• Journal of the Korea Society of Computer and Information
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• v.19 no.3
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• pp.63-71
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• 2014

We analyze the execution time of Reed-Solomon coding, which is the MAC-layer forward error correction scheme used in CDMA2000 1xEV-DO broadcast services, under different air channel conditions. The results show that the time constraints of MPEG-4 cannot be guaranteed by Reed-Solomon decoding when the packet loss rate (PLR) is high, due to its long computation time on current hardware. To alleviate this problem, we propose three error control schemes. Our static scheme bypasses Reed-Solomon decoding at the mobile node to satisfy the MPEG-4 time constraint when the PLR exceeds a given boundary. Second, dynamic scheme corrects errors in a best-effort manner within the time constraint, instead of giving up altogether when the PLR is high; this achieves a further quality improvement. The third, video-aware dynamic scheme fixes errors in a similar way to the dynamic scheme, but in a priority-driven manner which makes the video appear smoother. Extensive simulation results show the effectiveness of our schemes compared to the original FEC scheme.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.2 no.2 s.3
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• pp.43-54
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• 2003

As the demand for ubiquitous mobile wireless Internet grows, vehicles are receiving a lot of attention as new networking platforms. The demand for 4G all-IP networks encourages vehicle networks to be connected using IPv6. By means of network mobility (NEMO) support, we can connect sensors, controllers, local ,servers as well as passengers' devices of a vehicle to the Internet through a mobile router. The mobile router provides the connectivity to the Internet and mobility transparency for the rest of the mobile nodes of an in-vehicle nv6 network. So, it is .important for the mobile router to assure reliable connection and a sufficient data rate for the group of nodes behind it. To provide reliability, this paper proposes an adaptive multihoming architecture of multiple mobile routers. Proposed architecture makes use of different mobility characteristics of different vehicles. Simulation results with different configurations show that the proposed architecture increases session preservation thus increases reliability and reduces packet loss. We also show that the proposed architecture is adaptive to heterogeneous access environment which provide different access coverage areas and data rates. The result shows that our architecture achieves sufficient data rates as well as session preservation.

• The KIPS Transactions:PartC
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• v.12C no.6 s.102
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• pp.881-890
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• 2005

Over for the past 10 years, the increase in geometric progression for the internet traffic, has allowed the IP protocol framework to be the most important network technology. In addition, the internet service is being developed as a service mode differentiated, aiming to support the new-mode real-time multimedia services such as internet phone, video conference, cyber reality, and internet game, focusing on offering a latest service. These days, aiming to solve the need for broad bandwidth along with guaranteeing QoS, the WDM technology of offering multiple gigabit wavelengths is emerging as the core technology of next-generation optical internet backbone network. In the next-generation optical internet backbone network based on WDM, the QoS framework is one of fore subjects aiming to offer a service of guaranteeing QoS This study analyzes the requirements of performance related to QoS framework in IP Subnet and in WDM optical backbone network, and suggests optical QoS service framework differentiated. in order to guarantee end-to-end QoS through the next-generation optical internet backbone network, using GMPLS control protocol.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8A
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• pp.648-660
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• 2012

The low-power, low-cost femtocell network has been proposed not only to alleviate traffic load to the macro base station (eNB) but also to cover the indoor coverage hole problem. However, in the dense femtocell environment where many femtocells are deployed to cover the whole large office building, performance of such femtocell environment can be deteriorated due to severe co-channel interference problem between the eNB and femtocells and among neighboring femtocells. In particular, a macro UE(mUE) located within femtocell coverage may experience severe co-channel interference from surrounding femtocells. Therefore, In this paper, we propose a novel power control schemes to mitigate interference to a mUE under such dense LTE femtocell environment. With proposed femtocell power control schemes, performance of the mUE can be greatly improved in terms of the outage probability and the SINR while maintaining satisfying femtocell performance. Simulation based performance study shows that the proposed power control scheme is able to enhance mUE performance more than 30% than the conventional dense femtocell in terms of the two performance metrics.

• Archives of design research
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• v.11 no.1
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• pp.291-302
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• 1998

This paper covers the development process of multimedia evaluation system, especially focused on customer satisfactory factors while customers navigating net-based Interactive multimedia system. Customers usually experience new level of interaction cased by newly developed web-based technology In ordinary multimedia system. However, if it gives customers satisfactory experience is a matter of question. To find out the relationship between customer satisfaction and interactivity factors exposed by multimedia system, a model has been developed which describes the structure of web-based multimedia system and its relation to customer satisfactory factors. Five different experiments, including 'semantic differential', 'focus group interview', and 'expert review', has been conducted and four customer satisfactory factors were identified. Those are 'customery value', 'structural perfectness', 'visual perfectness', and 'contemporaneity'. With these factors and newly delveoped evaluation system, 7 different web-site has been evaluated and analyzed at the end of this report.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1330-1338
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• 2015

In wireless communication network, the amount of packet data for the video streaming in the playout buffer of the receiver is changed with time according to network condition. If the amount of packet data is less than a specific buffer amount, the buffer underflow problem is generated. On the contrary, if the amount of packet data is more than a given buffer amount, the buffer overflow problem is occurred. When the playout of the video streaming is processed, these buffer underflow and overflow problems cause stop and skip phenomenons and then provide the discontinuity of playout. Therefore, to solve the buffer underflow and overflow problems of the video streaming in wireless communication network, This paper analyzes the combined effect of Token Bucket scheme, which controls the bursty traffic, and AMP(Adaptive Media Playout) scheme, which adaptively changes the playout speed of receiver. Through simulation, we found that the combination of Token Bucket and AMP schemes provides the superiority in terms of the occurrence number of buffer underflow and overflow, the stop duration time and the number of removed frames generated by underflow and overflow, and PSNR.

