Receiving device, transmitting device, transmitting / receiving system, receiving method and program

Abstract

To enable more efficient data transmission and reception between communication devices. [Solution] The receiving device 200 includes a clock with accuracy above a predetermined standard and a processing unit 210. The processing unit 210 derives a delay time from the clock value and transmission time information when it receives transmission time information from the transmitting device 100, receives scheduled time information from the transmitting device 100 which includes at least information on the next scheduled transmission time, reads the next scheduled transmission time from the scheduled time information, and starts the receiving operation at a time obtained by subtracting a predetermined first margin from the value obtained by adding the delay time to the read scheduled transmission time.

Description

Technical Field

[0001] The present invention relates to a receiving device, a transmitting device, a transmission / reception system, a receiving method, and a program.

Background Art

[0002] Conventionally, a system for synchronizing time among a plurality of communication devices has been known. For example, Patent Document 1 discloses a time synchronization network that can efficiently maintain time synchronization according to absolute time.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The time synchronization network disclosed in Patent Document 1 is a network in which a plurality of communication devices having a communication function are connected and time synchronization of each communication device is performed. The communication device includes time information output means for outputting time information based on a stable internal clock, and time synchronization means for correcting the time information of the time information output means based on time difference information between the communication device and a communication device adjacent to the communication device. However, there is room for improvement in efficiently transmitting and receiving data in each communication device on the time synchronization network.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a receiving device, a transmitting device, a transmission / reception system, a receiving method, and a program that can more efficiently transmit and receive data between communication devices.

Means for Solving the Problems

[0006] To achieve the above objective, one embodiment of the receiving device according to the present invention comprises a clock having an accuracy of a predetermined standard or higher, and a processing unit, wherein the processing unit derives a delay time from the value of the clock when it receives transmission time information from a transmitting device and the transmission time information, receives scheduled time information from the transmitting device which includes at least information on the scheduled time of future transmissions, extracts the next scheduled transmission time from the scheduled time information, and starts the receiving operation at a time obtained by subtracting a predetermined first margin from the value obtained by adding the delay time to the extracted scheduled transmission time. [Effects of the Invention]

[0007] According to the present invention, data can be transmitted and received more efficiently between communication devices. [Brief explanation of the drawing]

[0008] [Figure 1] This is a block diagram showing the functional configuration of the transmission and reception system according to the embodiment. [Figure 2] This diagram illustrates the delay time and margin during data communication. [Figure 3] This is an example of a flowchart for the time information transmission process according to the embodiment. [Figure 4] This is an example of a flowchart for the delay time acquisition process according to the embodiment. [Figure 5] This is an example of a flowchart for the scheduled transmission process according to the embodiment. [Figure 6] This is an example of a flowchart for the schedule reception process according to the embodiment. [Figure 7] This figure shows an example of the receiving operation and sleep mode in conventional wireless communication. [Figure 8] This figure shows an example of the reception operation and sleep state when data communication is performed at the same time interval as in Figure 7 in the transmission / reception system according to the embodiment. [Figure 9] This figure shows an example of the reception operation and sleep state when data communication is performed with the same sleep time as in Figure 7 in the transmission / reception system according to the embodiment. [Figure 10] This is a diagram illustrating the details of the margins in the embodiment. [Figure 11] This is an example of a flowchart for the basic margin setting process according to the embodiment. [Figure 12] This is an example of a flowchart for the precision transmission process according to the embodiment. [Modes for carrying out the invention]

[0009] The transmission and reception system and other components according to the embodiment will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals. The transmission / reception system 1000 according to this embodiment is a communication system comprising a transmitting device 100 and a receiving device 200, as shown in Figure 1. The transmission / reception system 1000 may have two or more of either the transmitting device 100 or the receiving device 200, but for the sake of clarity, this explanation will be simplified to describe a case where there is one of each. Furthermore, as shown in Figure 1, both the transmitting device 100 and the receiving device 200 are equipped with processing units 110, 210, timing units 120, 220, and communication units 130, 230. In other words, the transmitting device 100 and the receiving device 200 are basically communication devices with the same configuration. For the sake of clarity, the same communication device is conveniently referred to as the transmitting device 100 (a communication device that transmits data) and the receiving device 200 (a communication device that receives data). Furthermore, if it is desired to distinguish between the components of the transmitting device 100 and the components of the receiving device 200, the terms "transmit" or "receive" shall be added to their respective names. That is, the processing unit 110 is also called the transmitting processing unit, and the processing unit 210 is also called the receiving processing unit. Also, the clock provided in the timing unit 120 is also called the transmitting clock, and the clock provided in the timing unit 220 is also called the receiving clock.

