JP6851223B2 - Wireless communication device and communication method control method - Google Patents

Description

The present invention relates to a wireless communication device and a communication method control method used in a wireless communication system that transmits signals using a plurality of frequency bands.

In a wireless communication system, data is transmitted by a communication method according to the required communication quality. For example, for an application that requires a small transmission delay, a code type and a code length that require a short time for decoding processing in the receiver are selected. Further, for an application that requires a low error rate, a modulation method having a small number of bits per symbol is selected. Alternatively, a low coding rate may be set for an application that requires a low error rate. Further, the number of decoding repetitions in the receiver may be selected according to the required communication quality.

By the way, in recent years, in order to increase the communication capacity, a communication method for transmitting data by simultaneously using a plurality of radio frequency bands has been studied. For example, data may be transmitted using two or more frequency bands of the 920 MHz band, 2.4 GHz band, and 5 GHz band. In a communication method for transmitting data using a plurality of frequency bands, the reception level (RSSI: Received Signal Strength Index) and / or the reception quality (SINR: Signal-to-Interference plus) measured for each frequency band is used. Based on Noise Ratio), a communication method suitable for the required communication quality is selected for each frequency band.

In addition, as a technique for selecting a communication method suitable for the required communication quality, a wireless LAN communication method and a communication channel with a communication terminal of a wireless LAN access point according to the communication status detected for each of a plurality of channels. A method of switching between the above has been proposed (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2011-188122

In the prior art of transmitting data using a plurality of radio frequency bands, a communication method is selected for each frequency band as described above. However, when the communication method is selected for each frequency band, the data transmission efficiency may decrease. Alternatively, the communication quality (for example, transmission delay, error rate) required by the user or application may not be satisfied. That is, in the prior art, it is difficult to achieve both high data transmission efficiency and satisfying the communication quality required by the user or the application in a well-balanced manner.

An object relating to one aspect of the present invention is to improve data transmission efficiency while satisfying the required communication quality.

The wireless communication device of one aspect of the present invention is a wireless communication device used in a wireless communication system that transmits code words using a plurality of frequency bands, and the quality of each frequency band and the use of each frequency band. Based on the available resources, the bit length of the data, the required quality given, the type of code for transmitting the data, the length of the information bits in the code word for transmitting the data, the coding of the code word. A control unit that determines the rate, the modulation method of each frequency band, a encoder that encodes the data to generate a code word according to the type of code and the length of the information bit determined by the control unit, and the above. A coding rate adjuster that adjusts the coding rate of the code word generated by the coding device according to the coding rate determined by the control unit, and a coding rate adjuster provided for each frequency band, which is determined by the control unit. A plurality of modulators that generate a modulation signal from a given bit string according to the modulation method of each frequency band, available resources of each frequency band, a code length calculated from the information bit length and the coding rate, A distributor that distributes each bit of a code word whose coding rate has been adjusted by the coding rate regulator to the plurality of modulators based on the modulation method of each frequency band is provided.

According to the above aspect, the data transmission efficiency can be improved while satisfying the required communication quality.

It is a figure which shows an example of the wireless communication system which concerns on embodiment of this invention. It is a figure which shows an example of the transmission circuit provided in the wireless communication device. It is a figure which shows an example of the receiving circuit provided in the wireless communication device. It is a flowchart which shows the outline of the method of determining a communication method. It is a figure which shows an example of the method of determining a communication system independently for each frequency band. It is a figure which shows an example of the method of determining the communication system in the transmission circuit which concerns on embodiment of this invention. It is a flowchart which shows an example of the method of determining a communication method. It is a figure explaining the difference of the characteristic by a modulation method. It is a figure explaining the difference of the characteristic by the type of a code. It is a figure explaining the difference of the characteristic by a code length and a coding rate. It is a figure explaining the difference of the characteristic by the number of times of decoding repetition.

FIG. 1 shows an example of a wireless communication system according to an embodiment of the present invention. The wireless communication system 1 shown in FIG. 1 is not particularly limited, but is, for example, a wireless LAN system. However, embodiments of the present invention are also applicable to other wireless communication systems such as Bluetooth®, WiMAX, and mobile phone systems. The wireless communication system 1 includes wireless communication devices 2 and 3. Each wireless communication device 2 and 3 is, for example, a user terminal. The user terminal may be a mobile terminal.

