JP5309266B1 - Wireless communication apparatus and transmission power control method - Google Patents

Abstract

When performing wireless communication simultaneously with a plurality of slave units, communication with all the slave units is maintained while suppressing radio wave interference to other radio communication systems as much as possible.
A level measurement unit 104a measures an RSSI level of a notification signal every time a parent device 1 receives a notification signal from each child device. The transmission power control unit 102a determines a transmission power value using a minimum value of the RSSI level of each slave unit at a predetermined timing, and an amplification unit so as to transmit a control signal to the slave unit with the determined transmission power value 104b is controlled.
[Selection] Figure 1

Description

  The present invention relates to a wireless communication apparatus and a transmission power control method applicable to a digital cordless telephone.

  2. Description of the Related Art Cordless telephones that have a cordless handset and are capable of talking with a calling party apart from a base unit connected to a telephone line have become widespread. Along with the spread, there are cases where a plurality of wireless communication systems exist in the same area. In such a case, if the master unit always transmits radio waves with the maximum power, it is possible to talk even if the master unit and the slave unit are separated from each other, but radio wave interference to other wireless communication systems becomes large. There was a problem.

  Accordingly, cordless telephones that variably control the transmission power of the base unit have been developed. For example, in Patent Document 1, transmission is performed with the maximum transmission power value of a wireless communication device at the start of communication, and the transmission power value is decreased by a predetermined amount each time transmission is successful. A technique is disclosed in which optimal transmission power is set by performing control such as increasing the power value by a predetermined amount.

  Patent Document 2 describes a technique for controlling transmission power of a parent device (connection device) depending on whether or not the child device is connected to a charging stand. That is, Patent Document 2 discloses a technology in which a slave unit communicates with a low transmission power when the slave unit is connected to a charging base and a high transmission power when the slave unit is separated from the charging base. Is disclosed. As a result, the technique disclosed in Patent Document 2 enables the communication between the slave unit and the connection device to be maintained even if an interference wave arrives in the process in which the slave unit moves away from the connection device.

JP 2001-332987 A JP 2002-345026 A

  However, Patent Document 1 is a technique for controlling the power between a slave unit and a master unit during a call (or during other data communication), and synchronization between the slave unit and the master unit other than during a call. It does not relate to power control of the control channel for control signal transmission. Patent Document 2 is an invention relating to control between a single slave unit and a master unit, and cannot be implemented when there are a plurality of slave units. Furthermore, the above prior art does not consider that the signal of the control channel interferes with other cordless telephone systems.

  FIG. 7 shows the state of interference with another adjacent cordless telephone system. As shown in FIG. 7, when there are a plurality of slave units registered in the master unit (slave unit A and slave unit B), the control channel transmitted by the master unit so as to be received by the slave unit B present in a distant place. Maximizing power can cause significant interference to other adjacent cordless telephone systems.

  Patent Document 2 describes that when one slave unit having the same terminal number as the connection device is connected to the charging stand, the connection device lowers the transmission power. However, the same terminal number as the connection device is described. The transmission power control of the control signal in the case where there are a plurality of slave units having is not described. For example, even when a nearby child device is placed on a charging stand, if the parent device lowers the transmission power of the control signal, communication between the child device and the parent device existing in the distance may be interrupted.

  An object of the present invention is to provide a wireless communication apparatus and a transmission capable of maintaining communication with all slave units while minimizing radio wave interference with other radio communication systems when performing wireless communication with a plurality of slave units. It is to provide a power control method.

  A wireless communication apparatus of the present invention is a wireless communication apparatus that performs TDMA wireless communication with a plurality of slave units, and includes a level measuring unit that measures a reception level of a signal transmitted from each slave unit, Transmission power control means for determining a transmission power value according to a minimum value and performing transmission power control so as to transmit a control signal with the determined transmission power value to the plurality of slave units using a control channel. The structure to do is taken.

