What is code division duplexing?

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Reducing interference in a cellular system is the most effective

approach to increasing radio capacity and transmission data rate in

the wireless environment. Therefore, reducing interference is a

difficult and important challenge in wireless communications.

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In every two-way communication system it is necessary to use

separate channels to transmit information in each direction. This

is called duplexing.Currently there exist only two duplexing

technologies in wireless communications, Frequency division

duplexing (FDD) and time division duplexing (TDD). FDD has been the

primary technology used in the first three generations of mobile

wireless because of its ability to isolate interference. TDD is

seemingly a more spectral efficient technology but has found

limited use because of interference and coverage problems.

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Code-division duplexing (CDD) is an innovative solution that can

eliminate all kinds of interference. CDMA is the best multiple

access scheme when compared to all others for combating

interference. However, the codes in CDMA can be more than one type

of code. A set of smart codes can make a high-capacity CDMA system

very effective without adding other technologies. The smart code

plus TDD is called CDD.