JPH11205260A - Parallel transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a parallel transmission method to realize high speed and high quality transmission without the need for a radio circuit having a broad band frequency characteristic and a processor to conduct sophisticated digital signal processings by using existing circuit techniques so as to set a frequency interval of a plurality of carriers at a coherence band width or over or in the vicinity of the band width and to conductor communication. SOLUTION: A frequency interval of a plurality of carriers is set at a coherence band width or over. Through this setting, a plurality of carriers receive sets of fading width almost non-correlation. Thus, even when a spectrum 112 of a specific carrier receives fading during a speech and the quality of channel is deteriorated, spectrums 111, 113 of the remaining carriers are used to continue the speech. The remaining reception signals are synchronously detected and the signals are synthesized at a maximum ratio. Since the carriers are regarded almost independent in this case, diversity reception with a synthesis at a maximum ratio or branches corresponding to the carriers used for communication is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parallel transmission method for performing radio communication, in particular, land mobile communication of a plurality of different baseband signals in a frequency division multiplex system using a plurality of carriers.

[0002]

2. Description of the Related Art In recent years, various radio communication systems have been proposed for realizing high quality transmission and high speed transmission in radio communication represented by land mobile communication requiring high speed transmission and high quality transmission. Was. For example, a code division multiple access (CDMA) scheme,
Adaptive modulation method, 16QAM-4 multicarrier transmission method, Orthogonal Frequency Division (Orthogonal Frequency Divis)
An ion multiplexing (OFDM) system and the like have been proposed.

[0003] Methods for ensuring the required transmission quality in these wireless transmission systems have hitherto been known as second-generation mobile communication systems such as PDC (Personal Digital Cellular) and GSM (Glo- ble).
balSystem for Mobile communication), error correction technology used in IS-95, etc., and diversity reception technology such as frequency diversity reception, space diversity reception, and polarization diversity reception used in fixed microwave links. is there.

In high-speed transmission, an adaptive modulation method for selecting an optimum modulation method according to the condition of a transmission path, a wideband CDM
A, O being considered for application as a digital broadcasting system
An FDM system and the like are known.

The above-described high-speed transmission and high-quality transmission systems split a single spectrum by a plurality of carriers,
Error correction technology and diversity reception technology were used for a wideband single carrier. In order to realize a wireless device used in these systems, a wireless circuit having required frequency characteristics over a wide band and a processor for performing advanced digital signal processing were required. For example, an RF wireless line such as a filter and a transmission power amplifier and a processor such as an error correction decoder are used.

[0006] In order to construct a radio communication system with high frequency utilization efficiency, a circuit technique for reducing the guard band between radio channels is indispensable. It is essential to improve the linearity of the transmission system.

In order to realize high-speed transmission and high-quality transmission, and to realize a radio communication system with high frequency utilization efficiency, advanced circuit technology was required. For example, 10M
In order to transmit bps information, if the modulation is QPSK and the roll-off filter coefficient is 0.5, a frequency bandwidth of 7.5 MHz is required. When this is transmitted by a single carrier, the pass bandwidth (3 dB bandwidth) of the reception filter used in the radio device is 4.6 MHz. If the mobile station needs 80 dB of the adjacent channel attenuation so that the mobile station does not suffer from the near-far problem with the adjacent carrier, the receiving filter needs a wide pass bandwidth and a steep attenuation characteristic. If a small and lightweight radio is to be made, it is necessary to develop a small filter with higher performance than before.

[0008]

As described above, in the conventional high-speed transmission and high-quality transmission systems as described above,
A single spectrum is divided by a plurality of carriers, and an error correction technique and a diversity reception technique are used for a single carrier in a wide band. In order to realize radio equipment used in these systems, a radio circuit having a wide frequency characteristic and a processor for performing advanced digital signal processing were required.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problem, and the frequency intervals of a plurality of carriers are set to be equal to or more than a coherence bandwidth by using existing circuit technology. To provide a parallel transmission method capable of realizing high-speed transmission and high-quality transmission that does not require a radio circuit having a wideband frequency characteristic and a processor that performs advanced digital signal processing by performing communication with a frequency interval set in the communication. It is in.

