KR101492542B1 - An apparatus and method for allocating wireless resource of telecommunication system using carrier aggregation - Google Patents

Abstract

An apparatus for allocating a wireless resource of a mobile communications system using carrier aggregation according to the present invention includes: a data transmission unit for transmitting downlink data to a terminal in a primary cell (Pcell) and secondary cell (Scell); a channel quality indicator (CQI) reception unit for receiving a CQI measured on the Scell from terminal, a wireless resource allocation unit for allocating a wireless resource block for the downlink data transmission on the Pcell and Scell set between the terminal and the data transmission unit; and a controller for reducing the wireless resource allocated to the terminal from the Scell while maintaining a channel with the terminal in the Scell, if the CQI of the received Scell is equal to or lower than the set CQI threshold.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a radio resource allocation apparatus and a method for allocating radio resources in a mobile communication system using a carrier wave,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for allocating radio resources in a mobile communication system and, more particularly, to a system and method for allocating radio resources in a mobile communication system for transmitting downlink data to a mobile station using a carrier wave, And more particularly, to a radio resource allocation apparatus and method capable of increasing the utilization of radio resources of a mobile station.

Long Term Evolution Advanced (LTE-A) system is suitable for IMT-Advanced condition of 4th generation mobile communication recommendation of LTE system in ITU-R (International Telecommunication Union - Radiocommunication sector) , And LTE-A system is defined in 3GPP that developed LTE system standard.

In LTE system, communication service is provided using 20MHz band. In LTE-A system, Carrier Aggregation (CA) technology is adopted to support a wider bandwidth than existing 20MHz.

Carrier aggregation technology is to integrate component carriers (CCs) of several frequency bands into one, so that data can be transmitted over a wider frequency band.

In the LTE-A system using the carrier aggregation technique, the terminal accesses the base station 10 via a Pcell (Primary Cell) 14 including a primary frequency band, and simultaneously transmits a Scell (Secondary Cell, 12) to receive data of Pcell and Scell.

In the case of using the carrier aggregation technique as described above, the UE can be included in both the Pcell and the Scell, but it is technically difficult to completely establish the coverage of the Pcell and the Scell that the BS has.

For example, when the terminal is connected to the Pcell 14 in the 850 MHz band and the Scell 12 in the 1.8 GHz band, the path loss is increased as the frequency increases, the difference in the beam width of the antenna transmitting the RF signals in each frequency band, The coverage 12 of the Scell may be narrower than the coverage 14 of the Pcell for various reasons such as concentration of traffic in one frequency band during traffic processing on the base station 10, .

In this way, when the coverage 14 of the Pcell is different from the coverage 12 of the Scell, the handover according to the movement of the terminal is generally determined according to the signal state of the Pcell.

The handover procedure is briefly described. The mobile station measures the signal strength of the Pcell and reports it to the source base station. The source base station compares the signal strength with a predetermined reference value, and when it is determined that the radio environment is bad, Can be requested.

At this time, handover is performed to the target base station by sending a handover acceptance message to the source base station at the target base station.

Since only the signal intensity of the Pcell is considered in the handover process as described above, when the signal intensity of the Pcell is normal but the signal intensity of the Scell is weak, the handover is not performed and the terminal transmits the weak signal of the Scell paired with the Pcell Should be used as is.

In the conventional mobile communication system, even if the strength of the signal received by the terminal in the Scell is weak, the base station 10 allocates a radio resource (Resource Block) to both the Pcell and the Scell to receive the downlink data in the terminal Respectively.

In this case, since the actual signal strength is weak, it is not helpful to improve the transmission rate through the carrier set, but the radio resources are allocated to the Scell as they are, so that the utilization of the radio resources can not be reduced.

In addition, the transmission resources that can be allocated to other terminals receiving the downlink data in the corresponding scell must be reduced so much that there is a fear that the transmission rate of the entire scell controlled by the base station 10 may be greatly reduced.

It is an object of the present invention to solve the above problems and to provide a mobile communication system that utilizes carrier aggregation to consider the signal quality of data transmitted to a terminal through a Scell and the utilization rate of a transmission resource of a base station The present invention provides a radio resource allocation apparatus and a radio resource allocation method capable of maximizing use efficiency of radio resources and improving overall transmission speed of a terminal in a scell by adjusting transmission resources allocated to terminals in Scell.

