JP2921036B2 - Radio channel control method for mobile communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field to which the Invention pertains 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 within 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 car 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. It uses the 250 / 380MHz band frequency, has 89 channels including control channels, and has a service radius of 50m for duplexing 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 system controller. 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): An incoming call and a telephone call can be made by converting a downlink signal from a radio system controller into a radio signal and transmitting it to a mobile phone. 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 sends and receives a fixed radio station that covers the radio wave 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. It is a device that is sometimes connected 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.

Hereinafter, a fixed wireless station having a plurality of sets will be described. Multiple fixed radio stations Multiple fixed radio stations
Called FRS. In a fixed wireless station capable of coping with a high-density traffic area, the concept of zone-based location registration is introduced into a service zone managed by the fixed wireless station. With the introduction of this concept, zone distinction has been diversified for control purposes.
In the case of FRS, any of the representative FRSs is the master FRS
When the other FRS is called a slave, it is distinguished by the self-identification information (SID) of the master FRS. However, the relationship between the master and the slave is not stationary but changes every moment. That is, when the master FRS starts communication with a certain mobile phone, the FRS in the slave state is changed to the master.

For example, (a normal this master FRS when powered on) four sets of transceivers FRS ₁ to a plurality of FRS, FRS _2, FRS
₃ and FRS ₄ , and the respective self-identification information is SIDa, SIDb, SIDc, and SIDd, and the self-identification information representing the multiplexed FRS is the master FRS at that time.
Is given by SIDa which is the self-identification information of the FRS ₁ in the state. Moreover, even if the master FRS enters the call and another slave FRS is changed to the master, the SIDZ (SIDa) once registered is unchanged.

Generally speaking, the self-identification information of the service zone of the multiplexed FRS represents the self-identification information of the master FRS owned by the multiplexed FRS in SIDZ. The location registration management inside the RCE will be performed in SIDZ units. However, when the master FRS is in a communication state with the mobile phone, the method of shifting the slave FRS to the master FRS can be performed by a method of managing the order of younger numbers.

Hereinafter, the fact that the above operation can be specifically executed will be described with reference to FIG.

FIG. 4 is a block diagram of the pluralized FRS, in which n radio base station units 1, 2,..., N are installed on the left side, and between these and the right main unit as shown in the figure. They are connected by bus lines and signal lines. The main unit has the function of controlling multiple wireless base stations on the left in common.
"RAM circuit (CRAM)" and its access right "CRAM"
An access right determination circuit "and a chain control circuit for connecting the control rights of the units in a chain.

 Hereinafter, each of the configurations in FIG. 4 will be described.

First, the CRAM will be described. The CRAM is for data saving shared by the units to be mounted, and the data mainly includes location registration information, incoming call information, and the like. What is noteworthy in terms of the hardware configuration is that this CRAM is a mere storage circuit, and does not include any complicated functions such as a CPU or a signal transmission circuit as in a general control circuit. Therefore, the circuit can be regarded as a passive circuit equivalently, so that it is economical with few obstacles.

Next, the CRAM access right determination circuit issues an access request from the unit to the CRAM access right determination circuit,
A handshake method is adopted in which the CRAM access right determination circuit issues access permission to the request unit. Also,
When access requests are issued from a plurality of units almost simultaneously, only one unit specified by the access right determination circuit becomes the access circuit.

Further, when a call (including incoming / outgoing call, location registration control) is generated, the chain control circuit performs selection control to cause only one of the plurality of units in the standby state to respond to the call.

And prioritize each mounted unit,
Further, a status signal indicating the status of the unit (waiting / talking) output from each unit is input, one of the units in the waiting state is selected, and the right to answer the call is given.

Also, when all of the mounted units are in a call state, they also have a function of selecting a unit having a higher priority among them.

Table 1 shows a method of selecting 3ch FRS units as an example.
If there is a unit that is not mounted, this state is apparently set to a call state, so that it is possible to respond according to Table 1.

The hardware configuration of the CRAM access right determination circuit and the chain control circuit described above can be regarded as a passive circuit which is almost the same as a simple logic switch circuit like the CRAM circuit, and is economical with few failures.

Further, the radio base station unit has all control functions and transmission / reception functions as one FRS in terms of system, and the FRS shown in FIG.
It has a function to output its own status to the chain control circuit in the main body. The output in this state is a binary value of a standby state / a call state.

Although the hardware configuration of the composite FRS has been described above, regarding the control of outgoing and incoming calls performed between the mobile phone and the fixed wireless station, the self-identification of the fixed wireless station in the multiple FRS is the same as in a normal fixed wireless station. This is possible in units of information (SID).