  A transmission power control method of the present invention is a transmission power control method for a wireless communication apparatus that performs TDMA wireless communication with a plurality of slave units, and includes measuring a reception level of a signal transmitted from each slave unit; Determining a transmission power value according to the minimum value of the reception level, and performing a transmission power control to transmit a control signal with the determined transmission power value to the plurality of slave units using a control channel; It has.

  According to the present invention, when TDMA wireless communication is performed with a plurality of slave units, the received signal level of the slave unit located far from the master unit slightly exceeds a predetermined threshold capable of maintaining communication. Since the transmission power can be controlled to the extent, communication with all the slave units can be maintained while suppressing radio wave interference to a plurality of other wireless communication systems as much as possible.

The block diagram which shows the structure of the main | base station which concerns on one embodiment of this invention The block diagram which shows the structure of the subunit | mobile_unit and charging stand which concern on one embodiment of this invention The external view which shows a mode that the subunit | mobile_unit which concerns on one embodiment of this invention is mounted in a charging stand The figure explaining the mode of communication of the main | base station and the subunit | mobile_unit in a standby state in a DECT system The figure which shows the information memorize | stored in the memory part of the main | base station which concerns on one embodiment of this invention The figure which shows the mode of the area adjustment of the control channel of the main | base station which concerns on one embodiment of this invention Diagram showing interference with another adjacent cordless telephone system

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, a digital cordless telephone conforming to the DECT (Digital Enhanced Cordless Telecommunication) standard will be described as an example. DECT is a method standardized by the European Telecommunications Standards Institute (ETSI), which is a European telecommunication standardization organization.

(Embodiment)
The digital cordless telephone is composed of one master unit 1 (see FIG. 1), a plurality of slave units 2 (see FIG. 2), and the same number of charging bases 3 (see FIG. 2). Base unit 1 (wireless communication apparatus) performs time division multiple access (TDMA) wireless communication with each handset 2.

  FIG. 1 is a block diagram showing a configuration of base unit 1 according to an embodiment of the present invention. As shown in FIG. 1, the base unit 1 includes a telephone line interface 101, a signal processing unit 102, a memory unit 103, a radio unit 104, an antenna 105, a display unit 106, an operation unit 107, and a microphone 108. And a speaker 109.

  The telephone line interface 101 is an interface that connects the telephone line and the signal processing unit 102, and performs incoming call processing and outgoing call processing to connect to an external telephone via the telephone line, and to open / close the line. To go.

  Based on a control program stored in the memory unit 103, the signal processing unit 102 processes signals output from the respective units and controls the respective units. In particular, the signal processing unit 102 performs ADPCM (Adaptive Differential Pulse Code Modulation) encoding processing on the digital audio data, adds control data, inserts it into a predetermined slot in the frame, and performs frequency modulation and the like. Modulation processing is performed to generate a baseband transmission signal. The signal processing unit 102 also performs demodulation processing on the baseband received signal, extracts control data and speech encoded data from a predetermined slot in the frame, and performs ADPCM decoding processing on the speech encoded data. To generate digital audio data.

  The memory unit 103 stores predetermined information such as a control program and a slave unit ID (Identification). Of the information stored in the memory unit 103, information related to the present invention will be described later.

  The radio unit 104 performs radio processing such as amplification and up-conversion on the baseband digital signal output from the signal processing unit 102, and transmits a radio signal from the antenna 105. The radio unit 104 also performs radio processing such as amplification and down-conversion on the radio signal received by the antenna 105 and outputs a baseband digital signal to the signal processing unit 102.

  A display unit (LCD: Liquid Crystal Display) 106 displays various types of information output from the signal processing unit 102. The operation unit 107 has various buttons, dials, and keys, and converts the operation content based on the user's will into an electric signal and outputs it to the signal processing unit 102.

  The microphone 108 collects the user's voice, converts it into a voice signal, and outputs it to the signal processing unit 102. The speaker 109 converts the sound signal output from the signal processing unit 102 into sound and generates a sound.

