KR101430072B1 - Prioritized data transmission method in wireless sensor networks - Google Patents

Abstract

In the present invention, a wireless sensor network sets up a route by avoiding a congestive section of a wireless sensor network, and determines a channel access priority based on QoS requirements. A method for transmitting data according to the present invention comprises a step of confirming channel status information based on a packet delivery time required in the current time point between an originator and a neighboring recipient in the wireless sensor network, an average transmission delay for a predetermined time period, and the average between the length of an available space of interface buffer of the originator at the current time point and the length of an available space of interface buffer for the predetermined time period; a step of selecting a route which has the minimum delay and congestion based on the accumulated value of the channel status information; a step of controlling a backoff value according to an access category defined on a packet to be transmitted; and a step of transmitting the packet using the backoff value. Therefore, the prioritized data can be transmitted to the destination more quickly and stably than the other data, and the load balancing of the entire wireless sensor network can be obtained.

Description

[0001] The present invention relates to a method for transmitting emergency data in a wireless sensor network,

The present invention relates to a method for transmitting data in a wireless sensor network, and more particularly, to a method for efficiently transmitting emergency data based on load balancing and QoS priority in a wireless sensor network based on IEEE 802.15.4 .

Since the IEEE 802.15.4-based wireless sensor network is basically a technology for supporting communication between individuals and peripherals using low-speed communication, it is difficult to process medical data and urgent quality of service (QoS) packets requiring urgent processing There are a lot of restrictions.

Of course, although it is possible to guarantee QoS through independent slots by using GTS (Guaranteed Time Slot), this method has many difficulties in maintaining communication state in terms of overhead for maintaining synchronization and expandability of network.

Also, all the nodes in the network access the channel using the same probability backoff algorithm in the MAC layer, and thus can not provide QoS and differentiated transmission.

In order to solve this, node-level hop-by-hop solutions have been proposed as previous studies, but there are few ways to consider multi-hop based end-to-end routing. There are, of course, end-to-end approaches, but routing standards such as the existing Ad Hoc On-Demand Distance Vector Routing (AODV) or Dynamic Source Routing (DSR) do not consider QoS.

In addition, many techniques to provide QoS in multi - hop environment have been proposed. However, when congestion of network occurs simultaneously due to increase of multimedia communication, there are not many methods to consider QoS while avoiding congestion. In addition, there is a lack of communication design applicable to medical application services.

SUMMARY OF THE INVENTION The present invention has been made in view of the above technical background, and it is an object of the present invention to provide a data transmission method capable of transmitting medical data urgently required in a wireless sensor network to a destination faster and more reliably than other data .

Another object of the present invention is to provide a data transmission method capable of ensuring quality of service in a wireless sensor network.

In order to solve the above problem, the present invention avoids a congestion period in a congested network, sets a path, and simultaneously determines a channel access priority based on QoS requirements.

That is, a method for transmitting data in a wireless sensor network according to the present invention is characterized in that a method of transmitting data in a wireless sensor network includes transmitting a packet transmission time required at a current point in time between a sender in the wireless sensor network and a receiver adjacent to the transmitter, Checking channel state information based on an average of a usable space length of the interface buffer of the sender at the current time and an available space length of the interface buffer during the predetermined time; Selecting a path having the least delay and congestion based on the accumulated value of the channel state information; Adjusting a backoff value according to an access category (AC) defined in a packet to be transmitted; And transmitting the packet using the backoff value.

Here, if the packet to be transmitted is a control packet, it is preferable that a header of the control packet includes a {channel state information, AC, timeout time} field, and the control packet includes a RREQ RREP (Route Reply) packet.

The packet delivery time includes packet processing time, queuing delay, backoff delay, transmission and propagation delay.

When the channel state information is QF (i), it can be determined by the following equation (1).

[Equation 1]

는 송신자와 수신자 사이에서 현재 시점 t에서 요구되는 패킷전달 시간,

는 일정 시간 θ 동안의 평균 전송지연,

는 t에서 송신자의 인터페이스 버퍼의 사용가능한 공간의 길이,

는 θ 동안의 인터페이스 버퍼의 사용가능한 공간의 길이의 평균이다)(From here,

Between the sender and the receiver, the packet delivery time required at the current time t,

Is the average transmission delay for a certain time?

Is the length of the available space of the sender's interface buffer at t,

Is the average of the available space length of the interface buffer for theta)

The AC may include urgent data, surveillance data, general data, concession data urgently required. In the step of adjusting the backoff value, emergency data, surveillance data, general data, It is preferable to adjust to have a large backoff value.

