Title of Invention	TURBO CHANNEL ENCODING/DECODING DEVICE AND METHOD FOR PROCESSING FRAME ACCORDING TO SERVICE QUALITY
Abstract	A turbo channel encoding/decoding device for a CDMA communication system. The device disassembles an input frame into multiple sub frames of an appropriate length when the input data frame is very long, and then encodes and decodes the sub frames. Otherwise, when the input data frames are very short, the device assembles input frames into one super frame of an appropriate length and then encodes and decodes the super frame. After frame encoding/decoding, the frames are reassembled into the original input frames. (FIG.Nil)

Title of Invention

TURBO CHANNEL ENCODING/DECODING DEVICE AND METHOD FOR PROCESSING FRAME ACCORDING TO SERVICE QUALITY

Abstract

A turbo channel encoding/decoding device for a CDMA communication system. The device disassembles an input frame into multiple sub frames of an appropriate length when the input data frame is very long, and then encodes and decodes the sub frames. Otherwise, when the input data frames are very short, the device assembles input frames into one super frame of an appropriate length and then encodes and decodes the super frame. After frame encoding/decoding, the frames are reassembled into the original input frames. (FIG.Nil)

Full Text	TURBO CHANNEL ENCODING/DECODING DEVICE AND METHOD FOR PROCESSING FRAME ACCORDING TO SERVICE QUALITY CLAIM OF PRIORITY This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application entitled TURBO CHANNEL ENCODING/DECODING DEVICE AND METHOD FOR PROCESSING FRAME ACCORDING TO SERVICE QUALITY earlier filed in the Korean Industrial Property Office on 31 March 1998, and there duly assigned Serial No. 98-11380. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device and method for encoding/decoding a channel in a mobile communication system, and in particular, to device and method for encoding/decoding a channel using a turbo code. 2. Description of the Related Art An encoder using a turbo code (hereinafter, referred to as a turbo encoder} encodes an N-bit input frame into parity symbols using two simple parallel concatenated codes, wherein an RSC (Recursive Systematic Convolutional) code is generally used as a component code. FIGs. 1 and 2 illustrate structures of conventional turbo encoder and decoder, which are disclosed in a paper entitled "Improved Turbo Coding for Voice Transmission in FPLMTS", pp. 423-427, 7th telecommunication information joint conference, Korean Electronics Society/Telecommunications Society, 17 April 1997. The turbo encoder of FIG. 1 includes a first constituent encoder 12, a second constituent encoder 14 and an interleaver 16 interconnected therebetween. For the first and second constituent encoders 12 and 14, an RSC encoder can be used, which is well known in the art. The interleaver 16 has the same size as a frame length N of the input data bit, and decreases a correlation among the data bits by rearranging the input data bits dk being provided to the second constituent encoder 14. Therefore, the parallel concatenated codes for the input data bits become xk (=dk), y1k and y2k. A turbo decoder for decoding the output of the turbo encoder shown in FIG. 1 is also well disclosed in the above-mentioned paper. FIG. 2 illustrates a structure of the turbo decoder, which includes an adder 18, subtracters 20 and 22, a soft decision circuit 24, delays 26, 28 and 30, and MAP (Maximum A Posterior Probability) decoders 32 and 34. Further, the turbo decoder includes an interleaver 36 which is identical to the interleaver 16 of FIG. 1, and deinterleavers 38 and 40. Such structured turbo decoder repeatedly decodes the received data by the frame unit using a MAP decoding algorithm, thereby increasing a bit error rate (BER). The turbo encoder has the interleaver 16 as shown in FIG. 1, which implies that encoding and decoding should be performed by the frame unit in order to use the turbo encoder. Accordingly, it can be appreciated that memories and calculations required for the MAP decoders 32 and 34 shown in FIG. 2 are proportional to a value obtained by multiplying the frame size by a state number of the first and second constituent encoders 12 and 14 of FIG. 1. In a mobile communication system, voice and data are transmitted at a data rate of several Kbps to several Mbps, and a frame length of data input to a channel encoder is variably from several ms (milliseconds) to several hundred ms in a time domain. For example, in the case where the data is transmitted and received at a data rate of over 32Kbps, if the data input to the turbo encoder is channel encoded and transmitted with a fixed length frame, the turbo decoder requires increased memories and calculations to decode the received data which has a very long frame length. The turbo encoder shows a property that an error correction performance is increased as the frame length of the input data is longer, whereas the channel interleaver increases in size, thereby increasing the memories and calculations required in a decoder. In addition, from the viewpoint of the turbo encoder, if the length of the input frame is too short, the interleaver 16 in the turbo encoder cannot sufficiently remove the correlation among the input data, deteriorating the error correction performance. That is, when the frame length of the input data is longer, the turbo encoder structured as shown in FIG. 1 and the turbo decoder structured as shown in FIG. 2 require the increased calculations and memories in the process of encoding and decoding. Otherwise, when the frame length of the input data is shorter, the turbo encoder may show a low performance, as compared with a convolutional encoder or a concatenated encoder, thereby decreasing the BER. Accordingly, it is possible to decrease the calculations and memory capacity required for decoding, by appropriately varying the frame size of the data input to the turbo encoder, independent of the data rate for the corresponding service, while fully securing the high BER required in the communication system. SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a channel encoding device and method for variably encoding input data frames to sub or super frames of appropriate length according to the service quality of user data to transmit. It is another object of the present invention to provide a channel decoding device and method for decoding encoded frame data whose frame length is appropriately varied according to the service quality of user data to transmit. It is still another object of the present invention to provide a turbo channel encoding/decoding device and method for disassembling a long input frame into multiple sub frames having an appropriate length to encode the disassembled sub frames, separately decoding the divided encoded sub frames and then reassembling the decoded sub frames into the original frame. It is further still another object of the present invention to provide a turbo channel encoding/decoding device and method for assembling short input frames into a super frame having an appropriate length to encode the assembled super frame, decoding the assembled encoded super frame and then reassembling the decoded super frame into the original frames. It is further still another object of the present invention to provide a turbo channel encoding/decoding device and method for determining an optimal length of the sub/super frames by analyzing a quality of service (QoS) such as a data rate and a service type of input frame data to be transmitted, and disassembling or assembling an input data frame into sub or super frames according to the determination. BRIEF DESCRIPTION OF THE/DRAWINGS 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 like reference numerals indicate like parts. In the drawings: FIG. 1 is a diagram illustrating a structure of a conventional turbo encoder; FIG. 2 is a diagram illustrating a structure of a conventional turbo decoder; FIG. 3 is a diagram illustrating a structure of a channel transmitter including a turbo encoder according to an embodiment of the present invention; FIG. 4 is a diagram illustrating how to assemble input frames and turbo encode the assembled frame according to an embodiment of the present invention; FIG. 5 is a diagram illustrating how to disassemble an input frame and turbo encode the disassembled frames according to an embodiment of the present invention; and FIG. 6 is a diagram illustrating a structure of a channel receiver including a turbo decoder according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment 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 since they would obscure the invention in unnecessary detail. A future communication system provides various services of different QoS (Quality of Service), and QoS parameters include a time delay, a BER or a frame error rate (FER), and so forth. In the communication system, the high error rate- permitted services includes a voice service which requires a relatively short time delay and a short message service (SMS) which permits even a long time delay. On the other hand, among the services requiring the low error rate, a video conference service requires a short time delay, and a still image or Internet file transfer service permits even the relatively long time delay. Even the same service may have the different time delay and data rate. For example, in the image service for transmitting and receiving moving picture information, a data rate is 32-2048Kbps and a permissible time delay is 10- 400ms: the data rate and the permissible time delay can be, however, varied according to a class of the user or terminal using the service, a class of the base station providing the service or a channel condition during the corresponding service. Particularly, in the mobile communication system, since an output power of a base station or a mobile station is limited, it is inadequate to increase a transmission power of only a certain user for a high quality service. This is because when the transmission power of the specific user is increased, interference to other users will increase in proportion to the increased transmission power. Therefore, there is a demand for a method capable of providing various multimedia services with the reduced interference to the other users, by minimizing an increase in the transmission power. In another example, a short packet transmission service requires a low data rate and a very low error rate. However, when the time delay is out of the question, it is reasonable to decrease the error rate even though the time delay is somewhat increased. In the meantime, the turbo encoder, one of channel encoders for error correction, shows a property that the bit error rate (BER) or the frame error rate (FER) are varied according to the frame length of the input data. That is, the turbo encoder consists of the constituent encoders having a short constraint length: however, the error correction capability is improved as the correlation between the data input to the respective constituent encoders is decreased, due to existence of the interleaver in the turbo encoder. The correlation between the data input to the respective constituent encoders becomes lower, as the frame length of the data input to the turbo encoder becomes longer. Therefore, an increase in the frame length of the input data improves the error correction capability. However, an increase in length of the input frame causes an increase in the time delay at the encoder and the decoder. FIG. 3 illustrates a structure of a channel transmitter including a turbo encoder according to an embodiment of the present invention. The turbo encoder shown in FIG. 3 disassembles one input frame into several sub frames or assembles several input frames into one super frame by counting bits of the input user data according to message information, and thereafter encoding the disassembled or assembled frames with a turbo code to transmit the encoded frames via a transmission channel. A term "message information" used in the specification refers to information about the QoS, i.e., service type, rate of data such as voice, character, image and moving picture data, size of the input data frame, permissible delay, and permissible error. The message information is exchanged between a base station and a mobile station during a call setup and the exchange of the message information is continued till termination of the corresponding service. Further, information predetermined between the base station and the mobile station during the call setup can be also varied during the corresponding service by data exchanging. That is, the message information includes information representing the size of the frame to be processed in the turbo encoder and the frame size information can be differently set according to a rate of the data to be serviced. For example, when 10ms frame data is serviced at a data rate of 2048Kbps, one frame data consists of 20480 bits. In this case, the turbo encoder according to the present invention disassembles (or divides) the 10ms frame into 10/4ms frames and then, turbo encodes four 8192-bit frames. The turbo decoder then decodes the four frames and reassembles into one 20480-bit frame. As shown in FIG. 3, upon receipt of user data UD having a data rate of over several tens Kbps such as character, image and moving picture data, which is not voice data having a data rate of several Kbps, a source data encoder 42 encodes the received user data UD by the fixed length frame according to the service type and then provides the encoded user data to an input of a bit counter 50. For example, the source data encoder 42 encodes the voice data with 10ms frame, the character data with 20ms frame, the image data with 80ms frame and the moving picture data with 40ms, and provides the respective encoded data in different frame lengths to the bit counter 50. A central processing unit (CPU) 46 transfers information about the QoS, i.e., service type of the user data to be transmitted (e.g., voice, character, image or moving picture) and the data rate to a message information receiver 108 of FIG. 6 via a message information transmitter 44. The channel transmission device of FIG. 3 can be equally applied to both the base station and the mobile station. Although the present invention is described with reference to an embodiment which transmits the message information to the decoder using a separate transmitter, it is also possible to transmit the message information by loading it in a head area of a transmission frame during data transmission. The CPU 46 reads, from a frame disassemble/assemble information storage 48, QoS