CN101990241B - Packet data transmission system and method - Google Patents

Abstract

The invention discloses a packet data transmission system, comprising: a base transceiver station BTS and a base station controller BSC. Correspondingly, the present invention also provides a packet data transmission method, including BTS forming a packet control unit PCU frame and encapsulating the formed PCU frame into a network protocol frame according to the carrier frequency, and sending it to the BSC; the BSC parses the PCU frame from the network protocol frame frame, and then analyze the PCU load from the PCU frame and sort the parsed PCU load, and select the sorted PCU load to form a logical link control frame and send it to the core network. Therefore, the present invention can optimize system delay and realize reliable transmission.

Description

A packet data transmission system and method

technical field

The invention relates to packet data transmission technology in the field of wireless communication, in particular to a packet data transmission system and method.

Background technique

Global System for Mobile Communication (GSM, Global System for Mobile Communication) is the most widely used communication system in mobile communication, and the wireless access network equipment of GSM is usually called Base Station Subsystem (BSS, Base Station System). The role played by the BSS in GSM mainly includes: on the one hand, the BSS is connected with the mobile terminal (MS, Mobile Station) through the wireless network, and performs wireless signal transmission, reception and wireless resource management; on the other hand, the BSS and the mobile switching center (MSC, MobileSwitching Center) or mobile switching center server (MSC Sever, Mobile Switching CenterSever) is connected to realize the communication connection between MSs, or between MSs and fixed network users, and the transmission of system information and user information. Among them, a typical BSS includes two logical nodes: Base Station Controller (BSC, Base Station Controller) and Base Transceiver Station (BTS, Base TransceiverStation). The communication interface between the BSC and the BTS is called the Abis interface, and is used to realize the remote interconnection between the BSC and the BTS. Generally, the Abis interface uses a standard 2.048Mbps or 64Kbps pulse code modulation (PCM, Pulse Code Modulation) transmission link to realize data transmission.

At present, General Packet Radio Service (GPRS, General Packet Service) is a mobile packet data service based on GSM, enabling users to send and receive data in an end-to-end packet transmission mode. GPRS provides the interface of packet data communication application for GSM user, introduces GPRS support node, service GPRS support node (SGSN, Serving GPRS Support Node) and GPRS gateway support node (GGSN, Gateway GPRS Support Node) at the core network side, wherein , SGSN is at the same level as MSC, as shown in Figure 1. Since the BSS of GSM is multiplexed in the GPRS network structure, a packet control unit (PCU, Packet Control Unite) is added in the BSS. Moreover, in recent years, with the introduction of softswitch technology into the core network, a switching network architecture based on the Internet Protocol (IP, Internet Protocol) has gradually formed. Among them, the Abis interface based on the IP transmission mode is referred to as the IP Abis interface for short. Compared with the traditional Abis interface based on the PCM transmission link, the IP Abis interface has higher transmission efficiency and flexibility.

Among them, the code conversion of the IP Abis interface service and the method of the packet data transmission of the rate adaptation unit are mainly that the sending end uses the service payload data and control parameters to form a service frame, and encapsulates multiple service frames in a real-time transport protocol (RTP , Real-Time Transport Protocol) frame, and use the network transport protocol to encapsulate the RTP frame in the network protocol frame, and send the encapsulated network protocol frame through the IP network; after the network protocol frame at the receiving end, the RTP frame is extracted from it, and then Extract the service frame from the analyzed RTP frame and analyze the service payload data and control parameters. Although the above-mentioned method can realize the transmission of data services at the IP Abis interface, because the packet data service is transmitted at the Abis interface, the PCU frame structure is adopted, and the upper layer processing protocol of the PCU frame is the wireless line control protocol (RLC, Radio Link Control). The window mechanism has a certain degree of fault tolerance, and can sort the PCU load in the PCU frame. Therefore, compared with the voice service, the packet service is not sensitive to disorder and jitter, and the RTP buffer processing mechanism will cause a large system delay and waste of network resources. Therefore, there is currently no transmission method for packet data services that is fully applicable to the IP Abis interface.

Contents of the invention

In view of this, the main purpose of the present invention is to provide a packet data transmission system and method, which can optimize system delay and realize reliable transmission.

