KR100520608B1 - Method for packet scheduling in a mobile communication system - Google Patents

Abstract

In a mobile communication system comprising a plurality of terminals and a base station connected to the plurality of terminals and providing a data service to the plurality of terminals according to priority in a predetermined time interval, the mobile communication system in a predetermined time interval by the base station. A method of selecting a terminal to be serviced will be described.

The present invention as described above is a process of obtaining a virtual data rate of each of the plurality of terminals according to the ratio of the amount of data to be transmitted and the amount of data that can be transmitted according to the data rate, and the plurality of terminals according to the virtual data rate The process of determining their priorities.

Description

Packet Scheduling Method in Mobile Communication System for High-Speed Data Transmission {METHOD FOR PACKET SCHEDULING IN A MOBILE COMMUNICATION SYSTEM}

The present invention relates to a scheduling method in a mobile communication system, and more particularly, to a scheduling method of forward data transmission in a mobile communication system.

In general, a mobile communication system has been developed to perform a voice call while ensuring user mobility. The mobile communication system focused on such voice calls has been developed to meet the needs of users, and has reached a level capable of performing short data services in parallel. That is, the mobile communication system basically provides a voice service, and as a data service, a short message transmission, a music file that is a ringtone of a terminal, a simple internet communication service, and a financial settlement service are provided.

As described above, in the mobile communication system, a method for providing more information to mobile subscribers at high speed is being discussed while the above data service is provided, and preparation work for commercialization is currently in progress. The method discussed as a method of providing such a high-speed data service is named "CDMA2000 1x EV-DO" (hereinafter referred to as 1x EV-DO) and is discussed as a system for transmitting high-speed data to a mobile communication terminal. It became. In the following description, a mobile communication system for performing high speed data communication refers to the 1x EV-DO system.

The present invention introduces an efficient scheduling method for providing data services to multiple users (or terminals) in a 1x EVDO system. In general, a mobile communication system performs scheduling to efficiently use a finite resource of a communication resource.

Conventional scheduling methods include a proportional process algorithm and Modified Largest Weighted Delay First (M-LWDF).

The proportional process algorithm is described in detail in Ref. [1] below.

[1] A. Jalali, R. Padovani, and R. Pankaj, "Data Throughput of CDMA-HDR a High Efficiency-High Data Rate Personal Communication Wireless System," proceedings of IEEE VTC 2000 , pp. 1854-1858, vol. 3

The M-LWDF method is described in detail in Ref. [2].

[2] M. Andrews, K. Kumaran, K. Ramanan, A. Stolyar, and P. Whiting, "Providing Quality of Service over a Shared Wireless Link," IEEE Communications Magazine , February 2001.

1 is a diagram illustrating a mapping relationship between packets in a mobile communication system performing high speed data communication.

Referring to FIG. 1, one packet of a physical layer includes one to four Protocol Data Units (MAPs) of a MAC (Media Access Control) layer according to a transmission rate. That is, the number of MAC PDUs that can be transmitted varies according to the channel status of each user.

The terminal measures the channel state and reports it to the base station, whereby the transmission rate of the forward link is determined. In more detail, the terminal calculates a carrier to interference ratio (C / I) using a pilot channel, and performs data rate control (DRC) according to the calculated C / I value through a reverse link. The value is informed to the base station.

The packet scheduling algorithm is to order the service of packets waiting in the buffer for each user. In general, service order is determined by a specific priority metric. The user with the highest priority value is serviced, and the priority value of the users is updated periodically. The simplest priority measure can be the DRC value. In this case, the maximum rate packet algorithm serves the user with the largest DRC value. That is, m It is expressed in the form of {DRC _i (t)}. Here, DRC _i is the maximum data rate that user i who wants to receive a service can transmit in time slot t, and actually represents the DRC value of user i.

However, this method has a problem that other users are not served because the channel service is always provided to the best user regardless of how long the packet waits in the buffer.

In practice, a proportional fair algorithm is applied, and the proportional fair algorithm determines the order of services in consideration of the average transfer rate. In this case, the average data rate considers packets transmitted for each user. In other words, the priority dimension of the proportional process algorithm is DRC _i (t) / _i (t). here _i (t) is the average rate at which user i is calculated in timeslot t. Service order is {DRC _i (t) / _i (t)}.

