Wireless ad-hoc network
Encyclopedia
A wireless ad-hoc network is a decentralized type of wireless network
. The network is ad hoc
because it does not rely on a preexisting infrastructure, such as routers in wired networks or access points
in managed (infrastructure) wireless networks. Instead, each node
participates in routing by forwarding data for other nodes, and so the determination of which nodes forward data is made dynamically based on the network connectivity. In addition to the classic routing
, ad hoc networks can use flooding
for forwarding the data.
The earliest wireless ad-hoc networks were the "packet radio
" networks (PRNETs) from the 1970s, sponsored by DARPA
after the ALOHAnet
project.
Minimal configuration and quick deployment make ad hoc networks suitable for emergency situations like natural disasters or military conflicts. The presence of a dynamic and adaptive routing protocols enable ad-hoc networks to be formed quickly.
Wireless ad hoc networks can be further classified by their application:
Links are influenced by the node's resources (e.g. transmitter power, computing power and memory) and by behavioral properties (e.g. reliability), as well as by link properties (e.g. length-of-link and signal loss, interference and noise). Since links can be connected or disconnected at any time, a functioning network must be able to cope with this dynamic restructuring, preferably in a way that is timely, efficient, reliable, robust and scalable.
The network must allow any two nodes to communicate, by relaying the information via other nodes.
A “path” is a series of links that connects two nodes. Various routing methods use one or two paths between any two nodes; flooding methods use all or most of the available paths.
by having the destination node combine self-interference and other-node interference to improve decoding of the desired signal.
, and NetSim
.
However, these tools focus primarily on the simulation of the entire protocol stack of the system. Although that can be important in the proof-of-concept implementations of systems, the need for a more advanced simulation methodology is always there. Agent-based modeling and simulation offers such a paradigm. Not to be confused with multi-agent systems and intelligent agents, agent-based modeling originated from social sciences, where the goal was to evaluate and view large-scale systems with numerous interacting "AGENT" or components in a wide variety of random situations to observe global phenomena. Unlike traditional AI systems with Intelligent agent
s, agent-based modeling is similar to the real world. Agent-based models are thus effective in modeling bio-inspired and nature-inspired systems. In these systems, the basic interactions of the components the system, also called Complex Adaptive System
, are simple but result in advanced global phenomena such as emergence
.
Wireless network
Wireless network refers to any type of computer network that is not connected by cables of any kind. It is a method by which homes, telecommunications networks and enterprise installations avoid the costly process of introducing cables into a building, or as a connection between various equipment...
. The network is ad hoc
Ad hoc
Ad hoc is a Latin phrase meaning "for this". It generally signifies a solution designed for a specific problem or task, non-generalizable, and not intended to be able to be adapted to other purposes. Compare A priori....
because it does not rely on a preexisting infrastructure, such as routers in wired networks or access points
Wireless access point
In computer networking, a wireless access point is a device that allows wireless devices to connect to a wired network using Wi-Fi, Bluetooth or related standards...
in managed (infrastructure) wireless networks. Instead, each node
Node (computer science)
A node is a record consisting of one or more fields that are links to other nodes, and a data field. The link and data fields are often implemented by pointers or references although it is also quite common for the data to be embedded directly in the node. Nodes are used to build linked, often...
participates in routing by forwarding data for other nodes, and so the determination of which nodes forward data is made dynamically based on the network connectivity. In addition to the classic routing
Routing
Routing is the process of selecting paths in a network along which to send network traffic. Routing is performed for many kinds of networks, including the telephone network , electronic data networks , and transportation networks...
, ad hoc networks can use flooding
Flooding algorithm
A flooding algorithm is an algorithm for distributing material to every part of a connected network. The name derives from the concept of inundation by a flood....
for forwarding the data.
The earliest wireless ad-hoc networks were the "packet radio
Packet radio
Packet radio is a form of packet switching technology used to transmit digital data via radio or wireless communications links. It uses the same concepts of data transmission via Datagram that are fundamental to communications via the Internet, as opposed to the older techniques used by dedicated...
