CN1214578C - Group domain communication method - Google Patents

Abstract

The invention relates to the field of mobile communication. A method of communication through the packet domain, characterized in that the user is grouped through the public land mobile network PLMN (Public Land Mobile Network) according to the mobile station international ISDN number MSISDN (Mobile Station International ISDNNumber) and the access point name APN (Access Point Name) The domain calls another user, automatically obtains the IP address of the other party, and establishes an IP-based communication link between the two users for communication. The method of the invention is simple and practical, enriches the functions of the WCDMA/GPRS system, effectively utilizes network resources, and reduces user costs.

Description

A method of communicating over a packet domain

technical field

The present invention relates to the field of mobile communication, in particular to the field of WCDMA/GPRS, and provides a method for two user terminals UE (User Equipment) to communicate through a public land mobile network PLMN (Public Land Mobile Network) packet domain.

technical background

In modern mobile communications, the communication network has gradually transitioned from traditional GSM to 2.5G general packet radio service GPRS (General Packet Radio Service) or wideband code division multiple access WCDMA (WideCode Division Multiple Access). , scientific researchers are constantly improving the work, among which the communication between end users is a relatively popular research field.

The WCDMA/GPRS system network consists of a core network and a wireless access network. The core network is divided into two subsystems, the circuit domain and the packet domain. The circuit domain includes the mobile switching center MSC (Mobile Switching Center) and the home location register HLR (Home Location Register) Provide users with voice services and bearer services based on circuit links, such as videophones, short messages, etc. It is characterized by high reliability, but low speed and high cost; the packet domain includes GPRS service support nodes SGSN (Serving GPRS SupportNode), GPRS gateway support node GGSN (Gateway GPRS Support Node), domain name system DNS (Domain Name System) and other equipment, provide users with IP-based packet bearer services, such as web browsing, online games, video-on-demand, etc., its The characteristic is that the reliability is not high, but the speed is high and the cost is low.

The network structure is shown in Figure 1:

The thick black line in the figure indicates a communication link formed after two UEs are connected through a CS domain call. When a UE calls another UE, the calling party transmits the call information to the MSC through the wireless access network, and the MSC calls the called UE according to the location information registered by the UE, and then establishes a circuit-based communication link between the two UEs. end-to-end voice services or other bearer services.

The thick black line in the figure indicates the bearer link used by the UE to access the external packet data network. When the UE actively initiates access to the external packet data network, the activation message is transmitted to the SGSN device through the wireless access network. The SGSN identifies the access point name APN (Access Point Name) according to the external network accessed by the UE, and obtains the accessed GGSN address through DNS resolution. , the SGSN then transmits the activation message to the GGSN, the GGSN terminates the activation message, and establishes a bearer link from the UE to the GGSN, and then the UE can use the bearer link to access the external data network. As a gateway device for accessing the external packet network, the GGSN can directly access the external network without establishing a link between the GGSN and the external server.

In the current WCDMA/GPRS network, there are mainly the following problems:

1. In the WCDMA/GPRS network complying with the 3GPP R99 and R4 version protocols, the UE mainly accesses the external packet data network through the PLMN packet domain, and cannot call another UE through the packet domain, and the call between two UEs can only pass through the circuit domain. With the evolution of the 3GPP protocol to the R5 version, the packet domain and the circuit domain of the core network will evolve into an all-IP packet network. Through the all-IP network, mutual calls between two UEs can be realized, but the current core network equipment needs to be modified. Big changes, and need to add other equipment, it will take time to develop and mature.

2. At present, in the WCDMA/GPRS network, two UEs can access each other in the following way: Both UEs have static IP addresses belonging to the same APN, and the UEs on both sides of the communication know the static IP address of the other party. When they are in the same APN at the same time When activating the context with the same GGSN (requires active activation and cannot call each other), use special equipment outside the GGSN equipment to route and forward their IP datagrams, so as to realize mutual access between the two UEs. But this method is inconvenient to use and has many limitations, it is difficult to carry out actual large-scale application, and it is more used for demonstration or experiment.

