Patent Document

FIELD OF THE INVENTION 
   This invention relates to a method for transmitting data in a mobile communication system; and more particularly, to a method for retransmitting erroneous data efficiently between a mobile station and a radio network in a mobile communication system. 
   DESCRIPTION OF THE PRIOR ART 
   Generally, in case erroneous data are received at a reception side, there is provided an automatic repeat request (ARQ) procedure by which the erroneous data can be recovered. The ARQ procedure includes an ARQ type I, an ARQ type II and an ARQ type III. 
   According to the ARQ type I, in case a reception side receives data that have an error-including data fragment, the reception side requests the transmission side to retransmit the data fragment without storing the error-including data fragment in a storage unit at the reception side. In response to the request, the transmission side retransmits the requested data fragment to the reception side at the same data coding rate as previous one. 
   According to the ARQ type II, in case the reception side receives data that have the error-including data fragment, the reception side stores the error-including data fragment in the storage unit and then requests the transmission side to retransmit the data fragment. In response to the request, the transmission side generates the requested data fragment at a modified data coding rate and then retransmits the generated data fragment to the reception side. 
   For example, if a data coding rate for the initial data transmission is “½”, the retransmission is performed at a lower data coding rate of “⅓”, “¼” or the like. Here, the retransmitted data is not intended to be used itself, but to used after being combined with data received at the reception side in the original retransmission. 
   The ARQ type III is similar to the ARQ type II. A difference between two types is that the retransmitted data from the transmission side can be used itself or be used after being combined with data received at the reception side before the retransmission. 
   In case of the ARQ type I, since the error-including data fragment is not stored in the storage unit of the reception side, and the data fragment is retransmitted at the same data coding rate from the transmission side, the problem is that there is a high possibility that the retransmitted data will also have errors again. 
   In case of the ARQ type II and III, the error correction capability is greater than that of the ARQ type I. However, the retransmitted data cannot be used unless a physical layer of the reception side recognizes in advance that the currently received data are data which the reception side requested a retransmission. Also, in order to use the retransmitted data, the physical layer should not perform combining of the retransmitted data until an upper layer checks if the currently received data is retransmission-requested data, with the stored data thereby causing a time delay. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a method for retransmitting data between two sides including a reception side and a transmission side in a mobile communication system including one or more mobile stations and one or more radio networks in order to restore erroneous data received by the reception side without a delay-time. 
   In accordance with an aspect of the present invention, there is provided a method for retransmitting data between two sides including a reception side and a transmission side in a mobile communication system including one or more mobile stations and one or more radio networks, the method including the steps of: by the reception side, storing data received from the transmission side in a first storage unit; as a result of an error-checking procedure, if the data are erroneous, requesting the transmission side to retransmit the data; by the transmission side, transmitting to the reception side a first information related to retransmission and retransmitting the requested data; by a combination unit included in the reception side, combining the retransmitted data with the data stored in the first storage unit; if the combined data are not erroneous, clearing the data and the retransmitted data from the first storage unit and transmitting the combined data to a first upper layer included in the reception side; and in response to an ACK signal from the reception side representing that normal data are received, clearing by the transmission side the retransmitted data from a second storage unit. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and aspects of the invention will become apparent from the following description of the embodiments with reference to the accompanying drawings, in which: 
       FIG. 1  shows the core network interface architecture of the asynchronous mobile communication system; 
       FIG. 2A  shows a configuration of an asynchronous radio network to which the present invention is applied; 
       FIG. 2B  shows a configuration of an asynchronous mobile station to which the present invention is applied; 
       FIG. 3  is a flow chart illustrating a method for retransmitting data using an upper layer message in accordance with the present invention; and 
       FIG. 4  is a flow chart illustrating a method for retransmitting data using a TFCI (transport format combination indicator) in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows the core network interface architecture of the asynchronous mobile communication system. 
   As shown in  FIG. 1 , an asynchronous mobile communication system to which the present invention is applied includes an asynchronous mobile station  100 , an asynchronous radio network  200  and an asynchronous core network  300 . 
   Particularly, in order to employ hybrid ARQ types II and III technique more efficiently, the present invention is embodied for data retransmission between the asynchronous mobile station  100  and the asynchronous radio network  200 . 
   In more detail, when the asynchronous radio network  200  transmits data to the asynchronous mobile station  100 , a transport format combination indicator (TFCI) is included in the data. The TFCI includes information of whether data received at the asynchronous mobile station  100  are retransmitted data or not. Also, An upper layer or a physical layer can analyze the TFCI without getting a support for the analysis from the other layers. 
