• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.4
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• pp.529-546
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• 2010

Greedy forwarding is the key mechanism of geographic routing and is one of the protocols used most commonly in wireless sensor networks. Greedy forwarding uses 1-hop local information to forward packets to the destination and does not have to maintain the routing table, and thus it takes small overhead and has excellent scalability. However, the signal intensity reduces exponentially with the distance in realistic wireless sensor network, and greedy forwarding consumes a lot of energy, since it forwards the packets to the neighbor node closest to the destination. Previous proposed greedy forwarding protocols are the sender-based greedy forwarding that a sender selects a neighbor node to forward packets as the forwarding node and hence they cannot guarantee energy efficient forwarding in unpredictable wireless environment. In this paper, we propose the receiver-based greedy forwarding called RGF where one of the neighbor nodes that received the packet forwards it by itself. In RGF, sender selects several energy efficient nodes as candidate forwarding nodes and decides forwarding priority of them in order to prevent unnecessary transmissions. The simulation results show that RGF improves delivery rate up to maximum 66.8% and energy efficiency, 60.9% compared with existing sender-based greedy forwarding.

• Journal of Korea Society of Digital Industry and Information Management
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• v.13 no.1
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• pp.79-85
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• 2017

Vehicular ad-hoc networks (VANETs) cause link disconnection problems due to the rapid speed and the frequent moving direction change of vehicles. Link disconnection in vehicle-to-vehicle communication is an important issue that must be solved because it decreases the reliability of packet forwarding. From the characteristics of VANETs, greedy forwarding protocols using the position information based on the inter-vehicle distance have gained attention. However, greedy forwarding protocols do not perform well in the urban environment where the direction of the vehicle changes greatly. It is because greedy forwarding protocols select the neighbor vehicle that is closest to the destination vehicle as the next transmission vehicle. In this paper, we propose a greedy anycast forwarding (GAF) protocol to improve the reliability of the inter-vehicle communication. The proposed GAF protocol combines the greedy forwarding scheme and the anycast forwarding method. Simulation results show that the GAF protocol can provide a better packet delivery rate than existing greedy forwarding protocols.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.5
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• pp.753-775
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• 2010

Greedy forwarding is a key mechanism of geographic routing using distance as a metric. As greedy forwarding only uses 1-hop neighbor node information, it minimizes routing overhead and is highly scalable. In existing greedy forwarding schemes, a node selects a next forwarding node based only on the distance. However, the signal strength in a realistic environment reduces exponentially depending on the distance, so that by considering only the distance, it may cause a large number of data packet retransmissions. To solve this problem, many greedy forwarding schemes have been proposed. However, they do not consider the unreliable and asymmetric characteristics of wireless links and thus cause the waste of limited battery resources due to the data packet retransmissions. In this paper, we propose a reliable and energy-efficient opportunistic greedy forwarding scheme for unreliable and asymmetric links (GF-UAL). In order to further improve the energy efficiency, GF-UAL opportunistically uses the path that is expected to have the minimum energy consumption among the 1-hop and 2-hop forwarding paths within the radio range. Comprehensive simulation results show that the packet delivery rate and energy efficiency increase up to about 17% and 18%, respectively, compared with the ones in PRR${\times}$Distance greedy forwarding.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12B
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• pp.1075-1082
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• 2008

A greedy forwarding algorithm is one of the most suitable solutions for routing in vehicular ad-hoc networks. Compared to conventional routing protocols for mobile ad-hoc networks, greedy forwarding based routing protocols maintain only local information of neighbors instead of per-destination routing entries, and thus they show better performance in highly-mobile vehicular ad-hoc networks. With greedy forwarding, each node learns its geographical position and periodically broadcasts a beacon message including its position information. Based on the position information, each node selects a neighbor node located closest to the destination node as the next forwarder. One of the most serious problems in greedy forwarding is the lost link problem due to the mobility of nodes. In this paper, we propose a new algorithm to reduce the lost link problem. The proposed algorithm aims to find an efficient and stable routing path by taking account of the position of neighbors and the last beacon reception time. Our simulation results show that the proposed algorithm outperforms the legacy greedy algorithm and its variants.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.8
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• pp.1388-1403
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• 2011

A vehicular ad-hoc network (VANET) consists of vehicles that form a network without any additional infrastructure, thus allowing the vehicles to communicate with each other. VANETs have unique characteristics, including high node mobility and rapidly changing network topology. Because of these characteristics, routing algorithms based on greedy forwarding such as greedy perimeter stateless routing (GPSR) are known to be very suitable for a VANET. However, greedy forwarding just selects the node nearest to the destination node as a relay node within its transmission range. This increases the possibility of a local maximum and link loss because of the high mobility of vehicles and the road characteristics in urban areas. Therefore, this paper proposes a reliability-improving position-based routing (RIPR) algorithm to solve those problems. The RIPR algorithm predicts the positions, velocities, and moving directions of vehicles after receiving beacon messages, and estimates information about road characteristics to select the relay node. Thus, it can reduce the possibility of getting a local maximum and link breakage. Simulation results using ns-2 revealed that the proposed routing protocol performs much better than the existing routing protocols based on greedy forwarding.

