Advances in wireless networking have prompted a new concept of computing, called mobile? computing? in? which? users? carrying? portable? devices? have? access? to? a? shared infrastructure, independent of their physical location. Mobile computing has fast become an crucial fresh prototype in nowadays world of networked computing systems. This provides flexible? communication between people and continuous access to networked services. Mobile computing is revolutionizing the way computers are used and in the coming years this will become even more? perceptible? although? many? of? the? devices? themselves? will? become? smaller? or? even invisible to users. This paper explicate different types of? mobile system ?that are used in distributed environment. It also explains mobility service architecture, technology, application and demerits of mobile computing. Finally, this paper explains the future direction of mobile computing.
?????????? A technology that allows transmission of data, via a computer, without having to be connected to a fixed physical link. Mobile computing has three aspects: mobile communication, mobile hardware, and mobile software. The first aspect addresses communication issues in ad-hoc and infrastructure networks as well as communication properties, protocols, data formats and concrete technologies. The second aspect is on the hardware, e.g., mobile devices or device components. The third aspect deals with the characteristics and requirements of mobile applications. Mobile voice communication is widely established throughout the world and has had a very rapid increase in the number of subscribers to the various cellular networks over the last few years. An extension of this technology is the ability to send and receive data across these cellular networks. This is the principle of mobile computing. Mobile data communication has become a very important and rapidly evolving technology as it allows users to transmit data from remote locations to other remote or fixed locations. This proves to be the solution to the biggest problem of business people on the move - mobility.
Mobile computing has several characteristics reminiscent of distributed systems. The following section is an explanation of the different types of distributed systems ranging from the traditional type to nomadic, ad-hoc and finally ubiquitous ones.
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TRADITIONAL DISTRIBUTED SYSTEM
Traditional distributed systems consist of a collection of fixed hosts that are themselves attached to a network? if hosts are disconnected from the network this is considered to be abnormal whereas in a mobile system this is quite the norm. These hosts are fixed and are usually very? powerful? machines? with? fast? processors? and? large? amount? of? memory.? The bandwidth in traditional systems is very high too. In a traditional system, location rarely changes as well and hosts are much less likely to be added or deleted from the network.
Traditional distributed? systems also need to guarantee non-functional requirements such? as? scalability? (accommodate? a? higher? load? at? some? time? in? the? future),? openness (possibility to extend and modify the system easily), heterogeneity (integration of components written? using? different? programming? languages,? running? on ?different? operating? systems, executing on different hardware platforms), fault-tolerance (recover from faults without halting the whole system) and finally resource-sharing (some form of access control).
NOMADIC DISTRIBUTED SYSTEM
This kind of system is composed of a set of mobile devices and a core infrastructure with fixed and wired nodes. Mobile devices move from location to location, while maintaining a connection to the fixed network. The mobile host has a home IP address and thus any packets? sent to the mobile host will be delivered to the home network and not the foreign network where the mobile host is currently located. Such problem can be solved by forwarding packets to the foreign network with the help of Mobile IP. Nevertheless, Mobile IP also suffers from efficiency (routing issues), QoS, security (authentication of mobile host at foreign network and end-to-end security required) and wireless access (reduced capacity) problems.
The non-functional requirements mainly differ, compared to the traditional distributed systems,? in? the? heterogeneity (affected? by? the? presence? of? both? fixed? and mobile devices across the network as well as the variations in technologies (e.g.: wireless)), resource sharing (must take into account different issues when the resources need to be discovered) and fault tolerance of? the? system (considered to? be quite the norm).
AD-HOC MOBILE DISTRIBUTED SYSTEM
Ad-hoc distributed systems are possibly the only type of network that comes close to mobile networks in the sense that every node is literally mobile. When nodes are detached from the fixed/mobile network they may evolve independently and? groups of? hosts? opportunistically form ?clusters? of mini-networks. A-hoc? systems? do? not? have? any? fixed? infrastructure? which? differs? them? both? from traditional and nomadic distributed systems. Security threats have to be dealt even more cautiously in ad-hoc networks.? Designing secure key distribution in an ad-hoc network might be an extremely hard task.
PORTABLE COMPUTING DEVICES:
A Portable computer is a general-purpose computer that can be easily moved from place to place, but cannot be used while in transit, usually because it requires some "setting- up" and an AC power source. The most famous example is the Osborne 1. Portable ?computers are also called a "transportable" or a "luggable" PC .A Tablet PC that lacks a ?keyboard (also known as a non-convertible Tablet PC) is shaped like slate or a paper ?notebook, features a touch-screen with a stylus and handwriting recognition software. An? Internet tablet is an Internet appliance in tablet form. Unlike a Tablet PC, an ?Internet tablet does not have much computing power and its applications suite is limited, and ?it cannot replace a general purpose computer. Internet tablets typically feature an MP3 and video player, a web browser, a chat application and a picture viewer.
