شبکههای اجتماعی بینخودرویی(VSNs) ، نوعی از شبکههای­ موردی هستند که امکان برقراری ارتباط بین دو وسیله نقلیه مجاور را بصورت بی­سیم برقرار میکنند. یکی از مشکلات موجود در شبکه­های VSN مشکل مسیریابی و ارتباط با گره­ها ی مجاور است؛ بنابراین با بررسی تحقیقا More
شبکههای اجتماعی بینخودرویی(VSNs) ، نوعی از شبکههای­ موردی هستند که امکان برقراری ارتباط بین دو وسیله نقلیه مجاور را بصورت بی­سیم برقرار میکنند. یکی از مشکلات موجود در شبکه­های VSN مشکل مسیریابی و ارتباط با گره­ها ی مجاور است؛ بنابراین با بررسی تحقیقات موجود در این زمینه مشخص شد که بعلت وسعت جغرافیایی و سرعت تحرک وسایل نقلیه با مشکل محدودیت زمان جهت انتقال داده و مسیریابی روبرو هستیم. در این مقاله با استفاده از الگوریتم بهینه سازی کرم شب­تاب تلاش می­شود یک راه حل نزدیک به بهینه با کمترین تاخیر برای مساله مسیریابی در این شبکه­ها ارائه شود که تا بحال در هیچ پژوهشی استفاده نشده است بطوریکه قابلیت بکارگیری در محیط پویا و وسعت جغرافیایی بزرگ را نیز دارا باشد. وسایل نقلیه (خودروها) در حکم کرمهای شبتاب لحاظ شده و حرکت بین خودروها در حکم جذب کرمهای شبتاب توسط سایرین لحاظ میشود. دو معیار میانگین فاصله و احتمال رسیدن دو خودرو به یکدیگر برای جذب خودروها و مسیریابی مورد آزمایش قرارگرفت. همچنین، تعداد خودروهای هر ناحیه که با چگالی متفاوت وسایل نقلیه در دو منطقه شهری و بینشهری سنجیده میشود نیز معیاری است که در صحت مسیریابی تاثیر مستقیم دارد. نهایتا روش پیشنهادی در حوزه شبکه­های نسل پنجم مخابراتی شبیه­سازی میشود و نتایج عددی نشان داد که روش پیشنهادی در مقایسه با نتایج استفاده از الگوریتم تقسیم پویای دسته جمعی از نظر میانگین فاصله مسیریابی خودروها، تفکیک مناطق شهری و بین شهری، تغییرات پارامتر میزان روشنایی، تغییرات پارامتر­ضریب جذب نور، تغییرات پارامتر عدد تصادفی بین صفر و یک، تغییرات پارامترحرکت اولیه خوردوها بطورتصادفی به­ترتیب 68.14، 63.13، 65.2، 08.20، 39.18، 57.17، 45.18بهبود حاصل شد.
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Introduction:
In the vehicular ad hoc networks (VANETs), routing is a challenging issue due to the nodes mobility speed and frequent changes in the network topology. In these networks, geographic routing algorithms are more popular and have attracted more attention. T More
Introduction:
In the vehicular ad hoc networks (VANETs), routing is a challenging issue due to the nodes mobility speed and frequent changes in the network topology. In these networks, geographic routing algorithms are more popular and have attracted more attention. The efficiency of geographic routing algorithms depends on the two factors: strategy of choosing the best neighbor and how to manage the mobility of neighbor nodes by the procedure of broadcasting Hello messages. Broadcasting Hello messages leads to the exchange of many control packets and causes the channel saturation and increases the probability of congestion and collision.
Method:
In this work, with the aim of reducing the control overhead messages, the broadcast rate of Hello messages is adjusted adaptively based on the congestion and link expiration time. By applying the proposed method on the PGRP (Predictive Geographic Routing Protocol) algorithm, the broadcast rate of Hello packets is adjusted according to the network conditions. As a result, routing overhead packets are reduced and service quality in the network is improved.
Results: Two groups of experiments have been conducted. In the first group, the aim is to investigate the effect of increasing the number of vehicles. In the second group experiments, the goal is to investigate the nodes speed increasing. The simulation results show that the proposed method improves the performance of the PGRP protocol in different scenarios. It has been shown the proposed method for a different number of vehicles increases the packet delivery ratio on average by 16%; decrease end to end delay on average by 7%; decreases normalized routing overhead by 18% compared to PGRP. Also, it has been shown the proposed method for a varying speed of vehicles increases the packet delivery ratio by 18%; decreases average end to end delay by 5% and decreases the normalized routing overhead by 22% compared to PGRP.
Discussion:
When the number of vehicles increases, the sources of broadcasting Hello messages increase, and the probability of collision increases. In the proposed method this situation is detected and the broadcast rate of Hello messages reduces. As the same way, when the speed of the nodes is low, the expiration time of links increases, and the proposed method reduces the broadcast of Hello messages to avoid wasting the network resources.
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Recently, much attention has been paid to Vehicular Ad hoc Network (VANET). VANETs address direct communication between vehicle-to-vehicle and vehicles to roadside units (RSUs). They are similar to the Mobile and Ad hoc Networks (MANET) in their rapid and dynamic networ More
Recently, much attention has been paid to Vehicular Ad hoc Network (VANET). VANETs address direct communication between vehicle-to-vehicle and vehicles to roadside units (RSUs). They are similar to the Mobile and Ad hoc Networks (MANET) in their rapid and dynamic network topology changes due to the fast motion of nodes. High mobility of nodes and network resources limitations have made the routing, one of the most important challenges in VANET researches. Therefore, guaranteeing a stable and reliable routing algorithm over VANET is one of the main steps to realize an effective vehicular communications. In this paper, a two-step AODV-based routing protocol is proposed for VANET networks. At first, node-grouping is done using their mobility information such as speed and movement direction. If the first step cannot respond efficiently, the algorithm enters the second step which uses link expiration time (LET) information in the formation of the groups. The goal of the proposed protocol is increasing the stability of routing algorithm by selecting long-lived routes and decreasing link breakages. The comparison of proposed algorithm with AODV and DSR protocols is performed via the Network Simulator NS-2. It is shown that the proposed algorithm increases the delivery ratio and also decreases the routing control overhead.
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Data exchange between vehicles as network nodes, like other ad-hoc networks, due to the lack of stability infrastructure and central management, and the complete distribution of the network platform, have led to attract many parts of today's researches. In this article, More
Data exchange between vehicles as network nodes, like other ad-hoc networks, due to the lack of stability infrastructure and central management, and the complete distribution of the network platform, have led to attract many parts of today's researches. In this article, an improved method has been presented in order to evaluate the encounter of the vehicle with the incident, and the interaction of data related to the incidents for use in the vehicle ad-hoc networks. The proposed method has been developed based on the basic indicators of evaluating the node's encounter with events in vehicle ad-hoc networks and has been strengthened based on the advantages and capabilities of fuzzy logic, so that the desired and expected result is obtained from the output of the set. In order to evaluate the performance of the proposed method, developments and implements were based on the OPNET simulator and this method was compared with the VESPA and VESPA-DM methods as the most important researches in this field. The simulation results indicated the superiority of the proposed method over past researches.
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