3. Two UEs call and communicate through the circuit domain, and need to monopolize the wireless resources and the circuit resources of the core network; while the packet domain adopts the IP-based packet transmission mode, and the corresponding wireless access network also adopts the sharing and multiplexing method, so if Communication between UEs through the packet domain can effectively utilize network resources and reduce costs.

4. The bearer link established by two UEs through the circuit domain is limited by the speed, and the bearer service is limited; while the UE and UE end-to-end communication link established through the packet domain, the speed can reach 384kbps, which can carry the current IP packet-based Any application business.

5. The cost of services such as voice and video telephony through the circuit domain is very high, while the transmission cost using the packet domain is relatively low.

In order to facilitate your examiners to have a clearer understanding of the technical background of the present invention, several existing key technologies in the field of mobile communications are now described.

Home Location Register HLR (Home Location Register): Home Location Register is used to manage the database of the mobile station. The main functions are: management and modification of all user parameters of the mobile station registered in the HLR, billing management, VLR update etc.

Access user remote authentication service RADIUS (Remote Authentication Dial in UserService): access user remote authentication service is a method of centralized management of customers on one switch or multiple switches VPN, RADIUS is used to integrate network access Authentication and authorization information between the server (VPN switch) and the central authentication and authorization server (RADIUS Server, defined in RFC 2138).

AAA SERVER: The AAA server is used to verify the identity of the visitor. This server will perform three steps of "authentication", "authorization" and "record". Generally, the Radius function including the Radius accounting function is called the AAA function.

Gateway support node GSN (GPRS Support Node): It is the most important network node in the GPRS network, and it is also used in the WCDMA network. GSN has the function of mobile routing management, it can be connected to various types of data networks, and can be connected to the home location register, which can complete the data transmission and format conversion between the mobile station and various data networks. GSN can be an independent device similar to a router, or it can be integrated with MSC in GSM. There are two types of GSN: one is the GPRS service support node SGSN (Serving GPRS Support Node), and the other is the GPRS gateway support node GGSN (GatewayGPRS Support Node). The main function of the SGSN is to record the current location information of the mobile station, and The transmission and reception of mobile packet data is completed between the mobile station and the GGSN. GGSN mainly acts as a gateway, and it can be connected to many different data networks, such as ISDN, PSPDN and LAN. In some documents, the GGSN is called a GPRS router. GGSN can convert the GPRS packet in the GSM network to the protocol, so that these packets can be sent to the remote TCP/IP or X.25 network.

Invention content:

The purpose of the present invention is to provide a simple and practical method for calling each other and establishing and maintaining an IP-based communication link between a UE and a UE through the PLMN, so as to enrich the functions of the WCDMA/GPRS system, effectively utilize network resources, and reduce the number of users. cost.

A method for communicating in a packet domain, characterized in that the user calls another user through the PLMN packet domain according to the mobile station international ISDN number MSISDN (Mobile Station International SDN Number) and the access point name APN (AccessPoint Name), between two users An IP-based communication link is established between terminals UE (UserEquipment) for communication.

The described establishment of a communication link includes the following steps:

A. UE1 initiates a request to the GGSN, and the request message carries the APN selected by the user;

B, GGSN analyzes the content of the request message, generates a new APN according to the APN carried in the message, and searches whether there is configuration information of this new APN at the GGSN, if there is, enter step C, if not, then process according to the normal activation process;

C. Search the activation configuration information on the network side of the GGSN according to the called number MSISDN, obtain the IMSI and IP address of the called user UE2, and proceed to step D; if the search fails, return the activation failure message to the SGSN of UE1, and the SGSN selects the GGSN again to activate;

D. GGSN creates the user context of UE1, initiates network side activation to UE2, and the APN in the message is regenerated and enters step E; if the network side activation fails, return a failure message to U1, and end the process;

E. GGSN receives UE2's context activation request message in response to network side activation, analyzes the content of the message, and performs conditional query. If it passes, continue to step F, and if it does not pass, end the process;

F. GGSN allocates resources for the UE1 context, creates a user context and allocates resources for UE2, returns an activation success response message to UE1 and UE2 after completion, and sets the context of UE1 and UE2 as an interrelated context for use between UE1 and UE2 Data forwarding; if the activation of any UE fails, the GGSN returns a failure response message and deletes the context of another UE;

