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In this paper, we propose a simple power and rate allocation scheme for uplink non-orthogonal multiple access based on a multicarrier system when a practical modulation and coding scheme is employed at each user. Since information-theoretic approaches with asymptotic settings are not considered, the proposed power and rate allocation scheme is able to provide a guaranteed performance with any practical block codes of finite length in terms of the probability of code word error. For the performance prediction in the power and rate allocation with given channel realizations, we employ non-asymptotic approaches for bounds on the probability of code word error. Through simulation results, we can confirm that the probability of code word error can be lower than or close to the target error rate using the proposed power and rate allocation. [ABSTRACT FROM AUTHOR]

One of the main objectives of multicarrier modulation is to provide multiple accesses for wireless communication systems with higher data rates while having minimum out of band radiation, high spectral efficiency and less complexity. Orthogonal frequency division multiplexing (OFDM), Universal filter multicarrier (UFMC), Filter bank multicarrier (FBMC) and Generalized frequency division multiplexing (GFDM) modulation techniques have been developed to support fourth generation and beyond 4G wireless systems. Demand of high data rate in fourth generation wireless communication systems has been fulfilled by OFDM techniques but it suffers from the limitation of less spectral efficiency and high PAPR (Peak to average power ratio). Thus to support next generation wireless systems other waveform models are getting attention. Among the techniques available, UFMC seems to be attractive due to high spectral efficiency and less complexity. It has not explored much so in this paper, performance of UFMC have been evaluated with different design factors such as number of sub bands, FFT (Fast Fourier Transform) size, filter characteristics and modulation under the light of PAPR. [ABSTRACT FROM AUTHOR]

Code division multiple access (CDMA) at its multicarrier version of image watermarking scheme that is robust against random gain operation as well as enables high embedding rate is developed in this paper. Watermark embedding is done on mutually orthogonal set of host image samples wherein data bits are embedded using an orthogonal set of code patterns. Watermark decoding is also proposed by exploiting the principle of minimum mean square error combining. The decision variable for the binary watermark is the resultant weighted decision statistics. A generalized model of attack that consists of multiplicative and additive degradation on the watermarked image is considered. The first one follows Rayleigh distribution and the second one Gaussian distribution. We mathematically show that the proposed decoder structure incorporates the effect of random gain (fading attack) unlike the widely used correlator decoder. The concept of multiuser detection principle which is widely used in CDMA is then explored to cancel the effect of multiple bit interference in watermarking. Two variants of combined interference cancellation (CIC), namely threshold combined interference cancellation (TCIC) and group combined interference cancellation (GCIC) are then developed. Mathematical analysis and the results through simulations show that TCIC and CIC offer similar decoding error rate performance. On the other hand, a significant improvement in decoding error performance and payload are achieved through GCIC. Finally, the proposed method is studied for image error concealment and performance comparison is reported over the existing methods. [ABSTRACT FROM AUTHOR]

Real-time and reliable transmission with high data rate is one of the most crucial design issues in underwater acoustic (UWA) communications. This paper is part of an operational project in the Persian Gulf which is known as a shallow water channel worldwide. Building on the promising combination of cooperative and multicarrier techniques, we first address the design of an efficient UWA communication system over the Persian Gulf channel. We assume sparse and frequency-selective Rician fading, non-white correlated Gaussian ambient noise, and non-uniform Doppler distortion among subcarriers. Based on the extensive field measurements, we adopt a comprehensive channel model including modified sound speed profile, modified absorption coefficient, reflections from the surface and bottom of the sea, and modified ambient noise model. In our work, carrier frequency is efficiently determined based on the system and environmental parameters. In addition, a simple criterion for Doppler scale calculation is proposed. Moreover, based on the approximate auto-correlation function of the ambient noise, whitening filter is utilized at the receiver. In many applications of underwater acoustic sensors network (UW-ASN), nodes may not be big enough to have more than one antenna. Therefore, to achieve spatial diversity, cooperation between nodes can be a proper alternate method. In another part of this research, toward a proper approach that each node operates under full-duplex mode, we address a cooperative virtually-aided transmission scenario which is called cooperative multiple input single output. Simulation results demonstrate that our proposed models can significantly improve the bit error rate performance of UW-ASN in the Persian Gulf channel. [ABSTRACT FROM AUTHOR]

This article proposes an N-finite Radon transform (N-FRAT) and a discrete framelet transform (FT) for the design of a new orthogonal frequency division multiplexing (OFDM) system. In the proposed system, the inverse FT (IFT) and FT were used instead of the inverse fast Fourier transform (IFFT) and fast Fourier transform (FFT) to realize multicarrier modulation and demodulation techniques, respectively. Simultaneously, it was suggested that the N-FRAT technique operate as a data mapper instead of the conventional phase shift keying (PSK) and quadrature amplitude mapping (QAM), which are usually used with the traditional OFDM system. The usage of the N-FRAT and FT in the proposed system led to an increase in the orthogonality between the subcarriers due to the application of IFFT in the N-FRAT, which was added to improve the orthogonality and time-frequency localization properties of the FT. Furthermore the proposed structure improved the bandwidth efficiency through the elimination of the cyclic prefix compared to the traditional system. The proposed system was simulated and compared with other OFDM systems, such as FFT based OFDM using N-FRAT mapping (N-FRAT-FFT-OFDM), FT based OFDM using QAM mapping (QAM-FT-OFDM), and FFT based OFDM using QAM mapping (QAM-FFT-OFDM). The simulation was performed over frequency selective fading channel using MATLAB technical programming language. The results of simulations showed that the new structure outperformed the other three systems by reducing the inter-symbol interference (ISI) and inter-carrier interference (ICI), which then improved the bit error rate (BER) performance. [ABSTRACT FROM AUTHOR]

