Method and apparatus for reestablishing a data connection with a wireless communication network

ES 2 256 756 T3

DESCRIPTION

Method and apparatus for re-establishing a data connection with a radio communications network.

Background

Field of the invention

The present invention relates in general to radio communication devices and associated networks, and more particularly to communication data from mobile stations within radio networks such as General Packet Radio Service (GPRS) networks.

Description of related art

A radio communications device, such as a mobile station, establishes a packet data protocol (PDP) context with a general packet radio transmission services (GPRS) radio network over a GPRS trunk connection. Trunking makes the radio device known to the network by sending identification and routing path information. The radio device goes from an idle state to an active state if the GPRS trunk connection is successful. During the GPRS trunk procedure, encryption parameters are established between the radio device and the GPRS network. When the data connection is restored to its initial state correctly, both the radio device and the GPRS network are restored to the initial state in their respective encryption parameters.

During the out of coverage condition with the network, however, the radio device can be deactivated or restored to the initial state. This will cause the radio device to be reset to the initial state in its data connection parameters (for example, its encryption parameter), but the radio network will fail to disconnect since the radio device will be in an out of coverage state. . When the radio device re-enters the network coverage and sends a GPRS trunk connection in an attempt to reestablish a PDP context, the encryption parameter of the radio device is out of sync with the encryption parameter of the GPRS network. Thus, encrypted data cannot be successfully transmitted between the device and the network, including requests from the PDP context.

The use of a Temporary Logical Link Identity (TLLI) for the GPRS system is described in the GSM document XP 2167429 A. After the terminal has been activated, a new TTLI has to be assigned; assigning a new TTLI corresponds to unassigning the previous assignment. However, the TLLI will not be able to be lost in memory when the terminal is deactivated, which suggests that the TLLI will not be reset to its initial value in the terminal in this situation.

Accordingly, there exists a resulting need for methods and apparatus for reestablishing a data connection that remedies the shortcomings of the prior art.

Summary

Methods and apparatus to be used for the reestablishment of a data connection with a radioelectric communications network will be described. Initially, the radio communication device maintains a data connection with a radio communication network. During an out of coverage condition with the network, the radio device is deactivated by turning it off. After being activated by turning it on, and recovering network coverage, the radio device transmits a message to the network that causes one or more parameters of the network associated with the data connection to be reset to the initial state. Subsequently, the radio device transmits one or more additional messages to the network to re-establish the data connection. In the particular embodiment described here, the data connection is a Packet Data Protocol (PDP) context, with a General Packet Radio Service (GPRS) trunk connection, in which the message is a disconnect frame. , and one or more additional messages include a trunk connection request to the General Packet Radio Service (GPRS). Advantageously, the data connection remains substantially uninterrupted with the radio device despite the complexities of the network connection.

Brief description of the drawings

The embodiments of the present invention will now be described by way of example with reference to the accompanying figures, in which:

Figure 1 is a block diagram showing the respective components of a radio communication device communicating within a radio communication network;

Figure 2 is a more detailed diagram of a preferred radio communication device of Figure

1;

Figure 3 is a particular structure of a system for communication with the radio communication device;

Figures 4 and 5 are flow charts describing a method for re-establishing a data connection with a radio communication network;

Figure 6 is a flow diagram of a system in relation to the method described with respect to Figures 4 and 5; and Figure 7 is an illustration of the format of a disconnect frame that can be used to reset the network parameters of the data connection.

Detailed description of the preferred embodiments

In the techniques described herein the radio communications device maintains a data connection with a radio communications network. During the condition of out of coverage with the network, the radio device is switched off. After being switched on again and with the recovery of coverage in the network, the radioelectric device transmits a message to the network, which causes one or more network parameters associated with the data connection to be restored to the initial state. Subsequently, the radio device transmits one or more additional messages to the network, to re-establish the data connection. In the particular embodiment described here, the data connection is a Packet Data Protocol (PDP) context, with a General Packet Radio Transmission Service (GPRS) connection, in which the message is a disconnect frame. , and one or more of the additional messages includes a General Packet Radio Transmission Service (GPRS) connection request. Advantageously, the data connection remains substantially uninterrupted for the radio device despite the complexities of the network connection.

