JP2008066778A - Wireless communication system and wireless communication terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow a plurality of wireless communication terminals of a wireless communication system, which uses a frequency-division multiplex (FDM) system in combination, to speedily receive transmission of the same contents from one base station device to multiple terminals according to respective reception states. <P>SOLUTION: A wireless communication terminal measures down reception quality (step S1), and makes settings adaptive to a fast rate and performs demodulation and decoding (steps S3 and S4) when reception at the fast transmission rate is possible ("YES" at a step S2). When the decoding at the fast rate is judged to be impossible or to have failure ("NO" at a step S2 or S5), demodulation and decoding with settings adaptive to an intermediate rate are performed (steps S7 and S8) on condition that reception at the intermediate transmission rate is possible ("YES" at a step S6). When the decoding at the intermediate rate is judged to be impossible or to have failure ("NO" at a step S6 or S9), demodulation and decoding are performed with settings adaptive to a slow transmission rate (steps S10 and S11). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radio communication system and a radio communication terminal, and more particularly to a radio communication system including a base station apparatus and a radio communication terminal in the configuration and the radio communication terminal.

  In recent years, due to the spread of the Internet and the like, there has been a demand for realization of high-speed data communication even in wireless communication including mobile communication, and as one of the responses to this demand, a service of a wireless system using adaptive modulation technology has been started. . As an example, a system based on 1xEV-DO (Evolution Data Only), which is a technical specification included in one standard (cdma2000) of a cellular phone system that applies code division multiple access (CDMA) technology, is known.

  In the 1xEV-DO system, a wireless communication terminal receives a pilot signal or the like from a base station apparatus, measures downlink reception quality, and selects a data transmission method in the downlink based on the measurement result for the base station apparatus. To request. The base station apparatus receives this request and selects a data transmission method for the wireless communication terminal. By this method, when the reception state of the wireless communication terminal is good, a high transmission rate is used even if the error resistance is low, and when the reception state of the wireless communication terminal is not good, the error resistance is high even if it is low. A transmission rate can be used.

  The wireless communication terminal holds a table for selecting a transmission rate with high accuracy obtained by adding prediction to statistical data such as a data transmission error rate in the downlink. The wireless communication terminal refers to the table and requests the base station apparatus to select the data transmission method as described above. As a result, it is possible to select an appropriate transmission rate corresponding to the downlink reception quality.

  The transmission method is represented by a transmission format including a combination of a coding rate and a modulation method corresponding to the transmission rate. For example, the 1xEV-DO system described above is represented as shown in FIG. Note that a method for adjusting the coding rate by periodically removing or inserting bits in a coded bit string is known (see, for example, Non-Patent Document 1).

  Based on the table shown in FIG. 14, for a wireless communication terminal having a low reception quality, for example, a modulation scheme QPSK (Quadrature Phase Shift Keying), a transmission scheme with a coding rate of 1/5 may be selected. it can. On the other hand, for a radio communication terminal having a high reception quality, for example, a modulation scheme 16QAM (Quadrature Amplitude Modulation) and a transmission scheme with a coding rate of two-thirds can be selected.

  In the downlink data communication of the 1xEV-DO system described above, time division multiplexing is performed by dividing the time into slots each having a width of 1/600 second and the base station apparatus assigning each slot to each associated wireless communication terminal. An access (Time Division Multiple Access, abbreviated as TDMA) system is used. Further, data to be transmitted to all the associated wireless communication terminals, such as certain types of broadcast information, is transmitted in a predetermined slot assigned for common use. The transmission rate is set to the lowest 38.4 kbps or 76.8 kbps shown in FIG. 14 in consideration of the wireless communication terminal in a state where the reception quality is low.

  A technique related to a device that performs multicast transmission to a plurality of subscriber devices belonging to the same group is known (see, for example, Patent Document 1). Here, multicast transmission refers to transmission in communication with a plurality of specific counterparts (see, for example, Non-Patent Document 2). According to the technique disclosed in Patent Document 1, the multicast transmission timing and transmission format are set so that a subscriber apparatus having the lowest reception quality among a plurality of subscriber apparatuses belonging to the same group can receive. It is stated that it will be adjusted.

A technique is known in which an information distribution apparatus distributes the same multicast information according to a plurality of different transmission conditions, and a wireless communication terminal receives multicast information distributed under any transmission condition (see, for example, Patent Document 2). .) According to the technique disclosed in Patent Document 2, it is described that each of a plurality of wireless communication terminals can receive multicast information while maintaining good reception quality.
JP 2005-525720 Gazette (2nd, 8th, 9th pages, FIG. 2) JP 2001-320324 A (2nd, 6th to 8th pages, FIG. 14) Tachikawa (supervised) “W-CDMA mobile communication system”, Maruzen, Tokyo, June 2001, page 51 The Institute of Electronics, Information and Communication Engineers, “Encyclopedia Electronic Information Communication Handbook”, Ohmsha, Tokyo, November 1998, page 885

  As in the 1xEV-DO system described above, in the method for determining the transmission rate for multi-terminal transmission based on a wireless communication terminal in which the reception quality is low, the reception time of the wireless communication terminal in which the reception quality is high There is a problem that is unnecessarily long. The technique disclosed in Patent Document 1 described above is intended to adjust the multicast transmission timing and transmission format on the basis of the subscriber apparatus having the lowest reception quality, and thus cannot solve the above problem. .