The growing progress in wireless communication services led to a demand in high data rates, spectral efficiency and flexibility requirements. The Block-Windowed Burst Orthogonal Frequency Division Multiplexing (BWB-OFDM) technique has been recently proposed to face these demands. This technique employs smoother, non-rectangular windows, allowing a power spectral density similar to the filtered OFDM approach, thus achieving high spectral efficiency; also, it packs together several OFDM symbols, with the addition of a sole zero-padding to accommodate the multipath channel’s propagation delay, thereby improving power efficiency. However, BWB-OFDM has the same drawbacks of OFDM when transmitting over hostile channel conditions, namely the performance degradation due to deep fades associated to severe frequency-selective channels. This paper proposes a new Time Interleaved BWB-OFDM (TIBWB-OFDM) technique that performs interleaving on the time-samples of each BWB-OFDM block, creating a kind of diversity effect at the frequency domain, granting a much better resilience against deep inband fades, while keeping all the mentioned advantages of BWB-OFDM at the cost of no added complexity. Also, by regarding TIBWB-OFDM as a hybrid technique combining single-carrier and multicarrier characteristics, this paper also proposes the use of non-linear frequency domain equalizers based on the Iterative Block Frequency Domain Equalization (IB-DFE) concept for TIBWB-OFDM detection. It is shown that noteworthy improvements can be achieved in bit error rate (BER) performance compared to conventional OFDM schemes when employing typical zero-forcing (ZF) and minimum mean-square error (MMSE) linear equalizers. [ABSTRACT FROM AUTHOR]

Universal Filter Multi-Carrier (UFMC) modulation is a potential candidate for next generation wireless communication due to its advantages like better sub carrier separation and less complexity. Higher peak to average power ratio (PAPR) affects the performance of UFMC and suitable PAPR reduction technique is required to mitigate the same. In this work, an improved PAPR reduction technique (CFC-UFMC) has been proposed for UFMC system. Performance of proposed technique is compared with existing Selective Mapping (SLM), Clipping, Companding and Clipping & Filtering methods as applied on UFMC. Simulation results show that proposed technique provides better PAPR reduction with variation in design parameters namely FFT Size, Filter Length and Bits per sub carrier as compared with other techniques. Various PAPR reduction techniques have also been compared on the basis of bit error rate. [ABSTRACT FROM AUTHOR]

Orthogonal frequency division multiplexing(OFDM) is a multicarrier modulation(MCM) system that enables high-speed communications using multiple carriers and has advantages of power and spectral efficiency. Therefore, this study aims to complement the existing shortcomings and to design an efficient MCM system. The proposed system uses the inverse discrete wavelet transform(IDWT) operation instead of the inverse fast Fourier transform(IFFT) operation. The bit error rate(BER), spectral efficiency, and peak-to-average power ratio(PAPR) performance were compared with the conventional OFDM system through the OFDM system design based on wavelet transform. Our results showed that the conventional OFDM and Wavelet-OFDM exhibited the same BER performance, and that the Wavelet-OFDM using the discrete Meyer wavelet had the same spectral efficiency as the conventional OFDM. In addition, all systems of Wavelet-OFDM based on various wavelets confirm a PAPR performance lower than that of conventional OFDM. [ABSTRACT FROM AUTHOR]

Offset-quadratic-amplitude-modulation-based filterbank multicarrier (FBMC-OQAM) has been shown to be a promising alternative to cyclic prefix-orthogonal frequency division multiplexing. More recently, the use of FBMC-OQAM has been proposed in combination with massive MIMO communications. In this context, it is interesting to study the overall effect of massive MIMO on the FBMC-OQAM intrinsic interference and its interaction with channel frequency selectivity. In this paper, the performance of an FBMC-OQAM uplink massive MIMO system is theoretically characterized in terms of the output mean squared error (MSE) of the estimated transmitted symbols and for three types of linear receivers, namely, zero forcer, linear minimum mean squared error, and matched filter. Using random matrix theory, the output MSE of these receivers is asymptotically characterized as the number of base station antennas $N$ and the number of users $K$ grow large, while keeping a finite ratio $N/K$. The obtained expressions allow to draw many conclusions, some of which were already noticed in the literature but not yet theoretically proven. First, the MSE becomes uniform across the frequency band as a result of the channel hardening effect. Second, it is shown that a good synchronization of the users is crucial in a massive MIMO scenario. Finally, if the users are well synchronized, the different terms that compose the MSE, such as noise, interuser interference, and the distortion caused by the channel frequency selectivity, become negligible for large values of the ratio $N/K$ . This effect was previously referred to as “self-equalization” in the literature. [ABSTRACT FROM AUTHOR]

A lot of attention has been given recently to future multicarrier (MC) modulation techniques, for high speed robust wireless systems, in order to serve upcoming envisioned needs. Generalized Frequency Division Multiplexing (GFDM), a candidate for 5G, is a non-orthogonal modulation technique, proposed as an alternative to Orthogonal Frequency Division Multiplexing (OFDM) for future wireless communication systems. However, due to its non-orthogonal nature, GFDM introduces intersymbol and intercarrier interference (ISI/ICI). To mitigate these effects and to improve Symbol Error Rate (SER) system performance we explored the near orthogonality concept based on Offset Quadrature Amplitude Modulation (OQAM) and made the adaptation to the conventional GFDM system model. In this paper, we investigate SER performance under the Nakagami- m and Nakagami- q (Hoyt) fading channels. Analytical expressions for this SER performance are derived and the obtained results match those of the simulations that were carried out and confirms the effectiveness of the proposed GFDM/OQAM model to that of conventional GFDM. [ABSTRACT FROM AUTHOR]

