JPH0767166A - Radio communication equipment - Google Patents

Abstract

(57) [Abstract] [Purpose] The time division multiple access method is used to communicate by time-multiplexing transmission and reception slots on the same carrier frequency, and multiple frames are configured to form a multi-frame, and at least one slot of each frame is As a control signal slot, a plurality of radio base stations transmit control signals to mobile terminals in control signal slots of different frames using the same carrier frequency, and when control signal transmission is newly started or restarted. Sometimes, in a wireless communication device that receives a control signal slot from another station and selects one with a low reception level for its own station, when a plurality of wireless base stations start or restart transmission of control signals at the same time, Prevent selecting the same control signal slot. [Configuration] Each of a plurality of radio base stations starts a control signal slot selection operation after a different rise time T has elapsed for each of the radio base stations after the radio base station becomes operable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time division multiple access communication system and a communication system for time-multiplexing transmission / reception slots with the same carrier frequency, that is, a TDMA-TDD system.

[0002]

2. Description of the Related Art In the TDMA-TDD system, a radio base station communicates with a plurality of mobile terminals, and one frame is composed of a portion in which N transmission slots are multiplexed and a portion in which n reception slots are multiplexed. It The radio base station transmits to each mobile terminal using each transmission slot, and receives from that mobile terminal in the reception slot corresponding to the transmission slot. The radio base station also transmits the control signal in a predetermined slot using a frequency different from the carrier frequency of the call signal.

Here, a case will be described in which a plurality of radio base stations are provided in a service area so that a mobile terminal can communicate while moving between them. In this case, if the wireless base station limits the slot for transmitting the control signal to only one slot in one frame, the mobile terminal receives a control signal from any one of the wireless base stations, and the mobile terminal does not specify the specific slot in one frame. All that is required is to receive the slot. At this time, in order to transmit the control signals with the same carrier frequency so that the radio base stations do not collide with each other, it is possible to configure a multi-frame with a plurality of frames and transmit the control signals with different frames. Good. By doing so, the mobile terminal can receive the control signal from any of the plurality of radio base stations by only receiving one carrier frequency in a specific slot for each frame.

When a radio base station is added, the control signal slot in each frame of the multi-frame is received, and the input is searched for a predetermined value or less. When there is a frame including such a slot, one of them is used as the control signal of the own station, and the control signal transmission is started using the control signal slot in the frame.

Further, the radio base station may stop transmitting the control signal for some reason and lose the information of the frame allocated for the control signal. This is called "system down". In this case as well, after removing the cause of the system down, in the same way as adding a new one, find the frame for transmitting the control signal of the own station, and use the control signal slot in that frame Control signals can be transmitted. Here, the state in which it becomes possible to search for a frame including a control signal slot whose input is equal to or less than a predetermined value by receiving radio waves from surrounding wireless base stations I did. "

[0006]

However, in such a case, when a plurality of radio base stations are simultaneously added or restored, the plurality of radio base stations transmit the control signal at the same carrier frequency and the same frame slot. Sometimes. When this happens, mutual interference occurs and the communication quality of the control signal deteriorates.

The present invention solves such a problem and a TDMA-T in which a control signal is not transmitted in the same slot even when a plurality of radio base stations are simultaneously installed or restored.
An object of the present invention is to provide a DD type wireless communication device.

[0008]

A radio communication apparatus of the present invention communicates with a plurality of mobile terminals by a time division multiple access system using a frame in which a transmission slot and a reception slot are time-multiplexed at the same carrier frequency. A plurality of radio base stations are provided, and each of the plurality of radio base stations uses at least one slot in the frame as a control signal slot, and uses the same carrier frequency to control signal slots of different frames to the mobile terminal. The means for transmitting the control signal and the control signal of the control signal when transmitting the control signal to the mobile terminal for the first time or after the transmission of the control signal is interrupted and the information on the control signal slot used by the own station is lost. One when the control signal slot is received and the reception level is below a predetermined value when transmission is restarted In a wireless communication device including a means for selecting a slot as a control signal slot to be transmitted by the local station, a plurality of wireless base stations respectively have different times after the wireless base station becomes operable. It is characterized by including means for activating the means for selecting after a lapse of time.

