Sensor node, base station, and sensor network system

• US 20060172784A1
• Filed: 08/23/2005
• Published: 08/03/2006
• Est. Priority Date: 01/31/2005
• Status: Active Grant

• Current Assignee: Maxell, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Shimura, Takanori, Ara, Koji, Yamashita, Shunzo, Ogata, Yuji
• Granted Patent: US 7,512,418 B2
• Time in Patent Office: Days
• US Class Current: 455/574
• CPC Class Codes: G01D 21/00 Measuring or testing not otherwise provided for
• CPC Class Codes: G01D 5/00 Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable G01D3/00 takes precedence; specially adapted for apparatus giving results other than momentary value of variable G01D1/00
• CPC Class Codes: H04W 28/06 Optimizing the usage of the radio link, e.g. header compression, information sizing , discarding information system modifying transmission characteristic according to link quality by modifying frame length H04L1/0007; dynamic adaptation of the packet size for flow control or congestion control H04L47/365
• CPC Class Codes: H04W 28/14 using intermediate storage
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 52/0219 where the power saving management affects multiple terminals
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

This invention achieves lower electric power consumption of a sensor node for carrying out an intermittent operation, in a sensor net system. A time when the sensor node transmits a signal to a base station is estimated. Then, in accordance with the estimation, a table for storing a signal transmitted from the sensor node is installed in a wireless section of the base station. Consequently, a communication time between the sensor node and the base station can be made shorter. Also, a start time of a micro computer is set for RTC inside the sensor node, so the micro computer inside the sensor node can be put in the standby state.

Claims

1. A base station for transmitting a first signal to each of a plurality of sensor nodes, comprising:

a first memory for storing the first signal to be transmitted to each of the plurality of sensor nodes;

a second memory which is connected through a serial interface to the first memory and stores the first signal stored in the first memory; and

a wireless communication module connected to the second memory, wherein

the number of the first signals stored in the second memory is smaller than the number stored in the first memory,

the first signal stored in the second memory is transmitted through the wireless communication module to the plurality of sensor nodes, and

the first signal, which is not stored in the second memory, is transmitted through the serial interface and the wireless communication module to each of the plurality of sensor nodes.

2. The base station according to claim 1, wherein

the base station receives a second signal from each of the plurality of sensor node,

the first memory and second memory further store a time when the second signal is received from each of the plurality of sensor nodes, and

the time stored in the first memory includes a time later than the time that is stored in the second memory.

3. The base station according to claim 2, wherein when the base station receives the second signal from any one of the plurality of sensor nodes, if the first signal to be transmitted to the sensor node is stored in the second memory, the first signal stored in the second memory is transmitted to the sensor node.

4. The base station according to claim 2, wherein when the base station receives the second signal from any one of the plurality of sensor nodes, if the first signal to be transmitted to the sensor node is not stored in the second memory, whether or not the first signal is stored in the first memory is judged.

5. The base station according to claim 4, wherein if the first signal is stored in the first memory, the first signal stored in the first memory is transmitted to the sensor node.

6. The base station according to claim 4, wherein if the first signal is not stored in the first memory, a third signal instead of the first signal is transmitted to the sensor node.

7. The base station according to claim 6, wherein

the first signal includes a command signal for controlling each of the plurality of sensor nodes,

the second signal includes data obtained from a sensor included in each of the plurality of sensor node, and

the third signal is an empty signal indicating that there is no command signal for controlling each of the plurality of sensor nodes.

8. The base station according to claim 2, wherein

each of the first signals, which are stored in the first memory and the second memory, is stored such that the plurality of sensor nodes are arrayed in an order of times when the second signals are received by the base station, and

the base station, after receiving the second signal from each of the plurality of sensor nodes, rewrites an order of the first signals which are stored in the first memory and the second memory.

9. The base station according to claim 1, further comprising:

a first CPU connected to the first memory;

a first interface controller connected to the first memory and the first CPU;

a second CPU connected to the second memory; and

a second interface controller connected to the second memory and the second CPU,

wherein the first memory and the second memory are connected through the first and second interface controllers to the serial interface.

10. The base station according to claim 2, wherein the base station periodically receives the second signal from each of the sensor nodes.

11. A sensor network system, comprising:

a sensor node comprising a first sensor, a first CPU for receiving data obtained from the first sensor, a first memory in which a software executed by the CPU is installed, a first wireless communication module for transmitting the data obtained from the first sensor, and a first interface controller; and

a base station comprising a second wireless communication module for receiving the data transmitted from the first wireless communication module of the sensor node, a second memory for storing the data to be transmitted to the sensor node, a second CPU for controlling the data stored in the second memory to be transmitted to the sensor node, a second sensor, and a second interface controller, wherein

the first sensor, the first CPU, the first memory, the first wireless communication module and the first interface controller are connected through a first bus, and

the second sensor, the second CPU, the second memory, the second wireless communication module and the second interface controller are connected through a second bus.

12. A sensor node for transmitting data to a base station, comprising:

a sensor;

a CPU for receiving the data obtained from the sensor; and

a real time clock that is installed outside of the CPU and connected to the CPU, wherein

when the data is not transmitted to the base station, the CPU transmits a start time to the real time clock, and the CPU becomes in a standby state.

13. The sensor node according to claim 12, wherein when the start time comes, the real time clock transmits a signal to the CPU.

14. The sensor node according to claim 12, wherein the start time is determined in accordance with a time when the sensor node transmits the data to the base station.

15. The sensor node according to claim 12, further comprising a memory for storing the data to be held by the CPU, wherein

the CPU, before transmitting the start time to the real time clock, stores the data to be held by the CPU in the memory.