This study proposes an iterative, joint channel estimation, equalization, and data detection method in the presence of high mobility for a multicarrier downlink system that communicates over rapidly time-varying channels. The proposed method uses a basis expansion method (BEM) which has low computational complexity and helps to reduce the number of coefficients needed to represent a time-varying channel and therefore is extremely easy to implement practically. Unlike the current literature, which is almost entirely focused on the uplink communication systems due to their computational costs, this method prioritizes the goal of being feasible in a downlink system with a reasonable performance. The proposed suboptimal algorithm is based on the space-alternating generalized expectation-maximization (SAGE) algorithm and the time-varying channel is represented by orthogonal basis functions obtained by means of discrete Walsh-Hadamard transform (DWHT). The resulting receiver iterates between maximum a posteriori (MAP) based channel estimation in the subspace spanned by the orthogonal basis functions and successive interference cancellation. Numerical examples show that the proposed algorithm has a satisfactory symbol error rate with low computational complexity and also has a reasonable peak-to-average power ratio (PAPR) reduction effect. [ABSTRACT FROM AUTHOR]

Among the multicarrier modulation techniques considered as an alternative to orthogonal frequency division multiplexing (OFDM) for future wireless networks, a derivative of OFDM based on offset quadrature amplitude modulation (OFDM/OQAM) has received considerable attention. In this paper, we propose an improved joint estimation method for carrier frequency offset, sampling time offset, and channel impulse response, needed for the practical application of OFDM/OQAM. The proposed joint ML estimator instruments a pilot-based maximum-likelihood (ML) estimation of the unknown parameters, as derived under the assumptions of Gaussian noise and independent input symbols. The ML estimator formulation relies on the splitting of each received pilot symbol into contributions from surrounding pilot symbols, non-pilot symbols and additive noise. Within the ML framework, the Cramer-Rao bound on the covariance matrix of unbiased estimators of the joint parameter vector under consideration is derived as a performance benchmark. The proposed method is compared with a highly cited previous work. The improvements in the results point to the superiority of the proposed method, which also performs close to the Cramer-Rao bound. [ABSTRACT FROM AUTHOR]

The universal filtered multicarrier (UFMC) is an appealing technique to eliminate out-of-band emission (OOBE) for fifth-generation (5G) networks. However, its signals that are modulated to the carriers, which are on the edges of one subband, are influenced by the filter. In this paper, an interference cancelation scheme is proposed to suppress the interference and to improve the multiuser system performance. Here, interference cancelation subcarriers are inserted on the edges to reduce the filter interference. This scheme ensures that the operating subregion or subband supports the variable bandwidth allocation to meet the requirements of 5G networks. Simulation results show that the bit error rate (BER) performance improves by 4 and 7 dB compared with that of the conventional UFMC when the corresponding Eb/N0 is 15 and 20 dB. Comparisons with both the standard OFDM and the GB OFDM are also reported. The results demonstrate that the proposed UFMC scheme outperforms the other two systems, especially compared with the GB OFDM system under the condition of the same spectral efficiency. [ABSTRACT FROM AUTHOR]

Passive intermodulation (PIM) potentially occurs in all high-power passive microwave devices. It can severely deteriorate the receiving performance of wireless communication and radar systems. To date, the simultaneous localization of multiple PIM sources in practical microwave devices is still a technical challenge. In this paper, we indicate that if a reference PIM source can be introduced into the standard PIM testing system, and the amplitude and frequency-dependent phase difference between the reference and the real PIM products can be used to construct a k-space multicarrier signal, PIM localization algorithms for both wideband and narrowband devices can be proposed based on the inverse k-space Fourier transform and inverse optimization of the partial multicarrier signal. Simulation and experimental results validate the effectiveness of the proposed approaches. These methods can solve the difficulty of multipoint PIM localization, and can be widely used in the design, production, testing, and troubleshooting of high-power microwave systems. [ABSTRACT FROM AUTHOR]

Orthogonal signal division multiplex (OSDM) is an emerging signal modulation technology which has a lower peak-to-average power ratio (PAPR) and a flexible subcarrier system architecture. Particularly, it can be seen as a bridge between the single-carrier modulation and the orthogonal frequency division multiplexing (OFDM) modulation in the frequency domain. Aiming at the development trend and demand of underwater acoustic hybrid and adaptive modulation communication technology, a pseudo-noise (PN) sequence-based underwater acoustic OSDM communication system is proposed in this paper. A data frame structure with PN sequence is designed to solve the multipath and Doppler effect of underwater acoustic channel. On the basis of the PN sequence, a compressive sensing method based on the orthogonal matching pursuit (OMP) algorithm and the minimum mean square error (MMSE) algorithm is designed for channel estimation and equalization. On the basis of the system construction, the relationship among the OSDM vector length M, the OSDM subcarrier number N, and the underwater acoustic channel length is further studied for adaptive modulation of underwater acoustic communication. Finally, the proposed system is verified by simulation. The OSDM system has lower and controllable PAPR. When the OSDM vector length M is bigger than the channel length, and the system subcarrier flexibility is guaranteed, the bit error rate (BER) of the OSDM system is lower than that of the OFDM system and the single-carrier system. The PN sequence-based compressive sensing channel estimation and equalization with the OMP and MMSE algorithms has a good performance to resist the multipath effect of underwater acoustic channel.

