WO2017203817A1

WO2017203817A1 - Communication device and communication control method

Info

Publication number: WO2017203817A1
Application number: PCT/JP2017/011663
Authority: WO
Inventors: 佐藤　雅典; 伊東　克俊
Original assignee: ソニー株式会社
Priority date: 2016-05-25
Filing date: 2017-03-23
Publication date: 2017-11-30
Also published as: JP6917682B2; JP2017212605A

Abstract

[Problem] To reduce the power consumed in order to manage communication resources in a system in which a plurality of reception signals are combined. [Solution] This communication device is provided with: an evaluation unit (130) for evaluating the frequencies of carrier waves of reception signals received from other communication devices; and a combination processing unit (140) which extracts, from the plurality of reception signals, two or more reception signals on the basis of the results of the evaluation performed by the evaluation unit, and executes combination processing on the two or more reception signals.

Description

Communication apparatus and communication control method

This disclosure relates to a communication device and a communication control method.

In recent years, wireless sensor networks for collecting information by wireless communication from terminals having a sensor function have attracted attention. The wireless sensor network has a wide variety of uses, such as a purpose of confirming a position of an object of interest and a purpose of managing the behavior of the object of interest.

In a wireless communication system such as an existing cellular system and wireless LAN (Local Area Network), a base station such as a base station or an access point manages communication resources. For example, the master station periodically transmits a reference signal, determines a communication resource for the communication terminal on the slave station side, notifies the determined communication resource to the communication terminal according to a predetermined control protocol, Communication is performed using the reception result of the reference signal and the notified communication resource. By this management, it is possible to avoid or suppress interference between communications performed by a plurality of communication terminals. With regard to the above wireless communication system, Patent Document 1 discloses a technique for controlling whether or not to continue the reception process based on the frequency offset of the received preamble.

Japanese Unexamined Patent Publication No. 2000-4177

In the wireless communication system described above, the cost of the terminal can be reduced by designing the hardware of the communication terminal so that the maximum available transmission power is limited. However, when the transmission power is limited, the communicable distance is also limited. In this regard, there is H-ARQ (Hybrid-ARQ) employed in cellular communication, for example, as a technique for a communication terminal to perform long-distance transmission with low transmission power. H-ARQ is a technique for improving reception sensitivity by repeatedly transmitting the same frame on the transmission side and combining a plurality of frames by signal processing on the reception side.

When H-ARQ is applied to a multi-access environment where a plurality of communication terminals may exist, it is possible to synthesize reception signals from the same communication terminal by identifying the transmission terminal of each reception signal before combining. Become. As described above, if communication for managing communication resources is performed in advance, identification of the transmission terminal of each received signal is easy.

However, in communication for management of communication resources, that is, in the communication according to the above-described reception of the reference signal and the predetermined control protocol, the power of the communication terminal is consumed.

Therefore, the present disclosure proposes a new and improved communication apparatus and communication control method capable of reducing power consumption for communication resource management in a system in which a plurality of received signals are combined.

According to the present disclosure, an evaluation unit that evaluates the frequency of a carrier wave of a reception signal received from another communication device, and two or more reception signals are extracted from a plurality of reception signals based on the evaluation result by the evaluation unit And a synthesis processing unit that performs synthesis processing of the two or more received signals.

Moreover, according to this indication, a processor evaluates the frequency of the carrier wave of the received signal received from the other communication apparatus, and extracts two or more received signals from a plurality of received signals based on the evaluation result. And a communication control method including combining the two or more received signals.

As described above, according to the present disclosure, it is possible to reduce power consumption for managing communication resources in a system in which a plurality of received signals are combined.

Note that the above effects are not necessarily limited, and any of the effects shown in the present specification, or other effects that can be grasped from the present specification, together with or in place of the above effects. May be played.

2 is an explanatory diagram illustrating a configuration of a wireless communication system according to an embodiment of the present disclosure. FIG. It is explanatory drawing which shows an example of the division of the communication resource on a time axis. It is explanatory drawing which shows the structural example of the flame | frame which a sensor terminal transmits. It is explanatory drawing which shows the structure of the sensor terminal by embodiment of this indication. 2 is an explanatory diagram illustrating a configuration of a base station according to an embodiment of the present disclosure. FIG. It is explanatory drawing which shows the structure of an evaluation part. 5 is a flowchart illustrating an operation of a sensor terminal according to an embodiment of the present disclosure. 5 is a flowchart illustrating an operation of a base station according to an embodiment of the present disclosure. It is explanatory drawing which shows the production | generation of a GOLD series. It is explanatory drawing which shows the structure of the evaluation part by a 1st application example. It is a flowchart which shows operation | movement of the sensor terminal by a 1st application example. It is a flowchart which shows operation | movement of the base station by a 1st application example. It is a flowchart which shows operation | movement of the sensor terminal by a 2nd application example. It is explanatory drawing which shows the specific example of a hopping pattern. It is explanatory drawing which shows the specific example of a hopping pattern. It is explanatory drawing which shows the specific example of a hopping pattern. It is explanatory drawing which shows an example of the reception result by a base station. It is explanatory drawing which shows the other example of the reception result by a base station. It is a flowchart which shows operation | movement of the sensor terminal by the 3rd application example. It is a flowchart which shows the operation | movement of the base station by the 3rd application example. It is explanatory drawing which showed the hardware constitutions of the sensor terminal.

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

In the present specification and drawings, a plurality of constituent elements having substantially the same functional configuration may be distinguished by adding different alphabets after the same reference numeral. For example, a plurality of configurations having substantially the same functional configuration or logical significance are distinguished as

sensor terminals

20A, 20B, and 20C as necessary. However, when it is not necessary to particularly distinguish each of a plurality of constituent elements having substantially the same functional configuration, only the same reference numerals are given. For example, when it is not necessary to distinguish the

sensor terminals

20A, 20B, and 20C, they are simply referred to as the sensor terminal 20.

Moreover, this indication is demonstrated according to the item order shown below.
1. 1. Overview of wireless communication system 2. Configuration of sensor terminal Configuration of base station 4. Operation 5. Application example 5-1. First application example 5-2. Second application example 5-3. Third application example 6. Hardware configuration Conclusion

<< 1. Overview of wireless communication system >>
Embodiments of the present disclosure relate to a wireless communication system that forms a wireless sensor network. First, an overview of a wireless communication system according to an embodiment of the present disclosure will be described with reference to FIG.

