KR20040064834A - Method and apparatus for controlling reverse data rate in mobile communication system for packet data service - Google Patents

Abstract

PURPOSE: A method for controlling a reverse rate in a mobile communication system supporting a packet data service and a device therefor are provided to use a higher rate for a terminal having a good channel state, and to use a lower rate for a terminal having a bad channel state, thereby reducing output consumption and improving a throughput of a reverse link. CONSTITUTION: A terminal receives a signal of a forward pilot channel(200), and calculates an SNR(Signal to Noise Ratio) of the received forward pilot channel signal(210). The SNR is calculated by including noise and interference of a forward link. If an average SNR is obtained by performing a low pass filtering process for the calculated SNR during a predetermined time, the terminal selects one transition probability set relative to the obtained average SNR among prestored plural transition probability sets(230). The terminal controls a reverse rate by using the selected transition probability set(240).

Description

METHOD AND APPARATUS FOR CONTROLLING REVERSE DATA RATE IN MOBILE COMMUNICATION SYSTEM FOR PACKET DATA SERVICE}

The present invention relates to a mobile communication system, and more particularly, to a method and an apparatus for controlling a reverse rate in order to efficiently use a reverse link load in a packet data service.

As communication technologies have developed, more and more users want to use packet data services such as web, file transfer protocol (FTP), and video in a wireless environment. The traffic of such a packet data service is very asymmetrical. That is, the amount of traffic moving from the server providing the service to the user is very large compared to the amount of traffic moving from the user to the server. Considering the data service using mobile communication, since the server is connected to the user terminal through the base station, the amount of traffic on the forward link transmitted from the base station to the terminal is much larger than the amount of traffic on the reverse link transmitted from the terminal to the base station.

CDMA2000 1x Evolution-Data Only (EV-DO) or High Rate Packet Data Air interface (HRPDA), 1x Evolution-Data and Voice (EV-DV), 3GPP (3GPP2) of 3rd Generation Partnership Project 2 (3GPP2) Mobile communication standards such as HSDPA (High Speed Downlink Packet Access) of the 3rd Generation Partnership Project are designed in consideration of this asymmetric characteristic.

In particular, EV-DO uses high-order modulation schemes and coding rates such as 16-ary quadrature amplitude modulation (16-QAM) and 8-ary phase shift keying (8PSK) on the forward link. Adaptive Modulation and Coding Scheme (AMCS), Hybrid Automatic Repeat reQuest (H-ARQ), Multi-User Diversity Using Fat-Pipe Scheduling It is designed to get high throughput by using techniques such as etc. In the reverse link, scheduling and load control schemes considering burst characteristics of packet data are applied.

1 shows a structure of a reverse traffic channel used in a typical EV-DO system.

Referring to FIG. 1, the reverse traffic channel 100 includes a pilot channel 110, a medium access control (MAC) channel 120, an acknowledgment (ACK) channel 130, and a data channel 140. 120 is further divided into a reverse rate indicator (RRI) channel 122 and a data rate control (DRC) channel 124.

The pilot channel 110 is continuously transmitted for synchronization and channel estimation for the traffic channel. The RRI channel 122 sends an indicator indicating the rate of the traffic channel and the DRC channel 124 feeds back channel state information of the forward link for adaptive modulation and coding (AMSC) on the forward link. The ACK channel 130 transmits an ACK / NACK indicating whether the data packet received on the forward link is in error in order to support the complex-ARQ. Data channel 140 transmits a user's data packet.

The reverse traffic channel 100 is designed to support six transmission rates such as 9.6 kbps, 19.2 kbps, 38.4 kbps, 76.8 kbps, and 153.6 kbps. Scheduling is necessary to determine the reverse traffic channel rates of the terminals and control the load of the reverse link accordingly. In the mobile communication system before EV-DO, a base station performs scheduling with feedback information received from a terminal to determine transmission rates of the terminals and informs the terminals of the determined transmission rates.

