JP3800462B2 - Multicarrier transmission apparatus, multicarrier reception apparatus, and multicarrier transmission method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multicarrier transmission apparatus that attempts to transmit a digitally modulated or unmodulated signal using a multicarrier as a strong transmission scheme in a multipath environment.
[0002]
[Prior art]
When performing digital wireless transmission, the transmitted signal includes a synchronization signal such as carrier synchronization, symbol synchronization, and sample synchronization, a reference signal, and an information signal. The received signal varies in both amplitude and phase. In addition to the static characteristics of the system and the Doppler shift due to movement, this is considered to be greatly affected by multipath.
For example, when QAM digital modulation is performed for information signal transmission, since the received signal fluctuates in both amplitude and phase, it is common to use a calibration means for correcting it. Yes, since the reference signal and synchronization signal are more important than the information signal, it is necessary to increase the reliability by increasing the reliability by increasing the interval from the transmission band of the information signal or by lowering the multi-level. ing.
There is also a ghost canceller for removing the interference wave itself due to multipath, but if this is introduced, it will be technically and costly.
[0003]
[Problems to be solved by the invention]
In a multipath environment, both the amplitude and phase of the received signal vary. The smaller the D / U ratio of the multipath interference wave, the greater the fluctuation. This variation is particularly noticeable when the transmission power is limited and indoor transmission is considered to be predominant.
In addition, since a reception point that becomes a trough of the reception electric field strength appears for each half wavelength of the carrier frequency at the shortest distance regardless of the moving speed, if a multipath interference wave having a sufficiently small D / U ratio exists, the carrier signal itself Will be lost.
Therefore, even if correction is performed as in the prior art or design is performed with some margin, demodulation is difficult if the signal itself is lost.
In order to avoid the influence of multipath interference waves, there are reception techniques such as a ghost canceller and diversity, but if these are introduced, the apparatus becomes structurally large.
[0004]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a multicarrier transmission apparatus that transmits an input signal to be transmitted on a plurality of carriers, wherein the carrier used for the transmission is a multicarrier of two or more waves, When the carrier frequency is expressed as an integer ratio, there are no more than two odd-numbered carriers, and the frequency of the multicarrier is such that none of the two waves of the multicarrier have an odd multiple relationship. Carrier frequency control means 4 for controlling the frequency, frequency conversion means 1A, 2A, 3A for converting the frequency of the input signal so as to be the multi-carrier frequency controlled by the carrier frequency control means, and the frequency conversion means. Band-pass filters 5A, 6A, 7A that pass each frequency band of the multi-carrier, And a synthesizing means 8A for combining signals output by the band pass filter.
[0005]
Further, the present invention provides a multicarrier transmission method for transmitting an input signal to be transmitted on a plurality of carriers, wherein the carrier used for the transmission is a multicarrier of two or more waves, and the frequency of the multicarrier is an integer ratio. As shown, there are two or more odd-numbered carriers, and a carrier frequency control step for controlling the frequency of the multicarrier so that any two waves of the multicarrier do not have an odd multiple relationship. A frequency conversion step for converting the frequency of the input signal so as to be the frequency of the multicarrier controlled by the carrier frequency control step, and passing each band of the multicarrier frequency-converted by the frequency conversion step. A bandpass filtering step and the bandpass filtering And a step of synthesizing a signal output by step.
[0006]
(Work)
In the present invention, when the carrier used for transmission is an n-wave multicarrier of two or more waves, and the frequency of the multicarrier is represented by an integer ratio, there are no two or more carriers having an odd value, and the multicarrier When there is a multipath interference wave by transmitting a signal by controlling the frequency of the multicarrier so that none of the two waves of the carrier have an odd multiple relationship, the received electric field strength of all the multicarriers The probability of becoming a valley at the same time is very small. Since the configuration of the apparatus is simple, it can be realized relatively easily. The signal to be transmitted may be either a modulated signal such as ASK or BPSK, or an unmodulated signal.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the multicarrier transmission / reception apparatus of the present invention will be described below.
