17-08-2012, 11:49 AM
Transmitter Implementation Using DS-CDMA Technique in FPGA Using Verilog HDL
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INTRODUCTION
MOBILE communications are rapidly becoming more and
more necessary for everyday activities. With so many
more users to accommodate, more efficient use of bandwidth
is a priority among cellular phone system operators.
Another very important objective in designing a
communication system is security. This is very essential in
military communication. In fact, the need for high security in
military communication led to the development of a
modulation system known as Spread Spectrum Modulation
during Second World War [5].
DS-CDMA is a type of spread-spectrum communication
system in which multiple signal channels occupy the same
frequency band, being distinguished by the use of different
spreading codes [3]. CDMA communication is employed in,
for example, digital cellular telephone systems and personal
communication services.
DESIGN OF CDMA TRANSMITTER
In this paper, CDMA communication system is
implemented with Maximum Length (ML) sequence PN code.
The following specifications are considered for design and
implementation of the CDMA transmitter and receiver. In this
project two CDMA communication systems are implemented,
one with Maximum Length (ML) sequence PN code and other
with gold code. In the PN sequence generator section both the
ML sequence and gold code generators are described.
The following specifications are considered for design and
implementation of the CDMA transmitter:
CONCLUSION
Verilog has become the linchpin for a complete design flow
from concept to digital component.It is a language which
allows switch-level modelling which some designers find
useful for exploring new circuits. Moreover, a designer can
describe a component in text rather than as a schematic in
verilog.
In this project, the transmitter was implemented on FPGA.
This has been tested using an arbitrary chosen data stream,
where these data have been transmitted through implemented
transmitter. Increasing the number of bits using the same
topology, it is possible to reach the standard rates specified for
CDMA.