Performance Analysis of OFDM in Combating Multipath Fading (original) (raw)
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Comparative BER Performance of M-ary QAM-OFDM System in AWGN & Multipath Fading Channel
2012
OFDM (Orthogonal Frequency Division Multiplexing) is a multicarrier technique where linearly modulated data streams are divided into number of substreams each occupying a bandwidth less than the total bandwidth of the signal. However, full justice was done in proper utilization of bandwidth in OFDM where subcarriers overlap orthogonally. M-ary modulation schemes are preferred because in these schemes more than one bit can be grouped & transmit at a time which is very effective for band limited channels. MQAM (M-ary Quadrature Amplitude Modulation) is the most effective digital modulation technique as it is more power efficient for larger values of M. The basic idea of M-ary QAM & OFDM has been discussed in the paper. The Simulink based model of the MQAM-OFDM system with normal AWGN channel and Rayleigh fading channel has been made for study error performance under different channel conditions. Lastly a comparative study of BER performance of 64QAM-OFDM & 128QAM-OFDM under AWGN channel & Rayleigh fading channel has been given.
Performance Estimation of OFDM in Multipath Rayleigh Fading Channel
In recent years high speed wireless data communications have increasingly been used in many application areas like Orthogonal Frequency Division Multiplexing (OFDM) .The principles of OFDM modulation have been in theory for a long time. But in recent years, this technology has crossed the limitations into the real world of modern communication systems to combat Inter-Symbol Interference (ISI) through multicarrier modulation. OFDM has proved to be very effective in mitigating adverse multipath effects of a broadband wireless channel. Counteracting the frequency selectivity of multipath channels by multiplexing information on different orthogonal carriers is the key to the OFDM success. In this research work, the aim is to figure out the way, for improving the performance of transmitting information. Various kinds of modulation techniques will be studied in terms of their performance in a virtual Rayleigh Channel environment. The average BER performance for different MPSK and M-QAM will be evaluated and use of gray coded bit mapping for different modulation schemes to get BER performance with OFDM technique The numerical results are computed and plotted for M=16 and 64. I. INTRODUCTION Orthogonal frequency-division multiplexing (OFDM) is the modulation technique for European standards such as the Digital Audio Broadcasting (DAB) and the Digital Video Broadcasting (DVB) systems. Orthogonal frequency-division multiplexing (OFDM) is a method of encoding digital data on multiple carrier frequencies. The data are sent over parallel sub-channels with each sub-channel modulated by a modulation scheme such as BPSK, QPSK, and 16 QAM etc. The advantage of OFDM is its ability to cope with severe channel conditions compared to a single carrier modulation scheme but still maintaining the data rates of a conventional scheme with the same bandwidth. As such it has received much attention and has been proposed for many other applications, including local area networks and personal communication systems. OFDM is a type of multichannel modulation that divides a given channel into many parallel sub-channels or subcarriers so that multiple symbols are sent in parallel. Furthermore, channel equalization is simplified because OFDM may be viewed as using many slowly modulated narrowband signals rather than one rapidly modulated wideband signal. Also, the low symbol rate naturally makes the use of guard interval between symbols reducing ISI. Orthogonal Frequency Division Multiplexing has become one of the mainstream physical layer techniques used in modern communication systems.
Orthogonal Frequency Division Multiplexing OFDM is a system in a communication used to transmit message signal (data) on multiple carrier over single communication channel. In this paper, the multipath fading channel otherwise known as the Rayleigh Fading channel is used in the modelling. The Rayleigh fading channel is characterized by the present of non-line-of-sight component. The BER of different digital modulation technique such as the BPAK, QPAK and QAM is used in an OFDM system in this paper. The BER output was compared to ascertain which is the best. The model used is the OFDM system model with IFFT/FFT application. The application used is the SIMULINK BLOCKs. The Result is then compared and conclusion drowned.
Analysis the Performance of OFDM Using BPSK, QPSK, 64-QAM, 128-QAM & 256-QAM Modulation Techniques
Journal of Electrical Engineering, Electronics, Control and Computer Science, 2021
At the present era of communication technology, every user wants a communication system that has higher data transmission capability and reliability. Orthogonal Frequency Division Multiplexing (OFDM) is a frequency division multiplexed multi carrier transmission method and each multiplexed signal is orthogonal to each other. This technology is known as core technology of the new generation wireless mobile communication systems. This technology has higher data transmission capability and reliability as well as has the ability to combat frequency selective fading or narrowband interference while maintaining high spectrum utilization. The aim of this paper is to analyze the performance of the OFDM technology using different modulation techniques. This paper is mainly focused on the calculation of the Bit Error Rate (BER) to analyze the performance of OFDM systems. In this paper, we considered BPSK, QPSK, 64-QAM, 128-QAM and 256-QAM modulation techniques. All the simulations has been accomplished by using the MATLAB framework.
