METHOD FOR ADAPTING A COMMUNICATION CHANNEL FOR URLLC SERVICES

Abstract

The present invention relates to a communications channel adaptation method for URLLC services which is configured for ensuring reliability when implementing said URLLC services and executed in a communications system with at least one transmitter node (eNode) and a receiver or mobile terminal, wherein the receiver or mobile terminal measures the desired signal-to-interference ratio (SIR) from the reference signal received in instant t=i−1 and saves this SIR value (SIR.sub.i-1) in a memory; wherein based on this SIR value in instant t=i−1 (SIR.sub.i-1), a CQI value (CQI.sub.i-1) is determined and sent to the transmitter node (eNode), which selects the modulation and coding format in the subsequent transmission (MCS.sub.i) in the downlink according to that CQI measured in instant t=i-1 (CQI.sub.i-1); and wherein upon receiving in instant t=i the data packet sent by the transmitter node (eNode), the receiver terminal measures the SIR (SIR.sub.i) and saves it in a memory.

Claims

1. A communications channel adaptation method for URLLC services which is executed in a communications system with at least a transmitter node (eNode) and a receiver or mobile terminal; wherein the receiver or mobile terminal measures the desired signal-to-interference ratio (SIR) from the reference signal received in instant t=i−1 and saves this SIR value (SIR.sub.i-1) in a memory; wherein based on this SIR value in instant t=i−1 (SIR.sub.i-1), a CQI value (CQI.sub.i-1) is determined and sent to the transmitter node (eNode), which selects the modulation and coding format in the subsequent transmission (MCS.sub.i) in the downlink according to that CQI measured in instant t=i−1 (CQI.sub.i-1); and wherein upon receiving in instant t=i the data packet sent by the transmitter node (eNode), the receiver terminal measures the SIR (SIR.sub.i) and saves it in a memory; wherein the method comprises the steps of: calculating a variation quantification parameter of the communications channel (α.sub.i) defined as the difference existing between the channel quality taking as a reference the instant in which the CQI is determined by means of the reference signals (CQIi-1) and the instant in which the receiver mobile terminal receives the data corresponding to that CQIi-1 in the subsequent reception and measures the channel quality again (CQIi); calculating a correction margin (margin.sub.i) depending at least on a plurality of values of the variation quantification parameter of the communications channel (α.sub.i); correcting the SIR measured by the terminal in instant t=i (SIR.sub.i) by applying the calculated correction margin (margin.sub.i) such that the SIR corrected in instant t=i (SIR.sub.i) is equal to the sum of the SIR in instant t=i (SIR.sub.i) plus the correction margin (margin.sub.i); and determining the CQI (CQI′i) corresponding to that received and corrected desired signal-to-interference ratio (SIR′.sub.i) in instant t=i.

2. The method according to claim 1, wherein the variation quantification parameter of the communications channel (a) is defined as the difference between the SIR values measured by the receiver mobile terminal for quantifying the variation experienced in the communications channel, such that α.sub.i=SIR.sub.i−SIR.sub.i-1.

3. The method according to claim 1, wherein the variation quantification parameter of the communications channel (α.sub.i) is defined as the calculation of the variation of the CQI value, such that α.sub.i=CQI.sub.i−CQI.sub.i-1.

4. The method according to claim 1, which comprises establishing a reliability index defined as: $\mathrm{Reliability}\mathrm{index}=\frac{\mathrm{number}\mathrm{of}\mathrm{slots}\left({\mathrm{BLER}}_i<{\mathrm{BLER}}_{\mathrm{target}}\right)}{\mathrm{total}\mathrm{number}\mathrm{of}\mathrm{slots}}$ where BLERi.sub.i is the real instantaneous block error rate and BLER.sub.target is the target mean block error rate of a URLLC service required by the receiver or mobile terminal; such that the calculation of the correction margin (margin.sub.i) is performed by means of a transformation function the two input parameters of which are the variation quantification parameter of the communications channel (α.sub.i) and, on the other hand, a target reliability which is established for the calculated reliability index.

5. The method according to claim 1, which comprises obtaining a plurality of values of the variation quantification parameter of the communications channel (α.sub.i); determining the n % percentile of the distribution, where n=100%−target reliability, and with the n % percentile being defined as that value below which n % of the plurality of obtained values is found; and determining the correction margin (margin.sub.i) based on said percentile:
margin.sub.i=percentile_∝.sub.i(100%−target reliability).