[0010]

According to the first aspect of the present invention,
In a parallel transmission method in which M (M> 1) different baseband signals are wirelessly communicated by frequency division multiplexing using M carriers, a frequency interval between each of the M carriers is greater than a coherence bandwidth. Communication is performed by setting the frequency interval.

According to a second aspect of the present invention, there is provided a parallel transmission method for performing frequency division multiplexing wireless communication of M (M> 1) different baseband signals using M carrier waves.
The communication is performed by setting the frequency interval of each of the M carrier waves near the coherence bandwidth.

The invention described in claim 3 is the first or second invention.
In the above, a plurality of M or less different modulation methods can be used for the M carrier waves.

According to a fourth aspect of the present invention, in the third aspect, the M or less different modulation methods are PSK, QAM
Alternatively, it can be selected from FSK.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an outline of a parallel transmission method according to the present invention will be described. According to the parallel transmission method of the present invention, in a multi-carrier wireless communication method capable of high-speed transmission, a frequency correlation value between each used carrier is set to a certain value or less. For example, the frequency correlation value between the carrier waves is set to a frequency interval equal to or larger than the coherence band in which the carrier waves can be regarded as substantially uncorrelated. Here, the frequency correlation value ρ (Ω) is such that the frequencies of the two fading reception waves are f ₁ and f ₁ + Ω, the intensity of the element wave arriving at the receiving station is almost the same, the spread of the propagation path length is Δl, and the shortest is If the length of the propagation path is l ₀ and the speed of light is c,
It is known that equation (1) is obtained.

[0015]

(Equation 1)

The frequency interval Ω at which | ρ (Ω) | is 0.5
Is known to be defined as the coherence bandwidth.
Generally, the frequency interval Ω that can be regarded as almost uncorrelated is ρ
It is known that Ω satisfies (Ω) ≦ 0.5.

According to the parallel transmission method of the present invention, even if some carriers do not achieve a predetermined line quality due to fluctuations in the propagation path such as fading, deterioration of the line quality of the entire radio line can be avoided. For this reason, for example, the parallel transmission method of the present invention maintains the transmission capacity while maintaining the transmission capacity, as compared with a parallel transmission method in which a plurality of carriers are made into a single spectrum such as a conventional frequency division multiplexing (FDM). Less susceptible to line quality degradation.

Since the frequency intervals of the carriers are so far as to be regarded as substantially uncorrelated, a radio circuit embodying the present invention can be realized by having a plurality of radio circuits having different local oscillation frequencies. This eliminates the need for a filter having a wide-band passband required by the conventional parallel transmission method. The linearity of the wireless circuit may be achieved for each independent wireless circuit, and does not require the wide-band linearity required in the wireless circuit for the conventional parallel transmission method. By using a substantially independent narrowband carrier wave for a processor that performs digital signal processing, a processor with lower processing capability can be used. This contributes to a reduction in the power consumption of the digital circuit.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 8 shows a configuration example of a transmitter used in the parallel transmission method of the present invention.

In FIG. 8, a plurality of baseband processing units 800, 805,. . . , 810 processed by the D / A converters 820, 82, respectively.
5,. . . , 830, the D / A conversion and the quadrature modulator 84
0, 845,. . . , 850 are orthogonally transformed. Thereafter, each of the frequency converters 860, 865,. . . , 870 by the controller 880 at f ₁ , f ₂ ,. . . , It is frequency-converted to f _N. Here, in the conventional parallel transmission method, f ₁ , f
₂ ,. . . , F _N although is set to be substantially equal to or respectively is not more than the coherence bandwidth, f _1, by the controller 880 in the parallel transmission method of the present invention f
₂ ,. . . , F _N are set to be equal to or larger than the coherence bandwidth. Thereafter, the signal is multiplexed by a signal multiplexer 890, power-amplified by a transmission power amplifier 895, and transmitted via an antenna 897.

FIG. 9 shows another configuration example of a transmitter used in the parallel transmission method of the present invention.

