JP2001156739A - Multi-carrier transmission system and multi-carrier transmission reception system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for transmitting information by using a plurality of orthogonal carriers in a multi-carrier transmission system. SOLUTION: The multi-carrier transmission system is provided with a frequency distribution control means 12 that assigns a transmission data sequence to a plurality of frequencies in an orthogonal frequency division relation, an N point IFFT means 13 that transforms a signal assigned on an orthogonal frequency sequence into a signal on an orthogonal time sequence, an orthogonal modulation means 14 that applies orthogonal modulation to a symbol signal sequence being an N point time sequence signal obtained by the IFFT means, a digital/analog converter means 15 that converts a time sequence digital signal outputted from the orthogonal modulation means into an analog signal, and a frequency conversion means 16 that converts the analog signal from the digital/analog converter means into a transmission band frequency. In the system, the frequency distribution control means 12 keeps an intermittent constant interval of M points and changes the assignment frequency to the IFFT means so as to conduct frequency hopping.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicarrier transmission system, and more particularly to a transmission system for transmitting information using a plurality of orthogonal carriers.

[0002]

2. Description of the Related Art FIG. 8 shows a multi-carrier transmission system using a conventional OFDM transmission system.
This is an example of a multicarrier transmission system configured with the above receiver. The OFDM system is a frequency-division multiplexing digital modulation system for transmitting digital information using a plurality of orthogonal carriers. The OFDM system is strong in multipath, hardly interferes with other transmission systems, is hardly affected by interference, and uses frequency. It has features such as relatively high efficiency, and has recently been put into practical use as a modulation method suitable for mobile digital audio broadcasting and digital television broadcasting.

FIG. 8 shows an example of a three-channel multicarrier transmission system using three transmitters and one receiver. In FIG. 3, the transmitter assigns frequencies to the signals of each channel to IFFTs 51, 71, and 81, and performs an inverse Fourier transform. The quadrature modulation circuits 52, 72, and 82 perform quadrature modulation on the time-series signal output after the inverse Fourier transform to generate an OFDM signal.
The OFDM signal is frequency-converted by the frequency conversion circuits 54, 74, and 84, up-converted to a desired band, and transmitted.

At this time, each channel has predetermined transmission bands 91, 92, 93, and frequency conversion circuits 54, 74,
The frequency at the time of the frequency conversion performed by 94 is f
1, f2 and f3, and any channel is converted into a transmission band without overlapping.

[0005] In the receiver, the received signals are converted into frequencies f1, f2, f by frequency conversion circuits 94, 95, 96.
3 to perform down-conversion to the baseband signal. Then, a desired channel is selected by the switch 97, and orthogonal transform is performed by the orthogonal demodulation circuit 62.
After time-sequential allocation of the demodulated signal to FFT 64, Fourier transform is performed to obtain a decoded signal of a frequency sequence.

[0006]

With the development of wireless technology and wireless devices, usable frequency bands are also restricted, resulting in extreme shortage of frequencies and at the same time the influence of wireless devices on other devices. ing. For this reason, a system capable of reusing frequencies and capable of transmission in a relatively local area, that is, a transmission system using a weak radio wave capable of reducing interference with other devices is effective.

However, when weak radio transmission is assumed in the configuration as in the conventional example, when carriers to be transmitted are arranged for each channel in the transmission band, transmission power within a predetermined band is concentrated on each channel. Therefore, it is necessary to suppress the transmission power in order to satisfy the regulation of the weak radio wave, and it becomes impossible to satisfy a desired transmission distance.

Further, in the conventional example, since a predetermined band is allocated to each channel, there is a problem that when a specific frequency in a transmission band of a channel is disturbed, a specific channel is greatly damaged.

