JP6160906B2 - Transmitting apparatus and transmitting method - Google Patents

Description

  The present invention relates to a transmission apparatus and a transmission method for transmitting a radio signal in which a plurality of subcarriers are arranged at predetermined frequency intervals.

  2. Description of the Related Art Conventionally, a transmission apparatus that transmits an OFDM (Orthogonal Frequency Division Multiplex) signal in which a plurality of subcarriers are arranged at predetermined frequency intervals is known. As shown in FIG. 1A, such a transmission apparatus is known to suppress side lobes (out-of-band leakage power) by not arranging subcarriers in the guard band at the band edge (for example, patents). Reference 1).

  On the other hand, in order to use the frequency band more efficiently, as shown in FIG. 1B, a technique of arranging a subcarrier (portion indicated by a thick line) at the band edge at the sacrifice of the guard band is also conceivable.

JP 2012-19420 A

  However, when subcarriers are arranged at the end of the band as shown in FIG. 1B, there is a problem that side lobes become large and the reception performance of other communication systems is adversely affected beyond the guard band.

  An object of the present invention is to provide a transmission apparatus and a transmission method capable of suppressing side lobes when subcarriers are arranged at band ends.

A transmission apparatus according to an aspect of the present invention is a transmission apparatus that transmits a radio signal in which a plurality of subcarriers are arranged from a first band edge to a second band edge at a predetermined frequency interval, and includes a plurality of subcarriers. A first band edge selection unit for selecting a subcarrier at the first band edge, which is one of an upper end and a lower edge of a frequency band, and the other one of the upper end and the lower end of the frequency band among the plurality of subcarriers. A second band edge selector that selects a subcarrier at the second band edge, and a subcarrier between band edges that is between the first band edge and the second band edge among the plurality of subcarriers. a band end between the selector for selecting for transmission symbols generated based on the subcarrier of the first band end, a first window function multiplying section length multiplied by a first window function is a predetermined length Between the multiplier and the band edge To the transmission symbols generated based on the sub-carrier, and a second window function multiplier for multiplying the second window function is a short multiplication section length than multiplication section length of the first window function, said second band end A third window function having a multiplication interval length shorter than a multiplication interval length of the first window function and longer than a multiplication interval length of the second window function, for a transmission symbol generated based on the subcarrier of A configuration having a third window function multiplication unit for multiplication is adopted.

A transmission method according to an aspect of the present invention is a transmission method for transmitting a radio signal in which a plurality of subcarriers are arranged from a first band edge to a second band edge at a predetermined frequency interval, and the transmission method includes: A first band edge selection step for selecting a subcarrier at the first band edge, which is one of an upper end and a lower edge of a frequency band, and the other one of the upper end and the lower end of the frequency band among the plurality of subcarriers. A second band edge selection step of selecting a subcarrier at the second band edge, and a subcarrier between band edges that is between the first band edge and the second band edge among the plurality of subcarriers. a selecting step between the band edge of selecting, with respect to transmission symbols generated based on the subcarrier of the first band end, a first window function multiplying section length multiplied by a first window function is a predetermined length Multiplication Step and to the transmission symbols generated based on the sub-carrier between the band edge, the second window function multiplying the second window function is a short multiplication section length than multiplication section length of the first window function multiplier And a multiplication interval shorter than the multiplication interval length of the first window function and longer than the multiplication interval length of the second window function for the transmission symbol generated based on the subcarrier at the second band edge A third window function multiplying step for multiplying a third window function having a length .

  The present invention can suppress side lobes when subcarriers are arranged at the band edges.

The figure which shows each example of the subcarrier arrangement | positioning in the conventional transmitter, and the magnitude | size of a side lobe The block diagram which shows the structural example of the transmitter which concerns on Embodiment 1 of this invention. The figure which shows an example of the division of the frequency band which concerns on Embodiment 1 of this invention The figure which shows each example of the OFDM symbol of the transmitter which concerns on Embodiment 1 of this invention. The figure which shows an example of the state by which the side lobe was suppressed by the transmitter which concerns on Embodiment 1 of this invention. The block diagram which shows the structural example of the transmitter which concerns on Embodiment 2 of this invention. The block diagram which shows the structural example of the transmitter which concerns on Embodiment 3 of this invention. The figure which shows an example of the state in which amplitude control was performed by the transmitter which concerns on Embodiment 3 of this invention. The figure which shows an example of the state of the subcarrier of the band edge when Embodiment 1 is applied to Embodiment 3 of this invention.

