JPH0229251B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a simple small-capacity wireless base station having a function of measuring interference conditions between call channels and reception level during a call, and a channel switching function.
The present invention relates to a mobile communication system that allows communication even indoors, in blind areas, etc. by distributing PRSs and has a high subscriber capacity.

In conventional mobile communication systems, the frequency is fixed to the radio base station PRS (for example, Kamata, Yoshikawa, and Sakamoto, ``Car Telephone Radio System,'' Tsuken Report)
Vol. 26, No. 7, 1977), when the traffic is small, such as when the system was introduced, a large zone covers the service area, and as the traffic gradually increases, the large zone is divided into smaller zones. A method (cellular method) is being used to improve the frequency utilization rate by increasing frequency repetition in a region (VHMacDcnald “The
Cellular Concept”BSTJ Vol.58, No.1,
1979).

That is, in conventional mobile communication, Z ₁ in FIG.
Areas with small traffic such as Z ₄ , Z ₅ , ..., Zn had a large zone, and areas with large traffic such as Z ₂ and Z ₃ had a small zone. In this case, one wireless base station PRS was placed in the center of each zone, and each wireless base station PRS was equipped with a plurality of transmitting and receiving devices with different frequencies.

For example, in Figure 5, zone Z ₁ with small traffic
In this case, m transmitting and receiving devices operating at different frequencies are placed in the center, and
In area Z ₂ , base stations each having a plurality of transmitting and receiving devices with different frequencies are placed in the center of small zones divided into Z ₂₁ , Z ₂₂ , and Z ₂₃ . Repeated use of the same frequency will result in zone Z ₁ and zones a certain distance apart.
The distance and location are determined by actual measurements to ensure that interference at _the same frequency (hereinafter simply referred to as interference) does not interfere with communication.

The conventional mobile communication system described above has the following drawbacks.

(a) When dividing zones, it is necessary to divide large zones into small zones in advance to avoid interference. However, in areas where a large zone before division and a small zone after division coexist, interference conditions become complicated, which limits the installation of wireless base stations and, therefore, limits the division of zones.

(b) When the system was initially introduced, small areas of traffic became large zones, making it difficult to provide mobile phone services using low-powered mobile devices. This is because when a low-power mobile device moves to the edge of a large zone, the radio waves of the low-power mobile device do not reach the wireless base station.

(C) In order to set up a service zone indoors or in a dead area, it is necessary to create a special shaped zone such as a long rectangle that does not interfere with the existing zone, and a special wireless base station must be designed. The system becomes complicated.

The present invention aims to eliminate these drawbacks by distributing and distributing simple, small-capacity wireless base stations that have a function of measuring interference conditions between call channels, a reception level during a call, and a channel switching function. This enables communication even in areas such as indoors and dead areas without the need for a special wireless base station.

Determination of the communication channel frequency in the radio base station PRS of the present invention will be explained below.

Here, to simplify the explanation, a case will be described in which the distributed radio base station PRS has a transmitting/receiving device for only one channel.

FIG. 2 shows the zone configuration in the present invention. The frequencies of all communication channels that are allowed to be used are divided into multiple subgroups (for example, S ₁ , S ₂ , S ₃ , S ₄ ), and within each subgroup, one channel is selected from among all channels while checking the interference conditions. Assign a call channel to use for calls. Frequency repetition is performed for each subgroup arrangement S ₁ , S ₂ , S ₃ , and S ₄ .

In this way, the frequency of the transmitter/receiver of the wireless base station PRS is the same as the frequency of the transmitter/receiver of one wireless base station, as in the conventional example shown in Fig. 5.
A feature of the present invention is that the frequency is not statically determined in the PRS, but can be dynamically accessed to any of all communication channels by changing the frequency at each distributed wireless base station. be.

At this time, the communication channel frequency to be used by each distributed radio base station PRS is based on the reception level from other radio base stations PRS, and the communication channel with the lowest interference level is selected by the peripheral control station PBS. determines and instructs each radio base station PRS.