In FIG. 9, a plurality of baseband processing units 900, 905,. . . , 910 are processed by the controller 920 to change the frequency in the signal multiplexer 915 to the above f ₁ , f ₂ ,. . . , F _N , shifted and multiplexed, and D / A converted by a D / A converter 925,
The orthogonal transform is performed by the orthogonal modulator 930. Thereafter, the frequency is converted by a frequency converter 935, the power is amplified by a transmission power amplifier 940, and transmitted via an antenna 945. Here, in the conventional parallel transmission method, f ₁ , f ₂ ,. . . , F
_N is set to be equal to or less than the coherence bandwidth, but in the parallel transmission method of the present invention, the controller 920 sets f ₁ , f ₂ ,. . . , F _N are set to be equal to or larger than the coherence bandwidth.

FIG. 10 shows a configuration example of a receiver used in the parallel transmission method of the present invention.

In FIG. 10, antennas 1000, 10
In the radio wave received at 05, the output of the receiving amplifiers 1020 and 1025 is changed by the switch 1010 to the level detector 1110,
Detected at 1115, the controller 1100 switches to the ANT 1000 or 1005 with the higher reception level, and the frequency converters 1030 and 1035 convert the signals to frequencies f ₁ and f ₂ by the controller 1040. Thereafter, band pass filters (BPF) 1050 and 1055,
Automatic Gain Control (AGC) 1
Detectors 1070, 1075 via 060, 1065
Is detected by the A / D converters 1080 and 1085.
The converted signal is input to a determinator 1095 that determines the sign by matching the phases in the in-phase combiner 1090.

(Embodiment 1) FIG. 1 shows an embodiment in which the frequency interval is set to be equal to or larger than the coherence bandwidth, wherein the vertical axis is a spectrum axis 100 and the horizontal axis is a frequency axis 110. FIG. 1 illustrates a parallel transmission method between wireless station 130 and wireless station 140 using three carriers for three different pieces of information.

In FIG. 1, frequency intervals 120, 12 of spectra 111, 112, 113 by three carrier waves are shown.
5 is set to be equal to or larger than the coherence bandwidth (115).
With this setting 115, the spectra 111, 112, and 113 of the three carriers in FIG. 1 undergo fading that is substantially uncorrelated with each other. Therefore, even if the spectrum 112 due to the second carrier is fading during the call and the line quality is degraded, the call can be continued by the spectrum 111 using the remaining first carrier and the spectrum 113 using the third carrier. is there. As shown in FIG. 10, the spectrum 111 based on the first carrier and the spectrum 113 based on the third carrier are synchronously detected, and the detector 1
After the detection by 070 and 1075, maximum ratio combining is performed. At this time, since the carrier waves can be regarded as substantially independent, it is possible to perform two-branch maximum ratio combining diversity reception.

(Embodiment 2) FIG. 2 shows an embodiment in which the frequency interval is set near the coherence bandwidth, where the vertical axis is the spectrum axis 100 and the horizontal axis is the frequency axis 110. FIG. 2 illustrates a parallel transmission method between the wireless station 130 and the wireless station 140 using three carriers for three different pieces of information.

Spectrum 21 with three carriers in FIG.
The frequency intervals 220 and 225 of 1, 212 and 213 are set near the coherence bandwidth (215). With this setting (215), the spectra 211, 212, and 213 of the three carriers in FIG. 2 undergo fading that is substantially uncorrelated with each other. Therefore, even if the spectrum 212 due to the second carrier is fading during communication and the line quality is degraded, the communication can be continued with the spectrum 211 using the remaining first carrier and the spectrum 213 using the third carrier. is there. As shown in FIG.
The spectrum 211 of the first carrier and the spectrum 213 of the third carrier are synchronously detected, and the detector 107
After the detection by 0 and 1075, the maximum ratio is synthesized. At this time, since the carrier waves can be regarded as substantially independent, it is possible to perform two-branch maximum ratio combining diversity reception.

(Embodiment 3) FIG. 3 shows an embodiment using a plurality of modulation methods, in which the vertical axis is the spectrum axis 100 and the horizontal axis is the frequency axis 110. In FIG. 3, the wireless station 130 and the wireless station 1 using three different information
Next, a parallel transmission method between H.40 and H.40 will be described.

