KR101202662B1 - Apparatus and method for selecting transmit path in a relay network - Google Patents

Abstract

The present invention relates to an apparatus and method for selecting a transmission path in consideration of interference in a relay network.
To this end, the indirect transmission path qualities corresponding to the plurality of indirect transmission paths indirectly connecting the destination node via the plurality of relay nodes and the direct transmission path quality corresponding to the direct transmission path directly connecting the destination node are measured. . And selecting the best indirect transmission path quality among the measured indirect transmission path qualities, and comparing the selected indirect transmission path quality with the measured direct transmission path quality to obtain the best indirect transmission path or the direct transmission path and the best. An indirect transmission path having an indirect transmission path quality is selected as a transmission path for transmitting data to the destination node.

Description

Transmission path selector and method in relay network {APPARATUS AND METHOD FOR SELECTING TRANSMIT PATH IN A RELAY NETWORK}

The present invention relates to an apparatus and a method for selecting a transmission path in a relay network, and more particularly, to an apparatus and a method for selecting a transmission path in consideration of interference in a relay network.

In general, in a communication system in which a base station and a terminal directly communicate with each other, it is difficult to provide a smooth communication service when the terminal is located in an area where signal quality is poor, such as a cell outer region or a shadow region.

In order to solve this problem, a relay network technology has been proposed, and the relay network can increase coverage and system capacity at a relatively low cost. In particular, by placing relays in sub-cell or shadowed areas with poor signal quality, system performance can be improved at a relatively low cost.

The relay network refers to a network that relays a signal between a source node and a destination node by using a relay node. Therefore, the signal transmitted by the source node may be transmitted not only directly to the destination node but also through the relay node to the destination node.

On the other hand, when the relay network has a multi-cell environment, signals propagated in adjacent cells serve as interference in a specific cell. In particular, relay nodes existing in one cell may have different magnitudes of interference due to adjacent cells as their positions are different from each other.

Therefore, when the source node selects a transmission path for transmitting data to the target node, a method for selecting a transmission path needs to be prepared in consideration of interference characteristics expected for each transmission path. In addition, in order to improve communication quality in a wireless environment where channel characteristics are severely changed, it is urgent to prepare a method for quickly or quickly allocating or changing an optimal communication path according to the change of channel environment.

An embodiment of the present invention proposes an apparatus and method for selecting a transmission path to transmit data in consideration of performance degradation due to interference in a relay network.

In addition, an embodiment of the present invention proposes an approximate analysis method of a channel in which an interference signal exists for easy performance analysis for a relay network in which an interference signal exists.

In addition, an embodiment of the present invention proposes an apparatus and method for analyzing a relay network through an approximation of a probability density function (PDF) of a transmission path in which performance degradation due to an interference signal occurs in the relay network.

Meanwhile, various other objects will be directly or implicitly disclosed in the detailed description of the preferred embodiment of the present invention.

An apparatus for selecting a data transmission path in a source node constituting a relay network according to an embodiment of the present invention includes an indirect transmission path corresponding to a plurality of indirect transmission paths that indirectly connect a target node via a plurality of relay nodes. A transmission path quality measuring unit measuring a direct transmission path quality corresponding to a direct transmission path directly connecting the qualities with the destination node, and an indirect transmission best among indirect transmission path qualities measured by the transmission path quality measuring unit; Select a path quality, compare the selected indirect transmission path quality with the measured direct transmission path quality, and indirect transmission having the best indirect transmission path quality with the direct transmission path or the direct transmission path according to the comparison result A transmission path selector for selecting a path, and the transmission path selector Through the selected transmission path comprises transmission unit configured to transmit data to the destination node.

In the method for selecting a data transmission path in a source node constituting a relay network according to an embodiment of the present invention, the indirect transmission path quality corresponding to a plurality of indirect transmission paths indirectly connecting a target node via a plurality of relay nodes. Transmission path quality measurement process for measuring a direct transmission path quality corresponding to a direct transmission path directly connecting the target node and the target node, and an indirect transmission path for selecting the best indirect transmission path quality among the measured indirect transmission path qualities. A quality selection process and comparing the selected indirect transmission path quality with the measured direct transmission path quality, and indirect transmission path having the best indirect transmission path quality with the direct transmission path or the direct transmission path according to the comparison result. Is selected as a transmission path for transmitting data to the destination node The transmission path selection process is included.

