JP2007036342A - Data communications system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a group of sensor slave stations to establish a reliable unidirectional radio communication with respect to a master station. <P>SOLUTION: In a radio communications system, comprising the plurality of sensor slave stations and the master station for receiving the data, the master and slave stations have a radio controlled watch, the transmission timing between the sensor slave stations is adjusted, and a specified plural number of past data are transmitted together in transmission, thus achieving a stable data communication system that comprises such a retry transmission. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a data communication system using radio timepiece means, and in particular, in a sensor system using a sensor that measures an environmental condition or the like indoors or outdoors, a plurality of sensor slave stations do not stagnate to a master station via communication means. The present invention relates to data transmission technology.

In recent years, in a ubiquitous sensor network for the purpose of enhancing the safety, convenience, and comfort of society, sensor tags are attached to all things and people to form a network.
Description will be made assuming that data from a plurality of sensors is collected by a master station (server) by wireless communication. In the first place, when each sensor (S1, S2,... Sn) transmits unilaterally, the clock frequency of each transmitting station is slightly different, so even if each station is set to transmit at the same period, multiple slave stations Data is not received correctly due to interference caused by simultaneous transmission. For example, as shown in FIG. 1, when the radio wave of the slave station collides (in the figure, the blacked out area), the master station does not receive correctly.

Here, if the polling call is individually made from the master station to the slave station, interference will not occur because each sensor slave station transmits regularly according to the instruction of the master station. However, in polling, each slave station needs a receiver for receiving the command radio wave of the master station. In general, a receiver has a complicated circuit configuration due to amplification, synchronization, and demodulation of weak received waves, and power consumption is often higher than that of a transmitter.

In addition, the receiver must be energized at all times in order to wait for a command from the master station that does not know when it will be sent. When a command is received from the master station at a constant cycle, the reception time can be predicted and shortened, but it is still necessary to prepare the power supply in advance by considering the rise time of the oscillator or the like. The sensor slave station is often driven by a battery in order to be portable, and there is a strong demand to suppress power consumption as much as possible in order to extend the battery life. Therefore, it is possible to realize unidirectional communication without using a receiver.

Patent Document 1 discloses a one-way communication technique, in which a radio clock is used on a communication line between a plurality of data terminals (corresponding to slave stations) and a data processing device (master station). The data transmission means for the data terminal to transmit outgoing data to the data processing device via a communication line at a predetermined transmission time is shown. This is basically in common with the present invention.
JP 2003-242586 A

However, in the invention disclosed in Patent Document 1, the communication line is mainly considered to be wired, and it is not assumed that transmission errors frequently occur. In the sensor slave station group that is also installed at an outdoor site to measure the environment as in the present invention, it is not easy to install a wired communication line, and a technique that takes into account an error rate in wireless communication is required. Also, the energy saving technology of the slave station is not an issue.

The power consumption of the sensor slave station when multiple sensor slave stations are distributed and environmental information is measured at the same time, and the measurement data is sent to the master station at a point where the sensor slave station is voluntarily separated. As much as possible to extend battery life. Alternatively, it is a problem to enable communication operation sufficiently even with power generation using natural energy such as sunlight.

The present invention, first,
In a wireless communication system comprising a slave station installed at multiple points and a master station that receives data transmitted from the slave station via a communication line, a clock means for managing a standard time received by a radio clock, A slave station having a transmission means for spontaneously transmitting the data in the allocated time slot, and the master station has a clock means for managing the standard time received by the radio clock, and from the slave station A data communication system comprising means for discriminating a received message from the originating slave station based on a time slot.

The second invention is the data communication system according to claim 1, wherein the slave station has a transmission means for transmitting a predetermined number of past data at the time of transmission. is there.

If the communication system between the sensor slave station and the master station according to the present invention is used, simultaneous measurement from a group of sensor devices placed at an arbitrary place becomes possible. It is suitable for collecting data measured simultaneously by arranging many sensors apart.

