JP2014120933A - Business office use digital cordless telephone system, switching channel selection method, and switching channel selection program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a business office use digital cordless telephone system capable of ensuring a communication quality by shortening a radio wave interference generation time in the PHS side, even communication areas for a business office use digital cordless telephone system in PHS and a digital cordless telephone system in a different system are overlapped.SOLUTION: A base station 12 includes at least: a communication quality observation section 121 for observing the generation of radio wave interference with regard to a communication channel to a terminal 13; a switching channel selection section 122 for selecting a channel of a frequency bandwidth, as a switching channel, different from a frequency being used by a digital cordless telephone system in other system when the communication observation section 121 detecting deterioration of communication quality lower than a prescribed threshold quality value or when receiving a channel switchover request from a communication destination terminal 13; and a channel switch control section 123 for controlling a channel causing a radio wave interference so as to switch the chanel into the switching channel selected by the switch channel selection section 122.

Description

  The present invention relates to a digital cordless telephone system for offices, a switching channel selection method, and a switching channel selection program, and in particular, the same frequency band is set within the communication area of a digital cordless telephone system for offices compliant with the second generation cordless telephone system standard. Digital cordless telephone system for offices that performs channel switching to avoid jamming from other mixed telephone systems when other telephone systems with different methods are used, switching channel selection method and switching It relates to a channel selection program. The present invention relates to a digital cordless telephone system (base station, digital cordless terminal) for offices in the 1.9 GHz band PHS system and 1.9 GHz band DECT (Digital Enhanced Cordless Telecommunications) newly standardized in Japan as another system. ) Type digital cordless telephone system (DECT master unit, DECT slave unit) is particularly effective when it exists in the same communication area.

  As a digital cordless telephone system, the DECT (Digital Enhanced Cordless Telecommunications) system, which uses the 1.9 GHz radio frequency band, has been newly standardized in Japan. As a second-generation cordless telephone system (Personal Handy-Phone System) The situation is overlapping with the PHS (Personal Handy-Phone System) type digital cordless telephone system compliant with the RCR STD-28 standard established by the Japan Radio Industry Association. Here, both of these digital cordless telephone systems are mixed in overlapping communication areas, the frequency bands of the communication channels used are overlapping, and the TDMA (Time Division Multiple Access) method is used. In such a case, the radio wave interference occurs, the communication quality is deteriorated, and a situation where a communication error occurs cannot be avoided.

  Usually, in order to avoid such radio wave interference, as described in Japanese Patent Application Laid-Open No. 2011-77985 “Radio Communication Device and Radio Communication Method” of Patent Document 1, a channel in communication that causes radio wave interference is disclosed. Channel switching for switching to another channel is effective. However, in the case of Patent Document 1, the digital cordless telephone system that performs channel switching is a wireless device on the DECT system side, and is not a wireless device on the side of the digital cordless telephone system for offices to which the PHS system is applied.

  The frequency bandwidth per call channel of the DECT method is wider than the bandwidth of the digital cordless telephone system for offices to which the PHS method is applied, and is about six times. Therefore, when the DECT method side performs channel switching. Can switch to a channel of a frequency band different from the channel on the PHS system side that caused the radio wave interference, but when the PHS system side performs channel switching, it is in the vicinity of the channel on the PHS system side that caused the radio wave interference. Even when switching to a frequency band channel, the DECT method side often exists in the frequency band used as the channel being communicated, and a communication error occurs in the switching destination channel, A situation occurs in which channel switching is repeated. During channel switching operations such as these, there will be a no-communication state, and communication content may be dropped (sound loss in the case of voice calls) or noise may be mixed. Frequent channel switching operations are used. This will be a significant service degradation factor for the users who do.

Japanese Patent Laying-Open No. 2011-77985 (page 6-8)

  As mentioned above, for business operators applying PHS (Personal Handy-Phone System) conforming to the RCR STD-28 standard established by the Radio Industries Association of Japan as a second-generation cordless telephone system (Personal Handy-Phone System) The digital cordless telephone system of the DECT (Digital Enhanced Cordless Telecommunications) method of the digital cordless telephone standard established by the European Telecommunications Standards Institute (ETSI) that uses the same radio frequency band (1.9 GHz) in the communication area of the digital cordless telephone system Even when a situation occurs where communication areas almost overlap and coexist, channel switching is still an effective means for avoiding interference.

