JPS6253098B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for transmitting and receiving digital code transmissions to and from a plurality of mobile stations moving over a wide area using a transmitting station and a receiving station located far from a communication control room of a fixed station. .

Conventionally, when transmitting digital codes over a radio link with poor transmission quality, bit synchronization correction using the dependent synchronization method was used, in other words, the receiving side constantly detected bit conversion points and performed bit and frame synchronization with the transmitting side. Ta. Particularly in lines that are subject to interference and fading, such as HF circuits, even if synchronization is achieved, bit synchronization may occur, which can cause frame synchronization, and this can reduce the chance of receiving code errors. Nakatsuta. In addition, once the bits and frames have been synchronized, the receiving side does not follow the bit synchronization as described above, increases the stability of the local oscillator, memorizes the phase of the bit synchronization timing, and thereafter performs independent synchronization. There is also a method of detecting the signal using a digital signal, but in a moving object that moves over a wide area at high speed, appropriate synchronization correction is required, such as constantly having to perform phase correction of the bit synchronization timing based on the received signal. The disadvantage was that communication lacked speed and reliability.

In order to eliminate these drawbacks, the present invention provides a mobile communication method that performs phase correction based on a settable distance using an independent synchronization method while the transmission and reception timing between a fixed station and a mobile station is phase corrected. be.

To achieve this objective, the present invention uses a transmitting station and a receiving station located far from the communication control room of a fixed station to transmit and receive digital code transmissions to and from multiple mobile stations moving over a wide area. The distance delay of the dedicated line to the transmitting station and receiving station is corrected in advance in the communication control room, and each mobile station synchronizes with the bit and frame synchronization signals transmitted from the fixed station. , and is configured to perform distance delay correction for variations in its position based on the radio spatial distance to the fixed receiving station.

The present invention is particularly effective when performing HF band digital code transmission. The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a diagram showing an example of the configuration of a mobile communication system in which the present invention is implemented, in which 1 is a communication control room of a fixed station, 2 is a transmitter T _x
3 is a transmitting station including a receiver R x and an antenna, and 3 is a receiving station including a receiver R _x and an antenna. 4, 5, 6, etc. are mobile stations. The communication control room 1 of the fixed station and the transmitting station 2 and the receiving station 3 and the control room 1 are connected by a dedicated line such as a microwave line or a land line. _D1 ,
D ₂ is the distance between dedicated lines 1-2 and 1-3, respectively. Also, d ₁₁ and d ₁₂ are mobile station 4 and transmitting station 2,
It is assumed that d ₂₁ and d ₂₂ are the radio spatial distances with each of the receiving stations 3, and similarly, d ₂₁ and d ₂₂ are the radio spatial distances between the mobile station 5 and the fixed station transmission and receiving stations, respectively.

Prior to the start of communication, bit synchronization between the fixed station and the mobile station is corrected as follows. First, let the delay time from the modulator output in the communication control room 1 to the transmitting antenna output be t ₁ (t ₁ is the sum of the delay of distance D ₁ and the delay of the transmitter and transmitting antenna 2 as a whole), and Let the delay time from the input to the demodulator input in the communication control room be t ₆ (t ₆ is the sum of the delay of distance D ₂ and the delay of the receiving antenna and receiver 3 as a whole). Next, to set the wireless space delay correction, use the distance correction digital changeover switch 7, a display example of which is shown in Figure 2.
The fixed station is set to 0000, and the mobile station is set to, for example, 1150 depending on its current location. Between the transmission timing and reception timing of the fixed station, the former is advanced in phase by t ₁ +t ₆ minutes than the latter (see FIG. 3, 13, and FIGS. 5 (1) and (2), described later).

FIG. 3 is a block diagram showing an example of the configuration of a transmitting/receiving device for a fixed station or a mobile station shown in FIG. 1, and in the case of a fixed station, it shows the device installed in a communication control room. 8-1
Reference numeral 2 denotes a transmitting side, 8 an input/output interface circuit with a terminal device such as a reader, a keyboard, or a computer, and 9 a buffer memory for adjusting the input/output time base between the terminal device and transmission output.
10 is a time division output circuit, and timing generation circuit 1
The data from the buffer memory 9 is converted into a serial signal and sent out according to the clock from the buffer memory 9. Reference numeral 11 denotes a preamble signal generation circuit for performing bit synchronization correction on the receiving side. A modulator 12 provides a modulated input signal to the transmitter via a dedicated line. The modulator 12 is a phase shift type (PSK) modulator, a frequency shift type (FSK) modulator, or the like for a wireless line. 15 to 19 are the receiving side. Reference numeral 13, which is common to both transmission and reception, is a timing generation circuit, and the clock timing for transmission and reception is determined by a switch provided in the control circuit 14 for distance correction and fixed delay time correction of a dedicated line, etc.
The control circuit 14 also has the role of switching transmission and reception and setting distance correction. A demodulator 19 on the receiving input side converts the receiver demodulated signal from the receiving station 3 into a digital signal. As the demodulator 19, a demodulator for a wireless line such as FSK or PSK is used. 18 is a reception bit synchronization detection circuit, 17 is a waveform shaping circuit that shapes the waveform based on the digital signal input from the demodulator 19, and 16 is a buffer memory circuit that handles the reception input signal and the reception terminal device (for example, puncher, printer, computer, etc.). It is provided to perform time base adjustment with the output to. 15 is an interface circuit for the receiving terminal device.

