KR100418909B1 - Method for adjusting a frame transmitting timing - Google Patents

Abstract

The present invention relates to a mobile communication system, and more particularly, to a method for adjusting a transmission timing of a downlink frame. Such a transmission timing adjustment method according to the present invention comprises the steps of measuring the reception time of the frame received from the control station; Determining a reception window in consideration of a start point, an end point, and a frame processing time of a frame counter and a signaled reception window included in the frame; And determining whether to adjust frame transmission timing by comparing the determined reception window with the frame reception time.

Description

Method for adjusting a frame transmitting timing

The present invention relates to a mobile communication system, and more particularly, to a method for adjusting a transmission timing of a downlink frame.

In general, timing control of an asynchronous IMT-2000 system is performed by a Radio Network Controller in a Frame Protocol (hereinafter abbreviated as FP) (see 3GPP standard document 25.427, 25.435). When transmitting, the base station notifies the control station of the time when the base station receives the frame so that the control station can adjust the downlink frame transmission rate.

In order to implement the timing adjustment function, the base station calculates a TOA-Time of Arrival of a frame each time a base station receives a downlink frame including a Connection Frame Number (CFN) field according to FP from the control station. If it is found that the frame does not arrive within the specified receive window, it sends a timing adjustment message to the control station to inform the control station of this fact. Here, the CFN field in the downlink frame includes a time point at which the downlink frame should be transmitted over radio waves, and is a second layer of the OSI 7 layer model between a user equipment (UE) and a universal terrestrial radio access network (UTRAN). Frame counter used for transport channel synchronization.

1 illustrates a determination of a reception window of a conventional FP downlink frame.

In FIG. 1, the Time of Arrival Window Startpoint (TOAWS) indicates the starting point of the receive window, expecting downlink data frames to be received after this window start point. This TOAWS is defined as a positive value compared to TOAWE. For a data frame arriving before this TOAWS, the base station NodeB gives a timing adjustment control frame response to the base station control station RNC.

The Time of Arrival Window Endpoint (TOAWE) represents the endpoint of the receive window, expecting downlink data frames to be received before this window endpoint. This TOAWE is defined as a positive value compared to the LTOA (Latest Time of Arrival). For a data frame arriving after this TOAWE, the base station NodeB gives a timing adjustment control frame response to the base station control station RNC.

The LTOA is the earliest time a base station can receive a data frame and is still able to process it. In other words, this LTOA means the maximum delayed reception time at which the base station can receive a data frame in view of the frame processing time, and data frames received after this LTOA cannot be processed and discarded. . Data frames received after TOAWE but before LTOA are processed by the base station. The LTOA is defined as the processing time before the data frame is transmitted to the air interface internally at the base station. This processing time t_proc is a reference for the TOAWE.

Time of Arrival (TOA) indicates the time difference between when a data frame is received and the TOAWE, where a positive TOA is received before the data frames and a negative TOA is received after the TOAWE. Means that.

The Cell System Frame Number counter (SFN) is transmitted on a broadcasting channel (BCH). This SFN is used for paging groups, system information scheduling, and the like.

Frame offset is used in the transport channel as a radio link specific L1 (Layer 1) parameter used to map the CFN to an SFN defining a specific radio frame for transmission on the air interface.

2 is a diagram illustrating a timing adjustment procedure for a downlink frame according to the prior art.

In Figure 2, at the base station, the reception window is determined by the TOAWE and TOAWS signaled above the CFN value in the downlink frame.

When the base station receives the downlink frame through the FP, the base station sets a reception window for the frame, and checks whether the frame has arrived within the set window.

If the frame is found to have arrived before the TOAWS, the base station transmits a positive TOA timing adjustment control frame to the control station and transmits the frame over the airwaves.

If the frame arrives after the TOAWE but before the LTOA, the base station transmits the negative TOA timing adjustment control frame to the control station and transmits the frame over the airwaves.

However, if a frame arrives after LTOA, the base station transmits a negative TOA timing adjustment control frame to the control station and does not transmit this frame over the airwaves.

Since there is no calculation formula of TOA in the related art, the determination of the reception window and the adjustment of the transmission timing of the downlink frame in the system increase the probability of error.

