Saifur Rahman Sabuj

Random cognitive radio network performance in Rayleigh-lognormal environment

Recently, considerable research has been focused on the design of random cognitive radio networks because base stations are randomly located in modern cellular networks and also because of an anticipated shortage of spectrum. This study investigates the performance of cognitive radio networks using a stochastic geometry approach in Rayleigh-lognormal fading. We present a geometric model of cognitive radio networks where primary transmitters, primary receivers, secondary transmitters, and secondary receivers are distributed as a Poisson point process. We analytically derive the coverage probability and transmission rate of that network. Moreover, we obtain closed-form expressions of coverage probability and transmission rate. We then numerically evaluate coverage probability and transmission rate performance. It is shown that for the coverage probability and transmission rate, the results are better for lower densities of primary transmitters and secondary transmitters.

Energy efficiency analysis of cognitive radio network using stochastic geometry

We investigate the energy efficiency with the relation of area spectral efficiency of a cognitive radio network using stochastic geometry approach. Network coverage probabilities are derived for the interference of cognitive transmitters and primary transmitters, with consideration of two important parameters: probability of ideal channel and probability of transmission schedule. Furthermore, we formulate the energy efficiency of this network for both perfect and imperfect detection of primary users and cognitive users. For this energy efficiency analysis, a constant base station power consumption model is used, and network power consumption is taken into account. The probabilities of ideal channel and transmission schedule are crucial parameters which affect both coverage probability and energy efficiency. Simulation results demonstrate that higher probabilities of ideal channel and transmission schedule are significantly more energy efficient than lower probabilities.

Outage and energy-efficiency analysis of cognitive radio networks: A stochastic approach to transmit antenna selection

Cognitive radio networks have recently attracted significant research attention owing to their promise for application in future cellular communication. In this light, given the intense power consumption of wireless networks, considerable research is now being directed at designing random cognitive radio networks with enhanced energy efficiency. In this study, we investigate the outage probability and energy efficiency in a cognitive radio network, modeling the locations of the primary users and cognitive users as a Poisson point process. We derive closed-form expressions for the outage probability and energy efficiency with consideration of the probabilities of unoccupied (not utilized by the primary users) channel selection and successful transmission for imperfect detection in an interference-limited environment of cognitive radio network. Furthermore, we propose a transmit antenna selection method for the cognitive transmitter in such networks and accordingly develop closed-form expressions for the outage probability and energy efficiency. The study reported here highlights the importance of combining the capabilities of unoccupied channel selection and successful transmission in cognitive radio networks to achieve optimal performance regarding outage probability and energy efficiency. In terms of energy efficiency, there is an optimal threshold that maximizes the energy efficiency. For implementation in transmit antenna selection, the outage probability can be significantly decreased by increasing the number of transmit antennas, even though the energy efficiency is maximized at the target outage probability.

Uplink modeling of cognitive radio network using stochastic geometry

Abstract In this study, we investigate the coverage probability and spectral efficiency of a cognitive radio network with a single-tier uplink model based on a stochastic geometry framework. The locations of cognitive transmitters, cognitive receivers, primary transmitters, and primary receivers are modeled as independent Poisson point processes. We derive the mathematical expressions for the coverage probability and spectral efficiency of this network, as well as closed-form expressions for a path-loss exponent equal to 4. For the uplink transmission, truncated channel inversion power control is employed for the cognitive transmitter with a cutoff threshold at the cognitive receiver because of the limited transmission power. We consider two locations of the cognitive receiver (i.e., inside and outside the primary exclusion region) for uplink transmission. We found that the location of the cognitive receiver impacts on coverage probability and spectral efficiency. Numerical analysis confirms that (i) the coverage probability is higher and (ii) the spectral efficiency is higher when the cognitive receiver is outside the primary exclusion region.

Detection of intelligent malicious user in cognitive radio network by using friend or foe (FoF) detection technique

In a cognitive radio network, dynamic spectrum must be shared with an unlicensed user because of the limited bandwidth of the wireless spectrum. As a regulation of cognitive radio networks, a secondary user is allowed to utilize the unoccupied spectrum when it is not being used by the primary user. However, an intelligent malicious user can attack a cognitive radio network and block the permitted channel for the secondary user. The invasion of an intelligent malicious user is a serious problem in the deployment of such networks. In this paper, we introduce a novel scheme based on friend or foe (FoF) detection with physical-layer network coding to detect a secondary user and an intelligent malicious user. The entire cognitive radio network is protected while the secondary user and intelligent malicious user are accurately detected. The effectiveness of the proposed approach is analyzed theoretically and by MATLAB simulation. It is shown that with the FoF detection technique and the proposed algorithm, the base station can detect the secondary user and intelligent malicious user with high accuracy. Computer simulations show that the probability of detection is almost 100% and that the probability of the false alarm is almost 0% for a low Eb/N0. Consequently, the proposed technique can be applied to a cognitive radio network to protect the entire network and ensure appropriate channel utilization by the secondary user.

