aVs SEMINARs

ZigBee

2009-08-02T18:22:00.000-07:00

ZigBee is a low-cost, low-power, wireless mesh networking standard. The low cost allows the technology to be widely deployed in wireless control and monitoring applications, the low power-usage allows longer life with smaller batteries, and the mesh networking provides high reliability and larger range.

The ZigBee Alliance, the standards body which defines ZigBee, also publishes application profiles that allow multiple OEM vendors to create interoperable products. The current list of application profiles either published or in the works are:

Home Automation
ZigBee Smart Energy
Commercial Building Automation
Telecommunication Applications
Personal, Home, and Hospital Care

The relationship between IEEE 802.15.4 and ZigBee is similar to that between IEEE 802.11 and the Wi-Fi Alliance. The ZigBee 1.0 specification was ratified on 14 December 2004 and is available to members of the ZigBee Alliance. Most recently, the ZigBee 2007 specification was posted on 30 October 2007. The first ZigBee Application Profile, Home Automation, was announced 2 November 2007.

ZigBee is a specification for a suite of high level communication protocols using small, low-power digital radios based on the IEEE 802.15.4-2003 standard for wireless personal area networks (WPANs), such as wireless headphones connecting with cell phones via short-range radio. The technology defined by the ZigBee specification is intended to be simpler and less expensive than other WPANs, such as Bluetooth. ZigBee is targeted at radio-frequency (RF) applications that require a low data rate, long battery life, and secure networking.The ZigBee Alliance is a group of companies which maintain and publish the ZigBee standard.For non-commercial purposes, the ZigBee specification is available free to the general public. An entry level membership in the ZigBee Alliance, called Adopter, costs US$3500 annually and provides access to the as-yet unpublished specifications and permission to create products for market using the specifications.

ZigBee operates in the industrial, scientific and medical (ISM) radio bands; 868 MHz in Europe, 915 MHz in the USA and Australia, and 2.4 GHz in most jurisdictions worldwide. The technology is intended to be simpler and less expensive than other WPANs such as Bluetooth. ZigBee chip vendors typically sell integrated radios and microcontrollers with between 60K and 128K flash memory, such as the Freescale MC13213, the Ember EM250 and the Texas Instruments CC2430. Radios are also available stand-alone to be used with any processor or microcontroller. Generally, the chip vendors also offer the ZigBee software stack, although independent ones are also available.

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Biocomputers

2009-07-29T07:26:00.000-07:00

Biocomputers use systems of biologically derived molecules, such as DNA and proteins, to perform computational calculations involving storing, retrieving, and processing data.

The development of biocomputers has been made possible by the expanding new science of nanobiotechnology. The term nanobiotechnology can be defined in multiple ways; in a more general sense, nanobiotechnology can be defined as any type of technology that uses both nano-scale materials, i.e. materials having characteristic dimensions of 1-100 nanometers, as well as biologically based materials ( A more restrictive definition views nanobiotechnology more specifically as the design and engineering of proteins that can then be assembled into larger, functional structures .The implementation of nanobiotechnology, as defined in this narrower sense, provides scientists with the ability to engineer biomolecular systems specifically so that they interact in a fashion that can ultimately result in the computational functionality of a computer.

The promising field of biocomputer research uses the science behind nano-sized biomaterials to create various forms of computational devices, which may have many potential applications in the future. One day, biocomputers using nanobiotechnology may become the cheapest, most energy-efficient, most powerful, and most economical of any commercially available computer. Already, scientists are making significant headway in the advancement of this science.

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corDECT Wireless Access System

2009-07-24T17:06:00.000-07:00

CorDECT Wireless in Local Loop System is based on Digital Enhanced Cordless Telecommunications (DECT) standard of European Telecommunications standards Institute (ETSI).
The CorDECT Wireless in Local Loop has been designed to be a modular system. The basic unit provides service to 10o00 subscriber. Multiple CorDECT systems can be connected together using a transit switch. The system has been designed in such a way that the initial investment for fixed part is very low and most of the cost is incurred on the Subscriber Unit, which needs to be obtained only when the operator signs up a subscriber. Further since CorDECT Wireless in Local Loop does not require frequency planning the installation need not be coordinated. Thus the low cost marks the system one of the most versatile in Local Loop System available today.

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Content-addressable memory

2009-07-24T16:59:00.000-07:00

Content-addressable memory (CAM) is a special type of computer memory used in certain very high speed searching applications. It is also known as associative memory, associative storage, or associative array, although the last term is more often used for a programming data structure. (Hannum et al., 2004)

Content-addressable memory is often used in computer networking devices. For example, when a network switch receives a data frame from one of its ports, it updates an internal table with the frame's source MAC address and the port it was received on. It then looks up the destination MAC address in the table to determine what port the frame needs to be forwarded to, and sends it out on that port. The MAC address table is usually implemented with a binary CAM so the destination port can be found very quickly, reducing the switch's latency.

