JPWO2006006208A1 - Radio base station - Google Patents

Abstract

The radio base station according to the present invention is a radio base station having a scheduling function for controlling the data transmission rate to the radio channel according to the radio channel status of the terminal. For example, the data holding unit (2) includes a host device ( 11) the received data from 11) is held in the buffer, the output amount monitoring unit (4) monitors the amount of data transmitted from the buffer, and the staying amount managing unit (5) has a range in which the data staying amount in the buffer is within a certain range. The process of determining the data reception rate (flow control) is performed so that the data reception rate is maintained, and the reception rate notification unit (6) notifies the higher-level device (11) of the data reception rate.

Description

  The present invention relates to a radio base station constituting a mobile communication system, and more particularly to a radio base station capable of realizing high throughput by performing flow control on data received from a host device.

  Hereinafter, a conventional radio base station will be described. In the conventional radio base station, the target transmission capacity of the wired line is obtained based on the effective transmission speed of the wireless line, and the transmission capacity request signal for requesting the relay station to increase or decrease the allowable transmission capacity is obtained. Sending. As a method for obtaining the target transmission capacity, the difference between the effective transmission speed of the wireless line and the effective transmission speed of the wired line is calculated. For example, when the difference exceeds a predetermined threshold value # 1, the transmission capacity is set to RQ #. When the difference falls below a predetermined threshold value # 2, it is decreased by RQ # 2 (see Patent Document 1 below).

Japanese Patent Laid-Open No. 2001-358663 FIG. 2 and FIG.

  However, the above-described conventional radio base station has the following problems.

In the prior art, since control is performed focusing only on the transmission capacity, the effective transmission speed of the wireless line (that is, the output speed from the wireless base station) is the effective transmission speed of the wired line (that is, the input speed to the wireless base station) If it exceeds, a state occurs in which no call data stays in the base station. In particular, HSDPA (High
In a system in which a wireless base station has a data transmission scheduling function such as (Speed Downlink Packet Access), the number of data that can be transmitted to each terminal at once is the number of data for each terminal staying in the wireless base station. Since the scheduling is performed in a state where the upper limit is limited, efficient scheduling cannot be performed and the throughput of the entire system is reduced.

  For example, transmission data stays in the host device of a radio base station, but there is no data for terminals with good radio channel status in the radio base station, and only data for terminals with poor radio channel status exists in the radio base station. A situation occurs that exists in the station. For this reason, it is necessary to allocate radio resources to terminals having poor radio channel conditions, and the overall system throughput decreases.

  Furthermore, when scheduling is performed in a state where the above upper limit is limited, even if the effective transmission rate of the wireless link is measured, it is different from the transmission rate when the original efficient scheduling is performed. There is a problem that a vicious circle occurs in which the target transmission capacity cannot be accurately calculated.

  The present invention has been made in view of the above, and an object of the present invention is to provide a radio base station capable of realizing the maximum throughput by effectively performing flow control.

  In order to solve the above-described problems and achieve the object, the radio base station according to the present invention has a scheduling function for controlling the data transmission rate to the radio channel according to the radio channel status of the terminal. For example, a data holding means for holding received data from a host device in a buffer, an output amount monitoring means for monitoring the amount of data transmitted from the buffer, and a data retention amount in the buffer being constant. A retention amount management unit that performs processing (flow control) for determining a reception rate (data reception rate) of data transmitted from the host device so as to maintain the range within the range, and notifies the host device of the data reception rate Receiving rate notification means.

  According to the present invention, the staying amount management means, for example, compares the data transmission rate obtained by monitoring the output amount monitoring means with the data reception rate notified to the host device, and based on the result. We decided to perform flow control.

  Since the radio base station according to the present invention performs flow control effectively, that is, the stay amount management means has notified the data transmission rate obtained by the output amount monitoring means and the host device. Since the data reception rate is compared and the flow control is performed based on the result, the maximum throughput can be realized.

