(Wireless) Ad hoc networking
In traditional networks, both wired and wireless, the connected devices, or nodes, depend on dedicated devices (edge devices) such as routers and/or servers for facilitating the throughput of information from one node to the other. These 'routing nodes' have the ability to determine where information is coming from and where it is supposed to go. They give out names and addresses (IP addresses) to each connected node and regulate the traffic between them. In wireless grids, such dedicated routing devices are not (always) available and the bandwidth that is permanently available to traditional networks has to be either 'borrowed' from an already existing network or publicly accessible bandwidth (open spectrum) has to be used.
A group addressing this problem is MANET (Mobile Ad Hoc Network).
Resource sharing
One of the intended aspects of wireless grids is that it will facilitate the sharing of a wide variety of resources. These will include both technical as information resources. The former being bandwidth, QoS, and web services, but also computational power and data storage capacity. Information resources can include virtually any kind of data from databases and membership lists to pictures and directories.
Ad hoc resource sharing between mobile devices in the wireless grid require for the devices to agree on sharing/communication protocols without the existence of dedicated servers.
Coordination Systems
Coordination Systems are the actual mechanisms that enable the sharing of resources between different devices. For different resources, devices use different coordination systems. Examples of such mechanisms are: SMB or NFS for sharing disk space and the distributed.net client for sharing processor cycles.
Trust Establishment
Before users are willing to share any resource, they demand a certain amount of trust between them and the users and/or systems they share resources with. The amount of trust required depends on the kind of information/resource that is to be shared. Sharing processor cycles requires less substantial trust then the sharing of personal information and commercial information can require another level of trust establishment altogether. There are systems currently in operation that can provide a certain amount of trust like the public key infrastructure that makes use of certificates; now often used in web based email systems, and Kerberos.
Resource discovery
Before any resource on a device in the grid can be utilized, those resources that are available must be discovered; all the devices that make up the grid and the resources they possess have to be identified. When a client enters the grid, such as a PDA, it has to be able to communicate to the other users that it is a PDA and it has a camera, GPS capabilities, a telephone function and various office applications such as a text editor. Protocols like UPnP and zeroconf can detect a new node in the network when it enters. When detected, other users can send a query to the new device to find out what it has to offer. Commercial service providers can 'advertise' the resources they have to offer through IP multicasts. Within large grids containing thousands of nodes, a kind of 'friend of a friend' mechanism can be used. There is a myriad of standards that include resource description protocols. Standards as IETF's zeroconf, Microsoft's UPnP, the Grid Resource Description Language (GRDL), the Web Services Description Language (WSDL) for describing various specific web services and parts of QoS that describe bandwidths all offer devices a way to describe and publish their specific resources and needs. There are also various systems currently available that can gather these resource descriptions and structure them for other devices to use. The OpenGrid Services Architecture (OGSA) uses a Web service-style IndexService. The Web services community has defined UDDI which can makes a database of services that are available on the network, and JXTA uses zeroconf to identify resources in a network. However, the problem with using these in wireless grids is that no stable publisher of these descriptions may exist.
Resource description
For any device to be able to use any resource, a way to identify and describe the resource has to be agreed on by all available devices. If, for instance, storage capacity is to be shared, it first has to be clear what the capacity of each device is and what the storage need is. As said, there are many techniques to describe certain resources but there is not one technique that is able to provide this service for all resources. The available techniques combined, however, cover most of what is needed.
Grid Computing
Grid computing came into existence as a manner of sharing heavy computational loads among multiple computers to be able to compute highly complex mathematical problems (a good real-world example being the SETI@Home project). However, it developed rapidly into a way of sharing virtually any resource that is available on any machine on the grid. Wired grids are now used to share not only computing power, but also hard disk space, data, and applications. The grid topology is highly flexible and easily scalable, allowing users to join and leave the grid without the hassle of time and resource hungry identification procedures, having to adjust their devices or install additional software on them. The goal of grid computing is described as "to provide flexible, secure and coordinated resource sharing among dynamic collections of individuals, institutions and resources" (McKnight, Howison, 2004).
It is intended to be a dynamic network without geographical, political, or cultural boundaries that offers real-time access to heterogeneous resources and still offer the same characteristics of the traditional distributed networks that are in use everywhere in our houses and offices. These characteristics being stability, scalability, and flexibility as the most important ones. Ian Foster offers a checklist for recognizing a grid.
