PAPR constrained power allocation for iterative frequency domain multiuser SIMO detector

In this paper we derive optimal power allocation scheme that minimizes bit error rate (BER) while satisfying the average power constraint and peak to average power ratio (PAPR) constraint (which translates to minimizing the PAPR). The power allocation is done in space and time for multiple-input single-output (MISO) systems over Rayleigh flat fading channels assuming perfect channel state information (CSI) is available both at the transmitter and receiver. This power allocation achieves exponential diversity while satisfying the PAPR constraint.

One major drawback of OFDM is the large Peak to Average Power Ratio (PAPR). OFDM is a linear modulation, therefore large PAPR requires large linear dynamic range of the transmitter (TX) as well as the receiver (RX) paths. The weak point in the TX-RX chain is the Power Amplifier (PA). As known, a linear PA which is able to amplify signals with large PAPR has to have a large dynamic range that results with low power efficiency, thus by reducing PAPR one may improve the efficiency of PA. A PAPR reducing method in OFDM, based on SeLective Mapping (SLM) is considered. As known, SLM requires transmitting a Side Information (SI). Increasing the SLM order reduces the PAPR but increases the size of SI. In order to transmit the SI some power and bandwidth are needed, those are taken from the total power and bandwidth budget and thus lowering the capacity. On the other hand the reduced PAPR improves the PA efficiency, thus increases the channel capacity. Accordingly maximal value of channel capacity is expected as well as an optimal SLM order.

Orthogonal frequency division multiplexing (OFDM) signals have a generic problem of high peak to average power ratio (PAPR) which is defined as the ratio of the peak power to the average power of the OFDM signal. The drawback of the high PAPR is that the dynamic range of the power amplifiers (PA) & digital-to-analog (D/A) converters required during the transmission and reception of the signal is higher. As a result, the total cost of the transceiver increases, with reduced efficiency. This paper includes an idea of the PAPR constraint, along with the implementation and analysis of some specific algorithms for PAPR reduction of the OFDM signals. All the PAPR reduction algorithms are implemented and tested in the OFDM transceiver designed using Matlab. Analyzing some specific algorithms, we propose a novel algorithm by combining the subcarrier phase adjustment and linear combination of the time domain OFDM signals. Simulation results for a OFDM system employing Quadrature Amplitude Shift Keying (QASK) symbols and Quadrature Amplitude Modulation (QAM) can achieve a PAPR reduction of 5 dB.

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.

Requirement of high data rate by the modern mobile communication system requires a linear power amplifier with extremely low power consumption and long battery life. Orthogonal frequency division multiplexing (OFDM) modulation technique promises to deliver high data rate with simple receiver structure. It is more spectral efficient and has been recommended to be used by many standards. But it has one major disadvantage of having high peak to average power ratio (PAPR). High PAPR drives the power amplifier in saturation region and causes it to operate in nonlinear region with reduced efficiency. There are several techniques to reduce PAPR of OFDM system. In this paper we have done FPGA implementation of selective mapping method (SLM) for PAPR reduction for 4 QAM baseband signal for 64, 128, 256, 512 and 1024 number of subcarriers. The result obtained have been compared with PAPR values obtained through mathematical analysis and Matlab simulations and also with original signal. For 1024 number of subcarriers at 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> of CCDF value the PAPR value obtained with hardware implementation is 9.8 dB which is 2.8 dB less form the original OFDM signal obtained without applying SLM technique but 0.9 dB higher than the Matlab simulated value. This technique is simple in implementation, utilizes less resources and is effective in PAPR reduction.

Multicarrier modulation technique also known as Orthogonal Frequency Division Multiplexing (OFDM) is considered to be the most rapidly growing technique for 4th Generation wireless communication system. Due to its high speed data rate and its ability of multipath fading channel robustness. OFDM becomes an attractive technique and it is widely adopted in many wireless communications system. OFDM signal carries its major drawback of high Peak to Average Power Ratio (PAPR) problem. Out of band radiation and in band distortion produced due to its high PAPR. Mobile phone communication suffer severe drawback during its amplification. When OFDM employed a non linear Power Amplifier (PA), it produces the fluctuation in amplitude of OFDM signal. This paper discusses the method to overcome PAPR in terms of its performance by using improved clipping technique for PAPR reduction. This method is easy to implement and reduces the amount of PAPR by clipping the peak of the maximum power signal. We present an improved method for PARR reduction for reducing peak magnitude of OFDM signal. This scheme simultaneously minimizes the peak magnitude of PAPR in OFDM signal.

