WO2021128482A1 - Method for realizing pdt packet cross-system interconnection - Google Patents

Abstract

The present invention relates to a method for realizing PDT packet cross-system interconnection. A PDC is in charge of external network device abutting, packet function creation and removal, packet resource management, and packet package compression/decompression; an ECN stores position information of a user and performs mobility management on the user and a group; and a BS has the functions of performing segmentation processing and channel transmission on a packet data package, wherein local terminal information, remote terminal information, local exchange information and remote exchange information are stored in the PDC; a plurality of PDCs are used to cascade a plurality of ECNs and BSs in a PDT system and a network device outside the PDT system; and by means of interacting with an ECN, the PDC acquires information of a BS visited by the user, thereby providing services for communication between the network devices inside and outside the system and terminals. The present invention is provided on the basis of the design of a PDC packet server network element, supplemented by a PDC internal module structure and an internal data transmission structure; and multi-switch connection and inter-PDC communication provide basic guarantees for the transmission of cross-system data.

Description

A Method for Realizing PDT Grouping Inter-system Interconnection Technical field

The invention relates to a method for implementing PDT packet cross-system interconnection.

Background technique

At present, the grouping function in the PDT system is mainly used in text-type long and short messages, OTAP, OTAR, MMS and other services. In the technical specifications of the police digital trunking (PDT) communication system, whether it is a packet data service function description or an interconnection technical specification, it is all There is no standard provision for packet cross-system interconnection, but in actual field use, there is a requirement for packet cross-system interconnection, such as OTAR air interface key update, one OTAR server provides services for terminals under multiple PDT systems, or there is terminal cross-system interconnection In the case of roaming, in order to ensure that the latest key can be accurately issued to the terminal, it is necessary to consider the realization of PDT packet inter-system interconnection.

Summary of the invention

In view of the problems existing in the prior art, the purpose of the present invention is to provide a technical solution for implementing a method for PDT packet cross-system interconnection.

The present invention is based on the design of the PDC packet server network element, supplemented by the PDC internal module structure and internal data transmission structure. The configuration information table query, user status query, multi-switch connection, inter-PDC communication, etc. are used in the establishment of PDT packet transmission. , Configuration information table query and user status query are used to obtain key terminal visiting information, so as to provide an information basis for the packet system to establish an effective packet connection with the terminal. Multi-switch connections and PDC communication provide basic information for cross-system data transmission. Guarantee; the design of multiple exchange connections at the same time is of great help to the improvement of system stability.

Description of the drawings

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

Figure 2 is a schematic diagram of the PDC module structure;

Figure 3 is a schematic diagram of the control data transmission structure between MS, BS, PDC, and ECN;

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

Detailed ways

The present invention provides an effective method for PDT packet cross-system interconnection. The method has certain versatility in the field of trunking communication. For example, TETRA communication can also use the key technology of the method to realize packet transmission.

As a packet server, PDC plays a core role in the realization of packet functions, responsible for docking external network equipment, packet function establishment and removal, packet resource management, packet compression/decompression, etc., ECN as a switching center, one of its functions is storage User location information and mobility management of users and groups are also part of the functions that this method needs to involve. As a base station, BS mainly plays the role of segmentation processing and channel transmission of packet data packets.

Store local terminal and remote terminal information, local exchange and remote exchange information in the PDC, and use multiple PDC devices to cascade multiple switches in the PDT system, base stations, and network devices outside the PDT system. In this way, the PDC can obtain the information of the base station visited by the user through the interaction with the switching center, so as to provide services for the communication between the network equipment and the terminal inside and outside the system. The basic network architecture of the system of the present invention is shown in Figure 1.