FIG. 1 is a diagram illustrating a configuration example of a radio base station according to the present invention. FIG. 2 is a diagram illustrating the operation of the staying amount management unit 5. FIG. 3 is a diagram illustrating a data reception rate determination method using data reception rate increase control and data reception rate decrease control. FIG. 4 is a diagram showing a data retention number target value table. FIG. 5 is a diagram illustrating an example of data reception rate increase control. FIG. 6 is a diagram illustrating an example of data reception rate reduction control. FIG. 7 is a diagram illustrating the operation of the reception rate notification unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wireless base station 2 Data holding part 3-1, 3-2, 3-m Queue 4 Output amount monitoring part 5 Staying amount management part 6 Reception rate notification part 7 Scheduler part 8 Call control part 9 Timer 10 Data transmission / reception part 11 Upper rank apparatus

  Embodiments of a radio base station according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 is a diagram illustrating a configuration example of a radio base station according to the present invention. The radio base station 1 of the present embodiment has a data holding unit 2 that holds received data, and this data holding unit 2 has a plurality of queues 3 (3-1, 3-2,..., 3-m). Possess. Further, the radio base station 1 cycles the output amount monitoring unit 4 that counts the number of data output from the queue 3 for each queue, the number of data stays for each queue 3 and the number of output data counted by the output amount monitoring unit 4. The retention rate management unit 5 for calculating the data reception rate, and the reception rate notification unit 6 for notifying the host device 11 of the data reception rate calculated by the retention amount management unit 5 via the data transmission / reception unit 10; And a call control unit 8 that notifies the retention amount management unit 5 of the start and completion of the handover of the terminal. Furthermore, the scheduler unit 7 performs data transmission scheduling according to the state of the wireless channel of the terminal, extracts data from the queue 3 and outputs it to the wireless channel.

  Here, an operation when the above configuration is applied to a radio base station of an HSDPA (High Speed Downlink Packet Access) method will be described as an example.

  Data transmitted from the host device 11 is received by the data transmitting / receiving unit 10 of the radio base station 1 and is classified and held in each queue 3 in the data holding unit 2 for each communication unit. With respect to the data held here, the scheduler unit 7 performs scheduling in consideration of the radio channel state for each terminal, data priority, fairness, and the like, and transmits it to the radio channel.

  As described above, in order for the scheduler unit 7 to perform data transmission scheduling, data must be held in the queue 3, and therefore it is necessary to sequentially receive data from the host device 11 by flow control. Hereinafter, this flow control operation will be described.

  When the scheduler unit 7 outputs the data held in the queue 3, the output amount monitoring unit 4 increments a counter corresponding to each queue 3. Here, for the sake of convenience, the output amount monitoring unit 4 and the scheduler unit 7 are described as being independent, but the increment of the counter may be performed by the scheduler unit 7.

  FIG. 2 is a diagram illustrating the operation of the staying amount management unit 5. The stay amount management unit 5 operates, for example, in a certain cycle by the timer 9 or a cycle according to the data reception capability of the terminal, and performs a data reception rate calculation process. The data reception capability of the terminal corresponds to the maximum reception rate that can be received by the terminal. Here, for simplicity, an operation using one queue, for example, the queue 3-1, will be described as an example.

  First, when the timer 9 times out, the staying amount management unit 5 refers to the counter of the output amount monitoring unit 4 and determines the number of data output from the queue 3-1 per unit time as the nth data transmission rate Ro. (N) is calculated (step S1). The data transmission rate Ro (n) may be calculated as an average value including past calculation results.

  Next, the staying amount management unit 5 compares the previously calculated data reception rate Ri (n-1) with the data transmission rate Ro (n) (step S2), and if Ro (n) is larger (step S2). (S2, Yes), data reception rate increase control (step S3) described later is performed. If Ro (n) is smaller (step S2, No), data reception rate decrease control (step S4) is performed. Here, the data reception rate Ri (n−1) is a value notified to the higher-level device 11 at the time of the previous data reception rate calculation. The host device 11 performs data transmission at a rate equal to or lower than the notified data reception rate.

