KR102062165B1 - Multi-hop cognitive radio networks communication system, method thereof - Google Patents

Abstract

The present invention relates to a multi-hop cognitive radio network communication system and a method thereof. The multi-hop cognitive radio network communication system of the present invention comprises: a secondary user coordinator (SUC) node included in a first layer, and forming a cluster head of a first cluster; and a secondary user relay (SUR) node for forming a cluster head of a second cluster included in a second layer different from the first layer, and included in the first layer. The SUR node included in the second layer relays data in accordance with any one of a first common hopping sequence of the first cluster included in the first layer and a second common hopping sequence of the second cluster included in the second layer on the basis of control of the SUC node of the first layer.

Description

MULTI-HOP COGNITIVE RADIO NETWORKS COMMUNICATION SYSTEM, METHOD THEREOF

The present invention relates to a system and method for coexistence of a primary user and a secondary user in a Cognitive Radio (CR) network composed of nodes having one radio.

Today, as the demand for the use of the radio spectrum in a variety of applications rapidly increases, techniques are being studied to more efficiently utilize spectrum resources. The conventional static spectrum allocation technique prevents the use of the allocated spectrum by other secondary users even in the situation where the allocated spectrum is not used by the primary user. Cognitive Radio (CR) technology, designed to efficiently manage the spectrum, is a technology in which a wireless communication device observes the surrounding frequency spectrum and takes action after recognizing the surroundings from this information. (Joseph Mitola) was first proposed by researchers. Specifically, CR technology uses a wireless device called a secondary user node (SU) to detect spectrum use by a primary user node (PU) and to access the unused spectral white space. It can be used efficiently.

In order to realize CR technology, SDR (Software Defined Radio) devices are necessary to change the operating waveform and parameters of the spectrum. However, because SDR devices cannot adjust their own parameters, a CR Medium Access Control (CR-MAC) protocol is required to control them.The CR-MAC protocol analyzes the spectral data collected by the SDR device to detect spectral data and move channels. It plays an important role in CR technology, such as resource allocation and spectrum sharing. Spectrum sensing is a feature that collects information about the surrounding wireless environment to maintain the dynamic status of available channels, and channel movement helps SU devices move their SU devices to those channels when they appear on a licensed PU. Giving function. Resource allocation is used for opportunistic allocation of available channels by SU, and spectrum sharing is a feature that helps SU avoid competition and interference with PU.

The key challenge of the CR-MAC protocol is the opportunistic approach to channel use. In the conventional multi-channel network, the number of available channels is fixed, but in the CR network, the number of available channels varies with time and space. In order to avoid interference with the PU, it is necessary to generate a channel map that can be used dynamically according to the change of time, and the opportunistic access of the available channel according to the change of time of the SU causes a hidden terminal problem. In addition, if there is no prior information on the PU activity, there is a problem that the SU can not predict when the channel is available.

One object of the present invention is to eliminate the need for hopping sequence synchronization between multiple hop nodes by using different hopping sequences for each layer by layering a plurality of clusters in a multi-hop aware radio network.

Another object of the present invention is to reduce waste of spectrum by allowing secondary users to use frequencies that are not used in cognitive radio (CR) networks.

The present invention relates to a multi-hop aware radio network communication system, which is included in a first layer and comprises a secondary user coordinator node (SCC) that forms a cluster head of a first cluster and the first layer. Forming a cluster head of a second cluster included in a second layer different from the second layer; and including a secondary user relay node (SUR) node connected to the SUC node included in the first layer, and included in the second layer. The SUR node may be configured to generate a first common hopping sequence of the first cluster included in the first layer and a second cluster of the second cluster included in the second layer based on the control of the SUC node of the first layer. A multi-hop aware radio network system characterized by relaying data according to any one of two common hopping sequences.

The apparatus may further include a SUR-1 node forming a cluster head of a third cluster included in a third layer different from the first layer and the second layer, and connected to the SUR node included in the second layer. The SUR-1 node included in the third layer includes a second common hopping sequence of the second cluster included in the second layer and a third common hopping sequence of the third cluster included in the third layer. It is characterized by relaying the data according to any one.

Here, the first cluster is an upper layer of the second cluster on the basis of the second cluster, and the third cluster forms a lower layer of the second cluster on the basis of the second cluster, and a cluster tree topology structure of different layers. It characterized in that to form.

