Q01. What is a Wireless LAN or WLAN ?
Q02. What are the main advantages of Wireless LANs ?
Q03. What are the disadvantages of Wireless LANs ?
Q04. What are the benefits of using a WLAN instead of a wired network connection ?
Q05. What is IEEE 802.11x ?
Q06. What is IEEE 802.11b ?
Q07. What is IEEE 802.11a ?
Q08. What is IEEE 802.11g ?
Q09. Why do WLANs operate on the 2.4 GHz Frequency range?
Q10. Will Bluetooth and Wireless LAN (WLAN) interfere with each other?
Q11. What does Bandwidth mean ?
Q12. What are the benefits between IEEE 802.11a, IEEE 802.11b and IEEE 802.11g ?
Q13. What are the standard Wireless LAN configurations ?
Q14. What is Ad Hoc mode ?
Q15. What is an Access Point ?
Q16. When do I need an Access Point?
Q17. How many wireless clients can use an Access Point ?
Q18. How many users can a WLAN system support ?
Q19. How many Access Points are required in a given area ?
Q20. What is Infrastructure mode ?
Q21. What is Roaming ?
Q22. Are WLAN secure ?
Q23. What is Encryption Key ?
Q24. What is WEP ?
Q25. What is the difference between 64-bit and 128-bit WEP ?
Q26. Is it possible to use products from a variety of vendors ?
Q27. What is SSID ?(also called ESSID)
Q28. What is Wi-Fi ?
Q29. What is WPA ?
Q30. How does WPA work ?
Q31. Will WPA work for home and small business users ?
Q32. What is WiMAX ?
Q33. What is 802.16a ?
Q34. Over what range will WLANs operate ?
Q35. Can radio signals pass through walls ?
Q36. How fast are wireless LANs ?
Q37. Will my microwave oven or cordless phone interfere with my Wi-Fi network?
Q38. What are potential factors that may causes interference among WLAN products ?

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Wireless LAN or WLAN is a type of Local Area Network (LAN) that uses high frequency radio waves rather than wires to communicate and transmit data among nodes. It is a flexible data communication system implemented as an extension to, or as an alternative for, a wired LAN within a building or campus. Typical bit-rates for current wireless devices are 11Mbps and 54Mbps. Wireless LANs can be formed simply by equipping PC's with wireless NICs. 

Wireless LANs provide all the functionality of wired LANs whilst offering simplicity of installation, facilitating user deployment and relocation. WLANs are particularly useful in buildings not conducive to premises distribution wiring. A wired LAN solution can be used to link networks in different buildings within line-of-sight distances.

High bandwidth applications may find the maximum bit-rate of 54 Mbps limiting. In practice data throughput may be half of this amount. Another concern is the known security failings of WEP, this concern can be overcome using VPN techniques.

• Increased Productivity : WLAN provides "untethered", campus-wide network and Internet access. WLAN offers the freedom to roam and stay connected.
• Fast and Simple Network Set-up : There are no cables to install.
• Installation Flexibility : WLAN can be installed in places where wires can't, and they facilitate temporary set-up and relocation.
• Reduced Cost-of-Ownership : WLAN reduce installation costs because there is no cabling; as a result, savings are greatest in frequently changing environments.
• Scalability : Network expansion and reconfiguration is uncomplicated, and users can be added to the network simply by installing a wireless LAN adapter to the client device.
• Interoperability : Most wireless solutions are compatible with products from other companies.
   

802.11x refers to a family of specifications developed by the IEEE for WLAN technology. The Institute of Electrical and Electronics Engineers (IEEE) is the leading authority in the specification and ratification of standards relating to technology.

 

Standard	Functionality
IEEE 802.11	Basic wireless technology standard provides 1 or 2 Mbps transmission in the 2.4 GHz ISM band using either FHSS or DSSS.
IEEE 802.11a	High speed Physical Layer at the 5 GHz band. Data speed up to 54Mbps.
IEEE 802.11b	High speed Physical Layer at the 2.4 GHz band. Data speed up to 11Mbps.
IEEE 802.11d	Specification for operation in additional domains.
IEEE 802.11e	A proposed IEEE standard that defines quality of service for various types of applications, whether data, video, or voice, that run on wireless networks.
IEEE 802.11f	Inter Access Point Protocol (IAPP) is a practice not a protocol.
IEEE 802.11g	Higher speed Physical Layer Extension in the 2.4 GHz band. Data speed up to 54Mbps.
IEEE 802.11h	Spectrum and Power Management extensions in the 5 GHz band in Europe .
IEEE 802.11i	A proposed IEEE standard that would provide added security specific to wireless LANs.
IEEE 802.11n	An IEEE WLAN standard, proposed for release in 2005 or 2006, which is expected to reach speeds between 100 and 320 Mbps.

