ISSN(Online): 2320-9801
ISSN (Print): 2320-9798
International Journal of Innovative Research in Computer and Communication Engineering
An ISO 3297: 2007 Certified Organization
Vol.3, Special Issue 3, April 2015
2nd National Conference On Emerging Trends In Electronics And Communication Engineering (NCETECE’15)
Organized by
Dept. of ECE, New Prince Shri Bhavani College Of Engineering & Technology, Chennai-600073, India during 6th & 7th April 2015
Minimum Wavelength for Optimal Waveband
in WDM Network Using Mesh Topology
B.Siva1, M.Kasthuri2
PG Student, S.Veerasamy Chettiar College of Engineering and Technology, Puliangudi, Tamil Nadu, India
Assistant Professor, Dept of ECE, S.Veerasamy Chettiar College of Engineering and Technology, Puliangudi, Tamil
Nadu, India
ABSTRACT: An optical cross-connect can be achieved by grouping together a set of consecutive wavelengths and
switching them as a single waveband. This technique is known as waveband switching. This paper focus on the number
of wavebands and their sizes for ring topologies. It presents a novel framework for optimizing the number of
wavebands in a ring network for deterministic traffic.The objective of the Band Minimization Problem is to minimize
the number of non uniform wavebands in the network while using the minimum possible number of wavelengths. I
have considered a specific type of traffic, namely all-to-all traffic, and present a construction method for achieving the
minimum number of wavebands in the ring. The results show that the number of ports can be reduced by a large
amount using waveband switching compared to wavelength switching, for both all-to-all traffic and random traffic.
And also numerically evaluate the performance of our waveband design algorithms under dynamic stochastic traffic.
I. INTRODUCTION
Wavelength Division Multiplexing (WDM) is the key technology in today’s optical networks. WDM multiplexes data
to be transmitted over the fiber onto multiple wavelengths. With the aim of exploiting the full capacity of the fiber, the
number of wavelengths that are multiplexed has in-creased substantially over the years (e.g., 40–80 wavelengths). A
common requirement in an optical network is to be able to switch each wavelength individually. This is known as
wave-length switching. Increasing the switching capacity to cope with the higher number of wavelengths is costly for
the following reason. Optical crossconnects (OXCs) and reconfigurable op-tical add/drop multiplexers (ROADMs) are
the switching nodes.
Fig. 1. (left) Wavelength cross-connect (WXC)/ROADM. (right) Wavelength switching element within the crossconnect for rings.
II. WAVEBANDING FOR DETERMINISTIC TRAFFIC
We consider ring topologies—both unidirectional (with a single fiber per link, oriented in one direction) and
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95
ISSN(Online): 2320-9801
ISSN (Print): 2320-9798
International Journal of Innovative Research in Computer and Communication Engineering
An ISO 3297: 2007 Certified Organization
Vol.3, Special Issue 3, April 2015
2nd National Conference On Emerging Trends In Electronics And Communication Engineering (NCETECE’15)
Organized by
Dept. of ECE, New Prince Shri Bhavani College Of Engineering & Technology, Chennai-600073, India during 6th & 7th April 2015
bidirectional (with two fibers per link, oriented in opposite directions). There is much work in optical networking that
focuses on ring topologies [18], [19]. Ring topologies are useful to study be-cause widely deployed synchronous optical
network (SONET) rings have evolved into WDM rings.
A.Inadequacy of Single-Node Solutions
We briefly explain the single -node solution of [13] for reader convenience. Suppose a node has one input fiber and,
say,
output fibers, and each fiber has
wavelengths. In order for the switch to support any breakdown of
wavelengths from the input fiber to the output fibers, the authors developed an optimal algorithm that finds the
nonuniform waveband sizes giving the minimum number of bands. The algorithm can be explained as follows:
Initializing
at the beginning, calculate the size of the band at each step as
, and update
as
. The algorithm stops when
. As an example, when
, the eight wavelengths are
grouped into four bands of size 4, 2, 1, and 1. The reader can easily verify that wavelengths can be switched to the
first output (and
switched to the other output), for any value of
by combining the bands
appropriately. For example, if five wavelengths are desired at the first output port, then the band of size 4 and one of
the bands of size 1 can be as-signed. Note that uniform banding would have required eight bands of size 1 (which is the
same as individual wavelength switching), and so nonuniform banding saves four switches in this case. A similar
banding algorithm is given for a single switch (equivalent to a star network with a single source node) in the case of port traffic in [8]. -port traffic model includes any possible traffic set that has at most connections to/from a node.
