Noisy and Dynamic-Index Partitioned Modulation for Physical Layer Security

Complex field network coding has been shown to achieve a throughput of 1/2 symbol per user per channel use in a multi-way relay channel (MWRC). To achieve this throughput, a superimposed combination of user symbols must be distinguishable at the relay. In [1], precoding vectors were designed for an MWRC with all users employing the same rectangular quadrature amplitude modulation (QAM) constellation. These precoding vectors guarantee that every superimposed combination of user symbols at the relay is distinguishable and a QAM constellation is received. There are many precoding vectors with such properties. In this paper, we consider a more general problem in which each user can employ an arbitrary rectangular QAM constellation and we design a precoding vector for the users such that the power efficiency of the received rectangular QAM constellation at the relay is maximized.

Quadrature amplitude modulation (QAM) constellation and Golay complementary sequences (GCSs) are usually applied in orthogonal frequency division multiplexing (OFDM) systems to obtain a higher data rate and a lower peak-to-mean envelope power ratio (PMEPR). In this paper, after a sufficient search of the literature, it was found that increasing the family size is an effective way to improve the data rate, and the family size is mainly determined by the number of offsets in the general structure of QAM GCSs. Under the guidance of this idea, we propose a new construction for -QAM GCSs through generalized Boolean functions (GBFs) based on a new description of a -QAM constellation, which aims to enlarge the family size of GCSs and obtain a low PMEPR. Furthermore, a previous construction of -QAM GCSs presented by Li has been proved to be a special case of the new one, and the family size of new sequences is much larger than those previously mentioned, which means that there was a great improvement in the data rate. On the other hand, a previous construction of 16-QAM GCSs presented by Zeng is also a special case of the new one in this paper, when . In the meantime, the proposed sequences have the same PMEPR upper bound as the previously mentioned sequences presented by Li when applied in OFDM systems, which increase the data rate without degrading the PMEPR performance. The theoretical analysis and simulation results show that the proposed new sequences can achieve a higher data rate and a low PMEPR.

A low complexity maximum likelihood (ML) detection method is proposed for the square quadrature amplitude modulation (QAM) constellation. In order to reduce the implementation complexity of ML detection, set-partition, subset-selection, and subset-shift are recursively applied to the square QAM constellation. The estimated square QAM symbol is finally given in a closed form as a function of the received signal and the estimated channel. Complexity analysis and numerical simulation confirm that the proposed detection method reduces the implementation complexity substantially and achieves exactly the same performance as the conventional ML detection irrespective of the channel estimation error.

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.

This study investigates the effects of polarization mode dispersion (PMD) on high-speed multimode fiber (MMF) optical communication systems, focusing on how differential group delay (DGD) and environmental conditions such as temperature and humidity influence signal quality. The research was conducted in Abuja, Nigeria, using two modulation formats—non-return-to-zero (NRZ) and quadrature amplitude modulation (QAM). Experimental measurements were carried out over fiber lengths ranging from 1 km to 38 km, and data rates from 15 Gbps to 240 Gbps. Key performance metrics such as bit error rate (BER), jitter, and signal-to-noise ratio (SNR) were analyzed in relation to DGD under varying environmental conditions. Results showed that DGD increased from 0.136 ps to 2.78 ps for NRZ and from 0.058 ps to 2.24 ps for QAM across the tested fiber lengths. Corresponding BER values for NRZ ranged from 1.18 × 10-7 to 1.35 × 10-7, while QAM showed slightly better performance with BER values between 1.18 × 10-7 and 1.29 × 10-7. Jitter rose from 4.26 ps to 31.20 ps in NRZ and from 4 ps to 33.54 ps in QAM. SNR values declined as DGD increased, with NRZ dropping from 34.59 dB to 54.56 dB and QAM from 34.83 dB to 52.90 dB. Environmental factors also played a role; temperature increases from 28.34°C to 29.90°C and humidity from 53.1% to 59.5% led to significant increases in DGD. The findings confirm that PMD, though less dominant in MMF than modal dispersion, still significantly affects signal quality in long-distance and high-speed MMF systems. QAM demonstrated greater resilience to PMD compared to NRZ. This study highlights the need for effective dispersion management and modulation format optimization in designing robust optical networks for environmentally dynamic regions like Abuja.

