Spectrum-sharing Networks Research Articles

Hybrid Hierarchical DRL Enabled Resource Allocation for Secure Transmission in Multi-IRS-Assisted Sensing-Enhanced Spectrum Sharing Networks

Hybrid Hierarchical DRL Enabled Resource Allocation for Secure Transmission in Multi-IRS-Assisted Sensing-Enhanced Spectrum Sharing Networks

5G Wireless Technology: Spectrum Sharing and Heterogeneous Networks

Abstract: This paper addresses the critical challenge of 5G network cell planning, emphasizing the essential role of estimating the number of cells or base stations required for a given area and user bandwidth. The proposed model explores four scenarios with varying network parameters to determine the optimal base station deployment. The increasing demand for 5G networks necessitates a focus on small cells or femtocells, offering advantages such as consistent coverage, power adjustment, energy efficiency, and higher data rates. However, deploying excessive femtocells may lead to unnecessary handovers, requiring optimization strategies. The study introduces an analytical model for heterogeneous cellular networks, integrating fourth and fifth-generation systems. The model, represented by a two dimensional Markov Chain, employs a novel decomposition approach for analyzing system performance measures. Validation is conducted through simulation and simultaneous equation systems. The proliferation of mobile devices and data traffic necessitates dense 5G network deployments, with small cells gaining traction due to their versatile coverage, power adaptability, energy efficiency, and higher data rates. However, an excessive deployment of small cells can lead to frequent handovers, prompting the need for enhanced handover strategies and coexistence with other technologies in the 5G landscape. The paper concludes by highlighting the impending need for practical implementation testing of 5G systems, emphasizing the significant role of small cell deployments. It discusses an initiative focusing on testing small cellenabled operator business models in real-world scenarios, anticipating the pivotal role of small cells in future 5G systems.

Contention or Symbiosis: The Model-Based and Model-Less Transmission Mode Selections for Internet of Things in Unlicensed Band

In this work, we investigate a spectrum-sharing network, where an Internet-of-Things (IoT) system and a WiFi system coexist in the unlicensed band. The IoT devices can actively transmit signal by contending for the channel with the WiFi users. Alternatively, they can also convey information by passively backscattering the ambient WiFi signal, and thus form symbiosis with the WiFi during the transmission. Since the active and the passive transmission mode have their own merits under specific circumstances, how to select one of them adaptively and efficiently with guaranteeing the normal service of the WiFi system is of high importance. To solve this problem, we firstly investigate the effective throughput of the IoT system from the cross-layer perspective. Then, by jointly considering the effective throughput and the power consumption of the IoT system, we formulate the transmission mode selection problem. Two solutions are given depending on whether the signaling between the two systems is available. By entailing the inter-system parameter sharing, the model-based transmission mode selection scheme is proposed, which gives the closed-form optimal solution. When the inter-system parameter sharing is absent, the model-less transmission mode selection scheme is proposed by using deep reinforcement learning (DRL) technique. Extensive simulation results validate the theoretical analysis, and demonstrate the effectiveness of the proposed transmission mode selection schemes.

Ambient Backscatter-Based Power Control Strategies for Spectrum Sharing Networks

Prior works on power control strategy need to estimate all users’ channel state information (CSI), which consumes both spectrum and time. Two efficient and low-complexity power control strategies, namely quality of experience (QoE) based power control scheme and distance based power control strategy, are proposed for an ambient backscatter based spectrum-sharing network. In the proposed power control schemes, there is no need to estimate all users’ CSI. In the QoE-based power control strategy, only the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> primary users with the highest priority feedback their CSI. We introduce an attenuation factor to reduce the transmit power to satisfy the interference threshold on primary users. Then, considering the short transmission distance of secondary backscatter communication and randomly distributed primary users, we propose the distance-based power control scheme, in which only the users within the backscatter distance need to feedback their CSI. Closed-form expressions for the outage probabilities of primary and secondary systems are derived over the Nakagami- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${m}$ </tex-math></inline-formula> channels under the proposed two power control strategies. The system energy efficiency are also analyzed. Simulation results are conducted to verify the analytical results. Finally, outage performance and energy efficiency of the proposed schemes are compared with that of the existing nearest- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> users based power control strategy. It is shown that the proposed power control strategies have lower outage probabilities and higher energy efficiency.

