Increase Spectrum Utilization Research Articles

DFT-spread OTFS-NOMA for downlink integrated positioning and communication

In this article, a non-orthogonal multiple-access (NOMA) transmission system that incorporates discrete Fourier transform (DFT) spread orthogonal time-frequency space (OTFS) modulation is proposed for the downlink integrated positioning and communication (IPAC). This system is designed to decrease the Peak-to-Average Power Ratio (PAPR) within the OTFS-NOMA system while simultaneously serving both communication user (CU) and positioning user (PU) within the same time-frequency resources. Firstly, we demonstrate the applicability of the proposed DFT-spread OTFS-NOMA (DFT-s-OTFS-NOMA) system for downlink transmission. It efficiently serves both the CU and PU concurrently within the same time and frequency resources, thereby increasing spectrum utilization. Subsequently, we develop a two-stage parameter estimation algorithm focusing on accurate positioning parameter estimation for PU and precise channel estimation for CU. Then, the position of the PU is estimated using the time of arrival (TOA) model and the linear least squares (LLS) approach. Simulation demonstrates a 9 dB PAPR reduction in the proposed system compared to the existing OTFS-NOMA system. Additionally, the proposed two-stage positioning method for the PU achieves centimeter-level accuracy in position estimation and near millimeter-per-second-level accuracy in velocity estimation. What is more, the performance of channel estimation and symbol detection, aided by the PU signal in the DFT-s-OTFS-NOMA system, demonstrates resilience against Doppler effects without the need for reliance on pilots. This ensures sustained an effective Bit Error Rate (BER) even in time-variant high mobility scenarios.

Application of Intelligent Cloud Computing Technology in Optical Communication Network Security of Smart Grid

In order to improve the security of smart grid optical communication network, this paper combines intelligent cloud computing technology to build a security system of optical communication network of power grid. In the aspect of improving communication security performance, multi-user access is realized by non-orthogonal power domain segmentation, and different users use different powers to add and superimpose the same spectrum resources, so as to increase spectrum utilization. At the sending end, this paper improves the safe channel capacity of users by means of pre-coding and artificial noise, and realizes the safe transmission of information. In terms of transmission stability, the cloud computing platform is used as a data processing platform, and multiple nodes are processed synchronously through optical communication state identification, which can more effectively improve the speed of optical communication state identification data. In order to test the performance of the power grid information dispatching model designed in this paper in optimizing power grid configuration and improving power grid load, simulation experiments are carried out. Through the experimental analysis, we can see that the communication method proposed in this paper can accurately identify the intrusion factors, and can effectively improve the security of smart grid optical communication network.

Intelligent Spectrum Management for Future Aeronautical Communications

The emergence of new aerial vehicles into the airspace and the continued growth of aviation operations will result in an increased demand for voice and data communications throughout the National Airspace System (NAS). However, recent studies have shown that the continued use of existing aviation spectrum allocations will not meet the anticipated needs of future aerospace applications; as a result, a new approach to aviation spectrum management is needed to support the forecasted needs of new airspace users. The National Aeronautics and Space Administration (NASA) is investigating the use of modern advancements in wireless communications, artificial intelligence (AI), machine learning (ML), and other advanced concepts in order to implement a novel spectrum management approach that allows for the intelligent utilization of aviation spectrum throughout the airspace. This technical investigation considers various airspace communications configurations, including air-ground and air-air communications, and can be applied to the existing air traffic control (ATC) system, as well as to future applications, such as the emerging Advanced Air Mobility (AAM) initiative. To support the evaluation of the proposed concepts and technologies, a modeling and simulation capability is currently under development, which will continue to evolve in support of new and advanced airspace applications. It is anticipated that this proposed spectrum management concept will allow for increased spectrum utilization efficiency and enhanced airspace capacity, which will better serve the needs of future NAS applications.

HBRO-AlexNet: Honey Badger Remora Optimization Integrated AlexNet for Cooperative Spectrum Sensing in Cognitive Radio Network

Cognitive radio (CR) technology enables a secondary user (SU) to make the most use of the licensed spectrum when the primary user (PU) is inactive, hence increasing spectrum efficiency. SUs are required to complete the spectrum sensing process to identify the spectrum utilization. It is required to effectively detect PU signal to SU for using the idle licensed spectrum bands. Even though various spectrum sensing techniques are designed in CR networks, designing test statistics still results in a complex task. To solve spectrum scarcity issues and to increase spectrum utilization, Honey Badger Remora Optimization-based AlexNet (HBRO-based AlexNet) is developed in this research and the test statistics model is modeled with a deep learning approach with signal parameters, like signal energy, and Eigen statistics. However, SU can use AlexNet to boost the spectrum efficiency of PU's licensed spectrum, which will then permit an increase in the chance of detection in the CR network (CRN). Though considering signal-to-noise ratio (SNR) at 5 dB, the proposed spectrum sensing approach yields the probability of detection and probability of false alarm for the Rician channel as 1 and 0.999, respectively.

