• Title/Summary/Keyword: Medium access

Search Result 723, Processing Time 0.026 seconds

The Effect of the Buffer Size in QoS for Multimedia and bursty Traffic: When an Upgrade Becomes a Downgrade

  • Sequeira, Luis;Fernandez-Navajas, Julian;Saldana, Jose
    • KSII Transactions on Internet and Information Systems (TIIS)
    • /
    • v.8 no.9
    • /
    • pp.3159-3176
    • /
    • 2014
  • This work presents an analysis of the buffer features of an access router, especially the size, the impact on delay and the packet loss rate. In particular, we study how these features can affect the Quality of Service (QoS) of multimedia applications when generating traffic bursts in local networks. First, we show how in a typical SME (Small and Medium Enterprise) network in which several multimedia flows (VoIP, videoconferencing and video surveillance) share access, the upgrade of the bandwidth of the internal network may cause the appearance of a significant amount of packet loss caused by buffer overflow. Secondly, the study shows that the bursty nature of the traffic in some applications traffic (video surveillance) may impair their QoS and that of other services (VoIP and videoconferencing), especially when a certain number of bursts overlap. Various tests have been developed with the aim of characterizing the problems that may appear when network capacity is increased in these scenarios. In some cases, especially when applications generating bursty traffic are present, increasing the network speed may lead to a deterioration in the quality. It has been found that the cause of this quality degradation is buffer overflow, which depends on the bandwidth relationship between the access and the internal networks. Besides, it has been necessary to describe the packet loss distribution by means of a histogram since, although most of the communications present good QoS results, a few of them have worse outcomes. Finally, in order to complete the study we present the MOS results for VoIP calculated from the delay and packet loss rate.

The Performance Analysis of Cognitive-based Overlay D2D Communication in 5G Networks

  • Abdullilah Alotaibi;Salman A. AlQahtani
    • International Journal of Computer Science & Network Security
    • /
    • v.24 no.2
    • /
    • pp.178-188
    • /
    • 2024
  • In the near future, it is expected that there will be billions of connected devices using fifth generation (5G) network services. The recently available base stations (BSs) need to mitigate their loads without changing and at the least monetary cost. The available spectrum resources are limited and need to be exploited in an efficient way to meet the ever-increasing demand for services. Device to Device communication (D2D) technology will likely help satisfy the rapidly increasing capacity and also effectively offload traffic from the BS by distributing the transmission between D2D users from one side and the cellular users and the BS from the other side. In this paper, we propose to apply D2D overlay communication with cognitive radio capability in 5G networks to exploit unused spectrum resources taking into account the dynamic spectrum access. The performance metrics; throughput and delay are formulated and analyzed for CSMA-based medium access control (MAC) protocol that utilizes a common control channel for device users to negotiate the data channel and address the contention between those users. Device users can exploit the cognitive radio to access the data channels concurrently in the common interference area. Estimating the achievable throughput and delay in D2D communication in 5G networks is not exploited in previous studies using cognitive radio with CSMA-based MAC protocol to address the contention. From performance analysis, applying cognitive radio capability in D2D communication and allocating a common control channel for device users effectively improve the total aggregated network throughput by more than 60% compared to the individual D2D throughput without adding harmful interference to cellular network users. This approach can also reduce the delay.

Relationship between Access to Lewd Internet Contents by Middle School Students and Their Awareness of Sex (중학생의 인터넷음란물 접속과 성 의식의 관계)