In order to achieve the above object, the present invention discloses a packet data transmission system, comprising: a base station controller BSC and a base transceiver station BTS; wherein, the BTS is used to form a packet control unit PCU frame and add The User Datagram Protocol UDP header and the Internet Protocol IP header encapsulate the PCU frame into a network protocol frame according to the network protocol and send it to the BSC; the BSC is used to parse the PCU frame from the network protocol frame and parse the PCU frame The PCU load is put into the receiving window for sorting according to the size of its block sequence number BSN, and the sorted PCU load is selected to determine whether the confirmation state variable VQ of the current receiving window is updated. When VQ is updated, select the previous VQ to The updated BSN continuous PCU load between the VQs forms a logical link control frame and sends it to the core network; or, BSC is used to split the logical link control frame received from the upper layer into PCU loads, in order Put it into the sending window, and take out the PCU load from the sending window according to the channel instance, add the PCU frame header, generate the PCU frame, and add the UDP header and IP header to the PCU frame of the same carrier frequency, and encapsulate it into a network protocol frame according to the network protocol. Sent to BTS; BTS, for parsing out PCU frames from the network protocol frame, sorting the PCU frames by frame number; and for performing rate adaptation on the PCU frames to be sent to the Um interface in sequence, and The PCU load obtained after the rate adaptation is sent to the mobile terminal; the rate adaptation of the PCU frames to be sent to the Um interface in order is: the PCU frame to be sent to the Um interface is analyzed to obtain the PCU load, and the PCU load Code modulation.

In the above-mentioned system, the BTS includes: a first frame building unit and a first network driver unit; wherein, the first frame building unit is used to build a PCU frame; the first network driver unit is used to form a PCU frame according to The carrier frequency is encapsulated in a network protocol frame, and the network protocol frame is sent to the BSC; the BSC includes: a radio link control unit, a frame processing unit, and a second network driver unit; wherein, the second network driver unit uses Receiving the network protocol frame and parsing it to obtain a PCU frame; and, for selecting the sorted PCU load, forming a logical link control frame and sending it to the core network; a frame processing unit, for parsing the PCU frame The PCU load is obtained; the radio link control unit is used to sort the PCU load.

In the above system, the BSC includes: a second frame building unit and a third network driver unit; wherein, the second frame building unit is used to build a PCU frame; the third network driver unit is used to build the PCU frame according to The carrier frequency is encapsulated in a network protocol frame, and the network protocol frame is sent to the BTS; the BTS includes: a fourth network driver unit and a rate adaptation unit; wherein, the fourth network driver unit is used to receive the network protocol frame The protocol frame is parsed to obtain the PCU frame; the rate adaptation unit is used to sort the PCU frame, and perform rate adaptation on the PCU frame to be sent to the Um interface in order to obtain the PCU load, and send the PCU load to mobile terminal.

Wherein, the rate adaptation unit also includes: a sorting subunit for sorting the PCU frames; a determination subunit for determining the PCU frames to be sent to the Um interface; a parsing and coding modulation subunit for ordering Analyzing the PCU frame to be sent to the Um interface to obtain the PCU payload, and encoding and modulating the PCU payload; the sending subunit is configured to send the encoded and modulated PCU payload to the mobile terminal.

Correspondingly, the present invention provides a packet data transmission method, comprising: BTS constructs PCU frames, and adds User Datagram Protocol UDP packet header and Internet Protocol IP packet header for the PCU frame of the same carrier frequency, and encapsulates the PCU frame into a network protocol according to the network protocol. The protocol frame is sent to the BSC; the BSC parses the PCU frame from the network protocol frame, then parses the PCU load from the PCU frame, and sorts the parsed PCU load into the receiving window according to the size of its block serial number BSN, and selects After sorting the PCU load, judge whether the confirmation state variable VQ of the current receiving window is updated. When the VQ is updated, select the PCU load with continuous BSN between the previous VQ and the updated VQ to form a logical link control frame and sent to the core network.

In the above method, after the BSC parses the PCU frame from the network protocol frame, it also includes: the BSC judges whether the parsed PCU frame needs frame number adjustment, and when the frame number adjustment is required, the PCU frame is adjusted according to the channel instance. Perform frame number adjustment to synchronize frame numbers.

Wherein, analyzing the PCU load from the PCU frame and sorting the analyzed PCU load is as follows: BSC parses the PCU load from the PCU frame according to the control parameters of the frame header, and sorts the PCU load according to its block sequence number BSN The size of the receiving window is put into the receiving window for sorting; wherein, the start sequence number of the response bitmap of the receiving window is the maximum value of the BSN of the received PCU load plus 1 minus twice the number of channels.