Due to the large time delay, it is difficult to timely use traffic and channel information in consideration of the unexpected nature of packet data, and the load on the forward link is increased because information for reverse scheduling (ie, transmission rate) is transmitted through the forward link. There is a problem. Therefore, the EV-DO uses a method of increasing or decreasing the transmission rate in a probabilistic manner when the base station measures the reverse load on a frame basis and indicates whether to increase or decrease the transmission rate. To this end, the Reverse Activity Bit (RAB), Transition Probability, and Rate Limit parameters are used.

The RAB is 1 bit of information included in every forward frame and indicates to increase or decrease the reverse rate. The base station controls the reverse load by observing the reverse link load and setting the RAB appropriately. That is, when the load of the reverse link is lower than the preset reference value, the RAB is set to '0' to increase the transmission rate, and when the reverse link is higher than the reference value, the RAB is set to '1' to lower the transmission rate.

There are two transition rates, one for each transmission rate, and one for the lower transmission rate. The terminal generates a random number between 0 and 1 when determining the rate of the reverse traffic channel and converts the random number to a higher transmission rate according to RAB (hereinafter referred to as a higher transition probability) or to a lower transmission rate. Change or maintain the current rate in comparison with (hereinafter referred to as lower transition probability).

The upper transition probability is expressed as Transition009k6_019k2, Transition019k2_038k4, Transition038k4_076k8, and Transition076k8_153k6 depending on the current transmission rate. Typically, Transition019k2_038k4 is a transition probability that can be increased to 38.4kbps when the current transmission rate is 19.2kbps. If the RAB received from the base station is '0', the generated random number is compared with the upper transition probability corresponding to the current transmission rate, and if it is smaller than this, the terminal transitions to the next higher transmission rate and otherwise maintains the current transmission rate.

The lower transition probability is expressed as Transition019k2_009k6, Transition038k4_019k2, Transition076k8_038k4 and Transition153k6_076k8 according to the current transmission rate. When the RAB received from the base station is '1', the generated random number is compared with the lower transition probability corresponding to the current transmission rate, and if it is smaller than this, the terminal transitions to the next lower transmission rate and otherwise maintains the current transmission rate.

The RateLimit parameter is the maximum rate that a terminal can transmit on the reverse link, determined by the base station and periodically (for example every 768 slots) to all terminals in data service over a synchronous control channel. Per broadcast) or transmitted per terminal using a separate designated signal.

Referring to the scheduling procedure by the terminal for controlling the reverse rate using the above parameters as follows. Hereinafter, the current rate indicates the transmission rate of the frame before scheduling (zero at the first transmission), the maximum rate indicates the maximum rate that can be allocated after the scheduling, and the new rate is determined by the scheduling. Indicates the assigned rate.

1. The terminal ORs the RABs received from all base stations in communication by soft handoff to generate a combined busy bit (CBB).

2. The terminal generates a random number X having a uniform distribution between 0 and 1, and the condition given by the current transmission rate and the combined congestion bit is true for the generated random number with reference to the condition table shown in FIG. ), If true, the maximum rate is determined as the maximum rate, and if false, the maximum rate is determined as the maximum rate.

3. The new rate is set to the lesser of the determined maximum rate and the predetermined limit rate.

4. The terminal determines whether data transmission at the predetermined new transmission rate is possible according to the available transmission power, and if not, lowers the new transmission rate to the maximum transmission rate.

5. The terminal also determines whether the amount of user data to be transmitted is smaller than the amount that can be transmitted according to the predetermined new rate, and if it is small, lowers the new rate to the minimum rate that can transmit all of the amount of data that can be transmitted.

6. Transfer data at the new optimized data rate through 4.5 procedures.

For example, if the current rate is 19.2 kbps, the RABs received from all base stations in soft handoff are '0', the Transition019k2_038k4 value is 0.3, and the limited rate is 153.6 kbps, then the combined congestion bit (CBB) is' 0 ', so it corresponds to the fourth line of FIG. If the generated random number X is 0.2, the condition is true, so the maximum data rate is 38.4 kbps. If both of the above-mentioned transmission power and packet data amount conditions are satisfied, the new frame rate of the next frame is determined to be 38.4 kbps.

