JP3232018B2 - Wireless communication terminal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission system used for wirelessly connecting one central terminal and a plurality of terminals for security information such as electricity, LP gas, water supply, and the like, and automatic usage meter reading thereof. The present invention relates to a wireless communication terminal.

[0002]

2. Description of the Related Art Conventionally, in security information such as electricity, LP gas, water supply, and the like, and automatic meter reading, transmission has been performed by radio in places where construction of telephone lines is difficult.

[0003] Conventionally, since a single terminal is connected to a central terminal and one terminal connected to a meter, the terminal performs carrier sense before transmission, and transmits a signal after confirming that no signal is transmitted. Was adopted.

[0004]

However, in the conventional wireless communication terminal, there is an error in the accuracy of the clock between the central terminal and the terminal, and the time cannot be accurately determined between the two terminals. . For this reason, the time during which the terminal performs the receiving operation must be set long, and the power consumption has increased.

In the case where the number of terminals becomes plural, it is necessary in such a system that the central terminal always transmits signals from the central terminal and that each terminal does not transmit a signal from the central terminal or to continue carrier sense. However, the power consumption of the device is large and it is difficult to operate the battery operation.

[0006] In view of the above problems, an object of the present invention is to provide a wireless communication terminal capable of reducing power consumption.

[0007]

In order to achieve the above object, a wireless communication terminal according to the first aspect of the present invention comprises a central terminal for each area and a terminal such as an electric, gas or water supply installed at home. With a plurality of terminals connected to the meter, the time is divided into slots of a predetermined length, and data communication is performed between the central terminal and the terminal using slots determined for each area ,
To adjust the time of the terminal in accordance with the signal from the central terminal
Wireless communication terminal, the
If there is no transmission message to the end, transmit a short carrier, and
Long carrier when there is a transmission message from the central terminal to the terminal
Is transmitted .

[0008]

Further, when there is an uplink message from each terminal to the central terminal , the wireless communication terminal according to claim 2 of the present invention synchronizes with the downlink message from the central terminal to each terminal transmitted for each slot. All terminals transmit carriers at the same timing to the central terminal to notify that there is an upstream message.

[0010] In addition, a wireless communication terminal according to a third aspect of the present invention is the wireless communication terminal according to the first or second aspect, wherein the terminal has an antenna having directivity,
It is characterized in that the directivity is set toward the central terminal.

According to the above configuration, the wireless communication terminal according to the first aspect of the present invention is configured such that the time of the terminal is adjusted in accordance with the signal from the central terminal. By doing so, the time of the slot can be accurately determined, and the time for receiving operation of the terminal can be accurately determined.
If there is no, transmit a short carrier,
A long carrier is transmitted when there is a transmission message to
Since there is no transmission message from the central terminal to the terminal because of the configuration
Transmission of short carriers reduces current consumption
Can be planned.

[0012]

Furthermore, the wireless communication terminal according to claim 2 of the present invention is the wireless communication terminal according to claim 1, when the respective terminal has uplink message to the central terminal, the downlink transmitted per slot Since all terminals transmit the carrier to the central terminal at the same timing in synchronization with the message to notify that there is an upstream message, in addition to the effect of claim 1, it is possible to prevent interference of the upstream message.

In addition, a wireless communication terminal according to a third aspect of the present invention is the wireless communication terminal according to the first or second aspect, wherein the terminal has an antenna having directivity,
Since arrangement of installed toward the directivity in the central terminal, before
In addition to the effect of claim 1 or claim 2 , interference between areas can be prevented.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a wireless communication terminal according to an embodiment of the present invention will be described.

The data transmission system using the wireless communication terminal is installed in ordinary households and is used for telemeters such as electricity, gas, water, and the like. In a normal use state, meter reading is performed once a month from the center. . Also, when the remaining amount of the LP gas cylinder is low, a call is made from the terminal to the center, and the center is notified that the remaining amount is low. As a result, it is a normal operation state that communication is performed about three times a month.

FIG. 1 is a diagram showing a home system using a wireless communication terminal according to an embodiment of the present invention.
FIG. 1 is a diagram showing an entire system using the wireless communication terminal.

In FIG. 1, reference numeral 13 denotes a central terminal connected to a center 11 via a telephone line 12, and reference numeral 14 denotes a terminal connected to a meter 15 for electricity, gas, water, and the like. 14, data communication is performed wirelessly.

Next, a description will be given of a communication protocol of a system in which one central terminal and a plurality of terminals are installed in a home and a meter is read by a gas meter.

