KR101415670B1 - System and method for assigning beam/polarized wave resource by use of polarized wave characteristics - Google Patents

Abstract

In the present invention, in a method of allocating a beam / polarization resource using a polarization characteristic in a wireless backhaul network that requires a high-capacity transmission technique, when a plurality of small base stations to be connected to a base station are densely present, When the service is performed, resources such as transmission power and polarization are allocated in consideration of polarization, so that an optimal capacity increase can be obtained. Also, through the resource allocation scheme considering the polarization-based characteristics of the beam-based system proposed in the present invention, it is possible to realize a communication service having a communication capacity greatly increased compared to the existing communication capacity.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a system and method for allocating beam /

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a beam-based wireless communication system, and more particularly, to a wireless backhaul network that requires a high-capacity transmission technology, when a large number of small- In this paper, we propose a polarization-based wireless communication system that can achieve optimal capacity by allocating resources such as transmission power and polarization in consideration of a polarized wave when performing a service to a small base station by forming a beam And more particularly, to a system and method for allocating used beam / polarization resources.

In general, a beam division multiple access (BDMA) transmission technique, also referred to as a smart antenna technique, has been proposed in order to adapt to high data rate and network changes. An adaptive It is a multiple access scheme using beamforming technology.

By using the BDMA transmission technique, service coverage can be increased, the state of a link can be improved in response to multipath fading, and frequency efficiency can be increased. In particular, the beamforming technique can increase the power of the received signal significantly while using low transmission power by forming a directional beam toward a desired user.

Also, by forming multiple directional beams using multiple antennas in a base station (BS), different data can be simultaneously transmitted to users at different locations.

Currently, research on BDMA backhaul network and BS-MS (mobile station) communication is underway in the cellular system, and it is considered to use not only the existing mobile communication frequency band but also the high frequency band.

FIG. 1 is an example of adaptive sectorization, which is a cellular communication system based on BDMA transmission technology. Adaptive sectoring and beam design are studied for design and performance analysis of the present system. A base station of a cellular communication system based on a BDMA transmission technology can form a plurality of beams toward a location of each user in a downlink and can maximize frequency efficiency by using several beams at the same frequency at the same time.

However, in the cellular system, it is difficult to use the BDMA transmission technique in the UE due to the constraints of the size and number of antennas and the maximum transmission power of the UE. In the cellular system, since it is difficult for the base station to grasp the exact position of the terminal in real time, the base station experiences difficulty in forming an accurate beam toward the terminal.

On the other hand, in the case of the wireless backhaul network, since the position of the small base station is static and is a stable system, the base station can accurately grasp the position of the small base station and form an accurate beam to the small base station. In addition, since there is no restriction on the size and number of antennas of a small base station and the maximum transmission power is much larger than that of a cellular system, it is possible to use the BDMA transmission technology in both the infrastructure and the small base station. Therefore, in the wireless backhaul network, the beam strength can be greatly increased by forming a beam according to the position of the small base station.

Multi-antenna connection technology (MIMO) is a technology that has made considerable progress in wireless communication. By using the degradation of the fading due to the reflected wave in the existing system to obtain multipath gain using fading And contributed to the performance improvement of wireless communication. Also, the acquisition of channel information using a pilot signal has been applied to transmission techniques such as eigenmode power transmission and waterfilling multiplexing, thereby improving communication capacity.

However, despite the advantages of this multi-antenna technique, implementation is difficult. Conventional multi-antenna studies are performed on single-polarized antennas. To achieve this, a gap of more than λ / 2 (half wavelength) is required between the antennas. This is not easy to achieve when considering the fact that the size of a small base station or a mobile node is getting smaller as the size of the air is about 7.5 cm when a general cellular frequency of 2 GHz is targeted. Accordingly, a multi-antenna technique with dual polarization or higher polarization has been devised. This technique realizes polarization by designing the radiation of signals from multiple antennas to be orthogonal, so that polarization diversity corresponding to the position diversity of the conventional multiple antennas can be obtained.

