Comparison of BER Analysis in OFDM Using Linear and Cyclic Block Codes for Different Digital Modulation Techniques

Recent wireless communications systems have adopted orthogonal frequency-division multiplexing (OFDM) due to its robustness against fading channels with simple receiver structure. However, it results in poor power amplifier (PA) efficiency or otherwise suffers from severe nonlinear distortion that causes adjacent channel interference (ACI) because of its high peak-to-average power ratio (PAPR) property of transmit signals. To mitigate this issue, DFT-precoded OFDM has been adopted in the LTE-A standard, which virtually forms single-carrier signals and thus generates lower PAPR than the original OFDM. Nevertheless, as the information rate increases for better spectral efficiency, the performance of DFT-precoded OFDM with simple linear detection becomes inferior to that of the original OFDM over frequency-selective fading channels when both the systems are protected by high-rate channel coding. In this work, we propose an adaptive use of DFT-precoding for OFDM where the DFT operation is applied only when the generated OFDM symbol has large dynamic range and thus causes severe nonlinear in-band distortion after clipping and filtering. It is shown that a good trade-off in terms of bit error rate (BER) performance can be achieved while maintaining the specified level of the PA efficiency and the amount of out-of-band radiation.

Orthogonal Frequency Division Multiplexing (OFDM) is one of the promising contendents in the race of very high data rate delivery, for 4G wireless systems. The conventional OFDM systems, so far deployed make use of Fast Fourier Transform (FFT) as their basic building block. Besides the numerous advantages, the restriction over the data rate imposed by the FFT in the form of cyclic prefix may be intolerable for the next generation OFDM systems. So, researches are on the way to replace FFT with a more suitable transform which is redundant free. DWT OFDM is one such system in which FFT in the conventional OFDM is replaced with Discrete Wavelet Transform (DWT). Using simulations, already it has been established that in ideal conditions, the performance of DWT OFDM is better than that of FFT OFDM. As phase noise can be considered as the major RF impairment and one of the leading performance limiting factors of the wireless systems, this paper analyses the Bit Error Rate (BER) performance of the DWT OFDM in presence of phase noise. BER performances of both DWT OFDM and FFT OFDM are analysed and compared in presence of phase noise. For this, Matlab Simulink model have been developed for both types of OFDM, and simulation is carried over in presence of phase noise for different modulation schemes. In all cases the BER performances of DWT OFDM is found to be fairly ahead that of FFT OFDM.

Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier modulation technique that has been widely applied in wireless broadband communications such as the fourth-generation (4G) and supports the development of the fifth-generation (5G) technology because it is efficient and effective. However, OFDM has a high Peak to Average Power Ratio (PAPR) value where the system must use a Power Amplifier (PA) with a high linear range so that the signal can work on PA. Whereas, PA is a nonlinear component that has limited linear region according to the component specifications. If an OFDM signal with high PAPR passes through the nonlinear region of PA, the signal will be distorted nonlinearly and ultimately worsen the OFDM performance. Although many researchers are interested in studying this issue, several scenarios are still not explored. This work investigates a way to mitigate nonlinear distortion by a combination of PAPR reduction and PA linearization with predistortion. Memory-Hammerstein has been suggested as a model for predistorter and PA. The input of the predistorter is the PAPR reduced signal with companding technique, which is a simple and effective PAPR reduction technique for OFDM. The system performance will be evaluated using signal spectrum, PAPR, and Bit Error Rate (BER). The simulation results obtained are that the performance drops dramatically to more than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> for the BER value when a nonlinear disturbance is given and the performance improves after a predistorter is applied. The combination of hybrid companding and predistorter offers better performance, it can reduce PAPR and compensating for nonlinear distortions caused by the PA. Hence, this combined scheme can be considered and adopted in future wireless communications systems including 5G.

