Description of Related Art Advances in microelectronic technology have provided numerous portable computer-like devices. Portable computer-like devices include, for example, Personal Digital Assistants (PDA), Handheld Personal Computers (HPC), and smart phones.

A PDA is a handheld device which acts like an electronic organizer or diary.

Among the functions performed by a PDA include small scale database applications, word processing, and appointment scheduling. A handheld personal computer, often referred to as a"palm top"provides personal computing in a handheld device. A smart phone is a microcontroller-controlled electronic telephone with a touch sensitive screen that interactively allows a user to place a call, send E-mail, and perform certain financial transactions.

Each of the foregoing devices provide a user with computer-like functions.

However, in contrast to desktop computers, the foregoing devices are portable, thereby permitting a user to be mobile. Additionally, with advances in cellular telecommunications, the functions of the foregoing devices are expanded to client/server applications as well.

Computer systems are often connected to another computer system, typically a server, to form a computer network. When networked together, communication between the separate computer systems is possible. A server is a class of shared computers that are used to handle service common to all connected computers, known as clients. A common use of the server also includes handling and maintaining databases, and controlling access to voice mail, E-mail, or facsimile.

Performing the foregoing functions at a server is advantageous because the same functions can be accessed from any of the clients which can be located about a large geographic area. Additionally, the functions can be simultaneously accessed by more than one client.

Clients often access servers using a wireline connection, such as through the public switched telephone network or a coaxial cable. However, advances in cellular telecommunications technologynow allow clients to access servers using the mobile air interface. Because a wireline connection is no longer required, handheld computer-like devices can access server functions without restricting the user's mobility. A computer, or computer-like device accessing a server using the air interface is known as a wireless client.

When a client/server connection is established, any information to be transmitted must be formatted in a manner suitable for transmission. Additionally, information regarding various transmission parameters, such as the speed, ready to send signals, and ready to receive signals, must also be formatted and transmitted.

Furthermore, the format of the information, as well as the convention for communicating the transmission parameters, must be known to the client or server receiving the transmission. The foregoing is accomplished using what is known in the art as a protocol. A protocol is a specific set of rules, procedures or conventions relating to the format and timing of data transmission. By establishing a common protocol between the client and server, information can be transmitted in a reliable manner understandable to both the client and the server.

The Wireless Application Protocol (WAP) was created to optimize data communication with wireless clients. Ideally, the WAP based service should be used on top of a packet switched transport such as Cellular Digital Packet Data (CDPD) or General Packet Radio Service (GPRS). However, due to standardization delays and the prohibitive cost of deploying a new packet radio service, operators are looking at other transports to offer WAP based service.

Another transport that has been considered is direct digital cellular circuit switched data calls (direct digital calls). Unlike conventional data calls which require a latency time for modem synchronization, direct digital calls do not involve any modems and therefore can be easily established and torn down as needed. The foregoing is ideal for many client/server and Internet applications which communicate in transmission bursts.

Applications which communicate in transmission bursts are characterized by very short periods of high data rate transmission, followed by longer periods of inactivity. Transmission in bursts is advantageous because the communication channel need only be maintained during the very short periods of transmission and can be torn down during the longer periods of inactivity.

The greatest limitation for using direct digital calls for a WAP based application is the fact that direct digital calls can only be used when the client originates the call to the server. The foregoing limitation is known in the art as an information pull model. The information pull model is a significant limitation for notification service applications, such as E-mail, stock price alert, and security alert, to name a few, where it is desirable for the server to notify the client of a particular event in a real-time fashion. A system where a server initiates a communication to the client and forwards information is known in the art as an information push model.

Accordingly, it would be advantageous if the server is able to push information to a wireless client in a direct digital call environment.

SUMMARY OF THE INVENTION The present invention is directed to a system, method, and apparatus for transmitting a digital data communication from a server to a wireless client, wherein the server initiates a call to push information to the client. A wireless application protocol gateway is interfaced by means of a signal link to a home location register of a cellular telecommunications system. The signal link permits the WAP Gateway to query the home location register for routing information needed to deliver a call with push information to the wireless client using the infrastructure of the cellular telecommunications system.

The present invention is also directed to a wireless application protocol gateway for routing a digital data communication from a server to a wireless client, wherein the server initiates a call to the client. The wireless application protocol gateway maintains a table that correlates Internet Protocol (IP) addresses with Mobile Services Integrated Services Digital Network (MSISDN) numbers or Mobile Identification Numbers (MIN) of the wireless clients. When the wireless application protocol gateway receives a digital data communication addressed to a particular IP address, the wireless application protocol gateway determines the corresponding MSISDN number of the wireless client. The MSISDN number can then be used to initiate an incoming call to the wireless client using the infrastructure of the cellular radio system.

