KR20170073520A - Method and apparatus for scheduling in mobile communication system - Google Patents

Abstract

A base station using a plurality of beams transmits a plurality of training beams and receives measurement information on a first number of training beams having a strong received signal strength from each of the plurality of terminals that have received the plurality of training beams, And generates a received signal strength table indicating the strength of the received signal strength of each of the terminals and the beam index based on the measurement information of the first number of training beams of each terminal and then transmits the received signal strength table to the plurality of terminals simultaneously using the received signal strength table And schedules the terminals.

Description

[0001] METHOD AND APPARATUS FOR SCHEDULING IN MOBILE COMMUNICATION SYSTEM [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scheduling method and apparatus in a mobile communication system, and more particularly, to a scheduling method and a scheduling method in a mobile communication system in which feedback of a mobile station and scheduling in a base station can be easily and simply performed in a mobile communication system using directional beams. ≪ / RTI >

Since the advent of mobile broadband services, mobile communication systems must meet the diverse needs of multiple users. In particular, in a voice-oriented data environment in which a certain minimum data rate guarantee is important, the demand for wireless transmission for various multimedia such as music, video, and web surfing has increased rapidly, and active scheduling according to the amount and type of information requested by the terminal ) Is very important.

The fifth generation mobile communication system must support a data rate of up to 20 Gbps in a terminal, and be able to maintain a data rate of 100 Mbps to 1 Gbps at any position in the cell. In addition, it should support latency of less than 1ms, simultaneous connection of multiple terminals at the same time. In order to achieve such a technical goal, it is becoming popular to adopt a millimeter wave band in a mobile communication system. The millimeter-wave band is advantageous for high-speed data transmission because it is easy to secure a wide bandwidth, and it is also advantageous in lowering the delay in the physical layer. On the other hand, the radio wave attenuation due to the distance of transmission and reception is significant and blockage due to buildings, Occurs.

Therefore, the mobile communication system using the millimeter wave band uses the directional beam at the transmitting and receiving end to compensate for the severe attenuation of the channel. In this case, in order to maximize the performance of the system, the base station must simultaneously support data to multiple terminals using multiple beams. That is, it is necessary to implement a multi-user multiple-input multiple-output (MU-MIMO) system. However, in multi-beam operation, inter-beam interference occurs and the performance of the system may be degraded, so scheduling in consideration of inter-beam interference is indispensable.

In addition, the CSI (Channel State Information) feedback structure of the existing LTE (Long Term Evolution) / LTE-A (Advanced) is designed based on the use of different resources for each user, thereby realizing a high performance MU- There is a lot of difficulty in this. Therefore, a new CSI feedback structure and a scheduling method are required to obtain maximum system performance in a mobile communication system using a directional beam.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a scheduling method and apparatus capable of improving system performance in a mobile communication system using a directional beam.

According to one embodiment of the present invention, a method is provided for scheduling a plurality of terminals in a cell in a base station using a plurality of beams. The scheduling method includes transmitting a plurality of training beams, receiving measurement information on a first number of training beams having a large received signal strength from each of the plurality of terminals that have received the plurality of training beams, Generating a received signal strength table indicating received signal strengths according to a terminal and a beam index based on measurement information on the first number of training beams, And scheduling.

The measurement information may include a received signal strength and a received phase and a beam index for each of the first number of training beams.

Wherein the step of scheduling comprises the steps of: selecting a terminal having a largest sum of squares of received signal strengths of the first number of training beams of each terminal among UEs in a schedulable terminal set, excluding the selected terminal from the terminal set, Removing a first number of training beams of the selected terminal from the set of beam indexes including the plurality of beams, selecting a first number of training beams of each terminal from among the terminals of the terminal set, Excluding, from the set of terminals, a terminal having a number of beams overlapping among the number of training beams that is greater than a set maximum allowable number, and selecting and scheduling terminals to be simultaneously transmitted by repeating the selecting, . ≪ / RTI >

The scheduling may further comprise generating a transmission beam to the selected terminal using the received signal strength of the first number of training beams of the selected terminal.

Wherein the scheduling method comprises: defining a beam set in which a first number of training beams of each of the scheduled UEs are unified; calculating a received signal strength of the beams not receiving feedback from the scheduled UEs among the beams in the unified beam set; Allocating a value of 0 to the reception phase and designing minimum mean square error (MMSE) or ZF (Zero-forcing, ZF) beamforming using the received signal strength and reception phase of all the beams of each terminal Step < / RTI >

The measurement information may include a reception phase and a beam index for each of the first number of training beams, and a sum of received signal strengths of the first number of training beams.

Wherein the scheduling comprises: selecting a UE having a largest sum of received signal strengths of the first number of training beams among a set of UEs capable of scheduling, using a reception phase for the first number of training beams of the selected UE Generating a transmission beam to the selected terminal, removing the selected terminal from the set of terminals, and excluding a first number of training beams of the selected terminal from a set of beam indexes including the plurality of beams, The method comprising the steps of: removing, from among the terminals of the terminal set, a terminal having a number of beams overlapping between the first number of training beams of the terminal and the first number of training beams of the selected terminal, Selecting and repeating the steps of generating, And scheduling terminals to be transmitted at a time.

The scheduling method may further include transmitting data of the UEs through a transmission beam of the scheduled UEs.

The measurement information may include a sum of a beam index for each of the first number of training beams and a received signal strength of the first number of training beams.

Wherein the scheduling comprises: selecting a UE having the largest sum of received signal strengths of the first number of training beams among the set of UEs capable of scheduling, excluding the selected UE from the set of UEs, The method comprising the steps of: excluding a first number of training beams of the selected terminal from the set of beam indexes, removing a first number of training beams of each terminal from the first set of training beams, Excluding a terminal having a number larger than the maximum allowable number from the set of terminals, and scheduling terminals to be simultaneously transmitted by repeating the selecting, generating and deleting steps.

