CN100393076C - Time adjustment method for radio access network and core network interface user plane - Google Patents

Abstract

The invention discloses a time adjustment method for a user plane of a wireless access network and a core network interface. SRNC first determines a reference frame; records the frame number and arrival time of the currently received data frame; and compares the frame number difference between the current frame and the reference frame Multiply the timing interval of the lu port and add the arrival time of the reference frame to get the ideal arrival time of the current frame, and judge whether the time difference between the arrival time of the current frame and the ideal arrival time is within a given range, if so, update the reference frame without making time adjustment, Continue to process the next frame, or trigger the time adjustment process with the core network. Further, in order to obtain a high-precision reference frame, the last frame can be used as the reference frame after the timing of multiple consecutive frames is accurate. The invention solves the Iu UP time adjustment function stipulated in the protocol in a simple way, can effectively control the time sequence of the downlink data on the Iu interface to the SRNC, and minimizes the buffer delay in the SRNC.

Description

Time adjustment method for radio access network and core network interface user plane

technical field

The present invention relates to the interface (defined as Iu mouth) of radio network controller (RNC, Radio Network Controller) and core network (CN: Core Network) in WCDMA system, particularly relate to this interface service radio network controller (SRNC: Sever Radio Network Controller , indicating the method for adjusting the user plane time on the RNC) side where the service exists.

Background technique

In the WCDMA system, the Iu port is a standard interface connecting the RNC and the CN, and the Iu port user plane (Iu UP, Iu User Plane) is the user data transmission protocol of the Iu port, which is mainly used to realize the transfer of user data between the CN and the RNC. transmission. The user plane of the Iu interface has two operation modes: transparent mode (TrM: Transparent Mode) and support mode for pre-defining the size of the service data unit (SDU: Service Data Unit) (SMpSDU: Support Mode for predefined SDUsize).

In SmpSDU mode, Iu UP has the following functions: transmission of user data, initialization, rate control, time adjustment, error event handling and frame quality classification. Among them, the purpose of the time adjustment process is to reduce the data buffering time in the SRNC where the Iu UP entity at the opposite end is located, and improve the real-time performance of the supported services by controlling the timing relationship of the downlink transmission data of the Iu UP protocol entity of the CN. Conversation and flow are both services that require high real-time performance. For these services, the frame number of the Iu UP protocol layer on the CN side generally adopts the form based on the lu interface timing interval (ITI: Iu Timing Interval), that is to say, every time a ITI then the number of the current frame=(the frame number of the previous frame+1) mod 16. The meaning of ITI here is the minimum transmission interval between Iu UP service data units of a radio access bearer (RAB: Radio Access Bearer). For session and stream ITI, it can be calculated by the following formula:

$\mathrm{<span\; class="notranslate">\; ITI</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; MaxSDUsize</span>}}{\mathrm{<span\; class="notranslate">\; Max\; Bitrate</span>}}$

Among them: MaxSDUsize: is the size of the largest SDU indicated in a given radio access bearer subflow combination (RFCS: RABsub Flow Combination);

MaxBitrate: is the maximum bit rate of the transmitted data

Therefore, the frame number actually reflects the sending time of each SDU at the Iu UP protocol layer on the CN side, and the time adjustment process is only done when the frame number is based on the ITI.

The 3GPP protocol 25.415 describes the time adjustment process in the support mode of the predefined SDU size as follows:

1) The time adjustment process on Iu UP is controlled by SRNC.

2) When it is detected that the Iu UP service data unit arrives at an inappropriate time, resulting in unnecessary buffer delay, the SRNC will invoke the time adjustment process. How triggers are detected in SRNC is an internal matter of SRNC, which is beyond the scope of this protocol.

3) The Iu UP protocol layer in the SRNC indicates the necessary delay or advance to the peer entity, with a step size of 500 us.

4) After sending the Iu UP time alignment frame, the monitoring timer T _TA (Time Alignment Timer) is started. This timer is used to monitor the receipt of time-adjusted Acknowledgment frames.

5) The Iu UP protocol layer entity requested by the peer node adjusts the timing relationship of the downlink transmission data according to the instructions of the SRNC.

6) If the format of the time adjustment frame received is correct, and the Iu UP protocol layer of the receiving end receives it, and the upper layer has correctly processed the time adjustment, the Iu UP protocol layer of the receiving end will send an acknowledgment frame for time adjustment.