The Orthogonal Frequency Division Multiplexing (OFDM) is a practical application of both amplitude and phase modulation scheme and has taking its place in Multiplexing Techniques where a number of independent message signal are at the same time transmitted over a single channel. OFDM is beneficial in transmission with high data rate and better performance. High data rates are achieved by the use of multiple carriers and performance improvement. This paper is based on the QPSK and QAM of Different Modulation order. The performance Evaluation is done using the Bit Error Rate (BER) Against the Signal to Noise Ratio (SNR) parameters which shows a low BER to High SNR. At the end of the work, it was found out that the QPSK has more better performance in OFDM system than the QAM. QPSK has lower BER than the QAM in AWGN, Rayleigh and Rician channel. The performance of QPSK in OFDM is better than the QAM in the OFDM system. The simulation was done using MATLAB/SIMULINK. 1. Introduction All electrical signals exist in continuous wave nature at a given time. Analog communication was the order of the day until recently, a digital form of communication has replaced it due to significant advantages over the analog means of communication. The most important features are the digital modulation techniques adopted by the digital communication systems. Some of the advantages of the techniques includes greater noise immunity and its robust channel impairment, easier multiplexing of various forms of information, accommodation of larger amount of digital error control codes with detection and correction transmission errors and implementation of digital modulation and demodulation scheme and techniques. The type of MODEM adopted depends largely on quality factors such as provision of low bit error rate at low received signal to noise ratio, good performance in an interference, multipath and fading environments, minimum bandwidth occupation and lastly easy and probably cost effective in implementation. This paper in based on BER and SNR analysis using the Digital Communication M-array Modulation Scheme such as PSK and QAM. The binary scheme of a digital data consists of only two symbols i.e. 1 and 0. The distinct waveform known as pulse is assign to these two symbols and transmitted over a channel and detected at the receiving end after converting it back to binary data. In an M-array scheme, a symbol consists of more than one binary digits of either 0 and 1 or both. OFDM as a transmission scheme is adopted by the broadband radio systems and its current used in a well-known standard IEEE 802.16 hence the part which determines the performance in a combination of the dynamic sub-carrier allocation, transmission power allotment, and adaptive modulation (Sivanagaruju & Siddiah, 2014). OFDM is beneficial in transmission with high data rate and better performance. High data rates are achieved by the use of multiple carriers and performance improvement caused by interference ISI which disports the expected signal (Mousumi et al. 2014). Other benefits include increase in spectral efficiency and also minimizes multipath distortion. In this paper, a total number of 128 subcarriers is used at a cyclic prefix of 32. The Maximum bit error is at 100 at 1e7 maximum number of errors. OFDM baseband signal is typically the sum of number of orthogonal sub-carriers, of which each subcarrier is modulated independently by its own data either QAM or PSK. As the name implies, simultaneous transmission is allowed without interference on a lot of sub-carrier from each other. The simplest form of PSK in the binary scheme BPSK. Though the QPSK will be used in this evaluation in detail. The BPSK like QAM overlap without interference other form of PSK is QPSK (Quadrature phase shift keying). QPSK is often used in the evaluation of the Bit Error rate (BER) due to its improved spectral efficiency requirement and for a given bit rate 1/T b, a QPSK system requires just half the bandwidth required for a BPSK system. Hence, QPSK is bandwidth efficient. The QPSK uses the points constellation diagram. QPSK encodes two bits per symbol. In this paper, QAM and PSK will be used in the analysis of the BER as they modulate both phase modulation and
The demand for high-speed mobile wireless communications is rapidly growing. Orthogonal Frequency Division Multiplexing (OFDM) technology promises to be a key technique for achieving the high data capacity and spectral efficiency requirements for wireless communication systems in the near future. An Orthogonal Frequency Division Multiplexing (OFDM) scheme offers high spectral efficiency and better resistance to fading environments. In OFDM the data is modulated using multiple numbers of sub-carriers that are orthogonal to each other because of which the problems associated with other modulation schemes such as Inter Symbol Interference (ISI) and Inter Carrier Interference (ICI) is reduced. This paper deals with the analysis of OFDM System utilizing different modulation techniques over Rayleigh, Rician and Additive White Gaussian Noise (AWGN) fading environments with the use of pilot aided arrangement and finally the results are conveyed. The aim of this thesis is to provide practical solutions for OFDM communication system by showing its better performance on different channel using different modulation technique. We applied different channel like AWGN, Rayleigh and Rician over OFDM system. We analyzed the performance of OFDM system regarding different channel. We analyzed the performance and showed the most suitable channel for OFDM communication system. Moreover, we also applied different modulation scheme over OFDM system to show which modulation technique is more efficient for OFDM system. Here we used BPSK, QPSK, 16-QAM and 64-QAM modulation technique. From our experiment we found that, among AWGN & the fading channels (Rayleigh & Rician), AWGN channel has less BER and P(e) than others. So we can say that, for OFDM system, AWGN channel is most suitable. We also found that, in all environments BPSK shows better performance than QPSK, 16QAM & 64QAM. When modulation level increased, corresponding BER & Probability of error P(e) also increased.
