Network system, cordless telephone device, and network control device

Abstract

To easily and surely eliminate so-called radio wave overlap, which is a state in which a slave unit receives signals from a plurality of master units.SOLUTION: When a slave unit PS2 is in a radio wave overlap state where the slave unit PS2 receives signals from two or more master units (step S1), the slave PS2 transmits an output control request to its own master unit CS2 (step S2). The master unit CS2 provides an output control request from its own slave unit PS2 to a main unit 1 (step S3). When the main unit 1 receives the output control request from the master unit CS2, the main unit provides an output control instruction to the master units CS1 and CS3 being other than the master unit CS2 being the master unit that sent the output control request (steps S4 and S5). When the master units CS1 and CS3 receive the output control instruction from the main unit 1, the master units determine whether it is possible to control a signal output level to be lowered, and when it is possible, the master units perform control to lower the signal output level (step S6).SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to a network system configured by connecting a cordless telephone device, in which a base unit and a handset are connected wirelessly, to a network control device such as a main unit, and to a device used in the network system. [Background technology]

[0002] In recent years, business phone systems (key telephone systems) have been configured by connecting cordless telephone devices to network control devices such as main units and SIP (Session Initiation Protocol) servers. A cordless telephone device functions as a single telephone device with a base unit and a handset wirelessly connected. For example, a communication method based on the DECT (Digital Enhanced Cordless Telecommunication) standard may be used between the base unit and the handset that make up the cordless telephone device.

[0003] The DECT standard stipulates that the downlink communication method from the base station to the handset is time division duplex using time division multiplexing, and the uplink communication method from the handset to the base station is time division multiple access.The DECT standard also stipulates that the frequency band to be used is the 1.9 GHz band, and the number of channels is limited to a maximum of five.

[0004] In the DECT standard, one channel of coded data is divided into frames of 10 milliseconds (ms), and each frame is divided into 24 time slots as shown in Fig. 16. In the following, time slots will be simply referred to as slots. Twelve slots S0 to S11 in the first half frame period of one frame are used for downlink from the parent unit to the child units, and 12 slots S12 to S23 in the second half frame period are used for uplink from the child units to the parent unit.

[0005] In DECT-compliant cordless telephone devices used in business phone systems, unless the power is off, one cordless telephone device uses one of the 12 slots in standby (idle) mode to transmit various control information, including synchronization signals, from the base unit to the handset. This slot is called a dummy bearer. Typically, multiple handsets can be connected to a base unit. However, whether only one handset is connected to a base unit or multiple handsets are connected, control information and the like is transmitted to each handset using one slot (dummy bearer) in standby mode. In this case, no information is transmitted from the handset to the base unit.

[0006] When an incoming call is received from this standby state and the telephone control device notifies the base unit of the incoming call, the base unit uses a dummy bearer to notify each handset of a data session connection request, and the handset searches for an available slot and contacts the base unit to attempt to acquire a slot to use for communication. The data session connection request is a request to create an environment in which the base unit and handset can communicate with each other, and is not a notification of the incoming call. Then, once a slot for mutual communication between the base unit and handset has been acquired in response to the data session connection request, the base unit releases the dummy bearer and notifies the base unit of the incoming call using the acquired downlink slot. At the same time, the base unit also identifies an uplink slot so that it can receive information from the handset.

[0007] In this way, the pair of downlink slots and uplink slots acquired for mutual communication between the parent device and the child device are called a traffic bearer. Various control information, including synchronization signals, is transmitted through the traffic bearer, and after a call line is connected to the other party, voice information is also transmitted. Because various control information and the like are transmitted through the traffic bearer, the process of identifying (acquiring) the traffic bearer and releasing the dummy bearer is called merging the dummy bearer into the traffic bearer.

[0008] In this way, after transitioning from standby mode to call mode, errors may occur in the call data, resulting in poor call quality (audio quality), due to interference from, for example, a nearby PHS (Personal Handy Phone System) telephone used by a third party. One solution to deal with such cases is disclosed in Patent Document 1, which will be described later. The invention disclosed in Patent Document 1 determines whether or not there is interference from a signal transmitted from a PHS fixed station, and if interference is determined to exist, sets the frequency band and slot timing to be used so as to avoid the interference. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-077985 Summary of the Invention [Problem to be solved by the invention]

[0010] However, in a business phone system using cordless telephone devices, the degradation of communication quality between the base unit and handset is not only caused by interference waves from PHS telephones and other devices unrelated to the business phone system. Depending on the installation location of the base unit of the cordless telephone device or the location where a movable handset is used, the handset may encounter a so-called radio wave overlap condition, in which it receives radio waves (signals) from multiple adjacent base units. Applying the invention disclosed in Patent Document 1 to such a case would require different communication channels and slot timings for each base unit, which would complicate control and is undesirable.

[0011] In view of the above, the object of the present invention is to easily and reliably eliminate the so-called radio wave overlap state in a network system configured using a communication device consisting of a parent unit and a child unit, in which a child unit receives signals from multiple parent units. [Means for solving the problem]

[0012] In order to solve the above problem, the network system of the invention described in claim 1 comprises: A network system comprising a network control device connected to a wide area network, a plurality of base units connected to the network control device, and one or more slave units that are capable of communicating by wirelessly connecting to one of the plurality of base units, wherein the plurality of base units and the one or more slave units use a predetermined frequency band as a communication channel, The slave unit is signal strength detection means for detecting the strength of each received signal received by the device itself; a first information notifying means for notifying a base station of the received signal strength of a signal from the base station, the received signal strength being detected by the signal strength detecting means; a second information notification means for forming an output control request and notifying the parent device when signals are received from two or more parent devices among the plurality of parent devices; Equipped with The parent device is a communication status storage means for storing and holding the received signal strength notified from the one or more slave devices, the slave device to which the own device is wirelessly connected being designated as the own slave device; a control request means for providing an output control request to the network control device when the output control request arrives from the slave device; a control determination means for determining whether or not an adjustment to lower an output signal level is possible based on the stored information of the communication status storage means when an output control instruction arrives from the network control device; a control execution means for executing an adjustment to lower the output signal level of the device itself when the control determination means determines that the adjustment to lower the output signal level is possible; Equipped with The network control device a connected master device storage means for managing each of the plurality of master devices connected to the own device; a control instruction means for, when the output control request arrives from the parent device, identifying the parent device that sent the output control request, and providing an output control instruction to a parent device other than the parent device that sent the output control request, among the plurality of parent devices, based on the stored data in the connected parent device storage means; The present invention is characterized by comprising:

[0013] According to the network system of the invention described in claim 1, the slave device includes a signal strength detection means, and a first information notification means of the slave device detects the received signal strength of a signal from the wirelessly connected master device and notifies the master device of the received signal strength. Furthermore, a second information notification means of the slave device transmits an output control request to the master device when it is in a radio wave overlap state, receiving signals from two or more master devices. The master device receives the received signal strength from its wirelessly connected slave device and manages it in a communication status storage means. A control request means of the master device provides an output control request from the slave device to the network control device. A control determination means of the master device determines whether or not control to lower the signal output level is possible when receiving an output control instruction from the network control device, and if control to lower the output level is possible, a control execution means controls to lower the signal output level. The network control device manages, in a connected master device storage means, which port each of the master devices connected to the slave device is connected to. A control instruction means of the network control device provides an output control instruction to master devices other than the master device that sent the output control request when an output control request is received from the master device. [Effects of the Invention]

[0014] According to this invention, in a network system configured using a communication device consisting of a parent unit and a child unit, the so-called radio wave overlap state in which a child unit receives signals from multiple parent units can be easily and reliably eliminated. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a diagram illustrating an example of the configuration of a business phone system according to an embodiment; [Figure 2]2 is a block diagram illustrating an example of the configuration of a main unit used in the business phone system according to the embodiment. FIG. [Figure 3] 1 is a block diagram illustrating an example of the configuration of a base unit of a cordless telephone device used in a business phone system according to an embodiment of the present invention. [Figure 4] 3 is a diagram illustrating an example of IDs (identification information) of a base unit and a handset used in the business phone system of the embodiment, a reception status level, and data stored in a communication status table. FIG. [Figure 5] 1 is a block diagram illustrating an example of the configuration of a handset of a cordless telephone device used in a business phone system according to an embodiment of the present invention. [Figure 6] FIG. 2 is a diagram for explaining a communication state (pattern 1) that may occur in the business phone system of the embodiment. [Figure 7] FIG. 10 is a diagram for explaining a communication state (pattern 2) that may occur in the business phone system of the embodiment. [Figure 8] 8 is a diagram for explaining a communication state after control in the case of pattern 2 shown in FIG. 7. FIG. [Figure 9] FIG. 10 is a diagram for explaining a communication state (pattern 3) that may occur in the business phone system of the embodiment. [Figure 10] 10 is a diagram for explaining a communication state after control in the case of pattern 3 shown in FIG. 9. FIG. [Figure 11] FIG. 10 is a diagram for explaining a communication state (pattern 4) that may occur in the business phone system of the embodiment. [Figure 12] FIG. 3 is a sequence diagram for explaining the operation of the business phone system according to the embodiment. [Figure 13] 10 is a flowchart illustrating a process for eliminating radio wave overlap, which is performed by a handset of a cordless telephone device of a business phone system according to an embodiment of the present invention. [Figure 14]10 is a flowchart for explaining a process performed by a base unit of a cordless telephone device in a business phone system according to an embodiment when an output control instruction is received. [Figure 15] 10 is a flowchart illustrating a process performed by the base unit of the cordless telephone device of the business phone system according to the embodiment when a reconfirmation result is received. [Figure 16] FIG. 1 is a diagram illustrating frames and slots of the DECT standard. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, with reference to the drawings, an embodiment of a network system according to the present invention, and a cordless telephone device and a network control device that are devices used in the network system will be described. In the embodiment described below, the network system according to the present invention will be described as being applied to a so-called business phone system formed, for example, in a company office. Furthermore, the main unit used in the business phone system is an embodiment of the network control device according to the present invention, and the cordless telephone device used in the business phone system is an embodiment of the cordless telephone device according to the present invention.

[0017] [Business phone system configuration example] Figure 1 is a diagram illustrating an example of the configuration of a business phone system according to this embodiment. For simplicity's sake, this embodiment will be described using an example in which a business phone system is configured by connecting three cordless telephone devices 21, 22, and 23 to a main unit 1, as shown in Figure 1. However, the present invention is not limited to this example, and it is of course possible to connect even more cordless telephone devices to the main unit 1 and configure a larger-scale business phone system.

[0018] Each of the cordless telephone devices 21, 22, and 23 comprises a cell station CS1, CS2, or CS3 as a base unit and a personal station PS1, PS2, or PS3 as a handset. Hereinafter, the cell stations CS1, CS2, and CS3 will be referred to as base units CS1, CS2, and CS3, and the personal stations PS1, PS2, and PS3 will be referred to as handset units PS1, PS2, and PS3. Each of the base units CS1, CS2, and CS3 and each of the handset units PS1, PS2, and PS3 are wirelessly connected.

[0019] It is also possible to wirelessly connect multiple handset units to each of the base units CS1, CS2, and CS3. However, for simplicity, this embodiment will be described assuming that one handset unit is connected to one base unit. Also, although not shown, the extension telephone units connected to the main unit 1 can be not only cordless telephone units 21, 22, and 23, but also digital key telephone terminals, as in a normal business phone system.