In the above method, the network protocol frame includes: a UDP header, an IP header, and a UDP payload, wherein the UDP payload includes more than one PCU frame belonging to the same carrier frequency.

Wherein, when forming the logical link control frame, the BSN of the PCU load is used for sorting.

Correspondingly, the present invention also provides a packet data transmission method, including: the BSC splits the logical link control frame received from the upper layer into PCU loads, puts them into the sending window in order, and takes them out from the sending window according to the channel instance PCU load, add PCU frame header, generate PCU frame, and add UDP packet header and IP packet header for the PCU frame of the same carrier frequency, encapsulate into network protocol frame according to network protocol, send the network protocol frame to BTS; BTS from the network protocol Analyzing the PCU frame in the frame, and sorting the PCU frame according to the frame number; the BTS performs rate adaptation on the PCU frame to be sent to the Um interface in sequence, and sends the PCU load obtained after the rate adaptation to the mobile terminal;

The rate adaptation of the PCU frames to be sent to the Um interface in sequence includes: analyzing the PCU frames to be sent to the Um interface to obtain a PCU payload, and encoding and modulating the PCU payload.

In the above method, before the described PCU frame is sorted by frame number, it also includes: BTS compares the frame number of the parsed PCU frame with the locally recorded frame number, if they are not the same, the frame number is out of sync, Calculate the frame number adjustment amount and notify the BSC to adjust the frame number so that the frame number is synchronized; if the same, then the frame number is synchronized, and then the PCU frame is sent and controlled and sorted; wherein, the PCU frame is sent and controlled and sorted as: The BTS sets up a buffer area, puts the received PCU frames into the buffer area, and sorts them by frame number.

As can be seen from the above technical solutions, the Abis interface packet data transmission implementation method and device based on the User Datagram Protocol (UDP, UserDatagram Protocol) protocol of the present invention can solve the problem of large system delay and waste of network delay in the prior art. question. This is mainly because, the present invention sets a kind of IP Abis interface protocol stack structure, has removed RTP agreement, has simplified IP Abis interface frame structure. Therefore, the RTP buffer processing delay, as well as the RTP scheduling delay and processing delay are optimized, thereby reducing the network delay. In this way, not only the delay of the system is greatly reduced, but also the frame structure of Abis interface transmission is simplified, which saves bandwidth resources.

For the IP Abis interface protocol stack structure without RTP, packets may be out of sequence during transmission. Therefore, the present invention performs fault-tolerant processing on uplink out-of-sequence messages by modifying the RLC sliding window mechanism in the process of uplink packet data processing, thus avoiding false retransmission under the premise of ensuring correct message sequence. Moreover, the present invention also adds a cache mechanism to the downlink rate adaptation unit to sort the PCU messages. In this way, the sequence of received and sent packets is guaranteed, thereby realizing reliable transmission. Therefore, the present invention realizes reliable transmission under the premise of optimizing time delay.

Description of drawings

Fig. 1 is the schematic diagram of BSS structure and interface;

2A is a schematic diagram of the composition of an embodiment of the packet data transmission system of the present invention;

FIG. 2B is a schematic composition diagram of another embodiment of the packet data transmission system of the present invention;

Fig. 3 is a schematic diagram of the implementation flow of the uplink packet data transmission method of the present invention;

Fig. 4 is Abis interface protocol stack structure;

Fig. 5 is a schematic diagram of the structural process of the network protocol frame of the present invention;

Fig. 6 is the receiving window of the wireless link control unit on the BSC side of the present invention;

Fig. 7 is a schematic diagram of the implementation flow of the downlink packet data transmission method of the present invention.

Detailed ways

The basic idea of the present invention is: set up the PCU frame based on the Abis interface protocol stack structure of UDP, and encapsulate more than one PCU frame in a UDP/IP protocol frame, and adjust the frame number jitter and disorder in the transmission process , improve the anti-jitter performance of the system.

It should be noted that the structure of the PCU frame includes the following composition methods: one composition method is that the frame number information and user data are respectively stored in different frames, such as the PCU synchronization frame used for frame number synchronization and the frame number carrying data block PCU data frame; another composition method is that frame number information and user data are in the same PCU frame, for example, a PCU frame includes a PCU frame header and a PCU payload.