  Further, after the data reception rate increase control is performed, the data reception rate is limited so as not to exceed the reception line bandwidth from the higher-level device 11 (step S5). This makes it possible to avoid problems such as data loss and congestion that occur in lower layers than flow control.

  FIG. 3 is a diagram showing a data reception rate determination method using data reception rate increase control (step S3) and data reception rate decrease control (step S4). In FIG. 3, the horizontal axis indicates whether to perform data reception rate increase control or data reception rate decrease control. The vertical axis indicates the number of data retention in the queue 3-1. After determining whether to perform the data reception rate increase control or the data reception rate decrease control as described above, the stay amount management unit 5 refers to the data stay number in the queue 3-1, and sets the data stay number target. The data reception rate is determined so as to approach the value T.

As a method of determining the data retention number target value T, for example, it is determined by the number of queues 3 (3-1 to 3-m) allocated to a communication unit, and the number of calls connected to the radio base station 1 increases. The data retention number target value is dynamically decreased. For example, assuming that the total number of buffers held by the data holding unit 2 is A and the target is to retain data for the ratio K%, and if m queues are set, the target number of data retention per queue T is determined by the following equation (1). The total number of buffers A and the ratio K% are predetermined constants.
T = AK / 100m (1)

  In the above, the case where the data retention target number T is dynamically changed according to the value of the set queue number m is shown, but the value of the set queue number m may be set as a predetermined maximum value. Is possible. In this case, the data retention target number T is a predetermined constant.

  As another method of determining the data retention number target value T, for example, there is a method of using the data reception capability of the terminal or the latest data transmission rate Ro (n). For example, when the data retention number target value T is determined according to the maximum reception rate W that can be received by the terminal, the retention amount management unit 5 prepares the data retention number target value table shown in FIG. The lower the capacity, the smaller the data retention target value). Then, the data retention target value T is obtained using the maximum reception rate W as an index. Similarly, when the latest data transmission rate Ro (n) is used, a data retention number target value table using Ro (n) as an index is prepared (the data retention target value is reduced as the terminal has a lower data transmission rate).

  Next, the first threshold value B1 shown in FIG. 3 will be described. The first threshold value B1 is a threshold value for determining whether the data reception rate is “increase” or “maintain current” in the data reception rate increase control (step S3). The value is smaller by the first control width H1 with respect to T. The first control width H1 may be a predetermined value, or may be a value that changes according to the value of the data retention number target value T. In the data reception rate increase control, the data reception rate is increased when the data retention number in the queue to be controlled falls below the first threshold value B1, and the data retention rate is equal to or greater than the first threshold value B1. In such a case, control is performed so as to maintain the current data reception rate.

  FIG. 5 is a diagram illustrating an example of data reception rate increase control. In the staying amount management unit 5, when L (n) is the number of data staying in the queue at the time when the data reception rate increase control is decided (step S3), L (n) ≦ B0 (step S11, Yes), the data reception rate Ri (n) is increased by the rate increase amount V1 with respect to the previous data reception rate Ri (n-1) (step S12). B0 is a value equal to or less than the first threshold value B1, may be a predetermined value, or may be a value that dynamically changes as a value indicating an instantaneous change amount of L (n). The rate increase amount V1 may be a predetermined value or a value that changes according to the value of the data reception rate Ri. In step S11, the data retention number L (n) in the queue is compared with B0. Instead of the data retention number L (n), the data retention number is averaged with the data reception rate calculation period. A value or a minimum value of the number of data stays within the period of data reception rate calculation may be used.

