KR101915666B1 - Priority Channel Scheduling and Assignment Method over Wireless Personal Area Network by Sharing Channel Information according to Priority between Devices - Google Patents

Abstract

The prioritized channel scheduling and allocation method in a wireless personal area network through sharing of channel information according to priority among devices can be realized by each PAN coordinator of a different personal area network scanning a channel, And assigning a priority to a coordinator in the channel from the channel management system; and when the device joins the PAN, the coordinator of the PAN notifies the coordinator priority and the device priority to the device; Comparing the address of the data frame with the address of the data frame received by the channel management system when the data frame is received in the waiting state for a time set by the channel management system; .

Description

[0001] Priority Channel Scheduling and Assignment Method over Wireless Personal Area Network by Sharing Channel Information According to Priority between Devices [0002] Priority Channel Scheduling and Assignment Method over Wireless Personal Area Network [

The present invention relates to a channel scheduling and allocation method that reflects priorities by sharing channel information between devices on a wireless personal area network, and more particularly, to a method and apparatus for scheduling and assigning priority among a coordinator and a coordinator, a coordinator and a device, The present invention relates to a channel allocation method capable of avoiding interchannel interference and using a channel efficiently through a channel occupation delay time considered.

Currently, the Internet of Things (IoT) is attracting much attention. IoT uses wireless communication to collect data from remote devices and to operate remote devices. As the wireless communication used in this case, the IEEE802.15.4 standard, which is a transmission standard of a local area network (WPAN), is often used.

IEEE 802.15.4 uses Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA) algorithm to avoid collision between users. This implements a function of avoiding collision by checking whether a channel is used after a certain time delay before transmitting data, thereby realizing an environment in which a plurality of devices can communicate through one channel.

The CSMA / CA algorithm measures the Received Signal Strength Indication (RSSI) value through a procedure called CCA (Clear Channel Assessment) before sending data. At this time, the data is transmitted only when the channel has the RSSI below the reference, and when the channel has the RSSI above the reference, the device undergoes a random back off delay. After a certain delay time, CCA is again performed to determine whether or not to transmit data based on the RSSI value of the channel. If the number of times of performing the CCA exceeds the number of back off specified by the user, It is determined that the transmission has failed.

Meanwhile, the main concepts for describing IEEE 802.15.4 are PAN, coordinator, and device. PAN (Personal Area Network) is a communication network in which one coordinator and one or more devices are composed of a star or mesh type topology. The coordinator is a device that performs the functions of configuring and managing the PAN. A device is a device that uses FFD (Full Function Device) or RFD (Reduced Function Device). When FFD is used, routing function can be used. However, when RFD is used, routing function can not be used. A device is a device that can only configure a limited type of star topology and communicate only with its parent router.

IEEE 802.15.4 operates in the wireless 2.4GHz band, and Wi-Fi and other wireless devices are using the same bandwidth. The communication interference caused by this causes a factor of hindering reliable communication.

There are 16 available channels in IEEE 802.15.4. However, the number of usable channels decreases due to a large number of Wi-fi APs having strong outputs in the same frequency band, and there is a possibility that a plurality of WPANs in a radio wave attenuating region can simultaneously use one channel due to the spread of IoT . Therefore, there is a need for a method for efficiently using a channel.

A problem to be solved by the present invention is to use a star topology type WPAN more efficiently in a single WPAN or in a plurality of WPANs using the same channel when using the existing CSMA / CA algorithm and avoid interchannel interference Based channel assignment method.

According to an aspect of the present invention, there is provided a priority channel scheduling and allocation method on a wireless personal area network through channel information sharing according to priority among devices, wherein each PAN coordinator of a different personal area network scans a channel Reporting a best channel to a channel management system and assigning a priority to a coordinator in the channel from the channel management system; and when the device joins the PAN, the coordinator of the PAN notifies the coordinator priority Comparing a data frame reception address with an address of the data frame reception address when the data frame is received in a waiting state for a time set by the channel management system; If there is a match, the step of receiving data It should.

The present invention is advantageous in that it can reduce the collision in the channel based on the priority, and can use the channel by reflecting the priority of the communication.

In addition, by sharing the length information of the data occupying the channel, the waiting time of the apparatus for transmitting / receiving can be minimized.

