Multicarrier Communication Systems Research Papers (original) (raw)

2025

OFDM is a subset of frequency division multiplexing in which a single channel utilizes multiple subcarriers on adjacent frequencies. In addition the sub-carriers in an OFDM system are overlapping to maximize spectral efficiency. That means OFDM is multi-carrier communication technique which is used in both wired and wireless communication. OFDM is the time domain signal which is a sum of several sinusoids and these sinusoids makes Peak to Average Power Ratio (PAPR).PAPR is major drawback of OFDM. There are several PAPR reduction techniques but, pre-coding is an efficient method for PAPR reduction. This paper represents a new pre-coding technique-Walsh Hadamard Transform (WHT). The obtained results show that WHT is attractive solution to PAPR problems of OFDM signals.

2024

In this paper, analytical assessment of overlayinband device-to-device (D2D) communications is investigated, under cellular-network-assisted (coordinated) scheduling. To this end, a simple scheduling scheme is assumed that takes into account only local (per cell) topological information of the D2D links. Stochastic geometry tools are utilized in order to obtain analytical expressions for the interferers density as well as the D2D link signal-to-interference-ratio distribution. The analytical results accuracy is validated by comparison with simulations. In addition, the analytical expressions are employed for efficiently optimizing the parameters of a cellular system with overlay D2D communications. It is shown that coordinated scheduling of D2D transmissions enhances system performance both in terms of average user rate as well as maximum allowable D2D link distance.

2024, Journal of Communications

Modern wireless communication like 5G systems are expected to serve a wider range of scenarios than current mobile communications systems. One of the major network applications related to 5G is Vehicle-to-Vehicle (V2V) communication that improves vehicle road safety, enhances traffic and travel efficiency, and provides convenience and comfort for passengers and drivers. However, supporting high mobility is a challenge on the air interface. Accordingly, multicarrer modulation as a multiple access is used to enhance the connection between vehicles and to overcome this challenge. In this paper, two multicarrier modulations are simulated. The first one is the Orthogonal Frequency Division Multiplexing (OFDM) while the second one is the Filter Bank Multi-Carrier with Offset Quadrature Amplitude Modulation (FBMC/OQAM) which is called FBMC. Simulation results show that all waveforms have comparable BER performance. The throughput of the FBMC is greater than the OFDM and the spectral effici...

2024

The increasing demand for wireless applications is making radio spectrum scarce. Meantime, studies show that the assigned spectrum is not thoroughly utilized. The cognitive radio (CR) technology is proposed as a feasible key technology to solve issues related to the spectrum scarcity. CR can improve the spectrum utilization by reusing the unused spectrum occupied by licensed users. Introduction of CR networks produces two kinds of interference: interference from the CR network (secondary network) to the primary network (PN) and the interference among secondary users. All unwanted interference should be adequately managed in order not to jeopardize the performance of the PN and at the same time improve the performance of CR systems. Interference alignment (IA) is a promising technique that can efficiently manage interference. One of the aims of this thesis is to mitigate the interference by deploying multiple antennas at both transmitter and receiver sides in order to improve the per...

2024, Journal of Signal Processing Systems

With the advent of 5G networks means for backhauling network traffic emerged as a major consideration. Densification via small cell deployment has made wired solution cost prohibitive, leading to the adoption of spectrally efficient wireless solutions, namely, Integrated Access and Backhaul (IAB). This paper discusses the different options for IAB and focuses on novel solutions for in-band IAB using Full Duplex (FD) enabled nodes. Dynamically reconfigured beam steering antennas are presented as a means of passively suppressing Self-Interference (SI). Experimental results confirm up to 65 dB of SI cancellation in a harsh environment with obstacle. Finally, robust methods for managing FD practical considerations including timing and frequency offsets are presented, with experimental results confirming performance.

2024, ZBORNIK RADOVA ČETRDESETOG SIMPOZIJUMA O NOVIM TEHNOLOGIJAMA U POŠTANSKOM I TELEKOMUNIKACIONOM SAOBRAĆAJU – POSTEL 2022

The growing demands for massive connectivity and data-hungry applications and services in wireless systems, stand out the non-orthogonal multiple access (NOMA) as a promising technique for 5G and beyond against orthogonal multiple access (OMA). Therefore, in this paper, we propose a novel power allocation algorithm based on the sum data rate for a power-domain two-user NOMA uplink system. Namely, the closed-form expression for the sum data rate is derived, for the system under consideration, over a composite Fisher-Snedecor (F) fading channel. Based on the proposed analytical presentation of the sum data rate, numerical results are also provided. The impact of the interplay of different fading/shadowing channel conditions and various users' positions on the performance metric is examined. Presented results have a high level of generality since F fading model provides accurate characterization of the multipath/shadowing conditions in numerous communication scenarios of interest.

