| 1. |
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| 2. |
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| 3. |
- Ahlfors, Ulf, et al.
(författare)
-
Overload control strategies in a multiprocessor system with distributed data
- 1995
-
Ingår i: Proceedings of the 5th IEE Conference on Telecommunications, Brighton, UK, March 1995. - 0852966342 ; , s. 145-149
-
Konferensbidrag (refereegranskat)abstract
- This paper addresses overload control issues for distributed control systems, i.e. multiprocessor systems, in telephone exchanges, signalling transfer points, service control points, home location registers, etc. Three different strategies for rejecting calls, due to severe overload conditions, are examined. The strategies differ in that they allow call rejection during different time epochs of the entire life time of the call. The optimal solution, i.e. the largest throughput, can only be obtained by a centrally placed overload control mechanism which collects data from all processors in the system
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| 4. |
- Ahlfors, Ulf, et al.
(författare)
-
Towards Efficient Call Admission Control Criterion for State-Dependent Routing in Multirate Networks
- 1999
-
Ingår i: Proceedings of the 1999 IEEE International Conference on Control Applications, (2):1607-1613, Hawaii, USA, August 1999. - 078035446X ; 2, s. 1607-1613
-
Konferensbidrag (refereegranskat)abstract
- We consider a link serving multiple service classes. We evaluate the properties of the link admission control policies that are obtained from an efficient scheme proposed by Krishnan and Hubner (1997). The Krishnan and Hubner approach suggests efficient calculations of state-dependent routing criteria for multi-rate networks through state-space aggregation. Through simple examples we show that it is possible that the approximations made in the approach might lead to degraded performance, instead of the expected improvement. We outline and discuss a possible extension to the Krishnan and Hubner approach in an effort to address this problem
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| 5. |
- Büntgen, Ulf, et al.
(författare)
-
Limited capacity of tree growth to mitigate the global greenhouse effect under predicted warming
- 2019
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- It is generally accepted that animal heartbeat and lifespan are often inversely correlated, however, the relationship between productivity and longevity has not yet been described for trees growing under industrial and pre-industrial climates. Using 1768 annually resolved and absolutely dated ring width measurement series from living and dead conifers that grew in undisturbed, high-elevation sites in the Spanish Pyrenees and the Russian Altai over the past 2000 years, we test the hypothesis of grow fast-die young. We find maximum tree ages are significantly correlated with slow juvenile growth rates. We conclude, the interdependence between higher stem productivity, faster tree turnover, and shorter carbon residence time, reduces the capacity of forest ecosystems to store carbon under a climate warming-induced stimulation of tree growth at policy-relevant timescales.
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| 6. |
|
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| 7. |
- Falk, Lars, et al.
(författare)
-
DQDB - some new characteristics
- 1995
-
Ingår i: [Host publication title missing]. - 0412711702 ; 3, s. 342-354
-
Konferensbidrag (refereegranskat)
|
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| 8. |
- Fitzgerald, Emma, et al.
(författare)
-
An analytic model for Throughput Optimal Distributed Coordination Function (TO-DCF)
- 2017
-
Ingår i: Telecommunication Systems. - : Springer Science and Business Media LLC. - 1018-4864 .- 1572-9451. ; 66:2, s. 197-215
-
Tidskriftsartikel (refereegranskat)abstract
- TO-DCF, a new backoff scheme for 802.11, has the potential to significantly increase throughput in dense wireless LANs while also opportunistically favouring nodes with heavier traffic loads and/or better channel conditions. In this paper we present an analytical model to investigate the behaviour and performance of the TO-DCF protocol with regards to operating parameters such as the number of nodes, the contention window size and the backoff countdown probabilities. We then compare numerical results from an implementation of our model with simulations. Our model shows a high level of accuracy, even when the model assumptions are relaxed, and provides guidance for network operators to correctly configure the weight functions for nodes running TO-DCF given the network’s operating conditions.
|
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| 9. |
- Franco, Antonio, et al.