In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

The present invention also provides a packet data transmission system, the system includes: BTS 201 and BSC 202. in:

BTS 201 is used to form PCU frames and encapsulate the formed PCU frames into network protocol frames according to the carrier frequency, and send them to BSC 202;

BSC 202, used to parse the PCU frame from the network protocol frame, and sort the PCU load parsed from the PCU frame; and select the sorted PCU load to form a logical link control frame and send it to the core through the Gb interface net; or,

BSC 202 is used to generate PCU frames, encapsulates the generated PCU frames into network protocol frames, and sends them to BTS 201;

BTS 201, for parsing the PCU frame from the network protocol frame, sorting the PCU frame; and for performing rate adaptation on the PCU frame to be sent to the Um interface in sequence, and the PCU obtained after the rate adaptation The payload is sent to the mobile terminal.

In the above system, the BTS 201 includes: a first frame building unit and a first network driver unit. Among them, as shown in Figure 2A:

The first frame building unit is used to form a PCU frame;

The first network driver unit is used to encapsulate the formed PCU frame in the network protocol frame according to the carrier frequency, and send the network protocol frame to the BSC 202;

The BSC 202 includes: a second network driver unit, a frame processing unit and a radio link control unit; wherein,

The second network driver unit is used to receive the network protocol frame and analyze it to obtain a PCU frame; and is used to select the sorted PCU load to form a logical link control frame and send it to the core network;

The frame processing unit is used to analyze the PCU frame to obtain the PCU load;

The radio link control unit is used to sequence the PCU load.

In the above system, the BSC 202 includes: a second frame building unit and a third network driver unit; wherein, as shown in Figure 2B:

The second frame building unit is used to form a PCU frame;

The 3rd network driving unit is used for encapsulating the formed PCU frame in the network protocol frame according to the carrier frequency, and sending the network protocol frame to the BTS 201;

The BTS 201 includes: a fourth network drive unit and a rate adaptation unit; wherein,

A fourth network driver unit, configured to receive the network protocol frame and analyze it to obtain a PCU frame;

The rate adaptation unit is configured to sort the PCU frames, perform rate adaptation on the PCU frames to be sent to the Um interface in sequence to obtain the PCU load, and send the PCU load to the mobile terminal.

Wherein, the rate adaptation unit also includes:

The sorting subunit is used to sort the PCU frame;

Determine the subunit, used to determine the PCU frame to be sent to the Um interface;

The analysis and encoding modulation subunit is used to analyze the PCU frames to be sent to the Um interface in order to obtain the PCU load, and perform encoding and modulation on the PCU load;

The sending subunit is configured to send the coded and modulated PCU payload to the mobile terminal.

The above is a packet data transmission system based on the IP Abis interface. The following describes the packet data transmission method, including: uplink data transmission and downlink data transmission, specifically:

I. Take the BTS as the sending end and the BSC as the receiving end as an example to illustrate the transmission and processing of uplink data:

As shown in Figure 3, it is the uplink data processing process in the packet data transmission method of the present invention, which mainly includes the following steps:

Step 301, the BTS receives user data through the Um interface, decodes the received user data, extracts service data therefrom as a PCU load, and constructs a PCU frame;

Here, the PCU frame structure of this embodiment takes frame number information and user data in the same PCU frame as an example, and the rate adaptation unit of the BTS completes the formation of the PCU frame. , Um port encoding and modulation mode of the PCU load, frame number adjustment amount, etc. to fill in. Then, add the filled frame header to the front end of the PCU payload, and the PCU frame is constructed. Among them, the current frame number and frame number adjustment are mainly used for frame number synchronization; the length of the PCU payload can be obtained through the Um coding modulation method of the PCU payload, and then the corresponding PCU payload can be obtained by analyzing the length of the PCU payload.

