Design Patterns

In software engineering, a design pattern is a general repeatable solution to a commonly occurring problem in software design. A design pattern isn't a finished design that can be transformed directly into code. It is a description or template for how to solve a problem that can be used in many different situations.

Uses of Design Patterns

Design patterns can speed up the development process by providing tested, proven development paradigms. Effective software design requires considering issues that may not become visible until later in the implementation. Reusing design patterns helps to prevent subtle issues that can cause major problems and improves code readability for coders and architects familiar with the patterns. Often, people only understand how to apply certain software design techniques to certain problems. These techniques are difficult to apply to a broader range of problems. Design patterns provide general solutions, documented in a format that doesn't require specifics tied to a particular problem. In addition, patterns allow developers to communicate using well-known, well understood names for software interactions. Common design patterns can be improved over time, making them more robust than ad-hoc designs.

Creational design patterns

This design patterns is all about class instantiation. This pattern can be further divided into class-creation patterns and object-creational patterns. While class-creation patterns use inheritance effectively in the instantiation process, object-creation patterns use delegation effectively to get the job done.

• Abstract Factory
  Creates an instance of several families of classes
• Builder
  Separates object construction from its representation
• Factory Method
  Creates an instance of several derived classes
• Object Pool
  Avoid expensive acquisition and release of resources by recycling objects that are no longer in use
• Prototype
  A fully initialized instance to be copied or cloned
• Singleton
  A class of which only a single instance can exist

Structural design patterns

This design patterns is all about Class and Object composition. Structural class-creation patterns use inheritance to compose interfaces. Structural object-patterns define ways to compose objects to obtain new functionality.

• Adapter
  Match interfaces of different classes
• Bridge
  Separates an object’s interface from its implementation
• Composite
  A tree structure of simple and composite objects
• Decorator
  Add responsibilities to objects dynamically
• Facade
  A single class that represents an entire subsystem
• Flyweight
  A fine-grained instance used for efficient sharing
• Private Class Data
  Restricts accessor/mutator access
• Proxy
  An object representing another object

Behavioral design patterns

This design patterns is all about Class's objects communication. Behavioral patterns are those patterns that are most specifically concerned with communication between objects.

• Chain of responsibility
  A way of passing a request between a chain of objects
• Command
  Encapsulate a command request as an object
• Interpreter
  A way to include language elements in a program
• Iterator
  Sequentially access the elements of a collection
• Mediator
  Defines simplified communication between classes
• Memento
  Capture and restore an object's internal state
• Null Object
  Designed to act as a default value of an object
• Observer
  A way of notifying change to a number of classes
• State
  Alter an object's behavior when its state changes
• Strategy
  Encapsulates an algorithm inside a class
• Template method
  Defer the exact steps of an algorithm to a subclass
• Visitor
  Defines a new operation to a class without change

to know more Click here

RADAR - Radio Detection and Ranging.

Radar is a system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain.

Working:
A radar system has a transmitter that emits either radio waves or (more usually these days) microwaves that are reflected by the target and detected by a receiver, typically in the same location as the transmitter. Although the signal returned is usually very weak, the signal can be amplified. This enables radar to detect objects at ranges where other emissions, such as sound or visible light, would be too weak to detect. Radar is used in many contexts, including meteorological detection of precipitation, measuring ocean surface waves, air traffic control, police detection of speeding traffic, and by the military.
There are basically five types of radar based on its use:

Detection and search radar: such as the "early warning radar," which is used for long-range detection of objects, and the Target Acquisition (TA) Radar Systems, used to locate surface-to-air missiles (SAM). These types of radar are frequently used in the military and in coastal surveillance, as well as for detecting car speed during highway patrol.

Missile guidance systems are radar used to locate the target of a missile. This is often present in military aircraft.

Radar for biological research: bird and insect radar are used frequently `by scientists to track the migration patterns of animals. Bird radar is also being used at NASA's Kennedy Space Center in Florida to track the presence of birds, especially vultures, near launching pads. Trap and release programs have been implemented to prevent birds accidentally impacting the shuttles after liftoff.

Air traffic control and navigation radar: used by airports to ensure the safety of planes, this type of radar detects the proximity of an aircraft and identifies the identity and altitude of the plane. Radio beacons and Distance Measuring Equipment (DME) also fall into this category.

Weather-sensing radar systems: mostly used to measure and locate precipitation, this type of radar can also measure wind direction and speed.

To know more about RADAR:

• Working of RADAR
• Radar
• Doppler Radar
• RADAR
• Uses of RADAR
• Radar - Radar Tracking Systems
• Radar - Basic Radar Operation, Radar Tracking Systems, Doppler Radar

GPRS - General Packet Radio Service

GPRS

The General Packet Radio Service (GPRS) network is an "always on", private network for data. It uses the existing GSM network to transmit and receive TCP/IP based data to and from GPRS mobile devices.

