CN111132134A - PDT (PDT) packet cross-system interconnection implementation method - Google Patents

Abstract

The invention relates to a PDT (PDT) grouping cross-system interconnection implementation method. The PDC is responsible for docking external network equipment, establishing and dismantling grouping functions, managing grouping resources and compressing/decompressing packet packets, the ECN stores the position information of users and performs mobility management on the users and the groups, and the BS performs segmented processing and channel transmission on the packet data; storing local terminal and allopatric terminal information, local exchange and allopatric exchange information in PDC, cascading a plurality of ECNs and BSs in the PDT system with network equipment outside the PDT system by using a plurality of PDCs, and acquiring the BS information visited by a user through interaction of the PDCs and the ECNs to provide service for communication between the network equipment inside and outside the system and the terminal. The invention mainly designs the network element of the PDC grouping server, is assisted by an internal module structure and an internal data transmission structure of the PDC, and provides basic guarantee for the transmission of cross-system data by multi-exchange connection and communication among the PDC.

Description

PDT (PDT) packet cross-system interconnection implementation method

Technical Field

The invention relates to a PDT (PDT) grouping cross-system interconnection implementation method.

Background

At present, a grouping function in a PDT system is mainly applied to text-type long and short messages, OTAP, OTAR, multimedia messages and other services, in a technical specification of a Police Digital Trunking (PDT) communication system, no matter a grouping data service function specification or an interconnection technical specification, a standard specification is not made on grouping cross-system interconnection, however, in actual field use, a requirement of grouping cross-system interconnection exists, for example, OTAR air interface key updating, one OTAR server provides service for terminals under a plurality of PDT systems, or a condition that the terminals roam cross-system exists, and in order to ensure that the latest keys can be accurately issued to the terminals, realization of PDT grouping cross-system interconnection needs to be considered.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a technical scheme of a PDT packet cross-system interconnection implementation method.

The PDT system consists of PDC, ECN, BS and MS, DS is connected with PDC, one PDC can be connected with a plurality of ECN and a plurality of BS, one PDC is connected with a plurality of ECN and a plurality of BS through wired network and is communicated through ICP protocol, BS is communicated with MS through wireless communication mode, ECN is connected with BS through communication connection, and the PDT system is characterized in that: the PDC is responsible for docking external network equipment, establishing and dismantling grouping functions, managing grouping resources and compressing/decompressing packet packets, the ECN stores the position information of users and performs mobility management on the users and the groups, and the BS performs segmented processing and channel transmission on the packet data packets; storing local terminal and allopatric terminal information, local exchange and allopatric exchange information in PDC, cascading a plurality of ECNs and BSs in the PDT system with network equipment outside the PDT system by using a plurality of PDCs, and acquiring the BS information visited by a user through interaction of the PDCs and the ECNs to provide service for communication between the network equipment inside and outside the system and the terminal.

The PDT grouping cross-system interconnection realization method is characterized in that when the DS is used as internal network equipment, the DS is connected with the PDC in an ICP mode; when the DS is used as an external network device, the DS is connected with the PDC through the Ethernet, UDP network protocols are used for communication between the DS and the PDC, and the IPSec protocol is used for providing safe encryption for IP data transmission between the DS and the PDC.

The PDT grouping cross-system interconnection implementation method is characterized in that the PDC comprises a control module and a data module, the control module works in a user mode, the data module works in a kernel mode, and the control module and the data module are communicated through interface control.

The PDT grouping cross-system interconnection realization method is characterized in that the control module comprises a configuration information table module, a user state query module, a resource management module and a B1 interface module, wherein the configuration information table module is used for storing the home location information of a target terminal or a group, the user state query module is used for querying the visiting location information of the target terminal, the resource management module is used for managing base station channel resources, and the B1 interface module is used for connection management among network elements;

the data module comprises an IP routing module, a GRE protocol module, a kernel data sending and receiving module and an IPSec protocol module, wherein the IP routing module is used for transmitting and routing an IP data packet, the GRE protocol module is used for carrying out GRE encapsulation and decapsulation on data, the kernel data sending and receiving module is used for receiving and sending user packet data, and the IPSec protocol module is used for authenticating and encrypting messages between the PDC and the DS; the DS sends the user data of the PDC, firstly extracts the key information of the target terminal in a control module of the PDC, and then transmits the data to a kernel module for GRE encapsulation and IP routing and sends the data to the BS after the packet flow is successfully established.