Figure 1 is a data packet that acts on the device sleep period of the present invention.
2 is a flowchart illustrating a method of determining a sleep period of a device when receiving a data frame as shown in FIG.
FIG. 3 is a view for explaining time delay for each device according to priority.
4 is a view for explaining a method in which inter-device priorities are cooperatively changed in one PAN.

It is to be understood that the specific structural or functional description of embodiments of the present invention disclosed herein is for illustrative purposes only and is not intended to limit the scope of the inventive concept But may be embodied in many different forms and is not limited to the embodiments set forth herein.

The embodiments according to the concept of the present invention can make various changes and can take various forms, so that the embodiments are illustrated in the drawings and described in detail herein. It is not intended to be exhaustive or to limit the invention to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises" or "having" and the like are used to specify that there are features, numbers, steps, operations, elements, parts or combinations thereof described herein, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings attached hereto.

In this specification, a protocol for transmitting data from a coordinator to a device and transmitting data from a device to a coordinator is dealt with. Each protocol is defined in one or more PANs and operates on the basis of one or more device priorities within the same PAN that have been given priority from the coordinator that manages each PAN. In this case, the success or failure of each communication is accomplished through reception of an ACK frame. The ACK frame herein refers to an ACK frame when a data transmitted from a transmitting side is correctly transmitted to a receiving side, Quot; Prior to describing the protocol, the coordinator priority is predetermined and operated by the user, and the device priority can be determined according to a process described later. In this specification, 'device' is defined as a configuration including a device and a coordinator.

Before describing the examples herein, the most important priorities are described. Coordinators and devices in the PAN process have priority over channel occupancy. Here, when a channel becomes usable, a time delay to a time point for using the channel is differentiated according to the priority order, thereby distinguishing the right order for channel occupancy. In this case, the priority of the coordinator may precede the priority of the device.

<Table 1> describes the priority of the coordinator and the device and the corresponding delay time. First, the coordinator has A, B, C, and D in bold, and the subscribed devices are {a1, a2}, {b1, b2, b3}, {c1, c2, c3, c4} , d3, d4, d5} are present. In this case, the priority of the coordinator is given as 1, 2, 3, 4 according to the upper channel management system, and each of the devices multiplies the device priority in the PAN by 10 which is a device constant and adds the coordinator priority . If this is expressed as a general formula, the delay time T in the case of the coordinator is given by the following equation.

T = (CR) * d,

At this time, CR is the coordinator priority and d is the delay constant 10. In the case of the device, the delay time T is given by the following equation.

T = {(DR * D) + CR} * d,

In this case, DR is the device priority in the PAN, D is the device constant 10, CR is the coordinator priority, and d is the delay constant 10.

In this case, the delay constant or the device constant is one of the embodiments applied to Table 1, which can be applied differently depending on the channel status.

In general, the coordinator always manages the PAN in an awake state, while the device has a sleep mode that reduces energy consumption and operates at low power. In this state, only a limited function is performed in order to minimize energy consumption, and the sleep period of a general device has a unique cycle for each device. Therefore, in order to transmit data to a device, the coordinator checks the status of a device called polling The process is necessary.

However, according to the present invention, since the delay time according to the length of the channel occupation data is grasped, all the devices in the channel have a cooperative sleep period, so that it is not necessary to check the status of the device such as polling.

Figure 1 is a data packet that acts on the device sleep period of the present invention.

Referring to FIG. 1, since the data frame and the MHR field used by the IEEE 802.15.4 are the same, the reception object of the corresponding data frame can be grasped as an existing method through an addressing field. The difference is the existence of the DATA Length Information including the length information of the data, from which the sleep time of the device can be determined by grasping the occupancy time of the channel.

2 is a flowchart illustrating a method of determining a sleep period of a device when receiving a data frame as shown in FIG.

Referring to FIG. 2, after the device awakes from the sleep mode, the device waits for a length set by the channel management system according to the channel status (S310). This waiting time has until the channel occupancy delay time of the device having the lowest lowest priority. If there is no data frame to be checked within this waiting time, all the devices in the channel operate in the sleep mode with the set length. If the data frame to be verified exists (S320), the addressing field of the MHR field is checked and the address of the data frame is compared with its own address (S330). If the device address matches, the data is received (S340) (S331) and operates in the sleep mode for the channel occupation time corresponding to the length (S333). At this time, the length of the channel occupancy data is checked by overhearing the device. If it is determined that the data transmission has been completed (S350), the ACK frame is transmitted to notify that the reception is successful (S360). If the data is not completely received, the channel occupancy length (S370) and operates according to the priority setting method of the device or the coordinator. On the other hand, if the data frame is not received (S320), the mobile terminal operates in the sleep mode with the set length (S321).

