• 센서학회지
• /
• 제25권5호
• /
• pp.365-370
• /
• 2016

The study about VR (Virtual Reality) has been done from the 1960s, but technical limits and high cost made VR hard to commercialize. However, in recent, high resolution display, computing power and 3D sensing have developed and hardware has become affordable. Therefore, normal users can get high quality of immersion and interaction. However, HMD devices which offer VR environment have high latency, so it disrupts the VR environment. People are usually sensitive to relative latency over 20ms. In this paper, as adding the Electromyogram (EMG) sensors to typical IMU sensor only system, the latency reduction method is proposed. By changing software and hardware components, some cases the latency was reduced significantly. Hence, this study covers the possibility and the experimental verification about EMG sensors for reducing the latency.

• 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.

• Journal of Information Processing Systems
• /
• 제4권4호
• /
• pp.133-144
• /
• 2008

Clusters have become a popular alternative for building high-performance parallel computing systems. Today's high-performance system area network (SAN) protocols such as VIA and IBA significantly reduce user-to-user communication latency by implementing protocol stacks outside of operating system kernel. However, emerging parallel applications require a significant improvement in communication latency. Since the time required for transferring data between host memory and network interface (NI) make up a large portion of overall communication latency, the reduction of data transfer time is crucial for achieving low-latency communication. In this paper, Eager Data Transfer (EDT) mechanism is proposed to reduce the time for data transfers between the host and network interface. The EDT employs cache coherence interface hardware to directly transfer data between the host and NI. An EDT-based network interface was modeled and simulated on the Linux-based, complete system simulation environment, Linux/SimOS. Our simulation results show that the EDT approach significantly reduces the data transfer time compared to DMA-based approaches. The EDTbased NI attains 17% to 38% reduction in user-to-user message time compared to the cache-coherent DMA-based NIs for a range of message sizes (64 bytes${\sim}$4 Kbytes) in a SAN environment.

• 방송공학회논문지
• /
• 제26권7호
• /
• pp.855-861
• /
• 2021

Neural Architecture Search (NAS) is cutting-edge technology in the machine learning community. NAS Without Training (NASWOT) recently has been proposed to tackle the high demand of computational resources in NAS by leveraging some indicators to predict the performance of architectures before training. The advantage of these indicators is that they do not require any training. Thus, NASWOT reduces the searching time and computational cost significantly. However, NASWOT only considers high-performing networks which does not guarantee a fast inference speed on hardware devices. In this paper, we propose a multi objectives reward function, which considers the network's latency and the predicted performance, and incorporate it into the Reinforcement Learning approach to search for the best networks with low latency. Unlike other methods, which use FLOPs to measure the latency that does not reflect the actual latency, we obtain the network's latency from the hardware NAS bench. We conduct extensive experiments on NAS-Bench-201 using CIFAR-10, CIFAR-100, and ImageNet-16-120 datasets, and show that the proposed method is capable of generating the best network under latency constrained without training subnetworks.

• 대한약리학회지
• /
• 제29권1호
• /
• pp.33-41
• /
• 1993

Capsaicin의 중추신경계에 대한 진통효과를 척수 수준에서 규명하고, 이에 대한 norepinephrine (NE)계의 역할을 규명하기 위하여 tail flick reflex (TFR) latency time의 증가와 척수 내 NE 양의 변화를 측정하였다. 웅성의 Sprague-Dawley 백서를 pentobarbital sodium으로 마취를 하여 femoral vein cannulation과 intrathecal catheterization을 하였고, 이를 통하여 시험약제를 투여하였다. TFR은 capsaicin 또는 용매 투여전, 투여후 10분, 30분, 60분, 때로는 2시간에 측정하였다. MK-801은 capsaicin 투여전 20분에 femoral vein을 통하여 주입하였다. $35{\sim}150{\mu}g$의 capsaicin을 intrathecal로 주었을 때, TFR latency가 최고치인 7초를 넘어 정상인 2.9초에 비해 100% 이상의 증가를 보였고, 척수 내 NE은 16 ng/mg protein에서 7 ng/mg protein으로 50% 이상 감소하였다. 이와 같은 TFR latency의 증가와 NE의 감소는 전 실험기간 (capsaicin 투여후 2시간)에 걸쳐 관찰되었다. 반면, 50mg/kg의 capsaicin을 피하로 전신투여 하였을 경우에 척수 NE은 같은 변화를 보였으나 TFR latency의 차이는 없었다. 또한, 0.5 mg/kg의 MK-801를 i.v.로 전처치 하였을 때, intrathecal capsaicin에 의한 TFR latency의 증가와 척수 내 NE의 감소가 모두 억제되었다. 이상의 결과는 capsain이 excitatory aminoacid (EAA)계 - NE계 - 척수 dorsal horn으로 이루어진 동통전달의 하행성 억제계 축의 활성을 항진시켜 진통효과를 가져옴을 보여준다. 또한, capsaicin의 피하 주사시에 진통효과를 볼 수 없음을 말초 동통전달신경의 흥분에 의한 중추 동통전달계 환성의 촉진이 진통 효과를 상쇄함을 암시한다.