MOBILE COMPUTING IS VERSATILE
Mobile computing is an extremely versatile technology. It can be instrumental in: (a) process reengineering; (b) reducing operational and administrative staff; (c) improving communications; (d) improving customer service; (e) reducing manufacturing costs; (f) shortening business cycles; and (g) many other benefits. The variety of hardware, software, and communications systems available and the many ways they can be integrated to solve problems add to the versatility of mobile computing. The versatility of mobile computing will continue to expand over the next few years as a predicted proliferation of new mobile computing devices and the expanded usage of existing devices comes to fruition.
LATEST TRENDS IN MOBILE COMPUTING:
Mobile computing devices are becoming smaller, lighter, and more powerful than their predecessors. They also come in various types and connectivity options. Two prominent classes of mobile computing devices today are those that use the PalmOS and the Pocket PC operating systems. These devices are capable of simple word processing, spreadsheet applications, web browsing, calendar notations, and address management. There are also low-end handheld computers with monochromatic displays, low resolution, limited memory, and somewhat bulky sizes. Higher-end devices are extremely thin, have a high-resolution, and can include color displays.Download your Full Reports for Mobile Computing
TECHNOLOGY IN MOBILE COMPUTING:
Recently, the free Linux operating system has been modified to run on handheld computers of different types. Some manufacturers are also adopting Linux for their handheld computers. As this operating system carries no licensing fee, it could further reduce the cost of handheld computers. In developing countries like India, voice activated Linux-based simputers have been developed for mass usage in rural areas where the computing infrastructure is limited. Device integration, such as the integration of cell phones and handheld computers, is also occurring. Location aware mobile computing?in which a person is able to obtain information on local restaurants, theaters, coffee-shops, maps, driving directions, traffic, weather, news, tourist attractions, and the like on a handheld computer?is also becoming prominent.
Wireless connectivity for handheld computers also comes in several varieties. Most handheld computers come with built-in infrared ports that can be used to exchange information with a network or another computer at short range. Many of them can connect to wireless local area networks (LANs) based on the IEEE 802.11 standard. Some cellular telephone service providers are also making cell phone modules available for attachment to the expansion slots of handhelds computers. Bluetooth, a new wireless standard for personal area networking , is also available for some handheld computers. Wireless technologies, includes 802.11b, otherwise known as Wi-Fi, Infrared Data Association (IrDA), Ultra-Wideband Radio (UWB), and Home RF are being applied to similar technologies that Bluetooth use with mixed results.
802.11 is the most well known technology, excluding Bluetooth, and uses the same radio frequency, meaning that they are not compatible as they cause interference with each other. 802.11 is being implemented into universities in the US, Japan and China, as well as food and beverage shops where they are being used to identify
students and customers. Even airports have taken up the 802.11 technology, with airports all over America, and three of America?s most prominent airlines promoting the use of it.
Infrared Data Association is extremely inferior to that of Bluetooth. Its limitations include only being able to communicate point-to-point, needing a line of sight, and it has a speed of fifty- six kilobytes per second, whereas Bluetooth is one megabyte per second. The Ultra- Wideband Radio is superior to that of Bluetooth in that it can transmit at greater lengths (up to 70 meters), with only half of the power that Bluetooth uses. HomeRF is a technology that is not very well known. It is used for data and voice communication and targeted for the residential market segment and does not serve enterprise- class. WLANs, public access systems or fixed wireless Internet access.
MOBILE COMPUTING ? BUSINESS APPLICATIONS
Much of the advances in mobile computing are currently focused on business applications. The technology available and being developed is designed to increase productivity, efficiency and connectivity for workers in a range of fields from retail to professional. The advent of wireless networking has created new opportunities in the design of instructional space. Computing systems are currently present in many forms of customer service, mobile computing has the potential to have applications for a greater range of these businesses. Traveling sales representatives have the potential to offer consumers a demonstration of their product, simply through the use of a PDA(Personal Digital Assistants), wireless laptop, or other mobile device.
DEMERITS IN MOBILE COMPUTING
Devices such as PDAs, smart phones and wireless laptops, along with the necessary peripherals should be easily upgraded to ensure businesses can remain current and effective. Further adoption of mobile computing should see the initial cost of investment for businesses fall, as the products become readily available and widely used.
Mobile computers offer many new options, however there are difficulties to consider. Generally, wireless laptops cost 50% to 100% more than their desktop counterparts. Laptops are also harder to upgrade most proprietary hardware components that limit future options. The cost of setup for mobile computing varies depending on the number of employees, and the hardware required. The initial investment in this technology remains risky, as the market is rapidly changing and improving.
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