Adaptive Mobile Gateway Management in Integrated … Mobile Gateway Management in Integrated VANET...

Adaptive Mobile Gateway Management in Integrated VANET – 3G Wireless Networks

V.REVATHI

PG Scholar, Telecommunication Networks, SRM University, Chennai, India. [email protected]

K.HARI SUDHA Department of Telecommunication Engineering

SRM University, Chennai, India. [email protected]

Abstract The main communication challenge of VANET lies in very poor connectivity caused by unbalanced

traffic. Deploying more RSU’s may relieve this problem, but it often requires a large amount of investment and elaborate design, especially at the city scale. To minimize the delay and to increase the efficiency of VANET with low cost, will be done by integrating the high data rates of IEEE 802.11p VANET with 3GPP networks i.e.) UMTS networks. In this paper, we introduced a novel architecture that integrates 3G/UMTS networks with VANET networks. Vehicles are dynamically clustered according to related metrics. Here clustering is based on Adaptive mobile gateway mechanism, in which vehicles act as gateways between other vehicles and UMTS networks. Gateways are used to broadcast the information efficiently to vehicles by considering the factors of traffic velocity, direction of movement and speed of vehicles in a network. Simulations are carried out by using NS2 to evaluate the performance of the envisioned architecture.

Keywords: Gateways, Hybrid mechanism, Proactive mechanism, Reactive mechanism. 1 Introduction

A vehicular network has become a very attractive field because it offers very high data rate, peer-to-peer content sharing and it has many new safety applications. So people can reach their destinations in a safe, efficient and comfortable way by using this network. The next generation of wireless communication systems, will be in need of rapid deployment of independent mobile users. Examples include establishing a survivable, efficient, dynamic communication for emergency/rescue operations, disaster relief efforts and military networks. Among the multiple available technologies, the leading examples are widely-deployed 3G technology and IEEE802.11P based VANET. Vehicular Ad-hoc networks can be considered as a subset of MANET with unique characteristics. A typical VANET consists of vehicles and access points along the road. When the Vehicles move on the roads, information can be shared between themselves and with the Internet through the access points. In these networks, each vehicle is equipped with communication equipments, computing devices and GPS receivers. GPS receiver provides all the information of a vehicle like speed, direction of movement of vehicle, time, location etc. Each vehicle stores the information about itself and other vehicles in a local database.

The records of this database are periodically broadcasted to other vehicles and road side equipments. VANET is based on IEEE802.11p standard [1]. FCC allocates 75MHZ frequency band for traffic applications [2]. VANET operates at 5.9GHZ unlicensed frequency band and provide the data rate of 6 to 27Mbps, but only used for shorter distances up to 300meters [3].

Fig.1. VANET Architecture

Communication of VANET is in two ways. 1) V2V communication, which is based on IEEE 802.11p, 2) V2I communication based on GPS, GSM and GPRS networks [4, 5].

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VANET provides features such as safety

and comfort for passengers, provides more efficient driving, provide more fun and easier maintenance of vehicles. The above described features enhanced a wide range of applications for vehicular networks. Some of the applications are related to safety, traffic management, commercial applications and general applications [6, 7]. Characteristics of VANET are high mobility of nodes, rapidly changing network topology, unbounded network size, decentralized control and real time sensitive data exchange [8]. 3G is the most popular wireless technology provides high data rates to handheld devices compare to existing wireless networks. 3G offers multimedia services and it combines voice and data services with high speed BW. Wide-area Cellular Network standardized by 3GPP, operated by WCDMA. 3G provides continuous connectivity and more security to devices. Some characteristics of 3G services are Always-on connectivity, Multi-media services with streaming audio and video, Email with full-fledged attachments such as PowerPoint files, instant messaging with video/audio clips, Access to corporate applications, fast downloads of large files such as faxes and PowerPoint files.

