KR20070106097A - Method and apparatus for low power communications in a beacon-enabled wireless communications system - Google Patents

Abstract

A low power communication method in a beacon type wireless communication system is provided to allow a wireless device to analyze a beacon frame transmitted from an upper node and maintain an active state only when there is data to be received by the wireless device. A lower node receives a beacon frame from an upper node and analyzes a pending address field of the beacon frame. The lower node checks whether there is data to be transmitted from the upper node to the lower node because the beacon frame includes an address of the lower node in a pending address field or whether there is data to be transmitted by the lower node to the upper node. When there is data to be received from the upper node or when there is data to be transmitted to the upper node, the lower node maintains an active mode during an active interval set by a system or the upper node or time required for data transmission. When the active interval is terminated or when data transmission is completed, the lower node is converted into an inactive mode or a sleep mode.

Description

Low power communication method in beacon wireless communication system {Method and Apparatus for low power communications in a beacon-enabled wireless communications system}

1 is a beacon transmission signal frame structure diagram used in a conventional wireless communication system.

2 is a structural diagram of a beacon frame used in the WPAN based on IEEE 802.15.4, which is one of conventional wireless communication systems.

3A and 3B are signal transmission flowcharts of a low power communication method in a wireless communication system according to an embodiment of the present invention.

4 is a structural diagram of a pending address field of a beacon frame in a wireless communication system according to an embodiment of the present invention.

5 is a flowchart of a low power communication method in a wireless communication system according to an embodiment of the present invention.

The present invention relates to a communication method in a wireless communication system, and more particularly, to a low power communication method for minimizing power consumption in a beacon-type wireless communication system using a beacon signal.

In general, the wireless network technology is largely classified into a wireless local area network (WLAN) technology and a wireless personal area network (WPAN) technology according to a recognition distance. WLAN is a technology based on IEEE 802.11 that can connect to a backbone network within a radius of 100m, whereas WPAN is a technology based on IEEE 802.15 that enables wireless connection between various devices within a radius of 10m with a focus on personal mobile devices. The technologies include Bluetooth, ZigBee, and Ultra Wide Band (UWB).

1 illustrates a beacon transmission signal frame structure used in a conventional wireless communication system.

As shown in FIG. 1, a frame structure that divides the time between two consecutive beacon frames into an active section and an inactive section is called a superframe structure.

In wireless networks such as WLANs and WPANs, it is very important to minimize battery power consumption in mobile devices because fixed devices that function as upper nodes typically receive trunk power, while mobile devices that function as lower nodes often operate on battery power. It becomes an important function. Accordingly, many mobile wireless devices have an active mode and an inactive mode (or sleep mode) as operating modes, and use the transmission signal of the superframe structure as described above to support this.

In the superframe structure, access to the channel and data transmission and reception are allowed only in the active period, and the power consumption of the device is reduced because all the wireless devices enter the sleep state in the inactive period. The active mode is an active mode in which wireless devices access a channel to transmit and receive data, and the inactive mode is an inactive mode or a low power mode in which the wireless devices stop operating some or all of the components. Typically, wireless devices cannot transmit or receive data in a low power mode.

The length of the active section and the inactive section is determined by the information of the beacon frame sent from the upper node to the lower node. The beacon frame is normally transmitted periodically from the upper node to the lower node for the purpose of providing synchronization of the system, identifying the wireless network, specifying the frame format, and the like. Wireless devices that are lower nodes receive the beacons generated by the upper nodes and interpret the beacons to determine the length of the active period.

The active period is set identically for all upper nodes and lower nodes belonging to the same wireless network, and communication between upper nodes and lower nodes is performed only during the active period following this beacon frame.

2 illustrates a structure of a beacon frame used in a WPAN based on IEEE 802.15.4, which is one of conventional wireless communication systems.

The beacon frame is composed of a MAC HeadeR (MHR), a MAC Service Data Unit (MSDU), and a MAC FooteR (MFR). MHR consists of MAC frame control field, beacon sequence number field (BSN) and addressing fields (MSD), and MSDU includes superframe specification field and GTS field. ), Pending address fields, and Beacon payload fields, and the MFR is composed of a 16-bit frame check sequence (FCS).

