JP7542688B2 - Wireless communication system and terminal wireless device - Google Patents

Description

The present invention relates to a wireless communication system, and in particular to a wireless communication system that includes a headquarters station device and a number of base station devices that are connected to the headquarters station device in a tree configuration and communicate with terminal wireless devices, and in which the headquarters station device, the number of base station devices, and the terminal wireless devices communicate in frame units at a fixed period.

A wireless communication system is known in which multiple base station devices are connected to a headquarters station device in a tree configuration, and the headquarters station device, multiple base station devices, and terminal wireless devices communicate in frame units at a fixed period.

In conventional technology (see, for example, Patent Documents 1 and 2), when the headquarters station equipment and the base station equipment are connected, the delay time between the headquarters station equipment and multiple base station equipment is measured to adjust the timing of the downlink and uplink directions, and the delay time of the own station is subtracted from the maximum delay time corresponding to the delay time of the farthest base station equipment and set for each base station, thereby performing simultaneous multi-station transmission to the terminal wireless device.

JP 2002-27534 A JP 2007-166278 A

In conventional technology, when a headquarters station device is connected to multiple base station devices, the line delay time between the headquarters station device and each base station device is measured, and simultaneous multi-station transmission is achieved by suspending transmission at each base station device for the amount of delay time of each line.

When a base station device whose line with the headquarters station device has been cut off performs base station return communication, a terminal wireless device located in an area where it can receive radio waves from both the base station device connected to the headquarters station device (normal base station device) and the base station device whose line with the headquarters station device has been cut off (return base station device) receives downstream signals from two different routes (first and second routes). The first route is a route that relays in the order of normal base station device, headquarters station device, and normal base station device, and the second route is a route that is returned by the return base station device.

When a base station device whose line with the headquarters station device has been cut off performs base station return communication, the signals transmitted by the normal base station device and the return base station device may differ when there is no call, and the signals transmitted from each base station device may interfere with each other, causing a loss of synchronization in the terminal wireless device.

The present invention has been made to solve the above problems, and aims to provide a wireless communication system and a terminal wireless device that can prevent loss of synchronization of the terminal wireless device during non-communication.

The wireless communication system of the present invention is a wireless communication system comprising a headquarters station device, a plurality of base station devices connected to the headquarters station device in a tree configuration and operating based on a common synchronization signal, and a terminal wireless device capable of wireless communication with the base station devices, wherein the base station device transmits a downlink signal of a first format including a user channel and a synchronization word to the terminal wireless device during the no-call period when no uplink signal is being received from the terminal wireless device, and another base station device which performs base station return communication transmits a downlink signal of a second format to the terminal wireless device during the no - call period, the downlink signal being composed of a synchronization word arranged at a position that allows synchronization with the synchronization word included in the first format , a guard arranged at a position that avoids signal collision with the user channel , and a power ramp arranged between the guard and the synchronization word , and the terminal wireless device receives the downlink signal of the first format and the downlink signal of the second format at the same timing during the no-call period.

The wireless communication system and terminal wireless device according to the present invention can suppress interference between the downlink signal of a base station device performing base station return communication and the downlink signal of a normal base station device during an idle call, thereby suppressing deviations in synchronization of the terminal wireless device.

1 is a schematic diagram showing a configuration of a wireless communication system according to a first embodiment and a normal communication state; 2 is a block diagram showing a configuration of a headquarters station device according to the first embodiment; 2 is a block diagram showing a configuration of a base station device according to the first embodiment; FIG. 2 is a diagram illustrating a hardware configuration of a headquarters station device according to the first embodiment. FIG. 2 is a diagram illustrating a hardware configuration of a base station device according to the first embodiment. 4 is a diagram showing the transmission timing of a downlink signal in a normal state of the wireless communication system according to the first embodiment; FIG. 1 is a schematic diagram showing a configuration of a wireless communication system according to a first embodiment and a communication state when a line is disconnected; 1 is a diagram showing a sequence of measuring a return delay time in a wireless communication system according to a first embodiment; 1 is a diagram showing the transmission timing of a downstream signal in a wireless communication system when a line is disconnected in accordance with the first embodiment; 4 is a flowchart showing an operation of the wireless communication system according to the first embodiment. 13 is a diagram showing a frame format transmitted by a normal base station device in accordance with embodiment 2 when no call is in progress. FIG. 13 is a diagram showing a frame format transmitted by a base station device in which the line with the headquarters station device in the second embodiment is disconnected when there is no call. FIG. A block diagram showing the configuration of a base station device according to embodiment 3. A diagram showing the transmission timing of notification information in a wireless communication system according to a third embodiment. A diagram showing the transmission timing of the generation number of the notification information of a wireless communication system according to embodiment 4.

<First embodiment>
<Configuration>
Fig. 1 is a diagram showing a configuration of a wireless communication system in the present embodiment 1. As shown in Fig. 1, the wireless communication system in the present embodiment 1 includes a headquarters station device 10 and first to third base station devices 201, 202, and 203. The first to third base station devices 201, 202, and 203 are connected to the headquarters station device 10 in a tree configuration. The first to third base station devices 201, 202, and 203 communicate with a terminal wireless device 30. In the following description, when the first to third base station devices 201, 202, and 203 are not to be distinguished from each other, they will simply be referred to as base station devices 20.

