WO1999035772A1

WO1999035772A1 - Parallel transmission method

Info

Publication number: WO1999035772A1
Application number: PCT/JP1999/000022
Authority: WO
Inventors: Yasunori Suzuki; Toshio Nojima
Original assignee: Ntt Mobile Communications Network Inc.
Priority date: 1998-01-09
Filing date: 1999-01-07
Publication date: 1999-07-15
Also published as: JP3507683B2; CA2285198C; CA2285198A1; JPH11205260A

Abstract

The intervals (120, 125) between the spectra (111, 112, 113) of carrier waves are greater than or around the coherent bandwidth, and hence the carrier waves can receive mutual correlative phasing. Therefore, even if the spectrum (112) receives phasing by a specific carrier wave during call and consequently the line quality degrades, the call can be continued by the other spectra (111, 113). In this case, the other received signals are synchronously detected and combined by a maximum ratio composite method, and carriers can be regarded as independent of each other. Therefore, diversity reception by a maximum ratio composite method of branches, the number of which is equal to the number of carriers used for communcation, is possible. Since the intervals between the frequencies are so set by using existing circuit techniques that the carriers are almost mutually in correlation, no radio circuit having frequency characteristics of wide band nor processor for high-degree digital signal processing is needed.

Description

Description Parallel transmission method Technical field

The present invention relates to parallel transmission when performing wireless communication of a plurality of different baseband signals using a plurality of carriers, and particularly to a parallel transmission method suitable for land mobile communication. Background art

In recent years, various wireless communication schemes have been proposed for realizing high quality transmission and high speed transmission in wireless communication typified by land mobile communication requiring high speed transmission and high quality transmission. For example, Code Division Multiple Access (CD MA), Adaptive Modification, 16 Q AM (Quadrature amplitude Modification) 14 Multi-carrier transmission, Orthogonal Frequency Division Multiplexing: OFDM) systems such as ^power? have been proposed. Methods for ensuring the required transmission quality in these wireless transmission systems have been developed using second-generation mobile communication systems such as PDC (Personal Digital Cellular), GSM (Global System for Mobile communication), and IS (interim Standard). For example, error correction techniques such as frequency diversity reception, spatial diversity reception, and polarization diversity reception used for fixed microphone mouth-wave lines are suitable. It is a method to use.

Also in high-speed transmission, adaptive modulation scheme for selecting an optimum modulation scheme in accordance with the situation of the transmission line, broadband CD MA, such as applying ^force? OFDM scheme being considered is known as digital broadcasting.

The high-speed and high-quality transmission systems described above use a single spectrum that is divided into multiple carriers, or a wideband single carrier that uses error correction technology and diversity reception technology. Was used. To implement the radio equipment used in these systems, a radio circuit having the required frequency characteristics over a wide band and a processor for performing advanced digital signal processing were required. For example, wireless circuits such as filters and transmission power amplifiers and processors such as error correction decoders.

In order to build a wireless communication system with high frequency utilization efficiency, circuit technology that reduces the guard band between wireless channels is indispensable. This wireless circuit technology includes, in particular, the out-of-band attenuation characteristics of the filter and the transmission. Improving the linearity of the system is essential.

Advanced circuit technology was required to realize high-speed transmission and high-quality transmission, and to realize a wireless communication system with high frequency use efficiency. For example, if the modulation is QPSK: and the roll-off filter coefficient is 0.5 in order to transmit 10 Mbps information, the frequency bandwidth is required to be 7.5 MHz. If this is transmitted on a single carrier, the passband (3 dB bandwidth) of the receive filter used in the radio is 4.6 MHz. If the mobile station needs an adjacent channel attenuation of 80 dB so as not to receive the adjacent channel interference with the adjacent carrier, the reception filter needs a wide pass bandwidth and a steep attenuation characteristic. If a small and lightweight radio is to be made, it will be necessary to develop a small filter with higher performance than before.

As described above, in the conventional high-speed transmission and high-quality transmission systems as described above, a single spectrum is divided into a plurality of carriers, and error correction technology and diversity reception technology are combined into a wideband single carrier. Was used. In order to implement the radio equipment used in these systems, a radio circuit with wideband frequency characteristics and a processor that performs advanced digital signal processing were required.

Therefore, an object of the present invention is to solve the above-mentioned problem, and using an existing circuit technology, the frequency of each of a plurality of carriers is adjusted so that the frequency interval is equal to or greater than or close to a coherent bandwidth. 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 wide-band frequency characteristic and a processor that performs advanced digital signal processing by performing communication by setting an interval. And there. Disclosure of the invention

The parallel transmission method of the present invention is a parallel transmission method for performing wireless communication of M (integral with M> 1) different baseband signals using M carrier waves, wherein each of the M carrier waves is The communication is performed by setting the interval between these frequencies to be equal to or greater than the coherent bandwidth or near the coherent bandwidth.

