KR20090095706A - Scheduling apparatus and method considering data buffer status in mobile communication system - Google Patents

Abstract

A scheduling apparatus considering a data buffer state in a mobile communication system and a method thereof are provided to increase the throughput by scheduling sub-bands corresponding to each resources block in consideration of data states of each terminal. Data state information is received from a base station controller(110). Information for assigning a resource block is received from terminals(120). By using the data state information and allocation information, terminals to which the resource block will be allocated are selected(130-150). The resource block for the selected terminals is included in a frame. The frame is transmitted. The allocation information is CQI(Channel Quality Information).

Description

Scheduling APPARATUS AND METHOD CONSIDERING DATA BUFFER STATUS IN MOBILE COMMUNICATION SYSTEM}

The present invention relates to a method and apparatus for efficiently allocating transmission resources in a mobile communication system. Particularly, in case of allocating transmission resources in LTE (Long Term Evolution) system, throughput is guaranteed while scheduling sub-bands corresponding to each resource block in consideration of the data state for each terminal to ensure fairness. It relates to a device and a method for raising the height.

The 3rd Generation Partnership Project (3GPPS) mobile communication system is responsible for standards for LTE systems following HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access), and performs tasks for higher speed data service. Doing. HSDPA is designed for up to 14Mbps and LTE for up to 10Mbps.

LTE uses an Orthogonal Frequency Division Multiplexing (OFDM) system to provide high speed data services. The OFDM method is a system suitable for a wireless communication environment in which a linear signal component (LOS) is not guaranteed in a multipath, and is known to provide an efficient platform for high-speed data transmission by using the strong advantage in multipath fading. That is, the OFDM divides all channels into narrowband sub-channels having a plurality of orthogonal sub-channels and transmits them, thereby efficiently overcoming selective fading of frequencies.

Orthogonal Frequency Division Multiplexing Access (OFDMA) divides a frequency domain into subchannels consisting of a plurality of subcarriers, divides the time domain into a plurality of timeslots, and then assigns subchannels for each user to determine a time and frequency domain. It is a multiple access method that can accommodate a large number of users with limited frequency resources by performing resource allocation considering all.

In a typical OFDM system, since one modulation symbol (for example, QPSK or 16 QAM, etc.) is generally transmitted through one subcarrier, the subcarriers are basic resources. Typically, one OFDM symbol is composed of a plurality of subcarriers, and a plurality of OFDM symbols are grouped together and set as a basic transmission unit. Hereinafter, a basic transmission unit composed of the multiple OFDM symbols will be referred to as a transmission time interval (TTI).

The implementation of the scheduler function at the base station began with the introduction of WCDMA and HSDPA technologies, which can support data rates up to 14.4 Mb / s. In the HSDPA technology, the scheduler allocates resources, that is, an Orthogonal Variable Spreading Factor (OVSF) code and power, to a selected UE.

For scheduling, max C / I, Proportional Fairness (PF), Round Robin (RR), etc. may be selectively used. In the HSDPA system, such scheduling is performed in units of Transmission Time Interval (TTI) of 2 ms.

In LTE, a TTI frame-based transmission technique consisting of OFDM-based resource blocks is used. The terminal receives the selected resource block. And LTE uses a TTI unit of 1ms. The difference from HSDPA is that resource blocks are allocated instead of OVSF codes allocated to UEs.

The base station performs scheduling based on the channel quality indication (CQI) to the terminals. The traffic of the terminals has quality characteristics corresponding to transmission delay limits and data error rates, respectively. Therefore, appropriate control of scheduling for each quality characteristic is needed. Control of scheduling is adjusted according to a scheduling priority indicator value, and is performed by a variable that guarantees constant fairness between terminals and a variable that increases system throughput.

However, up to now, the LTE scheduling scheme allocates resource blocks only according to channel states of respective terminals without considering the buffer status of the RLC stage. This method has a problem of causing a waste of resources. That is, there is a problem in that resources are allocated to a terminal having a small amount of data to be transmitted because of high CQI and priority.

An object of the present invention is to provide a scheduling apparatus and method considering a data buffer state in a mobile communication system.