  The technique disclosed in Patent Document 2 described above selects a spread spectrum processing gain, a combination of spreading codes or a modulation scheme as a multicast information transmission condition, and assigns multicast information given different transmission conditions to different time slots. It is. This technique is understood to be based on a code division multiple access (CDMA) system applied to a so-called third generation mobile phone.

  On the other hand, a technique of orthogonal frequency division multiplexing (abbreviated as OFDM), which is applied to a wireless local area network (wireless LAN) or is being studied for application to a so-called next-generation mobile phone, is known. It has been. The technique disclosed in Patent Document 2 described above has a problem that it cannot be applied to a system that divides and uses a frequency band like OFDM.

  For multicast transmission, transmission in communication with a plurality of unspecified partners is called broadcast transmission (for example, see Non-Patent Document 2). Hereinafter, multicast transmission and broadcast transmission performed from a base station apparatus to a plurality of wireless communication terminals are collectively referred to as multi-terminal transmission.

  The present invention has been made to solve the above problem, and in a wireless communication system using a combination of a frequency division multiplexing (FDM) system including OFDM, a plurality of wireless communication terminals are identical from one base station apparatus. It is an object of the present invention to provide a radio communication system and a radio communication terminal capable of promptly receiving a content-to-multi-terminal transmission according to each reception situation.

  In order to achieve the above object, the wireless communication system of the present invention assigns a combination of a frequency range and a time range for each data unit and can transmit from the base station apparatus to the wireless communication terminal. In the base station apparatus, the multi-terminal transmission signal generated based on a transmission format corresponding to each of a plurality of transmission rates determined for multi-terminal transmission is determined for the multi-terminal transmission. And transmitting to the wireless communication terminal in a combination of a frequency range and a time range given for each of the plurality of transmission rates, and the wireless communication terminal transmits a plurality of transmission rates determined for the multi-terminal transmission. 1 is selected, and the multi-terminal transmission signal transmitted from the base station apparatus is transmitted in the frequency range and time range given to the selected transmission rate. Received based on the transmission format corresponding to the transmission rate and said selected at registration saw, characterized by demodulating and decoding.

  The radio communication terminal according to the present invention is a radio communication terminal capable of receiving a signal transmitted from a base station apparatus in a combination of a frequency range and a time range assigned to each data unit, the base station A frequency range generated by a device based on a transmission format corresponding to each of a plurality of transmission rates determined for multi-terminal transmission and given for each of the plurality of transmission rates determined for multi-terminal transmission And receiving means capable of receiving, demodulating and decoding the transmission signal for multiple terminals transmitted in a combination of time ranges, and selecting one of a plurality of transmission rates determined for the multiple terminal transmission, The multi-terminal transmission signal transmitted from the base station device is a combination of a frequency range and a time range given to the selected transmission rate. Based on the transmission format corresponding to the-option the transmission rate received by the receiving means, characterized in that a control means for controlling so as to demodulate and decoding.

  According to the present invention, in a wireless communication system that performs communication by assigning a combination of a frequency range and a time range for each data unit, a plurality of wireless communication terminals perform the same content-to-multiple terminal transmissions transmitted from the base station apparatus. Reception can be performed according to the state of each reception quality.

  Embodiments of the present invention will be described below with reference to the drawings.

  Embodiment 1 of the present invention will be described below with reference to FIGS. FIG. 1 is a conceptual diagram of a wireless communication system 1 according to a first embodiment of the present invention. The wireless communication system 1 includes a base station device 2 and wireless communication terminals 3, 3a, 3b, and 3c. In the wireless communication system 1, it is assumed that packet-type data communication can be performed by assigning a combination of a frequency range and a time range for each data unit.

  Of the configurations of the wireless communication terminals 3 to 3c, the parts according to the present invention are the same. The wireless communication system 1 may include another wireless communication terminal (not shown) that includes the same part of the wireless communication terminal 3 as that of the present invention. The base station apparatus 2 is assumed to be connected to a mobile communication network (not shown).

  FIG. 2 is a block diagram of the base station apparatus 2. The base station device 2 includes a memory 20 that can store data (downlink transmission data) transmitted to the wireless communication terminal 3 or the like. The base station apparatus 2 can obtain downlink transmission data from the connected mobile communication network and store it in the memory 20. The base station apparatus 2 includes an error detection code adding unit 21. The error detection code adding unit 21 adds an error detection code (for example, a parity bit string) to a bit string composed of downlink transmission data read from the memory 20.