FIG. 2 illustrates an example of the above-described polarization multiplexing antenna.

However, when the transmission is performed using the polarization as in FIG. 2, the signal undergoes several reflections and scattering phenomenon, and thus the orthogonality of the polarization is impaired, thereby affecting each other's channel. In this case, in the 2 ㅧ 2 multi-antenna system using horizontal and vertical polarizations, the energy flowing into the other polarized wave is measured directly, and the ratio of the energy in the desired polarization direction to the energy flowing in the other polarization direction (XPD: cross -polar dicrimination) can be obtained experimentally.

[Table 1] shows the results of XPD in the case of LOS (line of sight) (when there is no obstacle between transmitting and receiving terminals) and NLOS (when obstacle exists between transmitting and receiving terminals).

Vertical polarization Horizontal polarization LOS 16.96 dB 14.50 dB NLOS 8. 58 dB 8. 29 dB

As can be seen in [Table 1], the depolarization phenomenon occurs differently depending on the polarization direction and the situation where the transmission / reception terminal is located. It should be designed to maximize the gain of polarization by taking into account the nature of such polarization. In the case of the wireless backhaul network considered in the present invention, considering the LOS situation, such a polarization decay phenomenon is not expected to appear largely. However, designing the system considering the interference between the polarizations is not limited to the capacity of the radio communication system using polarization It is an essential element to maximize.

As described above, researches on how to allocate beams to a user in a smart antenna system using beams have been mainly studied. The dynamic time allocation technique maximizes the system capacity by allocating the beams based on time. In order to maximize the system capacity, the arbitrary beam selection technique divides the total time into two sections, collects user information in the beam forming section, We have studied how to transmit data at transmission time after forming a forming vector.

However, such a beam resource allocation technique has a great difficulty in obtaining effective benefits due to users who do not receive services, such as adjusting the power or using a switching system. Also, in a situation where beam resources are limited, when a space between the beams is narrow and there are many users or small base stations, a signal of the side lobe of the beam acts as an interference, and the capacity of the network is rapidly reduced .

In this case, since the degree of freedom is improved by using the polarization, the interference problem can be effectively reduced. This is because several polarization gains can be obtained in one beam. However, in such a situation, there is no research on a method of assigning a beam and a polarization to a user in consideration of all the properties of beam-to-beam interference, polarization-to-interference, and polarization-attenuation.

Korean Patent No. 10-0713155, filed on Apr. 24, 2007, discloses a technique relating to a radar system having a single circularly polarized antenna.

Therefore, in a wireless backhaul network requiring a high-capacity transmission technique, when a large number of small base stations attempting to access a base station are present in a dense state, a beam is formed and a transmission power and a polarization And a method of allocating a beam / polarization resource using polarization characteristics that can obtain an optimal capacity increase by allocating resources such as a beam / polarization resource.

A beam / polarization resource allocation system in a wireless backhaul network environment, the system comprising: a beam / polarization resource allocation system in a wireless backhaul network environment that calculates a beamforming vector for each small base station, A base station for transmitting the plurality of beams to each of the small base stations using a polarization assigned to each of the small base stations after the plurality of beams are received from the base station, And the small base station extracts and receives the beam allocated to itself.

In addition, the base station allocates transmission power calculated corresponding to each of the small base stations to form the polarized wave.

In addition, the transmission power allocated to each small base station by the base station is set to be larger than 0 and smaller than the maximum transmission power of the base station.

The sum of the transmission power allocated to each small base station by the base station is set to be smaller than the maximum transmission power of the base station.

The base station is characterized in that the plurality of beams are formed in a number corresponding to the number of the small base stations.

Also, each of the beams within the plurality of beams has the same width and size.

In addition, the channel environment between the base station and the small base station is a line-of-sight (LOS) environment.

The base station may transmit the plurality of beams to each of the small base stations using a plurality of polarized antennas.

In addition, the small base station extracts a beam having a polarization assigned to itself from the plurality of beams using a polarized antenna.

