CN107277853A

CN107277853A - A kind of data transmission method and device

Info

Publication number: CN107277853A
Application number: CN201610212437.0A
Authority: CN
Inventors: 许建城; 符子建; 张劲林
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2016-04-07
Filing date: 2016-04-07
Publication date: 2017-10-20
Also published as: WO2017173923A1

Abstract

The embodiment of the invention discloses a kind of data transmission method and device, data transmission method includes：Main website obtains N (natural number of N >=1) individual packet waiting for transmission from order caching；The main website is according to the data volume of N number of packet, calculate expection time delay of the packet in multilink in each of the links, the multilink includes the first link and at least one second link, first link is the link between the main website and user terminal, and second link is the main website through the link between extension station and the user terminal；N number of packet delivery to the minimum Target Link of expected time delay is transmitted by the main website.Packet delivery to the minimum Target Link of expected time delay can be transmitted by the embodiment of the present invention, it is to avoid user terminal receives data latency time-out.

Description

Data transmission method and device

Technical Field

The present invention relates to the field of communications technologies, and in particular, to a data transmission method and apparatus.

Background

With the advent of the Mobile broadband (MBB) era, the demand of users for network traffic bandwidth is increasing, and it is expected that users can enjoy a good user experience at any time and place. The 3rd Generation Partnership Project (3 GPP) R12 standard introduces Dual Connectivity (DC) technology, which can be used by a user terminal to simultaneously receive data from a Master eNB (MeNB) and a Secondary eNB (SeNB), thereby improving user throughput.

As shown in fig. 1, which is a schematic diagram of DC Control plane connection, for a DC user, the Control plane interface (S1 for the Control plane, S1-MME) of S1 is terminated by the MeNB, and the MeNB and SeNB are interconnected through the X2 Control plane interface (X2-Control plane, X2-C).

As shown in fig. 2, which is a schematic diagram of a DC user plane connection, the protocol supports two different user plane architectures: one is that the S1 User plane interface (S1 for the User plane, S1-U) only terminates at the MeNB, and User plane data is transmitted from the MeNB to the SeNB using the X2 User plane interface (X2-User plane, X2-U); alternatively, S1-U may terminate in the SeNB.

However, different bearer types may be configured in different user plane architectures, with the user plane connections depending on the bearer type configuration. The bearer types mainly include Master Cell Group (MCG) bearers, Secondary Cell Group (SCG) bearers and packet Split bearers.

For MCG bearers, S1-U terminates with the MeNB, which does not participate in user plane data transmission for this bearer type.

For SCG bearers, the SeNB is directly connected to the S-GW through S1-U, and the MeNB does not participate in user plane data transmission for this bearer type.

For the Split bearer, the S1-U is terminated at the MeNB, and Packet Data Convergence Protocol (PDCP) Data is transmitted between the MeNB and the SeNB through the X2-U. Both MeNB and SeNB are involved in this bearer type of user plane data transmission. The data transmission method provided by the invention is suitable for the user plane data transmission of the Split bearing type.

In the prior art, a Protocol [ TS 36.425 ] defines an X2 user plane standard interface between the MeNB and the SeNB, that is, the SeNB feeds back a report of a SeNB direction downlink Data transmission status to the MeNB by using the standard interface, where the report includes a maximum PDCP PDU Serial Number (SN) in a PDCP Protocol Data Unit (PDU) received from the MeNB that has been successfully transmitted to the user terminal UE in sequence, an expected Data buffer size of an associated E-UTRAN Radio Access Bearer (E-RAB), a minimum expected buffer size of all E-RABs of the UE, and an X2 packet loss indication, but the standard interface specified in the Protocol does not solve how the MeNB performs allocation of transmission Data amount between the MeNB and the SeNB, how to transmit Data packets, and these factors have an important influence on the performance of dual connectivity.

Disclosure of Invention

Embodiments of the present invention provide a data transmission method and apparatus, which can distribute a data packet to a target link with a minimum expected time delay for transmission, so as to avoid a user terminal from waiting for timeout when receiving data.

A first aspect of the present invention provides a data transmission method, including:

the master station acquires N (natural numbers with N being more than or equal to 1) data packages to be transmitted from the receiving cache;

the master station calculates the expected time delay of the data packet on each link of a plurality of links according to the data volume of the N data packets, wherein the plurality of links comprise a first link and at least one second link, the first link is a link between the master station and the user terminal, and the second link is a link between the master station and the user terminal through an auxiliary station;

and the master station distributes the N data packets to a target link with the minimum expected time delay for transmission. By the method, the N data packets can be distributed to the target link with the minimum expected time delay for transmission, and the situation that the user terminal receives data and waits overtime is avoided.

Based on the first aspect, in a first possible implementation manner of the first aspect, before the master station obtains N data packets to be transmitted from the receive buffer, the method further includes:

the primary station receives a downlink data transmission status report sent by a secondary station, wherein the downlink data transmission status report contains the buffer size of data expected to be received by the secondary station;

the master station calculates a split period according to the size of the expected received data cache, wherein the split period is a period from the time when the master station receives the downlink data transmission state report to the time when the expected transmission is completed and the time when the size of the expected received data cache matches the data volume;

the master station obtains N data packets to be transmitted from the receiving cache, and the method comprises the following steps:

and in the shunting period, the master station circularly acquires N data packets to be transmitted from the receiving cache.

Based on the first possible implementation manner of the first aspect, in a second possible implementation manner of the first aspect, before the master station obtains N data packets to be transmitted from the receive buffer, the method further includes:

the primary station counts total data quantity accumulated and sent to the secondary station from the beginning time of the shunting period;

and if the total data volume is smaller than the size of the expected received data cache, the master station acquires N data packages to be transmitted from the received cache.

In a third possible implementation manner of the first aspect, based on the second possible implementation manner of the first aspect, the method further includes:

if the total data volume is larger than or equal to the size of the expected received data cache, the main station calculates the expected time delay of a second link between the main station and the auxiliary station;

the master station determines the size M (M is a natural number more than or equal to 0) of the data volume transmitted in the first link according to the expected time delay of the second link and the expected time delay of the first link;

and the master station acquires the M data packets to be transmitted from the receiving cache and distributes the M data packets to be transmitted to the first link for transmission.