[0010] The transmitting device 100 and receiving device 200 of the transmitting / receiving system 1000 synchronize their transmission and reception timings. To do this, the transmitting device 100 sends a Timetable (scheduled time information) to the receiving device 200, which contains the absolute time (scheduled transmission time) when it plans to transmit data. If the transmitting device 100 plans to transmit data multiple times, the Timetable lists all of these scheduled transmission times. The receiving device 200 then performs its receiving operation according to the scheduled transmission times recorded in the Timetable. For example, if the transmitting device 100 is a communication device (e.g., a smartwatch) that measures heart rate and transmits it every second, and the receiving device 200 is a communication device (e.g., a smartphone) that receives the heart rate data transmitted every second, then the Timetable will list the scheduled transmission times, increasing by one second from the initial scheduled transmission time, for the number of data transmissions. Note that the Timetable (scheduled time information) may include information other than the scheduled transmission times of future data transmissions by the transmitting device 100, but it will include information on at least one or more scheduled transmission times.

[0011] The processing units 110 and 210 include, for example, a processor such as a CPU (Central Processing Unit) and memory such as RAM (Random Access Memory) and ROM (Read Only Memory). The processors of the processing units 110 and 210 perform various processing functions as a communication device by executing programs stored in memory. Also, the processing units 110 and 210 have a sleep function to suppress power consumption. When the processing units 110 and 210 start to sleep, they enter a sleep state where the power consumption is reduced. Note that the "sleep state" in this embodiment means a state in which only some of the functions provided by the transmission device 100 and the reception device 200 can be used. In the sleep state, the normal operations of the normal processing units 110 and 210 cannot be performed (not all the functions provided by the transmission device 100 and the reception device 200 can be operated), but when an interrupt of some kind (for example, when the preset wake-up time arrives) occurs, the processing units 110 and 210 wake up from the sleep state and return to the normal state where normal operations can be performed. That is, the "wake-up" in this embodiment means releasing the state in which the processing units 110 and 120 (or the transmission device 100 and the reception device 200) are in the sleep state, and returning the transmission device 100 and the reception device 200 to the state where normal operations can be performed, that is, the state where all the functions provided by the transmission device 100 and the reception device 200 can be used (normal state). The timing units 120 and 220 include a clock having an accuracy above a predetermined standard (for example, an error of 0.1 seconds or less in one year), such as an atomic clock. The communication units 130 and 230 include a device and an antenna for the transmission device 100 and the reception device 200 to perform wireless communication with each other or with other communication devices. The processing unit 110, the timing unit 120, and the communication unit 130 are respectively connected via a bus 140. Similarly, the processing unit 210, the timing unit 220, and the communication unit 230 are respectively connected via a bus 240. When the processing units 110 and 210 or the communication units 130 and 230 perform transmission and reception processing according to, for example, a Timetable, they can access the timing units 120 and 220 via the buses 140 and 240, and obtain the time (clock) respectively measured by the timing units 120 and 220.

[0012] As described above, the transmitting device 100 and the receiving device 200 perform transmission and reception processing according to the Timetable. However, if they follow the Timetable too strictly, synchronization of transmission and reception will be lost if there is an error between the time measured by the timing unit 120 and the time measured by the timing unit 220, or if the distance between the transmitting device 100 and the receiving device 200 changes. For example, as shown in Figure 2, if the transmitting device 100 starts transmitting data at time t1, the receiving device 200 will receive the data at time t2, which is time t1 plus the delay time (Delay shown in Figure 2) it takes for the radio waves containing the data to reach the receiving device 200 from the transmitting device 100. If the time measured by the timing unit 120 of the transmitting device 100 and the time measured by the timing unit 220 of the receiving device 200 are the same, the receiving device 200 can start receiving the data from exactly time t2 if it starts receiving at time t2. However, if the time measured by the timing unit 220 is later than the time measured by the timing unit 120, the receiving device 200 may miss receiving the beginning of the data unless it starts receiving a little before time t2. Also, if the time measured by the timing unit 220 is earlier than the time measured by the timing unit 120, the data may not be received until a little after time t2.

