KR101433847B1 - Apparatus and method for burst scheduling in broadband wireless communication system - Google Patents

Abstract

The present invention relates to an apparatus and method for burst scheduling in a broadband wireless communication system. There is provided a burst scheduling method in a broadband wireless communication system for communicating a frame to which a fractional frequency reuse (FFR) scheme is applied, the method comprising the steps of: segmented zone having a frequency reuse pattern of 1 and a non-segmented zone having a frequency reuse pattern of 1, and configuring transmission bursts to be transmitted to the UEs using the received channel values Comparing the first MPR for the segment zone with the second MPR for the non-segment zone, and selecting a zone in which the corresponding burst is to be transmitted, for each of the transmission bursts.

Broadband wireless access, frequency reuse. Burst allocation

Description

[0001] APPARATUS AND METHOD FOR BURST SCHEDULING IN BROADBAND WIRELESS COMMUNICATION SYSTEM [0002]

The present invention relates to a broadband wireless communication system, and more particularly, to an apparatus and method for burst scheduling in a broadband communication system using a partial frequency reuse (FFR) technique.

A fourth generation (4th generation) communication system, which is a next generation communication system, wants to provide users with various quality of service (QoS) services having a transmission speed of about 100 Mbps. Particularly, the 4th generation communication system is currently being applied to a broadband wireless access (BWA) communication system such as a wireless local area network (LAN) system and a wireless metropolitan area network (MAN) mobility and quality of service (QoS), and its typical communication system is IEEE (Institute of Electrical and Electronics Engineers) 802.16 based communication system.

The IEEE 802.16 based broadband wireless communication system uses an Orthogonal Frequency Division Multiple Access (OFDMA) scheme for broadband transmission. The OFDMA scheme is a scheme for transmitting data using a plurality of orthogonal subcarriers. Since the OFDMA scheme has high frequency utilization efficiency and is robust against multi-path fading, high transmission efficiency can be obtained in high-speed data transmission .

In general, the broadband wireless communication system forms subchannels by grouping all subcarriers having orthogonality. Also, the broadband wireless communication system performs communication on a frame-by-frame basis. The base station transmits allocation information on bursts allocated in a frame through a MAP message, and the terminal decodes the MAP message to check the burst allocation status.

Meanwhile, the broadband wireless communication system can use '1' or 'N (> 1)' as a frequency reuse pattern (FRP). When the frequency reuse pattern is 1, all the subchannels are used by all the cells. However, when the UE is located at a cell boundary, co-channel interference (CCI) The reception performance of the terminal is deteriorated. On the other hand, if the frequency reuse pattern is large, neighboring cells can use different subchannels, thereby improving the reception performance of the UE, but the frequency efficiency is lowered.

Therefore, it is necessary to apply the frequency reuse pattern 1 to improve the frequency efficiency for a UE having a good reception environment, and to reduce inter-cell interference by applying the frequency reuse pattern N to the UE located at the cell boundary. That is, it is necessary to dynamically apply the frequency reuse pattern according to the reception environment of the terminal.

It is therefore an object of the present invention to provide an apparatus and method for a system to operate a plurality of frequency reuse patterns.

It is another object of the present invention to provide an apparatus and method for dividing a frame into a zone having a frequency reuse pattern of 1 and a zone having a frequency reuse pattern of N (> 1) in a broadband wireless communication system.

Another object of the present invention is to provide an apparatus and a method for dynamically allocating user data to a first zone and a second zone when a frame includes a first zone having a frequency reuse pattern of N and a second zone having a frequency reuse pattern of 1 .

It is another object of the present invention to provide a method and apparatus for allocating user data selectively to a first zone or a second zone according to resource efficiency when a frame includes a first zone having a frequency reuse pattern N and a second zone having a frequency reuse pattern 1 And to provide a method and an apparatus for the same.

According to an aspect of the present invention, there is provided a burst scheduling method in a broadband wireless communication system for communicating a frame to which a fractional frequency reuse (FFR) scheme is applied, the method comprising: generating a frequency reuse pattern Receiving a channel value for each of a segmented zone having N (> 1) and a non-segmented zone having a frequency reuse pattern of 1, For each of the transmission bursts, a first MPR for a segment zone and a second MPR for a non-segment zone are compared with each other, and the corresponding burst is transmitted And a process of selecting a zone.