According to a first aspect of the present invention, there is provided an apparatus for allocating radio resources in a mobile communication system using a carrier aggregation, the apparatus comprising: means for transmitting downlink data to a terminal in a primary cell (Pcell) A data transfer unit; A CQI receiver for receiving a CQI (Channel Quality Indicator) measured on the Scell from the terminal; A radio resource allocator allocating a radio resource for downlink data transmission on a channel of the Pcell and a channel of the Scell set between the terminal and the data transmission unit; And a controller for decreasing a radio resource allocated to the terminal in the Scell while maintaining a channel with the terminal in the Scell when the CQI of the received Scell is less than or equal to a preset CQI threshold Can be achieved.

Here, when the CQI of the Scell is maintained below the CQI threshold for a predetermined time or longer, the controller may reduce the radio resources allocated to the terminal in the Scell.

Here, if the CQI of the Scell is less than or equal to the CQI threshold, the controller may control the Scell to transmit downlink data to the terminal through the Pcell without allocating the radio resource to the terminal.

Here, if the CQI of the received Scell is less than or equal to the CQI threshold and the usage rate of the radio resource allocated by the radio resource allocator is equal to or greater than a preset cell load threshold, Can be reduced.

Here, the controller may decrease the CQI of the Scell to be greater than the CQI threshold or decrease the usage rate of the radio resource allocated by the radio resource allocator to the cell load If it is decreased below the threshold value, the scell may increase the radio resources allocated to the terminal.

Here, the usage rate of the radio resources can be determined by measuring PRB (Physical Resource Block) or BO (Buffer Occupancy) for a predetermined time.

Here, the controller may schedule a radio resource allocation for the MS using a PF (Proportional Fair) technique.

According to a second aspect of the present invention, there is provided a method of allocating radio resources in a mobile communication system using a carrier aggregation, comprising the steps of: Allocating a radio resource (Resource Block) for transmitting downlink data to the mobile station; Receiving a measured CQI (Channel Quality Indicator) on the Scell from the terminal; Determining whether a CQI of the Scell is less than or equal to a preset CQI threshold; And reducing a radio resource allocated to the UE in the Scell while maintaining a channel with the UE in the Scell if the CQI is less than or equal to the CQI threshold.

The checking whether the CQI of the Scell is less than or equal to the CQI threshold may include checking whether the CQI of the Scell is maintained below the CQI threshold for a predetermined time or longer.

The step of reducing the radio resources allocated to the UE in the Scell may include not allocating the radio resource to the UE in the Scell, and transmitting downlink data to the UE through only the Pcell As shown in FIG.

If the CQI of the received Scell is less than or equal to the CQI threshold, checking whether a usage rate of the currently allocated radio resource is equal to or greater than a predetermined cell load threshold, Reducing the radio resources allocated to the UE in the Scell if the usage rate of the radio resource is equal to or greater than the cell load threshold.

Here, after reducing the radio resources allocated to the UE in the Scell, if the CQI of the Scell is increased to exceed the CQI threshold or the usage rate of the radio resources allocated by the radio resource allocator is decreased below the cell load threshold ≪ / RTI > And increasing a radio resource allocated to the UE in the Scell if the CQI of the Scell is increased beyond the CQI threshold or the usage rate of radio resources allocated by the radio resource allocator is reduced below the cell load threshold Step < / RTI >

According to a third aspect of the present invention, there is provided a radio resource allocation method for a mobile communication system using a carrier aggregation, the method comprising: detecting a signal of a scell in a mobile station; Forming a channel on the scell with the terminal; Initiating transmission of downlink data by allocating radio resources on the Scell with the terminal; Measuring and transmitting a CQI (Channel Quality Indicator) of a signal transmitted from the Scell to the terminal by the terminal; Determining whether a CQI of the Scell is less than or equal to a preset CQI threshold; And reducing the allocated radio resource while maintaining the channel on the Scell if the CQI threshold is less than or equal to the CQI threshold.

The method of claim 1, further comprising: if the CQI of the received Scell is less than or equal to the CQI threshold, checking whether a usage rate of a currently allocated radio resource is equal to or greater than a preset cell load threshold, And reducing the radio resources allocated to the UE in the Scell if the utilization rate of the resources is equal to or greater than the cell load threshold.

Here, after reducing the radio resources allocated to the UE in the Scell, if the CQI of the Scell is increased to exceed the CQI threshold or the usage rate of the radio resources allocated by the radio resource allocator is decreased below the cell load threshold ≪ / RTI > And increasing a radio resource allocated to the UE in the Scell if the CQI of the Scell is increased beyond the CQI threshold or the usage rate of radio resources allocated by the radio resource allocator is reduced below the cell load threshold Step < / RTI >

According to the present invention, in a mobile communication system utilizing Carrier Aggregation, considering a signal quality of data transmitted to a terminal through a Scell and a utilization rate of a transmission resource of a base station managing a Scell, It is possible to provide a radio resource allocation apparatus and a radio resource allocation method capable of maximizing the use efficiency of radio resources and improving the overall transmission speed of a terminal in a Scell by adjusting allocated transmission resources.