Step 302, the BTS encapsulates the formed PCU frame into a network protocol frame according to the carrier frequency;

Here, encapsulation into a network protocol frame according to the carrier frequency means that the BTS adds a UDP header and an IP header to the PCU frame of the same carrier frequency according to the network protocol such as UDP/IP, and encapsulates it into a network protocol frame. Wherein, in order to save network resources, more than one PCU frame belonging to the same carrier frequency from the same cell is encapsulated in the same network protocol frame. That is to say, each network protocol frame includes: an IP header, a UDP header, and a UDP payload, and the UDP payload includes more than one PCU frame belonging to the same carrier frequency, as shown in FIG. 4 . Wherein, several PCU frames belonging to the same carrier frequency are encapsulated in the UDP payload. The network protocol frame used in this embodiment is based on the prior art Abis interface protocol stack structure, as shown in Figure 5, the RTP part in the existing Abis interface protocol stack is removed, and the out-of-order adjustment function receiver undertaken by RTP comes from Complete, for example, the jitter and disorder of the uplink data are adjusted and processed by the radio link control unit on the BSC side, while the jitter and disorder of the downlink data are processed by the rate adaptation unit on the BTS side. Among them, the wireless link control unit originally has a sorting mechanism, but the fault tolerance mechanism is poor, and disordered order will cause false retransmission of data. This embodiment reduces the start sequence number (SSN) by modifying the window mechanism, and enhances the fault tolerance mechanism. Prevent false retransmissions. In addition, in this embodiment, a buffer sorting function is added to the rate adaptation unit at the BTS side, so as to realize processing of jitter and disorder of downlink data.

Step 303, the BTS transmits the network protocol frame to the BSC through the IP network;

Step 304, the BSC receives the network protocol frame, and uses UDP/IP to parse out the PCU frame from the network protocol frame;

Step 305, the BSC adjusts the frame number of the PCU frame according to the channel instance to ensure that the frame number is synchronized;

Among them, adjusting the frame number of the PCU frame according to the channel instance is mainly to analyze the PCU frame header, and judge whether it needs to be adjusted and adjust the PCU frame whose frame number needs to be adjusted, that is: if the frame header contains the frame number adjustment amount then The frame number needs to be adjusted, and the frame processing unit on the BSC side adjusts the current frame number according to the frame number adjustment amount; otherwise, the frame header does not include the frame number adjustment amount, so the frame number adjustment of the PCU frame is not required. Specifically, the frame number adjustments received by the BSC are PNa, MNa, BNa, the current downlink frame number on the BSC side is PN=a, MN=b, BN=c; the maximum value of the downlink frame number PN MAX=A, MN_MAX =B, BN_MAX=C. The downlink frame numbers adjusted by the BSC are PN ₁ , MN ₁ , and BN ₁ , then:

PN ₁ =(a+PNa+A) mod (A);

MN ₁ =(b+MNa+B) mod (B);

BN ₁ =(c+BNa+C) mod (C).

Step 306, the BSC parses the PCU load from the PCU frame, and puts the parsed PCU load into the receiving window for sorting;

Wherein, the network driver unit at the BSC side obtains the length of the PCU payload according to the coding mode in the PCU frame, and analyzes the PCU payload through the length of the PCU payload. In addition, the radio link control unit on the BSC side puts the PCU loads into the receiving window for sorting, mainly through the control of the receiving window to ensure the order in which the PCU loads enter the receiving window. Specifically, the radio link control unit puts the arriving PCU payload into the corresponding receiving window according to the size of its Block Sequence Number (BSN, Block Sequence Number) value. Wherein, BSN is a sequence number included in the PCU payload, and the receiving window sorts the PCU payload according to the size of the BSN value, and also uses the BSN of the PCU payload to sort when constructing the logical link control frame.

Although the receiving window of the existing radio link control unit on the BSC side has an adjustment mechanism for the PCU load, in order to prevent excessive frame number adjustment and data retransmission, this embodiment changes the response mechanism of the receiving window by reducing The SSN of the uplink response bitmap is used to further reduce the impact of disorder on the system. Next, take GPRS as an example to illustrate the uplink response bitmap constructed in this embodiment: Referring to FIG. 6 , it shows the receiving window of the radio link control unit at the BSC side. Among them, the confirmation state variable VQ represents the minimum BSN value of the PCU payload not received within the receiving window, and the reception state variable VR specifies a BSN value that is 1 greater than the maximum BSN value of the received PCU payload. When constructing the uplink response bitmap, in this embodiment, the SSN of the response bitmap is reduced, and the SSN of the last received PCU load is set=VR−the number of channels×2. And the start sequence number SSN=VR of the existing response bitmap, when the mobile terminal receives the response bitmap, it retransmits the PCU payload marked as not received in the response bitmap. The out-of-order caused by network delay and channel jitter will cause the PCU load with a large BSN to be received first, and then the PCU load with a small BSN. It will respond to the request for retransmission, and there is enough time to wait for the arrival of the out-of-order PCU load. However, if the last block is received first and the PCU load before it is still being transmitted, the BSC will consider that the PCU load has been received, and it will Acknowledgments are sent to request retransmission of unreceived PCU payloads. In this way, some PCU loads that are not really lost are retransmitted, resulting in false retransmission of the PCU load on the mobile terminal side. Therefore, in this embodiment, by reducing the start sequence number of the response bitmap, the response to the recently received PCU loads is delayed, so that there is enough time to wait for the arrival of the PCU loads that have not arrived before. Therefore, the anti-jitter capability of the system is increased and unnecessary retransmissions are reduced.