왈시-하다마다 변환(Walsh-Hadamard Transform, WHT)을 적용한 OFDM(Orthogonal Frequency Division Multiplexing) 변조방법은 시스템의 PAPR(Peak-to-Average Power Ratio)을 줄여주고, 시스템의 BER(Bit Error Rate) 성능을 향상시키는 장점이 있다. 그러나 기존의 이러한 왈시-하다마다 변환에 기반한 OFDM 시스템은 여전히 비교적으로 높은 PAPR문제가 있다. 그러므로 본 논문에서는 DGT(Data Grouping Technique)이라고 부르는 기술을 제안하고, 이 기술과 왈시-하다마다 변환 기술을 적용하여 PAPR을 더욱 줄여주는 OFDM 시스템을 설계한다. 제안한 DGT기술은 WHT-OFDM뿐만 아니라 일반 OFDM에서 PAPR을 줄여주는 방법들 중에서 큰 단점이 되는 부가정보(side information)가 성능에 대해 독립성을 가진다는 특징이 있다. 컴퓨터 시뮬레이션을 통해 제안한 시스템의 유용성을 검사하고 성능을 검증하였다. The conventional OFDM (Orthogonal Frequency Division Multiplexing) modulation can be combined with WHT (Walsh-Hadamard Transform) to reduce PAPR (Peak-to-Average Power Ratio) and improve BER (Bit Error Rate) performance. However, this WHT-based OFDM system still suffers a relatively high PAPR. Therefore, we suggest a new technique, called DGT (Data Grouping Technique) and design an OFDM system employing it and WHT to further decrease PAPR without the BER performance degradation. h salient property of DGT is the independence of the side information which is inherently a principal drawback of the well-known PAPR reduction techniques for OFDM system as well as WHT-based OFDM. The simulation programs have been also performed to verify the validity of the proposed system.

A combination of orthogonal frequency division multiplexing (OFDM) with frequency-division multiple access (FDMA) called OFDMA is regarded as a promising solution for improving the performance of interactive wireless broadcasting systems. This work focuses on the performance of OFDM when used as a modulation and access technique for the uplink of an interactive wireless broadcasting system. In such an application, we present our investigations of the effects of symbol timing misalignments and peak-to-average power ratio (PAR). Under the condition of the same side information bits, the selective mapping (SLM) approach can be implemented by decimating OFDM samples, which is less complex compared to the ordinary SLM incurring a slight degradation of the PAR performance. Taking into account the effects of clipping operation and symbol timing misalignment, the bit error rate (BER) and throughput performances are investigated for a typical OFDMA uplink scenario.

Tone Reservation (TR) is a method used to reduce the Peak to Average Power Ratio (PAPR) in Orthogonal Frequency Division Multiplexing (OFDM) systems. In this paper, we assess the importance of considering an improved model of the power amplifier (PA) to accurately evaluate the performance of TR method based on Conjugate-Gradient algorithm. Simulation results were carried out in the context of WLAN IEEE 802.11a standard in presence of two memoryless models and nonlinear polynomial model with memory. These models are obtained by an experimental based method, including measurements and parameters identification with a 2.4 GHz class AB PA from RF Micro Devices. The evaluation results as well as the experimental comparison show that TR method considerably improves the transmission quality, in terms of Bit Error Rate (BER) and Error Vector Magnitude (EVM). These results highlight the importance of considering memory effects in PA modelling.

In this paper, we propose a novel peak to average power ratio (PAPR) reduction scheme of orthogonal frequency division multiplexing (OFDM) signals. In our proposed scheme we exploit the repeated rotation and recombination of the in-phase and the quadrature components of an OFDM symbol in time domain. Our proposed scheme has two main advantages over the previously known scheme such as iterative partial transmit sequence (I-PTS), which are 1) remarkably lower computational complexity and 2) less required side information overhead than the I-PTS scheme. Based on our derived complementary cumulative distribution (CCDF) of PAPR, we show that our proposed scheme gives only 0.2 - 0.3 dB loss compared to the I-PTS scheme in terms of PAPR threshold while the complexity for the implementation is much reduced. Furthermore, the proposed scheme does not cause any loss of bit error rate performance over both the additive white Gaussian noise (AWGN) channel and the frequency selective channel even though the simulation results regarding the bit error rate (BER) performance is not shown in this paper due to the limited space of the pages.

