KR102065172B1 - Method of frequency synchronization of distributed networks - Google Patents

Abstract

The present invention relates to a carrier frequency synchronization method and apparatus of a node included in a distributed network. A carrier frequency synchronization apparatus including a frequency offset estimator, an offset average value calculator, and a frequency adjustment value calculator, according to an embodiment of the present invention, Receiving a preamble from a plurality of adjacent nodes adjacent to the node, estimating an offset of a carrier frequency from the received preamble for each of the plurality of adjacent nodes, calculating a mean value of the estimated offsets, and using an average value The carrier frequency is adjusted by calculating an adjustment value of the carrier frequency for a plurality of adjacent nodes, and adjusting a carrier frequency of the node based on the adjustment value.

Description

Frequency synchronization method in distributed networks {Method of frequency synchronization of distributed networks}

The present invention relates to a frequency synchronization method in a distributed network.

In an orthogonal frequency division multiple access (OFDMA) based system, a frequency offset may occur due to a moving speed, an oscillator error, or an estimation error of each node. This frequency offset causes inter-node interference, which degrades the overall system performance.

In particular, in a distributed network in which there are a plurality of nodes, each node must synchronize with all neighboring nodes, and even if any node is synchronized, interference may be caused by other unsynchronized neighboring nodes.

Accordingly, an embodiment of the present invention provides a flexible and organic frequency offset synchronization method applicable to a distributed network.

According to one embodiment of the present invention, there is provided a carrier frequency synchronization method of a node included in a distributed network. The carrier frequency synchronization method may include receiving a preamble from a plurality of adjacent nodes adjacent to a node, estimating an offset of the carrier frequency from each of the plurality of adjacent nodes from the received preamble, Calculating an average value, calculating an adjustment value of the carrier frequency with respect to all the plurality of adjacent nodes based on the average value, and adjusting a carrier frequency of the node based on the adjustment value.

In the carrier frequency synchronization method, the neighbor node may be the specific node when the node receives a preamble a predetermined number of times or more from a specific node among the plurality of neighbor nodes.

In the carrier frequency synchronization method, the neighboring node includes a global positioning system (GPS) or one of one-hop nodes of the node when the distributed network is hierarchical. It may be a node synchronized with a node including a.

The carrier frequency synchronization method may further include calculating an adjustment request value of the carrier frequency based on the adjustment value and the average value, and transmitting the calculated adjustment request value.

The carrier frequency synchronization method may further include updating the average number of calculations of the offset, and transmitting the updated number of calculations of the average value.

)값 및 상기 평균값을 이용하여 상기 인접 노드 전체에 대한 상기 반송파 주파수의 조정값을 계산하는 단계를 포함할 수 있다.The calculating of the adjustment value in the carrier frequency synchronization method may include receiving the adjustment request value calculated at the neighbor node from the neighbor node, and calculating the average value of the offsets updated at the neighbor node from the neighbor node. Receiving a delta calculated from the received adjustment request value and the average number of calculations of the received offset;

Calculating an adjustment value of the carrier frequency for all the adjacent nodes using the value and the average value.

)로 고정하는 단계를 더 포함할 수 있다.In the carrier frequency synchronization method, when the average value calculation count of the offset exceeds a preset number, the average value calculation count is a constant (

It may further comprise a step of fixing to).

)값 및 상기 평균값을 이용하여 상기 인접 노드 전체에 대한 상기 반송파 주파수의 조정값을 계산하는 단계를 포함할 수 있다.The calculating of the adjustment value in the carrier frequency synchronization method may include receiving the adjustment request value calculated at the neighbor node from the neighbor node, and calculating the received number of adjustment request values and the average number of calculations of a fixed offset. Delta (

Calculating an adjustment value of the carrier frequency for all the adjacent nodes using the value and the average value.

According to another embodiment of the present invention, a carrier frequency synchronization apparatus of a node included in a distributed network is provided. The apparatus for synchronizing carrier frequencies includes a communication unit for receiving a preamble from a plurality of adjacent nodes adjacent to the node, a frequency offset estimator for estimating an offset of the carrier frequency for each of the plurality of neighbor nodes from the received preamble, An offset average value calculator for calculating an average value of the estimated offsets, a frequency adjustment value calculator for calculating the adjusted value of the carrier frequency for all of the plurality of adjacent nodes through the average value, and the adjusted value of the node based on the adjusted value. And a frequency adjusting unit for adjusting the carrier frequency.

