JPH0336341B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mobile radio communication system suitable for car telephones. The service area consists of multiple small wireless zones, and in addition to installing a base station in each small wireless zone, a control channel dedicated to controlling communication connections in addition to communication is established using a common frequency in all small wireless zones. The present invention relates to a mobile radio communication system to be provided. In particular, the present invention relates to a multi-station control signal timing adjustment method for monitoring and adjusting timing deviations of control signals transmitted from each base station through the control channel.

[Conventional technology]

Conventional land mobile communications with wide service areas, such as car phones, use a small wireless zone system that divides the service area into multiple wireless zones due to transmission power constraints and the ability to repeatedly use frequencies. . In the small wireless zone method, the transmission of digital control signals from the base station to the mobile station is described below as a multi-station control signal method in which the same wireless channel is assigned to each wireless base station and the same digital signals are simultaneously transmitted. It is adopted because of its advantages.

First of all, since this method allocates the same radio channel to each base station, frequency utilization is significantly improved compared to a method that uses different radio channels for each base station. Second, even if the mobile station moves from one wireless zone to another, there is no need to switch the control channel to be received, improving control efficiency and control signal transmission reliability.

As described above, when control signals are transmitted from each base station using the same frequency, if the mobile station is near the boundary of a wireless zone, it will receive control signals from multiple base stations simultaneously. At this time, if the transmission timings of control signals from each base station are shifted, the control signal received by the mobile station may be erroneously identified.

Conventionally, the following methods have been used to prevent this. That is, a receiving station is placed near the boundary of a wireless zone at a location where it can receive control signals from multiple base stations. This receiving station may be temporary or fixed. A plurality of base stations are provided with a line control station that controls them, and a fixed line is provided between each base station and the line control station. The line control station simultaneously transmits control signals to each base station via this fixed line. Each base station relays and transmits this control signal to a radio channel with a different frequency for each base station. At the receiving station, two receivers simultaneously receive the control signals of the respective wireless channels, and the phase difference between them is observed. The observation results are transmitted to the line control station. The line control station is provided with a delay circuit for the control signal transmitted over the fixed line to each base station, and the receiving station adjusts this delay circuit so that the phase difference between the control signals from each base station is eliminated.

[Problem to be solved by the invention]

According to such a method, control signals from multiple base stations will not be received with a time lag near the boundaries of wireless zones, but in order to perform the above-mentioned timing adjustment, it is necessary to use channels other than the control channel. However, it is necessary to use a plurality of communication channels with different frequencies, and there is a drawback that the communication channels cannot be provided for service during timing adjustment work.

The present invention improves on this and aims to provide a method that allows timing adjustment work to be performed without using any other channel in addition to the control channel.

[Means to solve the problem]

In the present invention, when adjusting the delay amount of a control signal transmitted from a line control station to each base station, the wireless channel transmitted by each base station is set to be one channel common to each base station, but each base station The base stations are characterized in that different time slots are assigned to each base station, and control signals transmitted from each base station to the wireless channel are transmitted within the assigned time slots.

〔Example〕

FIG. 1 is a conceptual diagram of an embodiment of the present invention.
1 is a line control station, 2 is a base station (reference station) that serves as a reference during timing adjustment, and 3 is a base station (adjustment station) that is adjusted during timing adjustment. 4 is a control channel receiving station which is temporarily provided for timing adjustment. 5 and 6 are fixed lines for control signal transmission, and 7 is a control channel radio signal transmitted from the base station 2. 8 represents a control channel radio signal transmitted from the coordination station 3. Reference numeral 9 denotes a fixed line for transmitting the control signal received by the receiving station 4 to the line control station 1. 10 indicates a wireless zone. Reference numeral 11 indicates a variable delay circuit, and the one installed inside the line control station 1 is particularly selected and displayed.

Control signals transmitted from the line control station 1 to the base stations 2 and 3 over the fixed lines 5 and 6 are transmitted from the base stations 2 and 3 via a radio control channel. This is received by the receiving station 4 and transmitted again to the line control station 1 via the fixed line 9.