G. UE1 and UE2 perform end-to-end PPP negotiation. If the negotiation passes, enter step H; if not, end the process;

H. According to the attributes of the APN, initiate the access user remote authentication service Radius (Remote Authentication Dial in User Service) billing process for the context of the two UEs. If it passes, enter step I. If any billing is unsuccessful, then Both contexts are deleted, ending the process;

1. The link connection is completed, and the UEs communicate with each other.

The described method of communicating through the packet domain also includes a step of setting the GGSN; its setting content includes:

A. Support UE to call UE's APN setting;

B. Add the MSISDN data item in the activation configuration on the network side.

The APN format in the step A is: called MSISDN. specific APN name, and the specific APN name can be empty.

The step B analyzing the content of the message includes: if the message is a PPP-type context activation message and conforms to the APN form in step A, then record the first label of the APN as the number of the called UE2, and use the latter part of the label as a The new APN name.

The APN format regenerated in step D is the same as the APN format generated in step A, and the first label of the APN used by UE1 is changed to the number of the calling user UE1 extracted from the UE1 activation message.

In the step E, analyzing the message content includes:

A. Whether it is a context activation message of the PPP type;

B. Whether the APN carried in the message is in the form described in step A and is the same as the APN in step D;

C. Whether the first label of the APN is the same as the MSISDN of the calling UE1 number. According to this MSISDN, there should be an active context when the GGSN searches;

D. The label behind the APN is used as a new APN to search for configuration information in the GGSN. The GGSN should configure the new APN as a special APN for the UE to call the UE, and the suffix part of the APN used by UE1 is the same.

The PPP negotiation process in the described step G includes:

A. LCP negotiation process;

B. Authentication process;

C. NCP negotiation process.

The LCP negotiation process includes:

The GGSN obtains the link quality negotiation data packet and maps it with the Qos stipulated in the GTP protocol. After the LCP negotiation is completed, it initiates the Qos update process on the network side to make the Qos of the two UE contexts consistent;

The GGSN negotiates the authentication mode with the two UEs, and decides whether to authenticate and use PAP or CHAP for authentication; if the LCP negotiation fails, the context of the two UEs will be deleted; otherwise, the authentication process will be performed.

The authentication process includes:

The GGSN analyzes the authentication request messages of the two UEs during the PPP negotiation authentication phase, and performs Radius authentication according to the APN attribute. If one UE fails to authenticate, the contexts of both UEs are deleted; if both succeed, NCP negotiation is performed. ;

The NCP negotiation process includes: GGSN allocates a dynamic IP address for UE1, and then GGSN simulates the IPCP negotiation behavior of UE, and performs IP address negotiation with two UEs respectively, so that the two UEs can obtain their own IP addresses and the IP address of the peer UE. address;

When UE2 uses a static address to negotiate with the peer, the GGSN needs to check the validity of the IP address according to the configured activation information on the network side;

In the process of communication, it also includes the process of QoS (Quality of Service) update. In the WCDMA system, the described Qos update process is:

(1) UE1 or SGSN initiates a Qos update request message. After receiving the Qos update request, the GGSN negotiates the Qos requested by the user, and initiates a network side update request message to UE2 according to the negotiated Qos;

(2) After SGSN and UE2 negotiate and process the Qos requested by the network side, return a Qos update response to GGSN; if GGSN receives UE2's update failure response, it returns a Qos update failure response to UE1, and the context remains unchanged;

(3) If the GGSN receives the Qos update success response returned by UE2, it will perform other processes of the update process on UE1 and UE2, and return the Qos update success response to UE1 after success; if the normal update process is unsuccessful, delete the two contexts ;

(4) If the GGSN receives the update process initiated by the SGSN for other reasons, it only updates the context of the current UE and does not initiate an update process for another UE, which is the same as the normal processing method.