information including information about service type of data to be transmitted, corresponding data rate, permissible delay, permissible error rate (BER or FER) and frame length, and information about service class of the base station or the mobile station. Next, the CPU 46 determines to disassemble the frame and also determines the size and number of the disassembled frames, using the read information. Alternatively, the CPU 46 may determine to assemble the frames and also determine the number of the frames to be assembled, using the read information. Based on the determination, the CPU 46 provides a frame disassemble/assemble control signal and an interleaving mode signal to the bit counter 50 and a programmable interleaver 52, respectively, to perform turbo encoding. That is, according to the QoS of the data to transmit, the CPU 46 determines how many consecutive input frames should be assembled to generate a super frame, or determines the number of sub frames which will be generated by disassembling one input frame. The turbo encoder then turbo encodes data bits of the super frame or data bits of the respective sub frames disassembled. Here, as stated above, the QoS may include size of the input frame data, permissible delay, permissible error rate, etc. In determining to disassemble or assemble the frames by the CPU 46, the following principles are considered. In general, for transmitting the voice data, the mobile communication system uses a low data rate of below several tens Kbps, has the transmission delay of several tens ms (milliseconds) and requires the BER of about 10-2-10-4. Since the most serious limitation in transmitting the voice data is the transmission delay, the system has a serious limitation in disassembling/assembling the input data of the turbo encoder, i.e., the output frame of the source data encoder 42. For example, if the output frame of the source data encoder 42 is 10ms long and the maximum delay time permitted in the turbo encoder is 20ms, it is possible to assemble two 10ms frames output from the source data encoder 42 into one super frame, which will be input to the turbo encoder. However, if the maximum delay time permitted in the turbo encoder is 10ms, it is reasonable to use the 10ms frame output from source data encoder 42 as it is, without assembling. In the meantime, for transmitting character, image and moving picture data, the system has the permissible transmission delay from several tens ms to several hundreds ms and requires the BER of 10-6-10-7. A performance of the turbo encoder is increased as the frame length of the input data is increased. However, since the number of calculations and memories required in the turbo decoder is directly proportional to the frame size, it is needed to select an appropriate frame size. Therefore, for the packet data service, it is possible to satisfy the required BER by enabling the CPU 46 to generate a sub/super frame control signal for disassembling/assembling the data frames of M-bit length output from the source data encoder 42 into sub/super frames of N-bit length. That is, the frame disassemble/assemble information storage 48 stores frame disassemble/assemble information for increasing the length N of the sub/super frame for the service requiring the low BER and decreasing the length N of the sub/super frame for the service requiring the short time delay and the high BER. The CPU 46 reads the frame disassemble/assemble information from the frame disassemble/assemble information storage 48 according to the service type and the frame length of the input data. Disassembling/assembling the frames input to the turbo encoder can be appreciated more apparently from the following descriptions. For example, a frame length of the data input to the turbo encoder is 2048 bits, for a service having a data rate 2048Kbps/10ms among the services requiring the low BER. In the mobile station for providing the above service, the turbo decoder requires a memory capacity for storing the bits obtained by multiplying 20480 bits by a soft decision value. An increase in the memory capacity of the mobile station causes an increase in complexity and cost of the mobile station. However, in the service having the data rate 2048Kbps/10ms, if the channel encoder divides (or disassembles) a frame input to the turbo encoder into four sub frames and encodes the disassembled sub frames and the turbo decoder in the channel decoder then decodes the sub frames and reassembles the decoded sub* frames into the original frame, the turbo decoder requires a memory capacity capable of storing the bits obtained by multiplying 8192 bits by the soft decision value, thereby causing a reduction in the required memory capacity. Furthermore, in the service having a low data rate of 32Kbps/10ms among the services requiring the low BER, each data frame input to the turbo encoder will consist of 320 bits. If encoding is performed at a data rate of 32Kbps/80ms (i.e., each frame consists of 2560 bits), the time delay is somewhat increased, as compared with the case where turbo encoding is performed at the data rate of 32Kbps/10ms (i.e., each frame consists of 320 bits). However, it is possible to decrease the BER for the same signal-to-noise ratio Eb/No and decrease the Eb/No value for the same BER, thereby increasing the overall system capacity. In the mobile communication system, not all the users or mobile stations are provided with the same services. Instead, the available data rate is limited according to the class of the user, the mobile station or the base station. In addition, the available data rate may be limited due to the memory capacity determined according to the class of the respective mobile stations. Accordingly, when the data rate is variable from 32Kbps to 2048Kbps according to the service type (or service option) and the permissible time delay also varies from 10ms to 400ms, the device according to the present invention can vary the length of the frames input to the turbo encoder according to the class of the user or mobile station, the class of the base station providing the corresponding service or the channel condition while using the corresponding service. For example, when the channel conditions is very bad, the device according to the present invention can satisfy the error rate required in the corresponding service by increasing the length of the frames input to the turbo ~ encoder and permitting an increase in the time delay rather than increasing the transmission power. The frame disassemble/assemble information which is the message information being exchanged between the base station and the mobile station, has information about the size of the frames to be encoded/decoded, wherein the frame size is determined according to the user class, the mobile station class, the base station class and the channel condition. The bit counter 50 counts N bits of the input data according to an N-bit frame disassemble/assemble control signal output from the CPU 46, and provides the counted N bits to the programmable interleaver 52 and first and second input buffers 54 and 56. Also, the bit counter 50 generates a bit count termination signal to the CPU 46 whenever it counts N bits of the input data. Therefore, it can be appreciated that the bit counter 50 disassembles or assembles the input frames into sub or super frames having a specific length, under the control of the CPU 46 which uses the QoS information, such as the service type and the data rate of the input data, stored in the frame disassemble/assemble information storage 48, and provides the sub or super frames to the programmable interleaver 52 and the first and second input buffers 54 and 56. An interleaving processor 72 in the programmable interleaver 52 reads interleaving parameters from an interleaving parameter storage 70 according to an interleaving mode control signal output from the CPU 46 to process the read interleaving parameters, and provides the processing result to an interleaving address mapper 74. Here, the CPU 46 provides the interleaver processor 72 with the following interleaving information. First, in the case where a turbo interleaver having a single interleaving method is used as the interleaver 52, optimal parameter values determined to have the highest performance according to the length of data information bits for interleaving and the variable length of the interleaver are provided as the interleaving information. The parameter values are determined by the structure of the turbo interleaver. Second, in the case where a turbo interleaver having one or more interleaving methods is used as the interleaver 52, optimal parameter values determined to have the highest performance through experiments according to the length of the information bits for interleaving and the variable length of the interleaver in the corresponding interleaving mode are provided as the interleaving information. For example, in the case where the required transmission delay time is short and the input data frame of the turbo encoder, i.e., the output data frame of the source data encoder 42 is small in size (or length), a uniform interleaver such as a block interleaver or a cyclic shift interleaver is used for the interleaver 52. Otherwise, in the case where the required transmission delay time is relatively long and the input data frame is large in size, a non-uniform interleaver such as a random interleaver is used for the interleaver 52. From the foregoing description, it can be understood that various interleavers can be used according to the size of the data to be interleaved. Upon receiving user data bits of the sub or super frames of N-bit length disassembled or assembled by the bit counter 50, the interleaving address mapper 74 maps the input bits to the addresses corresponding to the interleaving processing result so as to perform interleaving, and provides the interleaved data to an interleaved input data buffer (ILIB) 78 in the first buffer 54 or an ILIB 90 in the second buffer 56. The first and second input buffers 54 and 56 each consist of two input switches, two output switches, an input data save buffer (IDSB) with input and output ports connected to ones of the input and output switches, and the ILIB with input and output ports connected to the other ones of the input and output switches. In the drawing, reference numerals 76 and 88 denote IDSBs, reference numerals 78 and 90 denote ILIBs, reference numerals 80, 84, 92 and 96 denote input switches, and reference numerals 82, 86, 94 and 98 denote output switches. All the switches are controlled by the CPU 46. The switches 80, 82, 84 and 86 in the first input buffer 54 operate in alternation with the switches 92, 94, 96 and 98 in the second input buffer 56. That is, input switches 80 and 84 in the first input buffer 54 are in the ON state and the output switches 82 and 86 are in the OFF state, while the input switches 92 and 96 in the second input buffer 56 are in the OFF state and the output switches 94 and 98 are in the ON state; and conversely. Accordingly, when the bit counter 50 counts N bits of the input data under the control of the CPU 46, the data output from the bit counter is first stored in the IDSB 76 in the first buffer 54 through the input switch 80 which is initially in the ON state. At this moment, the counted data bits output from the bit counter 50 are interleaved by the programmable interleaver 52 and then stored in the ILIB 78 in the first input buffer 54 through the switch 84. If the bit counter 50 generates a bit count termination signal for the sub/super frame of N-bit length, the CPU 46 then repeats the above procedure after switching the first input buffer 54 to an output state and the second input buffer 56 to an input state. As a result, the next N bits counted from the bit counter 50 and the interleaved data from the programmable interleaver 52 are stored in the IDSB 88 and the ILIB 90 in the second input buffer 56, respectively. During this operation, a first RSC (RSC1) 58 and a second RSC (RSC2) 60 receive the N-bit sub/super frame data and the corresponding interleaved data output from the IDSB 76 and ILIB 78 in the first input buffer through the output switches 82 and 86, respectively, and then performs turbo encoding by the N-bit frame unit in the same principle as the turbo encoder of FIG. 1. Next, when the N-bit frame data is completely stored in the second input buffer 56, the first input buffer 54 is again switched to the input state and the second input buffer 56 to the output state. Therefore, the RSC1 58 and the RSC2 60 turbo encode the data which are alternately output by the N-bit frame unit from the first and second input buffers 54 and 56. The turbo encoded bits from the RSC1 58 and the RSC2 60 are multiplexed by a multiplexer 62 and then interleaved by a channel interleaver 64. In the case where the several input frames are assembled into one super frame and the data is turbo encoded by the super frame unit, the channel interleaver 64 performs channel interleaving by the super frame unit as shown in FIG. 4. On the other hand, when one input frame is disassembled into several sub frames and the data is turbo encoded by the sub frame unit, the channel interleaving is performed by the input frame unit as shown in FIG. 5. That is, the channel interleaver 64 performs channel interleaving by assembling the output symbols of the turbo encoder, encoded by the super frame or sub frame unit, as large in size as the input frame. The interleaved data is modulated by a modulator 66 and then transmitted through a transmission channel 68. Accordingly, the novel channel transmission device shown in FIG. 3 assembles the input data frames to increase the bit number N when the low BER is required from an analysis of the QoS information such as the user"s service type (e.g., voice, character, image and moving picture) and the data rate, but disassembles the input data frame to decrease the bit number N per frame when the low delay time is required. In this manner, the channel transmission device can maximize an efficiency of the turbo encoder. FIG. 4 is a diagram for explaining operation of the invention, wherein the frames are assembled at a low or medium data rate and then turbo encoded. A parameter J can be varied from 1 to 8 according to the number of the frames to be assembled. In the turbo encoder, the bit number of an input data frame, which is determined by a value obtained by multiplying the bit number per frame by the number, J, of the frames to be assembled, may be limited. FIG. 5 is a diagram for explaining operation of the invention, wherein a frame data is disassembled at a high data rate