Network coding schemes with efficient LDPC coded MIMO–NOMA in two-way relay networks

The combination of non-orthogonal multiple access (NOMA) and multi-input multi-output (MIMO) approaches has been considered as assuring multiple access for the fifth generation technology. In this study, the performance of a 2 × 2 MIMO- NOMA system with low-density parity check (LDPC) codes is investigated. Redundancy with randomly interleaved differential encoding (R-RIDE) is proposed and applied to LDPC encoded messages by two users. LDPC decoding is done using the sum-product algorithm (SPA), which has two types of decoding methods, hard-decision and soft-decision. For hard-decision, bit-flipping decoder is used and for soft-decision, probability domain, log-domain, and simplified log-domain decoders are used. Bit error rate (BER) versus signal-to-noise ratio (SNR) in (dB) and average mutual information (AMI) in (bps/Hz) versus SNR (dB) are evaluated to compare the performance of the proposed and conventional LDPC schemes in NOMA and MIMO-NOMA systems. Simulation results show that both AMI and BER of the proposed LDPC-R-RIDE in MIMO-NOMA system greatly outperforms conventional LDPC coded schemes in NOMA and MIMO-NOMA systems. Moreover, the proposed R-RIDE-LDPC in MIMO-NOMA system outperforms the proposed scheme in the NOMA system. From the simulation results, LDPC-R-RIDE with simplified log-domain decoder has the best AMI result and BER performance compared with other decoding methods

Cancelable iris Biometrics based on data hiding schemes

The Cancelable Biometrics is a template protection scheme that can replace a stolen or lost biometric template. Instead of the original biometric template, Cancelable biometrics stores a modified version of the biometric template. In this paper, we have proposed a Cancelable biometrics scheme for Iris based on the Steganographic technique. This paper presents a non-invertible transformation function by combining Huffman Encoding and Discrete Cosine Transformation (DCT). The combination of Huffman Encoding and DCT is basically used in steganography to conceal a secret image in a cover image. This combination is considered as one of the powerful non-invertible transformation where it is not possible to extract the exact secret image from the Stego-image. Therefore, retrieving the exact original image from the Stego-image is nearly impossible. The proposed non-invertible transformation function embeds the Huffman encoded bit-stream of a secret image in the DCT coefficients of the iris texture to generate the transformed template. This novel method provides very high security as it is not possible to regenerate the original iris template from the transformed (stego) iris template. In this paper, we have also improved the segmentation and normalization process

BER comparison of OFDM with M-QAM modulation scheme of AWGN and Rayleigh fading channels

The wireless channel environment is critical to develop wireless communication. In Quadrature Amplitude Modulation (QAM), the constellation points are in square grid with equal vertical and horizontal spacing. Because of higher order modulation formats, more bit per symbol can be transmitted. M-QAM is the efficient digital modulation method because of its higher constellation points. In this paper, the Bit Error Rate (BER) performance of Orthogonal Frequency Division Multiplexing (OFDM) systems and different arrays of QAM (4, 8, 16, and 64-QAM) modulation techniques has been compared under the Rayleigh fading and Additive White Gaussian Noise (AWGN) channels. All the simulations are carried out in MATLAB. The investigation results shows that the Quadrature Phase Shift Keying (QPSK) modulation scheme gives the best performance in term of BER in OFDM system compared to the M-QAM modulation scheme

Investigation of error performance in OFDM with network coding techniques in multiple relay networks

The aim of this paper proposes an orthogonal frequency-division multiplexing (OFDM) with network coding to improve the error performance of the system when the messages are transmitted from user to receiver. Two-way relay (TWR) networks are applied to reduce the transmission time slots. The exclusive-OR (XOR) coding is used for network coding in which source nodes exchange their information via TWR nodes. The XOR coded bits provides redundancy to achieve the transmit diversity gain which improves the error performance of the TWR network. OFDM is exploited for TWR to obtain the frequency selective fading nature of wireless channels. The different modulation schemes such as Quadrature Phase Shift Keying (QPSK), 16-Quadrature Amplitude Modulation (QAM) and 64-QAM with OFDM system are simulated and QPSK is selected as it gives the lowest bit error rate (BER). The multiple relaying schemes with different numbers of the information packets are also considered in this paper. Simulation results show that multiple relay schemes provide faster transmission time and better error rate performance. Moreover, different kinds of channel coding schemes such as Convolutional, Reed-Solomon (RS) and turbo codes are applied in OFDM system with network coding to compare and evaluate the BER performance of the proposed system. From the simulation results, network coded OFDM scheme with turbo codes give better BER performance for given Signal-to-Noise Ratio (SNR) in relaying scheme with different numbers of information packets compared to those of convolutional and RS codes. It shows that, the error rate performance and transmission time is reduced 10 percent than the conventional scheme at even at low SNR value

