KR20160047005A - Access Network system based on G.hn technology providing giga ethernet service without re-cabling construction, and method for auto pairing of giga wire reducing crosstalk using there - Google Patents

Abstract

According to the present invention, provided is a GIGA wire auto-pairing method which implements auto-pairing between domain masters and end points in an access network forming G.hn domains, the G.hn domains including a GAM in which a plurality of ports serve as the domain masters, GNTs which include the end points so as to form the G.hn domains along with the respective domain masters, and a bundle cable which connects the domain masters and the end points, the GIGA wire auto-pairing method comprising the steps of: activating the ports, and starting opening; linking the domain masters and the end points using a seed value; automatically registering, by the GAM, MAC addresses of the end points using previously stored MAC address information of the end points when the linking has been detected; and connecting the domain masters only to the registered end points when being linked again. According to the present invention, there is no concern that a line is erroneously recognized as the same line when the former line is not the same line.

Description

GAM, GNT, an access network that provides equipment-grade services by wiring the GAM and the GNT at both ends of a conventional telephone line without changing the line, forming a G.hn domain, and a crosstalk reducing unit METHODS < RTI ID = 0.0 > (Access Network < / RTI > system based on G.hn technology providing giga ethernet service without re-cabling construction,

The present invention relates to an access network for providing a device-level Ethernet service by forming a G.hn domain by wiring GAM and GNT at both ends of a conventional telephone line without adding or changing a line, and a method of implementing auto- More specifically, applying the G.hn standard to existing apartments with one-pair telephone lines embedded makes it possible to provide three to five times faster speeds than existing speeds without additional lines. However, crosstalk problems caused by high frequencies (Pre-configured domain name), the seed value is set in the DM only (pre-configured seed), the MAP is transmitted to the EP after the DM is opened, The seed value is inserted into the D frame and the pair is paired (no pre-configured seed), and the MAC is authenticated by the protocol authentication. Though fundamentally preventing the fear of mistaken for the same line and also relates to an access network G.hn and Giga wire automatic pairing method for removing a communication error is generated in the MAC verification process between the operator and the opening party.

Generally, as the rapidly increasing traffic increases, the 1 Gbps service is being expanded from the existing 100 Mbps service to the necessity of the bandwidth that must be provided to subscribers.

1 is a block diagram illustrating a configuration of a conventional DSL-based access network.

1, in the DSL-based access network of the related art, data communication is performed between an upper communication apparatus and a digital subscriber line access multiplexer (DSLAM) using optical fiber lines, and a DSLAM and a modem ), Data is transmitted using a telephone line.

Existing apartments or buildings that are 20 to 30 years old are equipped with a single pair of telephone lines. For example, in the case of an aged apartment, the wiring to the MDF terminal box and the home subscriber is provided by a pair of telephone lines. In the case of old apartments and buildings in Korea, 1Gbps gigabit service is impossible. (Even in the case of many European countries where there are many relics of ancient relics, it is supposed to be a dinner.)

It is troublesome to add or change the line of such a telephone line, or to obtain the consent of the residents even if it is possible. Therefore, telecom operators are demanding to expand services without adding or changing lines.

On the other hand, G.hn technology, which aims to increase the bandwidth from 100 Mbps to 1 Gbps without increasing the number of lines, has already been introduced.

For example, in an access network between a central office (hereinafter referred to as "CO") and a plurality of terminals (referred to as "CPE") having a plurality of ports, To attempt to expand the bandwidth from 100 Mbps to 1 Gbps.

However, theoretically, the G.hn standard can be applied to an access network using a telephone line to provide a maximum bandwidth of 1 Gbps. However, in actuality, in a bundled access network, due to crosstalk between adjacent lines, It is perceived to be the same line even if it is not a line, which is a great obstacle to providing a service in an access network.

For example, when an access network is connected through a telephone line, network communication is susceptible to interference by a bundle. In the high frequency band of 2 MHz to 100 MHz used by the G.hn standard, interference between lines becomes even worse Based access network does not cause a crosstalk problem because it uses a low frequency band), when the terminal is powered on (power up), when a link is established (Link Up) or when data is actually transmitted / received, The line signal of the other terminal is attenuated or distorted.