Meanwhile, the base station determines the RAB by measuring reverse load or rise over thermal (ROT). Here, a description of the method using ROT, ROT represents the ratio of the total received power to the thermal noise power, the ROT Z _j for the j th antenna when the base station uses a plurality of receiving antennas It is calculated as in <Equation 1>.

Where I _O is the sum of the received power I _OC and the thermal noise power N _O from the terminals belonging to the received power other cells adjacent to the I _SC from the terminal belonging to the cell corresponding to a total received power spectral density (Power spectral density) . The base station calculates the ROT Z _j for the j th antenna according to Equation 1 above, and sets RAB to '1' if the maximum value of the ROTs calculated for each antenna is greater than a predetermined reference value Z _T. Otherwise, set RAB to '0'.

Unlike the forward link, the rate control method of the reverse link does not utilize channel information between the terminal and the base station. In the forward link, a base station determines a channel state with a state of a forward channel fed back by a terminal, that is, a signal to noise ratio (SNR), and allocates a higher transmission rate to a terminal having a good channel state. On the contrary, as described above, in the reverse link having a controlled rate, the same transition probability, the RAB, and the limited rate are applied to all terminals regardless of the channel state, and the transmission rate is determined with the same probability in all terminals.

Terminals with good channel conditions on the reverse link use less transmit power for the same bit rate than terminals that do not. In addition, a terminal having a good channel state with respect to a specific base station generates relatively little interference with other base stations because it has a relatively far and poor channel state from other base stations. If a high data rate is assigned to a terminal near a base station (good channel condition), inter-cell interference can be greatly reduced than a high data rate is assigned to a terminal near a cell boundary. Nevertheless, the conventional method has a problem in that the inter-cell interference is large and the throughput is reduced because the channel information of the reverse link is not utilized.

In addition, since the conventional reverse rate control method is not associated with the forward rate, the reverse rate may be reduced, and thus the forward rate may be limited if protocol communication between upper application layers is not smooth. In other words, if the upper application layer requires fast acknowledgment through the reverse link, but the backward throughput is small, the forward throughput is also limited. As such, the reverse link throughput needs to be associated with the forward link throughput according to a service provided and a protocol of a higher application layer. However, since the conventional scheme does not consider the forward throughput, there is another problem of limiting the forward throughput.

Therefore, the present invention devised to solve the problems of the prior art operating as described above provides a method and apparatus for controlling the reverse rate in a mobile communication system.

The present invention provides a method and apparatus for controlling a reverse rate using a transition probability in a mobile communication system.

The present invention provides a method and apparatus for controlling the reverse rate by changing the transition probability according to the channel state in order to increase the reverse rate in the mobile communication system.

A first embodiment of the present invention for achieving the above object is a method for controlling the reverse data rate of the terminal in a mobile communication system that provides a packet data service to the terminal through a base station,

Obtaining a received signal-to-noise ratio for a predetermined time period for the forward channel from the base station;

Selecting one transition probability set corresponding to the received signal-to-noise ratio among a plurality of preset transition probability sets, wherein each of the transition probability sets indicates a transition probability to a higher transmission rate among a plurality of predetermined transmission rates; It consists of lower transition probabilities representing the upper and lower transition rates,

Selecting one transition probability corresponding to a current transmission rate among the selected set of transition probabilities according to the reverse rate control information received from the base station, and among the plurality of transmission rates in which the current transmission rate is predetermined according to the selected transition probability It characterized in that it comprises the step of changing to one transmission rate.

A second embodiment of the present invention for achieving the above object is a method for controlling the reverse rate by the terminal in a mobile communication system that provides a packet data service to the terminal through a base station,

Obtaining a forward data throughput rate for a predetermined time period for the forward channel from the base station;

Selecting one transition probability set corresponding to the data throughput from among a plurality of previously stored transition probability sets, wherein each of the plurality of transition probability sets indicates a higher probability indicating a transition rate to a higher transmission rate among a plurality of predetermined transmission rates; It consists of the transition probabilities and the lower transition probabilities representing the transition probability to the lower transmission rate,

Selecting one transition probability corresponding to a current transmission rate among the selected set of transition probabilities according to the reverse rate control information received from the base station, and among the plurality of transmission rates in which the current transmission rate is predetermined according to the selected transition probability It characterized in that it comprises the step of changing to one transmission rate.

