JP6558544B2 - Cordless telephone system, radio wave interference avoiding method and program - Google Patents

Description

  The present invention relates to a cordless telephone system, a radio wave interference avoiding method, and a program, and more particularly, even when radio wave interference occurs due to overlapping of communication areas of PHS and other types of digital cordless telephone systems, TECHNICAL FIELD The present invention relates to a cordless telephone system, a radio wave interference avoiding method, and a program that can prevent the inability to make and receive calls.

  Since 1995, the 1.9 GHz band is a band for the second-generation cordless telephone system (Personal Handy-Phone System, hereinafter referred to as PHS) compliant with the standard RCR STD-28 established by the Japan Radio Industry Association. However, in 2011, as a wireless standard using the same band, the Japanese version of Digital Enhanced Cordless Telecommunications (hereinafter referred to as J-DECT) was newly institutionalized. These two phone systems were shared.

  FIG. 16 shows channel allocation in each of PHS and J-DECT in the 1.9 GHz band shared here. As shown in the figure, 40 waves for communication and 2 waves for control are allocated in the PHS in the band of 1893.5 MHz to 1906.1 MHz. On the other hand, in J-DECT, five waves that serve both as communication and control are allocated in the same band.

  By the way, in PHS, all outgoing and incoming calls are controlled using two control waves, and no radio wave interference avoidance processing is performed for the two control waves. If the two waves for control become unusable, the telephone system itself becomes unusable. In order to avoid such a situation, PHS protection regulations are established when J-DECT is introduced, and if J-DECT detects two radio waves for PHS control, it will interfere with this. The ARIB standard stipulates that the use of three waves (F2, F3, and F4) that may occur is stopped. For this reason, in an environment where PHS and J-DECT are mixed, radio interference may actually occur because of the F1 channel of J-DECT and CH255 to CH5 of PHS, and F5 and PHS of J-DECT. Only CH23 to CH28.

  Non-Patent Documents 1 and 2 (standards for PHS and J-DECT) each define a mechanism for avoiding radio wave interference generated in a band shared by PHS and J-DECT.

  Patent Document 1 describes a technique for avoiding radio wave interference on the J-DECT side, and Patent Documents 2 and 3 describe techniques for avoiding radio wave interference on the PHS side.

JP 2011-77985 A JP 2014-120933 A Japanese Patent Laid-Open No. 2015-23565

ARIB-STD-T28 ARIB-STD-T101

  As mentioned above, the PHS protection regulations ensure that the two control waves in PHS are not subject to radio interference from J-DECT, and as a result, there are 18 communication waves near the two control waves. Will not receive radio interference from J-DECT. In the end, only 12 waves for communication can cause substantial radio wave interference with J-DECT in PHS.

  Also, on the PHS side, when radio interference occurs during a call, there is a mechanism for slot switching that moves to a timing without radio interference on the time axis and channel switching that moves to a channel without radio interference on the frequency axis. Since it is defined, radio wave interference can be avoided unless there is a margin in radio resources, that is, unless there is no space on the time axis and the frequency axis.

  In other words, the PHS base station has a mechanism for monitoring the occurrence status and reception level of error frames during a call, and when a predetermined number or more of error frames are detected despite the reception level being sufficiently high, the frequency Channel switching is performed by switching one or both of the channel and the slot on the time axis. More specifically, the PHS base station has a mechanism for detecting an empty channel for constantly monitoring the occurrence of radio wave interference in a combination of an arbitrary frequency channel and a slot on the time axis. By using the table of the occurrence status of radio wave interference in each frequency channel and time slot generated by channel detection, by using the combination of the frequency channel with the least radio interference and the slot on the time axis, Achieve interference avoidance.

  This mechanism for avoiding radio interference is based on the premise that a J-DECT radio frame can be reliably detected using an empty channel detection mechanism on the PHS side. May not be detected reliably by free channel detection on the PHS side.

  Hereinafter, this content will be described in more detail.

  FIG. 17 shows a mechanism of idle channel detection (carrier sense) in PHS, FIG. 18 shows a mechanism for detecting J-DECT audio frames on the PHS side, and FIG. 19 shows J-DECT on the PHS side. FIG. 20 shows a mechanism for failing to detect a J-DECT control frame on the PHS side.

  As shown in FIG. 17, in PHS, the time length of all radio frames (including a guard period of 25 μs) is an integral multiple of 625 μs, and free channel detection is performed at three timings of the leading edge, center, and trailing edge of each slot. It is prescribed to do in. The time interval between these three timings is about 310 μs, and if it is a PHS interference wave, this mechanism can always detect the interference wave regardless of synchronous interference or asynchronous interference.

