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1.
Providing differentiated services in IP/MPLS over WDM networks has attracted a lot of recent attention. This article extends
the Path Inflation Control (PIC) policy recently proposed by us to provide differentiated services in IP/MPLS over WDM networks
with traffic grooming. Three different algorithms are considered for provisioning differentiated services. The simulation
results show that, with two of the three algorithms, the network cannot only provide differentiated services when the traffic
load is high but also gives significantly lower blocking for the lower priority class traffic and for the overall traffic
at low traffic loads.
相似文献
Sanjay K. BoseEmail: |
2.
P. P. Sahu 《Photonic Network Communications》2008,16(3):233-238
In this paper, two traffic grooming approaches based on alternate path routing are proposed to accommodate a greater number
of connections in optical networks. In the first approach (called as Source_SWG), the connections of same source and different
destinations along a path are groomed in a wavelength channel, whereas in the second approach (called as Des_SWG), the connections
of the same destination and different sources along a path are groomed in a wavelength channel. These approaches are compared
with existing heuristic traffic grooming algorithms based on fixed routing. It is found that both the approaches provide less
wavelengths than the existing heuristic traffic grooming algorithms for establishment of all the connections present in the
network. The comparative studies of these approaches are also made under restricted shared protection. It is seen that in
case of Source_SWG, the number of wavelengths required for establishment of all the connections present in the network is
less than that for Des_SWG.
相似文献
P. P. SahuEmail: |
3.
The article addresses a simulation-based optimization approach for allocation of ADMs in WDM optical networks with stochastic
dynamic traffic. Since ADMs are expensive, it is desirable that if each node in WDM optical networks can use a minimum number
of ADMs to achieve a near-ideal performance. In this article, first, the utilization statistics of ADMs are gathered by simulation.
Then, ADMs are allocated based on the utilization statistics. In this respect, a simple sorting mechanism is used. The distinguished
feature of the proposed approach is that it shows the way to allocate ADMs at the nodes of WDM optical networks with stochastic
dynamic traffic. The experimental results ensure that the proposed approach can solve the problem of allocating ADMs in practical
WDM optical networks considering stochastic dynamic traffic.
相似文献
Mrinal Kanti NaskarEmail: |
4.
Providing grooming capability to optical crossconnects (OXCs) in wavelength division multiplexing (WDM) networks can allow
an effective use of the network bandwidth, however, it increases the node cost that operators must sustain when compared to
a non-grooming network. Therefore, operators might consider using sparse grooming instead of full grooming networks. In this
article we consider sparse groomed optical networks. Our contribution is 2-fold. First, we address the grooming placement
problem that seeks for a set of grooming nodes in the network that leads to the highest overall throughput. This problem is
separated into two sub-problems: (i) selection of nodes having grooming capability; (ii) maximization of network throughput
assuming the grooming nodes found by the previous step. These two sub-problems are mathematically formulated for different
OXC placing strategies considering a static traffic scenario. In the second part, we design a practical heuristic grooming
algorithm suitable for dynamic traffic scenarios. The benefit of using sparse grooming nodes, when compared with a non-grooming
scenario, is evaluated in terms of throughput and optical port utilization. Our analysis differs of previous ones since it
considers grooming at a granularity coarser than the traffic granularity, which is an important aspect since network cost
improvement can be obtained at the expense of irrelevant performance impairments. Results show that the insertion of coarse
granularity OXCs can be a viable solution for network throughput increase since this can be done at the expense of relatively
few or no extra optical ports.
相似文献
M. C. R. MedeirosEmail: |
5.
Distributed lightpath provisioning in wavelength-division multiplexing (WDM) networks has gained wide research interests.
In this article, we study the performance of distributed lightpath provisioning in WDM networks with dynamic routing and wavelength
assignment (RWA). Specifically, we consider the case where routing of each lightpath is calculated based on globally flooded
link-state information, and wavelength assignment is decided through local information exchanges. Simulation results show
that such schemes steadily outperform those schemes with only global flooding or only local information exchanges. More significantly,
the impacts of various factors on the proposed scheme, including RWA algorithm, network topology, number of wavelengths per
fiber, global flooding interval, and traffic load, have been evaluated. Such evaluations help to achieve some insights useful
for the future developments of efficient lightpath provisioning schemes.
相似文献
Gaoxi XiaoEmail: |
6.