   Conversely, the asynchronous mobile station  100  transmits to the asynchronous radio network  200  data including the TFCI by which the asynchronous radio network  200  is informed of retransmitted data or not. 
     FIG. 2A  shows a configuration of an asynchronous radio network to which the present invention is applied. 
   As shown in  FIG. 2A , when a radio frequency (RF) unit  210  receives radio data from an asynchronous mobile station, the RF unit  210  transmits the radio data to a buffer  221  of a layer  1   220 . Also, when receiving modulated data from a modulation unit  223  of the layer  1   220 , the RF unit  210  converts a modulated data format to a radio data format and then transmits the converted data to the asynchronous mobile station. 
   Radio data that are transmitted via the RF unit  210  from the asynchronous mobile station are stored in the buffer  221  of the layer  1   220  and, according to a direction of L  1  control unit  224 , the buffer  221  supplies the radio data to a demodulation unit  222  of the layer  1   220 . 
   Under control of the L  1  control unit  224 , the demodulation unit  222  demodulates the radio data supplied from the buffer  221  and then transmits the demodulated data to a data reception/analysis unit  231  of an upper layer  230 . 
   The modulation unit  223  modulates data from a buffer  233  of the upper layer  230  according to instructions of the L  1  control unit  224  and then transmits the modulated data to the asynchronous mobile station via the RF unit  210 . 
   As seen from described above, the L  1  control unit  224  controls the buffer  221 , the demodulation unit  222  and the modulation unit  223  that are included in the layer  1   220 . 
   The data reception/analysis unit  231  of the upper layer  230  receives and analyzes the demodulated data from the demodulation unit  222  according to a direction of an upper layer control unit  234  and then transmits the data to an asynchronous GSM-MAP core network  300 . 
   A data generation unit  232  of the upper layer  230  supplies data from the asynchronous core network  300  to the buffer  233  of the upper layer  230  under control of the upper layer control unit  234  and the buffer  233  supplies the data stored therein to the modulation unit  223  of the layer  1   220  according to a direction of the upper layer control unit  234 . 
   The upper layer control unit  234  controls the data reception/analysis unit  231 , the data generation unit  232  and the buffer  233  that are included in the upper layer  230 . 
     FIG. 2B  shows a configuration of an asynchronous mobile station to which the present invention is applied. 
   As shown in  FIG. 2B , when a radio frequency (RF) unit  210  receives radio data from an asynchronous radio network, the RF unit  210  transmits the radio data to a buffer  121  of a layer  1   120 . Also, when receiving modulated data from a modulation unit  123  of the layer  1   120 , the RF unit  210  converts a modulated data format to a radio data format and then transmits the converted data to the asynchronous radio network. 
   Radio data that are transmitted via the RF unit  210  from the asynchronous radio network are stored in the buffer  121  of the layer  1   120  and, according to a direction of L  1  control unit  124 , the buffer  121  supplies the radio data to a demodulation unit  122  of the layer  1   120 . 
   Under control of the L  1  control unit  124 , the demodulation unit  122  demodulates the radio data supplied from the buffer  121  and then transmits the demodulated data to a data reception/analysis unit  131  of an upper layer  130 . 
   The modulation unit  123  modulates data from a buffer  133  of the upper layer  130  according to instructions of the L  1  control unit  124  and then transmits the modulated data to the asynchronous radio network via the RF unit  110 . 
   As seen from the above description, the L  1  control unit  124  controls the buffer  121 , the demodulation unit  122  and the modulation unit  123  that are included in the layer  1   120 . 
   The data reception/analysis unit  131  of the upper layer  130  receives and analyzes the demodulated data from the demodulation unit  122  according to a direction of an upper layer control unit  134  and then transmits the data to an application part  400 . 
   A data generation unit  132  of the upper layer  130  supplies data from the application part  400  to the buffer  133  of the upper layer  130  under control of the upper layer control unit  134  and the buffer  133  supplies the data stored therein to the modulation unit  123  of the layer  1   120  according to a direction of the upper layer control unit  134 . 
   The upper layer control unit  134  controls the data reception/analysis unit  131 , the data generation unit  132  and the buffer  133  that are included in the upper layer  130 . 
