Jungmin So

Sogang University · Department of Computer Science and Engineering

State-of-the-art neural network models are actively used in various fields, but it is well-known that they are vulnerable to adversarial example attacks. Throughout the efforts to make the models robust against adversarial example attacks, it has been found to be a very difficult task. While many defense approaches were shown to be not effective, a...

We report that a very high accuracy on the MNIST test set can be achieved by using simple convolutional neural network (CNN) models. We use three different models with 3x3, 5x5, and 7x7 kernel size in the convolution layers. Each model consists of a set of convolution layers followed by a single fully connected layer. Every convolution layer uses b...

In this paper, we propose a data dissemination protocol for asynchronous duty-cycling wireless sensor networks. In an asynchronous duty-cycling network, each node independently selects its wake-up time. In this environment, data dissemination becomes energy consuming, because broadcasting a packet does reach all neighbors but only the neighbors tha...

As density of a wireless LAN grows, per-user throughput degrades severely, deteriorating user experience. To improve service quality, it is important to increase system spectral efficiency. Controlling carrier-sense threshold is one of the key techniques to achieve the goal, because frequently transmissions are unnecessarily blocked by carrier sens...

This paper presents G-DCF, a MAC protocol for wireless LANs that can improve system spectral efficiency of wireless LANs by allowing more concurrent transmissions. The 802.11 DCF creates exposed terminals which are nodes that can transmit successfully but are blocked by carrier sensing. More potential exposed terminals are created when APs are dens...

As the density of wireless LANs increases, performance degradation caused by hidden terminals and exposed terminals becomes significant. These problems come from carrier sensing based medium access control used in current wireless LANs. Hidden terminals are created if carrier sense threshold is too high, whereas exposed terminals are created if car...

Abstract This paper presents a medium access control protocol for wireless networks that improves system spectral efficiency using multiple channels. Use of multiple narrow channels has already been proposed as a solution to reduce MAC overhead, but merely dividing a wide channel into narrow channels cannot mitigate the negative effect of packet co...

This paper presents schemes that reduces ACK (acknowledgement) overhead in IEEE 802.11 wireless networks and further improve network performance in high error rate cases. While the ACK takes only 20us in 802.11a at 54Mbps, a combination of SIFS period and preamble makes ACK the second largest overhead next to channel access overhead. To reduce ACK...

Wireless interface bonding is an important technique in multi-radio systems, where multiple radios can be combined to establish a fast link between nodes. However, existing interface bonding modules are not well-suited for wireless interfaces due to lack of functionalities to cope with varying channel capacity. Variance in throughput and delay of t...

In duty-cycled wireless sensor networks running asynchronous MAC protocols, the time when a sender waits for its receiver to wake up and receive the packet is the major source of energy consumption. Opportunistic routing can reduce the sender wait time by allowing multiple candidate receivers, but by doing that it suffers from redundant packet forw...

Objectives: This study obtained quantitative measures reflecting phonological, semantic, syntactic, and morphological aspects of language in Korean two-year-old children from analysis of spontaneous utterances. The study investigated whether there were differences of speech-language development patterns between children age 24-30 months and 31-36 m...

Multi-radioroutersare widely deployed to exploit diversity of using multiple interfaces in endemic wireless networks. Although multi-radio nodes are capable of using multiple channels at the same time, it is not a typical practice to combine multiple radios to achieve high throughput for a single TCP flow. The major reason is due to the difference...

Multi-radio routers are widely deployed to exploit diversity of using multiple interfaces in endemic wireless networks. Although multi-radio nodes are capable of using multiple channels at the same time, it is not a typical practice to combine multiple radios to achieve high throughput for a single TCP flow. The major reason is due to the differenc...

This paper proposes an algorithm for exemplar-based image inpainting, which produces the same result as that of Criminisi's original scheme but at the cost of much smaller computation cost. The idea is to compute mean and standard deviation of every patch in the image, and use the values to decide whether to carry out pixel by pixel comparison or n...

Although Wi-Fi based indoor localization systems have been dominant in recent years due to its cost effectiveness, cumbersome offline surveying and high energy consumption were the main obstacles against their commercialization. Low-energy Bluetooth beacon is a good alternative to Wi-Fi in supporting indoor localization and navigation, since the ha...

Wireless sensor-actuator networks (WSANs) enhance the existing wireless sensor networks (WSNs) by equipping sensor nodes with actuators. The actuators work with the sensor nodes to perform application-specific operations. The WSAN systems have several applications such as disaster relief, intelligent building management, military surveillance, heal...

