KR101866412B1 - An channel quality estimation method and networking devices for energy-saving over IoT wireless network - Google Patents

Abstract

The present invention provides a method and a device, which increases an energy detection frequency to update the latest channel quality more frequently when a channel quality is severely changed in an IEEE802.15.4e E-TSCH (time slotted channel hopping) based network; and decreases the energy detection frequency to reduce power consumption when the variance in the channel quality is not severely changed, such that power consumption is reduced to reduce energy consumption while maintaining reliability of communications as much as E-TSCH. According to the present invention, the method comprises: a step (A) of making a corresponding time slot waited as much as an offset when an idle section is started if energy detection is started for all channels in the corresponding time slot; a step (B) of performing non-intrusive channel quality estimation (CQE) for all channels when the idle section is started; a step (C) of calculating interference dynamicity (ID) based on the estimated CQE value, and calculating an energy detection cycle adjusted in accordance with a value of the calculated ID; and a step (D) of waiting as much as the calculated energy detection cycle without detecting energy, and repeating a process from the step (A) at a corresponding start time slot after a time as much as the energy detection period.

Description

[0001] The present invention relates to a channel quality measuring method and a network device for saving energy in an IoT wireless network,

The present invention relates to an IoT wireless network, and more particularly, to a channel quality measuring method and a network apparatus for saving energy by flexibly adjusting the number of times of energy sensing within a range that does not impair the reliability of an E-TSCH network.

A wireless sensor network (WSN) is a network in which distributed sensor nodes are configured through a wireless medium in order to measure environmental conditions such as temperature and humidity, and physical conditions such as distance and weight. Since wireless communication is more advantageous than wired communication in terms of convenience, cost and mobility, wireless sensor networks are one of the key technologies in the coming IOT paradigm.

IEEE 802.15.4 is a standard for defining physical (PHY) and medium access control (MAC) layers for low-rate wireless personal area networks and is designed for large multi-hop mesh networks. This technology is lightweight and energy efficient for use in wireless sensor networks. Based on this, a more advanced MAC layer standard, IEEE 802.15.4e TSCH (Time Slotted Channel Hopping) mode has been proposed.

TSCH is a technology based on TDMA, in which several nodes synchronized with each other communicate with each other over several radio channels. It operates at low power and aims to improve the reliability of wireless sensor networks in a noisy environment.

Figure 1 shows a schematic diagram of a conventional 15.4e TSCH protocol communication.

As shown in Fig. 1, in the TSCH, two nodes communicate with each other in a predetermined band in a predetermined time zone. That is, the time axis is discretized into a time slot, and two nodes communicate with each other using a specific frequency offset (channel offset) as a medium.

Since the TSCH network has been started, a unique number is assigned to a time slot (a specific time point), and the time slot is incremented by one as time passes. This number is called ASN (Absolute Sequence Number). A predetermined number of timeslots are gathered to form a slot frame, and this slot frame is continuously repeated. A link defined by a time slot offset and a channel offset is in the form of an ordered pair of two nodes.

One of these nodes is the source node that sends the packet and the other is the destination node that receives the packet. At a particular slot offset (in a particular time zone), a particular node may take only one of the actions of sending or receiving a packet. In the IEEE 802.15.4e standard, 11 to 26 channels in the 2.4 GHz band, 16 channels in total, are used. In a TSCH network, nodes may have their own dedicated slot, which can be realized using scheduling.

The IEEE 802.15.4e standard contributes to the reliability of communication, but it can receive cross-technology interference by technologies using the 2.4 GHz frequency band such as Wi-Fi. The IEEE 802.15.4e standard enables smooth communication by intentionally avoiding a channel in which interference occurs with a time slotted channel hopping technique. This is the E (Enhanced) -TSCH protocol. The E-TSCH protocol measures the interference level of each channel through energy detection that can be performed on a radio transceiver, and channel hopping is performed alternately for high-quality channels.

The E-TSCH additionally includes two special techniques in the TSCH. One is Non-Intrusive Channel Quality Estimation (NICE), and the other is Enhanced Beacon Sequence List (EBSL).

NICE technology measures the quality of a channel by performing energy detection during an idle period in each slot for each time slot. Based on the quality of the measured channel, a good quality channel is selected and the channels are hopped alternately. Since the NICE technique can be performed in parallel with communication by energy sensing in the idle period, it has high reliability even in a dynamic environment in which the interference does not affect the network throughput such as time slot.

