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Code Division Multiple Access (CDMA)

Code Division Multiple Access (CDMA) is a popular technology used in wireless Internet (LAN) and cellular networks (Kurose & Ross, 2013, p. 522).  As a spread spectrum technology formerly used by the US government, it is chiefly known for its use in mobile phone networks due to being a reliable digital communications technology.  CDMA is one type of three cellular network access technologies, offering enhanced security, connectivity and flexibility (Couey, 1997).  It will be interesting to review more details about CDMA and how it compares to other wireless/cellular technology, while assessing strengths and weaknesses of CDMA.

CDMA, as indicated earlier, falls within the spread spectrum communications category.  What this means is a device does not need to broadcast over a single frequency for the duration of a call, but can actually use several frequencies as required.  CMDA will automatically adjust the sender and receiver frequencies, if the latter becomes necessary.  The implications of frequencies changing all the time are many – one of them being improved security.  While someone might be able to circumvent security and eavesdrop on a conversation on one signal, once a frequency changes, they will have to spend more time to find the new frequency, only to find the frequency changed yet again.  This also helps prevent frequency jamming in times of war, etc.  From a regular day to day usage perspective, with many people using their phones while walking or on the road, CDMA adapts to whatever location and frequency is required to best serve a call.  Similarly, more than one signal can be served on a frequency without causing any service delivery issues.  3G and 4G networks all interface with CDMA – specifically wideband CMDA (or W-CDMA) to help transfer data at high speeds (Southern New Hampshire University, n.d.)

So, how does CMDA compare against other forms of network technology?  Two other technologies, Advanced Mobile Phone Systems (AMPS) and Time Division Multiple Access (TDMA) are other possibilities.  AMPS used to be the standard (at least in North America) for mobile phones use, but is analog only.  IS-552, the AMPS cellular standard “divides 50 MHz of spectrum into 832 frequency channels, each 30 KHz wide” (Raciti, 1995).  TDMA is a digital alternative that did not get as much traction as CDMA did.  The primary reason behind this is because it only allows people to share the same frequency, or at least ones close to the one being presently utilized.  Each frequency used by TDMA is broken into “six time slots” with “two slots to each user” which can enhance network volume well over 100% (Raciti, 1995).  Raciti indicates CDMA can enhance network volume over AMPS “by a factor of ten” (Raciti, 1995).  As you can see, AMPS has some severe limitations compared to CDMA and TDMA is not as superior over CDMA when it comes to supporting more frequencies.

CDMA has a number of strengths as indicated above, but also has some weaknesses worth mentioning.  Beyond some of the other positive aspects CDMA has, as shared earlier, Raciti mentioned in his paper that CDMA also provides superior voice quality and integration with existing digital networks.  He pointed out digital access technologies such as CDMA may not be implemented everywhere however.  For example, there may still be some areas using AMPS devices, even in North America at the present time.  As such, communications devices utilizing CDMA should also provide fall back support for AMPS to allow digital and analog compatibility.  This will allow someone traveling on the road to continue a phone call in areas with digital support to analog only coverage without a high risk of a dropped call (Raciti, 1995).  As a result of cross compatibility, this may make devices more expensive until CDMA becomes the global standard, as one could imagine it costing manufacturers more to develop devices supporting multiple forms of communications capabilities (inclusive of time/resources required to test), before it can be made available to the general public.

Despite any weaknesses associated with CDMA, the technology is far more superior over current alternatives, as highlighted earlier.  As with any new standards however, we will need to ensure cross compatibility until older implementations are completely phased out – at least in key infrastructure (i.e. cell phone towers, military use, etc.)  The ability for someone to have a conversation with another over multiple frequencies is critical in today’s environment.  We hear of security vulnerabilities on the Internet fairly regularly – and although less frequent with mobile device usage, we all know phone conversations can easily be illegally tapped by civilians with the right equipment.  CDMA drastically reduces the risks associated with this threat, while providing enhanced voice clarity, data transfer rates and general reliability with the ability to quickly change frequencies.  We no longer need to experience a high number of phone call drops with CDMA and with implementation quickly climbing on a global scale, it can safely be said CDMA is here to stay, at least for some time.


Couey, A. (1997). The birth of spread spectrum. Retrieved from http://people.seas.harvard.edu/~jones/cscie129/nu_lectures/lecture7/hedy/lemarr.htm

Kurose, J. F., & Ross, K. W. (2013). Computer networking: A top-down approach (6th ed.). Boston, MA: Pearson.

Raciti, R.C. (1995, July). Cellular technology. Retrieved from http://scis.nova.edu/~raciti/cellular.html

Southern New Hampshire University. (n.d.). IT 640 module six lecture notes: Wireless and mobile networks. Retrieved from https://bb.snhu.edu/bbcswebdav/pid-578766-dt-content-rid-328807_1/xid-328807_1

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