JPH07123317B2 - Connection control method in mobile communication - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection control method for mobile communication, which can improve local frequency repetitive use efficiency without giving co-channel interference.

[0002]

2. Description of the Related Art In car telephones, the channels used by the base stations are predetermined for each base station, and these channels are repeatedly used by the base stations that are separated by a distance that does not cause interference, thereby making effective use of frequencies. I am trying to The level of radio waves received by mobile communication fluctuates over a wide range depending on the location of the mobile device, and as a result, co-channel interference from channels repeatedly used at a distance may exceed an allowable value. For this reason, the repetition distance is set so that the probability of interference deterioration caused by the fluctuation is equal to or less than a certain value. However, this means that most of the communication (of which the ratio of "1-the above-mentioned deterioration probability" out of the whole communication) is used under the interference condition of the allowable interference amount or less. In other words, depending on the channel, even though it can be repeated at a closer distance, it is repeatedly used at a far distance. Since such a method of using the channel is performed under a predetermined repeating condition, it can be called a centralized control method.

On the other hand, in a cordless telephone or the like, as a channel used for communication between a base station and a mobile device, a channel having a reception level below a certain level is found out from all channels provided to the system and the channel is used. Select and use. In this method, instead of predetermining the distance to be repeatedly used, if the interference condition allows, it is repeatedly used on the channel used by the adjacent base station, and conversely if the interference condition is severe, it will be used by the distant base station. Do not use it repeatedly for the channel you are using. That is, channels with an allowable interference amount or less can be automatically selected and used, which has the advantage of improving the channel repetition efficiency.
Such a method of using the channel is not a plan in advance but is decided and used by each base station according to the situation at that time, and thus can be called a distributed autonomous control method.

[0004]

However, in this distributed autonomous system, the interference condition is checked only by the base station or the mobile station which originates a call and newly allocates a channel. It was not possible to determine whether the new channel assignments would interfere with existing calls. In other words, it is guaranteed that there will be less interference when using a certain channel, but there may be cases where other base stations or mobile stations using this channel will receive more than acceptable interference. . This is because the amount of interference I receive and the amount of interference I receive do not always match.
Therefore, to prevent this, when checking the interference condition,
It is necessary to provide a margin for the allowable interference wave level so that it can be used only at a lower interference wave level. For example, an acceptable interference wave level (for example, 20
dBμ) and the difference between the amount of interference received by the user and the amount of interference given by the user (stochastic variation depending on the location of the mobile device), which is the possible worst value (margin, eg, 10 dB) 1
The interference check condition is 0 dBμ, and if the interference wave level of the channel to be used is 10 dBμ or less, the channel is used, but if it is 10 dBμ or more, the use of the channel is abandoned. If it is not necessary to consider other interference, this value is 20 dBμ, and therefore, the reuse efficiency is reduced by 10 dB.

As described above, in the conventional distributed autonomous control, when a channel is assigned to a new call, the amount of interference given to other calls using the same channel is unknown, so that the worst case is assumed. It was determined that the channel could be used only when the interference wave level received on the channel to be allocated was extremely low. Therefore, the advantage of distributed autonomous control, which is the advantage of improving local repetition, has not been fully exerted.

According to the present invention, when a channel is allocated to a new call, not only the amount of interference received by itself but also the amount of interference given to another call using the channel is below an allowable value. By confirming that there is something and using it, it is intended to improve the efficiency of spatial repetitive use of the channel to the limit where interference is always allowed.

[0007]

[Means for Solving the Problems] When allocating a channel to a new call, whether or not the amount of interference received by the user is below an allowable value is checked by a radio wave received on a channel to be allocated as usual. The level of the interference wave (that is, the interference wave for a new call) is measured, and it is determined whether this level is equal to or less than a predetermined value. When a channel is assigned to a new call, the amount of interference given to a call that is already using this channel is measured, and it is determined whether this amount of interference is also less than or equal to the allowable value. Make sure they are there before assigning channels.

