How Does a WiFi Work?


The term Wi-Fi technology is become common now a days. Wi-Fi is the short form of wireless fidelity. The emergence of Wi-Fi technology replaces most of the wired technology from the field of communication. This article is mainly intended to make you understand the working of Wi-Fi technology and also the terminologies associated with it.

Introduction


The term Wi-Fi technology is become common now a days. The wired technology is now becoming a threat to the Wi-Fi technology. The Wi-Fi technology replaces most of the wired technology from the field of communication. The Wi-Fi network is used to connect the devices such as PC and laptops in a wireless mode. The term Wi-Fi is abbreviated as Wireless Fidelity. The IEEE 802.11 is the standards which are set for the communication network such as Wireless Local Area Networks. The computers can be interlinked to the internet using the Wi-Fi network.

The Wi-Fi Technology


The radio technology is held responsible for transmission and reception of datas over the Wi-Fi Networks at a high data speed. The standards set for the Wi-Fi technology is as follows:
  • IEEE 802.11b
  • IEEE 802.11a
  • IEEE 802.11g


IEEE 802.11b
The IEEE 802.11b is introduced in the year of 1999. The operating frequency of the radio spectrum is around 2.4GHz. The Wi-Fi network is having a high speed of 11 Mbps. It is just the theoretical value. But the actual speed of this network is around 4-6 Mbps. The devices can be operated within the range of 100 -150 feet. This became popular because of the fact that they are actually cheaper. The transmission speed of the Wi-Fi network gets affected by the interference due to the devices such as mobile phones and radio.

IEEE 802.11a
The IEEE 802.11b is introduced in the year of 2001. The operating frequency of the radio spectrum is around 5GHz. It is not much popular around the world. This Wi-Fi network is having a high speed of 54 Mbps. It is just the theoretical value. Its actual value ranges between 15-20 Mbps. The devices can be operated within the range of 50-75 feet. The IEEE 802.11a is somewhat expensive. The IEEE 802.11a is not at all compatible with 802.11b.

IEEE 802.11g
The IEEE 802.11g is introduced in the year of 2003. It is actually the combination of the features of IEEE 802.11b and IEEE 802.11a. These devices can be operated within the range of 50-75 feet. This Wi-Fi network is having a high speed of 54 Mbps. The operating frequency of the radio spectrum is around 2.4GHz. it is compatible with IEEE 802.11b.

Physical Layer of 802.11


The physical layer of 802.11 composed of mainly three sub layers. They are as follows:
  • Direct Sequence Spread Spectrum
  • Frequency Hoping Spread Spectrum
  • Diffused Infrared - Wide angle

Direct Sequence Spread Spectrum of WiFi
The Direct Sequence Spread Spectrum have a total frequency of 2.4 GHz. It is divided into 11 channels. Each channel is having a frequency band of 22 MHz. Out of the 11 channels, the layers lying adjacently overlap with each other. But three of them will not overlap. The data in the WiFi network is sent over these channels without any frequency hopping.

Data Link Layer of IEEE 802.11 WiFi network.


The main two sub layers associated with the Data Link Layer of IEEE 802.11 are as follows:
  • LLC
  • MAC

The LLC can be abbreviated as Logical Link Control and MAC as Media Access Control. The LLC is common to all 802 type LANs. But for the wireless LAN, the MAC is unique.

Media Access Control of WiFi


There are several terminologies used in the media access control of a 802.11 WiFi network. They are as follows:
  • CSMA/CA
  • RTS/CTS
  • Power Management
  • Power Management
  • CRC checksum
  • Association & Roaming

The CSMA/CA can be abbreviated as Carrier Sense Medium Access with collision avoidance protocol. In this technique, the ACK packets undergo additional overhead. This is the main problem of it. But the collisions are avoided using the technique of explicit Acknowledgement. The RTS/CTS can be abbreviated as Request to Send/Clear to send protocol. The as Request to Send/Clear to send protocol is the perfect solution for the problems caused by the hidden node. But this too had some disadvantages. Under Power Management scheme, the battery life of the devices which can be carry along is conserved by MAC. There are two modes in the power management system. They are Power Save Polling Mode and Continuous Aware Mode. In Continuous Aware Mode, the drawing power will be the Radio power. In the CRC checksum, there exist a technique evaluate whether the data is lost or corrupted during the time of transmission.