3G has advantages such as more bandwidth, security, and reliability, Interoperability between service providers, Fixed and variable data rates, Asymmetric data rates, Back ward compatibility of devices with existing networks [9, 10]. Among this 3G, UMTS is one of the 3G wireless technology that is widely employed in present days and provides the data rate of up to 384kbps. In 3G/UMTS supports Licensed Uplink Frequency in the range of 1.925 GHz and Licensed Downlink Frequency in the range up to 2.115 GHz. Radio Communication Coverage Range of UMTS is 8 to 10 km per BST.

By integrating IEEE 802.11p based VANET with 3G/UMTS network, VANET can provide high data rate with wide range of connectivity. In this integrated architecture vehicles are clustered among them, CH selection based on some related metrics. CH’s are act as gateways and other vehicles are act as candidates within cluster. These gateway vehicles are connected with UMTS network by using 3G UTRAN interfaces. This integration minimizes the dead spots in UMTS networks compare to existing networks [11].

2 Review of Existing Literature

Here we are defining the existing research based on three parameters. Those are Gateways, Communication standards, Protocols in VANET.

2.1 VANET Gateways

Existing research work considers VANET gateways are static one which needs to be deployed at each particular smaller distance, considers more cost and it does not provide proper handoff. So Authors established some gateway mechanisms between vehicles and RSU’s for efficient communication among them. Gateway discovery mechanisms needed to the find efficient gateway, which will broadcast the information efficiently to vehicles. Different types of gateway discovery mechanisms have been used. The main gateway discovery mechanisms are proactive gateway discovery mechanism, reactive gateway discovery mechanism [12, 13]. 2.1.1 Proactive gateway discovery mechanism In proactive approach, gateways are advertising themselves in a network. By using gateway discovery process, all the vehicles will get updated information about neighboring gateways. Issues related to these gateways are stability metric, relay and rebroadcasting, relay selection, factor of driver behavior. The main advantage of this mechanism is, it achieves good connectivity and it reduces delay. But at the same time it increases the signaling overhead which is a major problem in this gateway. 2.1.2 Reactive gateway discovery mechanism

Reactive gateway discovery mechanism provides connectivity to vehicle, when the vehicle requires the gateway connectivity for sending messages in a network. When the nodes come to know the gateway position, it stops broadcasting of message about requirement of gateways. The vehicles select more suitable routing for sending information via gateways. Advantage of reactive approach is to reducing signaling overhead problem but it provides poor scalability.

2.2 VANET Communication Standards

For VANET communication, several wireless access standards have been used. The aim of wireless standards is to provide a set of air interface protocols and parameters for a high-speed vehicular communication. Some of the core technologies include IEEE 802.11p based technology and Combined wireless access.

2.2.1 IEEE 802.11p based technology

It is based on IEEE 802.11 standard and it supports communication between vehicles and the roadside, among vehicles operating at speeds up to


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200m, handles communication range up to 1,000 meters [14]. 2.2.2 Combined wireless access

This effort is done by ISO TC 204 WG16, called as CALM M5 (Continuous Air Interface for Long and Medium range). It builds on top of IEEE 802.11p standard and currently it supported the standard includes GSM/HSCSD/GPRS (2/2.5G) and UMTS (3G), Infrared Communication and wireless systems in 60GHz band. By combining all of these interfaces will result in increased flexibility and redundancy, thus improving the performance.

2.3 VANET Protocols

In the existing work ensures that three protocols are used widely for VANET. Those are DYMO, AODV+ and AODV

2.3.1 AODV Ad Hoc On-Demand Distance-Vector Routing Protocol is one of the reactive routing protocols, provides on-demand route discovery in MANET. AODV finds a route based on route discovery cycle, involving in broadcast network search and unicast reply containing discovered paths. Nodes in AODV maintain a routing table in which the next-hop routing information for destination nodes is stored [15].

Fig.2. path establishment in AODV

Lifetime is allocated for each node, while

entering in to routing table entry. If route is not utilized within a particular lifetime period, then the route will expire in a network. If each time, node uses the route and then the lifetime period is updated so that the route is not prematurely deleted. 2.3.2 DYMO protocol

The Dynamic MANET On-demand routing protocol is a newly proposed protocol, which is an improvement of AODV Routing Protocol. The Operation of DYMO is similar to AODV. It consists of two modes of operations. One is Route discovery and other mode is Route maintenance [16].

