In mobile communications, there have been two key paths for the deployment of 2G (second generation) and 3G (third-generation) mobile networks. The first path used GSM and UMTS technologies, while the other path adopted IS-95 and CDMA2000. In many parts of the world, especially in the European countries, we are more likely to come across GSM (Global System for Mobile) and UMTS (Universal Mobile Telecommunication System). However, in some other parts of the world especially the USA, CDMA networks (Code Division Multiple Access) have played an important role in the evolution of mobile networks. In this article, we will look at these CDMA-based technologies for 2G and 3G mobile networks.
What is IS-95?
IS-95 or Interim Standard 1995 was introduced for delivering 2G cellular services using the Code Division Multiple Access (CDMA) technology. The proprietary name for IS-95 is cdmaOne, and it was a digital technology that employed CDMA for its air interface to offer 2G cellular services in the same era when GSM and D-AMPS went live. The introduction of IS-95 led to various commercial 2G deployments around the world using CDMA technology. IS-95 is also a predecessor of IS-2000 (CDMA2000).
IS-95 was the first standard in mobile communications that was based on CDMA technology. Cellular services before that were using FDMA (Frequency Division Multiple Access) for the analogue mobile networks (1G), and a combination of FDMA and TDMA (Time Division Multiple Access) for digital mobile networks (2G). The standard IS-95 has two variants IS-95A and IS-95 B. The frequency band used by IS-95 A can be either 824MHz-894MHz or 1850-1990 MHz with separate frequency bands for the uplink and the downlink. The carrier frequencies used in IS-95 have a bandwidth of 1.25 MHz.
Data rates of up to 14.4 kbps can be achieved from IS-95 A which can be improved to 115 kbps with the technology enhancement in IS-95 B. IS-95 provided capacity advantages for its ability to accommodate more users per MHz of the bandwidth. The power consumption in these networks is low which allows users to be able to make phone calls in decent quality even when the signal strength is not at its best. Low power consumption also extends the cell coverage which in turn increases the size of the cell. Due to soft handovers (also known as handoffs), the calls are less likely to be dropped.
What is CDMA2000?
CDMA2000, also known as CDMA2000 1xRTT or IS-2000 is a technology standard used in mobile communications for delivering 3G cellular services. Mobile networks around the world usually follow two main paths for migrating from 2G to 3G. The first path one is the UMTS path which is for those networks that used GSM for launching 2G. The second path is CDMA2000 which allows both IS-95 (cdma2000) and D-AMPS (Digital Advanced Mobile Phone System) to migrate to 3G. 3G mobile networks can offer much higher data speeds as compared to the earlier 2G networks. Due to the higher data speeds, 3G networks can support multimedia services including video streaming.
CDMA2000 is a successor of the earlier standard IS-95 (cdmaOne), and it offers 3G mobile services as specified in IMT2000 (International Mobile Telecommunication specifications for the year 2000). CDMA2000 is backwards compatible with its predecessor IS-95, which makes the upgrade from IS-95 to CDMA2000 easy and seamless. It uses the same carrier bandwidth of 1.25 MHZ and is both circuit-switched as well as packet-switched. It can support peak data rates of up to 153 kbps in the downlink and the uplink. The access technology used in CDMA2000 is Code Division Multiple Access (CDMA) where all users share the same 1.25 MHz channel, but each user is assigned an individual pseudo-noise (PN) sequence to avoid interference.
In summary, IS-95 or Interim Standard 1995 was introduced for delivering 2G cellular services using the Code Division Multiple Access (CDMA) technology. CDMA2000 is a successor of IS-95 (cdmaOne) and offers CDMA-based 3G mobile communications services.
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