Earticle

We propose a robust joint time of flight and velocity estimation framework for ultrasonic sensing in near-range parking environments, where strong multipath often masks the direct path and degrades the reliability of conventional peak-based methods. The proposed approach integrates a direct-path likelihood function that reconstructs the physically valid first-arrival path and a zero-Doppler residual suppression method eliminating static-reflector clutter in the cross-ambiguity function domain. Simulation results confirm that the method significantly improves robustness under multipath-dominant conditions. The framework is highly suitable for practical automotive ultrasonic sensing systems.

Multipath TCP(MPTCP)는 다중 인터페이스를 이용하여 데이터를 동시에 전송하는 전송계층의 프로토콜이다. MPTCP는 비슷한특성의 망을 사용하는 네트워크 환경에서는 기존 TCP에 비해 우월한 성능을 보이지만 이종 망을 사용하는 MPTCP의 다중경로중 특정 경로에서 버퍼블로트 현상이 일어나게 되면 급격한 지연시간의 증가로 인해 느린 경로로 전송 된 패킷이 MPTCP 수신버퍼에 도착하지 않게 되어 다른 경로로 수신한 패킷이 수신버퍼에서 대기하는 Head-of-Line(HoL) blocking 현상을 초래하여 기존 TCP 대비 더욱 악화된 성능을 보이기도 한다. 따라서 본 논문에서는 이러한 버퍼블로트 문제를 해결하기 위해 Active Queue Management(AQM) 기법 중 Adaptive Random Early Detection(ARED), Controlled Delay(CoDel), Proportional Integral Controller Enhanced(PIE)를 네트워크에 적용하여 이종 망에서 MPTCP 성능 개선을 목표로 실험을 진행하였다. 성능 향상을 살펴보기 위해Linux 기반의 유선 테스트베드를 구축하고 기존 드롭 테일과 AQM을 비교분석하여 AQM 기반의 TCP가 bufferbloat가 있는 다중경로 MPTCP의 성능을 향상시키는 것을 살펴보았다.

Multipath TCP (MPTCP) is a transport layer protocol that simultaneously transmits data using multiple interfaces. MPTCP is superior to existing TCP in network environment with homogeneous subflows, but it shows worse performance compared to existing TCP in network environment with bufferbloat. If a bufferbloat occurs in one of the MPTCP multipaths, the packet will not arrive at the MPTCP receive buffer due to a sudden increase in delay time, resulting in a HoL blocking phenomenon. It makes the receive window of the other path to be zero. In this paper, we apply Adaptive Random Early Detection (ARED), Controlled Delay (CoDel) and Proportional Integral Controller Enhanced (PIE) among the proposed Active Queue Management (AQM) to limit the delay of bufferbloat path. Experiments were conducted to improve the performance of MPTCP in heterogeneous networks. In order to carry out the experiment, we constructed a Linux-based testbed and compared the MPTCP performance with that of the existing droptail.

본 논문에서 소개하는 새로운 라우팅 프로토콜은 무선 멀티미디어 센서 네트워크에서 다중경로와 다중 우선순위 기반의 라우팅 프로토콜 (MMRP)이다. 제안된 MMRP는 소스부터 싱크까지 다중 라우팅 경로를 선택하고, 선택된 라우팅경로 내의 잔여 에너지와 전송지연에 따라서 우선순위 레벨이 할당된다. 즉, MPEG 비디오의 경우 높은 우선순위를 갖는 I 프레임은 높은 우선순위의 라우팅 경로를 통해 전송이 되며, P와 B 프레임의 경우 낮은 우선순위를 갖는 라우팅 경로를 통해 전송되도록 한다. 제안된 MMRP 프로토콜은 무선 멀티미디어 센서 네트워크에서 낮은 전력소모 특성을 만족하면서 작은 전송 지연을 고려하는 시간 민감 응용 분야에 적용이 가능하다. MMRP 프로토콜에 대한 시뮬레이션 결과는 다중경로 라우팅을 지원하거나 지원하지 않는 프로토콜과 비교 시, 에너지 절약적인 부분에서는 23.48%에서 23.11% 그리고 지연 부분에서는 81.6%에서 32.01%로 향상을 보였다.