Another object of the present invention is to perform scheduling in consideration of not only the CQI from the UE but also the data state of the RLC terminal to be transmitted to the UE, and the CQI and the high priority do not allocate resources excessively to the UE having a small amount of data to be transmitted. Therefore, the present invention provides an apparatus and method for reducing waste of resources by performing effective terminal scheduling.

According to a first aspect of the present invention for achieving the object of the present invention, in the scheduling method considering the data buffer state of the base station in the mobile communication system, the process of receiving data state information from the base station controller and allocating resource blocks from the terminals And receiving the information for performing the selection, and selecting the terminals to which the resource block is to be allocated using the data state information and the information for allocating the resource block.

According to a second aspect of the present invention for achieving the object of the present invention, in the apparatus of the base station for performing scheduling in consideration of the data buffer status in the mobile communication system through a communication interface and the communication interface for communicating with other nodes A control unit for receiving data state information from a base station controller, receiving information for allocating resource blocks from terminals, and selecting terminals for allocating resource blocks using the data state information and information for allocating the resource blocks Characterized in that it comprises a.

According to the present invention, the LTE mobile communication system considers the buffer status of the RLC stage, and thus has high CQI and high priority, and thus does not allocate a lot of resources to a terminal having a small amount of data that can be sent.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when 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.

Hereinafter, the present invention will be described a scheduling apparatus and method considering the data buffer status in a mobile communication system.

The present invention largely consists of a base station, a terminal, and a base station controller (RNC: Radio Network Controller). The base station transmits a signal through a pilot channel, and the terminal transmits a channel quality indicator (CQI) for each sub-band to the base station based on this. The base station controller transmits a data state of a radio link control (RLC) stage to the base station.

The base station receives the CQI received from the terminal and the data state information received from the base station controller, and then transmits data through the downlink channel. The method of selecting a terminal by scheduling in the base station of the present invention facilitates data flow while maintaining a quality of service (QoS).

1 is a diagram illustrating an operation process of a base station according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the base station receives pi _j (t) and s _j (t), which are RLC data state information transmitted from a base station controller (RNC) (step 110). The RLC data state information (pi _j (t)) is a Priority Value (Priority Value) according to QoS, which is information on traffic requested by the UE, and s _j (t) indicates the state of the data buffer stored in the RLC. . In the above, the data buffer state represents the amount of data to be transmitted stored in the buffer.

Thereafter, the j-th terminal receives CQI information Q _j (t) for each subband (step 120). The CQI information is updated by a Channel Quality Indicator Channel (CQICH) value received from the UE, the channel being transmitted in uplink by measuring the SINR of the downlink channel.

Thereafter, the base station determines α, β, and γ for each traffic in consideration of QoS, fairness, and throughput. Α, β, and γ are weight values to be used in the following formula. The range of α, β, and γ is a value between 0 and 1 including 0 and 1.

In operation 130 _, M _{i , j} (t) of the j th terminal is calculated in the i th subband. The i th band represents any band of all bands, and the j th terminal represents any terminal among terminals existing in the base station. And, M _{i, j} (t) is defined as in Equation 1 below. M _{i , j} (t) is a scheduling metric value and indicates a selection priority value at the base station for the j th terminal in the i th subband.

Here, P _j (t) represents a priority value in consideration of the RLC data buffer state for the j th terminal and is expressed by Equation 2 below. And Q _i (t) is a periodic channel quality (periodic channel quality) is provided from the terminal, which represents the CQI value for the i-th subband. And, C _j (t) represents the cumulative value of the number of selection for the new data transmission up to the current TTI for the j-th terminal. C _j (t) is defined as in Equation 3 below.

Here, pi _j (t) represents RLC data state information and represents a priority value according to QoS, which is information on traffic requested by a j-th terminal, and is provided from a base station controller. And, S (t) is the sum of RLC data to be transmitted for all UEs that can be scheduled in the current TTI. And s _j (t) indicates the state of the data buffer stored in the RLC of the j-th terminal, and the data buffer state indicates the amount of data to be transmitted stored in the buffer and is provided from the base station controller.

Here, N _j (t) represents the number of times the j-th terminal is selected so far for new data transmission. And the value of T _c represents the unit time in TTI unit.

Thereafter, the base station sets the largest value among the calculated M _{i , j} (t) values to D _{i , j} (t) (step 140). In operation 150, the terminal corresponding to D _{i , j} (t) is selected. D _{i, j} (t) may be represented by Equation 4 below.

