JP2010219949A - Adaptive modulation system, radio communication system, mobile station, base station, and adaptive modulation control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To switch and use a plurality of MCS selection policies in adaptive modulation when switching SISO transmission and MIMO transmission in the radio communication system of an OFDM system. <P>SOLUTION: Adaptive modulation tables 10 storing candidates for a combination of a modulation system and an encoding rate corresponding to a propagation path state are provided for each of the candidates of the number (stream number) of data streams simultaneously transmitted by the SISO transmission or the MIMO transmission, and the adaptive modulation system includes a selection section 11 for selecting the adaptive modulation table 10 corresponding to the stream number from the adaptive modulation tables 10, and a determination part 12 for determining the combination of the modulation system and the encoding rate corresponding to the propagation path state using the selected adaptive modulation table 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an adaptive modulation system, a radio communication system, a mobile station, a base station, and an adaptive modulation control method.

  Conventionally, a wireless communication system combining MIMO (Multiple-Input Multiple-Output) transmission and adaptive modulation is known (see, for example, Non-Patent Document 1).

Authorized by the Communications Research Laboratory, Ministry of Posts and Telecommunications, edited by Shuichi Kajioka, “Wave Summit Course Mobile Communications”, Ohm Corporation, May 1998

  However, the above-described conventional wireless communication system has the following problems.

  In the OFDM (Orthogonal Frequency Division Multiplexing) type wireless communication system, the present inventor, when performing SISO (Single-Input Single-Output) transmission and performing MIMO transmission, Selection when selecting “combination of modulation scheme and error correction coding rate (hereinafter simply referred to as“ coding rate ”)” (MCS (Modulation and Coding Scheme)) according to the channel condition between base stations I found that the policy (MCS selection policy) is different. Specifically, in the case of SISO transmission, if the channel state is the same, the reception quality is better when the modulation level is large and the coding rate is low, whereas in the case of MIMO transmission, If the channel conditions are the same, the reception quality is better when the modulation multi-value number is smaller and the coding rate is higher. However, in the conventional wireless communication system, since there is only one MCS selection policy, a plurality of MCS selection policies cannot be switched and used in adaptive modulation. For this reason, when switching between SISO transmission and MIMO transmission between a mobile station and a base station in an OFDM wireless communication system, the adaptive modulation technique in the conventional wireless communication system cannot cope.

  The present invention has been made in consideration of such circumstances, and its purpose is to switch between a plurality of MCS selection policies in adaptive modulation when switching between SISO transmission and MIMO transmission in an OFDM wireless communication system. Is to be able to do that.

  In order to solve the above-described problems, an adaptive modulation system according to the present invention includes a modulation method and a coding rate of a data stream transmitted by SISO transmission or MIMO transmission in a radio channel in an orthogonal frequency division multiplexing wireless communication system. This is an adaptive modulation system that adaptively changes according to the state, and an adaptive modulation table that stores candidates for combinations of modulation schemes and coding rates corresponding to the propagation path state, and is transmitted simultaneously by SISO transmission or MIMO transmission. A selection unit that is provided corresponding to each of the candidates for the number of streams (number of streams) and that selects an adaptive modulation table corresponding to the number of streams from the adaptive modulation table, and uses the selected adaptive modulation table And a determining unit that determines a combination of a modulation scheme and a coding rate according to a propagation path state.

  In the adaptive modulation system according to the present invention, the adaptive modulation table can be selected such that the modulation scheme having the larger modulation multi-level number can be selected and the combination with the same modulation scheme as the propagation path state is improved. The adaptive modulation table with a high rate and the number of streams of 1 seems to select a modulation scheme having the maximum number of modulation multi-values from among selectable modulation schemes in a certain channel state. On the other hand, in the adaptive modulation table having two or more streams, the modulation scheme having the smallest number of modulation multi-values is selected from the selectable modulation schemes in a certain propagation path state. It is characterized by comprising.

  In the adaptive modulation system according to the present invention, the adaptive modulation table, the selection unit, and the determination unit are provided on both the modulation side and the demodulation side, respectively.

  The radio communication system according to the present invention switches between SISO transmission and MIMO transmission between a mobile station and a base station, and sets the modulation scheme and coding rate of a data stream transmitted by SISO transmission or MIMO transmission to a propagation path state. An orthogonal frequency division multiplexing wireless communication system that performs adaptive change according to the above is provided with any of the adaptive modulation systems described above.