Energy-Efficient Utility Function-Based Channel Resource Allocation and Power Control for D2D Clusters With NOMA Enablement in Cellular Networks

Device-to-device(D2D) communication combined with non-orthogonal multiple access(NOMA) can further improve the quality of service for future communications systems and increase spectrum utilization and connection density in cellular networks. In this paper, an effective power allocation scheme is designed to optimize the performance of a D2D communication system based on NOMA for imperfect Successive Interference Cancellation(SIC) decoding. To solve the non-convexity of the problem due to integer constraints and coupling variables, an alternate optimization algorithm was designed to obtain the optimal solution of each subproblem by Lagrange duality analysis and the sub-gradient descent method. Finally, the numerical simulation results demonstrate the performance advantages of the proposed joint optimization algorithm for channel resource allocation and power control in energy efficiency.

A Directly Connected OTA Measurement for Performance Evaluation of 5G Adaptive Beamforming Terminals

Spatially beamformed communication, which is achieved by antenna array and multiple-input and multiple-output (MIMO) technologies, has become the most critical technology to drastically increase spectrum utilization rate of 5G. To guarantee the successful deployment of 5G, different aspects of device design, particularly those related to radio-frequency front end and antenna array for enabling beamformed communication, have to be accurately verified. It is more cost effective to identify design imperfections through lab testing rather than using field testing-based trial and error approaches, especially for the explosive growth of 5G-enabled Internet of Things devices. In this article, a directly connected over-the-air (OTA) test solution for 5G MIMO OTA evaluations with the focus on dynamic beamforming devices is proposed. The proposed solution can mathematically achieve constructions among the S ports of base station (BS) and U ports of the receiving antenna array, which makes it possible for measuring the throughput of terminal with an adaptive beamforming array in an OTA way. All system parameters are emulated, including S elements BS antenna gain, U elements of receiving terminal performance, and 3-D <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S{\times }U$ </tex-math></inline-formula> propagation channel characteristics. To further validate the theoretical analysis and test procedure, a newly developed 4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\times }$ </tex-math></inline-formula> 4 5G MIMO device is measured in terms of its throughput. The results exactly reflect the true performance of the proposed solution under realistic operational conditions.

A Survey on Dynamic Spectrum Access Techniques in Cognitive Radio Networks

The idea of Cognitive Radio (CR) is to share the spectrum between a user called primary, and a user called secondary. Dynamic Spectrum Access (DSA) is a new spectrum sharing paradigm in cognitive radio that allows secondary users to access the abundant spectrum holes in the licensed spectrum bands. DSA is an auspicious technology to alleviate the spectrum scarcity problem and increase spectrum utilization. While DSA has attracted many research efforts recently, in this paper, a survey of spectrum access techniques using cooperation and competition to solve the problem of spectrum allocation in cognitive radio networks is presented.

Multifunctional Signal Design for Measurement, Navigation and Communication Based on BOC and BPSK Modulation

In a multi-node spacecraft or unmanned aerial vehicle (UAV) group, a multifunctional signal containing measurement, navigation, and communication functions is required to simplify the receiver structure, and to increase spectrum utilization. The paper proposes a multifunctional signal based on a binary offset carrier (BOC) and binary phase shift keying (BPSK) modulation. The signals which carry different functions are orthogonal in the frequency domain, which causes the data transmission signal to not be affected by BOC signal. In addition, in the high carrier to noise ratio (C/N0), the spreading gain of the BOC signal ensures that the communication signal has a slight influence on navigation signals. Moreover, the multifunctional signal can achieve communication and measurement functions at the same frequency point and fast switching in multinodes. These advantages can simplify the receiver design and improve the frequency band utilization. Finally, in this study we completed the design and verification of the hardware system.

Resource Allocation for D2D Cellular Networks With QoS Constraints: A DC Programming- Based Approach

Device-to-device (D2D) communications provide efficient ways to increase spectrum utilization ratio with reduced power consumption for proximity wireless applications. In this paper, we investigate resource allocation strategies for D2D communications underlaying cellular networks. To be specific, we study the centralized resource allocation algorithm for controlling transmit powers of the underlying D2D pairs in order to maximize the weighted sum-rate while guaranteeing the quality of service (QoS) requirements for both D2D pairs and cellular users (CUs). A novel DC (difference of convex function) programming-based method, called alternative DC (ADC) programming, is introduced to effectively solve this complicated resource allocation problem. Through updating each D2D pair’s power alternatively, the QoS requirement for each D2D pair can be solvable and incorporated systematically to the introduced ADC programming framework. The simulation results show that the introduced ADC programming achieves the highest weighted sum-rate compared to the state-of-the-art methods while ensuring that the QoS of each D2D pair and CU are satisfied.

