Performance comparison of Single Carrier Modulation with frequency domain equalization an OFDM for wireless communications (original) (raw)
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Orthogonal Frequency Division Multiplexing (OFDM) has the inherent problem of high peak to average power ratio (PAPR). Moreover, it suffers from high sensitivity to frequency offsets. In comparison to OFDM, Single Carrier Modulation (SCM) coupled with frequency domain equalization (FDE) offers a comparable performance and complexity while avoiding the drawbacks of high PAPR and frequency offset sensitivity, associated with multicarrier modulation. This paper presents a performance comparison between OFDM and SCM with FDE over multipath wireless channel with narrowband interference (NBI). SCM utilizes minimum mean square error (MMSE) algorithm for the training of the frequency domain equalizer. It is shown that SCM employing a frequency domain MMSE equalizer exhibits higher immunity to NBI as compared to an OFDM system, over multipath wireless channel.
International Journal of Communication Systems, 2011
In this paper, we study the performance of the continuous phase modulation (CPM)-based orthogonal frequency division multiplexing (CPM-OFDM) system. Also, we propose a CPM-based single-carrier frequency domain equalization (CPM-SC-FDE) structure for broadband wireless communication systems. The proposed structure combines the advantages of the low complexity of SC-FDE, in addition to exploiting the channel frequency diversity and the power efficiency of CPM. Both the CPM-OFDM system and the proposed system are implemented with FDE to avoid the complexity of the equalization. Two types of frequency domain equalizers are considered and compared for performance evaluation of both systems; the zero forcing (ZF) equalizer and the minimum mean square error (MMSE) equalizer. Simulation experiments are performed for a variety of multipath fading channels. Simulation results show that the performance of the CPM-based systems with multipath fading is better than their performance with single path fading. The performance over a multipath channel is at least 5 and 12 dB better than the performance over a single path channel, for the CPM-OFDM system and the proposed CPM-SC-FDE system, respectively. The results also show that, when CPM is utilized in SC-FDE systems, they can outperform CPM-OFDM systems by about 5 dB. Copyright © 2010 John Wiley & Sons, Ltd.
A comparison of an OFDM system and a single carrier system using frequency domain equalization
European Transactions on Telecommunications, 2002
In this work we compare an OFDM (Orthogonal Frequency Division Multiplexing) system and a SC/FDE (Single Carrier System with Frequency Domain Equalization) system in terms of their BER performance, channel estimation techniques, bandwidth-efficiency and other design parameters. In both systems an estimation of the channel transfer function is needed for equalization purposes. Different frequency domain based channel estimation techniques for both systems are presented and compared. BER-simulations have been performed for channel-coded data in typicd indoor multipath environments. The parameters of both systems are adapted to the Hiperlad and IEEE 802.1 la standards. It will be pointed out that OFDM shows slight advantages when taking the BER performance into account, while the SC/FDE system exhibits advantages in terms of signal processing complexity. Finally a combination of OFDM and SC/FDE is described that exhibits significant advantages.
Indonesian Journal of Electrical Engineering and Computer Science
The nature of future wireless applications requires high data rates and for this OFDM technique is used. OFDM stands for orthogonal frequency division multiplexing and is a type of multi-carrier transmission where all the subcarriers are orthogonal to each other. At high data rates, the channel distortion to the data is very important and it is somewhat impossible to recover the transmitted data with a simple receiver. So a complex receiver structure is needed which uses computationally expensive equalization and channel estimation algorithms to estimate the channel. These estimations can be used within the received data to recover the originally transmitted data. OFDM can simplify the equalization problem by changing the frequency-selective channel into a flat channel. The radio channels in mobile radio systems are usually multipath fading channels that results in intersymbol interference (ISI) in the received signal. To remove ISI from the signal, many kind of equalizers can be used. The need for equalizers arises from the fact that the channel has amplitude and phase dispersion which results in the interference of the transmitted signals with one another which is known as ISI .So, to solve this problem equalizers are designed. Equalizer is intend to work in such a way that Bit Error Rate (BER) should be low and Signal-to-Noise Ratio (SNR) should be high. An equalizer within a receiver compensates for the average range of expected channel amplitude and delay characteristics. This paper deals with the various equalization techniques (LMS, RLS and CMA) used for OFDM system .A comparative analysis of different equalization technique in terms of BER is done using MATLAB Simulink.