Fig.3. Path Establishment in DYMO

Protocol Routes are discovered for the nodes, when it

needs to send a packet within the network. Routing table consider the fields such as Destination address, Hop count, next hop address, next hop interface, sequence number and so on.

2.3.3. AODV+ Protocol

AODV+ Protocol is the modified version of AODV, which supports the mobile devices to communicate with fixed devices in a network. AODV+ has to discover the gateways for accessing internet. 3 Proposed 3G Integrated Network Architecture

In this integrated architecture, we consider two different tracks over a particular road and the direction of two tracks is opposite to each other. This architecture consists of IEEE 802.11p VANET vehicles, UMTS node B and main component of UMTS network. Here vehicles are equipped with GPS devices, having different UMTS signal strength at different regions of each track. VANET is based on multi hop communication and VANET nodes communicate with each other on peer to peer basis. UMTS main components are Radio Network Controller (RNC), Base Station Transceiver (BST), Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN) [17].

GGSN is used for connecting UMTS network to external IP networks and it is responsible for converting circuit-switched data from the external Network into packet-switched data. SGSN is responsible for routing data packets to the correct RNC from GGSN and vice versa [18]. There are two VANET active regions under the coverage of BST1 and BST 2 and they are called as 3G active regions. These regions may overlap depending on ITS system management. Vehicles which are integrated with IEEE 802.11p and UMTS interfaces, moving into 3G active region, called as gateway candidates.


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Here a minimum number of vehicles are considered as gateways per time instance, which will connect to both ordinary vehicles and with the UMTS network. In VANET/3G network, if one vehicle is connected to the UMTS network using its 3G UTRAN interface, it can serve as a relay node for other vehicles in its vicinity to access the UMTS network, by receiving data from them and relaying the data to the UMTS network. Route stability, mobility features and signal strength of vehicles are all taken into consideration when clustering vehicles and selecting vehicle gateways. This envisioned 3G/VANET integrated network is expected to prevent frequent handoffs at UMTS base stations with the association of signaling overhead.

Fig.4. Envisioned VANET - 3G Integrated Network Architecture

The main challenge of integrating these two network interfaces on a hybrid gateway node is that they lie in two different spectrum regions. The next challenge is to select a minimum number of gateways using relevant metrics. Advantage of integrating these two technologies enables mobile data access for a vehicle at anytime and anywhere. Additionally, the envisioned integration between VANET and UMTS enable mobile operators to provide vehicles with seamless data access to the operator services at affordable rates and with minimum investment in the core network technology.pro-active gateway discovery reduces delay and reactive discovery reduces signaling overhead. VANET uses hybrid gateway discovery

mechanism, which combines the advantage of both proactive and reactive gateway discovery mechanisms [19]. The main purpose of this paper is to select a minimum number of vehicles to act as gateways, which is integrated with UMTS networks. Here we are not integrating all the VANET vehicles with UMTS network for reducing bottleneck problem. On the other hand if we integrate all the VANET vehicles with UMTS networks then signaling overhead increases during roaming and handoff, because of its larger active region. So for avoiding this problem, we choose only a minimum number of vehicles as gateways, which have been connected with UMTS network. 4 VANET Clustering The main challenge in VANET is dynamic and dense network topology due to high mobility and high node-density of vehicles especially in urban environments. This dynamic topology has some routing difficulties and the link quality between vehicles is bad because of multipath fading, shadowing and Doppler shifts caused by the high mobility of vehicles. Clustered structure will overcome those problems, which can make the network as a smaller and more stable in the view of each vehicle. In clustering the first process is vehicles, which are near to each other in a network forms a cluster between them. Each cluster has one CH, which is responsible for intra and inter-cluster management functions. Intra-cluster nodes communicate with each other by using direct links, whereas inter-cluster communication is performed through cluster heads [20]. This clustering leads to effective broad-casting and relaying of messages and increases the stability of inter-vehicular links within the VANET. This integration depends on main three metrics for clustering. That metrics are Direction of Movement, UMTS Signal Strength, and IEEE 802.11p wireless transmission range [21, 22].