In the carrier frequency synchronization apparatus, the neighbor node may be the specific node when the node has received a preamble a predetermined number of times or more from a specific node among the plurality of neighbor nodes.

In the carrier frequency synchronization apparatus, the adjacent node includes a global positioning system (GPS) or one of the one-hop nodes of the node when the distributed network is hierarchical. It may be a node synchronized with a node including a.

The apparatus for synchronizing a carrier frequency may further include an adjustment request value calculator configured to calculate an adjustment request value of the carrier frequency based on the adjustment value and the average value, and transmit the calculated adjustment request value.

The apparatus for synchronizing a carrier frequency may further include a count calculator configured to update the average count count of the offset and transmit the updated average count count to the communication unit.

)값 및 상기 평균값을 이용하여 상기 인접 노드 전체에 대한 상기 반송파 주파수의 조정값을 계산할 수 있다.In the carrier frequency synchronization apparatus, the adjustment value calculator, receives the adjustment request value calculated in the neighbor node from the neighbor node, receives the average number of calculations of the offset updated in the neighbor node from the neighbor node, Delta calculated from the received adjustment request value and the average number of calculations of the offsets received.

) And the average value may be used to calculate the adjusted value of the carrier frequency for the entire adjacent node.

)로 고정할 수 있다.In the carrier frequency synchronization apparatus, the number calculating unit may determine the average number of calculations as a constant when the number of calculations of the average value of the offset exceeds a preset number.

) Can be fixed.

)값 및 상기 평균값을 이용하여 상기 인접 노드 전체에 대한 상기 반송파 주파수의 조정값을 계산할 수 있다. In the carrier frequency synchronization apparatus, the adjustment value calculator is configured to receive the adjustment request value calculated at the neighbor node from the neighbor node, and calculate the delta calculated from the received number of adjustment request values and the average value of the fixed offset.

) And the average value may be used to calculate the adjusted value of the carrier frequency for the entire adjacent node.

As such, according to an embodiment of the present invention, a node entering a distributed network through a method similar to the proposed algorithm may synchronize its own carrier frequency to synchronize with a carrier frequency of a newly entered network. Also, if there is a need to synchronize periodically, each node in the distributed network can synchronize the carrier frequency with surrounding nodes with low overhead.

1 is a diagram illustrating a distributed network according to an embodiment of the present invention.
2 is a block diagram illustrating a carrier frequency synchronization device according to an embodiment of the present invention.
3 is a flowchart illustrating a frequency synchronization process performed at node i at the k-th update point according to an embodiment of the present invention.
4 is a flowchart illustrating a frequency synchronization process performed at node i by limiting the number of average value calculations of frequency offsets according to another embodiment of the present invention.
FIG. 5 is a flowchart illustrating a frequency synchronization process performed at node i without updating the average number of calculation of a frequency offset according to another embodiment of the present invention.
6 is a flowchart illustrating a frequency synchronization process performed at node i according to another embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it may further include other components, except to exclude other components unless specifically stated otherwise. In addition, the terms “… unit”, “… unit”, “module”, “block”, and the like described in the specification mean a unit that processes at least one function or operation, which is hardware or software or a combination of hardware and software. It can be implemented as.

1 is a diagram illustrating a distributed network according to an embodiment of the present invention.

Referring to FIG. 1, a distributed network according to an embodiment of the present invention includes a plurality of nodes 100 connected by a communication link 110. Each node included in the distributed network synchronizes frequencies using a preamble received from an adjacent node. In this case, the frequency synchronization update period of each node may be set in consideration of the number of adjacent nodes. Alternatively, the frequency synchronization update period may be fixed to a predetermined value or may be defined as the number of preamble receptions from neighbor nodes.

2 is a block diagram illustrating an apparatus for synchronizing a carrier frequency according to an embodiment of the present invention, and FIG. 3 is a flowchart illustrating a frequency synchronization process performed at the node i at a k-th update point according to an embodiment of the present invention. .

2, the carrier frequency synchronization device 200 according to an embodiment of the present invention, the communication unit 210, the frequency offset estimation unit 220, the offset average value calculation unit 230, the frequency adjustment value calculation unit ( 240, and a frequency adjuster 250. The apparatus may further include an adjustment request value calculator 260 and a count operator 270.

