KR100580833B1 - Packet scheduling method for ensuring minimum transfer rate in mobile communication system and recording medium storing program embodying the same - Google Patents

Abstract

The present invention relates to a packet scheduling method for guaranteeing a minimum rate in a mobile communication system. According to this method, after calculating each normalized transmission rate for each set session, the order of scheduling target is determined based on the calculated normalized transmission rate. Transmission data of each session is allocated to the transmission area in the order determined above. In this case, the normalized transmission rate is calculated based on information including the most recently transmitted data amount of the session, the period from the most recent transmission time to the current slot, and the minimum guaranteed data transmission rate negotiated at the session establishment. . According to the present invention, it is possible to effectively reflect the radio channel conditions in the packetized mobile communication system to ensure the minimum rate requirements of real-time traffic.

Packet Scheduling, Scheduler, Minimum Rate, Base Rate, Normalized Rate

Description

PACKET SCHEDULING METHOD FOR ENSURING MINIMUM TRANSFER RATE IN MOBILE COMMUNICATION SYSTEM AND RECORDING MEDIUM STORING PROGRAM EMBODYING THE SAME}

1 is a conceptual diagram of a basic transmission unit (BU) expressed in a time and frequency domain in a mobile communication system.

2 is another conceptual diagram of a basic transmission unit expressed in a time and frequency domain in a mobile communication system.

3 is a diagram illustrating a data transmission situation of an arbitrary session in a packet scheduling method according to an embodiment of the present invention.

4 is a flowchart illustrating a packet scheduling method for guaranteeing a minimum transmission rate in a mobile communication system according to an exemplary embodiment of the present invention.

The present invention relates to a packet scheduling method in a mobile communication system, and more particularly, to a packet scheduling method for guaranteeing a minimum transmission rate and a recording medium storing a program for implementing the same.

In general, the fairness grant according to each transmission rate is the most important factor that the packet scheduler should have in the environment where the transmission rate requirement for each user or session is different. Granting long-term fairness in this fairness does not necessarily satisfy short-term fairness. For example, even if a certain amount of data is transmitted during the entire session to satisfy long-term fairness, there is a possibility that the data is not transmitted in a short time. Even if the data transmission is successful, the receiver may have to discard the data due to a large delay. Especially in a bursty traffic environment, providing short-term fairness can be an important factor in increasing user satisfaction.

Conventional scheduling methods provide two methodologies. First, there is a viewpoint of ensuring fairness at the expense of wireless resource efficiency, and second, there is a viewpoint of maximizing radio resource efficiency at the expense of fairness.

The first methodology is that the radio channel situation of a particular session is so good that allocating large amounts of data to that session is efficient in terms of the system's use of radio resources, but to ensure fairness between sessions or to meet minimum data rate requirements. This means giving up data transmission opportunities to sessions with relatively poor channel conditions, thus giving up some optimization of radio resource usage.

The second methodology does not guarantee fairness between sessions by providing transmission opportunities to sessions with relatively good radio channel conditions, but can optimize the use of radio resources in terms of systems.

In traditional scheduling methods, the main focus is on providing long-term fairness. This methodology has limitations as a transmission mechanism for bursted traffic, and there is a problem that the change in time is difficult to effectively reflect the radio channel situation.

Meanwhile, as a conventional technique for packet scheduling in a mobile communication system, "Providing Quality of Service over a Shared Wireless Link" (IEEE Communication Magazine, Feb. 2001, pp. 150-154) by M. Andrews is disclosed. According to this technique, (priority related parameter) X (buffer latency) X (channel condition reflection parameter) is used as a scheduling method for selecting a specific session, and when the Leaky Buket mechanism is introduced, the minimum transmission rate is guaranteed. At the same time, it is possible to maximize resource utilization. However, the prior art can service only one user at a specific time, and simulation must be performed off-line to calculate priority related parameters. Therefore, due to the constraint that only one user can serve at a certain time, efficient use of resources is questioned, an additional Leaky Bucket mechanism must be introduced, and no general methodology for calculating priority-related parameters is proposed. In addition, since it is not a transmission method for guaranteeing short-term fairness, there is a problem in that it is difficult to effectively reflect the bursty traffic situation.

