• Journal of Korea Society of Digital Industry and Information Management
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• v.16 no.4
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• pp.1-7
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• 2020

Over the past few years, Wi-Fi signal based indoor positioning system (IPS) has been researched extensively because of its low expenses of infrastructure deployment. There are two major aspects of location-related information contained in Wi-Fi signals. One is channel state information (CSI), and one is received signal strength indicator (RSSI). Compared to the RSSI, the CSI has been widely utilized because it is able to reveal fine-grained information related to locations. However, the conventional IPS that employs a single access point (AP) does not exhibit decent performance especially in the environment of non-line-of-sight (NLOS) situations due to the reliability degeneration of signals caused by multipath fading effect. In order to address this problem, in this paper, we propose a novel method that utilizes multiple APs instead of a single AP to enhance the robustness of the IPS. In our proposed method, a hybrid neural network is applied to the CSIs collected from multiple APs. By relying more on the fingerprint constructed by the CSI collected from an AP that is less affected by the NLOS, we find that the performance of the IPS is significantly improved.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.7
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• pp.2668-2717
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• 2021

Demands for high-speed wireless data services grow rapidly. It is a big challenge to increasing the network capacity operating on licensed spectrum resources. Unlicensed spectrum cellular networks have been proposed as a solution in response to severe spectrum shortage. Licensed Assisted Access (LAA) was standardized by 3GPP, aiming to deliver data services through unlicensed 5 GHz spectrum. Furthermore, the 3GPP proposed 5G New Radio-Unlicensed (NR-U) study item. On the other hand, artificial intelligence (AI) has attracted enormous attention to implement 5G and beyond systems, which is known as Intelligent Radio (IR). To tackle the challenges of unlicensed spectrum networks in 4G/5G/B5G systems, a lot of works have been done, focusing on using Machine Learning (ML) to support resource allocation in LTE-LAA/NR-U and Wi-Fi coexistence environments. Generally speaking, ML techniques are used in IR based on statistical models established for solving specific optimization problems. In this paper, we aim to conduct a comprehensive survey on the recent research efforts related to unlicensed cellular networks and IR technologies, which work jointly to implement 5G and beyond wireless networks. Furthermore, we introduce a positioning assisted LTE-LAA system based on the difference in received signal strength (DRSS) to allocate resources among UEs. We will also discuss some open issues and challenges for future research on the IR applications in unlicensed cellular networks.

• Journal of Korea Multimedia Society
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• v.18 no.6
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• pp.742-752
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• 2015

The communications through the power lines are called as the PLC and this is a common name for the communication modes for the information delivery. This technology transmits the data through the power lines on which the information is stored with the form of high frequency signal. The characteristic of the frequency signal is that the signal can be separated from the power line through exclusive power line modem and transmitted to the terminal devices. In this paper, 'In-home Headcount' checking algorithm using Wi-Fi and taking above mentioned advantages is proposed, and the basic Technology for such Solitary Senior Citizen's Lonely Death monitoring system has been designed and implemented. The comparative analysis has been conducted in this paper with the test-operated and test bed-completed 'Hyosimi 119 Safety-Welfare System' which is still being tested since 2008. With the 'In-home Headcount Checking Algorithm', Wi-Fi connection/disconnection status and SSIDs of relevant Wi-Fis will be checked. We expect that our proposed method will become as the basic Technology which can prevent lonely deaths of elderly people living alone. Since the PLC technology can be normally implement all the functions used on internet anticipate that the technology could be applied to many areas to construct a new form of communication network.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.1
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• pp.55-61
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• 2016

As the price-performance ratio of embedded PCs improves, the benefits of the PC-Fi can be maximized by designing an embedded PC-Fi system. In this paper presents the design of an embedded PC-Fi that can be manipulated by a remote controller based on mobile devices such as smart phones or tablets. Additionally, an interactive control system and its GUI, through which the user can select and play music as they like at ease, are presented. The case that a large amount of music is stored in the PC-Fi system requires a function allowing the user to easily select the music they want to listen to. In order to implement this function, a DB containing detailed information of each track can be used to find the location of the desired music with keywords provided by the user. In this proposed system, the embedded PC-Fi system and remote controller are mutually connected via a WiFi network, and more than one user can remotely control the embedded system with their own mobile device.

