KR0135361B1 - Method for talking over via cellular phones - Google Patents

Abstract

The present invention relates to a call method of a terminal suitable for making a call between specific persons by encrypting a voice signal. In the related art, voice data transmitted from a fixed station to a terminal is also initially set up with a terminal in the fixed station. In the process of being encrypted by a predetermined encryption key value in the process is divided into unit lengths according to the DECT regulations and then transmitted to the terminal, when the encryption key value is exposed, there is a drawback that the security of the contents of the call is impossible, but in the present invention After the first encryption process using the encryption key value that only the other parties knows, the existing encryption process is performed. Send and receive The taps when the taps to track only the encryption key values to be extremely difficult to improve the above drawbacks.

Description

Call method of terminal

1 is a block diagram showing an embodiment of a general DECT terminal.

2 is a flow chart showing step by step an embodiment of the general DECT terminal processing of FIG. 1 according to the DECT standard.

3 is a flow chart showing step by step an embodiment of a call method of a terminal according to the present invention.

The present invention relates to a portable terminal of the DECT (Digital European Cordless Telecommunications) method, and more particularly, to a communication method of a terminal suitable for making a call between specific persons by encoding a voice signal.

1 is a block diagram illustrating an embodiment of a general DECT terminal, and includes a central processing unit (CPU) 2 having a baseband processing function for controlling overall operation of the terminal, A power supply unit 4 controlled by the central processing unit 2 to indicate the current power state of the terminal, a power supply unit 6 controlled by the central processing unit 2 to supply power for operating the terminal to the terminal system; A microphone 8 for converting a voice signal into an electrical analog voice signal, an analog-digital converter 10 for converting an analog voice signal of the microphone 8 into a digital signal, Digital signal processing (DSP) processor (14) by converting the digital voice signal of the analog-to-digital converter 10 into ADPCM (Adaptive Differential Pulse Code Modulation) data Digital signal processing processor 14 which communicates with an applied ADPCM-PCM (Pulse Code Modulation) converter 12 and the central processing unit 2 to digitally process digital signals according to a speech coding method used in the DECT standard. And a PCM-ADPCM converter 16 for converting ADPCM data of the digital signal processor 14 into PCM data, and a digital-analog converter for converting PCM data of the PCM-ADPCM converter 16 into an analog signal. 18, a speaker 20 which is driven by an analog signal of the digital-to-analog converter 18 to output voice, and a carrier for modulating voice data encoded by ADPCM from the central processing unit 2; A signal synthesizer 22 for carrying a modulated signal on the carrier, a signal amplifier 24 for amplifying the modulated signal of the signal synthesizer 220 to a level defined by DECT, and amplified by the signal amplifier 24. Propagates signals to the atmosphere, An antenna 26 for receiving a frequency signal, a low noise amplifier 28 for receiving low frequency amplification of a high frequency signal from a fixed station received through the antenna 26 during a reception period, and a low noise amplification The intermediate frequency converter 30 which converts the received high frequency signal of the unit 28 into the intermediate frequency, and extracts the original signal transmitted from the intermediate frequency of the intermediate frequency converter 30 to the central processing unit 2. A demodulation unit 32 to be applied, a key input unit 34 for inputting a call to the central processing unit 2, a screen display unit 36 for displaying a longitudinal state by receiving a signal from the central processing unit 2, , The buzzer 38 for generating a special sound generated for use of a terminal such as a key input and a beep by receiving a signal from the central processing unit 2, and an initial state of the volume under the control of the central processing unit 2. And record various phone numbers EEPROM (Electrically Erasable Programmable Read Only Memory) 40, a ROM (Read Only Memory) 42 storing data for operation of the entire processor by the central processing unit 2, and central processing The device 2 comprises a RAM (Read Access Memory: RAM) 44 which temporarily stores the parameters for the longitudinal operation.

Referring to FIG. 2, a general DECT terminal made as described above is as follows.

First, the central processing unit 2 has a baseband processing function for controlling the overall operation of the terminal, and the power display unit 4 is controlled by the central processing unit 2 to indicate the current power state of the terminal. Displayed using a light emitting device such as a diode so that the user can know the current state of the power on / off of the terminal.

The power supply 6 is then controlled by the central processing unit 2 to supply power for terminal operation, and the microphone 8 converts the voice signal by the user into an electrical analog voice signal. The analog-digital converter 10 converts the analog voice signal of the microphone 8 into a digital signal.