An enhanced beacon (EB) is used to transmit information for controlling the network to other nodes. The EB delivers the HSL (Hopping Sequence List) containing the selected channel from the PAN Coordinator. The HSL mismatch between the nodes occurs as the EB loss (Enhanced Beacon loss) occurs, . EBSL technology is a technology that introduces EB-specific channel list (Sequence List) to reduce EB loss.

Examples of the environment to which the E-TSCH can be applied include a body area network, an in-vehicle network, and the like. When the vehicle is running, the internal network is susceptible to interference from other external sources, such as Wi-Fi. In particular, the quality of the channel is dynamic. Therefore, the E-TSCH, which measures the channel quality per time slot and uses only high-quality channels, can have reliability higher than that of the existing TSCH in a situation where the interference is dynamically changed, Power consumption, it has superiority over TSCH.

Performing energy sensing in a transceiver requires power consumption. In E-TSCH, PAN coordinator performs energy sensing based on star topology, and sends HSL (Hopping Sequence List) containing selected high-quality channel to EB. The E-TSCH is valid because the fan coordinator does not have to consider power consumption.

However, in order for the E-TSCH to be applied to a wider range of networks, a multi-hop tree or a mesh network must be constructed. In order for the E-TSCH to be generally extended, it is difficult for the fan coordinator to perform accurate energy sensing of the entire range of the mesh network. Therefore, not only the fan coordinator but also the router and the end nodes need to perform energy sensing. In E-TSCH, energy detection is performed for each slot irrespective of whether the interference change is dynamic or non-dynamic, and this operation is performed on normal nodes having power limitation on the extended E-TSCH This makes unnecessary power consumption. As a result, if the number of times of energy sensing can be adjusted depending on whether the interference is severe or not, the power consumption can be reduced without impairing the reliability of the communication.

Patent Registration No. 10-1437157 (Registration date 2014.08.27) Patent Registration No. 10-1639388 (registered date: 2016.07.07)

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide an E-TSCH based network in which a change in channel quality is severe, And to reduce power consumption by reducing the frequency of energy sensing when the channel quality is not significantly changed, thereby ultimately maintaining the reliability of the E-TSCH and reducing energy consumption.

Other objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

According to another aspect of the present invention, there is provided a channel quality measurement method and a network device for saving energy in an IoT wireless network, the method comprising: (A) when energy sensing is started for all channels in a corresponding time slot, (B) performing non-invasive Channel Quality Estimation (CQE) on all channels when an idle interval is started; (C) Calculating Interference Dynamics (ID) based on the channel quality measurement value and calculating an energy sensing period that is adjusted according to the calculated value of the interference dynamics; and (D) (A) step in the corresponding start time slot after a period of time corresponding to the energy sensing period, It is made of makin by comprising the step of repeating the process.

Preferably, the step (B) includes the steps of measuring RSSI (Received Signal Strength Indicator)

And a step of calculating a CQE value using Equation

Lt; RTI ID =

In a particular channel

Is the RSSI value of

Lt; RTI ID =

In a particular channel

To the CQE value of the current measured RSSI value

If you want to increase the value above the set threshold and make it more stable

And the value is decreased from the set threshold value.

Preferably, in the step (C), the interference dynamics may include a CQE value currently measured for a specific channel

), The CQE value measured immediately before (

Calculating a change amount of a specific channel quality with an absolute value of a CQE value difference obtained as a result of subtracting the CQE value difference from the result of subtracting the CQE value difference, Absolute Slot Number (ASN)

), The ASN (

Calculating a number of time slots (measurement time interval) from a time point at which the CQE value was measured to a time point at which the current CQE value was measured by subtracting the measurement time interval And calculating the interference dynamics with respect to time based on the total change amount of the CQE values.

Preferably, if the calculated interference dynamic value is greater than a preset threshold value, the step (C) determines that the change of the radio interference is severe, and if the interference dynamic value is smaller than a preset threshold value, .

Preferably, the period of the energy sensing in the step (C) is controlled according to the value of the interference dynamics through a periodic energy detection technique.

Preferably, the cycle of energy sensing in step (C)

Is calculated using the equation

Means the amount of change in the quality measurement value of all the channels between the energy sensing periods,

Is the previous interference dynamics.

According to another aspect of the present invention, there is provided a network device for measuring channel quality of an IoT wireless network, the method comprising: receiving an RSSI value from an IEEE 802.15.4 physical layer to calculate a channel quality measurement value; A non-intrusive channel quality measurement unit for transmitting the calculated channel quality measurement value to a high-quality channel selection unit and an energy-detection period determination unit, Channel quality measurement value input from the non-intrusive channel quality measurement unit, and calculates an interference dynamics level based on the channel quality measurement value input from the non-intrusive channel quality measurement unit, And determines an energy sensing cycle to be transmitted to the energy sensing performance unit of the IEEE 802.15.4 physical layer May consists of including.