Multiantenna Multisource Multirelay Spectrum Sharing Networks: Buffer-Aware Direct Link Activation for Higher Reliability and Lower Overhead

Cooperative relaying can be implemented in spectrum sharing networks to extend the range of reliable communication. In this paper, we incorporate multiple-antenna technology and buffer-aided relaying to guarantee a highly reliable connectivity for the secondary network with several source nodes. The multi-antenna configuration for the sources and destination nodes suggests that there are several potential source-to-destination channels which can be auspicious for the network in two ways. First: to balance up the buffer states. Second: to expand the link selection opportunity at each time step. Motivated by this rationale, we propose a buffer-aware communication protocol to incorporate the direct transmissions along the relaying links without incurring excess overhead for circulation of channel-state-information (CSI). Considering Nakagami-m fading, we derive closed-form expressions for the end-to-end ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ete</i> ) outage probability and average packet delay of the secondary network under the proposed protocol. Through Monte-Carlo simulations, we investigate the influential network parameters and evaluate the proposed technique in comparison to two benchmark schemes, one with buffer-based link-prioritization and one without prioritization. Findings demonstrate that the proposed protocol outperforms both benchmarks in terms of outage probability and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ete</i> delay, especially as the number of nodes scales up. However, the superior performance comes at the cost of more CSI circulation. Furthermore, it is shown that if the global CSI cannot be collected accurately, then the dependency of the link selection on the global CSI should be relaxed to mitigate the performance loss. The theoretical and Monte-Carlo results coincide in several simulation examples, verifying the presented theoretical analysis.

Full-Duplex Non-Orthogonal Multiple Access Cooperative Overlay Spectrum-Sharing Networks With SWIPT

This article proposes a novel non-orthogonal multiple access (NOMA) assisted cooperative spectrum-sharing network, in which one of the full-duplex (FD) secondary transmitters (STs) is chosen among many for forwarding the primary transmitter's and its own information to primary receiver and secondary receivers, respectively, using NOMA technique. To stimulate the ST to conduct cooperative transmission and sustain its operations, the simultaneous wireless information and power transfer (SWIPT) technique is utilized by the ST to harvest the primary signal's energy. In order to evaluate the proposed system's performance, the outage probability and system throughput for the primary and secondary networks are derived in tight closed-form approximations. Further, the sum rate optimization problem is formulated for the proposed cooperative network and a rapid convergent iterative algorithm is proposed to obtain the optimized power allocation coefficients. Numerical results show that FD, SWIPT, and NOMA techniques greatly boost the performance of cooperative spectrum-sharing network in terms of outage probability, system throughput, and sum rate compared to that of half-duplex NOMA and the conventional orthogonal multiple access-time division multiple access networks.

Full-Duplex Non-Orthogonal Multiple Access Cooperative Spectrum-Sharing Networks With Non-Linear Energy Harvesting

In this paper, we analyze the performance of a non-orthogonal multiple access (NOMA) cognitive relay system, where a multi-antenna full-duplex cognitive transmitter employs NOMA concept to assist the transmission from a wireless-powered primary transmitter to its corresponding receiver, while simultaneously communicating with a cognitive receiver. A practical non-linear energy harvesting (EH) model, which taking into account harvester's sensitivity and saturation effects is considered. We propose an optimum beamforming design at the cognitive transmitter such that the rate of cognitive network is maximized, under a constraint that the rate of the primary network is above a certain threshold. Results show that proposed optimization framework can substantially enlarge the rate region toward both primary and secondary networks. Furthermore, in order to characterize the network delay-constrained throughput, tractable outage probability expressions for primary and secondary networks assuming sub-optimum zero-forcing based beamforming scheme are derived. Our results reveal that due to required minimum power for harvesting operation as well as saturation of the harvested power at high transmit power levels, conventional linear EH model may lead to performance mismatches for practical non-linear EH circuits in both low and high transmit power regimes.

Throughput Maximization in Uncooperative Spectrum Sharing Networks

Throughput-optimal transmission scheduling in wireless networks has been a well considered problem in the literature, and the method for achieving optimality, MaxWeight scheduling, has been known for several decades. This algorithm achieves optimality by adaptively scheduling transmissions relative to each user’s stochastic traffic demands. To implement the method, users must report their queue backlogs to the network controller and must rapidly respond to the resulting resource allocations. However, many currently-deployed wireless systems are not able to perform these tasks and instead expect to occupy a fixed assignment of resources. To accommodate these limitations, adaptive scheduling algorithms need to interactively estimate these uncooperative users’ queue backlogs and make scheduling decisions to account for their predicted behavior. In this work, we address the problem of scheduling with uncooperative legacy systems by developing algorithms to accomplish these tasks. We begin by formulating the problem of inferring the uncooperative systems’ queue backlogs as a partially observable Markov decision process and proceed to show how our resulting learning algorithms can be successfully used in a queue-length-based scheduling policy. Our theoretical analysis characterizes the throughput-stability region of the network and is verified using simulation results.