Here, P _j (t) represents a priority value in consideration of the RLC data buffer state for the j th terminal, and Q _i (t) is provided from the terminal as a periodic channel quality value, which is the i th The CQI value is shown for the subband. And, C _j (t) represents the cumulative value of the number of selection for the new data transmission up to the current TTI for the j-th terminal. C _j (t) is defined as in Equation 2 above.

Thereafter, the above process is performed for all subbands (step 160), and a resource block for a selected terminal is allocated to each subband of a frame to be transmitted and transmitted through downlink (step 170).

Where γ is a parameter that controls the tradeoff of fairness of allocation opportunities, and γ is set to 1 in a typical PF scheduler. In the above equation, when γ is close to 0, the contribution of the denominator decreases, so that the effect of user diversity is increased, but the fairness of the allocation opportunity of the shared channel may be lost. Α, β, and γ can be variably operated according to the purpose or policy. And, as the priority value P _j (t) increases, the above scheduling metric value M _{i, j} (t) depends on P _j (t).

Then, the algorithm according to the present invention is terminated.

2 is a diagram illustrating an operation process of a base station controller according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the base station controller calculates a data state of a corresponding terminal (j-th terminal) while monitoring a data input / output state of the terminal (step 210).

Thereafter, when the above process is completed for all the terminals (all terminals under the base station) (step 220). In step 230, data status information on the terminal is transmitted to the base station. The data state information includes RLC data state information indicating a priority value according to QoS, which is information on traffic requested by the terminal, and a state of a data buffer indicating the amount of data to be transmitted stored in a buffer in the RLC of the terminal. Represent information.

Then, the algorithm according to the present invention is terminated.

3 is a block diagram of a base station according to an embodiment of the present invention.

Referring to FIG. 3, the base station includes the communication interface 310, the control unit 320, the storage unit 330, and the resource block allocation unit 340.

The communication interface 310 is a module for communicating with other nodes, and includes a wireless processor, a wireless baseband processor, a wired processor, and a wired baseband processor. The wireless processor converts a signal received through an antenna into a baseband signal to provide the baseband signal to the wireless baseband processor, and converts the baseband signal from the wireless baseband processor into a wireless signal so as to be transmitted on an actual wireless path. Transmit via antenna The wired processor converts a signal received through a wired path into a baseband signal and provides it to the wired baseband processor, and transmits a baseband signal from the wired baseband processor on an actual wired path. Change and transmit through the wired path.

The controller 320 controls the overall operation of the terminal. In particular, according to the present invention, the resource block allocation unit 340 is controlled.

The storage unit 330 stores a program for controlling the overall operation of the apparatus and a temporary data generated during program execution.

The RB allocation unit 340 transmits the RLC data state information pi _j (t) and the RLC data buffer state information s _j (t) according to the QoS transmitted from the base station controller (RNC) to the communication interface 310. CQI (Channel Quality Information) information (Q _j (t)) for each subband is received from the j th terminal. The CQI information is updated by a CQICH (Channel Quality Indicator Channel) value received from the UE, the channel being transmitted in uplink by measuring the SINR of the downlink channel.

The resource block allocator 340 determines α, β, and γ for each traffic in consideration of QoS, fairness, and throughput. Α, β, and γ are weight values to be used in the following formula. The range of α, β, and γ is a value between 0 and 1 including 0 and 1. Then, M _{i , j} (t) of the j th terminal is calculated in the i th subband. The i th band represents any band of all bands, and the j th terminal represents any terminal among terminals existing in the base station. In addition, M _{i , j} (t) is defined as in Equation 1 above. M _{i , j} (t) is a scheduling metric value and indicates a selection priority value at the base station for the j th terminal in the i th subband.

Thereafter, the RB allocation unit 340 sets the largest value among the calculated M _{i , j} (t) values to D _{i, j} (t), and sets the terminal corresponding to D _{i , j} (t). Choose.

Thereafter, the resource block allocator 340 performs the above process for all subbands, allocates data for the selected terminal to each subband of a frame to be transmitted, and transmits the data through the communication interface 310.

In the above-described block configuration, the controller 320 may perform a function of the resource block allocator 340. In the present invention, it is shown to configure them separately to explain each function separately.