Therefore, the mobile station or the base station or both of them (which will be referred to as a first wireless station group) in which a new call has occurred have a reception level of a certain value or less among all channels. The channel or the channel with the lowest reception level is selected as a candidate for the communication channel. Next, a communication start signal is transmitted to the partner station on this channel for a fixed time. The first wireless station group has a function of gradually changing the transmission power, and the communication start signal is first transmitted at the minimum transmission power, and the transmission power is gradually increased to the maximum value as described later. Up to. The partner station transmits a communication start confirmation signal when the communication start signal is received at a level higher than the reception level required for communication. The first wireless station group first transmits from the minimum level and gradually increases the transmission level, so the transmission power when the communication start confirmation signal is first received is the minimum required transmission required for communication. It will be electricity. Therefore, the first wireless station group stops the transmission of the communication start signal at the time of receiving the communication start confirmation signal from the partner station, and starts the communication with the transmission power at that time.

Another base station or mobile station that is communicating using the channel thus selected will receive this radio wave as an interference wave. Communication partner of the first wireless station group (this is called the second wireless station group)
The station in communication measures the amount of interference received in the channel in communication at regular intervals, encodes the result, and transmits it as an interference amount notification signal together with the communication signal in the channel in communication.

The first wireless station group stops transmitting after transmitting a radio wave for a certain period of time, and then within a certain period of time, an interference amount notification signal from a communicating station in the second wireless station group and a communication partner. It is determined whether or not a communication start confirmation signal from the station is received. If not received, the transmission power level is increased by one step and the communication start signal is transmitted again. If the interference amount notification signal is not received or the amount of interference represented by it is less than or equal to a predetermined value even if received, and when the communication start confirmation signal is received, at the transmission power level at that time,
Use the selected channel for communication as it is.

When the interference amount notification signal indicating that the interference amount is equal to or greater than a predetermined fixed value is received, or when the communication start confirmation signal cannot be received even if the signal is transmitted at the maximum transmission power, the selected channel is selected. Give up and choose another channel or give up on the communication itself.

[0012]

In this way, when a new call occurs and a channel is assigned, the transmission power can be set to the required minimum, and it is confirmed that the amount of interference that the user receives is below the allowable value, and that channel is If you use it, you can also check whether the amount of interference received by other mobile stations or base stations that are already using that channel is less than or equal to the allowable value, so you do not need to consider the margin when checking interference conditions, The frequency can be used repeatedly until the limit is allowed by the interference condition.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is the most simplified explanatory view of a mobile communication system in which base stations 1 and 2 constitute radio areas 3 and 4, and mobile stations 5 and 6 in the respective radio areas. Communicate with base stations 1 and 2.

As shown in FIG. 2, the structure of the mobile unit is an antenna 7, a transmitter 10, a receiver 9, a duplexer 8, a synthesizer 1 for supplying a local oscillation frequency to the transmitter and the receiver.
1, a control circuit 12, a transmitter 13, and a receiver 14.

Similarly, as shown in FIG. 3, the base station includes an antenna 15, a transmission / reception sharing device 16, and transmission / reception devices 17, 18, 1.
9, 20, and a control device 21. The control device 21 of the base station is further connected to the exchange through a transmission line, but it is omitted in the figure. Transmitter / receiver device 17, 18, 19,
20 is composed of a transmitter, a receiver, and a synthesizer as in the case of the mobile device. The transmitter / receiver 17 is a control channel transmitter / receiver described later, and 18-20 is a communication channel transmitter / receiver. 18-20 has a function of changing transmission power stepwise and transmitting.