In this paper, we propose a new PAPR reduction by using a partial transmit sequences (PTS) method with coded side information (SI) technique. These methods are used in an orthogonal frequency division multiplexing (OFDM) system. The OFDM employs orthogonal sub-carriers for data modulation. These sub-carriers unexpectedly present a large peak to average power ratio (PAPR) in some cases. In order to reduce PAPR, the sequence of input data is partitioned into disjoint sub-block of PTS. If number of sub-block increases, high efficiency of PAPR reduction can be obtained. However, a quite large calculation cost must be demanded and thus it is impossible to obtain the optimum PTS. In the proposed method, we introduce a coded side information technique assuming the pseudo-optimum condition into the PTS. The total calculation cost becomes drastically reduced and side information bits for recovering original data in demodulation. In simulation results, the proposed method demonstrated the improvement of PAPR and bit error rate (BER) performance.

SUMMARY The main disadvantage of orthogonal frequency divisionmultiplexing (OFDM) is the high time domain PAPR. The larger PAPRsignal would fatallydegrade BER performance in non-linear channels. Thispaper proposes an improved DSI method, which can achieve better PAPRand BER performances in the non-linear channel with less computationcomplexity than the conventional DSI method. The feature of proposedmethod is to employ the time-frequency domain swapping algorithm inthe determination of frequency data for dummy sub-carriers. This paperpresents various computer simulation results to verify the effectiveness ofproposed DSI method. key words: OFDM, PAPR, dummy sub-carriers, non-linear amplifier 1. Introduction The OFDM technique has been received a lot of attentionespecially in the field of wireless communications becauseof its efficient usage of frequency bandwidth and robustnessto multi-path fading. One of the limitations of using OFDMtechnique is the larger peak to averaged power ratio (PAPR)of its time domain signal [1]. The larger PAPR signal wouldcause the severe degradation of bit error rate (BER) perfor-mance due to the inter-modulation noise occurring in thenon-linear amplifier.To overcome the PAPR problem in OFDM systems,various PAPR reduction methods for OFDM signal havebeen proposed including the selected mapping method(SLM) [2], partial transmit sequence method (PTS) [3] anddummy sequence insertion method (DSI) [4]. All of thesemethods improve the PAPR performance by controlling thephase of data or dummy sub-carriers. The SLM and PTSmethods control the phase of data sub-carriers and the DSImethod controls the phase of dummy sub-carriers. First twomethods are required to inform the phase information con-trolled for the data sub-carriers to the receiver as the sideinformation. Since the side information is required to trans-mit separately from the data information through the data orcontrol channels with the higher signal quality for the cor-rect demodulation of data information at the receiver, the

High Peak-to-Average Power Ratio (PAPR) of the Orthogonal Frequency Division Multiplexing (OFDM) signal is one of the limitations to the transmission performance of optical OFDM system. In this paper, we propose a novel hybrid PAPR reduction technique called Hadamard Transform Combined with Partial transmit sequence (HTCP). The proposed HTCP scheme combines the merits of two complementary techniques, i.e., Hadamard transform and Partial Transmit Sequence (PTS), to improve the performance of the optical OFDM system in terms of PAPR and Bit Error Rate (BER). Simulation results show that the HTCP scheme has better performance with regard to PAPR and BER compared with the case of applying only the Hadamard transform or PTS technique.

