| 1. |
- Klockar, Annika, 1967-
(författare)
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Improving User Experience of Internet Services in Cellular Networks
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Internet has grown enormously since the introduction of the World Wide Web in the early 90's. The evolution and wide spread deployment of cellular networks have contributed to make the Internet accessible to more people in more places. The cellular networks of today offer data rates high enough for most Internet services. Even so, the service quality experienced by the users is often lower than in wired networks.The performance of TCP has a large impact on user experience. Therefore, we investigate TCP in cellular networks and propose functionality to improve the situation for TCP. We have studied sources of delay and data loss, such as link layer retransmissions, queuing, and handover. Measurements were conducted in a GSM/GPRS testbed. The results indicate that TCP interact efficiently with the GSM link layer protocol in most cases. From experiments of queuing in GPRS, we conclude that with a smaller buffer delay is reduced significantly, but that TCP throughput is about the same as with a larger buffer. Furthermore, we propose an improved buffer management when a connection loses all its resources to traffic with higher priority. We also propose a scheme for data forwarding to avoid negative impact on TCP during handover for WINNER, a research system that was used to test ideas for LTE.The achievable data rates in cellular networks are limited by inter-cell interference that vary over the cell. Inter-cell interference can be mitigated with Coordinated Multipoint techniques (CoMP), techniques that currently are being standardized for LTE-Advanced. System wide CoMP is, however, not an option, since it would be too resource consuming. In order to limit the required resources for CoMP, we propose an approach to select a subset of users for CoMP that is based on user experience. Simulation results indicate that user experience, represented with application utility, and fairness are improved compared to if only rate is considered in the user selection.
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| 2. |
- Klockar, Annika, et al.
(författare)
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Network Controlled Mobility Management with Policy Enforcement towards IMT-A
- 2008
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Ingår i: International Conference on Communications, Circuits and Systems, 2008. ICCCAS 2008. - Xiamen, China : IEEE conference proceedings. - 9781424420643 - 9781424420636 ; , s. 139-143
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Konferensbidrag (refereegranskat)abstract
- This paper introduces a framework of mobility management and call-handling based on policy enhancement towards the IMT-Advanced systems. The function allocation and several selected mechanisms for the framework are described. The framework is based on the EU IST WINNER research project results and enables scalable service provisioning by setting the end user satisfaction and overall system performance as general goals. This paper aims to serve as a reference for the design of IMT-Advanced systems.
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| 3. |
- Klockar, Annika, et al.
(författare)
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User-centric pre-selection and scheduling for coordinated multipoint systems
- 2014
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Ingår i: 2014 11th International Symposium on Wireless Communications Systems (ISWCS 2014). - : IEEE. - 9781479958634 ; , s. 888-894
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Konferensbidrag (refereegranskat)abstract
- The data traffic volumes are constantly increasing in cellular networks. Furthermore, a larger part of the traffic is generated by applications that require high data rates. Techniques including Coordinated Multipoint transmission (CoMP) can increase the data rates, but at the cost of a high overhead. The overhead can be reduced if only a subset of the users is served with CoMP. In this paper, we propose a user selection approach, including pre-selection of CoMP users and short term scheduling, that takes user requirements into account. Users that require a high data rate to reach an acceptable level of service satisfaction are selected to use coherent joint processing CoMP in some of their downlink transmission bandwidth. Simulation results show that both the number of satisfied users and fairness are improved with the proposed user selection as compared to user selection that does not consider individual user requirements.
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| 4. |
- Klockar, Annika, et al.
(författare)
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Utility as a User Selection Criterion for Coordinated Multi-Point Systems
- 2013
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Ingår i: 2013 IEEE 24th International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC). - London : IEEE conference proceedings. ; , s. 3123-3128, s. 3123-3128
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Konferensbidrag (refereegranskat)abstract
- Coordinated multipoint (CoMP) transmission and reception techniques have been proposed to combat inter-cell interference in cellular systems and, hence, to increase the data rates. Due to the overhead introduced, not all users may be served with CoMP. In this paper, we focus on how to select users for joint processing CoMP under limited backhaul capacity. The evaluated user selection schemes take user experience into account, quantified by the utility of Internet application types. We propose a heuristic algorithm utility based user selection that has low computational complexity. Utility based user selection and maximize utility, which maximizes the sum utilities, are compared to maximize rate, which maximizes the sum data rates. A range of traffic mixes and user locations are evaluated. The simulation results indicate that resources required for CoMP are more efficiently used if the user selection is based on utility rather than on maximizing the total data rate. If utility is taken into account a higher total utility can in many cases be achieved for the same limited backhaul capacity.