The scheduling method may include defining a beam set in which a first number of training beams of each scheduled UE are unified, requesting feedback to each scheduled terminal, receiving a beam in the unified beam set from each terminal, Receiving the signal strength and the reception phase, and designing the MMSE or ZF beamforming using the received signal strength and the reception phase of the beams in the unified set of beams of each scheduled UE.

According to another embodiment of the present invention, an apparatus is provided for scheduling a plurality of terminals in a cell in a base station using a plurality of beams. The scheduling apparatus includes a transceiver, and a processor. The transceiver transmits a plurality of training beams and receives measurement information on a first number of training beams having a strong received signal strength from each of the plurality of terminals receiving the plurality of training beams. The processor generates a received signal strength table indicating the strength of the received signal strength of each terminal and the beam index based on the measurement information of the first number of training beams of each terminal, And schedules the plurality of terminals using a table.

The measurement information may include a received signal strength, a receive phase, and a beam index for each of the first number of training beams.

Wherein the processor schedules a set number of terminals based on a sum of squares of received signal strengths of the first number of training beams of each of the UEs in the schedulable UE set and calculates a first number of UEs It is possible to exclude a terminal whose number of beams overlapping between the training beam and the first number of training beams of the scheduled terminals is greater than the set maximum allowable number in the scheduling.

The processor may combine received signal strengths for the first number of training beams of each scheduled terminal to generate the transmit beam for beamforming of a maximum ratio transmission (MRT) scheme.

The processor allocates a value of 0 to the received signal strength and the reception phase of the beams not receiving feedback from the scheduled terminals of the beams in the set of beams obtained by summing the first number of training beams of each terminal of the scheduled terminals, A minimum mean square error (MMSE) or zero-forcing (ZF) beamforming or an arbitrary beamforming can be designed using the received signal strength and the received phase of all the beams of each scheduled terminal.

The measurement information may include a received phase and a beam index for each of the first number of training beams and a sum of received signal strengths of the first number of beams.

Wherein the processor schedules a set number of terminals based on a sum of received signal strengths of the first number of training beams of each of the UEs in the schedulable terminal set and calculates a reception phase for the first number of training beams of each scheduled terminal And generates a transmission beam for beamforming of equal gain combining (EGC) scheme by combining the first number of training beams of each terminal and the first number of each scheduled terminal It is possible to exclude, from the scheduling, a UE whose number of overlapping beams among the training beams is larger than the set maximum allowable number.

The measurement information may include a sum of a beam index for each of the first number of training beams and a received signal strength of the first number of training beams.

Wherein the processor schedules a set number of terminals based on a sum of squares of received signal strengths of the first number of training beams of each of the UEs in the schedulable UE set and calculates a first number of UEs A scheduling step of excluding, from the scheduling, a terminal having a training beam and a number of beams overlapping the first number of training beams of each of the scheduled terminals, the number of which exceeds a set maximum allowable number, A scheduler for receiving a signal strength and a reception phase of the beams in the set from each scheduled terminal and requesting the received signal strength and a reception phase from the scheduled terminals to receive the signal strength and reception phase of the beams in the unified beam set received from the scheduled terminals, Can be used to design MMSE or ZF beamforming or any beamforming. have.

According to the embodiment of the present invention, it is possible to reduce the feedback amount of the terminal and effectively schedule the terminal with the reduced feedback, thereby improving the system performance.

1 is a diagram illustrating an example of a path between a Node B and a UE according to an embodiment of the present invention.
2 is a diagram illustrating a plurality of terminals in a region covered by a base station according to an embodiment of the present invention.
3 is a diagram illustrating beamforming of a base station according to an embodiment of the present invention.
4 is a diagram illustrating an example of a received signal strength table generated by a base station according to an embodiment of the present invention.
FIGS. 5 to 7 are flowcharts illustrating a feedback method and a base station scheduling method according to the first to third embodiments of the present invention, respectively.
FIG. 8 is a flowchart illustrating feedback of a terminal based on two-interval feedback and beamforming method of a base station according to a fourth embodiment of the present invention.
9 is a diagram illustrating a base station and a terminal according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out 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 order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification and claims, when a section is referred to as "including " an element, it is understood that it does not exclude other elements, but may include other elements, unless specifically stated otherwise.

Now, a scheduling method and apparatus in a mobile communication system according to an embodiment of the present invention will be described in detail with reference to the drawings.

1 is a diagram illustrating an example of a path between a Node B and a UE according to an embodiment of the present invention.

The millimeter wave band means the frequency band of 30 GHz to 300 GHz. The channel in the millimeter wave band has strong directivity, and diffraction and reflection characteristics due to the object in the path are not good and attenuation in the atmosphere is large. Therefore, there is a very limited number of paths between the base station and the terminal.

For example, as shown in FIG. 1, there can exist three paths between the base station and the terminal k. The first path is a path corresponding to the Line-of-Sight (LoS) It exists at a position rotated by an angle of θ _{k, 1} on a bore-sight basis, and has a channel gain of α _{k, 1} . The second path and the third path are paths that are reflected to the cluster and then enter the terminal k, respectively. The paths are located at angles θ _{k, 2} and θ _{k, 3} on the basis of boresight directed by the antenna of the base station , Channel gains a _{k, 2} and a _{k, 3} .

The channel between the base station and the terminal k as shown in FIG. 1 can be expressed by Equation (1).

_I is the complex channel gain corresponding to the path i of the terminal k, and a (? _{K, i} ) is the complex channel gain corresponding to the path i of the terminal k. Here, L is the number of paths between the base station and the terminal k, M is the number of antennas installed in the base station, Can be expressed by Equation (2).