FIG. 3 is a diagram showing an area configuration of the wireless communication terminal according to the embodiment of the present invention.

Areas in which wireless communication with the central terminal 13 is possible are designated as areas 32, 33, 34, 35 and 36.
The terminal 14 is installed inside 2, 33, 34, 35, 36. The terminal 14 installed in each of the areas 32, 33, 34, 35, 36 has an antenna having directivity.
The directional antenna of each terminal 14 is installed toward the central terminal 13. As a result, signals from other areas are not received.

The installation of the directional antenna and its effects will be described with reference to FIG.

When wireless communication is performed between the central terminal 13 and a large number of terminals 14 as in the present system, the omnidirectional antenna is used because the location of the terminal varies greatly from home to home. Normal. However, in this case, when a line is connected to avoid the danger of interference, a method of electronically directing the directivity of the antenna of the central terminal 13 toward the terminal 14 may be adopted.

This method is very expensive and cannot be used in a general home system.

In the present invention, on the contrary, an antenna having directivity is installed on the terminal 14, and the directivity is installed toward the central terminal 13. As a result, the terminal 14 can surely receive the carrier from the central terminal 13, but it is less likely to receive a carrier in another area or a carrier of another terminal 14. Further, when the antenna has directivity, the influence of fading due to multipath is reduced. In addition, it is possible to prevent the battery from being exhausted by receiving a carrier other than a regular radio wave and entering an unnecessary operation.

FIG. 4 is a diagram showing slot division of a wireless communication terminal according to an embodiment of the present invention.

[0027] In the wireless communication terminal, it is assumed that slots are divided at a fixed time for each area.

In area 1, slots 1, 6, 11, 1
6, 21,... In area 2, slots 2, 7, 12, 17, 22,.
・ Area 3, slots 3, 8, 13, 18, 23
・ Area 4, slots 4, 9, 14, 19, 24
In area 5, slots 5, 10, 15, 20, 25
・ ・ Assign.

As a result, it is possible to prevent signals in the area 1 and the area 2 from interfering with each other.

When data is transmitted between the central terminal 13 and the terminal 14 in each of the areas 32, 33, 34, 35, and 36, adjustment is performed once a day in order to prevent the timing from being shifted. At the time of arbitration, the current time is transmitted from the central terminal 13. Each terminal 14 receives a timing signal from the central terminal 13 and performs timing.

The timing at which timing is performed for each of the areas 32, 33, 34, 35, and 36 is determined by the area 32, 33, 34,
In order to prevent the signals 35 and 36 from interfering with each other, the time is shifted a little at a time.

FIG. 5 is a diagram showing a protocol when there is no downstream or upstream message of the wireless communication terminal according to the embodiment of the present invention.

The mode shown in FIG. 5 is the most frequently used operation mode and has the greatest effect on battery life.
Therefore, in the present invention, current consumption is minimized in this mode.

The carrier is transmitted at the beginning of the slot determined by the central terminal.

The carrier is 20 to 20 when there is no down message.
A carrier for a short time (T0) of about 30 ms is transmitted. A short width carrier indicates that there is no down message, and the short width of the carrier suppresses consumption of current consumption.

The carrier also serves as a starting point for transmitting an upstream message.

Each terminal turns on the power shortly before the short carrier 51 is transmitted, and starts receiving the carrier 51. As a result, it recognizes that it is a short carrier and knows that there is no downstream message. At this time, the terminal turns on the power shortly before the carrier 51 is transmitted. However, even if the time is shifted between the central terminal and each terminal, it is necessary to turn on the power from an early stage in order to reliably receive the carrier 51. And leads to an increase in current consumption. Therefore, in the present invention, as shown in FIG.
The current time is sent to and time is adjusted. As a result, the time error of the entire system is reduced, and the time at which the terminal 14 starts operating can be set accurately, leading to a reduction in current consumption.

Next, after a certain period of time (T10: about 50 ms) since each terminal receives the downstream carrier 51, a terminal having upstream data transmits the carrier 52.

When this terminal 52 is not transmitted from any terminal, it indicates that there is no uplink message from any terminal, and the central terminal ends the receiving operation 53.

In the figure, the signal T of the central terminal / terminal indicates signal transmission, and R indicates signal reception.

Here, each terminal transmits at the same time at the timing of the carrier 52, and the central terminal receives the carrier at this timing and can know the presence or absence of an upstream message, so that the determination can be made in a very short time. And leads to low power consumption.

As described above, the central terminal transmits a signal 51 (20 to 30 ms) and receives a signal 53 (70 to 80).
ms), a series of operations ends.

