Ofdm Simulation Research Papers - Academia.edu (original) (raw)

The high data transmission rates in the communication channel is a recent growing demand which is achieved by using the multiple input multiple output systems because of their unique properties.. The OFDM systems that adopt the cyclic require only one inverse discrete Fourier transform (IDFT) operation at the low-complexity by means of increasing the transmission diversity in MIMO pilot sequences which minimize the mean square error (MSE) of the channel estimate in traditional MIMO systems are inapplicable to CDD minimum MSE of both the least square (LS) channel estimate and the MMSE channel estimate in CDD systems. The derived criteria are then used to develop a general methodology for determining the sequence. Significantly, the proposed design methodology enables the status of the channel to be estimated using single OFDM symbol. We have compared the performances of channel estimation algorithm by measuring bit error rate vs. SNR with BPSK, QPSK 16

This paper compares the performance of various channel estimation techniques for OFDM systems over quasi-static channels using MATLab. It compares the performance of five channel estimation techniques, these are: decision directed (DD), linear interpolation, second-order interpolation, discrete Fourier transform (DFT) interpolation, minimum mean square error (MMSE) interpolation. The performance is evaluated in terms of two widely-used performance measures, namely, bit-error rate (BER) and the mean square error (MSE) for different levels of signal-to-noise ratio (SNR). The OFDM model is explained and implemented using MATLab to run different simulations. The simulation results demonstrate that the DD channel estimation provides the lowest BER and MSE as compared to interpolation techniques, at the cost of extra processing delay and comparatively sensitive to channel variations between OFDM symbols. Also, the MMSE interpolation outperforms all other interpolation techniques.

This paper studies control format indicator (CFI) estimation methods in 4G-LTE communication systems. CFI is an essential control signal in LTE, and must be correctly detected at the receiver to avoid degraded system performance. The standard method of CFI detection involves the use of the Maximum Likelihood (ML) estimation criterion. Unfortunately, ML decoding performance relies on accurate channel estimation, and as a consequence may result in poor CFI decoding when channel estimates are poor. To improve CFI detection in severe fading channel conditions, a time-domain decision rule that requires no channel estimation, is proposed. Results show that when compared with the ML approach, the proposed method reduces the probability of CFI estimation error in the form of reduced block error rate.

- by Saheed Adegbite and +1
- •
- Orthogonal Frequency Division Multiplexing (OFDM), Long Term Evolution (LTE), LTE physical layer, Data Recovery

Performance of pilot-aided channel estimation
techniques such as the Least Squares (LS) method depends on
not only on the signal-to-noise ratio (SNR), channel conditions
and pilot ratio, but also on the choice of interpolation method
for deriving channel estimates at non-pilot subcarriers. This
paper investigates the bit-error-rate (BER) performance of
linear, spline and Piecewise Cubic Hermite Interpolating
Polynomial (PCHIP) interpolation methods in LS channel
estimation over the three extended ITU channel profiles defined
for Long Term Evolution (LTE) testing. Simulation results
show that applying the linear interpolation method produces
the best BER performance over the fading channel with the
smallest multipath delay spread. It is also shown that the choice
of best interpolation method actually depends on the SNR in
some of the fading channel profiles.

The 3rd Generation Partnership Project (3GPP) introduced LTE to meet increasingly demands for communication services with high speed and quality. LTE uses OFDM in the form of OFDMA in the downlink and SCFDMA in the uplink combined with MIMO offering high data rate, high capacity and immunity against multipath channels. However, still the high PAPR of the LTE transmitted signal is the major problem affecting overall system performance degradation and power efficiency. A plenty of research has been devoted to reduce the performance degradation due to the PAPR problem inherent to LTE OFDM systems. A portion of the current techniques such companding methods have low-complexity, no constraint on modulation format and subcarrier size, good distortion and spectral properties; however, they have limited PAPR reduction capabilities. This paper proposes seven new hybrid schemes including Zaddoff Chu Matrix Transform (ZCT) precoding and six modern companding methods; Rooting Companding (RCT), New Error Function Companding (NERF), Absolute Exponential Companding (AEXP), Logarithmic Rooting Companding (LogR), Cosine Companding (COS) and Tangent Rooting Companding (TanhR). Furthermore, the seventh proposed hybrid scheme has been added incorporating ZCT precoding with new proposed companding called Advanced AEXP (AAEXP) companding. The developed methods are combining properties of both ZCT & Compandings, and achieving superior PAPR performance and optimal BER. Simulations results illustrate that the new seven proposed hybrid schemes achieve better PAPR reduction, and BER performance and the best achievement has been achieved by ZCT+AAEXP scheme.