Sun and Luo recently showed that if the vector-space single-beam interference alignment problem for a $K$ -user, $L$ -carrier interference channel is feasible, then $K\leq 2L-2$ . We prove the converse, that if $K\leq 2L-2$ , then the problem is feasible, i.e., that the requisite beamformers do exist. [ABSTRACT FROM PUBLISHER]

A multi-false-target jamming method is proposed for the linear frequency modulation pulse compression radar with order-statistic(OS) CFAR detector. According to the principle of OS-CFAR detector, a multi-carrier and blanking shift-frequency shifting Jamming method is proposed. Some key parameters are set by using the characteristics of OS-CFAR. As a result, multiple false targets with the quantity, amplitude and space distribution which can be controlled are produced around the true target. The simulated results show that the jamming method can be used to reduce the detection probability of target effectively. [ABSTRACT FROM AUTHOR]

Wavelets are brought into the wireless communication field as an orthogonal base of multi-carrier modulation and are now considered as a significant measure. Also, wavelets do contain the capability to improve bandwidth efficiency even more along with lower inter-symbol interference and inter-carrier interference. Appropriately, a BER versus SNR analysis is done for fast Fourier transform (FFT) based OFDM framework and wavelet haar transform (WHT) based OFDM framework in this work. The evaluationis demonstrated over Rayleigh and Rician fading channel utilizing dissimilar M-PSK modulation levels intended for FFT-OFDM and WHT-OFDM. The performance of the simulated test-bed is investigated via BER assessment as a function of SNR. The imitation outcome reports a significant improvement in BER of the simulated system using WHT-OFDM in comparison to FFT-OFDM for both Rayleigh and Rician fading channel. Also, the BER performance of both FFT-OFDM and WHT-OFDM is superior in Rician fading channel in comparison to Rayleigh fading channel. [ABSTRACT FROM AUTHOR]

Orthogonal frequency-division multiplexing (OFDM), special form of multicarrier modulation, is the cornerstone of broad range of current standards. In addition, fifth-generation (5G) terrestrial wireless networks, advancing at accelerated speed, continue to use OFDM air interface. The first part of this paper endeavors to apply OFDM-like signaling for broadband satellite transmission in the forward direction, from gateway to terminals. Two layers of multicarrier operation are invoked. One allows multiple signals to share single on-board high-power amplifier. The other layer permits transmitted symbols from individual signals to modulate multiple narrowband OFDM subcarriers, followed by interpolating filters to suppress interference into adjacent signals and limit out-of-band emission to be compatible with satellite uplink. The second part of this paper proposes novel nonlinear compensation techniques, applied at the transmitter or receiver, and combination of both. Two performance assessments are provided: one exploiting information-theoretic framework using ideal channel coding; another based on total degradation using practical forward-error correction codes. We show that performance loss from nonlinear distortion can be significantly reduced when adopting the proposed correction methods. Furthermore, it is possible to use OFDM-like signaling over satellite, while being competitive, and in some cases surpassing, traditional systems with single-carrier modulation employing state-of-the-art enhanced receiver architecture. [ABSTRACT FROM AUTHOR]

Multicarrier pulse width modulation (MC-PWM) techniques such as Level-shifted PWM (LS-PWM) and Phase-shifted PWM (PS-PWM) are the popular methods to control the output voltage of Multilevel Inverters (MLIs). The advantage of LS-PWM techniques over PS-PWMs is that they produce better harmonic profile, but the unequal power distribution problem of LS-PWMs imposes limitation to their usage in high power and medium voltage applications. For achieving the equal conduction periods and to evenly distribute the power among different cells, carrier rotation should be employed in LS-PWM. This paper proposes two rotation schemes introduced to LS-PWM for producing the collective benefit of equal power distribution from PS-PWM and better harmonic profile from LS-PWM. MATALB/Simulink has been used to create simulation models and the experimental validations are performed by a hardware setup using dSPACE-DS1104 R&D Controller board. Furthermore, experimental results of device conduction periods, conduction losses of individual cells, total harmonic distortions (THDs) and fundamental output voltages have been measured. The effectiveness of proposed methods are verified by comparing the obtained results with traditional MC-PWM techniques. [ABSTRACT FROM AUTHOR]

Image compression is an essential stage of the data archiving and transmitting process, as it reduces the num- ber of bits and the time required to complete the transmis- sion. In this article, a study of image transmission over the Multi-Carrier Code Division Multiple Access (MC-CDMA) downlink system is presented. The solution proposed relies on source coding combined with channel coding. The Dis- crete Wavelet Transform (DWT) method is used in conjunc- tion with the SPIHT coder to compress the image, then the data generated is transmitted with the MC-CDMA technique over a noisy channel. The results show that image transmis- sions performed over MC-CDMA using the SPIHT model are better than the traditional approach like MC-CDMA in the AWGN channel. [ABSTRACT FROM AUTHOR]

As a candidate alternative multicarrier scheme for the fifth generation (5G) communication, filter bank based multi-carrier with offset quadrature amplitude modulation (FBMC/OQAM) has better spectral containment, enhanced flexibility and higher spectral efficiency than the popular cyclic prefix orthogonal frequency division multiplexing, thus is more suitable for asynchronous fragmented spectrum access scenarios in future 5G. However, real orthogonality instead of complex orthogonality makes the channel estimation in FBMC/OQAM system challenging, especially when it is combined with MIMO. In this paper, an effective and low complexity compressive sensing based channel estimation method via Generalized approximate message passing (GAMP) algorithm was proposed for the time domain MIMO FBMC system. A Bayesian Cramér-Rao Bound-sparsity (BCRB-s) is obtained considering the sparsity constrain of the channel impulse response. Furthermore, a simplified preamble is brought out and evaluated. Simulation results demonstrate that the proposed scheme is more robust to channel frequency selectivity and always works well even in underdetermined cases. In particular, the performance of our GAMP-based method is close to the BCRB-s. It also showed that a tradeoff between complexity and spectrum efficiency can be made by adjusting the parameters of prototype filters used in FBMC/OQAM system. [ABSTRACT FROM AUTHOR]

