• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제11권3호
• /
• pp.1279-1300
• /
• 2017

In the interweave cognitive networks, the interference from the primary user degrades the performance of the cognitive user transmissions. In this paper, we propose an adaptive cooperation scheme in the interweave cognitive networks to improve the performance of the cognitive user transmissions. In the proposed scheme for the bidirectional communication of two end-source cognitive users, the bidirectional communication is completed through the non-relay direct transmission, the one-way relaying cooperation transmission, and the two-way relaying cooperation transmission depending on the limited feedback from the end-sources. For the performance analysis of the proposed scheme, we derive the outage probability and the finite-SNR diversity multiplexing tradeoff (f-DMT) in a closed form, considering the imperfect spectrum sensing, the interference from the primary user, and the power allocation between the relay and the end-sources. The results show that compared with the direct transmissions (DT), the pure one-way relaying transmissions (POWRT), and the pure two-way relaying transmissions (PTWRT), the proposed scheme has better outage performance. In terms of the f-DMT, the proposed scheme outperforms the full cooperation transmissions of the POWRT and PTWRT.

• 한국멀티미디어학회논문지
• /
• 제14권12호
• /
• pp.1559-1571
• /
• 2011

In wireless ad hoc networks, nodes communicate with each other using multihop routed transmission in which hop-by-hop cooperative diversity can be effectively employed. This paper proposes (i) two cooperation models for per-link cooperation (PLC) and per-node cooperation (PNC) for exploiting cooperative diversity in wireless ad hoc networks and (ii) a cooperative routing algorithm for the above models in which best relays are selected for cooperative transmission. First, two cooperation models for PLC and PNC are introduced and represented as an edge-weighted graph with effective link quality. Then, the proposed models are transformed into a simplified graph and a cooperative routing algorithm with O(n2) time is developed, where n is the number of nodes in the network. The effectiveness of the algorithm is confirmed for the two cooperation models using simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제10권9호
• /
• pp.4145-4164
• /
• 2016

Energy harvesting is an increasingly attractive source of power for cellular networks, and can be a promising solution for green networks. In this paper, we consider a cellular network with power beacons powering multiple mobile terminals with microwave power transfer in energy beamforming. In this network, the power beacons are powered by grid and renewable energy jointly. We adopt a dual-level control architecture, in which controllers collect information for a core controller, and the core controller has a real-time global view of the network. By implementing the water filling optimized power allocation strategy, the core controller optimizes the energy allocation among mobile terminals within the same cluster. In the proposed green energy cooperation paradigm, power beacons dynamically share their renewable energy by locally injecting/drawing renewable energy into/from other power beacons via the core controller. Then, we propose a new water filling optimized green energy cooperation management strategy, which jointly exploits water filling optimized power allocation strategy and green energy cooperation in cellular networks. Finally, we validate our works by simulations and show that the proposed water filling optimized green energy cooperation management strategy can achieve about 10% gains of MT's average rate and about 20% reduction of on-grid energy consumption.

• Journal of Communications and Networks
• /
• 제12권2호
• /
• pp.181-190
• /
• 2010

A multitude of overlay network designs for resilient routing, multicasting, quality of service, content distribution, storage, and object location have been proposed. Overlay networks offer several attractive features, including ease of deployment, flexibility, adaptivity, and an infrastructure for collaboration among hosts. In this paper, we explore cooperation among co-existing, possibly heterogeneous, overlay networks. We discuss a spectrum of cooperative forwarding and information sharing services, and investigate the associated scalability, heterogeneity, and security problems. Motivated by these services, we design Synergy, a utility-based overlay internetworking architecture that fosters overlay cooperation. Our architecture promotes fair peering relationships to achieve synergism. Results from Internet experiments with cooperative forwarding overlays indicate that our Synergy prototype improves delay, throughput, and loss performance, while maintaining the autonomy and heterogeneity of individual overlay networks.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• 제23권4호
• /
• pp.329-350
• /
• 2019

This paper examines individual and social strategies to form profitable cooperation networks. These two types of strategies measure network stability and efficiency that may not meet in a single network. We apply restrictions on knowledge flows (R&D spillovers) and links formation to integrate these benefits into structures that ensure high outcomes for both strategies. The results suggest that linking the spillovers to the firms' positions and restricting cooperation contribute to reducing the conflict between the individual and social strategies in the development of cooperative networks.

• 지역연구
• /
• 제13권2호
• /
• pp.55-74
• /
• 1997

This paper investigates the spatial characteristics of networks, which arise as a firm's strategy to enhance its competitiveness to cope with the changing economic environments characterized by technological changes and increasing competitiveness. The theoretical framework in this study proposes that networks emerge as a firm's strategies to promote its competitiveness through the vertical/horizontal disintegration of the production system. Futhermore, regional industries of networks. The study examines the types of cooperation and the spatial boundary of the computer industry networks in Korea. Questionnaire survey was conducted on 1, 128 computer companies which had more than 10 employees, with 126 questionnaires being used for analysis. In addition, newpaper articles were used to supplement the foregoing work on network characteristics. The review of these articles covers the period from Jan. 1994 to June 1996. Major findings of this study are as follows: The spatial range of cooperative networks varies according to the specific characters of cooperation(R & D, production, and seles). Intralocal networks are being developed in Kangnam and Youido area, the computer industry agglomeration clusres of Seoul. There are the regional differnces in the agents and contents of cooperation. In intra-national R & D and production networks, regional differnces in agglomeratins and non-agglomerations are not detercted. Most networks of this type are found between large firms and small firms. In contrast, foregn R & D and production networks, which are operated mostly by large firms, are found in Kangnam, Youido, and CBD. Intra-national and foreign productino networks are also focused in Kangnam, Youido, and CBD. Small firms are playing an active role in making this type of cooperation possible. In the perspective of localization-globalization, Korean computer industry can be analyzed in two respects: industrial and regional. The localization of small firms and the localization-globalization of large firms' networks are being developed in industrial contexts, while the localization-globalization of agglomerations and the localization of non-agglomerations networks are being developed in regional contexts. As networks for the localization-globalization of industry are growing in agglomerations, interfirm networks could be related to trends in the formation or intensification of industrial agglomerations. industrial agglomeration areas function as a facilitator of localization through subcontracts, intraregional network and interregional network. They also facilitate globalization via foregn networks. In non-agglomeratin areas, localization networks, which are connected with agglomeration areas via subcontracting, interregional R & D. or production cooperation.