The method for realizing PDT grouping cross-system interconnection is characterized in that DS transmits user data to MS, the size of a data packet depends on network setting restriction, the user data is encapsulated into a UDP packet and is sent to PDC, the PDC stores the data, a user configuration information table is inquired, a corresponding exchange initiation state is inquired according to an inquiry result, an attribution exchange and a registration base station of a target user are found, paging is initiated to MS, a standard grouping establishment flow is carried out between the PDC and the MS, BS serves as a transmission channel, and after a terminal responds, a resource management module of the PDC distributes a channel for grouping transmission and informs a target terminal that grouping establishment is successful;

after the packet flow is successfully established, the PDC encapsulates user data into a network packet in a GRE format by using an IP tunnel technology and sends the network packet to the BS, the BS unpacks the packet data content after receiving the network packet and transmits the packet data content to the MS in a segmented mode according to different sizes of user data packets so as to meet the requirement of air interface transmission rate.

The PDT packet cross-system interconnection implementation method is characterized in that GRE encapsulation facilitates transparent packet data to pass through the Internet without being limited by a two-layer encapsulation protocol of a packet, thereby facilitating expansion of the use of PDC; GRE encapsulation also facilitates intra-domain multicasting of packet data within the PDT system, primarily for group address-oriented packet transmission.

The PDT grouping cross-system interconnection realization method is characterized in that the information of the configuration information table module is stored in a file system, and after a PDC is started, four tables are established locally in a mode of reading a configuration file;

table 1 is an exchange ID-IP correspondence table in a local PDC, and configures exchange information associated with the local PDC, to find whether a visited place of a target user belongs to a local exchange, where one PDC may connect multiple exchanges;

table 2 shows local terminal prefixes and home exchange information, and configures a terminal number prefix of a local PDC, for querying whether a target user belongs to the local and home exchange information;

table 3 is a correspondence table between the terminal number prefix and the home PDC, and configures terminal number prefix information of an adjacent PDC to search for home PDC information of the target user;

table 4 is a table corresponding to the neighbor exchange ID and PDC IP, and configures corresponding information of the neighbor exchange ID and PDC IP, so as to search for the IP of the local user roaming the place PDC after roaming across PDCs.

The PDT grouping cross-system interconnection realizing method is characterized in that the PDC needs to acquire visited place exchange and base station information of a terminal in the process of establishing a grouping transmission link, inquiry process interaction is mainly carried out between the PDC and the exchange, mobility management information related to registration and roaming of a user is exchanged and stored, the information is inquired from a home place or a visited place exchange according to different conditions, and a state inquiry response mainly comprises the following elements:

(1) the terminal registration state comprises unregistered state, local user registered state, remote user roaming registration state, local user roaming state, user teleproned/remotely killed state, user not opened account, user not existed, user not supporting the grouping service;

(2) a call state;

(3) registering base station information, wherein when the terminal is registered under the current exchange, the parameter in the state inquiry response carries effective base station information;

(4) the visiting place exchanges information, when the terminal cross-exchanges roaming, the home place exchange can inquire the current visiting place exchange information of the terminal;

when receiving a data transmission request from an external network device, the PDC firstly looks up the table 2 to determine whether the user belongs to the local area;

if the user belongs to the local area, the home exchange information of the user can be obtained from the table 2, the user state query is firstly requested to the preferred home exchange, and if the user state query fails, the user state query is switched to the secondary home; if the inquiry result is directly returned to the base station list, the user is registered under the current home exchange; if the query result returns the exchange ID, the table 1 is queried according to the exchange ID, if the exchange exists in the table 1, the cross-exchange roaming of the user in the PDC system is indicated, otherwise, the cross-PDC roaming of the user is indicated; if the user is in the cross exchange roaming in the PDC system, the user state is inquired according to the returned exchange ID until the base station list is returned; if the user roams across PDC, the information is exchanged according to the roaming place, the table 4 is inquired, the information of the PDC of the roaming place is obtained, and the data transmission request is transferred to the PDC of the roaming place for processing;

if the user does not belong to the local, looking up the table 3, checking the PDC IP of the attribution of the prefix of the remote terminal, and forwarding the data transmission request to the adjacent-end PDC for processing.

The PDT grouping cross-system interconnection implementation method is characterized in that a plurality of ICP channels are established between the PDC and a plurality of exchanges through B1 interfaces, and control information is transmitted between the subsequent PDC and the exchanges through the ICP channels.