Private IP addresses are typically dynamically assigned within the network to mobile devices. However, Access Point Names (APN's) provide a gateway route to other networks such as the Internet, WAP services or private corporate networks. Firewalls typically reside at the APN to isolate the public and private networks. IP addresses allocated to mobile GPRS devices are therefore not addressable from outside the GPRS network (e.g. from the Internet) without specialised services or infrastructure.

GPRS benefits :

• Efficient - GPRS mobile devices only use the GSM network when data is transferred. The GSM connection is not dedicated to each user, therefore it can be shared with many users resulting in efficient use of the network.


• Speed - GPRS gives speeds of upto 5 time faster than GSM. GPRS offers maximum data rates of 56Kbps (down) and 14.4kbps (up), however this is shared bandwidth therefore actual data rates are potentially lower.
  
• Always on connectivity- GPRS is an always-on service. There is no need to dial up like you have to on a home PC for instance. This feature is not unique to GPRS but is an important standard that will no doubt be a key feature for migration to 3G. It makes services instantaneously available to a device.


• New and Better applications - Due to its high-speed connection and always-on connectivity GPRS enables full Internet applications and services such as video conferencing straight to your desktop or mobile device. Users are able to explore the Internet or their own corporate networks more efficiently than they could when using GSM. There is often no need to redevelop existing applications.


• GSM operator Costs- GSM network providers do not have to start from scratch to deploy GPRS. GPRS is an upgrade to the existing network that sits along side the GSM network. This makes it easier to deploy.


• Payment based on data usage - Billing is not based on time, but on the amount of data actually transferred.

To know more on GPRS:

• Working of GPRS
• GPRS Tutorial
• GPRS Info
• GPRS Applications

GSM - Global System for Mobile Communications

What is GSM:

Short for Global System for Mobile Communications, GSM is a digital cellular communications system. It was developed in order to create a common European mobile telephone standard but it has been rapidly accepted worldwide.

GSM is designed to provide a comprehensive range of services and features to the users not available on analogue cellular networks and in many cases very much in advance of the old public switched telephone network (PSTN). In addition to digital transmission, GSM incorporates many advanced services and features like worldwide roaming in other GSM networks.

GSM provides recommendations, not requirements. The GSM specifications define the functions and interface requirements in detail but do not address the hardware. The reason for this is to limit the designers as little as possible but still to make it possible for the operators to buy equipment from different suppliers. The GSM network is divided into three major systems: the switching system (SS), the base station system (BSS), and the operation and support system (OSS).


Architecture of the GSM Network:

(Click on the Image for a bigger picture)

Base Transceiver Station (BTS)
Base Station Controller (BSC)
Home Location Register (HLR)
Mobile Services switching Center (MSC)
Gateway Mobile Services switching Center (GMSC)
Visitor Location Register (VLR)
Authentication Center (AUC)
Equipment Identity Register (EIR)


Mobile Station:
The Mobile Station (MS) represents the only equipment the GSM user ever sees from the whole system. It actually consists of two distinct entities. The actual hardware is the Mobile Equipment (ME), which is anonymous and consists of the physical equipment, such as the radio transceiver, display and digital signal processors.

Base Station Subsystem:
The Base Station Subsystem is composed of two parts, the Base Transceiver Station (BTS) and the Base Station Controller (BSC). The BTS houses the radio transceivers that define a cell and transmits and receives signals on the cells' allocated frequencies with the mobile station.

Network Subsystem:
The central component of the Network Subsystem is the Mobile services Switching Center (MSC). It acts like a normal switching node of the normal telephones of the land lines and in addition provides all the functionality needed to handle a mobile subscriber, including registration, authentication, location updating and inter-MSC handovers.

To Know more on the topic:

• GSM Specifications
• GSM Overview
• GSM World
• GSM in Wikipedia
• GSM Specifications

Spread Spectrum Modulation

Living in a world of Digital Communication,we would need to know how secure the comunication is and what are the ways handled to have it secure.This article describes about Spread Spectrum Technology,the art of secure digital communications which was once restricted only for Military communicaton and that is now being exploited for commercial and industrial purposes too.

Applications for commercial spread spectrum range from "wireless" LAN's (computer to computer local area networks), to integrated bar code scanner/palmtop computer/radio modem devices for warehousing, to digital dispatch, to digital cellular telephone communications, to "information society" city/area/state or country wide networks for passing faxes, computer data, email, or multimedia data.
What is Spread Spectrum?
The process of using a second modulating signal which is independent of the data and has the effect of increasing the bandwidth of the transmitted signal to well beyond the bandwidth of the data signal.
How Spread Spectrum Works?
Spread Spectrum uses wide band, noise-like signals. Because Spread Spectrum signals are noise-like, they are hard to detect. Spread Spectrum signals are also hard to Intercept or demodulate. Further, Spread Spectrum signals are harder to jam (interfere with) than narrowband signals. These Low Probability of Intercept (LPI) and anti-jam (AJ) features are why the military has used Spread Spectrum for so many years. Spread signals are intentionally made to be much wider band than the information they are carrying to make them more noise-like.