1 is a diagram illustrating a reverse traffic channel structure of an EV-DO system according to the prior art.

2 is a condition table showing determination of reverse rate.

3 is a flowchart illustrating a reverse rate control operation using the received signal-to-noise ratio of the forward pilot channel according to the first embodiment of the present invention.

4 illustrates an example of transition probability sets.

5 is a diagram illustrating an apparatus for controlling a reverse rate of a terminal using a received signal-to-noise ratio of a forward pilot channel according to the first embodiment of the present invention.

6 is a flowchart illustrating a reverse rate control procedure using a throughput of a forward data channel according to a second embodiment of the present invention.

7 is a diagram illustrating an apparatus for controlling a reverse rate of a terminal using a throughput of a forward data channel according to a second embodiment of the present invention.

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 described below is to control the transition rates to the upper and lower transmission rate in controlling the transmission rate of the reverse traffic channel in the mobile communication system supporting the packet data service.

The first embodiment of the present invention described below uses the received signal-to-noise ratio measured in the forward pilot channel to estimate the channel state of the reverse link and thus uses different sets of transition probabilities. Here, the terminal has a plurality of sets of transition probabilities and controls the reverse rate using a set of transition probabilities according to the forward received signal-to-noise ratio.

In addition, the second embodiment of the present invention estimates the channel state of the reverse link using the throughput of the forward data channel and accordingly uses a different set of transition probabilities. Here, the terminal has a plurality of transition probability sets and controls the reverse rate by using a transition probability set designated according to the throughput of the forward data channel.

Hereinafter, the first embodiment and the second embodiment of the present invention will be described in detail.

<< first embodiment >>

3 is a flowchart illustrating a reverse rate control operation using a received signal to noise ratio (SNR) of a forward pilot channel according to the first embodiment of the present invention. The operation shown here is performed by a terminal performing packet data service with one or more base stations, and the terminal has a plurality of sets of transition probabilities having upper and lower transition probabilities, respectively. The upper transition probability indicates a transition probability to an upper transmission rate among a plurality of predetermined transmission rates, and the lower transition probability indicates a transition probability to a lower transmission rate.

Referring to FIG. 3, the terminal receives a signal of a forward pilot channel in step 200 and calculates a signal-to-noise ratio of the received forward pilot channel signal in step 210. The signal to noise ratio is calculated to include both noise and interference of the forward link. If the average signal-to-noise ratio is obtained by the low pass filtering for a predetermined time with respect to the calculated received signal-to-noise ratio in step 220, the terminal determines the average signal band of the plurality of transition probability sets previously stored in step 230. One transition probability set corresponding to the noise ratio is selected and a reverse rate is controlled in step 240 using the selected transition probability set.

As described above, the present embodiment estimates the channel state of the reverse link by using the received signal-to-noise ratio measured for the forward pilot channel, and controls the reverse link rate by selecting a corresponding set of transition probabilities. The received signal-to-noise ratio measured for the forward pilot channel is used to estimate the channel state of the reverse link. To this end, the terminal utilizes a forward signal-to-noise ratio that is periodically reported for adaptive modulation and coding (AMCS) and scheduling on the forward link.

The received signal-to-noise ratio corresponds to DRC (Data Rate Control) according to 1x EV-DO or CQI (Channel Quality Indicator) according to 1x EV-DV and HSDPA. Since both DRC and CQI are used to report the state of the forward pilot channel, that is, the received signal-to-noise ratio, to the base station, the average can be calculated by obtaining the corresponding received signal-to-noise ratio using the transitions.