In this case, preferably, each of the plurality of indirect transmission paths includes a first path connecting between the source node and the relay node and a second path connecting between the relay node and the destination node, and the first path in each of the plurality of indirect transmission paths. The signal-to-interference signal and the noise ratio at and the signal-to-noise ratio at the second path are measured as indirect transmission path quality.

Preferably, the indirect transmission path quality may be selected by selecting a smaller value of the signal-to-interference signal and noise ratio in the first path and the signal-to-noise ratio in the second path measured in each of the plurality of indirect transmission paths. The best indirect transmission path quality among the selected indirect transmission path quality is selected for each transmission path.

In the embodiment of the present invention, by selecting the data transmission path in consideration of performance degradation due to interference in the relay network, it is possible to ensure stable performance of the relay network. In addition, by proposing an approximation method of a relay network in which an interference signal exists, the performance of the relay network can be analyzed by a method similar to a situation in which there is no interference signal even when a plurality of interference signals exist.

Meanwhile, various other effects will be disclosed directly or implicitly in the detailed description of the preferred embodiment of the present invention.

1 is a diagram illustrating an example of a relay network requiring implementation of a transmission path selection scheme according to an embodiment of the present invention;
2 is a diagram illustrating an example of a specific operation for a source node to determine or select a transmission path in a relay network according to an embodiment of the present invention;
3 is a diagram illustrating a configuration of a data transmission path selection apparatus at a source node according to an embodiment of the present invention;
4 illustrates an example of a control flow to be performed to select a transmission path at a source node according to an embodiment of the present invention;
FIG. 5 is a diagram illustrating a performance comparison result between a conventional technique that always uses an indirect transmission path in a relay network and a technique proposed by the present invention that selectively uses an indirect transmission path. FIG.

In the following description of the present invention, a 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.

In the following embodiment of the present invention, a method of selecting a transmission path for transmitting data from a source node to a destination node in a relay network in consideration of interference signals generated in various paths will be described in detail.

In this case, for convenience of description, a transmission path for transmitting data is divided into a direct transmission path and an indirect transmission path. The direct transmission path refers to a path through which a source node directly transmits data to a target node without passing through a relay node. The indirect transmission path refers to a path through which a source node transmits data to a destination node through at least one relay node. The indirect transmission path includes at least one path connecting a source node and a relay node (hereinafter referred to as a 'source / relay path') and at least one path connecting a relay node and a destination node 220 (hereinafter referred to as' relay / 'Path of interest'.

In an embodiment of the present invention to be described below, as an example of an indirect transmission path, it is assumed that only a path through which a source node transmits data to a destination node through one relay. However, it will be apparent that one indirect transmission path may be configured by a plurality of relay nodes. In addition, it is obvious that a method of selecting a transmission path proposed in an embodiment of the present invention may be equally applied to an indirect transmission path composed of a plurality of relay nodes.

If only one indirect transmission path is configured by a plurality of relay nodes, there may be a difference in that the quality in the path connecting the relay node and another relay node should be further considered for the selection of the transmission path.

Meanwhile, in the embodiment of the present invention to be described below, the quality determined by the interference signal in the path connecting two nodes is defined as 'transmission path quality'. However, the transmission path quality represents a quality for supporting communication between nodes, and has a meaning of all channel quality, transmission quality, communication quality, channel environment, and wireless environment.

Signal-to-interference and noise ratio (SINR), signal-to-noise ratio (SNR), and the like may be used as values representing the transmission path quality.

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

1 illustrates an example of a relay network requiring the implementation of a transmission path selection scheme according to an embodiment of the present invention. 1 illustrates an example of a relay network in which an interference signal exists in a situation where a mobile terminal transmits data to a base station.

Therefore, it should be noted that the mobile terminal assumes the role of the source node and the base station plays the role of the destination node in FIG. 1. However, it is not necessary to limit the mobile terminal to the source node and the base station to the destination node.

Referring to FIG. 1, one or more relay nodes exist in a service area formed by at least one base station. In this case, the relay node may be implemented by a mobile relay as well as a fixed relay. The mobile relay may be a mobile terminal having a capability of relaying received data.

