mobile ad hoc network (MANET)
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24-02-2009, 12:33 AM
A mobile ad hoc network (MANET) is a type of wireless ad hoc network, and is a self-configuring network of mobile devices connected by any number of wireless links. Every device in a MANET is also a router because it is required to forward traffic unrelated to its own use. Each MANET device is free to move independently, in any arbitrary direction, and thus each device will potentially change its links to other devices on a regular basis. The primary challenge for building a MANET is for each device to continuously maintain the information required to properly route traffic.
Such networks may operate in a standalone fashion, or may be connected to the larger Internet.
MANET are special cases of several other types of wireless and mesh networks, but have some key differences, at least in common usage, as listed below:
Wireless ad hoc networks - MANET are a type and subset of ad hoc networks, but MANET usually implies the creation of a routeable networking environment on top of a Link Layer ad hoc network.
Mesh networks - MANET are a subset of mesh networks, but many mesh networks are not mobile or are not even wireless (e.g. BGP).
Wireless mesh networks - As above, MANET are a subset of wireless mesh networks, but many mesh networks are not mobile and are not designed to support mobility.
MANET are sometimes referred to as mobile mesh networks
MANETs have become a very popular research topic since the mid- to late 1990s due to the increasing availability of laptops and 802.11/Wi-Fi wireless networking. Many of the academic papers evaluate protocols and abilities assuming varying degrees of mobility within a bounded space, usually with all nodes within a few hops of each other, and usually with nodes sending data at a constant rate. Different protocols are then evaluated based on the packet drop rate, the overhead introduced by the routing protocol, and other measures.
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Joined: Feb 2010
28-02-2011, 09:21 AM
im swamy from visakhapatnam, ap, india. now im doing my final year
project and implimentation for m.tech. my project and implimentation title is:IMPROVING Quality of service in
mobile adhoc multipath network. im searching code for my project and implimentation.
if you have any related information please send to firstname.lastname@example.org.
please help me for this.
Thanks & Regards
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Joined: Jan 2012
02-01-2012, 08:32 PM
I want to make seminar and presentation for Mobile-Ad hoc networks for M.SC Computer Science Part-II .I have no idea how to start it because it is my first time to make a seminar and presentation project and implimentation.
Please Kindly help me and suggest me how to make it
Joined: Jul 2011
03-01-2012, 09:44 AM
to get information about the topic"mobile ad hoc network " refer the link bellow
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19-06-2012, 04:32 PM
mobile ad hoc network (MANET)
Mobile Ad-Hoc Network .docx (Size: 24.91 KB / Downloads: 26)
Mobile ad hoc network (MANET) is an autonomous system of mobile nodes connected by wireless links. Each node operates not only as an end system, but also as a router to forward packets. The nodes are free to move about and organize themselves into a network. These nodes change position frequently.
To accommodate the changing topology special routing algorithms are needed. For relatively small networks flat routing protocols may be sufficient. However, in larger networks either hierarchical or geographic routing protocols are needed. There is no single protocol that fits all networks perfectly. The protocols have to be chosen according to network characteristics, such as density, size and the mobility of the nodes. MANET does not require any fixed infrastructure, such as a base station, therefore, it is an attractive option for connecting devices quickly and spontaneous.
MANETs can be used alone (for example in the military) or as a hybrid together with the Internet or other networks. Different MANET applications have different needs, and hence the various MANET routing protocols may be suitable in different areas. The size of the network and the frequency of the change in topology are factors that affect the choice of the protocols. There is no best protocol for all applications.
There is still ongoing research on mobile ad hoc networks and the research may lead to even better protocols and will probably face new challenges. The current goal is to find an optimal balance between scalable routing and media access control, security, and service management.
Information technology is rapidly changing from regular desktop computing, where isolated workstations communicate through shared servers in a fixed network, to an environment where a large number of different platforms communicate over multiple network platforms. In this environment the devices adapt and reconfigure themselves individually and collectively, to support the requirements of mobile workers and work teams.
In the next generation of wireless communication systems, there will be a need for the rapid deployment of independent mobile users. Mobile Ad Hoc Networks (MANETs) provide communication between all nodes in the network topology without the presence of a centralized authority; instead all nodes can function as routers. This gives the MANETs two of its most desirable characteristics; adaptable and quick to deploy. MANET research is still in progress, and currently MANETs are not widely used. Suggested areas of use will include establishing efficient communication networks for mobile workers in desolate regions or in disaster areas where existing networks have been destroyed or do not exist. To communicate in an efficient way proper routing protocols are needed.