6. The method according to claim 1, wherein the correction margin (margin.sub.i) is iteratively calculated to the percentile value corresponding to the target reliability, such that the percentile estimate value is updated with each new value of the variation quantification parameter of the communications channel (α.sub.i) calculated by the mobile, increasing or decreasing the value thereof by means of a step-up (S.sub.up) or a step-down (S.sub.down), respectively, such that the target reliability defines the ratio between both steps, which must satisfy the following expression: $\frac{S_{\mathrm{up}}}{S_{\mathrm{up}}+S_{\mathrm{down}}}=\mathrm{Target}\mathrm{reliability}$ wherein the iterative process for updating margin.sub.i is performed according to the following method: If α.sub.i>margin.sub.i-1, then margin.sub.i=margin.sub.i-1−S.sub.down; If α.sub.i<margin.sub.i-1, then margin.sub.i=margin.sub.i-1+S.sub.up.

7. A communications system with at least a transmitter node (eNode) and a receiver or mobile terminal: wherein the receiver or mobile terminal is configured for measuring the desired signal-to-interference ratio (SIR) from the reference signal received in instant t=i−1 and saving this SIR value (SIR.sub.i-1) in a memory; and where it is further configured for determining a CQI value (CQI.sub.i-1) based on the SIR value in instant t=i−1 (SIR.sub.i-1) and sending the CQI value (CQI.sub.i-1) to the transmitter node (eNode); and wherein the transmitter node (eNode) is configured for selecting the modulation and coding format in the subsequent transmission (MCSi) in the downlink according to that CQI measured in instant t=i−1 (CQI.sub.i-1); and wherein upon receiving in instant t=i the data packet sent by the transmitter node (eNode), the receiver terminal measures the SIR (SIR.sub.i) and saves it in a memory; and wherein the receiver or mobile terminal comprises at least one or more processors and one or more programs, wherein said programs are stored in one or more memories and configured for being executed by means of the processor or processors, wherein the programs include instructions for: calculating a variation quantification parameter of the communications channel (α.sub.i) defined as the difference existing between the channel quality taking as a reference the instant in which the CQI is determined by means of the reference signals (CQIi-1) and the instant in which the receiver mobile terminal receives the data corresponding to that CQIi-1 in the subsequent reception and measures the channel quality again (CQIi); calculating a correction margin (margin.sub.i) depending at least on a plurality of values of the variation quantification parameter of the communications channel (α.sub.i); correcting the SIR measured by the terminal in instant t=i (SIR.sub.i) by applying the calculated correction margin (margin.sub.i) such that the SIR corrected in instant t=i (SIR.sub.i) is equal to the sum of the SIR in instant t=i (SIR) plus the correction margin (margin.sub.i); and determining the CQI (CQI′i) corresponding to that received and corrected desired signal-to-interference ratio (SIR′i) in instant t=i.

8. The system according to claim 7, wherein the variation quantification parameter of the communications channel (a) is defined as the difference between the SIR values measured by the receiver mobile terminal for quantifying the variation experienced in the communications channel, such that α.sub.i=SIR.sub.i−SIR.sub.i-1.

9. The system according to claim 7, wherein the variation quantification parameter of the communications channel (a) is defined as the calculation of the variation of the CQI value, such that α.sub.i=CQI.sub.i−CQI.sub.i-1.

10. The system according to claim 7, wherein the programs comprise instructions for: establishing a reliability index defined as: $\mathrm{Reliability}\mathrm{index}=\frac{\mathrm{number}\mathrm{of}\mathrm{slots}\left({\mathrm{BLER}}_i<{\mathrm{BLER}}_{\mathrm{target}}\right)}{\mathrm{total}\mathrm{number}\mathrm{of}\mathrm{slots}}$ where BLERi.sub.i is the real instantaneous block error rate and BLER.sub.target is the target mean block error rate of a URLLC service required by the receiver or mobile terminal; such that the calculation of the correction margin (margin.sub.i) is performed by means of a transformation function the two input parameters of which are the variation quantification parameter of the communications channel (α.sub.i) and, on the other hand, a target reliability which is established for the calculated reliability index.

11. The system according to claim 7, which comprises obtaining a plurality of values of the variation quantification parameter of the communications channel (α.sub.i); determining the n % percentile of the distribution, where n=100%−target reliability, and with the n % percentile being defined as that value below which n % of the plurality of obtained values is found; and determining the correction margin (margin.sub.i) based on said percentile:
margin.sub.i=percentile_∝.sub.i(100%−target reliability).