  On the other hand, if L (n)> B0 (step S11, No), the retention amount management unit 5 compares the data retention amount L (n) with the first threshold value B1 (step S13), and L (n ) ≧ B1 (step S13, Yes), the data reception rate Ri (n) is maintained as it was (step S14). If L (n) <B1 (No in step S13), the data reception rate Ri (n) is increased by the rate increase amount V2 with respect to the data transmission rate Ro (n) (step S15). The rate increase amount V2 may be a predetermined value, or may be a value that changes according to the difference between the data reception rate Ri (n−1) and the data transmission rate Ro (n).

  As described above, in the present embodiment, when the data reception rate increase control is performed (step S3), the data reception rate increase control based on the first threshold value B1 smaller than the data retention number target value is performed. Thereby, the data retention amount in the queue can be brought close to the data retention number target value T efficiently.

  Next, the second threshold value B2 and the third threshold value shown in FIG. 3 will be described. The second threshold value and the third threshold value are thresholds for determining the data reception rate to be “0”, “decrease”, or “maintain” in the data reception rate reduction control (step S4). Value. The second threshold value B2 is a value that is larger by the second control width H2 with the data retention number target value T as a reference. The second control width H2 may be a predetermined value, or may be a value that changes according to the value of the data retention number target value T. The third threshold value B3 is a maximum value of the data retention amount assumed in one queue, and is a value determined based on a predetermined value or the data reception capability of the terminal. However, the maximum value is a value used to stop data transmission from the host device 11, and does not discard data received exceeding the third threshold value B3. That is, as long as the buffer held by the data holding unit 2 is not exhausted, data reception is permitted even if the third threshold value B3 is exceeded.

  In the data reception rate decrease control (step S4), the current data reception rate is maintained when the data retention number of the queue to be controlled falls below the second threshold value B2, and the data retention number is the second threshold value. If it is greater than or equal to B2 and less than the third threshold B3, the data reception rate is decreased. If the data retention amount is greater than or equal to the third threshold B3, the data reception rate is set to “0”. Control. Here, the data reception rate = 0 means that data transmission is stopped in the host device 11.

  FIG. 6 is a diagram illustrating an example of data reception rate reduction control. In the stay amount management unit 5, when the number of data stays in the queue at the time when it is decided to perform the data reception rate reduction control (step S4) is L (n), first, L (n) is set to the third threshold. Comparison with the value B3 is performed (step S21). For example, if L (n) ≧ B3 (step S21, Yes), the staying amount management unit 5 immediately stops data transmission from the higher-level device 11, so that the data reception rate Ri (n) = 0 ( Step S22).

  On the other hand, if L (n) <B3 (No at Step S21), the staying amount management unit 5 next compares L (n) with the second threshold value B2 (Step S23). If L (n) <B2 (step S23, Yes), the data reception rate Ri (n) is maintained as it was last time (step S24). If L (n) ≧ B2 (No in step S23), the data reception rate Ri (n) is decreased by the rate decrease amount V3 with respect to the data transmission rate Ro (n) (step S25). The rate decrease amount V3 may be a predetermined value, or may be a value that changes according to the difference between the data reception rate Ri (n−1) and the data transmission rate Ro (n). Further, the calculation result in step S25 is limited to a predetermined minimum value so as not to become smaller than the minimum value.

  Further, in the data reception rate reduction control described above, when the data reception rate Ri (n) = 0 is determined, the retention amount management unit 5 is periodically operated. Not limited to this, the retention amount management unit 5 may compare the data retention amount in the queue with the third threshold value every time data is received from the host device 11. That is, when the data retention amount reaches the third threshold value, the host device 11 can be immediately notified of the data reception rate Ri (n) = 0. In this case, step S21 and step S22 shown in FIG. 6 are performed every time data is received, and can be omitted in data reduction control that operates periodically.

  As described above, in the present embodiment, when the data reception rate reduction control is performed (step S3), data reception based on the second threshold value B2 and the third threshold value B3 which are larger than the data retention number target value. Implement rate reduction control. Thereby, the data retention amount in the queue can be brought close to the data retention number target value T efficiently.

