Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-05-12
2003-07-22
Le, Thanh Cong (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S432300, C455S435100
Reexamination Certificate
active
06597910
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. Section 119 from an application for METHOD FOR MAKING NETWORK DIRECT SYSTEM SELECTION IN A CELLULAR COMMUNICATION SYSTEM filed earlier in the Korean Industrial Property Office on May 13, 1999 and there duly assigned Serial No. 17146/1999.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cellular mobile communications system, and more particularly, a method for directly connecting a mobile station (MS) in communication with a mobile switching center (MSC) from one network to an MSC in another network.
2. Description of the Related Art
In a cellular mobile communication system, a service area is divided into a plurality of cells, each with a base station system (BS) therein. The base stations are controlled by a mobile switching center (MSC) to enable the MS to make voice or data communication while roaming from one cell to another. With reference to
FIG. 1
, there is illustrated a conventional cellular communications system, which includes a mobile station (MS)
10
in communication with a base station (BS)
20
, and an MSC
30
coupled to a plurality of base stations, a PSTN Public Switched Telephone Network (PSTN)
60
, and another MSC
40
. The MSC coupled to the plurality of base stations (BSs) may be defined as one network.
The cellular network, as shown in
FIG. 1
, further includes a Home Location Register (HLR), which is a database maintaining all subscriber information, e.g., user profiles, current location information, International Mobile Subscriber Identity (IMSI) numbers, and other administrative information. The HLR
50
can service multiple MSCs, as shown in
FIG. 1. A
Visitor Location Register (VLR)
35
coupled to the MSC
30
is a database containing information about all MSs currently located within the MSC
30
/VLR
35
area. Thus, the MSC establishes a call connection upon receiving a call request from the user of an MS, by accessing the HLR
50
and VLR
35
/
45
for the requisite identification information of the MSs registered in the network. If an MS
20
roams into a new MSC
40
/VLR
45
area, the VLR
45
connected to the MSC
40
will request data about that MS
20
from the HLR
50
database. Accordingly, if the user of the MS
20
wishes to make a call, the local VLR
45
will have the requisite identification information. In the aforedescribed manner when the MS requests the call set-up or the location registration, the MS
30
/
40
first searches the VLR
35
or
45
, then the HLR
50
retrieves various subscriber information of the MS.
In such mobile communications network, the HLR
50
can selectively elect one of the MSCs
30
and
40
to be connected to the MS, depending on the type of service requested by the MS. This is known as the Network Direct System Selection (NDSS), used to provide a specific service that is requested by the MS. For example, if an MS in communication with an MSC requests the Internet service but the MSC is not equipped with the packet data service capability, the HLR having the requisite information can determine another MSC with the Internet service capability to be connected to the MS. The operation of NDSS involves transmitting NDSS signaling messages and processing the message through the network (BS, MSC, HLR, VLR, etc.) which enables the MS to roam between different networks to receive various services or the optimal route. This type of NDSS operation is usually performed when the MS requests the registration of an additional function (e.g., voice message service, Internet service, call forwarding service, etc.), the location registration, or the call transmission.
The information regarding the current location of the MS is received in the CM SERVICE REQUEST message. Thus, when an MS in communication with the BS transmits the CM SERVICE REQUEST message with an NDSS code to request a certain feature/service, the VLR of the MSC relays this message to the HLR. The same message is relayed when the MS transmits the LOCATION UPDATE REQUEST message for registering the location of the MS, or when the MS transmits the CM SERVICE REQUEST message for requesting a call set-up as requested by the MS. Thereafter, the HLR confirms the NDSS code of the MS and determines the new MSC for providing the service as indicated in the NDSS code, then transmits the QUALIFICATION DIRECTIVE message or the REGISTRATION NOTIFICATION RETURN message back to the VLR of the MSC. Then, the MSC transmits the SERVICE RE-DIRECTION message to the MS via the BS to register the MS in the new MSC area or request the new MSC to generate a call. The address of the new MSC area is represented by the ID information included in the SERVICE RE-DIRECTION message.
However, in the above conventional NDSS operation, there are areas that need to be addressed to improve the communication efficiency. First, there is no means for the user of the MS to know whether the HLR has successfully registered the MS with a specific service as requested by the MS. For example, if the MS requests the Internet service or the voice mailing service, the user is not notified of whether the MS has been provided with the voice mailing service in the current the NDSS operation. Also, there is no protocol or set method for the VLR to transmit the QUALIFICATION DIRECTIVE message with the SERVICE RE-DIRECTION message therein from the HLR to the MS. Moreover, when performing the location registration through the NDSS operation, the procedures for transmitting the LOCATION UPDATE REQUEST from the MS to the MSC and for exchanging the REGISTRATION NOTIFICATION RETURN message between the MSC and the HLR are not defined by the TSB-80 of A-Interface in the present EIA/TIA North America CDMA Communications Standard. Furthermore, when the MS, which is already registered in the VLR, requires a call generation and transmits an NDSS code requesting a specific service, the VLR has no means to determine whether the MS is registered for the specific service. Hence, the VLR may establish a call-set up without consulting with the HLR and fails to provide the appropriate MSC that has the capability to provide the requested service.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for performing the Network Direct Select System (NDSS) in a communication system whenever the MS transmits an NDSS code requesting a specific feature/service from the system.
It is another object of the present invention to provide a method for performing the Network Direct Select System (NDSS) in a communication system whenever the MS executes the location registration.
It is a further object of the present invention to provide a method for performing the Network Direct Select System (NDSS) in a communication system whenever the MS attempts to establish a call set-up.
According to one embodiment of the present invention, a method for performing the NDSS operation of an MS in a cellular communications system includes steps of: inserting, by a BS, a dialed phone number with an NDSS code in a CM SERVICE REQUEST message to be transferred to a first MSC; transmitting, by the first MSC, an NDSS FEATURE REQUEST INVOKE message of the MS to the HLR after confirming the dialed phone number of the NDSS; transmitting, by the first MSC, a FEATURE REQUEST INVOKE CONFIRMATION message to the MS via the BS; upon receiving the FEATURE REQUEST INVOKE message from the first MSC, determining, by the HLR, whether a second MSC needs to be designated for providing the requested service; transmitting, by the HLR, a QUALIFICATION DIRECTIVE message to a first VLR of the first MSC and including a service re-direction information in the QUALIFICATION DIRECTIVE message if is determined to require the second MSC service; determining, by the first VLR, whether the QUALIFICATION DIRECTIVE message contains the service re-direction information; transmitting, by the first VLR, the service re-direction message including the service re-direction informati
Cha & Reiter
Cong Le Thanh
Samsung Electronics Co,. Ltd.
Tran Tuan
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