In the parallel transmission method in which the interval between frequencies is set as described above, M or less different modulation methods can be used for the M carrier waves.

The M or less different modulation methods may be a combination including at least one of PSK :, QAM, or FSK.

Furthermore, the combination of these PSK :, QAM and FSK modulation methods may be each combination or a combination of different multi-level numbers of each modulation method. In other words, this means that three-carrier wireless communication using 16QAM, QPSK, and 4FSK may be used, or that 256QAM, 16QPSK, and 64QAM may be used.

Therefore, the M or less different modulation schemes can be selected from QAM, PSK, FSK and their respective multi-level numbers.

As described above, according to the parallel transmission method of the present invention, by using the existing circuit technology, communication is performed by setting the interval between the frequencies of a plurality of carriers to be equal to or more than the coherent bandwidth. In addition, 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 FIGURES

FIG. 1 is a diagram showing an embodiment in which the frequency interval is set to be equal to or more than the coherent bandwidth. It is.

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

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

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

FIG. 5 is a diagram showing an embodiment using carriers at 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 when voice and data transmission coexist. FIG. 8 is a diagram illustrating a configuration example of a transmitter used in the present invention.

FIG. 9 is a diagram showing another configuration example of the transmitter used in the present invention.

FIG. 10 is a diagram showing a configuration example of a receiver used in the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

First, the outline of the parallel transmission method of the present invention will be described. According to the parallel transmission method of the present invention, in the multi-carrier wireless communication method that enables high-speed transmission, the frequency correlation value between each carrier used is set to a certain fixed value or less. For example, the frequency correlation value between the carrier waves is set to a frequency interval equal to or more than the coherent band in which the carrier waves can be regarded as substantially uncorrelated. Here, the frequency correlation value p (Ω) is expressed as ί 1 and ί 1 + Ω for the frequencies of the two fading received waves, ΔΖ It is known that if the length of the shortest propagation path is Ζ ₀ and the speed of light is c, equation (1) is obtained.

(1)

It is known that the frequency interval Ω at which I p (Ω) I is 0.5 is defined as the coherent bandwidth. The frequency interval Omega regarded substantially uncorrelated typically are ^force? Known to be a p (Ω) ≤ 0. 5 Ω .

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

Since the frequency intervals of the carrier waves are so far as to be regarded as almost 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 with a wide passband, which was required in the conventional parallel transmission method. The linearity of the radio circuit need only be achieved for each independent radio circuit, and does not require the wideband linearity required in conventional radio circuits for parallel transmission methods. Processors that perform digital signal processing can also use processors with lower processing power by using almost independent narrowband carriers. This contributes to lower power consumption of digital circuits.

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, baseband signals processed by a plurality of baseband processing units 800, 805,..., 810 are DZA-converted by 07-oct converters 820, 825,. The orthogonal transform is performed by the devices 840, 845,. After that, the frequency converter 860, 865 870 and the controller 88

0 by fi, f 2,... , Is frequency-converted to f _N. Here, in the conventional parallel transmission method, the intervals of the respective frequencies ff ₂ ,..., F _N are set so as to be substantially equal to each other or equal to or less than the coherent bandwidth. Parallel transmission method Fi by the controller 8 8 0 by law, f 2, ·, intervals of the frequency f _N is Kohi -.. Is set to more than Les cement bandwidth. Thereafter, the signal is multiplexed by a signal multiplexer 890, amplified by a transmission power amplifier 895, and transmitted via an antenna 899.

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

In FIG. 9, a base span signal processed by a plurality of baseband processing sections 900, 905,... , F _N , and are shifted as in f 1, f ₂ ,..., F _N. 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, ff _2,..., Approximately equal intervals between the frequency of the I _New, had been set below the coherent bandwidth, in the parallel transmission method according to the present invention the controller 9 2 With 0, the intervals of the frequencies f ι, f 2,..., F _N are set to be equal to or greater than the coherent bandwidth.