Accordingly, the present invention has been made in view of the above-mentioned problems of the prior art, and is to provide an efficient downlink frame transmission timing adjustment method by accurate transmission timing adjustment calculation.

According to an aspect of the present invention for achieving the above object, the frame counter included in the frame received from the control station, the processing time of the frame, the endpoint of the receiving window signaled by the upper layer, the frame receiving time Calculating a parameter for adjusting frame transmission timing on a time axis based on the frame counter; It is determined whether the difference between the calculated parameter and the converted frame reception time is between the minimum value and the minimum value on the time axis or between the maximum value and the maximum value. Correcting the difference value according to the determination result; Here, if it is between the minimum value and the middle value of the minimum value on the time axis, the difference value is corrected by adding one cycle of the converted frame counter, and the value is between the maximum value and the middle value of the maximum value. In this case, the difference value is corrected by subtracting one period of the converted frame counter.

Preferably, the time axis is expressed in units of 0.125 ms. Since the frame counter is repeated with a value from 0 to 255, 0 is minimized on the time axis and 2559.875 ms is maximum.

Advantageously, the parameter is a remainder obtained by subtracting the converted frame processing time and the endpoint of the converted receiving window from the converted frame counter by the range of the frame counter.

The method may further include determining whether to transmit the frame in downlink and whether to transmit a frame transmission timing adjustment value to a control station according to the transmission timing adjustment value.

Preferably, in the step of correcting the difference value, using the frame counter included in the frame received from the control station, the processing time of the frame, the endpoint of the receiving window signaled by the higher layer, and the frame receiving time, Calculating a difference between the frame reception time and the endpoint of the actual reception window, which is the parameter; Correcting the calculated difference value when the difference between the frame reception time and the end point of the actual reception window is greater than a 2 / frame counter range; Here, the frame counter, the endpoint of the reception window signaled by the higher layer, the frame reception time, and the frame processing time are converted into variables on the same time axis, and the calculated difference value on this time axis. The calculated difference value is corrected by adding a frame counter range of one period if it is between the minimum value of this time axis and the minimum value, and the calculated difference on the time axis is the maximum value of the time axis and this maximum value. If it is in the middle of the value, the calculated difference value is corrected by subtracting the frame counter range of one period.

According to another aspect of the present invention for achieving the above object, the step of measuring the reception time of the frame received from the control station; Determining a reception window in consideration of a start point, an end point, and a frame processing time of a frame counter and a signaled reception window included in the frame; And determining whether to adjust frame transmission timing by comparing the determined reception window with the frame reception time.

Preferably, using the frame counter and the frame processing time to calculate the maximum delay reception time of the frame can be received; Calculating an actual reception endpoint from the calculated maximum delayed reception time and an endpoint of a reception window signaled by a higher layer; The method may further include determining whether to adjust the timing by calculating a frame transmission timing adjustment value by calculating a difference between the calculated reception endpoint and the reception time of the frame.

Preferably, the method further includes correcting the difference value when the calculated reception end point and the reception time of the frame are in different ranges based on a frame counter repeatedly increasing for each predetermined range. Here, when the calculated reception end point and the reception time of the frame are in different ranges based on a frame counter repeatedly increasing every predetermined range, and the difference value exceeds the '2 / frame counter range', the difference Correct the value.

Preferably, the calculated difference value is corrected by adding a frame counter range of one period to a difference value between a minimum value based on the frame counter and a middle value between the minimum value and correcting the calculated difference value. The calculated difference value is corrected by subtracting the frame counter range of one period from the difference value between the maximum value and the middle of this maximum value.

Preferably, if the calculated difference value is positive, transmitting information to the control station to delay the frame transmission time to the base station; And if the calculated difference value is negative, transmitting information to the control station to advance the transmission time of the frame to the base station.

Preferably, if the frame reception time exceeds the calculated maximum delay reception time, further comprising the step of discarding the received frame without transmitting (downlink).

Preferably, the time axis is expressed in units of 0.125 ms.

1 is a view showing the determination of the reception window of the FP downlink frame according to the prior art.

2 is a diagram illustrating a timing adjustment procedure for a downlink frame according to the prior art.