4.1 Clustering Based On Direction of Movement In clustering, the first step is to select a minimum number of mobile gateways per track, corresponding to each direction. Initially, it is carried out relative to their moving directions and then relative to the position of the UMTS Node B. For grouping the vehicles accurately directional-antenna-based MAC protocols can be utilized. This grouping depends on the basis of the direction of their movements in the Cartesian space.


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In such MAC protocols, the transmission surface of vehicles is split into M transmission angles (D1, D2. . . DM) of equal degrees (360/M). By assigning each transmission angle to a unique vehicle group, M directional groups are formulated. In a Cartesian space, each group is characterized by a vector [23].

SN = (Cos θN, Sin θN) (1)

Where,

θN denotes the angle of inclination. Angle of inclination θN of vehicle is determine by a vehicle GPS device and then determines its vector co-ordinates (SN) in the Cartesian space.

Fig. 5. Clustering Based On Direction of Movement

Then vehicles formed a group called sub clustered as a group of vehicles moving towards the BST and another group moving away from the BST. As a result, the vehicles are grouped into a number of different clusters.

4.2 Clustering Based On UMTS Signal Strength

The UMTS Received Signal Strength (RSS) is used for refining the cluster operation. The purpose behind using the UMTS signal strength lies on its better consistency compared to metrics such as mobility speed. Additionally, the mobility speed of vehicles, moving along a particular direction, is implicitly reflected in their UMTS RSS [24].

Fig.6 . Clustering based on UMTS RSS

The UMTS RSS keeps increasing if the vehicles move towards the base station, and vice versa. However, when a vehicle moves fastly towards BST, then the faster will be the increase in its received UMTS signal strength. Similarly, the faster the vehicle moves away from the base station, the faster will be its decline in the RSS.

UMTS RSS at time instant t, towards BST:

RSSt = RSSt-1 + (1 – e-| vt - vt-1|/a) (2) UMTS RSS at time instant t, away from BST:

RSSt = RSSt-1 - (1 – e- |vt - vt-1|/a) (3)

By using UMTS RSS, vehicles in each sub cluster equipped with the UTRAN and IEEE802.11p network interfaces, lying within or moving in to the 3G active region become GWC’s. The other vehicles form the ordinary vehicle sub cluster.

4.3 Clustering Based On IEEE 802.11p Wireless Transmission Range

The next step after having clustered vehicles based on their directions of movement and the UMTS signal strength, is to cluster them using their IEEE 802.11p wireless transmission range: a pair of GWCs, whose inter-vehicular distance is less than or equal to their IEEE 802.11p transmission range, form a new sub-cluster or join an existing one .


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Fig.7. Clustering Based On Wireless Transmission Range

The transmission range of a GWC vehicle is determined as follows:

R = Tr · (1 − υ) (4)

Where, Tr denotes the maximum IEEE 802.11p transmission range and υ reflects the wireless channel fading conditions in the current location.

5 Adaptive Mobile Gateway Management This integrated architecture considers two algorithms for gateway management named as multi metric gateway selection mechanism and multi metric gateway handover mechanism [25] [26]. 5.1 Multi Metric Gateway Selection Mechanism This integrated architecture uses hybrid gateway mechanism, which is more efficient than proactive and reactive mechanisms. Hybrid approach combines the advantages of both proactive and reactive approaches. Thus gateways advertise themselves in a predetermined number of hops and it provides gateways to the requested vehicle up to the advertised zone. This gateway selection mechanism employed depends on the available CH’s for other nodes. It uses an algorithm, which is based on SAW (simple additive weighting) technique. Here gateway i.e.) cluster head consider from the metrics of UMTS RSS, link stability and mobile speed. Links are defined by LET and RET metrics between source and cluster head. Let us consider two neighboring vehicles i and j moving at a speed of vi and vj along two roads inclined at i and j. At a

certain time instance the Cartesian coordinates of two neighboring vehicles denoted as (xi, yi, zi) and (xj, yj, zj) and R is the maximum wireless transmission range of two vehicles [27] [28]. Algorithm 1: Multi-metric mobile gateway selection algorithm

