KR20060136341A - Apparatus and method for scheduling for transmitting data packet in multichannel wireless communication system - Google Patents

Abstract

The present invention provides a method for scheduling data packets to be transmitted to a plurality of terminals supporting multiple quality of service classes in a multi-channel wireless communication system, wherein different scheduling metrics for each quality of service in the channel order are provided for each of the multiple channels. Selecting a scheduling metric suitable for each channel, selecting a terminal to transmit the data packet through the corresponding channel using the selected scheduling metric, and allocating a resource of the corresponding channel to the data packet of the selected terminal If the resource allocation for the multi-channel is all completed in the order of channels, transmitting the data packets of the plurality of terminals at a time by using the resources allocated for each channel.

Multichannel, Scheduler

Description

Apparatus and method for scheduling for transmitting data packet in multichannel wireless communication system

1 is a block diagram of an apparatus for scheduling data packet transmission in a multichannel wireless communication system according to the present invention.

2 is a structural diagram of a multi-channel frame transmitted in the present invention.

3 is a flow diagram of a first embodiment of a method for scheduling data packet transmission in a multichannel wireless communication system in accordance with the present invention.

4 is a flow diagram of a second embodiment of a method for scheduling data packet transmission in a multichannel wireless communication system in accordance with the present invention.

The present invention relates to a scheduling device, and more particularly, to an apparatus and method for scheduling data packet transmission in a multichannel wireless communication system.

Recently, in the mobile communication system for multimedia services, including high-speed data transmission, radio resource management (Radio Resource Management) has added importance for the efficient use and management of radio resources.

Scheduling is one of the technologies required for radio resource management. The Proportional Fair (PF) scheduler, which considers the system yield and the fair resource distribution of the user at the same time in the environment where the radio channels are time-variable and different from user to user, is used. It is used. However, the PF scheduler does not consider the quality of service (hereinafter referred to as 'QoS'). A scheduler considering QoS includes a Modified Largest Weighted Delay First (M-LWDF) scheduler. However, the M-LWDF scheduler is hard to trade off between QoS and system throughput, making it difficult to satisfy both QoS and system throughput. In addition, the PF scheduler and M-LWDF scheduler are both schedulers for a single channel.

On the other hand, there is a subchannel allocation algorithm of the OFDMA as a method of managing radio resources in consideration of multiple channels. This derives a data rate to be allocated to each terminal for each frame through a separate algorithm. However, there is a problem in that it is difficult to combine with the packet scheduler for this purpose, and considering the QoS on a frame basis, both the throughput and the QoS providing performance of the system are deteriorated.

Accordingly, an aspect of the present invention is to provide an apparatus and method for scheduling data packet transmission in consideration of multiple grades of QoS in a multichannel wireless communication system.

Another object of the present invention is to provide an apparatus and method for scheduling data packet transmission in consideration of multi-class QoS using a single channel scheduler in a multi-channel wireless communication system.

A method of the present invention for achieving the above object, in a method for scheduling data packets to be transmitted to a plurality of terminals that support multiple quality of service in a multi-channel wireless communication system, the channel for each of the multi-channel Selecting a scheduling metric suitable for each channel among the different scheduling metrics for each of the quality of service classes, selecting a terminal to transmit the data packet through the corresponding channel using the selected scheduling metric, and Allocating resources of a corresponding channel for a data packet and transmitting data packets of the plurality of terminals at once using resources allocated for each channel when resource allocation for the multiple channels is completed in channel order. do.

Another method of the present invention for achieving the above object is a method for scheduling data packets to be transmitted to a plurality of terminals supporting multiple quality of service in a multi-channel wireless communication system, for each of the multi-channel Selecting a channel having the highest channel rate in the corresponding channel in channel order, selecting a terminal using a scheduling metric in the selected channel, allocating a resource of the corresponding channel for the data packet of the selected terminal, When the resource allocation for the multi-channel is all completed in the order of the channel, the step of transmitting data packets of the plurality of terminals at a time by using the resources allocated for each channel.

An apparatus of the present invention for achieving the above object, in the multi-channel wireless communication system in the device for scheduling data packets to be transmitted to a plurality of terminals that support multiple quality of service, service for each of the plurality of terminals A storage means for storing the quality packet for each quality of service for each of the plurality of terminals, a different scheduling metric for each quality of service grade, and the channel order for each of the multiple channels. After selecting a scheduling metric suitable for each channel among different scheduling metrics for each quality of service class, selecting a terminal to transmit the data packet through the channel using the selected scheduling metric, and selecting resources of the channel for the data packet of the selected terminal. Assign and multiply When allocating the resources for the channel is completed in each channel order includes a scheduler to transmit the data packets of the plurality of terminals at once using the resources allocated for each channel.