2024, Security and Communication Networks

Cognitive radio network concept has been considered as a promising solution to improve the spectrum utilization. However, it may be vulnerable to security problems as the primary user (PU) and secondary user (SU) access the same resource. In this paper, we consider a system model where an eavesdropper (EAV) illegally listens to the PU communication in the presence of a SU transmitter (SU‐Tx) communicating with a SU receiver (SU‐Rx). The SU‐Tx transmit power is subject to the peak transmit power constraint of the SU and outage probability constraint of the PU. Given this context, the effect of the interference from the SU‐Tx to the EAV on the primary system security is investigated. In particular, analytical expressions of the probability of existence of non‐zero secrecy capacity and secrecy outage probability of the PU are derived. Moreover, the performance analysis of the secondary network is examined where closed‐form expressions of the symbol error probability and achievable rate...

2024

Akademisk avhandling som med tillstånd av Kungl Tekniska högskolan framlägges till offentlig granskning för avläggande av teknologie doktoralexamen i informationsoch kommunikationsteknik fredagen den 13 mars 2015 klockan 13.15 i hörsal... more

2024, 2016 IEEE International Conference on Communications (ICC)

Technologies for mmWave communication are at the forefront of investigations in both industry and academia, as the mmWave band offers the promise of orders of magnitude additional available bandwidths to what has already been allocated to cellular networks. The much larger number of antennas that can be supported in a small footprint at mmWave bands can be leveraged to harvest massive-MIMO type beamforming and spatial multiplexing gains. Similar to LTE systems, two prerequisites for harvesting these benefits are detecting users and acquiring user channel state information (CSI) in the training phase. However, due to the fact that mmWave channels encounter much harsher propagation and decorrelate much faster, the tasks of user detection and CSI acquisition are both imperative and much more challenging than in LTE bands. In this paper, we investigate the problem of fast user detection and CSI acquisition in the downlink of small cell mmWave networks. We assume TDD operation and channel-reciprocity based CSI acquisition. To achieve densification benefits we propose pilot designs and channel estimators that leverage a combination of aggressive pilot reuse with fast user detection at the base station and compressed sensing channel estimation. As our simulations show, the number of users that can be simultaneously served by the entire mmWave-band network with the proposed schemes increases substantially with respect to traditional compressed sensing based approaches with conventional pilot reuse.

2024, IEICE Transactions on Communications

In-phase and quadrature-phase imbalance (IQI) at transceivers is one of the serious hardware impairments degrading system performance. In this paper, we study the overall performance of massive multiuser multi-input multi-output (MU-MIMO) systems with IQI at both the base station (BS) and user equipments (UEs), including the estimation of channel state information, required at the BS for the precoding design. We also adopt a widely-linear precoding based on the real-valued channel model to make better use of the image components of the received signal created by IQI. Of particular importance, we propose estimators of the real-valued channel and derive the closed-form expression of the achievable downlink rate. Both the analytical and simulation results show that IQI at the UEs limits the dowlink rate to finite ceilings even when an infinite number of BS antennas is available, and the results also prove that the widely-linear precoding based on the proposed channel estimation method can improve the overall performance of massive MU-MIMO systems with IQI.

2024, IEEE Journal of Selected Topics in Signal Processing

2024

Massive multiple-input multiple-output (MIMO) and orthogonal frequency division multiplexing (OFDM) are wireless technologies adopted by the Fifth Generation (5G) of mobile communications. The channel estimation and pre/postequalization processes in coherent detection schemes for massive MIMO-OFDM are a challenging task, where several issues are faced, such as pilot contamination, channel calibration, matrix inversions, among others. Moreover, they increase the energy consumption and latency of the system. A non-coherent technique relying on DPSK constellation has been proposed for a singlecarrier scheme, assuming flat-fading. In our paper, we extend this technique to be combined with OFDM, where the channel is doubly dispersive (time and frequency). We will show that the differential modulation can be performed either in the time or frequency domain, where the latter suffers from an additional phase rotation, which should be estimated and compensated. We provide the analytical expression of the signal-to-interferenceand-noise ratio (SINR) for both cases, and we show numerical results in order to verify our analysis.

