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Copyright of Duzce University Journal of Science & Technology is the property of Duzce University Journal of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Duzce University Journal of Science & Technology is the property of Duzce University Journal of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: A descriptive statistical analysis was performed on Innovation, Science and Economic Development Canada's (ISED) spectrum consultations from 2008 to 2021, along with a qualitative case study of the 2019 consultation on the 3500 MHz band. Analysis: The statistical analysis evinces the dominance of corporate participation in spectrum consultations, particularly by large wireless service providers. This article examines the relationship between the complicated technical framing of spectrum management issues and the corresponding lack of public participation. Conclusions and implications: To address the lack of public participation in spectrum management, the article proposes an adaptation of the Broadcasting and Telecommunications Legislative Review Panel's recommendation for a public interest committee for ISED's consultation process. [ABSTRACT FROM AUTHOR]

This article applies deep learning-accelerated inverse design algorithms and discovers a spectrum of photonic power dividers with exceptional performance metrics despite the simplicity in the design geometry. The deep learning models exhibit high precisions on the order of 10−6 to 10−8 for both TE and TM polarizations of light. These models enable ultrafast search for an empirically describable subspace that simultaneously satisfy compact footprints, ultralow losses, ultrawide bandwidth, and exceptional robustness against fabrication randomness. We demonstrate a spectrum of devices for silicon photonics with programmable power splitting ratios, excess losses as small as 0.14 dB, to the best of our knowledge, the smallest footprints on the scale of sub-λ2, and low loss bandwidths covering the whole telecommunication spectrum of O, S, E, C, L and U-bands. The robustness of the devices is statistically checked against the fabrication randomness and are numerically verified using the full three-dimensional finite difference time domain calculation. [ABSTRACT FROM AUTHOR]

Transparent conducting oxides (TCOs) exhibit interesting linear and nonlinear optical properties in their epsilon‐near‐zero (ENZ) region. Studies so far have mostly focused on exploring the optical response of a limited number of these materials. It is therefore important to investigate new TCOs that could offer improved ENZ properties. This work reports for the first time measurements of the linear and nonlinear optical responses of polycrystalline indium‐zirconium oxide (IZrO) in the ENZ spectral region. The fabricated IZrO films exhibit high optical mobility (>60 cm2 V‐1 s‐1) and a broadening of the ENZ region due to a graded permittivity along the thickness, as suggested by spectroscopic ellipsometry. This in turn leads to a broadband nonlinear response with a full‐width‐at‐half‐maximum bandwidth as large as ≈260 nm, covering the entire spectral range of the C, L, and U optical telecommunication bands. This work introduces IZrO as a new, promising TCO that could be used for ultrafast and broadband modulation of light in the telecommunication region of the spectrum. [ABSTRACT FROM AUTHOR]

An efficient and secure use of the electromagnetic spectrum by different telecommunications and radar systems represents, today, a focal research point, as the coexistence of different radio-frequency sources at the same time and in the same frequency band requires the solution of a non-trivial interference problem. Normally, this is addressed with diversity in frequency, space, time, polarization, or code. In some radar applications, a secure use of the spectrum calls for the design of a set of transmitted waveforms highly resilient to interception and exploitation, i.e., with low probability of intercept/exploitation capability. In this frame, the noise radar technology (NRT) transmits noise-like waveforms and uses correlation processing of radar echoes for their optimal reception. After a review of the NRT as developed in the last decades, the aim of this paper is to show that NRT can represent a valid solution to the aforesaid problems. [ABSTRACT FROM AUTHOR]

Both cooperative non‐orthogonal multiple access (NOMA) and physical layer security (PLS) are promising techniques for future communication systems. This paper investigates the PLS performance of a cooperative NOMA system where multiple sources transmit a superposed message to two users by utilizing either amplify‐and‐forward (AF) or decode‐and‐forward (DF) relays in both non‐colluding and colluding eavesdropper scenarios. A source‐relay selection scheme is proposed for this system aiming at improving the secrecy performance. Additionally, the closed‐form expression of the secrecy outage probability (SOP) is derived for the proposed source‐relay selection schemes. It is demonstrated that in the proposed schemes, the theoretical results match well with the simulation results. In addition, the proposed schemes outperform the conventional OMA system in terms of SOP. [ABSTRACT FROM AUTHOR]