Ternary CAMs are often used in network routers, where each address has two parts: the network address, which can vary in size depending on the subnet configuration, and the host address, which occupies the remaining bits. Each subnet has a network mask that specifies which bits of the address are the network address and which bits are the host address. Routing is done by consulting a routing table maintained by the router which contains each known destination network address, the associated network mask, and the information needed to route packets to that destination. Without CAM, the router compares the destination address of the packet to be routed with each entry in the routing table, performing a logical AND with the network mask and comparing it with the network address. If they are equal, the corresponding routing information is used to forward the packet. Using a ternary CAM for the routing table makes the lookup process very efficient. The addresses are stored using "don't care" for the host part of the address, so looking up the destination address in the CAM immediately retrieves the correct routing entry; both the masking and comparison are done by the CAM hardware.

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Cell Phone Cloning

2009-07-24T16:52:00.000-07:00

Cell phone cloning is copying the identity of one mobile telephone to another mobile telephone.

Usually this is done for the purpose of making fraudulent telephone calls. The bill for the calls go to the legitimate subscriber. This made cloning very popular in areas with large immigrant populations, where the cost to "call home" was very steep. The cloner is also able to make effectively anonymous calls, which attracts another group of interested users.

Cell phone cloning started with Motorola "bag" phones and reached its peak in the mid 90's with a commonly available modification for the Motorola "brick" phones, such as the Classic, the Ultra Classic, and the Model 8000.

Cloning involved modifying or replacing the EPROM in the phone with a new chip which would allow you to configure an ESN (Electronic Serial Number) via software. You would also have to change the MIN (Mobile Identification Number).
When you had successfully changed the ESN/MIN pair, your phone was an effective clone of the other phone.
Cloning required access to ESN and MIN pairs. ESN/MIN pairs were discovered in several ways:

* Sniffing the cellular network
* Trashing cellular companies or cellular resellers
* Hacking cellular companies or cellular resellers

Cloning still works under the AMPS/NAMPS system, but has fallen in popularity as older clone-able phones are more difficult to find and newer phones have not been successfully reverse-engineered.
Cloning has been successfully demonstrated under GSM, but the process is not easy and it currently remains in the realm of serious hobbyists and researchers.
Motorola 8000: The most popular cell phone for cloning

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CakePHP

2009-07-24T16:42:00.000-07:00

Cake is an open source web application PHP framework, inspired by the concept of Ruby on Rails. The underlying principle is to help PHP developers avoid reinventing the wheel all the time. Rightway is actively using CakePHP framework for rapid and robust web application development. PHP experts at Rightway have developed some successful Web Projects based on CakePHP framework.

Key Features

Compatible with PHP4 and PHP5
Model, View, Controller (MVC) architecture
Code generation via Bake
Integrated CRUD for database and simplified querying
Request dispatcher with custom URLs
Templating (PHP syntax with helper methods)
View helpers for AJAX, Javascript, HTML forms
Website directory independent
Built-in validation
Access control lists (ACL)
Application scaffolding[4]
Data sanitization
Security, session, and request handling components
View caching

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CAPTCHA

2009-07-24T16:39:00.000-07:00

A CAPTCHA or Captcha (pronounced /ˈkæptʃə/) is a type of challenge-response test used in computing to ensure that the response is not generated by a computer. The process usually involves one computer (a server) asking a user to complete a simple test which the computer is able to generate and grade. Because other computers are unable to solve the CAPTCHA, any user entering a correct solution is presumed to be human. Thus, it is sometimes described as a reverse Turing test, because it is administered by a machine and targeted to a human, in contrast to the standard Turing test that is typically administered by a human and targeted to a machine. A common type of CAPTCHA requires that the user type letters or digits from a distorted image that appears on the screen.

The term "CAPTCHA" (based upon the word capture) was coined in 2000 by Luis von Ahn, Manuel Blum, Nicholas J. Hopper (all of Carnegie Mellon University), and John Langford (then of IBM). It is a contrived acronym for "Completely Automated Public Turing test to tell Computers and Humans Apart." Carnegie Mellon University attempted to trademark the term, the trademark application was abandoned on 21 April 2008., CAPTCHA creators recommend use of reCAPTCHA as the official implementation.