According to another aspect of the present invention, there is provided a method of allocating a beam / polarization resource in a wireless backhaul network environment, the method comprising: calculating a beamforming vector for each small base station in a base station to form a plurality of beams corresponding to each small base station; Allocating a polarization corresponding to each small base station at a base station; transmitting the plurality of beams to each small base station using a polarization assigned to each small base station; Receiving a plurality of beams from the base station; and extracting and receiving a beam allocated to the small base station by using the polarization allocated to the base station.

In addition, the base station allocates transmission power calculated corresponding to each of the small base stations to form the polarized wave.

In addition, the transmission power allocated to each small base station by the base station is set to be larger than 0 and smaller than the maximum transmission power of the base station.

The sum of the transmission power allocated to each small base station by the base station is set to be smaller than the maximum transmission power of the base station.

The base station is characterized in that the plurality of beams are formed in a number corresponding to the number of the small base stations.

Also, each of the beams within the plurality of beams has the same width and size.

In addition, the channel environment between the base station and the small base station is an LOS environment.

The base station may transmit the plurality of beams to each of the small base stations using a plurality of polarized antennas.

In addition, the small base station extracts a beam having a polarization assigned to itself from the plurality of beams using a polarized antenna.

In the present invention, in a method of allocating a beam / polarization resource using a polarization characteristic in a wireless backhaul network requiring a high-capacity transmission technique, when a large number of small base stations to be connected to a base station exist in a concentrated manner, It is advantageous to allocate resources such as transmission power and polarization in consideration of polarization in performing a service, thereby obtaining an optimal capacity increase.

In addition, through the resource allocation scheme considering the polarization-based characteristics of the beam-based system proposed in the present invention, there is an advantage that a communication service having a communication capacity greatly increased compared to the existing communication capacity can be realized.

1 is a diagram illustrating a communication system using a conventional BDMA transmission technology,
FIG. 2 is a diagram illustrating an example of multiple antennas using conventional polarization,
3 is a conceptual diagram of an interference due to a side lobe of a beam in a wireless backhaul network,
4 is a conceptual diagram of beam allocation using polarization in a wireless backhaul network according to an embodiment of the present invention,
5 is a graph illustrating a transmission failure probability graph according to the number of small base stations according to an embodiment of the present invention;

Hereinafter, the operation principle of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions of the present invention, and may be changed according to the intentions or customs of the user, the operator, and the like. Therefore, the definition should be based on the contents throughout this specification.

Conventional cellular communication systems provide services to users based on omnidirectional antennas, thereby effectively responding to mobility and providing services such as simple Internet search and applications. However, users are confused because of the mixed system of WLAN, femtocell, and so on to provide a large amount of wireless resources to the hot-spot area in addition to the cellular system. Therefore, it is necessary to provide a new integrated network in which various networks are organized organically in order to provide a desired service capacity through cooperation of small-sized base stations, while taking advantage of the characteristics of each network. However, in such a situation, it is necessary to construct a backhaul wirelessly from the viewpoint of economy because there is a limitation in connecting all small cells such as WLAN and femtocell to optical fiber.

In a base station having a relatively large capacity in such a wireless backhaul network, a high-capacity network can be implemented by effectively allocating pattern / polarization resources to a small base station existing at a lower level of a wireless backhaul network using a beam-based pattern / polarization technique. In the situation where a large traffic service such as a 3D augmented reality and a real-time multimedia stream service is required, the capacity of the existing mobile communication system will be greatly improved and a high-quality service can be provided

The network proposed in the present invention comprises a base station, a small base station, and a user terminal. A base station is a multi-antenna node that is connected by wire and manages radio resources among a plurality of small base stations. A small base station is an intermediate node of an intermediate layer that provides an access network to a plurality of terminals. And then communicates with other networks. In this situation, a wireless backhaul network is formed between the base station and the small base station. The wireless backhaul network maximizes the capacity by applying the aforementioned beam-based pattern / polarization technique. Particularly, the polarization technique is a technique that enables transmission and reception independently of each other using a plurality of polarized antennas in one beam. Therefore, even if they are in the same frequency and in the same beam, the use of polarization technology allows multiple users to use it at the same time.