(1-1. Configuration of Radio Communication System)
FIG. 1 is an explanatory diagram illustrating a configuration of a wireless communication system according to an embodiment of the present disclosure. As illustrated in FIG. 1, the wireless communication system according to the embodiment of the present disclosure includes a plurality of base stations 10, a plurality of sensor terminals 20, and an application server 30.

The base station 10 is a communication device having a function of performing wireless communication with the sensor terminal 20 and a function of performing wired communication with the application server 30. For example, the base station 10 performs wireless communication with the sensor terminal 20 located in the cell. In the example shown in FIG. 1, the base station 10A performs wireless communication with the

sensor terminals

20A, 20B, and 20C located in the cell of the base station 10A, and the base station 10B is a sensor located in the cell of the base station 10B. Wireless communication is performed with the

terminals

20D, 20E, 20F, and 20G. In particular, the base station 10 according to the present embodiment receives sensor data from the sensor terminal 20 and transmits the sensor data to the application server 30.

The sensor terminal 20 has a sensor function and a function of performing wireless communication with the base station 10. For example, the sensor function can be realized by various sensors such as an acceleration sensor, a gyro sensor, a temperature sensor, an atmospheric pressure sensor, a sound pressure sensor, a pulse sensor, or a GPS (Global Positioning System). The sensor terminal 20 transmits the sensor data acquired by the sensor function to the base station 10.

The application server 30 receives the sensor data obtained by the sensor terminal 20 from the base station 10 and provides a service using the received sensor data. There are a wide variety of services using sensor data, such as a service for confirming the position of an object of interest and a service for managing the behavior of an object of interest. Regarding the service for confirming the position of interest, for example, an elderly person or a child wears the sensor terminal 20 having a GPS function, and the application server 30 acquires position information from the sensor terminal 20 via the base station 10. Thus, it is possible to provide the positions of the elderly and children to the family and the administration. Regarding the service for managing the behavior of interest, for example, the sensor terminal 20 having an acceleration sensor is attached to livestock such as cows and pigs, and the application server 30 receives information on the movement of livestock from the sensor terminal 20 via the base station 10. It is possible to manage the behavior of livestock on grazing land.

In the present embodiment, the sensor terminal 20 having a sensor function will be described as an example of a communication device. However, the present embodiment can also be applied to a communication device having no sensor function. For example, the communication device may be supplied with data from an external device and transmit the supplied data to the base station 10. When the external device is a vending machine, the communication device may be supplied with sales data from the vending machine and transmit the sales data to the base station 10.

(1-2. Overview of wireless communication)
The configuration of the wireless communication system according to the embodiment of the present disclosure has been described above. Next, an outline of wireless communication between the base station 10 and the sensor terminal 20 in the wireless communication system will be described.

-Communication resource The base station 10 and the sensor terminal 20 share the start timing of each communication resource divided on the time axis. The sharing can be realized, for example, when the base station 10 transmits a reference signal for time synchronization and the sensor terminal 20 receives the reference signal. However, when the sensor terminal 20 continuously receives the reference signal, corresponding power is consumed. For this reason, the base station 10 and the sensor terminal 20 may share the start timing of each communication resource based on the absolute time managed by each. For example, the sensor terminal 20 can acquire the absolute time by GPS reception processing. Hereinafter, an example of communication resources on the time axis in which timing is shared by the base station 10 and the sensor terminal 20 will be described with reference to FIG.

FIG. 2 is an explanatory diagram showing an example of communication resource classification on the time axis. In the present embodiment, communication resources on the time axis are divided into resource units called superframes. In the example shown in FIG. 2, ten superframes composed of superframes # 0 to # 9 are repeated. The time width of each super frame is not particularly limited, and may be 6 seconds, for example. When the time width of each super frame is 6 seconds, the repetition period of the super frame is 1 minute. The sensor terminal 20 transmits a frame including sensor data using any one of the super frames.

Frame Configuration FIG. 3 is an explanatory diagram showing a configuration example of a frame transmitted by the sensor terminal 20. As shown in FIG. 3, the frame transmitted by the sensor terminal 20 includes a preamble 51, an SFD (Sync Frame Detector) 52, a terminal ID 53, data 54, a CRC (Cyclic Redundancy Check) 55, and a parity bit 56. And including.

The preamble 51 is a signal pattern used for frame detection in the base station 10. The SFD 52 is a signal pattern indicating the start position of the payload (terminal ID 53 to parity bit 56) within the frame. The base station 10 detects the SFD 52 from the frame in which the preamble 51 is detected, thereby recognizing that the subsequent is the payload.

Terminal ID 53 is an ID of the sensor terminal 20 that transmits a frame. The terminal ID 53 may be a unique number of the sensor terminal 20, for example. The data 54 is data for use in the application server 30, and sensor data such as acceleration information and position information can be included in the data 54. The CRC 55 is used to determine whether or not reception of the frame has been successful. The parity bit 56 is a redundant bit generated according to the terminal ID 53, the data 54, and the CRC 55, and the frame reception success rate at the base station 10 is improved by using the parity bit.

-Long distance transmission In order to realize a wireless communication system at a lower cost, it is effective to widen a cell area covered by one base station 10, that is, long distance transmission. In long-distance transmission, it is possible to reduce the number of base stations 10 constituting the wireless communication system.

Also, it is possible to reduce the cost of the sensor terminal 20 by designing the hardware of the sensor terminal 20 so that the maximum available transmission power is limited. However, when the transmission power is limited, the communicable distance is also limited. In this regard, there is H-ARQ (Hybrid-ARQ) employed in cellular communication, for example, as a technique in which the sensor terminal 20 performs long-distance transmission with low transmission power. H-ARQ is a technique for improving reception sensitivity by repeatedly transmitting the same frame on the transmission side and combining a plurality of frames by signal processing on the reception side.

Specifically, the sensor terminal 20 according to H-ARQ receives the frame described with reference to FIG. 3 until reception confirmation (ACK) is received from the base station 10 or until the number of transmissions reaches an upper limit. Send repeatedly. The base station 10 performs frame composition every time a new frame is received, and transmits ACK to the sensor terminal 20 when demodulation is successful.