Performance analysis of OFDM channel estimation under IQ imbalance

This study was done in attempt to investigate the effect of In-Phaseand- Quadrature Imbalance (IQI) presence in Orthogonal Frequency Division Multiplexing system (OFDM). Although OFDM system is widely used in the communication system, it is prone and sensitive to non-idealities such as IQI. This issue causes serious performance degradation in the system. Channel estimation plays an important part in an OFDM system. Thus, this study will investigate the effect of IQI in OFDM system channel estimation. There are two types of channel estimation scheme used in this paper. They are the Least Square (LS) and Linear Minimum Mean Square Error (LMMSE). The outcome for this channel estimation scheme will be compared with their theoretical values based on the channel’s Mean Square Error (MSE). To obtain the result, LS and LMMSE channel estimation was developed and simulated using MATLAB Simulink software. Then, the corresponding output was analyzed. From the analysis, the performance of these two-channel estimation schemes was affected after the addition of IQI. However, comparing both schemes, LMMSE has better performance compared to LS in terms of MSE

Investigation on methods of reducing high peak-to-average power ratio in MIMO-OFDM

In recent year, the demand on high data rates wireless communications has significantly increases. To achieve a high capacity of data and spectral efficiency in wireless communication system, the multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) is the key technology to meet the requirement. By having the benefit of resisting the effect of multipath fading and supporting ultra-high data rates, the MIMO-OFDM technology is the perfect candidate for the fourth generation (4G) or long-term evolution (LTE) system. However, the major disadvantage of this system is having a high peak-to-average power ratio (PAPR) due to the large number of subcarriers. Hence, it cannot be realized in many practical applications. There are many PAPR reduction techniques proposed by the previous researchers such as coding, phase-rotation, and clipping method. However, in this paper, the focus is on the performance investigation of phase rotation technique with partial transmit sequence (PTS) and selective mapping (SLM). The performance of both reduction method will be evaluated by comparing to the original PAPR value of OFDM

A Survey on Biometrics and Cancelable Biometrics Systems

Now-a-days, biometric systems have replaced the password or token based authentication system in many fields to improve the security level. However, biometric system is also vulnerable to security threats. Unlike password based system, biometric templates cannot be replaced if lost or compromised. To deal with the issue of the compromised biometric template, template protection schemes evolved to make it possible to replace the biometric template. Cancelable biometric is such a template protection scheme that replaces a biometric template when the stored template is stolen or lost. It is a feature domain transformation where a distorted version of a biometric template is generated and matched in the transformed domain. This paper presents a review on the state-of-the-art and analysis of different existing methods of biometric based authentication system and cancelable biometric systems along with an elaborate focus on cancelable biometrics in order to show its advantages over the standard biometric systems through some generalized standards and guidelines acquired from the literature. We also proposed a highly secure method for cancelable biometrics using a non-invertible function based on Discrete Cosine Transformation (DCT) and Huffman encoding. We tested and evaluated the proposed novel method for 50 users and achieved good results

Handover Decision-Making Algorithm for 5G Heterogeneous Networks

The evolution of 5G small cell networks has led to the advancement of vertical handover decision-making algorithms. A mobile terminal (MT) tends to move from one place to another and, as the 5G network coverage is small, user network access will change frequently and lead to a high probability of unnecessary handover, which is a waste of network resources and causes degradation of service quality. This paper aims to reduce the number of unnecessary handovers in 5G heterogeneous networks by proposing a handover decision-making algorithm that integrates the dwelling time prediction technique and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). The proposed algorithm reduces the number of unnecessary handovers by estimating the connection time to a small cell network using the dwell time prediction technique. The TOPSIS evaluates the network quality and chooses the best network based on user preference. The result shows that the proposed handover algorithm reduces the number of unnecessary handovers to small cell networks in high-speed scenarios. It also saves the network connection cost by up to 27.51% compared with the TOPSIS-based handover algorithm. As for throughput achievement, the proposed algorithm yields an improvement of 5.12%. The proposed algorithm significantly reduces the number of unnecessary handovers in the high-speed scenario while fulfilling user preferences

Quantum cascade laser: a novel light source

Abstract not available

Effect of substitution of sand stone dust for quartz and clay in triaxial porcelain composition

Quartz and kaolin were partially substituted by sand stone dust (a siliceous byproduct of Indian stone cutting and polishing industries) in a traditional triaxial porcelain composition consisting of kaolin, quartz and feldsper. The effect of substitution upon heating at different temperatures (1050-1150C) were studied by measuring the linear shrinkage, bulk density, porosity and flexural strength. Qualititative phase and microstructural analysis on selected samples were carried out using XRD and SEM/EDX technique. The results show that the samples of all the batches achieved higher density (250 g/cc) and almost full vitrification (01% apparent porosity) at around 1115C compared to around 1300C for traditional triaxial porcelain composition. As high as 70 MPa flexural strength was obtained in most of the vitrified samples. No significant variation in physico-mechanical properties was observed in between the composition. XRD studies on selected samples show presence of mainly quartz phase both at low and high temperatures. SEM photomicrographs of the 1115C heated specimen show presence of quartz grain and glassy matrix. Few quartz grains (20-40m) are associated with circumferential cracks around them