CDMA is a form of "the quilt - the spectrum," a family of digital communication techniques have been used in military applications for many years. The principle of spread spectrum center is the use of noise - the carrier waves, and, as the name implies, the bandwidth is wider than that required for simple point - to - point communication at the same rate of data.
Originally had two motivations: either to resist enemy efforts to block communications, or to hide the fact that communication was even taking place. It has a history that goes back to the days of World War II.
The use of CDMA for mobile radio applications of civilians is new. It was proposed theoretically in the 1940s, but the practical application in the civilian market place so soon after 40 years. Commercial applications are placed possibly due to two evolutionary developments.
One was the availability of very low cost, high-density digital integrated circuits that reduce the size, weight and cost of subscriber stations to an acceptably low level. The other was the optimum realization of multiple-access communication that requires all user stations in regulating transmitter powers to the lowest, it will achieve an adequate quality marked.
CDMA technology changes the nature of the subscriber station of a predominant predominant analog device to a digital device .. In CDMA receivers do not completely eliminate the analog process, but they separate communication channels by means of a pseudo - random modulation is applied and removed in the digital domain, not on frequency. Multiple users occupy the same frequency band. This universal frequency is not random. Rather, it is crucial to the very high spectral efficiency is the hallmark of CDMA.
Constitutes a radio communications solution that fits into what has been termed the second generation of radio systems (known as 2G), a generation of digital mobile character that appears in the early 90s as a continuation of the first, based on analog technology. The generation 2G is defined over five years, in particular, its origin is in 1992, coinciding with the deployment of GSM. In fact, consists of 2G GSM and CDMA systems, the latter with a significant presence in the U.S., together with NADC (North American Digital Cellular) and PDC (Personal Digital Cellular).
However, in those moments when germinated the 2G was still not highlight the growing popularity of the Internet. Consequently, these systems were not designed with sufficient capacity to provide access to high speed internet own cable-based networks.
To try to remedy this situation, we are working on developing the next generation of media capable of providing advanced services via radio transmission. Known as 3G or IMT-2000 (the plan launched by the International Telecommunication Union for 3G), this new generation adds the concept of the previous generation broadband. In particular, it is expected that 3G is to bypass the shortcomings of existing systems mainly in terms of network capacity, in order to accommodate the growing number of users, improve roaming or roaming levels and increase the transmission capacity information to multimedia and interactivity sopot.
Another problem that is expected to be third generation solution is the interoperability, because the different existing standards makes roaming will not be considered a real possibility in every way. Importantly, the achievement of a pattern of global and universal standards is crucial in the field of radio communications by their idiosyncrasies, as its fundamental value lies in the possibility of a global mobility, or what is the same , providing a seamless mobility scheme (seamless) worldwide.
CDMA is altering the face of cellular and PCS communication:
- Improving traffic capacity dramatically phone
- Improving voice quality dramatically and eliminating the audible effects.
- Reducing the incidence of dropped calls left.
- The transport mechanism for providing reliable data communications such as fax and Internet traffic,
- Reducing the number of sites needed to support any given amount of traffic
- Site selection simplifying
- Reducing deployment and operating costs because fewer cell sites are needed
- Reducing the average power transmitted
- Reducing interference from other electronic devices
- Reducing potential health risks
