CDMA TECHNOLOGY Code Division Multiple Access CDMA

CDMA TECHNOLOGY Code Division Multiple. Access

CDMA • • • The significant of my report are following: 1) Access schemes 2) Coding Key 3) Elements 4) Advantages

History of CDMA • By 1991 Qualcom corporation has demonstrated its first example of CDMA technology • By the year 1995, the first commercial CDMA network was installed in Hong Kong

Access Schemes For radio system there are two resources a)Frequency (FDMA) b)Time (TDMA) In Code Division Multiple Access (CDMA): a)Every communicator will be allocated the entire spectrum all of the time

Coding • a) CDMA uses unique spreading codes to spread the baseband data before transmission. • b) The signal is transmitted in a channel. • c) The receiver then uses a correlator to despread the wanted signal, which is passed through a filter • d) Unwanted signals will not be despread and will not pass through the filter • e) Codes take the form of a carefully designed one/zero sequence produced at much higher rate than of the baseband data • f) The rate of a spreading code is referred to as chip rate

Key elements of CDMA Use of wide bandwich This resultin a number of advantages including and increase immunity to interference or jamming, and multiple user access Spreading codes used In order to achieve the increased banwith, the data is spread by use of a code which is independent of the data Level of security In order to receive the data, the receiver must have knowledge of the spreading code, without this is not possible to decipher the transmitted data, and this gives a measure of security Multiple access The use of the spreading codes which are independent for each user along synchronous reception allow multiple users to access the same channel simultaneously

Advantages CDMA before GSM • 1) Improvement in capacity : CDMA is much better protected from listening that is not unimportant for private talks • 2) Level of radiation of the CDMA device is several times lower than GSM , therefore • 3) Such phones are almost harmless to health • 4) At the expense of smaller radiation , the accumulator if similar capacity works more time • 5)Capacity of a base station of CDMA is more than at GSM therefore for providing with communication of identical number of subscribers , CDMA will have less expenses • 6)It is easier to carry out transition to network 3 G and 4 G from CDMA equipment , by replacement of some components while at GSM it is necessary to change all platform

USE • a) One of the early application for code division multiplexing is in GPS. • b) The Qualcom standart IS-95, Qualcom standart IS-2000, used by several mobile phone companies

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