JP6296604B2 - OFDM signal transmitter - Google Patents

Description

  The present invention relates to an OFDM signal transmission apparatus that transmits orthogonal frequency division multiplexing (OFDM) signals, and in particular, in order to effectively suppress out-of-band radiation even when performing OFDM wireless communication in an operating frequency band with strict transmission spectrum regulations such as white space. The present invention relates to a suitable OFDM signal transmission apparatus.

  In response to the explosive demand for wireless communication in recent years, frequency resources available for wireless communication are becoming tighter. On the other hand, it is known that there is a frequency resource that is not used spatially and temporally in a frequency allocated for a primary user having a specific usage purpose. Such frequency resources that are not used by the primary user are called white space. In particular, white space in the TV broadcasting band is called TV white space, and studies on legal systems for using the frequency in other countries such as the United States and the United Kingdom have begun, and concrete standardization is also underway. It has been. Even in Japan, TV broadcast is performed in the 470 to 710 MHz band, and the use of TV white space for communication purposes is also expected in this band.

  IEEE802.11af, IEEE802.15.4m, IEEE802.22, etc. so that the secondary user can effectively utilize such TV white space or white space in which the primary user is not in use temporarily or continuously. Various international standardization standards are being promoted. In many of these standards, the introduction of an Orthogonal Frequency Division Multiplexing (OFDM) scheme that has high frequency utilization efficiency and strong resistance to multipath fading has been studied. In this OFDM system, data is mapped to a large number of subcarriers arranged so as to be orthogonal to each other, and a time series signal is derived by performing inverse Fourier transform on the data group, and a transmission symbol for radio transmission is created. On the receiving side, a transmitted data group is derived by Fourier transforming such symbols, and the transmission data is reproduced by restoring individual data associated with each subcarrier.

  By the way, when the secondary user uses the white space, it is important not to affect the communication of the primary user. For this reason, it is necessary to comply with the spectrum mask regulations for each country such as the transmission spectrum mask regulations of the US FCC (Federal Communications Commission). The transmission spectrum mask specification for wireless communication in this white space is stricter than the transmission spectrum mask specification for a 2.4 GHz band wireless LAN or the like. In order to satisfy this strict transmission spectrum mask, it is necessary to perform strict band limiting processing on the transmission side.

  Specifically, a technique for suppressing out-of-band radiation by performing waveform shaping using a technique called time axis windowing processing so as to satisfy a transmission spectrum mask is disclosed (for example, Non-Patent Document 1). reference.). This time-axis windowing process suppresses out-of-band radiation power by smoothing discontinuities at the boundary between OFDM symbols on the time axis by the windowing process. Since this time axis windowing process can be basically implemented with a single multiplier, an increase in circuit scale can be prevented. However, in such a method using time-axis windowing processing, the longer the windowing length (smoothing interval), the better the out-of-band radiation suppression performance. However, if an unnecessarily long windowing length is applied, demodulation is performed. The signal component necessary for the processing is also deleted, resulting in a problem that the throughput is lowered.

  In order to satisfy a strict transmission spectrum mask, a method using a digital low-pass filter having a high-order filter coefficient has also been proposed (see, for example, Non-Patent Document 2). However, since the disclosed technique of Non-Patent Document 2 is a convolution process on the time axis in mounting, there is a problem that the circuit scale increases as the filter coefficient increases, and mounting becomes difficult.

  Furthermore, a method of satisfying the transmission spectrum mask by reducing the power of the transmission signal in accordance with FCC regulations has been proposed. However, in this method, since the transmission signal power itself becomes small, the coverage is limited and it becomes impossible to deal with various services.

"P802.11-REVmb / D12, Nov 2011- IEEE Draft Standard for IT- Telecommunications and Information Exchange Between Systems-LAN / MAN-Specific Requirements-Part 11: Wireless LAN MAC and PHY Specifications." Mar.2012. S. Y. Chang, "Spectra and bandwidth overhead with and without ltering for TG4m OFDM," Doc.:IEEE802.15-12-0377-00-004m, Jul. 2012.

  Therefore, the present invention has been devised in view of the above-described problems, and the object of the present invention is to provide a band even when OFDM wireless communication is performed in an operating frequency band where transmission spectrum regulations are strict, such as white space. In order to effectively suppress external radiation, a combination of time-axis windowing processing, error correction code, and transmission power control can be used to achieve the maximum throughput under a given environment, and any spectrum. An object of the present invention is to provide an OFDM signal transmission apparatus that can satisfy the mask, can be realized without complicating the circuit configuration, and without unnecessarily reducing transmission signal power.

  The OFDM signal transmission apparatus according to claim 1, wherein the OFDM signal transmission apparatus transmits an orthogonal frequency division multiplexing (OFDM) signal, and a time-axis windowing process is performed on a boundary between OFDM symbols on a time axis constituting the OFDM signal. The relationship between the maximum transmission power with respect to the time-axis windowing length for performing the transmission or the maximum transmission PSD in the transmission band within the transmission band is related to the communication system standard, digital band limiting filter and RF circuit. Hardware performance including characteristics, conditions given as any one or more environments of arbitrary spectrum mask specifications, and a transmission power parameter table stored in advance for each design margin for the required spectrum mask specifications, and the transmission The power determined in the power parameter table Considering transmission power or in-band maximum transmission PSD, the relationship of throughput to the time axis windowing length is one or more of an error correction code, its coding rate, modulation scheme (modulation multi-level number), and guard interval length. In the relationship between the throughput parameter table stored in advance for each adjustable communication condition and the adjustable communication condition stored in the throughput parameter table and the throughput, the conditions given as the environment and the required Communication that selects one or more of time axis windowing length, error correction code and coding rate, modulation method (modulation multi-level number), and transmission power to maximize throughput based on design margin for spectrum mask specification The condition selection means and the communication selected by the communication condition selection means. OFDM signal transmitting means for transmitting an OFDM signal subjected to time-axis windowing processing over the time-axis windowing length in communication conditions based on the communication condition and the transmission power selected by the communication condition selecting means It is characterized by that.

  According to a second aspect of the present invention, there is provided the OFDM signal transmitting apparatus according to the first aspect of the present invention, wherein the transmission power upper limit parameter table includes a time axis windowing process type, an OFDM modulation scheme, an arbitrary spectrum mask specification, a digital band limiting filter. Or the hardware performance including the characteristics of the RF circuit and the OFDM communication standard, each of the communication conditions is stored for each communication condition.