• 한국빅데이터학회지
• /
• 제6권2호
• /
• pp.109-124
• /
• 2021

본 논문에서는 네트워크 분석방법을 활용하여 대학 중심의 산학협력 네트워크의 구조적 특성을 분석하였다. 최근 기술협력 및 공동연구가 성과창출에 긍정적 영향을 미치는 것이 증명됨에 따라, 혁신성과 창출을 위하여 주요 참여주체(대학 및 공공 등)를 중심으로 다양한 형태의 협력활동 추진과 정부의 정책적 지원이 활발하게 진행되고 있다. 하지만 이러한 노력에도 불구하고 성장동력 창출은 다소 미흡한 상황이기에 대학중심의 산학협력 활동강화를 위한 혁신 네트워크 구축 방안 마련이 필요한 시점이다. 이에 본 연구에서는 산학협력 유형(특허, 논문, 공동연구, 기술이전)에 따른 네트워크를 구축하고, QAP상관분석 및 QAP회귀분석을 실시하여 서로 다른 유형의 산학협력 네트워크간 관련성 및 연관성을 통계적 관점에서 분석하였다. 분석결과 공동연구 네트워크는 논문 네트워크와 밀접한 관련이 있으며, 다른 산학협력 네트워크와도 관련성을 가지고 있는 것으로 나타났다. 본 연구는 대학의 새로운 성장동력 창출에 필요한 산학협력 전략수립 및 협력 파트너 발굴 등과 같은 혁신활동을 지원할 수 있을 것이라 기대한다.

• Journal of Communications and Networks
• /
• 제17권5호
• /
• pp.499-505
• /
• 2015

We analyze the performance of multistage cooperation in decode-and-forward relay networks where the transmission between source and destination takes place in $T{\geq}2$ equal duration and orthogonal time phases with the help of relays. The source transmits only in the first time phase. All relays that can decode the source's transmission forward the source's message to the destination in the second time phase, using a space-time code. During subsequent time phases, the relays that have successfully decoded the source message using information from all previous transmitting relays, transmit the space-time coded symbols for the source's message. The non-decoding relays keep accumulating information and transmit in the later stages when they are able to decode. This process continues for T cooperation phases. We develop and analyze the outage probability of multistage cooperation protocol under orthogonal relaying. Through analytical results, we obtain the near-optimal placement strategy for relays that gives the best performance when compared with most other candidate relay location strategies of interest. For different relay network topologies, we also investigate an interesting tradeoff between an increased SNR and decreased spectral efficiency as the number of cooperation stages is increased. It is also shown that the largest multistage cooperation gain is obtained in the low and moderate SNR regime.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제9권10호
• /
• pp.3921-3944
• /
• 2015

Currently Energy-Saving (ES) methods in cellular networks could be improved, as compensation method for irregular Base Station (BS) deployment is not effective, most regional ES algorithm is complex, and performance decline caused by ES action is not evaluated well. To resolve above issues, a low-complexity energy efficient BS cooperation mechanism for Long Time Evolution (LTE) networks is proposed. The mechanism firstly models the ES optimization problem with coverage, resource, power and Quality of Service (QoS) constraints. To resolve the problem with low complexity, it is decomposed into two sub-problems: BS Mode Determination (BMD) problem and User Association Optimization (UAO) problem. To resolve BMD, regional dynamic multi-stage algorithms with BS cooperation pair taking account of load and geographic topology is analyzed. And then a distributed heuristic algorithm guaranteeing user QoS is adopted to resolve UAO. The mechanism is simulated under four LTE scenarios. Comparing to other algorithms, results show that the mechanism can obtain better energy efficiency with acceptable coverage, throughput, and QoS performance.

• ETRI Journal
• /
• 제44권4호
• /
• pp.588-598
• /
• 2022

Since multi-access edge computing (MEC) was established as a key enabler of 5G, MEC based on 5G networks (5G MEC) has been perceived as a new business opportunity for many industry players, including telecom operators. Numerous 5G MEC cooperation announcements among companies playing their respective roles in the MEC ecosystem have been recently released. However, because of cooperative and competitive relationships among key players in the MEC ecosystem and the uncertainty of 5G MEC, the announcement of 5G MEC cooperation can negatively affect the telecom operators' firm value. This study investigates the market reaction to announcements of 5G MEC cooperation for telecom operators using an event study methodology. The empirical results show that announcements of 5G MEC cooperation have a negative impact on the telecom operators' firm value. The results also show that the early deployment of 5G networks may reduce the negative impact of 5G MEC cooperation announcements by reducing uncertainty.