The CODYSUN Approach: A Novel Distributed Paradigm for Dynamic Spectrum Sharing in Satellite Communications.

With a constant increase in the number of deployed satellites, it is expected that the current fixed spectrum allocation in satellite communications (SATCOM) will migrate towards more dynamic and flexible spectrum sharing rules. This migration is accelerated due to the introduction of new terrestrial services in bands used by satellite services. Therefore, it is important to design dynamic spectrum sharing (DSS) solutions that can maximize spectrum utilization and support coexistence between a high number of satellite and terrestrial networks operating in the same spectrum bands. Several DSS solutions for SATCOM exist, however, they are mainly centralized solutions and might lead to scalability issues with increasing satellite density. This paper describes two distributed DSS techniques for efficient spectrum sharing across multiple satellite systems (geostationary and non-geostationary satellites with earth stations in motion) and terrestrial networks, with a focus on increasing spectrum utilization and minimizing the impact of interference between satellite and terrestrial segments. Two relevant SATCOM use cases have been selected for dynamic spectrum sharing: the opportunistic sharing of satellite and terrestrial systems in (i) downlink Ka-band and (ii) uplink Ka-band. For the two selected use cases, the performance of proposed DSS techniques has been analyzed and compared to static spectrum allocation. Notable performance gains have been obtained.

Towards Flexible and Truthful Incentive for Multichannel Allocation in DSA

Due to its potential of increasing spectrum utilization, dynamic spectrum access (DSA) is a promising platform to solve the so-called spectrum shortage problem, caused by a huge proliferation of wireless applications and services. Because of good allocation efficiency and fairness, auction based mechanisms have been extensively studied in DSA, in which truthfulness is a critical property to guarantee that each bidder can obtain her maximal utility by bidding with her true valuation of bidding spectrum. However, existing spectrum auction mechanisms on homogenous channels strictly require bidders to bid one channel or multiple channels with continuous demands, and does not consider the noncontinuous demands for channels. In this paper, we propose THIMBLE, the first TrutHful Incentive Mechanism for flexiBle muLtichannEl allocation by considering bidders’ continuous/noncontinuous demands for channels and spatial reusability. Specifically, bidders using the same channel without interference are formulated to a group, and a group bid recalculation method is presented for noncontinuous group bids. Next, a winner selection and charging method based on group bids is designed to achieve truthfulness. Extensive simulation results show that THIMBLE achieves not only truthfulness in continuous and noncontinuous channel demand cases, but also as good spectrum allocation efficiency as existing spectrum auction mechanisms.

Dynamic Threshold Based Throughput Enhancement in Cognitive Radio Network Using Hidden Markov Model with State Prediction

The enhancement of throughput is one of the key issues in the cognitive radio network. In this paper, a channel status prediction scheme based on hidden Markov model is proposed for enhancing the throughput of cognitive radio network. Unlike the conventional scheme which relies on channel sensing alone, the proposed scheme provides an additional advantage of being able to predict the primary user’s state along with channel sensing, thus increasing spectrum utilization and system throughput. For achieving enhanced reliability in spectrum sensing process of the network, a dynamic threshold based energy detection technique considering noise uncertainty and target detection probabilities is proposed. Comparative analyses of the performance of the dynamic threshold based energy detection technique with that of existing fixed and dynamic threshold based detection schemes are presented. The analyses reveal that the proposed detection scheme performs better than the existing detection schemes with regard to probability of detection and probability of false alarm. It is shown that the hidden Markov model-based prediction scheme makes the cognitive radio network more efficient in terms of throughput than existing schemes.