FIG. 1 is a block diagram of a communication system 100, which includes a mobile station 102 that communicates with a radio communication network 104. Mobile station 102 preferably includes a display screen 112, a keyboard 114, and perhaps one or more auxiliary user interfaces (UI) 116, which are coupled to a controller 106. Controller 106 is also coupled to a circuitry of a radio frequency (RF) transceiver 108 and an antenna 110.

Typically, controller 106 is implemented as a central processing unit (CPU), which runs operating system software on a memory component (not shown). Controller 106 will normally control all operations of mobile station 102, while signal processing operations associated with communications functions will typically be performed on the RF transceiver 108 circuitry. Controller 106 interfaces with display screen 112 to display received information, stored information, user input, and the like. The keyboard 114, which may be a telephone-type keyboard or a fully alphanumeric keyboard, is normally provided for the input of data for storage in the mobile station 112, information for transmission to the network 104, a telephone number to carry out a phone call, commands to be executed at mobile station 102, and possibly other inputs than the user.

Mobile station 102 sends communications signals or receives communications signals from network 104 over a radio link through antenna 110. RF transceiver circuitry 108 performs similar functions as station 118 and BSC 120 , including for example modulation / demodulation, and possibly encoding / decoding, and encryption / decryption. It is also contemplated that the RF transceiver 108 circuit may perform certain functions in addition to those performed by BSC 120. It will be apparent to those skilled in the art that the RF transceiver 108 circuit may be particularly tailored for the network or networks. radio stations in which the mobile station 102 is intended to be made operational.

Mobile station 102 includes a battery interface 134 for receiving one or more rechargeable batteries 132. Battery 132 provides electrical power to the electrical circuit in mobile station 102, and battery interface 132 provides the mechanical and electrical connection for battery 132 The battery interface 132 is coupled to a regulator 136, which regulates the electrical power to the device. When mobile station 102 is fully operational, the RF transmitter on RF transceiver circuit 108 is typically tampered with or turned on only when it is sending information to the network, and is otherwise turned off to conserve its resources. Similarly, the RF receiver in the RF transceiver circuitry 108 is typically turned off periodically to conserve the unit's electrical power, until it is necessary to receive the signals or information during the allotted time periods.

Mobile station 102 operates using Subscriber Identity Module (SIM) 140, which is connected or inserted into mobile station 102 at a SIM interface 142. SIM module 140 is a type of conventional "smart card" used to identify a end user (or subscriber) of mobile station 102, to personalize the device among other things. Without the SIM module 140, the mobile station terminal is not fully operational for communication over the radio network 104. By inserting the SIM module 140 into the mobile station 102, the end user can have access to any or all paid services. SIM module 140 generally includes a processor and memory for storing the information. Since the SIM 140 module

ES 2 256 756 T3 is coupled to the SIM interface 142, it will be coupled to the controller 106 through the communication lines 144. In order to identify the subscriber, the SIM 140 contains some user parameters such as the International Subscriber Identity of Mobiles (IMSI). An advantage of using the SIM module 140 is that the end users do not need to be linked by any physical mobile station. The SIM module 140 can store additional user information for the mobile station as well, including information from a data book (or calendar) and recent call information.

Mobile station 102 may be comprised of a single unit, such as a data communications device, a cell phone, a multi-function communications device with voice and data communications capabilities, a trained personal digital assistant (PDA). for radio communication, or a computer incorporating an internal modem. Alternatively, mobile station 102 may be a multi-module unit comprising a plurality of independent components, including but not limited to a computer or other device connected to a radio modem. In particular, for example, in the diagram of the mobile station of Figure 1, the circuit 108 of the RF transceiver and the antenna 110 can be implemented as a radio modem unit that can be inserted into a port on a laptop. In this case, the laptop could include a built-in display 112, keyboard 114, one or more auxiliary UI units 116, and controller 106 as well as the computer's CPU. It is also contemplated that the computer or other equipment not normally capable of radio communication could be adapted to effectively connect and take over control of the RF transceiver circuit 108 and the antenna 110 of a single unit device, such as as described above. Said mobile station 102 may have a particular implementation as described below in connection with mobile station 402 of FIG. 2.

