JP3235766B2 - Multicarrier peak power suppression transmitter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a peak power suppressing transmission apparatus capable of suppressing the peak power of a modulated wave in multicarrier (multicarrier) wireless communication.

[0002]

2. Description of the Related Art When a plurality of transmission data signal sequences are modulated and combined, the peak power ratio to the average power becomes larger than that of a modulated wave obtained by modulating a single data signal sequence. This means that when multiple modulated waves are all synthesized in phase,
This is because the output becomes very large. An example of such a composite modulated wave is a multicarrier signal. In order to transmit a high-speed broadband data signal sequence with good transmission characteristics in wireless communication, multicarrier transmission in which transmission is performed by dividing into a plurality of carriers (carriers) is effective. This transmission system is shown in FIG. N input terminals 11 ₁ to 1
The N series of data signals from 1 _N are generated by the waveform generating means 12 ₁ to 12 ₁ .
Each of the band-limited outputs at 12 _N and the carrier-wave generators 14 ₁ to 13 _N at the modulating means 13 _{1 to} 13 _{N according} to each band-limited output.
_N carrier signals from 14 _N are modulated. These modulation outputs are synthesized by the synthesizing means 15, and the output amplifier 16
Is amplified and transmitted. In multi-carrier transmission, the modulated signal of each carrier is a narrow band signal, so that the influence of frequency selective fading, which causes deterioration of transmission characteristics in wireless communication, can be reduced.

[0003] However, if the number of carriers is N in such a multicarrier signal, the peak power becomes N times or more the average power. Therefore, when a composite modulated wave such as a multicarrier signal is collectively amplified by the power amplifier 16, the average output of the power amplifier 16 must be considerably smaller than the maximum output, that is, a large back-off is required. Becomes

[0004]

However, taking a large back-off leads to a decrease in power amplification efficiency. Further, when amplifying a synthesized modulated wave having a large peak power, a power amplifier having a large maximum output is required. For this reason, when the number N of carriers increases, the power efficiency is significantly reduced due to the back-off, and the maximum output of the power amplifier needs to be extremely large, and such a transmission system is difficult to realize.

On the other hand, as a method for suppressing the peak power of a composite modulated wave, a method of appropriately setting the initial phase of each modulated wave has been proposed. (Reference S. Boyd, "Multiton
e signals with low crest factar ", IEEE vol.CAS-33,
No. 10, Oct. 1986) However, this method is effective when combining unmodulated waves, but has little effect when each is modulated independently, especially when phase modulated. Further, it is disclosed in Japanese Patent Application Laid-Open No. Hei 6-30069 "Multi-function" that a power control sub-carrier of the closest vector opposite to a synthesized vector of a plurality of sub-carriers respectively modulated by transmission data is synthesized for each symbol to reduce peak power. A QAM transmission method using subcarriers "has been proposed. However, in this method, since the mutual phase of the subcarrier changes during one symbol, the peak power cannot always be sufficiently suppressed. Also, there is no generality in the method of generating power control subcarriers.

[0006]

According to the first aspect of the present invention, the transmission data signal of N systems (N is an integer of 2 or more) is N
N whose frequencies are different from each other by
It is generated and output as a system modulation signal. Further, the N transmission data signals are input to the suppression data generating means,
For each symbol, suppression data of M systems (M is an integer of 1 or more) is output. The suppression data of this M system is M
The N suppression signals are output as M suppression signals having frequencies different from each other by the suppression signal generation means and different from the N modulation signals. The N-system modulation signal and the M-system suppression signal are combined by the combining means.
The signals are combined into a combined modulation signal, and the carrier signal is modulated by the modulating means using the combined modulation signal and output.
The suppression data generating means generates suppression data such that the peak power of the combined modulation signal in one symbol is minimized.

According to the invention of claim 2, N systems (N is 2
N) of transmission data signals are generated as N-system modulation signals by N waveform generation units, and the N-system transmission data signals are input to the suppression data generation unit. (M is an integer of 1 or more) suppression data is output. The M-system suppression data is input to M suppression signal generation units, and M-system suppression signals are generated and output. The N + M modulation means modulate carrier signals of mutually different frequencies by the N-system modulation signal and the M-system suppression signal,
The modulation outputs of these N + M modulation means are combined and output by the combining means. The suppression data generation means generates suppression data such that the peak power of the output signal of the synthesis means in one symbol is minimized.