Mobile Ad Hoc Networks (MANETs) consist of nodes that change position frequently. To accommodate the changing topology special routing algorithms are needed. For relatively small networks flat routing protocols may be sufficient. However, in larger networks either hierarchical or geographic routing protocols are needed. There is no single protocol that fits all networks perfectly. The protocols have to be chosen according to network characteristics, such as density, size and the mobility of the nodes.
Mobile ad hoc networking is one of the more innovative and challenging areas of wireless networking, one which promises to become increasingly present in our lives. Consisting of devices that are autonomously self-organizing in networks, ad hoc networks offer a large degree of freedom at a lower cost than other networking solutions.
A MANET is an autonomous collection of mobile users that communicate over relatively “slow” wireless links. Since the nodes are mobile, the network topology may change rapidly and unpredictably over time. The network is decentralized, where all network activity, including discovering the topology and delivering messages must be executed by the nodes themselves. Hence routing functionality will have to be incorporated into the mobile nodes.
Since the nodes communicate over wireless links, they have to contend with the effects of radio communication, such as noise, fading, and interference. In addition, the links typically have less bandwidth than a wired network. Each node in a wireless ad hoc network functions as both a host and a router, and the control of the network is distributed among the nodes. The network topology is in general dynamic, because the connectivity among the nodes may vary with time due to node departures, new node arrivals, and the possibility of having mobile nodes.
An ad hoc wireless network should be able to handle the possibility of having mobile nodes, which will most likely increase the rate at which the network topology changes. Accordingly the network has to be able to adapt quickly to changes in the network topology. This implies the use of efficient handover protocols and auto configuration of arriving nodes.
MANETs APPLICATION AREAS
Significant examples of MANETs include establishing survivable, efficient and dynamic communication for emergency/rescue operations, disaster relief efforts, and military networks. Such network scenarios cannot rely on centralized and organized connectivity, and can be conceived as applications of Mobile Ad Hoc Networks.
However, MANETs are not solely intended for disconnected autonomous operations or scaled scenarios (i.e. hundreds or even thousands of cooperation wireless nodes in a region). They may be used as hybrid infrastructure extensions and in fixed infrastructure operations. A hybrid infrastructure extension is a dynamic enhancement to a home or campus wireless networking environment. It provides extended service and allows low-cost, low complexity dynamic adjustments to provide coverage regions and range extensions away from the more fixed infrastructure backbone networks.
In hybrid infrastructure nodes move or operate on limited energy may be low-preference routing nodes, thus provides more physical stability to the overall routing grid as well. When allowing certain MANET nodes to be preferred over other nodes in a neighborhood, the more passive MANET nodes may provide range extension and dynamic routing functions on an as-needed basis. This may be appropriate within a campus, community, robotic, sensor, or localized business application. In contrast to the hybrid infrastructure extension there are no fixed access nodes or gateway points to provide confirmation coordination in a fixed infrastructure less operation. Here the participating nodes will have to operate in a peer-to-peer fashion, with appropriate applications and protocols. Examples of esoteric ad hoc applications are ad hoc conferencing, business meeting capabilities and ad hoc homeland defense and disaster relief networks. They will require more distributed forms of auto configuration, service discovery, and management.
There are also other network application areas; cooperatives and sensors. In cooperatives a community of interest (i.e. a small town government, infrastructure-lacking world region, group of interested individuals/club) own and operate a network infrastructure together. These networks could deploy MANET technology to support a self-organizing, adaptive infrastructure. This will be desirable in disadvantaged rural regions and developing countries with lack of resources or an environment not suited for significant fixed-infrastructure developments and services. MANET technology can be used here to help building and operating inexpensive network infrastructure services. Sensor networks may be more scaled and capable using MANET technology. Commercial, environmental and military applications are all interested in this. MANET technology can support broad applications of self-organizing and distributed sensor networks.
MANET ROUTING PROTOCOLS
Generally routing protocols in MANETs are either based on the link-state (LS) routing algorithm or on the distance-vector (DV) routing-algorithm. Common for both of these algorithms is that they try to find the shortest path from the source node to the destination node. The main difference is that in LS based routing a global network topology is maintained in every node of the network. In DV based routing the nodes only maintain information of and exchange information with their adjacency nodes. Keeping track of many other nodes in a MANET may produce overhead, especially when the network is large. Therefore one of the most important issues in MANET design is to come up with schemes that will contribute to reduce routing overheads.