  On the other hand, the time length of the radio frame of J-DECT is about 450 μs for the voice frame and about 750 μs for the image frame, as shown in FIGS. 18 and 19, and these time lengths are based on the empty channel detection timing on the PHS side. Therefore, the PHS side can always detect these radio frames. However, in J-DECT, when idle, that is, when no telephone call or image transmission is performed, as shown in FIG. 20, the base unit transmits a control frame for notifying the surroundings in a 10 ms cycle. Since the time length of the control frame is about 100 μs, there is a high possibility that this will be overlooked in the PHS side free channel detection mechanism. In this example, the J-DECT method uses F1ch, and the PHS side detects a free channel for ch1. J-DECT F1ch and PHS ch1 are channels that interfere with each other.

  In this way, the free channel detection on the PHS side cannot reliably detect the J-DECT control frame, and the PHS has a combination of the frequency channel on which the J-DECT control frame exists and the slot on the time axis. This may cause radio wave interference.

  Such PHS and J-DECT radio interference mainly occurs when a call is made or when a call is received. As described below, if radio interference occurs during a call or a call, Can be uncallable or unreceivable.

  The PHS base station performs a channel assignment operation for sharing a channel used at the time of outgoing / incoming call with a PHS terminal. Prior to that, the PHS base station performs a free channel determination, but if it cannot detect radio interference with J-DECT, the PHS base station determines that the channel is a free channel even in a channel with radio interference, and assigns the assigned channel. You may choose as If a channel with radio wave interference is selected as the allocation channel, radio channel interference may occur in the frequency band of the allocation channel after the channel allocation operation, and there is a possibility that calling / incoming calls will fail.

  FIG. 21 shows a sequence when a PHS call fails due to radio wave interference with J-DECT. This sequence is based on the RCR STD-28 standard. In FIG. 21, Seq1 and Seq2 communicate using two PHS control waves (ch12 or ch18), and therefore no radio wave interference with J-DECT occurs.

  In making a call, first, the PHS terminal transmits a link channel establishment request signal to the PHS base station (Seq1). The PHS base station performs idle channel detection using idle slots. Here, it is assumed that the PHS base station is operating to allocate ch1 as a result of the empty channel detection, and J-DECT is transmitting a control signal using F1ch. The ch1 used by the PHS cordless telephone system and the F1ch used by J-DECT are frequency bands that cause radio wave interference with each other.

  As mentioned above, PHS free channel detection is performed at an interval of about 310 μs, and the J-DECT control frame has a time length of 100 μs. Therefore, an environment where the PHS and J-DECT digital cordless telephone system coexist Below, depending on the timing at which the PHS side performs free channel determination, there may be cases where radio wave interference cannot be detected even though PHS and J-DECT use the same frequency band.

  If radio interference cannot be detected, the PHS base station sends a link channel assignment signal to the PHS terminal so that ch1 is assigned to the PHS terminal even though J-DECT is transmitting a control signal using F1ch. Send (Seq2).

  The transmission and reception of Seq3 synchronous burst signal is followed by PHS ch1. At this time, since J-DECT continues to transmit the control frame on F1ch, radio wave interference occurs and, for example, transmission / reception of a synchronous burst signal of Seq3 fails.

  When the PHS detects radio wave interference with J-DECT and fails to send or receive signals, a mechanism is in place to retransmit the signal during a call or to switch the frequency used to maintain the call. However, regarding outgoing / incoming calls, there is no mechanism for switching the frequency to be used, and the only mechanism for maintaining communication is signal retransmission. However, if radio wave interference occurs during signal transmission / reception and transmission / reception fails, it is likely that radio wave interference will continue even if the signal is retransmitted in the same frequency band as when transmission / reception failed. Signal transmission / reception fails, and as a result, outgoing / incoming calls fail. FIG. 21 shows a sequence in the case where the reception of the synchronization burst signal is repeated even if retransmission is performed and the outgoing call fails.

  Patent Document 2 focuses on a channel switching method during a call, and cannot prevent radio wave interference during outgoing / incoming calls. In Patent Document 3, it is assumed that a J-DECT radio frame can be reliably detected by using a mechanism for detecting an empty channel on the PHS side, but actually, as described above, the J-DECT radio frame is included in the J-DECT radio frame. May be subject to J-DECT radio interference because there are some that cannot be reliably detected by the empty channel detection on the PHS side.

  The object of the present invention is to solve the above-mentioned problems, and even when the communication area of the PHS and another type of digital cordless telephone system overlaps and radio wave interference occurs, PHS call / call by the radio wave interference occurs. It is an object of the present invention to provide a cordless telephone system, a radio wave interference avoiding method, and a program capable of preventing the inability.

