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Routing And Wavelength Assignment
The routing and wavelength assignment (RWA) problem is an optical networking problem with the goal of maximizing the number of optical connections. Definition The general objective of the RWA problem is to maximize the number of established connections. Each connection request must be given a route and wavelength. The wavelength must be consistent for the entire path, unless the usage of wavelength converters is assumed. Two connections requests can share the same optical link, provided a different wavelength is used. The RWA problem can be formally defined in an integer linear program (ILP). The ILP formulation given here is taken from. Maximize: :C_0(\rho,q) = \sum_^ m_i subject to :m_i \geq 0, integer, i = 1, 2, ..., N_ :c_ \in , i = 1, 2, ..., P, j = 1, 2, ..., W :C^TB \leq l_ :m \leq 1_WC^TA :m_i \leq q_i\rho, i = 1, 2, ..., N_ N_ is the number of source-destination pairs, while m_i is the number of connections established for each source-destination pair. L is the num ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Telecommunication
Optical communication, also known as optical telecommunication, is communication at a distance using light to carry information. It can be performed visually or by using electronic devices. The earliest basic forms of optical communication date back several millennia, while the earliest electrical device created to do so was the photophone, invented in 1880. An optical communication system uses a transmitter, which encodes a message into an optical signal, a channel, which carries the signal to its destination, and a receiver, which reproduces the message from the received optical signal. When electronic equipment is not employed the 'receiver' is a person visually observing and interpreting a signal, which may be either simple (such as the presence of a beacon fire) or complex (such as lights using color codes or flashed in a Morse code sequence). Modern communication relies on optical networking systems using optical fiber, optical amplifiers, lasers, switches, routers, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Routing
Routing is the process of selecting a path for traffic in a network or between or across multiple networks. Broadly, routing is performed in many types of networks, including circuit-switched networks, such as the public switched telephone network (PSTN), and computer networks, such as the Internet. In packet switching networks, routing is the higher-level decision making that directs network packets from their source toward their destination through intermediate network nodes by specific packet forwarding mechanisms. Packet forwarding is the transit of network packets from one network interface to another. Intermediate nodes are typically network hardware devices such as routers, gateways, firewalls, or switches. General-purpose computers also forward packets and perform routing, although they have no specially optimized hardware for the task. The routing process usually directs forwarding on the basis of routing tables. Routing tables maintain a record of the routes to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Branch And Bound
Branch and bound (BB, B&B, or BnB) is an algorithm design paradigm for discrete and combinatorial optimization problems, as well as mathematical optimization. A branch-and-bound algorithm consists of a systematic enumeration of candidate solutions by means of state space search: the set of candidate solutions is thought of as forming a rooted tree with the full set at the root. The algorithm explores ''branches'' of this tree, which represent subsets of the solution set. Before enumerating the candidate solutions of a branch, the branch is checked against upper and lower estimated ''bounds'' on the optimal solution, and is discarded if it cannot produce a better solution than the best one found so far by the algorithm. The algorithm depends on efficient estimation of the lower and upper bounds of regions/branches of the search space. If no bounds are available, the algorithm degenerates to an exhaustive search. The method was first proposed by Ailsa Land and Alison Doig whilst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Island Hopping
Leapfrogging, also known as island hopping, was a military strategy employed by the Allies in the Pacific War against the Empire of Japan during World War II. The key idea is to bypass heavily fortified enemy islands instead of trying to capture every island in sequence en route to a final target. The reasoning is that those islands can simply be cut off from their supply chains (leading to their eventual capitulation) rather than needing to be overwhelmed by superior force, thus speeding up progress and reducing losses of troops and materiel. Background By the late 19th century, the U.S. had several interests in the western Pacific to defend; namely, access to the Chinese market, and its colonies – the Philippines and Guam – which the U.S. had gained as a result of the Spanish–American War (1898). After Japan's victories in the Sino-Japanese War (1894–95) and the Russo-Japanese War of 1904, the U.S. began to regard Japan as a potential threat to its interests in th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Conference On Communications
The International Conference on Communications (ICC) is an annual international academic conference organised by the Institute of Electrical and Electronics Engineers' Communications Society. The conference grew out of the Global Communications Conference (GLOBECOM) when, in 1965, the seventh GLOBECOM was sponsored by the Communications Society's predecessor as the "IEEE Communications Convention". The following year it adopted its current name and GLOBECOM was disbanded (it has since been revived). The conference was held in the United States until 1984 when it was held in Amsterdam; it has since been held in several other countries. Some major telecommunications discoveries have been announced at ICC, such as the invention of turbo code In information theory, turbo codes (originally in French ''Turbocodes'') are a class of high-performance forward error correction (FEC) codes developed around 1990–91, but first published in 1993. They were the first practical codes to close ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Q Factor