How a Wi-Fi Network Works


The main elements of a WiFi network are as follows:
  • Access Point (AP)
  • Wi-Fi cards
  • Safeguards

Access Point: It can be simply defined as a base station. Without Access Points, the wireless devices cannot be connected to the internet.
Wi-Fi cards: the Wi-Fi cards are used to transmit or receive wireless signals. They are of two types namely internal and external.
Safeguards: These are the softwares used to secure the information over the WiFi channel.
The Walkie talkies are having the same technology as that of the WiFi technology. At first, an access point is installed to a specified internet connection. The WiFi hotspot is thus created by this method. The activities of a base station are done using the access points. Hotspot is held responsible for establishing the wireless connection between the internet and the WiFi enabled devices. Around 30 users can be accommodated under a single access point. Many access points can be interlinked to form a large network.

Network Topologies of Wi-Fi


The Wi-Fi network is mainly based on three topologies. They are as follows:
  • Infrastructure Mode
  • Ad-hoc Mode
  • Point-to-multipoint bridge topology


Infrastructure Mode


The Infrastructure Mode is also known as the AP-based topology. The access point is held responsible for the communication between the clients. The access point provides BSA-RF coverage. The roaming is made by overlapping two ESA cells. The ESA cells are composed of more than two BSA.

Ad-hoc Mode


The common name for the Ad-hoc Mode is the Peer-to-peer topology. The main advantage of the Peer-to-peer topology is that the access point is not required. Wireless network of this kind can be set up easily. It is possible for the clients to communicate each other without the help of any intermediate network.

Point-to-multipoint bridge topology


The Point-to-multipoint bridge topology is mainly used to interlink the LAN network in a building with that of the other building. By this technique, buildings separated by a huge distance can also be interlinked. The technique used here is the line of sight method. The line of sight range purely depends on the type of antenna installed and the type of wireless bridge used. Another factor contribute to it is the environmental condition.
The different types of Wi-Fi Configurations used now a days are as follows:
  • Home/SOHO network
  • Simple wireless network
  • Combined wireless network


Applications of Wi-Fi


The Wi-Fi network is being used in several areas. The main fields where there are huge applications for Wi-Fi is listed below:
1. For personal/home use.
2. For SOHO/small business purposes.
3. In the field of health care.
4. In the campuses of educational institutions and corporate offices
5. For the travellers
6. Can be used as a Wireless ISP or simply called as a WISP

Security Threats for Wi-Fi


Along with the conventional security issues related with the wireless technology, the Wi-Fi introduces many more other security threats. The major threats associated with a Wi-Fi network are as follows:
  • Eavesdropping: it can be performed easier. The main problem is that it cannot be detected easily. Since the transmission medium offers no security, the passwords and usernames are stolen. Different tools such as protocol analysers and Network sniffers are available over the internet to crack the password.
  • Man-in-the-middle attacks: This attack is simply known as MITM Attack. In this technique, the attacker uses the victim”s MAC address to connect to the actual AP of the user.
  • Denial of Service: this method mainly involves processes such as the attacker attacks the transmission frequecy. It includes the jamming of the frequency. They also perform attacks on the TCP/IP protocol and the MAC layer attack by the method of SYN Flooding


Security Techniques used by Wi-Fi networks


The Wi-Fi networks uses two main things during the security process. They are:
1. User Authentication and Server Authentication
2. Privacy
The User Authentication and Server Authentications are used to make the network inaccessible to the unauthorized users.
The main Security Techniques used by the Wi-Fi networks are as follows:
  • 802.1X Access Control
  • Wired Equivalent Privacy (WEP)
  • Service Set Identifier (SSID)
  • IEEE 802.11i
  • Wireless Protected Access (WPA)

The SSID identifies the 802.11 network. The WEP is used in order to provide the same security level that we enjoy in the wired network. The WPA provides additional security for the data to be transmitted.

Advantages and Limitations of Wi-Fi networks


The main advantages of the Wi-Fi networks are the speed of the Wi-Fi networks, Roaming, Reliability , Flexibility, Ease of Installation, Security, Ease of Installation etc. The main disadvantages of the Wi-Fi networks include the High power consumption, Interference, Limited range and the Degradation in performance.

Top 8 Vendors of WI-Fi modems


The top manufactures of the WI-Fi modems are as follows:
  • D-Link
  • Proxim
  • Enterasys
  • Aruba Networks
  • Netgear
  • Linksys
  • Cisco
  • Avaya


Conclusion



The term Wi-Fi is the short form of wireless fidelity. It uses networks such as 802.11b, 802.11a, 802.11g, dual-band, etc. The radio frequency is used by the Wi-Fi networks for the transmission of data in the Wi-Fi networks. This Wi-Fi networks have both advantages and disadvantages. But it is being widely used now a days.


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Comments

Author: Vandana29 Apr 2012 Member Level: Platinum   Points : 0

Well-researched and presented. Good work.



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