 

IEEE 802.11b is a technical specification issued by IEEE that defines the operation of 2.4 GHz 11 Mbps DSSS WLAN with a bandwidth of 11Mbps. The IEEE (Institute of Electrical and Electronic Engineers) is an international organization that develops standards for hundreds of electronic and electrical technologies.

IEEE 802.11a the second revision of 802.11 that operates in the unlicensed 5 GHz band and allows transmission rates of up to 54Mbps. 802.11a uses Orthogonal Frequency Division Multiplexing as opposed to FHSS or DSSS. IEEE 802.11a is not directly compatible with 802.11b or 802.11g networks. In other words, a user equipped with an 802.11b or 802.11g Wireless devices will not be able to communicate directly to an 802.11a device.

IEEE 802.11g is an extension to 802.11b. IEEE 802.11g increases 802.11b's data rates to 54 Mbps and still utilize the 2.4 GHz ISM. Modulation is based upon OFDM (Orthogonal Frequency Division Multiplexing) technology. An 802.11b wireless devices will interface directly with an 802.11g device ( And vice versa ) at data rates of 11Mbps or lower depending on range. The range at 54 Mbps is less than for 802.11b operating at 11 Mbps.

This frequency range has been set aside by the FCC, and is generally labeled the ISM (Industrial, Scientific and Medical) band. A few years ago Apple and several other large corporations requested that the FCC allow the development of wireless networks within this frequency range. What we have today is a protocol and system that allows for unlicensed use of radios within a prescribed power level. The ISM band is populated by Industrial, Scientific and Medical devices that are all low power devices.

No, both Bluetooth and WLAN can co-exist. Since Bluetooth devices use Frequency Hopping and most WLANs use Direct Sequence Spreading techniques they each appear as background noise to the other and should not cause any perceivable performance issues.

The amount of transmission capacity that is available on a network at any point in time. Available bandwidth depends on several variables such as the rate of data transmission speed between networked devices, network overhead, number of users, and the type of device used to connect PCs to a network. It is similar to a pipeline in that capacity is determined by size: the wider the pipe, the more water can flow through it; the more bandwidth a network provides, the more data can flow through it.

Standard 802.11b provides a bandwidth of 11 Mbps; 802.11a and 802.11g provide a bandwidth of 54 Mbps.

	IEEE 802.11a	IEEE 802.11b	IEEE 802.11g
Speed	Up to 54Mbps	Up to 11Mbps	Up to 54Mbps
Frequency	5GHz	2.4GHz	2.4GHz
Range	Typically 50~ 75ft	Typically 100~ 150ft	Typically 100~ 150ft
Compatibility	Incompatible with 802.11b & 802.11g	Widest adoption	Interoperates with 802.11b. Incompatible with 802.11a .
Popularity	New Technology	Widely adopted	Rapid Growth
Relative Cost	Relatively more expensive	Lowest Price	Relatively Inexpensive

• Peer-to-Peer Network (Ad-Hoc Mode)
  The simplest WLAN consists of two PCs equipped with wireless adapter cards. The PC's form an independent network when they are within a range of one another. Networks such as this need no configuration other than setting the NIC for ad-hoc operational mode.
• Several Clients and one Access Point (Infrastructure Mode)
  With an access point installed clients have mutual access and access to the wired network. Each access point can accommodate many clients.
• Multiple Access Points and Roaming
  Access points have a limited range of approximately 100m indoors (300m outdoors). Several Access Points will be needed to provide coverage over wider areas. The optimum positioning of AP's is determined by a facility survey. The objective is to position AP's so that their radius of coverage overlaps, thus ensuring continuous coverage over the required area. Access Points "hand-off" roaming clients to one to another in a transparent fashion to maintain reliable connectivity.
   

A wireless network consists of a number of stations without access points. It is a network characterized by temporary, short-lived relationships between nodes. Without using an access point or any connection to a wired network.

An Access Point (AP) is a bridge-like device that attaches wireless 802.11 stations to a wired backbone network and enables the sending and receiving of data between wireless clients and the wired network. The AP (access point also known as a base station) is typically a wireless server that with an antenna and a wired Ethernet connection that broadcasts information using radio signals. AP typically acts as a bridge for the clients. It can pass information to wireless LAN cards that have been installed in computers or laptops, allowing those computers to connect to the campus network and the Internet without wires.