  In order to solve the above problems, the present invention provides a PHS cordless telephone system in which a PHS base station determines whether its own PHS base station is currently making a call, is receiving a call, or is talking. A state determination unit that determines the state, and a channel storage unit that holds information about whether each channel of a PHS cordless telephone system is a channel that may cause radio wave interference with a channel of another type cordless telephone system And a channel resource management unit that stores information about whether each channel is free or in use for the channels held in the channel storage unit, and is used when the PHS base station communicates with the PHS terminal. A channel switching unit for assigning and switching channels, and switching when a channel switching occurs after switching the channel during a call by the channel switching unit. A channel switching management unit for holding the generated channel, wherein the channel switching unit refers to information of the channel storage unit and the channel resource management unit, and the state determination unit determines whether a call is being made or is being received If it is determined, the channel that is not likely to interfere with other channels of the cordless telephone system is selected and assigned, and if the state determination unit determines that the call is in progress, If necessary, switch to a channel that may cause radio interference with other types of cordless phone system channels, and if there is no possibility of radio interference with other types of cordless phone system channels as the call quality deteriorates It is characterized by selecting and switching.

  Here, the channel storage unit divides wireless communication channels used between the PHS base station and the PHS terminal into channels that may cause radio interference with other systems and channels that do not cause radio interference with other systems. Each is preferably stored as a channel table.

  In addition, when the channel switching unit switches the channel during a call and the error frame in the switching destination channel exceeds the allowable value, the channel switching unit holds the switching destination channel information, switches back to the switching source channel, and switches the channel again. Then, it is also preferable to switch to a channel other than the switching destination channel.

  In addition, it is preferable that the channel switching unit switches a channel during a call that is not likely to cause radio interference with another method to a channel that may cause radio interference with another method, using channel assignment as a trigger.

  In addition, it is preferable that the channel switching unit switches a channel during a call that is not likely to cause radio interference with another method to a channel that may cause radio interference with another method by a trigger signal at a certain time interval.

  It is also possible to switch channels that are already used in a call to channels that may cause radio interference with other systems, so that the number of free channels that are not likely to cause radio interference with other systems does not fall below a predetermined number. preferable.

  Here, the other type cordless telephone system is, for example, a J-DECT type cordless telephone system.

  The present invention can also be realized as a radio wave interference avoiding method or program in a PHS digital cordless telephone system.

  According to the present invention, even when communication areas of other types of digital cordless telephone systems, for example, J-DECT type digital cordless telephone systems, overlap in the PHS communication areas, Link channel assignment when a call / incoming call occurs can select and assign a channel that is not likely to cause radio interference with other types of digital cordless telephone systems, thus preventing calling / incoming calls from being disabled. .

  Here, as a result of allocating a channel that is not likely to cause radio interference with other types of digital cordless telephone systems, the channel resources that are not likely to cause radio interference and other types of digital cordless telephone systems are reduced below a predetermined number. Sufficient call capacity can be obtained by switching a channel that is not likely to interfere with other types of digital cordless telephone systems during a call to a frequency channel that may cause interference with other types of digital cordless telephone systems. You can get a city.

  Also, if you switch to a channel that may cause radio interference with another type of digital cordless telephone system during a call, radio interference may occur due to the presence of the control frame of the other type of digital cordless telephone system. When communication is disabled after switching and switching to the original channel occurs, switching to the channel different from the previous channel is performed in the next channel switching, so that a digital cordless telephone system of another method is used. And radio wave interference can be avoided. In addition, when switching back, since the call quality of the switch-destination channel is originally secured, the call can be continued without any problem.

  Furthermore, since the channel selection and switching operations in the present invention can be realized only by changing software, it can be realized at low cost.

1 is a block diagram schematically showing a PHS digital cordless telephone system to which the present invention can be applied. FIG. It is a block diagram which shows an example of a structure of the PHS base station to which this invention was applied. It is a figure which shows the example of the information which a channel memory | storage part hold | maintains. It is explanatory drawing which shows the channel allocation of PHS and J-DECT, and a radio wave interference condition. It is a figure which shows the example of the information stored in the channel resource management part. It is a sequence diagram which shows an example of the operation | movement at the time of the call origination of the cordless telephone system which concerns on this invention. It is a flowchart which shows an example of the operation | movement of the channel allocation at the time of the call origination in the cordless telephone system which concerns on this invention. It is a figure which shows the specific example of the information stored in the channel resource management part. It is a figure which shows the other specific example of the information stored in the channel resource management part. It is a figure which shows the other specific example of the information stored in the channel resource management part. It is a figure which shows the example of the update of the information stored in the channel resource management part. It is a figure which shows the other specific example of the information stored in the channel resource management part. It is a sequence diagram which shows an example of the operation | movement of the channel allocation at the time of the incoming call of the cordless telephone system which concerns on this invention. It is a flowchart which shows an example of the operation | movement of the channel allocation at the time of the incoming call in the cordless telephone system which concerns on this invention. It is a sequence diagram which shows an example of the operation | movement in the telephone call of the cordless telephone system which concerns on this invention. It is explanatory drawing which shows the channel arrangement | positioning in the band which PHS and J-DECT share. It is explanatory drawing which shows the mechanism of the carrier sense in PHS. It is explanatory drawing which shows the mechanism which detects the flame | frame for audio | voices of J-DECT on the PHS side. It is explanatory drawing which shows the mechanism which detects the flame | frame for J-DECT video on the PHS side. It is explanatory drawing which shows the mechanism in which the detection of the control frame of J-DECT fails on the PHS side. FIG. 6 is a sequence diagram showing a case where a PHS call fails due to radio wave interference with J-DECT.