Performance evaluation of various Channel Equalization Techniques in terms of BER for OFDM System
International Journal of Wireless and Mobile Communication for Industrial Systems, 2016
Orthogonal frequency division multiplexing is a type of multi-carrier transmission where all the subcarriers are orthogonal to each other. There is always a need for higher data rate and for this OFDM technique is used. At high data rates, the channel distortion to the data is very important and it is impossible to recover the transmitted data with a simple receiver. So, a complex receiver structure is needed which uses computationally expensive equalization and channel estimation algorithms to estimate the channel. These estimations can be used within the received data to recover the originally transmitted data. OFDM can simplify the equalization problem by changing the frequency-selective channel into a flat channel. The intersymbol interference (ISI) can occur in received signal due to multipath fading. In order to remove the ISI many kind of equalizers can be used. Equalizer is intend to work in such a way that Bit Error Rate (BER) should be low and Signal-to-Noise Ratio (SNR) should be high. An equalizer within a receiver compensates for the average range of expected channel amplitude and delay characteristics. This paper deals with the various equalization techniques (LMS, RLS and CMA) used for OFDM system. A comparative analysis of Bit error rate (BER) using different equalization technique along with different digital modulation is done using MATLAB Simulink. Simulation results shows that constant modulus algorithm (CMA) results in minimum value of BER which can be further used to enhance the performance of OFDM.
Analysis & Review Equalization & Channel Estimation for OFDM & CDMA
— Multi-carrier code division multiple accesses (MCCDMA) has been considered as a strong candidate for next generation wireless communication system due to its excellent performance in multi-path fading channel and simple receiver structure. However, like all the multi-carrier transmission technologies such as OFDM, the inter-carrier interference (ICI) produced by the frequency offset between the transmitter and receiver local oscillators or by Doppler shift due to high mobility causes significant BER (bit error rate) performance degradation in MC-CDMA system. Many ICI cancellation methods such as windowing and frequency domain coding have been proposed in the literature to cancel ICI and improve the BER performance for multi-carrier transmission technologies. However, existing ICI cancellation methods do not cancel ICI entirely and the BER performance after ICI cancellation is still much worse than the BER performance of original system without ICI.
2012
Orthogonal Frequency Division Multiplexing (OFDM) has recently been applied in wireless communication systems due to its high data rate transmission capability with high bandwidth efficiency and its robustness to multi-path delay. Fading is the one of the major aspect which is considered in the receiver. To cancel the effect of fading, channel estimation and equalization procedure must be done at the receiver before data demodulation. This paper mainly deals with pilot based channel estimation techniques for OFDM communication over frequency selective fading channels. This paper proposes a specific approach to channel equalization for Orthogonal Frequency Division Multiplex (OFDM) systems. Inserting an equalizer realized as an adaptive system before the FFT processing, the influence of variable delay and multi path could be mitigated in order to remove or reduce considerably the guard interval and to gain some spectral efficiency. The adaptive algorithm is based on adaptive filtering with averaging (AFA) for parameter update. Based on the development of a model of the OFDM system, through extensive computer simulations, we investigate the performance of the channel equalized system. The results show much higher convergence and adaptation rate compared to one of the most frequently used algorithms -Least Mean Squares (LMS)
Single-Carrier Frequency Domain Equalization and Wireless Applications
Applied Mechanics and Materials, 2011
In this paper, single carrier frequency domain equalization with space time transmit diversity was implemented and evaluated in real-time using a DSP-based wireless MIMO test-bed. The implemented schemes supported a large set of modulations, from BPSK up to QAM64. Zero padding is introduced to mitigate inter-block interference. Robust time and frequency synchronization together with channel estimation based on Kalman filtering is used to address the adverse intersymbol interference and the severe carrier frequency offset due to hardware impairments.
An investigation of MIMO singlecarrier frequency-domain MMSE equalization
2002
In recent years, the ambition to achieve very high data rates in wireless communication systems has fuelled the study of multiple-input multiple-output (MIMO) architectures and has resulted in the need for more advanced equalization techniques. Currently, the wireless industry is at a point where typical time-domain equalization solutions are becoming too complex to implement in MIMO systems. In this paper, a single-carrier frequency-domain equalization (SC-FDE) solution is presented that utilizes the minimum mean-squared error (MMSE) criterion to perform equalization on the received message. The error-rate performance of a system that employs this MMSE equalizer is analyzed.