AU1585600A - Data transmitting device and method in mobile communication system - Google Patents

Description

WO 00/33515 PCT/KR99/00727 DATA TRANSMITTING DEVICE AND METHOD IN MOBILE COMMUNICATION SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a data transmitting device and method in a mobile communication system, and in particular, to a device and method for controlling a variable data transmission rate according to the amount of transmission data. 2. Description of the Related Art A CDMA (Code Division Multiple Access) mobile communication system has evolved from the IS-95 standard, which focused on voice transmission, to the CDMA 2000 standard, which includes the transmission of high quality voice, moving pictures, and high speed data, and Internet browsing. CDMA 2000 is characterized by a dedicated control channel. The dedicated control channel has a low frame transmission error rate and basically supports a data rate of 9.6 or 14.4kbps. The dedicated control channel also supports a discontinuous transmission mode in which frame data is transmitted on a physical channel only as needed. That is, the discontinuous transmission mode is a transmission scheme of transmitting data on a corresponding channel only when the data to be transmitted is generated. Therefore, the dedicated control channel either transmits one frame data, at 9.6 or 14.4kbps, or no frame data over one frame duration of 20ms. A frame transmitted at a data rate allowable on a dedicated control channel, like 9.6 or 14.4kbps, will be referred to as a full rate frame hereinafter. Because the dedicated control channel supports the discontinuous transmission mode, a base station cannot estimate the amount of physical resources required by a mobile station. Given the worst case, where the mobile station WO 00/33515 PCT/KR99/00727 -2 continuously transmits full rate frames, the base station provides for a mobile station using physical resources at 9.6 or 14.4kbps continuously. However, if the mobile station is forced to transmit frames only when it 5 satisfies a full rate frame generation condition given by the base station, the average estimated size of the physical resource required by the mobile station can be reduced. For example, when the base station orders the mobile station to transmit data only in the first frame period of every two frame periods and stop transmission in the second frame period, the base station can estimate the size of the physical resource required 0 by the mobile station at a lower value than it would otherwise estimate. Using the above transmission control method the dedicated control channel, for instance, the base station can reduce the average physical resource assigned to the mobile station, thereby requiring less physical resources for a given number of mobile stations. 5 In addition, sometimes, it is necessary to process an urgent call while the base station provides a service to several mobile stations at its maximum transmission power. In this case, since the base station transmits a signal at the maximum transmission power, there is required a method for providing the urgent call service. 0 SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a device and method for controlling the number of transmissions according to the amount of transmission data on a channel operated in a discontinuous transmission mode in a 5 mobile communication system, so that the use efficiency of physical resources can be increased. It is another object of the present invention to provide a device and method for transmitting data transmission rate control information to a mobile station and then 0 transmitting data to the mobile station at a controlled data transmission rate by a base station in a mobile communication system. It is a further object of the present invention to provide a device and method for receiving data transmission rate control information from a base station, 5 controlling a data transmission rate based on the received control information, and WO 00/33515 PCT/KR99/00727 -3 communicating with the base station at the controlled data transmission rate by a mobile station in a mobile communication system. It is still another object of the present invention to provide a method for 5 enabling a base station to have spare power by decreasing an average data transmission rate for a specific duration by using a channel supporting discontinuous transmission. Briefly, these and other objects are achieved by providing a data transmitting 0 method for a base station. In accordance with the method to transmit frame data at a transmission rate decreased from a predetermined transmission rate on a channel supporting a discontinuous transmission mode, the base station determines a plural number N of frame periods at the predetermined transmission rate and the number L of frames transmitted at the decreased transmission rate. Here, L is smaller than N. 5 Then, the base station transmits L frames for N frame periods at the decreased transmission rate. BRIEF DESCRIPTION OF THE DRAWINGS 0 The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which: FIG. 1A is a block diagram of an RLP (Radio Link Protocol) frame data 5 transmitter in a mobile communication system in accordance with an embodiment of the present invention; FIG. 1B is a detailed block diagram of an RLP processor shown in FIG. 1A; 0 FIG. 2 is a flowchart illustrating an RLP frame data transmission control operation in the mobile communication system in accordance with the embodiment of the present invention; WO 00/33515 PCT/KR99/00727 -4 FIG. 3 is a flowchart illustrating an RLP frame data transmission control operation in a mobile communication system in accordance with another embodiment of the present invention; FIG. 4 is a flowchart illustrating an RLP frame data transmission control operation in a mobile communication system in accordance with a third embodiment of the present invention; FIG. 5 is a flowchart illustrating an operation of increasing values of first and second counters for control of RLP frame data transmission in the mobile communication system in accordance with the embodiments of the present invention; and FIG. 6 is a flowchart illustrating an operation of increasing the value of the first counter for control of RLP frame data transmission in the mobile communication system in accordance with the embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described hereinbelow with reference to the accompanying drawings. In the following description, well known functions or constructions are not described in detail to avoid obscuring the invention in unnecessary detail. To control data transmission in a mobile communication system according to an embodiment of the present invention, a base station provides a required condition for generating full rate frames to a mobile station so that the mobile station may transmit only when satisfying the condition. The resulting data transmission control between the base station and the mobile station reduces the average physical resources used. For example, when the base station orders the mobile station to transmit data in the first frame period of every two frame periods and stop transmission in the second frame period, the base station can estimate the size of a physical source for the mobile station at a lower value than it would otherwise. When packet data is communicated between the base station and the mobile station on a dedicated control channel or a fundamental channel in the mobile communication system, the amount of data WO 00/33515 PCT/KR99/00727 -5 transmitted on the dedicated control channel can be estimated to thereby control the data transmission. As a result, the base station can reduce the average physical resource use of the mobile station to an intended level. 5 FIG. 1A is a block diagram of an RLP frame data transmitter according to the embodiment of the present invention. In the embodiment shown in FIG. 1A, it is assumed that the physical channel device for transmitting RLP frame data is a dedicated control channel device. Referring to FIG. 1A, the RLP frame data transmitter includes a channel modulator 15a, 15b for modulating a frame to be D transmitted on a dedicated control channel, a multiplexer 13a, 13b for generating information bits of a transmission frame, and an RLP processor 11 a, 11 b. The channel modulator 15a, 15b may be a dedicated control channel modulator. The RLP frame data transmitter is commonly provided to the base station and the mobile station. 5 FIG. lB is a detailed block diagram of the RLP processor 11 shown in FIG. 1A. Referring to FIG. 1B, the RLP processor is comprised of an RLP controller 21 for controlling an RLP operation, an RLP frame generator 25, and a memory 23 for storing the previous and current transmission data. A first counter 31 stores the count NC of RLP frame periods and a second counter 33 stores the count LC of RLP frames D transmitted for the RLP frame periods. A register 27 stores the plural number N of RLP frame periods for which RLP frames can be transmitted at a determined transmission rate, and a register 29 stores the number L of frames transmitted at a decreased transmission rate. Here, L is less than N. L and N are reference values used to reduce a data transmission rate when packet data is transmitted on a dedicated 5 channel in a discontinuous transmission mode according to the embodiment of the present invention. With N=5 and L=3, for example, 3 RLP frames are actually transmitted over 5 RLP frame periods. A base station controller transmits N and L to a base station RLP processor D 11 a and a mobile station RLP processor 1 lb at an initialization state. N is a first reference for setting the number of RLP frame transmissions at a determined transmission rate and L is a second reference representing the number of new frame data transmissions for the N frames periods.