In FIG. 3, each modulation scheme of spectrums 311, 312, 313 by three carriers is represented by QPSK,
16QAM and FSK were used. Frequency intervals 320, 32 of spectra 311, 312, 313 by three carriers
5 is set to be equal to or larger than the coherence bandwidth (315).
With this setting (315), the spectra 311, 312, and 313 of the three carriers in FIG. 3 undergo fading that is substantially uncorrelated with each other. Here, even if the spectrum 313 due to the third carrier is fading and the line quality is deteriorated, the spectrum 31 due to the first carrier is used.
The communication can be continued by the spectrum 312 by the first and second carriers. Spectrum 313 with third carrier
, The information to be transmitted can be distributed to the spectrum 312 by the second carrier. Here, the spectrum 312 by the second carrier uses 16QAM.
As a result, the parallel transmission method according to the present invention can always maintain a predetermined transmission capacity without increasing the bandwidth even when affected by fading.

(Embodiment 4) FIG. 4 shows an embodiment using a plurality of modulation methods, in which the vertical axis is the spectrum axis 100 and the horizontal axis is the frequency axis 110. In FIG. 4, the wireless station 130 and the wireless station 14 using three carriers for three different pieces of information.
A parallel transmission method between 0 and 0 will be described.

In FIG. 4, each modulation scheme of spectra 411, 412, and 413 by three carriers is represented by QPSK,
16QAM, 16QAM. Frequency spacing 420 of spectra 411, 412, 413 by three carriers,
425 is set to be equal to or larger than the coherence bandwidth (415). With this setting (415), the spectra 411, 412, and 413 of the three carriers in FIG. Here, even if the spectrum 413 due to the third carrier is fading and the line quality is degraded, the spectrum 413 due to the first carrier is used.
The communication can be continued by the spectrum 412 by the 11th and 2nd carrier waves. Spectrum 41 with third carrier
In step 3, information to be transmitted is allocated to the spectrum 412 by the second carrier. Here, the spectrum 412 by the second carrier uses 16QAM. As a result, the parallel transmission method of the present invention can always maintain a predetermined transmission capacity without increasing the bandwidth even when affected by fading. As described above, a modulation method having a number (2) different from the number (3) of carrier waves can be used.

(Embodiment 5) FIG. 5 shows an embodiment using carriers at frequency intervals standardized by PDC.
The vertical axis is the spectrum axis 500, and the horizontal axis is the frequency axis 510. In FIG. 5, four different information are converted into spectra 511, 512, 513 and 514 by four different carriers.
A parallel transmission method between the wireless station 530 and the wireless station 540 using the method will be described.

In FIG. 5, the spectra 511, 512, 513, and 514 of each carrier are almost independent. Spectrum 511, 512, 513, 51 by each carrier
5, the transmission capacity in FIG. 5 is four times that of PDC. 11.2 kbps per spectrum with one carrier
Then, a transmission capacity of 44.8 kbps can be obtained. Thus, the parallel transmission method using the present invention is effective for high-speed transmission.

(Embodiment 6) FIG. 6 shows an embodiment in which the parallel transmission method of the present invention is applied to a broadcast service.
The vertical axis is the spectrum axis 600 and the horizontal axis is the frequency axis 610. In FIG. 6, a wireless station 63 using spectra 611, 612, 613, 614 with four different carriers.
A parallel transmission method between the wireless station 0 and the wireless station 640 will be described.

In the down link 650, the communication channel 6
11 and channels 612 and 6 for providing broadcast services
13, 614. On the uplink 655,
Assuming that only the communication channel 651 is used, the modulation method of the channels 612, 613, and 614 used in the downlink 650 may be the modulation method of the voice channel or another modulation method.

According to the present embodiment, a user can receive a broadcast service through downlink 650 while performing voice communication, for example, a PDC call, using his / her own mobile device. ITS (Intelligent Tutoring System) represented by car navigation etc. as a broadcast service
(For example, traffic information, weather forecast, various news services, etc.). In this way, different line capacities and reliability can be set for the upstream 655 and downstream 650.

