Method and device for operation based on multiple channels in sensor network

A method of transmitting control information by an end node in a wireless communication system supporting multi-channel transmission includes: transmitting control information to a center node on a first channel among multiple channels within a control period of a wireless frame when the first channel is in an idle state; transmitting the control information to the center node on a second channel when the first channel is not in the idle state and the second channel is in the idle state, the second channel being selected from channels other than the first channel among the multiple channels; and transmitting the control information to the center node in a subsequent wireless frame when the second channel is not in the idle state.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2017-0061479, filed May 18, 2017, the entire content of which is incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates generally to a sensor network. More particularly, the present disclosure relates to a method and device for operation based on multiple channels in a sensor network.

2. Description of Related Art

In a conventional sensor network, one network (e.g., a personal area network (PAN)) is configured for each channel. In a single-tier (tier-1) network structure in which one or more sensor devices are connected to one PAN coordinator as well as in a multi-tier (tier-2) network structure in which one or more intermediate nodes are connected to one PAN coordinator and one or more sensor devices are connected to each of the intermediate nodes, one PAN is configured per channel. In this case, in order to share the resource among multiple sensor devices on one channel, a time-division multiplexing scheme is applied, and thus the transfer rate that may be supported in one PAN is limited.

Thus, a method of overcoming the limitation of transfer rate on one wireless channel is required.

SUMMARY OF THE INVENTION

Accordingly, the present disclosure has been made keeping in mind the above problems occurring in the related art, and is intended to propose a method and device for supporting multi-channel operation.

Also, the present disclosure is intended to propose a method and device, which is an end node, for transmitting and receiving control information and data according to a wireless frame structure supporting multi-channel operation.

Also, the present disclosure is intended to propose a method and device, which is a center node, for transmitting and receiving control information and data according to a wireless frame structure supporting multi-channel operation.

It is to be understood that technical problems to be solved by the present disclosure are not limited to the aforementioned technical problems and other technical problems which are not mentioned will be apparent from the following description to a person with an ordinary skill in the art to which the present disclosure pertains.

The object of the present invention can be achieved by providing a method of transmitting control information by an end node in a wireless communication system supporting multi-channel transmission, the method comprising: transmitting control information to a center node on a first channel among multiple channels within a control period of a wireless frame when the first channel is in an idle state; transmitting the control information to the center node on a second channel when the first channel is not in the idle state and the second channel is in the idle state, wherein the second channel being selected from channels other than the first channel among the multiple channels; and transmitting the control information to the center node in a subsequent wireless frame when the second channel is not in the idle state.

In another aspect of the present invention, provided herein an end node device that transmits control information in a wireless communication system supporting multi-channel transmission, the end node device comprising: a transceiver; a memory; and a processor, wherein the processor is configured to, within a control period of a wireless frame, transmit control information to a center node on a first channel when the first channel is in an idle state among multiple channels; transmit the control information to the center node on a second channel when the first channel is not in the idle state and the second channel selected from channels other than the first channel among the multiple channels is in the idle state; and transmit the control information to the center node in a subsequent wireless frame when the second channel is not in the idle state.

In another aspect of the present invention, a method of operating a center node in a wireless communication system supporting multi-channel transmission, the method comprising: transmitting control information to an end node on a first channel among multiple channels within a control period of a wireless frame; and receiving the control information from the end node on the first channel or on a second channel among the multiple channels within the control period of the wireless frame, wherein when the first channel is not in an idle state, the second channel is a channel selected randomly by the end node.

In another aspect of the present invention, a center node device that operates in a wireless communication system supporting multi-channel transmission, the center node device comprising: a a transceiver; a memory; and a processor, wherein the processor is configured to, transmit control information to an end node on a first channel among multiple channels within a control period of a wireless frame; receive the control information from the end node on the first channel or on a second channel among the multiple channels within the control period of the wireless frame, wherein when the first channel is not in an idle state, the second channel is a channel selected randomly by the end node.

In another aspect of the present invention, the control period of the wireless frame includes a control information reception period of the end node and a control information transmission period of the end node.

In another aspect of the present invention, the wireless frame includes the control period and a data period.

In another aspect of the present invention, in a specific time period determined based on resource assignment information within the data period of the wireless frame, the end node transmits data to the center node on a third channel determined based on the resource assignment information among the multiple channels.

In another aspect of the present invention, the resource assignment information includes information on a channel on which transmission of the end node is allowed, a time at which transmission of the end node is allowed, a transmission size of the end node, and a transmission cycle of the end node.

In another aspect of the present invention, in the specific time period, data transmission on the third channel from the end node to the center node is performed simultaneously with data transmission on a fourth channel from, other than the end node, another end node to the center node.

In another aspect of the present invention, the third channel is one of the first channel and the second channel.

In another aspect of the present invention, the third channel is a channel other than the first channel and the second channel.

In another aspect of the present invention, the control information transmitted on the first channel is received by a master node of the center node, and the control information transmitted on the second channel is received by one sub-node corresponding to the second channel among one or more sub-nodes of the center node.

In another aspect of the present invention, the end node receives a beacon frame from the center node at a start time of the wireless frame.

In another aspect of the present invention, the control information includes at least one of registration request information and resource assignment request information of the end node.

In addition, the features briefly summarized above for this disclosure are exemplary aspects of the detailed description of the disclosure which follow, and are not intended to limit the scope of the disclosure.

According to the present disclosure, the method and device, which is the end node, for transmitting and receiving control information and data according to a wireless frame structure supporting multi-channel operation is provided.