First, an embodiment of the multicarrier transmission apparatus of the present invention will be described with reference to FIG.
The present invention is a multi-carrier transmission system in which a single input signal to be transmitted is transmitted on a plurality of carriers, and the carrier used for transmission is an n-wave multi-carrier of two or more waves.
[0008]
First, when the carrier frequency control circuit 4A indicates the frequency of the multicarrier to be used as an integer ratio, there are no more than two odd-numbered carriers, and any two waves of the multicarrier are odd multiples. The multicarrier frequency is controlled so as not to be related.
The frequencies satisfying the above relationship are, for example, frequencies f, 2f, 4f,.
2 ^{(n-1) An n-} wave multi-carrier having a relationship such as f.
Here, for example, the frequencies 3f, 5f, 6f, 7f, 9f,..., When the frequency of the multicarrier to be used is indicated by an integer ratio, there are two or more odd-numbered carriers, and the multicarrier These two frequencies 3f, 5f, 6f, 7f, 9f,... Are removed because the condition that the relationship of odd-numbered multiples is not satisfied in any two waves.
This is obtained by removing conditions that may cause loss of carriers during reception, and will be described later with reference to FIGS.
[0009]
It is assumed that multicarriers having this frequency relationship are used for transmission, and the frequency conversion circuits 1A to 3A are controlled by the carrier frequency control circuit 4A.
In general, there are n frequency conversion circuits, and an input signal is subjected to frequency conversion to a multicarrier frequency determined by the carrier frequency control circuit 4A.
At this time, the initial phases of all carriers subjected to frequency conversion are accurately matched by the carrier frequency control circuit 4A.
[0010]
The frequency-converted signal may be either a modulated wave or a non-modulated wave. That is, when the input signal is always 1 (when it does not change), the signals output by the frequency conversion circuits 1A to 3A are unmodulated waves, but when the input signal changes for each symbol, Signals output from the frequency conversion circuits 1A to 3A are modulated waves.
For example, if the input signal changes randomly with a binary value of 1 and 0 for each symbol, ASK modulation is performed, and if the input signal changes randomly with a binary value of 1 and -1 for each symbol, BPSK. Modulation. Of course, multi-level modulation may be used.
Further, even if the input signal itself is a modulated signal, there is no problem because it is converted to a desired carrier frequency by each of the frequency conversion circuits 1A to 3A.
[0011]
Each carrier frequency-converted by the frequency conversion circuits 1A to 3A passes only the band of each carrier by the BPFs 5A to 7A. In general, there are n BPFs corresponding to n-wave multicarriers. The signals having the desired bands by the BPFs 5A to 7A are combined by the combining circuit 8A and transmitted as transmission waves.
[0012]
Next, an embodiment of a multicarrier receiving apparatus corresponding to the transmitting apparatus of FIG. 1 shown in FIG. 2 will be described below.
The receiving apparatus receives the multicarrier transmitted on the transmitting apparatus side, and passes only the desired band by n BPF circuits BPF5B to 7B corresponding to the n-wave multicarrier as in the transmitting apparatus of FIG. .
The signals obtained by the BPFs 5B to 7B are demodulated corresponding to each carrier by the demodulation circuits 9 to 11.
For example, if ASK or BPSK modulation is performed on the transmission side, the demodulation circuits 9 to 11 perform demodulation by performing frequency conversion corresponding to the frequency of each carrier in the same manner as in the transmission device. At this time, demodulation may be performed by synchronous detection or delay detection.
[0013]
In addition, if the transmission side transmits each carrier without modulation and the reception device is intended to extract a specific frequency signal, the demodulation circuit considers the frequency to be extracted, and is the same frequency conversion circuit as the transmission device. The frequency conversion corresponding to the frequency of each carrier is performed to extract the target frequency signal.