The wireless communication devices 2 and 3 can transmit data using a plurality of frequency bands. Specifically, the wireless communication devices 2 and 3 can transmit data by using a plurality of frequency bands at the same time. In this embodiment, the wireless communication devices 2 and 3 can transmit data by simultaneously using two or more of the 920 MHz band, 2.4 GHz band, and 5 GHz band. The communication quality between the wireless communication devices 2 and 3 differs for each frequency band. Therefore, the wireless communication devices 2 and 3 may transmit data by a different modulation method and a different code for each frequency band.

FIG. 2 shows an example of a transmission circuit included in the wireless communication devices 2 and 3. In this embodiment, the transmission circuit 10 includes a encoder 11, a code rate adjuster 12, a distributor 13, a plurality of modulators 14a to 14c, a control unit 15, and a plurality of RF circuits 16a, as shown in FIG. It is provided with ~ 16c and a plurality of antennas 17a to 17c. The transmission circuit 10 may include other circuit elements not shown in FIG.

The encoder 11 encodes the input data according to the instruction given by the control unit 15 to generate one or more codewords. The codeword is composed of an information bit and a parity bit. The input data is stored in the codeword as information bits. When a plurality of codewords are generated from the input data, the input data is divided into a plurality of data blocks and stored in each codeword. Parity bits are generated based on the input data. The instruction given from the control unit 15 to the encoder 11 includes information indicating the type of the code and information indicating the length of the information bit. The code type identifies, for example, a convolutional code, a low density parity check code (LDPC), a turbo code, or the like. The length of the information bit represents the length of the information bit of each codeword.

The code rate adjuster 12 adjusts the code rate of the code word generated by the coder 11 according to the instruction given by the control unit 15. The instruction given from the control unit 15 to the code rate adjuster 12 includes information indicating the code rate. The code rate represents the length of the information bit relative to the length of the entire codeword. In this embodiment, for the sake of simplicity, the length of the entire codeword is assumed to correspond to the sum of the lengths of the information bits and the lengths of the parity bits.

The distributor 13 distributes each bit of the code word whose code rate has been adjusted by the code rate adjuster 12 to the modulators 14a to 14c according to the instruction given by the control unit 15. The instruction given from the control unit 15 to the distributor 13 includes information indicating the available resources of each frequency band, information indicating the code length, and information indicating the modulation method of each frequency band.

Modulators 14a to 14c are provided for each frequency band. In this example, the modulators 14a, 14b, and 14c are provided for the 920 MHz band, the 2.4 GHz band, and the 5 GHz band, respectively. Then, each of the modulators 14a to 14c generates a modulated signal from the bit string given by the distributor 13 according to the instruction given by the control unit 15. The instructions given by the control unit 15 to the modulators 14a to 14c include information indicating the modulation method. That is, the modulators 14a to 14c each generate a modulated signal from the input bit string according to the modulation method determined by the control unit 15.

Control information is given to the control unit 15. The control information includes information indicating the bit length of data and information indicating the required quality. Information representing the bit length of the data is given, for example, by the application that generated the data. Information representing the required quality is provided by the user, application, or network management system. The required quality represents, for example, the maximum transmission delay, the maximum error rate, and the like. Then, the control unit 15 transmits the data, the type of code for transmitting the data, and the data based on the communication quality of each frequency band, the available resources of each frequency band, the bit length of the data, and the given required quality. The length of the information bit in the codeword, the coding rate of the codeword, and the modulation method of each frequency band are determined. In this specification, the “transmission delay” may mean the time until a signal transmitted from a certain wireless communication device is received by another wireless communication device and decoded. That is, the transmission delay may include a decoding processing delay.

The control unit 15 includes a quality measurement unit 21 and a resource detection unit 22. The quality measuring unit 21 measures the communication quality between the own device and the other device for each frequency band. However, "measuring" includes a process of acquiring a value measured by the other device. For example, when the transmission circuit 10 transmits a reference signal to the other device, the other device uses the reference signal to measure RSSI and SINR. In this case, the quality measuring unit 21 measures the communication quality between the own device and the partner device by receiving the measured values of RSSI and SINR from the partner device. However, the quality measuring unit 21 may measure the communication quality by another method. For example, the quality measurement unit 21 may request the other device to transmit a reference signal and measure RSSI and SINR using the reference signal received from the other device. Alternatively, the quality measuring unit 21 may estimate the communication quality between the own device and the other device.

The resource detection unit 22 detects available communication resources for each frequency band. For example, in a wireless communication system in which a plurality of subchannels are provided in each frequency band, the resource detection unit 22 may detect unused subchannels. Further, the resource detection unit 22 may acquire information representing available communication resources from the network management system.