A review of industrial wireless communications, challenges, and solutions: A cognitive radio approach

AbstractIntegral and crucial to performance of wireless sensor networks (WSNs), and specifically industrial wireless sensor network (IWSN) is stable, robust, reliable, and ubiquitous communications system. Though, wired communications system is suitable for industrial communications and is resilient to shadowing and multipath fading effects of industrial‐WSN environments, yet its wireless counterpart is a much preferred industrial communications technology due to reduced cost and high flexibility which it offers in comparison to wired communications. However, overcrowding of the industrial, scientific, and medical band, where IWSN is deployed together with other heterogeneous technologies, as well as resultant scarcity of usable frequency spectrum has restrained exclusive application of wireless technology for industrial communications. Nonetheless, cognitive radio (CR) has ability to increase spectrum utilization efficiency and channel capacity for industrial wireless communications (IWC) through opportunistic/dynamic spectrum access (DSA) technique. In this review article, we examine how DSA can benefit IWC through exploitation of new perspectives of white space definitions in the licensed bands as well as unlicensed bands. While discussing the potential of DSA for IWC, we have considered the unique characteristics of IWC as well as technical challenges and issues imposed by industrial‐WSN. Accordingly, we have suggested and proffered appropriate CR‐based solutions in mitigating some of the challenges where necessary.

Index-Based Channel Hopping for Multi-Rendezvous Multi-Channel MAC

Multi-channel Medium Access Control (MAC) protocols aim to transmit in parallel on distinct channels in order to increase spectrum utilization. In this letter, we consider dynamic multi-channel access problem with independent and stochastically identical channels. We formulate the problem as a Restless Multi-Armed Bandit (RMAB) process and propose a novel load-adaptive frequency hopping method, namely Index-Based Channel Hopping (IBCH) algorithm, with the goal of optimal spectrum allocation and throughput maximization. We classify previous efforts by their spectrum decision mechanisms and rendezvous characteristics as single- and multi-rendezvous protocols. Later on, we compare performance of IBCH with various protocols from both rendezvous classes at varying transmission range, network size and spectrum availability. Simulation results show that IBCH significantly outperforms other spectrum assignment methods from both rendezvous classes.

Dynamic TDD Systems for 5G and Beyond: A Survey of Cross-Link Interference Mitigation

Dynamic time division duplex (D-TDD) dynamically allocates the transmission directions for traffic adaptation in each cell. D-TDD systems are receiving a lot of attention because they can reduce latency and increase spectrum utilization via flexible and dynamic duplex operation in 5G New Radio (NR). However, the advantages of the D-TDD system are difficult to fully utilize due to the cross-link interference (CLI) arising from the use of different transmission directions between adjacent cells. This paper is a survey of the research from academia and the standardization efforts being undertaken to solve this CLI problem and make the D-TDD system a reality. Specifically, we categorize and present the approaches to mitigating CLI according to operational principles. Furthermore, we present the signaling necessary to apply the CLI mitigation schemes. We also present information-theoretic performance analysis of D-TDD systems in various environments. As topics for future works, we discuss the research challenges and opportunities associated with the CLI mitigation schemes and signaling design in a variety of environments. This survey is recommended for those who are in the initial stage of studying D-TDD systems and those who wish to develop a more feasible D-TDD system as a baseline for reviewing the research flow and standardization trends surrounding D-TDD systems and to identify areas of focus for future works.

Beamforming Design for In-Band Full-Duplex Multi-Cell Multi-User MIMO LSA Cellular Networks

The in-band full-duplex (IBFD) mechanism offers many advantages over standard half duplex (HD) systems: it can potentially double the capacity and increase spectrum utilization efficiency. While IBFD renders many conventional research problems irrelevant, it unearths several new problems that urgently need attention. We focus on a the design of a Licensed Shared Access (LSA) based spectrum sharing framework with IBFD multi-cell multi-user multiple-input multiple-output (MIMO) communication network as the licensee, which operates in the service region of a multi-user MIMO incumbent network. We propose a modified LSA controller framework for the protection zone scenario of LSA, whereby the LSA controller ensures that the licensees always have access to data rates above a given threshold, for which aggregate interference towards the incumbents is also kept at minimum. Accordingly, we propose a hierarchical two-step beamforming framework, where i) the LSA controller first seeks the quality of service (QoS) requirements from the licensee network. Based on the QoS requirements, beamformers are designed to minimize the aggregate interference towards the incumbents. ii) In the second step, the interference minimized in the first step is considered as a constraint for the new beamformer design problem that maximizes the aggregate uplink and downlink throughput of the licensee network. Numerical results demonstrate the precedency of the proposed algorithms for IBFD LSA when compared to baseline HD LSA, whereby we observe i) over 60% improvement in throughput performance for the licensee network and ii) a reduction in interference exposure towards the incumbents from the licensees by at least 6.8315dB.