When DS is used as an internal network device, it can be connected to PDC via ICP. ICP is an internal inter-board communication protocol with heartbeat detection and message confirmation and retransmission mechanisms to ensure the reliability of data transmission. When the DS is used as an external network device, it is connected to the PDC via Ethernet, and the UDP network protocol is used for communication between the two, and the IPSec protocol is used to provide security encryption for the IP data transmission between the DS and the PDC. In actual usage scenarios, PDC can be connected to different external devices to meet different usage requirements. If the PDC is externally connected to the dispatching station, it can meet the purpose of command and dispatch of public security, fire protection and other systems. If the PDC is externally connected to the key management server, it can meet the needs of the cluster system. For the purpose of downloading the terminal key, if the PDC is externally connected to the web gateway, it can meet the purpose of connecting the terminal under the cluster system to the Internet. At the same time, this set of networking architecture is not only applicable to the PDT packet system, but also to the TETRA packet system. The difference between the two lies in the packet interaction process between PDC and BS. Depending on the type of end user, PDC can be compatible with PDT and TETRA at the same time. System grouping function, that is, a PDC can connect PDT base station and TETRA base station at the same time, and carry out grouping communication with PDT and TETRA terminal at the same time.

PDC, ECN, BS, and MS belong to a set of network elements within the PDT system. A PDC can be connected to multiple exchanges and multiple base stations. ECNn represents multiple exchanges, and BSn represents multiple base stations. PDC1 and ECNn, PDC1 and BSn are connected through a wired network, and communicate through the ICP protocol, and wireless communication between BSn and MS. In actual networking, there is a communication connection between ECNn and BSn.

The data between the PDC and the PDC is transmitted through the ICP mode, and the message is transmitted across the PDC, which is described as a cross-PDC system in the present invention. The terminal MS under the PDC1 of the present invention roams to the adjacent PDC2 system, which is called cross-PDC roaming. The MS under the PDC1 of the present invention roams among multiple exchanges connected to the PDC, which is called cross-exchange roaming. Cross-PDC roaming belongs to the category of cross-switch roaming, and cross-switch roaming does not necessarily belong to the category of cross-PDC roaming. Both cross-PDC roaming and cross-switch roaming belong to the category of cross-system roaming.

PDC module architecture

The software environment in which the PDC works in the description of the present invention is the Linux operating system. PDC adopts the strategy of separating control information and data information transmission. The internal module structure of PDC is shown as in Fig. 2. The control module works in the user mode, and the data module works in the kernel mode. The communication between the control module and the data module is controlled by the interface.

The control module includes a configuration information table module, a user status query module, a resource management module, and a B1 interface module. The configuration information table module is used to store the attribution information of the target terminal or group, the user status query module is used to query the visitation information of the target terminal, the resource management module is used to manage the channel resources of the base station, and the B1 interface module is used to connect between network elements. management.

The message exchanges between network elements during the packet establishment process all belong to the category of control data. The message structure of control data transmission between MS, BS, PDC, and ECN is shown in Figure 3, where CDATA represents control data.

The data module consists of an IP routing module, a GRE module, a core data sending and receiving module, and an IPSec protocol module. The IP routing module is used for the transmission and routing of IP data packets, the GRE module is used for GRE encapsulation and decapsulation of data, the kernel data sending and receiving module is used for sending and receiving user packet data, and the IPSec protocol module is used for messages between PDC and DS. Authentication and encryption.

For the user data sent by DS to PDC, first extract the key information of the destination terminal in the PDC control module, and after the grouping process is established successfully, then transmit the data to the kernel module for GRE encapsulation, IP routing and send it to the BS. The user data is in the MS and BS. The message structure transmitted between PDC and DS is shown in Figure 4. UDATA in the figure represents user data.

The interface control module uses I/O control technology to be responsible for the communication between the user mode and the kernel mode, mainly including the creation and deletion of virtual channels, and the sending and receiving interfaces of data information.

DS transmits user data to MS. The size of the data packet depends on the network setting limit. The user data is encapsulated into a UDP packet and sent to the PDC. The PDC saves the data, queries the user configuration information table, and initiates a status query to the corresponding exchange based on the query result to find the target The user’s home switching and registration base station initiates paging to the MS, and the standard packet establishment process is used between the PDC and the MS. The BS is used as the transmission channel. The air interface signaling process for the packet establishment is "Police Digital Trunking_PDT_Communication System Technology The standard process specified in "Specification-Air Interface Call Control Layer" is not detailed in the present invention. After the terminal responds, the resource management module of the PDC allocates channels for this packet transmission and informs the target terminal that the packet is successfully established. In this process, control data is transmitted between network elements.

