KR20050074222A - Method and system for controling data rate of mobile terminal in a mobile communication system - Google Patents

Abstract

The present invention is an invention of a system and method for controlling and determining a reverse rate of a mobile terminal in a mobile communication system.

The system according to the present invention is a mobile communication system for controlling the reverse rate of the mobile terminal by transmitting a packet data in the reverse direction and a common rate control scheme, the threshold value for the rapid rate reduction of the reverse rate in advance A base station transmitting and transmitting a common rate control message for controlling a reverse rate of the mobile terminal according to the common rate control scheme, and receiving the threshold value from the base station, and receiving a common rate control message. The mobile station includes a mobile station that performs an operation of directly reducing the current data rate when the common data rate control message is indicated to decrease when the condition for the fast data rate is satisfied every time.

Description

METHOD AND SYSTEM FOR CONTROLING DATA RATE OF MOBILE TERMINAL IN A MOBILE COMMUNICATION SYSTEM}

The present invention relates to a method and system for controlling a rate of a mobile terminal in a mobile communication system, and more particularly, to a method and system for controlling a reverse rate of a mobile terminal in a mobile communication system.

In general, a mobile communication system is a system developed to provide a voice service. Such mobile communication systems have appeared to support various data services due to the radical development of technology and the demand of users. Types of data services can support various types of services, from low speed packet data to high speed packet data.

A representative system of such a system is a code division multiple access (CDMA) mobile communication system. Such a mobile communication system supports a multimedia service using the same frequency band, and allows a plurality of users to simultaneously transmit data. In this case, the user is distinguished by a unique code assigned to each user.

Meanwhile, in the mobile communication system, reverse data transmission is performed in units of physical layer packets (hereinafter referred to as "PLPs") through a packet data channel, where the length of the packet is fixed. In the following description, the forward direction means the direction from the base station to the mobile terminal, and the reverse direction means the direction from the mobile terminal to the base station. As such, when the mobile terminal transmits packet data in the reverse direction, the packet length is fixed, but the data rate of each packet is variable for every packet. In this way, the reverse transmission is generally performed by the base station. That is, the base station controls the reverse rate of the various mobile terminals.

Factors for determining the reverse transmission rate of the mobile terminal include information such as power available to the mobile terminal and the amount of data to be transmitted. This information is reported by the mobile terminal to the base station. The base station performs scheduling of the transmission rate based on the mobile station. Accordingly, the transmission rate is determined.

As described above, a predetermined process of determining a data rate of a mobile terminal that is variable for each packet is called scheduling, and is performed by a scheduler of a base station. The scheduler of the base station is obtained from 'Rise of Thermal (hereinafter referred to as' RoT ')' or 'Receive signal-to-noise ratio' of a mobile station belonging to a base transceiver station (BTS). Scheduling is performed in consideration of load.

The base station controls the reverse data rate of the mobile terminal is largely divided into a fast scheduling method and a rate control (hereinafter referred to as RC). The mobile terminal operating in the fast scheduling scheme transmits a rate request message including information on the available power of the mobile terminal and a current buffer state. The base station receiving the rate request message of the mobile station transmits a rate grant message in consideration of the degree of thermal noise, service quality (QoS), fairness, etc. of the mobile station, and the mobile station receiving the rate request message is received. Data can be transmitted at the maximum data rate. The rate control scheme may be classified into dedicated rate control (hereinafter referred to as DRC) and common rate control (hereinafter referred to as CRC) according to a method of transmitting control information. A base station operating as a DRC transmits different rate control information for each mobile terminal belonging to the base station. On the other hand, a base station operating with a CRC delivers common rate control information for all mobile terminals in the base station. That is, since the base station operating in DRC transmits control information to all mobile terminals in the cell, the base station has a merit in that it is possible to control more detailed transmission rate than the CRC and a disadvantage in that more control information needs to be transmitted.

In the fast scheduling mode, the mobile station may transmit a request message including its buffer status and available power information to the base station, and the base station approves a specific transmission rate in consideration of the request message of the mobile terminal and the load situation in the cell. It can be assigned to the terminal through a message.