MIMO-OFDM (Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing) system has been recognized as one of the most popular and competitive technique in a wireless environment nowadays. The performance is calculated in terms of Bit Error Rate (BER) versus the Signal to Noise Ratio (SNR). In this paper we discuss the BER performance of the MIMO-OFDM system with two different equalizers (ZF and MMSE) for various modulation techniques i.e. BPSK, QPSK, 16-QAM and 64-QAM using multipath fading channels i.e. AWGN (Additive White Gaussian Noise), Rayleigh and Rician channel. The multicarrier modulation is employed, which gives advantages like inter symbol interference (ISI) reduction, high data rate, higher reliability, and better performance in multipath fading. The simulation results show that, with MMSE and ZF equalizers, the BER performances is better in MMSE equalizer. Further we analyzed in different fading channels for various modulation techniques in both the equalizers.
Performance Analysis of OFDM System with PSK Modulation over Rayleigh Fading Channel
International journal of multidisciplinary and current research, 2015
Orthogonal Frequency Division Multiplexing (OFDM) is a special form of multicarrier transmission technique. OFDM mitigates Inter Symbol Interference (ISI) caused by delay spread of wireless channel. Also it offers high data rate, high Spectral Efficiency (SE), and immunity against Narrow Band Interference (NBI). Therefore it has been adopted in many wireless standards such as worldwide interoperability for microwave access (WiMAX) and Long Term Evolution (LTE). Spectral Efficiency (SE) is one of the major issues in wireless communication system. In wireless communication system SE depends on modulation technique. This study investigates the SE and Bit Error Rate (BER) performance of OFDM system over Rayleigh fading channel for different Phase Shift Keying (PSK) modulation techniques. Simulation results show that minimum SE obtained with the Binary Phase Shift Keying (BPSK) modulation technique at lower SNR. The comparative study of BER over different modulation techniques show that ...
International Journal of Electrical and Computer Engineering (IJECE), 2022
Orthogonal frequency division multiplexing (OFDM) is a multicarrier modulation (MCM) technique that divides the wide bandwidth into parallel narrow bands, each of which is modulated by orthogonal subcarriers. Currently, OFDM is a high-spectral efficiency modulation technique that is used in a variety of wired and wireless applications. The transmitted signal in a wireless communication channel spreads from transmitter to receiver through multiple reflective paths. This triggers multipath fading, which causes variations in the received signal's amplitude and phase. Slow/fast and frequency-selective/frequency-nonselective are the main types of multipath fading channels. Therefore, in this paper, we proposed new models for modeling multipath fading channels, such as the exponential fading channel and the Gamma fading channel. In addition, new bit-error-rate (BER) derivations have been derived. The performance of the OFDM system over proposed channel models has been evaluated using Monte-Carlo simulation and compared to the Rayleigh fading channel model. The obtained results via simulations show that the exponential fading channel at a rate parameter (λ=0.5) outperforms the Rayleigh fading channel by 6 dB for all values of Eb/No, while the Gamma fading channel at (α=2) outperforms the Rayleigh fading channel by 3 dB for all values of Eb/No.
Study of Modulation Schemes over a Multipath Fading Channels
IJMTST, 2021
Communications systems concerted over wireless channels depend on the environment. Communications system can be more reliable and efficient by properly analyzing wireless channels. Today's most important features are a high data rate and reliable performance to exploiting viable networks during this new information age. The channel is not time-invariant in wireless communication, so the received signal exhibits amplitude, phase, and angle variations due to multipath fading. Increasing data rates and reducing bandwidth make Orthogonal Frequency Division Multiplexing (OFDM) an important component of wireless communication systems. The OFDM technique uses many carriers very efficiently. With this scheme, interference is robustly reduced, and fading scenarios are easily accommodated. Analyzing digital modulation schemes requires evaluating link performance with fading channels. The paper compares channel performance over varying fading environments using a variety of modulation schemes. We study the BER and SNR properties of the AWGN, Rician fading and Rayleigh fading channels modulated with BPSK, QPSK, and M-ary QAM.