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1.
Optical burst switching (OBS) presents itself as a promising technology for bridging the gap between optical wavelength switching
and optical packet switching. Increasingly, researchers attempt to incorporate more realistic constraints into the design
of OBS networks. Optical signal transmission quality is subject to various types of physical impairment introduced by optical
fibers, switching equipment, or other network components. The signal degradation due to physical impairments may be significant
enough such that the bit-error rate of received signals is unacceptably high at the destination, rendering the signal not
usable. In this paper, based on earlier work, we study the burst scheduling problem in OBS networks, taking into account physical
impairment effects. We propose three effective burst scheduling algorithms: (1) a JET based Physical Impairment Constrained
Algorithm (JETPIC), (2) an Integrated Physical Impairment Constrained Algorithm (IPIC), and (3) an Enhanced Integrated Physical
Impairment Constrained Algorithm (EIPIC). At an OBS node, the proposed algorithms schedule bursts for transmission by searching
for available resources as well as verifying signal quality. Our simulation results show that the proposed algorithms are
effective in terms of reducing the burst blocking probability. In general, algorithm JETPIC outperforms algorithms IPIC and
EIPIC in burst blocking probability and average end-to-end delay performance.
相似文献
Bin WangEmail: |
2.
Takuji Tachibana 《Photonic Network Communications》2009,17(3):245-254
Recently, optical switching and packet processing technologies have been developed and high-performance optical burst switching
(OBS) networks are constructed by using these technologies. In high-performance OBS networks, several types of applications
such as Grid computing and HDTV can be provided for users according to immediate reservation protocol. Because some applications
require that data is transmitted reliably over high-performance OBS networks, it is indispensable to provide reliable data
transfer service for high-priority users. Therefore, in this paper, we propose a reliable burst transmission method which
can be available for the immediate reservation protocol. In the proposed method, both burst-cluster transmission and probabilistic
pre-emption are used at edge and core nodes. By using these methods together, the reliable data transfer and the service differentiation
can be provided. We evaluate by simulation the performance of the proposed method in the 14-node NSFNET. Numerical examples
show that the proposed method can transmit higher-priority bursts more reliably than the conventional method while not increasing
the overall burst loss probability so much. In addition, we investigate effective parameter settings from some simulation
results.
相似文献
Takuji TachibanaEmail: |
3.
Optical burst switching (OBS) is regarded as one of the most promising switching technologies for next generation optical
networks. Contention resolution of data bursts is a critical mission to implement practical OBS. The use of fiber delay line
(FDL) buffers has received a lot of attention as a fundamental but effective solution to resolve burst contention. Several
studies have investigated the way to achieve the optimal performance of FDL buffers at a single-node level. However, this
article studies how to achieve the best performance of OBS networks with FDL buffers under varying traffic condition at a
network level. For this purpose, we propose an adaptive load-aware burst assembly (ALBA) scheme, which adaptively adjusts
the size threshold of burst assembler optimized to the current network traffic load. A piggybacking method used to deliver
the traffic-load information from core nodes to ingress edge nodes accelerates the adaptiveness of the proposed scheme by
reducing the update time of the size threshold. The effectiveness of the ALBA scheme is proved by comparing with No-FDL case
and fixed size-threshold cases under changing traffic-load environment from extensive simulation tests.
相似文献
JungYul ChoiEmail: |
4.
A service differentiation scheme in optical burst switching (OBS) networks, which is based on dynamic fiber delay line (FDL)
assignment, is shown. The effectiveness of the scheme is validated by numerical analysis and extensive simulations. Especially,
the feasibility conditions for the service differentiation scheme, which are considered as the minimum number of FDLs for
each sub-FDL group, are displayed. The feasibility conditions are derived numerically, and are verified through extensive
simulations. The results of extensive simulations show that the proposed scheme and the feasibility conditions are valid for
service differentiation in OBS networks.
相似文献
Minho KangEmail: |
5.
