Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1999-06-07
2002-11-19
Yao, Kwang Bin (Department: 2664)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C455S450000
Reexamination Certificate
active
06483822
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to protocols and systems for establishing a packet switched network model connection between a mobile terminal device and a packet network via a wireless connection formed between a wireless communication device and a base station.
2. Description of Background Information
Mobile computing generally involves the use of mobile terminal devices such as notebook computers connected to computing resources via a wireless communication device. As mobile computing becomes more prevalent, traveling users will be provided continuous connectivity, and thus full access, to their computing resources—data and files stored at their office LAN, email servers, etc. To make this a reality, efforts abound to develop and introduce new data services and technologies.
FIG. 1
is a block diagram of a simplified network reference model applicable to mobile computing data services. 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. 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), (hereinafter referred to as “IS-707”) as well as in the newer version thereof, i.e., IS-707-A. The content of each of IS-707 and IS-707-A is hereby expressly incorporated by reference herein in its entirety.
According to IS-707, mobile terminal device
12
, wireless communication device
14
, base station/mobile switching center
16
, and interworking function
18
are respectively referred to as a TE
2
device, an MT
2
device, a BS/MSC, and an IWF. The interface between mobile terminal device
12
and wireless communication device
14
is called an Rm interface. The interface between wireless communication device
14
and base station/mobile switching center
16
is referred to as a Um interface. The interface between base station/mobile switching center
16
and interworking function
18
may be implemented with 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 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 PSTN, ISDN, internet routers, and other network types and network 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 an internetwork 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, RFC 1332, “The PPP Internet Protocol Control Protocol (IPCP)” (May, 1992), RFC 1661, “The Point-To-Point Protocol (PPP)” (July, 1994), and RFC 2002, “IP Mobility Support” (October, 1996). 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, including, at the lowest layer, connections establishing a physical link. The relay layer disclosed in IS-707 is included in these lower layers above the physical layer.
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 communications between computers. It packages addressing data and manages the flow of transmissions. PPP (the point-to-point protocol) is described, for example, in RFC 1332 (May, 1992), 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 manufacturers over 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, a 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 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 network layer is responsible for getting data from one computer 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) protocol which is responsible for reliable, in-order delivery of data from one application to another.
Two types of mobile data calls may be placed by a mobile terminal device
12
through a wireless communication device
14
: circuit switched (including fax calls) and packet switched. In a circuit switched mobile data call, a circuit switched connection is made between mobile terminal device
12
and a given target network. Mobile terminal device
12
makes this connection by establishing a dial-up modem connection directly over a circuit switched network to a modem-accessible target network—e.g., to an internet service provider (ISP) or to an office network or LAN. In a packet switched call, a direct connection is established between mobile terminal device
12
at one end and a packet network at the other end through interworking function
18
.
There are generally two modes of operation in which packet switched calls can be placed: the network model and the relay model. In a relay model packet call, a packet switched connection is made between mobile terminal device
12
and the network through interworking function
18
, while wireless communication device
14
acts as a conduit, at the physical layer. Accordingly, if there is a change in the connection between interworking function
18
and wireless communication device
14
(e.g., the physical link therebetween is temporarily interrupted), the call may be dropped between mobile terminal device
12
and interworking function
18
.
On the other hand, in a network model packet call, two separate PPP lin
Abrol Nischal
Lioy Marcello
Brown Charles D.
Greenhaus Bruce W.
Harper Kevin C.
Wadsworth Philip
Yao Kwang Bin
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