The problem of forming and assigning beams in wireless networks using beams rather than omnidirectional antennas is becoming the biggest issue. The present invention proposes polarization and beam allocation schemes in a beam-based wireless backhaul system considering polarization. At this time, in the present invention, a beam switching system having relatively low complexity can be considered as a method of forming an existing beam. It is judged that the beam forming algorithm is suitable for a relatively static wireless backhaul system in that the time to calculate such a beam allocation is relatively small and uses a predetermined beam.

Also, in the present invention, when serving a beam, it is designed to minimize interference within one beam by serving one of the same beams using a polarization, and it is designed not only to satisfy a threshold value but also to satisfy a systematic transmission failure probability And its performance is verified.

In the present invention, a fixed beam-based beam switching system as shown in Fig. 3 is considered. In the fixed linear antenna array system of the base station 100, a fixed number of beams 101 are formed, and each beam is tailored to the small base station 102 to provide service. At this time, it can be assumed that the channel environment of the base station 100 and the small base station 102 is assumed to be a line of sight (LOS) environment, and that the small base station 102 has no mobility.

It is also assumed that each beam has the same width and size, and that the small base station 102 is arbitrarily formed. At this time, since the position of the small base station 102 is not changed once the position of the small base station 102 is formed, a beam forming vector suitable for each small base station 102 can be formed.

However, the serious problem that arises here is the interference between the formed beams. The side lobe of the beam causes severe interference in the adjacent beam to perform the service. For this purpose, there has been an attempt to solve the above-mentioned interference by dividing through beam scheduling. However, even if interference is considered in such a case, when there are a plurality of small base stations in one beam, the beam serving itself may be out of the priority of scheduling.

4 illustrates a concept of beam allocation using polarization in a wireless backhaul network according to an embodiment of the present invention.

That is, in the case where there is interference due to each beam, the method of efficiently providing the beam resources to the small base station 102 in the base station 100 may be most effective in the method using the polarization as shown in FIG. 4 have.

That is, when the polarized antenna 104 is used, signals of other polarized waves are not regarded as interference, so that the signal and interference-to-noise ratio (SINR) performance is greatly improved and eventually the system capacity is increased .

In the present invention, when an arbitrary small base station 102 sees a beam selected by itself as its own signal and a beam serving as another small base station as an interference signal, the transmission failure probability We propose an algorithm that minimizes the value obtained by mathematical methods. At this time, polarization using an electromagnetic field provides a new dimension, enabling the beam to be used without the aid of scheduling.

For example, suppose there are two adjacent small base stations 102 in a beam. If you do not use the existing polarization, you have to split the time and transmit to the two nodes, but with polarization you can service each one at the same time. At this time, it is necessary to consider the polarization attenuation existing between the respective polarized waves and to effectively represent the interference between the beams to realize the allocation of the optimum beam / polarization resources.

In the wireless backhaul network system environment based on the BDMA transmission technology proposed in the present invention, a total of n small base stations 102 exist in the service coverage of the base station 100, and a set of small base stations is N = {1, ..., n }.

으로 정의될 수 있다. 따라서 무선 백홀네트워크에서 자원할당은 기지국(100)이 소형 기지국i에 전송 파워(transmission power)(

)를 할당하여 빔j의 편파k(

)을 형성하는 것이다. In such a case, the resource allocation can be made as follows. The infrastructure may provide a total of m beams and p polarizations, so that the set of beam resources of the base station 100

. ≪ / RTI > Therefore, the resource allocation in the wireless backhaul network is performed such that the base station 100 transmits transmission power (i. E.

) To assign the polarization k (

).

)는 아래의 [수학식1]과, [수학식 2]에서와 같으며, 두 개의 파워 제약(power constraint)를 만족해야한다. At the time of resource allocation, the transmission power allocated by the infrastructure to the small base station i (

Is the same as in Equations (1) and (2) below, and must satisfy two power constraints.