Mobile station 102 communicates through radio communication network 104. In the embodiment of FIG. 1, radio network 104 is configured in accordance with General Packet Radio Service (GPRS) and Global Systems for Mobile (GSM) technologies. Radio network 104 includes a base station controller (BSC) 120 associated with an associated tower station 118, a Mobile Switching Center (MSC) 122, a Home Positioning Register (HLR) 132, a General Attention Service Packet Radio Transmission (GPRS), a Transmission Node (SGSN) 126, and a Gateway GPRS Support Node (GGSN) 128. The MSC 122 is coupled to the BSC 120 and a terrestrial network, such as the Public Switched Network of Telephony (PSTN) 124. The SGSN 126 is coupled to the BSC 120 and the GGSN 128, which in turn is coupled to a public or private data network 130 (such as the Internet). HLR 132 is coupled to MSC 122, SGSN 126, and GGSN 128.

Station 118 is a fixed transceiver station, and station 118 and BSC 120 are heretofore referred to as fixed transceiver equipment. Fixed transceiver equipment provides radio network coverage for a particular coverage area commonly referred to as a "cell". The fixed transceiver equipment transmits the communication signals and receives the communication signals from the mobile stations located within its cell, through the station 118. The fixed transceiver equipment normally performs functions such as modulation, and possibly encoding and / or encryption of the signals to be transmitted to the mobile station according to the particular, usually predetermined communication protocols and parameters, under the control of its controller. The fixed transceiver equipment similarly demodulates and possibly decodes and decrypts, if necessary, any communication signals from mobile station 102 within its cell. Communication protocols and parameters may vary between different networks. For example, a network may use a different modulation scheme and be able to operate at different frequencies than other networks.

The radio link shown in communication system 100 of FIG. 1 represents one or more different channels, channels of a typically different radio frequency (RF), and associated protocols used between radio network 104 and mobile station 102. A radio frequency channel RD is a limited resource that has to be conserved, typically due to limits on global bandwidth and electrical power from a limited battery of mobile station 102. Those skilled in the art will observe that a radio network in current practice may include hundreds of cells, each served by a station 118 (i.e., station sector), depending on the desired global expansion of station coverage. net. All relevant components can be connected by multiple telephone exchanges and routers (not shown), controlled by multiple network controllers.

For all mobile stations 102 registered with a network operator, the permanent data (such as the user profile of the mobile station 102), as well as the temporary data (such as the current position 102 of the mobile station) they are stored in the HLR 132. In the event of a voice call to the mobile station 102, the HLR 132 is requested to determine the current position of the mobile station 102. A Visitor Location Register (VLR) of MSC 122 is responsible for a group of location areas and stores the data of those mobile stations that are normally in its area of ​​responsibility. This includes portions of the data from permanent mobile stations that have been transmitting from the HLR 132 to the VLR for faster access. However, the VLR of MSC 122 can also allocate and store local data, such as temporary IDs. Optionally, the VLR of MSC 122 can be enhanced for more efficient coordination of GPRS and non-GPRS services and functionality (e.g. paging for circuit switched calls that can be performed more efficiently through SGSN 126, and in combination of GPRS and non-GPRS positioning updates).

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The GPRS Support Service Node (SGSN) 126 is on the same hierarchical level as the MSC 122, and keeps track of the individual positions of the mobile stations. The SGSN 126 also performs security and access control functions. The GPRS Gateway Support Node (GGSN) 128 provides the interconnection of networks with external packet switched networks, and is connected to SGSNs (such as SGSN 126) through a core GPRS network based on the IP system. . The SGSN 126 executes the authentication and encryption setup procedures based on the same algorithms, keys, and criteria as an existing GSM. In conventional operation, the selection of the cells can be performed autonomously by the mobile station 102 or by the mobile station 102 instructing the mobile transceiver equipment to select a particular cell. Mobile station 102 informs radio network 104 when another cell or group of cells is deselected, known as a routing area.