  • Lim, Jong-In;Choi, In-Sook
    • The Journal of Korean Society for School & Community Health Education
    • /
    • v.4
    • /
    • pp.117-139
    • /
    • 2003
  • The purpose of this research lies in presenting logical viability for the measures that curtail access to lewd Internet contents by middle school students amidst the reality in which lewd contents are circulated freely through the Internet, a medium that the middle school students find most easy to access. In order to establish right form of awareness towards sex, this research identified the ways they access the lewd Internet contents, their reaction after the exposure to those contents, their knowledge of sex, their concerns regarding sex and their accessibility to sexual activities in order to conduct a comparative analysis on the relationship between lewd Internet contents and their awareness of sex. First, realities of accessing lewd Internet contents and reactions according to the demographics of middle school students There isa significant difference in the experience of accessing lewd Internet contents in terms of gender. Mostly, male students tend to access the contents more. As for the way they access the lewd Internet contents, both male and female students replied that they access through spam mail of lewd nature. Thus, measures to address this problem are needed urgently. As to when they first accessed the lewd contents, most of the research subjects replied that they accessed either in elementary school period or in the early middle school period. This shows that most of the students got exposed to lewd contents even before they could establish positive, correct awareness of sex. Thus, there is a risk that they may formulate wrong kind of sexual awareness. Accordingly, it is necessary to develop measures through focused sex education. Students are divided into two groups according to the time they spend on the contents averagely: those who spend over one hour and those who spend less than an hour on the lewd contents. If the students spending longer hours are not to be checked and properly guided, it may lead to increasing cases of sexual delinquencies due to their wrongly formed awareness of sex. When the question of existence(non-existence) of guardian was addressed, students with both parents tend to access the lewd Internet contents in a more diverse manner and tend to access more compared to those students from single parent or no-parent families. Accordingly, guardians need to pay attention to how their children are using the Internet. Second, awareness of sex depending on the middle school students' demographics In case of sexual knowledge, middle school students shows relatively high level of knowledge. In particular, female students are found more knowledgeable than male students, and the students in upper years are more knowledgeable as well. As a result, this research recommends that the students in lower years should be guided with more basc and detailed information, while those in upper years need to be taught to form and express their own thoughts and attitudes and to build up independence on this matter. In case of worries about sex, both male and female students don't worry too much about it. However, male students are more concerned about sex than female students in a more diverse ways. As for the differences by academic year, concerns for sex increase, as students get older. Accordingly, sex education that helps establish sound perception of the opposite sex and that focuses on the etiquettes that one must adhere to at the presence of the opposite sex need to be conducted against middle school students. In case of accessibility to sex, male students manifest higher tendency than female students. As for the differences by academic year, those in the first and second years show higher accessibility than those in their third year. In general, younger students tend to be more open-minded toward sex. Accordingly, students in lower academic years need to undergo basic knowledge oriented sex education, whereas those in upper academic years need to undergo discussion centered sex education where they subject to questions regarding their attitude and opinion. Third, relationship between the reactions after the exposure to the lewd Internet contents and their awareness of sex As the frequency of contact with lewd Internet contents increases, awareness of sex increases as well. Thus, the lewd Internet contents contribute to the increase in students' concern for sex as well as increase in accessibility to sex, which eventually become barriers to students' establishment of a healthy perception of sex. Reactions to sex after the exposure to lewd Internet contents and awareness of sex indicate a significant correlation. However, negative correlation is manifested with knowledge of sex. Thus, it is possible to know that the greater access to lewd Internet contents does not necessarily translate into increase in knowledge of sex. However, the study showed there is a correlation between concerns for sex and the level of accessibility to sex. In more detail, the more reactions to the contents they show, the more concerns for sex they have and the more positively they take acceptability to sex. Moreover, it is necessary to develop necessary measures since textbooks today do not include measures needed to address the lewd Internet contents. Given the above findings, it is necessary to continue to complement structural measures in order to prevent easy access of lewd Internet contents by middle school students. Moreover, it is necessary to be considerate of the students so that they themselves can form a healthy Internet culture and grow up within positive framework for the sex education.

  • PDF

Isolation and Identification of Lactic Acid Bacteria from Spent Mushroom Substrate for Silage Making and Determination of Optimal Medium Conditions for Growth

  • Kim, Young-Il;Kwak, Wan-Sup
    • Journal of Animal Science and Technology
    • /
    • v.54 no.6
    • /
    • pp.435-442
    • /
    • 2012
  • This study was conducted to isolate and identify the lactic acid bacteria (LAB) from spent mushroom substrates (SMS) for the effective anaerobic fermentation to utilize SMS as an animal feed and to determine the optimal medium conditions for their growth. At first, a total of 23 strains were isolated from the ensiled SMS based on the LAB counts and pH tested. Then, a total of 16 strains which rapidly produce lactate and decreased the pH, were selected for a screening test. The optical density (OD), pH, and yellow clear zone were tested for the selected 16 strains. Among the strains, KU5 strain had wider yellow clear zone and lower pH and KU13 strain had higher OD at 24 hr of incubation and wider yellow clear zone compared to other strains and control strain (Lactobacillus plantarum KCCM 12116). Accordingly, KU5 and KU13 strains were finally selected. The KU5 and KU13 were identified as Lactobacillus plantarum by the 16S rRNA sequencing. The KU5 strain was named as Lactobacillus plantarum KU5, and the KU13 strain was named as Lactobacillus plantarum KU13. Lactobacillus plantarum KU5 and Lactobacillus plantarum KU13 were registered at the National Center for Biotechnology Information (NCBI). Access number of Lactobacillus plantarum KU5 was HQ542227 and that of Lactobacillus plantarum KU13 was HQ542228. The optimal medium conditions for growth of KU5 and KU13 were soybean meal 2% and formulated feed 2%, respectively.

The effects of compact city development on public transportation commuting -The cases of 54 medium and small-sized cities in korea (압축도시 개발이 대중교통을 이용한 통근 통행에 미치는 영향 -한국의 54개 중소도시를 대상으로-)

  • Lee, Kyung-Hwan
    • Journal of the Korean Society of Hazard Mitigation
    • /
    • v.10 no.2
    • /
    • pp.55-60
    • /
    • 2010
  • The purpose of this study is to analyze compact city planning indicators that have influence on public transportation commuting of residents in the 54 medium and small-sized cities. In the study, land use and transportation infrastructure of cities and other socio-demographic variables are used as explanatory variables in a causal model. 96,552 subjects from 54 cities in korea are selected as the final sample, and a statistical analysis is carried out by applying Random Intercept Logit Model. Analysis shows that a high level of density and jobs-housing balance in the city results in more public transportation commuting. And higher access to bus and subway station influence commuting, so subway & bus stop are important factors to increase public transportation commuting