Equation 2 represents the response of the antenna array between the antenna array of the base station and the angle [theta] _{k, i} . Equation (2) represents a phase difference according to a time delay that occurs when a signal arrives at an antenna array.

2 is a diagram illustrating a plurality of terminals in a region covered by a base station according to an embodiment of the present invention.

Referring to FIG. 2, a plurality of terminals 200 may be located in a cell region served by one base station 100. The base station 100 selects (schedules) the terminal 200 in order to achieve optimal performance among a plurality of terminals 200 in a cell region.

3 is a diagram illustrating beamforming of a base station according to an embodiment of the present invention.

Referring to FIG. 3, a base station 100 operating in a millimeter wave band fully covers a serving cell area and uses multiple directional beams to support multiple users.

The simplest method for generating a directional beam uses an antenna array, and in particular, a uniform linear array (ULA) method can be used. ULA is a system in which the antenna elements are arranged in a linear array structure while maintaining a constant gap between the antenna elements.

When the base station 100 uses M antenna elements having a ULA structure, the base station 100 may generate M training beams orthogonal to each other (w ₁ , w ₂ , ..., w _M ). Therefore, the base station 100 generates M training beams w ₁ , w ₂ ,..., W _M and transmits them through specific resources, thereby measuring the channel between itself and the base station 100 I can do it. The UE 200 may measure the signal-to-noise ratio (SNR) or the received signal strength for all the training beams w ₁ , w ₂ , ..., w _M. However, since the base station 100 uses only a part of the M training beams to transmit data in the same resource, the signal-to-interference and noise ratio (SINR) can not be known when the actual data is received .

One of the feedback and scheduling methods of the UE 200 in the multi-beam mobile communication system is to feedback the received signal strength (or SNR) to all the M training beams used by the Node B 100 , The base station 100 determines a terminal to be used for actual data transmission through an exhaustive search using the received signal strength (or SNR) corresponding to M training beams sent from all the terminals 200. [ Although this method can obtain the optimum performance given to the system, it is difficult to apply it to an actual system because the feedback amount and calculation complexity of the terminal 200 are very high.

Therefore, in the embodiment of the present invention, the UE 200 measures a beam index corresponding to N _FB training beams having a large received signal strength among the M received signal intensities measured through the training beam and a received signal strength of N _FB training beams, And feeds back to the base station 100. When the received signal strength and the beam index of the N _FB training beams are fed back to each terminal 200 in the cell, the base station 100 measures the received signal strength, which indicates the received signal strength corresponding to each terminal 200 and the beam index, A table can be generated.

4 is a diagram illustrating an example of a received signal strength table generated by a base station according to an embodiment of the present invention.

Referring to FIG. 4, in the received signal strength table, a location where each terminal feeds back the received signal strength is shown in black.

When generating the received signal strength table, the base station 100 allocates a corresponding received signal strength value to a beam index, which the terminal has fed back the received signal strength among the full beam indexes 1 to M, For indexes, zero or a specific value can be assigned. In FIG. 4, the area where the received signal strength is fed back to each terminal in the received signal strength table is represented in black for convenience.

Consists of a millimeter-band channel h _k is the path to the L sum can be expressed as shown in Equation 1, so that any training beam and the direction of which the received signal strength of the training beam is at least one of the L path toward the terminal path It is great when the direction in which it is oriented is well matched.

When the received signal strength table as shown in FIG. 4 is generated, the base station 100 can schedule the terminal using the received signal strength table. For example, the base station 100 may schedule a terminal using a greedy sequential scheduling algorithm using a received signal strength table. When the Gridi sequential scheduling algorithm is described briefly, the BS 100 first selects a beam and a beam having the highest received signal strength in the received signal strength table, selects a beam among the remaining beams except for the selected beam and the selected beam, and selects a terminal and a beam having a maximum sum data rate. This process is continued until the maximum number of UEs that can be scheduled is reached.

This greedy sequential scheduling scheme is a suitable method when the base station 100 selects one of a plurality of training beams for each terminal and uses it for data transmission. However, it is not optimal to transmit data to the UE by selecting one training beam in a channel of a millimeter band in which multiple paths exist as shown in Equation (1). Accordingly, there is a need for a method of combining a plurality of training beams and generating and using a beam to transmit data in accordance with the estimated channel.

In the embodiment of the present invention, the base station 100 combines a plurality of training beams and proposes a feedback method of the terminal and a scheduling method of the base station when generating a beam to transmit the data.

The use of the feedback scheme and the scheduling scheme of the base station proposed in the embodiment of the present invention allows the base station 100 to perform maximum ratio transmission (MRT) and equal gain combining (equal gain combining (EGC)) beamforming can be realized. The feedback scheme of the UE and the scheduling scheme of the base station are slightly different according to the beamforming scheme of the base station. Therefore, when the base station 100 performs the MRT beamforming or the EGC beamforming, And a scheduling method of the base station will be described. In addition, when the base station 100 uses the feedback of the terminal used in the MRT beamforming and the scheduling method of the base station, a minimum mean square error (MMSE) or a zero- forcing, ZF) beamforming is described. In addition, the base station 100 selects a beam to be used with the UE based on the feedback scheme of the UE having a smaller amount of feedback than the feedback amount of the UE used in the MRT and EGC beamforming in the first time interval, Feedback of a two-phase feedback based terminal, scheduling of a base station, and beamforming designing method for designing MMSE or ZF beamforming by receiving channel information corresponding to a selected beam from selected terminals will be described.