The received signal-to-noise ratio of the forward pilot channel is determined by the channel loss and the amount of interference. The channel loss is represented by the product of long-term loss and short-term loss as shown in Equation 2 below.

(Channel loss) = (long term loss) * (short term loss)

The long-term loss is a loss due to propagation loss and shadowing, which is caused by the distance between the base station and the terminal and the surrounding environment, and is the same on the forward link and the reverse link. Short-term loss is caused by multipath fading and varies depending on the moving speed and the frequency used, so they appear differently in the forward and reverse links using different bands. Because of this short-term loss, the reverse channel loss cannot be accurately estimated from the channel loss of the forward link. However, if a long-term average is taken for the channel loss of the forward link, the short-term loss is averaged to estimate the long-term loss, which approximates the long-term loss of the reverse link.

Therefore, the terminal obtains a long-term average of the received signal-to-noise ratios measured for the forward pilot channel, estimates the channel state information of the reverse link considering the long-term loss, and uses it for the reverse rate control. The time interval for calculating the average of the received signal-to-noise ratio is set to a period in which the short-term loss is negligible and is experimentally obtained according to system characteristics. As an example, the time period may be about 10 times the coherence time used to obtain the received signal-to-noise ratio.

Then, the long-term average signal-to-noise ratio SNR _k for the k-th base station among the plurality of base stations with which the terminal communicates is expressed by Equation 3 below.

Where _i is the long term loss (or gain) for the i th base station and I _or is the transmit power of the base station, where it is assumed to be the same for all base stations with which the terminal is communicating. N _O is the thermal noise power of the k-th base station. When ignoring thermal noise, the numerator of Equation 3 is the channel loss (or gain) for the k-th base station and the denominator is the sum of the channel loss (or gain) for other base stations.

The larger the numerator, the smaller the channel loss for the k-th base station, so the transmission power required when the terminal uses a higher reverse rate is smaller. The smaller the denominator, the greater the channel loss for other base stations. Less interference with In other words, by allocating a high data rate to a terminal with a high signal-to-noise ratio, it is possible to reduce interference with other base stations while saving the output of the terminal for the same data rate.

4 shows an example of sets of transition probabilities that the terminal can select based on the signal-to-noise ratio calculated as described above. Referring to FIG. 4, there are six possible transmission rates of the reverse traffic channel: 9.6 kbps, 19.2 kbps, 38.4 kbps, 76.8 kbps, 153.6 kbps, and a reverse activity bit (RAB), a transition probability, and a transition probability received from the base station. One of the six transmission rates is determined according to the Rate Limit parameter. For example, for set 1, the upper transition probabilities are Transition009k6_019k2 = 3/4, Transition019k2_038k4 = 1/4, Transition038k4_076k8 = 1/8, and Transition076k8_153k6 = 1/8, and the lower transition probabilities are Transition019k2_009k6 = 1/64, Transition02k / 3819 64, Transition076k8_038k4 = 1/32 and Transition153k6_076k8 = 1/32.

Table 1 below shows an example of the correspondence between the signal-to-noise ratio and the transition probability sets with reference to FIG. 4.

Forward Signal to Noise Ratio Transition probability set -5 dB or less Set 4 -5 to 0 dB Set 3 0 to 5 dB Set 2 5 dB or more Set 1

The larger the forward signal-to-noise ratio, the larger the probability of transition to the higher rate and the smaller the probability of transition to the lower rate is assigned. Then, a terminal with a large forward signal-to-noise ratio uses a relatively high data rate, and a small terminal uses a relatively low data rate, which can greatly reduce the sum of the overall output of the terminal and reduce interference to other base stations. You can increase throughput and make better use of reverse limit loads.

If the set of transition probabilities is selected, the terminal checks the value of the RAB included in every frame received from the base station, and if it is '0', selects an upper transition probability corresponding to the current transmission rate from the selected set of transition probabilities, 0 and 1 If the random number generated by the uniform distribution is smaller than the upper transition probability, the transition is made to the next higher transmission rate. On the other hand, if the RAB value is '1', the lower transition probability corresponding to the current transmission rate is selected. If the random number randomly generated between 0 and 1 is smaller than the lower transition probability, the transition is made to the next lower transmission rate.

