CN102611521B - Adjusting method for channel quality indicator (CQI) - Google Patents

Abstract

The present invention provides a channel quality indicator (CQI) adjustment method, the method will only adjust the CQI of the current subframe when it is judged that the current subframe is a subframe after the last adjusted CQI takes effect, so , it can be ensured that the feedback result used for adjusting the CQI this time is the feedback result calculated after the previous CQI adjustment took effect, so as to ensure the accuracy of the CQI adjustment this time. In addition, by limiting the length of the feedback result window for counting the number of error blocks, it can be ensured that the feedback result used for this CQI adjustment can better reflect the current channel conditions, making this CQI adjustment more accurate.

Description

A method for adjusting channel quality indicator

technical field

The invention relates to the data transmission technology in the mobile communication system, in particular to the adjustment method of the channel quality indicator in the transmission of the high-speed physical downlink shared channel (HS-PDSCH).

Background technique

HSDPA and HSPA+ systems use adaptive modulation and coding (AMC) to improve system performance. Users with good channel conditions use high-order modulation and coding schemes, while users with poor channel conditions use low-order modulation and coding schemes. The process of implementing AMC includes: the user equipment (UE) measures the channel quality, and generates a channel quality indicator (CQI) according to the measured channel quality lookup table. The CQI includes two parts of information, namely the recommended transport block size (RTBS) and the recommended modulation Mode (RMF), the UE also feeds back the CQI when feeding back the NACK or ACK information of the current frame transmission to the base station (Node B), and the Node B determines the modulation and coding scheme used for the next data transmission according to the CQI fed back by the UE.

In the above AMC process, Node B determines the transmission format for the next data transmission according to the CQI, and whether the determined transmission format is accurate will affect the link block error rate. It can be seen that the accuracy of the CQI fed back by the user has a great impact on the link block error rate. have a direct impact. However, in practical applications, the CQI fed back by the UE is often not very accurate due to the influence of measurement errors and time delays, thus resulting in a relatively high block error rate at the link layer.

For the fact that the CQI measured by the UE is difficult to be accurate in practical applications, the CQI is usually corrected according to the statistical information of the HS-DSCH block error rate, or the CQI is corrected by using the uplink and downlink channel correlation through channel estimation on the uplink HS-SICH. Or correct the CQI through the service code rate to offset the problem of poor measurement accuracy.

At present, several adjustment schemes for inaccurate channel quality indicators have been proposed. For example, in the technical scheme of Chinese patent application number CN200510115499.1, it is proposed to adjust the RTBS in the CQI by monitoring the block error rate of the high-speed downlink shared channel ; Chinese patent application number is CN200710063350.2 in the technical scheme, has proposed the method that produces and adjusts CQI at UE end, and the mode of adjustment has rough adjustment mode and fine adjustment mode, and wherein fine adjustment mode is to adjust CQI by block error rate (BLER) , while the coarse adjustment mode is directly obtained by looking up the signal-to-interference ratio (SIR). The use limit of coarse adjustment and fine adjustment is whether the SIR variation of two adjacent received data exceeds a certain upper limit; the Chinese patent application number is CN200810104651. In the solution X, it is proposed to reduce the jitter of the air interface, refer to the ACK, NACK and RTBS in the tolerance window, and adjust the RTBS of the current CQI.

In the above scheme of correcting CQI through HS-DSCH block error rate statistical information, the time correlation of the channel is not considered. That is to say, if the length of the time window for observing the block error rate is too large, the window head and tail will be There will be no correlation between the channels at the two time points, and the block error situation at the previous time point cannot reflect the deviation of the current feedback CQI. At this time, the block error rate observed in this time window is used to adjust the CQI , leading to an increase in the adjusted block error rate.

In addition, in practical applications, multiple base stations send data based on the adjusted CQI until receiving the ACK or NACK information fed back by the UE for the data transmission to know the adjustment effect of this CQI. There is a period of time between this. Delay. After adjusting the CQI once, whether to adjust next time and how to adjust should be based on the block error rate calculated after the previous CQI adjustment took effect, so as to ensure the decision of the next adjustment and the accuracy of the adjustment. accuracy. However, in the above technical solution, this point is not considered, so the block error rate referenced during CQI adjustment itself does not meet the reference requirement, resulting in errors in CQI adjustment.