and then turbo encoded. A parameter I can be varied from 1 to 4 according to the number of the disassembled sub frames. Likewise, in the turbo encoder, the bit number of an input data frame, which is determined by a value obtained by multiplying the bit number per frame by the number, I, of the disassembled sub frames, may be limited. The data on the transmission channel transmitted by the turbo channel encoder of FIG. 3 is decoded into the original data by the turbo channel decoder of FIG. 6, which can be understood more apparently from the following descriptions. FIG. 6 illustrates the turbo channel decoder structure according to an embodiment of the present invention. The turbo channel decoder of FIG. 6 counts bits of the user data input by the N-bit sub/super frame unit according to message information to decode the input user data and thereafter, assembles or disassembles the decoded data into the frames having the original length, thereby to reassemble the user data. Upon receiving the frame of N-bit length through the transmission channel 68, a demodulator 100 demodulates the received frame data and provides the demodulated data to a channel deinterleaver 102. The channel deinterleaver 102 descrambles the demodulated data frame and applies it to a demultiplexer 104, which demultiplexes the multiplexed data symbols and parity symbols and provides the demultiplexed symbols to a bit counter 106. Here, a message information receiver 108 shown in FIG. 6 receives the message information regarding the service type of the user and the data rate that the message information transmitter 44 of FIG. 3 has transmitted, and provides the received message information to a CPU 112. The CPU 112 analyzes the message information provided from the message information receiver 108 and reads frame disassemble/assemble information from a frame disassemble/assemble information storage 110 according to the analysis."" Also, the CPU 112 analyzes the interleaving information included in the message information and provides an interleaving mode signal and a parameter value to an interleaver and a deinterleaver in a turbo decoder 116 according to the analysis, thereby performing turbo interleaving. In addition, the CPU 112 performs turbo decoding and frame reassembling by outputting an N-bit frame disassemble or assemble control signal and a frame reassemble control signal according to the read frame disassemble/assemble information. Here, the information stored in the frame disassemble/assemble information storage 110 is similar to that stored in the frame disassemble/assemble information storage 48 of FIG. 3. The bit counter 106 consecutively provides the data output from the demultiplexer 104 to a frame buffer 114 by the N-bit sub/super frame unit according to the N-bit frame disassemble or assemble control signal. Switches 126 and 132 in the frame buffer 114 are initially in the ON state and the other switches 128 and 130 are initially in the OFF state. Therefore, the counted data bits output from the bit counter 106 are initially stored in a first N-frame buffer (N-FB1) 122. Upon completion of storing the N-bit data output from the bit counter 106 in the N-FB1 122, the bit counter 106 generates an N-bit count termination signal. Upon detecting the N-bit count termination signal, the CPU 112 turns off switches 126 and 132 in the frame buffer 114 and turns on the other switches 130 and 128. Then, the N-bit data output from the bit counter 106 is stored in a second N-frame buffer (N-FB2) 124. At this moment, the received data stored in the N-FB 1 122 is decoded by a turbo decoder 116 having the same structure as that of FIG. 2. Accordingly, under the control of the CPU 112, the N-FB1 122 and the N- FB2 124 in the frame buffer 114 alternately receive and store the data output by the N-bit unit from the bit counter 106, and the stored data is decoded by the turbo decoder 116. The decoded data output from the turbo decoder 116 is reassembled into the frames of the original length by a frame reassembler 118 which is controlled by the CPU 112, and then output as the user data through a source data decoder 120. In sum, the turbo decoder 116 receives a super frame consisting of multiple frames or multiple sub frames disassembled from a frame, and turbo decodes the received frames. The frame reassembler 118 reassembles, during the call setup, the output of the turbo decoder 116 into the frames in response to information about the number of the frames constituting the super frame and the size of the frames or information about the number of the sub frames disassembled from the input frame and the size of the sub frames, under the control of the CPU 112. The turbo encoder described above can be also implemented in the following method. In this exemplary method, any one of the bit counter 50 and the buffers 54 and 56 for interleaving, shown in FIG. 3, is not required. In frame assembling operation, the data bits are sequentially stored in the memory (i.e, buffer 54 or 56) for interleaving as many as the number of the frames to be assembled. To the RSC1 in the turbo encoder, data bits are sequentially output as many as the number of the non-interleaved assembled frames, and to the RSC2, the data bits are output as many as the number of the assembled frames which are interleaved to the addresses of the interleaving address mapper generated by the interleaving processor. In this manner, it is possible to turbo encode the input data by the data bits as many as the" size of the frame assembled with one or more frames. In another example, in the frame assembling operation, the input data bits are sequentially stored in the memory for interleaving. To the RSC1 in the turbo encoder, the data bits are sequentially output as many as the size of the disassembled frames, and to the RSC2, the data bits are interleaved and output as many as the size of the assembled frames. In this way, it is possible to turbo encode the input data by the data bits as many as the size of the sub frames disassembled from one frame. Accordingly, the turbo channel encoder of FIG. 3 and the turbo channel decoder of FIG. 6 assemble input data frames into a super frame to encode and decode the input frames by the super frame unit when the input data frames are too short, and disassemble an input frame into multiple sub frames to encode and decode the input frame by the sub frame unit when the input frame is too long, thereby to increase the efficiency thereof. As described above, the embodiment of the present invention disassembles/assembles input frames into sub/super frames of an appropriate length when the input data frame is very long or short, and then encodes and decodes the sub/super frames. In this manner, it is possible to reduce the calculations and memory capacity required in the decoder, while fully securing the performance of the turbo code encoder. While the invention has been shown and described with reference to a certain preferred embodiment 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. WE CLAIM A mobile communication system, comprising; a processor for determining a number and a size of sub frames which can be generated from the input data frame, according to a size of the input data frame; and a turbo encoder for encoding the sub frames individually. The mobile communication system as claimed in claim 1, wherein the turbo encoder comprises: a first constituent encoder for encoding data of the sub frame; an interleaver for interleaving the data of the sub frame; and a second constituent encoder, operabiy connected to said interleaver, for encoding the interleaved data of the sub frame. The mobile communication as claimed in claim 2, said interleaver includes an interleaver address mapper for interleaving data of said sub frame. The mobile communication system as claimed in claim 1, further comprising a multiplexer for multiplexing the data of the sub frame and respective outputs of the first and second constituent encoders. The mobile communication system as claimed in claim 1, further comprising a channel interleaving an encoded data frame, wherein the encoded data frame is constructed by concatenating the encoded sub frames. The mobile communication system as claimed in claim 1, wherein the processor determines to segment the input data frame when the size of the input data frame is 20480 bits. The mobile communication system as claimed in claim 1, wherein the number and size of the sub frames is determined by a permissible delay. The mobile communication system as claimed in claim 1, wherein the number and size of the sub frames is determined by a permissible error rate. The mobile communication system as claimed in claim 1, further wherein the number and the size of sub frames is determined by a receiver memory size. The mobile communication system as claimed in claim 1, wherein the size of said frames are equal. The mobile communication system as claimed in claim 1, wherein the size of the input data frame is variable. A channel encoding method for a mobile communication system having a turbo encoder, comprising the steps of: Segmenting an input data frame into plurality number of sub frames when the size of the input data frame is greater than a predetermined value; and encoding the sub frame individually. The channel encoding method as claimed in claim 12, wherein the encoding method comprising the steps of: a first encoding data of the sub frame to encode the input data; interleaving the data of the sub frame to generate a interleaved sub frame; and a second encoding data of the interleaved sub frame. .The channel encoding method as claimed in claim 12, further comprising the step of making an encoded input data frame by concatenating output of the turbo encoder for the input data frame; and channel interleaving the encoded input data frame. .The channel encoding method as claimed in claim 12, wherein the input data frame is segmented when the size of the input data frame is more than 20480 bits. The channel encoding method as claimed in claim 12, further wherein the number and the size of segment sub frames is determined by a permissible delay. The channel encoding method as claimed in claim 12, further wherein the number and the size of the segmented sub frames is determined by an error rate. The channel encoding method as claimed in claim 12, further wherein the number and the size of sub frames is determined by a receiver memory size. The channel encoding method as claimed in claim 12, wherein the size of said sub frames are all same. The channel encoding method as claimed in claim 12, wherein the size of the input frame is variable. A mobile communication system having turbo decoder, comprising: a decoder for segmenting a received data frame consisting of a plurality of sub frames into the plurality of sub frames, decoding said segmented sub frame individually; and a frame reconstructor for combining output of the decoder into the original input data frame in accordance with message information about the sub frames. The mobile communication system as claimed in claim 21, further comprising a processor for determining a number and a size of the sub frames upon receiving the message information about the number and the size frames, and providing the determined number and size information to the frame reconstructor. A channel decoding method in a mobile communication system having turbo decoder, comprising the steps of: segmenting a received data frame into a plurality of sub frames according to received message information. decoding said sub frames individually; and combining output of the decoder into the received data frame in response to said message information about a plurality of the sub frames. A mobile communication system as claimed in claim 1, having a turbo encoder, comprising: a processor for segmenting one input data frame to compose a plurality of sub frames when the size of a input data frame is more than a predetermined value; a turbo encoder for encoding the sub frames individually, wherein the turbo encoder comprising, a first constituent encoder for encoding data of the sub frame; an interleaver for interleaving the data of the sub frame; a second constituent encoder for encoding output of the interleaver; and a channel interleaver for interleaving a encoded input data frame, wherein the encoded input data frame is made by concatenated output of the turbo encoder for the input data frame. The mobile communication system as claimed in claim 24, wherein the predetermined value is 20480 bits. A mobile communication system as claimed as claimed in claim 24, comprising: a multiplexer for multiplexing respective outputs of the first and second constituent encoders. The mobile communication system as claimed in claim 24, comprising a channel interleaver (64) for interleaving said enclosed input data frame, wherein the encoded input data frame is made by concatenated output of the turbo encoder for the input data frame. The mobile communication system as claimed in claim 24, wherein the size of said sub frames are equal. The mobile communication system as claimed in claim 24, wherein the size of the input data frame is variable. A channel encoding method for a mobile communication system as claimed in claim 12 having a turbo encoder, comprising the steps of : comparing a bit number of a input data frame into the turbo encoder with a predetermined value; deciding to segment the input data frame into sub frames if the bit number is more than the predetermined value; and turbo encoding data of sub frame respectively which is segmented from the input data frame. The channel encoding method as claimed in claim 30, wherein the predetermined value is 20480 bits. The method as claimed in claim 30, comprising: a multiplexer for multiplexing respective outputs of the first and second constituent encoders. The method as claimed in claim 30, comprising a channel interleaver (64) for interleaving said encoded input data frame, wherein the encoded input data frame is made by concatenated output of the turbo encoder for the input data frame. The method as claimed in claim 30, wherein the size of said sub frames are equal. The method as claimed in claim 30, wherein the size of the input data frame is variable. The invention relates to an ultrasonic diagnostic apparatus (100) having an operation panel (101) provided with a plurality of key switches (1-1,1-2,1-6) for increasing/decreasing setting values relating to imaging and display of an ultrasonic image. One or more key switches (1-1, 1-3, 1-5, 1-2, 1-4, 1-6) are disposed slantingly with respect to the horizontal and vertical directions of the operation panel (101).