Spread Spectrum transmitters use similar transmit power levels to narrow band transmitters. Because Spread Spectrum signals are so wide, they transmit at a much lower spectral power density, measured in Watts per Hertz, than narrowband transmitters. This lower transmitted power density characteristic gives spread signals a big plus. Spread and narrow band signals can occupy the same band, with little or no interference. This capability is the main reason for all the interest in Spread Spectrum today.

Spread Spectrum Modulation is distinguished from wideband modulation schemes such as wideband Frequency Modulation (FM) by noting that in spread spectrum the waveform causing the spreading is independent of the data being transmitted. This permits the spreading waveform to be selected based on improving system performance in some way. PN sequences are selected as the spreading signals since they uniformly spread the signal power over the available bandwidth and provide other critical advantages such as permitting universal frequency reuse.


Three Types of Spread Spectrum Communications:

• Frequency hopping. The signal is rapidly switched between different frequencies within the hopping bandwidth pseudo-randomly, and the receiver knows before hand where to find the signal at any given time.

• Time hopping. The signal is transmitted in short bursts pseudo-randomly, and the receiver knows beforehand when to expect the burst.


• Direct sequence. The digital data is directly coded at a much higher frequency. The code is generated pseudo-randomly, the receiver knows how to generate the same code, and correlates the received signal with that code to extract the data.

Advantages:

• Resists intentional and non-intentional interference
• Has the ability to eliminate or alleviate the effect of multipath interference
• Can share the same frequency band (overlay) with other users
• Privacy due to the pseudo random code sequence (code division multiplexing)

Disadvantages:

• Complex circuitry
• Expensive to develop
• Very large bandwidths

To know more on the topic:

ABC of Spread Spectrum

Spreadspectrum Basics

CDMA and Spread Spectrum

Direct Sequence Spread Spectrum

Article on Spread Spectrum

Download material on Spread Spectrum

Spread spectrum System and its working

Article on Spread Spectrum

Bluetooth technology

The art of connecting things is becoming more and more complex every day. In this article, we will look at a method of connecting devices, called Bluetooth, that can streamline the process.

What is Bluetooth?
Bluetooth is an industrial specification for wireless personal area networks (PANs)or piconet. Bluetooth provides a way to connect and exchange information between devices such as mobile phones, laptops, Personal computer, printers, digital cameras, and video game consoles over a secure, globally unlicensed short-range radio frequency.

Bluetooth simplifies the discovery and setup of services between devices. Bluetooth devices advertise all of the services they provide. This makes using services easier because there is no longer a need to setup network addresses or permissions as in many other networks.

How Bluetooth Operates:
Bluetooth networking transmits data via low-power radio waves. It communicates on a frequency of 2.45 gigahertz (actually between 2.402 GHz and 2.480 GHz, to be exact). This frequency band has been set aside by international agreement for the use of industrial, scientific and medical devices (ISM).

One of the ways Bluetooth devices avoid interfering with other systems is by sending out very weak signals of about 1 milliwatt. By comparison, the most powerful cell phones can transmit a signal of 3 watts. The low power limits the range of a Bluetooth device to about 10 meters (32 feet), cutting the chances of interference between your computer system and your portable telephone or television. Even with the low power, Bluetooth doesn't require line of sight between communicating devices. The walls in your house won't stop a Bluetooth signal, making the standard useful for controlling several devices in different rooms.

Bluetooth can connect up to eight devices simultaneously. With all of those devices in the same 10-meter (32-foot) radius, you might think they'd interfere with one another, but it's unlikely. Bluetooth uses a technique called spread-spectrum frequency hopping that makes it rare for more than one device to be transmitting on the same frequency at the same time. In this technique, a device will use 79 individual, randomly chosen frequencies within a designated range, changing from one to another on a regular basis.

In the case of Bluetooth, the transmitters change frequencies 1,600 times every second, meaning that more devices can make full use of a limited slice of the radio spectrum. Since every Bluetooth transmitter uses spread-spectrum transmitting automatically, it’s unlikely that two transmitters will be on the same frequency at the same time. This same technique minimizes the risk that portable phones or baby monitors will disrupt Bluetooth devices, since any interference on a particular frequency will last only a tiny fraction of a second.