Optical burst switching (OBS) networks have been receiving much attention as a promising approach to build the next generation
optical Internet. In the bufferless DWDM switching technology, burst loss that should be minimized is the key design parameter.
One of the critical design issues in OBS network is how to plan the optimal routing path in order to minimize burst dropping
due to network resource contention. This study proposes the burst frequent-pattern tree (BFP-Tree) approach to pre-determine
a suitable routing path in the OBS network. The BFP-Tree approach essentially is a learning-based mechanism that is able to
determine a suitable transmission path from the historical network transaction data. The experiment results show that the
successful rates of routing paths obtained by the BFP-Tree approach are able to converge to those of the optimal results.
相似文献
Zen-Der ShyuEmail: |
6.
Igor M. Moraes Rafael P. Laufer Daniel de O. Cunha Otto Carlos M. B. Duarte 《Photonic Network Communications》2009,18(1):65-76
This article proposes the load-level-based admission control (LLAC) mechanism in order to provide service differentiation
for optical burst-switched networks. The LLAC mechanism admits bursts of a given service class according to the network load
and a class-associated parameter. Based on this parameter, called load level, the proposed mechanism differentiates the burst blocking probability experienced by each service class. We develop an analytical
model for the proposed mechanism and evaluate its performance for different configurations through mathematical analysis.
The results show that the load-level-based mechanism reduces the blocking probability of high-priority bursts by two orders
of magnitude or more depending on the analyzed scenario. In addition, compared to other similar mechanisms, the load-level-based
mechanism effectively differentiates the services in all analyzed configurations, requires less states in optical burst switching
(OBS) nodes, and does not suffer from priority inversion.
相似文献
Otto Carlos M. B. DuarteEmail: |
7.
In the past years, several signaling protocols were proposed for OBS networks and the most popular one is the Just-Enough-Time
(JET) protocol. JET not only efficiently utilizes the network capacity, but also effectively reduces the end-to-end transmission
delay. However, the most critical defect of JET is its intrinsic deficiency: Fairness. The fairness problem is a traditional
problem common to various kinds of networks. It results in a phenomenon that bursts with a shorter number of hops are generally
favorized and hence deteriorates the network utilization as well. In this article, we investigate this problem and propose
a fair channel scheduling algorithm as a solution. Usually there is a tradeoff between fairness and blocking performance.
Accordingly, the objective of our scheme is to achieve a balance between the two conflicting metrics as much as possible.
In our scheme, each burst is associated with a dynamic priority which is defined by several characteristics of the burst.
When contention occurs, the proposed scheme picks the preferable burst and drops the other one according to their priorities.
From simulation results, we observed that the proposed scheme could improve fairness without causing significant reduction
in dropping performance. Furthermore, it increases the effective link utilization as well.
相似文献
Ching-Fang HsuEmail: |
8.
Burst assembly mechanism is one of the fundamental factors that determine the performance of an optical burst switching (OBS)
network. In this paper, we investigate the influence of the number of burstifiers on TCP performance for an OBS network. The
goodput of TCP flows between an ingress node and an egress node traveling through an optical network is studied as the number
of assembly buffers per destination varies. First, the burst-length independent losses resulting from the contention in the
core OBS network using a non-void-filling burst scheduling algorithm, e.g., Horizon, are studied. Then, burst-length dependent
losses arising as a result of void-filling scheduling algorithms, e.g., LAUC-VF, are studied for two different TCP flow models:
FTP-type long-lived flows and variable size short-lived flows. Simulation results show that for both types of scheduling algorithms,
both types of TCP flow models, and different TCP versions (Reno, Newreno and Sack), TCP goodput increases as the number of
burst assemblers per egress node is increased for an OBS network employing timer-based assembly algorithm. The improvement
from one burstifier to moderate number of burst assemblers is significant (15–50% depending on the burst loss probability,
per-hop processing delay, and the TCP version), but the goodput difference between moderate number of buffers and per-flow
aggregation is relatively small, implying that an OBS edge switch should use moderate number of assembly buffers per destination
for enhanced TCP performance without substantially increasing the hardware complexity.