According to an embodiment of the present disclosure, in the relaying of data, the SUC node transmits a clock delay time to the SUR node, and the SUR node transmits a preset internal clock time of the SUR node and the received clock delay time. It compares the data and performs loopback time synchronization to relay data.

The SUR node included in the second layer may switch to one of the first common hopping sequence and the second common hopping sequence every preset duration.

According to an embodiment of the present invention, in order for the SUR to transmit data to the SUC, the SUR waits until it hops to the first common hopping sequence.

In addition, according to an embodiment of the present invention, in order for the SUR node to transmit data to the SUR-1 node, the time when the SUC node arrives at the common hopping sequence of the SUC node and the SUR node and the SUR-1 node Track an index and wait until the SUR node hops with the second common hopping sequence.

The present invention relates to a multi-hop aware radio network communication method, wherein a controller is included in a SUC node included in a first cluster of a first layer, and is included in a second cluster of a second layer that is different from the first layer. Connecting a SUR node and when the SUR node is connected to the SUC node, the SUR node relays data according to any one of a first common hopping sequence of a first cluster and a second common hopping sequence of a second cluster. A multi-hop aware radio network communication method comprising the steps of.

The relaying of the data may include switching to one of the first common hopping sequence and the second common hopping sequence for each preset duration.

According to still another embodiment of the present invention, a SUC node transmits a clock delay time to the SUR node, and the SUR node compares an internal clock time of a preset SUR node with the received clock delay time to perform a loopback time. A method for multi-hop aware radio network communication, further comprising the step of performing synchronization.

The present invention has the effect of eliminating the need for hopping sequence synchronization between multiple hop nodes by using different hopping sequences for each layer by layering a plurality of clusters in a multi-hop aware radio network.

In addition, the present invention can perform strict time synchronization between clusters in consideration of the internal transmission / reception clock time delay between the reference point and the receiver through the time synchronization of the loopback technique.

1 illustrates a cluster tree topology structure of a multi-hop aware radio network communication system according to an embodiment of the present invention.
2 illustrates a hierarchical cluster structure of a multi-hop aware radio network communication system according to an embodiment of the present invention.
3 and 4 are flowcharts of a multi-hop aware radio network communication method according to another embodiment of the present invention.
5 is a diagram illustrating a best path of a time synchronization protocol between a receiver and a sender according to an embodiment of the present invention.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings, and the same or similar components will be given the same reference numerals, and redundant description thereof will be omitted. The suffixes "module" and "unit" for components used in the following description are given or mixed in consideration of ease of specification, and do not have distinct meanings or roles. In addition, in the following description of the embodiments disclosed herein, when it is determined that the detailed description of the related known technology may obscure the gist of the embodiments disclosed herein, the detailed description thereof will be omitted. In addition, the accompanying drawings are only for easily understanding the embodiments disclosed in the present specification, the technical idea disclosed in the specification by the accompanying drawings are not limited, and all changes included in the spirit and scope of the present invention. It should be understood to include equivalents and substitutes.

The present invention relates to a MAC for Multi-hop Cognitive Radio Networks based on Slow Hopping and Cooperative Sensing (MSHCS-MAC) that supports multi-hop network communication and considers a real network environment, and a strict time synchronization technique for improving performance.

The following notation is used to describe the invention. Primary user (PU) node means an authorized user or primary user who uses the spectrum of a radio channel. A secondary user (SU) node refers to an unauthorized user or a secondary user using a spectrum of a radio channel. A secondary user coordinator node (SUC node) refers to a coordinator node of a secondary (unauthorized) user who adjusts a spectrum usage schedule of a secondary user. The SUR node (Secondary User Relay node) refers to a secondary user relay node which simultaneously serves as a SUC node. That is, the SUR node connects between the SUC node and the SU node, or connects between the SUC node and the SUR-1 node. Through the connection of SUR, data can be transmitted without collision between channels in multiple hops (multi hops).

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

1 illustrates a cluster tree topology structure of a multi-hop aware radio network communication system according to an embodiment of the present invention.

A plurality of clusters are connected through a connection between cluster heads and relay data through the cluster heads.

Here, the topology refers to a physical connection of elements (links, nodes, etc.) of a computer network, or a connection method thereof. The tree topology is a structure in which the network structure of the real world is closest to each other, and branches are formed around one vertex and other branches are formed at the end of the branch.