The PDT grouping cross-system interconnection realization method is characterized in that the PDC supports the establishment of connection with the adjacent PDC, and the communication module among the PDCs mainly has the task of providing interfaces for sending and receiving data among the PDCs and maintaining the communication connection;

communication among the PDCs has two modes, one mode uses a UDP mode and the other mode uses an ICP mode, if the UDP mode is adopted, the module needs to maintain connection state detection among the PDCs and confirm retransmission of data, and if the ICP mode is adopted, the ICP module can provide a heartbeat detection and data confirm retransmission mechanism;

adopting an ICP mode for treatment: when a PDC receives a packet transmission request from an external network device, a configuration information table is queried to find that a target user roams to other PDC systems across PDCs, or the target user is not a local user, data transmission occurs between the PDC and an adjacent PDC, which mainly includes the following two cases:

(1) when a local user roams to other PDC systems across PDC systems, the local PDC transmits a grouping request to an adjacent PDC, and the adjacent PDC receives the grouping transmission request and informs the local PDC of a grouping service transmission result after the whole process of the grouping service flow is finished according to the inquiry of the configuration information table, the inquiry of the user state and the PDT grouping standard;

(2) when the remote terminal is paged in a grouping way, when the remote terminal does not roam across the PDC, the other processes are the same as the local user roaming across the PDC except the difference of the query process of the configuration information table; when the cross-PDC roaming occurs in the remote terminal, the cross-PDC roaming to the third party PDC is divided into two cases, one is that the cross-PDC roaming to the third party PDC, the grouping request is transmitted to the user attributive PDC from the local PDC, and then transmitted to the third party PDC from the attributive PDC, and after the grouping process is finished, the third party PDC transmits the grouping result to the attributive PDC, and the attributive PDC is transmitted to the local PDC; the other is that the allopatric terminal roams to the local PDC across the PDC, the grouping request is firstly transmitted to the home PDC from the local PDC, and then is transmitted to the local PDC from the home PDC;

in order to prevent the transmission of the packet request between the local PDC and the neighboring PDC from falling into an infinite loop, each time the packet request is transmitted, a transmission path record is simultaneously added in the transmission message, for example, when the local PDC record is added in the message transmitted from the local PDC to the neighboring PDC and then transmitted from the neighboring PDC to the local PDC, the message simultaneously contains the local PDC and the neighboring PDC records, and once the receiver PDC of the packet transmission request knows that the message has been forwarded by the current PDC, the packet transmission request is not forwarded across PDCs no matter whether subsequent configuration channel table query and user state query can successfully acquire the information of the base station.

The method mainly comprises the design of a PDC grouping server network element and is assisted by a PDC internal module structure and an internal data transmission structure, configuration information table query, user state query, multi-exchange connection, inter-PDC communication and the like are used in the PDT grouping transmission establishment process, and the configuration information table query and the user state query are used for acquiring key terminal visiting place information, so that an information basis is provided for establishing effective grouping connection between a grouping system and a terminal, and the multi-exchange connection and inter-PDC communication provide basic guarantee for transmission of cross-system data; meanwhile, the design of multiple exchange connections greatly helps to improve the stability of the system.

Drawings

FIG. 1 is a schematic diagram of a network structure of the system of the present invention;

FIG. 2 is a schematic block diagram of a PDC;

FIG. 3 is a schematic diagram of a control data transmission structure among MS, BS, PDC, and ECN;

fig. 4 is a schematic diagram of the structure of user data transmission among MS, BS, PDC, and DS.

Detailed Description

The invention provides an effective method for PDT grouping cross-system interconnection, and the method has certain universality in the field of trunking communication, for example, TETRA communication can also adopt the key technology of the method to realize grouping transmission.

The PDC is used as a packet server, plays a core role in realizing a packet function, and is responsible for interfacing with external network equipment, establishing and removing the packet function, managing packet resources, compressing/decompressing packet packets, and the like, the ECN is used as a switching center, one of the functions is to store the location information of a user and perform mobility management on the user and the packet, and is also a part of functions required to be involved in the method, and the BS is used as a base station and mainly plays a role in performing segmentation processing and channel transmission on the packet data packets.