If the GGSN initiates the Qos update, it needs to update the Qos of the two UE contexts at the same time. The method for communicating through the packet domain also includes a process of dismantling the communication link:

(1) When a device such as UE1 or SGSN triggers the deletion of the communication link, the PPP link is deleted first, and the GGSN monitors the link removal process, reclaims resources such as the allocated dynamic IP address, and then UE1 sends a context deletion message to the GGSN;

(2) When the GGSN receives the delete message from UE1, it deletes the context resource allocated by the GGSN, then returns a delete success response message to the UE1, and then initiates the Radius charging end process;

(3) At the same time, the GGSN initiates the process of deleting the UE2 context on the network side. After the UE2 returns the deletion response, it deletes resources such as the UE2 context resources allocated by the GGSN, and then initiates the Radius charging end process, and the link deletion is completed.

If the deletion of a UE context is initiated by the GGSN, it needs to trigger the deletion of the context of another UE at the same time, and the GGSN also needs to participate in the PPP link teardown process to reclaim resources such as IP addresses.

The present invention provides a simple and practical method for calling each other and establishing and maintaining an IP-based communication link between UEs in the PLMN through the packet domain, enriches the functions of the WCDMA/GPRS system, effectively utilizes network resources, and reduces user costs.

Description of drawings

FIG. 1 is a schematic diagram of communication between UEs in the prior art;

FIG. 2 is a schematic diagram of communication between UEs after the implementation of the present invention;

Fig. 3 is a schematic diagram of a communication link connection flow chart of the present invention;

FIG. 4 is a schematic diagram of a QoS update process between UEs initiated by a non-GGSN;

FIG. 5 is a schematic diagram of the QoS update process between UEs actively initiated by the GGSN;

FIG. 6 is a schematic diagram of a process for dismantling a communication link initiated by a non-GGSN;

Fig. 7 is a schematic diagram of the process of dismantling the communication link initiated by the GGSN.

Detailed ways

The specific implementation manners of the present invention will be described below in conjunction with the accompanying drawings.

As shown in FIG. 2 , the present invention enables UEs to establish a communication link as shown by the thin black line in the figure for communication. The external hardware environment of the present invention includes GGSN, SGSN, HLR, DNS, UE, etc., calls other users through the PLMN packet domain according to the user number MSISDN and APN, and establishes an IP-based communication link for communication between the two users. Set the GGSN of the system as follows:

1. Support the UE to call the APN setting of the UE. If huawei.com is specified as this specific APN, and the user uses "called MSISDN.huawei.com" when calling, the attribute of this APN huawei.com needs to be configured on the GGSN: selection mode ＝1, supported service type＝PPP type, other attributes are the same as general configuration

2. Configure network-side activation information: add MSISDN data items in the standard network-side activation configuration, and other configurations are standard

As shown in Figure 3, the method of the present invention specifically comprises the following steps:

A. UE1 initiates a request to GGSN, and the request message carries the APN selected by the user; UE1 activates the PPP type context, and the request message initiated carries the APN selected by the user, and the APN format is as follows: called MSISDN.Specific APN name, such as 13641091737.wcdma. com, where the first label 13641091737 is the number of the called user, and the following label wcdma.com is the APN name specified by the operator when calling another UE through the packet domain. This label can be used casually, as long as it does not match Other label conflicts; the format of the request message "called MSISDN. specific APN name" is a new regulation of the present invention, and the APN name in the existing standard is the same as the generally used network address format, such as www.sina.com .cn etc. The "specific APN name" in the format can be empty, so the user only needs to enter the mobile phone number of the other party when using it, which can greatly facilitate the use of customers.

B, GGSN analyzes the content of the request, generates a new APN format, checks whether there is configuration information of this new APN at the GGSN, if yes, enters step C, if not, then processes according to the normal activation process;

After receiving the UE1 activation request message, the GGSN analyzes the content of the message. If it is a PPP type context activation message, and the APN carried in the message is in the form described in step A, then record the first label of the APN as being Call the UE2 number (MSISDN), use the latter part of the label as a new APN name, and check whether there is configuration information for this new APN in the GGSN. If there is such a configuration method, and the configuration is a special APN for UE to call UE, then this activation is considered to be an activation request for UE1 to call UE2; otherwise, it is processed according to the normal activation process.