• Journal of the Korea Society of Computer and Information
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• v.14 no.4
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• pp.59-67
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• 2009

In wireless sensor networks (WSNs), geographic greedy forwarding fails to move a packet further towards its destination if the sender does not have any closer node to the destination in its one hop transmission region. In this paper, we propose a enhanced geographic routing, called CGR(Cost based Geographic Routing) for efficient data delivery against void problem environment. CGR first establishes Shadow Bound Region and then accomplishes Renewing Cost Function Algorithm for effective greedy forwarding data delivery. Our simulation results show significant improvements compared with existing schemes in terms of routing path length, success delivery ratio and energy efficiency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.5B
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• pp.464-470
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• 2011

V2V (Vehicle-to-Vehicle) is a special kind of VANET (Vehicular Ad-hoc Network), which has high mobility and frequent topology changes and causes the link breakage problem. To resolve this problem, geographic routing protocols such as greedy forwarding are proposed. However, the greedy forwarding approach selects the node closest to the destination node as the transfer node within the transmission range so that it may cause many problems owing to many intersections and many changes in vehicular traffic in urban areas. The paper proposes a greedy perimeter urban routing (GPUR) algorithm considering the presence of 2-hop neighbor nodes and the road characteristics. Simulation results using ns-2 reveal that the proposed GPUR algorithm significantly reduces the routing error problem and the probability of local maximum than the existing routing protocols.

• Convergence Security Journal
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• v.10 no.1
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• pp.41-48
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• 2010

Greedy protocols show good performance in Vehicular Ad-hoc Networks (VANETs) environment in general. But they make longer routes causing by surroundings or turn out routing failures in some cases when there are many traffic signals which generate empty streets temporary, or there is no merge roads after a road divide into two roads. When a node selects the next node simply using the distance to the destination node, the longer route is made by traditional greedy protocols in some cases and sometimes the route ends up routing failure. Most of traditional greedy protocols just take into account the distance to the destination to select a next node. Each node needs to consider not only the distance to the destination node but also the direction to the destination while routing a packet because of geographical environment. The proposed routing scheme considers both of the distance and the direction for forwarding packets to make a stable route. And the protocol can configure as the surrounding environment. We evaluate the performance of the protocol using two mobility models and network simulations. Most of network performances are improved rather than in compared with traditional greedy protocols.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.11
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• pp.25-31
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• 2009

In this paper we propose an improved energy aware greedy perimeter stateless routing protocol (EAGPSR) for wireless ad hoc network. The existing greedy perimeter stateless routine (GPSR) has some problems with overloaded node and void situation. The improved EAGPSR protocol is proposed to remedy these problems. It also gives the solution for the fundamental problem in geographical routine called void communication. It considers two parameters (Residual Energy of battery and distance to the destination) for the next hop selection. In order to use efficiently limited-energy of node in wireless ad hoc network, network lifetime is focused. To evaluate the performance of our protocol we simulated EAGPSR in ns-2. The simulation results show that the proposed protocol achieves longer network lifetime compared with greedy perimeter stateless routing (GPSR) and the existing Energy aware greedy perimeter stateless routing protocol (EAGPSR).

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.4
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• pp.43-50
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• 2010

Vehicle-to-Vehicle (V2V) is a special type of vehicle ad-hoc network (VANET), and known as a solution to provide communication among vehicles and reduce vehicle accidents. Geographical routing protocols as Greedy Perimeter Sateless Routing (GPSR) are very suitable for the V2V communication due to special characters of highway and device for vehicles. However, the GPSR has problem that appears local maximum by some stale neighbor nodes in the greedy mode of the GPSR. It can lose transmission data in recovery mode, even if the problem is can be solved by the recovery mode of the GPSR. We therefore propose a Greedy Perimeter Reliable Routing (GPRR), can provide more reliable data transmission, to resolve the GPSR problem in the V2V environment. Simulation results using ns-2 shown that the GPRR reveals much better performance than the GPSR by remarkably reducing the local maximum rate in the greedy mode.