[0008]

FIG. 1 shows an embodiment of the present invention. The transmission data of the N systems is input from input terminals 11 _{1 to} 11 _N to waveform generating means 21 _{1 to} 21 _N and suppression data generating means 22. The waveform generators 21 _{1 to} 21 _N output the input data signal strings as modulation baseband signals (modulation signals) having different frequencies from each other, and include an initial phase setting function, a frequency offset setting function, And a band limiting function. For example, waveform generation means 2
As shown in 1 _1, the input transmission data is serial-parallel conversion circuit 23, for example, the input binary data signal shown in FIG. 2A is separated every second, I two series shown in FIG. 2B, C
Axis signal I _i (t) and Q axis signal Q _i (t)
4 is supplied. On the other hand, for each clock of the clock input terminal 27 in the accumulator 26, the numerical value set in the frequency register 28 ₁ is cumulatively added. The accumulator 26
Value stored in the phase register 29 ₁ is set as the initial value in the register. The cosine waveform memory 31 and the sine waveform memory 32 are read with the added value of the accumulator 26 as an address, respectively, and these read cosine waves,
The sine wave is processed by the calculator 24 into the I-axis signal I _i (t) and the Q-axis signal Q _i
(t) and the following calculations are performed respectively.

[0009] _{I'i (t) = I i} (t) cosθ i (t) -Q i (t) sinθ i (t) Q'i (t) = I i (t) sinθ i (t) + Q i (t) cosθ _i (t) output _I'i of the arithmetic unit 24 (t), after being band-limited to waveform shaping by _Q'i (t), respectively band-limiting filters 33 and 34, combined by the combining circuit 35 And output as a modulation signal.

[0010] The frequency of the modulation signal is determined by the numerical value stored in the frequency register 28 _1, the initial phase is determined by the numerical value stored in the phase register 29 _1. The phase of the modulation signal takes one of the four phases shown in FIG. 2D according to the I-axis signal and the Q-axis signal. Waveform generating means 21 ₂ to 2
1 _N is similarly configured, and the frequency registers 28 _{1 to} 28
Select each numerical value of _N and output modulation signals 36 _{1 to} 36 _N
However, for example, as shown in FIG.
The frequency is shifted, that is, a multicarrier is formed. FIG. 3A shows the case where N = 4.

The suppression data generating means 22 is composed of N systems (N is 2
The transmission data of the above integer is input, and suppression data of M systems (M is an integer of 1 or more) is output for each symbol. Generation of the suppression data will be described later. The suppression data of these M systems is supplied to the suppression signal generation means 37.
Is input to the ₁ to 37 _M, together with different in frequency, and outputs a suppression signal 38 ₁ to 38 DEG _M having different frequencies with the modulation signal 36 ₁ ~ 36 _N. Suppression signal generating means 37 ₁
To 37 _M may be configured similarly to the waveform generating means 21 _1, the frequency register 39 ₁ ~ 39 _M, the phase register 40 ₁ to 40 _M are provided, the frequency register 39
Depending on the value stored in _{1 to} 39 _M , the suppression signals 38 _{1 to} 38
Set each frequency of _M.

The modulation signals 36 ₁ to 36 3 from the waveform generating means.
6 _N and the suppression signals 38 _{1 to} 38 from the suppression signal generation means.
_M is synthesized by the synthesizing means 41, the carrier from the carrier generator 42 is modulated by the modulation output means 43 by the synthesized signal, and the modulated output is amplified and output by the power amplifier 16. The data pattern for each symbol of the suppression data signal from the suppression data generating means 22 is different from the pattern for each symbol of the transmission data signal within the symbol in the combining means 4.
1 are selected so that the peak of the output power is minimized. This can be achieved by previously obtaining a suppression data pattern for every combination pattern of transmission data and writing it in, for example, a ROM table, and reading this ROM table with the transmission data.

As an example of the present invention described above, N =
4, M = 1 multi-carrier transmission case
You. The number of carriers N + M is 5 (= 4 + 1). Also,
There is no band limiting at baseband and each signal is
Let it be a square wave. The suppression signal itself transmits the information signal directly.
Data modulation as the modulation method.
It need not be the same as the modulation scheme of the signal. Because of this peak
Select an appropriate modulation method so that the power is small.
No. At this time, for the suppression signal, set the phase finely.
If you use a modulation method that can
Therefore, the peak power suppression effect is large. However, the phase
Use polyphase PSK modulation for fine setting
Expected to increase hardware scale
Is done. Therefore, the modulation scheme of the suppression signal is the peak power suppression.
Decision considering both pressure effect and increase in hardware scale
There is a need to. Here, four data signal trains are
The signal is transmitted by the QPSK modulation method.
In other words, the transmission is made at 8PSK. Figure 4 shows an example of signal points
Shown in Each initial phase θ at this time₀₁, Θ₀₂, Θ₀₃,
θ₀₄, Θ₀₅About the waveform generation means 21₁~ 21_FourYou
And suppression signal generating means 37₁Initial phase setting function
Phase register 29₁~ 29_Four, 40₁Numeric value stored in
Set the frequency for the reference carrier.
Number offset Δf ₁, Δf_Two, Δf_Three, Δf_Four, Δf_Five
For the waveform generation means and the suppression signal generation means,
Wave number offset setting function, that is, frequency register 28
₁~ 28_Four,39₁Set by selecting the stored value for
You.