The ADPCM-PCM converter 12 converts the digital voice signal of the analog-digital converter 10 into ADPCM data and applies it to the digital signal processor 14, and the digital signal processor 14 performs central processing. It communicates with the device 2 and processes the digital signal according to the speech coding method used in the DECT standard.

In addition, the PCM-ADPCM converter 16 converts ADPCM data of the digital signal processing processor 14 into PCM data, and the digital-analog converter 18 converts the PCM data of the PCM-ADPCM converter 16 into analog. The speaker 20 converts the signal into a signal and outputs the voice by the analog signal of the digital-analog converter 18 so that the user can hear the voice.

Next, the signal synthesizing unit 22 receives the voice data encoded by the ADPCM from the central processing unit 2 and modulates it in a carrier for modulation of 1.8 GHz for wireless transmission, and the signal amplifying unit 24 performs the signal synthesizing unit 24. The modulated signal at 22 is amplified to the level defined by the DECT, and the antenna 26 propagates the amplified signal of the signal amplifier 24 in the air and receives the signal in the air.

Therefore, the low noise amplifier 28 receives the 1.8 kHz signal of the fixed station received through the antenna 26 during the reception period of the terminal to low noise amplification, and the intermediate frequency converter 30 of the low noise amplifier 28 The received frequency of 1.8 kHz is converted into an intermediate frequency of 110 MHz, and the demodulator 32 extracts the original signal transmitted from the intermediate frequency of 110 MHz of the intermediate frequency converter 30, and the central processing unit 2 To apply.

The key input unit 34 inputs a call to the central processing unit 2, and the screen display unit 36 receives a signal from the central processing unit 2 and uses a display element such as an LCD (Liquid Crystal Display). The bell state 38 is displayed, and the buzzer 38 receives a signal from the central processing unit 2 to generate a special sound generated for use of a terminal such as a key input and a beep so that the user can hear it. ) Records the initial state of the volume and various telephone numbers by the central processing unit 2, and the ROM 42 stores the non-volatile data for the operation of the entire terminal by the central processing unit 2, 44 temporarily stores the parameters for longitudinal operation by the central processing unit 2.

FIG. 2 shows a step-by-step flow chart showing one embodiment of the general DECT terminal processing of FIG. 1 according to the DECT standard, that is, the algorithm of the central processing unit 2.

First, when the power is turned on, the initial value of the hardware is read from the ROM 42 or EPI rom 40 to initialize the respective hardware, and the RAM 44 is inspected and cleared. After checking the basic abnormality of the hardware by operating the diagnostic program, etc., the signal of the wireless base station is received from the radio channels 0 to 9 in 10 (100, 102, 104, 106, 108, 110, 112).

Next, the received electric field strengths of all 10 radio channels are examined to determine the connection to the wireless base station which emits the strongest wireless signal, and based on the signals sent from the wireless base station, Motivate to be the reference (114).

After that, by checking the time slot usage state of the radio base station, it is checked whether there is an empty time slot, and then performs a registration procedure (116).

At this time, the terminal enters the standby state after completing the registration procedure, the operation of the terminal proceeding in the standby state can be divided into four.

First, the terminal checks whether there is a paging signal from the fixed station, and if there is a paging signal, first accesses a medium access control (MAC) layer to secure a time slot use right of a wireless channel. Then, the DLC (Data Link Control) layer connection, the network (Network) layer proceeds in order to form a call path to proceed with the call (118, 120, 122, 124, 126).

Subsequently, due to any one call disconnection situation, the network layer is disconnected, the DLC layer is disconnected, and then the MAC layer is disconnected to release the radio channel and enter the standby state again (128, 130, 132).

On the contrary, if there is no paging signal, the terminal user examines a connection request to a specific subscriber, and if a request occurs, if there is an empty time slot by checking the existence of an empty time slot to secure use of the time slot. Immediately requests the use of the time slot to the station, and if the time slot is not empty, waits until the time delay does not exceed the value set until another user's use of the time slot ends. When the use of another user's time slot ends, an attempt is made to access the MAC layer using the time slot (134, 136).

Subsequently, access to the MAC layer is secured to secure the time slot use rights of the wireless channel, and the DLC layer and the network layer are sequentially accessed to form a call path and then proceed with the call (138, 140, and 142). .