Another apparatus of the present invention for achieving the above object is an apparatus for scheduling data packets to be transmitted to a plurality of terminals supporting multiple quality of service in a multi-channel wireless communication system, for each of the plurality of terminals A storage means for storing a data packet for each quality of service for each of the plurality of terminals, and a channel rate for each of the plurality of terminals in the corresponding channel in channel order for each of the multiple channels. Select the highest channel, select the terminal using the scheduling metric for a single channel in the selected channel, allocate the resource of the channel for the data packet of the selected terminal, resource allocation for the multi-channel If all of them are completed in order, the resources allocated to each channel are used. It includes a scheduler to transmit the data packet of the plurality of terminals in turn.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted so as not to distract from the gist of the present invention.

The present invention relates to a communication system such as Orthogonal Frequency Division Multiplexing (OFDM) or Orthogonal Frequency Division Multiple Access (OFDMA). We propose a scheduling method and apparatus for transmitting a data packet in a communication system to which the method is applied. In the following embodiment of the present invention, for convenience of description, the communication system using the OFDM / OFDM method is described as an example, but the scheduling method and apparatus proposed in the present invention can be applied to other communication systems. Now, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of an apparatus for scheduling data packet transmission in a multichannel wireless communication system according to the present invention. As shown in FIG. 1, a scheduling apparatus according to the present invention includes a queue in which data packets to be transmitted to each terminal (MS1 to MSk, k is the number of terminals) are stored for each terminal and for each QoS level. (Queue) 10 and a scheduler 20 for scheduling data packets stored in the queue 10 and transmitting them through a transmission antenna (not shown). In FIG. 1, components not directly related to the present invention are omitted.

The queue 10 is provided for each terminal (MS1 to MSk), and the queue for each terminal is provided for each QoS class (QoS1 to QoSm and m is the number of QoS classes). In QoS class, priority exists according to class, and data packet is transmitted according to priority.

The scheduler 20 performs scheduling on a frame basis according to a scheduling metric for a single channel. In the present invention, the scheduler 20 performs scheduling in two ways. The first method is a method in which the scheduler 20 performs scheduling in consideration of various QoS in a single or multi-channel environment, and performs scheduling by changing scheduling metrics for each QoS class. The second method is performed by the scheduler 20. It is a method of performing scheduling by applying an arbitrary single channel scheduling metric including channel quality information to a multichannel environment, considering that channel quality information of several channels is simultaneously known in a multichannel environment. Each method is explained in more detail below. At this time, the reference numerals of the scheduler 20 are used the same.

First, according to the first method, the scheduler 20 performs scheduling by different scheduling metrics for each QoS class. Scheduling is performed in units of frames, and scheduling is sequentially performed for each channel of the multichannel. That is, as shown in FIG. 2, data packets for each channel (CH1 to CHn, where n is the number of channels) simultaneously transmitted form one frame at predetermined time intervals. The scheduler 20 first determines which QoS class it is desirable to use for the channel CH1. To this end, the scheduler 20 determines whether the selection conditions are satisfied for all the QoS class scheduling metrics in order of priority of the QoS class, and selects one scheduling metric that satisfies the selection condition. For example, the priority of QoS class is QoS1>... > QoSm, determine which scheduling metric satisfies the selection condition from scheduling metric for QoS1 to scheduling metric for QoSm for channel CH1, and when scheduling for channel CH1 is completed using the scheduling metric that satisfies the selection condition. Then, in the same manner as above for channel CH2, which is the next order, it is determined which scheduling metric satisfies the selection condition from the scheduling metric for QoS1 to the scheduling metric for QoSm, and again selects the scheduling metric for channel CH2, and selects the selected scheduling. Scheduling using the metric. In this way, the scheduling metrics satisfying the selection conditions are selected for all channels, and scheduling is performed for each channel (CH1 to CHn) so that all channels can transmit data packets satisfying QoS.

In this case, the scheduler 20 uses the information of the queue 10 to select a scheduling metric for a corresponding channel, and is referred to as channel quality information (CQI) hereinafter transmitted through feedback from the terminals MS1 to MSk. ). The information of the queue 10 includes a length of a queue corresponding to each QoS level (QoS1 to QoSm) for each terminal (MS1 to MSk), a head of line (HOL) packet delay value, and the like. . The CQI transmitted from the terminals MS1 to MSk includes an average throughput, an average channel rate, an instantaneous channel rate, and the like.

