Wireless LANs (IEEE 802.11, Wi-Fi, and Bluetooth Basics) in Computer Networks

 Wireless LAN (WLAN) kya hota hai?

• Wireless Local Area Network (WLAN) ek aisi network technology hai jo do ya do se zyada devices ko bina kisi physical cable ya wire ke high-frequency radio waves ke zariye aapas mein connect karti hai.

• Wired Ethernet (IEEE 802.3) mein users cable se bandhe rehte the. WLAN users ko mobility provide karta hai — aap apne laptop ya phone ko lekar room ya campus mein ghoomte hue bhi internet use kar sakte hain.

• IEEE ne Wireless LAN ke liye IEEE 802.11 standard family banayi, jise commercial market mein Wi-Fi ke naam se jaana jaata hai.

• Short-range Personal Area Networks (PAN) ke liye IEEE ne IEEE 802.15 (Bluetooth) standard develop kiya.

 1. IEEE 802.11 (Wi-Fi) Architecture

IEEE 802.11 do primary building blocks par kaam karta hai:

                [ Distribution System (DS) - Wired Backbone ]
                          |                     |
                   +------+                     +------+
                   |                                   |
           [ Access Point 1 ]                  [ Access Point 2 ]
             /            \                      /            \
       [ Station A ]  [ Station B ]        [ Station C ]  [ Station D ]
       <-------- BSS 1 ---------->         <-------- BSS 2 ---------->
       <==================== Extended Service Set (ESS) ====================>

A. BSS (Basic Service Set)

BSS wireless LAN ki fundamental building unit hai. Isme wireless stations (laptops, phones) shamil hote hain:

• Infrastructure BSS: Isme ek central coordinator hota hai jise Access Point (AP / Wi-Fi Router) kehte hain. Sabhi stations AP ke zariye hi aapas mein baat karte hain.

• Independent BSS (Ad-Hoc Network): Isme koi Access Point nahi hota. Stations peer-to-peer directly ek doosre se communicate karte hain (jaise phone-to-phone direct Wi-Fi share karna).

B. ESS (Extended Service Set)

Jab college campus ya bade offices mein ek single Access Point pure area ko cover nahi kar pata, toh multiple BSS ko ek wired backbone se connect kiya jaata hai jise Distribution System (DS) kehte hain. Is poore interconnected combination ko ESS (Extended Service Set) kehte hain. Iski madad se user bina connection break hue ek Access Point se doosre Access Point par roam kar sakta hai.

 Popular IEEE 802.11 Standards (Wi-Fi Generations)

 2. Bluetooth Basics (IEEE 802.15.1)

• Bluetooth ek short-range wireless technology hai jo Wireless Personal Area Networks (WPAN) banane ke liye use hoti hai.

• Yeh 10 meters ke range mein devices (smartphones, wireless headphones, smartwatches, mouse, keyboards) ko bina cables ke aapas mein communicate karne ki suvidha deti hai.

• Bluetooth 2.4 GHz ISM (Industrial, Scientific, and Medical) band par kaam karta hai aur interference se bachne ke liye FHSS (Frequency Hopping Spread Spectrum) technique use karta hai (1600 hops per second).

Bluetooth Network Architecture: Piconet aur Scatternet

Bluetooth devices do tarah ke network topologies form karte hain:

      [ Piconet 1 ]                             [ Piconet 2 ]
    +---------------+                         +---------------+
    | Master (M1)   |                         | Master (M2)   |
    |   /       \   |                         |       |       |
    | S1         S2 | <--- (Bridge Node) ---> |      S3       |
    +---------------+       (Slave in P1      +---------------+
                           Master/Slave in P2)

    <======================== Scatternet ========================>

1. Piconet:
– Ek Piconet mein maximum 8 active devices ho sakte hain.
– Inme se ek device Master hota hai aur baaki 7 devices Slaves hote hain.
– Master saare timing aur transmission clock ko control karta hai. Slaves aapas mein directly communicate nahi kar sakte; unhe hamesha Master ke through hi data bhejna padta hai.
– Iske alawa ek Piconet mein 255 tak Parked (inactive) devices ho sakte hain jo low-power mode mein rehte hain.

2. Scatternet:
– Jab do ya do se zyada Piconets aapas mein judte hain, toh use Scatternet kehte hain.
– Ek common device (Bridge Node) ek Piconet mein Slave aur doosre Piconet mein Master ya Slave ki tarah act karke dono piconets ke beech bridge ka kaam karta hai.

 Wi-Fi vs Bluetooth Comparison

 Summary Table