Advantages:
An economic wireless solution (both data & voice) for short distance.A global technology specification - an universal radio interface in 2.4 GHz ISM frequency band Stationary & mobile environments.No setup needed - always on in the background (Dynamic configurable).

Disadvantages:
The only real downsides are the data rate and security. Infrared can have data rates of up to 4 MBps, which provides very fast rates for data transfer, while Bluetooth only offers 1 MBps. The greater range and radio frequency (RF) of Bluetooth make it much more open to interception and attack. For this reason, security is a very key.

To know more on the topic:

• Bluetooth-Official Site
• A tutorial on Bluetooth
• Working of Bluetooth

Wireless LAN or WLAN

A wireless LAN or WLAN is a wireless local area network, which is the linking of two or more computers without using wires. WLAN utilizes spread-spectrum or OFDM modulation technology based on radio waves to enable communication between devices in a limited area, also known as the basic service set. This gives users the mobility to move around within a broad coverage area and still be connected to the network.

The benefits of wireless LANs include:
Convenience: The wireless nature of such networks allows users to access network resources from nearly any convenient location within their primary networking environment (home or office). With the increasing saturation of laptop-style computers, this is particularly relevant.

Mobility: With the emergence of public wireless networks, users can access the internet even outside their normal work environment. Most chain coffee shops, for example, offer their customers a wireless connection to the internet at little or no cost.

Productivity: Users connected to a wireless network can maintain a nearly constant affiliation with their desired network as they move from place to place.

Deployment: Initial setup of an infrastructure-based wireless network requires little more than a single access point. Wired networks, on the other hand, have the additional cost and complexity of actual physical cables being run to numerous locations (which can even be impossible for hard-to-reach locations within a building).

Expandability: Wireless networks can serve a suddenly-increased number of clients with the existing equipment. In a wired network, additional clients would require additional wiring.

Cost: Wireless networking hardware is at worst a modest increase from wired counterparts. This potentially increased cost is almost always more than outweighed by the savings in cost and labor associated to running physical cables.

Disadvantages:
Wireless LAN technology, with the conveniences and advantages described above, has its own limitations.

Security: Wireless LAN transceivers are designed to serve computers throughout a structure with uninterrupted service using radio frequencies. Because of space and cost, the antennas typically present on wireless networking cards in the end computers are generally relatively poor. In order to properly receive signals using such limited antennas throughout even a modest area, the wireless LAN transceiver utilizes a fairly considerable amount of power. On a wired network, any adversary would first have to overcome the physical limitation of tapping into the actual wires, but this is not an issue with wireless packets. To combat this consideration, wireless networks users usually choose to utilize various encryption technologies available such as Wi-Fi Protected Access (WPA). Some of the older encryption methods, such as WEP are known to have weaknesses that a dedicated adversary can compromise.

Range: The typical range of a common 802.11g network with standard equipment is on the order of tens of meters. While sufficient for a typical home, it will be insufficient in a larger structure. To obtain additional range, repeaters or additional access points will have to be purchased.

Reliability: Like any radio frequency transmission, wireless networking signals are subject to a wide variety of interference, as well as complex propagation effects that are beyond the control of the network administrator. In the case of typical networks, modulation is achieved by complicated forms of phase-shift keying (PSK) or quadrature amplitude modulation (QAM), making interference and propagation effects all the more disturbing. As a result, important network resources such as servers are rarely connected wirelessly.

Speed: The speed on most wireless networks (typically 1-108 Mbit/s) is reasonably slow compared to the slowest common wired networks (100 Mbit/s up to several Gbit/s). There are also performance issues caused by TCP and its built-in congestion avoidance. For most users, however, this observation is irrelevant since the speed bottleneck is not in the wireless routing but rather in the outside network connectivity itself. That is to say, in most environments, a wireless network running at its slowest speed is still faster than the internet connection serving it in the first place.

In summary, WLANs are best used as an addition to a copper-based network in situations where a percentage of users require mobility and/or where it is physically difficult, impossible or extremely expensive to deploy a copper solution.

WLAN technology can also be effectively used as a short haul backbone link between buildings on a single campus or across a road. WLANs are particularly appropriate when it is necessary to set up a small LAN quickly, either as a temporary or permanent solution. Standalone WLANs can also be used for public Internet access.


To know more on the topic:

• Focus: WLAN
• WLAN

Wireless Communication

Wireless communication is the transfer of information over a distance without the use of electrical conductors or "wires".The distances involved may be short (a few meters as in television remote control) or very long (thousands or even millions of kilometers for radio communications). When the context is clear the term is often simply shortened to "wireless". Wireless communications is generally a branch of telecommunications.