   As shown in  FIG. 2A  and  FIG. 2B , in case a data reception side of the asynchronous radio network or the asynchronous mobile station receives data including an erroneous fragment, a buffer in which the data is stored to be combined with retransmitted data is the buffer  121  and  221  included in the layer  1   120  and  220  of respective the asynchronous mobile station  100  and the asynchronous radio network  200 . Each buffer  121  and  221  can be placed behind respective demodulation unit  122  and  222 . 
   In case the data reception side requests data retransmission, a data transmission side needs to retransmit data that are previously transmitted to the data reception side. In this case, also there is needed a buffer for storing data that is used for data retransmission. Each buffer  133  and  233  of respective upper layer  130  and  230  is used for this case. 
     FIG. 3  is a flow chart illustrating a method for retransmitting data using an upper layer message in accordance with the present invention. 
   Referring to  FIG. 3 , there is provided how the transmission side transmits to the reception side, via an upper layer, a first message including information of the time when retransmission data will be transmitted before the transmission side transmits the retransmission data to the reception side. 
   Steps S 301  to S 309  illustrate a procedure of processing data in case a reception side receives non-erroneous data. 
   After a call connection, at the step S 301 , an upper layer  31  of a transmission side  30  transmits data to a buffer  32  of the upper layer  31 . 
   At the step S 302 , the data are stored in the buffer  32  of the upper layer  31  and then supplied to a physical layer  33  of the transmission side  30 . The physical layer  33  transmits the data to the reception side. 
   After receiving the data from the transmission side, at the step S 303 , a physical layer of the reception side transmits the data to a buffer  36  of the physical layer  35 . 
   At the step S 304 , the data are stored in the buffer  36  and then supplied to a cyclic redundancy check (CRC) unit  38 . The cyclic redundancy check unit  38  checks if the data stored in the buffer  36  are erroneous. 
   If non-erroneous data are stored in the buffer  36 , at the step S 305 , the cyclic redundancy check unit  38  transmits to the buffer  36  a signal representing that the data need to be cleared from the buffer  36 . The reason is that the non-erroneous data need not be stored in the buffer. 
   At the step S 306 , the cyclic redundancy check unit  38  transmits the data to an upper layer  39 . 
   At the step S 307 , the upper layer  39  transmits to the transmission side  30  an ACK (acknowledgement) signal representing that non-erroneous data was received. 
   At the step S 308 , the physical layer  33  of the transmission side  30  receives the ACK signal from the reception side  34 , and transmits the ACK signal to the upper layer  31  of the transmission side  30 . 
   At the step S 309 , the upper layer  31  transmits to the buffer  32  of the upper layer  31  a signal representing that the data transmitted to the reception side need to be cleared from the buffer  32  of the upper layer  31 . 
   In the above steps, a procedure of demodulating the data at the physical layer  35  of the reception side  34  can be performed prior or after the step S 303 . 
   Steps S 310  to S 327  illustrate a procedure of processing data in case the reception side receives erroneous data. 
   At the step S 310 , the upper layer  31  of the transmission side  30  transmits data to the buffer  32  of the upper layer  31 . 
   At the step S 311 , the data are stored in the buffer  32  of the upper layer  31  and then supplied to the physical layer  35  of the transmission side  34 . The physical layer  35  transmits the data to the reception side. 
   After receiving the data from the transmission side, at the step S 312 , the physical layer  35  of the reception side transmits the data to the buffer  36  of the physical layer  35 . 
   At the step S 313 , the data are stored in the buffer  36  and then supplied to the cyclic redundancy check unit  38 . The cyclic redundancy check unit  38  checks if the data stored in the buffer  36  is erroneous. As a result of the check, if the data is erroneous, the cyclic redundancy check unit  38  doesn&#39;t transmit the erroneous data to the upper layer  39  and the erroneous data remains stored in the buffer  36  of the physical layer  35 . 
   In case the upper layer fails to receive the desired data during a predetermined time or the other data that are supposed to be received later than the desired data are received ahead, at the step S 314 , the upper layer  39  of the reception side  34  transmits to the transmission side  30  a NACK (negative acknowledgement) signal representing that desired data are not received. 
   At the step S 315 , the physical layer  33  of the transmission side  30  that receives the NACK signal from the reception side  34 , transmits the NACK signal to the upper layer  31  of the transmission side  30 . 