FIG. 1 illustrates the coverage difference of each cell in a conventional mobile communication system.
2 is a block diagram of a radio resource allocation apparatus according to the present invention.
3A to 3C illustrate respective embodiments of a control method of a radio resource allocation apparatus in a case of a decrease in signal quality.
4 is a flowchart of a radio resource allocation method according to the present invention.

It is noted that the technical terms used herein are used only to describe specific embodiments and are not intended to limit the invention. It is also to be understood that the technical terms used herein are to be interpreted in a sense generally understood by a person skilled in the art to which the present invention belongs, Should not be construed to mean, or be interpreted in an excessively reduced sense. Further, when a technical term used herein is an erroneous technical term that does not accurately express the spirit of the present invention, it should be understood that technical terms that can be understood by a person skilled in the art are replaced. In addition, the general terms used in the present invention should be interpreted according to a predefined or prior context, and should not be construed as being excessively reduced.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals refer to like or similar elements throughout the several views, and redundant description thereof will be omitted. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. It is to be noted that the accompanying drawings are only for the purpose of facilitating understanding of the present invention, and should not be construed as limiting the scope of the present invention with reference to the accompanying drawings. The spirit of the present invention should be construed as extending to all modifications, equivalents, and alternatives in addition to the appended drawings.

2 is a block diagram of an apparatus 100 for allocating radio resources in a mobile communication system according to the present invention.

1, the radio resource allocation apparatus 100 includes a data transmission unit 110, a CQI reception unit 120, a radio resource allocation unit 130, and a control unit 140.

The mobile communication system according to the present invention may be configured as an LTE-Advanced (LTE-A) system using Carrier Aggregation. The radio resource allocation apparatus 100 is provided in the base station side, A radio channel setting between the base station and the base station, and a radio resource allocation for downlink data transmission.

In the LTE-A system, a carrier wave that can be used in a conventional LTE (Long Term Evolution) system is defined as a component carrier (CC), and the element carrier waves are theoretically combined to increase the data transmission rate by the number of element carriers The system is configured to allow.

A cell that controls the band of the primary component carrier wave is defined as Pcell (Primary Cell), and a cell that controls the band of the secondary component carrier is defined as Scell (Secondary Cell) among a plurality of component carriers. One of the frequency bands can be determined as Pcell, and the remaining bands can be determined as Scell.

Although one base station can be connected to a terminal 200 through one cell and a plurality of scelles, it is assumed herein that only one cell and one scell are used.

For example, the Pcell can use the 850 MHz band and the Scell can use the 1.8 GHz band, and the element carrier of each cell can have a bandwidth of 10 MHz.

On the other hand, due to the coverage difference between the Pcell and the Scell, the Pcell signal is normally received at the terminal 200 in a certain region, but the signal of the Scell is a weak signal containing a large amount of interference and noise Lt; / RTI >

This is because the handover of the terminal in the LTE-A system is determined based on the signal strength of the Pcell.

The data transmission unit 110 transmits downlink data to the terminals 200 in the Pcell (Primary Cell) and the Scell (Secondary Cell).

As a precondition for transmitting the downlink data to the terminal 200 using the Pcell and the Scell in the data transmission unit 110, the wireless channel setting and the radio resource allocation in the Pcell and the Scell are required.

When the terminal 200 first attempts to connect with the radio resource allocation device 100, the terminal 200 is connected to the terminal 200 through the Pcell. When the terminal 200 detects the signal of the scell and reports the signal, 200 may be connected to a Scell to set up a channel (ADD), allocate a resource block (RB) as a radio resource, and activate the Scell.

In this case, as in the conventional LTE system, the terminal 200 may be connected only to the Pcell and receive downlink data using only the frequency bandwidth of the Pcell (for example, 10 MHz) And receive downlink data using the respective bandwidths.

A specific example of detecting a Scell, setting a channel on a Scell, and allocating radio resources while the terminal 200 is connected to the Pcell will be described later in more detail with reference to FIGS. 3A to 3C.

Meanwhile, the data transmission unit 110 transmits downlink data to the terminal 200 according to an OFDM (Orthogonal Frequency Division Multiplexing) scheme in which data is transmitted in parallel through a plurality of subcarriers orthogonal to each other .