Wireless communication may be via:

• Radio frequency communication,
• Microwave communication, for example long-range line-of-sight via highly directional antennas, or short-range communication, or
• Infrared (IR) short-range communication, for example from remote controls or via IRDA

Wireless communication spans the spectrum from 9 KHz to 300 GHz.

Applications may involve point-to-point communication, point-to-multipoint communication, broadcasting , cellular networks and other wireless networks.

Common examples of wireless equipment in use today include:

1. Cellular phones and pagers: provide connectivity for portable and mobile applications, both personal and business.
2. Global Positioning System (GPS): allows drivers of cars and trucks, captains of boats and ships, and pilots of aircraft to ascertain their location anywhere on earth.
3. Cordless computer peripherals: the cordless mouse is a common example; keyboards and printers can also be linked to a computer via wireless.
4. Cordless telephone sets: these are limited-range devices, not to be confused with cell phones.
5. Satellite television: allows viewers in almost any location to select from hundreds of channels.

Wireless networking is used to meet a variety of needs. Perhaps the most common use is to connect laptop users who travel from location to location. Another common use is for mobile networks that connect via satellite. A wireless transmission method is a logical choice to network a LAN segment that must frequently change locations.

The uses of wireless technology:

• To span a distance beyond the capabilities of typical cabling,
• To avoid obstacles such as physical structures, EMI, or RFI,
• To provide a backup communications link in case of normal network failure,
• To link portable or temporary workstations,
• To overcome situations where normal cabling is difficult or financially impractical, or
• To remotely connect mobile users or networks.
  

More about Wireless LAN network, Wifi and Bluetooth in the forthcoming posts.

Fiber Optics

Fiber optics has become a buzzword these days in the field of telecommunication.

Lets explore about it...

Telecommunication applications are widespread, ranging from global networks to local telephone exchanges to subscribers homes to desktop computers. These involve the transmission of voice, data, or video over distances of less than a meter to hundreds of kilometers. Fiber optics is employed for this purpose.

What is Fiber Optics?

In its simplest terms, fiber optics is a medium for carrying information from one point to another in the form of light. A technology that uses glass (or plastic) threads (fibers) to transmit data.Unlike the copper form of transmission, fiber optics is not electrical in nature. A fiber optic cable consists of a bundle of glass threads, each of which is capable of transmitting messages modulated onto light waves. The fiber itself is passive and does not contain any active, generative properties.

Benefits of Fiber Optics :

Fiber optics has several advantages over traditional metal communications lines:

• Fiber optic cables are much thinner and lighter than metal wires.
• Fiber optic cables have a much greater bandwidth than metal cables. This means that they can carry more data.
• The low attenuation and superior signal integrity found in optical systems allow much longer intervals of signal transmission than metallic-based systems.
• Fiber optic cables are less susceptible than metal cables to interference.
• The voice-grade copper systems longer than a couple of kilometers (1.2 miles) require in-line signal repeaters for satisfactory performance, but optical systems go over 100 kilometers (km), or about 62 miles, with no active or passive processing.
• Data can be transmitted digitally (the natural form for computer data) rather than analogically.
• Unlike metallic-based systems, the dielectric nature of optical fiber makes it impossible to remotely detect the signal being transmitted within the cable. The only way to do so is by actually accessing the optical fiber itself.

The main disadvantage of fiber optics considered was that the cables are expensive to install but as electronics prices fall,Fiber optics is affordable today, and optical cable pricing remains low. As bandwidth demands increase rapidly with technological advances, fiber will continue to play a vital role in the long-term success of telecommunications.

Operational Principle of Fiber optics:Total Internal Reflection:

When a light ray traveling in one material hits a different material and reflects back into the original material without any loss of light, total internal reflection occurs.
Since the core and cladding are constructed from different compositions of glass, theoretically, light entering the core is confined to the boundaries of the core because it reflects back whenever it hits the cladding. For total internal reflection to occur, the index of refraction of the core must be higher than that of the cladding.

The index of refraction (IOR) is a way of measuring the speed of light in a material. Light travels fastest in a vacuum, such as outer space. The actual speed of light in a vacuum is 300,000 kilometers per second, or 186,000 miles per second. Index of Refraction is calculated by dividing the speed of light in a vacuum by the speed of light in some other medium.The Index of Refraction of a vacuum by definition has a value of 1.

The Information Transmission Sequence :

As depicted above, information (voice, data, or video) is encoded into electrical signals. At the light source, these electrical signals are converted into light signals.

It is important to note that fiber has the capability to carry either analog or digital signals. Many people believe that fiber can transmit only digital signals due to the on/off binary characteristic of the light source. The intensity of the light and the frequency at which the intensity changes can be used for AM and FM analog transmission.

Once the signals are converted to light, they travel down the fiber until they reach a detector, which changes the light signals back into electrical signals. This area from light source to detector constitutes the passive transmission subsystem; i.e. that part of the system manufactured and sold by Corning Cable Systems.