2024, ICC 2019 - 2019 IEEE International Conference on Communications (ICC)

2024, Indonesian Journal of Electrical Engineering and Computer Science

It is worth mentioning that the use of wireless systems has been increased in recent years and supposed to highly increase in the few coming years because of the increasing demands of wireless applications such as mobile phones, Internet of Things (IoT), wireless sensors networks (WSNs), mobile applications and tablets. The scarcity of spectrum needs to be into consideration when designing a wireless system specially to answer the two following questions; how to use efficiently the spectrum available for the available networks in sharing process and how to increase the throughput delivered to the serving users. The spectrum sharing between several types of wireless networks where networks are called cognitive networks is used to let networks cooperate with each other by borrowing some spectrum bands between them especially when there is an extra band that is not used. In this project, the simulation of spectrum sensing and sharing in cognitive networks is performed between two cogni...

2024, EURASIP Journal on Advances in Signal Processing

Cognitive radio (CR) is proposed to automatically detect and exploit unused spectrum while avoiding harmful interference to the incumbent system. In this paper, we emphasize the channel capacity comparison of a CR network using two types of multicarrier communications: conventional Orthogonal Frequency Division Multiplexing (OFDM) with Cyclic Prefix (CP) and Filter Bank based MultiCarrier (FBMC) modulations. We use a resource allocation algorithm in which subcarrier assignment and power allocation are carried out sequentially. By taking the impact of Inter-Cell Interference (ICI) resulting from timing offset into account, the maximization of total information rates is formulated under an uplink scenario with pathloss and Rayleigh fading, subject to maximum power constraint as well as mutual interference constraint between primary user (PU) and secondary user (SU). Final simulation results show that FBMC can achieve higher channel capacity than OFDM because of the low spectral leakage of its prototype filter.

2024, EMITTER International Journal of Engineering Technology

Understanding of channel propagation characteristics is a key to the optimal design of underwater acoustic communication. Generally, modelling of underwater acoustic channel is performed based on measurement result in certain site at certain times. Different sites might have different characteristics, each of which can generally be described by a model obtained by averaging measurement results at multiple points in the same environment. This paper describes a characterization of the underwater acoustic channel of tropical shallow water in a Mangrove estuary, which has sediment up to 60 cm at the bottom. Such a channel model is beneficial for the design of communication system in an autonomous underwater vehicle, for instance. The measurement result of delay spread parameter from three different points with the distance of 14 ~ 52 m, has various values. The root mean square (RMS) of delay spread ranges between 0.0621 ~ 0.264 ms, and the maximum delay spread varies with the value of 0...

2024, 2016 IEEE International Conference on Communications (ICC)

2024, Indonesian Journal of Electrical Engineering and Computer Science

2024, IEEE Access

A successive interference cancellation receiver is one of the important blocks in non-orthogonal multiple access (NOMA) transmission. The quality of detection of the strongest user signals often decides about the quality of the whole system and minimizes the error propagation effect. In this paper, we propose an improved detection algorithm, which allows for using the NOMA transmission in a much smaller range of power differences between the terminals sharing common radio resources in the uplink, as compared with standard successive cancellation. The idea lies in the application of tentative decisions about weaker signals in the detection of stronger ones and then, after improved detection of stronger user signals, achieving more reliable decisions about the weaker ones. The simulation results reported in the paper confirm our idea, showing a much higher detection quality of the proposed receiver when compared with the standard solution. INDEX TERMS Multi-carrier transmission, non-orthogonal multiple access, receiver, successive interference cancellation, uplink, WLAN.

2024, IEEE Access

2024, Wireless Personal Communications

A cyclic prefix of sufficient length is inserted (longer than the maximum delay spread of the channel) in Multi-Carrier CDMA (MC-CDMA) transmission over dispersive channels such that the channel, as seen by subcarrier, is a simple multiplicative distortion in the frequency domain, that can be compensated for by a one-tap Frequency Equalizer (FE). If, in addition to the spectral inefficiency caused by insertion of the cyclic prefix, the delay spread should exceed the designed prefix length, the FE will attempt to compensate for the mismatched signal model and the system performance will degrade significantly. In this paper, we derive a multi-input, multioutput (MIMO) model for received signal in synchronous MC-CDMA system over a multipath channel. Based on this model, a Frequency-Time MMSE Equalizer (FTE) is proposed. The performance of the FTE is studied as a function of key system parameters, such as prefix length and number of subcarriers, as well as sensitivity to channel estimation errors. The numerical result shows that system performance degradation due to insufficient guard time can be recovered with the FTE; i.e., full spectral efficiency can be achieved at the price of additional receiver complexity.