In order to apply the G.hn standard to the access network, it is necessary to remove the near-end crosstalk (NEXT) in the bundle. In the patent document 10-1403580, near-end interference is minimized by the following MAC authentication method have.

Prior to opening, referring to FIG. 2A, the CO 10 and the DM 15 have a domain name and a seed value in order to improve crosstalk. At this time, the domain names and the seed values of the DM 15 and the EPs 25a, 25b, and 25c are set to default values, respectively.

Referring to FIG. 2B, after the opening, the operator can register the MACs of the specific EPs 25a, 25b and 25c in the CO 10. For example, the operator can register MACs of a plurality of service subscribers to the CO 10. The CO 10 then searches for the EPs 25a, 25b and 25c having the same MAC as the registered MACs among the linked EPs 25a, 25b and 25c, 25a, 25b, and 25c can be determined. Accordingly, a plurality of EPs 25a, 25b, and 25c having MACs registered in the CO 10 can be linked to the CO 10.

The procedure of opening by MAC authentication will be described in more detail as follows.

The CO 10 may assign a specific domain name and seed value to a specific EP 25b among the EPs 25a, 25b, and 25c having the registered MAC. That is, the CO 10 may assign the domain name and the seed value to the specific EP 25b among the EPs 25a, 25b, and 25c having the registered MAC as X and Y, respectively.

The CO 10 may also give the DM 15 the same domain name X and the seed value Y given to the specific EP 25b. The DM 15 and EP 25b then relink the CO 10 and the EPs 25a, 25b and 25c so that the specific domain name X and the seed value Y, which are distinguished on the bundle, So that the link can be maintained without interference and interference with other EPs 25a and 25c.

Hereinafter, the conventional method of pairing through MAC authentication has the following problems.

The seed value can not be determined in advance because it is not known what equipment is to be connected between the DM (15) and EP (25a, 25b, 25c) before opening. Therefore, according to the related art, it is necessary to set a default at the time of factory shipment and to perform a separate opening procedure between the operator and the installer through MAC authentication.

However, the opening procedure is very complicated and inconvenient. Particularly, when MAC authentication is performed by reading the label attached to the equipment remotely between the operator and the operator while connecting the DM 15 and the EPs 25a, 25b and 25c at the time of opening, Many errors occur in the opening procedure due to incorrectly pronounced or mislabeled concrete values. For example, the reader reads "O2", and the operator can understand it as "0E".

Or the label on which the MAC address is printed is deviated from the shipping process or the opening process, and there is no way for the operator to notify the operator because there is no way to check the MAC address.

Patent No. 10-1403580

Recommendation ITU-G.9960

DISCLOSURE OF INVENTION Technical Problem Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a method and system for performing MAC authentication between a DM and an EP having an initial seed value In order to reduce the crosstalk caused by high frequencies, the domain name and the seed value are kept as they are. In order to solve the troublesome problem caused by pairing, G.hn Based access network and Giga wire auto-pairing method.

It is a further object of the present invention to provide a method and system for controlling a communication system in which at least the DM of each port has a seed value and the EP has a seed value in order to eliminate the hassle of an initialization procedure having a seed value through MAC authentication between a DM and an EP having a default value, A G.hn-based access network and a Giga wire auto-pairing method which prevent a seed value from being erroneously stored by setting a MAC authentication by a protocol having a seed value in an opening procedure.

According to an aspect of the present invention for achieving the above object, a giga wire auto-pairing method of the present invention is a method for automatically creating a G.hn domain between a GAM and a GNT connected by a telephone line, Wherein the domain name and the seed value of the domain master are set and the domain name of the endpoint is set and the GAM of the port to be opened and the GNT The domain master inserts the predetermined seed value into the MAP-D frame and transmits the inserted seed value to the end point, and the end point transmits the MAP D frame, and checks the Seed value of the MAP-D frame having the strongest signal among the received MAP-D frames, The domain master attempts to link up with the domain master at a seed value and the domain master starts a link by accepting a registration request coming with the seed value, And the GAM automatically stores the MAC address in the domain master, and the GAM stores the MAC address of the endpoint in the domain master, A MAC address stored in the domain master when the domain master is initialized, and the domain master can link only the end point having the MAC address.

As described above, according to the configuration of the present invention, the following effects can be expected.

