KR101415410B1 - An effentive frequency sharing system and method using spectrum etquette and genetic algorithm for the coexistence of wran and wlan in tv white space - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency sharing system and a method for reducing mutual interference due to the coexistence of various heterogeneous communication devices such as WRAN and WLAN in TV whitespace and improving communication performance.
A frequency sharing system, comprising: an information obtaining unit for obtaining information of a WRAN and a WLAN as a system for minimizing interference between two systems of a WRAN and a WLAN; An optimal resource allocation unit for allocating an optimal frequency sub-band based on information collected from the information acquisition unit; And a broadcasting unit for broadcasting an optimal frequency sub-band to each corresponding system.

Description

TECHNICAL FIELD The present invention relates to an efficient frequency sharing system and method for WRAN and WLAN using spectral etiquette and genetic algorithm in TV white space,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency sharing system and method for reducing mutual interference due to coexistence of various heterogeneous communication devices such as WRAN and WLAN in TV whitespace and improving communication performance.

Recently, with the emergence of various high-end multimedia devices, demand for high-quality services has been increasing, IT convergence technology has been proposed, which incorporates wireless communication technology in the field of public safety and efficient energy management. Resource shortage problems are emerging all over the world. Especially, since the frequency band having excellent radio wave characteristics of TV frequency band and 3GHz or less is inefficiently used in a considerable part, the importance of research for efficient use of such band is continuously being raised.

Thus, in 2008, the Federal Communications Commission (FCC) licensed non-licensed, non-exclusive services using the TV White Space, an idle frequency resource in the frequency band 54 MHz to 862 MHz, It is becoming a catalyst for movement.

In addition, we will form a standardization group for TV white space such as IEEE 802.22, which was completed and released in July 2011, and IEEE 802.11af, which are currently in progress, and will be responsible for standardization work on WRAN (Wireless Regional Area Network) and WLAN TVBD (TV Band Device) is being promoted through commercialization.

In the TV white space frequency band, the IEEE 802.22 base station, the customer premises equipment (CPE) and the IEEE 802.11af Various wireless communication networks such as an access point (AP) coexist. Therefore, a technology for solving the interference problem of heterogeneous systems is required. Therefore, standardization to solve the coexistence problem of heterogeneous systems such as IEEE 802.19.1 is still in progress, but research on a method of maximizing the performance improvement and efficiency of each system has not yet been made to be.

The IEEE 802.22 standard minimizes interference with adjacent cells through a spectrum etiquette process. However, in the current standard, WLAN coexisting in a cell is not considered, so there is a weakness in the interference to WLAN which is a heterogeneous system. Also, WLAN channel selection methods that have been studied so far also consider interference with users and like users, but do not deal with heterogeneous systems.

Therefore, it is necessary to study the technology that can optimize the performance of WLAN users and minimize the interference to WRAN through radio resource allocation technology considering heterogeneous and homogeneous systems.

An information acquisition unit that acquires information of WRAN and WLAN as a system that minimizes mutual interference between WRAN and WLAN; An optimal resource allocation unit for allocating an optimal frequency sub-band based on information collected from the information acquisition unit; And a broadcasting unit for broadcasting an optimal frequency sub-band to each corresponding system.

On one side, the frequency sharing system is based on TVWS (TV White Space), and TVWS is an idle frequency resource in the TV broadcast frequency band, which means a frequency channel space that can be utilized without any permission.

In another aspect, the information acquired by the information acquisition unit corresponds to a setting state of a peripheral device, a channel allocation state, an installation location, an access mode mode, and an AP (Access Point, access device) The above information can be obtained.

In another aspect, the optimal resource allocation unit may include a first channel selection unit for selecting a channel using an Isolated Channel Set (ICS); And a second channel selector for selecting a WLAN channel using a genetic algorithm.

In another aspect, the first channel selector uses WRAN spectrum etiquette, defines a set of consecutive channels without occupying an isolated channel set in a license user or an adjacent WRAN cell, and the number of channels Select fewer channels.

In another aspect, the second channel selection unit defines a chromosome, a gene, and a fitness evaluation function, applies the defined fitness evaluation function to each AP, and selects a trait having superior performance.

The method comprising: acquiring information of a WRAN and a WLAN as a method for minimizing interference between two systems of the WRAN and the WLAN; Allocating an optimal frequency sub-band based on the information collected from the information obtaining unit; And broadcasting an optimal frequency sub-band to each of the corresponding systems.

Through the present invention, a WLAN channel selection method using WRAN spectrum etiquette and genetic algorithm is applied in a situation where TV, wireless microphone, IEEE 802 wireless network and devices coexist within the same TV white space frequency band, Can be improved.