UMTS RSS and RET are the metrics with the positive criterion. Mobility speed will be considering in two ways. 1) If a direction of movement is toward BST, then the criterion is positive 2) where as if the direction of movement is away from BST, then the criterion is negative. By using hybrid gateway discovery mechanism, every gateway candidates belonging to a cluster knows the information about its CH. When the GWSOL message reaches any gateway candidates, this information is notified in to the source then source will select optimal gateway using MMGSA mechanism. And so Source vehicle can notify the newly elected gateway vehicles.

Each metric of the CH has its own threshold value. After a time interval ∆t, if another vehicle becomes an active source for communicating with the UMTS BST, that source checks if the UMTS RSS of the serving gateway and it’s RET With the gateway are greater than the respective threshold values SSTh and RETTh. If yes, the active source uses the same gateway for communicating with the UMTS BST. Otherwise, the source selects another gateway from the remaining CHs of the other clusters, by applying the MMGSA approach. Thus MMGSA selects only a minimum number of optimal gateways that saves the UTRAN access network resources, especially during handoff, by letting only a minimum number of gateways communicate with the UMTS BST at an instance. 5.2 Gateway Handover

The main concept behind the gateway handover approach is as follows. If the UMTS RSS of the gateway goes below the signal strength threshold and/or if the RET of the gateway with the source vehicle goes below its predetermined threshold, migration from the serving gateway to one or more gateways, selected by MMGSA, should take place for that vehicle.

Algorithm 2: Multi-metric Adaptive Mobile Gateway Handover Algorithm [29]

During the gateway selection, gateway may correspond with one of the CHs at a time. Due to dynamic clustering mechanism, the same gateway may not serve as a CH at a different time. It may also instantaneously lose all its neighbors which it


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had while being elected. It subsequently forms or joins with a new cluster, while still maintaining its role as gateway in case its optimality is not affected and gets new neighbors during the communication course.

There is no guarantee that it will be a CH for a new cluster. Before losing its optimality, a serving gateway selects Gateway-Elects (one or more) with respect to each of its active sources. It should be noted that a serving gateway may select more than one Gateway-Elects according to RET metric, which may differ from each of its active vehicular sources with each of the available CHs. 5.3 Gateway Discovery/Advertisement

The traditional gateway discovery mechanisms are proactive or reactive in nature. In this project, we adopt a hybrid one which combines the advantages of both approaches [30]. Depending on its election, a newly elected gateway broadcasts periodic GWADV messages within its sub cluster by using the TTL value, which determines the gateway advertisement zone [31].

Fig.8. Flowchart for Gateway Discovery

Mechanism

The TTL value for the source to broadcast GWSOL messages within the VANET is

computed as TTLs in a distributed approach, as follows:

TTLs = max (((d(S, V1)/Rs)), ((d(S, Vn)/Rs) + 1)) (5)

Where, V1 - the leading edge ordinary vehicle and Vn is tail edge ordinary vehicle in the cluster. d(S,V1) is the distance between the source and the leading edge V1 and d(S,Vn) is the distance between the source and the tail edge Vn Rs is the wireless transmission range of the source S. TTLs defines the maximum hop length between the source and the leading edge V1, and between the source and any GWCs belonging to a sub-cluster. The above flow chart is derived accordingly, so that GWSOL messages would reach all GWCs in a particular sub cluster. If any new source vehicle desires to connect to the UMTS network after a predefined time interval, it would directly connect to the gateway. 6 Priorities in Heterogeneous Networks

In priority resolving, the operation is carried out three phases [32]. Those are Identification of vehicle, Gateway resolving its priorities and Serving vehicle by broadcasting its arrival. In a normal environment the gateway serves all of its nodes in an equal manner without any priority. But there is an instance where a vehicle has to be given priority. Here the first process is, vehicle has to be identified by the gateway. Each vehicle fixed with its own IP address irrespective to the location and care is taken, such that normal nodes will not have the same IP address. Then gateway receives the request packets from the vehicle with IP address given to it [33].

