KR101154991B1 - Method of re-transmitting channel quality information and supporting thereof in mobile communication system - Google Patents

Abstract

The present invention relates to a method for exchanging channel quality information between a base station and a terminal in a mobile communication system. In the method for retransmitting channel quality information in a mobile communication system according to the present invention, in the method for transmitting channel quality information from a terminal to a base station in a mobile communication system, the channel quality information measured based on a signal received from the base station is determined by the base station. Transmitting the signal to the base station; receiving feedback information on the channel quality information from the base station; and matching the channel quality information transmitted by the terminal with the channel quality information received by the base station based on the feedback information. And transmitting the error information to the base station.

Mobile communication, channel quality information, CQI, scheduling, error information

Description

Method of re-transmitting channel quality information and supporting method in mobile communication system {Method of re-transmitting channel quality information and supporting information in mobile communication system}

1 is a process flow diagram of one preferred embodiment of the present invention.

The present invention relates to a mobile communication system, and more particularly, to a method for transmitting channel quality information between a base station and a terminal in a mobile communication system and a support method thereof.

In a mobile communication system, a terminal measures a quality of a downlink channel using a signal received from a base station and transmits channel quality information to the base station. The base station performs downlink scheduling according to channel quality information received from at least one terminal. Examples of the channel quality information may include a channel quality indicator (CQI), a signal to noise ratio (SNR), a carrier to interference and noise ratio (CINR), a bit error rate (BER), a frame error rate (FER), and the like. . The channel quality information is transmitted to the base station through an uplink control channel. The downlink scheduling is a procedure in which the base station allocates finite radio resources such as code, frequency, and time to the terminals, based on channel quality information received from each terminal.

In the related art, various types of channel quality information transmitting methods are disclosed according to types of mobile communication systems. In order to reduce the amount of physical channel control information when one of the UEs transmits the channel quality information, only one piece of information, such as differential information, is periodically or aperiodically transmitted as needed without reducing all channel quality information. This is a method of transmitting entire channel quality information. In this case, a method such as differential modulation (DM) may be used for partial channel quality information transmitted through the physical control channel.

According to the conventional channel quality information transmission method, when the terminal transmits the channel quality information to the base station, there is a risk that the base station receives inaccurate channel quality information in which an error occurs in the transmission process due to a sudden change in channel conditions. There is this. When the base station receives incorrect channel quality information and performs downlink scheduling based on this, the finite radio resource allocation cannot be efficiently performed, which adversely affects the performance of the entire system.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art as described above, and an object of the present invention is to reduce a reception error that may occur in channel quality information used as a base material by a base station in performing downlink scheduling. The present invention provides a method for retransmitting channel quality information and a method for supporting the same in a mobile communication system for efficiently allocating radio resources.

An aspect of the present invention for achieving the above technical problem is the terminal as a feedback information based on the data processing (data processing) performed on the part or all of the channel quality information received from the terminal or the channel quality information (feedback information) Will be sent to. The feedback information may be transmitted periodically, aperiodically or when a predetermined event occurs.

Another feature of the present invention is that the terminal compares the feedback information received from the base station with the channel quality information stored therein, the error for matching the channel quality information transmitted by the terminal to the base station and the channel quality information received by the base station Information is transmitted to the base station. The error information may be transmitted when a predetermined condition is satisfied. The predetermined condition and a parameter for determining whether the predetermined condition is satisfied may be transmitted from the base station to the terminal.

Another feature of the present invention is that the base station receives the error information transmitted from the terminal to modify the channel quality information stored in the base station according to the received error information and performs the downlink scheduling using the modified channel quality information will be.

In one aspect of the present invention, a method for retransmitting channel quality information in a mobile communication system according to the present invention is a method for transmitting channel quality information from a terminal to a base station in a mobile communication system, the measurement being based on a signal received from the base station Transmitting the received channel quality information to the base station, receiving the feedback information on the channel quality information from the base station, and transmitting the channel quality information transmitted by the terminal to the base station based on the feedback information. And transmitting the error information to match the channel quality information received by the base station.