The pending address field of the MSDU includes an address list of a lower node to receive data transmitted from an upper node. The address list of the lower node can be changed every beacon frame according to the operation status of the system, and the lower node always receives the beacon to check whether there is data to be transmitted to it.

Data to be transmitted from the upper node to the lower node is included in an active period following the beacon frame, and all lower nodes maintain their wireless devices in the active mode during the active period for receiving data from the upper node.

However, during a certain active period, the upper node and all the lower nodes do not communicate at the same time, and only the lower node having data to be transmitted from the upper node or data to be transmitted to the upper node in the active period communicates with the upper node. In the meantime, the other lower nodes maintain the active mode for a predetermined time according to the setting of the active period according to the system synchronization determined by the beacon frame, and then switch to the inactive mode.

A wireless device constituting an individual lower node communicates with a higher node only during a specific active period that requires communication between itself and a higher node, and most lower nodes that do not communicate data with a higher node during the active period are in the interval. It will remain in standby in active mode for a while. As a result, wireless devices constituting individual sub-nodes consume power in active mode by switching between active mode and inactive mode every beacon frame period, which is an active mode in which most of the system power is unnecessary from the perspective of the whole system. It is assigned to the maintenance of.

For example, if the period of the beacon is 1 second and the active period is 1/8 second, the inactive period is 7/8 seconds. Given that the typical length of the beacon frame is 1/1000 second, all lower nodes consume power for 1/8 second every 1 second. In other words, all the subordinates are always in an active state for a certain time even when communication is not necessary. Thus, the uniformly maintained active state is very inefficient in terms of power consumption as a whole.

An object of the present invention is to provide a low power communication method and system for selectively adjusting the active state of lower nodes in order to minimize power consumption in a beacon-type wireless communication system.

Another object of the present invention is to provide a wireless device that maintains an active state only when there is data to be received by analyzing a beacon frame transmitted from a higher node in order to minimize power consumption in a beacon-type wireless communication system. .

In addition, the present invention to provide a wireless device that is switched to the inactive state after completing the signal transmission to the upper node in the shortest time as soon as receiving the beacon from the upper node in order to minimize the power consumption in the beacon wireless communication system. The purpose.

The present invention is a beacon scheme in which a beacon frame is periodically transmitted from an upper node to a plurality of lower nodes, and an active period and an inactive period related to signal transmission between the upper node and the lower node are determined by the beacon frame. In a wireless communication system, each of the sub-nodes analyzes the beacon frame and maintains an active mode during the active period when there is data to be transmitted to itself, and immediately in an inactive mode when there is no data to be transmitted to itself. Characterized in that the conversion.

The present invention also provides a low power communication method in a beacon wireless communication system, comprising: inserting an extended address of a lower node requiring data transmission from an upper node into a beacon frame; Transmitting the beacon frame from the upper node to all lower nodes in the wireless communication system; Analyzing the beacon frame at each of the lower nodes to determine whether data is transmitted; And each of the lower nodes maintains an active mode only when there is data to be transmitted to the upper node or data to be transmitted to the upper node.

Furthermore, the present invention provides a beacon scheme in which a beacon frame is periodically transmitted from an upper node to a plurality of lower nodes, and an active period and an inactive period related to signal transmission between the upper node and the lower node are determined by the beacon frame. In a wireless device configuring the lower node in a wireless communication system, the beacon frame transmitted from the upper node is analyzed to maintain an active state only when there is data to be received or data to be transmitted to the upper node. It features.

Hereinafter, a low power communication method, system, and wireless device of the present invention will be described with reference to the drawings showing an embodiment of the present invention.

3A and 3B are structure diagrams of transmission signal frames in a wireless communication system according to an embodiment of the present invention.

FIG. 3A illustrates a transmission signal frame structure when data communication exists between an upper node and a specific lower node during one beacon interval.