12. The system according to claim 7, wherein the correction margin (margin.sub.i) is iteratively calculated to the percentile value corresponding to the target reliability, such that the percentile estimate value is updated with each new value of the variation quantification parameter of the communications channel (α.sub.i) calculated by the mobile, increasing or decreasing the value thereof by means of a step-up (S.sub.up) or a step-down (S.sub.down), respectively, such that the target reliability defines the ratio between both steps, which must satisfy the following expression: $\frac{S_{\mathrm{up}}}{S_{\mathrm{up}}+S_{\mathrm{down}}}=\mathrm{Target}\mathrm{reliability}$ and wherein the iterative process for updating margin.sub.i is performed according to the following method: If α.sub.i>margin.sub.i-1, then margin.sub.i=margin.sub.i−S.sub.down; If α.sub.i<margin.sub.i-1, then margin.sub.i=margin.sub.i-1+S.sub.up.

13. A software product with instructions configured for the execution thereof by one or more processors in a communications system which, when executed, cause the system to carry out the method according to claim 1.

14. The method according to claim 2, which comprises establishing a reliability index defined as: $\mathrm{Reliability}\mathrm{index}=\frac{\mathrm{number}\mathrm{of}\mathrm{slots}\left({\mathrm{BLER}}_i<{\mathrm{BLER}}_{\mathrm{target}}\right)}{\mathrm{total}\mathrm{number}\mathrm{of}\mathrm{slots}}$ where BLERi.sub.i is the real instantaneous block error rate and BLER.sub.target is the target mean block error rate of a URLLC service required by the receiver or mobile terminal; such that the calculation of the correction margin (margin.sub.i) is performed by means of a transformation function the two input parameters of which are the variation quantification parameter of the communications channel (α.sub.i) and, on the other hand, a target reliability which is established for the calculated reliability index.

15. The method according to claim 3, which comprises establishing a reliability index defined as: $\mathrm{Reliability}\mathrm{index}=\frac{\mathrm{number}\mathrm{of}\mathrm{slots}\left({\mathrm{BLER}}_i<{\mathrm{BLER}}_{\mathrm{target}}\right)}{\mathrm{total}\mathrm{number}\mathrm{of}\mathrm{slots}}$ where BLERi.sub.i is the real instantaneous block error rate and BLER.sub.target is the target mean block error rate of a URLLC service required by the receiver or mobile terminal; such that the calculation of the correction margin (margin.sub.i) is performed by means of a transformation function the two input parameters of which are the variation quantification parameter of the communications channel (α.sub.i) and, on the other hand, a target reliability which is established for the calculated reliability index.

16. The system according to claim 8, wherein the programs comprise instructions for: establishing a reliability index defined as: $\mathrm{Reliability}\mathrm{index}=\frac{\mathrm{number}\mathrm{of}\mathrm{slots}\left({\mathrm{BLER}}_i<{\mathrm{BLER}}_{\mathrm{target}}\right)}{\mathrm{total}\mathrm{number}\mathrm{of}\mathrm{slots}}$ where BLERi.sub.i is the real instantaneous block error rate and BLER.sub.target is the target mean block error rate of a URLLC service required by the receiver or mobile terminal; such that the calculation of the correction margin (margin.sub.i) is performed by means of a transformation function the two input parameters of which are the variation quantification parameter of the communications channel (α.sub.i) and, on the other hand, a target reliability which is established for the calculated reliability index.

17. The system according to claim 9, wherein the programs comprise instructions for: establishing a reliability index defined as: $\mathrm{Reliability}\mathrm{index}=\frac{\mathrm{number}\mathrm{of}\mathrm{slots}\left({\mathrm{BLER}}_i<{\mathrm{BLER}}_{\mathrm{target}}\right)}{\mathrm{total}\mathrm{number}\mathrm{of}\mathrm{slots}}$ where BLERi.sub.i is the real instantaneous block error rate and BLER.sub.target is the target mean block error rate of a URLLC service required by the receiver or mobile terminal; such that the calculation of the correction margin (margin.sub.i) is performed by means of a transformation function the two input parameters of which are the variation quantification parameter of the communications channel (α.sub.i) and, on the other hand, a target reliability which is established for the calculated reliability index.

18. A software product with instructions configured for the execution thereof by one or more processors in a communications system which, when executed, cause the system to carry out the method according to claim 2.