In another aspect of the present invention, a method for supporting retransmission of channel quality information in a mobile communication system according to the present invention comprises the steps of: receiving, from a terminal, channel quality information measured based on a signal transmitted from a base station; And transmitting feedback information to the terminal so that the received channel quality information and the channel quality information transmitted by the terminal can be compared.

The construction, operation and other features of the present invention will be readily understood by the preferred embodiments of the present invention described below with reference to the accompanying drawings.

1 is a process flow diagram of one preferred embodiment of the present invention. Referring to FIG. 1, the base station transmits a reference signal to the terminal in a call establishment process or data transmission process after call establishment with the terminal [S11]. The terminal measures the quality of the downlink channel using the reference signal received from the base station [S12]. The reference signal is a signal transmitted through a pilot channel in a code division multiple access (CDMA) system, or a preamble or midamble signal or pilot in an orthogonal frequency division multiplexing (OFDM) or orthogonal frequency division multiple access (OFDMA) system. This means a signal that both the base station and the terminal know, such as a signal. The terminal may determine the degree of deformation of the reference signal to measure the quality of the downlink channel. On the other hand, the terminal may divide the frequency band allocated to it into a plurality of sections to measure the channel quality for each section. In the following description, the term “section” is used in the same sense as the “CQI band” in the sense of a unit band for measuring channel quality.

The terminal transmits channel quality information to the base station after measuring the quality of a downlink channel [S13]. In the embodiment of FIG. 1, a CQI (Channel Quality Indicator) is used as the channel quality information. CINR, BER, FER, etc. may also be used as the channel quality information. CQI refers to an indicator indicating each class when the quality of the channel is divided into classes. For example, if the quality of the channel is subdivided into 32 steps, each class may be identified by a 5-bit CQI. When channel quality is measured by dividing a frequency band allocated to the terminal into a plurality of sections (CQI bands), CQI for each section is transmitted to the base station. The specific method of transmitting the CQI to the base station by the terminal may vary according to a specific channel quality information transmission scheme.

The base station transmits feedback information on the CQI received from the terminal to the terminal [S13]. The feedback information may be configured in various forms using the CQI received from the terminal. As an example, the base station may transmit the CQI received from the terminal as the feedback information as it is received. As another example, the base station receives the CQI for the partial band from the terminal, estimates the channel quality information for the entire band from the CQI for the received partial band, and then transmits the channel quality information for the estimated full band. It is also possible.

The base station may transmit the feedback information to the terminal periodically or aperiodically. Alternatively, the feedback information may be transmitted to the terminal when a predetermined event occurs or a request from the terminal. When the base station periodically transmits the feedback information to the terminal, it is preferable to transmit through a control channel. When the base station transmits the feedback information aperiodically to the terminal, the base station preferably transmits the feedback information through a traffic channel using medium access control (MAC) signaling. In the feedback information, even when an error occurs in the transmission process, it is preferable to perform channel encoding so that the terminal can detect and correct the error.

Hereinafter, the process of S13 and S14 of FIG. 1 will be described with a specific example. An example described below is an example in which a UE divides a frequency band into 12 sections (CQI bands) and transmits CQI in DM (Differential Modulation) form by dividing it into 32 Modulation and Coding Set (MCS) levels for each section.

Table 1 illustrates a process of calculating the differential CQI information to be transmitted to the base station by measuring the downlink channel quality at the time t = 1.

section One 2 3 4 5 6 7 8 9 10 11 12 Full CQI
(t = 0) 11 10 9 6 5 7 9 13 10 7 4 2 Full CQI
(t = 1) 12 11 10 5 4 6 10 14 9 6 3 One DM CQI
(t = 1) One One One -One -One -One One One -One -One -One -One

In Table 1, 'section' means each CQI band when the entire frequency band is divided into 12 CQI bands. 'Full CQI (t = 0)' is the CQI for each section measured by the UE at the time t = 0, and 'Full CQI (t = 1)' is the angle measured by the UE at the time t = 1 CQI for each section. 'DM CQI' refers to differential information of 'Full CQI (t = 1)' and 'Full CQI (t = 0)' for each section. CQI information transmitted by the UE to the base station at t = 1 to be.