In a fourth possible implementation manner of the first aspect, based on any one of the first possible implementation manner of the first aspect to the third possible implementation manner of the first aspect, the expected time delay includes a one-way time delay;

the master station calculates the expected time delay of the N data packets on each link in a plurality of links according to the data volume of the N data packets, and the method comprises the following steps:

the master station calculates the one-way time delay of the N data packets in the first link according to the data volume of the N data packets and the air interface rate of the master station;

and for each second link, the master station calculates the one-way delay of the N data packets in the second link according to the transmission delay of the X2 interface between the master station and the auxiliary station corresponding to the second link, the transmission waiting delay of the data packets of the auxiliary station corresponding to the second link, the data volume of the N data packets, and the air interface rate of the auxiliary station corresponding to the second link.

Based on the fourth possible implementation manner of the first aspect, in a fifth possible implementation manner of the first aspect, if the primary station and the secondary station corresponding to the second link are synchronized, the transmission delay of the X2 interface is obtained from a downlink data transmission status report sent by the secondary station corresponding to the second link;

if the primary station and the secondary station corresponding to the second link are asynchronous, the transmission delay of the X2 interface is obtained according to a timestamp carried in signaling interaction performed by an X2 interface between the primary station and the secondary station corresponding to the second link and a timestamp carried in a message for transmitting/responding a data packet by the X2 interface.

Based on the fourth possible implementation manner of the first aspect, in a sixth possible implementation manner of the first aspect, the packet transmission waiting time delay is obtained from a downlink data transmission status report sent by a secondary station corresponding to the second link; or,

the data packet transmission waiting time delay is obtained according to the data volume of the secondary station corresponding to the second link sending the cache when the distribution period starts, the secondary station air interface rate corresponding to the second link, the distribution period starting time and the first packet distribution time of the secondary station corresponding to the second link sending the cache after the distribution period starts.

In a seventh possible implementation manner of the first aspect, based on any one of the first possible implementation manner of the first aspect to the third possible implementation manner of the first aspect, the expected latency includes a round trip latency;

the master station calculates the loopback delay of the N data packets in the first link according to the data volume of the N data packets and the loopback rate of the master station;

for each second link, the master station calculates the loopback delay of the N data packets in the second link according to the data volume of the N data packets and the loopback rate of the secondary station corresponding to the second link;

the loopback rate of the master station is obtained through data packet confirmation information contained in a Radio Link Control (RLC) status report; the loopback rate of the secondary station is obtained through data packet confirmation information contained in a downlink data transmission status report sent by the secondary station corresponding to the second link.

Based on the first aspect, in an eighth possible implementation manner of the first aspect, the downlink data transmission status report includes an identifier of a retransmitted data packet, and the method further includes:

the master station acquires a retransmission data packet according to the retransmission data packet identifier;

and the master station inserts the retransmission data packet into the N data packets according to the sequence number of the retransmission data packet.

In a ninth possible implementation manner of the first aspect, based on the first aspect, the method further includes:

the master station calculates the total data transmission rate on the first link and the at least one second link in a preset period, wherein the preset period comprises a plurality of shunting periods;

the master station judges whether the total data transmission rate is greater than a preset threshold value or not;

and if so, the master station determines that the master station meets the preset quality of service (QoS).

A second aspect of the present invention provides a data transmission apparatus, applied to a master station, including:

the first acquisition module is used for acquiring N (natural numbers with N being more than or equal to 1) data packages to be transmitted from the receiving cache;

a first calculating module, configured to calculate, according to a data amount of the N data packets, an expected time delay of the data packet on each of multiple links, where the multiple links include a first link and at least one second link, the first link is a link between the master station and a user terminal, and the second link is a link between the master station and the user terminal via an auxiliary station;

and the distribution module is used for distributing the N data packets to a target link with the minimum expected time delay for transmission. By the method, the N data packets can be distributed to the target link with the minimum expected time delay for transmission, and the situation that the user terminal receives data and waits overtime is avoided.

In a first possible implementation manner of the second aspect, based on the second aspect, the apparatus further includes:

a receiving module, configured to receive a downlink data transmission status report sent by a secondary station, where the downlink data transmission status report includes a buffer size of data expected to be received by the secondary station;

a second calculating module, configured to calculate a split period according to the size of the expected received data buffer, where the split period is a period from when the primary station receives the downlink data transmission status report to when the expected transmission is completed and when the size of the expected received data buffer matches the data size;

the first obtaining module is specifically configured to obtain N data packets to be transmitted cyclically from a receiving buffer in the splitting period.

In a second possible implementation manner of the second aspect, based on the first possible implementation manner of the second aspect, the apparatus further includes:

the statistical module is used for counting the total data quantity accumulated and sent to the secondary station from the beginning time of the shunting period;

the first obtaining module is specifically configured to obtain N data packets to be transmitted from a receiving cache if the total data amount is smaller than the size of the expected receiving data cache.

In a third possible implementation manner of the second aspect, based on the second possible implementation manner of the second aspect, the apparatus further includes:

a third calculating module, configured to calculate an expected time delay of a second link between the primary station and the secondary station if the total data amount is greater than or equal to the size of the expected received data cache;

a first determining module, configured to determine, according to the expected time delay of the second link and the expected time delay of the first link, a data size M (M ≧ 0) transmitted on the first link;

and the obtaining and distributing module is used for obtaining the M data packets to be transmitted from the receiving cache and distributing the M data packets to be transmitted to the first link for transmission.

In a fourth possible implementation manner of the second aspect, based on any one of the first possible implementation manner of the second aspect to the third possible implementation manner of the second aspect, the expected time delay comprises a one-way time delay;

the calculating, by the first calculation module, the expected time delay of the N data packets on each of the plurality of links according to the data amount of the N data packets specifically includes:

the first calculation module calculates the one-way time delay of the N data packets in the first link according to the data volume of the N data packets and the air interface rate of the master station;

for each second link, the first calculation module calculates the one-way delay of the N data packets in the second link according to the transmission delay of the X2 interface between the primary station and the secondary station corresponding to the second link, the transmission waiting delay of the data packet of the secondary station corresponding to the second link, the data volume of the N data packets, and the air interface rate of the secondary station corresponding to the second link.

