JP2011097185A - Radio communication system and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication system and a radio communication method for starting direct communication without performing test transmission of both terminals when both the terminals are close to a relay station and are located at a distance allowing the direct communication. <P>SOLUTION: The relay station includes a means of measuring a signal strength of a transmission signal from each terminal, a means of estimating a distance to each terminal by the measured signal strength and transmission output information from each terminal, and a means of obtaining the sum of the estimated distance to each terminal. When the sum of the estimated distance is more than or equal to a preset distance, transition to the direct communication is indicated to each terminal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wireless communication system and a wireless communication method.

Conventionally, in wireless communication between terminals, the electric field strength decreases depending on the distance, and communication becomes impossible when the electric field strength falls below a demodulating level of the receiving terminal. There was a distance limit.
Therefore, in order to expand the communicable distance, a relay station that receives radio waves from the transmitting terminal in a good location condition for communications such as hills and building rooftops, and transmits the received radio waves to the receiving terminal Is widely used.
In addition, in wireless communication between mobile terminals, the communication environment changes depending on the location conditions of buildings, etc., and stable communication may be difficult even at a communicable distance. Even relay stations are used.
A mobile phone or the like is a method of communicating via a base station, and as a reliable communication method, it is common to communicate via a relay station.

  In wireless communication via a relay station, different frequencies may be used for transmission and reception.

In a wireless communication system composed of relay stations and terminals, even if the distance between multiple terminals is close and the terminals can communicate directly with each other, communication must always be performed via the relay station. Must not. Since the relay station is used regardless of the distance between the terminals, there is a problem that the frequency is not used effectively.
Therefore, there is a method described in Patent Document 1 below as a method of directly communicating between terminals. In Patent Document 1, after the mobile station is connected to the base station, the control device of the base station transmits a test instruction as to whether or not direct communication is possible to the mobile station using the transmission device. Change the channel of the mobile station to the designated channel according to the instruction from the base station, and the mobile station performs a test transmission to confirm whether direct communication is possible, and if possible, set the channel for direct communication and the communication possible time value to the mobile station. The relay operation to the mobile station is terminated, and the mobile station starts direct communication on the designated channel.

JP-A-6-90480

However, in the invention described in Patent Document 1, even when both terminals are close to the relay station and are capable of direct communication, a procedure for allowing the terminals to perform test transmission is necessary as a process leading to direct communication. It was.
The present invention has been made in view of such problems, and when both terminals are close to the relay station and capable of direct communication, direct communication is started without performing test transmission of both terminals. An object of the present invention is to provide a wireless communication system and a wireless communication method.

In order to solve the above-described problems of the prior art, the present invention provides a wireless communication system comprising a plurality of terminals and a relay station.
The terminal
Means for direct communication between the terminals;
Means for communicating via the relay station;
Means for transmitting the transmission output information representing the transmission output of the terminal included in the call transmission signal and the response transmission signal, and
The relay station is
Signal strength measuring means for measuring the signal strength of the call transmission signal and the response transmission signal from the terminal;
Distance estimation means for estimating a distance to each of the terminals from the measured signal strength and transmission output information from each of the terminals;
Inter-terminal distance estimation means for obtaining the sum of the estimated distance to each terminal that has called and responded via the relay station, and
If the distance estimated by the inter-terminal distance estimating means is greater than or equal to a predetermined distance, start the relay operation of communication between the terminals,
If the distance estimated by the inter-terminal distance estimation means is not equal to or greater than a predetermined distance, the relay station transmits a direct communication transition signal instructing each terminal to shift to direct communication, and the terminal A wireless communication system characterized by starting direct communication is provided.

The invention according to claim 2 is a wireless communication system comprising a plurality of terminals and relay stations.
The terminal is
Means for direct communication between the terminals;
Means for communicating via the relay station;
Means for transmitting transmission output information representing the transmission output of the terminal in a transmission signal;
With
The relay station is
Signal strength measuring means for measuring the signal strength of the signal from the terminal;
Distance estimation means for estimating a distance to each of the terminals from the measured signal strength and transmission output information from each of the terminals;
An inter-terminal distance estimation means for obtaining a sum of the estimated distances of each terminal communicating with the relay station,
If the distance estimated by the inter-terminal distance estimation means is equal to or greater than a predetermined distance, the communication relay operation between terminals is continued.
A wireless communication system characterized in that if the distance estimated by the inter-terminal distance estimating means is not equal to or greater than a predetermined distance, the terminal is instructed to shift to direct communication, and the terminal shifts to direct communication. Is to provide.

