Question

Which of the following statements are correct regarding CDMA?

1. It is similar to GSM.

2. It allows each station to transmit over the entire frequency spectrum all the time.

3. It assumes that multiple signals add linearly.

Select the correct answer using the code given below.

1. 1 and 2 only
2. 1 and 3 only
3. 2 and 3 only
4. 1, 2 and 3

Answer 1

Correct Answer - Option 3 : 2 and 3 only

CDMA: Code division multiple access

• CDMA is a channel access method that is based on spread-spectrum technology.
• It this, multiple users can send information simultaneously over a single channel.
• Each user uses the same frequency spectrum all the time without interference.
• In CDMA, multiple signals add linearly to avoid intermixing during the transmission and receiving process.

GSM: Global System for Mobile communication

• GSM is a wireless cellular network technology for better mobile communication.
• Each mobile user uses the pair of the frequency channel, one for sending and another for receiving purpose.
• Time-division multiplexing is used to share frequency pairs by several users.

Important Notes:

Difference between FDMA, TDMA, and CDMA is explained with the help of the following table:

FDMA	TDMA	CDMA
Frequency division multiple access	Time-division multiple access	Code division multiple access
Bandwidth is divided	Time-sharing is required.	Bandwidth and time-sharing are required.
No need for synchronization	High synchronization is needed	No need for synchronization
No unique codeword is required	No unique codeword is required	A unique codeword is necessary.