KR20100116099A - Method and apparatus for acquiring synchronization between nodes, and method for organizing multiple physical channel - Google Patents

Abstract

PURPOSE: A method and an apparatus for obtaining synchronization between nodes, and a method for organizing multiple physical channels are provided to use physical channels as a common resource, thereby realizing collision avoidance and a collision solution algorithm with improved performance. CONSTITUTION: If power is applied to a type-2 node, a pulse generation unit(420) outputs a pulse at an output time of an initially effective peak waveform at each predetermined cycle in case of output of a preamble detection unit(410). A generated pulse row(403) and a self-running clock are provided as input of a PLL(Phase Locked Loop)(430). The PLL generates stable preamble transmission time. If output of the PLL is stabilized in the type-2 node, the type-2 node starts preamble transmission.

Description

Method and apparatus for acquiring synchronization between nodes, and method for organizing multiple physical channel

The present invention relates to an inter-node synchronization acquisition method and apparatus, and a multiple physical channel configuration method. In particular, the present invention relates to a method and apparatus for obtaining inter-node synchronization in an ad-hoc / mesh network, and to a method for configuring multiple physical channels.

Wireless communication systems can be broadly classified into infrastructure systems and infrastructureless systems. A representative example of the base system is an existing cellular system, where each cell consists of one base station and a plurality of terminals. In a cell, a base station allocates resources to terminals with centralized control. In other words, the base system needs a central coordinator having a centralized control such as a base station.

A system without an underlying network represented by Ed Hoc / Mesh does not have a central coordinator and each node is a coordinator and uses resources. In such a system, since all terminals transmit and receive information using a common resource (or channel), an algorithm for avoiding a collision problem caused by using the same channel at the same time and an algorithm for solving the collision are required.

Throughput performance is greatly improved if nodes have a common time base in the ad hoc / mesh network. In addition, when the ad hoc / mesh network is composed of multiple physical channels rather than a single physical channel, spectrum use efficiency is improved.

The technical problem to be achieved by the present invention is a method for each node to obtain synchronization for improving the performance of the ad hoc / mesh network, a method for configuring multiple physical channels to efficiently use the common propagation resources, which is a communication medium between the nodes It is about.

According to an aspect of the present invention, there is provided a method for acquiring synchronization between nodes in a network in which first and second nodes do not have full time criteria.

Detecting a preamble by the second nodes within a specific range of the first node, generating a pulse at a time point at which a peak waveform is output for each period set in the detected preamble, and preamble based on the generated pulse and a specific clock Generating a transmission time, and transmitting the preamble based on the transmission time generated by the second node.

According to another aspect of the present invention, an apparatus for acquiring synchronization between nodes in a network in which first nodes having an entire time reference and second nodes not having the same is mixed.

A detector for detecting preambles of the second nodes existing within a specific range of the first node, a generator for generating a pulse at a point of time at which a peak waveform is output for each period set in the detected preamble, and a generated pulse and self-running And a phase synchronization circuit for generating a preamble transmission time based on a clock and transmitting the preamble to a second node based on the generated preamble transmission time.

In addition, the method for configuring multiple physical channels in the Ed Hoc / mesh network according to another aspect of the present invention

Configuring multiple physical channels based on a single radio device, multiple control common physical channels, multiple data common physical channels, and multiple broadcast common physical channels, and configuring the multiple physical channels based on a single Mac that manages the multiple physical channels as a whole. It includes a step.

According to an embodiment of the present invention, by using a plurality of physical channels as a common resource, it is possible to devise improved collision avoidance and collision resolution algorithms, and to improve channel usage efficiency when all nodes are synchronized in a system without an underlying network. It can be greatly improved.

In addition, according to an embodiment of the present invention, nodes having no global time reference in an EdHok / Mesh network may obtain the global time reference in a completely distributed manner without exchanging information with each other. By using multiple control physical channels, multiple data physical channels, and multiple broadcasting channels, nodes can apply collision avoidance and collision resolution algorithms to node-to-node synchronization acquisition devices to improve overall throughput in ad hoc / mesh networks. can do.