In other words, the sensor slave station does not have a receiver, but since it has a radio clock reception function, time synchronization within the slave station system can be achieved, so data transmission can be performed in the time slot for each sensor slave station based on the standard time There is no radio wave interference between the slave stations (see Fig. 2).
Since the master station also has a radio clock receiving function, it is possible to identify which slave station the received radio wave is from. For example, as shown in FIG. 3, the server master station 100 can collect and manage data such as tags A, B, and C of the sensor slave station 10 at regular intervals (see FIG. 3).

In this way, each slave station need only transmit measurement data in a predetermined time slot. There is no need for the slave station to transmit data with an address number and a time stamp, the transmission data amount can be reduced, the transmission time can be shortened, and the power consumption can be further reduced. Further, in preparation for the occurrence of an error due to radio communication due to disturbance of radio wave conditions, an error recovery function can be substantially realized by a retry effect by sending a predetermined number of data many times.

The configuration of the sensor slave station will be described with reference to FIG.
Temperature, sunshine, humidity, and other measured quantities are measured by the sensor 1 installed in the sensor slave station 10. It is taken in by the input unit 2 and then subjected to analog / digital conversion 3. They are collectively controlled by the MPU 4 as input means. The MPU 4 includes a microprocessor, a program, a work memory, and the like.

Next, the radio clock unit will be described. A long wave signal from the transmitting station (not shown) is received by the antenna 5, and the radio wave receiving unit 6 decodes the received signal and corrects the time data of the clock unit 7 so as to represent the standard time used by itself. The standard time of the standard radio signal is normally transmitted in a cycle of about 1 minute. However, in order to reduce power consumption, the clock unit 7 performs internal processing in such a way that the correct time is set at a lower cycle (1Hr to 1 day). It's okay.

The MPU 4 stores the measurement data and time data obtained sequentially as a set, and stores them in the storage unit 20 through the interface 19. The measurement data is not limited to one, but is often a plurality of measurement data sets, for example, temperature and sunshine value, but for the sake of simplicity of explanation, a mode in which time and measurement data are paired is shown ( FIG. 6).

Now, the stored data set is voluntarily transmitted to the master station 100 through the communication means 8 as appropriate. As an example, FIG. 5 shows a time chart.
Here, data measurement is performed once per minute at each sensor slave station (in time blocks of 11 and 12), and transmission from all sensor slave stations is performed once per minute (13-1 to n). , 14-1 to n time slots).
That is, the time block 11 means a section from an arbitrary year / month / date hour: 00 minutes: 00 seconds, and each sensor device that knows this time from the radio clock in this section independently performs measurement simultaneously. . Then, after the passage of the time block 11, each sensor slave station has its own node number n (individually set in advance (not shown)) in the time zone (time slot) allocated to itself. Send data. If the sensor slave station has a node number of 1, the time slot 13-1 can be occupied by itself, and if the node number is n, the time slot 13-n can be occupied by itself. At the next hour, the measurement is performed in the time block 12 and the data transmission is performed in each time slot 14-n, and this is repeated every minute thereafter.

The amount of data that can be transmitted at one time is determined by the balance with the amount of communication bits allowed in the time slot, but the sensor device does not send only the latest data, but also sends a predetermined number of past data. Thus, in preparation for a case where the wireless state has been bad in the past, the data is repeatedly transmitted unconditionally many times. A so-called unconditional retry is realized.

Next, the storage state of time data and measurement data will be described with reference to FIG.
In this example, measurement data is input at 00 seconds per minute, and these (one in this example) are stored as one record row with a time and a set (pair in this example).
In the storage unit 20, the time data accompanies the measurement data as a time stamp 21, and the measurement data constitutes a measurement data string.
The MPU 4 is provided with an In pointer 23 for managing this storage unit. The In pointer 23 indicates an address position for storing a newly input data set. Since this pointer is a circular rolling pointer, it returns to the beginning of the memory when it reaches the bottom of the memory. Then, for example, the pointer is advanced by one address every minute and data is sequentially accumulated. On the other hand, since the data at the In pointer-1 address is the latest, the transmission data is transmitted up to a predetermined number of data. For example, the operation of sending 10 data (10 minutes worth of data) leads to repeating 9 retries.
Since data writing and data transmission move synchronously, only one pointer is required. For example, an overflow or underflow error that occurs in a mechanism that operates two or more pointers asynchronously such as an In pointer and an Out pointer. Needless to say, does not occur.