[0013] Therefore, in order to accommodate cases where the time measured by the timing unit 220 is ahead of or behind the time measured by the timing unit 120, the receiving device 200 has a margin (Margin shown in Figure 2) before and after the time t2 and performs the receiving operation within the width of this margin. As shown in Figure 2, the margin can be divided into a margin before the original scheduled reception time (t2 shown in Figure 2) (first margin) and a margin after the original scheduled reception time (t2) (second margin). Then, the start time of the receiving operation becomes a time earlier than the original scheduled reception time (t2) by the amount of the front margin, and the end time of the receiving operation becomes a time later than the original scheduled reception time (t2) by the amount of the rear margin. In the present embodiment, it is assumed that the values of these margins (the first margin and the second margin) are preset according to the accuracy of the clocks provided in the timekeeping units 120 and 220. For example, the higher the timekeeping accuracy of the clocks provided in the timekeeping units 120 and 220, the smaller the value of the margin can be set. And the smaller the value of the margin, the higher the efficiency of data communication (such as speed efficiency, power efficiency, etc.) can be achieved.

[0014] As can be understood from the above description, when the transmission / reception system 1000 transmits and receives data according to the Timetable, the receiving device 200 needs to acquire in advance the Delay (delay time) shown in FIG. 2. The processing for this (which consists of the time information transmission processing of the transmitting device 100 and the delay time acquisition processing of the receiving device 200) will be described with reference to FIGS. 3 and 4. These processes are started by the receiving device 200 sending a start request for the time information transmission processing to the transmitting device 100 when the receiving device 200 has not yet acquired the delay time or when it has moved more than a reference distance (for example, 30 km) from the position where the previous delay time acquisition processing was performed (the transmitting device 100 that has received the start request starts the time information transmission processing, and the receiving device 200 that has sent the start request starts the delay time acquisition processing). Also, when the transmitting device 100 has moved more than the reference distance from the position where the previous time information transmission processing was performed, the process is started by the transmitting device 100 sending a start request for the delay time acquisition processing to the receiving device 200 (the transmitting device 100 that has sent the start request starts the time information transmission processing, and the receiving device 200 that has received the start request starts the delay time acquisition processing). Note that the change in the position where the transmitting device 100 or the receiving device 200 is installed (presence or absence of movement, amount of movement) can be obtained from the detection results of a sensor unit (acceleration sensor, angular velocity sensor, GPS, etc., not shown) provided in the transmitting device 100 or the receiving device 200. Note that it is not necessary to strictly determine whether or not the movement is more than the reference distance, and these processes may be started simply according to the instruction of the user (who wants to update the delay time). However, if the scheduled transmission process and scheduled reception process described later are already being executed according to the Timetable, the transmitting device 100 or receiving device 200 that is attempting to send a start request will send the start request at a time when it is guaranteed that the time information transmission process and delay time acquisition process will not overlap with the time period during which data is transmitted and received in the scheduled transmission process and scheduled reception process, based on the Timetable. This is to ensure that the time information transmission process and delay time acquisition process do not conflict with the transmission and reception of data in the scheduled transmission process and scheduled reception process.

[0015] First, the time information transmission process performed by the processing unit 110 of the transmitting device 100 will be explained with reference to Figure 3. When the time information transmission process is started, the processing unit 110 obtains the current time (Timestamp 1) measured by the timing unit 120 and transmits the Timestamp 1 to the receiving device 200 via the communication unit 130 (step S101). If the communication unit 130 can directly obtain the current time (Timestamp 1) from the timing unit 120, the processing unit 110 may instruct the communication unit 130 to obtain the current time from the timing unit 120 and transmit it to the receiving device 200. In this case, the communication unit 130 obtains the current time (Timestamp 1) from the timing unit 120 and transmits it to the receiving device 200. Then, the processing unit 110 determines whether or not it has received an ACK signal transmitted from the receiving device 200 (step S102). If it has not received an ACK signal (step S102; No), it returns to step S102. If an ACK signal is received (step S102; Yes), the time information transmission process is terminated.

