Portable internet access device back page cache
The present invention aims to provide a system that allows multiple users operating a PDA (Personal Digital Assistant), receiving information from a server via a cellular phone, to access the Internet or the World Wide Web (WWW), view and interact with these images remotely on a display screen. The invention relates to the priority in which packets or blocks of information are transferred to and displayed on the screen of the PDA device. The invention further relates to various methods to reduce the amount of data sent to the PDA for back pages or previously viewed web pages, stored in the cache memory of the PDA and also mirrored on the server's memory. Various algorithms may be used by the server to determine what information is to be removed from the PDA's cache memory, as it approaches its full capacity.
1. A host computer which receives information from an outside source, contains a browser with a window which renders and freezes the information onto a virtual display in its memory, wherein a software program reduces the color depth of the virtual display, compresses the virtual display and sends it to a remote device capable of receiving, decompressing, storing into memory and displaying it to a user on a display screen, wherein if the user clicks on the display screen or enters text on the remote device, the display is unfrozen at the browser and the virtual display sent again to the remote device only if the information has changed.
2. The device as claimed in claim 1 such that:
if the user clicks on the display screen or enters text on the remote device, the display is unfrozen at the browser and the virtual display sent again to the remote device with all moving parts.
3. The device as claimed in claim 1 such that the virtual display must be completely downloaded and rendered first on the host computer, before any information is sent to the remote device.
4. The device as claimed in claim 1 such that:
the remote device saves information in a cache memory and the host computer also saves into memory the same information sent to the remote device, and where in memory it is stored on the remote device;
if the user instructs the remote device to display previously viewed information, the host computer is informed by the remote device and would instruct the remote device what to display and where this information is located in cache memory;
if the information the user wants to view has changed at the outside source, the host computer would send the parts of information that have changed to the remote device to be stored in cache and displayed;
the host computer uses algorithms to decide what information is stored in cache memory on the remote device.
5. The device as claimed in claim 1 such that the host computer may vary the rate at which information is sent to the remote device or vary the time taken to send information to the remote device.