Earticle

최근에 무선 센서 네트워크는 여러 분야에서 다양하게 활용되고 있으며 간단한 환경 모니터링 시스템에서부터 기계, 구조물, 교량, 비행기와 같은 모션 모니터링과 군사, 텔레매틱스와 같은 정보량이 많고 복잡한 시스템에 적용이 시도되고 있다. 따라서 간단한 역할만 수행하면서 저 전력으로 오랜 시간 동안 운용을 목표로 해온 무선 센서 네트워크는 어려운 작업을 수행하도록 요구되고 있다. 일반적으로 무선 센서 네트워크의 MAC 프로토콜들은 주기적으로 sleep / wake를 반복하여 필요한 에너지 소비를 줄이며 이를 Duty Cycling이라고 한다. 하지만 이러한 Duty Cycling은 sleep 구간 동안에 전송할 수 없어서 홉(Hop)이 늘어날수록 전송지연이 증가하는 단점이 있다. 이러한 전송지연은 비행기 날개, 군사, 텔레매틱스 등의 복잡한 시스템이나 교통사고위험 감지 경고 시스템과 같이 빠른 데이터 처리가 필요한 시스템에서 큰 문제점이 될 수 있다. 본 논문에서는 수신 구간을 분산 배치 알고리즘(Distributed Duty Cycling, DDC)을 통하여 무선 센서 네트워크 MAC(Media Access Control) 프로토콜에서 발생하는 전송지연을 크게 줄이는 기법을 제안한다. 제안한 알고리즘은 CC2420DBK를 이용한 필드 테스트를 통해서 검증되었으며 실험 결과를 통해서 DDC 알고리즘을 통해서 전송지연을 크게 줄이고 에너지 소비 또한 감소한다는 것을 확인 할 수 있다.

Recently, wireless sensor networks are deployed in various applications range from simple environment monitoring systems to complex systems, which generate large amount of information, like motion monitoring, military, and telematics systems. Although wireless sensor network nodes are operated with low-power 8bit processor to execute simple tasks like environment monitoring, the nodes in these complex systems have to execute more difficult tasks. Generally, MAC protocols for wireless sensor networks attempt to reduce the energy consumption using duty cycling mechanism which means the nodes periodically sleep and wake. However, in the duty cycling mechanism. a node should wait until the target node wakes and the sleep latency increases as the number of hops increases. This sleep latency can be serious problem in complex and sensitive systems which require high speed data transfer like military, wing of airplane, and telematics. In this paper, we propose a solution for reducing transmission latency through distributed duty cycling (DDC) in wireless sensor networks. The proposed algorithm is evaluated with real-deployment experiments using CC2420DBK and the experiment results show that the DDC algorithm reduces the transmission latency significantly and reduces also the energy consumption.

IoT 서비스는 경량 디바이스 발전으로 그 범위가 계속 확대되고 있으며, 이에 따라 네트워크의 혼잡성은 크게 증가하고 있다. IoT 네트워크 환경에서 CoAP를 위한 기존 혼잡 제어 메커니즘은 동적 네트워크 조건에 대한 적응력이 부족하다. 본 연구에서는 IoT 서비스 환경의 네트워크 환경의 네트워크 혼잡 문제를 해결하기 위해 적응 형 신경망 기반 혼잡 제어(ANN-CoCC) 알고리즘을 제안한다. 정적 매개변수나 휴리스틱 규칙에 의존하는 기존의 혼잡 제어 방식과 달리 ANN-CoCC는 머신러닝 모델을 적용하여 실시간 네트워크 상태에 따라 재전송 시간 초과 (RTO), RTT 분산, 혼잡 윈도우와 같은 주요 전송 매개변수를 동적으로 최적화한다. 다양한 패킷 손실률과 노드 밀도에서 실험 평가를 수행한 결과, 본 연구에서 제안하는 알고리즘은 CoCoA+, BDP-CoAP, pCoCoA과 같은 기존 방식과 비교했을 때 처리량을 30% 이상 향상시키며, 지연 시간 감소, 패킷 손실을 최소화하는 것으로 확인되 었다.