  According to the second aspect of the present invention, the direct communication shift instruction information may be included in a transmission signal from the relay station that is communicating via the relay station to the terminal. The distance estimation by the inter-terminal distance estimation means may be performed twice or more, and the average value may be used to determine the shift to direct communication.

  In the first to fourth aspects of the present invention, the transmission frequency and the reception frequency for direct communication may be the same frequency.

The wireless communication method according to the present invention described in claim 6
Transmitting a call transmission signal to the second terminal including the transmission output information of the first terminal from the first terminal to the relay station;
The relay station receiving the call transmission signal from the first terminal, relaying the call transmission signal to the second terminal, and transmitting.
The relay station measuring the signal strength of the call transmission signal;
The relay station analyzing transmission output information included in the call transmission signal;
The second terminal receives a call transmission signal from the relay station, and transmits a response transmission signal to the first terminal including transmission output information of the second terminal to the relay station. When,
The relay station measuring the signal strength of the response transmission signal;
The relay station analyzing transmission output information included in the response transmission signal;
The relay station estimates a first distance to the first terminal from a signal strength of the call transmission signal and a result of analyzing transmission output information included in the call transmission signal;
The relay station estimates a second distance to the second terminal from a result of analyzing signal strength of the response transmission signal and transmission output information included in the response transmission signal;
Determining the sum of the first and second distances;
Starting a relay communication via the relay station if the sum is greater than or equal to a predetermined distance;
Sending a direct communication instruction to the first and second terminals if the sum is not greater than a predetermined distance;
The first and second terminals receiving a direct communication instruction from the relay station;
The communication method is characterized in that the first and second terminals shift to a direct communication state.

The wireless communication method of the present invention as set forth in claim 7 comprises:
A relay station receiving transmission signals from the first and second terminals and measuring the signal strength;
Analyzing transmission output information included in the transmission signal;
Estimating a first distance and a second distance from the signal strength and the transmission output information to the first and second terminals;
Determining the sum of the first and second distances;
Continuing the relay if the sum result is greater than or equal to a predetermined distance;
Transmitting a direct communication instruction included in a transmission signal from a relay station to the first and second terminals if the result of the sum is not greater than a predetermined distance;
The first and second terminals receiving a direct communication instruction from the relay station;
The communication method is characterized in that the first and second terminals make a transition to a direct communication state.

Further, the wireless communication method of the present invention described in claim 6 and claim 7 is:
The transmission frequency and the reception frequency for direct communication may be the same frequency.

  According to the present invention, when the terminals are relatively close to the relay station and can directly communicate with each other, it is possible to effectively utilize the frequency of the relay station by allowing the communication to be performed without using the relay station. it can.

1 is a block diagram illustrating an embodiment of a terminal according to the present invention. It is a block diagram which shows one Embodiment of the relay station which concerns on this invention. It is a block diagram which shows the detailed structure of the control part in the terminal of one Embodiment. It is a block diagram which shows the detailed structure of the control part in the relay station of one Embodiment. 6 is a flowchart for explaining determination of inter-terminal distance estimation performed by a relay station in a call and response from terminal A to terminal B in Example 1 of an embodiment. 7 is a flowchart for explaining the process from the transition to the direct communication mode to the end and the transition to the relay mode in Example 1 of one embodiment. 10 is a flowchart for explaining the start of communication in relay mode in Example 1 of an embodiment. 10 is a flowchart for explaining a determination of distance estimation between terminals by a relay station communicating in a relay mode in Example 2 of an embodiment. 10 is a flowchart for explaining a transition from a relay mode to a direct communication mode in Example 2 of an embodiment. It is a figure for demonstrating the method of enabling direct communication between the terminals in a fixed distance from a relay station. It is a figure for demonstrating the direct communication range in one Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .

FIG. 1 shows a typical structure of a terminal.
The microphone 1a4 collects sound, converts it into a sound signal, and outputs the sound signal to the modulation unit 1a1.
The modulation unit 1a1 modulates the audio signal into a transmission signal and outputs the transmission signal to the transmission unit 1a2.
The modulation unit 1a1 also modulates various data signals from the control unit 1c and outputs a transmission signal to the transmission unit 1a2.
As the modulation method of the audio signal, there are analog methods such as FM, AM, and SSB, and digital methods such as QPSK, 4-level FSK, and π / 4DQPSK, which are arbitrary. The modulation of the data signal may be any digital method such as FSK, BPSK, 4-value FSK, or an analog method in which a tone signal is superimposed on an audio signal.

