• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제3권3호
• /
• pp.266-284
• /
• 2009

The challenges of rapidly growing numbers of mobile nodes in IPv6-based networks are being faced by mobile computing researchers worldwide. Recently, IETF has standardized Mobile IPv6 and Fast Handover for Mobile IPv6(FMIPv6) for supporting IPv6 mobility. Even though existing literatures have asserted that FMIPv6 generally improves MIPv6 in terms of handover speed, they did not carefully consider the details of the whole handover procedures. Therefore, in conventional protocols, the handover process reveals numerous problems manifested by a time-consuming network layer based movement detection and latency in configuring a new care of address with confirmation. In this article, we study the impact of the address configuration and confirmation procedure on the IP handover latency. To mitigate such effects, we propose a new scheme which can reduce the latency taken by the movement detection, address configuration and confirmation from the whole handover latency. Furthermore, a mathematical analysis is provided to show the benefits of our scheme. In the analysis, various parameters are used to compare our scheme with the current procedures, while our approach is focused on the reduction of handover latency. Finally, we demonstrate total handover scenarios for the proposed techniques and discussed the major factors which contribute to the handover latency.

• 한국정보컨버전스학회:학술대회논문집
• /
• 한국정보컨버전스학회 2008년도 International conference on information convergence
• /
• pp.199-204
• /
• 2008

Sensor nodes have various energy and computational constraints because of their inexpensive nature and ad-hoc method of deployment. Considerable research has been focused at overcoming these deficiencies through faster media accessing, more energy efficient routing, localization algorithms and system design. Our research attempts to provide a method of improvement MAC performance in these issues. We show that traditional carrier-sense multiple access(CSMA) protocols like IEEE 802.11 do not handle the first constraint adequately, and do not take advantage of the second property, leading to degraded latency and throughput as the network scales in size, We present more efficient method of a medium access for real-time wireless sensor networks. Proposed MAC protocol is a randomized CSMA protocol, but unlike previous legacy protocols, does not use a time-varying contention window from which a node randomly picks a transmission slot. To reduce the latency for the delivery of event reports, it carefully decides a fixed-size contention window, non-uniform probability distribution of transmitting in each slot within the window. We show that it can offer up to several times latency reduction compared to legacy of IEEE 802.11 as the size of the sensor network scales up to 256 nodes using widely used simulator ns-2. We, finally show that proposed MAC scheme comes close to meeting bounds on the best latency achievable by a decentralized CSMA-based MAC protocol for real-time wireless sensor networks which is sensitive to latency.

• 전자공학회논문지
• /
• 제52권8호
• /
• pp.40-48
• /
• 2015

본 논문에서는 다중 입력 다중 출력 시스템을 위한 전 처리 과정인 QR Decomposition (QRD) 과 Lattice Reduction (LR)에 대하여, 두 과정의 연산의 공유성을 바탕으로 이를 공동으로 처리하는 프로세서를 제안한다. 제안하는 전 처리 프로세서는 다중 사이클 아키텍처로 설계하여 하드웨어 복잡도를 낮추었고, 두 전 처리 과정을 채널 환경에 따라 선택적으로 수행한다. 제안하는 전 처리 프로세서는 $0.18-{\mu}m$ CMOS공정의 셀 라이브러리를 사용하여 139K의 논리 게이트로 구현되었고, 최대 117MHz의 동작주파수에서 $8{\times}8$ 행렬에 대한 QRD와 LR의 수행에 대하여 $5{\mu}s$의 latency를 갖는다.

• 정보와 통신
• /
• 제32권9호
• /
• pp.17-23
• /
• 2015

This paper presents design methodologies for 5G architecture ensuring lower latency than 4G/LTE. Among various types of 5G use cases discussed in standardization bodies, we believe mobile broadband, massive IoT(Internet of Things) and mission-critical IoT will be the main 5G use cases. In particular, a mission-critical IoT service such as remote controlled machines and connected cars is regarded as one of the most distinguished use cases, and it is indispensable for underlying networks to support sufficiently low latency to support them. We identify three main strategic directions for end-to-end network latency reduction, namely new radio access technologies, distributed/flat network architecture, and intelligent end-to-end network orchestration.

• International journal of advanced smart convergence
• /
• 제13권2호
• /
• pp.7-15
• /
• 2024

6G network technology represents the next generation of communications, supporting high-speed connectivity, ultra-low latency, and integration with cutting-edge technologies, such as the Internet of Things (IoT), virtual reality, and autonomous vehicles. These advancements promise to drive transformative changes in digital society. However, as technology progresses, the demand for efficient data transmission and energy management between smart devices and network equipment also intensifies. A significant challenge within 6G networks is the optimization of interactions between satellites and smart devices. This study addresses this issue by introducing a new game theory-based technique aimed at minimizing system-wide energy consumption and latency. The proposed technique reduces the processing load on smart devices and optimizes the offloading decision ratio to effectively utilize the resources of Low-Earth Orbit (LEO) satellites. Simulation results demonstrate that the proposed technique achieves a 30% reduction in energy consumption and a 40% improvement in latency compared to existing methods, thereby significantly enhancing performance.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제15권8호
• /
• pp.3025-3047
• /
• 2021