" networks (PRNETs) from the 1970s, sponsored by DARPA
Defense Advanced Research Projects Agency
The Defense Advanced Research Projects Agency is an agency of the United States Department of Defense responsible for the development of new technology for use by the military...
after the ALOHAnet
ALOHAnet
ALOHAnet, also known as the ALOHA System, or simply ALOHA, was a pioneering computer networking system developed at the University of Hawaii. ALOHAnet became operational in June, 1971, providing the first public demonstration of a wireless packet data network.The ALOHAnet used a new method of...
project.
Application
The decentralized nature of wireless ad-hoc networks makes them suitable for a variety of applications where central nodes can't be relied on, and may improve the scalability of wireless ad-hoc networks compared to wireless managed networks, though theoretical and practical limits to the overall capacity of such networks have been identified.Minimal configuration and quick deployment make ad hoc networks suitable for emergency situations like natural disasters or military conflicts. The presence of a dynamic and adaptive routing protocols enable ad-hoc networks to be formed quickly.
Wireless ad hoc networks can be further classified by their application:
- mobile ad-hoc networks (MANET)
- wireless mesh networks (WMN)
- wireless sensor networks (WSN)
Technical requirements
An ad-hoc network is made up of multiple “nodes” connected by “links”.Links are influenced by the node's resources (e.g. transmitter power, computing power and memory) and by behavioral properties (e.g. reliability), as well as by link properties (e.g. length-of-link and signal loss, interference and noise). Since links can be connected or disconnected at any time, a functioning network must be able to cope with this dynamic restructuring, preferably in a way that is timely, efficient, reliable, robust and scalable.
The network must allow any two nodes to communicate, by relaying the information via other nodes.
A “path” is a series of links that connects two nodes. Various routing methods use one or two paths between any two nodes; flooding methods use all or most of the available paths.
Medium-access control
In most wireless ad hoc networks, the nodes compete for access to shared wireless medium, often resulting in collisions (interference). Using cooperative wireless communications improves immunity to interferenceElectromagnetic interference
Electromagnetic interference is disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source. The disturbance may interrupt, obstruct, or otherwise degrade or limit the effective performance of the circuit...
by having the destination node combine self-interference and other-node interference to improve decoding of the desired signal.
Simulation of wireless ad-hoc networks
One key problem to Wireless Ad Hoc networks is foreseeing the variety of possible situations that can occur. As a result, Modeling and Simulation using extensive parameter sweeping and what-if analysis becomes an extremely important paradigm for use in ad hoc networks. Traditional M&S tools for modeling and simulation include the likes of NS2,(and recently NS3), OPNET ModelerOPNET
OPNET Technologies, Inc. is a software business that provides performance analysis for computer networks and applications.The company was founded in 1986 and went public in 2000. It is headquartered in Bethesda, Maryland and has offices in Cary, North Carolina; Nashua, New Hampshire; Dallas,...
, and NetSim
NetSim
NetSim is a popular network simulation tool used by the academic community for teaching, network lab experimentation and research. Various technologies such as Ethernet, Wireless LAN, Wi Max, TCP, IP, etc are covered in NetSim.-History:...
.
However, these tools focus primarily on the simulation of the entire protocol stack of the system. Although that can be important in the proof-of-concept implementations of systems, the need for a more advanced simulation methodology is always there. Agent-based modeling and simulation offers such a paradigm. Not to be confused with multi-agent systems and intelligent agents, agent-based modeling originated from social sciences, where the goal was to evaluate and view large-scale systems with numerous interacting "AGENT" or components in a wide variety of random situations to observe global phenomena. Unlike traditional AI systems with Intelligent agent
Intelligent agent
In artificial intelligence, an intelligent agent is an autonomous entity which observes through sensors and acts upon an environment using actuators and directs its activity towards achieving goals . Intelligent agents may also learn or use knowledge to achieve their goals...
s, agent-based modeling is similar to the real world. Agent-based models are thus effective in modeling bio-inspired and nature-inspired systems. In these systems, the basic interactions of the components the system, also called Complex Adaptive System
Complex adaptive system
Complex adaptive systems are special cases of complex systems. They are complex in that they are dynamic networks of interactions and relationships not aggregations of static entities...
, are simple but result in advanced global phenomena such as emergence
Emergence
In philosophy, systems theory, science, and art, emergence is the way complex systems and patterns arise out of a multiplicity of relatively simple interactions. Emergence is central to the theories of integrative levels and of complex systems....
.