  The base station apparatus 2 includes an encoding unit 22. The encoding unit 22 performs, for example, turbo encoding on the bit string in which the error detection code is added to the bit string of the downlink transmission data. The base station apparatus 2 includes a coding rate adjustment unit 23 and a control unit 24. The coding rate adjusting unit 23 converts the coding rate of the output bit string encoded by the encoding unit 22 by, for example, a method of periodic bit removal (period) or periodic bit insertion (repetition). Adjust and set. The control unit 24 instructs the coding rate adjustment unit 23 on the coding rate to be set (in FIG. 2, the instruction from the control unit 24 is represented by a broken line with an arrow; the same applies hereinafter).

  The base station apparatus 2 includes a modulation unit 25. The modulation unit 25 is instructed by the control unit 24 about the modulation method. The modulation unit 25 generates a transmission signal sequence (baseband signal) that represents the bit sequence output from the coding rate adjustment unit 23 based on the set modulation scheme. The base station apparatus 2 includes a transmission mapping unit 26. The transmission mapping unit 26 assigns a combination (which may be plural) of the frequency range and time range instructed by the control unit 24 to the transmission signal sequence for each unit of downlink transmission data.

  The base station apparatus 2 includes a radio unit 27 and an antenna 28. The radio unit 27 generates a modulated wave (downlink transmission wave) from the transmission signal sequence output from the transmission mapping unit 26, and transmits the modulated wave (downlink transmission wave) from the antenna 28 in the time range and frequency range assigned to each unit of downlink transmission data. .

  The radio unit 27 receives a signal wave transmitted from the radio communication terminal 3 or the like including downlink quality information (downlink quality information) via the antenna 28. The radio unit 27 extracts downlink quality information from the signal wave and sends it to the control unit 24. Based on the downlink quality information of each wireless communication terminal, the control unit 24 sets the coding rate, modulation scheme, and combination of time range and frequency range in transmission to each wireless communication terminal, the coding rate adjustment unit 23, and the modulation unit 25. And the transmission mapping unit 27 as described above. The base station apparatus 2 may include other configurations not shown in FIG.

  FIG. 3 is a block diagram of the wireless communication terminal 3. The wireless communication terminal 3 includes an antenna 30 and a wireless unit 31. The radio unit 31 receives a downlink transmission wave transmitted from the base station device 2 via the antenna 30.

  The wireless communication terminal 3 includes a control unit 32 and a demodulation unit 33. The control unit 32 includes a device (single or plural) such as a microprocessor or a digital signal processor (DSP). The control unit 32 monitors and controls the entire wireless communication terminal 3 and each unit. The control unit 32 includes a transmission format information acquisition unit 32a, a mapping information acquisition unit 32b, and a data selection unit 32c as subordinate components. These lower components 32a to 32c can be realized as function blocks by software, for example. The processing of the control unit 32 including the operations of these lower components 32a to 32c will be described later.

  The demodulator 33 receives an instruction from the control unit 32 regarding the time range, frequency range, and modulation method assigned to each unit of downlink transmission data (in FIG. 3, the instruction from the control unit 32 is represented by a broken line with an arrow. Similarly, in the instructed time range and frequency range, the received signal sequence for each unit of downlink transmission data is demodulated from the output signal of the radio unit 31. The control unit 32 can obtain the soft decision value information of the received signal sequence after demodulation from the demodulation unit 33 and store it in the memory 37.

  The wireless communication terminal 3 includes a coding rate adjustment unit 34. The coding rate adjustment unit 34 receives an instruction from the control unit 32 regarding the coding rate set in the coding rate adjustment unit 23 of the base station apparatus 2, and performs processing corresponding to the received signal sequence (for example, coding) If puncture processing is performed in the rate adjusting unit 23, puncture processing is performed.

  The wireless communication terminal 3 includes a decoding unit 35 and an error detection unit 36. The decoding unit 35 performs decoding (for example, turbo decoding) corresponding to the encoding performed in the encoding unit 22 of the base station apparatus 2 on the output of the coding rate adjustment unit 34. The error detection unit 36 performs error detection on the output of the decoding unit 35 based on the error detection code added by the error detection code addition unit 21 of the base station apparatus 2. The error detection unit 36 sends downlink transmission data including the presence / absence of an error and the decoded information bit string to the control unit 32.

  The wireless communication terminal 3 includes a memory 37 and a user interface unit 38. The control unit 32 can store the received downlink transmission data in the memory 37. The memory 37 can store data (uplink transmission data) transmitted toward the base station apparatus 2. The user interface unit 38 includes a display device and a plurality of key switches. The control unit 32 can display the received downlink transmission data on the display device of the user interface unit 38.