2023

In order to provide high data rate over wireless channels and improve the system capacity, Multiple-Input Multiple-Output (MIMO) wireless communication systems exploit spatial diversity by using multiple transmit and receive antennas. Moreover, MIMO systems are equipped with High Power Amplifiers (HPA). However, HPA causes nonlinear distortions and affect the receiver's performance. Since a few decades, Neural Networks (NN) have shown excellent performance in solving complex problems like classification, recognition and approximation. In this paper, we present a receiver technique based on NN schemes for the compensation of HPA non linearization in MIMO Space-Time Block Coding (STBC) systems. Specifically, we assess the impact of HPA nonlinearity and NN on the average symbol error rate (SER) and the error vector magnitude (EVM) of MIMO-STBC in uncorrelated Rayleigh fading channels. Computer simulation results confirm the accuracy and validity of our proposed analytical approach.

2023, Qatar Foundation Annual Research Conference Proceedings Volume 2016 Issue 1

2023

Due to the battery-limited nature of mobile devices, improving energy efficiency (EE) of individual users and ensuring EE fairness among those users are one of the key design issues in uplink transmission of cellular networks. In this paper, we consider the joint optimization of discrete power and resource blocks allocations to maximize the minimum EE among users subject to individual power budget constraints. The optimization problem is combinatorial. Thus, we propose an efficient algorithm, based on semidefinite relaxation with Gaussian randomization, to solve the resultant non-convex problem in polynomial time complexity. The numerical results show how well the proposed algorithm performs against the optimal one and indicate the impact of discrete power levels on the fairness-oriented EE optimization.

2023, 2018 IEEE Wireless Communications and Networking Conference (WCNC)

2023

In this paper we present methods for reduction of Peak-to-Average Power Ratio (PAPR) in multi-carrier Orthogonal Frequency Division Multiplexing (OFDM) through the joint use of coding, weighting, and signal mapping. Simple and easyto-implement coding schemes have been identified that when employed with suitable weighting functions can reduce PAPR considerably. Indeed it is shown that PAPR can be controlled by appropriate choice of coding scheme and weighting function for a given signal mapping. A thorough numerical investigation using computer simulations is presented and schemes that offer considerable reduction in PAPR are identified as a function of number of sub-carriers in OFDM systems.

2023, 2010 Conference Record of the Forty Fourth Asilomar Conference on Signals, Systems and Computers

Accurate time scale compensation is a problem of significance for underwater acoustic channels. Using our proposed partial FFT Demodulation technique, we consider two algorithms for fast and accurate data detection over time scale distorted channels. We present a theoretical analysis to characterize the performance of these algorithms and determine the optimal values of their key parameters. Our analysis supports the observed performance trends and validates the performance gains of partial FFT demodulation.

2023

The research on techniques to perform simultaneous transmission and reception on the same frequency bands has become a topic of high interest in recent years. Nevertheless, the applicability of digital self-interference cancellers is hindered by the dynamic range limitations of current analog-to-digital converters (ADCs). We show that it is possible to suppress the selfinterference component immediately before the signal digitalization by taking samples of the received signals when the interference crosses the zero-amplitude level, and that this method preserves the useful information in the desired signal samples. We also present simulated performance results for this new transceiver architecture.

2023, European Wireless Conference

2023

This paper is devoted to the analytic investigation of a maximum-ratio-combining based regenerative multi-relay cooperative wireless network over non-homogeneous scattering environments. Such propagation conditions are rather realistic as they are encountered often in practical wireless transmission scenarios. Novel analytic expressions are derived for the symbolerror-rate of M −ary phase shift keying (M −PSK) over independently and non-identically distributed fading channels. The derived expressions are based on the moment-generating-function (MGF) approach and are given in closed-form in terms of the generalized Lauricella series. A simple algorithm for computing this special function is also proposed while the offered results are validated extensively through comparisons with respective results from computer simulations. Based on this, they are particularly useful in the analytic performance evaluation of such cooperative systems. To this end, it is shown that the performance of the cooperative system is significantly affected, as expected, by the number of employed relays as well as by the value of the involved fading parameters η and µ.