The scope of IoT services continues to expand with the development of lightweight devices, and network congestion is increasing significantly. In this study, we propose an adaptive neural network-based congestion control (ANN-CoCC) algorithm to solve the network congestion problem in the network environment of IoT service environments. Unlike existing congestion control methods that rely on static parameters or heuristic rules, ANN-CoCC applies a machine learning model to dynamically optimize key transmission parameters such as retransmission timeout (RTO), RTT distribution, and congestion window according to real-time network conditions. The experimental evaluation results under various packet loss rates and node densities show that the proposed algorithm improves throughput by more than 30%, reduces delay, and minimizes packet loss compared to existing methods such as CoCoA+, BDP-CoAP, and pCoCoA.

Skip list는 확률적인 자료 구조로써 RocksDB와 같은 키-밸류 스토어에서 메모리상에 존재하는 키-밸류 쌍을 관 리하는 핵심 구성 요소로 사용된다. 이 논문에서는 skip list를 분석하기 위한 방법론과 이를 활용한 분석 결과를 제시한다. 제시한 방법론은 다양한 패턴의 워크로드(workload) 생성과 측정이라는 기본 기능뿐만 아니라 확률적 자료 구조에서 필요한 일관된 비교 방법, 시간 측정의 정밀도 향상, CPU 내부 마이크로아키텍처 고려 등과 같은 확장 기능으로 구성된다. 제안된 방법론을 이용한 실험 결과 skip list의 검색 부하는 키-밸류 쌍의 구조상에서 위 치와 워크로드 크기에 의존하는 것으로 분석되었다. 이뿐만 아니라 검색 부하는 참조 패턴에도 영향을 받았다. 구체 적으로 Zipfian 패턴과 같은 CPU 캐시(cache) 친화적인 패턴은 다른 패턴에 비해 더 좋은 성능을 보였으며, 이것 은 skip list의 검색 부하가 캐시나 TLB (Translation Lookaside Buffer) 같은 CPU 내부의 마이크로아키텍처 영향도 받는 것을 의미한다.

The Skip list is a probabilistic data structure, being an essential component that manages in-memory key-value pairs in a key-value store such as RocksDB. This paper presents a methodology for analyzing behaviors of the skip list structure and several analysis results. Our methodology consists of not only basic functionalities including workload generation with diverse patterns and measurement, but also extended ones including consistent comparisons required in a probabilistic structure, enhanced measurement precision, and CPU microarchitecture consideration. Analysis results using our methodology reveal that the search overhead of the skip list depends on both the location of a key-value pair in the structure and the total size of workload. In addition, the overhead is affected by reference patterns. Specifically a CPU cache friendly pattern, Zipfian pattern, shows better performance than others, which implies that CPU microarchitecture such as cache and TLB (Translation Lookaside Buffer) give a substantial impact on the performance of the skip list structure.

국내외적으로 V2X 통신기술을 접목한 C-ITS 사업 및 자율주행 고도화 실증연구가 활발히 진행되고 있다. 실증 초기 1단계에서는 경고메시지, 차량주행정보, 교통정보 등의 방송서비스 에서 점차 실시간성을 요구하는 군집주행, 원격주행, 인식정보공유 등의 고도화된 서비스로 발 전하고 있다. 또한, 네트워크 서비스 고도화를 위해 전송속도와 지연시간 등을 개선하기 위한 기술개발이 여러모로 진행되고 있다. 본 논문에서는 3GPP 표준 기반 C-V2X 기술을 바탕으로 안정적인 드로이드 형태의 저속 로봇의 원격주행 서비스 제공을 위해 네트워크 지연시간 측면 에서 요구사항을 분석하였다. 원격주행 성능평가를 위해 오퍼레이터를 포함한 시스템 모델링 을 통한 시뮬레이션을 수행하였고, 해당 실험 조건에서 90% 이상의 성능 만족을 위해 30ms 이내의 코어 및 액세스 네트워크 지연시간이 요구된다는 것을 알 수 있었다.