Therefore, when the product is actually implemented, all of the functions of the resource block allocator 340 may be configured to be processed by the controller 320, and only some of the functions may be configured to be processed by the controller 320. have.

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

Referring to FIG. 4, the base station controller includes the communication interface 410, the controller 420, the storage 430, and the RLC data state manager 440.

The communication interface 410 is a module for communicating with other nodes, and includes a wired processor, a wired baseband processor, and the like. The wired processor converts a signal received through a wired path into a baseband signal and provides the wired baseband processor, and converts a baseband signal from the wired baseband processor into a wired signal so as to be transmitted on an actual wired path. Transmit through the wired path.

The controller 420 controls the overall operation of the terminal. In particular, the RLC data state manager 440 is controlled according to the present invention.

The storage unit 430 stores a program for controlling the overall operation of the apparatus and a temporary data generated during program execution.

The RLC data state management unit 440 calculates the data state of the corresponding terminal (jth terminal) while monitoring the data input / output state of the terminal, and performs the above process for all terminals (all terminals under the base station). Upon completion, the data state information of the terminal is transmitted to the base station through the communication interface 410.

In the above-described block configuration, the controller 420 may perform a function of the RLC data state manager 440. In the present invention, it is shown to configure them separately to explain each function separately.

Therefore, when the product is actually implemented, all of the functions of the RLC data state management unit 440 may be configured to be processed by the controller 420, and only some of the functions may be configured to be processed by the controller 420. have.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

1 is a view illustrating an operation process of a base station according to an embodiment of the present invention;

2 is a flowchart illustrating an operation of a base station controller according to an embodiment of the present invention;

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

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

Claims (18)

A scheduling method in consideration of a data buffer state of a base station in a mobile communication system, Receiving data status information from a base station controller; Receiving information for allocating resource blocks from terminals; And selecting terminals to which a resource block is to be allocated using the data state information and information for allocating the resource block. The method of claim 1, And including the resource block for the selected terminals in a frame to be transmitted. The method of claim 1, The data state information, RLC data status information indicating a priority value according to QoS, which is information on traffic requested by the terminal, and data buffer status information indicating the amount of data to be transmitted stored in a buffer in the RLC of the terminal. How to. The method of claim 1, Information for allocating the resource block, CQI (Channel Quality Information) information. The method of claim 1, The process of selecting terminals to which a resource block is to be allocated using the data state information and information for allocating the resource block includes: Obtaining scheduling metric values of all terminals belonging to the base station in all subbands; And selecting terminals having the largest value among the calculated scheduling metric values in all subbands. The method of claim 5 Obtaining scheduling metric values of all terminals belonging to the base station in all the subbands, Method characterized in that it is carried out using the equation (5).

Here, M _{i , j} (t) is a scheduling metric value and indicates a selection priority value at the base station for the j th terminal in the i th subband. P _j (t) represents a priority value in consideration of the RLC data state for the j-th terminal and is expressed by Equation 6 below. And Q _i (t) is a periodic channel quality (periodic channel quality) is provided from the terminal, which represents the CQI value for the i-th subband. And, C _j (t) represents the cumulative value of the number of selection for the new data transmission up to the current TTI for the j-th terminal. C _j (t) is defined as in Equation 7 below. Α, β, and γ are weight values. The range of α, β, and γ is a value between 0 and 1 including 0 and 1.

Here, pi _j (t) represents RLC data state information and represents a priority value according to QoS, which is information on traffic requested by the j-th terminal, and is provided from a base station controller. And, S (t) is the sum of RLC data to be transmitted for all UEs that can be scheduled in the current TTI. And s _j (t) indicates the state of the data buffer stored in the RLC of the j-th terminal, and the data buffer state indicates the amount of data to be transmitted stored in the buffer and is provided from the base station controller.

Here, N _j (t) represents the number of times the j-th terminal is selected so far for new data transmission. And the value of T _c represents the unit time in TTI unit. The method of claim 5, The process of selecting terminals having the largest value among the calculated scheduling metric values in all the subbands, Method characterized in that it is carried out using the equation (8).