19. A software product with instructions configured for the execution thereof by one or more processors in a communications system which, when executed, cause the system to carry out the method according to claim 3.

20. A software product with instructions configured for the execution thereof by one or more processors in a communications system which, when executed, cause the system to carry out the method according to claim 4.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] A series of drawings and diagrams which help to better understand the invention and are expressly related with an embodiment of said invention, presented as a non-limiting example thereof, is described very briefly below.

[0027] FIG. 1 shows a next generation (5G) network structure.

[0028] FIG. 2 shows a time-frequency grid with signal planning.

[0029] FIG. 3 shows a diagram of the operation of the methods of the state of the art.

[0030] FIG. 4 shows a diagram of the determination of CQI thresholds.

[0031] FIG. 5 shows a diagram of the operation of the method of the invention.

DESCRIPTION OF A DETAILED EMBODIMENT OF THE INVENTION

[0032] FIG. 1, for example, shows a diagram of the structure of a next generation (5G) mobile communications network as described in the state of the art. Said structure includes therein, at one communication end, user mobile terminals to which voice and data service is provided, and at the other end, the communications network the first access point of which are base stations or communications nodes, referred to as eNode in 4G and 5G nomenclatures. The network is made up of multiple base stations or eNodes (hereinafter, base stations or eNodes will be referred to as “nodes” to simplify the notation), each of which provides service to a group of mobile terminals located within a coverage area. This coverage area of each node is in turn subdivided into different coverage cells, which provide 360° coverage of an area around the node and have their own radio resources. These cells are depicted as hexagons in FIG. 1.

[0033] In FIG. 2, reference signals on a time-frequency grid typical of resource planning in LTE are depicted in black. For the different transmissions, the data and control information is multiplexed in time and frequency using this grid, which has a time dimension of 1 ms and a frequency dimension of 180 KHz. These reference signals are then used by the receiver to determine link quality.

[0034] FIG. 3 graphically shows the state of the art prior to the present invention in terms of the methodology of determining the CQI and the associated problems of the CQI not being updated to the actual link quality at the moment in which the transmitter receives the feedback from the receiver and perform a new data planning. In that sense: [0035] In instant t=i−1, the mobile terminal (receiver) receives a reference signal according to the pattern shown in FIG. 2 and uses it to estimate the desired signal-to-interference ratio (SIR.sub.i-1). By applying the threshold algorithm, the receiver determines the CQI.sub.i-1 value from the measured SIR and sends it to the node (eNode or transmitter). [0036] In instant t=i−1+Δ, the transmitter receives the CQI.sub.i-1 value reported by the mobile terminal and determines the modulation and coding format (MCS) of the data to be transmitted in the downlink corresponding to the received CQI, i.e., MCS.sub.i=f(CQI.sub.i-1). Again, the node codes the data to be transmitted (DATA(MCS.sub.i)) according to the determined format and sends it to the mobile terminal (receiver). [0037] In instant t=i, the mobile terminal receives the data, accompanied by the reference signals sent by the transmitter according to the CQI.sub.i-1, calculates the level of SIR, and demodulates the received data. In parallel, communication quality is measured in terms of BLER based on the received signal. Lastly, FIG. 3 depicts how the mobile terminal (receiver) determines channel quality from the measured SIR and determines the CQI.sub.i to be sent to the node (transmitter) for subsequent transmission.

[0038] FIG. 4 depicts the methodology for determining the thresholds that will be applied to the SIR by the mobile terminal. The mobile terminal uses, internally, a threshold algorithm based on these curves to enable determining the CQI sent to the transmitter node for subsequent planning in the downlink. The target communication quality (target BLER) is depicted in the figure by means of the horizontal line 401 and usually takes the value of 10% or 0.001%. The CQI must be determined such that it ensures that the error rate is less than the target rate for the SIR measured by the receiver or mobile terminal. Therefore, the thresholds are defined as the cut-off point of the SIR-BLER curves for different CQIs with the horizontal line of the target BLER, and the threshold SIR values are obtained from those correspondences.

[0039] FIG. 5 depicts a diagram of the operation of the preferred embodiment of the method object of the present invention. To that end, an example of communication between a mobile terminal and a node (eNode), i.e., between the receiver and the transmitter of a communication, depicted as two ends thereof, and the information exchange between them, are shown.

