JP6619320B2 - Scheduling apparatus and method - Google Patents

Description

  The present invention relates to a radio network control technique, and more particularly to a scheduling technique for assigning radio resources possessed by a radio network by designating the operation content (transmission state) of each transmission point in the radio network.

  With the widespread use of smartphones, social demands on wireless networks, such as improved communication speed and increased bandwidth usage, are increasing. Against this background, wireless network systems to which wireless interface specifications of the next generation mobile communication system called LTE (Long Term Evolution) are applied are becoming widespread. In this LTE, as one of radio access technologies, CoMP (Coordinated Multi-point transmission / reception: CoMP) in which a plurality of transmission points (TP: base station) cooperate with each other to transmit / receive signals to / from user terminals (UE: user radio terminals). Inter-cell cooperative transmission / reception is employed (see Non-Patent Document 1).

  The CoMP technique is one of important techniques for improving frequency utilization efficiency and cell edge user throughput. For example, in downlink communication (transmission from TP to UE), the use efficiency of radio resources can be improved by simultaneously transmitting a plurality of transmission points to each UE using the same frequency band. However, when each transmission point transmits to a different UE, for a UE capable of receiving signals from a plurality of transmission points, signals from other transmission points become interference of a desired reception signal. There is a risk of lowering. Therefore, CoMP has become an indispensable technology for improving the communication speed while suppressing such interference.

  In addition, when applying CoMP to a wireless network, for the purpose of maximizing system throughput, priority is given to resource allocation to users with good reception conditions, which causes a problem in fairness among users. Scheduling in consideration of the average rate so far is considered desirable (see Non-Patent Document 2).

  As one type of LTE, there is a TD-LTE (Time Division Long Term Evolution) method using a TDD (Time Division Duplex) method. In normal LTE, different frequency bands are used to perform uplink (uplink) communication and downlink (downlink) communication simultaneously, whereas TD-LTE periodically increases the same frequency band. This is a method for performing time-division communication while switching between a link and a downlink in a short time.

Taoka et al., "MIMO and inter-cell cooperative transmission / reception technology in LTE-Advanced", NTT DOCOMO Technical Journal, Vol. 18, No. 2, pp.22-30, July 2010, https: //www.nttdocomo. co.jp/binary/pdf/corporate/technology/rd/technical_journal/bn/vol18_2/vol18_2_022jp.pdf T. Girici, C. Zhu, JR Agre, and A. Ephremides, “Proportional Fair Scheduling Algorithm in OFDMA-Based Wireless Systems with QoS Constraints”, Journal of Communications and Networks, Vol. 12, No. 1, pp. 30- 42, February 2010

  In a wireless network system, when performing such scheduling, the scheduling device designates a transmission state for each TP, that is, a UE serving as a transmission destination or a transmission stop for each TP, as a combination of the TP and the UE having the maximum evaluation value. Decide what information you want. In order to determine this combination, an evaluation value of a large number of TP / UE combinations is calculated, a process for finding a combination having the best evaluation value is performed, and the combination is determined within a scheduling period (for example, within a time of 1 millisecond). Need to complete.

  A reliable way to obtain the optimal combination is to calculate an evaluation value for each possible combination and find a combination that maximizes the evaluation value, that is, perform a brute force search. Therefore, as the number of TPs and the number of UEs included in the wireless network increase and the scale increases, the search space (the number of possible combinations) also increases. For this reason, the above-described conventional technique has a problem that when the size of the wireless network increases, it takes a long time to find the optimal combination, and the optimal combination cannot be determined within the scheduling period.

  The present invention is intended to solve such a problem, and an object thereof is to provide a scheduling technique capable of efficiently executing a scheduling process within a certain scheduling period.

In order to achieve such an object, a scheduling apparatus according to the present invention is configured to perform time division switching between a downlink period composed of a plurality of subframes and an uplink period composed of one or a plurality of subframes. Based on the (Duplex) method, the antenna is used in a wireless network that performs wireless communication with a plurality of wireless terminals using a plurality of antennas. A scheduling device for searching for and determining an optimal combination pattern, wherein the processing extension period is set in synchronization with a processing extension period that is set within the uplink period and includes a part or all of the uplink period. A processing control unit that outputs a processing control signal indicating the downlink period and the processing control. In the period consisting of the processing extension period indicated signal, the optimum combination pattern used in each of the plurality of sub-frames of the downlink period, and a scheduling processing unit that searches prior to each of the plurality of downlink sub frame period I have.