  The wireless communication terminal 3 includes a CIR measurement unit 41. The CIR measurement unit 41 can detect, for example, a pilot signal included in a downlink transmission wave and measure a carrier power to interference power ratio (CIR) in the downlink transmission wave. The CIR measurement unit 41 sends the measured CIR data to the control unit 33. The control unit 32 can generate downlink quality information (downlink quality information) based on the CIR data.

  The wireless communication terminal 3 includes a transmission data generation unit 42. The transmission data generation unit 42 receives the uplink transmission data and the downlink quality information read from the memory 37 by the control unit 32 from the control unit 32, multiplexes them, performs encoding, modulation, etc., and sets the radio unit 31 and the antenna 30. Can be transmitted to the base station apparatus 2. Since processing such as encoding and modulation by the transmission data generating unit 42 is the same as the contents described in the description of the base station apparatus 2, details thereof are omitted.

  With reference to FIG. 4 thru | or FIG. 9, the allocation of the combination of the frequency range for every unit of downlink transmission data and a time range is demonstrated. FIG. 4 is a diagram for explaining a combination of a frequency range and a time range to which the assignment is made (since it is an explanation of the concept, a specific numerical example is omitted). In the wireless communication system 1, one or more predetermined numbers of a series of subcarriers form one subcarrier group in the frequency direction, and one subframe consists of one or more predetermined numbers of symbols in the time direction. A resource block allocated to one radio communication terminal uses one subframe and one subcarrier group as a minimum unit.

  In FIG. 4, “downlink transmission data allocatable time width per unit” and “downlink transmission data allocatable frequency band” are each 10 subframes (identified by symbols a to j) and 10 respectively. Are divided into equal subcarrier groups (identified by reference numerals 0 to 9). The base station apparatus 2 can assign any combination of the above subframes and any subcarrier group (may be plural) for each unit of downlink transmission data.

  Assume that the base station apparatus 2 gives three (low, medium, and high speed) transmission rates to downlink transmission data transmitted to a plurality of terminals. Assume that a coding rate and a modulation scheme corresponding to each of the above three transmission rates are determined in advance. The control unit 24 instructs the coding rate adjustment unit 23 as described above for the coding rate corresponding to the given transmission rate, and the modulation unit corresponding to the given transmission rate as described above. 25.

  The number of combinations of subframes and subcarrier groups required for each unit of downlink transmission data to which each transmission rate is assigned may be smaller as the transmission rate is higher. FIG. 5 is a diagram illustrating the number of combinations of subframes and subcarrier groups required for each unit of downlink transmission data at each transmission rate described above. As shown in FIG. 5, 5 for low speed (represented by hatching with hatching), 3 for medium speed (represented by wire mesh hatching), and 1 for high speed (from lower speed and medium speed) The sub-frame and sub-carrier group combinations are expressed for each unit of downlink transmission data.

  FIG. 6 is a first diagram illustrating allocation of combinations of subframes and subcarrier groups at each transmission rate described above for a unit of downlink transmission data transmitted to a plurality of terminals. In this example, five combinations of subframe a and subcarrier groups 0 to 4 at a low transmission rate, three combinations of subframe a and subcarrier groups 5 to 7 at a medium transmission rate, and high speed One combination of subframe a and subcarrier group 8 is assigned to each transmission rate. The control unit 24 instructs the transmission mapping unit 26 as described above for combinations of subframes and subcarrier groups corresponding to these transmission rates.

  FIG. 7 is a second diagram illustrating assignment of combinations of subframes and subcarrier groups at each transmission rate described above for a unit of downlink transmission data transmitted to a plurality of terminals. In this example, five combinations of subframes a to e and subcarrier group 0 at a low transmission rate, three combinations of subframes f to h and subcarrier group 0 at a medium transmission rate, high speed One combination of subframe i and subcarrier group 0 is assigned at each transmission rate.

  FIG. 8 is a third diagram exemplifying assignment of combinations of subframes and subcarrier groups at each transmission rate described above for a unit of downlink transmission data transmitted to a plurality of terminals. In this example, five combinations of subframes a to e and subcarrier group 0 at a low transmission rate, three combinations of subframes f to h and subcarrier group 1 at a medium transmission rate, Each combination of subframe i and subcarrier group 2 is assigned at the transmission rate of.

  FIG. 9 is a fourth diagram illustrating assignment of combinations of subframes and subcarrier groups at each transmission rate described above for the unit of downlink transmission data transmitted to a plurality of terminals. In this example, five combinations including a combination of subframe a and subcarrier group 2 at a low transmission rate, three combinations including a combination of subframe c and subcarrier group 4 at a medium transmission rate, Each combination of subframe e and subcarrier group 0 is assigned at each transmission rate. In addition, the above-described allocation of combinations of subframes and subcarrier groups at each transmission rate can be arbitrarily performed as long as the necessary number is maintained.

