Binod Prasad

Outage performance of cognitive relay network with imperfect channel estimation under proactive DF relaying

Spectrum sharing in cognitive radio network helps to improve the spectrum utilization. In underlay spectrum sharing model, the secondary users (SU) are allowed to share the licensed spectrum of the primary user (PU) without degrading the performance of PU significantly. The SU needs to obtain channel state information (CSI) of the channel between its transmitter and primary receiver which may be imperfect. Due to this imperfect CSI, transmission of SU may cause excess interference to the primary receiver. In this paper outage performance of SU in a cognitive relay network (CRN) based on underlay spectrum sharing model using proactive decode-and-forward relaying scheme is studied. We assume that the CSI of the interfering links, i.e. links from both the secondary transmitter and secondary relays to the primary receiver is imperfect. The transmit power of SU is controlled by imposing a scaling factor so as to reduce the excessive interference due to imperfect CSI. A closed form expression for the outage probability of SU in absence as well as in presence of PU interference is also derived over Rayleigh faded channel under the constraint of PU outage and verified through simulation. Further, the effect of PU interference on outage probability of SU has been studied under a PU outage constraint. We highlight the effects of imperfect CSI, interference threshold, number of relays, and the PU interference on the outage probability of SU.

Performance of Cognitive Radio Network with Novel Hybrid Spectrum Access Schemes

In this paper two novel spectrum access schemes, a hybrid spectrum access scheme (HSAS) and a modified hybrid spectrum access scheme (MHSAS) combining underlay and overlay, are proposed to enhance the performance of cognitive radio (CR) enabled secondary user (SU) in terms of throughput and outage probability in a CR network. The CR employs an energy detection to detect the presence of primary user (PU). If PU is sensed to be present, the CR employs an underlay scheme of co-existence while the CR works in an overlay mode if the PU is sensed to be absent. In underlay mode, the transmit power of CR is controlled so as to maintain the interference at PU receiver within a tolerable limit. An imperfect CSI of the interfering link between CR transmitter and PU receiver is assumed. In HSAS, CR transmits either in underlay scheme or in overlay scheme only during the transmission phase of the detection cycle whereas in MHSAS, the CR transmits for the entire frame including the sensing period of a detection cycle. Closed form analytical expressions for the throughput and outage of CR have been developed. Impact of several sensing parameters such as sensing time, channel estimation error, tolerable interference threshold, maximum allowable transmit power of CR is investigated. The impact of collision probability on the performance of CR network due to re-arrival of PU under proposed scheme is investigated. Furthermore the performances of the proposed schemes are also compared with the conventional i.e. only underlay or only overlay schemes. Our schemes are found to outperform the conventional schemes, in terms of secondary performance.

Outage performance of SU under spectrum sharing with imperfect CSI and primary user interference

Cognitive radio refers to smart technology aims to improve the spectrum utilization and alleviate the spectrum shortage by allowing the secondary user (SU) (unlicensed user) to share the existing spectrum allocated to primary user (PU). In spectrum sharing approach secondary users are allowed to access the same spectrum used by primary user provided the interference produced at PU receiver due to SU transmission remains below the predefined interference threshold defined for the PU. We consider the channel state information available at SU transmitter of the interfering link i.e. link from SU-Tx to PU-Rx is imperfect. The SU estimates its transmit power based on CSI of interfering link if PU is present, while it transmits with maximum power Pm in absence of PU. In this paper we assume the CSI available, based on MMSE estimation, at SU-Tx is imperfect. We derive closed form expression of the outage probability of SU over Rayleigh faded channel with imperfect CSI of link between SU Transmitter and PU Receiver for a given outage constraint of PU. We also studied the impact of PU interference, channel estimation error, tolerable interference threshold, and acceptable limit of PU outage on SU performance. A MATLAB based simulation has also been carried out to support the analytical result.

Novel features and a cascaded classifier based Arabic numerals recognition system

Individuality of handwriting inserts varying curvatures and angles whenever someone writes a sample of a particular numeral which makes the task of its off-line recognition more challenging. The paper addresses both these issues in novel and robust ways by merging two Digital domains, namely Digital Communications and Digital Image Processing. Curvature is treated by finding analytical features based on distance and slope. Distance based treatment is done by means of Delta Distance Coding whereas slope based analysis is executed with Delta Slope Coding. Angular variations have been countered with the help of rotation invariant physical feature i.e., Pixel Moment of Inertia. A due stress has been laid on Pixel Moment of Inertia by finding it both globally and locally in terms of Centroidal Moment of Inertia and Zonal Moment of Inertia respectively. The above mentioned features are further supported with statistical features in order to differentiate very similar looking numeral pairs like (3, 8), (1, 7), (7, 9). Feature extraction methods are devoid of cumbersome calculations, and classifiers are capable of yielding instantaneous results. Therefore, the current system is a real time system. The system has been tested on unconstrained MNIST dataset. The overall recognition accuracy of 99.26% has been obtained.