相似文献
Ezhan Karasan (Corresponding author)Email: |
9.
By taking advantage of statistical multiplexing gain in the burst level, optical burst switching (OBS) technology enables
optical Internet to handle huge volume of data in an efficient manner without requiring optical buffers in the optical domain.
However, when congestion builds up in the optical network core, large amount of data might be lost. In this article, we propose
an efficient optical burst control algorithm that operates based on the awareness of future burst traffic condition to eliminate
the effect of congestion reaction delay. The proposed algorithm takes advantage of multiple statistics to improve the estimation
accuracy.Through performance evaluation, it is verified that the proposed algorithm proactively controls inbound burst traffic
so that the OBS network can stay in a stable traffic condition while keeping the network throughput high.
相似文献
Myungsik YooEmail: |
10.
The negative impact of cascaded wavelength conversions has been largely ignored in optical burst switching performance evaluations.
When optical bursts are transmitted all optically from source to destination, each wavelength conversion performed along the
lightpath may cause some signal-to-noise deterioration. If the distortion of the signal quality becomes significant enough,
the receiver would not be able to recover the original data. In this paper we examine the performance degradation when an
upper bound on the number of wavelength conversions that a signal can go through is enforced. We refer to this constraint
as conversion cascading constraint. We propose a novel proactive routing scheme under this constraint that considers the instantaneous link congestion at the
moment when the bursts arrive. It has three major advantages: (1) utilize the same offset times for the same node pairs while
providing dynamic routing without using any fiber delay lines (FDL); (2) decrease burst loss probability to a great extent;
(3) mitigate unfairness among the bursts with different hop counts, which is even worse under the conversion cascading constraint
if without any special treatment. We also extend the proposed mechanism to embrace a variant of regulated deflection routing
which can further improve network performance.
相似文献
Guifang LiEmail: |
11.
A new fault-management method using congestion-avoidance routing for optical burst-switched networks 总被引:1,自引:0,他引:1
Yurong? Huang Jonathan?P.?Heritage Biswanath?Mukherjee 《Photonic Network Communications》2008,16(2):117-125
Optical burst switching (OBS) has been proposed as a promising technique to support high-bandwidth, bursty data traffic in
the next-generation optical Internet. This study investigates a new fault-management framework for an OBS network. In an OBS
network, burst-loss performance is a critical concern. In OBS, the data-burst transmission is delayed by an offset time (relative
to its burst control packet (BCP), or header), and the burst follows its header without waiting for an acknowledgment for
resource reservation. Thus, a burst may be lost at an intermediate node due to contention, which is generally resolved according
to the local routing and bandwidth information. The routing table maintained in each OBS node is generally pre-computed and
fixed to forward the data bursts. Such a static forwarding feature might have limited efficiency to resolve contentions. Moreover,
a burst may be lost and the network may be congested when a network element (e.g., fiber link) fails. Therefore, for reliable
burst transport, we develop dynamic routing approaches for preplanned congestion avoidance. Our goal is to proactively avoid
congestion during the route-computation process, and our approach employs wavelength-channel utilization, traffic distribution,
and link-distance information in the proposed objective functions for routing. Two update mechanisms for maintaining a dynamic
routing table are presented to accommodate bursty data traffic. Based on our routing mechanisms, we also propose a new congestion-avoidance-and-protection
(CAP) approach, which employs a primary route and a group of backup routes for each node pair against failures and congestion.
The performance of the proposed protection strategy using congestion-avoidance routing is demonstrated to be promising through
illustrative numerical examples.
相似文献
Biswanath MukherjeeEmail: |
12.
Advances in enabling technologies and the explosive growth of Internet traffic has led to the widespread proliferation of
network systems in recent years. With their relatively low cost, high throughputs, high-bandwidth utilization, and low-transmission
latency, Optical Burst Switching (OBS) networks represent an ideal solution for next-generation Internet applications. However,
in OBS networks, Burst Header Packet (BHP) contentions occur when two or more BHPs are switched simultaneously to the same
output port of a given core node. These contention events result in significant losses of the corresponding data burst. Accordingly,
this study presents a Store-and-forward COntention-REsolution mechanism, designated as SCORE, which utilizes fiber delay line
buffers to resolve the BHP collision problem, thereby minimizing the burst loss rate. The results of a series of simulations
performed using an OIRC OBS-ns simulator confirm the effectiveness and efficiency of the proposed scheme.