In the wireless communication system of the first embodiment, the headquarters station device 10, the multiple base station devices 20, and the terminal wireless devices 30 communicate in frames at a fixed interval. The wireless communication system of the first embodiment is a system that performs voice communication using the press-to-talk method.

The headquarters station device 10 is a device that houses multiple base station devices 20 and controls the wireless communication system. Each base station device 20 is connected to a terminal wireless device 30 via a wireless line, and relays voice signals between the headquarters station device 10 and controls the wireless line.

Area R1 shown in FIG. 1 is an area in which communication with the first base station device 201 is possible, and is not subject to radio wave interference from the second base station device 202. Area R2 shown in FIG. 1 is an area in which communication with the second base station device 202 is possible, and is not subject to radio wave interference from the first base station device 201. Area R3 shown in FIG. 1 is an area in which communication with both the first and second base station devices 201 and 202 is possible.

The upstream signal transmitted from the terminal radio device 30 is returned by the headquarters station device 10 and transmitted as a downstream signal to all base station devices 20. Here, the upstream signal refers to a signal transmitted in the order of the terminal radio device 30, the base station device 20, and the headquarters station device 10. Also, the downstream signal refers to a signal transmitted in the order of the headquarters station device 10, the base station device 20, and the terminal radio device 30.

The downlink signals from each base station device 20 are assumed to be transmitted using the same frequency. In addition, the uplink communications from the terminal radio device 30 to each base station device 20 are assumed to be transmitted using the same frequency.

Figure 2 is a block diagram showing the configuration of the headquarters station device 10 in this embodiment 1. As shown in Figure 2, the headquarters station device 10 includes a return processing unit 11, a control unit 12, a downlink transmission timing adjustment unit 13, and a base station communication unit 14.

The loopback processing unit 11 has the function of receiving an uplink signal from a base station device 20 via the base station communication unit 14, looping back the signal, and transmitting it to multiple base station devices 20 via the base station communication unit 14.

The control unit 12 generates information necessary for the terminal radio device 30 to communicate and notifies the terminal radio device via the base station device 20. The control unit 12 also controls each part within the headquarters station device 10.

The downlink transmission timing adjustment unit 13 includes a simultaneous transmission possible time determination unit 131 and a transmission hold time determination unit 132. The simultaneous transmission possible time determination unit 131 determines the time when multiple base station devices 20 can transmit simultaneously in order to realize multi-station simultaneous transmission. The transmission hold time determination unit 132 determines the transmission hold time for each of the multiple base station devices 20. The base station communication unit 14 transmits signals to the base station devices 20 and receives signals from the base station devices 20.

Fig. 3 is a block diagram showing the configuration of the base station device 20 in the present embodiment 1. As shown in Fig. 3, the base station device 20 includes a higher-level station communication unit 21, an upstream communication processing unit 22, a loopback processing unit 23, a downstream communication processing unit 24, a downstream transmission timing adjustment unit 25, a control unit 26, a lower-level station communication unit 27, and a terminal wireless device communication unit 28.

The higher-level station communication unit 21 receives signals from the headquarters station device 10 directly or via the higher-level base station device 20. The higher-level station communication unit 21 also transmits signals to the headquarters station device 10 or the higher-level base station device 20.

The upstream communication processing unit 22 normally relays signals received from the terminal radio device 30 or the lower base station device 20 to the headquarters station device 10 or the higher base station device 20. In addition, when the higher line is disconnected, the upstream communication processing unit 22 transmits signals received from the terminal radio device 30 or the lower base station device 20 to the loopback processing unit 23.

When the upper line is disconnected, the loopback processing unit 23 transmits the signal received from the upstream communication processing unit 22 to the downstream communication processing unit 24 after the time equal to the loopback delay time plus the transmission hold time has elapsed.

The downstream communication processing unit 24 normally transmits signals received from the headquarters station device 10 or the higher-level base station device 20 to the terminal radio device 30 or the lower-level base station device 20. In addition, when the higher-level line is disconnected, the downstream communication processing unit 24 transmits signals received from the loopback processing unit 23 to the terminal radio device 30 or the lower-level base station device 20.

The downstream transmission timing adjustment unit 25 includes a line delay time measurement unit 251, a return delay time measurement unit 252, a transmission hold time memory unit 253, and a return delay time memory unit 254.

The line delay time measurement unit 251 measures the line delay time between the headquarters station device 10 and the base station device 20 to realize simultaneous multi-station transmission. The return delay time measurement unit 252 measures the line delay time when a signal from the base station device 20 is returned by the headquarters station device 10 and received by the base station device 20.

The transmission hold time memory unit 253 stores the transmission hold time notified by the headquarters station device 10.