  The present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram schematically showing a PHS digital cordless telephone system to which the present invention can be applied.

  The digital cordless telephone system includes a main device 10, a PHS base station 20 (20-1, 20-2, ..., 20-n) and a PHS terminal 30 (30-1, 30-2, ..., 30- m), for example, configured as a digital cordless telephone system for business use.

  The main apparatus 10 controls the entire system in an integrated manner, and the PHS base station 20 is connected to the main apparatus 10 to establish a communication channel between the PHS terminals 30. As a result, the PHS terminals 30 can communicate with each other via the PHS base station 20. Note that at least one PHS base station 20 is required, and there are as many PHS terminals 30 as are necessary for a call between users. In general, a plurality of PHS terminals 30 exist within the communication area of one PHS base station 20.

  Hereinafter, an embodiment in which the present invention is applied to this digital cordless telephone system will be described.

  FIG. 2 is a block diagram showing an example of the configuration of the PHS base station 20.

  The PHS base station 20 of this example includes a state determination unit 200, a channel storage unit 210, a channel switching unit 220, a channel resource management unit 230, a carrier sense unit 240, and a channel switchover management unit 250.

  The state determination unit 200 determines the state of the PHS base station 20 itself, whether the PHS base station 20 is currently making a call, is receiving a call, or is talking. The result of this determination is referred to when the channel switching unit 220 performs channel allocation.

  The channel storage unit 210 stores information on whether each channel in the PHS system is a channel that may cause radio interference with another system, for example, a J-DECT system channel.

  FIG. 3 shows an example of information held by the channel storage unit 210.

  The channel storage unit 210 divides the wireless communication channel used between the PHS base station 20 and the PHS terminal 30 into a channel that may cause radio interference with other schemes and a channel that may not interfere with other schemes, These are respectively stored as “channel table 211 that may cause radio interference with other systems” and “channel table 212 that may not cause radio interference with other systems”.

  FIG. 4 is an explanatory diagram showing channel assignment and radio wave interference status in the PHS system and the J-DECT system.

  As shown in Fig. 4, PHS channels 255ch, 1ch to 5ch and J-DECT F1ch may interfere with each other, and PHS channels 23ch to 28ch and J-DECT F5ch There is a possibility of interference. Therefore, the “channel table 211 that may cause radio interference with other systems” in the channel storage unit 210 stores information of 1ch to 5ch, 23ch to 28ch, and 255ch, and “there is no possibility of radio interference with other systems. The channel table 212 "holds information of 6ch to 11ch, 13ch to 17ch, 19ch to 22ch, 29ch to 37ch, 251ch to 254ch. Note that the 12ch and 18ch information are channels used for control, and are not held in either table.

  Depending on the result of the determination in the state determination unit 200, the channel switching unit 220 may select “channel table 211 that may cause radio interference with other systems” and “can cause radio interference with other systems” in the channel storage unit 210. One channel is selected from the “no channel table 212”, and the channel is assigned as a communication channel to be used between the PHS base station 20 and the PHS terminal 30. At this time, the channel resource management unit 230 and the channel switchover management unit 250 are referred to, and a channel that is determined to be free and that has not switched back is selected. When a switchover occurs in the channel switched by the channel switcher 220, the channel switch manager 250 records information on the channel / slot number when the switchover occurs. If no switchover occurs, the information in the switchback management unit 250 is deleted.

  The channel resource management unit 230 stores information on whether or not each channel can be used for all the channels stored in the channel storage unit 210. This information is referred to when the channel switching unit 220 selects a channel.

  FIG. 5 shows an example of information stored in the channel resource management unit 230.

  The channel resource management unit 230 stores “in use” in the use status for the channel if the channel of the wireless communication used between the PHS base station 20 and the PHS terminal 30 is currently in use, otherwise Store “free”.

  The carrier sense unit 240, for example, periodically performs carrier sense, and as a result, wireless communication used between the PHS base station 20 and the PHS terminal 30 depending on whether or not the reception level is equal to or higher than a preset threshold value. Determine if any channel is currently in use. That is, as a result of carrier sense, it is determined that a channel whose reception level is equal to or higher than a preset threshold is being used, and other channels are determined to be free. Information of the channel resource management unit 230 is updated according to the determination result.

  The channel switching management unit 250 switches to a frequency channel that may cause radio wave interference with the J-DECT digital cordless telephone system, and then becomes unable to communicate due to radio wave interference and switches back. Used to hold information on the frequency channel and the slot on the time axis. Next, when channel switching occurs, it is possible to prevent continuous radio wave interference by avoiding and selecting channels / slots on the channel switching management unit 250. This information is deleted when no switchover occurs after channel switching.