In the IoT wireless network according to the present invention as described above, a method of measuring channel quality and a network device that saves energy can reduce power consumption and provide a base on which E-TSCH technology can be applied in a wider range locally .

That is, in order for the E-TSCH defined by a specific topology (star topology) to be extended to any multi-hop tree or mesh topology, it is necessary to perform channel scanning not only for the pan-coordinator but also for normal nodes. This is because the range covered by the network is so wide that it is possible to determine which channel is high quality depending on which region the node is located in. If the channel scan, like the existing E-TSCH, is operated regardless of the change in interference, the power consumption of the entire network will be greatly increased. Therefore, the present invention can reduce the power consumption by adjusting the number of times of energy sensing within a range that does not compromise the reliability of the E-TSCH network.

1 is a schematic diagram of a conventional 15.4e TSCH protocol communication;
2 is a flowchart for explaining a channel quality measurement method for saving energy in an IoT wireless network according to an embodiment of the present invention.
FIG. 3 is a view showing channels in which energy sensing is performed in a specific time slot in FIG. 2; FIG.
Fig. 4 is a diagram showing a method of performing energy sensing when the vehicle is moving in Fig. 2
FIG. 5 is a diagram schematically illustrating the operation flow of periodic energy sensing in FIG. 2; FIG.
FIG. 6 is a diagram illustrating an operation method of an energy saving channel quality measurement method based on E-TSCH according to the present invention
7 is a block diagram of a network device illustrating a structure of a communication layer and an execution unit in an IoT wireless network according to the present invention

Other objects, features and advantages of the present invention will become apparent from the detailed description of the embodiments with reference to the accompanying drawings.

A method of measuring channel quality and a network device for saving energy in an IoT wireless network according to the present invention will now be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. It is provided to let you know. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and are not intended to represent all of the technical ideas of the present invention. Therefore, various equivalents It should be understood that water and variations may be present.

FIG. 2 is a flowchart illustrating a method of measuring energy-saving channel quality in an IoT wireless network according to an embodiment of the present invention.

Referring to FIG. 2, when energy sensing is started for the entire channel in the corresponding time slot (S10), the corresponding time slot is waited for an offset at which the idle interval starts (S20).

When the idle period starts (S30), non-invasive channel quality measurement (CQE) is performed on all the channels (S40).

At this time, the channel quality measurement is a proposed measurement technique for stabilizing a Received Signal Strength Indicator (RSSI) value, which is oscillated by an adaptive TSCH scheme. The RSSI value can be measured through energy detection and the CQE value can be calculated by Equation 1 as follows.

here

Lt; RTI ID =

In a particular channel

Quot; RSSI value " And

Lt; RTI ID =

In a particular channel

Quot; CQE " Also,

The value can be increased when you want to reflect more of the currently measured RSSI value, and can be decreased when you want to stabilize more.

Then, an interference dynamicity (ID) is calculated based on the measured channel quality measurement value, and a period of energy sensing is calculated according to the calculated interference dynamic value (S50).

The interference dynamics can be calculated using the following equation (2), and it can be determined whether the interference change (change in channel quality) is severe or not in the network through the calculated interference dynamics.

As shown in Equation (2), the CQE value currently measured for a specific channel (

), The CQE value measured immediately before (

) Is subtracted from the absolute value of the difference in the CQE value resulting from the change in the specific channel quality. Then, the total sum of the changes in the channel quality is obtained by performing a total of 16 channels from 11th to 26th channels (all channels used in 11th to 26th channels in the 2.4GHz band in the IEEE 802.15.4e standard). Then, the current ASN (Absolute Slot Number) (

), The ASN (

), It is possible to know the number of time slots (measurement time interval) from the point of time when the CQE value was measured immediately before to the point of time when the current CQE value was measured. By dividing the measurement time interval to the total sum of the channel quality change amounts, the interference dynamics with respect to time can be calculated with respect to the total variation amount of the CQE values.

Equation (2) is a formula for calculating the total amount of channel quality measurement values changed during a specific time. If the calculated interference dynamics value is larger than a predetermined threshold value, the change of radio interference is severe, Is less than the preset threshold value, it can be determined that the change of the radio interference is not severe. At this time, the threshold value to be set has fluidity according to the applied network environment.