(författare)
-
Analysis of Age of Information threshold violations
- 2019
-
Ingår i: ACM International Conference on Modeling, Analysis and Simulation of Wireless and Mobile Systems. - New York, NY, USA : ACM. - 9781450369046
-
Konferensbidrag (refereegranskat)abstract
- We study a scenario where a monitor is interested in the freshest possible update from a remote sensor. The monitor also seeks to minimize the number of updates that exceed a certain freshness threshold, beyond which, the information is deemed to be too old. Previous work has presented results for First Come First Served (FCFS) systems. However, it has been shown that Last Come First Served (LCFS) with preemption is more effective in terms of average Age of Information (AoI); we therefore study an M/G/1 LCFS system with preemption. The generality of the busy time distribution gives the advantage of applicability on any distribution inside the model. For example, one can use a deterministic distribution to study a TDMA system, a gamma distribution to model a routing network, or a more complicated distribution to study a CSMA access scheme. We find a general procedure to derive the exact expression of the outage update probability -- i.e. the portion of time updates have information older than a certain threshold. We compare different busy time distributions to the ones already present in literature for equivalent FCFS systems, showing the benefit of using the former discipline. We further study how the variance of the busy time distribution affects the update outage probability. We compare the M/D/1 LCFS with preemption against the M/$\Gamma$/1 LCFS with preemption and let the variance of the busy time of the latter vary, while maintaining the same average busy time for both systems. We find that at low thresholds and low loads, higher variance gives an advantage in terms of update outage probability.
|
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| 10. |
- Franco, Antonio, et al.
(författare)
-
Extended Analysis of Age of Information Threshold Violations
- 2020
-
Ingår i: Computer Communications. - : Elsevier BV. - 0140-3664. ; 161, s. 191-201
-
Tidskriftsartikel (refereegranskat)abstract
- We study a scenario where a monitor is interested in the freshest possible update from a remote sensor. The monitor also seeks to minimize the number of updates that exceed a certain freshness threshold, beyond which, the information is deemed to be too old. Previous work has presented results for First Come First Served (FCFS) systems. However, it has been shown that Last Come First Served (LCFS) with preemption is more effective in terms of average Age of Information (AoI); we therefore study an M/G/1 LCFS system with preemption. The generality of the busy time distribution gives the advantage of applicability on any distribution inside the model. For example, one can use a deterministic distribution to study a TDMA system, a gamma distribution to model a routing network, or a more complicated distribution to study a CSMA access scheme. We find a general procedure to derive the exact expression of the outage update probability -- i.e. the portion of time updates have information older than a certain threshold. We compare different busy time distributions to the ones already present in literature for equivalent FCFS systems, showing the benefit of using the former discipline. We further study how the variance of the busy time distribution affects the update outage probability. We find two instances of the busy time distribution, where at low thresholds and low loads, higher variance gives an advantage in terms of update outage probability. First, we compare the M/D/1 LCFS with preemption against the M/$\Gamma$/1 LCFS with preemption and let the variance of the busy time of the latter vary, while maintaining the same average busy time for both systems. We further compare various M/$H_2$/1 LCFS with preemption with different coefficient of variation and same expected value, thus covering a wider spectrum of variation of the busy time.
|
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| 11. |
- Franco, Antonio, et al.
(författare)
-
Load Reduction for Timely Applications in the Cloud
- 2021
-
Ingår i: IEEE Networking Letters. - 2576-3156. ; 3:3, s. 142-146
-
Tidskriftsartikel (refereegranskat)abstract
- In many IoT applications, sensor data is sent remotely to be processed, but only the freshest result is of interest. In this paper we investigate a feedback mechanism that aborts the processing of stale data at the remote end to reduce the load and save costs. The process is approximated by an M/M/∞ queueing system with a feedback loop. We find the exact expression of the average computational time saved and show that with the feedback loop in place the computation time per CPU can be cut up to 25%, making the technique very promising.
|
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| 12. |
- Franco, Antonio, et al.