Based on the fourth possible implementation manner of the second aspect, in a fifth possible implementation manner of the second aspect, if the primary station and the secondary station corresponding to the second link are synchronized, the transmission delay of the X2 interface is obtained from a downlink data transmission status report sent by the secondary station corresponding to the second link;

In a sixth possible implementation manner of the second aspect, based on the fourth possible implementation manner of the second aspect, the packet transmission waiting time delay is obtained from a downlink data transmission status report sent by a secondary station corresponding to the second link; or,

In a seventh possible implementation manner of the second aspect, based on any one of the first possible implementation manner of the second aspect to the third possible implementation manner of the second aspect, the expected latency includes a round trip latency;

the first calculation module calculates the loopback delay of the N data packets in the first link according to the data volume of the N data packets and the loopback rate of the master station;

for each second link, the first calculation module calculates the loopback delay of the N data packets in the second link according to the data volume of the N data packets and the loopback rate of the secondary station corresponding to the second link;

In an eighth possible implementation manner of the second aspect, based on the first possible implementation manner of the second aspect, the downlink data transmission status report includes an identifier of a retransmitted data packet, and the apparatus further includes:

the second acquisition module is used for acquiring the retransmission data packet according to the retransmission data packet identifier;

and the inserting module is used for inserting the retransmission data packet into the N data packets according to the sequence number of the retransmission data packet.

In a ninth possible implementation manner of the second aspect, based on the first possible implementation manner of the second aspect, the apparatus further includes:

a fourth calculating module, configured to calculate a total data transmission rate on the first link and the at least one second link in a preset period, where the preset period includes multiple shunting periods;

the judging module is used for judging whether the total data transmission rate is greater than a preset threshold value or not;

and the second determining module is used for determining that the main station meets the preset quality of service (QoS) if the total data transmission rate is greater than the preset threshold.

In the embodiment of the invention, the master station obtains N data packets to be transmitted from the receiving cache, and calculates the expected time delay of the data packets on each link of a plurality of links according to the data volume of the N data packets, wherein the plurality of links comprise a first link and at least one second link, the first link is a link between the master station and the user terminal, the second link is a link between the master station and the user terminal via the auxiliary station, the N data packets are distributed to a target link with the minimum expected time delay for transmission, and the expected time delay of each link is calculated, so that the data packets are distributed to the target link with the minimum expected time delay for transmission in a process, and the user terminal is prevented from receiving data and waiting for overtime.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic diagram of a DC control plane connection provided by the present invention;

FIG. 2 is a schematic diagram of a DC user plane connection provided by the present invention;

fig. 3 is an architecture diagram of an LTE DC system according to the present invention;

fig. 4 is a schematic diagram of WIFI offloading provided by the present invention;

FIG. 5 is a flowchart illustrating a data transmission method according to the present invention;

FIG. 6 is a flow chart illustrating another data transmission method according to the present invention;

fig. 7 is a schematic diagram of a dual-connection data offloading architecture according to the present invention;

FIG. 8 is a schematic diagram of a shunting period provided by the present invention;

fig. 9 is a schematic diagram of a SeNB data offloading reception process according to the present invention;

fig. 10 is a flow chart of data offloading processing provided by the present invention;

fig. 11 is a schematic structural diagram of a data transmission device according to the present invention;

fig. 12 is a schematic structural diagram of another data transmission apparatus provided in the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The data transmission method of the embodiment of the present invention may be applied to the system architecture of fig. 3 or fig. 4, and as shown in fig. 3, the present invention may be applied to offloading in a Long Term Evolution (LTE) system. As shown in the figure, the MeNB obtains data from a Serving Gateway (S-GW), where the data may be divided into two sub-streams in the MeNB, one sub-stream is directly transmitted to the UE through the MeNB, and the other sub-stream is transmitted to the UE through the SeNB.

The invention can also be applied to the shunting among different system systems. As shown in fig. 4, for example, for offloading between LTE and WiFi, an application scenario is as shown in the figure, where an MeNB acquires data from an S-GW, the data is divided into two sub-streams at an eNB, one sub-stream is directly transmitted to a UE through the eNB, and the other sub-stream is transmitted to the UE through a WiFi wireless Access Point (AP).

Referring to fig. 5, a flowchart of a data transmission method according to an embodiment of the present invention is shown, where the method can be applied to a primary station, for example: MeNB in fig. 3 or eNB in fig. 4. Fig. 5 is a flowchart of the data transmission method, which includes the following specific steps:

s500, the master station acquires N (natural numbers with N being more than or equal to 1) data packages to be transmitted from the receiving cache;

in the embodiment of the invention, the master station MeNB acquires N data packets to be transmitted to the UE from the receiving cache of the master station, wherein N represents the time delay estimation granularity and depends on the hardware distribution processing capacity. The smaller N is, the higher the requirement on the hardware shunt processing capacity is. As shown in fig. 7, which is a schematic structural diagram of an MeNB according to an embodiment of the present invention, as shown in the figure, the RxBuffer _ MeNB is a master station receive buffer queue, and buffers a data packet sent from the S-GW.

S501, the master station calculates an expected time delay of the data packet on each of a plurality of links according to the data amount of the N data packets, where the plurality of links includes a first link and at least one second link, the first link is a link between the master station and a user terminal, and the second link is a link between the master station and the user terminal via an auxiliary station;

in this embodiment of the present invention, the primary station calculates the expected time delay of the data packet on each of the multiple links according to the data amount of the N data packets, where a specific calculation method is not limited herein, and optionally, the multiple links include a first link and at least one second link, as shown in fig. 3, the first link is a link between the primary station MeNB and the user terminal UE, and the second link is a link between the primary station MeNB and the user terminal UE via the secondary station SeNB. Note that, if the secondary station SeNB includes a plurality of links, the number of the second links includes a plurality of links.

Optionally, if the expected delay includes a one-way delay, the master station specifically calculates, according to the data amount of the N data packets, the expected delay of the N data packets on each of the plurality of links, including the following steps S50 to S51;

s50, the master station calculates the one-way time delay of the N data packets in the first link according to the data volume of the N data packets and the air interface rate of the master station;

in this embodiment of the present invention, the first link is a link between the master station MeNB and the UE, as shown in fig. 7, which is a schematic structural diagram of the master station MeNB provided in this embodiment of the present invention, as shown in the figure, the master station includes a receive buffer queue (RxBuffer _ MeNB): the data caching device is used for caching the data packet sent by the S-GW; master station transmit buffer queue (TxBuffer _ MeNB): the buffer is used for buffering data packets which are shunted to a master station (MeNB) and have not received the successful delivery confirmation indication of the lower layer RLC (namely, the data packets which are buffered and sent to the first link); secondary station transmit buffer queue (TxBuffer _ SeNB): and the buffer is used for buffering data packets which are shunted to the secondary station (SeNB) and have not received the successful delivery confirmation indication (fed back through port X2) of the SeNB lower-layer RLC (namely, the data packets which are buffered and sent to the second link).