Fig 2.two possible configurations of the
band with bidirectional ring.
Fig. 3. (a) Inadequacy of two bands for all-to-all
Fig 4.illustration of banding in three
node unidirectional ring.
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Traffic, and (b) a valid solution with three bands in a
five-node bidirectional ring. B: Bypass. A/D: Add/Drop.
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ISSN(Online): 2320-9801
ISSN (Print): 2320-9798
International Journal of Innovative Research in Computer and Communication Engineering
An ISO 3297: 2007 Certified Organization
Vol.3, Special Issue 3, April 2015
2nd National Conference On Emerging Trends In Electronics And Communication Engineering (NCETECE’15)
Organized by
Dept. of ECE, New Prince Shri Bhavani College Of Engineering & Technology, Chennai-600073, India during 6th & 7th April 2015
The five nodes in the allow any LP to be provisioned on wavelength 1, while
will let one LP be provisioned,
but leaves wavelength 1 unuti-lized on the other links, and is therefore not sufficient to support the given traffic. Now,
when
,
, tively, and wavelength 3 would have the same problem. There-fore, it is not possible to
support all-to-all traffic using just the two bands. An example illustrating this impossibility is given in Fig. 3(a). It can
be seen that two bands are sufficient if there are four nodes, but the addition of a fifth node requires one of the nodes to
have three bands. A valid band assignment for all-to-all traffic is shown in Fig. 3(b).
It can be shown that two bands are not sufficient for the case of a unidirectional ring in a similar manner. Here, just a
three-node example suffices. Three wavelengths are required for a three node unidirectional ring as in Fig. 4.
III.HEURISTIC SOLUTIONS
We now present two heuristic solutions to the BMP called ROWSWAP and GREEDY. ROWSWAP is our own
heuristic, whereas GREEDY is a heuristic from the literature to solve the DOP.
A. Rowswap algorithm
This is implemented with a recursive function that takes the matrix as input. Given the row vectors of , it takes a
pivot vector and moves it to another row only if this reordering reduces
, which is the current
minimum value obtained by the algorithm until that point. The output matrix of this reordering is denoted by . If a
reordering occurs.
B. Greedy
Greedy can be modified easily to be used with don’t cares. The Hamming distance calculation is done considering the
don’t cares such that if any of the elements is a don’t care , then the dis-tance between them is considered to be 0. At
each iteration, the value of the don’t care of the chosen row is assigned to the corre-sponding element of the just added
row at the same column. For example, if
with ’s denoting don’t cares is added next to (1, 1, 0, 0), then it
would be added as (1, 1, 1, 1).
IV.APPLICATION TO ALL-TO-ALL TRAFFIC
We now apply this problem formulation and the heuristic algorithms to a speci fic type of deterministic traffic, namely
all-to-all traffic. This is a special case of deterministic traffic, and it is possible to provide an optimal wavebanding
algorithm for this traffic. Recall that in all-to-all traffic, there is exactly one LP between every ordered pair of nodes.
Fig 5.illustration of the optimal RWA algorithm of bidirectional ring:(a) initial three node;(b)first step with adding two
more node.