相似文献
Tse-Sheng LinEmail: |
13.
Jae-Gwan Kim Chang-Joon Chae Hai L. Vu Min-Ho Kang 《Photonic Network Communications》2009,18(2):129-136
In this paper, we propose and evaluate a new deflection transmission scheme for communication between local customers in a
passive optical network (PON). In particular, we provide an analytical model to approximate the average packet delay of the
proposed scheme in a local area network (LAN) operating within the PON (referred to as LAN-PON system). The accuracy of our
model is validated by simulation. Furthermore, our simulation results show that a LAN-PON with a deflection scheme can achieve
> 80% bandwidth gain using < 125 μs switching time compared to that of the traditional PON system for the cases studied.
相似文献
Min-Ho KangEmail: |
14.
An analytical model is derived to evaluate the performance of an optical switch using a feed-forward fiber delay line (FDL)
per output for contention resolution. Two different forwarding algorithms for the switch are presented and evaluated: a simple
forwarding algorithm (SFA) that is easier to implement, and an enhanced algorithm that provides better performance in terms
of both packet loss probability and packet delay. The analytical model can be utilized with both packet and burst switching
schemes to characterize the performance of the proposed architecture. Results show that the proposed architecture reduces
the packet loss probability compared to that without FDLs. Finally, the same architecture is shown to be capable of supporting
Quality of Service (QOS).
相似文献
Anura Jayasumana (Corresponding author)Email: |
15.
Li-Mei Peng Kyoung-Min Yoo Kyeong-Eun Han Young-Chon Kim 《Photonic Network Communications》2008,15(3):213-225
Optical burst switching (OBS) has been proposed as a new optical switching paradigm for the next generation Internet due to
its flexibility and feasibility compared to OCS and OPS. Moreover, serving as a backbone that interconnects a number of access
networks, OBS ring topologies have been a good choice for solving the current metro gap problem between core network and access
network owning to its simplicity and scalability. In this paper, we provide an insight into the OBS ring network that consists
of nodes using TT–TR (Tunable Transmitter–Tunable Receiver). The node architectures with TT–TR may make efficient use of network
resources even though traffic pattern, such as IP traffic with self-similarity dynamically change, and can support good expandability.
However, all nodes share the limited network resources. This may result in contention such as wavelength contention and transceiver
contention leading to burst loss. In order to use the shared network resources fairly and efficiently as well as reducing
the resource contention, we focus on the design of medium access control (MAC) protocols based on multiple tokens. Each token
is allocated to one wavelength to denote the accessibility of that wavelength, i.e., once the token is captured, the corresponding
wavelength can be used to transmit a burst. As tokens hold the key for using wavelengths to transmit bursts, token management
including the token release time is crucial in the proposed MAC protocols. Thus, two kinds of multiple-token based MAC protocols
with different token release times are proposed: token release after transmitting burst (TRTB) and token release after transmitting
control header (TRTC). Each of them is classified into two schemes called TRTB/TRR and TRTB/RCA and correspondingly TRTC/TRR
and TRTC/ RCA. RCA stands for receive collision avoidance. The target is to increase the performance while reducing the processing
overhead at each node. The performance of the TRTB and TRTC protocols are evaluated and compared in terms of queuing delay,
burst loss rate, and channel utilization by OPNET simulation. The effects of various design parameters are also investigated
through simulation in order to evaluate their scalability. In all the proposed schemes, tokens are just used to denote the
accessibility of each wavelength. Finally, as an alternative, we also propose a new scheme based on the TRTC protocol called
TRTC/CAT (collision avoidance by tokens) to avoid contention by using tokens.