First, since the link is tried with the seed value, and the MAC address is confirmed again after linking to form the domain, there is no fear that the non-identical line is mistaken for the same line.

Second, MAC authentication is established and stored by the system according to the protocol, so there is no fear of communication error between the operator and the operator.

Thirdly, when the opening of the port is started, once all the procedures are started by the system, the MAP-D frame in which the seed value is inserted by the domain master of the GAM is transmitted to the end point, And the installer, and it is possible to prevent an error caused by the intervention of the operator and the operator.

1 is a block diagram showing a configuration of a conventional DSL-based access network;
2A and 2B are block diagrams illustrating a method of pairing through MAC authentication in an access network to which a G.hn standard according to the related art is applied.
FIG. 3A is a block diagram of an access network system forming a G.hn domain according to the present invention, and FIG. 3B is a block diagram showing a configuration of a GAM.
Figures 4A and 4B are block diagrams illustrating procedures before and after opening to form a G.hn domain according to the present invention.
5A and 5B are flowcharts illustrating an auto-pairing method for forming a G.hn domain according to the present invention.

Brief Description of the Drawings The advantages and features of the present invention, and how to achieve them, will become apparent with reference to the embodiments described in detail below with reference to 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. The dimensions and relative sizes of layers and regions in the figures may be exaggerated for clarity of illustration. Like reference numerals refer to like elements throughout the specification.

Hereinafter, a preferred embodiment of an access network system to which the G.hn standard according to the present invention having the above-described configuration is applied will be described in detail with reference to the accompanying drawings.

The Giga wire auto-pairing of the present invention includes GAM in which a plurality of ports perform a domain master function, GAM in which a plurality of GNTs functioning as an end point forming a domain master and a G.hn domain are connected by a bundle cable, Environment.

In order to improve the crosstalk generated on the bundle cable, the G.hn standard access network transmits and receives signals synchronized at a frequency of 40 Hz to 60 Hz. The domain master and the end point have intrinsic seed values, Communication is possible.

In particular, the domain master has an intrinsic seed value before forming the G.hn domain, but the endpoint has a unique seed value in the procedure of forming the G.hn domain, thereby greatly improving crosstalk.

3A, the G.hn standard access network system 100 for reducing crosstalk between bundled cables according to the present invention includes a G.hn access (hereinafter, referred to as " G.hn " A multiplexer (G.hn Access Multiplexer) 110, an endpoint (EP) to form a G.hn domain with each domain master (DM), a domain master (DM) (G.hn) network terminal (hereinafter referred to as " GNT ") 120 and a plurality of domain masters DM and an end point EP via a bundle cable And a telephone line (130) to which the telephone line (130) is connected.

The present invention is for implementing a Giga class service by applying the G.hn standard to an access network. In an exemplary embodiment of the present invention, the access network is a fiber to the phone line (FTTP). For example, if the access network is in the FTTP environment, the GAM 110 may be installed in an MDF terminal box located in an underground of an apartment, building, or other facility, or in an IDF terminal box installed in each layer or every two to three layers , The GNT 120 may be installed on the subscriber side.

Referring to FIG. 3B, the GAM 110 includes an uplink 112 connected to an upper communication device, a switch 114 connected to 8 to 24 domain masters DM to provide a synchronization signal, And a domain master (DM) composed of a domain master (116). Here, the domain master DM defines a port 116 that forms the end point EP and the G.hn domain.

The uplink 112 may be connected to the OLT in the case of FTTH based and may be connected to the L3 aggregation switch in the case of DSL based. The uplink may be uplinked to 1GE (Gigabit Ethernet) or 10GE.

The switch 114 can convert one 1GE (Gigabit Ethernet) or 10GE into 24 1GEs.

The domain master (DM) allocates other resources such as adjusting the bandwidth of the end point (EP) belonging to the domain and monitors the state of the end point (EP). In particular, the domain master (DM) can control data transmission / reception with the end point (EP) and other various operations according to a Medium Access Plan (MAP).

The end point EP is connected to the domain master DM through a bundle cable using the telephone line 130 and can communicate with the domain master DM in synchronization with a frequency of 40 Hz to 60 Hz.