5, when the base station 100 uses the EGC beamforming, the feedback of the terminal and the scheduling method of the base station for MRT beamforming when the base station 100 uses the MRT beamforming will be described with reference to FIG. Feedback of a terminal and scheduling method of a base station suitable for EGC beamforming will be described with reference to FIG. Referring to FIG. 7, a method of designing MMSE or ZF beamforming when the base station 100 uses the feedback of a terminal used in MRT beamforming and the scheduling method of a base station will be described with reference to FIG. 7, , The scheduling of the base station and the beamforming design scheme will be described with reference to FIG.

5 is a flowchart illustrating a feedback method of a UE and a scheduling method of a Node B according to the first embodiment of the present invention.

Referring to FIG. 5, the BS 100 transmits M training beams (S502).

A terminal receiving M training beams can select N _FBs of main training beams having a large received signal strength. The N _FB training beams can be considered to be well matched to the L paths between the BS and the MS and can be considered to simulate the channel between the MS and the BS.

,

및

와 같이 나타낼 수 있다.

는 단말 k에서 주요 트레이닝 빔 w_b의 수신 신호 세기를 나타낸다.

는 단말 k에서 주요 트레이닝 빔 w_b의 수신 위상을 나타낸다. 그리고

는 단말 k에서 선택한 수신 신호 세기가 큰 N_FB개의 주요 트레이닝 빔의 빔 인덱스 집합을 나타낸다. When the base station 100 uses MRT beamforming, the UE _{feeds back} the received signal strength, the reception phase, and the index of the beam corresponding to each of the N _FB main training beams. The received signal strength, phase value and index of the corresponding beam fed back by the terminal are

,

And

As shown in Fig.

Represents the received signal strength of the main training beam w _b at the terminal k.

Represents the reception phase of the main training beam w _b at the terminal k. And

_Represents a beam index set of N _FB main training beams having a strong received signal strength selected at terminal k.

When the base station 100 receives the feedback including the received signal strength, reception phase, and corresponding beam index corresponding to each of the N _FB main training beams from each terminal (S504), the base station 100 performs scheduling in the following manner.

]과 트레이닝 빔의 빔 인덱스 집합[

] 및 j를 초기화한다(S506). 스케줄링 가능한 단말 집합[

]은 스케줄링 가능한 전체 단말을 포함하도록 초기화하고, 빔 인덱스 집합[

]은 전체 빔 인덱스를 포함하도록 초기화한다. 그리고 j=1로 초기화한다. 여기서, j는 단말 스케줄링 알고리즘의 반복 횟수를 나타낸다. The base station 100 includes a schedulable terminal set [

] And the beam index set of the training beam [

] And j are initialized (S506). Schedulable terminal set [

] Is initialized to include all schedulable terminals, and the beam index set [

] Is initialized to include the entire beam index. Then initialize j = 1. Here, j represents the number of repetitions of the terminal scheduling algorithm.

In step S508, the base station 100 selects a terminal having the highest received signal strength when the main training beam is used among the set of terminals that can be scheduled using Equation (3). The selected terminal in the j-th iteration is called k _j .

Next, the base station 100 generates a beam to be used for transmitting data to the terminal k _j as shown in Equation (4) (S510). That is base station 100 to send data to the mobile station k _j by combining the N _FB major training beam for the terminal _j k produces a beam used for transmission to the terminal k _j. That is, MRT beamforming is performed by combining N _FBs of main training beams.

이 결정되면, 스케줄링 가능한 단말 집합을 수학식 5와 같이 업데이트하고(S512), 빔 인덱스 집합을 수학식 6과 같이 업데이트한다(S514). 즉, 스케줄링 가능한 단말 집합에서 단말 k_j을 제외시키고, 빔 인덱스 집합에서 빔

을 제외시킨다. As described above, the base station 100 transmits the beam k to be used for transmitting data to the terminal k _j and the terminal k _j ,

(S512), the beam index set is updated as shown in Equation (6) (S514). That is, the terminal k _j is excluded from the set of schedulable terminals,

.

In this way, the base station 100 transmits the best k _j And the beam to be used for transmission to the terminal k _j , the following procedure is further performed to leave only those terminals with little interference due to the beam.

에 남아 있도록, 스케줄링이 가능한 단말 집합

를 수학식 7에 따라서 업데이트한다(S516). The base station 100 includes a terminal group capable of scheduling only those terminals with low interference due to a beam used for transmission to the terminal k _j

, A set of terminals that can be scheduled

Is updated according to Equation (7) (S516).

Here, N _OL is the maximum allowable number of main training beams to be overlapped among different terminals.

를 업데이트하면, 기지국(100)은 현재 선택된 단말과 동시에 스케줄링 되었을 때 간섭이 적은 단말만을 스케줄링 가능한 단말 집합

에 남겨둘 수 있다. ≪ RTI ID = 0.0 > Equation 7 < / RTI >

The base station 100 determines whether or not the currently selected terminal is scheduled,

.

,

,

를 모두 만족시키면(S518), j=j+1로 증가시킨 후(S520), 단계(S508)로 이동하여 단계(S508~S518)를 반복하고, 그렇지 않으면 스케줄링 알고리즘을 종료한다(S522). 여기서, K_s,max(≤M)는 미리 정해놓은 상수값(자연수)이다. If the base station 100

,

,

J is incremented to j = j + 1 (S520), and then the process proceeds to step S508 to repeat steps S508 to S518. Otherwise, the scheduling algorithm is terminated (S522). Here, Ks _{, max} (M) is a predetermined constant value (natural number).

When the base station 100 performs MRT beamforming, it can be seen that the feedback amount of the UE when using the scheduling scheme is 2N _FB real number and N _FB number integer.

FIG. 6 is a flowchart illustrating a feedback method of a UE and a scheduling method of a Node B according to a second embodiment of the present invention.

Referring to FIG. 6, the BS 100 transmits M training beams (S602).