The time different for each radio base station may be determined in advance, or may be set randomly for each radio base station.

Each radio base station detects that the transmission of the control signal by the transmitting means is stopped, the information regarding the control signal slot used by the own station is lost, and the operation of the selecting means is stopped. It is preferable to include system down detection means and recovery detection means for operating the means for detecting and activating that the means for transmitting and the means for selecting become operable.

[0011]

After the rise time T elapses after it becomes operable with the radio base station, radio waves from surrounding stations are received, and a search for a slot free from interference is started. If the rise time T is set differently for each radio base station in advance, even if a plurality of radio base stations are added or restored at the same time, the slots are not searched at the same time. It is never selected as a slot.

The rising time T may be fixedly set in advance for each radio base station, but may be set randomly each time. When fixedly set in advance, it is possible to completely prevent a plurality of radio base stations from selecting the same slot, but since all the radio base stations are fixedly set, flexibility of expansion and replacement becomes poor. On the other hand, if the random setting is made each time, it is possible to add or replace without having to consider the rise time of each wireless base station. If the rise time T is set at random, there is a possibility that a plurality of radio base stations will be set to the same rise time, but the probability is very small and there is no practical problem.

[0013]

1 is a block diagram showing a radio communication apparatus according to an embodiment of the present invention, and FIG. 2 is an example of its frame configuration.
FIG. 3 shows the structure of a multiframe.

This wireless communication device comprises a plurality of wireless base stations connected to the fixed network 11, and each wireless base station is
Using a communication method (TDD) that time-multiplexes slots, which are units of transmission / reception signals that are multiple-accessed in a frame that is a unit of signal transmission by the time division multiple access (TDMA) method, within a communicable range It is possible to communicate with a plurality of mobile terminals located. Wireless base station
A control signal for transmitting information necessary for setting a line with the mobile terminal is transmitted.

As shown in FIG. 2, a plurality of n transmission slots and reception slots are provided in each frame, and at least one of the transmission slots and reception slots can be used as a control signal, and the remaining transmission slots and reception slots can be used. Is used for call signals. The control signals transmitted by each radio base station have the same frequency. A plurality of radio base stations combine a plurality of frames into a multi-frame as shown in FIG. 3, and use one of the transmission slots available for control signals in the frame.

The reception of the control signal is performed by the reception slot. The control signal uses a carrier frequency common to all radio base stations, and uses the remaining transmission slots and reception slots as speech signals. The call signal uses a carrier frequency other than the carrier frequency used for the control signal.

To determine which frame in the multi-frame the transmitted control signal is determined, the received signal in the slot is detected in the control signal slot of each frame in the multi-frame and the received signal is predetermined. A slot that is less than or equal to the specified value is searched, and one of the slots is defined as the slot for transmitting the control signal.

Here, the communication between one radio base station 12 and the mobile terminals 13 and 14 will be described. The radio base station 12 uses a predetermined slot, which is the first slot in this example, to transmit a control signal including information necessary for channel setting. F1 is used as the carrier frequency of the control signal. The radio base station 12 further
The call signal to the mobile terminal 13 is transmitted through the second slot, and the call signal to the mobile terminal 14 is transmitted through the third slot. A frequency different from f1 is used as the carrier frequency of the call signal. Further, the call signal is transmitted to the other mobile terminals using the fourth slot and thereafter.
The mobile terminals 13, 14, ... Transmit a call signal to the radio base station 12 after a predetermined time elapses from their reception slots. The radio base station 12 receives the signal from each mobile terminal at the reception slot position corresponding to the transmission slot in one frame.