In addition, in FIG. 2, multiple distributed radio base stations PRS are made to correspond to one peripheral control station PBS, and peripheral control stations PBS of subgroups S ₁ to _{S 4} are collected to form a central control station.
This shows the configuration accommodated in the PCS. Note that the central control station PCS is the unit of location registration of the mobile device PU.

Distributed radio base station PRS during call is control channel
Since CCH is not being transmitted or received, other portable PUs in this zone other than those currently on a call cannot make or receive calls. Therefore, in the distributed radio base station system according to the present invention, when the traffic increases, the PRS zone of one distributed radio base station is overlapped with another distributed radio base station PRS zone in a double or triple manner. You can freely arrange zones while Furthermore, since each distributed radio base station PRS has a frequency synthesizer and can access any of all call channels, other mobile devices PU that are in the zone of the distributed radio base station PRS that is in use can also make and receive calls. You will be able to do this. In addition, since overlapping zones are allowed even in indoor areas, blind areas, etc., which were previously difficult to handle, there is no need for transmitters and receivers that form specially shaped zones, and the service area can be expanded freely.

Next, an embodiment of the mobile communication system according to the present invention will be specifically described.

FIG. 1 shows the line configuration of the present invention. PU is a portable device,
PRS is a distributed radio base station. PBS is a peripheral control station,
PCS is the central control station.

Between the peripheral control station PBS and the radio base station PRS, there is one line each for up and down lines that share the communication channel SCH and the control channel CCH in a time-division manner according to the control sequence, the interference state of each communication channel, and the communication from the mobile device PU. The measurement results of the radio wave reception level are sent to the peripheral control station.
A total of three lines, including one monitor channel MCH, are provided for transmission to PBS.

Between the peripheral control station PBS and the central control station PCS, only the control line D ₁ CH is connected, and between the peripheral control station PBS and the switching station
Only the communication channel SCH is provided between PESs.

Figure 3a shows the configuration of the portable device PU.

The portable device PU includes a transmitting/receiving section, a frequency synthesizer,
It consists of a modulation/demodulation section, a control section, and a handset, and has the functions of making and receiving calls, switching channels, controlling transmission output, ending calls, and registering location.

FIG. 3b shows the configuration of the distributed radio base station PRS.

The distributed radio base station PRS is composed of a control section, a transmitter/receiver section, a monitor section, a frequency synthesizer, and the like. When the transmitting/receiving unit is not making a call or measuring the interference state, it switches the frequency synthesizer to the frequency of the control channel CCH by a signal from the control unit, and broadcasts position information and uses the control channel CCH. Receiving registration signals, calling all at once,
Sends and receives signals related to control such as call channel SCH designation. On the other hand, during a call, the frequency synthesizer is set to the call channel SCH by a signal from the control unit.
transmits and receives modulated audio signals.

The monitor unit measures the reception level of each communication channel at regular intervals (this is called searching) and sends the results to the peripheral control station PBS via the monitor channel (MCH).

Here, each communication channel SCH in the distributed wireless base station PRS, which is one of the major features of the present invention, is
This section explains how to measure the interference level of , and the reception level of the mobile device PU during a call.

For example, as shown in Fig. 4a, subgroup S ₁
When each radio base station PRS in the network is not making a call, its frequency synthesizer switches to the control channel CCH transmission/reception state (CCH transmission/reception).

Next, at regular intervals of T seconds, the frequency synthesizer is sequentially switched to the frequency of each speech channel SCH used in this subgroup _S1 , and the reception level of each speech channel is measured by the monitor section.

FIG. 4a shows the output of the monitor section.