  The mobile station according to the present invention switches between SISO transmission and MIMO transmission between the mobile station and the base station, and changes the modulation scheme and coding rate of the data stream transmitted by SISO transmission or MIMO transmission according to the propagation path state. An adaptive modulation table for storing candidates for combinations of modulation schemes and coding rates corresponding to propagation path states in the mobile station in an orthogonal frequency division multiplexing wireless communication system. Selection for selecting an adaptive modulation table corresponding to the number of streams from among the adaptive modulation tables provided corresponding to each of the number of data streams (number of streams) transmitted simultaneously in SISO transmission or MIMO transmission And a determination unit that determines a combination of a modulation scheme and a coding rate according to a propagation path state using the selected adaptive modulation table , Characterized by comprising a.

  The base station according to the present invention switches the SISO transmission and the MIMO transmission between the mobile station and the base station, and changes the modulation scheme and coding rate of the data stream transmitted by the SISO transmission or the MIMO transmission according to the propagation path state. An adaptive modulation table for storing candidates for combinations of modulation schemes and coding rates corresponding to propagation path conditions in the base station in an orthogonal frequency division multiplexing wireless communication system. Selection for selecting an adaptive modulation table corresponding to the number of streams from among the adaptive modulation tables provided corresponding to each of the number of data streams (number of streams) transmitted simultaneously in SISO transmission or MIMO transmission And a determination unit that determines a combination of a modulation scheme and a coding rate according to a propagation path state using the selected adaptive modulation table , Characterized by comprising a.

  An adaptive modulation control method according to the present invention adaptively changes a modulation method and a coding rate of a data stream transmitted by SISO transmission or MIMO transmission in an orthogonal frequency division multiplexing wireless communication system according to a propagation path state. An adaptive modulation control method for an adaptive modulation system, in which an adaptive modulation table storing candidates for combinations of modulation schemes and coding rates corresponding to propagation path states is transmitted simultaneously by SISO transmission or MIMO transmission A step of selecting an adaptive modulation table corresponding to the number of streams from the adaptive modulation table, wherein the means for selecting an adaptive modulation table is provided corresponding to each of the number of streams (number of streams), and a modulation scheme And a means for determining a combination of coding rates, using the selected adaptive modulation table, according to the propagation path state Characterized in that it comprises determining a combination of tone scheme and a coding rate, a.

  According to the present invention, when switching between SISO transmission and MIMO transmission in an OFDM wireless communication system, there is an effect that a plurality of MCS selection policies can be switched and used in adaptive modulation.

1 is a block diagram showing a configuration of an OFDM wireless communication system according to an embodiment of the present invention. FIG. 2 is a block diagram showing a configuration of an MCS selection unit 217 of the mobile station 200 shown in FIG. It is a block diagram which shows the structure of the MCS extraction part 117 of the base station 100 shown in FIG. 3 is a configuration example of an adaptive modulation table 10. It is a conceptual diagram for demonstrating the structure method of the adaptive modulation table 10 whose number of streams is 1. FIG. It is a conceptual diagram for demonstrating the structure method of the adaptive modulation table 10 whose number of streams is two or more. This is a configuration example in which two adaptive modulation tables are combined into one.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of an OFDM wireless communication system according to an embodiment of the present invention. FIG. 1 shows only a configuration for transmitting user data from the base station 100 to the mobile station 200. Hereinafter, for convenience of explanation, a case where user data is transmitted from the base station 100 to the mobile station 200 will be described as an example, but the same applies to a case where user data is transmitted from the mobile station 200 to the base station 100.

  In FIG. 1, a base station 100 and a mobile station 200 have a plurality of antennas (two in this embodiment), and switch between SISO transmission and MIMO transmission between the base station 100 and the mobile station 200. In the case of SISO transmission, the number of data streams transmitted simultaneously is one. In the case of MIMO transmission, the number of data streams transmitted simultaneously is two. Hereinafter, the number of data streams transmitted simultaneously in SISO transmission or MIMO transmission is referred to as “number of streams”.

