al.
    Chalmers University of Technology.
    Aulin, Tor M.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    Chalmers University of Technology.
    Iterative detectors for trellis-code multiple-access2002Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 50, nr 9, s. 1478-1485Artikel i tidskrift (Refereegranskat)
  • 295.
    Brännström, Fredrik
    et al.
    Chalmers University of Technology.
    Aulin, Tor M.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    Chalmers University of Technology.
    Iterative multi-user detection of trellis code multiple access using a posteriori probabilities2001Ingår i: IEEE International Conference on Communications, 2001, s. 11-15Konferensbidrag (Refereegranskat)
  • 296.
    Brännström, Fredrik
    et al.
    Chalmers University of Technology.
    Aulin, Tor M.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Grant, Alex J.
    University of South Australia.
    Convergence analysis of iterative detectors for narrow-band multiple access2002Ingår i: IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE, 2002, s. 1373-1377Konferensbidrag (Övrigt vetenskapligt)
  • 297.
    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 codes2007Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 11, nr 5, s. 437-439Artikel i tidskrift (Refereegranskat)
    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.

  • 298.
    Brännström, Fredrik
    et al.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Classification of 8PSK mappings for BICM2007Ingår i: IEEE International Symposium on Information Theory, 2007, s. 2136-2140Konferensbidrag (Refereegranskat)
    Abstract [nb]

    The performance of bit-interleaved coded modulation with iterative decoding is significantly influenced by the mapping of bits to the symbol constellation. A range of mappers have been suggested in the literature, however, no attempt has been made to systematically enumerate all unique mappers for a given signal constellation. In this paper, we classify 8PSK mappers based on bit-wise distance spectra for no prior information, and full prior information, respectively.

  • 299.
    Brännström, Fredrik
    et al.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Classification of Unique Mappings for 8PSK Based on Bit-Wise Distance Spectra2009Ingår i: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 55, nr 3, s. 1131-1145Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The performance of bit-interleaved coded modulation (BICM) with (or without) iterative decoding (ID) is significantly influenced by the mapping of bits to the symbol constellation. Our main objective in this paper is to develop a systematic design approach for BICM-ID schemes, ensuring the best possible performance with iterative decoding. Although useful mappings for BICM-ID have been found based on various search strategies, no attempt has been made to systematically enumerate and classify all unique mappers for a given constellation. As the basis for a systematic enumeration and classification, we define the average bit-wise distance spectrum for a mapping from bits to symbols. Different bit-wise distance spectra are derived assuming no prior information or full prior information, respectively. The bit-wise distance spectra determine correspondingbit-wise error probability and bit-wise mutual information. The latter allows us to use theclassification of mappings with unique bit-wise distance spectra to also classifymappings with unique extremal points in the corresponding extrinsic information transfer (EXIT) curves. As an example of our approach, we classify 8PSK mappings into 86 classes of unique mappings according to bit-wise distance spectra. The classificationcan be used to significantly reduce the complexity of the search for suitable mappers for BICM-ID. For 8PSK and a given encoder, only 86 different mappings need to be investigated. As examples of the systematic design approach, the best 8PSK mappingsfor minimizing the convergence threshold are found for concatenation with the rate 1/2 (5, 7)8 and (133,1718 convolutional codes, and the rate 1/2 UMTS turbo code with identical constituent convolutional codes (15/13)8.

  • 300.
    Brännström, Fredrik
    et al.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Multiple parallel concatenated codes with optimal puncturing and energy distribution2005Ingår i: IEEE International Conference on Communications, 2005, s. 622-626Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we show how to find optimal energy distribution together with optimalpuncturing ratios for parallel concatenated codes with two or more constituent codes. The energy distribution and the puncturing ratios are optimal in terms of minimizing the average signal-to-noise ratio convergence threshold. The extrinsic information transfer functions of the constituent codes are used for the optimization. Using this technique we obtain additional degrees of freedom for constructing codes with low convergence thresholds over a large range of code rates.

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