• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.3A
• /
• pp.219-224
• /
• 2008

In the c-DSDV routing protocol proposed to improve the scalability of DSDV, clusterheads manage a routing table that has only clusterheads as potential destinations and flood update request message to its neighbor clusterheads periodically or at the time of topology change. Accordingly, the convergence range of topology change by a single update request message was expanded nine times as wide as that of DSDV, increasing routing correctness; however, c-DSDV suffers from the congestion of clusterheads since data packets always go through clusterheads of the clusters on the routing path. To improve this problem, we propose an adaptive routing scheme that judges if detouring clusterhead is possible on the fly while packets are forwarded. As a result, a routing path length is shortened and an end-to-end delay is improved by the reduced queue length. It shows that the end-to-end delay is reduced by almost 40% through simulation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2007.10a
• /
• pp.79-82
• /
• 2007

Recently the diffusion of the advancement of mobile communication technique and mobile terminal increased, The users were demanded seamless services when carrying and moving. It proposed the FMIPv6 (Fast Handoff for Mobile IPv6) from the IETF like this meeting this requirement. The handover procedure of the FMIPv6 causes to defecate with movement detection, new CoA configuration and binding update. But, the delay occurs from each process, when the DAD(Duplicate Address Detection) of the CoA executing, the big delay occurs. This paper proposes a scheme of delay reduction, it omits DAD process and stores in the AR(Access Router) relates in the CoA of the mobile terminal information.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.3
• /
• pp.556-563
• /
• 2009

HMIP, an extending version of MIP, makes the signaling traffic low, thereby reducing the packet losses and delay. However, it still has the same problem in MIPv6 in the case of macro mobility, though it can reduce the out-signaling in the case of a micro mobility, a regional mobility with the MAP protocol. To overcome this problem, this paper proposes a handover which exploits an address insurance with selective buffering for the HMIP macro handover. This scheme can decrease the lost packets and the delay time and provide better performance for high QoS traffic and real-time multimedia transmission. The simulation result shows that the proposed scheme makes the transmission delay time and the lost packets smaller than the existing schemes.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.11 no.11
• /
• pp.2027-2031
• /
• 2007

Recently the diffusion of the advancement of mobile communication technique and mobile terminal increased, The users were demanded seamless services when carrying and moving. It proposed the FMIPv6(Fast Handoff for Mobile IPv6) from the IETF like this meeting this requirement. The handover procedure of the FMIPv6 causes to defecate with movement detection, new CoA configuration and binding update. But, the delay occurs from each process, when the DAD(Duplicate Address Detection) of the CoA executing, the big delay occurs. This paper proposes a scheme of delay reduction, it omits DAD process and stores in the AR(Access Router) relates in the CoA of the mobile terminal information.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.46 no.9
• /
• pp.39-45
• /
• 2009

When Mobile IPv6 is deployed in commercial network, a mobile node needs AAA services for an authentication, authorization and accounting. AAA and Mobile IPv6 are protocols which are operated independently. Then schemes which merge these protocols have been emerged. These schemes can enable a mobile node to establish a security association between the mobile node and a home agent and to perform a binding update for the home agent using AAA authentication request. But these schemes introduce many signal messages and long handover latency during the handover, since Route Optimization mode for Mobile Ipv6 is performed using Return Routability procedure. To solve this problem, we propose a scheme for Route Optimization mode that the home agent performs the binding update for a correspondent node via the AAA infrastructure between the home agent and the correspondent node instead of Return Routability procedure. For performance evaluation, we analyze signal message transmission costs and handover latencies during handover. We show performance improvement of the proposed scheme which reduces handover latency as 61% compared with the existing scheme.

• KIISE Transactions on Computing Practices
• /
• v.23 no.6
• /
• pp.379-385
• /
• 2017

In enterprise environments, hybrid storage typically utilizes SSDs over disk-based RAID. Typically, SSDs over RAID are used as the data cache. Recently, the LeavO caching scheme was introduced to reduce the parity update overhead of the underlying RAID. In this paper, we combine the data caching and LeavO caching schemes and derive cost models of the combined cache to determine the optimal data and LeavO cache sizes. We also propose the Adaptive Combined Cache that dynamically adjusts the data cache and LeavO cache sizes for evolving workloads. Experimental results show that the performance of the Adaptive Combined Cache is significantly superior to that of the conventional data caching scheme and is comparable with that of the off-line optimal scheme.

• Proceedings of the Korean Information Science Society Conference
• /
• 2006.06a
• /
• pp.151-153
• /
• 2006