The terminal then determines the reverse rate according to the transition rate, the predetermined limit rate, the available transmission power, and the amount of packet data to transmit, and transmits the reverse rate according to the determined reverse rate.

5 illustrates an apparatus for controlling a reverse rate of a terminal using a received signal-to-noise ratio of a forward pilot channel according to the first embodiment of the present invention.

Referring to FIG. 5, the pilot channel receiver 300 receives and demodulates a signal of a pilot channel in a forward link, and the signal-to-noise ratio measurer 310 calculates a signal-to-noise ratio for the demodulated pilot channel signal. The average calculator 320 calculates a long-term average of the calculated signal-to-noise ratio. The transition probability set selector 330 selects a transition probability set corresponding to the average signal-to-noise ratio obtained by the average calculator 320 among a plurality of preset transition probability sets, and the reverse rate controller 340 selects the selected transition probability. The set is used to determine the rate of the reverse data channel.

<< 2nd Example >>

6 is a flowchart illustrating a reverse rate control operation using throughput of a forward data channel according to a second embodiment of the present invention. The operation shown here is performed by a terminal performing packet data service with one or more base stations, and the terminal has a plurality of sets of transition probabilities having upper and lower transition probabilities, respectively. The upper transition probability indicates a transition probability to an upper transmission rate among a plurality of predetermined transmission rates, and the lower transition probability indicates a transition probability to a lower transmission rate.

Referring to FIG. 6, the terminal receives a signal of a forward data channel for a predetermined time period in step 400 and calculates a throughput of the received forward data channel signal in step 410. Then, the terminal selects one transition probability set corresponding to the obtained signal-to-noise ratio among the plurality of transition probability sets previously stored in step 420, and controls a reverse rate using the selected transition probability set in step 430. do.

In this embodiment, the throughput of the forward data channel for each terminal is used to estimate the channel state of the reverse link. The forward data throughput of each terminal depends on the scheduling method of the forward link, but is determined by the number of terminals in the cell and the state of the forward link channel of the terminal.

When determining the reverse rate, the number of terminals in the cell can increase the reverse rate per terminal, and if the number of terminals in the cell, the reverse rate per terminal should be decreased. In addition, if a terminal having a high average signal-to-noise ratio uses a relatively high data rate and a terminal having a low signal-to-noise ratio uses a low data rate, the output of the terminal may be lowered for the same data rate and interference to other base stations may be reduced. The throughput per terminal of the forward link is generally related to the number of terminals and the average received signal-to-noise ratio of the forward link of the terminal. The smaller the number of terminals in a cell, the larger the average received signal-to-noise ratio of the forward link of the terminal. Therefore, in consideration of this point, the forward throughput can be utilized as an index for determining the reverse transmission rate. In other words, if the terminal has a high forward throughput, a high transmission rate is assigned, and a low transmission rate is assigned to lower the output of the terminal, reduce interference with other base stations, and transmit more efficiently.

Table 2 below shows an example of the correspondence between the forward link throughput and the transition probability set. Here, the transition probability sets shown in FIG. 4 are considered.

Forward throughput Transition probability set 30 kbps or less Set 4 30 to 100 kbps Set 3 100 to 300 kbps Set 2 300 kbps or more Set 1

Here, the forward throughput is obtained by dividing the amount of data received for each terminal by time.

As shown in Table 2, the higher the forward throughput, the higher the probability of transition to the higher rate and the smaller the probability of transition to the lower rate is selected. Then, a terminal with a high forward throughput uses a relatively high data rate, and a small terminal uses a relatively low data rate.

7 illustrates an apparatus for controlling reverse rate of a terminal using throughput of a forward data channel according to a second embodiment of the present invention.