  The OFDM signal transmitting apparatus according to claim 3 is the invention according to claim 1 or 2, wherein the throughput parameter table includes a time axis windowing process type, an OFDM modulation method, a channel coding type, a coding rate, It is stored for each communication condition consisting of one or more of the guard interval length and the OFDM communication standard.

  According to a fourth aspect of the present invention, there is provided the OFDM signal transmitting apparatus according to any one of the first to third aspects, wherein the communication condition selecting means selects a communication condition capable of achieving a maximum throughput in the throughput parameter table. Features.

  The OFDM signal transmission apparatus according to claim 5 is the time axis windowing type and time axis set for the preamble added to the beginning of the OFDM signal in the invention according to any one of claims 1 to 4. It is characterized by comprising notification means for notifying one or more of the windowing length, the type of the band limiting filter, and the response of the band limiting filter in advance to the receiving apparatus side.

  An OFDM communication system design program according to claim 6 is an OFDM communication system design program for designing an OFDM communication system for transmitting and receiving orthogonal frequency division multiplexing (OFDM) signals, and between OFDM symbols on a time axis constituting the OFDM signal. The relationship between the maximum transmission power or the maximum in-band transmission PSD with respect to the time-axis windowing length for performing time-axis windowing processing on the boundary of the network includes the specifications of the communication system, the characteristics of the digital band limiting filter and the RF circuit. A transmission power parameter acquisition step that is acquired in advance for each design margin with respect to a wear performance, a condition given as one or more environments of any spectrum mask specification, and a required spectrum mask specification, and the transmission power parameter acquisition step In consideration of the maximum transmission power or the maximum in-band transmission PSD determined in step 1, the relationship of the throughput to the time axis windowing length is the error correction code, its coding rate, modulation scheme (modulation multi-level number), guard interval length. A throughput parameter acquisition step acquired in advance for each of one or more adjustable communication conditions, and a condition given as the environment in the relationship between the adjustable communication conditions acquired in the throughput parameter acquisition step and the throughput, and One or more of time axis windowing length, error correction code and coding rate, modulation scheme (modulation multi-level number), and transmission power that maximize throughput based on the design margin for the required spectrum mask specification. A communication condition selection step for selecting the communication condition selection step Time axis selected by-up windowing length and an output step of outputting the communication condition as the solution causing a computer to execute.

  In the OFDM signal transmission apparatus according to the present invention, the relationship of the throughput with respect to the time axis windowing length is stored in advance for each communication condition in the throughput parameter table. Then, the time axis windowing length that satisfies the out-of-band radiation suppression condition is selected from the communication conditions satisfying the above condition items in relation to the throughput stored in the throughput parameter table. These operations can be automatically performed. For this reason, in order to effectively suppress out-of-band radiation, by combining the time axis windowing process and the error correction code, an arbitrary spectrum mask can be satisfied without degrading the throughput, and the circuit This can be realized without complicating the configuration and without inadvertently reducing transmission signal power.

1 is a block configuration diagram of an OFDM communication system to which an OFDM signal transmission apparatus to which the present invention is applied is applied. It is a flowchart for producing | generating the OFDM signal which should be actually transmitted in an OFDM signal transmitter. It is a figure for demonstrating operation | movement of the OFDM communication system with which the OFDM signal transmitter to which this invention is applied is applied. It is a figure for demonstrating a time-axis windowing process. IEEE802.11 after time axis windowing processing. It is a figure which shows the transmission spectrum of the OFDM signal based on af standard. It is a figure which shows the relationship of the relative value band edge part PSD with respect to the time-axis windowing length of an OFDM signal. IEEE 802.11. It is a figure which shows the relationship of the throughput with respect to the time-axis windowing length ( _TTR ) of the OFDM signal based on af standard. It is a figure which shows the relationship between the transmission spectrum mask prescribed | regulated by the absolute value with respect to the secondary user in TV white space, and the transmission signal spectrum which performed power control. It is another figure which shows the relationship of the absolute value in-band maximum PSD and average received Eb / N0 gain with respect to the time-axis windowing length of an OFDM signal. It is another figure which shows the relationship of the throughput at the time of considering transmission power control with respect to the time-axis windowing length ( _TTR ) of an OFDM signal.

  Hereinafter, an OFDM signal transmission apparatus that transmits an Orthogonal Frequency Division Multiplexing (OFDM) signal as an embodiment for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a block configuration of an OFDM communication system 10 to which an OFDM signal transmission apparatus 1 to which the present invention is applied is applied. In addition to the OFDM signal transmission device 1, the OFDM communication system 10 includes an OFDM signal reception device 2 that receives the OFDM signal transmitted from the OFDM signal transmission device 1.

  The OFDM signal transmission apparatus 1 includes a modulation / coding processing unit 11 to which transmission signal data is supplied, an OFDM signal generation unit 20 connected to the modulation / coding processing unit 11, and an OFDM signal generation unit 20. The time axis windowing processing unit 12, the band limiting filter 13 connected to the time axis windowing processing unit 12, the parameter table storage unit 17, the time axis windowing processing unit 12, and the parameter table storage unit 17 are connected. A communication condition selection unit 19 and a condition acquisition unit 18 connected to the parameter table storage unit 17 are provided.

  The OFDM signal transmitting apparatus 1 further includes a synchronization parameter setting unit 15 and a time axis windowing processing unit 16 to which a preamble portion for synchronization of an OFDM signal is supplied, and a band limiting filter 31 connected thereto, And a symbol concatenation processing unit 14 connected to the band limiting filters 13 and 31.

  In addition, the OFDM signal transmission apparatus 1 includes a transmission power control unit 32 that controls transmission power of an OFDM signal in which a transmission signal data portion and a synchronization preamble portion are symbol-connected. The transmission power control unit 32 is connected to the modulation / coding processing unit 11 and the symbol concatenation processing unit 14.

  The OFDM signal receiver 2 includes a synchronization detector 21 that transmits an OFDM signal from the OFDM signal transmitter 1, an OFDM demodulator 22 connected to the synchronization detector 21, and a demodulator / receiver connected to the OFDM demodulator 22. And a decryption processing unit 23.

  The modulation / coding processing unit 11 performs error correction coding and modulation on the transmission signal data with reference to the throughput parameter table and transmission power parameter table information stored in the parameter table storage unit 17. The modulation / coding processing unit 11 outputs transmission signal data generated through coding and modulation to the OFDM signal generating unit 20.