In order to access GPRS services, mobile station 102 makes its presence known to radio network 104 by executing what is known as the GPRS "connection." This operation establishes a logical link between the mobile station 102 and the SGSN 126 system, and makes the mobile station 102 available to receive for example the pages through the SGSN, notifications of the incoming GPRS data, or the SMS messages through of the GPRS. In order to send and receive GPRS data, the mobile station 102 assists in activating the data addresses of the packets that it needs to use. This operation makes the mobile station 102 aware of the GGSN system 128; then beginning the interconnection of reces with external data networks. User data can be transparently transferred between mobile station 102 and external data networks, using for example encapsulation and pipelining. The data packets are equipped with the information of the specific GPRS protocol, and being transferred between the mobile station 102 and the GGSN system 128.

Those skilled in the art will observe that a radio network may be connected to other systems, possibly including other networks, not explicitly shown in Figure 1. A network will normally be transmitting at least some class of system pages and information on a progressive basis. even if there is no packet data page exchange process. Although the network comprises many parts, these parts work together to give rise to a certain behavior on the radio link.

Figure 2 is a detailed block diagram of a preferred mobile station 202. Mobile station 202 is preferably a two-way communications device that has at least advanced voice and data communication capabilities, including the capabilities to communicate with other communication systems. computers. Depending on the functionality provided by mobile station 202, it may be referred to as a data messaging device, a two-way pager, a cellular phone with data messaging capabilities, a radio internet device, or a data communications device (with or without telephony capabilities). Mobile station 202 can communicate with any other fixed transceiver stations 200 within its geographic coverage area.

Mobile station 202 will typically incorporate a communications subsystem 211, which may include a receiver 212, a transmitter 214, and associated components, such as one or more antenna elements 216 and 218 (preferably embedded or internal), local oscillators ( LO) 213, and a processing module such as a digital signal processor (DSP) 220. Communications subsystem 211 is analogous to RF transceiver circuitry 108 and antenna 110 shown in Figure 1. As will be apparent to those skilled in the communications field, the particular design of communication subsystem 211 it will depend on the communication network in which mobile station 202 is intended to operate.

Mobile station 202 can send and receive communication signals over the network after it has completed network registration or activation procedures. The signals received by the antenna 216 through the network are input to the receiver 212, which can perform such common receiver functions such as signal amplification, frequency downconversion, filtering, channel selection, and similar, and in the example shown in figure 2, the analog-digital (A / D) conversion. The A / D conversion of the received signal allows more complex communication functions, such as demodulation and decoding to be performed in the DSP 220. In a similar way, the signals to be transmitted are processed, including modulation and encoding, by For example, by DSP 220. These DSP-processed signals are input to transmitter 214 for digital-to-analog (D / A) conversion, up-frequency conversion, filtering, amplification, and transmission over the communications network through antenna 218. The DSP 220 not only processes communications signals, but also provides receiver and transmitter control. For example, the gains applied to the communications signals at receiver 212 and transmitter 214 can be adaptively controlled through automatic gain control algorithms implemented in DSP 220.

Access to the network is associated with a subscriber or user of mobile station 202, and therefore mobile station 202 requires a Subscriber Identity Module or "SIM" card 262 to be inserted into an interface of SIM 265, with the order to operate on the network. SIM card 262 includes the features described in relation to page 1. Mobile station 202 is a battery powered device, so it also includes a battery interface 254 for receiving one or more rechargeable batteries 256. Said battery 256 provides electrical power to most or all of the electrical circuitry of the mobile station. 202, wherein a battery interface 254 provides the mechanical and electrical connection thereto. The battery interface 254 is coupled to a regulator (not shown), which supplies V + electrical power to the entire circuit.