The present invention is also directed to a method for transmitting a digital data communication from a server to a wireless client, wherein the server initiates an incoming call to the client. When a digital data communication is received at a wireless application protocol gateway, the wireless application gateway queries a database storing location information for the wireless client. In response to the query, a dynamic IP address is allocated to the wireless client and transmitted to the wireless application protocol gateway. The wireless application protocol gateway then transmits the digital data communication using the dynamic IP address as a destination address.

BRIEF DESCRIPTION OF THE DRAWINGS The disclosed invention will be described with reference to the accompanying drawings, which show important sample embodiments of the invention and which are incorporated in the specification hereof by reference, wherein: FIGURE 1 is a block diagram of a telecommunications system wherein the present invention can be practiced; FIGURE 2 is a block diagram of a Wireless Application Protocol (WAP) gateway configured in accordance with the present invention; and FIGURE 3 is a signal flow diagram describing the operation of the telecommunications system of FIGURE 1 in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EXEMPLARY EMBODIMENTS Referring now to FIGURE 1, there is illustrated a block diagram of an exemplary telecommunications system, referred to generally by the numeral 100, configured in accordance with the principles of the present invention. The telecommunications system includes a wireless client 105 which can establish a client/server connection with a server 110 and vice versa. Although servers 110 are accessible over a direct link, such as a Local Area Network (LAN), servers 110 are commonly accessed over the Internet 112 via an Internet connection 113. A server 110 with an Internet connection 113 can then be accessed by clients 105 with Internet 112 access anywhere in the world.

The wireless client 105 can include a computer, or computer like system capable of establishing a communication link 115 over the air interface. The communication link 115 over the air interface is often supported by a cellular telephone network 116. The cellular telephone network 116 includes at least one area 117 served by a Mobile Switching Center (MSC) 120. The MSC 120 is in communication with at least one Base Station 125. The base station 125 is the physical equipment that provides radio coverage to a particular geographical portion (known as a cell) of the area 117.

The MSC 120 is associated with a Home Location Register (HLR) 126, which is a database maintaining and storing subscriber information such as subscriber profiles, current location information, International Mobile Subscriber Identity (IMSI) numbers, and other administrative information. The subscriber services associated with the wireless client 105 are defined in a subscriber profile that is stored in the HLR 126. The subscriber profile identifies wireless clients 105 using Mobile Station Integrated Services Digital Network (MSISDN) numbers. The HLR 126 may be co-located with a given MSC 120, integrated with the MSC 120, or alternatively can service multiple MSCs 120.

The Wireless Application Protocol (WAP) was established to optimize data communications with wireless clients 105. However, a large portion of Internet 112 traffic is communicated pursuant to the hypertext transmission protocol (HTTP) using Internet Protocol (IP) addresses. In accordance with the WAP, the wireless client 105 accesses the Internet 112 via a WAP gateway 140. The WAP gateway 140 receives data communications over the Internet 112 in HTTP format, translates the data communications to WAP format, and forwards the translated data communications in WAP format to the wireless client 105. Likewise, the WAP gateway 140 receives data communications from the wireless client 105 in WAP format, translates the data communications to HTTP format, and forwards the translated data communications to the Internet 112.

The WAP protocol can be used on top of the packet switched transport, direct digital cellular circuit switched data calls (direct digital calls). Unlike conventional data calls which would require a latency time for modem synchronization, direct digital calls do not involve any modems and therefore can be easily established and torn down as needed. The wireless client 105 establishes a direct digital call through an InterWorking Function/Direct Access Unit (IWF/DAU) 145 at the MSC 120. The IWF/DAU 145 terminates the radio interface and provides access to a Direct Access Unit (DAU) 150. The DAU 150 functions as a router and routes data between the WAP gateway 145 and the wireless client 105. Additionally, the IWF/DAU 145 is equipped with a timer that tears down the direct digital call after a predetermined period of inactivity.

Direct Digital Calls are advantageous for applications which communicate in bursts. During the period of high data rate transmission, a communication channel, including communication link 115 between the wireless client 105 and the WAP gateway is maintained. However, during the period of inactivity, the communication channel, e. g., the communication link 115 can be torn down.

An information pull model refers to a system where the wireless client 105 is the calling party in a direct digital call. Numerous applications, such as E-mail, stock price alert, and security alert use an information push model where the server 110 contacts the wireless client 105 in a real-time fashion, responsive to the occurrence of a particular event.