  The operation of the PHS digital cordless telephone system according to the present invention will be described below.

  As described above, when the communication area of another type of digital cordless telephone system, for example, the J-DECT type digital cordless telephone system, overlaps with the communication area of the PHS digital cordless telephone system, PHS call origination / incoming calls There is a possibility that the situation that cannot be performed normally will occur. This occurs when the PHS carrier sense may fail to detect radio interference if the J-DECT digital cordless telephone system is in a standby state. This is because radio wave interference occurs during the operation.

  Therefore, in outgoing / incoming calls, a PHS digital cordless telephone system selects and assigns a channel that has no possibility of radio wave interference with other digital cordless telephone systems. As a result, it is possible to reliably make and receive calls without causing radio wave interference. In addition, by switching the channel used by the PHS terminal 30 in a call after call origination / incoming call to a channel that may cause radio wave interference with another type of digital cordless telephone system, sufficient call capacity can be obtained. You can get a city.

  As described above, in the present invention, channel assignment is performed preferentially using the “channel table 212 that is not likely to cause radio interference with other schemes”. In some cases, all the channels held by “212” are used, and a new call / incoming call cannot be made as it is. Therefore, in order to avoid such a situation, it is possible to cause radio wave interference by switching the channel that is not likely to cause radio wave interference with other types of digital cordless telephone systems during a call to a channel that may cause radio wave interference. Open a non-sex channel. This will be specifically described later.

  The above operation can be performed by providing the PHS base station 20 with the state determination unit 200 and the channel storage unit 210.

  That is, the channel storage unit 210 may cause radio interference with the other schemes in the “channel table 211 that may cause radio interference with other schemes” and the “channel table 212 that may not interfere with other schemes”. Since information on a certain channel and information on a channel that has no possibility of radio wave interference with other systems are held, when the state determination unit 200 determines that the incoming call / calling of the PHS base station 20 is in progress, A channel that is not likely to interfere with other systems is selected from the channel table 212 that is not likely to interfere and is assigned to a communication channel with the PHS terminal 30. As a result, it is possible to reliably make and receive calls without causing radio wave interference.

  By doing this, radio interference does not become a problem because a channel that has been confirmed to have no radio interference or a sufficiently low radio interference level is allocated, so PHS free channel detection This makes it possible to reliably make and receive calls without detecting radio wave interference with the J-DECT system.

  FIG. 6 is a sequence diagram showing an example of an operation at the time of outgoing call of the PHS digital cordless telephone system according to the present invention.

  First, the PHS terminal 30 transmits a link establishment request signal to the PHS base station 20 (Seq1). When the PHS base station 20 receives the link channel establishment request, the PHS base station 20 uses the channel resource management unit 230 among the channels stored in the “channel table 212 that has no possibility of radio interference with other systems” in the channel storage unit 210. One channel whose status is “free” is selected and assigned to communication with the PHS terminal 30 (Seq2). Note that the above communication is performed using a control channel.

  Communication after Seq3 is performed using the channel allocated in Seq2. Since this sequence is the same as the sequence at the time of calling specified in RCR STD-28, the description is omitted. When the call is established and the call is started at Seq10, the state determination unit 200 determines that the call is completed and the call is in progress.

  FIG. 7 is a flowchart showing an example of channel assignment operation at the time of calling in the PHS digital cordless telephone system according to the present invention.

  When the PHS base station 20 receives the link channel establishment request from the PHS terminal 30, first, the channel resource management among the channels in the “channel table 212 that has no possibility of radio interference with other systems” in the channel storage unit 210. It is checked whether there is a channel whose usage status of the section 230 is “free” (S1). For example, as illustrated in FIG. 8, if the channel 2124 is “free”, the condition of S1 is satisfied. If the condition of S1 is satisfied, the free channel 2124 is allocated for communication with the PHS terminal 30.

  If the condition of S1 is not satisfied, for example, as shown in FIG. 9, if there is no free channel in the “channel table 212 that is not likely to interfere with other systems”, the channel resource management unit 230 and the channel storage Refer to section 210 to see if there is a channel in communication in “Channel table 212 that is not likely to cause radio interference with other methods” and “Channel table 211 that is likely to cause radio interference with other methods”. Check for "free" channels (S2). In the example of FIG. 9, there is a channel in communication in the “channel table 212 that is not likely to cause radio interference with other methods”, and “channel table 211 that is likely to cause radio interference with other methods” Since there is a “vacant” channel 2112, the condition of S 2 is satisfied. If the condition of S2 is satisfied, the channel that is used for the call by one previously established call is selected (S3). As a call selection criterion, for example, the time when a call is established may be recorded, and the last established call may be selected. Here, for example, as shown in FIG. 10, if the channel 2122 is selected, then, as shown in FIG. 11, the other PHS terminal 30 sets the channel 2122 that is talking to “the possibility of radio wave interference with other systems”. Is switched to an empty channel 2112 in the “channel table 211” having a certain number (S4). By this switching, the channel 2112 is updated to “in use” and the channel 2122 is updated to “free”. After channel switching, it is checked whether switching has occurred in the switched channel (S5). When the condition of S5 is satisfied, that is, when channel switching occurs, the channel / slot number where switching has occurred is recorded in the “channel switching management unit 250”. When the condition of S5 is not satisfied, that is, when channel switching does not occur, the information of “channel switching management unit 250” is deleted (S7). As a result, the empty channel 2122 can be allocated for communication with the PHS terminal 30 that has transmitted the link channel establishment request.