The period of the energy sensing is controlled according to the value of the interference dynamics through a periodic energy detection technique. For reference, the time required to perform the energy sensing of one channel is 128 μs, and two energy sensing is possible considering the idle period existing in one time slot. FIG. 3 is a diagram illustrating channels in which energy sensing is performed in a specific time slot. The time for energy sensing of 16 channels is 8 time slots. The time of one time slot is defined as 10 ms in the IEEE 802.15.4e standard. The energy sensing of the 16 channels is then considered as one cycle.

At this time, the reason for adjusting the value according to the value of the interference dynamics is that, for example, when the vehicle is stopped, the change of the radio channel is not severe. In this case, since frequent energy sensing is not needed, the energy sensing period is increased, and when the vehicle is moving rapidly, the radio channel is very changed, so frequent energy sensing is required, so that the energy sensing period is shortened to quickly update the interference dynamics.

4 is a view showing a manner of performing energy sensing when the vehicle is moving.

As shown in Fig. 4,

m. < / RTI > This is due to the limited range of possible communication technologies (eg Wi-Fi).

In this case, the calculation of the energy sensing period with respect to the speed of the vehicle is performed according to the following equation (3).

here

Is the average velocity in the energy sensing interval,

Is the time (10ms) that one slot takes. And

The distance of the vehicle moving between the energy sensing zones (the energy performing distance shown in FIG. 2

m). For reference, the energy sensing period in Equation (3) is expressed by the number of slots.

On the other hand, the position of the moving vehicle at a specific time point may correspond to a channel quality measurement value at a specific point in time. The displacement, which is the change in the position, corresponds to the change in the quality measurement value of all the channels. Therefore, since the average velocity can be a concept corresponding to the interference dynamics, the following equation (4) can be applied to the following equation (3).

here

Is an equation for the average speed of the energy sensing period

And the amount of change in the quality measurement value of all the channels between the energy sensing intervals with a corresponding constant,

Means the previous interference dynamics. At this time, the amount of change in time, which is the denominator of the interference dynamics, is expressed by the number of time slots

Can be omitted.

FIG. 5 is a simplified diagram of the operational flow of periodic energy sensing in FIG. 2, wherein the downward arrow shown in FIG. 5 refers to energy sensing for sixteen channels, i.e. one cycle of energy sensing (= 8 time slots) .

In Equation (4)

When the value is set to 2c,

If the value of the interference dynamics measured in step

And energy sensing is performed after a time of 2c has elapsed. after

If the measured interference dynamics value is 2, then the energy sensing interval is

. That is, if the interference dynamics value increases, the energy sensing period decreases. Point

Lt; RTI ID = 0.0 >

If the energy detection interval is

. That is, when the interference dynamic value decreases, the energy sensing interval increases.

The energy sensing cycle is waited for without sensing the energy (S60). At this time, the period is calculated in units of time slots.

If the time period corresponding to the energy sensing period has elapsed, the process is repeated from the beginning in the corresponding start time slot (S70).

As described above, according to the present invention, as shown in FIG. 6, if a change in channel quality is severe in an IEEE802.15.4e E-TSCH based network, the frequency of energy detection may be increased to update the latest channel quality more frequently, If the quality change is not severe, the energy consumption is reduced by reducing the frequency of energy sensing, so that the energy consumption is reduced while maintaining the reliability of the E-TSCH.

7 is a block diagram of a network device illustrating a structure of a communication layer and an execution unit in an IoT wireless network according to the present invention.

As shown in FIG. 7, the network device basically has the IEEE 802.15.4 physical layer 10 and the MAC layer 20 of IEEE 802.15.4e.

The non-intrusive channel quality measurement unit 40 receives the RSSI value from the physical layer 10 to calculate a channel quality measurement value, and then outputs the calculated channel quality measurement value to the high-quality channel selection unit 50 and the energy- (60). At this time, the channel quality measurement value is calculated using Equation (1).

Then, the high-quality channel selection unit 50 generates a list of channels based on the channel quality measurement value transmitted from the non-intrusive channel quality measurement unit 40 and transmits a list of channels selected by the medium access control layer 20 do.