[0016] Next, the delay time acquisition process performed by the processing unit 210 of the receiving device 200 will be explained with reference to Figure 4. When the delay time acquisition process is started, the processing unit 210 receives Timestamp1 from the transmitting device 100 via the communication unit 230 and acquires the reception time of Timestamp1 as Timestamp2 from the timing unit 220 (step S121). If the communication unit 230 can directly acquire the reception time from the timing unit 220, the processing unit 210 may instruct the communication unit 230 to acquire the time of Timestamp1 as Timestamp2 from the timing unit 220. In this case, the communication unit 230 acquires the time from the timing unit 220 at the moment Timestamp1 is received and sets it as Timestamp2. Then, the processing unit 210 derives the delay time (Delay) from Timestamp2 - Timestamp1 and sends an ACK signal to the transmitting device 100 via the communication unit 230 (step S122), and terminates the delay time acquisition process.

[0017] The time information transmission process and delay time acquisition process have been explained above. Next, the process by which the transmitting device 100 and the receiving device 200 transmit and receive data according to the Timetable (consisting of the scheduled transmission process of the transmitting device 100 and the scheduled reception process of the receiving device 200) will be explained with reference to Figures 5 and 6. This process is executed when transmitting and receiving data according to the Timetable, but prior to execution, the receiving device 200 must have acquired the delay time (Delay) (through the delay time acquisition process described above). Therefore, if the receiving device 200 has not yet acquired the delay time when attempting to transmit or receive data, the receiving device 200 sends a request to the transmitting device 100 to start the time information transmission process, and after executing the time information transmission process and delay time acquisition process described above, it performs the following process.

[0018] First, the scheduled transmission process performed by the processing unit 110 of the transmitting device 100 will be explained with reference to Figure 5. When the scheduled transmission process starts, the processing unit 110 sends a data transmission timetable to the receiving device 200 (step S201). Then, the processing unit 110 determines whether or not it has received an ACK signal from the receiving device 200 (step S202). If an ACK signal has not been received (step S202; No), it returns to step S202. If an ACK signal has been received (step S202; Yes), the processing unit 110 transmits data according to the timetable (step S203). That is, the processing unit 110 reads the next scheduled transmission time from the timetable, and when the current time measured by the timing unit 120 reaches the read scheduled transmission time, it transmits the data using the communication unit 130. If the communication unit 130 can directly obtain the current time from the timing unit 120, the processing unit 110 may instruct the communication unit 130 to transmit data to the receiving device 200 when the current time obtained by the timing unit 120 reaches the scheduled transmission time. Then, the processing unit 110 determines whether there are any further scheduled transmission times in the Timetable (step S204). That is, it determines whether there is any data in the Timetable that should be sent to the receiving device 200 at any subsequent scheduled transmission times. If there are scheduled transmission times (step S204; Yes), it returns to step S203 and continues sending data according to the Timetable. If there are no more scheduled transmission times (step S204; No), the processing unit 110 terminates the scheduled transmission process.

[0019] Next, the scheduled reception processing performed by the processing unit 210 of the receiving device 200 will be explained with reference to Figure 6. When the scheduled reception processing starts, the processing unit 210 receives a Timetable from the transmitting device 100 via the communication unit 230 (step S221). Then, to indicate that the Timetable has been received, the processing unit 210 sends an ACK signal to the transmitting device 100 via the communication unit 230 (step S222). The processing unit 210 then reads the next scheduled transmission time from the Timetable, subtracts the first margin (the time of the preceding margin) from the read scheduled transmission time (reception operation start time), sets the processing unit 210 to wake up at that time, and then enters sleep mode (step S223). When the set wake-up time (reception operation start time) arrives, the processing unit 210 wakes up and starts the reception operation at the communication unit 230 (step S224).