FIG. 3 is a view for explaining time delay for each device according to priority.

Referring to FIG. 3, it is assumed that a device having a 0th priority, which is the highest priority, waits for a delay time set until devices of priority 1, 2, and 3 simultaneously occupy a channel do. At this time, it is shown that the length of data may vary from device to device, and this figure is a simplified diagram showing a time delay until occupancy of a channel according to priority.

The device having the 0th priority is completed after receiving the ACK frame after passing the SIFS (Short Interframe Space), which is a very short time from transmitting the data and receiving the ACK signal from the receiving side device. At this time, it can be confirmed that the data transmission time is different according to the priority 1, 2, and 3. Since the transmission of the device having the priority 0 is completed, the device 1 having the highest priority among the devices having the priority 1, Can be transmitted faster than the remaining devices 2 and 3. According to the result shown in FIG. 2, the devices 2 and 3 wait in the sleep mode for the length of the channel occupation data and wake up from the sleep mode at the time indicated by the solid line, indicating that the data transmission is completed, It can be confirmed that it has a delay time.

In the case of data transmission from the coordinator to the device, the operation after the transmission fails or is successful is determined entirely by the coordinator. If there is no data to be sent from the coordinator to another device after the successful transmission of data from the coordinator to the device, the device repeats the predetermined sleep cycle. If there is data to be transmitted to another device or a beacon frame indicating the occupation of the channel of the coordinator having a higher priority is received, the device repeats the above process and has a sleep period. Even if the communication fails, the operation of the PAN is performed by the coordinator. Therefore, when there is data to be sent to one or more devices by one PAN internal coordinator, the priorities of the PANs are prioritized according to the operating environment of the coordinator set by the upper channel management system .

The following is a description of the case where data is sent from the device to the coordinator.

First, it is assumed that a plurality of devices send data to one coordinator in the PAN. Unlike a device, a coordinator does not operate in a sleep mode, which is a low power operation characteristic. Therefore, each device can immediately try to occupy a channel if there is data to be sent to the coordinator. If the priorities of the devices are not changed even within the same PAN, there are cases where other devices can not use the channels due to the exclusive channel occupancy of the specific devices. In order to solve this problem, the embodiment of FIG. 4 illustrates a way in which priority among devices is cooperatively changed in one PAN.

4 is a view for explaining a method in which inter-device priorities are cooperatively changed in one PAN.

Referring to FIG. 4, the device priority is cooperatively changed in the form of FIG. 4 in one PAN. For example, when four devices A, B, C, and D are to transmit data to the coordinator, the initial priority may have 0, 1, 2, 3 according to the user's initial value designation or coordinator designation. According to the result shown in FIG. 3, as the device has a high priority, the waiting time for channel occupation is shortened after the device wakes up from the sleep mode. Therefore, if there is no data to be sent to the device by the coordinator, The 0th priority device is occupied. In this case, even if the device is of priority 0, it has a longer delay time than the coordinator until it occupies the channel.

The device with priority 0 informs the coordinator of the length information of the data before transmitting this data and other devices in the same PAN overhear it for the delay time according to the respective priority, , 3 operates in the sleep mode according to the length information of the current channel occupancy attempt data. If the data is successfully transmitted, the device that succeeds transmission and the device that wakes up from sleep mode decrements the current priority by one. At this time, the device whose priority is -1 has priority of 3. Then, each priority is calculated by modulo 4, which is the number of the internal devices of the current PAN, and priority is determined. That is, if the A, B, C, and D devices in one PAN have priorities of 0, 1, 2, and 3, after data transmission between the device A and the coordinator is successfully performed, A, B, C, and D have priority of 3, 0, 1, and 2. This ensures that only certain devices will not monopolize the channel and ensures the use of even channels in other device and coordinator communication within the PAN.

This is expressed by a general expression, and when a communication from a device in a PAN to a coordinator is performed, the device priority is determined as follows.