First, when the upper node has data to be transmitted to a specific lower node, when the upper node transmits a beacon frame, the wireless device, which is the lower node, receives the beacon frame and an address indicating a lower node having data to be transmitted from the upper node. It checks whether it is included in the list field, maintains its operation mode in an active state, and performs data reception during the active period.

In addition, when the specific lower node has data to be transmitted to the upper node, the lower node performs data transmission during the active period after receiving the beacon from the upper node. In this case, as soon as the lower node receives the beacon from the upper node in order to minimize power consumption, the lower node completes data transmission to the upper node in the shortest time and then switches to the inactive state or the sleep mode. In this case, the lower node which has completed the data transmission is switched to the inactive state within the active period defined by the system.

3B is a transmission signal frame structure when there is no data communication between an upper node and a specific lower node during the same beacon period.

First, if the upper node does not have data to be transmitted to the lower node, when the upper node transmits the beacon frame, the wireless device, the lower node receives the beacon frame, and confirms that it does not include itself in the address list field. It immediately goes into inactive or sleep mode to minimize power consumption.

In addition, when a lower node does not have data to be transmitted to a higher node, the lower node receives a beacon periodically according to a beacon period and immediately goes into inactive or sleep mode to minimize power consumption.

4 is a structural diagram of a pending address field of a beacon frame in a wireless communication system according to an embodiment of the present invention.

The structure of a beacon frame transmitted from an upper node to a lower node shows in detail a pending address field including an address list of a lower node to which data is to be transmitted from an upper node.

The pending address field includes a pending address specification field and an address list field indicating the type and number of address of the lower node to receive data transmitted from the upper node.

The size of the address list field is determined by a value determined in the pending address structure field of the beacon frame, and includes an address list of a lower node to which data is to be transmitted from the current upper node. The Number of short address pending subfield pending in the pending address structure field indicates the number of 16-bit short addresses included in the address list field of the beacon frame. In addition, the number of extended address pending subfields indicates the number of 64-bit extended addresses included in the address list field of the beacon frame.

Typically, when an upper node operates to form its own network, lower nodes are incorporated into the network through an association process. At this time, the upper node allocates a short address for each lower node indicating the relative address of each lower node in the corresponding network by 16 bits. In the case of communication without association, since the relative position in the network is not determined between the upper node and the lower node, both the upper node and the lower node communicate using the other party's extension address.

In the wireless communication system of the present embodiment, while data communication is not required between an upper node and a specific lower node, the lower node transitions from the sleep mode to the active mode according to the beacon period, and immediately after receiving the beacon frame, the sleep mode immediately. Return to. Therefore, the association process may not be performed between the upper node and the lower node, in which case the upper node communicates using the extension address of the lower node. In this case, the number of short addresses held in the pending address structure field of the beacon frame is set to 0, and only an extended address exists in the address list.

5 is a flowchart of a low power communication method in a wireless communication system according to an embodiment of the present invention.

The upper node periodically transmits a beacon frame to a plurality of lower nodes, and each lower node performs the steps shown in FIG. 5 by itself.

First, the lower node receives the beacon frame from the upper node, and analyzes the pending address field of the beacon frame (step S110).

Subsequently, the lower node includes its own address in the pending address field of the beacon frame to determine whether there is data to be transmitted from the upper node to itself or whether the lower node has data to be transmitted to the upper node (step 120).

If it is determined that there is data to be transmitted from the higher node or data to be transmitted to the higher node, the active mode is maintained in the system or during the active period set by the higher node or for a time required for data transmission (step 130).

Subsequently, the lower node switches to the inactive mode or the sleep mode according to the end of the active period or the completion of the data transmission (step 140).

On the other hand, if it is determined in step 120 that data transmission is not necessary during the beacon period, the lower node immediately switches to inactive mode or sleep mode to minimize power consumption (step 150).

In the inactive mode or the sleep mode, the wireless device corresponding to the lower node may selectively switch some or all of the components, such as a transmit / receive module such as an RF chip and a main controller (MCU), to the sleep mode.