  Also, base station 100 and mobile station 200 adaptively change the modulation scheme and coding rate of the data stream transmitted by SISO transmission or MIMO transmission according to the propagation path state between base station 100 and mobile station 200. Adaptive modulation is performed. Examples of the modulation scheme include QPSK (Quadrature Phase Shift Keying), 16QAM (16 Quadrature Amplitude Modulation), and 64 QAM (64 Quadrature Amplitude Modulation). It is done. The modulation multi-level number (unit: bit / modulation symbol) of each modulation method is 2 for QPSK, 4 for 16QAM, and 6 for 64QAM.

First, the base station 100 will be described with reference to FIG.
The user data encoding unit 101 performs error correction encoding on user data at the encoding rate specified by the MCS extracting unit 117. The user data modulation unit 102 modulates the encoded data that has been error correction encoded by the user data encoding unit 101 using the modulation scheme specified by the MCS extraction unit 117. MIMO transmission processing section 103 multiplexes the modulation symbols modulated by user data modulation section 102 by the number of streams designated by stream number extraction section 116. At this time, when the number of streams is 2, two modulation symbols are multiplexed so that MIMO transmission is performed. MIMO transmission processing section 103 outputs a multiplexed data stream in which modulation symbols for the number of streams are multiplexed to mixing section 105.

  Pilot signal generation section 104 generates a known pilot signal in base station 100 and mobile station 200. Mixing section 105 multiplexes the pilot signal and the multiplexed data stream received from MIMO transmission processing section 103. The multiplexed signal is OFDM-modulated by the wireless transmission unit 106 and then wirelessly transmitted on the downlink (link from the base station to the mobile station).

  A signal wirelessly received on the uplink (link from the mobile station to the base station) in the wireless reception unit 110 is separated into a pilot signal and control information by the separator 111. The propagation path information estimation unit 112 estimates the uplink propagation path state using the pilot signal separated by the separator 111. The control information detection unit 113 uses the uplink propagation path information that is the estimation result of the propagation path information estimation unit 112 to compensate for the waveform distortion of the control information due to the propagation path. The compensated control information is demodulated by the control information demodulator 114 and then decoded by the control information decoder 115.

  The stream number extraction unit 116 extracts the number of streams (for downlink next data transmission) sent from the mobile station 200 from the signal decoded by the control information decoding unit 115. The stream number extraction unit 116 designates the extracted number of streams to the MIMO transmission processing unit 103 and the MCS extraction unit 117 as the number of streams for the next data transmission.

  The MCS extraction unit 117 extracts the MCS number (for downlink next data transmission) sent from the mobile station 200 from the signal decoded by the control information decoding unit 115. Based on the extracted MCS number and the number of streams specified by the stream number extraction unit 116, the MCS extraction unit 117 determines a combination (MCS) of a modulation scheme and a coding rate. Details of the MCS extraction unit 117 will be described later. The MCS extraction unit 117 designates the determined coding rate to the user data coding unit 101 as the coding rate for the next data transmission. Similarly, the MCS extraction unit 117 designates the determined modulation method to the user data modulation unit 102 as the modulation method for the next data transmission.

Next, the mobile station 200 will be described with reference to FIG.
A signal wirelessly received on the downlink by the wireless reception unit 210 is OFDM demodulated and then separated into a pilot signal and user data by the separator 211. The propagation path information estimation unit 212 estimates the downlink propagation path state using the pilot signal separated by the separator 211. The MIMO detection unit 213 uses the downlink propagation path information, which is the estimation result of the propagation path information estimation unit 212, from the user data separated by the separator 211, for the number of streams specified by the stream number extraction unit 216. Separate data streams. Thereby, each data stream mixed in the propagation path is separated.

  The user data demodulator 214 demodulates each data stream separated by the MIMO detector 213 using the modulation scheme specified by the MCS selector 217. User data decoding section 215 decodes the demodulated data demodulated by user data demodulation section 214 at the coding rate specified by MCS selection section 217.

  The number-of-streams selection unit 216 selects the number of streams for the next data transmission from among the candidates for the number of streams, using the downlink channel information that is the estimation result of the channel information estimation unit 212. Specifically, the stream number selection unit 216 calculates the rank number of the propagation path matrix or the correlation value of the propagation path information between the data streams by performing a matrix operation on the propagation path information, and determines the number of streams based on the calculation result. Select. The number-of-streams selection unit 216 specifies the number of selected streams as the number of streams for the next data transmission to the MIMO detection unit 213, the MCS selection unit 217, and the control information encoding unit 201.