FIG. 4b shows that 1CH of the communication channels SCH is being received at a high level, and the other communication channels (2CH to mCH) are being received at low levels. This indicates that the call channel (1CH) is used for a call within the subgroup _S1 , and the reception level of the mobile device PU during the call at the distributed radio base station PRS is _I1 . If this communication channel (1CH) is to be used for a telephone call, the interference wave level I ₁ will be too large and will have a negative effect on the telephone call.

The call channel (2CH) is the corresponding subgroup S ₁
Although it is an empty channel within S 1, the frequency is used for calls within another subgroup S ₁ where the frequency is repeatedly used, so there is a slight interference level.
This shows that I have passed the exam at I ₂ . Similarly, the communication channel mCH also has an interference level Im. That is, the communication channels (2CH to mCH) are not used for communication within subgroup _S1 , but are used for communication in other subgroups whose frequencies are repeatedly used. The radio base station PRS sends the measured interference level values I ₂ , I ₃ , . . . Im to the peripheral control station PBS.

The radio base station PRS returns to the control channel CCH transmission/reception state (CCH transmission/reception) for the next T seconds. After T seconds, the device enters the search state again and measures the reception level of each communication channel (SCH).

In this way, the radio base station PRS alternately repeats the transmission/reception state (CCH transmission/reception) and the search state in which the reception level of each speech channel (SCH) is measured.

Under such conditions, the mobile device is activated while the control channel CCH is operating as shown in Figure 4a.
If a call is made from the PU, the peripheral control station PBS
Now, compare and judge the interference level values I ₂ , I ₃ , ...Im sent from the radio base station PRS, and judge that the interference level I ₃ of the communication channel (3CH) is the smallest,
Instruct the wireless base station PRS to switch the call channel to 3CH.

When the call channel is switched to 3CH and the call state is entered, the monitor unit starts measuring the reception level from the mobile device PU during the call. The output of this monitor section is transmitted to the peripheral control station PBS via channel MCH.

Figure 3c shows an example of a peripheral control station PBS.

The decoder DEC ₂ reads the radio circuit interference level, reception level, etc. sent from the radio base station PRS through the monitor channel MCH, and stores it in the RAM via the buffer register. The central processing unit CPU processes these data and sets a new call channel SCH and controls the transmission output of the channel in use.

Figure 3d shows the configuration of the central control station PCS. The central control station PCS transmits location registration information and relays data exchange between peripheral control stations PBS. Relay decoder DEC ₄ reads location registration signals, call signals, call termination signals, etc. sent via D ₁ CH.
Store in RAM.

The encoder ENC ₅ encodes these location registration signals, calling signals, call termination signals, etc., and transfers them to the switching center PES via the D ₂ CH.

Also, the decoder DEC ₅ receives D ₂ CH from the exchange PES
It reads location registration acceptance signals, incoming call signals, call termination signals, etc. sent via the .

On the other hand, the central processing unit CPU refers to these signals and the contents of the RAM, and selects the corresponding peripheral control station.
Transmit via encoder ENC ₄ and D ₁ CH to PBS.

FIG. 3e is a diagram showing the configuration of the exchange PES.

The switching center PES has an interface with the existing network, and uses the switching network to selectively connect and open the communication channels SCH to each other and the communication channels SCH to the existing network lines. Also D ₂ CH
In addition to updating the subscriber memory using the location registration information sent via _the The memory is controlled and operated using a controller.

With the configuration and operation described above, the present invention has the following effects.

(i) Radio base stations PRS do not measure the amount of interference in each communication channel in advance and place the station, as in the past, but instead measure the interference status during operation after setting up the station and select channels that can be used. Restrictions on stations will be relaxed.

(ii) Radio base station PRS covering a small area
Since this is a method of distributing the devices, it is possible to provide mobile services using low-power mobile devices from the beginning of the system.

(iii) Distributed wireless base stations for increasing traffic
This can be addressed by sequentially increasing PRS.
Therefore, there is no need to modify the existing large-capacity radio base station PRS to a small-capacity radio base station as in the past in response to an increase in traffic.

