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MULTICARRIER SYSTEMS BASED ON MULTISTAGE
LAYERED IFFT STRUCTURE
ABSTRACT:
This letter extends our previous work on layered inverse Fast Fourier Transform (IFFT)
structure to a multistage layered IFFT structure where data symbols can input at different stages
of the IFFT. We first show that part of the IFFT in the transmitter of an OFDM system can be
shifted to the receiver, while a conventional one-tap frequency-domain equalizer is still
applicable. We then propose two IFFT split schemes based on decimation-in-time and
decimation-in-frequency IFFT algorithms to enable interference-free symbol recovery with
simple linear equalizers. Applications of the proposed schemes in multiple access
communications are investigated. Simulation results demonstrate the effectiveness of the
proposed schemes in improving bit-error-rate performance.
EXISTING SYSTEM:
Discrete Fourier Transform (DFT) converts a finite list of equally
spaced samples of a function into the list of coefficients of a finite combination
of complex sinusoids, ordered by their frequencies, that has those same sample values. It can be
said to convert the sampled function from its original domain to the frequency domain. The input
samples are complex numbers (in practice, usually real numbers), and the output coefficients are
complex too. The frequencies of the output sinusoids are integer multiples of a fundamental
frequency is used.
EXISTING SYSTEM ALGORITHM:
Discrete Fourier Transform
EXISTING SYSTEM DRAWBACKS:
Multicarrier communication is difficult
Computation is difficult
PROPOSED SYSTEM:
We first show that part of the IFFT in the transmitter in an OFDM system can be shifted
to the receiver, while a conventional one-tap frequency-domain equalizer is still applicable. We
then introduce the multistage layered IFFT structure and two IFFT split schemes where symbols
can be input at different stages and can be recovered without inter-symbol interference. We show
that by inputting information symbols at the intermediate domain, the receiver can recover the
symbols using the same one-tap frequency-domain equalizer as that in conventional OFDM
systems.
PROPOSED SYSTEM BLOCK DIAGRAM:
IFFT STRUCTURE FOR 8-POINT DECIMATION-IN-TIME IFFT:
TRANSCEIVER STRUCTURE:
PROPOSED SYSTEM ALGORITHM:
IFFT Algorithm
PROPOSED SYSTEM ADVANTAGES:
More efficient
Speed is increased
It is implement Multicarrier communication
SOFTWARE REQUIREMENT: ModelSim6.4c
Xilinx 9.1/13.2
HARDWARE REQUIREMENT:
FPGA Spartan 3/ Spartan 3AN
REAL TIME APPLICATION:
Multiple access communications
Satellite Communication
Mobile Communication & OFDM
FUTURE ENHANCEMENT:
Implementation of 16 Point IFFT Design using verilog and verification using system
verilog will be done.
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