After the packet process is successfully established, PDC uses IP tunnel technology to encapsulate user data into a network packet in GRE format and sends it to the BS. After receiving it, the BS unpacks the packet data content, and transmits it to the MS in segments according to different user data packet sizes. , To meet the requirements of the air interface transmission rate. GRE encapsulation has two main purposes. One is to facilitate the transparent traversal of packet data through the Internet, without being limited to the Layer 2 encapsulation protocol of packet packets, and to facilitate the expansion of the use of PDC, such as the expansion of TETRA packet data SNDCP protocol Encapsulation, the second is to facilitate intra-domain multicast of packet data in the PDT system, and is mainly used for group address-oriented packet transmission. In this process, user packet data is transmitted between network elements.

Configuration information table

The information of the configuration information table is stored in the file system. After the PDC is started, four tables are created locally by reading the configuration file.

Table 1. Configure the exchange information associated with the local PDC, which is used to find whether the visitor of the target user belongs to the local exchange. One PDC can be connected to multiple exchanges.

Table 1 Correspondence table of exchange ID-IP in the local PDC

Local exchange ID	Local exchange IP
Local exchange ID	Local exchange IP
…	To

Table 2. Configure the terminal number prefix of the local PDC, which is used to query whether the target user belongs to the local and exchange information at the attribution.

Table 2 Local terminal prefix and belonging exchange information

Local MS prefix	Road selection attribution exchange ID	Second choice attribution exchange ID
…	To	To

Table 3, configure the terminal number prefix information of the neighboring PDC, used to find the PDC information of the target user's home.

Table 3 Return table of terminal number prefix and home PDC

MS prefix	Home PDC IP
…	To

Table 4 configures the corresponding information between the neighbor exchange ID and the PDC IP, which is used to find the IP of the PDC where the local user roams after roaming across the PDC.

Table 4 Correspondence table between neighbor exchange ID and PDC IP

Neighbor exchange ID	Neighbor PDC IP
…	To

User status query

In the process of establishing a packet transmission link, the PDC needs to obtain the visitor exchange and base station information of the terminal. The query process interaction is mainly carried out between the PDC and the exchange, and the exchange and storage of the user's registration and roaming-related mobility management information. This information can be queried from the home or visitor exchange according to different situations. The status query response mainly contains the following elements:

(1) Terminal registration status, including unregistered, local user registered, remote user roaming registration, local user roaming, user remotely fainted/remotely killed, user has not opened an account, user does not exist, user does not support grouping services, etc.;

(2) Call status;

(3) Register base station information. When the terminal is registered under the current exchange, this parameter in the status query response carries valid base station information;

(4) The visited place exchanges information. When the terminal roams across the exchange, the home exchange office can inquire about the terminal’s current visited place to exchange information;

When the PDC receives a data transmission request from an external network device, it first looks up Table 2 to determine whether the user belongs to the local device.

If the user belongs to the local, the user's home exchange information can be obtained from Table 2, and the user status query is first requested from the preferred home exchange. If it fails, the second home exchange is inquired. If the query result is directly returned to the base station list, it means that the user is registered under the current home exchange. If the query result returns the exchange ID, query Table 1 based on the exchange ID. If the exchange exists in Table 1, it means that the user has roamed across the exchange in the PDC system, otherwise it means that the user has roamed across the PDC. If the user is roaming across exchanges in the PDC system, the user status will be inquired according to the returned exchange ID until the base station list is returned. If the user roams across the PDC, exchange information according to the roaming location, query Table 4 to obtain the information of the roaming PDC, and transfer the data transmission request to the roaming PDC for processing.

If the user does not belong to the local, then look up Table 3, check the home PDC IP of the prefix of the remote terminal, and forward the data transmission request to the neighboring PDC for processing.

Multi-switch connection

In order to support user dual-homing, group multi-homing, and users roaming across exchanges in the PDC system, the PDC needs to support the establishment of connections with multiple exchanges. The PDC and multiple exchanges create multiple ICP channels through the B1 interface. The subsequent PDC The control information is transmitted through the ICP channel between the exchange and the exchange.

The user dual-homing and group multi-homing mechanism is mainly used to ensure the stability of system operation. When one of the home switches fails, it does not affect the normal operation of packet services and other cluster services.