According to the present disclosure, the method and device, which is the center node, for transmitting and receiving control information and data according to a wireless frame structure supporting multi-channel operation is provided.

Effects that may be obtained from the present disclosure will not be limited to only the above described effects. In addition, other effects which are not described herein will be apparent to those skilled in the art from the following description.

DETAILED DESCRIPTION OF THE INVENTION

Hereinbelow, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings such that the disclosure can be easily embodied by one of ordinary skill in the art to which this disclosure belongs. However, the present disclosure may be variously embodied, without being limited to the exemplary embodiments.

In describing embodiments of the present disclosure, it is noted that when the detailed description of known configurations or functions related to the present disclosure may make the gist of the present disclosure unclear, the detailed description of thereof will be omitted. Also, portions that are not related to the present disclosure are omitted in the drawings, and like reference numerals designate like elements.

In the present disclosure, when an element is “coupled to”, “combined with”, or “connected to” another element, it can be directly coupled to the other element or intervening elements may be present therebetween. Also, when a constituent “comprises” or “includes” an element, unless there is another opposite description thereto, the constituent does not exclude other elements but may further include the elements.

In the present disclosure, the terms “first”, “second”, etc. are only used to distinguish one element from another element. Unless specifically stated otherwise, the terms do not denote an order or importance. Thus, without departing from the scope of the present disclosure, a first element of an embodiment could be termed a second element of another embodiment. Similarly, a second element of an embodiment could also be termed a first element of another embodiment.

In the present disclosure, elements that are distinguished from each other to clearly describe each feature do not necessarily denote that the elements are separated. That is, a plurality of elements may be integrated into one hardware or software unit, or one element may be distributed into a plurality of hardware or software units. Accordingly, even if not mentioned, the integrated or distributed embodiments are included in the scope of the present disclosure.

In the present disclosure, elements described in various embodiments do not denote essential elements, and some of the elements may be optional. Accordingly, an embodiment that includes a subset of elements described in another embodiment is included in the scope of the present disclosure. Also, an embodiment that includes the elements which are described in the various embodiments and additional other elements is included in the scope of the present disclosure.

Center node: a node that configures and manages a network supporting multiple frequencies (or multiple channels). The center node includes one master node and one or more sub-nodes. As an example, there is a coordinator in a sensor network.

Master node: a node in charge of sending and receiving on a basic frequency (or a basic channel) in the center node.

Sub-node: a node in charge of receiving on each frequency (or channel) in the center node.

End node: a node that is connected to the center node, exchanges control information with the center node, and transmits data to the center node. As an example, there is a sensor device in a sensor network.

The definitions of the terms are merely illustrative, and the scope of the present disclosure is not limited by the definitions. For example, the definitions of the terms do not exclude basic meanings of the terms, which can be easily understood by a person skilled in the art.

Hereinafter, a method and device for operation based on multiple channels according to the present disclosure will be described.

Wireless sensor communication is a communication method of transmitting data (e.g., sensing information) generated by a sensor to a final destination in a wireless manner. The wireless sensor communication is based on low data-transfer rate, compared to cellular communication or mobile communication such as 3GPP LIE, and may support a battery-driven environment in an environment where it is difficult to supply power to sensor devices by wire.

Thus, in the wireless sensor communication, devices are required to support operation in a limited power condition, so that intensity of the signal transmitted by the device is also limited, which may result in relatively short radio wave coverage.

IEEE 802.15.4 is developed as the representative international standard for the wireless sensor communication. IEEE 802.15.4 defines the physical layer (PHY) for low power communication, the medium access control (MAC) layer, and an interface with the upper layers for application service. The basic performance level defined in IEEE 802.15.4 ensures the data-transfer rate of up to 250 kbps when offset quadrature phase-shift keying (OQPSK) modulation applies, and a basic channel coding mechanism is not included for low power consumption.

FIG. 1is a view illustrating an example of channel configuration in 2.4 GHz band

FIG. 1shows 16 exemplary channels defined in the frequency domain. The width of each channel may be defined as 5 MHz, and intervals between center frequencies of respective channels may be defined also as 5 MHz. For example, a first channel (CH1) may be defined at a frequency position with the center frequency (Fc) of 2405 MHz, and a second channel (CH2) may be defined at a frequency position with the center frequency of 2410 MHz. Similarly, a sixth channel (CH16) may be defined at a frequency position with the center frequency of 2475 MHz.

The example ofFIG. 1shows that multiple channels divided in the frequency domain may be defined in the operating frequency band of the wireless sensor communication. The scope of the present disclosure is not limited to the example of the operating frequency band, the number of channels, the center frequency of the channel, etc.

As shown inFIG. 1, total 16 channels in 5 MHz units may be defined and operated, and one a personal area network (PAN) may be configured for each channel. One PAN is a basic unit of the sensor network.

FIG. 2is a view illustrating an example of a PAN structure.

The PAN may consist of one PAN coordinator100and N devices200_1,200_2, . . . , and2001_N. The example ofFIG. 2shows a single-tier (tier-1) PAN structure in which one PAN coordinator100is in direct association with one or more devices200.

FIG. 3is a view illustrating an example of a wireless frame format.

In the example ofFIG. 3, the PAN coordinator100may transmit a beacon frame300. The beacon frame contains information related to the PAN configuration, and may be broadcast to all devices200in the PAN. Also, the beacon frame300may be transmitted periodically at predetermined time intervals. The time interval at which the beacon frame300is transmitted may be referred to as a beacon interval (BI)305. Each of the devices in the PAN receives the beacon frame300and performs time synchronization based thereon, and then performs data transmission/reception.