WO 00/33515 PCT/KR99/00727 -6 The RLP processor 11 a, 1 lb functions as both a decrease rate determiner for determining N and L and a frame data generator for generating L frames for N frame periods according to a decreased transmission rate. 5 In the embodiment of the present invention, a channel on which frame data is transmitted or not, depending on the amount of transmission data (a discontinuous transmission channel), can be a dedicated control channel, a fundamental channel, and/or a supplemental channel. It is assumed that the discontinuous transmission channel is a dedicated control channel and has been already established between the base station and the mobile station in the following description. For control of RLP frame data transmission between the base station and the mobile station according to the embodiment of the present invention, the base station controller notifies the base station RLP processor 11 a and the mobile station RLP > processor 1 lb of N and L. Here, N is the number of RLP frames transmittable at a predetermined transmission rate and L is the number of RLP frames transmittable at a decreased transmission rate for N periods. The base station controller transmits 1-byte control information to the RLP processor 1 lb of the mobile station by use of a signaling message. The base station controller also transmits the 1-byte control information to the RLP processor 11a of the base station. The control information is constituted as shown below. (Table 1) Field length Control value index 3 bits Reserved 2 bits Information type 3 bits If the information type field is set to 101, it implies that the control information suggested in the embodiment of the present invention is included in the signaling message. The RLP controller 21 detects the number of generated frames and the maximum number of new full rate frames which can be generated referring to ) such a table as shown below.