• Journal of the Korea Society of Computer and Information
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• v.20 no.4
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• pp.87-93
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• 2015

Recently, an idea has been suggested in which members construct the network by sharing their surplus bandwidth of their own access point. This kind of network is called public-shared network. As an application, SVC video streaming delivery system on public-shared network has been proposed. To send video stream from the stream server to clients, a tree structure is constructed where the root is a stream server, internal nodes are sharable access points, and leafs are clients. The previous researches have focused on constructing the minimal sharable-bandwidth tree which can serve all video streaming requests using the minimal sharable bandwidth. In this paper, we have shown that the problem of constructing a tree structure with given sharable access points to serve maximal video streaming requests is NP-hard. We also have developed an efficient heuristic algorithm for this problem and evaluated experimentally our algorithm.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.1
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• pp.8-13
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• 2022

This paper investigates the method to implement a RF (Radio Frequency) energy harvesting sensor node and to build a sensor network using a CATV network and a leaky coaxial cable. The power supply of a sensor node is designed with the WPTS (Wireless Power Transfer System) receiver operating at 915MHz. A sensor network has limited coverage by the loss of RF signal at a wireless transmission link. The paper proposes to build a sensor network that the BLE signal of a sensor and the signal of a WPTS power transmitter are transmitted through a coaxial cable of a CATV network by utilizing WOC (WiFi over Coax) technology and radiates at a leaky coaxial cable. The length of a leaky coaxial cable and the total loss of a wire link are allowed to the point that the RSSI of a sensor node is more than the minimum value (-78dBm) and lead to extend wireless coverage.

• The Journal of Society for e-Business Studies
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• v.16 no.3
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• pp.145-158
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• 2011

Recently, the rapidly increased use of smartphone devices provides both opportunity and problems at the same time to the telecom companies in domestic and world wide. It provides a great opportunity to overcome the market stagnation of the existing voice- centric communications, and also problems of building a highly efficient new wireless access networks to accommodate huge volume of data traffic among smart devices. Facing with the age of keen competition, telecom companies have two kinds of strategies for network transition; a strategy of building uniform LTE -based 4G networks as fast as possible, and a hybrid network enhancement strategy compounding 3G and 4G networks using HSP A+, WiFi, cloud computing, etc. It is difficult to predict which strategy will have more successful outcome in the near future. This paper studies the trends and issues of network enhancement policies and transition strategies to the 4G network era, and tries to draw appropriate and efficient ways for network enhancement and operation.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.10
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• pp.169-177
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• 2007

Existing wireless access (mobile) routers are based commonly on the network address and port translation (NAPT) technique which permits simultaneously sharing a subscriber's connection to the network with multiple users. However, the NAPT architecturally makes the users invisible on the network side, thus becoming a user-oriented connection technique. In this paper, we propose a novel service provider-oriented unlicensed nomadic access relay station (WiNNERS) for helping wireless broadband network service providers to make their business more lucrative by accommdating unlicensed band users as subscribers into their network. The WiNNERS offers service providers the capability to directly manage each of the unlicensed band users at the network side. This direct management allows the service providers to flexibly and simply handle QoS, access control, and billing for each user. In order to distinguish each of the unlicensed band users the WiNNERS constructs a virtual tunnel from each user's terminal to the network access router using connection identifiers which is defined for service flow management within the WiBro system, Consequently, our proposed service provider-oriented relay station can be included into the WiBro network system with minimum modifications.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.12 no.4
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• pp.76-86
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• 2013

As the basic Kalman filter is limited to be used for indoor navigation, and particle filters incur serious computational overhead, especially in mobile devices, we propose an adaptive hybrid filter for WiFi-based indoor positioning systems. The hybrid filter utilizes the same prediction framework of the basic Kalman filter, and it adopts the notion of particle filters only using a small number of particles. Restricting the predicts of a moving object to a small number of particles on a way network and substituting a dynamic weighting scheme for Kalman gain are the key features of the filter. The adaptive hybrid filter showed significantly better accuracy than the basic Kalman filter did, and it showed greatly improved performance in processing time and slightly better accuracy compared with a particle filter.

• ETRI Journal
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• v.37 no.5
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• pp.877-887
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• 2015

This paper is a first-hand summary on our comprehensive live trial of cellular-assisted device-to-device (D2D) communications currently being ratified by the standards community for next-generation mobile broadband networks. In our test implementation, we employ a full-featured 3GPP LTE network deployment and augment it with all necessary support to provide realtime D2D connectivity over emerging Wi-Fi-Direct (WFD) technology. As a result, our LTE-assisted WFD D2D system enjoys the required flexibility while meeting the existing standards in every feasible detail. Further, this paper provides an account on the extensive measurement campaign conducted with our implementation. The resulting real-world measurements from this campaign quantify the numerical effects of D2D functionality on the resultant system performance. Consequently, they shed light on the general applicability of LTE-assisted WFD solutions and associated operational ranges.