A Driving Path Based Opportunistic Routing in Vehicular Ad Hoc Network

Vehicular Ad Hoc Networks is a promising technologythat can widely apply to monitor the physical world in urban areas.Efficient data delivery is important in these networks and optimalroute selection is vital to improve this factor. Vehicular mobility isa reflection of human social activity and human trajectories show ahigh degree of temporal and spatial regularity. Therefore, vehiculardriving paths are predictable in a large extent. A new opportunisticrouting protocol (DPOR) is proposed in this study that uses drivingpath predictability and vehicular distribution in its route selectionprocedure. This protocol is composed of two phases: intersectionand next hop selection phases. A utility function is calculated toselect the next intersection and a new mechanism is also proposedfor the next hop selection phase. Simulation results show thatDPOR achieves high delivery ratio and low end-to-end delay in thenetwork

Novi algoritam preusmjeravanja bez spajanja zasnovan na korištenju različitih slojeva unutar MANET komunikacije

Routing is a key issue in wireless ad-hoc networks. The goal of an efficient routing strategy is to improve packet delivery ratio (PDR) and end-to-end delay in MANETs. Limited ability of layered architecture leads to the cross-layer design usage for routing operation in wireless environment. In this paper, a cross-layer connectionless routing is proposed based on Dynamic Virtual Router (DVR). In this algorithm, virtual route discovery process is controlled by restricting the request packets\u27 broadcast to the relatively slow speed, and low loaded nodes located in suitably crowded areas. Each destination decides to choose or discard the found route based on several cross-layer metrics. Using NS-2 simulator, the proposed algorithm is compared with standard DVR and it shows higher packet delivery ratio and lower end-to-end delay compared to DVR.Preusmjeravanje je ključni problem u bežičnim ad-hoc mrežama. Cilj je efikasne strategije preusmjeravanja unaprijediti omjer isporučenih paketa (PDR) i smanjiti ukupno kašnjenje u MANET komunikaciji. Ograničena mogućnost višeslojne arhitekture dovodi do korištenja različitih slojeva za operacije preusmjeravanja u bežičnom okruženju. U radu se predlaže preusmjeravanje bez spajanja zasnovano na dinamičkom virtualnom ruteru (DVR). U predloženom algoritmu, postupak otkrivanja virtualnih puteva upravljan je ograničenjem odašiljanja traženih paketa na relativno sporu brzinu i slabo opterećene čvorove locirane u odgovarajuće prometnim područjima. Svako odredište odlučuje o odabiru ili zanemarivanju pronađenog puta komunikacije, a zasnovano je na temelju nekoliko metrika za različite slojeve. Korištenjem NS-2 simulatora, predloženi algoritam uspoređen je sa standardnim DVR-om te pokazuje veći omjer isporučenih paketa i manje ukupno kašnjenje

Joint Congestion and Contention Avoidance in a Scalable QoS-Aware Opportunistic Routing in Wireless Ad-Hoc Networks

Opportunistic routing (OR) can greatly increase transmission reliability and network throughput in wireless ad-hoc networks by taking advantage of the broadcast nature of the wireless medium. However, network congestion is a barrier in the way of OR\u27s performance improvement, and network congestion control is a challenge in OR algorithms, because only the pure physical channel conditions of the links are considered in forwarding decisions. This paper proposes a new method to control network congestion in OR, considering three types of parameters, namely, the backlogged traffic, the traffic flows\u27 Quality of Service (QoS) level, and the channel occupancy rate. Simulation results show that the proposed algorithm outperforms the state-of-the-art algorithms in the context of OR congestion control in terms of average throughput, end-to-end delay, and Packet Delivery Ratio (PDR). Due to the higher PDR at different traffic loads and different node densities, it can be concluded that the proposed algorithm also improves network scalability, which is very desirable given the recent changes in wireless networks

A New Cache Replacement Policy in Named Data Network Based on FIB Table Information

Named Data Network (NDN) is proposed for the Internet as an information-centric architecture. Content storing in the router’s cache plays a significant role in NDN. When a router’s cache becomes full, a cache replacement policy determines which content should be discarded for the new content storage. This paper proposes a new cache replacement policy called Discard of Fast Retrievable Content (DFRC). In DFRC, the retrieval time of the content is evaluated using the FIB table information, and the content with less retrieval time receives more discard priority. An impact weight is also used to involve both the grade of retrieval and stale parameters in the discard priority calculation. This weight adjusts the relative impact of these two parameters on the discard priority. The grade of retrieval reflects the content’s retrieval time, and the stale parameter indicates its popularity. The reinforcement Learning method is used to calculate the suitable weight dynamically and based on the network condition. Simulation results show that DFRC improves hit rate and round-trip time compared to Least Recently Used, Optimized Cache Replacement algorithm for Information-Centric Networks, Efficient Popularity-aware Probabilistic Caching, and Shortest Round-Trip Time

A fair access mechanism based on TXOP in IEEE 802.11e wireless networks

IEEE 802.11e is an extension of IEEE 802.11 that provides Quality of Service (QoS) for the applications with different service requirements. This standard makes use of several parameters such as contention window; inter frame space time and transmission opportunity to create service differentiation in the network. Transmission opportunity (TXOP), that is the focus point of this paper, is the time interval, during which a station is allowed to transmit packets without any contention. As the fixed amounts of TXOPs are allocated to different stations, unfairness appears in the network. And when users with different data rates exist, IEEE 802.11e WLANs face the lack of fairness in the network. Because the higher data rate stations transfer more data than the lower rate ones. Several mechanisms have been proposed to solve this problem by generating new TXOPs adaptive to the network's traffic condition. In this paper, some proposed mechanisms are evaluated and according to their evaluated strengths and weaknesses, a new mechanism is proposed for TXOP determination in IEEE 802.11e wireless networks. Our new algorithm considers data rate, channel error rate and data packet lengths to calculate adaptive TXOPs for the stations. The simulation results show that the proposed algorithm leads to better fairness and also higher throughput and lower delays in the network.

Conservative Treatment of an Invaginated Maxillary Lateral Incisor with a C-shaped Canal Using Cone-Beam Computed Tomography

This report describes the non-surgical treatment of an invaginated maxillary lateral incisor with two fused roots. The mesial root had a C-shaped canal, while the distal one had a type III dens invagination. Cone-beam computed tomography (CBCT) was used to help with the diagnosis and treatment decision making. Clinical and radiographic follow-up revealed satisfactory periapical repair and absence of symptoms after 15 months.Keywords: C-Shaped Canal; Cone-Beam Computed Tomography; Dens Invagination; Dens Invaginatus; Dens in Dente; Invaginated Teeth; Maxillary Lateral Inciso