An example of a condition that the scheduler 20 selects a scheduling metric to be used for scheduling a corresponding channel among scheduling metrics for each QoS class is that the number of UEs for which the ratio of the HOL packet delay and the required delay exceeds a certain threshold is constant for each QoS class. Is it equal to or more than a threshold value, or is the number of UEs exceeding a certain threshold ratio between the queue length and the average channel rate for each QoS class being equal to or greater than a certain threshold value. If the selection condition is satisfied, the scheduler 20 selects a corresponding scheduling metric and performs scheduling for data packet transmission for the corresponding channel using the selected scheduling metric.

Meanwhile, in the scheduler 20, when a scheduling metric for the highest priority QoS level is not selected and a scheduling metric for the lower priority QoS level is selected and the terminal to be allocated to the channel is determined, the scheduler 20 according to the QoS class of the corresponding terminal is determined. For queues, consider all the queues for all QoS classes, not just the queues for the lower priority QoS classes. Because each terminal can receive data packets corresponding to several QoS levels simultaneously by supporting multiple QoS classes, only the data packets in the QoS class queues corresponding to the scheduling metrics selected from the QoS class queues of the UEs can be transmitted. Rather, data packets present in the QoS class-specific queues of the terminal are transmitted in order of priority of the QoS class. For example, suppose that the scheduling metric for the channel CH1 is selected as the scheduling metric for the QoSm having the lowest priority. In this case, it is assumed that the scheduler 20 performs scheduling for data packet transmission using the scheduling metric for the QoSm class, and as a result, determines that the data packet for the terminal MS1 is transmitted through the channel CH1. Then, the scheduler 20 first checks the states of the data packets existing in the QoS class-specific queue of the terminal MS1 as shown in FIG. 1. At this time, the MS1 has not only data packets present in the queue for QoSm but also data packets in the queue for QoS1 having higher priority than QoSm. Therefore, the scheduler 20 does not transmit the data packet in the queue for QoSm first, but instead transmits the data packet in the queue for QoS1 first, and then the data packet in the queue for the QoSm in QoS priority order. To be transmitted. Referring to FIG. 2, each channel (CH1 to CH4) frame is composed of different blocks, which shows the division of data packets stored in a queue for each QoS class for one UE.

The first scheduling method as described above will be described in more detail with reference to the flowchart of FIG. 3.

The scheduler 20 first collects scheduling parameters for selecting a scheduling metric to be used for scheduling for the first channel (S302). The scheduling parameter is the information of the queue 10 as described above and the CQI transmitted feedback from the terminals MS1 to MSk.

The scheduler 20 sets the priority of the QoS class to the highest one (here 1) (S304) and determines whether the scheduling metric having the highest priority of the QoS class satisfies the selection condition of the scheduling metric (S306). . At this time, if the scheduling metric for the QoS class of the corresponding priority satisfies the selection condition, the scheduler 20 uses the scheduling metric for the selected QoS class to identify the terminals that will transmit data packets through the corresponding channel, that is, the first channel. It is selected from (MS1 to MSk) (S310).

However, if the metric for the QoS class of the corresponding priority does not satisfy the selection condition, the scheduler 20 lowers the priority by one step (assuming that the priority is lower as the number increases) (S308) and repeats the above-described S306 process. In step S310, the scheduling metric that satisfies the selection condition among the scheduling metrics for each QoS class is found.

The scheduler 20 determines that the QoS level queues of the terminal selected in this way are transmitted in the corresponding channels one by one in order of priority, starting from data packets existing in the queue for the high priority QoS level (S312).

If there is an extra resource even if the packet currently determined to be transmitted on the channel is filled, or if a data packet for which transmission is not determined remains in the queue of the selected terminal (S314), the above-described step S312 is performed. All data packets present in the queue are determined to be transmitted or are repeated until no resources for transmitting data packets of the selected UE remain in the channel.

If all data packets present in the queue of the selected terminal are all transmitted or resources for the channel are all allocated, the parameters of the scheduling metric are updated except for considering the packet for which the transmission of the terminal is already transmitted. S316).

After determining whether the current scheduling is performed for the last channel (S318), if the scheduling for the last channel is not performed, the process moves to the next channel (S320) and repeats from the above-described step S304.

That is, the first scheduling method is a method in which one scheduler 20 has a single channel scheduling metric for each QoS, selects a scheduling metric considering QoS for each channel, and performs scheduling using the selected scheduling metric. . In FIG. 3, all resources are transmitted at the same time after allocating resources. However, when allocating the next channel, subtract the packet already transmitted from the packets in each terminal queue according to the resource allocation contents up to the previous channel, and recalculate parameters such as the queue length and HOL packet delay to allocate the next channel. Since it should be carried out for the convenience of description it has been described including the above-described S314, S316 process. This first scheduling method is applicable to all types of wireless communication systems such as OFDMA, FDMA, TDMA, CDMA.