According to an embodiment of the present invention, a multi-hop aware radio network communication system is composed of a plurality of clusters. Here, the description will be made using 'first, second, etc.' to clearly express the plurality of clusters. However, the first cluster and the second cluster do not necessarily have a parent-child relationship.

Referring to FIG. 1, a plurality of clusters are composed of a first cluster, a second cluster, and a third cluster. However, the cluster is not limited to three, but a plurality of clusters may be further included. Three clusters are shown for explanation.

SUC node 101 is the cluster head of first cluster 100. SUC node 101 may be connected to a plurality of SU nodes. In order for any one node of the plurality of SU nodes to transmit data to different nodes, data may be transmitted through the SUC node 101 corresponding to the cluster head.

The SUC node 101 is connected to the SUR node 201 forming the cluster head of the second cluster 200 which is different from the first cluster 100.

The SUR node 201 may be connected with a plurality of SU nodes. In order for any one node of the plurality of SU nodes to transmit data to different nodes, data may be transmitted through the SUR node 201 corresponding to the cluster head.

The SUR node 201 may be connected to the SUR-1 node 301 forming the cluster head of the third cluster 300 which is different from the first cluster and the second cluster.

 The SUR-1 node 301 may be connected with a plurality of SU nodes. In order for any one node of the plurality of SU nodes to transmit data to different nodes, data may be transmitted through the SUR node 301 corresponding to the cluster head.

2 illustrates a hierarchical cluster structure of a multi-hop aware radio network communication system according to an embodiment of the present invention.

As described above, the multi-hop aware radio network communication system is configured in the form of a cluster tree topology, where each cluster has a hierarchical structure as shown in FIG.

By layering multiple clusters per cluster, the need for hopping sequence synchronization between multiple hop nodes is eliminated, thereby solving the beacon rebroadcast problem between SURs. Layered SUR clusters can reduce the beacon impulse potential by broadcasting their beacons in each hopping sequence, and additionally the carrier sense multiple access / collision avoidance (CSMA / CA) that randomizes beacon broadcasts over the beacon duration It can be applied to to further reduce the possibility of beacon collision.

In addition, the layering of the hopping sequence eliminates the need for time synchronization across multiple hops for SUR beacon rebroadcast, and reduces the time synchronization problem to a single hop problem inside each cluster.

FIG. 2 is a side view of the above-described cluster tree topology structure, and the plurality of clusters are configured in different layers. In the first cluster of the first layer 110, the SUC node 101 is configured as the cluster head, and in the second cluster of the second layer 210, the SUR node 201 is configured as the cluster head. In addition, in the third cluster of the third layer 310, the SUR node 301 is configured as a cluster head.

When transmission is required from each node to a different node, data may be transmitted through the nodes 101, 201, and 301 corresponding to the cluster head.

In a multi-hop aware radio network communication system according to an embodiment of the present invention, a plurality of clusters are hierarchical tree topology structures, and each cluster has a unique ID. In addition, the SUC node 101 or the SUR nodes 201 and 301 may be selected as the cluster head. Data relay in multiple hops is possible via SUC node 101 or SUR nodes 201 and 301. Therefore, SU nodes present in the cluster transmit data to other nodes via SUC node 101 or SUR nodes 201 and 301. In this case, the SUR node 201 may be designed to have two independent hopping sequences in order to relay data. First, when the SUR node 201 first participates in the network after the bootstrap, the SUR node 201 participates as a subordinate node of the first cluster 100 existing in the existing network. In this case, the connected lower second cluster 200 follows a common hopping sequence of the upper cluster (the first cluster 100) to maintain the connection with the upper first cluster 100. Second, the second sub-cluster 200 may have its own cluster ID and the first to manage the SU node added to the sub-cluster head SUR node 201 or the SUR-1 node 301 of the third cluster 300. The two clusters 200 have a common hopping sequence. That is, the SUR node is a node that combines the functions of the SU node and the SUC node. The SUR node is layered and operated as SU in the upper cluster and SUC node in its own cluster.

 In a multi-hop aware radio network communication system according to an embodiment of the present invention, an SUR node needs to repeatedly switch between hopping sequences in order to process two independent hopping sequences using a single transceiver.

