Iterative Clipping Filtering and Saleh Model Predistorter on a MIMO-OFDM System Testbed Using Software Defined Radio

The advances in the communication field results in need for higher data rates in addition to both increase in power efficiency and lower bit error rate (BER). Multiple input multiple output-Orthogonal frequency division multiplexing (MIMO-OFDM) is extensively used in current and next generation broadband wireless communications to yield a high data rate of transmission and spectral efficiency over the multipath fading channels. The MIMO-OFDM systems has a major drawback as is it suffers from high peak-to-average power ratio (PAPR) which in turn requires designing of efficient power amplifier (PA), in order to maintain a wider linear region for preventing signal clipping, which therefore increases hardware complexity and power consumption. The various PAPR reduction algorithms have been developed which provide a maximum PAPR reduction ranging from 0.5 to 6 dB. The maximum SNR loss after applying a Beamforming technique is reported around 0.2 dB with BER of around 10−4 to 10−6. In the current work. Performance of PAPR analysis and reduction algorithms for beam-forming techniques include Maximum Ratio Transmission (MRT), Equal Gain Transmission (EGT) and receive combining techniques Maximum Ratio Combining (MRC), Equal Gain Combining (EGC) for MIMO-OFDM system is evaluated and reported. Measurement of MIMO-OFDM is done in terms of BER, PAPR reduction, Signal to Noise ratio (SNR) with two major PAPR reduction scheme Selective Level Mapping (SLM) and Partial Transmit Sequence (PTS).

This paper presents a study of peak-to-average power ratio (PAPR) reduction using coded partial transmit sequence (PTS) in 8×8 multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. MIMO-OFDM achieves large-capacity wireless communication, and has been adopted in such as IEEE802.11n/ac standard wireless LAN systems. PAPR indicates the ratio of peak power to average power. High PAPR causes waveform distortion due to nonlinear amplifier characteristics. PTS is one of PAPR reduction methods to prevent communication quality degradation. PTS performs phase rotation to OFDM modulated signals to reduce the peak power. We have to increase the number of possible phase patterns in order to obtain enough PAPR reduction. Coded PTS is used to reduce computational cost of PTS by using codebook. In the case of MIMO-OFDM systems, we have to use the same phase pattern of PTS for each stream due to difficulty of detection. In this paper, we have evaluated PAPR reduction by the proposed coded PTS in 8×8 MIMO-OFDM systems. The evaluation result shows that low error transmission can be achieved by using coded PTS and RS code, and PAPR reduction is about 1.7 dB. In comparison with PTS, coded PTS can achieve 94% computational cost reduction.

In this paper, a reduced-complexity cross-antenna rotation and inversion (CARI) scheme based on the cross-entropy (CE) method is proposed for the reduction of peak-to-average power ratio (PAPR) in multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems with space-time block coding (STBC). A few PAPR reduction techniques for STBC MIMO-OFDM systems have been proposed in the literature, among which the CARI technique can significantly reduce the PAPR by fully utilizing additional degrees of freedom provided by employing multiple transmit antennas. However, the CARI technique requires an exhaustive search over all combinations of rotation and inversion, whose complexity increases exponentially with the number of subblocks. To simultaneously reduce the complexity and offer lower PAPR, the PAPR reduction with CARI technique is formulated as a combinatorial optimization problem and then the CE method is applied to search the optimal combination of rotation and inversion. Simulation results show that the proposed CE-based scheme is an efficient method to greatly reduce the complexity for larger numbers of subblocks while still achieving significant PAPR reduction of STBC MIMO-OFDM systems.

Multiple-input Multiple-output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) is a promising candidate for 4G high-data-rate broadband wireless communications. However, MIMO-OFDM inherited the problem of high Peak-to-Average Power Ratio (PAPR) from OFDM which leads to in-band distortion, undesired spectral spreading, low power efficiency and increases the cost of the RF power amplifier. Many PAPR reduction techniques were developed in last two decades to reduce the PAPR of OFDM, among them Partial Transmit Sequence (PTS) and Selected Mapping (SLM) are the important ones. This paper proposes two PAPR reduction technique; SLM and Optimum -PTS for reducing the PAPR and does performance comparison of these two techniques on the basis of reduction in PAPR level, BER and the number of redundant bits required. It shows that the use of Optimum-PTS technique with QPSK modulation comprising of 128 subcarriers provides better PAPR reduction and good BER as compared to SLM.

Multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) system have been proposed in the recent past for providing high data-rate services over wireless channels. When combined with space time coding it provides the advantages of space-time coding and OFDM, resulting in a spectrally efficient wideband communication system. However, MIMO-OFDM system suffer with the problem of inherent high peak-to-average power ratio (PAPR) due to the intersymbol interference between the subcarriers. In order to obtain an optimal PAPR reduction using the partial transmit sequence (PTS), the total search for the number of subblocks and the rotation factors must be accomplished. As the number of subblocks and rotation factors increases, PAPR reduction improves. The number of calculation increases as the number of subblocks increases, such that complexity increases exponentially and the process delay occur simultaneously. In this paper, PAPR reduction based on a modified PTS scheme combined with interleaving and pulse shaping method in MIMO-OFDM has been presented. The paper analyses the influence of the number of the detected peaks on PAPR reduction performance and on complexity, and then obtain the optimal parameter to achieve better PAPR reduction performance and lower complexity. Simulation results have shown that modified PTS with interleaving and the pulse shaping method can obviously improve PAPR performance in the MIMO-OFDM.

This paper proposes a novel method to reduce the peak-to- average power ratio (PAPR) of multicarrier signals in multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems by frequency block exploitations, named cross-frequency permutation and inversion (CFPI). Our design improves the performance and framework flexibility (compatible with both space-time and space-frequency patterns) of PAPR reduction in MIMO-OFDM system, which utilizes additional degrees of frequency freedom. Especially, this proposed design can be freely combined with many good-featured space-time or space-frequency coding to achieve better whole system performance, which is unlike the previous typical methods strictly based on space-time block coding structure with relative low data rate. Simulation results show that the good performance is achieved by our novel design.

This study presents a proper way to improve the multiple-input multiple-output orthogonal frequency division multiplexing (OFDM) system by proposing a new tackling method to reduce the peak-to-average power ratio (PAPR). It is attained by reconstructing the fast Fourier transform block in the OFDM based on the wavelet packet transform, called forward wavelet frequency division multiplexing. In addition, a new pre-processing technique has been introduced to increase the orthogonality among the tested data which is based on imposing the eigenvalues/eigenvector extracting features. Numerical and simulation results show that the combination between the new structure of OFDM transceivers and the pre-processing block has lower PAPR values. It is compared with the conventional OFDM structures and showed that the bit error rate performance has been improved for the same bandwidth occupancy, which is attained at the cost of introducing additional complexity to the transceiver's structure. The simulation results show that 6'60' reduction in PAPR over current values in the literature can be achieved depending on the system type.

Digital predistortion (DPD), based on complex-valued memory polynomials (MP), is established as an efficient method for power amplifier (PA) linearization. The DPD facilitates compliance of the telecommunication infrastructure to strict standard specifications (transmit spectrum mask (TSM), error vector magnitude (EVM), bit error rate (BER), [Formula: see text]) by making PA more linear, while at the same time reduces the running cost of the wireless infrastructure (at both Base Transceiver Station (BTS) and User Equipment (UE) sides) by making PA more power efficient. Even when DPD is utilized, signals with high peak-to-average power ratio (PAPR) produce out-of-band PA spectrum emission due to intermodulation products affecting all above-mentioned critical standard specified parameters. The novelty proposed in this paper is as follows. PA is restricted to operate within “reasonably above” PA linear region using PAPR reduction technique. The residual nonlinearity is taken care of by DPD. The combination of DPD and PAPR PA linearization methods is implemented on software-defined radio board. The necessary steps for efficient PA linearization are presented, compensating both out-of-band and in-band signal distortions. We achieved EVM = 2.0%, ACPR [Formula: see text]50[Formula: see text]dBc, at 10[Formula: see text]W LTE modulated PA output, antenna point and PA output power of 39.5[Formula: see text]dBm.

Multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) technology is a promising solution for next generation wireless communications, due to high bandwidth efficiency, resistance to RF interference, and robustness to multipath fading. A major drawback of OFDM is its high peak-to-average power ratio (PAPR) which results in non-linearities in the output signal. In this paper, two methods based on spatial/temporal processing are proposed to reduce the PAPR of MIMO-OFDM systems. These methods divide the OFDM block at each transmit antenna into some subblocks. Then, spatial and temporal processing in the form of circular shifting or interleaving are applied to generate different candidate sequences. Finally, for each transmit antenna the candidate sequence with the lowest PAPR is chosen for transmission. Compared to the conventional PAPR reduction schemes such as ordinary partial transmit sequences (O-PTS), the proposed methods require lower computational complexity and have superior PAPR reduction performance.