This letter proposes a method exploiting constructive interference (CI) to reduce the transmit signal's peak-to-average power ratio (PAPR), while keeping the total transmission power as low as possible. An optimization problem that jointly performs power minimization and PAPR reduction is formulated, which is however difficult to solve directly due to the non-convex PAPR constraint. To obtain a feasible solution in low complexity, by using the vectorization method and introducing a regularization factor, we relax the PAPR constraint. The original optimization problem is transformed into a convex problem that can be solved with an improved fast iterative shrinkage-thresholding algorithm (FISTA). Numerical results are presented to show 1dB savings in terms of transmission power and 52% savings in terms of PAPR compared with state-of-the-art PAPR minimization techniques.

It is important to design a spectrum-efficient and power-efficient wireless communication system, which is the main design target in cellular and wireless communication engineering. Basically, to make it, the desired system must have a low peak-to-average power ratio (PAPR), low-level of out-of-band (OOB) power emission and can provide a high throughput. In this paper, we propose a high-throughput cellular communication system, namely Discrete Fourier Transform-Spread Windowing and Restructuring Orthogonal Frequency Division Multiplexing (DFT-Spread WR-OFDM), which has considerably low PAPR and low OOB power emission for upcoming next-generation beyond 5G (B5G) and 6G cellular communication systems. High PAPR is still one of the challenging issues for the MIMO-OFDM system. The proposed system is an effective arrangement of DFT-Spreading and windowing techniques to reduce PAPR and OOB power emission, respectively. Multiuser diversity is obtained using localized subcarrier mapping. We take advantages of spatial multiplexing to enhance the data throughput significantly. Additionally, frequency-domain equalization (FDE)-minimum mean squared error (MMSE) is used to combat the inter-symbol interference (ISI) effect. Simulation results verify that the suggested system considerably lowers PAPR and OOB power emission compared to the conventional systems. Furthermore, the proposed scheme shows better bit error rate (BER) performance over the MIMO Rayleigh fading channel environment. Simulation results also confirmed that the channel capacity of our suggested system is better than the conventional multi-carrier systems.

Multi-band Orthogonal Frequency Division Multiplexing (MB-OFDM) is an efficient approach for Ultra Wideband (UWB) wireless communication applications. However, the high Peak to Average Power Ratio (PAPR) of MB-OFDM UWB signals, limits the power efficiency of the Solid State Power Amplifier (SSPA) due to nonlinear distortion caused by high PAPR. Hence, it is necessary to reduce the PAPR of MB-OFDM UWB signals. In this paper, we used a tunable Pre-Distorter (PD) based on the High Power Amplifier (HPA) characteristics for PAPR reduction of MB-OFDM UWB signals. The PD configuration is self-tuning, i.e., it can automatically readjust itself by tracking changes in the HPA characteristics with very few (typically two) training symbols. Through Computer simulations, the performance of the predistorter is evaluated in comparison with filtering after clipping, and clipping with turbo coding for PAPR reduction. The Bit-Error Rate (BER) is used as performance measure in this evaluation.

OFDM has Major disadvantage is that it leads to high Peak to Average Power Ratio (PAPR) which is consider to be as the main implementation drawback. In this paper we are discussing about PAPR which affects the performance and efficiency of Power Amplifier (PA) and its influence by utilizing the Selective Mapping (SLM) technique in OFDM system for reduction of PAPR. the idea for improved SLM produces several independent signals based on converting the original data lock into many independent signal and then the signal has lowest PAPR that specific signal is transmitted. Also data rate trade-off exist at the receiver end when side information is detected for the recovery of data block. which leads to the reduction of data rate. Improved SLM techniques for reducing the PAPR is the most promising reduction technique in its non-uniform phase factor for PAPR reduction in multicarrier OFDM system. Furthermore the estimate expression by using Complementary Cumulative Distribution Function (CCDF) for PAPR has been discussed. Simulated results demonstrate that OFDMA signals using improved SLM technique carried significant effects in reduction of PAPR in OFDM system.