)가 0 보다는 크고 기지국(100)의 최대전송 파워

보다는 작아야 한다는 것이다. 두 번째 power constraint는 기지국(100)이 소형 기지국(102)에 할당한 전송파워의 합은 기지국(100)의 최대전송 파워

보다는 작아야 한다는 것이다. The first power constraint is a power constraint that the base station 100 assigns to each small base station 102 the transmit power

) Is greater than 0 and the maximum transmission power of the base station 100

. The second power constraint is that the sum of the transmission power allocated to the small base station 102 by the base station 100 is the maximum transmission power of the base station 100

.

가 결정되면 간섭 채널의 이득을 구할 수 있다. 따라서 임의의 빔과편파에 파워가 할당 되었을때 그 사이의 각도를 이용하여 자신의 파워와 다른 소형 기지국에 할당된 파워를 계산하여, 채널용량을 구하게 되고 그러한 채널용량을 최대화하는 빔과편파를 할당하게 된다.In the proposed method of the present invention, the channel between the base station 100 and the small base station 102 considers the path loss model and the antenna model. Thus, the angle between the beam assigned to the target small base station 102 and any small base station i

The gain of the interference channel can be obtained. Therefore, when power is allocated to arbitrary beams and polarizations, the power allocated to the small base station is calculated by using the angle between the power and the power, and the channel capacity is obtained. The beam and polarization are allocated to maximize the channel capacity .

Meanwhile, the antenna model in the BDMA transmission technique can be expressed by the following Equation (3).

는 대상빔의 방향과 다른빔 방향의 각도,

는 신호가 3dB 감쇠되는beam-width,

은 최대 감쇠값, 그리고

은 안테나 이득을 나타낸다. 따라서 안테나 모델의 이득은 빔방향과 다른 빔방향사이의 각도인

에 따라 결정되며 이때 편파와 편파 사이의 간섭은 실험적으로 구해진 XPD 값을 사용하여 모델링한다.At this time,

Is the angle of the beam direction with respect to the direction of the object beam,

Is the beam-width at which the signal is attenuated by 3 dB,

Is the maximum attenuation value, and

Represents the antenna gain. Thus the gain of the antenna model is the angle between the beam direction and the other beam direction

Where the interference between polarization and polarization is modeled using the experimentally obtained XPD value.

FIG. 5 shows a simulation result of the proposed scheme according to the dimension expansion of polarization.

5 shows the transmission failure probability according to an increase in the number of small base stations randomly generated in a 120-sector sector. When there are six fixed beams, each 3dB angle is 17.5 degrees, and the beamforming algorithm used in the 3GPP standard is used.

In order to maximize the gain of the polarization, it is assumed that the polarization can be transmitted in a non-overlapping manner when polarization is supported in the beam. In the case of an antenna having two non-overlapping polarizations, The triple-polarized antenna is indicated.

As can be seen from the results of FIG. 5, in the beamforming-based algorithm which does not consider the existing polarization, the probability of transmission failure increases drastically as the number of small base stations increases. However, by using the polarized antenna, it can be seen that the increase of the transmission failure probability due to the increase of the users can be greatly alleviated. It can be seen that the probability of transmission failure in a dense environment is more effectively decreased with an antenna having a high dimensionality (an antenna having a high polarization factor).

In the present invention, a beam selection algorithm is proposed in a next generation wireless backhaul system including a base station and a small base station. In the situation where small base stations are integrated and the beam has to be integrated, the interference between the beams brings the interference of the system capacity. However, in the proposed method of the present invention, an electromagnetic field polarized wave system is designed to provide an efficient service even in a high density of small base stations. Considering the characteristics of a wireless backhaul network in which a base station transmits a small-sized base station using a very high frequency, a small-sized base station is required to maintain a stable connection so that a high-capacity service corresponding to the role of a backhaul network can be guaranteed. Further, in order to realize realistic beam allocation, a beam switching system is considered so that the already calculated beam forming vectors can be used.

