The Vertical Blanking Interval

The TVnet™ system is built on two key technologies. The first is based on a standards-based methodology of placing Internet traffic on multiple vertical blanking interval (VBI) lines in a TV signal. Incorporated with a telephone line (wireless or wireline) backchannel, PC/TVnet has developed a patented technology enabling the "bonding" of multiple TV channel data paths thus providing data links at one-way speeds of up to 200Kbps per TV channel. PC/TVnet-placed equipment at local partner stations sends out requests for data to be gathered by redundant West and East Coast servers called "Distributors." These requests are defined by an end user profile that the user creates to specify the desired email server, cached web pages and ticker information. Data is compressed, encrypted, and routed to the correct station where it is stored at the Local Collector server. If the end user has established a network session, the data is sent in the VBI to the uniquely addressed PC hardware receiver for that user. Data streams to the laptop or desktop PC equipped with a VBI capable TV tuner card. As the TV signal is a constant transmission medium, end users receive email, web and ticker updates constantly. The back channel, provided by a wireless or wireline phone connection, is only required for sending email, the occasional syncing with the server, and profile configuration. When a back channel connection occurs, a background resynchronization task carefully uses phone bandwidth to update the proxy profile and to retrieve any email and Web pages missed due to a PC being turned off or a power or transmission failure.

This network diagram shows the various components in the TVnet system architecture. During session initiation, the client goes online via a cellular data call, updates its profile to the Distributor and goes off-line. Then, the proxy client, running on the Distributor can make requests (i.e. get mail, get web updates, stock ticker info) for the client and comply with TCP/IP (especially TCP "acks"). The Distributor will route received data from the requested web server or mail server to the Local Collector/Inserter Controller at the TV station that broadcasts to the client. If the client's profile indicates that he is receiving, the data is passed to the TVnet (VBI) inserter where it is introduced into the TV signal and broadcast. Upon receipt of the TV signal, the client decodes the TVnet data signal.


The second key to the system is the TVnetNow™ caching technology. The TVnet service introduces the concept of a proxy server running on a client. The proxy receives the continually streaming IP traffic, constantly updating the changed web pages. This unique method of web caching allows web page content to stream to the end user's laptop or desktop PC at all times the system is powered. When requesting a page that is part the predefined profile or the bookmark collection, access is lighting fast and always current. The TVnet service works with Windows 95 and 98 platforms enabled with a VBI capable TV tuner card. The service uses the IP over VBI methodology for integrating and separating the data streams from the TV signal. The service also works with the standard market-leading Internet applications on the end user laptop such as the browsers Netscape Navigator and Microsoft Internet Explorer and the email clients Eudora and Microsoft Outlook. No special browser or email applications are needed. In addition to the traditional applications for web browsing and email, the TVnet service also includes a ticker for news, stocks, sports, weather and other information. A web interface to the Distributor allows the end user to define the profile.