In this article, we consider the problem of traffic grooming in optical wavelength division multiplexed (WDM) mesh networks under static traffic conditions. The objective of this work is to minimize the network cost and in particular, the electronic port costs incurred for meeting a given performance objective. In earlier work, we have shown the benefits of limited grooming switch architectures, where only a subset of wavelengths in a network are equipped with expensive SONET Add Drop Multiplexers (SADM) that provide the grooming functionality. In this work, we also consider the wavelength conversion capability of such groomers. This can be achieved using a digital cross-connect (DCS) in the grooming switch to switch low-speed connections between the SADMs (and hence, between wavelengths). The grooming switch thus avoids the need for expensive optical wavelength converters. Based on these observations, we propose a limited conversion-based grooming architecture for optical WDM mesh networks. The local ports at every node in this architecture can be one of three types: an add-drop port, a grooming port that allows wavelength conversion or a grooming port that does not allow wavelength conversion. The problem studied is: given a static traffic model, where should the different ports be placed in a network? We formulate this as an optimization problem using an Integer Linear Programing (ILP) and present numerical results for the same. We also present a heuristic-based approach to solve the problem for larger networks. 相似文献
7.
In optical wavelength-division multiplexing (WDM) networks, traffic can be unevenly distributed across the network causing
inefficient utilization of resources. To solve this problem, an improved soft preemptive (SP) scheme is proposed by considering
dynamic resource distribution to deal with the uneven network utilization. A novel unevenly distributed traffic model in cross-time-zone
networks is also presented to evaluate the efficiency of the new scheme. Compared with other schemes such as normal shortest
path first (SPF) routing and wavelength conversion (WC), the new proposed scheme results demonstrate significantly better
performance with respect to the network utilization and overall network blocking probability.
相似文献
Nan HuaEmail: |
8.
In this article, a genetic evolutionary algorithm is proposed for efficient allocation of wavelength converters in WDM optical
networks. Since wavelength converters are expensive, it is desirable that each node in WDM optical networks uses a minimum
number of wavelength converters to achieve a near-ideal performance. The searching capability of genetic evolutionary algorithm
has been exploited for this purpose. The distinguished feature of the proposed approach lies in handling the conflicting circumstances
during allocation of wavelength converters considering various practical aspects (e.g., spatial problem, connectivity of a
node with other nodes) rather than arbitrarily to possibly improve the overall blocking performance of WDM optical networks.
The proposed algorithm is compared with a previous approach to establish its effectiveness and the results demonstrate the
ability of the proposed algorithm to efficiently solve the problem of Optimal Wavelength Converters Allocation (OWCA) in practical
WDM optical networks.
相似文献
Mrinal K. NaskarEmail: |
9.
Der-Rong Din 《Photonic Network Communications》2009,18(2):174-182
Wavelength-division multiplexing (WDM) technology has emerged as a promising technology for backbone networks. The set of
all-optical communication channels (lightpaths) in the optical layer defines the virtual topology for the upper layer applications. Since the traffic demand of upper layer
applications fluctuates from time to time, it is required to reconfigure the underlying virtual topology in the optical layer
accordingly. However, the reconfiguration for the virtual topology is reluctantly disruptive to the network since some lightpaths
should be torn down and some traffic has to be buffered or rerouted during the reconfiguration process. Therefore, it needs
to have an efficient transition method to shift the current virtual topology to the new one so as to minimize the effect of
the reconfiguration on the upper layer traffic. In this article, the WDM virtual topology transition sequence problem (WVTTSP)
which minimizes the average weighted delay (AWD) is studied. Since the WVTTSP is NP-hard, a heuristic solution model is proposed
to solve it. Simulation results show that the proposed least weighted distance first (LWDF) method can find the best result
and the time spent by it is less than 4 s for a middle-sized network with 100 links and with 30 wavelengths per link.
相似文献
Der-Rong DinEmail: Email: |
10.
Traffic grooming refers to techniques used to combine low-speed traffic streams onto high-speed wavelengths in order to minimize the networkwide cost in terms of line terminating equipment and/or electronic switching. Such techniques become increasingly important for emerging network technologies, including SONET/WDM rings and MPLS/MP/spl lambda/S backbones, for which traffic grooming is essential. In this article we formally define the traffic grooming problem, and we provide a general formulation that captures the features of a wide range of problem variants. We then present a comprehensive comparative survey of the literature that unveils the significant amount of research on this subject (the traffic grooming past). We also offer a broad set of ambitious research directions (the traffic grooming future) that are motivated by the exciting new challenges arising with the advent of MP/spl lambda/S technology. 相似文献
11.