Finally, the electrical signals are decoded into information in the form of voice, data, or video.

Transmission Modes:

Once light enters an optical fiber, it travels in a stable state called a mode. There can be from one to hundreds of modes depending on the type of fiber. Each mode carries a portion of the light from the input signal.

Every telecommunications fiber falls into one of two categories: single-mode or multimode.
It is impossible to distinguish between single-mode and multimode fiber with the naked eye. There is no difference in outward appearance, only in core size. Both fiber types act as a transmission medium for light, but they operate in different ways, have different characteristics, and serve different applications.

Fiber optic Applications :

Optical fiber is used extensively for transmission of data signals. Private networks are owned by firms such as IBM, Rockwell, Honeywell, banks, universities, Wall Street firms, and more. These firms have a need for secure, reliable systems to transfer computer and monetary information between buildings to the desktop terminal or computer, and around the world. The security inherent in optical fiber systems is a major benefit.

Cable television or community antenna television (CATV) companies also find fiber useful for video services. The high information-carrying capacity, or bandwidth, of fiber makes it the perfect choice for transmitting signals to subscribers.

Finally, one of the fastest growing markets for fiber optics is intelligent transportation systems, smart highways with intelligent traffic lights, automated toll booths, and changeable message signs to give motorists information about delays and emergencies.

Related Sites:

• Corning Cable Systems
• Working of Fiber optics
• The basics of fiber optic cable
• More on Fiber optics

[Diagrams courtesy: Corning Cable Systems]

Some Fun in Electronics too.............

Found a Funny Invite...thought will post it here :)

You are electronically invited on occasion of the marriage of

Mr. TRANSISTOR BC107

(working as amplifier in "CE" configuration)

The Son of Mr & Mrs. Aluminium

With

Miss. DIODE 2N2222

(working as a rectifier in Electronic Circuits)

The only Daughter of Mr & Mrs. Phosphorous

MUHURTAM Oct 30, 2K8 @ 10-45 Amplitude Modulation

VENUE

At Peizo Electric Palace, Near Wein Bridge,

Nyquist criterion Road-2,Electricity -508085.

Yours inductively

Mr. & Mrs. EDC PDC Near P-N Junction, IC Road, Zener breakdown.

With BEST COMPLIMENTS FROM,

Inductor, Resistor, Capacitor, Transformer Near & Dear

Note: Musical Night by Motors and Generators

Neural Networks

Neural Network- Biological Inspiration:

Neural networks grew out of research in Artificial Intelligence; specifically, attempts to mimic the fault-tolerance and capacity to learn of biological neural systems by modeling the low-level structure of the brain.The brain is principally composed of a very large number (circa 10,000,000,000) of neurons, massively interconnected (with an average of several thousand interconnects per neuron, although this varies enormously).

Each neuron is a specialized cell which can propagate an electrochemical signal. The neuron has a branching input structure (the dendrites), a cell body, and a branching output structure (the axon). The axons of one cell connect to the dendrites of another via a synapse. When a neuron is activated, it fires an electrochemical signal along the axon. This signal crosses the synapses to other neurons, which may in turn fire. A neuron fires only if the total signal received at the cell body from the dendrites exceeds a certain level (the firing threshold).

The strength of the signal received by a neuron (and therefore its chances of firing) critically depends on the efficacy of the synapses. Each synapse actually contains a gap, with neurotransmitter chemicals poised to transmit a signal across the gap.Thus, from a very large number of extremely simple processing units (each performing a weighted sum of its inputs, and then firing a binary signal if the total input exceeds a certain level) the brain manages to perform extremely complex tasks.

Of course, there is a great deal of complexity in the brain which has not been discussed here, but it is interesting that artificial neural networks can achieve some remarkable results using a model not much more complex than this.

Artificial Neural Network:

An Artificial Neural Network (ANN) is an information processing paradigm that is inspired by the way biological nervous systems, such as the brain, process information. The key element of this paradigm is the novel structure of the information processing system. It is composed of a large number of highly interconnected processing elements (neurones) working in unison to solve specific problems. ANNs, like people, learn by example. An ANN is configured for a specific application, such as pattern recognition or data classification, through a learning process. Learning in biological systems involves adjustments to the synaptic connections that exist between the neurones. This is true of ANNs as well.


Why use Neural networks?

Neural networks, with their remarkable ability to derive meaning from complicated or imprecise data, can be used to extract patterns and detect trends that are too complex to be noticed by either humans or other computer techniques. A trained neural network can be thought of as an "expert" in the category of information it has been given to analyse. This expert can then be used to provide projections given new situations of interest and answer "what if" questions.Other advantages include:

Adaptive learning: An ability to learn how to do tasks based on the data given for training or initial experience.