Further, the master station MeNB further comprises an X2 port feedback receiving processing module: and the data distribution sending and processing module is used for carrying out corresponding processing according to the received downlink data transmission state report and outputting a processing result to the data distribution sending and processing module as a decision basis for data distribution.

As shown, the secondary station SeNB includes a secondary station receive buffer queue (RxBuffer _ SeNB): the method is used for buffering the data packets shunted (forwarded through an X2 port) by the master station (MeNB). These packets have not been sent to the UE, or have been sent to the UE but have not received an Acknowledgement (ACK) frame for the UE.

Specifically, optionally, the feedback receiving processing module at the X2 port in the master station MeNB extracts information carried in the downlink data transmission status report, where the carried information may include, in addition to standard interface information (including but not limited to a maximum PDCP PDU SN among PDCP PDUs received from the MeNB that have been successfully sent to the UE in sequence, an expected data buffer size of a relevant E-RAB, a total minimum expected buffer size of all E-RABs of the UE, and an X2 port packet loss indication), information such as a transmission delay at the X2 port (MeNB- > SeNB), an air interface rate of a SeNB user, and a transmission waiting delay of a SeNB user packet.

And the master station MeNB retransmits the lost data packet according to the X2 port packet loss indication contained in the downlink data transmission state report. The lost data packet may be retransmitted on the first link or on the second link.

And if the lost data packet is retransmitted in the first link, the lost data packet is inserted into the transmission queue according to the sequence number of the data packet, so that the data packet in the transmission queue is ensured to be transmitted in sequence.

And if the lost data packet is retransmitted in the second link, the lost data packet is transmitted preferentially.

And clearing the successfully transmitted data packet from the TxBurrer _ SeNB according to the data packet confirmation information contained in the downlink data transmission state report.

And extracting standard interface information carried in the downlink data transmission state report, and calculating the size of data volume which is allowed to be newly sent to the SeNB.

The MeNB further comprises a data distribution sending processing module, and the MeNB determines distribution of the data packets in the master station receiving buffer queue RxBuffer _ MeNB to different links according to the processing result output by the X2 feedback receiving processing module. When shunting, the module considers the QoS requirement of the user at the same time.

For each Split bearer, a new offloading period is started each time the MeNB receives a downlink data transmission status report fed back from the SeNB. The offloading period indicates a period from a time when the downlink data transmission status report is received to a time when the amount of data to be offloaded to the SeNB is allowed to be offloaded in anticipation of completion of transmission.

The QoS guarantee period Tp indicates that the total offloading rate of the data towards the MeNB and SeNB must meet the user QoS requirement during this period. Fig. 8 illustrates a relationship between the offloading period Tsp and the period Tfp of the downlink data transmission status report. In the implementation, the downlink data transmission status report may be periodic feedback or event feedback. The time length of the shunting period depends on the hardware shunting processing capacity, and the time lengths of the preceding shunting period and the following shunting period can be different. The duration of the QoS guarantee period is variable.

Specifically, optionally, the expected delay may include a one-way delay, and the one-way delay calculation method for the first link may be implemented by the following calculation method:

the one-way delay of the first link is (the data volume of the N taken out data packets + the data volume of the data packets that have been accumulated to be shunted to the MeNB after the start of the current shunting period + the data volume in the TxBuffer _ MeNB at the start of the current shunting period)/the air interface rate of the MeNB link. The air interface rate of the MeNB link is the transmission rate of the MeNB link when the TxBuffer _ MeNB is not empty.

And S51, for each second link, the master station calculates the one-way delay of the N data packets in the second link according to the transmission delay of the X2 interface between the master station and the auxiliary station corresponding to the second link, the transmission waiting delay of the data packets of the auxiliary station corresponding to the second link, the data volume of the N data packets, and the air interface rate of the auxiliary station corresponding to the second link.

In the embodiment of the present invention, the unidirectional time delay calculation mode for each second link may be calculated by using information of the secondary station corresponding to the second link, and the specific calculation mode may be the following calculation mode:

the second link unidirectional delay (MeNB- > SeNB) + SeNB data packet transmission waiting delay + (data amount of N data packets taken out + data amount of data packets already accumulated to the SeNB after the start of the current offloading period)/the second link air interface rate.

Optionally, if the primary station and the secondary station corresponding to the second link are synchronized, the transmission delay of the X2 interface may be obtained from a downlink data transmission status report sent by the secondary station corresponding to the second link.

And the transmission time delay of the X2 interface of the data packet is the time when the data packet is received from the X2 interface-the transmission time recorded when the data packet is shunted by the MeNB, and the secondary station smoothes the measured value and adopts an alpha filtering mechanism for smoothing.

It should be noted that the transmission delay of the X2 interface of the data packet is calculated and processed by the X2 feedback sending processing module of the secondary station corresponding to the second link.

Optionally, if the primary station and the secondary station corresponding to the second link are asynchronous, the transmission delay (MeNB- > SeNB) of the X2 interface may also be obtained by measuring and estimating the transmission/reception timestamp by carrying a timestamp in the message of the signaling interaction and the data packet transmission/response of the X2 interface. The specific measurement mode is as follows:

when the MeNB adds the SeNB, the signaling interaction flow based on the X2 SeNB Addition obtains the initial loopback delay of X2, and calculates as follows:

RTTx2 ═ (T SENB ADDITION ACKNOWLEDGE available-T SENB ADDITION immediate request); wherein, the T SENB ADDITION REQUEST is the time when the MeNB sends the SENB ADDITION REQUEST message, and the T SENB ADDITION acknowledgement message is the time when the MeNB receives the SENB ADDITION acknowledgement message.