We present optimal designs for nanowaveguides on standard 220-nm SOI platform yielding ultra-broadband phase-matching over bandwidths >500-nm spanning the entire telecommunication spectrum (O-, E-, S-, C-, L-, U- bands, ~1250-1750 nm) for degenerate-pump four-wave mixing (FWM). A complete study of FWM bandwidth as a function of waveguide dimensional parameters like width, etching depth and sidewall slant-angle is presented. Extensive numerical mode simulations show that the proposed device designs exhibit promising tolerances towards fabrication inaccuracies. These designs can be used for WDM (wavelength division multiplexing) systems in classical optical communication and/or broadband photon-pair sources for multi-channel quantum communication. [ABSTRACT FROM AUTHOR]

Lamb wave delay lines with acoustoelectri-cally-induced non-reciprocity are demonstrated in suspended lithium niobate-on-silicon waveguides for the first time. An electric current is fed through the silicon layer in the same axis as the piezoelectrically-transduced acoustic waves which are attenuated or amplified depending on the direction of the energy exchange with drifting electrons (i.e. acoustoelectric (AE) effect). Therefore, the insertion loss (IL) and non-reciprocity of the delay line is adjustable by controlling the current bias which varies the electron drift velocity and the subsequent momentum transfer. Proof-of-concept delay lines in the range of 600 MHz to 700 MHz are demonstrated with a fractional bandwidth as high as 2.8% and AE gain as high as 5.6 dB resulting in ~20 dB of non-reciprocity. These non-reciprocal components could offer a monolithic and dynamically-tunable solution to the numerous issues that arise from the increasing congestion and interferences in the telecommunication spectrum and suggests the possibility of developing fully-switchable low-IL delay lines through design/fabrication optimizations. [ABSTRACT FROM AUTHOR]

The rapid deployment of 5G spectrum by the telecommunication industry is intended to promote better connectivity and data integration among various industries. However, since exposures to radio frequency radiations (RFR) >2.4 GHz are still uncommon, concerns about their potential health impacts are ongoing. In this study, we used the embryonic zebrafish model to assess the impacts of a 3.5 GHz RFR on biology- a frequency typically used by 5G-enabled cell phones and lies within the 4G and 5G bandwidth. We established a plate-based exposure setup for RFRs, exposed developing zebrafish to 3.5 GHz RFR, specific absorption rate (SAR) ≈ 8.27 W/Kg from 6 h post fertilization (hpf) to 48 hpf, and measured a battery of morphological and behavioral endpoints at 120 hpf. Our results revealed no significant impacts on mortality, morphology or photomotor response and a modest inhibition of startle response suggesting some levels of sensorimotor disruptions. This suggests that the cell phone radiations at low GHz-level frequencies are likely benign, with subtle sensorimotor effects. Through this assessment, we have established a robust setup for zebrafish RFR exposures readily amenable to testing various powers and frequencies. Future developmental exposure studies in zebrafish will evaluate a wider portion of the radio frequency spectrum to discover the bioactive regions, the potential molecular targets of RFR and the potential long-term effects on adult behavior. [ABSTRACT FROM AUTHOR]

In this paper we consider a link, characterized by specific capacity, that services multi-rate random or quasi- random traffic. Random traffic is generated by an infinite number of traffic sources, while quasi-random traffic is gen- erated by a finite population of traffic sources. The link is modeled as a multi-rate loss system. Handover and new calls are distinguished. New calls compete for the available band- width under a threshold call admission policy. In that pol- icy, a new call of a particular service-class is not allowed to enter the system if the in-service handover and new calls of the same service-class plus the new call, exceed a predefined threshold (which can be different for each service-class). On the other hand, handover calls compete for the available band- width based on the complete sharing policy. We show that the steady state probabilities in the proposed models have a prod- uct form solution (PFS). The PFS leads to a convolution algo- rithm for accurate calculation of congestion probabilities and link utilization. [ABSTRACT FROM AUTHOR]

