Sourabh Solanki

Outage Analysis of Cognitive Opportunistic Relay Networks With Direct Link in Nakagami-

This letter presents a unified framework for the outage performance analysis of cognitive opportunistic amplify- and-forward relay networks with a direct link using maximum ratio combining (MRC) and selection combining (SC) schemes in the presence of multiple primary receivers. Specifically, we derive unified closed-form expressions of outage probability and asymptotic outage behavior for both the schemes under Nakagami-m fading. We manifest analytically that the primary network affects only the coding gains of these schemes, and not the diversity gains that are found to be same in both cases. Moreover, we provide an analytical high signal-to-noise ratio (SNR) gap expression between the two schemes, which is shown to be independent of the primary network parameters. Numerical and simulation results validate our theoretical analysis.

m

In this paper, we investigate the outage performance of a decode-and-forward (DF) underlay cognitive two-way relay system with direct link using time division broadcast protocol in the presence of primary users interference. Herein, relying on the practicability and low-complexity of statistical channel state information (CSI), the secondary transmissions satisfy the fading-averaged interference constraints at the primary receiver. We study an efficient link utilization scheme that can exploit both direct and relay links with appropriate combining methods to improve the performance of secondary users. Considering Nakagami-m fading channels, we derive a tight closed-form expression of outage probability for the secondary communications. We further perform the asymptotic high signal-to-interference noise ratio (SINR) analysis to gain more insight. We quantify the implications of primary users interference on the secondary system performance and present several useful insights. With the proposed scheme, secondary system is shown to harness full diversity as long as the primary interference remains limited otherwise outage floor phenomenon occurs. Numerical and simulation results corroborate our theoretical developments.

Fading

In this paper, we investigate the secrecy performance of an underlay cognitive decode-and- forward relay network (CDRN) by exploiting an active direct link in the presence of primary users (PUs) interference. Herein, a secondary user (SU) transmitter strives to maintain a secure communication link with a legitimate SU receiver in presence of a passive eavesdropper. On account of systems viability, we consider the presence of a PU transmitter as well as a PU receiver, wherein the secondary transmissions satisfy the fading- averaged interference constraints at the PU receiver. Specifically, we focus on utilizing the interference from primary transmission as a jamming signal for ameliorating the secrecy performance of secondary network. We derive closed-form expressions of secrecy outage probability for the secondary network with and without PUs interference. Numerical and simulation results validate our analysis and reveal the secrecy performance improvement of considered CDRN.

Average interference-constrained cognitive two-way relaying with efficient link utilization

This study investigates the performance of a cognitive relay sharing system (CRSS) wherein two primary users (PUs) exchange the information bidirectionally. The overall transmission in CRSS takes place using an amplify-and-forward-based multiple access broadcast protocol. Herein, besides assisting the transmission of secondary users, the relay also provides an aid for the bidirectional communication between PUs. In addition, the secondary system employs an opportunistic user scheduling with multiple destinations to further ameliorate the performance of secondary network. Here, by considering Nakagami-m fading channels, the authors derive novel closed-form expressions of outage probability (OP) and average error probability for both primary and secondary systems. Based on the derived expressions of OP, the authors also quantify the average system throughput. With bidirectional primary communications, the proposed CRSS offers higher spectral efficiency and incentivises the secondary communication through multiuser diversity. Finally, numerical and simulation results are provided for the validation of the theoretical analysis.

Secure Underlay Cognitive Relay Networks in Presence of Primary User's Interference

In this paper, we investigate the performance of an underlay cognitive two-way relay system with direct link using time division broadcast protocol in the presence of primary users interference. Herein, relying on the practicability and low complexity of statistical channel state information, the secondary transmissions are in compliance with the fading-averaged interference constraints imposed by the primary receiver. For this setup, we study an adaptive link utilization scheme (ALUS) that can exploit both direct and relay links with appropriate diversity combining methods to improve the performance of secondary users. Based on ALUS, we evaluate and compare the performance of two decode-and-forward based relaying strategies viz., fixed relaying and incremental relaying. We derive the tight closed-form expressions of outage probability of the secondary communications for both the strategies over Nakagami-m fading channels. We further conduct asymptotic high signal-to-interference-plus-noise ratio analysis to examine the achievable diversity order of the considered system. In addition, we quantify the expected spectral efficiency and average transmission time for both relaying strategies. Our results illustrate that the incremental relaying strategy can significantly improve the system performance in comparison with fixed relaying. Numerical and simulation results are provided to attest our theoretical studies.