The control unit 15 is realized by a processor system or a digital signal processing circuit that processes a digital signal. The processor system includes a processor element and a memory, and provides the function of the control unit 15 by executing a given program. The digital signal processing circuit is, for example, an FPGA (field-programmable gate array) and provides the function of the control unit 15.

RF circuits 16a to 16c are provided for each frequency band. In this embodiment, the RF circuits 16a, 16b, and 16c are provided for the 920 MHz band, the 2.4 GHz band, and the 5 GHz band, respectively. Then, the RF circuits 16a to 16c up-convert the modulated signals generated by the modulators 14a to 14c to the corresponding frequency bands, respectively. The antennas 17a to 17c output RF modulation signals generated by the RF circuits 16a to 16c, respectively.

FIG. 3 shows an example of a receiving circuit included in the wireless communication devices 2 and 3. In this embodiment, as shown in FIG. 3, the receiving circuit 30 includes a plurality of antennas 31a to 31c, a plurality of down converters 32a to 32c, a control unit 33, a plurality of demodulators 34a to 34c, a reverse distributor 35, and a reference numeral. The conversion rate reverse adjuster 36 and the decoder 37 are provided. The receiving circuit 30 may include other circuit elements not shown in FIG.

The receiving circuit 30 receives a wireless signal transmitted from another wireless communication device. In this embodiment, the receiving circuit 30 receives the radio signal transmitted from the transmitting circuit 10 shown in FIG. This radio signal is received via the plurality of antennas 31a to 31c, and is down-converted to the baseband band by the down converters 32a to 32c. The down converters 32a, 32b, and 32c down-convert the received signal with the station-generated signals of 920 MHz, 2.4 GHz, and 5 GHz, respectively. Therefore, signals transmitted using the 920 MHz band, 2.4 GHz band, and 5 GHz band are guided to the demodulators 34a, 34b, and 34c, respectively.

By sharing control information with the control unit 15 mounted on another wireless communication device, the control unit 33 includes a plurality of demodulators 34a to 34c, a reverse distributor 35, a code rate reverse adjuster 36, and the like. Controls the decoder 37. The control unit 33, for example, provides information indicating the code type, information indicating the code length, information indicating the coding rate, and a modulation method for each frequency band with the control unit 15 mounted on another wireless communication device. The information to be represented and the information to represent the number of repetitions of decoding may be shared. The information shared between the control unit 15 mounted on the transmission circuit 10 and the control unit 33 mounted on the reception circuit 30 may be directly notified between the wireless communication devices 2 and 3. However, it may be notified via the network management system.

The control unit 33 is realized by a processor system or a digital signal processing circuit that processes a digital signal. The processor system includes a processor element and a memory, and provides the function of the control unit 33 by executing a given program. The digital signal processing circuit is, for example, an FPGA and provides the function of the control unit 33.

The demodulators 34a to 34c demodulate the received signals in the corresponding frequency bands according to the instructions given by the control unit 33, respectively. At this time, the demodulators 34a to 34c execute the demodulation process corresponding to the modulation process by the modulators 14a to 14c. The reverse distributor 35 synthesizes the bit strings output from the demodulators 34a to 34c according to the instruction given by the control unit 33. At this time, the reverse distributor 35 executes the reverse distribution process corresponding to the distribution process by the distributor 13. The code rate reverse adjuster 36 adjusts the code rate of the bit string output from the reverse distributor 35 according to the instruction given by the control unit 33. At this time, the code rate reverse adjuster 36 executes the reverse processing of the adjustment process by the code rate regulator 12.

The decoder 37 decodes the bit string output from the code rate inverse adjuster 36 according to the instruction given by the control unit 33. At this time, the decoder 37 executes the decoding process corresponding to the coding by the encoder 11. The instruction given from the control unit 33 to the decoder 37 may include information indicating the number of times of decoding repetition. In this case, the decoder 37 executes the decoding process a number of times specified by the control unit 33.

FIG. 4 is a flowchart showing an outline of a method for determining a communication method. The processing of this flowchart is executed by the control unit 15 mounted on the transmission circuit 10. Further, the processing of this flowchart is executed, for example, when a request for transmitting data to another wireless communication device is given to the control unit 15 from the application.

In S1, the control unit 15 measures the quality of each frequency band. In this embodiment, the control unit 15 measures RSSI and SINR for each of the 920 MHz band, 2.4 GHz band, and 5 GHz band. As described above, the quality measurement includes the case of acquiring the measurement result in the other device.