The GNT 120 may be connected to the home IPTV and the Internet by an RJ45 connector or an equivalent connector, or by an in-house POTS and RJ11 connector or an equivalent connector.

The telephone line 130 may be grouped into twenty-four bundles. The telephone line 130 is exemplified as a transmission medium, but is not limited thereto and may include a UTP cable. For example, a pair of UTP cable may be used as a Giga wire in a conventional one-paired telephone line 130 or a UTP cable having four pairs. It can also be connected via CPEV, F / S, TIV, etc.

As described above, in order to improve crosstalk generated on the bundle cable, the domain master DM and the end point EP synchronize in a range of 40 Hz to 60 Hz, which is a specific frequency, do.

In particular, in order to prevent the cable from being recognized as the same line even though it is not the same line due to crosstalk between adjacent lines because the cable is bundled in the mutual communication, the domain master DM and the end point EP And has an intrinsic seed value (Seed).

The domain master (DM) has an intrinsic seed value (Seed) before forming the G.hn domain. On the other hand, the end point EP has an intrinsic seed value (Seed) in the procedure for forming the G.hn domain.

For example, the domain master DM uses a MAP-D frame, which is a kind of control signal, for data transmission / reception and other monitoring between the end points EP as described above. The domain master DM May be inserted into the MAP-D frame and transmitted to the end point EP.

4A, the first domain master DM1 has a domain name of "HomeGrid", a seed value of "Seed 1", a second domain master DM2 has a domain name of "HomeGrid", a "Seed 2" And the third domain master DM3 are set at the factory with the domain name of " HomeGrid " and the seed value of " Seed 3 ".

On the other hand, in the first endpoint EP1 to the third endpoint EP3, the domain name of "HomeGrid" is determined at the time of shipment from the factory, but the seed value is not set. Referring to FIG. 4B, the seed values of the first to third end points EP1 to EP3 are determined by a pairing procedure corresponding to the seed values of the first to third domain masters DM1 to DM3 according to the opening procedure .

Hereinafter, with reference to FIGS. 5A and 5B, an opening procedure in which the domain master DM and the end point EP are stepped on to form a G.hn domain on the access network will be described.

<Preparations before opening>

The domain name (Dmain Name) and the seed value (Seed) of the domain master (DM) are predetermined (S110)

For example, the domain name of the domain master DM is defined as &quot; HomeGrid &quot;, the seed value Seed is &quot; Seed 1 &quot;, &quot; Seed 2 &quot;, &quot; Seed 3 & , &Quot; Seed 299 &quot; or the like, so that each domain master (DM) has an intrinsic seed value (Seed). Seed may be set to a seed value of 1 to 24 and the GAM 110 may be set to a seed value when a bundle cable is connected to 24 pairs of telephone lines 130. [ The seed value can be changed in any amount depending on the number of the seeds.

The domain name of the end point EP is predetermined (S120). However, the seed value (Seed) is not predetermined.

Since the domain master DM can form a plurality of end points EP and G.hn domains, the domain name of the end point EP can be predetermined as &quot; HomeGrid &quot; . However, the seed value (Seed) is not determined because it is unknown to which domain master (DM) the end point (EP) can be connected.

All ports 116 of the GAM are in a deactivated state prior to opening.

<Auto-pairing after opening>

And connects the GAM 110 of the port to be opened with the wiring of the GNT 120 (S210)

The gateway establishes the GNT 120 on the site and routes the GAM 110 and the GNT 120 to both ends of the existing telephone line 130.

The operator activates the port 116 to be opened and notifies the start of pairing of the port 116 to be opened (S220)

The operator activates the port 116 to be opened at the request of the operator. In the present invention, the procedure necessary for opening the operator is performed up to this point. Then, the opening procedure is automatically performed by the system, and each domain master (DM) and the end point (EP) are paged to form one G.hn domain.

The domain master DM transmits a MAP-D frame (Frame) including a seed value already set before starting the pairing to the end point EP (S230)

The domain master DM sends a seed value Seed of a predetermined domain master DM to the end point EP in the MAP-D frame in the pairing preparation step at the beginning of pairing. Here, the MAP-D frame is used to control overall operation such as registration and assignment as a communication protocol of G.hn. In the present invention, a seed value is inserted into a MAP-D frame.