Spread spectrum is a technique used for transmitting telecommunications signals. This topic is relatively complex and can be challenging for students. Thus, programming language Octave has been introduced in the course curriculum of Telecommunication Systems as one of the powerful tools that aid in student understanding of the spread‐spectrum principles. The purpose of this paper is to elaborate on the teaching method of spread‐spectrum technique and its application in telecommunications, with the aim to make this topic understandable to students. The participants of the experiment were fifth‐semester electrical engineering students (N = 86) at a college of applied sciences. To test the previous knowledge of students needed to understand the theory of spread spectrum, a pretest was carried out which refers to general terms from the fundamentals of telecommunications. With the aim to deeper apprehend the necessary theory from this area, the students had to solve examples from engineering practice using open source software Octave, as well as computational tasks, regarding both methods in spread‐spectrum technology. It has been shown that thanks to the visualization of appropriate material, students of the experimental group understood in more detail the method of generating spread‐spectrum signals and the influence of individual parameters on partial signals, in relation to students who did not have the opportunity to use Octave. The results of the research lead us to conclude that software like Octave should be included in courses like Telecommunication Systems as a supplement to the traditional teaching and learning methods. [ABSTRACT FROM AUTHOR]

Copyright of Lámpsakos is the property of Fundacion Universitaria Luis Amigo, Facultad de Ingenierias and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article reports on a litigation related to the arrangement of a procurement procedure before allocation of telecommunication frequencies in Germany. A demand assessment procedure preceding the allocation of frequencies is not unlawful because it involves frequencies that are involved in it and are still allocated for a longer period of time.

Highlights • Increasingly, all new technologies depend on wireless digital connectivity. • Digital ecosystem actors benefit from cost-efficient wireless connectivity. • A supply-drive and demand-driven analysis is undertaken for The Netherlands. • 5G provides an average per user traffic capacity improvement of ∼40% over 4G LTE. Abstract Many of the technologies driving both the global economy and societal development, such as the Internet of Things, Industry 4.0 and Smart Healthcare, depend on adequate capacity and coverage of digital connectivity. It is therefore essential that wireless connectivity can be delivered in a cost-efficient way by Mobile Network Operators, for the benefit of all digital ecosystem actors. The contribution of this paper is to analyse the capacity, coverage and cost of different enhanced Mobile Broadband (eMBB) infrastructure strategies, as the industry moves towards integrating new 5G spectrum bands and densifying existing networks. Both a supply-driven and demand-driven investment analysis is undertaken using a case study of the Netherlands. The supply-driven analysis estimates the capacity that can be provided to users via new spectrum, before network densification via small cells is required. The demand-driven analysis tests a range of required per user speeds including 30, 100 or 300 Mbps and quantifies the performance of investment strategies in meeting this demand. The key contribution is estimating the traffic threshold delivered per user from integrating 5G spectrum bands on the existing Dutch macrocell network. Based on the inputs of this analysis, we find that 5G spectrum bands provide an average per user traffic capacity improvement of approximately 40% for the Netherlands in comparison with the existing LTE capacity. [ABSTRACT FROM AUTHOR]

The spectrum sharing approach (SSA) has emerged as a cost-efficient solution for the enhancement of spectrum utilization to meet the stringent requirements of 5G systems. However, the realization of SSA in 5G mmWave cellular networks from technical and regulatory perspectives could be challenging. Therefore, in this paper, an analytical framework involving a flexible hybrid mmWave SSA is presented to assess the effectiveness of SSA and investigate its influence on network functionality in terms of independence and fairness among operators. Two mmWave frequencies (28GHz and 73 GHz) are used with different spectrum bandwidths. Various access models have been presented for adoption by four independent mobile network operators that incorporate three types of spectrum allocation (exclusive, semipooled, and fully pooled access). Furthermore, an adaptive multi-state mmWave cell selection scheme is proposed to associate typical users with the tagged mmWave base stations that provide a great signal-to-interference plus noise ratio, thereby maintaining reliable connections and enriching user experience. Numerical results show that the proposed strategy achieves considerable improvement in terms of fairness and independence among operators, which paves the way for further research activities that would provide better insight and encourage mobile network operators to rely on SSA. [ABSTRACT FROM AUTHOR]