(1-3. Background)
When the above-described H-ARQ is applied to a multi-access environment where a plurality of communication terminals can exist, it is possible to combine frames from the same communication terminal by identifying the transmitting terminal of each frame before combining. Become. In a wireless communication system such as a cellular system and a wireless LAN, a base station such as a base station or an access point performs communication for communication resource management with a communication terminal. If communication for management of such communication resources is performed in advance, the transmission terminal of each frame can be easily identified.

However, since communication for managing communication resources includes, for example, reception of a reference signal in a communication terminal and communication in accordance with a predetermined control protocol, power of the communication terminal is consumed. In particular, it is assumed that the data transmitted by the sensor terminals belonging to the sensor network is a small amount of data of about several bytes. In this case, the power consumed for management of communication resources is consumed for data transmission. The ratio to the power to be increased.

Therefore, the present inventor came to create an embodiment of the present disclosure by focusing on the above circumstances. According to the embodiment of the present disclosure, it is possible to reduce power consumption for communication resource management in a system in which a plurality of frames are combined. Hereinafter, the configuration and operation of the embodiment of the present disclosure will be sequentially described in detail.

<< 2. Configuration of sensor terminal >>
FIG. 4 is an explanatory diagram illustrating a configuration of the sensor terminal 20 according to the embodiment of the present disclosure. As illustrated in FIG. 4, the sensor terminal 20 according to the embodiment of the present disclosure includes a wireless communication unit 220, a sensor unit 230, a carrier wave generation unit 240, and a control unit 250.

(Wireless communication part)
The radio communication unit 220 performs reception processing of a radio signal transmitted from the base station 10 and transmission processing of a radio signal to the base station 10. More specifically, the radio communication unit 220 converts a radio signal (for example, a radio signal in a 920 MHz band) transmitted from the base station 10 into a high frequency reception signal by an antenna, and performs analog processing and downsampling on the high frequency reception signal. By performing the conversion, a baseband received signal is output. Also, the radio communication unit 220 up-converts the baseband transmission signal supplied from the control unit 250 into a high-frequency transmission signal in the carrier frequency band, and converts the high-frequency transmission signal obtained by the up-conversion into a radio signal using an antenna. Send. Note that the up-conversion to the high-frequency transmission signal and the down-conversion to the baseband reception signal are performed using the carrier wave generated by the carrier wave generation unit 240.

(Sensor part)
The sensor unit 230 includes one or more sensors. In FIG. 4, a GPS processing unit 232 is shown as an example of a sensor. The GPS processing unit 232 acquires position information and time information of the sensor terminal 20 by processing satellite signals transmitted from GPS satellites. The sensor unit 230 may include other sensors such as an acceleration sensor, a gyro sensor, a temperature sensor, an atmospheric pressure sensor, a sound pressure sensor, and a pulse sensor in addition to the GPS processing unit 232 or instead of the GPS processing unit 232. Good.

(Carrier generation unit)
The carrier generation unit 240 generates a carrier used for up-conversion from a baseband transmission signal to a high-frequency transmission signal and for down-conversion from a high-frequency reception signal to a baseband reception signal. The carrier wave generation unit 240 generates a carrier wave by adjusting the frequency of a reference signal generated by an oscillator such as a crystal resonator, for example.

(Control part)
The control unit 250 controls overall communication in the sensor terminal 20. For example, the control unit 250 generates a frame including the sensor data obtained by the sensor unit 230 and causes the wireless communication unit 220 to repeatedly transmit the frame. The control unit 250 stops frame transmission when ACK is received from the base station 10 or when the number of repeated transmissions reaches the upper limit.

<< 3. Base station configuration >>
The configuration of the sensor terminal 20 according to the embodiment of the present disclosure has been described above. Next, the configuration of the base station 10 according to the embodiment of the present disclosure will be described with reference to FIG.

FIG. 5 is an explanatory diagram illustrating a configuration of the base station 10 according to the embodiment of the present disclosure. As illustrated in FIG. 5, the base station 10 according to the embodiment of the present disclosure includes a periodic signal generation unit 110, a wireless communication unit 120, an evaluation unit 130, a demodulation unit 140, a control unit 150, and a wired communication unit. 160.

(Periodic signal generator)
Periodic signal generation section 110 generates a periodic signal used for up-conversion from baseband transmission signal to high-frequency transmission signal and down-conversion from high-frequency reception signal to baseband reception signal in radio communication section 120. The periodic signal generation unit 110 generates the periodic signal by adjusting the frequency of a reference signal generated by an oscillator such as a crystal resonator, for example.

(Wireless communication part)
The wireless communication unit 120 performs reception processing of a wireless signal transmitted from the sensor terminal 20 and transmission processing of a wireless signal to the sensor terminal 20. More specifically, the wireless communication unit 120 converts the wireless signal transmitted from the sensor terminal 20 into a high frequency reception signal by an antenna, performs analog processing and down conversion on the high frequency reception signal, and thereby performs baseband reception. Output a signal. Also, the wireless communication unit 120 up-converts the baseband transmission signal supplied from the control unit 150 into a high-frequency transmission signal in the carrier frequency band, and converts the high-frequency transmission signal obtained by the up-conversion into a radio signal using an antenna. Send. Note that the up-conversion to the high-frequency transmission signal and the down-conversion to the baseband reception signal are performed using the periodic signal generated by the periodic signal generation unit 110.

(Evaluation Department)
The evaluation unit 130 evaluates the carrier wave of the received signal received from the sensor terminal 20. Specifically, the evaluation unit 130 detects a frequency error between the carrier wave of the reception signal received from the sensor terminal 20 and the periodic signal generated by the periodic signal generation unit 110. Hereinafter, the configuration of the evaluation unit 130 will be described in more detail with reference to FIG.

FIG. 6 is an explanatory diagram showing the configuration of the evaluation unit 130. As illustrated in FIG. 6, the evaluation unit 130 includes a plurality of correlation detection units 132 and a comparison unit 138.

The baseband received signal from the wireless communication unit 120 is input to the plurality of correlation detection units 132. Each correlation detection unit 132 performs different adjustments on the frequency of the input baseband received signal, and detects the correlation between the preamble included in the adjusted baseband received signal and a predetermined comparison pattern.

Specifically, each correlation detection unit 132 includes a plurality of phase adjusters r, a plurality of delay units d, a plurality of multipliers m, an addition unit 134, and a correlation output unit 136. As shown in FIG. 6, the phase adjusters r and the delay devices d are alternately arranged in series, and the multiplier m is arranged between the phase adjusters r and the delay devices d.