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

(Embodiment 1)
FIG. 2 is a block diagram showing a configuration example of transmitting apparatus 100 (an example of the transmitting apparatus of the present invention) according to Embodiment 1 of the present invention. The transmission device 100 is, for example, a base station.

  In FIG. 2, a transmission apparatus 100 includes a multiplexing unit 10, a modulation unit 11, an S / P 12, band selection units 13 and 14, IFFT units 15 and 16, CP addition units 17 and 18, window function multiplication units 19 and 20, and transmission. Unit 21, antenna 22, band selection control unit 23, and selection band information generation unit 24.

  The multiplexing unit 10 multiplexes data from a selection band information generation unit 24 described later with data to be transmitted.

  The modulation unit 11 modulates data from the multiplexing unit 10. For example, BPSK, QPSK, 16QAM, 64QAM or the like is used as the modulation method.

  The S / P 12 parallelizes the data from the modulation unit 11 and outputs it as a plurality of subcarriers.

  Each of the band selection units 13 and 14 selects a subcarrier in the frequency band instructed by the band selection control unit 23 from the plurality of subcarriers output from the S / P 12. For example, the band selection unit 13 selects a subcarrier at the band edge. On the other hand, the band selection unit 14 selects, for example, a subcarrier between two band ends (hereinafter referred to as “between band ends”).

  Here, an example of the division of the frequency band is shown in FIG. In FIG. 3, a and c are band ends selected by the band selecting unit 13, and b is a band end selected by the band selecting unit 14. Band ends a and c overlap with part of the guard band. It should be noted that the subcarrier at the band edge a and the subcarrier at the band edge c have the same requirements for side lobe reduction.

  IFFT units 15 and 16 perform IFFT (Inverse Fast Fourier Transform) processing on the subcarriers selected by band selection units 13 and 14, respectively. Thereby, an OFDM symbol is generated.

  CP adding sections 17 and 18 add a CP (cyclic prefix) to the OFDM symbols generated by IFFT sections 15 and 16, respectively. At this time, for example, a certain portion from the end of the IFFT-processed signal is added as a CP to the top of the IFFT-processed signal. CP is a duplication of an OFDM symbol, and is used to improve reception quality when a delayed wave is received in communication using OFDM. In general, the longer the CP on the time axis, the easier it is to remove the influence of delayed waves from the received OFDM symbol, and the reception quality improves.

  The window function multipliers 19 and 20 multiply the OFDM symbol to which the CP is added by the CP addition units 17 and 18 by the window function, respectively. The window function is, for example, H (t) = 0.5−0.5 × cos (2π × t / w). w is the window function multiplication section length, and indicates the length of the window function on the time axis. Further, w is a value greater than or equal to t, and t is a value greater than or equal to 0. The window function is a function that suppresses signals outside the desired band, and in this embodiment, the window function is used to suppress side lobes caused by subcarriers arranged at the band edges. Here, the shorter the multiplication interval length w of the window function, the shorter the period during which the signal is suppressed, while the change in the amplitude of the signal on the time axis becomes steeper. A sharp change in amplitude on the time axis corresponds to superposition of signals in a wider frequency band on the frequency axis. Accordingly, as the window function having a shorter multiplication section length w is used, the reception quality of the signal is improved while the side lobe is expanded.

  In the present embodiment, based on the nature of the window function, the window function multipliers 19 and 20 perform multiplication with different window functions by using different w. That is, the window function multiplication unit 19 performs multiplication using a window function (hereinafter referred to as “first window function”) in which w is the CP length (the length of the entire CP). On the other hand, the window function multiplication unit 20 performs multiplication using a window function (hereinafter referred to as “second window function”) in which w is ½ of the CP length. An example of the OFDM symbol at this time is shown in FIG. In FIG. 4, (1) indicates an OFDM symbol that is not multiplied by a window function. (2) shows an OFDM symbol multiplied by the first window function. (3) shows an OFDM symbol multiplied by the second window function.

  The transmission unit 21 receives a signal obtained by combining the output signals from the window function multiplication units 19 and 20 into one, and performs digital / analog conversion and orthogonal modulation to obtain a baseband signal. Then, the transmission unit 21 frequency-converts the obtained baseband signal into a radio signal and transmits it from the antenna 22.