This paper proposes an opportunistic routing protocol for wireless sensor networks that works on top of an asynchronous duty-cycling medium access control (MAC) protocol. The proposed protocol is designed for applications that are not real-time but still have some requirements on packet delay. The main idea is that if a packet has time to spare, it...

In cloud storage system, when we search similar documentation files, keyword-based similarity evaluation scheme is well performed. However, if we want to find similar binary files then it is very difficult to satisfy user request. Because there is no widely used binary file search system that supports similarity evaluation among files. File similar...

Recently, there have been tremendous interests in the acceleration of general computing applications using a Graphics Processing Unit (GPU). Now the GPU provides the computing powers not only for fast processing of graphics applications, but also for general computationally complex data intensive applications. On the other hand, power and energy co...

In this paper, we propose techniques that reduce the MAC overhead in IEEE 802.11-based wireless networks. As the channel bit rate increases, MAC overhead becomes a major source of throughput degradation. This is due to the fact that the MAC overhead is rate-independent; it is fixed regardless of the data rate. Rate-independent overhead can be reduc...

This letter presents a scheme to improve the running time of exemplar-based image inpainting, first proposed by Criminisi et al. In the exemplar-based image inpainting, a patch that contains unknown pixels is compared to all the patches in the known region in order to find the best match. This is very time-consuming and hinders the practicality of...

Manycore processor architectures are currently very widely used in almost all computer systems. Furthermore, many computer science department have started to teach parallel programming on manycore system platforms. To best understand the parallel programming on those manycore processors, the classes on manycore processor architecture also have to b...

In this paper, we propose an analytical method for duty cycle adaptation in wireless sensor networks so that delay requirement is guaranteed while power consumption is minimized. The proposed method, named Dual-QCon, provides a formal method for stabilizing controller design based on queue management in order to control both duty cycle and queue th...

We propose an opportunistic routing protocol for wireless sensor networks designed to work on top of an asynchronous duty-cycled MAC. Opportunistic routing can be very effective when used with asynchronous duty-cycled MAC because expected waiting time of senders—when they stay on active mode and transmit packet streams—is significantly reduced. If...

The Accurate indoor localization is a challenging task due to the absence of GPS. Among numerous proposals, Wifi fingerprint-based localization is one of the most promising approach, since most buildings are nowadays equipped with Wifi access points for wireless network coverage. Due to the nature of Wifi access points in which any user can deploy...

Existing protocols for in-network fusion of data, in wireless sensor networks, are either single-path (i.e., tree-based) or multi-path. Tree-based fusion protocols have small message overhead but low reliability under node and link failures, while multi-path protocols have good reliability, but potentially higher overhead. This paper presents a sui...

Data aggregation, a process of delivering data from measurement sources (sensors) to the sink, is a major task in wireless sensor networks (WSNs). A data aggregation protocol often has two goals: reliability and energyefficiency. Reliability of data aggregation considers how many packets from sources successfully arrive at the sink, whereas energy-...

For large-scale sensor networks, multiple sinks are often deployed in order to reduce source-to-sink distance and thus cost of data delivery. However, having multiple sinks may work against cost reduction, because routes from sources can diverge towards different sinks which reduces the benefit of in-network data aggregation. In this letter we prop...

This paper proposes a control-based approach to duty cycle adaptation for wireless sensor networks. The proposed method controls duty cycle through queue management in order to achieve high performance under variable traffic rates. To have energy efficiency while minimizing the delay, we design a feedback controller, which adapts sleeping interval...

The Internet and Web technologies have originally been developed assuming an ideal world where all users are honorable. However, the dark side has emerged and bedeviled the world. This includes spam, malware, hacking, phishing, denial of service attacks, click fraud, invasion of privacy, defamation, frauds, violation of digital property rights, etc...

Purpose A botnet is a network of computers on the internet infected with software robots (or bots). There are numerous botnets, and some of them control millions of computers. Cyber criminals use botnets to launch spam e‐mails and denial of service attacks; and commit click fraud and data theft. Governments use botnets for political purposes or to...

As the demands for various multimedia services requiring high capacity increase, shortage of wireless resources becomes a serious problem in cellular networks. In order to reduce the heavy load and increase overall capacity of cellular networks, internetworking between WLANs and cellular net- works has being considered. However, in the internetwork...

A botnet is a network of computers on the Internet infected with software robots, bots. There are numerous botnets. Some of them control millions of computers. Botnets have become the platform for the scourge of the Internet, namely, spam e-mails, launch denial of service attacks, click fraud, theft of sensitive information, cyber sabotage, cyber w...

