KR101937986B1 - System and Method on the N-hierarchical cell configuration - Google Patents

Abstract

The present invention relates to a multi-layer cell configuration method and system that combines large capacity mobile backhaul technology and small cell technology. The mobile backhaul dramatically increases the transmission capacity of the wireless backhaul by utilizing a wide frequency band (SHF / EHF) without using the cellular band that has a restriction on the frequency resource expansion, and the small group cell formed at the final stage of the mobile backhaul moves By using fixed relay group cells and mobile group cells according to radio wave environment by using relay, moving relay, wafar, and femto, it is possible to effectively achieve miniaturization of cells and to provide a large wireless system capacity to subscribers.

Description

TECHNICAL FIELD [0001] The present invention relates to a multi-

The present invention relates to a method and system for constructing a multi-layered cell that combines a large capacity mobile backhaul technology and a small cell technology based on a multi-layer cell and a multi-layer spectrum structure in a wireless access system. A mobile backhaul can use a super high frequency (SHF) / extremely high frequency (EHF), and a small group cell can use a wireless relay and a woofie.

Recently, smart devices are expected to become big bang due to N-screen and cloud services after the full-scale introduction of smart devices, but there is a limit to accept the current cellular based technology which is promoting some additional expansion of cellular band or performance improvement of 4G wireless transmission system Seems to be.

Moreover, demand for Internet multimedia services in high-speed group mobile devices (trains, buses, passenger cars) due to the spread of smart devices is also expected. However, in the present cellular system, high-speed data service is very difficult due to rapid spectral efficiency degradation .

An embodiment of the present invention provides a cell configuration method of a wireless communication system configured with a multi-layer cell structure and a multi-layer frequency band in order to increase traffic capacity.

The embodiment of the present invention provides a multi-layer cell structure and a multi-layer frequency band including N links and N frequency bands in an N-layer overlay cell structure using the same radio transmission method (RAT) The system provides a system.

The embodiment of the present invention improves the utilization efficiency of radio resources by optimizing the spectrum management, interference management, and radio resource management among the multi-tiers according to radio environment change (real-time learning) in a multi-layer cell structure .

The embodiment of the present invention provides for offloading mobile traffic of a conventional cellular cell to a group cell through seamless mobility between a conventional cellular cell and a proposed group cell.

A system configured with a multi-layer cell according to an embodiment of the present invention includes a service infrastructure providing accumulated knowledge, a device infrastructure configured with devices and provided with the accumulated knowledge from the service infrastructure, A network infrastructure for providing a network connection between the infrastructures, and a platform infrastructure for performing tasks for processing the data collected in the device infrastructure and the network infrastructure with knowledge and accumulating the data in the service infrastructure.

A handover method according to an inbound movement in a device of a multi-layer cell configuration according to an embodiment of the present invention includes receiving measurement guide information of a group cell from a measurement control message from the cellular cell, The method comprising the steps of: measuring a reception intensity by searching adjacent group cells according to measurement guide information of a group cell; determining a group cell having the largest received measurement strength as a target to be handed over; Transmitting a handover report message (Measurement Report) to the cellular cell only when the handover report threshold is greater than a handover report threshold; and receiving system information of the target group cell from the cellular cell, And preparing for handover and handover to the target group cell It can hamhal.

The present invention relates to a multi-layer cell configuration method and system combining a large capacity mobile backhaul technology and a small cell technology, and it is possible to increase a capacity of a wireless system and provide a high quality service through a combination of a large capacity mobile backhaul technology and a small cell technology .

And, the possibility of obtaining the visible distance (LoS) between the wireless backhaul and the device clustering is improved by using the multi-layer link. Through the global resource manager located in the digital cloud center, real-time reconfiguration and utilization efficiency of overall spectrum resources, interference levels, and virtual radio resources among jurisdictions can be improved. In addition, the effect of mobile traffic offloading through seamless mobility between the cellular cell and the small group cell can be increased.