The terminal 200 includes a mobile communication module (not shown), a Wi-Fi (Wireless LAN), a Wimax (World Interoperability for Microwave Access), HSDPA (Not shown), a user input module (not shown), a display module (not shown), and the like, for receiving a user's key input for operating the terminal 200 But it is not limited to a specific implementation.

The CQI receiver 120 receives the measured CQI information from the terminal 200.

The CQI (Channel Quality Indicator) is an index indicating the quality of the downlink channel between the terminal 200 and the base station. The terminal 200 periodically measures the quality of the channel and transmits the CQI information to the radio resource allocation device 100 to the CQI receiving unit 120 of FIG.

The CQI information may be generated based on the SINR (Signal to Interference Ratio) value of the downlink signal received by the terminal 200 on the channel of the Pcell and / or the Scell, And the terminal may transmit the CQI generated based on the SINR value to the radio resource allocation device 100 through the uplink control channel.

As described above, in the LTE-A using the carrier aggregation technique, the inter-base station handover of the terminal 200 can be based on the Pcell only, even though the coverage of the Pcell and the Scell are different.

For this reason, as a result of experiments using LTE-A in a certain area, the Pcell can maintain the quality of the radio wave at a certain level or higher because the handover is performed to the target base station located in the neighbor when the quality of the radio wave is weak , And the rate of SINR dropping below 0 dB was measured to be very low, less than 2%.

However, in the case of the Scell, the SINR is 0dB or less, that is, the region where the negative value is 9% or more, which is very high because the handover is not performed even if the scell signal is weak.

The radio resource allocation unit 130 allocates radio resources for downlink data transmission on a channel of a Pcell and a channel of a Scell set between the terminal 200 and the data transmission unit 110.

In the present invention, a radio resource may refer to a resource block (RB). The resource block is a combination of time and frequency resources required for data transmission from the base station to the mobile station 200, and typically includes 12 subcarriers a sub-carrier and 6 to 7 data symbols.

The maximum value of the resource blocks that can be simultaneously allocated by the base station is limited and the amount of data requested by the terminal 200 connected to the number of the terminals 200 simultaneously connected to the base station is greatly increased or decreased A scheduling technique for allocating radio resources is required.

The scheduling technique may be a PF (Proportional Fair) scheme in which radio resources are fairly allocated according to the ratio of the average transmission rate and the current channel state of the terminal 200 to the traffic of all the terminals 200 connected thereto .

The control unit 140 controls radio resource allocation for each terminal 200 connected to the Pcell and the Scell in the radio resource allocation apparatus 100 and may be configured as a PF (Proportional Fair) scheduler.

As described above, due to the difference in coverage between the Pcell and the Scell, even if the same radio resource is allocated in the radio resource allocator 130, in the case of the terminal 200 located in a region where the signal quality of the Scell is low, The effect of improving the data transmission rate can not be obtained, and the limited radio resources can be wasted.

If the CQI of the signal transmitted to the terminal on the Scell is lower than the preset CQI threshold, the control unit 140 decreases the radio resource allocated to the terminal 200 in the Scell while maintaining the channel with the terminal 200 in the Scell .

In this case, the CQI threshold can be determined by the quality of the received signal, that is, the CQI value when the SINR is equal to or less than 0 dB. If the CQI received from the terminal 200 is equal to or less than the CQI threshold, It can be judged that the quality of the cursor channel is considerably degraded.

Meanwhile, since the CQI of the terminal 200 can be dynamically increased or decreased in the vicinity of the CQI threshold according to the movement of the terminal 200, the controller 140 refers to the received CQI information, If the CQI is maintained below the CQI threshold, the radio resource allocated to the terminal 200 in the Scell can be reduced.

Here, the predetermined time may be appropriately set to 1 second to 10 seconds depending on the radio environment of the base station.

When the control unit 140 reduces the radio resources, it is possible to reduce the radio resources according to the respective intervals with a plurality of intervals according to the CQI value.

For example, when the SINR of the Scell determined through the received CQI is 10 dB or less, only 50% of the resource blocks allocated in the case where the signal quality of the Scell is normal is assigned to the terminal 200, and when SINR is 0 dB or less And may not allocate a resource block when measured for a predetermined time.

In another embodiment, when the CQI is maintained for a predetermined time period below the CQI threshold, downlink data can be transmitted to the terminal only through the Pcell without allocating radio resources to the terminal in the Scell.

On the other hand, when there is a margin of radio resources that can be allocated to the Scell, that is, when other terminals in the base station perform communication that does not require a lot of traffic such as simple web surfing, chatting, voice call, It will not affect the communication quality of the other terminal 200 due to the lack of radio resources without reducing the allocated radio resources.