As public deployment of wireless local area networks (WLANs) has increased and various applications with different service requirements have emerged, fairness and quality of service (QoS) are two imperative issues in allocating wireless channels. This study proposes a fair QoS agent (FQA) to simultaneously provide per-class QoS enhancement and per-...

A hybrid wireless network is an extension to an infrastructure network, where a mobile host may connect to an access point (AP) using multihop wireless routes via other mobile hosts. The APs are configured to operate on one of multiple available channels. Mobile hosts and wireless routers can select their operating channels dynamically through chan...

This paper proposes a routing scheme that exploits multiple heterogeneous wireless interfaces: a primary 802.11a interface and a secondary 802.11b (or 802.11) interface. In normal conditions, a TCP flow uses a primary path over the 802.11a interface discovered by a reactive routing protocol. But in presence of route breakage due to node mobility, i...

A hybrid wireless network is an extension of an infrastructure network, where a mobile host may connect to an access point (AP) using multihop wireless routes, via other mobile hosts. The APs are configured to operate on one of multiple available channels. Mobile hosts and wireless routers can select its operating channel dynamically through channe...

Supporting high throughput is an important challenge in multihop mesh networks. Popular wireless LAN standards, such as IEEE 802.11, provision for multiple channels. In this article, we consider the use of multiple wireless channels to improve network throughput. Commercially available wireless network interfaces can typically operate over only one...

Wireless networks have been widely deployed in the past few years. With rapidly increasing number of users, it is important to maximize utilization of given resources to achieve high performance. Among many approaches, the aim of this dissertation is in utilizing available frequency spectrum, which may be divided into multiple non-overlapping chann...

In a typical in-network aggregation problem, data originates from multiple source nodes, and moves towards single sink node or root node. Along the way, i.e., inside the network, the data may be partially aggregated, thus reducing message overhead. Two well-known classes of solutions to this problem are: tree-based aggregation and multipath aggrega...

In this paper, we study the performance of IEEE 802.11 broadcast scheme in multihop wireless networks using an analytical model. Previous works have evaluated the performance of IEEE 802.11 proto- col assuming unicast communication, but there has not been an analysis considering broadcast communication. Analyzing performance of broad- cast communic...

A hybrid wireless network is an extension to an infrastructure network, where a mobile host may connect to an access point using multi-hop wireless routes, via other mobile hosts. The access points are configured to operate on one of multiple available channels. Mobile hosts and wireless routers can select its operating channel dynamically through...

Abstract In this paper, we present a routing and channel assignment protocol for multi-channel multi-hop wireless networks. We view a multi-hop network as an extension to infrastructure networks, where a mobile host may connect to an access point using multi-hop wireless routes, via other mobile hosts or wireless routers. The access points are conf...

This paper proposes a medium access control (MAC) protocol for ad hoc wireless networks that utilizes multiple channels dynamically to improve performance. The IEEE 802.11 standard allows for the use of multiple channels available at the physical layer, but its MAC protocol is designed only for a single channel. A single-channel MAC protocol does n...

Wireless ad hoc networks often suffer from rapidly degrading performance as the number of users increases in the network. One of the major reasons for this rapid degradation of performance is the fact that users are sharing a single channel. Al- though widely deployed standards such as IEEE 802.11 provides multiple non-overlapping channels, most pr...

This paper proposes a medium access control (MAC) protocol for ad hoc wireless networks that can utilize multiple channels dynamically to improve performance. IEEE 802.11 standard provides multiple channels for use, but its MAC protocol is designed only for a single channel. We can achieve improved throughput with multiple channels because multiple...

In this paper, we present a routing and channel assignment protocol for multi-channel multi-hop wireless net- works. We view a multi-hop network as an extension to infrastructure networks, where a mobile host may connect to an access point using multi-hop wireless routes, via other mobile hosts or wireless routers. The access points are configured...

In this paper, we present a routing and channel as- signment protocol for multi-channel multi-hop wireless networks. We consider a multi-hop network, where a mobile host may con- nect to an access point using multi-hop wireless routes, via other mobile hosts or wireless routers. Also, we consider a multi-channel network where multiple non-overlappi...

In this paper, we propose a protocol for synchro-nizing time in multihop wireless networks. Protocols for power management or dynamic channel assignment often require syn-chronous operations, such as waking up at the same time or listen-ing to a common channel. Having the nodes synchronized in time is often crucial for these protocols to work. Howe...