In addition, through the mutual coexistence technology, when various heterogeneous systems and similar systems coexist in different frequency bands other than TV whitespace in the future, they can be used as an efficient frequency sharing technology.

1 is a block diagram illustrating an internal configuration of a frequency sharing system according to an embodiment of the present invention.
2 is a diagram illustrating an embodiment of a spectral etiquette process in an embodiment of the present invention.
3 is a diagram illustrating a channel selection method of a WRAN considering WLAN in an embodiment of the present invention.
4 is a flowchart illustrating a spectrum etiquette process in an embodiment of the present invention.
5 is a diagram illustrating a structure of a WLAN optimization system from the center proposed by the present invention in an embodiment of the present invention.
6 is a diagram illustrating a structure and a method of a WLAN channel selection system using a genetic algorithm in an embodiment of the present invention.
7 is a flowchart illustrating a frequency sharing method according to an embodiment of the present invention.
Figure 8 is a performance graph illustrating the cumulative SINR distribution probability of a WLAN user in an individual channel usage scenario, in accordance with an embodiment of the present invention.
9 is a cumulative distribution probability graph illustrating throughput (throughput per unit time) performance of a WLAN user in an individual channel usage scenario, in an embodiment of the present invention.
FIG. 10 is a graph illustrating an outage probability (accident rate) of a WLAN user as a user increases in an individual channel usage scenario according to an embodiment of the present invention.
11 is a graph illustrating the cumulative SINR performance probability of a WLAN user in a shared channel usage scenario, according to an exemplary embodiment of the present invention.
FIG. 12 is a graph illustrating a throughput cumulative distribution probability of a WLAN user in a shared channel usage scenario according to an exemplary embodiment of the present invention.
13 is a graph illustrating an SINR performance cumulative distribution probability of a WRAN user in a shared channel usage scenario according to an exemplary embodiment of the present invention.
14 is a graph illustrating outage probabilities of WLAN users in a shared channel usage scenario in an embodiment of the present invention.
15 is a graph illustrating outage probability of a WRAN user in a shared channel usage scenario according to an exemplary embodiment of the present invention.

First, the frequency sharing system is based on TVWS (TV White Space), and TVWS refers to a frequency channel space that can be used as an idle frequency resource in a TV broadcast frequency band without any special permission. Therefore, various wireless communication networks can coexist, and a technology for solving the interference problem among each other is required.

The system proposed in the present invention can reduce the interference between heterogeneous systems by using WRAN channel selection method with complementary spectrum etiquette and WLAN channel selection method based on genetic algorithm considering heterogeneous system, Through the selection method, WLAN users coexisting in the frequency cell can use a wider bandwidth, and through the proposed WLAN channel selection method, it is possible to minimize the interference to both the WRAN which is a heterogeneous system and the WLAN which is a homogeneous system. Therefore, the WLAN and WRAN transmission performance can be maximized and the outage probability (accident rate) of the number of users can be reduced.

1 is a block diagram showing the configuration of a frequency sharing system 100 according to an embodiment of the present invention. 1, an information obtaining unit 110, an optimal resource allocating unit 120, and a broadcasting unit 130. [

The information obtaining unit 110 obtains information on the setting state and the channel use of the neighboring WRAN and the WLAN device and obtains information on the channel allocation state, the installed location, the access mode scheme, the number of APs, The WRAN, and the RF channel, and collects the acquired information and transmits the collected information to the optimal resource allocation unit 120. [

Using the information received from the information acquisition unit 110, the optimal resource allocation unit 120 allocates a first channel selection unit 121 using an isolated channel set (ICS), a second channel selection unit 121 using a genetic algorithm, And the selection unit 122 to efficiently allocate resources.

Here, the first channel selector 121 uses WRAN spectrum etiquette, defines a set of isolated channels as a set of consecutive channels, which is not occupied by a license user or an adjacent WRAN cell, and the number of channels You can select a channel.

The isolated channel set defined in the present invention obtains consecutive channels that are not occupied by a licensee user or an adjacent WRAN frequency cell as shown in the lower part of FIG. As shown in FIG. 2, when there is a licensed user, ICS1 has two channel sets # 1 and # 4 and # 5, and there exists an intersection with LPS (Local Priority Set) If the ICS1 channel having the smallest number of consecutive channels is selected, the WLAN AP can use a wider channel as shown in FIG. 3 than using the existing spectrum etiquette. ICS1 and ICS2 do not take into account the operating channels of neighboring cells, respectively, and the flowchart of the spectrum etiquette operation proposed by the present invention is shown in FIG.