Full Text

TURBO CHANNEL ENCODING/DECODING DEVICE AND METHOD
FOR PROCESSING FRAME ACCORDING TO SERVICE QUALITY
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims
all benefits accruing under 35 U.S.C. §119 from an application entitled TURBO
CHANNEL ENCODING/DECODING DEVICE AND METHOD FOR
PROCESSING FRAME ACCORDING TO SERVICE QUALITY earlier filed in
the Korean Industrial Property Office on 31 March 1998, and there duly assigned
Serial No. 98-11380.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device and method for encoding/decoding
a channel in a mobile communication system, and in particular, to device and
method for encoding/decoding a channel using a turbo code.
2. Description of the Related Art
An encoder using a turbo code (hereinafter, referred to as a turbo encoder}
encodes an N-bit input frame into parity symbols using two simple parallel
concatenated codes, wherein an RSC (Recursive Systematic Convolutional) code
is generally used as a component code.
FIGs. 1 and 2 illustrate structures of conventional turbo encoder and decoder,
which are disclosed in a paper entitled "Improved Turbo Coding for Voice
Transmission in FPLMTS", pp. 423-427, 7th telecommunication information joint
conference, Korean Electronics Society/Telecommunications Society, 17 April
1997.
The turbo encoder of FIG. 1 includes a first constituent encoder 12, a second
constituent encoder 14 and an interleaver 16 interconnected therebetween. For the
first and second constituent encoders 12 and 14, an RSC encoder can be used,
which is well known in the art. The interleaver 16 has the same size as a frame
length N of the input data bit, and decreases a correlation among the data bits by
rearranging the input data bits dk being provided to the second constituent encoder
14. Therefore, the parallel concatenated codes for the input data bits become xk
(=dk), y1k and y2k.
A turbo decoder for decoding the output of the turbo encoder shown in FIG.
1 is also well disclosed in the above-mentioned paper. FIG. 2 illustrates a structure
of the turbo decoder, which includes an adder 18, subtracters 20 and 22, a soft
decision circuit 24, delays 26, 28 and 30, and MAP (Maximum A Posterior
Probability) decoders 32 and 34. Further, the turbo decoder includes an interleaver
36 which is identical to the interleaver 16 of FIG. 1, and deinterleavers 38 and 40.
Such structured turbo decoder repeatedly decodes the received data by the frame
unit using a MAP decoding algorithm, thereby increasing a bit error rate (BER).
The turbo encoder has the interleaver 16 as shown in FIG. 1, which implies
that encoding and decoding should be performed by the frame unit in order to use
the turbo encoder. Accordingly, it can be appreciated that memories and
calculations required for the MAP decoders 32 and 34 shown in FIG. 2 are
proportional to a value obtained by multiplying the frame size by a state number of
the first and second constituent encoders 12 and 14 of FIG. 1.
In a mobile communication system, voice and data are transmitted at a data
rate of several Kbps to several Mbps, and a frame length of data input to a channel
encoder is variably from several ms (milliseconds) to several hundred ms in a time
domain. For example, in the case where the data is transmitted and received at a
data rate of over 32Kbps, if the data input to the turbo encoder is channel encoded
and transmitted with a fixed length frame, the turbo decoder requires increased
memories and calculations to decode the received data which has a very long frame
length. The turbo encoder shows a property that an error correction performance is
increased as the frame length of the input data is longer, whereas the channel
interleaver increases in size, thereby increasing the memories and calculations
required in a decoder.
In addition, from the viewpoint of the turbo encoder, if the length of the
input frame is too short, the interleaver 16 in the turbo encoder cannot sufficiently
remove the correlation among the input data, deteriorating the error correction
performance. That is, when the frame length of the input data is longer, the turbo
encoder structured as shown in FIG. 1 and the turbo decoder structured as shown
in FIG. 2 require the increased calculations and memories in the process of
encoding and decoding. Otherwise, when the frame length of the input data is
shorter, the turbo encoder may show a low performance, as compared with a
convolutional encoder or a concatenated encoder, thereby decreasing the BER.
Accordingly, it is possible to decrease the calculations and memory capacity
required for decoding, by appropriately varying the frame size of the data input to
the turbo encoder, independent of the data rate for the corresponding service, while
fully securing the high BER required in the communication system.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a channel
encoding device and method for variably encoding input data frames to sub or super
frames of appropriate length according to the service quality of user data to
transmit.
It is another object of the present invention to provide a channel decoding
device and method for decoding encoded frame data whose frame length is
appropriately varied according to the service quality of user data to transmit.
It is still another object of the present invention to provide a turbo channel
encoding/decoding device and method for disassembling a long input frame into
multiple sub frames having an appropriate length to encode the disassembled sub
frames, separately decoding the divided encoded sub frames and then reassembling
the decoded sub frames into the original frame.
It is further still another object of the present invention to provide a turbo
channel encoding/decoding device and method for assembling short input frames
into a super frame having an appropriate length to encode the assembled super
frame, decoding the assembled encoded super frame and then reassembling the
decoded super frame into the original frames.
It is further still another object of the present invention to provide a turbo
channel encoding/decoding device and method for determining an optimal length
of the sub/super frames by analyzing a quality of service (QoS) such as a data rate
and a service type of input frame data to be transmitted, and disassembling or
assembling an input data frame into sub or super frames according to the
determination.
BRIEF DESCRIPTION OF THE/DRAWINGS
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 like reference numerals
indicate like parts. In the drawings:
FIG. 1 is a diagram illustrating a structure of a conventional turbo encoder;
FIG. 2 is a diagram illustrating a structure of a conventional turbo decoder;
FIG. 3 is a diagram illustrating a structure of a channel transmitter including
a turbo encoder according to an embodiment of the present invention;
FIG. 4 is a diagram illustrating how to assemble input frames and turbo
encode the assembled frame according to an embodiment of the present invention;
FIG. 5 is a diagram illustrating how to disassemble an input frame and turbo
encode the disassembled frames according to an embodiment of the present
invention; and
FIG. 6 is a diagram illustrating a structure of a channel receiver including a
turbo decoder according to an embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A preferred embodiment 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 since
they would obscure the invention in unnecessary detail.
A future communication system provides various services of different QoS
(Quality of Service), and QoS parameters include a time delay, a BER or a frame
error rate (FER), and so forth. In the communication system, the high error rate-
permitted services includes a voice service which requires a relatively short time
delay and a short message service (SMS) which permits even a long time delay. On
the other hand, among the services requiring the low error rate, a video conference
service requires a short time delay, and a still image or Internet file transfer service
permits even the relatively long time delay. Even the same service may have the
different time delay and data rate.
For example, in the image service for transmitting and receiving moving
picture information, a data rate is 32-2048Kbps and a permissible time delay is 10-
400ms: the data rate and the permissible time delay can be, however, varied
according to a class of the user or terminal using the service, a class of the base
station providing the service or a channel condition during the corresponding
service. Particularly, in the mobile communication system, since an output power
of a base station or a mobile station is limited, it is inadequate to increase a
transmission power of only a certain user for a high quality service. This is because
when the transmission power of the specific user is increased, interference to other
users will increase in proportion to the increased transmission power. Therefore,
there is a demand for a method capable of providing various multimedia services
with the reduced interference to the other users, by minimizing an increase in the
transmission power.
In another example, a short packet transmission service requires a low data
rate and a very low error rate. However, when the time delay is out of the question,
it is reasonable to decrease the error rate even though the time delay is somewhat
increased.
In the meantime, the turbo encoder, one of channel encoders for error
correction, shows a property that the bit error rate (BER) or the frame error rate
(FER) are varied according to the frame length of the input data. That is, the turbo
encoder consists of the constituent encoders having a short constraint length:
however, the error correction capability is improved as the correlation between the
data input to the respective constituent encoders is decreased, due to existence of
the interleaver in the turbo encoder. The correlation between the data input to the
respective constituent encoders becomes lower, as the frame length of the data input
to the turbo encoder becomes longer. Therefore, an increase in the frame length of
the input data improves the error correction capability. However, an increase in
length of the input frame causes an increase in the time delay at the encoder and the
decoder.
FIG. 3 illustrates a structure of a channel transmitter including a turbo
encoder according to an embodiment of the present invention. The turbo encoder
shown in FIG. 3 disassembles one input frame into several sub frames or assembles
several input frames into one super frame by counting bits of the input user data
according to message information, and thereafter encoding the disassembled or