[0020] In this embodiment, wireless connections between base units CS1, CS2, and CS3 of cordless telephone devices 21, 22, and 23 and respective handset units PS1, PS2, and PS3 are made by the TDMA / TDD method using the DECT standard (method) for digital cordless telephones. Main unit 1 can accommodate one or more telephone lines L1 to Lm (m is an integer of 2 or greater). Base units CS1, CS2, and CS3 of cordless telephone devices 21, 22, and 23 are connected to main unit 1. In the example of FIG. 1, base units CS1, CS2, and CS3 are connected to main unit 1 by wire, but they may also be connected wirelessly.

[0021] The main unit 1 performs call control and circuit switching control for the multiple cordless telephone devices 21, 22, and 23, as well as other business phone control functions, and also has the function of supplying a reference synchronization signal SYNC to each of the multiple cordless telephone devices 21, 22, and 23. In this example, the reference synchronization signal SYNC is a signal with a period of 130 milliseconds (ms).

[0022] Each of base units CS1, CS2, and CS3 of cordless telephone devices 21, 22, and 23 synchronizes with reference synchronization signal SYNC from main unit 1 to generate a frame synchronization signal as a synchronization signal with a period of one frame (10 milliseconds (ms)), which is the unit communication period of a DECT-standard digital cordless telephone, and performs TDMA / TDD wireless communication using the DECT standard with handset units PS1, PS2, and PS3 based on the generated frame synchronization signal. Therefore, all of multiple cordless telephone devices 21, 22, and 23 operate in synchronization with reference synchronization signal SYNC from main unit 1.

[0023] 1, each of cordless telephone devices 21, 22, and 23 is a telephone terminal that is connected to main unit 1 and forms part of a business phone system. For this reason, call control signals such as incoming call notifications and outgoing call requests, as well as other control signals, are sent and received between main unit 1. Note that other control signals include, for example, control signals for controlling the LCDs (Liquid Crystal Displays) and LEDs (Light Emitting Diodes) of cordless telephone devices 21, 22, and 23 to notify the user of the operating status of other cordless telephone devices connected to main unit 1.

[0024] In some cordless telephone devices, the base unit is equipped with a user interface such as a ringer, LCD, LED, and operation panel. However, in some cases, the base unit only functions to connect the main unit and the handset, and the handset is equipped with a user interface such as a ringer, LCD, LED, and operation panel. In this case, various control signals are transmitted and received between the base unit and the handset. In this embodiment, the base units CS1, CS2, and CS3 of the cordless telephone devices 21, 22, and 23 basically do not have a user interface, but rather function to connect the main unit 1 and the handset PS1, PS2, and PS3.

[0025] Typically, each of the base units CS1, CS2, and CS3 is installed at a predetermined location in an office. As a result, as shown in Fig. 1, the base unit CS1 can communicate with the slave units PS1 and the like within a wireless communication area Ar1, and the base unit CS2 can communicate with the slave units PS2 and the like within a wireless communication area Ar2. Furthermore, the base unit CS3 can communicate with the slave units PS3 and the like within a wireless communication area Ar3.

[0026] In this way, each of the base units CS1, CS2, and CS3 and each of the slave units PS1, PS2, and PS3 form wireless communication areas Ar1, Ar2, and Ar3, respectively, where wireless communication is possible, based on their respective communication functions. The wireless communication areas Ar1, Ar2, and Ar3 are set up so that they overlap slightly. This allows the slave units PS1, PS2, and PS3 to switch between the base units CS1, CS2, and CS3 with which they communicate, allowing them to communicate while moving within the wireless communication areas Ar1, Ar2, and Ar3.

[0027] However, the locations of the base units CS1, CS2, and CS3 may be shifted or changed due to, for example, rearrangements of seats or layout changes involving the addition or removal of desks. In such cases, the sub units PS1, PS2, and PS3 may encounter a signal overlap situation in which they are able to receive signals from multiple base units. This signal overlap situation can cause inconveniences such as poor wireless communication quality and difficulty in making calls.

[0028] Therefore, in the business phone system of this embodiment, each of the handsets PS1, PS2, and PS3 has a function for detecting when it is in a radio wave overlap state. Each of the handsets PS1, PS2, and PS3 notifies its own base unit, to which it is wirelessly connected, that it is in a radio wave overlap state. In this specification, a base unit that is already wirelessly connected and ready for communication from the perspective of a handset is referred to as its own base unit, meaning a base unit that can wirelessly communicate with the handset. Also, a handset that is already wirelessly connected and ready for communication from the perspective of the base unit is referred to as its own handset, meaning a handset that can wirelessly communicate with the handset. Note that, as mentioned above, "wirelessly connected" does not simply mean a state in which the base unit provides control information to the handset via a dummy bearer. It means a state in which a downlink slot and an uplink slot have been selected between the base unit and the handset, i.e., a traffic bearer has been selected, and the base unit and the handset are ready for wireless communication with each other.

[0029] When the master unit receives a notification from its own slave unit that it has entered a radio wave overlap state, it notifies the main unit 1 of this. When the main unit 1 receives a notification from the master unit that it has entered a radio wave overlap state, it provides an output control instruction to master units other than the master unit that sent the notification, instructing them to control the transmission level of their signals to be lowered. The master unit that has received the output control instruction determines whether it is possible to lower the transmission level of the signal to the slave unit, and if it determines that it can be lowered, it performs processing to lower the transmission level (output level) of the signal to the slave unit. In this way, it realizes the function of eliminating the radio wave overlap state in the slave unit.

[0030] Furthermore, in the business phone system of this embodiment, a base unit that has performed processing to lower the signal transmission level in response to a control instruction from main unit 1 notifies main unit 1 of this fact. If there is a base unit that has performed processing to lower the signal transmission level, main unit 1 requests, via the base unit that has notified the occurrence of radio wave overlap, a handset that is wirelessly connected to that base unit to perform a reconfirmation process to confirm whether the radio wave overlap state has been resolved. In response, the handset that has notified the occurrence of radio wave overlap again checks whether radio wave overlap is occurring and notifies main unit 1 of the reconfirmation result via its own base unit.

[0031] The main unit 1 notifies the base unit that performed the process of lowering the signal transmission level of the reconfirmation result. If the reconfirmation result indicates that the signal overlap has been resolved, the base unit does nothing. However, if the reconfirmation result indicates that the signal overlap has not been resolved, the base unit processes the signal transmission level that it had lowered, since lowering the signal transmission level did not resolve the signal overlap. This prevents each base unit CS1, CS2, and CS3 from unnecessarily lowering the signal transmission level by returning the signal transmission level to its original level, preventing any interference with subsequent wireless communication with the base unit.

[0032] In this way, in the business phone system of this embodiment, if radio wave overlap occurs among the handsets PS1, PS2, and PS3, the signal transmission levels of the base units CS1, CS2, and CS3 can be controlled to be lowered to automatically resolve the situation. If the radio wave overlap is not resolved even after the base units CS1, CS2, and CS3 are controlled to resolve the radio wave overlap among the handsets, the base unit that lowered the signal transmission level can be controlled to return the signal transmission level to its original level.

[0033] The following is a detailed description of the configuration of the main unit 1, cordless telephone base units CS1, CS2, and CS3, and cordless telephone handset units PS1, PS2, and PS3 that make up the business phone system of this embodiment, which realizes the above functions. Because the cordless telephone base units CS1, CS2, and CS3 each have the same configuration, the following description will focus on the configuration of the main unit CS1 as an example. Similarly, the cordless telephone handset units PS1, PS2, and PS3 each have the same configuration, so the following description will focus on the configuration of the handset PS1 as an example.

[0034] [Configuration example of main unit 1] Fig. 2 is a block diagram illustrating an example of the configuration of main unit 1 used in the business phone system of the embodiment. As shown in Fig. 2, main unit 1 is configured to include line I / F (Interface) 11 to which telephone lines L1 to Lm are connected, control circuit 12 equipped with a computer for controlling main unit 1 as a whole, line LSI (Large Scale Integrated Circuit) unit 13, and reference oscillator 14.

[0035] Under the control of the control circuit 12, the line I / F 11 supplies voice signals (received voice signals) from the lines L1 to Lm to the line LSI unit 13, and supplies control signals such as call control signals from the lines to the control circuit 12. Also, under the control of the control circuit 12, the line I / F 11 transmits voice signals (transmitted voice signals) from the line LSI unit 13 to the other party via the lines L1 to Lm, and also transmits control signals such as call control signals from the control circuit 12 to the other party via the lines L1 to Lm.

[0036] The line LSI unit 13 includes n extension processing circuits 131, 132, ..., 13n corresponding to n extension telephone devices, and a timing signal generating unit 130. The subscript n basically means an integer of 1 or more. However, since the extension processing circuits 131 and 132 already exist in FIG. 2, the letter n in FIG. 2 means an integer of 3 or more.

[0037] The timing signal generator 130 generates a transmission clock signal CK and a multiplexing / division timing signal TM from a reference clock signal from a high-precision reference oscillator 14 using a quartz crystal resonator, and supplies these to n extension processing circuits 131 to 13n. The n extension processing circuits 131 to 13n have the same configuration, and each includes an audio signal processor 31, a control signal processor 32, a synchronization signal processor 33, and a multiplexing / division processor 34.

[0038] The audio signal processing unit 31 is connected to the line I / F 11 and also to the multiplexing / division processing unit 34, and is a processing circuit for processing the received audio signal from the line I / F 11 and the transmitted audio signal from the multiplexing / division processing unit 34. A transmission clock signal CK is supplied to the audio signal processing unit 31 from the timing signal generating unit 130.

[0039] The control signal processing unit 32 is connected to the control signal input / output terminal of the control circuit 12 and also to the multiplexing / division processing unit 34, and is a processing circuit for control signals such as call control signals when making and receiving calls, and when terminating a call. In other words, the control signal processing unit 32 is a processing circuit for both control signals from the main unit 1 to the cordless telephone device and control signals from the cordless telephone device to the main unit 1. The transmission clock signal CK from the timing signal generating unit 130 is also supplied to the control signal processing unit 32.

[0040] The synchronization signal processing unit 33 is connected to the synchronization signal output terminal of the control circuit 12 and also to the multiplexing / division processing unit 34, and is a processing circuit for the reference synchronization signal SYNC having a predetermined synchronization signal pattern from the control circuit 12. Similarly, the transmission clock signal CK from the timing signal generating unit 130 is also supplied to this synchronization signal processing unit 33.

[0041] The multiplexing / division processing unit 34 is connected to the audio signal processing unit 31, the control signal processing unit 32, and the synchronization signal processing unit 33, and is also connected to each of the base units CS1 to CSn of the cordless telephone devices 21 to 2n. The multiplexing / division processing unit 34 performs processing based on the timing signal TM from the timing signal generating unit 130. The multiplexing / division processing unit 34 multiplexes (time division multiplexes) the audio signal from the audio signal processing unit 31, the control signal from the control signal processing unit 32, and the reference synchronization signal SYNC from the synchronization signal processing unit 33 to generate a multiplexed signal. The multiplexing / division processing unit 34 supplies the generated multiplexed signal to each of the base units CS1 to CSn.

[0042] Furthermore, the multiplexing / division processing unit 34 divides (separates) the multiplexed signal from each of the master units CS1 to CSn into an audio signal and a control signal based on the timing signal TM from the timing signal generating unit 130. The multiplexing / division processing unit 34 supplies the divided (separated) audio signal to the audio signal processing unit 31, and supplies the divided (separated) control signal to the control signal processing unit 32.