When the stream carries packets and is sent to the SeNB, a timestamp Tsent needs to be marked in each packet. After the SeNB receives the data packet, when feeding DL DATA DELIVERY STATUS message packet back to the MeNB, the SeNB takes the information of the timestamp Tsent of the data packet from the MeNB received most recently by the SeNB and the time difference Δ T between the time when the SeNB sends the DL DATA DELIVERY STATUS message packet and the time when the SeNB receives the data packet to the MeNB along with the DL DATA DELIVERY STATUS message. When the MeNB receives DL DATA DELIVERY STATUS message packets each time, recording the receiving time as received, and calculating the loopback delay RTTx2n of the X2 interface:

RTTx2n＝T_receivedn–T_sentn–ΔT

then, filtering is carried out:

RTTx2n＝(1-a)*RTTx2n-1+a*RTTx2n；

the initial value of RTTx2 may be the X2 round-trip delay obtained by the signaling interaction procedure based on X2 SeNB Addition when SeNB is added. a is a filter coefficient.

When the Split bearer has no data packet to send to the SeNB for a period of time, the MeNB needs to actively construct and send a separate measurement packet to send to the SeNB, the loopback delay of X2 is measured according to the above processing method, and the measurement result is calculated according to the above processing method and participates in filtering.

The transmission delay (MeNB- > SeNB) of port X2 is one half of the loop-back delay of port X2.

For the data packet waiting delay, the data packet waiting delay may be calculated by an X2 feedback sending processing module of the secondary station corresponding to the second link, and then the X2 feedback sending processing module encapsulates the data packet transmission waiting delay into a downlink data transmission status report and feeds back the data packet transmission waiting delay to an X2 feedback receiving processing module of the primary station for processing, optionally, the data packet transmission waiting delay may be calculated by adopting the following calculation method:

packet latency RxBuffer SeNB the time at which the packet is scheduled for transmission-the time at which the packet is received from port X2. And then smoothing the measured value by adopting an alpha filtering mechanism.

In some optional embodiments, for example, in a scenario where the secondary station does not feed back the packet transmission waiting delay, the packet transmission waiting delay may also be estimated and approximated in the MeNB to obtain:

the data packet transmission waiting time delay is (data volume-MIN of TxBuffer _ SeNB at the beginning of the current shunting period, data volume of TxBuffer _ SeNB at the beginning of the current shunting period, and air interface rate of the SeNB link (the beginning time of the current shunting period-the first packet shunting time in TxBuffer _ SeNB))/air interface rate of the SeNB link.

Optionally, if the expected delay includes a loopback delay, the master station calculates the expected delay of the N data packets on each of the plurality of links according to the data amount of the N data packets, specifically including the following steps S52 to S53;

s52, the master station calculates the loopback delay of the N data packets in the first link according to the data volume of the N data packets and the loopback rate of the master station;

in this embodiment of the present invention, the expected time delay may be a loopback time delay, and calculating the expected time delay of each link is calculating the loopback time delay of the first link and the loopback time delay of each second link in the at least one second link.

The calculation of the loopback delay in the master station MeNB may be performed by a data distribution transmission processing module, and the specific calculation manner may be:

the first link loopback delay (data volume of the N taken out data packets + data volume of data packets which have been accumulated to be shunted to the MeNB after the start of the current shunting cycle)/the first link loopback rate + (data volume of TxBuffer _ MeNB at the start of the current shunting cycle-MIN (data volume of TxBuffer _ MeNB at the start of the current shunting cycle, first link loopback rate (start time of the current shunting cycle-first packet shunting time in TxBuffer _ MeNB))/the first link loopback rate).

The first link loopback rate estimation can be obtained by estimating the data packet acknowledgement information contained in the RLC status report, and the specific acknowledgement mode can adopt the following two optional modes:

packet-based acknowledgement delay measurement method: the time delay from the transmission of each packet to the acknowledgement frame is measured. Dividing the size of the data packet by the time delay to obtain the instantaneous time delay of the data packet, smoothing the instantaneous time delay to obtain the average time delay of each byte, and taking the reciprocal as the average speed. It should be noted that the smoothing process employs an α filtering mechanism.

Statistical measurement method based on validation data per unit time: and transmitting the confirmation data quantity of the buffer TxBuffer _ MeNB in the non-empty time within the unit time. And smoothing the measured value by adopting an alpha filtering mechanism.

S53, aiming at each second link, the primary station calculates the loopback delay of the N data packets in the second link according to the data volume of the N data packets and the loopback rate of the secondary station corresponding to the second link;

in this embodiment of the present invention, for each second link, the primary station calculates, according to the loopback rate of the secondary station corresponding to the second link and the data amount of the N data packets, the loopback delay of the second link:

the second link loopback delay (data volume of the N taken out data packets + data volume of data packets already accumulated to the SeNB after the start of the current shunting period)/a second link loopback rate + (data volume of TxBuffer _ SeNB at the start of the current shunting period-MIN (data volume of TxBuffer _ SeNB at the start of the current shunting period, second link loopback rate (start time of the current shunting period-time of first packet shunting in TxBuffer _ SeNB))/a second link loopback rate.

The second link loopback rate estimation can be obtained by adopting an X2 port feedback receiving processing module of the main station to estimate data packet confirmation information contained in a downlink data transmission status report.

The second link loopback rate estimation can adopt two optional implementation modes as follows:

packet-based acknowledgement delay measurement method: the time delay from the transmission of each packet to the acknowledgement frame is measured. Dividing the time delay by the size of the data packet to obtain the instantaneous time delay of the packet, smoothing the instantaneous time delay to obtain the average time delay of each byte, and taking the reciprocal of the average speed as the average speed, wherein the alpha filtering mechanism is adopted for smoothing.

Statistical measurement method based on validation data per unit time: and transmitting the confirmation data quantity of the buffer TxBuffer _ SeNB in the non-empty time within the unit time. The measured values are smoothed using an alpha filtering mechanism.

S502, the main station distributes the N data packets to a target link with the minimum expected time delay for transmission.

In the embodiment of the present invention, the master station distributes the N data packets to the target link with the smallest expected delay for transmission, and it should be noted that the target link may be a first link or a second link. The expected delay includes, but is not limited to, a one-way delay or a round trip delay.

Referring to fig. 6, a schematic flow chart of another data transmission method according to an embodiment of the present invention is shown, where the data transmission method includes the following steps:

s600, the main station receives a downlink data transmission state report sent by an auxiliary station, wherein the downlink data transmission state report contains the buffer size of data expected to be received by the auxiliary station;

in the embodiment of the present invention, the X2 feedback sending processing module in the secondary station calculates and processes the downlink data transmission status report, and feeds back the downlink data transmission status report to the MeNB. The downlink data transmission status report includes the buffer size of the data expected to be received by the secondary station.

