JP2823938B2 - Radio channel control method for mobile communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) TECHNICAL FIELD The present invention relates to mobile communication using a small zone configuration.
The present invention relates to a communication method and system that constantly secures incoming and outgoing calls with a mobile terminal from an arbitrary location in a service area and satisfies the communication quality of a mobile terminal during communication. The present invention relates to a communication system that is excellent in communication quality, communication quality, wireless line control capability, and the like.

(2) Conventional technology and its problems There is a high demand for a mobile phone service that can move anywhere in a service area to make and receive calls. Nippon Telegraph and Telephone Corporation (NTT) has developed a small portable device using the wireless switching network of the automated telephone system to provide a wide area mobile phone service.

On the other hand, with the spread of cordless telephones, the cordless telephone system has been expanded, and a private mobile telephone system in a limited area can be realized as a system cordless telephone as shown in FIG. This uses the 250 / 380MHz band frequency, has 89 channels including control channels, and has a service radius of 50m for duplex using a small antenna power of 10mW.
It is of the small zone type (micro zone type). As shown in FIG. 1, this system comprises, for example, a radio system controller 10, fixed radio stations A to N, and mobile phones a to n. Each element of this configuration will be briefly described.

* Mobile phone: has the function of accessing a fixed wireless station wirelessly and automatically performing location registration with the fixed wireless station or the wireless control device. It has a function of registering a location with another fixed wireless station or a radio system controller as the mobile phone moves, and changing the location registration. The outgoing / incoming call operation can be performed from any place in the service area.

* Fixed radio station (FRS): A downlink signal from a radio system controller is converted into a radio signal and transmitted to a mobile phone so that incoming calls and calls can be made. On the other hand, a transmission operation and a communication by transmission can be performed by receiving and demodulating an uplink wireless signal from a mobile phone and transmitting the signal to a wireless system control device by wire.
Also, it sends out a notification signal necessary for location registration.

* Radio system controller (RCE): The radio system controller transmits and receives a fixed radio station that covers the radio zone where the mobile phone is located and the extension of the private branch exchange PABX that has a one-to-one relationship with the mobile phone. A device that connects to form a communication path. In some systems, the radio system controller itself has an exchange function.

In this way, a mobile phone system can be realized at hand. These systems have not yet been provided with a nationwide Internet service, but have been actively used in limited areas such as limited buildings. When a large number of people start using a mobile phone at the same time in a limited area, wireless traffic naturally increases, and a situation arises in which connection is difficult. In order to solve this, there have been cases where a plurality of transceivers are incorporated in a fixed wireless station.

A fixed radio station FRS in which a plurality of transceivers are incorporated may transmit a plurality of radio waves at the same time.

In such a case, transmission intermodulation occurs. Therefore, consideration must be given to the channel arrangement.

Intermodulation refers to the generation of a signal of a third frequency different from the input signal frequency when multiple signals are input to a circuit having nonlinear characteristics such as a transmitter or a receiver. Is called an intermodulation wave. The intermodulation wave is sometimes called IM for English Intermodulation.

The level of the intermodulation wave is sufficiently lower than the level of the input wave causing the intermodulation wave. However, in mobile communication, the base station reception level varies greatly depending on the position of the mobile device,
Various levels of signals have been received, from very high level signals to very low level signals. For this reason,
Interference occurs when an intermodulation wave generated in a base station receiver or the like by a signal of a high input level matches the frequency of a low input level signal from another mobile station. Also, when receiving a mobile station, if an intermodulation wave of a frequency not used by the base station is generated inside the mobile station due to a high-level signal of the base station transmission wave, the mobile station transmits the intermodulation wave to the base station. Misunderstanding as a wave is a problem.

Now, when inputting the signal f ₁ and f ₂ to the non-linear circuit, the frequency f _i of the intermodulation wave generated _{is, f i = | m · f} 1 ± n · f 2 | (m, n is a positive integer ). m + n is called the order of the intermodulation wave. In mobile communications, the system bandwidth is small compared to radio frequencies,
The problem is that f ₁ −n · f ₂ and n = m ± 1. This can be easily understood from the fact that the intermodulation wave is outside the system band, for example, in the case of the 80 MHz band and in other cases, such as the 1600 MHz band and the 2,400 MHz band. Further, since the generated intermodulation wave has a higher level as the order is lower, the third order intermodulation having the lowest dimension satisfying the above condition, that is, the intermodulation in the form of 2f ₁ -f ₂ becomes a practical problem. In addition to the above-described two-wave input, the third-order intermodulation has a form of f ₁ + f ₂ −f ₃ which is generated when three waves f ₁ , f ₂ , and f ₃ are input. One is the problem.