We develop and analyze a new user-centric networking model for ubiquitous spectrum sharing where every user can share and use the spectrum under uncertainty of their traffic models. In this concept, users when connected to the Internet (wired/wireless) can dynamically serve as access points for other users in their vicinity. For this reason, the concept is referred to as user-centric distributed spectrum sharing. Each user in spectrum sharing mode utilizes a part of its available spectrum for its own traffic and remaining part to share with users in spectrum demanding modes. The model is designed as an operator supervised double-Stackelberg game with network operators, access points, and users as main players. We study network reliability and latency of the system under uncertainty of users’ traffic patterns. The numerical results show that the proposed model, depending on different settings, can significantly improve both profit and utility for network operators and users, respectively. Furthermore, network reliability is significantly improved depending on the network parameters for both users and operators. [ABSTRACT FROM AUTHOR]

This paper investigates the fundamental issues of mode selection and spectrum partition in cellular networks with in-band device-to-device (D2D) communication from the physical-layer security (PLS) perspective. We consider a mode selection scheme allowing each D2D pair to probabilistically switch between the underlay and overlay modes, and also a spectrum partition scheme where the system spectrum is orthogonally partitioned between cellular and overlay D2D communications. We first develop a general theoretical framework to model the secrecy outage and secrecy capacity performance of cellular users as well as the outage and capacity performance of D2D pairs. Optimization problems are also solved to identify the optimal mode selection and spectrum partition for secrecy capacity maximization and secrecy outage probability minimization. A case study is then provided to demonstrate the application of our theoretical framework for performance modeling and optimization, and also to illustrate the impacts of mode selection and spectrum partition on the PLS performances of in-band D2D communications. [ABSTRACT FROM AUTHOR]

In this paper, we present some results about the spectrum of the matrix associated with the computation of the Multiplex PageRank defined by the authors in a previous paper. These results can be considered as a natural extension of the known results about the spectrum of the Google matrix. In particular, we show that the eigenvalues of the transition matrix associated with the multiplex network can be deduced from the eigenvalues of a block matrix containing the stochastic matrices defined for each layer. We also show that, as occurs in the classic PageRank, the spectrum is not affected by the personalization vectors defined on each layer but depends on the parameter α that controls the teleportation. We also give some analytical relations between the eigenvalues and we include some small examples illustrating the main results. [ABSTRACT FROM AUTHOR]

Network densification via small cell deployments can enhance the network capacity in a cost-effective manner. Co-tier and cross-tier interferences form barriers to boost the network performance. In this paper, an interference coordination scheme with the aid of cognitive radio is proposed for dense small cell networks. Based on the theory of stochastic geometry, the network spectral efficiency is derived as a function of the radius of exclusion zone. Furthermore, the optimal radius of exclusion zone that maximizes system spectral efficiency is obtained by one-dimension searching. Simulation results show that the proposed interference coordination scheme with the optimal exclusion zone outperforms the existing ones in terms of system spectral efficiency. [ABSTRACT FROM AUTHOR]

Heterogeneous two-tier network with hybrid deployed small cells and macrocells is a promising solution for fifth generation (5G) wireless networks. However, with the higher and higher spectrum band used in 5G, the coverage and capacity of indoor environment is not good enough for the users' increasing demand. In this paper, we proposed a self-organizing capacity and coverage optimization scheme using power adaptation to enhance the capacity and improve the coverage. Simulation results show that the proposed self-organizing scheme can effectively improve the capacity and coverage. [ABSTRACT FROM AUTHOR]

We present Wi-5, a spectrum programming architecture for radio resource management in unlicensed frequency bands. It introduces a spectrum control plane that offers fine grained allocation of radio resources, flexible configuration of radio and wireless networking parameters, and continuous monitoring of the wireless network status. These features, along with the centralized nature of this architecture, can effectively address spectrum congestion which often occurs in unlicensed frequency bands. To demonstrate Wi-5's capabilities, we show results obtained from emulating various use case scenarios on our open source proof-of-concept. [ABSTRACT FROM AUTHOR]

