Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1998-07-23
2003-08-19
Olms, Douglas (Department: 2661)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S229000, C370S328000
Reexamination Certificate
active
06608832
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to mobile communications, and more particularly, to different services and features that may be employed to establish and enhance communications between a mobile station in a mobile communications network and an external network entity.
BACKGROUND AND SUMMARY OF THE INVENTION
The main application of most mobile radio systems like the Global System for Mobile communications (GSM) has been mobile telephony which typically only supports circuit-switched communications where guaranteed, “fixed” circuits are dedicated to a user for the duration of a call. However, packet-switched applications, like facsimile transmission and short message exchange, are becoming popular in mobile networks. Example data applications include wireless personal computers, mobile offices, electronic funds transfer, road transport telemetry, field service businesses, fleet management, etc. These data applications are characterized by “bursty” traffic where a relatively large amount of data is transmitted over a relatively short time interval followed by significant time intervals when little or no data is transmitted.
While bursty traffic can be transmit using a circuit-switched channel, such a transmission underutilizes that channel because there are likely large intervals between bursts when the channel is reserved but is not being used, there is no information to be transmit from or received by the user. From an efficiency view point, this is a waste of transmission resources which are particularly limited for radio communications. However, from a customer service view point, because a circuit-switched channel is not shared with other users, the user is essentially guaranteed a certain quality of service. In addition to inefficiency, it takes a relatively long time to set up and take down a circuit-switched call compared with individual packet routing in packet-switched sessions. In bursty traffic situations, packet-switched bearers better utilize the transmission bandwidth because a communications resource is used only when there is data to transmit. Communication channels are therefore typically shared by many users. Another advantage is that in contrast to time-oriented charging applied for circuit-switched connections, packet-switched data services allow charging depending on the amount of data actually transmitted and on the quality of service of that transmission.
In order to provide such mobile data applications, packet radio network services accommodate connectionless, packet-switched data services with high bandwidth efficiency. One example is the General Packet Radio Service (GPRS) incorporated into the existing circuit-switched GSM network. Another is the Cellular Digital Packet Data (CDPD) network used into the existing D-AMPS network. A significant interest of end users of a mobile packet data service such as GPRS is that wireless PCs support conventional Internet-based applications like file transfer, submission and reception of e-mail, and “surfing” the Internet via the worldwide web. Conferencing and playback applications, including video and multimedia, are also important services to be supported by mobile networks.
Although circuit-switched services are well known in mobile networks, mobile packet-switched services are quite new. Therefore, a brief description of the latter using GSM/GPRS as an example is now provided.
FIG. 1
shows a mobile data service from a user's point of view in the context of a mobile communications system
10
. An end user communicates data packets using a mobile host
12
including for example a laptop computer
14
connected to a mobile terminal
16
. The mobile host
12
communicates for example with a fixed computer terminal
18
incorporated in a local area network (LAN)
20
through a mobile packet data support node
22
via one or more routers
24
, a packet data network
26
, and a router
28
in the local area network
20
. Of course, those skilled in the art will appreciate that this drawing is simplified in that the “path” is a logical path rather than an actual physical path or connection. In a connectionless data packet communication between the mobile host
12
and fixed terminal
18
, packets are routed from the source to the destination independently and do not necessarily follow the same path (although they can).
Thus, independent packet routing and transfer within the mobile network is supported by a mobile packet data support node
22
which acts as a logical interface or gateway to external packet networks. A subscriber may send and receive data in an end-to-end packet transfer mode without using any circuit-switched mode network resources. Moreover, multiple point-to-point, parallel applications are possible. For example, a mobile host like a mobile PC might run at the same time a video conference application, an e-mail application, a facsimile application, a web browsing application, etc. The video conference application would typically require more than one data stream (hereafter referred to as an application flow).
FIG. 2
shows a more detailed mobile communications system using the example GSM mobile communications model that supports both circuit-switched and packet-switched communications and includes a circuit-switched network
35
and a packet-switched network
51
. A mobile host
12
including a computer terminal
14
and mobile radio
16
communicates over a radio interface with one or more base stations (BSs)
32
. Each base station
32
is located in a corresponding cell
30
. Multiple base stations
32
are connected to a base station controller (BSC)
34
which manages the allocation and deallocation of radio resources and controls handovers of mobile stations from one base station to another. A base station controller and its associated base stations are sometimes referred to as a base station subsystem (BSS). The BSC
34
is connected to a mobile switching center (MSC)
36
in the GSM circuit-switched network
35
through which circuit-switched connections are set up with other networks
38
such as the Public Switched Telephone Network (PSTN), Integrated Services Digital Network (ISDN), etc.
The MSC
36
is also connected via a Signaling System Number 7 (SS7) network
40
to a Home Location Register (HLR)
42
, a Visitor Location Register (VLR)
44
, and Authentication Center (AUC)
46
. The VLR
44
includes a database containing the information about all mobile stations currently located in a corresponding location or service area as well as temporary subscriber information needed by the MSC to provide services to mobiles in its service area. Typically, when a mobile station enters a visiting network or service area, the corresponding VLR
44
requests and receives data about the roaming mobile station from the mobile's HLR and stores it. As a result, when the visiting mobile station is involved in a call, the VLR
44
already has the information needed for call setup.
The HLR
42
is a database node that stores and manages subscriptions. For each “home” mobile subscriber, the HLR contains permanent subscriber data such as the mobile station ISDN number (MSISDN) which uniquely identifies the mobile telephone subscription in the PSTN numbering plan and an international mobile subscriber identity (IMSI) which is a unique identity allocated to each subscriber and used for signaling in the mobile networks. All network-related subscriber information is connected to the IMSI. The HLR
42
also contains a list of services which a mobile subscriber is authorized to use along with a current subscriber location number corresponding to the address of the VLR currently serving the mobile subscriber.
Each BSC
34
also connects to the GSM packet-switched network corresponding to GPRS network
51
at a Serving GPRS Support Node (SGSN)
50
responsible for delivery of packets to the mobile stations within its service area. The gateway GPRS support node (GGSN)
54
acts as a logical interface to external data packet networks such as the IP data network
56
. SGSN nodes
50
Nguyen Brian
Nixon & Vanderhye P.C.
Olms Douglas
Telefonaktiebolaget LM Ericsson
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