Table 2 is for explaining a process of calculating the feedback information to be transmitted to the terminal by the base station when t = 2.

section One 2 3 4 5 6 7 8 9 10 11 12 DM CQI
(t = 2) One One One -One -One -One One One -One -One One One Full CQI
(t = 1) 11 10 9 6 5 7 9 13 10 7 4 2 Full CQI
(t = 2) 12 11 10 5 4 6 10 14 9 6 5 3

In Table 2, 'DM CQI (t = 2)' means DM CQI for each section that is transmitted from the terminal at a time t = 1 and received by the base station at t = 2. In the example of Table 2, an error occurs during transmission in the 11th and 12th sections. 'Full CQI (t = 1)' is a CQI for each section known to the base station until t = 2, and it is assumed that there is no error until then. 'Full CQI (t = 2)' is the CQI for each section at time point t = 2 calculated by the base station from 'DM CQI (t = 2)' and 'Full CQI (t = 1)'. Feedback information transmitted to the terminal. In this case, the base station may transmit 'DM CQI (t = 2)' received from the terminal to the terminal as feedback information.

The terminal compares the feedback information received from the base station with the CQI information stored in the terminal [S15]. Table 3 shows a comparison result for each section when t = 3, assuming that the terminal receives the feedback information without error.

section One 2 3 4 5 6 7 8 9 10 11 12 Full CQI
(t = 1) 12 11 10 5 4 6 10 14 9 6 3 One Full CQI
(t = 3) 12 11 10 5 4 6 10 14 9 6 5 3 Δ 0 0 0 0 0 0 0 0 0 0 -2 -2

In Table 3, 'Full CQI (t = 1)' is a CQI for each section known to the UE, and 'Full CQI (t = 3)' is feedback information received from the base station at a time t = 3. 'Δ' represents an error between 'Full CQI (t = 1)' and 'Full CQI (t = 3)'. In Table 2, since it is assumed that an error occurs in the 11th section and the 12th section, even when the terminal compares the feedback information received from the base station with the CQI information stored in the terminal, the 11th section and the 12th section An error occurred at.

When the terminal satisfies a predetermined condition as a result of comparing the feedback information received from the base station and the CQI information stored by the terminal, the terminal matches the CQI information received by the base station with the CQI information at the time of transmission by the terminal. It is determined whether it is necessary to transmit the error information for [S16]. Examples of predetermined conditions for determining that the error information needs to be transmitted are as follows.

First, it may be determined that the error information needs to be transmitted when an error occurs in a section that is greater than or equal to the first threshold value, that is, when the number of sections in which the 'Δ' value is not 0 in Table 3 is greater than or equal to the first threshold value. The first threshold value may be one or more values.

Second, when the absolute value of the 'Δ' value is larger than the second threshold value K, it may be determined that an error has occurred in the corresponding section, and it may be determined that error information of the corresponding section or the entire section needs to be transmitted.

Third, it may be determined that the error information needs to be transmitted when the CQI band in which the absolute value of the 'Δ' value is larger than the second threshold value K is greater than or equal to the third threshold value among all N sections, that is, the N CQI bands. .

Fourth, when the error average of all N CQI bands is equal to or greater than a fourth threshold value Y, it may be determined that the error information needs to be transmitted.

Fifth, it may be determined that the error information needs to be transmitted when the error average of the CQI bands in which an error occurs among the total N CQI bands is greater than or equal to a fourth threshold value Z.