2023, 2015 IEEE Global Communications Conference (GLOBECOM)

This work is devoted to the outage probability analysis of full-duplex (FD) regenerative relay systems over multipath fading channels. Unlike the majority of analyses that assume basic symmetric fading conditions, the present work considers asymmetric generalized fading conditions, which are more realistic in practical communications scenarios. To this end, we assume that the source-relay path is subject to κ − µ multipath fading conditions, that can also account for lineof-sight communications, whereas the source-to-destination and relay-to-destination paths are subject to η−µ fading conditions that typically hold for non-line-of-sight communications. Novel analytic expressions are derived for the outage probability (OP) of the considered FD as well as for the corresponding halfduplex (HD) relay case for comparisons. These expressions are given in closed-form and have a tractable algebraic representation which renders them convenient to handle both analytically and numerically. Based on this, they are subsequently employed in analyzing the corresponding performance for different communication scenarios. It is shown that the OP of the FD relay system is highly dependent upon the severity of fading and that its performance outperforms significantly the corresponding HD performance as the spectral efficiency increases.

2023, IEEE Transactions on Wireless Communications

This paper is devoted to the end-to-end performance analysis, optimal power allocation (OPA), and energyefficiency (EE) optimization of decode-and-forward (DF)-based full-duplex relaying (FDR) and half-duplex relaying (HDR) systems. Unlike existing analyses and works that assume simplified transmission over symmetric fading channels, we consider the more realistic case of asymmetric multipath fading and shadowing conditions. To this end, exact and asymptotic analytic expressions are first derived for the end-to-end outage probabilities (OPs) of the considered DF-FDR set ups. Based on these expressions, we then formulate the OPA and EE optimization problems under given end-to-end target OP and maximum total transmit power constraints. It is shown that OP in FDR systems is highly dependent upon the different fading parameters and that OPA provides substantial performance gains, particularly, when the relay self-interference (SI) level is strong. Finally, the FDR is shown to be more energy-efficient than its HDR counterpart, as energy savings beyond 50% are feasible even for moderate values of the SI levels, especially at larger link distances, under given total transmit power constraints and OP requirements.

2023, arXiv (Cornell University)

Energy efficiency and its optimization constitute critical tasks in the design of low-power wireless networks. The present work is devoted to the error rate analysis and energy-efficiency optimization of regenerative cooperative networks in the presence of multipath fading under spatial correlation. To this end, exact and asymptotic analytic expressions are firstly derived for the symbol-error-rate of M −ary quadrature amplitude and M −ary phase shift keying modulations assuming a dual-hop decode-andforward relay system, spatially correlated Nakagami−m multipath fading and maximum ratio combining. The derived expressions are subsequently employed in quantifying the energy consumption of the considered system, incorporating both transmit energy and the energy consumed by the transceiver circuits, as well as in deriving the optimal power allocation formulation for minimizing energy consumption under certain quality-of-service requirements. A relatively harsh path-loss model, that also accounts for realistic device-to-device communications, is adopted in numerical evaluations and various useful M. K. Fikadu and M. Valkama are with the

2023, arXiv (Cornell University)

This paper studies a multi-antenna network integrated sensing and communication (ISAC) system, in which a set of multi-antenna base stations (BSs) employ the coordinated transmit beamforming to serve their respectively associated single-antenna communication users (CUs), and at the same time reuse the reflected information signals to perform joint target detection. In particular, we consider two target detection scenarios depending on the time synchronization among BSs. In Scenario I, these BSs are synchronized and can exploit the target-reflected signals over both the direct links (from each BS to target to itself) and the cross links (from each BS to target to other BSs) for joint detection. In Scenario II, these BSs are not synchronized and can only utilize target-reflected signals over the direct links for joint detection. For each scenario, we derive the detection probability under a specific false alarm probability at any given target location. Based on the derivation, we optimize the coordinated transmit beamforming at the BSs to maximize the minimum detection probability over a particular target area, while ensuring the minimum signal-to-interferenceplus-noise ratio (SINR) constraints at the CUs, subject to the maximum transmit power constraints at the BSs. We use the semi-definite relaxation (SDR) technique to obtain highly-quality solutions to the formulated problems. Numerical results show that for each scenario, the proposed design achieves higher detection probability than the benchmark scheme based on communication design. It is also shown that the time synchronization among BSs is beneficial in enhancing the detection performance as more reflected signal paths are exploited.

