Is-95, the cdma one
The IS-95, cdma one system has been deployed worldwide because of its superior voice quality, robust performance and large air interface capacity. The third generation evolution of IS-95, known as cdma2000,uses wideband CDMA technology to meet and exceed all the requirements of IMT2000.
IS-95 introduction and history:
- IS-95 was the first CDMA mobile phone system to gain widespread use and it is found widely in North America.
- It uses CDMA - code division multiple access system.
- Its brand name is cdmaOne and the initial specification for the system was IS95A, but its performance was later upgraded under IS-95B.
- For IS-95B it is able to carry data at rates up to 14.4 kbps for IS-95A and 115 kbps.
- The idea for using the form of modulation known as direct sequence spread spectrum (DSSS) for a multiple access system for mobile telecommunications came from a California based company called Qualcomm in the 1980s.
- The system involved multiplying the required data with another data stream with a much higher data rate. Known as a spreading code, this widened the bandwidth required for the transmission, spreading it over a wide frequency band.
- In order to prove that the new system was viable a consortium was set up and Qualcomm was joined by US network operators Nynex and Ameritech to develop the first experimental code division multiple access (CDMA) system.
- Later the team was expanded as Motorola and AT&T (now Lucent) joined to bring their resources to speed development. As a result the new standard was published as IS-95A in 1995 under the auspices of the Cellular Telecommunications Industry Association (CTIA) and the Telecommunications Industry Association (TIA).
- As part of the development of CDMA an organization called the CDMA Development Group (CDG) was formed from the founding network and manufacturers. Its purpose is to promote CDMA and evolve the technology and standards, although today most of the standards work is carried out by 3GPP2.
- With the success of the initial IS95 format, improvements were made and the standard was upgraded to IS95B. The main improvement was that this provided for an increased data rate of 115 kbps as data traffic was starting to be carried.
- The basic CDMA system was later further improved and evolved into a 3G system carrying much higher data rates and introducing new improvements. The 3G migration of IS95 was given the brand name cdma2000, and was available in a variety of flavors including cdma2000 1x, cdma2000 1x ev-do (evolution data only or data optimized) and another version was termed cdma2000 1x ev-dv (evolution data and voice), although this version was never seriously deployed.
- IS-95 Specification:
- A greater number of users to be supported.
- Requires lower transmit power
- Can be operated in conjunction with other technologies
- A problem of coverage optimization because the CDMA coverage can expand and shrink. This phenomenon is known as breathing.
- With the increase noise power of the canal / other users, then the channel / user located some distance to the base station must be running out of transmit power (maximum already) that can result in broken call.