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Aspect-Oriented Programming

2009-07-24T16:32:00.000-07:00

Aspect-oriented programming (AOP) is a programming paradigm that increases modularity by enabling improved separation of concerns. This entails breaking down a program into distinct parts (so-called concerns, cohesive areas of functionality). All programming paradigms support some level of grouping and encapsulation of concerns into separate, independent entities by providing abstractions (e.g. procedures, modules, classes, methods) that can be used to implement, abstract and compose these concerns. But some concerns defy these forms of implementation and are called crosscutting concerns because they "cut across" multiple abstractions in a program.

Logging is a common example of a crosscutting concern because a logging strategy necessarily affects every single logged part of the system. Logging thereby crosscuts all logged classes and methods.

All AOP implementations have some crosscutting expressions that encapsulate each concern in one place. The difference between implementations lies in the power, safety, and usability of the constructs provided. For example, interceptors that specify the methods to intercept express a limited form of crosscutting, without much support for type-safety or debugging. AspectJ has a number of such expressions and encapsulates them in a special class, an aspect. For example, an aspect can alter the behavior of the base code (the non-aspect part of a program) by applying advice (additional behavior) at various join points (points in a program) specified in a quantification or query called a pointcut (that detects whether a given join point matches). An aspect can also make binary-compatible structural changes to other classes, like adding members or parents.

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Airborne Internet

2009-07-24T16:15:00.000-07:00

Airborne Internet refers to installing a broadband network hub in an aircraft flying at 52,000 to 69,000 feet above sea level - high enough to be out of weather disturbances and way outside the flight envelope of commercial aircraft. The aircraft will provide Internet connection to places and establishments within its range.

The Need for Airborne Internet

Airborne Internet is seen as the perfect answer to the demand for fast, reliable access to the Internet as well as quick and easy file 'sharing.' Currently, the problem lies in the physical limitations of the channels used for the purpose: telephone wires, TV cable systems and satellite transmission.

Conventional telephone lines, for example, are capable of transmitting only 56,000 bits (56k) per second under ideal conditions - too slow and often unreliable for large file transmission. Cable or direct subscription lines (DSL) lines can handle up to 100 million bits per second but the service is not widely available; setting up the infrastructure for a land-based broadband network with universal access requires enormous investments in time, money and resources.

Satellite-based Internet provides a way around the 'wired' problem - since data is sent over the air, there are no physical limitations on the amount of data that can be transmitted. The only problem with satellite Internet is a perceivable 'time lag' involved in transmitting data to and from satellites orbiting hundreds of miles above the earth. A second issue is the cost involved in sending an internet-capable satellite out of the earth's atmosphere.
Components and Advantages
Accessing the airborne Internet is relatively simple. The end user (whether individual or company users in residential or commercial areas) will have to have an external antenna which will be provided by an Internet Service Provider with 'wired' and wireless systems which will act as distributors.

The relative proximity of the aircraft virtually eliminates the time lag issue with satellite-based Internet systems. The flight pattern that the aircraft takes ensures coverage of a wide area and a large population of users. Finally, having an Internet hub installed in an aircraft implies that there is no need to set up a 'wired' infrastructure - which reduces the costs involved in Internet access.
An airborne Internet system also provides an answer to the growing legions of mobile Internet users. Having a flying network hub implies a reduction in the cost of setting up a wireless Internet with its network of nodes, ground-based transmitters, etc.

There are at least three US companies working on the airborne Internet concept. One company envisions the use of lighter-than-air crafts (blimps or dirigibles) as their main Internet carriers in the sky. A second company has developed an aircraft specifically for the purpose; this company has identified at least 3,500 cities and towns from which their planes can be based.
All three companies believe their systems will be operational within the first decade of the 21st century. If the idea proves commercially viable, Internet users can expect wider access to broadband Internet sooner than originally planned or anticipated.

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Dual-Band HyperLAN 2

2009-07-24T15:43:00.000-07:00

The IST BroadWay project, [1], introduces the ad-hoc networking paradigm in the traditional 5 GHz HiperLAN/2. The ad-hoc networking paradigm is employed at the 60 GHz
frequency band, which allows for a high transmission rate communication. The dual mode of operation primarily aims at offloading the 5 GHz HiperLAN/2 cell in very dense urban
deployments (high traffic needs and number of users), while the peculiarities of the BroadWay system induce modifications on the existing HiperLAN/2 system and make the development of a routing scheme a rather challenging task. The Centralized Ad-hoc Network Architecture (CANA) is described as a means to efficiently support multimedia applications that require very high bit rates in low mobility environments; several ad-hoc specific functionalities are included such as neighborhood discovery, clustering and route selection. BroadWay introduces
modifications to the MAC of HiperLAN/2 regarding new messages and framing considerations at both frequency bands to cater for the new requirements imposed by the dual mode of
operation.

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