[0043] In this embodiment, the control circuit 12 of the main unit 1 has four functional units: a connected base unit storage unit 121, a control instruction unit 122, a reconfirmation request providing unit 123, and a reconfirmation result providing unit 124. The connected base unit storage unit 121 functions as a so-called address management unit, and stores and holds the correspondence between terminal identification information (such as extension numbers and MAC addresses) of the cordless telephone devices 21, 22, and 23 connected to the main unit 1 and each of the extension processing circuits 131-13n. The control instruction unit 122 functions to provide an output control instruction to base units other than the base unit that sent the notification (transmitter) to lower the signal transmission level when it receives a notification from the base unit of a subordinate cordless telephone device that radio wave overlap has occurred in its own handset. This makes it possible to resolve the radio wave overlap occurring in the handset.

[0044] In order to identify which parent device has notified the user of the occurrence of radio wave overlap, the control circuit 12 of the main device 1 stores, in a predetermined memory thereof, for example, the MAC address of the parent device that has been included in the notification. This allows the control instruction unit 122 to identify a parent device other than the parent device that has notified the user based on the information stored in the connected parent device storage unit 121, and to transmit an output control instruction to the identified parent device.

[0045] When the reconfirmation request providing unit 123 receives a notification that output control has been performed from the parent device to which the output control instruction was sent, it sends a reconfirmation request to the parent device that notified the parent device that the signal overlap has occurred. This allows the parent device that notified the parent device to reconfirm whether signal overlap has occurred. The child device that has reconfirmed the signal overlap transmits the reconfirmation result to the main device 1 via its parent device. The reconfirmation result providing unit 124 performs processing to provide the reconfirmation result to parent devices other than the parent device that provided the reconfirmation result.

[0046] Even in this case, the control circuit 12 of the main device 1 can identify the parent device that provided the reconfirmation result by storing, for example, the MAC address of the parent device that sent the notification, included in the notification of the reconfirmation result. Therefore, the reconfirmation result providing unit 124 can identify a parent device other than the parent device that sent the notification based on the information stored in the connected parent device storage unit 121 and transmit the reconfirmation result to the identified parent device. As a result, if the reconfirmation result indicates the occurrence of radio wave overlap, the parent device's process of lowering the signal transmission level does not resolve the radio wave overlap, so the parent device can return the signal transmission level to its original level. This prevents the parent device from needlessly keeping the signal transmission level lowered.

[0047] [Configuration example of cordless telephone devices 21, 22, and 23] Next, an example of the configuration of the cordless telephone devices 21, 22, and 23 of this embodiment, which are composed of a base unit and a handset, will be described. As mentioned above, an example of the configuration of the base unit CS1 and handset PS1 that make up the cordless telephone device 21 will be described.

[0048] <Configuration example of parent unit> 3 is a block diagram illustrating an example of the configuration of base unit CS1 of cordless telephone device 21 used in the business phone system of this embodiment. As shown in FIG. 3, base unit CS1 is configured to include a control circuit 41 for controlling the entire base unit CS1, a line LSI unit 42, a synchronization signal generating circuit 43, a wireless communication circuit 44, and oscillators 45 and 46. Control circuit 41 is configured with a computer mounted thereon, and realizes functions such as call control in base unit CS1. Control circuit 41 also includes a communication status table 411, a request providing unit 412, a control determining unit 413, and a control executing unit 414. Details of control circuit 41 will be described later.

[0049] The line LSI unit 42 is a circuit for exchanging audio signals, control signals, and synchronization signals with the main unit 1. The line LSI unit 42 comprises a division / multiplexing processing unit 421, a control signal processing unit 422, an audio signal processing unit 423, a synchronization signal detection unit 424, and a PLL (Phase Locked Loop) unit 425. The PLL unit 425 is supplied with an oscillation signal of a reference frequency from an oscillator 45, and is also supplied with a multiplexed signal from the main unit 1. In this example, the frequency of the oscillation signal of the oscillator 45 is set to, for example, 2048 MHz (0.488 nanoseconds (ns)).

[0050] The PLL unit 425 extracts the clock signal CK component from the timing signal generation unit of the main unit 1 by so-called self-clocking from the multiplexed signal from the main unit 1. The PLL unit 425 compares the phase of the extracted clock signal CK component with that of the oscillation signal from the oscillator 45, and based on the comparison result, generates a system clock signal SCK for the main unit CS1 that is synchronized with the clock signal CK component from the oscillation signal of the oscillator 45. The PLL unit 425 supplies the generated system clock signal SCK to the division / multiplexing processing unit 421, the control signal processing unit 422, the audio signal processing unit 423, and the synchronization signal detection unit 424 as a clock signal for signal processing, and also supplies it to the synchronization signal generation circuit 43.

[0051] The division / multiplexing processing unit 421 is connected to the main unit 1, and is also connected to the control signal processing unit 422, the audio signal processing unit 423, and the synchronization signal detection unit 424. The division / multiplexing processing unit 421 divides (separates) the multiplexed signal from the main unit 1 into a control signal, an audio signal, and a reference synchronization signal SYNC. The control signal, the audio signal, and the reference synchronization signal SYNC divided (separated) by the division / multiplexing processing unit 421 are supplied to the control signal processing unit 422, the audio signal to the audio signal processing unit 423, and the synchronization signal detection unit 424, respectively.

[0052] Furthermore, the division / multiplexing processing unit 421 multiplexes the control signal from the control signal processing unit 422 and the audio signal from the audio signal processing unit 423 to generate a multiplexed signal, and supplies the generated multiplexed signal to the main unit 1. The control signal processing unit 422 is connected to the control signal input / output terminal of the control circuit 41, and is also connected to the division / multiplexing processing unit 421. The control signal processing unit 422 is a processing circuit for control signals such as call control signals when making and receiving calls, and when ending a call (both control signals from the main unit 1 to the cordless telephone device 21 and control signals from the cordless telephone device 21 to the main unit 1).

[0053] The audio signal processing unit 423 is connected to the wireless communication circuit 44 and the division / multiplexing processing unit 421, and is a processing circuit for processing the transmitted audio signal received from the handset PS1 via the wireless communication circuit 44 and the received audio signal from the division / multiplexing processing unit 421. The synchronization signal detection unit 424 receives the reference synchronization signal SYNC from the division / multiplexing processing unit 421 and detects a predetermined synchronization signal pattern contained in the reference synchronization signal SYNC. As a result, the synchronization signal detection unit 424 generates a reference synchronization pulse PS that is synchronized with the reference synchronization signal SYNC and has the same period (130 ms) as the reference synchronization signal SYNC as the signal at the time of detection. The synchronization signal detection unit 424 supplies the generated reference synchronization pulse PS to the synchronization signal generation circuit 43.

[0054] The synchronization signal generating circuit 43 comprises a counter 431 and a synchronization signal generating unit 432. A reference synchronization pulse PS having a period of 130 ms is supplied to a preset terminal PRE of the counter 431 from the synchronization signal detecting unit 424 of the line LSI unit 42, and a system clock signal SCK is supplied as a count input from the PLL unit 425. An output count value CNT of the counter 431 is supplied to the synchronization signal generating unit 432. The synchronization signal generating unit 432 generates a synchronization signal FL having a frame period (10 ms) of the DECT standard from the output count value CNT of the counter 431. The synchronization signal generating circuit 43 supplies the frame synchronization signal FL generated by the synchronization signal generating unit 432 to the wireless communication circuit 44.

[0055] The wireless communication circuit 44 is configured to include a control unit 441, a TDMA modulation / demodulation unit 442, and a wireless communication unit (denoted as "RF" in FIG. 4) 443. The wireless communication unit 443 is a circuit unit for performing wireless communication with the slave PS1. When outputting a signal from the slave PS1, the wireless communication unit 443 transmits the signal at a predetermined transmission level. However, the wireless communication unit 443 is capable of controlling the signal transmission level at least in the direction of lowering it according to the control of the control unit 441. Of course, the wireless communication unit 443 can also be configured to control the signal transmission level in the direction of increasing it.

[0056] The control unit 441 is connected to the TDMA modulation / demodulation unit 442 and the wireless communication unit 443, and is also connected to the control circuit 41. The control unit 441 controls the overall operation of this wireless communication circuit 44, and can control the signal transmission level of the wireless communication unit 443 in accordance with instruction information addressed to itself from the main device. The control unit 441 also has the function of supplying the TDMA modulation / demodulation unit 442 with a control signal based on a control signal obtained from the control circuit 41, and supplying information obtained from the TDMA modulation / demodulation unit 442 to the control circuit 41.

[0057] The TDMA modulation / demodulation unit 442 is connected to the control unit 441 and the audio signal processing unit 423 of the line LSI unit 42, and is also connected to the wireless communication unit 443, and modulates the control signal from the control unit 441 and the audio signal from the audio signal processing unit 423 in order to transmit them to the slave unit PS1. The signals modulated by this TDMA modulation / demodulation unit 442 are transmitted to the slave unit PS1 via the wireless communication unit 443. The TDMA modulation / demodulation unit 442 also demodulates the audio signal and control signal from the signal received from the slave unit PS1 by the wireless communication unit 443, supplies the demodulated audio signal to the audio signal processing unit 423, and supplies the demodulated control signal to the control unit 441.

[0058] The TDMA modulation / demodulation unit 442 includes a PLL unit 4421 for clock generation. The PLL unit 4421 is supplied with an oscillation signal from the oscillator 46 and a frame synchronization signal FL from the synchronization signal generation circuit 43. The PLL unit 4421 compares the phase of the frame synchronization signal FL from the synchronization signal generation circuit 43 with that of the oscillation signal from the oscillator 46, and generates a timing signal and a clock signal synchronized with the frame synchronization signal FL from the oscillation signal of the oscillator 46 based on the comparison result. The TDMA modulation / demodulation unit 442 uses the timing signal and the clock signal synchronized with the frame synchronization signal FL to generate a transmission signal to the slave unit PS1 in a period corresponding to an allocatable downlink slot, and processes a reception signal from the slave unit PS1 using an uplink slot.

[0059] Normally, when the master CS1 is connected to the main unit 1 and in standby mode, it starts synchronization processing for communication with the slave PS1, and constantly transmits synchronization signals and control information to the slave PS1 via a dummy bearer to maintain a communication-enabled state. That is, the control unit 441 of the wireless communication circuit 44 of the master CS1 sends a transmission signal generated by the TDMA modulation / demodulation unit 442 to the slave PS1 via the wireless communication unit 443, using one slot set in the master CS1, and when a response is returned from the slave PS1, it controls the slot used to transmit the transmission signal to be used for downlink and the slot receiving the response from the slave PS1 to be used for uplink, establishing synchronization and performing transmission and reception.

[0060] Furthermore, when the base station CS1 is notified of an incoming call, it sends this to the handset PS1. Upon receiving the notification of an incoming call, the handset PS1 searches for an available slot, identifies the slot (traffic bearer) to be used for communication, notifies the base station CS1, and uses the acquired slot to connect the base station CS1 and the handset PS1, thereby establishing a state in which communication can be carried out.

[0061] Furthermore, the TDMA modem unit 442 includes an information detector 4422. The information detector 4422 realizes a function of extracting necessary information from a signal transmitted from the slave unit PS1 and notifying the control circuit 41 via the control unit 441. The information detector 4422 also realizes a function of modulating information to be transmitted from the control circuit 41 to the slave unit PS1, which information is supplied from the control unit 441, and providing the information to the slave unit PS1 via the wireless communication unit 443.