[0009]

SUMMARY OF THE INVENTION A transmission system according to the present invention has been made in view of the above points, and a first aspect of the present invention is a frequency distribution control for allocating a transmission data sequence to a plurality of frequencies having an orthogonal frequency division relationship. Means, N-point IFFT means for converting a signal allocated on an orthogonal frequency sequence into an orthogonal time-series signal, and orthogonal modulation of a symbol signal sequence of the N-point time-series signal obtained from the IFFT means Quadrature modulating means, D / A converting means for converting a time series signal of a digital signal output from the quadrature modulating means into analog, and a frequency for converting an analog signal from the D / A converting means into a transmission band frequency. A multi-carrier transmission transmission system comprising: a frequency converter for converting the frequency of the N points into 0 + k M + k, 2M + k, ···, pM +
By intermittently allocating the frequency while maintaining a constant interval such as k (where M is the interval of the used frequency, p is an integer less than N / M, and k is a value from 0 to (M-1)) Said I
The present invention provides a multicarrier transmission system in which frequency hopping is performed by changing the value of the k to a frequency assigned to FFT means, and the invention of claim 2 provides the multicarrier transmission system according to claim 1. In a multicarrier transmission reception system for receiving a signal from a carrier transmission transmission system, the multicarrier transmission reception system includes frequency conversion means for down-converting a time-series orthogonal multicarrier signal from a transmission band to an intermediate frequency; and A / D conversion means for converting an analog time-series signal obtained by the conversion means into digital,
An orthogonal demodulator for orthogonally demodulating a digital time-series signal obtained from the D converter, and an F for performing Fourier transform on an N-point symbol signal sequence output from the orthogonal demodulator.
FT means and frequency selection / extraction means for selecting a frequency including transmission data from N-point frequency sequence signals obtained from the FFT means, wherein the frequency selection / extraction means comprises N frequency signals obtained from the FFT means. A multicarrier transmission / reception system, wherein a transmission data sequence is extracted by selecting a frequency in synchronization with the frequency hopping from a frequency sequence signal of a point, and a multicarrier transmission / reception system is provided. In a multi-carrier transmission transmission system between a transmitter and a plurality of transmitters, each of the transmitters is allocated to a plurality of frequencies in an orthogonal frequency division relationship with a transmission data sequence, and frequency distribution control means, and is allocated on the orthogonal frequency sequence. N-point IFFT means for converting a signal into an orthogonal time-series signal;
Orthogonal modulation means for orthogonally modulating a symbol signal sequence which is an N-point time-series signal obtained by the FT means, and D / A conversion means for converting the digital signal time-series signal output by the orthogonal modulation means into analog. , The D / A
Frequency conversion means for converting an analog signal from the conversion means into a transmission band frequency, wherein the frequency distribution control means sets 0 + k, M +
k, 2M + k,..., pM + k (where M is an interval of operating frequencies, p is an integer less than N / M, k is 0 to (M−
Frequency allocation is performed intermittently while maintaining a constant interval as in the value of 1), the frequency assigned to the IFFT means is changed and the value of k is changed, and frequency hopping is performed. A multicarrier transmission and transmission system is provided, wherein the frequency of the frequency hopping is not matched between the plurality of transmitters. The invention of claim 4 provides the multicarrier transmission and transmission according to claim 3. In a multicarrier transmission reception system that receives a signal from a system, the multicarrier transmission reception system includes a frequency conversion unit that downconverts a time-series orthogonal multicarrier signal from a transmission band to an intermediate frequency, and the frequency conversion unit. A / D conversion means for converting the obtained analog time-series signal into digital,
Orthogonal demodulation means for orthogonally demodulating a digital time-series signal obtained from the A / D conversion means, FFT means for performing Fourier transform on a (N-point) symbol signal sequence output from the orthogonal demodulation means, and FFT means Frequency selecting and extracting means for selecting a frequency including the transmission data from the plurality of transmitters from the N-point frequency sequence signal obtained from the above, and the frequency selecting and extracting means selects N from the FFT means. A multicarrier transmission / reception system, wherein a frequency is selected in synchronization with the frequency hopping from a frequency sequence signal of a point, and transmission data sequences transmitted from the plurality of transmitters are extracted. Is what you do.