2023, Wireless Engineering and Technology

When implementing an appropriate windowing, the interference from a Cognitive Radio (CR) system to licensed systems (primary users) will be significantly reduced. Consequently, power allocated to subcarriers can be increased, especially subcarriers having far spectral distance to primary user bands can be allocated full of its maximum possible power. In this paper, we propose a new class of sub-optimal subcarrier power allocation algorithm that significantly reduces complexity of OFDMA-based CR systems. Two sub-optimal proposals, called Pre-set Filling Range (PFR) and Maximum Filling Range (MFR) are studied. Investigations show that this new power allocating algorithm allows CR systems obtain high throughput while retaining low complexity.

2023, arXiv (Cornell University)

Recent advances in self-interference cancellation enable radios to transmit and receive on the same frequency at the same time. Such a full duplex radio is being considered as a potential candidate for the next generation of wireless networks due to its ability to increase the spectral efficiency of wireless systems. In this paper, the performance of full duplex radio in small cellular systems is analyzed by assuming full duplex capable base stations and half duplex user equipment. However, using only full duplex base stations increases interference leading to outage. We therefore propose a mixed multi-cell system, composed of full duplex and half duplex cells. A stochastic geometry based model of the proposed mixed system is provided, which allows us to derive the outage and area spectral efficiency of such a system. The effect of full duplex cells on the performance of the mixed system is presented under different network parameter settings. We show that the fraction of cells that have full duplex base stations can be used as a design parameter by the network operator to target an optimal tradeoff between area spectral efficiency and outage in a mixed system.

2023, 2016 IEEE International Conference on Communications (ICC)

2023, Anais de VII International Telecommunications Symposium

High data rate systems usually employ Orthogonal Frequency Division Multiplexing and Space-Time Coding to improve the performance on a mobile time-variant frequency-selective channel. Nonlinearities introduced by the power amplifier can be minimized by performing a Wash-Hadamard Transform on the data symbol prior the Inverse Fast Fourier Transform (IFFT) at the transmitter. This procedure reduces the peak-to-average power ratio of the OFDM symbol. An extra advantage of the WHT combined with OFDM is the performance improvement on a frequency-selective channel. The aim of this paper is to present an analytical expression to estimate the performance of the WHT-STC-OFDM taking into account the receiver/transmitter mobility, the channel frequency response and the noise added by the channel. The theoretical results are corroborated by computer simulations.

2023, IEEE Transactions on Vehicular Technology

Energy efficiency and its optimization constitute critical tasks in the design of low-power wireless networks. This paper is devoted to the error rate analysis and energy efficiency optimization of regenerative cooperative networks in the presence of multipath fading under spatial correlation. To this end, exact and asymptotic analytic expressions are first derived for the symbol error rate (SER) of M-ary quadrature amplitude and M-ary phase-shift keying modulations (M-QAM and M-PSK), respectively, assuming a dual-hop decode-and-forward (DF) relay system, spatially correlated Nakagami-m multipath fading, and maximum ratio combining (MRC) at the destination. The derived expressions are subsequently employed in quantifying the energy consumption of the considered system, incorporating both transmit energy and the energy consumed by the transceiver circuits, and in deriving the optimal power allocation (OPA) formulation for minimizing energy consumption under certain quality-ofservice (QoS) requirements. A relatively harsh path-loss (PL) model, which also accounts for realistic device-to-device communications, is adopted in numerical evaluations, and various useful insights are provided for the design of future low-energy wireless networks deployments. Indicatively, it is shown that, depending on the degree of spatial correlation, severity of fading, transmission distance, relay location, and power allocation strategy, target performance can be achieved with much overall energy reduction compared with direct transmission (DT) reference.

2023, Wireless Communications and Mobile Computing

The nature of the multipath channel and the peak-to-average power ratio (PAPR) are regarded as the main challenges restricting the design of a multicarrier reliable underwater acoustic (UWA) communication. This paper proposes a new scheme, precoded index modulation orthogonal frequency division modulation spread spectrum (IM-OFDM-SS), for UWA communication. The precoded IM-OFDM-SS is proposed to increase the transmission efficiency and exploit the spreading and multipath diversities and, at the same time, reduce the PAPR to achieve a reliable communication system. Two different precoders, discrete Hartley transform (DHT) and discrete cosine transform (DCT), are utilized in the proposed scheme and compared with the conventional IM-OFDM-SS scheme. Simulation and real experimental results demonstrate the outperformance of the proposed precoded IM-OFDM-SS in comparison to the conventional benchmarks in terms of PAPR and bit error rate (BER) performance.