According to another aspect of the present invention, there is provided a base station apparatus for communicating a frame to which a fractional frequency reuse (FFR) scheme is applied, the base station apparatus including: a segment zone having a frequency reuse pattern of N (> 1) segmented zone having a frequency reuse pattern of 1 and a non-segmented zone having a frequency reuse pattern of 1, and a transmitter configured to construct transmission bursts to be transmitted to the terminals using the received channel values, For each of the transmission bursts, a first MPR for a segment zone and a second MPR for a non-segment zone to select a zone to which the corresponding burst is to be transmitted, .

As described above, in the broadband wireless communication system using the FFR scheme, the burst is selectively allocated to the segment zone and the non-segment zone according to the reception environment of the terminal, so that the resource efficiency can be improved and the QoS degradation can be reduced have. That is, bursts of terminals located at cell boundaries and having poor reception environments are allocated to segment zones to improve reception performance, and bursts of terminals with good reception environments are allocated to non-segment zones to increase frequency efficiency, The entire resources of the system can be efficiently used.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions of the present invention, and may be changed according to the intentions or customs of the user, the operator, and the like. Therefore, the definition should be based on the contents throughout the specification.

Hereinafter, a method for operating a plurality of frequency reuse patterns in a broadband wireless communication system will be described. To this end, the present invention divides the downlink subframe into a first zone having a frequency reuse pattern (FRP) N (> 1) and a second zone having a frequency reuse pattern of 1. The entire subchannel of the first zone is divided into a plurality of segments, and adjacent cells perform communication using different segments, thereby reducing inter-cell interference.

As described above, a method of using some subchannels in a specific time interval is defined as "fractional frequency reuse (FFR). &Quot;

In IEEE 802.16, the use of a subchannel in a downlink zone (downlink subframe) can be restricted by a bitmap. Quot; DL sub-channel assignment bitmap "and " TUSC1 permutation sub-channel bitmap " which are Type / Length / value (TLV) values of a DCP (Downlink Channel Descriptor) , And "TUSC2 permutation active subchannels bitmap ".

For example, FFR can be implemented by limiting the use of subcarriers in the first PUSC zone through the "Used subchannel bit map" of the FCH. Hereinafter, in the present invention, a zone using a limited subcarrier is defined as a "segmented zone ", and a zone using the entire subcarrier is defined as a" non-segmented zone ". It is assumed that the segment zone has a frequency reuse pattern of 3.

1 illustrates a downlink frame structure to which FFR is applied according to an embodiment of the present invention.

As shown in the figure, the downlink frame includes a preamble zone 100, a MAP zone 102, a segment zone 104, and a non-segment zone 106. Here, the horizontal axis is divided into OFDMA symbols on the time axis, and the vertical axis is divided into subchannels on the frequency axis. The preamble zone 100 transmits a preamble signal for providing synchronization (time and frequency synchronization) and cell information to the UE, and the MAP zone 102 transmits an FCH message and a MAP message. The MAP zone 102 is divided into three segment areas according to FFR application, and each cell (or sector) transmits an FCH message and a MAP message (DL-MAP / UL-MAP) through the corresponding segment area. The FCH message includes basic configuration information for a frame and decoding information of a MAP message. The MAP message includes burst allocation information for the non-segment zone 106 as well as the corresponding segment area.

The entire subchannel of the segment zone 104 is divided into three groups. At this time, the total subcarrier may be expressed by the sum of subchannel group 1, subchannel group 2, and subchannel group 3. Here, an area using subchannel group 1 is defined as a segmented zone for Cell A, an area using subchannel group 2 is defined as a segmented zone for cell B, And a region using subchannel group 3 is defined as a third segmented region (Cell B). At this time, it is possible to reduce interference between adjacent cells by allowing adjacent cells (or sectors) to use different segment regions. The number of subchannels used in each segment region is assumed to be the same, but may vary depending on the case.

In this manner, when FFR is applied, up to a particular K-th OFDMA symbol can be used as a segment zone, and after the k-th OFDMA symbol, it can be used as a non-segment zone. That is, the FRP3 system operates in the Kth OFDMA symbol within one frame, and the FRP1 system is used in the FRC3 system after the kth OFDMA symbol. At this time, it is assumed that the k value is fixed to a configuration value. The present invention dynamically allocates a downlink data burst to be transmitted to a mobile station to a segment zone 104 or a non-segment zone 106 according to a reception environment of the mobile station, thereby dynamically operating the mobile station in the FRP1 system or the FRP3 system.

As described above, when the downlink subframe includes the segment zone 104 and the non-segment zone 106, user data (data burst) can be selectively allocated to the two zones in consideration of resource efficiency I need a plan.

