HK1036379B - Method and apparatus for reducing messaging traffic in a wireless communication system - Google Patents

Description

Method and apparatus for reducing messaging traffic in a wireless communication system

Background

Field of the invention

The present invention relates generally to wireless communication systems, and more particularly to a method and apparatus for reducing messaging traffic by disabling registration procedures for an open-ended mobile phone.

Description of related Art

Registration in a cellular communication system is the process by which a mobile station informs the cellular communication system whether the station is powered on and communicating through which base station. The mobile station may be a cellular radiotelephone or a personal communication device in the form of a typical car radio or portable radio.

Calls directed to a mobile station are often referred to as mobile terminated calls. The communication system must determine whether the mobile station is already on and which base station the mobile station is receiving. To locate a mobile station, a cellular communication system broadcasts a message, commonly referred to as a page, from a number of base stations. If the mobile station responds to this, the cellular communication system then processes the call with further communications to the base station of the coverage area in which the mobile station is located. It should be further appreciated that the paging process is often used for mobile station location to facilitate other transactions with the mobile station. A base station and its coverage area are often referred to as a cell.

If the system does not know the location of the mobile station, the system must broadcast pages in sectors of each base station. As the volume of mobile terminated traffic increases, the communication resources supporting the system for extensive paging rapidly become enormous in most metropolitan areas.

For communications directed to a mobile station, the cellular communication system uses registration information to reduce the amount of paging required to locate, initiate or establish a communication link with the mobile station. The registration information is also used to determine the group of base stations broadcasting the paging signal.

There are many registration methods known in the art, including power-up registration and registration into the coverage area of each new base station. Many communication systems, such as the "advanced mobile phone service" (AMPS) and "global system for mobile communications" (GSM) classes, employ a periodic or counter method to determine the location of a mobile station. These methods, while far from ideal, can effectively reduce the amount of paging required in a communication system. The registration process is similar for various modulation schemes, including AMPS, TDMA, and CDMA. The CDMA registration method IS described in detail in the American Telecommunications industry Association IS-95 and IS-95A (referred to herein as IS-95 for short).

The mobile station may operate in one of a number of different states. For example, IS-95 describes an initialization state, an idle state, a system access state, and a traffic channel state. A mobile station operating in this idle state typically requires registration at regular intervals to inform the base station of its location. However, not all mobile stations need to be registered. Specifically, registration is not required for a mobile station that is not currently subscribed to a communication system. These mobile stations are not authorized to operate in the system, but under current registration agreements, require registration in the same manner as subscribed mobile stations. With the increasing number of mobile stations manufactured and marketed today, the number of mobile stations not actively subscribed to the system is becoming more and more. Therefore, the number of unregistered unnecessary traffic caused by such invalid mobile stations starts to be generated in an unacceptable amount, which negatively affects system resources and network bandwidth.

Currently, mobile stations are not able to discover whether their subscription is valid or not, and registration procedures specified by cellular communication standards do not allow communication system operators to selectively prohibit registration of invalid or unsubscribed mobile stations.

One solution to this problem is to completely disable the mobile station until its subscription to the communication system is initiated. This approach has a number of disadvantages. The key point is that the mobile station cannot utilize cross-space (OTA) programming, which is becoming a popular method for programming mobile stations. In addition, if the mobile station is completely disabled, no other communication is possible. For example, an emergency call cannot be completed. Even if the mobile station subscription to the system is not valid, service providers still have a strong desire for mobile station operators to be able to make such calls. Moreover, future rules and standards will likely require such characteristics.

There is a need for a method and apparatus for selectively cutting off the registration process for mobile stations that have not been enabled or have a service discontinuity while still allowing other communications to occur.

Summary of the invention

The present invention is a method and apparatus for inhibiting the registration process of a mobile station in an inactive communication system. This greatly reduces the message traffic on the air interface, as well as between communication systems, which in turn allows the communication systems to increase capacity and reduce interference between mobile stations.

The present invention provides information on the status of its subscription to each mobile station in the communication system. The subscription status of the mobile station is stored in a storage device within the mobile station. If the mobile station subscription status is "dormant," the air interface registration procedure normally performed by the mobile station is released. All other communications between the mobile station, one or more base stations, and the system controller can still occur.

A new mobile station that has never been used will be initialized at the factory first to set the subscription status to "dormant", thereby preventing unnecessary registrations. When the service is opened, the subscription state of the mobile station is switched to 'on' through manual programming or cross-space (OTA) programming of the storage device so as to work normally. Later, if service needs to be terminated for a particular mobile station, the subscription status is changed to "dormant" under the management of the MSC's communication system, with the status being communicated to the mobile station to be deactivated. The deactivation command changes the mobile station subscription status to "inactive" and prevents any further registration until the subscription status returns to "active".