Here, D _{i , j} (t) is the largest value among M _{i , j} (t) values calculated by Equation 5 above. P _j (t) represents a priority value in consideration of the RLC data state for the j-th terminal, and Q _i (t) is provided from the terminal as a periodic channel quality value, which is the i-th subband Represents the CQI value for. And, C _j (t) represents the cumulative value of the number of selection for the new data transmission up to the current TTI for the j-th terminal. Α, β, and γ are weight values. The range of α, β, and γ is a value between 0 and 1 including 0 and 1. An apparatus of a base station for performing scheduling considering a data buffer state in a mobile communication system, A communication interface for communicating with other nodes, Receive data status information from a base station controller through the communication interface, receive information for allocating resource blocks from terminals, and allocate resource blocks using the data state information and information for allocating the resource blocks. And a control unit for selecting terminals. The method of claim 8, The control unit includes a resource block for the selected terminal in the frame to be transmitted, characterized in that for transmitting through the communication interface. The method of claim 8, The data state information, RLC data status information indicating a priority value according to QoS, which is information on traffic requested by the terminal, and data buffer status information indicating the amount of data to be transmitted stored in a buffer in the RLC of the terminal. Device. The method of claim 8, Information for allocating the resource block, Device characterized in that the channel quality information (CQI). The method of claim 8, The control unit, By obtaining scheduling metric values of all terminals belonging to the base station in all subbands, and selecting terminals having the largest value among the calculated scheduling metric values in all subbands, And selecting terminals to which a resource block is to be allocated using the data state information and information for allocating the resource block. The method of claim 12 The control unit And a scheduling metric value of all terminals belonging to the base station in all subbands using Equation 9 below.

Here, M _{i , j} (t) is a scheduling metric value and indicates a selection priority value at the base station for the j th terminal in the i th subband. P _j (t) represents a priority value in consideration of the RLC data buffer state for the j th terminal and is expressed by Equation 10 below. And Q _i (t) is a periodic channel quality (periodic channel quality) is provided from the terminal, which represents the CQI value for the i-th subband. And, C _j (t) represents the cumulative value of the number of selection for the new data transmission up to the current TTI for the j-th terminal. C _j (t) is defined as in Equation 11 below. Α, β, and γ are weight values. The range of α, β, and γ is a value between 0 and 1 including 0 and 1.

Here, pi _j (t) represents RLC data state information and represents a priority value according to QoS, which is information on traffic requested by a j-th terminal, and is provided from a base station controller. And, S (t) is the sum of RLC data to be transmitted for all UEs that can be scheduled in the current TTI. And s _j (t) indicates the state of the data buffer stored in the RLC of the j-th terminal, and the data buffer state indicates the amount of data to be transmitted stored in the buffer and is provided from the base station controller.

Here, N _j (t) represents the number of times the j-th terminal is selected so far for new data transmission. And the value of T _c represents the unit time in TTI unit. The method of claim 12, The control unit, The apparatus of claim 12, wherein the terminals having the largest value among the calculated scheduling metric values are selected in all the subbands using Equation 12 below.

Here, D _{i , j} (t) is the largest value among M _{i , j} (t) values calculated by Equation 5 above. P _j (t) represents a priority value in consideration of the RLC data state for the j-th terminal, and Q _i (t) is a periodic channel quality, which is provided from the terminal, which is the i-th sub CQI values for the bands. And, C _j (t) represents the cumulative value of the number of selection for the new data transmission up to the current TTI for the j-th terminal. Α, β, and γ are weight values. The range of α, β, and γ is a value between 0 and 1 including 0 and 1. A method of transmitting data state information of a base station controller in a mobile communication system, Calculating data state information about terminals; And transmitting the data state information to a base station. The method of claim 15, The data state information, RLC data status information indicating a priority value according to QoS, which is information on traffic requested by the terminal, and data buffer status information indicating the amount of data to be transmitted stored in a buffer in the RLC of the terminal. How to. In the apparatus of the base station controller for transmitting data status information in a mobile communication system, A communication interface for communicating with other nodes, And a control unit for calculating data state information for terminals and transmitting the data state information to a base station through the communication interface. The method of claim 17, The data state information, RLC data status information indicating a priority value according to QoS, which is information on traffic requested by the terminal, and data buffer status information indicating the amount of data to be transmitted stored in a buffer in the RLC of the terminal. Device.

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