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.