KR20070082783A - Apparatus and method for feedback channel quality indicator in mobile communication system - Google Patents

Abstract

An apparatus and a method for feeding back a CQI(Channel Quality Indicator) in a mobile communication system are provided to control uplink radio resources for CQI feedback effectively and to feed back CQI information selectively to increase system capacity. A base station for receiving CQI feedback information from a mobile terminal comprises an RoT(Rise over Thermal) measurement part(500), an RF part(502), and a control part(504). The RoT measurement part measures an RoT value to measure the power control and interference of the mobile terminal. The RF part receives a CQI from the mobile terminal, and transmits a TPR(Traffic to Pilot Ratio) command to the mobile terminal in order to control the CQI feedback of the mobile terminal. The control part compares the measured RoT value with a preset threshold, transmits the TPR command, and executes AMC(Adaptive Modulation and Coding) and channel sensitive scheduling on the basis of the received CQI.

Description

APPARATUS AND METHOD FOR FEEDBACK CHANNEL QUALITY INDICATOR IN MOBILE COMMUNICATION SYSTEM {APPARATUS AND METHOD FOR FEEDBACK CHANNEL QUALITY INDICATOR IN MOBILE COMMUNICATION SYSTEM}

1 is a diagram illustrating a method for configuring a localized resource channel (LRCH) and a dedicated resource channel (DRCH) channel in a mobile terminal of an OFDMA system to which the present invention is applied;

2 is a diagram illustrating a method for configuring a MIMO channel in an OFDMA system to which the present invention is applied;

3 is a diagram illustrating an embodiment in which a mobile terminal adjusts a CQI feedback amount according to TPR control of a base station according to the method proposed by the present invention;

4 is a block diagram of a base station according to an embodiment of the present invention;

5 is a flowchart for determining a TPR command of a base station according to an embodiment of the present invention;

6 is a block diagram of a mobile terminal according to an embodiment of the present invention;

7 is a flowchart for generating a backward transmission signal including a CQI feedback signal in a mobile terminal according to an embodiment of the present invention;

8 is a flowchart illustrating a method of receiving CQI feedback information at a base station according to an embodiment of the present invention;

9 is a block diagram for generating a CQI channel in a mobile terminal according to an embodiment of the present invention.

The present invention relates to an apparatus and method for improving transmission efficiency in a wireless communication system, and more particularly, to an apparatus and method for feeding back a channel quality indicator in a mobile communication system.

The present invention also relates to an apparatus and method for configuring a CQI feedback channel for supporting an adaptive modulation and coding method and a channel sensitive scheduling resource management method in a wireless packet data communication system.

In general, a wireless communication system is a system developed as a means for allowing a user to communicate without a distance constraint. A representative system of such a wireless communication system is a mobile communication system. The mobile communication system has evolved into a high-speed, high-quality wireless packet data communication system for providing data services and multimedia services beyond the initial voice-oriented services. Currently, 3GPP-based High Speed Downlink Packet Access (HSDPA) and 3GPP2-based EV-DV and EV-DO are standardized for 3GPP high-speed and higher than 2Mbps. It is a representative proof of the effort to find a solution for high quality wireless packet data transmission service.

The mobile communication system has evolved into a high-speed, high-quality wireless packet data communication system for providing data services and multimedia services, instead of providing an initial voice-oriented service. Recently, various mobile communication standards such as 3GPP's High Speed Downlink Packet Access (HSDPA), HSUPA (High Speed Uplink Packet Access), 3GPP2's High Rate Packet Data (HRPD), and IEEE's 802.16 are high-speed, high-quality wireless packet data transmission services. Was developed to support it.

Existing third generation wireless packet data communication systems such as HSDPA, HSUPA, and HRPD use techniques such as adaptive modulation and coding (AMC) and channel sensitive scheduling to improve transmission efficiency. By using the AMC method, the transmitter can adjust the amount of data to be transmitted according to channel conditions. In other words, if the channel condition is not good, the amount of data to be transmitted can be reduced to meet the desired level. If the channel condition is good, the amount of data to be transmitted can be increased to effectively transmit a large amount of information while the reception error probability is set to the desired level. By using the channel sensitive scheduling resource management method, the transmitter selectively services a user having excellent channel status among multiple users, thus increasing system capacity compared to allocating and serving a channel to one user. This increase in capacity is called the multi-user diversity gain. In short, the AMC method and the channel-sensitive scheduling method are methods of applying an appropriate modulation and coding technique at a time when it is determined to be the most efficient by receiving partial channel state information from the receiver.

In order to realize the AMC method and the channel sensitive scheduling method, the receiver needs to feed back channel state information to the transmitter. The channel state information fed back by the receiver is called a channel quality indicator (CQI).

Recently, a researcher is trying to change Code Division Multiple Access (CDMA), which is used in 2nd and 3rd generation mobile communication systems, to Orthogonal Frequency Division Multiple Access (OFDMA) in next generation systems. It is actively underway. 3GPP and 3GPP2 have begun standardizing on evolutionary systems using OFDMA.