Meanwhile, the present invention can be optimized and applied in a Zigbee network, which is a WPAN network based on IEEE 802.15.4. The devices used in the Zigbee network have a reduced functional device (RFD) and a network that operate with a minimum protocol that can operate in the network. It is classified as a Full Functional Device (FFD) that operates with a complete set of protocols. RFD has no routing function, no communication function between RFDs, and is mainly used as an end device for simple applications using limited resources, memory, and batteries. FFD has a multi-hop routing function using multiple frequencies. It can communicate with multiple RFDs and FFDs, and can transmit beacon signals to function as coordinators and routers. Therefore, in the Zigbee network, a coordinator or router which is an FFD is mainly a device corresponding to an upper node of the present invention, and a terminal which is an RFD is a device mainly corresponding to a lower node of the present invention.

ZigBee terminals operate as batteries mainly as sub-nodes of the network. The batteries may be provided as separate batteries connected to the terminals or embedded in the terminals. Since the Zigbee network is mainly used as a sensor network, the Zigbee terminal may be used in the form of being attached to an object to be sensed or a packaging material of the object.

According to the present invention, there is provided a low power communication method and system for selectively adjusting the active state of lower nodes in order to minimize power consumption in a beacon wireless communication system.

In addition, according to the present invention, in order to minimize power consumption in a beacon-type wireless communication system, a wireless device is provided that maintains an active state only when there is data to be received by analyzing a beacon frame transmitted from a higher node.

In addition, the present invention provides a wireless device that is switched to the inactive state after completing the signal transmission to the upper node in the shortest time as soon as receiving the beacon from the upper node in order to minimize power consumption in the beacon wireless communication system.

Although the present invention has been described above according to a preferred embodiment of the present invention, the scope of the present invention is not limited to the above embodiments or the accompanying drawings, and is not limited to the scope of the present invention as set forth in the appended claims. Various variations are possible in.

Claims (10)

In a beacon wireless communication system in which a beacon frame is periodically transmitted from an upper node to a plurality of lower nodes, and an active period and an inactive period related to signal transmission between the upper node and the lower node are determined by the beacon frame. , Each of the lower nodes analyzes the beacon frame and maintains an active mode during the active period when there is data to be transmitted to itself, and immediately switches to an inactive mode when there is no data to be transmitted to itself. Beacon wireless communication system. The method of claim 1, If there is data to be transmitted from the lower node to the upper node, the lower node transmits the data to the upper node after receiving the beacon frame, characterized in that the beacon-type wireless communication system. The method according to claim 1 or 2, And the upper node inserts an extension address of a lower node to transmit data into the beacon frame. The method of claim 4, wherein The system is a beacon wireless communication system, characterized in that the WPAN system according to the IEEE 802.15 standard. The method of claim 5, The system is a beacon wireless communication system, characterized in that the ZigBee system according to the IEEE 802.15.4 standard. A low power communication method in a beacon wireless communication system, Inserting an extended address of a lower node requiring data transmission in an upper node into a beacon frame; Transmitting the beacon frame from the upper node to all lower nodes in the wireless communication system; Analyzing the beacon frame at each of the lower nodes to determine whether data is transmitted; And And each lower node maintains an active mode only when there is data to be transmitted to it or data to be transmitted to the higher node. The method of claim 6, The lower node further comprises the step of transmitting the data using the extension address of the upper node when transmitting data to the upper node. The method according to claim 6 or 7, The lower node further comprises the step of switching to an inactive mode as soon as the data transmission is completed during the active mode. In the beacon-type wireless communication system, a beacon frame is periodically transmitted from an upper node to a plurality of lower nodes, and an active period and an inactive period related to signal transmission between the upper node and the lower node are determined by the beacon frame. In a wireless device constituting a node, And analyzing the beacon frame transmitted from the upper node and maintaining an active state only when there is data to be received or data to be transmitted to the upper node. The method of claim 9, The wireless device is converted to an inactive state after completing the data transmission and reception with the upper node in the shortest time as soon as receiving the beacon from the upper node.

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