Step 307: After receiving the PCU payloads, the BSC selects the sorted PCU payloads from the receiving window, constructs a logical link control frame, and sends the constructed logical link control frame to the core network through the Gb interface.

Among them, the specific implementation process of composing the logical link control frame with the extracted PCU load is as follows: each time the PCU load is received, the situation of the current receiving window is judged, such as whether the VQ is updated, and if the VQ is updated, the previous VQ is taken out in order. The updated BSN continuous PCU load between the VQs tries to form a logical link control frame. Moreover, the BSN of the PCU load is used for sorting when constructing the logical link control frame.

Among them, judging whether the logical link control frame is completed is mainly based on the identification bits in the PCU payload, such as the length value indicating bit L and more bits M, so that different logical link control frames are delimited by different identification bits. For example: through the set L and M values in the PCU payload, it is judged whether the current logical link control frame has been established, and if the establishment is completed, it can be sent to the Gb interface and sent to the core network. Among them, the Gb interface is the interface between the BSC and the core network, as shown in Figure 1, user data will be sent to the logical link control layer of the core network for processing.

II. Take BSC as the sending end and BTS as the receiving end as an example to illustrate the downlink data transmission and processing process:

The uplink data transmission and processing process is described above, and the downlink data transmission and processing process is described next, as shown in Figure 7, the main processing steps are as follows:

Step 701, the BSC splits the logical link control frame received from the upper layer into PCU loads, and puts them into the sending window in sequence;

Wherein, when the BSC splits the logical link control frame received from the upper layer into PCU loads, it adds a BSN to each PCU load, and then puts the PCU loads into the sending window in the order of the BSNs.

Step 702, the BSC takes out the PCU load from the sending window according to the channel instance, adds the PCU frame header, and generates the PCU frame;

Here, the PCU frame includes: a PCU frame header and a PCU payload, wherein the PCU frame header includes: control parameters such as frame number, frame number adjustment amount, and coding mode.

Step 703, the BSC adds a UDP header and an IP header to the PCU frame, and encapsulates it into a network protocol frame according to the carrier frequency;

Here, the encapsulation into a network protocol frame according to the carrier frequency refers to encapsulating the PCU frame of the same carrier frequency into a network protocol frame according to the network protocol.

Step 704, the BSC transmits the network protocol frame to the BTS through the IP network;

Step 705, BTS parses out the PCU frame from the received network protocol frame;

Step 706, BTS judges whether the frame number of the PCU frame is out of sync, if the frame number is out of sync, then execute step 707; otherwise, if the frame number is synchronous, then execute step 708;

The BTS compares the frame number of the parsed PCU frame with the locally recorded frame number. If they are not the same, the frame numbers are out of sync; if they are the same, the frame numbers are synchronized.

Step 707, the BTS calculates the frame number adjustment amount, and notifies the BSC to adjust the frame number, so that the frame numbers are synchronized, and then executes step 708;

Among them, the main process of calculating the frame number adjustment amount on the BTS side is: the downlink frame number received by the BTS: PN=a, MN=b, BN=c; the downlink frame number stored locally by the BTS is PN=a ₁ , MN =b ₁ , BN=c ₁ ; PN_MAX=A, MN_MAX=B, BN_MAX=C; then the frame number adjustment of the downlink PCU calculated by the BTS is:

PNa = (a ₁ -a+A) mod (A);

MNa = (b ₁ -b+B) mod (B);

BNa=(c ₁ -c+C) mod (C).