In S2, the control unit 15 selects the modulation method to be used in each frequency band based on the quality of each frequency band measured in S1. Here, a modulation method having a high degree of multivalue (that is, a modulation method having a large number of bits per symbol) is selected for a frequency band having good communication quality. On the other hand, for a frequency band having poor communication quality, a modulation method having a low degree of multivalue (that is, a modulation method having a small number of bits per symbol) is selected. For example, it is assumed that QPSK and 16QAM can be used in a wireless communication system. In this case, QPSK is selected for a frequency band whose communication quality is lower than a predetermined threshold level, and 16QAM is selected for a frequency band whose communication quality is equal to or higher than a predetermined threshold level.

In S3, the control unit 15 determines the code type and the number of decoding repetitions according to the required quality of the transmission data. As the required quality of transmission data, the maximum transmission delay and / or the maximum error correction capability is specified in this embodiment. Information representing the required quality is provided by the user, application, or network management system.

When a small transmission delay is required, the control unit 15 selects a code having a short processing time and specifies a small value as the number of decoding repetitions. For example, it is assumed that a convolutional code and a low density parity check (LDPC) can be used in a wireless communication system. Here, the time required for the decoding process is shorter for the convolutional code than for the LDPC. Therefore, when a small transmission delay is required, the control unit 15 selects the convolutional code as the code type and selects “1” as the number of decoding repetitions.

When a low error rate is required, the control unit 15 selects a code having a high error correction capability and specifies a large value as the number of decoding repetitions. Here, the error correction capability of the LDPC is higher than that of the convolutional code. Further, it is possible to improve the error rate by repeatedly executing the decoding process. Therefore, when a low error rate is required, the control unit 15 selects LDPC as the code type and "64" as the number of decoding repetitions.

In S4, the control unit 15 determines the resource, the code length, and the coding rate of each frequency band based on the required quality of the transmission data and the resource information. Here, the control unit 15 may reselect the modulation method. Resource information represents available frequencies and / or available times. The usable frequency represents, for example, an unused subchannel in a wireless communication system in which a plurality of subchannels are provided in each frequency band. The available time represents an unused time slot. The control unit 15 may receive resource information from the network management system.

When a small transmission delay is required, the control unit 15 shortens the code length and increases the coding rate. On the other hand, when a low error rate is required, the control unit 15 lengthens the code length and lowers the code rate. In general, the shorter the code length, the shorter the time required for the decoding process, and the lower the coding rate, the higher the error correction capability.

Next, an example of a method for determining the communication method will be shown. In the following description, first, a method of independently determining a communication method for each frequency band will be described, and then a method according to an embodiment of the present invention will be described.

In the following example, it is assumed that the transmission circuit 10 transmits 24-bit data using two frequency bands X and Y. Three subchannels can be used in frequency band X, and six subchannels can be used in frequency band Y. The communication quality of the frequency band X is high, and the communication quality of the frequency band Y is low. In the frequency band X with high communication quality, the 16QAM signal is transmitted through each subchannel, and in the frequency band Y with low communication quality, the QPSK signal is transmitted through each subchannel.

FIG. 5 shows an example of a method of independently determining a communication method for each frequency band. In this example, as shown in FIG. 5A, 12-bit data is transmitted using the frequency bands X and Y, respectively. Since the communication quality of the frequency band X is high, the coding rate is high (the number of parity bits added is small). Therefore, in the frequency band X, 8-bit parity is added to the 12-bit information bit, and a 20-bit codeword X is generated. On the other hand, since the communication quality of the frequency band Y is low, the coding rate is low (many parity bits are added). Therefore, in the frequency band Y, a 22-bit parity bit is added to the 12-bit information bit, and a 34-bit codeword Y is generated.

Further, in the frequency band X, a modulation method having a high multi-level degree (here, 16QAM) is applied, and in the frequency band Y, a modulation method having a low multi-level degree (here, QPSK) is applied. That is, in the frequency band X, 4 bits are assigned to one symbol, and in the frequency band Y, 2 bits are assigned to one symbol. As a result, the codeword X transmitted using the frequency band X is mapped to three information bit symbols and two parity bit symbols. Further, the codeword Y transmitted using the frequency band Y is mapped to 6 information bit symbols and 11 parity bit symbols. In FIG. 5, "I" represents an information bit symbol for transmitting an information bit, and "P" represents a parity bit symbol for transmitting a parity bit.