Further, examples of the configuration of the scheduling apparatus according to the present invention, the scheduling processing unit, the most suitable candidate for combination patterns, a plurality of the combination and the combination generator, which is generated for sequentially generating a plurality of combination patterns A combination evaluation unit that calculates an evaluation value related to a pattern, and an optimum combination holding unit that selects, from among the plurality of generated combination patterns, the one having the maximum evaluation value, holds and outputs the optimum combination pattern And a search processing unit including

Also, in one configuration example of the scheduling device according to the present invention, the scheduling processing unit is configured to combine the antenna with the antenna using a plurality of the combination patterns generated by the combination generation unit among all the wireless terminals. A scheduling unit that selects the optimum combination pattern to be used in each of a plurality of subframes in the downlink period by the search processing unit in the downlink period. A search process for searching is executed, and a terminal selection process for selecting the target wireless terminal used for generating a plurality of the combination patterns in each of the search processes is performed by the terminal selection unit in the process extension period. It is something to be executed.

Further, the scheduling method according to the present invention is based on a TDD (Time Division Duplex) system that switches a downlink period composed of a plurality of subframes and an uplink period composed of one or a plurality of subframes in a time division manner. Used in a wireless network that performs wireless communication with a plurality of wireless terminals using a plurality of antennas, and searches for and determines an optimal combination pattern from among a plurality of combination patterns indicating combinations of the antenna and the wireless terminal that perform the wireless communication And a process control unit configured to process the process control period indicating the process extension period in synchronization with a process extension period that is set within the uplink period and includes a part or all of the uplink period. A process control step for outputting a signal, and a scheduling processing unit, In the period consisting of the processing extension period indicated period and the processing control signal, the optimum combination pattern used in each of the plurality of sub-frames of the downlink period, to search prior to each of the plurality of downlink sub frame period Scheduling processing steps.

  According to the present invention, part or all of the uplink period during which data transmission from the antenna to the radio terminal is stopped is used as a process extension period for the scheduling process for determining the optimum combination pattern. . For this reason, of the limited time of the radio frame period, the time when the scheduling process is stopped in accordance with the stop of the data transmission can be effectively utilized for the search process of the optimum combination pattern. It is possible to extend the time available for determining the optimal combination.

  Therefore, it is possible to efficiently execute the scheduling process within a certain scheduling period, to search for more combination patterns, and to find a better optimal combination pattern. As a result, not only is the system throughput expected to be improved, but it is also possible to expand the range supported by existing processing capabilities for expanding the search space due to the increase in the number of antennas and wireless terminals included in the wireless network. Become.

It is a block diagram which shows the structure of the scheduling apparatus concerning 1st Embodiment. It is a timing chart which shows the scheduling process concerning 1st Embodiment. It is a flowchart which shows the process expansion control process concerning 1st Embodiment. It is a flowchart which shows the search process concerning 1st Embodiment. It is a graph which shows the relationship between search processing time and system throughput. It is a block diagram which shows the structure of the scheduling apparatus concerning 2nd Embodiment. It is a timing chart which shows the scheduling process concerning 2nd Embodiment. It is a flowchart which shows the scheduling process concerning 2nd Embodiment. It is a flowchart which shows the terminal group classification | category process concerning 2nd Embodiment.

Next, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
First, a scheduling apparatus 10 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration of a scheduling apparatus according to the first embodiment.

  This scheduling device 10 is based on a TDD (Time Division Duplex) system that switches between a downlink period and an uplink period in a time division manner, and a plurality of radio terminals (hereinafter referred to as TP) by a plurality of antennas (hereinafter referred to as TP). , Which is used in a wireless network that performs wireless communication with UE), and has a function of searching for and determining an optimal combination pattern from among a plurality of combination patterns indicating combinations of TP and UE that perform wireless communication .

[Principle of the Invention]
Normally, when determining a UE that is a transmission destination of data transmitted from each TP, combination patterns of TP and UE are sequentially generated as candidates, and evaluation values of these combination patterns are calculated. This trial is repeatedly executed based on a preset search algorithm, and when the search period (scheduling cycle) expires, the combination pattern with the maximum evaluation value obtained so far is used for actual data transmission. The optimum combination pattern to be used is determined.

Here, in the TTD scheme, a downlink period in which data is transmitted from the TP to the UE and an uplink period in which data is transmitted from the UE to the TP are allocated to a plurality of subframes provided in a time division manner in the radio frame. FIG. 2 is a timing chart illustrating the scheduling process according to the first embodiment. In this example, 10 subframes having a time length _TSL are provided in a radio frame repeated at a period _TRF . Special subframes and uplink subframes are assigned to the second and third subframes from the beginning of the radio frame, respectively, and downlink subframes are assigned to the other subframes. ing.

  The special subframe is a subframe that can be set to either an uplink subframe or a downlink subframe by setting. Therefore, when the special subframe is set as the uplink subframe, the 2-3th subframe from the head is the uplink period, and the other 8 subframes are the downlink period.

