KR20120107167A - Evolvoed node b and packet scheduling method - Google Patents

Abstract

PURPOSE: A base station and packet scheduling method are provided to allocate a RB(resource block) satisfied with a CNIR(carrier-to-noise-and-interference-ratio) which is necessary for an MBMS(Multimedia Broadcast Multicast Service). CONSTITUTION: A scheduler(140) determines the number of user terminals allocated by a plurality of RB. The scheduler determines a final RB as the RB to which the most user terminals are allocated. The scheduler creates scheduling information allocated to the determined final RB. A transmission unit(150) creates a transmission signal for transmitting a data channel according to the scheduling information. The transmission unit transmits the created transmission signal to a plurality of user terminals. [Reference numerals] (110) Broadcast service processing unit; (120) Reception unit; (130) CINR measurement unit; (140) Scheduler; (150) Transmission unit

Description

Base station and packet scheduling method {Evolvoed Node B and Packet Scheduling Method}

The present invention relates to a packet scheduling method, and more particularly, to a base station and a packet scheduling method for dynamically allocating a resource block allocated to a multimedia broadcast multi-cast service (MBMS) user terminal.

In 3GPP Long Term Evolution (LTE), a broadcast service and a multimedia broadcast multi-cast service (MBMS) supporting multimedia became an essential requirement.

MBMS allows transmitting downlink data from a single source to multiple receivers in broadcast mode or multicast modes.

The 3GPP LTE (Long Term Evolution) system supports the MBMS service and activates the multimedia service at the base station (Evolvoed Node B, eNB). In the 3GPP LTE system, there are a single cell MBMS transmission method and a multi cell MBMS transmission method as an MBMS service.

The single cell MBMS transmission method transmits the same service in one eNB, and the multi-cell MBMS transmission method transmits the same service in an eNB configured as a group.

In addition, the 3GPP LTE system is studying RRM (Radio Resource Management), a scheduler based on packet switching.

When the MBMS subscriber requests resource block (RB) allocation, the packet scheduling algorithm allocates RBs so as to allocate RB to the MBMS subscriber.

Each RB is assigned an RB to the corresponding MBMS subscriber in accordance with the determination of the manner of the packet scheduling algorithm. Modulation and Coding Scheme (MCS) in the single-cell MBMS transmission scheme is applied to the MBMS subscribers with the lowest quality of service among the MBMS subscriber groups in order to guarantee the quality of service (QoS) of all MBMS subscribers. MCS must be matched.

Conventional packet scheduling algorithms that allow the allocation of RBs to MBMS subscribers determine RB allocations to MBMS subscribers without considering Channel Quality Indicators (CQIs) from MBMS subscribers. The RB allocation of the MBMS subscriber does not change during the simulation time.

Since the packet scheduling algorithm allocates a fixed RB without considering the CQI and the channel state of the user terminal, there is a problem in that the performance and efficiency of packet scheduling are deteriorated. Cell throughput is not good because the user does not satisfy the CQI.

In order to solve such a problem, an object of the present invention is to provide a base station and a packet scheduling method for allocating an RB that maximizes the number of MBMS user terminals satisfying CNIR above a predetermined threshold required for MBMS broadcasting service. .

In accordance with an aspect of the present invention, a base station determines a number of user terminals allocated according to each resource block among a plurality of resource blocks, and assigns the resource blocks having the largest number of allocated user terminals to a data channel. A scheduler that determines a final resource block to allocate and generates scheduling information so that the determined final resource block is allocated; And a transmitter for generating a transmission signal for transmitting a data channel according to the scheduling information and transmitting the signal to the plurality of user terminals.

Packet scheduling method according to an aspect of the present invention comprises the steps of: identifying the number of user terminals allocated according to each resource block of the plurality of resource blocks; Determining a resource block having the largest number of allocated user terminals as a final resource block for allocating a data channel, and generating scheduling information to allocate the determined final resource block; And generating a transmission signal for transmitting a data channel according to the scheduling information and transmitting the same to a plurality of user terminals.

According to the above configuration, the present invention has an effect of improving outage probability and cell throughput by applying a packet scheduling algorithm for finding the RB having the largest number of MBMS user terminals satisfying the MBMS broadcast service.