  Here, as a characteristic configuration of the present invention, the signal processing unit 102 includes a transmission power control unit 102a. The radio unit 104 includes a level measurement unit 104a and an amplification unit 104b.

  The transmission power control unit 102a calculates transmission power based on the RSSI (Received Signal Strength Indicator) level of the received signal from each slave unit 2 measured by the level measurement unit 104a, and amplifies the control signal indicating the calculation result To the unit 104b. A specific transmission power control method in the transmission power control unit 102a will be described later.

  The level measurement unit 104a measures the RSSI level of the received signal from each slave unit 2 installed on the charging stand 3, and outputs an RSSI signal indicating the measurement result to the transmission power control unit 102a.

  The amplifying unit 104b amplifies the power of the radio signal transmitted from the antenna 105 based on the control of the transmission power control unit 102a.

  FIG. 2 is a block diagram showing the configuration of the slave unit 2 and the charging stand 3 according to the embodiment of the present invention. As shown in FIG. 2, the handset 2 includes a signal processing unit 201, a memory unit 202, a wireless unit 203, an antenna 204, a display unit 205, an operation unit 206, a microphone 207, a speaker 208, The charging circuit 211, the secondary battery 212, and the constant voltage circuit 213 are mainly configured. Moreover, the subunit | mobile_unit 2 has terminal T21, T22.

  The signal processing unit 201 performs processing of signals output from each unit and control of each unit based on a control program stored in the memory unit 202. When the signal processing unit 201 receives the charge detection signal from the charging circuit 211, the signal processing unit 201 sends a notification signal for notifying that the handset 2 is installed on the charging stand 3 via the wireless unit 203 and the antenna 204. 1 to send.

  The memory unit 202 stores predetermined information such as a control program.

  The radio unit 203 performs radio processing such as amplification and up-conversion on the baseband digital signal output from the signal processing unit 201, and transmits a radio signal from the antenna 204. The wireless unit 203 also performs wireless processing such as amplification and down-conversion on the wireless signal received by the antenna 204 and outputs a baseband digital signal to the signal processing unit 201.

  The display unit 205 displays various information output from the signal processing unit 201. The operation unit 206 has various buttons, dials, and keys, and converts the operation content based on the user's will into an electrical signal and outputs the electrical signal to the signal processing unit 201.

  The microphone 207 collects the user's voice, converts it into a voice signal, and outputs it to the signal processing unit 201. The speaker 208 converts the sound signal output from the signal processing unit 201 into sound and generates a sound.

  Terminals T21 and T22 are terminals for inputting charging current by contacting the terminals T31 and T32 when the handset 2 is placed on the charging stand 3.

  The charging circuit 211 inputs the charging current supplied from the charging stand 3 and supplies it to the secondary battery 212 and the constant voltage circuit 213. In addition, the charging circuit 211 outputs a charge detection signal to the signal processing unit 201 when the slave unit 2 is placed on the charging stand 3 and a charging current from the charging stand 3 is detected.

  The secondary battery 212 stores the charging current from the charging circuit 211 and discharges it to the constant voltage circuit 213.

  The constant voltage circuit 213 is a constant voltage source that supplies a stable DC voltage to the signal processing unit 201. The DC voltage (for example, 2.5 V) from the charging circuit 211 or the secondary battery 212 is reduced to a lower voltage (for example, 1). .8V).

  The charging stand 3 is mainly composed of an external power supply connector 301 and a power supply circuit 302. The charging stand 3 includes terminals T31 and T32.

  Terminals T31 and T32 are terminals for supplying a charging current to the slave unit 2.

  The external power supply connector 301 is connected to an external power supply and inputs a direct current.

  The power supply circuit 302 is a DC / DC converter that converts a DC voltage (for example, 6.5 V) from the external power connector 301 into an appropriate voltage (for example, 2.5 V) and supplies the converted voltage to the charging circuit 211 of the slave unit 2.