The transmission unit 1a2 amplifies the transmission signal to a predetermined power, performs filtering to remove unnecessary radiation, and outputs the filtered signal to the antenna switch 1e. The transmission frequency transmitted from the transmitter 1a2 is determined by an oscillator (not shown).
The transmission output control unit 1a3 performs transmission output control of the transmission unit 1a2 by a transmission output control signal output from the control unit 1c.

The antenna switch 1e outputs a transmission output from the transmission unit 1a2 to the antenna 1f at the time of transmission, and outputs a signal received by the antenna 1f to the reception unit 1b2 at the time of reception. Switching in the antenna switching unit 1e is controlled by the control unit 1c.
The antenna 1f is a common antenna for transmission and reception, and outputs a transmission signal as a radio wave during transmission and converts the received radio wave into a reception signal during reception.

The receiver 1b2 performs amplification, frequency conversion, filtering to remove interference waves, and the like on the reception signal received by the antenna 1f. The reception frequency at which the reception unit 1b2 performs reception is determined by an oscillator (not shown).
The demodulator 1b1 demodulates the received signal from the receiver 1b1 into an audio signal or a data signal. The audio signal is output to the speaker 1b3. The demodulated data signal is analyzed by the control unit 1c and processed as necessary.
The demodulation method is arbitrary, but generally a method capable of demodulating a modulation method signal used for transmission is used.
The speaker 1b3 reproduces the demodulated audio signal.

  The display operation unit 1d includes an operation unit operated by a user of the terminal and a display unit representing the state of the terminal. The user operates from the display operation unit 1d, and performs transmission / reception operations and the like via the control unit 1c.

FIG. 2 shows a typical example of a relay station.
The receiving antenna 2d receives radio waves from the terminal and outputs a received signal to the receiving unit 2a1.
The receiving unit 2a1 performs amplification, frequency conversion, filtering, etc. on the received signal, and outputs a received signal from which unnecessary signals are removed to the demodulating unit 2a2.
The receiving unit 2a1 outputs an RSSI signal representing the received signal strength to the control unit 2c.
The demodulator 2a2 demodulates the audio signal and the data signal included in the received signal.
The demodulated data signal is output to the control unit 2c, analyzed by the control unit 2c, and processed as necessary.

The modulation unit 2b1 performs modulation including the audio signal demodulated by the demodulation unit 2a2 and the transmission data signal from the control unit 2c, and converts it into a transmission signal.
Similarly to the terminal, the relay station can use any method for modulation and demodulation of voice and data, but the same method is used for the relay station and the terminal.
The transmitter 2b2 performs a filtering process to amplify the transmission signal from the modulator 2b1 to a necessary output and remove unnecessary radiation. Further, the transmission unit 2b2 performs the same processing as the terminal in response to an instruction from the control unit 2c, and performs transmission output control.
The transmission antenna 2e transmits a signal from the relay station to the terminal as a radio wave.

  In general, in a relay station that performs transmission and reception operations at the same time, the frequency received by the receiving unit 2a1 and the frequency transmitted by the transmitting unit 2b2 do not use the same frequency in order to avoid mutual interference.

FIG. 3 shows details of the control unit 1c of the terminal.
As shown in FIG. 3, the control unit 1c includes a setting information storage unit 3a that stores transmission and reception frequencies and transmission output settings, a control processing unit 3b that controls various controls, analysis, and operation of the entire terminal, and a transmission system. And an interface unit 3c that mediates control of the circuit 1a, the reception system circuit 1b, and the like.

The setting information storage unit 3a stores transmission and reception frequency setting information, transmission output setting information, and the like in a storage device. The storage medium of the storage device is arbitrary such as a semiconductor memory or a hard disk.
In response to an instruction from the arithmetic processing unit 3b3, the control processing unit 3b reads information from the setting information storage unit 3a, writes information to the setting information storage unit 3a, hardware control, data analysis, and display operation unit 1d. Input information analysis, display instruction to the display operation unit 1d, and the like.
The interface unit 3c converts the hardware into a controllable signal according to an instruction from the control processing unit 3b. The interface unit 3c converts the data signal from the demodulation unit into a format that can be recognized by the control processing unit 3c.

The transmission output setting information 3a1 and the frequency setting information 3a2 stored in the control information storage unit 3a are calculated based on the information change by the operation from the display operation unit 1d and the data analysis result of the received signal from the data analysis unit 3b4. The processing unit 3b3 can also change the information.
Further, both or one of the transmission output setting information 3a1 and the frequency setting information 3a2 may not be changed by a special command or hardware setting.