In each downlink period, a TP is assigned to each UE based on a new optimal combination pattern. Therefore, it is necessary to determine the optimum combination pattern to be used by performing a scheduling process prior to the downlink period.
FIG. 2A is a timing chart showing a basic process allocation method, in which a search process for searching for an optimum combination pattern used in the next downlink period is executed in the search process in each downlink period. The present invention is also applicable to an FDD (Frequency Division Duplex) scheme in which uplink subframes and downlink subframes are wirelessly communicated at different frequencies. Therefore, it is not necessary to execute the search process in the uplink period, and the scheduling process is stopped.

  However, in the scheduling apparatus, it is not necessary to stop the scheduling process in the uplink period, and the scheduling process may be executed. The present invention pays attention to such an uplink period that arrives in a time division manner in the TDD scheme, and in this uplink period, a part or all of the processing extension period is set in advance, and scheduling is also performed in this processing extension period. The processing is executed.

FIG. 2B is a timing chart showing the processing period extension method according to the first embodiment. Here, the processing extension time is set for all of the uplink periods.
As a result, the optimal combination pattern used in each of the eight downlink periods allocated in the radio frame is not searched in the eight subframe periods, but is used in the ten subframe periods. You can search. Therefore, the search processing time for one optimum combination pattern can be extended. In the case of FIG. 2, the time Ta (T _SL ) can be extended to time Tb by 1.25 times (= 10/8). Thus, when Ta (T _SL ) = 1 ms, Tb = 1.25 ms. Note that the search processing execution timing may be calculated in accordance with an available period, or may be set in advance.

[Scheduling device]
Next, the configuration of the scheduling apparatus 10 according to the present embodiment will be described in detail with reference to FIG.
The scheduling apparatus 10 shown in FIG. 1 includes a processing control unit 11 and a scheduling processing unit 12 as main functional units. The scheduling processing unit 12 includes a search processing unit 13 as a main processing unit. The search processing unit 13 includes a combination generation unit 14, a combination evaluation unit 15, and an optimum combination holding unit 16. It has been. These functional units and processing units may be realized by dedicated circuits, or may be realized by executing a pre-registered program on the CPU.

The processing control unit 11 outputs a processing control signal CNT indicating a processing extension period in synchronization with a processing extension period that is set in the uplink period and includes part or all of the uplink period in the radio frame. By doing so, it has a function of instructing to extend the execution period of various processes executed by the scheduling processing unit 12.
At this time, the timing of the subframes indicating the uplink period and the downlink period may be acquired from the outside of the scheduling apparatus 10 such as an apparatus or a processing block that mainly processes the main signal in the radio network system.

  The process control unit 11 detects the arrival of the process extension period set in the uplink period at each time based on the acquired timing of the subframe and the preset time position of the process extension period. When the arrival of the processing expansion period is detected, the processing control signal CNT is output to the scheduling processing unit 12, and the output of the processing control signal CNT is stopped when the processing expansion period expires.

  Note that when the arrival of the processing expansion period is detected, the arrival of the processing expansion period may be detected based on the processing timing generated inside the scheduling apparatus 10 instead of the timing of the subframe from the outside. For example, since the uplink period and the downlink period are switched at a fixed period in synchronization with the radio frame, the elapsed time from the start of the scheduling process is measured inside the apparatus, and the process extension period arrives based on the measured result Can also be detected.

  The scheduling processing unit 12 has a function of searching for an optimum combination pattern to be used in each downlink period prior to each downlink period in both the downlink period and the processing extension period indicated by the process control signal in the radio frame. have.

  The search processing unit 13 executes a pipeline process in a search period corresponding to each downlink period, and thereby indicates a plurality of combinations of TPs and UEs that perform wireless communication based on a preset search algorithm. It has a function of searching for an optimum combination pattern from among the combination patterns.

  The combination generation unit 14 has a function of sequentially generating combination pattern candidates indicating combinations of UEs and TPs. The combination generation unit 14 may stop generating the combination pattern when a predetermined time has elapsed from the start of generation of the combination pattern or when generation of the predetermined number of combination patterns is finished. As a pattern combination generation method, a generally known search algorithm is used. For example, in addition to the brute force method for generating all combinations comprehensively, a known approximate solution for a combination optimization problem such as a hill climbing method or a greedy method can be applied. Further, when generating the combination pattern, the combination pattern is generated including the combination in which the TP is in a transmission stop state.

  The combination evaluation unit 15 has a function of sequentially calculating evaluation values related to the combination of UE and TP for each combination pattern generated by the combination generation unit 14. The evaluation value is calculated based on a preset evaluation formula. The parameters used in the evaluation formula include the sum of the radio throughput of each TP, that is, the radio throughput of the entire system, and the throughput value obtained when transmission is performed using a combination of each TP and UE, which is generally used in a radio network system. A value (Proportional Fairness, PF metric) divided by an average throughput value accumulated for a predetermined period may be used.