The program flow of the sensor slave station is shown in FIG.
First, starting from Start 40, initialization of hardware, pointer, and other software processing is performed (41).
Loop execution is started, and the arrival of its own transmission slot (42) and the monitoring of the fixed time (minutes) are performed (43).
In the transmission slot process, a predetermined number of data sets are extracted from the storage unit from the In pointer-1 (46), and the measurement data set is transmitted (47).

Next, when the fixed time (in this example, the hour and minute (00 seconds)) has elapsed (43), the measurement data is promptly input (44), and the data is indicated by the In pointer with a time stamp. (45). Thereafter, the In pointer is updated (simply +1, but with a scroll function) (48).

However, it should be noted here that it is not necessary to transmit the time data up to the master station.
This is because the master station itself has a radio clock function, and therefore the system time is common, and it is sufficient for the slave station to transmit only measurement data. That is, the slave station does not need to transmit the address and time data for identifying the station. In this way, the amount of transmission data is limited only to the measurement data, so the communication time is shortened.
Repeating these steps is the basic movement of the sensor slave station of the present invention.

[Example]
(1) A monitoring system that collects various measurement data such as temperature, humidity, pressure, and wind speed in a certain space in real time and issues an alarm in case of an abnormality. For example, in a clean room that needs to maintain a certain environment, local abnormalities are detected by disposing sensors at various locations in the room. In this case, each sensor transmits measured data to the master station (server).

(2) A home security system is also conceivable in which an open / close sensor is attached to each door / window of the house to centrally manage the door lock in the house. In FIG. 8, S1, S2,... Are open / close sensors, and C is a master station (server). In this case, since the transmission information only needs to know the open / closed state, the data length is only 1 bit. Even if each sensor does not send address information, a time slot is assigned, so that the master station can identify which door / window is open.

(3) The present invention can also be applied to a system for confirming that an asset has not been taken away by an asset management system. For example, it can be applied to a motor pool for storing new cars, used cars, heavy machinery, etc., and ranches for raising many livestock such as cattle and sheep. Check whether assets such as cars and livestock are within reach of radio waves. In this case, the presence / absence is determined by the received radio wave intensity, so there is no need to transmit data. That is, it is only necessary to emit an unmodulated carrier in a predetermined time slot. Unlike an ID tag, it is not necessary to bring a reader close to an object or pass through a reading gate, and there is an advantage that existence in a wide range of several hundred meters can be confirmed even with a low-power radio.

In either example, the power consumption of the slave station can be remarkably suppressed as compared with the conventional method, and the battery life can be extended. In addition, a configuration in which a fixed power source or the like is not used can be formed by combining a solar cell and a large-capacity capacitor.
Many other applications are possible, and the essence of the present invention is not limited to the above embodiments.

The time chart in case each transmission node of the prior art example is not synchronized is shown. The time chart in case each transmission node of this invention is synchronized is shown. Fig. 4 shows the data collection result of time synchronization according to the present invention It is a functional block diagram of a sensor slave station of the present invention. 3 shows an overall time chart of data measurement and transmission slot processing in the system of the present invention. The storage part record general condition in this invention, arrangement | positioning of a pointer, and a transmission data matrix are shown. The program flow of the sensor slave station of this invention is shown. An application example of the security sensor system is shown.

Claims (2)

In a wireless communication system comprising a slave station installed at multiple points and a master station that receives data transmitted from the slave station via a communication line, a clock means for managing a standard time received by a radio clock, A slave station having a transmission means for spontaneously transmitting the data in the allocated time slot; a clock means for managing a standard time received by the radio clock; and a received message from the slave station based on the time slot. A data communication system comprising: a master station having a means for discriminating data transmitted from the slave station. 2. The data communication system according to claim 1, wherein the slave station has transmission means for transmitting a predetermined plurality of past data at the time of transmission.

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