Mobile Ad Hoc on Demand Data Delivery Routing Protocol
In the
proceedings of the 3
rdAnnual Post-Graduate Symposium on the Convergence of
Telecommunications, Networking and Broadcasting, June 2002, Liverpool, UK.
Humayun Bakht, Madji d Merabti, and Bob Askwith School of Computing and Mathematics
Liverpool John Moores Univeristy Byrom Street, Liverpool L3 3AF, UK
Email: {cmshbakh, M.Merabti, R.Askwith} @livjm.ac.uk
Abstract
Routing in mobile adhoc network is an unresolved issue. Much effort has been undergoing to invent a mechanism for achieving efficient and reliable routing in mobile adhoc networks. In this paper we presented a routing algorithm at very abstract level for mobile adhoc networks. The proposed algorithm adopts an intermediate approach in between the two existing techniques i.e. Table driven and on demand routing.
We believe, efficient routing in mobile adhoc network could be achieved if route discovery and data delivery could occur at the same time, based on the presented algorithm a more advance form could be develop which would be helpful in providing a effective solution for the routing problem of mobile adhoc networks.
1) Introduction
Mobile adhoc networks are relatively a new field, which is mainly used in a dynamic or unpredictable environment. These types of networks give opportunity for users to enjoy networking facilities where either there is no fixed network infrastructure available or to make one is not cost effective.
Mobile Ad hoc networking is an advantageous way of exchanging peer-to-peer information among different types of network devices such as fixed, portable and mobile nodes. The use of these network are increased dramatically and are being in use for implementing solutions for business, entertainment and safety applications in the office, residential and industrial areas. The key characteristic of a mobile ad hoc network is the ability of any node to route traffic for other nodes.
Ad-hoc network is a collection of mobile nodes connected together forming a communication network without any centralized support. The problem here relates to how mobile hosts can communicate with one other, over the wireless media, in the absence of any fixed infra structured. To provide communication ability, a routing
protocol must be able to support unicast, multicast and broadcast.
Existing Internet protocols are specifically designed for fixed networks, i.e. some supporting structure. These protocols are not therefore well suited for mobile adhoc networks; therefore there is a need of inventing some new mechanism for supporting routing in mobile adhoc network.
Routing in mobile adhoc network is a growing research topic in wireless networks research community. There are a number of protocols, which have been specifically designed for mobile adhoc networks. Examples of some early work in this area is [1,2] while some current effort could be found in [3,4]. These protocols do not work well in all environments [5], which suggest more efficient techniques need to be developed for mobile adhoc networks.
In an ad-hoc network all nodes cooperate each other in order to dynamically establish and maintain routing in the network, forwarding packets for each other to allow communication between nodes not directly within wireless transmission range. Rather then using then using the periodic or background exchange of routing information common in most routing protocols.
One traditional way of achieving routing in mobile adhoc network is to consider each host as a router. In mobile adhoc network a route between a pair of mobile nodes may go through several other mobile nodes. These routes can change when hosts change location. Therefore a good amount of research has been done in this area for both unicast routing [6] and multicast routing [7,8,9] of mobile adhoc networks, also a significant amount of research [10,11,12,13] has been done addressing routing problem in mobile adhoc networks.
2) Related Work
users of laptop computers can use to communicate with each other.
Link state routing is one of the old way of acquiring routing in mobile adhoc network, based on broadcast, in this type of routing each node maintains information on the state of the links established between the other nodes in the network. However link state routing is very expensive especially in terms of bandwidth. Current protocols for mobile adhoc networks are based on one of two main techniques, table driven and on demand. In Table driven routing nodes attempts to maintain a consistent overview of the network by requiring periodic updates, it records all information in the routing tables, which is use whenever a transmission is required. On Demand protocols discover a route only on demand i.e. eliminate the need of routing table and updates. We believe if one side routing table in table driven protocols can be helpful in effective and fast transmission on the other hand it causes Updates overhead, especially in presence of high mobility, large routing tables, low scalability which results in consummation of bandwidth and battery life. In On Demand protocol [14] there are number of advantages such as reducing control overhead, increasing bandwidth and conserving power at the mobile station, However these networks are relatively slow i.e. may not be appropriate for real time communication, Bottleneck may occur due to latency of route discovery. Most of the work done so far in this field is either based on or extension one of these two techniques.
One other type of existing routing techniques is GPS-enabled Adhoc routing algorithm, In this types of routing nodes are equipped with positing system devices (e.g. Global positioning System receivers) that make them aware of their position, this enable “directional” routing, however positional solution differ on how the location information of the destination could be achieved. Some of the draw back of this technique are, need extra hardware, depends on the extra hardware limitation and scalability.
