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To enhance the spectrum scarcity of cooperative heterogeneous networks (HetNets) with unreliable backhaul connections, we examine the impact of cognitive spectrum sharing over multiple small-cell transmitters in Nakagami-m fading channels. In this system, the secondary transmitters are connected to macro-cell via wireless backhaul links and communi...
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Citations
... In AF, the relay amplifies the received signal, and then transmits the amplified signal to the destination. Cognitive radio (CR) is a rising technology that can address the spectrum inadequacy challenge, it exploits the assigned spectrum by unlicensed users or secondary users (Sus) [4][5][6][7][8][9][10]. The system performance of the secondary network was analyzed and discussed in multi-hop relaying networks [4,5], heterogeneous networks with unrelia-ble backhaul connection [6], and the cognitive cooperative non-orthogonal multiple access (NOMA) networks [7,8]. ...
... Cognitive radio (CR) is a rising technology that can address the spectrum inadequacy challenge, it exploits the assigned spectrum by unlicensed users or secondary users (Sus) [4][5][6][7][8][9][10]. The system performance of the secondary network was analyzed and discussed in multi-hop relaying networks [4,5], heterogeneous networks with unrelia-ble backhaul connection [6], and the cognitive cooperative non-orthogonal multiple access (NOMA) networks [7,8]. The authors in [9] considered the impact of imperfect channel state information on the system performance in the cooperative cognitive radio network. ...
In this paper, the authors investigate secrecy outage performance of a vehicular cognitive relaying network consisting of a stationary primary user, a secondary mobile source, a secondary mobile destination, and a secondary mobile relay. To evaluate the performance, we derive the exact and approximate closed-form expressions for secrecy outage probability in two cases: one involving a stationary eavesdropper and one involving a mobile eavesdropper. We use a Monte Carlo simulation to verify our mathematical analysis. The results show that the secrecy outage performance is improved when the distances between the primary user, the eavesdropper, and the secondary source and relay are increased. Additionally, increasing the secrecy target rate of the system by increasing the interference levels of the primary network improves the system's performance.
... In underlay CRNs, secondary users are permitted to utilize the spectrum allocated to primary users as long as the interference they cause to primary users is tolerable, hence overall capacity can be improved. In heterogeneous CRNs, * Cheng Yin Email: cyin01@qub.ac.uk the effect of backhaul unreliability on the system performance has been presented [5][6][7][8]. In [5], a single small cell acting as a secondary transmitter was considered. ...
... In [5], a single small cell acting as a secondary transmitter was considered. As an extension to [5], multiple small cells acting as secondary transmitters were considered in the system model in [6]. Based on the research in [6], a relay was deployed between the transmitters and the receiver to enhance the coverage in [7]. ...
... As an extension to [5], multiple small cells acting as secondary transmitters were considered in the system model in [6]. Based on the research in [6], a relay was deployed between the transmitters and the receiver to enhance the coverage in [7]. The author in [8] considered both multiple small cells as well as multiple primary users and this scenario was more practical and realistic than the system models in [5][6][7]. ...
This paper presents a comprehensive model including a wireless backhaul as a cost-effective backhaul alternative to wired backhaul for vehicular networks, a heterogeneous underlay cognitive vehicular network with multiple mobile secondary transmitters acting as mobile small cells, a mobile secondary receiver and a mobile primary user. To increase the spectrum utilization in this proposed vehicular network, multiple mobile secondary transmitters forward the signal to a mobile secondary receiver while using the same spectrum with a mobile primary user on the condition that the interference caused by secondary transmitters is tolerable at the primary user. A Bernoulli process is applied to model wireless backhaul reliability. The analytical closed-form expressions for outage probability as well as the asymptotic expression are derived to reveal the effects of backhaul reliability on the network performance over double-Rayleigh fading channels.
... In [14], the impact of the primary network on the secondary network is investigated when the primary transmitter is close to the 3 secondary transmitter or further away. Impacts of unreliable backhaul links on the cooperative HetNets in spectrum sharing environment is studied in [15]. ...