assembled frames with a turbo code to transmit the encoded frames via a
transmission channel. A term "message information" used in the specification refers
to information about the QoS, i.e., service type, rate of data such as voice, character,
image and moving picture data, size of the input data frame, permissible delay, and
permissible error. The message information is exchanged between a base station and
a mobile station during a call setup and the exchange of the message information
is continued till termination of the corresponding service. Further, information
predetermined between the base station and the mobile station during the call setup
can be also varied during the corresponding service by data exchanging. That is, the
message information includes information representing the size of the frame to be
processed in the turbo encoder and the frame size information can be differently set
according to a rate of the data to be serviced. For example, when 10ms frame data
is serviced at a data rate of 2048Kbps, one frame data consists of 20480 bits. In this
case, the turbo encoder according to the present invention disassembles (or divides)
the 10ms frame into 10/4ms frames and then, turbo encodes four 8192-bit frames.
The turbo decoder then decodes the four frames and reassembles into one 20480-bit
frame.
As shown in FIG. 3, upon receipt of user data UD having a data rate of over
several tens Kbps such as character, image and moving picture data, which is not
voice data having a data rate of several Kbps, a source data encoder 42 encodes the
received user data UD by the fixed length frame according to the service type and
then provides the encoded user data to an input of a bit counter 50. For example, the
source data encoder 42 encodes the voice data with 10ms frame, the character data
with 20ms frame, the image data with 80ms frame and the moving picture data with
40ms, and provides the respective encoded data in different frame lengths to the bit
counter 50. A central processing unit (CPU) 46 transfers information about the QoS,
i.e., service type of the user data to be transmitted (e.g., voice, character, image or
moving picture) and the data rate to a message information receiver 108 of FIG. 6
via a message information transmitter 44. The channel transmission device of FIG.
3 can be equally applied to both the base station and the mobile station.
Although the present invention is described with reference to an embodiment
which transmits the message information to the decoder using a separate transmitter,
it is also possible to transmit the message information by loading it in a head area
of a transmission frame during data transmission.
The CPU 46 reads, from a frame disassemble/assemble information storage
48, QoS information including information about service type of data to be
transmitted, corresponding data rate, permissible delay, permissible error rate (BER
or FER) and frame length, and information about service class of the base station
or the mobile station. Next, the CPU 46 determines to disassemble the frame and
also determines the size and number of the disassembled frames, using the read
information. Alternatively, the CPU 46 may determine to assemble the frames and
also determine the number of the frames to be assembled, using the read
information. Based on the determination, the CPU 46 provides a frame
disassemble/assemble control signal and an interleaving mode signal to the bit
counter 50 and a programmable interleaver 52, respectively, to perform turbo
encoding. That is, according to the QoS of the data to transmit, the CPU 46
determines how many consecutive input frames should be assembled to generate a
super frame, or determines the number of sub frames which will be generated by
disassembling one input frame. The turbo encoder then turbo encodes data bits of
the super frame or data bits of the respective sub frames disassembled. Here, as
stated above, the QoS may include size of the input frame data, permissible delay,
permissible error rate, etc.
In determining to disassemble or assemble the frames by the CPU 46, the
following principles are considered.
In general, for transmitting the voice data, the mobile communication system
uses a low data rate of below several tens Kbps, has the transmission delay of
several tens ms (milliseconds) and requires the BER of about 10-2-10-4. Since the
most serious limitation in transmitting the voice data is the transmission delay, the
system has a serious limitation in disassembling/assembling the input data of the
turbo encoder, i.e., the output frame of the source data encoder 42. For example, if
the output frame of the source data encoder 42 is 10ms long and the maximum delay
time permitted in the turbo encoder is 20ms, it is possible to assemble two 10ms
frames output from the source data encoder 42 into one super frame, which will be
input to the turbo encoder. However, if the maximum delay time permitted in the
turbo encoder is 10ms, it is reasonable to use the 10ms frame output from source
data encoder 42 as it is, without assembling.
In the meantime, for transmitting character, image and moving picture data,
the system has the permissible transmission delay from several tens ms to several
hundreds ms and requires the BER of 10-6-10-7. A performance of the turbo encoder
is increased as the frame length of the input data is increased. However, since the
number of calculations and memories required in the turbo decoder is directly
proportional to the frame size, it is needed to select an appropriate frame size.
Therefore, for the packet data service, it is possible to satisfy the required BER by
enabling the CPU 46 to generate a sub/super frame control signal for
disassembling/assembling the data frames of M-bit length output from the source
data encoder 42 into sub/super frames of N-bit length.
That is, the frame disassemble/assemble information storage 48 stores frame
disassemble/assemble information for increasing the length N of the sub/super
frame for the service requiring the low BER and decreasing the length N of the
sub/super frame for the service requiring the short time delay and the high BER.
The CPU 46 reads the frame disassemble/assemble information from the frame
disassemble/assemble information storage 48 according to the service type and the
frame length of the input data.
Disassembling/assembling the frames input to the turbo encoder can be
appreciated more apparently from the following descriptions. For example, a frame
length of the data input to the turbo encoder is 2048 bits, for a service having a data
rate 2048Kbps/10ms among the services requiring the low BER. In the mobile
station for providing the above service, the turbo decoder requires a memory
capacity for storing the bits obtained by multiplying 20480 bits by a soft decision
value. An increase in the memory capacity of the mobile station causes an increase
in complexity and cost of the mobile station.
However, in the service having the data rate 2048Kbps/10ms, if the channel
encoder divides (or disassembles) a frame input to the turbo encoder into four sub
frames and encodes the disassembled sub frames and the turbo decoder in the
channel decoder then decodes the sub frames and reassembles the decoded sub*
frames into the original frame, the turbo decoder requires a memory capacity
capable of storing the bits obtained by multiplying 8192 bits by the soft decision
value, thereby causing a reduction in the required memory capacity.
Furthermore, in the service having a low data rate of 32Kbps/10ms among
the services requiring the low BER, each data frame input to the turbo encoder will
consist of 320 bits. If encoding is performed at a data rate of 32Kbps/80ms (i.e.,
each frame consists of 2560 bits), the time delay is somewhat increased, as
compared with the case where turbo encoding is performed at the data rate of
32Kbps/10ms (i.e., each frame consists of 320 bits). However, it is possible to
decrease the BER for the same signal-to-noise ratio Eb/No and decrease the Eb/No
value for the same BER, thereby increasing the overall system capacity.
In the mobile communication system, not all the users or mobile stations are
provided with the same services. Instead, the available data rate is limited according
to the class of the user, the mobile station or the base station. In addition, the
available data rate may be limited due to the memory capacity determined according
to the class of the respective mobile stations. Accordingly, when the data rate is
variable from 32Kbps to 2048Kbps according to the service type (or service option)
and the permissible time delay also varies from 10ms to 400ms, the device
according to the present invention can vary the length of the frames input to the
turbo encoder according to the class of the user or mobile station, the class of the
base station providing the corresponding service or the channel condition while
using the corresponding service. For example, when the channel conditions is very
bad, the device according to the present invention can satisfy the error rate required
in the corresponding service by increasing the length of the frames input to the turbo ~
encoder and permitting an increase in the time delay rather than increasing the
transmission power.
The frame disassemble/assemble information which is the message
information being exchanged between the base station and the mobile station, has
information about the size of the frames to be encoded/decoded, wherein the frame
size is determined according to the user class, the mobile station class, the base
station class and the channel condition.
The bit counter 50 counts N bits of the input data according to an N-bit
frame disassemble/assemble control signal output from the CPU 46, and provides
the counted N bits to the programmable interleaver 52 and first and second input
buffers 54 and 56. Also, the bit counter 50 generates a bit count termination signal
to the CPU 46 whenever it counts N bits of the input data. Therefore, it can be
appreciated that the bit counter 50 disassembles or assembles the input frames into
sub or super frames having a specific length, under the control of the CPU 46 which
uses the QoS information, such as the service type and the data rate of the input
data, stored in the frame disassemble/assemble information storage 48, and provides
the sub or super frames to the programmable interleaver 52 and the first and second
input buffers 54 and 56.
An interleaving processor 72 in the programmable interleaver 52 reads
interleaving parameters from an interleaving parameter storage 70 according to an
interleaving mode control signal output from the CPU 46 to process the read
interleaving parameters, and provides the processing result to an interleaving