WO 00/33515 PCT/KR99/00727 -7 (Table 2) control value index Number of generated frames maximum number 000 1 1 001 4 3 010 2 1 011 4 1 Upon receipt of the control information from the base station controller, the RLP controller 21 stores N (the number of RLP frames transmittable at a predetermined transmission rate) in the register 27 and L (the number of RLP frames transmittable at a decreased transmission rate) in the register 29. If the RLP processor 11 a, 11 b has not received N and L from the base station controller, it sets N and L to 1 and an infinite number, respectively. The RLP controller 21 can be the base station RLP controller or the mobile station RLP controller. That is, the base station controller transmits the variables to the base station RLP controller and the mobile station RLP controller simultaneously during a channel set-up or conversation so that each RLP controller controls transmission of corresponding channel data based on the variables. It is assumed here that the data transmission controlled channel is a dedicated control channel or a fundamental channel and packet data is transmitted on the channels. If N and L are newly set and the RLP frame data is transmitted, the RLP controller 21 sets NC and LC to Os after N frame periods are passed. NC counts the number of RLP frame periods passed, and LC is the counted number of RLP frames transmitted the frame periods. For an RLP frame transmission period on the dedicated control channel, the above devices operate in the following way. First, the multiplexer 13a, 13b determines for each 20ms intervals whether an RLP frame can be transmitted. If it can be, the multiplexer 13a, 13b determines the size of an RLP frame to be transmitted, and requests generation of the RLP frame, while notifying the RLP processor 11 a, 11 b of the determined RLP frame size.

WO 00/33515 PCT/KR99/00727 -8 The RLP controller 21 receives the frame generation request from the multiplexer 13a, 13b and checks whether a new RLP frame can be generated. If a data frame to be transmitted again or a transmission request control frame exists, the frame is transmitted with the highest priority in the RLP. Therefore, the new data frame can be transmitted only if these high-priority frames do not exist. In addition, transmission data must be present in the memory 23 to transmit the new data frame. When these conditions are met, the RLP controller 21 controls the RLP frame generator 25 to generate an appropriate frame based on the RLP. In the situation where the new data frame can be generated, the RLP controller 21 determines whether the RLP frame size determined in the multiplexer 13a, 13b is equal to a full rate frame size. If they are different, the RLP controller 21 controls the RLP frame generator 25 to generate a new data frame of the determined size. Then, the RLP frame generator 25 generates the ordered frame in response to a frame generation signal received from the RLP controller 21 and feeds the frame to the multiplexer 13a, 13b. If the new data frame can be generated and the full rate frame size is allowed, the RLP controller 21 operates in the procedure specified in FIG. 2. Referring to FIG. 2, the RLP controller 21 compares the value of LC stored in the counter 33, indicating the number of frames actually transmitted, with L stored in the register 29, indicating the number of frames transmittable at a predetermined decreased data transmission rate, in step 211. If L is less than LC, the RLP controller 21 transmits no RLP frame data and controls the RLP frame generator 25 to generate idle frames in step 215. Then, the RLP frame generator 25 generates idle frames and feeds them to the multiplexer 13a, 13b. The multiplexer 13a, 13b discards the received idle frames and orders the channel modulator 15 to set a transmission gain to 0. The channel modulator 15 sets the transmission gain to 0 accordingly so that no data frame is transmitted on a channel operated in the discontinuous transmission mode. On the other hand, if LC is less than or equal to L in step 211, the RLP controller 21 controls the RLP frame generator 25 to generate new full rate data WO 00/33515 PCT/KR99/00727 -9 frames and increases LC of the counter 33 by one in step 213. The RLP frame data is transmitted on a dedicated control channel. After step 213 or 215, the RLP controller 21 increases NC of the first counter 5 31 by one in step 217 and determines whether NC is greater than or equal to N of the register 27 in step 219. If NC is greater than or equal to N, the RLP controller 21 sets NC and LC to initial values in step 221. If NC is less than N, the operation ends. Upon receipt of a new full rate data frame generating command from the RLP controller 21, the RLP frame generator 25 receives new transmission data from the memory 23, generates the new full rate data frame out of the received data, and feeds the generated data frame to the multiplexer 13a, 13b. The multiplexer 13a, 13b converts the received data frame to information bits of a dedicated control channel frame and applies them to the channel modulator 15a, 15b. The channel modulator 15a, 15b constructs a dedicated control channel frame with the received information bits and transmits the frame on the dedicated control channel. FIG. 3 is a flowchart illustrating a data transmission control operation in a mobile communication system according to another embodiment of the present invention. Referring to FIG. 3, the RLP controller 21 compares LC with L in step 311. If L is less than or equal to LC, the RLP controller 21 transmits no RLP frame data in step 319. On the contrary, if LC is less than L in step 311, the RLP controller 21 determines whether N is a finite number and N-L NC-LC in step 313. If the base station controller does not notify N, N has an infinite value as stated above to RLP processor 11 a, 11 b this invention is not applied. If N is normally applied to the RLP controller 21, N is a finite value. The number resulting from subtracting L being the number of actually transmitted RLP frames from N being a plurality of frame periods, that is, (N-L) is the number of discontinued RLP transmissions, that is, the number of RLP frames which are not transmitted due to the decrease of a transmission rate among frames transmittable at a predetermined transmission rate. (NC-LC) is the number of RLP frames not transmitted during an RLP transmission.