... Other important aspects of such network were missing. For example, [15], [19], [20], [34] only considered interference on the primary network and neglected interference at the secondary network from primary users. ...
We investigate the secrecy performance of an underlay small-cell cognitive radio network under unreliable backhaul connections. The small-cell network shares the same spectrum with the primary network, ensuring that a desired outage probability constraint is always met in the primary network. {To improve the security of the small-cell cognitive network, we propose three sub-optimal small-cell transmitter selection schemes,} namely sub-optimal transmitter selection, minimal interference selection, and minimal eavesdropping selection. Closed-form expressions of the non-zero secrecy rate, secrecy outage probability, and ergodic secrecy capacity are provided for the schemes along with asymptotic expressions. {We also propose an optimal selection scheme and compare performances with the sub-optimal selection schemes.} {Computable expressions for the non-zero secrecy rate and secrecy outage probability are presented for the optimal selection scheme.} Our results show that by increasing the primary transmitter's power and the number of small-cell transmitters, the system performance improves. The selection scheme, the backhaul reliability, and the primary user quality-of-service constraint also have a significant impact on secrecy performance.
... As such, frequency sharing using a CR network is essential to increase the capacity and spectral efficiency of the system. The authors in [10] studied the impact of unreliable backhaul links on cooperative HetNets in a CR environment. The authors in [11] proposed various relay selection schemes and multiuser scheduling for cognitive networks with unreliable backhaul links. ...
... The authors in [12] studied the performance of the best relay selection scheme in cognitive HetNets in the presence of unreliable backhaul connections. However, the authors in [10]- [12] neglected the interference to the secondary network and only considered the interference to the primary network, without any secrecy constraint. ...
A small-cell network with multiple transmitters and unreliable wireless backhaul is considered for secrecy enhancement. The small-cell network is operating under a spectrum sharing agreement with a primary network in a cognitive radio system. A constraint on the desired outage probability at the primary receiver is assumed as a part of the spectrum sharing agreement. The reliability of the wireless backhaul links are modeled by a set of independent and identically distributed Bernoulli random variables. A sub-optimal and an optimal small-cell transmitter selection (TS) scheme is proposed to improve the performance of the system, depending on the availability of channel state information. Selection schemes are designed for the scenario where knowledge is available regarding which backhaul links are active. The corresponding secrecy outage probabilities along with their asymptotic expressions are derived. It is shown that the secrecy performance is significantly improved compared to the case where knowledge of the active backhaul links is unavailable.
... As such, frequency sharing using a CR network is essential to increase the capacity and spectral efficiency of the system. The authors in [10] studied the impact of unreliable backhaul links on cooperative HetNets in a CR environment. The authors in [11] proposed various relay selection schemes and multiuser scheduling for cognitive networks with unreliable backhaul links. ...
... The authors in [12] studied the performance of the best relay selection scheme in cognitive HetNets in the presence of unreliable backhaul connections. However, the authors in [10]- [12] neglected the interference to the secondary network and only considered the interference to the primary network, without any secrecy constraint. ...
A small-cell network with multiple transmitters and unreliable wireless backhaul is considered for secrecy enhancement. The small-cell network is operating under a spectrum sharing agreement with a primary network in a cognitive radio system. A constraint on the desired outage probability at the primary receiver is assumed as a part of the spectrum sharing agreement. The reliability of the wireless backhaul links are modeled by a set of independent and identically distributed Bernoulli random variables. A sub-optimal and an optimal small-cell transmitter selection (TS) scheme is proposed to improve the performance of the system, depending on the availability of channel state information. Selection schemes are designed for the scenario where knowledge is available regarding which backhaul links are active. The corresponding secrecy outage probabilities along with their asymptotic expressions are derived. It is shown that the secrecy performance is significantly improved compared to the case where knowledge of the active backhaul links is unavailable.