In addition, during the frame number adjustment process, the transmission of the PCU load will be suspended between the BTS and the BSC.

Step 708, sorting the PCU frames, and selecting the normally arriving PCU frames;

Here, the BTS adds a buffer area in the rate adaptation unit, and sorts the received PCU frames according to the frame numbers. Among them, the main process of controlling the transmission of PCU frames includes: first sorting the received PCU frames according to the frame number, and then comparing the smallest frame number with the current frame number on the side of the rate adaptation unit in the BTS, and then judging the cache Whether there is a PCU frame in the area that has arrived early or has expired. If the minimum frame number is greater than the current frame number, it means that the PCU frame has arrived early. If the minimum frame number is less than the current frame number, it means that the PCU frame has expired, so as to determine whether to send the PCU frame to the Um interface. Because the BTS will send the normally arrived PCU frame to the Um interface, so as to send it to the mobile terminal.

In step 709, the BTS performs rate adaptation on the normally arriving PCU frames in sequence, and sends the PCU payload obtained after the rate adaptation to the mobile terminal through the Um interface.

Among them, after the BTS obtains the PCU frame, it performs rate adaptation on the PCU frame that needs to be sent to the Um interface, that is, decomposes the PCU frame to obtain information such as the encoding type and the current frame number, and then extracts different lengths to be encoded according to different encoding types. The PCU payload is encoded and modulated on the retrieved PCU payload, so that the PCU payload can be transmitted on the Um interface.

For the above-mentioned embodiments, for the sake of simple description, they are expressed as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the described action sequence, because according to the present invention, a certain The steps can be performed in other order or simultaneously.

In the foregoing embodiments, the descriptions of each embodiment have their own emphases, and for parts not described in detail in a certain embodiment, refer to the relevant descriptions of other embodiments. The above descriptions are only preferred embodiments of the present invention, which are only used to illustrate and explain the present invention, and are not used to limit the protection scope of the present invention. Within the spirit of the present invention and the protection scope of the claims, any modifications and equivalent replacements made to the present invention fall within the protection scope of the present invention.

Claims (11)