The return delay time memory unit 254 stores the return delay time. The control unit 26 processes and stores the notification information received from the headquarters station device 10. The control unit 26 also controls each processing unit within the base station device 20.

The lower-level station communication unit 27 has a function of transmitting signals received from each processing unit to the lower-level base station device 20, and a function of transmitting signals received from the lower-level base station device 20 to each processing unit. The terminal radio device communication unit 28 has a function of transmitting signals received from each processing unit to the terminal radio device 30, and a function of transmitting signals received from the terminal radio device 30 to each processing unit.

Figure 4 is a diagram showing the hardware configuration of the headquarters station device 10. The base station communication unit 14 is realized by the base station communication circuit HW11. The return processing unit 11, the control unit 12, and the downlink transmission timing adjustment unit 13 are realized by the processing circuit HW12 and the memory HW13. The processing circuit HW12 may be dedicated hardware or a CPU (also called a Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, microcontroller, processor, or DSP) that executes a program stored in the memory HW13.

When the processing circuit HW12 is dedicated hardware, the processing circuit HW12 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination of these.

When the processing circuit HW12 is a CPU, the functions of the loopback processing unit 11, the control unit 12, and the downstream transmission timing adjustment unit 13 are realized by software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in the memory HW13. The processing circuit HW12 realizes the functions of the loopback processing unit 11, the control unit 12, and the downstream transmission timing adjustment unit 13 by reading and executing the program stored in the memory HW13. In addition, this program can also be said to cause a computer to execute the procedures and methods of the loopback processing unit 11, the control unit 12, and the downstream transmission timing adjustment unit 13. Here, the memory HW13 corresponds to, for example, a non-volatile or volatile semiconductor memory such as RAM, SDRAM, ROM, flash memory, EPROM, EEPROM, etc., a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD, etc.

The functions of the loopback processing unit 11, the control unit 12, and the downlink transmission timing adjustment unit 13 may be partially realized by dedicated hardware and partially realized by software or firmware.

Figure 5 is a diagram showing the hardware configuration of the base station device 20. The higher-level station communication unit 21 is realized by the higher-level station communication circuit HW21. The lower-level station communication unit 27 is realized by the lower-level station communication circuit HW22. The terminal radio device communication unit 28 is realized by the terminal radio device communication circuit HW23. The uplink communication processing unit 22, the loopback processing unit 22, the downlink communication processing unit 24, the downlink transmission timing adjustment unit 25, and the control unit 26 are realized by the processing circuit HW24 and the memory HW25. The processing circuit HW24 may be dedicated hardware or a CPU (also called a Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, microcontroller, processor, or DSP) that executes a program stored in the memory HW25.

When the processing circuit HW24 is dedicated hardware, the processing circuit HW24 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination of these.

When the processing circuit HW24 is a CPU, the functions of the upstream communication processing unit 22, the loopback processing unit 22, the downstream communication processing unit 24, the downstream transmission timing adjustment unit 25, and the control unit 26 are realized by software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in the memory HW25. The processing circuit HW24 realizes the functions of the upstream communication processing unit 22, the loopback processing unit 22, the downstream communication processing unit 24, the downstream transmission timing adjustment unit 25, and the control unit 26 by reading and executing the program stored in the memory HW25. In addition, this program can also be said to cause the computer to execute the procedures and methods of the upstream communication processing unit 22, the loopback processing unit 22, the downstream communication processing unit 24, the downstream transmission timing adjustment unit 25, and the control unit 26. Here, memory HW25 refers to, for example, non-volatile or volatile semiconductor memory such as RAM, SDRAM, ROM, flash memory, EPROM, EEPROM, etc., as well as magnetic disks, flexible disks, optical disks, compact disks, mini disks, DVDs, etc.

The functions of the upstream communication processing unit 22, the loopback processing unit 22, the downstream communication processing unit 24, the downstream transmission timing adjustment unit 25, and the control unit 26 may be partially realized by dedicated hardware and partially realized by software or firmware.

<Normal operation>
First, the operation of the wireless communication system in a normal state will be described. Here, "normal state" means that no disconnection of the line between the headquarters station device 10 and the base station device 20 under its control occurs.

Figure 6 is a diagram showing the transmission timing of downlink signals in a wireless communication system under normal conditions. The timing in the upper part of Figure 6 is 1 PPS (one-second pulse) received from a GPS (Global Positioning System) satellite. The headquarters station device 10 and all base station devices 20 perform signal processing based on the 1 PPS received from a GPS satellite as a synchronization signal. Each of the headquarters station device 10 and all base station devices 20 has a synchronization signal receiving unit (not shown), which receives the synchronization signal.

The downstream signal transmitted from the headquarters station device 10 is delayed by the signal processing time within the headquarters station device 10, starting from the 1 PPS reference. This is defined as the offset time. In the example of FIG. 6, the offset time is 4 ms. In addition, a line delay time occurs as the time it takes for the downstream signal transmitted from the headquarters station device 10 to be received by the base station device 20.

