JPS6410971B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an out-of-band signal wireless transmission system that makes it possible to detect same-wireless channel interference, especially when a digital signal is superimposed and transmitted outside the voice band in a mobile communication system. It is something.

<Background> In mobile communication systems, the mobile area is, for example, the
Divided into multiple zones Z ₁ to _{Z 9} as shown in the figure,
Different radio channels are assigned to adjacent zones. In Figure 1, zones Z ₁ , Z ₃ , Z ₇ ,
Z ₉ has wireless channels f ₁ to _{f o} , zones Z ₂ and Z ₈ have wireless channels f _o+1 to f _2o , zones Z ₄ and Z ₆ have wireless channels f _2o+1 to f _3o , and zone Z ₅ to wireless channel f _3o+1 ~
f _4o is allocated to each to make effective use of fewer wireless channels.

However, in the out-of-band signal wireless transmission method, a digital signal is directly superimposed outside the lower voice band and modulated and transmitted over a wireless channel, or a subcarrier is provided outside the upper voice band, and the subcarrier is used as a digital signal for FSK transmission. It is modulated, superimposed on audio, and then modulated and transmitted over a wireless channel. When these systems are applied to the mobile communication system, interference may occur in these same wireless channels because the same wireless channels are used in different zones. If interference occurs, digital signals cannot be detected correctly.
For example, it is necessary to switch to another wireless channel for transmission. From this point of view, it is necessary to detect and evaluate interference, and it is conceivable to perform this evaluation based on error rate. However, in this case, since the signal transmission speed is slow in out-of-band signal transmission, detection time is long and it is difficult to separate the effects of thermal noise and interference. In contrast, multiple tone signals are superimposed outside the upper or lower audio band specifically for interference detection, and each tone signal is assigned to each zone. If tone signals from other zones are detected, interference is detected. One possible method is to assume that there is.

FIG. 2 shows the state of the baseband spectrum in this case. FIG. 2A shows a case where the digital signal 12 is placed outside the lower band of the audio signal 11, and the tone signals F ₁ and F ₂ are allocated outside the upper band. Second
In Figure B, a signal 13 obtained by FSK modulating the subcarrier f _s with a digital signal is placed outside the upper band of the audio signal 11.
Tone signals F ₃ and F ₄ are present outside the lower band of the audio signal 11.
This is the case when . In these methods, it is necessary to transmit signals separately for digital signal transmission and interference detection, so it is difficult to provide a sufficient number of tone signals for zone differentiation in a wireless channel with a limited transmission band. The disadvantage is that the reliability of the signal also decreases.

<Summary of the Invention> The purpose of this invention is to provide an out-of-band signal that can detect interference from many same radio channels, does not reduce the reliability of digital signals, and can detect interference in a short time. The purpose is to provide a wireless transmission method.

According to this invention, the digital signal transmission frequency signal and the interference detection frequency signal are used together. That is, a plurality of subcarriers are allocated outside a band-limited main signal band such as an audio signal, and each different combination of two subcarriers is allocated to a different same radio channel source. These radio channel sources use the two assigned subcarriers to superimpose a digital signal on the main signal, modulate the radio channel, and transmit. The subcarriers can demodulate the digital signal and provide interference from the presence or absence of other subcarriers.

<Example> FIG. 3 shows an example of the present invention. On the transmitting side, the audio signal from the terminal 101 is sequentially passed through an audio instantaneous amplitude limiter (IDC) 102 and a bandpass waver 103 with a passband of 0.3 to 3KHz, and then sent to an adder 104.
supplied to On the other hand, the digital signal from the code generator 105 causes the subcarrier generators 106 and 10 to
7 is keyed ON and OFF, and the subcarrier signals of keyed frequencies f _l1 and f _u1 from subcarrier generators 106 and 107 respectively pass through band pass wave generators 108 and 109 of passing frequencies f _l1 and f _u1 , respectively. , added by adder 110, and further added by adder 10
4, it is synthesized with the analog audio signal. As shown in FIG. 5, the baseband spectrum in this case includes subcarriers f _l1 ,
Signals 14 and 15 are arranged with f _u1 as the center and spread out as much as the transmission speed of the digital signal. This combined output from adder 104 causes transmitter 111
The dotted carrier wave is FM modulated and transmitted. The subcarriers f _l1 and f _u1 have been previously assigned to zone Z ₁ in FIG. 1, for example.

FIG. 4 shows an example of the receiving side. FM receiver 20
The audio signal received and demodulated in step 2 is outputted to an output terminal 204 through a bandpass waveform generator 203. The demodulated output is separated into f _l1 and f _u1 components by band pass wave generators 205 and 206, respectively, and further integrated by integrators 209 and 210. The difference between these integrated outputs is taken by a difference circuit 213, and the difference output is is decoded by the decoder 215 to obtain a digital signal.