Storing local terminal and long-distance terminal information, local exchange and long-distance exchange and other information in PDC, and cascading multiple exchanges in PDT system, base station and network equipment outside PDT system by using multiple PDC devices. Therefore, the PDC can acquire the information of the base station visited by the user through interaction with the switching center, and service is provided for communication between network equipment inside and outside the system and the terminal. The basic network architecture of the system of the present invention is shown in fig. 1.

When the DS is used as an internal network device, the DS can be connected with the PDC in an ICP mode, the ICP is a communication protocol between internal boards, and the ICP has a heartbeat detection mechanism, a message confirmation mechanism and a retransmission mechanism, so that the reliability of data transmission is ensured. When the DS is used as an external network device, the DS is connected with the PDC through the Ethernet, UDP network protocols are used for communication between the DS and the PDC, and the IPSec protocol is used for providing safe encryption for IP data transmission between the DS and the PDC. Under the actual use scene, different external equipment can be satisfied in PDC connection, if PDC allies oneself with the dispatch table outward, can satisfy the purpose of system command dispatch such as policeman, fire control, if PDC allies oneself with key management server outward, can satisfy the purpose that terminal key downloaded under the cluster system, if PDC allies oneself with web gateway outward, can satisfy the purpose of terminal connection internet under the cluster system. Meanwhile, the networking architecture is not only suitable for PDT (PDT) grouping systems, but also suitable for TETRA (terrestrial trunked radio) grouping systems, the difference between the PDT and the TETRA grouping systems lies in the grouping interaction process between the PDC and the BS, and the PDC can be compatible with PDT and TETRA system grouping functions at the same time according to different types of terminal users, namely, one PDC can be connected with the PDT base station and the TETRA base station at the same time and is in grouping communication with the PDT and TETRA.

PDC, ECN, BS and MS belong to a set of network elements in a PDT system. One PDC can connect multiple exchanges and multiple base stations, ECNn stands for multiple exchanges and BSn stands for multiple base stations. The PDC1 is connected to ECNn, PDC1 and BSn via a wired network, and communicates via an ICP protocol, and the BSn communicates with the MS via a wireless communication method. In an actual networking, the ECNn is in communication connection with the BSn.

Data between the PDC and PDC are transmitted in an ICP manner, and messages are transmitted across the PDC, which is described in the present invention as a cross PDC system. A terminal MS under PDC1 of the present invention roams under a neighboring PDC2 system, referred to as cross-PDC roaming, and an MS under PDC1 of the present invention roams between multiple exchanges connected to the PDC, referred to as cross-exchange roaming. The cross-PDC roaming belongs to a cross-exchange roaming category, the cross-exchange roaming does not necessarily belong to the cross-PDC roaming category, and both the cross-PDC roaming and the cross-exchange roaming belong to a cross-system roaming category.

PDC module framework

The software environment in which the PDC operates in the description of the present invention is a Linux operating system. The PDC adopts a strategy in which control information and data information are transmitted separately from each other. The internal module structure of the PDC is shown in fig. 2. The control module works in a user mode, and the data module works in a kernel mode. The control module and the data module are communicated through interface control.

The control module comprises a configuration information table module, a user state query module, a resource management module, a B1 interface module and the like. The configuration information table module is used for storing the attribution information of the target terminal or group, the user state query module is used for querying the visiting place information of the target terminal, the resource management module is used for managing the channel resources of the base station, and the B1 interface module is used for the connection management between the network elements.

The message interaction among network elements in the packet establishing process all belongs to the category of control data, the message structure of the control data transmitted among MS, BS, PDC and ECN is shown in figure 3, and CDATA in the figure represents the control data.

The data module comprises an IP routing module, a GRE module, a kernel data sending and receiving module and an IPSec protocol module. The IP routing module is used for transmitting and routing IP data packets, the GRE module is used for carrying out GRE encapsulation and decapsulation on data, the kernel data sending and receiving module is used for receiving and sending user grouped data, and the IPSec protocol module is used for message authentication and encryption between the PDC and the DS.

The DS extracts the key information of the destination terminal from the control module of the PDC, when the packet flow is successfully established, the data is transmitted to the kernel module to be processed by GRE encapsulation and IP routing and transmitted to the BS, the message structure of the user data transmitted among the MS, the BS, the PDC and the DS is shown in figure 4, and UDATA in the figure represents the user data.

The interface control module uses an I/O control technology and is responsible for communication between a user mode and a kernel mode, and the interface control module mainly comprises a virtual channel creation and deletion interface, a data information sending and receiving interface and the like.

