Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1999-01-19
2001-08-07
Olms, Douglas (Department: 2661)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S352000, C370S401000
Reexamination Certificate
active
06272129
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
This invention relates to the fields of telecommunications and wireless Internet Protocol (IP) network routing. More particularly, the invention relates to a process by which a mobile communications device, for example, a laptop computer equipped with a cellular telephone modem, is located and communication between the device and a terminal on an IP network is initiated.
B. Description of Related Art
Wireless communications networks offer much flexibility to the user, in that they allow users of portable communications devices, such as personal digital assistants, laptop computers, telephones, and other appliances to get connected to the public switched telephone network from any location within the region served by the wireless network. Connolly et al., U.S. Pat. No. 5,325,419, discloses a personal communication system by which a user uses an RF link to a communicate with an intelligent base station. The intelligent base stations provide radio access along with an Integrated Services Digital Network (ISDN) interface to the public switched telephone network. The PSTN aspect of the system has three components: a personal communications switching center, where telephone central office switches have certain characteristics, a signaling transfer point, and a service control point where an intelligent data base exists maintaining certain user features and records.
The patent application of Yingchun Xu, et al., Ser. No. 08/887,313, assigned to the assignee of the present invention and which is fully incorporated by reference herein, describes a system by which a wireless communications device such as laptop computer may access a packet-switched (e.g., IP) data network such as a corporate backbone network or the Internet. In the Xu et al. system, a frame relay line connected to the wireless network couples the remote wireless user to the packet-switched network via an all-digital network access server. This type of network access server may be configured as an InterWorking Unit (IWU) and the two terms are occasionally used interchangeably herein. The network access server provides an interface to the frame relay line and wireless network and an interface (including router functionality) to the packet switched network. The Xu et al. application further discloses certain accounting and routing techniques that permit the network access to authorized users, while at the same time providing convenient authorization and accounting techniques to be performed by the entity operating the network access server. Network access servers suitable for use as a platform for an IWU are, per se, known in the art and commercially available from companies such as 3Com Corporation. They are also described in the patent literature. See, e.g., the patent awarded to Dale M. Walsh et al., U.S. Pat. No. 5,528,595, incorporated by reference herein.
In the prior art, the mobile device typically must dial into the IP network through a network access server in order to gain access to the IP network and communicate with a terminal on the network. If a terminal on the network were to attempt to initiate communication with the mobile terminal on its own, the terminal on the network and/or other communications elements in the IP network or wireless network would have to know several things: where the mobile terminal is located, whether it was within range of the wireless network, whether it was ready to receive the data (i.e., booted up), and possibly still other pieces of information, such as the information uniquely identifying the device in the wireless network such as its International Mobile Subscriber Identity (IMSI) number and/or its Electronic Serial Number (ESN). Obviously, this circumstance makes it quite cumbersome, if not impossible, heretofore, for a terminal on the IP network to initiate communication with the wireless device. For example, if a home agent for the mobile device receives an incoming IP packet for the device but does not have a record of where the device is located (e.g., a mobility binding record indicating where to send the packets received from the terminal), it would simply drop the packets.
The present invention attempts to overcome these problems and provide a simple, efficient and automatic way of permitting the terminal on the IP network to initiate communication with the mobile wireless communications device. More specifically, the invention uses the paging ability of the wireless network to locate the wireless mobile communications device whenever a terminal on the IP network attempts to send a packet whose IP destination address matches that of the mobile device. Once the mobile device has been paged the mobile node device automatically becomes connected to the IP network and is able to communicate with the remote terminal.
SUMMARY OF THE INVENTION
A method is provided for automatically locating and connecting a mobile wireless communications device (“device”) to an IP network. The nature of the device is unimportant, and for illustrative purposes could be a laptop computer equipped with a cellular telephone modem, a personal digital assistant such as the Palm Pilot product from 3Com Corporation, or some other suitable appliance. Regardless of its nature, the device should be capable of being paged via a wireless communications network.
The method comprises the steps of receiving an Internet Protocol (IP) packet from a terminal on the network and destined for the device. The IP packet is received at a home agent for the device, which may be a router on the IP network which acts as mechanism for coordinating the receipt and transmission of communication sessions for the device in conjunction with other telecommunications equipment, described in more detail below. In a preferred embodiment, the home agent comprises a router that is coupled to a local area network (LAN) on which resides an authentication server, one or more InterWorking Units (network access servers coupling the wireless network to the local area network and IP network) and a Signaling System 7 network agent coupling the local area network to a Signaling System 7 network.
The home agent then transmits an Access-Request message to the authentication server for authentication. An example of such an authentication server is a RADIUS server (a known device) providing accounting, authorization and authentication functions for a plurality of mobile users. The Access-Request message includes a destination IP address for the wireless device that was included in the IP packet from the terminal on the network.
The authentication server responsively issues an Access-Accept message to the home agent if the device is authorized to receive the IP packet, in other words, if the user operating the device has paid its bills, is a subscriber to the service, etc. The Access-Accept message includes two pieces of data: (a) information uniquely identifying the device that is being “called” by the remote terminal, such as the IMSI/ESN number of the device, and (b) information identifying a particular network to use to locate the device, such as the local area network or the Signaling System 7 network.
In the event that the local area network is specified, the home agent transmits a message, such as an Address Resolution Protocol (ARP) packet containing the IMSI/ESN number or other information uniquely identifying the device, on the designated network to a mobile node location server. In a preferred embodiment, one of the network access servers on the LAN is configured to be the mobile node location server. The mobile node location server maintains a table mapping current IP addresses for a plurality of mobile communication devices to the information uniquely identifying the devices. In the event that the IMSI/ESN number for the device is not found by the mobile node location server in the table, indicating that the device is not currently registered with or communicating with the IP network and has no current, valid IP routing address, the mobile node location server responsively ini
Bezaitis Andrew
Cichosz Wayne A.
Dynarski Richard J.
Xu Yingchun
3Com Corporation
McDonnell & Boehnen Hulbert & Berghoff
Nguyen Brian
Olms Douglas
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