Clarify concepts: WANET, MANET, WMN, WSN, DTN

Take nodes to understand the characterizes of several type of networks related to wireless ad hoc network.

1. WANET

A wireless ad hoc network (WANET) is a decentralized type of wireless network. An ad hoc network typically refers to any set of networks where all devices have equal status[1]. Here are the key features:

  • infrastructure-less, self-configuring, self-forming, self-healing network
  • nodes are static, network is connected (exist end-to-end path)
  • transmission through multiple hops
  • the decentralized nature improves the scalability.

How to build a network? In ad hoc networks, nodes are not familiar with the topology of their networks. Instead, they have to discover it: typically, a new node announces its presence and listens for announcements broadcast by its neighbors. Each node learns about others nearby and how to reach them[1].

How to route packets? An ad hoc routing protocol is a convention that controls how nodes decide which way to route packets between nodes.

2. WMN

A wireless mesh network (WMN) is a form of wireless ad hoc network, which is a communications network made up of radio nodes organized in a mesh topology where all nodes cooperate in the distribution of data in the network (i.e.,each node relays data for the network)[5]

  • wireless mesh infrastructure is, in effect, a network of routers minus the cabling between nodes. It’s built of peer radio devices that don’t have to be cabled to a wired port like traditional WLAN access points (AP) do
  • WMNs have a relatively stable topology except for the occasional failure of nodes or addition of new nodes. It can self form and self heal
  • Wireless mesh networks often consist of mesh clients, mesh routers and gateways. The mesh routers forward traffic to and from the gateways which may, but need not, connect to the Internet.

Here is a paragraph to depict the relationship between WMN and MANET[6].

为了改进MANET使其适用于民用网络,无线网状网络(Wireless Mesh Network)最近几年被提出,其核心思想是将传统MANET中既充当路由器又充当主机的对等节点在物理上分离为无线网状路由器(wireless mesh router)节点和无线网状客户端(wireless mesh client)节点,并且通过边界网关将无线网状路由器接入Internet。(值得注意的是,WMN的节点是几乎不移动的)

3. WSN

If I understood well, WSNs are a sub-class of WANET (wireless ad hoc network). A wireless sensor network (WSN) of spatially distributed autonomous sensors to monitor physical or environmental conditions, such as temperature, sound, pressure, etc. and to cooperatively pass their data through the network to a main location. Here is an example to illustrates this point.

Fig 1. Typical multi-hop wireless sensor network architecture (image from here)

In speaking of the difference between WSN and WANET,

  • the main purpose of WSN is used for information gathering or monitoring.
  • WSN usually consists of one sink (or base station) able to manage all the communications between other nodes[4]. (I don’t think so, to be more precise, nodes pass their data through the network to a main location)

4. MANET

Mobile ad hoc network (MANET)s are a kind of Wireless ad hoc network where 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[2]. Here are the key features:

  • a highly dynamic, autonomous topology

The primary challenge in building a MANET is equipping each device to continuously maintain the information required to properly route traffic. The ad hoc routing protocol for MANET can be classified as: 

For more information, please refer to List of ad hoc routing protocols.

4.1 VANET

A vehicular ad hoc network (VANET) uses cars as mobile nodes in a MANET to create a mobile network. Rather than moving at random in MANETs, vehicles tend to move in an organized fashion[2], according to roadside, traffic light, highway and etc.

4.2 SPANs

Smart Phone Ad hoc Networks (SPANs) leverage the existing hardware (primarily Bluetooth and Wi-Fi) in commercially available smart phones to create peer-to-peer networks without relying on cellular carrier networks, wireless access points, or traditional network infrastructure.

5. DTN

Delay-tolerant networks or disruption-tolerant networks (DTN) are such networks that may lack continuous connectivity. A lot of terminologies are used for DTNs in the literature: opportunistic networks, disconnected mobile ad hoc networks, time-varying network, intermittently connected network (ICNs), extreme networks, etc.

Anyway, the key features of DTN are:

  • no end-to-end path most of time
  • the way routing packets is store-carry-forward, not just store-and-forward.

Popular ad hoc network protocols, such as AODV and DSR, do not work, because they fail to route messages if there is no end-to-end path at all times.

The following figure depicts how challenge DTN is.

File:Disciplines-delay.png

Fig. 2 How challenge DTN is (image from here)

5.1 Interplanetary Internet

The interplanetary internet (based on IPN, also called InterPlaNet) is a conceived computer network in space, consisting of a set of network nodes which can communicate with each other.Communication would be greatly delayed by the great interplanetary distances, so the IPN needs a new set of protocols and technology that are tolerant to large delays and errors[7].

5.2 Pocket Switched Networks

Pocket Switched Networks (PSN) make use of both human mobility and local/global connectivity in order to transfer data between mobile users’ devices[8].

5.3 Village Communication Networks

Imagine that there is no communication infrastructure between a remote village and the city, which means that it does not exist end-to-end paths from the city to the village to transmit messages. A data mule moves along the track. It is equipped with an antenna that communicates with base stations located in the city and (in) the village. While the data mule enters the village, it can deliver the messages to the village by connecting to the base station and download the data that goes back to the city.

5.4 Others

The ZebraNet project is wildlife tracking application aimed at monitoring wild species in unmanned scenarios.

SWIM, underwater delay-tolerant networks.

6. Summary

A wireless local area network (WLAN) is built of peer radio devices cabled to a wired port like traditional WLAN access points (AP). WLAN extends the range of wire networks, but no capable of self-healing, self-organizing. Imagine what wifi does, a wireless router + wireless devices, no direct communication among devices.

Wireless Mesh Networks (WMNs) is a network composed of, in layman’s terms, a network of routers minus the cabling between nodes. WMNs stretch the range of WLAN. Wireless mesh networks often consist of mesh clients, mesh routers and gateways. The mesh routers forward traffic to and from the gateways which may, but need not, connect to the Internet.

Wireless Sensor Networks (WSNs) are used for information gathering or monitoring. Distributed autonomous sensors cooperatively pass their data through the network to a main location. WSNs makes no distinction between routers and clients as WMNs do. All radio devices are equal or peer.

Delay tolerant networks (DTNs) are such networks that are often disconnected, which means there is no end-to-end path most of time. Packets are delivered via mobile nodes.

References:
[1]Wikipedia: wireless ad hoc network, List of ad hoc routing protocols
[2]Wikipedia: Mobile ad hoc network, vehicular ad hoc network, Smart Phone Ad hoc Networks
[3]Wikipedia: wireless sensor network
[4]Quora: What is the difference between wireless sensor networks and ad hoc?
[5]Wikipedia: wireless mesh network, Mesh networking
[6]博文《WMN, MANET, WLAN 关系
[7]Wikipedia: interplanetary internet
[8]HUI, Pan, CHAINTREAU, Augustin, SCOTT, James, et al. Pocket switched networks and human mobility in conference environments. In : Proceedings of the 2005 ACM SIGCOMM workshop on Delay-tolerant networking. ACM, 2005. p. 244-251.

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