DS transmits user data to MS, the size of data packet depends on network setting restriction, packaging user data into UDP packet and sending to PDC, PDC stores the data, inquires user configuration information table, according to inquiry result to corresponding exchange initiation state inquiry, finds out target user's attribution exchange and register base station, initiates paging to MS, the standard grouping establishment flow is carried out between PDC and MS, BS is used as transmission channel, the air interface signaling flow established by grouping is the standard flow specified in police digital cluster _ PDT _ communication system technical specification-air interface call control layer. In this process, control data is transmitted between network elements.

After the packet flow is successfully established, the PDC encapsulates user data into a network packet in a GRE format by using an IP tunnel technology and sends the network packet to the BS, the BS unpacks the packet data content after receiving the network packet and transmits the packet data content to the MS in a segmented mode according to different sizes of user data packets so as to meet the requirement of air interface transmission rate. GRE encapsulation mainly has two purposes, one is to facilitate transparent packet data to pass through the Internet without being limited by a two-layer encapsulation protocol of a packet, so that the purpose of PDC is conveniently expanded, for example, the expansion is used for encapsulating a TETRA packet data SNDCP protocol, and the other is to facilitate the packet data to carry out intra-domain multicast in a PDT system and mainly used for packet sending facing to a group address. In the process, user packet data is transmitted between network elements.

Configuration information table

And storing the information of the configuration information table in a file system, and after the PDC is started, establishing four tables locally in a mode of reading the configuration file.

Table 1, the exchange information associated with the local PDC is configured to find whether the visited place of the target user belongs to the local exchange, and one PDC may connect multiple exchanges.

Table 2, configuring the terminal number prefix of the local PDC, for inquiring whether the target user belongs to the local and exchanging information at the home.

And 3, configuring the prefix information of the terminal numbers of the adjacent PDC for searching the attributive PDC information of the target user.

Table 4, configure the corresponding information between the neighboring exchange ID and the PDC IP for finding the IP of the PDC of the roaming location after the local user roams across PDCs.

User status query

The PDC needs to acquire visited place exchange and base station information of the terminal in the process of establishing the packet transmission link, and the query process interaction is mainly performed between the PDC and the exchange to exchange and store mobility management information related to registration and roaming of the user. The information can be inquired from the home location or the visiting location exchange according to different situations, and the state inquiry response mainly comprises the following elements:

(1) the terminal registration state comprises unregistered state, local user registered state, remote user roaming registration state, local user roaming state, user teleproned state/remote death state, user not opened account, user not existed, user not supporting packet service, etc.;

(2) a call state;

(3) registering base station information, wherein when the terminal is registered under the current exchange, the parameter in the state inquiry response carries effective base station information;

(4) the visiting place exchanges information, when the terminal cross-exchanges roaming, the home place exchange can inquire the current visiting place exchange information of the terminal;

when the PDC receives a data transmission request from an external network device, the PDC searches the table 2 first to determine whether the user belongs to the local area.

If the user belongs to the local area, the home exchange information of the user can be obtained from the table 2, the user state query is firstly requested to the preferred home exchange, and if the user state query fails, the user state query is inquired to the secondary home exchange. If the inquiry result is directly returned to the base station list, the user is registered under the current home exchange. If the query result returns the exchange ID, the table 1 is queried according to the exchange ID, if the exchange exists in the table 1, the cross exchange roaming of the user in the PDC system is indicated, otherwise, the cross PDC roaming of the user is indicated. If the user is roaming across exchanges in the PDC system, the user state is inquired according to the returned exchange ID until the base station list is returned. If the user roams across PDC, the information is exchanged according to the roaming place, the table 4 is inquired, the information of the PDC of the roaming place is obtained, and the data transmission request is transferred to the PDC of the roaming place for processing.

If the user does not belong to the local, looking up the table 3, checking the PDC IP of the attribution of the prefix of the remote terminal, and forwarding the data transmission request to the adjacent-end PDC for processing.

Multiple switch connection

In order to support the situations of dual homing, multi-homing and cross exchange roaming of the user in the PDC system, the PDC needs to support connection establishment with a plurality of exchanges, a plurality of ICP channels are created between the PDC and the exchanges through B1 interfaces, and control information is transmitted between subsequent PDCs and exchanges through the ICP channels.