As an easy-to-understand example, assuming that 10 waves (= channels) are allocated at equal intervals to the mobile communication system, examples of channel combinations in which the third-order IM does not occur are 1, 2, 5, 7
Are only four channels. The third channel generates IM at f ₁ = channel 2 and f ₂ = channel 1 in the equation 2f ₁ −f ₂ . The fourth channel IM occurs in f ₁ = channel 2, f ₂ = channel 7, f ₃ = channel 5 by the equation f ₁ + f ₂ -f _3. In the other 6, 8, 9, and 10 channels, similarly, IM occurs in a combination of 1, 2, 5, and 7 channels.

 For example, FIG. 2 will be described.

FIG. 2 shows two FRSs with three sets of transceivers each for three channels in close proximity and four portables. Each of them is the # 1 portable device and the channel is FRS-1 Connected by # 2 portable device is also FRS-1 and channel Connected by # 3 handset near FRS-1 is a channel Is connected to FRS-2. In this system, it is assumed that 10 wireless channels are provided at equal intervals. Under such a condition, the portable device # 4 is likely to make or receive a call near the FRS-1. Conventionally, FRS-
1 detects 2,4,5,
It knows that a total of 7, 8, 9, 10 and 7 channels are empty. Since the IM is not considered, any of the channels may be used, and thus it is assumed that channel 2 is selected. When the FRS-1 transmits the radio wave to the channel 2, the IM wave is transmitted to the three channels together with the radio wave of the channel 1 which has already been transmitted.
There was a problem of interfering with the 3-channel call between the S-2 and the portable device # 3. , The call quality was degraded.

(3) Object of the Invention The present invention is directed to an IM that is generated when a fixed wireless station incorporating these wireless units attempts to transmit a plurality of radio waves.
An object of the present invention is to provide a radio channel control method of a mobile communication system capable of performing comfortable communication without IM by avoiding disturbance by waves as much as possible.

(4) Configuration and Operation of the Invention The first embodiment of the present invention relates to a channel of an IM wave generated when a plurality of radio waves are transmitted from one fixed wireless station (hereinafter referred to as a channel).
Examine the C _i), the C _i when another station was using,
Investigate the radio waves of other channels so as not to cause interference by IM, and transmit the radio waves.

Here, an example of a fixed wireless station transmitting a plurality of radio waves is shown in FIG. In this example, there are three transceiver units,
Each right hand is connected to an antenna via an antenna distributor. The left hand is connected to the wireless controller via the network controller.
The lower part is connected to a common controller, which is further connected to a storage unit.

 FIG. 4 shows an example of the processing flow at this time.

Referring first to have landing or incoming -1, the controller of the fixed radio station to the first radio unit, to set the C ₁ channel, receives whether the C ₁ channel is empty, determines. If the channel is blocked, another channel is set and it is determined whether the channel is empty. Knowing that the channel is vacant, the call stores the C ₁ channel -
Move to 1.

Next, when there is a second or third call or incoming call-2, the control unit of the fixed wireless station designates the second wireless unit. The control unit sets a channel for the second wireless unit. When this channel is blocked, another channel is set and it is determined whether or not it is empty. After dealing with this channel as the second of the scheduled channel C _2. Here, the channel C ₁ of the first radio unit ever is sent to calculate the channel C _i generated by the IM in the case where the second wireless unit has sent a C ₂ channel plan to use at the same time. The C _i channel is customary to multiple occurrences within all the channels that are allowed to to check for all.

If in use any one of the plurality of C _i, it means that disturb by issuing a wave of C ₂ that the setting, the C ₂ channel radio can not be delivered. Therefore, C ₂
After re-setting the channel and judging whether it is empty, calculate the IM wave C _i channel with the C ₁ wave, and if all C _i are empty, change the C ₂ channel from the scheduled to the execution channel, and Make settings. Storage unit of fixed radio station stores this C ₂ channels. This storage is because the third radio is specified, using the calculation of IM when the third channel C ₃ is scheduled.

If the C _i channel by C ₂ channel scheduled to when it was occupied even one examines all, it is only necessary to stop the non-turning line setting out a busy tone. As a result, it does not interfere with other wireless stations.

FIG. 5 shows the flow of the second embodiment of the present invention. Fifth
After setting the first C ₁ channel as in the fourth figure in FIG., The second channel (this time CE) different methods to set. After the first of the C ₁ channel has been set, when an attempt is made to set the second channel, try to examine the use presence or absence of all the radio channels. This checked state is stored in the check file of the storage unit. It picked only empty channel among the stored channels, with a C ₁ channel has already sent this empty channel, then the second radio channel CE delivering
Toko of CE, determine whether fit into an empty channel, which examined IM channel made of a C _1. This may be calculated, but a table calculated in advance may be used, and the determination may be made with reference to this table.

In this way, when a transmittable channel CE is found, channel setting is performed, and the call shifts to call-2. This channel CE stores in the storage unit that it is in use to calculate the IM when setting up the third radio link.
The same applies to the case where the third non-turn line is set.