(författare)
-
Reliability, timeliness and load reduction at the edge for cloud gaming
- 2020
-
Ingår i: International Performance Computing and Communications Conference. - 9781728110257
-
Konferensbidrag (refereegranskat)abstract
- In this paper we study reliability, timeliness and load reduction in an hybrid Mobile Edge Computing (MEC)/Cloud game streaming infrastructure. In our scenario, a user plays a game streamed by the producer to their handheld device -- or User Equipment (UE). The UE communicates user actions to the edge/cloud via the mobile communication infrastructure; the object is to retrieve the latest game status, of which the most important information is the rendered frame. Particularly, we study reliability through replication in a number of MEC-servers, timeliness through Age of Information (AoI) and load reduction by leveraging the X2 interface at the edge, in order to abort useless frame rendering computations. We translate it as a scenario where a sink -- representing the UE -- is interested in the freshest possible update from distributed nodes. Each node sends updates following a Last Come First Served (LCFS) policy with preemption. We consider two scenarios; the first is $n$ parallel LCFS systems sending updates, and the second adds a feedback loop aimed at decreasing the number of jobs sent per second by the nodes, thus decreasing the load per node. We analyze the number of jobs sent per second and average peak Age of Information at the sink, showing that the second scheme achieves a significantly lower rate of jobs compared with the first, while maintaining constant AoI, thus reducing the load at the edge. We also find that using the feedback loop, we achieve the maximum saving in transmitted jobs per second when the average arrival rate per system is equal to the inverse of the average busy time in every node.
|
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| 13. |
- Franco, Antonio, et al.
(författare)
-
Statistical guarantee of timeliness in networks of IoT devices
- 2022
-
Ingår i: Telecommunication Systems. - : Springer Science and Business Media LLC. - 1018-4864 .- 1572-9451.
-
Tidskriftsartikel (refereegranskat)abstract
- The Internet of Things (IoT) paradigm, has opened up the possibility of using the ubiquity of small devices to route information without the necessity of being connected to a Wide Area Network (WAN). Use cases of IoT devices sending updates that are routed and delivered by other IoT devices have been proposed in the literature. In this paper we focus on receivers only interested in the freshest updates from the sending device. In particular, the dynamic network created by routing/gossiping through small devices creates the possibility of delivering updates out of order. Thus, the entire process can be studied well through a queueing system with infinitely many servers, all serving updates with a random service time. Age of Information (AoI) was proposed as the main metric to measure information freshness. We study the amount of time that the AoI is over a certain threshold at the receiver end as a Quality of Service (QoS) measure, called update outage probability. Particularly, given the recent interest in the literature for time domain analysis of the AoI, we obtain the exact expressions for the AoI, peak AoI (pAoI), effective service time and effective departure time distributions for an M/M/∞ queuing system from a time domain perspective, and study the interdependence between the various parameters involved in order to satisfy a given statistical constraint on timeliness.
|
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| 14. |
- Hamidian, Ali, et al.
(författare)
-
An Enhancement to the IEEE 802.11e EDCA Providing QoS Guarantees
- 2006
-
Ingår i: Telecommunication Systems. - : Springer Science and Business Media LLC. - 1018-4864 .- 1572-9451. ; 31:2-3, s. 195-212
-
Tidskriftsartikel (refereegranskat)abstract
- One of the challenges that must be overcome to realize the practical benefits of ad hoc networks is quality of service (QoS). However, the IEEE 802.11 standard, which undeniably is the most widespread wireless technology of choice for WLANs and ad hoc networks, does not address this issue. In order to support applications with QoS requirements, the upcoming IEEE 802.11e standard enhances the original IEEE 802.11 MAC protocol by introducing a new coordination function which has both contention-based and contention-free medium access methods. In this paper, we consider the contention-based medium access method, the EDCA, and propose an extension to it such that it can be used to provide QoS guarantees in WLANs operating in ad hoc mode. Our solution is fully distributed, uses admission control to regulate the usage of resources and gives stations with high-priority traffic streams an opportunity to reserve time for collision-free access to the medium.
|
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| 15. |
- Hamidian, Ali, et al.
