Wireless ad hoc network
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A wireless ad hoc network
Such wireless networks lack the complexities of infrastructure setup and administration, enabling devices to create and join networks "on the fly".[3]
Each device in a MANET is free to move independently in any direction, and will therefore change its links to other devices frequently. Each must forward traffic unrelated to its own use, and therefore be a router. The primary challenge in building a MANET is equipping each device to continuously maintain the information required to properly route traffic. This becomes harder as the scale of the MANET increases due to 1) the desire to route packets to/through every other node, 2) the percentage of overhead traffic needed to maintain real-time routing status, 3) each node has its own goodput to route independent and unaware of others needs, and 4) all must share limited communication bandwidth, such as a slice of radio spectrum.
Such networks may operate by themselves or may be connected to the larger Internet. They may contain one or multiple and different transceivers between nodes. This results in a highly dynamic, autonomous topology. MANETs usually have a routable networking environment on top of a link layer ad hoc network.
History
Packet radio
The earliest wireless data network was called
Another third wave of academic and research activity started in the mid-1990s with the advent of inexpensive
Early work on MANET
The growth of
In the early 1990s, Charles Perkins from SUN Microsystems USA, and
Applications
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 networks compared to wireless managed networks, though theoretical and practical limits to the overall capacity of such networks have been identified.[citation needed] Minimal configuration and quick deployment make ad hoc networks suitable for emergency situations like natural disasters or military conflicts. The presence of dynamic and adaptive routing protocols enables ad hoc networks to be formed quickly.
Mobile ad hoc networks (MANETs)
A mobile ad hoc network (MANET) is a continuously self-configuring, self-organizing, infrastructure-less[14] network of mobile devices connected without wires. It is sometimes known as "on-the-fly" networks or "spontaneous networks".[15]
Vehicular ad hoc networks (VANETs)
Smartphone ad hoc networks (SPANs)
A SPAN leverages existing hardware (primarily Wi-Fi and Bluetooth) and software (protocols) in commercially available smartphones to create peer-to-peer networks without relying on cellular carrier networks, wireless access points, or traditional network infrastructure. SPANs differ from traditional hub and spoke networks, such as Wi-Fi Direct, in that they support multi-hop relays and there is no notion of a group leader so peers can join and leave at will without destroying the network. Apple's iPhone with iOS version 7.0 and higher is capable of multi-peer ad hoc mesh networking.[18]
Wireless mesh networks
Mesh networks take their name from the topology of the resultant network. In a fully connected mesh, each node is connected to every other node, forming a "mesh". A partial mesh, by contrast, has a topology in which some nodes are not connected to others, although this term is seldom in use. Wireless ad hoc networks can take the form of a mesh networks or others. A wireless ad hoc network does not have fixed topology, and its connectivity among nodes is totally dependent on the behavior of the devices, their mobility patterns, distance with each other, etc. Hence, wireless mesh networks are a particular type of wireless ad hoc networks, with special emphasis on the resultant network topology. While some wireless mesh networks (particularly those within a home) have relatively infrequent mobility and thus infrequent link breaks, other more mobile mesh networks require frequent routing adjustments to account for lost links.[19]
Army tactical MANETs
Military or tactical MANETs are used by military units with emphasis on data rate, real-time requirement, fast re-routing during mobility, data security, radio range, and integration with existing systems.[20] Common radio waveforms include the US Army's JTRS SRW, Silvus Technologies MN-MIMO Waveform (Mobile Networked MIMO),[21][22][23][24] and Persistent System's WaveRelay. Ad hoc mobile communications come in well to fulfill this need, especially its infrastructureless nature, fast deployment and operation. Military MANETs are used by military units with an emphasis on rapid deployment, infrastructureless, all-wireless networks (no fixed radio towers), robustness (link breaks are no problem), security, range, and instant operation.
