• The Journal of the Institute of Internet, Broadcasting and Communication
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• 제11권5호
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• pp.179-184
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• 2011

In this paper, we analyze the sharing parameters in order to co-use of different communication systems in adjacent channels. We analyze the performance result according to various density of interfering transmitter and transmitter output in hetero systems. In order to get the relationship with between density of interfering transmitter and transmitter output, we consider the case that WiBro is an interfering transmitter an WLAN is a victim receiver. When the center frequency of WLAN is 687MHz and interferer density is 50/$km^2$, required guard band is 10MHz. Analyzed coexistence results may be widely applied into the technique developed to get the coexisting condition for wireless devices using many communication protocols in same frequency.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제38A권3호
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• pp.249-257
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• 2013

Recently, data traffic is significantly increased by high rate data service. As a result, radio spectrum is considered one of the most scarce and valuable resources for wireless communications. For the solution of this problem, cognitive radio(CR) has been proposed as an efficient means to opportunistic spectrum sharing between primary (licensed) users and cognitive radio users. In this paper, user selection scheme in CR networks is proposed for additional consideration of secondary system. The proposed user selection scheme mitigates interference to primary user by using orthogonal channel vectors while improves performance of secondary system. Simulation results show that the proposed scheme achieves 1.62bps/Hz higher average throughput of whole system than one of the existing scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권4호
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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.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권11호
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• pp.5253-5270
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• 2016

With device-to-device (D2D) communications, an inactive user terminal can be utilized as a relay node to support multi-hop communication so that connective experience of the cell-edge user as well as the capacity of the whole system can be significantly improved. In this paper, we investigate the spectrum sharing for a cooperative relay assisted D2D communication underlying a cellular network. We formulate a joint relay selection and channel assignment problem to maximize the throughput of the system while guaranteeing the quality of service (QoS) requirements of cellular users (CUs) and D2D users (DUs). By exploiting coalition formation game theory, we propose two algorithms to solve the problem. The first algorithm is designed based on merge and split rules while the second one is developed based on single user's movement. Both of them are proved to be stable and convergent. Simulation results are presented to show the effectiveness of the proposed algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제28권3A호
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• pp.140-150
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• 2003

In this paper, we propose a novel code sharing method for downlink transmission of mobile satellite communication systems using a multibeam geosynchronous-orbit satellite. In the proposed system, spreading codes are shared among downlink beams in order to increase the system capacity. We also propose efficient radio resource and transmit power allocation schemes for the proposed system. Simplified analysis and simulation results on the system capacity show the capacity improvement by the proposed scheme. The simulation results show that the capacity of the proposed system is more than 2 times as large as that of a conventional multibeam satellite system. In the frequency-selective fading channel, the capacity improvement increases as the interference between orthogonal spreading codes decrease.

• ETRI Journal
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• 제41권2호
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• pp.176-183
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• 2019

Spectrum sensing plays an important role in spectrum sharing. Energy detection is generally used because it does not require a priori knowledge of primary user (PU) signals; however, it is sensitive to noise uncertainty. An order statistics (OS) detector provides inherent protection against nonhomogeneous background signals. However, no analysis has been conducted yet to apply OS detection to spectrum sensing in a wireless channel to solve noise uncertainty. In this paper, we propose a robust spectrum sensing scheme based on generalized order statistics (GOS) and analyze the exact false alarm and detection probabilities under noise uncertainty. From the equation of the exact false alarm probability, the threshold value is calculated to maintain a constant false alarm rate. The detection probability is obtained from the calculated threshold under noise uncertainty. As a fusion rule for cooperative spectrum sensing, we adopt an OR rule, that is, a 1-out-of-N rule, and we call the proposed scheme GOS-OR. The analytical results show that the GOS-OR scheme can achieve optimum performance and maintain the desired false alarm rates if the coefficients of the GOS-OR detector can be correctly selected.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제30권8A호
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• pp.656-663
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• 2005