  The optimum combination holding unit 16 has a function of holding the combination pattern having the maximum evaluation value calculated by the combination evaluation unit 15 as the optimum combination pattern. Specifically, each time the combination generation unit 14, the combination evaluation unit 15, and the optimum combination holding unit 16 operate in conjunction with pipeline processing and a new combination pattern is generated by the combination generation unit 14, a combination is generated. Only when the evaluation value of the new combination pattern is larger than the evaluation value of the optimum combination pattern held so far, the evaluation unit 15 calculates the evaluation value of the new combination pattern. The combination pattern and its evaluation value are held as the optimum combination pattern.

  Note that, when the scheduling processing is executed by the scheduling processing unit 12 during the processing expansion period based on the processing control signal CNT output from the processing control unit 11, the processing operation of the entire search processing unit 13 is executed. On the other hand, when the output of the processing control signal CNT is stopped in the uplink period, the processing operation of the entire search processing unit 13 may be stopped by the scheduling processing unit 12, but only the processing operation of the optimum combination holding unit 16 May be instructed to stop the output of the optimum combination pattern and continue to hold it, and explicitly instruct the combination generation unit 14 or the combination evaluation unit 15 to continue the processing operation.

[Operation of First Embodiment]
Next, the operation of the scheduling apparatus 10 according to the present embodiment will be described with reference to FIG. 3 and FIG. FIG. 3 is a flowchart illustrating a process expansion control process according to the first embodiment. FIG. 4 is a flowchart illustrating the search process according to the first embodiment.

[Process extension control processing]
First, with reference to FIG. 3, the process expansion control process in the scheduling apparatus 10 according to the present embodiment will be described. The process control unit 11 of the scheduling apparatus 10 always executes the process expansion control process of FIG.
In the process expansion control process of FIG. 3, first, the process control unit 11 confirms the arrival of the uplink period based on the timing of the subframe acquired from the outside or the internal timing result (step 100).

When the arrival of the uplink period is detected (step 100: YES), the process control unit 11 confirms the arrival of the process extension period based on the preset process extension period (step 101).
Here, when the arrival of the process extension period is detected (step 101: YES), the process control unit 11 outputs a process control signal CNT indicating the arrival of the process extension period (step 102), and returns to step 100.

On the other hand, when the arrival of the process extension period is not detected (step 101: NO), the process control unit 11 stops outputting the process control signal CNT indicating the arrival of the process extension period (step 103), and proceeds to step 100. Return.
When the arrival of the uplink period is not detected in step 100 (step 100: NO), the process control unit 11 stops outputting the process control signal CNT indicating the arrival of the process extension period (step 103). Return to step 100.

[Search process]
Next, with reference to FIG. 4, the scheduling process in the scheduling apparatus 10 according to the present embodiment will be described. The scheduling processing unit 12 of the scheduling apparatus 10 includes a downlink period indicated by the timing of a subframe acquired from the outside, and an extended processing period within the uplink period indicated by the processing control signal CNT from the processing control unit 11. The search processing unit 13 executes the search process of FIG.

First, the combination generation unit 14 generates one new combination pattern candidate indicating a combination of UE and TP to be scheduled according to a predetermined search algorithm (step 110). When the combination pattern is generated, the combination pattern is generated including a combination in which each TP is in a transmission stop state.
Subsequently, the combination evaluation unit 15 calculates a new evaluation value related to the combination of the target UE and TP for the new combination pattern generated by the combination generation unit 14 (step 111).

  Thereafter, the optimum combination holding unit 16 compares the new evaluation value of the new combination pattern calculated by the combination evaluation unit 15 with the holding evaluation value of the holding combination pattern held so far (step 112). Here, when the new evaluation value is higher than the holding evaluation value and indicates the maximum value of the combination pattern generated so far (step 112: YES), the new combination pattern and the new evaluation value are updated and held ( Step 113).

Next, the optimum combination holding unit 16 determines whether or not to end the search process when the convergence of the currently executed search process is confirmed or when the next downlink period arrives (step 114) If not finished (step 114: NO), the process returns to step 110 to generate and evaluate a new combination pattern.
In step 112, if the new evaluation value is equal to or less than the holding evaluation value (step 112: NO), the process returns to step 110 in the same manner, and generation / evaluation of a new combination pattern is started.

  On the other hand, when the search process is completed (step 114: YES), the optimum combination holding unit 16 outputs the held combination pattern finally held in the search process so far as the optimum combination pattern (step 115). Thereby, based on this optimal combination pattern, the combination of UE and TP in the next downlink period will be set.

  FIG. 5 is a graph showing the relationship between search processing time and system throughput. Here, when the number of TPs is 32 and the number of UEs is 256, the result of calculating the wireless throughput of the entire system in each search processing time by simulation is shown. Therefore, in the example of FIG. 2B described above, the search processing time can be extended from 1 ms to 1.25 ms, so that more optimal combination patterns can be found by searching for more combination patterns. As a result, it can be seen that the system throughput is improved by about 2%.