Accordingly, when the CQI received from the MS 200 is less than or equal to the CQI threshold, the controller 140 determines whether the usage rate of the radio resource allocated by the radio resource allocator 130 is equal to or greater than a predetermined cell load threshold.

As a result of the determination, if the cell load is equal to or greater than the cell load threshold, the scaling reduces radio resources allocated to the mobile station 200, and if the received CQI is below the CQI threshold, Scell can allocate radio resources.

Here, the cell load threshold value may be expressed as a percentage of a predetermined radio resource utilization rate, and may be determined as a value of 30% or 40% depending on the environment of the base station.

In this case, the control unit 140 can determine a usage rate of radio resources by measuring a PRB (Physical Resource Block) or a BO (Buffer Occupancy) for a predetermined time.

For example, if the SINR is less than 0 dB and the PRB usage rate is more than 40%, the Scell may not allocate radio resources. If the SINR is less than 0 dB and the PRB usage rate is more than 30% Scell may not allocate radio resources.

After the CQI of the Scell is increased to exceed the CQI threshold or the usage rate of the radio resource allocated by the radio resource allocator 130 is higher than the cell the mobile station 200 can increase the radio resources allocated to the mobile station 200 in the Scell again.

In this case, since the channel with the base station remains on the Scell, the downlink data can be transmitted using the Scell without a separate Scell search and RRC connection process.

Hereinafter, a more specific embodiment of the present invention will be described with reference to Figs. 3A to 3C.

3A to 3C are diagrams illustrating a method of detecting a scell in a state in which a terminal 200 is connected to a base station via a Pcell and then connecting to a Scell. The operation of the allocating apparatus 100 is described.

3A shows an embodiment in which radio resources allocated to the Scell are maintained as they are even if the CQI of the received Scell decreases.

When the terminal 200 makes a data transmission request, it can access only the first Pcell (3a-1).

At this time, when the terminal 200 detects a signal of a scell, it transmits a connection request to the base station, thereby adding a scell and connecting it.

The process of the terminal 200 accessing the Scell on the LTE-A system is defined by the RRC layer (Radio Resource Control). The RRC layer is located at the top of the third layer on the OSI reference model and is defined only in the control plane , And controls logical channels, transport channels, and physical channels in connection with setting, resetting, and releasing the radio bearer.

The terminal 200 can perform a RRC connection with a Scell through which a signal is detected through a cell selection, form a radio channel with the base station on the Scell, and enter a service standby state such as RRC_IDLE.

When the MS 200 and the BS form a radio channel through the RRC connection, the BS then allocates radio resources for transmitting downlink data, which is defined by the MAC layer.

The MAC layer can activate or deactivate the transmission of the downlink data through the Scell by allocating the radio resources to the Scell connected to the RRC.

When a scell is activated by forming a channel by connecting to the Scell described above and allocating radio resources necessary for data transmission, the base station can simultaneously transmit the data of the Pcell and the Scell to the terminal 200 (3a-2).

At this time, when the CQI measured by the Scell is lower than the predetermined CQI threshold due to the handover depending on the Pcell, in this embodiment, the radio resources allocated on the Scell are maintained (3a-3).

As described above, the CQI (Channel Quality Indicator) is an index indicating the quality of the downlink channel between the terminal 200 and the base station. The terminal 200 periodically measures the quality of the channel and transmits the CQI information to the uplink control channel To the CQI receiving unit 120 of the radio resource allocation apparatus 100 through the RNC.

In the present embodiment, since the Scell keeps the state of the add and activate, if the CQI increases, that is, the quality of the radio channel of the Scell is improved, a larger amount of data is transmitted to the Scell (3a-4).

However, in the embodiment of FIG. 3A, the allocation of radio resources is maintained even when the CQI of the Scell is low. In this case, even if a large amount of radio resources are allocated, data transmission on the scell is not performed smoothly. The effect of the speed improvement can not be obtained but can also result in wasting limited radio resources

3B shows an embodiment of releasing the connection with the Scell when the CQI of the Scell is decreased as a second embodiment.

In FIG. 3B, the terminal 200 connects to the first Pcell (3b-1), and the Scell signal is detected and connected on the Scell and allocated radio resources to transmit data (3b-2) -1) and (3a-2).

When the CQI of the Scell transmitted from the MS 200 is lowered in the process of transmitting the downlink data through the Pcell and the Scell, the present embodiment releases the connection with the Scell and performs data transmission only by the Pcell (3b-3).

After that, the CQI is increased due to the improvement of the channel quality. In order to connect with the Scell again like 3b-4, the Scell signal is detected and the RRC connection is performed again. It is necessary to perform a process of checking the radio quality of the Scell by leaving a certain period of time between the communication with the Pcell.