3 to 6 are diagrams showing the timing relationship between the reception time of a frame received from the control station and the end point TOAWE of the reception window.

Hereinafter, a configuration and an operation according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

In general, an implementation of a timing adjustment procedure for a frame for transmission to a base station is performed by calculating a TOA and determining whether a timing adjustment message is transmitted and whether a frame is transmitted.

The present invention presents an algorithm for each of the above steps. In this case, the present invention proposes a calculation algorithm of the TOA in consideration of CFN having a range of 0 to 255, which increases by 1 every 10 ms.

First, the TOA calculation of the frame received from the control station to the base station can be obtained by the following principle.

First, the base station arrival time (Farr) of the frame received from the control station to the base station is measured.

Second, the reception window of the frame is determined by CFNtx, t_proc, toawe, and toaws.

The CFNtx is a variable representing the CFN of the received frame. The t_proc is a variable representing a processing time at a corresponding base station of the received frame, and the toawe and toaws are a start point and an end point variable of a reception window signaled by a higher layer. Here, CFNtx is in units of 10ms and toawe is in units of 1ms.

The LTOA by t_proc is calculated by the following equation. This LTOA calculates the maximum receivable delay time of the frame in consideration of t_proc from the CFN.

LTOA = CFNtx-t_proc

The TOAWE (end point of the actual receive window) by the toawe signaled at the top is calculated by the following equation.

TOAWE = LTOA-toawe

The TOAWS (starting point of the actual receiving window) by the toaws signaled at the top is calculated by the following equation.

TOAWS = TOAWE-toaws

The TOA (difference value between the actual receiving end point and Farr) is calculated by Equation 4 according to the base station arrival time Farr and Equation 1 and Equation 2.

TOA = TOAWE-Farr

The algorithm for determining whether to send the timing adjustment message and whether to transmit the frame on the radio wave is as follows.

If the frame arrives before the TOAWS or later than the TOAWE, the timing adjustment message is sent to the control station.

If the frame arrives before the TOAWS or later than the LTOA, the frame is discarded.

On the other hand, in the TOA calculation algorithm, since CFN has a characteristic of increasing repeatedly from 0 to 255, there is a case where the arithmetic expression cannot be reflected in the actual TOA calculation.

Therefore, the present invention additionally introduces the concept of a time axis for representing the absolute time in CFN (Connection Frame Number) in units of 125 Usec for the calculation of the TOA. The time axis is referred to as CFN_timing_axis.

Since the CFN is a counter that repeats indefinitely with a value of 0 to 255 increasing by 1 every 10 ms with respect to the absolute time, a point x on the time axis CFN_timing_axis representing the CFN in units of 125 Usec may be represented by the following Equation 5.

x = n * 0.125ms

N is an integer greater than or equal to 0 and less than 20480. Thus, x is greater than or equal to 0 and less than or equal to 2559.875 ms.

In the present invention, all parameters necessary for the TOA calculation are represented as follows on CFN_timing_axis.

When CFNtx is represented in units of 125Usec, it is defined as CFNtx_in125Usec. In addition, the toawe is defined as toawe_in125Usec when expressed in units of 125Usec. The coordinate on CFN_timing_axis of the TOAWE is defined as ToAWE_OnCFN_in125Usec.

The TOA is finally determined by TOAWE and Farr, which have the relationship of FIGS. 3, 4, 5, and 6. Here, the inverted triangular dotted line Farr represents the actual reception time of the frame, and the inverted triangle flat pattern Farr represents the reception time of the frame inferred from the above-described equation. Since the CFN is repeatedly increased from 0 to 255 by the proposed method, in the case of using the TOAWE and the Farr in different CFN ranges, the Farr is different from the actual Farr (inverted triangle shown in FIGS. 4 to 6). Since it is possible to calculate the correct TOA, it can be used.

3 to 6 are diagrams showing the timing relationship between the reception time of a frame received from the control station and the end point TOAWE of the reception window. The TOA must have a range greater than or equal to -CFN length / 2 (-1275ms) and less than or equal to + CFN length / 2 0.125ms (1274.875ms). (See 3GPP Standard Document 25.402)

3 is a case where (Farr <TOAWE) and (| Farr-TOAWE | <2 / (CFN Range: 255)).