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

In FIG. 10, the radio waves received by antennas 100 and 105 are transmitted to the receiving amplifiers 100 and 125 detected by the level detectors 111 and 115. The output is switched to the higher reception level ANT 1 00 0, 1 0 5 by the controller 1 1 0 0, and the frequency fi, f by the controller 1 04 0 by the frequency converter 1 3 0, 1 3 5 Converted to 2. After this, the bandpass filters (BandPass Filter: BPF) 1 0 5 0 and 1 0 5 5, the automatic gain control (Automatic Gain Control: AGO 1 0 60, 1 065), the detector 1 0 7 0, Detector 1 0 7 5, A / D conversion by AZD converters 1 0 8 0, 1 0 8 5, Judgment 1 0 9 5 Is input to

(Embodiment 1)

FIG. 1 shows an embodiment in which the frequency interval is set to be equal to or larger than the coherent bandwidth, in which the vertical axis is the spectrum axis 100 and the horizontal axis is the frequency axis 110. In Fig. 1, A parallel transmission method including the transceiver shown as an example and transmitting three different pieces of information between the radio station 130 and the radio station 140 using three carriers will be described.

In FIG. 1, the frequency intervals 120 and 125 of the spectra 11 1, 1 12 and 113 by three carriers are set to be equal to or larger than the coherent bandwidth (1 15). With this setting 115, the spectrums 111, 112, and 113 of the three carriers in FIG. 1 undergo fusing almost uncorrelated with each other. Therefore, even if the spectrum 1 12 due to the second carrier is fuzzed during a call and the line quality is degraded, the spectra 1 1 1 and 3 due to the remaining 1st carrier are obtained. It is possible to continue the call by spectrum 113 with the th carrier. In other words, on the receiver side, as shown in FIG. 10, the spectrum 11 1 of the first carrier and the spectrum 113 of the third carrier are synchronously detected, and after the detection by the detectors 1070 and 1075, Combine at maximum ratio. At this time, since each carrier can be regarded as almost independent, diversity reception of 2-branch maximum ratio combining is possible.

(Embodiment 2)

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

The frequency intervals 220, 225 of the spectrums 211, 212, 213 by the three carriers in FIG. 2 are set near the coherent bandwidth (215). With this setting (2 15), the spectrums 211, 212, and 213 of the three carriers in FIG. 2 undergo fusing almost uncorrelated with each other. Therefore, even if the spectrum 212 due to the second carrier is fading during a call and the line quality is degraded, the spectrum 2111 due to the remaining first carrier and the spectrum due to the third carrier are used. Call 2 13 allows you to continue the call. In other words, on the receiver side, as shown in Fig. 10, the spectrum with the first carrier and the spectrum with the third carrier are used. Synchronous detection of spectrum 2 13 is performed, and maximum ratio combining is performed after detection by detectors 1070 and 1075. At this time, since the carrier waves can be regarded as almost independent, diversity reception of 2-branch maximum ratio combining is possible.

(Embodiment 3)

FIG. 3 shows an embodiment using a plurality of modulation methods, in which the vertical axis is spectrum axis 100 and the horizontal axis is frequency axis 110. FIG. 3 illustrates a parallel transmission method for transmitting three different pieces of information between a wireless station 130 and a wireless station 140 using three carriers. In FIG. 3, the modulation schemes of the spectrums 311, 312, and 313 using three carriers are QP SK, 16 QAM, and FSK. The frequency intervals 320, 325 of the spectra 311, 312, 313 by three carriers are set to be equal to or greater than the coherent bandwidth (315). With this setting (3 15), the spectra 311, 312, and 313 of the three carriers in FIG. 3 receive almost uncorrelated fusing. Here, even if the spectrum 3 13 due to the third carrier undergoes fading and the line quality deteriorates, the spectrum 3 11 due to the first carrier and the spectrum 3 13 due to the second carrier 2 allows the call to continue. Information to be originally transmitted in the vector 3 13 by the third carrier can be distributed to the spectrum 3 12 by the second carrier. Here, the spectrum 312 using the second carrier uses 16 QAM. As a result, the parallel transmission method according to the present invention can always maintain a predetermined transmission capacity without increasing the bandwidth even if it is affected by fusing. (Embodiment 4)

FIG. 4 shows an embodiment using a plurality of modulation methods, in which the vertical axis is spectrum axis 100 and the horizontal axis is frequency axis 110. FIG. 4 illustrates a parallel transmission method for transmitting three different pieces of information between the wireless station 130 and the wireless station 140 using three carriers. In FIG. 4, the modulation schemes of the spectrums 4 11, 4 12, and 4 13 using three carriers are QP SK, 16 QAM, and 16 QAM. Spectrum with four carriers 411, 412, and 413 frequency intervals 420 and 425 are coherent bands Set near the width (4 1 5). With this setting (4 15), the spectra 4 11 1, 4 12 and 4 13 of the three carriers in FIG. 4 undergo almost uncorrelated fading. Here, for example, even if spectrum 4 13 due to the third carrier is subjected to faging and the line quality is degraded, spectrum 4 11 due to the first carrier and spectrum due to the second carrier are obtained. Calls can be continued with Vector 4 1 2. Information to be transmitted originally in spectrum 4 13 by the third carrier is allocated to spectrum 4 12 by the second carrier. Here, the spectrum 4 12 by the second carrier uses 16 QAM. As a result, the parallel transmission method of the present invention can always maintain a predetermined transmission capacity without expanding the bandwidth even if it is affected by fusing. Thus, it is possible to use a different number of modulation methods (here, 2) than the number of carrier waves (here, 3).

