Code Division Multiplexing

Multiplexing is a method that can be used to send multiple analog or digital signals over communication channels such as radio waves or fiber optic cables and convert them into a single signal. When the destination is reached, the signal is demultiplexed. The main purpose of using this method is to share limited resources. A real-world example of multiplexing is in the telecommunications industry, where multiple calls can be made using a single connection.

Code Division Multiplexing

Code division multiplexing is a multiplexing process in which various information can be combined for instantaneous transmission of a frequency band. This multiplexing technique is used to allow multiple users to send a single communication, it is called CDMA or Code Division Multiple Access. It does not affect the bandwidth of the digital signal or frequency. It has less interference, thus providing a better and safer method of communication. The number division multiplexing scheme is shown below. The chart below shows how each transmission method works simultaneously. CDM uses spread spectrum technology in wireless communication because each channel is encoded to broadcast over a wider range than the original signal used.

Working of Code Division Multiplexing

Code division multiplexing separates one signal from another by giving each signal a series of bits called the spreading code. This spreading is combined with the original signal to form a new coded data stream, which is then sent to the shared medium. Then the demultiplexer, knowing the code, can recover the original signal by removing the spread code, called backpropagation.

CDMA

CDMA stands for Code Division Multiple Access, a type of multiplexing that allows multiple signals to manage a single communication and optimize bandwidth usage.

CDMA systems are very different when compared to their frequency and time equivalents. That is, in this type of system, the operator has the right to use the entire bandwidth throughout the entire loop. The principle is to use different CDMA codes to distinguish users. This CDMA technology is used in UHF (Ultra High Frequency) mobile phones at 800 MHz & 1.9 GHz band. The features of CDMA basically include the following points.

• CDMA allows many users to connect simultaneously, providing better data and communication.
• There is no limit to the number of users in a CDMA system, but performance decreases as the number of users increases.
• The CDMA system eliminates noise and interference and improves network quality.
• CDMA allows its signal to enter different and unique codes of user transmissions to protect its signals.
• In CDMA all channels use the full spectrum.
• All the cells within CDMA systems can utilize a similar frequency.

Advantages of CDM

• It has better signal quality.
• Since the sender and receiver only know the spreading code, it prevents eavesdropping and disturbance.
• Protected from hackers.
• Adding users is easy and there is no limit to the number of users.
• Large signal bandwidth reduce multipath fading.
• Effective use of private spectrum.
• Resource allocation is flexible.
• It is very efficient process.
• No synchronization required.
• In this multiplexing, many users can share the same bandwidth.
• CDM is scalable.
• Compatible with other types of cellular technology.
• Uses a fixed frequency spectrum.
• The interference was reduced due to different code words assigned to each user.
• Enhance security, avoid crashes and collisions, and use bandwidth effectively. CDMA’s spread spectrum technology makes it difficult for eavesdroppers to catch signals, and the special spread spectrum code makes it possible to avoid interference and block transmission.

Disadvantages of CDM

• As the number of users increases, the overall service quality will decrease.
• It needs time synchronization.
• In CDM, the transmitted bandwidth of each user is increased than the digital data speed of the source.
• The data transfer rate is low.
• CDM is complex mechanism.

Applications of CDM

• CDM is widely used in second generation (2G) and third generation 3G wireless communication. These systems are used in Ultra High Frequency (UHF) mobile phones in the 800 MHz and 1.9 GHz bands. It is a combination of analog-to-digital conversion and spread spectrum techniques.
• CDM network technology is used to combine multiple data signals for simultaneous transmission on multiple frequency lines.
• This type of multiplexing is commonly used in 2G & 3G wireless communications.
• It is used in UHF (Ultra High Frequency) mobile phones in the 800 MHz and 1.9 GHz bands. So it’s a combination of analog-to-digital conversion and spread spectrum technology.

Conclusion

Multiplexing is a very important technique in telecommunications that allows multiple signals to share limited communication resources efficiently. Code Division Multiplexing is one form of multiplexing which uses codes to enable multiple users to communicate over a single channel without significantly affecting bandwidth. CDMA systems offer various advantages, including improved signal quality, security, and flexible resource allocation, making them suitable for applications in 2G and 3G wireless communication.

Frequently Asked Questions

1. How does CDM enhance security?

CDM’s unique spread spectrum codes make it difficult for eavesdroppers to intercept signals and prevent interference, enhancing security.

2. What is the significance of multiplexing in modern communication?

Multiplexing plays a crucial role in optimizing the use of communication channels, enabling efficient data transmission and resource sharing, which is essential for modern communication systems.