In the example of Figure 6, the line delay times of the first to third base station devices 201, 202, and 203 are 41 ms, 66 ms, and 86 ms, respectively. From this, it can be seen that the signal arrives the most late at the third base station device 203. Also, as shown in Figure 6, the time from when the third base station device 203 receives the downstream signal to when the next frame that can be transmitted is 30 ms.

The simultaneous transmission time is the time from when the headquarters station device 10 transmits a downstream signal until all base station devices 20 can transmit downstream signals simultaneously. The simultaneous transmission time is determined based on the line delay time (86 ms) of the third base station device 203, which is the device that receives the signal the slowest. In other words, the simultaneous transmission time is calculated by adding up the offset time (4 ms) inside the headquarters station device 10, the line delay time (86 ms) of the third base station device 203, which is the device that receives the signal the slowest, and the time (30 ms) from when the third base station device 203 receives a downstream signal until the next frame that can be transmitted. In the case of Figure 6, the simultaneous transmission time is 120 ms.

The method for measuring the simultaneous transmission possible time will be explained. The headquarters station device 10 transmits a line delay time measurement instruction to all base station devices 20 (first to third base station devices 201, 202, 203) under its umbrella. This instruction includes the time when the headquarters station device 10 transmits the instruction.

The line delay time measurement unit 251 of each base station device 20 that receives the line delay time measurement instruction responds to the headquarters station device 10 with the time when the instruction was received (downstream signal reception timing). Alternatively, the line delay time measurement unit 251 may calculate the line delay time by subtracting the time when the headquarters station device 10 sent the instruction from the time when the instruction was received, and respond with the line delay time.

The headquarters station device 10 receives the downstream signal reception timing from each of the base station devices 20 under its control and calculates the line delay time for each base station device 20. Note that if the base station device 20 under its control responds with the line delay time, the headquarters station device 10 does not need to calculate the line delay time.

Then, the headquarters station device 10 determines the timing of the frame in which the downstream signal can be transmitted as the simultaneous transmission possible time based on the base station device 20 with the longest line delay time (the third base station device 203 in the example of Figure 6). In the example of Figure 6, the simultaneous transmission possible time is 120 ms.

Next, the headquarters station device 10 transmission hold time determination unit 132 calculates the time (transmission hold time) for which each base station device 20 holds off on transmitting the downlink signal after receiving the downlink signal. The transmission hold time for each base station device 20 is calculated as the time available for simultaneous transmission minus the line delay time and offset time.

In the example of Figure 6, the transmission suspension time of the first base station device 201 is 75 ms, calculated by 120 ms - 4 ms - 41 ms. The transmission suspension time of the second base station device 202 is 50 ms, calculated by 120 ms - 4 ms - 66 ms. The transmission suspension time of the third base station device 203 is 30 ms, calculated by 120 ms - 4 ms - 86 ms.

Then, the headquarters station device 10 notifies the corresponding base station device 20 of the transmission hold time of each base station device 20. When each base station device 20 receives the transmission hold time, it stores the transmission hold time in the transmission hold time memory unit 253. In the example of FIG. 6, 75 ms, 50 ms, and 30 ms are stored in the transmission hold time memory unit 253 of the first to third base station devices 201, 202, and 203, respectively.

In addition, instead of the headquarters station device 10 calculating the transmission hold time, the transmission hold time may be calculated at each base station device 20. In this case, the headquarters station device 10 transmits the simultaneous transmission possible time and the offset time to each base station device 20, and each base station device 20 calculates and stores the transmission hold time using the line delay time.

Each base station device 20 under the headquarters station device 10 transmits a downstream signal when the transmission hold time has elapsed since receiving the downstream signal. As a result, when the simultaneous transmission possible time (120 ms in the example of FIG. 6) has elapsed starting from 1 PPS, downstream signals are transmitted simultaneously from each base station device 20. Through the above operation, synchronization is maintained on the wireless line, making simultaneous transmission from multiple stations possible.

<Operation when line is disconnected>
Next, the operation of the wireless communication system when communication between the headquarters station device 10 and the base station device 20 is disconnected will be described. Fig. 7 is a schematic diagram showing the communication state of the wireless communication system when the line is disconnected. In Fig. 7, the line is disconnected between the headquarters station device 10 and the second base station device 202. The second base station device 202 continues the communication service in area R2 by performing base station return communication, which returns a signal (voice) by itself.

In conventional technology, interference of downstream signals occurred in area R3, which receives radio waves from both a first base station device 201 (normal base station device) connected to the headquarters station device 10, and a second base station device 202 (loopback base station device) whose line with the headquarters station device 10 has been cut off.

A terminal radio device 30 located in area R3 receives downlink signals from two different routes (first and second routes). If the timing of the downlink signals passing through these routes is out of sync, interference with the audio signals occurs, and the terminal radio device 30 is unable to receive the signals correctly. Here, the first route is a route that relays in the order of the first base station device 201, the headquarters station device 10, and the first base station device 201. The second route is a route that loops back at the second base station device 202. This embodiment 1 is intended to solve the above problem.