The codewords X and Y are assigned to available resources, respectively, as shown in FIG. 5 (b). FIG. 5B shows the relationship between subchannels and symbol assignments for unit time (time slot) in each frequency band. In the frequency band X, three information bit symbols are assigned to the first time slot, and two parity bit symbols are assigned to the second time slot. In the frequency band Y, 6 information bit symbols are assigned to the 1st time slot, 6 parity bit symbols are assigned to the 2nd time slot, and 5 parity bit symbols are assigned to the 3rd time slot. .. In FIG. 5B, the shaded area represents a resource to which the symbol is not transmitted.

As described above, in the example shown in FIG. 5, it takes 3 time slot periods to transmit 24-bit data. Further, in order to reproduce the data in the receiving circuit 30, it is necessary to receive the entire codeword. Therefore, the decoding process of the signal transmitted using the frequency band X is started after the two time slot periods have elapsed. Further, the decoding process of the signal transmitted using the frequency band Y is started after the three time slot periods have elapsed. In addition, there are unused resources that have not been assigned a transmission symbol.

In the method according to the embodiment of the present invention, the communication method and resource allocation are determined so as to increase the data transmission efficiency while satisfying the required communication quality. For example, the communication method and resource allocation are determined so as to satisfy at least one of the following requirements.
(1) Reduce the time (number of time slots) required to transmit data (2) Advance the start timing of decoding processing in the receiving device to reduce decoding processing delay (3) Increase resource usage efficiency That is, the communication method is determined over the entire plurality of frequency bands so that the overhead is reduced and the coding gain is increased.

FIG. 6 shows an example of a method of determining a communication method in the transmission circuit 10 according to the embodiment of the present invention. In this example, as shown in FIG. 6A, a 12-bit parity bit is added to a 12-bit information bit to generate a 24-bit codeword. A part of this codeword is transmitted using the frequency band X, and the rest is transmitted using the frequency band Y. Specifically, the information bit is transmitted using the frequency band X, and the parity bit is transmitted using the frequency band Y. However, the embodiment of the present invention is not limited to the example shown in FIG. That is, the information bit may be transmitted using both the frequency band X and the frequency band Y, or the parity bit may be transmitted using both the frequency band X and the frequency band Y. May be good.

Similar to the example shown in FIG. 5, 16QAM is applied in frequency band X and QPSK is applied in frequency band Y. That is, in the frequency band X, 4 bits are assigned to one symbol, and in the frequency band Y, 2 bits are assigned to one symbol. As a result, the information bits (12 bits) transmitted using the frequency band X are mapped to the three information bit symbols. The parity bits (12 bits) transmitted using the frequency band Y are mapped to six parity bit symbols. By generating two codewords shown in FIG. 6A, 24-bit data is transmitted.

Each codeword is assigned to an available resource, as shown in FIG. 6 (b). FIG. 6B shows the relationship between subchannels and symbol assignments for unit time (time slot) in each frequency band. In this example, the first codeword is assigned to the first time slot and the second codeword is assigned to the second time slot. That is, in the first time slot, the three information bit symbols I are assigned to the three subchannels of the frequency band X, and the six parity bit symbols P are assigned to the six subchannels of the frequency band Y. Be done. Also in the second time slot, the three information bit symbols I are assigned to the three subchannels of the frequency band X, and the six parity bit symbols P are assigned to the six subchannels of the frequency band Y. ..

As described above, in the example shown in FIG. 6, 24-bit data can be transmitted in a two-time slot period. Further, in this example, one codeword is transmitted in one time slot period. That is, the receiving device can start the decoding process when the one time slot period has elapsed. Therefore, the decoding processing delay is reduced as compared with the method shown in FIG. Further, in the example shown in FIG. 6, there are no unused resources in the first and second time slots. That is, the resource usage efficiency is improved as compared with the method shown in FIG.

As shown in FIG. 6, the communication method control method according to the embodiment of the present invention has a code type and a length of information bits in a code word so that the decoding processing delay is small and the resource usage efficiency is high. The coding rate, the modulation method for each frequency band, etc. are determined. The procedure for determining these communication parameters will be described below.

FIG. 7 is a flowchart showing an example of a method of determining a communication method. The processing of this flowchart corresponds to S2 to S4 of the flowchart shown in FIG. In the embodiment shown in FIG. 7, it is assumed that an acceptable transmission delay is required by the user or the application.

In S11, the control unit 15 selects a code to be used from a plurality of codes that can be used in the wireless communication system. At this time, the control unit 15 selects, for example, the code having the highest error correction capability from a plurality of codes that can be used in the wireless communication system.

In S12, the control unit 15 specifies the information bit length. The information bit length represents the length of the data stored in the codeword. That is, the number of bits of data stored in each codeword is specified. At this time, the control unit 15 specifies, for example, the bit length of the input data as the information bit length.