Resource Allocation Combining Heuristic Matching and Particle Swarm Optimization Approaches: The Case of Downlink Non-Orthogonal Multiple Access

The ever-increasing requirement of massive connectivity, due to the rapid deployment of internet of things (IoT) devices, in the emerging 5th generation (5G) mobile networks commands for even higher utilization of the available spectrum. Non-orthogonal multiple access (NOMA) is a promising solution that can effectively accommodate a higher number of users, resulting in increased spectrum utilization. In this work, we aim to maximize the total throughput of a NOMA system, while maintaining a good level of fairness among the users. We propose a three-step method where the first step matches the users to the channels using a heuristic matching algorithm, while the second step utilizes the particle swarm optimization algorithm to allocate the power to each channel. In the third step, the power allocated to each channel is further distributed to the multiplexed users based on their respective channel gains. Based on extensive performance simulations, the proposed method offers notable improvement, e.g., 15% in terms of system throughput and 55% in terms of user fairness.

A delay-aware spectrum handoff scheme for prioritized time-critical industrial applications with channel selection strategy

Cognitive radio has emerged as an enabling technology in the realization of a spectrum-efficient and delay-sensitive industrial wireless communication where nodes are capable of responding in real-time. However, particularly for time-critical industrial applications, because of the link-varying channel capacity, the random arrival of a primary user (PU), and the significant delay caused by spectrum handoff (SH), it is challenging to realize a seamless real-time response which results in a quality of service (QoS) degradation. Therefore, the objectives of this paper is to increase spectrum utilization efficiency by allocating channel based on the priority of a user QoS requirements, to reduce SH delay, to minimize latency by preventing avoidable SHs, and to provide real-time response. To achieve an effective spectrum utilization, we proposed an integrated preemptive/non-preemptive priority scheme to allocate channels according to the priority of user QoS requirements. On the other hand, to avoid significant SH delays and substantial latency resulting from random PU arrival, a unified spectrum sensing technique was developed by integrating proactive sensing and the likelihood estimation technique to differentiate between a hidden and a co-existence PU, and to estimate the mean value of the busy and the idle periods of a channel respectively. Similarly, to prevent poor quality channel selection, a channel selection technique that jointly combines a reward system that uses metrics, e.g. interference range, and availability of a common channel to ranks a set of potential target channels, and a cost function that optimizes the probability of selecting the channel with the best characteristics as candidate channels for opportunistic transmission and for handoffs was developed. The simulation results show a significant performance gain of the delay-PritSHS in terms of number of SHs, Latency, as well as throughput for time-critical industrial applications in comparison to other schemes.

An incentive mechanism with bid privacy protection on multi-bid crowdsourced spectrum sensing

Crowdsourced spectrum sensing (CSS) has been regarded as an excellent technique to increase spectrum utilization and enhance spectrum service. To improve the participation of mobile users, some auction-based mechanisms have been proposed for crowdsourced spectrum sensing system. However, both multi-bid crowdsourced spectrum sensing and the bid privacy of participants in it have never been taken into consideration in those mechanisms. In this paper, we propose BPriCSS, the first mechanism to protect the bid privacy in spectrum-sensing participants selecting process in multi-bid CSS system. Moreover, considering different aims of the administrator, BPriCSS-MSC and BPriCSS-MAE are presented for minimizing the social cost and maximizing the average cost efficiency of winners, respectively. We prove that both BPriCSS-MSC and BPriCSS-MAE can simultaneously achieve differential bid privacy and truthfulness by theoretical analysis and simulation.

Joint Banding-Node Placement and Resource Allocation for Multigranular Elastic Optical Networks

The fine-grained grid of elastic optical networks (EONs) facilitates flexible bandwidth allocation and increased spectrum utilization efficiency and is seen as a promising solution to handle ever-increasing traffic demands. Despite this, fiber capacity exhaustion is imminent, and multifiber links are expected to be prevalent in future optical networks. A challenge this brings about is the high port count of optical cross-connects (OXCs). Conventional OXCs built using flex-grid wavelength selective switches do not scale well. To achieve scalability of OXCs, a flexible wavebanding OXC architecture (FLEX) has been proposed recently. FLEX reduces the complexity and cost of OXCs while sacrificing some performance in terms of limited switching flexibility. Taking the reduced switching capability into consideration, a cost-function pluggable auxiliary layered-graph framework has been proposed in our previous work to solve the routing, fiber, waveband, and spectrum assignment (RFBSA) problem in multifiber-based EONs with flexible wavebanding nodes. In this paper, we address the following problem. Given the total number of available WSSs for the network as a budget, we determine how many FLEX nodes to deploy and where to deploy them, and solve the RFBSA problem jointly to optimize the network performance. An integer linear programming formulation is proposed for a set of traffic requests. We also propose a heuristic algorithm to solve this joint problem efficiently. The results show that our algorithm achieves good network performance, which is indicated by the average maximum spectrum usage as well as considerably reducing hardware costs. We also evaluate our algorithm for dynamically arriving traffic requests in terms of demand blocking ratio.