  However, as described above, since the communication channel of the DECT method requires a frequency band about six times that of the PHS method, even if the channel switching for switching the channel in which the radio wave interference occurs on the PHS method side, the radio wave interference It is not always possible to switch to a channel different from the frequency band of the communication channel on the DECT system side, and even if channel switching is performed, the error rate does not fall below a predetermined threshold. there is a possibility. When such a case occurs, no matter how many times the channel switching is repeated on the PHS system side, radio interference cannot be avoided and communication quality is continuously deteriorated. The possibility of degrading will arise.

(Object of the present invention)
The present invention has been made in view of such circumstances, and in addition to the communication area of the PHS digital cordless telephone system installed for business use, the communication area of another type of digital cordless telephone system such as the DECT digital cordless telephone system is provided. Even in the case where there are duplicates, the channel selection method on the PHS system side is devised to enable quick channel switching, thereby reducing the time of occurrence of radio wave interference, An object of the present invention is to provide a digital cordless telephone system for offices, a switching channel selection method, and a switching channel selection program capable of ensuring communication quality.

  In order to solve the above-described problems, the digital cordless telephone system for offices, the switching channel selection method, and the switching channel selection program according to the present invention mainly adopt the following characteristic configuration.

  (1) An office digital cordless telephone system according to the present invention is an office digital comprising a base station and a terminal adopting a PHS (Personal Handy-Phone System) standardized as a second generation digital cordless telephone system. In the cordless telephone system, in the case where there is a wireless device of another type of digital cordless telephone system that uses the same frequency band in the communication area of the base station, the base station communicates with the terminal. Communication quality monitoring means for monitoring whether radio wave interference has occurred on a channel used for communication and a decrease in communication quality during communication has occurred, and communication quality during communication is predetermined by the communication quality monitoring means When it is detected that the quality has fallen below the threshold, or a channel switching request is received from the communication partner terminal. A switching channel selection means for selecting a channel having a frequency band different from the frequency used by the digital cordless telephone system of the other system as a switching channel, and a channel in which radio wave interference has occurred by the switching channel selection means. Channel switching control means for controlling an operation of switching to the selected switching channel.

  (2) The switching channel selection method according to the present invention is a digital cordless telephone for offices composed of a base station and a terminal adopting a PHS (Personal Handy-Phone System) standardized as a second generation digital cordless telephone system. A switching channel selection method in a system, provided that a wireless device of a digital cordless telephone system of another method using the same frequency band exists in a communication area of the base station, the base station, A communication quality monitoring step for monitoring whether or not a decrease in communication quality during communication has occurred due to radio wave interference with a channel used for communication with a terminal, and communication during communication in the communication quality monitoring step When it is detected that the quality has fallen below a predetermined quality threshold value, or the channel from the terminal of the communication partner When a replacement request is received, a switching channel selection step for selecting a channel having a frequency band different from the frequency used by the digital cordless telephone system of the other method as a switching channel; and a channel in which radio wave interference has occurred A channel switching control step for controlling an operation of switching to the switching channel selected in the switching channel selection step.

  (3) The switching channel selection program according to the present invention is characterized in that at least the switching channel selection method described in (2) is implemented as a program executable by a computer.

  According to the digital cordless telephone system for offices, the switching channel selection method, and the switching channel selection program of the present invention, the following effects can be obtained.

  Even if the communication area of a digital cordless telephone system of another system, for example, the communication area of a DECT digital cordless telephone system overlaps with the communication area of a digital cordless telephone system for a PHS business operator, the PHS system side Therefore, it is possible to quickly and surely select a channel that does not cause radio wave interference with another system such as the DECT system side, so that channel switching can be performed. It can be shortened and communication quality can be ensured. Moreover, such channel selection operation and channel switching operation can be realized only by software change without introducing new hardware implementation means, and the introduction cost can be greatly reduced. It is.