Hence the problems associated with the existing schemes motivate us to describe a better routing approach to support mobile adhoc networks.
3) Proposed Protocol
We want our protocol inherited the best characteristics from table driven and from on demand protocols. When the local connectivity of the mobile nodes is of interest each mobile node can become aware of the other nodes in its neighbourhood by the use of one of several techniques such as broadcasting hello messages.
The routing tables of the nodes within the neighbour hood are organized and each node update it table with the received information such as sequence number and hop count to all other nodes in the network.
Some of the primary objective of purposed algorithm is as follows.
n Broadcast information to deliver data only when requires (On demand data delivery)
n To provide fast effective means of transmission (Deliver data as soon as destination is found)
n Minimizing the battery power usage
n Minimizing bandwidth usage
Any node wants to deliver data to any other node in the network invoke the route discovery and data delivery process very similar to on demand protocols however it differs in some respects, which are as follows.
There are three possibilities when a node broadcast some data packet
1) Either it reached to any intermediate node, which on receiving it transfer it to the destination.
2) Destination it self
3) Un- delivers and returned to the source.
3.1) Basic Mechanism
Each node in the network maintains a routing table, which recorded destination IP address, Destination Sequence number, hop count to destination and next hop for routes to other nodes in the network. New entries are placed in the route table following the reception of hello message, issued by the node on joining the network, route request and data delivery process.
in the network; This node is then recorded as invalid or inactive, a sequence number of ∞ is assign to it while sequence numbers of all other nodes are rearranged accordingly.
The proposed algorithm can be separated into three basic functions, route discovery and data delivery process, route table management and local connectivity management. Creating a route from a given node to destination node requires establishment of a sequence of links from the source to the destination. The method use to accomplish this is route discovery and data delivery process, in which not only route discovery is done but also transferring of data to other node is performed. Routing tables are used to hold the information about other nodes in the network while local connectivity management is required to keep update with the current status of all other neighbouring nodes. Detail description of each process is as follows.
3.2) Route Discovery and Data Delivery Process
The path discovery process is very similar to Adhoc on demand distance vector protocol and it initiated whenever a source node needs to communicate with another node for which it has no routing information in its table. Every node maintains two separate pieces of information: a node sequence number and a broadcast_id. The source node initiates route discovery and data delivery process by broadcasting a route request (RREQ) + (Data) packet to its neighbours. The RREQ contains the following fields.
<source_addr, source_sequence_#, broadcast_id, dest_addr, dest_sequence_#, hop_cnt>
The pair <source_addr, broadcast_id> uniquely identified a RREQ. Broadcast_id is incremented each time source issue a new process. Each neighbour on receiving this message performs the following two functions. First of all it recorded the sequence number and next hop information for the source node. Secondly it look into the routing table weather it has a route to the destination or not if it has route it forward the packet to the destination otherwise broadcast this packet to the closest neighbour in its table. Any intermediate node before forward the packet to the destination makes sure that the route is current by comprising the destination sequence number in its own route entry to the destination sequence number in the RREQ however if the broadcast-id and source address is similar to the one it
has received before it simply ignore the request and does not rebroadcast it. This process continues until either the packet reach to the destination or it returned to the source node as undelivered.
3.3) Route Table Management
In addition to the source and destination sequence numbers, other useful information is stored in the route table entries. In each route table entry the address of active neighbours through which packets for the given destination are received is also maintained. A route entry in the route table is recorded active if use by any other active neighbour which is followed by the acknowledge packet from the destination.
A mobile node maintains a route table entry for each destination of interest. Each route table entry contains the following information.
n Destination address
n Next Hop
n Sequence number for the destination
n Active neighbours for this route
If a new route is offered to a mobile node, the mobile node compares the destination sequence number of the new route to the destination sequence number of the current route.
3.4) Local Connectivity Management
A Node can adopt two ways to know about its neighbours. Whenever a node receive a broadcast from a neighbour its updates its local connectivity information to ensure that it includes this neighbours. In the event when the node is not in transmission, it itself can broadcast a hello message to inform all other nodes about it status.