Der-Rong Din 《Photonic Network Communications》2009,18(1):1-13
In a Wavelength Division Multiplexing (WDM) network, the performance of the virtual topology (VT) designed for a pre-specified traffic pattern can be improved
by performing virtual topology reconfiguration (VTR). Simultaneously, the provision of survivability of WDM networks is important, because the transmission of huge data
should be protected when a fiber fails. Thus, the combination of survivability and reconfiguration is an important issue in
WDM networks. In this paper, the Virtual Topology Reconfiguration Problem (VTRP) in survivable WDM networks with a reconfiguration constraint is studied. Given the physical topology, dedicated path-protection VT, and a new traffic demand matrix, the goal of VTRP
is to reconfigure the current VT under the pre-specified reconfiguration constraint so that the objective value can be minimized.
The object cost of VTRP is the average weighted propagation delay (AWPD). Because designing a polynomial time algorithm to find the optimal solution of VTRP is impractical, in this paper,
a simulated annealing (SA) algorithm and a genetic algorithm (GA) are proposed to solve this problem. Experimental results of these algorithms are also given.
相似文献
Der-Rong DinEmail: Email: |
12.
Megumi Isogai Nobuo Funabiki Toru Nakanishi Yosuke Isshiki 《Photonic Network Communications》2009,18(2):218-226
The wavelength-division multiplexing (WDM) technology has been extensively studied and actually deployed as a key technology
to solve global information explosions by multiplexing plural signal paths using different wavelengths into one optical fiber.
Among WDM-based network architectures, this article focuses on a double-ring one for a next-generation metropolitan area network
(MAN), where each node is normally equipped with two pairs of fast-tunable transmitters and wavelength-fixed receivers (TT-FR)
as interface to two fibers. To enhance the network performance, additional transmitters/receivers at nodes and receiver wavelengths
should be assigned optimally, so that the bandwidth bottleneck can be resolved both on nodes and fiber links. This article
formulates this node configuration problem with bandwidth bottleneck resolution as a combinatorial optimization problem, and
proves the NP-completeness of its decision version. Then, it presents the two-phase heuristic algorithm composed of a greedy
method and a variable depth search (VDS) method. Our algorithm is evaluated through extensive network simulations, where the
results support the effectiveness of this joint assignment approach.
相似文献
Nobuo FunabikiEmail: |
13.
In this paper, we present a traffic grooming problem of the SONET-WDM ring. The objective is to minimize the total cost of
optical add-drop multiplexers (OADMs) and inter-ring hub equipment, while satisfying intra-ring and inter-ring capacities.
We develop integer programming (IP) formulations for the problem and devise some reformulations for enhancing the mathematical
representation of the proposed IP model. By investigating the polyhedral structure of the problem, we develop some valid inequalities
that provide a tight lower bound for the problem. Dealing with the inherent computational complexity of the problem, we also
devise an effective tabu search procedure for finding a feasible solution of good quality within reasonable computation time.
Computational results are provided to demonstrate the relative strength of the proposed formulations, and to reveal the efficacy
of the lower and upper bound procedures for solving the problem.
相似文献
Youngjin KimEmail: |
14.
Jae-Hoon Kim 《Wireless Personal Communications》2008,45(1):121-129
This paper deals with one of the most important cell planning issues in a CDMA based multicast network. In a CDMA based wireless
network, a terminal can significantly reduce the bit error rate via the cohesion of data streams from multiple base stations
that share a common time line and are operated according to it. The cells whose base stations are operated as such are called
soft-combining cells. Therefore, a terminal in a soft-combining cell can take advantage of error rate reduction, if the cell
has at least one neighboring soft-combining cell. However, as soft-combining operation gives heavy burden to the network controller,
the number of soft-combining cells should be limited. Our problem is to find a limited number of soft-combining cells such
that each soft-combining cell has at least one neighboring soft-combining cell and that the sum of traffic demands of the
selected cells is maximized.
相似文献
Jae-Hoon KimEmail: |
15.
This article proposes a new approach for routing and wavelength assignment (RWA) for permanent and reliable wavelength paths
(WP) in wide all-optical WDM networks with wavelength continuity constraint. Given a number of available wavelengths on each
optical fiber, for each simple link failure of the network, we seek to maximize the number of satisfied requests for connections.
This is known as RWAP problem. In our algorithm, called RWA with Minimum Loaded Link for Permanent and Reliable wavelength
paths (MLL-PR), routing is based on the search for the optimal path while trying to minimize the maximum load on the links of the network
in order to minimize the maximum link capacity and then minimize the number of dropped lightpaths after any link failure.
The wavelength assignment is based on a graph coloring method using tabu-search. A series of experiments using two well-known
networks (ARPANET and NSFNET) have been carried out in order to evaluate the performance of our approach, in terms of the
number of blocked demands, for different failure scenarios. Generally, our results are better than those provided by the current
solving approaches taken as reference.