At this time, if no suppression signal is synthesized, the peak power ratio to the average power is 6 dB. This is FIG. 5A
When four-wave 36 _{1-36 4} was synthesized in phase as shown in, 16 times the average power of the output power is 1 wave (= 4 ^2), i.e., because the four times the average power of the four-wave is there. However, by modulating for example the suppression signal 38 ₁ as shown in FIG. 5B synthesized and can reduce the peak power ratio to the average power. In the example of N = 4 and M = 1 described here, the peak power ratio to the average power is about 4 dB, which can be reduced by about 2 dB compared to the case where the suppression signal is not combined.

As described above, peak power can be reduced by synthesizing and modulating the suppression signal. As a result, the efficiency of the power amplifier 16 that amplifies the composite modulated wave can be improved. Also, when the maximum output is determined, the peak power ratio to the average power is reduced,
Because the average power during transmission can be set higher,
The reception power increases, and the transmission characteristics are improved.

FIG. 6 shows an embodiment of the second aspect of the present invention, in which parts corresponding to those in FIG. 1 are denoted by the same reference numerals. In this embodiment, an N-system data signal sequence is input and the waveform generation means 2
1 ₁ to 21 modulation signal 36 ₁ of the same frequency with _N ~ 36 _N
Generates, similarly generates a suppression signal 38 ₁ to 38 DEG _M of the same frequency suppression signal generating means 37 ₁ to 37 _M, by these modulation means 51 ₁ ~51 _{N + M,} the carrier generator 52
The carrier waves having different frequencies from each other are modulated, and the modulated outputs of the modulating means 51 _{1 to} 51 _{N + M} are combined by the combining means 41 to obtain a multicarrier signal, which is supplied to the power amplifier 16. The carrier generation means 52 generates each required carrier from the reference signal of the reference signal source 53. Waveform generating means 21 ₁ to
21 _N and the suppression signal generation means 37 _{1 to} 37 _M are frequency offset setting functions, that is, frequency registers 28 ₁ to
28 _N, 39 ₁ ~39 _M can be omitted, the processing in the baseband can be simplified. For example, when N = 4 and M = 1, the modulation signal 36 from the waveform generation means 21 _{1 to} 21 ₄ is used.
_{1 to} 36 ₄ , the suppression signal 38 from the suppression signal generation means 37 _1
1 is a same frequency band as shown in FIG. 3B, they are a multi-carrier signal as shown in FIG. 3A by the modulation means 51 ₁ to 51 _5.

[0017] it can also be weighted to the suppression signal 38 ₁ ~38 _M. For example, assuming a case where one wave is added to four carriers, and the modulation of the four waves is QPSK, there are 256 signal patterns of 4 (value) raised to the power of 4 (wave). As for the suppression signal, the modulation phase is set for each of the 256 signal patterns so that the peak is the lowest. Also set the amplitude as well phase at the time of generating the suppression signal 38 ₁ to 38 DEG _M, i.e., rather than adding a suppression signal for all the same amplitude with respect to 256 patterns, sets the amplitude and phase for each signal pattern . Since the amplitude and phase of the composite signal of the information signal for between each carrier has a frequency difference is not constant in one symbol period, also rotates the synthesized signal by the frequency difference for suppression signal 38 ₁ to 38 DEG _M. Accordingly, there is simply to increase the amplitude of the suppression signal 38 ₁ to 38 DEG _M can not be obtained a large suppression effect, also be contrary to the suppression effect is reduced. Therefore, the amplitude and phase can be finely set for each signal pattern to improve the suppression effect.

That is, among the signal patterns of information signals (256 patterns in the case of QPSK with four waves), there are patterns in which the output power is not so large and it is not necessary to add a suppression signal. For this pattern, for example, by setting the signal level of the suppression signal to 0, it is possible to prevent the radio wave from being output more than necessary. Also, for example, when one suppression signal is added to a four-wave multi-carrier signal, if the signal level of the suppression signal is about −2 dB relative to the level of the information signal transmission carrier, the information signal transmission carrier is reduced. There is an even greater suppression effect than adding a suppression signal at the same level. The above-described setting of the level of the suppression signal can be performed by, for example, multiplying the suppression signal by the amplitude a (t) to be set in the suppression signal. Also, when setting the signal level of the suppression signal for each signal pattern of the information signal, it is easily realized by configuring a table using a memory such as a ROM and reading the suppression signal level for each signal pattern from this table. it can.