In S13, the control unit 15 specifies the MCS and the number of decoding repetitions based on the communication quality of each frequency band. A modulation method is specified as the MCS for each frequency band. For example, the higher the communication quality or the higher the error correction capability, the higher the multi-valued modulation method is specified. In other words, the lower the communication quality or the lower the error correction capability, the lower the multi-valued modulation method is specified. The relationship between communication quality and error correction capability and the modulation method is preferably determined in advance by measurement, simulation, or the like.

Further, in S13, the coding rate is also specified. However, in the embodiment of the present invention, one codeword is transmitted using a plurality of frequency bands. Therefore, the coding rate is not specified individually for each frequency band, but is specified for communication using a plurality of frequency bands. The number of repetitions of decoding is also specified for communication using a plurality of frequency bands.

In S14, the control unit 15 calculates the transmission delay when data transmission is executed with the parameters selected or specified in S11 to S13. Here, the transmission delay includes the time required for the decoding process executed in the receiving device (hereinafter, the decoding processing time). The transmission delay strongly depends on the decoding processing time. The decoding processing time depends on the type of code. Further, the longer the code length or the information bit length in the code word, the longer the decoding processing time. Further, the larger the number of repeated decodings, the longer the decoding processing time.

In S15, the control unit 15 compares the allowable transmission delay requested by the user or the application (hereinafter referred to as the required delay) with the transmission delay calculated in S14. Then, if the transmission delay calculated in S14 is smaller than the required delay, the processing of the control unit 15 proceeds to S16. That is, when the current parameter satisfies the required quality, the process of the control unit 15 proceeds to S16. The "current parameter" means the parameter selected or specified in S11 to S13. However, after the parameters have been updated in S17, S20, S22 or S23, the "current parameter" means the updated parameter.

In S16, the control unit 15 determines whether or not there are surplus resources when transmitting a predetermined amount of data within a predetermined time with the current parameters. The "remainder resource" corresponds to an unused resource in this embodiment. For example, in the example shown in FIG. 5B, the resource represented by the shaded area is a surplus resource. Here, the transmission circuit 10 preferably transmits a signal using all available resources.

Therefore, when there is a surplus resource in the current parameter, the control unit 15 changes the MCS in S17 so that the surplus resource is minimized. In this case, the control unit 15 lowers the coding rate by adding a parity bit, for example. If the coding rate is lowered, it is expected that the error correction capability of the receiving device will be improved. That is, the error correction capability can be improved without increasing the transmission delay by increasing the parity bit by using the surplus resources. The control unit 15 may increase the parity bit length and change the modulation method and / or the code type.

When it is determined that there are not many resources in the current parameter, or when the processing of S17 is completed, the processing of the control unit 15 proceeds to S18. In S18, the control unit 15 sets parameters for each circuit element in the transmission circuit 10. That is, the control unit 15 sets the information indicating the type of the code and the information indicating the length of the information bit in the encoder 11. The control unit 15 sets information representing the code rate to the code rate adjuster 12. The control unit 15 sets the distributor 13 with information indicating the available resources of each frequency band, information indicating the code length, and information indicating the modulation method of each frequency band. The control unit 15 sets information indicating the modulation method for the modulators 14a to 14c. Further, the control unit 15 notifies the receiving circuit 30 of the determined parameter. At this time, the control unit 15 also notifies the receiving circuit 30 of information indicating the number of repetitions of decoding.

If the transmission delay calculated in S14 based on the current parameters is larger than the required delay (S15: No), the control unit 15 executes the processes S19 to S23 in order to reduce the transmission delay. That is, in S19, the control unit 15 determines whether or not the number of decoding repetitions specified as the current parameter is 1. When the number of decoding repetitions is 2 or more, the control unit 15 reduces the number of decoding repetitions in S20. At this time, the control unit 15 reduces the number of decoding repetitions by, for example, by 1.

After that, the process of the control unit 15 returns to S13, and the MCS is reselected. That is, in S13 to S15, S19, and S20, it is determined whether or not the transmission delay is smaller than the required delay by reducing the number of decoding repetitions. This processing loop is repeatedly executed until the transmission delay becomes smaller than the required delay. However, if the transmission delay is equal to or greater than the required delay even though the number of decoding repetitions is 1, the processing of the control unit 15 proceeds to S21.

In S21, the control unit 15 determines whether or not the information bit length designated as the current parameter is the minimum information bit length in the selected code type. Here, if the information bit length is small, the code length is also short, and it is expected that the transmission delay will be reduced. Therefore, when the information bit length specified as the current parameter is not the minimum bit length, the control unit 15 shortens the information bit length in S22. That is, by dividing the input data, the length of the data stored in each codeword is shortened.