It is now assumed that the base station 1 and the mobile device 5 are in communication using the channel N1. The mobile device 5 is communicating with the base station 1 in the format shown in FIG. 22 and 24 are communication signals such as voice signals, and 23 and 25 are interference amount notification signals. The communication signals 22 and 24 are composed of a plurality of bits, but include check bits specially prepared for the present invention. That is, FIG. 5 (22, 24 in FIG. 4)
The inside of the) is a check bit, which is a check bit, and it is inserted at a certain place between the unhatched bits. The check bit is a certain code such as all "1" or "0" or repetition of "1" and "0". If there is interference in this channel, a code error will occur, but this error will naturally occur in the check bits as well. Since the code of the check bit is known in advance, this error can be easily detected. The mobile unit 5 measures the number of check bit errors in 22 or 24, encodes the measurement result, and transmits it in 23 or 25. That is, the mobile device measures a code error during a fixed time T1 corresponding to a frame, encodes the number of errors, and transmits it as an interference amount notification signal in the direction of the base station via the channel in communication. At this time, a code error occurs not only when receiving interference, but also when the reception level of the mobile terminal itself is lowered. In order to measure only the code error due to the interference, for example, it may be determined that the error due to the interference occurs only when a code error occurs even though the reception level is a certain value or more.

The operation when the base station 2 and the mobile unit 6 start communication will be described with reference to FIG. The wireless channel is divided into a control-dedicated channel (this is called a control channel) and a plurality of communication channels, and each base station intermittently sends a signal including its own identification number to the control channel transceiver 17. . The mobile station receives the control channel while waiting, and always selects the base station that receives the highest level.

When an incoming call arrives at the mobile station 6 from the fixed exchange via the base station 2, the base station controller 21 selects a transceiver (eg 19) which is not in use among the transceivers 18, 19, 20 for communication. The communication channel is selected and the communication channel is sequentially switched to 19 for reception, and the reception level is measured. Among these communication channels, a channel having the minimum reception level or a channel having a fixed value or less (this is referred to as channel N2) is selected. Next, the base station control device 21 causes the mobile device 6 to transmit a channel switching signal to the channel N2 via the control channel transmitter / receiver 17, and causes the transmitter / receiver device 19 to be constant in the channel N2 with the minimum transmission power. Time T2
The communication start signal is transmitted during the period. The fixed time T2 may be selected to be, for example, about twice as long as the frame 22 or 24 of the communication signal.

When the mobile station 6 receives the channel switching signal, it switches to the designated channel N2 and also monitors whether or not the communication start signal is received at a predetermined level or higher on the switched channel. If received, it transmits a communication start confirmation signal to the base station 2.

On the other hand, the other mobile station using the channel N2 causes interference by the signal transmitted by the transmitter / receiver 19 as described above, and if a code error is detected, it is 23.
Alternatively, it is displayed on 25. The base station 2 transmits a signal for a fixed time T2 and then transmits a signal 2 for a fixed time T3.
Check if 3,25 can be received. The fixed time T3 may be selected to be, for example, about twice as long as the frame of the communication signal. When the base station 2 receives the interference amount notification signal indicating that the interference amount is equal to or greater than a predetermined fixed value, the base station 2 immediately gives up the use of this channel and re-selects another channel as a candidate channel. And repeat the same operation.

When the interference amount notification signal indicating that the interference amount is equal to or greater than a predetermined value is not received and the communication start confirmation signal is received, the base station 2
Transmits a communication permission signal at the transmission power level at that time and starts communication with the mobile device 6. When the communication start confirmation signal is not received, the control device 21 causes the transmission / reception device 19 to increase the transmission power by one step and then transmits the communication start signal again. The following operation is the same as the operation already described. If the communication start confirmation signal cannot be received even when the transmission power of the base station 2 is increased to the maximum, the use of the selected channel is abandoned and another channel is selected again.