2023, Engineering, Technology & Applied Science Research

Intelligent algorithms in artificial intelligence have brought several benefits to digital signal processing. The boom in machine learning and intelligent systems provides new perspectives and methods to solve many research problems in Underwater Acoustic (UWA) Orthogonal Frequency Divisional Multiplexing (OFDM) communication. Partial transmit sequence is a tremendous technique for the mitigation of high Peak-to-Average Power Ratio (PAPR) in OFDM communication systems, but finding the optimum phase factors has still a few problems. In this paper, a Partial Transmit Sequence (PTS) based on an Intelligent Detoxification Function of Liver Algorithm-Partial Transmit Sequence (IDFLA-PTS) is proposed for the mitigation of PAPR in the UWA OFDM communication systems. This algorithm reduces the PAPR and the complexity of the proposed UWA OFDM model. The IDFLA-PTS is also compared with the Genetic Algorithm-Partial Transmit Sequence (GA-PTS). Besides this, the Bit Error Rate (BER) performance...

2023, Indonesian Journal of Electrical Engineering and Computer Science

Spectrum Sensing (SS) is cognitive radio's (CR’s) fundamental and essential mechanism to locate idle spectrum. Multipath effects in wireless channels, on the other hand, reduce CR's sensing accuracy, resulting in a significant risk of missing data. Optimal Spectrum Sensing Technique with Energy Harvesting (OSSTEH) used to solve this problem suffers from poor performance due to only one Primary User (PU) branch used. Hence, in this paper, an enhanced SS with energy harvesting technique is proposed using Maximal Ratio Combiner (MRC). The multiple copies of the PU signal were received using 'N' number of secondary users (SU) antennas and divided into two equal fractions. The first fraction was used for spectrum sensing, while the latter was used for energy harvesting. The first set of SU antennas received a PU signal, which was combined using MRC, and the output of the combiner was used as an input to the energy detector to calculate the received signal's energy. To...

2023, Eurasip Journal on Wireless Communications and Networking

In recent years, the cognitive radio technology has attracted the attention of all the players in the telecommunication field (i.e., researchers, industry, service providers, and regulatory agencies) as a way of facing the spectrum scarcity. In this regard, and after having reviewed the vast activity linked to this concept it is quite easy to realize that the spectrum sensing task turns out to be the keystone of this technology. However, nowadays it is still unclear which is (are) going to be the globally recommended technique(s) for carrying out this procedure. So, and aiming at finding an alternative to the technical impediments behind the spectrum sensing task, this research work proposes that the advanced knowledge that is already being collected at the modern primary networks be used in benefit of the cognitive radios. Here, the 3GPP LTE network has been adopted as the primary system providing the information that the cognitive radio transceiver will be using for co-transmitting opportunistically (i.e., at specific moments) through the licensed radio resources, being the secondary access based on a novel model which proposes to overlay the secondary transmission whenever extreme channel conditions be found in the radio link of a particular primary user.

2023, Wireless Personal Communications

High Peak-to-average power ratio (PAPR) is one of the main issues in multicarrier modulation systems. PAPR is mainly caused due to the summation of various signals having high amplitude values. Several PAPR reduction techniques were employed, out of which Selective Mapping (SLM) proved to be one of the most effective schemes. Some drawbacks in SLM technique are high computational complexity and phase search complexity. Selection of phase sequences in SLM plays a major role in the reduction of PAPR as well as the computational complexity. Modified SLM was introduced to reduce computational complexity in SLM technique. In this paper, we apply various phase sequences such as Riemann, Centering, Centered Riemann and New Centered to Modified SLM technique and their effect on PAPR reduction are analyzed. From the simulation results, it can be inferred that the modified SLM with New Centered scheme achieves a significant PAPR reduction of the range 8.3-9.3 dB with respect to Conventional OFDM and 3-5.5 dB with respect to Conventional SLM technique. The Modified SLM-New Centered scheme is most suitable for 64-QAM applications as it provides good PAPR reduction performance at lower computational complexity.