Meanwhile, when the RoT value measured by the base station exceeds a predetermined limit value, the base station operating in the CRC mode transmits control information indicating that the uplink transmission state is 'Busy' for all mobile terminals in the cell. If the limit value is not reached, control information indicating that the reverse transmission state is 'Not Busy' is transmitted. The mobile terminal receiving the control information indicating the 'busy' state may lower the RoT level in the cell by lowering its data rate or the TPR described below. On the other hand, the mobile terminal receiving the control information indicating the 'Not Busy' state may increase its data rate or TPR. Such 'Busy' and 'Not Busy' information may be transmitted through a bit rate control bit (hereinafter referred to as "RCB").

On the other hand, the method of controlling the reverse data rate of the mobile station by the base station operating in the DRC mode is again based on the transition rate of the reverse data rate of the mobile terminal (Full Rate Transition) method and the limited transition rate (Limited) Rate Transition). The full rate transition is a method in which the base station does not limit the transition of the data rate in controlling the reverse data rate of the mobile terminal. The limited rate transition method is a method in which the base station limits the transition of the data rate in one step in controlling the reverse data rate of the mobile terminal.

For example, a possible set of data rates include 9.6 kbps, 19.2 kbps, 38.4 kbps, 76.8 kbps, 153.6 kbps, 307.2 kbps, and at a certain point in time, the rate of packet data currently being transmitted in the reverse direction is 38.4 kbps. Suppose It is apparent that the number and specific values of the data rates included in the data rate set may vary from system to system. In the total transition rate method, the base station determines all data rates in determining the data rate of the next packet for the mobile terminal. That is, a system that allows the mobile station to change the transmission rate of the mobile terminal that was transmitting at 9.6 kbps to 307.2 kbps at one time. The reverse rate of the mobile station that the base station can tolerate is not limited by the previous transmission rate of the mobile terminal. will be. On the other hand, in the limited transition rate method, the base station limits the range of one step up or down from the previous packet rate in determining the data rate of the next packet of the mobile terminal. For example, the rate control of the next packet of the base station for the mobile terminal transmitting at 76.8kbps is limited to one of 38.4kpbs, 76.8kbps, 153.6kpbs. In other words, one step up or one step down or the current rate is maintained at the current rate of 76.8kbps. This is to limit the change in the data rate of the mobile terminal. The one step up or one step down or maintenance command may be transmitted in the form of 'UP', 'DOWN', 'HOLD', respectively, and signal mapping to '+1', '-1' and '0', respectively. Mapping can be done.

The full rate transition method and the limit rate transition method have advantages and disadvantages, respectively. While the overall rate scheme has an advantage in that there is no limitation in determining the data rate of the mobile terminal, there is a disadvantage that many bits are required to transmit the scheduling result to the mobile terminal. For example, if six data rates exist as described above, three bits are required to represent all data rates. In general, in order to transmit such transmission rate information to each mobile terminal individually, it should be transmitted together with an identifier of the mobile terminal. Therefore, a large amount of information must be transmitted for the transmission of the information. In addition, a drawback of the full rate transition method is that the change in the amount of interference affecting other cells is severe as the data rate of a specific mobile terminal changes significantly. As a result, the channel change of mobile terminals belonging to different cells is severe, which may adversely affect the system.

On the other hand, the limit rate transition method has a disadvantage in that the base station is limited to one step change in determining the data rate of the mobile terminal. On the other hand, the rate limiting method has an advantage that it is possible to transmit one bit in transmitting the scheduling result. In other words, the overhead is small. In addition, the limit rate transition method has an advantage in that the change in the amount of interference to other cells is relatively small by limiting the change in the data rate of the mobile terminal to one step.

Meanwhile, the base station may set the maximum autonomous rate and whether autonomous transmission is possible for a specific service of the mobile terminal in order to reduce the delay caused by the rate control. When the data of the service capable of autonomous transmission is generated, the mobile station can transmit data by selecting a random transmission rate within the allocated maximum autonomous transmission rate, thereby minimizing possible delay. Since it is difficult to predict when such autonomous transmission occurs, the base station should reserve resources corresponding to the sum of autonomous transmission rates allocated to the mobile stations.