Air Force UAV ad hoc networks
Flying ad hoc networks (FANETs) are composed of unmanned aerial vehicles, allowing great mobility and providing connectivity to remote areas.[25]
Unmanned aerial vehicle, is an aircraft with no pilot on board. UAVs can be remotely controlled (i.e., flown by a pilot at a ground control station) or can fly autonomously based on pre-programmed flight plans. Civilian usage of UAV include modeling 3D terrains, package delivery (Logistics), etc.[26]
UAVs have also been used by US Air Force[27] for data collection and situation sensing, without risking the pilot in a foreign unfriendly environment. With wireless ad hoc network technology embedded into the UAVs, multiple UAVs can communicate with each other and work as a team, collaboratively to complete a task and mission. If a UAV is destroyed by an enemy, its data can be quickly offloaded wirelessly to other neighboring UAVs. The UAV ad hoc communication network is also sometimes referred to UAV instant sky network. More generally, aerial MANET in UAVs are now (as of 2021) successfully implemented and operational as mini tactical reconnaissance ISR UAVs like the BRAMOR C4EYE from Slovenia.
Navy ships traditionally use satellite communications and other maritime radios to communicate with each other or with ground station back on land. However, such communications are restricted by delays and limited bandwidth. Wireless ad hoc networks enable ship-area-networks to be formed while at sea, enabling high-speed wireless communications among ships, enhancing their sharing of imaging and multimedia data, and better co-ordination in battlefield operations.[28] Some defense companies (such as Rockwell Collins, Silvus Technologies and Rohde & Schwartz) have produced products that enhance ship-to-ship and ship-to-shore communications.[29]
Sensor networks
Sensors are useful devices that collect information related to a specific parameter, such as noise, temperature, humidity, pressure, etc. Sensors are increasingly connected via wireless to allow large-scale collection of sensor data. With a large sample of sensor data, analytics processing can be used to make sense out of these data. The connectivity of wireless sensor networks rely on the principles behind wireless ad hoc networks, since sensors can now be deploy without any fixed radio towers, and they can now form networks on-the-fly. "Smart Dust" was one of the early projects done at U C Berkeley, where tiny radios were used to interconnect smart dust.[30] More recently, mobile wireless sensor networks (MWSNs) have also become an area of academic interest.
Robotics
Efforts have been made to co-ordinate and control a group of robots to undertake collaborative work to complete a task. Centralized control is often based on a "star" approach, where robots take turns to talk to the controller station. However, with wireless ad hoc networks, robots can form a communication network on-the-fly, i.e., robots can now "talk" to each other and collaborate in a distributed fashion.[31] With a network of robots, the robots can communicate among themselves, share local information, and distributively decide how to resolve a task in the most effective and efficient way.[32]
Disaster response
Another civilian use of wireless ad hoc network is for public safety. At times of disasters (floods, storms, earthquakes, fires, etc.), a quick and instant wireless communication network is necessary. Especially at times of earthquakes when radio towers had collapsed or were destroyed, wireless ad hoc networks can be formed independently. Firefighters and rescue workers can use ad hoc networks to communicate and rescue those injured. Commercial radios with such capability are available on the market.[33][34]
Hospital ad hoc network
Wireless ad hoc networks allow sensors, videos, instruments, and other devices to be deployed and interconnected wirelessly for clinic and hospital patient monitoring, doctor and nurses alert notification, and also making senses of such data quickly at fusion points, so that lives can be saved.[35][36]
Data monitoring and mining
MANETS can be used for facilitating the collection of
Challenges
Several books[41][42] and works have revealed the technical and research challenges[43][44] facing wireless ad hoc networks or MANETs. The advantages for users, the technical difficulties in implementation, and the side effect on radio spectrum pollution can be briefly summarized below:
Advantages for users
The obvious appeal of MANETs is that the network is decentralised and nodes/devices are mobile, that is to say there is no fixed infrastructure which provides the possibility for numerous applications in different areas such as environmental monitoring, disaster relief and military communications. Since the early 2000s, interest in MANETs has greatly increased which, in part, is due to the fact mobility can improve network capacity, shown by Grossglauser and Tse along with the introduction of new technologies.[45]