Subsequently, due to any one call disconnection situation, the network layer is disconnected, the DLC negotiation is disconnected, and then the MAC layer is disconnected to release the radio channel and enter the standby state again (144, 146, 148).

At this time, after there is no paging signal and the user's transmission request or the processing (step 132 or step 148) is completed, the state check in the terminal is performed.

A typical internal condition check is the voltage level check of the supply battery.

First, input the voltage of the battery through a circuit that converts an analog signal into a digital signal to check whether it is at an appropriate level. If it is below the appropriate level, a battery charge warning signal is generated to display a message such as, for example, a need for charging. It informs the state of the need for charging and receives a signal from the fixed station to check whether it maintains an appropriate signal level or whether the signal level is too low to attempt to connect to an adjacent fixed station (150, 152, 154, 156, 158).

If the station's signal level is higher than -83 dBm, the signal state of the station currently registered is maintained as it is, and if the signal level falls below a certain value and a mobile connection to the previous station is required, the radio channel is 0 to 9. Accepted over ten (160, 162, 164, 166, 168, 170, 172).

Therefore, the received electric field strengths of all 10 radio channels are examined to determine the connection to the radio base station which emits the strongest radio signal, and the various timings within the terminal are determined based on the signal sent from the radio base station. Motivate to be the reference (174, 176).

After that, the time slot usage state of the radio base station is checked to determine whether there is an empty time slot, and then handover is newly performed.

That is, in the standby state, as described above, it is determined whether or not there is a paging signal from the fixed station, and the processing thereof is performed, the transmission request of the user is processed and the processing thereof is performed, and it is checked whether the battery voltage is at an appropriate level. The basic form of the entire DECT terminal processing is to perform a process for it, inspect the signal level of the fixed station, proceed with it, and perform various timer processing of other terminals.

The encryption process for the voice of the prior art is performed between the DECT fixed station and the terminal, that is, the encoded voice sent from the fixed station to the exchange or received from the exchange is transmitted in the form of unencrypted normal voice data. Is done only between the station and the terminal.

And, the encryption process between the fixed station and the terminal in the initial connection procedure between the fixed station and the terminal, the terminal receives the encryption key value from the fixed station and encrypts the encoded voice data between the fixed station and the terminal based on the encryption key value to avoid exposure to others. It is structured to be.

Therefore, when another person receives a signal propagated in the air in the process of initial setting between the fixed station and the terminal, it is possible to find out the contents of the call by receiving the encryption key value.

In this case, an additional encryption process is required to increase the security of the voice.

The speech processing in each DECT terminal is as follows.

First, when a user speaks, the voice is digitized by an analog-digital conversion circuit, and the digitized PCM data is converted into ADPCM data to compress the voice information.

The compressed data is encrypted by the encryption key value provided from the fixed station during the initial setting of the time slot of the fixed station and the wireless channel, and then the data is divided into data in a form conforming to the DECT specification and stored in the time slot of the DECT. It is loaded onto the station.

In addition, the fixed station receives the encrypted data, decrypts the encrypted data with the stored encryption key value, extracts the original ADPCM data, and sends the data to the exchange.

Accordingly, the ADPCM data transmitted from the fixed station to the terminal is also divided into unit lengths according to the DECT rule after being encrypted by the encryption key value determined during initial setting with the terminal in the fixed station. Is sent.

Therefore, such a conventional encryption process is impossible to secure the contents of the call when the encryption key value is exposed.

The present invention has been made to solve the above-mentioned drawbacks, and an object of the present invention is to provide a communication method of a terminal that can have a function for an additional encryption process in the terminal.

Hereinafter, described in detail by the accompanying drawings an embodiment of the present invention as follows.

Referring to FIG. 3, FIG. 3 is a flowchart illustrating a step-by-step embodiment of a method of calling a terminal according to the present invention, that is, an algorithm of the central processing unit 2 of FIG.

Here, the description of FIG. 2 will be referred to without referring again.

First, the voice data is received after the start of the call, and the voice data is decrypted by the encryption key, and in the case of the double encryption state, secondly decrypted by the personally set encryption key (200, 202, 204, 206).

Next, the ADPCM voice data is converted into PCM voice data, and the digital voice signal is converted into an analog voice signal and output to the speaker (208, 212).