The transmission output setting information 3a1 stores transmission output setting data determined by hardware adjustment and transmission output data representing the transmission output.
The frequency setting information 3a2 stores data for setting the oscillation frequency of the oscillator necessary for transmission and reception.
The transmission output setting information 3a1 and the frequency setting information 3a2 may be stored as an associated channel.

The arithmetic processing unit 3b3 reads a necessary value from the transmission output setting information 3a1 of the setting information storage unit 3a, and sets the value in the transmission output selection control 3b1.
The transmission output selection control 3b1 outputs data of information indicating the transmission output and data for determining the transmission output to the interface unit 3c.
The arithmetic processing unit 3b3 reads a value from the frequency setting information 3a2 in the setting information storage unit 3a, and sets the value in the frequency selection control unit 3b2. The frequency selection control unit 3b2 selects necessary frequency information according to transmission and reception from the value, and outputs the frequency setting information to the interface unit 3c.

The data signal demodulated by the demodulator 1b1 is converted into a data signal that can be analyzed by the data analyzer 3b4 by the data demodulator 3c5, and the data is analyzed by the data analyzer 3b4.
The arithmetic processing unit 3b3 takes in the result analyzed by the data analysis unit 3b4 and performs necessary processing such as frequency change and transmission output change in a timely manner.

The modulation information conversion unit 3c1 converts information data representing the transmission output sent from the transmission output selection control 3b1 into a signal that can be modulated by the modulator.
The transmission output setting conversion unit 3c2 converts the data for determining the transmission output sent from the transmission output selection control 3b1 into a signal that can be controlled by the transmission output control unit 1a3.

  The frequency data converter 3c3 converts the frequency setting information required for transmission or reception received from the frequency selection control 3b2 into a signal that can control the frequency oscillator 3i.

  The transmission / reception circuit switching unit 3c4 outputs a control signal for turning on / off a circuit that needs to operate at the time of transmission or reception.

  The data demodulating circuit 3c5 in the interface unit 3c converts the received data signal received from the demodulating unit 1b1 into a data signal that can be analyzed by the control processing unit 3c.

FIG. 4 shows details of the control unit 2c of the relay station.
The control unit 2c includes an interface unit 4a and a control processing unit 4b.
The interface unit 4a includes a received signal strength converting unit 4a1 that converts an RSSI signal representing received signal strength from the receiving unit 2a1 into data that can be analyzed by the control processing unit,
The demodulated data converter 4a2 converts the received data signal demodulated by the demodulator 2a2 into a format that can be analyzed by the control processor 4c, and the instruction data to the terminal determined by the arithmetic processor 4b1 is sent to the modulator 2b1. And a data modulation conversion unit 4a3 for converting into a format that can be modulated.

The control processing unit 4b controls the analysis of demodulated data and the overall control of the relay station.
The data analysis unit 4b2 analyzes the demodulated data signal and outputs the analysis result to the arithmetic processing unit.
When high-speed digital signal processing such as clock recovery or synchronization processing is required for data analysis, a DSP or the like may be used for the data analysis unit 4b2.
When the demodulated data is a tone signal or the like, the data analysis unit 4b2 may be configured with a filter that detects a specific frequency and outputs the result.
The arithmetic processing unit 4b1 acquires the signal strength information of the signal from the terminal, the terminal information from the data analysis unit, and the like from the received signal strength conversion unit 4a1, and performs necessary processing in a timely manner.
The arithmetic processing unit 4b1 also supervises various controls of the entire relay station.

The operation and signal flow of the wireless communication system of this embodiment will be described.
When the display operation unit 1d instructs the terminal shown in FIG. 1 to be turned on by the user operation, the control unit 1c supplies power to the reception system circuit unit 1b and can receive the transmission frequency of the relay station. Set the reception frequency as follows. Accordingly, it is possible to receive a call signal from another terminal via the relay station.
When a call signal is received from another terminal through the relay station, as described in the description of the structure, a reception operation is performed, an audio signal is reproduced by the speaker 1b3, and a data signal is analyzed by the control unit 1c. .
The operation in the case of direct communication is the same.
The reception frequency is set by the frequency setting information set in advance in the setting information storage unit 3a. The frequency at which the signal from the relay station is received may be different from the frequency at which direct communication is performed.