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Mobile station 202 includes a microprocessor 238 (which is an implementation of controller 106 in FIG. 1), which controls the overall operation of mobile station 202. Communications functions, including at least data and communication communications. voice, run through communications subsystem 211. The microprocessor 238 also interfaces with additional device subsystems such as the display 222, Flash memory 224, the random access memory (RAM) 226, auxiliary input / output (I / O) subsystems 228, serial port 230, the keyboard 232, speaker 234, microphone 236, short-range communications subsystem 240, and any other device subsystems designated generally by 242. Some of the subsystems shown in Figure 2 perform functions related to communications, while other subsystems can provide functions "resident" or embedded in the devices. In a special way, some subsystems such as the keyboard 232 and the display 222, for example, can be used for functions related to communications, such as entering a text message for transmission over a communications network, and device-resident functions such as a calculator or a to-do list. The operating system software used by the microprocessor 238 is preferably stored in persistent storage such as a Flash memory 224, which may alternatively be a read-only memory (ROM) or similar storage element (not shown). Those skilled in the art will note that the operating system, device-specific applications, or parts thereof, may be temporarily downloaded to volatile storage such as RAM 226.

The microprocessor 238, in addition to its operating system functions, preferably allows the execution of software applications on the mobile station 202. The predetermined set of applications with basic control device operations, including at least the data communications applications and voice (such as the network restoration scheme), will normally be installed in mobile station 202 during manufacture. A preferred application that can be downloaded to mobile station 202 may be a personal information manager (PIM) application, which has the ability to organize and manage user-related data, such as (but not limited to) email, events. calendar, voicemails, appointments and tasks. Naturally, one or more memory stores are available in mobile station 202 and SIM 256 to facilitate the storage of PIM data and other information.

The PIM application preferably has the ability to send and receive data over the radio network. In a preferred embodiment, the PIM data is seamlessly integrated, and updated through the radio network, with corresponding mobile station user data stored and / or associated with a dual server computer system, thereby creating a parallel computer at mobile station 202 with respect to such information. This is especially advantageous when the server computer system is the mobile station user central computer system. Additional applications may be downloaded to mobile station 202 via the network, an auxiliary I / O subsystem 228, serial port 230, short-range communications subsystem 240, or any other suitable subsystem 242, and installed by a user at RAM 226 or preferably in non-volatile storage (not shown) for execution by microprocessor 238. Such flexibility in application installation increases the functionality of mobile station 202, and can provide enhanced functions on the device, functions related to communications, or both. For example, secure communication applications can enable electronic commerce functions and execute other financial transactions using mobile station 202.

In a data communication mode, the received signal such as a text message, an email message, or a download from a WEB page, will be processed by the communications subsystem 211 and being input into the microprocessor 238. The microprocessor 238 will preferably further process the signal to be supplied to display 222 or alternatively to auxiliary I / O device 228. The user of a mobile station 202 can compose data, such as email messages, for example, using keyboard 232 in conjunction with display 222, and possibly auxiliary I / O device 228. The keyboard 232 is preferably a full alphanumeric keyboard and / or a telephone type keyboard. These composite units can be transmitted over the communications network by means of the communications subsystem 211.

For voice communications, the overall operation of mobile station 202 is substantially similar, except that received signals would be supplied to speaker 234, and signals for transmission would be generated by microphone 236. Alternate I / O subsystems Voice or audio devices, such as voice recording subsystems, can also be implemented in mobile station 202. Although the output of the voice or audio signal is preferably carried out through the speaker 234, the display 222 can also be used to provide an indication of the identity of the calling party, the duration of a voice call, or other information related to the voice call, such as examples to cite.

Serial port 230 in FIG. 2 is typically implemented in a personal digital assistant (PDA) type communication device, for which synchronization with a user's desktop computer is desirable, although it is an optional component. Serial port 230 allows the user to configure preferences through an external device or software application, and by expanding the capabilities of mobile station 202, by supplying information or software downloads to mobile station 202, at rather than through a radio communications network. The alternate download path, for example, can be used to upload an encryption key to mobile station 202 through a therefore reliable and secure connection to provide secure device communication.