The present invention has an effect of improving the system throughput by applying a packet scheduling algorithm for finding the RB with the largest number of MBMS user terminals satisfying the MBMS broadcast service not only in a single service and a single cell environment but also in a multi-service and a multi-cell environment.

1 is a diagram illustrating a schematic configuration of a multimedia broadcast multicast service (MBMS) broadcasting service system according to an exemplary embodiment of the present invention.
2 is a block diagram briefly illustrating an internal configuration of a base station according to an embodiment of the present invention.
3 is a diagram illustrating packet scheduling of a scheduler according to an embodiment of the present invention.
4 is a diagram illustrating a packet scheduling method in a base station according to an embodiment of the present invention.
FIG. 5 is a diagram illustrating a result of comparing a cell-edge with an outage probability and an outage probability of a conventional blind packet scheduling algorithm, a channel-aware packet scheduling algorithm, and a packet scheduling MBMS algorithm proposed by the present invention.
FIG. 6 shows the result of comparing the Cell-Thoughput in the Cell-Thoughput and Cell-Edge parts of the conventional blind packet scheduling algorithm, the channel-aware packet scheduling algorithm, and the packet scheduling MBMS algorithm proposed by the present invention. The figure shown.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise.

The packet scheduling MBMS algorithm proposed in the present invention is applicable to both a single-cell MBMS transmission method and a multi-cell MBMS transmission method. However, for convenience of description, the packet scheduling MBMS algorithm focuses on a single cell MBMS transmission method.

Single cell MBMS transmission consists of Point to Point (PtP) using a transport channel and Point to Multi-point (PtM) transmission using a common channel.

An embodiment of the present invention is based on a Long Term Evolution (LTE) system model using an Orthogonal Frequency Division Multiplexing (OFDM) downlink modulation scheme.

1 is a diagram illustrating a schematic configuration of a multimedia broadcast multicast service (MBMS) broadcasting service system according to an exemplary embodiment of the present invention.

MBMS system according to an embodiment of the present invention includes a plurality of base station (Evolved Node B, eNB) (100) and Serving Gateway (Serving Gateway) (200). In addition, it includes a plurality of MBMS user terminal 300 in a certain cell and broadcasting the MBMS broadcast service.

The plurality of base stations 100 determine the RBs allocation according to the CINR of the MBMS subscriber station. Each base station 100 performs packet scheduling that allocates an RB to an MBMS user terminal 300 that broadcasts an MBMS broadcast service that satisfies a CNIR equal to or more than a preset threshold and has the same modulation and coding scheme (MCS). To perform. Here, the MBMS subscriber station refers to a terminal that asks the base station 100 to subscribe to a service before receiving the MBMS broadcast service, and the MBMS user terminal 300 refers to a terminal broadcasting an MBMS broadcast service among the MBMS subscriber stations.

The serving gateway 200 receives the plurality of MBMS broadcast services and transmits the same MBMS broadcast service to the plurality of base stations 100.

2 is a block diagram schematically illustrating an internal configuration of a base station according to an embodiment of the present invention, and FIG. 3 is a diagram illustrating packet scheduling of a scheduler according to an embodiment of the present invention.

The base station 100 according to the embodiment of the present invention includes a broadcast service processor 110, a receiver 120, a carrier to noise and interference ratio (CNIR) measuring unit 130, a scheduler 140, and a transmitter ( 150).

The broadcast service processor 110 receives wireless signals from the plurality of MBMS user terminals 300 and stores information on the broadcast service activated in each MBMS user terminal 300.

The broadcast service processor 110 may determine which channel is activated and which service is performed in each MBMS user terminal 300.

The receiver 120 receives information necessary for allocation of a resource block including channel quality indicator (CQI) information and resource block size from each MBMS user terminal 300.

The CNIR measurement unit 130 calculates CNIR information based on the CQI information.

The scheduler 140 performs time scheduling and frequency scheduling based on CNIR information and resource block size and generates scheduling information.