  With reference to FIG. 10, the operation of the wireless communication terminal 3 according to the first embodiment of the present invention will be described. FIG. 10 is a flowchart showing the operation of the wireless communication terminal 3. Before starting the processing according to the first embodiment, the wireless communication terminal 3 transmits and transmits the transmission rate of downlink transmission data transmitted to a plurality of terminals (as described above, low speed, medium speed, and high speed). It is assumed that transmission format information and mapping information for each rate are obtained from the base station apparatus 2. Here, the transmission format information refers to information necessary for demodulating and decoding the coding rate, modulation scheme, and other downlink transmission data. The mapping information refers to allocation information of combinations of subframes and subcarrier groups at the respective transmission rates illustrated in FIGS.

  The transmission format information acquisition unit 32a of the control unit 32 acquires and holds the above transmission format information via, for example, a control channel between the base station apparatus 2 and the wireless communication terminal 3. The mapping information acquisition unit 32b of the control unit 32 acquires and holds the mapping information via the control channel, for example.

  After the start of processing (“START”), the control unit 32 instructs the CIR measurement unit 41 to measure the CIR value of the downlink transmission wave based on, for example, detection of a pilot signal included in the downlink transmission wave, and the reception quality thereof Is evaluated (step S1).

  As a result, when it is evaluated that the reception quality is such that downlink transmission data transmitted to a plurality of terminals at a high transmission rate can be received (“YES” in step S2), the control unit 32 performs mapping information. The demodulator 33 is instructed to assign a combination of subframes and subcarrier groups at a high transmission rate held by the acquisition unit 32b. Further, the control unit 32 instructs the coding rate adjustment unit 34 on the coding rate value at the high transmission rate held by the transmission format information obtaining unit 32a (step S3).

  As described above, the demodulator 33 receives each unit of downlink transmission data from the signal received via the antenna 30 and the radio unit 31 in the time range and frequency range corresponding to the combination of the subframe and the subcarrier group. Demodulate the signal sequence. As described above, the coding rate adjustment unit 34 performs a process corresponding to the coding rate adjustment in the coding rate adjustment unit 23 of the base station apparatus 2 (for example, although it is a redundancy process, it is not limited thereto). The decoding unit 35 performs the above-described decoding on the output of the coding rate adjustment unit 34 (step S4).

  The error detection unit 36 performs the above-described error detection on the output of the decoding unit 35. As a result, if no error is detected, the control unit 32 determines that the reception is completed (“YES” in step S5), and ends the process (“END”).

  When it is evaluated in step S2 that reception quality sufficient to receive downlink transmission data sent at a high transmission rate is not obtained ("NO" in step S2), or an error is detected in step S5. When it is determined that reception has not been completed (“NO” in step S5), whether or not reception is possible at a medium transmission rate is determined based on the reception quality of the downstream transmission wave.

  As a result, when it is evaluated that the reception quality is such that downlink transmission data transmitted to a plurality of terminals can be received at a medium transmission rate (“YES” in step S6), the control unit 32 performs mapping. The demodulator 33 is instructed to assign a combination of subframes and subcarrier groups at a medium transmission rate held by the information acquisition unit 32b. In addition, the control unit 32 instructs the coding rate adjustment unit 34 on the coding rate value at the medium transmission rate held by the transmission format information obtaining unit 32a (step S7).

  Since the processing of step S8 and step S9 following step S7 is the same as the processing of step S4 and step S5 described above except for the difference in transmission rate, description thereof will be omitted. If no error is detected in step S9, the control unit 32 determines that the reception has been completed ("YES" in step S5), and ends the process ("END").

  When it is evaluated in step S6 that reception quality sufficient to receive downlink transmission data transmitted at a medium transmission rate is not obtained ("NO" in step S6), or an error is detected in step S9 When it is determined that the reception has not been completed (“NO” in step S9), the control unit 32 demodulates the allocation of the combination of subframes and subcarrier groups at the low transmission rate held by the mapping information acquisition unit 32b. 33 is instructed. In addition, the control unit 32 instructs the coding rate adjustment unit 34 about the coding rate value at the low transmission rate held by the transmission format information acquisition unit 32a (step S10).

  Since the process of step S11 following step S10 is the same as the process of step S4 or step S8 described above except for the difference in transmission rate, description thereof will be omitted. The control unit 32 ends the process following “S11” (“END”).

  Note that the data selection unit 32c included in the control unit 32 selects downlink transmission data transmitted at any transmission rate and determined to have been received, and stores it in the memory 37 or a user interface unit. The display at 38 is performed.

  According to the first embodiment of the present invention, the wireless communication terminal 3 can receive downlink transmission data transmitted to a plurality of terminals at the highest receivable transmission rate based on the result of measuring the reception quality of the downlink transmission wave. it can. As a result, the problem that the reception time of the wireless communication terminal in a state of high reception quality becomes unnecessarily long is improved.

