Performance Analysis of Turbo Based Multiple Input Multiple Output Systems

Orthogonal Frequency Division Multiplexing (OFDM) has been considered as a strong candidate for next generation wireless communication systems. Compared to traditional OFDM, Single Carrier OFDM (SC-OFDM) has demonstrated excellent bit error rate (BER) performance, as well as low peak to average power ratio (PAPR). Similar to other multi-carrier transmission technologies, SC-OFDM suffers significant performance degradation resulting from intercarrier interference (ICI) in high mobility environments. Existing techniques for OFDM can be directly adopted in SC-OFDM to improve performance, however, this improved performance comes at costs such as decreased throughput. In this paper, we analyze the effect of ICI on an SC-OFDM system and propose a novel modulation scheme. The proposed Magnitude-Keyed Modulation (MKM) modulation provides SC-OFDM system immunity to ICI and with an easy implementation it significantly outperforms OFDM, SC-OFDM and MC-CDMA systems with Phase Shift Keying (PSK) modulation and Quadrature Amplitude Modulation (QAM) in severe ICI environment. Analysis also illustrates the proposed SC-OFDM system with MKM modulation maintains low PAPR compared to traditional OFDM and SC-OFDM systems with PSK and QAM modulations. Simulation results for different modulation schemes in various ICI environments confirm the effectiveness of the proposed system.

The significance of digital communication has been well accepted all over the world. It has been widely used in wireless networks like satellite communication, and 4G and 5G technologies as it provides high data connectivity and efficiency. For long-distance transmission and reception of signals, maintaining the signal quality is very important and therefore an efficient modulation and demodulation scheme is required. In this paper, the quadrature phase shift keying (QPSK) modulation scheme is being presented. Its several advantages over other digital modulation techniques made it one of the best forms of digital modulation. The concept of software-defined radio has been used as a test bed for implementing QPSK modulation. Simulation of QPSK modulation and demodulation process is performed in Laboratory Virtual Instrument Engineering Workbench software, and the digital transmission and reception of signals are done through Universal Software Radio Peripheral. The signal experiences sampling, quantization, filtering, encoding, modulation, demodulation, decoding, with and without the addition of additive white Gaussian noise on the graphical interface of NI LabVIEW. Several investigations have been done on digital modulation, but they are covered entirely on simulation in any software. In this paper along with the implementation of modulation and demodulation part, the transmission and reception of the signal are also performed using USRP.

With the advent of 5G communications, the demand for high data rates and improved spectral efficiency has necessitated the exploration of advanced modulation techniques. Orthogonal Frequency Division Multiplexing (OFDM) and Universal Filtered Multi-Carrier (UFMC) are two prominent modulation schemes for 5G systems. However, both OFDM and UFMC suffer from a high Peak-to-Average Power Ratio (PAPR), leading to signal distortion and inefficient power amplification. The Partial Transmit Sequence (PTS) approach is a promising strategy to minimize PAPR in OFDM and is applied to UFMC to minimize PAPR in UFMC and is known as scrambled UFMC (S-UFMC). PTS, however, involves an extensive search to identify the best phase factors that increase computational complexity. The artificial bee colony algorithm is proposed to reduce the computational complexity S-UFMC and OFDM. A novel modulation scheme, amplitude phase shift keying (APSK), is used instead of quadrature phase shift keying (QPSK) and quadrature amplitude modulation (QAM) in S-UFMC and OFDM, which has better performance than conventional modulation schemes. In this research, OFDM, PTS OFDM, UFMC and S-UFMC are compared and it is found that the proposed scrambled UFMC with APSK modulation using ABC algorithm performs better than OFDM and UFMC in terms of PAPR, spectral efficiency and computational complexity.

The average bit error rate (ABER) performance of low-density parity-check (LDPC)-coded orthogonal frequency-division multiplexing (OFDM) free-space optical communication system with K-ary quadrature amplitude modulation (QAM) and phase shift keying (PSK) modulation schemes is investigated over the composite Málaga fading channel with atmospheric attenuation and pointing errors considered. The probability density function and cumulative distribution function regarding the aggregated channel model are derived with the help of the generalized Gauss-Laguerre quadrature rule, the analytical ABER expressions for both QAM and PSK OFDM systems are then obtained. On the basis of them, the ABER performance is analyzed with different turbulence strengths, weather conditions, normalized beam width, normalized jitter, and specifically, different values of Málaga distribution parameter ρ. Monte Carlo simulation is offered to confirm the correctness of the proposed ABER models. Moreover, LDPC codes are added into the simulation to enhance system performance. The result shows that, for the same turbulence, weather, and pointing error conditions, whether the LDPC codes are taken into account or not, the ABER performance of 16-QAM OFDM system is better than that of 16-PSK OFDM system over the Málaga fading channel, and the ABER result decreases with higher ρ for both modulation schemes. Furthermore, the LDPC coding can significantly improve the system performance over this aggregated fading channel for these two modulation schemes, and a lower LDPC code rate can obtain a better ABER performance. This work is beneficial for free-space optical system design.