First, a CQICH (Channel Quality Indicator CHannel) for a segment zone and a CQICH for a non-segment zone are operated in order to determine which zone is effective to allocate to the corresponding zone. The UE measures a Carrier to Interference and Noise Ratio (CINR) corresponding to frequency reuse 3 and a second CINR corresponding to frequency reuse 1 using a preamble or a pilot signal, Values are reported to the base station through two pre-allocated CQICHs. Then, the base station calculates the MCS level and the modulation order product coding rate (MPR) for each of the first CINR and the second CINR reported from the UE, and compares the MPRs of the two zones thus calculated to select a zone with a high resource efficiency .

2 shows a configuration of a base station in a broadband wireless communication system according to an embodiment of the present invention.

As illustrated, the BS includes a scheduler 200, a message generator 202, a burst generator 204, an encoder 206, a modulator 208, a resource mapper 210, an OFDM modulator 212, an RF (Radio Frequency) transmitter 214 and a CQICH receiver 216.

Referring to FIG. 2, the CQICH receiver 216 first demodulates each CQI channel to obtain a CQI value, and provides the obtained CQI value to the scheduler 200. According to the present invention, a base station allocates a CQICH for a segment zone and a CQICH for a non-segment zone to each terminal. Accordingly, the UE measures the CINR of the frequency reuse pattern 3 and the CINR of the frequency reuse pattern 1 using a preamble or a pilot signal, and reports to the base station through two CQICHs.

The scheduler 200 classifies CQI values from the CQICH receiver 206 for each UE. Here, the first CINR value (segment zone) and the second CINR value (non-segment zone) for the same terminal are simultaneously received in one frame through two CQI channels, or two frames Respectively. The scheduler 200 determines two CINR values for each terminal and determines MCS and MPR for each CINR value. The scheduler 200 compares the value obtained by multiplying the MPR for FRP (Frequency Reuse Pattern) 1 by 3 and the MPR for FRP3. If the MPR for FRP3 is greater than or equal to the MPR, To the zone, and if not, to the non-segment zone. When the burst allocation is completed for the current frame, the scheduler 200 provides scheduling information (resource allocation information (e.g., resource location and size, MCS level, etc.) for each burst) to the message generating unit 202. Detailed functions and operations of the scheduler 200 will be described in detail below with reference to FIGS. 3 to 5. FIG.

The message generator 202 generates a MAC management message to be transmitted to the MS. For example, the message generator 202 generates a MAP message using the scheduling information from the scheduler 200. Here, the MAP message is transmitted to the corresponding segment area, and includes not only the resource allocation information of the corresponding segment area but also the resource allocation information of the non-segment zone.

The burst configuration unit 204 configures a signaling message and a user packet (MAC PDU) from the message generation unit 202 as a burst, which is a physical layer transmission unit, under the control of the scheduler 200. The burst may comprise at least one packet (MAC PDU) to be transmitted at the same MCS level.

The encoder 206 of the physical layer encodes the bursts from the burst configuration unit 204 according to a modulation and coding scheme (MCS) level and outputs the encoded bursts. The encoder 206 may use a convolutional code (CC), a turbo code (TC), a convolutional turbo code (CTC), or a low density parity check (LDPC) code. The modulator 208 modulates the encoded packet from the encoder 206 according to the MCS level to generate modulation symbols. For example, the modulator 208 may use QPSK, 16QAM, 64QAM, or the like.

The resource mapper 210 maps the data from the modulator 208 to a sub-channel and outputs the sub-channel. At this time, the resource mapper 210 allocates the data burst to the segment zone or the non-segment zone in accordance with the scheduling result of the scheduler 200. 1, the resource mapper 210 maps a preamble signal, performs mapping on a segment zone, and then performs mapping on a non-segment zone.

The OFDM modulator 212 OFDM-modulates the sub-channel mapped data from the resource mapper 210 to generate an OFDM symbol. Here, the OFDM modulation includes an IFFT (Inverse Fast Fourier Transform) operation, a CP (Cyclic Prefix) insertion, and the like. The RF transmitter 214 converts the sample data from the OFDM modulator 212 into an analog signal, converts the analog signal into a signal of a radio frequency (RF) band, and transmits the signal through an antenna.

3 is a detailed functional block diagram of the scheduler 200. As shown in FIG.

2, the scheduler 200 includes an MCS determination unit 300, a zone determination unit 302, a priority determination unit 304, a MAP estimation unit 306, and a scheduling information determination unit 308 .