MANET routing protocols fall into two general categories:
• Proactive routing protocols
• Reactive routing protocols
There is also a new class of routing protocols known as the hybrid routing protocols, which tries to encompass the advantages of both the proactive and reactive routing protocols.
DIFFERENT ROUTING PROTOCOLS
FLAT ROUTING PROTOCOLS
• Pro-Active / Table Driven routing Protocols
• Reactive / On Demand Routing Protocols
HYBRID ROUTING PROTOCOLS
HIERARCHICAL ROUTING PROTOCOLS
GRAPHICAL ROUTING PROTOCOLS
FLAT ROUTING PROTOCOLS
Flat routing protocols are divided into two classes; proactive routing (table driven) protocols and reactive (on-demand) routing protocols. Common for both protocol classes is that all nodes participating in routing play an equal role. They have further been classified after their design principles; proactive routing is mostly based on LS (link-state) while on-demand routing is based on DV (distance-vector).
• Pro-Active / Table Driven routing Protocols
Proactive MANET protocols are table-driven and will actively determine the layout of the network. Through a regular exchange of network topology packets between the nodes of the network, a complete picture of the network is maintained at every single node. There is hence minimal delay in determining the route to be taken. This is especially important for time-critical traffic (Scientific Research Corporation, 2004).
However, a drawback to a proactive MANET of protocol is that the life span of a link is significantly short. This phenomenon is brought about by the increased mobility of the nodes, which will render the routing information in the table invalid quickly.
When the routing information becomes invalid quickly, there are many short-lived routes that are being determined and not used before they turn void. Hence, another drawback resulting from the increased mobility is the amount of traffic overhead generated when evaluating these unnecessary routes. This is especially aggravated when the network size increases. The fraction of the total control traffic that consists of actual practical data is further decreased.
Lastly, if the nodes transmit infrequently, most of the routing information is deemed redundant. The nodes, however, continue to expend energy by continually updating these unused entries in their routing tables (Scientific Research Corporation, 2004). As mentioned, energy conservation is very important in a MANET system design. Hence, this excessive expenditure of energy is not desired.
Thus, proactive MANET protocols work best in networks that have low node mobility or where the nodes transmit data frequently.
Examples of Proactive MANET Protocols include:
- Optimized Link State Routing, or OLSR
- Topology Broadcast based on Reverse Path Forwarding, or TBRPF
- Fish-eye State Routing, or FSR
- Destination-Sequenced Distance Vector, or DSDV
- Landmark Routing Protocol, or LANMAR
- Clusterhead Gateway Switch Routing Protocol, or CGSR
• Reactive / On Demand Routing Protocols
On-demand routing is a popular routing category for wireless ad hoc routing. It is a relatively new routing philosophy that provides a scalable solution to relatively large network topologies. The design follows the idea that each node tries to reduce routing overhead by only sending routing packets when communication is requested. Common for most on-demand routing protocols are the route discovery phase where packets are flooded into the network in search of an optimal path to the destination node in the network.
There exist numerous on-demand routing protocols, but only two of them is significantly more important. These are Ad Hoc On-Demand Distance Vector Routing (AODV) and Dynamic Source Routing (DSR). These two have been chosen because both have been extensively evaluated in the MANET literature and are being considered by the Internet Engineering Task Force (IETF) MANET Working Group as the leading candidates for standardization.
Thus, reactive MANET protocols are most suited for networks with high node mobility or where the nodes transmit data infrequently.
Examples of Reactive MANET Protocols include:
- Ad Hoc On-Demand Distance Vector, or AODV
- Dynamic Source Routing, or DSR
- Temporally Ordered Routing Algorithm, or TORA
HYBRID ROUTING PROTOCOLS
Since proactive and reactive routing protocols each work best in oppositely different scenarios, there is good reason to develop hybrid routing protocols, which use a mix of both proactive and reactive routing protocols. These hybrid protocols can be used to find a balance between the proactive and reactive protocols.
The basic idea behind hybrid routing protocols is to use proactive routing mechanisms in some areas of the network at certain times and reactive routing for the rest of the network. The proactive operations are restricted to a small domain in order to reduce the control overheads and delays. The reactive routing protocols are used for locating nodes outside this domain, as this is more bandwidth-efficient in a constantly changing network.