The future wireless communication systems demand enhanced security and reliability than the current systems. In this work, we propose a more simple yet efﬁcient physical layer security (PLS) technique for achieving reliable and secure communication in the multiple-input single-output non-orthogonal multiple access (MISO-NOMA) system. This system is capable of providing enhanced conﬁdential communication as well as inter-user interference cancellation without using the successive interference cancellation (SIC) method. As conventional NOMA was already adopted under the name of multi-user superposition transmission (MUST) in release 13 of 3GPP and is improved in terms of receiver design for 3GPP-release 16, which still suffers from several security risks and drawbacks. In this work, we have analyzed these drawbacks and presented a new kind of NOMA with better performance results in cases where conventional NOMA fails. The proposed algorithm combines the beneﬁt of pre-coder matrices with simultaneous transmission using antenna diversity to provide simple, reliable, and secure communication without complex processing at the receivers in downlink scenarios. The effectiveness of the proposed algorithm is veriﬁed and proven by extensive numerical simulations.

The paper describes how to improve channel estimation in Single Carrier Frequency Division Multiple Access (SC-FDMA) system, using a Hybrid Artificial Neural Networks (HANN). The 3 rd Generation Partnership Project (3GPP) standards for uplink Long Term Evolution Advanced (LTE-A) uses pilot based channel estimation technique. This kind of channel estimation method suffers from a considerable loss ofbitrate due to pilot insertion; all data frame sent contains reference signal. The HANN converts data aided channel estimator to semi blind channel estimator. To increase convergence speed, HANN uses some channel propagation Fuzzy Rules to initialize Neural Network parameters before learning instead of a random initialization, so its learning phase ismore rapidly compared to classic ANN.HANN allows more bandwidth efficient and less complexity. Simulation results show that HANN has better computational efficiency than the Minimum Mean Square Error (MMSE) estimator and has faster convergence than classic Neural Networks estimators.

Growth in technology has led to unprecedented demand for high speed architectures for complex signal processing applications. In 4G wireless communication systems, bandwidth is a precious commodity, and service providers are continuously met with the challenge of accommodating more users with in a limited allocated bandwidth. To increase data rate of wireless medium with higher performance, OFDM (orthogonal frequency division multiplexing) is used. Recently DWT (Discrete wavelet transforms) is adopted in place of FFT (Fast Fourier transform) for frequency translation. Modulation schemes such as 16-QAM, 32-QAM, 64-QAM and 128-QAM (Quadrature amplitude modulation) have been used in the developed OFDM system for both DWT and FFT based model. In this paper we propose a DWT-IDWT based OFDM transmitter and receiver that achieve better performance in terms SNR and BER for AWGN channel. It proves all the wavelet families better over the IFFT-FFT implementation. The OFDM model is developed using Simulink, various test cases have been considered to verify its performance. The DWT-OFDM using Lifting Scheme architecture is implemented on FPGA optimizing hardware, speed & cost. The wavelet filter used for this is Daubechies (9, 7) with N=2. The RTL code is written in Verilog-HDL and simulated in Modelsim. The design is then synthesized in Xilinx and implemented on Virtex5 FPGA board and the results were validated using ChipScope.

- by shanmukha swamy
- •
- Henri Bergson, Bertrand Russell, OFDM, OFDMA

This paper presents a model which is Finite Radon Transform based Orthogonal Frequency Division Multiplexing-Interleaver Division Multiple Access (OFDM-IDMA) system for next generation wireless communication system. FRAT is the underlying fundamental concept used for computerized tomography scanning, as well for a wide range of other disciplines, including radar imaging, Geophysical imaging, nondestructive testing and medical imaging. Recently Finite Radon Transform (FRAT) was proposed as a mapping technique in OFDM system Conventional OFDM/QAM systems are robust for multi-path channels due to the cyclically prefixed guard interval which is inserted between consequent symbols to Remove ISI. An interleaver-based multiple access schemes have also been studied in for high spectral efficiency, improved performance and low receiver complexity. This scheme relies on interleaving as the only means to distinguish the signals from different users, and hence it has been called interleave-division multiple-access (IDMA). From the simulation results the FRAT-OFDM-IDMA system performs better as compared to DFT-OFDM-IDMA and DWT-OFDM-IDMA system in term of BER performance for next generation wireless communication system. OFDM is a digital modulation scheme in which a wideband signal is split into a number of narrowband signals. Because the symbol duration of a narrowband signal will be large than that of a wideband signal, the amount of time dispersion caused by multipath delay spread is reduced.