The phase adjuster r has a function of rotating the phase of the signal. Here, the amount by which each phase adjuster r rotates the phase varies depending on which correlation detector 132 includes the phase adjuster r. That is, each correlation detection unit 132 has a function of shifting the frequency of the baseband reception signal, and the amount of frequency shifted by each correlation detection unit 132 is different.

Each multiplier m receives an output from each phase adjuster r and an element signal of a comparison pattern corresponding to a preamble used by the sensor terminal 20, and each multiplier m receives a signal from each phase adjuster r. The output is multiplied by the conjugate of the component signal of the comparison pattern.

The addition unit 134 adds the multiplication results input from each multiplier m. The correlation output unit 136 converts the complex signal obtained by the adding unit 134 into a power signal, and outputs the power signal as a correlation value.

Here, the difference between the amount of the carrier frequency generated by the carrier generation unit 240 of the sensor terminal 20 and the frequency of the periodic signal generated by the periodic signal generation unit 110 of the base station 10 due to the individual difference of the oscillator ( Hereinafter referred to as a frequency error). Then, among the plurality of correlation detection units 132, the maximum correlation value is output by the correlation detection unit 132 whose frequency shift amount is the same as the frequency error.

For this reason, the comparison unit 138 compares the correlation value output from each correlation detection unit 132 with a threshold value, and detects a frequency shift amount by the correlation detection unit 132 that outputs a correlation value exceeding the threshold value as a frequency error. Since the frequency error may vary depending on the sensor terminal 20 that is the transmission source, it is possible to identify the sensor terminal 20 that is the transmission source of each received signal based on the frequency error.

(Demodulator)
The demodulator 140 extracts two or more received signals that are estimated to be the same from the source sensor terminal 20 based on the result of the evaluation performed by the evaluating unit 130, and performs a process of combining the extracted two or more received signals. It has the function of the synthesis processing unit to perform. Specifically, the demodulator 140 sequentially extracts received signals in which the same frequency error is detected by the evaluation unit 130, and cumulatively synthesizes the payloads of the extracted received signals. Then, the demodulation unit 140 attempts to demodulate the combined payload. Whether the demodulation is successful is confirmed using the CRC 55 included in the payload described with reference to FIG.

The control unit 150 controls the overall communication of the base station 10. For example, when the demodulation unit 140 succeeds in demodulating the payload, the control unit 150 controls the wireless communication unit 120 so that ACK is transmitted as a reception confirmation to the sensor terminal 20 that is the transmission source of the payload.

The wired communication unit 160 is an interface with the application server 30. The wired communication unit 160 transmits the terminal ID and data included in the payload demodulated by the demodulation unit 140 to the application server 30.

<< 4. Operation >>
The configurations of the base station 10 and the sensor terminal 20 according to the embodiment of the present disclosure have been described above. Subsequently, the operations of the base station 10 and the sensor terminal 20 according to the embodiment of the present disclosure are organized with reference to FIGS. 7 and 8.

(Operation of sensor terminal)
FIG. 7 is a flowchart illustrating an operation of the sensor terminal 20 according to the embodiment of the present disclosure. As shown in FIG. 7, first, the control unit 250 of the sensor terminal 20 generates the frame described with reference to FIG. 3 (S410), and the wireless communication unit 220 transmits the frame as a wireless signal (S420). . Thereafter, the control unit 250 waits for reception of an ACK until a time-out, that is, until a predetermined waiting time elapses (S430 / NO, S450 / NO), and ends the transmission operation when an ACK is received (S450 / YES).

On the other hand, when a predetermined standby time has elapsed without receiving an ACK (S430 / YES), the control unit 250 determines whether or not the number of frame transmissions has reached the upper limit (S440). If the number of frame transmissions has not reached the upper limit (S440 / NO), the processing from S410 is repeated, and if the number of frame transmissions has reached the upper limit (S440 / YES), the transmission operation ends.

(Operation of base station)
FIG. 8 is a flowchart illustrating an operation of the base station 10 according to the embodiment of the present disclosure. When the radio communication unit 120 of the base station 10 receives the radio signal and outputs the baseband received signal to the evaluation unit 130, the evaluation unit 130 calculates the frequency error based on the correlation detection process using the plurality of correlation detection units 132. It is detected (S504).

Then, when there is a payload stored in association with the frequency error detected by the evaluation unit 130 (S508 / YES), the demodulation unit 140 stores the payload cut out from the baseband received signal. The payload is synthesized (S512). Then, the demodulation unit 140 performs demodulation processing on the combined payload (S516). On the other hand, when there is no payload stored in association with the frequency error detected by the evaluation unit 130 (S508 / NO), the demodulation unit 140 performs demodulation processing on the payload cut out from the baseband received signal. (S516).

When demodulation fails in S516 (S520 / NO), the demodulator 140 stores the payload subjected to demodulation processing in association with the frequency error detected in S504 (S524). On the other hand, when the demodulation is successful in S516 (S520 / YES), the control unit 150 confirms the terminal ID included in the payload, and causes the wireless communication unit 120 to transmit ACK to the sensor terminal 20 that is the transmission source of the wireless signal. (S528) The demodulator 140 deletes the payload stored in association with the frequency error detected in S504 (S532).

Note that a plurality of frequency errors may be detected in S504. When a plurality of frequency errors are detected in S504, the processing of S508 to S532 is executed for each frequency error.

As described above, according to the embodiment of the present disclosure, the base station 10 does not perform prior communication with the sensor terminal 20 for management of communication resources, but based on the frequency error of the carrier wave of each received signal. It is possible to identify the sensor terminal 20 that is the transmission source of each received signal. Accordingly, it is possible to reduce power consumption for managing communication resources.

<< 5. Application example >>
As described above, the frequency error of the carrier waves of the received signals received from the plurality of sensor terminals 20 may be different due to the individual difference of the oscillators that each sensor terminal 20 has. However, it may happen that the frequency errors of the carrier waves of the received signals received from different sensor terminals 20 are the same. In this case, it is difficult to identify the sensor terminal 20 that is the transmission source of the received signal only from the frequency error. Therefore, some application examples that can further improve the discrimination power of the transmission source will be described below. In addition, each application example demonstrated below may be applied independently to embodiment mentioned above, and may be applied in combination.