It is known that the capacity can be increased in the OFDMA method as compared to the CDMA method. One of various causes of capacity increase in the OFDMA scheme is that frequency domain scheduling can be performed on the frequency axis. Just as channel gains are gained through channel-sensitive scheduling as the channel changes over time, more capacity gains can be achieved if the channel utilizes different characteristics depending on frequency. However, in order to support frequency domain scheduling, the transmitter needs to know channel state information for each frequency. That is, the CQI feedback burden increases because CQI feedback is required for each frequency.

Meanwhile, in the next generation system, the introduction of MIMO (Multiple Input Multiple Output) technology using multiple transmit / receive antennas is being actively studied. MIMO is a technology for transmitting a plurality of data streams using the same resources at the same time using multiple transmit and receive antennas. It is known that transmitting a plurality of low modulation order data streams may increase the transmission amount at the same error probability, rather than increasing the modulation order when the channel condition is good. In the MIMO scheme, a dimension in which individual data streams are transmitted is called a layer, and a method of applying AMC separately according to the channel state of the layer is effective for increasing capacity. For example, Per Antenna Rate Control (PARC) is a technique for transmitting different data streams for each transmitting antenna, and the layer becomes a transmitting antenna. A plurality of transmission antennas undergo different channels. In the PARC scheme, the AMC is applied to transmit more data to a transmission antenna having a good channel condition, and the amount of data transmitted is reduced with a transmission antenna having a poor channel condition. Another example is Per Common Basis Rate Control (PCBRC), which is a transmit beam with a fixed layer. Therefore, in the PCBRC technique, more data is transmitted through a transmission beam having a good channel condition, and the amount of data transmitted is reduced with a transmission beam having a poor channel condition.

On the other hand, SDMA (Space Division Multiple Access) technology is a technique for allocating different users to a plurality of transmission beams, and SDMA can increase its capacity through space domain scheduling, just as OFDMA can increase its capacity through frequency domain scheduling. have.

In order to improve AMC performance and scheduling gain through the MIMO technology and the SDMA technology, the transmitter needs to know channel state information for each transmission layer. That is, the CQI feedback burden increases because CQI feedback is required for each transmission layer.

Meanwhile, since CQI feedback is transmitted by each mobile station to the base station for AMC and channel sensitive scheduling, the CQI feedback channel should be designed on the reverse link. As a method for configuring a channel for a plurality of mobile terminals in the reverse link, there are largely an orthogonal channel configuration method and a non-orthogonal channel configuration method. The orthogonal channel configuration method allocates orthogonal channel resources for each mobile terminal, so that interference does not occur between mobile terminals in a cell. Therefore, in the orthogonal channel, a high signal-to-interference plus noise ratio (SINR) can be guaranteed, thereby enabling communication at a high data rate.

However, the number of orthogonal channels in a limited radio resource is limited. Therefore, the base station needs a process of allocating an orthogonal channel according to the state of the mobile terminal. In general orthogonal channel allocation, when a mobile terminal requests an orthogonal channel allocation based on the amount of data to be transmitted and the channel state, the base station accepts the request and grants a specific orthogonal channel to each mobile terminal. It is a request-grant process. The non-orthogonal channel configuration method is characterized by allowing interference by not guaranteeing orthogonality to channel resources allocated to mobile terminals. In the case of the non-orthogonal channel, there is an advantage that the number is not limited in the limited radio resources, but the base station must control the amount of interference to guarantee the desired SINR.

Accordingly, the base station should control the transmission power of the mobile terminals using the non-orthogonal channel through power control and rise over thermal (RoT) control, which is a ratio between total power and thermal noise received from the mobile terminals. The current 3rd generation mobile communication system is taking a CDMA non-orthogonal channel configuration method in the reverse link. Feedback information such as CQI may be transmitted in the orthogonal channel or the non-orthogonal channel in the reverse link. The former method, that is, a method of allocating an orthogonal channel for CQI feedback, is advantageous when the mobile terminal always feeds back a certain amount of CQI. However, considering that a large amount of CQI feedback occurs in order to apply techniques such as frequency domain scheduling or MIMO, most of the limited reverse link radio resources may be used only for CQI feedback.

On the other hand, if the amount of CQI feedback is not constant and variable, the request-approval process may be frequently performed to allocate orthogonal channels variably. However, since the CQI information should be delivered to the base station as soon as possible, it may be a problem that the time is too delayed in the request-approval process because it helps in AMC and channel sensitive scheduling. Therefore, the latter method, that is, a method of allocating a non-orthogonal channel for CQI feedback may be advantageous.

In the non-orthogonal channel configuration method, RoT control is performed in a manner of allowing a traffic to pilot ratio (TPR) to a mobile terminal. When the transmission power of the pilot, which is essential for coherent demodulation, is controlled by the power control, controlling the TPR means controlling the total power transmitted by each mobile terminal in the non-orthogonal channel. That is, if it is determined that the communication amount becomes difficult due to an increase in the amount of interference, the mobile terminal is controlled to lower the TPR, and if the amount of interference decreases, it is possible to increase the amount of transmission information by increasing the transmission power of the mobile terminal. Control.

