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On Energy Cooperation in Energy Harvesting Underlay Cognitive Radio Network [article]

Kalpant Pathak, Adrish Banerjee
2016 arXiv   pre-print
In this paper, we consider an energy harvesting cognitive radio network (EH-CRN), where a primary and a secondary user coexist in underlay mode. Both the transmitters have energy harvesting capability and are equipped with finite capacity battery to store the harvested energy. In addition, the secondary user (SU) has an independent energy transfer unit such that it can transfer some portion of it's harvested energy to the primary user (PU). We obtain an optimal transmit power and energy
more » ... policy for single-slot and a suboptimal policy for multi-slot scenario maximizing the number of bits transmitted by SU under the primary sum-rate constraint in an offline setting. For both cases, the effect of energy cooperation on the system performance is studied and it is observed that energy cooperation results in higher SU throughput.
arXiv:1603.03248v1 fatcat:nu7y7vrcvrh4pbyrbqxtv34swa

Optimal Harvest-or-Transmit Strategy for Energy Harvesting Underlay Cognitive Radio Network [article]

Kalpant Pathak, Adrish Banerjee
2018 arXiv   pre-print
An underlay cognitive radio network with energy harvesting is considered which operates in slotted fashion. The primary user (PU) transmits with a constant power in each slot, while the secondary user (SU) either harvests energy from primary's transmission or transmits its data. We propose an optimal offline harvest-or-transmit strategy where in each slot, SU takes a decision whether to harvest energy or transmit its data limiting interference at the primary receiver. We aim to maximize the
more » ... evable rate of SU under energy causality and interference constraints. The optimization problem is formulated as a mixed integer non-linear program and the optimal harvest-or-transmit policy is obtained using generalized Benders decomposition algorithm. Through simulations, we analyze the effects of various system parameters and interference constraint at the primary receiver on the optimal policy.
arXiv:1805.02022v1 fatcat:v4zmelawhvfhxlnpx6i5o2eymy

On Optimal Offline Time Sharing Policy for Energy Harvesting Underlay Cognitive Radio [article]

Kalpant Pathak, Adrish Banerjee
2016 arXiv   pre-print
RF energy harvesting can be used to power communication devices so that perpetual operation of such devices can be ensured. We consider a RF energy harvesting underlay cognitive radio system operating in slotted fashion. The primary user (PU) is equipped with a reliable power source and transmits with a constant power in all the slots. However, the secondary user (SU) harvests energy from primary's transmission and simultaneously transmits it's own data such that interference at the primary
more » ... iver (PR) remains below an acceptable threshold. At the secondary transmitter (ST), each time slot is divided into two phases: energy harvesting (EH) phase and information transfer (IT) phase. We formulated the problem of maximizing the achievable secondary sum rate under primary receiver's protection criteria as a convex optimization problem and obtained the optimal time sharing between EH and IT phase, and optimal secondary transmit power under offline setting. The optimal offline scheme is then compared with an online myopic policy, where the optimal time sharing between EH and IT phase, and optimal secondary transmit power are obtained based on instantaneous channel gains only.
arXiv:1605.00211v1 fatcat:xgcnz6v22je7nasiowdgo5tjvu

Online Time Sharing Policy in Energy Harvesting Cognitive Radio Network with Channel Uncertainty [article]

Kalpant Pathak, Prachi Bansal, Adrish Banerjee
2017 arXiv   pre-print
This paper considers an energy harvesting underlay cognitive radio network operating in a slotted fashion. The secondary transmitter scavenges energy from environmental sources in half duplex fashion and stores it in finite capacity rechargeable battery. It splits each slot into two phases: harvesting phase and transmission phase. We model the energy availability at the secondary user as first order stationary Markov process. We propose a robust online transmission policy by jointly optimizing
more » ... he time sharing between the two phases and transmit power of secondary user, which maximizes its average throughput by a given time deadline.We show the comparison of our proposed policy with the offline and myopic policies.
arXiv:1709.00352v1 fatcat:ybb4x4o3yrfabpz4twhkxfyneu

Optimal User Scheduling in Energy Harvesting Wireless Networks [article]

Kalpant Pathak, Sanket S. Kalamkar, Adrish Banerjee
2018 arXiv   pre-print
We consider a wireless network where multiple energy harvesting transmitters communicate with the common receiver in a time sharing manner. In each slot, a transmitter can either harvest energy or send its data to the receiver. Given a time deadline, the goal is to maximize the sum-rate of transmitters under random energy arrivals with both perfect and imperfect channel state information (CSI) at the receiver. The original sumrate maximization (SRM) problem is a non-convex mixed integer
more » ... ar program (MINLP). To obtain the optimal scheduling policy, we first reduce the original optimization problem to a convex MINLP and solve it using the generalized Benders decomposition algorithm. We observe that the SRM problem results in an unfair rate allocation among transmitters, i.e., the transmitter closer to the receiver achieves a higher rate than that by the transmitter farther from the receiver. Hence, to induce fairness among transmitters, we consider the minimumrate maximization (MRM) problem. For the bounded channel estimation error, we obtain a robust scheduling policy by solving the worst-case SRM and MRM problems. Finally, we compare the proposed policies with myopic policies studied in the literature and show that the former outperform the latter in terms of achievable rates.
arXiv:1804.09040v2 fatcat:33ipb6lpfvcy7hhc7tkm36l7je

On the Road with Kālidāsa. Countries, cities and sacred places

Péter Száler, Csaba Dezső
2020
Pathak considered the Hūnas to be Hephthalites, who ruled the Oxus basin from the middle of the fifth century.  ...  of a further place of pilgrimage: tatra <Himālaye> vyaktaṃ dṛṣadi caraṇa-nyāsam ardh^êndu-mauleḥ śaśvat siddhair upahṛta-baliṃ bhakti-namraḥ parīyāḥ| yasmin dṛṣṭe karaṇa-vigamād ūrdhvam uddhūta-pāpāḥ kalpante  ... 
doi:10.15476/elte2019.112 fatcat:3xm3dwqxpjc55k5myszase542q