• Journal of KIISE:Computing Practices and Letters
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• v.7 no.2
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• pp.165-182
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• 2001

In this paper, we describe a design and implementation of the Wireless Markup Language(WML) compiler to deploy wireless Internet services effectively. The WML compiler translates textual WML decks into binary ones in order to reduce the traffic on wireless links that have relatively low bandwidth to wireline links and mitigate the processing overhead of WML decks on, wireless terminals that have relatively low processing power to fixed workstations. In addition, it takes over the overhead of eXtensible Markup Language(XML) well-formedness and validation processes. The WML compiler consists of the lexical analyzer and parser modules. The granunar for the WML parser module is LALR(1) context-free grammar that is designed based on XML 1.0 and WML 1.2 DTD(Document Type Definition) with the consideration of the Wireless Application Protocol Binary XML grammar. The grammar description is converted into a C program to parse that grammar by using parser generator. Even though the tags in WML will be extended or WML DTD will be upgraded, this approach has the advantage of flexibility because the program is generated by modifying just the changed parts. We have verified the functionality of the WML compiler by using a WML decompiler in the public domain and by using the Nokia WAP Toolkit as a WAP client. To measurethe compressibility gain of the WML compiler, we have tested a large number of textual WML decks and obtained a maximum 85 %. As the effect of compression is reduced when the portion of general textual strings increases relative to one of the tags and attributes in a WML deck, an extended encoding method might be needed for specific applications such as compiling of the WML decks to which the Hyper Text Markup Language document is translated dynamically.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.4
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• pp.387-396
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• 2004

A scheme to evaluate the number of users and cell coverage of a WCDMA supporting multi-rate traffic is newly presented through calculation of the realizable Erlang capacity from a derived blocking probability and the path loss from the COST231 Walfisch-Ikegami(W) model. We evaluate the voice-data Erlang capacities at various data rates of 15 kbps to 960 kbps and it is shown that they have a linear relationship to each other. When the E$\_$b//N$\_$o/ is low from 4 ㏈ to 3 ㏈ in case of voice capacity of 50 Erlang at 8 kbps, the result shows the increase for the data capacity of 10 Erlang and the enlargement of 100 m for the cell coverage at low rate of 15 kbps, and the increase of 0.11 Erlang and the enlargement of 40 m at high rate of 960 kbps. The increase of the blocking probability results in the increase of the Erlang capacity, but not an effect on the cell coverage, and the increase of active users in a cell results in the decrease of the coverage.

• The KIPS Transactions:PartB
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• v.11B no.5
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• pp.603-610
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• 2004

The distributed Information Retrieval System centrally controlled by mediator or meta search engine result in congestion of heavy traffic and int he problem of increment of cost for the reason of the design of complicated algorithm for central control and installation of hardware. So to figure out this problem, the way is needed that has independent retrieval functionality and can cooperate each other without dependency. In this paper, we overview a few works involved in distributed information retrieval system, then, implement algorithm and design the frame-work of distributed information retrieval system using sequential transferring method(STM) including multiple information retrieval system separated from central control. For this first of all, we present a web partition policy which devide and manage web logically and we present the sequential query processing way by means of illustration through changing numbered information retrieval system. Then, we also present 3-layered structure of framework and function and module of each layer suitable for information retrieval system. Last of ail, for effective implementation of STM algorithm we analysis module structure and present description of pseudocode of this, and show that the proposed STM algorithm works smoothly by demonstration of sequential query transfer process between servers.

• Journal of the Korea Society for Simulation
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• v.15 no.1
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• pp.77-85
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• 2006

The cost of downloading content from the Internet may be costly for mobile device users using its 3G connection, because the 3G connection cost to download data from the Internet is a function of the amount of data downloaded. This paper introduces an approach in which mobile devices, called peers, form an ad hoc network and share their downloaded content with others. As an example, spectators may want to collect/share information about players and game records in a stadium. In an art gallery, visitors may want to retrieve some background information about the displayed work from the nearby ad hoc network. In an outdoor class, a teacher may download today's topic files from the Internet, and all students may share the content with minimal or no cost paid. This is possible if mobile device has both a 3G interface and a wireless LAN interface. If the peers want to improve privacy md discourage traffic analysis when sharing content, this paper describes a low-delay anonymous connection between the sending peer and the receiving peer using two additional peers. Simulation results show that the transmission time overhead of the anonymous connection may increase 50% or less as the number of peers increase or the peers are scattered over the larger area.