  Hereinafter, Embodiment 2 of the present invention will be described with reference to FIG. The wireless communication system and the wireless communication terminal according to the second embodiment of the present invention are the same as the wireless communication system 1 and the wireless communication terminal 3 described in the first embodiment, and the drawings referred to in the first embodiment are also referred to as appropriate. FIG. 11 is a flowchart illustrating the operation of the wireless communication terminal 3 according to the second embodiment. As in the case of the first embodiment, before starting the processing according to the second embodiment, the wireless communication terminal 3 stores the transmission rate information of the downlink transmission data transmitted to the plurality of terminals, the transmission format information for each transmission rate, and the mapping information. It is assumed that it is obtained from the station apparatus 2.

  After the start of processing (“START”), the processing from step S21 to step S27 is the same as the processing from step S1 to step S7 in FIG. In step S24, the control unit 32 stores, in the memory 37, the soft decision value information of the received signal sequence after demodulation for the high transmission rate as described above.

  Subsequent to step S27, the demodulator 33 transmits the downlink transmission transmitted at the medium speed transmission rate as described above in the time range and the frequency range corresponding to the combination of the subframe and the subcarrier group at the medium speed transmission rate. The received signal sequence is demodulated from the wave (step S28). In step S28, the control unit 32 stores, in the memory 37, soft decision value information of the received signal sequence after demodulation for the medium transmission rate as described above.

  If the high-speed transmission rate is demodulated in the processing flow up to step S28 ("YES" in step S29), the control unit 32 stores the soft decision value information of the received signal sequence after demodulation for the high-speed transmission rate in the memory. 37, the demodulated received signal sequence and the packet are combined for the medium transmission rate at the output stage of the demodulator 33. Packet combining is known as a technique that contributes to improving packet error rate and throughput characteristics in combination with hybrid automatic repeat request (ARQ) (see, for example, page 49 of Non-Patent Document 1). As described above, the signal sequence after the packet synthesis is processed in the coding rate adjustment unit 34 and decoded in the decoding unit 35 (step S30). Packet combining can further improve the signal power to interference or noise power ratio to reduce errors.

  If the high-speed transmission rate is not demodulated in the processing flow up to step S28 ("NO" in step S29), the coding rate adjustment unit is applied to the reception signal sequence demodulated in step S28 as described above. The process in 34 and the decoding in the decoding unit 35 are performed (step S31). Since the process of step S32 following step S30 or step S31 is the same as the process of step S25, description is abbreviate | omitted.

  The processing in step S33 following “NO” in step S26 or “NO” in step S32 is the same as the processing in step S10 in FIG. Subsequent to step S33, the demodulator 33 starts from the downlink transmission wave transmitted at the low transmission rate as described above in the time range and the frequency range corresponding to the combination of the subframe and the subcarrier group at the low transmission rate. The received signal sequence is demodulated (step S34).

  If demodulation for a high-speed or medium-speed transmission rate is performed in the processing flow up to step S34 (“YES” in step S35), the control unit 32 performs post-demodulation for high-speed, medium-speed, or both transmission rates. The soft decision value information of the received signal sequence is read from the memory 37, and the demodulated received signal sequence and the packet are combined at the output stage of the demodulator 33 for the low transmission rate. As described above, the processing performed by the coding rate adjustment unit 34 and the decoding by the decoding unit 35 are performed on the signal sequence after the packet synthesis (step S36).

  If the high-speed or medium-speed transmission rate is not demodulated in the processing flow up to step S34 ("NO" in step S35), the received signal sequence demodulated in step S34 is as described above. Processing in the coding rate adjustment unit 34 and decoding in the decoding unit 35 are performed (step S37).

  Similar to the case described with reference to FIG. 10, after the processing is completed, the data selection unit 32 c selects the downlink transmission data transmitted at any transmission rate and determined to have been received, and the memory 37. Storage or display on the user interface unit 38.

  According to the second embodiment of the present invention, there is an additional effect that the reception characteristics of the wireless communication terminal can be improved by applying packet combining.

  The third embodiment of the present invention will be described below with reference to FIGS. The wireless communication system and the wireless communication terminal according to the third embodiment of the present invention are the same as the wireless communication system 1 and the wireless communication terminal 3 described in the first embodiment, and the drawings referred to in the first embodiment are also referred to as appropriate. However, the wireless communication terminal 3 according to the third embodiment may not include the CIR measurement unit 41 described with reference to FIG.

  FIG. 12 is a flowchart illustrating the operation of the wireless communication terminal 3 according to the third embodiment. As in the case of the first embodiment, before starting the processing according to the third embodiment, the wireless communication terminal 3 sets the transmission rate information of the downlink transmission data transmitted to the plurality of terminals, the transmission format information for each transmission rate, and the mapping information as a base. It is assumed that it is obtained from the station apparatus 2.

  After the start of processing (“START”), the control unit 32 instructs the demodulation unit 33 to assign a combination of subframes and subcarrier groups at a high transmission rate held by the mapping information acquisition unit 32b. In addition, the control unit 32 instructs the coding rate adjustment unit 34 on the coding rate value at the high transmission rate held by the transmission format information obtaining unit 32a (step S41).