The user dual-homing and group multi-homing mechanisms are mainly used for guaranteeing the operation stability of the system, and when one of the home exchanges fails, the normal operation of the packet service and other trunking services is not influenced.

inter-PDC communication

In order to support the conditions of user cross-system roaming and grouping paging of a foreign terminal, the PDC supports the establishment of connection with an adjacent PDC, and the main task of the communication module among the PDCs is to provide an interface for sending and receiving data among the PDCs and maintain the communication connection. There are two modes for communication between PDC, one using UDP and one using ICP, if the former is used, the module needs to maintain connection state detection between PDC and acknowledge retransmission of data, if the latter is used, the ICP module provides heartbeat detection and acknowledge retransmission mechanism of data, and the method uses ICP to process.

When a PDC receives a packet transmission request from an external network device, a configuration information table is queried to find that a target user roams to other PDC systems across PDCs, or the target user is not a local user, data transmission occurs between the PDC and an adjacent PDC, which mainly includes the following two cases:

(1) when a local user roams to other PDC systems across PDC systems, the local PDC transmits a grouping request to an adjacent PDC, and the adjacent PDC receives the grouping transmission request and informs the local PDC of a grouping service transmission result after the whole process of the grouping service flow is finished according to the inquiry of the configuration information table, the inquiry of the user state and the PDT grouping standard;

(2) when the remote terminal is paged in a grouping way, when the remote terminal does not roam across the PDC, the other processes are the same as the local user roaming across the PDC except the difference of the query process of the configuration information table. When the foreign terminal has the cross-PDC roaming, the cross-PDC roaming to the third party PDC is divided into two cases, one is that the cross-PDC roaming to the third party PDC, the grouping request is transmitted to the user attributive PDC from the local PDC, and then transmitted to the third party PDC from the attributive PDC, after the grouping process is finished, the third party PDC transmits the grouping result to the attributive PDC, and the attributive PDC is transmitted to the local PDC. The other is that the allopatric terminal roams to the local PDC across the PDC, and the grouping request is firstly transmitted to the home PDC from the local PDC and then transmitted to the local PDC from the home PDC.

In order to prevent the transmission of the packet request between the local PDC and the neighboring PDC from falling into an infinite loop, each time the packet request is transmitted, a transmission path record is simultaneously added in a transmission message, for example, when the local PDC is added in a message transmitted from the local PDC to the neighboring PDC and then transmitted from the neighboring PDC to the local PDC, the message simultaneously contains the local PDC and the neighboring PDC records, and once the receiver PDC of the packet transmission request knows that the message has been forwarded by the current PDC, the packet transmission request is not forwarded across PDCs no matter whether subsequent configuration channel table query and user status query can successfully acquire the visited base station information.

Interpretation of terms:

PDT: professional Digital Trunking

PDC: packet Data Controller, Packet server

ECN: switching center

And (2) DS: dispatching desk, the invention is used as external network equipment

BS: base station

MS: mobile station

UDP: user datagram protocol

ICP: inter-board communication protocol

AI-1: physical layer

MAC: data link layer

R0: this document refers to radio links in an air interface

Raw socket: original socket

Dgram socket: datagram socket

GRE: generic routing encapsulation protocol

ID: identity, herein referred to as a token;

IP: internet Protocol, Internet Protocol

B1: interface layer of PDC and interactive network element

ICP: inter-board communication protocol

TETRA: trans European Trunked Radio, Pan-Europe Trunked Radio

SNDCP: subnet Dependent Convergence Protocol (subnet Dependent Convergence Protocol)

OTAR: over The Air Rekeying, Air interface key update

OTAP Over The Air Programming, Air Programming.

Claims (10)

1. A PDT grouping cross-system interconnection realization method, the PDT system is composed of PDC, ECN, BS and MS, DS is connected with PDC, one PDC can be connected with a plurality of ECN and a plurality of BS, one PDC is connected with a plurality of ECN, one PDC is communicated with a plurality of BS through wired network connection and ICP protocol, BS is communicated with MS through wireless communication mode, ECN is communicated with BS, characterized in that: the PDC is responsible for docking external network equipment, establishing and dismantling grouping functions, managing grouping resources and compressing/decompressing packet packets, the ECN stores the position information of users and performs mobility management on the users and the groups, and the BS performs segmented processing and channel transmission on the packet data packets; storing local terminal and allopatric terminal information, local exchange and allopatric exchange information in PDC, cascading a plurality of ECNs and BSs in the PDT system with network equipment outside the PDT system by using a plurality of PDCs, and acquiring the BS information visited by a user through interaction of the PDCs and the ECNs to provide service for communication between the network equipment inside and outside the system and the terminal.