  The band selection control unit 23 instructs the band selection unit 13 which frequency band the band selection unit 13 should select (hereinafter referred to as “band edge frequency”). The band edge frequency is, for example, the frequency band of band edges a and c shown in FIG. Further, the band selection control unit 23 instructs the band selection unit 14 to select a frequency band to be selected by the band selection unit 14 (hereinafter referred to as “interband end-to-end frequency”). The band edge frequency is, for example, the frequency band b between band edges shown in FIG. Note that the band edge frequency and the band edge frequency may be predetermined values or values that are appropriately changed.

  In addition, when the band selection control unit 23 instructs the band edge frequency and the band edge frequency, the band selection control unit 23 notifies the selection band information generation unit 24 of them.

  The selection band information generation unit 24 generates data indicating the band edge frequency and the frequency between the band edges notified from the band selection control unit 23 (hereinafter referred to as “selection band information”), and notifies the multiplexing unit 10 of the data. As described above, the multiplexing unit 10 multiplexes the selected band information with the transmission target data. Thereby, the transmission apparatus 100 can notify the receiving side which frequency band has been selected.

  As described above, transmitting apparatus 100 according to the present embodiment is characterized in that subcarriers at the band edges are multiplied by the first window function, and subcarriers between the band edges are multiplied by the second window function. To do. Thereby, as shown in FIG. 5, transmitting apparatus 100 according to the present embodiment can suppress side lobes when subcarriers are arranged at the band ends. That is, the transmitting apparatus 100 can increase the transmission capacity by arranging subcarriers at the band edge, and suppress the side lobes by multiplying the band edge subcarriers by the first window function. The influence on the adjacent communication system can be suppressed. Further, the transmission apparatus 100 can improve the frequency utilization efficiency without degrading the reception quality by multiplying the subcarriers between the band edges by the second window function.

  In addition, transmission apparatus 100 of the present embodiment can simplify the apparatus configuration and reduce the circuit scale and current consumption by collectively multiplying the subcarriers at the end of the band with the same side lobe request by the first window function. Further, the w applied to the first window function and the second window function is not limited to the CP length or 1/2 of the CP length as long as w of the second window function is shorter than w of the first window function. .

(Embodiment 2)
FIG. 6 is a block diagram showing a configuration example of the transmission apparatus 101 (an example of the transmission apparatus of the present invention) according to Embodiment 2 of the present invention. The transmission apparatus 101 is a base station, for example.

  In FIG. 6, the transmission apparatus 101 is different from the transmission apparatus 100 shown in FIG. 1 in that a band selection unit 25, an IFFT unit 15, a CP addition unit 17, and a window function multiplication unit 19 are replaced with a band selection unit 25, 26, IFFT units 27 and 28, CP adding units 29 and 30, and window function multiplying units 31 and 32 are different. Below, description about a structure common to the transmitter 100 is abbreviate | omitted, and only a different structure is demonstrated.

  Each of the band selection units 25 and 26 selects a subcarrier in the frequency band from a plurality of subcarriers output from the S / P 12 based on an instruction from the band selection control unit 23. The band selection unit 25 selects, for example, the subcarrier at the upper end of the band among the two band ends. The upper end of the band is, for example, the band end c shown in FIG. On the other hand, the band selection unit 26 selects, for example, the subcarrier at the lower end of the band among the two band ends. The lower band end is, for example, a band end a shown in FIG. It should be noted that the subcarriers at the band edge a and the subcarriers at the band edge c have different specifications regarding the side lobe reduction.

  IFFT units 27 and 28 perform IFFT processing on the subcarriers selected by band selection units 25 and 26, respectively, to generate OFDM symbols.

  CP adding units 29 and 30 add CPs to the OFDM symbols generated by IFFT units 27 and 28, respectively. The CP addition method here is the same as in the first embodiment.

  The window function multiplying units 31 and 32 multiply the OFDM symbol to which the CP is added by the CP adding units 29 and 30 by the window function, respectively. The window function expression here is the same as in the first embodiment.

  Here, the window function multipliers 31 and 32 perform multiplication with different window functions by using different w. That is, the window function multiplication unit 31 performs multiplication using a window function in which w is the CP length, that is, the first window function. On the other hand, the window function multiplication unit 32 performs multiplication using a window function (hereinafter referred to as “third window function”) in which w is ¾ of the CP length.

  The transmitter 21 receives a signal obtained by combining the output signals from the window function multipliers 20, 31, and 32 into one, and performs digital / analog conversion and orthogonal modulation to obtain a baseband signal. Then, the transmission unit 21 frequency-converts the obtained baseband signal into a radio signal and transmits it from the antenna 22.

