02-05-2013, 02:41 PM
MOBILE AD-HOC NETWORKS
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ABSTRACT:
MOBILE AD-HOC NETWORKS has fast become an important new paradigm in today's world of networked computing systems. Ranging from wireless laptops to cellular phones and WiFi/Bluetooth-enabled PDAs to wireless sensor networks, MOBILE AD-HOC NETWORKS has become ubiquitous in its impact on our daily lives. The debut if iPhones and the proliferation of other handheld devices has spurred excitement and interest in this evolving field. In this seminar, we will study the state-of-the-art in both the research and commercial communities with respect to MOBILE AD-HOC NETWORKS. We will investigate standard protocols and platforms, the capabilities of today's commercial devices, and proposed next-generation solutions. In the process, we will seek to gain an improved understanding about where the field is headed, and what is the importance in the MOBILE AD-HOC NETWORKS.
INTRODUCTION:
MOBILE AD-HOC NETWORKS : A technology that allows transmission of data, via a computer, without having to be connected to a fixed physical link.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 across these cellular networks. This is the principle of MOBILE AD-HOC NETWORKS. 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. In this article we give an overview of existing cellular networks and describe in detail the CDPD technology which allows data communications across these networks. Finally, we look at the applications of MOBILE AD-HOC NETWORKS in the real world.
EXISTING CELLULAR NETWORK ARCHITECTURE:
Mobile telephony took off with the introduction of cellular technology which allowed the efficient utilisation of frequencies enabling the connection of a large number of users. During the 1980's analogue technology was used. A cellular network consists of mobile units linked together to switching equipment, which interconnect the different parts of the network and allow access to the fixed Public Switched Telephone Network (PSTN). The technology is hidden from view; it's incorporated in a number of tranceivers called Base Stations (BS). Every BS is located at a strategically selected place and covers a given area or cell - hence the name cellular communications. A number of adjacent cells grouped together form an area and the corresponding BSs communicate through a so called Mobile Switching Centre (MSC). The MSC is the heart of a cellular radio system. It is responsible for routing, or switching, calls from the originator to the destinator. It can be thought of managing the cell, being responsible for set-up, routing control and termination of the call,
MOBILE SWITCHING CENTRE:
The frequencies used vary according to the cellular network technology implemented. For GSM, 890 - 915 MHz range is used for transmission and 935 -960 MHz for reception. The DCS techology uses frequencies in the 1800MHz range while PCS in the 1900MHz range.Each cell has a number of channels associated with it. These are assigned to subscribers on demand. When a Mobile Station (MS) becomes 'active' it registers with the nearest BS. The corresponding MSC stores the information about that MS and its position. This information is used to direct incoming calls to the MS. If during a call the MS moves to an adjacent cell then a change of frequency will necessarily occur - since adjacent cells never use the same channels. This procedure is called hand over and is the key to Mobile communications. As the MS is approaching the edge of a cell, the BS monitors the decrease in signal power. The strength of the signal is compared with adjacent cells and the call is handed over to the cell with the strongest signal. During the switch, the line is lost for about 400ms. When the MS is going from one area to another it registers itself to the new MSC. Its location information is updated, thus allowing MSs to be used outside their 'home' areas.
CDPD TECHNOLOGY:
Today, the mobile data communications market is becoming dominated by a technology called CDPD. There are other alternatives to this technology namely Circuit Switched Cellular, Specialised Mobile Radio and Wireless Data Networks. As can be seen from the table below the CDPD technology is much more advantageous than the others. CDPD's principle lies in the usage of the idle time in between existing voice signals that are being sent across the cellular networks. The major advantage of this system is the fact that the idle time is not chargeable and so the cost of data transmission is very low. CDPD networks allow fixed or mobile users to connect to the network across a fixed link and a packet switched system respectively. In the case of a mobile end user, the user can, if CDPD network facilities are non-existent, connect to existing circuit switched networks and transmit data via these networks.
Circuit Switched CDPD
Service coverage is a fundamental element of providing effective wireless solutions to users and using this method achieves this objective. Where CDPD is available data is split into packets and a packet switched network protocol is used to transport the packets across the network. This may be of either Datagram or Virtual Circuit Switching form. The data packets are inserted on momentarily unoccupied voice frequencies during the idle time on the voice signals. CDPD networks have a network hierarchy with each level of the hierarchy doing its own specified tasks.
CONCLUSION:
According to my aims and objectives of this paper I have done the detailed research and get the knowledge about it and the factors that need to be consider carefully. At this stage we are facing different types of problems and threats to the mobile industry, the two major aspects are the security and the usability issue. Detailed analysis of security issues is very important at least for a mobile wireless device, there are numbers of ways that it can be compromised, but I would like to draw an attention on the usability issues as well. They both need to be carefully planned and designed that the mobile user or target audience get used to it easily, effectively and securely.