In this embodiment 1, all base station devices 20 under the headquarters station device 10 measure the return delay time in advance when the line to the headquarters station device 10 is connected (i.e., normal state). Figure 8 is a diagram showing the sequence of measuring the return delay time. For ease of viewing, Figure 8 shows only the sequence related to the first base station device 201.

The headquarters station device 10 transmits a return delay time measurement instruction to all base station devices 20 (first to third base station devices 201, 202, 203) under its umbrella. When the first base station device 201 receives the return delay time measurement instruction, it transmits a delay time measurement signal to the headquarters station device 10. When the headquarters station device 10 receives the delay time measurement signal from the first base station device 201, it performs a return process and transmits the delay time measurement signal to the first base station device 201. The return process requires the signal processing time (offset time) within the headquarters station device 10.

The return delay time measurement unit 252 of the first base station device 201 that receives the delay time measurement signal measures the return delay time using the time when the first base station device 201 transmits the delay time measurement signal to the headquarters station device 10. Specifically, the return delay time determination unit 252 calculates the return delay time by subtracting the time when the delay time measurement signal is transmitted from the time when the delay time measurement signal is received. The return delay time is then stored in the return delay time storage unit 254.

The above describes the turn-back delay time for the first base station device 201, but the turn-back delay times for the second and third base station devices 202 and 203 are determined in a similar manner and stored in the turn-back delay time storage unit 254.

Figure 9 is a diagram showing the transmission timing of downstream signals in a wireless communication system when a line is disconnected. In Figure 9, as in Figure 6, the headquarters station device 10 and all base station devices 20 perform signal processing based on 1 PPS. As shown in Figure 9, the first and third base station devices 201 and 203 under the headquarters station device 10 transmit downstream signals when the transmission hold time has elapsed after receiving the downstream signal returned by the headquarters station device 10.

The second base station device 202 under the headquarters station device 10 also transmits a downstream signal back to the terminal radio device 30 when the time equal to the return delay time plus the transmission hold time has elapsed since receiving the upstream signal from the terminal radio device 30. This allows the second base station device 202, whose line is disconnected, to transmit signals in synchronization with the normal base station devices (the first and third base station devices 201 and 203).

Figure 10 is a flowchart showing the operation of the base station device 20. When the line with the headquarters station device 10 is not disconnected (normal state), the base station device 20 executes steps S1 to S4 in advance. That is, the base station device 20 receives a transmission hold time from the headquarters station device 10 and stores it in the transmission hold time memory unit 253 (steps S1 and S2). The base station device 20 also measures the return delay time and stores it in the return delay time memory unit 254 (steps S3 and S4).

Next, in step S5, the base station device 20 receives an upstream signal from the terminal radio device 30 or a lower base station device. The base station device 20 then determines whether the upper line is normal or disconnected.

Below, we will explain the operation when the upper line is determined to be normal in step S6. If the upper line is determined to be normal in step S6, the base station device 20 transmits an uplink signal to the headquarters station device 10 or the upper base station device 20 (step S7). Then, the base station device 20 receives a downlink signal returned from the headquarters station device 10 or the upper base station device 20 (step S8).

Next, the base station device 20 determines whether or not to transmit the downlink signal to the lower base station device 20 (step S10). If it is determined in step S10 that the downlink signal should be transmitted to the lower base station device 20, the downlink signal is transmitted to the lower base station without any hold time (step S11). On the other hand, if it is determined in step S10 that the downlink signal should be transmitted to the terminal radio device 30 rather than the lower base station device 20, the downlink signal is transmitted to the terminal radio device 30 when the transmission hold time has elapsed (step S12).

If it is determined in step S6 that the upper line is not normal (i.e., the line is disconnected), the base station device 20 holds the uplink signal for the return delay time (step S9). Then, in step S10, it is determined whether or not to transmit the downlink signal, which is the return signal of the uplink signal, to the lower base station device 20. If it is determined to transmit the downlink signal to the lower base station device 20, it transmits the downlink signal to the lower base station without any further hold time (step S11). On the other hand, if it is determined in step S10 to transmit the signal to the terminal radio device 30 instead of the lower base station device 20, it transmits the downlink signal to the terminal radio device 30 when the return delay time plus the transmission hold time has elapsed (step S12).

＜Effects＞
The wireless communication system in the first embodiment includes a headquarters station device 10 and a plurality of base station devices 20 connected to the headquarters station device 10 in a tree configuration and communicating with a terminal wireless device 30, and is a wireless communication system in which the headquarters station device 10, the plurality of base station devices 20, and the terminal wireless devices 30 communicate with each other in frames at a constant period. Each of the plurality of base station devices 20 includes a transmission suspension time memory unit 253 that stores a transmission suspension time, and a turn-back delay time memory unit 254 that stores a turn-back delay time. The transmission suspension time is a suspension time from when each of the plurality of base station devices 20 receives a downlink signal from the headquarters station device 10 until when it simultaneously transmits the downlink signal to the terminal wireless device 30, and the turn-back delay time is a turn-back delay time stored in the plurality of base station devices 20. This is the time required for an upstream signal transmitted from each of devices 20 to the headquarters station device 10 to be returned by the headquarters station device 10 and received by the base station device 20 as a downstream signal. A base station device 20 whose line with the headquarters station device 10 has been disconnected returns and transmits a downstream signal to the terminal radio device 30 when the time equal to the return delay time plus the transmission hold time has elapsed since receiving an upstream signal from the terminal radio device 30, and a base station device 20 whose line with the headquarters station device 10 has not been disconnected transmits the upstream signal transmitted from the terminal radio device 30 to the headquarters station device 10, and transmits a downstream signal to the terminal radio device 30 when the transmission hold time has elapsed since receiving the downstream signal returned by the headquarters station device 10.