Contents of the invention

In view of this, the main purpose of the present invention is to provide a channel quality indicator adjustment method, which can effectively improve the accuracy of CQI adjustment.

In order to achieve the above object, the technical scheme proposed by the present invention is:

A method for adjusting a channel quality indication, the method comprising the following steps:

a. When entering each subframe, the base station judges whether the current subframe is a subframe after the last adjusted CQI takes effect, and if so, executes step b, otherwise, exits the CQI adjustment process of the current subframe;

b. Judging whether the length L of the current feedback result window reaches the preset length threshold T, and if so, deleting the feedback result of the subframe at the end of the current feedback result window;

c. Insert the feedback result of the current subframe at the head of the feedback result window, wherein, when the current subframe does not receive the feedback result of the user equipment, the inserted feedback result is information indicating no feedback; according to the current For the feedback result of the subframe, update the number F of subframes whose feedback result is NACK in the feedback result window, and update the number W of subframes whose feedback result is recorded as NACK or ACK in the feedback result window;

d. Adjust the CQI received this time according to the currently determined F, the W, and the length of the current feedback result window.

To sum up, the adjustment method of the channel quality indication proposed by the present invention only performs the CQI adjustment of the current subframe when it is judged that the current subframe is a subframe after the last adjusted CQI takes effect. It is ensured that the feedback result used for this adjustment of the CQI is the feedback result calculated after the previous adjustment of the CQI took effect, so as to ensure the accuracy of the current CQI adjustment. In addition, by limiting the length of the feedback result window used to count the number of error blocks within T, it can be ensured that the feedback result used for this CQI adjustment can better reflect the current channel conditions, making this CQI adjustment more accurate. precise.

Description of drawings

FIG. 1 is a schematic flow chart of Embodiment 1 of the present invention.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

The main idea of the present invention is: before deciding whether to adjust the CQI in the current subframe, first determine whether the current frame is after the effective subframe of the last adjusted CQI; Record the feedback information of the current subframe, and decide whether to adjust the CQI according to the record information in the current feedback result window and perform the corresponding adjustment steps. In this way, it can be ensured that the feedback information used for this adjustment of the CQI is effective for the last adjustment of the CQI Post-statistical information to ensure the accuracy of this CQI adjustment. In addition, considering the influence of channel correlation in time on CQI adjustment, the upper limit of the length of the feedback result window is also limited here to ensure that the feedback information used for this CQI adjustment can better reflect the current channel conditions , making this CQI adjustment more accurate.

FIG. 1 is a schematic flow chart of Embodiment 1 of the present invention. As shown in Figure 1, this embodiment mainly includes:

Step 101. When entering each subframe, the base station judges whether the current subframe is a subframe after the last adjusted CQI takes effect. If yes, execute step 102. Otherwise, exit the CQI adjustment process of the current subframe.

Here, the last adjusted CQI takes effect, that is, the last adjusted CQI is used for data transmission.

With this step, it can be ensured that the feedback result information used for CQI adjustment thereafter corresponds to the data transmission after the last adjusted CQI takes effect, so that the CQI adjustment in the subsequent steps is more accurate.

Step 102, judging whether the length L of the current feedback result window reaches a preset length threshold T, and if so, deleting the feedback result of the tail subframe of the current feedback result window.

Here, using this step can ensure that the maximum length of the feedback result window is T.

The T is used to limit the maximum length of the feedback result window to ensure that the feedback result information in the feedback result window used for this CQI adjustment has time correlation, that is, to ensure that the feedback results in the window can be better It reflects the current channel condition and makes this CQI adjustment more accurate. In practical applications, those skilled in the art can determine a better T value that can ensure the temporal correlation of the feedback results within the feedback result window through simulation according to actual needs, and details will not be repeated here.

Step 103, inserting the feedback result of the current subframe at the head of the feedback result window, wherein, when the current subframe does not receive the feedback result of the user equipment, the inserted feedback result is information indicating no feedback; according to For the feedback result of the current subframe, update the number F of subframes whose feedback result is NACK in the feedback result window, and update the number W of subframes whose feedback result is recorded as NACK or ACK in the feedback result window.