(författare)
-
Deployment and Evaluation of a Wireless Mesh Network
- 2009
-
Ingår i: [Host publication title missing]. ; , s. 66-72
-
Konferensbidrag (refereegranskat)abstract
- Wireless Mesh Networks (WMNs) have the potentialities to greatly penetrate the marketplace in the next decade. They can be considered a hybrid between wireless infrastructure and ad-hoc networks; no other network infrastructure is needed other than the mesh points, thus providing flexibility in building and expanding the network, allowing for automatic discovery of neighboring nodes, increased reliability and redundancy. In this work, we discuss how WMNs can be practically employed to support wireless multihop communications in an office-wide area. To this aim, we have deployed a real WMN testbed utilizing state-of-the-art technology and analyzed the performance of this architecture when supporting multihop heterogeneous traffic.
|
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| 16. |
- Hamidian, Ali, et al.
(författare)
-
Distributed reservation-based QoS in Ad Hoc networks with internet access connectivity
- 2009
-
Ingår i: 2009 21ST INTERNATIONAL TELETRAFFIC CONGRESS (ITC 21). - 9781424447442 ; , s. 33-40
-
Konferensbidrag (refereegranskat)abstract
- Real-time applications introduce new requirements on wireless networks and impose quality thresholds on parameters like delay, jitter, throughput, and packet loss in order to run smoothly. This paper addresses this issue by presenting a MAC scheme that offers real-time applications the opportunity to reserve transmission time based on their QoS requirements for contention-free medium access. Our scheme, which is called EDCA with Resource Reservation (EDCA/RR), operates in a fully distributed manner, is compatible with IEEE 802.11, and provides both prioritized and parameterized QoS. In this study, we have extended EDCA/RR to handle reservation collisions and, through extensive simulations, we show that our proposal can handle multiple reservations as well as the hidden station problem while providing QoS guarantees. We compare EDCA/RR with EDCA and our results show that, as the traffic in the network increases, EDCA/RR succeeds providing the required service to QoS-demanding applications whereas EDCA fails in this task; especially if there are hidden stations. In addition, when the medium is lossy we show that, not only does EDCA/RR give better service to real-time traffic, but also to contending non-real-time traffic.
|
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| 17. |
- Hamidian, Ali, et al.
(författare)
-
Exploring wireless mesh networks for collaborative augmented reality environments
- 2010
-
Ingår i: The International Journal of Virtual Reality. - 1081-1451. ; 9:2, s. 21-30
-
Tidskriftsartikel (refereegranskat)abstract
- Augmented Reality (AR) has emerged as a technology able to greatly support the interaction between people and digital information by merging virtual objects with the real environment. So far, research in this field has been mainly focused on single-user scenarios with pre-stored digital data whose visualization needs to be appropriately and promptly aligned with physical objects. Instead, latest developments of AR also involve collaborative scenarios where several participants share the same AR environment, generating and exchanging data in real-time, and communicating with each other through VoIP. To this aim, in this work we consider networking issues and possible solutions, as they represent crucial aspects when dealing with collaborative AR environments. Through the use of a real testbed, we discuss how Wireless Mesh Networks (WMNs) can be practically employed to support communications in a department-wide AR environment without the need of a fixed infrastructure. We also analyze the performance limitations of this architecture and, finally, we evaluate a possible practical QoS solution to overcome them.
|
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| 18. |
- Hamidian, Ali, et al.