Access points are required for network access but not for Peer-to-Peer connections. A wireless network only requires an access point when connecting notebook or desktop computers to a wired network. Some important advantages make access points a valuable addition to your wireless network, with or without a wired network. First, a single access point can nearly double the range of your wireless LAN compared to a simple peer-to-peer network. Second, the wireless access point acts as a traffic controller, directing all data on the network, allowing wireless clients to run at maximum speed. Finally, an access point can be your central connection to the outside world, providing Internet sharing.

Theoretically, 254 client stations.

The number of users is virtually unlimited. The number of users can be expanded simply by adding network access points. By introducing overlapping access points, set at different frequencies (channels), the wireless network can expand to accommodate additional simultaneous users in the same area. Up to three overlapping channels can be used concurrently without interference, which effectively triples the number of supported network users. Similarly, the WLAN can support more users by installing additional access points in various locations in the building. This increases the total number of users and allows roaming throughout the building or across the campus.

This depends on the surrounding terrain, the diameter of the client population, and the number of clients. If an area is large with dispersed pockets of populations then extension points can be used for extend coverage.

Infrastructure mode is a network composed of Stations and Access Points. It can connect the wireless LAN to a wired LAN, allowing wireless computers access to LAN resources, such as file servers or existing Internet connectivity. In short, Infrastructure mode implies connectivity to a wired communications infrastructure.

Roaming is the ability to allow a client device to move freely from the coverage area of one access point to another without breaking an existing communications session. Before using the roaming function, the workstation must make sure that it is set to the same channel with the Access Point of dedicated coverage area.

Yes, WLAN are highly secure. Because wireless technology has roots in military applications, security provisions have long been designed into wireless devices and wireless LANs are typically more secure than most wired LANs. In addition, all wireless users on your network can identify themselves with a system ID that prevents unauthorized users from gaining access. Users with particularly sensitive data can enable Wired Equivalent Privacy (WEP), which further encrypts the signal and verifies the data with an electronic “Security Key”. In general, individual nodes must be security-enabled before participating in network traffic.

Encryption Key is an alphanumeric (letters and/or numbers) series that enables data to be encrypted and then decrypted so it can be safely shared among members of a network. WEP uses an encryption key that automatically encrypts outgoing wireless data. On the receiving side, the same encryption key enables the computer to automatically decrypt the information so it can be read.

Wired Equivalent Privacy. WEP is a security mechanism defined within the 802.11 standard and designed to make the security of the wireless medium equal to that of a wired cable. A WEP key is a user defined string of characters used to encrypt and decrypt data. WEP allows the administrator to define a set of respective "Keys" for each wireless network user based on a "Key String" passed through the WEP encryption algorithm. Access is denied by anyone who does not have an assigned key. WEP comes in 40/64-bit and 128-bit encryption key lengths. 

WEP is available in 40-bit (also called 64-bit), or in 108-bit (also called 128-bit) encryption modes. As 108-bit encryption provides a longer algorithm that takes longer to decode, it can provide better security than basic 40-bit (64-bit) encryption.

The lower level of WEP encryption uses a 40 bit as “Secret Key” (set by user), and a 24 bit “Initialization Vector” ( not under user control ). Some vendors refer to this level of WEP as 40 bit, others as 64 bit. The 128 bit WEP also uses a 24 bit Initialization Vector, but it uses a 104 bit as secret key. Users need to use the same encryption level in order to make a connection.
128-bit WEP will not communicate with 64-bit WEP.

Yes. So long as the products comply to the same IEEE 802.11 standard. The Wi-Fi logo is used to define 802.11b compatible products. Wi-Fi5 is a compatibility standard for 802.11a products running in the 5GHz band.

SSID also called ESSID. SSID is a 32-character unique identifier attached to the header of packets sent over a WLAN that acts as a password when a mobile device tries to connect to the BSS. (Also called ESSID.) The SSID differentiates one WLAN from another, so all access points and all devices attempting to connect to a specific WLAN must use the same SSID.

A device will not be permitted to join the BSS unless it can provide the unique SSID. Because an SSID can be sniffed in plain text from a packet, it does not supply any security to the network. An SSID is also referred to as a Network Name because essentially it is a name that identifies a wireless network.

Wi-Fi is the trademarked name that WECA uses to signify WLAN product interoperability. The name stands for “Wireless Fidelity”. Products certified as Wi-Fi are interoperable with each other even if they are from different manufacturers. A user with a Wi-Fi product can use any brand of access point with any other brand of client hardware that is built to the Wi-Fi standard. WECA performs elaborate tests on WLAN products; those that meet the interoperability standard are awarded the Wi-Fi logo.