- A grid allows:
- Coordination of resources that are not subject to centralized control
- Use of standard, open, general-purpose protocols and interfaces
- Delivery of nontrivial qualities of service
The Wireless Grid
One of the biggest limitations of the wired grid is that users are forced to be in a fixed location as the devices they use are to be hard wired to the grid at all times. This also has a negative influence on the flexibility and scalability of the grid; devices can only join the grid in locations where the possibility exists to physically connect the device to the grid (i.e. there is the need for a hub or a switch to plug into).
One description of the wireless grid is "an augmentation of a wired grid that facilitates the exchange of information and the interaction between heterogeneous wireless devices" (Argawal, Norman & Gupta, 2004)
Argawal, Norman & Gupta (2004) identify three forces that drive the development of the wireless grid:
New user interaction modalities and form factors
Applications that exist on current wired grids need to be adapted to fit the devices used in wireless grids. These devices are usually hand held and therefore the user interface devices (screens, keyboards (if any)) are significantly smaller and availability of additional input devices like a mouse are limited. This means the traditional graphical interfaces found on PCs are not suitable.
Limited computing resources
Wireless devices do not possess the computing power nor the storage capacity of full size devices like a PC or laptop. Therefore, wireless applications need to have access to additional computing resources to be able to offer the same functionality that wired networks do.
Additional new supporting infrastructure elements
In the case of an unforeseen event, there will be the need for major amounts of computational and communications bandwidths. An urban catastrophe, for example, would require a dynamic and adaptive wireless network to alert people within the population as well as those in the various coordination and aid services like the police, army, medical services, and government. Applications to provide for these bandwidths and 'instant' networks need to be addressed.
Wireless Grids infrastructure
The infrastructure of the wireless grid consists of three basic levels:
- The physical layer technologies and policies. The physical layer contains the spectrum on which the wireless devices can operate and communicate.
- Network infrastructure
- Middleware to provide communications between heterogeneous devices
Peer-to-peer (P2P) computing or networking is a distributed application architecture that partitions tasks or workloads between peers. Peers are equally privileged, equipotent participants in the application. They are said to form a peer-to-peer network of nodes.
Quality of service (QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network or a cloud computing service, particularly the performance seen by the users of the network. To quantitatively measure quality of service, several related aspects of the network service are often considered, such as packet loss, bit rate, throughput, transmission delay, availability, jitter, etc.
A wireless LAN (WLAN) is a wireless computer network that links two or more devices using wireless communication to form a local area network (LAN) within a limited area such as a home, school, computer laboratory, campus, or office building. This gives users the ability to move around within the area and remain connected to the network. Through a gateway, a WLAN can also provide a connection to the wider Internet.
A wireless network is a computer network that uses wireless data connections between network nodes.
Grid computing is the use of widely distributed computer resources to reach a common goal. A computing grid can be thought of as a distributed system with non-interactive workloads that involve many files. Grid computing is distinguished from conventional high-performance computing systems such as cluster computing in that grid computers have each node set to perform a different task/application. Grid computers also tend to be more heterogeneous and geographically dispersed than cluster computers. Although a single grid can be dedicated to a particular application, commonly a grid is used for a variety of purposes. Grids are often constructed with general-purpose grid middleware software libraries. Grid sizes can be quite large.
Wi-Fi is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio waves. These are the most widely used computer networks in the world, used globally in home and small office networks to link desktop and laptop computers, tablet computers, smartphones, smart TVs, printers, and smart speakers together and to a wireless router to connect them to the Internet, and in wireless access points in public places like coffee shops, hotels, libraries and airports to provide the public Internet access for mobile devices.
In computer networking, a wireless access point (WAP), or more generally just access point (AP), is a networking hardware device that allows other Wi-Fi devices to connect to a wired network. As a standalone device, the AP may have a wired connection to a router, but, in a wireless router, it can also be an integral component of the router itself. An AP is differentiated from a hotspot which is a physical location where Wi-Fi access is available.
Zigbee is an IEEE 802.15.4-based specification for a suite of high-level communication protocols used to create personal area networks with small, low-power digital radios, such as for home automation, medical device data collection, and other low-power low-bandwidth needs, designed for small scale projects which need wireless connection. Hence, Zigbee is a low-power, low data rate, and close proximity wireless ad hoc network.
