Wireless Ad-hoc and Mesh Networks
- (Madison, Wisconsin - Alvin Wei-Cheng Wong)
- Ad-hoc Networks
An ad-hoc network refers to technologies that allow network communications on an ad-hoc basis. "Ad-hoc" is actually a Latin phrase that means "for this purpose." It is often used to describe solutions that are developed on-the-fly for a specific purpose. In computer networking, an ad-hoc network refers to a network connection established for a single session and does not require a router or a wireless base station. For example, if you need to transfer a file to your friend's laptop, you might create an ad hoc-network between your computer and his/her laptop to transfer the file. This may be done using an Ethernet crossover cable, or the computers' wireless cards to communicate with each other. If you need to share files with more than one computer, you could set up a mutli-hop ad-hoc network, which can transfer data over multiple nodes. Basically, an ad-hoc network is a temporary network connection created for a specific purpose (such as transferring data from one computer to another). If the network is set up for a longer period of time, it is just a plain old local area network (LAN).
Ad-hoc networking covers a variety of network paradigms including mobile ad-hoc networks (MANETs), wireless sensor networks (WSNs), vehicular ad-hoc networks (VANETs), airborne networks, underwater networks, underground networks, personal area networks, and home networks, etc. It promises a wide range of applications in civilian, commercial, and military areas.
In recent years, ad-hoc networks have been attracting increased attention from the research and engineering communities.
- Difference between Ad-hoc and Mesh Networks
Ad-hoc networks are multi-hop networks where most nodes are wireless and connections and routes are extremely dynamic as the network builds and changes. Most ad-hoc network traffic is peer-to-peer. Mesh networks on the other hand are also multi-hop networks where there is a mixture of wireless, mobile, and fixed nodes. Mesh networks connections and routes are not as dynamic as ad-hoc networks and the primary traffic is from user-to-gateway. Ad-hoc networks are primarily used for temporary extensions to an infrastructure network where cabling requirements are prohibited due to time and resource constraints. Extending a wireless network through an ad-hoc extension to accommodate a conference meeting is a perfect application use for ad-hoc networks. During the conference wireless coverage is made available and when the conference is over the ad-hoc network is no longer needed.
- Mobile Ad-hoc Networks (MANETs)
An wireless ad-hoc network is a wireless system, in which mobile or static nodes are connected using wireless links and cooperate to self-organize into a network without the requirement for any infrastructure such as access points or base stations.
A wireless ad-hoc network[ (WANET) or Mobile ad hoc network (MANET) is a decentralized type of wireless network. The network is ad-hoc because it does not rely on a pre-existing 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, so the determination of which nodes forward data is made dynamically on the basis of network connectivity and the routing algorithm in use.
The nodes in a wireless ad-hoc network move frequently and the topology changes continuously. This makes the routing process in ad-hoc networks a big research issue. The organizing and controlling of the network are distributed among the devices itself. Two key challenges of wireless ad-hoc networks are self organizing and transferring information through wireless medium.
Bandwidth constraint is a major challenge in MANETS. As the wireless links have lower capacity, and due to multiple access, fading, noise, and interference conditions, the wireless links have low throughput.
Energy consumption is another important performance metrics in wireless ad-hoc networks, because the lifetime of the network depends on energy consumed for various activities such as sending, receiving, processing, etc. As the nodes in a MANET rely on batteries, the important system design criteria for optimization is energy conservation.
The research in the field of MANETS is focusing more on the performance comparisons and trade-off studies between various low energy routing and self-organization protocols.
[More to come ...]