) 및 반송파 주파수 조정 요청값(

) 등)를 송수신할 수 있다. 각종 파라미터의 송수신 여부는 각 노드에서 본 발명의 실시예에 따른 알고리즘을 수행할 때 필요한 오버헤드에 따라서 결정될 수 있다.The communication unit 210 receives the preamble from another node in the distributed network, and transmits the preamble to another node. In addition, various parameters (number of frequency offset calculations)

) And carrier frequency adjustment request value (

), Etc.). Whether to transmit or receive various parameters may be determined according to the overhead required when performing an algorithm according to an embodiment of the present invention at each node.

The frequency offset estimator 220 estimates the frequency offset of the corresponding node using the preamble received from each node in the distributed network. That is, the frequency offset estimator 220 estimates the frequency offset by the number of times the preamble is received for each node.

The offset average value calculator 230 calculates an average value of the frequency offsets estimated for each node in the distributed network. When the frequency offset estimator 220 estimates the frequency offset of a specific node in the distributed network several times, the offset average value calculator 230 may calculate an average value of the estimated frequency offsets for each node.

The frequency adjustment value calculator 240 calculates the frequency adjustment value of the node based on the average value of the frequency offsets calculated by the offset average value calculator 230. The frequency adjustment value calculator 240 may use various parameters received by the communication unit when calculating the frequency adjustment value.

The frequency adjusting unit 250 adjusts the frequency of the node equipped with the carrier frequency synchronizing device based on the frequency adjusting value calculated by the frequency adjusting value calculator 240.

In addition, the adjustment request value calculation unit 260 calculates an average value of the frequency adjustment value calculated by the frequency adjustment value calculation unit 240 and the frequency offset calculated by the offset average value calculation unit 230 and transmits the average value to another node. Calculate the frequency adjustment request value.

In addition, the number calculating unit 270 updates the average value calculation frequency of the frequency offset and transmits the updated average value calculation number to the communication unit 210 so that the average value calculation frequency of the frequency offset can be transmitted to another node. On the other hand, in order to reduce the overhead of the algorithm, the number calculating unit 270 may fix the average number of calculations to a constant without updating the number of times of calculating the average value more than the predetermined number of times.

Hereinafter, a frequency synchronization process of a node entering a distributed network through FIG. 3 and pseudo code 1 below will be described.

Doctor code 1

Node i in pseudocode 1 is a node that performs frequency synchronization according to an embodiment of the present invention.

에 포함된 노드로부터 프리앰블을 수신(S301)할 때마다 집합

에 포함된 노드에 대한 주파수 옵셋을 1차 추정한다(S302). 이때, 집합

는, 노드 i에 인접한 노드 중, 노드 i에서 미리 정해진 횟수(

) 이상 수신된 프리앰블을 전송한 노드의 집합이다. 본 발명의 실시예에서, 집합

에 포함된 노드를 '노드 m'이라고 한다. First, node i is a set

Set each time the preamble is received from the node included in the (S301)

First, estimate the frequency offset for the node included in (S302). At this time,

Is a predetermined number of times in node i among nodes adjacent to node i (

) Is a set of nodes that transmitted the received preamble. In an embodiment of the invention, a set

The node included in is called 'node m'.

는 k번째 업데이트 시점에서 노드 i가 노드 m에게서 r번째 수신한 프리앰블로부터 노드 m에 대한 주파수 옵셋을 임시적으로 추정한 값이다.

Is a value obtained by temporarily estimating the frequency offset of the node m from the preamble received by the node i from the node m at the k-th update point.

)를 바탕으로 1차 추정한 주파수 옵셋의 평균값을 계산한다. 즉, 1차 추정한 주파수 옵셋의 평균값인

은 노드 i가 노드 m으로부터 프리앰블을

₍

₎회 수신한 후(S303) 노드 m의 주파수 옵셋을 최종적으로 추정한 값이다(S304).Since then, node i has received the preamble from node m so far (

Calculate the average value of the first estimated frequency offset. That is, the average value of the first-order estimated frequency offset

Node i takes the preamble from node m

₍

_{This is the} final estimation of the frequency offset of the node m after reception (S303).

)는

이다.Thereafter, the node i updates the number of times that the average value of the frequency offsets for the node m is calculated until the k-th update time point (S305). In pseudocode 1, the number of times node i computed the average value of the frequency offset for node m (

)

to be.