Conventionally, when a base station device 20 whose line with the headquarters station device 10 was cut off switched to base station return communication, it was not possible to maintain multi-station simultaneous transmission with other normal base station devices 20. This caused signal interference in the downlink signal, which resulted in the problem that the terminal radio device 30 was unable to receive the signal normally.

In this embodiment 1, a base station device 20 whose line with the headquarters station device 10 has been cut off suspends signal transmission for a time equal to the return delay time plus the transmission hold time, and then returns the signal from the terminal radio device 30. A normal base station device 20 whose line with the headquarters station device 10 has not been cut off suspends signal transmission for the transmission hold time, and then transmits a downstream signal. This makes it possible to maintain simultaneous multi-station transmission with other normal base station devices 20, even if a base station device 20 whose line with the headquarters station device 10 has been cut off switches to base station return communication. This makes it possible to suppress signal interference in the downstream signal, and allows the terminal radio device 30 to receive a signal with suppressed interference.

In addition, in the wireless communication system according to the first embodiment, each of the multiple base station devices 20 further includes a line delay time measurement unit 251 that measures the line delay time, and a return delay time measurement unit 252 that measures the return delay time, and the line delay time is the time required to transmit a downstream signal from the headquarters station device to the base station device, and the transmission hold time stored in each of the transmission hold time storage units 253 of the multiple base station devices 20 is determined based on the timing of the frame that can be transmitted by the base station device 20 with the largest line delay time.

Therefore, by each of the multiple base station devices 20 being equipped with a line delay time measurement unit 251 and a return delay time measurement unit 252, it becomes possible to obtain the line delay time and the return delay time in all of the multiple base station devices 20. In addition, since the transmission hold time of each base station device 20 is determined based on the timing of the frame that the base station device 20 with the largest line delay time can transmit, simultaneous multi-station transmission of downlink signals is possible in all of these base station devices 20.

In addition, in the wireless communication system in this embodiment 1, the headquarters station device 10 includes a transmission hold time determination unit 132, which determines the transmission hold time to be stored in the transmission hold time memory unit 253 of the multiple base station devices 20 based on the line delay time measured by the line delay time measurement unit 251 of the multiple base station devices 20.

Therefore, by determining the transmission hold time for each base station device 20 in the headquarters station device 10, it is possible to notify each base station device 20 of its respective transmission hold time.

In addition, in the wireless communication system of this embodiment 1, the terminal wireless device 30 performs voice communication using the press-to-talk method. In this embodiment 1, even if a base station device 20 is disconnected from the headquarters station device and switched to return communication, it is possible to suppress interference of downstream signals with other normal base station devices 20. Therefore, when performing voice communication using the press-to-talk method, the terminal wireless device 30 can receive high-quality voice signals with suppressed interference.

In addition, in the wireless communication system of this embodiment 1, the headquarters station device 10 and the multiple base station devices 20 operate based on a common synchronization signal, which is a time pulse transmitted from a GPS satellite. Therefore, by using the time pulse transmitted from a GPS satellite as the synchronization signal, it is possible to achieve high-precision synchronization between the headquarters station device 10 and the multiple base station devices 20.

<Embodiment 2>
In the first embodiment, the state in which the terminal radio device 30 is engaged in a voice call has been described, but when no call is being made, there may be cases where the synchronization of the terminal radio device 30 located in area R3 (interference area) is lost. This is because the signals transmitted by a normal base station device 20 and a base station device 20 whose line is disconnected may differ, causing interference between the signals transmitted from the respective base station devices 20.

The present embodiment 2 suppresses signal interference when there is no call. In the present embodiment 2, when there is no call, the base station device 20 whose line with the headquarters station device 10 is disconnected stops transmitting the frame format area (i.e., the user channel) that affects the content of the downstream signal of the normal base station device 20, and transmits only the area necessary for frame format synchronization.

Figure 11 is a diagram showing the frame format of a downlink signal transmitted by a normal base station device 20. As shown in Figure 11, the frame format transmitted by a normal base station device 20 consists of a ramp (R), a user channel (USC), a synchronization word (SW), and a guard (G). Here, the ramp (R) is a power ramp that indicates the start of a TDMA (time division multiplexing) time slot. The user channel (USC) is an area that contains the content of the communication. The synchronization word (SW) is an area that contains a bit pattern for synchronization. The guard (G) is an area that contains a guard time to avoid signal collisions.