On receiving the request packets from vehicle, the gateway has to check its table of IP addresses, which is serving now. Then it uses priority resolving method which is static, in allocating priority to vehicle IP address. This kind of priority Method is known as fixed priority method. Here gateway acts as a Wi-Fi access Point. So it can serve all the nodes at a time. But the main drawback is delay. Because gateway has to transmit the information to all of its nodes at the same time, which causes communication delay and results in traffic jam journey for vehicles.

This is solved by giving priority to a node in need of priority. Priority node sent the information to base station for broadcasting purpose by the gateway prior to the information coming from


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remaining nodes. The performance of the integrated network will evaluate in terms of Data Packet Delivery Ratio (DPDR), Control Packet Overhead (CPO), throughput, Packet Drop Fraction and delay Parameters by using NS2 6.1 Algorithm Steps The envisioned architecture performance will be evaluated by using ns2. In ns2 there are three main files used for node creation, node communication and for running simulation. Those files named as .tcl file (main file), CP (connection pattern), SC (scenario) file. In main file the following steps were defined for simulation.

Step1: defining of parameter values and initializes global variables The first step is to define the parameter values for simulation. Parameters like channel, propagation, network interface, interface queue length, link layer, antenna, IFQ length, MAC, X and Y values and the number of node will be defined here. IFQ is used for packet transmission between nodes, by setting up a queue between nodes.

Omni directional antenna is used here, for covering all the direction in a network. Routing is based on AODV. In step 1 CP is named as CBR file and SC is named as scenario file. The simulation ending time is defined in step 1 and the traffic is based on TCP. Threshold value, frequency and SINR and slot time of WPAN is defined here. Step2: initialize global variables. In step 2, we are initializing global variables and creating a new simulator instance, which is nothing but a creation of syntax. After the syntax creation topography settings will be taken place. Topography setting is used for allocating node position. Step3: create trace object for NS and NAM In step 3, we are creating a trace object for network simulator and network animator under the name of trace and namtrace. These objects will automatically generate a report file about the opening of main file, while running the program. Under this trace definition, we are defining topology for x and y. XY parameters are used for defining areas. Step4: create GOD After creating trace files and topography, the next step is to create GOD (general operational directory) file. GOD file is used for directing all the events like packet sending, packet receiving, packet drop, En queue, De queue and it collects all the information about nodes. In a network, protocols get the information from GOD for routing its packet.

Step5: global node setting In step 5, global node setting has to be taken place. We already defined the parameter values in step 1. Here we are configuring those defined parameters for node creation in NAM window. Setting up of bandwidth for MAC layer will be done in this step. Here we are creating specified number of nodes and we attached those nodes with corresponding channels. Step6: define node movement model and traffic model In step 6, we are setting up a loading CP and loading SC file for movement of nodes. Node initial position for a Nam window and node size also will be defined here. We can adjust this node size with SC. The node function will be called after defining mobility model. Step 7: tell nodes where the simulation ends In step 7, we are allocating the ending simulation time for a nodes to stop their communication at a particular instance. After setting up of this process execution setup for trace fd and namtrace will be defined here. Step 8: defining the graph values and execution of graph In this step, we are defining the X value and Y value for a graph X and Y axis, according to node movement. AWK is the one used here for generation of graph. The border width and length for a graph is defined in step 8. The name of each axis and defining of numbers and execution of graph will be done here. Step9: printing XY values By using puts command we are printing the values of tracefd, number of nodes, routing, CP, seed, propagation and antenna. Step 10: Run the simulation

We are defining the nodes to start the simulation and creating a command for running the program. The second file is named as CBR, which is nothing but CP. CBR is used for improving the communication efficiency. In CBR we are setting up the source UDP and defining source node as a node 0, destination node as a null 0. FTP is used for file transmission. Like node 0 and null 0, all the nodes are allocated as a source and as a destination and packet transmission between nodes will occur for a particular instance. The third file is SC, which is used for setting up GOD. All of the node connection will be defined here. Transmission speed from node to destination will be defined in CP. Nodes position setup denoted in meters.


