Orthogonality Measurent of Ofdm Signal

ABSTRACT


INTRODUCTION
Orthogonal Frequency Division Multiplexing (OFDM) is one of the emerging fields in wireless local area network that are also targeted for ad hoc network.OFDM can also be exploited in MANET to improve the energy and speed performance Mobile nodes in MANET are communicated directly through radio frequency range and wireless links.This process referred as peer o peer or single ad hoc network If the destination mobile node is out of range, then other nodes between source and destination act as router to transmit information between source and destination.This process is referred as multi-hop ad hoc networks.Single and Multi-hop ad hoc networks is illustrated in Figure 1.

BACKGROUND
Mobile Ad Hoc Networks are self-configurable and infrastructure less networks consisting of mobile devices and routers which are able to support mobility and organize themselves arbitrarily [1].It requires an extremely flexible technology for establishing communications between source and destination nodes.Design and performance analysis of MIMO-OFDM system using different antenna configurations is discussed in [2].Hash based technique to identify the selfish node in Mobile Ad-hoc Network is explained in [3].
For the Modulation/De-modulation part of OFDM, Quadrature Amplitude Modulation (QAM) is frequently used for better Bit Error Rate (BER) and Signal to Noise Ratio (SNR).For the Channel Encoder/Channel Decoder of OFDM, Hamming codes are widely used for improving the error detecting probability [4].Similarly, Single-path Delay Feedback (SDF) based IFFT/FFT structure is used for converting the time domain signal into frequency domain signal and vice versa [5].Reconfigurable Metamaterial Structure at Millimeter Wave Frequency Range has been explained in [6].In [7] presented the maximizing energy efficiency for consumption circuit power in downlink massive MIMO wireless networks The receiver side of OFDM consists of cyclic prefix removal for remove the added bits in transmitter side, Fast Fourier Transformation (FFT) for convert the time domain signal into frequency one, De-modulation (reverse process of modulation), Channel Decoder for decode the encoded word, and Source decoder to convert digital decoded binary information to analog one.Low power 128 point split radix fft for LTE application has been described in [8]- [9].

THE PROBLEM
OFDM technique faces many challenges like configuring different types of hardware architecture based on different types of application requirement.However, due to more complexity of hardware parts, single part adaptation is not sufficient to implement at appropriate time.

THE PROPOSED SOLUTION
The structure of OFDM transmitter and receiver is illustrated in

RESULTS AND DISCUSSION
The performance of the OFDM system and nature of the OFDM signal during the difficulty condition was analyzed using the Matlab simulation.Signal orthogonality, Bit error rate (BER), Spectrum analysis are predicted and evaluated.The results are shown in the Figure 3 and 4.

Figure 1 .
Figure 1.Single hop ad hoc network

Figure 2 .
The Encoder and Decoder of OFDM transmitter and receiver act as channel encoder and channel decoder which converts the source signals into set of binary information.One of the key techniques in which OFDM can be implemented on the sender side and receiver side for efficient communication is Fast Fourier Transformation (FFT).In general FFT is used to convert the time domain signals into frequency domain signals and vice versa.

Figure 2 .
Figure 2. Architecture of OFDM System

Figure 3 .
Figure 3. Spectrum Analyzes of OFDM Signal