2023, IEEE Access

In this paper, a renewable energy-based resource allocation method is proposed for full-duplex small cell networks. This method presents an outage-aware power allocation scheme as an optimal transmission policy for a two-way communication system between a base station and user equipment (UE) in one single small cell network, where each node is solar-powered and equipped with a finite capacity battery. A full-duplex (FD) scheduling scheme is presented by utilizing Markov decision process (MDP) action parameters to maximize throughput and minimize outage probability. With two different techniques, scheduling and power transmission, the MDP action sets are formulated to maximize the reward function. Outage probability is investigated by comparing our proposed FD scheme to the conventional half-duplex scheme. Furthermore, the throughput performance of the FD scheme is investigated by varying the scenarios. Finally, the outage probability and throughput performance of the FD scheme are demonstrated, in which the FD scheduling scheme has achieved 87.5 % capacity, and the outage probability is linearly decreased and degraded at 15 dB of SNR. However, with the constraint of a five-meter distance between the UE and interferers, the simulation results show that our proposed optimal transmission policy outperforms the half-duplex system despite dealing with intra-cell interference, inter-cell interference, and limited battery power. INDEX TERMS Resource allocation, Markov decision process, energy harvesting, small cell networks, full duplex.

2023, 2013 Asilomar Conference on Signals, Systems and Computers

In an in-band full-duplex system, radios transmit and receive simultaneously in the same frequency band at the same time, providing a radical improvement in spectral efficiency over a half-duplex system. However, in order to design such a system, it is necessary to mitigate the self-interference due to simultaneous transmission and reception, which seriously limits the maximum transmit power of the full-duplex device. Especially, large differences in power levels in the receiver frontend sets stringent requirements for the linearity of the transceiver electronics. We present an advanced architecture for a compact full-duplex multiantenna transceiver combining antenna design with analog and digital cancellation, including both linear and nonlinear signal processing.

2023

This deliverable provides description of algorithms and protocols for full-duplex operation in small area wireless networks. Different wireless network scenarios are covered, including point-to-point connection, single radio cell, multi-cell network, relaying and mobile ad-hoc network. Developed solutions for hybrid full-duplex and half-duplex operation are also reported. Keyword list: full-duplex, scheduling, power control, radio resource management, protocols Ref. Ares(2015)2277212 01/06/2015

2023, 2008 4th IEEE International Conference on Circuits and Systems for Communications

This paper describes the implementation of a digital compensation scheme, called CSAD, for correcting the effects of wideband gain and phase imbalances in dual-branch OFDM receivers. The proposed scheme is implemented on a Xilinx Virtex-4 field programmable gate array (FPGA). The flexible architecture of the implementation makes it readily adaptable for different broadband applications, such as DVB-T/H, WLAN, and WiMAX. The proposed correction scheme is resilient against multipath fading and frequency offset. When applied to DVB-T, it is shown that an 11-bit arithmetic precision is sufficient to achieve the required BER of 2x10-4 at an SNR of 16.5 dB. Using this bit-precision, the implementation consumes 1686 Virtex-4 slices equivalent to about 42600 gates. Index Terms-direct-conversion receiver, gain and phase imbalances, field programmable gate array, orthogonal frequency division multiplexing.

2023, International journal of Computer Networks & Communications

This paper proposes a Multi-Code Multi-Carrier Code Division Multiple Access (CDMA) scheme for next generation wireless communication systems. This system retains the advantages of Multi-Carrier CDMA in combating multipath and rejecting interference, and provides variable and adaptive data rates through the use of Multi-Code scheme. The rate adaptation algorithm proposed computes the user data rate as a function of the instantaneous channel condition and application dependent data rates. Exploiting the channel information improves the effective data rate and overall capacity of the system. The performance improvement of the proposed system to the Multi-Code CDMA system is shown through simulations. Walsh-Hadamard, Gold and Kasami codes are explored as possible choices for the multiple codes in the system.

2023, ICC 2019 - 2019 IEEE International Conference on Communications (ICC)

Single-antenna full-duplex communication technology has the potential to substantially increase spectral efficiency. However, limited propagation domain cancellation of singleantenna system results in a higher impact of receiver chain nonlinearities on the residual self-interference (SI) signal. In this paper, we offer a comprehensive SI model for single-antenna fullduplex systems based on direct-conversion transceiver structure considering nonlinearities of all the transceiver radio frequency (RF) components, in-phase/quadrature (IQ) imbalances, phase noise effect, and receiver noise figure. To validate our model, we also propose a more appropriate digital SI cancellation approach considering receiver chain RF and baseband nonlinearities. The proposed technique employs orthogonalization of the design matrix using QR decomposition to alleviate the estimation and cancellation error. Finally, through circuit-level waveform simulation, the performance of the digital cancellation strategy is investigated, which achieves 20 dB more cancellation compared to existing methods.