This paper proposes a novel method to reduce the peak-to-average power ratio (PAPR) of multicarrier signals in multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems by jointly frequency-block operations. Our design improves the performance and framework flexibility (compatible with both space-time and space-frequency patterns) of PAPR reduction in MIMO-OFDM system, which utilizes additional degrees of frequency freedom. Especially, this proposed design can be freely combined with many good-featured space-time or space-frequency coding to achieve better whole system performance, which is unlike the previous typical methods strictly based on space-time block coding structure with relative low data rate. Simulation results show that the good performance is achieved by our novel design.

A bandwidth efficient selective mapping technique for the PAPR reduction in spatial multiplexing MIMO-OFDM wireless communication system

Frequency switched transmit diversity (FSTD) is a simple diversity technique which can be easily combined with existing multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) schemes to support an increased number of transmit antennas. For the MIMO-OFDM based on FSTD, this letter proposes a reduction scheme of peak-to-average power ratio (PAPR). The proposed scheme generates signal candidates (SCs) by mapping the subparts of OFDM symbols onto multiple antennas under the criterion of reducing correlation among the SCs. The proposed scheme is shown to provide good PAPR performance and to allow a low-complexity detection of the transmitted SC without side information.

In last few decades the demand for multimedia data services has grown up fastly. One of the most promising multicarrier system, Orthogonal Frequency Division Multiplexing (OFDM) allow large number of capacity the number of subcarriers, high data rates and ubiquitous coverage with high mobility. But OFDM is extensively affected by peak to average power ratio (PAPR). Unfortunately, the high PAPR inherent to OFDM signal envelopes will frequently drive high power amplifiers (HPAs) which are operate in the nonlinear region. The nonlinearity of the High Power Amplifier exhibits phase and amplitude distortions, which causes loss of orthogonality between the subcarriers; also (ICI) is introduced in the source signal. This dissertation is basically focused on PAPR reduction in OFDM system and measuring BER in different Modulation Technique. In PAPR reduction Signal companding methods have low complication, high distortion and spectral properties; however, we have limited PAPR reduction capabilities. Partial transmit sequences (PTS) and selected mapping (SLM), have also been considered for PAPR reduction. Such kind of techniques are very efficient and distortion less, Also the SLM is very good technique to the PAPR problem in single carrier system. This method has low complexity as well as it is data independent. 
 In this paper, we are describing a combine technique of SLM and PTS to minimize the PAPR. In PTS scheme, number of sub blocks increases; the IFFT block to be performed for sub blocks also increases. Simulation results have shown that the reductions of PAPR of proposed scheme is more than PTS and SLM methods as well as the difficulty reduced considerably.

In this paper, we propose an improved selective mapping (SLM) cascaded with iterative tone reservation (TR) method for peak-to average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) system. In the simple SLM cascaded with iterative TR method, the candidate signal which has the minimum PAPR is selected. However, since the number of iteration L of the largest peak values will be reduced by TR, in the proposed method, the candidate signal which has the minimum (L+1)th peak to average power ratio is selected among other candidates in the SLM process. From the performance comparisons between various PAPR reduction methods, we verified that the PAPR reduction performance of the proposed method achieves the better reduction performance and power efficiency.

High peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems seriously impacts power efficiency in radio frequency section due to the nonlinearity of high-power amplifiers. In this article, an improved gamma correction companding (IGCC) is proposed for PAPR reduction and investigated under multipath fading channels. It is shown that the proposed IGCC provides a significant PAPR reduction while improving power spectral levels and error performances when compared with the previous gamma correction companding. IGCC outperforms existing companding methods when a nonlinear solid-state power amplifier (SSPA) is considered. Additionally, with the introduction of $$\alpha , \beta , \gamma $$ź,β,ź, and $$\varDelta $$Δ parameters, the improved companding can offer more flexibility in the PAPR reduction and therefore achieves a better trade-off among the PAPR gain, bit error rate (BER), and power spectral density (PSD) performance. Moreover, IGCC improves the BER and PSD performances by minimizing the nonlinear companding distortion. Further, IGCC improves signal-to-noise ratio (SNR) degradation ($$\varDelta _{\mathrm{SNR}}$$ΔSNR) and total degradation performances by 12.2 and 12.8 dB, respectively, considering an SSPA with input power back-off of 3.0 dB. Computer simulation reveals that the performances of IGCC are independent of the modulation schemes and works with arbitrary number of subcarriers (N), while it does not increase computational complexity when compared with the existing companding schemes used for PAPR reduction in OFDM systems.