  Based on the downlink channel information that is the estimation result of the channel information estimation unit 212 and the number of streams specified by the stream number extraction unit 216, the MCS selection unit 217 combines the modulation scheme and the coding rate (MCS). To decide. Details of the MCS selection unit 217 will be described later. The MCS selection unit 217 designates the determined modulation method to the user data demodulation unit 214 as the modulation method for the next data transmission. Similarly, the MCS selection unit 217 designates the determined coding rate to the user data decoding unit 215 as the coding rate for the next data transmission. Similarly, the MCS selection unit 217 specifies the MCS number indicating the determined MCS to the control information encoding unit 201 as the MCS number for the next data transmission.

  The control information encoding unit 201 performs error correction encoding on the MCS number specified by the MCS selection unit 217 and the number of streams specified by the stream number selection unit 216. The control information modulation unit 202 modulates the encoded data that has been error correction encoded by the control information encoding unit 201. The pilot signal generation unit 204 generates a known pilot signal in the base station 100 and the mobile station 200. Mixing section 205 multiplexes the pilot signal and the modulation data from control information modulation section 202. The multiplexed signal is wirelessly transmitted on the uplink by the wireless transmission unit 206. Thus, the base station 100 is notified of the MCS number and the number of streams for the next data transmission.

  FIG. 2 is a block diagram showing a configuration of MCS selection section 217 of mobile station 200 shown in FIG. In FIG. 2, the MCS selection unit 217 includes a plurality of adaptive modulation tables 10, a selection unit 11, an MCS determination unit 12, and an SNR calculation unit 13.

  The adaptive modulation table 10 is provided for each of the candidates for the number of data streams (number of streams) transmitted simultaneously in SISO transmission or MIMO transmission. In the present embodiment, as shown in FIG. 2, two adaptive modulation tables 10 corresponding to each of “1” and “2”, which are candidates for the number of streams, are provided.

The adaptive modulation table 10 stores MCS candidates corresponding to propagation path conditions. FIG. 4 is a configuration example of the adaptive modulation table 10. In FIG. 4, the adaptive modulation table 10 stores a set of MCS number, modulation method name, coding rate, band efficiency, and signal-to-noise power ratio for each MCS. In the present embodiment, the signal-to-noise power ratio (SNR) is used as a measure representing the quality of the propagation path state. Band efficiency (unit: bits / modulation symbol) represents how many bits of information can be transmitted per modulation symbol, and is calculated by the following equation.
Band efficiency = number of modulation multi-value x coding rate

  In the adaptive modulation table 10, as the SNR (propagation channel state) is improved, the modulation scheme with the larger modulation multi-level number can be selected and the coding rate that can be combined with the same modulation scheme increases. . For example, the better the SNR in FIG. 4, the more QPSK (modulation multilevel number is 2) to 16QAM (modulation multilevel number is 4), and 16QAM (modulation multilevel number is 4) to 64QAM (modulation multilevel number is 6), the modulation scheme with the larger modulation multi-value number can be selected. Further, as the SNR in FIG. 4 is improved, the coding rate that can be combined with the same modulation method, for example, the coding rate that can be combined with QPSK is “1/12” to “7/12”. To be high.

  The selection unit 11 selects the adaptive modulation table 10 corresponding to the number of streams specified from the stream number extraction unit 216. Specifically, when the number of streams designated by the stream number extraction unit 216 is “1”, the selection unit 11 connects the adaptive modulation table 10 with the number of streams 1 and the MCS determination unit 12. Accordingly, the MCS determination unit 12 can refer to the adaptive modulation table 10 in which the number of streams is 1. In addition, when the number of streams specified by the stream number extraction unit 216 is “2”, the selection unit 11 connects the adaptive modulation table 10 with the number of streams 2 and the MCS determination unit 12. Accordingly, the MCS determination unit 12 can refer to the adaptive modulation table 10 in which the number of streams is 2.

  The SNR calculation unit 13 calculates the SNR based on the downlink propagation path information that is the estimation result of the propagation path information estimation unit 212.