It is a system configuration | structure figure which shows an example of the system configuration | structure of the digital cordless telephone system for offices by this invention. It is a schematic diagram for demonstrating the channel allocation state of the digital cordless telephone system for business offices of a PHS system, and the digital cordless telephone system of a DECT system. The figure which shows the table which classify | corresponds the corresponding relationship of the channel allocation state with the digital cordless telephone system 20 of the DECT system of the digital cordless telephone system 10 for PHS systems and classify | categorizes into the applicable band and the non-applicable band beforehand is there. 3 is a flowchart for explaining an example of channel switching operation in the business digital cordless telephone system shown in FIG. 1. It is a sequence chart for demonstrating the concrete channel switching operation | movement in the digital cordless telephone system for offices shown in FIG.

  Preferred embodiments of a digital cordless telephone system for offices, a switching channel selection method, and a switching channel selection program according to the present invention will be described below with reference to the accompanying drawings. In the following description, the digital cordless telephone system for offices and the switching channel selection method according to the present invention will be described. However, the switching channel selection method may be implemented as a switching channel selection program executable by a computer. However, it goes without saying that the switching channel selection program may be recorded on a computer-readable recording medium.

(Features of the present invention)
Prior to the description of the embodiments of the present invention, an outline of the features of the present invention will be described first. In general, PHS (1.9 GHz band) wireless devices and other wireless devices such as DECT (1.9 GHz band) wireless devices coexist in the same communication area, and PHS second generation digital cordless. During communication between PS (Personal Station: mobile station, terminal) and CS (Cell Station: base station) in a digital cordless telephone system for offices compliant with telephone system standards, the same frequency band as the communication channel being used is used. When interference radio waves from other types of wireless devices such as DECT wireless devices are generated, a communication error of communication data such as voice data occurs, and the phenomenon of communication noise continues. As a result, in the case of a voice call, the voice is interrupted, resulting in noise and sound loss. It is necessary to perform channel switching for switching the communication channel between the (CS) and the terminal (PS) to a channel of another frequency band.

  In the present invention, when a communication error occurs in communication data during communication, the base station (CS) uses a communication channel during communication as another type of wireless device, for example, a DECT (1.9 GHz band) type wireless device. Selects a channel of a frequency band different from the frequency band used by the mobile phone as a switching channel quickly and accurately, instructs the terminal (PS) to change to the switching channel, The main feature is that the communication quality can be quickly restored to a good state by enabling a DECT (1.9 GHz band) type wireless device to switch to a frequency band free of interference radio waves in a short time.

(Configuration example of embodiment)
Next, an example of the system configuration of the office digital cordless telephone system according to the present invention will be described with reference to FIG. FIG. 1 is a system configuration diagram showing an example of a system configuration of an office digital cordless telephone system according to the present invention, and adopts a PHS (Personal Handy-Phone System) system of a 1.9 GHz band second generation digital cordless telephone system. As an example of a digital cordless telephone system for offices according to the present invention and another digital cordless telephone system using the same frequency band as the digital cordless telephone system for offices, 1.9 GHz having the same frequency band as the digital cordless telephone system for offices This shows a case where both communication areas with a digital cordless telephone system of a DECT (Digital Enhanced Cordless Telecommunications) system using a band overlap each other.

  That is, in the system configuration example shown in FIG. 1, the digital cordless telephone system 10 for offices includes a communication area 10 </ b> A of a base station (CS: Cell Station) 12 that operates under the control of the main apparatus (ME) 11, and other As an example of the digital cordless telephone system, a state where the communication area 20A of the DECT digital cordless telephone system 20 exists in an overlapping area is shown.

  Further, in the system configuration example shown in FIG. 1, communication is performed between the base station (CS) 12 and the terminal (PS: Personal Station) 13 of the digital cordless telephone system 10 for offices using a 25 ch channel of the PHS system. It is assumed that communication is started between the DECT master unit 21 and the DECT slave unit 22 of the DECT type digital cordless telephone system 20 using the DECT type F5 channel. doing.

  Here, channel assignment states of the digital cordless telephone system 10 for offices of the PHS system and the digital cordless telephone system 20 of the DECT system will be described with reference to FIGS. 2A and 2B. FIG. 2A and FIG. 2B are schematic diagrams for explaining channel assignment states between the digital cordless telephone system 10 for business use of the PHS method and the digital cordless telephone system 20 of the DECT method, and FIG. 2A (1) is a diagram of the PHS method. The channel assignment state of the digital cordless telephone system 10 for offices is shown, and FIG. 2A (2) shows the channel assignment state of the digital cordless telephone system 20 of the DECT system. Further, FIG. 2B shows that the correspondence relationship of the channel assignment state of the digital cordless telephone system 10 for the PHS system digital cordless telephone system 10 with the DECT system cordless telephone system 20 is classified into a corresponding band and a non-corresponding band and set and registered in advance. It is a table.