Subsequently, the voice signal is converted into a digital voice signal and the PCM voice data is converted into ADPCM voice data and then encrypted using an encryption key (214, 216, 218).

In the double encryption state, the ADPCM voice data is secondly encrypted and transmitted (220, 222, and 224).

Next, when setting up double encryption again when not ending the call, the encryption key value is input and stored to set the double encryption state (226, 228, 230, 232, 234).

Subsequently, when the double encryption is released, the encryption key value is deleted to set a single encryption state and then maintain a reception state (236, 238, 240).

That is, in the present invention, each DECT terminal uses the encryption key value received from the fixed station in the call access procedure to perform the ADPCM voice data encoded using the preset password with the call partner before performing the existing encryption process. After the first encryption, the encryption process of the existing DECT standard is performed.

And the encryption key value for the encryption to know each other by negotiating with the other party for the call in advance.

In the use of such an encryption function, after the connection with the other party is established, each terminal performs encryption of the encoded voice signal based on each encryption key.

As described above, since the encryption process according to the present invention only knows each other's call partners, and the encryption key value is not data exposed to the air, this method is replaced with the existing call steps 126 and 142, respectively. As a result, it is extremely difficult to eavesdrop on the contents of a call in the case of an encryption process.

Claims (1)

Initializing each hardware, accepting all the channels of the base station (100, 102, 104, 106, 108, 110, 112), and the base station to investigate the electric field strength of all the received channels, respectively, and emit the strongest of them Determining the connection to the network, and synchronizing to the reference of various timings in the terminal based on the signal sent from the base station (114), checking whether there are any free time slots in the base station, and then performing the registration procedure. In step 116, if the paging signal is present, the MAC layer is accessed to secure the time slot usage of the wireless channel, and the DLC layer is connected to the network layer in order to form a call path. Steps 118, 120, 122, 124, and 126 to proceed, disconnection of the network layer, disconnection of the DLC layer, and then MAC by either call disconnection situation Step (128, 130, 132) of releasing the radio channel and re-entering the radio channel by disconnection of the layer, and when there is no paging signal, if a request for access to a specific subscriber is generated, it is empty to secure the use of time slots. If there is an empty time slot, check the existence of the existing time slot, and if there is an empty time slot, request the use of the time slot to the fixed station. Waiting as long as the value is not exceeded, and when another user's use of time slot ends, attempting to access the MAC layer using the time slot (134 and 136), and proceeding to access the MAC layer. To secure the channel's time slots, and to access the DLC layer and the network layer in sequence, Proceed with the voice call (138, 140, 142), disconnection of the network layer, disconnection of the DLC layer, and subsequent disconnection of the MAC layer by any one of the call disconnection situation to release the license of the wireless channel and wait again. Enter the state (144, 146, 148), and if the voltage of the battery is at an inadequate level, generate a battery charge warning signal to inform the user of the need for charging, and receive a signal from the fixed station to maintain the proper signal level or Step (150, 152, 154, 156, 158) of checking whether the signal level is so low that an attempt is made to connect to an adjacent fixed station; and if the signal level of the fixed station is appropriate, the signal state of the currently registered station is maintained as it is. When the signal level falls below a certain value and a mobile connection to the previous station is required, all channels are accepted (160, 162, 164, 166, 16). 8, 170, 172) and the received electric field strengths for all channels to determine the connection to the wireless base station which emits the strongest wireless signal, and based on the signal sent from the wireless base station, In a terminal comprising steps 174 and 176 to synchronize to be a reference, the call steps 126 and 142 receive the voice data after the start of the call and decrypt the voice data, and in case of double encryption, second decryption. (200, 202, 204, 206); Converting ADPCM voice data into PCM voice data and converting the digital voice signal into an analog voice signal and outputting the voice (208, 212); Converting the voice signal into a digital voice signal and converting the PCM voice data into ADPCM voice data and then encrypting the voice signal (214, 216, 218); (220, 222, 224) and secondly encrypting ADPCM voice data when it is in a double encryption state; Setting a double encryption state again (226, 228, 230, 232, 234) without ending the call; If the double encryption is to be released, the method of calling a terminal comprising the step of setting the single encryption state by deleting the corresponding encryption key value and maintaining the listening state (236, 238, 240).