The energy detection period determiner 60 calculates the interference dynamics based on the channel quality measurement value and determines the energy detection period. The determined energy sensing period is sent to the energy sensing unit 10 of the IEEE 802.15.4 physical layer 10 and reflected in the policy. At this time, the interference dynamics are calculated using Equation (2).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It will be apparent to those skilled in the art that various modifications may be made without departing from the scope of the present invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims (10)

(A) when energy sensing is started for the entire channel in the corresponding time slot, the corresponding time slot is awaited by an offset at which the idle interval starts;
(B) when an idle period starts, performing non-intrusive Channel Quality Estimation (CQE) on all channels,
(C) calculating an interference dynamicity (ID) based on the measured channel quality measurement value and calculating an energy sensing period to be adjusted according to the calculated value of the interference dynamic intensity;
(D) waiting without energy sensing for the calculated energy sensing period, and repeating the process from step (A) in a corresponding start time slot after a period of time corresponding to an energy sensing period,
If the interference dynamic value calculated in the step (C) is greater than a predetermined threshold value, it is determined that the change of the radio interference is severe. If the interference dynamic value is smaller than the preset threshold value, it is determined that the change of the radio interference is not severe Wherein the IoT wireless network is a wireless network. 2. The method of claim 1, wherein step (B)
Measuring a Received Signal Strength Indicator (RSSI) value through energy sensing;
Equation

And calculating a CQE value using the CQE value,
At this time,

Lt; RTI ID =

In a particular channel

Is the RSSI value of

Lt; RTI ID =

In a particular channel

To the CQE value of the current measured RSSI value

If you want to increase the value above the set threshold and make it more stable

Value is less than a set threshold value. ≪ Desc / Clms Page number 20 > 2. The method of claim 1, wherein in step (C)
The currently measured CQE value for a particular channel (

), The CQE value measured immediately before (

Calculating a variation amount of a specific channel quality with an absolute value of a CQE value difference obtained as a result of subtracting the CQE value difference,
Obtaining a total sum of changes in channel quality by performing the correction on the frequencies of all channels,
Absolute Slot Number (ASN) at the time of the current measurement

), The ASN (

Calculating a number of time slots (a measurement time interval) from a time point at which the CQE value was previously measured to a time point at which the current CQE value was measured;
And calculating an interference dynamics with respect to time in a total variation amount of the CQE value by dividing the measurement time interval by the total sum of the calculated channel quality variation amounts. How to measure. delete The method according to claim 1,
Wherein the period of energy sensing in the step (C) is adjusted according to a value of interference dynamics through a periodic energy detection technique. The method of claim 1, wherein the cycle of energy sensing in step (C)
Equation

, ≪ / RTI >
At this time,

Means the amount of change in the quality measurement value of all the channels between the energy sensing periods,

Is a previous interference dynamics. ≪ RTI ID = 0.0 > 1 < / RTI > An RSSI value is received from the IEEE 802.15.4 physical layer to calculate a channel quality measurement value, and then the calculated channel quality measurement value is transmitted to the high-quality channel selection unit and the energy- Wealth,
A high quality channel selection unit for generating a list of channels based on the channel quality measurement value input from the non-intrusive channel quality measurement unit and transmitting the list to channels of the IEEE 802.15.4e medium access control;
And an energy detection period determiner for calculating an interference dynamics based on the channel quality measurement value input from the non-intrusive channel quality measurer, determining an energy detection period, and transmitting the determined energy period to an energy sensing performance unit of an IEEE 802.15.4 physical layer,
When the calculated interference dynamics value is greater than a preset threshold value, it is determined that the change of radio interference is severe, and when the interference dynamics value is smaller than a preset threshold value, it is determined that the radio interference variation is not severe. A network device for channel quality measurement that conserves energy in a wireless network. 8. The apparatus of claim 7, wherein the non-intrusive channel quality measurement unit
Equation

To calculate channel quality measurements,
At this time,

Lt; RTI ID =

In a particular channel

Is the RSSI value of

Lt; RTI ID =

In a particular channel

To the CQE value of the current measured RSSI value

If you want to increase the value above the set threshold and make it more stable

Wherein the threshold value is less than a predetermined threshold value. 8. The apparatus of claim 7, wherein the energy sensing period determiner
Equation

To calculate the interference dynamics,
At this time,

Is a currently measured CQE value for a particular channel,

Is a CQE value measured immediately before,

Is an Absolute Slot Number (ASN) at the time of the present measurement,

Is an ASN at the time of the previous measurement. ≪ RTI ID = 0.0 >< / RTI > 7. The apparatus of claim 6, wherein the energy sensing period determiner
Equation

To calculate an energy sensing period,
At this time,

Means the amount of change in the quality measurement value of all the channels between the energy sensing periods,

Wherein the channel quality measure is a previous interference dynamics measure.

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