1 illustrates a schematic configuration of a wireless communication system configured with a multi-layer cell structure and a multi-layer frequency band according to an embodiment of the present invention;
FIG. 2 is a diagram showing a configuration of the network infrastructure of FIG. 1;
3 is a diagram illustrating a method of configuring networking between cells for overall management in a digital cloud center according to an embodiment of the present invention;
4 is a diagram illustrating a configuration example of a system in which a multi-layer cell is configured as a two-layer cell according to an embodiment of the present invention;
5 is a diagram illustrating a practical example of a two-layer cell referred to as a large cell (L-cell) and a small cell (S-cell) according to an embodiment of the present invention.
Figure 6 illustrates an example of linking to a device in a system comprised of small cells based on a multi-layer cell structure and a multi-layer band in accordance with an embodiment of the present invention;
7 is a diagram illustrating a communication method in a situation where communication is poor due to a non-LoS environment between a base station and a device;
8 is a diagram illustrating an example of movement between a group cell and a general cellular cell in a multi-layer cell system according to an embodiment of the present invention.
9 is a diagram illustrating a handover procedure when a device performs an inbound move in a system configured with multi-layer cells according to an embodiment of the present invention; and
10 is a flowchart illustrating a handover process in an inbound mobile device in a system of a multi-layer cell system according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

For reference, the terminology and technology background used in the following description are based on 3GPP LTE / LTE-A (Long-Term Evolution-Advanced) or IEEE Mobile WiMAX standard. In the following description, a group cell refers to a cell in which a specific group operates as if it is a single terminal, and a group cell is connected to a network through one or more backhaul.

FIG. 1 is a diagram illustrating a schematic configuration of a wireless communication system configured with a multi-layer cell structure and a multi-layer frequency band according to an embodiment of the present invention.

Referring to FIG. 1, a wireless communication system includes a service infrastructure 101, a network infrastructure 103, a device infrastructure 104, and a platform infrastructure 105.

The service infrastructure 101 provides accumulated knowledge 111 through the device infrastructure 104 and the network infrastructure 103 using various applications / content.

The device infrastructure 104 is composed of smart devices and portable terminals and is provided with accumulated knowledge 111.

Network Infrastructure 103 Provides a network connection between the service infrastructure 101 and the device infrastructure 104.

The platform infrastructure 105 processes the data 102 collected in the device infrastructure 104 and the network infrastructure 103 for the application / content provided through the service infrastructure 101 into the knowledge 111 to obtain the service infrastructure 101 ) In the same manner as in the first embodiment.

The platform infrastructure 105 may include a content domain 106, a device domain 108, a network domain 107, a server platform 109 and a device platform 110.

The content domain 106 performs a task required for the service infrastructure 101 based on a multi-processing basis.

The device domain 108 performs the tasks required for the device infrastructure 104 on a single-processing basis.

The network domain 107 performs the tasks required for the network infrastructure 103.

The server platform 109 is a device utilized by the content domain 106 or the network domain 107.

Device platform 110 is a device utilized by network domain 107 or device domain 108.

2 is a diagram showing a configuration of the network infrastructure of FIG.

Referring to FIG. 2, the network infrastructure 103 includes a core network 213 and a radio access network 214.

The radio access network 214 is composed of a plurality of cells 203 under control of a radio resource of a global resource manager 207 performed in a digital cloud 202 and a digital cloud 202.

The multi-layered cells 203 may be composed of a plurality of large and small cell types. When the multi-layered cell 203 is composed of N cells, up to N links and up to N frequency bands may be utilized for each cell type.

Herein, the radio access network 214 function is located in the digital cloud center 202 in the base station modem, the MAC, and the protocol SW functions in comparison with the current base station function, and the RF / ) Are distributedly installed on the basis of the cells 203 of the multiple layers as shown in the following example;

The first layer cell 208 is installed in an area having a large visible range, such as a rural area, and can be classified as a macro cell.

Tier-2 cells 209 and 210 are installed in a road or a city area, and can be classified into micro cells smaller than macro cells.

The third layer cell 211 is installed in a groove, a train, an automobile or the like, and can be classified into a smaller picocell than a microcell.

A multi-layer cell composed of N layers in an N-tier cell topology can be configured with an N-layer link (Link-n) and an N-layer frequency band (Band-n). At this time, each layer cell may be connected to an upper layer cell or a same layer cell through a wireless link (for example, an RF cable) or a wired link (for example, an optical cable).