FIG. 6 shows the flow of the third embodiment of the present invention. In this embodiment, the level of the IM wave transmitted from the fixed wireless station is
Although it depends on the performance of the hardware, the transmitted IM wave does not reach a distant place because it is several tens of dB lower than the fundamental wave. Therefore, if the signal of the mobile station received by the fixed wireless station is weak, the mobile station is located far from the fixed wireless station, and the IM wave does not interfere with other mobile stations communicating distantly.
Therefore try to receive a C _i channel for generating computationally IM determines available since no disturbing if below a level where there is a signal of the channel, but to proceed with the following processing. This method reduces the condition of the no-turn busy because the available channels are widened.

When considering IM, if a table in which IM does not occur is held in advance as shown in Table 1, it is not necessary to calculate each time, and this table is stored in the storage unit in FIG. Good.

A fourth embodiment of the present invention will be described. 1st fixed radio station
Wireless unit 1 is talking on channel 1 and wireless unit 2 is talking on channel 2. Since the third wireless unit has not yet set up a wireless line, the receiver switches the channels variously and sends the channel usage status as data to the storage unit every moment. Here, a receiver for checking the use status of this channel may be a dedicated search receiver instead of the receiver of the third wireless unit. The fixed radio station generates an IM wave on the third channel when the radio units 1 and 2 transmit radio waves of one channel and two channels, respectively. When the radio wave of the third channel is strong in the search receiver, this means that this mobile station has approached the fixed wireless station, and is subject to interference from the first and second channels. Therefore, the common controller checks the strength of the radio wave of the partner station currently setting the wireless channel. For example, if it is assumed that the signal of the partner station of one channel is strong, it means that the telephone is talking immediately. Therefore, even if the transmission output of channel 1 is lowered, it is possible to talk, and the transmission output of channel 1 is reduced. The amount of reduction depends on the range of the radio wave, but 1/10 to 1 /
Be able to select about 100. Accordingly, the IM waves to the three channels also decrease. That is, the degree of interference is reduced. The same is true even if the transmission output of the second channel is reduced. FIG. 8 shows the flow at this time.

(5) Advantageous Effects of the Invention As described above, according to the present invention, it is possible to avoid interference by an IM wave transmitted from a fixed wireless station having a plurality of wireless units, and to achieve comfortable communication without interference. There are effects that can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a schematic diagram for explaining IM interference caused when a fixed radio station FRS having a plurality of radio units simultaneously emits radio waves, and FIG. FIG. 4 is a block diagram showing a main part of a fixed wireless station having a wireless unit. FIG. 4 is an operation flowchart for explaining a method of checking a channel causing IM interference at the time of radio wave transmission and searching for another transmission channel if the channel is blocked. FIG. 5 is a flow chart for explaining a method of collectively processing empty channel information while processing one wave at a time in FIG. 4;
FIG. 6 is an operation flowchart for explaining a method of transmitting a radio wave by judging the electric field level of a radio station of a channel that gives IM interference and judging that there is no IM interference when weak, and FIG. 5 is an operation flow for explaining a processing operation for reducing transmission power so as not to cause interference when a signal is strong.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Fumiyasu Hayakawa 1-4-10 Irifune, Chuo-ku, Tokyo Tokyo Electric Power Company System Research Laboratory (56) References JP-A-64-86635 (JP, A) 60-64650 (JP, U) JP-B 51-4361 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04B 7/24-7/26 H04Q 7/00-7 / 38

Claims (2)

(57) [Claims] 1. A fixed radio station which covers a plurality of zones using a predetermined number of radio channels to form a service area, and wherein said fixed radio station and said radio station are present in said service area. A plurality of mobile phones capable of communicating using one of the channels as an assigned wireless channel; connecting the fixed wireless stations to a general telephone network to enable good communication with the mobile phone and the mobile phone; A wireless control device for registering identification information of at least one fixed wireless station and for making and receiving a call to and from the mobile phone via the registered fixed wireless station; In the mobile communication system in which the mobile station is installed, each fixed wireless station transmits a radio wave to the vacant channel as a result of the investigation of the presence or absence of the vacant channel. If an attempt is made to transmit a radio wave to the vacant channel at the time of the attempt, a channel in which tertiary transmission intermodulation will occur due to radio waves with another channel already used by another transmitter of the same fixed wireless station. The radio channel control method for a mobile communication system, wherein the assigned radio channel is set when the electric field strength of the radio wave at the time of the investigation is lower than a predetermined level. 2. When the fixed radio station transmits a plurality of radio waves, it is determined that a radio wave already in use exists on an IM channel generated by the transmitted radio waves and the electric field strength of the radio waves exceeds a predetermined level. 2. The wireless channel control method according to claim 1, wherein the output level of the transmitted radio wave is reduced in a range where the communication by the transmitted radio wave is maintained.