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The short-range communications subsystem 240 of FIG. 2 is an additional optional component, which provides communication between the mobile station 202 and different systems or devices, which need not necessarily be like devices. For example, subsystem 240 may include an infrared device and associated circuitry and components, or a Bluetooth ™ communications module to provide communication with similarly enabled systems and devices. Bluetooth ™ is a registered trademark of Bluetooth SIG, Inc.

Figure 3 shows a structure of a particular system for communication with a mobile station. In particular, figure 3 shows the basic components of a radio data network based on the IP protocol that can be used. Mobile station 100 communicates with a packet data radio network 145, and may also be capable of communicating with a voice radio network (not shown). As shown in FIG. 3, the gateway 140 may be coupled to an internal or external address resolution component 335, and at one or more network entry points 305. The data packets are transmitted from the gateway 140, which is the source of information to be transmitted to the mobile station 100, through the network 145 by configuring a channel 325 of the radioelectric network from the gateway 140 to the station. mobile 100. In order to create this radio channel 325, a unique network address is associated with mobile station 100. In a radio network based on the IP protocol, network addresses are typically not permanently assigned to mobile station 100 in particular, but are instead dynamically allocated on a demand-needed basis. It is therefore preferable for mobile station 100 to acquire a network address, and for gateway 140 to determine this address in order to establish radio channel 325.

Gateway point 305 is generally used for multiplexing and demultiplexing between many gateways, corporate servers, and backbones such as the Internet, for example. There are normally a few points of entry 305 in the network, since they are intended to centralize the externally available radio network services. Network entry points 305 frequently utilize some form of the address resolution component 335 that aids in addressing allocation and consultation between gateways and mobile stations. In this example, the address resolution component 335 is shown as Dynamic Server Configuration Protocol (DHCP) as a method of providing an address resolution mechanism.

A central internal component of the radio data network 345 is the network router 315. Typically, the network routers 315 are proprietary for a particular network, but could alternatively be built from standard type commercially available hardware. The purpose of the network routers 315 is to centralize thousands of fixed transceiver stations 320, which are typically implemented in a relatively large network in a central location for a long-haul connection back to the network entry point 305. In some networks, there may be multiple connections of the network routers 315, and cases where there are master routers 315 and network servers, but in all of the aforementioned cases the functions are similar. Often times the router on the network 315 will have access to a name server 307, in the case shown as a dynamic name server (DNS) 307, as used on the Internet, to query the destination of routing data messages . Fixed transceiver stations 320, as described above, provide radio links to mobile stations such as mobile station 100.

Radio network channels such as radio channel 325 are opened through radio network 345 in order to allocate the necessary memory, routing, and addressing resources for the delivery of the IP packets. Said channels 325 are established as part of what is referred to as Packet Data Protocol or "PDP contexts" (ie, data sessions). To open radio channel 325, mobile station 100 has to use a specific technique associated with radio network 345. The opening stage such as radio channel 325 may require mobile station 100 to indicate the domain, or point of entry. network 305 with which you want to open radio channel 325. In this example, the channel first reaches the router 315, which uses the name server 307 to determine which is the network entry point 305 that matches the supplied domain. Multiple radio channels can be opened from mobile station 100 for redundancy, or access to multiple gateways and services in the network. Once the domain name has been found, the channel is extended to entry point 305 of the network and the necessary resources are allocated at each of the nodes along the way. Network entry point 305 then uses the address resolution component (or DHCP 335) to assign an IP address for mobile station 100. When an IP address has been assigned to mobile station 100 and communicated to gateway 140, the information can be sent from gateway 140 to mobile station 100.

Radio channel 325 typically has a limited life, depending on the coverage profile of mobile station 100 and its activity. The radioelectric network 145 will cancel the radioelectric channel 325 after a certain period of inactivity or a period of lack of coverage, in order to recapture the resources maintained by this radioelectric channel 325 for other users. The main reason for this is to reclaim the IP address temporarily reserved for mobile station 100 when radio channel 325 was first opened. Once the IP address has been lost and radio channel 325 has been overridden, gateway 140 will lose all its ability to initiate IP data packets for mobile station 100, either through Transmission Control Protocol (TCP) or through User Datagram Protocol (UDP).