WO 00/33515 PCT/KR99/00727 -10 Therefore, if N is a finite number and (N-L) is less than or equal to (NC-LC) in step 313, that is, when the RLP controller 21 transmits frame data, the RLP controller 21 generates new full rate data frames, transmits the data frames on the dedicated control channel, and increases LC by one in step 321. However, if N is a finite number and (N-L) is not less than (NC-LC) in step 313, the RLP controller 21 generates a random number P between 0 and 1 and stores the random number P in a register in step 315. In step 317, the RLP controller 21 compares the random number P with a predetermined random number Pr. If P > Pr, the RLP controller 21 generates new full rate data frames and transmits the generated data frames in step 321. If P < Pr, the RLP controller 21 generates no RLF frames in step 319. After step 321 or 319, the RLP controller 21 increases NC by one in step 323 and determines whether NC N in step 325. If NC > N, the RLP controller 21 sets both NC and LC to Os in step 327. Otherwise, the RLP controller 21 ends the control operation. As shown in FIG. 2, the RLP controller 21 determines whether the base station controller generates a predetermined number of new full rate data frames. If LC < L, more new full rate data frames can be generated. If LC < L, the RLP controller 21 determines whether the base station controller paused without transmitting the predetermined number of new full rate data frames. If N is not an infinite number, the number predetermined by the base station controller, that is, (N-L) is the number of pauses. The RLP controller 21 determines whether (N-L) (NC-LC). If (N-L) (NC-LC), this implies that the discontinuation of RLP transmission is enough. Thus, the RLP controller 21 generates new full rate data frames and transmits them. If (N-L) > (NC-LC), the RLP controller 21 determines whether new full rate data frames can be generated. To do so, the RLP controller 21 generates a random number between 0 and 1. If the generated random numb < Pr, the RLP controller 21 generates no frames so that no RLP frames are transmitted on either a dedicated control channel or a fundamental channel. On the other hand, if the generated random number > Pr, the RLP controller 21 generated new full rate data frames and transmits them on the dedicated control channel.