[Effect of the first embodiment]
As described above, according to the present embodiment, the process control unit 11 performs the process indicating the process extension period in synchronization with the process extension period that is set in the uplink period and includes a part or all of the uplink period. A control signal is output, and the scheduling processing unit 12 searches for an optimal combination pattern used in each downlink period prior to each downlink period in both the downlink period and the process extension period indicated by the process control signal. It is what I did.

  As a result, a part or all of the uplink period during which data transmission from the antenna to the wireless terminal is stopped is used as a process expansion period for the scheduling process for determining the optimum combination pattern. For this reason, of the limited time of the radio frame period, the time when the scheduling process is stopped in accordance with the stop of data transmission can be effectively utilized for the search process of the optimum combination pattern, and the optimum of the TP and UE This makes it possible to extend the time that can be used to determine the appropriate combination.

  Therefore, it is possible to efficiently execute the scheduling process within a certain scheduling period, to search for more combination patterns, and to find a better optimal combination pattern. As a result, not only is the system throughput expected to be improved, but it is also possible to expand the range supported by existing processing capabilities for expanding the search space due to the increase in the number of antennas and wireless terminals included in the wireless network. Become.

[Second Embodiment]
Next, with reference to FIG. 6, the scheduling apparatus 10 concerning the 2nd Embodiment of this invention is demonstrated. FIG. 6 is a block diagram illustrating a configuration of the scheduling apparatus according to the second embodiment.

  Usually, in the scheduling process, it is not necessary to assign all UEs to any TP in one downlink period. This is because the downlink period repeatedly arrives at a very short period, for example, 1 millisecond, so even if any UE is not assigned to any TP in a certain downlink period, it is assigned in the subsequent downlink period. This is because there is no significant influence on data transmission.

On the other hand, the number of combination patterns varies greatly depending on the number of UEs to be allocated in the combination pattern. For example, when the numbers of UE and TP are X and Y, respectively, (X + 1) ^Y combination patterns are required to cover all combinations of UE and TP. In this trial calculation, the number when no UE is assigned to the TP is also taken into consideration.

The present embodiment pays attention to the relationship between the downlink period and the allocation of UEs to the TP, and from among all UEs, a plurality of target UEs to be transmitted in the next downlink period are downlinked. The selection is made for each period.
In addition, in the processing extension period of the uplink period focused on in the first embodiment, terminal selection is performed, and search processing is performed in the downlink period.

  Specifically, as illustrated in FIG. 6, the scheduling processing unit 12 includes a terminal selection unit 17 that selects a UE to be combined with a TP as a target UE from among all UEs in the combination pattern generated by the combination generation unit 14. The scheduling processing unit 12 executes search processing for searching for the optimum combination pattern used in each downlink period by the search processing unit 13 during the downlink period, and by the terminal selection unit 17 during the process expansion period. The terminal selection process for selecting the target UE used for generating the combination pattern in each of the search processes is executed.

As a selection method of the target UE in the terminal selection unit 17, all UEs are classified into a plurality of terminal groups, and one of these terminal groups is sequentially selected for each downlink period, and the selected terminal group is selected. There is a method of selecting a UE included in the target UE as a target UE.
FIG. 7 is a timing chart illustrating a scheduling process according to the second embodiment. Compared to FIG. 2B, the terminal selection process is assigned to the process extension period of the uplink period, and the search process is executed in the downlink period as in FIG. Note that the search processing execution timing may be calculated in accordance with an available period, or may be set in advance.

  Here, UEs are classified into two terminal groups Ga and Gb based on channel information updated once in one radio frame, for example, by terminal selection processing in the terminal selection unit 17, and UEs belonging to Ga among them are classified. The UE that is used as the target UE in the four search processes subsequent to the process extension period, and the UE that belongs to Gb is used as the target UE in the subsequent four search processes. The channel information CH is data indicating the reception intensity of radio waves from surrounding TPs in each UE, which are periodically measured and notified by each UE or estimated periodically.

  In addition, although FIG. 7 demonstrated the case where each UE was classified into a terminal group based on channel information, it is not limited to this, and each UE is based on other data, such as the transmission data amount of each UE. May be classified into terminal groups. Further, the number of terminal groups is not limited to two as shown in FIG. 7, but may be classified into three or more terminal groups.

  Moreover, about the allocation of the downlink period with respect to a terminal group, you may allocate equally with respect to each terminal group, and you may allocate based on the number of UEs which belong to a terminal group, and the transmission data amount of these UEs. For example, in the example of FIG. 7, when the number of UEs classified into the terminal group Ga is less than the upper limit of the number of UEs that can be transmitted in four downlink periods, the number of downlink periods allocated to Ga is reduced, and the terminal group Gb You may make it increase the number of downlink periods allocated to.