When the slot interval T is set to about 1 minute and terminals in a certain area transmit a carrier every 5 slots, the operation interval is 5 × 60 = 300S, the operation time during that period is about 100 ms, and the duty Is about 1/30
00. The operating current of the wireless device is about 25 mA, the average current is about 9 μA,
It can be operated for 10 years using a battery of about mAH, and when the device is operated with a battery, the construction becomes very simple and the device can be installed outdoors. Have.

Next, timing once a day will be described.

In the timing between the central terminal and each terminal, it is necessary to maintain the accuracy as much as possible because current consumption increases due to the accuracy.

That is, each terminal needs to reliably receive the carrier 51 transmitted from the central terminal. Therefore, the receiving mode 54 of the terminal needs to enter the receiving mode slightly before the carrier 51 is transmitted. If the precision of the clock is poor, it is necessary to enter the reception mode earlier, which causes an increase in circuit current consumption.

The accuracy of a normal clock is 15S per month, and 1 day
When S is set, it is possible to suppress the timing deviation within 1S by adjusting once a day.

If no timing is performed, 15 months
S, a cumulative error of about 15S × 12 = 180S in one year, and finally the terminal must always be turned on in order to reliably receive the carrier 51.

In practice, even if errors do not accumulate so much, timing is not only necessary in view of the reliability of the system, but it is also a useful technique for reducing current consumption.

FIG. 6 is a diagram showing a protocol of the wireless communication terminal according to the embodiment of the present invention when there is no downlink message and when there is an uplink message.

Referring to FIG. 6, a mode having an upstream message will be described.

Each terminal transmits the carrier 52 when there is a message to be transmitted after a certain timing (T10) after receiving the downlink message 51.

At this timing, the carrier is transmitted from each terminal at the same time, so that the central terminal can determine that there is an upstream message, but cannot determine from which terminal the signal has been transmitted. However, with this configuration, the presence / absence of an upstream message can be determined at the timing of the carrier 52, so that the presence / absence of an upstream message can be known in a short time.

Subsequently, each terminal continues after a predetermined time (n × T
10) The carrier 63 is transmitted to secure the transmission right.

The transmission timing of the carriers 61 to 65 is determined for each terminal in order (n = 1, 2,...), And the carriers do not interfere with each other.

When there are a plurality of transmitting terminals, the carrier after T10 after receiving the downlink message causes interference. However, the carrier after (n × T10) has a fixed timing for each terminal, and the interference may not occur. Absent.

When a plurality of terminals indicate that there is transmission data, data is transmitted and received in order from the first terminal.

At T20 after the transmission of the downlink message, the downlink message from the central terminal is transmitted and received. Subsequently, each terminal transmits data from the terminal having the higher priority (61>62>...). Receive the message.

FIG. 7 is a diagram showing a protocol of the wireless communication terminal according to the embodiment of the present invention when there is a downlink message and when there is no uplink message.

When there is a downstream message at the beginning of the slot from the central terminal, the carrier 71 for a long time (T1) is transmitted. The transmission of the long-width carrier 71 indicates that there is a downstream message. The carrier 71 is used as a starting point of the timing for transmitting an upstream message.

Each terminal transmits the carrier 52 after a certain period of time (T10) after receiving the downlink carrier 71. This carrier 5 from any terminal
When 2 is not transmitted, it indicates that there is no uplink message from any terminal, and the communication in the slot ends.

In the figure, the signal T of the central terminal / terminal indicates signal transmission, and R indicates signal reception.

T21 after the transmission of the downlink carrier 71
Later, a down message 72 is transmitted from the central terminal, and each terminal receives it.

About once a day, the message from the central terminal contains the current time, and each terminal performs timing.

The communication between the central terminal and each terminal includes a terminal ID in the message, and each terminal sequentially communicates with the central terminal.

FIG. 8 is a diagram showing a protocol of the wireless communication terminal according to the embodiment of the present invention when there is a downlink message and when there is an uplink message.

When there is a downlink message at the beginning of the slot from the central terminal, a carrier for a long time (T1) is transmitted. It indicates that there is a downstream message by transmitting a long-width carrier.

This carrier is used as the starting point of the timing for transmitting an upstream message.

Each terminal transmits the carrier after a certain period of time (T10) after receiving the downstream carrier.

The central terminal receiving the carrier knows that there is an upstream message. Subsequently, each terminal transmits a carrier after a predetermined time (n × T10) to secure a transmission right.