Throughput performance under primary user emulation attack in cognitive radio networks

Summary Spectrum sensing in cognitive radio networks imposes some security threats to the secondary users (SUs) such as primary user emulation attack (PUEA). In the present paper, throughput of an SU is studied for cognitive radio network under PUEA where SU spectrum access is hybrid, ie, either in overlay mode or in underlay mode. A novel analytical expression for throughput of an SU in presence of PUEA is developed. Impact of several parameters such as sensing time, attacker strength, attackers presence probabilities, maximum allowable SU transmit power, and tolerable interference limit at primary user on the throughput of an SU is investigated. The throughput performance under PUEA and without PUEA is compared.

Throughput and outage of a wireless energy harvesting based cognitive relay network

This paper evaluates the throughput and outage probability (OP) of a secondary user (SU) in a cognitive relay network with an energy harvesting (EH) decode-and-forward (DF) relaying scheme. A potential relay, selected from a set of relays using a proactive relaying scheme, harvests energy. The power transmitted by source and relay nodes are constrained by an interference threshold of the primary receiver. Two schemes of relaying, a time switching based relaying (TSR) and a power splitting based relaying (PSR) are studied. Considering EH and cognitive constraint at the relay node, we analyse the achievable throughput and outage performance of a cognitive DF relaying network. We study the impact of EH time, power splitting ratio, number of relays and tolerable interference threshold of PU on the throughput and outage performance of SU.

Secondary throughput in underlay cognitive radio network with imperfect CSI and energy harvesting relay

In this paper performance of a cognitive relay network (CRN) is studied under imperfect channel state information (CSI) where a secondary user (SU) transmits using a decode and forward (DF) relay. The DF relay is assumed to harvest energy from the radio frequency (RF) signal transmitted by SU. The performance is evaluated in terms of throughput in an underlay scenario with the energy harvesting relay. The CSI of the interfering links i.e. links from SU transmitter as well as from relay to the primary user (PU) receiver, available at the SU transmitter and the relay, are assumed to be imperfect. A scaling factor based power control is used for the SU and relay in order to protect the PU satisfying an outage constraint. The impact of energy harvesting time, imperfect CSI, PU outage constraint and interference threshold on the throughput of the SU network is indicated. Further the impact of the above parameters on the average transmit power of the relay is also indicated. The performance is assessed using a test bed developed in MATLAB.

Computation of coverage area of cognitive radio network under shadowed environment with spectrum underlay

Cognitive radio provides an efficient way to utilize the underutilized radio spectrum. In underlay spectrum sharing, the secondary user is allowed to transmit in the presence of primary user provided it does not produce any harmful interference to the primary user. In this paper coverage area of a secondary user is computed which allows secondary transmission maintaining the QoS of primary user under the effect of shadow fading in the channel. The network performance is evaluated in terms of secondary outage. The impact of several network parameters on secondary outage is indicated.

Performance of an Energy harvesting Cooperative Cognitive Radio Network with Hybrid Spectrum Access Scheme

In this paper, a hybrid spectrum access scheme is investigated for a relay based energy harvesting cooperative cognitive radio (CR) network. In the considered network model, a relay harvests energy from RF signal of primary user (PU) as well as from RF signal of CR also. The relay node forwards the CR data to the respective destination and also cooperates in PU transmission as well. The CR follows a hybrid spectrum access scheme, i.e., it employs an underlay scheme of co-existence if PU is found to be present in the given channel else it switches to the overlay scheme of transmission. In overlay scheme, a CR transmits with maximum transmission power while in underlay scheme, it controls its transmission power based on the knowledge of channel state information of the link between CR and PU receiver, to limit the interference at PU receiver. Three new ratio parameters namely, PU–CR time allocation parameter, PU two hop transmission parameter and CR two hop transmission parameter are considered to model the cooperative transmission of PU and CR network where the parameter β takes care of the allocated time for PU and CR transmission and the other two parameters θ and ϕ take care of two hop transmission for PU and CR respectively. Analytical expressions of combined throughput of a CR and PU are developed under the considered network scenario. The performance is investigated in terms of combined throughput of CR, combined throughput of PU, and the overall network throughput for several sensing parameter and new ratio parameters.

Performance of cognitive relay network with energy harvesting relay under imperfect CSI: Performance of cognitive relay network with energy harvesting relay under imperfect CSI

Correspondence Binod Prasad, Department of ECE, NIT, Durgapur, WB, India. Email: binod.ece@gmail.com Summary This paper evaluates the performance of an underlay cognitive relay network under imperfect channel state information (CSI) where a secondary user (SU) transmits using a secondary relay (SR) based on decode and forward scheme. The outage probability (OP) of SU is investigated in a scenario where the decode and forward relay harvests energy from radio frequency signal of SU. The relay uses a fraction of time for harvesting in time switching–based relaying (TSR) while a fraction of received power is used for harvesting in power splitting–based relaying (PSR) scheme. The SU and relay control their transmit power using a scaling factor, based on CSI of the interfering links (ie, links from SU transmitter and SR to the primary user [PU] receiver) to protect the quality of service of PU. The available CSI at the SU and SR are imperfect due to practical limitation. Analytical expressions of the OP are derived for TSRand PSR-based schemes. The impact of harvesting time, power splitting ratio, imperfect CSI, PU outage constraint and interference threshold on the OP of the SU network, and average transmit power of SR is indicated. Further, the impact of multiple SRs is also shown.