Recently, cooperative intelligent transport systems (C-ITS) testbeds have been deployed in great numbers, and advanced autonomous driving research using V2X communication technology has been conducted actively worldwide. In particular, the broadcasting services in their beginning days, giving warning messages, basic safety messages, traffic information, etc., gradually developed into advanced network services, such as platooning, remote driving, and sensor sharing, that need to perform real-time. In addition, technologies improving these advanced network services' throughput and latency are being developed on many fronts to support these services. Notably, this research analyzed the network latency requirements of the advanced network services to develop a remote driving service for the droid type low-speed robot based on the 3GPP C-V2X communication technology. Subsequently, this remote driving service's performance was evaluated using system modeling (that included the operator behavior) and simulation. This evaluation showed that a respective core and access network latency of less than 30 ms was required to meet more than 90 % of the remote driving service's performance requirements under the given test conditions.

무선 센서 네트워크에서 사용되는 센서 노드는 확장성, 이동성, 휴대성 등을 위해서 작은 크기의 디바이스 형태로 제작되고 있다. 이러한 센서 노드의 소형화는 가용 전지의 양, 메모리 크기, 처리속도를 제한하고 무선센서 네트워 크의 수명을 단축시킨다. 무선센서 네트워크에서는 수명을 늘리는 것이 매우 중요하다. 하지만 센서노드는 데이터 전송 시 가장 많은 전력이 소모 된다. 데이터 압축 기법은 이를 해결하기 위한 대표적인 방법 중 하나이다. 따라서 본 논문에서는 패킷손실 확률에 따라서 압축 기법의 이득을 분석하였다. 데이터 압축 기법은 최소한의 전송량으로 데이터를 줄이므로 전송에 따른 에너지 소모를 최소화하여 무선센서 네트워크에서의 수명을 증가시킬 뿐만 아니라 센서노드 시스템의 처리량을 최대화 하고 작업의 수행시간을 최소화한다. 본 논문의 실험에서 패킷 전송 시 데이터 압축을 통해 전송하였을 경우 패킷손실 확률과 데이터의 전송량에 따라서 성능에 미치는 영향을 실험하고, 데이터 압축 전과 비교하였다. 실험결과, 패킷손실 확률이 40%일 경우 최대 68ms정도의 응답지연시간이 감소되고 처리량 은 30%가 증가된다. 그러므로 압축 기법을 사용하였을 때 압축 기법을 사용하기 전보다 응답 지연시간은 더욱 감 소하고 처리량은 증가 시킨다. 또한, 패킷손실 확률이 증가할수록 응답시간과 처리량측면에서 얻는 이득은 더욱 향 상된다.

Size of sensor nodes which used in wireless sensor networks has been decreasing for its scalability, mobility, and portability. This miniaturization of sensor node limits resources such as limited battery power, processing speed, and memory space. In addition, limited resources reduce the lifetime of wireless sensor networks. The advance of the lifetime is a very important part considered in wireless sensor networks. However, most of the power consuming tasks are data transmission. Data compression is one field of studies to resolve this problem. Thus, we analysis the benefit of compression techniques according to packet loss probability. Compression techniques improves the performance and extends the 논문투고일자: 2009. 11. 2 심사일자: 2009. 11. 20 게재확정일자: 2009. 12. 11 【논 문 】한국차세대컴퓨팅학회 논문지 2009년 12월 57 life time of wireless sensor networks(WSNs). In our experiment, we evaluate the impact of data compression depending on packet loss probability and data size. Experimental results describe that compared to baseline(no compression), latency is decreased by 68ms and throughput is increased by 30% in case of packet loss probability of 40%. Therefore, applying compression techniques can reduce latency and increase throughput than baseline. In addition, as the packet loss probability is increased, we can achieve more enhancement in the perspective of latency and throughput by using compression techniques.