... In [14], the impact of the primary network on the secondary network is investigated when the primary transmitter is close to the secondary transmitter or further away. Impacts of unreliable backhaul links on the cooperative HetNets in spectrum sharing environment is studied in [15]. ...
... Other important aspects of such network were missing. For example, [15], [19], [20], [34] only considered interference on the primary network and neglected interference at the secondary network from primary users. Backhaul reliability was considered for PLS in [31]- [33], however, not in CR networks. ...
We investigate the secrecy performance of an underlay small-cell cognitive radio network under unreliable backhaul connections. The small-cell network shares the same spectrum with the primary network, ensuring that a desired outage probability constraint is always met in the primary network. To improve the security of the small-cell cognitive network, we propose three sub-optimal small-cell transmitter selection schemes, namely sub-optimal transmitter selection, minimal interference selection, and minimal eavesdropping selection. Closed-form expressions of the non-zero secrecy rate, secrecy outage probability, and ergodic secrecy capacity are provided for the schemes along with asymptotic expressions.We also propose an optimal selection scheme and compare performances with the sub-optimal selection schemes. Computable expressions for the non-zero secrecy rate and secrecy outage probability are presented for the optimal selection scheme. Our results show that by increasing the primary transmitter's power and the number of small-cell transmitters, the system performance improves. The selection scheme, the backhaul reliability, and the primary user quality-of-service constraint also have a significant impact on secrecy performance.
... It will be more practical to deploy several small cells connected to a macrocell to cooperate and achieve better system performance. In [10], a macrocell was transmitting to a secondary user via multiple secondary transmitters (small cells). The transmit power of secondary transmitters was limited by a single PU. ...
... The transmit power of secondary transmitters was limited by a single PU. As an extension to research in [10], a relay was considered to extend the coverage from transmitters to destination in [12]. However, both [10] and [12] considered a simplified scenario where there was only one PU in the system. ...
... As an extension to research in [10], a relay was considered to extend the coverage from transmitters to destination in [12]. However, both [10] and [12] considered a simplified scenario where there was only one PU in the system. As discussed before, a single PU is neither realistic nor sufficient in real scenarios. ...
Wireless backhaul has emerged as a suitable and flexible alternative to wired backhaul, however, it is not as reliable as its wired counterpart. This paper presents for the first time a comprehensive model including a heterogeneous underlay cognitive network with small cells also acting as multiple secondary users, multiple primary users and unreliable wireless backhaul. In this system, a macro-base station connects to multiple secondary transmitters via wireless backhaul links. In addition, multiple secondary transmitters send information to a secondary receiver by sharing the same spectrum with multiple primary users. A Bernoulli process is adopted to model the backhaul reliability. A selection combining protocol is used at the secondary receiver side to maximize the received signal-to-noise ratio. We investigate the impact of the number of secondary transmitters, the number of primary users as well as the backhaul reliability on the system performance in Rayleigh fading channels. Two key constraints are considered on the system performance, namely, 1) maximum transmit power at the secondary transmitters. 2) peak interference power at the primary users caused by secondary transmitters. Closedform expressions for outage probability, ergodic capacity and symbol error rate and the asymptotic expressions for outage probability and symbol error rate are derived. Moreover, closedform expressions are also applicable to non-cooperative scenarios.
... In [20], the authors examined the achievable signal-to-noise ratio (SNR) at the single receiver with two different aggregation schemes, i.e. selection combining and maximum ratio transmission protocol in cooperative systems. To improve the spectrum scarcity, the authors in [21] extended the investigation of unreliable backhaul links on cooperative cognitive networks but neglecting the aids from relaying networks. Focusing on cognitive relay networks, the authors in [22] analysed the whole system performance under the presence of single wireless backhaul links. ...
... • We introduce a framework to investigate the impacts of backhaul reliability [Reliability is a condition of wireless backhaul links, which is affected by delay, channel propagation and synchronisation among transceivers [17]. Since the wireless links are unreliability due to its nature characteristics, the reception status at the receiver side includes success or failure transmission [18,20,21].] on the performance of the energy harvesting systems in cooperative system, where the energy-constrained relay harvests the energy from the selected small-cell transmitter to process its next hop transmission based on TSR protocol [14]. ...