[0020] Then, the processing unit 210 determines whether or not data reception by the communication unit 230 has been completed (step S225). If data reception has not been completed (step S225; No), the processing unit 210 obtains the current time from the timing unit 220 and determines whether or not the current time has reached the time obtained by adding the second margin (the time of the later margin) to the scheduled transmission time read in step S223 (the reception operation completion time) (step S226). If the reception operation end time has not been reached (step S226; No), the processing unit 210 returns to step S225 and continues the reception operation. If the reception operation completion time is reached (step S226; Yes), proceed to step S227. The determination of whether or not data reception is complete can be made using conventional techniques. For example, the total length of a packet can be obtained by reading the information in the area indicating the data length contained in the IP header that constitutes the data used in IP (Internet Protocol) communication. The receiving device 200 can determine that data reception is complete when the total length of the received data is equal to the total length of the obtained packet. The method for determining data reception completion is not limited to this, and other conventional techniques may be used.

[0021] On the other hand, if data reception is complete (step S225; Yes), proceed to step S227. In step S227, the processing unit 210 terminates the receiving operation. Then, the processing unit 210 determines whether there are any further scheduled transmission times in the Timetable (step S228). That is, it determines whether there is any data in the Timetable that the receiving device 200 should receive at subsequent scheduled transmission times. If there is a scheduled transmission time (step S228; Yes), return to step S223 and repeat the transition to sleep mode and reception operation according to the Timetable. If there is no longer a scheduled transmission time (step S228; No), the processing unit 210 terminates the scheduled reception process.

[0022] Although the above-described scheduled transmission process does not mention the sleep operation of the processing unit 110 of the transmitting device 100, the processing unit 110 may also perform a sleep operation in the scheduled transmission process, similar to what the processing unit 210 does in the scheduled reception process. That is, in the scheduled transmission process, the processing unit 110 may wake up a little before the scheduled transmission time (just before the time required to wake up) and transmit data, and then set the wake-up time a little before the next scheduled transmission time (just before the time required to wake up) and enter a sleep state, and repeat this process.

[0023] As described above, the scheduled transmission and reception processes enable the transmitting device 100 and receiving device 200 to send and receive data according to the Timetable, allowing for efficient communication, such as reducing power consumption by entering a sleep state during periods when operation is not required. Furthermore, if the accuracy of the clocks (timing accuracy) of the timekeeping units 120 and 220 is high, the margin can be reduced, allowing for longer sleep times to further reduce power consumption, or increasing the number of transmissions within a predetermined period to improve communication speed. Furthermore, once the data reception is complete, the processing unit 210 can terminate the reception operation and enter a sleep state. In this case, there is a high probability that the unit can enter a sleep state earlier than the reception operation termination time based on the Timetable, thus further enhancing power saving. Furthermore, if the receiving operation is not completed by the time obtained by adding a delay time to the scheduled transmission time and then adding a second margin (the time when the receiving operation will end), the receiving device 200 will terminate the receiving operation. Therefore, if the receiving device 200 fails to transmit data from the transmitting device 100 for any reason, or if the transmitted data fails to be received for any reason, the receiving device 200 will not have to wait for an unnecessarily long period of time for data transmission from the transmitting device 100.

[0024] For example, if the accuracy of the clock in the timekeeping unit is low, as in conventional technology, it is necessary to set a larger margin as shown in Figure 7, which shortens the sleep time. In contrast, if the accuracy of the clocks in the timekeeping units 120 and 220 is high, the margin can be reduced as shown in Figure 8, and the sleep time can be extended, thereby reducing the power consumption of the receiving device 200. Furthermore, if the sleep time is kept at the same level as the conventional technology (Figure 7), the number of data transmissions can be increased as shown in Figure 9 (3 times in Figure 7 compared to 4 times in Figure 9 within the same time period), thus improving the communication speed.

