Patent Application
20100142510
This application claims the benefit of Korean Patent Application No. 10-2008-0122336, filed on Dec. 4, 2008, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a communication apparatus and method for enhancing a reliability in a low power time division access scheme of a sensor network, and more particularly, to a communication apparatus and method that may maximize a reliability in a low power time division access scheme using an asynchronous response, a channel hopping, and a congestion control function.
2. Description of the Related Art
Generally, a sensor node constituting a sensor network may operate by a battery. In order to maximize a battery lifetime, a battery consumption may need to decrease by lowering a duty cycle. One of schemes to lower the duty cycle may be a time division access scheme of allocating a time slot for each sensor node such as an Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 standard. However, the time division access scheme may not secure a completely reliable communication. Accordingly, there is a need for a communication apparatus and method that may satisfy a low power characteristic and may also maximize a reliability in a time division access scheme of a sensor network.
An aspect of the present invention provides a communication apparatus and method that may maximize a reliability in a low power time division access scheme of a sensor network using an asynchronous response, a channel hopping, and a congestion control function.
According to an aspect of the present invention, there is provided a sensor node for enhancing a reliability in a low power time division access scheme of a sensor network, the sensor node including: a transmitter to transmit a MAC frame to another sensor node in a first time slot that is allocated to the sensor node; and a receiver to receive a response frame with respect to the MAC frame from the other sensor node in a second time slot that is allocated to the other sensor node.
According to another aspect of the present invention, there is provided a communication method for enhancing a reliability in a low power time division access scheme, the method including: transmitting, by a first sensor node, a Media Access Control (MAC) frame to a second sensor node in a first time slot that is allocated to the first sensor node; and receiving, by the first sensor node, a response frame with respect to the MAC frame from the second sensor node in a second time slot that is allocated to the second sensor node.
Additional aspects, features, and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention.
According to embodiments of the present invention, there may be provided a communication apparatus and method that may maximize a reliability in a low power time division access scheme of a sensor network using an asynchronous response, a channel hopping, and a congestion control function.
These and/or other aspects, features, and advantages of the invention will become apparent and more readily appreciated from the following description of exemplary embodiments, taken in conjunction with the accompanying drawings of which:
Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. Exemplary embodiments are described below to explain the present invention by referring to the figures.
Referring to
The channel decision unit 103 may determine a beacon channel for transmitting a beacon and a data channel for transmitting data, so that the beacon channel and the data channel may not overlap.
Specifically, the channel decision unit 103 may determine a starting portion of a time slot as the fixed beacon channel and determine, as the data channel, the remaining portion of the time slot excluding the beacon channel, that is, a portion of a data area. The channel decision unit 103 may determine a different data channel for each data. Also, the channel decision unit 103 may select only a stable data channel using a noise strength, and a previous transmission/reception success rate, and the like.
When there is no data to be transmitted, the mode setting unit 105 may enter a sleep mode.
The transmitter 107 may transmit a Media Access Control (MAC) frame to the second sensor node 111 in a first time slot that is allocated to the first sensor node 101.
In this instance, the transmitter 107 may transmit a beacon to the second sensor node 111 via a beacon channel of the determined first time slot, and may hop from the beacon channel to a data channel to thereby transmit data of the MAC frame to the second sensor node 111 via the data channel. Here, the beacon may include a destination address of the second sensor node 111 of the reception side, and a number of the data channel used in the data area.
For example, as shown in
Referring again to
The receiver 109 may receive response data with respect to the transmitted data from the second sensor node 111 in the second time slot that is allocated to the second sensor node 111. Here, the second time slot may be different from the first time slot that is allocated to the first sensor node 101.
The receiver 109 may receive a beacon from the second sensor node 111 via a beacon channel of the second time slot, and may hop from the beacon channel to a data channel included in the beacon to thereby receive a response frame with respect to the MAC frame from the second sensor node 111 via the data channel. Here, the response frame may include an acknowledgement (ACK) frame or a NACK frame.