When the user performs transmission on his / her own intention to the terminal shown in FIG. 1, a transmission instruction is issued from the display operation unit 1d to the terminal by the user's operation.
The control unit 1c received a transmission instruction from the display operation unit 1d turns off the power supply to the reception system circuit unit 1b and supplies power to the transmission system circuit unit 1a.
The controller 1c sets the reception frequency of the relay station when performing communication via the relay station, and sets the reception frequency of the counterpart terminal when performing direct communication.
The user speaks into the microphone 1a4, and the voice is transmitted from the antenna 1f as a transmission signal by the transmission circuit system 1a.

  The relay station shown in FIG. 2 relays the received signal and performs an operation suitable for the condition based on the result of analyzing the received signal.

FIG. 5 is a flowchart showing the first embodiment of the wireless communication system according to the present invention.
The terminal A and the terminal B in the flowchart will be described using the terminal having the configuration described in FIGS. 1 and 2 as an example. The relay station will be described by taking the relay station having the configuration described in FIGS. 3 and 4 as an example.
When the flow starts as shown in FIG. 5, both the terminal A and the terminal B are in a relay communication mode in which communication is performed via the relay station (step S101), and both the terminals A and B are connected via the relay station. The call is waiting (step S102).

As shown in FIG. 5, first, a user of terminal A performs a call operation for calling terminal B (step S103), and transmits a terminal B calling signal (step S104).
The relay station receives the terminal B call signal from the terminal A, relays the terminal B call signal, and transmits the terminal B call signal (step S106).
Further, the relay station acquires the RSSI signal of the terminal B calling signal from the terminal A from the receiving unit 2a, and the received signal strength converting unit 4a1 converts the RSSI signal into received signal strength data that can be analyzed, and the control processing unit 4b measures the received signal strength from the received signal strength data (step S108).
Further, the relay station demodulates the transmission output information included in the calling signal by the demodulator 2a2, the demodulated data converter 4a2 converts the demodulated signal into data that can be processed by the data analyzer 4b2, and the data analyzer 4a2 The demodulated data is analyzed, and the arithmetic processing unit 4b1 recognizes the transmission output of the terminal A from the analyzed transmission output information (step S109).

The terminal B receives the terminal B call signal (step S111), and if the terminal B can respond, transmits a response signal to the relay station (step S112).
The relay station receives the response signal from the terminal B, relays the response signal, and transmits the response signal to the terminal A (step S114).
The terminal A confirms that the terminal B has responded by receiving the response signal (step 121).
Further, the relay station acquires the RSSI signal of the response signal from the terminal B from the receiving unit 2a1, the received signal strength converting unit 4a1 converts the RSSI signal into the received signal strength data that can be analyzed, and the control processing unit 4b receives the received signal. The received signal strength is measured from the signal strength data (step S116).
Further, the relay station demodulates the transmission output information included in the response signal by the demodulator 2a2, the demodulated data converter 4a2 converts the demodulated signal into data that can be processed by the data analyzer 4b2, and the data analyzer 4a2 The demodulated data is analyzed, and the arithmetic processing unit 4b1 recognizes the transmission output of the terminal B from the analyzed transmission output information (step S117).

The arithmetic processing unit 4b1 of the relay station estimates the distance to the terminal A from the signal strength of the terminal B calling signal from the terminal A and the transmission output information of the terminal A (step S110).
Further, the arithmetic processing unit 4b1 estimates the distance to the terminal B from the signal strength of the response signal from the terminal B and the transmission output information of the terminal B superimposed on the response signal (step S118).
The relationship between signal strength, transmission power and distance will be described later.
The arithmetic processing unit 4b1 of the relay station obtains the sum of the distance from the relay station to the terminal A and the distance to the terminal B, and compares the sum with a predetermined distance (step 120).

FIG. 6 is a flow in the case where the sum of the distance from the relay station to the terminal A and the distance to the terminal B is not equal to or greater than a predetermined distance as a result of step S120 in FIG.
The control unit 2c of the relay station determines that direct communication is possible because the sum of the distances is not equal to or greater than a predetermined distance (step S201), and the control unit 2c transmits transmission data instructing the terminal A and the terminal B to perform direct communication. Is modulated and amplified by the transmission system circuit unit 2b, and a communication instruction signal is directly transmitted from the antenna 2e to the terminal A and the terminal B (step S202).
Terminal A and terminal B receive the direct communication instruction signal from the relay station, and the control processing unit 3b analyzes the direct communication instruction signal and provides information necessary for direct communication such as direct communication frequency setting. Set and shift to the direct communication mode (step S205).

Information necessary for direct communication may be sent together with a direct communication shift instruction signal from the relay station.
When the terminal A and the terminal B shift to the direct communication mode, in order to notify the user that the direct communication mode has been switched, a function for performing a display for confirming the shift to the display operation unit 1d and a warning sound from the speaker 1b3 You may provide the function to emit.