FIG. 2 shows a time chart of the control signals at this time. FIG. 2a shows a control signal transmitted from the line control station 1. b1 and b2 are control signals transmitted from base stations 2 and 3 to a common radio control channel, respectively. C is a control signal received by the receiving station 4. d is a control signal received by the line control station 1 from the receiving station 4. Figure 2 F is a signal frame for synchronization, T ₂ is base station 2
_T3 is a time slot to be transmitted only from base station 3, and S is a signal frame to be transmitted from both base stations simultaneously. The shaded area indicates that two time slots or signals overlap. The rectangular waves shown here in time slots T ₂ and T ₃ are virtual representations of parts of the digital waveforms as examples of the signals in each time slot. Indicates the amount of delay.

The signal shown in FIG. 2a is transmitted from the line control station 1 to the fixed lines 5 and 6. This signal is from base station 2
3, phase delays Da and Db shown in FIG. 2 b1 and b2 are added to the transmitted signal due to the line delay and the delay within the equipment of the base station 2 or 3. When receiving these signals at receiving station 4,
As shown in Figure 2c, since the phase delay in the wireless section is relatively small, the time slot of base station 2
The amount of phase delay at time slot T ₂ and time slot T ₃ of base station 3 can be considered to be Da and Db, respectively. FIG. 2d shows the control signal received by the line control station 1. Here, Dr is the amount of phase delay from the receiving station 4 to the line control station 1 via the fixed line 9,
As for the overall phase delay amount for base station 2,
Da', and Db' for base station 3.

FIG. 3 is a block diagram of a control signal relay section in base station 2 or 3. 16 is a control signal input terminal from the control station 1, 17 is a control signal repeater, and 18 is a signal output gate. 19 is a control signal output terminal to the transmitter. 20 is a synchronization signal detector, 21 is a bit counter, and 22 is a signal output terminal for controlling transmission on/off of the transmitter.

The operation of the base station will be explained below with reference to FIGS. 2 and 3.

The control signal transmitted from the control station 1 to each base station 2, 3 includes a synchronization signal F indicating a time slot for broadcasting channel information at each base station 2, 3.
Based on this synchronization signal, each base station 2, 3 can know the position of a time slot that is determined in advance so that the base stations 2, 3 do not overlap. That is, since the length of each control signal is usually the same, when the synchronization signal is detected by the synchronization signal detector 20 in each base station 2, 3, the synchronization signal detector 20 is activated by starting the bit counter 21. The position of a predetermined time slot can be known by the bit counter 21 activated at the same time. As a result, the signal output gate 18 is opened, and at the same time, the transmitter is placed in a transmitting state from the signal output terminal 22. When the signal transmission is completed, the bit counter 21 is activated and the above operation is repeated until the next transmission timing. In addition to the above channel information, this control channel requires a notification signal 15 such as a normal incoming call signal and service area information.
In this case as well, by predetermining the length of the control signal, it is possible to know the timing of transmission in the same manner as described above.

FIG. 4 is a block diagram of the transmission timing adjustment section in the line control station 1. 23 is a control signal input terminal, and 24 and 24' are control signal relay sections.
25 is a variable delay circuit, which corresponds to the circuit 11 in FIG. 26 is a control signal output terminal connected to the base station (reference station) 2 via the fixed line 5;
7 is a control signal output terminal connected to the base station (coordination station) 3 via the fixed line 6. 28 is a phase difference measuring device, and 29 is a delay adjustment control section. 30 is a synchronization signal detection section, and 31 is a bit counter. 3
Reference numeral 2 denotes a control signal input terminal connected to the timing adjustment receiving station 4 via a fixed line 9.

The operation related to timing adjustment of the line control station 1 will be explained below with reference to FIGS. 2 and 4. Here, "timing adjustment" is as shown in Figure 2c.
The phase delay amount Da of the signals of base stations 2 and 3 and
The purpose is to equalize the values of Db. For this purpose, since Da′=Da+Dr Db′=Db+Dr, the phase delay amount Da′ in Fig. 2 d is
Just make the values of Db′ equal.

