WO2013035467A1

WO2013035467A1 - Base station and communication control method

Info

Publication number: WO2013035467A1
Application number: PCT/JP2012/069846
Authority: WO
Inventors: 義顕大藤; 尚人大久保; 耕平清嶋
Original assignee: 株式会社エヌ・ティ・ティ・ドコモ
Priority date: 2011-09-09
Filing date: 2012-08-03
Publication date: 2013-03-14
Also published as: JP5848924B2; JP2013059001A

Abstract

Provided are a base station and communication control method such that when, in a subframe, small-size user data for a plurality of mobile stations are multiplexed in a downlink shared physical channel, it is possible to increase use efficiency of the downlink shared physical channel even in conditions such that there is a limit to the possible number of mobile stations multiplexed in a downlink control physical channel. The base station (100) is provided with a PDSCH scheduler (103) that schedules in a manner so that a large data size mobile station having a user data size larger than a predetermined size threshold is included as a mobile station that is the subject of user data multiplexing. The PDSCH scheduler (103) selects a mobile station that is the subject of multiplexing of user data in accordance with a predetermined priority ranking when the number of schedulable residual downlink control physical channel resources or schedulable residual downlink shared physical channels that can be multiplexed is at least a predetermined multiplexing threshold, and when same is at or below the predetermined multiplexing threshold, schedules prioritizing the large data size mobile station.

Description

Base station and communication control method

The present invention schedules user data for a plurality of mobile stations on a downlink shared physical channel, and transmits user data scheduling results to one or more mobile stations that transmit and receive the user data multiplexed on the downlink shared physical channel. The present invention relates to a base station and a communication control method that notify a plurality of mobile stations via a control physical channel.

In Long Term Evolution (LTE), which is standardized in 3rd Generation Partnership Project (3GPP), multiple mobile stations can be scheduled in a subframe of 1 msec length and user data can be multiplexed onto the downlink shared physical channel (PDSCH) . It is stipulated that a mobile station (user) scheduling result (DL scheduling info) to PDSCH is notified to the mobile station using a downlink control physical channel (PDCCH) (for example, Non-Patent Document 1). Here, the scheduling result is notified using a different PDCCH for each mobile station where user data is multiplexed on the PDCCH.

When the bandwidth is 5 MHz, the number of PDCCHs that can be multiplexed is about 6 to 8 (/ subframe) on average including DL scheduling info and UL scheduling grant. That is, the number of mobile stations that can be multiplexed in each of the downlink and uplink directions is about 3 to 4 on average.

However, the above-described conventional scheduling method of the mobile station to the PDSCH has the following problems. In other words, since there is a limit on the number of mobile stations that can be multiplexed onto the PDCCH, when the data size per mobile station is small, there is a problem that user data for mobile stations cannot be multiplexed even though the PDSCH has room. It was.

In general, scheduling of user data for a mobile station to a PDSCH in a base station is a priority determined in consideration of indexes such as service priority, QoS (Quality of Service), radio quality of each mobile station, and whether or not it is retransmission data. It is done according to the ranking. In this case, the above-described problem occurs when a mobile station with a small user data size occupies the highest priority. The priority order is determined by, for example, quantifying the priority of each index, calculating the sum after multiplying the numerical priority of each index by a weighting factor, and determining the priority based on the calculated value. Can be considered.

The present invention has been made in view of such a situation. In the case where small-size user data for a plurality of mobile stations is multiplexed on a downlink shared physical channel (PDSCH) in a subframe, the downlink control physical channel An object of the present invention is to provide a base station and a communication control method that can improve the use efficiency of the downlink shared physical channel even in a situation where the number of multiplexable mobile stations is limited.

The first feature of the present invention is that scheduling user data for a plurality of mobile stations (

mobile stations

200A and 200B) is scheduled on a downlink shared physical channel (PDSCH), and the user data multiplexed on the downlink shared physical channel is transmitted and received. A base station (base station 100) for notifying one or more mobile stations of the scheduling result of the user data via a downlink control physical channel (PDCCH), the mobile station being the target of multiplexing of the user data A scheduler (PDSCH scheduler) for scheduling such that a mobile station having a large data size in which the size of the user data or the number of radio resource blocks necessary for transmitting the user data is larger than a predetermined size threshold (TH _SIZE ) is included 103), and the scheduler is a remaining downlink control physical channel resource that can be scheduled. Alternatively, when the number of schedulable remaining downlink shared physical channel multiplexes is equal to or greater than a predetermined multiplex threshold, the mobile station that is to be multiplexed with the user data is selected according to a predetermined priority, and the remaining downlink control physical channel resource or The gist is to preferentially schedule the large data size mobile station when the remaining downlink shared physical channel multiplexing number is equal to or less than the predetermined multiplexing threshold.

According to a second aspect of the present invention, at least one mobile station that schedules user data for a plurality of mobile stations on a downlink shared physical channel and transmits and receives the user data multiplexed on the downlink shared physical channel, A communication control method for notifying a scheduling result of user data via a downlink control physical channel, which is necessary for transmitting the user data size or the user data as a mobile station to be multiplexed with the user data Scheduling to include a large data size mobile station having a larger number of radio resource blocks than a predetermined size threshold, and the scheduling step includes scheduling remaining downlink control physical channel resources or scheduling capable Residual downlink shared physical channel multiplexing When the number is equal to or greater than a predetermined multiplexing threshold, the step of selecting a mobile station to be multiplexed with the user data according to a predetermined priority, and the remaining downlink control physical channel resource or the remaining downlink shared physical channel multiplexing number And a step of preferentially scheduling the mobile station having the large data size when the predetermined multiple threshold value is reached.

FIG. 1 is an overall schematic configuration diagram of a radio communication system according to an embodiment of the present invention. FIG. 2 is a functional block configuration diagram of the base station 100 according to the embodiment of the present invention. FIG. 3 is a diagram showing a scheduling operation flow of the base station 100 according to this embodiment according to the embodiment of the present invention. FIG. 4 is a diagram showing an example of a table used when N _{UE_LargeData according} to the embodiment of the present invention is variably controlled.

Next, an embodiment of the present invention will be described. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones.

Therefore, specific dimensions should be determined in consideration of the following explanation. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(1) Overall Schematic Configuration of Radio Communication System FIG. 1 is an overall schematic configuration diagram of a radio communication system according to the present embodiment. As shown in FIG. 1, the radio communication system according to the present embodiment employs a Long Term Evolution (LTE) scheme, and includes a core network 50, a base station 100 (eNB), and

mobile stations

200A and 200B (UE). Including.

The base station 100 is connected to the core network 50. Base station 100 forms cell C1 and performs radio communication with

mobile stations

200A and 200B according to the LTE scheme. In particular, in this embodiment, the base station 100 schedules user data for a plurality of mobile stations (

mobile stations

200A and 200B) on the downlink shared physical channel (PDSCH), and the scheduling result of the user data is transmitted to the downlink control physical channel. Notify the plurality of mobile stations via (PDCCH).

Note that many mobile stations may exist in the cell C1 other than the

mobile stations

200A and 200B. In addition, as described above, the priority order of the mobile station is calculated by calculating the sum of the priority of each index by multiplying the priority of each index by the weighting factor. A method of determining based on the value can be considered. In the present embodiment, it is assumed that the higher the numerical priority, the higher the priority.

(2) Functional Block Configuration of Radio Communication System Next, a functional block configuration of the radio communication system according to the present embodiment will be described. FIG. 2 is a functional block configuration diagram of the base station 100. As shown in FIG. 2, the base station 100 includes a transmission buffer 101, a PDSCH scheduler 103, a transmission data generation unit 105, a control information generation unit 107, a signal multiplexing unit 109, a signal transmission unit 111, a signal reception unit 113, and a signal separation unit. 115 and CQI management unit 117.

The transmission buffer 101 stores data transmitted in the downlink direction, that is, from the base station 100 to the mobile station 200A. The transmission buffer 101 sets a Queue for each bearer set with the mobile station 200A, stores transmission data for the mobile station 200A, and manages a retention amount of the transmission data.

The PDSCH scheduler 103 allocates a downlink shared physical channel (PDSCH) to the mobile station 200A. In particular, in the present embodiment, as a mobile station to which user data is multiplexed, the size of the user data is larger than a predetermined size threshold (TH _SIZE ), or a radio resource block necessary for transmitting user data Scheduling is performed so that mobile stations (large data size mobile stations) whose number is larger than a predetermined size threshold (TH _RB ) are included.

Specifically, the PDSCH scheduler 103 prioritizes user data for a normal data size mobile station excluding a large data size mobile station (UE_LaregeData) whose user data size is larger than a predetermined value over a large data size mobile station. And schedule to PDSCH.

When a mobile station that multiplexes user data on PDSCH in a certain subframe is selected from a plurality of mobile stations (

mobile stations

200A, 200B,...), The PDSCH scheduler 103 has a margin in the remaining PDCCH resources or the remaining PDCCH multiplexing number In some cases, the mobile station is selected according to a predetermined priority order determined in advance.

On the other hand, when the remaining PDCCH resource or the number of remaining PDCCH multiplexes is equal to or smaller than a predetermined multiplexing threshold, the PDSCH scheduler 103 transmits the user data with a size of user data larger than a predetermined size threshold (TH _SIZE ). For this reason, a mobile station (large data size mobile station) having a larger number of radio resource blocks necessary for this purpose is larger than a predetermined size threshold value (TH _RB ).

The PDSCH scheduler 103 is necessary for transmitting user data in a mobile station having the predetermined priority level equal to or lower than the predetermined priority threshold value or the user data size being equal to or _larger than the predetermined size threshold value (TH _SIZE ). If there is no mobile station whose number of radio resource blocks is equal to or greater than the predetermined size threshold (TH _RB ), user data is transferred to the PDSCH in order from the mobile station with a predetermined priority regardless of the remaining PDCCH resource or the remaining PDSCH multiplexing number. Multiplexed mobile stations can be selected.

Further, the PDSCH scheduler 103 is based on a specific index in a mobile station in which the size of user data is equal to or larger than TH _SIZE or the number of radio resource blocks necessary for transmitting user data is equal to or larger than a predetermined size threshold (TH _RB ). When the priority is lower than the priority based on the index of an unselected mobile station that is higher than the mobile station, the PDSCH can be scheduled from user data for a mobile station having a predetermined high priority.

For example, the PDSCH scheduler 103 is based on a specific index of a mobile station having a high priority that is lower than the maximum number of multiplexed PDSCHs (N _MAX ) based on a specific index specified in advance in a large data size mobile station. If it is lower than the priority, it is possible to perform scheduling on the PDSCH from the user data for the mobile station having the predetermined high priority without giving priority to the mobile station having a large data size.

Further, the PDSCH scheduler 103 does not give priority to the normal data size mobile station when the reception quality information (Channel Quality Indicator) of the mobile station to be scheduled is equal to or lower than a predetermined quality threshold, and the mobile station having a high priority level. It is also possible to schedule to PDSCH from user data for the target.

In this embodiment, the PDSCH scheduler 103 allocates PDSCH radio resource blocks to a plurality of mobile stations that have decided to multiplex user data on the PDSCH, and the mobile station requires fewer radio resource blocks to transmit user data. Radio resource blocks are allocated from The PDSCH scheduler 103 allocates the radio resource block to the mobile station up to a value obtained by dividing the number of radio resource blocks that can be allocated to the mobile station by the maximum multiplexing number (N _MAX ) of the mobile station to the PDCCH.

The transmission data generation unit 105 performs channel coding and data modulation of transmission data stored in the transmission buffer 101, and generates transmission data output to the signal multiplexing unit 109. The control information generation unit 107 performs PDCCH channel coding and data modulation.

The signal multiplexing unit 109 multiplexes the data output from the transmission data generation unit 105 and the control information generation unit 107, and outputs the multiplexed signal to the signal transmission unit 111.

The signal reception unit 113 outputs the received signal to the signal separation unit 115. The signal separation unit 115 separates the signal output from the signal reception unit 113 into uplink data, BSR, and CQI.

The CQI management unit 117 manages the CQI separated by the signal separation unit 115.

(3) Operation of Base Station Next, the operation of the radio communication system according to this embodiment will be described. Specifically, the scheduling operation of user data to PDSCH by base station 100 will be described. FIG. 3 shows a scheduling operation flow of the base station 100 according to the present embodiment.

As shown in FIG. 3, the base station 100 determines scheduling priorities for the mobile stations to be scheduled (S10). The priority order determined in S10 is hereinafter referred to as a predetermined priority order.

The base station 100 determines the multiplexable number (N _remain ) on the PDCCH as the maximum multiplex number N _MAX of mobile stations on the PDCCH (S20). In addition, when PDCCH is used for common channel transmission such as broadcast information, a value obtained by subtracting the usage amount from N _{MAX is} defined as N _remain .

Next, the base station 100 selects a mobile station that multiplexes user data on the PDSCH from the top of a predetermined priority order, and decrements N _remain each time a mobile station is selected. When N _remain ≤ N _{UE_LargeData} , a mobile station that satisfies one or both of the following conditions is selected (S30 to S90).

Specifically, the base station 100 moves a mobile station in which the size of user data to be transmitted is greater than or equal to TH _SIZE (predetermined size threshold), or a move in which the number of radio resource blocks necessary for transmitting user data is greater than or equal to TH _RB. Select a station.

However, even when N _remain ≦ N _{UE_LargeData} , in the following case, base station 100 selects mobile stations (users) in order from the top of the original predetermined priority. Specifically, within a mobile station range R _search for a predetermined priority, the size of user data is equal to or greater than TH _SIZE , or the number of radio resource blocks required for transmitting user data is equal to or greater than TH _RB . In a mobile station in which there is no user and the size of user data is equal to or greater than TH _SIZE , or the number of radio resource blocks required for transmitting user data is equal to or greater than TH _RB , the priority based on a specific index is predetermined. This is a case where the priority is lower than the priority based on the index of an unselected mobile station higher than the mobile station.

The “priority based on a specific index” may be a priority based on a traffic type, for example. When the priority of the voice service is higher than the priority of the best effort service, the mobile station using the best effort service is not given priority even if the size of the transmission data is large.

Even when the CQI of the mobile station is equal to or lower than a predetermined quality threshold (TH _CQI ), it is preferable to select mobile stations (users) in order from the top of the predetermined priority. Even if the mobile station has large user data, if the reception quality is low, the PDCCH multiplex number decreases or the PDSCH transmission rate decreases because it consumes a lot of PDCCH resources for the UE. This is because usage efficiency does not increase.

After selecting a mobile station that multiplexes user data on PDSCH, it is preferable that the PDSCH radio resource block allocation is executed in order from the mobile station having the smallest number of radio resource blocks necessary for transmitting user data. The number of radio resource blocks necessary for transmitting user data may be determined from the sum of all user data related to the mobile station and the value of CQI. This makes it possible to allocate radio resource blocks with good reception status to mobile stations with a small number of allocated radio resource blocks. Furthermore, all surplus radio resource blocks can be allocated to a mobile station having a large user data size.

However, it is preferable that the upper limit of the number of allocated radio resource blocks per mobile station is 1 / (number of multiplexing-number of mobile stations to which radio resource block has been allocated) of the number of radio resource blocks that can be allocated. The number of assignable radio resource blocks is the number of usable radio resource blocks excluding the number of radio resource blocks assigned to a common channel and the like and the number of radio resource blocks already assigned to another mobile station.

_Further, the value of the number of mobile stations N _{UE_LargeData} may be variably controlled according to the number of downlink bearers set in the cell C1. FIG. 4 shows an example of a table used when N _{UE_LargeData} is variably controlled.

Since the number of multiplexing per subframe differs for each system bandwidth, the threshold for the number of bearers and the value of N _{UE_LargeData} may refer to different tables depending on the system bandwidth. According to such a table, the PDSCH scheduler 103 increases TH _SIZE and TH _RB (predetermined size threshold) as the number of radio access bearers in the downlink set with the mobile station increases. Can be increased.

(4) Modification Example The operation flow described above may be modified as follows. Specifically, the base station 100 may set the remaining resource amount (the number of CCEs) of the PDCCH to N _{CCE_remain} . Here, N _{CCE_remain} is the number of CCEs that can be used without including the CCE consumed in the PDCCH for common channel transmission such as broadcast information.

Next, the base station 100 selects a mobile station that multiplexes user data on the PDSCH from the top of the predetermined priority. Each time the base station 100 selects a mobile station, the base station 100 calculates the number of CCEs consumed to transmit the PDCCH to the selected mobile station. The calculated number of CCE's was subtracted from the N _{CCE_remain} value as a new N _{CCE_remain.} When N _{CCE_remain} ≦ TH _CCE , a mobile station that satisfies the above-described condition is selected (see S30 to S90 described above). TH _CCE is a threshold for the number of remaining CCEs.

(5) Operation / Effect According to the base station 100 according to the present embodiment described above, a large data size mobile station having a user data size larger than a predetermined value can be appropriately allocated to the PDSCH. When the user data for the mobile station is multiplexed on the PDSCH, the use efficiency of the PDSCH can be improved even when the number of mobile stations that can be multiplexed on the PDCCH is limited.

(6) Other Embodiments As described above, the contents of the present invention have been disclosed through one embodiment of the present invention. However, it is understood that the description and drawings constituting a part of this disclosure limit the present invention. should not do. From this disclosure, various alternative embodiments will be apparent to those skilled in the art.

For example, in the above-described embodiment of the present invention, the value of N _{UE_LargeData} is variably controlled according to the number of downlink bearers set in the cell C1, but such control is not necessarily required. .

Thus, it goes without saying that the present invention includes various embodiments that are not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the appropriate claims from the above description.

Note that the entire content of Japanese Patent Application No. 2011-197595 (filed on September 9, 2011) is incorporated herein by reference.

According to the characteristics of the present invention, when small-size user data for a plurality of mobile stations is multiplexed on a downlink shared physical channel (PDSCH) in a subframe, the number of multiplexable mobile stations on the downlink control physical channel is limited. Even in such a situation, it is possible to provide a base station and a communication control method that can improve the utilization efficiency of the downlink shared physical channel.

50 ... Core network 100 ... Base station 101 ... Transmission buffer 103 ... PDSCH scheduler 105 ... Transmission data generation unit 107 ... Control information generation unit 109 ... Signal multiplexing unit 111 ... Signal transmission unit 113 ... Signal reception unit 115 ... Signal separation unit 117 ...

CQI management unit

200A, 200B ... mobile station cell ... C1

Claims

Scheduling user data for a plurality of mobile stations on a downlink shared physical channel, and sending the user data scheduling result to one or more mobile stations that transmit and receive the user data multiplexed on the downlink shared physical channel A base station notifying via a channel,
The mobile stations to be multiplexed with the user data include a mobile station with a large data size in which the size of the user data or the number of radio resource blocks necessary for transmitting the user data is larger than a predetermined size threshold. With a scheduler to schedule
The scheduler moves the user data to be multiplexed according to a predetermined priority when the schedulable remaining downlink control physical channel resource or the schedulable remaining downlink shared physical channel multiplex number is equal to or greater than a predetermined multiplexing threshold. A base station that selects a station, and schedules the mobile station with priority to the large data size mobile station when the remaining downlink control physical channel resource or the remaining downlink shared physical channel multiplexing number is equal to or less than the predetermined multiplexing threshold.
When the large data size mobile station does not exist among the mobile stations having the predetermined priority level equal to or lower than the predetermined priority threshold value, the scheduler determines the user data for the mobile station with the predetermined high priority level. The base station according to claim 1, wherein scheduling is performed on the downlink shared physical channel.
The scheduler is configured such that the priority based on a specific index specified in advance in the large data size mobile station is higher than the maximum multiplexing number of mobile stations to the downlink shared physical channel, and the specific of the mobile station having a high priority. The scheduling apparatus according to claim 1, wherein when the priority is lower than an index-based priority, scheduling is performed on the downlink shared physical channel from the user data for the mobile station having the predetermined high priority without giving priority to the mobile station having the large data size. Base station.
If the received quality information of the mobile station to be scheduled is equal to or lower than a predetermined quality threshold, the scheduler does not give priority to the large data size mobile station, but from the user data for the mobile station with the predetermined high priority. The base station according to claim 1, wherein scheduling is performed on the downlink shared physical channel.
The base station according to claim 1, wherein the scheduler increases the predetermined size threshold as the number of downlink radio access bearers set with the plurality of mobile stations increases.
The base station according to claim 1, wherein the scheduler allocates the radio resource block from a mobile station having a small number of radio resource blocks necessary for transmitting the user data in the allocation of the radio resource block to the downlink shared physical channel.
The scheduler sets, as an upper limit, a value obtained by dividing the number of radio resource blocks that can be allocated to the mobile station by the number of mobile stations that are not allocated radio resource blocks among the mobile stations that have determined multiplexing of the user data, The base station according to claim 6, wherein the radio resource block is allocated to a mobile station.
Scheduling user data for a plurality of mobile stations on a downlink shared physical channel, and sending the user data scheduling result to one or more mobile stations that transmit and receive the user data multiplexed on the downlink shared physical channel A communication control method for notification via a channel,
The mobile stations to be multiplexed with the user data include a mobile station with a large data size in which the size of the user data or the number of radio resource blocks necessary for transmitting the user data is larger than a predetermined size threshold. Scheduling to
The scheduling step includes:
When the schedulable remaining downlink control physical channel resource or the schedulable remaining downlink shared physical channel multiplex number is equal to or greater than a predetermined multiplexing threshold, the mobile station to be multiplexed with the user data is selected according to a predetermined priority Steps,
A communication control method including: preferentially scheduling the mobile station with a large data size when the remaining downlink control physical channel resource or the number of multiplexed remaining downlink shared physical channels is equal to or less than the predetermined multiplexing threshold.