In general, there are two methods for controlling the TPR at the base station. The first method is an individual control method for controlling the allowable TPR for each mobile terminal. To do this, a request-approval process is required as in the orthogonal channel configuration method. The second method is a common control method of controlling the TPR as a whole by notifying all users in the cell of the current interference situation with one control signal. In other words, if it is predicted that the RoT is increased and the communication level is reached, the level of interference is high, and all mobile terminals in the cell are notified so that each mobile terminal lowers the TPR and transmits the interference. Notify each mobile terminal to increase the TPR by itself to transmit. Higher TPR can increase the amount of information that can be delivered because more power can be allocated to traffic channels. The advantage of the common control method is that the request-approval process is not necessary.

In the following description of the present invention, it is assumed that a reverse link channel for CQI feedback is configured as a non-orthogonal channel and RoT control is performed by a common control method.

In general, high-speed packet data communication systems such as HSDPA of 3GPP and HRPD system of 3GPP2 use a method of transmitting signals through CDMA or Code Division Multiplexing (CDMA) over 5MHz and 1.25MHz. Accordingly, each mobile station feeds back only CQIs for all system bands, and the base station collects the CQI information from all mobile stations and performs channel sensitive scheduling with AMC. In the mobile communication system, since the user of the mobile terminal supports handoff to prevent a disconnection during a call, the mobile terminal attempts to communicate with a base station having a good channel state. Therefore, when the mobile terminal feeds back the CQI, it is necessary to inform which base station the CQI is from the channel state information. That is, CQI is meaningful when transmitted with sector information. As such, the feedback of the CQI with the sector information is used in the HRPD system.

However, in order to apply techniques such as frequency domain scheduling or MIMO, a large amount of CQI feedback is generated from the mobile terminal. Therefore, as the amount of CQI feedback increases, the base station can perform channel sensitive scheduling based on more channel information, which helps to increase system capacity, while increasing the radio resources of the reverse link that should be allocated for CQI feedback. Occurs.

The present invention provides an apparatus and method for allowing a user to selectively feed back CQI information that effectively controls radio resources of a reverse link used for CQI feedback and helps increase system capacity.

The present invention adjusts the amount of reverse link radio resources used by the base station for CQI feedback according to the load status of the reverse link, but does not take a certain time for resource allocation like a request-approval procedure and quickly controls the TPR common. The present invention provides an apparatus and method for controlling resources for CQI feedback.

The present invention provides an apparatus and method for efficiently utilizing reverse link radio resources by selectively feeding back only CQIs of resources that are likely to be allocated resources on the forward link within an allowed TPR. .

In the mobile communication system according to the present invention, a base station for receiving feedback of a channel quality indicator of a mobile terminal includes: a RoT measuring unit measuring a rise over thermal value to measure power control and interference of the mobile terminals, and the channel from the mobile terminal. A wireless unit for receiving a quality indicator, and transmits a traffic to pilot ratio command to the mobile terminal to control the feedback of the channel quality indicator of the mobile terminal, and the RoT measurement unit A control unit for transmitting the traffic to pilot ratio command by comparing the measured rise over thermal value with a preset threshold value and performing AMC and channel sensitive scheduling based on the received channel quality indicator. Include.

A method for receiving a feedback of a channel quality indicator of a mobile station by a base station of a mobile communication system according to the present invention includes measuring a rise over thermal value to measure power control and interference amount of the mobile terminal, and the measured rise over And comparing a thermal value with a preset threshold value, and transmitting a traffic-to-pilot radio command for controlling channel quality indicator feedback information to be transmitted by the mobile terminal based on the comparison result.

A method for a base station of a mobile communication system to receive feedback of a channel quality indicator of a mobile terminal according to the present invention includes receiving a reverse link signal from the mobile terminal, and when the reverse link signal is received, a channel quality indicator of a specific index. Checking whether the information is fed back, and if the channel quality indicator information of the specific index is fed back, restoring the channel quality indicator information, and performing scheduling and AMC based on the restored channel quality indicator information. Include.

In the mobile communication system according to the present invention, a mobile terminal for feeding back a channel quality indicator of a mobile terminal includes: a traffic-to-pilot radio command interpreter for interpreting a traffic-to-pilot radio (TPR) command received from a base station; A channel quality indicator message constructing unit for generating a channel quality indicator message to be transmitted to the base station according to a traffic-to-pilot ratio command, and a priority of a channel quality indicator to be transmitted to the base station based on a result of the traffic-to-pilot ratio command analyzing unit; And a controller for controlling to generate a channel quality indicator message according to the selected rank.

A method for a mobile terminal for feeding back a channel quality indicator to a base station of a mobile communication system according to the present invention includes the steps of: receiving a traffic to pilot ratio command and a power control command from the base station; Calculating the allowable traffic-to-pilot ratio based on the command; determining the power required to transmit a reverse base channel different from the pilot transmission power based on the power control command; and measuring channel quality indicators to measure channel quality. Constructing an indicator message, determining a priority of the channel quality message, and transmitting channel quality indicator information having a high priority according to the allowed traffic to pilot ratio to the base station.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, specific details appear in the following description, which is provided to help a more general understanding of the present invention, and the present invention may be practiced without these specific matters. Will be self-evident. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Prior to describing the present invention, the present invention basically assumes that a reverse link channel for CQI feedback is configured as a non-orthogonal channel. The basic assumption is that power control and RoT control necessary for the operation of the non-orthogonal channel for CQI feedback are performed by the base station.