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. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. 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 can further include other components, without excluding other components unless specifically stated otherwise.

Now, a method and apparatus for acquiring synchronization between nodes in an ad hoc / mesh network and a method for configuring multiple physical channels will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating a general ed hoc / mesh network.

First, assume an ad hoc / mesh network composed of multiple nodes. In addition, at least one of the nodes in the ad hoc / mesh network has a global time reference and most of the nodes do not have a global time reference and are operated by a self-running clock. Assume that The above environment setting is a situation that can be sufficiently considered in military, disaster and disaster prevention situations.

Referring to FIG. 1, an ad hoc / mesh network consisting of nodes having a full time reference (hereinafter referred to as "Type-1 node") and nodes not having (hereinafter referred to as "Type-2 node") Indicates.

One of the objects of the present invention is to propose a method in which the nodes operated by the self-learning clock obtain the full time reference in the above situation.

2A to 2C are diagrams illustrating a case where nodes having an entire time criterion and nodes having no total time criterion are mixed.

In order to grasp the problem related to node synchronization acquisition, it is assumed in FIG. 2A that an ad hoc / mesh network composed of one type-1 node (node-1) and two type-2 nodes (node-2 and node-3). Also, in FIG. 2A, it is assumed that node-2 can receive from node-1 and node-3, and node-3 can receive from node-2 but not from node-1. All nodes can transmit a preamble of a given waveform for synchronization purposes. Type-1 nodes have a full time reference, so they send preambles at scheduled intervals. Since the Type-2 node does not have a full time reference, the type-2 node may indirectly use the preamble transmitted by the type-1 node to acquire the entire time reference and then transmit the preamble.

2b to 2c illustrate problems that may occur in this case.

2B illustrates a case in which Node-2 transmits its preamble based on Node-1 preamble reception and Node-3 transmits its preamble based on Node-2 preamble reception. In this case, only errors due to propagation delay exist and synchronization of all nodes is possible. However, as shown in FIG. 2C, when the node-2 transmits its preamble based on the reception of the preamble of the node-3, synchronization may not be obtained. If the number of nodes increases and the network scales up, it becomes more difficult to obtain synchronization.

Next, when the nodes receive the preamble, the preamble output waveform of the receiving node will be described in detail with reference to FIGS. 3A to 3B.

3A to 3B are diagrams illustrating a case in which nodes receive a preamble and a preamble output waveform of a corresponding reception node.

Referring to FIG. 3A, preambles are sequentially received to a receiving node with a time difference according to a transmitting node position and a propagation path. When using the same type of preamble waveform promised, even if the node-301 and the node-302 simultaneously transmit the preamble, the node-303 preamble detector (not shown) outputs a plurality of detected peak waveforms due to the propagation path difference. In general, the preamble detector detects the preamble using a correlation scheme.

3B illustrates the preamble detector output waveform of the receiving node.

Referring to FIG. 3B, as a method for solving the problem occurring when the inter-node synchronization described in FIG. 2C is obtained, type-1 nodes transmit preambles at predetermined intervals based on a total time criterion and type-2 nodes. Can obtain a global time reference and send a preamble by the following procedure.

4 is a block diagram illustrating an apparatus for obtaining a total time reference of a node having no total time reference according to an embodiment of the present invention.

Referring to FIG. 4, the apparatus 400 for acquiring a type-2 node includes a preamble detector 410, a pulse generator 420, and a phase-locked loop (PLL) 430. It includes.

A) When power is applied to the Type-2 node, the pulse generator 420 outputs a pulse at the time when the first valid peak waveform is output for every period promised at the output of the preamble detector 410. 401 shows an output waveform of the preamble detector 410 and 403 shows an output waveform form of the pulse generator 420.

B) The pulse train 403 and the self-running clock 406 generated in the above a) are provided to the PLL 430 input so that the PLL 430 of the type-2 node generates a stable preamble transmission time.

C) When the output of the PLL 430 is stabilized in the type-2 node, the type-2 node starts transmitting the preamble.