Generalised frequency division multiplexing (GFDM) is a multicarrier transmission scheme that offers a flexible framework to address diverse requirements of fifth generation of cellular networks. Compared to orthogonal frequency division multiplexing (OFDM), the application of pulse shaping in GFDM can control the out of band (OOB) radiation and enables relaxed synchronisation requirements. However, the sub-carriers in GFDM are no longer orthogonal and there is inherent interference. Since this interference is known at the transmitter, it can be mitigated by means of precoding techniques. In this paper, Tomlinson-Harashima precoding (THP) scheme is applied to GFDM transceiver and its performances is compared to previous methods in terms of bit error rate (BER) and peak to average power ratio (PAPR). The results show that the proposed precoder outperforms previous methods in both BER and PAPR.

The impact of high power amplifier (HPA) on the performance of orthogonal frequency division multiplexing (OFDM) based wireless systems using link adaptation (LA) is analyzed in this work. LA maximizes throughput while maintaining a target bit error rate (BER) at the receiver. The non linear behaviour of the HPA introduces distortion in the OFDM signal which has high peak to average power ratio (PAPR). It is found in this work that this causes LA schemes to fail to meet the target BER. It is shown in this work that to make the LA system satisfy the BER constraint, the signal to noise ratio thresholds for changing the adaptive modulation needs to be updated.

Orthogonal frequency division multiplexing (OFDM) is a multi-carrier digital modulation technique that has been under extensive study and research in recent years, in terms of considering its various advantage in combating the severe effects of the frequency selective fading. However, the OFDM system suffers from the strong sensitivity to the nonlinear distortion, introduced by the transmitting high power amplifier (HPA), since the OFDM system has the high peak-to-average power ratio (PAPR). Clipping is the simple but infective method to low the high PAPR; however, it causes nonlinear distortion too. So in this paper, we propose a new approach to compensate the nonlinearity caused by clipping and HPA. Its performance is verified through computer simulations. Specifically, the enhanced performance in terms of the bit error rate (BER) is documented for both the traveling wave tube amplifier (TWTA) and the solid state power amplifier (SSPA).

Orthogonal frequency division multiplexing (OFDM) is the advanced transmission scheme utilized in 4G. Nevertheless, it has several shortcomings like guard band, peak-to-average power ratio (PAPR), high power consumption, incapable to accommodate various other devices (an IOT application). Hence, OFDM cannot be considered in 5G due to the several disadvantages mentioned above. Filter bank multi-carrier (FBMC) is believed to be one of the most promising technologies which can be used in 5G. FBMC and OFDM are multi-carrier system. It is obvious that it agonizes from PAPR which hamper the efficiency of the system. The conventional peak reduction methods utilized in OFDM cannot be used in FBMC due to the overlapping structure of FBMC. In this work, a novel selective mapping (SLM) and partial transmit sequence (PTS) PAPR reduction technique is suggested for FBMC. The proposed techniques are implemented by using an elementary successive optimization technique that upsurge the PAPR performance and ensure the design difficulty is taken low. PAPR and bit error rate (BER) parameters are analyzed and simulated for the proposed and conventional PAPR reduction techniques. The simulation results show that the SLM and PTS accomplished an excellent PAPR reduction up to 2.8 and 4.8 dB as compared to other peak power minimization techniques.

In this paper, we present a novel 3B/4B coding scheme for the reduction of peak-to-average power ratio (PAPR) in the orthogonal frequency division multiplexing (OFDM) communication system. In the proposed technique, we apply the encoding in the time domain of the OFDM transmitter to redistribute the power distribution of each transmitting signal samples. PAPR of the OFDM signal at the CCDF (Complementary Cumulative Distribution Function) of 10-5 can be reduced to about 11, 15 and 17 dB for N = 16, 64, and 256 respectively by applying the proposed scheme. Our analysis also shows that the proposed method would have bounded PAPR as the number of OFDM subcarriers N approaches infinity. Moreover, the method has very low complexity and the complexity does not increase as the number of OFDM sub-carriers increases. The proposed scheme also has error correction capability to reduce bit error rate (BER) at the same time.