To maximize spectrum utilization in efficient manner, Cognitive Radio Networks CRNs are proposed. These networks have the ability to adapt its communication parameters to communicate concurrent using the same band with licensed system by using limited interference at primary users (PUs) while assuring it's QOS and improvement Quality of Services (QoS) of Secondary Users (SUs). In this paper, improvements in QoS of SUs are achieved by maximizing the total system throughput in CRN. Then, the CRNs throughput maximization can be achieved by selecting the efficient Multicarrier (MCM) technique and using intelligent and logically power allocation strategy. Moreover, calculating the total system throughput in downlink CRN using Generalized Frequency Division Multiplexing (GFDM) and Orthogonal Frequency Division multiplexing (OFDM) modulation techniques will be made. Furthermore, simple and logic proposed optimization technique based on Fuzzy Logic (FL) algorithm will be applied for power allocation strategy to maximize throughput under different constraints such as, maximum transmit power at Access Point (AP) of SUs and interference threshold level at PU receiver to assuring its QOS. Also, system performance in downlink CRN with different number of PUs, SUs, and subcarriers will be investigated. Finally, the effect of the noise level on the system throughput under both constraints will be done. [ABSTRACT FROM AUTHOR]

Orthogonal frequency division multiplexing with index modulation (OFDM-IM) performs transmission by considering two modes over OFDM subcarriers, which are the null and the conventional $M$ -ary signal constellation. The spectral efficiency (SE) of the system, however, is limited, since the null mode itself does not carry any information and the number of subcarrier activation patterns increases combinatorially. In this paper, a novel IM scheme, called multiple-mode OFDM-IM (MM-OFDM-IM), is proposed for OFDM systems to improve the SE by conveying information through multiple distinguishable modes and their full permutations. A practical and efficient mode selection strategy, which is constrained on the phase shift keying/quadrature amplitude modulation constellations, is designed. Two efficient detectors that provide different tradeoffs between the error performance and detection complexity are also proposed. The principle of MM-OFDM-IM is further extended to the in-phase and quadrature components of OFDM signals, and the method of generating multiple modes from the $M$ -ary pulse amplitude modulation constellation for this modified scheme is also introduced. Bit error rate (BER) analyses are provided for the proposed schemes. Monte Carlo simulations on BER corroborate the analyses and show that the proposed schemes appear as promising multi-carrier transmission alternatives by outperforming the existing OFDM-IM counterparts. [ABSTRACT FROM AUTHOR]

Filter bank multi-carrier (FBMC) entitles many advantages over orthogonal frequency division multiplexing (OFDM) and is considered to be a more competitive waveform in the future generation cellular communications. In current FBMC, the prototype filter is deliberately designed to meet the perfect reconstruction (PR) constraint to establish subband orthogonality in real domain, which may not be optimal from communication perspective. In this paper, we challenge the necessity of PR constraint by proposing a new FBMC framework, which directly accepts non-orthogonal transmission. The resulting imperfect reconstruction FBMC (iPR-FBMC) has several advantages over its PR FBMC counterpart: 1) the constraint on the prototype filter is relaxed; 2) more importantly, the prototype filter can now be optimized with new goal of improving the detection performance rather than having to meet the PR condition; and 3) it allows for more flexible subband management in multi-user scenario. We will show how those advantages can be exploited. Simulations show that with moderate increase in computational complexity, the proposed iPR-FBMC with optimized prototype filter has superior bit error rate (BER) performance to existing FBMC with PR constraint and even outperforms OFDM, especially in highly frequency selective channels. The findings may shed light into potential research on non-orthogonal FBMC without PR constraint. [ABSTRACT FROM AUTHOR]

In this paper, we study power-efficient resource allocation for multicarrier non-orthogonal multiple access systems. The resource allocation algorithm design is formulated as a non-convex optimization problem which jointly designs the power allocation, rate allocation, user scheduling, and successive interference cancellation (SIC) decoding policy for minimizing the total transmit power. The proposed framework takes into account the imperfection of channel state information at transmitter and quality of service requirements of users. To facilitate the design of optimal SIC decoding policy on each subcarrier, we define a channel-to-noise ratio outage threshold. Subsequently, the considered non-convex optimization problem is recast as a generalized linear multiplicative programming problem, for which a globally optimal solution is obtained via employing the branch-and-bound approach. The optimal resource allocation policy serves as a system performance benchmark due to its high computational complexity. To strike a balance between system performance and computational complexity, we propose a suboptimal iterative resource allocation algorithm based on difference of convex programming. Simulation results demonstrate that the suboptimal scheme achieves a close-to-optimal performance. Also, both proposed schemes provide significant transmit power savings than that of conventional orthogonal multiple access schemes. [ABSTRACT FROM AUTHOR]

5G will have to cope with a high degree of heterogeneity in terms of services and requirements. Among these latter, flexible and efficient use of all available non-contiguous spectra for different network deployment scenarios is one challenge for the future 5G. To maximize spectrum efficiency, a flexible 5G air interface technology capable of mapping various services to the best suitable combinations of frequency and radio resources will also be required. In this work, a fair comparison of several 5G waveform candidates (UFMC, FBMC-OQAM, and FBMC-QAM) is proposed under a common framework. Spectral efficiency, power spectral density, peak to average power ratio and performance in terms of bit error rate under various realistic channel conditions are assessed. The waveforms are then compared in an asynchronous multi-user uplink transmission. Based on these results, in order to increase the spectral efficiency, a bit loading algorithm is proposed to cope with the non-uniform distribution of the interference across the carriers. The benefits of these new waveforms for the foreseen 5G use cases are clearly highlighted. It is also stressed that some concepts still need to be improved to achieve the full range of expected benefits of 5G. [ABSTRACT FROM AUTHOR]