A major challenge in designing a spectral co-existence between radar and communication systems is how to simultaneously provide efficient utilization of the shared spectrum while maintaining a reliable performance for both systems. Due to its flexibility in using linear independent waveforms and superiority in terms of target detection and estimation, the collocated multiple-input-multiple-output (MIMO) radars provide a paramount capability in realizing spectrum sharing with communication systems. In this paper, we consider the use of joint transmit and receive beamformers for both the MIMO radar and MIMO communication systems. Specifically, we design a two-tier alternating optimization spectrum sharing framework that is based on interference alignment (IA) approach. The effectiveness of spectrum sharing between radar and communication systems is guaranteed by mitigating the mutual interference signals in the shared spectral band. Subsequently, motivated by the excellent performance provided by IA in different wireless network scenarios, we propose a spectrum sharing framework that consists of a main iterative algorithm with two subalgorithms included within its operation. The first subalgorithm is used to maximize the signal-to-interference-plus-noise ratio of the radar system, whereas the second one is utilized to maximize the average sum-rate of the communication system. The main iterative algorithm is proposed to jointly optimize the transmit and receive beamforming filters of both systems by performing alternating optimization between the two subalgorithms. The convergences of the proposed algorithm and its subalgorithms are numerically verified. Simulation results are provided to confirm the superiority of the proposed framework for both systems. [ABSTRACT FROM AUTHOR]

In this paper, a spectrum efficient secure transmission scheme based on directional polarization modulation (DPM) is proposed. Specifically, the polarized signals are divided into two parts, i.e., I and Q, and a dual-polarized antenna array is designed to form beams to transmit these signals. Naturally, the constellation structure is associated with the beam gain, which can be controlled to make the constellation structure distort in undesired directions. Thus the security is enhanced for the symbol error rate performance deteriorates in undesired directions. Additionally, a kind of directional modulation technique is utilized to transform one component of the polarized signal into QPSK signal and thus improves the modulation order without extra transmitting power consummation. Finally, theoretical analysis and simulation results demonstrate that the proposed scheme can improve the transmission efficiency and provide a security transmission method for wireless communication systems. [ABSTRACT FROM AUTHOR]

Recently, orbital angular momentum (OAM) based vorticose communication has attracted much attention because of its potential to significantly increase the spectrum efficiency (SE) of wireless communications. However, the multiple radio frequency (RF) chains used for multiple OAM modes lead to an unexpected cost for wireless vorticose communications. In this paper, we first propose the mode modulation (MM) based OAM system to allow multiple OAM modes sharing a common RF chain. The proposed MM cannot only reduce the hardware cost, but also boost the SE by introducing the mode as an additional dimension for data transmission. Moreover, without the channel state information (CSI) feedback, we develop an equal-probability mode modulation (EMM) scheme to maximize the SE of MM-based OAM systems with the limited RF chains. In addition, with the CSI feedback, we develop a Huffman coding based adaptive mode modulation (AMM) scheme, which can adaptively choose the OAM modes to further increase the SEs of OAM-based wireless communications. We also develop the joint power and probability allocation policy for the AMM scheme to achieve the maximum SEs for OAM-based vorticose communications. Numerical results demonstrate that the MM can offer a new mode dimension for vorticose communications and the AMM scheme can achieve larger SE than the EMM scheme. [ABSTRACT FROM AUTHOR]

For sensor network aided cognitive radio, cooperative wideband spectrum sensing can distribute the sampling and computing pressure of spectrum sensing to multiplesensor nodes(SNs). However, this may incur high latency due to distributed data fusion, especially when the number of SNs is large. In this paper, we propose a novel cooperative wideband spectrum sensing scheme using over-the-air computation. Its key idea is to utilize the superposition property of wireless channel to implement the summation of Fourier transform. This avoids distributed data fusion by computing the target function directly. The performance of the proposed scheme is analyzed with imperfect synchronization between different SNs considered. Furthermore, asynchronization phase offsetestimation and equalization method is proposed. The corresponding performance after equalization is also derived. Both a working prototype based onuniversal software radio peripheraand Monte Carlo simulations are provided to verify the performance of the proposed scheme. [ABSTRACT FROM AUTHOR]

Cooperative communication is a promising technique to mitigate channel impairment and improve spectral efficiency. Due to the mobility of relay nodes (RNs) and the unfavourable effects of wireless channels, channel conditions may change as time passes. Therefore, how to design proper long-term incentive mechanisms for RNs in such dynamic communication environments is an essential issue. This paper investigates the contract incentive method underasymmetric informationscenario, where the relay channel condition and cost are the RNs’ private information. To capture the dynamic characteristic of the RNs’ cooperative information during the long-term cooperation, two dynamic contract mechanisms are introduced into long-term relay incentive with different RNs’ relay information structures. The optimal contract is derived to maximize the source's expected utility for bothindependent asymmetric informationandcorrelated asymmetric information. Numerical results are presented to evaluate the effectiveness of the proposed dynamic contract-based incentive mechanism. [ABSTRACT FROM AUTHOR]