On the other hand, in some systems, as described above, instead of the base station controlling the data rate of the terminal, there is also a system in which the base station controls the traffic to pilot power ratio (hereinafter referred to as "TPR") of the mobile terminal. . In a typical mobile communication system, reverse transmission of a mobile terminal is power controlled by a base station. In the power control process, the mobile terminal receives a power control command from the base station to directly control the power of the pilot channel of the mobile terminal, and controls a channel other than the pilot channel with a fixed value of TPR. For example, assuming that the TPR is 3 dB, this means that the ratio of the power of the traffic channel transmitted by the mobile terminal to the power of the pilot channel is 2: 1. Therefore, when the mobile terminal determines the power gain of the traffic channel, the mobile station adjusts to double the power of the pilot channel. In the same principle as for the other types of channels, the gain of the corresponding channel relative to the gain of the pilot channel is controlled with a fixed value. Instead of controlling the transmission rate of the mobile station, the system for controlling the TPR refers to scheduling each of the mobile stations of the base station in reverse transmission and controlling each of them, instead of directly informing the data rate of the scheduled result. A method of informing a TPR allowed for a mobile terminal. In general, the higher the data rate, the larger the TPR. For example, doubling the data rate means that the power allocated to the traffic channel by the terminal is about twice as large, which means that the TPR is doubled. In a typical mobile communication system, since a relationship between the data rate of the reverse traffic channel and the TPR is known by the terminal and the base station in advance through a table, controlling the data rate of the mobile terminal and controlling the TPR of the mobile terminal are the same. It can be interpreted as meaning. In the following description, for the sake of brevity, only the manner in which the base station controls the TPR of the terminal will be described. However, as described above, even if a specific system takes a method of controlling the transmission rate instead of controlling the TPR of the UE, it is a matter of course that the same method may be used.

As we saw earlier. Mobile terminals operating in the common rate control mode continuously update and manage target power ratio (Target TPR) information, which means load information in the reverse direction, using a common control bit transmitted from a base station. If the difference between the target power ratio and the available power ratio (Authorized TPR, or available resource amount) available for the current transmission is greater than the threshold value (REV_PDCH_QUICK_START_THRESH) specified by the base station at the time of service setting, the mobile station performs a quick ramp up operation. Can be performed.

When the general mobile terminals receive a signal indicating that the common control bit is up from the base station, the available power ratio is increased by the step_up which is a value designated by the base station. On the other hand, if the received common power control bit indicates a down, the mobile station decreases the available power ratio by a step_down, which is a value designated by the base station. On the contrary, even if the mobile station performing the high-speed uplink operation receives the decrease in the CRC mode, the mobile terminal maintains the available power ratio without decreasing its power rate. The power ratio corresponds to a transmission rate that is one greater than the current maximum available transmission rate. This fast rate up process helps to quickly increase the reverse rate when the number of UEs in the cell is low and the amount of uplink resources is sufficient.

As described above, in the common rate control mode, a fast rate up process is defined so that the mobile station can quickly increase the rate. That is, the mobile terminal continuously updates and manages a target power ratio (Target TPR) indicating load information in the reverse direction using a common control bit transmitted from the base station. This is because when the mobile station starts to transmit the actual data and updates the available power ratio, if the difference between the target power ratio and the available power ratio is larger than the boundary value (REV_PDCH_QUICK_START_THRESH), which is capable of increasing the high data rate, the available power ratio decreases in the common rate control mode. Even when receiving, it performs an operation of maintaining without reducing its available power ratio. When the available power ratio increase is received, the available power ratio is set to a power ratio corresponding to a transmission rate one greater than the current maximum available transmission rate.

As described above, in the conventional technology, when a sufficient amount of spare resources is sufficient, a high data rate can be quickly increased by using a high data rate uplink operation. On the contrary, when the reverse load is larger than the maximum possible, the mobile station should quickly reduce the transmission rate to minimize the occurrence of reverse congestion. However, according to the proposal up to now, the available power ratio can be adjusted only by the step_down, which is a reduction of the available power ratio given by the base station in advance, so that the actual transmission power ratio is adjusted only after a few reduction commands are received. That is, even if a situation in which the load in the reverse direction exceeds a predetermined threshold occurs, there is a problem in that there is no way to stabilize the system quickly. If such a case lasts for a long time, there is a problem that communication itself becomes impossible or the system operates abnormally. Therefore, there is a problem that can cause a decrease in the overall quality of service.