In addition, one or more mobile terminals exist in the service area. The mobile terminal transmits data to the base station via at least one of the indirect transmission path via at least one relay node and the direct transmission path without any relay node.

To this end, the mobile terminal determines or selects a transmission path for actually transmitting data in consideration of transmission path quality for all or most transmission paths capable of data transmission to the base station. The transmission path quality may be represented by SINR or SNR. That is, the mobile terminal determines or selects a transmission path in consideration of an interference signal resulting from data transmission of a mobile terminal located in an adjacent service area in order to determine or select a transmission path.

Meanwhile, the mobile terminal corresponding to the relay node or the source node includes most terminals having a communication function such as a mobile phone, a smart phone, a PDA, a note PA, and the like.

2 illustrates an example of a specific operation for a source node to determine or select a transmission path in a relay network according to an embodiment of the present invention. For example, FIG. 2 assumes a relay network in which one direct transmission path and three indirect transmission paths exist. However, in applying the embodiment of the present invention, the number of indirect transmission paths is not limited. That is, the embodiment of the present invention may be equally applied to a relay network in which two or more indirect transmission paths exist between one source node and a destination node.

In FIG. 2, it is assumed that a mobile terminal plays a role of a source node, and a base station determines or selects a transmission path corresponding to an uplink that plays a role of a target node. However, it is obvious that the embodiment of the present invention may be equally applicable to an environment in which a base station plays a role of a source node and a mobile terminal determines or selects a transmission path corresponding to a downlink that plays a role of a destination node. In order to generalize this, the following description with reference to FIG. 2 will be described using a source node and a destination node instead of a mobile station and a base station.

Referring to FIG. 2, a transmission path capable of transmitting data from the source node 210 to the destination node 220 includes first to third indirect transmission paths and one direct transmission path. The first indirect transmission path is a first source / relay path connecting the source node 210 and the first relay node 232 and a first connection node connecting the first relay node 232 and the destination node 220. It consists of 1 relay / destination path.

The second indirect transmission path may include a second source / relay path connecting the source node 210 and the second relay node 234, and a second connecting node connecting the second relay node 234 and the destination node 220. It consists of two relay / destination paths.

The third indirect transmission path may include a third source / relay path connecting the source node 210 and the third relay node 236, and a third connecting node connecting the third relay node 236 and the destination node 220. It consists of 3 relay / destination paths.

The source node 210 measures the indirect transmission path quality for each of the first to third indirect transmission paths and the direct transmission path quality for the direct transmission path to determine or select a transmission path. The indirect transmission path quality measured for each of the first to third indirect transmission paths is referred to as first to third indirect transmission path quality.

The first to third indirect transmission path quality may be defined by any one of the transmission path quality measured for the source / relay path and the transmission path quality measured for the relay / destination path in each indirect transmission path.

For example, the transmission path quality measured for the source / relay path may be SINR measured on a specific channel available for communication between the source node 210 and the relay nodes 232, 234, and 236. The transmission path quality measured for the relay / destination path may be an SNR measured on a specific channel available for communication between the relay nodes 232, 234, and 236 and the destination node 220. However, in applying the embodiment of the present invention, the transmission path quality is not limited to SINR or SNR. That is, in an embodiment of the present invention, the transmission path quality may be commonly applied as long as it is quality information that can identify good and bad transmission paths.

For example, the source node 210 determines the indirect transmission path quality that is relatively poor among the transmission path quality measured for the source / relay path and the transmission path quality measured for the relay / destination path corresponding to each indirect transmission path. You can decide or choose. However, a relatively good transmission path quality may be determined or selected as the path quality corresponding to the indirect transmission path.

In order to determine or select the indirect transmission path quality according to the above-described example, the source node 210 measures the transmission path quality in each of the source / relay path and the relay / destination path constituting the first to third indirect transmission paths. To be done. For example, the transmission path quality in the source / relay path may be measured by the relay nodes 232, 234, and 236 and reported to the source node 210, and the transmission path quality in the relay / destination path may be a destination node. Measured by 220 and reported to source node 210.