  The OFDM signal generation unit 20 generates an OFDM signal based on the transmission signal data transmitted from the modulation / coding processing unit 11. The OFDM signal generator 20 generates subcarrier data necessary for generating an OFDM signal. The OFDM signal generation unit 20 performs an inverse Fourier transform on the generated subcarrier data, performs orthogonal frequency division multiplexing, and adds a guard interval (GI) to generate an OFDM data symbol. The OFDM signal generation unit 20 transmits the generated OFDM signal to the time axis windowing processing unit 12.

  The condition acquisition unit 18 is essential for the OFDM signal to be transmitted by the OFDM signal transmission apparatus 1 (communication system standards, hardware performance including characteristics of a digital band limiting filter and an RF circuit, and an arbitrary spectrum). Acquire condition items given as an environment (such as mask specifications) and design margin items for the required spectrum mask specifications. This condition item may be any one or more of a communication system standard, hardware performance including characteristics of a digital band limiting filter and an RF circuit, and an arbitrary spectrum mask specification. As this acquisition method, direct input may be performed directly, or it may be acquired from a public communication network such as the Internet. In addition, such a condition may be input in advance in the condition acquisition unit 18. The condition acquisition unit 18 transmits information regarding the acquired condition items to the communication condition selection unit 19.

  The communication condition selection unit 19 selects any one communication condition from the relationship of the throughput with respect to the time axis windowing length for each communication condition stored in the parameter table storage unit 17. The communication condition selection unit 19 can achieve the maximum throughput based on the essential condition items acquired by the condition acquisition unit 18 and the essential condition items acquired by the condition acquisition unit 18 when the communication conditions are selected. Select communication conditions. The communication condition selection unit 19 transmits any one or more of the selected error correction code type, coding rate, and modulation method to the demodulation / decoding processing unit 23 on the OFDM signal receiving apparatus 2 side. The communication condition selection unit 19 notifies the time axis windowing processing unit 12 of the time axis windowing length of the selected communication condition. The communication condition selection unit 19 notifies the transmission power control unit 32 of the transmission power value among the selected communication conditions.

  The time axis windowing processing unit 12 subjects the OFDM signal transmitted from the OFDM signal generation unit 20 to time axis windowing processing with a time axis windowing length corresponding to the communication condition selected by the communication condition selection unit 19. . Details of the time axis windowing process executed in the time axis windowing processing unit 12 will be described later. The time axis windowing processing unit 12 outputs the windowed OFDM signal to the band limiting filter 13.

  The band limiting filter 13 performs transmission digital filter processing such as a band limiting filter on the OFDM symbol constituting the OFDM signal from the time axis windowing processing unit 12.

  The transmission power parameter table is a condition item given as an environment (any one or more of communication system standards, hardware performance including characteristics of digital band limiting filters and RF circuits, and arbitrary spectrum mask specifications), and required. In-band maximum corresponding to the maximum transmission power for the time-axis windowing length for performing time-axis windowing processing or the maximum value of the PSD of the transmission signal in the transmission band under the condition of the design margin item for the spectrum mask specification The transmission PSD relationship is stored in advance for each condition item, such as a hard disk, a memory, or the like, or a program that can calculate the relationship.

  The throughput parameter table is based on the maximum transmission power or the maximum in-band transmission PSD given from the parameter table storage unit 17, and the relationship between the throughput and the time axis windowing length for performing the time axis windowing process is previously determined for each communication condition. It is a stored hard disk, memory, etc., or a program that can calculate the above relationship.

  The time axis windowing processing unit 16 performs arbitrary time axis windowing processing on the preamble portion constituting the OFDM signal. Incidentally, the time axis windowing processing unit 16 may pass, for example, only the preamble portion through the band limiting filter instead of performing such time axis windowing processing. The time axis windowing processing unit 16 transmits the data symbol of the preamble portion of the OFDM signal subjected to such processing to the symbol concatenation processing unit 14. In addition, the time axis windowing processing unit 16 notifies the synchronization parameter setting unit 15 of information on the time axis windowing length in the time axis windowing process executed for the preamble unit and the band limiting filter.

  The synchronization parameter setting unit 15 extracts parameters for synchronization that are attached to the preamble portion of the OFDM signal. The synchronization parameter setting unit 15 extracts time axis windowing length notified from the time axis windowing processing unit 16 and information related to the band limiting filter. The synchronization parameter setting unit 15 notifies the synchronization detection unit 21 in the OFDM signal receiving apparatus 2 of the parameters for achieving synchronization, the time axis windowing length, and information on the band limiting filter. As a notification method, for example, a radio signal may be transmitted.

  In addition to notifying the OFDM signal receiving apparatus 2 of the information about the time axis windowing length and the band limiting filter, the information set on the OFDM signal transmitting apparatus 1 side, for example, is set in the OFDM signal receiving apparatus 2 side. May be set in advance on the OFDM signal receiving apparatus 2 side. As a result, it is possible to provide information on the preamble portion set on the OFDM signal transmitting apparatus 1 side in advance on the OFDM signal receiving apparatus 2 side without notifying the information.

  The band limiting filter 31 performs transmission digital filter processing such as a band limiting filter on the preamble portion constituting the OFDM signal from the time axis windowing processing unit 16.

  The symbol concatenation processing unit 14 concatenates the actual data portion of the OFDM signal output from the band limiting filter 13 and the preamble portion of the OFDM signal output from the band limiting filter 31.

  The transmission power control unit controls the transmission power of the OFDM signal output from the symbol concatenation processing unit 14 based on the transmission power value selected by the communication condition selection unit 19. The transmission power control unit wirelessly transmits the transmission power controlled OFDM signal.

  In addition to the above-described configuration, the OFDM signal transmission apparatus 1 includes general circuits and blocks (not shown) necessary for transmitting an OFDM signal.

  The OFDM signal receiving apparatus 2 receives the OFDM signal transmitted from the transmission power control unit 32 and performs processing for synchronization. At this time, the synchronization detection unit 21 is notified of a parameter for synchronization from the synchronization parameter setting unit 15, and based on this, synchronization can be achieved. In addition, when the synchronization parameter setting unit 15 is notified of the time axis windowing length in the preamble part or information on the band limiting filter, the synchronization detection unit 21 refers to these information for synchronization. . Further, the preamble portion can be demodulated based on the notified time axis windowing length.

  Based on the synchronization information detected by the synchronization detector 21, the OFDM demodulator 22 performs frame synchronization, frequency synchronization, and GI removal, and converts the subcarrier signal by Fourier transform. The subcarrier signal is subjected to transmission path equalization and transmitted to the demodulation / decoding processing unit 23.

