JP2000134666A - Radio communication system for time division multiplex system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To almost eliminate the simultaneous emission of radio waves by base stations with each other by allocating a communication channel time divided on the same radio frequency in common to at least two or more base stations to plural mobile stations in common. SOLUTION: In the case of utilizing a time division multiplex system for dividing a time channel which is a time slot and dividing it to respective users, a time band not to be actually used in which the generation of a call is little occupies a considerable part. Then, the time not to be actually utilized is divided into the time slot in which a different base station performs communication with a different mobile station. A diagram indicates the case of dividing the mutual time slots into different timings between the two base stations A and B. As the division method of the time slot, there are the method of deciding a semi-fixedly utilizable time slot and allocating a channel to the respective base stations beforehand and the method of deciding the time slot at random before starting the communication and allocating the channel, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication system for performing paging, voice communication, and data communication with a plurality of moving workers in a self-employed system such as a work site or a factory.

[0002]

2. Description of the Related Art Conventionally, simultaneous paging and paging in a factory or the like have been performed by wired speaker broadcasting. However, recently, there has been a demand for noise suppression and a desire to call only specific individuals. Paging using a wireless communication method has been used relatively more often than the wireless communication method. In particular, in local systems such as on premises, taking advantage of the fact that there is no need to use radio waves,
This is done by a low-power wireless communication system specified for self-employment. Also, in this case, since the transmission power is small, it may not be possible to cover all of the wide area as a service area. Therefore, the coverage is provided by arranging a plurality of base stations.

Further, in a digital mobile radio system for voice communication with a plurality of workers, a time channel is shortened by using an information compression / expansion technique to multiplex channels of a plurality of users. The split multiple access system is the mainstream. FIG. 9 shows a time chart thereof. Further, frequency multiplexing that reduces interference between base stations by using different radio frequencies between adjacent base stations is well known. FIG. 10 shows an example of the relationship between the arrangement of base stations and frequency allocation in that case. FIG. 11 is a time chart showing the communication timing between the base station and the mobile station in that case.

[0004]

However, in the above-mentioned conventional radio communication system, it is impossible to use the same radio frequency between adjacent base stations. This is because, if the same frequency is used in the same space at the same time, the two become interference sources and the reliability of communication is rapidly deteriorated. That is, it is necessary to separate the installation positions of the base stations using the same radio frequency until there is almost no mutual influence. By doing so, the same radio frequency can be used (frequency folding). At this time, in order to set a sufficiently large place to be in a range in which communication is possible, as shown in FIG. 10, base stations 2, 3, which perform communication using another radio frequency between base station A and base station B. It is necessary to arrange 4,.

[0005] If the number of available radio frequencies is as small as about two, the above method cannot be used, and a place where communication is impossible is created. Furthermore, even when several radio frequencies are available, it is a difficult task to find the frequency repetition distance at which the same frequency can be used every time after grasping complicated radio wave propagation characteristics that differ depending on the system introduction location. In other words, a base station layout design that considers which base station is to be assigned which frequency requires a designer with specialized knowledge, and also requires enormous effort and cost of system construction. However, there is a problem that the number increases.

[0006]

When a time-division multiplexing system is used in which a time channel, which is a time slot, is divided and assigned to each user, the occurrence of calls is reduced as shown in FIG. However, the time zone not actually used occupies a considerable part. Accordingly, the present invention eliminates interference between base stations using the same radio frequency by allocating the time not actually used to a time slot in which another base station communicates with another mobile station. And efficient communication.

FIG. 1 shows a timing chart when two base stations A and B allocate their time slots to different timings. As a method of allocating this time slot, for each base station in advance,
A method of allocating a channel by determining a semi-fixed available time slot, a method of allocating a channel by randomly determining a time slot before starting communication, and another means such as wired communication between base stations. In this case, when information transmission is possible, each base station transmits time slot information used by its own station and allocates a channel based on the information.