An object of the present invention for solving the above problems is to ensure long-term fairness by ensuring the minimum transmission rate given during session establishment, and to perform packet scheduling using a normalized transmission rate reflecting the modified minimum transmission rate at each transmission time point. Accordingly, the present invention provides a packet scheduling method for guaranteeing a minimum transmission rate and a recording medium storing a program for implementing the same in a mobile communication system capable of adaptively providing a transmission opportunity to a traffic condition that changes in time, thereby ensuring short-term fairness.

Packet scheduling method according to an aspect of the present invention for achieving the above object,

A packet scheduling method for guaranteeing a minimum transmission rate in a mobile communication system,

a) calculating a normalized transmission rate for each established session; b) determining an order of scheduling objects based on the calculated normalized transmission rate; And c) assigning transmission data of each session to the transmission region in the determined order.

Here, step c) may include: i) allocating a basic number of transmission units for each session; And ii) allocating the transmission data to the allocated number of basic transmission units.

In addition, the normalized transmission rate is calculated based on information including the most recently transmitted data amount of the session, the period from the most recent transmission time to the current slot, and the minimum guaranteed data transmission rate negotiated at the session establishment. It is characterized by.

In addition, the basic transmission unit is the number of time and frequency for transmitting data using the AMC characteristic when the mobile communication system transmits data using the adaptive modulation control (AMC) characteristic, which is an indicator indicating a wireless channel state. It is characterized in that the minimum unit.

The method may further include setting the total number of basic transmission units of the slot to the number of surplus basic transmission units before step i), and after the step ii), assigning the surplus basic transmission units in step ii). Reducing the number of basic transmission units configured; And if the reduced number of remaining basic transmission units remains, allocating transmission data of another session with respect to the remaining number of remaining basic transmission units.

In addition, in step b), the order of scheduling targets is determined in order of increasing value of the calculated normalized transmission rate.

Also, in step ii), an area remaining after allocating the transmission data to the allocated number of basic transmission units may be padded.

Hereinafter, a packet scheduling method for guaranteeing a minimum transmission rate in a mobile communication system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a conceptual diagram of a basic transmission unit (BU) expressed in a time and frequency domain in a mobile communication system.

Referring to FIG. 1, reference numeral 101 denotes a slot which is a radio resource on the time axis, and reference numerals 102 and 103 denote radio resources on a frequency, respectively. At this time, the radio resource 102 is a radio resource on a frequency allocated for traffic to which the present invention is not applied, and the radio resource 103 is a radio resource on a frequency allocated for traffic to which the present invention is applied. .

Meanwhile, although the radio resource 102 and the radio resource 103 may be different for each slot, the sum thereof is constant for each slot.

In addition, a transmission area formed of the radio resource 101 and the radio resource 103 represents a transmission area per slot (105), and the scheduler sets a session and a transmission amount (in bytes) to be transmitted to fill the transmission area per slot for each slot. Decide

Reference numeral 106 denotes a basic transmission unit, and is defined as the minimum unit of the number of times and frequencies capable of transmitting data with the same Adaptive Modulation Control (AMC) characteristics. The AMC characteristic is an index indicating a radio channel state, and the better the radio channel state, the better the AMC characteristic between the base station and a specific terminal. That is, the better the AMC characteristic, the more data can be transmitted per basic transmission unit.

2 is another conceptual diagram of a basic transmission unit expressed in a time and frequency domain in a mobile communication system.

Referring to FIG. 2, reference numeral 203 denotes a total radio resource on a frequency, and reference numerals 201 and 202 are added to represent one slot which is a radio resource on a time axis. In this case, the radio resource 201 and the radio resource 202 may be different for each slot, but the sum thereof is constant.

Meanwhile, an area formed of the radio resource 202 and the radio resource 203 represents a transmission area per slot (205), and the scheduler determines a session and a transmission amount (in bytes) to transmit to fill the transmission area per slot for each slot. do. Reference numeral 206 denotes a basic transmission unit (BU), and since it is conceptually the same as reference numeral 106 in FIG. 1, a separate description thereof will be omitted.