[Terminal grouping (similarity of channel information)]
Next, UE terminal grouping in the terminal selection unit 17 will be described in detail.
First, a case where terminal grouping is performed based on UE channel information will be described.
The channel information is data indicating the reception intensity of radio waves from surrounding TPs in each UE, which is periodically measured and notified by each UE or estimated periodically.

  Here, when the channel information regarding different UEs shows the same reception intensity for radio waves from the same TP, it is considered that the locations of these UEs are close. Therefore, when transmitting transmission data to these UEs in the same downlink period, it is highly possible that these UEs are assigned to the same TP. In such a case, traffic concentration on the TP occurs and radio waves are transmitted. The possibility of communication failure due to interference also increases.

  For this reason, in this Embodiment, when the terminal selection part 17 classify | categorizes each UE, UE with low similarity of the channel information which shows the electromagnetic wave state regarding TP among UE is classify | categorized into the same terminal group. You may do it. As a result, UEs with close locations are classified into different groups, so these UEs are included in different combination patterns. Therefore, the possibility that these UEs are assigned to the same TP in the same downlink period is avoided, and it is possible to suppress the concentration of traffic on the TP and the occurrence of communication failure due to radio wave interference, thereby providing a good radio service. It becomes.

[Terminal grouping (channel information fluctuation)]
On the other hand, the fluctuation amount per unit time of the received strength obtained by the UE is greatly influenced by the moving speed of the UE. This is because as the moving speed of the UE increases, the change in the distance from the TP increases, so that the change in the radio wave transmitted from the TP also increases.
Therefore, when the variation amount of the channel information is large, there is a high possibility that the radio environment of the UE will change in a short time from the time when the channel information is obtained, and the accuracy of the channel information is likely to deteriorate. On the other hand, when the variation amount of the channel information is small, the radio environment of the UE is unlikely to change even after a certain amount of time has elapsed since the channel information was obtained, and the accuracy of the channel information is unlikely to deteriorate.

  Therefore, in the present embodiment, when the terminal selection unit 17 classifies each UE, the UE is classified into a terminal group based on the amount of temporal variation in channel information indicating the radio wave state related to the TP, You may make it select in order from a terminal group with a big fluctuation amount among these terminal groups. As a result, UEs whose channel information accuracy is likely to deteriorate are first selected and a combination pattern is generated, and TPs are assigned to these UEs with priority from the immediately subsequent downlink period. Therefore, it is possible to minimize the allocation error between the UE and the TP, which occurs due to deterioration of the accuracy of the channel information, and it is possible to provide a good radio service by reducing the transmission error due to this.

[Terminal grouping (data transmission amount)]
Also, when the amount of transmission data to be transmitted from the UE is large, the time required to complete the transmission of these transmission data becomes relatively long, so there is a high possibility that the radio environment of the UE will change before the transmission is completed. The accuracy of is easy to deteriorate. On the other hand, when the amount of transmission data is small, the time required to complete the transmission of these transmission data is relatively short, so the possibility that the radio environment of the UE will change before the transmission is completed is low, and the accuracy of the channel information deteriorates. Hateful.

  For this reason, in this Embodiment, when the terminal selection part 17 classify | categorizes each UE, it classify | categorizes UE into a terminal group based on the magnitude of the transmission data amount of each UE, Transmission data among these terminal groups You may make it select in an order from a terminal group with big quantity. As a result, UEs whose channel information accuracy is likely to deteriorate are first selected and a combination pattern is generated, and TPs are assigned to these UEs with priority from the immediately subsequent downlink period. Therefore, it is possible to minimize the allocation error between the UE and the TP, which occurs due to deterioration of the accuracy of the channel information, and it is possible to provide a good radio service by reducing the transmission error due to this.

  About grouping of these UE, you may apply individually, respectively, and may apply combining these. For example, UEs with a large channel information fluctuation amount and large transmission data amount are classified into a first terminal group, others are classified into a second terminal group, and TPs are allocated in order from UEs belonging to the first terminal group. You may make it hit. As a result, it is possible to preferentially select a UE whose radio environment is likely to change as a target UE, and to provide a good radio service as a whole.

[Operation of Second Embodiment]
Next, the operation of the scheduling apparatus 10 according to the present embodiment will be described with reference to FIGS. FIG. 8 is a flowchart illustrating a scheduling process according to the second embodiment. FIG. 9 is a flowchart illustrating terminal group classification processing according to the second embodiment.

[Scheduling process]
First, the scheduling process according to the present embodiment will be described with reference to FIG.
Based on the processing control signal CNT from the processing control unit 11, the scheduling processing unit 12 performs the target UE selection processing of FIG. 9 described later by the terminal selection unit 17 in the processing expansion period within the uplink period. Then, all UEs to be scheduled are classified into a plurality of terminal groups (step 200).

Next, the scheduling process part 12 performs the search process based on the terminal group classified by the terminal selection part 17 by the search process part 13 for every downlink period.
First, the combination generation unit 14 selects an arbitrary terminal group from among terminal groups, for example, in descending order of channel information variation, or in descending order of transmission data amount (step 201). A list of terminal IDs of UEs belonging to the terminal group thus obtained is acquired from the terminal selection unit 17 as a combination generation condition of the target UEs to be transmitted in the corresponding downlink period (step 202).

Subsequently, the combination generation unit 14 generates one new combination pattern candidate indicating the combination of the target UE and the TP specified by the combination generation condition in accordance with a predetermined search algorithm (step 203). When the combination pattern is generated, the combination pattern is generated including a combination in which each TP is in a transmission stop state.
Next, the combination evaluation unit 15 calculates a new evaluation value related to the combination of the target UE and TP for the new combination pattern generated by the combination generation unit 14 (step 204).

  Thereafter, the optimum combination holding unit 16 compares the new evaluation value of the new combination pattern calculated by the combination evaluation unit 15 with the holding evaluation value of the holding combination pattern held so far (step 205). Here, when the new evaluation value is higher than the holding evaluation value and indicates the maximum value of the combination pattern generated so far (step 205: YES), the new combination pattern and the new evaluation value are updated and held ( Step 206).

Next, the optimum combination holding unit 16 determines whether or not to end the search process when the convergence of the currently executed search process is confirmed or when the next downlink period arrives (step 207) If not finished (step 207: NO), the process returns to step 203 to generate / evaluate a new combination pattern.
In step 205, if the new evaluation value is equal to or less than the holding evaluation value (step 205: NO), the process returns to step 203 in the same manner, and generation / evaluation of a new combination pattern is started.

  On the other hand, when the search process is completed (step 207: YES), the optimum combination holding unit 16 outputs the held combination pattern finally held in the search process so far as the optimum combination pattern (step 208). Thereby, based on this optimal combination pattern, the combination of UE and TP in the next downlink period will be set.

Thereafter, the search processing unit 13 confirms whether a series of downlink periods has ended and an uplink period has arrived (step 209). If the series of downlink periods has not ended (step 209: NO) ), Returning to step 201, the search process for the new downlink period is started.
If a series of downlink periods has ended (step 209: YES), the process returns to step 200 to start terminal group classification processing based on new channel information.

[Terminal group classification processing]
Next, terminal group classification processing according to the present embodiment will be described with reference to FIG. In step 200 of FIG. 8, the terminal selection unit 17 executes the terminal group classification process shown in FIG. Here, a case will be described as an example where these UEs are classified into two terminal groups Ga and Gb based on the channel information and transmission data amount of each UE. Among these, Ga is a group of UEs to which TP is assigned prior to Gb.

In the terminal group classification process of FIG. 9, first, the terminal selection unit 17 acquires channel information regarding all UEs to be scheduled (step 210), and calculates a variation amount from the previously acquired channel information for each UE (step 210). Step 211).
Next, the terminal selection unit 17 acquires the amount of data related to the data addressed to the UE accumulated in, for example, a frame buffer (not shown), thereby transmitting each transmission data amount (UE) to be transmitted in the next downlink period ( (Maximum value) is acquired (step 212).

  Thereafter, the terminal selection unit 17 selects one unclassified UE from each UE (step 220), and calculates the variation amount of the selected UE obtained in step 211 and a variation amount threshold value set in advance. Compare (step 221). Here, when the channel variation amount of the selected UE exceeds the variation amount threshold value (step 221: YES), the terminal selection unit 17 is preset with the transmission data amount of the selected UE obtained in step 212. The transmission amount threshold is compared (step 222).

Here, when the transmission data amount of the selected UE exceeds the transmission amount threshold value (step 222: YES), the terminal selection unit 17 classifies the selected UE into the terminal group Ga (step 223).
On the other hand, when the variation amount of the selected UE is equal to or smaller than the variation amount threshold value in step 211 (step 221: NO), and when the transmission data amount of the selected UE is equal to or smaller than the transmission threshold value in step 222 (step 222: NO), the terminal selection unit 17 classifies the selected UE into the terminal group Gb (step 224).

Thereafter, the terminal selection unit 17 confirms whether the classification of all UEs has been completed (step 225), and if there is an unclassified UE (step 225: NO), the terminal selection unit 17 returns to step 220 and returns to the new UE. Start the classification process.
On the other hand, when the classification has been completed for all the UEs (step 225: YES), a series of terminal group classification processes are terminated.