This step is used to update the feedback result information in the feedback result window according to the feedback result of the current frame, and at the same time, update the number of error blocks F required for CQI adjustment and reflect the effective sample space in the feedback result window W in order to adjust the CQI based on the information in the subsequent process.

In practical applications, if non-adaptive retransmission is used in the system, the size of the time slot code channel resource block and the size of the transport block used for retransmission are the same as those used in the first transmission, that is, the retransmission scheduling does not change at this time The modulation and coding method of the first transmission of the data block. If the time of the first transmission of the data with transmission errors is before the last adjustment of the recommended transmission block size, then the subsequent retransmission results have nothing to do with the adjusted transmission block size. It affects the block error rate. The impact is not related to the adjusted transmission block size, so the retransmission NACK information corresponding to the transmission before the last adjustment should not be counted in the F, and the NACK of the retransmission schedule cannot be counted in the feedback sample. Within a few W.

Therefore, in the case where non-adaptive retransmission is used in the system, in order to improve the accuracy of the statistics of F and W, preferably, if the current subframe receives the feedback result of the user equipment, and the feedback result corresponds to When the data transmission before the last CQI adjustment is retransmitted, the inserted feedback result is information for indicating no feedback. In this way, the feedback information irrelevant to the last CQI adjustment can be excluded from the F and W, thereby ensuring the accuracy of the current CQI adjustment in the subsequent process.

In practical application, the F may be updated based on all the feedback results recorded in the current feedback result window as NACK or ACK, that is, if the feedback result in the current subframe is NACK, an operation of adding one to F is performed. Preferably, the F value can be calculated only according to a limited number of feedback results in the current feedback result window, that is, the F value can be obtained only by using the feedback results of the last Q subframes that receive NACK or ACK. Here, F It reflects the number of error blocks in Q samples, and the specific method of updating F is as follows:

Judging whether the number of subframes whose feedback results are recorded as NACK or ACK in the current feedback result window is greater than or equal to the preset statistical sample threshold Q, if yes, the F is the latest Q in the current feedback result window The number of subframes in which the feedback result is NACK or ACK in the subframes in which the feedback result is NACK; otherwise, the F is the number of subframes in which the feedback result is recorded as NACK in the current feedback result window.

Here, the sample threshold Q is used to limit the size of the sample space used when counting the number of error blocks F. Obviously, Q should be smaller than the above T. In practical applications, the Q value only needs to ensure that the F based on its statistics can be better. It only needs to reflect the channel condition, and those skilled in the art can set an appropriate value for Q through simulation according to actual needs.

Step 104: Adjust the CQI received this time according to the currently determined F, the W, and the current length of the feedback result window.

Specifically, this step can be implemented by the following methods:

Step 1041, determine whether the F exceeds the preset maximum NACK threshold, if so, adjust the adjustment range R of the current recommended transmission block size according to R'=R-Step _down , and execute step 1042, otherwise, determine Whether the W is greater than or equal to the preset statistical sample threshold Q and the F is smaller than the preset minimum NACK threshold, if yes, adjust the R according to R'=R+Step _up , and execute step 1042, Otherwise, judge whether the length of the current feedback result window reaches the T and whether the feedback results of all subframes in the feedback result window are recorded as information indicating no feedback, and if so, repeat the R Set to zero, execute step 1042, otherwise, exit the CQI adjustment process of the current subframe.

Wherein, the R' is the adjustment range of the adjusted recommended transmission block size, the Step _up is the preset upward adjustment step, and the Step _down is the preset downward adjustment step, Step _up and Step _down are greater than 0.

In this step, the adjustment range of the recommended transmission block size will be adjusted according to the current statistical error block number F, so that the adjustment range can more accurately reflect the changes in the current channel environment, thereby ensuring that the CQI is adjusted based on the adjustment range in the future. The adjustments made to the recommended transport block size in are more accurate.

Here, it should be noted that the adjustment range of the recommended transport block size obtained during each adjustment will be used as the basis for the next adjustment, that is, the adjustment of the adjustment range of the recommended transport block size is continuous, not in The adjustment range is reset to zero after each adjustment of the CQI, so as to ensure that the adjustment of the CQI based on the adjustment range is continuous.