3 is a diagram illustrating a data transmission situation of an arbitrary session in a packet scheduling method according to an embodiment of the present invention.

Referring to FIG. 3, reference numeral 301 denotes the amount of data most recently transmitted for any session, and reference numeral 302 denotes the time point (slot) most recently transmitted. In addition, reference numeral 303 denotes a current slot, and reference numeral 304 denotes a period from the most recently transmitted time point 302 to the current slot 303 in the number of slots.

For any session i, the most recently transmitted amount of data 301 is represented in bits and represented by M (i), and the time period 304 from the most recently transmitted time point 302 to the current slot 303. Is represented by E (i). G (i) also represents the minimum guaranteed data rate negotiated at session establishment of any session i.

After defining the state for each session as described above, the scheduler according to an embodiment of the present invention is an index for selecting a session for data transmission, and is a normalized transfer rate (NTR) calculated for session i as shown in Equation 1 below. ).

Here, Q (i) represents the modified minimum guaranteed data rate of session i, and this value of Q (i) is updated at each transmission time by Equation 2 below.

는 가장 최근에 도착한 N개의 SDU(Service Data Unit)들의 양으로 비트 단위로 표현되며,

는 세션 시작부터 현재 슬롯까지 도착한 총 SDU들의 양에서 상기

를 뺀 값으로 비트 단위로 표현되고, W는 0에서 1사이의 값을 갖는 실수이다.Here, T is the time from the start of the session to the current slot, expressed in slot units,

Is the number of N SDUs (Service Data Units) most recently arrived, expressed in bits.

Is recalled in the total amount of SDUs arriving from the beginning of the session to the current slot.

Expressed in bits, minus, W is a real number with a value between 0 and 1.

Therefore, the packet scheduler prioritizes sessions with a large normalized transmission rate (NTR) of a session for transmission efficiency of radio resources, and the normalized transmission rate is the minimum guaranteed data rate negotiated at the time of setting up each session. Is calculated to ensure. In addition, since the normalized data rate includes a modified minimum guaranteed data rate for each transmission time point, the normalized data rate may be adaptively applied to traffic having bursty attributes.

On the other hand, when session i is selected by the scheduler, all data in the transmission buffer of session i is transmitted. For the selected session i, if the amount of data waiting in the transmission buffer in slot k is P (i, k), the number of basic transmission units (BU) to be allocated is calculated by Equation 3 below. .

는 x보다 큰 최소 정수를 의미한다.Where A (i, j, k) is the maximum number of bytes that can be sent to AMC option j in the next slot (k + 1)

Is the smallest integer greater than x.

Hereinafter, a packet scheduling method for guaranteeing a minimum transmission rate in a mobile communication system according to an exemplary embodiment of the present invention will be described in detail.

First, the current slot is called k, and scheduling is performed for data transmission in the next slot in the current slot k (S401).

Next, the total number of BUs that can be allocated to each preset slot is set as an initial surplus BU (S403).

Thereafter, it is determined whether the number of surplus BUs that can be allocated remains (S403), and if the number of surplus BUs remains, scheduling is terminated. Otherwise, it is determined whether there is data to be transmitted in the buffer (S404).

If there is data to be sent in the buffer, for each session, the data rate (NTR) normalized by Equation 1 using M (i), E (i), Q (i) and G (i) values, respectively Calculate (S405).

Packet scheduling is prioritized in order of sessions with the normalized transmission rate (NTR) value calculated in step S405 above. Therefore, the packet scheduler first sorts each session in descending order of the normalized data rate, and then allocates transmission data starting with the session having the largest normalized data rate value.

First, as many BUs as C (i, k) determined by Equation 2 are allocated to each session (S406).

Next, P (i, k) bytes of transmission data are allocated to the allocated C (i, k) BUs (S407). At this time, the remaining portion after allocating transmission data to the allocated C (i, k) BUs, that is, the bytes C (i, k) * A (i, j, k)-P (i, k) are padded. Process.