For example, as shown in
When a multi-time mode is set in a received beacon, the receiver 109 may receive the beacon and data from the second sensor node 111 in multiple time slots. Here, the multiple time slots may include the second time slot allocated to the second sensor node 111 and an added third time slot. The third time slot may be different from the first time slot allocated to the first sensor node 101, and the second time slot allocated to the second sensor node 111. In this instance, the second time slot and the third time slot may be continuous or discontinuous time slots. The continuous time slots may be used as if they are a single time slot.
For example, as shown in
Also, as shown in
Referring again to
The receiver 113 may receive the MAC frame from the first sensor node 101 in the first time slot that is allocated to the first sensor node 101. In this instance, the receiver 113 may scan the first time slot and receive a beacon from the first sensor node 101 via a beacon channel that is fixed to a starting portion of the first time slot. Next, the receiver 113 may hop from the beacon channel to a data channel and receive the MAC frame from the first sensor node 101 via the data channel. Here, the receiver 113 may be aware of the data channel using a number of the data channel that is included in the received beacon.
For example, as shown in
Also, when a multi-time mode is set in a received beacon, the receiver 113 may receive the beacon and data from the first sensor node 101 in multiple time slots. Here, the multiple time slots may include the first time slot allocated to the first sensor node 101, and an added third time slot. The third time slot may be different from the first time slot allocated to the first sensor node 101, and the second time slot allocated to the second sensor node 111.
When an address of the second sensor node 111 is not included in a destination address included in the beacon, the mode setting unit 105 may enter a sleep mode. Also, the mode setting unit 105 may recognize the existence of received data using the beacon. When no data is received, the mode setting unit 105 may enter the sleep mode.
The transmitter 117 may transmit, to the first sensor node 101, response data with respect to data that is received in the first time slot allocated to the first sensor node 101, in the second time slot allocated to the second sensor node 111. Here, the second time slot may be different from the first time slot allocated to the first sensor node 101.
The transmitter 117 may transmit a beacon to the first sensor node 101 via a beacon channel of the second time slot, hop from the beacon channel to a data channel included in the beacon, and transmit response data with respect to received data to the first sensor node 101 via the data channel.
For example, as shown in
When a transmission success rate with respect to transmitted data is less than or equal to a predetermined success rate, the transmitter 117 may set a multi-time mode in the beacon, and transmit the beacon and data to the first sensor node 101 in multiple time slots. Here, the multiple time slots may include the second time slot allocated to the second sensor node 111, and an added third time slot. The third time slot may be different from the first time slot allocated to the first sensor node 101, and the second time slot allocated to the second sensor node 111. In this instance, the second time slot and the third time slot may be continuous or discontinuous time slots. The continuous time slots may be used as if they are a single time slot.
In a communication apparatus for enhancing a reliability in a low power time division access scheme according to an embodiment of the present invention, a sensor node may transmit data only in a time slot allocated to the corresponding sensor node. Accordingly, when data is received in a reception time slot, the sensor node may transmit response data with respect to the received data in another allocated time slot, instead of transmitting the response data in the reception time slot. Through this, it is possible to prevent collision of data that are transmitted and are received between sensor nodes. Also, in a sensor network apparatus, a sensor node positioned around a sync node with much traffic may transmit and receive data in multiple time slots to thereby increase a number of occupied time slots and a traffic transfer rate. Through this, it is possible to solve a traffic unbalance with sensor nodes that are positioned in an end of a network with small traffic. Also, as all the sensor nodes fix a beacon channel in a starting portion of a time slot, it is possible to decrease a beacon scan time.
Referring to
The first sensor node 101 may be allocated with a time slot that is different from time slots that are allocated to the second sensor node 111 and the third sensor node 121. Also, the first sensor node 101 may be allocated with the same time slot as a time slot that is allocated to the fourth sensor node 131, and may also be assigned with a different time slot. Here, the fourth sensor node 131 may be separated away from the first sensor node 101 by greater than two hops.
Even when the first sensor node 101 is allocated with the same time slot as the time slot allocated to the fourth sensor node 131 that is located around a 2-hop boundary, the first sensor node 101 may transmit data to the second sensor node 111 via a different channel from a channel of the fourth sensor node 131. Through this, the second sensor node 111 may receive data from the first sensor node 101 without interference of the fourth sensor node 131 against the data.