相似文献
Young-Chon KimEmail: |
16.
In this paper, we consider a multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system
operating over frequency-selective fading channels. We propose a novel scheme for joint carrier-frequency offset (CFO) and
channel estimation based on the expectation–maximization (EM) algorithm. Furthermore, the Cramer-Rao bounds (CRBs) for both
CFO and channel estimators are exploited to evaluate the performance of the proposed scheme. Computer simulations show that
the proposed algorithm achieves almost ideal performance compared with the CRBs for both channel and frequency offset estimations.
相似文献
M. AhmadianEmail: |
17.
Performance comparisons of restoration techniques in optical burst switching networks 总被引:1,自引:0,他引:1
This paper describes restoration techniques for OBS networks. First, we introduce the design issues to be essentially considered,
when restoration techniques will be built into OBS networks. Second, considering the design issues, we propose a novel restoration
model named “Recover-Then-Reserve,” which can enhance the restoration performance. Third, we develop a simulator using the
NS-2 platform to verify the performance of the restoration techniques (path, link, and sub-path) designed by each restoration
model (GMPLS-based OBS restoration and our proposal). Performance is evaluated on the following metrics: restoration success
rate, restoration time, connection availability, and burst loss probability. The effects of the failure frequency and the
number of the restoration attempts on the restoration performance are also investigated. Our experiments show that the proposal
can reduce the restoration time by about 25 ms compared to the GMPLS-based OBS restoration model. Also, path restoration technique
has better performance than link and sub-path restoration techniques because it has the highest restoration success rate,
allowing similar restoration time. Our experiments also show that the more the restoration attempts made and the less the
failure frequency becomes, the better the restoration performance obtained.
相似文献
Hong Shik Park (Corresponding author)Email: |
18.
A peak-to-average power ratio (PAPR) reduction scheme with low complexity is proposed for the multicarrier spread spectrum
(MC-SS) system in personal area network (PAN). Traditional clipping and filtering scheme requires a high oversampling rate
to meet the emission mask requirements. This would cause high power consumption for mobile PAN devices in personal network.
To solve the problem, upsampling is introduced between clipping and filtering in this paper to reduce the oversampling rate.
A simplified implementation structure is also derived for the proposed scheme. Simulation results show that its complexity
is about 65% of the conventional scheme while achieving satisfying performance.
相似文献
Lu RongEmail: |
19.
In this paper, we consider a joint packet scheduling algorithm for wireless networks and investigate its characteristics.
The joint scheduling algorithm is a combination of the Knopp and Humblet (KH) scheduling, which fully exploits multiuser diversity,
and the probabilistic weighted round-robin (WRR) scheduling, which does not use multiuser diversity at all. Under the assumption
that the wireless channel process for each user is described by the Nakagami-m model, we develop a formula to estimate the tail distribution of the packet delay for an arbitrary user under the joint scheduling.
Numerical results exhibit that under the joint scheduling, the ratio of the number of slots assigned for the WRR scheduling
to that for the KH scheduling dominates the characteristics of the delay performance.
相似文献
Gang Uk HwangEmail: |
20.
In TCP over OBS networks, consecutive multiple packet losses are common since an optical burst usually contains a number of
consecutive packets from the same TCP sender. In this paper, we first present a new theoretical method to analyze the behavior
of Reno when consecutive multiple packet losses occur. Results of the analysis indicate that even a small number of consecutive
multiple packet losses can force Reno to timeout. Then we propose B-Reno, a newly designed TCP implementation that can overcome
Reno’s inefficiency in dealing with consecutive multiple packet losses over OBS networks and can avoid the shortcomings of
New-Reno and SACK. Results of comprehensive simulations indicate that B-Reno over OBS networks can achieve a performance better
than Reno and New-Reno, and that it can also achieve a performance similar to that of SACK. Moreover, B-Reno only needs some
simple modifications to New-Reno at the sender’s protocol stack, and thus has less difficulty in deployment and less protocol
complexity than that of SACK.
相似文献
Sheng WangEmail: |