[0062] The control circuit 41 of the master CS1 functions and cooperates with the slave PS1 and the main unit 1 to eliminate radio wave overlap occurring among the slaves PS1, PS2, and PS3. The communication status table 411 of the control circuit 41 stores and holds the communication status between the master CS1 and the slave PS1 based on slave communication status data from the slave PS1. The request providing unit 412 provides (notifies) the main unit 1 via the line LSI unit 42 an output control request from the slave PS1, a control execution response when control is performed to lower the transmission level of the signal transmitted to the slave, and a reconfirmation response from the slave PS1. The request providing unit 412 also provides (notifies) the main unit 1 of a reconfirmation request from the main unit 1 via the wireless communication circuit 44.

[0063] Furthermore, when an output control instruction is received from the main apparatus 1, the control determination unit 413 performs processing to determine whether it is possible for the local apparatus to lower the transmission level of the signal transmitted to the slave apparatus. If the control determination unit 413 determines that it is possible for the local apparatus to lower the transmission level of the signal transmitted to the slave apparatus PS1, the control execution unit 414 supplies a control signal to the wireless communication circuit 44 and executes control to lower the transmission level of the signal transmitted to the slave apparatus PS1. Furthermore, if the control execution unit 414 receives a reconfirmation result from another master apparatus from the main apparatus 1, and radio wave overlap has not been resolved and the local apparatus has lowered the transmission level of the signal transmitted to the slave apparatus PS1, the control execution unit 414 supplies a control signal to the wireless communication circuit 44 and executes control to restore the transmission level of the signal transmitted to the slave apparatus PS1 to its original level.

[0064] Therefore, in the parent device CS1 of this embodiment, the communication status table 411 functions as a communication status storage means, the request providing unit 412 functions as a control request means, a control execution response providing means, a reconfirmation request providing means, and a reconfirmation result providing means, the control determining unit 413 functions as a control determining means, and the control executing unit 414 functions as a control executing means and a readjustment control means.

[0065] In this embodiment, the main unit 1 can individually recognize each of the subordinate base units CS1, CS2, and CS3 by the MAC address of the base unit. Furthermore, each of the base units CS1, CS2, and CS3 can individually recognize each of the slave units PS1, PS2, and PS3 by the MAC address of the slave unit. Figure 4 is a diagram for explaining examples of the ID (identification information) of the base unit, the ID (identification information) of the slave unit, the reception status level, and data stored in the communication status table 411 used in the business phone system of this embodiment.

[0066] As shown in Figure 4(A), in this embodiment, the ID of the master device CS1 is "111111," and the ID of the master device CS2 is "111112." Also, as shown in Figure 4(B), in this embodiment, the ID of the slave device PS1 is "222221," and the ID of the slave device PS2 is "222222." As mentioned above, the IDs of the master device and the slave devices are, for example, MAC addresses, but for simplicity's sake, a six-digit number that is a simplified version of the MAC address will be used as the IDs of the master device and the slave devices.

[0067] The reception status level based on RSSI (Received Signal Strength Indication) used in the business phone system of this embodiment is understood as one of three levels: low output, medium output, and high output, as shown in Figure 4(C). Note that in Figure 4(C), the level values ​​are marked with a minus sign, so a smaller number indicates a larger value (higher value). That is, -10 dBm > -20 dBm > -30 dBm.

[0068] 4(C), the reception state level for low output is shown as an RSSI level less than -20 dBm and greater than -30 dBm, with the level value for low output being the upper limit of -30 dBm or greater. The reception state level for active output is shown as an RSSI level less than -10 dBm and greater than -20 dBm, with the level value for active output being the upper limit of -20 dBm or greater. The reception state level for high output is shown as an RSSI level less than -0 dBm and greater than -10 dBm, with the level value for high output being the upper limit of -10 dBm or greater. Note that when the reception state level is lower than low output, i.e., when the RSSI is less than -30 dBm (for example, -40 dBm or -50 dBm), consistently good wireless communication becomes difficult.

[0069] The reception status levels are expressed as low output, medium output, and high output because they are understood as corresponding to the output signal of the parent unit. Therefore, when the reception status level of the signal from the parent unit at the child unit is "low output," it means that the distance from the parent unit is long and the RSSI of the signal from the parent unit received by the child unit is small (low). Also, when the reception status level of the signal from the parent unit at the child unit is "medium output," it means that the distance from the parent unit is medium and the RSSI of the signal from the parent unit is medium. Also, when the reception status level of the signal from the parent unit at the child unit is "high output," it means that the distance from the parent unit is short and the RSSI of the signal from the parent unit is large (high).

[0070] Each of the slave devices PS1, PS2, and PS3 notifies its own master device of the signal level of the signal received from the master device with which it is wirelessly connected and capable of communicating with the master device. This allows the master device to grasp the communication status with its own wirelessly connected slave device, as shown in FIG. 4(D). In the case of FIG. 4(D), the wirelessly connected slave device is slave device PS1 with ID "222221," and the communication status is "low output (-30 or higher)." This indicates that the slave device can communicate with its own slave device PS1 but is located far from the master device. Therefore, if the communication status between the slave devices is "-30 or higher" as indicated by the RSSI and low output as shown in FIG. 4(D), it can be determined that the signal transmission level of the master device to the slave devices cannot be lowered any further.

[0071] <Example of handset configuration> Fig. 5 is a block diagram illustrating an example of the configuration of handset PS1 of cordless telephone device 21 used in the business phone system of the embodiment. As shown in Fig. 5, handset PS1 is configured to include a wireless communication circuit 51, a control circuit 52, a codec circuit 53, an oscillator 54, a microphone 55, and a speaker 56. Microphone 55 constitutes a transmitter, and speaker 56 constitutes a receiver. Wireless communication circuit 51 is configured to include a control unit 511, a TDMA modulation / demodulation unit 512, and a wireless communication unit (denoted as "RF" in Fig. 5) 513. Wireless communication unit 513 is a circuit unit for performing wireless communication with base unit CS1.

[0072] Control unit 511 is connected to TDMA modulation / demodulation unit 512 and wireless communication unit 513, and is also connected to control circuit 52. Control unit 511 controls the overall operation of wireless communication circuit 51, and supplies a control signal to TDMA modulation / demodulation unit 512 based on a control signal obtained from control circuit 52. Control unit 511 also includes information notification processing unit 5111. Information notification processing unit 5111 realizes the function of forming three pieces of notification information and notifying its own base unit via TDMA modulation / demodulation unit 512 and wireless communication unit 513.

[0073] That is, information notification processing unit 5111 forms notification information notifying the communication state between its own device and its own base device, including the received signal strength of the signal from its own base device detected by TDMA modulation / demodulation unit 512, which will be described later, and realizes the function of first information notification means for notifying its own base device of this. Information notification processing unit 5111 forms notification information notifying the state of radio wave overlap, in which signals from multiple base devices are being received, based on the received signal strength detected by TDMA modulation / demodulation unit 512, which will be described later, and realizes the function of second information notification means for notifying its own base device of this. Information notification processing unit 5111 realizes the function of third information notification means for, when a reconfirmation request arrives from its own base device, reconfirming whether radio wave overlap has occurred and notifying its own base device of the reconfirmation result.

[0074] The TDMA modulation / demodulation unit 512 is connected to the control unit 511 and the wireless communication unit 513, and is also connected to the codec circuit 53, and modulates the control signal from the control unit 511 and the audio signal from the codec circuit 53 in order to transmit them to the base unit CS1. The signal modulated by the TDMA modulation / demodulation unit 512 is transmitted to the base unit CS1 via the wireless communication unit 513. Therefore, as described above, the TDMA modulation / demodulation unit 512 also realizes the function of modulating the notification information formed by the information notification processing unit 5111 of the control unit 511 and transmitting it to its own base unit via the wireless communication unit 513. The TDMA modulation / demodulation unit 512 also demodulates the audio signal and control signal from the signal received from the base unit CS1 by the wireless communication unit 513, supplies the demodulated audio signal to the codec circuit 53, and supplies the demodulated control signal to the control unit 511.

[0075] TDMA modulation / demodulation unit 512 includes PLL unit 5121 for clock generation and RSSI detection unit 5122. PLL unit 5121 is supplied with an oscillation signal from oscillator 54 and a demodulated signal of the received signal from wireless communication unit 513, and PLL unit 5121 generates a clock signal synchronized with the clock component of the demodulated signal of the received signal, from the oscillation signal from oscillator 54. The clock signal from PLL unit 5121 is used as a clock signal for processing in TDMA modulation / demodulation unit 512.

[0076] The RSSI detection unit 5122 of the TDMA modem unit 512 detects the RSSI (received signal strength) of each received signal. Assume that the slave device PS1 in this example is receiving a transmission signal from the master device CS1 and a transmission signal from the master device CS2. In this case, the RSSI detection unit 5122 associates and holds the MAC address of the master device CS1 included in the demodulated transmission signal from the master device CS1 with the received signal strength of the transmission signal from the master device CS1. Similarly, the RSSI detection unit 5122 associates and holds the MAC address of the master device CS2 included in the demodulated transmission signal from the master device CS2 with the received signal strength of the transmission signal from the master device CS1. When a transmission signal is received from a source other than the master devices CS1 and CS2, the RSSI detection unit 5122 associates and holds the identification information of the source of the transmission signal with the received signal strength of the transmission signal.

[0077] In this way, the RSSI detection unit 5122 can determine from which source a transmitted signal is being received and at what received signal strength. Therefore, when the RSSI detection unit 5122 receives multiple signals from different sources and detects the respective received signal strengths, it can be determined that the PS1 itself is experiencing radio wave overlap.

[0078] The codec circuit 53 decodes the voice signal demodulated by the TDMA modulation / demodulation unit 512, converts it into an analog voice signal, and supplies the analog voice signal to the speaker 56 to emit it as a received voice. The codec circuit 53 also encodes the analog voice signal picked up by the microphone 55 and supplies it to the TDMA modulation / demodulation unit 512. When a call is made from the handset PS1, the control circuit 52 transmits a call control signal at the time of making a call to the base unit CS1 via the wireless communication circuit 51, and when a call control signal at the time of receiving an incoming call from the base unit CS1 is received, the control circuit 52 performs processing such as emitting a ring tone from the speaker 56.

[0079] The control unit 511 of the wireless communication circuit 51 controls the TDMA modulation / demodulation unit 512 in response to a control signal from the base unit CS1 itself, searches for and identifies slots to be used for communication in the downlink and uplink, and performs reception / transmission processing. That is, during standby, the base unit CS1 and the handset PS1 can transmit and receive control signals through one predetermined slot (dummy bearer) in the downlink and uplink. For example, when a simultaneous incoming call occurs and the main unit 1 notifies the handset PS1 of the incoming call notification from the base unit CS1 via the base unit CS1, the handset PS1 searches for an available slot to acquire an available slot to use for the call. Then, the handset PS1 cooperates with the base unit CS1 to use the acquired available slot as a traffic bearer to make the call.

[0080] In this way, the control unit 511 of the wireless communication circuit 51 can specify a slot to be used for communication with the parent device CS1 in response to a control signal from the parent device CS1, and connect to the parent device CS1. The control unit 511 of the wireless communication circuit 51 can also release (disconnect) the connection with the parent device CS1 in response to a control signal from the parent device CS1. Furthermore, the control unit 511 of the wireless communication circuit 51 can specify a slot to be used for communication with another parent device in response to a control signal from the other parent device with which communication is possible, and connect to the other parent device. As described above, the control unit 511 can also receive notification information notifying the communication status between the device itself and the parent device, To realize a function of notifying a base unit of notification information notifying the state of radio wave overlap when the base unit is in the state of radio wave overlap and a result of reconfirmation whether radio wave overlap has occurred.