The growing demands on high-speed data transmission over long distances require optimized communication systems with bandwidth efficient modulation techniques like Quadrature Amplitude Modulation (QAM). However, the various design parameters of these QAM based systems conflict each other and the complex interdependence makes it difficult and time consuming to appropriately tune the parameters towards an optimal solution for a given set of constraints. Therefore, throughout this paper we analyze various conflicting design parameters of QAM and derive objective optimized trade-offs. More specifically, we study in detail the effects and interdependencies of parameters in the matched filter, the Forward Error Correction (FEC) code pair and the modulation order and span the design and solution space through experimental and numerical results. We discuss the observed effects and show how a selection of parameters can be concluded under various constraints. Furthermore, a pareto optimality search on our design space points out the best combinations of modulation order, filter and FEC design parameters for maximizing the performance under various Signal-to-Noise Ratio (SNR) conditions of the channel. For instance, if the channel is constrained by a SNR of 10dB and the tolerable Bit Error Rate (BER) is 10−3, then 16-QAM with a required 2/3 FEC yields 33.3% higher performance than 64-QAM with a required 1/3 FEC. Thus, the outcomes of this paper are a comprehensive elaboration on the cross-effects of conflicting design parameters and a set of optimized solutions under various constraints.

The interference levels that may be expected for a range of conventional cellular and microcellular clusters used in personal communication networks (PCNs) and personal communication systems (PCSs) are discussed. Simulation results show that for conventional size cells, 32- and 64-level quadrature amplitude modulation (QAM) schemes are preferred for bit error rates (BER) above 1*10/sup -2/, while 4PSK or variable-rate QAM schemes are better for lower BER. For microcells with communications at both 900 MHz and 1.8 GHz, four- or six-cell clusters are advocated, depending on the SNR expected. Based on the expected signal-to-noise ratio (SNR) and interference levels, it is argued that variable-rate QAM schemes are superior to the other modulation schemes considered. For low BERs 4PSK may often provide the best performance, whereas for high BERs, particularly when the SNR is high, 32- and 64-level star QAM are the most suitable.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A general expression for the bit-error rate (BER) performance of quadrature amplitude modulation (QAM), have been presented in this paper, considering arbitrary branch Maximal Ratio Combining (MRC) Receiver, over two-wave diffuse power (TWDP) Fading Channels. Analysis of the impact caused by the fading parameters Δ and K, on the performance of the M branch-MRC receiver, have been done for different QAM constellations. Numerical evaluation of the expressions and finally the verification of the results using Monte Carlo Simulation have been done.

This paper introduces a joint equalizer compensating chromatic dispersion, nonlinearity with reduced complexity and improved performance for Optical orthogonal frequency multiplexing (OOFDM) transmission. It presents performance comparison for M-ary Quadrature amplitude modulation (QAM) by varying M to 16 and 64. Simulated results with dispersion and non-linearity compensation achieve bit error rate (BER) of 10−9 at 21 dB SNR for 16-QAM-OOFDM transmission, at 23 dB SNR for 64-QAM-OOFDM transmission. Proposed equalizer reports improvement in signal to noise ratio (SNR) by approximately 1–1.5 dB in comparison to conventional results.

Underwater acoustic channels are affecting by many factors like time varying multipath propagation, Doppler spread, and salinity, which can greatly limit the quality of data rate and transmission distance. Underwater optical communication represents a crucial technology that supporting higher data rate, secure links and low latency. In his paper the use of 64- Quadrature Amplitude Modulation (64-QAM) in underwater optical communication systems is investigated. The system is designed to offer higher data rate than those of acoustic communication system. The proposed design achieve data rate of 10 Gbps over a challenging transmission distance of 50 km. In our study, a simulation technique is used to evaluate the performance of the proposed design in the underwater conditions, focusing on factors such as Bit Error Rate (BER), constellation diagram and Quality factor (Q-factor). The achieved BER is of about 10-10 with a minimum signal to noise ratio (SNR) of about 30dB. This paper provides valuable results for the design of next-generation underwater communication systems for applications such as pollution monitoring, oil control and oceanography research.

The performance analysis of a space–time block coded multiple input multiple output system with variable-power (VP) adaptive modulation (AM) over Rician fading channels for imperfect channel state information is presented. The optimum switching thresholds for attaining maximum spectrum efficiency (SE) subject to a target bit error rate (BER) and an average power constraint are derived. In the derivation, a very tight BER expression of quadrature amplitude modulation (QAM) is used to develop a new power adaptation scheme that can fulfil the target BER even at low signal-to-noise ratio (SNR) and achieve higher SE than the scheme using the BER upper bound commonly adopted in the literature. The existence and uniqueness of the Lagrange multiplier used in the constrained optimisation are investigated. It is shown that the Lagrange multiplier is unique when it exists. By using the switching thresholds, the authors obtain closed-form expressions of SE and average BER of the system. Computer simulation shows that the theoretical analysis is in good agreement with simulation. The results show that the proposed VP-AM scheme provides better SE than the constant-power counterparts and the VP-AM scheme using the commonly used BER bound.