Alternatively, the target frequency signal is extracted by performing frequency division corresponding to each carrier in each demodulation circuit.
Using any one of the above means, the signal demodulated by each carrier by each demodulating circuit 9-11 can be synthesized by the synthesizing circuit 8B to obtain a synthesized demodulated signal, and the target frequency signal can be extracted.
[0014]
Next, a transmission / reception apparatus using two-wave multicarrier will be specifically described below.
FIG. 3 shows another embodiment of the transmission apparatus using the two-wave multicarrier of the present invention. FIG. 3 is substantially the same as the transmission apparatus of FIG. 1, but is limited to a multi-carrier of two waves. The carrier frequency used here is a multi-carrier of two waves of a carrier frequency f and a carrier frequency 2f corresponding to twice the carrier frequency f. The relationship between the carrier frequencies of the two waves satisfies the multi-carrier frequency relationship according to claim 1, and when the multi-carrier frequency is represented by an integer ratio, there are two or more carriers having an odd value. In addition, the relationship of the odd multiples is not established in any two waves of the multicarrier.
[0015]
Here, a signal to be transmitted is a carrier synchronization signal for information transmission having a frequency of f / k. k is an arbitrary natural number. The carrier frequency control circuit 4C controls the frequency conversion circuits 1C and 2C so that the initial phases are matched at the carrier frequencies f and 2f. Each frequency conversion circuit 1C, 2C performs frequency conversion so that an input signal has an integer ratio of f, 2f. Here, since the input signal is always 1, the signal after frequency conversion is an unmodulated carrier having the frequencies f and 2f.
The signals frequency-converted by the frequency conversion circuits 1C and 2C are passed through the bands of the respective carriers by the BPFs 5C and 6C. The signals limited to the desired band by the BPFs 5C and 6C are synthesized by the synthesis circuit 8C and become transmission waves.
[0016]
Next, FIG. 5 shows an example of a state in which multipath interference waves exist in the transmission path. When the multicarrier frequency, which is a condition of the present invention, is represented by an integer ratio, the number of carriers having odd values is two or more. The case where the condition that the relation does not exist and the two waves of the multicarrier do not have an odd multiple relationship is shown.
When transmission is performed with two-wave multicarriers having a frequency f and a frequency 2f that is twice the frequency f and a direct wave is received as shown in FIG. 5A, if a multipath exists, FIG. A multipath interference wave having a certain delay amount as shown in b) is received. Here, it is assumed that there is one multipath interference wave and the D / U ratio is 0 dB.
[0017]
As shown in FIG. 5, when there is a multipath interference wave delayed by a half wavelength λ / 2 of the frequency f, the received electric field intensity at the carrier frequency f is 0 in the received signal. The same applies when the multipath interference wave is received with an integer multiple of the wavelength λ of the frequency f. This also applies to the carrier frequency 2f. As shown in FIG. 5B, ◯ is the delay amount at which the received electric field strength at the carrier frequency f is 0, and x is the received electric field strength at the carrier frequency 2f is 0. Indicates the amount of delay. Considering the amount of delay in terms of distance, there is a point where the received electric field strength is 0, that is, a valley, at the shortest intervals of frequency f and frequency 2f.
[0018]
The vertical axis in FIG. 5 (c) indicates the received electric field strength of each carrier with the frequencies f and 2f, and the horizontal axis indicates the delay amount (reception point).
As can be seen from this figure, at the point where the received electric field strength at the carrier frequency f becomes a trough, the received electric field strength at the carrier frequency 2f becomes a peak, and conversely, at the point where the received electric field strength of the carrier at the frequency 2f becomes a trough. The received electric field strength at the carrier frequency f is 1, that is, the same strength as when only a direct wave is received.
In other words, if the multicarrier used for transmission has the frequency relationship described in claim 1, it is found that the possibility that the received electric field strengths of all the multicarriers simultaneously become valleys in the received signal becomes very small.