<5-1. First application example>
First, as a first application example, a mechanism for identifying the transmission source sensor terminal 20 from the preamble pattern in addition to the frequency error will be described.

(Constitution)
The control unit 250 of the sensor terminal 20 according to the first application example determines a preamble pattern used for frame transmission. Specifically, the control unit 250 determines a preamble pattern using the terminal ID of the sensor terminal 20. For example, in the GOLD sequence generation method for obtaining an output by combining different M sequences shown in FIG. 9, the control unit 250 uses at least a part of the terminal ID as one M sequence, and uses the obtained GOLD sequence as a preamble pattern. May be determined as

If the control unit 250 determines the preamble pattern using the entire terminal ID, the sensor terminal 20 can be uniquely identified from the preamble pattern. However, it is assumed that the terminal ID is expressed by 24 bits or 32 bits. In this case, the length of the preamble determined by using the entire terminal ID is 2 to the 24th power or 2 to the 32nd power. A long preamble is not preferable from the viewpoint of reducing power consumption.

In this regard, in the first application example, since the frequency error is also used for identifying the sensor terminal 20, the sensor terminal 20 can be determined by determining the preamble pattern using a part of the terminal ID as described above. It is possible to improve the discriminating power. For example, the control unit 250 may generate a GOLD sequence using the lower 12 bits of the terminal ID and determine the GOLD sequence as a preamble pattern.

As described above, in the first application example, the preambles of various patterns can be transmitted from the sensor terminal 20, so that the base station 10 performs the correlation detection process on the preambles of the patterns that may be transmitted from the sensor terminal 20. Do. This point will be described more specifically with reference to FIG.

FIG. 10 is an explanatory diagram showing the configuration of the evaluation unit 130 according to the first application example. As illustrated in FIG. 10, the evaluation unit 130 according to the first application example includes a plurality of sets S1 and S2 of the correlation detection unit 132, and each set S includes a plurality of correlation detection units 132. The same comparison pattern C is applied to the correlation detection units 132 included in the same set S, and the comparison pattern C applied to each set S is different. For example, the comparison pattern C1 is applied to the set S1 illustrated in FIG. 10, and the comparison pattern C2 is applied to the set S2. Further, as described with reference to FIG. 6, the amount of frequency of the baseband reception signal shifted by each correlation detection unit 132 included in the same set S is different. Although FIG. 10 shows two sets S1 and S2, the evaluation unit 130 can have more sets S.

In the above configuration, the maximum correlation value is output by the correlation detection unit 132 to which the frequency shift amount is the same as the frequency error and the comparison pattern corresponding to the preamble transmitted from the sensor terminal 20 is applied. .

Therefore, the comparison unit 138 compares the correlation value output from each correlation detection unit 132 with a threshold value, detects a frequency shift amount by the correlation detection unit 132 that outputs a correlation value exceeding the threshold value as a frequency error, and The comparison pattern applied to the correlation detection unit 132 is detected as the transmitted preamble. The detected frequency error and preamble are used for identification of the sensor terminal 20.

The demodulator 140 sequentially extracts received signals in which the same frequency error and preamble are detected by the evaluating unit 130, and cumulatively synthesizes the payloads of the extracted received signals. Then, the demodulation unit 140 attempts to demodulate the combined payload.

(Operation)
The configuration of the first application example has been described above. Subsequently, the operation of the first application example is organized with reference to FIGS. 11 and 12.

FIG. 11 is a flowchart showing the operation of the sensor terminal 20 according to the first application example. As shown in FIG. 11, first, the control unit 250 of the sensor terminal 20 determines a preamble pattern using a part of the terminal ID (S402). Then, the control unit 250 generates a frame having the determined pattern preamble (S412), and the wireless communication unit 220 transmits the frame as a wireless signal (S422). Since the subsequent operation is as described with reference to FIG. 7, detailed description thereof is omitted.

FIG. 12 is a flowchart showing the operation of the base station 10 according to the first application example. When the radio communication unit 120 of the base station 10 receives a radio signal and outputs a baseband received signal to the evaluation unit 130, the evaluation unit 130 is based on correlation detection processing using a plurality of sets S of the correlation detection unit 132. A frequency error and a preamble are detected (S506).

Then, when there is a payload stored in association with the frequency error and preamble detected by the evaluation unit 130 (S510 / YES), the demodulation unit 140 stores the payload cut out from the baseband received signal. The existing payload is synthesized (S514). Then, the demodulation unit 140 performs demodulation processing on the combined payload (S518). On the other hand, when there is no payload stored in association with the frequency error and preamble detected by the evaluation unit 130 (S510 / NO), the demodulation unit 140 demodulates the payload extracted from the baseband received signal. (S518).

When demodulation fails in S518 (S522 / NO), the demodulator 140 stores the payload subjected to demodulation processing in association with the frequency error and preamble detected in S506 (S526). On the other hand, when the demodulation is successful in S518 (S522 / YES), the control unit 150 confirms the terminal ID included in the payload, and causes the wireless communication unit 120 to transmit ACK to the sensor terminal 20 that is the transmission source of the wireless signal. (S530) The demodulator 140 deletes the payload stored in association with the frequency error and preamble detected in S506 (S534).

As described above, according to the first application example, received signals from the same sensor terminal 20 can be identified using the preamble pattern in addition to the frequency error. Therefore, compared with the case where only the frequency error is used for identification, it is possible to identify the received signals from the same sensor terminal 20 with higher accuracy.

<5-2. Second application example>
Next, as a second application example, a mechanism for identifying the transmission source sensor terminal 20 from the superframe in which the frame is transmitted in addition to the frequency error will be described.

(Constitution)
The control unit 250 of the sensor terminal 20 according to the second application example determines a super frame for frame transmission. For example, the control unit 250 divides the terminal ID by the number of superframes for one cycle (10 in the example shown in FIG. 2), and determines a superframe having a remaining number as a superframe for transmission. May be. Then, the control unit 250 causes the wireless communication unit 220 to repeatedly transmit the frame in the determined superframe.

The evaluation unit 130 of the base station 10 detects the frequency error of the received signal as described in the embodiment of the present disclosure. The demodulator 140 sequentially extracts received signals that have been detected in the same frequency error by the evaluating unit 130 and are received in the same superframe, which is the same time resource segment. The received signal payloads are cumulatively synthesized. Then, the demodulation unit 140 attempts to demodulate the combined payload.