Referring to FIG. 3, the MCS determination unit 300 determines the MCS level and MPR for each of the segment zone and the non-segment zone for each of the transmission bursts. Here, it is assumed that the transmission burst is composed of packets having the same user level or packets having the same MCS level.

The zone determination unit 302 selects a zone to be transmitted for each of the transmission bursts. For example, the zone determination unit 302 compares the value obtained by multiplying the MPR (Frp1Mpr) for the FRP (Frequency Reuse Pattern) 1 by 3 and the MPR (Frp3Mpr) for the FRP3 for each burst, If it is greater than or equal to, or greater than, the corresponding burst is assigned to the segment zone, and if not, to the non-segment zone.

The priority determining unit 304 aligns the transmission bursts based on MPR to determine a priority. At this time, the priority determining unit 302 may sort the transmission bursts based on the Frp1Mpr (MPR for the segment zone) or the MPR of the zone to which the burst is to be allocated to determine the priority.

The MAP estimator 306 maps the transmission bursts to a corresponding zone determined in order of priority. At this time, the MAP estimator 306 controls the transmission bursts to be compactly allocated within a frame through a MAP estimation algorithm. If there is no available resource in the predetermined zone, the zone determination unit 304 allocates the corresponding burst to another zone. For example, if the zone selected based on the MPR is a segment zone and there is no available resource in the segment zone, the zone determination unit 304 allocates the corresponding burst to the non-segment zone. To support this zone switching, the MPR of the lowest MCS level in each zone should be set to be three times the difference. In one example, the lowest MCS level of the segment zone may be set to QPSK1 / 4, and the lowest MCS level of the non-segment zone may be set to QPSK1 / 12.

The scheduling information determination unit 308 determines scheduling information (e.g., the position and size of a burst, an MCS level, etc.) for each burst allocated to the current frame, and provides the scheduling information to the message generating unit 202.

FIG. 4 illustrates a procedure for dynamically allocating bursts to a segment zone and a non-segment zone in a base station according to an embodiment of the present invention.

Referring to FIG. 4, in step 401, the BS acquires a CINR value for a segment zone and a CINR value for a non-segment zone for each transmission burst. Here, it is assumed that the burst consists of packets having the same MCS level.

In step 403, the base station determines an MCS level and an MPR for each of the segment zone and the non-segment zone based on the obtained two CINR values. Here, the MPR is the number of bits that can be transmitted through one subcarrier, and is calculated as a product of the modulation order and the code rate.

After calculating the two MPRs Frp3Mpr and Frp1Mpr for the transmission burst, the base station compares the two MPRs in step 405 and selects a zone to which the corresponding burst is to be transmitted. For example, as shown in FIG. 1, if the number of subchannels used in each segment region is the same, the base station compares the value obtained by multiplying the MPR of FRP1 by the MPR value of FRP3. At this time, if the MPR value of the FRP 3 is equal to or greater than the MPR value (or the MPR value of the FRP 3 is large), the BS proceeds to step 407 and allocates the corresponding burst to the segment zone. On the other hand, if the MPR value of the FRP 3 is small (or smaller or equal), the BS proceeds to step 409 and allocates the corresponding burst to the non-segment zone.

However, in the case where there is no available resource in the zone determined based on MPR as described above, zone switching is required to prevent resource waste.

FIG. 5 illustrates a procedure for zone switching in a base station according to an embodiment of the present invention.

Referring to FIG. 5, in step 501, the BS selects a zone to which a transmission burst is allocated. At this time, the zone selection can be performed as shown in FIG. If the segment zone is selected, the base station proceeds to step 503 and checks whether there is an available resource (slot) for transmitting the burst in the segment zone. Here, the slot can be defined as a two-dimensional minimum resource unit for burst allocation. If there is available resources, the BS proceeds to step 505 and allocates the burst to the segment zone.

On the other hand, if there is no available resource, the BS proceeds to step 507 and checks whether there is available resources that can transmit the burst in the non-segment zone. If there is no available resource, the base station determines to transmit the burst in the next frame, and if there is available resources, allocates the burst to the non-segment zone.

If the non-segment zone is selected in step 501, the BS proceeds to step 509 and determines whether there is available resources for transmitting the burst in the non-segment zone. If there is available resources, the BS proceeds to step 511 and allocates the burst to the non-segment zone. On the other hand, if there is no available resource, the BS proceeds to step 513 to check whether there is available resources for transmitting the burst in the segment-zone. If there is no available resource, the base station determines to transmit the burst in the next frame, and if there is available resources, allocates the burst to the segment zone.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited by the illustrated embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

1 is a diagram illustrating a downlink frame structure to which FFR is applied according to an embodiment of the present invention.