FIG. 4 is a time chart showing an example of a code structure for transmission and reception, in which (1) is a transmission code, (2) is a reception code, and (3) is a bit synchronization code, which is called a preamble signal. FIG. 5 is a time chart for explaining phase correction, with numbers for each signal on the vertical axis and time t on the horizontal axis. These explanations will be made during the explanation of the operation shown in FIG. 3 below.

In the case of a fixed station in the circuit of FIG. 3, the fixed delay correction amount of t ₁ +t ₆ in the fixed station is corrected at the input of the timing generation circuit 13, that is, the output of the control circuit 14. Note that the fixed delay of the dedicated line is compensated in advance using a semi-fixed switch on the equipment. The top row (1) in FIG. 5 represents the timing of reception detection input to the fixed station. In Fig. 3, this can be expressed as the demodulator 19
This is the timing at which the wave was detected. That is, if the bit conversion point is a line, the time length between any one and its immediate right neighbor is one bit. The output timing from the fixed modulation unit 12 becomes the transmission timing shown in FIG. 5(2) due to the fixed delay correction circuit inside the control circuit 14 as described above. Fifth
As is clear from a comparison between (1) and (2) in the figure, the transmission timing in (2) is ahead of the reception timing by t ₁ +t ₆ in phase. FIG. 5 (3) shows the phase timing of the antenna output of the fixed station transmitting station, which is emitted into the radio space with a delay of t ₁ from (2) as described above. In this way, when the fixed station adjusts the timing of transmission and reception phases, if each mobile station corrects the phase timing of transmission and reception according to the fixed station, the preamble signal generation circuit shown in Figure 3 of the fixed station is used. 11 to transmit a preamble signal as shown in FIG. 4(3) for an arbitrary period of time. Assuming that the configuration of the receiving section of the mobile station is as shown in the lower half of Fig. 3, the mobile station performs bit synchronization tracking correction on the received bit synchronization detection circuit 18 after receiving and detecting this signal, and after receiving the signal for a certain period of time, Stop bit tracking and store at this phase timing. The stored timing information is sent to the timing generation circuit 13, which determines the 1-bit integration time of reception detection and the reception bit sampling time after detection. FIG. 5(4) shows the receiving antenna input timing of the mobile station. For example, if this is the timing of input to the receiving antenna of mobile station 4 in Figure 1, the radio space delay of d ₁₁ becomes t ₂ , which is calculated as d ₁₁ = 1000 km, which is approximately
The delay will be about 3.3msec. FIG. 5(5) shows the timing of the detection output of the demodulation circuit 19. The delay t ₃ from (4) is the delay in the receiver and demodulation circuit 19.

At this point, the mobile station estimates the distance from its own location to the fixed station's receiving location, and controls the control circuit 14 in FIG.
The distance is set by a digital changeover switch (distance correction switch, Fig. 2) included in the camera. Note that FIG. 2 shows correction for 1150 km as an example. Depending on the distance correction settings, for example, the timing of the transmitting antenna output of two mobile stations will be as shown in Figure 5 (6) and
The solid line part of (7) (i.e. the part to the right of the center) f ₂ , g ₂
It's the timing. Although the fixed station and mobile station generally do not emit at the same time, only the relative phase with the bit timing is important, so to explain the relationship between phase timing in an easy-to-understand manner, (6)
Let us explain by rewriting the timings of f ₂ and g ₂ of the mobile station in (7) as the broken lines on the left. That is, the timing of the output of the transmitting antenna of the mobile station is made to be output at a phase that is t ₄ ahead of the transmitting antenna output line of the fixed station in FIG. Here, t ₄ = t ₂ + t ₃ . _t3 is a delay between the receiving antenna, receiver, and demodulation circuit, and is set in advance in the control circuit 4 of the mobile station. Therefore, the transmission timing of one mobile station is determined by the sum of the distance correction switch setting and K (a constant value corresponding to _t3 ). The transmission timing of this mobile station is t ₂ + t ₃ for its demodulator output.
+t ₄ = 2 (t ₂ +t ₃ ). In the same way, the phase of the lines of other mobile stations (FIG. 5, 7) is corrected by _t5 .