Examples of Hybrid Routing Protocols include:
- Cornell's Zone Routing Protocol (ZRP)
- Scientific Research Corporation's Wireless Ad hoc Routing Protocol (WARP) - based on ZRP with additional enhancements for Quality of Service, or QoS support (MobileRouteTM)
The most recognized protocol among these is the ZRP. In this protocol, the radius of each node's local routing zone plays an important part in determining the proactive zone. The proactive routing protocol is used to determine the topology within the radius of the node. The reactive routing protocol is then used to locate nodes outside the radius of the node on demand.
The adjustment of the zone radius will allow the protocol to adapt to different MANET environments. A larger radius will favors the proactive routing protocol, optimal for slow-moving nodes or large amounts of traffic (Scientific Research Corporation, 2004). Consequently, a smaller zone radius will favors the reactive protocol, which is optimal for fast-moving nodes or small amounts of traffic.
The WARP, on the other hand, constantly updates all the active routes between the nodes in the network. This is done using routing tables and link-update propagations (De Renesse and Aghvami, 2004). When there are link breakages, the destination may become unreachable. In this scenario, WARP will use reactive protocols to find alternative routes to break the deadlock.
HIERARCHICAL ROUTING PROTOCOLS
As the size of the wireless network increases, the flat routing protocols may produce too much overhead for the MANET. In this case a hierarchical solution may be preferable. CGSR, HSR, ZRP and LANMAR are four hierarchical routing protocols that have different solutions to the organization of the routing of nodes in a MANET.
Examples of Hierarchical Routing Protocols include:
- CGSR (Clusterhead-Gateway Switch Routing)
- HSR (Hierarchical State Routing)
- ZRP (Zone Routing Protocol)
- LANMAR (Landmark Ad Hoc Routing Protocol)
GEOGRAPHICAL ROUTING PROTOCOLS
There are two approaches to geographic mobile ad hoc networks:
1. Actual geographic coordinates (as obtained through GPS – the Global Positioning System).
2. Reference points in some fixed coordinate system.
An advantage of geographic routing protocols is that they prevent network-wide searches for destinations. Control and data packets can be sent in the general direction of the destination if the recent geographical coordinates are known. This reduces control overhead in the network. A disadvantage, however, is that all nodes must have access to their geographical coordinates all the time to make the geographical routing protocols useful. The routing update must be done faster than the network mobility rate to make the location-based routing effective. This is because the nodes’ locations may change quickly in a MANET.
Examples of Geographical Routing Protocols include:
- GeoCast (Geographic Addressing and Routing)
- DREAM (Distance Routing Effect Algorithm for Mobility)
- GPSR (Greedy Perimeter Stateless Routing)
All the routing protocols mentioned in this essay are either on-demand or proactive. There is a trade-off between sending updates often or just when needed. Sending updates may produce overhead in mobile ad hoc networks because the nodes are moving frequently. When the size of the network is small a flat routing protocol will be sufficient. Then each node keeps track of the other nodes in its routing table. How the nodes discover other nodes and how they send requests for a destination, differs between the routing protocols.
Flat routing protocols are available immediately and they support quality of service in MANETs. However, when the size of a MANET increases the flat routing protocols may not be sufficient. Then either a hierarchical or a geographic routing protocol would be a better solution. The hierarchical routing protocols organize the nodes in hierarchies and have smaller routing tables because the nodes only need to keep track of their levels in the hierarchy. Also, in search for destinations the amount of flooding packets is reduced.
However, the hierarchical routing protocols may also produce overhead to maintain the hierarchical structure. The geographic routing protocols use the knowledge of node locations to organize the structure of a MANET. They may produce overhead when exchanging coordinates, but all in all they can become more scalable and effective than the flat routing protocols.
MANETs can be used alone (for example in the military) or as a hybrid together with the Internet or other networks. Different MANET applications have different needs, and hence the various MANET routing protocols may be suitable in different areas. The size of the network and the frequency of the change in topology are factors that affect the choice of the protocols. There is no best protocol for all applications. For flat, hierarchical and geographic routing protocols, scalability is a big challenge. There is still ongoing research on mobile ad hoc networks and the research may lead to even better protocols and will probably face new challenges. The current goal is to find an optimal balance between scalable routing and media access control, security, and service management.