A terminal receiving M training beams can select N _FBs of main training beams having a large received signal strength.

를 기지국(100)에 피드백한다.When the EGC beamforming is performed in the base station 100, the UE calculates a beam index set of N _FB main training beams having a large received signal strength and Equation (8) and Equation (9)

To the base station 100.

When the base station 100 performs the beam forming of the EGC method, the terminal receives the signal strength is not to feed back the received signal strengths of the large N _FB major training beam, received signal strength is of great N _FB major training beam The feedback amount of the UE can be reduced more than the feedback amount of the UE in the case of performing the beamforming of the MRT scheme in the base station 100. [

를 포함하는 피드백을 수신하면(S604), 다음과 같은 방법으로 스케줄링을 수행한다. MRT 방식일 때와 비교하여 단말을 선택하는 방식 및 해당 단말에 데이터를 전송할 빔을 생성하는 방식이 다르다.The base station 100 calculates the sum of the received signal strengths of N _FB main training beams from each terminal, the reception phase of N _FB main training beams,

(S604), scheduling is performed in the following manner. A method of selecting a terminal and a method of generating a beam to transmit data to the terminal are different from those in the MRT method.

]과 트레이닝 빔의 빔 인덱스 집합[

] 및 j를 초기화한다(S606). 스케줄링 가능한 단말 집합[

]은 스케줄링 가능한 전체 단말을 포함하도록 초기화하고, 빔 인덱스 집합[

]은 전체 빔 인덱스를 포함하도록 초기화한다. 그리고 j=1로 초기화한다. 여기서, j는 단말 스케줄링 알고리즘의 반복 횟수를 나타낸다. The base station 100 includes a schedulable terminal set [

] And the beam index set of the training beam [

] And j are initialized (S606). Schedulable terminal set [

] Is initialized to include all schedulable terminals, and the beam index set [

] Is initialized to include the entire beam index. Then initialize j = 1. Here, j represents the number of repetitions of the terminal scheduling algorithm.

In step S608, the BS 100 selects a UE having the highest received signal strength when the main training beam is used among the sets of UEs that can be scheduled using Equation (10). The selected terminal in the j-th iteration is called k _j .

Next, the base station 100 to perform (S610), EGC beam forming by creating, as the beam used to transmit data to the MS k and _j Equation (11).

이 결정되면, 스케줄링 가능한 단말 집합을 수학식 12와 같이 업데이트하고(S612), 빔 인덱스 집합을 수학식 13과 같이 업데이트한다(S614). 즉, 스케줄링 가능한 단말 집합에서 단말 k_j을 제외시키고, 빔 인덱스 집합에서 빔

을 제외시킨다. As described above, the base station 100 transmits the beam k to be used for transmitting data to the terminal k _j and the terminal k _j ,

(S612), the beam index set is updated as shown in Equation (13) (S614). That is, the terminal k _j is excluded from the set of schedulable terminals,

.

When the base station 100 determines a beam to be used for transmission to the optimal terminal k _j and terminal k _j in this manner, the base station 100 additionally performs the following procedure to leave only the terminals with less interference due to the corresponding beam do.

에 남아 있도록, 스케줄링이 가능한 단말 집합

를 수학식 14에 따라서 업데이트한다(S616). The base station 100 includes a terminal group capable of scheduling only those terminals with low interference due to a beam used for transmission to the terminal k _j

, A set of terminals that can be scheduled

Is updated according to Equation (14) (S616).

Here, N _OL is the maximum allowable number of main training beams to be overlapped among different terminals.

를 업데이트하면, 기지국(100)은 현재 선택된 단말과 동시에 스케줄링 되었을 때 간섭이 적은 단말만을 스케줄링이 가능한 단말 집합

에 남겨둘 수 있다. ≪ EMI ID = 14.0 >

The base station 100 transmits a scheduling request message to the UE 100,

.

,

,

를 모두 만족시키면(S618), j=j+1로 증가시킨 후(S620), 단계(S608)로 이동하여 단계(S608~S618)를 반복하고, 그렇지 않으면 스케줄링 알고리즘을 종료한다(S622). 여기서, K_s,max(≤M)는 미리 정해놓은 상수값(자연수)이다. If the base station 100

,

,

J is incremented to j = j + 1 (S620), and the process proceeds to step S608 to repeat steps S608 to S618. Otherwise, the scheduling algorithm is terminated (S622). Here, Ks _{, max} (M) is a predetermined constant value (natural number).

When using the ECG beamforming in the base station 100, the amount of feedback of the UE when using such a scheduling scheme is (N _FB +1) real numbers and N _FB integers, compared to the amount of feedback when MRT beamforming is used The feedback amount of the terminal is reduced.

7 is a flowchart illustrating a feedback method of a UE and a scheduling method of a Node B according to a third embodiment of the present invention.

Referring to FIG. 7, the BS 100 transmits M training beams (S702).

When the base station 100 receives the feedback including the received signal strength, the reception phase, and the corresponding beam index corresponding to each of the N _FB main training beams from each terminal (S704), the base station 100 performs scheduling in the following manner.

]과 트레이닝 빔의 빔 인덱스 집합[

] 및 j를 초기화한다(S706). The base station 100 includes a schedulable terminal set [

] And the beam index set of the training beam [

] And j are initialized (S706).

The base station 100 selects a terminal having the highest received signal strength when using the main training beam among the sets of terminals that can be scheduled using Equation (15) (S708). The selected terminal in the j-th iteration is called k _j .

을 제외시킨다. When the terminal k _j is determined, the BS 100 updates the schedulable set of UEs as shown in Equation 16 (S710), and updates the beam index set as Equation 17 (S712). That is, the terminal k _j is excluded from the set of schedulable terminals,

.

