• 한국ITS학회 논문지
• /
• 제23권2호
• /
• pp.173-188
• /
• 2024

자율주행차량(AV)의 기술 발전으로 실도로 내 자율주행이 가능해졌지만, 주변 요소로 AV의 인지 범위 또는 능력이 제한되는 인지 음영으로 완전한 자율주행에 어려움이 있다. 오늘날 Lv 4+ 자율주행 테스트 시나리오를 개발하기 위해서는 실제 도로에서 발생할 수 있는 다양한 인지 음영 상황을 파악하고 대비 전략을 구상하는 것이 중요하다. 따라서, 본 연구는 미국 캘리포니아 차량관리국(DMV)의 AV 사고 데이터를 통해 자율주행 모드 활성화 여부에 따라 AV와 일반차량의 사고 형태와 특성을 비교하고, AV 제어권 전환 데이터를 단계적으로 분류하여 인지 음영으로 인한 제어권 전환의 유형과 실제 사례를 도출하였다. 분석 결과, AV의 안전 운전 기동으로 일반 차량과 다른 사고 유형이 나타났으며, 3가지 유형의 인지 음영 사례를 파악하였다. 본 연구 결과는 Lv 4+ 자율주행 테스트 시나리오 개발의 중요한 기초자료가 될 것이며, 다양한 인지 음영이 고려된 테스트 시나리오를 통해 상황별 인지 음영을 해소하는 효율적인 전략을 마련할 수 있다. 이를 통해 실제 도로에서의 AV 주행 안전성을 효과적으로 평가하고 향상할 수 있을 것으로 기대된다.

• 전기학회논문지
• /
• 제67권2호
• /
• pp.301-307
• /
• 2018

Unmanned Aerial Vehicles (i.e., drone) are gaining a lot of interest from a wide range of application domains such as infrastructure monitoring and parcel delivery service. In those service scenarios, multiple UAVs are involved and should be reliably operated by so-called UAV management system. For that, we propose oneM2M standard based UAV management and control system which is specifically targeted at traffic management of low-altitude UAVs. In this paper, we include oneM2M platform architecture and its implementation for UAV management system in conjunction with UAV interworking procedure.

• Wind and Structures
• /
• 제20권2호
• /
• pp.275-292
• /
• 2015

The presence of traffic on a slender long-span bridge deck will modify the cross-section profile of the bridge, which may influence the flutter derivatives and in turn, the critical flutter wind velocity of the bridge. Studies on the influence of vehicles on the flutter derivatives and the critical flutter wind velocity of bridges are rather rare as compared to the investigations on the coupled buffeting vibration of the wind-vehicle-bridge system. A typical streamlined cross-section for long-span bridges is adopted for both experimental and analytical studies. The scaled bridge section model with vehicle models distributed on the bridge deck considering different traffic flow scenarios has been tested in the wind tunnel. The flutter derivatives of the modified bridge cross section have been identified using forced vibration method and the results suggest that the influence of vehicles on the flutter derivatives of the typical streamlined cross-section cannot be ignored. Based on the identified flutter derivatives, the influence of vehicles on the flutter stability of the bridge is investigated. The results show that the effect of vehicles on the flutter wind velocity is obvious.

• Journal of Communications and Networks
• /
• 제7권4호
• /
• pp.509-524
• /
• 2005

Due to the strict requirements of emerging applications, per-flow admission control is gaining increasing importance. One way to implement per-flow admission control is using an on­path resource reservation protocol, where the admission decision is made hop-by-hop after a new flow request arrives at the network boundary. The next-steps in signaling (NSIS) working group of the Internet engineering task force (IETF) is standardising such an on-path signaling protocol. One of the reservation methods considered by NSIS is reduced-state mode, which, suiting the differentiated service (DiffServ) concept, only allows per-class states in interior nodes of a domain. Although there are clear benefits of not dealing with per-flow states in interior nodes-like scalability and low complexity-, without per-flow states the handling of re-routed flows, e.g., after a failure, is a demanding and highly non-trivial task. To be applied in carrier-grade networks, the protocol needs to be resilient in this situation. In this article, we will explain the consequences of a route failover to resource reservation protocols: Severe congestion and incorrect admission decisions due to outdated reservation states. We will set requirements that handling solutions need to fulfill, and we propose extensions to reduced-state protocols accordingly. We show with a set of simulated scenarios that with the given solutions reduced-state protocols can handle re-routed flows practically as fast and robust as stateful protocols.

• 인터넷정보학회논문지
• /
• 제19권2호
• /
• pp.33-41
• /
• 2018

In recent years, technology is rapidly changing to support new service consumption and distribution models in multimedia service systems and hybrid delivery of media services is a key factor for enabling next generation multimedia services. This phenomenon can lead to rapidly increasing network traffic and ultimately has a direct and aggravating effect on the user's quality of service (QOS). To address the issue, we propose a novel system architecture to provide smart hybrid media services efficiently. The architecture is designed to apply the software-defined networking (SDN) method, detect changes in traffic, and combine the data, including user data, service features, and computation node status, to provide a service schedule that is suitable for the current state. To this end, the proposed architecture is based on 2-level scheduling, where Level-1 scheduling is responsible for the best network path and a computation node for processing the user request, whereas Level-2 scheduling deals with individual service requests that arrived at the computation node. This paper describes the overall concept of the architecture, as well as the functions of each component. In addition, this paper describes potential scenarios that demonstrate how this architecture could provide services more efficiently than current media-service architectures.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제11권9호
• /
• pp.4242-4263
• /
• 2017