  Next, the operation of the reception rate notification unit 6 will be described with reference to FIG. First, the data reception rate Ri (n) determined by the staying amount management unit 5 is converted into a parameter that can be interpreted by the host device 11 by the reception rate notification unit 6 (step S31). This parameter conversion differs depending on the system to which the present invention is applied, but when applied to HSDPA, it is converted into two flow control parameters, Interval and Credits. These parameters mean that the upper apparatus 11 is allowed to transmit data equal to or less than the number of Credits during the interval. For this parameter conversion, a method of conversion using a table may be applied, or a method of obtaining by calculation may be applied.

  Further, the reception rate notifying unit 6 determines whether or not it is necessary to notify the upper apparatus 11 of the data reception rate Ri (n), and performs suppression control of the data reception rate notification (step S32). That is, since the value already notified to the host device 11 does not need to be notified again, when the determined data reception rate Ri (n) is equal to the previously determined data reception rate Ri (n−1), Do not send notifications. However, when Ri (n−1) is “0”, it is allowed to autonomously notify the higher-level device 11 of the same data reception rate Ri (n) = 0 again.

  In the determination in the suppression control of the data reception rate notification, it has been described that the determination is made using the data reception rate. However, if an error occurs due to the parameter conversion of the data reception rate as described above, the parameter conversion is performed. The determination may be made using a later value.

  As described above, in this embodiment, by performing data reception rate suppression control, it is not necessary to perform useless data reception rate notification, and the bandwidth of the communication line that performs flow control processing load reduction and data reception rate notification Effective use can be realized. Furthermore, even when the data reception rate notification for the data reception rate Ri (n−1) = 0 disappears, the data transmission from the higher-level device can be reliably stopped.

  Next, an operation when the terminal performs a handover will be described. The call control unit 8 shown in FIG. 1 manages states such as call setup, call release, and handover of a terminal by transmitting and receiving call control information to and from the host device 11. When the call control unit 8 receives information about the start and completion of the handover of the terminal from the higher-level device 11, the call control unit 8 notifies the stay amount management unit 5 of the status. When notified that the handover has started, the staying amount management unit 5 changes the value of the data staying number target value T shown in FIG. 3 to a predetermined small value, and accordingly, the first threshold value, After resetting the second threshold value, the data reception rate Ri is recalculated according to the operation of FIG. The recalculated data reception rate is notified to the higher-level device 11 by the reception rate notification unit 6. As a result, the data reception rate can be reduced during the handover, and the amount of data transmitted by the host device 11 can be reduced.

  Further, when the call control unit 8 notifies completion of the handover, the staying amount management unit 5 resets the data staying number target value T shown in FIG. After resetting the first threshold value and the second threshold value, the data reception rate Ri is recalculated according to the operation of FIG. The recalculated data reception rate is notified to the higher-level device 11 by the reception rate notification unit 6. Thereby, after the handover is completed, the data reception rate can be returned to the normal state, and the amount of data transmitted by the host apparatus 11 can be returned to the normal state.

  Alternatively, when the call control unit 8 notifies the staying amount management unit 5 that the handover has been started, the value of the third threshold value B3 shown in FIG. 3 is set to “0”, and FIG. The data reception rate Ri is set to “0” by immediately executing the indicated data reception rate reduction control. The reception rate notification unit 6 notifies the higher-level device 11 of the data reception rate, and stops data transmission from the higher-level device 11 during handover. When notified from the call control unit 8 that the handover has been completed, the value of the third threshold value B3 shown in FIG. 3 is reset by a normal method, and the operation shown in FIG. Recalculate the data reception rate Ri. The data reception rate is notified by the reception rate notification unit 6 to the higher-level device 11, and data transmission from the higher-level device 11 is resumed after the handover is completed.