The scheduler 140 determines scheduling information so that a resource block is allocated based on CNIR information. Here, the scheduling information includes information indicating a combination of modulation and coding schemes and channel coding rates, scheduling times, intervals, and data rates, in addition to information indicating which resource blocks are allocated to which terminals.

The scheduler 140 determines a resource block allocated to the data channel according to the packet scheduling MBMS algorithm.

Hereinafter, a packet scheduling MBMS algorithm proposed by the present invention will be described.

Packet scheduling MBMS algorithm is to maximize the number of MBMS user terminal 300 that satisfies CNIR above a predetermined threshold for MBMS service in PtM type MBMS transmission.

The scheduler 140 determines scheduling information such that the number of RBs in which the number of MBMS user terminals 300 satisfying the CNIR equal to or greater than a predetermined threshold required for the MBMS service is allocated, as shown in Equation 1 below. do.

Here, i and j are independent, i denotes the number of RBs, j denotes the number of MBMS user terminals 300 that can be serviced when an arbitrary RB (i) is selected, and N and M denote integers.

Accordingly, i ^* denotes an RB in which the maximum number of MBMS user terminals 300 satisfying CNIR equal to or greater than a predetermined threshold required for MBMS service is maximized.

i represents the number of RBs allocated to support the MBMS service among N total RBs N allocated to the base station 100, and j represents the number of MBMS user terminals 300 according to the selected i when i is selected from the base station 100. Indicates a number.

Table 1 below shows j indicating the number of MBMS user terminals 300 according to the selected i when the number of RBs capable of supporting the MBMS service is n.

As shown in Table 1 and FIG. 3, let N be the number of RBs. RB 1 is assigned to 100 MBMS user terminal 300, RB n is 105 MBMS user terminal 300, RB N is assigned 99 MBMS user terminal 300.

Accordingly, the scheduler 140 selects the RB n having the largest number of MBMS user terminals 300. Here, each MBMS user terminal 300 of the RB satisfies a CINR above a preset threshold and performs a broadcast service having the same modulation and coding scheme (MCS).

The scheduler 140 determines the final RB allocated to the data channel as RB n.

The transmitter 150 generates a transmission signal for transmitting a data channel according to the scheduling information of the scheduler 140 and transmits it to the MBMS user terminal 300.

The present invention improves system throughput by applying a packet scheduling algorithm for finding the RB with the largest number of MBMS user terminals 300 satisfying the MBMS broadcast service not only in a single service and a single cell environment but also in a multi-service and multi-cell environment.

4 is a diagram illustrating a packet scheduling method in a base station according to an embodiment of the present invention.

The scheduler 140 determines the number of MBMS user terminals 300 allocated according to each RB among the plurality of RBs (S100).

The scheduler 140 determines the final RB for allocating the RB having the largest number of MBMS user terminals 300 allocated to the data channel, and generates scheduling information so that the final RB is allocated (S102).

The transmitter 150 generates a transmission signal for transmitting a data channel according to the scheduling information and transmits it to the plurality of MBMS user terminals 300 (S104).

As shown in FIG. 3, RB 1 is allocated to 100 MBMS user terminals 300, RB n is allocated to 105 MBMS user terminals 300, and RB N is 99 MBMS user terminals 300. Is assigned to).

That is, 100 MBMS user terminals 300 are broadcasting MBMS broadcast service A, 105 MBMS user terminals 300 are broadcasting MBMS broadcast service B, and 99 MBMS user terminals 300 are MBMS broadcast services. It can be said that it is broadcasting C.

The scheduling method of the present invention can be seen as one-to-one correspondence with the MBMS user terminal 300 allocated according to each RB and the MBMS broadcasting service broadcasted by the terminal 300. Allocating an RB to a Service

When the scheduler 140 selects the RB with the largest number of MBMS user terminals 300 allocated according to each RB, the final RB is allocated to the plurality of MBMS user terminals 300 broadcasting the same MBMS broadcast service in the cell. Done.

A scheduling method in a base station 100 according to an embodiment of the present invention includes a plurality of terminals that satisfy a CNIR of a predetermined threshold or more requiring an MBMS broadcast service and perform the same MBMS broadcast service having the same modulation and coding scheme. Allocate RB.

