08-09-2016, 12:28 PM
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1.1 INTRODUCTION
Wireless Local Area Network (WLAN) is very interesting and a gee-whiz factor to know how computers send and receive the information across the communication links. Computers do this job by the help of data communication software (802.11). It is the software that enables computers to communicate with each other. The data transmission software is for-fee, which tells the devices and computers how to send information to the other computers. The software that is used for the data transmission is known as protocol. The data transmission software or protocols perform the following basic functions.
Data sequencing, Data Routing, Flow control, Error Control etc., The transmission modes are simplex, half-duplex and full duplex and basic type of computer networks are Local Area Network (LAN), Wide Area Network (WAN) and Metropolitan Area Network (MAN)[5]. Wireless Networks are the computer networks that communicate through the use of the radio waves and the standard for this purpose is the Institute of Electrical and Electronics Engineers (IEEE) 802.11x. Currently there are three 802.11standards a, b and g mostly used. 802.11b was the first Wi-Fi standard and has a maximum speed of 11 Mbps. A wireless local area network links two or more computers or devices using Spread-spectrum techniques.
Spread Spectrum techniques are used most widely used in the transmission technology. Spread spectrums are methods by which electromagnetic energy generated in a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth
xxiii
[39]. These techniques are used for a variety of reasons, including the establishment of secure communications, increasing resistance to natural interference, jamming, and to prevent detection.
A computer network can be divided into a small segment called LAN, networking between computers in a building of an office. MAN networking between two offices in a city and WAN networking between the computers, one is locally placed and the other can be thousands of miles away. The local Area Networking is classified in to two categories. 1. Wired LAN 2.Wireless LAN.
A wireless LAN or WLAN is a wireless local area network, which is the linking of two or more computers without using wires. It uses radio communication to accomplish the same functionality that a wired LAN has. WLAN uses radio waves, micro waves, and laser beams to connect between computers in the wireless local area network. WLAN utilizes spread-spectrum technology based on radio waves to enable communication between devices in a limited area, also known as the basic service set.
This technology is becoming more and more popular, especially with the rapid emergence of small portable devices such as Personal Digital Assistants (PDA) [47]. Data communication is a process of sharing data and shared resources between two or more connected computers. The shared resources can include printer, Compact Disks or Digital Versatile Disk (CD/DVD) Rom, Database and the data files [36]. Data flow or communication can be divided into seven logical layers called Open System Interconnection (OSI) layers model that was standardized by International Standard Organization (ISO).
Wireless networking was first developed by the Australian Commonwealth Scientific and Industrial Research Organization (CSIRO), who as of 2006 is engaged in a controversial battle with software and hardware giant’s looking to undermine the royalties of the patents held by CSIRO on these technologies [31] [32].
1.3 BENEFITS OF WIRELESS LAN
Wireless LANs offer users an array of benefits ranging from cost efficiency to seamless integration with other networks. The benefits Wireless LANs include:
xxv
1. Deployment advantages: Installation flexibility, speed and scalability
2. Wireless networks have a better chance of surviving disasters
3. 802.11 Wireless LANs, Worldwide Interoperability for Microwave Access (Wi-MAX) and third generation (3G) + cellular networks.
1.4 ARCHITECTURE OF WIRELESS LAN
This type of network allows wireless devices to directly
communicate with each other. Wireless devices within range of each other can discover and communicate directly without involving central access points. The architecture of the network is shown in Fig.1.2.
If you have a strength meter for the signal coming from all the other ad-hoc devices the meter will not read the strength accurately, and can be misleading, because it is registering the strength of the strongest signal, such as the closest computer
1.5 COMPARISION BETWEEN WLAN AND WIRED LAN
Wireless Local Area Networks (WLAN) have become common in organizations and home use. Most of the leading organization of the world tries to implement the Wi-Fi standards. The price of the wireless equipment is no longer a problem for home users. How good and reliable is the wireless network compared to a traditional wired one? Which choice is the better one? The following aspects describe some advantages and disadvantages of wireless networks [29] [30].