  If the condition of S2 is not satisfied, channel allocation is determined as failure. FIG. 12 shows an example of information of the channel resource management unit 230 when the condition of S2 is not satisfied. In this example, all of the channels in “Channel table 212 that is not likely to cause radio interference with other methods” and “Channel table 211 that is likely to cause radio interference with other methods” are “in use”. Since the condition is not satisfied, channel assignment fails.

  FIG. 13 is a sequence diagram showing an example of an operation at the time of an incoming call of the PHS digital cordless telephone system according to the present invention.

  When the PHS base station 20 transmits an incoming call signal to the PHS terminal 30 (Seq1), the PHS terminal 30 transmits a link channel establishment request signal to the PHS base station 20 (Seq2). When the PHS base station 20 receives the link channel establishment request, the usage status of the channel resource management unit 230 among the channels held in the “channel table 212 that has no possibility of radio wave interference with other systems” is “free”. Is selected and assigned to communication with the PHS terminal 30 (Seq3). Note that the above communication is performed using a control channel.

  Communication after Seq4 is performed using the channel assigned in Seq3. Since this sequence is the same as the sequence at the time of an incoming call defined in RCR STD-28, the description is omitted. When the call is established and the call is started at Seq10, the state determination unit 200 determines that the call is completed and the call is in progress.

  FIG. 14 is a flowchart showing an example of channel assignment operation at the time of an incoming call in the PHS digital cordless telephone system according to the present invention.

  When the PHS base station 20 transmits an incoming call signal to the PHS terminal 30 and receives a link channel establishment request signal for the PHS base station 20, first, the “table 212 having no possibility of radio interference with other systems” in the channel storage unit 210. ”Is checked whether there is a channel whose usage status of the channel resource management unit 230 is“ free ”(S1). For example, as illustrated in FIG. 8, if the channel 2124 is “free”, the condition of S1 is satisfied. If the condition of S1 is satisfied, the free channel 2124 is allocated for communication with the PHS terminal 30.

  If the condition of S1 is not satisfied, for example, as shown in FIG. 9, if there is no empty channel in the “channel table 212 that is not likely to interfere with other systems,” the channel resource management unit 230 and the channel storage unit 210 To see if there is a channel on the call in “Channel table 212 that is not likely to cause radio interference with other methods” and “Free” in “Channel table 211 that is likely to cause radio interference with other methods”. "Check if there is a channel (S2). In the example of FIG. 9, there is a channel in communication in the “channel table 212 that is not likely to cause radio interference with other methods”, and there is an empty space in the “channel table 211 that is likely to cause radio interference with other methods”. Since the channel 2112 exists, the condition of S2 is satisfied. If the condition of S2 is satisfied, the channel used by the call established earlier is selected (S3). As a call selection criterion, for example, the time when a call is established may be recorded, and the last established call may be selected. Here, as shown in FIG. 10, if the channel 2122 is selected, then, as shown in FIG. 11, the other PHS terminal 30 sets the channel 2122 during the call to “There is a possibility of radio interference with other systems. Switching to the channel 2112 that is empty in the channel table 211 "(S4). By this switching, the channel 2112 is updated to “in use” and the channel 2122 is updated to “free”. After channel switching, it is checked whether switching has occurred in the switched channel (S5). When the condition of S5 is satisfied, that is, when channel switching occurs, the channel / slot number where switching has occurred is recorded in the “channel switching management unit 250”. When the condition of S5 is not satisfied, that is, when channel switching does not occur, the information of “channel switching management unit 250” is deleted (S7). As a result, the empty channel 2122 can be allocated for communication with the PHS terminal 30 that has transmitted the link channel establishment request.

  If the condition of S2 is not satisfied, channel allocation is determined as failure. FIG. 12 shows an example of information of the channel resource management unit 230 when the condition of S2 is not satisfied. In this example, all of the channels in “Channel table 212 that is not likely to cause radio interference with other methods” and “Channel table 211 that is likely to cause radio interference with other methods” are “in use”. Since the condition is not satisfied, channel assignment fails.