Figure 12 is a diagram showing the frame format of a downstream signal transmitted by a base station device 20 whose line with the headquarters station device 10 is disconnected when there is no call. As shown in Figure 12, a base station device 20 whose line is disconnected transmits a downstream signal in a signal frame format that includes information necessary for synchronization and does not include a user channel (USC) when there is no call. In other words, as shown in Figure 12, the downstream signal is transmitted in a frame format that includes a guard (G), a ramp (R), and a synchronization word (SW) but does not include a user channel (USC).

＜Effects＞
In the wireless communication system of the second embodiment, a base station device 20 whose line with the headquarters station device 10 is disconnected transmits a signal in a format including information required for synchronization and not including a user channel to the terminal radio device 20 when the terminal radio device 30 is not in a call. Therefore, when there is no call, it is possible to suppress interference between the downlink signal of the base station device 20 whose line with the headquarters station device 10 is disconnected and the downlink signal of another normal base station device 20, and it is possible to suppress deviation in synchronization of the terminal radio device 30.

<Third embodiment>
In the first embodiment, an example of voice communication is shown in the multi-station simultaneous transmission, but the multi-station simultaneous transmission can be applied not only to voice communication but also to broadcast information. Broadcast information is system control information related to a frequency, a communication channel, and a communication service that is broadcast from the headquarters station device 10 to the terminal radio device 30.

Figure 13 is a block diagram showing the configuration of base station device 20A in this embodiment 3. Base station device 20A further includes a notification information storage unit 29 in addition to base station device 20 (Figure 3) in embodiment 1. The rest of the configuration is the same as base station device 20, so the description is omitted.

When all base station devices 20A are operating normally, they store one cycle of the notification information received from the headquarters station device 10 in the notification information storage unit 29. The notification information storage unit 29 also stores the time when the notification information was received and the period during which the notification information was received.

In this third embodiment, as shown in FIG. 7, the first and third base station devices 201 and 203 are normally connected to the headquarters station device 10, and the second base station device 202 is disconnected from the headquarters station device 10.

Figure 14 is a diagram showing the timing of transmission of notification information in a wireless communication system when a line is disconnected. In Figure 14, as in Figure 6, the headquarters station device 10 and all base station devices 20A perform signal processing based on 1 PPS. The notification information is a signal transmitted from the headquarters station device 10 at regular intervals using multiple frames.

As shown in FIG. 14, the first and third base station devices 201 and 203 connected to the headquarters station device 10 transmit notification information to the terminal wireless device 30 when the transmission hold time has elapsed since receiving the notification information transmitted from the headquarters station device 10.

Also, as shown in FIG. 14, the second base station device 202, whose line with the headquarters station device 10 is disconnected, refers to the reception time and reception cycle of the notification information stored in the notification information storage unit 29, and predicts the timing at which the notification information will be received if the line is assumed to be normal. Then, the notification information stored in the notification information storage unit 29 is transmitted to the terminal wireless device 30 at a timing shifted by the transmission hold time (66 ms in FIG. 14) from the timing at which the notification information is predicted to be received.

As a result, the second base station device 202, whose line with the headquarters station device 10 is disconnected, can transmit notification information in synchronization with the normal base station devices (the first and third base station devices 201 and 203) at the same timing.

＜Effects＞
In the wireless communication system of this embodiment 3, each of the multiple base station devices 20 further includes a notification information storage unit 29, and the headquarters station device 10 periodically transmits notification information to the multiple base station devices 20. Upon receiving notification information, each of the multiple base station devices 20 stores the notification information, the reception time and reception cycle of the notification information in the notification information storage unit 29, and transmits the notification information to the terminal radio device 30 when the transmission suspension time has elapsed. A base station device 20 whose line with the headquarters station device 10 has been disconnected refers to the reception time and reception cycle of the notification information stored in the notification information storage unit 29, and transmits the notification information stored in the notification information storage unit 29 to the terminal radio device 30 at a timing shifted by the transmission suspension time from the timing predicted to receive the notification information.

Therefore, even if the line between the base station device 20 and the headquarters station device 10 is disconnected, the base station device 20 can continue to transmit notification information at the same timing as other normal base station devices 20.

<Fourth embodiment>
In the third embodiment, the simultaneous transmission of the broadcast information to multiple stations has been described, but it can also be applied to the transmission of the generation number of the broadcast information. As a method for preventing the terminal radio device 30 from receiving the broadcast information all the time, there is a method of managing the generation of the broadcast information, notifying the terminal radio device 30 of the generation number, and making the terminal radio device 30 receive the broadcast information only when the content of the broadcast information has changed.

The configuration of the base station device in this embodiment 4 is the same as that of the base station device 20A in embodiment 3, so it will be described with reference to FIG. 13. In this embodiment 4, all base station devices 20A store the generation number of the notification information received from the headquarters station device 10 in the notification information storage unit 29 during normal operation. The notification information storage unit 29 also stores the reception time of the generation number of the notification information and the reception period of the generation number of the notification information.

