Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1999-12-22
2002-07-23
Vincent, David (Department: 2732)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S331000, C370S469000, C455S440000
Reexamination Certificate
active
06424639
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods and systems related to notifying a mobile terminal device when an interworking function to which it is connected by a wireless link changes to a new interworking function.
2. Description of Background Information
Mobile computing generally involves the use of mobile terminal devices such as notebook computers connected to a computer network (e.g., the Internet) via a wireless communication device (e.g., a mobile phone). “Mobile IP” is a functionality in wireless communications where mobile terminal devices connected to the Internet may send and receive packets addressed with their home network IP (Internet Protocol) address (a static IP address) while their current point of attachment to the Internet (i.e., their current interworking function) changes. This allows the mobile terminal device to maintain its connection with another entity through a packet-based link, and facilitates two-way communication over that link.
FIG. 1
is a block diagram of a simplified network reference model applicable to mobile computing data services, including mobile IP support. The model shows select network entities forming a communications subsystem
10
. A mobile terminal device
12
is coupled to a wireless communication device
14
, which is in turn connected to a base station/mobile switching center
16
via a wireless interface. The base station/mobile switching center
16
is connected to an interworking function
18
. The simplified network reference model is described in the document entitled “Data Service Options for Wideband Spread Spectrum Systems,” TIA/EIA/IS-707, Published Version (February, 1998), the content of which is hereby expressly incorporated by reference herein in its entirety (herein referred to as “IS-707”).
According to IS-707, mobile terminal device
12
, communication device
14
, base station/mobile switching center
16
, and interworking function
18
are respectively referred to as a TE2 device, an MT2 device, a BS/MSC and an IWF. The interface between mobile terminal device
12
and the wireless communication device
14
is called a Rm interface. The interface between wireless communication device
14
and base station/mobile switching center
16
is referred to as an Um interface. The interface between base station/mobile switching center
16
and interworking function
18
is referred to as an L interface.
Mobile terminal device
12
may comprise, for example, a notebook computer, a personal digital assistant, or any other computing device capable of computer network communications, including packet-based communications or communications via a dial-up modem. Wireless communication device
14
may comprise, for example, a wireless terminal used by subscribers to access the network services over a radio link. The wireless terminal may comprise a hand-held cellular telephone, or a unit installed in a vehicle. Wireless communication device
14
may,also be fixed to a particular location.
Base station/mobile switching center
16
is shown in
FIG. 1
as a single functional entity, although it need not be. The base station portion of the illustrated base station/mobile switching center allows wireless communication device
14
to access network services using a radio link or another type of wireless link. The mobile switching center portion handles the switching of traffic between the wireless link and a telecommunications network to which the wireless link is connected. The telecommunications network may comprise one or a combination of public switched telephone: network (PSTN), integrated services digital network (ISDN), internet routers, and other network types and entities.
Interworking function
18
represents the point at which a gateway or bridge connection is formed between mobile terminal device
12
and/or wireless communication device
14
at one end and the Internet at the other end.
FIG. 2
is a simplified diagram of a protocol stack adhered to by many mobile computing environments, including those adhering to IS-707. The stack comprises one or more lower layer(s)
28
, a data link layer
26
, a network layer
24
, and one or more upper layers
22
. One or more lower layers
28
are provided. These lower layers include, among other things, connections establishing a physical link, and may also include a relay layer as disclosed in IS-707, a paging channel
30
, and a traffic channel
32
.
Data link layer
26
is immediately above lower layer(s)
28
. Data link layer
26
may utilize such protocols as PPP and/or SLIP. This layer deals with point-to-point communication between two computers. It packages addressing data, and manages the flow of transmissions. PPP is described, for example, in RFC 1661, “The Point-to-Point Protocol,” (July 1994), the content of which is hereby expressly incorporated by reference herein in its entirety. PPP facilitates the transmission of datagrams between data communications equipment from different manufactures over a dial-up and dedicated serial point-to-point links. PPP can simultaneously transmit multiple protocols across a single serial link, without the need to set up a separate link for each protocol. PPP also allows the interconnection of dissimilar devices, such as host bridges and routers, over serial links. The PPP protocol is comprised of three main components, including an encapsulation scheme, the link control protocol, and network control protocols. These components are respectively responsible for creating the frame, controlling the link, and managing the network layer protocol.
Network layer
24
is just above data link layer
26
, and may comprise such protocols as IP or connectionless network protocol (CLNP). The network layer ensures that information arrives at its intended destination. That is, it is concerned with the actual movement of information from one network entity to another. The internet protocol (IP) breaks up data messages into packets, routes the packets from a sender to a destination network entity, and reassembles the packets into the original data messages at the destination. The IP protocol contains an IP header which contains source and destination address fields that uniquely identify host computers respectively acting as the source and destination of the packets being transferred.
Upper layer(s) portion
22
comprises one or more protocol layers above network layer
24
, including, for example, the TCP (transmission control protocol) that facilitates the reliable in-order delivery of an input data stream.
Various protocol techniques are specified to achieve IP mobility support in RFC 2002, “IP Mobility Support,” (October, 1996) (hereinafter referred to as “RFC 2002”), the content of which is hereby expressly incorporated by reference herein in its entirety. As described in RFC 2002, IP mobility support allows a mobile node to communicate with other nodes after changing its link layer point of attachment to the Internet, yet without changing its IP address. The mobile node will ideally be able to communicate with other nodes that do not implement these mobility functions, and there should be no need for protocol enhancements in hosts, routers, or bridges that are involved in the routing of packets to and from the given mobile node that supports IP mobility.
“Agent discovery” is a method disclosed by RFC 2002 by which a mobile node will determine whether it is currently connected to the Internet via its home network or via a foreign network, and when it is connected through a foreign network, the mobile node detects when it has moved from one foreign network to another. Agent discovery involves both agent advertisements and agent solicitations which can be sent and received by mobile nodes, foreign agents, and home agents. Network entities called “Mobility Agents” send agent advertisements which are received by the mobile node and which indicate when a given foreign network changes. These agent advertisements are sent over traffic channel
32
to the mobile node which, in the network model sho
Abrol Nischal
Lioy Marcello
Brown Charles D.
Pappas George C.
Qualcomm Incorporated
Vincent David
Wadsworth Philip
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