To permit the server 110 to contact the wireless client 105, the present invention proposes interfacing the WAP gateway 140 to the cellular radio telecommunications network, thereby permitting the WAP gateway to initiate calls to the wireless client 105. The WAP gateway 140 is interfaced to the cellular telephone network by means of a signal link 150 connecting the WAP gateway to the HLR 126. The WAP gateway 140 uses the signal link 150 to query the HLR 126 and route incoming calls to the wireless client 105 as will be described below.

Referring now to FIGURE 2, there is illustrated a block diagram of an exemplary WAP gateway 140 in accordance with the present invention. The WAP gateway 140 maintains a table 205 correlating the mobile station integrated service digital network (MSISDN) numbers 210 associated with each wireless client 105 to static IP addresses 215 for the clients. Alternatively, the WAP gateway 140 can maintain a table 205 correlating the mobile identification numbers (MIN) 210 associated with each wireless client 105 to the IP addresses 215 for the clients. Those skilled in the art will recognize that the IP addresses can be assigned when a subscriber at a wireless client 105 initially registers for Internet access. The IP addresses assigned to subscribers during initial registration are known as static IP addresses. A server 110 contacting a wireless client 105 sends a communication to the static IP address corresponding to the wireless client 105. The communication is received over the Internet 112 by the WAP gateway 140. A processor 220 within the WAP gateway 140 looks up the static IP address 215 in the table 205 and determine the MSISDN 210 number associated therewith. The WAP gateway 140 uses the MSISDN 210 associated with the static IP address 215 to query the HLR 126 via signal link 150 and set up a call to the wireless client 105 as will be described below.

Referring now to FIGURE 3, there is illustrated a signal flow diagram describing the operation of the telecommunications system of FIGURE 1 in accordance with the present invention. The server 110 contacts the wireless client 105 by addressing a communication to the static IP address corresponding with MSISDN of the wireless client 105, and sending the communication (signal 305) to the WAP Gateway 140 via the Internet 112. The WAP gateway 140 receives the communication (signal 305) and determines the MSISDN corresponding the received static IP address (action 310).

The WAP gateway 140 uses the determined MSISDN to transmit a location request (signal 315) to the HLR 126 to determine the MSC/VLR location area 117 and the MSC 120 serving the wireless client 105. The location request (signal 315) includes a parameter identifying the call as a direct digital call from a WAP gateway 140. The HLR 126 determines the MSC/VLR location area 117 and the serving MSC 120, and transmits a routing request (signal 320) from the HLR to the serving MSC 120 that includes the parameter identifying the call as a direct digital call.

The serving MSC 120 determines, to some selected degree of granularity, the location of the wireless client 105 by paging (signal 325) the wireless client having the identified MSISDN. The paging signal (signal 325) includes the parameter identifying the call as a direct digital call from a WAP gateway 140, thereby permitting the wireless client 105 to take appropriate actions (action 330), such as setting up the requisite WAP stack. The wireless client 105 responds by transmitting a page acknowledgment to the MSC 120 (signal 335). The serving MSC 120 uses the acknowledgment (signal 335) to determine the location of the wireless client 105 (signal 337) and the serving base station 125. The MSC 120 then directs the serving base station 125 to allocate a traffic channel to the wireless client 105 (signal 340) to which the client replies with an acknowledgment (signal 342).

Additionally, the MSC 120 uses the IWF/DAU 145 to establish (action 343) a communication link with the WAP gateway 140 and allocates (action 344) a dynamic IP address/port number to the call and the traffic channel associated therewith by the base station in signal 340. The IP address/port number allocated to the call is considered dynamic because the IP address/port number is temporarily allocated for the duration of the direct digital call, and at the conclusion of the direct digital call, the IP address/port number is deallocated and available for reallocation for another direct digital call.

The serving MSC 120 transmits a route request return result message (signal 345) to the HLR 126 which includes the dynamically allocated IP address/port number allocated during action 344. The HLR 126 transmits a location request return message (signal 350) to the WAP gateway 140. Upon receiving the IP address/port number from the location request return message (signal 350), the WAP gateway 140 pushes the communication (signal 355) towards the dynamic IP address/port number, thereby causing the communication to be routed to the IWF/DAU 145 at the MSC 120. Because the dynamic IP address/port number identifies the channel, the MSC 120 forwards the communication (signal 360) to the serving base station 125 determined during action 337. The serving base station 125 then transmits (signal 365) the communication to the wireless client 105 over the air interface using the traffic channel previously allocated.

Although the invention has been described with a certain degree of particularity, it should be recognized that elements thereof maybe altered bypersons skilled in the art without departing from the spirit and scope of the invention. For example, although the description contained herein depicts embodiments of the invention in a GSM environment, it should be understood that other embodiments of the invention can practiced in other telecommunication network environments.

Therefore, the invention is limited only by the following claims and their equivalents.