address mapper 74. Here, the CPU 46 provides the interleaver processor 72 with the
following interleaving information.
First, in the case where a turbo interleaver having a single interleaving
method is used as the interleaver 52, optimal parameter values determined to have
the highest performance according to the length of data information bits for
interleaving and the variable length of the interleaver are provided as the
interleaving information. The parameter values are determined by the structure of
the turbo interleaver.
Second, in the case where a turbo interleaver having one or more interleaving
methods is used as the interleaver 52, optimal parameter values determined to have
the highest performance through experiments according to the length of the
information bits for interleaving and the variable length of the interleaver in the
corresponding interleaving mode are provided as the interleaving information. For
example, in the case where the required transmission delay time is short and the
input data frame of the turbo encoder, i.e., the output data frame of the source data
encoder 42 is small in size (or length), a uniform interleaver such as a block
interleaver or a cyclic shift interleaver is used for the interleaver 52. Otherwise, in
the case where the required transmission delay time is relatively long and the input
data frame is large in size, a non-uniform interleaver such as a random interleaver
is used for the interleaver 52. From the foregoing description, it can be understood
that various interleavers can be used according to the size of the data to be
interleaved.
Upon receiving user data bits of the sub or super frames of N-bit length
disassembled or assembled by the bit counter 50, the interleaving address mapper
74 maps the input bits to the addresses corresponding to the interleaving processing
result so as to perform interleaving, and provides the interleaved data to an
interleaved input data buffer (ILIB) 78 in the first buffer 54 or an ILIB 90 in the
second buffer 56.
The first and second input buffers 54 and 56 each consist of two input
switches, two output switches, an input data save buffer (IDSB) with input and
output ports connected to ones of the input and output switches, and the ILIB with
input and output ports connected to the other ones of the input and output switches.
In the drawing, reference numerals 76 and 88 denote IDSBs, reference numerals 78
and 90 denote ILIBs, reference numerals 80, 84, 92 and 96 denote input switches,
and reference numerals 82, 86, 94 and 98 denote output switches. All the switches
are controlled by the CPU 46. The switches 80, 82, 84 and 86 in the first input
buffer 54 operate in alternation with the switches 92, 94, 96 and 98 in the second
input buffer 56. That is, input switches 80 and 84 in the first input buffer 54 are in
the ON state and the output switches 82 and 86 are in the OFF state, while the input
switches 92 and 96 in the second input buffer 56 are in the OFF state and the output
switches 94 and 98 are in the ON state; and conversely.
Accordingly, when the bit counter 50 counts N bits of the input data under
the control of the CPU 46, the data output from the bit counter is first stored in the
IDSB 76 in the first buffer 54 through the input switch 80 which is initially in the
ON state. At this moment, the counted data bits output from the bit counter 50 are
interleaved by the programmable interleaver 52 and then stored in the ILIB 78 in the
first input buffer 54 through the switch 84. If the bit counter 50 generates a bit count
termination signal for the sub/super frame of N-bit length, the CPU 46 then repeats
the above procedure after switching the first input buffer 54 to an output state and
the second input buffer 56 to an input state. As a result, the next N bits counted
from the bit counter 50 and the interleaved data from the programmable interleaver
52 are stored in the IDSB 88 and the ILIB 90 in the second input buffer 56,
respectively.
During this operation, a first RSC (RSC1) 58 and a second RSC (RSC2) 60
receive the N-bit sub/super frame data and the corresponding interleaved data output
from the IDSB 76 and ILIB 78 in the first input buffer through the output switches
82 and 86, respectively, and then performs turbo encoding by the N-bit frame unit
in the same principle as the turbo encoder of FIG. 1.
Next, when the N-bit frame data is completely stored in the second input
buffer 56, the first input buffer 54 is again switched to the input state and the second
input buffer 56 to the output state. Therefore, the RSC1 58 and the RSC2 60 turbo
encode the data which are alternately output by the N-bit frame unit from the first
and second input buffers 54 and 56.
The turbo encoded bits from the RSC1 58 and the RSC2 60 are multiplexed
by a multiplexer 62 and then interleaved by a channel interleaver 64. In the case
where the several input frames are assembled into one super frame and the data is
turbo encoded by the super frame unit, the channel interleaver 64 performs channel
interleaving by the super frame unit as shown in FIG. 4. On the other hand, when
one input frame is disassembled into several sub frames and the data is turbo
encoded by the sub frame unit, the channel interleaving is performed by the input
frame unit as shown in FIG. 5. That is, the channel interleaver 64 performs channel
interleaving by assembling the output symbols of the turbo encoder, encoded by the
super frame or sub frame unit, as large in size as the input frame. The interleaved
data is modulated by a modulator 66 and then transmitted through a transmission
channel 68.
Accordingly, the novel channel transmission device shown in FIG. 3
assembles the input data frames to increase the bit number N when the low BER is
required from an analysis of the QoS information such as the user"s service type
(e.g., voice, character, image and moving picture) and the data rate, but
disassembles the input data frame to decrease the bit number N per frame when the
low delay time is required. In this manner, the channel transmission device can
maximize an efficiency of the turbo encoder.
FIG. 4 is a diagram for explaining operation of the invention, wherein the
frames are assembled at a low or medium data rate and then turbo encoded. A
parameter J can be varied from 1 to 8 according to the number of the frames to be
assembled. In the turbo encoder, the bit number of an input data frame, which is
determined by a value obtained by multiplying the bit number per frame by the
number, J, of the frames to be assembled, may be limited.
FIG. 5 is a diagram for explaining operation of the invention, wherein a
frame data is disassembled at a high data rate and then turbo encoded. A parameter
I can be varied from 1 to 4 according to the number of the disassembled sub frames.
Likewise, in the turbo encoder, the bit number of an input data frame, which is
determined by a value obtained by multiplying the bit number per frame by the
number, I, of the disassembled sub frames, may be limited.
The data on the transmission channel transmitted by the turbo channel
encoder of FIG. 3 is decoded into the original data by the turbo channel decoder of
FIG. 6, which can be understood more apparently from the following descriptions.
FIG. 6 illustrates the turbo channel decoder structure according to an
embodiment of the present invention. The turbo channel decoder of FIG. 6 counts
bits of the user data input by the N-bit sub/super frame unit according to message
information to decode the input user data and thereafter, assembles or disassembles
the decoded data into the frames having the original length, thereby to reassemble
the user data.
Upon receiving the frame of N-bit length through the transmission channel
68, a demodulator 100 demodulates the received frame data and provides the
demodulated data to a channel deinterleaver 102. The channel deinterleaver 102
descrambles the demodulated data frame and applies it to a demultiplexer 104,
which demultiplexes the multiplexed data symbols and parity symbols and provides
the demultiplexed symbols to a bit counter 106. Here, a message information
receiver 108 shown in FIG. 6 receives the message information regarding the
service type of the user and the data rate that the message information transmitter
44 of FIG. 3 has transmitted, and provides the received message information to a
CPU 112.
The CPU 112 analyzes the message information provided from the message
information receiver 108 and reads frame disassemble/assemble information from
a frame disassemble/assemble information storage 110 according to the analysis.""
Also, the CPU 112 analyzes the interleaving information included in the message
information and provides an interleaving mode signal and a parameter value to an
interleaver and a deinterleaver in a turbo decoder 116 according to the analysis,
thereby performing turbo interleaving. In addition, the CPU 112 performs turbo
decoding and frame reassembling by outputting an N-bit frame disassemble or
assemble control signal and a frame reassemble control signal according to the read
frame disassemble/assemble information. Here, the information stored in the frame
disassemble/assemble information storage 110 is similar to that stored in the frame
disassemble/assemble information storage 48 of FIG. 3.
The bit counter 106 consecutively provides the data output from the
demultiplexer 104 to a frame buffer 114 by the N-bit sub/super frame unit according
to the N-bit frame disassemble or assemble control signal. Switches 126 and 132 in
the frame buffer 114 are initially in the ON state and the other switches 128 and 130
are initially in the OFF state.
Therefore, the counted data bits output from the bit counter 106 are initially
stored in a first N-frame buffer (N-FB1) 122. Upon completion of storing the N-bit
data output from the bit counter 106 in the N-FB1 122, the bit counter 106 generates
an N-bit count termination signal. Upon detecting the N-bit count termination
signal, the CPU 112 turns off switches 126 and 132 in the frame buffer 114 and
turns on the other switches 130 and 128. Then, the N-bit data output from the bit
counter 106 is stored in a second N-frame buffer (N-FB2) 124. At this moment, the
received data stored in the N-FB 1 122 is decoded by a turbo decoder 116 having the
same structure as that of FIG. 2.
Accordingly, under the control of the CPU 112, the N-FB1 122 and the N-
FB2 124 in the frame buffer 114 alternately receive and store the data output by the
N-bit unit from the bit counter 106, and the stored data is decoded by the turbo
decoder 116. The decoded data output from the turbo decoder 116 is reassembled