In another embodiment of the present invention, when the number of RBs allocated to the MBMS broadcast service is one or more, if the number of RBs allocated to each MBMS broadcast service is small and the number of RBs is the same, the MBMS user terminal 300 The RB with the largest number of is selected.

For example, if there is a broadcast service A, a broadcast service B, and a broadcast service A requires two RBs and a broadcast service B requires three RBs, the base station 100 selects a broadcast service A that requires less RB, and among the plurality of RBs. An RB having a large number of allocated MBMS user terminals 300 is selected and allocated to the terminal 300 broadcasting broadcast service A.

For example, if there is a broadcast service A, a broadcast service B, a broadcast service c, and a broadcast service A requires two RBs, a broadcast service B requires three RBs, and a broadcast service C requires two RBs, the base station 100 has a low RB. The necessary broadcast services A and C are selected, and among the broadcast services A and C, a broadcast service having a large number of MBMS user terminals 300 allocated to the RB is selected to allocate an RB.

Table 2 below shows simulation parameter values of the packet scheduling MBMS algorithm used in the present invention.

Simulation Parameter Value Cell radius 1 km Antenna type Omni-directional Downlink transmission power 36 dBm Noise density -174 dBm / Hz Noise fgure 6 dB Pathloss exponent 3.74 Standard deviation of shadowing 8 dB Shadowing correlation between cells 0.5 System bandwidth 5 MHz Carrier frequency 2.3 GHz FFT size 512 Number of occupied subcarriers 324 Number of total RBs 27 Number of RBs for non-MBMS 22 Number of subcarriers per RB (Nsc) 12 Number of OFDM symbols per TTI (Nsymbol) 12 Required minimum CNIR 3 dBm Traffic model Full buffer

The cell radius consists of 1000 m and uses one omni-directional antenna per cell.

The user's location was generated using the uniform probability variable, and the same distribution was made for each simulation to generate the same interference effect.

In order to measure performance according to the number of users and to vary the number of users in each cell, the average number of users in each cell is generated as a Poison distribution.

The downlink base station transmit power was 36 dBm, and the path loss was 3.74 for the measurement of the CINR. In addition, regardless of the distance between the base station 100 and the user, the standard deviation of shadowing, which is an attenuation component generated by the surrounding environment, was set to 8 dB, even though the distance between the base station 100 and the user was the same. Depending on the situation, the attenuation effect experienced by the signal may vary.

The system bandwidth is 5 MHz and the carrier frequency is 2.3 GHz. In this case, the FFT size is 512 and has 324 data subcarriers.

Since each subcarrier interval is 15 KHz, there are 27 RBs having 12 consecutive subcarriers.

And since it is assumed to be a frequency non-selective fading channel, 12 subcarriers of each RB have the same MCS. By using this, the number of bits transmitted through one RB in one TTI can be defined, as shown in Equation 2 below.

은 MCS(n)에 따른 코딩율이고, Nsc는 하나의 RB에 속한 부반송파의 수이며, Nsymb는 하나의 RB에 속한 OFDM 심벌의 수이다.Where Mn is MCS level n according to CNIR,

Is the coding rate according to MCS (n), Nsc is the number of subcarriers belonging to one RB, and Nsymb is the number of OFDM symbols belonging to one RB.

The maximum number of retransmissions is limited to 4 and the coding rate is 1/2 or 3/4. Modulation methods include QPSK, 16QAM, and 64QAM.

Six coding modulation and coding schemes are shown in Table 3 below.

MCS Modulation Coding rate One QPSK 1/2 2 QPSK 3/4 3 16QAM 1/2 4 16QAM 3/4 5 64QAM 1/2 6 64QAM 3/4

As shown in FIGS. 5 and 6, the simulation result compares the outage probability and the cell-thoughput between the conventional blind packet scheduling algorithm, the channel-aware packet scheduling algorithm, and the packet scheduling MBMS algorithm proposed by the present invention.

The MBMS user terminal 300 that does not satisfy the minimum CNIR for performing the MBMS broadcast service is defined as Outage.