If it is checked that the CQI of the Scell is improved again, the terminal 200 must add a Scell to access it, allocate radio resources, and perform an activation process.

In the case of the second embodiment of FIG. 3B, the problem of radio resource waste does not arise. However, the terminal 200 periodically checks the CQI of the Scell by leaving a certain period of time in the process of receiving downlink data from the Pcell, The transmission of the downlink data through the Pcell may be interrupted during the time, and the data transmission speed may be lowered.

FIG. 3C shows an embodiment of reducing the allocation of radio resources while maintaining the channel connected between the Scell and the UE, when the CQI of the Scell is reduced, as the third embodiment.

In FIG. 3C, the terminal 200 connects to the first Pcell (3c-1) and detects a Scell signal and is connected on the Scell, allocates radio resources and transmits data (3c-2) -1) and (3a-2).

In the process of transmitting the downlink data through the Pcell and the Scell by the data transmission unit 110 of the radio resource allocation apparatus 100, the terminal 200 measures the SINR of the signal transmitted from the Scell, and based on the SINR value CQI information and transmits the CQI information to the radio resource allocation apparatus 100.

The PF scheduler 145 reduces the radio resources allocated to the UE 200 in the Scell while maintaining the channel with the UE 200 in the Scell when the CQI of the received Scell is less than or equal to the predetermined CQI threshold.

At this time, as shown in (3c-3), the PF scheduler 145 can transmit downlink data only through the Pcell without allocating radio resources to the corresponding terminal 200 in the Scell.

Thereafter, when the CQI increases again to the CQI threshold or more and it is determined that the communication environment on the Scell has become good, or the number of terminals connected on the Scell decreases, thereby decreasing the radio resource allocation rate, (3c-4) by allocating radio resources to the terminal 200 and activating the scell.

In this embodiment, the RRC connection with the Scell is not released even if the CQI is reduced, as in the first embodiment of FIG. 3A. However, unlike the second embodiment of FIG. 3B, There is no.

In addition, since the allocation of radio resources is reduced with respect to the Scell whose CQI is measured to be low, utilization of the radio resources can be increased for the entire network by utilizing limited radio resources for the other terminals 200. [

Meanwhile, if the CQI of the Scell is less than or equal to the predetermined CQI threshold, the PF scheduler 145 compares the usage rate of the currently allocated radio resource with a preset cell load threshold, and if the CQI is equal to or greater than the cell load threshold, The radio resources allocated to the mobile station can be reduced.

As mentioned earlier, this is because there is room for radio resources that can be allocated to the Scell, that is, the load on the Scell is not high, and it does not affect the overall transmission speed of the network.

According to the above-described radio resource allocation apparatus 100 of the present invention, in the terminal 200 connected to the Pcell and the Scell in the LTE-A system, when the CQI of the Scell is low, As a result, it is possible to reduce unnecessary radio resource allocation waste in the area where the coverage of the pcell and the scell are inconsistent.

4 is a flowchart of a radio resource allocation method according to the present invention.

The mobile communication system according to the present invention may be configured as an LTE-Advanced (LTE-A) system using Carrier Aggregation, and the radio resource allocation apparatus 100 may be provided on the base station side.

The terminal 200 can receive signals of the respective component carrier bands in the area of the Pcell and Scell that the base station manages.

The radio resource allocation apparatus 100 allocates a radio resource for transmitting downlink data to the terminal 200 through a channel formed on the Scell (S110).

Herein, the radio resource may mean a resource block (RB), and the resource block is a combination of time and frequency resources required when data is transmitted from the base station to the mobile station 200, and typically includes 12 sub- carrier and 6 to 7 data symbols.

The radio resource allocation apparatus 100 receives the CQI information from the terminal 200 while transmitting the downlink data to the terminal 200 through the Pcell and the Scell (S120).

The CQI (Channel Quality Indicator) is an index indicating the quality of the downlink channel between the terminal 200 and the base station. The terminal 200 periodically measures the quality of the channel and transmits the CQI information to the radio resource allocation device 100).

The CQI information may be generated based on the SINR (Signal to Interference Ratio) value of the downlink signal received by the terminal 200 on the channel of the Pcell and / or the Scell, And the terminal may transmit the CQI generated based on the SINR value to the radio resource allocation device 100 through the uplink control channel.

As described above, in the LTE-A using the carrier aggregation technique, since handover between the base stations of the mobile station 200 is based on Pcell only, even if the coverage of the Pcell and the Scell are different, when the SINR of the Scell falls to 0 dB or less Handover may not be performed.

