[Technology Report]
My Embedded System Is On The Internet–What About Yours?
In the fight for seamless communications, embedded and information systems are joining forces and drawing upon the Net.
Virtually every embedded designer is looking to use digital communications to enhance or expand the reach of embedded systems. With new designs breaking ground and existing ones adding capabilities, the competition to develop the most compelling communications model is fierce.
The answer won't be found by looking at what others are trying to do. The "me too" approach was useful in providing alternatives to established products in the past. But it simply won't make the grade in product cycles measured in months, rather than years.
Engineers have to look to embedded communications architectures that might become viable in the future. They must examine the communications infrastructure, as well as existing and emerging standards for embedded systems and communications. New models for communications networks and embedded architectures also will have to be investigated.
Wireless protocols and standards comprise one enabling technology for the class of information appliances currently under development. That's a critical issue, because the full potential of mobile devices will depend on improvements in the digital wireless technologies needed to deliver high-bandwidth data to small portable devices. So far, the devices are arriving on the scene much faster than the bandwidth needed to support them.
But wire-based technologies are far from dead. They're actively vying for the lead in delivering data to an interconnected world. The telecoms have an advantage right now, with an array of medium and bandwidth options ranging from analog plain old telephone service (POTS) to T-3 and beyond with the optical carrier (OC) standards. But delays and misunderstandings remain common in the installation and configuration of anything with higher bandwidth than POTS. It also boasts a complex pricing strategy. So telecoms may not be best prepared to provide the communications infrastructure.
By taking advantage of that telecom infrastructure, some vendors have adapted copper wire to several different types of digital-subscriber-line (DSL) service. Currently, DSL technologies are being offered to commercial and residential customers as alternatives to POTS and ISDN. But the DSL signal has range limitations that prevent large parts of the potential user base from taking advantage of it. Plus, installing it in telephone-company head offices all over the country requires expensive equipment. Broadband through cable lines is growing steadily, but it's primarily a residential-only alternative.
High-End Systems Being Served Special-purpose networks are emerging, however, for those who can justify their own infrastructure. For high-end embedded systems, vendors like CETIA offer ATM networking for VME bus systems. Gigabit Ethernet interconnections also are available. Typically, these systems use networking to deliver streaming video or multimedia, or to multiplex a large number of data channels.
Meanwhile, wireless standards for data communications are advancing. The latest specification to become available is the Wireless Application Protocol, or WAP. It can be built on any operating system and provides service interoperability even between different device families. WAP specifies two essential elements of wireless communication: an end-to-end application protocol and an application environment based on a browser.
The application protocol is known as the Wireless Transfer Protocol (WTP). It's a lightweight communications protocol that's based on TCP/IP and embedded in each WAP-enabled device. On the application side, there's a language called the Wireless Markup Language (WML). Derived from the XML meta language, it's designed for use on devices without keyboards.
The network side includes a server gateway implementing the other end of the protocol, which is capable of communicating with any WAP devices. This gateway handles requests from the device and goes out onto the Internet or other network to gather the requested data. It then formats the data and sends it to the device.
WAP presents an intriguing model for wireless applications. But not all devices need both the capabilities and the limitations of wireless communications. In reality, embedded communications will be some combination of wired and wireless. Wireless communications is simply too convenient, especially for mobile devices. Significant problems stand to be overcome, however, with both bandwidth and RF interference.
Devices will want to take advantage of the elaborate wire networks already in existence. They're likely to be fixed in the home or office, and will need a new or existing LAN to connect with one another, the gateway, and the rest of the entire world.
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