에 포함된 노드로부터

및

를 수신한다(S306). 이때, 집합

는, 집합

에 포함된 노드 중, 노드 i에서 수신된 반송파 주파수 조정 요청값(

)을 전송한 노드의 집합이다. Node i is then aggregated

From nodes contained in

And

Receive (S306). At this time,

A set

Among the nodes included in, the carrier frequency adjustment request value received at node i (

) Is the set of nodes that sent.

에 포함된 노드를 '노드 n'이라 하고,

는 k번째 업데이트 시점에서 노드 n이 노드 i에게 전송하는 반송파 주파수 조정 요청값을 나타내며,

는 k번째 업데이트 시점에서 노드 n이 노드 i에 대해서 주파수 옵셋의 평균값을 계산한 횟수를 나타낸다.In an embodiment of the invention, a set

The node included in is called 'node n',

Denotes a carrier frequency adjustment request value transmitted from node n to node i at the k-th update time point,

Denotes the number of times node n computes the average value of the frequency offset with respect to node i at the k-th update point.

및

과, 앞서 계산한 주파수 옵셋의 평균값(

)을 바탕으로 노드 n에 대한 최종 주파수 옵셋값(

)을 계산한다(S307). After that, node i receives

And

And the average value of the frequency offset

Based on the final frequency offset for node n

) Is calculated (S307).

는 노드 n과 노드 i의 관계에서 결정될 수 있다. 즉, 노드 i가 노드 n으로부터 반송파 주파수 조정 요청값은 수신하지 못하고 미리 정해진 횟수(

) 이상 프리앰블만을 수신한 경우,

는 0으로 결정될 수 있고, 반송파 주파수 조정 요청값은 수신하였으나 프리앰블은 미리 정해진 횟수 이상 수신하지 못한 경우

는 1로 결정될 수 있다.At this time,

May be determined in the relationship between node n and node i. That is, the node i does not receive the carrier frequency adjustment request value from the node n and the predetermined number of times (

) If only the preamble is received,

May be determined to be 0 and the carrier frequency adjustment request value is received but the preamble is not received more than a predetermined number of times.

May be determined as 1.

는 0에서 1 사이의 임의의 값으로 결정될 수 있으며, 이때에는 아래 수학식 1에 따라

가 결정될 수 있다.In addition, when the node i also receives the carrier frequency adjustment request value from the node n, and also receives the preamble a predetermined number or more

May be determined as any value between 0 and 1, in which case

Can be determined.

)을 이용하여 집합

에 포함된 모든 노드에 대한 반송파 주파수의 조정값(

)을 계산하고, 자신의 반송파 주파수를 조정한다(S308). 이때,

는 노드 집합

에 포함된 노드의 수이다. Finally, node i is the last frequency offset value for node n (

) Using

The adjusted value of the carrier frequency for all nodes in

) And adjust its carrier frequency (S308). At this time,

Set of nodes

The number of nodes in the.

)을 이용하여 자신의 반송파 주파수를 조정함으로써, 노드 i는 새롭게 진입한 네트워크의 반송파 주파수와 동기화 할 수 있다.As above, node i is the final calculated carrier frequency adjustment value (

Node i can synchronize with the carrier frequency of the newly entered network.

)과 노드 n대한 최종 주파수 옵셋값(

)의 차이를 계산하여, 반송파 주파수 조정 요청값(

)를 계산(S309)할 수 있고, 노드 n에 대한 반송파 주파수 조정 요청값(

) 및 주파수 옵셋의 평균값 계산 횟수(

)를 노드 n으로 전송할 수 있다(S310). 도 3에 도시된 발명의 한 실시예는 노드 n과 노드 m이 동일한 경우이다. Further, node i is an adjustment value of the carrier frequency (

) And the final frequency offset for node n (

), Calculate the difference between the carrier frequency adjustment request value (

) Can be calculated (S309), and the carrier frequency adjustment request value for node n (

) And the number of averages of frequency offsets calculated (

) May be transmitted to the node n (S310). One embodiment of the invention shown in FIG. 3 is where node n and node m are identical.