At the end of each link, small group cells 210 and 212 (hereinafter, small group cells are referred to as small cells) are connected, and the small cells serve various devices located inside their own cells. Here, the device (D) includes various smart devices, automobiles, household appliances, trains, and buses. The small cell 212 is a structure capable of supporting a device network configuration that is directly connected to a device such as a home appliance, a smart device, a robot device, and a medical device.

FIG. 3 is a diagram illustrating a method of configuring networking between cells for overall management in a digital cloud center according to an embodiment of the present invention. Referring to FIG.

Referring to FIG. 3, a network configuration method of each cell managed by the digital cloud center 307 through the global resource manager 308 includes a P2P connection method 301, a tree connection method 302, a Ring connection method 303 A Mesh connection method 304, and a Chain connection method 305, for example.

In the P2P connection method 301, each cell is configured in the P2P format with the digital cloud center 307. [ The tree access method 302 is networked in a tree format between large and small cells. Ring connection method 303 is configured for networking in a multi-layer ring format between cells. The mesh connection scheme 304 is networked between the cells in a mesh format. The chain connection method 305 is networked in a chain format between cells.

3, various devices can be connected to the appropriate cell types 301 to 305 according to the characteristics of the device. For example, the smart device 309 can use a tree connection method 302 connected in an N-layer wireless link so as to create a radio wave environment in which a line-of-sight (LoS) exists between a cell and a device , And the high-speed rail 310 can be connected to the cell 303 of the ring connection type. The device network 311 can be connected using one of the cell types 301 to 305 through the main device serving as a gateway.

4 is a diagram illustrating a configuration example of a system in which a multi-layer cell is configured as a two-layer cell according to an embodiment of the present invention.

4, a base station connected to the Internet through a packet core network (EPC) 401 comprises a digital section (BS-DU) 402 and a wireless section (BS-RU) 404 do.

A terminal connected to a base station via a mobile wireless backhaul in a high-speed bus that is a mobile corresponds to a high-speed bus group cell. 4, a moving relayer 406 or a WiFi router 408 corresponds to a high-speed bus group cell.

In the case of a high-speed bus group cell, a terminal converter 405 having a function of receiving a signal of a wireless transceiver as a base station wireless sector 404 and converting the signal into a layer-2 cell signal may be attached to a top board of a high-speed bus.

Here, the terminal converter 405 has a function of serving as a terminal in correspondence with the wireless sector 404 of the base station and a function of using the wireless sector 404 corresponding to the first hierarchical cell and the high- (RAT: Radio Transmission Tech) is different from the radio transmission method (RAT).

In the case of the second layer cell, a signal received through the terminal converter 405 is transmitted to a final-stage radio interface 406 via a mobile relay 406 or a WiFi router 408, To the general terminal.

FIG. 5 is a diagram showing a practical configuration example of a two-layer cell referred to as a large cell (L-cell) and a small cell (S-cell) according to an embodiment of the present invention.

Referring to FIG. 5, the digital cloud 501 is connected to a large cell (L-cell) 511, 512 or a small cell (S-cell) 521-530 through a wired link or a wireless link such as an optical cable. Here, the types of links formed by the large cell, the small cell, and the device MS include a link (Link-1) between a large cell and a small cell, a link (Link-2) between a small cell and a device, (Link-3).

A backhaul link can be used for the link (Link-1) between the large cell and the small cell, and the backhaul link can be connected through the SHF / EHF Wireless or the optical cable.

A radio link may be used for a link between a small cell and a device (Link-2), and a wireless link may be connected through a SHF / EHF Wireless, a Cellular, or a WiFi .

A direct radio link can be used for the link between the large cell and the device (Link-2), and the radio link can be connected through the high frequency band (SHF / EHF Wireless).

In the embodiment of the present invention, Link-1 in the present invention can utilize a very high frequency band (SHF / EHF) capable of extracting a sufficiently wide frequency band.

5, the digital cloud center 501 accesses the spectrum resource (SM), the interference level (IM), and the (virtual) radio resource availability scale VM and RRM of all the cells managed by the digital resource center 501 through the global resource manager 502, And the like to maximize the resource utilization efficiency of the entire system managed by the digital cloud center 501.