로 표시하였으며, 릴레이/목적 경로에서 측정된 전송 품질을

로 표시하였다. 여기서 간접 전송 경로를 식별하는 인덱스 i의 범위는

으로 정의하며, M은 소스 노드(210)와 목적 노드(220) 간에서 사용될 수 있는 간접 전송 경로의 총 수를 정의한다.Figure 2 shows the transmission quality measured in the source / relay path.

, The transmission quality measured in the relay / destination path

Marked as. Where the range of index i identifying the indirect transmission path is

M defines the total number of indirect transmission paths that can be used between the source node 210 and the destination node 220.

로 표시하고, 소스 노드(210)와 두 번째 릴레이 노드(234)를 연결하는 제2 소스/릴레이 경로에서의 전송 품질은

로 표시하며, 소스 노드(210)와 M 번째 릴레이 노드(236)를 연결하는 제3 소스/릴레이 경로에서의 전송 품질은

로 표시한다.Therefore, the transmission quality in the first source / relay path connecting the source node 210 and the first relay node 232 is

And the transmission quality in the second source / relay path connecting the source node 210 and the second relay node 234 is

The transmission quality in the third source / relay path connecting the source node 210 and the M th relay node 236 is

To be displayed.

로 표시하고, 두 번째 릴레이 노드(234)와 목적 노드(220)를 연결하는 제2 릴레이/목적 경로에서의 전송 품질은

로 표시하며, M 번째 릴레이 노드(236)와 목적 노드(220)를 연결하는 제3 릴레이/목적 경로에서의 전송 품질은

로 표시한다.In addition, the transmission quality in the first relay / destination path connecting the first relay node 232 and the destination node 220 is

, And the transmission quality in the second relay / destination path connecting the second relay node 234 and the destination node 220 is

The transmission quality in the third relay / destination path connecting the M th relay node 236 and the destination node 220 is

To be displayed.

과 제1 릴레이/목적 경로에서의 전송 품질

중 하나를 제1 간접 전송 경로 품질로 추정하고, 제2 소스/릴레이 경로에서의 전송 품질

과 제2 릴레이/목적 경로에서의 전송 품질

중 하나를 제2 간접 전송 경로 품질로 추정하며, 제M 소스/릴레이 경로에서의 전송 품질

과 제M 릴레이/목적 경로에서의 전송 품질

중 하나를 제M 간접 전송 경로 품질로 추정한다.Thus, the source node 210 can transmit the transmission quality in the first source / relay path.

And transmission quality in primary relay / destination path

Estimate one of the first indirect transmission path quality and the transmission quality in the second source / relay path

Quality of transmission in the control and secondary relay / destination paths

Estimates one of the second indirect transmission path quality and transmit quality in the M source / relay path

Transmission quality in the M relay / destination path

Estimate one of the M indirect transmission path quality.

과 릴레이/목적 경로에서의 전송 품질

중 상대적으로 좋지 않은 전송 품질을 간접 전송 경로 품질로 추정할 수 있다. 이와 같이 상대적으로 좋지 않은 전송 품질을 간접 전송 경로 품질로 추정하는 것은 열악한 구간에서의 전송 품질이 간접 전송 경로에 상응하는 전체 구간에서의 전송 품질을 결정하는 주요한 요소로 간주하는 것이 일반적이기 때문이다. 하지만 상대적으로 좋은 전송 품질을 간접 전송 경로에 상응하는 전체 구간에서의 전송 품질로 간주하는 것도 가능하다.As described above, the source node 210 has a transmission quality in the source / relay path.

Quality of transmission in the network and relay / destination paths

Relatively poor transmission quality can be estimated as indirect transmission path quality. The reason why the relatively poor transmission quality is estimated as the indirect transmission path quality is because it is generally considered that the transmission quality in the poor interval is the main factor for determining the transmission quality in the entire interval corresponding to the indirect transmission path. However, it is also possible to regard the relatively good transmission quality as the transmission quality in the entire section corresponding to the indirect transmission path.

When the source node 210 estimates the indirect transmission path quality for each indirect transmission path, the source node 210 selects the best indirect transmission path quality among the estimated indirect transmission path qualities. The indirect transmission path estimated from the selected indirect transmission path quality may be regarded as an indirect transmission path having the highest quality among indirect transmission paths connecting the source node 210 and the destination node 220.