In the above multiple FRS, a plurality of radio waves may be transmitted 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 communication, since the system bandwidth is small compared to the radio frequency, m
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, 2f ₁ −
Intermodulation in the form of 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 generated when three waves f ₁ , f ₂ , and f ₃ are input.
These two are problems.

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, an IM also occurs in a combination of 1, 2, 5, and 7 channels.

In the worst case, such as when the channels are almost full, 2 combinations are selected from the 10 channels to calculate the formula of 2f ₁ −f ₂ .
Also, there are 360 combinations for calculating the formula of f ₁ + f ₂ −f ₃ ,
450 calculations are required in addition to the above. Further, since it is necessary to determine whether or not this calculation result will interfere with the required channel, some calculation time is required.

If the number of channels is at this level, the amount of calculation is not so large, but if there are 89 channels such as the cordless telephone channels currently allocated to Japan, this calculation is required about 350,000 times, and one of these results is one of the results. Since the determination is made for one, the processing time is time consuming and the utility is poor.

(3) Object of the Invention The present invention prepares a table calculated in advance in order to avoid intermodulation (IM) that occurs when a fixed wireless station in which a plurality of wireless units are incorporated operates, and prepares an IM in this table. A wireless channel control method for a mobile communication system capable of smoothly performing wireless connection and performing comfortable communication without IM interference by mutually specifying wireless channel groups that do not cause a problem. .

(4) Configuration and Function of the Invention For example, FIG. 2 will be described.

In FIG. 2, there are two FRSs for three channels in close proximity and four portable devices. In each of them, the portable device of # 1 is connected to FRS-1 by channel 1. The # 2 portable device is also FRS-
1 and channel 6. The portable device of # 3 near FRS-1 is connected to FRS-2 on channel 3. 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, when the FRS-1 detects an empty channel from 10 channels, it knows that a total of 7, 2, 4, 5, 7, 8, 9, and 10 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. It interferes with the call of 3ch with machine-3.

In order to prevent IM interference, FRS-1 calculates 4 channels, 5 channels, 7 channels, and confirms that there will be no interference before deciding on a channel. After the confirmation, the notification is made to the wireless station of the communication partner (in this case, the mobile station), but there is a disadvantage that the calculation takes time. Contrary to this example, after confirming the empty channel, when calculating whether or not to disturb 3ch when transmitting radio waves to this empty channel, use it for other stations during the calculation time There was also a problem that it was done. this
In order to avoid IM, it is preferable to calculate in advance a channel group in which IM does not occur and to make a table.

The following Table 2 shows an example of combinations of channels in which the number of channels can be increased as much as possible without generating IM in all 10 channels.

In the example of FIG. 2, channels 1, 3, and 6 are in use, and a search is made in Table 2 to determine whether one more wave can be used for this channel set. It can be seen that seven channels can be used. With such a processing method, the channel can be determined in a short time, so that the connection time can be greatly reduced.

From another point of view, when the FRS designates an empty channel for the portable device, when the portable device confirms the channel, it is not detected by FRS-1 by chance, but the portable device detects that it is in use. At this time, since the portable device requests the FRS-1 to also specify an empty channel again, there is a problem that it takes time for the connection. this is
The FRS-1 specifies a radio channel group that does not cause IM to the portable device, and the portable device checks empty channels of some of the radio channels to search for another even if one is blocked. Since there is no need to make a retransmission request to FRS-1, a wireless channel can be set up in a short time. Another advantage is that since the data transmitted by the FRS is only a radio channel group, the amount of data can be reduced and transmission can be performed in a short time, and since the data length is short, interference is caused by noise during transmission. There are advantages such as difficulty.

As described in the above example, a description has been given of the maximum combination of 4 channels in which no IM occurs in 10 waves. However, a combination of 3 channels which is not the maximum combination can be obtained in a larger number of groups, and is added to the table. Good. For example, it is a group of 1, 2, 4 channels, 7, 9, 10 channels, and the like. Table 3 shows this example.

As shown in the above example, if the total number of channels is as small as 10 waves, it seems that the effect is small, but if there are 89 channels like a cordless telephone channel, the effect is enormous. For example, in the case of 89 channels, the number of channels in which IM interference does not occur is 12.

The hardware configuration of this embodiment is basically the same as that shown in the conventional example of FIG. However, in the CRAM circuit in the main unit shown in FIG. 4, empty channel information, in-use channel information for each wireless unit, a proximity portable unit number and signal strength, a CH group table which does not generate IM,
The difference is that it has a CH group table. Further, the above-described determination processing is performed by a CRAM access right determination circuit.

An example of the details of the operation follows the flowchart of FIG. An example in which an incoming call is received by the connection device will be described.