Furthermore, if an appropriate fixed delay amount is given to the fixed line 5, Da′>Db′ can always be established, so the phase delay amount of the control signal transmitted to the base station 3 at the line control station 1 is set to Da′ By increasing by -Db', the phases of control signals transmitted from base stations 2 and 3 through a common control channel can be matched. In the line control station 1, from the control signal input terminal 32 in FIG. 4, as shown in _{FIG .}
Then, a control signal with a phase delay of Db′ is received.
The phase difference measuring device 28 measures the phase difference between the control signal being transmitted and the control signal being received.
Since the time slots T ₂ and T ₃ are known by the synchronization signal detection section 30 and the bit counter 31, the delay adjustment control section 29 calculates the respective phase delay amounts Da' and Db' from the phase difference measuring device 28 at each time slot. The value Da'-Db' is calculated from the reading and the value is set in the variable delay circuit 25. As a result, the values of the delay amounts Da' and Db' become equal, the phases of the control signals match, and the timing becomes correct.

Next, a case will be described in which the timings of two or more base stations are adjusted. In the case of multiple stations, the adjustment receiver of each adjustment station is installed so that it can receive the control channel of one reference station, and the delay amount of the reference station is set to be the largest among all the stations. Accordingly, by sequentially performing the adjustment procedure for one adjustment station for each adjustment station, it is also possible to perform timing adjustment for a plurality of base stations.

Regarding the multi-station control signal transmission system in the actual car telephone system, the following is detailed in the literature: Proceedings of the 1985 National Conference of the Telecommunications Division of the Institute of Electronics and Communications Engineers, No. 540 "Study of Mobile Communication Zone Selection Control Method" by Koho Utano and Hiroshi Inaba. In the operational state, control signals as shown in FIGS. 5a to 5d are transmitted from the control station to each base station, or from each base station to a mobile station.

FIG. 5a shows transmission signals on the wired transmission path from the control station to each base station. FIG. 5b shows a control signal transmitted from base station #1 to the mobile station. Figure 5c
is a control signal transmitted from base station #2 to the mobile station. FIG. 5d shows a control signal transmitted from the base station #N to the mobile station. Synchronization signal SY and incoming call signal
PS is simultaneously transmitted from each base station to the mobile station. On the other hand, B ₁ , B _{2 . .} . _BN are signals sent individually from each base station to the mobile station. In this embodiment, B 1 to B ₁ which are the base station individual information in FIGS.
By receiving B _N at the control channel receiving station 4, it is possible to measure the amount of delay of each base station in the operating state without adding a new signal.

〔Effect of the invention〕

As explained above, the delay amount of the control signal transmitted by each base station can be monitored and adjusted at the same time for each time slot while the control channel line and transceiver remain in operation. There is an advantage that transmission timing can be monitored and adjusted without using a channel for adjusting transmission timing. This eliminates the need for processing such as temporarily reusing communication channels for adjustment, improving service and making frequent timing adjustments.
This has the effect of constantly maintaining quality.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing the configuration of a mobile radio communication system to which the present invention is applied. FIG. 2 is a time chart of control signals in each device according to an embodiment of the present invention. FIG. 3 is a block diagram of a control signal relay section in a base station according to an embodiment of the present invention. FIG. 4 is a block diagram of a transmission timing adjustment section in a control station according to an embodiment of the present invention. FIG. 5 is a time chart showing the signal transmission state in the operational state in the embodiment of the present invention. 1...Line control station, 2...Base station that serves as a reference during timing adjustment (reference station), 3...Base station that is adjusted during timing adjustment (adjustment station), 4...Control channel receiving station, 5, 6... ...Fixed line for control signals, 7...Control channel transmitted from base station 2, 8...Control channel transmitted from base station 3, 9...Fixed line for control signals of receiving station 4, 1
0...Wireless zone, 11...Variable delay circuit.

Claims (1)

[Claims] 1. A plurality of base stations are arranged, a wireless zone is set for each base station, the base station is connected to one line control station via a fixed line, and under the control of this line control station, A mobile communication system configured to simultaneously transmit control signals from two or more of the base stations to control channels of the same radio frequency, wherein a receiving station is provided near the boundary of the two or more radio zones of the base station, The receiving station is equipped with a means for observing the phase of the control signals transmitted from the two or more of the base stations, and the timing of the control signals transmitted from the two or more of the base stations coincides at the receiving station. In this adjustment method, when adjusting the timing, a time slot assigned to each base station is set for the control signal, and a control signal of the same radio frequency is transmitted to each base station within this time slot. A method for adjusting control signal timing, characterized in that it is configured as follows.