  As shown in FIG. 3, the handset 2 has a structure that allows the user to easily place the handset 2 on the charging stand 3 and separate it from the charging stand 3. When the handset 2 is placed on the charging stand 3, the handset 2 is electrically connected to the charging stand 3 and stores the charging current from the charging stand 3 in the secondary battery 212. Note that there is a master unit 1 having a structure that allows the slave unit 2 to be charged. In this case, when the handset 2 is placed on the charging unit of the base unit 1, the handset 2 is electrically connected to the base unit 1 and stores the charging current from the base unit 1 in the secondary battery 212.

  Next, communication between the parent device and the child device in the standby state in the DECT method will be described with reference to FIG.

  As shown in FIG. 4, in the DECT system, a TDMA / TDD (Time Division Multiple Access / Time) configured by including 24 slots (12 slots for the uplink and 12 slots for the downlink) in one frame with a period of 10 ms. Division Duplex) is adopted. In addition, at least one control channel slot is provided, and both the control channel and the communication channel are transmitted and received at a frame period of 10 ms.

  The master unit determines a predetermined slot (second slot in FIG. 4) of each frame as a control channel to the slave unit, and transmits a control signal (Beacon) using this control channel.

  In the standby state, no signal is transmitted from the slave unit to the master unit. When an event occurs such as when the slave unit is placed on the charging stand, the slave unit transmits a notification signal to the master unit in a predetermined slot (14th slot in FIG. 4). To do.

  Base unit 1 of the present embodiment measures the RSSI level of the notification signal transmitted from each handset 2 and controls transmission power based on the measurement result.

Next, information stored in the memory unit 103 of the parent device 1 will be described with reference to FIG. As shown in FIG. 5, the memory unit 103 of the parent device 1 stores, for each child device 2, the child device ID number (ID _i ), the measured RSSI level (Ppp _i ) of the notification signal, and the notification signal reception time. (Tpp _i ) is stored in association with each other.

  The level measuring unit 104a measures the RSSI level of the notification signal every time the parent device 1 receives the notification signal from each child device 2, and outputs the measurement result to the signal processing unit 102 (transmission power control unit 102a).

  When the signal processing unit 102 receives a notification signal from any one of the slave units 2, the signal processing unit 102 stores the ID, RSSI level, and reception time of the slave unit 2 in association with each other in the memory unit 103.

  Next, a transmission power control method when the base unit according to the present embodiment transmits a control signal on the control channel will be described.

The transmission power control unit 102a calculates the transmission power value using the minimum value of the RSSI level (Ppp _i ) stored in the memory unit 103 at a predetermined timing. Note that the timing at which the transmission power control unit 102a performs transmission power control includes the timing at which the information content stored in the memory unit 103 illustrated in FIG. 5 is updated.

Specifically, the transmission power control unit 102a reads each RSSI level (Ppp _i ) stored in the memory unit 103 when receiving the notification signal transmitted from each slave unit 2, and selects the minimum value thereof. . The transmission power value of each handset 2 that can communicate with the base unit 1 is set to the same value. Alternatively, the parent device 1 may know the transmission power value of each child device 2 in advance. Further, at the time of the registration operation, the respective transmission output values may be notified from the slave units 2 to the master unit 1. The transmission power value of each slave unit 2 is stored in advance in the memory unit 103 of the master unit 1 at the product manufacturing stage.

In the present embodiment, the amplification degree of the amplifying unit 104b when the control signal is transmitted in accordance with the handset 2 having the weakest received signal level is controlled. Specifically, base unit 1 reads the RSSI level (minimum value RSSI level) of handset 2 having the weakest received signal level from the information stored in memory unit 103, and from the transmission power value of the known handset. Then, by subtracting the minimum RSSI level (Ppp _i ), the propagation path loss relating to the handset 2 having the weakest received signal level is calculated. Note that, in a cordless telephone in which the parent device 1 and the child device 2 transmit with the same transmission power, the transmission path loss to the child device 2 is calculated using the transmission power of the parent device 1 instead of the transmission power of the child device 2 be able to.