2 is a diagram illustrating a configuration of a base station in a broadband wireless communication system according to an embodiment of the present invention.

3 is a detailed functional block diagram of the scheduler 200;

4 illustrates a procedure for dynamically allocating a burst to a segment zone and a non-segment zone in a base station according to an embodiment of the present invention.

5 illustrates a procedure for zone switching in a base station according to an embodiment of the present invention.

Claims (17)

A burst scheduling method in a broadband wireless communication system for communicating a frame to which a fractional frequency reuse (FFR) scheme is applied, Receiving a channel value for each of a segmented zone having a frequency reuse pattern of 2 or more and a non-segmented zone having a frequency reuse pattern of 1 from the UEs; A process of comparing a first MPR value, which is a value of a modulation order product coding rate (MPR) of a segment zone, with a MPR value of a non-segment zone and a second MPR value of which a frequency reuse pattern value of a segment zone is weighted, ≪ / RTI > The method according to claim 1, Determining whether there is an available resource in the selected zone; Allocating a corresponding burst to the selected zone if the available resources exist; And performing zone switching to allocate the burst to another zone when the available resources are not available. 3. The method of claim 2, Checking whether there is an available resource in the other zone; Allocating the burst to the another zone when the available resources exist; And determining to transmit the burst in the next frame if there is no available resource. The method of claim 1, Comparing the value obtained by multiplying the MPR of the non-segment zone by N and the first MPR value; Selecting a segment zone if the first MPR value is greater than or equal to the N multiplied value; And selecting the non-segment zone if the first MPR value is less than the N times multiplied value. The method according to claim 1, Wherein the subchannel usage state for the segment zone is transmitted through an FCH message. The method according to claim 1, Wherein the first PUSC zone in the frame is comprised of the segment zone. The method according to claim 6, Dividing all subchannels of the segment zone into an equal number of segments to form a plurality of segment regions, wherein neighboring cells communicate through different segment regions. The method according to claim 6, Wherein the lowest MCS level of the segment zone is set to QPSK1 / 4, and the lowest MCS level of the non-segment zone is set to QPSK1 / 12. 1. A broadband wireless communication system base station apparatus for communicating a frame to which a fractional frequency reuse (FFR) scheme is applied, A receiver for receiving a channel value for each of a segmented zone having a frequency reuse pattern of 2 or more and a non-segmented zone having a frequency reuse pattern of 1, A first MPR value which is a value of a modulation order product coding rate (MPR) of the segment zone and a second MPR value which is a weight of the frequency reuse pattern value of the segment zone are added to the MPR value of the non-segment zone, And a scheduler. 10. The apparatus of claim 9, wherein the scheduler comprises: And performs zone switching to allocate the burst to the selected zone if the available resource exists and allocate the burst to another zone when the available resource does not exist. . 11. The apparatus of claim 10, wherein the scheduler comprises: Determining whether there is an available resource in the other zone when performing the zone switching, allocating the burst to the other zone when the available resource exists, and determining to transmit the burst in the next frame when there is no available resource Characterized in that. 10. The apparatus of claim 9, wherein the scheduler comprises: An MCS level determination unit for determining an MCS level and an MPR for each of the segment zone and the non-segment zone for each of the transmission bursts, A zone determination unit for comparing the MPR of the segment zone and the MPR of the non-segment zone with respect to each of the transmission bursts and selecting a zone to which the corresponding burst is to be transmitted; A priority determining unit for sorting the transmission bursts based on MPR and determining a priority; And a MAP estimator for allocating the transmission bursts to a corresponding zone sequentially determined according to a priority order through a MAP estimation algorithm. 13. The apparatus of claim 12, Segment zone is selected when the first MPR value is greater than or equal to the N-fold value, and the first MPR value is greater than or equal to the N And selects a non-segmented zone when the value is smaller than the multiplied value. 10. The method of claim 9, And the subchannel use state for the segment zone is transmitted through an FCH message. 10. The method of claim 9, And wherein the first PUSC zone in the frame is comprised of the segment zone. 16. The method of claim 15, And divides all subchannels of the segment zone by the same number to form a plurality of segment regions, wherein adjacent cells communicate through different segment regions. 17. The method of claim 16, Wherein the lowest MCS level of the segment zone is set to QPSK1 / 4 and the lowest MCS level of the non-segment zone is set to QPSK1 / 12.

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