Specifically, optionally, the secondary station SeNB calculates the size of the buffer of the expected received data as follows:

when the buffer data of the SeNB is lower than a certain threshold, the SeNB is triggered to calculate the expected received data buffer size, and it can be understood that the data buffer size can also be calculated periodically.

The specific process of calculating the expected received data buffer size by the SeNB is as follows: and calculating the buffer size of the data expected to be received by the SeNB according to the air interface rate of the SeNB and the target buffer time of the SeNB.

The SeNB expects to receive a data buffer size (SeNB air interface rate) and a SeNB target buffer time.

The SeNB target buffer time is variable.

The SeNB user air interface rate refers to an SeNB air interface transmission rate when RxBuffer _ SeNB is not empty.

S601, the master station calculates a split cycle according to the size of the expected received data cache, wherein the split cycle is a period from the time when the master station receives the downlink data transmission state report to the time when the expected transmission is completed and the time when the size of the expected received data cache matches the data volume;

in the embodiment of the present invention, the master station calculates the split period according to the size of the expected received data buffer, as shown in fig. 8, where the split period is a period from when the master station receives the downlink data transmission status report to when the expected transmission is completed and when the size of the expected received data buffer matches the data size.

It should be noted that, in the offloading period, the master station cyclically obtains N data packets to be transmitted to the user terminal from the receiving buffer, and performs offloading processing on the N data packets in each cycle, thereby determining which target link the N data packets are transmitted on.

It should be noted that the number of N data packets obtained in each splitting time slot in the splitting period may be different, that is, N may be different.

S602, the primary station counts the total data quantity accumulated and sent to the secondary station from the beginning time of the shunting period;

in the embodiment of the present invention, the primary station counts the total data amount that is sent to the secondary station after the start time of the split cycle, for example, if two data packets are sent to the secondary station in an accumulated manner, where each data packet is N data packets, the total data amount is the data amount of 2N data packets, and the data amounts of each data packet may be inconsistent.

S603, if the total data volume is smaller than the size of the expected received data cache, the master station acquires N data packages to be transmitted from the received cache.

In the embodiment of the present invention, if the total data amount is smaller than the expected received data cache size of the secondary station, it indicates that data can be continuously sent to the UE through the secondary station, and the primary station acquires N data packets to be transmitted from the received cache, updates the data shunted to the MeNB and the SeNB in the current shunting period, and further updates the total shunting rate of the data shunted to the MeNB and the SeNB.

S604, the master station calculates an expected time delay of the data packet on each of a plurality of links according to the data amount of the N data packets, where the plurality of links includes a first link and at least one second link, the first link is a link between the master station and the user terminal, and the second link is a link between the master station and the user terminal via the secondary station;

s605, the main station distributes the N data packets to a target link with the minimum expected time delay for transmission.

Referring to steps S501 to S502 of fig. 5, steps S604 to S605 of the embodiment of the present invention are not described again.

S606, if the total data volume is larger than or equal to the size of the expected received data cache, the primary station calculates the expected time delay of a second link between the primary station and the secondary station;

in this embodiment of the present invention, if the total data amount accumulated and sent to the secondary station in the split period is greater than or equal to the size of the data cache expected to be received by the secondary station, it indicates that data cannot be continuously sent to the UE through the secondary station, and the primary station calculates the expected time delay of the current second link.

S607, the master station determines the size M (M is a natural number more than or equal to 0) of the data volume transmitted in the first link according to the expected time delay of the second link and the expected time delay of the first link;

in the embodiment of the invention, the master station determines the size M of the data volume transmitted in the first link according to the expected time delay of the second link and the expected time delay of the first link, wherein M is a natural number which is greater than or equal to 0.

Specifically, optionally, M data packets to be shunted are taken out from the RxBuffer _ MeNB queue in a First-in-First-out (FIFO) queue manner, an estimation result of an expected time delay of the data packets in the First link just reaches an expected time delay of the second link, and it should be noted that if the expected time delay of the data packets in the First link is greater than the expected time delay of the second link, M is 0.

When the RxBuffer _ MeNB queue has insufficient data, the expected delay estimation result of all the data packets in the queue will be smaller than the expected delay of the second link, and M is the number of all the data packets in the queue.

S608, the master station obtains the M data packets to be transmitted from the receiving cache, and distributes the M data packets to be transmitted to the first link for transmission.

In the embodiment of the invention, the master station distributes the M data packets to be transmitted, which are acquired from the receiving cache, to the first link for transmission, wherein the first link is a link between the master station and the user terminal UE. And simultaneously updating the total shunting rate of the data shunted to the MeNB and the SeNB.

Optionally, if the downlink data transmission status report includes the retransmitted data packet identifier, the data transmission method may further include the following steps S60 to S61;

s60, the master station acquires a retransmission data packet according to the retransmission data packet identifier;

in the embodiment of the invention, the downlink data transmission status report comprises the identification of the retransmission data packet, and the retransmission data packet is obtained from the corresponding sending cache according to the identification of the retransmission data packet.

And S61, the master station inserts the retransmission data packet into the N data packets according to the sequence number of the retransmission data packet.

In the embodiment of the invention, the main station acquires the serial number of the retransmission data packet, inserts the serial number into the transmission queue according to the serial number of the retransmission data packet, and ensures that the data packets in the transmission queue are transmitted in sequence.

It should be noted that, as shown in fig. 9, when the secondary station SeNB data offloading reception processing module receives a retransmission packet lost from X2 ports, the secondary station SeNB data offloading reception processing module inserts the retransmission packet into the transmission queue according to the sequence number of the packet, so as to ensure that the packets in the transmission queue are transmitted in sequence.

It can be understood that, when receiving the non-retransmitted data packet, the secondary station SeNB inserts the non-retransmitted data packet into the transmission queue according to the sequence number of the data packet, so as to ensure that the data packets in the transmission queue are transmitted in sequence.

Further optionally, the data transmission method of this embodiment may further include the following steps S62 to S64;

s62, the master station calculates a total data transmission rate on the first link and the at least one second link in a preset period, where the preset period includes a plurality of offloading periods;

in this embodiment of the present invention, the preset period may be a QoS guarantee period, as shown in fig. 8, the preset period includes a plurality of offloading periods, and the total data transmission rate on the first link and the at least one second link in the preset period is calculated.