(Embodiment 7) FIG. 7 shows an embodiment in which voice and data transmission coexist, in which the vertical axis represents the spectrum axis 700 and the horizontal axis represents the frequency axis 710. In FIG. 7, spectra 711, 71 with three different carriers.
A method of parallel transmission between the wireless station 730 and the wireless station 740 using 2,713 will be described.

In the downlink 750, the modulation scheme of each channel is QPSK for channel 711, 16QAM for channel 712, and FSK for channel 713. In the uplink 755, the modulation scheme of each channel is channel 75
1 is 16QAM, channel 752 is QPSK, and channel 753 is FSK. According to the present embodiment, if the bandwidth is the same, spectra 711 and 71 due to each carrier wave are obtained.
There is no limitation on the modulation method of 2,713. This is P
Data transmission using 16QAM modulation using DC is also possible. As described above, the parallel transmission method of the present invention can flexibly realize services with different required line qualities, such as voice and data transmission, using the same transmission method.

[0041]

As described above, according to the parallel transmission method of the present invention, communication is performed by setting the frequency interval of each of a plurality of carriers to be equal to or larger than the coherence bandwidth using the existing circuit technology. By doing so, it is possible to provide a parallel transmission method capable of realizing high-speed transmission and high-quality transmission that does not require a radio circuit having wideband frequency characteristics and a processor that performs advanced digital signal processing.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment in which a frequency interval is set to be equal to or larger than a coherence bandwidth.

FIG. 2 is a diagram showing an embodiment in which a frequency interval is set near a coherence bandwidth.

FIG. 3 is a diagram showing an embodiment using a plurality of modulation methods.

FIG. 4 is a diagram showing an embodiment using a plurality of modulation methods.

FIG. 5 is a diagram showing an embodiment using carriers with frequency intervals standardized by PDC.

FIG. 6 is a diagram showing an embodiment in which the present invention is applied to broadcast communication.

FIG. 7 is a diagram showing an embodiment in a case where voice and data transmission are mixed.

FIG. 8 is a diagram illustrating a configuration example of a transmitter.

FIG. 9 is a diagram illustrating a configuration example of a transmitter.

FIG. 10 is a diagram illustrating a configuration example of a receiver.

[Explanation of symbols]

100, 500, 600, 700 Spectral axis 110, 510, 610, 710 Frequency axis 111, 112, 113, 211, 212, 213, 3
11, 312, 313, 411, 412, 413, 51
1, 512, 513, 514, 611, 612, 61
3,614,651,711,712,713,75
Spectrum with 1,752,753 carriers 120,125,220,225,320,325,4
20, 425 Frequency interval 130, 140, 530, 540, 630, 640, 7
30, 740 Radio stations 800, 805, 810, 900, 905, 910 Baseband processing units 820, 825, 830, 925 D / A converters 840, 845, 850, 930 Quadrature modulators 860, 865, 870, 935, 1030, 1035
Frequency converter 880, 920, 1040, 1100 Controller 890, 915 Signal multiplexer 895, 940 Transmission power amplifier 897, 945, 1000 Antenna (ANT) 1010 Switcher 1020, 1025 Receive amplifier 1050, 1055 Bandpass filter (BPF) 1060, 1065 Automatic gain controller (AGC) 1070, 1075 Detector 1080, 1085 A / D converter 1090 In-phase combiner 1095 Judge 1110, 1115 Level detector

Claims (4)

[Claims] 1. A parallel transmission method for performing wireless communication of M (M> 1) different baseband signals by frequency division multiplexing using M carriers, wherein each of the M carriers has a frequency interval. A parallel transmission method wherein communication is performed by setting a frequency interval equal to or larger than a coherence bandwidth. 2. A parallel transmission method for performing frequency division multiplexing wireless communication of M (M> 1) different baseband signals using M carriers, wherein each of the M carriers has a frequency interval. A parallel transmission method, wherein communication is performed by setting a frequency interval near a coherence bandwidth. 3. The parallel transmission method according to claim 1, wherein a plurality of M or less different modulation methods are used for the M carrier waves. 4. The parallel transmission method according to claim 3, wherein the M or less different modulation methods are selected from PSK, QAM or FSK.