(författare)
-
Extending EDCA with Distributed Resource Reservation for QoS Guarantees
- 2008
-
Ingår i: Telecommunication Systems. - : Springer Science and Business Media LLC. - 1018-4864 .- 1572-9451. ; 39:3-4, s. 187-194
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we describe how the contention-based medium access mechanism of 802.11e, EDCA, can be enhanced in order to allow stations to reserve medium access for their real-time applications with QoS requirements. We present our proposed scheme, which is called EDCA with resource reservation (EDCA/RR), and describe how it can be extended in order to be used in wireless multi-hop networks. EDCA/RR operates in a completely distributed manner and manages to provide deterministic, contention-free medium access, making it an attractive scheme for wireless networks.
|
|
| 19. |
- Hamidian, Ali, et al.
(författare)
-
Performance of Internet Access Solutions in Mobile Ad Hoc Networks
- 2004
-
Ingår i: [Host publication title missing]. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0302-9743 .- 1611-3349. - 3540253297 ; 3427, s. 189-201
-
Konferensbidrag (refereegranskat)abstract
- Although an autonomous mobile ad hoc network (MANET) is useful in many scenarios, a MANET connected to the Internet is more desirable. This interconnection is achieved by using gateways, which act as bridges between a MANET and the Internet. Before a mobile node can communicate with an Internet host it needs to find a route to a gateway. Thus, a gateway discovery mechanism is required. In this paper the MANET routing protocol ad hoc on-demand distance vector (AODV) is extended to achieve the interconnection between a MANET and the Internet. Moreover, the paper investigates and compares three approaches for gateway discovery. The question of whether the configuration phase with the gateway should be initiated by the gateway, by the mobile node or by mixing these two approaches is being discussed. We have implemented and simulated these three methods and we discuss the advantages and disadvantages of the three alternatives
|
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| 20. |
- Hamidian, Ali, et al.
(författare)
-
Providing QoS in Ad Hoc Networks with Distributed Resource Reservation
- 2007
-
Ingår i: [Host publication title missing]. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349 .- 0302-9743. - 9783540729891 ; 4516, s. 309-320
-
Konferensbidrag (refereegranskat)abstract
- As the use of WLANs based on IEEE 802.11 increases, the need for QoS becomes more obvious. The new IEEE 802.1 le standard aims at providing QoS, but its contention-based medium access mechanism, EDCA, provides only service differentiation, i.e. soft QoS. In order to provide hard QoS, earlier we have proposed an extension called EDCA with resource reservation (EDCA/RR), which enhances EDCA by offering also hard QoS through resource reservation. In this paper, we extend EDCA/RR to cope with the hidden terminal problem, outline a solution for multi-hop scenarios, and compare the proposed scheme with EDCA.
|
|
| 21. |
- Hamidian, Ali, et al.
(författare)
-
Towards a solution providing QoS in ad hoc networks
- 2005
-
Ingår i: [Host publication title missing]. ; 6A-6C, s. 791-800
-
Konferensbidrag (refereegranskat)abstract
- One of the challenges that must be overcome to realize the practical benefits of ad hoc networks is quality of service (QoS). However, the IEEE 802.11 standard, which undeniably is the most widespread wireless technology of choice for WLANs and ad hoc networks, does not address this issue. In order to support applications with QoS requirements the upcoming IEEE 802.11e standard enhances the original IEEE 802.11 MAC layer by introducing a new coordination function which has both contention-based and contention-free medium access methods. However, the new coordination function cannot be used to provide QoS guarantees in ad hoc networks. We propose an extension to IEEE 802.11e which makes use of the advantages of the two medium access methods and integrates them in order to provide QoS guarantees in ad hoc networks. Our solution is fully distributed and gives stations with high-priority traffic an opportunity to reserve medium time.
|
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| 22. |
|
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| 23. |
|
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| 24. |
|
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| 25. |
|
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| 26. |
- Johansson, Niklas, et al.