Main disadvantage of a multicarrier communication system is high peak to average power ratio (PAPR) of the transmitted signal. The high PAPR causes the performance degradation due to nonlinear distortion in the high power amplifier (HPA). PAPR value is closely depends on transmitted power and correlation properties of the user’s spreading code. High peak and low average value of the transmitted power increases the PAPR. On the other side high auto correlation function (ACF) value and low cross correlation function (CCF) value of the spreading code also increases the PAPR. But to eliminate the multiple access interference (MAI) in receiver end, ACF should be peak and CCF should be posses zero for all time shifts. So, there is a conflicting nature of PAPR and bit error rate (BER). That’s why an exhaustive effort has been made in this paper for proper distribution of transmitted power within an acceptable range of peak transmitted power and evaluates the new spreading codes using Genetic Algorithms (GA). In general, to obtain optimum PAPR reduction using GA, total searching time to find out the proper amplitude and phase parameters must be accomplished. Simulation results show that PAPR and BER performance using this proposed technique is better than conventional network.

Cognitive radio (CR) is considered nowadays as a strong candidate solution for the spectrum scarcity problem. On standards level, many cognitive radio standards have chosen Non-Contiguous Orthogonal Frequency Division Multiplexing (NC-OFDM) as their modulation scheme. Similar to OFDM, NC-OFDM suffers from the problem of having a high Peak to Average Power Ratio (PAPR). If not solved, either the transmitted signal will be distorted, which will cause interference to primary (licensed) users, or the effeciency of the power amplifier will be seriously degraded. The effect of the PAPR problem in NC-OFDM based cognitive radio networks is worse than normal OFDM systems. In this paper, we propose enhanced techniques to reduce the PAPR in NC-OFDM systems. We start by showing that combining two standard PAPR reduction techniques (interleaver-based and selective mapping) results in a lower PAPR than using them individually. Then, an “adaptive number of interleavers” will be proposed that achieves the same performance of conventional interleaver-based PAPR reduction while reducing the CPU time by 41.3%. Finally, adaptive joint interleaver with selective mapping is presented, and we show that it gives the same performance as conventional interleaver-based technique, with reduction in CPU time by a factor of 50.1%.

Long Term Evolution (LTE) chose Single Carrier Frequency Division Multiple Access (SC-FDMA) for uplink communications due to lower signal envelope changes in SC-FDMA signal. This enables low peak to average power ratio (PAPR) in SC-FDMA in contrast to Orthogonal Frequency Division Multiple Access (OFDMA). High PAPR cannot be ignored as it reduces energy efficiency due to the requirement of large range linear power amplifiers. As the mobile devices are power restricted, there is a requirement to mitigate PAPR in the uplink SC-FDMA systems, especially for higher order modulations. Companding is an attractive technique to mitigate PAPR without any bandwidth extension. This paper suggests a companding transform using exponential function to mitigate PAPR in SC-FDMA systems. The suggested transform maintains the average signal power contrary to $\mu$ law companding. Simulation results demonstrate that exponential companding technique without any decompanding operation reduces PAPR by a significant value by maintaining the average signal power and BER performance.

5th generation systems (5G) will be based on Orthogonal Frequency Division Multiplexing (OFDM) multicarrier modulation technique. This modulation has a very high Peak to Average Power Ratio (PAPR). This high PAPR is a drawback when nonlinear Power Amplifiers (PA) are operated near the saturation region, for energy efficiency purposes, due to in-band and out-of-band impairments. In this paper, a new PAPR reduction technique called Iterative Dichotomy PAPR (IDP) is proposed. This method is suited for any multicarrier modulation and is studied here using realistic PA model. For evaluating the signal distortions, two main metrics have been considered to evaluate the performance of IDP technique: bit error rate (BER) and power spectrum density (PSD). The analytical expressions of the IDP technique for any dichotomy order $M$ is firstly described and subsequently the energy efficiency for different $M$ values is compared. We have shown that the proposed IDP method reduces the PAPR by $2.2dB$ for $M=2$ and $4dB$ for $M=4$ . Regarding the energy efficiency, for the same Error Vector Magnitude (EVM) and the same PA power consumption, the output signal power obtained with the IDP based technique outperforms classical OFDM by 20%, 50% and 80% for $M=2$ , $M=3$ and $M=4$ , respectively.

Orthogonal frequency division multiplexing (OFDM) may be combined with antenna arrays at the transmitter and receiver side to increase the diversity gain and system competence on time variant along with the frequency selective channels, which results in a multiple-input multiple-output composition. The major drawback in case of MIMO-OFDM is its high value of Peak to Average Power Ratio (PAPR) which causes to frequency spread spectrum along with the in-band distortion. This is due to the presence of nonlinearity in the high power amplifiers. In this paper, a hybrid technique of PTS and CP is proposed for PAPR reduction. Using the QAM modulated MIMO-OFDM systems and 2×2 number of antennas, it has been observed that the proposed technique has better performance for PAPR reduction.