JPH08130765A - Radio telephone master station system - Google Patents

Abstract

PURPOSE: To provide a radio telephone master station system of multi-carrier TDMA system hard to receive interference from another station. CONSTITUTION: This system is equipped with a radio control part 20 which measures the TDMA frame period of a working slot and allocates a slot neighboring to the side opposite to the moving direction of the working slot by the error of a frame period to a radio channel for communication with a slave station In the case that a slot on a frequency (carrier) on which a time slot being used by another station exists is allocated to a radio channel when it is allocated to start communication in the radio telephone master station system of multi-carrier TDMA system. Therefore, a long time is required until the interference begins to generate when no synchronization of a TDMA frame or time slot with that of another station is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is installed under conditions where it is difficult to communicate with a wireless slave station by time division multiplex or time division multiple access and to synchronize time slots between master stations. The present invention relates to a radio telephone master station device.

[0002]

2. Description of the Related Art In recent years, digitalization of wireless communication has progressed in the field of mobile communication represented by car telephones from the viewpoints of improving confidentiality, compatibility with ISDN networks and computers, effective use of frequency resources, and the like. are doing. In digital wireless communication, one wireless channel is assigned to one carrier frequency (hereinafter referred to as a carrier) similar to the conventional analog system, and different carriers are used to perform simultaneous communication without interfering with each other. Multiple access (hereinafter F
In addition to (DMA), one carrier (hereinafter referred to as a carrier) is divided into units called time slots of a certain time as has already been put to practical use in sanitary communication and the like, and two or more wireless channels are provided. Also, time-division multiple access (hereinafter referred to as TDMA) is used in which communication is simultaneously performed without interfering with each other even on the same carrier by allocating in a time-division manner and using different time slots for each radio channel. In land mobile communications, for example, the standard for digital cellular telephones or digital cordless telephones in Japan is the Radio System Development Center standard RCRSTD.
-27 or RCRSTD-28, a multi-carrier TDMA system capable of switching carriers for each time slot is often used.

Further, a time division duplex (hereinafter referred to as TDD) system in which transmission and reception are alternately performed on the same carrier is RCRSTD.
It is adopted in -28. However, when the reference clock common to each master station cannot be obtained for the timing of the time slot (such as a cordless telephone connected to an existing analog telephone network), the slot timing is generally shifted from the other master stations, In addition, the amount of deviation changes slowly with time.

On the other hand, when the wireless channel is changed for the purpose of newly starting wireless communication or avoiding interference, it is necessary to select an appropriate wireless channel. In a cellular telephone, a channel to be used for each parent station (base station) is fixedly assigned in advance so as not to cause interference on the same radio channel, and the base station is assigned its own radio channel among the assigned radio channels. A fixed channel allocation method that uses an appropriate wireless channel that is not currently used is common, but in a cordless telephone, a master station as defined in the RCRSTD-28 proposal, or both a master station and a slave station are used. In general, a dynamic channel allocation method is used in which a wireless channel is searched, and if the received electric field strength is below a certain reference value, it is determined to be usable and the same channel is used.

A conventional radio telephone master station device will be described below with reference to the drawings. FIG. 3 is a configuration diagram of a conventional radiotelephone master station device, and FIG. 4 is a time slot layout diagram of the radiotelephone master station device. In FIG. 3, reference numeral 10 denotes a wireless unit, which modulates a carrier wave with digital data such as voice converted into a digital value and transmits it as a radio wave to a slave station, and also receives a radio wave from the slave station and demodulates it to original digital data. A wireless control unit 20 selects a wireless channel that can be used for communication with the child station from the wireless channels that can be transmitted and received by the wireless unit 10, and sets the wireless channel in the wireless unit 10. 30
Is a line interface unit for converting communication data such as voice, line control data such as incoming and outgoing calls, line connection and disconnection between the radio unit 10 and the radio control unit 20 and a public telephone line or a terminal device. This radio telephone master station device has eight slots for transmission per one TDMA frame,
Communication is performed in a TDMA-TDD system with 8 slots for reception and 16 slots in total.