The end point EP may receive a plurality of MAP-D frames and check the seed value (Seed) of the MAP-D frame having the strongest signal among the received MAP-D frames (S240)

When each port 116 is activated as described above, the GAM 110 generates a MAP-D frame and sends the MAP-D frame to the end point EP. The end point EP is filtered and modulated, D frame (Frame).

At this time, the end point EP connected to the domain master DM through the bundle cable and the single telephone line 130 receives a plurality of MAP-D frames (e.g., Frame 1, 2, and 3 can be scanned. A MAP-D frame (e.g., Frame 1) having the largest signal among a plurality of scanned signals can be selected. Thus, the seed value (e.g., Seed 1) inserted in the MAP-D frame (e.g., Frame 1) is extracted, and the end point EP can then perform the registration procedure.

The end point EP tries to link up with the domain master DM with the confirmed seed value (S250) (S250)

As described above, since the end point EP forms a link with the domain master DM with an intrinsic seed value Seed, there is no fear that the end point EP will be linked even if it is physically adjacent to another end point EP that does not form the same domain .

The domain master DM accepts a registration request coming in with the same seed value and starts a link (S260)

Since the GAM 110 has information on the MAC address of the end point EP before the start of the GAM 110, the GAM 110 uses the MAC address of the end point EP requesting the registration, Respectively.

The GAM 110 checks the MAC address of the linked end point EP to set the MAC to be registered in the domain master DM and transmits the MAC address to the GAM 110. [ The MAC address of the corresponding port is automatically stored in the domain master DM (S270)

The procedure for setting the MAC address is performed automatically according to the protocol, and the operator does not instruct the GNT 120 to store the MAC address.

Then, the GAM 110 sets a MAC address stored in the domain master (DM) when the domain master (DM) is initialized, and the domain master (DM) sets an end point EP) and connects the link only (S280)

For example, when the GAM 110 is powered on after the blackout, or when the port 116 is activated again after the port 116 is in the inactive state, the domain master DM transmits the MAC address, (EP) and allows a link, so that there is no case where the G.hn domain is erroneously formed between adjacent telephone lines (130).

The end point EP tries to link with the seed value Seed stored at the start of each link but deletes the seed value Seed when the link is not connected for a predetermined time, The process can be repeated and repeated.

&Lt; Opening step &

The operator deletes the pairing information of the port 116 to be released (S310)

The GAM 110 deletes the MAC address of the end point EP stored in the corresponding port 116 in operation S320.

The operator will shut down the port 116 to be released (S330)

As described above, according to the present invention, a GAM in which a plurality of ports performs a domain master function and a plurality of GNTs functioning as an end point forming the G.hn domain are connected to each other by a bundle cable, In the G.hn standard access network system for implementing autofiling between points, the seed value is stored in the domain master at the factory before opening, and the seed value inserted in the MAP-D frame is extracted after the opening, And the seed value is stored so as to prevent the formation of the G.hn domain even if it is not the same line. Many other modifications will be possible to those skilled in the art, within the scope of the basic technical idea of the present invention.

100: G.hn access network
110: GAM 112: Uplink
114: switch 116: port
120: GNT 130: telephone line
DM: Domain Master EP: Endpoint

Claims (14)