   Before the upper layer  31  transmits retransmission data requested from the reception side, at the step S 316 , the upper layer  31  generates information data and then transmits the information data to the physical layer  35  of the reception side  34  via the physical layer  33  of the transmission side  30 . The information data includes information about a retransmission time when the transmission side  30  will transmit the retransmission data to the reception side  34 , information about how the transmission side will perform data processing (for example, a data coding rate, puncturing and so on) or the like. 
   At the step S 317 , the physical layer  35  of the reception side  34  transmits the information data from the transmission side  30  to the upper layer  39  of the reception side. 
   At the step S 318 , the upper layer  39  analyzes the information data, selects necessary information to be used at the physical layer  35  and then transmits the necessary information to the physical layer  35 . 
   At the step S 319 , the upper layer  31  of the transmission side  30  selects the retransmission data from the buffer  32  of the transmission side. 
   At the step S 320 , the buffer  32  of the upper layer  31  transmits the retransmission data to the physical layer  33  and then the physical layer  33  transmits the retransmission data to the reception side. In this case, a way of processing the retransmission data, for example, a data coding rate and a puncturing, at the physical layer  33  is different from that of processing the data for the initial transmission from the transmission side to the reception side. Also, the way of processing the retransmission data is required to conform to the information data that are transmitted to the reception side. Accordingly, it is required that the information data are transmitted to the physical layer  33  earlier than the retransmission data. 
   At the step S 321 , the physical layer  35  of the reception side  34  stores the retransmission data from the transmission side in the buffer  36  and then the buffer  36  transmits the retransmission data to a combiner  37  in order to combine the retransmission data with the erroneous data previously stored in the buffer  36 . 
   At the step S 322 , the buffer  36  transmits the erroneous data to the combiner  37 . 
   At the step S 323 , the combiner  37  performs combining the retransmission data with the erroneous data and the cyclic redundancy check unit  38  checks if the combined data are erroneous, and if not, transmits to the buffer  36  a clear signal representing that the combined data need to be cleared from the buffer  36 . 
   At the step S 324 , the cyclic redundancy check unit  38  transmits the combined data to the upper layer  39 . 
   At the step S 325 , the upper layer  39  transmits to the transmission side the ACK signal representing that non-erroneous data was received. 
   At the step S 326 , the physical layer  33  of the transmission side transmits the ACK signal to the upper layer  31  of the transmission side. 
   At the step S 327 , the upper layer  31  transmits to the buffer  32  of the upper layer  31  a clear signal representing that the retransmission data needs to be cleared from the buffer  32 . 
     FIG. 4  is a flow chart illustrating a method for retransmitting data using a TFCI (transport format combination indicator) in accordance with the present invention. 
   Referring to  FIG. 4 , there is provided how the transmission side retransmits erroneous data to the reception side using the TFCI including information indicating that currently transmitted data are retransmission data. A physical layer can interpret the TFCI in a radio frame without the support of the other layer. 
   Steps S 401  to S 409  illustrate a procedure of processing data in case a reception side receives non-erroneous data. 
   After a call connection, at the step S 401 , an upper layer  31  of a transmission side  30  transmits data to a buffer  32  of the upper layer  31 . 
   At the step S 402 , the data are stored in the buffer  32  of the upper layer  31  and then supplied to a physical layer  35  of the transmission side  34 . The physical layer  35  transmits the data to the reception side. 
   After receiving the data from the transmission side, at the step S 403 , a physical layer of the reception side transmits the data to a buffer  36  of the physical layer  35 . 
   At the step S 404 , the data is stored in the buffer  36  and then supplied to a cyclic redundancy check (CRC) unit  38 . The cyclic redundancy check unit  38  checks if the data stored in the buffer  36  is erroneous. 
   If non-erroneous data is stored in the buffer  36 , at the step S 405 , the cyclic redundancy check unit  38  transmits to the buffer  36  a signal representing that the data can be cleared from the buffer  36 . The reason is that the non-erroneous data need not be stored in the buffer. 
   At the step S 406 , the cyclic redundancy check unit  38  transmits the data to an upper layer  39 . 
   At the step S 407 , the upper layer  39  transmits to the transmission side  30  an ACK (acknowledgement) signal representing that the non-erroneous data were received. 
   At the step S 408 , the physical layer  33  of the transmission side  30  that receives the ACK signal from the reception side  34 , transmits the ACK signal to the upper layer  31  of the transmission side  30 . 
   At the step S 409 , the upper layer  31  transmits to the buffer  32  of the upper layer  31  a signal representing that the data transmitted to the reception side need to be cleared from the buffer  32  of the upper layer  31 . 