An active period310is a time period during which data transmission/reception is performed, and an inactive period340is a time period during which data transmission/reception is not performed.

The active period310may include a contention access period (CAP)320and a contention free period (CFP)330.

In the CAP320, data transmission of an arbitrary device may be performed according to carrier sense multiple access with collision avoidance (CSMA/CA) scheme in which a device to transmit data senses a wireless channel first and performs transmission only when the channel is idle (i.e., when transmission of another device is not sensed).

In the CFP320, transmission may be performed on the basis of a time slot (i.e., a guaranteed time slot (GTS)) in which transmission of only a particular device is allowed and transmission of other devices is not allowed. For example, the GTS332, the GTS334, and the GTS336may be assigned to different devices.

Thus, in the CAP320, all devices in the PAN may attempt to transmit data anytime, so that collision may occur when different devices attempt to perform transmission at the same time. In the meantime, in the CFP330, a unique transmission/reception time (GTS) for a particular device is assigned to avoid transmission collision.

A time period containing a transmission period of the beacon frame300, the CAP320, and the CFP330may be referred to as superframe duration (SD)350. In the example ofFIG. 3, the active period310may be defined as a combination, excluding the transmission period of the beacon frame300, of the CAP320and the CFP330. However, the active period310is not limited thereto, the active period310may be defined as the same time period as the SD350.

When using the wireless frame structure as shown inFIG. 3, the number of GTSs332,334, and336that may be assigned within the active period310or the SD350is limited. For example, when the number of devices200in association with the PAN coordinator100is large, time periods of the GTSs to be assigned to the devices are insufficient.

Also, the device200in the PAN basically attempts to perform transmission in the CAP320in CSMA/CA scheme, which will be described in detail with reference toFIG. 4.

FIG. 4is a view illustrating operation of a device in CSMA/CA scheme.

The device having data to be transmitted may attempt to perform channel access in the CAP320in CSMA/CA scheme, after receiving the beacon frame300and completing synchronization, etc.

First, the device may initiate backoff400in an arbitrary slot of the CAP320. Backoff400means an operation that delays transmission during the number of time slots (or backoff counter) determined based on a value randomly selected within a given range. By performing backoff400operation, the values of the back off counters selected randomly by several devices are likely to be different from each other, such that the number of devices that simultaneously start data transmission may be reduced. For example, the unit backoff period may be given as the length of 20 symbols. The period from the start to the end of the entire backoff counter may contain 2N−1 unit backoff periods, and the value of N may be a value randomly selected by the device.

When the backoff400period is completed (or when countdown of the backoff counter is completed), the device may perform carrier sensing410in which whether or not the wireless channel is in an idle state is determined. Carrier sensing410may include a method of checking whether reception power exceeding a predetermined threshold value is present on the wireless channel, etc. When the reception power exceeding the predetermined threshold value is sensed, it may be determined that the wireless channel is in use (busy) and transmission may be further delayed until the wireless channel is in the idle state. When the reception power which is equal to or less than the predetermined threshold value is sensed, it may be determined that the wireless channel is in an idle state and transmission420may start. The period in which the device performs carrier sensing may be the period of first eight symbols each time slot, rather than the entire period of the time slot.

Alternatively, backoff400and carrier sensing410operations may be performed in such a manner as to count down the backoff counter, only when the wireless channel is in the idle state.

After completing transmission420, the device may wait for receiving acknowledgement (ACK) information. An ACK may be information indicating that a target device has successfully received data. For example, the length of time the device waits for ACK reception may be given as the length of 22 symbols. When the device does not start ACK reception within the period of 12 symbols, it may be determined that previous transmission has failed, and re-transmission, etc. may be performed.

When ACK reception440is performed within the ACK reception waiting time, the device may determine that previous transmission was successful. The length of the ACK packet may be, for example, a length of 22 symbols.

As described above with reference toFIG. 4, the device may continuously monitor within the CAP320whether or not the wireless channel is occupied. When operating in this manner, the device continuously consumes power for a reception attempt within the CAP320.

FIG. 5is a view illustrating an additional example of a PAN structure.

In order to solve the problem that only limited communication coverage is supported due to low transmission power in the single-tier PAN structure as shown in the example ofFIG. 2, a device similar to a relay in a mobile communication system may be introduced to extend the communication coverage.

Unlike devices200_x,200_y, etc. in direct association with the highest PAN coordinator100, the example ofFIG. 5shows a structure where devices200_1,200_2, . . . , and200_M are in direct association with a coordinator150, which is an intermediate node, and the coordinator150is in direct association with the highest PAN coordinator100. That is, the coordinator150may function as a device in terms of the PAN coordinator100, and may function as a coordinator in terms of devices200_1,200_2, . . . , and200_M. The PAN structure as shown in the example ofFIG. 5may be a multi-tier (tier-2) PAN structure.

FIG. 6is a view illustrating an additional example of a wireless frame format.

Within an inactive period340of a beacon interval305of the PAN coordinator100, the coordinator150may transmit its own beacon frame600(i.e., a coordinator beacon frame), and may configure its own active period610(i.e., a coordinator active period).

The coordinator150may transmit a beacon frame independently of the PAN coordinator100, and a beacon period of the coordinator150may form a unique wireless frame of each coordinator.