본 논문은 NAND 플래시 메모리를 기반으로 한 임베디드 시스템에서 빠른 부팅을 지원하는 파일 시스템을 제안한다. 플래시 메모리는 비휘발성이며 기존의 하드디스크와 같은 자기 매체에 비해서 크기가 작고 전력소모도 적으며 내구성이 높은 장점을 지니고 있다. 그러나 제자리 덮어쓰기가 불가능하고 지움 연산단위가 쓰기 연산 단위보다 크다. 또한 지움 연산 획수가 제한되는 단점이 있다. 이러한 특성 때문에 기존의 파일 시스템들은 갱신 연산 발생 시, 갱신된 데이터를 다른 위치에 기록한다. 따라서 마운팅 시, 최신의 데이터를 얻기 위해 전체 플래시 메모리 공간을 읽어야만 한다. 이러한 파일 시스템의 마운팅 과정은 전체 시스템의 부팅 시간을 지연시킨다. 본 논문은 임베디드 시스템에서 빠른 부팅을 제공할 수 있는 NAND 플래시 메모리 파일 시스템의 구조를 제안한다. 제안된 시스템은 플래시 메모리 이미지 정보와 메타 데이터 블록만을 읽어 파일 시스템을 구축한다. 메타 데이터가 데이터 위치를 포함하기 때문에 마운팅 시, 전체 플래시 메모리 영역을 읽을 필요가 없으며 파일 데이터 위치 저장을 위한 별도의 자료 구조를 RAM 상에 유지할 필요가 없다. 실험 결과, YAFFS에 비해 $76%{\sim}85%$ 마운팅 시간은 감소시켰다. 또한 YAFFS에 비해 $64%{\sim}75%$ RAM 사용량을 감소시켰다.

• 한국공간정보시스템학회:학술대회논문집
• /
• 2003.11a
• /
• pp.123-128
• /
• 2003

최근 프로세서와 메인 메모리간의 속도 차이가 커지면서 캐시 실패가 메인 메모리에서 동작하는 R-Tree의 성능 저하에 미치는 영향이 커짐에 따라 캐시 실패를 줄여 캐시 성능을 개선하려는 연구가 많이 진행되고 있다. 일반적인 캐시 성능 개선 방법은 엔트리 정보를 줄설 노드에 더 않은 엔트리를 저장함으로써 펜-아웃(fanout)을 증가시키고 캐시 실패를 최소화한다. 그러나 이러한 방법은 엔트리 정보를 줄이는 추가 연산으로 인해 갱신 성능이 떨어지고, 노드간 이동시 발생하는 캐시 실패는 여전히 해결하지 못하고 있다. 본 논문은 이를 해결하기 위해 선반입(prefetching)을 적용한 확장된 R-Tree인 PR-tree(Prefetching R-Tree)를 제안하고 평가하였다 PR-Tree는 펜-아웃을 증가시키고 트리의 높이를 낮추기 위해 실제 캐시 라인의 정수 배인 노드를 생성하고, 선반입을 적용하여 노드 캐시로 인한 메모리 지연을 최소화하였다. 또한 접근할 노드를 선반입하여 노드간 이동시 발생하는 캐시 실패도 최소화하였다. PR-Tree는 실험에서 R-Tree보다 검색 연산에서 최대 38%의 성능 향상을 보였으며, 갱신 연산에서도 최대 30%의 성능 향상을 보였다.

• Proceedings of the Korea Contents Association Conference
• /
• 2009.05a
• /
• pp.51-56
• /
• 2009

Flash memory has rapidly deployed as data storage. However, the flash memory has a major disadvantage that recorded data cannot be dynamically overwritten. In order to solve this "erase-before-write" problem, the log block buffer scheme used Flash memory file system. however, the current managements of the log buffer, in case random write pattern, BAST technique have problem of frequent merge operation, but FAST technique don't consider merge operation by frequently updated data. Previous methods not consider merge operation cost and frequently updated data. In this paper, we propose a new log buffer management scheme, called JBB. Our proposed method evaluates the worth of the merge of log blocks, so we conducts the merge operation between infrequently updated data and its data blocks, and postpone the merge operation between frequently updated data and its data blocks. Through the method, we prevent the unnecessary merge operations, reduce the number of the erase operation, and improve the utilization of the flash memory storage. We show the superiority of our proposed method through the performance evaluation with BAST and FAST.

• Journal of Korea Spatial Information System Society
• /
• v.11 no.2
• /
• pp.133-142
• /
• 2009

Recently, with the advance of wireless internet and the frequent use of mobile devices, demand for LBS(Location Based Service) is increasing, and research is required on spatial indexes for the storage and maintenance of spatial data to provide efficient LBS in mobile device environments. In addition, the use of flash memory as an auxiliary storage device is increasing in order to store large spatial data in a mobile terminal with small storage space. However, the application of existing spatial indexes to flash-memory lowers index performance due to the frequent updates of nodes. To solve this problem, research is being conducted on flash-memory based spatial indexes, but the efficiency of such spatial indexes is lowered by low utilization of buffer and flash-memory space. Accordingly, in order to solve problems in existing flash-memory based spatial indexes, this paper proposed FR-Tree (Flash-Memory based R-Tree) that uses the node compression technique and the delayed write operation technique. The node compression technique of FR-Tree increased the utilization of flash-memory space by compressing MBR(Minimum Bounding Rectangle) of spatial data using relative coordinates and MBR size. And, the delayed write operation technique reduced the number of write operations in flash memory by storing spatial data in the buffer temporarily and reflecting them in flash memory at once instead of reflecting the insert, update and delete of spatial data in flash-memory for each operation. Especially, the utilization of buffer space was enhanced by preventing the redundant storage of the same spatial data in the buffer. Finally, we perform ed various performance evaluations and proved the superiority of FR-Tree to the existing spatial indexes.