Cell-Thoughput is calculated as the sum of the throughput of the MBMS user terminal 300 excluding Outage in the single cell MBMS transmission scheme.

In the simulation of the present invention, the data modulation technique and the coding technique are defined as shown in [Table 3], but the same data modulation technique and the coding technique should be applied to synchronize the MBMS broadcasting service.

Therefore, in the simulation of the present invention, QPSK 1/2 was used, which considers the MBMS subscriber station in the Cell-Edge.

FIG. 5 is a diagram illustrating a result of comparing a cell-edge with an outage probability and an outage probability of a conventional blind packet scheduling algorithm, a channel-aware packet scheduling algorithm, and a packet scheduling MBMS algorithm proposed by the present invention.

As shown in FIG. 5, the packet scheduling MBMS algorithm of the present invention maximizes the number of MBMS user terminals 300 satisfying a Signal to Interference Noise Ratio (CNIR) above a predetermined threshold. Shows better performance because the probability of outage is lower than that of blind packet scheduling algorithm and channel-aware packet scheduling algorithm.

FIG. 6 shows the result of comparing the Cell-Thoughput in the Cell-Thoughput and Cell-Edge parts of the conventional blind packet scheduling algorithm, the channel-aware packet scheduling algorithm, and the packet scheduling MBMS algorithm proposed by the present invention. The figure shown.

As shown in FIG. 6, the packet scheduling MBMS algorithm of the present invention shows that Cell-Thoughput provides higher performance than the blind packet scheduling algorithm and the channel-aware packet scheduling algorithm.

The embodiments of the present invention described above are not implemented only by the apparatus and / or method, but may be implemented through a program for realizing functions corresponding to the configuration of the embodiment of the present invention, a recording medium on which the program is recorded And such an embodiment can be easily implemented by those skilled in the art from the description of the embodiments described above.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (7)

A base station supporting a multimedia broadcast multicast service (MBMS) broadcasting service,
Determine the number of user terminals allocated according to each resource block among a plurality of resource blocks, determine the final resource block that allocates the resource block having the largest number of allocated user terminals to the data channel, and determine the final resource block determined above. A scheduler for generating scheduling information to be assigned; And
A transmitter for generating a transmission signal for transmitting a data channel according to the scheduling information and transmitting the signal to the plurality of user terminals
A base station comprising a. The method of claim 1,
The user terminal allocated according to each resource block provides a broadcast service that satisfies a carrier to noise and interference ratio (CNIR) above a predetermined threshold and has the same modulation and coding scheme (MCS). A base station, characterized in that performing. The method of claim 1,
Receiving a radio signal from a plurality of user terminals includes a broadcast service processing unit for analyzing information on the broadcast service activated in each user terminal,
The transmitter base station, characterized in that for transmitting the transmission signal to a terminal that performs the same broadcast service in a specific area. The method of claim 1,
The plurality of resource blocks indicate the number of resource blocks allocated to support the MBMS broadcast service, and the final resource block indicates a signal to interference noise ratio above a predetermined threshold that requires the MBMS broadcast service. , The base station characterized in that the user terminal that satisfies the CNIR (number of resource blocks) indicates the most resource block. The method of claim 3,
The scheduler analyzes the activated broadcast service to determine the final resource block allocated to the data channel in consideration of the number of resource blocks allocated to each broadcast service and the number of user terminals allocated according to each resource block. Characterized by a base station. A packet scheduling method in a base station supporting a multimedia broadcast multicast service (MBMS) broadcasting service,
Determining the number of user terminals allocated according to each resource block among the plurality of resource blocks;
Determining a resource block having the largest number of allocated user terminals as a final resource block for allocating a data channel, and generating scheduling information to allocate the determined final resource block; And
Generating a transmission signal for transmitting a data channel according to the scheduling information and transmitting it to a plurality of user terminals
Packet scheduling method comprising a. The method according to claim 6,
The step of transmitting to the plurality of user terminals,
The transmission signal is a terminal that satisfies a carrier to noise and interference ratio (CNIR) above a predetermined threshold in a specific region and performs a broadcast service having the same modulation and coding scheme (MCS). Packet scheduling method comprising the step of transmitting.

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