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MANET (Mobile Ad hoc Network)에서 라우팅은 네트워크 토폴로지의 동적인 변화에 큰 영향을 받는다. AntHocNet은 집단 개미가 최적 경로를 통해 먹이를 찾아가는 원리를 모방한 집단생태 특성 기반 MANET 라우팅 프로토콜이다. 하지만, AntHocNet은 다른 MANET 라우팅 프로토콜과 달리 단방향 경로만을 지원하여 양방향 통신이 요구되는 다양한 응용 환경에서 사용하기에 많은 제약이 따른다. 또한, AntHocNet은 다중 경로를 통한 확률적 라우팅으로 인해 루핑 문제 (looping problems)를 빈번히 발생시킨다. 본 논문에서는 AntHocNet에서 양방향 경로 수립을 위한 향상된 경로 수립 방안을 제안한다. 또한, 다양한 시나리오별 루핑 문제의 발생 원인을 분석하고 루프 방지를 위한 해결 방안을 제시한다. NS-2 시뮬레이션을 통해 기존 AntHocNet과의 성능을 비교하였으며, 제안 방안이 라우팅 오버헤드, 종단간 지연 시간, 패킷 전달률 측면에서 기존 방안에 비해 우수한 성능을 보임을 확인하였다.

In mobile ad-hoc networks (MANETs), nodes use hello messages to detect neighbor nodes and to maintain link connectivity. In a typical MANET routing, a node broadcasts hello messages at a fixed interval. However, a fixed hello interval causes a long delay of neighbor discovery (too long hello intervals) or a more bandwidth waste by unnecessary protocol overhead (too short hello intervals). In this paper, we investigate the impact of node speed and transmission range on hello intervals in terms of network throughput. Through simulations for a mobile ad-hoc network using AODV routing protocol, we show that the hello interval to maximize the network throughput can be determined as a function of node speed and transmission range.

Drones can play important roles in various applications, such as search and rescue, situation awareness in natural disasters, environmental monitoring, and perimeter surveillance. Using a group of small drones has many advantages compared with developing and operating one large drone. In this paper, we propose a multi-drone real-time control scheme based on the Flying Ad-Hoc Network (FANET) for controlling drones that fall outside the communication range of the ground control system. We also propose a fast recovery scheme with neighbor location information in highly dynamic networks. We verified the operation of the proposed schemes using a FANET test bed implementation.

The increased life expectancy of human due to the advance of medical techniques has led to many social problems such as rapidly aging populations, increased medical expenses and a lack of medical specialists. Thus, studies on improving the quality of life with the least amount of expense have been going on by incorporating advanced technologies, especially for Personal Health Devices (PHDs), into the medical service market. However, compatibility and extensibility among manufacturers of PHDs have not been taken into account in most of the researches done on the development of PHDs because most of them have been supported by individual medical organizations. The interoperability among medical organizations can not be guaranteed because each medical organization uses different format of the messages. Therefore, in this paper, an expansion module that can enable commercially-available non-standard PHDs to support the IEEE 11073, and a smart-phone-based manager that can support easy and comprehensive management on receiving and transmitting the collected data from each PHD using IEEE 11073 standard were developed. In addition, a u-health system that can transmit the data collected in the manager using the standard data format HL 7 to medical center for real-time medical service from every medical institutions that support this standard was designed and developed.

Delay Tolerant Networks (DTNs) are one of the most interesting evolutions of Mobile Ad Hoc Networks (MANETs). DTNs can be characterized by intermittent connectivity, frequent end-to-end path disruption, and topology changes. In these networks, the sending of multiple copies of a message can increase the delivery ratio and decrease the delay of the message transmission. However, sending multiple copies of a message can result in a significant communication overhead. Therefore, this paper proposes an enhanced DTN routing protocol based on Message Delivery Predictibility (MDP). The proposed scheme controls the spread of messages throughout the network using MDP. Simulation results confirm that the proposed scheme outperforms original PRoPHET routing protocol in terms of the network overhead, delivery ratio, and number of dropped messages.

PRoPHET is a probabilistic routing protocol for Delay Tolerant Networks (DTNs). In PRoPHET, the delivery probability is calculated based on the history of encounters and transitivity. However, if two nodes meet frequently during a short time interval, the delivery probability between these nodes increases rapidly. To solve this problem, PRoPHETv2 uses the inter-meeting time. Yet, the contact duration is still not considered. Therefore, this paper proposes an enhanced PRoPHETv2 routing protocol that considers the contact duration. Simulation results show that the proposed scheme outperforms PRoPHETv2 in terms of the delivery ratio and overhead ratio.