After that, the process of the control unit 15 returns to S13, and the MCS is reselected. That is, in S13 to S15, S21, and S22, it is determined whether or not the transmission delay is smaller than the required delay by shortening the information bit length. This processing loop is repeatedly executed until the transmission delay becomes smaller than the required delay. However, if the transmission delay is greater than or equal to the required delay even though the information bit length has been reduced to the minimum bit length, the process of the control unit 15 proceeds to S23.

In S23, the control unit 15 changes the code type. In this case, a code having a short decoding processing time is newly selected. For example, in LDPC, when the transmission delay is equal to or greater than the required delay, the convolutional code is selected.

After that, the process of the control unit 15 returns to S12. In this case, since the processing after S13 is executed for the newly selected code, the initial value of the information bit length is specified in S12. For example, the control unit 15 specifies the bit length of the input data as the information bit length.
Then, by changing the code type, it is determined whether or not the transmission delay is smaller than the required delay. This processing loop is repeatedly executed until the transmission delay becomes smaller than the required delay.

An embodiment of the flowchart shown in FIG. 7 will be described with reference to the case shown in FIG. In the following description, it is assumed that the input data is 24 bits.
In S11, a predetermined code type (hereinafter, code A) is selected. In S12, 24 bits are specified as the information bit length. In S13, 16QAM is designated for the frequency band X, and QPSK is designated for the frequency band Y. Further, N (N is an integer of 2 or more) is specified as the number of repetitions of decoding. In S14 to S15, it is assumed that the transmission delay is larger than the required delay. In this case, in S19 to S20, after the number of decoding repetitions is changed from N to 1, the processing of the control unit 15 returns to S13, and the MCS is reselected.

In S13, the MCS is changed as needed. Here, in S14 to S15, it is assumed that the transmission delay is larger than the required delay again. In this case, in S21 to S22, after the information bit length is changed from 24 to 12, the processing of the control unit 15 returns to S13, and the MCS is reselected.

In S13, the MCS is changed as needed. In S14 to S15, it is assumed that the transmission delay is larger than the required delay again. In this case, in S23, after the code type is changed from the code A to the code B, the processing of the control unit 15 returns to S12. It is assumed that the decoding processing time of the reference numeral B is shorter than that of the reference numeral A. Then, since the code type is changed from the code A to the code B, the transmission delay is assumed to be smaller than the required delay in S14 to S15. Here, it is assumed that the determination condition of S16 is "the remaining resource is the minimum". Then, in the example shown in FIG. 6, the determination result of S16 becomes “Yes”.

After that, in S18, preparation for data transmission is executed. That is, "code type: code B" and "information bit length: 12" are set for the encoder 11. “Code rate: 1/2” is set for the code rate adjuster 12. “Frequency band X: 3 subchannels, 16QAM”, “frequency band Y: 6 subchannels, QPSK”, and “code length: 24” are set for the distributor 13. The "modulation method: 16QAM" is set for the modulator corresponding to the frequency band X (for example, the modulator 14a), and the "modulation method: 16QAM" is set for the modulator corresponding to the frequency band Y (for example, the modulator 14b). QPSK ”is set.

FIG. 8 is a diagram for explaining the difference in characteristics depending on the modulation method. Here, the bit error rates (BER) of modulation methods having different multivalue degrees are compared in the case where error correction is not performed. The multilevel degrees (number of bits transmitted per symbol) of BPSK, QPSK, 8PSK, 16QAM, and 64QAM are 1, 2, 3, 4, and 6, respectively. Then, for example, in QPSK, 16QAM, and 64QAM, the signal-to-noise ratios at which the bit error rate is 1% are 8 dB, 14 dB, and 22 dB, respectively. That is, the higher the multi-value degree, the higher the signal-to-noise ratio is required. Therefore, in the frequency band where the communication quality is good, the modulation method having a high multi-value degree can be used, and in the frequency band where the communication quality is poor, only the modulation method having a low multi-value degree can be used.

FIG. 9 is a diagram for explaining the difference in characteristics depending on the type of reference numeral. Here, the packet error rate (PER) is compared for the case where error correction is not performed, the case where a convolutional code is used, and the case where LDPC is used. As shown in FIG. 9, the required SNR is lowered by performing error correction. Moreover, the error correction capability of the LDPC is higher than that of the convolutional code. However, the decoding processing time of the LDPC is longer than that of the convolutional code. Therefore, in wireless communication systems that can use these codes, a convolutional code is selected when a small transmission delay is required, and an LDPC is selected when a low error rate is required.

