• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9B
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• pp.745-750
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• 2008

In a cognitive radio based system, quality of service (QoS) for the secondary user must be maintained as much as possible even while that of the primary user is protected all he time. In particular, switching wireless links for the secondary user during the transmission of multimedia data causes delay and information loss, and QoS degradations occur inevitably. The efficient resource management scheme is necessary to support the seamless multimedia service to the secondary user. This paper proposes a novel frequency selection method based on Multi-Criteria Decision Making (MCDM), in which uncertain parameters such as received signal strength, cell load, data rate, and available bandwidth are considered during the decision process for the frequency selection with the fuzzy set theory. Through simulation, we show that our proposed frequency selection method provides a better performance than the conventional methods which consider the received signal strength only.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.1
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• pp.152-167
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• 2016

This paper investigates the simultaneous wireless information and power transfer (SWIPT) for two-hop orthogonal frequency division multiplexing (OFDM) decode-and-forward (DF) relay network, where a relay harvests energy from radio frequency signals transmitted by a source and then uses the harvested energy to assist information transmission from the source to its destination. The power splitting receiver is considered at the relay. To explore the performance limit of such a SWIPT-enabled system, a resource allocation (RA) optimization problem is formulated to maximize the achievable information rate of the system, where the power allocation, the subcarrier pairing and the power splitting factor are jointly optimized. As the problem is non-convex and there is no known solution method, we first decompose it into two separate subproblems and then design an efficient RA algorithm. Simulation results demonstrate that our proposed algorithm can achieve the maximum achievable rate of the system and also show that to achieve a better system performance, the relay node should be deployed near the source in the SWIPT-enabled two-hop OFDM DF relay system, which is very different from that in conventional non-SWIPT system where the relay should be deployed at the midpoint of the line between the source and the destination.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.sup2
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• pp.19-24
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• 2016

Quitline activity in Rajasthan, India is a voluntary activity of Rajasthan Cancer Foundation (RCF) since April 2013. To kick-off, it took the benefit of the State Government- PIRAMAL SWASTHYA (PS)1 collaborative 104 Health Information Helpline that existed already in public-private partnership. It is a reactive quitline that helps callers through the counselors and nursing staff trained specifically through the weekly sessions held by the first author, the RCF resource on quitline. Besides structuring of the scripts for primary intervention and follow-ups after 1 week, 1 month, 6 months and a year, he also monitors calls, advices and coordinates with the supervisors to manage and analyze the data base, and reports to the PS lead at the Jaipur Center on overall performance and to plan strategic communication with the State Government on its outcomes. The quitline has limitations of its informal existence through a voluntary effort of RCF, no specific resource allocation, suboptimal data management, minimal awareness in the masses due to poor IEC (Information, Education and Communication; except its efforts made by RCF in last 1 year through the government-run State TV and City Radio) and staff shortage and its attrition due to lack of plan for career advancement. Despite these challenges in the year 2013, the quit line has registered a quit rate (for complete abstinence) of 19.93% amongst 1525 callers. The quit rate were 58.01% (304/ 524) among the responders at the 3rd follow-up at 18 months (in September 2014)2. In view of an increase in quit rate by 5- 9 times over the prevailing quit rate in the former ever daily users [both smokers and the users of smokeless tobacco (SLT)], efforts are being made by RCF in concurrence with PS to have this cost-effective model established formally with optimal resource allocation in collaboration with willing agencies (the State and Central Governments and the International Quitline Agencies) and its replication in 4 more states where PS is collaborating with the respective state governments similarly (Assam, Chhattisgarh, Jharkhand and Karnataka).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.10
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• pp.885-894
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• 2012

Currently, Demand of data traffic has rapidly increased by popular of smart device. It is very difficult to accommodate demand of data traffic by limited resource of base station (BS). To solve this problem, method has proposed that the Device-to-Device (D2D) reduce frequency overload of the BS and all of the user equipment (UE) inside the BS and neighbor BS don't allow communicating directly to BS. However, in LTE-Advance system cellular link and sharing radio resources of D2D link, the strong interference of the cellular network is still high. So we need to eliminate or mitigate the interference. In this paper, we use the transmission power control method and Soft Frequency Reuse (SFR) resource allocation method to mitigate the interference of the cellular link and D2D link. Simulation results show that the proposed scheme has high performance in terms of Signal to Noise Ratio (SINR) and system average throughput.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.4
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• pp.371-380
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• 2013