P = (P ₀ -1)% N,

In this case, P is the device priority of the next cycle, P ₀ is the current device priority, and N is the number of devices of the current channel.

If the data frame for occupying the channel does not exist on the channel after the devices wake up from the sleep mode, the present priority is maintained as it is, and the priorities are overlapped due to the error or have an ordered priority If not, the coordinator will re-prioritize by default. FIG. 4 shows an embodiment in which the PAN is expanded based on the foregoing description.

FIG. 5 is a view for explaining an operation mode of three PANs, a coordinator, and a coordinator in one channel according to a preparation time and a priority order for devices subscribed to each coordinator to occupy the channel.

5, each column is defined in units of time. In the case of data transmission from the coordinator to the device, columns are filled according to the color of each coordinator. When the device transmits data to the coordinator, It is filled with O in the row. In this case, the occupancy time of the channel is indicated by the moment when each column starts to be filled with color or O. When an arbitrary device occupies the channel, all the devices in the channel operate in the sleep mode as described above, And the time at which the devices awaken from the sleep mode are indicated by solid lines in the channel occupancy table of FIG.

In this embodiment, it is intended to show the channel occupancy time according to the priority and the delay time at the time when the transmission preparation is completed. Therefore, when actual data is included, the length of each column may be longer.

In FIG. 5, the channel occupancy time is set as described in Table 1, and the device constant and the delay time constant are optimally applied to the number of coordinators and devices. As described above, it can be seen that the priority of the coordinator precedes the priority of the device, and the priority of the devices joined to each coordinator is also not distributed exclusively in one PAN but evenly distributed.

The transmission indicator in FIG. 5 indicates the time when the access preparation for the channel is completed. As soon as the coordinators A, B, and the device c2 are started, it is confirmed that the access to the channel is completed, and it is confirmed that the channel occupancy table is filled in accordance with the channel occupancy time table. The channel occupancy of the coordinator A is prioritized according to the priority order. At this time, the remaining devices receiving the length of the data occupying the channel operate in the sleep mode. After the coordinator A completes the transmission, As shown in Fig. At this time, the device b2 awakes from the sleep mode immediately after the coordinator A finishes occupying the channel and has a waiting time for channel occupation, but it can be seen that the coordinator B has precedence because it has a high priority. It can be confirmed that it operates according to the delay time up to the channel occupation according to the priority among the devices through the data transmission waiting list and the channel occupancy table.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

none.

Claims (5)

A priority channel scheduling and allocation method on a wireless personal area network through channel information sharing according to priority between devices,
(a) each PAN coordinator in a different personal area network scans a channel to report a best channel to a channel management system, and assigning a priority to a coordinator in the channel from the channel management system;
(b) when the device joins the PAN, the coordinator of the corresponding PAN notifies the device of the coordinator priority and the device priority;
(c) comparing a data frame reception address with an address of the data frame when the data frame is received in the waiting state for a time set by the channel management system;
(d) receiving data if the address of the data frame matches its address;
(e) checking the data length information of the data frame if the address of the data frame does not match the address of the data frame, and entering the sleep mode based on the data length information; And
(f) If the device receiving the data confirms that the transmission of data is completed, an ACK frame is transmitted to notify that the reception is successful. If the device can not receive all the data, the device waits for the channel occupation length in the received data length, Operating according to a priority or a coordinator priority setting,
Wherein the priority of the coordinator is higher than the priority of the device, the priority of the coordinator is sequentially assigned by the channel management system, the priority of the device is multiplied by the device priority in the PAN and the device constant, Is determined as a value obtained by adding the rank,
The delay time T is determined according to the following equations (1) and (2)
[Equation 1] T = CR * d,
CR is the coordinator priority, d is the delay time 10, DR is the device priority in the PAN, D is the device constant 10, and DR is the device priority in the PAN. T = {(DR * D) + CR} * d,
In the step (e), the data length information check of the data frame is performed through overhearing of the apparatus, and the priority of the data on the wireless personal area network operating in the sleep mode by the occupancy time of the channel according to the data length information Channel scheduling and assignment method. delete delete delete The method according to claim 1,
(g) reducing the current priority of the device successfully transmitted and the device awakened from the sleep mode by 1 when the data is successfully transmitted.

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