In order to increase the resource utilization efficiency, the digital cloud 501 analyzes the location measurement and propagation environment information of the device terminal, and analyzes the information (for example, communication quality such as the SIR (Signal-Interference Ratio) Band (Band-n) in real time, and reconfigures the shape of the corresponding cell according to the band. The means for realizing this can utilize the SDR base station platform management function which is generally available.

In addition, the global resource manager 502 may have a mobility management function (corresponding to MME in 3GPP LTE; Mobility Management Entity) and a CCN (Contents Centric Network) function of the device.

Next, the case for each cell type of FIG. 5 will be described.

Case-1 is a super-WiFi picocell suitable for home, office and indoor environments.

Case-2 is a picocell that uses a moving-relay, and is suitable for a group cell that moves outdoors such as a train, a bus, and the like.

Case-3 is a picocell using the ultra-fast frequency band (SHF / EHF), and is suitable for device backbone such as visible distance (LoS) hot spot, vehicle networking.

Case-4 is a cellular cell-based microcell that is suitable for outdoor non-LoS hotspots.

Case-5 is a macro cell that uses a hybrid communication method that uses cellular and high-speed frequency band (SHF / EHF) at the same time. It is suitable for rural areas where there is not a large number of base stations and high buildings.

Case-6 is suitable for device networks using ultra high-speed frequency band (SHF / EHF) or cellular. At this time, the device network can provide communication to the devices in the included network through the device acting as a gateway. Devices can be sensors, consumer devices, medical devices, automotive devices, robot devices, and so on.

In the case not mentioned above, it is possible to communicate using conventional cellular communication (3G, 4G), and continuity of communication can be achieved through interworking with cellular if necessary.

Figure 6 is an illustration of an example of linking to a device in a system comprised of small cells based on a multi-layer cell structure and a multi-layer band in accordance with an embodiment of the present invention.

Referring to FIG. 6, the construction of a multi-layer cell structure and a multi-layer band-based small cell is performed in the following three steps.

In the first step, the general communication service provider determines the location (positioning) of the small cell and the number of the base stations in consideration of the following items in the communication business area. Telecom operators can use their own design tools (such as simulation methods) for this purpose.

The location of the small cell 611-619 is determined to maximize the propagation environment of the LoS, and the maximum number of simultaneous subscribers, the maximum supported transmission rate per subscriber, and the average QoS per subscriber are considered.

In a region where a small cell is difficult to configure (a region where visibility is difficult to secure, a communication service provider determines through field test, etc.), communication is supported by a general cellular cell.

In the second step, the number of positioning and installation of the digital cloud sensor 601 is determined in consideration of the computing power of the digital cloud center, the capacity of the storage, and the server.

In a third step, the digital cloud center 601 determines a radio link path from the global resource manager 602 to each of the small cells 611-619.

Here, an example of the path of the radio link is as follows.

A single-link refers to a wireless link that links from a digital cloud center 601 to a small cell 614 in a single hop.

The multi-links means a row of wireless links connected from the digital cloud center 601 to the small-size cell 613 so as to maximally support the visibility within the small cell.

The wireless link can utilize the very high frequency band (SHF / EHF) as well as the cellular band. The wireless link has advantages such as cost (construction cost) and easy installation compared to a wired link such as an optical cable.

The concept of Cognitive Radio System (CRS) is applied to each link, so that the frequency band can be changed in real time according to the propagation environment. (For example, you can see that Band 1x of Link-1x changes to Band 1y.)

The base station equipment of the small cell (T3z) 613 formed at the last stage in the link configuration is not limited but can be configured as a femtocell in an outdoor environment and a WiFi cell in an indoor environment.

Here, the small cell can be configured in real time, dynamically, or if necessary, to maximize the total performance of a small cell managed by a specific digital cloud center. As a total performance maximization parameter of the digital cloud center, path cost and bandwidth resource utilization efficiency for forming a radio link from the digital cloud center to each small cell, traffic processing capacity of a small group cell, and cell coverage can be considered.

The functions to be supported by the global resource manager 602 function to configure a small group cell are as follows.

The global resource manager 602 dynamically searches for a signal-interference ratio (SIR) of a small cell adjacent to the subscriber in real time (for example, based on Discontinuities Reception (DRX)), calculates a maximum SIR (i) to the target group cell to reconfigure link and cell coverage.

7 is a diagram illustrating a communication method in a situation where communication is poor due to a non-LoS environment between a base station and a device.