For fast access to the cell, we propose an enhanced random access scheme exploiting multiple transmissions of random access preambles and random access responses. The proposed random access scheme decreases the latency of the random access procedure, by avoiding random access retrials from the beginning of the random access procedure due to the expiry of a random access response window. We also provide a model and analysis of random access latency with the average delay and the failure probability of random access procedure. The model of random access latency considers the collisions of random access preambles transmitted by multiple mobile stations to a base station as well as the error of random access response corresponding to the received random access preamble transmitted by the base station to the mobile station. Our numerical results in accordance with the model show that the proposed scheme provides lower latency.

In recent developments within large-scale Unmanned Aerial Vehicle (UAV) networking, ensuring the accuracy and timeliness of real-time status updates has become increasingly critical. This paper proposes a new Centralized Message Queuing Telemetry Transport (MQTT)-based Communication framework(CMQC) specifically designed to improve real-time data transmission within a simulated large-scale UAV network. The primary objective of this study is to demonstrate the superior performance of the proposed framework in comparison to traditional communication methods such as MQTT, Transmission Control Protocol (TCP) socket-based communication, and Constrained Application Protocol (CoAP). Key performance metrics such as inter-process time interval, total completion time, jitter, and Age of Information (AoI) are evaluated to substantiate these improvements. Experimental results confirm that the MQTT-based framework significantly enhances real-time update capabilities, reduces latency, and improves overall network efficiency. These findings suggest that the proposed framework is a viable solution for enabling low-latency digital twins in large-scale UAV networks.

Objective To identify the difference of quantitative radiologic stenosis between a normal latency group and an abnormal latency group, and to investigate the association of dermatomal somatosensory-evoked potential (DSEP) with magnetic resonance imaging (MRI) findings of narrowing in patients with lumbar spinal stenosis (LSS). Methods We retrospectively reviewed the clinical records and P40 latencies of L5 DSEP of 40 patients with unilateral symptoms of LSS at the L4?5 disc level. Quantitative assessments of stenosis in lumbar spine MRI were performed with measurements of the anteroposterior diameter (APD), cross-sectional area (CSA) of the dural sac, ligamentous interfacet distance (LID), CSA of the neural foramen (CSA-NF), and subarticular zone width. Analyses were conducted through comparisons of radiologic severity between the normal and abnormal latency groups and correlation between radiologic severity of stenosis and latency of DSEP in absolute (APD <10 mm) and relative (APD <13 mm) stenosis. Results The radiologic severities of lumbar stenosis were not significantly different between the normal and abnormal latency groups. In absolute and relative stenosis, latency showed a significant negative correlation with APD (r=-0.539, r=-0.426) and LID (r=-0.459, r=-0.494). In patients with relative stenosis, a weak significant positive correlation was found between latency and CSA-NF (r=0.371, p=0.048). LID was the only significant factor for latency (β=-0.930, p=0.011). Conclusion The normal and abnormal DSEP groups showed no significant differences inradiologic severity. The latency of DSEP had a negative correlation with the severity of central stenosis, and LID was an influencing factor.

In recent years, massive MIMO systems have been widely researched to realize high-speed data transmission. Since massive MIMO systems use a large number of antennas, these systems require huge complexity to detect the signal. In this paper, we propose a novel detection method for massive MIMO using parallel detection with maximum likelihood detection with QR decomposition and M-algorithm (QRM-MLD) to reduce the complexity and latency. The proposed scheme obtains an R matrix after permutation of an H matrix and QR decomposition. The R matrix is also eliminated using a Gauss?Jordan elimination method. By using a modified R matrix, the proposed method can detect the transmitted signal using parallel detection. From the simulation results, the proposed scheme can achieve a reduced complexity and latency with a little degradation of the bit error rate (BER) performance compared with the conventional method.

