JP2007295185A - Sound adaptor apparatus and clock synchronizing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voice adaptor apparatus capable of performing voice communication using a PHS public network by using a key telephone and having high communication quality. <P>SOLUTION: The sound adaptor apparatus 2 connected to a private branch exchange 3 includes a slot for loading a PHS card terminal 1 and a reference clock frequency correction part for transmitting a reference clock to the private branch exchange 3, receiving a voice data frame from a PHS public base station 4 through the PHS card terminal 1 loaded to the slot and correcting the frequency of the reference clock on the basis of the average transmission rate of the voice data frame. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a PHS public voice call using a card type PHS (Personal Handyphone System) terminal.

Card type PHS terminals having a PC (personal computer) card interface and a CF (compact flash) card interface are provided. Patent Document 1 discloses a PBX (private branch exchange) connected to an outside line and an extension, a plurality of public base stations (CS: Cell Station) connected to the PBX, and a radio communication with any of these CSs. A private telephone system having a type PHS terminal and a PHS terminal is described. According to this private telephone system, a user can make a voice call with a terminal connected to an external line or an internal line by using a card-type PHS terminal or a PHS terminal.
JP 2004-40535 A

  Recently, various services (for example, flat-rate services) have been provided for voice calls using PHS terminals. When a voice call is performed using a key telephone connected to the PBX, if a service in such a PHS network can be received, the call charge can be kept low.

  However, in the private telephone system described in Patent Document 1, a voice call using the PHS network can be performed using a card-type PHS terminal or a PHS terminal, but a terminal (key telephone) connected to an extension is used. Thus, a voice call using the PHS network cannot be performed. As described above, the private telephone system described in Patent Document 1 cannot receive a service in the PHS network in a voice call using a key telephone.

  By connecting an adapter device that can be equipped with a card type PHS terminal to the PBX, and connecting a key telephone connected to the PBX and an external PHS public base station via the card type PHS terminal, It is possible to make a voice call using the PHS network. In order to realize such a voice call using the PHS network, it is necessary to synchronize the PBX with the card type PHS terminal. Specifically, it is necessary to transmit and receive an audio data frame with a reference clock having a predetermined frequency (8 kHz reference clock supplied from the network side) between the PBX and the adapter device equipped with the card type PHS terminal. However, since the transmission rate of the voice data frame received from the PHS public base station via the card type PHS terminal usually changes depending on the communication environment, when the frequency of the reference clock is fixed, when the voice data frame is transmitted, The bit signal of the audio data frame may not fit within the frame, and the audio may be interrupted. There is no system provided that can synchronize the clock by changing the frequency of the reference clock according to the change in the transmission rate of the audio data frame.

  In addition, in each of the adapter devices equipped with PBX and PHS terminal, when self-running with the internally generated reference clock, there is an error between the reference clock on the PBX side and the reference clock on the adapter device side, A clock phase shift occurs between both reference clocks. For this reason, frame synchronization loss occurs between audio data frames processed by both the PBX and the adapter device. Also in this case, there arises a problem that the bit signal of the audio data frame does not fit in the frame and the audio is interrupted.

  An object of the present invention is to provide a voice adapter device that can solve the above-described problems, can perform a voice call using a PHS public network using a key telephone, and can suppress deterioration of communication quality due to voice interruption. There is to do.

  To achieve the above object, the present invention provides a voice adapter device connected to a private branch exchange, the voice adapter device connected to the private branch exchange, and a slot for mounting a card-type PHS terminal; A reference clock is transmitted to the private branch exchange, and a voice data frame in which voice data is stored in units of frames is received from a PHS public base station via a card type PHS terminal installed in the slot. And a reference clock frequency correction unit that corrects the frequency of the reference clock based on an average transmission rate.

  According to the voice adapter device described above, the voice adapter device and the private branch exchange can be synchronized by transmitting a reference clock to the private branch exchange.