One main advantage to a decentralised network is that they are typically more robust than centralised networks due to the multi-hop fashion in which information is relayed. For example, in the cellular network setting, a drop in coverage occurs if a base station stops working, however the chance of a single point of failure in a MANET is reduced significantly since the data can take multiple paths. Since the MANET architecture evolves with time it has the potential to resolve issues such as isolation/disconnection from the network. Further advantages of MANETS over networks with a fixed topology include flexibility (an ad hoc network can be created anywhere with mobile devices), scalability (you can easily add more nodes to the network) and lower administration costs (no need to build an infrastructure first).[46][47]
Implementation difficulties
With a time evolving network it is clear we should expect variations in network performance due to no fixed architecture (no fixed connections). Furthermore, since network topology determines interference and thus connectivity, the mobility pattern of devices within the network will impact on network performance, possibly resulting in data having to be resent a lot of times (increased delay) and finally allocation of network resources such as power remains unclear.[45] Finally, finding a model that accurately represents human mobility whilst remaining mathematically tractable remains an open problem due to the large range of factors that influence it.[48] Some typical models used include the random walk, random waypoint and levy flight models.[49][50] [51][52]
Side effects
- Use of unlicensed frequency spectrum, contributing to radio spectrum pollution.
Radios and modulation
Wireless ad hoc networks can operate over different types of radios. All radios use modulation to move information over a certain bandwidth of radio frequencies. Given the need to move large amounts of information quickly over long distances, a MANET radio channel ideally has large bandwidth (e.g. amount of radio spectrum), lower frequencies, and higher power. Given the desire to communicate with many other nodes ideally simultaneously, many channels are needed. Given radio spectrum is shared and regulated, there is less bandwidth available at lower frequencies. Processing many radio channels requires many resources. Given the need for mobility, small size and lower power consumption are very important. Picking a MANET radio and modulation has many trade-offs; many start with the specific frequency and bandwidth they are allowed to use.
Radios can be
ad hoc uses the unlicensed ISM 2.4 GHz radios. They can also be used on 5.8 GHz radios.The higher the frequency, such as those of 300 GHz, absorption of the signal will be more predominant. Army tactical radios usually employ a variety of UHF and SHF radios, including those of
Next generation Wi-Fi known as
At 60 GHz, there is another form of Wi-Fi known as WiGi – wireless gigabit. This has the ability to offer up to 7 Gbit/s throughput. Currently, WiGi is targeted to work with 5G cellular networks.[53]
Circa 2020, the general consensus finds the 'best' modulation for moving information over higher frequency waves to be orthogonal frequency-division multiplexing, as used in 4G LTE, 5G, and Wi-Fi.
Protocol stack
The challenges
A major limitation with mobile nodes is that they have high mobility, causing links to be frequently broken and reestablished. Moreover, the bandwidth of a wireless channel is also limited, and nodes operate on limited battery power, which will eventually be exhausted. These factors make the design of a mobile ad hoc network challenging.
The cross-layer design deviates from the traditional network design approach in which each layer of the stack would be made to operate independently. The modified transmission power will help that node to dynamically vary its propagation range at the physical layer. This is because the propagation distance is always directly proportional to transmission power. This information is passed from the physical layer to the network layer so that it can take optimal decisions in routing protocols. A major advantage of this protocol is that it allows access of information between physical layer and top layers (MAC and network layer).
Some elements of the software stack were developed to allow code updates in situ, i.e., with the nodes embedded in their physical environment and without needing to bring the nodes back into the lab facility.[55] Such software updating relied on epidemic mode of dissemination of information and had to be done both efficiently (few network transmissions) and fast.
Routing
Routing[56] in wireless ad hoc networks or MANETs generally falls into three categories, namely: proactive routing, reactive routing, and hybrid routing.
Proactive routing
This type of protocols maintains fresh lists of destinations and their routes by periodically distributing routing tables throughout the network. The main disadvantages of such algorithms are:
- Respective amount of data for maintenance.