The above distance setting is, for example, 0.33 per 100Km.
The value of t ₂ can be set by assigning a spatial transmission time of ms. In addition, the transmission time difference between the fixed station transmitting station and the mobile station, and between the mobile station and the fixed station receiving station is not strictly zero, but is usually 0.5 to 1 m.
It is about s or less. Furthermore, in practice, there are transmission time fluctuations due to multipath, and since the binary data is usually detected at the center of each bit, excluding the phase fluctuation part due to these fluctuation factors, the length of each bit is This difference can be almost ignored when data is transmitted for about 20 ms.

When the mobile station outputs a signal under these conditions, the receiving antenna input timing of the fixed station and the detection input timing of the demodulation circuit are as shown in Figure 5 (8) and (9), respectively.
The positions are h ₂ and i ₂ , but to make it easier to understand, the explanation will be moved to the positions h ₁ and i ₁ as shown by the broken line on the left. h ₁
It will be understood that is the same as the transmitting antenna output timing of the fixed station transmitting station in FIG. 5(3). Furthermore, the detection input timing of the fixed station is at the position i1 at a phase timing delayed from _h1 by a time _t6 including the delay of line _D2 in Figure 1, but this is due to the reception bit conversion of _the fixed station. Correct bit output can be obtained even at a fixed station by integrating the bits between and coincident with the points.

If the bit synchronization between transmission and reception is corrected in this manner, transmission and reception are performed with frame synchronization in accordance with the code structures shown in FIGS. 4(1) and (2). As mentioned above, (1) is a transmitted signal, and (2) is a received signal. First, on the transmitting side, the preamble signal P is first transmitted in multiple bits, and then frame synchronization signals A ₁ , A ₂ , Send A ₃ , A ₄ , A ₅ . These signals usually have M of 2 ^n-1 (n is an integer greater than or equal to 1).
It consists of a series code. As shown in FIG. 4(1), the receiving side performs frame synchronization determination after receiving the _A5 signal, and then the transmitting side transmits data D ₁ , D ₂ , . . . _Do. Figure 4 (2) shows the received signal on the receiving side in response to the signal (1) on the transmitting side, and the P, A, and D signals are erroneous due to noise and interference.
Signals such as P' and A' may be included, but this does not affect the timing and their correction is a separate issue.

As described above, in the method of the present invention, the fixed station transmits
Fixed delay time correction for the reception system hardware and transmission, dedicated line between the reception station and the communication control room is performed in advance by the distance correction switch and phase correction circuit in the control circuit 14, and fixed delay time correction is performed on the mobile station side. In addition to the correction, it is characterized by sequentially performing delay correction based on the distance to the fixed receiving station depending on the position, and as a result, the transmission and reception timing between the fixed station and the mobile station is set in an independent synchronization method, and the digital There is an advantage that code transmission is easily performed as always correct code detection.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of a communication system implementing the present invention.
FIG. 2 is a display example of a digital switch for distance correction, FIG. 3 is a configuration example of a transmitting/receiving device of a fixed station or mobile station in FIG. FIG. 5 is a time chart explaining phase correction. 1... Communication control room, 2... Fixed station transmitting station, 3...
...Fixed station receiving station, 4,5,6...Mobile station, d ₁₁ ,
d ₂₁ , d ₃₁ ... distance between transmitting station 2 and mobile station, d ₁₂ ,
d ₂₂ , d ₃₂ ... Distance between receiving station 3 and mobile station, 7...
Distance correction digital switch, 8, 15...Interface circuit, 9, 16...Buffer memory circuit, 10...Time division output circuit, 11...Preamble signal generation circuit, 12...Modulator, 13...
...Timing generation circuit, 14...Control circuit, 17
... Shaping circuit, 18 ... Reception bit synchronization detection circuit, 19 ... Demodulator.

Claims (1)

[Scope of Claims] 1. When performing mutual transmission and reception of digital code transmission with mobile stations existing in a wide area through transmitting stations and receiving stations installed far away from the fixed station communication control room, is equipped with a transceiver that modulates the digital code and sends it to the transmitting station, and also demodulates the received signal to the digital code, and transmits the phase of the modulator input code to the mobile station from the modulator input in the communication control room based on the reference bit phase. Bit and frame synchronization signals are generated at a timing advanced by the sum of the signal delay (t ₁ ) to the antenna output and the signal delay (t ₆ ) from the reception antenna input to the demodulator output in the communications control room, t ₁ + t ₆ . After each mobile station synchronizes with the above signal from the fixed station, the transmission timing is determined by the signal delay from the receiving antenna input to the demodulator output (t ₃ , fixed value) and _the spatial transmission time (t ₂ , change value) between the fixed station transmitting antenna and _the mobile station receiving antenna. A mobile communication method that performs phase correction based on distance, characterized by performing synchronous transmission and reception between a mobile station and a mobile station.