(iv) In the conventional method of dividing a large zone into small zones, if the zones are made very small, radio waves of the same frequency from other zones overlap in one zone due to geographical conditions such as buildings, causing interference. However, in the method according to the present invention, a channel with less interference is selected for each communication channel, so a different frequency can be used at a short distance, and communication may be interrupted. Never.

(v) In the distributed base station system of the present invention, the zones of a plurality of radio base stations PRS overlap to form a zone, so a plurality of portable devices PU in one radio base station PRS can communicate.

(vi) Since all radio base stations PRS can have the same configuration, mass production is possible and common spare equipment can be prepared. In addition, since the radio base station PRS has the same configuration and is smaller, it can be used anywhere.
For example, it can be installed on the roof of a building or on a utility pole, and the interface of the peripheral control station PBS is only three lines, one each for the upper and lower S/C channels and one line for the monitor channel, so the wireless base station PRS It is also possible to easily replace it by using a connector type.

(vii) In the present invention, when each radio base station PRS is in a call, it measures the transmission level of the mobile device PU during the call, and when it is not in a call, it searches for other mobile devices at regular intervals. The transmission level of the machine PU is measured and sent to the peripheral control station PBS.

Therefore, the peripheral control station PBS collates the PU transmission output level of each mobile device from each wireless base station PRS, and transmits the mobile device at a level higher than necessary.
For a pair communicating between a PU and a radio base station PRS, it is determined that the two are talking very close to each other, and the control unit sends instructions to each transmitter to limit the transmission output of either or one of them. It can also have a function of issuing a control signal. This makes it possible to further reduce the level of co-frequency interference with other regions, and to improve the geographical efficiency of frequency use.

(viii) In addition, in conventional mobile communication systems, the control channel
The CCH is provided independently from the speech channel SCH, and no matter how low the traffic is, the control channel CCH and the speech channel
Two types of SCH transmitting and receiving equipment were required at the base station.

However, in the present invention, as shown in FIG. 3b, one transmitter/receiver can perform the functions of both channels, so the equipment configuration of the radio base station PRS is simplified and the radio base station becomes more economical.

In the present invention, the effect when the radio base station PRS has a one-channel transmitter/receiver is described, but the same effect occurs even when the radio base station PRS has two to several channels.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a station configuration of a mobile communication system according to the present invention, FIG. 2 is a diagram showing an example of a zone configuration of a mobile communication system according to the present invention, and FIGS. 3a to 3e are configurations of a mobile device and each station according to the present invention. A diagram showing an example, Figure 4
FIG. 5 is a diagram showing the search state of the received signal and the monitor unit output in the distributed wireless base station of the present invention.
FIG. 2 is a diagram showing a station configuration of a conventional mobile communication system. PU...Mobile device, PRS...Wireless base station, PBS...
...Peripheral control station, PCS...Central control station, PES...Switching station.

Claims (1)

[Claims] 1. A wireless base station equipped with a transceiver capable of transmitting and receiving frequencies of all assigned channels.
Multiple PRSs are distributed, and each radio base station PRS measures the interference signal level of all call channels at regular intervals with a monitor unit, and transmits the measured interference signal level to the peripheral control station PBS via the monitor line MCH.
The peripheral control station PBS refers to the interference signal level and selects the communication channel of the frequency with the lowest interference signal level to the wireless base station PRS.
A mobile communication system that is characterized by being assigned as a call channel. 2 The peripheral control station PBS refers to the transmission level from each mobile device PU during a call measured by each wireless base station PRS, and determines which pair of mobile device PU and wireless base station PRS is communicating with a transmission output higher than necessary. 2. The mobile communication system according to claim 1, wherein the transmission output of at least one channel is controlled to reduce interference with other communication channels. 3. The mobile communication system according to claim 1, wherein the transceiver of each radio base station PRS transmits and receives both a communication channel and a control channel in a time-division manner.