7) After receiving the time adjustment confirmation frame, the Iu UP protocol layer in the SRNC will stop monitoring the timer T _TA . In order to avoid frequent time adjustments, it is necessary to ensure that the time adjustment process can be initiated again after a certain period of time.

8) This procedure can be initiated at any time when user data transfer is not pending by other control procedures.

It can be seen that the protocol does not specify how the SRNC detects the trigger time adjustment. However, based on the principle of sending Iu UP service data units by the Iu UP protocol layer on the CN side, it can be seen that the SRNC can judge whether the current sending frame is sent at an inappropriate time by comparing the actual receiving time of the Iu UP service data unit with the ideal receiving time. The SRNC can obtain the receiving moment of the current Iu UP service data unit, but how the SRNC determines the ideal arrival time of the service data unit, and how to judge whether the service data unit is being received in advance or behind is a key issue to be solved.

Contents of the invention

The technical problem to be solved by the present invention is to provide a time adjustment method for the user plane of the interface between the wireless access network and the core network, so that the SRNC can correctly trigger the call time adjustment process and effectively control the downlink data transmission time of the CN.

In order to solve the above-mentioned technical problems, the present invention provides a method for adjusting the time of a radio access network and a core network interface user plane, comprising the following steps:

(a) the serving radio network controller determines a reference frame;

(b) record the frame number and arrival time of the currently received data frame;

(c) Multiply the frame number difference between the current frame and the reference frame by the lu port timing interval, add the arrival time of the reference frame to obtain the ideal arrival time of the current frame, and judge whether the time difference between the current frame arrival time minus the ideal arrival time is within a given In the first range (can be set to a very small range), if yes, execute the next step, otherwise, execute step (e);

(d) No time adjustment, update the reference frame, and return to step (b);

(e) Triggering a time adjustment process with the core network.

Further, in order to reduce the cumulative error, in the step (d), the frame number of the reference frame is updated to the frame number of the current frame, and the arrival time of the reference frame is updated to the ideal arrival time of the current frame .

Further, the first range in the step (c) may be defined by a positive threshold and a negative threshold, if the time difference is greater than the positive threshold, the current frame arrives late, in step (e) Send a time adjustment frame indicating advance to the core network; if the time difference is less than the negative threshold, the current frame arrives ahead of time, and send a time adjustment frame indicating lag to the core network in step (e).

Further, in the step (e), the time adjustment amount required by the time adjustment frame may be taken as the time difference.

Furthermore, in order to obtain a high-precision reference frame and avoid inaccurate timing due to transmission delay fluctuations, etc., it is necessary to determine the reference frame after comparing multiple frames, and update the reference frame in real time under the premise of accurate timing. For this reason, The step (a) adopts the following steps to determine the reference frame:

(a1) Set the frame number and arrival time of the first frame data as initial reference frame frame number and arrival time;

(a2) For the subsequent current frame, multiply the frame number difference between it and the reference frame by the lu port timing interval, add the arrival time of the reference frame to obtain the ideal arrival time of the current frame, and judge whether the time difference between the current frame arrival time and the ideal arrival time is Within the set second range, if yes, execute the next step, otherwise, execute step (a4);

(a3) think that the timing of this frame is accurate, and update the reference frame to this frame, and then continue to process the next frame until the number of data frames with continuous timing and accurate timing reaches the preset value, with the last frame as the reference frame, perform the step ( c);

(a4) Think that the frame timing is inaccurate, count again, and continue to process the next frame.

Further, when the difference between the SRNC processing time and the arrival time of the Iu UP business data unit is too close, in order to ensure that the downlink data can be processed in time, time adjustment can be initiated to adjust the sending timing of the CN, that is, execute after the step (a2) The following steps:

(a21) judging whether the deviation between the arrival time of the current frame and the processing time of the serving radio network controller is within a set third range, if yes, perform step (a3), otherwise perform the next step;

(a22) Sending a time adjustment frame to the user plane of the lu port on the peer port, indicating to send in advance, and the advance amount is a variable that can be set, and then execute step (a4).

Further, after the time adjustment process with the core network is triggered in the step (e), first judge whether it is within the time adjustment protection time, if not within the protection time, send a time adjustment frame to the core network, and continue the protocol For the specified follow-up processing, continue the processing of the next frame within the protection time without sending an adjustment frame.