- Slow reaction on restructuring and failures.
Example: Optimized Link State Routing Protocol (OLSR)
Distance vector routing
As in a fix net nodes maintain routing tables. Distance-vector protocols are based on calculating the direction and distance to any link in a network. "Direction" usually means the next hop address and the exit interface. "Distance" is a measure of the cost to reach a certain node. The least cost route between any two nodes is the route with minimum distance. Each node maintains a vector (table) of minimum distance to every node. The cost of reaching a destination is calculated using various route metrics. RIP uses the hop count of the destination whereas IGRP takes into account other information such as node delay and available bandwidth.
Reactive routing
This type of protocol finds a route based on user and traffic demand by flooding the network with Route Request or Discovery packets. The main disadvantages of such algorithms are:
- High latency time in route finding.
- Excessive flooding can lead to network clogging.[57]
However, clustering can be used to limit flooding. The latency incurred during route discovery is not significant compared to periodic route update exchanges by all nodes in the network.
Example: Ad hoc On-Demand Distance Vector Routing (AODV)
Flooding
Is a simple routing algorithm in which every incoming packet is sent through every outgoing link except the one it arrived on. Flooding is used in bridging and in systems such as Usenet and peer-to-peer file sharing and as part of some routing protocols, including OSPF, DVMRP, and those used in wireless ad hoc networks.
Hybrid routing
This type of protocol combines the advantages of proactive and reactive routing. The routing is initially established with some proactively prospected routes and then serves the demand from additionally activated nodes through reactive flooding. The choice of one or the other method requires predetermination for typical cases. The main disadvantages of such algorithms are:
- Advantage depends on number of other nodes activated.
- Reaction to traffic demand depends on gradient of traffic volume.[58]
Example: Zone Routing Protocol (ZRP)
Position-based routing
Position-based routing methods use information on the exact locations of the nodes. This information is obtained for example via a GPS receiver. Based on the exact location the best path between source and destination nodes can be determined.
Example: "Location-Aided Routing in mobile ad hoc networks" (LAR)
Technical requirements for implementation
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 behavioral properties (e.g., reliability), as well as 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.[59]
Medium-access control
In most wireless ad hoc networks, the nodes compete for access to shared wireless medium, often resulting in
Simulation
One key problem in wireless ad hoc networks is foreseeing the variety of possible situations that can occur. As a result, modeling and simulation (M&S) using extensive parameter sweeping and what-if analysis becomes an extremely important paradigm for use in ad hoc networks. One solution is the use of simulation tools like OPNET, NetSim or ns2. A comparative study of various simulators for VANETs reveal that factors such as constrained road topology, multi-path fading and roadside obstacles, traffic flow models, trip models, varying vehicular speed and mobility, traffic lights, traffic congestion, drivers' behavior, etc., have to be taken into consideration in the simulation process to reflect realistic conditions.[61]
Emulation testbed
In 2009, the U.S. Army Research Laboratory (ARL) and Naval Research Laboratory (NRL) developed a Mobile Ad-Hoc Network emulation testbed, where algorithms and applications were subjected to representative wireless network conditions. The testbed was based on a version of the "MANE" (Mobile Ad hoc Network Emulator) software originally developed by NRL.[62]
Mathematical models
The traditional model is the random geometric graph. Early work included simulating ad hoc mobile networks on sparse and densely connected topologies. Nodes are firstly scattered in a constrained physical space randomly. Each node then has a predefined fixed cell size (radio range). A node is said to be connected to another node if this neighbor is within its radio range. Nodes are then moved (migrated away) based on a random model, using random walk or brownian motion. Different mobility and number of nodes present yield different route length and hence different number of multi-hops.
These are
Security
Most wireless ad hoc networks do not implement any network access control, leaving these networks vulnerable to resource consumption attacks where a malicious node injects packets into the network with the goal of depleting the resources of the nodes relaying the packets.[66]
To thwart or prevent such attacks, it was necessary to employ authentication mechanisms that ensure that only authorized nodes can inject traffic into the network.[67] Even with authentication, these networks are vulnerable to packet dropping or delaying attacks, whereby an intermediate node drops the packet or delays it, rather than promptly sending it to the next hop.