Accordingly, an object of the present invention is to provide a stable reverse rate control system and method in a mobile communication system.

Another object of the present invention is to provide a system and method capable of controlling a reverse rate in a fast time in a mobile communication system.

Another object of the present invention is to provide a system and method capable of stably controlling a reverse rate in a common rate control scheme.

A system of the present invention for achieving the above objects is a mobile communication system for controlling the reverse data rate of the mobile terminal in a mobile terminal for transmitting packet data in the reverse direction, and a common data rate control method, a fast data rate reduction of the reverse rate A base station transmitting a common rate control message for controlling a reverse rate of the mobile station according to the common rate control scheme, and then receiving the threshold value from the base station, When a rate control message is received every time a condition for fast rate reduction is received, the mobile station performs an operation of directly reducing the current rate when the decrease rate of the common rate control message is indicated.

The method of the present invention for achieving the above object, the method for determining the reverse rate in the mobile terminal for transmitting the packet data in the reverse direction, and the mobile terminal of the mobile communication system for controlling the reverse rate of the mobile terminal in a common rate control scheme The method may further include receiving a threshold value for fast rate reduction of a reverse rate from the base station in advance, and then checking whether a condition for fast rate reduction is satisfied every time a common dedicated rate control message is received, Reducing the reverse rate when the common rate control message indicates a decrease in rate when the rate decrease condition is satisfied.

In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

The present invention proposes a Quick Ramp Down operation in which a congestion situation can be eliminated by rapidly reducing the transmission rates of mobile terminals when the reverse load in a sector under common rate control is larger than the maximum allowable value. The mobile terminal according to the present invention determines whether to operate in a high data rate down mode in consideration of the available power ratio or available resource amount allocated to the mobile station, the load situation in the sector, the parameters allocated by the base station, and the like. In this case, a target power ratio (Target TPR) continuously updated by a common control bit may be used as a value or a variable indicating a load situation in a sector. Also, the parameters set by the base station may include a minimum value of the target power ratio (REV_PDCH_MIN_TARGET_TPR) or a power ratio boundary value (REV_PDCH_QUICK_DOWN_THRESHOLD) for fast transmission rate down.

The mobile terminal must manage the reverse load situation in order to determine the criterion of the high rate uplink operation. One criterion for determining the reverse load is a method of using a target power ratio. The mobile station sets an initial value of the target power ratio to a value assigned by the base station when configuring the reverse service. Each time the common bit rate control bit is received, the target power ratio is adjusted up by one step if the bit is increased in the common bit rate control mode, and the target is reduced if the bit is received in the common bit rate control mode. A step of adjusting the power ratio by one step is performed.

1 is a control flowchart of a target power ratio adjustment operation in a mobile terminal according to an exemplary embodiment of the present invention. Hereinafter, a control flow when adjusting a target power ratio in a mobile terminal according to an exemplary embodiment of the present invention will be described in detail with reference to FIG. 1.

In step 101, the mobile terminal calculates a maximum encoder packet size corresponding to a target power ratio indicating a current reverse load situation. This EP size can be interpreted as a value indicating the maximum EP size that can be supported at the current target power ratio, that is, the transmission rate. After calculating the maximum EP corresponding to the target power ratio, the process proceeds to step 103 and checks whether the common rate control bit received from the base station indicates an increase (UP). If the check result of step 103 indicates that the common rate control bit indicates an increase, the process proceeds to step 105; otherwise, the process proceeds to step 109. In step 105, the mobile terminal increases the target power ratio by setp_up, which is a target power ratio increase defined for the current maximum EP size. In step 107, the target power ratio is reset so that the increased target power ratio becomes less than or equal to the maximum value REV_PDCH_MAX_TARGET_TPRs of the target power ratio set by the base station.