Brief description of the drawings

The features, objects, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings. The same letter and meaning are the same throughout the drawings, in which:

FIG. 1 illustrates an exemplary wireless communication system;

FIG. 2 shows a detailed view of the components of a communication system incorporating components of the present invention;

FIG. 3 is a flow chart of steps of a processor employed by the present invention.

Detailed description of the preferred embodiments

In most wireless communication systems, such as cellular, PCS or satellite communication systems, some scheme is required to track the position and status of mobile stations within the system. In the absence of such information, the control information to a particular mobile station requires a page prepared solely for the particular mobile station and broadcast in some predetermined common format throughout the system coverage area to ensure that the particular mobile station is linked. In a registration mode, the mobile station informs the system controller or Mobile Switching Center (MSC) of its own status and location. The MSC records location information in a database, commonly referred to as a Visitor Location Register (VLR), and upon receipt of a message intended for a particular mobile station, references the VLR to determine which base station(s) to use to relay signals for the particular mobile station.

Referring to fig. 1, when a mobile station 10 registers with a Mobile Switching Center (MSC)40 through a base station 30, one or more identification parameters are transmitted to enable the MSC40 to track the mobile station 10 as it operates throughout the communication system. MSC40 represents any communication center in the communication system that stores information regarding the status of mobile stations and is not limited to the embodiment in the communication system of fig. 1. Such a communication center also performs other functions such as billing and interfacing to the Public Switched Telephone Network (PSTN). The identification parameters transmitted include information about the mobile station serial number, unique telephone number or other unique identifier, mobile station slot cycle index number, mobile station class number, or a combination of these or other parameters. The registration information is received by a transceiver (not shown) located at a base station 30 of the coverage area where the mobile station 10 is located. The registration information is relayed by the base station 30 to the MSC 40. Although not shown in fig. 1, many base stations are typically employed in a typical communication system and each base station is coupled to the MSC40 by a wired interface, such as T1, or by fiber optic cables.

The information sent during registration is stored with registration information from other mobile stations in a database, referred to as a Visitor Location Register (VLR), typically located within the MSC 40. For example, mobile station 20 is another mobile station that is in a different location than mobile station 10, and the information for mobile station 20 is also stored in the VLR. In a registration event, such as power-on or entering the service area of base station 30, mobile station 10 and mobile station 20 each transmit a registration message to base station 30 indicating that they are active within the coverage area of base station 30. Registration information is stored in the VLR so that the MSC uses this information to determine the location of a mobile station in the communication system when it needs to contact a particular mobile station.

When a mobile station leaves the coverage area of a particular base station, its registration information is changed in the VLR. For example, if the mobile station leaves the coverage area of a base station 30 and enters the coverage area of another base station, the mobile station registration information will change to reflect that the mobile station is no longer in contact with the base station 30. If a mobile station leaves the coverage area of the entire communication system, its registration information is completely removed from the VLR associated with the system.

The coverage area of each base station in a communication system is often represented as a hexagon. It should be appreciated, however, that in an actual cellular communication environment, the base station coverage areas may vary in size and shape. It should further be appreciated that base station footprints tend to overlap with footprint boundaries defined by footprint shapes other than the ideal hexagonal footprint shape. Also, a base station may be sectorized, such as three sectors, as is known in the art. The cellular communication system of figure 1 may be an analog or digital communication system and employ one or more types of multiple access modulation schemes, such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), or frequency division multiple access (FDM).

Before a mobile station in a communication system makes and receives calls, the mobile station must be subscribed to by a service provider. For example, when a mobile station, such as a wireless telephone, is initially purchased from a retailer, it should be enabled by the service provider process or a subscription initiated. This is typically a two-step process. First, the mobile station is programmed with parameters such as Mobile Identification Number (MIN), telephone number, class, etc. which are provided by the network management center 60. This information is also provided to the Home Location Register (HLR) 50. HLR50 is a database containing information about individual mobile stations subscribed to by the communication system controlled by network management center 60. This information is provided to the mobile station manually or in a cross-space programmed manner.

The MSC40 is in direct contact with the HLR50 for several reasons. One reason for this is to determine whether the subscription status of a mobile station in the communication system is enabled or inactive. If the status of the mobile station is dormant, calls to or from the particular mobile station will not be allowed.