In physics and engineering, the quality factor or ''Q'' factor is a dimensionless parameter that describes how underdamped an oscillator or resonator is. It is defined as the ratio of the initial energy stored in the resonator to the energy lost in one radian of the cycle of oscillation. Q factor is alternatively defined as the ratio of a resonator's centre frequency to its bandwidth when subject to an oscillating driving force. These two definitions give numerically similar, but not identical, results. Higher ''Q'' indicates a lower rate of energy loss and the oscillations die out more slowly. A pendulum suspended from a high-quality bearing, oscillating in air, has a high ''Q'', while a pendulum immersed in oil has a low one. Resonators with high quality factors have low damping, so that they ring or vibrate longer. Explanation The Q factor is a parameter that describes the resonance behavior of an underdamped harmonic oscillator (resonator). Sinusoidally driven resonators ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Simple Extension
In field theory, a simple extension is a field extension which is generated by the adjunction of a single element. Simple extensions are well understood and can be completely classified. The primitive element theorem provides a characterization of the finite simple extensions. Definition A field extension is called a simple extension if there exists an element in ''L'' with :L = K(\theta). This means that every element of can be expressed as a rational fraction in , with coefficients in . There are two different sort of simple extensions. The element may be transcendental over , which means that it is not a root of any polynomial with coefficients in . In this case K(\theta) is isomorphic to the field of rational functions K(X). Otherwise, is algebraic over ; that is, is a root of a polynomial over . The monic polynomial F(X) of minimal degree , with as a root, is called the minimal polynomial of . Its degree equals the degree of the field extension, that is, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hill Climbing
numerical analysis, hill climbing is a mathematical optimization technique which belongs to the family of local search. It is an iterative algorithm that starts with an arbitrary solution to a problem, then attempts to find a better solution by making an incremental change to the solution. If the change produces a better solution, another incremental change is made to the new solution, and so on until no further improvements can be found. For example, hill climbing can be applied to the travelling salesman problem. It is easy to find an initial solution that visits all the cities but will likely be very poor compared to the optimal solution. The algorithm starts with such a solution and makes small improvements to it, such as switching the order in which two cities are visited. Eventually, a much shorter route is likely to be obtained. Hill climbing finds optimal solutions for convex problems – for other problems it will find only local optima (solutions that cannot be imp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Switch
An optical transistor, also known as an optical switch or a light valve, is a device that switches or amplifies optical signals. Light occurring on an optical transistor's input changes the intensity of light emitted from the transistor's output while output power is supplied by an additional optical source. Since the input signal intensity may be weaker than that of the source, an optical transistor amplifies the optical signal. The device is the optical analog of the electronic transistor that forms the basis of modern electronic devices. Optical transistors provide a means to control light using only light and has applications in optical computing and fiber-optic communication networks. Such technology has the potential to exceed the speed of electronics, while conserving more power. Since photons inherently do not interact with each other, an optical transistor must employ an operating medium to mediate interactions. This is done without converting optical to electronic signals ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yen's Algorithm
In graph theory, Yen's algorithm computes single-source ''K''-shortest loopless paths for a graph with non-negative edge cost. The algorithm was published by Jin Y. Yen in 1971 and employs any shortest path algorithm to find the best path, then proceeds to find ''K'' − 1 deviations of the best path. Algorithm Terminology and notation Description The algorithm can be broken down into two parts, determining the first k-shortest path, A^1, and then determining all other ''k''-shortest paths. It is assumed that the container A will hold the ''k''-shortest path, whereas the container B, will hold the potential ''k''-shortest paths. To determine A^1, the shortest path from the source to the sink, any efficient shortest path algorithm can be used. To find the A^k, where k ranges from 2 to K, the algorithm assumes that all paths from A^1 to A^ have previously been found. The k iteration can be divided into two processes, finding all the deviations _i and choosing a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Link
An optical link is a telecommunications link that consists of a single end-to-end optical circuit. A cable of optical fibers, possibly concatenated into a dark fiber link, is the simplest form of an optical link. Other forms of optical link can include single-"colour" links over a wavelength division multiplex infrastructure, and/or links that use optical amplifiers to compensate for attenuation over long distances. Other forms of optical links include free-space optical telecommunication links. In the rail transport sector, optical links are used in two forms depending on whether the feeding station is a main station or not. Thus main stations are called 'long halls', and all remaining stations are said to be 'short halls'. See also *100 Gigabit Ethernet *10 Gigabit Ethernet *Active cable *Cloud computing *CXP (connector) *C form-factor pluggable * Data center * Fibre channel * Fiber-optic communication *Green computing *HDMI *High-performance computing *InfiniBand * Infi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hop Count
In wired computer networking, including the Internet, a hop occurs when a packet is passed from one network segment to the next. Data packets pass through routers as they travel between source and destination. The hop count refers to the number of network devices through which data passes from source to destination (depending on routing protocol, this may include the source/destination, that is, the first hop is counted as hop 0 or hop 1). Since store and forward and other latencies are incurred through each hop, a large number of hops between source and destination implies lower real-time performance. Hop count In wired networks, the hop count refers to the number of networks or network devices through which data passes between source and destination (depending on routing protocol, this may include the source/destination, that is, the first hop is counted as hop 0 or hop 1). Thus, hop count is a rough measure of distance between two hosts. For a routing protocol using 1-or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