Secure Cooperative Transmission for Mixed RF/FSO Spectrum Sharing Networks

This paper is concerned with the secrecy rate based optimization problems in a mixed radio frequency (RF) / free space optical (FSO) spectrum sharing network, wherein multiple single-antenna secondary users (SUs) are connected to a decode and forward (DF) single-antenna relay through RF links and the relay is connected with the secondary destination through an FSO link. The RF and FSO channels are assumed to follow Rayleigh and Gamma-Gamma distributions with the effect of pointing errors, respectively. The three schemes, i.e., direct transmission, single-user cooperative jamming and multi-user cooperative beamforming jamming, are proposed to improve the physical-layer information security in the presence of a single-antenna eavesdropper. The mutual interference between the primary and secondary networks is considered. The problems are to jointly optimize the SU transmit power and jamming power for the best secrecy performance under both the RF and FSO dominant cases. Such problems are nonconvex. The Dinkelbach approach is adopted to solve the optimization in the direct transmission and single-user cooperative jamming schemes and a two-level optimization approach with semi-definite relaxation (SDR) is applied to obtain the solution for the multi-user cooperative beamforming scheme. Moreover, the SDR optimality is proved by Karush-Kuhn-Tucker conditions analysis. Simulation results are provided, and the results show that the proposed multi-user cooperative beamforming jamming can attain the higher achievable secrecy rate than the zero-forcing beamforming scheme and other two suboptimal designs.

Robust Design of Spectrum-Sharing Networks

In spectrum-sharing networks, primary users have the right to preempt secondary users, which can significantly degrade the performance of underlying secondary users. In this paper, we use backup channels to provide reliability guarantees for secondary users. In particular, we study the optimal white channel assignment that minimizes the amount of recovery capacity (i.e., bandwidth of backup channels) needed to meet a given reliability guarantee, where both deterministic and probabilistic requirements are considered. This problem is shown to be coupled by two NP-hard objectives. We characterize the structure of the optimal assignment and develop bi-criteria approximation algorithms. Moreover, we investigate the scaling of the recovery capacity as the network size becomes large. It is shown that the recovery capacity is negligible as compared to the total traffic demands in a large-scale network.

SIR Statistics and Average Rates in Cooperative Spectrum-Sharing Networks

In this paper, we analyze cooperative wireless primary networks operating under randomly located interfering nodes (secondary networks). Applying Poisson point processes to modeling of network and interfering node locations, we derive the statistics of signal-to-interference ratio (SIR) under different operational scenarios and show that the SIR statistical models can be viewed as special cases of the H-function distribution. On this basis, we obtain formulas for the average information rates. The presented results are general, and they are applicable to arbitrary fading conditions.

A Secure Wireless Information and Energy Cooperation Transmission Strategy in Spectrum Sharing Networks With Untrusted Dual-Relay

Spectrum efficiency, energy efficiency, and physical layer security are three critical issues in designing wireless networks, such as an energy-constrained device-to-device (D2D) communication in secure spectrum sharing femtocell networks. In this paper, we investigate a problem of security cooperation transmission between a single-antenna primary system and a multi-antenna wireless-powered untrusted secondary system, where the untrusted secondary devices can be regarded as potential malicious decoders. A novel artificial noise-aided (AN-aided) joint time division- and power splitting-based three-phase secure wireless information and energy cooperation transmission strategy is proposed for spectrum sharing networks with untrusted cooperative dual-relay. Furthermore, we consider two scenarios that the untrusted secondary system knows perfect and imperfect channel state information (CSI). We focus on the design of time division ratios, power splitting ratios, and beamforming vectors, with the objective to maximize the data rate of the untrusted secondary system, subject to the target data rate requirement of the primary system and the untrusted secondary system's confidentiality constraints, energy harvesting requirements, and power consumption constraints. Simulation results demonstrate that our proposed strategy is the best and significantly improves the average data rate of the untrusted secondary system under different primary user target data rate requirements, primary transmitter rated transmit power, untrusted secondary user initial power, and primary transmitter power allocation ratios. Finally, a large number of simulations show that the time division ratios have a significant impact on the performance of the system, and these simulation results also verify the feasibility and effectiveness of the proposed strategy.

