The accelerating implementation and remarkable popularity of sophisticated mobile devices, including notebook computers, cellular phones, sensors, cameras, portable GPS (Global Positioning System) receivers, and wireless handhelds such as PDAs (personal digital assistants), contribute to development of wireless grids. Wireless grids feature a flexible and adaptable cyberinfrastructure that supports coordinated and economical access to distributed resources and next-generation applications and services. Generally, wireless grids are classified as ad hoc or standalone, and mixed-mode or hybrid. Ad hoc wireless grids enable diverse applications via MANETs (mobile ad hoc networks) and consist of mobile devices that operate in infrastructureless environments. Mobile network nodes process tasks and provide best effort delivery service to support wireless grid applications (Lima, Gomes, Ziviani, Endler, Soares, & Schulze, 2005). In the healthcare environment, for example, ad hoc wireless grids equipped with sensors monitor the status of critically ill patients and track the location of hospital equipment and supplies. Hybrid or mixed-mode wireless grids augment and extend the capabilities of wireline grids to remote locations; facilitate the shared use of resources and processing power; and consist of components ranging from supercomputers to distributed or edge devices such as very small satellite aperture terminals (VSATs) (Harrison & Taylor, 2006). This chapter features an introduction to factors contributing to the development of present-day wireless grids. Wireless grid technical fundamentals, specifications, and operations are examined. Security challenges associated with safeguarding wireless grids are reviewed. Finally, the distinctive characteristics of innovative wireless grid initiatives are explored and research trends in the wireless grid space are described.
Established by virtual organizations (VOs), wireline grids facilitate trusted resource exchange in environments that cross multiple administrative domains. Wireline grids consist of substantial collections of shared networked components and resources for enabling reliable and dependable multimedia delivery; implementation of sophisticated bandwidth-intensive applications; scientific discovery in fields that include high-energy physics, medicine, astronomy, and bioinformatics; and e-collaborative problem resolution (Littman, 2006).
Wireline grids increasingly employ a high-performance DWDM (Dense Wavelength Division Multiplexing) cyberinfrastructure that supports wavelengths of light, or lambdas, on demand to facilitate reliable and dependable access to computational simulations, metadata repositories, large-scale storage systems, and clusters of supercomputers (Littman, 2006). Also called lambda-grids, DWDM grids, such as the TeraGrid, enable terabit and petabit transmission rates; teraflops and petaflops of compute power; seamless connectivity to feature-rich resources; and extendible grid and inter-grid services across multi-institutional distributed environments.
The popularity of multifunctional 3G (third generation) wireless technologies and devices and demand for anytime and anywhere access to grid resources are major factors contributing to design and implementation of wireless grids by mobile dynamic virtual organizations (MDVOs). MDVOs are extensions of VOs that facilitate wireless grid deployment in infrastructureless and hybrid wireless environments. Wireless grid operations are dependent on network node mobility (Waldburger, Moraiu, Racz, Jahnert, Wesner, & Stiller, 2006). As a consequence, wireless grids are not as reliable as wireline grids in seamlessly and dependably supporting multimedia applications and services.
Key Terms in this Chapter
Lambda: Lightpath or wavelength of light that interlinks two network endpoints.
Cyberinfrastructure: Advanced network platform that supports wireless and/or wireline grid research initiatives, applications, and experimentation. Used by the National Science Foundation (NSF) to describe next-generation grid initiatives.
Wireless Grid: A cyberinfrastructure that interconnects wireless devices in ad hoc or infrastructureless and hybrid or mixed-mode wireline and wireless grid configurations.
Web Services (WSs): Collections of protocols and open standards for enabling the convergence of WSs and wireless and/or wireline grid operations.
Web Services Description Language (WSDL): Defines an XML (extensible markup language) grammar for describing network services as collections of network endpoints that enable information exchange.
Global Toolkit Version 4 (GT4): A grid toolkit that supports grid interoperability and works in concert with the Web Services Resource Framework (WSRF).
Dense Wavelength Division Multiplexing (DWDM): Provides flexible and dynamic optical lightpaths on-demand to support extendible, scaleable, and reliable wireline grid and intergrid services and supports access to next-generation applications requiring high-bandwidth connections.
Network node: An endpoint or redistribution point for data transport.