C. Find the network side activation configuration information of GGSN according to the called number, obtain the IMSI and IP address of UE2, and enter step D; if the search fails, return an activation failure message to the SGSN of UE1, and SGSN reselects GGSN for activation;

Check the network-side activation configuration information of GGSN according to the recorded called number MSISDN. Each user with the network-side activation function has at least the following configuration content: MSISDN, IMSI, user IP address, and the APN to which the IP address belongs. In the general regulations Only configuration parameters: IMSI, user IP address and APN to which the IP address belongs, the present invention only adds an MSISDN in the configuration.

Obtain the IMSI and IP address of the called user UE2 through this search; if the search fails, it means that the GGSN does not support the network side activation of the called user, and then return an activation failure message to the SGSN of UE1, and the SGSN of UE1 will restart according to the protocol Select the GGSN that supports the network side activation of the called user UE2 for activation;

D. GGSN creates the user context of UE1, initiates network side activation to UE2, regenerates the APN in the message, and enters step E; if the network side activation fails, returns a failure message to U1, and ends the process;

GGSN creates the user context of UE1, initiates the activation process on the network side for the called user UE2, the APN in the message is regenerated, the format is as described in A, but the first label is modified to the calling user extracted from the UE1 activation message The number of UE1, the content of the latter part of the label is the same as the APN used when UE1 is activated, such as 13688856789.wcdma.com, where 13688856789 is the calling party number; if the activation fails on the network side and the call fails, the GGSN should delete all the calls related to the call. resources, return an activation failure response message to UE1; otherwise, wait for UE2 to initiate an activation request message in response to network activation;

E. GGSN analyzes the content of the message and performs conditional query. If passed, continue to step F, and if not passed, then end the process;

After receiving the response activation request message from UE2, the GGSN analyzes the content of the message and checks whether the following conditions are met:

a. It is a PPP type context activation message;

b. The APN carried in the message is in the form described in (1) and is the same as the APN used by UE1;

c. The first label of the APN is the same as the MSISDN of the calling UE1 number. According to this MSISDN, there should be an active context when searching in the GGSN;

d. The label behind the APN is used as a new APN to search for configuration information in the GGSN. The GGSN should configure the new APN as a special APN for the UE to call the UE, and the suffix part of the APN used by UE1 is the same;

If the above conditions are all satisfied, it is considered that UE2 responds to the call activation message of UE1; if any condition is not satisfied, the process ends.

F. GGSN allocates resources for the UE1 context, creates a user context and allocates resources for UE2, returns an activation success response message to UE1 and UE2 after completion, and sets the context of UE1 and UE2 as an interrelated context for use between UE1 and UE2 Data forwarding; if any activation fails, the GGSN returns a failed response message and deletes the context of another UE;

The GGSN allocates resources for the context of UE1, and returns an activation success response message to UE1 after completion; creates a user context and allocates resources for UE2, and needs special handling when negotiating the context Qos of the called user UE2, so that its negotiation value is as close as possible to the UE1 context The difference between the Qos negotiation values of the two is the smallest, and returns a successful activation response message to UE2 after completion;

If the activation of UE1 or UE2 fails, the GGSN returns a failure response message and actively triggers the deletion of the context of the other UE; if both succeed, set the context of the two UEs as an interrelated context for data forwarding between the two UEs; if After deleting the context of another UE, release all resources related to the GGSN.

G. Carry out PPP negotiation between UE1 and UE2. If the negotiation passes, enter step H; if not, end the process and initiate the request again;

So far, the communication link between the two UEs (equivalent to the physical layer of the PPP protocol) has been established, and then the PPP negotiation between the two UEs (complying with the 3GPP protocol and the RFC protocol) is divided into LCP negotiation, authentication, and NCP negotiation three phases. The GGSN monitors the PPP negotiation process. As a relay for two UEs to perform PPP negotiation, it needs to analyze and process PPP negotiation data packets such as link quality negotiation, authentication, and IP address negotiation, but the behavior of the GGSN should be transparent to the two UEs. .