Referring to FIG. 7, the data channel receiver 500 receives and demodulates a data channel signal of a forward link for a predetermined time period, and the throughput calculator 510 processes the predetermined time period with respect to the demodulated data channel signal. Calculate Then, the transition probability set selector 520 selects a transition probability set corresponding to the calculated throughput from among a plurality of previously stored transition probability sets, and the reverse rate controller 530 uses the selected transition probability set to perform a reverse data channel. Determine the transmission rate of.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The present invention estimates the reverse channel state according to the forward received signal-to-noise ratio or the forward throughput rate for each terminal for the probability of transition used in determining the data rate of the reverse data channel of the mobile communication system for packet data, and applies the transition probability differently accordingly. . The present invention reduces the sum of the outputs of the entire terminals for the same reverse load and interferes with other base stations by allowing a terminal having a good channel state to be assigned a high transmission rate and a low rate being allocated to a terminal having a poor channel state. Lowering improves throughput of reverse link and makes efficient use of reverse load.

Claims (14)

A method of controlling a reverse data rate of a terminal in a mobile communication system providing a packet data service to a terminal through a base station, Obtaining an average received signal-to-noise ratio for a predetermined time period for the forward channel from the base station; Selecting one transition probability set corresponding to the received signal-to-noise ratio among a plurality of predetermined transition probability sets, wherein each of the transition probability sets indicates a transition probability to a higher transmission rate among a plurality of predetermined transmission rates; Consisting of the upper and lower transition probabilities indicating and the lower transition probabilities indicating the transition probability to the lower transmission rate, Selecting one transition probability corresponding to a current transmission rate among the selected set of transition probabilities according to the reverse rate control information received from the base station, and among the plurality of transmission rates in which the current transmission rate is predetermined according to the selected transition probability Changing to one transmission rate. The method of claim 1, wherein the calculating of the received signal to noise ratio comprises: And estimating the received signal-to-noise ratio measured for the forward pilot channel received from the base station for estimating the long term loss of the reverse link. The method of claim 1, wherein the higher transition probabilities have a larger value as the received signal-to-noise ratio corresponding to the corresponding set of transition probabilities is larger, and the lower transition probabilities have a smaller value as the received signal-to-noise ratio corresponding to the corresponding set of transition probabilities is larger. How to have. The method of claim 3, wherein the changing of the current transmission rate comprises: If the reverse rate control information indicates congestion of the reverse link, one lower transition probability corresponding to the current rate is selected from the selected set of transition probabilities, so that random numbers generated with a uniform distribution between 0 and 1 are selected. Less than the transition probability, the current rate is reduced to a lower rate indicated by the selected lower transition rate, If the reverse rate control information does not indicate congestion of the reverse link, one of the selected sets of transition probabilities corresponding to the current rate is selected, and the random number generated with a uniform distribution between 0 and 1 is selected. If less than an upper transition probability, increases the current rate to an upper rate indicated by the selected upper transition probability. An apparatus for controlling a reverse rate by a terminal in a mobile communication system providing a packet data service to a terminal through a base station, A measuring instrument for measuring a received signal-to-noise ratio for the forward channel from the base station, An average calculator for calculating an average of the received signal-to-noise ratio measured by the measuring instrument for a predetermined time period, A selector for selecting one transition probability set corresponding to the average received signal-to-noise ratio among a plurality of predetermined transition probability sets, wherein each of the transition probability sets is a transition probability to a higher transmission rate among a plurality of predetermined transmission rates; Consists of upper and lower transition probabilities indicating the transition probability to the lower transmission rate, Selecting one transition probability corresponding to a current transmission rate among the selected set of transition probabilities according to the reverse rate control information received from the base station, and among the plurality of transmission rates in which the current transmission rate is predetermined according to the selected transition probability And a reverse rate controller for changing to one rate. 6. The method of claim 5, wherein the higher transition probabilities have a larger value as the received signal-to-noise ratio corresponding to the set of transition probabilities is larger, and the lower transition probabilities have a smaller value as the received signal-to-noise ratio corresponding to the corresponding set of transition probabilities is larger. Device having. The method of claim 6, wherein the reverse rate controller, If the reverse rate control