[0010] As described above, the transmission system of the present invention enables high-rate transmission with a low transmission power density and a high resistance to frequency interference under the condition that the frequency band and the transmission power are limited. It is. That is, to provide a multi-carrier transmission system capable of satisfying the transmission power restriction condition without concentrating the transmission power within a predetermined band and reducing the influence of interference to a specific frequency. It is.

(Operation) The transmission system of the present invention comprises:
The transmission data sequence is allocated to carriers of a plurality of frequencies having an orthogonal frequency division relationship, but the frequency is always intermittently allocated while maintaining a constant orthogonal frequency division interval, and the plurality of carriers are fixed at predetermined time intervals. The frequency hopping is performed with the intermittent arrangement maintaining the orthogonal frequency division intervals of. In the case of a transmission system having a plurality of transmission channels, different hopping frequencies are used for each channel so that frequencies of a plurality of carriers transmitting the information of each channel do not overlap.

With the above arrangement, a plurality of frequency-hopping carriers are arranged with a certain frequency interval therebetween, so that transmission power does not concentrate in a predetermined band, and a specific frequency In the case where interference occurs, the effect can be reduced and high-rate transmission can be performed. In the case of a plurality of channels, a hopping frequency different for each channel can be used to configure a transmission system having a plurality of transmission channels.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the multicarrier transmission system of the present invention will be described below with reference to the drawings. One embodiment of the multicarrier transmission system of the present invention shown in FIG. 1 includes an S / P converter 11, a frequency distribution circuit 12, an inverse FFT circuit 13, a quadrature modulation circuit 14, and a D / A conversion circuit 1.
5, a frequency conversion circuit 16 and a BPF 17.

In the embodiment of the present invention, the input data is serial-parallel converted into (p + 1) parallel data by the S / P converter 11, and the frequency distribution circuit 12 allocates the frequency to the subsequent N-point inverse FFT circuit 13. Perform At this time,
0 + k, M + k, 2M +
k,..., pM + k (where M is an interval between operating frequencies,
(p is an integer less than N / M, k is a value from 0 to (M-1)), and frequency allocation is performed intermittently at regular intervals of the frequency of M points, and the inverse FFT circuit 13 performs an inverse Fourier transform. To obtain a time-series symbol signal sequence.

Here, the value of k ranges from 0 to 0 as shown in FIG.
In the range of (M-1), every predetermined symbol time,
Frequency allocation is performed so as to perform frequency hopping. That is, FIG. 2 shows one embodiment of M = 8, and after being assigned to 0, M, 2M,..., PM, after a predetermined time, 0 + 5, M + 5, 2M + 5,. , PM
+5, and after a predetermined symbol time, 0 + 3, M + 3, 2M + 3,..., PM + 3
FIG.

As described above, the signal whose frequency has been intermittently assigned at a constant interval while each carrier is frequency hopping is then subjected to an inverse FFT transformation by an N-point IFFT (inverse FFT) circuit 13, The obtained time-series symbol signal sequence is quadrature-modulated by digital processing in the quadrature modulation circuit 14 to output a modulated signal sequence.

The quadrature signal sequence from the quadrature modulation circuit 14 is D /
After being converted into an analog signal by the A conversion circuit 15, the frequency conversion is performed by the frequency conversion circuit 16 and up-converted into a transmission frequency band. The up-converted signal is band-limited by the BPF 17 and transmitted via an antenna.

FIG. 3 shows the operation described above on the frequency-time axis in an easy-to-understand manner. As shown in the figure, for frequencies of N points in an orthogonal frequency division relationship,
The figure shows a state in which (p + 1) transmission carriers (frequency) are frequency-hopped at predetermined time intervals while always maintaining a constant interval for M points so as to be intermittent.

As described above, according to the multicarrier transmission system of the present invention, (p + 1) carriers are intermittently arranged at regular intervals in a plurality of multicarriers having an orthogonal frequency division relationship. High-speed transmission is possible without the transmission power being concentrated in the band, and the transmission frequency is hopping, so that even if interference occurs at a specific frequency, the effect can be reduced. There is.