In this paper, we present a new routing protocol, multipath and multi-priority based routing protocol, (MMRP) for wireless multimedia sensor networks. The proposed MMRP chooses the multiple routing paths from source to the sink, then the selected paths are assigned with different priority levels depending upon the residual energy and transmission delay in the routing paths. That is, the highly prioritized I frames of the MPEG video are transmitted over the high priority routing paths, and other P and B frames are transmitted over the lower priority routing paths. The proposed MMRP protocol can be applied to time critical applications which require both lower latency and low power consumption over wireless multimedia sensor network. Simulations results of MMRP protocol show respectively an improvement of 23.48% and 23.11% in energy conservation and 81.6% and 32.01% improvement in latency as compared to protocols without and with multipath routing.

본 논문은 애드 혹 네트워크에서 다중 경로 설정을 위한 탐색 기법을 제안한다. 데이터 경로 설정은 요구기반 방식으로 동작하며, 소스와 목적지 노드 간의 다중 경로는 초기 경로 설정 과정에서 함께 구해진다. 이러한 다중 경로는 데이터 경로의 백업이나 부하 분산에 사용될 수 있다. 제안 방식에서는 소스와 목적지 노드 간 다중 경로를 찾기 위해, 사전 질의 방법을 사용한다. 이 방안은 중간 노드에서 응답 메시지를 처리할 때, 주변 노드와의 정보 교환을 통해 최적의 다음 노드를 선택하는 방안이다. 시뮬레이션 결과를 통해, 제안된 다중 경로 체계가 경로간의 만나는 횟수를 감소시켜 다중 경로의 더 좋은 분리도를 주고, 노드들이 이동하는 환경에서 더 높은 경로 생존 확률을 달성함을 알 수 있었다.

This paper suggests a multipath establishing scheme for ad hoc networks. Data paths are established by on-demand manner. Multipath are made as a sequence of route control message exchange at route setup process. Multipath can be used as a backup path or load balancing for data exchange. Proposed scheme uses a one-hop pre-search scheme for establishing multipath between source and destination. When a node selects a next node for route reply, the node finds optimal route by exchanging route information with neighbor nodes. Simulation results show that the proposed multipath scheme has better split characteristics among multipath and higher route survivability at the environment where nodes are moving.

연합학습은 데이터를 중앙 서버에 모아서 학습하는 중앙집중식 학습과 달리 개별 기기에서 모델 학습을 진행한 후 중앙 서버로 가중치들을 전송하는 분산식 학습 방식을 가진다. 따라서 개별 기기의 연산 성능과 통신 성 능 및 상황이 모델 학습에 큰 영향을 끼칠 수 있으므로 적절한 기기와 통신 방식을 선택해야 한다. 하지만 기존 연 합학습은 클라이언트 주위의 신뢰할 수 있는 가용 유휴 장치와 다양한 통신 및 다중 경로를 사용하지 않는 한계가 존재한다. 이를 극복하기 위해, 본 논문에서는 Learning agent 활용 및 다중 경로 기반 모델 분할 전송을 통한 연 합학습 개선 연구를 수행하였다. 시뮬레이션과 실제 장치를 활용한 실험을 통해 제안한 기법을 평가하였으며, 기존 연합학습과 비교하여 제안한 기법을 활용한 경우 학습 시간의 감소 및 학습 성능의 향상을 확인할 수 있었다.

Unlike centralized learning, federated learning has a distributed learning method that individual devices perform model training locally and then transmit weights to the central server. Therefore, the appropriate devices and communication methods should be selected as the computational and communication performance, and situation of individual devices can have a great impact on learning. However, the existing federated learning has limitations in not using various communications through multiple paths simultaneously and reliable and available idle devices around clients. To overcome this, in this paper, we conduct a study on improvement of federated learning using learning agent and multipath-based model split transmission. We evaluated the proposed technique through simulations and experiments using the real devices. The evaluation results show that the training time was reduced and the learning performance improved when the proposed technique was used compared to the existing method.

본 논문에서 다중 경로 T-DMB 환경에서 신호검출 알고리즘을 적용하여 성능을 분석하였다. 가우시안, Rayleigh, COST 207 채널을 각각 적용하여 다중 환경에서 다양한 파라미터를 변화시켜 연구하였다. 최종 실험결과는 주파수 유무에 따라 비트화로 정의하여 비교 분석하였으며, 검출하기 위한 신호는 T-DMB 표준을 참고하여 생성하였다. 실험에 있어서 적용된 신호검출 기법은 에너지 검출 기법을 적용하였으며, 생성 신호의 길이에 따라 실험을 하였다. 실험결과로써는 다중 환경에 따른 다양한 결과값을 얻을 수 있었으며, 뿐만 아니라 신호 길이에 따른 성능 분석을 할 수 있었다. 신호의 길이가 증가할수록 검출시간이 길어져 성능과 비례함을 확인할 수 있었다. 우리는 이번 신호검출 실험을 실제 T-DMB 환경에서 적용할 수 있도록 연구를 하였다.