The terminal A and the terminal B that are in the direct communication mode perform direct communication without going through the relay station (steps S206 to S210).
When the direct communication is completed, the direct communication mode is canceled and the operation proceeds to the standby operation from the relay station (step 212 to step S215).

FIG. 7 is a flow when the sum of the distance from the relay station to the terminal A and the distance to the terminal B is equal to or greater than a predetermined distance as a result of step S120 in FIG.
The control unit 2c of the relay station determines that direct communication is impossible because the sum of distances is equal to or greater than a predetermined distance (step S301), and the terminal A and the terminal B start communication via the relay station. (Steps S302 to S306).

FIG. 8 is a flowchart of the second embodiment of the present invention.
The terminal A and the terminal B are already in communication via the relay station, and a flow for shifting from the state to direct communication will be described.
The terminal A and the terminal B in the flowchart will be described using the terminal having the configuration described in FIGS. 1 and 2 as an example. The relay station will be described by taking the relay station having the configuration described in FIGS. 3 and 4 as an example.

Terminal A transmits a transmission signal to terminal B to the relay station (step S401).
The relay station receives the terminal A transmission signal and relays it to the terminal B (step S403).

Further, the relay station acquires the RSSI signal of the transmission signal from the terminal A from the reception unit 2a1, the reception signal strength conversion unit 4a1 converts the RSSI signal into received signal strength data that can be analyzed, and the control processing unit 4b receives the signal. The received signal strength is measured from the signal strength data (step S405).
Further, the relay station demodulates the transmission output information included in the calling signal by the demodulator 2a2, the demodulated data converter 4a2 converts the demodulated signal into data that can be processed by the data analyzer 4b2, and the data analyzer 4a2 The demodulated data is analyzed, and the arithmetic processing unit 4b1 recognizes the transmission output of the terminal A from the analyzed transmission output information (step S406).
Also, the arithmetic processing unit 4b1 of the relay station estimates the distance to the terminal A from the received signal strength of the transmission signal from the terminal A and the transmission output information of the terminal A (step S407).

  The terminal B receives the relay transmission from the terminal A to the terminal B (step S408).

The terminal B transmits a transmission signal for the terminal A to the relay station (step S409).
The relay station receives the terminal B transmission signal and relays it to the terminal A (step S411).

Further, the relay station acquires the RSSI signal of the transmission signal from the terminal B from the reception unit 2a1, the reception signal strength conversion unit 4a1 converts the RSSI signal into received signal strength data that can be analyzed, and the control processing unit 4b receives the signal. The received signal strength is measured from the signal strength data (step S413).
Further, the relay station demodulates the transmission output information included in the calling signal by the demodulator 2a2, the demodulated data converter 4a2 converts the demodulated signal into data that can be processed by the data analyzer 4b2, and the data analyzer 4a2 The demodulated data is analyzed, and the arithmetic processing unit 4b1 recognizes the transmission output of the terminal B from the analyzed transmission output information (step S406).
Further, the arithmetic processing unit 4b1 of the relay station estimates the distance to the terminal B from the received signal strength of the transmission signal from the terminal B and the transmission output information of the terminal B (step S416).

  The terminal A receives a relay signal from the terminal B to the terminal A (step S415).

The arithmetic processing unit 4b1 of the relay station obtains the sum of the distance from the relay station to the terminal A and the distance to the terminal B (step S417), compares the sum with a predetermined distance, and directly determines the result. It is determined whether or not communication is possible (step S418).
If the sum of the distances is equal to or greater than the predetermined distance, the arithmetic processing unit 4b1 determines that direct communication is impossible and continues the relay mode (step S420).
If the sum of the distances is not equal to or greater than the predetermined distance, the arithmetic processing unit 4b1 determines that direct communication is possible, and the relay station instructs the terminal A and the terminal B to perform direct communication (step S419).

FIG. 9 is a flow when the relay station determines a direct communication instruction in step S419 of FIG. 8 and shifts to the direct communication with the terminal A and the terminal B.
Since the terminal A and the terminal B do not receive a direct communication instruction at the present time, they communicate with each other via the relay station.