Performance Analysis of SFBC and Data Conjugate in MIMO-OFDM System over Nakagami Fading Channel

An integration of multiple input and multiple output (MIMO) and orthogonal frequency division multiplexing (OFDM) exploit spatial diversity for high data rate transmission of signals over wireless channel. In this paper, analytical models have been developed to suppress signal to noise plus interference ratio incorporating inter carrier interference and average probability of error with the concept of space frequency block code (SFBC) and data conjugate (DC) over Nakagami-m fading channel. Results show that average probability of error performance of MIMO-OFDM system in Nakagami fading channel decreases if fading parameter m is increased. The performance of SFBC has improved about 3 dB at average probability of error of 10-4 than MIMO-OFDM with DC system.

Energy-Efficiency Maximisation in Random Cognitive Radio Networks

Energy-efficient cognitive radio network has received considerable attention recently because of improving spectrum and energy efficiency. In light of such observations, we present a model for cognitive radio network based on stochastic geometry theory where transmitters and receivers are distributed according to Poisson point process. In this paper, we focus on the optimization problem where energy efficiency is maximized under the constraint of outage probability for primary network and secondary network. We show that the energy efficiency is increased with the increment of threshold for primary network. However, the energy efficiency is maximum for a certain value of threshold in secondary network.

Two-slope path-loss design of energy harvesting in random cognitive radio networks

Abstract There has recently been substantial interest in applying the principles of wireless radio frequency energy harvesting in battery-operated devices to cognitive radio networks. Although implementation of energy harvesting technique increases the complexity of network planning, it reduces battery power usage and enables eco-friendly cognitive radio network. In this paper, we report a comprehensive study of energy harvesting cognitive radio network where locations of users of primary and secondary networks follow a Poisson point process. In the design of random cognitive radio network, we focus on the two-slope path-loss function so as to have a realistic scenario of propagation environments. First, a new expression of outage probability is theoretically derived for secondary receiver in active mode. Second, we obtain an explicit expression of harvested energy for secondary receiver in active and inactive modes. Finally, we investigate the harvested energy maximization problem under a particular outage probability constraint, and also obtain an optimal solution of transmission power and density of secondary transmitters. Numerical results for outage probability, harvested energy, and maximization of harvested energy are presented for evaluation of the performance and characteristics of this network.

Approaches to the dynamic efficiency in wireless communications

The electromagnetic pollution and bandwidth problems in the wireless industry nowadays are considered crucial issues, but both have already been solved by using green communication, which reduces carbon dioxide (CO2) emissions as well as energy consumption, and cognitive radio, which provides high bandwidth to mobile users. This paper proposes and analyzes a new efficiency for future wireless communication, called dynamic efficiency (m.b/s/W or m.b.Hz/s/Hz/W) metrics. The proposed efficiency is design tactic for “cognitive radio” and “green communication” consisting of the monitoring of transmission frequency, power and distance. The dynamic efficiency is either a convex or a concave function depending on the transmission frequency with respect to transmission power and distance. If the transmission frequency is between 82.37 MHz and 657.35 MHz, dynamic efficiency function is convex; otherwise it is concave.

Reduction of ICI in MIMO-OFDM system using self-cancellation with space frequency block code

In the MIMO-OFDM system, the carrier frequency offset and phase noise cause loss of orthogonality among subcarriers and leads to intercarrier interference (ICI). This paper considers ICI self-cancellation schemes using space frequency block code (SFBC) in MIMO-OFDM system. In this paper we have analytically derived expression for common phase error (CPE), ICI, carrier to interference (CIR) and BER of the system. The performance of the system in the presence of frequency offset and phase noise has been evaluated in terms of BER. Results show that BER of SFBC can be increased when normalized frequency offset increases. The BER performance for SFBC in MIMO-OFDM system has been reduced about 3.8 dB at BER of 10−8 respectively than OFDM system.