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7 Simulation Results Table.1.Simulation parameters

Intermediate Simulation Results will be shown by using NS2 NAM (network animator) window. 7.1 Resulting of node Deployment in NAM window As we mentioned before 50 nodes were deployed in Nam window. We used different color between nodes for simple identification. Here we denote green node as a 3G network and pink color nodes are BST’s. Red color node and black color denotes emergency and clustering nodes.

Fig.9.1.Node Deployment

Time is fixed as 35seconds.black color nodes forming dynamic clustering between them and CH will be selected based on related metrics.

7.2 Communication between Nodes, Access Points and CH’s

Fig.9.2.Communication between Clusters, Access

Points and GW’s Here the different color circles were shown

for simplification. CH’s are selected and they are relaying messages between other nodes and RSU. 7.3 Emergency Response Finding the Dangerous Conditions of Moving Nodes

As mentioned before, based on priority if any node needs any help at emergency, there is a access point specially allocated for helping to vehicles at emergency time.

Fig.9.3.Emergency Response

7.4 Nodes are reduces their speeds for avoiding accidents

Fig.9.4. Accident Prevention in Network


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Emergency AP broadcast the warning message to other vehicles accident. So other vehicle can prevent accidents by reducing their speeds. 7.5 Performance Evaluations For enabling communication between vehicles or between vehicles and RSU networks, IEEE802.11 WAVE has been used here. By using this we have to measure throughput, average delay and packet loss. Generally clustering mechanism is based on dynamic one. So we are considering reactive AODV which copes efficiently with highly dynamic nature of VANETS. Here we are implementing CMGM (clustering based multi metric adaptive mobile gateway management mechanism) in AODV, MGSA (multi metric gateway selection algorithm)over AODV+ and DYMO and we are comparing the result of our proposed CMGM mechanism with other two mechanisms. The main difference between DYMO and AODV is that DYMO stores information for each intermediate hop, whereas AODV stores information about only the source and destination nodes.

Fig.10.1.Performance Of Three Protocols By Considering Different NumberOf Vehicular Sources vs. DPDR

The graph shown in above figure implies the good performance of the proposed CMGM in terms of high DPDR versus number of vehicular sources in VANET. From graph we can realize that DPDR decreases along with as increase in number of vehicular sources. It is due to increase in packet drop ratio which is proportional to number of vehicular sources, mainly when the gateway loses its optimality. It will overcome by handover procedure which means that another gateway takes responsibility for proceeding transactions and hence good performance of CMGM. In this figure CMGM over AODV results in high DPDR compared to MGSA over AODV+ and DYMO in integrated VANET.

Fig.10.2. Performance of Three Protocols By Considering CPO Versus Number Of Vehicular Sources

In figure 10.2 CPO increases against the number of sources. CMGM over AODV shows less CPO compare to other protocols. It is due to only minimum numbers of gateways are elected for proceeding transaction, which significantly reduces CPO due to multiple gateways as in case of MGSA.

Fig.10.3.Protocols Performance In Terms Of DPDR Vs Range Of Variation in Mobility Speed

In figure 10.3 DPDR is achieved by considering different mobility speed of vehicles in a network. Here we consider two different cases.1) when the elected gateway is moving towards BST, 2) when the elected gateway moves away from BST. In first case DPDR increases if mobility speed of the vehicles increases up to some limit then it will tend to decrease. But compare with second case, when the gateway moving towards BST DPDR is high. Our proposed CMGM mechanism exhibit high DPDR compared to DYMO and AODV+. Figure 4 shows the three protocols performance in terms of CPO by considering different mobility speed. By considering the above two different cases when the serving GW moving towards BST, it will receive continuously good UMTS RSS and maintains its optimality and minimize the number of control messages else it will be associated with GW handover. .