In this fourth embodiment, as shown in FIG. 7, the first and third base station devices 201 and 203 are normally connected to the headquarters station device 10, and the second base station device 202 is disconnected from the headquarters station device 10.

Figure 15 is a diagram showing the timing of transmission of the generation number of the notification information of a wireless communication system when a line is disconnected. In Figure 15, as in Figure 6, the headquarters station device 10 and all base station devices 20A perform signal processing based on 1 PPS. The generation number of the notification information is a signal transmitted from the headquarters station device 10 at regular intervals when there is no call.

As shown in FIG. 15, the first and third base station devices 201 and 203 connected to the headquarters station device 10 transmit the generation number of the notification information to the terminal wireless device 30 when the transmission hold time has elapsed since receiving the generation number of the notification information transmitted from the headquarters station device 10.

Also, as shown in FIG. 15, the second base station device 202, whose line with the headquarters station device 10 is disconnected, refers to the reception time and reception cycle of the generation number of the broadcast information stored in the broadcast information storage unit 29, and predicts the timing at which it will receive the generation number of the broadcast information assuming that the line is normal. Then, it transmits the generation number of the broadcast information stored in the broadcast information storage unit 29 to the terminal wireless device 30 at a timing shifted by the transmission hold time (66 ms in FIG. 14) from the timing at which it is predicted that the generation number of the broadcast information will be received.

As a result, the second base station device 202, whose line with the headquarters station device 10 is disconnected, can transmit the generation number of the notification information in synchronization with the normal base station devices (the first and third base station devices 201 and 203) at the same timing.

＜Effects＞
In the wireless communication system of this embodiment 4, a generation number indicating the generation of the notification information is associated with the notification information, and the headquarters station equipment 10 periodically transmits the generation number to the multiple base station equipment 20, and upon receiving the generation number, each of the multiple base station equipment 20 stores the generation number, the reception time of the generation number and the reception period of the generation number in the notification information memory unit 29, and transmits the generation number to the terminal radio equipment 30 when the transmission suspension time has elapsed, and a base station equipment 20 whose line with the headquarters station equipment has been disconnected refers to the reception time and reception period of the generation number stored in the notification information memory unit 29, and transmits the generation number stored in the notification information memory unit 29 to the terminal radio equipment 30 at a timing shifted by the transmission suspension time from the timing when the generation number is predicted to be received.

Therefore, even if the line between the base station device 20 and the headquarters station device 10 is disconnected, the base station device 20 can continue to transmit the generation number of the notification information at the same timing as other normal base station devices 20.

In addition, within the scope of the present invention, each embodiment can be freely combined, modified, or omitted as appropriate.

10 Headquarters station device, 11 Loopback processing unit, 12 Control unit, 13 Downstream transmission timing adjustment unit, 131 Simultaneous transmission possible time determination unit, 132 Transmission hold time determination unit, 14 Base station communication unit, 20, 20A Base station device, 21 Upper station communication unit, 22 Upstream communication processing unit, 23 Loopback processing unit, 24 Downstream communication processing unit, 25 Downstream transmission timing adjustment unit, 251 Line delay time measurement unit, 252 Loopback delay time measurement unit, 253 Transmission hold time storage unit, 254 Loopback delay time storage unit, 26 Control unit, 27 Lower station communication unit, 28 Terminal radio device communication unit, 29 Notification information storage unit, 201 First base station device, 202 Second base station device, 203 Third base station device, 30 Terminal radio device.

Claims (2)

A wireless communication system including a headquarters station device, a plurality of base station devices connected to the headquarters station device in a tree configuration and operating based on a common synchronization signal, and a terminal wireless device capable of wireless communication with the base station devices,
the base station device transmits a downstream signal in a first format including a user channel and a synchronization word to the terminal radio device during a non-call period when the base station device is not receiving an upstream signal from the terminal radio device ;
Another base station device performing base station return communication transmits, during the no-call period, a downstream signal of a second format to the terminal radio device , the downstream signal being composed of a synchronization word arranged at a position where synchronization can be achieved with a synchronization word included in the first format , a guard arranged at a position where signal collision with the user channel can be avoided, and a power ramp arranged between the guard and the synchronization word;
the terminal wireless device receives the downstream signal in the first format and the downstream signal in the second format at the same timing during the no-call period;
Wireless communication system. A wireless communication system including a headquarters station device, a plurality of base station devices connected to the headquarters station device in a tree configuration and operating based on a common synchronization signal, and a terminal wireless device capable of wireless communication with the base station devices, the terminal wireless device comprising:
receiving a downstream signal in a first format transmitted from the base station device and a downstream signal in a second format transmitted from another base station device performing base station loopback communication at the same timing during no call in which no upstream signal is being transmitted ;
the first format includes a user channel and a synchronization word;
the second format is composed of a sync word arranged at a position where it can be synchronized with the sync word included in the first format , a guard arranged at a position where it can avoid signal collision with the user channel , and a power ramp arranged between the guard and the sync word .
Terminal radio equipment.

Images