PAPR reduction using tent map for multiple data rate OFDMA system

In wireless communication, the physical layer should facilitate multiuser, multirate transmission to support large number of users and applications with diverse needs. In this work chaotic sequences generated using logistic map were used to achieve multiple data rate in Orthogonal Frequency Division Multiple Access (OFDMA) system. Performance was compared with that of Orthogonal Variable Spreading Factor (OVSF) code. Increase in Peak to average power ratio (PAPR) due to variable spreading could be reduced by spreading using chaotic sequences. The spreading sequences could be chosen irrespective of the data rates used. It was also observed that chaotic sequences gave constant PAPR values for different combinations of data rates. Bit error rate was found to be comparable with that for OVSF codes.

A new family of low density parity-check (LDPC) codes, called as invertible subset LDPC (IS-LDPC) codes, was proposed for peak-to-average power ratio (PAPR) reduction in OFDM systems recently. In this paper, we propose a PAPR reduction scheme for orthogonal frequency-division multiple access (OFDMA) systems based on IS-LDPC codes. The proposed scheme maps the invertible subsets of IS-LDPC codewords onto subcarriers to construct invertible symbol subsets. Then, the invertible symbol subsets are inverted independently for reducing the PAPR of downlink OFDMA systems. There is no need to transmit the side information by extra channels, which significantly reduces the system overhead and eases the system design. Simulation results show that the PAPR reduction scheme based on IS-LDPC codes produces remarkable PAPR reduction performance and good error correction performance in downlink OFDMA systems. Therefore, the proposed PAPR reduction scheme could be an efficient solution to reduce the PAPR of downlink OFDMA systems.

Statistical characterization of complex baseband signals for multicarrier multiuser systems is studied. In particular, we derive rigorously the asymptotic distribution of uplink orthogonal frequency division multiple access (OFDMA) baseband signals for different subcarrier allocation schemes. This allows us to establish some useful statistical properties of the power process of the corresponding baseband signals. We show that, in most scenarios, the power process converges to a /spl chi//sup 2/ process. This result allows us to characterize the peak-to-average power ratio (PAPR) for OFDMA signals, a parameter considered critical to real system implementation. Specifically, we are able to compare, both qualitatively and quantitatively, the PAPR for different subcarrier allocation schemes. We show first that the contiguous subcarrier allocation and equally spaced interleaving share identical PAPR. Further, we show that random interleaving, which is implemented in the existing OFDMA standard, has a larger PAPR than that of an equally spaced interleaving scheme. The complementary cumulative distribution function of PAPR for random interleaving is shown to be greater than that of equally spaced interleaving by a factor that is identical to the number of users in the OFDMA system.

Cellular communication systems need to support simultaneous transmission of multiple data rates over the same medium. A major aspect of design of cellular systems is simultaneous sharing of channel resources avoiding multiple access interference between users. For high quality communication this must be done without severe degradation in performance of the system. Orthogonal frequency division multiple access (OFDMA) is a multiple access technique that can accommodate many users with widely varying applications, data rates and quality of service requirements. This paper presents analysis of transmission of multiple data rates by using orthogonal variable spreading factor (OVSF) codes in an OFDMA system, which gives increase in spectral efficiency. The performance of the system is analyzed using bit error rate (BER), for additive white gaussian noise (AWGN) and Rayleigh fading channels.

Orthogonal frequency division multiple access (OFDMA) has bright era of wireless communication system. An OFDM system is combined with multiple-input multiple-output (MIMO) in order to increase the diversity gain and system capacity over the time variant frequency-selective channels. However major drawback of MIMO-OFDM high peak-to-average power ratio (PAPR). The Probabilistic techniques: SLM scheme and PTS are the most popular PAPR reduction techniques. A major disadvantage of the SLM scheme is the transmission of the Side Information (SI) bits to enable the receiver to recover the transmitted data. A new version i.e. directed PTS whose performance is compared with the directed SLM. This work deals with reduction of PAPR and other performance metrics like Bit Error Rate (BER), Probability detection of SI bits and Bandwidth degradation.

The multiple access scheme for the long term evolution (LTE) physical layer is based on Orthogonal Frequency Division Multiple Access (OFDMA) in the downlink. The main drawback of OFDMA is the peak-to-average power ratio (PAPR) problem. Dummy sequence insertion (DSI) concept can be an efficient PAPR reduction method for the LTE downlink system because it is very simple to implement and side information is not needed. However, the DSI has to sacrifice a decrease in the transmitted data rate for a large number of dummy subcarriers. In this paper, a novel approach to the DSI concept is proposed for complete application to an LTE system. For effective utilization of physical resources, the unused space of the LTE system is calculated, and dummy subcarriers are inserted into the unused space. Therefore, there is no degradation in transmitted data rate. Simulation results show that the proposed method can reduce PAPR considerably without degradation of bit error rate (BER) performance as a LTE downlink system.

Orthogonal Frequency-Division Multiple Access (OFDMA) systems have attracted considerable attention through technologies such as 3GPP Long Term Evolution (LTE) and Worldwide Interoperability for Microwave Access (WiMAX). OFDMA is a flexible multiple-access technique that can accommodate many users with widely varying applications, data rates, and Quality of Service (QoS) requirements. OFDMA has the advantages of handling lower data rates and bursty traffic at a reduced power compared to single-user OFDM or its Time Division Multiple Access (TDMA) or Carrier Sense Multiple Access (CSMA) counterparts. In our work, we propose a Particle Swarm Optimization based resource allocation and scheduling scheme (PSORAS) with improved quality of service for OFDMA Systems. Simulation results indicate a clear reduction in delay compared to the Frequency Division Multiple Access (FDMA) scheme for resource allocation, at almost the same throughput and fairness. This makes our scheme absolutely suitable for handling real time traffic such real time video-on demand.