The public network 70 is in contact with the MSC40 and the HLR 50. Public network 70 represents the Public Switched Telephone Network (PSTN) or the SS7 public network and interfaces with public networks in other communication systems. As a mobile station moves from one communication system to another, its location is transmitted to base stations located in those communication systems through a registration process. The location of the mobile station is communicated to the communication system to which the mobile station is "affiliated," i.e., the communication system to which the mobile station is actively subscribed. The location of the mobile station is stored in its "home" HLR 50. Calls to mobile stations located in other communication systems are then routed to the other communication systems based on the information stored in HLR 50.

To stop the mobile station's service, the network management center 60 sends a message requesting a change of the subscription status of a certain mobile station to "dormant". The signal is sent to HLR50 where the mobile station subscription status changes to reflect that the mobile station is no longer a valid subscriber in the system. However, in existing communication systems, no message is forwarded to the mobile station informing of the status change. As a result, all functions of the mobile station are still enabled. For example, the mobile station may then monitor nearby ambles, perform a null switch, and acknowledge messages sent by the MSC 40. Details of these and other functions performed by the mobile station 10 may be found in issued U.S. patent 5,577,022. The patent entitled "pilot signal searching techniques for cellular communication systems" is incorporated herein by reference. The mobile station continues to perform registration procedures in accordance with protocols established by international standards, i.e., AMPS, GSM, CDMA, etc. These registrations are unnecessary since the mobile station is not authorized to make or receive calls in the communication system.

These unnecessary registrations negatively affect the communication system in two ways: they affect the air interface, wasting network resources. In a CDMA system, transmissions from a mobile station cause interference to other mobile stations, resulting in a need for more energy to transmit, thereby reducing system capacity. Another negative impact on the air interface results in a reduction in circuitry, i.e., modulators, demodulators and modems, in the particular base station with which the mobile station communicates. The increased costs associated with the transmission of unnecessary information between different communication systems results in network resources also being negatively affected by the amount of unnecessary message traffic. For example, as a mobile station roams from one communication system to another, it will register with the MSC of each communication system. At the same time, a signal is sent to the mobile station's "home" communication system alerting it to the location of the mobile station. The cost of this message traffic is relatively high and is unnecessary in the case of unsubscribed mobile stations.

Fig. 2 is a more detailed illustration of the MSC40, base station 30, and mobile station 10, showing the necessary components to implement the present invention in a communication system 200. Mobile switching center 40, processor 210, HLR50, network management center 60, public network 70, timer 218, VLR220, transceiver 270, and antenna 275 represent communication system 200. It should be appreciated that although only one base station 230 is illustrated in fig. 2, the communication system 200 typically employs a plurality of base stations, each in communication with the MSC 40.

For purposes of discussion, it will be assumed that mobile station 10 is an active subscriber in communication system 200 and has been programmed with the necessary information to contact MSC 40. For example, mobile identification numbers and telephone numbers have been assigned to mobile station 10 and stored in memory device 260 and HLR 50. Such information may be received through manual programming or via cross-space programming over the air interface. Further, assuming that the mobile station 10 is already registered with the base station 30, the registration information of the base station 30 is stored in the VLR 220. It should be appreciated that although HLR50 is shown in fig. 2 as a separate entity from MSC40, HLR50 may in another embodiment be located within MSC40 or within MSC 40.

In an exemplary embodiment of the present invention, the mobile station 10 includes a storage device 260 for storing various other information including the status of the mobile station subscription. The mobile station subscription state is one of two states: "active" or "inactive". If the mobile station subscription status is in the "enabled" state, the mobile station 10 is permitted to perform all of the various functions associated with communicating with the MSC 40. For example, a mobile station user may place or receive telephone calls, and the mobile station 10 may perform various basic tasks to support such calls, registration, air-switching, preamble searching, and energy control. In summary, the mobile station 10 has complete functionality when the mobile station subscription status is "subscribed to. In the exemplary embodiment, storage 260 is non-volatile, meaning that once mobile station 10 is powered down, the data stored therein is not lost and is retrievable upon subsequent power-up.

According to the invention, if the mobile station subscription status is "dormant", the registration process is simply prohibited. Other functions that may be implemented by the mobile station 10 will be performed in the usual manner. For example, the mobile station 10 may still search for an amble signal, respond to a paging signal, and implement a null handoff. The mobile station 10 may even send an origination message for the call attempt. However, because the mobile station subscription status is stored in HLR50, the call cannot be connected. If the MSC40 determines that the subscription status of the mobile phone is "dormant," the call cannot be connected to its intended recipient.