  The demodulation / decoding processing unit 23 performs demodulation and error correction decoding processing on the subcarrier signal equalized in the transmission path. The demodulation / decoding processing unit 23 may be any other modulation method such as BPSK or QPSK, or any other coding method such as block convolutional coding. The demodulation / decoding processor 23 performs demodulation and decoding based on the communication condition selected by the communication condition selector 19. Received signal data is obtained through demodulation and decoding processing by the demodulation / decoding processor 23.

  In addition to the above-described configuration, the OFDM signal receiving apparatus 2 includes general circuits and blocks (not shown) necessary for receiving an OFDM signal.

  Next, the operation of the OFDM signal transmission apparatus 1 to which the present invention is applied will be described. In the OFDM signal transmitting apparatus 1 to which the present invention is applied, for example, IEEE 802.15... For the secondary user to effectively use the TV white space or the white space in which the primary user is not in use temporarily or continuously. 4m, IEEE 802.11. An OFDM signal is transmitted based on a standard such as af or IEEE 802.22 / 22b. However, the OFDM signal transmitting apparatus 1 is not limited to the case where such a white space is used by a secondary user, and can be applied to other normal OFDM communications. .

  FIG. 2 shows a flowchart for generating an OFDM signal to be actually transmitted in the OFDM signal transmitting apparatus 1. This OFDM generation flow is roughly classified into a frequency domain from steps S11 to S14 and a time domain from steps S14 to S19. FIG. 3 is a flowchart for explaining the operation of the OFDM signal transmitting apparatus 1 to which the present invention is applied.

  First, in step S11, serial-parallel conversion is performed on transmission signal data, and then channel coding is performed in step S12. This channel coding corresponds to error correction channel coding processing mainly performed in the modulation / coding processing section 11. In step S13, the input data series is subjected to convolutional interleaving and the like. Next, the process proceeds to step S14, where the inverse Fourier transform is performed collectively in units of OFDM symbols to generate a time-domain baseband OFDM signal. That is, in step S14, the frequency domain is shifted to the time domain. Incidentally, the processes of steps S13 and S14 are performed in the OFDM signal generation unit 20, respectively.

  Next, the process proceeds to step S15, and after parallel-serial conversion is performed, the process proceeds to step S16 to add a guard interval to the OFDM signal. This makes it possible to withstand multipath fading.

  Next, the process proceeds to step S17, where the time axis windowing processing unit 12 performs time axis windowing processing for reducing discontinuity between symbols. Next, in step S18, the OFDM signal subjected to the time-axis windowing process is subjected to a filtering process by the band limiting filter 13, and finally a digital analog (D / A) conversion process is performed (step S19).

FIG. 4 is a diagram for explaining the time axis windowing process performed in step S16. When the horizontal axis is the time axis, the OFDM signal of this time axis is, as shown in FIG. 4A, a guard interval consisting of the period T _G given in step S16 and a period T _F corresponding to the OFDM signal. And the symbol. The OFDM symbol length including the guard interval is Ts. The time zone centered on the period _{TG of the} guard interval is configured by copying the latter half symbol in the OFDM signal.

  By the way, although this OFDM signal is configured as a continuous signal within the symbol, a discontinuity occurs at the boundary between symbols. Since this discontinuous point includes many frequency components, an unnecessary radiation component is generated outside the band. Therefore, in step S16, the time-axis windowing process is performed on the discontinuous points generated at the boundaries between the symbols, thereby smoothing the signal waveform and suppressing unnecessary out-of-band radiation.

The m-th symbol OFDM time axis transmission signal; x ^m (t), in which this time axis windowing function is introduced, is shown in the following equation (1).

Here, X _n ^m is the n-th subcarrier signal of the m-th symbol, Δf = fs / N is the subcarrier interval (Fs is the sampling frequency, N is the total number of subcarriers), and L is a multiple of oversampling.

Further, w (t) is a time axis windowing function for smoothing the discontinuity at the symbol end. This w (t) is embodied by a raised cosine window or the like shown in the following equation (2) as a time axis windowing function generally used in IEEE 802.11a / g / n, for example. By the way, _TTR is the windowing length.

  Such a windowing function; w (t) is also reflected in the time axis of FIG. It is shown that the windowing function; w (t) is inclined in a curved line at the boundary between OFDM symbols. FIG. 4C shows a state where the OFDM signal is multiplied by such a windowing function; w (t). FIG. 4D shows a state in which such a windowing function; w (t) is multiplied and combined with other adjacent m-1 and m + 1 symbol OFDM signals.

  The time axis windowing length in FIG. 4 corresponds to the time for which windowing is actually performed based on the above-described windowing function; w (t). The longer the time axis windowing length is, the longer the time period for which windowing is performed by the windowing function; w (t). The shape of the windowing function; w (t) has a gentler slope. On the other hand, as the time axis windowing length is shorter, the windowing function; the time zone in which windowing is performed by w (t) is shortened, and the shape of the windowing function; It becomes steep.

  FIG. 5 shows IEEE802.11 after time axis windowing processing. The transmission spectrum of the OFDM signal based on the af standard is shown. The horizontal axis represents the deviation from the center frequency, and the vertical axis represents the PSD defined by the relative value amount from the maximum value, hereinafter, the relative value PSD (dBr / 100 kHz).

As shown in FIG. 5, it can be seen that the out-of-band radiation with respect to the spectrum mask decreases as the windowing length; _TTR increases. When time axis windowing processing is not performed at all (T _TR = 0 μs), frequency components exceeding the spectrum mask are very large outside the band, whereas when time axis windowing processing is performed to some extent ( (T _TR = 1.5 μs), the radiation power outside the band of the OFDM signal is suppressed. If the time axis windowing length is further increased (T _TR = 6.0 μs), the radiation power outside the band of the OFDM signal is further suppressed. In the example of FIG. 5, the time axis windowing length; in the case where the T _TR and 6.0Myuesu, on it is possible to satisfy the spectrum mask, ensuring 10dB or more design margin for the required spectral mask requirement It is shown that it can be done.

  Especially in the wireless communication of secondary users in white space, the condition of the transmission spectrum mask is strict to prevent interference with the primary user, but search for the time axis windowing length that satisfies such conditions. Will be.

FIG. 6 shows IEEE802.11. Time axis windowing length of the OFDM signal based on af standard; for T _TR, relative value PSD in the band end portion, hereinafter, the relative value band end _{PSD; P oob (dBr / 100kHz} ), and the margin for the spectrum mask; P The relationship of _m (dB) is shown. As T _TR and lengthening, relative value band end PSD;; time axis windowing length P _oob decreases, the margin for the spectrum mask; P _m is shown a tendency increases. Therefore, at first glance, it is shown that as the time axis windowing length _TTR is increased, the power radiated out of the band can be effectively suppressed.