We study a resource allocation problem for the uplink of a virtualized massive multiple-input multiple-output system, where the antennas at the base station are priced and virtualized among the service providers (SPs). The mobile network operator (MNO) who owns the infrastructure decides the price per antenna, and a Stackelberg game is formulated for the net profit maximization of the MNO, while the minimum rate requirements of SPs are satisfied. To solve the bi-level optimization problem of the MNO, we first derive the closed-form best responses of the SPs with respect to the pricing strategies of the MNO, such that the problem of the MNO can be reduced to a single-level optimization. Then, via transformations and approximations, we cast the MNO’s problem with integer constraints into a signomial geometric program (SGP), and we propose an iterative algorithm based on the successive convex approximation (SCA) to solve the SGP. Simulation results show that the proposed algorithm has performance close to the global optimum. Moreover, the interactions between the MNO and SPs in different scenarios are explored via simulations. [ABSTRACT FROM AUTHOR]

This paper treats the problem of optimal resource allocation over time in a finite-horizon setting, in which the resource become available only sequentially and in incremental values, and the utility function is concave and can freely vary over time. Such resource allocation problems have direct applications in data communication networks (e.g., energy harvesting systems). This problem is studied extensively for special choices of the concave utility function (time invariant and logarithmic) in which case the optimal resource allocation policies are well-understood. This paper treats this problem in its general form and analytically characterizes the structure of the optimal resource allocation policy and devises an algorithm for computing the exact solutions analytically. An observation instrumental to devising the provided algorithm is that there exist time instances at which the available resources are exhausted, with no carryover to future. This algorithm identifies all such instances, which in turn, facilitates breaking the original problem into multiple problems with significantly reduced dimensions. Furthermore, some widely used special cases in which the algorithm takes simpler structures are characterized, and the application to the energy harvesting systems is discussed. Numerical evaluations are provided to assess the key properties of the optimal resource allocation structure and to compare the performance with the generic convex optimization algorithms. [ABSTRACT FROM AUTHOR]

We consider systems in which the transmitter conveys messages to the receiver through a capacity-limited relay station. The channel between the transmitter and the relay station is assumed to be a frequency-selective additive Gaussian noise channel. It is assumed that the transmitter can shape the spectrum and adapt the coding technique so as to optimize performance. The relay operation is oblivious (nomadic transmitters), that is, the specific codebooks used are unknown. We find the reliable information rate that can be achieved with Gaussian signaling in this setting, and to that end, employ Gaussian bottleneck results combined with Shannon’s incremental frequency approach. We also prove that, unlike classical water pouring, the allocated spectrum (power and bit rate) of the optimal solution could frequently be discontinuous. These results can be applied also to a MIMO transmission scheme. We also investigate the case of an entropy-limited relay. We show that the optimal relay function is always deterministic, present lower and upper bounds on the optimal performance (in terms of mutual information), and derive an analytical approximation. [ABSTRACT FROM AUTHOR]

The possibility of flexibly assigning spectrum resources with channels of different sizes greatly improves the spectral efficiency of optical networks, but can also lead to unwanted spectrum fragmentation. We study this problem in a scenario where traffic demands are categorized in two types (low or high bit-rate) by assessing the performance of three allocation policies. Our first contribution consists of exact Markov chain models for these allocation policies, which allow us to numerically compute the relevant performance measures. However, these exact models do not scale to large systems, in the sense that the computations required to determine the blocking probabilities—which measure the performance of the allocation policies—become intractable. In order to address this, we first extend an approximate reduced-state Markov chain model that is available in the literature to the three considered allocation policies. These reduced-state Markov chain models allow us to tractably compute approximations of the blocking probabilities, but the accuracy of these approximations cannot be easily verified. Our main contribution then is the introduction of reduced-state imprecise Markov chain models that allow us to derive guaranteed lower and upper bounds on blocking probabilities, for the three allocation policies separately or for all possible allocation policies simultaneously. [ABSTRACT FROM AUTHOR]