Meanwhile, according to the second scheduling method, the scheduler 20 uses one single channel scheduling metric, but generates and applies a new parameter for a channel appropriately considering channel rates for all channels to apply to multiple channels. . That is, for example, the channel quality information of the channel having the highest channel quality information value among the channels for which the resource allocation has not yet been made in the current frame for each terminal is used to calculate a single channel scheduling metric by making the channel parameter of the corresponding scheduling system. can do.

In this case, two scheduling metrics can be used. The scheduling metric differs when using an infinite buffer and when using a limited buffer. Here, the buffer means FIG. 1 as the queue 10. Equation 1 is a scheduling metric when the scheduler 20 uses an infinite buffer.

는 단순 증가 함수로서, 스케줄러(20)가 채택한 스케줄링 종류에 따라 달리 정의되며, 수학식 2는 Maximal Rate 스케줄링에 대한

의 예이다.

는 각 단말별 채널율을 나타낸다.Equation 1 is a scheduling metric for determining the terminal MSk to be allocated to the channel CHn. here

Is a simple increment function, which is defined differently according to the type of scheduling adopted by the scheduler 20, and Equation 2 is

Is an example.

Denotes a channel rate for each terminal.

Equation 3 is a scheduling metric when the scheduler 20 uses a limited buffer.

는 상수,

는 각 단말별 채널율, 는 각 단말별 HOL 패킷 지연값을 나타낸다.

는 단순 증가 함수로서, 스케줄러(20)가 채택한 스케줄링 종류에 따라 수학식 4 및 수학식 5와 같이 달리 정의된다. Equation 3 is also a scheduling metric for determining the terminal MSk to be allocated to the channel CHn. here

Is a constant,

Is the channel rate for each terminal, Denotes a HOL packet delay value for each terminal.

Is a simple increment function, and is defined differently as in Equations 4 and 5 according to the scheduling type adopted by the scheduler 20.

이고, 수학식 5는 Exponential Rule을 이용한 스케줄러에 대한

이다.Equation 4 is for the M-LWDF scheduler

Equation 5 is for the scheduler using the Exponential Rule

to be.

According to the second scheduling method, since the scheduler 20 knows the channel rate values for several channels in the same frame at the same time, the scheduler 20 selects a channel corresponding to the channel rate for each terminal (MS1 to MSk). In other words, the scheduler 20 selects a channel having the largest channel rate among channels not yet allocated in the corresponding frame for each terminal (MS1 to MSk).

In this scheduling method, since the channel having the largest channel rate for each terminal (MS1 to MSk) can be generally different, it is not necessary to search again for all the terminals every time according to resource allocation, and the increase in complexity is not significant. not. In addition, by comparing the scheduling metrics using the channel having the largest channel rate for each terminal (MS1 to MSk), it is always possible to select the best channel in the current state. According to the design of the scheduler 20, the maximum channel rate is not necessarily used for each terminal (MS1 to MSk), but may be appropriately changed. For example, in consideration of fairness, the scheduler 20 selects a channel having a maximum channel rate for each terminal whose average SNR is less than or equal to a predetermined threshold value, and selects a channel having a channel rate corresponding to an intermediate value. will be.

A second scheduling method as described above will be described in more detail with reference to the flowchart of FIG. 4.

First, the scheduler 20 updates parameters of a scheduling metric for allocation of channels not yet allocated in the corresponding frame (S402).

The scheduler 20 selects a channel having the largest channel rate among the channels not yet allocated in the corresponding frame for each terminal (S404). That is, when a random terminal is selected from the respective terminals, the scheduler 20 assigns a channel having the highest channel rate of the random terminal among the channels not yet allocated in the corresponding frame, to be assigned to the random terminal. Choose. In this way, the scheduler 20 recognizes a channel rate of each terminal, thereby recognizing a channel allocated to each terminal.

Then, the scheduler 20 determines a terminal to allocate a channel that is not allocated in the corresponding frame among the respective terminals by using the above-described scheduling metric, for example, a single channel metric (S406). In this case, as described in Equations 1 and 3, the scheduler 20 selects a channel using a single channel metric corresponding to the channel rate for each terminal and the scheduling parameters updated in S402, for example, a packet delay value. Determine the assigned terminal.