On the other hand, FIG. 7 shows IEEE802.11. The relationship of the throughput with respect to the time-axis windowing length (T _TR ) of the OFDM signal based on the af standard is shown. Incidentally, the tendency shown in FIG. 7 is an example when the modulation scheme is 16QAM and block convolutional coding and soft decision Viterbi coding are used. As shown in FIG. 7, when block convolutional coding is not performed, when the time axis windowing length; _TTR exceeds the guard interval length; _TG , the throughput rapidly decreases. The reason for this is that OFDM symbols exceeding the guard interval are difficult to recover because the time axis signal necessary for demodulation is deleted by this time axis windowing process, resulting in a lower throughput. is there.

However, when block convolutional coding is performed, even if the time-axis windowing length; _TTR exceeds the guard interval length; _TG , by changing the coding rate, the tolerance to deterioration in throughput is increased. It becomes possible to do. For example, if the code rate was 5/6, the time axis windowing length; whereas a substantially constant without throughput decreases in within 15μs is T _TR, rapid throughput degradation if it exceeds 15μs is Begins. Similarly, when coding rate 3/4, the time axis windowing length; whereas a substantially constant without T _TR throughput decreases in within 16 .mu.s, rapidly throughput when it exceeds 16 .mu.s Deterioration begins. In the following, it can be seen that as the coding rate is lowered, the time-axis windowing length; _TTR, where the deterioration of the throughput begins, becomes longer. On the other hand, the maximum throughput itself decreases as the coding rate decreases, but even if the transmission time is somewhat longer, it can satisfy the conditions of out-of-band radiation in a severe spectrum mask, and it prevents the deterioration of the throughput. Reliable signal demodulation is possible.

As described above, according to the present invention, even when the time axis windowing length; _TTR exceeds the guard interval length; _TG , it is possible to increase the resistance to the deterioration of the throughput by changing the coding rate. It shows that. However, basically, there is a trade-off relationship between the out-of-band radiation power suppression performance by the time axis windowing process, that is, the relative value band edge PSD; _Poob, and the throughput. For system design, it is necessary to link the relationship between the out-of-band radiation power suppression performance (relative value band edge PSD; _Poob ) by the time axis windowing process and the throughput.

By the way, as shown in Table 1, transmission spectrum mask regulations for secondary users in FCC TV white space, for example, in-band transmission power upper limit value (dBm / 6 MHz), in-band transmission PSD upper limit value, as shown in Table 1. P _tx ^mask (dBm / 100 kHz), out-of-band transmission PSD upper limit; P _edge ^mask (dBm / 100 kHz) are all defined as absolute values.

For example, in the spectrum mask specification for the portable device 2 of the FCC, the in-band transmission power upper limit is 30 dBm / 6 MHz, the in-band transmission PSD upper limit is P _tx ^mask = 2.6 dBm / 100 kHz, and the out-of-band transmission PSD upper limit is P _edge ^mask = −52.8 dBm / 100 kHz.

Therefore, the maximum transmission PSD within the band specified by the absolute value of the OFDM signal to be actually transmitted, hereinafter, the maximum PSD within the absolute value band is referred to as P _tx ^max (dBm / 100 kHz), and the band edge specified by the absolute value. If the absolute value band edge PSD is P _edge (dBm / 100 kHz), for example, the absolute value in-band maximum PSD; the in-band transmission PSD upper limit value that is an upper limit value for which P _tx ^max can be set; when set to P _tx ^mask, a time axis windowing length; relative value band end PSD in the time axis windowing processing by T _TR; in P _oob, requested band transmission PSD limit in the transmission spectrum mask defined by; and P _edge ^mask, the required transmit spectrum design margin with respect to the mask; is determined by the P _m ^R (dB), Mitasube in the band end portion Design maximum PSD that in absolute value is defined, below, the absolute value band ends up PSD; If ^{_{P edge max = P edge mask -P}} m can not be satisfied ^R (dBm / 100kHz), i.e. ^{_{P edge = P tx max + P}} oob If> P _edge ^max , this can also be satisfied by reducing the power of the entire transmission signal.

  FIG. 8 shows a transmission spectrum mask defined by an absolute value for a secondary user (portable device 2) in TVC white space of FCC, and IEEE802.11 after time axis windowing processing. The transmission signal spectrum of the OFDM signal based on the af standard is shown. The horizontal axis represents the deviation from the center frequency, and the vertical axis represents the PSD defined by the absolute value, hereinafter, the absolute value PSD (dBm / 100 kHz).

For example, if the design margin is P _m ^R = 10 dB, P _tx ^{max that} is P _tx ^mask = 2.6 dBm / 100 kHz or less in the band, and P _edge ^max = P _edge ^mask −P _m ^R = at the band edge. It is necessary to generate an OFDM signal having P _edge that is −52.8−10 = −62.8 dBm / 100 kHz or less.

If you do not time axis windowing processing, that is, the time axis windowing length; for T _TR = 0us, relative value band end PSD; P _oob is about -25dBr / 100kHz. Therefore, the in-band transmission PSD upper limit defined by the spectrum mask specification for the portable device 2 of the FCC; P _tx ^mask = 2.6 dBm / 100 kHz is the absolute value maximum in-band PSD of the OFDM signal; P _tx ^max band end the ^{_{PSD, P edge = P tx mask +}} P oob = 2.6-25 = -22.4dBm / 100kHz next, in the band end, the P _edge ^max = -62.8dBm / 100kHz to 40.4dB exceeded End up. Therefore, in such a case, the required condition can be achieved by reducing the total transmission power by 40.4 dB, but reducing the total transmission power by 40.4 dB means that the bit energy versus noise power at the receiving side. Density ratio; Eb / N0 (dB) is also shown to be reduced by 40.4 dB, which causes a significant deterioration in reception quality.

On the other hand, in the case of performing the time axis windowing processing, for example, the time axis windowing length; for T _TR = 6.0us, relative value band end PSD; P _oob is about 39dBr / 100kHz. That is, the out-of-band radiation is suppressed by about 14 dBr / 100 kHz compared to the case of the time axis windowing length T _TR = 0 us. Therefore, the time base windowing length; 14 dB transmission power can be increased as compared with the case of T _TR = 0 us, and the reduction of the entire transmission power can be suppressed to 40.4-14 = 26.4 dB.

