# Optic fiber Electronic switch the fiber serves as a transmission medium Optical networks - 1 st...

date post

18-Dec-2015Category

## Documents

view

212download

0

Embed Size (px)

### Transcript of Optic fiber Electronic switch the fiber serves as a transmission medium Optical networks - 1 st...

- Slide 1
- Optic fiber Electronic switch the fiber serves as a transmission medium Optical networks - 1 st generation 1. Optical networks basic notions
- Slide 2
- Routing in the optical domain Two complementing technologies: - Wavelength Division Multiplexing (WDM): Transmission of data simultaneously at multiple wavelengths over same fiber - Optical switches: the output port is determined according to the input port and the wavelength Optical networks - 2 nd generation
- Slide 3
- lightpaths ADM OADM Data in electronic form
- Slide 4
- lightpaths p1 p2 Valid coloring
- Slide 5
- Optical switch lightpath OADM (optical add-drop multiplexer) No two inputs with the same wavelength should be routed on the same edge.
- Slide 6
- Electronic device at the endpoints of lightpaths ADM (electronic add-drop multiplexer)
- Slide 7
- Where can we save? an ADM can be shared by two lightpaths 2 ADMs1 ADM
- Slide 8
- 123 123
- Slide 9
- low capacity requests can be groomed into high capacity wavelengths (colors). colors can be assigned such that at most g lightpaths with the same color can share an edge g is the grooming factor Traffic grooming
- Slide 10
- lightpaths - with grooming Valid coloring g=2
- Slide 11
- Optical networks ADMs, OADMs, grooming Graph theoretical model Coloring and routing
- Slide 12
- 12 W=2, ADM=8 W=3, ADM=7 2. Minimize number of ADMs
- Slide 13
- minADM Input: a graph, a set of lightpaths, t>o. Output: can the lightpath be colored such that #ADMs t ? Output: can the lightpath be colored such that #ADMs t ?
- Slide 14
- The problem is easy on a path network
- Slide 15
- k = 4 Reminder: coloring of an interval graph
- Slide 16
- Go from left to right
- Slide 17
- 2.1 minADM is NPC for a ring minADM Input: a graph, a set of lightpaths, t>o. Output: can the lightpath be colored such that #ADMs t ? Output: can the lightpath be colored such that #ADMs t ?
- Slide 18
- Coloring of a circular arc graph
- Slide 19
- Not always possible with max load
- Slide 20
- Input: circular arc graph G, k>o. Output: can the arcs be colored by k colors? Output: can the arcs be colored by k colors? Coloring of a circular arc graph
- Slide 21
- Input: circular arc graph G, k>o. Output: can the arcs be colored with k colors? Output: can the arcs be colored with k colors? minADM Input: a graph, a set of lightpaths, t>o. Output: can the lightpath be colored such that #ADMs t ? Output: can the lightpath be colored such that #ADMs t ? G
- Slide 22
- Given an instance of the circular arc graph problem, construct an instance H of minADM:
- Slide 23
- Claim: Claim: can color G with k colors iff can color H with k colors iff can color H with #ADMs N. G H
- Slide 24
- Assume a coloring with 3 colors Claim: Claim: can color H with 3 colors iff can color H with #ADMs 13
- Slide 25
- Claim: Claim: can color with 3 colors iff ca n color the lightpaths with 13 ADMs Assume a coloring with 13 ADMs
- Slide 26
- 2.2 three basic observations
- Slide 27
- #ADMs = N + #chains N lightpaths cycles chains Cycles are good, chains are bad A. Structure of a solution
- Slide 28
- In the approximation algorithms there are two common techniques for saving ADMs: Eliminate cycles of lightpaths Find matchings of lightpaths #ADMs = N + #chains
- Slide 29
- cost(S) = N + chains=13+6=19 costs Every path costs 1 ADM cost(S) = 2N-savings=26-7=19 saves Every connection saves 1 ADM N lightpaths N=13
- Slide 30
- w/out grooming: ALG 2N N OPT ALG 2 OPT N: # of lightpaths ALG: #ADMs used by algorithm OPT: #ADMs used by an optimal solution w/ grooming: ALG 2N N/g OPT ALG 2g OPT B. The competitive ratio
- Slide 31
- Lemma: Assume that a solution ALG saves y ADMs, and OPT saves x ADMs. C. A basic lemma
- Slide 32
- Optimal solution OPT saves x ADMs a solution ALG saves y ADMs

*View more*