Communication between PDCs

In order to support user roaming across systems and packet paging of remote terminals, PDC supports the establishment of connections with neighboring PDCs. The main task of the inter-PDC communication module is to provide an interface for sending and receiving data between PDCs and to maintain the communication connection. There are two ways to communicate between PDCs, one uses UDP and the other uses ICP. If the former is used, this module needs to maintain the connection status detection between PDCs and the confirmation and retransmission of data. If the latter is used, the ICP module will provide heartbeat. Detection and data confirmation retransmission mechanism, this method uses ICP processing.

When the PDC receives a packet transmission request from an external network device and queries the configuration information table and finds that the target user roams across the PDC to another PDC system, or the target user is not a local user, data transmission will occur between the PDC and the neighboring PDC, mainly as follows Two situations:

(1) Local users roam across PDC to other PDC systems. The local PDC transparently transmits the packet request to the neighboring PDC, and the neighboring PDC receives the packet transmission request, and completes the standard business process according to the configuration information table query, user status query, and PDT grouping. After the whole process, notify the local PDC packet service transmission result;

(2) In the case of packet paging of remote terminals, when the remote terminals do not roam across PDCs, except for the difference in the query process of the configuration information table, the other processes are the same as those for local users when roaming across PDCs. When a cross-PDC roaming occurs in a remote terminal, there are two situations here. One is cross-PDC roaming to a third-party PDC. The grouping request will be transparently transmitted from the local PDC to the user’s home PDC, and then the home PDC will be transparently transmitted to the third PDC. For three-party PDC, after the grouping process ends, the third-party PDC sends the grouping result to the home PDC, and the home PDC then transfers it to the local PDC. The other is that the remote terminal roams across the PDC to the local PDC, and the grouping request is first transparently transmitted from the local PDC to the home PDC, and then from the home PDC to the local 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 a packet request is transmitted, the transmission path record will be added to the transmission message. For example, the local PDC record is added to the message transmitted from the local PDC to the neighboring PDC. , When it is transmitted from the neighboring PDC to the local PDC, the message will contain both the local PDC and the neighboring PDC record. Once the receiver PDC of the packet transmission request knows that the message has been forwarded by the current PDC, regardless of the subsequent configuration channel table query and user Whether the status query can successfully obtain the visited base station information, the packet transmission request is no longer forwarded across the PDC.

Term explanation:

PDT: Professional Digital Trunking, professional digital trunking

PDC: Packet Data Controller, packet server

ECN: Exchange Center

DS: Dispatcher, the present invention is collectively referred to as external network equipment

BS: base station

MS: mobile station

UDP: User Datagram Protocol

ICP: internal inter-board communication protocol

AI-1: Physical layer

MAC: data link layer

R0: This article refers to the wireless link in the air interface

Raw socket: raw socket

Dgram socket: datagram socket

GRE: General Routing Encapsulation Protocol

ID: Identity, this article refers to the logo;

IP: Internet Protocol, Internet Protocol

B1: Interface layer between PDC and interactive network elements

ICP: internal inter-board communication protocol

TETRA: Trans European Trunked Radio, pan-European trunked radio

SNDCP: SubNetwork Dependent Convergence Protocol, subnet-related convergence protocol

OTAR: Over The Air Rekeying, air interface key update

OTAP: Over The Air Programming, air interface programming

Claims (10)