As can be seen from the above, the present invention first determines the frame number and arrival time of the reference frame, then uses the reference frame as a reference, compares the frame number and arrival time of the current frame with the reference frame, and calculates the deviation between the ideal arrival time and the actual arrival time, thereby Determine whether the CN needs to adjust the time. Calculate the time adjustment amount if necessary, and send a time adjustment control frame to the CN. Furthermore, a high-precision reference frame can be obtained by using the statistical method proposed by the present invention. Thereby, the present invention solves the Iu UP time adjustment function stipulated in the agreement with a kind of simple method, can effectively control the timing of the downlink data on the Iu interface to the SRNC, and make the buffer delay in the SRNC minimum.

Description of drawings

Figure 1 is a functional model diagram of the user plane protocol layer of the Iu interface in the support mode.

Fig. 2 is a schematic diagram of the time adjustment lag adjustment of the Iu port.

FIG. 3 is a schematic diagram of the advance adjustment of the time adjustment of the Iu port.

Fig. 4 is a flowchart of determining a reference frame required for a time-adjusted frame according to an embodiment of the present invention.

FIG. 5 is a flowchart of time adjustment processing during normal data transmission according to an embodiment of the present invention.

Detailed ways

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

Fig. 1 is the functional model diagram of the Iu UP protocol layer in the support mode of CN and UTRAN (radio access network, including RNC) connected through the Iu port. As shown in the figure, the Iu UP protocol layers on both CN and RNC have the following three types of functions:

1) Frame Handler function (Frame Handler function);

2) Procedure Control functions (Procedure Control functions);

3) Functions for non-access stratum (NAS: Non Access Stratum) data streams (Non AccessStratum Data Streams specific functions);

The time adjustment function involved in the present invention belongs to the process control function, and is used to control the timing of the downlink data on the Iu interface to the RNC.

Figure 2 and Figure 3 show the time adjustment process between SRNC and CN, where PT(i) (Process Time) represents the RNC processing time.

In Figure 2, the actual sending time of frame i+1 on the CN side is earlier than the supposed sending time, and the Iu UP of SRNC compares the actual receiving time of the frame with the supposed receiving time at PT(i) time, and judges that the frame data is ahead of time When Delta t arrives, send a time alignment frame (Time alignment) to the CN to indicate its delayed transmission; after the CN receives the time adjustment frame, it returns a time-adjusted acknowledgment frame (ACK) to the SRNC, and accepts the required lag adjustment, and sends The sending time of i+2 frames is delayed by Delta t.

In Figure 3, the actual sending time of frame i+1 on the CN side is later than the supposed sending time, and the Iu UP of SRNC compares the actual receiving time of the frame with the supposed receiving time at PT(i+1) time to judge the frame When the data arrives with a delay of Delta t, a time alignment frame (Time alignment) is sent to the CN to indicate that it is sent in advance; after the CN receives the time alignment frame, it returns a time adjustment acknowledgment frame (ACK) to the SRNC and accepts the required advance adjustment amount , advance the sending time of frame i+2 by Delta t.

From the time adjustment process in Figure 2 and Figure 3, it can be seen that even if the sending time of a certain Iu UP service data unit is wrong, after the time adjustment, the sending time of the subsequent service data unit can still be adjusted to the ideal time for sending, which is not necessary. All subsequent frames will be advanced or delayed due to an error in the sending time of a certain frame.

In order to judge whether CN needs to perform time adjustment and calculate the amount of time adjustment, the present invention first uses statistical methods to obtain accurate reference frames, and determines its frame number and arrival time; The time is compared with the reference frame, and the deviation between the ideal arrival time and the actual arrival time is calculated, so that it can be judged whether adjustment is needed and the time adjustment amount can be calculated.