For PPP data packets that do not need to be analyzed and processed by the GGSN, the GGSN is only responsible for forwarding between the two UEs: for the uplink datagram sent by UE1, after the GGSN finds the context, it sends it as downlink data according to the relationship between the two contexts of UE1 and UE2 To UE2; for the uplink datagram sent by UE2, GGSN sends it to UE1 in the same way;

The first is the LCP negotiation process: GGSN obtains the link quality negotiation data packet, and maps it with the Qos stipulated in the GTP protocol. After the LCP negotiation is completed, it initiates the Qos update process on the network side to make the Qos of the two UE contexts consistent (this function is optional, Refer to the Qos update process initiated by GGSN); GGSN also needs to negotiate with the two UEs on the authentication method, decide whether to authenticate and use PAP or CHAP for authentication; if the LCP negotiation fails, delete the context of the two UEs, otherwise perform authentication rights process;

Authentication process: GGSN analyzes the authentication request messages of two UEs in the PPP negotiation authentication phase, and performs Radius authentication according to the APN attribute. If one UE fails authentication, the context of both UEs is deleted; if both succeed , to carry out NCP negotiation; after deleting the message, all related resources of the GGSN need to be cleared, and whether to re-initiate is determined by the user;

NCP negotiation process: NCP negotiation includes network layer negotiation such as IPCP and IPXCP. Here, IPCP is used as an example for illustration. GGSN assigns a dynamic IP address to UE1 (if UE2 uses a dynamic address network side activation, it also needs to assign an IP address to UE2), then GGSN simulates the IPCP negotiation behavior of UE, and conducts IP address negotiation with two UEs respectively, so that the two UEs can obtain The dynamic IP address assigned by the GGSN and the IP address of the peer UE;

When UE2 uses a static address and negotiates with the peer, the GGSN needs to check the validity of the IP address according to the configured activation information on the network side.

H, according to the attribute of APN, initiate Radius billing process to the context of two UEs, if pass, enter step 1, if any billing is unsuccessful, then two contexts are all deleted, end flow process;

After the PPP negotiation between the two UEs is completed, according to the attributes of the APN, the Radius charging process is initiated for the contexts of the two UEs. If any one of them fails to charge, both contexts will be deleted; after deleting the message, you need to All relevant resources of the GGSN are cleared, and it is up to the user to decide whether to re-initiate.

1. The link connection is completed, and the UEs communicate with each other.

So far, the call is successful and the communication link is established, and any IP-based application software can be run; GGSN is responsible for forwarding data packets between two UEs: receiving an uplink data packet from a UE, searching for the context, checking, and serving as a downlink datagram forwarded to another UE.

As shown in Figures 4 and 5, the present invention may also include a Qos update process in the communication process between UEs through PLAM. In a WCDMA system, the Qos update process is:

(1) UE or SGSN initiates a Qos update request message. After receiving the Qos update request, GGSN negotiates the Qos requested by the user, and initiates a network side update request message to UE2 according to the negotiated Qos;

(2) After SGSN and UE2 negotiate and process the Qos requested by the network side, return a Qos update response to GGSN; if GGSN receives UE2's update failure response, it returns a Qos update failure response to UE1, and the context remains unchanged;

(3) If the GGSN receives the Qos update success response returned by UE2, it will perform other processes of the update process on UE1 and UE2, and return the Qos update success response to UE1 after success; if the normal update process is unsuccessful, delete the two contexts ;

(4) If the GGSN receives the update process initiated by the SGSN for other reasons, only the context of the current UE is updated, and the update process is not initiated for another UE, which is the same as the normal processing method.

If the aforementioned Qos update is initiated by the GGSN, the Qos of the two UE contexts need to be updated at the same time as required.

As shown in Figures 6 and 7, in the present invention, a process of dismantling the communication link is also included:

(1) When a device such as UE1 or SGSN triggers the deletion of the communication link, first delete the PPP link according to the 3GPP protocol and the RFC protocol, and the GGSN monitors the link removal process, reclaims resources such as the allocated dynamic IP address, and then UE1 sends the GGSN Initiate a context delete message;

(2) When GGSN receives UE1's deletion message, it deletes the context resources allocated by GGSN, then returns a deletion success response message to UE1, and then initiates the Radius charging end process;

(3) At the same time, the GGSN initiates the process of deleting the UE2 context on the network side. After UE2 returns the deletion response, it deletes the resources such as the UE2 context resources allocated by the GGSN, and then initiates the Radius charging end process, and the link deletion is completed.