Delay Tolerant Networks (DTNs) are one of the most interesting evolutions of Mobile Ad Hoc Networks (MANETs). DTNs can be characterized by intermittent connectivity, frequent end-to-end path disruption, and topology changes. In these networks, mobile nodes have the ability to communicate with each other, even if a route connecting them does not exist. When considering the routing protocols of DTNs, a forwarding decision and buffer management scheme are both important to improve successful message delivery. Therefore, this paper, proposes an improved spray-and-wait routing protocol based on the delivery probability. Moreover, a buffer management policy is introduced to drop the queued messages with the most replicate copies in the network. Simulation results show that the proposed method provides a better delivery ratio and lower communication overhead, compared to existing schemes.

Delay Tolerant Networks (DTNs) are one of the most interesting evolutions of MANETs. In DTNs which can be characterized by intermittent connectivity, frequent end-to-end path disruption and topology changes, mobile nodes are enabled to communicate with each other even if a route connecting them never exists. When considering routing protocols of DTNs, a forwarding decision and the buffer management scheme are important to improve the opportunity of successful message delivery. In this paper, we propose improved spray and wait routing based on the delivery probability. The simulation results show that the proposed method provides a better delivery ratio and lower communication overhead compared to existing schemes such as epidemic, spray and wait, and PRoPHET routing protocols.

In vehicular ad hoc networks (VANETs), the efficient and reliable dissemination of emergency messages in a highly mobile environment under a dense or sparse network is a significant challenge. This paper proposes a robust broadcast scheme for VANETs, called the virtual slotted p-persistence scheme, which operates efficiently regardless of the vehicle density and distribution. Via the exchange of hello messages, each vehicle maintains position information on neighbor vehicles in a neighbor table. When a vehicle receives an emergency message, it determines its vehicle group, called a virtual slot, based on the position information in its neighbor table. The proposed scheme guarantees that the vehicles in the farthest group from the broadcaster probabilistically rebroadcast the message first. Simulation results demonstrate that the proposed scheme outperforms the slotted p-persistence scheme in terms of the end-to-end delay, collision ratio, and network overhead, regardless of the vehicle density and distribution.

This paper proposes a source-based vehicular broadcast protocol to mitigate broadcast storms and to reduce the end-to-end delay. To alleviate a broadcast storm in VANETs, it is ideal that the vehicle furthest away from the broadcaster performs the rebroadcasting. Therefore, the proposed scheme selects the best rebroadcasting vehicles that are farther away from the broadcaster based on a neighbor table. The performance of the proposed scheme was compared with DV-CAST. The simulation results show that the performance of the proposed SB-CAST protocol is better than that of DV-CAST in terms of end-to-end packet delay and network overhead.

This paper proposes a new vehicular broadcast protocol that can operate in dense as well as in sparse highway traffic scenarios. BL-CAST is a low overhead multi-hop broadcast protocol that does not rely on periodic exchange of hello messages. The performance of the proposed scheme was compared with DV-CAST. Simulation results showed that the performance of the proposed BL-CAST protocol is better than DV-CAST in terms of end-to-end packet delay and packet delivery ratio.

This paper proposes a new vehicular broadcast protocol that can operate in a dense as well as in sparse highway traffic scenarios. ACK-CAST is a distributed multihop broadcast protocol that relies on acknowledgment messages from one-hop neighbors to select next rebroadcasting vehicle in VANETs. The performance of the proposed scheme was compared with SERVUS. Simulation results demonstrate that the proposed scheme performs better in terms of efficiency, reliability and scalability.

This paper proposes an efficient broadcast scheme based on a neighbor table to mitigate broadcast storms and to reduce the end-to-end delay. To alleviate a broadcast storm in a VANET, it is ideal that the rebroadcasting is performed by the vehicle furthest away from the broadcaster. Thereby the proposed scheme selects the furthest rebroadcasting vehicle based on neighbor tables. Simulation results demonstrate that the proposed scheme outperforms exiting schemes in terms of the end-to-end delay and collision ratio.

In vehicular ad hoc networks, the end-to-end path between the source and destination vehicle is not guaranteed due to frequent network partitioning caused by fast moving vehicles. For such sparse networks, Delay Tolerant Networks are proposed where a packet is carried by an intermediate vehicle until it meets with another vehicle or destination. This approach introduces variable amounts of delays in the networks. Therefore, an intelligent decision is required to select the next intermediate vehicle that can deliver a packet to the destination as soon as possible without any further delays. In this paper, we introduce a minimum delay routing protocol that utilizes the neighbor vehicles' velocity and distance from destination information to calculate the delivery delay for intermediate vehicles. The performance of the proposed scheme is compared with FFRDV. Using an ns-2 simulation, we have verified that our scheme shows better performance and reduces end-to-end delay and average inter-meeting time by 70% as compared to FFRDV.