[0025] In the embodiment described above, the margin value was predetermined according to the accuracy of the clocks in the timekeeping units 120 and 220. However, the delay time, which is the time it takes for radio waves to travel from the transmitting device 100 to the receiving device 200, actually depends not only on the distance between the two devices but also on the environment through which the radio waves travel (amount of water vapor in the air, the effect of reflection by buildings, etc.). The greater the distance, and therefore the greater the delay time, the more uncertain factors there are in the environment through which the radio waves travel, so it is considered better to increase the margin accordingly. Therefore, the pre-set margin values ​​(the first margin, which is the front margin, and the second margin, which is the rear margin) may be corrected based on the delay time obtained in the delay time acquisition process. Specifically, for example, the corrected margin value may be obtained by multiplying the pre-set margin value by the value obtained by dividing the delay time (seconds) by 10 + 1. Alternatively, a margin correction table may be prepared in which a coefficient to be multiplied by the pre-set margin value is set for each delay time, and the margin value may be corrected based on this table. By correcting the margin in this way, it is possible to set a margin that takes into account variations in radio wave propagation speed even in environments where these variations occur due to factors such as water vapor and tall buildings. Furthermore, in this embodiment, any clock can be used as long as the clocks in the timekeeping units 120 and 220 have an accuracy of a predetermined standard or higher, but by using an atomic clock, this accuracy condition can be reliably met.

[0026] A closer examination of the margins reveals that, as shown in Figure 10, the front margin (first margin) is the sum of the wake-up margin, which takes into account the time required for the processing unit 210 to wake up from sleep mode (wake-up time), the environmental margin, which takes into account the environment through which the radio waves pass (variation in radio wave propagation speed), and the base margin, which takes into account clock accuracy. The rear margin (second margin) is the sum of the environmental margin, which takes into account the environment through which the radio waves pass (variation in radio wave propagation speed), and the base margin, which takes into account clock accuracy, etc. The basic margin is determined, more specifically, based on the accuracy of the clocks in the timekeeping unit 120 of the transmitter 100 and the timekeeping unit 220 of the receiver 200, according to the validity period of the Timetable. The validity period of the Timetable can be set arbitrarily, but it is usually set to a period within which the effect of the errors in the clocks of the timekeeping units 120 and 220 can be ignored, and to the period from the first scheduled transmission time to the last scheduled transmission time in the Timetable. In the following explanation, we will assume that the validity period of the Timetable is 3 days. If the accuracy of the timing unit 120 of the transmitting device 100 is 3 nanoseconds per month (30 days), and the accuracy of the timing unit 220 of the receiving device 200 is 2 nanoseconds per month (30 days), then the time on both devices will drift by a maximum of 0.3 nanoseconds and 0.2 nanoseconds, respectively, over the 3-day validity period of the Timetable. If we consider the case where this drift is in the opposite direction (worst case), then in this example we need to accommodate a drift of 0.3 nanoseconds + 0.2 nanoseconds = 0.5 nanoseconds, so we can see that the basic margin value should be set to 0.5 nanoseconds.

[0027] The process of setting the basic margin according to the accuracy of the clock and the validity period of the timetable (consisting of the basic margin setting process of the transmitter 100 and the accuracy transmission process of the receiver 200) will be explained with reference to Figures 11 and 12. The basic margin setting process is executed in the transmitter 100 and the receiver 200 when it is desired to set the value of the basic margin. The accuracy transmission process is executed when the receiver 200 receives an accuracy request sent from the transmitter 100. Since these processes correct the time of the clocks in each timekeeping unit 120, 220, the basic margin setting process may be executed when a sufficient amount of time (for example, one year) has elapsed since the last execution to require time correction.

[0028] First, the basic margin setting process performed by the processing unit 110 of the transmitting device 100 will be explained with reference to Figure 11. When the basic margin setting process is started, the processing unit 110 performs time correction (step S301). This is done by the processing unit 110 communicating with a time server or the like that provides accurate time information via the communication unit 130. At that time, the processing unit 110 obtains how much the time on the clock of the timing unit 120 has deviated since the last time correction and calculates the clock accuracy of the timing unit 120. The processing unit 110 then sends a precision request to the receiving device 200 via the communication unit 130 (step S302). This precision request is a packet that prompts the receiving device 200 to perform time correction and requests that it transmit the clock precision of the timing unit 220 obtained during time correction. Upon receiving the precision request, the receiving device 200 calculates the precision (the clock precision of the timing unit 220 of the receiving device 200) through the precision transmission process described later and transmits it to the transmitting device 100.