Briefly, the concept of the present invention is characterized in that the base station measures the RoT to determine the TPR, and adjusts the CQI Feedback of the mobile terminal with the determined TPR.

More types of CQIs are defined in a wireless packet data communication system employing OFDMA and MIMO techniques. In order for the base station to increase the capacity of the system through scheduling with the AMC, the mobile station should provide sufficient CQI information. However, because radio resources are limited in the reverse link, too many resources cannot be allocated for CQI feedback. Therefore, the base station allocates resources of the reverse link to be used for CQI feedback, and the mobile terminal should define a method of feeding back CQI information to the corresponding resources. The present invention provides a method for the user to selectively feed back CQI information that effectively controls the radio resources of the reverse link used for CQI feedback and helps increase system capacity. The base station manages the reverse link resources through TPR control, and the mobile terminal is controlled by the TPR control and feeds back CQI information selected in the allowed TPR. The mobile terminal adds and transmits all codewords representing CQI information for different forward link resources. To this end, CQI encoding uses orthogonal coding or bi-orthogonal coding.

1 illustrates a method for configuring a localized resource channel (LRCH) and a dedicated resource channel (DRCH) channel in a mobile terminal of an OFDMA system to which the present invention is applied. The LRCH and DRCH are channels formed on the forward link through the OFDMA scheme, and the mobile station feeds back the CQI of each channel to the reverse link.

First, reference numeral 201 is an example in which a channel is composed only of DRCH such as DRCH 1 203 and DRCH 2 204. Reference numeral 202 denotes an LRCH such as LRCH 1 205, LRCH 2 206, LRCH N 207, and the like. This is an example that consists only of. DRCH is a channel that is designed to obtain a frequency diversity gain, characterized in that one channel is composed of frequency-time symbols scattered on the frequency as shown. The LRCH is a channel designed to obtain frequency domain scheduling gain, characterized in that one channel is composed of adjacent frequency-time symbols on a frequency as shown at 202.

In a frequency selective fading environment, adjacent frequencies experience similar channel responses, while distant frequencies experience different channel responses. Thus, the symbols sent to the LRCH will experience similar channel responses and the symbols delivered to the DRCH will experience different channel responses.

In FIG. 1, the CQIs of DRCH 1 and DRCH 2 are not significantly different. This is because the DRCH uses a CQI that represents the channel response of the entire frequency band. For example, a method of easily calculating the CQI of the DRCH is to use the average of the CQIs experienced by each symbol as the representative CQI over the entire band. Therefore, the mobile station needs to feed back only one value of the CQI for the DRCH. However, the CQIs of LRCH 1 205, LRCH 2 206, and LRCH N 207 are different. Therefore, the CQI for the LRCH must separately transmit the CQI according to the type of the LRCH. That is, in order to feedback the CQI of the LRCH, when the CQI of the LRCH is informed, it should be known which LRCH.

The above is summarized as follows. The CQI of DRCH (hereafter DRCH_SISO_CQI) is

{DRCH_SISO_CQI, SECTOR_INDEX}

Feedback in the form of. DRCH_SISO_CQI indicates a CQI representing all bands, and SECTOR_INDEX indicates whether a DRQ_SISO_CQI is a CQI value associated with which sector. Here, SISO (Single Input Single Output) is indicated to distinguish it from the case of applying the MIMO technique. The CQI of LRCH (hereinafter LRCH_SISO_CQI) is

{LRCH_SISO_CQI, SECTOR_INDEX, LRCH_INDEX}

Feedback in the form of. LRCH_SISO_CQI indicates the CQI for a specific LRCH and SECTOR_INDEX and LRCH_INDEX indicate the CQI value for which LRCH when LRCH_SISO_CQI is connected to which sector.

2 illustrates a MIMO channel configuration method in an OFDMA system to which the present invention is applied. Through the MIMO scheme, a plurality of layers may be constructed on the same frequency-time resource and different data streams may be transmitted to each layer. Reference numeral 208 and 209 denote layer 1 and layer M, which are identical frequency-time resources but transmit different data streams by MIMO. That is, in the example of FIG. 2, a total of M layers are constructed on the same frequency-time resource, and a total of M data streams are transmitted.

How to build a layer depends on the MIMO technology. In the MIMO technology of transmitting different data streams according to transmission antennas, layers are divided by transmission antennas. In the MIMO technology in which a base station forms a plurality of beams and transmits different data streams for each beam, layers are divided by transmission beams. In addition, depending on the MIMO technology, the CQI may be the same or different for each layer. If the CQI is the same for each layer, one CQI may represent the CQIs of all layers. If the CQI is different for each layer, it is necessary to feedback a plurality of CQIs classified as LAYER_INDEX.