At this time, (n = 1, 2, 2, 3)
...) The transmission timing is determined, and no carrier interference occurs for each terminal.

When there are a plurality of transmitting terminals, the carrier after T10 after the reception of the downlink message causes interference, but the carrier after (n × T10) has a timing determined for each terminal, and the interference may not occur. Absent.

When a plurality of terminals indicate that there is transmission data, the data is transmitted in order from the first terminal.

At T20 after transmitting the down message, the central terminal transmits the message, and the terminal transmits the message.

Subsequently, a message is transmitted from the terminal to the central terminal in order.

[0076]

As described above, according to the first aspect of the present invention,
According to the described wireless communication terminal, the time of the terminal is adjusted in accordance with the signal from the central terminal, so that the time of the slot can be accurately determined by adjusting the time approximately once a day, for example. It is possible to accurately determine the time at which the terminal performs the receiving operation. Therefore, power consumption can be reduced and the battery can be put to practical use.
Also, if there is no transmission message from the central terminal to the terminal, the
Carrier is transmitted and there is a transmission message from the central terminal to the terminal.
Is configured to transmit a long carrier when
In addition to the effect of item 1, the transmission message from the central terminal to the terminal
By transmitting a short carrier when there is no current consumption
Can be reduced.

[0077]

Further, according to the wireless communication terminal of the second aspect of the present invention, in the wireless communication terminal of the first aspect, when there is an upstream message from each terminal to the central terminal, the message is transmitted for each slot. In synchronization with the downlink message, all terminals transmit a carrier to the central terminal at the same timing to notify that there is an uplink message, so in addition to the effect of claim 1,
It is possible to prevent interference of upstream telegrams.

In addition, according to the wireless communication terminal of the third aspect of the present invention, in the wireless communication terminal of the first or second aspect , the terminal has an antenna having directivity, Is arranged toward the central terminal, so that interference between areas can be prevented in addition to the effect of claim 1 or claim 2 . Therefore, the terminal receives only radio waves from the central terminal, and can reduce power consumption without receiving radio waves from other terminals.

[Brief description of the drawings]

FIG. 1 is a diagram showing a home system using a wireless communication terminal according to an embodiment of the present invention.

FIG. 2 is a diagram showing an entire system using the wireless communication terminal according to the embodiment of the present invention.

FIG. 3 is a diagram showing an area configuration of a wireless communication terminal according to the embodiment of the present invention.

FIG. 4 is a diagram showing slot division of the wireless communication terminal according to the embodiment of the present invention.

FIG. 5 is a diagram showing a protocol of the wireless communication terminal according to the embodiment of the present invention when there is no downstream message and no upstream message.

FIG. 6 is a diagram showing a protocol of the wireless communication terminal according to the embodiment of the present invention when there is no downlink message and there is an uplink message.

FIG. 7 is a diagram showing a protocol of the wireless communication terminal according to the embodiment of the present invention when there is a downstream message and no upstream message.

FIG. 8 is a diagram showing a protocol when the wireless communication terminal according to the embodiment of the present invention has a downstream message and an upstream message.

[Explanation of symbols]

 11 center 12 telephone line 13 central terminal 14 terminal 15 gas meter 32,33,34,35,36 area

────────────────────────────────────────────────── (5) References JP-A-9-23185 (JP, A) JP-A-9-23277 (JP, A) JP-A 64-19836 (JP, A) JP-A-63-23 6699 (JP, A) JP-A-47-2504 (JP, A) JP-A-1-309424 (JP, A) JP-A 8-79166 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04Q ^7/ 00-7/38 H04B ⁷ /24-7/26

Claims (3)

(57) [Claims] 1. Each area is provided with a central terminal and a plurality of terminals connected to meters for electricity, gas, water, etc. installed in the home. using a defined slot and the data communication between the central terminal and the terminal, contact the wireless communication terminal which is formed by to adjust the time of the terminal in accordance with the signal from the central terminal
Short when there is no transmission message from the central terminal to the terminal
Carrier is transmitted and there is a transmission message from the central terminal to the terminal.
A wireless communication terminal , wherein a long carrier is transmitted when the terminal is used. 2. When there is an uplink message from each terminal to the central terminal, all terminals transmit carriers to the central terminal at the same timing in synchronization with a downlink message from the central terminal to each terminal transmitted for each slot. 2. The wireless communication terminal according to claim 1, wherein the terminal notifies that there is an upstream message. 3. The terminal has an antenna having directivity,
3. The wireless communication terminal according to claim 1, wherein the directivity is set to face a central terminal.