• Journal of Communications and Networks
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• v.2 no.1
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• pp.5-17
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• 2000

cdma2000 offers several enhancement as compared to TIA/EIA-95, although it remains fully compatible with TIA/EIA-95 systems and allows for a smooth migration from one to the other-Major new capability include:1)connectivity to GSM-MAP in addition to IP and IS-41 networks; 2) new layering with new LAC and MAC architectures for improved service multiplexing and QoS management and efficient use of radio resource ;3) new bands and band widths of operation in support of various operator need and constraints, as well as desire for a smooth and progressive migration to cdma 2000; and 4) flexible channel structure in support of multiple services with various QoS and variable transmission rates at up to 1 Mbps per channel and 2 Mbps per user. Given the phenomenal success of wireless services and desire for higher rate wireless services. improved spectrum efficiency was a major design goal in the elaboration of cdma2000. Major capacity enhancing features include; 1) turbo coding for data transmission: 2)fast forward link power control :3) forward link transmit diversity; 4) support of directive antenna transmission techniques; 5) coherent reverse link structure; and 6) enhanced access channel operation. As users increasingly rely on their cell phone at work and at home for voice and data exchange, the stand-by time and operation-time are essential parameters that can influence customer's satisfaction and service utilization. Another major goal of cdma2000 was therefore to enable manufacturers to further optimize power utilization in the terminal. Major battery life enhancing features include; 1) improved reverse link performance (i.e., reduced transmit power per information bit; 2) new common channel structure and operation ;3) quick paging channel operation; 4) reverse link gated transmission ; and 5) new MAC stated for efficient and ubiquitous idle time idle time operation. this article provides additional details on those enhancements. The intent is not to duplicate the detailed cdma2000 radio access network specification, but rather to provide some background on the new features of cdma2000 and on the qualitative improvements as compared to the TIA/EIA-95 based systems. The article is focused on the physical layer structure and associated procedures. It therefore does not cover the MAC, LAC, radio resource management [1], or any other signaling protocols in any detail. We assume some familiarity with the basic CDMA concepts used in TIA/EIA-95.

• Journal of the Korea Society of Computer and Information
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• v.18 no.2
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• pp.1-8
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• 2013

TIn this paper, we propose a high performance L1 cache structure on the high clock CPU of 4GHz. The proposed cache memory consists of three parts, i.e., a direct-mapped cache to support fast access time, a two-way set associative buffer to exploit temporal locality, and a buffer-select table. The most recently accessed data is stored in the direct-mapped cache. If a data has a high probability of a repeated reference, when the data is replaced from the direct-mapped cache, the data is selectively stored into the two-way set associative buffer. For the high performance and low power consumption, we propose an one way among two ways set associative buffer is selectively accessed based on the buffer-select table(BST). According to simulation results, Energy $^*$ Delay product can improve about 45%, 70% and 75% compared with a direct mapped cache, a four-way set associative cache, and a victim cache with two times more space respectively.

• Journal of Communications and Networks
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• v.12 no.2
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• pp.174-180
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• 2010

Automatic Repeat reQuest (ARQ) is a very effective technique against transmission error at the medium access control (MAC) layer. An erroneous MAC protocol data unit can be typically retransmitted within a given limit. In order to improve the IP-level performance, which directly affects the user-perceived quality-of-service (QoS), we propose a new truncated ARQ strategy, called MAC service data unit-based ARQ (S-ARQ), where the finite number of opportunities for retransmissions are shared by multiple fragments out of an IP datagram. We describe how SARQ can be implemented in a practical system, and then propose another variant of S-ARQ employing a functionality called early detection of failure. Basically, we evaluate the performance of SARQ in two different manners. First, assuming i.i.d. error process, we analyze both the probability of the delivery failure and the average delay of IP datagram. Then, we assess the performance of S-ARQ via simulation over a 2-state Markov channel.

• Journal of KIISE
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• v.43 no.5
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• pp.524-530
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• 2016

The desire to access data faster and the growth of next-generation memories such as non-volatile memories, contribute to the development of research on memory file systems. It is recommended that memory mapped file I/O, which has less overhead than read-write I/O, is utilized in a high-performance memory file system. Memory mapped file I/O, however, brings a page table overhead, which becomes one of the big overheads that needs to be resolved in the entire file I/O performance. We find that same overheads occur unnecessarily, because a page table of a file is removed whenever a file is opened after being closed. To remove the duplicated overhead, we propose the mapping cache, a technique that does not delete a page table of a file but saves the page table to be reused when the mapping of the file is released. We demonstrate that mapping cache improves the performance of traditional file I/O by 2.8x and web server performance by 12%.