Note that, for the fluctuation amount of an arbitrary UE calculated in step 212 in FIG. 9, the average value of fluctuation amounts of radio wave reception strength from the UE and each TP may be used, and the reception strength is the best for the UE. You may use the fluctuation amount regarding only TP.
Moreover, although the example of classifying the UE using the channel information and the transmission data amount is shown in the example of FIG. 9, the example of the classification of the UE is not limited to this. For example, it may be classified into a plurality of terminal groups using only channel information and its variation. Also, UEs may be classified using only the transmission data amount.

  Also, UEs with low channel information similarity may be classified into the same terminal group. In this case, first, based on the TP with the best reception sensitivity in each UE, each UE is classified into a TP group, and a UE is selected to generate a terminal group so that UEs in the same TP group are not selected. May be. Thereby, UEs with low similarity in channel information can be classified into the same terminal group.

[Effects of the present embodiment]
Thus, this Embodiment makes the terminal selection part 17 select a part of UE as object UE made into transmission object in a corresponding downlink period for every search process. More specifically, the terminal selection unit 17 classifies UEs into a plurality of terminal groups, selects one of these terminal groups for each search process, and selects UEs included in the selected terminal group. The target UE is selected. In addition, the terminal selection unit 17 performs terminal selection processing in the processing extension period of the uplink period, and the search processing unit 13 executes search processing in the downlink period.

Thereby, since the number of UEs used in one combination pattern can be reduced, the number of combination patterns used as candidates in the search process for the optimum combination pattern is greatly reduced. Therefore, it is possible to significantly reduce the time required for the process of calculating the evaluation value of the combination pattern, and further the time required to reach the optimum combination pattern.
Further, since the terminal selection process by the terminal selection unit 17 is executed in the uplink period in which the search process is originally stopped, the search process time is not shortened even if the terminal selection process is added. For this reason, a sufficient search for the optimum pattern can be executed.

[Extended embodiment]
The present invention has been described above with reference to the embodiments, but the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention. In addition, each embodiment can be implemented in any combination within a consistent range.

  DESCRIPTION OF SYMBOLS 10 ... Scheduling apparatus, 11 ... Processing control part, 12 ... Scheduling processing part, 13 ... Search processing part, 14 ... Combination production | generation part, 15 ... Combination evaluation part, 16 ... Optimal combination holding part, 17 ... Terminal selection part.

Claims (4)

Based on a TDD (Time Division Duplex) system in which a downlink period composed of a plurality of subframes and an uplink period composed of one or a plurality of subframes are switched in a time division manner, wireless communication is performed with a plurality of wireless terminals by a plurality of antennas. A scheduling apparatus for searching for and determining an optimal combination pattern from a plurality of combination patterns indicating a combination of the antenna and the wireless terminal used for the wireless communication.
A processing control unit configured to output a processing control signal indicating the processing expansion period in synchronization with a processing expansion period that is set within the uplink period and includes a part or all of the uplink period;
In the period consisting of the downlink period and the processing extension period indicated by the processing control signal, the optimum combination pattern used in each of the plurality of subframes in the downlink period is prior to each of the plurality of subframes in the downlink period. And a scheduling processing unit for searching. The scheduling apparatus according to claim 1, wherein
The scheduling processing unit includes:
As a candidate for the optimum combination pattern, a combination generation unit that sequentially generates a plurality of the combination patterns ;
A combination evaluation unit that calculates evaluation values for the plurality of generated combination patterns;
A search processing unit including: an optimum combination holding unit that selects, from among the plurality of generated combination patterns, the one having the maximum evaluation value, holds and outputs the optimum combination pattern, and Scheduling device. The scheduling apparatus according to claim 2, wherein
The scheduling processing unit further includes a terminal selection unit that selects, as a target wireless terminal, the wireless terminal to be combined with the antenna in the plurality of combination patterns generated by the combination generation unit among all the wireless terminals,
The scheduling processing unit performs a search process for searching for the optimum combination pattern used in each of a plurality of subframes of the downlink period by the search processing unit during the downlink period, and the process extension period In the scheduling apparatus, the terminal selection unit executes a terminal selection process for selecting the target wireless terminal used for generating a plurality of the combination patterns in each of the search processes. Based on a TDD (Time Division Duplex) method in which a downlink period composed of a plurality of subframes and an uplink period composed of one or a plurality of subframes are switched in a time division manner, wireless communication with a plurality of wireless terminals is performed by a plurality of antennas. A scheduling method for searching for and determining an optimum combination pattern from among a plurality of combination patterns indicating a combination of the antenna that performs the wireless communication and the wireless terminal.
A process control step in which the process control unit outputs a process control signal indicating the process extension period in synchronization with a process extension period which is set within the uplink period and which is part or all of the uplink period. When,
Scheduling processing unit, in the period consisting of the process expansion period in which the processing control signal and the downlink period shows, the optimum combination pattern used in each of the plurality of downlink sub frame period, a plurality of sub-downlink period And a scheduling process step for searching prior to each of the frames .

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