  Note that processing corresponding to steps S1 and S2 in FIG. 10 (measurement of downlink reception quality and branching of processing based on the result) is omitted. Since the process of step S41 thru | or step S43 is the same as the process of step S3 thru | or step S5 of FIG. 10, description is abbreviate | omitted about step S42 and step S43.

  When it is determined in step S43 that an error has been detected and reception has not been completed (“NO” in step S43), the control unit 32 determines the subframe and subcarrier group at the medium speed transmission rate held by the mapping information acquisition unit 32b. Is assigned to the demodulator 33. Further, the control unit 32 instructs the coding rate adjustment unit 34 on the coding rate value at the medium transmission rate held by the transmission format information obtaining unit 32a (step S44).

  Note that the processing corresponding to step S6 in FIG. 10 (the branching of processing based on the result of downlink reception quality measurement) is omitted. Since the process of step S44 thru | or step S46 is the same as the process of step S7 thru | or step S9 of FIG. 10, description is abbreviate | omitted about step S45 and step S46.

  When it is determined in step S46 that an error has been detected and reception has not been completed (“NO” in step S46), the control unit 32 determines the subframe and subcarrier group at the low transmission rate held by the mapping information acquisition unit 32b. The demodulator 33 is instructed to assign combinations. Further, the control unit 32 instructs the coding rate adjustment unit 34 about the coding rate value at the low transmission rate held by the transmission format information obtaining unit 32a (step S47). Since the process of step S47 and step S48 is the same as the process of step S10 and step S11 of FIG. 10, description is abbreviate | omitted about step S48.

  Similar to the case described with reference to FIG. 10, after the processing is completed, the data selection unit 32 c selects the downlink transmission data transmitted at any transmission rate and determined to have been received, and the memory 37. Storage or display on the user interface unit 38.

  According to the processing flow of FIG. 12, if no error is detected in step S43 or step S46, the control unit 32 determines that the reception has been completed (“YES” in step 43 or step S46) and ends the processing. ("END"), demodulation and decoding are not performed under the condition that the transmission rate is lowered. As described above, since the downlink reception quality measurement described with reference to FIG. 10 and the processing branch based on the result are not performed, the processing flow can be simplified.

  FIG. 13 is a flowchart illustrating a modified example of the operation of the wireless communication terminal 3 according to the third embodiment. As in the case of FIG. 12, before starting the processing according to the third embodiment, the wireless communication terminal 3 transmits the transmission rate of downlink transmission data transmitted to a plurality of terminals, the transmission format information for each transmission rate, and the mapping information to the base station. Assume that it is obtained from device 2.

  After the start of processing (“START”), the processing from step S51 to step S54 is the same as the processing from step S41 to step S44 in FIG. In step S52, the control unit 32 stores, in the memory 37, the soft decision value information of the received signal sequence after demodulation for the high transmission rate as described above.

  Subsequent to step S54, the demodulator 33 transmits the downlink transmitted at the medium speed transmission rate as described above in the time range and frequency range corresponding to the combination of the subframe and the subcarrier group at the medium speed transmission rate. The received signal train is demodulated from the wave (step S55). This is the same as the processing in step S28 in FIG. In step S55, the control unit 32 stores, in the memory 37, the soft decision value information of the received signal sequence after demodulation for the medium transmission rate as described above.

  Next, the control unit 32 reads out the soft decision value information of the received signal sequence after demodulation for the high-speed transmission rate from the memory 37, and receives the demodulated reception signal sequence for the medium-speed transmission rate at the output stage of the demodulation unit 33. Packet combining is performed, and the processing in the coding rate adjusting unit 34 and the decoding in the decoding unit 35 are performed on the signal sequence after the packet combining as described above (step S56). This is the same as the process of step S30 in FIG. Since the process of step S57 following step S56 is the same as the process of step S53, description thereof will be omitted.

  The processing in step S58 and step S59 following “NO” in step S57 is the same as the processing in step S33 and step S34 in FIG. Next, the control unit 32 reads out the soft decision value information of the received signal sequence after demodulation for the high-speed and medium-speed transmission rates from the memory 37, and receives the demodulated received signal for the low-speed transmission rate at the output stage of the demodulation unit 33. Causes a sequence and packet composition to be performed. This is the same as the processing in the case of performing packet synthesis with the received signal sequence after demodulation for both the high-speed and medium-speed transmission rates in step S36 of FIG.

  As described above, the signal sequence after the packet synthesis is processed in the coding rate adjusting unit 34 and decoded in the decoding unit 35 (step S60).

  Similar to the case described with reference to FIG. 10, after the processing is completed, the data selection unit 32 c selects the downlink transmission data transmitted at any transmission rate and determined to have been received, and the memory 37. Storage or display on the user interface unit 38. According to the processing flow of FIG. 13, it is possible to improve the reception characteristics of the wireless communication terminal by applying packet synthesis to the processing flow of FIG. 12.