The UMTS network is complementary to GSM and GPRS. The GSM network covers the features required for voice-type services in a circuit mode, the network brings GFPRS the first features to the introduction of services such as packet data, and UMTS networks complement these by
offering voice and data services on an additional packet. UMTS is thus an extension of GPRS and also works in packet mode. The transmission speed offered by UMTS networks to 2Mbit/s. UMTS infrastructure enables expansion of frequencies as well as changes in data coding. In this
paper, the use of OFDM signals in the UMTS access network UTRANFDD and 64QAM modulation allowed us to improve the rate 2Mbit/s to 22.5 Mbit/s. The results, including improved throughput to 22.5Mbit/s, show us that the power frequency spectrum of a
single OFDM signal is centered around the fundamental frequency, but the spectral width of the power spectrum of the OFDM signals is higher than that of the power spectrum is a function that is typically used in UMTS. We also noted that the greater the number of carriers increases, the more important
the spectral width is. The multicarrier modulation was based, in our case, on the choice of the multiplexing of signals without noise and with noise.

Filter bank multicarrier (FBMC) is considered a competitive waveform candidate for 5G that can replace orthogonal frequency division multiplexing (OFDM). However, channel estimation (CE) is a big challenge in FBMC because it suffers from intrinsic interference which is due to the orthogonality of the subcarrier functions in the real field only. In this paper, we investigate a proposed modified interference approximation scheme (M-IAM) by approximating the intrinsic interference from the neighbouring pilots to accommodate the complex channel frequency and thus improving CE performance besides simplifying its processing. The M-IAM scheme has a larger pseudo pilot magnitude than other conventional preamble schemes, namely the interference approximation method (IAM) with its versions (IAM-C) and (E-IAM-C); in addition to the novel preamble design (NPS). In addition, the proposed (M-IAM) scheme is characterized by the lower transmitted power needed. The CE performance of the M-IAM is investigated through 512 and 2048 subcarriers via different types of outdoor and indoor multipath fading channels that are time-invariant such as IEEE 802.22, IEEE 802.11, Rician, and additive white Gaussian noise (AWGN), as well as time-varying channels such as Rayleigh and Vehicular A (Veh-A). Simulation results demonstrate that the proposed M-IAM scheme achieves a lower bit error rate (BER), lower normalized mean square error (NMSE) and lower peak-to-average power ratio (PAPR) over the conventional preamble schemes under the aforementioned channel models. The proposed scheme has the advantage of saving the transmitted power, a requirement that could match 5G low power requirements. KEYWORDS Filter bank multicarrier (FBMC), intrinsic interference, preamble based channel estimation methods

- by shanmukha swamy
- •
- Henri Bergson, Bertrand Russell, OFDM, OFDMA
- by M. Aboul-dahab
- •
- Distributed Computing, MIMO-OFDM systems, Intrinsic motivation, OFDMA

This paper studies the frame synchronization of Orthogonal Frequency Division Multiple Access-Time Division Duplexing (OFDMA-TDD) systems and proposes a new method for downlink of IEEE 802.16 to improve frame synchronization performance. In this paper, we adapt three existing timing metrics for frame synchronization in OFDM mode of WiMAX. Among the methods considered, it is shown that direct application of these metrics, is not possible for frame synchronization in OFDMA mode of WiMAX. Modifications to these timing metrics are done to adapt them for OFDMA mode. Simulations are conducted for AWGN and frequency selective channels to demonstrate the performance of the modified timing metrics. Simulation results show that the proposed method outperforms the existing algorithms in both frequency selective and AWGN channels and is robust to the range of the timing offsets and carrier frequency offset (CFO).

- by Meisam Naderi
- •
- Computer Science, IEEE 802.16 (WiMAX), Synchronization, MIMO-OFDM systems

This paper proposes an enhanced pilot-aided channel estimation algorithm for the second generation of the digital video broadcast for terrestrial (DVB-T2) standard. Two channel estimation techniques are discussed; the first is based on the 3-points averaging technique, while the second is based on studying the frequency domain pattern of the channel response. The second technique leads to a 0.5 dB reduction in the SNR needed to guarantee a specific bit error rate (BER) requirement when compared to the conventional estimation technique recommended by the DVB-T2 implementation guide lines.

To reduce the occurrence of high peak-to-average power ratio (PAPR), this paper introduces prolate-binary sequences, and their application in orthogonal frequency division multiplexing (OFDM) systems that implement selected mapping (SLM). Through computer simulation, it is shown that the proposed prolate-binary sequences offer combined improved PAPR reduction performance, and reduced computational complexity compared with Riemann-binary sequences.