[0008] By doing so, according to the present invention, it is almost impossible for the base stations to emit radio waves at the same time, and even if there is, the probability of interfering with each other is greatly reduced. That is,
Even when the distance between two base stations using the same frequency is very short, the mobile station can secure a channel for communicating with a desired base station without being affected by interference. Furthermore, by determining the channel to be used in advance with respect to the time until the start of the call, which is an issue in the present invention, the person who possesses the mobile station can actually start the call after the operation of starting the call. The time until the operation becomes possible is reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram showing a configuration of a base station to which the present invention is applied. In the figure, 1 is a transmitting / receiving antenna, 2 is a high frequency circuit unit, 3 is a modulation unit, 4 is a demodulation unit, 5 is a time slot generation processing unit, 6 is a voice compression / expansion processing unit, 7 is an external interface unit, 8 Is the CPU,
9 is a dip switch, 10 is EEPROM, 11 is RO
M and 12 are RAMs.

In this configuration, in order to allocate an available time channel semi-fixedly, a dip switch 9 is attached to a normal base station function to use it as an initial set value at the start of operation of the base station. A possible time channel, that is, a time slot number, is stored in the EEPROM 10. The time slot generation processing unit 5 of the base station operates according to the set values for the transmission timing and the reception timing. If the setting of the dip switch 9 is different between adjacent base stations or the like, the transmission / reception timings are different from each other, and it is possible to eliminate the influence of interference even if the same frequency is used.

Next, a method of dynamically changing a use time slot to determine a communication channel during a communication will be described. FIG. 3 shows a call start flow. When the call start sequence starts, the EEPROM
The communication is started with the channel number N stored in 10 (process S1 in FIG. 3). At this time, if another base station uses this channel, communication quality is degraded due to the influence of interference. In order to avoid this, it is determined in step S2 whether or not the communication quality is higher than a certain level. If the communication quality is good, the call is continued, and if not, the operation proceeds to step S6.

In the process S6, at the time of starting the call for the first time from the initial setting, the random number generating program is activated based on the seed by the unique identification number set in each base station to obtain the random number P. An algorithm for obtaining the next P by generating a random number using the P as a seed. With this process,
The independent event of the number P, that is, the channel number N always increases. This independence increases as the number of time slots in one frame increases. As another method, the random number table may be stored in a memory in advance in order to reduce the processing time, and the number P may be obtained by incrementing the number P extracted from the random number table each time a call is started. . This P
Is stored in the EEPROM 10 as the channel number N in step S7.

Next, if the communication quality is good in the process S2, the call is continued until the end, and if the communication is finished, the process proceeds to the process S4 (process S3). The processing S4 and the processing S5 are the same as the processing S6 described above.
And the same processing as processing S7. In this way, by previously determining the next use channel number in advance, it is possible to greatly reduce the time until the actual call starts.

FIG. 4 is a block diagram of a base station having another configuration. In the configuration of this base station, the parts different from the base station of FIG.
3 is provided, whereby control can be easily realized. The description of the parts common to FIG. 2 is omitted. A method of transmitting which time channel each base station is currently using to start communication in a time slot other than the used time slot will be described later.

Next, as an embodiment of the present invention, an example will be described in which the present invention is applied to a system for calling a worker in a factory and making a voice call by using a spectrum radio means having a small number of radio frequency channels usable for the radio communication means. FIG. 5 shows the basic configuration of this system. Base stations 22A, 22B, 23A to 23C connected to a paging room 25 in a factory by a wired local network 21 are appropriately arranged. Each worker carries out work while carrying the mobile station 24, and moves from the paging room 25 to the base stations 22 A, 22 B, and 23.
This system calls the mobile station 24 via A to 23C, and a worker holding the mobile station 24 uses the mobile station 24 to talk with the paging room 25.

For example, when spectrum radio communication means is used in the present system, at most about two radio frequency channels can be used. Therefore, base station 2
The radio frequency f2 is assigned to the base stations 23A and 22B.
Radio frequencies f1 are assigned to A to 23C. At this time,
Between the base station and the mobile station, a time-division multiple access method as shown in the timing chart of FIG. 6 is provided with #N time channels including a plurality of time slots. As a result, communication with mobile stations of this number of channels can be performed. However, in actual operation, it is rare that all channels are used in all base stations as described above.