  The band selection control unit 23 instructs the band selection unit 25 to select a frequency band to be selected by the band selection unit 25 (hereinafter referred to as “band upper end frequency”). The band upper end frequency is, for example, the frequency band of the band end c shown in FIG. In addition, the band selection control unit 23 instructs the band selection unit 26 to select a frequency band to be selected by the band selection unit 26 (hereinafter referred to as “band lower end frequency”). The lower band frequency is, for example, the frequency band of the band edge a shown in FIG. Similarly to the first embodiment, the band selection control unit 23 instructs the band selection unit 14 about the frequency between band edges (frequency band between band edges b shown in FIG. 3). The band upper end frequency and the band lower end frequency may be predetermined values or values that are appropriately changed.

  In addition, when the band selection control unit 23 instructs the band upper end frequency, the band end band frequency, and the band lower end frequency, the band selection control unit 23 notifies the band selection control unit 23 of them.

  The selection band information generation unit 24 generates selection band information indicating the upper band frequency, the interband frequency, and the lower band frequency notified from the band selection control unit 23 and notifies the multiplexing unit 10 of the selection band information.

  As described above, transmitting apparatus 101 according to the present embodiment multiplies subcarriers at the upper end of the band by the first window function, multiplies subcarriers between the band ends by the second window function, and The subcarrier is multiplied by a third window function. Thereby, even when the side lobe requests are different at the two band edges, the transmitting apparatus 101 of the present embodiment can obtain the same effect as the above-described first embodiment by using each window function that satisfies each request. Can do.

(Embodiment 3)
FIG. 7 is a block diagram showing a configuration example of the transmission apparatus 102 (an example of the transmission apparatus of the present invention) according to Embodiment 3 of the present invention. The transmission apparatus 102 is a base station, for example.

  In FIG. 7, the transmission device 102 is different from the transmission device 100 shown in FIG. 1 in that an amplitude control unit 33 is provided between the band selection unit 13 and the IFFT unit 15. Below, description about a structure common to the transmitter 100 is abbreviate | omitted, and only a different structure is demonstrated.

  The amplitude control unit 33 decreases the amplitude of the signal selected by the band selection unit 13 by a predetermined amount (for example, half) and outputs the signal to the IFFT unit 15. An example in which the amplitude is controlled is shown in FIG. As shown in FIG. 8, the amplitude controller 33 reduces the amplitude of the subcarriers at the band edges a and c to half the amplitude of the subcarrier at the band edge b.

  It is preferable that the amplitude control unit 33 reduce the amplitude while limiting side lobes and limiting the value to allow transmission without error. In addition, it is preferable that the modulation unit 11 adopts a modulation system that can transmit without error.

  As described above, transmitting apparatus 102 according to the present embodiment multiplies subcarriers at the band edges by the first window function, and multiplies subcarriers between the band edges by the second window function, It is characterized in that the amplitude of the subcarrier at the band edge is reduced. Thereby, the transmission apparatus 102 of this Embodiment can further suppress a side lobe.

  Although the embodiment of the present invention has been described above, the above description is an example, and various modifications can be made. Hereinafter, modified examples will be described.

  For example, in Embodiments 1 to 3 described above, one OFDM signal band has been described as a processing target as shown in FIG. 3, but a plurality of discretely arranged OFDM signal bands can also be processed. is there.

  Further, for example, in Embodiment 3 described above, the amplitude of the subcarriers at the two band ends is reduced, but only the amplitude of the subcarrier at one of the band ends may be decreased.

  For example, in Embodiment 1 described above, the first window function having a long multiplication section length is applied to each subcarrier arranged at the end of the band. However, the present invention is not limited to this. The first window function may be applied not only to the subcarriers at both ends but also to N (N> 1) subcarriers at each band end. As a result, side lobes can be further suppressed than in the first embodiment.

  Further, for example, in the second embodiment, the first window function and the third window function having a long multiplication section length are applied only to the subcarriers arranged at the extreme ends of the band upper end and the band lower end. It is not something that can be done. A window function having a long multiplication section length may be applied to a plurality of subcarriers at the band upper end and the band lower end. In this case, the number of subcarriers to which a window function having a long multiplication section length is applied may be different between the upper band end and the lower band end.

  Further, for example, in Embodiment 3 described above, the amplitude of only the subcarriers at the band edge is reduced, but not only the subcarriers at the band edge, but the subcarriers up to the Nth (N> 1) from the subcarriers. The carrier amplitude may be decreased.