(författare)
-
TCP/IP over the Bluetooth wireless ad-hoc network
- 2000
-
Ingår i: NETWORKING 2000. Broadband Communications, High Performance Networking, and Performance of Communication Networks / Lecture Notes in Computer Science. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349 .- 0302-9743. - 354067506X ; 1815, s. 799-810
-
Konferensbidrag (refereegranskat)abstract
- Bluetooth is a wireless ad-hoc network concept that was presented in February 1998 by its five original promoters Ericsson, Nokia, IBM, Toshiba and Intel. With Bluetooth, mobile terminals within range of each other can set up ad-hoc connections for both synchronous traffic, e.g. voice, and asynchronous traffic, e.g. IP-based data traffic. In this paper we analyse how well Bluetooth can carry TCP/IP traffic and in particular we show that though the radio channel is very disturbed the TCP Vegas protocol with its flow control mechanism can be carried very well. With ARQ handled at the Bluetooth level, retransmissions are made immediately after a packet error and thus the delays, normally introduced are kept acceptably short. In our model important mechanisms in TCP Vegas as well as Bluetooth mechanisms are modelled in detail and we show that TCP throughput is quite high and delays are kept short for packet error probabilities up to 50% and moderate loads.
|
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| 27. |
- Körner, Ulf, et al.
(författare)
-
A distributed MAC scheme to achieve QoS in ad hoc networks
- 2011
-
Ingår i: Annales des Télécommunications. - : Springer Science and Business Media LLC. - 1958-9395. ; 66:9-10, s. 491-500
-
Tidskriftsartikel (refereegranskat)abstract
- Real-time applications introduce new requirements on wireless networks and impose quality thresholds on parameters like delay, jitter, throughput, and packet loss in order to run smoothly. This paper addresses this issue by presenting a MAC scheme that offers real-time applications the opportunity to reserve transmission time based on their QoS requirements for contention-free medium access. Our scheme, which is called EDCA with Resource Reservation (EDCA/RR), operates in a fully distributed manner, is compatible with IEEE 802.11, and provides both prioritized and parameterized QoS. In this study, we have extended EDCA/RR to handle reservation collisions and, through extensive simulations, we show that our proposal can handle multiple reservations as well as uninformed stations that lie outside the transmission range of both the transmitter and the receiver while providing QoS guarantees. We compare EDCA/RR with EDCA and our results show that, as the traffic in the network increases, EDCA/RR succeeds providing the required service to QoS-demanding applications whereas EDCA fails in this task. In addition, when the medium is lossy we show that, not only does EDCA/RR give better service to real-time traffic, but also to contending non-real-time traffic.
|
|
| 28. |
- Körner, Ulf, et al.
(författare)
-
Bandwidth allocation in Bluetooth scatternets
- 2003
-
Ingår i: Proceedings of the 17th International Symposium on Computer and Information Sciences. - 9780849314902 ; , s. 367-371
-
Konferensbidrag (refereegranskat)abstract
- This paper deals with bandwidth allocation in a Bluetooth scatternet. The proposed assignment of transmission rights provides a controlled traffic transfer between Bluetooth piconets and represents a key component in an ad-hoc wireless Bluetooth network in order to provide with efficient data packet passing within and across piconets. This assignment is obtained by executing a distributed algorithm in each node. The algorithm works for unrestricted topologies of both stationary and mobile networks and also deals with assignment changes caused by network re-configurations without the use of a centralized factor. The effect of this re-assignment can be limited to the locality of that topology change. The construction of a link schedule of minimum length in a Bluetooth scatternet is NP-complete.
|
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| 29. |
|
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| 30. |
- Körner, Ulf
(författare)
-
Congestion Control in Packet Switching Computer Communication Networks
- 1982
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The objective of this research is in general to develop analytic tools for the performance study of computer networks, and is in particular motivated by a need to understand how restricted buffer sharing policies can be used for congestion control in the nodes of a packet switching computer communication network. Models of a single packet switching node with finite storage and restricted buffer sharing policies are developed. Effexts of acknowledgement signals as well as retransmission are considered. We introduce the concept of "penalty functions" and incorporate these in the packet switching node model in order to give priority to packets that have reached their destination node and thus should be lost. The single packet switching node models are used to form a model of a complete packet switching network. We present for the different models comprehensive results as thoughput, delays, blocking probabilities and buffe allocation schemes. We derive a number of analytic tools, inroduce some new concepts and clarify some techniques, used in our models, to compute the main performance characteristics.