  2A and 2B show only the communication channel except the control channel and the adjacent channel, and the channel of the digital cordless telephone system 10 for offices adopting the PHS method is the channel of the digital cordless telephone system 20 of the DECT method. Each channel in the PHS system is a frequency band corresponding to the frequency band of each channel of the DECT system digital cordless telephone system 20 by grouping the communication channels into the band 0 to the band 5 so as to be easily associated with each other. And the total bandwidth of each channel in the PHS system which is a frequency band not corresponding to the frequency band of each channel of the DECT digital cordless telephone system 20 is not applicable. Bandwidth (ie It shows a case in which the preset registered as a pass 0).

  As shown in FIG. 2A (2), the call channel permitted in Japan as the DECT digital cordless telephone system 20 in the 1.9 GHz band is F1ch (189.762 MHz to 189.65 MHz to 1905.95 MHz). 1896.48 MHz) to 5 channels for F5ch (1901.064 MHz to 1903.392 MHz), these frequency bands are for 1.9 GHz PHS system offices as shown in FIG. 2A (1). In the digital cordless telephone system 10, the frequency bands 1 to 5 and the frequency band 5 having 5 channels from 24ch to 28ch overlap each other as corresponding bands. Assigned.

  That is, as shown in FIG. 2B, in the digital cordless telephone system 10 for PHS-type offices in the 1.9 GHz band, the number of channels 1 and 5 is 5 and the number of channels 6 and 10 is 5 channels. The frequency band of the band 2, the band 3 consisting of the number of three channels 14ch to 16ch, the band 4 consisting of the number of four channels 20ch to 23ch, and the band 5 consisting of the number of the five channels 24ch to 28ch are DECT F1ch (189.762 MHz to 1896.48 MHz), F2ch (189.48 MHz to 1898.208 MHz), F3ch (1898.208 MHz to 1899.906 MHz), F4ch (189.906 MHz to 1901.064 MHz) and F5ch Is a frequency band that overlaps with each 1901.064MHz~1903.392MHz).

  Here, in the digital cordless telephone system 10 for offices, as shown in FIG. 2B, among the frequency bands of 1893.65 MHz to 1905.95 MHz, 5 ch of 251 ch to 255 ch shown in band 0 and 9 ch of 29 ch to 37 ch Is a non-corresponding band and is a frequency band with no frequency overlap with a DECT communication channel.

  Therefore, as shown in FIG. 1, between the base station (CS) 12 and the terminal (PS: Personal Station) 13 of the digital cordless telephone system 10 for offices, a 25-channel channel (that is, band 5) belongs to the PHS system. When communication is started using the DECT F5 channel between the DECT master unit 21 and the DECT slave unit 22 of the DECT digital cordless telephone system 20 in a state where communication is being performed using Depending on the timing of TDMA (Time Division Multiple Access), the 25-channel channel (that is, the channel belonging to band 5) of the digital cordless telephone system 10 for offices and the F5ch communication of the DECT digital cordless telephone system 20 are mutually connected. Will cause digital interference in the office. A communication error occurs in communication data of 25 channels during communication of the telephone system 10, and the phenomenon of communication noise mixing continues. As a result, in the case of a voice call, the voice is interrupted and a phenomenon of noise and sound loss occurs. Therefore, as a means for eliminating such a phenomenon, it is necessary to perform channel switching for switching the communication channel to another frequency band on the digital cordless telephone system 10 for office use.

  However, even if the channel of the digital cordless telephone system 10 for offices is switched to the adjacent channel of 25 ch that is communicating, for example, 26 ch, the interference state with the F5 ch communication of the DECT digital cordless telephone system 20 is eliminated. As a result, a communication error of communication data occurs and the phenomenon of mixing communication noise continues.

  That is, as shown in FIG. 2B, the frequency band of each channel of F1ch to F5ch of the DECT digital cordless telephone system 20 is 3 to 3 than that of the office digital cordless telephone system 10 having a bandwidth of 300 kHz per channel. 6 times wider bandwidth is used. Therefore, since the communication channel of the DECT system shown in FIG. 1 uses about 6 times the bandwidth of the PHS system, even if the channel is switched on the PHS system side, it moves from the frequency band of one communication channel on the DECT system side. It may not always be possible.