  Further, when suppressing side lobes for a plurality of subcarriers from the band edge, a plurality of Embodiments 1 to 3 may be used in combination. For example, FIG. 9 shows a state in which the third embodiment is applied to the subcarrier arranged at the extreme end of the band edge and the first embodiment is applied to the second subcarrier from the band edge. Show. Among the first to third embodiments, the third embodiment that adjusts both the amplitude and the window function has the highest effect of suppressing the side lobes. In general, since the sub-carrier located at the end of the band has a larger influence on the side lobe, when the first to third embodiments are used together, the embodiment is applied to the sub-carrier located at the end of the band. It is desirable to apply 3.

  For example, the amplitude control unit 33 described in the third embodiment may be applied to the transmission device 101 illustrated in FIG. In this case, the amplitude control unit 33 is preferably provided between the band selection unit 25 and the IFFT unit 27, for example.

  For example, in the first to third embodiments, the case where the present invention is configured by hardware has been described as an example. However, the present invention can also be realized by software in cooperation with hardware.

  The present invention can be applied to all techniques for performing wireless transmission of OFDM signals.

10 Multiplexer 11 Modulator 12 S / P
13, 14, 25, 26 Band selection unit 15, 16, 27, 28 IFFT unit 17, 18, 29, 30 CP addition unit 19, 20, 31, 32 Window function multiplication unit 21 Transmission unit 22 Antenna 23 Band selection control unit 24 selection band information generation unit 33 amplitude control unit 100, 101, 102 transmission device

Claims (6)

A transmission device that transmits a radio signal in which a plurality of subcarriers are arranged from a first band end to a second band end at a predetermined frequency interval,
A first band edge selection unit that selects a subcarrier of the first band edge that is one of an upper end and a lower end of a frequency band among the plurality of subcarriers ;
A second band edge selector that selects a subcarrier at the second band edge, which is the other of the upper end and the lower end of the frequency band, among the plurality of subcarriers ;
Among the plurality of subcarriers, a band edge selection unit that selects a subcarrier between band edges that is between the first band edge and the second band edge;
To the transmission symbols generated based on the subcarrier of the first band end, and a first window function multiplier that multiplies section length multiplied by a first window function is a predetermined length,
To the transmission symbols generated based on the sub-carrier between the band edges, and a second window function multiplier for multiplying the second window function is a short multiplication section length than multiplication section length of the first window function,
The transmission symbol generated based on the subcarrier at the second band edge has a multiplication interval length shorter than the multiplication interval length of the first window function and longer than the multiplication interval length of the second window function. A third window function multiplier for multiplying the third window function;
A transmission device. Said first band end is Ri bottom der of the frequency band, the second band end Ru upper der of said frequency bands,
請 Motomeko 1 transmitting apparatus according. An amplitude controller that reduces the amplitude of at least one of the first band edge selected by the first band edge selector and the second band edge selected by the second band edge selector ;
The transmission device according to claim 1 or 2. The data indicating the frequency band of the second band edge selected by the first band edge and the second band edge selecting part selected by the first band edge selecting part, and the band edge selecting part selected by the band edge selecting part In addition, it further includes a multiplexing unit that multiplexes the data indicating the frequency band between the band ends with the data to be transmitted.
The transmission device according to any one of claims 1 to 3. The transmission symbol is an OFDM symbol;
The multiplication interval length of the first window function is the length of a cyclic prefix added to the transmission symbol.
The transmission device according to any one of claims 1 to 4. A transmission method for transmitting a radio signal in which a plurality of subcarriers are arranged from a first band edge to a second band edge at a predetermined frequency interval,
A first band edge selection step of selecting a subcarrier at the first band edge that is one of an upper end and a lower end of a frequency band among the plurality of subcarriers ;
A second band edge selection step of selecting a subcarrier at the second band edge, which is the other one of the upper end and the lower end of the frequency band, among the plurality of subcarriers ;
A band edge selection step of selecting a subcarrier between band edges that is between the first band edge and the second band edge among the plurality of subcarriers;
A first window function multiplying step of multiplying a transmission symbol generated based on the subcarriers at the first band edge by a first window function having a multiplication interval length of a predetermined length;
A second window function multiplication step of multiplying a transmission symbol generated based on subcarriers between the band edges by a second window function having a multiplication interval length shorter than a multiplication interval length of the first window function;
The transmission symbol generated based on the subcarrier at the second band edge has a multiplication interval length shorter than the multiplication interval length of the first window function and longer than the multiplication interval length of the second window function. A third window function multiplication step of multiplying the third window function;
A transmission method.

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