Applications Enabled by Direct Broadcast Satellite Technology

Before we describe our strategies for supporting applications within the DBS system, it is important to gain a better understanding of the kinds of applications that are suited to broadcast-based information dissemination. Consider the following applications scenarios, which illustrate some of the possibilities inherent in the DBS system:

· Rapid Information Dissemination: A major forest fire is burning out of control in a National Park. Firefighters are being brought in from several adjacent states, and they are not familiar with the disaster area. Detailed forest service maps are needed to help them plan their disaster response, but there are not enough to go around. A DBS dish is rapidly installed in the disaster management command center, a complete set of digital maps are quickly downloaded over the DBS broadcast channel. Depending on where the individual teams are to be sent, selected maps are further distributed to mobile computers (perhaps over a WLAN in the command center) or computers embedded in support vehicles (perhaps via a campus-area packet relay network that spans the depot around the command center) that are then taken into the field by the firefighter teams.

· Integrated Broadcast Video and Interactive Data Services: Rural health centers around the country are equipped with DBS dishes. A “medical practitioners channel” is established to transmit DirectTV broadcasts of the latest medical procedures. During these broadcasts, a viewing physician can use the system’s data communications capabilities to interactively select from a collection of medical journal articles that describe the procedure or treatment currently on view be downloaded into his or her personal computer.

· Information on Demand: Up-to-the-minute weather reports are captured for the entire country and fed into a DBS “digital weather channel.” For major metropolitan areas (or areas in which the weather is changing rapidly or is particularly severe), these reports are frequently scheduled. They may include high resolution “moving” weather maps (e.g., in MPEG) as well as detailed textual descriptions of the current weather conditions, perhaps specialized to specific regions of the metropolitan area. DirectPC users can enable filtering programs to capture the reports for their areas (or where they are planning to travel to). Users in less populated regions will receive their reports on a much less frequent basis. Nevertheless, they can use the system’s uplink capabilities to request a report “on demand,” and the network will schedule its delivery for a future time slot. If multiple users request the same information, its priority can be increased, and a sooner slot can be allocated to transmit the requested information.

DBS systems can be installed rapidly, even in areas without a well developed communications infrastructure, although some uplink path will be needed, perhaps through the public switched telephone system. This makes DBS ideal for establishing communications in support of emergency response activities, and the system is particularly effective at distributing critical information to the field.

DBS was developed primarily to deliver video to users. However, the ability to integrate interactive data access with simultaneous video broadcasts opens new opportunities for information dissemination combined with television. Distance learning applications that combine broadcast telelectures on DirectTV with simultaneous access to instructional materials on DirectPC is but one example.

The final scenario shows how a broadcast channel could be efficiently structured to combine frequent and less frequent data retrieval requests.

Text 6

1. Read the text.

2. Divide the text into paragraphs.

3. Express the idea of each paragraph in one sentence.

4. Write a summary of the text in English.