FDMA operates by dividing the available frequency spectrum into distinct sub-channels, with each user assigned a dedicated frequency band for continuous transmission1. In contrast, CDMA allows all users to transmit simultaneously across the entire frequency band, using unique pseudorandom noise codes to differentiate individual signals2. This fundamental difference in approach impacts various aspects of their performance:

• FDMA requires guard bands between channels to prevent interference, while CDMA relies on code separation

• Synchronization is not necessary for FDMA, but CDMA may require time synchronization for optimal performance

• FDMA transmits data via continuous signals, whereas CDMA utilizes digital signals for transmission13

Bandwidth allocation differs significantly between these two access methods. FDMA shares the available bandwidth among stations by dividing it into sub-channels, with each user assigned a dedicated frequency band. In contrast, CDMA allows all users to share both bandwidth and time simultaneously across the entire frequency spectrum12. Another key distinction lies in the use of codewords. FDMA does not require any codeword for transmission, whereas CDMA necessitates a unique codeword for each user to differentiate their signals13. This code-based approach enables CDMA to support multiple users on the same frequency band without interference, a feature not possible with FDMA's frequency-division method.

Interference management differs significantly between the two systems. FDMA utilizes guard bands to prevent interference between adjacent channels, while CDMA relies on the orthogonality of codes to separate signals. This difference impacts transmission rates, with CDMA supporting higher data rates compared to FDMA's lower rates12. Additionally, CDMA is more susceptible to the near-far problem, where stronger signals can overpower weaker ones, a challenge not present in FDMA systems3.

Offering greater flexibility and capacity, CDMA outperforms FDMA in several key areas. The code-based system of CDMA allows for a higher number of simultaneous users and more efficient use of the available spectrum, resulting in a larger system capacity that is primarily limited by interference rather than channel availability12. In contrast, FDMA's rigid frequency allocation scheme leads to a lower overall system capacity and less flexibility in accommodating varying user demands3. This difference becomes particularly significant in high-traffic scenarios, where CDMA's ability to dynamically allocate resources provides a distinct advantage over FDMA's fixed channel assignments.