Toward Reliable Data Delivery for Highly Dynamic Mobile Ad Hoc Networks

ABSTRACT:
This paper addresses the problem of delivering data packets for highly dynamic mobile ad hoc networks in a reliable and timely manner. Most existing ad hoc routing protocols are susceptible to node mobility, especially for large-scale networks. Driven by this issue, we propose an efficient Position-based Opportunistic Routing (POR) protocol which takes advantage of the stateless property of geographic routing and the broadcast nature of wireless medium. When a data packet is sent out, some of the neighbor nodes that have overheard the transmission will serve as forwarding candidates, and take turn to forward the packet if it is not relayed by the specific best forwarder within a certain period of time. By utilizing such in-the-air backup, communication is maintained without being interrupted. The additional latency incurred by local route recovery is greatly reduced and the duplicate relaying caused by packet reroute is also decreased. In the case of communication hole, a Virtual Destination-based Void Handling (VDVH) scheme is further proposed to work together with POR. Both theoretical analysis and simulation results show that POR achieves excellent performance even under high node mobility with acceptable overhead and the new void handling scheme also works well.



ARCHITECTURE:


EXISTING SYSTEM:

Geographic routing (GR) uses location information to forward data packets, in a hop-by-hop routing fashion. Greedy forwarding is used to select next hop forwarder with the largest positive progress towards the destination while void handling mechanism is triggered to route around communication voids. No end-to end routes need to be maintained, leading to GR’s high efficiency and scalability.
In the operation of greedy forwarding, the neighbor which is relatively far away from the sender is chosen as the next hop. If the node moves out of the sender’s coverage area, the transmission will fail.


DISADVANTAGES OF EXISTING SYSTEM:

·     GR is very sensitive to the inaccuracy of location information.

·     If the node moves out of the sender’s coverage area, the transmission will fail.

·     Due to the error prone wireless channel and the dynamic network topology, reliable data delivery in MANETs, especially in challenged environments with high mobility remains an issue.

·     Owing to the constantly and even fast changing network topology, it is very difficult to maintain a deterministic route. The discovery and recovery procedures are also time and energy consuming. Once the path breaks, data packets will get lost or be delayed for a long time until the reconstruction of the route, causing transmission interruption.


PROPOSED SYSTEM:

We propose a novel Position based Opportunistic Routing protocol (POR) is proposed, in which several forwarding candidates cache the packet that has been received using MAC interception. If the best forwarder does not forward the packet in certain time slots, suboptimal candidates will take turn to forward the packet according to a locally formed order. In this way, as long as one of the candidates succeeds in receiving and forwarding the packet, the data transmission will not be interrupted. Potential multi-paths are exploited on the- fly on a per-packet basis, leading to POR’s excellent robustness.

ADVANTAGES OF PROPOSED SYSTEM:

·        Position based opportunistic routing mechanism which can be deployed without complex modification to MAC protocol and achieve multiple receptions without losing the benefit of collision avoidance.

·        Opportunistic routing can still be achieved while handling communication voids.

SYSTEM CONFIGURATION:
HARDWARE REQUIREMENTS:

ü System                 :         Pentium IV 2.4 GHz
ü Hard Disk            :         40 GB
ü Floppy Drive       :         1.44 MB
ü Monitor                :         15 VGA color
ü Mouse                  :         Logitech
ü Keyboard             :         110 Keys enhanced
ü RAM                    :         256MB



SOFTWARE REQUIREMENTS:

ü O/S                       :         Windows XP.
ü Language              :          C#.Net
ü Database              :         SQL-Server 2005

MOUDULES:
Multi-hop infrastructure-less transmission Network Creation Module
Position-based Opportunistic Routing (POR) Module
Selection and Prioritization of Forwarding Candidates
Memory Consumption and Duplicate Relaying

MODULES DESCRIPTION:
Multi-hop infrastructure-less transmission Network Creation Module
In this paper, a novel Position-based Opportunistic Routing (POR) protocol is proposed, in which several forwarding candidates cache the packet that has been received using MAC interception. If the best forwarder does not forward the packet in certain time slots, suboptimal candidates will take turn to forward the packet according to a locally formed order. In this way, as long as one of the candidates succeeds in receiving and forwarding the packet, the data transmission will not be interrupted. Potential multi paths are exploited on the fly on a per packet basis, leading to POR’s excellent robustness.
Position-based Opportunistic Routing (POR) Module
The design of POR is based on geographic routing and opportunistic forwarding. The nodes are assumed to be aware of their own location and the positions of their direct neighbors. Neighborhood location information can be exchanged using one-hop beacon or piggyback in the data packet’s header. While for the position of the destination, we assume that a location registration and lookup service which maps node addresses to locations is available. When a source node wants to transmit a packet, it gets the location of the destination first and then attaches it to the packet header. Due to the destination node’s movement, the multihop path may diverge from the true location of the final destination and a packet would be dropped even if it has already been delivered into the neighborhood of the destination. To deal with such issue, additional check for the destination node is introduced. At each hop, the node that forwards the packet will check its neighbor list to see whether the destination is within its transmission range. If yes, the packet will be directly forwarded to the destination, similar to the destination location prediction scheme

Selection and Prioritization of Forwarding Candidates
One of the key problems in POR is the selection and prioritization of forwarding candidates. Only the nodes located in the forwarding area would get the chance to be backup nodes. The forwarding area is determined by the sender and the next hop node. A node located in the forwarding area satisfies the following two conditions: 1) it makes positive progress toward the destination; and 2) its distance to the next hop node should not exceed half of the transmission range of a wireless node (i.e., R=2) so that ideally all the forwarding candidates can hear from one another.
Memory Consumption and Duplicate Relaying
One main concern of POR is its overhead due to opportunistic forwarding, as several copies of a packet need to be cached in the forwarding candidates, leading to more memory consumption, and duplicate relaying would possibly happen if the suppression scheme fails due to node mobility. We first look into the issue of memory consumption. If a packet is received by a forwarding candidate Ci;i2½1;N_, it will be cached for a period of i_T at most according to the forwarding scheme. Therefore, we can get the following upper bound for the length (number of packets cached) of the packet list. Then, we look into the overhead due to duplicate relaying.


REFERENCE:
Shengbo Yang, Chai Kiat Yeo, and Bu Sung Lee, “Toward Reliable Data Delivery for Highly Dynamic Mobile Ad Hoc Networks”, IEEE TRANSACTIONS ON MOBILE COMPUTING, VOL. 11, NO. 1, JANUARY 2012.