In the above method, if all nodes do not have a full time reference, if the same procedure is applied to all nodes, all nodes in the network may operate in synchronization with the timing of the authorized node.

It is also well known that throughput increases in multiple access protocols as well as in the presence of a full time criterion.

FIG. 5 is a diagram illustrating the structure of a multiple radio device, a plurality of common physical channels, and one medium access control layer for ed / mesh.

Specifically, FIG. 5 illustrates a plurality of physical control channels (e.g., three channels) for handshaking that a node may have, and a plurality of physical data channels (e.g., four channels for data transmission). Channel), a plurality of physical broadcast channels (for example, two channels) for providing broadcast information, individual radio devices (or RF transceivers, RF-1 to RF-9) for each physical layer, and all physical channels Illustrates a single Media Access Control (MAC) layer associated with this.

The content of a broadcast channel may consist of a header and a payload, and may be used to transmit information to all or some group nodes existing in the ad hoc / mesh network. The control channel can be used to transmit information that negotiates various parameters necessary for channel configuration between nodes before the channel is opened. The data channel may consist of a header and payload, and the payload consists of user data.

Each node may include a multi-RF, a common multi-physical channel, and a single-MAC as shown in FIG. 5 in order to improve throughput in an ad hoc / mesh network. However, when the node is configured as shown in FIG. 5, the cost increase factor cannot be ignored.

Orthogonal frequency-division multiple access (hereinafter referred to as "OFDMA") in an ad hoc / mesh network assuming a full time reference, the multi-channel of Figure 5 without significant cost increase , Single MAC effect can be obtained.

An OFDM symbol consists of a number of subcarriers. Subcarriers can be divided to allocate some subcarriers to multiple broadcast channel configurations, assign some other subcarriers to multiple control channel configurations for handshaking purposes, and assign some other subcarriers to multiple data channel configurations for data transmission purposes. have. In this case, a single radio unit (single RF) can operate a number of common channels.

FIG. 6 is a diagram illustrating an example of a method of configuring a plurality of common physical channels in a single radio device, a plurality of common physical channels, a single MAC structure, and OFDMA for the ed / mesh.

601 of FIG. 6 illustrates a node configuration of a multi-channel, single-RF, and single-MAC structure in OFDMA. 602 of FIG. 6 shows an example in which three subcarriers are divided into three control physical channels, four data physical channels, and two broadcast physical channels. The preamble 603 of FIG. 6 is required when using the above-described synchronization scheme, but may not be required when the node acquires synchronization in another manner.

In the case of FIG. 5, transmission and reception may be performed at the same time, but in case of 601 of FIG. 6, transmission and reception at the same time may not be possible, but implementation cost may be greatly reduced. In the case of single-RF and multi-channel, since a broadcast cannot be received while transmitting another channel, it is effective to allocate all subcarriers to the broadcast channel as shown in 611 and 612 of FIG.

FIG. 7 is a diagram illustrating that each node transmits and receives information using a plurality of common physical channels in an ad hoc / mesh network.

Referring to FIG. 7, assuming that a node acquires synchronization in the above-described manner, multi-channel of each node is used in an ad hoc / mesh network. Each node can transmit / receive control information, user data information to other nodes for routing purposes by using multi-channel by distributed collision avoidance / collision resolution MAC based on measurement (for example, carrier sensing). .

In the inter-node synchronization acquisition scheme described above with reference to FIG. 7, nodes 704, 705, 706, and 709 having the entire time reference transmit their own preambles at predetermined time intervals. The remaining nodes transmit the preamble using the time reference obtained using the reception preamble. Each node transmits and receives control and user information by using a channel that is not used by neighboring nodes through measurements such as carrier sensing. When the node receives the broadcast channel, if the node retransmits the broadcast channel received at the next broadcast channel transmission time, broadcast information may be delivered to all nodes over several hops. Information such as control common to all nodes may be transmitted to all nodes in a multi-hop manner using a broadcast channel. FIG. 7 shows an example of using multi-channel, in which node 706 uses data physical channel-1, node 710 uses data physical channel-3, node 703 uses control physical channel-2, and node 711 uses data physical channel-2. It shows the appearance of transmitting and receiving. In this way, if the collision avoidance and collision resolution algorithm is implemented using multi-channels, the throughput can be improved.