[0081] The above explanation has been given for the base unit CS1 and handset PS1 of the cordless telephone device 21, but as mentioned above, the base units CS2-CSn and handset PS2-PSn of the other cordless telephone devices 22-2n have similar configurations. Furthermore, the handset PS1, PS2, and PS3 can also move and communicate with nearby base units CS1, CS2, and CS3 to make calls. Therefore, the base units CS1, CS2, and CS3 can treat the handset wirelessly connected to them as their own handset and perform the same processing as that performed between the base unit CS1 and handset PS1 described above.

[0082] [Examples of communication status patterns and level control] Next, specific examples of communication states that may occur in the business phone system of this embodiment and control of signal transmission levels in the base unit will be described. For simplicity, the following description focuses on cordless telephone device 21, which consists of base unit CS1 and handset PS1, and cordless telephone device 22, which consists of base unit CS2 and handset PS2, and does not include a description of cordless telephone device 23 shown in FIG. 1.

[0083] <Communication status pattern 1> 6A and 6B are diagrams illustrating a communication state (pattern 1) that may occur in the business phone system of this embodiment. As shown in FIG. 6A, base units CS1 and CS2 are installed at a certain distance from each other. Under normal conditions, base units CS1 and CS2 have the same transmission level and output transmission signals at a predetermined transmission level. As a result, base unit CS1 forms a wireless communication area Ar1, and base unit CS2 forms a wireless communication area Ar2.

[0084] The wireless communication coverage areas Ar1 and Ar2 can be divided into three areas shown by concentric circles centered around the positions of the master devices CS1 and CS2. These areas are divided by the received signal strength (RSSI) at the slave devices of the signals transmitted from the master devices CS1 and CS2. That is, when the master devices CS1 and CS2 are outputting signals at a predetermined transmission level, the innermost area is a high-output area (hereinafter referred to as a high-output area) where the RSSI of the signals transmitted from the master devices is large (high). The middle area in this case is an area where the RSSI of the signals from the master devices is medium (hereinafter referred to as a medium-output area) where the output is in progress. The outermost area in this case is a small-output area (hereinafter referred to as a small-output area) where the RSSI of the signals from the master devices is small (low).

[0085] In the case of pattern 1 shown in Fig. 6(A), the slave PS1 is located in the middle output area of ​​the wireless communication area Ar1 formed by the master CS1, and the slave PS2 is located in the middle output area of ​​the wireless communication area Ar2 formed by the master CS2. Therefore, as shown in Fig. 6(B), the notification information sent from the slave PS1 to the master CS1 to notify the communication status between the slave PS1 and the master CS1 simply indicates that the signal from the master CS1 is being received at a medium level (-20 dBm or higher). Similarly, the notification information sent from the slave PS2 to the master CS2 to notify the communication status between the slave PS2 and the master CS2 simply indicates that the signal from the master CS2 is being received at a medium level (-20 dBm or higher).

[0086] As described above, in the case of pattern 1 shown in Fig. 6(A), slave PS1 receives only signals from master CS1, and slave PS2 receives only signals from master CS2, and there is no overlapping state in which signals from multiple masters are received. Therefore, in the case of pattern 1 shown in Fig. 6(A), slaves PS1 and PS2 do not send output control requests due to overlapping signals to masters CS1 and CS2, and masters CS1 and CS2 do not perform control to lower the signal transmission level. In other words, the signal transmission level is maintained in masters CS1 and CS2.

[0087] <Communication status pattern 2> 7A and 7B are diagrams illustrating a communication state (pattern 2) that may occur in the business phone system of this embodiment. As shown in FIG. 7A, base units CS1 and CS2 are installed slightly closer to each other than in FIG. 6A. As described above, under normal conditions, base units CS1 and CS2 have the same transmission level and output signals at a predetermined transmission level. As a result, base unit CS1 forms a wireless communication area Ar1, and base unit CS2 forms a wireless communication area Ar2.

[0088] As in the example shown in Fig. 6(A), the wireless communication areas Ar1 and Ar2 can be divided into three areas shown by concentric circles centered around the positions of the master devices CS1 and CS2. In the example shown in Fig. 7(A), when the master devices CS1 and CS2 are outputting signals at a predetermined transmission level, the slave device PS1 wirelessly connected to the master device CS1 is located in the large-output area of ​​the wireless communication area Ar1 formed by the master device CS1. In this case, the slave device PS2 wirelessly connected to the master device CS2 is located in the area where the small-output area of ​​the wireless communication area Ar1 formed by the master device CS1 overlaps with the small-output area of ​​the wireless communication area Ar2 formed by the master device CS2.

[0089] 7B, the notification information transmitted from the slave PS1 to the master CS1, which notifies the communication status between the slave PS1 and the master CS1, simply indicates that the signal from the master CS1 is being received at a high level (-10 dBm or higher). In contrast, the notification information transmitted from the slave PS2 to the master CS2, which notifies the communication status between the slave PS2 and the master CS2, indicates that the signal from the master CS2 is being received at a low level, and that the signal from the other master CS1 is being received at a low level. Here, the other master refers to a master that is not connected wirelessly, but is merely a master that is the source of the received signal and is merely detecting its presence, in contrast to the master that is connected wirelessly.

[0090] As described above, in the case of pattern 2 shown in Fig. 7(A), as shown in Fig. 7(B), slave PS1 is not in a radio wave overlap state, while slave PS2 is in a radio wave overlap state. Therefore, slave PS2 transmits an output control request to its own master CS2. The output control request is transmitted to the main unit 1 via its own master CS2, and then transmitted as an output control instruction via the main unit 1 to master CS1, which is a master other than the output sender. As a result, master CS1 determines whether the signal transmission level can be lowered, and if it determines that the signal transmission level can be lowered, it controls the signal transmission level to be lowered.

[0091] FIG. 8 is a diagram for explaining the communication state after control in the case of pattern 2 shown in FIG. 7. As shown in FIG. 7(A), the slave device PS1 is located in the high-output area of ​​the wireless communication area Ar1 formed by the master device CS1 itself. Therefore, it is determined that the signal transmission level of the master device CS1 itself can be lowered by one level and the maximum area of ​​the wireless communication area Ar1 can be reduced to the medium-output area shown in FIG. 7(A). Therefore, the master device CS1 lowers its own signal transmission level to reduce the wireless communication area Ar1. In this case, since the master device CS1 has lowered its signal transmission level, the inner area becomes the medium-output area and the outer area becomes the small-output area, as shown in FIG. 8(A), and the wireless communication area Ar1 is reduced.

[0092] 8B, the notification information sent from the slave PS1 to the master CS1 to notify the communication status between the slave PS1 and the master CS1 simply indicates that the signal from the master CS1 is being received at a medium level. Similarly, the notification information sent from the slave PS2 to the master CS2 to notify the communication status between the slave PS2 and the master CS2 simply indicates that the signal from the master CS2 is being received at a low level. This indicates that the signal overlap condition at the slave PS2 has been resolved.

[0093] <Communication status pattern 3> 9A and 9B are diagrams illustrating a communication state (pattern 3) that may occur in the business phone system of this embodiment. As shown in FIG. 9A, base units CS1 and CS2 are installed closer to each other than in FIG. 7A. As described above, in a normal state, base units CS1 and CS2 have the same transmission level and output signals at a predetermined transmission level. As a result, base unit CS1 forms a wireless communication area Ar1, and base unit CS2 forms a wireless communication area Ar2.

[0094] As in the examples shown in Figures 6(A) and 7(A), the wireless communication areas Ar1 and Ar2 can be divided into three areas shown by concentric circles centered around the positions of the master devices CS1 and CS2. In the example shown in Figure 9(A), when the master devices CS1 and CS2 are outputting signals at a predetermined transmission level, the slave device PS1 wirelessly connected to the master device CS1 is located in the large-output area of ​​the wireless communication area Ar1 formed by the master device CS1. Furthermore, the slave device PS2 wirelessly connected to the master device CS2 is located in the area where the medium-output area of ​​the wireless communication area Ar1 formed by the master device CS1 and the small-output area of ​​the wireless communication area Ar2 formed by the master device CS2 overlap.

[0095] 9B, the notification information sent from the slave PS1 to the master CS1 to notify the communication status between the slave PS1 and the master CS1 simply indicates that the signal from the master CS1 is being received at a high level. In contrast, the notification information sent from the slave PS2 to the master CS2 to notify the communication status between the slave PS2 and the master CS2 indicates that the signal from the master CS2 is being received at a low level and that the signal from the other master CS1 is being received at a medium level.

[0096] As described above, in the case of pattern 3 shown in FIG. 9(A), while slave PS1 is not in a signal overlap state, slave PS2 is in a signal overlap state, as shown in FIG. 9(B). Therefore, slave PS2 transmits an output control request to its own master CS2. The output control request is transmitted to the main unit 1 via its own master CS2, and then transmitted as an output control instruction to master CS1, a master other than the output sender, via the main unit 1. As a result, master CS1 determines whether the signal transmission level can be lowered, and if it determines that the signal transmission level can be lowered, it controls the signal transmission level to be lowered.

[0097] FIG. 10 is a diagram for explaining the communication state after control in the case of pattern 3 shown in FIG. 9. As shown in FIG. 9(A), the slave device PS1 is located in the high-output area of ​​the wireless communication area Ar1 formed by the master device CS1 itself. Therefore, it can be determined that the signal transmission level of the master device CS1 itself can be lowered by two levels, and the maximum area of ​​the wireless communication area Ar1 can be reduced to the high-output area shown in FIG. 9(A). Therefore, the master device CS1 lowers the signal transmission level of its own device to reduce the wireless communication area Ar1. In this case, since the master device CS1 has lowered the signal transmission level by two levels, the wireless communication area Ar1 becomes a low-output area (an area where only the received signal strength is -30 dBm or higher).

[0098] 10B, the notification information sent from the slave PS1 to the master CS1 to notify the communication status between the slave PS1 and the master CS1 is information that simply indicates that a signal from the master CS1 is being received at a low level. Similarly, the notification information sent from the slave PS2 to the master CS2 to notify the communication status between the slave PS2 and the master CS2 is information that simply indicates that a signal from the master CS2 is being received at a low level. This indicates that the radio wave overlap condition at the slave PS2 has been resolved.

[0099] <Communication status pattern 4> 11 is a diagram illustrating a communication state (pattern 4) that may occur in the business phone system of this embodiment. As shown in FIG. 11(A), base units CS1 and CS2 are installed somewhat close to each other, similar to the case of pattern 2 shown in FIG. 7(A). As described above, in a normal state, base units CS1 and CS2 have the same transmission level and output signals at a predetermined transmission level. As a result, base unit CS1 forms a wireless communication area Ar1, and base unit CS2 forms a wireless communication area Ar2.

[0100] As in the examples shown in FIGS. 6A, 7A, and 8A, the wireless communication areas Ar1 and Ar2 can be divided into three concentric areas centered on the positions of the master devices CS1 and CS2. In the example shown in FIG. 11A, the wireless communication areas Ar1 and Ar2 are formed when the master devices CS1 and CS2 output signals at a predetermined transmission level. As shown in FIG. 11A, the slave device PS1 wirelessly connected to the master device CS1 is located in the overlapping area between the small output area of ​​the wireless communication area Ar1 formed by the master device CS1 and the small output area of ​​the wireless communication area Ar2 formed by the master device CS2. In the example shown in FIG. 11A, the slave device PS2 wirelessly connected to the master device CS2 is located in the overlapping area between the small output area of ​​the wireless communication area Ar1 formed by the master device CS1 and the small output area of ​​the wireless communication area Ar2 formed by the master device CS2.