After the SUR node 201 is connected with the SUC node 101, the common hopping sequence of the first cluster 100 including the SUC node 101 and the second cluster 200 common hopping sequence including the SUR node 201 are included. Follow. That is, the common hopping sequence of the first cluster 100 is maintained for one slot length, that is, for a preset time, and the common hopping sequence of the second cluster 200 is switched during the duration of the next slot. By switching to a common hopping sequence of the first cluster 100 and the second cluster 200 every one slot time, that is, at predetermined times, the SUR node 201 may maintain the upper and lower connections.

In addition, according to an embodiment of the present invention, the second cluster 200 including the SUR node 201 may perform a hopping sequence of the first cluster 100 including the upper SUC node 101 and the SUR node 201. Since the second cluster 200 is layered in its own hopping sequence, it is possible to reduce the possibility that two transmission flows (spectrums) collide in two different clusters. Moreover, independent hopping sequences between clusters help to ensure that the radio spectrum is fairly distributed among the clusters.

According to an embodiment of the present invention, the neighbor discovery problem may be solved by using an active beacon broadcast and a common hopping sequence. In the MSHCS-MAC design, since the SUC node 101 and all SUR nodes 201 of each hop always broadcast beacons, the SUR node 201, or SUR-1 node 301, is configured to provide the SUC node (during the bootstrapping period). The beacon of 101) may be obtained and may always participate in the corresponding cluster by using the obtained hopping sequence information of the beacon. Therefore, it is possible to prevent the neighbor node discovery problem that the channel search fails because the channel is different from the neighbor node.

Since the SUR node 201 switches from time to time between two independent hopping sequences, a method is needed to solve the hearing loss problem. The method is divided into four communication processes.

1) On data transfer from the SUR node 201 to the parent SUC node 101 (or optionally the parent SUR node), the common hopping of the parent cluster to initiate the transfer of the SUR node 201 to the SUC node 101. It solves the problem of hearing loss by waiting until it hops in sequence.

2) When transmitting data from the SUR node 201 to the lower SU, the hearing loss problem is solved by waiting for the SUR node 201 to hop in its own common hopping sequence.

3) When transmitting data from the SU to the higher SUR node 201, the SUR node 201 is not always present in its common hopping sequence, so the SU solves the hearing loss problem by waiting for the beacon broadcast of the SUR node 201. .

4) When data is transmitted from the upper SUC node 101 to the lower SUR-1 node 301, different SUR nodes 201 and SUR-1 nodes 301 associate with the SUC node 101 in different channel hops. As such, the SUC node 101 must track the time index at which each SUR node 201 and SUR-1 node 301 arrive at the common hopping sequence of the SUC node 101. For example, if the SUR node 201 is hopping on a channel with an odd index and the SUR-1 node 301 is hopping on a channel with an even index, the SUC node 101 is assigned to each SUR node 201 and By storing the index for the SUR-1 node 301 and waiting for the corresponding index channel to return, the hearing loss problem is solved.

Further, according to one embodiment of the present invention, if there is a lot of data to be sent to the SUR node 201 in the queue of another node or SUR node 201, the queue is empty or stopped due to PU activity. You can stay on the current channel to perform extended work until you do. To this end, during the expansion operation, the SUR node 201 updates the index of the hopping sequence to return to the correct hopping sequence after the expansion operation is completed.

3 and 4 are flowcharts of a multi-hop aware radio network communication method according to another embodiment of the present invention.

First, a description will be given with reference to FIG. 3.

The control unit controls the second cluster 200 of the second layer 210 that is different from the first layer 110 to the SUC node 101 included in the first cluster 100 of the first layer 110. Connect the SUR node 201 included in the (S100).

When the SUR node 201 is connected to the SUC node 101, the SUR node 201 is connected to the first common hopping sequence S111 of the first cluster 100 and the second common hopping of the second cluster 200. The channel is determined according to any one of the sequences S112, and data is relayed (S113).

4 further includes a time synchronization step, in comparison with the flowchart of FIG. 3.

The control unit controls the second cluster 200 of the second layer 210 that is different from the first layer 110 to the SUC node 101 included in the first cluster 100 of the first layer 110. Connect the SUR node 201 included in the (S200).

When the SUR node 201 is connected to the SUC node 101, the SUR node 201 is connected to the first common hopping sequence S211 of the first cluster 100 and the second common hopping of the second cluster 200. The channel is determined according to any one of the sequences S212. After loop-based time synchronization is performed (S213), data is relayed (S214).