As shown in Fig. 4, first, it is confirmed whether ICS1 is applicable or not. If ICS1 is not present, the WRAN channel is not allowed to move to a channel that the adjacent frequency cell is not using. In this case, the same situation as the LPS3 step is selected. Therefore, the ICS2 channel having the smallest size and the channel belonging to the intersection are selected without going through the LPS1 and LPS2 steps. On the other hand, if ICS1 exists, LPS can be obtained according to the existing spectral etiquette order and the channels belonging to the intersection with the smallest ICS1 channel can be selected.

If the smallest ISC1 or the smallest ISC2 is three or more in size, i.e., the smallest isolated channel is composed of three or more consecutive channels, the outermost channel can be selected at random. For example, if the smallest ISC1 is 3, 4, or 5, if you select the 3rd or 5th channel, the WLAN APs will transmit channels 3, 4, 4 and 5 Lt; / RTI > can be additionally obtained. Thus, WRAN spectrum etiquette, which prioritizes isolated channels, can improve the performance of both WRAN and WLAN.

Unlike the existing WLAN protocol, TV whitespace must be connected to the database in accordance with FCC regulations. In addition, all IEEE 802 standard devices update the location information and user authentication information in the database and share the TV frequency band with the available channel information and permission from the database. Since all WLAN APs are directly or indirectly dependent on the database, it is possible to allocate dynamic spectrum through a central optimization process as shown in FIG. 5 as well as dispersive mutual coexistence. In the present invention, a WLAN performance optimization process from the center is proposed through an operation process using the genetic algorithm described above.

The second channel selection unit 122 can select an optimum frequency using a genetic algorithm. At this time, the second channel selection unit 122 defines a chromosome, a gene, and a fitness evaluation function, applies the defined fitness evaluation function to each AP, You can choose a trait.

One of the most important applications of genetic algorithms is to define chromosomes, genes and fitness evaluation functions for the system. A WLAN channel selection method using the genetic algorithm proposed in the present invention is shown in FIG. Bandwidth and channel selection and TPC (Transmit Power Control) are optimized through a genetic algorithm. Randomly generating information of N APs sharing a frequency resource in one WRAN cell, To form populations. Here, one entity is a chromosome that can be used to evaluate the overall performance of a WLAN, and information such as the bandwidth, allocated transmission power, and channel number of each AP is used as a gene, The performance of the overall network can be determined.

In the fitness evaluation process, Shannon's capacity (Shannon Capacity) formula is applied to each AP, and then the average is obtained. Thus, the best trait can be selected by evaluating the performance of the entire system.

Equations (1) and (2) are formulas for obtaining channel capacities of WLAN and WRAN users, respectively, and Equation (3) is a formula for obtaining thermal noise N. P _{t - AP (i)} and P _{t - BS (i)} are the transmit power intensities of the WLAN AP and the WRAN base station, respectively, and Γ (d) is the path loss to the corresponding client. I _{AP (i-)} in Equation (1 ₎ represents interference from other APs in the same cell, and I _{WRAN - BS} represents interference by heterogeneous and homogeneous devices received by WLAN users due to interference from WRAN base stations. I _{WLAN - APs} in Equation (2) is the amount of interference received by the WRAN CPE from the WLAN AP, which is a heterogeneous device in the cell, and the interference between WRAN-like devices is negligible because the inter-cell interference in the OFDMA cell is zero.

In the present invention, two mutually coexistent scenarios of heterogeneous systems or homogeneous systems are defined. First, the scenario of individually using a channel (Individaul Channel Use) refers to a scenario in which different channels are allocated to each system, and a shared channel Use scenario refers to a scenario in which the same frequency band is shared by a homogeneous system or a heterogeneous system when the available frequency band is insufficient or limited.

The performance of the WLAN AP and the WRAN CPE can be evaluated using the above Equation 1 and Equation 2. The WLAN channel allocation fitness evaluation function can be evaluated as fit _individual and fit _shared according to the individual channel use or shared channel use scenario, 4 and Equation (5).

In the case of the individual channel usage scenario, the WLAN AP does not consider the interference _{WRAN - BS} from the WRAN since the WRAN base station does not use the channel being used. K represents the total number of CPEs in the WRAN cell and M represents the total number of APs.

As shown in the above two mathematical expressions, the system performance average of each AP and the CPEs can be calculated to calculate the chromosome fitness of the genetic algorithm, thereby improving the overall system performance. After the fitness assessment process, two chromosomes with superior traits are subjected to a mating process, and thereafter, the mutation process increases the probability of obtaining a better solution.