... • Specially, the closed-form expressions of the throughput at the receiver are also attained with two effective transmission schemes: (i) delay-limited transmission and (ii) delay-tolerance transmission. • Different from the recent works on wireless backhaul links [21,22], the non-identical backhaul links as well as independent but not necessarily identically distributed (i.n.i.d.) Nakagami-m fading channels are employed in the system model to provide various practical scenarios [23,24]. Our results show that the backhaul reliability performs an important role on the scaling of the outage probability and the achievable throughput. ...
In this study, the performance of energy harvesting systems in the presence of unreliable backhaul links is investigated over independent but not necessarily identically distributed Nakagami-m fading channels. In particular, the energyconstrained relay uses the amount of harvested energy from the best small-cell transmitter based on time switching-based relaying protocol to process for the next hop transmission. The authors derived the closed-form expressions of the outage probability and the effective throughput with two distinct transmission schemes: (i) delay-limited transmission, and (ii) delaytolerance transmission are attained. In order to assess the impacts of unreliable backhaul links, they thus obtain the asymptotic expression of the outage probability in high signal-to-noise ratio (SNR) regime. The numerical results are conducted to analyse the effects of energy harvesting fraction time, energy efficiency, backhaul reliability, and the fading parameters on the system performance. The authors' results show that under the unreliable backhaul links the outage probability yields the error-floor in the high SNR regime which demonstrates the significant impact of the backhaul unreliability.
... Thus, the transmissions via backhaul links are not intrinsically reliable in the context of wireless communication systems. It has been shown that the presence of unreliable backhaul links strongly deteriorates the network performance since the asymptotic limitation is mainly determined by reliability levels [6], [7]. ...
... For example, the authors in [4]- [6] developed the analytical frameworks to examine the performance of cooperative wireless systems. Additionally, the investigation on backhaul reliability was extended to spectrum sharing environments by considering the primary user interference constraints [7]- [9]. However, without considering the presence of eavesdroppers, the information between the source and destination could be left vulnerable. ...
... Due to the nature of wireless channels, the reception status at the K transmitters is presented by success/failure transmission. Thus, the reliability of the wireless backhaul links follows a Bernoulli process I k , i.e., the message is successfully received at the receivers with a successful probability of λ k [4], [7]. The failure probability is accordingly given by 1 − λ k . ...
In this paper, the impacts of unreliable backhaul links on the secrecy performance of cooperative single carrier heterogeneous networks (HetNets) in the presence of eavesdroppers are investigated. A two-phase transmitter/relay selection scheme is proposed, where the best transmitter is selected to maximize signal-to-noise ratio (SNR) at the relays in the first phase and the best relay is chosen in the second phase to minimize the signal-to-interference-plus-noise ratio (SINR) of the eavesdroppers with the aid of a friendly jammer. Closedform expressions are derived for the secrecy outage probability, probability of non-zero achievable secrecy rate, and ergodic secrecy rate. The asymptotic performance analysis is further performed to explicitly reveal the impacts of unreliable backhaul links on the secrecy performance. Our results show that the diversity gain cannot be achieved in the presence of imperfect backhaul links.
In this paper, the authors investigate secrecy outage performance of a vehicular cognitive relaying network consisting of a stationary primary user, a secondary mobile source, a secondary mobile destination, and a secondary mobile relay. To evaluate the performance, we derive the exact and approximate closed-form expressions for secrecy outage probability in two cases: one involving a stationary eavesdropper and one involving a mobile eavesdropper. We use a Monte Carlo simulation to verify our mathematical analysis. The results show that the secrecy outage performance is improved when the distances between the primary user, the eavesdropper, and the secondary source and relay are increased. Additionally, increasing the secrecy target rate of the system by increasing the interference levels of the primary network improves the system’s performance.