Thus, according to the present invention, the absolute value in-band maximum PSD; P _tx ^max is the in-band transmission PSD upper limit value given by the spectrum mask specification; P _tx ^mask , The design margin and time axis windowing length; whichever value is controlled by T _TR , P _edge ^mask −P _m ^R −P _oob (dBm / 100 kHz), is selected and determined.

FIG. 9 shows transmission spectrum mask specifications for secondary users (portable devices) in the TVC white space of FCC, and when each design margin is P _m ^R = 0, 10, 20, 30, 40 [dB]. IEEE802.11 using a raised cosine function for time axis windowing processing. For an OFDM signal based on the af standard, the time axis windowing length obtained by the procedure described above; the relationship between T _TR and the absolute value in-band maximum PSD; P _tx ^max (left vertical axis), and It is an example of a power parameter table according to the present invention showing the relationship between the absolute value in-band maximum PSD; received Eb / N0 gain determined along with P _tx ^max ; Γ (dB) (right vertical axis).

Here, the average Eb / N0 at the receiving side; γ (dB) is not used in the time axis windowing process (time axis windowing length; T _TR = 0 μs) as shown in the equation (4), and the design margin In the case of none (P _m ^R = 0 dB), the average received Eb / N0 when the signal is transmitted; γ ₀ (dB) and the received Eb / N0 gain determined by FIG. ing.

When the time axis windowing length _TTR is small, the absolute value in-band maximum PSD _Ptx ^max is suppressed to the in-band transmission PSD upper limit value _Ptx ^mask or less so as to satisfy the spectrum mask specification. As the time axis windowing length _TTR increases, the absolute value maximum PSD in the band; P _tx ^max increases. When the time axis windowing length; _TTR is sufficiently large, the absolute value in-band maximum PSD; P _tx ^max is equal to the in-band transmission PSD upper limit value; P _tx ^mask .

As the absolute value in-band maximum PSD; P _tx ^max increases, the reception Eb / N0 gain; Γ also increases correspondingly. That is, it is shown that the power intensity of the signal on the receiving side can be improved by increasing the time axis windowing length; _TTR .

On the other hand, as described above, a large time-axis windowing length; _TTR causes a decrease in throughput. Figure 10 is a time axis windowing length shown in FIG. 9; T _TR transmit power control in accordance with, and in consideration of the increase and decrease of the average received Eb / N0 with it, the time axis windowing length of Figure 7; for T _TR Throughput; FIG. 4 is an example of a throughput parameter table according to the present invention when γ ₀ = 0 dB and P _m ^R = 0 dB when the relationship with R is recalculated.

The throughput parameter table of FIG. 10 shows MCS0 to MCS7 (detailed in Table 2), which are combinations of modulation coding rates essential in the IEEE802.11af standard. When the time axis windowing length; _TTR is small, the transmission power is suppressed and the average received Eb / N0 deteriorates. As a result, the throughput; R significantly deteriorates. However, if the time axis windowing length; _TTR is increased to some extent, unnecessary radiation power outside the band is suppressed, and the transmission power is increased within the range specified by the spectrum mask and within the range that satisfies the requirements at the band edge. It will not be a problem. Therefore, throughput; R increases. However, if the time axis windowing length _TTR is increased more than necessary, the signal component necessary for demodulation and decoding is scraped off on the receiving side, and as a result, the throughput R is deteriorated.

For example, when the MCS number is 4, the time axis windowing length; the throughput when T _TR is 0 μs to 2.25 μs and 15.0 μs or more; R deteriorates, but the time axis windowing length; T _TR is 2.25 μs. Throughput in the range of ˜15.0 μs; R does not deteriorate.

Therefore, according to the present invention, the optimum time axis windowing length _TTR ^opt that can achieve the maximum throughput should be selected by the throughput table considering the transmission power control. Optimal time windowing length; if there is a range of possible values for T _TR ^opt , it should be set to a value that can achieve its maximum throughput in as many MCSs as possible.

For example, in FIG. 10, it can be seen that the maximum throughput can be obtained with all the MCSs in the time axis windowing length; T _TR = 3.75 μs. Therefore, in such a case, this T _TR = 3.75 μs should be selected as the optimal time axis windowing length; T _TR ^opt .

When the optimum time axis windowing length; T _TR ^opt is determined, the transmission signal power control value is automatically determined from the transmission power parameter table shown in FIG. For example, when T _TR ^opt = 3.75 μs is selected, the maximum PSD within the absolute value band at that time is determined as P _tx ^max of 2.6 dBm / 100 kHz from FIG.

  Once the optimal time windowing length and transmission power control value are determined by the given environment and design conditions, the received signal level varies depending on the wireless communication environment, as in the case of adaptive modulation that is normally performed. Accordingly, a modulation scheme, a coding rate (MCS), and the like are determined.

  As described above, according to the present invention, it is possible to obtain the maximum throughput that can be achieved while satisfying a given environment and design conditions by performing optimal windowing length and transmission power control.

  In the above-described embodiment, attention is paid to a specific condition item for the sake of simplification. However, even if this condition item is replaced with another value, system, or the like, these similar tendencies appear.

Table 3 is a list showing an example of the condition items. Condition item 1 relates to spectrum mask specification. Condition item 2 relates to the system to be used. Condition item 3 relates to the guard interval length T _G , and is composed of, for example, a ratio of OFDM symbol lengths. Condition item 4 relates to error correction coding, and includes block convolutional coding and LDPC coding. Condition item 5 relates to error correction decoding, and includes hard decision Viterbi decoding, soft decision Viterbi decoding, and the like. Condition item 6 relates to the coding rate. Condition item 7 relates to the type of time-axis windowing processing, such as raised cosine, straight line, or the like. Condition item 8 relates to a modulation method, and includes BPSK, QPSK, 16QAM, 64QAM, 256QAM, and the like.

  As shown in FIGS. 1 and 3 described above, these condition items include items given as an environment (for example, condition items 1 to 3) and items made variable to optimize the system (for example, condition item 4). To 8).

  Note that all the condition items in Table 1 are not essential, but at least the system (OFDM communication standard), guard interval length, error correction coding type, error correction decoding type, coding rate, time axis Any one of at least one of the type of windowing process and the modulation method may be used. In addition, the condition items are not limited to the condition items shown in Table 1, and any other communication items may be added over any number of types.

