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.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.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. This paper will
elaborate on a set of smart codes that will make an efficient CDD system a reality.
The CDMA system based on this is known as the LAS-CDMA, where LAS is a set of
smart codes. LAS-CDMA is a new coding technology that will increase the capacity
and spectral efficiency of mobile networks. The advanced technology uses a set
of smart codes to restrict interference, a property that adversely affects the
efficiency of CDMA networks.To utilize spectrum efficiently, two transmission
techniques need to be considered: one is a multiple access scheme and the other
a duplexing system. There are three multiple access schemes namely TDMA, FDMA
and CDMA. The industry has already established the best multiple access scheme,
code-division multiple access (CDMA), for 3G systems. The next step is to select
the best duplexing system.