  In order to eliminate such a situation, the base station (CS) 12 of the digital cordless telephone system 10 for offices, as shown in FIG. 1, has a communication quality monitoring unit 121, a switching channel selection unit 122, and a channel switching control unit 123. At least. The communication quality monitoring unit 121 is a part that monitors the quality of communication data during communication (frame error rate: FER (Frame Error Rate)), and the communication quality drops below a predetermined quality threshold value, and the value of FER Is greater than a predetermined threshold value, it is assumed that interference with the DECT digital cordless telephone system 20 has occurred, and the channel switching request is switched to switch the communication channel. Output to the selector 122.

  Further, the switching channel selection unit 122 receives the channel switching request from the communication quality monitoring unit 121 or receives the channel switching request from the communication partner terminal (PS) 13, so that the DECT digital cordless This is a part for selecting an empty channel that does not cause interference with the telephone system 20. First, the band 1 shown in FIG. 2A and FIG. 2B defined as the corresponding band corresponding to each channel in the DECT digital cordless telephone system 20 ~ Abandoned channels belonging to bands other than the band to which the channel in which interference occurs are preferentially selected as a switching channel among the bands 5.

  Here, if there is no free channel that can be switched in any of the bands 1 to 5, which is the corresponding band, there is no frequency overlap with the DECT digital cordless telephone system 20 in the end. An empty channel is selected as a switching channel from channels belonging to band 0 of the corresponding band. Alternatively, even after switching to the selected switching channel, when the communication quality decreases to a predetermined quality threshold or less as a monitoring result of the communication quality monitoring unit 121, and the FER value becomes larger than the predetermined threshold In this case, an empty channel is immediately selected as a switching channel from the channels belonging to the band 0 of the non-corresponding band that does not overlap with the DECT digital cordless telephone system 20.

  The channel switching control unit 123 is a part that controls the operation of switching to the switching channel selected by the switching channel selection unit 122, and calls the designated switching channel to the communication partner terminal (PS) 13. A TCH (Traffic Channel) switching instruction to switch channels is transmitted to switch the calling channel, and after establishing synchronization of the switched calling channel with the terminal (PS) 13, SACCH (Slow Associated control channel (low-speed associated control channel) is used to control the exchange operation of SABM (Set Asynchronous Balanced Mode) command and UA (Unnumbered Acknowledgment) response for call setting.

(Description of operation of embodiment)
Next, an example of the channel switching operation in the office digital cordless telephone system 10 shown in FIG. 1 will be described with reference to the flowchart of FIG. FIG. 3 is a flowchart for explaining an example of the channel switching operation in the business-use digital cordless telephone system 10 shown in FIG.

  In the flowchart of FIG. 3, as described above, communication is being performed between the base station (CS) 12 and the terminal (PS) 13 of the digital cordless telephone system 10 for offices using a 25 ch channel of the PHS method. As a result of starting communication between the DECT master unit 21 and the DECT slave unit 22 of the DECT type digital cordless telephone system 20 using the DECT type F5 channel, the base station (CS) The FER (frame error rate) of communication between the terminal 12 and the terminal (PS) 13 exceeds a predetermined threshold, and a request for switching the call channel is transmitted from the terminal (PS) 13 side to the base station (CS) 12 The operation of the base station (CS) 12 is shown.

  In the flowchart of FIG. 3, when the switching channel selection unit 122 of the base station (CS) 12 receives a call channel switching request, that is, (RT TCH switching request) from the terminal (PS) 13 side (step S1), A search is made as to which of the band 0 to band 5 shown in FIGS. 2A and 2B the call channel currently being used, for example, 25ch, which is the target, belongs (step S2). Thereafter, as a search result, it is confirmed whether or not it belongs to the band 0 of the non-corresponding band whose frequency does not overlap with that of the DECT digital cordless telephone system 20 (step S3).

  If the currently used call channel, for example, 25ch does not belong to the band 0 (NO in step S3), the currently used call channel, for example, 25ch, which is the target of the band 0 and the switching request of the non-corresponding area. A free channel of any band is selected from the remaining bands excluding the band 5, for example, the band 5 (corresponding band), and the selected channel is notified to the channel switching control unit 123 as a switching channel.