The new generation global navigation satellite systems will broadcast multiple direct sequence spread spectrum signals on multiple different central frequencies, with complex spreading chip waveforms. There is a strong demand for efficient and flexible multiplexing techniques to combine these signals into a constant envelope composite signal. In this paper, a high efficiency generalized multicarrier joint constant envelope multiplexing (CEM) technique for multilevel DSSS signals is proposed. The basic idea of this technique is adding an auxiliary component into the direct superposition of signals to keep the envelope of the integrated signal constant. Design principle, constraints, and optimization method of the auxiliary component are investigated. An analysis with typical case studies demonstrates the high efficiency and high flexibility of the proposed technique. Compared with existing CEM techniques, the proposed technique has much higher design flexibility in the number of subbands, the number of signal components, power ratio and phase relationship among components, and the spreading chip waveforms. It can be applied to any number of bipolar or multilevel DSSS signals with arbitrary power distribution at one or more subcarrier frequencies. Such high-level design flexibility provides system designers great room in signal scheme optimization for varied navigation applications in the future. [ABSTRACT FROM AUTHOR]

This paper addresses power allocation problems for a dual-hop full-duplex multicarrier decode-forward relay system with or without a direct link from the source to the destination. The full-duplex relay has a residual self-interference proportional to its transmitted power. We consider two schemes of decode-forward at the relay: carrier-wise decode-forward (CDF) and group-wise decode-forward (GDF). For the CDF scheme, we consider problems of optimal power allocation subject to system-wise total power constraint, node-wise individual power constraint and system-wise rate constraint, respectively. All these problems are shown to be equivalent to convex problems, and fast algorithms for finding the exact solutions are developed. For the GDF scheme, we focus on the case of node-wise individual power constraint. This problem is non-convex for which we develop fast algorithms for finding locally optimal solutions. Using the algorithms developed in this paper, we are able to show that the system capacity with optimal power allocation based on either CDF or GDF is higher than that of the half-duplex relay (HDR) system at power levels where HDR outperforms the direct transmission via the direct link. Furthermore, the system capacity based on GDF is consistently higher than that of HDR for all power levels while both have the same degree of freedom. This paper also shows new insights of algorithmic development, which should be useful for other related problems. [ABSTRACT FROM AUTHOR]

The newly discovered “long-term” multicarrier multipactors that can be induced by low-energy electric fields potentially threatens the reliability of spaceborne microwave systems. It also causes a new technical challenge to the prediction of the global occurrence threshold of multicarrier multipactors. In this paper, we propose efficient approaches to rapidly compute the fluctuation of space electrons in the evolving process of a multicarrier multipactor, based on which Monte Carlo approaches are developed to efficiently find the global “worst case” waveforms and the occurrence thresholds for both “single-event” and “long-term” multipactors. The proposed approaches can be used for wideband devices, providing an efficient integrated solution for the multicarrier multipactor analysis for practical high-power microwave devices with inhomogeneous field distribution. [ABSTRACT FROM PUBLISHER]

Presents the table of contents for this issue of the publication. [ABSTRACT FROM PUBLISHER]

Future wireless systems will be characterized by a large range of possible uses cases. This requires a flexible allocation of the available time-frequency resources, which is difficult in conventional orthogonal frequency division multiplexing (OFDM). Thus, modifications of OFDM, such as windowing or filtering, become necessary. Alternatively, we can employ a different modulation scheme, such as filter bank multi-carrier (FBMC). In this paper, we provide a unifying framework, discussion, and performance evaluation of FBMC and compare it with OFDM-based schemes. Our investigations are not only based on simulations, but are substantiated by real-world testbed measurements and trials, where we show that multiple antennas and channel estimation, two of the main challenges associated with FBMC, can be efficiently dealt with. In addition, we derive closed-form solutions for the signal-to-interference ratio in doubly-selective channels and show that in many practical cases, one-tap equalizers are sufficient. A downloadable MATLAB code supports reproducibility of our results. [ABSTRACT FROM AUTHOR]

With the development of 5G communication, the new non-orthogonal multi-carrier transmission technology has been paid more attention. A filtering operation is made on a group of continuous subcarriers in Universal-filtered multi-carrier (UFMC), making the orthogonality among the subcarriers no longer exist. Such feature has relaxed the strict constraint of synchronization between the various devices, and makes it more suitable for the needs of 5G. On the other hand, the non orthogonality causes the mutual interference among the subcarriers and sub-bands. If the interference is effectively reduced, the performance of UFMC can be improved. In this paper, the factor of true power ratio is proposed to evaluate the inter-band interference. Furthermore, with the specific filter parameters, an appropriate sub-band interval can reduce the energy interference between the sub-bands especially in the uplinks. Simulation result shows that the method can reduce the symbol error rate and improve the transmission performance of UFMC by deploying the sub-band with optimized interval. Especially in high SNR environment, the deployment of shorter filter and neighboring sub-bands shows a better performance. [ABSTRACT FROM AUTHOR]

This paper considers a method for improving physical layer security of wireless networks with full-duplex radio. In particular, fast algorithms are developed to compute power allocations in subcarriers, subject to power and rate constraints, to maximize the secrecy capacity of a three-node network consisting of a source, a full-duplex destination, and an eavesdropper. A residual level of radio self-interference channel is considered. The optimal power allocation at the destination is found to be significant especially when its power budget is high. Also studied in this paper are a network with multiple full-duplex destinations and another network with multiple sources. Using the algorithms developed in this paper, we are able to show that a multiuser strategy that optimizes the power distributions among the users (in terms of either the sources or the destinations) can yield a substantial gain of secrecy capacity over a single-user strategy. [ABSTRACT FROM PUBLISHER]