In cognitive radio network, the secondary users (SUs) use the spectrum of primary users for communication which arises the security issues. The status of SUs as legitimate users is compulsory for the stability of the system. This paper addresses the issue of delay caused by a band-selection decision process that directly affects the security and performance. The model cluster-based distributed cooperative spectrum sensing is proposed. In this model, cluster heads (CHs) exchange control information with other CHs and ordinary nodes. This model significantly reduced the delay, sensing, convergence, routing, in band-selection process. This also reduces the energy consumption while sensing the spectrum which seriously leads to performance upgradation. The simulated results show the improved performance of cognitive radio networks in terms of delay, packet loss ratio and bandwidth usage as compared to cluster-based cooperative spectrum sensing model. The opportunity for primary user emulation attacker is minimized as the overall delay is reduced. [ABSTRACT FROM AUTHOR]

This paper proposes a new spectrum sensing technique, referred to as autonomous compressive sensing (CS)-augmented spectrum sensing, which can be developed to provide more efficient spectrum opportunity identification than geolocation database methods. First, we propose an autonomous CS-based sensing algorithm that enables the local secondary users (SUs) to automatically choose the minimum sensing time without knowledge of spectral sparsity or channel characteristics. The compressive samples are collected block-by-block in time, while the spectral is gradually reconstructed until the proposed stopping criterion is reached. Moreover, a CS-based blind cooperating user selection algorithm is proposed to select the cooperating SUs via indirectly measuring the degeneration of the signal-to-noise ratio experienced by different SUs. Numerical and real-world test results demonstrate that the proposed algorithms achieve high detection performance with reduced sensing time and number of cooperating SUs in comparison with the conventional compressive spectrum sensing algorithms. [ABSTRACT FROM AUTHOR]

The technological growth combined with the exponential increase of wireless traffic are pushing the wireless community to investigate solutions to maximally exploit the available spectrum. Among the proposed solutions, the operation of Long Term Evolution (LTE) in the unlicensed spectrum (LTE-U) has attracted significant attention. Recently, the 3rd Generation Partnership Project announced specifications that allow LTE to transmit in the unlicensed spectrum using a Listen Before Talk (LBT) procedure, respecting this way the regulator requirements worldwide. However, the proposed standards may cause coexistence issues between LTE and legacy Wi-Fi networks. In this article, it is discussed that a fair coexistence mechanism is needed to guarantee equal channel access opportunities for the co-located networks in a technology-agnostic way, taking into account potential traffic requirements. In order to enable harmonious coexistence and fair spectrum sharing among LTE-U and Wi-Fi, an adaptive LTE-U LBT scheme is presented. This scheme uses a variable LTE transmission opportunity (TXOP) followed by a variable muting period. This way, co-located Wi-Fi networks can exploit the muting period to gain access to the wireless medium. The scheme is studied and evaluated in different compelling scenarios using a simulation platform. The results show that by configuring the LTE-U with the appropriate TXOP and muting period values, the proposed scheme can significantly improve the coexistence among LTE-U and Wi-Fi in a fair manner. Finally, a preliminary algorithm is proposed on how the optimal configuration parameters can be selected towards harmonious and fair coexistence. [ABSTRACT FROM AUTHOR]

In this paper, we evaluate the detection and false alarm probabilities for relay based spectrum sensing techniques using the energy detector. The communication process consists of two phases. In the first phase, the primary user P transmits and K relays listen. In the second phase, the relays amplify the signal to the fusion center where spectrum sensing based on the energy detector is performed. All relays transmit over orthogonal channels. We also consider cooperative spectrum sensing with best relay selection. Both opportunistic amplify and forward, partial and reactive relay selection are considered. The results are valid for Rayleigh fading channels in the absence or presence of a direct link between P and the fusion center D. [ABSTRACT FROM AUTHOR]

This correspondence paper investigates a novel non-orthogonal multiple access (NOMA) assisted overlay spectrum sharing framework for multiuser cognitive radio networks toward an enhanced spectrum utilization. In particular, one secondary user is scheduled to help forward the primary signal and convey its own signals as well by applying the NOMA principle. A reliability-oriented secondary user scheduling (R-SUS) scheme is first proposed with a target at minimal primary and secondary outage probabilities. Then, a fairness-oriented secondary user scheduling (F-SUS) scheme is proposed, such that all the candidate secondary users have an equal opportunity to be scheduled for the cooperation. Expressions of primary and secondary outage probabilities are derived in closed form to evaluate the resultant network reliability performance. The results reveal that: 1) the proposed R-SUS and F-SUS schemes can achieve a full diversity order for the primary and secondary transmissions, and 2) although the F-SUS scheme enhances user fairness, it suffers a higher secondary outage probability compared with the R-SUS scheme. [ABSTRACT FROM AUTHOR]