Specifically, when F exceeds the preset maximum NACK threshold, it indicates that the current block error rate is too high, and the adjustment range of the currently recommended transport block size needs to be reduced. At this time, it is not necessary to consider whether the number of samples in the current feedback result window is sufficient More, just reduce the adjustment range of the currently recommended transmission block size directly to achieve the effect of rapid reduction.

When W is greater than or equal to the preset statistical sample threshold Q (that is, the minimum number of statistical samples, reaching this value indicates that the number of samples in the current feedback result window can reflect the real state of the current channel) and the F is smaller than the preset minimum When the NACK threshold is set, it means that the current block error rate is too small, and the recommended transport block size can be adjusted upwards, that is, the size of the recommended transport block is increased.

When the length of the feedback result window reaches the T and the feedback results of all subframes in the feedback result window are recorded as information indicating no feedback, it means that the channel has not been used for too long, and the channel quality has probably improved. At this time, the previous adjustment to the channel quality may no longer be applicable to the current channel environment. Therefore, the adjustment range R of the recommended transmission block size is reset to zero, so that the next adjustment will no longer be based on meaningless The adjustment range of the recommended transport block size is to adjust the transport block size reported by the user.

Preferably, Step _up <Step _down . In this way, the bit error rate can be quickly reduced when the bit error rate is high, and the transmission rate can be quickly increased when the bit error rate is low, thereby ensuring that the transmission block error rate is guaranteed. Under the premise of improving the throughput as much as possible.

In practical applications, the upper limit and lower limit of the adjustment range of the recommended transmission block size can also be limited separately, that is, when the calculated R' is greater than the upper limit of the adjustment range, then R' takes the value of the upper limit, when When the calculated R' is smaller than the lower limit of the adjustment range, then R' takes the value of the lower limit, wherein the upper limit is greater than zero and the lower limit is less than zero.

Preferably, the minimum NACK threshold can be obtained from the product of Q and the minimum block error rate of the system, and if the result is not an integer, it can be rounded down.

The maximum NACK threshold can be obtained by adding 1 to the product of Q and the maximum block error rate of the system, and if the result is not an integer, it can be rounded down.

In practical applications, if the sample space used for statistical F is not limited to Q sample spaces, the maximum NACK threshold and the minimum NACK threshold adjusted up and down need to be adjusted according to the actual number of feedback subframes in the feedback window and The maximum and minimum block error rates of the system are calculated in real time.

Step 1042: According to the R', adjust the recommended transport block size RTBS in the received CQI according to TBsize=RTBS+R', to obtain the adjusted recommended transport block size TBsize.

What needs to be explained here is that the existing CQI adjustment method used on the base station side does not take into account that the feedback modulation method needs to be changed with the adjustment of the recommended transport block size RTBS to obtain a lower link error rate. block rate. Preferably, in this step, the recommended modulation scheme can be adjusted while adjusting the size of the transport block, so that the modulation scheme used can adapt to changes in the channel environment as much as possible, thereby obtaining a lower link error rate. block rate. The specific method of adjusting the modulation mode is as follows:

According to ρ=TBsize/B, calculate the transmission block coding efficiency ρ when the recommended modulation scheme in the CQI received this time and the transmission block size is TBsize, where B is the recommended modulation scheme in the CQI received this time The amount of data that can be carried on the resource block occupied by the transport block corresponding to the recommended transport block size in the received CQI this time.

When the ρ is greater than the highest coding efficiency corresponding to the recommended modulation method in the preset modulation and coding method conversion table, the modulation method that is one order higher than the recommended modulation method is used as the adjusted recommended modulation method, and according to the adjusted recommended The modulation method and the TBsize are used to calculate the transmission block coding efficiency ρ′ when the adjusted recommended modulation method and the transmission block size are TBsize.

When the ρ is less than the minimum coding efficiency corresponding to the recommended modulation method in the preset modulation and coding method conversion table, the modulation method that is one order lower than the recommended modulation method is used as the adjusted recommended modulation method, according to the adjusted The recommended modulation scheme and the TBsize are used to calculate the transmission block coding efficiency ρ′ when the adjusted recommended modulation scheme and the transmission block size are TBsize.

Here, the method for calculating ρ' is similar to the method for calculating ρ described above, and will not be repeated here.

Step 1043, clear the current feedback result window.