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Figures 4 and 5 are flow charts describing a method for re-establishing a data connection with a radio communication network. The flow chart of Figure 4 pertains to the operation of the device in advance of the radio device being turned off, and the flow chart of Figure 5 pertains to the operation of the device after the radio device has been turned on again. .

Beginning with start block 402 of FIG. 4, the radio device (eg, a mobile station) maintains a data connection with a radio communication network (step 404). During the establishment of the data connection, the encryption parameters are established between the radio device and the network. In this particular embodiment, the data connection includes a connection and a PDP context between the radio device and the network. In general, a "connection" means that the radio device registers with the network. The connection also allows mobility (that is, the network is capable of tracking the movements of the radioelectric device). Additionally, the radio device is authenticated and encryption is enabled. When the Packet Data Protocol (PDP) context is activated, an IP address is assigned for the radio device and subscriber-related parameters are provided so that the data is capable of being transferred. When the data application is activated in the radio device, for example, a PDP context is created between the radio device and the network. When the application is terminated, the PDP context is terminated but registration is maintained in the radio network.

Sometimes after the data connection has been established, the radio device experiences a particular set of events. In one of them, the radio device may be out of range when, for example, the device can no longer successfully send or receive data over the radio network. While in the out of coverage state, the radio device is turned off (step 408). The shutdown may be due, for example, to a manual actuation of the ON / OFF switch of the radio device, to the automatic shutdown of the radio device, or to an inadvertent return to the initial state that the radio device may experience.

Since the radio device receives the information that it is out of range, it does not transmit a "disconnect" request to the radio network in advance of the shutdown operation. Alternatively, just before being turned off, the radio device transmits a "disconnect" request that is not received by the network because it is in an out-of-coverage condition. The radio device also resets its parameters for the data connection, including its encryption parameter. However, the network does not reset its corresponding network parameters for the unreleased data connection. When the encryption setting on the device has been reset, it will be out of sync with the encryption setting on the radio network.

Upon starting at the start block 502 of FIG. 5, the radio device is turned on again (step 504). Powering up again may be due, for example, to manual actuation of an ON / OFF switch on the radio device, automatic power-up of the radio device, or an inadvertent reset that the radio device may have undergone. Next, the radio device identifies a coverage state with respect to the radio network (step 506). Conventionally, in this situation, the radio device transmits a connection request followed by the transmission of a PDP context request. In at least some networks, however, data communication is subsequently not possible because the network does not reestablish the first data connection and still maintains the previous encryption parameter.

In the present application, the radio device transmits a disconnect frame message to the radio network (step 508) in advance of establishing a connection and a PDP context. This disconnect frame causes the radio network to reestablish the previous data connection between the radio device and the network, including resetting the network parameters (for example, the network encryption parameter) associated with the first connection of the network. data. Next, the radio device transmits a connection request to the radio network (step 510). Because the encryption parameters are now in sync, the radio network can communicate with the radio device. Finally, the radio device transmits a PDP Context request and a PDP Context is subsequently established (step 512).

Fig. 6 is a system flow diagram describing a system flow for re-establishing a data connection with a radio network in accordance with the present application. Prior to the method described in Figure 6, the radio device communicates with an SGSN, and in turn with a GGSN in a GPRS network through the base station. A little later, the radio device goes out of range and will not be able to communicate properly with any surrounding base station. Although the radioelectric device goes to the out-of-coverage state, it loses power and its electrical circuit is switched off. This shutdown state can occur for a short or long period of time. Since the radio device receives the information that it is out of range, it does not transmit the "reconnection" request to the radio network in advance of the shutdown. Alternatively, just before being switched off, the radioelectric device transmits a "disconnection" request, which is not received by the network due to the out-of-coverage state.