In this case, the resultant values of Equations 1, 2, and 4 are equal to the actual TOA values.

4 shows a case where (Farr <TOAWE) and (| Farr-TOAWE |> 2 / (CFN Range: 255)).

In this case, the resultant values of Equations 1, 2, and 4 are different from actual TOA values. Therefore, in this case, correction is performed by using the following TOA calculation algorithm for correct TOA calculation.

5 is a case where (Farr> TOAWE) and (| Farr-TOAWE | <2 / (CFN Range: 255)).

In this case, the resultant values of Equations 1, 2, and 4 are equal to the actual TOA values.

6 shows a case where (Farr> TOAWE) and (| Farr-TOAWE |> 2 / (CFN Range: 255)).

In this case, the resultant values of Equations 1, 2, and 4 are different from actual TOA values. Therefore, in this case, correction is performed by using the following TOA calculation algorithm for correct TOA calculation.

In other words, when the difference between Farr and TOAWE is larger than 2 / (frame counter range), it is necessary to correct the TOA. To this end, the following TOA algorithm is used. Hereinafter, ToA refers to a value before correction and TOA refers to a value after correction.

The present invention calculates the corrected TOA in consideration of the case where the correction is necessary as follows.

First, the parameters for the TOA calculation are Farr indicating when the frame was received (in 125usec units), CFNtx indicating when the frame should be transmitted in the air (in 10ms units), and toawe indicating the endpoint of the receiving window (in 1ms units). And t_proc indicating the frame processing time (125usec units). The variables used in the TOA formula are CFNtx_in125Usec (CFNtx (125usec units)), toawe_in125Usec (toawe (125usec units)), ToAWE_OnCFN_in125Usec (TOAWE coordinates on CFN_timing_axis), algebraTOA (arithmetic calculated units of TOA); Parameter), ToA (TOA's coordinates on CFN_timing_axis).

TOA calculation algorithm

Part1)

CFNtx_in125Usec = CFNtx * 80 --- 1)

toawe_in125Usec = toawe * 8 --- 2) ToAWE_OnCFN_in125Usec = (CFNtx_in125USec-(t_proc + toawe_in125Usec)}% 256 --- 3)

algebraToA = ToAWE_OnCFN_in125USec-Farr --- 4_

Part2)

if (-256 * 80 ≤algebraTOA <-(256 * 80/2)) --- 5)

ToA = algebraToA + (256 * 80)

else if (256 * 80/2 ≤algebraToA <256 * 80) --- 6)

ToA = algebraToA-(256 * 80)

Part 1) calculates the parameter algebraToA for ToA correction.

1) is the process of converting CFN of 10ms unit received through FP into variable of 125Usec unit.

2) is a process of converting a 1 ms unit of toawe received through signaling of a higher layer into a variable of 125 Usec unit.

3) is a process of calculating a value obtained by subtracting the transformed t_proc and the transformed toawe from the transformed CFN, that is, TOAWE, and converting it to a value on CFN_timing_axis.

4) is a process of generating a parameter for ToA correction by subtracting a reception time (Farr) in units of 125 Usec from the converted TOAWE.

Part2) is a process of performing correction when the Farr and TOAWE difference are larger than 2 / (frame counter range).

That is, the parameter for ToA correction (this parameter indicates the difference between the received time of the frame and the end point of the calculated receive window, as described above) is the minimum value on the time axis in units of 125 Usec above. And in the middle of this minimum value, adds one cycle (or one cycle CFN range) of the converted CFN to the parameter on the time axis to produce a frame transmission timing adjustment value.

Also, if the parameter is between the maximum value on the time axis in units of 125 Usec above and in between the maximum value, one period (or one (or one) of the converted CFN from the parameter on the time axis. Frame transmission timing adjustment value is generated by subtracting the period).

Then, it is determined whether the frame received from the control station is transmitted on the downlink and whether the frame transmission timing adjustment value is transmitted to the control station.