[0040] The method object of the invention is included within a wireless communications system like the one shown in FIG. 1, wherein the receiver or mobile terminal measures the desired signal-to-interference ratio (SIR) from the reference signal received in instant t=i−1 and saves this SIR value (SIR.sub.i-1) in a memory. Based on this SIR value (SIR.sub.i-1), a CQI value (CQI.sub.i-1) is determined and sent to the transmitter node, which selects the modulation and coding format in the subsequent transmission (MCSi) in the downlink according to that measured CQI (CQI.sub.i-1). Upon receiving in instant “t” the data packet sent by the transmitter node, the receiver terminal measures the SIR (SIR.sub.i) and saves it in a memory.

[0041] The present invention proposes for the receiver or mobile terminal to calculate, based on the comparison between the measurements taken coming from the transmitter node in different time instants, a parameter (α.sub.i) which allows the variation experienced by the communications channel between said transmissions to be determined. The variation quantification parameter of the communications channel (α.sub.i) therefore precisely reflects the difference existing between the channel quality taking as a reference the instant in which the CQI is determined by means of the reference signals (CQI.sub.i-1) and the instant in which the receiver mobile terminal receives the data corresponding to that CQI.sub.i-1 in the subsequent reception and measures the channel quality again (CQI.sub.i).

[0042] In a preferred embodiment of the invention, the variation quantification parameter of the communications channel (α.sub.i) is defined as the difference between the SIR values measured by the receiver mobile terminal for quantifying the variation experienced in the communications channel. In other words:

α.sub.i=SIR.sub.i−SIR.sub.i-1

[0043] Nevertheless, the variation quantification parameter of the communications channel (a) can be defined alternatively with other time variations or differences since, unlike other approaches described in the state of the art, the present invention does not have frequency variation or discrimination. A possible formation of the variation quantification parameter of the communications channel (a) would be performed by means of calculating the variation of the CQI value, such that:

α.sub.i=CQI.sub.i−CQI.sub.i-1

[0044] One skilled in the art will appreciate that other variations of this definition can also be valid for the purposes of this invention, such as differences between average or weighted values of SIR or CQI measurements in different frequency bands, or the use of values corresponding to more than two time instants with coefficients weighing same in the event that there is an uncertainty concerning which measuring instant i−1 is the one that brings about the determination of the data received in i.

[0045] A second essential point of the present invention is the calculation of a correction margin by means of a transformation function the two input parameters of which are the variation quantification parameter of the communications channel (α.sub.i) and, on the other hand, the target reliability to be fixed for the communication of the offered services. In that sense:

margin.sub.i=f(∝.sub.i,target reliability)

[0046] Target reliability is the value to be ensured with the present invention for a reliability index which can be defined according to the following equation:

[00002]$\mathrm{Reliability}\mathrm{index}=\frac{\mathrm{number}\mathrm{of}\mathrm{slots}\left({\mathrm{BLER}}_i<{\mathrm{BLER}}_{\mathrm{target}}\right)}{\mathrm{total}\mathrm{number}\mathrm{of}\mathrm{slots}}$

[0047] where BLERi.sub.i is the real instantaneous block error rate and BLER.sub.target is the target mean block error rate of the service.

[0048] In the present invention, there is a need to resort to defining the concept of reliability index in order to complement the concept of target mean block error rate (BLER.sub.target) of the 5G service because, as mentioned above, although the BLER.sub.target is complied with on average, it is occasionally not complied with for all the transmissions due to imprecision in the determination of the CQI, and therefore this causes the occasional failure to satisfy the final latency of the system for all the cases. The present invention proposes ensuring that said reliability index is greater than a certain target reliability for the service by means of applying a correction margin to the calculation of the CQI performed by the mobile terminal before reporting the CQI to the transmitter node.

[0049] As indicated above, a correction to the calculation of the CQI based directly on received block errors is not effective due to such a low target error rate used in URLLC services. However, indirect correction through the reliability index which has been defined allows using higher reliability, allowing an effective correction that is compatible with the use of very low target block error rates.

[0050] If the reliability index is defined as the percentage of blocks or time that must satisfy the maximum BLER established for the services used, the present invention will have the effect that, once the channel state has been modified and therefore the CQI has been sent to the transmitter, the final block error rate of the system will be the target rate (10% in the case of LTE or less in URLLC services) in a percentage of time determined by the fixed target reliability.