|
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| 31. |
|
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| 32. |
- Körner, Ulf
(författare)
-
Future infocom systems
- 1999
-
Ingår i: European telecommunications liberalisation. - 0415187818
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
|
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| 33. |
- Körner, Ulf
(författare)
-
Köteori
- 2003
-
Bok (övrigt vetenskapligt/konstnärligt)
|
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| 34. |
|
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| 35. |
- Körner, Ulf, et al.
(författare)
-
Load control procedures for intelligent networks
- 1993
-
Ingår i: Proceedings of the IFIP TC6 Task Group/WG6.4 International Workshop on Performance of Communication Systems: Modelling and Performance Evaluation of ATM Technology. - 0444815120
-
Konferensbidrag (refereegranskat)
|
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| 36. |
|
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| 37. |
|
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| 38. |
|
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| 39. |
- Körner, Ulf
(författare)
-
Overload control of SPC systems
- 1991
-
Ingår i: Teletraffic and datatraffic in a period of change/ North-Holland Studies in Telecommunications. - 0444886664 ; 14, s. 105-114
-
Konferensbidrag (refereegranskat)
|
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| 40. |
- Körner, Ulf, et al.
(författare)
-
Protocols and control schemes in the NGN
- 2008
-
Ingår i: International Journal of Network Management. - : Wiley. - 1099-1190 .- 1055-7148.
-
Tidskriftsartikel (refereegranskat)
|
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| 41. |
|
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| 42. |
|
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| 43. |
|
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| 44. |
- Llona-Minguez, Sabin, et al.
(författare)
-
Identification of Triazolothiadiazoles as Potent Inhibitors of the dCTP Pyrophosphatase 1
- 2017
-
Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 60:5, s. 2148-2154
-
Tidskriftsartikel (refereegranskat)abstract
- The dCTP pyrophosphatase 1 (dCTPase) is involved in the regulation of the cellular dNTP pool and has been linked to cancer progression. Here we report on the discovery of a series of 3,6-disubstituted triazolothiadiazoles as potent dCTPase inhibitors. Compounds 16 and 18 display good correlation between enzymatic inhibition and target engagement, together with efficacy in a cellular synergy model, deeming them as a promising starting point for hit -to-lead development.
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| 45. |
|
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| 46. |
- Nilsson, Anders, et al.
(författare)
-
Micro mobility and internet access performance in Ad Hoc networks
- 2004
-
Ingår i: Proceedings - 5th World Wireless Congress. ; , s. 352-357
-
Konferensbidrag (refereegranskat)abstract
- In ad hoc mobile networks nodes typically communicate over wireless channels and are capable of movement. These are networks that support multihop communication and can be formed on a temporary basis. This paper evaluates a solution that allows mobile nodes to access the wired Internet and roam from base station to base station. The solution is based on the extension of Mobile IP capabilities to the ad hoc network while a micro mobility protocol is adapted to support local migration. We evaulate the performance of this solution with regard to reliable transport layer connections. It is shown that a high throughput is possible to achieve for high mobility speeds. It is also observed that as the number of hops between a mobile node and the base station increases, the throughput is decreased because of the characteristics of the wireless environment and the medium access layer protocol.
|
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| 47. |
- Nilsson Plymoth, Anders, et al.