[0019]
Next, FIG. 6 shows an example of a state when a multipath interference wave exists in the transmission line, and a case where the condition of the present invention is not met.
When transmission is performed using a multi-carrier of two waves having a frequency f and a frequency 3f that is three times the frequency f and a direct wave is received as shown in FIG. A multipath interference wave having a certain delay amount as shown in b) is received. Here, it is assumed that there is one multipath interference wave and the D / U ratio is 0 dB.
[0020]
As shown in FIG. 6, when there is a multipath interference wave delayed by a half wavelength λ / 2 of the frequency f, the received electric field strength of the carrier frequencies f and 3f is 0 in the received signal.
The same applies when the multipath interference wave is received with an integer multiple of the wavelength λ of the frequency f. This also applies to the carrier frequency 3f. As shown in FIG. 6B, ◯ is the amount of delay at which the received electric field strength at the carrier frequency f is zero, and x is the received electric field strength at the carrier frequency 3f is zero. Indicates the amount of delay.
Considering the amount of delay in terms of distance, there is a point where the received electric field strength is 0, that is, a valley, at the shortest intervals of the frequency f and frequency 3f.
[0021]
In FIG. 6C, the vertical axis indicates the received electric field strength of each carrier of the frequencies f and 3f, and the horizontal axis indicates the delay amount (reception point).
As can be seen from this figure, at the point where the received electric field intensity at the carrier frequency f becomes a valley, the received electric field intensity at the carrier frequency 3f also becomes a valley.
That is, if the multicarrier used for transmission does not have the frequency relationship described in claim 1, it is found that the possibility that the received electric field strengths of all the multicarriers simultaneously become valleys in the received signal becomes very large.
[0022]
Next, another embodiment of the receiving apparatus using the two-wave multicarrier of the present invention corresponding to the transmitting apparatus of FIG. 3 shown in FIG. 4 will be described below.
The multi-carrier signal of 2 waves with the frequency of f and 2f transmitted by the transmission apparatus of FIG. 3 is received, and the signal of only the band of each carrier is passed by the band pass filters BPF5D and 6D, similarly to the transmission apparatus. Let
[0023]
Each of the signals having only a desired band by the band pass filters BPF5D and 6D is divided by 1 / k by the frequency dividing circuit 12 with respect to the signal of the carrier frequency f, and the signal of the carrier frequency 2f is obtained. Then, the frequency dividing circuit 13 divides the frequency by ½k. The signals output by the frequency dividing circuits 12 and 13 are both signals having the frequency f / k. The signals output from the frequency dividing circuits 12 and 13 are combined by the combining circuit 8D. When transmitting a carrier synchronization signal for information transmission in a transmission system, as shown in FIGS. 3 and 4, the multi-carriers having a frequency relationship according to claim 1 are transmitted without modulation, and at the receiving side. By performing frequency division and synthesizing the same frequency signal together, it is possible to realize a transmission apparatus that can more reliably transmit a carrier synchronization signal for information transmission that is not easily affected by multipath interference waves.
[0024]
In addition to the carriers having the relationship of f and 2f described with reference to FIGS. 3 and 4, for example, even if two-wave carriers of 2f and 3f or 10f and 11f are used, an odd-numbered carrier has two waves. The above condition does not exist, and any two waves of the multicarrier satisfy the condition that the relationship is not an odd multiple.
[0025]
When a multipath interference wave exists, the probability that the received electric field strengths of all multicarriers simultaneously become valleys can be made extremely small.
Therefore, since it is possible to receive the carrier signal without loss due to the multipath interference wave, it is possible to demodulate the signal transmitted even in a severe multipath environment. In the case of indoor transmission, the multipath environment is very severe because there are many reflections and the attenuation of multipath interference waves is small, but it is also effective in such a case. The signal to be transmitted may be any of an information signal, a reference signal, and a synchronization signal.