Next, the scheduler 20 determines that the queues for each QoS class of the terminal selected in step S406 are to be transmitted on the corresponding channels, one by one, in order of priority, from the data packets present in the queue for the QoS class of high priority (S408). ).

If there is an extra resource or a data packet for which transmission is not determined in the queue of the selected terminal remains even after filling the packet determined to be transmitted in the corresponding channel (S410), the process S408 described above is performed. All data packets present in the queue are determined to be transmitted or are repeated until no resources for transmitting data packets of the selected UE remain in the channel.

After determining whether the current scheduling is performed for the last channel (S412), if the scheduling for the last channel is not performed, the process moves to the next channel (S414) and repeats from the above-described step S402.

This second scheduling method is applicable to wireless communication systems of OFDMA and FDMA.

As described above, since the present invention can apply a low complexity single channel scheduler to a multi-channel wireless communication system, the system can be implemented by reducing the complexity of the overall scheduler.

In addition, the present invention has an effect of improving the throughput of the system while considering the QoS by performing scheduling for each QoS.

Claims (8)

An apparatus for scheduling data packets to be transmitted to a plurality of terminals supporting multiple quality of service classes in a multichannel wireless communication system, Storage means including a queue for each quality of service for each of the plurality of terminals, and storing data packets for each quality of service for each of the plurality of terminals; Using different scheduling metrics for each of the quality of service classes, selecting a scheduling metric suitable for each channel among the different scheduling metrics for each quality of service in the channel order for each of the multiple channels, and then using the selected scheduling metric. Selecting a terminal to transmit the data packet through, and allocates the resources of the channel to the data packet of the selected terminal, and when the resource allocation for the multi-channel is completed in each channel order using the resources allocated for each channel And a scheduler for transmitting data packets of the plurality of terminals at one time. The method of claim 1, The scheduler selects a scheduling metric suitable for each channel by using the storage information of the data packet of the storage means and the channel quality information transmitted from the plurality of terminals. Scheduling device for data packet transmission in the. A method for scheduling data packets to be transmitted to a plurality of terminals supporting multiple quality of service classes in a multichannel wireless communication system, Selecting a scheduling metric suitable for each channel among the different scheduling metrics for each of the quality of service in channel order for each of the multiple channels; Selecting a terminal to transmit the data packet through a corresponding channel using the selected scheduling metric; When allocating resources of a corresponding channel to data packets of the selected terminal and allocating resources for the multiple channels are completed in channel order, transmitting data packets of the plurality of terminals at once using the resources allocated for each channel. Scheduling method for data packet transmission in a multi-channel wireless communication system comprising the step of. The method of claim 3, The selecting of the scheduling metric may include selecting a scheduling metric suitable for each channel by using the storage information of the data packet and channel quality information transmitted from the plurality of terminals. Scheduling Method for Data Packet Transmission in BCH. An apparatus for scheduling data packets to be transmitted to a plurality of terminals supporting multiple quality of service classes in a multichannel wireless communication system, Storage means including a queue for each quality of service for each of the plurality of terminals, and storing data packets for each quality of service for each of the plurality of terminals; For each of the multi-channels, the channel having the highest channel rate is selected for each of the plurality of terminals in the corresponding channel in the channel order, and the terminal is selected using a scheduling metric in the selected channel, and the data packet of the selected terminal. And a scheduler for allocating resources of a corresponding channel and transmitting data packets of the plurality of terminals at a time by using resources allocated for each channel when resource allocation for the multichannel is completed in channel order. Scheduling apparatus for data packet transmission in a multi-channel wireless communication system, characterized in that. The method of claim 5, The scheduler performs data packet transmission in a multi-channel wireless communication system using storage information of the data packet of the storage means and channel quality information including the channel rate fed back from the plurality of terminals. Scheduling device for. A method for scheduling data packets to be transmitted to a plurality of terminals supporting multiple quality of service classes in a multichannel wireless communication system, Selecting a channel having the highest channel rate for each of the plurality of terminals in the corresponding channel in channel order for each of the multiple channels; Selecting a terminal by using a scheduling metric in the selected channel; When allocating resources of a corresponding channel to data packets of the selected terminal and allocating resources for the multiple channels are completed in channel order, transmitting data packets of the plurality of terminals at once using the resources allocated for each channel. Scheduling method for data packet transmission in a multi-channel wireless communication system comprising the step of. The method of claim 7, wherein The selecting of the terminal may include selecting a scheduling metric suitable for each channel using channel quality information including the storage information of the data packet and the channel rate fed back from the plurality of terminals. Scheduling method for data packet transmission in a multichannel wireless communication system.

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