On the contrary, if the common rate control bit does not indicate an increase as a result of the check in step 103, the process proceeds to step 109 to check whether the common rate control bit received from the base station is decreased (DOWN). When the check result of step 109 indicates that the common rate control bit indicates a decrease, the process proceeds to step 111 and the target power ratio is reduced by setp_down, which is a target power ratio reduction defined for the current maximum EP size. In operation 113, the target power ratio is reset such that the reduced target power ratio is equal to or greater than the minimum value REV_PDCH_MIN_TARGET_TPRs of the target power ratio set by the base station. However, if the check result of step 109 indicates that the common rate control bit does not indicate a decrease, that is, the increase or decrease of the common rate control bit proceeds to step 115, the current target power ratio is maintained.

The above-described method is for the case where the common rate control bit indicates the increase / decrease / maintenance. However, if the common rate control bit indicates only the increase / decrease, steps 109 and 115 are not necessary.

2A and 2B are control flowcharts when updating an available power ratio of a mobile terminal according to a preferred embodiment of the present invention. Hereinafter, a control process in the case of updating the available power ratio in the mobile terminal according to the present invention will be described in detail with reference to FIGS. 2A and 2B.

In step 201, the mobile terminal calculates the maximum EP size (max_indx) that can be supported by the available power ratio available to the mobile terminal. Thereafter, the process proceeds to step 203 to check the conditions of the high rate uplink operation. Examining the conditions of the high rate uplink operation is the operation in the CDMA 2000 mobile communication system described in the prior art. This high-speed transfer rate up operation may be performed by checking whether the value of the available power ratio is smaller than a value obtained by subtracting a predetermined upper boundary value of the high-speed rate from the target power ratio. That is, looking at it simply as an equation, it can be shown as Equation 1 below.

authorized_tpr <target_tpr-REV_PDCH_QUICK_START_THRESHOLD

In Equation 1, authorized_tpr is an available power ratio, target_tpr is a target power ratio, and REV_PDCH_QUICK_START_THRESHOLD is a high data rate upward boundary value.

As a result of checking whether the fast data rate up operation is necessary in the same manner as in <Equation 1>, if it is necessary to increase the fast data rate, the process proceeds to step 205, and otherwise proceeds to step 211.

First, a case of proceeding to step 205, that is, a case in which a high data rate up operation is required will be described. In step 205, the mobile terminal checks whether the common rate control bit received from the base station is increased (UP). If the check result of step 205 indicates that the common rate control bit indicates an increase, the process proceeds to step 207; otherwise, the process proceeds to step 209. When the mobile terminal proceeds to step 207, the new available power ratio is set to a power ratio that satisfies Equation 2 below.

new_authorized_tpr = tpr_normal [min (max_index + 1, 10)]

In Equation 2, new_authorized_tpr is a new available power ratio, and tpr_normal [min (max_index + 1, 10)] is a power ratio selected by one step larger than the current maximum index value or smaller than 10. Therefore, the new available power ratio is corrected as shown in Equation 2 above. Equation (2) means resetting the available power ratio to a resource corresponding to an EP greater than the maximum EP that can be supported in the current available power ratio. On the contrary, if the common rate control bit received from the base station is not increased, the mobile station proceeds to step 209 to reset the new available power ratio to the current available power ratio.

On the other hand, if the check result of step 203 does not satisfy the condition of the high-speed upstream operation, the mobile terminal proceeds to step 211. When the mobile terminal proceeds to step 211, it checks the high-speed downlink operation condition. Conditions for the downward operation according to the present invention can be determined as shown in Equation 3 below.

authorized_tpr> target_tpr + REV_PDCH_QUICK_DOWN_THRESHOLD

In Equation 3, authorized_tpr is an available power ratio, target_tpr is a target power ratio, and REV_PDCH_QUICK_DOWN_THRESHOLD is a high data rate down threshold. The conditions used in Equation 3 may be various depending on the implementation. In the embodiment of the present invention, as described above, when the available power ratio is larger than the sum of the target power ratio and the fast downlink boundary value, the fast data rate down condition Judged to satisfy.