WO 00/33515 PCT/KR99/00727 - 11 If the base station controller sets Pr to 0 during the above operation, the RLP controller 21 generates new full rate data frames and transmits them. Of the base controller sets Pr to 1, the RLP controller 21 transmits no new full rate RLP frames on 5 either the dedicated control channel or the fundamental channel. When transmitting no new full rate RLP frames, the RLP controller 21 transmits idle RLP frames to the multiplexer 13 and the multiplexer 13 transmits the idle RLP frames in the case of the fundamental channel and no idle RLP frames in the case of the fundamental channel. 0 If LC > L, the RLP controller 21 transmits no new full rate RLP frames on either of the dedicated control channel and the fundamental channel. Then, the RLP controller 21 increases NC by one. If NC > N, the RLP controller 21 sets both NC and LC to Os. Then, the RLP 5 controller 21 ends the procedure. FIG. 4 is a flowchart illustrating a data transmission control operation in a mobile communication system according to a third embodiment of the present invention. Referring to FIG. 4, the RLP controller 21 generates a random number P 0 between 0 and 1 and stores the random number P in a register in step 411. The RLP controller 21 compares the random number P with a predetermined random number Pr in step 413. If P Pr, the RLP controller 21 generates new full rate data frames and transmits them in step 415. If P < Pr, the RLP controller 21 generates no RLP frames in step 417. 5 After step 415 or 417, the RLP controller 21 increases NC by one in step 419 and determines whether NC N in step 421. If NC > N, the RLP controller 21 sets both NC and LC to initial values Os in step 423 and ends the procedure. If N > NC, the RLP controller 21 ends the one procedure. 0 FIG. 4 illustrates a simplified transmission control method modified from the transmission control method shown in FIG. 2. The former is different from the latter in that P is directly generated and compared with Pr and new full rate data frames are generated for transmission if P Pr. 5 WO 00/33515 PCT/KR99/00727 - 12 The RLP controller 21 can transmit new data frames as full rate RLP frames and performs the procedure shown in FIG. 2, 3, or 4 in the presence of new RLP data frames to be transmitted. 5 When new full rate data frames cannot be transmitted but the system needs to, the RLP controller 21 increases LC and NC by 1, respectively. If the increased NC > N, the RLP controller 21 sets NC and LC to Os. The increase of LC and NC will be described referring to FIG. 5. When new 0 full rate data frames are transmitted or both NC and LC are increased concurrently, LC and NC are increased by 1 in steps 511 and 513, respectively. In step 515, it is determined whether NC N. if NC N, NC and LC are set to Os in step 517 and the procedure ends. On the other hand, if NC < N, the procedure ends. 5 In accordance with the embodiments of the present invention, LC and NC are concurrently increased in the following situations: 1. when full rate RLP frames are transmitted as retransmission frames; 2. when new data frames or retransmission frames are smaller in size than 0 full rate RLP frames; 3. when a control RLP frame is generated; and 4. when a blank RLP frame is generated according to a command issued from a multiplexer. 5 The base station controller sets none of the above conditions or several conditions to thereby increase LC and NC by the RLP controller 21. When new full rate data frames cannot be transmitted, the RLP controller 21 increases NC by one as long as the condition set by the base station controller is satisfied. If the increased NC N, the RLP controller 21 sets NC and LC to Os. 0 The increase of NC will be described referring to FIG. 6. In a situation where NC should be increased, NC is increased by one in step 611 and it is determined whether NC N in step 613. If NC N, NC and LC are set to Os in step 615 and the procedure ends. On the other hand, if NC < N, the procedure ends. 5 WO 00/33515 PCT/KR99/00727 - 13 NC is increased in the following conditions in accordance with the embodiments of the present invention: 5 1. when full rate RLP frames are transmitted as retransmission frames; 2. when new data frames or retransmission frames are smaller in size than full rate RLP frames; 3. when a control RLP frame is generated; 4. when a blank RLP frame is generated according to a command issued 0 from a multiplexer; and 5. when no RLP frames are transmitted on a dedicated control channel. If any of the above five conditions is set for increasing LC and NC simultaneously, the condition is not set for increasing NC only. The base station 5 controller sets none of the above conditions or several conditions other than those for increasing NC and LC concurrently, to thereby increase NC using the RLP controller 21. The RLP controller 21 can reset a transmission control method in which data D frames are generated and transmitted at predetermined intervals by setting NC and LC to Os if reset conditions are satisfied. The reset conditions in accordance with the embodiments of the present invention are: 1. when no new transmission data remains after new full rate data frames are 5 generated in RLP; and 2. when idle frames are autonomously generated in RLP. By resetting the transmission control method of transmitting data frames at predetermined intervals according to the above conditions, when new transmission D data is generated, the RLP controller 21 can transmit new full rate data frames immediately. For resetting the transmission control method, upon receipt of a frame generation request from the multiplexer 13, the RLP controller 21 follows the above 5 transmission control procedure when it can generate new data frames, and otherwise, WO 00/33515 PCT/KR99/00727 -14 it controls the RLP frame generator 25 to generate appropriate frames based on RLP standards. However, if no transmission data exists in the memory 23, the RLP controller 21 resets the transmission control method by controlling the RLP frame generator 25 to generate idle frames and setting NC and LC to Os. The resetting procedure enables immediate transmission of new data frames when the new transmission data exists in the memory 23. As described above, the present invention is advantageous in that physical channel resources can be efficiently used for a mobile station in a mobile communication system by estimating the amount of data communicated between a base station and the mobile station, setting a maximum number of new data frames transmittable with respect to the number of generated frames, and transmitting data or discontinuing the data transmission based on the set number. While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (13)

1. A data transmitting method in a base station in a mobile communication system, for transmitting frame data at a transmission rate decreased 5 from a predetermined transmission rate on a channel supporting a discontinuous transmission mode, the method comprising the steps of: a number N of frame periods at the predetermined transmission rate and a number L of frames transmitted at the predetermined periods, whereby L is smaller than N; and D controlling transmission L frames for N frame periods for decreased average transmission rate in N frame periods.