We address the issues of difference in latency tolerance with heterogeneous IoT users from ground and aviation space by proposing a collaborative satellite terrestrial EDGE computing network. Based on the variability in latency tolerance we propose three offloading schemes under two distinctive scenarios. Optimization in resource sharing while offloading is carried out by adopting DDPG-based actor-critic framework which is suggested as a suitable algorithm by recent studies. We validated the schemes evaluating four performance parameters. Results showed that schemes that tolerate delays between 0.25 to 2.00 s outperformed other schemes in terms of reward, delay and energy consumption.

Objective: To obtain the reference value of N20 latency of median and ulnar nerve somatosensory-evoked potentials (SEPs) in infants. Method: Medical data from infants diagnosed with lumbosacral lipomyelomeningocele who underwent SEP analysis were reviewed retrospectively. Multiple regression analyses were performed to determine the factors that affect N20 latency of median and ulnar nerves (N20median and N20ulnar) considering age, weight, total arm length, upper arm length, and forearm length. Pearson’s correlation analysis was performed between N20 latencies and upper arm length. Results: Total arm length (p < 0.01; p < 0.01), upper arm length (p < 0.001; p < 0.01), and forearm length (p < 0.01; p < 0.01) contributed to N20median and N20ulnar in simple regression analyses. Upper arm length (p < 0.001; p < 0.01) was the only contributing factor for N20median and N20ulnar following multiple regression analyses. The regression equations for estimating N20 latencies in infants from upper arm length were N20median = -0.47 × upper arm length + 22.53 (R2 = 0.21) and N20ulnar = -0.46 × upper arm length + 22.66 (R2 = 0.19). Conclusion: Upper arm length was negatively correlated with N20 latency of upper extremity SEPs in infants. The equations derived from the medical data can be clinically applied as references for infant SEPs.

The application placement strategies in the hierarchical fog-cloud environment based on the directed acyclic graph (DAG) for rapid execution is an NP-hard optimization problem. Although heuristics have been proposed to generate sub-optimal solutions based on non-preemptive placement policy, merging multiple DAG-based applications into one application is simple but ineffective for minimizing the overall makespan due to the lack of consideration of fairness among multiple DAG-based applications. We design an application placement strategy based on dynamic scheduling that can effectively utilize the schedule gaps in the virtual machines of the different layers to minimize the makespan that meets the deadlines.

Advances in next-generation wireless network technology is boosting the demand for ultra-low latency and reliable data-transmission technologies. Particularly, industries are adopting robust end-to-end encryption to enhance security. However, the delays inherent in conventional encryption methods make them unsuitable for meeting these demands. Therefore, this paper presents the Shamir secret sharing?partial encryption (SSS?PE) method, which encrypts only the minimal secret fragments within an SSS environment wherein data are distributed and transmitted. Experimental results indicate that SSS?PE improves secrecy throughput by 1.86 times and reduces latency by 1.38 times compared to the Advanced Encryption Standard.

Objective To examine the usefulness of the second lumbrical-interosseous (2L-INT) distal motor latency (DML) comparison test in localizing median neuropathy to the wrist in patients with absent median sensory and motor response in routine nerve conduction studies.Methods Electrodiagnostic results from 1,705 hands of patients with carpal tunnel syndrome (CTS) symptoms were reviewed retrospectively. All subjects were evaluated using routine nerve conduction studies: median sensory conduction recorded from digits 1 to 4, motor conduction from the abductor pollicis brevis muscle, and the 2L-INT DML comparison test.Results Four hundred and one hands from a total of 1,705 were classified as having severe CTS. Among the severe CTS group, 56 hands (14.0%) showed absent median sensory and motor response in a routine nerve conduction study, and, of those hands, 42 (75.0%) showed an abnormal 2L-INT response. Conclusion The 2L-INT DML comparison test proved to be a valuable electrodiagnostic technique in localizing median mononeuropathy at the wrist, even in the most severe CTS patients.