Referring to FIG. 7, a device clustering 720 (also referred to as a device network) composed of any n devices can provide communication to devices existing in non-LoS through a bypass link path. Here, the clustering 720 is connected through the following method using a smart device or an inter-vehicle mesh or relay networking method.

A master device 721 serving as a gateway in real time (determined on the basis of SNR) by examining the devices 721 to 723 included in the device clustering 720 in the best manner with the base station 710, .

The selected master device 721 can collect traffic of other devices 722 and 723 belonging to the device clustering 720 and transmit and receive the traffic to and from the base station 710 in the representative device status.

Alternatively, the path from the base station 710 to the target device 723 may be transmitted / received by relay networking.

At this time, WPAN, etc. can be applied to the inter-device communication

FIG. 8 is a diagram illustrating an example of movement between a group cell and a general cellular cell in a multi-layer cell system according to an embodiment of the present invention.

Referring to FIG. 8, in the movement between the group cell and the general cellular cell, outbound mobility from the group cell 803 to the cellular cell 802, and outbound mobility from the cellular cell 802 into the group cell 803 There is inbound mobility.

Outbound mobility is a movement in the case where a handover of a corresponding device terminal to an adjacent cellular cell occurs when communication quality drops below a certain threshold (SIR-based) due to an instantaneous obstacle or a poor propagation environment such as a bus . At this time, the operation procedure of the outbound movement applies the same principle as the handover mechanism in the general cellular environment.

Inbound mobility handles cellular-band traffic to non-cellular bands (SHF / EHF) cells (eg, small cell 803) .

9 is a diagram illustrating a handover procedure when a device performs an inbound move in a system configured with a multi-layer cell according to an embodiment of the present invention.

9, when a device (UE) 901 is in an active state (communicating state) with a cellular cell (cell-A) 903 in steps 906 and 907, a measurement control ) Message to receive the measurement instruction information of the group cell. At this time, the Measurement Control message is transmitted immediately after the entry of the communication step.

In step 908, the device 901 searches adjacent group cells according to the measurement guide information of the group cell (Gap pattern information as the search time information of the adjacent cell) to measure the signal-interference ratio (SIR). (K), the group-cell (i) (i = 1 to n) determines the group cell having the largest received measurement strength as the target to be handed over.

In step 909, the device 901 compares the reception strength of the determined target group cell (Group-cell (k)) with the internally stored handover reporting threshold (THreport), and only when the reception strength is greater than the threshold, Measurement Report) 909, thereby reducing the signaling overhead.

In step 910-911, the cellular base station 903 receiving the handover report message transmits a system information message to the corresponding device 901 using the SI Reception Command to broadcast the target group cell (cell-B) Command. At this time, the device 901 receives detailed system information such as random access information necessary for initial synchronization with the target group cell (group-cell (k)) to prepare for handover.

When the device 901 proceeds to step 911 of receiving the system information, the device 901 performs a handover procedure through steps 912-917, which is the same method as in the general cellular case. (Inbound mobility procedure of 3GPP Rel-10 is applicable.) At this time, the device re-transmits the handover report message (Measurement Report) for triggering the general handover procedure in step 912.

10 is a flowchart illustrating a handover process in an inbound mobile device in a system of a multi-layer cell system according to an embodiment of the present invention.

Referring to FIG. 10, if the device detects cell movement of the device in step 1012 while operating in the active mode in step 1010, it checks in step 1014 whether the cell movement of the device is inbound movement or outbound movement.

If it is determined in step 1014 that the cell movement of the device is an outbound movement, the device applies the same principle as the handover mechanism in the conventional general cellular environment.

If it is determined in step 1014 that the cell movement of the device is an inbound movement, the device receives measurement guide information of the group cell from the cellular cell through a measurement control message in step 1016.

In step 1018, the device searches adjacent group cells according to the measurement instruction information of the group cell.

In step 1020, the device measures reception intensities of adjacent group cells and determines a group cell having the largest received measurement strength as a target to be handed over.

In step 1022, the device determines whether the received signal strength of the target group cell is greater than a predetermined handover reporting threshold.