  Also, since the frequency of the reference clock transmitted to the private branch exchange is adjusted based on the average transmission rate of the voice data frame received from the PHS public base station, if the transmission rate of the voice data frame changes, the change The frequency of the reference clock also changes by that amount. Specifically, when the average transmission rate decreases, the frequency of the reference clock decreases according to the amount of decrease, and conversely, when the average transmission rate increases, the frequency of the reference clock increases according to the amount of increase. In this way, it is possible to achieve clock synchronization by changing the frequency of the reference clock in accordance with the change in the transmission rate of the audio data frame. Therefore, for example, when a 32 Kbps voice data frame received from a PHS public base station is transmitted to the private branch exchange side with a reference clock of 8 kHz, the voice data frame based on the 32 Kbps voice data frame supplied from the card type PHS terminal is used. It is possible to finely adjust the frequency of the 8 kHz clock so as not to cause a bit shift of the data frame.

  According to the present invention, clock synchronization can be established between the voice adapter device and the private branch exchange, and the frequency of the reference clock can be changed according to the change in the transmission rate of the voice data frame. When a voice call using the PHS public network is performed using a key telephone connected to, communication quality deterioration due to voice interruption can be suppressed.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of a PHS public voice call system according to an embodiment of the present invention. Referring to FIG. 1, this PHS public voice call system includes a PHS card terminal 1 that performs radio communication with a PHS public base station 4 that constructs a PHS public communication network (PHS network), and a voice that can be attached to the PHS card terminal 1. It has an adapter device 2, a PBX 3 to which the audio adapter device 2 is connected, and a key telephone 5 connected to the PBX 3.

  The key telephone 5 is an existing one. The PHS card terminal 1 is a card type PHS terminal including a PC card interface and a CF card interface, and performs wireless communication (including voice and data communication) with the PHS public base station 4. The PHS public base station 4 is an existing PHS base station.

  The voice adapter device 2 generates a reference clock and finely adjusts the frequency in order to synchronize the clock between the slot for mounting the PHS card terminal 1 and the PHS card terminal 1 mounted in the slot and the PBX 3. Data transmitted from the reference clock frequency correction unit and the PHS card terminal 1 to the PBX 3 based on the reference clock from the reference clock frequency correction unit, the audio data frame storing the audio data received from the PHS public base station 4 And a transmission unit. The reference clock frequency correction unit receives a voice data frame from the PHS public base station 4 via the PHS card terminal 1 mounted in the slot, and corrects the frequency of the reference clock based on the average transmission rate of the voice data frame. .

  The PBX 3 transmits a key telephone interface for connecting the key telephone 5 and a voice data frame from the key telephone 5 to the PHS public base station 4 via the voice adapter device 2 and the PHS card terminal 1, A frame processing function for transmitting a voice data frame from the PHS public base station 4 received through the adapter device 2 and the PHS card terminal 1 to the key telephone 5; The PBX 3 includes a PLL (Phase Locked Loop) circuit for synchronizing an internally generated reference clock with a reference clock supplied from the audio adapter device 2, and the frame processing function is based on the clock from the PLL circuit. Send and receive data frames.

  FIG. 2 shows a schematic configuration of the reference clock frequency correction unit of the audio adapter device 2. Referring to FIG. 2, the reference clock frequency correction unit includes a data reception unit 21, a data frame timing acquisition unit 22, a frequency correction calculation unit 23, and a reference clock transmission unit 24.

  The data receiving unit 21 is a part that receives an audio data frame from the PHS card terminal 1. The audio data frame from the PHS card terminal 1 is, for example, an ADPCM (Adaptive Differential Pulse Code Modulation) signal, which is a 32-kbps audio data frame. The audio data frame is a data frame that stores audio data in units of frames. The data frame has a fixed length of 240 bits and includes information such as a start symbol at the beginning of the frame. The frame also includes information capable of recognizing the end.

  The data frame timing acquisition unit 22 acquires the data frame time for each frame of the audio data frame received by the data reception unit 21. The data frame time is acquired based on the start symbol and information that can recognize that the frame is the end. In the data frame timing acquisition unit 22, the data frame time is detected for each frame, and the detection result is supplied to the frequency correction calculation unit 23. Since the data frame time changes in the process of receiving the voice data frame from the PHS public base station 4 by the PHS card terminal 1, the data frame time detected for each frame is not necessarily the same value.

  Based on the data frame time for each frame supplied from the data frame timing acquisition unit 22, the frequency correction calculation unit 23 calculates the transmission rate of the data frame by the following equation.