  According to the above channel assignment at the time of call origination / incoming call, unless all channels have been used, a new call is made to an empty channel held in the “channel table 212 with no possibility of radio wave interference with other systems”. A call / incoming call can be assigned, or a channel in the “channel table 212 that has no possibility of radio interference with other systems” can be changed to an “empty” channel, and a new outgoing / incoming call can be assigned to it. .

  FIG. 15 is a sequence diagram showing an example of an operation during a call of the PHS digital cordless telephone system according to the present invention.

  During a call, as described above, channel switching is performed in order to make the channel of “channel table 212 that is not likely to interfere with other systems radio waves” as an “empty” channel, and as described below, Channel switching is performed when call quality deteriorates.

  When the call quality deteriorates while the PHS base station 20 and the PHS terminal 30 are talking (Seq1), a TCH (call channel) switching request signal is transmitted from the PHS terminal 30 to the PHS base station 20 (Seq2) .

  When the PHS base station 20 receives the TCH switching request signal from the PHS terminal 30, the channel resource management unit 230 is usable (free), and an appropriate channel is selected from the channels held in the channel storage unit 210. Select a switching destination channel, and transmit a TCH switching instruction signal including information on the selected channel to the PHS terminal 20 (Seq3), and then use the switching source channel to send a synchronization burst signal to the PHS terminal 30. (Seq4).

  The PHS base station 20 waits for a synchronous burst signal transmitted from the PHS terminal 30 in the switching destination channel (Seq5). Here, the switching destination channel is preferably selected from the “channel table 212 that is not likely to cause radio interference with other schemes”, but the “channel table 212 that is not likely to cause radio interference with other schemes” is “free”. If there is no channel, it may be selected from “channel table 211 that may cause radio interference with other systems”.

  After receiving the synchronization burst signal on the switching destination channel, the PHS base station 20 transmits the synchronization burst signal to the PHS terminal 30 (Seq6). After that, the call on the switching destination channel becomes in accordance with the sequence (Seq7, Seq8) at the time of the call defined in RCR STD-28.

  As described above, when the PHS base station 20 is making or receiving a call, the channel to be allocated for communication with the PHS terminal 20 is selected from the “channel table 212 that has no possibility of radio interference with other systems”, and a call is in progress. If the call quality of the PHS terminal is deteriorated, a channel is appropriately selected from the “channel table 212 with no possibility of radio interference with other systems” and assigned to the communication of the PHS terminal 20. You can make and receive calls without radio interference with the system. If there is no “vacant” channel in the “channel table 212 that is not likely to interfere with other systems”, the call established on the channel “channel table 212 that is not likely to interfere with other systems” is established. By appropriately switching the channel to the channel of “channel table 211 that may cause radio wave interference with other systems”, the call capacity can be sufficiently maintained.

  Although the embodiment has been described above, the present invention is not limited to the above embodiment, and includes various modifications.

  For example, in the above embodiment, when there is no empty channel in the “channel table 212 that is not likely to interfere with other systems,” another PHS terminal 30 is busy when a new call / incoming call occurs. Switch to a free channel in “Channel table 211 that may cause radio interference with other systems”, and create a free channel in “Channel table 212 that may not cause radio interference with other systems”. However, an empty channel may be created in the “channel table 212 that has no possibility of radio wave interference with other systems” at an appropriate timing. For example, by giving a trigger at a certain time interval, a channel that the PHS terminal 30 is using for a call at that timing that has no possibility of radio interference with other systems is displayed as `` Possibility of radio interference with other systems ''. You may make it switch to the empty channel in "a certain channel table 211". According to this, for example, a channel that is used in a call for a newly established call is switched to a channel that may cause radio interference with another method, and a channel table that is not likely to cause radio interference with another method is displayed. It is possible to prevent the “free channels” in “212” from being less than a predetermined number.

  In addition, when selecting the channel, all the channels in the channel storage unit 210, the table 211, and the table 212 may be selected, or some channels in the channel storage unit 210, the table 211, and the table 212 may be selected. It is good also as a candidate for selection.

  The above embodiment is a case where the present invention is implemented as a PHS digital cordless telephone system, but the present invention can also be implemented as a radio wave interference avoiding method or program in a PHS digital cordless telephone system.

  In addition, although the other type of digital cordless telephone system has been described as being a J-DECT type digital cordless telephone system, the present invention generally refers to the other type of digital cordless telephone system as a PHS type digital cordless telephone system. This is effective for a system that may cause radio interference with some channels.