into the frames of the original length by a frame reassembler 118 which is
controlled by the CPU 112, and then output as the user data through a source data
decoder 120.
In sum, the turbo decoder 116 receives a super frame consisting of multiple
frames or multiple sub frames disassembled from a frame, and turbo decodes the
received frames. The frame reassembler 118 reassembles, during the call setup, the
output of the turbo decoder 116 into the frames in response to information about the
number of the frames constituting the super frame and the size of the frames or
information about the number of the sub frames disassembled from the input frame
and the size of the sub frames, under the control of the CPU 112.
The turbo encoder described above can be also implemented in the following
method. In this exemplary method, any one of the bit counter 50 and the buffers 54
and 56 for interleaving, shown in FIG. 3, is not required. In frame assembling
operation, the data bits are sequentially stored in the memory (i.e, buffer 54 or 56)
for interleaving as many as the number of the frames to be assembled. To the RSC1
in the turbo encoder, data bits are sequentially output as many as the number of the
non-interleaved assembled frames, and to the RSC2, the data bits are output as
many as the number of the assembled frames which are interleaved to the addresses
of the interleaving address mapper generated by the interleaving processor. In this
manner, it is possible to turbo encode the input data by the data bits as many as the"
size of the frame assembled with one or more frames.
In another example, in the frame assembling operation, the input data bits are
sequentially stored in the memory for interleaving. To the RSC1 in the turbo
encoder, the data bits are sequentially output as many as the size of the
disassembled frames, and to the RSC2, the data bits are interleaved and output as
many as the size of the assembled frames. In this way, it is possible to turbo encode
the input data by the data bits as many as the size of the sub frames disassembled
from one frame.
Accordingly, the turbo channel encoder of FIG. 3 and the turbo channel
decoder of FIG. 6 assemble input data frames into a super frame to encode and
decode the input frames by the super frame unit when the input data frames are too
short, and disassemble an input frame into multiple sub frames to encode and
decode the input frame by the sub frame unit when the input frame is too long,
thereby to increase the efficiency thereof.
As described above, the embodiment of the present invention
disassembles/assembles input frames into sub/super frames of an appropriate length
when the input data frame is very long or short, and then encodes and decodes the
sub/super frames. In this manner, it is possible to reduce the calculations and
memory capacity required in the decoder, while fully securing the performance of
the turbo code encoder.
While the invention has been shown and described with reference to a certain
preferred embodiment 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.
WE CLAIM
A mobile communication system, comprising;
a processor for determining a number and a size of sub frames which can
be generated from the input data frame, according to a size of the input
data frame; and
a turbo encoder for encoding the sub frames individually.
The mobile communication system as claimed in claim 1, wherein the
turbo encoder comprises:
a first constituent encoder for encoding data of the sub frame;
an interleaver for interleaving the data of the sub frame; and
a second constituent encoder, operabiy connected to said interleaver, for
encoding the interleaved data of the sub frame.
The mobile communication as claimed in claim 2, said interleaver includes
an interleaver address mapper for interleaving data of said sub frame.
The mobile communication system as claimed in claim 1, further
comprising a multiplexer for multiplexing the data of the sub frame and
respective outputs of the first and second constituent encoders.
The mobile communication system as claimed in claim 1, further
comprising a channel interleaving an encoded data frame, wherein the
encoded data frame is constructed by concatenating the encoded sub
frames.
The mobile communication system as claimed in claim 1, wherein the
processor determines to segment the input data frame when the size of
the input data frame is 20480 bits.
The mobile communication system as claimed in claim 1, wherein the
number and size of the sub frames is determined by a permissible delay.
The mobile communication system as claimed in claim 1, wherein the
number and size of the sub frames is determined by a permissible error
rate.
The mobile communication system as claimed in claim 1, further wherein
the number and the size of sub frames is determined by a receiver
memory size.
The mobile communication system as claimed in claim 1, wherein the size
of said frames are equal.
The mobile communication system as claimed in claim 1, wherein the size
of the input data frame is variable.
A channel encoding method for a mobile communication system having a
turbo encoder, comprising the steps of:
Segmenting an input data frame into plurality number of sub frames when
the size of the input data frame is greater than a predetermined value;
and
encoding the sub frame individually.
The channel encoding method as claimed in claim 12, wherein the
encoding method comprising the steps of:
a first encoding data of the sub frame to encode the input data;
interleaving the data of the sub frame to generate a interleaved sub
frame; and a second encoding data of the interleaved sub frame.
.The channel encoding method as claimed in claim 12, further comprising
the step of making an encoded input data frame by concatenating output
of the turbo encoder for the input data frame; and
channel interleaving the encoded input data frame.
.The channel encoding method as claimed in claim 12, wherein the input
data frame is segmented when the size of the input data frame is more
than 20480 bits.
The channel encoding method as claimed in claim 12, further wherein the
number and the size of segment sub frames is determined by a
permissible delay.
The channel encoding method as claimed in claim 12, further wherein the
number and the size of the segmented sub frames is determined by an
error rate.
The channel encoding method as claimed in claim 12, further wherein the
number and the size of sub frames is determined by a receiver memory
size.
The channel encoding method as claimed in claim 12, wherein the size of
said sub frames are all same.
The channel encoding method as claimed in claim 12, wherein the size of
the input frame is variable.
A mobile communication system having turbo decoder, comprising:
a decoder for segmenting a received data frame consisting of a plurality of
sub frames into the plurality of sub frames, decoding said segmented sub
frame individually; and
a frame reconstructor for combining output of the decoder into the
original input data frame in accordance with message information about
the sub frames.
The mobile communication system as claimed in claim 21, further
comprising a processor for determining a number and a size of the sub
frames upon receiving the message information about the number and the
size frames, and providing the determined number and size information to
the frame reconstructor.
A channel decoding method in a mobile communication system having
turbo decoder, comprising the steps of:
segmenting a received data frame into a plurality of sub frames according
to received message information.
decoding said sub frames individually; and
combining output of the decoder into the received data frame in response
to said message information about a plurality of the sub frames.
A mobile communication system as claimed in claim 1, having a turbo
encoder, comprising:
a processor for segmenting one input data frame to compose a plurality of
sub frames when the size of a input data frame is more than a
predetermined value;
a turbo encoder for encoding the sub frames individually, wherein the
turbo encoder comprising,
a first constituent encoder for encoding data of the sub frame;
an interleaver for interleaving the data of the sub frame;
a second constituent encoder for encoding output of the interleaver; and
a channel interleaver for interleaving a encoded input data frame, wherein
the encoded input data frame is made by concatenated output of the
turbo encoder for the input data frame.
The mobile communication system as claimed in claim 24, wherein the
predetermined value is 20480 bits.
A mobile communication system as claimed as claimed in claim 24,
comprising:
a multiplexer for multiplexing respective outputs of the first and second
constituent encoders.
The mobile communication system as claimed in claim 24, comprising a
channel interleaver (64) for interleaving said enclosed input data frame,
wherein the encoded input data frame is made by concatenated output of
the turbo encoder for the input data frame.
The mobile communication system as claimed in claim 24, wherein the
size of said sub frames are equal.
The mobile communication system as claimed in claim 24, wherein the
size of the input data frame is variable.
A channel encoding method for a mobile communication system as
claimed in claim 12 having a turbo encoder, comprising the steps of :
comparing a bit number of a input data frame into the turbo encoder with
a predetermined value;
deciding to segment the input data frame into sub frames if the bit
number is more than the predetermined value; and
turbo encoding data of sub frame respectively which is segmented from
the input data frame.
The channel encoding method as claimed in claim 30, wherein the
predetermined value is 20480 bits.
The method as claimed in claim 30, comprising:
a multiplexer for multiplexing respective outputs of the first and second
constituent encoders.
The method as claimed in claim 30, comprising a channel interleaver (64)
for interleaving said encoded input data frame, wherein the encoded input
data frame is made by concatenated output of the turbo encoder for the
input data frame.
The method as claimed in claim 30, wherein the size of said sub frames
are equal.
The method as claimed in claim 30, wherein the size of the input data
frame is variable.
The invention relates to an ultrasonic diagnostic apparatus (100) having an
operation panel (101) provided with a plurality of key switches (1-1,1-2,1-6) for
increasing/decreasing setting values relating to imaging and display of an
ultrasonic image. One or more key switches (1-1, 1-3, 1-5, 1-2, 1-4, 1-6) are
disposed slantingly with respect to the horizontal and vertical directions of the
operation panel (101).