In addition, each node included in the wireless sensor network maintains a neighbor table having fields of {neighbor node's ID, neighbor node's AC, timeout time}, and each node refers to the neighbor table, If the AC of the first packet to be transmitted is general data and the AC of the second packet to be transmitted by its neighbor node is emergency data, AC of the first packet can be set as concession data.

In the step of adjusting the backoff value, the backoff value may be adjusted by further using the channel state information.

A node included in a wireless sensor network according to another aspect of the present invention includes an AC definition unit defining an access category (AC) for a packet to be transmitted; A packet transmission time required at a current point in time between a sender in the wireless sensor network and a receiver adjacent to the sender, an average transmission delay during a predetermined fixed time, a length of a usable space of the sender's interface buffer at the current point, A monitoring unit for monitoring channel state information based on an average of the available space length of the interface buffer for the predetermined time; A routing controller for selecting a route with the least congestion to transmit the packet in the wireless sensor network based on the accumulated value of the channel state information; A routing table managed by the routing control unit; A backoff setting unit for adjusting a backoff value according to the defined AC; And a transmitter for transmitting the packet using the backoff value.

According to the present invention, when various data including urgent data such as medical data are mixed in a wireless sensor network, even if congestion occurs due to the characteristics of the multi-hop network, a route with the least congestion is selected, a different backoff value is set, The urgent medical data can be delivered to the destination more quickly and stably than other data.

Also, the load balancing effect of the entire wireless sensor network can be obtained.

FIG. 1 is a flowchart schematically showing an entire data transmission method of a wireless sensor network according to an embodiment of the present invention.
2 shows fields added to the RREQ and RREP headers in the data transmission method of the wireless sensor network according to the embodiment of the present invention.
3 is a flowchart illustrating a data transmission method of a wireless sensor network according to an embodiment of the present invention.
4 and 5 are flowcharts illustrating specific operations in the MAC layer in the data transmission method of the wireless sensor network according to the embodiment of the present invention.
6 shows a configuration of a transmission system included in each node to implement a data transmission method of a wireless sensor network according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being 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. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. It is noted that the terms "comprises" and / or "comprising" used in the specification are intended to be inclusive in a manner similar to the components, steps, operations, and / Or additions.

Hereinafter, a method for transmitting data in a wireless sensor network according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a flowchart schematically showing an entire data transmission method in a wireless sensor network according to an embodiment of the present invention.

As shown in FIG. 1, in a data transmission method in a wireless sensor network according to an embodiment of the present invention, a source node selects a transmission path that minimizes a QF value using a QF value, which is a channel estimation metric (S110 ).

The QF value, which is a channel estimation metric, is defined to check the channel state in a sensor network in which congestion is expected. In each node i, QF (i) is defined as follows.

는 송신자와 이와 이웃하는 수신자 사이에서 현재시간 t 시점에서 요구되는 패킷전달 시간이다.

는 미리 정해진 θ시간 동안의 평균 전송지연이다. 즉 θ는 [t-θ, t]로 표현이 가능하다. 유사하게

는 현재시간 t에서 노드 i의 인터페이스 버퍼의 사용가능한 공간의 길이이며,

는 θ시간 동안의 평균적인 버퍼길이를 의미한다. 한편, 패킷 전달 시간은 패킷 가공시간, 큐잉 지연, 백오프(backoff) 지연, 전송 및 전파지연을 포함한다. 이때, 전송지연이라 함은 채널의 대역폭(bandwidth)에 기반한 데이터 전송률(data rate)을 의미한다. At this time,

Is the packet delivery time required at the current time instant t between the sender and its neighbor.

Is an average transmission delay over a predetermined &thetas; time. That is, θ can be expressed as [t-θ, t]. Similarly

Is the length of the available space of the interface buffer of node i at the current time t,

The means the average buffer length over the [theta] time. On the other hand, the packet delivery time includes packet processing time, queuing delay, backoff delay, transmission and propagation delay. Here, the transmission delay means a data rate based on a bandwidth of a channel.

Using the QF metric as described above, the source node performs a path search to the destination node. In other words, the source node s broadcasts its measured value QF (s) in a RREQ (Route Request) packet, and the neighboring node that received it sums its QF value again and retransmits it to the destination node. Finally, the destination node receives the route with the smallest sum of QFs and sends the route reply (RREP) to the source node to complete the route setup.

This is similar to using RREQ / RREP in existing AODV and DSR, but it differs in that it finds the minimum QF value rather than the minimum hop path selection. As a result, the path with the least delay and congestion is selected through the algorithm according to the embodiment of the present invention, and it can be expressed by the following equation (2).

At this time, R is a set of nodes constituting one path.