에 남아 있도록, 스케줄링이 가능한 단말 집합

를 수학식 18에 따라서 업데이트한다(S714). Next, the base station 100 determines whether only the terminal where the main training beam of the terminal k _j and the main training beam are overlapped is a schedulable terminal set

, A set of terminals that can be scheduled

Is updated according to Equation (18) (S714).

Here, N _OL is the maximum allowable number of main training beams to be overlapped among different terminals.

를 업데이트하면, 기지국(100)은 현재 선택된 단말과 동시에 스케줄링 되었을 때 채널이 서로 거의 직교하는 단말만을 스케줄링 가능한 단말 집합

에 남겨둘 수 있다. ≪ RTI ID = 0.0 > Equation 18 < / RTI >

The base station 100 transmits a scheduling request message to the UE 100, which is capable of scheduling only the UEs whose channels are almost orthogonal to each other,

.

,

,

를 모두 만족시키면(S716), j=j+1로 증가시킨 후(S718), 단계(S708)로 이동하여 단계(S708~S716)를 반복하고, 그렇지 않으면 단말 스케줄링 알고리즘을 종료한다. 여기서, K_s,max(≤M)는 미리 정해놓은 상수값(자연수)이다. If the base station 100

,

,

(S716), j is increased to j + 1 (S718), and then the process goes to step S708 to repeat steps S708 to S716. Otherwise, the terminal scheduling algorithm is terminated. Here, Ks _{, max} (M) is a predetermined constant value (natural number).

In this way, the base station 100 can define the beam set B * by unifying the main training beams of each terminal scheduled as shown in Equation 19, after scheduling the terminals.

Here, J is the value of j when the process moves from step S716 to step S720.

에 해당하는 빔들의 수신 신호 세기와 수신 위상만을 알고 있다. 따라서 각 단말 k_j마다

에 해당하는 빔들의 수신 신호 세기와 수신 위상을 모르기 때문에,

에 해당하는 빔들의 수신 신호 세기와 수신 위상에 0의 값을 할당한다(S720). 그러면 기지국(100)은

내에 있는 빔 인덱스에 해당하는 빔들에 의해 스팬(span)하는 부공간(subspace) 내에선 각 단말의 채널 정보 상태(channel state information, CSI)(즉, 각 단말의

내의 모든 빔들의 수신 신호 세기와 수신 위상)을 정확히 아는 것으로 간주할 수 있다. 이 부공간 내의 정확한 CSI 정보를 기반으로 기지국(100)은 MMSE이나 ZF 빔포밍을 설계한다(S722). 또한 기지국(100)은 이 부공간 내의 CSI 정보를 기반으로 MMSE이나 ZF 빔포밍과 다른 임의의 빔포밍을 설계할 수도 있다. The base station 100 includes a main beam training set for each scheduled terminal k _j

Only the received signal strength and received phase of the beams corresponding to the received signals are known. Therefore, for each terminal k _j

Since the received signal strength and the reception phase of the beams corresponding to "

And a value of 0 is assigned to the reception phase and the reception phase of the beams corresponding to the beams (S720). Then, the base station 100

The channel state information (CSI) of each terminal in the subspace spanned by the beams corresponding to the beam index within each terminal

The reception signal strength and the reception phase of all the beams in the received signal). Based on the precise CSI information in the subspace, the base station 100 designs MMSE or ZF beamforming (S722). The base station 100 may also design the MMSE or ZF beamforming and other arbitrary beamforming based on the CSI information in the subspace.

It can be seen that the feedback amount of the UE when using the scheduling scheme and beamforming in the base station 100 is 2N _FB real number and N _FB integer, as in the case of MRT beamforming.

FIG. 8 is a flowchart illustrating feedback of a terminal based on two-interval feedback and beamforming method of a base station according to a fourth embodiment of the present invention.

Referring to FIG. 8, the BS 100 transmits M training beams (S802).

The base station 100 receives only the index of each of the N _FB main training beams from each terminal and the received signal strength sum of the main training beams (S804).

]과 트레이닝 빔의 빔 인덱스 집합[

] 및 j를 초기화한다(S806). The base station 100 includes a schedulable terminal set [

] And the beam index set of the training beam [

] And j are initialized (S806).

The base station 100 selects a terminal having the highest received signal strength when the main training beam is used among the sets of terminals that can be scheduled using Equation (20) (S808). The selected terminal in the j-th iteration is called k _j .

을 제외시킨다. When the terminal k _j is determined, the BS 100 updates the schedulable set of UEs as shown in Equation 21 (S810), and updates the beam index set as Equation 22 (S812). That is, the main beam of the training, except for terminal k _j in scheduling a terminal set and, in the beam index set B terminal k _j

.

에 남아 있도록, 스케줄링이 가능한 단말 집합

를 수학식 23에 따라서 업데이트한다(S814). The base station 100 includes a terminal group kj capable of scheduling only a terminal in which a main training beam of the terminal k _j and a main training beam are less overlapped,

, A set of terminals that can be scheduled

Is updated according to the equation (23) (S814).

Here, N _OL is the maximum allowable number of main training beams to be overlapped among different terminals.

를 업데이트하면, 기지국(100)은 현재 선택된 단말과 동시에 스케줄링 되었을 때 채널이 서로 거의 직교하는 단말만을 스케줄링 가능한 단말 집합

에 남겨둘 수 있다. ≪ RTI ID = 0.0 > (23) < / RTI >

The base station 100 transmits a scheduling request message to the UE 100, which is capable of scheduling only the UEs whose channels are almost orthogonal to each other,

.