We consider a multiple access channel (MAC) problem where several users communicate with a base station and in which the users may have different applications or communication purposes for using the network, which is reflected via associated communication metrics. Specifically, we use throughput as the metric to reflect regular data transmission purposes, and latency, modeled by the inverse throughput, is used to reflect data transmission speed as another metric. The problem is formulated as a non-zero sum game. The equilibrium is derived in closed form. Stability in communication for such a heterogeneous network is established by proving the uniqueness of the equilibrium, except for particular cases where stability still can be maintained via cooperation of users with throughput metric or their switching to latency metric.

연구는 반응동작에 따른 장 잠재기반사(long-latency reflex; LLR) 출현양식에 대해서 검증하는데 목적이 있 다. 전기자극강도는 M wave를 기준으로 설정하였으며 진폭이 최대진폭의 5%, 10%가 되는 강도 및 M파역치의 3종류의 강도에서 자극했다. 수의수축량은 MVC을 측정하고 10% 및 20%의 2종류의 수축을 이용했다. 반응과제는 경고신호 (Warning Signals)후 등척성의 수의수축을 유지하고, 반응신호(Response Signal)에 대해서 최대한 신속하게 모지의 외전동작을 실시하도록 했다. 전기자극은 경고신호부터 반응신호까지를 설정한 6개소(반응신호 전)에 렌덤으로 부과했 다. 이상이 연구방법과 절차를 통해서 다음과 같은 결과를 얻었다.첫째.전기자극 강도 및 수의수축량을 변화시켜 LLR을 유발 할 경우 수의수축량이 많을수록 큰 LLR을 유발하는 경향을 나타냈다.둘째.운동준비기의 후반에 LLR을 유발 할 경우 유의한 변화는 나타나지 않았지만 그 변화는 H반사(Hoffmann-reflex)의 변화와 비슷하게 나타났다. 셋째. 운동준 비기 후반에 있어서 LLR가 저하한 group에서는 배경 근 활동량이 감소하는 경향을 나타냈다.이상이 결과로부터 본 실험 에 있어서 유발된 LLR는 척추성의 기원임을 나타냈다.

The purpose of this study was to examine how the LLR(Long-latency Reflex) occurred according to reactive motion long-latency reflex. The strength of electrical stimulation was set based on M wave and stimulus was given at levels of strength with maximum amplitude of 5%, 10% as well as three kinds of M waves. In terms of the volume of voluntary contraction, the study measured MVC using two kinds of contract such as 10% and 20%. Related with responses, isometric voluntary contraction was maintained following the WS and supination on the thumb was conducted as quickly as possible to the RS. The following results were obtained using the above methods and processes. One. If the LLR was induced by changing the strength of electrical stimulation and volume of voluntary contraction, the more the volume of voluntary contraction, the stronger LLR occurred. Two. If the LLR was induced in the latter part of warm-up exercises, no significant change occurred but it was similar to the change of Hoffmann-reflex. Three. Groups with the lower LLR in the latter part of warm-up exercises tended to have less surrounding muscular activity. The LLR as induced from this experiment turned to come from spines.

In this study we evaluate a production-style OpenTelemetry (OTel) pipeline on Google Kubernetes Engine (GKE) Autopilot under a sustained trace workload, instrumenting end-to-end ingestion→processing→export and scraping Collector self-telemetry and spanmetrics with Prometheus over a 30-minute run. The Collector averaged 573 spans/s accepted and 561 spans/s exported, yielding 97.84% within-window export efficiency and peaking near 924 spans/s. A brief saturation interval (150 s) produced a queue peak of 6.38, short drops (peak 3.49 spans/s, ~358 total), and p95 inflation to 116 ms; median latency remained low (p50 ≈ 12.9 ms) and recovered after pressure subsided. Resource footprint was modest (≈0.36 CPU cores, 0.21 GiB memory, sub-Mbps network), indicating headroom. We document integration pitfalls (OTLP endpoint/protocol) and show that queue growth and exporter errors anticipate p95 tails. The study contributes reproducible methodology, quantitative evidence of cloud-scale OTel scalability, and operator guidance for capacity planning and alert design.