One of the wireless units of the connection device is always in a receiving state and receives a predetermined number of wireless channels. With this reception, the empty channel number EC is stored in the CRAM. At the same time, the channel SC used by the mobile station, which can be strongly received, is stored. This is because a portable device that can receive a strong signal is connected to another FRS except for the one connected to its own FRS, and since it is located far from the connected FRS, the radio wave from the FRS is generally weak. This is because giving out an IM wave to this channel causes interference, so that care must be taken so that this channel does not emit an IM wave. Conversely, portable devices with weak radio waves are not considered because they are determined to be far away and may not interfere.

Next, the channel UC used by some wireless units of the own FRS is stored. The stored SC and UC, the received empty channel EC, and the information are stored in a previously stored IM-less channel group table, and a group of a satisfactory combination is stored.

Next, check whether there is an arrival / departure request. If there is no request, the above operation is repeated, and the channel information is rewritten with new information.

Here, when there is an incoming call, the connection device sends out the designated mobile phone number, the incoming call information, and the previously selected CH group through the control channel. The mobile phone that has received the incoming call information extracts the CH number from its own “CH group table that does not generate IM” from the received CH group, sets the channel, and checks for an empty channel. If it is, pull out the channels in the group in the table, reset the channels and check for empty channels. When the empty can be confirmed, the empty channel confirmed together with the incoming response is designated in the control channel. The connection device receives this and changes the channel. The mobile device also changes the channel. Here, the connection device sends out a ringing tone (not shown), and the operator of the portable device responds to the ringing tone to start a call.

If a channel group with a high channel usage rate and no IM in such a series of flows cannot be found, a busy tone indicating that the network is blocked may be output, or IM generation may be unavoidable. Whether or not to ignore is related to the policy of the device design, and may be appropriately selected.

Although the example of the incoming call is described with reference to FIG. 3, the same processing is performed when a call is requested from the portable device to the connection device.

(5) Effects of the Invention As described in detail above, an IM signal transmitted from a fixed wireless station having a plurality of wireless units interferes with other communications, but this is easily avoided according to the spirit of the present invention. I knew I could do it. Therefore, comfortable communication can be performed without interfering with each other.

In addition, although the calculation of IM is simple, but the number of combinations is very large, a large amount of time is required when the number of channels to be calculated is large, and time is required for circuit connection, but as shown in the present invention, If each radio station has a pre-calculated table,
Since only the wireless CH group information needs to be transmitted, connection can be made for a short time without transmission errors. In addition, since data is transmitted in a group, even if one channel in the group is busy, another channel in the group can be used without making an inquiry, so that the time for detecting an empty channel is further reduced. There are advantages.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing a channel used by a fixed wireless station and a portable device for explaining an embodiment of the present invention. FIG. 3 is a diagram showing a connection device and a portable device showing a flow for wireless connection showing one embodiment of the present invention. FIG. 4 is a hardware configuration diagram showing a conventional example and an example for implementing the present invention.

Continued on the front page (72) Inventor Kazuhide Okamura 1-4-10, Irifune, Chuo-ku, Tokyo Tokyo Electric Power Co., Inc. (72) Inventor Fumiyasu Hayakawa 1-4-10, Irifune, Chuo-ku, Tokyo Tokyo Electric Power (56) References JP-A-2-249326 (JP, A) JP-A-64-86635 (JP, A) JP-A-60-64650 (JP, U) JP-B-51-4361 ( JP, B1) (58) Field surveyed (Int. Cl. ⁶ , DB name) H04B 7/24-7/26 H04Q 7/00-7/38

Claims (1)

(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 the fixed radio station and the radio channel exist in the service area. A plurality of mobile phones capable of communicating using one of them as an assigned radio channel, and connecting each of the fixed radio 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, wherein a plurality of sets of transceivers are provided for one fixed wireless station. Is installed,
When one set of the transceivers has a function as a wireless device for control and communication related to identification information and outgoing / incoming calls, one transceiver is used as a master according to a certain rule, and a plurality of other transceivers are used. In a mobile communication system in which a set of devices is set as a slave, and the transceiver of the master performs an operation enabling communication of information necessary for transmission and reception of the mobile phone, each of the fixed wireless station and the wireless device of the mobile phone Has a table of channel groups that do not cause mutual tertiary transmission intermodulation determined according to a predetermined number of the radio channels, and the radio station requested to connect is the tertiary An optimal group is selected from the channel groups that do not cause transmission intermodulation, transmitted to the connection requesting radio station, and the radio station receiving the information selects Wireless channel control method for a mobile communication system, characterized in that the idle channel searched from the communication channel is transmitted to the wireless station of the connection request destination, and the allocated wireless channel is set to the idle channel.