The base stations 22A and 22B and the base station 23
Since A to 23C have different radio frequencies, they can communicate with each other without interference. However, for example, for base stations 23A to 23C used at the same radio frequency, interference occurs and communication becomes difficult. Take advantage of the present invention.
Further, in the present invention, since it is necessary to synchronize between the base stations, a synchronization signal is notified to each base station using, for example, a wired communication means by a local network. FIG. 7 shows the timing of the wired communication means and the wireless communication means, and FIG. 8 shows the frame format of the synchronization signal in the wired communication means. In this illustrated example, five base stations are:
The case where N channels are used is shown.

As shown in the frame format of FIG. 8, information indicating which base station is using which channel is added to the synchronization signal. Thereby, the base station constantly monitors this synchronization signal and determines whether there is an available free channel. In addition, when starting communication, each base station takes the timing of channel generation by this synchronization signal, selects an available time channel, and starts communication with the mobile station, that is, communication.

[0019]

As described above, according to the present invention, it is possible to arrange a plurality of base stations even with radio communication means having a small number of frequency channels, more specifically, radio communication means having only one frequency channel. The occurrence of interference due to interference from another base station is eliminated, and transparent communication such as a telephone call becomes possible. In addition, even a system designer who does not have specialized knowledge such as radio wave propagation can easily design the arrangement of base stations.

[Brief description of the drawings]

FIG. 1 is a timing chart in the case where time slots are allocated to different timings in the present invention.

FIG. 2 is a block diagram illustrating a configuration of a base station according to the embodiment of the present invention.

FIG. 3 is a flowchart showing an operation at the time of starting a call in the embodiment of the present invention.

FIG. 4 is a block diagram showing another configuration of the base station according to the embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of a configuration of a system according to an embodiment of the present invention.

FIG. 6 is a timing chart showing an operation in the embodiment of the present invention.

FIG. 7 is a timing chart showing an operation in the embodiment of the present invention.

FIG. 8 is a diagram illustrating a frame format of a synchronization signal according to the embodiment of the present invention.

FIG. 9 is a timing chart showing a conventional example.

FIG. 10 is a diagram illustrating the relationship between the arrangement of base stations and frequencies in a conventional example.

FIG. 11 is a timing chart showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmission / reception antenna 2 High frequency circuit part 3 Modulation part 4 Demodulation part 5 Time slot generation processing part 6 Audio compression / decompression processing part 7 External interface part 8 CPU 9 Dip switch 10 EEPROM 11 ROM 12 RAM 21 Wired local network 22A, 22B, 23A -23C Base station 24 Mobile station 25 Paging room

Continuation of the front page F term (reference) 5K018 AA04 BA03 CA06 5K028 AA06 BB06 CC02 CC05 DD01 DD02 LL02 LL41 LL42 MM19 NN21 RR01 5K067 AA44 BB08 BB44 CC04 DD25 DD33 DD57 EE02 EE10 EE59 JJ02 JJ12

Claims (5)

[Claims] 1. A time-division multiplexing wireless communication system used between a plurality of base stations and a plurality of mobile stations, wherein at least two or more base stations use a time-division communication channel on a common radio frequency. A time-division multiplexing wireless communication system characterized by being assigned to a plurality of common mobile stations. 2. The wireless communication system according to claim 1, wherein a plurality of base stations using a common time division communication channel are connected by a communication line, and the time division communication channels between the respective base stations are synchronized. A time-division multiplexing wireless communication system. 3. The time-division multiplexing wireless communication system according to claim 1, wherein an assignment of a common time-division communication channel to a mobile station is set at the start of system operation. 4. The wireless communication system according to claim 1, wherein allocation of a common time-division communication channel to a mobile station is randomly set at the start of communication. . 5. The wireless communication system according to claim 2, wherein the base station uses a common time-division communication channel and exchanges setting information of each other via a communication line. A time-division multiplexing wireless communication system, wherein a time-division communication channel is assigned to a mobile station.