In-Ho Ra

Two-Relay-Based Cooperative MAC Protocol for Wireless Ad hoc Networks

The cooperative communication approach promises improved throughput and delay performance by effective use of spatial diversity in wireless ad hoc networks. The CoopMAC I protocol proposed by Liu picks either a direct path or a relay path based on rate comparison to enhance average throughput and delay performances. However, its performance deteriorates under fading conditions due to lower direct path or relay path reliability. UtdMAC, which was proposed by Agarwal , performs better than CoopMAC I in terms of average throughput and delay performances due to improved transmission reliability provided by the backup relay path. Although it is better than CoopMAC I, UtdMAC does not fully benefit from higher throughput relay path (compared with the direct path) since it uses relay path only as a secondary backup path. In this paper, a new cooperative medium access control (MAC) protocol, which is termed the 2rcMAC protocol, is proposed for a small-sized network. The protocol makes use of two cooperating nodes to achieve superior throughput and delay performances, compared with the existing cooperative MAC protocols. The secondary relay path is invoked as a backup path for better transmission reliability and higher throughput through the relay path. Moreover, handshaking and single-bit feedbacks resolve contentions among relay nodes in proximity at the time and further provide the source node with rate information on source-to-destination, source-to-relay, and relay-to-destination links. Performance gains achieved by the 2rcMAC protocol under fast-fading conditions over the existing cooperative MAC protocols are compared and discussed. Simulation results clearly show an average throughput improvement of 7% and 25% and an average delay improvement of 94.8% and 98.9%, compared with UtdMAC and CoopMAC I, respectively.

Coherence time-based cooperative MAC protocol 1 for wireless ad hoc networks

In this article, we address the goal of achieving performance gains under heavy-load and fast fading conditions. CoopMACI protocol proposed in Proceedings of the IEEE International Conference on Communications (ICC), Seoul, Korea, picks either direct path or relay path based on rate comparison to enhance average throughput and delay performances. However, CoopMACI performance deteriorates under fading conditions because of lower direct path or relay path reliability compared to UtdMAC (Agarwal et al. LNCS, 4479, 415-426, 2007). UtdMAC was shown to perform better than CoopMACI in terms of average throughput and delay performances because of improved transmission reliability provided by the backup relay path. Although better than CoopMACI, UtdMAC does not fully benefit from higher throughput relay path (compared to the direct path), since it uses relay path only as a secondary backup path. In this article, we develop a cooperative MAC protocol (termed as instantaneous relay-based cooperative MAC--IrcMAC) that uses channel coherence time and estimates signal-to-noise ratio (SNR) of source-to-relay, relay-to-destination, and source-to-destination links, to reliably choose between relay path or direct path for enhanced throughput and delay performances. Unique handshaking is used to estimate SNR and single bit feedbacks resolve contentions among relay nodes, which further provides source node with rate (based on SNR) information on source-to-destination, source-to-relay, and relay-to-destination links. Simulation results clearly show that IrcMAC significantly outperforms the existing CoopMACI and the UtdMAC protocols in wireless ad hoc network. Results show average throughput improvements of 41% and 64% and average delay improvementd of 98.5% and 99.7% compared with UtdMAC and CoopMACI, respectively.

Polarization-based cooperative directional MAC protocol for ad hoc networks

Numerous directional medium access control (DMAC) protocols have been developed to enhance the capacity of ad hoc networks using the underlying advanced physical layer techniques, such as beam-forming, multiuser detection (MUD), and multiple-input-multiple-output (MIMO). In this paper, we propose an innovative fully distributed DMAC protocol that cooperatively makes use of polarization diversity in low-mobility urban/suburban outdoor wireless ad hoc network environment. In the proposed cooperative polarization DMAC protocol (CPDMAC), each node directionally senses on both vertical and horizontal polarizations and dynamically adapts polarization that minimizes overall interference in the ad hoc network. Analysis is performed to establish relationship between vertically and horizontally polarized nodes in the network. Further, a theoretical lower bound is derived for probability of successful transmission to show capacity improvement as a function of cross polarization ratio (CPR). Simulation results confirm from 2% up to 400% improvement in average node throughput at data rate of 1.95Mbps when compared to the traditional DMAC protocol. Moreover, our study clearly shows that the average throughput difference increases with increasing node density when compared to the traditional DMAC protocol.

Message Delivery and Energy Consumption Analysis on Pocket Switched Network Routing Protocols

인터넷 기술의 발전과 사용범위 및 영역이 지속적으로 확장되고 있지만 아직도 네트워크 연결성을 제공할 수 없는 원격 지역과 상황들이 상당히 존재한다. Pocket Switched Network(PSN)은 모바일 송수신 장치를 휴대한 사람이 제공하는 이동성을 활용하여 인터넷을 사용할 수 없는 지역에서도 데이터 전송을 가능케 하는 네트워크로서 PSN에서는 노드의 이동성, 링크 고장, 배터리 방전 등의 문제점을 고려하여 데이터 전송을 위한 네트워크 연결성을 계속적으로 유지해 주는 것이 매우 중요하다. 본 논문에서는 현재까지 제안된 주요 PSN 라우팅 기법들을 살펴보고 이것들의 성능을 분석하기 위해 네트워크 노드 수를 증가시키면서 전송 확률, 오버헤드 비율, 평균 전송지연, 평균 잔여에너지양의 변화를 실험을 통해 비교한다. 또한, 실험 결과를 통해 데이터 전송을 최대화하면서 에너지 소비는 최소화하여 네트워크 수명을 연장할 수 있는 기법을 제시한다.

