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Wireless Tutorial

August 12th, 2011 Go to comments

In this article we will discuss about Wireless technologies mentioned in CCNA.

Wireless LAN (WLAN) is very popular nowadays. Maybe you have ever used some wireless applications on your laptop or cellphone. Wireless LANs enable users to communicate without the need of cable. Below is an example of a simple WLAN:

Wireless_Applications.jpg

Each WLAN network needs a wireless Access Point (AP) to transmit and receive data from users. Unlike a wired network which operates at full-duplex (send and receive at the same time), a wireless network operates at half-duplex so sometimes an AP is referred as a Wireless Hub.

The major difference between wired LAN and WLAN is WLAN transmits data by radiating energy waves, called radio waves, instead of transmitting electrical signals over a cable.

Also, WLAN uses CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) instead of CSMA/CD for media access. WLAN can’t use CSMA/CD as a sending device can’t transmit and receive data at the same time. CSMA/CA operates as follows:

+ Listen to ensure the media is free. If it is free, set a random time before sending data
+ When the random time has passed, listen again. If the media is free, send the data. If not, set another random time again
+ Wait for an acknowledgment that data has been sent successfully
+ If no acknowledgment is received, resend the data

IEEE 802.11 standards:

Nowadays there are three organizations influencing WLAN standards. They are:

+ ITU-R: is responsible for allocation of the RF bands
+ IEEE: specifies how RF is modulated to transfer data
+ Wi-Fi Alliance: improves the interoperability of wireless products among vendors

But the most popular type of wireless LAN today is based on the IEEE 802.11 standard, which is known informally as Wi-Fi.

* 802.11a: operates in the 5.7 GHz ISM band. Maximum transmission speed is 54Mbps and approximate wireless range is 25-75 feet indoors.
* 802.11b: operates in the 2.4 GHz ISM band. Maximum transmission speed is 11Mbps and approximate wireless range is 100-200 feet indoors.
* 802/11g: operates in the 2.4 GHz ISM band. Maximum transmission speed is 54Mbps and approximate wireless range is 100-200 feet indoors.

ISM Band: The ISM (Industrial, Scientific and Medical) band, which is controlled by the FCC in the US, generally requires licensing for various spectrum use. To accommodate wireless LAN’s, the FCC has set aside bandwidth for unlicensed use including the 2.4Ghz spectrum where many WLAN products operate.

Wi-Fi: stands for Wireless Fidelity and is used to define any of the IEEE 802.11 wireless standards. The term Wi-Fi was created by the Wireless Ethernet Compatibility Alliance (WECA). Products certified as Wi-Fi compliant are interoperable with each other even if they are made by different manufacturers.

Access points can support several or all of the three most popular IEEE WLAN standards including 802.11a, 802.11b and 802.11g.

WLAN Modes:

WLAN has two basic modes of operation:

* Ad-hoc mode: In this mode devices send data directly to each other without an AP.

Wireless_Ad-hoc_mode.jpg

* Infrastructure mode: Connect to a wired LAN, supports two modes (service sets):

+ Basic Service Set (BSS): uses only a single AP to create a WLAN
+ Extended Service Set (ESS): uses more than one AP to create a WLAN, allows roaming in a larger area than a single AP. Usually there is an overlapped area between two APs to support roaming. The overlapped area should be more than 10% (from 10% to 15%) to allow users moving between two APs without losing their connections (called roaming). The two adjacent APs should use non-overlapping channels to avoid interference. The most popular non-overlapping channels are channels 1, 6 and 11 (will be explained later).

Wireless_Infrastructure_mode.jpg

Roaming: The ability to use a wireless device and be able to move from one access point’s range to another without losing the connection.

When configuring ESS, each of the APs should be configured with the same Service Set Identifier (SSID) to support roaming function. SSID is the unique name shared among all devices on the same wireless network. In public places, SSID is set on the AP and broadcasts to all the wireless devices in range. SSIDs are case sensitive text strings and have a maximum length of 32 characters. SSID is also the minimum requirement for a WLAN to operate. In most Linksys APs (a product of Cisco), the default SSID is “linksys”.

In the next part we will discuss about Wireless Encoding, popular Wireless Security Standard and some sources of wireless interference.

Comments (18) Comments
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  1. NathanX
    March 9th, 2017

    Hi NathanX

    Please share the CCNA Wireless 200-355 dumps, to be send to hbokgola at gmail dot com

    Thanks
    Chillz

  2. Said
    March 22nd, 2017

    some can share the CCNA Wireless 200-355 dumps,
    Please

  3. Xee
    April 18th, 2017

    Hello 9tut , are these questions enough to clear CCNA 200-125??

  4. Al
    April 19th, 2017

    “Fortunately, Bluetooth does not cause as much trouble as cordless phone because it usually transfers data in a short time (for example you copy some files from your laptop to your cellphone via Bluetooth) within short range.”

    That’s not the case with something like Bluetooth speakers, Bluetooth headsets, etc. :D

  5. Mega
    May 8th, 2017

    Thanks, it was so helpful & informative

  6. guardian
    May 25th, 2017

    Can anybody tell me about valid study material about 200-355?
    @NathanX
    If you have valid questions may you share me trough {email not allowed}?
    Thanks for advance.

  7. guardian
    May 25th, 2017

    @NathanX
    If you have valid questions may you share me trough ocanner at gmail dot com
    Thanks for advance.

  8. Kinwe
    June 22nd, 2017

    Hey guardain,Preparing CCIE Wireless Lab and in search of CCIE Wireless Practical Questions? i think you once visit https://www.lab4ccie.com/ccie-wireless-lab-workbook.on this Site All provided CCIE Wireless Practical Questions are verified by experts which make it more authentic.

  9. Gio
    June 26th, 2017

    Hy Guy where I can buy a official study guide for 300-370 and 300-375 ?
    thanks in advance

  10. Amogh
    June 30th, 2017

    Hi,
    If any one has a valid CCNA 200-125 dumps, please email it to {email not allowed}

  11. ASSSYA
    July 7th, 2017

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  12. Sam
    July 27th, 2017

    Hi please anyone provide me ccna 200-355 questions, I just failed my exam.

  13. Kevin
    August 17th, 2017

    Hello to all. Would someone please assist and send the 200-125 dumps to anewmlm(at)gmail(dot)com. thx K

  14. Keelyn
    September 13th, 2017

    Hello! Can I please have the 200-355 dumps? keelyn.henning(at)gmail(dot)com. Thanks!

  15. Eddy
    November 10th, 2017

    Hi Guys,

    Please can someone provide me with the ccna 200-355 questions?
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  16. Marcone
    November 14th, 2017

    Can someone send dumps to thecowandi @ hotmail dot com. I am so stressed out.

  17. Anonymous
    November 17th, 2017

    Hi everyone

    I’m studying to the certificacion ccna wireless Do some you any have study guides apart from the Cisco guide?

    Thanks

  18. BlindMan
    November 21st, 2017

    Hello everyone.

    I have certified CCNA R&S and CCNA Sec. and planning to do certifie CCNA WiFi.

    Does anybody here have a free download link for

    CCNA Wireless 200-355 Video Course cbt nuggets (Keith Barker) ?

    (or any other video tutorial on the subject)

    Thanks a lot ;)

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