In consideration of the MIMO technology, CQI is expressed as follows. When MIMO technology is applied, the CQI of DRCH (DRCH_MIMO_CQI) is

{DRCH_MIMO_CQI, SECTOR_INDEX, LAYER_INDEX}

Feedback in the form of. DRCH_MIMO_CQI indicates the CQI for a specific layer, and SECTOR_INDEX and LAYER_INDEX indicate the CQI value for which layer when LRCH_MIMO_CQI is connected to which sector. When MIMO technology is applied, the CQI of LRCH (hereafter LRCH_MIMO_CQI) is

{LRCH_MIMO_CQI, SECTOR_INDEX, LRCH_INDEX, LAYER_INDEX}

Feedback in the form of. LRCH_MIMO_CQI indicates a CQI for a specific layer of a specific LRCH, and SECTOR_INDEX, LRCH_INDEX, and LAYER_INDEX indicate a CQI value for which layer of a LRCH when LRCH_MIMO_CQI is connected to which sector.

For reference, SISO and MIMO are not distinguished by the use of multiple antennas, but by the number of transmission data streams. For example, even when multiple transmit / receive antennas are used, the case of using multiple antennas for transmit diversity is classified as an SISO technique. If the base station can freely change the multiple transmit / receive antennas to the SISO technique or the MIMO technique without depending on the environment and conditions, both the CQI for DR (DRCH_SISO_CQI, LRCH_SISO_CQI) and the MIMO CQI (DRCH_MIMO_CQI, LRCH_MIMO_CQI) are fed back. Receiving helps.

Similarly, if the base station can freely change the channel of OFDMA to DRCH or LRCH according to the environment and conditions without any limitation to the DRCH or LRCH, if the base station receives feedback from both the CQI for DRCH (DRCH_SISO_CQI, DRCH_MIMO_CQI) and the LRCH CQI (LRCH_SISO_CQI, LRCH_MIMO_CQI) do.

Generally speaking, the above CQI feedback message type

{CQI, INDEX}

It can be represented as. That is, it identifies the INDEX of a specific resource and feeds back the CQI for that resource. For example, in the case of LRCH_MIMO_CQI, the resource INDEX is {SECTOR_INDEX, LRCH_INDEX, LAYER_INDEX}.

There are two methods for specifying a resource INDEX when feeding back CQI: an explicit method and an implicit method. The external method specifically specifies the resource INDEX, which is effective when not feeding back the CQI of all resources. For example, when feeding back LRCH_SISO_CQI, an external method is effective if only CQI for one LRCH is fed back among N LRCHs. The implicit method is to feed back CQIs in the form of an array so that the individual CQIs can be known to know which resource they are related to without indicating the resource INDEX. The implicit method is effective when feeding back the CQI of almost any resource. In the above example, if all N of LRCH_SISO_CQI are fed back, since displaying LRCH_INDEX becomes unnecessary information, it is possible to reduce the amount of radio resources consumed by feeding back N LRCH_SISO_CQI at once without displaying LRCH_INDEX. However, the order of the CQI should enable the base station to identify the resource INDEX inherently.

As such, the mobile terminal should feedback various types of CQI. In order for the base station to efficiently perform channel sensitive scheduling, it is helpful to receive feedback of all kinds of CQIs, but it uses too much radio resources of the reverse link. In order to solve this problem, the base station according to the present invention effectively controls radio resources of the reverse link used for CQI feedback, and the mobile terminal according to the present invention can selectively feed back CQI information to help increase system capacity. Suggest a method.

Hereinafter, an apparatus and method for feeding back CQI information according to the present invention will be described. First, it is assumed that CQI feedback is transmitted through a reverse link non-orthogonal channel. The base station controls the transmission power of the mobile terminal through the Rote (Rise of Thermal) control. That is, the base station controls the RoT by instructing whether or not to raise or lower the TPR of the mobile terminal. The mobile terminal determines the transmission power according to the TPR command of the base station. The mobile terminal uses the remaining power for CQI feedback transmission except for the power required to transmit the basic channel.

In general, since the mobile station cannot feed back all CQI information with the allowed power, the mobile station selects and feeds back CQI information that is worth notifying the base station within the allowed power limit. Since the mobile terminal can measure the CQI of all resources, it is possible to determine which resource has a good channel state and can receive more data if the corresponding resource is allocated. For example, if there are N LRCHs and a specific LRCH is determined to have the highest CQI, the mobile station may receive more data than the other LRCH is allocated to the LRCH. Therefore, it is appropriate for the mobile terminal to perform CQI information selection that is worth notifying the base station.

3 illustrates an embodiment in which a mobile station adjusts a CQI feedback amount according to TPR control of a base station according to the method proposed by the present invention. Reference numeral 400 is a transmission power of a pilot or training signal transmitted from the base station. Since the reverse link non-orthogonal channel is power controlled, the transmission power of a pilot or training signal is controlled by power control. Therefore, the transmission power of the pilot or training signal is variable according to the power control command of the base station. In FIG. 3, the transmission power of the pilot or training signal is shown as a constant value for convenience. Reference numerals 401, 403, and 405 denote allowable TPR and are adjusted by TPR control of the base station. When the base station issues a command to increase the TPR as shown by reference numeral 402 in the allowed TPR of reference numeral 401, the mobile station increases the allowed TPR to the TPR of reference numeral 403.