[0029] Next, the processing unit 110 receives the accuracy transmitted by the receiving device 200 (the clock accuracy of the timing unit 220 of the receiving device 200) via the communication unit 130 (step S303). Then, the processing unit 110 determines the validity period of the Timetable to a predetermined value (for example, n days) and calculates the basic margin based on the clock accuracy of the timing unit 120 calculated in step S301, the clock accuracy of the timing unit 220 received in step S303, and the validity period of the Timetable (step S304). For example, if the clock of the timing unit 120 is off by t1 seconds in m1 days, the clock of the timing unit 220 is off by t2 seconds in m2 days, and the validity period of the Timetable is n days, then the basic margin is calculated as (t1 / m1+t2 / m2)×n. The processing unit 110 then transmits the calculated basic margin to the receiving device 200 via the communication unit 130 (step S305), and the basic margin setting process is completed.

[0030] Next, the accuracy transmission process performed by the processing unit 210 of the receiving device 200 will be explained with reference to Figure 12. Upon receiving the accuracy request transmitted by the transmitting device 100 via the communication unit 230, the processing unit 210 performs time correction (step S321). This is done by the processing unit 210 communicating with a time server or the like that provides accurate time information via the communication unit 230. At that time, the processing unit 210 obtains how much the time on the clock of the timing unit 220 has drifted since the last time correction and calculates the clock accuracy of the timing unit 220. Next, the processing unit 210 transmits the calculated clock accuracy to the transmitting device 100 via the communication unit 230 (step S322). Then, the processing unit 210 receives the basic margin from the transmitting device 100 via the communication unit 230 (step S323) and terminates the accuracy transmission process.

[0031] By performing the basic margin setting process and accuracy transmission process described above, the transmitting / receiving system 1000 can set basic margins that match the clock accuracy of the timing unit 120 of the transmitting device 100 and the clock accuracy of the timing unit 220 of the receiving device 200, thereby further improving communication efficiency and power saving efficiency. Furthermore, if the clock accuracy of the timing unit 120 or timing unit 220 does not meet a predetermined standard, the total margin value calculated from the basic margin set in the basic margin setting process (i.e., basic margin × 2 + environmental margin × 2 + wake-up margin) may become larger than the interval of scheduled transmission times listed in the Timetable. In this case, data communication according to the Timetable cannot be performed, so it is necessary to update the Timetable (to make the interval of scheduled transmission times larger than the margin value). Therefore, in such cases, the transmitting device 100 may have a function to notify the developer or other person who created the Timetable that the Timetable needs to be updated.

[0032] In the above-described embodiment, the transmitting device 100 and the receiving device 200 were described separately for the sake of clarity, but in reality, both are communication devices with the same configuration. Therefore, even with the same communication device, when transmitting data according to the timetable, the processing on the transmitting device 100 side should be performed, and when receiving data according to the timetable, the processing on the receiving device 200 side should be performed. However, if the necessary data (e.g., basic margin) can be shared between the transmitting device 100 and the receiving device 200 by performing only one of the processes, such as the basic margin setting process and the accuracy transmission process, then it is sufficient to perform only one of the processes.

[0033] Furthermore, in the above embodiment, it was described that the programs for various processes (such as time information transmission processing and delay time acquisition processing) executed by the processors in the processing units 110 and 210 are pre-stored in the memory of the processing units 110 and 210. However, a computer capable of executing the above processes may be configured by distributing programs stored on non-temporary computer-readable recording media such as flexible disks, CD-ROMs (Compact Disc Read Only Memory), DVDs (Digital Versatile Discs), MOs (Magneto-Optical discs), memory cards, and USB memory, and then loading and installing those programs into a computer.

[0034] Furthermore, the program can be superimposed on a carrier wave and applied via a communication medium such as the Internet. For example, the program could be posted and distributed on a bulletin board system (BBS) on a communication network. This program could then be launched and executed under the control of the operating system (OS), just like any other application program, to perform the aforementioned processes.