Here, after the adjustment of the recommended modulation scheme in the CQI received this time is completed, the feedback result window needs to be cleared so as to be applied to the next CQI adjustment.

To sum up, the above are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (6)

1. a method for adjusting channel quality indication CQI, is characterized in that, the method comprises the following steps: a. When entering each subframe, the base station judges whether the current subframe is a subframe after the last adjusted CQI takes effect, and if so, executes step b, otherwise, exits the CQI adjustment process of the current subframe; b. Judging whether the length L of the current feedback result window reaches the preset length threshold T, and if so, deleting the feedback result of the subframe at the end of the current feedback result window; c. Insert the feedback result of the current subframe at the head of the feedback result window, wherein, when the current subframe does not receive the feedback result of the user equipment, the inserted feedback result is information indicating no feedback; according to the current For the feedback result of the subframe, update the number F of subframes whose feedback result is NACK in the feedback result window, and update the number W of subframes whose feedback result is recorded as NACK or ACK in the feedback result window; d. Adjust the CQI received this time according to the currently determined F, the W, and the length of the current feedback result window; Described step d is: d1. Determine whether the F exceeds the preset maximum NACK threshold, if yes, adjust the adjustment range R of the recommended transport block size in the CQI received this time according to R'=R-Step _down , and execute step d2 , otherwise, judge whether the W is greater than or equal to the preset statistical sample threshold Q and the F is smaller than the preset minimum NACK threshold, if yes, adjust the R according to R'=R+Step _up , Execute step d2, otherwise, judge whether the length of the current feedback result window reaches the T and whether the feedback results of all subframes in the feedback result window are recorded as information indicating no feedback, and if so, record The R is reset to zero, and step d2 is performed, otherwise, the CQI adjustment process of the current subframe is exited; wherein, the R' is the adjustment range of the adjusted recommended transmission block size, and the Step _up is the preset upward Adjust the step size, 0<Step _up , the Step _down is the preset downward adjustment step size, 0<Step _down ; d2. Using the R', adjust the recommended transport block size RTBS in the received CQI according to TBsize=RTBS+R', to obtain the adjusted recommended transport block size TBsize; d3. Clear the current feedback result window. 2. The method according to claim 1, wherein step c further comprises: when the feedback result is received in the current subframe, and the feedback result corresponds to the retransmission of the data transmission before the last CQI adjustment , the inserted feedback result is information indicating no feedback. 3. The method according to claim 1, wherein updating said F in step c is: Judging whether the number of subframes whose feedback results are recorded as NACK or ACK in the current feedback result window is greater than or equal to the preset statistical sample threshold Q, if yes, the F is the latest Q in the current feedback result window The number of subframes in which the feedback result is NACK or ACK in the subframes in which the feedback result is NACK; otherwise, the F is the number of subframes in which the feedback result is recorded as NACK in the current feedback result window. 4. The method according to claim 1, wherein Step _up <Step _down . 5. The method according to claim 1, wherein the step d2 further comprises: adjusting the recommended modulation scheme in the CQI received this time according to the adjusted recommended transport block size TBsize. 6. The method according to claim 5, wherein the adjustment to the recommended modulation scheme in the CQI received this time is: According to ρ=TBsizeB, calculate the transmission block coding efficiency ρ when the recommended modulation method in the CQI received this time and the transmission block size is TBsize, where B is the recommended modulation method in the CQI received this time. The amount of data that can be carried on the resource block occupied by the transport block corresponding to the recommended transport block size in the received CQI; When the ρ is greater than the highest coding efficiency corresponding to the recommended modulation method in the preset modulation and coding method conversion table, the modulation method that is one order higher than the recommended modulation method is used as the adjusted recommended modulation method, and according to the adjusted recommended The modulation method and the TBsize are calculated using the adjusted recommended modulation method and the transmission block coding efficiency ρ' when the transmission block size is TBsize; When the ρ is less than the minimum coding efficiency corresponding to the recommended modulation method in the preset modulation and coding method conversion table, the modulation method that is one order lower than the recommended modulation method is used as the adjusted recommended modulation method, according to the adjusted The recommended modulation scheme and the TBsize are used to calculate the transmission block coding efficiency ρ′ when the adjusted recommended modulation scheme and the transmission block size are TBsize.