As described above, in the multi-hop aware radio network communication method according to the present invention, it is configured to have an independent channel hopping sequence in each cluster. Therefore, if two or more adjacent clusters stay on the same channel at the same time or if the number of clusters is larger than the number of available channels, a spectral collision problem may occur due to a time synchronization problem between clusters. In order to solve this problem, a synchronization technique is required.

RBS-LB (Reference Broadcast Synchronization with active Loop-Back), a strict time synchronization scheme according to the present invention, applies a loopback scheme based on the RBS protocol. The basic RBS protocol can handle the time delay while maintaining a small overhead through the reference time broadcast, but there is a problem that does not take into account the internal transmit / receive clock time delay between the reference point and the receiver.

5 is a diagram illustrating a best path of a time synchronization protocol between a receiver and a sender according to an embodiment of the present invention. Measure the transmit / receive clock delays occurring in your MAC (Media Access Control) and PHY (Physical Layer) through loopback techniques at the reference point as shown by the dotted line, and measure the measured delay in the data period. By broadcasting, the receiver performs strict time synchronization through the transmit / receive clock delay calculation of itself and the reference point.

A linear regression function is used to predict the calculation of the transmit and receive clock delays over time. The linear regression function derives the delay calculation between the sender and the receiver based on the reference point. The derived linear regression function can be used to predict and synchronize the time slots, spectrum detection, beacon reception, reception reporting, and start time of data periods in the MSHCS-MAC protocol. In a real multi-hop CR network, the sender becomes the head of each cluster (SUC / super SUR), and the receiver becomes the node of the cluster (child SUR / SU) to maintain strict time synchronization between each cluster through RBS-LB.

 The foregoing detailed description should not be construed as limiting in all respects, but should be considered as illustrative. The scope of the present invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention.

100: first cluster
101: Secondary user coordinator node
110: first layer
200: second cluster
201: SUR node (Secondary User Relay node)
210: second layer
300: third cluster
301: SUR-1 node (or child SUR node)
310: third layer

Claims (10)

A secondary user coordinator node included in the first layer and forming a cluster head of the first cluster; And
And a SUR node (Secondary User Relay node) forming a cluster head of a second cluster included in a second layer different from the first layer and connected to the SUC node included in the first layer.
The SUR node included in the second layer is
Based on a control of the SUC node of the first layer, among a first common hopping sequence of the first cluster included in the first layer and a second common hopping sequence of the second cluster included in the second layer Relay data according to which one,
And switching to any one of the first common hopping sequence and the second common hopping sequence at predetermined time intervals. The method of claim 1,
The SUR node,
And a SUR-1 node connected to the SUR node and forming a cluster head of a third cluster included in a third layer.
The SUR-1 node included in the third layer is
Relaying data according to any one of a second common hopping sequence of the second cluster included in the second layer and a third common hopping sequence of the third cluster included in the third layer. Cognitive Radio Network System. The method of claim 2,
The first cluster is,
Based on the second cluster, an upper layer of the second cluster,
The third cluster is,
On the basis of the second cluster, forming a lower layer of the second cluster,
Multi-hop aware radio network system, characterized by forming a cluster tree topology structure of different layers. The method of claim 1,
The SUC node sends a clock delay time to the SUR node,
The SUR node compares a preset SUR node internal clock time with the received clock delay time to perform loopback time synchronization to relay data. delete The method of claim 1,
When the SUR transmits data to the SUC,
And the SUR waits until it hops according to the first common hopping sequence. The method of claim 2,
For the SUR node to transmit data to the SUR-1 node,
The SUC node tracks a time index at which the SUR node and the SUR-1 node arrive at a common hopping sequence of the SUC node, and waits for the SUR node to hop to the second common hopping sequence Multi-hop aware radio network system. Connecting, by the controller, the SUR node included in the second cluster of the second layer, which is a layer different from the first layer, to the SUC node included in the first cluster of the first layer; And
If the SUR node is coupled to the SUC node, the SUR node includes relaying data according to one of a first common hopping sequence of a first cluster and a second common hopping sequence of a second cluster,
The step of relaying the data,
And switching to one of the first common hopping sequence and the second common hopping sequence at preset time intervals. delete The method of claim 8,
The step of relaying the data,
The SUC node sends a clock delay time to the SUR node,
The SUR node is a multi-hop-aware radio network communication method for relaying data by performing loopback time synchronization by comparing a preset SUR node internal clock time with the received clock delay time.

Images