In this paper, an Expectation-Maximization (EM) based iterative data detection method for downlink of a multicarrier system is proposed. The proposed method has low computational cost when compared with the other iterative ones since it does not require any matrix inversion if the requirements on users' data are met. The performance of the resulting algorithm is compared with Minimum Mean Squared Error (MMSE) estimator in terms of Symbol Error Rate (SER) for downlink of a Multi Carrier-Code Division Multiple Access (MC-CDMA) system in the presence of frequency selective channels using computer simulations. It is illustrated that the proposed algorithm outperforms the MMSE. [ABSTRACT FROM AUTHOR]

Non-orthogonal multiple access (NOMA) is one of the potential candidates for future radio access to address the increasing demands of mobile traffic. NOMA-based systems employ orthogonal frequency division multiplexing (OFDM) for multicarrier modulation which induces peak-to-average power ratio (PAPR). High PAPR makes conventional NOMA systems spectrally and energy inefficient. Thus, in this paper, precoded NOMA system is proposed to overcome the PAPR problem in downlink NOMA. Different unitary transforms such as Walsh Hadamard transform (WHT), Zadoff chu transform (ZCT), and discrete Hartley transform are applied as linear precoding techniques to overcome the PAPR problem in NOMA. Moreover, a new precoding technique-transform is also proposed which is a hybrid combination of WHT and ZCT. Link-level performance of power domain NOMA is analysed in terms of PAPR, spectral efficiency, bit error rate, and computational complexity. Simulation results show that in the presence of linear precoding techniques, performance of classic NOMA systems improve at the cost of slight increment in complexity. [ABSTRACT FROM AUTHOR]

We study parallel two-user interference channels when the interference is bursty and feedback is available from the respective receivers. Presence of interference in each subcarrier is modeled as a memoryless Bernoulli random state. The states across subcarriers are drawn from an arbitrary joint distribution with the same marginal probability for each subcarrier and instantiated independent and identically distributed (i.i.d.) over time. For the linear deterministic setup with symmetric interference in each subcarrier, we give a complete characterization of the capacity region. For the analogous setup with Gaussian noise, we give outer bounds and a tight generalized degrees of freedom characterization. We propose a novel helping mechanism, which enables subcarriers in very strong interference regime to help in recovering interfered signals for subcarriers in strong and weak interference regimes. Depending on the interference and burstiness regime, the inner bounds either employ the proposed helping mechanism to code across subcarriers or treat the subcarriers separately. The outer bounds demonstrate a connection to a subset entropy inequality by Madiman and Tetali. [ABSTRACT FROM PUBLISHER]

Filterbank-based multicarrier (FBMC) scheme is one of the candidate waveforms to handle possible problems in next-generation communication systems, such as high out-of-band (OOB) emission and large peak-to-average power ratio (PAPR). In LTE (Long Term Evaluation), the frequency spectrum is shared by users with pre-defined bandwidths (i.e., 1,4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, 20 MHz), which is not a flexible solution for users having different data rate demands. Similarly, in conventional FBMC systems, bandwidth is divided into equal subbands. Recent studies on FBMC modulation have not provided an effective remedy for such users. Motivated by this requirement, we propose a novel FBMC waveform design that allows an adaptive bandwidth allocation scheme. Accordingly, users will not be restricted to the specified bandwidth schedules. In the paper, subband-based and subcarrier based filtering models are constructed with polyphase filter structures. The proposed structures are realized analytically and tested through computer simulations for different scenarios. [ABSTRACT FROM AUTHOR]

The present section deals with a new type of technique for designing an efficient two channel Quadrature Mirror Filter Bank with constant phase in frequency. For achieving the Perfect Reconstruction Condition in Filter bank, an attempt has been made to design the low pass prototype filter with its impulse response and frequency response in three regions namely pass band, stop band and transition band region. With the error in terms of Reconstruction and the attenuation in the stop band as seen in the prototype filter response, one can evaluate the performance of the introduced filter with the help of filter coefficients generated in the design examples that affects the quality of filter bank design under the constraints of Near Perfect Reconstruction Conditions. [ABSTRACT FROM AUTHOR]

In this paper, we study secure multiple access based on multicarrier (MC) code division multiple access (CDMA) systems with induced random (chip) flipping of spreading sequence, which is suitable for machine-type communications (MTC). In MTC, devices may use low-cost hardware-based random number generators for pseudo-random noise (PN) sequences in secure communications. Since PN sequences can be estimated by correlation attacks at an eavesdropper, induced random (chip) flipping of spreading sequences is proposed to make correlation attacks infeasible. However, induced random flipping can also degrade the performance of detection and decoding at a legitimate receiver that only knows original spreading sequences. To avoid the performance degradation, we derive low-complexity iterative receiver algorithms for multiuser signal detection and decoding based on the expectation-maximization (EM) algorithm. [ABSTRACT FROM AUTHOR]

A multicarrier signal can be synthesized thanks to a symbol sequence and a Gabor family (i.e., a regularly time-frequency shifted version of a generator pulse). In this article, we consider the case where the signaling density is increased such that inter-pulse interference is unavoidable. Over an additive white Gaussian noise channel, we show that the signal-to-interference-plus-noise ratio is maximized when the transmitter and the receiver use the same tight Gabor frame. What is more, we give practical efficient realization schemes and show how to build tight frames based on usual generators. Theoretical and simulated bit-error probability are given for a non-coded system using quadrature amplitude modulations. Such a characterization is then used to predict the convergence of a coded system using low-density parity-check codes. We also study the robustness of such a system to errors on the received bits in an interference cancellation context. [ABSTRACT FROM AUTHOR]