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| 5. |
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| 6. |
- Klockar, Annika, et al.
(författare)
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Utility of Joint Processing Schemes
- 2010
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Ingår i: 2010 7th International Symposium on Wireless Communication Systems (ISWCS 2010). - : IEEE Communications Society. - 9781424463152 ; , s. 76-80, s. 76-80
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Konferensbidrag (refereegranskat)abstract
- Joint processing between base stations has been shown as an efficient technique to mitigate inter-cell interference and increase data rates, in particular at the cell edges. In this paper, we evaluate the utility of Internet applications in a joint processing enabled cluster of base stations. Utility is used to quantify system performance as experienced by the end user. In particular, the utility of three joint processing schemes for the downlink is characterized and compared within the cluster area. The qualitative results indicate that joint processing can significantly improve the utility of hard real-time and adaptive applications. For elastic applications, joint processing is not worthwhile, since almost as high utility is achieved also with conventional single base station assignment
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| 7. |
- Klockar, Annika, et al.
(författare)
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Utility of joint processing schemes
- 2010
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Ingår i: 7th International Symposium on Wireless Communication Systems, ISWCS, York, UK.
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Konferensbidrag (refereegranskat)
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| 8. |
- Mihovska, Albena, et al.
(författare)
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Requirements and Algorithms for Cooperation of Heterogeneous Radio Access Networks
- 2008
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Ingår i: Wireless Personal Communications. - : Springer.
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Tidskriftsartikel (refereegranskat)abstract
- This paper defines the requirements for cooperation of heterogeneous radio access networks (RANs) and proposes a novel radio resource management (RRM) framework for support of mobility and quality of service (QoS) in a heterogeneous communication environment comprising IMT-Advanced and legacy systems. The reference IMT-Advanced system is the one developed within the IST project WINNER (IST-2003-507581 Project Wireless Initiative New Radio, http://www.ist-winner.org). The RRM mechanisms are evolved from traditional ones to comply with the requirements imposed by a simplified new (RAN) architecture as proposed for IMT-Advanced systems. The RRM mechanisms are evaluated for the scenario of intra-RAN and inter-RAN user mobility. The RRM framework incorporates as novelty improved triggering mechanisms, a network-controlled mobility management scheme with policy enforcement on different levels in the RAN architecture, and a distributed handover and admission control mechanism for fast decision polling at different levels of the RAN. The RRM framework is further enhanced with computational intelligence based on fuzzy logic algorithms to enhance the process of handover. The RRM framework has been evaluated in terms of reduced user blocking probabilities
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| 9. |
- Wennström (Klockar), Annika, et al.
(författare)
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A GPRS Testbed for TCP Performance Measurements
- 2002
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Ingår i: 4th International Workshop on Mobile and Wireless Communications Network. - : IEEE conference proceedings. - 0780376056 ; , s. 320-324
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Konferensbidrag (refereegranskat)abstract
- In this paper a GPRS measurement testbed for TCP performance evaluation is presented. Unlike simulations and live measurements, the testbed combines the use of real network equipment and protocol implementations with a precise control over radio channel conditions. Some initial TCP measurements obtained with the GPRS testbed are also presented. The effect of varying numbers of PDCH and of buffering in the GPRS system is investigated.
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| 10. |
- Wennström (Klockar), Annika, et al.
(författare)
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A GSM/GPRS Testbed for TCP Performance Evaluation
- 2002
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Ingår i: Proceedings of International Workshop on Wired/Wireless Internet Communications. - : CSREA Press. - 1892512386 ; , s. 19-26
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Investigating the wireless Internet is a nontrivial task dueto the complexity of wireless systems and the many protocolinteractions that appear. In this paper we present a measurementtestbed that allows us to investigate the performanceof Internet traffic over a real GSM network but witha controlled radio environment and traffic load. A detailedperformance evaluation of TCP over GSM is presented. Arange of radio conditions are considered with a focus on theinteraction between TCP and the GSM link layer. With respectto efficient protocol layer interaction, the results showthat high variability in round trip times is more problematicthan poor radio conditions. How the testbed has been extendedfor GPRS and planned measurements for this systemare also discussed.
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