On the other hand, in order to detect interference signals, FM receiver 2
From the output of 02, frequency f _l2 and f _u2 components are taken out by band pass wave generators 207 and 208, and these f _l2 and f _u2 components are integrated by integrators 211 and 212, respectively.
They are added by an adder 214 and then sent to an interference signal detector 216.
Interference is detected by

In the above, the digital signal is transmitted by, for example, assigning a carrier wave with a width of f _l1 to the mark and a subcarrier wave of f _u1 to the space, respectively, and transmitting the keying, or keying a subcarrier wave of f _l1 to the mark. After sending out, the subcarrier of f _u1 is keyed and sent out, and conversely for the space, after the subcarrier of f _u1 is keyed and sent out, the subcarrier of f _l1 is keyed and sent out. This latter method has the characteristic that even if all marks or all spaces are used, the clock timing is not lost on the receiving side and synchronization is stabilized.

In the example shown in FIG. 1, in zones Z ₁ , Z ₃ , Z ₇ , Z ₉ using the same radio channel, e.g., f ₁ to _{f o} , two different sets of subcarriers, e.g., f _l1
f _u1 , f _l2 f _u2 , f _l1 f _u2 , f _l2 f _u1 are respectively assigned,
When the mobile device moves to another zone, the subcarrier assigned to that zone is used. For this purpose, for example, as shown in FIG. 6, the frequency of the carrier waves generated by the subcarrier generators 106 and 107 can be changed by the controller 301, and accordingly, as shown in FIG. Passing wave device 205, 206,
The center passing frequency of 207 and 208 is controlled by the controller 302.
It is made possible to change it.

There are two subcarriers each outside the lower band and outside the upper band, so there are a total of four subcarriers, so there are 4C ₂ = 6 combinations, and it is possible to separate the same wireless channel. becomes. Similarly, if n waves of subcarriers are provided, the same wireless channel can be divided into _two ways, and out-of-band signal transmission is possible.

In the above, the digital signal is transmitted outside the upper and lower bands of the audio signal, but it is not limited to the audio signal, and the digital signal is superimposed and transmitted outside the upper and lower bands of the main signal band whose frequency band is limited in advance. This invention can also be applied to cases where: Furthermore, this invention can be applied not only to mobile radio, but also to cases where there is a risk of interference between the same radio channels due to weather conditions, detecting that interference, and taking measures such as stopping digital signal communication. can.

As explained above, according to the present invention, two waves are set outside the main signal band as subcarriers for digital signal transmission, and the subcarrier frequencies are set for radio signals that are on the same radio channel but may interfere with each other. Since one or both of the subcarriers are different between the sources, this subcarrier can also be used for interference detection, which has the advantage of increasing signal transmission reliability and interference detection accuracy. Also, since there is no need to send a signal specifically for interference detection, the configuration on the transmitting side is simplified.
In addition, many subcarriers can be set within a limited radio channel band, and a large number of the same radio channel signal sources can be distinguished.
Furthermore, since interference is detected from a subcarrier different from the own subcarrier, interference can be detected in a shorter time than when interference is detected from the error rate of the own subcarrier digital signal. Furthermore, it is also possible to allocate each subcarrier wave to the same radio channel source, and use the subcarrier to perform FSK modulation with a digital signal so that the subcarrier serves both the digital signal transmission and interference detection, but in this case, the subcarrier The sideband spread of is relatively large and many distinctions cannot be made.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of zone and frequency allocation in a mobile communication system, Fig. 2 is a diagram showing a frequency spectrum of out-of-band signal transmission, and Fig. 3 is an example of an out-of-band signal wireless transmission system according to the present invention. FIG. 4 is a block diagram showing an example of the receiving side in FIG. 3, FIG. 5 is a diagram showing an example of the baseband frequency spectrum in the out-of-band signal wireless transmission system according to the present invention, and FIG. FIG. 7 is a block diagram showing another embodiment of the invention. FIG. 7 is a block diagram showing an example of the receiving side corresponding to FIG. 101: Audio input terminal, 103, 108, 10
9,203,205-208; band pass wave device,
104, 110, 214: Adder, 111: FM
Transmitter, 105: Digital signal generator, 10
6, 107: subcarrier generator, 202: FM receiver, 204: audio output terminal, 209 to 212: integrator, 213: difference circuit, 215: digital signal decoder, 216: interference detector.

Claims (1)

[Claims] 1 In an out-of-band signal wireless transmission system that superimposes a digital signal outside the band onto a main signal within a predetermined band, modulates the wireless channel, and transmits the signal, multiple subcarriers are allocated outside the main signal band. , wherein the digital signal is transmitted using two of the plurality of subcarriers, and both or one of the two subcarriers are made different in different regions using the same wireless channel. Signal wireless transmission method.