The subscription of a mobile station may in many cases be changed from an "active" state to a "dormant" state and vice versa. For example, in a typical embodiment, the subscription status is set to the "dormant" status after the mobile station is initially produced. To enable telephone service, the subscription status in both the mobile station and the HLR50 is changed. The subscription status of mobile station 10 or HLR50 will change to a "dormant" status if telephone service is to be terminated, for example if the mobile station user no longer requires the service, or if the user is late for a communication service fee that must be paid.

In current communication systems, the mobile station subscription status is changed only in the HLR50, allowing the mobile station 10 to continue to perform various communication functions such as paging, communication, and registration. The present invention provides mobile station subscription status for the mobile station 10 when the HLR50 changes. When the subscription status changes to "dormant", only the registration process is prohibited, thereby eliminating unnecessary registrations. Other paging and communication functions may still be possible.

The mobile station subscription status may be changed manually or by programming across space. If manual programming is employed, the user of the mobile station typically may take the mobile station to a service center, such as network management center 60, for manual programming. The I/O device 265 provides an interface to change the status of a mobile station subscription. The I/O device 265 is typically a keyboard in combination with a display, where the display allows authorized personnel to enter desired changes through the keyboard to change the predetermined state. The access code is required to change the subscription status to avoid the user from changing. The subscription status is provided to the information processor 255 which accesses the storage device 260 as required by the I/O device 265 while changing the mobile station subscription status. Once the mobile station subscription status has changed, the status remains stored in the storage device 260 until the next change. The network management center 60 then notifies the HLR50 that the mobile station is now a valid subscriber in the communication system 200.

Alternatively, the mobile station subscription status may be changed by programming across space, as shown in fig. 3. The mobile station user or network management center 60 may make a request to change the status of the subscription, as shown in step 300 of fig. 3. In either case, a request to change subscriptions is sent from the network management center 60 to the processor 210 and the HLR 50. The mobile station subscription status is changed in HLR50 to reflect the current subscription status, i.e., active or inactive.

As shown in step 305 of fig. 3, processor 210 communicates the mobile station subscription status to mobile station 10 informing mobile station 10 of the updated subscription status stored by HLR 50. The processor 210 records the subscription status transfer with the timer 218 for confirmation, as will be described below. The transceiver 225 modulates the mobile station subscription information in accordance with communication protocols well known in the art to transmit data to the base station 30. The modulated mobile station subscription information is transmitted to the base station 30 by the data link 230. The data link 230 is typically a T1 link, although wired or wireless communication links may be employed. The base station 30 is one of a plurality of base stations throughout the communication system 200. The mobile station subscription status is sent to at least one base station 30 with which the mobile station has recently registered. In a related embodiment, the mobile station subscription status is transmitted by a paging channel reserved for communication channels used by the mobile station to receive and transmit overhead information in the communication system.

The base station 30 modulates the mobile station subscription status information using some well-known modulation scheme, such as TDMA, CDMA, AMPS. The subscription status information is transmitted as a single message by one of a plurality of communication channels, such as a traffic channel or a paging channel. Alternatively, other techniques known in the art may be used to transmit the subscription status information, such as appending this information to existing information, or combining this information with other information to be transmitted to the mobile station 10. The modulated subscription status is transmitted via antenna 240 to the mobile station 10 via antenna 275. The transceiver 270 demodulates the mobile station subscription status so that it may be passed to the processor 255. Upon receiving the demodulated mobile station subscription status, the processor 255 accesses the storage device 260 and changes the mobile station subscription status to conform to the received subscription status. The latest mobile station subscription status is thus stored in the mobile station 10, as shown in step 310 of fig. 3.

If the mobile station subscription status change in the memory device 260 is successful, the processor 255 sends an acknowledgement signal to the MSC40 informing it that the subscription status has changed. This step is illustrated in figure 3, step 315. If the mobile station subscription status is not received by the mobile station 10 for some reason or if the mobile station subscription status is received without a change in the memory 260, no acknowledgement signal is sent.

At MSC40, processor 210 waits to receive an acknowledgement from mobile station 10. The subscription status is again transmitted if the acknowledgement signal is not received within the predetermined time of the processor 210 and the timer 218. As shown in step 320 of fig. 3. This process is repeated until an acknowledgement is received or a predetermined number of failed attempts are recorded.

If the subscription status changes to the "dormant" status, the mobile station 10 is prevented from transmitting further registration information. For example, in a typical CDMA communication system based on IS-95, there are nine registrable types. The nine registration types are power-up, power-down, timer registration, distance registration, area registration, parameter change, ordered registration, implicit registration, and traffic channel registration. When processor 255 determines that an event has occurred requiring registration, memory 260 is first accessed to determine whether the mobile station subscription status is in the "enabled" or "dormant" state. If the subscription status is "dormant", registration is prohibited, thereby reducing unnecessary transmissions, avoiding increased interference between mobile stations, and wasting valuable system bandwidth and resources.