This paper presents the latest Ethernet standardization of in-vehicle network and the future trends of automotive Ethernet technology. The proposed system provides design and optimization algorithms for automotive networking technology related to AVB (Audio Video Bridge) technology. We present a design of in-vehicle network system as well as the optimization of AVB for automotive. A proposal of Reduced Latency of Machine to Machine (RLMM) plays an outstanding role in reducing the latency among devices. RLMM's approach to real-world experimental cases indicates a reduction in latency of around 41.2%. The setup optimized for the automotive network environment is expected to significantly reduce the time in the development and design process. The results obtained in the study of image transmission latency are trustworthy because average values were collected over a long period of time. It is necessary to analyze a latency between multimedia devices within limited time which will be of considerable benefit to the industry. Furthermore, the proposed reliable camera and video streaming through optimized AVB device settings would provide a high level of support in the real-time comprehension and analysis of images with AI (Artificial Intelligence) algorithms in autonomous driving.

• 한국통신학회논문지
• /
• 제34권8A호
• /
• pp.600-609
• /
• 2009

기존의 IEEE 802.11 DCF(Distributed Coordination Function)와 같은 전통적인 CSMA(carrier sense multiple access) 프로토콜은 네트워크 규모가 커짐에 따라서 성능의 급격한 감쇠와 전송 지연 증가를 초래한다. 이러한 문제를 효과적으로 해결하기 위하여 본 논문에서는 무선 센서 네트워크에 적합한 MAC(medium access control) 프로토콜을 제안한다. 기존의 DCF 프로토콜은 데이터 전송을 위한 슬롯(slot)을 선택할 때 패킷 충돌로 인한 재전송이 반복될 때 마다 크기가 커지는 경쟁 윈도우(contention window) 내에서 일반 확률 분포(uniform probability distribution)를 이용한 랜덤(random) 선택 기법을 사용하지만 제안한 프로토콜에서는 전송 지연을 최대한 감소시키기 위하여 경쟁 윈도우의 크기를 고정시키고, 전송 슬롯을 보다 효율적으로 선택하도록 비 균등(non-uniform)확률 분포를 사용하여 전송 슬롯을 랜덤하게 선정한다. 시뮬레이션을 통하여 제안한 프로토콜이 802.11 MAC 표준에 비하여 전송 지연이 감소함을 보여 전송 지연에 민감한 실시간 무선 센서 네트워크의 최적 지연 한계점(best latency bound)을 충족시키는 프로토콜임을 입증한다.

• 정보과학회 논문지
• /
• 제42권11호
• /
• pp.1322-1331
• /
• 2015

vCPU(virtual CPU)는 하이퍼바이저 스케줄러에 의해서 실행 상태와 정지 상태를 반복하는 특징을 갖는다. 정지 상태인 vCPU에게 전달된 이벤트는 vCPU가 실행 상태가 될 때까지 처리되지 못하고 지연 된다. 이러한 이벤트 지연 현상은 I/O 지연 현상으로 나타난다. SMP(symmetric multiprocessing) 가상 머신은 다수의 vCPU를 이용하기 때문에 이벤트를 어느 vCPU에게 전달하는지에 따라 SMP 가상 머신의 이벤트 지연 시간이 달라 질 수 있다. SMP 가상 머신의 이벤트 지연 시간을 줄이기 위해서 본 논문에서는 각 vCPU의 동작 상태에 따라서 이벤트를 전달하는 새로운 기법인 이벤트 라우팅 기법을 제안한다. 제안한 이벤트 라우팅 기법을 Xen ARM 하이퍼바이저에 적용하였고 다양한 실험 환경에서 네트워크 RTT(round trip time)와 TCP 대역폭 측정을 통해 I/O 지연 시간 감소를 확인하였다. 기존 Xen ARM과 비교하여 네트워크 RTT는 최대 94% 감소하였고, TCP 대역폭은 최대 35% 증가하였다.

• 한국통신학회논문지
• /
• 제30권6C호
• /
• pp.450-456
• /
• 2005

In this paper, we propose a high-speed turbo decoding algorithm and present results of its implementation. The latency caused by (de)interleaving and iterative decoding in conventional MAP turbo decoder can be dramatically reduced with the proposed scheme. The main cause of the time reduction is to use radix-4, center to top, and parallel decoding algorithm. The reduced latency makes it possible to use turbo decoder as a FEC scheme in the real-time wireless communication services. However the proposed scheme costs slight degradation in BER performance because the effective interleaver size in radix-4 is reduced to an half of that in conventional method. To ensure the time reduction, we implemented the proposed scheme on a FPGA chip and compared with conventional one in terms of decoding speed. The decoding speed of the proposed scheme is faster than conventional one at least by 5 times for a single iteration of turbo decoding.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 1998년도 추계종합학술대회 논문집
• /
• pp.123-126
• /
• 1998

Generally, in a VOD(video on Demand) system, batching technique is oten used to improve throughput. Since subscribers to VOD servives tend to withdraw their requests as the latency becomes large, an optimal scheduling scheme should consider not only batching size but also withdrawal rae, service latency and fairness between different programs. In this paper, we propose a new scheduling scheme, which shows improvement in fairness and reduction in withdrawal rate and service latency compared with other well known schemes. When there are 2 or more streams are available in the VOD server, proposed scheme apply different program selection policies to each streams. Using this approach effectiveness of stream usage can be improved.