  The MCS determination unit 12 refers to the adaptive modulation table 10 of the selection result by the selection unit 11 and selects the MCS having the maximum bandwidth efficiency from among the MCSs that satisfy the SNR of the calculation result of the SNR calculation unit 13. For example, when the SNR is 9 dB, MCSs with MCS numbers from 0 to 6 in FIG. 4 can be selected, and the MCS with the MCS number “6” having the maximum bandwidth efficiency is selected. The MCS determination unit 12 reads the MCS number of the selected MCS, the name of the modulation scheme, and the coding rate from the adaptive modulation table 10. The MCS determination unit 12 designates the MCS number, the modulation method, and the coding rate for the next data transmission to each predetermined unit according to the MCS number read from the adaptive modulation table 10, the name of the modulation method, and the coding rate.

  FIG. 3 is a block diagram showing a configuration of MCS extraction section 117 of base station 100 shown in FIG. 3, parts corresponding to the MCS selection unit 217 shown in FIG. The MCS extraction unit 117 includes an MCS number extraction unit 20 instead of the SNR calculation unit 13 of the MCS selection unit 217.

  The MCS extraction unit 117 of the base station 100 has the same as the adaptive modulation table 10 included in the MCS selection unit 217 of the mobile station 200. Therefore, in the present embodiment, as shown in FIGS. 2 and 3, two adaptive modulation tables 10 corresponding to each of the stream number candidates “1” and “2” are included in the base station 100. The MCS extraction unit 117 and the MCS selection unit 217 of the mobile station 200 are provided in common.

  The selection unit 11 selects the adaptive modulation table 10 corresponding to the number of streams designated from the stream number extraction unit 116. This selection operation is the same as that of the MCS selection unit 217 of the mobile station 200.

  The MCS number extraction unit 20 extracts the MCS number sent from the mobile station 200 from the signal decoded by the control information decoding unit 115. The MCS determination unit 12 refers to the adaptive modulation table 10 of the selection result by the selection unit 11 and selects the MCS of the MCS number extracted from the MCS number extraction unit 20. The MCS determination unit 12 reads the name of the selected MCS modulation scheme and the coding rate from the adaptive modulation table 10. The MCS determination unit 12 designates the modulation scheme and coding rate for the next data transmission to each predetermined unit according to the modulation scheme name and coding rate read from the adaptive modulation table 10.

  5 and 6 are conceptual diagrams for explaining a method of configuring the adaptive modulation table 10 according to the present embodiment. FIG. 5 is a conceptual diagram for explaining a configuration method of the adaptive modulation table 10 in which the number of streams is 1, and FIG. 6 is a conceptual diagram for explaining a configuration method of the adaptive modulation table 10 in which the number of streams is 2 or more. It is.

[When the number of streams is 1 (SISO transmission)]
When the number of streams is 1, it is SISO transmission. In the case of SISO transmission in the OFDM wireless communication system, the present inventor has found that the reception quality is better when the modulation multi-value number is larger and the coding rate is lower if the channel state is the same. . In other words, the modulation scheme with the larger modulation multi-level number is used rather than the modulation scheme with the smaller modulation multi-level number being used while increasing the coding rate combined with the modulation scheme as the propagation path condition is improved. As soon as a selectable channel state is reached (the coding rate at this time is lower than the coding rate of the modulation scheme with the smaller modulation multilevel number), the modulation scheme with the larger modulation multilevel number is switched. The reception quality is better. Based on this knowledge, the adaptive modulation table 10 with the number of streams is configured so that the modulation scheme having the maximum number of modulation multi-values is selected from the selectable modulation schemes in a certain propagation path state.

  In the example of FIG. 5, as the SNR improves, the 16QAM can be selected as soon as the SNR capable of selecting 16QAM is reached, from QPSK having the smallest number of modulation multivalues to 16QAM having the largest number of modulation multivalues. Then, 64QAM can be selected as soon as the SNR capable of selecting 64QAM is reached from 16QAM to 64QAM having a larger modulation multi-level number. In the same modulation system, as the SNR improves, the coding rate that can be combined increases stepwise. In the example of FIG. 5, as the SNR improves, QPSK is in four stages from # 0 to # 3, 16QAM is in two stages from # 4 to # 5, and 64QAM is in five stages from # 6 to # 10. The coding rate that can be combined with each other is increased. The SNR range corresponding to each stage from # 0 to # 10 in FIG. 5 is uniformly the same. Thereby, the selectable SNR range of QPSK remains in four stages from # 0 to # 3. The selectable SNR range of 16QAM remains in two stages from # 4 to # 5 from the selectable SNR of 16QAM. On the other hand, the selectable SNR range of 64QAM is very large from the selectable SNR of 64QAM to five stages from # 6 to # 10.