Self-Organisation: An ANN can create its own organisation or representation of the information it receives during learning time.

Real Time Operation: ANN computations may be carried out in parallel, and special hardware devices are being designed and manufactured which take advantage of this capability.

Fault Tolerance via Redundant Information Coding: Partial destruction of a network leads to the corresponding degradation of performance. However, some network capabilities may be retained even with major network damage.

Neural networks versus conventional computers:
Neural networks take a different approach to problem solving than that of conventional computers. Conventional computers use an algorithmic approach i.e. the computer follows a set of instructions in order to solve a problem. Unless the specific steps that the computer needs to follow are known the computer cannot solve the problem. That restricts the problem solving capability of conventional computers to problems that we already understand and know how to solve. But computers would be so much more useful if they could do things that we don't exactly know how to do.

Neural networks process information in a similar way the human brain does. The network is composed of a large number of highly interconnected processing elements(neurones) working in parallel to solve a specific problem. Neural networks learn by example. They cannot be programmed to perform a specific task. The examples must be selected carefully otherwise useful time is wasted or even worse the network might be functioning incorrectly. The disadvantage is that because the network finds out how to solve the problem by itself, its operation can be unpredictable.

On the other hand, conventional computers use a cognitive approach to problem solving; the way the problem is to solved must be known and stated in small unambiguous instructions. These instructions are then converted to a high level language program and then into machine code that the computer can understand. These machines are totally predictable; if anything goes wrong is due to a software or hardware fault.

Neural networks and conventional algorithmic computers are not in competition but complement each other. There are tasks are more suited to an algorithmic approach like arithmetic operations and tasks that are more suited to neural networks. Even more, a large number of tasks, require systems that use a combination of the two approaches (normally a conventional computer is used to supervise the neural network) in order to perform at maximum efficiency.

Pattern Recognition - an example of ANN:
An important application of neural networks is pattern recognition. Pattern recognition can be implemented by using a feed-forward (figure 1) neural network that has been trained accordingly. During training, the network is trained to associate outputs with input patterns. When the network is used, it identifies the input pattern and tries to output the associated output pattern. The power of neural networks comes to life when a pattern that has no output associated with it, is given as an input. In this case, the network gives the output that corresponds to a taught input pattern that is least different from the given pattern.

Neural Networks in Practice :

Given this description of neural networks and how they work, what real world applications are they suited for? Neural networks have broad applicability to real world business problems. In fact, they have already been successfully applied in many industries.
Since neural networks are best at identifying patterns or trends in data, they are well suited for prediction or forecasting needs including:

• Sales forecasting
• Industrial process control
• Customer research
• Data validation
• Risk management
• Target marketing
  

But to give you some more specific examples; ANN are also used in the following specific paradigms: recognition of speakers in communications; diagnosis of hepatitis; recovery of telecommunications from faulty software; interpretation of multimeaning Chinese words; undersea mine detection; texture analysis; three-dimensional object recognition; hand-written word recognition; and facial recognition

Neural networks in medicine:
Artificial Neural Networks (ANN) are currently a 'hot' research area in medicine and it is believed that they will receive extensive application to biomedical systems in the next few years. At the moment, the research is mostly on modelling parts of the human body and recognising diseases from various scans (e.g. cardiograms, CAT scans, ultrasonic scans, etc.).
Neural networks are ideal in recognising diseases using scans since there is no need to provide a specific algorithm on how to identify the disease. Neural networks learn by example so the details of how to recognise the disease are not needed. What is needed is a set of examples that are representative of all the variations of the disease. The quantity of examples is not as important as the 'quantity'. The examples need to be selected very carefully if the system is to perform reliably and efficiently.

Neural Networks in business:
Business is a diverted field with several general areas of specialisation such as accounting or financial analysis. Almost any neural network application would fit into one business area or financial analysis. There is some potential for using neural networks for business purposes, including resource allocation and scheduling. There is also a strong potential for using neural networks for database mining, that is, searching for patterns implicit within the explicitly stored information in databases. Most of the funded work in this area is classified as proprietary. Thus, it is not possible to report on the full extent of the work going on. Most work is applying neural networks, such as the Hopfield-Tank network for optimization and scheduling.

Neural networks do not perform miracles. But if used sensibly they can produce some amazing results.

Related Topics:

• Fuzzy Logic
• Artificial Intelligence
• Architecture of neural networks

Digital Signal Processing

DSP in day-to-day life:
DSP technology is nowadays commonplace in such devices as mobile phones, multimedia computers, video recorders, CD players, hard disc drive controllers and modems, and has replaced analog circuitry in TV sets and telephones as well. An important application of DSP is in signal compression and decompression. Signal compression is used in digital cellular phones to allow a greater number of calls to be handled simultaneously within each local "cell". DSP signal compression technology allows people not only to talk to one another but also to see one another on their computer screens, using small video cameras mounted on the computer monitors, with only a conventional telephone line linking them together. In audio CD systems, DSP technology is used to perform complex error detection and correction on the raw data as it is read from the CD.