   In the above steps, a procedure of demodulating the data at the physical layer  35  of the reception side  34  can be performed prior or after the step S 403 . 
   Steps S 410  to S 424  illustrate a procedure of processing data in case the reception side receives erroneous data. 
   At the step S 410 , the upper layer  31  of the transmission side  30  transmits data to the buffer  32  of the upper layer  31 . 
   At the step S 411 , the data is stored in the buffer  32  of the upper layer  31  and then supplied to the physical layer  35  of the transmission side  34 . The physical layer  35  transmits the data to the reception side. 
   After receiving the data from the transmission side, at the step S 412 , the physical layer  35  of the reception side transmits the data to the buffer  36  of the physical layer  35 . 
   At the step S 413 , the data is stored in the buffer  36  and then supplied to the cyclic redundancy check unit  38 . The cyclic redundancy check unit  38  checks if the data stored in the buffer  36  is erroneous. As a result of the check, if the data is erroneous, the cyclic redundancy check unit  38  doesn&#39;t transmit the erroneous data to the upper layer  39  and the erroneous data remain stored in the buffer  36  of the physical layer  35 . 
   In case the upper layer fails to receive the desired data during a predetermined time or the other data that are supposed to be received later than the desired data are received ahead, at the step S 414 , the upper layer  39  of the reception side  34  transmits to the transmission side  30  a NACK (negative acknowledgement) signal representing that desired data was not received. 
   At the step S 415 , the physical layer  33  of the transmission side  30  that receives the NACK signal from the reception side  34 , transmits the NACK signal to the upper layer  31  of the transmission side  30 . 
   At the step S 416 , the upper layer  31  of the transmission side  30  selects the retransmission data from the buffer  32  of the transmission side. 
   At the step S 417 , the buffer  32  of the upper layer  31  transmits the retransmission data to the physical layer  33  and then the physical layer  33  transmits the retransmission data to the reception side. In this case, a way of processing the retransmission data, for example, a data coding rate and a puncturing, at the physical layer  33  is different from that of processing the data that is transmitted initially from the transmission side to the reception side. 
   Information about the way of processing the retransmission data is included in the TFCI. The physical layer  35  of the reception side can interpret the TFCI without getting a support from the other layers. The retransmission data together with the TFCI are transmitted to the reception side. 
   At the step S 418 , the physical layer  35  of the reception side  34  stores the retransmission data from the transmission side in the buffer  36 . The buffer  36  determines if the stored data are the retransmission data by interpreting the TFCI of the received data, and if the received data are the retransmission data, the buffer  36  transmits the retransmission data to a combiner  37  in order to combine the retransmission data with the erroneous data previously stored in the buffer  36 . 
   At the step S 419 , the buffer  36  transmits the erroneous data to the combiner  37 . Interpreting the TFCI at the above step S 418  can be performed after or before storing the retransmission data in the buffer  36  of the physical layer  35 . 
   At the step S 420 , the combiner  37  performs combining the retransmission data with the erroneous data and the cyclic redundancy check unit  38  checks if the combined data are erroneous, and if not, transmits to the buffer  36  a clear signal representing that the combined data need to be cleared from the buffer  36 , otherwise the logic flow returns to the step S 414 . 
   At the step S 421 , the cyclic redundancy check unit  38  transmits the combined data to the upper layer  39 . 
   At the step S 422 , the upper layer  39  transmits to the transmission side the ACK signal representing that non-erroneous data were received. 
   At the step S 423 , the physical layer  33  of the transmission side transmits the ACK signal to the upper layer  31  of the transmission side. 
   At the step S 424 , the upper layer  31  transmits to the buffer  32  of the upper layer  31  a clear signal representing that the retransmission data may be cleared from the buffer  32 . 
   A procedure of demodulating the retransmission data from the transmission side at the physical layer  35  of the reception side  34  can be performed after or prior the step S 418 . 
   In the hybrid ARQ types II/III in accordance with the present invention, there is provided an advantageous effect that erroneous data can be restored without a time delay since the reception side recognizes when the retransmission data will be transmitted thereto. Also, the hybrid ARQ types II/III can be applied to a mobile communication system without modifying system hardware. 
   Although the preferred embodiments of the invention have been disclosed for illustrative purpose, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the scope and sprit of the invention as disclosed in the accompanying claims.

Technology Category: h