Code Division Multiple Access (CDMA) is a technique used in telecommunications to allow multiple users to share the same frequency spectrum simultaneously. Unlike other multiple access techniques, such as Time Division Multiple Access (TDMA) or Frequency Division Multiple Access (FDMA), CDMA employs a different approach by using unique codes to distinguish between different users.

CDMA operates by assigning a specific code to each user, which is then used to spread the user's signal across the entire available bandwidth. This spreading process is achieved by multiplying the user's data signal with a much higher rate pseudorandom binary code. The use of these unique codes allows multiple users to transmit their signals simultaneously over the same frequency range without interfering with each other.

One of the key advantages of CDMA is its ability to mitigate interference and increase the overall capacity of the system. Since each user has their own unique code, the receiver can separate the desired user's signal from other users' signals even if they are transmitted at the same time and frequency. This process, known as correlation, makes CDMA highly resistant to noise, multipath interference, and fading, resulting in improved call quality and higher data rates.

Another notable feature of CDMA is its flexibility to support both voice and data services. CDMA systems can allocate variable-sized channels depending on users' requirements, allowing efficient utilization of the available bandwidth. This flexibility makes CDMA suitable for various applications, including mobile telephony, wireless data communication, and broadband access technologies like 3G and 4G.

CDMA also offers increased security compared to other multiple access techniques. Since each user's signal is uniquely identified by their specific code, unauthorized users find it extremely challenging to intercept or decode the transmitted signals. This inherent security feature makes CDMA particularly appealing for applications that require secure communication, such as government and military systems.

In summary, Code Division Multiple Access (CDMA) is a multiplexing technique that utilizes unique codes to enable multiple users to simultaneously share the same frequency range. Its ability to provide high capacity, resistance to interference, flexibility, and enhanced security has made it a popular choice in various wireless communication systems.