23 December 2017

What is CDMA | Features | Advantages | Applications

Definition of CDMA :

CDMA is a digital cellular network standard and it can utilize speed spectrum technology. In this method, the user may transmit at the same time using the same frequency band but it can be using different codes so that we can decode to identify a particular user. 

Detailed information :

  • CDMA is very different from the time and frequency multiplexing, It is digital cellular technology that uses spread spectrum techniques.
  • In this technology, many users share the same carrier frequency. This frequency also multiplexed with the spreading signal of larger bandwidth. This spreading signal is a pseudo-noise code sequence has a higher chip rate than the data rate of the message signal.
  • CDMA is commonly used in an ultra-high-frequency cellular telephone system, band ranging between the 800 Mhz and 1.9 GHz.
  • The main advantage of CDMA, when compared to another multiple access method, is a reduced level of interference. As each user is allocated an individual pseudo-random codeword is orthogonal to the code words of the other users at the receiver end. Receiver tunes at the receiver end receive the intended signal of the user.
  • Power control is essential to minimize the near-far problem in these systems. Power control is implemented at the base station by sampling the radio signal strength indicator level of each mobile and then a power change command over the forward radio link.

Features of CDMA : 

  • Soft capacity limit.
  • Higher user capacity
  • CDMA is an interference-limited system.
  • Higher frequency reuse. 
  • Share the same frequency
  • As the number of users increases, system performance decreases.
  • The near-far problem arises at the receiver end.
  • Multipath fading can be reduced as the signal is spread over a large spectrum.
For detailed information : 
Read more >> CDMA features

Application of CDMA :

  • Used for the cellular system.
  • Most important for the GPS system. 
  • Used for subscriber access control.
  • Used for personal communication service.
  • Used for over the air activation.
  • Used for short message service.
  • The US-based Qualcomm standard marketed as CDMAOne. 
  • Used by UMTS 3G mobile phone standard.
  • Used in the OmniTRACS satellite system for transportation logistics. 
For detailed information : 
Read more >> CDMA applications