• Annual Conference of KIPS
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• 2018.10a
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• pp.216-217
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• 2018

IEEE 1609.2 표준은 WAVE (Wireless Access in Vehicular Environment) 표준에서 차량간(V2V, Vehicle-to-Vehicle) 혹은 차량과 인프라간(V2I, Vehicle-to-Infrastructure)통신 상의 응용 메시지 보호를 위해 제정되었다. 이 표준은 메시지 이증 및 무결성 검증을 위하여 NIST p256 타원 곡선 커브 기반의 ECDSA 전자서명 기법을 사용한다. 매우 복잡한 도신 상의 출퇴근 환경에서는 수백대의 자동차가 전송하는 메시지를 정상적으로 처리하기 위하여, 차량의 OBU(On-Board Unit) 혹은 노상의 RSU(Road-Side Unit)에서 서명된 메시지의 검증 성능이 매우 중요한 이슈가 될 수 있다. 본 논문에서는 V2X 통신에서 효율적인 ECDSA 서명 검증을 위하여, OBU 혹은 RSU 환경에서 CPU 상의 병렬 처리 성능을 테스트 한 후 시사점을 살펴본다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.6
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• pp.111-116
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• 2012

Vehicular communication is one of main convergence technologies which combines information and communication technology (ICT) with vehicle and road industries. In general, vehicular communication adopts IEEE 802.11p standard which is commonly referred as wireless access in vehicular environments (WAVE). In this paper, we investigate a multi-hop communication scheme for IEEE 802.11p based communication systems which support both vehicle-to-infrastructure (V2I) and vehicle-to-vehicle (V2V) communications. First, we briefly overview the performance of IEEE 802.11p based communication systems. Then, a multi-hop communication scheme is introduced for both broadcast and unicast. The performance of proposed scheme is presented via experimental measurements.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.9
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• pp.799-808
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• 2012

Bit operation of scrambler in the WAVE System become less efficient because parallel processing is impossible in terms of hardware and software. In this paper, we propose algorism to find the starting position of the matrix table. Also, when bit operation algorithm of scrambler and algorithms for matrix table, algorithm used to find starting position of the matrix table were compared with the performance as 8 bit, 16bit, 32 bit processing units. As a result, the number of processing times per second could be done 2917.8 times more in an 8-bit, 5432.1 times in a 16-bit, 10277.8 times in a 32 bit. Therefore, algorithm to find the starting position of the matrix table improves the speed of the scrambler in the WAVE and the receiving speed of a variety of information gathering and precision over the Vehicle to Infra or Vehicle to Vehicle in the Intelligent Transport Systems.

• Journal of the Korean Society for Library and Information Science
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• v.33 no.1
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• pp.129-144
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• 1999

The purpose of this research is to compare the opinions of three different groups - subject specialist librarians(group I) . students of department programs(group II) and students of college programs(group III) - as to whether these groups have a different way of thinking from each other concerning a general culture for subject specialist librarianship. Questionnaire are carried out for this research and the responses analyzed to draw a conclusion. Major findings are as follows: 1) The subject specialist librarianship to be important to all three groups and a desirable academic career of group I shows a tendency to have both B.A. degree in the subjet field and M.A. degree in library & information science, $15.3\%$ of group II and $82.9\%$ of group III appear to be belonging to either minor or double major programs, 2) the 37-45 major credits to be ideal to group I & III, and 46-55 group II, 3) a knowledge in 'Computer' and 'English' is mostly demanded to all three groups as the general culture for subject apecialist librarianship, 4) theoretical courses to be very important to group I and technical courses to group II & III, 5) the collection and access of library materials to be regarded to all three groups as an important role for future librarians.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.2
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• pp.184-188
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• 2014

There is a trade-off between read stability and writability under a full-/half-select condition in static random access memory (SRAM). Another trade-off in the minimum operating voltage between the read and write operation also exists. A new peripheral circuit for SRAM arrays, called a variation sensor, is demonstrated here to balance the read/write margins (i.e., to optimize the read/write trade-off) as well as to lower the minimum operation voltage for both read and write operations. A test chip is fabricated using an industrial 45-nm bulk complementary metal oxide semiconductor (CMOS) process to demonstrate the operation of the variation sensor. With the variation sensor, the word-line voltage is optimized to minimize the trade-off between read stability and writability ($V_{WL,OPT}=1.055V$) as well as to lower the minimum operating voltage for the read and write operations simultaneously ($V_{MIN,READ}=0.58V$, $V_{MIN,WRITE}=0.82V$ for supply voltage $(V_{DD})=1.1V$).

• Journal of Korean Library and Information Science Society
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• v.30 no.1
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• pp.219-241
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• 1999

For an efficient access to Internet resources, these resources need to be organized systematically for accessibility. and their cataloging technique has been developing. Consequently, after I compared and analyzed OCLC manual applying AACR2 techniques and procedures, with Dublin core metadata used for cataloging Internet resources, I examined their mapping into MARC format. Dublin core metadata elements should be transformed to MARC format fields. In methodology of integration into different types of the metadata, an update of MARC format and its new field should be provided. Especially, Internet resources cataloging experts familiar with these technology will be really wanted nowadays.