FIG. 4 is a diagram for explaining the method of determining the control signal slot. Here, three radio base stations 41, 4
A case where the wireless base stations 44 and 44 have already been operated and the wireless base station 44 is newly operated will be described.

The radio base stations 41 to 43 use the same carrier frequency f1 for control signals and transmit control signals in different frames F1, F4, F6 (strictly, in control signal slots in each frame). . The radio base station 44 which is about to operate newly transmits radio waves from the surroundings to the carrier frequency f in each frame in the multi-frame.
The control signal slot received at 1 and whose input is less than or equal to a predetermined constant value is searched. If such a slot is found, the radio base station 44 determines that one of the slots is its own control signal slot and starts transmitting the control signal.

5 and 6 are diagrams for explaining a conventional system down recovery method, FIG. 5 shows a state before the system down, and FIG. 6 shows a state after the recovery.

In this example, before the system goes down, the radio base station 51 transmits the control signal at the carrier frequency f1 and the frame F1 (correctly, the control signal slot in the frame F1). 52 transmits a control signal at carrier frequency f1 and frame F6.

Here, the wireless base station 51 stops transmitting the control signal for some reason, and information about the control signal slot used by the own station, for example, the position of the frame assigned to transmit the control signal. Suppose you have lost information. This is the system down. In addition, the radio base station 51 which once falls into a system down again receives a radio wave from the surroundings at the carrier frequency f1 in each frame in the multiframe and searches for a slot whose level is equal to or lower than a predetermined constant value. When it becomes possible to do this, "the wireless base station 51 is restored"
Say.

Further, in the case where the wireless base station 51 goes down, and the wireless base station 52 goes down before the wireless base station 51 receives the control signal slot allocation again and starts transmitting the control signal, this is done. "Wireless base station 5
1,52 went down the system at the same time. " Also,
When the radio base station 51 is restored and the radio base 52 is further restored before the transmission of the control signal is started, the “radio base station 5
1 and the radio base station 52 were restored at the same time. "

When the radio base station 51 recovers, it receives radio waves of control signals from the surroundings in the multi-frame generated by itself, searches for slots whose input is below a predetermined constant value, and transmits. Decide which slot to play. Here, it is assumed that the slot is determined as the control signal slot of frame F3.

The problem here arises when the radio base station 51 and the radio base station 52 are down at the same time and are restored at the same time. In such a case, if one of the radio base stations 51 and 52 starts the transmission of the control signal and the other searches for a slot, the same frame F3 may be controlled in some cases, as shown in FIG. It may select the signal slot. In such cases,
Mutual interference of control signals occurs, and the communication quality of control signals deteriorates.

Therefore, in this embodiment, the rise time T is set when the radio base station detects the system down, and the restoration of the radio base station is detected after the system down state is detected. After the rise time elapses, the radio base station receives radio waves from the surroundings, searches for a slot that does not receive interference, determines the slot for transmitting the control signal, and starts transmitting the control signal. . The flow of this control is shown in FIG. 7, and the temporal flow is shown in FIG. The rising time T is defined as the time from when the radio base station detects the restoration to when the search for the slot is started. The state during which this time elapses is referred to as the "standby waiting state".

9 to 11 are diagrams for explaining the operation of system down recovery according to the embodiment of the present invention. Here, the operation of the three radio base stations 91, 92, 93 will be described.

FIG. 9 shows a state where all the radio base stations 91 to 93 are in operation. At this time, the wireless base stations 91 to 9
3 use the same carrier frequency and transmit control signals using the control signal slots of frames F1, F4 and F6, respectively. A multi-frame consists of 20 frames.

The radio base stations 91 to 9 due to some cause
When 3 systems are down at the same time and they are later restored at the same time, the wireless base stations 91 to 93 respectively set the rising time T of their own stations. At this time, the rising time T = T1 of the wireless base station 91, the rising time T = T2 of the wireless base station 92, and the rising time T = T3 of the wireless base station 93.
Is set. However, T1 <T2 <T3. Here, the rising time T is set to be random at each restoration, but the time may be fixedly assigned in advance.

