IS offered interoperation including handoff with the analog cellular network. Besides technical improvements, the IS documents are much more mature in terms of layout and content. They also provide backwards-compatibility to IS Protocol details[ edit ] cdmaOne network structure The IS standards describe an air interface, a set of protocols used between mobile units and the network. Physical layer[ edit ] IS defines the transmission of signals in both the forward network-to-mobile and reverse mobile-to-network directions. All forward transmissions are QPSK with a chip rate of 1,, per second.

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Assume we have a few students gathered in a classroom who would like to talk to each other simultaneously. Nothing would be audible if everyone starts speaking at the same time. Either they must take turns to speak or use different languages to communicate. The second option is quite similar to CDMA — students speaking the same language can understand each other, while other languages are perceived as noise and rejected.

Similarly, in radio CDMA, each group of users is given a shared code. Many codes occupy the same channel, but only those users associated with a particular code can communicate. Individual conversations are encoded with a pseudo-random digital sequence and then transmitted using a wide frequency range. CDMA consistently provides better capacity for voice and data communications, allowing more subscribers to connect at any given time.

CDMA is the common platform on which 3G technologies are built. This has a single 5 MHz channel. WCDMA uses a single carrier per channel and employs a spreading rate of 3.

It works together to lead the growth and evolution of advanced wireless telecommunication systems. CDG is comprised of service providers, infrastructure manufacturers, device vendors, test equipment vendors, application developers, and content providers. Its members jointly define the technical requirements for the development of complementary systems CDMA and 4G. Further, the interoperability with other emerging wireless technologies are meant to increase the availability of wireless products and services to consumers and businesses worldwide.

IMT System.


IS-95, cdmaOne

It is this later specification that is synonymous with cdmaOne. Apart from voice the mobile phone system is also able to carry data at rates up to IS history 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 s. Previously DSSS had been mainly used for military or covert communications systems as the transmissions were hard to detect, jam and eavesdrop. 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. Only when the original spreading code was used in the reconstruction of the data, would the original information be reconstituted.



Mokasa A CDMA subscriber has an account established with one wireless carrier, which provides the user with wireless voice and data services. Simple IP service does not include any tunneling scheme providing mobility on a network layer described in the beginning of this chapter and supports mobility only within certain geographical boundaries. The network will control the transmitted power of the traffic channel to keep the signal quality just good enough, thereby keeping the noise level seen by all other users to a minimum. The variable-rate nature of traffic channels provide lower-rate frames to be transmitted at lower power causing less noise for other signals still to be correctly received.


CDMA - Introduction


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