2. A method for implementing a PDT packet cross-system interconnection as claimed in claim 1, wherein said DS is connected to the PDC in an ICP manner when serving as an internal network device; when the DS is used as an external network device, the DS is connected with the PDC through the Ethernet, UDP network protocols are used for communication between the DS and the PDC, and the IPSec protocol is used for providing safe encryption for IP data transmission between the DS and the PDC.

3. A method as claimed in claim 1, wherein said PDC includes a control module and a data module, said control module operating in a user mode, said data module operating in a kernel mode, said control module and said data module communicating via an interface control.

4. A method for implementing PDT packet cross-system interconnection as claimed in claim 3, wherein said control module comprises a configuration information table module, a user status query module, a resource management module, and a B1 interface module, wherein the configuration information table module is used for storing home location information of a target terminal or group, the user status query module is used for querying visited location information of the target terminal, the resource management module is used for managing channel resources of a base station, and the B1 interface module is used for connection management between network elements;

the data module comprises an IP routing module, a GRE protocol module, a kernel data sending and receiving module and an IPSec protocol module, wherein the IP routing module is used for transmitting and routing an IP data packet, the GRE protocol module is used for carrying out GRE encapsulation and decapsulation on data, the kernel data sending and receiving module is used for receiving and sending user packet data, and the IPSec protocol module is used for authenticating and encrypting messages between the PDC and the DS; the DS sends the user data of the PDC, firstly extracts the key information of the target terminal in a control module of the PDC, and then transmits the data to a kernel module for GRE encapsulation and IP routing and sends the data to the BS after the packet flow is successfully established.

5. The method as claimed in claim 4, wherein the DS transmits user data to the MS, the size of the packet depends on network setup restrictions, the user data is encapsulated into UDP packets and sent to the PDC, the PDC stores the data, queries a user configuration information table, queries a corresponding exchange initiation status according to a query result, finds an affiliation exchange and a registration base station of a target user, initiates paging to the MS, goes through a standard packet setup procedure between the PDC and the MS, the BS serves as a transmission channel, and after a terminal responds, a resource management module of the PDC allocates a channel for this packet transmission and notifies the target terminal that the packet setup is successful;

after the packet flow is successfully established, the PDC encapsulates user data into a network packet in a GRE format by using an IP tunnel technology and sends the network packet to the BS, the BS unpacks the packet data content after receiving the network packet and transmits the packet data content to the MS in a segmented mode according to different sizes of user data packets so as to meet the requirement of air interface transmission rate.

6. A method for implementing a PDT packet cross-system interconnection as claimed in claim 5, wherein said GRE encapsulation facilitates packet data to transparently traverse the Internet without being limited to packet two-layer encapsulation protocol, facilitating expansion of PDC usage; GRE encapsulation also facilitates intra-domain multicasting of packet data within the PDT system, primarily for group address-oriented packet transmission.

7. A method for implementing a PDT packet cross-system interconnection as claimed in claim 4, wherein said configuration information table module information is stored in a file system, and after PDC startup, four tables are created locally by reading configuration files;

table 1 is an exchange ID-IP correspondence table in a local PDC, and configures exchange information associated with the local PDC, to find whether a visited place of a target user belongs to a local exchange, where one PDC may connect multiple exchanges;

table 2 shows local terminal prefixes and home exchange information, and configures a terminal number prefix of a local PDC, for querying whether a target user belongs to the local and home exchange information;

table 3 is a correspondence table between the terminal number prefix and the home PDC, and configures terminal number prefix information of an adjacent PDC to search for home PDC information of the target user;

table 4 is a table corresponding to the neighbor exchange ID and PDC IP, and configures corresponding information of the neighbor exchange ID and PDC IP, so as to search for the IP of the local user roaming the place PDC after roaming across PDCs.