In addition, the source node defines an AC (Access Category) and sets it together with RREQ and RREP to set QoS requirements when routing for emergency medical data transmission. The AC information is used to reserve a differentiated priority access when transmitting a data packet in the MAC layer. In the data transmission method in the wireless sensor network according to the embodiment of the present invention, And the MAC layer transmits the packet using the value (S120).

The fields added to the RREQ and RREP headers to transmit a packet through steps S110 and S120 are as shown in FIG.

The value of the first field is the cumulative value of QF (i), and the second field is the AC value of the source node s, AC (s). T _EX is a timeout value, which indicates that the AC setting value is valid for the time. This T _EX value is updated every time a node receives a new data packet from the source, and if T _EX times out, it sends the packet in the usual best effort manner.

On the other hand, the destination node can receive the QF summation values from multiple routes. If all the routes have the same value, the route is set based on the minimum hop as in the existing routing protocol.

When the optimal path is set in step S110 as described above, the nodes in the path transmit the packet in the MAC layer (S120). At this time, different back-off parameters for each AC reserved in advance as shown in [Table 1] To access the channel.

Data type AC adaptive backoff Medical data 3 MinBE = 1
MaxBE = 5
If (BE-QF> MinBE) then
Adaptive Backoff = 2 ^{BE - QF} -1,
Else
Adaptive Backoff = 2 ^MinBE -1 Monitoring Data 2 MinBE = 3
MaxBE = 5
| Default Backoff - QF | Best effort data One Default Backoff Yield data 0 MinBE = 3
MaxBE = 6
If (BE + QF < MaxBE) then
Adaptive Backoff = 2 ^{BE + QF} -1,
Else
Adaptive Backoff = 2 ^MaxBE -1

In the general IEEE 802.15.4 standard, the backoff time for channel access is arbitrarily selected at (2 ^BE -1), and MinBE (minimum BE value) and Max BE (maximum BE value) are fixed at 3 and 5, respectively. This makes it difficult to access different channels in various environments. Therefore, in the embodiment of the present invention, it is dynamically adjusted according to AC as shown in Table 1 above.

In Table 1, AC3 refers to urgent medical data. For fast channel access, MinBE is reduced to 1, and the adaptive backoff value is newly calculated according to the measured QF value. AC2 refers to surveillance data that is relatively lower in priority than medical data but somewhat higher than general data. (Eg, environmental monitoring sensors such as temperature, humidity, and gas).

AC1 represents the best effort data with the default value, and AC0 defines the data that yields access to the channel to AC3. In other words, AC0 is to set its own backoff time to AC0 so that AC3 can smoothly access the channel when its neighbor node transmits data of AC3 from AC1 data. This is because, in a situation where medical traffic is heavy, if many nodes reduce the backoff time, the probability of a packet collision increases, thereby also mitigating a channel collision through the yield data.

For this purpose, each node monitors its neighboring nodes to transmit an ending AC, and maintains the result as a neighbor table (Neighbor Table). The field information included in the neighbor table is as follows.

{ID of neighbor node, AC of neighbor node, T _EX }

This table is also valid only for the time according to the timeout field T _{EX and} is updated every time a new data packet is received or overhear. Using this table information, when there is a node having AC3 among the neighbor nodes and its data is AC1, it changes its data to AC0 and yields the channel.

FIG. 3 is a flowchart illustrating a data transmission method in a wireless sensor network according to an embodiment of the present invention. FIGS. 4 and 5 are flowcharts of a method of transmitting data in a wireless sensor network according to an embodiment of the present invention. Fig.

As shown in FIG. 3, when a packet is received at an arbitrary node (S300), it is determined whether the packet is a control packet (S310). If it is not a control packet, that is, if it is a data packet ("NO" in S310), the routing table is searched (S312), and the QF value is calculated (S314) to determine whether congestion is expected (S316). If congestion is expected ("YES" in S316), RERR is generated. The data packet (if NO in S316) or the generated RERR packet (S318) is transmitted to the MAC layer and transmitted (S360).

If the received packet is a control packet (Yes in S310), if the received packet is a RREQ (Yes in S320), it is determined whether the node receiving the packet is a destination node (S322) ), Selects a path having the minimum QF value (S324), and transmits the RREP accordingly (S326, S360).

If the node receiving the packet is not the destination node (No in S322), it is determined whether it is a new RREQ (S330). If it is a new RREQ (Yes in S330), the QF value is calculated and added to the received QF value (SS332) and rebroadcasts the RREQ with the corresponding QF value (S334, S360). If it is not a new RREQ ("NO" in S330), the RREQ is discarded (S336).