If the removal is initiated by the GGSN to delete the context of one UE, it needs to trigger the deletion of the context of another UE at the same time, and the GGSN also needs to participate in the PPP link removal process and reclaim resources such as IP addresses.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person familiar with the technology can easily think of changes or replacements within the technical scope disclosed in the present invention. , should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (16)

1. A method for communicating through a packet domain, characterized in that it comprises the steps of: The GPRS gateway support node GGSN (Gateway GPRS Support Node) receives the call request of the user terminal UE1 (User Equipment), generates a new APN on the GGSN according to the APN (Access Point Name) carried by the call request, and searches Whether there is configuration information of the new APN on the GGSN, if not, proceed according to the normal activation process, if yes, obtain the international mobile subscriber identity of the called user terminal UE2 on the GGSN according to the international ISDN number MSISDN of the called mobile station IMSI and IP address, the GGSN creates the user contexts of UE1 and UE2 and allocates resources, and sets the contexts of UE1 and UE2 as interrelated contexts for data forwarding between UE1 and UE2. communication. 2. The method for communicating in a packet domain as claimed in claim 1, wherein said link connection further comprises the following specific steps: A. UE1 initiates a request to the GPRS gateway support node GGSN (Gateway GPRS Support Node), and the request message carries the APN selected by the user; B, GGSN analyzes the content of this request message, generates new APN according to the APN carried in the message, searches whether there is the configuration information of this new APN at GGSN, if yes, enters step C, if not, then process according to normal activation process; C. Find the network side activation configuration information of the GGSN according to the called number MSISDN, obtain the IMSI (International Mobile Subscriber Identity) and IP address of the called user UE2, and enter step D; if the search fails, send the GPRS service to UE1 The support node SGSN (Serving GPRS Support Node) returns an activation failure message, and the SGSN reselects the GGSN for activation; D. GGSN creates the user context of UE1, initiates network side activation to UE2, regenerates the APN in the message, and enters step E; if the network side activation fails, GGSN returns a failure message and ends the process; E. GGSN receives UE2's context activation request message in response to network side activation, analyzes the content of the message, and performs conditional query. If it passes, continue to step F, and if it does not pass, end the process; F. GGSN allocates resources for UE1 context, creates user context and allocates resources for UE2, and returns an activation success response message to UE1 and UE2 after completion, and sets the context of UE1 and UE2 as an interrelated context for use between UE1 and UE2 Data forwarding; if the activation of any UE fails, the GGSN returns a failure response message and deletes the context of another UE; G. UE1 and UE2 perform end-to-end PPP negotiation. If the negotiation passes, enter step H; if not, end the process; H, according to the attribute of APN, initiate Radius billing process to the context of two UEs, if pass, enter step 1, if any billing is unsuccessful, then two contexts are all deleted, end flow process; I. The link connection is completed, and communication between UEs is performed. 3. The method for communicating in the packet domain as claimed in claim 2, further comprising a step of setting the GGSN; the setting content includes: A. Support UE to call UE's APN setting; B. Add the MSISDN data item in the activation configuration on the network side. 4. The method for communicating through the packet domain as claimed in claim 2 or 3, wherein the APN format in the step A is: called MSISDN. specific APN name, wherein the specific APN name can be empty. 5. The method for communicating in a packet domain as claimed in claim 4, wherein said step B analyzing the content of the message comprises: if the message is a context activation message of the Point to Point Protocol (PPP) type, and If it conforms to the APN form in step A, record the first label of the APN as the called UE2 number, and use the latter part of the label as a new APN name. 6. The method for communicating in the packet domain according to claim 5, wherein the APN format regenerated in step D is the same as the APN format generated in step A, and the first label of the APN used by UE1 is modified to The number of the calling user UE1 extracted from the UE1 activation message. 