  That is, the band 1 to 5 of the corresponding band whose frequency overlaps with the DECT digital cordless telephone system 20 rather than the band 0 of the non-corresponding band where the DECT digital cordless telephone system 20 does not use the frequency. Priority is given to the switching channel selection operation of any one of the bands 1 to 5 for the band 1 to 4 other than the band 5 to which the currently used call channel, for example, 25ch belongs, among the bands 1 to 5. An operation of selecting an empty channel belonging to the as a switching channel is performed. The channel switching control unit 123 that has received the notification from the switching channel selection unit 122 transmits an RT TCH switching instruction for instructing switching to the received switching channel to the terminal (PS) 13, and the communication channel is transmitted to the switching channel. Are switched (step S4).

  On the other hand, when the currently used call channel belongs to band 0 of the non-corresponding band (NO in step S3), the frequency of the channel belonging to band 0 overlaps with that of the DECT digital cordless telephone system 20. Since there is no channel, the channel switching control unit 123 is notified of a free channel different from the currently used speech channel among the channels belonging to the band 0 as the switching channel. The channel switching control unit 123 that has received the notification from the switching channel selection unit 122 transmits an RT TCH switching instruction for instructing switching to the received switching channel to the terminal (PS) 13, and the communication channel is transmitted to the switching channel. Are switched (step S5).

  After that, the channel switching control unit 123 performs synchronization with the terminal (PS) 13 for the switched switching channel, and then performs call control to control to return to the communication state. . The specific channel switching operation in the channel switching control unit 123 is as shown in the sequence chart of FIG. FIG. 4 is a sequence chart for explaining a specific channel switching operation in the office-use digital cordless telephone system 10 shown in FIG. 1, and channel switching between the base station (CS) 12 and the terminal (PS) 13. An example of the exchange of signals regarding the start of communication is shown.

  In the sequence chart of FIG. 4, when the channel of frequency 1 is used to communicate between the base station (CS) 12 and the terminal (PS) 13 (sequence Seq1), the data being communicated is When an error occurs (sequence Seq2), for example, the terminal (PS) 13 that detected the error transmits an RT TCH switching request for requesting switching of the communication channel to the base station (CS) 12 (sequence Seq3). . The channel switching control unit 123 of the base station (CS) 12 that has received the RT TCH switching request switches the frequency 1 currently in use to the switching channel of the frequency 2 selected as the switching destination channel by the switching channel selection unit 122. An RT TCH switching instruction for instructing switching of the original channel is transmitted to the terminal (PS) 13 (sequence Seq4).

  When the channel switching operation to the frequency 2 in the terminal (PS) 13 is completed, a synchronization burst signal and an idle TCH burst signal are transmitted to the terminal (PS) 13 in order to establish bit synchronization and frame synchronization of the frequency 2 channel. Exchanges are made with the base station (CS) 12 (sequences Seq5 to Seq8). As a result, when synchronization between the terminal (PS) 13 and the base station (CS) 12 is established, a SABM (SACCH) signal for performing call setup is transmitted from the terminal (PS) 13 (sequence Seq9). ). The channel switching control unit 123 of the base station (CS) 12 that has received the SABM (SACCH) signal sends back a UA signal as a response (sequence Seq10), whereby the base station (CS) 12 and the terminal (PS) 13 is restored to the state of communication using the switched channel of frequency 2 (sequence Seq11).

  When the base station (CS) 12 and the terminal (PS) 13 are restored to the state of communication by the channel switching operation as described above, the communication of the base station (CS) 12 returns to the description of the flowchart of FIG. Whether the quality monitoring unit 121 performs an operation of monitoring the communication quality with the terminal (PS) 13 and whether the FER (frame error rate) value of the voice data being communicated is smaller than a predetermined threshold value. (Step S6). If the FER value of the voice data being communicated is smaller than the threshold value (YES in step S6), as a result of switching to the switching channel, normal quality communication is restored. The channel switching operation is terminated.

  On the other hand, when the FER value of the voice data being communicated becomes greater than or equal to the threshold (NO in step S6), the communication quality cannot be ensured even after switching to the switching channel. Therefore, it is confirmed whether or not the number of channel switching times is equal to or less than a predetermined limit number (step S7).