Here, the number of data frame bits is the number of bits per frame, which is 240 bits here. Further, the frequency correction calculation unit 23 calculates an average value of the transmission rate of the audio data frame calculated for each frame. The number of data frames for calculating the average transmission rate can be set as appropriate. Specifically, the number of data frames for calculating the average value is several tens to several hundreds. Further, the frequency correction calculation unit 23 divides the value of the average transmission rate of the audio data frame by a predetermined ratio, and calculates the frequency of the reference clock to be transmitted. Here, since it is assumed that a 32 kbps audio data frame is transmitted with an 8 kHz clock, the predetermined ratio is 1/4 (= 8 ÷ 32). The frequency correction calculation unit 23 calculates the frequency of the reference clock to be transmitted by dividing the value of the calculated average transmission rate of the audio data frame by 1/4.

  The reference clock sending unit 24 sends a reference clock to the PBX 3 and includes a PLL circuit so that the frequency of the output reference clock becomes the frequency of the reference clock to be transmitted calculated by the frequency correction calculation unit 23. It is configured.

  The audio adapter device 2 transmits the audio data frame from the PHS card terminal 1 to the PBX 3 based on the reference clock transmitted from the reference clock transmission unit 24. That is, the reference clock from the reference clock transmission unit 24 is used as a clock for the interface between the audio adapter device 2 and the PBX 3.

  Next, the operation of the PHS public voice call system of this embodiment will be specifically described.

  FIG. 3 shows a clock synchronization procedure by the audio adapter device 2.

  When the user performs an input operation to start a PHS voice call on the key telephone 5, the key telephone 5 is connected to the PHS public base station 4 via the PBX 3, the voice adapter device 2, and the PHS card terminal 1. Then, a voice call through the PHS public network is started (step 100).

  When a voice call is started, in the voice adapter device 2, the data receiving unit 21 receives a voice data frame (voice data frame for the key telephone 5) from the PHS public base station 4 via the PHS card terminal 1. (Step 101). Next, the data frame timing acquisition unit acquires the data frame time for each data frame of the audio data frame received by the data reception unit 21, and supplies the acquired data frame time to the frequency correction calculation unit 23 (step) 102).

  Next, the frequency correction calculation unit 23 calculates a transmission rate for each data frame received by the data reception unit 21 based on the data frame time supplied from the frequency correction calculation unit 23, and sets the average transmission rate to a predetermined value. The frequency of the reference clock to be transmitted is divided by this ratio (step 103). Then, the reference clock sending unit 24 generates a reference clock having the frequency calculated by the frequency correction calculation unit 23 and sends it to the PBX 3 (step 104).

  According to the above-described clock synchronization processing, the audio adapter device 2 transmits the reference clock to the PBX 3, so that the audio adapter device 2 and the PBX 3 can be synchronized.

  Further, since the frequency of the reference clock transmitted to the PBX 3 is adjusted based on the average transmission rate of the voice data frame received from the PHS public base station 4, when the average transmission rate changes, the reference is increased by the changed amount. The clock frequency also changes. Specifically, when the average transmission rate decreases, the frequency of the reference clock decreases according to the amount of decrease, and conversely, when the average transmission rate increases, the frequency of the reference clock increases according to the amount of increase. In this way, it is possible to achieve clock synchronization by changing the frequency of the reference clock in accordance with the change in the transmission rate of the audio data frame. Therefore, for example, an 8 kHz reference clock is sent to the PBX 3 side, and based on the 32 Kbps audio data frame supplied from the PHS card terminal 1, the frequency of the 8 kHz clock is set so as not to cause a bit shift of the audio data frame. Fine adjustment is possible. This suppresses the occurrence of bit shift in the audio data frame.

  When making a call from the key telephone 5, the clock synchronization process is not performed by the voice adapter device 2 at the start of the voice call, but the reference clock is supplied to the PBX 3 from the voice adapter device 2. The PBX 3 transmits the audio data frame from the key telephone 5 to the PHS card terminal 1 side with a clock synchronized with the supplied reference clock. Thereby, the PBX 3 and the PHS card terminal 1 are synchronized.