Selected Mapping (SLM) is the assuring peak to average power reduction (PAPR) technique for OFDM system. But this technique undergoes a very complex process for finding optimum phase sequence for the reduction of PAPR. Hence, in this paper highly optimized phases are derived and analyzed from proposed algorithm for selected mapping using several modulation schemes such as binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), 8-PSK, 64-PSK, and 64-quadrature amplitude modulation (QAM). The simulation results are performed in MATLAB using complementary cumulative distribution function (CCDF) which clearly depicts that the performance of proposed schemes HIGHLY-OPTIMIZED-SLM2 (HOS-2) and HIGHLY-OPTIMIZED-SLM1 (HOS-1) is remarkable under 64-QAM because gain achieved are 2.95 dB, 1.35 dB respectively as compared with original OFDM system.

The typical subcarrier modulation schemes used in orthogonal frequency division multiplexing (OFDM) system includes; binary phase shift keying (BPSK), quadrature phase shift keying (QPSK) and quadrature amplitude modulation (QAM). This paper analyses the performance of OFDM system that uses various number of modulation QAM constellation points over various fading channels. Simulation is done for various numbers of QAM (8 to 64-points) and with various Doppler frequency values (5 to 500 Hz) over flat and frequency selective fading channels. Results show that the best performance of OFDM system is with the number of QAM of 8 and maximum Doppler shift (MDS) of 5 Hz at all channels.

Shaped offset quadrature phase shift keying (SOQPSK) modulation scheme and its application in optical wavelength-division multiplexed (DWDM) transmission

It is well known that CDMA systems are capacity limited because of the code division multiple access noise. Most of the CDMA systems today use single modulation format such as non-return-to-zero with modulation schemes such as Gaussian minimum shift keying (GMSK) some form of quadrature phase shift keying (QPSK) or quadrature amplitude modulation (QAM). Because of the centered peak in the power spectral density (PSD) of these signals, the bandwidth is not efficiently utilized. There is another formatting scheme based on a generalization of Manchester coding which leads to signals with their PSD peak away from the center, and the PSD of these signals around the center is very small. These are generally known as split spectrum modulation signals, and the binary offset carrier (BOC) is one such example. Bandwidth efficiency can be improved by combining these two modulation formats beyond what is achievable using a single format. The capacity in this case is set by both the CDMA noise of each differently formatted signal and by the mutual interference between the NRZ and BOC signals. Mutual interference is reduced by the separation of the PSD peaks of the two formats there by resulting in the overall improved capacity. This concept of mixing the formats on the same link also will potentially provide the means to share the same frequency between two categories of users by assigning each group different formats possibly at different performance levels. In this paper a brief description of a scheme using this concept of mixing the modulation formats to achieve bandwidth efficiency is discussed. Simulation performed using SystemView/sup @/ software is described and the results obtained in support of the viability of this concept are also presented.

One of the most important multi-carrier transmission techniques used in the latest wireless communication arena is known as Orthogonal Frequency Division Multiplexing (OFDM). It has several characteristics such as providing greater immunity to multipath fading & impulse noise, eliminating Inter Symbol Interference (ISI) & Inter Carrier Interference (ICI) using a guard interval known as Cyclic Prefix (CP). A regular difficulty of OFDM signal is high peak to average power ratio (PAPR) which is defined as the ratio of the peak power to the average power of OFDM Signal. An improved design of amplitude clipping & filtering technique of us previously reduced significant amount of PAPR with slightly increase bit error rate (BER) compare to an existing method in case of Quadrature Phase Shift Keying (QPSK) & Quadrature Amplitude Modulation (QAM). This paper investigates a comparative performance analysis of the different higher order modulation techniques on that design.