If the mobile station satisfies the condition as a result of step 211, the mobile terminal proceeds to step 213; otherwise, the mobile terminal proceeds to step 227. First, a case of satisfying the fast downlink condition according to the present invention will be described. In step 213, the mobile station satisfying the fast rate down condition checks whether the common rate control bit received from the base station indicates an increase. If the common rate control bit indicates an increase as a result of the check in step 213, the mobile terminal proceeds to step 219; otherwise, the mobile terminal proceeds to step 215. In step 219, the mobile terminal sets the new available power ratio of the mobile terminal as the sum of the current power ratio and the power ratio increment step_up defined by the current available power ratio. In contrast, if the common rate control bit is not increased, the process proceeds to step 215 and it is checked whether the common rate control bit is decreased. If the result of the check of step 215 is that the common data rate control bit is decreased, the process proceeds to step 221;

On the other hand, if the process proceeds from step 215 to step 221, the mobile station checks whether the additional high data rate can be further reduced because the current maximum EP size is greater than one. If it is possible to further reduce the high data rate in step 221, the process proceeds to step 223 and sets the new available power ratio to a larger value between the maximum autonomous transmission power ratio and the power ratio required to transmit the EP corresponding to max_index 1. That is, the power ratio is calculated in the same manner as in <Equation 4>.

new_authorized_tpr =

max (REV_PDCH_MAX_AUTO_TPRs, tpr_normal [min (max_index + 1)

In Equation 4, new_authorized_tpr is a new available power ratio, and max (REV_PDCH_MAX_AUTO_TPRs, tpr_normal [min (max_index + 1) means a value which is one step larger than the current maximum index value and a reverse maximum automatic transmission rate value. .

On the contrary, if it is impossible to further reduce the high data rate as a result of the test of step 221, the process proceeds to step 225 to set the new available power ratio as the maximum autonomous transmission power ratio.

On the other hand, if the check result of step 211 does not satisfy the fast data rate down condition, the mobile terminal proceeds to step 227. Operation below step 227 becomes a normal operation. Now, the normal operation will be described.

First, when the mobile terminal proceeds to step 227, it checks whether the common power control bit received from the base station is increased. If the common power control bit is increased as a result of the checking in step 227, the mobile terminal proceeds to step 231 to increase the transmission rate by one step. However, if the common power control bit is not increased in step 227, the process proceeds to step 229 to determine whether the common power control bit is decreased. If the common power control bit is reduced, the mobile terminal proceeds to step 233 and sets the new available power ratio to the sum of the available power ratio minus the power ratio reduction step_down defined by the current available power ratio. That is, an operation of lowering the available power ratio by one step is performed. However, if no increase or decrease is indicated, that is, if the maintenance is indicated, the mobile terminal proceeds from step 229 to step 235 to maintain the current available power ratio.

As described above, the present invention can not only rapidly increase low-speed data in the system, but also have an advantage of achieving stabilization in a saturation state of a threshold that can be tolerated by the system. In addition, since the system is stabilized faster, data is transmitted more stably and there is an advantage of improving service quality.

1 is a control flowchart of a target power ratio adjustment operation in a mobile terminal according to an embodiment of the present invention;

2A and 2B are control flowcharts when updating an available power ratio of a mobile terminal according to a preferred embodiment of the present invention.

Claims (2)

A mobile terminal for transmitting packet data in a reverse direction, and a mobile communication system for controlling the reverse rate of the mobile terminal in a common rate control scheme, A base station transmitting a common rate control message for controlling a reverse rate of the mobile station according to the common rate control scheme and then transmitting a preset threshold for fast rate reduction of a reverse rate; Receiving the threshold value from the base station, and whenever a common rate control message is received, if the condition for fast rate reduction is satisfied, when the common rate control message is indicated to decrease, performing the operation of immediately reducing the current rate Said system comprising a mobile terminal. A method of determining a reverse rate in a mobile terminal transmitting packet data in a reverse direction and a mobile terminal of a mobile communication system for controlling the reverse rate of the mobile terminal in a common rate control scheme, Receiving a threshold for fast rate reduction of a reverse rate from the base station in advance, and then checking whether a condition for fast rate reduction is satisfied whenever a common dedicated rate control message is received; And reducing the reverse rate when the common rate control message indicates a rate decrease when the fast rate decrease condition is satisfied.