codedivision

Codedivision is a method in digital communications for transmitting multiple signals over a common channel by encoding each signal with a unique code. It is a form of spread-spectrum communication and is most widely known through code division multiple access (CDMA) systems.

In codedivision, each user’s data is multiplied by a pseudorandom code sequence and transmitted as a widened spectrum. At the receiver, the same code is used to correlate and recover the original signal. The spread-spectrum approach makes the signal appear like noise to non-coinciding codes and helps separate simultaneous transmissions.

Key code properties include code length, cross-correlation between codes, and autocorrelation of each code. Direct-sequence codedivision (DS-CDMA) spreads the signal in frequency, while other variants, such as frequency-hopped codedivision, use code sequences to select time and frequency resources. Good codes have low cross-correlation to minimize interference.

Applications include mobile and satellite communications, notably CDMA-based cellular networks and Global Positioning System signals. Codedivision can offer interference resistance and security advantages, along with flexible capacity. Challenges include the near-far problem, which requires power control, and the complexity of code management and receiver design.

The concept developed from spread-spectrum research in the mid-20th century and has become integral to several modern communications standards. The term codedivision is sometimes used interchangeably with code-division or spread-spectrum techniques.