[0101] Therefore, notification information sent from the slave PS1 to its own master CS1 to notify the communication status between the slave PS1 and the master CS1 indicates that the signal from its own master CS1 is received at a low level, and that the signal from the other master CS2 is received at a low level (upper part of FIG. 11(B)). Also, notification information sent from the slave PS2 to its own master CS2 to notify the communication status between the slave PS2 and the master CS2 indicates that the signal from its own master CS2 is received at a low level, and that the signal from the other master CS1 is received at a low level (lower part of FIG. 11(B)).

[0102] In this way, in the case of pattern 4 shown in FIG. 11(A), both the slave devices PS1 and PS2 are in a state of radio wave overlap, as shown in FIG. 11(B). Therefore, the slave device PS1 transmits an output control request to its own parent device CS1. The output control request is transmitted to the main unit 1 via the parent device CS1 of the slave device PS1, and then transmitted as an output control instruction via the main unit 1 to the parent device CS2, which is a parent device other than the output sender. Similarly, the slave device PS2 transmits an output control request to its own parent device CS2. The output control request is transmitted to the main unit 1 via the parent device CS2 of the slave device PS2, and then transmitted as an output control instruction via the main unit 1 to the parent device CS1, which is a parent device other than the output sender.

[0103] As a result, the master devices CS1 and CS2 determine whether or not the signal transmission level can be lowered, and if it is determined that the signal transmission level can be lowered, control is performed to lower the signal transmission level. However, as shown in FIG. 11(A), since the slave device PS1 is located in the small output area of ​​the wireless communication area Ar1, if the master device CS1 lowers the signal transmission level, the wireless connection with the slave device PS1 itself will not be maintained. Similarly, since the slave device PS2 is located in the small output area of ​​the wireless communication area Ar2, if the master device CS2 lowers the signal transmission level, the wireless connection with the slave device PS2 itself will not be maintained. Therefore, in the case of pattern 4 shown in FIG. 11, both the master devices CS1 and CS2 determine that the signal transmission level cannot be lowered, and therefore do not perform control to lower the signal transmission level.

[0104] 7 and 8 with the case of pattern 3 shown in FIGS. 9 and 10, the master CS1, which has received an output control instruction from the main unit 1, must determine how much to lower the transmission level of its own transmission signal. For this reason, the master CS2, which is the sender of the output control request, includes in the output control request the information shown in the lower row of FIG. 7(B) or the information shown in the lower row of FIG. 9(B), which is notification information from its own slave PS2 notifying the master CS2 of the communication status between the slave PS2 and the master CS2, and transmits this information to the main unit 1. The main unit 1 includes in the output control instruction the notification information contained in the master CS2 notifying the communication status between the slave PS2 and the master CS2, and transmits this information to the master CS1 to be controlled.

[0105] As a result, the master device CS1 to be controlled can grasp information indicating the reception status of the slave devices PS1 and PS2 shown in Figures 7(B) and 9(B). Therefore, in the case of Figure 7(B), the other slave device PS2 receives a signal from the master device CS1 in the small output area of ​​the wireless communication area Ar1 formed by the master device CS1. Therefore, the master device CS1 can determine that the signal overlap at the slave device PS2 can be eliminated by lowering the transmission level of the transmitted signal by one level and reducing the wireless communication area Ar1 to the medium output area shown in Figure 7(A). In this case, as shown in Figure 8(A), the outermost area of ​​the wireless communication area Ar1 formed by the master device CS1 becomes the small output area.

[0106] In the case of Fig. 9(B), the other slave device PS2 receives a signal from the master device CS1 in the medium-output area of ​​the wireless communication area Ar1 formed by the master device CS1. Therefore, the master device CS1 determines that it can eliminate the radio wave overlap at the slave device PS2 by lowering the transmission level of the transmitted signal by two levels and reducing the wireless communication area Ar1 to the high-output area shown in Fig. 9(A). In this case, the wireless communication area Ar1 formed by the master device CS1 itself becomes a low-output area, as shown in Fig. 10(A).

[0107] In this way, the masters CS1 and CS2 grasp the notification information from their own slaves notifying them of the communication status between the master and the slave, and the notification information from the slave that sent the output control request notifying them of the communication status between the slave and the master, thereby grasping the level of output control that is necessary when their own slaves perform output control, and determining whether it is possible to lower the signal transmission level to the grasped level.

[0108] [Summary of operations performed by business phone systems] Figure 12 is a sequence diagram illustrating the operation of the business phone system according to the embodiment. The sequence diagram shown in Figure 12 is an example assuming the case of pattern 2 described with reference to Figures 7 and 8, and the case of pattern 3 described with reference to Figures 9 and 10. Note that here, the cordless telephone device 23 consisting of the base unit CS3 and the handset PS3 is also subject to control. However, since the handset PS3 is located in the small output area of ​​the wireless communication area Ar3 formed by the base unit CS3, it is determined that control to lower the signal transmission level cannot be performed.

[0109] As shown in the upper left corner of Fig. 12, it is assumed that the wireless communication unit 513, TDMA modulation / demodulation unit 512, and control unit 511 of the slave PS2 are functioning, and the slave PS2 is receiving signals from multiple master units and detecting that it is in a state of radio wave overlap (step S1). In this case, the control unit 511 of the slave PS2 forms an output control request and transmits this to its own master unit CS2 (step S2). The output control request from the slave PS2 to its own master unit CS2 includes the information shown in the lower part of Fig. 7(B) and the lower part of Fig. 9(B).

[0110] Assume that base unit CS2 receives the output control request through wireless communication circuit 44. In this case, the request providing unit 412 of control circuit 41 functions to transmit the output control request to main unit 1 via control signal processing unit 422 and division / multiplexing processing unit 421 of wireless circuit LSI 42 (step S3). Main unit 1 records the arrival of the output request from base unit CS2 in a memory (not shown in FIG. 2) in control circuit 12. Furthermore, main unit 1 functions to control instruction unit 122 to form an output control instruction and transmit it to base units CS1 and CS3, which are base units other than base unit CS2 that sent the output control request (steps S4 and S5). The output control request is transmitted through an extension processing circuit corresponding to the destination base units CS1 and CS3 among extension processing circuits 131, 132, ..., 13n. The output control request from the main device 1 also includes the information in the lower part of FIG. 7(B) and the lower part of FIG. 9(B).

[0111] Based on the communication state between itself and its own slave PS1 and the output control instruction from the main apparatus 1, the master CS1 determines whether it is possible to control the master CS1 to lower the transmission level of the signal, and if so, executes control to lower the transmission level (step S6). The determination process of step S6 is performed by the control determination unit 413 of the control circuit 41, and the control to lower the transmission level is performed by the control execution unit 414 of the control circuit 41 by controlling the wireless communication unit 443 via the control unit 441 of the wireless communication circuit 44. If it is determined in step S6 that it is not possible to control the master CS1 to lower the transmission level of the signal, the control to lower the transmission level is not executed.

[0112] In this example, it is assumed that in step S6, the master CS1 determines that it is possible to control the master CS1 to lower the signal transmission level, and executes control to lower the transmission level. In this case, the request providing unit 412 of the control circuit 41 of the master CS1 functions to generate a control execution notification (OK notification) notifying that control to lower the signal transmission level has been executed, and transmits this to the main device 1 (step S7).

[0113] Meanwhile, the master unit CS3 determines whether it is possible to control the master unit CS3 to lower the signal transmission level based on the communication state between itself and its slave unit PS3 and the output control command from the main unit 1, and if so, executes control to lower the transmission level (step S8). The process of step S8 is the same as the process of step S6 described above. That is, the determination process of step S8 is performed by the control determination unit 413 of the control circuit 41 of the master unit CS3, and the control to lower the transmission level is performed by the control execution unit 414 of the control circuit 41 by controlling the wireless communication unit 443 via the control unit 441 of the wireless communication circuit 44. If it is determined in step S8 that it is not possible to control the master unit CS3 to lower the signal transmission level, control to lower the transmission level is not executed.

[0114] In this example, in step S8, the master device CS3 determines that its own slave device PS3 is located in the small output area of ​​the master device CS3's wireless communication coverage area Ar3. Therefore, it determines that its own device is unable to control the signal transmission level and does not execute control to lower the transmission level. In this case, the master device CS3 causes the request providing unit 412 of the control circuit 41 to function, and generates a control non-execution notice (NG notice) notifying the master device 1 that control to lower the signal transmission level was not executed, and sends this notice to the main device 1 (step S9).

[0115] In steps S6 and S8, it is determined whether the PS2 can lower its signal transmission level based on the communication status between the PS2 and the slave device and the output control command from the main unit 1. However, this is not a limitation. First, it is determined whether the signal overlap can be resolved by lowering the signal transmission level based on the output control command from the main unit 1. If it is determined that the signal overlap can be resolved, it is determined whether the signal transmission level can be reduced based on the communication status between the PS2 and the slave device. In this example, if it is determined that lowering the signal transmission level of the master unit CS3 will not contribute to resolving the signal overlap of the slave device PS2, it is possible to prevent the master unit CS3 from lowering its signal transmission level. In other words, if the slave device PS2 does not receive a signal from the master unit CS3, it is possible to prevent the master unit CS3 from lowering its signal transmission level.

[0116] Assume that the main unit 1 receives a control execution notification (OK notification) from at least one of the master units that sent the output control instruction. In this case, the reconfirmation request providing unit 123 of the control circuit 12 of the main unit 1 functions to form and transmit a reconfirmation request to the master unit that the main unit 1 recognizes as the sender of the output control request, in this example, master unit CS2, requesting that the master unit CS2 reconfirm the signal overlap (step S10). Having received the reconfirmation request, the request providing unit 412 of the control circuit 41 functions to transmit a reconfirmation request to its own slave unit PS2 (step S11).

[0117] In the slave PS2, the TDMA modulation / demodulation unit 512 and the control unit 511 function mainly to reconfirm the signal overlap (step S12), generate a reconfirmation result, and transmit this to the master CS2 (step S13). The reconfirmation result is either an OK notification indicating that the signal overlap has been resolved, or an NG notification indicating that the signal overlap has not been resolved. In the master CS2, the request etc. providing unit 412 functions to provide the reconfirmation result from the slave PS2 to the main unit 1 (step S14). In the main unit 1, the reconfirmation result providing unit 124 of the control circuit 12 functions to provide the reconfirmation result from the master CS2 to the masters CS1 and CS3, which are masters other than the master CS2 that sent the output control request (steps S15 and S16).

[0118] In the master units CS1 and CS3, the control execution unit 414 of the control circuit 41 functions, and if the reconfirmation result is NG and the master unit is controlling to lower its own signal transmission level, the control execution unit 414 performs processing to return the master unit's signal transmission level to its original level. Note that even if the reconfirmation result is NG, if the master unit is not controlling to lower its own signal transmission level, the control execution unit 414 does not perform processing to return the master unit's signal transmission level to its original level. Also, in the master units CS1 and CS2, if the reconfirmation result is OK, the radio wave overlap at the slave unit PS2 has been resolved, and the control execution unit 414 does not perform processing to return the master unit's signal transmission level to its original level.

[0119] In this way, in a business phone system configured using cordless telephone devices 21, 22, and 23, the handset, base unit, and main unit work together to properly and reliably eliminate the radio wave overlap occurring in handsets PS1, PS2, and PS3.