1.5.1 Flexibility of WLAN
Wireless networks have many advantages compared to wired networks. One of the advantages of wireless network is its flexibility. The radio waves go through the walls (or wooden floors, typically maximum of 2m) and the wireless computer can be anywhere within range of an access point (up to 100 feet for 802.11b with few obstructions) [60].
1.5.2 Easy to Use
The wireless networks are superficially very easy to set-up and use. Just plug-in a base station and equip your laptops with wireless LAN cards (or purchase new Laptops with built in WLAN capability). This is seen as a big advantage, however ignoring the need to configure the Wireless LAN with the same care as a wired network is one of the main reasons.
1.5.3 Planning
Wireless networks have some advantages related to planning. Both types of network must be carefully planned and of course the Wireless base-stations still have to be plugged into the wired LAN at some point. The
xxvii
physical components of wired networks have to be planned carefully while wireless networks are much easier in that sense [16]. Using simple planning it is possible to establish the wireless network.
1.5.4 Setting of Equipment
A Wireless LAN can be almost invisible. Equipment can be placed in roof cavities or behind screens. A Wireless LAN is especially suited to sites where a wired network could be very awkward (or expensive) to implement, such as large open spaces, museums and 'one-off' usage [70].
1.5.5 Robustness
Wireless networks can be robust. If one base station goes down, users may be able to physically move their Personal computers (PCs) to be in range of another. It is also possible to site base stations with overlapping ranges so that users can remain connected if one base station goes down, although this is more expensive and requires careful planning. However wireless networks can suffer from radio-interference from other devices (like microwave ovens), and performance can collapse when too many users attempt to use the same access point [42].
1.5.6 Safety and Security
Security is a major concern in any type of networks. The fact that someone can sit in the car park , pick-up and store all of a business's wireless traffic, and crack the most common implementation of wireless encryption in less than a week has to be a concern to any business operation [19] [1]. Wireless Fidelity (Wi-Fi) Wireless Protected Access (WPA) is now available in most access points and provides adequate security for most purposes [27].
1.1 INTRODUCTION
Wireless Local Area Network (WLAN) is very interesting and a gee-whiz factor to know how computers send and receive the information across the communication links. Computers do this job by the help of data communication software (802.11). It is the software that enables computers to communicate with each other. The data transmission software is for-fee, which tells the devices and computers how to send information to the other computers. The software that is used for the data transmission is known as protocol. The data transmission software or protocols perform the following basic functions.
Data sequencing, Data Routing, Flow control, Error Control etc., The transmission modes are simplex, half-duplex and full duplex and basic type of computer networks are Local Area Network (LAN), Wide Area Network (WAN) and Metropolitan Area Network (MAN)[5]. Wireless Networks are the computer networks that communicate through the use of the radio waves and the standard for this purpose is the Institute of Electrical and Electronics Engineers (IEEE) 802.11x. Currently there are three 802.11standards a, b and g mostly used. 802.11b was the first Wi-Fi standard and has a maximum speed of 11 Mbps. A wireless local area network links two or more computers or devices using Spread-spectrum techniques.
Spread Spectrum techniques are used most widely used in the transmission technology. Spread spectrums are methods by which electromagnetic energy generated in a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth
xxiii
[39]. These techniques are used for a variety of reasons, including the establishment of secure communications, increasing resistance to natural interference, jamming, and to prevent detection.
A computer network can be divided into a small segment called LAN, networking between computers in a building of an office. MAN networking between two offices in a city and WAN networking between the computers, one is locally placed and the other can be thousands of miles away. The local Area Networking is classified in to two categories. 1. Wired LAN 2.Wireless LAN.
A wireless LAN or WLAN is a wireless local area network, which is the linking of two or more computers without using wires. It uses radio communication to accomplish the same functionality that a wired LAN has. WLAN uses radio waves, micro waves, and laser beams to connect between computers in the wireless local area network. WLAN utilizes spread-spectrum technology based on radio waves to enable communication between devices in a limited area, also known as the basic service set.