That is, by using a particular period of the inactive period340of the PAN coordinator100, the coordinator150may transmit its beacon frame600to be in association with its sub-devices200_1,200_2, . . . , and200_M and to perform synchronization, and may set the coordinator active period610to induce data transmission/reception for the sub-devices200_1,200_2, . . . , and200_M.

When the wireless frame is configured as shown in the example ofFIG. 6, a transmission period of each coordinator in the entire wireless frame may be a type of time division multiplexing (TDM) structure divided in the time domain.

Here, the wireless frame structure defined in IEEE 802.15.4 has a restriction that the use of the GTS is not allowed for the devices200_1,200_2, . . . , and200_M in association with the coordinator150which is an intermediate node. That is, for the devices200_1,200_2, . . . , and200_M in association with the coordinator150which is an intermediate node, contention based transmission using the CAP610is only allowed. This restriction on the multi-tier PAN structure does not allow dedicated channel transmission (i.e., the GTS) using the coordinator150, and thus the fixed transfer rate of the device may not be guaranteed. Also, the same channel (i.e., the same frequency) is used by the devices in association with the coordinator150which is an intermediate node of the PAN coordinator100, and by the devices in direct association with the PAN coordinator100. Therefore, the number of devices that may be acceptable in the entire multi-tier PAN structure configured by one PAN coordinator100is limited, and the transfer rate for each device is also limited. Thus, when an application requires a high fixed transfer rate, the scope of service to be provided by using the multi-tier PAN structure as shown inFIG. 5and the wireless frame format as shown inFIG. 6may be limited.

As described above, when only one frequency (or one channel) is supported in one PAN structure, there is a problem that the number of acceptable devices and the fixed transfer rate may not be guaranteed.

In the present disclosure, in order to solve the problem and to enhance efficiency of low power device operation and of wireless resource utilization, a method of supporting multiple frequencies (or multiple channels) in one PAN structure will be described.

According to the various examples of the present disclosure, one center node may perform control to support and to manage overall transmission/reception using multiple wireless channels. More specifically, according to the various examples of the present disclosure, a wireless frame structure where the control period and the data period are separated for each channel (or frequency) may be provided. Thus, the efficiency of wireless resource utilization may be enhanced, an application requiring a higher fixed transfer rate may be supported, and the overall system throughput may be enhanced ultimately.

FIG. 7is a view illustrating an example of a configuration of a center node according to the present disclosure.

The MN710may perform transmission and reception on a fundamental or basic channel (e.g., the 0-th channel (CH_0)).

For example, CH_0may correspond to a channel with the lowest center frequency, and CH_1, CH_2, . . . , and CH_K may correspond to respective channels with other center frequencies. Alternatively, CH_0may correspond to a channel with the highest center frequency, and CH_1, CH_2, . . . , and CH_K may correspond to respective channels with other center frequencies. Alternatively, CH_0may correspond to a basic channel or a primary channel, and CH_1, CH_2, . . . , and CH_K may correspond to additional channels or secondary channels.

The scope of the present disclosure is not limited by the channel number or the frequency position, and includes that when one center node700supports multiple channels (or multiple frequencies), any one thereof is managed by the MN710and the remaining ones are managed by the SNs720.

Signals and data may be transmitted and received via a communication interface715between the MN710and one or more SNs720. Communications between the MN710and one or more SNs720may use various wired or wireless communication protocols.

The center node700may be in association with one or more end nodes (ENs)730_1,730_2, . . . , and730_L. Each EN730may operate at a specific time on any one of multiple channels (or multiple frequencies). That is, each EN730may support both transmission and reception on multiple channels (or multiple frequencies), but may operate on only one channel (or one frequency) thereof at a specific time.

Due to the characteristic of the sensor network, it is often the case that the wireless channel is used to receive, by the center node700, sensing data collected from the EN730, rather than to transmit a signal from the center node700to the EN730. Also, a signal transmitted from the center node700to the EN730mostly contains control information for registration, association, synchronization, resource assignment, etc. of the EN730, and rarely contains data. Therefore, substantial wireless channel resources are not required for the center node700to transmit control information to the EN730and to receive control information and data from the EN730, and thus the MN710may be in charge of transmission and reception on one specific channel (e.g., CH_0). Also, substantial wireless channels are required for the center node700to receive data from the EN730, and thus respective SNs720_1,720_2, . . . , and720_K are in charge of reception on respective wireless channels (e.g., CH_1, CH_2, . . . , and CH_K).

FIG. 8is a view illustrating an example of a wireless frame structure according to the present disclosure.

In the example ofFIG. 8, a wireless frame800may contain a control period810and a data period820.

The control period810may be defined as a period in which the center node700transmits control information to the EN730and receives control information from the EN730. That is, the control period810may be defined as a period in which the EN730receives control information from the center node700and transmits control information to the center node700.

The data period820may be defined as a period in which the center node700receives data from the EN730. That is, the data period820may be defined as a period in which the EN730transmits data to the center node700.

In terms of the MN710, the wireless frame800is a basic unit for performing transmission/reception, and one duty cycle may consist of a beacon frame transmission period805, a CH_0transmission (Tx) period812, a CH_0reception (Rx) period814, and a CH_0Rx period822. The wireless frame800may be configured to repeat in time.

The SN720may attempt to receive data on a channel (or frequency) managed by itself during the wireless frame period, and may transmit the received data to the MN710. For example, in the example ofFIG. 8, during a reception (Rx) period840on the CH_2, the SN_2720_2may attempt to receive control information and data from the EN730on the relevant channel, and may transmit the received control information and data to the MN710.