FIG. 4 is a block diagram showing an embodiment of the multicarrier transmission / reception system according to the present invention. One embodiment of the multicarrier transmission / reception system of the present invention includes a BPF 21, a frequency conversion circuit 22, an A / D converter 23, a quadrature demodulation circuit 24, an FFT circuit 25, a frequency selection and extraction unit 26, and a P / S converter 27. It is composed of

In FIG. 4, the received signal is a BPF
After being band-limited by 21, the frequency is converted in the frequency conversion circuit 22 and down-converted to the same frequency as the transmitter. The down-converted intermediate frequency signal is converted into a digital signal by the A / D converter 23, and the obtained time-series data is quadrature-demodulated by digital processing in the quadrature demodulation circuit 24. The N-point symbol signal sequence obtained by the quadrature demodulation is converted into an FFT circuit 2
At 5, a Fourier transform is performed to obtain an N-point frequency sequence signal.

Of the N-point frequencies, the frequencies to which transmission data are assigned are 0 + k, M + k, and 2M +
k,..., pM + k (where M is an interval between operating frequencies, p is an integer less than N / M, and k is a value from 0 to (M−1)). The frequency selection means 26 selects / extracts (p + 1) frequency hoppings from the N points at a constant interval of P / S
The data is subjected to P / S conversion by the converter 27 and becomes a received data output.

Although not shown, it is necessary to synchronize the symbol between the transmitter and the receiver, and to select the hopping frequency and the hopping timing. Therefore, the transmitter transmits a symbol synchronization or a frame synchronization signal to the receiver. It is assumed that a means for transmitting control information such as selection of a hopping frequency or a synchronization means such as insertion of a hopping frequency is employed. Alternatively, conversely, means for transmitting a signal for synchronization and control from the receiver to the transmitter may be employed.

Next, a second embodiment, which is a multicarrier transmission receiving system of the present invention and performs wireless transmission of a plurality of channels between a receiver and a predetermined number of two or more transmitters, will be described below with reference to the drawings. I do. FIG. 5 shows transmitters 1, 2, and 3
1 shows one embodiment between a receiver and one receiver. The configuration of each transmitter is a serial-parallel conversion circuit, frequency distribution means, inverse FFT circuit, quadrature modulation circuit, D / A conversion circuit, frequency conversion circuit,
And BPF, and has the same configuration as that of FIG.

In the frequency distribution means of each transmitter, the second
Also in the embodiment, the frequency is intermittently assigned at a constant interval of M points, but in the transmitter 1, 0+
k, M + k, 2M + k,... pM + k are assigned, and in the transmitter 2, 0 + 1, M + 1, 2M
.., PM + 1 in the transmitter 3, 0+
Frequency allocation is performed for m, M + m, 2M + m,..., pM + m. Here, k, l, and m are different values, and are within a range of 0 to (M−1) every predetermined symbol time.
A changing value is chosen.

FIG. 6 explains the operation in the second embodiment (wireless transmission of a plurality of channels) in an easy-to-understand manner on the frequency-time axis. As shown in FIG. 6, (P + 1) transmission carriers of each of the transmitters 1, 2, and 3 are always intermittently spaced by M at regular intervals for N frequencies having an orthogonal frequency division relationship. , And operates so as to perform frequency hopping every predetermined time.

At this time, the hopping frequency is selected so that the frequencies of the transmitters do not overlap. That is, each transmitter specifies a hopping frequency pattern unique to each transmitter before transmission, and performs a frequency hopping operation according to the pattern. Therefore, up to M transmitters can transmit without overlapping hopping frequencies.

FIG. 7 shows a block configuration of an embodiment of the multicarrier transmission / reception system of the present invention. One embodiment of the multi-carrier transmission / reception system of the present invention includes a BPF 31, a frequency conversion circuit 32, an A / D converter 33, a quadrature demodulation circuit 34, an FFT circuit 35, a frequency selection means 36, and a P / S converter 37-. 1, 37-2, 37
-3. In the figure, a received signal is band-limited by a BPF 31, then frequency-converted in a frequency conversion circuit 32, and down-converted to the same frequency as the transmitter.