Multi-User Multiple-Input Multiple-Output (MU-MIMO) technology has recently attracted significant attention from academia and industry because of it is increasingly important role in improving networks' capacity and data rate. Moreover, MU-MIMO systems for the Fifth Generation (5G) have already been researched. High Quality of Service (QoS) and efficient operations at the Medium Access Control (MAC) layer have become key requirements. In this paper, we propose a downlink MU-MIMO MAC protocol based on adaptive Channel State Information (CSI) feedback (called MMM-A) for Wireless Local Area Networks (WLANs). A modified CSMA/CA mechanism using new frame formats is adopted in the proposed protocol. Specifically, the CSI is exchanged between stations (STAs) in an adaptive way, and a packet selection strategy which can guarantee a fairer QoS for scenarios with differentiated traffic is also included in the MMM-A protocol. We then derive the expressions of the throughput and access delay, and analyze the performance of the protocol. It is easy to find that the MMM-A protocol outperforms the commonly used protocols in terms of the saturated throughput and access delay through simulation and analysis results.

• 한국통신학회논문지
• /
• 제33권10B호
• /
• pp.904-910
• /
• 2008

본 논문에서는 군의 요구사항을 고려하여 군 통신망의 서비스와 관련 파라미터들을 연구하고, u-Army 실험망을 시뮬레이션을 통해 성능 측정을 하였다. 이를 바탕으로 전 군에 VoIP를 적용할 수 있는 VoIP 설계 가이드라인을 제시하였다. 측정은 패킷과 콜 시그널링 관점에서 지연과 손실에 관하여 몇 가지 시나리오에 대해 측정하였다. 첫 번째는 독립적인 네트워크 서비스에 따라 만족하는 요구사항을 측정하였다. 두 번째는 통합 서비스에서 지연과 손실에 관하여 백그라운드 트래픽을 증가시키면서 그 결과를 측정하였다. 마지막으로 시뮬레이션에 근거하여 IP PBX 장비의 설치 위치에 따라 네트워크의 구성을 분류하여 설계 가이드라인을 제시하였으며, 현재 군의 고정된 링크의 상황에 맞추어 VoIP 단말기의 수를 정할 수 있도록 계산 방법을 제시하였다.

• ETRI Journal
• /
• 제28권3호
• /
• pp.282-290
• /
• 2006

In vertically overlaid cellular systems, a temporary traffic concentration can occur in a hot-spot area, and this adversely affects overall system capacity. In this paper, we develop an adaptive hot-spot operating scheme (AHOS) to mitigate the negative effects from the nonuniform distribution of user location and the variation in the mixture of QoS requirements in orthogonal frequency division multiple access downlink systems. Here, the base station in a macrocell can control the operation of picocells within the cell, and turns them on or off according to the system overload estimation function. In order to determine whether the set of picocells is turned on or off, we define an AHOS gain index that describes the number of subcarriers saved to the macrocell by turning a specific picocell on. For initiating the picocell OFF procedure, we utilize the changes in traffic concentration and co-channel interference to the neighboring cells. According to computer simulation, the AHOS has been proved to have maximize system throughput while maintaining a very low QoS outage probability under various system scenarios in both a single-cell and multi-cell environments.

• ETRI Journal
• /
• 제37권5호
• /
• pp.856-866
• /
• 2015

A heterogeneous network (HetNet) is a network topology composed by deploying multiple HetNets under the coverage of macro cells (MCs). It can improve network throughput, extend cell coverage, and offload network traffic; for example, the network traffic of a 5G mobile communications network. A HetNet involves a mix of radio technologies and various cell types working together seamlessly. In a HetNet, coordination between MCs and small cells (SCs) has a positive impact on the performance of the networks contained within, and consequently on the overall user experience. Therefore, to improve user-perceived service quality, HetNets require high-efficiency network protocols and enhanced radio technologies. In this paper, we introduce a 5G HetNet comprised of MCs and both fixed and mobile SCs (mSCs). The featured mSCs can be mounted on a car, bus, or train and have different characteristics to fixed SCs (fSCs). In this paper, we address the technical challenges related to mSCs. In addition, we analyze the network performance under two HetNet scenarios-MCs and fSCs, and MCs and mSCs.

• ETRI Journal
• /
• 제37권5호
• /
• pp.1032-1043
• /
• 2015

ETRI's Co-Pilot project is aimed at the development of an automated vehicle that cooperates with a driver and interacts with other vehicles on the road while obeying traffic rules without collisions. This paper presents a core block within the Co-Pilot system; the block is named "Co-Pilot agent" and consists of several main modules, such as road map generation, decision-making, and trajectory generation. The road map generation builds road map data to provide enhanced and detailed map data. The decision-making, designed to serve situation assessment and behavior planning, evaluates a collision risk of traffic situations and determines maneuvers to follow a global path as well as to avoid collisions. The trajectory generation generates a trajectory to achieve the given maneuver by the decision-making module. The system is implemented in an open-source robot operating system to provide a reusable, hardware-independent software platform; it is then tested on a closed road with other vehicles in several scenarios similar to real road environments to verify that it works properly for cooperative driving with a driver and automated driving.