It is assumed that the MN710knows the number (i.e., K in the example ofFIG. 7) of channels (or frequencies) supported by the center node700and the characteristics of the channels (e.g., center frequencies, etc.).

The MN710may periodically transmit a beacon frame in the beacon frame transmission period805on a specific channel (e.g., CH_0). The beacon frame in the beacon frame transmission period805may contain control information for each EN730. That is, each EN730may periodically receive, in a beacon frame reception period830, the beacon frame transmitted on the specific channel (e.g., CH_0) from MN710.

Specifically, the center node700is required to obtain or set the control information related to each EN730. For example, the control information related to the EN730may include information, such as a transmission frequency, a transmission channel, a transmission start time, a transmission size (i.e., the size of the data packet to be transmitted), etc. The control information may be exchanged between the center node700and the EN730during the control period810. More specifically, the MN710of the center node700may transmit the control information to the EN730on the specific channel (e.g., CH_0), and may receive the control information from the EN730.

For example, the MN710may transmit the beacon frame in the beacon frame transmission period805during the transmission period812within the control period810, so that the control information (e.g., information such as a frequency (or a channel), data transmission time, etc.) for the EN_1730_1may be transmitted to the EN_1730_1. The EN_1730_1may receive the control information (e.g., a beacon, a registration response message, a resource assignment message, etc.) from the center node700during an Rx period832of the control period810.

The EN_1730_1may transmit the control information to the center node700during a Tx period834within the control period810. Here, the EN_1730_1may transmit the control information during the Tx period834within the control period810by using a channel in an idle state.

Here, transmission of the control information through the channel in the idle state includes selecting one channel randomly from all channels including the basic channel (e.g., CH_0) and additional channels (e.g., CH_1, CH_2, . . . ) that are supported by the center node700, and transmitting the control information when the selected channel is in the idle state. Also, when the basic channel (e.g., CH_0) is in the idle state, the EN730transmits the control information first through the basic channel. When the basic channel is not in the idle state, one channel is selected randomly from the remaining channels, and when the selected channel is in the idle state, the control information may be transmitted.

For example, the EN_1730_1may transmit a registration request message to the center node700during the Tx period834within the control period810through the CH_2in the idle state in order to register a unique address of the EN_1730_1in the center node700.

When the SN_2720_2receives the registration request message from the EN_1730_1during the Rx period840on the CH_2, the SN_2720_2may transmit the registration request message to the MN710.

When the MN710receives the registration request message from the EN_1730_1, the MN710may transmit a registration response message to the EN_1730_1through the CH_0during the Tx period812of the control period810.

Thus, the control information transmitted by the EN730to the center node700may be transmitted during the transmission period834of the control period810. Here, the channel that the EN730used to transmit the control information is not assigned by the center node700, but may be randomly selected by the EN730. That is, one channel is randomly selected from multiple channels, and the control information may be transmitted when the selected channel is in the idle state. That is, the EN730may transmit the control information on the randomly selected channel in CSMA/CA scheme.

Also, in the example ofFIG. 8, the Tx periods812and834and the Rx periods814and832are set only once within one control period810, but the scope of the present disclosure is not limited thereto, and includes that the Tx period812,834and the Rx periods814,832in pairs are repeated several times within the control period810of one wireless frame.

Furthermore, in the example ofFIG. 8, the control period810and the data period820are set only once within one wireless frame800, but the scope of the present disclosure is not limited thereto, and includes that the control period810and the data period820in pair are repeated several times within one wireless frame800.

As additional, example, the EN_1730_1may transmit a transmission permission request message containing its Tx size to the center node700through the CH_2in the idle state during the control period810.

When the SN_2720_2receives the transmission permission request message from the EN_1730_1during the Rx period840on the CH_2the SN_2720_2may transmit the transmission permission request message to the MN710.

When the MN710receives the transmission permission request message from the EN_1730_1, the MN710may transmit a transmission permission response message to the EN_1730_1through the CH_0during the Tx period812or the beacon transmission period805of the control period810.

The transmission permission response message may include an address of the EN to which the transmission permission response message is transmitted and a transmission parameter set. The transmission parameter set may include transmission-allowed channel (or frequency) identification information, information on a transmission time, on a transmission size, on a transmission cycle (a cycle within the wireless frame), etc.

For example, the MN710may provide the EN_1730_1with resource assignment information for dividing and transmitting data into multiple channels (or frequencies) according to the Tx size requested by the EN_1730_1. Thus, according to the resource assignment information provided by the MN710, the EN_1730_1may transmit a data packet at a transmission time approved on the relevant channel (or frequency).

In the example ofFIG. 8, the EN_1730_1, which obtained transmission parameters via the transmission permission response message, may transmit data to the center node700on the assigned channel (e.g., CH_2) during a Tx period836. When the SN_2720_2receives data on the CH_2from the EN_1730_1, the SN_2720_2may transmit the data to the MN710.

Also, the EN_1730_1, which obtained the transmission parameters via the transmission permission response message, may transmit data to the center node700on the assigned channel (e.g., CH_0) during a Tx period838. The MN710may receive, in a master node data reception period824, data from the EN_1730_1during the Rx period822on the CH_0.

FIG. 9is a view illustrating an additional example of a wireless frame structure according to the present disclosure.

