Ddo-ofmd With Ct Coding To Improve Signal Quality And System Performance In Mmw Fiwi Systems

Fiber-Wireless (FiWi) access networks are hybrid networks with a wireless frontend and a fiber backbone. These networks are classified as the networks suitable for next generation communication systems. There are three ways to transmit wireless signals over the fiber link:RF-Over-Fiber, IF-Over-Fiber, and Baseband-Over-Fiber. We focus on RF-Over-Fiber (RoF) in our research. RoF technology has several benefits like larger bandwidth, reduced power consumption, resistance to EMI etc., which makes it attractive in the implementation for various communication systems.Orthogonal Frequency Division Multiplexing (OFDM) is a special case of multicarrier transmission technique, which divides large signals into several smaller signals before transmission; its uniqueness compared to other multicarrier modulation techniques is the fact that its signals are mathematically orthogonal to each other.This thesis looks into the reduction of the PAPR in a DDO-OFDM system, using CT coding technique to reduce the PAPR in order to increase transmission distance and improve signal quality. We use OptiSystem as the simulation tool, and the implementation of the OFDM transmitter and receiver was accomplished using MATLAB codes. The system design has one LD, one MZM, and a LO at the CO. The BS has a PD, a mixer and a LO. In the simulation, a pseudo random bit sequence generator generates lOGbits/s data signal to the OFDM transmitter. The S/P converter converts the input digital data from serial to parallel, and divides into blocks; these symbol blocks are then mapped using QPSK. IFFT is applied to produce the time-domain samples of the OFDM symbols. Then the signal is converted back to a parallel data stream, CP is added and the CT coding technique implemented. A DAC generates the analog OFDM baseband signal, and modulates it onto a dual band MZM at the CO.The total number of subcarriers used in the simulation is256,192for data transmission, and8for pilots,1/8for CP, and56are set to null. The CW lasers frequency is193.1THz, and the power OdBm. It generates a continuous wavelength at1550nm. The LO frequency and phase is60GHz and90°respectively. A MZM generates the optical baseband OFDM signal, which is modulated over a50km standard SMF. At the BS, the PIN PD receives the optical baseband OFDM signal and converts it to an electrical signal; the frequency of the LO is set to60GHz and90°for frequency and phase respectively. The signal is passed onto the OFDM receiver through a mixer. The receiver has also been implemented using MATLAB codes. The ADC at the receiver converts the electrical received signal to a digital signal, and reverse transmitter process is performed to obtain our original signal.To evaluate the effects of the CT coding on PAPR, we plot the CCDF against the PAPR. Our results show that for a CCDF of10"3the PAPR was reduced by about3dB. The optical spectrum analyzers, which have been used to analyze the signal as it travels along the optical link, shows that despite the losses and noise in the optical link we could obtain a strong signal at the Photo Detector. Constellation diagram is used to evaluate transmitted and received signal quality, for the signal with CT coding implementation the constellation shows a cleaner signal as compared to the signal without the technique.