In this paper, we analyzed performance of signal detection for terrestrial digital multimedia broadcasting (T-DMB) system in various channel environments that applied gaussian, Rayleigh and COST 207 environments that estimate response of real channel state. In order to detect the signal, a signal detection scheme based on energy detection is employed. We generated T-DMB signals so that estimate properly simulation result. For evaluating the signal detection performance, detection probability is derived. We consider two kinds of detection segment, which are three segments and five segments. And we compare the system performances in accordance with the detection segment. From simulation results, it is confirmed that the performance of signal detection is raised as increase the number of segments. The result of this paper can be applied to implement signal detection of broadcasting system.

Multiple antenna technology, such as multiple input multiple output (MIMO), beamforming is one of the most promising technology for broadband wireless communication. In OFDM environment, we found that as the number of paths is increased, smart antenna system cannot fully exploit beamforming gain. In this paper, we propose a beamforming scheme and analyze the performance of the proposed beamforming scheme in WiBro smart antenna system. WiBro is an OFDMA-based multiple access service for wireless broadband multimedia environment. The proposed beamforming technique for WiBro smart antenna system can effectively improve the performance of the systems in multipath fading environment.

In this paper, we analyze the performance of RAKE receiver for impulse radio-ultra wide band (IR-UWB) systems in indoor multipath radio channel. Pulse position modulation-time hopping (PPM-TH) signal is considered. And we also consider three types of RAKE receivers, which are ideal RAKE, selective RAKE, and partial RAKE receivers. The indoor channel is modeled as the modified Saleh and Valenzuela (SV) model which has been proposed as a UWB channel model by the IEEE group, IEEE 802.15.SG3a.

현재의 인터넷에서 경로 장애가 자주 발생한다는 것은 잘 알려진 사실이다. 높은 신뢰성을 요하는 응용 프로그램은 점점 많이 나오고 있지만 인터넷은 요구되는 수준의 신뢰성을 제공하지 못한다. 경로 장애 발생시 그 영향을 응용 프로그램에게는 최대한 감추고 종단간의 신뢰성을 개선하려는 여러 가지 방안들이 제시되었지만 그러한 방식들은 단일 경로 방식이어서 장애 경로를 감지하고 새로 찾은 길로 패킷을 전송시킬 때까지 패킷들을 연이어 잃어버리게 된다. 이에 반해 선제 다중 경로 라우팅 방식은 동작하는 경로로 패킷을 전송함으로 연이은 패킷 손실을 줄일 수 있다. 본 연구에서는 단일 경로 라우팅 방식과 비교하기 위하여 오버레이 네트워크에서 동작하는 다중 경로 라우팅 프로그램을 리눅스 상에서 구현하고 PlanetLab에서 실험하였다. 또한 다중 경로 라우팅 방식의 평가를 위해서는 기존의 성능 메트릭이 부적합함을 지적하고 연이어 잃어버리는 패킷의 수를 새로운 성능 메트릭으로 사용할 것을 제안한다. 실험 결과는 새로운 성능 메트릭으로 신뢰성을 측정했을 때 다중 경로 라우팅이 물리적 경로의 독립성 보장 없이도 많은 효과가 있음을 보여준다.

While emerging applications require high reliability, the current Internet does not provide such levels of reliability: it is reported that path disruptions occur frequently in the current Internet. Thus far there have been several studies to attempt to mask path failures and to improve end-to-end reliability. A common feature of the approaches is that they take a reactive single path approach, which cannot avoid a burst of packet losses while detecting path failures and trying to switch to another path. Proactive multipath routing approaches can reduce bursts of packet losses by still allowing some packets to be delivered to the destination. To evaluate the effectiveness of proactive multipath routing, we implement an multipath overlay routing for Linux and perform experiments in PlanetLab. Also we propose a new performance metric for reliability of routing schemes. Experimental results show that compared to single path routing, proactive multipath routing can improve reliability even when independency of physical paths in overlay networks are not guaranteed.