A wireless mesh network (WMN) is a communications network made up of radio nodes organized in a mesh topology. It can also be a form of wireless ad hoc network.
The Optimized Link State Routing Protocol (OLSR) is an IP routing protocol optimized for mobile ad hoc networks, which can also be used on other wireless ad hoc networks. OLSR is a proactive link-state routing protocol, which uses hello and topology control (TC) messages to discover and then disseminate link state information throughout the mobile ad hoc network. Individual nodes use this topology information to compute next hop destinations for all nodes in the network using shortest hop forwarding paths.
Wireless sensor networks (WSNs) refer to networks of spatially dispersed and dedicated sensors that monitor and record the physical conditions of the environment and forward the collected data to a central location. WSNs can measure environmental conditions such as temperature, sound, pollution levels, humidity and wind.
Wireless security is the prevention of unauthorized access or damage to computers or data using wireless networks, which include Wi-Fi networks. The term may also refer to the protection of the wireless network itself from adversaries seeking to damage the confidentiality, integrity, or availability of the network. The most common type is Wi-Fi security, which includes Wired Equivalent Privacy (WEP) and Wi-Fi Protected Access (WPA). WEP is an old IEEE 802.11 standard from 1997. It is a notoriously weak security standard: the password it uses can often be cracked in a few minutes with a basic laptop computer and widely available software tools. WEP was superseded in 2003 by WPA, or Wi-Fi Protected Access. WPA was a quick alternative to improve security over WEP. The current standard is WPA2; some hardware cannot support WPA2 without firmware upgrade or replacement. WPA2 uses an encryption device that encrypts the network with a 256-bit key; the longer key length improves security over WEP. Enterprises often enforce security using a certificate-based system to authenticate the connecting device, following the standard 802.11X.
Delay-tolerant networking (DTN) is an approach to computer network architecture that seeks to address the technical issues in heterogeneous networks that may lack continuous network connectivity. Examples of such networks are those operating in mobile or extreme terrestrial environments, or planned networks in space.
A home network or home area network (HAN) is a type of computer network that facilitates communication among devices within the close vicinity of a home. Devices capable of participating in this network, for example, smart devices such as network printers and handheld mobile computers, often gain enhanced emergent capabilities through their ability to interact. These additional capabilities can be used to increase the quality of life inside the home in a variety of ways, such as automation of repetitive tasks, increased personal productivity, enhanced home security, and easier access to entertainment.
A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are made up of telecommunication network technologies, based on physically wired, optical, and wireless radio-frequency methods that may be arranged in a variety of network topologies.
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 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.
In computing, Microsoft's Windows Vista and Windows Server 2008 introduced in 2007/2008 a new networking stack named Next Generation TCP/IP stack, to improve on the previous stack in several ways. The stack includes native implementation of IPv6, as well as a complete overhaul of IPv4. The new TCP/IP stack uses a new method to store configuration settings that enables more dynamic control and does not require a computer restart after a change in settings. The new stack, implemented as a dual-stack model, depends on a strong host-model and features an infrastructure to enable more modular components that one can dynamically insert and remove.
Windows Rally is a set of technologies from Microsoft intended to simplify the setup and maintenance of wired and wireless network-connected devices. They aim to increase reliability and security of connectivity for users who connect the devices to the Internet or to computers running Microsoft Windows. These technologies provide control of network quality of service (QoS) and diagnostics for data sharing, communications, and entertainment. Windows Rally technologies provide provisioning for the following devices:
IEEE 802.11s is a wireless LAN standard and an IEEE 802.11 amendment for mesh networking, defining how wireless devices can interconnect to create a wireless LAN (WLAN) mesh network, which may be used for relatively fixed topologies and wireless ad hoc networks. The IEEE 802.11s task group drew upon volunteers from university and industry to provide specifications and possible design solutions for wireless mesh networking. As a standard, the document was iterated and revised many times prior to finalization.
Device-to-Device (D2D) communication in cellular networks is defined as direct communication between two mobile users without traversing the Base Station (BS) or core network. D2D communication is generally non-transparent to the cellular network and it can occur on the cellular frequencies or unlicensed spectrum.