(Operation)
FIG. 13 is a flowchart showing the operation of the sensor terminal 20 according to the second application example. As shown in FIG. 13, first, the control unit 250 of the sensor terminal 20 determines a superframe for transmission using a part of the terminal ID (S404). Then, the control unit 250 generates a frame (S414), and the wireless communication unit 220 transmits the frame as a wireless signal in the determined superframe (S424). Since the subsequent operation is as described with reference to FIG. 7, detailed description thereof is omitted.

As described above, the demodulator 140 of the base station 10 sequentially extracts reception signals that are detected in the same superframe and are received signals in which the same frequency error is detected. Synthesize the payload cumulatively.

Thus, according to the second application example, in addition to the frequency error, a received signal from the same sensor terminal 20 can be identified using the superframe in which the frame is transmitted. Therefore, compared with the case where only the frequency error is used for identification, it is possible to identify the received signals from the same sensor terminal 20 with higher accuracy.

<5-3. Third application example>
Furthermore, as a third application example, a mechanism for identifying the sensor terminal 20 as a transmission source from a hopping pattern of a frequency used in addition to a frequency error is proposed.

(Constitution)
The control unit 250 of the sensor terminal 20 according to the third application example determines a frequency hopping pattern, and causes the wireless communication unit 220 to repeatedly transmit a frame according to the determined hopping pattern. Here, specific examples of some hopping patterns will be described with reference to FIGS.

FIG. 14 is an explanatory diagram showing the hopping pattern 1. As shown in FIG. 14, the hopping pattern 1 is a pattern in which the four frequencies F0 to F4 are switched in the order of F0 → F2 → F1 → F3 → F0. When the controller 250 determines that the hopping pattern 1 is to be used, the first frame transmission is performed at the frequency F0, the second frame transmission is performed at the frequency F2, and the third frame transmission is performed. Is transmitted at the frequency F1, and the transmission of the fourth frame is performed at F3.

FIG. 15 is an explanatory diagram showing the hopping pattern 2. As shown in FIG. 15, the hopping pattern 2 is a pattern in which the four frequencies F0 to F4 are switched in the order of F2-> F3-> F0-> F1-> F2. When the control unit 250 determines that the hopping pattern 2 is to be used, the first frame transmission is performed at the frequency F2, the second frame transmission is performed at the frequency F3, and the third frame transmission is performed. Is transmitted at the frequency F0, and the transmission of the fourth frame is performed at F1.

FIG. 16 is an explanatory diagram showing the hopping pattern 3. As shown in FIG. 16, the hopping pattern 3 is a pattern in which the four frequencies F0 to F4 are switched in the order of F0 → F3 → F1 → F2 → F0. When the controller 250 determines that the hopping pattern 3 is to be used, the first frame is transmitted at the frequency F0, the second frame is transmitted at the frequency F3, and the third frame is transmitted. Is transmitted at the frequency F1, and the transmission of the fourth frame is performed at F2.

The control unit 250 may determine the hopping pattern to be used from the plurality of hopping patterns based on the terminal ID. For example, the control unit 250 can divide the terminal ID by the number of hopping patterns determined according to the number of usable frequencies and determine the hopping pattern according to the remaining value as a hopping pattern to be used. .

The evaluation unit 130 of the base station 10 evaluates the frequency error of the received signal and the frequency of the carrier wave of the received signal. The demodulator 140 extracts two or more received signals whose carrier frequencies are switched according to one of the hopping patterns from the received signals having the same frequency error evaluated by the evaluating unit 130. The demodulator 140 synthesizes the extracted received signal payloads cumulatively and attempts to demodulate the combined payload.

Here, the extraction and identification of the received signal using the hopping pattern in addition to the frequency error will be described with reference to a specific example.

FIG. 17 is an explanatory diagram illustrating an example of a reception result by the base station 10. FIG. 17 shows an example in which frames are received at frequencies F0 and F2 at time t1, and frames are received at frequencies F2 and F3 at time t2.

Here, if the frequency errors of the frames received at each time are different, the frames transmitted from the same sensor terminal 20 can be identified based on the frequency errors. However, if the frequency of the frames received at each time is the same, it is difficult to identify the frames transmitted from the same sensor terminal 20 only from the frequency error.

Therefore, the demodulator 140 identifies a frame transmitted from the same sensor terminal 20 in consideration of the hopping pattern in addition to the frequency error. In the example shown in FIG. 17, the frame (D3) is received at the frequency F2 at time t2. In the hopping pattern 1, the frequency at the time before the frequency F2 is the frequency F0, and in the hopping

pattern

2 or 3, the frequency at the time before the frequency F2 is the frequency F1. However, no frame is received at frequency F1 at time t1, which is the previous time. Therefore, the demodulator 140 transmits the frame (D3) according to the hopping pattern 1 and transmits the frame (D1) transmitted at the frequency F0 at the time t1 from the same sensor terminal 20 as the frame (D3). Can be identified. Accordingly, the demodulation unit 140 can also recognize that the other frame (D2) and the frame (D4) are frames transmitted from the same sensor terminal 20.

FIG. 18 is an explanatory diagram showing another example of a reception result by the base station 10. FIG. 18 shows an example in which frames are received at frequencies F0 and F2 at time t3 and frames are received at frequencies F1 and F3 at time t4.

In this example, it is difficult to identify the sensor terminal 20 that is the transmission source of each received signal only from the hopping pattern. For the frame (D7) transmitted at the frequency F1 at time t4, in the hopping pattern 1, the frequency at the time before the frequency F1 is the frequency F2, and in the hopping pattern 2, the frequency at the time before the frequency F1 is The frequency is F0. Here, at time t3, which is the previous time, a frame is received at both frequencies F0 and F2. For this reason, it is difficult to uniquely identify the frame transmitted at the time t3 from the same sensor terminal 20 as the frame (D7). Similarly, for the frame (D8) transmitted at the frequency F3 at time t4, in the hopping pattern 2, the frequency at the time before the frequency F3 is the frequency F2, and in the hopping pattern 3, at the time before the frequency F3. Is the frequency F0. Here, at time t3, which is the previous time, a frame is received at both frequencies F0 and F2. For this reason, it is also difficult to uniquely identify the frame transmitted at the time t3 from the same sensor terminal 20 as the frame (D8).