S63, the master station judges whether the total data transmission rate is greater than a preset threshold value;

and S64, if yes, the master station determines that the master station meets the preset quality of service (QoS).

In the embodiment of the present invention, if the total data transmission rate is greater than the preset threshold, the master station determines that the master station meets the preset quality of service QoS, and does not perform data offloading processing within a preset period (i.e., the QoS guarantee period in fig. 8).

Referring to fig. 10, a schematic diagram of an MeNB data offloading transmission process provided in the present invention is shown, which includes the following steps:

step 1: if the master station receives the cache queue and still has data which is not sent, turning to the step 2; otherwise, the current shunting cycle is finished.

Step 2: if the accumulated data amount shunted to the SeNB exceeds the expected received data cache size calculated according to the current X2 port downlink data transmission state report, turning to step 3; otherwise go to step 6.

Step 3: and taking out M data packets to be shunted from the RxBuffer _ MeNB queue in a FIFO mode, wherein the expected time delay estimation results of the data packets just reach the expected time delay of the SeNB link. (when the RxBuffer _ MeNB queue has insufficient data, the estimated result of the expected time delay of all the data packets in the queue is smaller than the expected time delay of the SeNB link, and M is the number of the data packets in the queue.)

Step 4: and distributing the extracted M data packets to the first link.

Step 5: updating the total offloading rate for data offloaded to the MeNB and the SeNB. The current shunting cycle is finished.

Step 6: and taking out N data packets to be shunted from the RxBuffer _ MeNB queue in a FIFO mode. And N represents the granularity of delay estimation and depends on the processing capacity of hardware shunt. The smaller N is, the higher the requirement on the hardware shunt processing capacity is.

Step 7: and estimating the expected time delay of the data quantity of the N taken data packets.

Step 8: and distributing the extracted N data packets to a target link with smaller expected delay according to the result of the expected delay estimation.

Step 9: and updating the total shunting rate of the data shunted to the MeNB and the SeNB in the current shunting period according to the result of the step 8.

Step 10: if the total shunting rate of the user meets the QoS requirement of the user, ending the shunting period; otherwise, turning to the step 1.

Referring to fig. 11, fig. 11 is a schematic structural diagram of a data transmission device according to an embodiment of the present invention, and as shown in the drawing, the data transmission device of the present embodiment includes;

a first obtaining module 100, configured to obtain N (N is a natural number greater than or equal to 1) data packets to be transmitted from a receiving cache;

a first calculating module 101, configured to calculate, according to a data amount of the N data packets, an expected time delay of the data packet on each of multiple links, where the multiple links include a first link and at least one second link, the first link is a link between the master station and a user terminal, and the second link is a link between the master station and the user terminal via a secondary station;

optionally, the expected delay comprises a one-way delay;

the calculating, by the first calculation module 101, the expected time delay of the N data packets on each of the plurality of links according to the data amount of the N data packets specifically includes:

the first calculation module 101 calculates the one-way delay of the N data packets in the first link according to the data volume of the N data packets and the air interface rate of the master station;

for each second link, the first calculation module 101 calculates, according to the transmission delay of the X2 interface between the primary station and the secondary station corresponding to the second link, the transmission waiting delay of the data packet of the secondary station corresponding to the second link, the data amount of the N data packets, and the air interface rate of the secondary station corresponding to the second link, the one-way delay of the N data packets in the second link.

Preferably, if the primary station and the secondary station corresponding to the second link are synchronized, the transmission delay of the X2 interface is obtained from a downlink data transmission status report sent by the secondary station corresponding to the second link;

Preferably, the data packet transmission waiting delay is obtained from a downlink data transmission status report sent by the secondary station corresponding to the second link; or,

Optionally, the expected delay includes a loopback delay;

the first calculation module 101 calculates the loopback delay of the N data packets in the first link according to the data volume of the N data packets and the loopback rate of the master station;

for each second link, the first calculation module 101 calculates the loopback delay of the N data packets in the second link according to the data amount of the N data packets and the loopback rate of the secondary station corresponding to the second link;

A distributing module 102, configured to distribute the N data packets to a target link with a minimum expected latency for transmission.

Optionally, the apparatus further includes a receiving module 103, a second calculating module 104, and a counting module 105;

a receiving module 103, configured to receive a downlink data transmission status report sent by a secondary station, where the downlink data transmission status report includes a buffer size of data expected to be received by the secondary station;

a second calculating module 104, configured to calculate, according to the size of the expected received data buffer, a split period, where the split period is a period from when the primary station receives the downlink data transmission status report to when an expected transmission is completed and when the size of the expected received data buffer matches a data amount;

the first obtaining module 100 is specifically configured to obtain N data packets to be transmitted from a receiving buffer in a circulating manner in the splitting period.

A counting module 105, configured to count total data amount accumulated and sent to the secondary station after the start time of the offloading period;

the first obtaining module 100 is specifically configured to obtain N data packets to be transmitted from a receiving cache if the total data amount is smaller than the size of the expected receiving data cache.

Optionally, the data transmission apparatus may further include a third calculation module 106, a first determination module 107, and an acquisition and distribution module 108;

a third calculating module 106, configured to calculate an expected time delay of a second link between the primary station and the secondary station if the total data amount is greater than or equal to the size of the expected received data cache;

a first determining module 107, configured to determine, according to the expected time delay of the second link and the expected time delay of the first link, a size M of data volume transmitted on the first link (where M is greater than or equal to 0);

the obtaining and distributing module 108 is configured to obtain the M data packets to be transmitted from the receiving cache, and distribute the M data packets to be transmitted to the first link for transmission.

Further optionally, the data transmission apparatus may further include a second obtaining module 109 and an inserting module 110;

a second obtaining module 109, configured to obtain a retransmission data packet according to the retransmission data packet identifier;

an inserting module 110, configured to insert the retransmission data packet between the N data packets according to the sequence number of the retransmission data packet.

Further optionally, the apparatus may further include a fourth calculating module 111, a judging module 112, and a second determining module 113;

a fourth calculating module 111, configured to calculate a total data transmission rate on the first link and the at least one second link in a preset period, where the preset period includes multiple shunting periods;

a determining module 112, configured to determine whether the total data transmission rate is greater than a preset threshold;

a second determining module 113, configured to determine that the primary station meets a preset quality of service QoS if the total data transmission rate is greater than the preset threshold.