The transmission power control unit 102a calculates a transmission power value for the parent device 1 to transmit a control signal according to a value obtained by adding the received power reference value to the propagation path loss for the child device 2 having the weakest level. The received power reference value is a value obtained by adding a margin to the received power value necessary for maintaining communication between the parent device 1 and the child device 2 or suppressing communication interference. For example, when it is recognized that all the slave units 2 are placed on the charging stand 3, the RSSI level (Ppp _i ) of a signal received from a certain slave unit 2 is lower than the received power reference value. The base unit 1 may stop the transmission power control and transmit the control signal with full power.

  Then, the transmission power control unit 102a controls the amplification unit 104b so as to transmit a signal with the calculated transmission power value.

  FIG. 6 is a diagram illustrating how the signal arrival area is adjusted when the parent device transmits a control signal through the control channel in the present embodiment. The RSSI level in the master unit of the notification signal transmitted by the slave unit of ID1 is Ppp1, the RSSI level in the master unit of the notification signal transmitted by the slave unit of ID2 is Ppp2, and the RSSI level in the master unit of the notification signal transmitted by the slave unit of ID3 When the level is Ppp3, if the RSSI level of the notification signal of each slave unit (ID1, ID2, ID3) in the master unit is Ppp1> Ppp2> Ppp3, the master unit uses the minimum value Ppp3 to transmit power value Is calculated.

  As a result, even a slave unit that is located far from the master unit 1 and has a large propagation path loss can receive a control signal transmitted from the master unit 1 through the control channel with a reception power value necessary for maintaining communication. it can. Moreover, since the transmission power of the main | base station 1 is reduced, the electromagnetic wave interference to another radio | wireless communications system can be suppressed.

  As described above, according to the present embodiment, when performing TDMA wireless communication with a plurality of slave units, it is possible to maintain communication with the reception signal level of the slave unit located far from the master unit. Since the transmission power can be controlled to a level slightly exceeding a possible predetermined threshold, communication with all the slave units can be maintained while suppressing radio wave interference to other radio communication systems as much as possible.

  In the above embodiment, the case where the RSSI level of the received notification signal is stored in the memory unit 103 has been described. However, the present invention is not limited to this, and the propagation path loss is calculated and stored first. Other values may be stored.

  The wireless communication apparatus of the present invention is suitable for use in a digital cordless telephone.

DESCRIPTION OF SYMBOLS 1 Master unit 2 Subunit 3 Charging stand 101 Telephone line interface 102, 201 Signal processing unit 102a Transmission power control unit 103, 202 Memory unit 104, 203 Radio unit 104a Level measurement unit 104b Amplification unit 105, 204 Antenna 211 Charging circuit 212 2 Secondary battery 213 Constant voltage circuit 301 External power connector 302 Power circuit

Claims (3)

A wireless communication device that performs TDMA wireless communication with a plurality of slave units,
Level measuring means for measuring the reception level of the signal transmitted from each slave unit;
Transmission power control means for determining transmission power value according to the minimum value of the reception level and performing transmission power control so as to transmit a control signal with the determined transmission power value to the plurality of slave units using a control channel When,
A wireless communication apparatus comprising: A memory for storing the ID of each slave and the reception level in association with each other
The transmission power control means calculates a transmission power value at a timing when the information stored in the memory is updated.
The wireless communication apparatus according to claim 1. A transmission power control method for a wireless communication apparatus that performs TDMA wireless communication with a plurality of slave units,
Measuring a reception level of a signal transmitted from each slave unit;
Determining a transmission power value according to the minimum value of the reception level, and performing transmission power control to transmit a control signal with the determined transmission power value to the plurality of slave units using a control channel;
A transmission power control method comprising:

Images