Terminal A transmits a signal for terminal B to the relay station (step S501).
The reception circuit unit 2a of the relay station receives the transmission signal of the terminal A and outputs a demodulated signal to the transmission system circuit unit 2b, and the modulation unit 2b1 of the transmission system circuit unit 2b outputs the relay signal to the terminal B. The control unit 2c modulates the terminal B including the transmission data of the direct communication instruction, the transmitting unit 2b2 amplifies the modulated signal, and the antenna 2e relays and transmits to the terminal B (step S503).
The receiving circuit unit 1b of the terminal B receives and demodulates a relay signal from the relay station to the terminal B (step S505), and the control processing unit 3b of the terminal B transmits a direct communication instruction included in the received signal. Are analyzed (step S506).
The speaker 1b3 of the terminal B outputs a demodulated audio signal.

The terminal B transmits a signal for the terminal A to the relay station (step S507).
The reception circuit unit 2a of the relay station receives the transmission signal of the terminal B and outputs a demodulated signal to the transmission system circuit unit 2b, and the modulation unit 2b1 of the transmission system circuit unit 2b outputs the relay signal to the terminal A. The control unit 2c modulates the terminal A including the transmission data of the direct communication instruction, the transmitting unit 2b2 amplifies the modulated signal, and the antenna 2e relays and transmits to the terminal A (step S509).
The receiving circuit unit 1b of the terminal A receives and demodulates the relay signal from the relay station to the terminal A (step S512), and the control processing unit 3b of the terminal A transmits a direct communication instruction included in the received signal. Are analyzed (step S513).
The speaker 1b3 of the terminal A outputs a demodulated audio signal.

  After the next transmission in which the terminal B receives the direct communication instruction, the terminal A ends the relay mode after completion of the reception of the direct communication instruction (step S515), and sets the direct communication mode (step S518). . At that time, a display notifying that the mode has been changed to the direct communication mode is displayed on the operation display 1d, and a confirmation sound is generated from the speaker 1b3 (S519).

  The relay station ends the relay between the terminals A and B (step S516) and enters a standby state from the terminal (step S517).

The operation after the direct communication shift is the same as that of the first embodiment, and the users of the terminal A and the terminal B can shift from the relay mode to the direct communication mode without performing a special operation.
Further, the first embodiment and the second embodiment may be combined.

  When the terminal is moving, if the signal strength from the terminal to the relay station is temporarily lowered due to an obstacle, it may be determined that it is not possible to shift to direct communication. In that case, the communication between the terminals A and B is performed a plurality of times in the relay mode, the distance between the terminals A and B is estimated a plurality of times, and the average of the estimated distances is obtained to determine whether or not the direct communication is possible. May be.

It is known that the distance can be obtained by the following equation from the free space loss and the frequency.
r = √L × λ / 4π
L: Free space propagation loss [W]
r: Distance between transmitting antenna and receiving antenna [W]
λ: Wavelength [m]

The free space loss L is power obtained by subtracting the antenna gain on the transmission side and the reception side from the difference between the transmission output power and the reception power received by the reception antenna.
Although the relay station knows its own antenna gain, the terminal-side antenna gain is unknown, and in portable devices, the effective radiation efficiency of the antenna changes depending on the use state, and may not be constant.
By adding an identifier for distinguishing portable and vehicle-mounted antennas as transmission data, it is possible to estimate the distance in consideration of the antenna gain. However, unlike large-sized and high-gain antennas such as relay stations, terminal antennas are small and have little gain, and in-vehicle devices and portable devices have a difference of about several dB. There is no big difference.

As a means for shifting the terminal to direct communication, there is a method in which the position of the terminal is specified.
The terminal is equipped with GPS or the like to transmit position information, and APRS is famous as a means for the other station to acquire the position information. In this case, although the positional relationship between the terminals is obvious, GPS Such a position acquisition device is required, which leads to an increase in cost, weight and power consumption of the terminal.

  Further, as a simple method, there may be a method of making a direct communicable area within a certain distance from the relay station 10g in any direction as in the terminal 10c and the terminal 10d. In the case of communication between the terminal 10e and the terminal 10f, even if the distance between the terminals is close, if either one of the terminals (in this case, the terminal 10f) leaves the direct communication area, the direct communication is It becomes impossible.

The feature of this embodiment is to estimate the distance from the relay station to the terminal, and determine whether direct communication is possible or impossible based on the sum of the distances regardless of the direction of each terminal communicating with the relay station. There is.
Therefore, it is necessary to determine the distance that can be directly communicated as the longest condition of the distance that can be directly communicated when the terminal 10a and the terminal 10b in FIG.

According to the present embodiment, since it is the sum of the distance between the terminal and the relay station, in the case where the terminals 10a and 10b can communicate directly in FIG. 11, the terminal 11a and the terminal 11b that are close to the relay station. Alternatively, if 11c is the same distance between the terminal 10a and the terminal 10b, it can be determined that direct communication is possible.
When either one of the terminals approaches X [m] to the relay station, it can be determined that the other terminal can communicate directly even if it is away from the X [m] relay station. When close to each other, direct communication is possible even with a terminal that is theoretically about twice as large as the method of FIG.