  As described above, during the handover of the terminal, it is possible to minimize the data loss in the radio base station 1 during the handover by reducing or stopping the data transmission amount from the higher-level device 11. As a result, data retransmission in the upper layer is reduced, and throughput during handover can be improved.

  Thus, in this embodiment, the maximum throughput can be realized by effectively performing the flow control.

  In this embodiment, an embodiment has been described in which effective flow control is performed in a radio base station having a scheduling function, but the data reception rate is determined for the characteristic operation of this embodiment. Thus, the present invention can be applied to all communication devices that perform flow control. For example, when a data flow is performed from a radio base station to a host device, flow control is executed on the host device side that receives data. Therefore, the flow control of the present invention is performed on the host device. Apply.

  As described above, the radio base station according to the present invention is useful as a radio base station constituting a mobile communication system, and is particularly suitable for a radio base station that performs flow control on data received from a host device.

Claims (11)

In a radio base station having a scheduling function for controlling the data transmission rate to the radio line according to the radio line status of the terminal,
Data holding means for holding received data from the host device in a buffer;
Output amount monitoring means for monitoring the amount of data transmitted from the buffer;
A retention amount managing means for performing processing (flow control) for determining a reception rate (data reception rate) of data sent from the host device so that the data retention amount in the buffer is maintained within a certain range;
A reception rate notification means for notifying the host device of the data reception rate;
A radio base station comprising: The retention amount management means includes:
Compare the data transmission rate obtained by monitoring the output amount monitoring means and the data reception rate notified to the host device,
The data reception rate increase control is performed when the data transmission rate is larger than the data reception rate, and the data reception rate decrease control is performed when the data transmission rate is smaller than the data reception rate. Radio base station. The retention amount management means includes:
Set a fixed target value for the number of data stays in the buffer,
The radio base station according to claim 2, wherein the data reception rate is determined so as to approach the target value in the data reception rate increase control and the data reception rate decrease control. The retention amount management means includes:
Providing a first threshold value smaller than the target value;
When performing the data reception rate increase control, the data retention amount in the buffer is compared with the first threshold,
When the data retention amount is less than the first threshold value, control is performed to increase the data reception rate, and when the data retention amount reaches the first threshold value, the data reception rate is maintained. The radio base station according to claim 3, wherein control for controlling the radio base station is performed. The retention amount management means includes:
A second threshold value greater than the target value and a third threshold value greater than the second threshold value, respectively,
When the data reception rate reduction control is performed, the data retention amount in the buffer is compared with the second threshold value and the third threshold value,
When the data retention amount reaches the third threshold value, control is performed to stop data transmission from the host device, and the data retention amount reaches the second threshold value and reaches the third threshold value. A control for decreasing the data reception rate is performed when the data retention rate is not satisfied, and a control for maintaining the data reception rate is performed when the data retention amount is less than the second threshold value. Item 4. The radio base station according to Item 3. The retention amount management means includes:
The radio base station according to claim 3, wherein the target value is determined based on a total number of queues assigned to communication units, and the target value is decreased as the number of calls increases. The retention amount management means includes:
The radio base station according to claim 3, wherein the target value is determined according to a data reception capability of a terminal, and the target value is decreased as the terminal has a lower reception capability. The retention amount management means includes:
The radio base station according to claim 3, wherein the target value is determined in accordance with a data transmission rate of a terminal, and the target value is decreased as the terminal has a lower data transmission rate. The retention amount management means includes:
The radio base station according to claim 2, wherein when the data reception rate increase control is performed, a maximum value thereof is set as a reception line band. The reception rate notification means includes
When the new data reception rate determined by the stay amount management unit is equal to the previous data reception rate notified to the host device, the newly determined data reception rate is not communicated to the host device. The radio base station according to claim 1. The retention amount management means includes:
When a specific terminal starts handover, control to reduce the data reception rate from the current level or to stop data transmission by the host device,
The radio base station according to claim 1, wherein when the handover is completed, control is performed to restore the data reception rate.

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