The intermediate frequency is converted into a digital signal by the A / D converter 33, and the obtained time-series data is subjected to quadrature demodulation by digital processing in the quadrature demodulation circuit 34.
The N-point symbol signal sequence obtained by the quadrature demodulation is Fourier-transformed in the FFT circuit 35 to obtain an N-point frequency sequence signal.

Of the N point frequencies, the frequencies including the transmission data from the transmitter 1 are 0 + k, M + k, 2M +
, pM + k, and the frequencies including the transmission data from the transmitter 2 are 0 + 1, M + 1, 2M + 1,.
, PM + 1, and the frequencies including the transmission data from the transmitter 3 are 0 + m, M + m, 2M + m,..., PM +
m. The frequency selection / extraction circuit 36 selects / extracts (p + 1) frequency hoppings from the N points at a constant interval of M points according to the values of k, l, and m different for each transmitter. Separately, P / S converters 37-1, 37-2, and 37-3 respectively perform P / S conversion to obtain respective outputs of received data.

Although not shown, it is necessary to synchronize the symbol between the receiver and a plurality of transmitters, and to select the hopping frequency and synchronize the hopping timing.
It is assumed that a means for transmitting a signal for synchronization and control from the receiver is employed.

As a special example of the wireless transmission of a plurality of channels, if the values of k, l, and m are not changed and are fixed values, a fixed interval for the frequency of M points is maintained without frequency hopping. And intermittent carrier placement,
Transmission of a plurality of channels (maximum M) is also possible.

As another special example, when a plurality of transmission systems as shown in FIG. 5 are serviced using the same frequency band in a neighboring area, the mutual interference between the transmission systems affects each other. However, if the frequency hopping pattern is made different in the adjacent area system, code error correction using data when the hopping frequency does not overlap works and complete transmission is not possible, and some transmission is possible. You can expect the effect of becoming.

[0034]

According to the present invention, high-rate information transmission using a plurality of carriers is possible, and since the plurality of carriers have a fixed frequency interval, the transmission power is kept within a predetermined band. Since the plurality of carriers are frequency hopping while maintaining a constant frequency interval without being concentrated, even if interference to a specific frequency occurs, the effect can be reduced. .

In the case of a plurality of channels, different hopping frequencies are set for the respective channels,
A multi-channel transmission system having the same effects as above can be configured. In the present invention, since the frequency is selected to be a frequency having an orthogonal frequency division relationship, the hopping frequency can be set without taking up a frequency space, and thus there is also an advantage in terms of frequency utilization efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram showing a block configuration of a first embodiment of a transmitter of a multicarrier transmission system according to the present invention.

FIG. 2 is a diagram showing the principle of information signal allocation in the present invention.

FIG. 3 is a diagram showing information signal allocation in the first embodiment.

FIG. 4 is a diagram showing a block configuration of a first embodiment of the receiver of the multicarrier transmission system according to the present invention.

FIG. 5 is a diagram showing a block configuration of a second embodiment of the transmission / reception system having a plurality of channel configurations of the present invention.

FIG. 6 is a diagram showing information signal allocation in the second embodiment.

FIG. 7 is a diagram showing a block configuration of a second embodiment of the receiver of the multicarrier transmission system of the present invention.

FIG. 8 is a diagram illustrating a block configuration of an example of a conventional multicarrier transmission system having a plurality of channel configurations.