This technology is becoming more and more popular, especially with the rapid emergence of small portable devices such as Personal Digital Assistants (PDA) [47]. Data communication is a process of sharing data and shared resources between two or more connected computers. The shared resources can include printer, Compact Disks or Digital Versatile Disk (CD/DVD) Rom, Database and the data files [36]. Data flow or communication can be divided into seven logical layers called Open System Interconnection (OSI) layers model that was standardized by International Standard Organization (ISO).
Wireless networking was first developed by the Australian Commonwealth Scientific and Industrial Research Organization (CSIRO), who as of 2006 is engaged in a controversial battle with software and hardware giant’s looking to undermine the royalties of the patents held by CSIRO on these technologies [31] [32].
1.3 BENEFITS OF WIRELESS LAN
Wireless LANs offer users an array of benefits ranging from cost efficiency to seamless integration with other networks. The benefits Wireless LANs include:
xxv
1. Deployment advantages: Installation flexibility, speed and scalability
2. Wireless networks have a better chance of surviving disasters
3. 802.11 Wireless LANs, Worldwide Interoperability for Microwave Access (Wi-MAX) and third generation (3G) + cellular networks.
1.4 ARCHITECTURE OF WIRELESS LAN
This type of network allows wireless devices to directly
communicate with each other. Wireless devices within range of each other can discover and communicate directly without involving central access points. The architecture of the network is shown in Fig.1.2.
If you have a strength meter for the signal coming from all the other ad-hoc devices the meter will not read the strength accurately, and can be misleading, because it is registering the strength of the strongest signal, such as the closest computer
1.5 COMPARISION BETWEEN WLAN AND WIRED LAN
Wireless Local Area Networks (WLAN) have become common in organizations and home use. Most of the leading organization of the world tries to implement the Wi-Fi standards. The price of the wireless equipment is no longer a problem for home users. How good and reliable is the wireless network compared to a traditional wired one? Which choice is the better one? The following aspects describe some advantages and disadvantages of wireless networks [29] [30].
1.5.1 Flexibility of WLAN
Wireless networks have many advantages compared to wired networks. One of the advantages of wireless network is its flexibility. The radio waves go through the walls (or wooden floors, typically maximum of 2m) and the wireless computer can be anywhere within range of an access point (up to 100 feet for 802.11b with few obstructions) [60].
1.5.2 Easy to Use
The wireless networks are superficially very easy to set-up and use. Just plug-in a base station and equip your laptops with wireless LAN cards (or purchase new Laptops with built in WLAN capability). This is seen as a big advantage, however ignoring the need to configure the Wireless LAN with the same care as a wired network is one of the main reasons.
1.5.3 Planning
Wireless networks have some advantages related to planning. Both types of network must be carefully planned and of course the Wireless base-stations still have to be plugged into the wired LAN at some point. The
xxvii
physical components of wired networks have to be planned carefully while wireless networks are much easier in that sense [16]. Using simple planning it is possible to establish the wireless network.
1.5.4 Setting of Equipment
A Wireless LAN can be almost invisible. Equipment can be placed in roof cavities or behind screens. A Wireless LAN is especially suited to sites where a wired network could be very awkward (or expensive) to implement, such as large open spaces, museums and 'one-off' usage [70].
1.5.5 Robustness
Wireless networks can be robust. If one base station goes down, users may be able to physically move their Personal computers (PCs) to be in range of another. It is also possible to site base stations with overlapping ranges so that users can remain connected if one base station goes down, although this is more expensive and requires careful planning. However wireless networks can suffer from radio-interference from other devices (like microwave ovens), and performance can collapse when too many users attempt to use the same access point [42].
1.5.6 Safety and Security
Security is a major concern in any type of networks. The fact that someone can sit in the car park , pick-up and store all of a business's wireless traffic, and crack the most common implementation of wireless encryption in less than a week has to be a concern to any business operation [19] [1]. Wireless Fidelity (Wi-Fi) Wireless Protected Access (WPA) is now available in most access points and provides adequate security for most purposes [27].