Fig. 4 describes the process of determining the reference frame in this embodiment. Considering that the timing of a certain frame of data may be inaccurate due to fluctuations in transmission delay, etc., it is necessary to compare multiple frames to determine the reference frame, and update the reference frame in real time under the premise of accurate timing. During this period, the deviation between the SRNC processing time and the arrival time of the Iu UP service data unit is also considered. If the difference is too close, time adjustment should be initiated to adjust the sending timing of the CN to ensure that the downlink data can be processed in time. The process includes the following steps:

Step 110, record the frame number and arrival time (i.e. receiving time) of the currently received data frame;

Step 120, judging whether the current data frame is the first frame data received, if yes, execute the next step, otherwise, execute step 140;

Step 130, set the reference frame as this frame, record its frame number and arrival time, return to step 110 (continue to process the next frame);

Step 140, judging whether the count value TaReferCounter with continuous timing and accuracy is greater than the preset value N, if yes, turn to the normal data receiving process flow (see Figure 5), otherwise, execute the next step;

Step 150: subtract the arrival time dwTickArrive of the current frame from the arrival time dwTaTickRefer of the reference frame, and then subtract the product of the frame number difference between the current frame and the reference frame byFrmOffset and ITI from the obtained difference to obtain the time difference TickOffset between the arrival time of the frame and the ideal arrival time ,Right now:

TickOffset＝dwTickArrive-dwTaTickRefer-byFrmOffset*ITI (1)

At the same time, calculate the deviation ProcOffset between the arrival time of the frame and the processing time;

Step 160, judge whether TickOffset is in the scope 1 of setting (set as very little scope), if yes, think that this frame arrives accurately, carry out step 180, otherwise carry out next step;

Step 170, set the count value TaReferCounter that is continuously and accurately counted as zero, and return to step 110;

Step 180, judging whether the ProcOffset is within the set range 2, if yes, execute step 200, otherwise execute the next step;

Step 190, add 1 to the count value TaReferCounter with continuous timing accuracy, update the reference frame to this frame, and return to step 110;

Step 200, setting the count value TaReferCounter with continuous timing and accuracy is zero;

Step 210, judging whether it is within the time adjustment protection time, if yes, return to step 110, otherwise, execute the next step;

Step 220, send a time adjustment control frame to the opposite end lu UP, indicating to send in advance, and the advance time adopts a variable that can be set by the user, and returns to step 110.

It should be noted that the specific implementation steps of the above process can be adjusted. For example, the judgment of the count value of continuous timing in step 140 can also be judged after adding 1 to the count value in step 180. If it is greater than the preset value Go directly to the normal data processing flow.

Figure 5 describes the time adjustment process during normal data transmission, as shown in the figure, including the following steps:

Step 310, recording the frame number and arrival time (i.e. receiving time) of the currently received data frame;

Step 320, refer to the reference frame, calculate the time difference TickOffset between the arrival time of the frame and the ideal arrival time according to the current frame frame number and the arrival time, the calculation method is the same as that in Figure 4;

Step 330, judge whether TickOffset is greater than the threshold value 1 of setting (being a positive number), if yes, explain that this frame arrives later than ideal time, execute step 360; Otherwise, execute next step;

Step 340, judge whether TickOffset is less than the threshold value 2 (being negative number) of setting, if yes, explain that this frame arrives earlier than ideal time, execution step 370; Otherwise, execution next step;

Step 350, do not make time adjustment, update the frame number of the reference frame to the frame number of the frame, and update the reference arrival time of the reference frame to the ideal arrival time of the frame, which is equal to the arrival time of the original reference frame plus the frame numbers of the current frame and the reference frame The product of difference and ITI is: dwTaTickRefer+byFrmOffset*ITI, return to step 310;

Step 360, determine that the sending time of the next frame needs to be advanced, and the advanced time is TickOffset, and then process according to the steps stipulated in the agreement;

Step 370, determine that the sending time of the next frame needs to be delayed, and the delay time is TickOffset, and then process according to the steps stipulated in the protocol.

In step 350, the arrival time of the reference frame is updated to the ideal arrival time of the current frame instead of its actual arrival time, which can reduce the cumulative error. At the same time, it also makes it unnecessary to judge the deviation between the arrival time of the current frame and the processing time in the normal data receiving process flow, because this factor has been taken into account when the arrival time of the reference frame determined before entering the flow chart in Figure 5, and the ideal arrival time of the current frame The moment is extrapolated from that moment.