Referring to fig. 12, fig. 12 is a schematic structural diagram of a data transmission device according to an embodiment of the present invention. As shown in fig. 12, the apparatus may include: a memory 1201, a communication interface 1202, at least one processor 1203 (such as a CPU), and at least one communication bus 1204, where the memory 1201 may be a high-speed RAM memory, or may be a non-volatile memory (such as at least one disk memory), and optionally, the memory 1201 may also be at least one storage device located remotely from the processor 1103. Wherein:

a communication bus 1204 is used to enable connective communication between these components.

A set of program codes is stored in the memory 1201 and the processor 1203 is configured to call the program codes stored in the memory 1201 to perform the following operations:

acquiring N (natural numbers with N being more than or equal to 1) data packages to be transmitted from a receiving cache;

calculating the expected time delay of the data packet on each link of a plurality of links according to the data volume of the N data packets, wherein the plurality of links comprise a first link and at least one second link, the first link is a link between the master station and the user terminal, and the second link is a link between the master station and the user terminal through an auxiliary station;

the communication interface 1202 is configured to distribute the N data packets to a target link with a minimum expected latency for transmission.

In an alternative embodiment, the processor 1203 is configured to call the program code stored in the memory 1201, and may be further configured to:

receiving, through the communication interface 1202, a downlink data transmission status report sent by a secondary station, where the downlink data transmission status report includes a buffer size of data expected to be received by the secondary station;

calculating a distribution cycle according to the size of the expected received data cache, wherein the distribution cycle is a period from the time when the main station receives the downlink data transmission state report to the time when the expected transmission is completed and the time when the size of the expected received data cache is matched with the data volume;

and circularly acquiring N data packets to be transmitted from the receiving cache in the shunting period.

Optionally, the processor 1203 is configured to call the program code stored in the memory 1201, and may be further configured to perform the following operations:

counting the total data quantity accumulated and sent to the secondary station from the beginning time of the shunting period;

and if the total data volume is smaller than the size of the expected receiving data cache, acquiring N data packages to be transmitted from the receiving cache.

Further optionally, the processor 1203 is configured to call the program code stored in the memory 1201, and may be further configured to perform the following operations:

if the total data volume is larger than or equal to the size of the expected received data cache, calculating the expected time delay of a second link between the main station and the auxiliary station;

determining the size M (M is a natural number more than or equal to 0) of the data volume transmitted in the first link according to the expected time delay of the second link and the expected time delay of the first link;

and acquiring the M data packets to be transmitted from a receiving cache, and distributing the M data packets to be transmitted to the first link for transmission.

Optionally, the expected delay comprises a one-way delay;

the calculating, by the processor 1203, an expected time delay of the N data packets on each link of the multiple links according to the data amount of the N data packets specifically includes:

the processor 1203 calculates the one-way delay of the N data packets in the first link according to the data amount of the N data packets and the air interface rate of the master station;

Optionally, the expected delay includes a loopback delay;

calculating the loopback delay of the N data packets in the first link according to the data volume of the N data packets and the loopback rate of the master station;

for each second link, calculating the loopback delay of the N data packets in the second link according to the data volume of the N data packets and the loopback rate of the secondary station corresponding to the second link;

Further optionally, the downlink data transmission status report includes an identifier of a retransmission data packet, and the processor 1203 is configured to call a program code stored in the memory 1201, and may also be configured to perform the following operations:

acquiring a retransmission data packet according to the retransmission data packet identifier;

and inserting the retransmission data packet among the N data packets according to the sequence number of the retransmission data packet.

calculating a total data transmission rate on the first link and the at least one second link in a preset period, wherein the preset period comprises a plurality of shunting periods;

judging whether the total data transmission rate is greater than a preset threshold value or not;

and if the total data transmission rate is greater than the preset threshold value, determining that the main station meets the preset quality of service (QoS).

It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.

The steps in the method of the embodiment of the invention can be sequentially adjusted, combined and deleted according to actual needs.

The modules in the data transmission device of the embodiment of the invention can be merged, divided and deleted according to actual needs.

The components such as the microcontroller according to the embodiment of the present invention may be implemented by a general-purpose integrated Circuit, such as a Central Processing Unit (CPU), or an Application Specific Integrated Circuit (ASIC).

Claims

1. A method of data transmission, comprising:

and the master station distributes the N data packets to a target link with the minimum expected time delay for transmission.

2. The method of claim 1, wherein prior to the master station retrieving the N data packets for transmission from the receive buffer, further comprising:

3. The method of claim 2, wherein prior to the master station retrieving the N data packets for transmission from the receive buffer, further comprising:

4. The method of claim 3, wherein the method further comprises:

5. The method of any of claims 2-4, wherein the expected delay comprises a one-way delay;

6. The method of claim 5, wherein if the primary station is synchronized with the secondary station corresponding to the second link, the transmission delay of the X2 interface is obtained from a downlink data transmission status report sent by the secondary station corresponding to the second link;

7. The method of claim 5, wherein the packet transmission waiting delay is obtained from a downlink data transmission status report sent by the secondary station corresponding to the second link; or,

8. The method of any of claims 2-4, wherein the expected latency comprises a round trip latency;

9. The method of claim 2, wherein the downlink data transmission status report includes an identification of a retransmitted data packet, the method further comprising:

10. The method of claim 2, wherein the method further comprises:

11. A data transmission apparatus applied to a master station, comprising:

and the distribution module is used for distributing the N data packets to a target link with the minimum expected time delay for transmission.

12. The apparatus of claim 11, wherein the apparatus further comprises:

13. The apparatus of claim 12, wherein the apparatus further comprises:

14. The apparatus of claim 13, wherein the apparatus further comprises:

15. The apparatus of any of claims 12-14, wherein the expected delay comprises a one-way delay;

16. The apparatus of claim 15, wherein if the primary station is synchronized with the secondary station corresponding to the second link, the X2 interface transmission delay is obtained from a downlink data transmission status report sent by the secondary station corresponding to the second link;

17. The apparatus of claim 15, wherein the packet transmission latency is obtained from a downlink data transmission status report sent by the secondary station corresponding to the second link; or,

18. The apparatus of any of claims 12-14, wherein the expected latency comprises a round trip latency;

19. The apparatus of claim 12, wherein the downlink data transmission status report includes an identification of a retransmitted data packet, the apparatus further comprising:

20. The apparatus of claim 12, wherein the apparatus further comprises: