JP6266469B2 - Base station apparatus and control method - Google Patents

Description

  The present invention relates to the field of mobile communication, and more particularly to resource allocation control when a user apparatus has a transmission power upper limit.

  In LTE (Long Term Evolution) and LTE-A (Long Term Evolution-Advanced), which are standardization standards of 3GPP (Third Generation Partnership Project), PUFR (Physical Uplink Shared Channel) TFR (Transport Format and Resource: Transport format and resource) selection control is defined.

  One of the TFR selection controls is PUSCH resource block allocation control when the transmission power of a user equipment (UE: User Equipment) sticks to the upper limit.

  FIG. 1 shows a conventional control flow when a UE transmission power upper limit is attached. The base station (eNB: Evolved Node B) measures the reception quality of the signal from the UE in advance (S101). The eNB determines allocation of uplink (UL) communication opportunities for this UE (S102), and determines a PUSCH resource block (RB: Resource Block) to be allocated (S103). Then, when UE transmits by RB which decided allocation, it is judged whether sticking of the upper limit of transmission power occurs in UE (S105).

  When the upper limit of the transmission power does not occur, a modulation and coding scheme (MCS) according to the reception quality of the UE is selected (S107). If there is an upper limit on the transmission power of the UE and reception quality cannot be realized (YES in S105), the number of RBs allocated to this UE is reduced (S106), and an MCS corresponding to the reception quality of the UE is selected. (S107).

  With this method, UE reception quality can be maintained, and it is not necessary to select a low MCS.

3GPP TS36.213 v8.8.0, 5.1 Uplink power control

  However, if the number of RBs assigned to the UE is reduced when the upper limit of transmission power occurs in the UE, the amount of information that can be transmitted per unit time, for example, the transmittable data size (TBS: Transport Block Size) is limited, and the throughput May deteriorate.

  Therefore, it is an object to provide a control technique that can suppress degradation of throughput even when UE transmission power upper limit sticks.

  In order to solve the above problem, the reduction of the number of RBs of the uplink channel allocated to the UE is suppressed as much as possible, and the uplink throughput is maintained.

Specifically, in one aspect of the present invention, a base station that performs wireless communication with a user apparatus is provided. Base station equipment
A resource allocation unit that allocates radio resources to the user apparatus;
A calculation unit that calculates reception quality that should be obtained in the base station when the user apparatus transmits uplink data using the allocated radio resource;
Based on the calculated reception quality, a replacement processor that replaces the maximum transmission power value of the user apparatus with a value equal to or higher than the actual maximum transmission power;
A communication method determination unit for determining a communication method according to the calculated reception quality for the user device;
Have

  As a good configuration example, the base station apparatus determines whether or not the calculated reception quality satisfies the quality that should be guaranteed at the minimum, and the calculated reception quality does not satisfy the quality that should be guaranteed as the minimum In addition, the radio resources allocated to the user apparatus are reduced by an amount necessary to satisfy the quality to be guaranteed at a minimum.

  Even when the transmission power upper limit sticks to the user apparatus (UE), it is possible to suppress the reduction of the uplink throughput by suppressing the reduction of the number of RBs allocated to the UE.

It is a figure which shows the control flow at the time of the conventional UE transmission power upper limit sticking generation | occurrence | production. It is a figure which shows the concept of control of embodiment at the time of UE transmission power upper limit sticking occurrence comparing with the conventional method. It is a figure which shows the control flow of 1st Embodiment. It is a figure which shows the control flow of 2nd Embodiment. It is a figure which shows the concept of control of 2nd Embodiment compared with the conventional method. It is a figure which shows the structural example of a base station.

  FIG. 2 is a conceptual diagram showing the control method of the embodiment when the UE has a transmission power upper limit sticking in comparison with the conventional method. 2A and 2B, the horizontal axis represents the number of assigned RBs, and the vertical axis represents received power from the UE. In the conventional method of FIG. 2 (B), the number of RBs allocated to this UE is reduced so that the reception quality is maintained within the frame of the maximum transmission power of the UE. The UE can transmit uplink data without causing an upper limit of transmission power, but the amount of information that can be transmitted per unit time is reduced.

  On the other hand, in the embodiment, as shown in FIG. 2A, the allocated number of RBs is maintained and a decrease in power density is allowed. The maximum total transmission power of the UE is the same in the case where the number of RBs to be allocated is reduced (FIG. 2B) and in the case where the decrease in power density is allowed (FIG. 2A).

  When the two methods are compared, even if the possibility that a low MCS is selected in response to a decrease in power density is considered, transmission in FIG. 2A is possible per unit time, for example, 1 TTI (Transmission Time Interval) There is a high possibility that a large amount of information can be maintained.

In the following embodiments, a new control method is provided when a UE has a transmission power upper limit stuck without greatly changing the operation of an existing control module.
<First Embodiment>
FIG. 3 is a flowchart of the control process of the first embodiment. In the first embodiment, even if an upper limit of the UE transmission power occurs in the RB for which allocation is determined, the reception quality that should be obtained when the UE transmits using the allocated RB without reducing the number of RBs. The MCS is selected accordingly.

  The eNB measures the reception quality of the UE to be controlled in advance (S11). This measured reception quality is defined as “reception quality A”. The eNB determines allocation of uplink (UL) communication opportunities to the UE (S12), and determines a PUSCH resource block (RB) to be allocated (S13). Up to this point, the flow is the same as the conventional flow.

  Next, the eNB calculates reception quality that will be obtained when the UE transmits with the assigned number of RBs (S14). This estimated reception quality is defined as “reception quality B”. Since there is SIR (Signal to Interference Ratio) as one index representing the reception quality, “reception quality B” to be calculated is denoted as “SIR ′” in this example. SIR ′ can be obtained by, for example, the equation (1).

SIR '= SIR1-Max (0 , P tmp -P max) (1)
Here, the reception power SIR1 is obtained when it is assumed that there is no upper limit of the transmission power in the UE, P _tmp is UE transmit power needed to obtain the SIR1, P _max is the actual maximum transmit power of the UE It is.

The maximum transmission power P _max of the UE may be the maximum transmission power specified by the UE capability, or may be the maximum transmission power specified or allowed by the network. When uplink data can be transmitted within the maximum transmission power of the UE in the allocated RB, the second term on the right side of Equation (1) is 0, and SIR ′ = SIR1. On the other hand, when the transmission power of the UE is insufficient in the allocated RB, SIR ′ becomes small corresponding to the shortage of transmission power (P _tmp −P _max ).

Next, the eNB replaces the maximum transmission power of the UE with a value larger than the actual maximum transmission power using the estimated reception quality B (that is, SIR ′) (S15). As described above, P _tmp −P _max in the equation (1) represents a shortage of transmission power originally required for the UE to transmit using the allocated RB. If this shortage is ΔP _max , the eNB reads the maximum transmission power of the UE as a value (P _max + ΔP _max ) that is larger than the actual maximum transmission power P _max by ΔP _max . This replacement is a process for preventing the existing control module from reducing the number of RBs.

Since ΔP _max corresponds to the difference between SIR1 (reception quality when the UE has no upper limit in transmission power) and SIR ′ (reception quality that should be obtained when transmitting with the assigned RB),
ΔP _max = Max (0, SIR1−SIR ′) (2)
May be labeled.

  Next, the eNB determines whether or not the transmission power upper limit sticking occurs in the UE with the assigned RB (S16). This determination is performed according to the procedure of the existing control module. However, since the maximum transmission power of the UE is replaced in S15, it is determined that there is no transmission power upper limit sticking. Therefore, the number of RBs assigned to the UE is not reduced.

Next, the eNB determines the MCS according to the estimated UE reception quality B (ie, SIR ′). The MCS selected here may be a lower MCS than the MCS assigned to the reception quality A measured in advance. However, since the number of RBs that the UE can use for transmission is maintained, the amount of information transmitted per unit time can often be maintained higher than when RB is reduced.
Second Embodiment
FIG. 4 is a flowchart of the control process of the second embodiment. In the second embodiment, the minimum reception quality is guaranteed by reducing the number of RBs assigned only when the minimum reception quality cannot be maintained.

  The eNB measures the reception quality of the UE to be controlled in advance (S21). This measured reception quality is defined as “reception quality A”. The eNB determines allocation of uplink (UL) communication opportunities to the UE (S22), and determines a PUSCH resource block (RB) to be allocated (S23). Up to this point, the flow is the same as the conventional flow.

  Next, the eNB calculates reception quality that will be obtained when the UE transmits with the assigned number of RBs (S24). This estimated reception quality is defined as “reception quality B”. The eNB determines whether or not the calculated reception quality B is lower than the reception quality that should be guaranteed at least (S25). If it is below the reception quality that should be guaranteed at the minimum (YES in S25), the reception quality B is set to the value of the reception quality that should be guaranteed at the minimum (S26), and the process proceeds to step S27. If the calculated reception quality B satisfies the minimum reception quality to be guaranteed (NO in S25), the calculated value of the reception quality B is maintained, and the process proceeds to step S27.

  You may perform the process of S24-S26 using Formula (3).

SIR '= Min (SIR1, Max (SIR tmp, SIR min))
SIR _tmp = SIR1-Max (0, P _tmp −P _max ) (3)
Is required. here,
SIR ′ is the reception quality B obtained when the UE transmits with the assigned RB,
SIR1 is the received power obtained when the UE has no upper limit of transmission power,
SIR _min is the reception quality that must be satisfied at a minimum,
P _tmp is the UE transmit power required to obtain SIR1,
P _max is the actual maximum transmission power of the UE,
It is.

In equation (3), if SIR _tmp is greater than or equal to SIR _min ,
SIR ′ = SIR _tmp = SIR1-Max (0, P _tmp −P _max )
This is the same as in the first embodiment. If SIR _tmp is below SIR _min ,
SIR '= SIR _min (4)
(S26).

Next, the eNB replaces the maximum transmission power P _max of the UE with (P _max + ΔP _max ) using the reception quality B (S27). When the calculated reception quality B satisfies SIR _min , it is read as a value that covers the actual shortage of transmission power, as in the first embodiment. When the reception quality B is lower than SIR _min , from the expressions (2) and (4), ΔP _max = Max (0, SIR1−SIR _min )
Thus, ΔP _{max which} is smaller than the actual power shortage is added.

  Next, the eNB determines whether an upper limit sticking occurs in the UE transmission power (S28). When the reception quality B satisfies the quality that should be guaranteed at least (NO in S25), it is determined that there is no upper limit sticking to the transmission power (NO in S28) and calculated as in the first embodiment. The MCS corresponding to the reception quality B is selected (S30).

If the reception quality B does not satisfy the quality that should be guaranteed at the minimum (YES in S25), the maximum transmission power of the UE is read as ΔP _max that is smaller than the transmission power that is actually insufficient. It is determined that the upper limit of power is generated (YES in S28). In this case, the number of RBs to be allocated is reduced to a number in which the transmission power of the UE does not stick to the upper limit (S29), and an MCS corresponding to the reception quality B is selected (S30).

FIG. 5 is a diagram showing the concept of control of the second embodiment in comparison with the conventional method. As described above, the conventional method in FIG. 5B reduces the number of RBs to be allocated up to the point where the upper limit of the UE transmission power does not occur. On the other hand, in the method of the embodiment of FIG. 5A, the number of RBs to be allocated is maintained as much as possible to allow the reception power density to decrease, but only the RBs necessary for guaranteeing the minimum reception quality. Reduce the number. Thereby, it is possible to suppress a decrease in throughput while maintaining the minimum reception quality.
<Device configuration>
FIG. 6 is a schematic configuration diagram of the eNB 10. The radio communication unit 11 performs radio communication with UEs that are in the area. The reception quality measuring unit 12 measures the reception quality of each UE in advance. The reception quality measured here corresponds to “reception quality A” in FIGS. 3 and 4. The memory 21 stores the maximum transmission power of each UE. The control unit 20 executes the control shown in FIG. 3 or FIG.

  The resource allocation unit 13 of the control unit 20 determines allocation of uplink communication opportunities to the UE, and determines a PUSCH resource block (RB) to be allocated to the UE. The reception quality estimation unit 15 calculates reception quality obtained when the UE transmits with the assigned number of RBs. The reception quality calculated here corresponds to “reception quality B” in FIGS. 3 and 4.

  The minimum quality assurance determination unit 16 determines whether or not the reception quality B calculated by the reception quality estimation unit 15 satisfies the minimum necessary quality, and is calculated when the reception quality B is lower than the minimum necessary quality. The received reception quality B is set to the minimum required reception quality.

The maximum transmission power replacement unit 17 replaces the maximum transmission power P _max of the UE with a value (P _max + ΔP _max ) obtained by adding a shortage with respect to the transmission power necessary for transmission with the allocated number of RBs. When uplink data transmission is possible with the allocated number of RBs within the range of the maximum transmission power of the UE, the deficit ΔP _max becomes zero, so the value of P _max does not change before and after the replacement process. When the transmission power is insufficient with the allocated number of RBs, P _max is read as a value larger than the actual maximum transmission power value of the UE.

The transmission power upper limit sticking determination unit 18 determines whether or not the transmission power upper limit sticking of the UE occurs based on the replaced maximum transmission power value _Pmax . As long as the calculated reception quality B satisfies the necessary minimum quality, it is determined that no upper limit sticking occurs even when the transmission power is insufficient. When the reception quality B is lower than the minimum required quality, it is determined that the upper limit sticking occurs.