Documents:

00292-cal-1999-abstract.pdf

00292-cal-1999-claims.pdf

00292-cal-1999-correspondence.pdf

00292-cal-1999-description (complete).pdf

00292-cal-1999-drawings.pdf

00292-cal-1999-form 1.pdf

00292-cal-1999-form 18.pdf

00292-cal-1999-form 2.pdf

00292-cal-1999-form 3.pdf

00292-cal-1999-form 5.pdf

00292-cal-1999-letter patent.pdf

00292-cal-1999-pa.pdf

00292-cal-1999-priority document others.pdf

00292-cal-1999-priority document.pdf

00292-cal-1999-reply f.e.r.pdf

292-CAL-1999-FORM-27.pdf

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Patent Number

216330

Indian Patent Application Number

292/CAL/1999

PG Journal Number

11/2008

Publication Date

14-Mar-2008

Grant Date

12-Mar-2008

Date of Filing

31-Mar-1999

Name of Patentee

SAMSUNG ELECTRONICS CO., LTD

Applicant Address

416, MAETAN-DEONG, PALDAL-GU, SUWON-CITY KOREA.

Inventors:

#	Inventor's Name	Inventor's Address
1	CHANG-SOO PARK	72-2, MUNJONG JONG DONG, SONGPA GU SEOUL KOREA
2	JOONG- HO JEONG	63-34 CHAMWAR -DONG SOCHJ-GU SEOUL KOREA
3	HYEON-WOOD LEE	BYECKSAN APT 806-901, KWONSON-DONG KWON SON-GU SUWON SHI KOREA

PCT International Classification Number

D04B 15/48

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	1998-11380	1998-03-31	Republic of Korea