However, the demodulator 140 according to the third application example identifies received signals transmitted from the same sensor terminal 20 based on both the frequency error and the hopping pattern. For this reason, as shown in FIG. 18, even if the reception result that is difficult to identify is obtained only from the hopping pattern, the same sensor terminal can be used as long as the frequency error of the frames received at each time is different. The received signal transmitted from 20 can be identified.

(Operation)
The configuration of the third application example has been described above. Subsequently, the operation of the third application example is organized with reference to FIGS. 19 and 20.

FIG. 19 is a flowchart showing the operation of the sensor terminal 20 according to the third application example. As shown in FIG. 19, first, the control unit 250 of the sensor terminal 20 determines a hopping pattern for transmission using the terminal ID (S406). Then, the control unit 250 generates a frame (S416), and the wireless communication unit 220 repeatedly transmits the frame according to the determined hopping pattern (S426). Since the subsequent operation is as described with reference to FIG. 7, detailed description thereof is omitted.

FIG. 20 is a flowchart showing the operation of the base station 10 according to the third application example. When the radio communication unit 120 of the base station 10 receives a radio signal and outputs a baseband received signal to the evaluation unit 130, the evaluation unit 130 detects a frequency error and a carrier frequency (S604). Then, the demodulation unit 140 identifies the frequency that would have been used in the previous section based on the predetermined hopping pattern and the frequency detected by the evaluation unit 130 (S608).

Subsequently, when there is a payload stored in association with the detected frequency error and the identified frequency (S612 / YES), the demodulator 140 stores the payload cut out from the baseband received signal and stored. The existing payload is synthesized (S616). Then, the demodulation unit 140 performs demodulation processing on the combined payload (S620). On the other hand, when there is no payload stored in association with the detected frequency error and the identified frequency (S612 / NO), the demodulator 140 performs a demodulation process on the payload extracted from the baseband received signal. Perform (S620).

When demodulation fails in S620 (S624 / NO), the demodulation unit 140 stores the payload subjected to demodulation processing in association with the detected frequency error and the specified frequency (S628). On the other hand, when the demodulation is successful in S620 (S624 / YES), the control unit 150 confirms the terminal ID included in the payload, and causes the wireless communication unit 120 to transmit an ACK to the sensor terminal 20 that is the transmission source of the wireless signal. (S632) The demodulator 140 deletes the payload stored in association with the detected frequency error and the identified frequency (S636).

As described above, according to the third application example, received signals from the same sensor terminal 20 can be identified using a hopping pattern in addition to a frequency error. Therefore, compared with the case where only the frequency error is used for identification, it is possible to identify the received signals from the same sensor terminal 20 with higher accuracy.

In addition, although the example which performs the specification regarding the hopping pattern with reference to the reception result of the previous section has been described above, the reference from the same sensor terminal 20 in more cases by referring to the reception result of two or more sections. The received signal can be identified.

<< 6. Hardware configuration >>
The embodiments and application examples of the present disclosure have been described above. Each information processing for communication mentioned above is realized by cooperation of software and hardware of sensor terminal 20 explained below. Note that the hardware configuration described below is also applicable to the base station 10.

FIG. 21 is an explanatory diagram showing a hardware configuration of the sensor terminal 20. As shown in FIG. 21, the sensor terminal 20 includes a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, a RAM (Random Access Memory) 203, an input device 208, an output device 210, A storage device 211 and a communication device 215 are provided.

The CPU 201 functions as an arithmetic processing unit and a control unit, and controls the overall operation in the sensor terminal 20 according to various programs. Further, the CPU 201 may be a microprocessor. The ROM 202 stores programs used by the CPU 201, calculation parameters, and the like. The RAM 203 temporarily stores programs used in the execution of the CPU 201, parameters that change as appropriate during the execution, and the like. These are connected to each other by a host bus including a CPU bus. The functions of the control unit 250 (the functions of the evaluation unit 130, the demodulation unit 140, and the control unit 150 in the base station 10) are realized by the cooperation of the CPU 201, the ROM 202, the RAM 203, and the software.

The input device 208 includes input means for a user to input information, such as a mouse, keyboard, touch panel, button, microphone, switch, and lever, and an input control circuit that generates an input signal based on the input by the user and outputs the input signal to the CPU 201. Etc. The user of the sensor terminal 20 can input various data and instruct processing operations to the sensor terminal 20 by operating the input device 208.

The output device 210 includes a display device such as a liquid crystal display (LCD) device, an OLED (Organic Light Emitting Diode) device, and a lamp. Furthermore, the output device 210 includes an audio output device such as a speaker and headphones. For example, the display device displays a captured image or a generated image. On the other hand, the audio output device converts audio data or the like into audio and outputs it.

The storage device 211 is a data storage device configured as an example of a storage unit of the sensor terminal 20 according to the present embodiment. The storage device 211 may include a storage medium, a recording device that records data on the storage medium, a reading device that reads data from the storage medium, a deletion device that deletes data recorded on the storage medium, and the like. The storage device 211 stores programs executed by the CPU 201 and various data.

The communication device 215 is a communication interface configured with, for example, a communication device for connecting to the base station 10.

<< 7. Conclusion >>
As described above, according to the embodiment of the present disclosure, the base station 10 does not perform prior communication with the sensor terminal 20 for management of communication resources, but based on the frequency error of the carrier wave of each received signal. It is possible to identify the sensor terminal 20 that is the transmission source of each received signal. Accordingly, it is possible to reduce power consumption for managing communication resources.

Furthermore, in addition to the frequency error, it is possible to further improve the discriminating power of the source sensor terminal 20 by taking into account the preamble, superframe or hopping pattern.

In addition, although the preferred embodiment of this indication was described in detail, referring an accompanying drawing, the technical scope of this indication is not limited to this example. It is obvious that a person having ordinary knowledge in the technical field of the present disclosure can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that it belongs to the technical scope of the present disclosure.

For example, each step in the processing of the base station 10 and the sensor terminal 20 in this specification does not necessarily have to be processed in time series in the order described as the flowchart. For example, each step in the processing of the base station 10 and the sensor terminal 20 may be processed in an order different from the order described as the flowchart, or may be processed in parallel.

It is also possible to create a computer program for causing hardware such as the CPU 201, the ROM 202, and the RAM 203 built in the base station 10 and the sensor terminal 20 to perform the same functions as the respective configurations of the base station 10 and the sensor terminal 20 described above. It is. A storage medium storing the computer program is also provided.