In a multicast and dynamic environment, establishing temporary 1:1 secure 'sessions' using
Trust management
Trust establishment and management in MANETs face challenges due to resource constraints and the complex interdependency of networks. Managing trust in a MANET needs to consider the interactions between the composite cognitive, social, information and communication networks, and take into account the resource constraints (e.g., computing power, energy, bandwidth, time), and dynamics (e.g., topology changes, node mobility, node failure, propagation channel conditions).[68]
Researchers of trust management in MANET suggested that such complex interactions require a composite trust metric that captures aspects of communications and social networks, and corresponding trust measurement, trust distribution, and trust management schemes.[68]
Continuous monitoring of every node within a MANET is necessary for trust and reliability but difficult because it by definition is dis-continuous, 2) it requires input from the node itself and 3) from its 'nearby' peers.
See also
- Ad hoc wireless distribution service
- Delay-tolerant networking
- Independent basic service set(IBSS)
- List of ad hoc routing protocols
- Mobile wireless sensor network
- Personal area network (PAN)
- Smart meter
- Wi-Fi Direct
- Wireless community network
- Wireless mesh network
- Wireless sensor network
References
- ISBN 9780792398226.
- .
- ^ ISBN 9780130078179.
- ^ "Robert ("Bob") Elliot Kahn". A.M. Turing Award. Association for Computing Machinery.
- .
- )
- ^ ARRL's VHF Digital Handbook. American Radio Relay League. 2008. pp. 1–2.
- S2CID 14335563.
- ^ Toh, Chai Keong (31 March 1999). "IETF MANET DRAFT: Long-lived Ad Hoc Routing based on the Concept of Associativity".
- ^ "Experimenting with an Ad Hoc Wireless Network on Campus: Insights & Experiences", ACM SIGMETRICS Performance Evaluation Review, Vol. 28, No. 3, 2001".
- ISBN 9780132442046.
- ^ Chakeres, Ian D. "AODV Implementation Design and Performance Evaluation" (PDF).
{{cite journal}}
: Cite journal requires|journal=
(help) - .
- ^ "Ad Hoc Mobile Wireless Networks:Protocols and Systems, 2001".
- )
- S2CID 206470694.
- S2CID 25800906.
- ^ "MultipeerConnectivity from Apple".
- ^ ""Everyone is a node: How Wi-Fi Mesh Networking Works by Jerry Hildenbrand, 2016". 2016-10-13.
- ^ Toh; Lee; Ramos (2002). "Next Generation Tactical Ad Hoc Mobile Wireless Networks". TRW Systems Technology Journal.
- ^ "U.S. Army Adopts Silvus for Integrated Tactical Network Capability Set '21". Prnewswire. 2021.
- ^ Silvus Technologies (24 May 2022). "#StreamCaster radios have received the Joint Electronics Type Designation: AN/PRC-169. AN/PRC-169 radios connect the dismounted soldier, deployed command posts, ISR sensors, and unmanned vehicles via an Electronic Attack resistant #MANET". Twitter. Archived from the original on 24 May 2022. Retrieved 10 June 2022.
Image shows " SC4400E AN/PRC-169(V)1 5820-01-691-2906 SC4200EP AN/PRC-169(V)2 5820-01-691-2880"
- ^ "STREAMCASTER 4400 Enhanced 4x4 MIMO Radio" (PDF). Silvus Technologies. April 2021. Archived from the original (PDF) on 21 January 2022. Retrieved 10 June 2022.
- ^ "StreamCaster 4200 Enhanced Plus 2x2 MIMO Radio" (PDF). Silvus Technologies. April 2021. Archived from the original (PDF) on 21 January 2022. Retrieved 10 June 2022.
- )
- ^ "The future is here: Five applications of UAV technology". 2013-12-06.