Referring to
Specifically, the first sensor node may determine a starting portion of the first time slot as a fixed beacon channel, and may determine the remaining portion of the first time slot excluding the beacon channel, that is, a portion of a data area, as a data channel.
Next, the first sensor node may transmit a beacon to the second sensor node via the beacon channel of the first time slot, hop from the beacon channel to the data channel, and transmit data of a MAC frame to the second sensor node via the data channel. Here, the beacon may include a destination address with respect to a sensor node of a reception side, and a number of a data channel used in the data area.
Where there is no data to be transmitted, the first sensor node may enter a sleep mode.
When a transmission success rate with respect to the transmitted data is less than or equal to a predetermined success rate in operation S703, the first sensor node may set a multi-time mode in the beacon in operation S705. In operation S707, the first sensor node may transmit the beacon and data to the second sensor node in multiple time slots.
Specifically, the first sensor node may transmit the beacon and data to the second sensor node in multiple time slots including the first time slot and an added third time slot. Here, the added third time slot may be different from the first time slot allocated to the first sensor node, and the second time slot allocated to the second sensor node.
In operation S709, the first sensor node may receive response data with respect to the received data from the second sensor node in the second time slot that is allocated to the second sensor node.
Specifically, the first sensor node may receive the beacon from the second sensor node via a beacon channel of the second time slot, hop from the beacon channel to a data channel included in the beacon, and receive a response frame with respect to a MAC frame from the second sensor node via the data channel. Here, the second time slot may be different from the first time slot allocated to the first sensor node.
Referring to
Specifically, the second sensor node may scan the first time slot and receive the beacon via a beacon channel that is fixed in a starting portion of the first time slot. Next, the second sensor node may hop from the beacon channel to a data channel to receive a MAC frame from the first sensor node via the data channel. Here, the second sensor node may be aware of the data channel using a number of the data channel that is included in the received beacon.
When an address of the second sensor node is not included in a destination address included in the beacon, the second sensor node may enter a sleep mode. Also, the second sensor node may recognize the existence of received data using the received beacon. When no data is received, the second sensor node may enter the sleep mode.
When a multi-time mode is set in the received beacon in operation S803, the second sensor node may receive the beacon and data from the first sensor node in multiple time slots in operation S805.
Specifically, the second sensor node may receive the beacon and data from the first sensor node in the multiple time slots including the first time slot that is allocated to the first time slot, and an added third time slot. Here, the added third time slot may be different from the first time slot allocated to the first sensor node, and the second time slot allocated to the second sensor node.
In operation S807, the second sensor node may transmit response data with respect to data that is received in the first time slot allocated to the first sensor node, to the first sensor node in the second time slot allocated to the second sensor node.
Specifically, the second sensor node may transmit the beacon to the first sensor node via a beacon channel of the second time slot and hop from the beacon channel to a data channel include in the beacon. Next, the second sensor node may transmit a response frame with respect to a MAC frame to the first sensor node via the data channel. Here, the second time slot may be different from the first time slot allocated to the first sensor node.
In the aforementioned communication method for enhancing a reliability in the low power time division access scheme according to an embodiment of the present invention, each of sensor nodes may transmit data only in a time slot that is allocated to the corresponding sensor node. Accordingly, when data is received in a reception time slot, each of the sensor nodes may transmit response data with respect to the received data in another allocated time slot, instead of transmitting the response data in the reception time slot. Through this, it is possible to prevent collision of data that are transmitted and are received between sensor nodes. Also, each of the sensor nodes may use a different data channel for each data through hopping of the data channel. Accordingly, it is possible to decrease interference between the sensor nodes. Also, when there is no data to be transmitted and be received, each of the sensor nodes may enter the sleep mode to decrease a duty cycle. Through this, a battery consumption may be reduced.
Although a few exemplary embodiments of the present invention have been shown and described, the present invention is not limited to the described exemplary embodiments. Instead, it would be appreciated by those skilled in the art that changes may be made to these exemplary embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2008-0122336 | Dec 2008 | KR | national |