If it is determined in step 1022 that the reception strength of the target group cell is not greater than the preset handover reporting threshold, the device returns to step 1020 to re-measure the reception strength of adjacent group cells, The target to be reassigned.

If it is determined in step 1022 that the reception strength of the target group cell is greater than the predetermined handover reporting threshold, the device transmits a handover report message (Measurement Report) to the cellular cell in step 1024. [

When receiving the system information of the target group cell from the cellular cell in step 1026, the device receives the system information from the target group cell in step 1028 and prepares for handover.

In step 1030, the device retransmits the handover report message (Measurement Report) for the purpose of triggering the general handover procedure.

In step 1032, the device performs handover to the target group cell.

The methods according to embodiments of the present invention may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the present invention or may be available to those skilled in the art of computer software.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the equivalents of the claims, as well as the claims.

Claims (16)

A service infrastructure providing accumulated knowledge;
A device infrastructure configured from devices and provided with the accumulated knowledge from the service infrastructure;
A network infrastructure for providing a network connection between the service infrastructure and the device infrastructure; And
And a platform infrastructure for processing data collected in the device infrastructure and the network infrastructure as knowledge and performing a task for accumulating the data in the service infrastructure,
The network infrastructure is divided into a core network and a radio access network,
Wherein the radio access network is comprised of a plurality of cells under control and management of radio resources of a digital cloud and a global resource manager performed in the digital cloud center,
The multi-layered cell may include at least one of a macro cell, a micro cell, and a picocell,
The digital cloud center analyzes location information and propagation environment information of the device, selects and allocates a frequency band most suitable for the cell in real time, and reconfigures the shape of the corresponding cell according to the allocated frequency band.
A system consisting of multi-layer cells.
The method according to claim 1,
The platform infrastructure includes:
A content domain for performing a task required for the service infrastructure on a multi-processing basis;
A device domain that performs tasks required for the device infrastructure based on a single processing;
A network domain for performing tasks required for the network infrastructure;
A server platform utilized by the content domain or the network domain; And
A device platform utilized by the network domain or the device domain
A system consisting of multi-layer cells.
delete The method according to claim 1,
The digital cloud center comprises:
And a resource utilization efficiency is maximized by managing at least one of a spectrum available resource, an interference level, and a radio resource utilization scale of the multi-layer cell managed through the global resource manager
A system consisting of multi-layer cells.
delete The method according to claim 1,
Wherein the global resource manager comprises:
A mobility management function of the device or a contents center network (CCN) function
A system consisting of multi-layer cells.
The method according to claim 1,
The multi-
The number of links is equal to the number of layers and the number of frequency bands is equal to the number of layers.
A system consisting of multi-layer cells.
The method according to claim 1,
Each of the cells included in the multi-
It is possible to use a wireless link or a wired link to connect to an upper layer cell or a same layer cell
A system consisting of multi-layer cells.
The method according to claim 1,
The small cells included in the multi-
The position is determined so that the propagation environment of the LoS is maximally ensured by the communication service provider.
A system consisting of multi-layer cells.
10. The method of claim 9,
The small cells included in the multi-
When the location is determined, at least one of the maximum number of simultaneous subscribers, the maximum supported transmission rate per subscriber, and the average QoS per service of the subscriber is considered
A system consisting of multi-layer cells.
The method according to claim 1,
The location and the number of the digital cloud center are,
And the capacity of the server serving the digital cloud center is determined by the communication carrier in consideration of the calculation capability, the size of the storage space, or the capability of the server serving the digital cloud center
A system consisting of multi-layer cells.
The method according to claim 1,
Wherein the digital cloud center is connected to each small cell included in the multi-layer cell by a single hop wireless link,
Wherein each of the small cells included in the multi-layer cell is connected by multiple radio links so as to maximally support a visible distance within the small cell.
A system consisting of multi-layer cells.
13. The method of claim 12,
The wireless link includes:
Cellular or ultra-harmonic band (SHF / EHF)
A system consisting of multi-layer cells.
13. The method of claim 12,
The wireless link includes:
Cognitive Radio System (CRS) is applied and the frequency band is changed in real time according to the radio wave environment
A system consisting of multi-layer cells.
13. The method of claim 12,
The small-
A femtocell in an outdoor environment, and a wifi cell in an indoor environment.
A system consisting of multi-layer cells.
delete

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