  One communication condition is determined by selecting one of these condition items. For example, in the example of MCS number 3 in FIG. 10 described above, the spectrum mask definition of condition item 1 is FCC portable type 2, and the system of condition item 2 is IEEE 802.11. af, condition item 3 guard interval length is 1/4, condition item 4 error correction coding is block convolution coding, condition item 5 error correction decoding is soft decision Viterbi decoding, condition item 6 code The conversion rate is 1/2, the windowing type of the condition item 7 is raised cosine, and the modulation method of the condition item 8 is 16QAM, so that one communication condition is formed. Other communication conditions are also configured by selecting one from condition items 1 to 8 respectively. For this reason, the communication conditions can be hundreds or thousands depending on the number of items in the condition items 1 to 7.

Moreover, each one communication conditions are selected one by one each respectively from condition items 1-6, 9, adjustable maximum range of transmission power with respect to time axis windowing length T _TR shown in FIG. 10, and Throughput relationships can be obtained one by one. In the present invention, for each communication condition, the relationship of the range of the maximum transmit power that can be adjusted with respect to the time axis windowing length T _TR is shown in the transmission power parameter table, and the relationship of the throughput with respect to the time axis windowing length T _TR is Each is stored in the throughput parameter table.

Communication condition selection unit 19, access the parameter table storage section 17, to select the communication condition based on a relationship of throughput to the time axis windowing length T _TR stored thereto. In selecting the communication condition, the communication condition selecting unit 19 needs to acquire the out-of-band radiation suppression condition required for the OFDM signal to be transmitted this time. The out-of-band radiation suppression condition is acquired via the condition acquisition unit 18. Based on the acquired out-of-band radiation suppression condition, the communication condition selection unit 19 selects a communication condition that satisfies this condition. Table 4 shows an example in which the communication condition selection unit 19 selects communication conditions including items filled in for each of the condition items 1 to 8. It is shown that one condition is selected for each of the condition items 1 to 6.

  At this time, in addition to the above-described out-of-band radiation suppression condition, the communication condition selection unit 19 acquires in advance the condition items that are essential in the OFDM signal to be transmitted by the OFDM signal transmission device 1 via the communication condition selection unit 19. You may make it do.

  Table 5 shows the result of acquiring the condition items that are essential in the OFDM signal to be transmitted by the OFDM signal transmission apparatus 1. A bold part surrounded by a thick frame in the table indicates an indispensable condition item. Condition item 1 is FCC portable type 1, Condition item 2 is IEEE 802.15.4m, Condition item 3 is 1/4, Condition item 4 is block convolutional coding, Condition item 5 is hard decision Viterbi decoding, Condition 7 is a straight line The state is an essential condition item in the OFDM signal transmitted this time. In such a case, the communication condition selection unit 19 further selects the unconfirmed condition items 6 and 8 after satisfying these essential condition items.

The communication condition selection unit 19 accesses the parameter table storage unit 17, and shows the relationship of the throughput with respect to the range of the adjustable transmission power and the time axis windowing length T _TR satisfying such essential condition items 1 to 5 and 7. Identify. From the relationship between the throughput for a range of the identified adjustable transmit power and time axis windowing length T _TR, it becomes possible to select a compatible communication items 6 and 8 suppression condition of the obtained out-of-band. Concept in the selection of such communication items 6,8, above as well as the relationship between the adjustable transmit power and throughput for a range of time axis windowing length T _TR shown in FIG. 9 and 10, the suppression of out-of-band A coding rate, a modulation scheme, and the like that satisfy the conditions are selected, and the communication items 6 and 8 and the optimum transmission power and time axis windowing length _TTR are determined.

  Incidentally, in the above-described example, the case where the condition items 1 to 5 and 7 are determined in advance has been described as an example. However, the present invention is not limited to this, and the condition items 6 and 8 are determined in advance. Therefore, other condition items that satisfy the condition are determined by accessing the parameter table storage unit 17 in the same manner as described above.

  Finally, one specific item is selected for each condition item 1 to 8, and one communication condition is determined. The communication condition selection unit 19 notifies the time axis windowing processing unit 12 of the determined communication condition. The time axis windowing processing unit 12 performs time axis windowing processing based on the notified communication conditions. As a result, the OFDM signal to be transmitted is subjected to time-axis windowing processing that satisfies the out-of-band radiation suppression condition, and is configured with communication conditions that can prevent deterioration in throughput.

  The communication condition selecting unit 19 also notifies the selected communication condition to the error demodulation / decoding processing unit 23 in the OFDM signal receiving apparatus. The demodulation / decoding processing unit 23 can decode the received OFDM signal based on the notified communication condition.

  As described above, the OFDM signal transmission apparatus 1 to which the present invention is applied has the relationship of the throughput to the time axis windowing length in consideration of the maximum transmission power or the maximum in-band transmission PSD determined by the parameter table, It is stored in advance for each adjustable communication condition of one or more of coding rate, modulation scheme (number of modulation multi-values), guard interval length, maximum transmission power or in-band maximum transmission PSD. Then, the transmission power and the time-axis windowing length that satisfy the out-of-band radiation suppression condition are selected from the communication conditions satisfying the above condition items in relation to the throughput stored in the parameter table storage unit 17. Specifically, in the relationship between the throughput parameter table and the adjustable communication condition stored in the transmission power parameter table and the throughput, the throughput is determined based on the conditions given as the environment and the design margin for the required spectrum mask specification. Is selected from among one or more of the time-axis windowing length, the error correction code and its coding rate, the modulation scheme (the number of modulation multi-values), and the transmission power. Since these operations can be automatically performed, when the OFDM communication system 10 is constructed, the conditions for suppressing out-of-band radiation are automatically set by inputting conditions via the condition acquisition unit 18. It is possible to select an optimal communication condition that satisfies the conditions and can prevent the deterioration of the throughput.

  These processes are executed in the procedure as shown in FIG. First, as the condition acquisition, one or more conditions are acquired from any one of the communication system standard, the type of the band limiting filter and its filter coefficient, the performance of the RF circuit, and the spectrum mask specification.

  Next, in the throughput parameter table, a windowing function, its windowing length, transmission power, modulation multi-level number, error correction code and coding rate thereof are stored as freely adjustable parameter groups. Transmission power parameter table Stores a windowing function, its windowing length, and maximum transmission power (maximum PSD), and the range of transmission power adjustable to this maximum PSD is controlled. Throughput is calculated from information stored in these parameter tables and acquired conditions, and communication conditions are selected based on the calculated throughput. This selection is nothing but to determine the optimum combination of adjustment parameters (the windowing function and its windowing length, the modulation multi-value number, the error correction code and its coding rate, and the transmission power) that maximize the throughput. .