  Here, in order to use the frequency band more effectively, the limited number of times is the free space in all the remaining bands except the band to which the currently used call channel belongs among the 0 to 5 bands. It may be set as the number of times a channel is selected (that is, five times), or it is free in any band except the band to which the currently used call channel belongs among bands 1 to 5 of the corresponding band. You may set so that it may select only twice with the channel and the empty channel in the band 0 of a non-corresponding band. In the present embodiment shown in FIG. 3, in order to enable channel switching that can quickly obtain a switching effect while effectively using the frequency band, the limit number is set to 2 times. Is illustrated.

  That is, in FIG. 3, when the number of channel switching is equal to or less than the limit number (YES in step S7), the selection operation of the free channel belonging to the band 0 of the non-corresponding band has not been performed yet. In step S5, the DECT digital cordless telephone system 20 performs an operation of reselecting a free channel from the channels belonging to the band 0 where the frequencies do not overlap, and then moves to step S6. . On the other hand, when the number of channel switching exceeds the limit number (NO in step S7), the channel switching is performed as a case where a failure that cannot restore the call quality occurs even when the channel is switched. End the operation.

  In general, when the channel currently in use is channel 25 belonging to band 5, and communication in DECT digital cordless telephone system 20 causes interference with channel 25ch, the DECT system side performs communication using F5 channel. As described above as a problem in the prior art, even if the channel is switched to a nearby channel belonging to the same band 5, such as ch24 and ch28, the DECT digital cordless telephone is the same as in the case of ch25. Since it falls within the frequency band of the F5 channel of the system 20, there is a high possibility that a voice data communication error will continue to occur, and a silent state will occur every time the channel is switched, resulting in voice communication noise. The situation of being recognized by the user continues.

  On the other hand, in the present embodiment, by operating as described in the flowchart of FIG. 3, the same band as the currently used channel, for example, 25ch, is used as the switching channel when switching the currently used channel, for example, 25ch. For example, since the operation of selecting a channel belonging to the band 5 is prohibited, a channel having a frequency different from the frequency band of the channel of the DECT digital cordless telephone system 20, such as the F5 channel, can be selected. It is possible to switch to a channel that can ensure normal communication quality by the switching operation. Here, even if the DECT digital cordless telephone system 20 is in use for the switched channel after switching, even if the normal communication quality cannot be ensured, Since the DECT digital cordless telephone system 20 selects a channel belonging to a non-corresponding band (that is, band 0) that does not use a frequency as a switching channel, interference can be reliably avoided by at least two channel switching operations. .

  The configuration of the preferred embodiment of the present invention has been described above. However, it should be noted that such embodiments are merely examples of the present invention and do not limit the present invention in any way. Those skilled in the art will readily understand that various modifications and changes can be made according to a specific application without departing from the gist of the present invention.

10 Business Digital Cordless Telephone System 10A Communication Area 11 Main Equipment (ME)
12 Base station (CS)
13 Terminal (PS)
20 DECT digital cordless telephone system 20A Communication area 21 DECT master unit 22 DECT slave unit 121 Communication quality monitoring unit 122 Switching channel selection unit 123 Channel switching control unit

Claims (10)

