Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-03-16
2001-03-06
Maung, May (Department: 2681)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S552100, C455S560000
Reexamination Certificate
active
06198920
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to the transportation of data through dissimilar communications media. More particularly, the present invention relates to an apparatus and method for transporting data between a remote mobile or fixed terminal device and a host system over multiple, dissimilar communications media. The communications media over which the data is transported include wireless data links, wired data links or a combination of wireless and wired data links which are selected based upon a set of preference metrics.
2. Background Information
The ability to transport data between mobile and/or fixed terminal devices and host computer systems have been generally available for many years. Networks designed to transport this data currently exist in a wide variety of wireless and wired network architectures. Both apparatus and method exists for transporting data through multiple, similar media types as well as the automatic selection of alternate communication paths based upon a plurality of preference metrics.
Often, when multiple networks are available from a common location such as a vehicle, great benefit may be derived by allowing uniform communications through all available networks. Certain networks may perform better for bulk data transfers where another may perform interactive messaging in an optimal fashion. One network may be preferable because of its low cost but an alternate, more expensive network may be acceptable as a backup if the low-cost network is unavailable.
Other examples include U.S. Pat. No. 5,412,375, to WOOD, which discloses a system for selecting one of a plurality of interfaces to a single wireless communications system in accordance with the capabilities of a subscriber unit and the capabilities of a base unit. A list of air interface capabilities of the subscriber unit and the base unit are compared by a controller to determine a compatible interface. As disclosed in WOOD, the plurality of air interfaces include Analog Mobile Phone System (AMPS), Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA). While the WOOD system does select from one of a plurality of interfaces which may be applicable for data communication, the routing decision is based on the capabilities of the endpoints rather than the preference metrics of the transporting networks. The endpoint devices, in this case, must be aware of the peculiarities of the wireless environment.
U.S. Pat. No. 5,420,574, to ERICKSON et al., discloses a subscriber unit attached to a trunked mobile radio having a data input. The mobile radio communicates both voice and data message formats over a wireless network to a base station via channels that are allocated by a trunked data controller which is connected to a host network. Channel states and communication parameters are set in accordance with the type of information (e.g., voice or data) that is being transmitted or received. While the ERICKSON et al. system dynamically switches between incompatible message formats without the intervention of the endpoint devices, only a single data path is provided. In addition, the incompatibility of the two alternate paths arises from a difference in message formats rather than the use of independent, incompatible networks.
Further, the transportation of data through alternate, incompatible communications media is a problem that does not have a uniform solution in the art. This problem is exacerbated in wireless communication networks where protocols, timing and other incompatibilities render an otherwise acceptable level of service inadequate. Attempts to provide data links through incompatible networks have suffered from the same obstacles that hindered data communications prior to open standards becoming widely accepted, i.e., proprietary protocols visible to the endpoint terminal devices make the devices inflexible and expensive and the interoperation of similar devices with incompatible networking components is difficult and complex.
Networks may be interconnected by routers which operate at the network level and convey messages between compatible networks. Routers make logical decisions about the pathway through which data is to be directed in the networks based upon a variety of preference metrics. A router is generally implemented as an autonomous device with multiple connections to the networks through which data is to be routed. Routers operate at the network layer and can recognize and manage protocols and multiple connections to networks. Routers usually operate in accordance with the address provided by the particular protocol of the network, and normally provide routing between and through networks utilizing the same network protocol and can route between networks that use different data-link layers, such as Ethernet, Token-Ring, Serial PPP, etc. Another type of router includes two routers loosely-coupled through a protocol-neutral data-link, where the linked routers are considered as a single “virtual” router.
Dissimilar networks may be connected by gateways which are devices that interconnect two or more dissimilar networks. A gateway differs from a router in that the endpoint terminal devices may implement a dissimilar or incompatible protocols. Gateways often perform specific protocol conversions at the layers above the network layer to move data from one type of network to another. In this regard, the Open Systems Interconnection (OSI) model includes seven “layers” to provide communications between heterogeneous (i.e., incompatible) systems. The layers, from lowest to highest, are: the physical layer, the data link layer, the network layer, the transport layer, the session layer, the presentation layer, and the application layer. Each of the layers performs a specific task in transporting data between two or more entities. Such a layered structure is shown in The
TCP/IP Companion,
by Martin R. Arick, Wiley-QED, pp. 18-19.
U.S. patent application Ser. No. 08/456,860, to DOVIAK et al., for example, discloses a system in which a distant mobile or fixed terminal device transports data through a plurality of wireless network to an endpoint which may or may not implement the same network protocol as the distant device. However, while the DOVIAK et al. system is capable transmitting data over a plurality of dissimilar wireless communications networks, the system does not automatically transmit data through differing ones of a plurality of dissimilar networks in accordance with preference metrics to reach the data-link endpoints. Thus, the system does not automatically provide redundant or alternate pathways through which data may be delivered.
U.S. Pat. No. 5,537,220 to EZUMI et al., discloses a portable facsimile apparatus provided with a capability to communicate over a plurality of communications lines. As disclosed in EZUMI et al., the facsimile machine may communicate over telephone lines or a mobile communication unit. A NCU (controller) is provided within the facsimile machine to discriminate whether the facsimile machine is connected to the telephone line or to the mobile communication unit. The NCU functions to adjust the data rate, and transmitting and receiving signal levels based on which communication system it is communicating. Although this concept may be extended to a generic protocol-neutral data networking environment, the EZUMI et al. system provides for the selection of only one single path to the exclusion of other, possible viable path based solely on which link is plugged into the NCU. Further, the EZUMI et al. system does not switch communication paths within the boundaries of a communication session thereby further limiting its usefulness in a connectionless, packet data environment such as a TCP/IP network.
U.S. Pat. No. 5,602,843, to GRAY, discloses a PBX-based integrated telecommunications system having a wired subsystem connected to wired terminals, and a wireless system for connecting to mobile terminals. A controller is provided which manages base stations and communicates to wireless han
Doviak William
Houvig Flex
Whitmore David L.
Gelin Jean A
Greenblum & Bernstein P.L.C.
Maung May
PADCOM, Inc.
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