및

는 각각 집합

및

가 될 수 있다. 이 경우,

및

는 본 발명의 실시예에 따른 분산 네트워크가 계층 구조일 때 집합

및

의 상위 그룹에 속하는 노드의 집합이다. 이때, 상위 그룹은 글로벌 위치 결정 시스템(global positioning system, GPS)을 장착한 노드 또는 GPS를 장착한 노드와 동기화된 노드의 집합이 될 수 있다.On the other hand, set from pseudocode 1.

And

Each set

And

Can be in this case,

And

Is Aggregation when distributed network is hierarchical according to an embodiment of the present invention

And

A set of nodes belonging to the parent group of. In this case, the upper group may be a node equipped with a global positioning system (GPS) or a set of nodes synchronized with a node equipped with a GPS.

In this case, the pseudo code 1 may be expressed as pseudo code 1-1.

Doctor Code 1-1

4 is a flowchart illustrating a frequency synchronization process performed at node i by limiting the number of average value calculations of frequency offsets according to another embodiment of the present invention.

In the pseudo code 2 below, the overhead of the frequency synchronization process can be reduced by updating the average number of frequency offset calculations counted by the node i only a predetermined number of times.

Hereinafter, a process of performing frequency synchronization with low overhead by a specific node included in a distributed network will be described with reference to FIG. 4 and the pseudo code 2 below.

Doctor code 2

는 의사코드1에서와 같이 노드 m의 주파수 옵셋을 임시적으로 추정한 값을 나타낸다.In pseudo code 2, each time node i receives a preamble from node m (S401), first estimates a frequency offset of node m (S402).

Denotes a value of temporarily estimating the frequency offset of the node m as in pseudo code 1.

) 이상 수신(S403)한 노드 i는 그때까지 인접 노드 m으로부터 프리앰블을 수신한 횟수(

)를 기준으로 1차 추정한 주파수 옵셋의 평균값(

)을 계산한다(S404).

도 의사코드1에서와 같이 노드 m의 주파수 옵셋을 최종적으로 추정한 값을 나타낸다.Thereafter, the preamble is determined a predetermined number of times (

Node i has received more than one preamble from the neighbor node m until then (

, Based on the first-order estimated frequency offset (

) Is calculated (S404).

As shown in Pseudo Code 1, the frequency offset of node m is finally estimated.

)의 업데이트를 제한한다(S405). 즉,

가 미리 정해진 횟수(

)보다 작으면,

를 업데이트 하지만(S406), 커지면,

를 업데이트 하지 않고, 더 이상 전송하지도 않는다. 따라서,

인 경우에는

가 상수로 고정된다(

)(S407).However, unlike the pseudo code 1, in the algorithm proposed by the pseudo code 2, the average value of the frequency offset calculation (

) Update is restricted (S405). In other words,

Is a predetermined number of times (

Less than)

Update (S406), but when it grows,

It doesn't update and doesn't send anymore. therefore,

If is

Is fixed as a constant (

(S407).

)과 반송파 주파수 조정 요청값(

)이 계산되고 다른 노드로 전송되는 것은 의사코드1에서 제안된 바와 같다(S408 내지 S411).Then, the adjustment value of the carrier frequency (

) And carrier frequency adjustment request value (

) Is calculated and transmitted to another node as suggested in pseudo code 1 (S408 to S411).

FIG. 5 is a flowchart illustrating a frequency synchronization process performed at node i without updating the average number of calculation of a frequency offset according to another embodiment of the present invention.

)를 카운트 하여 전송하지 않고, 주파수 옵셋의 평균값 계산 횟수(

)를 이용하여 계산되는

를 상수(

)로 고정함으로써, 주파수 동기화 과정의 오버헤드를 줄일 수 있다.In the following pseudo code 3, the average value of frequency offset calculation (

) Without calculating and transmitting the average value of the frequency offset

Calculated using

Is a constant (

By reducing the overhead of the frequency synchronization process.

Hereinafter, a process of performing frequency synchronization with low overhead by a specific node included in a distributed network will be described with reference to FIG. 5 and the pseudo code 3 below.

Doctor code 3

는 의사코드1에서와 같이 노드 m의 주파수 옵셋을 임시적으로 추정한 값을 나타낸다.In the pseudo code 3, the node i first estimates the frequency offset of the node m every time the preamble is received from the node m (S501) (S502).

Denotes a value of temporarily estimating the frequency offset of the node m as in pseudo code 1.