,

,

를 모두 만족시키면(S816), j=j+1로 증가시킨 후(S818), 단계(S808)로 이동하여 단계(S808~S816)를 반복하고, 그렇지 않으면 단말 스케줄링 알고리즘을 종료한다. 여기서, K_s,max(≤M)는 미리 정해놓은 상수값(자연수)이다. If the base station 100

,

,

J is incremented to j = j + 1 (S818), and then the process goes to step S808 to repeat steps S808 to S816. Otherwise, the terminal scheduling algorithm is terminated. Here, Ks _{, max} (M) is a predetermined constant value (natural number).

After scheduling the UEs, the Node B 100 can unify the main training beams of each UE and define a B * set as shown in Equation (24).

Here, J is the value of j when the process goes from step S816 to step S820.

내의 빔 인덱스에 해당하는 빔들의 수신 신호 세기와 수신 위상 정보의 피드백을 추가적으로 요청하여, 해당 단말로부터

내의 빔 인덱스에 해당하는 빔들의 수신 신호 세기와 수신 위상 정보를 포함하는 피드백을 수신한다(S822). The base station 100 transmits the scheduling information

And further receives feedback of the received signal strength and received phase information of the beams corresponding to the beam index in the received signal,

(Step S822). The received signal strength and the received phase information of the beams corresponding to the beam index in the received signal are received.

내의 모든 빔의 수신 신호 및 수신 위상을 알고 있으므로,

내에 있는 빔 인덱스에 해당하는 빔들에 의해 스팬하는 부공간 내에선 각 단말의 CSI를 정확히 알게 된다. 이를 기반으로 기지국(100)은 이 부공간 내의 CSI 정보를 기반으로 MMSE이나 ZF 빔포밍을 설계한다(S824). 또한 기지국(100)은 이 부공간 내의 CSI 정보를 기반으로 MMSE이나 ZF 빔포밍과 다른 임의의 빔포밍을 설계할 수도 있다. When the base station 100 receives the feedback from the terminal,

The reception signal and the reception phase of all the beams in the beam are known,

The CSI of each terminal can be known accurately in the subspace spanned by the beams corresponding to the beam index in the subframe. Based on this, the base station 100 designs MMSE or ZF beamforming based on CSI information in the subspace (S824). The base station 100 may also design the MMSE or ZF beamforming and other arbitrary beamforming based on the CSI information in the subspace.

개의 실수임을 알 수 있다. The amount of feedback of the UE when using this scheduling scheme and beamforming is one real number and N _FB integer in the feedback step of the first section,

It is a mistake.

The scheduling method described above can be applied as it is in the structure considering hybrid analog / digital beamforming in a situation where the number N _RF of RF chains in the base station 100 is smaller than the number M of antennas of the base station . Specifically, in the hybrid analog digital beamforming situation, the analog beam training is performed, and at this time, the terminal can be scheduled according to the scheduling method of the MRT and EGC schemes described above, and an analog beam to be used when data is transmitted to the terminal can be generated. However _, since the number of terminals that can simultaneously transmit is limited to N _RF , K _{s, max} ≤N _RF .

9 is a diagram illustrating a base station and a terminal according to an embodiment of the present invention.

9, the base station scheduling apparatus 910 includes a processor 912, a transceiver 914, and a memory 916. [ The processor 912 may be configured to implement functions, operations, procedures, and methods, etc., for beamforming and scheduling at the base station as described in the embodiments of the present invention. The processor 912 may execute instructions stored in or loaded into the memory 916 to implement the functions, operations, procedures, and methods for scheduling at the base station described above. The transceiver 914 is coupled to the processor 912 to transmit and / or receive wireless signals. The transceiver 914 may include a plurality of antenna elements. The memory 916 is coupled to the processor 912 to store various information for driving the processor 912. The memory 916 stores instructions to be executed by the processor 912 or temporarily stores instructions by loading the instructions from a storage device (not shown).

The feedback device 920 of the terminal includes a processor 922, a transceiver 924, and a memory 926. The processor 922 may be configured to implement functions, operations, procedures and methods, etc., for feedback at the terminal as described in the embodiments of the present invention. The processor 922 may implement the functions, operations, procedures, and methods for feedback at the terminal described above by executing instructions stored or loaded in the memory 926. The transceiver 924 is coupled to the processor 922 to transmit and / or receive wireless signals. The memory 926 is coupled to the processor 922 to store various information for driving the processor 922. The memory 926 stores instructions to be executed by the processor 922 or temporarily stores instructions by loading the instructions from a storage device (not shown).

Processors 912 and 922 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed.

Memory 916 and 926 may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and / or other storage devices.

The embodiments of the present invention are not limited to the above-described apparatuses and / or methods, but may be implemented through a program for realizing functions corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded, Such an embodiment can be readily 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 (20)