The method of selecting an indirect transmission path proposed as an example in the above description may be generalized to Equation 1 below.

는 j번째 간접 전송 경로에서 추정된 경로 품질을 나타내고,

는 j번째 간접 전송 경로를 구성하는 소스/릴레이 경로에서 측정된 경로 품질을 나타내며,

는 j번째 간접 전송 경로를 구성하는 릴레이/목적 경로에서 측정된 경로 품질을 나타낸다.here

Denotes the estimated path quality in the jth indirect transmission path,

Represents the path quality measured in the source / relay path constituting the jth indirect transmission path,

Represents path quality measured in the relay / destination path constituting the jth indirect transmission path.

According to Equation 1, the source node 210 selects a path having a relatively poor transmission quality among the source / relay path and the relay / destination path corresponding to each of the M indirect transmission paths, and selects the M selected paths. Among the paths, one path having the best transmission quality is selected.

)을 비교한다. 그리고 상기 소스 노드(210)는 상기 비교 결과를 기반으로 데이터를 전송할 전송 경로를 최종적으로 결정하거나 선택한다.When the source node 210 selects one indirect transmission path among a plurality of indirect transmission paths, the indirect transmission path quality estimated in response to the selected indirect transmission path and the direct transmission path quality estimated for the direct transmission path (

). The source node 210 finally determines or selects a transmission path to transmit data based on the comparison result.

For example, if the selected indirect transmission path quality is better than the estimated direct transmission path quality, the source node 210 transmits data through both the selected indirect transmission path and the direct transmission path. However, if the estimated direct transmission quality is better than the selected indirect transmission quality, data is transmitted only through the direct transmission path. In other words, if the estimated direct transmission quality is better than the selected indirect transmission quality, the indirect transmission path is not used.

In this way, by selectively using the indirect transmission path, it is possible to limit the use of unnecessary resources can increase the capacity of the entire relay network.

FIG. 5 shows a performance comparison result between a conventional technique that always uses an indirect transmission path in a relay network and a technique proposed by the present invention that selectively uses an indirect transmission path.

According to the performance comparison results shown in FIG. 5, when the same SNR is satisfied under the same experimental conditions, a lower probability of reception (Outage Probability) can be obtained when applying the technique proposed by the present invention compared to the existing technique. can confirm.

Reference numeral 230 denotes a set of relay nodes 232, 234, 236 capable of relaying data transmitted from one source node 210 to the destination node 220 in the same service area.

Each of the relay nodes 232, 234, and 236 constituting the relay set 230 receives data transmitted from the source node 210, and transmits the received data to the destination node 220 by a predetermined relay technique. Relay). Relay techniques that can be applied for this include post-amplification transmission (AF) and post-decoding transmission (DF) techniques.

Meanwhile, each of the relay nodes 232, 234, and 236 measures a quality of a source / relay path connecting the source node 210 in consideration of external interference, and measures the measured source / relay path quality. Report to source node 210.

The destination node 220 receives data from the source node 210 via a direct transmission path or receives data from the source node 210 through at least one indirect transmission path as well as a direct transmission path.

Meanwhile, the target node 220 measures the quality of each relay / target path in consideration of external interference in each relay / target path connecting the relay nodes 232, 234, and 236, and measures the quality. The relay / destination path quality may be reported to the source node 210.

3 is a block diagram illustrating an apparatus for selecting a data transmission path in a source node according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the transmission path quality measuring unit 310 measures the indirect transmission path quality for each of the plurality of indirect transmission paths and the direct transmission path quality for the direct transmission path. Each of the plurality of indirect transmission paths refers to a path for indirectly connecting a destination node via different relay nodes, and the direct transmission path refers to a path for directly connecting the destination node.

In addition, as defined above, the indirect transmission path includes a source / relay path and a relay / destination path. The source / relay path is a path connecting the source node and the relay node, and the relay / destination node is a path connecting the relay node and the destination node.