Signal detection plays a significant role at the receiver of current multiple-input multiple-output (MIMO) communication systems. In this paper, we propose a deep learning aided Douglas-Rachford network (DRNet) for MIMO signal detection. Specifically, DRNet is developed based on Douglas-Rachford splitting approach, which is a classic method for non-smooth convex signal recovery. It is known that the transmitted signal in MIMO systems is drawn from a discrete quadrature amplitude modulation (QAM) constellation and ordinary least square (OLS), namely zero-forcing (ZF), performs poorly in small size MIMO systems. In order to obtain better performance, we design an implicit penalty for the unknown transmitted signal and use a deep neural network (DNN) to learn the corresponding proximal gradient of the penalty. Meanwhile, we vectorize the hyper-parameters in the Douglas-Rachford splitting approach and make them learnable. Simulation results show that the proposed DRNet outperforms the original Douglas-Rachford splitting approach and is robust to varying signal-to-noise ratio (SNR). Moreover, compared with existing model-driven deep MIMO detectors, DRNet also has lower bit-error-rate (BER).

The performance of encoded opportunistic transmission schemes in wireless channels affected by Rayleigh fading and additive white Gaussian noise (AWGN) is analyzed. In opportunistic transmission, the information is transmitted only when the fading amplitude is above a threshold. For this, the receiver with the knowledge of the channel state information notifies the instants the transmitter should transmit. Opportunistic systems with convolutional error correcting codes or with trellis coded modulation are analyzed in terms of closed-form bit error rate (BER) expressions. Nevertheless, the approach presented can be employed with any kind of error correcting codes. Hence, the performance of turbo codes is also presented in the simulations. Monte Carlo simulations verify the accuracy of the derived expressions and provide insights on the system performance. Performance results show that uncoded and encoded opportunistic systems are superior to uncoded and encoded ordinary systems (non-opportunistic), respectively. In particular, the BER curves of the opportunistic system decay exponentially when the signal-to-noise ratio (SNR) increases. On the other hand, BER curves for ordinary transmission decay linearly, where the slope is proportional to the diversity that depends on the error correcting code. Thus, opportunistic systems require less SNR to guarantee the same BER of ordinary transmission. The BER gain increases as the SNR increases. It is also observed that uncoded opportunistic systems are even superior to encoded ordinary ones. The results are validated guaranteeing the same spectral efficiency for all the scenarios. Finally, due to the exponential decay of the BER curves, coding gain expressions, used in ordinary systems over AWGN, can be used as approximations for opportunistic transmission in fading channels.

When it comes to studies on smart receiver designs, using machine learning and deep learning techniques for the development of automatic modulation classifiers as well as demodulators which require little to no information about the transmitted signal or the channel state is an area of interest. Through this study, we have proposed a combined classifier-demodulator system that is entirely deep learning-based and one that is focused on higher-order quadrature amplitude modulation (QAM) schemes such as 64QAM and 256QAM that can be used in next-generation mobile technologies. The system was developed by training a bidirectional long-short-term memory (BiLSTM) and long-short-term memory (LSTM) network for the classifier and demodulator, respectively, using randomly generated data, demodulated using binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), 16QAM, 64QAM, and 256QAM transmitted through a simulated additive white Gaussian noise (AWGN) channel of varying signal to noise ratio (SNR) levels. The classifier was then tested for its prediction accuracy while the demodulator models were tested against traditional mathematical models while calculating the effective capacity. The results showcased that the classifier worked extremely well for the QAM schemes across all SNR levels and less so with the PSK models. Considering the demodulator models’ performance, all schemes except the 256QAM demodulator were able to reach a zero or near zero bit error rate (BER) level within minimum acceptable SNR ranges.

This paper presents the first concerted look at low correlation sequence families over quadrature amplitude modulation (QAM) constellations of size and their potential applicability as spreading sequences in a code-division multiple-access (CDMA) setting. Five constructions are presented, and it is shown how such sequence families have the ability to transport a larger amount of data as well as enable variable-rate signaling on the reverse link. Canonical family has period , normalized maximum-correlation parameter bounded above by , where ranges from in the 16-QAM case to for large . In a CDMA setting, each user is enabled to transfer bits of data per period of the spreading sequence which can be increased to bits of data by halving the size of the sequence family. The technique used to construct is easily extended to produce larger sequence families and an example is provided. Selected family has a lower value of but permits only -bit data modulation. The interleaved 16-QAM sequence family, has and supports 3-bit data modulation. The remaining two families are over a quadrature-pulse amplitude modulation (Q-PAM) subset of size of the -QAM constellation. Family has a lower value of in comparison with Family , while still permitting -bit data modulation. Interleaved Family , over the 8-ary Q-PAM constellation, permits 3-bit data modulation and interestingly achieves the Welch lower bound on .