The modulation schemes of P SK :, 0 8] ^ 1 and 3 used in the above embodiment may be a combination of each, or a combination of multi-valued numbers of the respective modulation schemes.

In other words, depending on the design of the wireless communication system, different multi-level numbers may be used for each carrier.For example, for three-carrier wireless communication using 16QAM, QP SK, and 4F SK. Or 256 QAM, 16 QPS :, or 64 QAM.

(Embodiment 5)

FIG. 5 shows an embodiment using carriers with frequency intervals standardized by PDC, in which the vertical axis is the spectrum axis 500 and the horizontal axis is the frequency axis 510. In Figure 5, a parallel transmission method for transmitting four different pieces of information between radio station 530 and radio station 540 using spectrums 511, 512, 513, 514 with four different carriers. Explain.

In FIG. 5, the spectrums 511, 512, 513, and 514 by each carrier are almost independent. Spectrum 5 11 1, 5 1 2, 5 1 3, 5 1 4 by each carrier If used, Figure 5 has four times the transmission capacity of PDC. If the spectrum per carrier is 11.2 kbps, a transmission capacity of 44.8 kbps can be obtained. As described above, 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, in which the vertical axis is a spectrum axis 600 and the horizontal axis is a frequency axis 610. FIG. 6 illustrates a parallel transmission method between a wireless station 630 and a wireless station 640 using spectra 611, 612, 613, and 614 with four different carriers.

On the down link 650, in addition to the communication channel 611, it is allocated to channels 612, 613, and 614 that provide a broadcast service. Assuming that only the communication channel 651 is used in the uplink 655, the modulation scheme of the channels 612, 613, and 614 used in the downlink 650 may be the modulation scheme of the voice channel or another modulation scheme.

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 or her mobile device. As a broadcast service, you can receive services similar to the Intelligent Tutoring System (ITS) represented by power navigation, etc. (for example, traffic jam information, weather forecasts, 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. FIG. 7 illustrates a parallel transmission method between a wireless station 730 and a wireless station 740 using spectra 711, 712, and 713 with three different carriers.

In the downlink 750, the modulation scheme of each channel is QPSK for channel 711, s'l6 QAM for channel 712, and FSK for channel 713. Uplink 755 , The modulation scheme of each channel is 16 QAM for channel 751, QPSK for channel 752, and FSK for channel 753. According to the present embodiment, as long as the bandwidth is the same, there is no limitation on the modulation scheme of spectrums 711, 712, and 713 by each carrier. It is also possible to use PDC for voice and to perform overnight transmission using 16 QAM modulation. 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.

Claims

The scope of the claims

1. In a parallel transmission method for performing wireless communication of M different baseband signals (an integer with M> 1) using M carrier waves,

A parallel transmission method, wherein communication is performed by setting an interval between frequencies of the M carrier waves to be equal to or greater than a coherent bandwidth.

2. The parallel transmission method according to claim 1, wherein the M carriers are modulated by a plurality of M or less different modulation schemes.

3. The parallel transmission method according to claim 2, wherein the M or less different modulation methods are a combination including at least one of PSK, QAM, and FSK.

4. The parallel transmission method according to claim 3, wherein the combination of the PSK :, QAM, and FSK modulation methods includes a combination of respective multi-level numbers of the modulation methods.

5. In a parallel transmission method in which M (integer where M> l) different baseband signals are wirelessly communicated using M carrier waves,

A parallel transmission method characterized in that communication is performed by setting an interval between frequencies of the M carrier waves near a coherent bandwidth.

6. The parallel transmission method according to claim 5, wherein the M carrier waves are modulated by a plurality of M or less different modulation schemes.

7. The M or less different modulation methods are: PSK: 081? 7. The parallel transmission method according to claim 6, wherein the combination includes at least one of 51 ^.

8. The parallel transmission method according to claim 7, wherein the combination of the PSK, QAM, and FSK modulation methods includes a combination of respective multi-level numbers of the modulation methods.