In addition, the processing steps stipulated in the agreement are as follows:

First judge whether it is within the time adjustment protection time, if yes, process the next frame, otherwise send a time adjustment frame to the CN, and start a timer, waiting for the reception of the confirmation frame of the time adjustment frame;

If the time adjustment does not support signal is received, Iu UP will turn off the time adjustment function and end;

If the requested time adjustment is temporarily unable to receive a signal, delay for a period of time, and then determine whether the time adjustment is still required, and if so, re-trigger the time adjustment;

If a confirmation frame for time adjustment is received, a timer is started, and the time adjustment can be performed again after the timer expires;

If the time adjustment confirmation frame is not received within the time limit, the number of failures is increased by 1, and when the number of failures reaches the specified number, it is reported to the control plane and the time adjustment function is turned off.

After the above steps, the Iu UP protocol entity of SRNC simply and effectively solves the process of detection and trigger time adjustment. After obtaining a fairly accurate reference frame using statistical methods, it can be accurately calculated in the actual data transmission process to obtain the early or delayed transmission of the CN side. As well as the exact amount of time for adjustment, the timing relationship of CN's Iu UP protocol entity data transmission is controlled by the time adjustment frame, which reduces the downlink buffer delay of SRNC and ensures the real-time requirements of specific business types. Further, by updating the frame number and arrival time of the reference frame in real time in the subsequent data transmission, the cumulative error is reduced and misadjustment is avoided.

The above specific embodiments are only used to illustrate the present invention, but not to limit the present invention.

Claims (7)

1. A time adjustment method for a wireless access network and a core network interface user plane, comprising the following steps: (a) the serving radio network controller determines a reference frame; (b) record the frame number and arrival time of the currently received data frame; (c) Multiply the frame number difference between the currently received data frame and the reference frame by the lu port timing interval, add the arrival time of the reference frame to obtain the ideal arrival time of the currently received data frame, and determine the arrival time of the currently received data frame minus the ideal Whether the time difference of the arrival moment is within the given first range, if yes, execute the next step, otherwise, execute step (e); (d) No time adjustment, update the reference frame, and return to step (b); (e) triggering the time adjustment process with the core network; Wherein, the process of determining the reference frame in the step (a) further includes the following steps: (a1) Set the frame number and arrival time of the first frame data as initial reference frame frame number and arrival time; (a2) For the subsequent current frame, multiply the frame number difference between it and the reference frame by the lu port timing interval, add the arrival time of the reference frame to obtain the ideal arrival time of the current frame, and judge whether the time difference between the current frame arrival time and the ideal arrival time is Within the set second range, if yes, execute the next step, otherwise, execute step (a4); (a3) think that the timing of the current frame is accurate, and update the reference frame to this frame, and then continue to process the next frame until the number of consecutive data frames with accurate timing reaches the preset value, and take the last frame as the reference frame, and perform the steps (b); (a4) Think that the timing of the current frame is inaccurate, count again, and continue to process the next frame. 2. The time adjustment method according to claim 1, wherein in the step (d), the frame number of the reference frame is updated to the frame number of the currently received data frame, and the arrival of the reference frame The time is updated to the ideal arrival time of the currently received data frame. 3. The time adjustment method according to claim 1, wherein the first range in the step (c) is limited by a positive threshold and a negative threshold, if the time difference is greater than the positive threshold , the currently received data frame arrives with a delay, and in step (e) sends a time adjustment frame indicating an advance to the core network; if the time difference in the step (c) is less than the negative threshold, the currently received data frame The frame arrives ahead of time, and in step (e), a time adjustment frame indicating lag is sent to the core network. 4. The time adjustment method according to claim 3, wherein in the step (e), the time adjustment amount required by the time adjustment frame is equal to the time difference in the step (c). 5. time adjustment method as claimed in claim 1, is characterized in that, also comprises the following steps after described step (a2): (a21) judging whether the deviation between the arrival time of the current frame and the processing time of the serving radio network controller is within a set third range, if yes, perform step (a3), otherwise perform the next step; (a22) Sending a time adjustment frame to the user plane of the lu port on the peer port, indicating sending in advance, and then performing step (a4). 6. The time adjustment method according to claim 5, characterized in that, in the step (a22), the user plane of the opposite port lu port is prompted to send in advance by a set amount of time. 7. The time adjustment method according to claim 1, characterized in that, after the time adjustment process with the core network is triggered in the step (e), it is first judged whether it is within the time adjustment protection time and not within the protection time. Then send a time adjustment frame to the core network within the protection time, and continue the follow-up processing specified in the protocol, and continue the processing of the next frame within the protection time without sending an adjustment frame.

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