The operation of the conventional radiotelephone master station apparatus configured as described above will be described below. First, when starting communication between a master station and a slave station, the master station must first select an appropriate wireless channel (hereinafter simply referred to as channel). At this time, if the same parent station is already communicating with the slave station, target channels on slots other than the time slot used for communication with the slave station, and if there is no communicating slave station, target all channels. First, one channel is selected.

Next, the selected channel is received, and the availability is checked. That is, the wireless control unit 20 to the wireless unit 1
The channel is set to 0, and the wireless unit 10 to the wireless control unit 2
At 0, the reception level (reception field strength) is transmitted to the wireless control unit. Then, if the reception level is lower than a specified value such as a standard, it is possible to use, that is, it is judged that there is no risk of causing interference to other stations even if radio waves are emitted in the same channel, and communication is started in the same channel. If the reception level is equal to or higher than the specified value, it is determined that the channel is in use, one channel is selected from the remaining other channels, and the reception level is inspected. The search is performed until a usable channel is found or the inspection of all target channels is completed. Further, if the carrier frequency interval is narrower than the occupied frequency bandwidth, interference may occur in adjacent carriers of the channel being used and channels in the same time slot, so it must be regarded as the channel in use.

A specific example of the channel selection operation will be described below with reference to FIG. FIG. 4 shows the time slots in the master station and the master station 2 and the slave station which are in communication with the master station 2 and are located in a place where they interfere with each other when the same channel is used and are not in TDMA frame synchronization with each other. FIG. 6 is a diagram showing a relationship with a burst wave, that is, a time slot already in use in the same station. The numbers in FIG. 4 indicate slot numbers.

First, when the master station 2 starts communication while the master station 2 is communicating on a channel of a certain time slot having a certain carrier frequency, a time slot which is not interfered with by the same carrier as the same channel is shown in FIG. As shown in a), there are six such as 1, 2, 3, 4, 5, and 6. Therefore, it is assumed that the channel of time slot 2 is selected and communication is started. However, as shown in the figure, the frame length Tf, the slot length Ts,
When the frequencies of the standard oscillators of the master station have an error of ε with respect to each other, a shift of one time slot occurs at the time of Ts / ε, and a shift of one frame occurs at the time of Tf / ε. For example, the error is 3 ppm and the TDMA frame length is 10
In ms, there is a time shift of about 3 minutes and 28 seconds for one time slot, and about 55 minutes for one frame. Therefore, even if the master station 1 and the master station 2 can use the carrier 1 at the same time as shown in FIG. 4 (a), they may interfere with each other as shown in FIG. 4 (b) if the call time exceeds several minutes. It is highly likely. In such a case, the master station 1 needs to use channels of carriers other than the carrier 1 for communication.

[0010]

In the above-mentioned conventional radio telephone master station device, the timing of the time slot is made by an oscillator independent for each master station, and the TDM between the master stations is made.
If A time slot synchronization is not performed, a radio channel having the same or adjacent carrier frequency as the radio channel used by another station is used, and the time slot of the radio channel used by the own station and the radio channel being used by another station are used. When the time interval of the channel to the time slot is short, interference starts to occur immediately, and it becomes necessary to re-search / assign the radio channel. Therefore, in the case of the wireless telephone, there is a problem that the call is interrupted, and in the case of the data communication, the average data transmission rate is lowered.

Therefore, an object of the present invention is to provide a radiotelephone master station device which is less likely to be interfered with by another station.

[0012]

To this end, according to the present invention, when the radio control unit selects the first radio channel, the radio frequency control unit selects the carrier frequency at which the second radio channel already used by another station exists. When selecting the first wireless channel from the empty wireless channels of the same carrier frequency, the frame period of the received signal of the second wireless channel is compared with the length of the frame period of the own station, and the frame period of the other station is determined. Is short, the time interval from the second radio channel is the front, that is, the empty radio channel that is the longest in the past, and when the frame period of the own station is shorter, the time interval from the second radio channel is later. That is, the longest available wireless channel for the future is preferentially set as the wireless channel for communication with the slave station.

