• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.14 no.3
• /
• pp.1313-1336
• /
• 2020

Cognitive radio (CR) is regarded as an effective approach to avoid the inefficient use of spectrum. However, CRNs have more special security problems compared with the traditional wireless communication systems due to its open and dynamic characteristics. Primary user emulation attack (PUEA) is a common method which can hinder secondary users (SUs) from accessing the spectrum by transmitting signals who has the similar characteristics of the primary users' (PUs) signals, and then the SUs' quality of service (QoS) cannot be guaranteed. To handle this issue, we first design a multiple-phase energy detection scheme based on the cooperation of multiple SUs to detect the PUEA more precisely. Second, a joint SUs scheduling and power allocation scheme is proposed to maximize the weighted effective capacity of multiple SUs with a constraint of the average interference to the PU. The simulation results show that the proposed method can effectively improve the effective capacity of the secondary users compared with the traditional overlay scheme which cannot be aware of the existence of PUEA. Also the good delay QoS guarantee for the secondary users is provided.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.11 no.1
• /
• pp.484-510
• /
• 2017

Network security is rapidly developing, but so are attack methods. Network worms are one of the most widely used attack methods and have are able to propagate quickly. As an active defense approach to network worms, the honeynet technique has long been limited by the closed architecture of traditional network devices. In this paper, we propose a closed loop defense system of worms based on a Software-Defined Networking (SDN) technology, called Worm-Hunter. The flexibility of SDN in network building is introduced to structure the network infrastructures of Worm-Hunter. By using well-designed flow tables, Worm-Hunter is able to easily deploy different honeynet systems with different network structures and dynamically. When anomalous traffic is detected by the analyzer in Worm-Hunter, it can be redirected into the honeynet and then safely analyzed. Throughout the process, attackers will not be aware that they are caught, and all of the attack behavior is recorded in the system for further analysis. Finally, we verify the system via experiments. The experiments show that Worm-Hunter is able to build multiple honeynet systems on one physical platform. Meanwhile, all of the honeynet systems with the same topology operate without interference.

• Journal of Communications and Networks
• /
• v.14 no.1
• /
• pp.51-62
• /
• 2012

The exponential growth in wireless services has resulted in an overly crowded spectrum. The current state of spectrum allocation indicates that most usable frequencies have already been occupied. This makes one pessimistic about the feasibility of integrating emerging wireless services such as large-scale sensor networks into the existing communication infrastructure. Cognitive radio is an emerging dynamic spectrum access technology that can be used for flexibly and efficiently achieving open spectrum sharing. Cognitive radio is an intelligent wireless communication system that is aware of its radio environment and that is capable of adapting its operation to statistical variations of the radio frequency. In ad hoc cognitive radio networks, a common control channel (CCC) is usually used for supporting transmission coordination and spectrum-related information exchange. Determining a CCC in distributed networks is a challenging research issue because the spectrum availability at each ad hoc node is quite different and dynamic due to the interference between and coexistence of primary users. In this paper, we propose a novel CCC selection protocol that is implemented in a distributed way according to the appearance patterns of primary systems and connectivity among nodes. The proposed protocol minimizes the possibility of CCC disruption by primary user activities and maximizes node connectivity when the control channel is set up. It also facilitates adaptive recovery of the control channel when the primary user is detected on that channel.

• Journal of Internet Computing and Services
• /
• v.15 no.3
• /
• pp.63-69
• /
• 2014

For the safety messages in IEEE 802.11p vehicles network environment(WAVE), strict periodic beacon broadcasting requires status advertisement to assist the driver for safety. WAVE standards apply multiple radios and multiple channels to provide open public road safety services and improve the comfort and efficiency of driving. Although WAVE standards have been proposed multi-channel multi-radio, the standards neither consider the WAVE multi-radio environment nor its effect on the beacon broadcasting. Most of beacon broadcasting is designed to be delivered on only one physical device and one control channel by the WAVE standard. also conflict-free channel assignment of the fewest channels to a given set of radio nodes without causing collision is NP-hard, even with the knowledge of the network topology and all nodes have the same transmission radio. Based on the latest standard IEEE 802.11p and IEEE 1609.4, this paper proposes an interference aware-based channel assignment algorithm with Nash bargaining solution that minimizes interference and increases throughput with wireless mesh network, which is deigned for multi-radio multi-cahnnel structure of WAVE. The proposed algorithm is validated against numerical simulation results and results show that our proposed algorithm is improvements on 8 channels with 3 radios compared to Tabu and random channel allocation algorithm.