When a polarization system is applied, an option with a higher degree of freedom is given to the resource that can be allocated. Simulation results show that a system that selects a nearest beam and provides a beam considering the polarization in a situation where a small base station is scattered in a beam switching system at an arbitrary probability shows an efficiency increase of about 60% or more as compared with a conventional single polarization system Respectively.

As described above, according to the present invention, in a method of allocating a beam / polarization resource using a polarization characteristic in a wireless backhaul network requiring a high-capacity transmission technique, when a large number of small base stations to be connected to a base station exist in a concentrated manner, Therefore, considering the polarization, it is possible to allocate resources such as transmission power and polarization to achieve optimal capacity increase. Also, through the resource allocation scheme considering the polarization-based characteristics of the beam-based system proposed in the present invention, it is possible to realize a communication service having a communication capacity greatly increased compared to the existing communication capacity.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should not be limited by the described embodiments but should be defined by the appended claims.

100: base station 102: small base station
104: polarized antenna

Claims (18)

A beam / polarization resource allocation system in a wireless backhaul network environment,
A beamforming vector corresponding to each small base station is calculated to form a plurality of beams corresponding to the respective small base stations and then the plurality of beams are transmitted to each small base station using the polarization allocated to each small base station A base station,
And a small base station for extracting and receiving a beam allocated to itself by using a polarization assigned to itself when a plurality of beams are received from the base station,
The base station comprises:
Wherein the base station allocates transmission power calculated corresponding to each of the small base stations to form the polarized wave and transmits the plurality of beams to each small base station using a plurality of polarized antennas. Beam / polarization resource allocation system.
delete The method according to claim 1,
Wherein the transmission power allocated by the base station to each of the small base stations is set to be larger than 0 and smaller than a maximum transmission power of the base station.
The method of claim 3,
The sum of the transmission powers allocated to the respective small base stations by the base station,
And is set to be smaller than a maximum transmission power of the base station.
The method according to claim 1,
The base station comprises:
And the plurality of beams are formed in a number corresponding to the number of the small base stations.
The method according to claim 1,
Each beam in the plurality of beams comprising:
Wherein the bandwidth and the size of the beam / polarization resource allocation in the wireless backhaul network environment are the same.
The method according to claim 1,
The channel environment between the base station and the small-
LOS (line of sight) environment in a wireless backhaul network environment.
delete The method according to claim 1,
The small-
And extracting a beam having a polarization assigned to itself from the plurality of beams using a polarized antenna.
A method of allocating beam / polarization resources in a wireless backhaul network environment,
Calculating a beamforming vector for each small base station in a base station to form a plurality of beams corresponding to the respective small base stations,
Allocating a polarization corresponding to each of the small base stations at the base station;
Transmitting the plurality of beams to each small base station using a polarization assigned to each small base station;
Receiving a plurality of beams from the base station at each of the small base stations;
And extracting and receiving a beam allocated to the small base station by using the polarization allocated to the small base station,
The base station comprises:
Wherein the mobile station allocates transmission power calculated corresponding to each of the small base stations to form the polarized wave and transmits the plurality of beams to each of the small base stations using a plurality of polarized antennas. Beam / polarization resource allocation method.
delete 11. The method of claim 10,
Wherein the transmission power allocated by the base station to each of the small base stations is set to be larger than 0 and smaller than a maximum transmission power of the base station.
13. The method of claim 12,
The sum of the transmission powers allocated to the respective small base stations by the base station,
Wherein the transmission power is set to be smaller than a maximum transmission power of the base station.
11. The method of claim 10,
The base station comprises:
And forming the plurality of beams in a number corresponding to the number of the small base stations.
11. The method of claim 10,
Each beam in the plurality of beams comprising:
Wherein the bandwidth and the size are the same.
11. The method of claim 10,
The channel environment between the base station and the small-
LOS environment in a wireless backhaul network environment.
delete 11. The method of claim 10,
The small-
And extracting a beam having a polarization assigned to itself from the plurality of beams using a polarized antenna.

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