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ISSN(Online): 2320-9801
ISSN (Print): 2320-9798
International Journal of Innovative Research in Computer and Communication Engineering
An ISO 3297: 2007 Certified Organization
Vol.3, Special Issue 3, April 2015
2nd National Conference On Emerging Trends In Electronics And Communication Engineering (NCETECE’15)
Organized by
Dept. of ECE, New Prince Shri Bhavani College Of Engineering & Technology, Chennai-600073, India during 6th & 7th April 2015
For the bidirectional ring, we adopt the optimal RWA al-gorithm presented in [20], which uses the minimum number of
wavelengths. For simplicity, we assume that the number of nodes in the ring is odd in order to remove the ambiguity in
routing (so that there is exactly one shortest path between any two nodes) and is denoted by .4 However, similar
results can be obtained for even . The optimal algorithm in [20] uses
wavelengths for odd . For reader
convenience, we describe this algorithm in Section VI-A because our bound depends on the algorithm. Every
wavelength is fully utilized as a result of this algorithm (i.e., all of the wavelengths are used on all links).
V .APPLICATION TO RANDOM TRAFFIC
We apply the fi rst-fit wavelength assignment with alternate routing as the RWA algo-rithm, in which we try to
assign each LP to the first available wavelength (e.g., lowes numbered) first on the shortest path di-rection, and if no
such wavelength exists, in the opposite di-rection. If no wavelength is found on either direction, a new wavelength is
created and assigned to the LP on the shortest path. Moreover, contrary to the optimal RWA algorithm used for all-to all traffic, the wavebands used for switching on both links (e.g., east/west) at a node are not symmetrical Therefore, we
create a new matrix of size
that has a column for each link of a node. Note that the RWA strategy used here
results in the occurrence of don’t cares as elements of due to underutilization of some of the wavelengths. We show
this strategy on a four -node ring network with one LP between node pairs (1, 2), (2, 3), (1, 4); two LPs between (3, 4)
and (2, 4) in Fig. 10. We then apply the heuristics to and calculate the average percentage reduction in the number of
switching elements over 100 trials.
Table 1. bidirectional ring for random traffic.(k-3)
Because of the uncertainty due to don’t cares, heuristics do not improve the waveband results in some cases. For such
cases, we just use the number of bands in the original . For GREEDY, making a decision one step at a time based on
the Hamming distances to the next pair of rows instead of a holistic approach makes it less efficient with the added
degree of complexity with don’t cares. In Table II, the column Overall shows the overall reduction compared to
wavelength switching with
switching elements. Further reduction achieved with the heuris-tics compared to
are shown in the Further column.
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ISSN(Online): 2320-9801
ISSN (Print): 2320-9798
International Journal of Innovative Research in Computer and Communication Engineering
An ISO 3297: 2007 Certified Organization
Vol.3, Special Issue 3, April 2015
2nd National Conference On Emerging Trends In Electronics And Communication Engineering (NCETECE’15)
Organized by
Dept. of ECE, New Prince Shri Bhavani College Of Engineering & Technology, Chennai-600073, India during 6th & 7th April 2015
Table 2. bidirectional ring with random traffic(N-12)
We conclude that both algorithms are successful, however GREEDY is preferable for larger networks. We show
similar results for different values of with
in Table III. We observe that further reduction with greedy increases with , and it is higher than ROWSWAP for
. On the other hand, ROWSWAP’s further reduction reaches
a maximum of 26.4% at
and starts decreasing after that. GREEDY is more successful with denser traffic (larger
).
VI. RESULT
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International Journal of Innovative Research in Computer and Communication Engineering
An ISO 3297: 2007 Certified Organization
Vol.3, Special Issue 3, April 2015
2nd National Conference On Emerging Trends In Electronics And Communication Engineering (NCETECE’15)
Organized by
Dept. of ECE, New Prince Shri Bhavani College Of Engineering & Technology, Chennai-600073, India during 6th & 7th April 2015
VII. CONCLUSION
Hence, hereby we have found an efficient solution to perform efficient transmission of data in heavy traffic zone
network. Here, the data is transmitted without any loss of packets to the destination crossing through removing all
unwanted wavelengths without any compromise with the appropriate output to be obtained.
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