In the example ofFIG. 9, an EN_3730_3and an SN_1720_1are added, compared to the example ofFIG. 8. That is, it is an example illustrating that data transmission/reception is performed on different channels (or frequencies) simultaneously within a network composed of one center node700.

The EN_3730_3may receive, in a beacon frame reception period930, the beacon frame periodically transmitted in the beacon frame transmission period805on the CH_0from the MN710. Also, the EN_3730_3may receive the control information, such as the resource assignment information, etc., from the MN710during an Rx period932within the control period810.

Also, the EN_3730_3may select a channel randomly during a Tx period934within the control period810, and when the selected channel (e.g., CH_1) is in the idle state, the control information may be transmitted. The control information transmitted on the CH_1by the EN_3730_3may be received by the SN_1720_1, and then may be transmitted to the MN710.

The EN_3730_3may transmit data to the center node700during a Tx period936on the channel (e.g., CH_1) assigned according to the resource assignment information provided by the MN710. When the SN_1720_1receives data on the CH_1from the EN_3730_3, the SN_1720_1may transmit the data to the MN710.

Also, the EN_3730_3may transmit data to the center node700during a Tx period938on the channel (e.g., CH_0) assigned according to the resource assignment information provided by the MN710. The MN710may receive, in a master node data reception period826, data from the EN_1730_1during the Rx period822on the CH_0.

In the example ofFIG. 9, during the Tx period936on the CH_1and the Tx period836on the CH_2, data transmission of the EN_3730_3and of the EN_1730_1may be simultaneously performed respectively, and data may be received by the SN_1720_1and the SN_2720_2in charge of respective channels.

Also, in the example ofFIG. 9, on the CH_0, the Tx period838assigned to the EN_1730_1and the Tx period938assigned to the EN_3730_3may be assigned as time periods divided in a TDM scheme.

As described above, in one network composed of one center node700, data transmission/reception performed on multiple channels (or multiple frequencies) simultaneously is supported, so that the overall system throughput may be greatly enhanced.

In the examples of the present disclosure described with reference toFIGS. 8 and 9, the index of the end node (EN) and the index of the sub-node (SN) are merely exemplary and are not limited thereto.

That is, according to the various examples of the present disclosure, the master node (MN) of the center node may transmit the control information to one or more end node on a predetermined basic channel (e.g., CH_0) during a center node transmission period (i.e., an EN reception period) within the control period, and may receive the control information from one or more end node on a randomly selected channel (i.e., the basic channel preferentially, or a random channel among the basic channel and additional channels) through a sub-node or a master node corresponding to the selected channel during an EN transmission period (i.e., a center node reception period) within the control period.

Also, in the various examples of the present disclosure, one or more end node may transmit data to the center node on the channel and in the time period (i.e., the EN transmission period, an SN reception period, or an MN reception period) assigned by the center node. Here, the channel assigned by the center node may be the basic channel (e.g., CH_0) and one or more additional channels (e.g., CH_1, CH_2, . . . ). That is, a data transmission period assigned to each end node in the data period of the wireless frame may include a data transmission period for each of one or more channels, and data transmission periods for different channels may be divided in the time domain. Also, time periods in which multiple end nodes transmit data to the center node on different channels may be partially or all overlapped. That is, resources are assigned in such a manner that multiple end nodes transmit data to the center node simultaneously on different channels. In terms of the center node, the master node or the sub-nodes managing the respective channels may receive data from the end nodes.

FIG. 10is a flowchart illustrating operation of an end node according to the present disclosure.

The example ofFIG. 10shows that the end node730transmits the control information. Although not shown inFIG. 10, it is assumed that the end node730has obtained, from the center node700via a beacon, etc., set information on the period814in which transmission of the end node730is allowed within the control period810of the wireless frame800.

At step S1010, the control information (or a control packet) to be transmitted by the end node730to the center node700may be generated.

At step S1020, the end node730may attempt to perform channel access on the basic channel (e.g., CH_0), among K+1 channels (e.g., CH_0, CH_1, . . . , and CH_K) supported by the center node700. An attempt to perform channel access may include checking whether the relevant channel is in the idle state by performing backoff, carrier sensing, etc. on the relevant channel according to CSMA/CA scheme.

At step S1030, the end node730may determine a channel to transmit the control information depending on whether the basic channel is in the idle state.

When the basic channel is in the idle state, the end node730may transmit the control information on the basic channel at step S1070. At step S1080, data may be transmitted during the data period within the relevant wireless frame according to the resource assignment information, or waiting for a subsequent wireless frame may be performed when there is no data to transmit.

Here, the channel assigned for data transmission of the end node730may be the same as or different from the basic channel (e.g., CH_0) on which the end node730transmits the control information. Also, data may be transmitted to the center node700(i.e., the master node710or the sub-node720of the center node700, which corresponds to the assigned channel) on the assigned channel during the assigned time period within the data period820of the wireless frame800.

When the basic channel is not in the idle state, the end node730may select one channel randomly among the additional channels (e.g., CH_1, CH_2, . . . , and CH_K) at step S1040. For example, it is assumed that CH_2is selected.

At step S1050, the end node730may attempt to perform channel access on the selected channel (e.g., CH_2). An attempt to perform channel access may include checking whether the relevant channel is in the idle state by performing backoff, carrier sensing, etc. on the relevant channel according to CSMA/CA scheme.

At step S1060, the end node730may determine a channel to transmit the control information depending on whether the selected channel (e.g., CH_2) is in the idle state.