A method for scheduling a plurality of terminals in a cell in a base station using a plurality of beams,
Transmitting a plurality of training beams,
Receiving measurement information on a first number of training beams having a large received signal strength from each of the plurality of terminals receiving the plurality of training beams,
Generating a received signal strength table indicating a received signal strength for each of the terminal and the beam index based on the measurement information for the first number of training beams of each terminal,
Scheduling terminals to be simultaneously transmitted among the plurality of terminals using the received signal strength table
/ RTI > The method of claim 1,
Wherein the measurement information comprises a received signal strength, a received phase and a beam index for each of the first number of training beams. 3. The method of claim 2,
Wherein the scheduling comprises:
Selecting a terminal having the largest sum of the received signal strengths of the first number of training beams of each terminal among the terminals in the schedulable terminal set,
Excluding the selected terminal from the set of terminals and excluding a first number of training beams of the selected terminal from a set of beam indices comprising the plurality of beams,
The method comprising the steps of: removing, from among the terminals of the terminal set, a terminal having a number of beams overlapping between the first number of training beams of the terminal and the first number of training beams of the selected terminal,
And scheduling the terminals to be simultaneously transmitted by repeating the selecting, generating, and deleting steps. 4. The method of claim 3,
Wherein the scheduling further comprises generating a transmission beam to the selected terminal using a received signal strength of the first number of training beams of the selected terminal. 4. The method of claim 3,
Defining a beam set which is a union of a first number of training beams of each scheduled UE,
Assigning a value of 0 to the received signal strength and the received phase of the beams not receiving feedback from the scheduled terminals, among the beams in the combined beam set, and
Designing a minimum mean square error (MMSE) or ZF (Zero-forcing, ZF) beamforming using the received signal strength and the received phase of all beams of each scheduled UE
≪ / RTI > The method of claim 1,
Wherein the measurement information includes a received phase and a beam index for each of the first number of training beams and a sum of received signal strengths of the first number of training beams. The method of claim 6,
Wherein the scheduling comprises:
Selecting a terminal having the largest sum of received signal strengths of the first number of training beams among a group of terminals capable of scheduling,
Generating a transmission beam to the selected terminal using the reception phase for the first number of training beams of the selected terminal,
Excluding the selected terminal from the set of terminals and excluding a first number of training beams of the selected terminal from a set of beam indices comprising the plurality of beams,
The method comprising the steps of: removing, from among the terminals of the terminal set, a terminal having a number of beams overlapping between the first number of training beams of the terminal and the first number of training beams of the selected terminal,
And scheduling the terminals to be simultaneously transmitted by repeating the selecting, generating, and deleting steps. 8. The method of claim 7,
Transmitting data of the corresponding UEs through a transmission beam of the scheduled UEs
≪ / RTI > The method of claim 1,
Wherein the measurement information comprises a sum of a beam index for each of the first number of training beams and a received signal strength of the first number of training beams. The method of claim 9,
Wherein the scheduling comprises:
Selecting a terminal having the largest sum of received signal strengths of the first number of training beams among a group of terminals capable of scheduling,
Excluding the selected terminal from the set of terminals and excluding a first number of training beams of the selected terminal from a set of beam indices comprising the plurality of beams,
The method comprising the steps of: removing, from among the terminals of the terminal set, a terminal having a number of beams overlapping between the first number of training beams of the terminal and the first number of training beams of the selected terminal,
And scheduling the terminals to be simultaneously transmitted by repeating the selecting, generating, and deleting steps. 11. The method of claim 10,
Defining a beam set in which a first number of training beams of each of the scheduled UEs are unified,
Requesting feedback to each scheduled UE and receiving a received signal strength and a received phase of the beams in the unified beam set from each of the UEs;
Designing MMSE or ZF beamforming using the received signal strength and received phase of the beams in the unified set of beams of each scheduled UE
≪ / RTI > An apparatus for scheduling a plurality of terminals in a cell in a base station using a plurality of beams,
A transceiver for transmitting a plurality of training beams and receiving measurement information for a first number of training beams having a strong received signal strength from each of the plurality of terminals receiving the plurality of training beams,
And generating a received signal strength table indicating the strength of the received signal strength of each of the terminal and the beam index based on the measurement information of the first number of training beams of each terminal, and using the received signal strength table according to the beamforming method of the base station A processor for scheduling the plurality of terminals,
. The method of claim 12,
Wherein the measurement information comprises received signal strength, receive phase and beam index for each of the first number of training beams. The method of claim 13,
Wherein the processor schedules a set number of terminals based on a sum of squares of received signal strengths of the first number of training beams of each of the UEs in the schedulable UE set and calculates a first number of UEs And excludes, from the scheduling, a terminal having a training beam and a number of beams overlapping the first number of training beams of each of the scheduled terminals, which is greater than a set maximum allowable number. The method of claim 14,
Wherein the processor combines the received signal strengths for the first number of training beams of each of the scheduled terminals to generate a transmission beam for beamforming of a maximum ratio transmission (MRT) scheme. The method of claim 14,
The processor allocates a value of 0 to the received signal strength and the reception phase of the beams not receiving feedback from the scheduled terminals of the beams in the set of beams obtained by summing the first number of training beams of each terminal of the scheduled terminals, A scheduling apparatus for designing minimum mean square error (MMSE) or zero-forcing (ZF) beamforming or arbitrary beamforming using the received signal strength and received phase of all beams of each scheduled UE. The method of claim 12,
Wherein the measurement information comprises a received phase and a beam index for each of the first number of training beams and a sum of received signal strengths of the first number of beams. The method of claim 17,
Wherein the processor schedules a set number of terminals based on a sum of received signal strengths of the first number of training beams of each of the UEs in the schedulable terminal set and calculates a reception phase for the first number of training beams of each scheduled terminal And generates a transmission beam for beamforming of equal gain combining (EGC) scheme by combining the first number of training beams of each terminal and the first number of each scheduled terminal And excludes, from the scheduling, a terminal whose number of overlapping beams between the training beams is greater than a set maximum allowable number. The method of claim 12,
Wherein the measurement information comprises a sum of a beam index for each of the first number of training beams and a received signal strength of the first number of training beams. 20. The method of claim 19,
Wherein the processor schedules a set number of terminals based on a sum of squares of received signal strengths of the first number of training beams of each of the UEs in the schedulable UE set and calculates a first number of UEs A scheduling step of excluding, from the scheduling, a terminal having a training beam and a number of beams overlapping the first number of training beams of each of the scheduled terminals, the number of which exceeds a set maximum allowable number, A scheduler for receiving a signal strength and a reception phase of the beams in the set from each scheduled terminal and requesting the received signal strength and a reception phase from the scheduled terminals to receive the signal strength and reception phase of the beams in the unified beam set received from the scheduled terminals, To design MMSE or ZF beamforming or any beamforming Scheduling device.

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