D2D (Device-to-Device) communication on an underlying cellular infrastructure which exploits the same spectrum has several advantages such as increased resource utilization and improved cellular coverage. However, D2D communication system needs to cope with ICI (Inter-Cell Interference) and interference between cellular and D2D links. As a result, macro UEs (User Equipments), especially those located near cell edge, will suffer from serious link performance degradation. We propose a novel interference avoidance mechanism assisted by SRN (Shared Relay Node) in this paper. SRN not only performs data re-transmission as a usual Type II relay but also has several features newly defined to avoid interference between cellular and D2D links. In particular, we suggest resource allocation methods based on the SRN for effective interference avoidance, and evaluate their performance through computer simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.12B
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• pp.1647-1658
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• 2011

This paper suggests the methods to improve the wireless backhaul link of the Relay FDD mode that 3GPP LTE-Advanced supports. New RRC message and Relay startsup procedure are introduced to apply Carrier Aggregation in the Relay wireless backhaul. Also, we design new reference signal that makes Type 1 Relay operated in full-duplexing, expecting to maximize the radio resource utilization. And, we propose the efficient configuration for the periodic uplink control information under the backhaul subframe allocation method in LTE-Advanced Relay. Hereafter, the standard activities in the 3GPP RAN is supposed to focus on the improvement of the LTE-Advanced features. Therefore, the suggestions in this paper are expected to be actively discussed in the LTE-Advanced future releases.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.1
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• pp.68-78
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• 2013

In this paper, we propose an early spectrum sensing(ESS) as an advance preparation for radio-access trial, which enables multi-mode terminals to access the most appropriate radio-access system in a cloud-conceptual base station system where multiple radio access technologies(RATs) coexist. Prior to a random access to one of RATs, a multi-mode terminal conducts a spectrum sensing over entire frequency bands of whole RATs, then select the RAT with the lowest sensing power, that is likely to have the most available spectrum. Thus, an access failure caused by that the selected RAT has no available radio spectrum could be avoidable in advance. In computer simulation, we consider as various RATs as possible. First, circuit and packet systems are taken into consideration. In addition, the packet systems are classified according to the feasibility of carrier aggregation(CA). In case of terminal, three modes are considered with circuit-only, packet-only, and multi-mode. Subsequently, packet traffic is classified into real-time and non-real-time traffic with three different tolerable delay levels. The simulation includes a call process starting with a call generation and ending up with a resource allocation reflecting individual user's QoS requirements and evaluates the proposed scheme in terms of the successful access probability, system access time, system balancing factor and packet loss probability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9A
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• pp.853-866
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• 2008

In this paper, a multi-hop relaying transmission scheme is analyzed regarding its feasibility and potentiality in the IEEE 802.22-based cognitive radio (CR) environment. Shortly, basic design issues are addressed such as relay station (RS) deployment and a frame structure of physical channel to escape inter-hop interference. This paper mainly develops a radio resource management scheme based on spectrum sensing results aggregated from CR secondary nodes and improves the opportunistic spectrum sharing efficiency. In particular, a decision rule about a channel availability is made using a distributed sensing method. Subsequently, spectrum allocation and routing path decision procedures are proposed to establish a link from source to destination with a hop-by-hop manner. Simulation results show that the proposed multi-hop relaying scheme is substantially profitable in CR environments if the number of hops and RS deployment are designed in such a way that the spectrum sharing gain is larger than spectrum division loss which is inherently induced in multi-hop relaying systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.8
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• pp.651-659
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• 2014

In this paper, we consider a two way relay network for ship-to-ship communications in a fleet, where two communicating ships exchange the information with the help of a multi-antenna relay ship. For the network, we propose a rate-aware three-phase analog network coding to improve the reliability of the information exchange with asymmetric rates. The proposed scheme allows low-complex implementation of the relay without channel estimation by generating an improved analog network coded signal with the orthogonally received signals from two ships by using only the received signal power at each antenna. In addition, the proposed scheme reduces outages in the data exchange at asymmetric rates by adopting a rate-aware relay power allocation, which is confirmed by evaluating the outage performance via simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.4
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• pp.1192-1207
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• 2014

Dynamic spectrum sharing is a key technology to improve spectrum utilization in wireless networks. The elastic spectrum management provides a new opportunity for licensed primary users and unlicensed secondary users to efficiently utilize the scarce wireless resource. In this paper, we present a game-theoretic framework for dynamic spectrum allocation where the primary users rent the unutilized spectrum to the secondary users for a monetary profit. In reality, due to the ON-OFF behavior of the primary user, the quantity of spectrum that can be opportunistically shared by the secondary users is limited. We model this situation with the renewal theory and formulate the spectrum pricing scheme with the Bertrand game, taking into account the scarcity of the spectrum. By the Nash-equilibrium pricing scheme, each player in the game continually converges to a strategy that maximizes its own profit. We also investigate the impact of several properties, including channel quality and spectrum substitutability. Based on the equilibrium analysis, we finally propose a decentralized algorithm that leads the primary users to the Nash-equilibrium, called DST. The stability of the proposed algorithm in terms of convergence to the Nash equilibrium is also studied.