[When the number of streams is 2 or more (MIMO transmission)]
When the number of streams is 2 or more, it is MIMO transmission. The present inventor has found that, in the case of MIMO transmission in an OFDM wireless communication system, the reception quality is better when the modulation multi-value number is smaller and the coding rate is higher if the channel state is the same. . In other words, as soon as the channel state in which the modulation scheme with the larger modulation level is selectable is reached, the coding rate is set lower than the coding rate of the modulation scheme with the lower modulation level. Rather than switching to the higher modulation scheme, the reception quality is better if the modulation scheme with the lower modulation multi-level number is used continuously while increasing the coding rate combined with the modulation scheme as the propagation path condition improves. Get better. Based on this knowledge, the adaptive modulation table 10 having the number of streams of 2 or more is configured so that the modulation scheme having the smallest number of modulation multi-values is selected from the selectable modulation schemes in a certain propagation path state. .

  In the example of FIG. 6, even when the SNR (step # 4) at which 16QAM can be selected is reached, 16QAM is not selectable, and QPSK with the smallest number of modulation multilevels is selected. Then, 16QAM can be selected only after the QPSK encoding rate cannot be increased (# 6). Similarly, even when the SNR (step # 6) at which 64QAM can be selected is reached, 64QAM is not selectable, and the 16QAM having the smaller modulation multilevel number is selected. Then, 64QAM can be selected only after the 16QAM encoding rate cannot be increased (# 8). As a result, the selectable SNR range of QPSK is as large as six steps from # 0 to # 5. On the other hand, the selectable SNR range of 16QAM remains in two stages from # 6 to # 7. The selectable SNR range of 64QAM remains in three steps from # 8 to # 10.

As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the specific structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.
For example, a plurality of adaptive modulation tables may be combined into one. FIG. 7 is a configuration example in which two adaptive modulation tables are combined into one. In the example of FIG. 7, the MCS number has the number of streams in the first digit. As a result, the number of streams corresponding to the MCS can be identified by the first digit of the MCS number.

  In the above embodiment, the mobile station 200 (reception side) selects the number of streams and the MCS, but the mobile station 200 (reception side) sends the propagation path information to the base station 100 (transmission side) The base station 100 (transmission side) may select the number of streams and the MCS. In this case, the base station 100 (transmission side) includes the number of streams and the MCS number in the control information and transmits simultaneously with the data, and the mobile station 200 (reception side) extracts the number of streams and the MCS number included in the control information, The adaptive modulation table and MCS are selected using the number of streams and the MCS number, and data is demodulated and decoded.

  In the above-described embodiment, the number of antennas included in the base station 100 and the mobile station 200 is two and the number of streams is two, “1” and “2”. However, the number of streams is three and the number of streams is three or more. In addition to “1” and “2”, an integer of “3” or more corresponding to the number of antennas may be added. For example, when the number of antennas is 4, the number of stream candidates is “1”, “2”, “3”, and “4”, and the number of SISO transmission streams is 1, but the MIMO transmission stream is 1 The number can be anywhere from 2 to 4.

  According to the above-described embodiment, when switching between SISO transmission and MIMO transmission in an OFDM wireless communication system, there is an effect that a plurality of MCS selection policies can be switched and used in adaptive modulation. As a result, although the MCS suitable for the SISO transmission and the MCS suitable for the MIMO transmission are different even in the same propagation path state, the MCS suitable for each of the SISO transmission and the MIMO transmission can be used. As a result, a significant performance improvement can be expected in an OFDM wireless communication system.

  Further, according to the above-described embodiment, the adaptive modulation table 10, the selection unit 11, and the MCS determination unit 12 are provided in both the base station 100 and the mobile station 200, so that the mobile station 200 transmits to the base station 100. The amount of information can be reduced.

