Multiplexing in Computer Networks

 Multiplexing kya hota hai?

Multiplexing ek technique hai jisme multiple signals (data streams) ko ek hi communication channel ke through bheja jata hai.

Simple shabdon mein:
Bohot saari data lines ko combine karke ek wire se bhejna.

 Multiplexing kyu zaroori hai?

• Ek hi channel (jaise ek wire) ka efficient use karna

• Cost bachti hai (kam wires lagti hain)

• Ek medium se multiple users ka data bheja ja sakta hai

• Transmission fast aur smooth hoti hai

 Real Life Example

Sochiye 5 log alag-alag car mein Delhi se Jaipur ja rahe hain. Isme petrol bhi zyada lagega aur road bhi jam ho jayegi. Ab agar sab ek hi bus mein chale jayein to petrol bhi bachega aur road bhi free rahegi.

Yahi kaam multiplexing karti hai — multiple signals ko combine karke ek line se bhejna.

 Multiplexing kaise kaam karta hai?

2 Important Devices:

1. Multiplexer (MUX): Sender side pe hota hai, jo saare signals ko combine karta hai

2. Demultiplexer (DEMUX): Receiver side pe hota hai, jo combined signal ko wapas alag-alag signals mein todta hai

 Simple Diagram:

 Types of Multiplexing

Multiplexing ke main 3 types hote hain:

1. Frequency Division Multiplexing (FDM)

• Har signal ko alag frequency band diya jata hai

• Sab signals same time pe bheje jaate hain, but alag frequencies pe

 Example: Radio – FM pe multiple stations hote hain, sabki frequency alag hoti hai (jaise 93.5 MHz, 98.3 MHz)

 Diagram:

 Use: Radio, TV channels, analog transmission

2. Time Division Multiplexing (TDM)

• Channel ko time slots mein divide kar dete hain

• Har signal ko ek ek time slot milta hai

• Ek time pe sirf ek signal ka data jata hai, fir doosre ka, fir teesre ka… aur ye cycle repeat hoti hai

 Example: Classroom mein har student ko 1 minute diya jaye bolne ke liye. Ek time pe ek hi student bolega.

 Diagram:

 Use: Digital telephone lines, basic computer networks

3. Wavelength Division Multiplexing (WDM)

• Ye optical fiber communication mein use hota hai

• Alag-alag light wavelengths (colors) ko data bhejne ke liye use kiya jata hai

 Example: White light prism mein se nikalke 7 colors mein toot jata hai — waise hi data alag-alag colors mein bheja jata hai

 Use: Fiber optic internet (Jio, Airtel Fiber, etc.)

 Other Advanced Types

• STDM (Statistical Time Division Multiplexing): Time slots fixed nahi hote, jo signal active hote hain unhe milte hain → efficient

• CDM/CDMA (Code Division Multiplexing): Har user ko ek unique code diya jata hai. Sab ek saath data bhejte hain, receiver code ke basis pe alag karta hai.

 Use: Mobile communication (Jio, Airtel phones)

 Summary Table:

 Advantages of Multiplexing

• Ek hi medium mein zyada data transfer hota hai

• Cost kam hoti hai (kam wires, kam hardware)

• Bandwidth ka best use hota hai

• Network ki efficiency badhti hai

 Disadvantages

• Sync ka issue aa sakta hai (MUX aur DEMUX ka timing match hona chahiye)

• Agar signal corrupt ho jaye to saare data streams affect ho sakte hain

• Kuch types mein complex hardware chahiye

 Conclusion

Multiplexing ek powerful technique hai jisse multiple users ya signals ek hi channel se efficiently data bhej sakte hain. Aaj ke time mein, telecom, internet, broadcasting, networking sab mein multiplexing ka role important hai.