Then, the radio resource allocation apparatus 100 receives the CQI measured on the Scell from the UE 200 and determines whether the CQI of the received Scell is less than a preset CQI threshold (S130).

In this case, the CQI threshold can be determined by the quality of the received signal, that is, the CQI value when the SINR is equal to or less than 0 dB. If the CQI received from the terminal 200 is equal to or less than the CQI threshold, It can be judged that the quality of the cursor channel is considerably degraded.

At this time, it is possible to confirm whether the CQI of the Scell is maintained below the CQI threshold for a predetermined time or longer.

This is because the CQI can be dynamically increased or decreased in the vicinity of the CQI threshold in the terminal 200 according to the positional movement of the terminal 200 and a time of about 1 second to 10 seconds is set, It is determined that the quality of the signal is lowered.

When the CQI received from the terminal 200 is equal to or less than the CQI threshold, the radio resource allocation apparatus 100 decreases the radio resources allocated to the terminal 200 in the Scell while maintaining the channel with the terminal 200 in the Scell (S150).

In this case, it is possible to reduce the radio resources according to each section with a plurality of intervals according to the CQI value.

For example, when the SINR of the Scell determined through the received CQI is 10 dB or less, only 50% of the resource blocks allocated in the case where the signal quality of the Scell is normal is assigned to the terminal 200, and when SINR is 0 dB or less And may not allocate a resource block when measured for a predetermined time.

In addition, when the CQI of the Scell is maintained below the CQI threshold for a predetermined time or longer, downlink data can be transmitted to the terminal 200 using only the Pcell without allocating radio resources to the Scell.

Meanwhile, even if the radio resource allocation apparatus 100 according to the present invention reduces the radio resources allocated to the mobile station 200 in the Scell, as described above with reference to FIG. 3C, the channel set through the RRC connection with the Scell is maintained do.

On the other hand, when there is a margin of radio resources that can be allocated to the Scell, that is, when other terminals in the base station perform communication that does not require a lot of traffic such as simple web surfing, chatting, voice call, The communication quality of the other terminal 200 may not be affected due to the lack of radio resources even if the allocated radio resources are not reduced.

Therefore, if the CQI received from the terminal 100 is less than or equal to the CQI threshold, the radio resource allocation apparatus 100 determines whether the usage rate of the radio resource is equal to or greater than a preset cell load threshold (S140) The radio resources allocated to the terminal 200 may be reduced (S150).

Here, the cell load threshold value may be expressed as a percentage of a predetermined radio resource utilization rate, and may be determined as a value of 30% or 40% depending on the environment of the base station.

If the CQI increases again to a level exceeding the CQI threshold in the process of transmitting the downlink data using the reduced radio resources on the scell, or if the cell load on the scell, that is, the radio resource utilization rate decreases below the cell load threshold (S160) The radio resource allocation apparatus 100 can increase the radio resources allocated to the Scell again (S170).

In this case, since the channel between the terminal and the base station is maintained as it is in the Scell, downlink data can be transmitted using a scell without a separate Scell search and RRC connection process.

According to the above-described radio resource allocation method of the present invention, in a terminal connected to a Pcell and a Scell in an LTE-A system, when the CQI of a Scell is low, It is possible to reduce the unnecessary waste of the radio resource allocation for the area where the coverage of the radio resource is inconsistent.

The radio resource allocation method according to an embodiment of the present invention may be implemented in the form of a program command that can be executed through various computer means and recorded in a computer readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the present invention or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

According to the radio resource allocation apparatus and method of the mobile communication system using the carrier set according to the present invention, in a terminal connected to the Pcell and the Scell, if the CQI of the Scell is low, As a result, it is possible to reduce the unnecessary waste of radio resource allocation in the area where the coverage of the pcell and the scell are inconsistent. Therefore, by overcoming the limitations of the existing technology, It is an invention that is industrially applicable because it has enough possibilities of business and can be implemented practically and clearly.