相似文献
Zouhair GuennounEmail: |
16.
A hierarchical network model can effectively reduce the complexity of routing and wavelength assignment (RWA) in wavelength
division multiplexing (WDM) networks compared to a flat model. However, the resource utilization may greatly suffer if the
hierarchical architecture is not properly arranged. By considering the degree of each WDM node and the location effect, this
paper proposes a systematic approach to construct the hierarchical topology in WDM networks so that resource utilization can
be maximized. Simulation results demonstrate that the performance of the proposed scheme is superior to that of another scheme.
相似文献
Yen-Wen Chen (Corresponding author)Email: |
17.
Haitham S. Hamza 《Photonic Network Communications》2009,17(3):277-291
In this paper, we propose a new Benes-type wavelength division multiplexing (WDM) optical network with space-wavelength switching
capability. Intuitively, adding wavelength switching capability to space Benes networks requires the use of additional hardware
components (i.e., wavelength converters). However, in this paper, we show that a Benes network with full-permutation capability
in both space and wavelength domains can be designed using a smaller number of hardware components but the same number of
stages as that in a space-only Benes network. In addition, wavelength conversion in the proposed network occurs only between
two pre-defined wavelengths, eliminating the need for any expensive wide-range wavelength converters. The proposed Benes network is based
on the newly proposed concept of wavelength-exchangeable permutation networks. Wavelength-exchangeable networks implement
single-step space and wavelength switching and hence reduces the number of hardware components. We show that, such wavelength-exchangeable
networks possess some interesting properties that can be used for designing routing algorithms to improve signal quality.
相似文献
Haitham S. HamzaEmail: |
18.
This paper proposes the use of the saturated cut (SC) method to improve the network performance through efficient dynamic
traffic grooming in IP/MPLS over WDM networks using an overlay model. With the SC information from the IP/MPLS layer, the
optical layer can calculate a lightpath between two node sets rather than the earlier suggested approach of calculating such
paths just between two nodes for better performance. We have used two criteria, bandwidth and path length, to find SCs and
have proposed two algorithms which incorporate this in the path inflation control (PIC) policy proposed earlier. Two typical
networks, NSF and COST239, were used for examining the network performance. The simulation results show that though both methods
can significantly improve the overall network performance the SC method is more efficient for a sparse network like the NSF
network rather than for a dense network like the COST239 network. Since calculating lightpaths for all node pairs for a SC
is time consuming, we propose a considerably simpler heuristic approach that can provide almost the same level of performance
improvement as the SC method but with much lower complexity.
相似文献
Hui WangEmail: |
19.
In optical wavelength-division multiplexing (WDM) networks, traffic can be very “bursty” at a fine time scale, even though
it may seem to be smooth at coarser scales (e.g., Poisson or Poisson-related traffic). This paper analyzes the instantaneous
characterization of Poisson traffic at a fine time scale. The analysis shows that the irregular oscillation of the instantaneous
traffic load and the occurrence of blockings in a light-loaded network are highly correlated. Specifically, most blockings
occur concentratively at the peaks of the instantaneous load. In some other time, network resources may not be sufficiently
utilized. To make better utilization of network resources, a novel wavelength-buffering (WB) scheme is proposed for the first
time in this paper. By reserving a portion of resources in a “wavelength buffer” under light loading and releasing them when
the load goes up, a number of blockings brought by the oscillation of the traffic load can be avoided. Simulation results
show that compared with other schemes such as adaptive routing, wavelength conversion (WC), and rerouting, the novel wavelength-buffering
scheme achieves significantly better performance with respect to the network utilization and overall blocking probability.
相似文献
Nan HuaEmail: |
20.
Jean-Marc Hyppolite Philippe Galinier Samuel Pierre 《Photonic Network Communications》2008,15(2):123-130
This paper proposes a tabu search heuristic for solving the routing and wavelength assignment problem in multigranular optical
networks, considering the wavelength-continuity constraint and a set of connections to satisfy. For a number of fibers per
link, a number of wavebands per fiber, and a number of wavelengths per waveband, this algorithm attempts to minimize the total
number of ports used in the network by efficiently grouping lightpaths into bands and fibers, and switching the whole bands
and fibers. The algorithm has been implemented and tested on the NSFNET network, and comparisons have been made with the Balanced
Path Routing and Heavy Traffic First (BPHT) algorithm in terms of number of ports. Generally, the results obtained with our
tabu search heuristic are better than those provided by this algorithm.
相似文献
Samuel PierreEmail: |