In the next step, if the base station issues a command to reduce the TPR as shown by reference numeral 404, the mobile station decreases the allowed TPR from the TPR of the reference numeral 403 to the TPR of the reference numeral 405. Each mobile station for which an allowable TPR is determined selects and feeds back CQI information that is valuable to inform the base station within an allowed power limit. If the allowable TPR is 401, the channel 410 and the CQI channel 411 are transmitted. Here, the channel 410 shows basic channels. The remaining power is used for CQI feedback transmission except for the power required to transmit the channel 410.

The mobile terminal determines that the feedback of the CQI_A of the resource corresponding to the INDEX_A is the highest priority among the various CQIs. It is possible to feed back CQI_A within the limits of the allowable TPR 401, but not to feed back additional CQI information. For this reason, this step transmits only the channel 410 and the CQI_A channel 411. In the next step, the base station issues a command to increase the TPR as shown by reference numeral 402 so that the allowed TPR is referred to by reference numeral 403. In this case, the amount of information transmitted by the basic channel increases, so that the TPR of reference number 420 increases from the TPR of 410. The mobile terminal has determined that among the various CQIs, the priority of CQI_B of the resource corresponding to INDEX_B has the highest priority, and that the CQI_C of the resource corresponding to INDEX_C has the next priority. It is possible to feedback CQI_B and CQI_C within the limits of the allowable TPR 403, but not to feed back additional CQI information. For this reason, in this step, only the channel 420 and the CQI_B and CQI_C channels 421.422 are transmitted. In the next step, the base station issues a command to reduce the TPR as shown at 404 so that the allowed TPR is as shown at 405.

Although the allowable TPR decreased from reference numeral 403 to reference numeral 405, the amount of information transmitted by the basic channel was further reduced, so that the TPR of reference numeral 430 was lower than that of reference numeral 420 or 410. The mobile terminal has determined that among the various CQIs, the priority of CQI_D of the resource corresponding to INDEX_D has the highest priority, and the CQI_E of the resource corresponding to INDEX_E has the next priority. It is possible to feedback CQI_D and CQI_E within the limits of the allowable TPR 405, but not to feed back additional CQI information. For this reason, in this step, only the channel 420 and the CQI_D and CQI_E channels 431 and 432 are transmitted.

In the embodiment shown in FIG. 3, CQI_A, CQI_B, CQI_C, CQI_D, and CQI_E may be any one of DRCH_SISO_CQI, LRCH_SISO_CQI, DRCH_MIMO_CQI, LRCH_MIMO_CQI, and need not be the same.

4 is a block diagram of a base station according to an embodiment of the present invention. The base station according to the embodiment of the present invention includes a RoT measuring unit 500, a wireless unit 502, and a controller 504.

The RoT measuring unit 500 measures the RoT and reports it to the control unit 504 to measure the amount of interference experienced by the base station. The wireless unit 502 performs filtering and transmission power adjustment, and converts the baseband signal into a high frequency signal or converts the high frequency signal into a baseband signal and transmits the same to the control unit 504. In particular, according to an embodiment of the present invention, after receiving the CQI received from the mobile terminal and down-converted, it is transmitted to the control unit 504 or transmits a TPR increase or decrease command determined under the control of the control unit 504 through an antenna. In addition, if a reverse link is received from the mobile terminal, the downlink signal received on the reverse link is transmitted to the control unit 504.

The controller 504 compares the RoT value measured by the RoT measuring unit 500 with a preset reference value, and if the measured RoT value is smaller than the preset reference value, the controller 504 increases the TPR through the wireless unit 502. Controls the sending of commands. On the other hand, if the measured RoT value is larger than the preset reference value, the wireless unit 502 controls to transmit a command to reduce the TPR.

In addition, if the reverse link signal is received from the mobile station, it is checked whether the CQI of the specific index is detected by checking whether the CQI for the corresponding resource is fed back, and if the CQI is fed back, the CQI information is reflected in scheduling and AMC, If not fed back, the resource of the index is excluded from scheduling or the old CQI is used.

5 is a flowchart illustrating a TPR command determination of a base station according to an embodiment of the present invention. The base station measures RoT indicating the amount of interference experienced by the base station in step 601. In step 602, the base station compares the RoT measured in step 601 with a predefined threshold. If the RoT is less than the reference value, the base station moves to step 603 and transmits a command to increase the TPR (TPR up). If the RoT is greater than the reference value, the base station moves to step 604 to decrease the TPR (TPR down). Send the command.

6 is a block diagram of a mobile terminal according to an embodiment of the present invention. The mobile terminal according to an exemplary embodiment of the present invention includes a radio unit 700, a TPR command interpreter 702, a controller 704, and a CQI message constructing unit 706.

First, the wireless unit 700 performs filtering and transmission power adjustment, and converts a baseband signal into a high frequency signal or converts a high frequency signal into a baseband signal and transmits the same to the control unit 704. In particular, according to an embodiment of the present invention, after receiving the TPR command and the power control command received from the base station, down-converted and transmitted to the control unit 704 or the CQI message, pilot, and basic channel configured under the control of the control unit 704, Send to the base station through. The TPR command analysis unit 702 calculates the allowable TPR by interpreting the TPR command received by the control unit 704 by the control. The allowable TPR may be converted into an amount of transmit power authorized by the mobile station by the TPR value allowed by the base station. Since the pilot or training signal is already power controlled, the power of other signals can be calculated by the transmission power of the pilot or training signal and the TPR allowed by the base station. Higher allowable TPR means that the mobile terminal can transmit signals to the base station at higher power.