) 이상 프리앰블을 수신(S503)한 노드 i는 그때까지 인접 노드 m로부터 프리앰블을 수신한 횟수(

)를 기준으로 1차 추정한 주파수 옵셋의 평균값을 계산한다(S504). Since then, a predetermined number of times (

Node i that has received the above preamble (S503) has received the preamble from the neighbor node m until then (

In step S504, the average value of the first-order estimated frequency offset is calculated.

은 k번째 업데이트 시점에서 노드 i가 노드 m으로부터 프리앰블을

회 수신한 후 노드 m의 주파수 옵셋을 최종적으로 추정한 값이다. 이후, 추정한 주파수 옵셋의 평균값(

)을 바탕으로 노드 m에 대한 최종 주파수 옵셋값(

)을 계산한다.That is, the average value of the first-order estimated frequency offset

At node k, node i takes the preamble from node m.

The frequency offset of node m is finally estimated after the first reception. Then, the average value of the estimated frequency offset (

), Then the final frequency offset for node m (

Calculate

)의 계산에는 상수(

)를 이용한다. In this case, the algorithm proposed by pseudo code 3 does not update the average number of calculations of the frequency offset, and therefore the adjusted value of the carrier frequency (

) Has a constant (

).

를 이용하여 반송파 주파수의 조정값을 계산하므로, 주파수 옵셋의 평균값 계산 횟수(

)를 카운트하고

를 계산하는데 소모되는 자원을 줄일 수 있다. That is, node i is a constant

Since the adjustment value of the carrier frequency is calculated using, the average value of the frequency offset calculation (

)

It can reduce the resources consumed to calculate.

i는

,

, 그리고 노드 n으로부터 수신한 반송파 주파수 조정 요청값(

)을 이용(S505)하여 반송파 주파수의 조정값(

)을 계산하고, 계산한 반송파 주파수의 조정값에 따라 주파수를 조정한다(S506). Then, node

i is

,

, And the carrier frequency adjustment request value received from node n (

(S505) to adjust the carrier frequency (

) And adjust the frequency according to the calculated adjustment value of the carrier frequency (S506).

)과 주파수 옵셋의 평균값으로부터 반송파 주파수 조정 요청값(

)을 계산하여, 노드 n으로 전송한다(S507).Then, as in pseudo code 1, the adjusted value of the carrier frequency (

) And the carrier frequency adjustment request value (

) Is calculated and transmitted to node n (S507).

6 is a flowchart illustrating a frequency synchronization process performed at node i according to another embodiment of the present invention.

) 및 주파수 옵셋의 평균값 계산 횟수(

)를 전송하지 않는다.In the pseudo code 4 below, node i receives a preamble from node m, adjusts a carrier frequency, and transmits a carrier frequency adjustment request value to node n.

) And the number of averages of frequency offsets calculated (

) Is not sent.

Doctor code 4

를 계산한다(S602). 노드 m은 집합

에 포함되고 노드 i에 포함된 노드 중 하나이다.Referring to FIG. 6, each time node i receives a preamble from node m (S601), node i first estimates a frequency offset of node m.

To calculate (S602). Node m is a set

Is one of the nodes contained in node i.

를 바탕으로 집합

에 포함된 모든 노드에 대하여 반송파 주파수 조정값(

)을 계산(S604)하여 자신의 주파수를 조정(S605)함으로써, 노드 간 동기화를 수행할 수 있다.And, calculated

Set based on

For all nodes included in the carrier frequency adjustment value (

), By adjusting the frequency (S604) and adjusting its frequency (S605), it is possible to perform node-to-node synchronization.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (16)