Simultaneous Wireless Information and Power Transfer for Dynamic Cooperative Spectrum Sharing Networks

In this paper, we provide a comprehensive performance analysis of simultaneous wireless information and power transfer (SWIPT) for cognitive relay networks with different relay schemes. In the considered system, the energy-constrained secondary transmitter harvests the energy from the primary signal and then employs the harvested energy to forward the primary signal along with the secondary signal simultaneously. To improve the spectral efficiency, we propose a novel cooperative spectrum sharing protocol with dynamic time-slot allocation based on energy harvesting, namely, dynamic time-power-based cooperative spectrum sharing protocol. Considering the delay-limited transmission mode, we analytically derive the exact closed-form expressions of outage probabilities and achievable throughput for both the primary and secondary networks with amplify-and-forward and decode-and-forward relaying schemes, respectively. More importantly, different from the existing works, we take into account the power outage probability at the energy-constrained secondary transmitter to better match the reality. Finally, the numerical results are provided to evaluate the effect of different key parameters on the system performance, which demonstrate that the dynamic cooperative spectrum sharing protocol improves the outage performance compared with the uniform time-slot allocation scheme.

Performance Analysis of Collaborative Beamforming With Outdated CSI for Multi-Relay Spectrum Sharing Networks

Prior works on performance analysis for cognitive radio networks often assume perfect channel state information (CSI), which may not be readily available. This paper investigates the effects of the outdated CSI on the performance of a dual-hop multi-antenna multi-relay spectrum sharing system. To exploit the benefits of available multiple antennas, collaborative zero-forcing beamforming is considered at the secondary user (SU) source node with the outdated CSI and maximum ratio combining diversity reception at the destination node. The $N$ th best relay selection strategy is adopted at the relays. Analytical outage probability and bit-error rate expressions are derived for the SU. Moreover, we examine the high signal-to-noise ratio regime and present closed-form expressions for the asymptotic outage probability and asymptotic bit-error rate with and without feedback delay. In addition, we derive the closed-form ergodic capacity expression for the special case of our considered system, and analyze the effects of delay on the capacity. Furthermore, the closed-form outage probability expression for the primary user is obtained and the impact of delay on the interference on the primary user is investigated. Monte Carlo simulations are carried out to verify our analysis.

Prolonging User Battery Lifetime Using Green Communication in Spectrum Sharing Networks

In this letter, a zonal-based approach is proposed for a spectrum sharing (SS) network, with the primary transmitter (PT) forming device-to-device (D2D) communication links with multiple primary receivers (PRs), in contemplation of green communication. The transmission power of the PT is iteratively optimized within a zone, such that it is adequate to meet the target rates of the applications demanded by the PRs. This results in lower energy consumption at the PT, thus prolonging its battery lifetime. If the transmission power at the PT is insufficient to meet the target rates over the PT $\rightarrow$ PR D2D links, the PT relays information through a suitable secondary transmitter (ST) to guarantee the quality of service (QoS) in the network. The ST acts as an amplify-and-forward (AF) relay for forwarding the primary information and achieving the target rates. The ST selection is based on its remainder transmission power level and the PT $\rightarrow$ ST channel states. The performance of the proposed scheme, in terms of energy efficiency (EE) and battery lifetime, is demonstrated through simulations.

An Efficient Transmit Power Control Strategy for Underlay Spectrum Sharing Networks With Spatially Random Primary Users

With the ever-increasing spectrum requirements for transmitting explosively growing mobile data, spectrum-efficient solutions need to be integrated into future mobile networks. Spectrum sharing enables the primary system to share licensed spectrum with the secondary system. Thus, it is conceived as an appealing solution for improving spectrum usage to eliminate the spectrum supply-demand gap. In this paper, we develop an efficient transmit power control strategy for underlay spectrum sharing networks with spatially Poisson-distributed primary users. A distinguishing feature of the proposed strategy is that it only requires channel state information and location information of a few primary users close to the secondary transmitter, rather than those for all primary users. Furthermore, we evaluate the outage performance of the secondary system and the interference situation of the primary system under this kind of transmit power control strategy. Numerical results demonstrate that the proposed transmit power control strategy can achieve near-optimal outage performance compared to the perfect power control strategy, while reducing the control complexity and the feedback burden significantly at the same time.