[0013]

According to the present invention, when the radio channel of the same carrier as the radio channel being used by another station is selected, the radio channel having the longest time until interference starts due to a frame synchronization error is prioritized. Since it is selected and used, interference due to frame period deviation is avoided,
Alternatively, the time until interference starts to occur can be maximized.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. In addition, in the same part as the above-mentioned conventional example,
The same code is given to each. FIG. 1 is a configuration diagram of a radio telephone master station device according to an embodiment of the present invention, and FIG. 2 is a time slot arrangement diagram of the radio telephone master station device. In FIG. 1, 10 is a wireless unit, 20 is a wireless control unit, and 30 is a line interface unit, and the role of each unit is the same as that described in the conventional example. The master station in this embodiment has eight slots for transmission, eight slots for reception, and one frame for each TDMA frame.
The TDMA-TDD system communication with a total of 16 slots is performed.

The operation of the radio telephone master station device configured as described above will be described below. First, when the master station starts communication with the slave station, the master station must first select an appropriate wireless channel (hereinafter simply referred to as channel). At this time, if the same parent station is already communicating with the slave station, there is a slave station that is communicating with a channel on a slot other than the time slot (hereinafter simply referred to as a slot) used for communication with the slave station. If not, one channel is first selected for all channels. Next, the selected channel is received and availability is checked. That is, a channel is set from the radio control unit 20 to the radio unit 10, and the reception level (reception electric field strength) is transmitted from the radio unit 10 to the radio control unit 20 to the radio control unit. If the reception level is lower than the specified value such as the standard, it can be used, that is, it is judged that there is no risk of giving interference to other stations or receiving interference from other stations even if radio waves are emitted on the same channel, and communication on the same channel To start. If the reception level is equal to or higher than the specified value, it is determined that it is in use, and one channel is selected again from the remaining other channels,
Check the reception level. The search is performed until a usable channel is found or the inspection of all target channels is completed.

A specific example of the channel selection operation will be described below with reference to FIG. FIG. 2 shows that the slots are transmitted from the slot in the master station 1 and the master station 2 and the slave station which are in communication with the master station 2 and are located in a place where they interfere with each other when the same channel is used and are not in TDMA frame synchronization. FIG. 6 is a diagram showing a relationship with a burst wave, that is, a time slot already in use in the same station. The numbers in FIG. 2 indicate slot numbers.

First, when the master station 1 starts communication while the master station 2 is communicating on a channel of a time slot having a certain carrier frequency, the master station 1 first sets an appropriate carrier frequency in the radio section 10, The same carrier frequency is received continuously or in all reception slot periods except for slots that are already in use, and it is confirmed whether or not there is communication that receives interference or gives interference. When there is communication that receives or gives interference, that is, communication of the master station 2, the wireless control unit 20
Measures the communication frame period of the master station 2.

The frame period can be measured, for example, by comparing the received level signal obtained from the radio unit with an appropriate threshold value, binarizing it, and measuring the period of the binarized pulse. Alternatively, the received signal may be demodulated, and a period called a unique word, in which a specific bit pattern existing at a fixed position in a transmission burst appears, may be measured. Further, in the case of a receiver having a structure in which the reception level is obtained as an average value within a slot on a slot-by-slot basis, the average of adjacent slots (for example, slots 7 and 8 in FIG. 2) whose reception level exceeds a specified threshold value. The change in the reception level may be compared. That is, if the reception level of the previous slot increases in time and the reception level of the subsequent slot decreases, the frame period of the master station 2 is shorter than that of its own station (master station 1) and the reception level of the later slot in time is If it increases and the reception level of the previous slot decreases, it is determined that the frame cycle of the master station 2 is longer than that of its own station (master station 1).

When the frame cycle of the master station 2 is shorter than the frame cycle of its own station (master station 1), the adjacent slot that is after the slot interfered by the communication of the master station 2 in time is reversed. When it is very long, the adjacent slot that is earlier in time than the slot that is interfered by the communication of the master station 2 is assigned as the communication channel of the own station. Figure 2
When the communication of the master station 2 interferes with the slots 7 and 8 of the master station 1 as shown in (a) and the frame cycle of the master station 2 is shorter than the frame cycle of the master station 1 (that is, ε <0), The radio controller 20 assigns slot 1 to a communication channel. In this case, since the frame cycle of the master station 2 is shorter than the frame cycle of the master station 1, the slots affected by the interference change to 6 and 5 with the passage of time, but because the slot 1 is used, the interference occurs, or You can maximize the time to start giving.