  According to the third embodiment of the present invention, unlike the first or second embodiment, since the downlink reception quality is not measured and the processing based on the result is not branched, the processing flow can be simplified. An effect is obtained. The configurations, connections, processing flows, types and numbers of transmission rates, etc., of the wireless communication system or wireless communication terminal described in the first to third embodiments are examples, and various types are possible without departing from the scope of the present invention. Deformation is possible.

1 is a conceptual diagram of a wireless communication system according to Embodiment 1 of the present invention. 1 is a block diagram of a base station device of a wireless communication system according to a first embodiment. 1 is a block diagram of a wireless communication terminal according to Embodiment 1 of the present invention. The figure explaining the combination of the frequency range and time range which are allocated in Example 1. FIG. FIG. 6 is a diagram illustrating the number of combinations of subframes and subcarrier groups required in the first embodiment. FIG. 3 is a first diagram illustrating assignment of combinations of subframes and subcarrier groups in the first embodiment. FIG. 5 is a second diagram illustrating assignment of combinations of subframes and subcarrier groups in the first embodiment. FIG. 9 is a third diagram illustrating assignment of combinations of subframes and subcarrier groups in the first embodiment. FIG. 4 is a fourth diagram illustrating assignment of combinations of subframes and subcarrier groups in the first embodiment. 3 is a flowchart of the operation of the wireless communication terminal according to the first embodiment. The flowchart of operation | movement of the radio | wireless communication terminal which concerns on Example 2 of this invention. The flowchart of operation | movement of the radio | wireless communication terminal which concerns on Example 3 of this invention. The flowchart of the modification of operation | movement of the radio | wireless communication terminal which concerns on Example 3 of this invention. The figure which illustrates the conventional combination of the transmission format corresponding to a transmission rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wireless communication system 2 Base station apparatus 3 Wireless communication terminal 20, 37 Memory 21 Error detection code addition part 22 Encoding part 23, 34 Encoding rate adjustment part 24, 32 Control part 32a Transmission format information acquisition part 32b Mapping information acquisition part 32c Data selection unit 25 Modulation unit 26 Transmission mapping unit 27, 31 Radio unit 28, 30 Antenna 33 Demodulation unit 35 Decoding unit 36 Error detection unit 38 User interface unit 41 CIR measurement unit 42 Transmission data generation unit

Claims (5)

In a wireless communication system in which a combination of a frequency range and a time range is assigned to each data unit and can be transmitted from the base station apparatus to the wireless communication terminal.
The base station apparatus generates a plurality of terminal transmission signals generated based on a transmission format corresponding to each of a plurality of transmission rates determined for the plurality of terminal transmissions. Transmitting to the wireless communication terminal in a combination of frequency range and time range given for each transmission rate,
The radio communication terminal selects one of a plurality of transmission rates determined for the multi-terminal transmission, and a multi-terminal transmission signal transmitted from the base station apparatus is given to the selected transmission rate. A radio communication system characterized in that reception, demodulation and decoding are performed based on a transmission format corresponding to the selected transmission rate in a combination of a frequency range and a time range. A wireless communication terminal capable of receiving a signal transmitted from a base station apparatus in a combination of a frequency range and a time range allocated for each unit of data,
The base station device generates a transmission format corresponding to each of a plurality of transmission rates determined for multi-terminal transmission, and is provided for each of the plurality of transmission rates determined for the multi-terminal transmission. Receiving means capable of receiving, demodulating, and decoding a multi-terminal transmission signal transmitted in a combination of a frequency range and a time range;
Select one of a plurality of transmission rates determined for the multi-terminal transmission, and a frequency range and a time range given to the multi-terminal transmission signal transmitted from the base station apparatus to the selected transmission rate And a control means for controlling the receiving means to receive, demodulate, and decode based on a transmission format corresponding to the selected transmission rate in the combination.   Evaluation means for evaluating the quality of the signal received by the receiving means is further provided, and the control means is configured to perform transmission to the multi-terminal transmission based on a result of the evaluation means evaluating the quality of the signal received from the base station apparatus. The wireless communication terminal according to claim 2, wherein 1 is selected from a plurality of transmission rates determined as described above.   The control means selects one of a plurality of transmission rates determined for the multi-terminal transmission in descending order, and selects the multi-terminal transmission signal transmitted from the base station apparatus as the selected transmission rate. 3. The receiving means attempts to receive, demodulate and decode the data based on a transmission format corresponding to the selected transmission rate in a combination of frequency range and time range given in FIG. The wireless communication terminal described in 1.   The control means is further configured to synthesize the packet obtained by receiving, demodulating, and decoding the reception signal received from the base station apparatus corresponding to two or more of the plurality of transmission rates. The wireless communication terminal according to any one of claims 2 to 4, wherein the wireless communication terminal is controlled.

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