실내에서의 위치 인식 기술에 대한 연구가 매우 활발하며 음향 신호를 이용한 TDOA 기술이 많이 사용되고 있다. 그러나 TDOA 기술의 단점은 신호의 전송 과정에서 다중 경로에 의한 신호의 왜곡에 매우 취약하다는 것이다. 특히 스마트폰의 위치를 인식하는 경우에는 스마트폰에서 음향신호의 왜곡이 심하며, 무선랜이나 블루투스를 이용하여 시간 기준 신호를 전송하는 경우에는 무선 신호의 지터가 발생하여 위치 측정기에서 시간 기준 신호로 사용하기가 어렵다. 본 논문에서는 위치 측정을 위한 음향 신호를 전송하기 전에 위치 측정기에서 신호의 수신을 준비할 수 있도록 음향 트리거 신호를 전송하는 방법을 제안하고, 다중경로 영향의 감소 효과를 실험을 통해 검증하였다.

A study on the indoor positioning system has been active recently, and TDOA technique using acoustic signal has been used generally. The drawback of the TDOA is very weak against signal distortion due to multipath effect. Especially to estimate the smartphone position, the sound distortion is very severe, and the generated radio signal jitter when using WLAN or Bluetooth as a time reference signal makes the receiver difficult to estimate the position. In this paper, acoustic trigger signal for the receiver preparing the positioning signal reception is proposed, and the mitigation of the multipath effect is shown.

IR (impulse radio)를 사용하는 IR-UWB 방식은 짧은 펄스를 전송하기 때문에 송수신기를 간단히 구현할 수 있고, 저 전력으로 구현 가능하며, 다중 경로 지연과 같은 외부 환경에 강한 특성을 가진다. 더불어, 짧은 펄스를 사용하므로 데이터 수신시 채널의 특징을 파악하기 위해 정확한 채널 추정 방법이 요구 된다. 채널 추정한 후 추정된 채널 이득과 지연 값은 레이크 수신기의 경로 선택에 이용되고, 데이터 수신시 파라메타를 정확히 찾는 정도에 따라서 성능이 좌우된다. 본 문서에서는 수신된 프리엠블 등의 신호를 이용하여 채널의 특성을 파악하여 관련 파라메터를 추출하는 채널 추정 알고리즘 및 다양한 관련 기술에 대하여 소개한다.

Impulse Radio Ultra-wideband (IR-UWB) system employing the short pulse has the tolerable characteristics for the multipath environment. The corresponding transceiver with low power consumption can be simply implemented. On the other hand, in the receiver side, the precise channel estimation is required for the knowledge of essence in channel due to the short period of pulse. The estimated gains and delays in channel are used in the rake receiver. The resulting parameters we search have a strong influence on the performance in the entire system. We introduce that the essential parameters can be obtained more precisely through the preamble in receiver side for the channel estimation and related technologies are presented.

본 논문에서는 디지털 워터마킹 기법을 이용하여 부가데이터를 전송하기 위해 일반화된 K 페이딩 채널에서의 채널용량 수식을 유도하였다. 대역확산 워터마킹 기법(Spread Spectrum Watermarking: SSW)은 디지털 워터마킹 기법 중의 하나로 무선 채널에서 잡음에 대해 강인한 특성을 지니며, 수신단에서의 신호 검출이 상관기에 의해 간단히 이루어지기 때문에 널리 사용되는 방식이다. 대역확산 워터마킹 기법에 의해 생성된 부가데이터를 무선통신 시스템에 적용하기 위해서는 워터마킹 신호가 무선 채널에 의해 받는 영향에 대한 연구가 필수적으로 요구된다. 모의실험 결과로부터 대역확산 워터마킹 시스템의 채널용량이 HWR, WNR, fx, 그리고 PN 시퀀스의 길이에 따라 변화함을 확인하였고, 또한 적정 데이터를 전송하기 위하여 필요한 HWR과 WNR의 레벨을 수식으로부터 결정할 수 있음을 보였다. 본 논문의 결과는 PN 시퀀스를 이용하는 일반적인 대역확산 워터마킹 시스템에 적용할 수 있다.

In this paper, we derive the channel capacity in order to transmit an additional data by using digital watermarking method in generalized-K fading channel. Spread spectrum watermarking is one of the digital watermarking methods which is the most promising technique due to it's very robustness to the channel noise and easy achieving of the signal detection by correlators at the receiver. It is important to analyze the channel capacity to transmit an additional data through wireless channel because the transmitted data would be affected by the channel fading effects. From the results, we confirm that the channel capacity of the SSW system can be determined by the HWR, WNR, PN length and host sampling frequency. Also, we verified that the level of HWR and WNR can be determined by the derived capacity formula. The results of this paper can be applied to general spread spectrum watermarking system.