Wi-Fi Protected Access (WPA). WPA is a security technology for wireless networks that improves on the authentication and encryption features of WEP (Wired Equivalent Privacy). WPA provides Wi-Fi wireless LAN users with a high level of assurance that their data will remain safe and protected and that only authorized users can access the network. WPA is especially attractive for enterprise customers, satisfying the demanding security needs of large business networks. In fact, WPA was developed by the networking industry in response to the shortcomings of WEP. One of the key technologies behind WPA is the Temporal Key Integrity Protocol (TKIP). TKIP addresses the encryption weaknesses of WEP. Another key component of WPA is built-in authentication that WEP does not offer. With this feature, WPA provides roughly comparable security to VPN tunneling with WEP, with the benefit of easier administration and use. This is similar to 802.1x support and requires a RADIUS server in order to implement.

In the WPA-enabled network, the client first associates with the Access Point. The Access Point blocks LAN access until the user can be authenticated. If the client proves credentials to the authentication server, the client is allowed to join the LAN. If not, the client stays blocked from joining the LAN. Once the client joins the LAN, the authentication server distributes a TKIP encryption key to both the client and the access point. The client can then begin communicating on the LAN, encrypting data back and forth with the access point.

Yes. Wi-Fi Protected Access has a special mode designed for home and small business users who do not have access to network authentication servers. In this mode, known as Pre-Shared Key, the user manually enters the starting password in their Access Point or gateway, as well as in each PC on the wireless network. Wi-Fi Protected Access takes over automatically from that point, keeping unauthorized users that don't have the matching password from joining the network, while encrypting the data traveling between authorized devices.

WiMAX is a non-profit corporation that was formed by leading communications component and equipment companies to help promote and certify the compatibility and interoperability of broadband wireless access equipment that conforms to the IEEE 802.16 standard. IEEE 802.16 Task Group provides a specification for fixed broadband wireless access systems employing a point-to-multipoint (PMP) architecture. The deployment of 802.16-compliant equipment into the marketplace will accelerate last-mile broadband deployment. The 802.16a standard is a wireless metropolitan area network (MAN) technology that will provide a wireless alternative to cable and DSL for last mile broadband access and connect 802.11 hot spots to the Internet.

The IEEE 802.16a standard is a wireless metropolitan area network (MAN) technology that will provide a wireless alternative to cable and DSL for last mile broadband access as well as connect 802.11 hot spot to the Internet. It provides for up to 50-kilometers of service area range, allows users to get broadband connectivity without needing direct line of sight with the base station, and provides shared data rates of up to 70 Mbps, which is enough bandwidth to simultaneously support more than 60 businesses with T1-type connectivity and hundreds of homes with DSL-type connectivity with a single base station. In addition the standard is designed to deliver latency sensitive services such as voice and video.

Transmission distance differs according to surroundings.  Access points typically have a 100m range indoors, and 300m outdoors. For obvious reasons AP's are ideally placed at the center of the client population with few obstructions between the AP and the clients.

Transmitting through a wall is possible depending upon the material used in its construction. In general, metals and substances with a high water content do not allow radio waves to pass through. Metals reflect radio waves and concrete attenuates radio waves. The amount of attenuation suffered in passing through concrete will be a function of its thickness and amount of metal re-enforcement used.

802.11b and 802.11a /g standards specify maximum bit-rates of 11Mbps and 54Mbps respectively. The true data-rate is invariably less than this, because of 802.11 protocol overhead, contention, and fallback due to weak signals. As clients move further from an access point, their transmitters fallback to lower bit-rates to optimize signal reception.

Microwave ovens and many cordless phones operate in the 2.4 GHz spectrum, the same radio spectrum used by 802.11b Wi-Fi wireless networks. That means they can cause interference — but in most instances this will just slow down the Wi-Fi connection; it won't stop transmission or break the connection.

To reduce interference, you can move a 2.4 GHz cordless phone away from your Wi-Fi equipped computer or base station. Interference usually only happens with older microwave ovens. You can also try changing the channel on which your Wi-Fi network operates.

• Factors of interference :
  a. Obstacles: walls, ceilings, furniture… etc.
  b. Building Materials: metal door, aluminum studs.
  c. Electrical devices: microwaves, monitors, electric motors.
   
• Solution :
  a. Minimizing the number of walls and ceilings
  b. Antenna is positioned for best reception
  c. Keep WLAN products away from electrical devices, eg: microwaves, monitors, electric motors, etc.
  d. Add additional APs if necessary.