On the other hand, considering the case that the packet length of the user of the good channel condition is shorter than the packet length of the user of the bad channel, as shown in FIG. In FIG. 2, DRC ₁ (t) = 2,456.6 kbps of User 1 and DRC ₂ (t) = 1,228.8 kbps of User 2, each of which can transmit four and two MAC PDUs in one physical channel packet. However, there are 1 and 4 packets waiting for each user. If the maximum rate scheduling method is used, User 1 is serviced first. This not only wastes User 1's bandwidth, but User 2 with longer packets has to wait for the service sequence. This problem occurs because scheduling does not consider the length of packets actually waiting. In particular, there is a problem of a rate-packet length mismatch problem when there are users with high data rates and short queued packets.

Accordingly, an object of the present invention is to provide an efficient scheduling method by solving a problem according to the prior art.

Another object of the present invention is to provide a scheduling method considering the waiting packet length for each user.

The present invention to achieve these objects

In the mobile communication system comprising a plurality of terminals and a base station for transmitting data in accordance with the priority given to the terminal, the method of the base station to give priority to the terminal,

Obtaining a virtual data rate of each of the plurality of terminals, and determining a priority of the terminals based on the virtual data rate obtained by the terminal,

The virtual data rate is determined by the ratio of the amount of data to be transmitted to the target terminal and the amount of data that can be transmitted by the data rate required by the target terminal.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that those skilled in the art may better understand the detailed description of the invention that follows.

Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. Those skilled in the art should recognize that the disclosed concepts and specific embodiments of the invention may be readily used as a basis for modifying or designing other structures for achieving the same purposes of the present invention. Those skilled in the art should also recognize that structures equivalent to the invention do not depart from the spirit and scope of the broadest form of the invention.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that reference numerals and like elements among the drawings are denoted by the same reference numerals and symbols as much as possible even though they are shown in different drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

The present invention provides a mobile communication system including a plurality of terminals and a base station connected to the plurality of terminals and providing a data service to the plurality of terminals according to priority in a predetermined time interval. The present invention relates to a method of selecting a terminal to be serviced in a time interval. That is, the present invention is applicable to other systems similar to the 1x EVDO system. However, for convenience of description, the following embodiment will be described based on the 1x EVDO system.

In the following description, a virtual data rate control (Virtual DRC) value means the DRC value according to an embodiment of the present invention. In the following, the principles of the present invention will first be described. Next, an embodiment according to the principles of the present invention will be described.

In order to solve the rate-packet length mismatch problem, a principle of the present invention is a DRC value, that is, a virtual data rate control value in consideration of a ratio between the amount of data queued in a predetermined queue and the amount of data that can be transmitted by a data rate in a predetermined time interval. Will be introduced. The packet scheduling method according to the principles of the present invention is as follows.

1. Obtaining a virtual data rate control value of each of the terminals.

2. Determining priorities of the plurality of terminals according to the virtual data rate control values.

3. Update average rate.

3 is a flowchart illustrating a packet scheduling method according to an embodiment of the present invention. The process of FIG. 3 is performed every time slot to select a serviced terminal.

Referring to FIG. 3, in step 310, values necessary for scheduling are set. First, the virtual DRC value is set to Equation 1 below.

Here, B _i (t) means the amount of packets of the individual queue that stores the packet to be transmitted to the terminal, Means the amount of data that can be transmitted by the transmission rate per one slot. i is 1,2..n, where the base station is the number of UEs having packets to be transmitted by the base station in timeslot t. Inefficiency is eliminated by reducing the priority of a terminal having a rate-packet length mismatch problem by readjusting the DRC value according to Equation (1).

Next, G (t), which is a set of terminals to be transmitted by the base station in timeslot t, is set. At this time, the transmission capacity of each user is determined by DRC _i and is i∈G (t).

In step 320, all terminals are divided into two groups according to the length of packets waiting. That is, B _i (t) and Compare the size of.

As a result of the comparison, if the value of B _i (t) is small, in step 330, i∈G ⁻ (t) is set, and the virtual data rate control value is set to Equation 1 above. As a result of the comparison, if the value of B _i (t) is not small, _i ∈ G ⁺ (t) is set in step 340, and the virtual data rate control value is set to DRC _i (t). A ^{(t) ∪G + (t)} - As a result, G (t) = G.

In operation 350, the terminal i, i∈G (t), and B _i (t) given in Equation 1 according to G ⁻ (t) or G ⁺ (t), which is a group belonging to Equation 2 Is defined as>.