Multipath routing protocols improve the load balancing and quality of service in WSN and also provide reliable communication. This paper investigates various multi-path routing protocols of the WSN in the literature and illustrates its benefits. The main elements of these schemes and their classifications based on their attributes have been also discussed. A comparison of these protocols which are of great help to understand the properties and limitations of existing solutions have been done in the following study.

Network virtualization is an important technology that allows multiple heterogeneous networks running simultaneously share substrate network, it can effectively solve the problem of network ossification. Earlier research has made many heuristic algorithms, but it does not consider the time factor in the embedding process, existing algorithm often make decision according to the present available substrate network resource. This paper, we first explore the time and space of the two dimensional network model, form the perspective of the two-dimensional space-time, we proposed two-dimensional discrete weighted method and multi commodity flow virtual network embedding with time-varying model. We also proposed a virtual network algorithm based on space–time. The simulation result show that the proposed algorithm can effectively utilize the network resources and make substrate network resources maintain the load balance for a long term.

The issue of data transmission in wireless sensor networks was studied. The video data collection was chosen as the object of the study, and the quality of service (QoS) problem of video transmission was analyzed. Video applications were generally characterized by large data size and many QoS requirements, which made the transmission of video always a hard problem. In this dissertation, a cross-layer and multi-path video transmission strategy (MVTS) was presented. MVTS introduced the idea of differentiated service and multipath routing, and operated in both application layer and network layer. In application layer, different types of video frames were distinguished and marked with different tags. Then in network layer these frames were identified by the tags and MVTS forwarded them in different paths. In this way, the key frames could be sent to the sink node reliably. Simulation tests were carried out, and simulation results showed that MVTS extended the network lifetime greatly and provided better assurance for quality of video applications.

This paper focuses on the multipath interference by an obstruction or rough terrain is studied. The detriment of Glide path information to an aircraft that is approaching the airport with a precision ILS (Instrument Landing System) landing is due to the wrong siting. Terrain irregularity or roughness is the worst and most common glide slope siting deficiency. The degrading effect of rough terrain results from the random dispersion and/or phase shift of ground plane signal. In order to study the possibility of glide path signal interference, the new site that is under construction a big apartment complex and 3km distance away from glide path antenna is selected as a representative model in domestic airport. In the study, computerized simulation technic is employed to predict the probable reflected energy caused by the multipath conditions from antenna, obstructions and siting criteria. This study suggests the solution of a similar case through this analysis method.

Network coding in Mobile Ad hoc Network (MANET) is well-known in reducing delay, increasing throughput, and improving transmission reliability. While the data throughput capacity of MANETs is unknown, the scaling of capacity with the number of nodes has recently received increasing attention. This paper proposes a Complex Field Network Coding-based Multipath Routing in MANETs (CFNC-MRM). The performance of this routing method is studied using NS2 and evaluated in terms of the packet overhead, packet delivery ratio, and packet loss ratio when a packet is transmitted. Simulation shows that the CFNC-MRM is efficient, providing reliable multipath, promising and applicable in MANETs.

Network coding is a new paradigm in data transport and promises to change many aspects of wireless sensor network (WSN). Thanks to the recently developed network coding techniques, a high-throughput low-complexity hierarchical protocol can be facilitated due to the multiple-source relay-based data transmissions built on the network coding schemes, especially for the data communications between the source node and destination node. In this paper, we propose an Energy efficient that carefully couples Network coding and Multipath routing algorithm in Wireless Sensor Networks (ENM-WSN). Through an analytical study, we provide guidance on how to choose parameters in our scheme and demonstrate that the scheme is efficient in both multipath and energy consumption. We also present an algorithm for deciding the network coding scheme for a node to further reduce energy consumption by minimizing redundant packet transmissions. Simulation results show that, with the proposed energy efficient with network coding in WSN multipath routing protocol (ENM-WSN), energy consumption, packet delivery ratio, and network lifetime can be improved in most of cases. It is an available approach to multipath routing decision.

A single flow stream could be divided into several sub-flows to be sent across multiple paths. This method obtains obvious advantages against traditional TCP as it maintains higher reliability and makes bettaer use of the network resources. Congestion control algorithm is an essential part to be considered. This paper first reviews the existing multipath TCP congestion control algorithms and then analyzes and formulates the goals and problems need to be achieved and solved. A delay-based congestion control algorithm named Weighted Vegas (wVegas) is provided. Finally, two possible modifications are demonstrated including adjusting the congestion control window according to how far the path is from congestion and redefining the behavior when loss occurs.