GAM in which a domain master performs a master function in each port and GNTs in which an end point performs a client function are connected by a bundle cable and are synchronized at a specific frequency in order to improve crosstalk generated on the bundled cable, Wherein the domain master and the endpoint have an inherent seed value and a G.hn standard for communicating by the synchronization signal is applied,
Wherein the domain master has an intrinsic seed value before forming the G.hn domain,
Wherein the endpoint has an inherent seed value in a procedure of forming the G.hn domain. The method according to claim 1,
In the GAM,
FTTH-based OLT or DSL-based L3 aggregation switch, uplink to 1GE or 10GE,
A switch for converting the one 1GE or 10GE into 24 1GEs, and
And a domain master comprising 24 ports and forming the end point and the G.hn domain. 3. The method of claim 2,
The GAM is installed in an MDF terminal box and connected to an upper communication device including the OLT or the L3 aggregation switch,
Wherein the GNT is installed on the subscriber side and is connected to the home IPTV, the Internet, and the POTS. A pairing method for forming a G.hn domain by a GAM having a domain master as a port and a GNT having an end point on a subscriber side,
Activating the port to be opened;
The domain master transmitting a signal including a predetermined seed value (Seed) to the end point;
The endpoint receiving the signal and determining a Seed of the strongest signal among the received signals;
The endpoint attempts to link up with the domain master with the seed value, the domain master accepts a registration request coming to the seed value, and initiates a link;
Checking the MAC address of the linked endpoint, setting the MAC address as a MAC address registered in the domain master, and automatically storing the MAC address in the domain master; And
And connecting the link to only the endpoint having the MAC address when the domain master initializes the domain master. 5. The method of claim 4,
Before the port to be opened is activated,
The GAM and the GNT are interconnected by an operator; And
Further comprising the step of notifying the start of pairing of the port by activating the port to be opened in the GAM by the operator,
Before starting the pairing,
In the domain master, the seed value is specified together with a domain name,
Wherein only the domain name is specified in the end point. 6. The method of claim 5,
Wherein the signal comprises a MAP-D frame for controlling data transmission and reception with the endpoint, and the seed value is inserted in the MAP-D frame. Way. A GAM in which a plurality of ports function as a domain master, a GNT including an end point to form each G.hn domain with each of the domain master, and a bundle cable connecting between the domain master and the end point. A method for pairing an endpoint with a domain master of an access network,
Activating the port and starting the opening;
Linking the domain master and the endpoint using a seed value;
If the link is confirmed, the GAM automatically registers the MAC address of the endpoint using the previously stored MAC address information of the endpoint; And
Wherein the domain master is connected only to the registered end point when a re-link is established. 8. The method of claim 7,
Wherein the step of linking using the seed value comprises:
Transmitting a MAP-D frame including a seed value set before the opening from the domain master to an end point (EP);
The end point EP receiving the MAP-D frame, confirming the seed value of the MAP-D frame having the strongest signal among the received MAP-D frames;
The end point EP attempts to link up with the domain master DM with the identified seed value Seed; And
And the domain master (DM) accepting a registration request coming in with the same seed value to initiate a link. &Lt; Desc / Clms Page number 19 &gt; 9. The method of claim 8,
The step of automatically registering the MAC address includes:
The GAM checks MAC address of the linked EP and sets a MAC (MAC) registered in the domain master (DM) as a registered MAC (MAC); And
Wherein the GAM automatically stores the MAC address of the corresponding port in the domain master. A method for implementing auto-pairing between a domain master and an endpoint to form a G.hn domain between a GAM connected to a telephone line and a GNT,
Setting a domain name and a seed value of the domain master;
Setting a domain name of the endpoint;
Connecting the GAM of the port to be opened with the wiring of the GNT;
The port is activated and pairing is started;
Inserting the predetermined seed value (Seed) into the MAP-D frame and transmitting the inserted seed value to the end point;
The end point receiving the MAP-D frame and confirming a seed value (Seed) of the MAP-D frame having the strongest signal among the received MAP-D frames;
The endpoint attempting to link up with the domain master with the identified seed value Seed;
The domain master initiating a link by accepting a registration request coming in with the seed value;
The GAM checks the MAC address of the linked endpoint to set the MAC address to which the MAC address is registered in the domain master, and the GAM automatically stores the MAC address in the domain master ; And
Wherein the GAM sets a MAC address stored in the domain master when the domain master is initialized, and the domain master links a link only to the endpoint having the MAC address. A method of giga wire auto-pairing that forms .hn domains. An uplink for communicating with an upper communication device using an optical fiber;
A switch for converting one 1GE or 10GE to 24 1GE; And
And a domain master for performing data communication with a subscriber using a telephone line and inserting and transmitting a seed value in sending a control signal for controlling the data communication to a subscriber side. 12. The method of claim 11,
Wherein the control signal includes a MAP-D frame signal, and the seed value is inserted into the MAP-D frame. Wherein the G.hn network is wired to one side of a telephone line, receives a predetermined seed value from a domain master, and initiates a link with the received seed value to form a G.hn domain. terminal. 14. The method of claim 13,
Wherein the receipt of the seed value comprises scanning a plurality of signals from the domain master and verifying and storing a seed value of a signal having the largest signal strength among the scanned signals.

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