FIG. 10 is a diagram for explaining the difference in characteristics depending on the code length and the coding rate. Here, the packet error rate is compared with respect to the code length (L = 512, 1024, 2048, 4096) and the coding rate (R = 1/3, 1/2, 2/3, 3/4). .. As shown in FIG. 10, the longer the code length, the better the PER characteristic, and the lower the coding rate, the better the PER characteristic. However, when the coding rate is low, the ratio of the parity bits is high, so that the effective data rate is low.

FIG. 11 is a diagram illustrating a difference in characteristics depending on the number of repetitions of decoding. Here, the bit error rate is compared with respect to the number of repetitions of decoding. As shown in FIG. 11, increasing the number of decoding repetitions improves the error correction capability. However, if the number of times of decoding repetition is increased, the decoding processing time inevitably increases, so that the transmission delay becomes large.

The characteristics shown in FIGS. 8 to 11 are obtained in advance by measurement or simulation. Then, the control unit 15 executes the processing of the flowchart shown in FIG. 7 by utilizing the characteristics shown in FIGS. 8 to 11.

1 Wireless communication system 2, 3 Wireless communication device 10 Transmission circuit 11 Encoder 12 Code rate regulator 13 Distributor 14a to 14c Modulator 15 Control unit 16a to 16c RF circuit 17a to 17c Antenna 21 Quality measurement unit 22 Resource detection Unit 30 Reception circuit 31a to 31c Antenna 32a to 32c Down converter 33 Control unit 34a to 34c Demodulator 35 Reverse distributor 36 Code rate reverse adjuster 37 Decoder

Claims (7)

A wireless communication device used in a wireless communication system that transmits code words using a plurality of frequency bands.
And the control section,
According to the length of the classification and the information bits of the code determined by the control unit, and an encoder for generating a code word data is encoded,
A code rate adjuster that adjusts the code rate of the codeword generated by the coder according to the code rate determined by the control unit.
A plurality of modulators provided for each frequency band and each generating a modulation signal from a given bit string according to the modulation method of each frequency band determined by the control unit.
The code rate was adjusted by the code rate adjuster based on the available resources of each frequency band, the length of the information bit, the code length calculated from the code rate, and the modulation method of each frequency band. A distributor that distributes each bit of a code word to the plurality of modulators is provided.
The control unit
Determine the modulation method for each frequency band based on the quality of each frequency band,
Based on the required quality of the data, the type of code for transmitting the data and the length of the information bit in the code word for transmitting the data are determined.
The code rate of the codeword is determined based on the required quality and the available resources of each frequency band.
A wireless communication device characterized by the fact that. Wherein, based on the required quality and available resources of the frequency band of the data, the wireless communication apparatus according to claim 1, characterized in that re-determines a modulation scheme for each frequency band. The control unit determines the type of code, the length of information bits, the coding rate, and the modulation method for each frequency band.
The wireless communication device according to claim 1, wherein the receiver is notified. The control unit further determines the number of decoding repetitions for decoding the modulated signal in the receiver based on the given required quality, and notifies the receiver of the determined number of decoding repetitions. The wireless communication device according to claim 3. The required quality is an acceptable transmission delay,
The wireless communication device according to any one of claims 1 to 4, wherein the control unit determines the bit length of the information bit in the codeword based on an acceptable transmission delay. The required quality is an acceptable transmission delay,
The wireless communication device according to any one of claims 1 to 4, wherein the control unit determines a code type based on an acceptable transmission delay. A communication method control method for controlling a communication method for each frequency band in a wireless communication device used in a wireless communication system that transmits code words using a plurality of frequency bands.
Determine the modulation method for each frequency band based on the quality of each frequency band,
Based on the required quality of the data, the type of code for transmitting the data and the length of the information bit in the code word for transmitting the data are determined.
The code rate of the codeword is determined based on the required quality and the available resources of each frequency band.
The data is encoded to generate a code word according to the determined code type and the length of the information bit.
The coding rate of the codeword is adjusted according to the determined code rate.
The available resources, the code length calculated from the determined length of the information bits and the coding rate of each frequency band, based on the modulation scheme of each frequency band determined, the codeword encoding rate is adjusted Each bit is distributed to the plurality of frequency bands,
A modulation signal is generated from each bit string distributed in the plurality of frequency bands according to the determined modulation method of each frequency band.
A communication method control method characterized by the fact that.

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