Spectrum Sharing Network With Wireless Energy Harvesting at Finite Blocklength Regime

In this paper, a spectrum sharing communication system with wireless energy harvesting is investigated at finite blocklength regime over Rayleigh quasi-static block-fading channels. We analyze the error probability and average delay of the secondary user (SU). The closed-form approximations for the SU error probability and average delay are derived, as functions of the number of channel uses in its information transfer phrase. Under the error probability constraint of the primary user (PU), we investigate the power constraint on the SU. Meanwhile, the error probability and energy supply constraints on the SU are also explored. Numerical results demonstrate that the approximation is very tight for a wide range of signal-to-noise ratio (SNRs). The existence of an optimum number of channel uses for SU information transfer is also verified. Moreover, under the error probability constraint of PU, the SU maximum transmit power is validated to increase with the length of an entire block. In addition, for a given target error probability, we show that the SU error probability constraint can be satisfied within the boundary numbers of channel uses in its information transfer phrase. Finally, the energy supply probability is shown as the harvested energy in each channel use with independent and exponential distribution.

Outage and Diversity Analysis of Underlay Cognitive Mixed RF-FSO Cooperative Systems

We investigate the performance of asymmetric radio frequency (RF) and free-space optical (FSO) dual-hop cognitive amplify-and-forward relay networks where RF links are subject to independent and nonidentically distributed Nakagami-m fading. We consider that the RF link transmitter and receiver are secondary users of an underlay cognitive network. Specifically, the transmit power conditions of the proposed spectrum-sharing network are governed by either the combined power constraint of the interference on the primary network and the maximum transmission power at the secondary network, or the single power constraint of the interference on the primary network. Also, we consider a double generalized gamma fading channel with pointing error and both heterodyne and intensity modulation/direct detection methods in the FSO link. The closed-form and asymptotic expressions of outage probability for this system are calculated for fixed gain and channel-state-informationassisted relaying techniques. It is demonstrated that the diversity order is a function of the fading severity of the RF link, turbulence parameters of the FSO link, and pointing error, regardless of the interference channel parameter of the primary user. However, the coding gain is impressed by the interference link parameter and RF-FSO links parameters. The diversity-multiplexing trade-off analysis is done for this network, where we show that this trade-off is independent of the primary network.

On Spectrum Trading for 5G Cognitive Spectrum Sharing Networks with Hybrid Access: A Game-Theoretic Approach

Cognitive radio (CR) networks employing dynamic spectrum access have been proposed in the framework of enabling 5G wireless networks to enhance efficient use of spectrum resources. Communication requirements with regard to spectrum in 5G networks demand dynamic spectrum access giving rise to new types of spectrum markets and spectrum trading issues. Cognitive secondary users (SUs) may employ opportunistic spectrum access (OSA) to access vacant frequency bands (FBs) primarily allocated to primary users provided that they do not cause interference. Moreover, the SUs can employ exclusive spectrum access (ESA) in FBs leased at a certain price. In this work, different types of spectrum operators (SOs) are considered with regard to the type of spectrum access offered to SUs. A novel two-stage spectrum access and pricing game is proposed for two scenaria, namely: (1) a duopoly comprising an opportunistic SO and an exclusive SO and (2) a monopoly of a hybrid SO offering both ESA and OSA. In the first stage of the game, non coordinated SUs choose the access option that maximizes their utility. This symmetric N-SU spectrum access selection game has a unique mixed strategy equilibrium which depends: (1) on the prices set by the SOs in either the duopoly or the monopoly examined and (2) on the bandwidth available to the SUs under each scenario. In the second stage of the game, the bandwidth-pricing policy planned by the SOs is determined as the solution to an optimization problem maximizing the SOs revenues at the SUs equilibrium. Two algorithms are proposed to solve the optimization problems arising in each scenario examined. The numerical results obtained under the two spectrum market scenaria demonstrate how the proposed two-stage spectrum access and pricing scheme behaves for various network parameters.

Performance analysis of SIMO spectrum sharing networks over correlated [formula omitted]-[formula omitted] shadowed fading relying on MRC reception

The real-world wireless channels are accurately modeled by the composite multipath fading and shadowing channel models. The performance of a typical cognitive spectrum sharing (SS) network under a composite fading and shadowing model is rarely analyzed, and hence, needs considerable attention. In this paper, a cognitive SS network is considered having multiantenna at the secondary/cognitive receiver (SR), and the signals received at different antennas are combined using maximal ratio combining scheme. The channels at SR are considered to be spatially correlated κ-μ shadowed distributed. The analytical expressions for the outage probability and the ergodic capacity are derived under peak interference power constraint (PIPC) of the primary receiver (PR). It is shown that the performance of the SS network degrades as the spatial correlation increases at SR. It is also observed that the severity of fading/shadowing at the interfering link is favorable to the secondary user’s communication up to a certain value of PIPC of PR.