The predetermined condition and the first to fourth threshold values according to each condition for determining whether the terminal needs to transmit the error information are transmitted when the base station transmits the feedback information or during a signaling process for call setup. It can be transmitted to the terminal. Alternatively, it is possible to set by prior appointment of the base station and the terminal. As another method, when the terminal determines itself and transmits the error information, it is also possible to inform the base station of the condition and the corresponding threshold value together.

Referring back to FIG. 1, when the terminal determines that it is necessary to transmit error information to the base station, the error information is transmitted [S16]. The terminal may transmit some or all of the entire CQI information as the error information. In case of transmitting part of CQI information, 'Full CQI' value or 'Δ' value for CQI band in which an error occurs can be transmitted, and in case of transmitting all the CQI information, the entire CQI band including the CQI band in which an error is issued can be transmitted. A 'full CQI' value or a 'Δ' value can be transmitted.

The terminal may transmit the error information to the base station by a contention-based transmission method or a scheduled transmission method. The contention-based transmission scheme is also called a non-scheduled or autonomous transmission scheme and is a channel pre-allocated on a contention basis by the base station without requesting a separate channel allocation for transmitting the error information to the base station. Through the error information transmission method. The scheduling transmission method is a method in which the terminal requests a channel assignment from the base station to transmit the error information, allocates a channel from the base station, and transmits the error information through the assigned channel.

The base station receives the error information from the terminal and modifies the CQI information of an errored CQI band stored by the base station using the received error information [S18]. The base station performs downlink scheduling using the modified CQI information [S19].

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

According to the method for retransmitting channel quality information and the supporting method in a mobile communication system according to the present invention, the following effects are obtained.

First, an error occurring in the process of transmitting downlink channel quality information by the terminal to the base station can be healed.

Second, since the base station performs downlink scheduling using accurate channel quality information, it is possible to efficiently allocate finite radio resources, thereby improving the performance of the entire system.

Claims (16)

In the mobile communication system in the terminal transmits the channel quality information to the base station, Transmitting channel quality information measured based on a channel quality measurement reference signal received from the base station to the base station; Receive feedback information on the channel quality information (hereinafter, referred to as transmission channel quality information) transmitted from the base station to the base station from the base station, wherein the feedback information is received from the base station (hereinafter, referred to as reception channel quality information). Comprising information indicating; And Transmitting error information indicating an error between the transmission channel quality information and the reception channel quality information to the base station based on the feedback information. The method of claim 1, And transmitting the error information to the base station when the comparison result of the transmission channel quality information and the reception channel quality information satisfies a predetermined condition. 3. The method of claim 2, And receiving a parameter for determining whether the predetermined condition is satisfied from the base station. The method of claim 3, And the parameter is received together with the feedback information. The method of claim 3, And the parameter is received in the call setup step between the base station and the terminal. The method of claim 1, And the feedback information is received periodically or aperiodically. The method of claim 6, And when the feedback information is periodically received, the channel quality information retransmission method. The method of claim 6, And if the feedback information is aperiodically received via a data channel. The method of claim 1, And the error information is transmitted in a contention-based manner. The method of claim 1, The error information is transmitted by a scheduled transmission (scheduled transmission) method, characterized in that the channel quality information retransmission method. In the base station receives the channel quality information from the terminal in a mobile communication system, Transmitting a reference signal for measuring channel quality to the terminal; Receiving channel quality information from the terminal; Transmitting feedback information including information representing the channel quality information (hereinafter, referred to as reception channel quality information) received by the base station to the terminal; And And receiving error information indicating an error between the reception channel quality information and the channel quality information transmitted by the terminal (hereinafter, referred to as transmission channel quality information) from the terminal. The method of claim 11, And transmitting a parameter for determining whether the terminal satisfies a predetermined condition for transmitting the error information to the terminal. The method of claim 12, And the parameter is transmitted together with the feedback information. The method of claim 12, And the parameter is transmitted in the call setup step between the base station and the terminal. The method of claim 12, And the feedback information is transmitted periodically or aperiodically. delete

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