As described above, since the correct reception window is calculated according to the algorithm according to the present invention, and thus the frame transmission timing adjustment value is generated, the transmission timing of the frame can be efficiently controlled.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (14)

Frame transmission on the time axis based on the frame counter using the frame counter included in the frame received from the control station, the processing time of this frame, the endpoint of the receiving window signaled by the higher layer, and the frame receiving time. Calculating a parameter for timing adjustment; It is determined whether the difference between the calculated parameter and the converted frame reception time is between the minimum value and the minimum value on the time axis or between the maximum value and the maximum value. Correcting the difference value according to the determination result; Here, if it is between the minimum value and the middle value of the minimum value on the time axis, the difference value is corrected by adding one cycle of the converted frame counter, and the value is between the maximum value and the middle value of the maximum value. And correcting by subtracting one period of the converted frame counter from the difference value. The method of claim 1, wherein the time axis is expressed in units of 0.125 ms. 3. The method of claim 2, wherein the frame counter is repeated with a value from 0 to 255, so that 0 is minimized on the time axis and 2559.875 ms is maximum. The frame transmission as claimed in claim 1, wherein the parameter is a remainder obtained by dividing a value obtained by subtracting the converted frame processing time and the end point of the converted reception window from the converted frame counter by a range of the frame counter. How to adjust the timing. The method of claim 1, further comprising determining whether to transmit the frame in a downlink and whether to transmit a frame transmission timing adjustment value to a control station according to the transmission timing adjustment value. How to adjust. The method of claim 1, wherein in correcting the difference value, This frame reception time and the actual reception parameter, using the frame counter included in the frame received from the control station, the processing time of this frame, the endpoint of the reception window signaled by the upper layer, and the frame reception time, Calculating a difference from an endpoint of the window; Correcting the calculated difference value when the difference between the frame reception time and the end point of the actual reception window is greater than a 2 / frame counter range; Here, the frame counter, the endpoint of the reception window signaled by the higher layer, the frame reception time, and the frame processing time are converted into variables on the same time axis, and the calculated difference value on this time axis. The calculated difference value is corrected by adding a frame counter range of one period if it is between the minimum value of this time axis and the minimum value, and the calculated difference on the time axis is the maximum value of the time axis and this maximum value. And adjusting the calculated difference value by subtracting the frame counter range of one period when it is in the middle of the value. Measuring a reception time of a frame received from the control station; Determining a reception window in consideration of a start point, an end point, and a frame processing time of a frame counter and a signaled reception window included in the frame; And determining whether to adjust a frame transmission timing by comparing the determined reception window with the frame reception time. 8. The method of claim 7, further comprising: calculating a maximum receivable delay reception time of a frame using the frame counter and frame processing time; Calculating an actual reception endpoint from the calculated maximum delayed reception time and an endpoint of a reception window signaled by a higher layer; And calculating the difference between the calculated reception end point and the reception time of the frame to obtain a frame transmission timing adjustment value, and determining whether to adjust the timing. The method of claim 8, further comprising correcting the difference value when the calculated reception end point and the reception time of the frame are in different ranges based on a frame counter repeatedly increasing for each predetermined range. Frame transmission timing adjustment method, characterized in that. 10. The apparatus of claim 9, wherein the calculated reception end point and the reception time of the frame are in different ranges based on a frame counter repeatedly increasing every predetermined range, and the difference value exceeds the '2 / frame counter range'. The frame transmission timing adjusting method characterized in that for correcting the difference value. 11. The method of claim 10, wherein the calculated difference value is corrected by adding a frame counter range of one period to a difference value between the minimum value based on the frame counter and the minimum value. And correcting the calculated difference value by subtracting the frame counter range of one period from the difference value between the maximum value as a reference and the middle value between the maximum value and the maximum value. 11. The method of claim 10, further comprising the steps of: when the calculated difference value is positive, transmitting information to a control station to delay a frame transmission time to the base station; And if the calculated difference value is negative, transmitting information indicating to advance the transmission time of the frame to the base station to the control station. 11. The method of claim 10, further comprising: if the frame reception time exceeds the calculated maximum delay reception time, discarding the received frame without transmitting the downlink. How to adjust the transmission timing. 12. The method of claim 10, wherein the time axis is expressed in units of 0.125 ms.