Modified MANET protocol to extend the emergency network
Abstract—Today, wireless network communication has become part of everyday life. The age-independent use, the design principles for everyone are present virtually in every area of mobile applications. Assistive technologies are getting more and more supportive in the field of information technology. There may also be a situation where certain services are lost due to a malfunction in areas covered by the network. In this article a new network communication protocol modification will be presented, which can be seen as a small step, but it can certainly be extended with the help of an emergency call coverage to areas where it has not been possible to date. Based on already well-established ad-hoc networks, a method based on direct communication between network devices is presented, utilizing the benefits of the Cluster-based Routing Protocol (CBRP) and the Bacup Cluster Head Protocol (BCHP). Using a newly developed method for clustering communication is continuous, replacing the missing central nodes in a very short time, presenting a new, suitable node within the cluster that keeps moving nodes.
Keywords—Assistive Technology; Emergency Networks; MANET; routing protocols; Artificial cognitive capabilities of ICT; Cognitive networks
Although the number of mobile devices grows year after year, community nets offer a number of options that can be used, for example, to quickly and efficiently solve a weather chaos or even an outbreak, but there are geographic anomalies that are simply unavailable via cellular networks areas, but there are also some which are popular places of excursion. As an example, the areas covered by mobile operators in Hungary by the 2/3 / 4G / LTE network, which can be seen in Fig. 1.
As can be seen from the geographic peculiarities, there are a number of “white” spots on the maps, meaning network defects. There may also be a situation where certain services are lost due to a malfunction in areas covered by the network. It is not necessary to foresee any unfavorable situations that may cause perceived loss in one of these major communication networks, but it is still worth finding a solution that will allow you to extend mobile network access through the Wi-Fi network connection of your devices.
A mobile ad hoc network (MANET) represents a complex distributed system that contains a group of similar mobile nodes that can move freely and dynamically.
This type of networks is infrastructure-less and has no centralized administration, because of the mobility of nodes, Manets have no fixed topology and that’s why we need dynamic routing protocols to achieve the network functionality.
Design of MANETs routing protocol must be fully distributed, scalable, localized, adaptive to topology changes and optimally use the available resources such as: battery, bandwidth, memory …etc. 1.
Fig.1. 3/4G Cellular coverage sample
Manets are used in Many applications nowadays. The domain of applications is ranging from small and static to large and dynamic networks.
Some examples are: military sector, commercial sector: emergency and rescue operations, disaster operations like earthquakes, patient monitoring …. etc. 2.
Security for this type of networks is very critical and it is a big challenge as it is very important factor when developing Manets Protocols.
In a MANET, nodes rely on batteries so that the energy conservation is very important fore those nodes, and this should be considered in designing and implementing routing protocols.
Emergency telecommunication MANETs need efficient distributed algorithms to specify network organization (connectivity), link scheduling, and routing, and that what makes the design of network protocols for these networks a very complex issue 3.
Manets are dynamic self-adaptive wireless networks and that makes them suitable to be used in emergency and rescue operations when we have different rescue teams. In like in an extreme emergency scenario. The network architecture consists of a mixture of leader nodes that may or not move in the disaster area and normal nodes that are mobile. The leader nodes are the hierarchically superior policemen, firemen, etc. that supervise the emergency operation, while the mobile nodes are normal emergency workers operating in the field of the disaster 4.
Fig.2. Manet Architecture for emergency 4
The cognitive infocommunication’s wide area covers the multidisciplinary of the protocol development, which focuses on the artificial cognitive capabilities of MANETs, and targets on the humans, gives a novel approach to extend the human emergency services 12, 13. With the rapid evolution and increasing complexity of communication devices (smartphones, PDAs etc.) it is becoming necessary to review and understand the novel need which occurred in human-device communication 12 and nowadays in the device-device communication also.
II. BACKGROUND: MANET ROUTING
We can define routing protocols as a collection of rules that specify how the message mechanism works to transfer packets from source node to destination nose in a network.
Fig.3: Ad hoc networks routing protocols
A. Proactive (Table driven routing) Protocols
In this type of protocols, each node will have routes to all other nodes within the network, and when a change in the network topology occurs, these routes will be refreshed periodically through distributing nodes’ routing tables within the network periodically. The main disadvantage of table driven routing protocols is that when failure occurs (link is broken) or in case of network restructuring, the reaction is slow, and in dynamic networks we need lot of resources to be able to keep the routing information up-to-date 5.
examples of proactive routing protocols are Destination- Sequenced Distance Vector (DSDV), Wireless Routing Protocol (WRP), Global State Routing (GSR).
B. On-Demand Routing Protocols (reactive)
In this type of protocols, we don’t have to keep the routing information up-to-date. when the node needs to send packets to a destination node, it establishes the requires path through initiating a route discovery within the network. The main disadvantage of this type of protocols is that it causes to flood the network with route request packets and the route-finding process can take longer time 5.
Examples of reactive protocols are: Ad hoc On-Demand Distance Vector (AODV), Temporally Ordered Routing Algorithm (TORA), Dynamic Source Routing (DSR).
C. Hybrid Routing
This type of protocols has the advantages of the previous two types. Here we define for a certain node, a region called routing zone which is a group of nodes within a certain region, we use proactive protocol for routing within this zone, and out of this zone we use reactive protocol 6.
Examples of this type of routing protocols are Enhanced Interior Gateway Routing Protocol (EIGRP), ZRP protocol.
A simple classification of presented routing protocols is shown in Fig.3.
D. MANET Hierarcical Routing
Hierarchical routing protocols reorganize the network nodes in structures called clusters. In each cluster, there is a cluster head node which is elected to be used for distributing the information within the cluster. An example of this type of protocols is Cluster Based Routing Protocol (CBRP) .
