Browsing by Subject "Telecommunication links"

Now showing 1 - 6 of 6

Open Access
Available bit rate traffic engineering in MPLS networks with flow-based multipath routing
(Institute of Electronics Information and Communication Engineers, 2004) Akar, N.; Hökelek, İ.; Karasan, E.
In this paper, we propose a novel traffic engineering architecture for IP networks with MPLS backbones. In this architecture, two link-disjoint label switched paths, namely the primary and secondary paths, are established among every pair of IP routers located at the edges of an MPLS backbone network. As the main building block of this architecture, we propose that primary paths are given higher priority against the secondary paths in the MPLS data plane to cope with the so-called knock-on effect. Inspired by the ABR flow control mechanism in ATM networks, we propose to split traffic between a source-destination pair between the primary and secondary paths using explicit rate feedback from the network. Taking into consideration the performance deteriorating impact of packet reordering in packet-based load balancing schemes, we propose a traffic splitting mechanism that operates on a per-flow basis (i.e., flow-based multipath routing). We show via an extensive simulation study that using flow-based multipath traffic engineering with explicit rate feedback not only provides consistently better throughput than that of a single path but is also void of out-of-order packet delivery.
Open Access
The effect of terrain roughness in the microwave line-of-sight multipath fading estimation based on Rec. ITU-R P.530-15
(IEEE, 2014-08) Göktas, Polat; Altıntaş, Ayhan; Topçu, Satılmış; Karasan, Ezhan
Multipath fading is an important constraint on the prediction of path loss for terrestrial line-of-sight microwave links. The International Telecommunication Union - Radiocommunication (ITU-R) Rec. P.530 [1] is one of the most widely used methods providing guidelines for the design of terrestrial line-of-sight links. The purpose of the study presented in this paper is to make an investigation of the effect of both terrain roughness and geoclimatic factor parameters in the path loss characteristics of microwave line-of-sight (LOS) propagation in NATO Band 3+ (1350-2690 MHz) and NATO Band 4 (4440-5000 MHz) frequency ranges. The two parameters led to significantly different results for the link availability due to multipath fading as a function of the fade margin. © 2014 IEEE.
Open Access
FPGA implementation of a fault-tolerant application-specific NoC design
(IEEE, 2016-04) Yeşil, Şerif; Tosun, S.; Öztürk, Özcan
Today's integrated circuits are more susceptible to permanent link failures than before as a result of diminishing technology sizes. Even a single link failure can make an entire chip useless. Single link failure problem is fatal to application-specific Network-on-Chip (NoC) designs as well if they cannot tolerate such failures. One solution to this problem can be having alternative routing options on the network for each communicating pair. In this study, we present an FPGA implementation of such a method for application-specific NoCs. This method adds additional network resources to the non-fault-tolerant design in an attempt to make it fault-tolerant. We show the effects of the presented fault-tolerant method on an FPGA implementation of Mp3 encoder based on energy consumption and area increase against non-fault-tolerant case. © 2016 IEEE.
Open Access
Switching resilient PI controllers for active queue management of TCP flows
(IEEE, 2007) Üstebay, Deniz; Özbay, Hitay
Active Queue Management (AQM) is used in computer networks to increase link utilization with less queueing delays. The fluid flow model or TCP based on delay differential equations supplies the mathematical background for modelling the AQM as a feedback system. Recently various PI and PID controllers arr designed for this feedback system, [7], [18]. In this paper, we consider the case for which the Round Trip Time (RTT) is time varying and we propose switching resilient PI controllers using the design method introduced in [18].
Open Access
Transmit beamforming with cooperative base stations
(IEEE, 2005-09) Ng, B. L.; Evans, J. S.; Hanly, S. V.; Aktaş, Defne
We consider a cellular network where base stations can cooperate to determine the signals to be transmitted on the downlink. In such a scenario, it would be possible to use "macroscopic" transmit beamforming to improve system performance. The downlink beamformer of interest is generalised from some transmit beamformers that have been shown to meet various optimality criteria in the literature. The particular down-link beamformer structure enables us to recast our downlink beamforming problem as a virtual LMMSE estimation problem. Based on this virtual set up, we exploit the structure of the channel and develop distributed beamforming algorithms using local message passing between neighbouring base stations. Two algorithms are outlined, both of which are based on the Kalman smoothing framework. The first algorithm is a forward-backward algorithm that produces optimal performance, but it has the disadvantage of a delay that grows linearly with array size. The second algorithm, which is a limited extent algorithm, solves the delay problem by using only local information.
Open Access
A zone-based shared-tree multicast protocol for mobile ad hoc networks
(IEEE, 2003) Rangnekar, A.; Zhang, Y.; Selçuk, Ali A.; Bicak, A.; Devarapalli V.; Sidhu, D.
This paper proposes a new multicast protocol for mobile ad hoc networks (MANETs). The proposed protocol, Shared-Tree MZR, is a shared tree variant of the Multicast Routing Protocol based on Zone Routing (MZR). The concept of zone-based multicast routing for mobile ad hoc networks was originally proposed in MZR. The new protocol utilizes the advantages of the shared-tree together with the advantages of the zone-based routing. The performance of the protocol is analyzed for various network conditions. The test results show that the new protocol performs well and has significantly low overhead in scenarios with multiple sources.