[0026]
【The invention's effect】
In the present invention, when a carrier used for transmission is a multi-carrier of two or more waves, and the frequency of the multi-carrier is represented by an integer ratio, there are no two or more odd-number carriers, and any of the multi-carriers When there is a multipath interference wave by controlling the frequency of the multicarrier and transmitting a signal so that the relationship between the two waves is not an odd multiple, the received electric field strength of all the multicarriers simultaneously decreases. The probability of becoming can be made very small.
[0027]
Therefore, the carrier signal can be received without loss due to the multipath interference wave, and the signal transmitted in a severe multipath environment can be demodulated.
In the case of indoor transmission, the multipath environment is very severe because there are many reflections and the attenuation of multipath interference waves is small, but it is also effective in such a case.
A transmission / reception apparatus using a two-wave carrier may have a simple configuration and is suitable for the case where an existing apparatus is improved.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a multicarrier transmission apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating a configuration of a multicarrier receiver according to a first embodiment of the present invention.
FIG. 3 is a diagram illustrating a configuration of a multicarrier transmission apparatus according to a second embodiment of the present invention.
FIG. 4 is a diagram showing a configuration of a multicarrier receiving apparatus according to a second embodiment of the present invention.
FIG. 5 is a diagram showing a state of received electric field intensity due to a multipath interference wave when the condition of the present invention is met.
FIG. 6 is a diagram showing a state of received electric field strength due to a multipath interference wave when the condition of the present invention is not met.
[Explanation of symbols]
1A, 1C, 2A, 2C, 3A Frequency conversion circuit 4A, 4C Carrier frequency control circuit 5A, 5B, 5C, 5D, 6A, 6B, 6C, 6D, 7A, 7B Band pass filter (BPF)
8A, 8B, 8C, 8D Synthesis circuit 9, 10, 11 Demodulation circuit 12, 13 Dividing circuit

Claims (4)

In a multi-carrier transmission apparatus that transmits an input signal to be transmitted on a plurality of carriers,
When the carrier used for the transmission is a multi-carrier of two or more waves, and the frequency of the multi-carrier is represented by an integer ratio, there are no two or more odd-number carriers, and any two waves of the multi-carrier So as not to have an odd multiple relationship, carrier frequency control means for controlling the frequency of the multicarrier,
Frequency conversion means for frequency-converting the input signal so as to be the multi-carrier frequency controlled by the carrier frequency control means;
A bandpass filter that passes each band of the multicarrier frequency-converted by the frequency conversion means;
And a means for synthesizing signals output from the band-pass filter. The multicarrier transmission apparatus according to claim 1,
By using a two-wave carrier having a multi-carrier frequency of carrier frequency f and a carrier frequency 2f that is twice the carrier frequency f, the input signal is fixed without changing its level. A multicarrier transmission apparatus for transmitting a wave multicarrier without modulation. In the multicarrier receiver which receives the signal from the multicarrier transmitter according to claim 2 ,
A bandpass filter that passes each band of the multicarrier;
Means for dividing the signal of the carrier frequency f obtained from the bandpass filter into 1 / k (k is an arbitrary natural integer);
Means for dividing the signal of the carrier frequency 2f obtained from the band-pass filter into 1 / 2k;
And a means for synthesizing signals from the frequency dividing means. In a multi-carrier transmission method for transmitting an input signal to be transmitted on a plurality of carriers,
When the carrier used for the transmission is a multi-carrier of two or more waves, and the frequency of the multi-carrier is indicated by an integer ratio, there are no two or more odd-number carriers, and in any two waves of the multi-carrier The frequency of the input signal is converted so as to be the frequency of the multicarrier controlled by the carrier frequency control step that controls the frequency of the multicarrier and the carrier frequency control step A frequency conversion step; a band-pass filtering step for passing each band of the multicarrier frequency-converted by the frequency conversion step; and a step of synthesizing a signal output by the band-pass filtering step. Multi-carrier transmission method.

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