Accordingly, the transmission path quality measuring unit 310 measures the source / relay path quality of the source / relay path constituting each indirect transmission path and the relay / destination path quality of the relay / destination path. In this case, the transmission path quality is measured in consideration of the interference and the like that exist independently in each path. The existence of interference independently in each path assumes a communication environment in which interference characteristics in each path are different from each other. However, the interference characteristics in some paths may be the same.

Representative examples of transmission path quality in consideration of the interference characteristics may be SINR, SNR, and the like. In this case, the source / relay path quality and the relay / destination path quality may use different types of values or values of the same type. For example, when different values are used, SINR may be used as the source / relay path quality and SNR may be used as the relay / destination path quality. In the case where values of the same format are used, SINR may be used as source / relay path quality and relay / destination path quality.

As an example of the actual measurement of the transmission path quality in each path, it may be made by the relay node or the destination node corresponding to the receiving side in the path. In this case, the measurement of the transmission path quality in the transmission path quality measuring unit 310 may be regarded as receiving the transmission path quality from the relay node or the destination node.

Meanwhile, the indirect transmission path qualities and the direct transmission path qualities may be measured using an approximation of a probability density function corresponding to a path where performance degradation occurs due to an interference signal. Specific solutions to this will be described later.

The transmission path quality measuring unit 310 measures the source / relay path quality and relay / destination path quality measured for each source / relay path and relay / destination path constituting each indirect transmission path, and the direct measurement of the direct transmission path. The transmission path quality is provided to the transmission path selector 312.

The transmission path selecting unit 312 selects a transmission path to transmit data based on the transmission path quality reported by the transmission path quality measuring unit 310. For example, the transmission path selector 312 selects a relatively poor transmission quality among source / relay path quality and relay / destination path quality for each indirect transmission path. The best one of the selected transmission qualities is selected for each indirect transmission path. The selection of indirect transmission path quality according to the above example is well represented in Equation 1 defined above.

The transmission path selecting unit 312 compares the selected indirect transmission path quality with the direct transmission path quality reported by the transmission path quality measuring unit 310 and transmits data based on the comparison result. Determine or select In the above description, only the case where the direct transmission path quality is reported to the transmission path selection unit 312 by the transmission path quality measuring unit 310 is limited. However, it is obvious that the direct transmission path quality can be reported directly from an external node.

For example, if the selected indirect transmission path quality is higher than the direct transmission path quality, the transmission path selector 312 selects both the indirect transmission path and the direct transmission path corresponding to the selected indirect transmission path quality as the transmission path for transmitting data. . However, if the direct transmission path quality is better than the selected indirect transmission path quality, the direct transmission path is selected as the transmission path for transmitting data.

The transmission path selector 312 provides the transmission unit 316 with information about the transmission path finally selected for data transmission.

The transmitter 316 receives the data generated by the data generator 314 as an input, and transmits the received data through the transmission path selected by the transmission path selector 312. For example, when only the direct transmission path is selected by the transmission path selection unit 312, the transmission unit 316 transmits data to the destination node only through the selected direct transmission path. However, when the indirect transmission path and the direct transmission path are selected together by the transmission path selection unit 312, the transmission unit 316 transmits data to the destination node through the selected direct transmission path and the indirect transmission path.

4 shows an example of a control flow to be performed to select a transmission path at a source node according to an embodiment of the present invention.

Referring to FIG. 4, the source node measures transmission path quality in step 410. That is, the source node measures the indirect transmission path quality for each of the plurality of indirect transmission paths and the direct transmission path quality for the direct transmission path.

For example, as the indirect transmission path is composed of a source / relay path and a relay / destination path, the source / relay path quality for the source / relay path constituting each indirect transmission path and the relay / destination path quality for the relay / destination path. Measure

In the transmission path quality measured by the source node, it is preferable to consider an interference characteristic that exists independently for each transmission path. That is, it is preferable to measure the quality of each transmission path in consideration of a relay network environment having different interference characteristics in each path. As an example, the transmission path quality for each path may be measured using an approximation of a probability density function corresponding to a path where performance degradation occurs due to an interference signal. In this case, each path means a source / relay path, a relay / destination path, and a direct transmission path constituting the indirect transmission path.

A representative example of transmission path quality in consideration of the interference characteristics may be SINR, SNR, etc. In this case, the transmission path quality of each path may be a value having a different format or a value having the same format. SINR may be used as the source / relay path quality and SNR may be used as the relay / destination path quality.