[0051] The reliability index is measured indirectly because the real instantaneous block error rate cannot be measured directly. However, as described in FIG. 4, there is a direct relationship between the error rate and the received SIR or the estimated CQI. The embodiments that will be described below assume that if the conditions when receiving the data (for example, SIR or CQI) are worse than those under which the transport format, with which data was transmitted, was determined, this means that the instantaneous block error rate will be higher than the target block error rate. In other words, the invention is since the defined variation quantification parameter of the communications channel (α.sub.i) can be used as a basis for calculating the reliability index which in turn allows the CQI to be corrected in order to adapt same to the conditions more quickly than with BLER.

[0052] A first embodiment for this step of calculating the correction margin is the calculation of same based on the distribution function of the variation quantification parameter of the communications channel (α.sub.i). The concept of reliability index, as defined above, is equivalent in statistical terms to that cut-off percentile or probability. Specifically, to assure that the channel has a reliability index higher than a certain target reliability, a margin based on the percentile (100%−target reliability) of the distribution of α.sub.i must be used.

[0053] According to this embodiment, the calculation of the correction margin based on the SIR or CQI would comprise the following steps: [0054] Obtaining a plurality of values of the variation quantification parameter of the communications channel (α.sub.i). [0055] Determining the n % percentile of the distribution, where n=100%−target reliability, and with the n % percentile being defined as that value below which n % of the plurality of obtained values is found.

[0056] Determining margin.sub.i based on said percentile:

margin.sub.i=percentile_∝.sub.i(100%−target reliability)

[0057] Another possible embodiment for this second step of determining the correction margin consists of an algorithm which gradually approaches, in an iterative manner, the percentile value corresponding to the target reliability described in the preceding embodiment. Specifically, in this embodiment the percentile estimate value is updated with each new value of α.sub.i calculated by the mobile, increasing or decreasing the value thereof by means of a step-up (S.sub.up) or a step-down (S.sub.down), respectively. The target reliability defines the ratio between both steps, which must satisfy the following expression:

[00003]$\frac{S_{\mathrm{up}}}{S_{\mathrm{up}}+S_{\mathrm{down}}}=\mathrm{Target}\mathrm{reliability}$

[0058] The iterative process for updating margin.sub.i is performed according to the following method: [0059] If α.sub.i>margin.sub.i-1, then margin.sub.i=margin.sub.i-1−S.sub.down; [0060] If α.sub.i<margin.sub.i-1, then margin.sub.i=margin.sub.i-1+S.sub.up.

[0061] This method is advantageous compared to the preceding one because it does not require storing old α.sub.i values, whereby the use of memory is reduced.

[0062] Following the methodology proposed in the present invention, an adjustment is successfully performed on the CQI reported to the transmitter to eliminate the effect of the change of channel conditions from when the receiver calculates the CQI to the moment in which the transmitter will perform data planning in the downlink. The described method applies a correction margin on the calculation of the CQI determined by channel variation; it is conceptually equivalent to modifying the decision thresholds in the SIR-CQI correspondence performed by the receiver when it measures the reference signal and reports same to the transmitter, making them more demanding. Setting a higher level of demand on decision thresholds would imply that a shift thereof to higher SIR values will take place, such that, for one and the same SIR, a CQI that is lower than the previous one will be obtained.

Example of Practical Embodiment of the Invention

[0063] As indicated above, a diagram of the operation of the preferred embodiment of the method object of the invention is depicted in FIG. 5. To that end, an extract of a communication between the mobile terminal and the node (eNode), i.e., between the receiver and the transmitter of a communication, represented as two ends thereof, and information exchange between them, are shown. In that sense, every time the mobile receiver receives data in the downlink, the downlink performs the following steps in instant i: [0064] estimating the received desired signal-to-interference ratio (SIR.sub.i); saving the SIR.sub.i value; [0065] determining the SIR error value defined as the difference between the SIR of instant [i−1], SIR.sub.i-1, and the SIR of the current instant [i], SIR.sub.i, where α.sub.i=SIR.sub.i−SIR.sub.i-1; saving the α.sub.i value; [0066] calculating the correction margin by applying the desired reliability index on the statistics, where margin.sub.i=f(α, reliability); [0067] correcting the SIR measured by the terminal in the current instant, SIR.sub.i, by applying the correction margin, margin.sub.i, before determining the CQI corresponding to that SIR.sub.i, such that SIR.sub.i′=SIR.sub.i+margin; and [0068] determining the CQI corresponding to that received and corrected desired signal-to-interference ratio SIR.sub.i′, CQI.

REFERENCES

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