100: Radio resource allocation apparatus 110: Data transmission unit
120: CQI receiving unit 130: Radio resource allocation unit
140: control unit 200:

Claims (15)

1. A radio resource allocation apparatus of a mobile communication system using a carrier aggregation,
A data transmission unit for transmitting downlink data to terminals in Pcell (Primary Cell) and Scell (Secondary Cell);
A CQI receiver for receiving a CQI (Channel Quality Indicator) measured on the Scell from the terminal;
A radio resource allocator allocating a radio resource for downlink data transmission on a channel of the Pcell and a channel of the Scell set between the terminal and the data transmission unit; And
And a controller for decreasing a radio resource allocated to the MS in the Scell while maintaining a channel with the MS in the Scell when the CQI of the received Scell is less than or equal to a preset CQI threshold.
The method according to claim 1,
Wherein,
And decreasing a radio resource allocated to the UE in the Scell if a CQI of the Scell is maintained below the CQI threshold for a predetermined time or longer.
The method according to claim 1,
Wherein,
And controls the Scell to transmit downlink data to the UE through the Pcell without allocating the radio resource to the UE if the CQI of the Scell is less than or equal to the CQI threshold.
The method according to claim 1,
Wherein,
When the CQI of the received Scell is less than or equal to the CQI threshold and the usage rate of the radio resource allocated by the radio resource allocator is equal to or greater than a preset cell load threshold, Device.
5. The method of claim 4,
Wherein,
If the CQI of the scell increases to the CQI threshold or more after the scell has reduced the radio resources allocated to the UE or if the usage rate of the radio resources allocated by the radio resource allocator is reduced below the cell load threshold And increases the radio resources allocated to the MS in the Scell.
The method of claim 3,
Wherein,
Wherein a radio resource utilization rate is determined by measuring a PRB (Physical Resource Block) or a BO (Buffer Occupancy) for a predetermined time.
The method according to claim 1,
Wherein,
A radio resource allocation apparatus for scheduling a radio resource allocation for a terminal using a PF (Proportional Fair) scheme.
1. A radio resource allocation method for a mobile communication system using a carrier aggregation,
Allocating a resource block for transmitting downlink data to a terminal through a channel formed on a primary cell (Pcell) and a secondary cell (Scell);
Receiving a measured CQI (Channel Quality Indicator) on the Scell from the terminal;
Determining whether a CQI of the Scell is less than or equal to a preset CQI threshold; And
And decreasing a radio resource allocated to the MS in the Scell while maintaining a channel with the MS in the Scell if the CQI is below the CQI threshold.
9. The method of claim 8,
The step of verifying that the CQI of the Scell is equal to or less than the preset CQI threshold value,
And checking whether the CQI of the Scell is maintained below the preset CQI threshold for a predetermined time or more.
9. The method of claim 8,
The step of reducing the radio resources allocated to the terminal in the Scell comprises:
And not allocating the radio resource to the terminal in the Scell,
And transmitting downlink data to the MS only through the Pcell.
9. The method of claim 8,
If the CQI of the received Scell is less than or equal to the CQI threshold, checking whether the usage rate of the currently allocated radio resource is equal to or greater than a preset cell load threshold,
The step of reducing the radio resources allocated to the MS in the Scell may include reducing a radio resource allocated to the MS in the Scell when the usage rate of the radio resource is equal to or greater than the cell load threshold .
12. The method of claim 11,
Confirming whether the CQI of the Scell is increased to the CQI threshold or higher or the usage rate of the allocated radio resource is reduced to be less than the cell load threshold after decreasing radio resources allocated to the UE in the Scell; And
If the CQI of the Scell is increased beyond the CQI threshold or the usage rate of the allocated radio resource is reduced below the cell load threshold, the step of increasing the radio resource allocated to the UE in the Scell Radio resource allocation method.
1. A radio resource allocation method for a mobile communication system using a carrier aggregation,
Detecting a signal of the Scell at the terminal;
Forming a channel on the scell with the terminal;
Initiating transmission of downlink data by allocating radio resources on the Scell with the terminal;
Measuring and transmitting a CQI (Channel Quality Indicator) of a signal transmitted from the Scell to the terminal by the terminal;
Determining whether a CQI of the Scell is less than or equal to a preset CQI threshold; And
And decreasing the allocated radio resource while maintaining the channel on the Scell if the CQI is below the CQI threshold.
14. The method of claim 13,
If the CQI of the Scell is less than or equal to the CQI threshold, checking whether a usage rate of a currently allocated radio resource is equal to or greater than a preset cell load threshold,
Wherein the step of reducing the radio resource comprises reducing radio resources allocated to the terminal in the Scell if the usage rate of the radio resource is equal to or greater than the cell load threshold.
15. The method of claim 14,
After reducing the radio resources allocated to the MS in the Scell, it is checked whether the CQI of the Scell is increased to the CQI threshold or more and whether the usage rate of the radio resource allocated by the radio resource allocator is reduced below the cell load threshold ; And
Increasing the CQI of the Scell to the CQI threshold or increasing the radio resource allocated to the MS in the Scell if the usage rate of the radio resource allocated by the radio resource allocator is reduced below the cell load threshold, Further comprising the steps of:

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