FIG. 10 shows a state in which the radio base stations 91 to 93 are simultaneously restored and a time T4 of T1 <T4 <T2 has elapsed. At this point, the radio base station 91 receives a radio wave from the surroundings, searches for a control signal slot that is not interfered with, selects the control signal slot of the frame F5, and then transmits the control signal using the slot. To start.
The radio base stations 92 and 93 are in a stand-by waiting state because the rise time T has not yet elapsed at this point.

When the time T2 elapses after the simultaneous recovery, the radio base station 92 similarly searches for a control signal slot that is not interfered with and starts transmitting the control signal.

When time T3 elapses after the simultaneous recovery, the radio base station 93 similarly searches for a control signal slot that is not interfered with and starts transmitting the control signal.

FIG. 11 shows a state in which a time T5 of T5 >> T3 has elapsed after the synchronization is restored. By this time, all the wireless base stations 91 to 93 have transmitted control signals, and the system down recovery is completed and the system is in the operating state.

Although the recovery after system down has been described here, the same applies to the case where a plurality of radio base stations simultaneously start transmitting control signals.

[0036]

As described above, the radio communication apparatus of the present invention sets the rise times of the radio base stations so that they are different from each other, so that even if the radio base stations that are system down at the same time are restored at the same time, It is possible to prevent the radio base station from transmitting a control signal with the same carrier frequency and the same slot. Therefore, it is possible to prevent deterioration of the communication quality of the control signal.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing a wireless communication device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a frame structure.

FIG. 3 is a diagram showing a structure of a multi-frame.

FIG. 4 is a diagram illustrating a method of determining a control signal slot.

FIG. 5 is a diagram illustrating a conventional system down recovery method, showing a state before a system down.

FIG. 6 is a diagram illustrating a conventional system down recovery method, showing a state after recovery.

FIG. 7 is a diagram showing a control flow of the embodiment.

FIG. 8 is a diagram showing a temporal flow of control.

FIG. 9 is a diagram for explaining the system down recovery operation of the embodiment, and is a diagram showing a state in which all three wireless base stations are in operation.

FIG. 10 is a diagram for explaining an operation of system down recovery of the embodiment, showing a state in which three wireless base stations are simultaneously system down and then simultaneously recovered, and one wireless base station starts transmission of a control signal. Fig.

FIG. 11 is a diagram for explaining a system down recovery operation according to the embodiment, and is a diagram showing a state in which all three wireless base stations are transmitting control signals.

[Explanation of symbols]

11 Fixed Network 12, 41-44, 51, 52, 91-93 Radio Base Station 13, 14 Mobile Terminal

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04Q 7/34 7304-5K H04Q 7/04 B

Claims (2)

[Claims] 1. A plurality of radio base stations for communicating with a plurality of mobile terminals by a time division multiple access system using a frame in which a transmission slot and a reception slot are time-multiplexed at the same carrier frequency, and the plurality of radio base stations are provided. Each base station uses at least one slot in the frame as a control signal slot, means for transmitting a control signal to the mobile terminal by control signal slots of different frames using the same carrier frequency, and means for transmitting to the mobile terminal. When the control signal transmission is started for the first time, or when the control signal transmission is interrupted and information about the control signal slot used by the local station is lost and the control signal transmission is restarted, Control to receive one and transmit one slot whose reception level is less than or equal to a predetermined value In the wireless communication device including means for selecting as a signal slot, each of the plurality of wireless base stations has a means for selecting after a different time has passed since the wireless base station became operable. A wireless communication device comprising means for activating. 2. Each of the plurality of radio base stations stops transmission of a control signal by the transmitting means, loses information about a control signal slot used by the own station, and operates the selecting means. 2. A system down detecting means for detecting that the means has stopped, and a recovery detecting means for operating the means for starting by detecting that the means for transmitting and the means for selecting become operable. Wireless communication device.