(författare)
-
Cross layer routing and media access control with channel dependant forwarding in wireless ad-hoc networks
- 2007
-
Ingår i: Wireless Systems and Mobility in Next Generation Internet / Lecture Notes in Computer Science. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0302-9743 .- 1611-3349. - 9783540709688 ; 4396, s. 73-86
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Konferensbidrag (refereegranskat)abstract
- Wireless ad hoc networks have the last 10 years gained a lot of attention within the research community. A wireless ad hoc network is a special type of wireless network where nodes are typically mobile and doesn’t rely on any fixed infrastructure to operate correctly. Much work has been done on developing robust and stable routing algorithms that consider the dynamic nature of an ad hoc network: nodes are very mobile and enter and leave the network in random ways. Much work has also been done on developing medium access control (MAC) algorithms that consider many wireless characteristics such as interference and the hidden terminal problems. Little work has so far been done on developing joint routing and MAC layer solutions that consider the variations of the wireless channel. We present a solution where the routing protocol can cooperate with the MAC layer to provide power control and channel dependent forwarding. By establishing non-disjoint multiple paths between each source and destination, nodes may be able to avoid links that are currently in a deep signal fade by choosing a more beneficial next hop path.
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| 48. |
- Nilsson Plymoth, Anders, et al.
(författare)
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Micro mobility and internet access performance for TCP connections in Ad Hoc networks
- 2004
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Konferensbidrag (refereegranskat)abstract
- In ad hoc mobile networks nodes typically communicate over wireless channels and are capable of movement. These are networks that support multihop communication and can be formed on a temporary basis. This paper evaluates a solution that allows mobile nodes to access the wired Internet and roam from base station to base station. The solution is based on the extension of Mobile IP capabilities to the ad hoc network while a micro-mobility protocol is adapted to support local migration. We evaluate the performance of this solution with regard to reliable transport layer connections. It is shown that a high throughput is possible to achieve for high mobility speeds. It is also observed that, as the number of hops between a mobile node and the base station increases, the throughput is decreased because of the characteristics of the wireless environment and the medium access layer protocol.
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| 49. |
- Nilsson Plymoth, Anders, et al.
(författare)
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Urban mesh ad hoc networks
- 2008
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Ingår i: International Journal of Network Management. - : Wiley. - 1099-1190 .- 1055-7148. ; 18, s. 107-127
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Mesh networking is currently gaining much attention, within both academia and industry. Mesh networking allows cheap and fast deployment of wireless services. It is regarded as a very promising solution for urban deployment scenarios as well as for temporary emergency response situations. Another related promising field is that of ad hoc wireless networking, which consists of mobile nodes that dynamically create and maintain a network without the need for any infrastructure. We propose a solution and architecture for urban mesh ad hoc networks, a network that combines mesh networking with ad hoc networks for urban environments. We present four types of ad hoc mesh and ad hoc mesh networks. The most general one consists of mesh nodes, called mesh points (MP), that act as a type of access point for user nodes (UN). The MPs have at least two interfaces: one which is used to communicate with UNs, and one which is used to maintain the mesh access network and transport data. These two interfaces can basically use any type of technology (IEEE 802.11 a/b/g, WiMax, etc.), and for capacity reasons it is generally regarded that the best solution is to let the mesh interface operate on a separate high-capacity channel or channels. An intricate part of these types of networks are routing and location services. In our solution, UN devices operate in ad hoc mode running an ad hoc routing protocol. This allows UNs that wish to communicate to connect directly in an ad hoc manner, or through an MP. An important question is therefore whether two UNs that wish to communicate should connect through the mesh or connect directly. We show that from a capacity point of view whether a UN should route its packets to the closest available MP, or through a ad hoc network, depends on the environment the network is located, the amount traffic and the type of protocols used. Since MPs need to know where to route packets within the mesh, i.e., locating the MP closest to the destination UN, each UN run a small application that registers the UN to the mesh network. In addition to the above features we have developed a new MAC that quickly queries two candidate nodes, which picks the candidate with the currently best radio conditions. This enable nodes to cope with deep dips in signal strength due to fast fading, a well-known problem in urban environments. We show that this new protocol achieves significantly lower delays. We also show that in dense urban environments performance and battery lifetime can be improved if ad hoc technologies are used.
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| 50. |
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