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Fig.10.4. Protocols Performance In Terms Of CPO Vs Range Of Variation in Mobility Speed As a result when the gateway moves towards BST CPO is negative and when the GW moves away from BST its positive. As compared with DYMO and MGSA in AODV, our proposed CMGM mechanism yields improvement in reducing CPO.

Fig.10.5. Three Protocol Performance In Terms Of CPO Vs IEEE 802.11 Transmission Range

The above graph indicates the performance of three protocols in terms of CPO vs. different IEEE 802.11 wireless transmission range. In this graph, transmission ranges of less than 225m may correspond to urban scenarios and the transmission ranges exceeding 250m may correspond to highway scenarios. Many clusters with small sizes will be formed within short transmission ranges, which lead to high CPO. Short transmission ranges would result in frequent GW handoff.

Fig.10.6. Performance of Three Protocols In Terms Of Throughput Vs Number of Clusters

By considering different number of clusters average individual throughput is achieved at the UMTS BST shown in figure 10.6. If we consider many VANET clusters, CMGM would be able to select optimal CH as a gateway and to support continuity if the numbers of clusters are exceeded three, then our proposed AODV over CMGM shows improvement as compared to AODV+ in MGSA and DYMO in integrated VANET network. Figure 10.7 implies the importance of having an optimal value of number of sub clusters. When the number of clusters increases, the generation of control messages will increase during the selection of gateways from CH’s.

Fig.10.7.Performance Of Three Protocols By Considering Packet Drop Fraction Vs. Number Of Clusters

This may produce congestion within the network, resulting in occupying available bandwidth unnecessarily. Because of consuming more BW error messages are flooded in the network. Our proposed mechanism CMGM in AODV shows less packet drop fraction over DYMO and MGSA in AODV+. Below figure shows that time extends till the establishment of path between a source and an adequate GW’s.

Fig.10.8.Performance of Three Protocols In Terms Of Delay Vs. Number Of Clusters


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The difference between CMGM and MGSA is that, CMGM choose a minimum number of clusters as gateways. These gateways elected for handover support, provided that the optimality of serving GW reduces by certain ratio. But in MGSA each vehicular source chooses its own gateway without considering threshold value of the metrics. Because of the selection of multiple gateways delay is increased. Hence, CMGM mechanism has less delay compare to DYMO and MGSA in AODV+.

8 Conclusion & Future Work

The envisioned 3G/VANET integrated network with minimum number of gateways are expected to prevent frequent handoffs at UMTS base stations and the associated signalling overhead, an event more likely to occur when all vehicles connect directly to the UMTS network. Nodes are created in NAM WINDOW by using NS-2 coding, which allocates the function, position and operation of each nodes in a NAM window. Screen shots of node operations in NAM window are shown and graph ensure that by using this integrated network delay and handoff process can be minimized compared to existing work. This emergency response is used to prevent further accidents in highways and traffic. This is the work done by coding in ns2. Compared to 3G technologies, 4G technology has many features and it’s compatible with 3G networks. So in future the integration of 4G/ LTE with VANET may reduce the delay further and it may provide high data rate compared to 3G networks. REFERENCES

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http://www.umtsworld.com/technology/overview.html

V.Revathi is presently doing Master of Technology, Department of Telecommunication Networks, in SRM University, Chennai, India. She has obtained her Bachelor’s Degree in Electronics and Communication Engineering from Ganadhipathy Tulsis

Engineering College under Anna University in the year 2011. Her area of Interest is Wireless Networking, Mobile Communication, Wireless Network Security, Optical Communication, 3G & 4G Networks.

K.Harisudha is presently working as an Assistant Professor, Department of TCE, SRM University, Chennai, India. She has obtained her Bachelor’s Degree in Electronics and Communication Engineering from IFET College of Engineering under Madras

University in the year 2002. She has obtained her Master’s Degree in Communication Systems from SRM University in the year 2010. She has supervised 15 number of undergraduate students for their project. Her area of Interest is Networking, Satellite Communications, Ultra wideband communication, Digital Communication. She is also a Member of following professional bodies ISCA, IEEE.


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