A cost effective Kerr nonlinearity based spectrum sliced (SS) WDM free space optical communication system is demonstrated under different weather instabilities. The investigated supercontinuum spectrum sliced WDM FSO system is evaluated at 2.5 Gbps up to 5 km of link distance. A highly nonlinear fiber is a channel for the generation of high power broad spectrum for spectrum slicing. A dense SS-WDM is investigated at 75 GHz channel spacing among 4 channels to make system bandwidth efficient. The system is investigated for different line coding (return to zero, non return to zero) and advanced modulation format such as compressed spectrum return to zero. A major degrading factor in free space communication i.e. beam divergence is also analyzed for investigated work. Antenna diameters of receiver and transmitter play a vital role in FSO, thus various diameters performances are also studied. The approach is to cater the high-speed data demands and thus system deliberated and demonstrated from 2.5 to 10 Gbps. To strengthen the signal in this FSO system, three optical amplifiers are scrutinized such as erbium doped fiber amplifier (EDFA), semiconductor optical amplifier (SOA) and Raman amplifier in terms of bit error rate and quality factor. Results revealed that EDFA is the best amplifier in investigated SS-WDM-FSO system. [ABSTRACT FROM AUTHOR]

The enormous developments in the field of wireless communication technologies have made the unlicensed spectrum bands crowded, resulting uncontrolled interference to the traditional wireless network applications. On the other hand, licensed spectrum bands are almost completely allocated to the licensed users also known as Primary users (PUs). This dilemma became a blackhole for the upcoming innovative wireless network applications. To mitigate this problem, the cognitive radio (CR) concept emerges as a promising solution for reducing the spectrum scarcity issue. The CR network is a low cost solution for efficient utilization of the spectrum by allowing secondary users (SUs) to exploit the unoccupied licensed spectrum. In this paper, we model the PU’s utilization activity by a two-state Discrete-Time-Markov Chain (DTMC) (i.e., Free and busy states), for identifying the temporarily unoccupied spectrum bands,. Furthermore, we propose a Cognitive Radio Sense-and-Wait assisted HARQ scheme, which enables the Cluster Head (CH) to perform sensing operation for the sake of determining the PU’s activity. Once the channel is found in free state, the CH advertise control signals to the member nodes for data transmission relying on Stop-and-Wait Hybrid- Automatic Repeat-Request (SW-HARQ). By contrast, when the channel is occupied by the PU, the CH waits and start sensing again. Additionally, the proposed CRSW assisted HARQ scheme is analytical modeled, based on which the closed-form expressions are derived both for average block delay and throughput. Finally, the correctness of the closed-form expressions are confirmed by the simulation results. It is also clear from the performance results that the level of PU utilization and the reliability of the PU channel have great influence on the delay and throughput of CRSW assisted HARQ model. [ABSTRACT FROM AUTHOR]

Dynamic spectrum access is promising for mitigating worldwide wireless spectrum shortage. Crowdsourced spectrum sensing (CSS) refers to recruiting ubiquitous mobile users to perform real-time spectrum sensing at specified locations and has great potential in mitigating the drawbacks of current spectrum database operations. Without strong incentives and location privacy protection in place, however, mobile users will be reluctant to act as mobile crowdsourcing workers for spectrum-sensing tasks. In this paper, we first formulate participant selection in CSS systems as a reverse auction problem, in which each participant’s true cost for spectrum sensing is closely tied to his current location. Then, we demonstrate how the location privacy of CSS participants can be easily breached under the framework. Finally, we present PriCSS, a novel framework for a CSS service provider to select CSS participants in a differentially privacy-preserving manner. In this framework, we propose PriCSS− and PriCSS+, two different schemes under distinct design objectives and assumptions. PriCSS− is an approximately truthful scheme that achieves differential location privacy and an approximate minimum payment, while PriCSS+ is a truthful scheme that achieves differential location privacy and an approximate minimum social cost. The detailed theoretical analysis and simulation studies are performed to demonstrate the efficacy of both schemes. [ABSTRACT FROM AUTHOR]