  According to the PHS public voice call system of the present embodiment, synchronization can be established between the PBX 3 and the voice adapter device 2 to which the PHS card terminal 1 is attached, so that the voice data frame from the card-type PHS terminal 1 is used in the PBX 3. , The occurrence of a phenomenon in which the audio data frame bit signal does not fit within the frame and the audio is interrupted can be suppressed. Therefore, it is possible to realize a voice call with high communication quality that suppresses voice interruption.

  In addition, by realizing a PHS public network voice call using the key telephone 5, it is possible to receive various services (such as voice flat-rate services) provided in the PHS network, thereby reducing communication costs in the company. be able to.

  The PHS public voice call system of the present embodiment described above is an example of the present invention, and the configuration and operation thereof can be changed as appropriate without departing from the spirit of the present invention.

  For example, in the system shown in FIG. 1, there may be a plurality of key telephones connected to the PBX 3.

  Moreover, CS and an external line may be connected to PBX3.

  Furthermore, although the frequency of the reference clock is 8 kHz, it may be a different frequency.

It is a block diagram which shows schematic structure of the PHS public voice call system which is one Embodiment of this invention. It is a block diagram which shows schematic structure of the reference | standard clock frequency correction | amendment part of the audio | voice adapter apparatus shown in FIG. It is a flowchart which shows the clock synchronization procedure by the audio | voice adapter apparatus shown in FIG.

Explanation of symbols

1 PHS card terminal 2 Voice adapter device 3 Private branch exchange 4 PHS public base station 5 Key telephone

Claims (6)

A voice adapter device connected to a private branch exchange,
A slot for mounting a card-type PHS terminal;
A reference clock is transmitted to the private branch exchange, and a voice data frame storing voice data is received from a PHS public base station via a card type PHS terminal installed in the slot, and an average transmission of the voice data frame is performed. And a reference clock frequency correction unit that corrects the frequency of the reference clock based on a rate. The reference clock frequency correction unit is
A data receiving unit for sequentially receiving voice data frames from the PHS public base station via a card-type PHS terminal installed in the slot;
A data frame timing acquisition unit for acquiring a data frame time for each of the audio data frames received by the data reception unit;
Based on the data frame time for each audio data frame supplied from the data frame timing acquisition unit, a transmission rate is calculated for each audio data frame, an average value of the transmission rate is calculated, and an average value of the transmission rate is calculated. A frequency correction calculation unit that calculates the frequency of a reference clock to be divided and transmitted at a predetermined ratio;
A reference clock sending unit that generates the reference clock and adjusts the frequency of the reference clock based on the frequency of the reference clock to be transmitted supplied from the frequency correction calculation unit. The voice adapter device described.   The data transmission part which transmits the voice data frame received from the PHS public base station via the card type PHS terminal to the private branch exchange based on the reference clock from the reference clock transmission part is further provided. The voice adapter device described. Private branch exchange,
A card-type PHS terminal for wireless communication with a PHS public base station;
A voice adapter device connected to the private branch exchange,
The voice adapter device is
A slot for mounting the card type PHS terminal;
A reference clock is transmitted to the private branch exchange, and a voice data frame storing voice data is received from the PHS public base station via a card type PHS terminal installed in the slot, and an average of the voice data frames is received. A reference clock frequency correction unit that corrects the frequency of the reference clock based on a transmission rate,
The PHS public voice call system, wherein the private branch exchange processes a voice data frame from the voice adapter device based on a clock synchronized with a reference clock from the reference clock frequency correction unit. A clock synchronization method performed in a voice adapter device connected to a private branch exchange,
Transmitting a reference clock to the private branch exchange;
Receiving a voice data frame storing voice data from a PHS public base station via a card-type PHS terminal, and correcting the frequency of the reference clock based on an average transmission rate of the voice data frame. , Clock synchronization method. The step of correcting the frequency of the reference clock includes:
Obtaining a data frame time for each of the voice data frames sequentially received from the PHS public base station;
Calculating a transmission rate for each audio data frame based on the obtained data frame time for each audio data frame, and calculating an average value of the transmission rates;
6. The method of calculating a frequency of a reference clock to be transmitted by dividing an average value of the transmission rates by a predetermined ratio and adjusting the frequency of the reference clock based on the frequency. Clock synchronization method.

Images