• Korean Journal of Clinical Laboratory Science
• /
• v.37 no.2
• /
• pp.71-77
• /
• 2005

We experienced the specimen that contains a hemoglobin variant known as interference from HbAS in October 2003. It was the first case of Hb variants since Samsung Medical Center began conducting glycohemoglobin College of American Pathologists surveys in 1997. The purpose of this study is to share our experience with the specimen and promote the understanding of Hb variants & derivatives. We've performed cross checks to examine HbA1c by using two pieces of equipment; the TOSHOH G7 and BIO-RAD VARIANT-T(turbo), and Automatic High Performance Liquid Chromatography(HPLC) as an analytic measurement method. HPLC provides different fractional information of hemoglobin with a two-dimensional graph as well as numeric results. We have been performing a "Systematic Checking Process". Three specimen suspicious of Hb variants & derivatives were found through this process. College of American Pathologists notified that it is important for users to be aware of the limitation of their glycohemoglobin method to avoid reporting incorrect results due to interference from hemoglobin variants or hemoglobin adducts. Therefore, laboratory findings of Hb variants & derivatives are very important. The experience of qualified technicians with professional knowledge in Hb variants is the most important aspect in finding Hb variants. Korea is homogeneous in race and is not in an area with a higher finding rate of Hb variants. While 1,024 cases of Hb variants have been found in Japan, we do not have specific data on how many cases of Hb variants have been found in Korea. Considering Hb variant cases in Japan, which is geographically close to us, it is presumed that there must be various Hb variant cases in Korea. If domestic laboratories set a systemic protocol and build a network to share our experience in Hb variants, I expect the Korean Hb variants could also be listed on the world's Hb variant list.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.12
• /
• pp.2443-2449
• /
• 2015

Downlink (DL) data rate for a MS is influenced by not only the signal to interference and noise ratio (SINR) but also the amount of radio resources allocated to the MS. Therefore, when a MS uses SINR to select a cell to associate with, it cannot receive the fastest DL data rate all the time if it associates with a congested cell. Moreover, the SINR-based cell selection may result in cell loads unbalance, which decreases the efficiency of a network. To address the issue, we propose a novel cell selection method by considering not only SINR but also a cell load which are combined into two cell selection criteria. One is the maximum achievable data rate and the other is the minimum outage probability. The simulation results show that the cell selection based on the maximum achievable data rate is superior to the SINR-based method and the method using the minimum outage probability in terms of the system efficiency and the fairness in cell loads while the cell selection method based on the minimum outage probability is superior to the others in terms of the outage probability of a MS.

• The Mathematical Education
• /
• v.56 no.1
• /
• pp.63-80
• /
• 2017

By analysing the examination papers from third grade high school students, we classified the errors occurred in the problem solving process of high school 'Geometry and Vectors' into several types. There are five main types - (A)Insufficient Content Knowledge, (B)Wrong Method, (C)Logical Invalidity, (D)Unskilled Expression and (E)Interference.. Type A and B lead to an incorrect answer, and type C and D cannot be distinguished by multiple-choice or closed answer questions. Some of these types are classified into subtypes - (B1)Incompletion, (B2)Omitted Condition, (B3)Incorrect Calculation, (C1)Non-reasoning, (C2)Insufficient Reasoning, (C3)Illogical Process, (D1)Arbitrary Symbol, (D2)Using a Character Without Explanation, (D3) Visual Dependence, (D4)Symbol Incorrectly Used, (D5)Ambiguous Expression. Based on the these types of errors, answers of each problem was analysed in detail, and proper ways to correct or prevent these errors were suggested case by case. When problems that were used in the periodical test were given again in descriptive forms, 67% of the students tried to answer, and 14% described flawlessly, despite that the percentage of correct answers were higher than 40% when given in multiple-choice form. 34% of the students who tried to answer have failed to have logical validity. 37% of the students who tried to answer didn't have enough skill to express. In lessons on curves of secondary degree, teachers should be aware of several issues. Students are easily confused between 'focus' and 'vertex', and between 'components of a vector' and 'coordinates of a point'. Students often use an undefined expression when mentioning a parallel translation. When using a character, students have to make sure to define it precisely, to prevent the students from making errors and to make them express in correct ways.