1. A method for realizing the interconnection of PDT packets across systems. The PDT system is composed of PDC, ECN, BS and MS. DS is connected to PDC. One PDC can connect to multiple ECNs and multiple BSs. One PDC and multiple ECNs and one PDC are connected to multiple ECNs. Multiple BSs are connected through a wired network and communicate through the ICP protocol. The BS and the MS are wirelessly communicated, and there is a communication connection between the ECN and the BS. The feature is that the PDC is responsible for docking with external network equipment and grouping functions. Creation and removal, packet resource management, packet packet compression/decompression, ECN stores user location information and performs mobility management for users and groups, BS performs segmentation processing and channel transmission on packet data packets; stores in PDC Local terminal and remote terminal information, local exchange and remote exchange of information, use multiple PDCs to cascade multiple ECNs and BSs in the PDT system with network equipment outside the PDT system, and the PDC can obtain user information through interaction with the ECN. The visited BS information provides services for the communication between network equipment and terminals inside and outside the system.
2. The method for implementing PDT packet cross-system interconnection according to claim 1, wherein when the DS is used as an internal network device, it is connected to the PDC through ICP; when the DS is used as an external network device, it is connected to the PDC Through the Ethernet connection, the UDP network protocol is used to communicate between the two, and the IPSec protocol is used to provide secure encryption for the IP data transmission between DS and PDC.
3. The method for implementing PDT packet cross-system interconnection according to claim 1, wherein the PDC includes a control module and a data module, the control module works in the user mode, the data module works in the kernel mode, and the control module and the data module Communication is carried out through interface control.
4. A method for implementing PDT packet cross-system interconnection according to claim 3, wherein the control module includes a configuration information table module, a user status query module, a resource management module, and a B1 interface module, and the configuration information table module is used for Store the attribution information of the target terminal or group, the user status query module is used to query the visit information of the target terminal, the resource management module is used to manage the channel resources of the base station, and the B1 interface module is used to manage the connection between network elements;

   The data module includes an IP routing module, a GRE protocol module, a core data sending and receiving module, and an IPSec protocol module. The IP routing module is used for the transmission and routing of IP data packets, and the GRE protocol module is used for GRE encapsulation and decapsulation of data. , The kernel data sending and receiving module is used to send and receive user packet data, and the IPSec protocol module is used for message authentication and encryption between PDC and DS; user data sent by DS to PDC, first extract the key information of the target terminal in the control module of PDC, After the grouping process is successfully established, the data is then transmitted to the kernel module for GRE encapsulation, IP routing, and sent to the BS.
5. The method for implementing PDT packet cross-system interconnection according to claim 4, characterized in that the DS transmits user data to the MS, the size of the data packet depends on the network setting limit, the user data is encapsulated into a UDP packet and sent to the PDC, The PDC saves the data, queries the user configuration information table, initiates a status query to the corresponding exchange according to the query result, finds the target user's home exchange and registered base station, initiates a paging to the MS, and uses the standard grouping establishment process between the PDC and the MS, and the BS As a transmission channel, after the terminal responds, the resource management module of the PDC allocates a channel for this packet transmission and informs the target terminal that the group is successfully established;

   After the packet process is successfully established, PDC uses IP tunnel technology to encapsulate user data into a network packet in GRE format and sends it to the BS. After receiving it, the BS unpacks the packet data content, and transmits it to the MS in segments according to different user data packet sizes. , To meet the requirements of the air interface transmission rate.
6. The method for implementing PDT packet cross-system interconnection according to claim 5, characterized in that the GRE encapsulation facilitates the transparent traversal of packet data through the Internet, does not need to be limited to the Layer 2 encapsulation protocol of the packet, and facilitates the PDC The use is expanded; GRE encapsulation also facilitates intra-domain multicast of packet data in the PDT system, and is mainly used for group address-oriented packet transmission.
7. A method for implementing PDT packet cross-system interconnection according to claim 4, characterized in that the information of the configuration information table module is stored in the file system, and after the PDC is started, the configuration file is read and the configuration file is read locally. Sheet

   Table 1 is the exchange ID-IP correspondence table in the local PDC. The exchange information associated with the local PDC is configured to find whether the visitor of the target user belongs to the local exchange. One PDC can be connected to multiple exchanges;

   Table 2 shows the local terminal prefix and home exchange information. The terminal number prefix of the local PDC is configured to query whether the target user belongs to the local and the home exchange information;

   Table 3 is the correspondence table between the terminal number prefix and the home PDC. Configure the terminal number prefix information of the neighboring PDC to find the home PDC information of the target user;

   Table 4 is the correspondence table between the neighbor exchange ID and the PDC IP. The corresponding information between the neighbor exchange ID and the PDC IP is configured to find the IP of the PDC where the local user roams after roaming across the PDC.
8. The method for implementing PDT packet cross-system interconnection according to claim 7, characterized in that the PDC needs to obtain the terminal's visitor exchange and base station information in the process of establishing the packet transmission link, and the query process interaction is mainly in the PDC , Exchange between exchanges, exchange and store user registration and roaming-related mobility management information. The above information can be queried from the home or visited exchange according to different situations. The status query response mainly contains the following elements:

   (1) Terminal registration status, including unregistered, local user registered, remote user roaming registration, local user roaming, user remotely dizzy/remotely killed, user not opened an account, user does not exist, and user does not support grouping services;

   (2) Call status;

   (3) Register base station information. When the terminal is registered under the current exchange, this parameter in the status query response carries valid base station information;

   (4) The visited place exchanges information. When the terminal roams across the exchange, the home exchange office can inquire about the terminal’s current visited place to exchange information;

   When the PDC receives a data transmission request from an external network device, it first looks up Table 2 to determine whether the user belongs to the local device;

   If the user belongs to the local, the user's home exchange information can be obtained from Table 2. First, request the user status query from the preferred home exchange. If it fails, then query the second home exchange; if the query 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, query Table 1 according to the exchange ID. If the exchange exists in Table 1, it means that the user has roamed across the exchange in the PDC system, otherwise it means that the user has roamed across the PDC; If the user roams across exchanges in this PDC system, query the user status according to the returned exchange ID until the base station list is returned; if the user roams across PDC, exchange information according to its roaming location, query Table 4 to obtain its roaming location PDC Transfer the data transmission request to the roaming PDC for processing;

   If the user does not belong to the local, then look up Table 3, check the home PDC IP of the remote terminal prefix, and forward the data transmission request to the neighboring PDC for processing.
9. The method for implementing PDT packet cross-system interconnection according to claim 8, wherein multiple ICP channels are created between the PDC and multiple exchanges through the B1 interface, and subsequent PDC and exchanges transmit control information through the ICP channel .
10. A method for implementing PDT packet cross-system interconnection according to claim 9, characterized in that the PDC supports the establishment of connections with neighboring PDCs, and the main task of the inter-PDC communication module is to provide an interface and pairing for sending and receiving data between PDCs. Maintenance of communication connection;

    There are two ways to communicate between PDCs, one using UDP and the other using ICP. If UDP is used, this module needs to maintain the connection status between PDCs and confirm the retransmission of data. If ICP is used, the ICP module will provide Heartbeat detection and data confirmation retransmission mechanism;

    ICP processing: When the PDC receives a packet transmission request from an external network device, it queries the configuration information table and finds that the target user roams across the PDC to another PDC system, or the target user is not a local user, data will be generated between the PDC and the neighboring PDC Transmission is mainly divided into the following two situations:

    (1) Local users roam across PDC to other PDC systems. The local PDC transparently transmits the packet request to the neighboring PDC, and the neighboring PDC receives the packet transmission request, and completes the standard business process according to the configuration information table query, user status query, and PDT grouping. After the whole process, notify the local PDC packet service transmission result;

    (2) In the case of packet paging of remote terminals, when the remote terminal does not roam across PDC, except for the configuration information table query process, the other processes are the same as the local user's cross-PDC roaming; when the remote terminal roams across PDC, There are two situations. One is roaming across PDC to a third-party PDC. The grouping request will be transparently transmitted from the local PDC to the user’s home PDC, and then from the home PDC to the third-party PDC. After the grouping process is over, the grouping request will be transparently transmitted from the home PDC to the third-party PDC. The three-party PDC sends the grouping result to the home PDC, and the home PDC then transfers it to the local PDC; the other is that the remote terminal roams across the PDC to the local PDC, and the grouping request is first transparently transmitted from the local PDC to the home PDC, and then the home PDC Pass the local PDC to the local 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, the transmission path record will be added to the transmission message. For example, the local PDC record is added to the message transmitted from the local PDC to the neighboring PDC. When transmitted from the neighboring PDC to the local PDC, the message will contain both the local PDC and the neighboring PDC records. Once the receiver PDC of the packet transmission request knows that the message has been forwarded by the current PDC, regardless of the subsequent configuration channel table query and user status Query whether the visited base station information can be successfully obtained, and the packet transmission request is no longer forwarded across the PDC.

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