Further, as shown in FIG. 2B, the frame period of the master station 2 is longer than that of the frame of the master station 1 (that is, ε> 0).
At this time, the radio control unit 20 can allocate the slot 6 to a communication channel and similarly maximize the time until the interference or the start of giving interference. Channels (slots) like this
As will be apparent from FIG. 2, the interference does not generally occur until the frame period shifts by (the number of slots−3) slots. Frame length Tf, slot length T
s, when there is an error of ε with respect to the frequencies of the standard oscillators of the master station, a time slot deviation of Ts / ε occurs. Therefore, for example, in the example of FIG.
Approximately 3 minutes 28 when the frame length is 8 ms and 8 slots
Since a timing shift of one time slot occurs in seconds, there is no time interference of 17 minutes or more.

[0021]

As described above, according to the present invention, when the self station uses the same radio channel as that already used by another station or an empty channel of an adjacent carrier, the same due to an error in the frame period between the master stations. The time when the channel interference starts to occur can be maximized, and the interference does not occur if the communication is for a short time. Also, since the time until the occurrence of interference becomes long, the number of times of channel switching due to the occurrence of interference is reduced, the temporary interruption of calls and click noise caused by channel switching in voice calls are reduced, and the data transmission rate in data transmission is reduced. improves. Further, by using the received signal strength averaged for each slot for measuring the frame period, it is possible to realize a very excellent radio telephone master station device in which malfunctions due to noise are reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a radio telephone master station device according to an embodiment of the present invention.

FIG. 2 is a time slot layout diagram of a radio telephone master station device according to an embodiment of the present invention.

FIG. 3 is a block diagram of a conventional radio telephone master station device.

FIG. 4 is a time slot layout diagram of a conventional radio telephone master station device.

[Explanation of symbols]

 10 wireless unit 20 wireless control unit

Claims (4)

[Claims] 1. A radio unit for communicating with a slave station by time division multiplex and time division multiple access for transmitting and receiving a high frequency signal modulated with data such as a voice signal, and a slave station connected to the radio unit. A wireless control unit that selects a first wireless channel to be used for communication and sets the first wireless channel in the wireless unit, wherein the wireless control unit selects the first wireless channel. , When selecting the first wireless channel from free wireless channels having the same carrier frequency as the carrier frequency in which the second wireless channel already used by another station exists,
The frame period of the received signal of the second wireless channel and the length of the frame period of the own station are compared, and when the frame period of the other station is shorter, the time interval from the second wireless channel is earlier, That is, when the frame period of the local station is shorter than the empty radio channel that is the longest in the past, the time interval from the second radio channel is later, that is, the idle radio channel that is the longest in the future is the slave station. A radio telephone master station device characterized by being preferentially set to a radio channel for communication with. 2. The radio section outputs the received signal strength to the radio control section, and the radio control section measures the fluctuation cycle of the received signal strength to determine the frame cycle of the received signal and the frame cycle of the own station. The radio telephone master station device according to claim 1, wherein the length is compared. 3. The radio unit outputs to the radio control unit the received signal strength averaged in each time slot for each time slot, and the radio control unit receives the reception signal exceeding a threshold value set appropriately. When the signal strength is obtained, it is determined that the time slot is the second radio channel already used by another station, and the received signal strength exceeding the threshold value is obtained in two or more adjacent time slots. In this case, the change of the received signal strength of the two or more time slots is monitored, and the length of the frame cycle of the received signal and the frame cycle of the own station are shortened by the change of the received signal strength of the first and last time slots. The wireless telephone master station device according to claim 1, wherein 4. The cycle in which the radio control unit monitors the data of the radio channel already demodulated by the radio unit and used by another station, and a specific bit pattern existing at a fixed position in a transmission burst appears. 2. The wireless telephone master station device according to claim 1, wherein the frame period of the received signal of the wireless channel and the length of the frame period of the own station are compared with each other.