1. A packet data transmission system, characterized in that it comprises: a base station controller BSC and a base transceiver station BTS; wherein, BTS is used to form the PCU frame of the packet control unit, and add a User Datagram Protocol UDP header and an Internet Protocol IP header to the PCU frame of the same carrier frequency, encapsulate the PCU frame into a network protocol frame according to the network protocol, and send it to the BSC; BSC is used to parse the PCU frame from the network protocol frame, and put the PCU load parsed from the PCU frame into the receiving window according to the size of its block sequence number BSN for sorting, and select the sorted PCU load to judge the current reception Whether the confirmation state variable VQ of the window is updated, when the VQ is updated, select the BSN continuous PCU load between the previous VQ and the updated VQ, form a logical link control frame and send it to the core network; or, BSC is used to split the logical link control frame received from the upper layer into PCU payloads, put them into the sending window in sequence, and take out the PCU payloads from the sending window according to the channel instance, add the PCU frame header, generate the PCU frame, and Add UDP header and IP header to the PCU frame of the same carrier frequency, encapsulate it into a network protocol frame according to the network protocol, and send it to the BTS; BTS, for parsing the PCU frame from the network protocol frame, sorting the PCU frame by frame number; and for performing rate adaptation on the PCU frame to be sent to the Um interface in sequence, and rate adaptation The obtained PCU load is sent to the mobile terminal; The rate adaptation of the PCU frames to be sent to the Um interface in sequence includes: analyzing the PCU frames to be sent to the Um interface to obtain a PCU payload, and encoding and modulating the PCU payload. 2. The packet data transmission system according to claim 1, characterized in that, The BTS includes: a first frame building unit and a first network driver unit; wherein, The first frame building unit is used to form a PCU frame; The first network driver unit is used to encapsulate the formed PCU frame in the network protocol frame according to the carrier frequency, and send the network protocol frame to the BSC; The BSC includes: a radio link control unit, a frame processing unit, and a second network driver unit; wherein, The second network driver unit is used to receive the network protocol frame and analyze it to obtain a PCU frame; and is used to select the sorted PCU load to form a logical link control frame and send it to the core network; The frame processing unit is used to analyze the PCU frame to obtain the PCU load; The radio link control unit is used to sequence the PCU load. 3. The packet data transmission system according to claim 1, wherein: The BSC includes: a second frame building unit and a third network driving unit; wherein, The second frame building unit is used to form a PCU frame; The third network driver unit is used to encapsulate the formed PCU frame in the network protocol frame according to the carrier frequency, and send the network protocol frame to the BTS; The BTS includes: a fourth network driver unit and a rate adaptation unit; wherein, A fourth network driver unit, configured to receive the network protocol frame and analyze it to obtain a PCU frame; The rate adaptation unit is configured to sort the PCU frames, perform rate adaptation on the PCU frames to be sent to the Um interface in sequence to obtain the PCU load, and send the PCU load to the mobile terminal. 4. The packet data transmission system according to claim 1, wherein the rate adaptation unit further comprises: The sorting subunit is used to sort the PCU frame; Determine the subunit, used to determine the PCU frame to be sent to the Um interface; The analysis and encoding modulation subunit is used to analyze the PCU frames to be sent to the Um interface in order to obtain the PCU load, and perform encoding and modulation on the PCU load; The sending subunit is configured to send the coded and modulated PCU payload to the mobile terminal. 5. A packet data transmission method, characterized in that, comprising: BTS constructs PCU frames, adds User Datagram Protocol UDP headers and Internet Protocol IP headers to PCU frames of the same carrier frequency, encapsulates PCU frames into network protocol frames according to network protocols, and sends them to BSC; The BSC parses the PCU frame from the network protocol frame, then parses the PCU load from the PCU frame, puts the parsed PCU load into the receiving window according to the size of its block serial number BSN, and selects the sorted PCU load to judge Whether the confirmation state variable VQ of the current receiving window is updated. When the VQ is updated, select the BSN continuous PCU load between the previous VQ and the updated VQ to form a logical link control frame and send it to the core network. 6. The packet data transmission method according to claim 5, characterized in that, after the BSC resolves the PCU frame from the network protocol frame, it also includes: The BSC judges whether the parsed PCU frame needs frame number adjustment, and when frame number adjustment is required, adjusts the frame number of the PCU frame according to the channel instance, so that the frame number is synchronized. 7. The packet data transmission method according to claim 5 or 6, wherein the PCU load is parsed from the PCU frame and the PCU load parsed is sorted as: BSC parses the PCU load from the PCU frame according to the control parameters of the frame header, and puts the PCU load into the receiving window according to the size of its block sequence number BSN for sorting; Wherein, the start sequence number of the response bitmap of the receiving window is the maximum value of the BSN of the received PCU load plus 1 minus twice the number of channels. 8. The packet data transmission method according to claim 5 or 6, characterized in that, The network protocol frame includes: a UDP header, an IP header, and a UDP payload, wherein the UDP payload includes more than one PCU frame belonging to the same carrier frequency. 9. The packet data transmission method according to claim 5 or 6, wherein when forming the logical link control frame, the BSN of the PCU load is used for sorting. 10. A packet data transmission method, characterized in that, comprising: The BSC divides the logical link control frame received from the upper layer into PCU payloads, puts them into the sending window in sequence, and takes out the PCU payloads from the sending window according to the channel instance, adds the PCU frame header, generates a PCU frame, and sends Add UDP header and IP header to the frequent PCU frame, encapsulate it into a network protocol frame according to the network protocol, and send the network protocol frame to the BTS; The BTS parses the PCU frame from the network protocol frame, and sorts the PCU frame by frame number; The BTS performs rate adaptation on the PCU frames to be sent to the Um interface in sequence, and sends the PCU payload obtained after the rate adaptation to the mobile terminal; The rate adaptation of the PCU frames to be sent to the Um interface in sequence includes: analyzing the PCU frames to be sent to the Um interface to obtain a PCU payload, and encoding and modulating the PCU payload. 11. The packet data transmission method according to claim 10, characterized in that, before the described PCU frame is sorted by frame number, it also includes: BTS compares the frame number of the parsed PCU frame with the locally recorded frame number, if not the same, the frame number is out of sync, calculates the frame number adjustment amount and notifies the BSC to adjust the frame number to synchronize the frame number; if they are the same, Then the frame number is synchronized, and the PCU frame is sent to control and sort; Wherein, the sending control and sorting of the PCU frames is as follows: the BTS sets a buffer area, puts the received PCU frames into the buffer area, and sorts according to the frame number.

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