In addition, the effects described in this specification are merely illustrative or illustrative, and are not limited. That is, the technology according to the present disclosure can exhibit other effects that are apparent to those skilled in the art from the description of the present specification in addition to or instead of the above effects.

The following configurations also belong to the technical scope of the present disclosure.
(1)
An evaluation unit that evaluates the frequency of the carrier wave of the received signal received from another communication device;
A plurality of received signals are extracted from a plurality of received signals based on a result of the evaluation by the evaluation unit, and a combining processing unit that combines the two or more received signals;
A communication device comprising:
(2)
The communication device
An oscillator that generates a periodic signal;
The said evaluation part is a communication apparatus as described in said (1) which evaluates the difference of the frequency of the carrier wave of the said received signal, and the frequency of the periodic signal produced | generated by the said oscillator.
(3)
The evaluation unit includes a plurality of correlation detection units that execute a correlation detection process on a preamble included in the received signal in parallel.
The plurality of correlation detection units perform different adjustments on the frequency with respect to the preamble, and detects a correlation between the adjusted preamble and the comparison pattern,
The evaluation unit evaluates the amount of adjustment performed in the correlation detection unit that detects the correlation satisfying a predetermined condition as a difference between the frequency of the carrier wave of the received signal and the frequency of the periodic signal generated by the oscillator. The communication device according to (2).
(4)
The evaluation unit has two or more sets of the plurality of correlation detection units,
A different comparison pattern is applied to each set of the plurality of correlation detection units,
The evaluation unit evaluates a comparison pattern applied to a correlation detection unit that detects a correlation satisfying a predetermined condition among two or more sets of the plurality of correlation detection units as a preamble included in the received signal; The communication device according to (3).
(5)
The communication device according to (4), wherein the comparison pattern is a pattern generated using a part of identification information that the other communication device may have.
(6)
The synthesis processing unit extracts the two or more reception signals from which the same evaluation result is obtained by the evaluation unit from the plurality of reception signals, according to any one of (1) to (5). Communication equipment.
(7)
The evaluation unit evaluates a time resource classification in which the received signal is received;
The synthesis processing unit extracts the two or more received signals from the received signals evaluated by the evaluation unit when received in the same time resource section, any one of (1) to (6) The communication apparatus as described in.
(8)
The other communication device transmits a signal while regularly switching the frequency of the carrier wave,
The combination processing unit receives two or more received signals whose carrier waves are switched according to a predetermined rule among the received signals having the same amount of adjustment performed in the correlation detecting unit that detects the correlation satisfying the predetermined condition. The communication device according to (3), wherein the communication device is extracted.
(9)
The communication device
A demodulator that demodulates a composite signal obtained by the synthesis of the synthesis processor;
A communication unit that transmits a reception confirmation to a communication device having identification information included in a result of demodulation based on the demodulation unit succeeding in demodulating the combined signal;
The communication device according to any one of (1) to (8), comprising:
(10)
A processor evaluating a frequency of a carrier wave of a received signal received from another communication device;
Extracting two or more received signals from a plurality of received signals based on an evaluation result, and performing a process of combining the two or more received signals;
Including a communication control method.

10 base station 20 sensor terminal 30 application server 110 periodic signal generation unit 120 wireless communication unit 130 evaluation unit 132 correlation detection unit 134 addition unit 136 correlation output unit 138 comparison unit 140 demodulation unit 150 control unit 160 wired communication unit 220 wireless communication unit 230 Sensor unit 232 GPS processing unit 240 Carrier wave generation unit 250 Control unit 260 Control unit

Claims

An evaluation unit that evaluates the frequency of the carrier wave of the received signal received from another communication device;
A plurality of received signals are extracted from a plurality of received signals based on a result of the evaluation by the evaluation unit, and a combining processing unit that combines the two or more received signals;
A communication device comprising:
The communication device
An oscillator that generates a periodic signal;
The communication device according to claim 1, wherein the evaluation unit evaluates a difference between a frequency of a carrier wave of the reception signal and a frequency of a periodic signal generated by the oscillator.
The evaluation unit includes a plurality of correlation detection units that execute a correlation detection process on a preamble included in the received signal in parallel.
The plurality of correlation detection units perform different adjustments on the frequency with respect to the preamble, and detects a correlation between the adjusted preamble and the comparison pattern,
The evaluation unit evaluates the amount of adjustment performed in the correlation detection unit that detects the correlation satisfying a predetermined condition as a difference between the frequency of the carrier wave of the received signal and the frequency of the periodic signal generated by the oscillator. The communication device according to claim 2.
The evaluation unit has two or more sets of the plurality of correlation detection units,
A different comparison pattern is applied to each set of the plurality of correlation detection units,
The evaluation unit evaluates, as a preamble included in the received signal, a comparison pattern applied to a correlation detection unit that detects a correlation that satisfies a predetermined condition among two or more sets of the plurality of correlation detection units. Item 4. The communication device according to Item 3.
The communication device according to claim 4, wherein the comparison pattern is a pattern generated using a part of identification information that the other communication device may have.
The communication device according to claim 1, wherein the synthesis processing unit extracts the two or more reception signals from which the same evaluation result is obtained by the evaluation unit from the plurality of reception signals.
The evaluation unit evaluates a time resource classification in which the received signal is received;
The communication apparatus according to claim 1, wherein the synthesis processing unit extracts the two or more reception signals from the reception signals evaluated by the evaluation unit when received in the same time resource section.
The other communication device transmits a signal while regularly switching the frequency of the carrier wave,
The combination processing unit receives two or more received signals whose carrier waves are switched according to a predetermined rule among the received signals having the same amount of adjustment performed in the correlation detecting unit that detects the correlation satisfying the predetermined condition. The communication device according to claim 3, wherein the communication device is extracted.
The communication device
A demodulator that demodulates a composite signal obtained by the synthesis of the synthesis processor;
A communication unit that transmits a reception confirmation to a communication device having identification information included in a result of demodulation based on the demodulation unit succeeding in demodulating the combined signal;
The communication apparatus according to claim 1, comprising:
A processor evaluating a frequency of a carrier wave of a received signal received from another communication device;
Extracting two or more received signals from a plurality of received signals based on an evaluation result, and performing a process of combining the two or more received signals;
Including a communication control method.