Remediation Characteristics that Appear in the Change of MP3Player II: Re-mediation through Appearance Changes, Cultural and Social Paradigms (MP3Player의 변화에서 나타나는 재매개적 특성 II: 외형적 변화와 문화, 사회적 패러다임을 통한 재매개성)

  • Lee, Jin-Hyuk;Lee, Young-Chun;Koo, Yoon-Hee
    • The Journal of the Korea Contents Association
    • /
    • v.13 no.11
    • /
    • pp.69-78
    • /
    • 2013
  • A Korean MP3player also has become complex multimedia device which can provide various functions such as DMB, image playback, radio, electronic dictionary, storage device, and Internet. However, these functions are not provided through one-time mediation. Therefore, studying which changes were made for obtaining or installing these functions and what made such changes possible will be a basis to approach the change factors of medium through medium. Ultimately, by enabling to access the factors of cultural and social changes through MP3player, the main point of this study, it will be a methodological attempt to study a social aspect through medium. This study approached re-mediation according to the genealogical change of MP3player. This study researched the change of media through mediation of MP3player, and approached the change in social contextuality through this. The factors for which a medium is changed are various, but in the change of MP3 player there is re-mediation of each medium in addition to technical change. That is, it is deemed that there are 're-mediation among devices' and 'socially contextual re-mediation' in the change through re-mediation of MP3player.

Electronic Publishing and Its Impact on the Library Fuctions (전자출판의 발전과 도서관기능의 다변화)

  • Kwon Eun-Kyung
    • Journal of the Korean Society for Library and Information Science
    • /
    • v.32 no.4
    • /
    • pp.159-186
    • /
    • 1998
  • The emergence of digital library has been recognized as the paradigm shift of medium from paper to electronic, or that of the library function from ownership to access. From the point of view that digital information is the core constituent of digital library and is produced by electronic publishing, this paper explores the relationship between electronic publishing and digital library with special attention on recent digital library projects. And investigates the possibility of the transformation of scholarly communication system through digital library function as well as the impact of electronic publishing on the library functions.

  • PDF

Cognitive Radio 통신망을 위한 MAC 프로토콜

  • Lee, Dong-Heon;Ha, Gi-Ung;Jeon, Hwa-Suk;Jeong, Dong-Geun
    • The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.20 no.3
    • /
    • pp.25-35
    • /
    • 2009
  • 인지 무선(CR: Cognitive Radio) 기술은 특정 사용자에게 허가되었으나 일정 시간, 일정 지역에서 사용되지 않는 주파수 대역을 찾아 한시적으로 사용함으로써 주파수 사용 효율을 높이는 기술이다. CR 기술을 사용하는 무선 통신 시스템을 구현하기 위해서는 효과적인 채널 센싱 스케쥴링, 채널 선택, 채널 전환 기법을 제공하는 매체 접근 제어(MAC: Medium Access Control) 프로토콜의 개발이 필수적이다. 이글에서는 CR MAC 프로토콜의 특징과 설계시 고려 사항을 검토하고, 현재까지 제안된 몇 가지 CR MAC 프로토콜을 살펴본다. 이를 통해 최신 연구 동향을 파악하고 향후 연구 과제를 제시한다.

Genetic Algorithm based Methodology for an Single-Hop Metro WDM Networks

  • Yang, Hyo-Sik;Kim, Sung-Il;Shin, Wee-Jae
    • Proceedings of the Korea Institute of Convergence Signal Processing
    • /
    • 2005.11a
    • /
    • pp.306-309
    • /
    • 2005
  • We consider the multi-objective optimization of a multi-service arrayed-waveguide grating-based single-hop metro WDM network with the two conflicting objectives of maximizing throughput while minimizing delay. We develop and evaluate a genetic algorithm based methodology for finding the optimal throughput-delay tradeoff curve, the so-called Pareto-optimal frontier. Our methodology provides the network architecture and the Medium Access Control protocol parameters that achieve the Pareto-optima in a computationally efficient manner. The numerical results obtained with our methodology provide the Pareto-optimal network planning and operation solution for a wide range of traffic scenarios. The presented methodology is applicable to other networks with a similar throughput-delay tradeoff.

  • PDF

A Selected Multicast Polling Scheme for IEEE 802.11 Point Coordination Function

  • Lee Sang Don;Cho Chi Woo;Kim Kyung Jun;Kim Hyun Sook;Han Ki Jun
    • Proceedings of the IEEK Conference
    • /
    • 2004.08c
    • /
    • pp.536-539
    • /
    • 2004
  • IEEE 802.11 Point Coordination Function (PCF) mode is defined to support time bounded traffic, such as voice in wireless LANs. The poll scheduling plays an important role in IEEE 802.11 PCF mode operation. This paper proposed a Multicast Polling Scheme (MPC) to increase the performance of wireless LANs. Moreover, we proposed a polling schedule scheme for our proposed multi-poll to serve real-time traffic. The results show that the proposed mechanism is more efficient than the original IEEE 802.11 PCF.

  • PDF