US 5406643 Method and apparatus for selecting between a plurality of communication paths

ABSTRACT – In a data communication system (100), a method is provided to distinguish between and select from multiple communication paths (4,6,and 8)to a designated end point (10). The communications path selection is done locally, on a portable subscriber unit (2). The communications path is transparent to requesting software application (30). The method manages a plurality of communications devices (42,44) using existing communications infrastructure.


This invention relates generally to data communication and, in particular, to a method for distinguishing between a plurality of communication paths and selecting from those a communications path for use.


Data and voice communications technologies have advanced rapidly in recent years, leading to the immergence of different and typically incompatible communication systems, such as paging, cellular, telephone data, and radio packet data. Initially, the users of such systems accepted their inherent incompatibility. The modern trend, however, is for system users to expect and demand higher levels of compatibility between and interconnection to the currently available communications platforms. Thus, a cellular radiotelephone communication system must interconnect with the land-line telephone system, and wireless LAN (local area network) systems must now operate as extensions of wired LANs in order to achieve and sustain commercial viability.

In response to this pressure, manufacturers of communication-capable portable and fixed devices, such as personal organizers and laptop computers, are beginning to incorporate multiple communication technologies into their products. It is anticipated that the device user will learn to view the different technologies as merely alternatives for performing the same type of operation.

As the level of systems interoperability increases, the differences between the various communications technologies, hereinafter referred to as media or medium, will become less important. Ultimately, it is anticipated that user involvement in the selection process will diminish to a point where the user may not even know which media is being used at any given instant.

To achieve this end, there is need for a method for enabling a portable subscriber unit to automatically select one of a plurality of available communications media based at least partly upon its knowledge of potential communication paths. A need also exists for a data communications method that creates, for different software applications, a common interface to communications systems which typically employ incompatible communications protocols.

Current techniques for providing communications media selection suggest routing all such inquiries to a central host for processing. Selection of the appropriate media is performed by the central host, whose decision may or may not be returned to the requesting device. As is appreciated, this process necessitates transmitting request traffic over a communications network. Such message traffic can significantly impact overall system throughput. Moreover, the centralized control of communications media selection may result in overloading during periods of high volume. Such systems typically require infrastructure upgrades and modifications in order to provide the requisite centralized control.

It would be extremely advantageous therefore to provide a method and apparatus whereby a portable subscriber unit automatically selects one of a plurality of available communications media based on knowledge of the available communication paths.


Briefly described, the present invention is a method and apparatus for permitting a subscriber unit to select from amongst a plurality of communications media, that particular media for establishing a communications path to a specified end point. According to one aspect of the invention, the method for permitting a subscriber unit having memory and communication resources to select one of a plurality communications paths to a designated destination comprises the steps of: storing in memory a list of communication paths having associated attributes; receiving a connection command comprising destination and communications criteria; selecting from the list, at least one communications path, as a function of destination; and establishing a connection to the selected communications path.

A preferred embodiment of the present invention comprises a packet server module and at least one device manager module, wherein a number of software application programs request data communications by interfacing to the packet server. The packet server maintains a session list identifying currently available connections (virtual links) to a specific end point, and selects a communications path based at least partly upon knowledge of the destination. The device manager maintains a list specifying the possible communications paths to specific end points and actually controls the communications resources responsible for establishing a communications path.

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