Claims (8)

In a wireless communication system comprising a plurality of terminals and relay stations,
The terminal is
Means for direct communication between the terminals;
Means for communicating via the relay station;
Means for transmitting the transmission output information representing the transmission output of the terminal included in the call transmission signal and the response transmission signal;
With
The relay station is
Signal strength measuring means for measuring the signal strength of the call transmission signal and the response transmission signal from the terminal;
Distance estimation means for estimating a distance to each of the terminals from the measured signal strength and transmission output information from each of the terminals;
Inter-terminal distance estimation means for obtaining the sum of the estimated distance to each terminal that has called and responded via the relay station;
With
If the distance estimated by the inter-terminal distance estimating means is greater than or equal to a predetermined distance, start the relay operation of communication between the terminals,
If the distance estimated by the inter-terminal distance estimation means is not equal to or greater than a predetermined distance, the relay station transmits a direct communication transition signal instructing each terminal to shift to direct communication, and the terminal A wireless communication system, wherein direct communication is started. In a wireless communication system comprising a plurality of terminals and relay stations,
The terminal is
Means for direct communication between the terminals;
Means for communicating via the relay station;
Means for transmitting transmission output information representing the transmission output of the terminal in a transmission signal;
With
The relay station is
Signal strength measuring means for measuring the signal strength of the signal from the terminal;
Distance estimation means for estimating a distance to each of the terminals from the measured signal strength and transmission output information from each of the terminals;
An inter-terminal distance estimation means for obtaining a sum of the estimated distances of the respective terminals communicating via the relay station;
With
If the distance estimated by the inter-terminal distance estimation means is equal to or greater than a predetermined distance, the communication relay operation between terminals is continued.
A wireless communication system characterized in that if the distance estimated by the inter-terminal distance estimating means is not equal to or greater than a predetermined distance, the terminal is instructed to shift to direct communication, and the terminal shifts to direct communication.   3. The wireless communication system according to claim 2, wherein the direct communication shift instruction information is transmitted by being included in a transmission signal from the relay station communicating with the relay station to the terminal.   The wireless communication system according to claim 2 or 3, wherein the distance estimation by the inter-terminal distance estimation means is performed twice or more, and the shift to direct communication is determined by the average value.   The radio communication system according to any one of claims 1 to 4, wherein the direct communication transmission frequency and reception frequency are the same. Transmitting a call transmission signal to the second terminal including the transmission output information of the first terminal from the first terminal to the relay station;
The relay station receiving the call transmission signal from the first terminal, relaying the call transmission signal to the second terminal, and transmitting.
The relay station measuring the signal strength of the call transmission signal;
The relay station analyzing transmission output information included in the call transmission signal;
The second terminal receives a call transmission signal from the relay station, and transmits a response transmission signal to the first terminal including transmission output information of the second terminal to the relay station. When,
The relay station measuring the signal strength of the response transmission signal;
The relay station analyzing transmission output information included in the response transmission signal;
The relay station estimating a first distance to the first terminal from a result of analyzing a signal strength of the call transmission signal and transmission output information included in the call transmission signal;
The relay station estimating the second distance to the second terminal from the signal strength of the response transmission signal and the result of analyzing the transmission output information included in the response transmission signal;
Determining the sum of the first and second distances;
Starting a relay communication via the relay station if the sum is greater than or equal to a predetermined distance;
Sending a direct communication instruction to the first and second terminals if the sum is not greater than a predetermined distance;
The first and second terminals receiving a direct communication instruction from the relay station;
The first and second terminals include a step of shifting to a direct communication state. A relay station receiving transmission signals from the first and second terminals and measuring the signal strength;
Analyzing transmission output information included in the transmission signal;
Estimating a first distance and a second distance from the signal strength and the transmission output information to the first and second terminals;
Determining the sum of the first and second distances;
Continuing the relay if the sum result is greater than or equal to a predetermined distance;
Transmitting a direct communication instruction included in a transmission signal from a relay station to the first and second terminals if the result of the sum is not greater than a predetermined distance;
The first and second terminals receiving a direct communication instruction from the relay station;
The wireless communication method, wherein the first and second terminals include a step of shifting to a direct communication state. The wireless communication method according to claim 6 or 7, wherein the direct communication transmission frequency and reception frequency are the same.

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