[0120] [Summary of processes performed on the child and parent units] Next, the operation of the handset and base unit of the cordless telephone device in the business phone system of the above-described embodiment will be summarized with reference to a flowchart. Here, too, the explanation will be given using handset PS1 and base unit CS1 of cordless telephone device 21 as an example. However, similar processing is also performed for handsets PS2 and PS3 of cordless telephone devices 22 and 23 and base units CS2 and CS3. In the following explanation, it is assumed that handset PS1 and base unit CS1 are wirelessly connected and ready to communicate with each other.

[0121] [Processing performed on the PS1 slave device] <Notification process of communication status between child device PS1 and parent device CS1> To resolve the radio wave overlap occurring in the slave PS1, the slave PS1 executes two important processes. One is a process that checks at predetermined intervals whether a wirelessly connected master unit is present, and if a wirelessly connected master unit is present, notifies the master unit of the communication status between the slave unit and the master unit. This process receives a transmission signal from the master unit itself, in this example, master unit CS1, detects the RSSI, forms notification information including the detected RSSI, and notifies the master unit itself of this information.

[0122] This process is performed at predetermined intervals, such as every few seconds or every few tens of seconds, by RSSI detection unit 5122 of TDMA modem unit 512 and information notification processing unit 5111 of control unit 511 in cooperation with each other. By this process, as explained with reference to Fig. 6(A), for example, the parent device can determine in which of the high output area, medium output area, or low output area of ​​the wireless communication coverage area formed by the parent device its child device is located.

[0123] <Processing to eliminate radio wave overlap> Another important process performed by handset PS1 is a process for eliminating radio wave overlap. The process for eliminating radio wave overlap will be described in detail below. Fig. 13 is a flowchart for explaining the process for eliminating radio wave overlap performed by handset PS1 of cordless telephone device 21 used in the business phone system of this embodiment. The process of the flowchart shown in Fig. 13 is executed in handset PS1 under the control of control unit 511.

[0124] The process shown in the flowchart of Fig. 13 is also executed at predetermined intervals, such as every few seconds or every few tens of seconds. Therefore, the process shown in Fig. 13 is executed, for example, immediately after the process of notifying the communication status between the slave device PS1 and the master device CS1 described above. That is, after the slave device PS1 notifies the master device CS1 of the communication status between the slave device PS1 and the master device CS1, the slave device PS1 itself checks whether or not radio wave overlap is occurring, and if so, executes a process to resolve the overlap.

[0125] First, the control unit 511 of the slave PS1 checks the operating status of the TDMA modulation / demodulation unit 512 and the wireless communication unit 513, and determines whether or not there is a master unit with which the slave PS1 is wirelessly connected and with which communication is possible (step S101). If it is determined in the determination process of step S101 that there is no master unit with which wireless communication is possible, the slave PS1 is not in a state where telephone communication is possible and there is no need to consider radio wave overlap, so the process of Fig. 13 is terminated and the next execution timing of the process of Fig. 13 is awaited.

[0126] If it is determined in the determination process of step S101 that a wirelessly connected master unit exists, the control unit 511 acquires a detection result of received signal strength from the RSSI detection unit 5122 of the TDMA modem unit 512 (step S102). As described above, when the slave unit PS1 receives a plurality of different signals, the RSSI detection unit 5122 detects the MAC addresses of the respective senders and the received signal strengths, and stores these in association with each other. Therefore, the control unit 511 determines whether radio wave overlap is occurring in the slave unit PS1 itself based on the detection result from the RSSI detection unit 5122 (step S103). If it is determined in the determination process of step S103 that radio wave overlap is not occurring (only signals from the slave unit PS1 itself are being received), the control unit 511 ends the process of FIG. 13 and waits for the next execution timing of the process of FIG. 13.

[0127] Assume that it is determined in the determination process of step S103 that radio wave overlap has occurred in the base station CS1 itself. In this case, the control unit 511 controls the information notification processing unit 5111 to form an output control request and performs output control request issuance processing to provide the output control request to the base station CS1 itself via the TDMA modulation / demodulation unit 512 and the wireless communication unit 513 (step S104). Thereafter, a request to reconfirm radio wave overlap from the base station CS1 itself is received (step S105). If the reconfirmation request is received, the control unit 511 acquires the detection result of received signal strength from the RSSI detection unit 5122 of the TDMA modulation / demodulation unit 512, as in the process of step S102 (step S106).

[0128] Next, similar to the determination process of step S103, the control unit 511 determines whether or not radio wave overlap is occurring in the own device based on the detection result from the RSSI detection unit 5122 (step S107). Assume that the determination process of step S107 determines that radio wave overlap is occurring (the radio wave overlap has not been resolved). In this case, the control unit 511 controls the information notification processing unit 5111 to form a reconfirmation result (NG notification) indicating that the radio wave overlap has not been resolved, and performs NG issuance processing to provide the result to the own base device CS1 via the TDMA modem unit 512 and the wireless communication unit 513 (step S108).

[0129] Also, assume that it is determined in the determination process of step S107 that radio wave overlap has not occurred (radio wave overlap has been resolved). In this case, the control unit 511 controls the information notification processing unit 5111 to form a reconfirmation result (OK notification) indicating that radio wave overlap has been resolved, and performs OK issuing process to provide the result to the parent device CS1 via the TDMA modem unit 512 and the wireless communication unit 513 (step S109). After the process of step S108 and the process of step S109, the process of Fig. 13 is terminated, and the next execution timing of the process of Fig. 13 is awaited.

[0130] [Processing performed on the parent machine CS1] The master CS1 receives and demodulates notification information periodically provided by its own slave PS1, which notifies the master CS1 of the communication status between the slave PS1 and the master CS1, via the wireless communication circuit 44, and the demodulated information is then provided to the control circuit 41 via the control unit 441. In this case, the control circuit 41 stores the notification information in the communication status table 411. This series of processes enables the master CS1 to grasp the communication status between itself and the slave PS1. Specifically, as described with reference to FIG. 6A, the master CS1 can grasp whether its own slave PS1 is located in the high-output area, medium-output area, or low-output area within its own wireless communication coverage area Ar1.

[0131] Furthermore, in the master CS1, the output control request from the slave PS1 is received through the wireless communication circuit 44, demodulated, and provided to the control circuit 41 through the control unit 441. In this case, the request providing unit 412 of the control circuit 41 functions to provide the output control request to the main unit 1 through the line LSI unit 42. As a result, the output control request from the slave PS1 can be provided to masters CS2 and CS3 other than the master (master CS1) through the main unit 1.

[0132] Furthermore, when radio wave overlap occurs between the other slave devices PS2 and PS3 that are wirelessly connected to the other master devices CS2 and CS3, the master device CS1 executes two processes to resolve this issue. One is a process to be performed when an output control instruction is received from the main device 1, and the other is a process to be performed when a reconfirmation request is received from the main device 1. Each of these processes will be described in detail below.

[0133] <Processing when an output control instruction is received from the main unit 1> 14 is a flowchart for explaining the processing performed by base unit CS1 of cordless telephone device 21 of the business phone system according to the embodiment when an output control request is received. The processing of the flowchart in FIG. 14 is executed mainly by control circuit 41 functioning when an output control instruction is received from main unit 1. First, control circuit 41 checks the operating status of TDMA modem unit 512 and determines whether there is a handset that is wirelessly connected to its own handset CS1 and capable of communication (step S201). Here, as described above, it is assumed that base unit CS1 and handset PS1 are wirelessly connected.

[0134] Assume that in the determination process of step S201, it is determined that there is a local slave device that is wirelessly connected to the local device CS1 and can communicate with it. In this case, the control circuit 41 controls the control determination unit 413 to check the data stored in the communication status table 411 (step S202) and determine whether or not it is possible to control the local device CS1 to lower the signal transmission level (step S203). In the determination process of step S203, it is determined that it is possible to control the local device CS1 to lower the signal transmission level. In this case, the control circuit 41 controls the control execution unit 414 to perform control (output change) to lower the signal transmission level of the wireless communication unit 443 via the control unit 441 of the wireless communication circuit 44 (step S204). Thereafter, the control circuit 41 controls the request etc. providing unit 412 to form a control execution notification (an execution OK notification notifying that the transmission level has been lowered) and provides this to the main device 1 via the line LSI unit 42 (step S205).

[0135] Furthermore, if it is determined in the determination process of step S201 that there is no wirelessly connected slave unit, or if it is determined in the determination process of step S203 that control to lower the signal transmission level is not possible (not possible), a control non-execution notice is formed and provided (step S206). The process of step S206 is a process of forming a control non-execution notice (an execution NG notice notifying that the transmission level could not be lowered) and providing this to the main unit 1 through the line LSI unit 42. After the processes of steps S205 and S206, the process shown in FIG. 14 ends, and the system waits for the next output control instruction to arrive from the main unit 1.

[0136] In this way, the master unit CS1 can control the signal transmission level of its own unit to be lowered when it is in a state where it can do so in response to an output control command from the main unit 1. This can eliminate radio wave overlap occurring between the other slave units PS2 and PS3 that are wirelessly connected to the other master units CS2 and CS3.

[0137] <Processing when reconfirmation results are received from main unit 1> FIG. 15 is a flowchart illustrating the processing performed by the base unit CS1 of the cordless telephone device 21 of the business phone system according to the embodiment when a reconfirmation result is received. The processing of the flowchart in FIG. 15 is executed mainly by the control circuit 41 functioning when a reconfirmation result is received from the main unit 1. First, the control circuit 41 determines whether the signal transmission level of the device itself has been lowered (whether the output has been changed) by the processing described with reference to FIG. 14 (step S301). This determination processing may be performed by storing information indicating that the signal level has been lowered when the signal transmission level of the device itself has been lowered by the processing described with reference to the flowchart in FIG. 14. Alternatively, the control circuit 41 may refer to the signal transmission level of the wireless communication unit 443 of the wireless communication circuit 44, and determine that the signal transmission level of the device itself has been lowered (the output has been changed) if the signal transmission level is lower than a predetermined level.

[0138] If it is determined in the determination process of step S301 that the transmission level of the signal of the main unit 1 has been lowered (after the output has been changed), it is then determined whether the reconfirmation result received from the main unit 1 is an OK notification indicating that the signal overlap has been resolved (step S302). In other words, the determination process of step S302 is a process for determining whether the control to lower the signal transmission level of the main unit 1 has been successful and the signal overlap at the requesting slave unit has been resolved. In the determination process of step S302, it is assumed that the reconfirmation result from the main unit 1 is not an OK notification indicating that the signal overlap has been resolved (it is an NG notification indicating that the signal overlap has not been resolved). In this case, the process of FIG. 14 is performed to return the signal transmission level that was lowered to its original level (step S303).

[0139] If it is determined in the determination process of step S301 that the transmission level of the signal of the own device has not been lowered (the output has not been changed), the process shown in Fig. 15 ends without doing anything and waits for the next reconfirmation result to arrive from the main unit 1. Also, if it is determined in the determination process of step S302 that the reconfirmation result from the main unit 1 is an OK notification indicating that the radio wave overlap has been resolved, the process shown in Fig. 15 ends without doing anything and waits for the next reconfirmation result to arrive from the main unit 1. Also, after the process of step S303, the process shown in Fig. 15 ends and waits for the next reconfirmation result to arrive from the main unit 1.

[0140] In this way, suppose that another slave device is experiencing radio wave overlap and has lowered its own signal transmission level in response to an output control instruction. In this case, if the radio wave overlap has not been resolved, the process of lowering the signal transmission level of the slave device has not contributed to the resolution of the radio wave overlap, and the lowered signal transmission level can be restored. This makes it possible to minimize the impact of the process of lowering the signal transmission level of the slave device.