The control unit 704 controls the TPR command analyzing unit 702 or interprets the TPR and power control command received through the wireless unit 700 to calculate the allowable TPR, or determines the pilot transmission power. It also controls the CQI message constructing unit 706 to construct the CQI message by measuring the CQI, and gives priority to the CQI message within the allowed TPR.

The CQI message constructing unit 706 configures the CQI message according to the CQI of each resource measured by the control unit 704 under the control of the control unit 704.

7 illustrates a flowchart of generating a backward transmission signal including a CQI feedback signal in a mobile terminal according to an embodiment of the present invention.

First, in step 802, the mobile station receives a TPR command and a power control command transmitted by the base station through the process described with reference to FIG. In step 804, the mobile terminal interprets the TPR command to interpret the allowed TPR. In step 806, the mobile terminal interprets the power control command to determine pilot transmission power. In step 808, the mobile station determines the power required to transmit another reverse base channel.

In step 810, the mobile station configures a CQI message by measuring the CQI of each resource. In step 812, the mobile terminal prioritizes the CQI message configured in step 810. In addition, since the mobile station selects to feed back only the high priority CQI information within the TPR limit allowed in step 814, the mobile terminal prioritizes the CQI message. Finally, in step 816, the mobile terminal generates a transmission signal by collecting a pilot, a basic channel, a CQI message, and the like to transmit to the base station.

8 is a flowchart illustrating a method of receiving CQI feedback information at a base station according to an embodiment of the present invention.

First, in step 900, the base station receives a reverse link signal transmitted by the mobile terminals. In step 902, the base station detects CQI information of a specific INDEX and determines whether the CQI of the corresponding resource is fed back. If the CQI of the corresponding resource is detected, in step 906, the CQI information of the specific INDEX is restored and the value is used in scheduling and AMC. However, if the CQI of the corresponding resource is not detected in step 902, the mobile terminal excludes the resource of the INDEX from the scheduling in step 904 or uses the previously restored CQI value.

The former method, that is, the method of excluding a resource of the INDEX from the scheduling, determines that the CQI of the resource is not transmitted because the mobile terminal does not prefer to allocate the resource of the INDEX. The latter method, that is, the method using the previously restored CQI value in order to consider the resources of the INDEX in scheduling, is that the MS transmits the CQI to allocate the resources of the INDEX but the base station has not received it. The next best thing is to use the previously restored CQI value. Utilizing the previously restored CQI value at step 906 may degrade the performance of AMC and channel sensitive scheduling, if the previous CQI value is too long to assume that the channel has already changed. Since steps 904 and 906 have advantages and disadvantages, each of operations 904 and 906 may be selected from two if the CQI of a specific resource is not received.

FIG. 9 is a block diagram for generating a CQI channel in a mobile terminal according to an embodiment of the present invention. The CQI message constructing unit 706 of FIG. 6 is shown in detail.

The mobile terminal measures the CQI for each resource in step 810 of FIG. 7 and configures a CQI message. Reference numerals 1001, 1002, and 1003 denote a plurality of CQI messages configured as described above.

Reference numeral 1001 denotes a message indicating that the CQI for a resource designated by INDEX_A is CQI_A. Likewise, reference numerals 1002 and 1003 are CQI messages for resources designated by INDEX_B and INDEX_C, respectively. The CQI messages are orthogonal encoded or bi-orthogonal encoded by orthogonal encoding or bi-orthogonal encoders 1004, 1005,... 1006, respectively.

The CQI codewords encoded by the orthogonal encoding or bi-orthogonal encoders 1004, 1005, .., 1006 are converted to 0 by +1 in the signal point mappers 1007, 1008,. The signal conversion process to 1 is performed.

Meanwhile, when configuring a CQI channel, according to step 814 of FIG. 7, the priority of the allowed TPR and the CQI of each resource is transferred from the controller 704 to the switches 1011, 1012,..., 1013, as shown by reference numeral 1010. Is entered. The controller 704 determines whether the CQI messages 1001, 1002, and 1003 are transmitted according to the priority of the allowed TPR and the CQI. The switches 1011, 1012, and 1013 pass only the CQI for which the CQI feedback is determined by the controller 704. The CQI messages determined to be transmitted are added together in the adder 1014 to proceed to multiplexing with other channels not shown.

In the present invention, the reason for proposing orthogonal coding or bi-orthogonal coding (1004, 1005, 1006) as the CQI coding method is as follows.

A plurality of CQI messages indicating CQIs of different resources are added together and transmitted. Therefore, CQI codewords should be able to be decoded even if they are added together and there should be no performance degradation. In order to satisfy this condition, the CQI codewords have to satisfy orthogonal characteristics. An encoding method satisfying this condition is an orthogonal encoding method. Bi-orthogonal coding can also be used as the CQI coding. This is because a plurality of CQI messages to be added are CQIs of different resources, so that the INDEX needs to satisfy orthogonality between different codewords. In other words, bi-orthogonal coding has the characteristic that INDEX is orthogonal between different codewords unless the input bit used for XOR (exclusive OR) and each bit of an orthogonal codeword is selected in INDEX.