An Intrusion Detection System Based on Multi-Level Clustering for Hierarchical Wireless Sensor Networks.

In this work, an intrusion detection system (IDS) framework based on multi-level clustering for hierarchical wireless sensor networks is proposed. The framework employs two types of intrusion detection approaches: (1) “downward-IDS (D-IDS)” to detect the abnormal behavior (intrusion) of the subordinate (member) nodes; and (2) “upward-IDS (U-IDS)” to detect the abnormal behavior of the cluster heads. By using analytical calculations, the optimum parameters for the D-IDS (number of maximum hops) and U-IDS (monitoring group size) of the framework are evaluated and presented.

Throughput and delay analysis in Aeronautical Data Networks

Evergrowing consumer demand for wireless connectivity is opening a new paradigm of communications, “Aeronautical Data Networks (ADN)”. The desire is to provide high throughput and cost effective data network not only for an aeronautical applications, but also for terrestrial networks by using aeronautical platforms as a backbone. An aeronautical station (AS) could be a commercial plane, a helicopter, or any other low orbit station, i.e., Unmanned Air Vehicle, High Altitude Platforms. In this paper, we study an aeronautical broadband wireless access scheme to provide throughput and delay analysis for ADN. First, a simple topology of ADN is presented as a mobile ad-hoc network (MANET). A two-hop network model is considered where each packet makes two hops, one from the source AS to a relay AS and one from the relay AS to the destination AS. Then, based on the method of finding the maximum number of concurrent successful transmissions, the ADN throughput upper bound is obtained. Closed-form end-to-end delay expression is also derived, to provide a general ADN system performance in terms of throughput and delay. Numerical results are presented, which show the alignment with our theoretical analysis.

Intelligent Drowsiness Drive Warning System

In this paper. we propose the real-time vision system which judges drowsiness driving based on levels of drivers` fatigue. The proposed system is to prevent traffic accidents by warning the drowsiness and carelessness using face-image analysis and fuzzy logic algorithm. We find the face position and eye areas by using fuzzy skin filter and virtual face model in order to develop the real-time face detection algorithm, and we measure the eye blinking frequency and eye closure duration by using their informations. And then we propose the method for estimating the levels of drivel`s fatigue based on measured data by using the fuzzy logic and for deciding whether drowsiness driving is or not. Finally, we show the effectiveness and feasibility of the proposed method through some experiments.

Throughput and delay of single-hop and two-hop aeronautical communication networks

Aeronautical communication networks (ACN) is an emerging concept in which aeronautical stations (AS) are considered as a part of multi-tier network for the future wireless communication system. An AS could be a commercial plane, helicopter, or any other low orbit station, i.e., Unmanned air vehicle, high altitude platform. The goal of ACN is to provide high throughput and cost effective communication network for aeronautical applications (i.e., Air traffic control (ATC), air traffic management (ATM) communications, and commercial in-flight Internet activities), and terrestrial networks by using aeronautical platforms as a backbone. In this paper, we investigate the issues about connectivity, throughput, and delay in ACN. First, topology of ACN is presented as a simple mobile ad hoc network and connectivity analysis is provided. Then, by using information obtained from connectivity analysis, we investigate two communication models, i.e., single-hop and two-hop, in which each source AS is communicating with its destination AS with or without the help of intermediate relay AS, respectively. In our throughput analysis, we use the method of finding the maximum number of concurrent successful transmissions to derive ACN throughput upper bounds for the two communication models. We conclude that the two-hop model achieves greater throughput scaling than the single-hop model for ACN and multi-hop models cannot achieve better throughput scaling than two-hop model. Furthermore, since delay issue is more salient in two-hop communication, we characterize the delay performance and derive the closed-form average end-to-end delay for the two-hop model. Finally, computer simulations are performed and it is shown that ACN is robust in terms of throughput and delay performances.

ADMAC with Integrated Destination Discovery for Ad Hoc Networks

Directional antennas have shown to increase spatial reuse by allowing multiple transmitters and receivers to concurrently communicate using directional beams as long as they do not significantly interfere with each other. This appreciably increases average aggregate throughput of the network. Generally, for high throughput performance the directional MAC (Medium Access Control) protocols choose a random direction for destinations location and subsequent data transmissions. Under situations of heavy load, high mobility and narrow beam-width, frequent updates are required to track the destinations. However, frequent updates may degrade the effective throughput of the network. Hence, we propose a novel Adaptive Directional MAC (ADMAC) protocol with integrated destination discovery that estimates destinations possible search span and then initiates transmission in that search span direction. Another major contribution is the average throughput performance comparison between last sector (LS), random sector (RS) and search span approaches. Average throughput results show an improvement of up to 40 % and greater than 400 %, when compared to the LS and the RS based DMAC protocols, respectively.

A Fault-Tolerant QoS Routing Scheme based on Interference Awareness for Wireless Sensor Networks

In this paper, we propose a fault-tolerant QoS routing scheme based on interference awareness for providing both high throughput and minimum end-to-end delay for wireless sensor networks. With the proposed algorithm, it is feasible to find out the optimal transmission path between sensor nodes to the sink node by using cumulative path metric where real-time delivery, high energy efficiency and less interference are considered as in path selection. Finally, simulation results show that network throughput and delay can be improved by using the proposed routing scheme.