For a carrier for information transmission, if a very complicated (large number of phase division) modulation method is performed,
The peak suppression effect due to the initial phase setting is reduced. Conversely, for the suppression signal, in order to increase the degree of freedom in phase setting, it is advantageous to employ a modulation method having a large number of phase divisions.
K, 16PSK, 32PSK, 64PSK and the like. What is important here is that since information is not added to the suppressed signal, it is not always necessary to perform demodulation on the receiving side, and it is not necessary to consider reception characteristics. That is, the reception characteristic deteriorates in the case of multi-level PSK, but it is not necessary to consider this point. On the other hand, the modulation scheme of the carrier for transmitting information signals is determined in consideration of the reception characteristics. Therefore, when applied to mobile communication, the QPSK rank is appropriate.

It has been found that when a peak power suppression signal is added to a multicarrier signal, the peak power suppression effect differs depending on the position of the suppression signal on the frequency axis. For example, a suppression signal 38 is added to a four-wave multicarrier signal.
When adding ₁ to 1 wave is the position on the frequency axis of the suppression signal 38 ₁ There are five arrangement patterns as shown in FIG. At this time, the arrangement pattern D and the arrangement pattern B, and the peak power suppressing amount of about 2dB with respect to the peak power when not adding the suppression signal 38 ₁ is obtained, so great for the arrangement pattern other than those The amount of suppression cannot be obtained. However, the optimum position on the frequency axis of the suppression signal 38 ₁ changes by the number of multi-carrier signals and suppression signal. For this reason, it is necessary to add a suppression signal to an optimal position according to the number of carriers. These relationships may be examined in advance, and the number and arrangement of the suppression signals may be determined according to the number of information transmission carriers to be used.

In the present invention, when the frequency offset setting function of the waveform generation means and the suppression signal generation means is omitted and the frequency offset is set to 0, the present invention can be applied to a system for transmitting a plurality of channels at the same frequency as in the CDMA system.

[0022]

As described above, according to the present invention, the peak power ratio to the average power is suppressed,
There is no need to take a large back-off in the power amplifier, and the power amplification efficiency is improved. Further, since the peak power is suppressed, it is not necessary to use a power amplifier having a large maximum output. Further, when the maximum output is fixed, the average power at the time of transmission can be increased by using the present invention. As a result, the reception power increases and the transmission characteristics are improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2A is a diagram showing an example of input data, B and C are diagrams showing the data as two-series data, and D is a diagram showing signal points corresponding to the data.

3A is a diagram illustrating an example of a multicarrier signal including a suppression signal, and FIG. 3B is a diagram illustrating an information modulation signal and a suppression signal having the same frequency.

FIG. 4 is a diagram illustrating an example of signal points and initial phases of a data modulation signal and a suppression signal.

5A is a diagram illustrating an example of a composite modulated wave of an information modulation signal, and FIG. 5B is a diagram illustrating an example in which a suppression signal is superimposed thereon.

FIG. 6 is a block diagram showing an embodiment of the invention of claim 2;

FIG. 7 is a diagram showing various states of frequency allocation of an information modulation signal and a suppression signal.

FIG. 8 is a block diagram showing a conventional multicarrier transmission device.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-321861 (JP, A) JP-A-7-143098 (JP, A) JP-A-8-274748 (JP, A) JP-A-6-274748 204959 (JP, A) JP-A-5-276210 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 27/00-27/38 H04J 1/00

Claims (2)

(57) [Claims] 1. N waveform generating means for inputting N transmission data signals (N is an integer of 2 or more) and outputting N modulation signals having different frequencies, respectively. Suppression data generating means for inputting a transmission data signal of the system and outputting suppression data of M systems (M is an integer of 1 or more) for each symbol, and inputting the suppression data of the M system, And M suppression signal generating means for outputting M suppression signals having different frequencies from the N modulation signals, and the N modulation signals and the M suppression signals. And a modulating means for modulating a carrier signal with the synthesized modulation signal and outputting the modulated signal. The suppression data generating means comprises: Signal Multicarrier peak power suppression transmission apparatus characterized by over click power and generates a suppression data as a minimum. 2. N waveform generating means for inputting N transmission data signals (N is an integer of 2 or more) and outputting N modulation signals, and receiving the N transmission data signals Suppression data generating means for outputting M-system (M is an integer of 1 or more) suppression data for each symbol, and M for receiving the M-system suppression data and outputting M-system suppression signals, respectively. And N + M for modulating carrier signals of different frequencies with the N-system modulation signal and the M-system suppression signal, respectively.
And a synthesizing means for synthesizing the modulation outputs of the N + M modulation means, wherein the suppression data generating means suppresses the peak power of the output signal of the synthesizing means in one symbol to a minimum. A multi-carrier peak power suppression transmission device for generating data.