After completing the transmission data allocation, the number of surplus BUs is reduced by the number of allocated BUs (S408).

As such, when the transmission data allocation for the specific session determined by the priority is finished, it is determined whether there is an excess number of BUs (S409), and if there is no excess number of BUs, the scheduling is terminated, otherwise the transmission data is allocated. If the number of surplus BUs remains, it is determined whether a target session to which transmission data is allocated exists (S410).

If the target session does not exist, scheduling is terminated, otherwise, the steps S406 to S410 are repeated to allocate transmission data for the next session, and this repetition does not exist in the target session in step S410. Is performed until not.

On the other hand, the packet scheduling method according to an embodiment of the present invention as described above is implemented as a program to be stored in a recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.) in a computer-readable form Can be.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited thereto, and various other changes and modifications are possible.

According to the present invention, it is possible to effectively reflect the radio channel conditions in the packetized mobile communication system to ensure the minimum rate requirements of real-time traffic.

It can also be effectively applied to bursty traffic.

Claims (10)

A packet scheduling method for guaranteeing a minimum rate in a mobile communication system, a) calculating a normalized transmission rate for each established session; b) determining an order of scheduling objects based on the calculated normalized transmission rate; And c) assigning transmission data of each session to the transmission region in the determined order; Packet scheduling method comprising a. The method of claim 1, C), i) allocating a basic number of transmission units for each session; And ii) allocating the transmission data to the allocated number of basic transmission units Packet scheduling method comprising a. The method of claim 2, The basic transmission unit is a minimum unit of the number of times and frequencies capable of transmitting data using the AMC characteristic when the mobile communication system transmits data using an adaptive modulation control (AMC) characteristic, which is an indicator indicating a wireless channel state. Packet scheduling method characterized in that. The method of claim 2, Before step i), Setting the total number of basic transmission units in the slot to the number of surplus basic transmission units, After step ii), Reducing the number of basic transmission units allocated in step ii) from the number of surplus basic transmission units; And Allocating transmission data of another session with respect to the remaining number of remaining basic transmission units when the number of the remaining redundant basic transmission units remains. Packet scheduling method further comprising. The method of claim 1, In step b), the scheduling method of the packet, characterized in that for determining the order of the scheduling target in the order of the higher value of the normalized transmission rate. The method according to claim 1 or 2, The normalized transmission rate is calculated based on information including the most recently transmitted data amount of the session, the period from the most recent transmission time to the current slot, and the minimum guaranteed data transmission rate negotiated at the session establishment. A packet scheduling method. The method of claim 6, The normalized transmission rate is

Where M (i) is the amount of data most recently transmitted in session i,         E (i) is the period from the most recently transmitted point in session i to the current slot,         G (i) is the minimum guaranteed data rate negotiated at session establishment in session i,         Q (i) is the modified minimum guaranteed data rate of session i. Is calculated according to The modified minimum guaranteed data rate of session i is given by

Where T is the time from the start of the session to the current slot,

Is the amount of the most recent N Service Data Units (SDUs) arrived.

Is the total amount of SDUs arriving from the start of the session to the current slot,         W is a real number with a value between 0 and 1. Packet scheduling method comprising the following. The method according to any one of claims 2 to 4, The number of basic transmission units allocated for each session is as follows.

Where P (i, k) is the amount of data waiting in the transmit buffer of session i in slot k,         A (i, j, k) is the maximum number of bytes that can be sent from slot k + 1 to AMC option j, sign

Is the smallest integer greater than x. Packet scheduling method, characterized in that calculated according to. The method according to any one of claims 2 to 4, In step ii), an area remaining after allocating the transmission data to the allocated number of basic transmission units is padded. In a recording medium storing a program for implementing a packet scheduling method for guaranteeing a minimum transmission rate in a mobile communication system, a) calculating each normalized transmission rate for each established session; b) determining an order of a scheduling object based on the calculated normalized transmission rate; And c) assigning transmission data of each session to a transmission area according to the determined order; Record medium that stores the program to implement.

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