[0035] Furthermore, the processors provided in the processing units 110 and 210 may consist of any single processor, such as a single processor, a multi-processor, or a multi-core processor, or they may be configured in combination with processing circuits such as ASICs (Application Specific Integrated Circuits) or FPGAs (Field-Programmable Gate Arrays).

[0036] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these specific embodiments, and the present invention includes the invention described in the claims and its equivalents. [Explanation of Symbols]

[0037] 100...Transmitter, 110, 210...Processing unit, 120, 220...Timer, 130, 230...Communication unit, 140, 240...Bus, 200...Receiver, 1000...Transmit / receive system

Claims

1. A watch that has an accuracy of a certain standard or higher, A processing unit, and The aforementioned processing unit, The delay time is derived from the clock value at the time the transmission time information is received from the transmitting device and the transmission time information. The transmitting device receives scheduled time information, which includes at least information about the scheduled time of future transmissions. Read the next scheduled transmission time from the aforementioned scheduled time information, The receiving operation is initiated at a time obtained by subtracting a predetermined first margin from the value obtained by adding the delay time to the read transmission scheduled time. Receiving device.

2. The aforementioned processing unit, The first margin is set according to the accuracy. The receiving device according to claim 1.

3. The aforementioned processing unit, After initiating the receiving operation, once the reception of data from the transmitting device is complete, the receiving operation is terminated. The receiving device according to claim 2.

4. The aforementioned processing unit, If, after initiating the receiving operation, the time measured by the clock reaches the time obtained by adding the delay time to the read transmission scheduled time plus a predetermined second margin, but the reception of data from the transmitting device is not completed, then the receiving operation is terminated. The receiving device according to claim 3.

5. The aforementioned processing unit, The second margin is set according to the accuracy. The receiving device according to claim 4.

6. The aforementioned processing unit, The first margin and the second margin are corrected based on the aforementioned delay time. The receiving device according to claim 5.

7. The aforementioned clock is an atomic clock. A receiving device according to any one of claims 1 to 6.

8. A transmitting device that communicates with the receiving device described in claim 1, A transmitting clock that has an accuracy of a specified standard or higher, It comprises a transmission processing unit, The transmission processing unit, The transmission time information obtained from the transmission clock is transmitted to the receiving device. The receiving device is sent scheduled time information, which includes at least the information of the scheduled time of future transmission. The receiving device transmits data according to the scheduled time information. Transmitter.

9. A transmitting and receiving system comprising a transmitting device and a receiving device, The transmitting device is A transmitting clock that has an accuracy of a specified standard or higher, It comprises a transmission processing unit, The transmission processing unit, The transmission time information obtained from the transmission clock is transmitted to the receiving device. The receiving device is sent scheduled time information, which includes at least the information of the scheduled time of future transmission. Data is transmitted to the receiving device according to the scheduled time information. The receiving device is, A receiving clock that has an accuracy of a specified standard or higher, It comprises a receiving processing unit, The receiving processing unit, The delay time is derived from the value of the received clock at the time the transmission time information is received from the transmitting device and the transmission time information. The scheduled time information is received from the transmitting device. Read the next scheduled transmission time from the aforementioned scheduled time information, The receiving operation is initiated at a time obtained by subtracting a predetermined first margin from the value obtained by adding the delay time to the read transmission scheduled time. A transmission and reception system.

10. The processing unit, The delay time is derived from the clock value at the time the transmission time information is received from the transmitting device and the said transmission time information. The transmitting device receives scheduled time information, which includes at least information about the scheduled time of future transmissions. Read the next scheduled transmission time from the aforementioned scheduled time information, The receiving operation is initiated at a time obtained by subtracting a predetermined first margin from the value obtained by adding the delay time to the read transmission scheduled time. Reception method.

11. In the processing unit, The delay time is derived from the clock value at the time the transmission time information is received from the transmitting device and the said transmission time information. The transmitting device receives scheduled time information, which includes at least information about the scheduled time of future transmissions. Read the next scheduled transmission time from the aforementioned scheduled time information, The receiving operation is initiated at a time obtained by subtracting a predetermined first margin from the value obtained by adding the delay time to the read transmission scheduled time. A program that executes a process.

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