If the received packet is RREP (YES in S340), the routing table is updated (S342), and it is determined whether the node is a source node (S344). If the received packet is not a source node, RREP is transmitted (S326, S360) If it is a node, in step S342, a route is established according to the updated routing table (S346).

If the received packet is a RERR (Yes in S350), a transmission error has occurred and thus the path is updated (S352).

In step S360, the packet transmission in the MAC layer is performed. When a packet is transmitted from the upper layer in step S362, the neighboring AC table is updated in step S400, a differential backoff is determined on a reserved AC basis in step S500, And delivering the packet to the layer (S364).

Among these, the step of updating the neighboring AC table (S400) and the step S500 of determining the back-off discriminated for each reserved AC are shown in detail in FIG. 4 and FIG. 5, respectively.

4, when a packet is transferred from the upper layer to the MAC layer in step S362, the preprocessor inserts an entry into the neighboring AC table (step S422) , ( "Yes" in S430) If the RERR, and updates the T _EX of deleting an entry from the neighbor table AC (S432), then AC neighbor table (S440).

Now, a differential backoff is determined based on the updated neighboring AC table, and channel access is performed accordingly.

That is, as shown in FIG. 5, if there is a neighbor node having AC1 node and AC3 (YES in S510), the corresponding AC1 node changes to AC0 to yield access to the channel (S512).

If the corresponding node is not the AC1 node or there is no neighboring node with AC3 (No in S510), AC is mapped to the MinBE and MaxBE values (S520). Next, NB = 0 and BE = MinBE (AC) (S522), and a differential backoff delay according to AC is performed (S524). If the channel is in an idle state (Yes in S528), a frame is transmitted (S530).

If the channel is not in the idle state (NO in S528), NB = NB + 1 and BE = Min (BE + 1, MaxBE (No in S542), the process returns to step S524 in which differential backoff delay according to AC is performed. If NB is greater than MaxCSMABACKoffs (YES in S542), transmission fails (S544).

6 illustrates a configuration of a transmission system included in each node to implement a data transmission method according to an embodiment of the present invention.

As shown in FIG. 6, there is an AC definition unit 610 for defining an AC in the application layer, and a routing control unit 620 for setting a route in the IP layer manages the routing table 630.

The monitoring unit 640 monitors the QF and the neighbor table, and sets a different back-off delay in the back-off setting unit 650 accordingly.

While the invention has been described in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit of the invention.

Claims (5)

A method of transmitting data in a wireless sensor network,
A packet transmission time required at a current point in time between a sender in the wireless sensor network and a receiver adjacent to the sender, an average transmission delay during a predetermined fixed time, a length of a usable space of the sender's interface buffer at the current point, Determining channel state information based on an average of the available space length of the interface buffer for the predetermined time;
Selecting a path with the least congestion based on the cumulative value of the channel state information;
Adjusting a backoff value according to an access category (AC) defined in a packet to be transmitted; And
Transmitting the packet using the backoff value;
And transmitting the data to the wireless sensor network. 2. The method of claim 1, wherein if the packet to be transmitted is a control packet,
In the header of the control packet,
{Channel state information, AC, timeout time}
The method comprising the steps of: 2. The method of claim 1,
A method for transmitting data in a wireless sensor network, including packet processing time, queuing delay, backoff delay, transmission and propagation delay. The method according to claim 1,
The AC includes emergency data, monitoring data, general data, concession data,
In the step of adjusting the backoff value,
The backoff value is adjusted to have a large backoff value in the order of the urgent data, the monitoring data, the general data, and the concession data,
Each node included in the wireless sensor network,
{Identifier of neighboring node, AC of neighboring node, timeout time}
Lt; RTI ID = 0.0 &gt; field &lt; / RTI &gt;
Each node refers to the neighbor table, and if the AC of the first packet to be transmitted by the node is general data and the AC of the second packet to be transmitted by its neighbor node is emergency data, A method for transmitting data in a wireless sensor network that sets AC as concession data. As a node included in a wireless sensor network,
An AC definition unit for defining an access category (AC) for a packet to be transmitted;
A packet transmission time required at a current point in time between a sender in the wireless sensor network and a receiver adjacent to the sender, an average transmission delay during a predetermined fixed time, a length of a usable space of the sender's interface buffer at the current point, A monitoring unit for monitoring channel state information based on an average of the available space length of the interface buffer for the predetermined time;
A routing controller for selecting a route with the least congestion to transmit the packet in the wireless sensor network based on the accumulated value of the channel state information;
A routing table managed by the routing control unit;
A backoff setting unit for adjusting a backoff value according to the defined AC; And
And a transmitter for transmitting the packet using the backoff value.

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