The number of data physical channels, control physical channels, and broadcast physical channels is variable. However, all nodes must be aware of this. If it is necessary to change the number of channels, it is possible to notify all nodes in the network by using the broadcast channel.

When a node receives a broadcast message on a broadcast physical channel in a slot, the node retransmits the same broadcast message using the broadcast physical channel of the next slot. In OFDM, when multiple nodes transmit the same information in the same waveform, reception is possible (SFN: single frequency network). In this multi-hop method, all nodes can receive broadcast information. However, if all nodes continuously retransmit the broadcast message, the same broadcast message is constantly retransmitted in the network. In order to prevent this, a message number may be assigned to a broadcast message, and each node may be prevented from transmitting a broadcast message having the same message number more than n times.

The embodiments of the present invention described above are not only implemented by the apparatus and method but may be implemented through a program for realizing the function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded, The embodiments can be easily implemented by those skilled in the art from the description of the embodiments described above.

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.

1 is a diagram illustrating a general ed hoc / mesh network.

2A to 2C are diagrams illustrating a case where nodes having an entire time criterion and nodes having no total time criterion are mixed.

3A to 3B are diagrams illustrating a case in which nodes receive a preamble and a preamble output waveform of a corresponding reception node.

4 is a block diagram illustrating an apparatus for obtaining a total time reference of a node having no total time reference according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating the structure of a multiple radio device, a plurality of common physical channels, and one medium access control layer for ed / mesh.

FIG. 6 is a diagram illustrating an example of a method for configuring multiple public physical channels in single-radio, multiple public physical channels, single MAC structure, and OFDMA for ed / mesh.

FIG. 7 is a diagram illustrating that each node transmits and receives information using a plurality of common physical channels in an ad hoc / mesh network.

Claims (8)

A method for acquiring synchronization between nodes in a network in which first and second nodes having a total time criterion do not have, Detecting, by the second nodes existing within a specific range of the first node, a preamble, Generating a pulse at a time point at which a peak waveform is output at each set period in the detected preamble, Generating a preamble transmission time based on the generated pulse and a specific clock, and The second node transmitting the preamble based on the generated transmission time Inter-node synchronization acquisition method comprising a. The method of claim 1, Sending the preamble is Causing the second nodes to acquire the full time reference using a phase locked loop (PLL) Inter-node synchronization acquisition method comprising a. The method of claim 1, The first node further comprises the step of transmitting a preamble at intervals set based on the total time reference. An apparatus for acquiring synchronization between nodes in a network in which first nodes having an entire time criterion and second nodes not having a total time reference are mixed. A detector configured to detect preambles of the second nodes existing within a specific range of the first node, A generator for generating a pulse at a point in time at which the peak waveform is output at a set period in the detected preamble, and A phase synchronization circuit for generating a preamble transmission time based on the generated pulse and the self-running clock, and transmitting the preamble to the second node based on the generated preamble transmission time. Inter-node synchronization acquisition apparatus comprising a. The method of claim 4, wherein The phase synchronization circuit part And the second nodes acquire the overall time reference. In the method of configuring multiple physical channels in the ad hoc / mesh network, Configuring multiple physical channels based on a single radio device, multiple control common physical channels, multiple data common physical channels and multiple broadcast common physical channels, and Configuring the multiple physical channels based on a single Mac that manages the multiple physical channels as a whole Multiple physical channel configuration method comprising a. The method of claim 6, The number of the control common physical channel, the data common physical channel and the broadcast common physical channel is configured to be variable, And all nodes in the ad hoc / mesh network recognize that the number of channels is variable. The method of claim 7, wherein When at least one of all the nodes retransmits a broadcast message, And assigning a unique number to the broadcast message and preventing the node from transmitting a broadcast message having the same unique number more than a set number of times.

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