[0141] [Effects of the embodiment] As described above, the business phone system of this embodiment, which is configured using a cordless telephone device, can appropriately detect when radio wave overlap occurs in any of the handset devices wirelessly connected to the base unit. Furthermore, the handset device experiencing radio wave overlap can send an output control request to the main unit 1 via its own base unit in order to resolve the radio wave overlap. Based on the output control request from a subordinate cordless telephone device, the main unit 1 can transmit an output control instruction to the base unit other than the source of the output control request. The base unit that receives the output control instruction executes control to lower the signal transmission level within itself if possible. This allows the radio wave overlap occurring in the handset device that requested the output control to be resolved.

[0142] Furthermore, after the master unit lowers the signal transmission level, the slave unit that sent the output control request can recheck whether radio wave overlap is occurring, and if the result shows that radio wave overlap has not been resolved, the master unit can restore the lowered signal transmission level. This prevents the master unit from unnecessarily narrowing the wireless communication area with the slave unit by lowering the signal transmission level.

[0143] Through these measures, by varying the transmission level (output level) of the signal from the base unit depending on the radio wave usage status between cordless telephone devices, radio wave interference (radio wave overlap) between cordless telephone devices can be reduced, and radio waves can be used more effectively.

[0144] [Variations] In the network system of the present invention, even when the master unit transmits radio waves by dividing the slots used by the dummy bearer and the slots used by the traffic bearer, the slave unit notifies the connected master unit of the received signal strength of the signal from the other master unit. As described above, the master unit and the slave unit function at timings according to the synchronization signal from the main unit 1, and can determine which slots are used by the other master unit according to the timing of receiving the signal from the other master unit. For this reason, the slave unit also provides information indicating the slots used by the other master unit to the master unit.

[0145] This allows the parent device to request the other parent devices to use a downlink slot different from the one it uses via main unit 1, and have the other parent devices change the slot. Alternatively, the parent device can change the downlink slot it uses so that it does not overlap with the slot used by the other parent devices. In particular, in the case of one-to-multiple accommodation where multiple child devices are connected to the parent device, it becomes possible for the parent device to compile information when the multiple child devices detect other parent devices and determine the appropriate slot position.

[0146] In this case, taking the case of slave device PS1 as an example, the received signal strength of the signal sent from the other master device and the used slot are detected by RSSI detection unit 5122 of TDMA modulation / demodulation unit 512. The detected received signal strength and used slot are notified to the master device by information notification processing unit 5111 of control unit 511. In addition, taking the case of master device CS1 as an example, when requesting another master device via main unit 1 to change the used slot, request providing unit 421 sends an output control request to main unit 1 including information indicating the slot to be changed.

[0147] Furthermore, when the master CS1 functions as another master, the control determination unit 413 of the control circuit 41 determines whether or not it is possible to control the signal output level to be lowered or whether or not it is possible to change the slot in use in response to an output control request from the main device 1. If the control determination unit 413 determines that the control is possible, the control execution unit 414 of the control circuit 41 functions to control the signal output level to be lowered or the slot in use to be changed, and this control is performed through the control unit 441 of the wireless communication circuit 44. Also, when changing its own slot in use in response to notification information from its own slave, rather than requesting the other master to change the slot in use, the control execution unit 414 of the control circuit 41 functions and performs this control through the control unit 441 of the wireless communication circuit 44.

[0148] In the above-described embodiment, the cordless telephone devices used to build the business phone system are described as employing the DECT system, but this is not a limitation. For example, the present invention can also be applied to a business phone system built using cordless telephone devices employing the PHS (Personal Handy-phone System) system or the SXGP (Shared eXtended Global Platform) system. [Explanation of symbols]

[0149] 1...Main unit, 11...Line I / F, 12...Control circuit, 121...Connection base unit memory unit, 122...Control instruction unit, 123...Reconfirmation request providing unit, 124...Reconfirmation result providing unit, 13...Line LSI unit, 14...Reference transmitting device, 21, 22, 23...Cordless telephone device, CS1, CS2, CS3...Base unit, PS1, PS2, PS3...Handset, 41...Control circuit, 411...Communication status table, 412...Request providing unit, 413...Control discrimination unit, 414...Control execution unit, 42...Line L SI unit, 43... synchronization signal generation circuit, 44... wireless communication circuit, 441... control unit, 442... TDMA modulation / demodulation unit, 4422... information detection unit, 443... wireless communication unit, 51... wireless communication circuit, 511... control unit, 5111... information notification processing unit, 512... TDMA modulation / demodulation unit, 5121... PLL unit, 5122... RSSI detection unit, 513... wireless communication unit, 52... control circuit, 53... codec circuit, 54... transmitter, 55... transmitter (microphone), 56... receiver (speaker)

Claims

1. A network system comprising a network control device connected to a wide area network, a plurality of base units connected to the network control device, and one or more slave units that are wirelessly connected to one of the plurality of base units and are capable of communicating with each other, wherein the plurality of base units and the one or more slave units use a predetermined frequency band as a communication channel, The slave unit is signal strength detection means for detecting the strength of each received signal received by the device itself; a first information notifying means for notifying a base station to which the own base station is wirelessly connected of the plurality of base stations, the first information notifying means notifying the own base station of the received signal strength of the signal from the own base station detected by the signal strength detecting means; a second information notification means for forming an output control request and notifying the parent device when signals are received from two or more parent devices among the plurality of parent devices; Equipped with The parent device is a communication status storage means for storing and holding the received signal strength notified from the one or more slave devices, the slave device to which the own device is wirelessly connected being designated as the own slave device; a control request means for providing an output control request to the network control device when the output control request arrives from the slave device; a control determination means for determining whether or not an adjustment to lower an output signal level is possible based on the stored information of the communication status storage means when an output control instruction arrives from the network control device; a control execution means for executing an adjustment to lower the output signal level of the device itself when the control determination means determines that the adjustment to lower the output signal level is possible; Equipped with The network control device a connected master device storage means for managing each of the plurality of master devices connected to the own device; a control instruction means for, when the output control request arrives from the parent device, identifying the parent device that sent the output control request, and providing an output control instruction to a parent device other than the parent device that sent the output control request, among the plurality of parent devices, based on the stored data in the connected parent device storage means; A network system comprising:

2. 2. The network system according to claim 1, The slave unit is a third information notification means for, when a reconfirmation request arrives from the base unit itself, reconfirming whether signals have been received from two or more base units including the base unit itself among the plurality of base units, and notifying the base unit itself of the reconfirmation result; The parent device is a control execution response providing means for providing a control execution response to the network control device when the control execution means has performed an adjustment to lower the output signal level of the device itself; a reconfirmation request providing means for providing the reconfirmation request to the slave device when the reconfirmation request arrives from the network control device; a reconfirmation result providing means for providing the reconfirmation result to the network control device when the reconfirmation result arrives from the slave device; a readjustment control means for controlling the output signal level to return to the original level when the reconfirmation result from another master unit arrives from the network control device and the reconfirmation result indicates that signals are being received from two or more master units including the master unit itself among the plurality of master units, and the master unit itself is adjusting to lower its output signal level; The network control device a reconfirmation request providing means for providing the reconfirmation request to the parent device that transmitted the output control request when the control execution response arrives from the parent device; a reconfirmation result providing means for, when the reconfirmation result arrives from the parent device, providing the reconfirmation result to a parent device other than the parent device that sent the output control request; A network system comprising:

3. 3. The network system according to claim 1, Between the parent device and the child device, the communication channel is divided into frames of a predetermined time unit, each of the frames is further divided into a plurality of time slots, and wireless communication is performed through the time slot selected for each frame, the signal strength detection means of the slave unit is capable of detecting the time slot in which the received signal is transmitted, the second information notification means of the slave device can transmit information indicating the time slot in which a signal from a master device other than the master device itself, detected by the signal strength detection means, is transmitted, by including the information in the output control request; the control request means of the master device is capable of providing, when the time slot used by a master device other than the master device itself is identical to the time slot used by the master device itself, a time slot change request including information indicating the time slot in the output control request; the control determination means of the parent device is capable of determining, when the output control request received from the network control device includes the time slot change request, whether or not the time slot used by the parent device to transmit a signal to the child device is the same as the time slot indicated in the time slot change request; When it is determined that the time slot used by the device to transmit a signal to the slave device is the same as the time slot indicated in the time slot change request, the control execution means executes control to change the time slot used to transmit a signal to the slave device. A network system comprising:

4. A cordless telephone device comprising a network control device connected to a wide area network, a plurality of base units connected to the network control device, and one or more handset units that are capable of communicating by wirelessly connecting to one of the plurality of base units, the plurality of base units and the one or more handset units being of a network system that uses a predetermined frequency band as a communication channel, The network control device comprises a connected parent device storage means for managing each of the plurality of parent devices connected to the network control device itself, and a control instruction means for, when an output control request arrives from a parent device, identifying the parent device that sent the output control request, and providing an output control instruction to a parent device among the plurality of parent devices other than the parent device that sent the output control request, based on data stored in the connected parent device storage means; The slave unit is signal strength detection means for detecting the strength of each received signal received by the device itself; a first information notifying means for notifying a base station to which the own base station is wirelessly connected of the plurality of base stations, the first information notifying means notifying the own base station of the received signal strength of the signal from the own base station detected by the signal strength detecting means; a second information notification means for forming the output control request and notifying the output control request to the master device when signals are received from two or more master devices among the plurality of master devices; Equipped with The parent device is a communication status storage means for storing and holding the received signal strength notified from the one or more slave devices, the slave device to which the own device is wirelessly connected being designated as the own slave device; a control request means for providing the output control request to the network control device when the output control request arrives from the slave device; a control determination means for determining whether or not an adjustment to lower an output signal level is possible based on the stored information of the communication status storage means when an output control instruction arrives from the network control device; a control execution means for executing an adjustment to lower the output signal level of the device itself when the control determination means determines that the adjustment to lower the output signal level is possible; A cordless telephone device comprising:

5. a network control device connected to a wide area network, a plurality of base units connected to the network control device, and one or more slave units that are wirelessly connected to one of the plurality of base units to be able to communicate, the plurality of base units and the one or more slave units being the network control device of a network system that uses a predetermined frequency band as a communication channel; The slave device comprises a signal strength detection means for detecting the received signal strength of each signal received by the slave device itself, a first information notification means for notifying the master device of the received signal strength of the signal from the master device itself detected through the signal strength detection means, with the master device to which the slave device itself is wirelessly connected being designated as the master device among the plurality of master devices, and a second information notification means for forming an output control request and notifying the master device of the received signal strength when signals from two or more master devices among the plurality of master devices are received, The master unit defines a slave unit to which the master unit is wirelessly connected as its own slave unit among the one or more slave units, and includes: a communication status storage means for storing and holding the received signal strength notified from the slave unit; a control request means for, when an output control request arrives from the slave unit, providing the output control request to the network control device; a control determination means for, when an output control instruction arrives from the network control device, determining whether or not an adjustment to lower an output signal level is possible based on information stored in the communication status storage means; and a control execution means for executing an adjustment to lower the output signal level of the master unit when the control determination means determines that an adjustment to lower the output signal level is possible, a connected master device storage means for managing each of the plurality of master devices connected to the own device; a control instruction means for, when the output control request arrives from the parent device, identifying the parent device that sent the output control request, and providing an output control instruction to a parent device other than the parent device that sent the output control request, among the plurality of parent devices, based on the stored data in the connected parent device storage means; A network control device comprising:

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