• Pediatric Gastroenterology, Hepatology & Nutrition
• /
• v.19 no.3
• /
• pp.162-167
• /
• 2016

Purpose: To determine the socio-economic impact of gluten free diet (GFD) on Saudi children and their families Methods: A cross-sectional study was conducted in which an online questionnaire was sent to all families registered in the Saudi celiac patients support group. We included only children (age 18 years of age and younger) with biopsy-confirmed celiac disease (CD). Results: A total of 113 children were included in the final analysis, the median age was 9.9 years; 62.8% were females. One hundred (88.5%) of the participating families reported that GFD food was not easily available in their areas, 17% of them reported that it was not available at all in their area. One hundred and six (93.8%) reported that the price of GFD food was very expensive and 70 (61.9%) families that the diet was heavily affecting their family budget. Significant social difficulties were reported among the participating families and their children including interference with the child's interaction with other children (49.6%), the families' ability to attend social gatherings (60.2%), the families' ability to eat in restaurants (73.5%), and the families' ability to travel (58.4%). Conclusion: There is significant negative socio-economic impact of GFD on children with CD & their families. Health care providers should be aware of these psycho-social difficulties and be well trained to provide a proper education and psychological support for these patients and their families.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.4B
• /
• pp.704-712
• /
• 2010

Recently, the lack of the frequency have been emerged due to the use of various wireless terminals. To find solutions for obtaining new frequency resources and for avoiding an interference, a cognitive radio technology have focused on as the new technology that can use the whitespace in TV broadcasting band. In this paper, the Cognitive Radio terminal system for whitespace in TV band is first introduced. The purpose of the CR terminal platform is to evaluate the feasibility of the unlicensed wireless service in the TV band. Then, we design and develop the software for Sensing MAC applied the cognitive radio terminal system. The developed Sensing MAC software based on IEEE 802.22 specification can be aware of using the whitespace in TV band that operates on cognitive radio terminal system. Finally, we have tested for evaluating the sensing MAC module.

• Archives of Plastic Surgery
• /
• v.37 no.1
• /
• pp.95-98
• /
• 2010

Purpose: One of the most common cause of upper extremity lymphedema is breast cancer surgery. We experienced the nerve entrapment syndrome which was associated with postmastectomy lymphedema. To the best of our knowledge, this is the first case report of lymphedema induced nerve entrapment syndrome on upper extremity in Korea. Methods: A 54-year-old woman presented with a tingling sensation on her right hand, which had been present for 1 year. On her history, she had a postmastectomy lymphedema on her right upper extremity for 20 years. Initial electromyography (EMG) showed that the ampulitude of the median, ulnar, and dorsal ulnar cutaneous nerve were decreased, and conduction block was also seen in median nerve across the wrist. In needle EMG, incomplete interference patterns were observed in the muscles innervated by median and ulnar nerves. In conclusion, electrophysiologic study and clinical findings suggested right median and ulnar neuropathy below the elbow. Therefore, we performed surgical procedures, which were release of carpal tunnel, Guyon's canal, and cubital tunnel. Results: The postoperative course was uneventful until the first two years. The tingling sensation and claw hand deformity were improved, however, the motor function decreased progressively. In 7 years after the operation, patient could not flex her wrist and thumb sufficiently. EMG which was performed recently showed that ulnar motor response was of low ampulitude. Moreover, median, ulnar, dorsal ulnar cutaneous, lateral antecubital cutaneous and median antebrachial cutaneous sensory response were unobtainable. Abnormal spontaneous activities were observed in upper arm muscles. In conclusion, multiple neuropathies were eventually developed at above elbow level. Conclusion: On treating nerve entrapments associated with lymphedema, medical professionals should be fully aware of the possibility of unpredictable results after the surgery, because of the pathophysiologic traits of chronic lymphedema.