When the selected channel (e.g., CH_2) is in the idle state, the end node730may transmit the control information on the selected channel (e.g., CH_2) at step S1070. At step S1080, data may be transmitted during the data period within the relevant wireless frame according to the resource assignment information, or waiting for a subsequent wireless frame may be performed when there is no data to transmit.

Here, the channel assigned for data transmission of the end node730may be the same as or different from the channel (e.g., CH_2) selected by the end node730to transmit the control information. Also, data may be transmitted to the center node700(i.e., the master node710or the sub-node720of the center node700, which corresponds to the assigned channel) on the assigned channel during the assigned time period within the data period820of the wireless frame800.

When the selected channel (e.g., CH_2) is not in the idle state, the end node730may determine whether the control period remains within the current wireless frame. More specifically, within the control period of the wireless frame, whether the transmission period of the end node is equal to or greater than the minimum time (e.g., a backoff time, a carrier sensing time, a control packet time length, etc.) required for the end node to transmit the control information may be determined.

When the remaining control period within the wireless frame is insufficient, data may be transmitted during the data period within the relevant wireless frame according to the resource assignment information at step S1080, or waiting for a subsequent wireless frame may be performed when there is no data to transmit.

Here, the channel assigned for data transmission of the end node730may be the same as or different from the channel (e.g., CH_1) selected by the end node730to transmit the control information. Also, data may be transmitted to the center node700(i.e., the master node710or the sub-node720of the center node700, which corresponds to the assigned channel) on the assigned channel during the assigned time period within the data period820of the wireless frame800.

When the remaining control period within the wireless frame is sufficient, the end node730may select one channel randomly among, except for the previously selected channel (e.g., CH_2), the remaining additional channels (e.g., CH_1, CH_3, . . . , and CH_K) at step S1064. For example, it is assumed that the CH_1is selected.

Thus, the end node730may attempt to perform channel access on the selected channel (e.g., CH_1) at step S1050, and the control information may be transmitted at step S1070depending on whether the selected channel (e.g., CH_1) is in the idle state. Alternatively, another channel may be further selected at step S1064, or data transmission or waiting for a subsequent wireless frame may be performed at step S1080.

FIG. 11is a flowchart illustrating operation of a center node according to the present disclosure.

At step S1110, the center node700may wait until a wireless frame start time, and at step S1112, may transmit the beacon frame at the wireless frame start time.

At step S1120, the center node700may determine whether a remaining control period within the wireless frame is present.

In the case where the control period is present, when the control information to be transmitted is present at step S1122, the master node710of the center node700may transmit the control information on the basic channel (e.g., CH_0) within the relevant control period.

At step S1124, when the control information is received on the basic channel (e.g., CH_0) within the relevant control period, the control information received through the master node710may be processed. Also or alternatively, when the control information is received on the additional channel (e.g., CH_1, CH_2, . . . , and CH_K), the control information received through a corresponding sub-node720may be transmitted to the master node710and may be processed.

At step S1126, the center node700may determine whether the relevant control period is terminated. In the case where the relevant control period is not terminated, when the control information to be transmitted is present and the transmission period812of the center node700remains, the control information may be transmitted at step S1122. When the control information to be transmitted is not present or when the transmission period812of the center node700does not remain, but a reception period814of the center node700remains within a control period810, the control information may be received at step S1124. As described above, it is possible to support the wireless frame structure in which the transmission period812of the center node and the reception period814of the center node are present only once as well as several times repeatedly within one control period.

When the relevant control period is terminated or when the remaining control period is not present, the center node700may determine whether a remaining data period is present at step S1130. In the case where the data period is present, when data is received on the basic channel (e.g., CH_0) within the relevant data period at step S1132, the data received through the master node710may be processed. Also or alternatively, when the data is received on the additional channel (e.g., CH_1, CH_2, . . . , and CH_K), the data received through the corresponding sub-node720may be transmitted to the master node710and may be processed.

At step S1134, the center node700may determine whether the relevant data period is terminated. When the relevant data period is not terminated at step S1134, the center node700may receive data through at least one channel of the basic channel or the additional channel(s).

When the relevant data period is terminated or when the remaining data period is not present, the center node700may determine whether the relevant wireless frame is terminated at step S1140.

When the relevant wireless frame is terminated, waiting for the start of a subsequent wireless frame may be performed, going back to step S1110.

When the relevant wireless frame is not terminated, whether the remaining control period is present may be determined, going back to step S1120. As described above, it is possible to support the wireless frame structure in which the control period810and the data period820are present only once as well as several times repeatedly within one wireless frame.

FIG. 12is a block diagram illustrating a structure of an end node device according to the present disclosure.

The end node device, which is also referred to as the end node730, may include a transmitter/receiver1210, a memory1220, and a processor1230. The configuration of the end node730is merely exemplary, and is not limited to the example ofFIG. 12. Some or all of the constituents inFIG. 12may be included, or additional constituents may be further included.

The transmitter/receiver1210may transmit the control information, the data packet, etc. to another device, or may receive the control information, the data packet, etc. from another device.

The memory1220may store the control information, data, calculation results, etc. that are necessary for operation of the end node730.

The processor1230may control overall operation of the end node730.

For example, the processor1230may include a wireless frame set information acquisition unit1232, a control information reception set unit1234, a control information transmission set unit1236, and a data transmission set unit1238.

The wireless frame set information acquisition unit1232may acquire, from the center node, information on the length of the wireless frame between beacon intervals, on the number of repetitions of control period and data period within the wireless frame and respective lengths thereof, etc.