  When it is determined that the transmission power upper limit sticking occurs, the RB reduction processing unit 14 reduces the number of assigned RBs as much as necessary to guarantee the minimum reception quality.

  The MSC determination unit 19 selects an MSC corresponding to the calculated reception quality B.

  With this configuration, it is possible to prevent a decrease in throughput by suppressing a reduction in the number of RBs allocated to the UE while maintaining an existing control module. Further, by performing reception quality determination, it is possible to guarantee the minimum reception quality while maintaining the number of RBs allocated to the UE as much as possible.

  In the embodiment, the reception quality B obtained when transmitting with the number of assigned RBs is calculated using the SIR, but other indicators such as a bit error rate (BER) and a block error rate (BLER) may be used. In addition to the MCS, a precoding vector may be selected as a communication method according to the calculated reception quality B.

10 eNB (base station)
DESCRIPTION OF SYMBOLS 11 Wireless communication part 12 Reception quality measurement part 13 Resource allocation part 14 RB reduction process part 15 Reception quality estimation part 16 Minimum quality assurance determination part 17 Maximum transmission power replacement part 18 Transmission power upper limit sticking determination part 19 MSC determination part (communication system determination) Part)
20 Control unit 21 Memory

Claims (10)

A base station that wirelessly communicates with user equipment,
A resource allocation unit that allocates radio resources to the user apparatus;
A calculation unit that calculates reception quality that should be obtained in the base station when the user apparatus transmits uplink data using the allocated radio resource;
Based on the calculated reception quality, a replacement processor that replaces the maximum transmission power value of the user apparatus with a value equal to or higher than the actual maximum transmission power;
A communication method determination unit for determining a communication method according to the calculated reception quality for the user device;
A base station characterized by comprising: A quality determination unit that determines whether or not the calculated reception quality satisfies a quality that should be guaranteed at a minimum;
If the calculated reception quality does not satisfy the minimum guaranteed quality, the radio resources allocated to the user apparatus are reduced by an amount necessary to satisfy the minimum guaranteed quality. A reduction processing unit;
The base station according to claim 1, further comprising:   The replacement processing unit performs the replacement processing by replacing the calculated reception quality with the minimum guaranteed quality when the calculated reception quality does not satisfy the minimum guaranteed quality. The base station according to claim 2. Based on the maximum transmission power after the replacement, an upper limit sticking determination unit that determines whether or not an upper limit sticking of transmission power occurs in the user apparatus at the time of uplink data transmission on the assigned radio resource,
Further comprising
The said reduction process part reduces the said radio | wireless resource only by the amount required in order to satisfy | fill the quality which should be guaranteed at the minimum, when the upper limit sticking of the said transmission power generate | occur | produces. Base station.   The replacement processing unit, based on a difference between the calculated reception quality and the reception quality obtained with the allocated radio resource when it is assumed that there is no upper limit on the transmission power of the user apparatus, The base station according to claim 1, wherein processing is performed. A control method in a base station,
When the user equipment transmits uplink data using radio resources allocated from the base station, the reception quality that should be obtained at the base station is calculated,
Based on the calculated reception quality, perform a process of replacing the maximum transmission power value of the user apparatus to a value greater than or equal to the actual maximum transmission power,
Determining a communication scheme according to the calculated reception quality for the user equipment;
A control method including a step of suppressing a reduction in the radio resource allocated to the user apparatus by the replacement process. Determining whether the calculated reception quality satisfies a quality that should be guaranteed at a minimum;
If the calculated reception quality does not satisfy the minimum guaranteed quality, the radio resources allocated to the user apparatus are reduced by an amount necessary to satisfy the minimum guaranteed quality. ,
The control method according to claim 6, further comprising a step.   The replacement process replaces the maximum transmission power by replacing the calculated reception quality with the minimum guaranteed quality when the calculated reception quality does not satisfy the minimum guaranteed quality. The control method according to claim 7, wherein: Determining whether or not an upper limit of transmission power occurs in the user apparatus when uplink data is transmitted on the allocated radio resource, based on the maximum transmission power after the replacement,
Further including
9. The control method according to claim 8, wherein, when the upper limit of the transmission power is generated, the radio resource is reduced by an amount necessary for satisfying the minimum guaranteed quality.   The replacement process is based on a difference between the calculated reception quality and a reception quality obtained with the allocated radio resource when it is assumed that there is no upper limit on the transmission power of the user apparatus. The control method according to claim 6, wherein:

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