- by Saheed Adegbite and +1
- •
- Computational Complexity, Orthogonal Frequency Division Multiplexing (OFDM), Long Term Evolution (LTE), Ofdm Systems

This paper addresses the issue of high computational complexity associated with side information (SI) estimation in orthogonal frequency division multiplexing (OFDM) systems that implement selected mapping (SLM) to reduce peak-to-average power ratio (PAPR). The proposed method is based on a slightly modified SLM approach that enables the use of a low complexity binary detection criterion for SI estimation, without the need for SI transmission. Simulations show that the combined PAPR reduction and BER performance of the proposed method is similar to both pilot-assisted Maximum-Likelihood (PAML) SI estimation scheme and standard SLM that presumes perfect knowledge of SI. In addition, relative to the PAML scheme, the proposed method offers significantly reduced computational complexity.

Chaotic-Binary (CB) sequences have been successfully
employed in selected mapping (SLM) schemes to reduce peak-toaverage
power ratio (PAPR) in Orthogonal Frequency Division Multiplexing
(OFDM) systems. However, construction and implementation
of CB sequences on a Digital Signal Processor (DSP) require a
significant number of complex computations and therefore put additional
constraints on limited DSP resources. This paper presents and
investigates the PAPR reduction capabilities of Binary-Polynomial
(BP) sequences whose coefficients are selected from numbers in a
Fibonacci series. Simulations compare PAPR reduction performance
and the computational complexity of the proposed sequences over
CB sequences. Results show that the proposed BP sequences offer
comparable PAPR reduction performance to CB sequences but have
the advantage of significantly reduced computational complexity.

- by Meisam Naderi
- •
- Computer Science, IEEE 802.16 (WiMAX), Synchronization, MIMO-OFDM systems

As the demand for higher data rates has rapidly been increasing day after day, researchers around the world have given serious attention and made significant efforts towards exploring new techniques that can improve the spectral efficiency of future wireless systems. Among these methods, the modulation technique named as orthogonal frequency division multiplexing with subcarrier power modulation (OFDM-SPM) is considered as a key potential candidate transmission method, which has the potential to effectively improve the per-user spectral efficiency of wireless networks. However, the reliability performance efficiency of OFDM-SPM is not that high, where it was found that the additional data stream conveyed by sub-carriers’ power has higher bit error rate (BER) performance compared to the data stream conveyed by conventional modulation schemes. To improve the reliability performance of OFDM-SPM furthermore, in this paper, we propose the use of Convolutional Neural Networks (CNN) based...

This paper focuses on the channel estimation in OFDM system and it implemented by using pilot type channel estimation by hybrid LS-LMMSE. A LTE system is basically MIMO-OFDM system, where a cyclic prefix is inserted at the beginning of each OFDM symbol in order to suppress both inter-carrier interference (ICI) and inter symbol interference (ISI). The inserted CP is usually longer or equal to the channel length but in some cases, the CP can be shorter. In case of LS and LMMSE channel estimation technique, simulation results shows that LMMSE performs better than LS estimator where cyclic prefix is equal to or longer than the channel length. In other case, LMMSE gives better performance than LS only for low SNR values and for high SNR value, LS gives better performance. Therefore, a hybrid LS-LMMSE channel estimation technique is to reduce the effect of the channel length on system. Simulation results for hybrid system shows its true efficiency and specially for the case where the channel length exceeds the cyclic prefix length.

- by IAEME Publication
- •
- Hybridity, MIMO Systems, Ion Channels, Ofdm Simulation

Several factors drive the use of visible light communication systems as an alternative communication method besides RF communication, one of which is energy saving because the VLC system uses the same device for room lighting, i.e., LED. This study aims to model the VLC systems based on multi-carrier modulation (DCO-OFDM) by using MATLAB software. In this study, VLC the system is modeled on two parts, namely Digital Signal Processing (DSP) and optical channels. The DSP block consists of FFT, convolutional encoder, modulator-demodulator, interleaver-deinterleaver, and synchronizer. For error control coding (ECC), the Viterbi decoder algorithm is used. The results showed that DCO-OFDM frames had been successfully designed. Based on mathematical calculations through the MATLAB approach, the VLC system can work well in 5m x 5m x 3m rooms size: BER equals to zero for the minimum SNR of 10 dB has been obtained while the highest SNR value that can be achieved is ~ 30 dB.

- by Paolo Banelli
- •
- OFDM, Time-Varying Channel, Ofdm Simulation