Joined: Nov 2012
03-11-2012, 01:04 PM
Mobile Ad Hoc Networks
Mobile Ad Hoc.ppt (Size: 540.5 KB / Downloads: 17)
MANET.docx (Size: 47.14 KB / Downloads: 19)
Routing Protocol.docx (Size: 91.16 KB / Downloads: 16)
PRORTOCOL.docx (Size: 263.36 KB / Downloads: 16)
Interzone.docx (Size: 16.43 KB / Downloads: 15)
manet work.docx (Size: 19.75 KB / Downloads: 17)
algorithm.docx (Size: 23.99 KB / Downloads: 17)
MANET..docx (Size: 20.89 KB / Downloads: 19)
Need: Access computing and communication services, on the move
traditional cellular systems (base station infrastructure)
Infrared (IrDA) or radio links (Wavelan)
very flexible within the reception area; ad-hoc networks possible
low bandwidth compared to wired networks (1-10 Mbit/s)
Ad hoc Networks
useful when infrastructure not available, impractical, or expensive
military applications, rescue, home networking
Single hop wireless connectivity to the wired world
Space divided into cells
A base station is responsible to communicate with hosts in its cell
Mobile hosts can change cells while communicating
Hand-off occurs when a mobile host starts communicating via a new base station
Why Ad Hoc Networks ?
Setting up of fixed access points and backbone infrastructure is not always viable
Infrastructure may not be present in a disaster area or war zone
Infrastructure may not be practical for short-range radios; Bluetooth (range ~ 10m)
Ad hoc networks:
Do not need backbone infrastructure support
Are easy to deploy
Useful when infrastructure is absent, destroyed or impractical
Challenges in Mobile Environments
Limitations of the Wireless Network
packet loss due to transmission errors
variable capacity links
limited communication bandwidth
Broadcast nature of the communications
Limitations Imposed by Mobility
dynamically changing topologies/routes
lack of mobility awareness by system/applications
Limitations of the Mobile Computer
short battery lifetime
Medium Access Control in MANET Motivation
Can we apply media access methods from fixed networks?
Carrier Sense Multiple Access with Collision Detection
send as soon as the medium is free, listen into the medium if a collision occurs (original method in IEEE 802.3)
Medium access problems in wireless networks
signal strength decreases proportional to the square of the distance
sender would apply CS and CD, but the collisions happen at the receiver
sender may not “hear” the collision, i.e., CD does not work
CS might not work, e.g. if a terminal is “hidden”
Multiple Access with Collision Avoidance (MACA)
MACA uses signaling packets for collision avoidance
RTS (request to send)
sender request the right to send from a receiver with a short RTS packet before it sends a data packet
CTS (clear to send)
receiver grants the right to send as soon as it is ready to receive
Signaling packets contain
Variants of this method are used in IEEE 802.11
Wireless links are prone to errors. High packet loss rate is detrimental to transport-layer performance.
Solution: Use of acknowledgements
When node B receives a data packet from node A, node B sends an Acknowledgement (Ack).
If node A fails to receive an Ack, it will retransmit the packet
This approach adopted in many protocols [Bharghavan94, IEEE 802.11]
IEEE 802.11 Wireless MAC
Distributed and centralized MAC components
Distributed Coordination Function (DCF)
Point Coordination Function (PCF)
DCF suitable for multi-hop ad hoc networking
MAC: Collision Avoidance
With half-duplex radios, collision detection is not possible
Collision avoidance: Once channel becomes idle, the node waits for a randomly chosen duration before attempting to transmit
IEEE 802.11 DCF
When transmitting a packet, choose a backoff interval in the range [0,cw]; cw is contention window
Count down the backoff interval when medium is idle
Count-down is suspended if medium becomes busy
When backoff interval reaches 0, transmit RTS
Time spent counting down backoff intervals is a part of MAC overhead
large cw leads to larger backoff intervals
small cw leads to larger number of collisions
MAC Protocols: Summary
Wireless medium is prone to hidden and exposed terminal problems
Protocols are typically based on CSMA/CA
RTS/CTS based signaling
Acks for reliability
Contention window is used for congestion control
IEEE 802.11 wireless LAN standard
Fairness issues are still unclear
Traditional distributed shortest-path protocols
Maintain routes between every host pair at all times
Based on periodic updates; High routing overhead
Example: DSDV (destination sequenced distance vector)
Determine route if and when needed
Source initiates route discovery
Example: DSR (dynamic source routing)
Adaptive; Combination of proactive and reactive
Example : ZRP (zone routing protocol)
Location-Aided Routing (LAR)
Exploits location information to limit scope of route request flood
Location information may be obtained using GPS
Expected Zone is determined as a region that is expected to hold the current location of the destination
Expected region determined based on potentially old location information, and knowledge of the destination’s speed
Route requests limited to a Request Zone that contains the Expected Zone and location of the sender node