This paper presents a multi-channel enhancement scheme for the MAC protocol of IEEE 802.15.3 High-rate WPAN (Wireless Personal Area Network). The current MAC protocol of the IEEE 802.15.3 High-rate WPAN is designed for sharing a single channel among DEVs of a piconet; that is, within a single piconet, PNC prevents interference through MAC layer assignment of time slots to other DEVs using time-division multiple access. When the number of DEVs that communicate with each other frequently, is increased in a single WPAN, the size of the superframe becomes inevitably large, and this may result in a significant throughput drop or a failure to provide QoS guarantee. A multi-channel enhancement scheme for the MAC protocol of IEEE 802.15.3 High-rate WPAN is proposed to significantly increase the aguegate throughput and more reliably provide the QoS guarantees in a piconet

• Journal of Korea Society of Industrial Information Systems
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• 제19권2호
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• pp.1-13
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• 2014

In IEEE 802.11p/1609-based vehicular networks, vehicles are allowed to exchange safety and control messages only within time periods, called control channel (CCH) interval, which are scheduled periodically. Currently, the length of the CCH interval is set to the fixed value (i.e. 50ms). However, the fixed-length intervals cannot be effective for dynamically changing traffic load. Hence, some protocols have been recently proposed to support variable-length CCH intervals in order to improve channel utilization. In existing protocols, the CCH interval is subdivided into safety and non-safety intervals, and the length of each interval is dynamically adjusted to accommodate the estimated traffic load. However, they do not consider the presence of hidden nodes. Consequently, messages transmitted in each interval are likely to overlap with simultaneous transmissions (i.e. interference) from hidden nodes. Particularly, life-critical safety messages which are exchanged within the safety interval can be unreliably delivered due to such interference, which deteriorates QoS of safety applications such as cooperative collision warning. In this paper, we therefore propose a new interference-aware Dynamic Safety Interval (DSI) protocol. DSI calculates the number of vehicles sharing the channel with the consideration of hidden nodes. The safety interval is derived based on the measured number of vehicles. From simulation study using the ns-2, we verified that DSI outperforms the existing protocols in terms of various metrics such as broadcast delivery ration, collision probability and safety message delay.

• Journal of Communications and Networks
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• 제14권2호
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• pp.162-168
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• 2012

This paper considers the scenario in which a set of nodes share a common channel. Some nodes have a rechargeable battery and the others are plugged to a reliable power supply and, thus, have no energy limitations. We consider two source-destination pairs and apply the concept of cognitive radio communication in sharing the common channel. Specifically, we give high-priority to the energy-constrained source-destination pair, i.e., primary pair, and low-priority to the pair which is free from such constraint, i.e., secondary pair. In contrast to the traditional notion of cognitive radio, in which the secondary transmitter is required to relinquish the channel as soon as the primary is detected, the secondary transmitter not only utilizes the idle slots of primary pair but also transmits along with the primary transmitter with probability p. This is possible because we consider the general multi-packet reception model. Given the requirement on the primary pair's throughput, the probability p is chosen to maximize the secondary pair's throughput. To this end, we obtain two-dimensional maximum stable throughput region which describes the theoretical limit on rates that we can push into the network while maintaining the queues in the network to be stable. The result is obtained for both cases in which the capacity of the battery at the primary node is infinite and also finite.

• Journal of Advanced Navigation Technology
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• 제20권6호
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• pp.595-603
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• 2016

In the Republic of Korea, the LTE-based public safety (PS-LTE) network is being built for the 700 MHz frequency band. However, the same bands are also assigned to the LTE-based high-speed railway (LTE-R) network. Therefore, it is essential to utilize the co-channel interference management schemes for the coexistence of two LTE networks in order to increase the system throughput and to reduce the user outage probability. In this paper, we focus on the downlink (DL) system for the coexistence of PS-LTE and LTE-R networks by considering non radio access network (RAN) sharing and LTE-R RAN sharing by PS-LTE users (UEs) to analyze the UE throughput. Moreover, we also utilize the cooperative communications schemes, such as coordinated multipoint (CoMP) for the coexistence of PS-LTE and LTE-R networks in order to reduce the UE outage probability. We categorize the coexistence of PS-LTE and LTE-R networks into four different scenarios, and evaluate the performance of each scenario by the important performance indexes, such as UE average throughput and UE outage probability.