  10 ... Main unit, 20 (20-1,20-2, ..., 20-n) ... PHS base station, 30 (30-1,30-2, ..., 30-m)・ ・ ・ PHS terminal, 200 ・ ・ ・ State discriminating unit, 210 ・ ・ ・ Channel storage unit, 211 ・ ・ ・ Channel table that may interfere with other systems, 212 ・ ・ ・ Possible to interfere with other systems Incompatible channel table, 220 ... Channel switching unit, 230 ... Channel resource management unit, 240 ... Carrier sense unit, 250 ... Channel switching management unit, 2111-211n ... Radio interference with other systems Channels that are likely to be affected, 2121 to 212n ... Channels that are not likely to interfere with other systems

Claims (15)

In cordless telephone system of PHS (Personal Handy-Phone System) system,
The PHS base station
A state determination unit that determines whether the own PHS base station is currently calling, receiving a call, or talking;
A channel storage unit that holds information on whether each channel of the PHS cordless telephone system is a channel that may cause radio wave interference with a channel of another type cordless telephone system;
A channel resource management unit for storing information about whether each channel is free or in use for the channels held in the channel storage unit;
A channel switching unit for assigning and switching channels used when the PHS base station communicates with the PHS terminal;
A channel switching management unit for holding a channel in which switching occurs when channel switching occurs after switching the channel during a call by the channel switching unit;
The channel switching unit
With reference to the information of the channel storage unit and the channel resource management unit, when the state determination unit determines that a call is being made or a call is being received, there is no possibility of radio wave interference with a channel of another type of cordless telephone system A function for selecting and assigning a channel, a function for switching a channel during a call to a channel that may cause radio interference with a channel of a cordless telephone system of another method, and a call quality A cordless telephone system having a function of selecting and switching from a channel that is not likely to cause radio wave interference with a channel of another type of cordless telephone system according to deterioration. The channel storage unit
The wireless communication channels used between the PHS base station and the PHS terminal are divided into channels that may cause radio interference with other systems and channels that do not cause radio interference with other systems, and each is stored as a channel table. The cordless telephone system according to claim 1. The channel switching unit
If the error frame in the switching destination channel exceeds the allowable value during channel switching during a call, the switching destination channel information is retained and switched back to the switching source channel. 3. The cordless telephone system according to claim 1, wherein the cordless telephone system is switched to a channel. The channel switching unit
The channel assignment is used as a trigger to switch a channel during a call that is not likely to cause radio interference with another method to a channel that is likely to cause radio interference with another method. Cordless phone system as described in The channel switching unit
4. A channel during a call that is not likely to cause radio interference with another method is switched to a channel that is likely to cause radio interference with another method by a trigger signal at a predetermined time interval. The cordless telephone system according to one.   It is characterized by switching channels that are already used in a call to channels that may cause radio interference with other systems, so that the number of free channels that are not likely to cause radio interference with other systems does not fall below a predetermined number. The cordless telephone system according to claim 5.   The cordless telephone system according to any one of claims 1 to 6, wherein the other type cordless telephone system is a J-DECT type cordless telephone system. A method for avoiding radio wave interference in a cordless telephone system of PHS (Personal Handy-Phone System),
A state determination step of determining whether the own PHS base station is currently calling, receiving a call, or talking;
Stored in the channel storage unit is information on whether each channel of the PHS cordless telephone system is a channel that may cause radio wave interference with the channel of the other cordless telephone system and the channel resource management unit The channel storage unit stores information on whether each channel is free or in use, and the state determination step determines whether a call is being made or received. Function to select and assign a channel that has no possibility of radio interference with the channel of the other method cordless telephone system. Switch to a channel that may cause radio wave interference with the cordless phone system channel, and others depending on the deterioration of call quality. Radio interference avoidance method characterized by having a function channel switching step of to switch by selecting from the equation of a cordless telephone system channel and radio interference potential-free channels.   The channel storage unit divides wireless communication channels used between the PHS base station and the PHS terminal into channels that may cause radio interference with other systems and channels that do not cause radio interference with other systems. The radio wave interference avoiding method according to claim 8, wherein the radio wave interference avoiding method is stored as a channel table.   In the channel switching step, when the error frame in the switching destination channel exceeds the allowable value in channel switching during a call, the switching destination channel information is retained and switched back to the switching source channel. The radio wave interference avoiding method according to claim 8 or 9, wherein the channel is switched to a channel other than the switching destination channel.   9. The channel switching step, wherein channel assignment is used as a trigger to switch a channel during a call that is not likely to cause radio interference with another method to a channel that is likely to cause radio interference with another method. The radio wave interference avoiding method according to any one of 10.   The channel switching step is characterized in that, based on a trigger signal at a certain time interval, a channel during a call that is not likely to cause radio interference with another method is switched to a channel that may cause radio interference with another method. The radio wave interference avoiding method according to any one of 8 to 10.   In the channel switching step, a channel that is already used in a call is switched to a channel that may cause radio interference with another method so that the number of free channels that are not likely to cause radio interference with the other method does not fall below a predetermined number. The radio wave interference avoiding method according to claim 12, wherein:   14. The radio wave interference avoiding method according to claim 8, wherein the other type cordless telephone system is a J-DECT type cordless telephone system.   A program for causing a computer to execute each step of the radio wave interference avoiding method according to any one of claims 8 to 13.