Multicarrier modulation techniques are gaining attention to support high data transmission rate in next generation wireless communication systems. With increasing number of users and to support diversified services, more efficient and reliable modulation techniques are required. This work presents a comparative analysis of three multicarrier modulation techniques as OFDM, UFMC and FBMC on the basis of Peak To Average Power Ratio (PAPR) and Power Spectral Density (PSD). OFDM offers comparatively lower value of PAPR but suffers from the limitation of poor spectral efficiency. UFMC, on the other hand provides better spectral efficiency but at the cost of high PAPR. FBMC provides better spectral efficiency and rejection to inter-symbol interference as compared with OFDM but complexity is also increased. In this work, these modulation techniques have been analyzed for variation in FFT size and bits/sub carrier. QAM is used as basic modulation method for performance evaluation of three multicarrier modulation techniques. [ABSTRACT FROM AUTHOR]

Block-based transceivers are widely used in wireless communication systems, mostly due to their well-defined structure and blockwise encoding. Interblock interference caused by superpositions of delayed signal copies is among their main physical-layer challenges, which is commonly eliminated with redundancy between adjacent data-blocks. Besides, channel equalization is also employed to further mitigate multipath channel interferences. The chosen amount of redundancy, however, may be overestimated, which opens an opportunity for reduced-redundancy superfast transceivers, whose key features include high spectral efficiency and low computational cost. Although superfast approaches aim at low complexity, proper equalizer-coefficient design and update procedures are still very intricate tasks, and most approaches are rather computationally cumbersome. This paper addresses such problem by proposing a new design strategy for reduced-redundancy block-based transceivers, which provides semi-blind equalization with data-selective update, in addition to the possibility of using redundant parallel equalizer structures, which are based on the use of fast Fourier transforms and one-tap equalizers. Simulation results indicate that the proposed methodology is effective and also able to achieve a performance comparable to what is obtained with state-of-the-art techniques, depending on the target application. [ABSTRACT FROM AUTHOR]

Multi carrier-code division multiple access (MC-CDMA) system is a promising wireless communication technology with high spectral efficiency and system performance. Though the multiple access techniques provide high spectral efficiency, these techniques were prone to multiple access interference (MAI). So, this paper mainly aims at the design of the MC-CDMA receiver to mitigate MAI. The classical receivers like maximal ratio combining (MRC), equal gain combining (EGC), and minimum mean square error (MMSE) fails to cancel MAI when the MC-CDMA is subjected to non-linearistic degradations. By contrast, being highly non-linear classifiers, the neural network (NN) receivers could be better alternative under such a case. The feasibility, efficiency and effectiveness of the proposed multilayer perceptron (MLP) NN based receiver are studied in detail for the MC-CDMA with nonlinearistic degradations. [ABSTRACT FROM AUTHOR]

LTE-Advanced aims to provide a transmission bandwidth of 100 MHz by using carrier aggregation to aggregate LTE Rel. 8 carriers. In order to increase the system capacity, resource allocation becomes a very good tool, and, in the context of the existence of multiple component carriers in LTE-Advanced becomes a complex optimization problem. This paper proposes a Multi-Carrier Scheduling Algorithm that takes into account the user's QoS requirements and also targets the maximization of the user throughput. The algorithm is evaluated in a scenario with both macro and femto base stations (i.e. a HetNet scenario) that respects the 3GPP specifications. Numerical results show that this algorithm has better performances than the traditional round robin and proportionally fair resource scheduling algorithms. [ABSTRACT FROM AUTHOR]

This new era is emerging towards the fast telecommunication technologies and this paper here is also explaining the newest technologies that are 4G & 5G and their evolution from the different projects working all over the world. Every forum uses different frequency band in GHz. Although here this paper will discuss the main issue of 5G technology and that is the power issue. FBMC as the main 5G technology aspirant and this also suffers from the problem of power which is being composed by the term PAPR ratio. PAPR reduction techniques like DSLM is used and the paper proposes this as the superior technique for improving the PAPR by deep scrutiny. [ABSTRACT FROM AUTHOR]

This paper presents the design of a multi-carrier correlation delay-shift keying (MC-CDSK) system for the operation in wireless environments. In the proposed system, the sum of a chaotic sequence and it delayed version is considered to be a reference sequence and transmitted through a predefined subcarrier. The input data is divided into multiple pairs of bit sub-sequences, where the first and second ones of each pair are spread in the frequency domain by directly multiplying with the chaotic sequence and the delayed version, respectively. The sum of two resulting signals for each pair is then transmitted on a corresponding subcarrier. In the receiving side, the reference sequence retrieved from the predefined subcarrier and the signal retrieved from each of the remaining subcarriers are correlated with the delayed version of the other ones to recover the corresponding bit sub-sequence pair. The recovered pairs are combined to an output data. Schemes for the transmitter and receiver are designed and their operation over a multipath Rayleigh fading channel is described. The system performance is evaluated via theoretical analysis and then verified by numerical simulation. Our findings show that MC-CDSK system can improve communication features, i.e., bit error rate (BER) performance, energy and spectrum efficiency compared to those of the conventional CDSK. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the performance of a modified evolutionary multi-user detector (MUD) in multi-carrier direct-sequence code-division multiple-access (MC-CDMA) communication systems over frequency-selective fading channels. The genetic algorithm (GA), which tries to reduce the complexity in optimal detection due to greedy exhausted searching, performs using the adequate sub-optimal multi-user detector for MC-CDMA systems. In this paper, we propose a forcing mutation scheme for the genetic algorithm (GA) to perform a forcing mutation evolutionary multi-user detector (FME-MUD) and to largely reduce computational complexity. Simulation results show that with six generations, the proposed FME-MUD scheme outperforms the conventional GA-MUD, especially at heavy system loads. [ABSTRACT FROM AUTHOR]