• Journal of Korean Institute of Industrial Engineers
• /
• v.27 no.4
• /
• pp.406-412
• /
• 2001

IP address lookup is to determine the next hop destination of an incoming packet in the router. The address lookup is a major bottleneck in high performance router due to the increased routing table sizes, increased traffic, higher speed links, and the migration to 128 bits IPv6 addresses. IP lookup time is dependent on data structure of lookup table and search scheme. In this paper, we propose a new approach to build a lookup table that satisfies the memory constraint. The design of lookup table is formulated as an optimization problem. The objective is to minimize average depth from the root node for lookup. We assume that the frequencies with which prefixes are accessed are known and the data structure is level compressed trie with branching factor $\kappa$ at the root and binary at all other nodes. Thus, the problem is to determine the branching factor k at the root node such that the average depth is minimized. A heuristic procedure is proposed to solve the problem. Experimental results show that the lookup table based on the proposed heuristic has better average and the worst-case depth for lookup.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.44 no.10
• /
• pp.162-168
• /
• 2007

TCAM(Ternary content-addressable memory) has been widely used to perform fast routing lookup. It is able to accomplish the LPM(longest prefix matching) search in O(1) time without considering the number of prefixes and their lengths. As compared to software-based solutions, especially for IPv6, TCAM can oner sustained throughput and simple system architecture. However, There is no research for Priority-TCAM which can assign priority to each memory block. This paper addresses the difference or priority-TCAM compared to the existing TCAM and proposes CAO-PA algerian to manage the lookup table efficiently.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.41 no.12
• /
• pp.75-81
• /
• 2004

AE-CORDIC improves the CORDIC operation speed with a rotation direction pre-computation algorithm. Its CORDIC iteration stages consist of non-predictable rotation direction states and predictable rotation stages. The non-predictable stages are replaced with lookup-table which has smaller hardware size than CORDIC iteration stages. The predictable stages can determine rotation direction with the input angle and simple encoder. In this paper, a rotation direction pre-computation algorithm with input angle encoder is proposed. and AE-CORDIC which have optimized Lookup-table is compared with the P-CORDIC algorithm. Hardware size, delay, and SQNR of the AE-CORDIC are verified with Samsung 0.18㎛ technology and Synopsys design compiler when input angle bit length is 16.

• Journal of Communications and Networks
• /
• v.3 no.4
• /
• pp.374-382
• /
• 2001

Nowadays, the commonly used table lookup scheme for IP routing is based on the sc-called classless interdomain routing (CIDR). With CIDR, routers must find out the best matching prefix (BMP) for IP packets forwarding, this complicates the IP lookup. Currently, this process is mainly performed in software and several schemes hale been proposed for hardware implementation. Since the IP lookup performance is a major design issue for the new generation routers, in this article we investigate the properties of the routing table and present a new approach for IP lookups, our approach is not based Gn BMP and significantly reduces the complexity, thus the computation cast of existing schemes can be significantly reduced. We also propose an efficient IP lookup algorithm, with which we improve the binary search on prefixes to 30 millions of packets per second (MPPS) and 5,000 route updates/s under the same experiment setup with an even larger routing table.

• Journal of Institute of Control, Robotics and Systems
• /
• v.17 no.4
• /
• pp.321-327
• /
• 2011

This paper proposes an equipment and an algorithm for modeling the magnetic force of electromagnets in magnetic levitation systems. We assume that the magnetic force model is represented in terms of a 2D lookup table. The 2D lookup table is constructed by applying noncausal filtering and interpolation to data measured by the proposed modeling equipment. The proposed modeling equipment is designed such that it can measure the magnetic force exerted on the levitation object while it changes the voltage applied to the electromagnet and position of the levitation object. The algorithm of making a 2D lookup table has two stages. The data measured by the proposed modeling equipment is smoothed by a noncausal filter and then the 2D lookup table is obtained by interpolating filtered data. The proposed modeling method has advantages of time-saving, model consistency, and chance of automation for mass production. We show the validity of proposed method through control experiments.

• Proceedings of the Korea Multimedia Society Conference
• /
• 2003.11a
• /
• pp.367-370
• /
• 2003

최근 급속하게 증가하는 멀티미디어 정보를 효율적으로 다루기 위하여 멀티미디어 데이터에 대한 표현을 표준화하는 MPEG-7 표준안이 제정되었다 본 논문에서는 표준안의 Visual Descriptor 중 Edge Histogram Descriptor(EHD)에 기반한 효과적인 내용기반 이미지 검색 시스템을 설계한다. EHD의 경우 질의 이미지와 데이터베이스의 이미지 간의 유사도 연산을 통해 검색을 하는데 모든 이미지에 대해 연산을 수행하는 것은 비효율적이다. 저장된 에지 히스토그램 정보를 ‘이미지 당 빈 값’에서 ‘빈 값 당 이미지’ 정보로 매핑하는 Lookup Table를 이용하여 유사도 연산을 수행할 이미지 범위를 한정함으로써 검색 효율을 높일 수 있는 검색 방법을 제안한다.

• Proceedings of the IEEK Conference
• /
• 1998.10a
• /
• pp.799-802
• /
• 1998

As we know, gigabit ethernet is a new technology to be substituted for current fast ethernet used widely in local area network. The switch used in gigabit ethernet should deal with frames in giga-bps. To do such a fast switching, we need that serveral processes meet the budgets, such as MAC address table lookup, several giga speed path setup, fast scheduling, and etc. Especially MAC address table lookup has to be processed in the same speed with speed of incoming packets, thus the bottleneck in the process can cause packet loss by the overflow in the input buffer. We devise new practical hardware hashing method to perform fast table lookup by minimizing the number of external memory access and accelerating with hardware.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.31A no.2
• /
• pp.125-134
• /
• 1994

This paper proposes a new top-down technology mapping algorithm for minimizing the chip area and the path delay time of lookup table-based field programmable gate array(FPGA). First, we present the decomposition and factoring algorithm using common subexpre ssion which minimizes the number of basic logic blocks and levels instead of the number of literals. Secondly, we propose a cube packing algorithm considering the decomposition of gates which exceed m-input lookup table. Previous approaches perform the cube packing and the gate decomposition independently, and it causes to increase the number of basic logic blocks. Lastly, the efficiency.

• Korean Journal of Optics and Photonics
• /
• v.8 no.3
• /
• pp.194-198
• /
• 1997

We realized CGH display of moving objects with an optical addressed spatial light modulator. CGH was calculated by the horizontal parallex method for saving a calculating time, and calculation speed was improved by making a lookup table of trigonometric function and root calculation. This lookup table was applied to a low resolution SLM, and succeeded in a simultaneous display of the three hologram images by the scanning method.

• Journal of IKEEE
• /
• v.5 no.1 s.8
• /
• pp.24-34
• /
• 2001

IP address lookup is a major bottleneck of IP packet processing in high speed router. Existing IP lookup methods are focused only on lookup throughput without considering lookup table update. So their slow update can lead to lookup blocking or wrong routing decision based on obsolete routes. Especially existing IP lookup methods based on CAM(content addressable memory) have slow update of O(n) cycles in spite of their high throughput and low area complexity In this paper we proposes a new IP address lookup method based on pipelined CAM architecture(PICAM) with fast update of O(1) cycle of lookup table and high throughput and low area complexity.