Referring to Equation 2, the terminal having a smaller amount of data waiting for transmission than the amount of data that can be transmitted by the data rate in the predetermined time interval has a virtual data rate control value according to Equation 1. In addition, the data rate control value transmitted from the terminal becomes the virtual data control value for the terminal whose amount of data being waiting is not smaller than the amount of data that can be transmitted by the data rate in the predetermined time period.

Then, in step 360, the terminal j ∈ G (t) to be serviced in this time slot is selected according to Equation 3 below.

If the terminal j has received the service in this time slot t, in step 370, the average transmission rate of the serviced terminal is updated by Equation 4 below.

Where t _c is any constant. The average transmission rate of the terminals other than the terminal receiving the service is updated by Equation 5 below.

If the average rate is updated, the process returns to step 320 to repeat the same operation in successive timeslots. Here, the B _i (t) and Can be set again according to the transmitted data and the transmission rate.

In operation 360, the process of obtaining a terminal to be serviced may be selected by Equation 6 below.

Where a _i is a QoS parameter required by the UE, R _i is an average channel rate, and W _i is a delay time of a packet of the HOL. Priority determination according to Equation (6) uses the M-LWDF scheduling method.

4A to 4C are diagrams showing an application example of a scheduling method according to an embodiment of the present invention. Assume that there is no number of Mac PDUs waiting in the buffer before timeslot 0. And all packets are assumed to arrive at the timeslot boundary. Initial average transfer rate is = 1,228.8 kbps = 614.4kbps. 4A shows the number of Mac packets arriving at the beginning of each timeslot. 4B and 4C show the number of bits that are served when DRC and virtual DRC are used for the proportional process algorithm, respectively. If there is no packet to send to the terminal, the priority value (Priority Value) is set to 0. 4A to 4C show different results by different scheduling methods. In other words, it can be seen that it works differently from the conventional method by using the virtual DRC. The existing algorithm using DRC to service all the arriving packets in FIG. 4A used six timeslots. However, by using virtual DRC, we can reduce it to five timeslots.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications may be made 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.

As described above, the present invention has an advantage of providing a scheduling method in consideration of a waiting packet length for each user. According to the present invention, in a mobile communication system, it is possible to have a high yield per cell to provide a more competitive service.

1 is a diagram illustrating a mapping relationship between packets in a mobile communication system performing high speed data communication;

2 is a diagram showing the amount of packets waiting in an individual queue;

3 is a flowchart illustrating a packet scheduling method according to an embodiment of the present invention;

4A to 4C are diagrams showing an application example of a scheduling method according to an embodiment of the present invention.

Claims (15)

In the mobile communication system comprising a plurality of terminals and a base station for transmitting data in accordance with the priority given to the terminal, the method of the base station to give priority to the terminal, Obtaining a virtual data rate of each of the plurality of terminals; Determining priorities of the terminals based on the virtual data rates obtained by the terminal, The virtual data rate is determined by the ratio of the amount of data to be transmitted to the target terminal and the amount of data that can be transmitted by the data rate required by the target terminal. delete The method as claimed in claim 1, wherein the virtual data rate of the terminal whose amount of data to be transmitted is smaller than the amount of data that can be transmitted by the data rate is calculated by Equation 7 below. Here, B _i (t) is the amount of data to be transmitted to the terminal i, S _DRCi (t) is the amount of data that can be transmitted by the data rate required by the terminal i. The method of claim 1, wherein the virtual data rate of the terminal is greater than or equal to the amount of data that can be transmitted by the data rate is determined by the data rate. delete delete delete delete delete Receiving a request data rate from terminals; Determining a virtual data rate for the terminals in consideration of the amount of data to be transmitted to the terminal and the amount of data that can be transmitted based on the requested data rate; Assigning priorities to the terminals by the virtual data rate determined by the terminal; Selecting a terminal to be serviced in a corresponding time slot according to the priority given to the terminal; And transmitting data to the selected terminal based on the virtual data rate determined for the selected terminal. The method of claim 10, wherein the priority of a random terminal is determined by a ratio of a virtual data rate determined for the random terminal and an average rate of the random terminal. 12. The method of claim 11, wherein the priority of the arbitrary terminal is determined by further considering a quality of service parameter and a delay time of a packet. 12. The method of claim 11, further comprising updating the average transmission rate for the terminals by the virtual data transmission rate. The method of claim 13, wherein the average transmission rate of the selected terminal is updated by Equation (8). Where t _c is any constant. 15. The method of claim 14, wherein the average transmission rate of the remaining terminals except for the selected terminal is updated by Equation (9). Where t _c is any constant.