- ^ "U.S. Air Force Chief Scientist: Stealth Drones and Killer Swarms Could Be Coming Soon". 2017-02-23.
- ^ "We connect your naval forces by Rohde & schwartz" (PDF).
- ^ "The first fully mobile, cross-platform ad hoc IP network utilizing legacy radio systems".
- ^ "A Study on Smart Dust Networks, Linkoping University, 2011".
- ^ "Protocols and Applications of Ad-hoc Robot Wireless Communication Networks: An Overview" (PDF).
- ^ "Ad-hoc Wireless Network Coverage with Networked Robots that cannot Localize, 2009" (PDF).
- ^ "GoTenna Militrary-Grade Mesh Networking" (PDF).
- ^ "GoTenna Pro meshing radio aspires to deploy next to rescue, fire and security teams". 27 March 2017.
- S2CID 14208144.
- S2CID 35790010.
- PMID 27879895.
- S2CID 1639100.
- S2CID 5879608.
- S2CID 9755353.
- ^ ISBN 9780133007060.
- ISBN 9780792398226.
- ^ "Research Challenges for Ad hoc mobile wireless networks, University of Essex, 2005".
- ^ "An Overview of Mobile Ad Hoc Networks: Applications and Challenges" (PDF).
- ^ a b Grossglauser, M; Tse, D (2001). Mobility increases the capacity of ad-hoc wireless networks. Twentieth Annual Joint Conference of the IEEE Computer and Communications Societies. Vol. 3. IEEE Proceedings. pp. 1360–1369.
- ^ Helen, D; Arivazhagan, D (2014). "Applications, advantages and challenges of ad hoc networks". JAIR. 2 (8): 453–457.
- ^ Giordano, S (2002). "Mobile ad hoc networks". Handbook of wireless networks and mobile computing. pp. 325–346.
- S2CID 4419468.
- S2CID 4330122.
- S2CID 15031580.
- S2CID 6352586.
- .
- ^ "Making Sense on what's happening on Wi-Fi". 11 June 2016.
- ISBN 9780792398226.
- S2CID 8240984.
- .
- .
- .
- ISBN 9780849392542.
- ^ ISBN 978-1107039889.
- doi:10.1002/wcm.859.
- S2CID 14810551.
- S2CID 54549743.
- S2CID 928409.
- ^ M.D. Penrose (2003). "Random Geometric Graphs". Oxford University Press.
- ISBN 978-3-540-67381-1.
- S2CID 7082229.
- ^ S2CID 14849884.
Further reading
- Satyajeet, D.; Deshmukh, A. R.; Dorle, S. S. (January 2016). "Article: Heterogeneous Approaches for Cluster based Routing Protocol in Vehicular Ad Hoc Network (VANET)". International Journal of Computer Applications. 134 (12): 1–8. .
- Royer, E.; .
- Mauve, M.; Widmer, J.; Hartenstein, H. (December 2001). "A Survey on Position-Based Routing in Mobile Ad Hoc Networks". IEEE Network. 1 (6): 30–39. .
- Djenouri, D.; Kheladi, L.; Badache, N. (October 2005). "A Survey of Security Issues in Mobile Ad hoc and Sensor Networks". IEEE Communications Surveys and Tutorials. 7 (4): 2–28. S2CID 11135536.
- Cano, Jose; Cano, Juan-Carlos; Toh, Chai-Keong; Calafate, Carlos T.; Manzoni, Pietro (2010). "EasyMANET: an extensible and configurable platform for service provisioning in MANET environments". IEEE Communications Magazine. 48 (12): 159–167. S2CID 20381835.
- .
- Jubin, J.; Tornow, J. D. (January 1987). "The DARPA Packet Radio Network Protocols". Proceedings of the IEEE. 75 (1): 21–32. S2CID 13345464.
- Schacham, N.; Westcott, J. (January 1987). "Future directions in packet radio architectures and protocols". Proceedings of the IEEE. 75 (1): 83–99. S2CID 1779198.