According to the present application, once the radio device recovers electrical energy and network coverage, it preferably transmits a disconnect frame to the GPRS network, which reaches the SGSN (stream 602). In response, the GPRS network resets the network parameters associated with the data connection (eg, the encryption parameter), so that the radio device and the network can communicate again. The radioelectric device preferably transmits a GPRS connection request to the GPRS network, which reaches the

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SGSN (stream 604). In response, the SGSN informs the HLR of the connection, and the HLR acknowledges receipt (stream 606). The SGSN then sends a connection acceptance to the radio device (stream 608). The radio device then transmits a PDP Context Request to the SGSN (stream 610). In response, the SGSN sends a request to the SGSN to create a PDP context (flow 612). Because the encryption parameters of the radio device and the SGSN are now synchronized, the SGSN sends a response to the SGSN (stream 614). Subsequently, the SGSN sends an Accept message to the radio device (stream 616). Once the data connection is fully established, the radio device goes into standby or ready mode.

FIG. 7 is a block diagram showing a GPRS disconnect frame 700 that may be transmitted by the radio device upon returning to coverage after being restored during an out-of-coverage state. In the present embodiment, this particular message causes the network parameters associated with the old data connection to be restored, so that a newly established data connection can be made. However, any suitable message can be used to achieve the same results depending on the network.

The disconnect frame 700 is defined in the Logical Link Control (LLC) Specification (GSM 04.64), which is used for packet transfer between the device and the serving SGSN. The LLC layer exchanges are done using frames. The disconnect frame 700 preferably comprises an address field 702, a control field 704, or a frame check sequence (PCS).

Address field 702 consists of a protocol discriminator bit (PD) 710, a command / response bit (CR) 712, a service access point identifier (SAPI 714). Bit PD 710 indicates which protocol the frame is using. LLC frames set PD bit 710 to "0". A frame with the PD 710 bit set to "1" is invalid. Bit CR 712 identifies a frame as a command or response. If the device sends a command to the network, bit CR 712 is set to "0". If the network sends a command to the device, bit CR 712 is set to "1". Since the disconnect frame 700 is sent from the device, the CR bit 712 in this embodiment is set to "0". The SAPI 714 identifies the identifier of the data link controller for which the frame is intended. In a disconnect frame, SAPI bits 1-4 are set to 1,0,0,0, respectively. Control field 704 identifies the type of frame and typically comprises between one and three octets. In this case, because the frame is a control function, bits 8-6 220 are all set to "1". Bit 5 722 is the final bit or poll bit. When the frame is issued as a command, the bit is a poll bit. When the frame is broadcast as a response, the bit is the final bit. In this embodiment, they are preferably set to 0, 0, 1, 0, respectively. Typically, LLC frames have an information field, which normally contains the various commands and responses. In a disconnect frame, no information field is allowed. The frame check sequence field 708 (FCS) comprises a 24-bit cyclic redundancy check code (CRC). The CRC-25 is used to detect bit errors in the header of the frames and in the information fields. The sequence of frame checks is determined in the Logical Link Control (LLC) Specification (GSM 04.64).

Final comments. Methods and apparatus for use in re-establishing a data connection with a radio communication network have been described. Initially, a radio communications device maintains the data connection with a radio communications network. During a state of out of coverage with the network, the radio device is switched off. This causes the radio device to reset its parameters associated with the data connection, but since the radio device is out of range, the radio network will fail to disconnect. Preferably, after being turned on again and regaining network coverage, the radio device transmits a message to the network, which causes one or more network parameters associated with the data connection to be restored. Subsequently, the radio device transmits one or more messages to the network to re-establish the data connection. In the preferred embodiment, this data connection is a Packet Data Protocol (PDP) context with a General Packet Radio Transmission Service (GPRS) connection, the message is a disconnect frame, and wherein one or more messages Additional ones include a connection request from the General Packet Radio Service (GPRS). Advantageously, the data connection remains substantially uninterrupted for the radio device, despite the complexities of network connection by the radio device.

The above-described embodiments of the present application are intended to serve as examples only. Technicians skilled in the art can make alterations, modifications, and variations to particular embodiments, without deviating from the scope of the application. The invention herein described in the stated claims is intended to cover and encompass all changes in technology.