Accordingly, according to the present invention, there can be provided an apparatus and method for effectively controlling the radio resources of the reverse link used for CQI feedback in a mobile communication system and allowing the mobile terminal to selectively feed back CQI information to help increase system capacity. have.

The base station quickly controls radio resources of the reverse link through TPR control according to the load state of the reverse link. Since the mobile station selects and feeds back a CQI having a high priority within the allowable TPR limit, the amount of radio resources used for CQI feedback in the reverse link can be reduced. That is, if the load of the reverse link is large, the amount of CQI information fed back by the mobile terminal is reduced, thereby reducing the amount of radio resources occupied by the CQI feedback. On the other hand, if the load of the reverse link is low, more CQI feedback is allowed to the mobile station, thereby improving performance of AMC and channel sensitive scheduling, thereby increasing system capacity.

That is, the present invention can provide an apparatus and method capable of adaptively adjusting the amount of CQI feedback according to a reverse link load situation.

Claims (11)

A base station for receiving feedback of a channel quality indicator of a mobile terminal in a mobile communication system, RoT measuring unit for measuring the rise over thermal value to measure the power control and interference amount of the mobile terminal, The wireless unit receives the channel quality indicator from the mobile terminal and transmits a traffic to pilot ratio command to control the feedback of the channel quality indicator of the mobile terminal to the mobile terminal. Wow, The rise over thermal value measured by the RoT measurement unit is compared with a preset threshold value to transmit the traffic to pilot ratio command, and AMC and channel sensitive scheduling is performed based on the received channel quality indicator. And a control unit for performing the feedback of the channel quality indicator in the mobile communication system. According to claim 1, And the controller transmits a traffic-to-pilot ratio increase command when the rise over thermal value is less than the threshold value. According to claim 1, And the control unit transmits a traffic-to-pilot ratio reduction command when the rise over thermal value is greater than the threshold value. A mobile terminal for feeding back a channel quality indicator of a mobile terminal in a mobile communication system, A traffic-to-pilot radio command interpreter for interpreting a traffic-to-pilot radio (TPR) command received from the base station; A channel quality indicator message constructing unit for generating at least one channel quality indicator to be transmitted to the base station according to the traffic to pilot ratio command; And a controller configured to select priorities of channel quality indicators to be transmitted to the base station based on a result of the traffic-to-pilot radio command interpreter, and to generate at least one channel quality indicator according to the selected priority. And feeding back a channel quality indicator in a mobile communication system. The method of claim 4, wherein The channel quality indicator configuration unit, An orthogonal encoder for orthogonally encoding channel quality indicators and outputting codewords; A signal point mapper for signal-converting the orthogonal coded codeword; And a switch for overlapping and outputting only one or more indicators of which feedback is determined among the channel quality indicators output from the signal point mapper according to the priority of the allowed traffic to pilot ratio information and the channel quality indicator from the control unit. And an apparatus for feeding back a channel quality indicator in a mobile communication system. A method for a base station of a mobile communication system to receive feedback of a channel quality indicator of a mobile terminal, Measuring a rise over thermal value to measure power control and interference of the mobile terminal; Comparing the measured rise over thermal value with a preset threshold value; And transmitting a traffic-to-pilot radio command for controlling channel quality indicator feedback information to be transmitted by the mobile station based on the comparison result. The method of claim 6, The process of transmitting the traffic to pilot race command, And transmitting a traffic to pilot ratio increase command when the rise over thermal value is less than the threshold value. The method of claim 6, The process of transmitting the traffic to pilot race command, And transmitting a traffic-to-pilot ratio reduction command when the rise over thermal value is greater than the threshold value. A method for a mobile terminal of a mobile communication system to feed back a channel quality indicator to a base station, the method comprising: Receiving a traffic to pilot ratio command and a power control command from the base station; Calculating an allowable traffic to pilot ratio based on the received traffic to pilot ratio command; Determining a power required for transmitting a reverse base channel different from a pilot transmission power based on the power control command; Configuring at least one channel quality indicators by measuring channel quality of each resource; Determining a priority of the channel quality indicator and transmitting at least one channel quality indicator having a high priority according to the allowed traffic-to-pilot ratio to transmit to the base station. Method for feeding back the channel quality indicator. A method for a base station of a mobile communication system to receive feedback of a channel quality indicator of a mobile terminal, Receiving a reverse link signal from the mobile terminal; When the reverse link signal is received, checking whether a channel quality indicator of a specific index is fed back; Restoring the channel quality indicator if the channel quality indicator information of the specific index is fed back; And performing scheduling and adaptive modulation and coding (AMC) on the basis of the reconstructed channel quality indicator. The method of claim 10, If the channel quality indicator of the particular index has not been fed back, Excluding a resource of the index from the scheduling; and feeding back a channel quality indicator in a mobile communication system.

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