Since the interference amount notification signal is a signal that arrives from a distant mobile unit, it is generally received at a lower level than the communication start confirmation signal. Therefore, the interference amount notification signal is transmitted at a timing that does not collide with the communication start confirmation signal. There is a need. This can be easily realized by predetermining the transmission timing of each signal when the base station is operating at the synchronization timing, and even when the synchronization is not achieved, for example,
The mobile station transmits a communication start confirmation signal immediately after receiving the communication start signal, and the base station immediately after transmitting the communication start signal (that is, communication from the mobile station 6) when the base station can receive the interference amount notification signal of the N2 channel interference wave. The transmission timing of the communication start signal may be adjusted so that the transmission timing of the start confirmation signal) and the timing of the interference amount notification signal do not overlap.
(If the base station cannot receive the interference amount notification signal, it means that there is no interference. In this case, the communication start signal may be sent at an arbitrary timing.)

The above control operations are summarized in FIG.

In the above description, the base station transmits a signal for a certain period of time and the mobile station measures the amount of interference. However, the roles of the mobile station and the base station may be reversed, or the mobile station and the base station may be reversed. Signal transmission and interference measurement may be performed at both stations.

Further, although the method of performing the interference detection by the error of the digital signal has been described, the invention is not limited to this, and it is possible to detect the degree of deterioration of the eye pattern caused by the interference, the jitter, etc., and the envelope caused by the interference in the analog method. The amount of interference can also be detected by the method of detecting the beat of a line.

[0026]

As described above, since the channel is assigned after checking the amount of interference on both the side where the call originates and the side during communication, the call during communication is interfered with more than the allowable amount. Since there is no need to give a margin to interference more than necessary because there is no fear of giving interference, the channel can be repeatedly used at an optimum distance as long as the interference allows. Further, since the transmission power can be set to the minimum required value, it is possible to minimize the transmission of interference radio waves to others.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a mobile communication system.

FIG. 2 is a configuration example of a mobile device.

FIG. 3 is a configuration example of a base station.

FIG. 4 shows a format of a signal transmitted from a mobile device.

5 is a detailed view of 22 or 24 of FIG.

FIG. 6 is a diagram showing a control operation of the present invention.

[Explanation of symbols]

 1, 2 Base station 3, 4 Wireless area 5, 6 Mobile device 7, 15 Antenna 8 Transmitter / receiver 9 Receiver 10 Transmitter 11 Synthesizer 12 Control circuit 13 Transmitter 14 Handset 16 Transmitter / receiver shared device 17, 18, 19, 20 transmitter / receiver 21 control device 22,24 communication signal 23,25 interference amount notification signal

Claims (1)

[Claims] 1. A mobile communication system in which a plurality of base stations are dispersedly installed in a service area, and each base station selects one from a plurality of common channels and uses it for communication with a mobile device. In the first wireless station group of at least one of the base station and the mobile station, when a new communication channel is allocated to the communication partner station, the reception level of the communication start signal transmitted from the partner station is used for communication. If the level is equal to or higher than the required level, a communication start confirmation signal is transmitted on the communication channel, and the amount of interference received on the communication channel after the communication is started is measured for a first fixed time period, and in addition to the communication signal, An interference amount notification signal indicating the amount of interference is transmitted through the communication channel, and the second wireless station group, which is a communication partner of the first wireless station group, has means for transmitting the signal by gradually changing the transmission power. Have and newly allocate communication channel The second wireless station group, which has been required to establish a connection, sequentially switches and receives a plurality of communication channels and measures the reception level on the channels, and the channel whose reception level is less than or equal to a predetermined value or the reception level is The lowest channel is selected, the transmission power is changed stepwise from the lowest level transmission power of the transmission power to the highest level transmission power in the selected channel, and the second constant is set at each stage. A condition for transmitting a communication start signal for a period of time and not receiving an interference amount notification signal indicating that interference of a certain value or more has been received during a third certain time period after the transmission of each of the above steps; When the condition for receiving the start confirmation signal is satisfied, the communication is started at the transmission power level at that time on the communication channel, and when the interference amount notification signal indicating that the interference of a certain value or more is received is received. Is Connection control method in the mobile communication at the time of, characterized in that stop using the communication channel.