2. The method of claim 1, wherein the channel supporting the discontinuous transmission mode is a dedicated control channel. 5

3. The method of claim 1, wherein the channel supporting the discontinuous transmission mode is a fundamental channel.

4. The method of claim 1, further comprising the step of transmitting N D and L to a mobile station.

5. The method of claim 1, wherein the transmitted frame data is full rate RLP (Radio Link Protocol) frame data. 5

6. A data transmitting method in a base station in a mobile communication system, for transmitting frame data at a transmission rate decreased from a predetermined transmission rate on a channel supporting a discontinuous transmission mode, the method comprising the steps of: determining a number N of frame periods at the predetermined transmission D rate and a number L of frames transmitted at the decreased transmission rate, whereby L is smaller than N; and transmitting L frames for N frame periods; wherein the frame transmitting step comprises the steps of: comparing L with a number LC of transmitted frames at the time when the 5 frame data is transmitted; WO 00/33515 PCT/KR99/00727 -16 generating the frame data, transmitting the frame data, and increasing LC, if L is greater than LC; generating no frame data if L is not greater than LC; increasing a number NC of frame periods after transmission of the frame data; 5 and setting LC and NC to initial values and waiting until next frame data is transmitted, if N is less than NC.

7. The method of claim 6, wherein the frame data transmitting step D further comprises the step of generating a random number if L is greater than LC, transmitting the frame data if the generated random number is greater than a reference random number, and transmitting no frame data if the generated random number is not greater than the reference random number. 5

8. The method of claim 6, wherein the frame data is transmitted on a dedicated control channel.

9. The method of claim 6, wherein the transmitted frame data is full rate frame data. 0

10. A data transmitting method in a mobile station, for transmitting frame data at a transmission rate decreased from a predetermined transmission rate on a channel supporting a discontinuous transmission mode, the method comprising the steps of: 5 receiving a number N of frame periods at the predetermined transmission rate and a number L of frames transmitted at the predetermined frame periods, whereby L is smaller than N, from a base station; and transmitting L frames for N frame periods for the decreased average transmission rate in N frame periods. 0

11. A data transmitting method in a mobile station, for transmitting frame data at a transmission rate decreased from a predetermined transmission rate on a channel supporting a discontinuous transmission mode, the method comprising the steps of: WO 00/33515 PCT/KR99/00727 - 17 receiving a number N of frame periods at the predetermined transmission rate and a number L of frames transmitted at the predetermined frame periods, whereby L is smaller than N, from a base station; and transmitting L frames for N frame periods; 5 wherein the frame transmitting step comprises the steps of: comparing L with a number LC of transmitted frames at the time when the frame data is transmitted; generating the frame data, transmitting the frame data, and increasing LC, if L is greater than LC; D generating no frame data if L is not greater than LC; increasing a number NC of frame periods after transmission of the frame data; and setting LC and NC to initial values and waiting until the next frame data is transmitted, if N is less than NC. 5

12. A data transmitting device in a base station, for transmitting frame data at a transmission rate decreased from a predetermined transmission rate on a channel supporting a discontinuous transmission mode, comprising: a determiner for determining a number N of frame periods at the D predetermined transmission rate and a number L of frames transmitted at the predetermined frame periods, whereby L is smaller than N; a frame data generator for generating L frames for N frame periods; and a channel transmitter for transmitting the generated frame data in the discontinuous transmission mode. 5

13. A data transmitting device in a mobile station, for transmitting frame data at a transmission rate decreased from a predetermined transmission rate on a channel supporting a discontinuous transmission mode, comprising: a circuit for receiving a number N of frame periods at the predetermined D transmission rate and a number L of frames transmitted at the predetermined frame periods, whereby L is smaller than N, from a base station, and storing N and L; a frame data generator for generating L frames for N frame periods; and a channel transmitter for transmitting the generated frame data in the discontinuous transmission mode.