• The Journal of Korean Physical Therapy
• /
• 제9권1호
• /
• pp.89-96
• /
• 1997

The purpose of this study was to determine the effect of Ga-Al-As (Gallium-Aluminum-Arsenid) laser radiation on the tail-flick latency in rat. Thirty Sprague-Dawley male and female rats Were divided into five groups : that is control, laser 15sec radiation, laser 30sec radiation, laser 60sec radiation, and Tramadol Hcl injection groups. The continuous Ga-Al-As laser with, wave length 780-830nm and diameter of probe in the 3mm, averse output of 100mw radiation was applied to the meridian point(Gv 1 : Governing vessel) of the rats. Tail-flick latency were measured with hot plate at $55^{\circ}C$ : before treatment and immediately, 30 minutes, 1 hour, 2 hours, 24 hours, 24 hours and 48 hours after treatment. The result were as follows ; 1. The tail-flick latency according to time varition, control group was not significance. 2. The tail-flick latency according to time varition, laser 15 sec irradiate rats in post-treared was significance(P<0.05). 3. The tail-flick latency according to time varition, laser 30 sec irradiate rats group was not significance. 4. The tail-flick latency according to time varition, laser 60 sec irradiate rats in post 30 minute was significance(P<0.05). 5. The tail-flick latency according to time varition, Tramadol Hcl injection rats in post-treated (P<0.05), post 30 minute(P<0.05), post 60 minute (P<0.01) and 2 hour(P<0.05) was significance. This study suggest that Ga-Al-As (Gallium-Aluminum-Arsenid) laser applied to meridian point of the rat with 15 sec, 30 sec, and 60 set radiation could induc no analgesic effect, but Tramadol Hcl injection rat is good analgesic effect.

• 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.

• 인터넷정보학회논문지
• /
• 제5권3호
• /
• pp.25-33
• /
• 2004

Mobile IP Low Lattency Handoffs(1)는 Mobile IP 등록 요청 절차를 처리하는데 발생하는 지연을 최소화시켜 실시간 서비스를 가능하게 해준다. 그러나 인증, 권한 검증, 과금을 지원하는 AAA 기반의 Mobile IP 망에서는 매 지역등록이 일어날 때마다 새로운 세션 및 세션 키가 필요하며, 이를 위해 홈 망까지 등록 절차가 수행되어야 한다. 이로 인해, 이동 노드 재인증 절차와 방문 망에서 홈 망까지의 트랜잭션으로 인한 통신 지연이 발생한다. 이러한 지연을 줄이기 위해서 본 논문에서는 홈 망의 AAA 서버를 관여시키지 않고, 이전에 할당된 세션 키를 재사용하여 Low Latency Handoffs를 수행하는 기법을 제안한다. 이 기법에서는 이전 방문 에이전트와 새로운 방문 에이전트가 세션 키를 교환하는 단계에서 발생하는 보안 취약점을 해결하기 위하여 게이트웨이 방문 에이전트를 신뢰한 수 있는 제 3자 역할을 수행하도록 하고 이를 통해 키를 공유한다. 제안한 기법에 의하면 홈 망까지의 트랜잭션이 필요없고, 세션 키의 기밀성과 무결성이 보장되므로 이동 노드가 빠르고 안전하게 핸드오프를 수행할 수 있다.

• 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.