7 is a flowchart showing a frequency sharing method proposed by the present invention. A method of minimizing inter-system interference between a WLAN and a WLAN, comprising: obtaining (710) information of a WLAN and a WLAN; Allocating (720) an optimal frequency sub-band based on information collected from the information obtaining unit; And broadcasting an optimal frequency sub-band to each corresponding system in step 730. Each step of the frequency sharing method according to the embodiment may be performed by the frequency sharing system 100 described with reference to FIG. .

A method and system for selecting WRAN and WLAN channels using complementary spectral etiquette and genetic algorithm in the TV white space frequency band have been proposed. Based on the system described above, a simulation model is set up to demonstrate the performance of the invention. In the embodiment of the present invention, the graphs of FIGS. 8 to 15 show the performance of the system through simulation.

FIGS. 8 to 10 illustrate the SINR performance, WLAN throughput performance, and outage probability of each WLAN in the individual channel usage scenario, respectively. The WLAN random channel selection method, the self-coexistence method, and the channel selection method of the WLAN using the genetic algorithm And WLAN selection method applying the supplementary WLAN spectrum etiquette and genetic algorithm proposed in the present invention.

Referring to FIG. 8, it can be seen that the SINR performance is superior to the self-coexistence method and the genetic algorithm using the random selection method. However, the WLAN channel selection method using only the genetic algorithm rather than the WLAN selection method proposed in the invention SINR performance is shown to be slightly better. This is because the interference due to the WRAN spectrum etiquette process is increased due to the increase of the interference between the same type of system. The method according to the present invention can provide a wide bandwidth to the WLAN user. .

The outage probabilities of the individual channel usage scenarios are shown in FIG. 10, which also shows that the method of using the genetic algorithm is less than the random selection method or the self-coexistence method.

In the shared channel usage scenario, the performance of the frequency sharing system can be evaluated through the graphs of FIGS. 11 to 15, in which the same simulation as the individual channel usage scenario is applied.

Referring to FIGS. 11 and 12, the shared channel usage scenario is also superior to the random channel selection method or the self-coexistence method, such as the individual channel usage scenario, in the SINR and throughput performance of the WLAN according to the genetic algorithm or the method proposed by the present invention However, it can be seen from FIG. 13 that the performance of the WLAN is improved by applying the WRAN spectrum etiquette proposed in the invention, but the improvement of the SINR performance of the WRAN can be confirmed.

14 and 15 are graphs showing outage probabilities of WLAN APs and WRAN CPEs according to the number of users in a shared channel usage scenario. As can be seen from the two graphs, it can be seen that interference can be effectively reduced regardless of the number of users when the technique proposed by the present invention is used.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, 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.

100: Frequency Sharing System
110: Information obtaining unit
120: Optimum resource allocation unit
121: first channel selector
122: second channel selector
130: Broadcasting section

Claims (7)

In a frequency sharing system,
An information obtaining unit for obtaining information of the WLAN and the WLAN;
An optimal resource allocation unit for allocating an optimal frequency sub-band based on the information collected from the information obtaining unit; And
A broadcasting section for broadcasting the optimal frequency sub-band to each corresponding system,
The frequency sharing system. The method according to claim 1,
The frequency sharing system is based on TVWS (TV White Space), and the TVWS refers to a frequency channel space that can be utilized as an idle frequency resource in a TV broadcast frequency band without any separate permission
The frequency sharing system comprising: The method according to claim 1,
The information obtained by the information acquiring unit
A channel allocation state, an installation location, an access mode, and the number of access points (APs)
The information may be obtained over a WLAN, WRAN, or RF channel
The frequency sharing system comprising: The method according to claim 1,
The optimal resource allocation unit
A first channel selection unit for selecting a channel using an isolated channel set (ICS);
A second channel selection unit for selecting a WLAN channel using a genetic algorithm,
The frequency sharing system comprising: 5. The method of claim 4,
Wherein the first channel selector comprises:
Using WRAN spectrum etiquette,
The set of isolated channels is defined as a set of consecutive channels that do not occupy a license user or an adjacent WRAN cell,
Selecting a channel having the smallest number of channels among the consecutive channel sets
The frequency sharing system comprising: 5. The method of claim 4,
Wherein the second channel selection unit defines a chromosome and a gene, and a fitness evaluation function,
Applying the defined fitness evaluation function to each AP to select a trait with superior performance
The frequency sharing system comprising: In a frequency sharing method,
Obtaining information of the WLAN and the WLAN;
Allocating an optimal frequency sub-band based on information collected from the step of acquiring information of the WRAN and the WLAN; And
Broadcasting the optimal frequency sub-band to each corresponding system
/ RTI >

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