information indicates congestion of the reverse link, one lower transition probability corresponding to the current rate is selected from the selected set of transition probabilities, so that random numbers generated with a uniform distribution between 0 and 1 are selected. Less than the transition probability, the current rate is reduced to a lower rate indicated by the selected lower transition rate, If the reverse rate control information does not indicate congestion of the reverse link, one of the selected sets of transition probabilities corresponding to the current rate is selected, and the random number generated with a uniform distribution between 0 and 1 is selected. Less than an upper transition probability, increases the current transmission rate to an upper transmission rate indicated by the selected upper transition probability. A method of controlling a reverse rate by a terminal in a mobile communication system that provides a packet data service to a terminal through a base station, Obtaining a forward data throughput rate for a predetermined time period for the forward data channel from the base station; Selecting one transition probability set corresponding to the data throughput among a plurality of predetermined transition probability sets, wherein each of the transition probability sets indicates a transition probability to a higher transmission rate among a plurality of predetermined transmission rates; It consists of lower transition probabilities representing the upper and lower transition rates, Selecting one transition probability corresponding to a current transmission rate among the selected set of transition probabilities according to the reverse rate control information received from the base station, and among the plurality of transmission rates in which the current transmission rate is predetermined according to the selected transition probability Changing to one transmission rate. The method of claim 8, wherein the calculating of the forward data throughput rate comprises: And dividing the amount of data received during the time period from the base station through the forward data channel by dividing the time period by the time period. 10. The method of claim 8, wherein the upper transition probabilities have a larger value as the forward data throughput corresponding to the corresponding set of transition probabilities is larger, and the lower transition probabilities have a smaller value as the forward data throughput corresponding to the corresponding set of transition probabilities is larger. How to have. The method of claim 10, wherein the changing of the current transmission rate comprises: If the reverse rate control information indicates congestion of the reverse link, one lower transition probability corresponding to the current rate is selected from the selected set of transition probabilities, so that random numbers generated with a uniform distribution between 0 and 1 are selected. Less than the transition probability, the current rate is reduced to a lower rate indicated by the selected lower transition rate, If the reverse rate control information does not indicate congestion of the reverse link, one of the selected sets of transition probabilities corresponding to the current rate is selected, and the random number generated with a uniform distribution between 0 and 1 is selected. If less than an upper transition probability, increases the current rate to an upper rate indicated by the selected upper transition probability. An apparatus for controlling a reverse rate by a terminal in a mobile communication system providing a packet data service to a terminal through a base station, A throughput calculator for calculating forward data throughput for the forward data channel from the base station, A selector for selecting one transition probability set corresponding to the forward data throughput among a plurality of predetermined transition probability sets, wherein each of the transition probability sets indicates a transition probability to a higher transmission rate among a plurality of predetermined transmission rates; Consisting of the upper and lower transition probabilities indicating and the lower transition probabilities indicating the transition probability to the lower transmission rate, Selecting one transition probability corresponding to a current transmission rate among the selected set of transition probabilities according to the reverse rate control information received from the base station, and among the plurality of transmission rates in which the current transmission rate is predetermined according to the selected transition probability And a reverse rate controller for changing to one rate. The method of claim 12, wherein the higher transition probabilities have a higher value as the forward data throughput corresponding to the corresponding set of transition probabilities is larger, and the lower transition probabilities have a smaller value as the forward data throughput corresponding to the corresponding set of transition probabilities is larger. Device having. The method of claim 13, wherein the reverse rate controller, If the reverse rate control information indicates congestion of the reverse link, one lower transition probability corresponding to the current rate is selected from the selected set of transition probabilities, so that random numbers generated with a uniform distribution between 0 and 1 are selected. Less than the transition probability, the current rate is reduced to a lower rate indicated by the selected lower transition rate, If the reverse rate control information does not indicate congestion of the reverse link, one of the selected sets of transition probabilities corresponding to the current rate is selected, and the random number generated with a uniform distribution between 0 and 1 is selected. Less than an upper transition probability, increases the current transmission rate to an upper transmission rate indicated by the selected upper transition probability.