We address the throughput maximization problem for downlink transmission in DF-relay-assisted cognitive radio networks (CRNs) based on simultaneous wireless information and power transfer (SWIPT) capability. In this envisioned network, multiple-input multiple-output (MIMO) relay and secondary user (SU) equipment are designed to handle both radio frequency (RF) signal energy harvesting and SWIPT functional tasks. Additionally, the cognitive base station (CBS) communicates with the SU only via the MIMO relay. Based on the considered network model, several combined constraints of the main problem complicate the solution. Therefore, in this paper, we apply heuristic guidelines within the convex optimization framework to handle this complexity. First, consider the problem of maximizing throughput on both sides of the relay separately. Second, each side progresses to solve the complex problem optimally by adopting strategies for solving sub-problems. Finally, these optimal solutions are synthesized by proposing a heuristic iterative power allocation algorithm that satisfies the combinatorial constraints with short convergence times. The performance of the optimal proposed algorithm (OPA) is evaluated against benchmark algorithms via numerical results on optimality, convergence time, constraints’ compliance, and imperfect channel state information (CSI) on the CBS-PU link.

Either natural or man-made a disaster is defined as unexpected destructive event that causes damages and malfunction of existing systems and services all around the disaster area, these destructive effects are unfortunately beyond the capability of local authorities to recover and respond immediately, the disaster recovery plans are immediately initiated so that rescue and aid operations can help those who are trapped in disaster area to survive, those efforts need to be controlled and coordinated with reliable communication systems that are more likely partially or fully disabled due to the disaster, the capabilities of cognitive radio technology enables it to play a significant role in providing efficient communication services for the rescue teams and headquarters as well as trapped victims, in this paper, we survey the cognitive radio architectures that can replace the Software Defined radio SDR in order to reduce the network expenses in terms of network size and network computational complexity.

cognitive radio is a revolutionary technology that made significant progress in the effective use of the frequency spectrum. The technology itself can be dynamically adjusted so that the proper utilization of the available radio spectrum can be made. According to various studies conducted, it is observed that the bulk of each frequency band allocated to users leaving unused. The cognitive radio can use these parts of the spectrum that called spectrum holes.Inherent nature of this technology creates the chance for the attacker in these networks. This vulnerability that created due to the inherent nature of cognitive radio technology, Can severely impact on the safety and quality of service in these networks. In this paper, we focus on the primary user emulation attack. In this attack, an adversary transmits signals whose characteristics emulate those of incumbent signals. We proposed the method for reducing the effects of primary user emulation attacks in cognitive radio networks. This method suggests the technique that can merge with spectrum sensing method and can resistant these networks against the primary user emulation attacks. Finally, with run some simulation, we examined the performance of this proposed method in detection of primary user emulation attacks in these networks.

Ever increasing development of wireless devices and wireless networks have increased the value of spectral space. Many efforts have been conducted to increase spectral utilization. The radio environment mapping opens new gates for developing low cost wireless devices. In this paper, a new method is proposed for increasing spectral utilization in distributed networks. In this method distributed Kalman filter, which is modified to increase estimation accuracy, is used to estimate position, velocity and power of primary transmitters. These data are used to select spectrum holes optimally and increase spectral utilization compared to centralized methods. Obtained r esults are evaluated through practical implementations and simulations. Innovations of this research include introducing and employing a linear model for estimating position of a transmitter using received power in line of sight (LoS) and non-line of sight (NLS) conditions, modifying extended kalman filter and implementation of distributed spectrum sensing; advantages of this method are illustrated compared to centralized methods.

The lack of frequency, low utilization and static allocation of spectrum have been important problems in wireless network in prior methods. To solve this problem, a concept called cognitive radio Network was introduced to allow the use of empty spaces of licensed spectrum. The purpose of this paper was to provide an intelligent method for detecting and allocating spectrum in cognitive radio network. In this method, Hidden Marcov model is used to predict the status of free or occupied channels, then some types of learning automata are used to allocate channel to secondary users. Also, it is a way to reduce the waiting time of users who were simultaneously requesting a channel to use a mechanism for fairness in this algorithm. The simulation results indicated that the proposed method is more effective in channel allocation to secondary users thanks to using the proposed mechanisms whose results have a greater convergence speed.

Interference Alignment is an efficient method of reducing interference in wireless networks, which can be used in radio cognitive networks. In the interference alignment, a suitable pre-encoder matrix will be found in each transmitter that all interferences are limited to a part of the signal subspace in each receiver, which causes the desired signal to be placed in the other part. Therefore, the desired signal can be easily received by a suitable interference removal filter. In this paper, an efficient method for using interference homogeneity in a cognitive radio network is presented. In the proposed method, the selection of radiation vectors for the formation of selection vectors based on adjacent vectors is done in equal steps. Selecting equal steps improves the convergence speed of the algorithm. The results show that computational efficiency and complexity have been greatly improved. To evaluate the proposed method of power allocation in the network, they are evaluated to maximize the network energy efficiency and the other to maximize the total rate of the cognitive radio network while keeping the initial user rate at the threshold level. The simulation results reveal the improvement of network performance using this method in both strategies.

In this paper, a new joint admission and power control scheme is introduced for wireless cognitive radio networks. It is assumed that the cognitive Users (CUs) arrive sequentially in time and exploit the spectrum simultaneous to the licensed primary users. The objective is to minimize the blocking probability of the new arriving CUs while the interference limit constraint of primary users is not violated and the quality of service (QoS) requirements of the current admitted CUs is satisfied.To these aims, an algorithm is developed for CUs admission in which the power of the new arriving CU gradually increases according to two predefined parameters, Primary Interference Margin (PIM) and Secondary Interference Margin (SIM). In addition to protect the QoS of the current CUs, their powers are boosted by a particular parameter, which is calculated based on PIM and their maximum allowable power. Moreover, the PIM guarantees the protection of the primary users during the admission phase of the new arriving CU. Two admission control algorithms have been proposed, a safe admission which tightly admits a new CU and a moderate one which loosely accepts a new CU. Simulation results are provided to evaluate the performance of the proposed algorithms in terms of the blocking and outage probability and compared with recent proposed schemes.These results show that the proposed algorithms outperform the similar schemes while they are more suitable for a practical scenario.