  In addition, in the OFDM communication system 10 once installed, when a condition item that is essential in the OFDM signal to be transmitted is changed, the condition item is automatically acquired by acquiring the condition item via the condition acquisition unit 18. It is possible to select optimal communication conditions.

  In particular, according to the present invention, the circuit configuration can be realized without complicating the circuit configuration and without reducing unnecessary transmission signal power. Therefore, it is possible to achieve a configuration that is extremely inexpensive and has excellent spread. .

  Furthermore, according to the present invention, it is possible to adaptively select a time axis windowing length for band limitation with respect to various strict transmission spectrum mask specifications including, for example, the regulations defined in the US FCC. In addition, the TV white space or the white space can be efficiently used by controlling the transmission power in consideration of the out-of-band radiation power suppression performance of the time axis windowing and other communication conditions.

  Further, according to the present invention, the present invention is not limited to the case where it is embodied as the above-described OFDM signal transmitting apparatus 1, and may be embodied as a design program for designing an OFDM communication system. In such a case, for example, it is embodied as a program installed in an electronic device such as a personal computer (PC), and the operations of the components shown in FIGS. 1 and 3 are executed as program steps. It will be followed.

  First, the relationship between adjustable transmission power and throughput with respect to the time-axis windowing length for performing time-axis windowing processing is acquired in advance for each communication condition, and this is stored in the PC storage means (hard disk, memory, etc.) in the throughput parameter. Store as a table. Next, when shifting to the actual design phase, the condition items that are essential in the OFDM signal to be transmitted from the OFDM signal transmission apparatus and the out-band radiation suppression conditions are acquired. Next, the transmission power and time-axis windowing length that satisfy the suppression conditions for the acquired out-of-band radiation are related to the transmission power stored in the transmission power parameter table and the throughput stored in the throughput parameter table. Select from the communication conditions that satisfy the condition items. Finally, the selected time axis windowing length, transmission power, and communication conditions are output as a solution.

DESCRIPTION OF SYMBOLS 1 OFDM signal transmitter 2 OFDM signal receiver 10 OFDM communication system 11 Modulation / coding processing unit 12 Time axis windowing processing unit 13, 31 Band limiting filter 14 Symbol concatenation processing unit 15 Synchronization parameter setting unit 16 Time axis windowing process Unit 17 throughput parameter table storage unit 18 condition acquisition unit 19 communication condition selection unit 20 signal generation unit 21 synchronization detection unit 22 OFDM demodulation unit 23 demodulation / decoding processing unit 32 transmission power control unit

Claims (6)

In an OFDM signal transmitting apparatus that transmits an orthogonal frequency division multiplexing (OFDM) signal,
Maximum transmission power or maximum value of transmission signal power spectrum density (PSD) within the transmission band for the time-axis windowing length of the time-axis windowing process performed on the boundary between the time-axis OFDM symbols constituting the OFDM signal The relationship between the maximum in-band transmission PSD corresponding to the conditions given by the communication system standard, the hardware performance including the characteristics of the digital band limiting filter and the RF circuit, and any one or more environments of any spectrum mask specification, And a transmission power parameter table stored in advance for each design margin for the required spectrum mask specification,
Considering the maximum transmission power or in-band maximum transmission PSD determined in the transmission power parameter table, the relationship of the throughput to the time axis windowing length is the error correction code, its coding rate, modulation scheme (number of modulation multi-levels) ), A throughput parameter table stored in advance for each adjustable communication condition of one or more of the guard interval lengths;
A time axis window that maximizes the throughput based on the conditions given as the environment and the design margin for the required spectrum mask specification in the relationship between the adjustable communication conditions stored in the throughput parameter table and the throughput. A communication condition selection means for selecting one or more of an inching length, an error correction code and its coding rate, a modulation scheme (number of modulation multi-values), and transmission power;
Based on the communication condition and the transmission power selected by the communication condition selection unit, the OFDM signal subjected to the time axis windowing process over the time axis windowing length in the communication condition selected by the communication condition selection unit An OFDM signal transmitting apparatus comprising: an OFDM signal transmitting means for transmitting. The above transmission power upper limit parameter table is one of the types of time axis windowing processing, OFDM modulation scheme, arbitrary spectrum mask specification, hardware performance including characteristics of digital band limiting filter and RF circuit, and OFDM communication standard. The OFDM signal transmitting apparatus according to claim 1, wherein the OFDM signal transmitting apparatus is stored for each communication condition including one or more condition items. The throughput parameter table is a communication composed of condition items including one or more of time axis windowing processing type, OFDM modulation method, channel coding type, coding rate, guard interval length, and OFDM communication standard. The OFDM signal transmitting apparatus according to claim 1 or 2, wherein the OFDM signal transmitting apparatus is stored for each condition. The OFDM signal transmission apparatus according to any one of claims 1 to 3, wherein the communication condition selection unit selects a communication condition that can achieve a maximum throughput in the throughput parameter table. At least one of the time-axis windowing type, time-axis windowing length, band-limit filter type, and band-limit filter response set for the preamble added to the beginning of the OFDM signal is set in advance on the receiving device side. The OFDM signal transmitting apparatus according to claim 1, further comprising a notification unit that notifies the information. In an OFDM communication system design program for designing an OFDM communication system for transmitting and receiving orthogonal frequency division multiplexing (OFDM) signals,
The relationship between the maximum transmission power or the maximum in-band transmission PSD with respect to the time-axis windowing length for performing the time-axis windowing process on the boundary between the time-axis OFDM symbols constituting the OFDM signal is a communication system standard, Hardware performance including the characteristics of the digital band limiting filter and RF circuit, conditions given as one or more environments of any spectrum mask specification, and transmission power acquired in advance for each design margin for the required spectrum mask specification A parameter acquisition step;
Considering the maximum transmission power or the in-band maximum transmission PSD determined in the transmission power parameter acquisition step, the relationship of the throughput to the time axis windowing length is the error correction code, its coding rate, modulation scheme (modulation multilevel). Number), a throughput parameter acquisition step that is acquired in advance for each adjustable communication condition of one or more of the guard interval lengths;
A time axis window that maximizes the throughput based on the conditions given as the environment and the design margin for the required spectrum mask specification in the relationship between the adjustable communication condition acquired in the throughput parameter acquisition step and the throughput. A communication condition selection step of selecting any one or more of an ing length, an error correction code and its coding rate, a modulation method (modulation multi-level number), and transmission power;
An OFDM communication system design program for causing a computer to execute a time axis windowing length selected in the communication condition selection step and an output step for outputting the communication condition as a solution.