8. The method as claimed in claim 7, wherein the PDC is required to obtain visited place exchange and base station information of the terminal during establishing the packet transmission link, the query process interaction is mainly performed between the PDC and exchange, the mobility management information related to registration and roaming of the user is exchanged and stored, the mobility management information is queried from the home place or the visited place exchange according to different situations, and the status query response mainly includes the following elements:

(1) the terminal registration state comprises unregistered state, local user registered state, remote user roaming registration state, local user roaming state, user teleproned/remotely killed state, user not opened account, user not existed, user not supporting the grouping service;

(2) a call state;

(3) registering base station information, wherein when the terminal is registered under the current exchange, the parameter in the state inquiry response carries effective base station information;

(4) the visiting place exchanges information, when the terminal cross-exchanges roaming, the home place exchange can inquire the current visiting place exchange information of the terminal;

when receiving a data transmission request from an external network device, the PDC firstly looks up the table 2 to determine whether the user belongs to the local area;

if the user belongs to the local area, the home exchange information of the user can be obtained from the table 2, the user state query is firstly requested to the preferred home exchange, and if the user state query fails, the user state query is switched to the secondary home; if the inquiry result is directly returned to the base station list, the user is registered under the current home exchange; if the query result returns the exchange ID, the table 1 is queried according to the exchange ID, if the exchange exists in the table 1, the cross-exchange roaming of the user in the PDC system is indicated, otherwise, the cross-PDC roaming of the user is indicated; if the user is in the cross exchange roaming in the PDC system, the user state is inquired according to the returned exchange ID until the base station list is returned; if the user roams across PDC, the information is exchanged according to the roaming place, the table 4 is inquired, the information of the PDC of the roaming place is obtained, and the data transmission request is transferred to the PDC of the roaming place for processing;

if the user does not belong to the local, looking up the table 3, checking the PDC IP of the attribution of the prefix of the remote terminal, and forwarding the data transmission request to the adjacent-end PDC for processing.

9. A method for implementing a PDT packet cross-system interconnection as claimed in claim 8, wherein said PDC and exchanges create ICP channels via B1 interfaces, and control information is transmitted between subsequent PDCs and exchanges via the ICP channels.

10. A method for implementing a PDT packet cross-system interconnect as claimed in claim 9, wherein said PDC supports connection with neighboring PDCs, and the primary task of the inter-PDC communication module is to provide an interface for sending and receiving data between PDCs and to maintain communication connection;

communication among the PDCs has two modes, one mode uses a UDP mode and the other mode uses an ICP mode, if the UDP mode is adopted, the module needs to maintain connection state detection among the PDCs and confirm retransmission of data, and if the ICP mode is adopted, the ICP module can provide a heartbeat detection and data confirm retransmission mechanism;

adopting an ICP mode for treatment: when a PDC receives a packet transmission request from an external network device, a configuration information table is queried to find that a target user roams to other PDC systems across PDCs, or the target user is not a local user, data transmission occurs between the PDC and an adjacent PDC, which mainly includes the following two cases:

(1) when a local user roams to other PDC systems across PDC systems, the local PDC transmits a grouping request to an adjacent PDC, and the adjacent PDC receives the grouping transmission request and informs the local PDC of a grouping service transmission result after the whole process of the grouping service flow is finished according to the inquiry of the configuration information table, the inquiry of the user state and the PDT grouping standard;

(2) when the remote terminal is paged in a grouping way, when the remote terminal does not roam across the PDC, the other processes are the same as the local user roaming across the PDC except the difference of the query process of the configuration information table; when the cross-PDC roaming occurs in the remote terminal, the cross-PDC roaming to the third party PDC is divided into two cases, one is that the cross-PDC roaming to the third party PDC, the grouping request is transmitted to the user attributive PDC from the local PDC, and then transmitted to the third party PDC from the attributive PDC, and after the grouping process is finished, the third party PDC transmits the grouping result to the attributive PDC, and the attributive PDC is transmitted to the local PDC; the other is that the allopatric terminal roams to the local PDC across the PDC, the grouping request is firstly transmitted to the home PDC from the local PDC, and then is transmitted to the local PDC from the home PDC;

in order to prevent the transmission of the packet request between the local PDC and the neighboring PDC from falling into an infinite loop, each time the packet request is transmitted, a transmission path record is simultaneously added in the transmission message, for example, when the local PDC record is added in the message transmitted from the local PDC to the neighboring PDC and then transmitted from the neighboring PDC to the local PDC, the message simultaneously contains the local PDC and the neighboring PDC records, and once the receiver PDC of the packet transmission request knows that the message has been forwarded by the current PDC, the packet transmission request is not forwarded across PDCs no matter whether subsequent configuration channel table query and user state query can successfully acquire the information of the base station.

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