The demand for a high bit rate data transmission in space applications has been rapidly increasing especially where one deals with Earth observing missions. In a multi-carrier operation, the problem of interference between carrier spectra appears. Several modulation techniques for digital transmission have recently been investigated for the purpose of achieving narrow signal spectra with power concentrated within a given bandwidth. While designing a communication system, particularly a satellite communication system, special attention is needed to use the primary resources namely, the transmitted power and channel bandwidth. Space communication links are both bandwidth- and power-limited. The quadrature phase shift keying (QPSK) modulation scheme is best suited for satellite communication since bandwidth and power required is optimum. In this paper, some observations on QPSK spectral spikes and the methods to eliminate them as well as pulse shaping circuits to improve spectrum bandwidth are presented.

The WiMax (Worldwide Interoperability for Microwave Access) is a technology in<strong> </strong>broadband wireless access, which employs OFDM (Orthogonal Frequency Division Multiplexing) as an alternative transmission to enable high speed data in communication system. This research aim is to analyze the performance system of the OFDM-Based WiMAX, which used the cyclic prefix. The model was designed in four schemes of simulation method, the BPSK (Binary Phase Shift Keying, QPSK (Quadrature Phase Shift Keying), 16 QAM (Quadrature Amplitude Modulation) and 64 QAM. Each scheme was investigated BER (Bit Error Rate) on AWGN (Additive White Gaussian Noise) channel and multipath Rayleigh fading channel, which had applied the cyclic prefix. By simulation of the cyclic prefix was produced the modulation measurement of the BPSK, QPSK, 16 and 64 QAM. The performance result of Eb/No 15 dB was obtained the BER of BPSK and QPSK of 1.11E-11, the BER of 16 QAM and 64 QAM of 8.69E-06 and 0.00333 respectively. Those results indicated much smaller BER value than EbNo 0 dB which BPSK and QPSK of 1 BER, 1.5 and 1.75 BER for 16 QAM and 64 QAM respectively. In conclusion, a higher value of EbNo, hence the BER value would be lower.

The present paper deals with design and development of a generalized parametrizable modulator (GPM) that can perform Gaussian minimum shift keying (GMSK) modulation and Quadrature Phase Shift Keying (QPSK) modulation in a reconfigurable baseband modulator for software defined radio (SDR) architecture. GMSK is the underlying modulation scheme for the Global System for mobile (GSM) standard, while QPSK technique is the basic modulation scheme for Code Division Multiple Access (CDMA) standard. Although GMSK is an inherently non-linear modulation technique, the present work uses a linearly approximated GMSK technique to take the advantage of the simplicity of the filter structure. The normalised error in amplitude as a function of modulation index and bandwidth time product has been simulated. The proposed GPM is capable of working at a maximum data rate of 13.75 Mbps, thus satisfying the requirements of almost all 2G and 3G air interface standards. The GPM can perform QPSK using four pulse shaping filters, two Raised Cosine (RC) filters and two Root Raised Cosine (RRC) filters. The proposed GPM architecture is implemented on a Spartan 3E starter kit.

Design, comparative study and analysis of CDMA for different modulation techniques

In order to pursue rapid development of the new generation of wireless communication systems and elevate their security and efficiency, this paper proposes a novel scheme for automatic dual determination of modulation types and signal to noise ratios (SNR) for next generations of wireless communication systems, fifth-generation (5G) and beyond. The proposed scheme adopts unique signatures depicted in two-dimensional asynchronously sampled in-phase-quadrature amplitudes' histograms (2D-ASIQHs)-based images and applies the support vector machines (SVMs) tool. Along with the estimation of the instantaneous SNR values over 0-35 dB range, the determination of nine modulation types that belong to different modulation categories i.e., phase-shift keying (Binary-PSK, Quadrature-PSK, and 8-PSK), amplitude-shift keying (2-ASK and 4-ASK) and quadrature-amplitude modulation (4-QAM, 16-QAM, 32-QAM, and 64-QAM) could be achieved by this scheme. The application of this scheme has been simulated using a channel model that is impaired by additive white Gaussian noise (AWGN) and Rayleigh fading, covering a broad range of SNRs of 0-35 dB. The performance of this dual-determination scheme shows high modulation recognition accuracy and low mean SNR estimation error. Therefore, it can be a better alternative for designers of next generation wireless communication systems.

New expressions for the average probability of packet error in case of intermediate Nakagami (1960) fading channels are derived. The correlation among bits within the packet is assumed to obey the first order Markovian process. Both non-coherent frequency shift keying (NCFSK) and quadrature phase shift keying (QPSK) modulation schemes are addressed. The average probability of packet error is used to obtain an expression for the modified throughput for the non-persistent carrier sense multiple access (NPCSMA) protocol. The different fading parameters affecting the modified throughput expression such as the average signal to noise ratio (SNR), fading margin and correlation factor among bits of the same packet are also analyzed.