A method in which a node entering a distributed network synchronizes carrier frequencies,
Receiving a preamble from a plurality of adjacent nodes adjacent to the node, wherein the node and the plurality of adjacent nodes transmit and receive signals to each other in an orthogonal frequency division multiple access (OFDMA) scheme;
Estimating an offset of the carrier frequency for each of the plurality of adjacent nodes from the received preamble,
Calculating an average value of the estimated offsets,
Receiving an adjustment request value of the carrier frequency, calculated by the plurality of neighbor nodes,
Calculating an adjustment value of the carrier frequency for all of the plurality of adjacent nodes based on the adjustment request value and the average value, and
Adjusting a carrier frequency of the node based on the adjustment value
Including,
And each of the plurality of adjacent nodes is a node that has transmitted a preamble received by the node more than a predetermined number of times. delete In claim 1,
Each of the plurality of adjacent nodes,
When the distributed network is hierarchical, a node comprising a global positioning system (GPS) or a node synchronized with a node comprising the GPS. In claim 1,
Calculating a first adjustment request value of the carrier frequency based on the adjustment value and the average value, and transmitting the first adjustment request value to the plurality of neighbor nodes.
Carrier frequency synchronization method further comprising. In claim 4,
Updating the average number of calculations of the offset, and
Sending the updated average calculation count
Carrier frequency synchronization method further comprising. In claim 5,
Calculating the adjustment value,
Receiving a second adjustment request value calculated by the first node from a first node of the plurality of adjacent nodes,
Receiving from the first node the number of average value calculations of the offset updated by the first node,
Calculating a final frequency offset value for the first node using a delta (δ) value, the second adjustment request value, and the average value calculated based on the number of calculations of the average value of the offsets received; and
Calculating an adjustment value of the carrier frequency for all the plurality of adjacent nodes using the final frequency offset value.
The carrier frequency synchronization method comprising a. In claim 5,
Fixing the average number of times of calculating the average value to a constant N _th when the number of times of calculating the average value of the offset exceeds a preset number of times.
Carrier frequency synchronization method further comprising. In claim 7,
Calculating the adjustment value,
Receiving a second adjustment request value calculated by the first node from a first node of the plurality of adjacent nodes,
Calculating a final frequency offset value for the first node using the delta (δ) value, the second adjustment request value, and the average value calculated based on the number of average values of the fixed offsets, and
Calculating an adjustment value of the carrier frequency for all the plurality of adjacent nodes using the final frequency offset value.
Carrier frequency synchronization method comprising a. An apparatus for synchronizing carrier frequencies in a node included in a distributed network, the apparatus comprising:
A communication unit for receiving a preamble from a plurality of neighboring nodes adjacent to the node and receiving an adjustment request value of the carrier frequency calculated by the plurality of neighboring nodes, wherein the node and the plurality of neighboring nodes divide orthogonal frequency with each other Transmitting and receiving signals in an orthogonal frequency division multiple access (OFDMA) scheme;
A frequency offset estimator for estimating an offset of the carrier frequency for each of the plurality of adjacent nodes from the received preamble,
An offset average value calculator for calculating an average value of the estimated offsets;
A frequency adjustment value calculator for calculating an adjustment value of the carrier frequency for all the plurality of adjacent nodes based on the adjustment request value and the average value, and
Frequency adjusting unit for adjusting the carrier frequency of the node based on the adjustment value
Including,
And each of the plurality of adjacent nodes is a node that has transmitted a preamble received more than a predetermined number of times by the node. delete In paragraph 9
Each of the plurality of adjacent nodes,
When the distributed network is hierarchical, a node comprising a global positioning system (GPS) or a node synchronized with the node comprising the GPS. In claim 9,
An adjustment request value calculator configured to calculate a first adjustment request value of the carrier frequency based on the adjustment value and the average value, and transmit the first adjustment request value to the plurality of neighbor nodes.
Carrier frequency synchronization device further comprising. In claim 12,
A number calculating unit for updating the average value count of the offset and transmitting the updated average value count to the communication unit;
Carrier frequency synchronization device further comprising. In claim 13,
The frequency adjustment value calculation unit,
Receiving a second adjustment request value calculated by the first node from a first node of the plurality of adjacent nodes, and receiving an average number of calculations of the average value of the offsets updated by the first node from the first node,
The final frequency offset value for the first node is calculated using the delta (δ) value, the second adjustment request value, and the average value calculated based on the number of calculations of the average value of the offsets received, and the calculated final frequency offset. And calculating an adjustment value of the carrier frequency for all of the plurality of adjacent nodes using a value. In claim 13,
The count operation unit,
And when the average value calculation number of the offset exceeds a preset number, fixing the average value calculation number to a constant (N _th ). The method of claim 15,
The frequency adjustment value calculation unit,
Receiving a second adjustment request value calculated by the first node from a first node of the plurality of adjacent nodes,
The final frequency offset value for the first node is calculated using the calculated delta (δ) value, the second adjustment request value, and the average value based on the calculated number of average values of the fixed offset, and the calculated final frequency offset value. Calculating an adjustment value of the carrier frequencies for all of the plurality of neighboring nodes by using;

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