The control information reception set unit1234may check identification information of the basic channel on which the control information is received by the end node from the center node, and information on the length, the position, the number of repetitions of the reception period within the control period. Also, the control information reception set unit1234may set the transmitter/receiver1210to attempt to receive the control information on the relevant channel and in the relevant time period.

The control information transmission set unit1236may check information on the channel on which the control information is transmitted by the end node to the center node, and information on the length, the position, the number of repetitions of the transmission period within the control period. Also, the control information transmission set unit1236may set the transmitter/receiver1210to transmit the control information on the relevant channel and in the relevant time period. Here, as a channel on which the control information is transmitted, the basic channel is preferentially selected. When the basic channel is not in the idle state, the channel may be determined in such a manner as to select one randomly from additional channels.

The data transmission set unit1238may check, based on the control information, such as the resource assignment information provided from the center node, a channel and a data time period where transmission is allowed, and may set the transmitter/receiver1210to transmit data on the relevant channel and in the relevant time period.

FIG. 13is a block diagram illustrating a structure of a master node according to the present disclosure.

As described above with reference toFIG. 7, a center node device, which is also referred to as the center node700, may include one master node710, one or more sub-nodes720, and a communication path715therebetween. Each sub-node720may include a transmitter/receiver operating on a relevant channel, a memory, etc., and is assumed to be controlled by the master node710.

As shown inFIG. 13, the master node710may include a transmitter/receiver1310, a memory1320, and a processor1330. The configuration of the master node710is merely exemplary, and is not limited to the example ofFIG. 13. Some or all of the constituents inFIG. 13may be included, or additional constituents may be further included.

The transmitter/receiver1310may transmit the control information, the data packet, etc. to another device, or may receive the control information, the data packet, etc. from another device.

The memory1320may store the control information, data, calculation results, etc. that are necessary for operation of the master node710.

The processor1330may control overall operation of the center node700that includes the master node710.

For example, the processor1330may include a wireless frame set unit1332, a control information transmission set unit1334, a control information reception set unit1336, and a data reception set unit1338.

The wireless frame set unit1332may determine information on the length of the wireless frame between beacon intervals, on the number of repetitions of the control period and the data period within the wireless frame and respective lengths thereof, etc. Also, the wireless frame set unit1332may transmit the wireless frame set information to the end node730, etc. through the beacon frame, upper layer signaling, etc.

The control information transmission set unit1334may set the transmitter/receiver1310to transmit the control information on the relevant channel and in the relevant time period on the basis of the basic channel on which the master node710transmits the control information to the end node730and of setting on the length, the position, the number of repetitions of the transmission period within the control period.

The control information reception set unit1336may set the transmitter/receiver1310to attempt to receive the control information on the relevant channel and in the relevant time period on the basis of the channel on which the master node710and the sub-node720receive the control information from the end node730and of setting on the length, the position, the number of repetitions of the transmission period within the control period. Here, the master node710may monitor whether the control information is received on the basic channel, and may control the sub-nodes720to monitor whether the control information is received by the sub-nodes720corresponding to the additional channels.

The data reception set unit1338may check, based on the control information such as the resource assignment information provided to the end node730, a channel and a time period where data transmission of the end node730is allowed, and may control to perform an attempt to reception. For example, the master node710may monitor whether data is received on the basic channel in the time period where data reception is allowed, and may control the sub-nodes720to monitor whether data is received by the sub-nodes720corresponding to the additional channels. Here, data may be received from one end node730in a specific time period, or data may be received from multiple end nodes730simultaneously on different channels in a specific time period.

In the above described various examples of the present disclosure, methods of enhancing flexibility of wireless resource assignment in the sensor network, of performing low power based operation, and of accommodating multiple nodes have been described. According to the various examples of the present disclosure, in order to overcome the limitation of the transfer rate on one wireless channel, a method of overall controlling multi wireless channel transmission by one center node has been proposed. Also, according to the various examples of the present disclosure, in order to maximize the efficiency of wireless resource utilization, dynamic channel assignment is possible by separating the control period and the data period for each channel (or frequency), a fixed transfer rate is guaranteed for multiple nodes, and a control channel is assigned flexibly, whereby a wireless frame configuration method for optimal utilization of wireless resources may be provided. Thus, multiple devices with high transfer rate are accommodated and multiple wireless channels are controlled overall based on a single center node, whereby the system throughput may be enhanced ultimately.

Although exemplary methods of the present disclosure are represented as a series of operations for clarity of description, the order of the steps is not limited thereto. When necessary, the illustrated steps may be performed simultaneously or in a different order. In order to implement the methods according to the present disclosure, the illustrative steps may further include other steps, or some steps are excluded and the remaining steps are included, or some steps are excluded and additional other steps are included.

The various embodiment of the present disclosure do not list all possible combinations, and are intended to be illustrative the representative aspects of the present disclosure. The matters described in the various embodiments may be independently applied or in a combination of two or more.

Also, the various embodiments of the present disclosure may be implemented by hardware, firmware, software, or a combination thereof. With hardware implementation, the embodiment may be implemented by using at least one selected from a group of application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), general-purpose processors, controllers, micro controllers, micro processors, etc.

The scope of the present disclosure includes software or machine-executable instructions (e.g., an operating system, an application, firmware, a program, etc.) that cause operation according to the methods of the various embodiments to be performed on a device or a computer, and includes a non-transitory computer-readable medium storing such software or instructions to execute on a device or a computer.