[Explanation of symbols]

 Reference Signs List 11 S / P converter 12 Frequency distribution circuit 13 Inverse FFT circuit 14 Quadrature modulation circuit 15 D / A conversion circuit 16, 22, 32 Frequency conversion circuit 17, 21, 31, BPF 23, 33 A / D converter 24, 34 Quadrature Demodulation circuit 25, 35 FFT circuit 26, 36 Frequency selection and extraction means 27, 37-1, 37-2, 37-3 P / S converter M Interval of used frequencies (points) N Number of used frequencies (points) k 0 To the value of (M-1) p an integer less than N / M

Claims (4)

[Claims] 1. A frequency distribution control means for allocating a transmission data sequence to a plurality of frequencies having an orthogonal frequency division relationship, and N points for converting a signal allocated on the orthogonal frequency sequence into an orthogonal time series signal. IFFT means, orthogonal modulation means for orthogonally modulating the symbol signal sequence of the N-point time-series signal obtained from the IFFT means, and D / D for converting the digital signal time-series signal output from the orthogonal modulation means into analog. A multicarrier transmission / transmission system comprising: A conversion means; and frequency conversion means for converting an analog signal from the D / A conversion means into a transmission band frequency, wherein the frequency distribution control means includes On the other hand, 0 + k, M + k, 2
M + k,..., PM + k (where M is the interval of the used frequency, p is an integer less than N / M, and k is a value from 0 to (M−1)) intermittently while maintaining a constant interval. A multicarrier transmission and transmission system, wherein frequency hopping is performed by performing frequency allocation and changing the value of k to a frequency allocated to the IFFT means. 2. A multi-carrier transmission receiving system according to claim 1, wherein said multi-carrier transmission receiving system receives a signal from the multi-carrier transmission transmitting system and converts a time-series orthogonal multi-carrier signal from a transmission band. Frequency converting means for down-converting to an intermediate frequency, A / D converting means for converting an analog time-series signal obtained from the frequency converting means into digital, and orthogonalizing the digital time-series signal obtained from the A / D converting means. Orthogonal demodulation means for demodulating, FFT means for performing Fourier transform of a symbol signal sequence of N points output from the orthogonal demodulation means,
Frequency selection and extraction means for selecting a frequency including transmission data from N-point frequency sequence signals obtained from the FT means, wherein the frequency selection and extraction means comprises an N-point frequency sequence signal obtained from the FFT means , A transmission data sequence is extracted by selecting a frequency in synchronization with the frequency hopping. 3. A multicarrier transmission system between a receiver and a plurality of transmitters, wherein each of the transmitters allocates a transmission data sequence to a plurality of frequencies having an orthogonal frequency division relationship, N-point IFFT means for converting a signal allocated on a stream into an orthogonal time-series signal, and quadrature modulation means for orthogonally modulating a symbol signal sequence which is an N-point time-series signal obtained by the IFFT means D / A conversion means for converting a time series signal of a digital signal output by the quadrature modulation means into analog, and frequency conversion means for converting an analog signal from the D / A conversion means into a transmission band frequency. The frequency distribution control means comprises: 0 + k, M + k, 2
M + k,..., PM + k (where M is the interval of the used frequency, p is an integer less than N / M, and k is a value from 0 to (M−1)) intermittently while maintaining a constant interval. The frequency hopping is performed by allocating a frequency and changing the value of k to the frequency allocated to the IFFT means, and the frequency hopping frequency is not matched between the plurality of transmitters. A multi-carrier transmission transmission system characterized in that: 4. A multi-carrier transmission receiving system for receiving a signal from a multi-carrier transmission system according to claim 3, wherein said multi-carrier transmission receiving system converts a time-series orthogonal multi-carrier signal from a transmission band. Frequency converting means for down-converting to an intermediate frequency, A / D converting means for converting an analog time-series signal obtained from the frequency converting means into digital, and orthogonalizing the digital time-series signal obtained from the A / D converting means. Orthogonal demodulation means for demodulating, FFT means for performing Fourier transform of a symbol signal sequence of N points output from the orthogonal demodulation means,
Frequency selecting and extracting means for selecting a frequency including transmission data from the plurality of transmitters from an N-point frequency sequence signal obtained by the FT means, wherein the frequency selecting and extracting means obtains from the FFT means A multi-carrier transmission / reception system wherein a frequency is selected in synchronism with the frequency hopping, and transmission data sequences sent from the plurality of transmitters are extracted from N-point frequency sequence signals to be transmitted. .