7. The method for communicating in the packet domain as claimed in claim 4, characterized in that analyzing the message content in the step E includes: a. Whether it is a context activation message of PPP type; b. Whether the APN carried in the message is in the form described in step A and is the same as the APN in step D; c. Whether the first label of the APN is the same as the MSISDN of the calling UE1 number. According to this MSISDN, there should be an active context in the GGSN search; d. The label behind the APN is used as a new APN to search for configuration information in the GGSN. The GGSN should configure the new APN as a special APN for the UE to call the UE, and the suffix part of the APN used by UE1 is the same. 8. The method for communicating in the packet domain as claimed in claim 2 or 3, characterized in that the PPP negotiation process in the step G includes: a. Link Control Protocol LCP (Link Control Protocol) negotiation process; b. Authentication process; c. Network Control Protocol NCP (Network Control Protocol) negotiation process. 9. The method for communicating in the packet domain according to claim 8, characterized in that the LCP negotiation process includes: The GGSN obtains the link quality negotiation data packet, and maps it with the QoS (Quality of Service) stipulated in the GTP protocol. After the LCP negotiation is completed, it initiates the QoS process on the network side to make the QoS of the two UE contexts consistent; The GGSN negotiates the authentication mode with the two UEs, decides whether to authenticate and uses PAP or CHAP for authentication; If the LCP negotiation fails, the contexts of the two UEs are deleted; otherwise, the authentication process is performed. 10. The method for communicating in the packet domain as claimed in claim 8, characterized in that said authentication process includes: The GGSN analyzes the authentication request messages of the two UEs during the authentication phase of the PPP negotiation, and performs Radius (Remote Authentication Dial in UserService) authentication for the access user according to the APN attribute. The contexts of all UEs are deleted; if all succeed, NCP negotiation is performed. 11. The method for communicating in the packet domain as claimed in claim 8, characterized in that said NCP negotiation process includes: The GGSN assigns a dynamic IP address to UE1, and then the GGSN simulates the IPCP negotiation behavior of the UE, and performs IP address negotiation with the two UEs, so that the two UEs can obtain their own IP addresses and the IP address of the peer UE; When UE2 uses a static address and negotiates with the peer, the GGSN needs to check the validity of the IP address according to the configured activation information on the network side. 12. The method for communicating in the packet domain as claimed in claim 1, 2 or 3, characterized in that the communication process also includes a Qos update process. 13. The method for communication between UEs via packet domain as claimed in claim 12, characterized in that in the WCDMA system, the Qos update process is: (1) UE1 or SGSN initiates a Qos update request message. After receiving the Qos update request, the GGSN negotiates the Qos requested by the user, and initiates a network side update request message to UE2 according to the negotiated Qos; (2) After SGSN and UE2 negotiate and process the Qos requested by the network side, return a Qos update response to GGSN; if GGSN receives UE2's update failure response, it returns a Qos update failure response to UE1, and the context remains unchanged; (3) If the GGSN receives the Qos update success response returned by UE2, it will perform other procedures of the update process on UE1 and UE2, and return the Qos update success response to UE1 after success; if the normal update process is unsuccessful, delete the two contexts ; (4) If the GGSN receives the update process initiated by the SGSN for other reasons, it only updates the context of the current UE and does not initiate an update process for another UE, which is the same as the normal processing method. 14. The method for communicating in the packet domain according to claim 13, wherein if the GGSN initiates the Qos update on its own initiative, it needs to update the Qos of the two UE contexts at the same time. 15. The method for communicating through the packet domain as claimed in claim 2 or 3, further comprising a step of dismantling the communication link: (1) When a device such as UE1 or SGSN triggers the deletion of the communication link, the PPP link is deleted first, and the GGSN monitors the link removal process, reclaims resources such as the allocated dynamic IP address, and then UE1 sends a context deletion message to the GGSN; (2) When the GGSN receives the delete message from UE1, it deletes the context resource allocated by the GGSN, then returns a delete success response message to the UE1, and then initiates the Radius charging end process; (3) At the same time, the GGSN initiates the process of deleting the UE2 context on the network side. After the UE2 returns the deletion response, it deletes resources such as the UE2 context resources allocated by the GGSN, and then initiates the Radius charging end process, and the link deletion is completed. 16. The method for communicating in the packet domain as claimed in claim 15, characterized in that if the deletion of a UE context is initiated by the GGSN, it needs to trigger the deletion of the context of another UE at the same time, and the GGSN also needs to participate in the PPP link teardown process, Recycle resources such as IP addresses.

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