  In a digital cordless telephone system for offices composed of a base station and a terminal adopting the PHS (Personal Handy-Phone System) standardized as a second generation digital cordless telephone system, it is identical within the communication area of the base station. In preparation for the case where there is a wireless device of another type of digital cordless telephone system using a frequency band, the base station is in communication due to radio wave interference with a channel used for communication with the terminal. Communication quality monitoring means for monitoring whether or not a decrease in communication quality has occurred, and the communication quality monitoring means detects that the communication quality during communication has fallen below a predetermined quality threshold, or Used by other types of digital cordless telephone systems when a channel switching request is received from the terminal of the communication partner Switching channel selection means for selecting a channel of a frequency band different from the frequency being switched as a switching channel, and channel switching control for controlling an operation of switching a channel in which radio wave interference has occurred to the switching channel selected by the switching channel selection means And a digital cordless telephone system for business use.   The switching channel selection means uses the total band of each channel in the PHS system as a frequency band corresponding to the frequency band of each channel of the digital cordless telephone system of the other system as a corresponding band, The total band of each channel in the PHS system that is a frequency band not corresponding to the frequency band of each channel of the digital cordless telephone system is set and registered in advance as a non-corresponding band, and the non-corresponding band is selected when the switching channel is selected. The priority channel is selected, and an empty channel is selected as the switching channel from channels belonging to any one of the corresponding bands other than the corresponding band to which the channel in which radio interference has occurred belongs. Item 1. A digital cordless telephone system for business use according to Item 1.   After the channel for controlling communication with the terminal is switched to the switching channel selected by the switching channel selection means by the channel switching control means, and the communication state with the terminal is reached, the communication quality When the monitoring means detects that the communication quality of communication using the switching channel has decreased below the predetermined quality threshold, the switching channel selection means has not yet selected the switching band as the switching channel. 3. The digital cordless telephone system for offices according to claim 2, wherein an empty channel is selected as the switching channel from channels belonging to any of the remaining remaining bands.   After the channel for controlling communication with the terminal is switched to the switching channel selected by the switching channel selection means by the channel switching control means, and the communication state with the terminal is reached, the communication quality When the monitoring means detects that the communication quality of the communication using the switching channel has decreased below the predetermined quality threshold, the switching channel selection means immediately selects from among the channels belonging to the non-corresponding band. When a free channel is selected as the switching channel, or when there is no remaining corresponding band that has not yet been selected as a switching channel among the corresponding bands, a free channel is selected from the non-corresponding bands. The office data according to claim 2 or 3, wherein a channel is selected as the switching channel. Tal cordless telephone system.   The communication quality monitoring means monitors the FER (Frame Error Rate) of communication data as the communication quality of communication, and when the value of the FER exceeds a predetermined threshold value, the communication quality of communication is determined in advance. 5. The digital cordless telephone system for offices according to claim 1, wherein the digital cordless telephone system is detected as being deteriorated below the quality threshold value.   The digital cordless telephone system for offices according to any one of claims 1 to 5, wherein the other type of digital cordless telephone system is a DECT (Digital Enhanced Cordless Telecommunications) digital cordless telephone system.   A switching channel selection method in a digital cordless telephone system for offices composed of a base station and a terminal adopting a PHS (Personal Handy-Phone System) system standardized as a second generation digital cordless telephone system, In the case where there is a wireless device of another type of digital cordless telephone system that uses the same frequency band in the communication area of the station, the base station performs radio wave interference on a channel used for communication with the terminal. And the communication quality monitoring step for monitoring whether or not the communication quality during communication has deteriorated, and the communication quality during communication in the communication quality monitoring step has fallen below a predetermined quality threshold. Or when a channel switching request is received from the terminal of the communication partner. A switching channel selection step for selecting a channel having a frequency band different from the frequency used by the digital cordless telephone system as a switching channel, and a channel in which radio wave interference has occurred is switched to the switching channel selected by the switching channel selection step. And a channel switching control step for controlling the operation.   In the switching channel selection step, the total band of each channel in the PHS system that is a frequency band corresponding to the frequency band of each channel of the digital cordless telephone system of the other system is set as the corresponding band, and The total band of each channel in the PHS system that is a frequency band not corresponding to the frequency band of each channel of the digital cordless telephone system is set and registered in advance as a non-corresponding band, and the non-corresponding band is selected when the switching channel is selected. The priority channel is selected, and an empty channel is selected as the switching channel from channels belonging to any one of the corresponding bands other than the corresponding band to which the channel in which radio interference has occurred belongs. Item 8. The switching channel selection method according to Item 7.   The communication quality after the channel for performing communication with the terminal is switched to the switching channel selected by the switching channel selection step by the channel switching control step and becomes a communication state with the terminal. In the monitoring step, when it is detected that the communication quality of the communication using the switching channel has dropped below the predetermined quality threshold, the switching channel selection step immediately selects from the channels belonging to the non-corresponding band. When a free channel is selected as the switching channel, or when there is no remaining corresponding band that has not yet been selected as a switching channel among the corresponding bands, a free channel is selected from the non-corresponding bands. 8. A channel is selected as the switching channel. Other switching channel selection method according to 8.   10. A switching channel selection program, wherein the switching channel selection method according to claim 7 is implemented as a program executable by a computer.

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