Signals -- December 1994
Researchers at ISR's Center for Satellite and Hybrid Communication Networks (CSHCN) have collaborated with Hughes Network Systems engineers to develop a low-cost hybrid (terrestrial and satellite) network service that can deliver data from the Internet to the user at much faster rates. Hughes announced the commercial availability of the technology in November of 1994, and will begin to market their new line of products, DirecPC(TM), to businesses and computer enthusiasts early next year.
Satellite technology makes it possible for DirecPC(TM) to provide nationwide service immediately, eliminating the need for incremental upgrades to the cable or telephone plants in each locality. According to Hughes representatives, users equipped with a 9,600 bps modem could experience a 40-fold increase in speed in receiving material using DirecPC(TM).
DirecPC(TM) is a hybrid system consisting of a receive-only satellite dish coupled with a special SLIP telephone/modem connection. Increasing the rate at which users can receive information is desirable because most computer users, especially those in a home environment, want to consume much more information than they generate. A receive-only satellite terminal is considerably less expensive to manufacture and much easier to install than one that can also transmit. Internet protocol encapsulation manipulates the transmission control protocol/internet protocol (TCP/IP) to route packets away from and back to the user asymmetrically.
"Our joint effort to develop inexpensive hybrid terminals that can provide a variety of services to the user and to foster hybrid communications is the most promising path to the National Information Infrastructure, both technically and financially" said Dr. John Baras, director of the Systems Integration Laboratory and the CSHCN. "As the most direct demonstration of these capabilities we are developing a variety of tools that can extend Internet services through satellite broadcasting, while at the same time providing the end user with higher quality service."
DirecPC(TM) uses a device driver developed at ISR's CSHCN that breaks the network link into two physical channels: the terrestrial dial-up that carries data from the terminal into the Internet and a receive-only satellite link that carries information from the Internet to the user. This system is aimed at supporting bandwidth-hungry Internet applications such as Mosaic and FTP and it works with the Internet without any modifications. In addition, it is compatible with any Intel 80386/486 or Pentium PC.
A market analysis conducted prior to the development of the system imposed four design requirements for the commercial success of the product. The system must reduce delay responding to requests for large data files using a modem; work with any commercial TCP/IP package and any commercial SLIP service provider; access any Internet host; and support Internet initiated connections.
A wireless broadcast mode of communication offers extraordinary efficiencies compared to wireline communications, even where the wireline service employs sophisticated packet switching techniques. Traditional radio and TV broadcasting have exploited the efficiencies of the broadcast mode for years using terrestrial radio frequencies. Newer satellites offer TV and radio broadcasts from the vantage of a geosynchronous orbit in space. Hughes currently markets a satellite dish and television set top box called DirecTV(TM) designed on this basis. DirecTV(TM) provides 150 channels of digital television.
DirecPC(TM) expands the scope of the evolution from terrestrial to satellite broadcast beyond radio and TV to data services delivered to the remote personal computer. The Internet and numerous commercial online data services, such as Reuters New Media, America Online(TM), Compuserve(TM) and Prodigy(TM), could benefit from this enhancement to satellite-based broadcasting.
The system and resulting products can now be used to provide high performance, affordable services in several areas, including linking elementary and high schools to digital libraries (with images), providing telemedicine and cooperative diagnosis systems, and linking news and business services.
Participants in this work were Douglas Dillon, Ilya Faenson and William Stanton, of Hughes Network Systems, and Dr. Baras, Aaron Falk, Narin Suphasindhu, Vivek Arora and Tim Kirkwood, of ISR. It was supported by ISR's CSHCN, a NASA Center for the Commercial Development of Space; Hughes Network Systems; and the state of Maryland, under a cooperative industry-University contract from Maryland Industrial Partnerships.