DESCRIPTION OF SYMBOLS 10 ... Adaptive modulation table, 11 ... Selection part, 12 ... MCS determination part, 13 ... SNR calculation part

Claims (7)

In an orthogonal frequency division multiplexing wireless communication system, an adaptive modulation system that adaptively changes a modulation scheme and a coding rate of a data stream transmitted by SISO transmission or MIMO transmission according to a propagation path state,
An adaptive modulation table that stores candidates for combinations of modulation schemes and coding rates corresponding to propagation path conditions corresponds to each of the candidates for the number of data streams (number of streams) transmitted simultaneously in SISO transmission or MIMO transmission. Provided,
A selection unit that selects an adaptive modulation table corresponding to the number of streams from the adaptive modulation table;
A determination unit that determines a combination of a modulation scheme and a coding rate according to a propagation path state using the selected adaptive modulation table;
An adaptive modulation system comprising: The adaptive modulation table is such that as the propagation path state is improved, a modulation scheme with a larger modulation multi-value number can be selected, and a coding rate that can be combined with the same modulation scheme increases.
The adaptive modulation table in which the number of streams is 1 is configured such that a modulation scheme having the maximum number of modulation multi-values is selected from among selectable modulation schemes in a certain propagation path state.
On the other hand, the adaptive modulation table in which the number of streams is 2 or more is configured such that a modulation scheme with the smallest number of modulation multi-values is selected from among selectable modulation schemes in a certain propagation path state.
The adaptive modulation system according to claim 1.   The adaptive modulation system according to claim 1, wherein the adaptive modulation table, the selection unit, and the determination unit are provided on both a modulation side and a demodulation side, respectively. Switching between SISO transmission and MIMO transmission between a mobile station and a base station, and adaptively changing the modulation scheme and coding rate of a data stream transmitted by SISO transmission or MIMO transmission according to the propagation path state; In an orthogonal frequency division multiplexing wireless communication system,
A wireless communication system comprising the adaptive modulation system according to any one of claims 1 to 3. Switching between SISO transmission and MIMO transmission between a mobile station and a base station, and adaptively changing the modulation scheme and coding rate of a data stream transmitted by SISO transmission or MIMO transmission according to the propagation path state; In the mobile station in the orthogonal frequency division multiplexing wireless communication system,
An adaptive modulation table that stores candidates for combinations of modulation schemes and coding rates corresponding to propagation path conditions corresponds to each of the candidates for the number of data streams (number of streams) transmitted simultaneously in SISO transmission or MIMO transmission. Provided,
A selection unit that selects an adaptive modulation table corresponding to the number of streams from the adaptive modulation table;
A determination unit that determines a combination of a modulation scheme and a coding rate according to a propagation path state using the selected adaptive modulation table;
A mobile station characterized by comprising: Switching between SISO transmission and MIMO transmission between a mobile station and a base station, and adaptively changing the modulation scheme and coding rate of a data stream transmitted by SISO transmission or MIMO transmission according to the propagation path state; In the orthogonal frequency division multiplexing wireless communication system, in the base station,
An adaptive modulation table that stores candidates for combinations of modulation schemes and coding rates corresponding to propagation path conditions corresponds to each of the candidates for the number of data streams (number of streams) transmitted simultaneously in SISO transmission or MIMO transmission. Provided,
A selection unit that selects an adaptive modulation table corresponding to the number of streams from the adaptive modulation table;
A determination unit that determines a combination of a modulation scheme and a coding rate according to a propagation path state using the selected adaptive modulation table;
A base station characterized by comprising: Adaptive modulation control method in adaptive modulation system for adaptively changing modulation scheme and coding rate of data stream transmitted by SISO transmission or MIMO transmission according to orthogonal frequency division multiplexing wireless communication system Because
An adaptive modulation table that stores candidates for combinations of modulation schemes and coding rates corresponding to propagation path conditions corresponds to each of the candidates for the number of data streams (number of streams) transmitted simultaneously in SISO transmission or MIMO transmission. Provided
Means for selecting an adaptive modulation table, selecting an adaptive modulation table corresponding to the number of streams from the adaptive modulation table;
Means for determining a combination of a modulation scheme and a coding rate, using the selected adaptive modulation table, determining a combination of a modulation scheme and a coding rate according to a propagation path state;
An adaptive modulation control method comprising:

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