Hari Krishna Boddapati

Outage Analysis of Cluster-Based Multi-Hop Cognitive Radio Networks

In this paper, we study the performance of cluster based multi-hop underlay cognitive radio networks using an ad-hoc path selection mechanism. Both peak power and peak interference constraints are taken into account. The exact end-to-end outage probability of the considered system employing decode-and-forward relays is derived for Rayleigh fading channels. Also, an approximate expression of the outage probability at high signal-to-noise ratio is derived. For fixed-rate and fixed distance between the source and destination, an expression is derived for the number of hops that minimizes the outage probability. Simulation results are presented to validate the derived analytical expressions.

Ad-Hoc Relay Selection Protocols for Multi-Hop Underlay Cognitive Radio Networks

In underlay cognitive radio networks (CRNs), transmit power of secondary user (SU) is a function of fading channel gain between the SU and primary destination. By exploiting this unique characteristic of CRNs, in this paper, we propose and study two novel ad-hoc routing protocols for path selection in cluster-based underlay multi- hop CRNs (MHCRNs). These protocols are termed as highest transmit power relay selection (HTPRS) protocol and improved HTPRS (IHTPRS) protocol. The exact end-to-end outage probability of cluster-based MHCRN is derived by taking both peak-power and peak-interference constraints into account for both proposed routing protocols. Moreover, we derive the average number of channel-state-information (CSI) estimates of forward channels required by the IHTPRS protocol. It is shown that the HTPRS is suitable for the systems with less implementation complexity, whereas the IHTPRS finds its application where high quality of service is required with slight increment in the CSI overhead.

Performance of Cooperative Multi-Hop Cognitive Radio Networks with Selective Decode-and-Forward Relays

Multi-hop relaying is used to extend the reach of wireless communication systems whereas cooperative relaying is used to improve the performance gain by exploiting the spatial diversity. In this study, the authors combine these two techniques to improve the range as well as the performance gain of cognitive radio networks (CRNs). Selective decode-and-forward relays are considered and two relay selection schemes are used to study the performance of multi-hop CRNs over Rayleigh fading channels. The exact outage probability and throughput of the considered system are derived for both the schemes by considering the effect of both peak-power and peak-interference constraints. By using the derived outage probability, the diversity gains for both considered schemes are determined. Numerical results show that the outage probability monotonically improves, whereas the throughput has concave behaviour with respect to increasing number of relaying hops.

Throughput analysis of cooperative multi-hop underlay CRNs with incremental relaying

To increase the communication range of multi-hop cognitive radio networks (CRNs) while avoiding the implied loss in throughput, use of incremental relaying has been suggested. In this paper, we discuss an incremental relaying (IR) protocol for cooperative multi-hop CRNs (CMHCRNs). A CMHCRN with multiple decode-and-forward relays in each hop is considered. In each hop, the relays whose received signal-to-noise-ratio (SNR) values are greater than a predefined threshold constitute a qualified relay set (QRS). The performance of an IR protocol that selects a relay from the QRS that has the highest SNR to the destination at each hop of the CMHCRN is analyzed. Both peak transmit power and peak interference power constraints are taken into account. The end-to-end outage probability and throughput expressions are derived for the considered network over Rayleigh fading channels. Closed-form expressions for floor values of outage probability and throughput are also derived. Based on the derived expressions, we demonstrate that with increase in number of hops, throughput first increases and then decreases.

Secrecy Performance of Imperfect One Bit Feedback Based Alamouti MISO System

We study the secrecy performance of one bit imperfect feedback-based diagonal precoder for Alamouti multiple-input single-output (MISO) system in the presence of a single antenna equipped eavesdropper. An error-tolerant weighting (ETW) scheme is employed for transmit power allocation. The exact and asymptotic closed-form expressions of the secrecy outage probability (SOP) of the considered MISO system are derived with the ETW scheme. Also, the SOPs of uniform power allocation (UPA) scheme and best transmit antenna selection (BTAS) scheme with erroneous feedback are derived. Analysis shows that the proposed ETW scheme provides a significant secrecy performance gain in comparison to UPA scheme and remains insensitive to feedback error, unlike the BTAS scheme.

Outage analysis of cluster-based multi-hop cognitive networks using BLAR routing protocol

In this paper, we study the performance of cluster-based multi-hop underlay cognitive radio network using best-last arbitrary-rest routing protocol. The exact end-to-end outage probability of the considered system is derived for Rayleigh fading channels assuming decode-and-forward relays. Both peak-power and peak-interference constraints are taken into account. An exact expression for outage probability of the BLAR protocol is not available even in the non-cognitive context. We deduce this as a special case from the derived expressions. Simulations are presented to validate the obtained results.

BER analysis of improved path selection criterion for cluster-based multi-hop cooperative networks

In this paper, we study path selection criteria in cluster-based multi-hop cooperative networks with decode-and-forward relays over Rayleigh fading channels. The hop-by-hop path selection criterion, in which routing is done based on local channel state information, loses diversity gain due to lack of relay selection in the last hop. To overcome this issue, we study an improved path selection strategy, in which final two hops are selected jointly to achieve the maximum spatial diversity. The exact and asymptotic expressions of bit-error-rate are derived for both the path selection schemes. Numerical results show that the improved path-selection criterion performs far better than that of hop-by-hop selection criterion with a little increase in implementation complexity.