What is DSP?

Digital signal processing ('DSP') is the study of signals in a digital representation and the processing methods of these signals. DSP and analog signal processing are subfields of signal processing. DSP includes subfields like: audio and speech signal processing, sonar and radar signal processing, sensor array processing, spectral estimation, statistical signal processing, image processing, signal processing for communications, biomedical signal processing, etc.
Since the goal of DSP is usually to measure or filter continuous real-world analog signals, the first step is usually to convert the signal from an analog to a digital form, by using an analog to digital converter. Often, the required output signal is another analog output signal, which requires a digital to analog converter.

Digital Signal Processors:

The algorithms required for DSP are sometimes performed using specialized computers, which make use of specialized microprocessors called digital signal processors by electronics manufacturers such as Texas Instruments, Analog Devices and Motorola. These process signals in real time and are generally purpose-designed application-specific integrated circuits (ASICs). When flexibility and rapid development are more important than unit costs at high volume, DSP algorithms may also be implemented using field-programmable gate arrays (FPGAs).

DSP Techniques and Algorithms:

Although some of the mathematical theory underlying DSP techniques, such as Fourier and Hilbert Transforms, digital filter design and signal compression, can be fairly complex, the numerical operations required actually to implement these techniques are very simple, consisting mainly of operations that could be done on a cheap four-function calculator. The architecture of a DSP chip is designed to carry out such operations incredibly fast, processing hundreds of millions of samples every second, to provide real-time performance: that is, the ability to process a signal "live" as it is sampled and then output the processed signal, for example to a loudspeaker or video display. All of the practical examples of DSP applications mentioned earlier, such as hard disc drives and mobile phones, demand real-time operation.


Fourier transform (in the form of FFT) is a very commonly used technique for analyzing and filtering digital signals. FFT is not very optimal in many filtering applications because it assumes that the frequency spectrum is not changing over time. There are other digital-signal-processing (DSP) techniques that are more advantageous for filtering a real-world signal. The infinite-impulse-response (IIR) and finite-impulse-response (FIR) filters can be implemented very inexpensively, and they work on continuous stream of data. The wavelet transform is worth investigating new technique for signal analyzing and filtering. Like the FFT, wavelet transform converts time-domain data into the frequency domain. The wavelet transform assumes that the frequency spectrum is changing over time. The result of a wavelet transform is a bit harder to read, but more meaningful for many applications.There are also many other relevant signal processing techniques targeted for different kind of applications.

Related Sites:

• Signal processing
• MATLAB DSP Signal Processing Toolbox
• Fourier transform
• Digital Signal Processors

Embedded systems

I was just browsing on Embedded systems for real time applications just publishing some basic information I infered.

Role in day-to-day life:

Embedded systems are playing important roles in our lives every day, even though they might not necessarily be visible. Some of the embedded systems we use every day control the menu system on television, the timer in a microwave oven,Traffic Lights,video game console,PDA,Digital Cameras,DVD Player,Cellphone, an MP3 player or any other device with some amount of intelligence built-in. Embedded systems is a rapidly growing industry where growth opportunities are numerous.

What's Embedded system?

An Embedded system is a special-purpose computer system designed to perform one or a few dedicated functions, sometimes with real-time computing constraints. It is usually embedded as part of a complete device including hardware and mechanical parts. In contrast, a general-purpose computer, such as a personal computer, can do many different tasks depending on programming. Since the embedded system is dedicated to specific tasks, design engineers can optimize it, reducing the size and cost of the product, or increasing the reliability and performance.

The software written for embedded systems is often called firmware, and is stored in read-only memory or Flash memory chips rather than a disk drive. It often runs with limited computer hardware resources: small or no keyboard, screen, and little memory.

Because the tasks must solve diverse problems, a language general-purpose enough to solve them all would be difficult to write, analyze, and compile. Instead, a variety of languages have evolved, each best suited to a particular problem domain. For example, a language for signal processing is often more convenient for a particular problem than, say, assembly, but might be poor for control dominated behavior.

Languages used :

The languages used may be hardware, software,dataflow and hybrid languages, each of which excels a certain problems.Hardware languages for hardware description and modeling.Software languages describe sequences of instructions for a processor to execute. Dataflow languages are good for signal processing,and hybrid languages combine ideas from the other three classes.

Related sites:

• Embedded Internet
• Embedded Systems
• Embedded System Design
• Design Languages for Embedded Systems