The IS-95 no reserved variable now indicates the mobile station subscription status. Thus, in one embodiment, new subscription state variables must be defined. In the exemplary embodiment, the new variable is called "MOBILE SUBSCRIPTION STATUS" (MOBILE _ SUBSCRIPTION _ STATUS), and is 1 bit long. The variable is set to "0" to indicate an invalid subscription status, and "1" to indicate a valid subscription status. This variable is transmitted from the MSC40 to the mobile station 10 in accordance with the transmission procedure described above. IS-95 does not have the clause set for this variable and therefore changes must be made to the system.

In another embodiment, no new subscription state variables are required. Thus, no significant system changes are required for communication systems employing IS-95 CDMA. In another embodiment, an existing MOB _ TERM _ XXXP variable, stored in storage 260 and specified by IS-95, IS used to disable the registration process. There are also three IS-95 specified MOB _ TERM _ XXXP variables, which are MOB _ TERM _ HOMEP, MOB _ TERM _ FOR _ SIDP, and MOB _ TERM _ FOR _ NIDP. IS-95 also specifies a variable REG _ ENABLED that enables or disables autonomous registration. Autonomous registration is initiated by the mobile station's response to the event without explicit indication of registration by the base station or mobile switching center. Examples of autonomous registrations are registrations when a mobile station is powered on or off, registrations after a predetermined time has elapsed since a previous registration, and registrations based on the location of the mobile station. When autonomous registration is disabled, the mobile station registration process actually ends. The REG _ ENABLED state depends in part on the MOB _ TERM _ XXXP variable. The autonomous registration is disabled by setting the three MOB _ ERM _ XXXp variables to '0' and REG _ ENABLED to 'NO'. It should be appreciated that other forms of registration are possible, even if autonomous registration is not possible. For example IS-95 specifies many other forms of registration controlled by base stations or mobile system controllers. IS-95 specifies such registrations as parametric transformation registrations, ordered registrations, traffic channel registrations, and implicit registrations. This type of registration is possible even when autonomous registration is prohibited. However, most of the registration traffic can be cancelled with the cancellation of the autonomous registration.

The previous description of the embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (12)

1. A method for reducing messaging traffic in a wireless communication system, the traffic including over-the-air messaging with a network, said system including a mobile switching center, at least one mobile station, and at least one base station, said method comprising the steps of:

providing a mobile station subscription status for at least one mobile station;

storing the subscription status of the mobile station in a storage device;

if the mobile station subscription status indicates that the mobile station is dormant, the mobile station is prohibited from registering with the communication system.

2. The method of claim 1, further comprising the steps of:

allowing said at least one mobile station to also communicate with said mobile switching center even if said mobile station subscription status indicates that said mobile station is dormant.

3. The method of claim 1, further comprising the steps of:

transmitting an acknowledgement signal from the mobile station to the mobile switching center immediately after storing the mobile station subscription status in the storage means;

and re-transmitting the mobile station subscription status by the mobile switching center if the confirmation signal is not received by the mobile station switching center within a predetermined time.

4. The method of claim 3 wherein the step of retransmitting the mobile station subscription status is repeated a predetermined number of times.

5. The method of claim 2, wherein the step of allowing the at least one mobile station to also communicate with the mobile switching center comprises enabling an emergency call to be placed.

6. The method of claim 2, wherein the step of allowing the at least one mobile station to also communicate with the mobile switching center comprises providing the at least one mobile station with the capability of cross-space programming.

7. An apparatus for reducing messaging traffic in a wireless communication system, the traffic including over-the-air messaging with a network, the system including a mobile switching center, at least one mobile station, and at least one base station, the apparatus comprising:

a storage device for storing the subscription status of the mobile station;

a first processor, connected to the storage device, for storing the mobile station subscription status and storing the mobile station subscription status in the storage device;

and prohibiting registration of the mobile station with the communication system if the mobile station subscription status is inactive.

8. The apparatus of claim 7 wherein said first processor issues an acknowledgement signal if said mobile station subscription status has changed.

9. The apparatus of claim 8 further comprising a timer coupled to said second processor for providing time to transmit a mobile station subscription status, said second processor retransmitting said mobile station subscription status if said acknowledgment signal is not received within the time of subscription from a last transmission of said subscription status.

10. The apparatus of claim 7, wherein the storage device is a non-volatile memory.

11. The apparatus of claim 7, further comprising I/O means for changing the mobile station subscription status in said storage means.

12. The apparatus of claim 11, wherein the I/O device comprises a keyboard and a display.