This paper proposes an enhancement to a previously reported adaptive peak-to-average power ratio (PAPR) reduction method based on clipping and filtering (CF) for eigenmode multiple-input multiple-output (MIMO) - orthogonal frequency division multiplexing (OFDM) signals. We enhance the method to accommodate the case with adaptive modulation and channel coding (AMC). Since the PAPR reduction process degrades the signal-to-interference and noise power ratio (SINR), the AMC should take into account this degradation before PAPR reduction to select accurately the modulation scheme and coding rate (MCS) for each spatial stream. We use a lookup-table-based prediction of SINR after PAPR reduction, in which the interference caused by the PAPR reduction is obtained as a function of the stream index, frequency block index, clipping threshold for PAPR reduction, and input backoff (IBO) of the power amplifier. Simulation results show that the proposed PAPR reduction method increases the average throughput compared to the conventional CF method for a given adjacent channel leakage power ratio (ACLR) even when we assume AMC.

The dual functionality of assuring ‘illumination’ and “communication” contemporaneously by relying on sustainable and energy-efficient opto-electronic devices like light emitting diodes (LEDs) has enabled visible light communication to garner the attraction of research era. This paper proposes a discrete sine transform (DST)-based optical orthogonal frequency division multiplexing (OFDM) system bestowing as the simplest and alternative multicarrier scheme complying the requirements of intensity modulated and direct detection systems. Moreover, this paper addresses the most vital issue like peak to average power ratio (PAPR) that emerges principally due to the limited dynamic range of LEDs when exploiting DC-biased optical OFDM (DCO-OFDM). Therefore, this paper imparts DST spreading to DST-based DCO-OFDM (DST-S-DCO-OFDM), and consequently, the PAPR performance is compared with other PAPR reduction schemes for the same system. Furthermore, in order to serve multiple subscribers with high-data rates as well as to significantly reduce the amount of PAPR of the multicarrier system, this work investigates a DST-based single carrier frequency division multiple access (DST-SC-FDMA) and derives the mathematical analysis of the time-domain signal formats for different subcarrier mapping strategies like DST-based optical interleaved frequency division multiple access (DST-OIFDMA) and optical localized frequency division multiple access (DST-OLFDMA). The simulated results evidences that the reduction in PAPR for DST-S-DCO-OFDM is more predominant when compared with other PAPR reduction schemes and among the multiple access schemes, the DST-OIFDMA is more power efficient upon comparison with DST-OLFDMA. However, both the schemes exhibit a significant reduction in PAPR when compared with DST-based optical OFDM (DST-OOFDMA).

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.

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.

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.

Multicode - Code Division Multiple Access (MC-CDMA) system is very good for the several kinds of service rates with various quality of service requirement because it can affordable by assigning multiple codes and controlling the flexible capacity. However, the so many multi-code signals are summed in the time domain so that it suffers from the serious problem of high peak to average power ratio (PAPR). Therefore, the expensive linear amplifier or large input back-off is necessary to overcome the problem but it makes power consumption of high power amplifier (HPA) very poor. In this paper, we propose a new method that can reduce PAPR efficiently by constraint codes based on the opposite correlation property of the incoming information data. PAPR reduction performance depends on the length and indices of constraint codes in the MC-CDMA system. There is a trade-off between PAPR reduction and the length of constraint codes. We also study the BER improvement in AWGN channel. The simulation results show that BER performance can be very close to the linear amplifier in two cases: 1) when the exact constraint codes are used without input back-off and 2) when a few constraint codes are used with small input back-off.

In this paper, we propose a novel peak-to-average power ratio (PAPR) reduction method for multi-rate orthogonal frequency division multiplexing (OFCDM) based on an orthogonal variable spreading factor (OVSF) code. In the method, the base station assigns two signs of code sequence to each user to maintain the orthogonality among the code sequences that have different lengths. After that, one sign of the code sequence is selected for reducing the PAPR of the OFCDM symbol. Based on theoretical analysis and computer simulation, we show that the proposed method reduces the PAPR for two data rate classes.

One of the widely adopted multicarrier modulation technique in wireless communication system is Orthogonal Frequency Division Multiplexing (OFDM), because of its enhanced robustness against channel dispersion. However, Inter Carrier Interference (ICI) caused by time varying wireless channel and Peak to Average Power Ratio (PAPR) due to the presence of a large number of subcarriers with varying amplitude are the critical issues faced in OFDM. One of the efficient ICI self-cancellation scheme is correlative precoder but it introduces increased PAPR. To overcome this shortcoming a new form of circulantly precoded OFDM system is implemented to enhance ICI reduce and also employed with Selective Mapping (SLM) which is effective in PAPR reduction and uncomplicated. BER performance of correlative and circulantly precoded OFDM system is evaluated for LMMSE and OLMMSE equalizers. Simulation results show that circulantly precoded OFDM with SLM can achieve jointly better ICI self cancellation and PAPR reduction than correlative precoding technique over time varying channel.