In CBRP 7 the ad-hoc network nodes are divided into interconnected structures called clusters. Each cluster elects a node as cluster head. also, in each cluster there are gateway nodes to make CH able to communicate with other cluster head.
The cluster head selection can be in one of two ways:
-The node with lowest/highest ID in its neighborhood.
-The nose that has the most neighbor nodes.
Each node has a neighbor table contains: node ID, role(cluster head or member ), link status(unidirectional/bidirectional).
CBRP uses two structures for routing: the cluster adjacency table(CAT) which contains information about neighboring clusters and the two-hop topology database.
Advantages of CBRP is that it minimizes the routing traffic and increases the packet delivery ratio , its advantages is that when the cluster size increases , the transmission time also increases 8.
Fig.4: Clustered ad-hoc network sample
E. Backup Cluster Head Protocol (BCHP)
Rommel T, Liliana E and Luis M suggested a new hierarchical model for cluster-based routing protocol using redundant cluster head called BCHP 9.
In each cluster , there will be an additional node called the Backup Cluster Head (BCH) which will play the role of cluster head(CH) when a failure occurs to CH. BCH will get an updated information about the nodes of the cluster and the state of CH itself through a periodical communication between CH and BCH .
By using a redundant node BCH the convergence of MANETs can be improved since the cluster will not select a new CH.
The authors of this model compared CBRP and BCHP and showed that BCHP improves the availability and convergence of MANETs.
Fig.5: MANET network management model proposed by Rommel et al. 9
There is communication between CH and BCH through using synchronization messages, and when CH does not obtain the acknowledgement receipt of the synchronization it means that BCH is not available, so a new BCH will be elected. But when BCH does not receive synchronization message from CH, it means that CH is not available, and BCH will be the new CH and a new BCH will be elected.
In some moment when CH is not available and before BCH becomes the new CH, the nodes within the cluster are still sending information to CH which is not available, and that means failure.
The BCH here is working in a reactive manner, but if we could make it work with a proactive behavior, this will improve also the availability of the network.
III. PROPOSED SOLUTION FOR CLUSTER BASED ROUTING PROTOCOL WITH BACKUP CLUSTER HEAD
To improve the accessibility and effectiveness of MANETs, the authors propose a new method in this section. This method based on CBRP and combines the main advantages with the BCHP protocol advantage, and the required result is a more stable behavior, wider range of geographical areas can be covered with active nodes.
Choosing of the cluster head will be according to a power aware clustering which is weighted clustering algorithm (WCA) 10.
The algorithm depends on four parameters for selection process of cluster head:
1) Degree Difference (?v): for each node v, it is calculated as |dv – ?| .
dv represents the degree of a node and ? is a pre-defined threshold.
2) Distance Summation (Dv): it is computed for one node as the sum of distances from that node to all its neighbors.
3) Mobility (Mv): it is calculated during time T by calculating the average speed of each node during that time.
4) Remaining Battery Power (Pv): defines the consumed amount of battery power in the node.
The algorithm selects cluster head depending on weight value for every node.
For a node n , its weight is calculated:
Wn = W1 ?v + W2 Dv + W3 Mv + W4 Pv (1)
W1, W2. W3. W4 : weight factors,
We select the node that has the first minimum weight as a cluster head , and we choose the factors :
W1 + W2 + W3 + W4 = 1 (2).
The node first does not belong to any cluster and starts with non-defined state. Using the algorithm, the node calculates its own weight and later sends a broadcast message to all nodes, which includes the sender’s state and weight. The node then creates its own routing table with this information. After, we are able to choose the best two nodes and select the CH and BCH. After that, each node in the cluster stores the address of the actual CH and BCH.
The selection algorithm finishes when all the nodes in the cluster define their status : either a cluster head or a backup cluster head or a member of a cluster.
CH and BCH exchange synchronization messages in every predefined time, and when CH resources such as battery power, memory, bandwidth and free capacity for processing reach to a low level, in this situation we can give the role of cluster head to BCH in a proactive behavior, so the new strategy will be as following:
a) Exchanging information about resources level between CH and BCH within synchronization messages.
b) When resources level in CH is lower than determined level:
b-1) BCH will send broadcasting message to the member nodes informing about the new state using the last update information synchronized with the CH.
b-2) The member nodes will identify the BCH as a new CH, as they have reference information of it.
b-3) The cluster head will call the algorithm again to choose a new BCH.
This strategy will improve the availability and convergence of the network more by enhancing the rate of sent packets, average delay and packet delay variation.
To test the new strategy for the protocol, the network simulator NS211 will be used with emergency and rescue mobility model.
In this paper, a new modification is proposed for Manets’ cluster-based routing protocol with a redundant cluster head for the emergency and rescue operations. The new solution aims to increase the availability and convergence of the network by changing the backup cluster head to work with proactive behavior; and in this way the rate of sent packets, average delay and packet delay variation will be enhanced; which means that the information message exchange between rescue teams will be more quick and dynamic, which leads to improve the overall rescue operation.
The new procedure is under testing with a network simulator and the first results let us conclude that the planned goal of the proposed improvement could be achieved.
With the using of new behavioral property of MANET it could be extend to the emergency covered area and provides opportunities for devices to reach each other. New in this protocol modification that the selected cluster head and backup cluster head state is not a predefined state; and every
dynamically changing network can select their own best cluster head and backup cluster head. This solution gives an extra opportunity to keep any cluster alive, each device will have a simple path to its own cluster head, each cluster has a path to its neighboring clusters. The main advantage is that this protocol is transparent, works hidden from the user, and the background processes do not need any human intervention but need to define some new security rule for continuous use on the devices in the future. Based on human aspect this kind of cognitive communication between smart devices could serve the human needs.
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