4) Analysis and Discussion
n It does not require keeping consistent overview of the network as in the case of link state protocols. Thus does not create unnecessary network overhead.
n Some on demand protocols such as AODV and DSR [15] uses periodic beaconing to keep routing table updated thus adding a significant overhead to the protocol where’s in the case our proposed algorithm, No periodic updates is require as the proposed algorithm discover route to deliver the data only when requires.
n In the case of existing on demand protocol by the time a suitable route establish between a source and destination there is a chance of link failure or topology changes between any of these two nodes or by an intermediate node which could results either in transmission failure or invoke route maintenance mechanism, Therefore we can avoid this situation by delivering the packets directly to the destination node.
n It is not always true especially in mobile adhoc networks that all the routes are always valid no matter weather recorded in the routing table or by caching. So even if a source node has a valid route recorded (link state) or cache (on demand) it is not necessary there is no guarantee that the route will always be available throughout the transmission or some time even for a single successful transmission, By giving freedom of choice to all nodes to transfer the packet to the destination either if they a link to the destination or rebroadcast it until the route is found eliminates possibility of route invalidity. As if the destination node is in the transmission range and still active the data will be transfer otherwise would be returned to the source node as undelivered.
n Route discovery creates unnecessary time delay thus effects the overall performance of the network, which make on demand existing protocols unsuitable for real time communication, Where’s our proposed protocol does not require route to be established before being transfer the packet and thus make it possible to achieve real time communication.
n A Bottleneck occurs either when the node send query packet to discover the best possible route to the destination node or it issues a route error messages. We believe the possibility of bottleneck could be minimize by adopting our algorithm.
n We like to emphasize, that though we do adopt routing table strategy of link state protocols but does not depend entirely on the recorded information, we used these information as a starting point instead and to returned the undelivered data packet.
n In our approach, we do not suggest any route maintenance mechanism however in the case when the source node could not discover the data it can retransmit it if require.
n Based on the availability issue some protocol such as global positioning system enable protocol requires use of global positioning system receiver for directional routing in mobile ad hoc network. However in our approach no extra hardwire is required.
In the light of the above discussion it can easily be realized that this approach is an does not require continuous updates, it does not require route discovery process for each transmission, no route maintenance mechanism is required, does not create network overhead and no extra hardware is needed, which prove it as a bandwidth efficient, minimize battery usage and a reliable algorithm.
5) Further Work
In this paper we presented our thoughts by considering the existing work in the area of routing in mobile adhoc networks, and in effort to develop some new techniques that can be helpful to accomplish successful and reliable routing in mobile adhoc networks. As mentioned earlier current existing table driven and on demand protocols does not work well in all environments, which impose a challenge of developing some new protocols which not only full fill the basic routing requirement of on demand protocols but also shows significant results in different types of environment.
extensive comparisons are available for proactive and reactive protocols but our research shows these comparison mainly based on numerical results and there is a lack of analytical results available in this area. This comparison is very important as we regard as one of the most important in successful implementation of our routing protocol. We are particularly interested in the functionality of Ad hoc on demand routing protocol, as most of the function of our proposed protocol is very similar to it.
Mobility, bandwidths and battery life are some of the important miles stones in achieving efficient routing in mobile adhoc networks. Minimizing energy consumption is an important challenge in mobile computing. Mobility causes variation between the lifetimes of two hosts. And limited bandwidth makes a network to be easily congested by control signalling, we consider these issues as some of the important issue, Our proposed protocol could be use to minimize bandwidth usage and to give battery a longer life. However a series of test needs to be done in order to obtain a clear view about the over all performance of the protocol i.e. up to what extend it could minimize the bandwidth usage and maximize the battery life.
Multicast routing and packet forwarding in mobile adhoc network is a fairly unexplored. Since fixed network multicast routing is based on state in routers, it is fundamentally unsuitable for an AHN environment with unconstrained mobility. Our own going work looking into possibility of extending the initial model of the proposed protocol to support both unicast and multicast routing.
The above discussion gives a picture of our long-term research plan, Once implemented, we believe our protocol will be able to provide a reliable and efficient mechanism for routing in mobile adhoc networks.
6) Conclusion
We have proposed a routing algorithm, based on the idea of route discovery and data delivery at the same time. We believe the algorithm could be well suited for operation in mobile adhoc network. The main features of proposed protocol are as follows
n Established routes and deliver data at the same time.
n All routes are loop- free through the use of destination sequence numbers.
n Discover route and deliver data at the same time
n Inactive routes can easily be identified.
n Does not require periodic updates
n Reduce network overhead
n Minimize bandwidth usage
n Increase battery life.
n Provide real time communication
Efficient routing could be achieved if source does not need to wait to establish route to the destination rather then it invoke route discovery and data delivery process at the same time. This algorithm can be utilize to minimize bandwidth, maximize the battery life and to achieve fast reliable transmission when require.
7) References
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