The source node selects indirect transmission path quality in step 412. That is, the source node selects a relatively poor transmission quality among source / relay path quality and relay / destination path quality for each indirect transmission path as the final indirect transmission path quality. The best one of the selected transmission qualities is selected for each indirect transmission path. Equation 1 defined above illustrates an example of selecting an indirect transmission path quality.

When the source node selects one indirect transmission path quality, the source node compares the selected indirect transmission path quality with the measured direct transmission path quality in step 414. The source node determines or selects a transmission path for transmitting data based on the comparison result.

For example, if the selected indirect transmission path quality is better than the direct transmission path quality, the source node selects both the indirect transmission path and the direct transmission path corresponding to the selected indirect transmission path quality as a transmission path for transmitting data. However, if the direct transmission path quality is better than the selected indirect transmission path quality, the direct transmission path is selected as the transmission path for transmitting data.

Therefore, if the selected indirect transmission path quality is better than the direct transmission path quality, the source node proceeds to step 416 and transmits data to the destination node through both the indirect transmission path and the direct transmission path corresponding to the selected indirect transmission path quality. . Otherwise, if the direct transmission path quality is better than the selected indirect transmission path quality, the source node proceeds to step 418 and transmits data to the destination node only through the direct transmission path.

As mentioned earlier, an approximation process of the probability density function is used to facilitate performance analysis in relay networks with interfering signals. That is, for ease of performance analysis in a relay network, it is desirable to define an approximation process of a probability density function of channel power in which performance degradation is caused by a plurality of interference signals.

First, an approximation of the probability density function may be defined by Equations 2 to 4 below.

는 간섭신호가 존재하는 경우 j 번째 간접 전송 경로를 구성하는 소스/릴레이 경로의 채널 품질,

는 간섭신호가 존재하지 않는 경우 j 번째 간접 전송 경로를 구성하는 소스/릴레이 경로의 평균 채널 품질을 의미하고,

는 감마함수, N은 간섭 신호의 개수,

는 간섭 신호의 평균 채널 품질을 의미한다. here

Is the channel quality of the source / relay path constituting the j-th indirect transmission path when interference signals exist,

Means the average channel quality of the source / relay path constituting the j-th indirect transmission path when there is no interference signal,

Is the gamma function, N is the number of interfering signals,

Denotes the average channel quality of the interference signal.

Equation 2 defines the precise SINR probability density function difference of the SINR measured in the source / relay path constituting the j-th indirect transmission path. That is, the probability density function presented in Equation 2 represents a probability density function of the SINR of a channel using one hop without using a relay.

Therefore, it is very difficult to analyze the performance of the relay network by applying the definition in Equation 2 to the relay network in which the interference signal exists.

Therefore, the method to be considered in the embodiment of the present invention proposes two approximation methods. In this case, the approximation method is to obtain an approximate probability density function of the SINR, and corresponds to a method of making a performance distribution of a channel with an interference signal into a Rayleigh distribution, which is a channel performance distribution in the absence of an interference signal.

The first approximation method to propose is to simplify the definition of Equation 2 by dividing the noise ratio '1' by the average power of the interference signal in SINR. That is, by dividing the fixed value of '1' by the probability average of the interference signals, the probability density function can be approximated by Equation 3 below.

로 정의되는

를

로 근사화시키고, 상기 근사화된 SINR을 상기 <수학식 2>에 적용함으로써 얻을 수 있다. Equation 3 is

Defined as

To

Can be obtained by applying the approximated SINR to Equation (2).

는 간섭신호의 채널 품질,

는 근사화된 간섭신호의 채널 품질을 의미하며,

는 근사화된 간섭신호의 평균 채널 품질을 뜻한다. 이를 위해서는

임을 가정한다.here

Is the channel quality of the interfering signal,

Denotes the channel quality of the approximate interference signal,

Denotes the average channel quality of the approximated interference signal. For this

Assume that

A second approximation method to propose is to simplify the definition of Equation 2 by using a Taylor Series. That is, if x has a small value, the probability density function may be approximated by Equation 4 using a commonly used Taylor series approximation method.

은 간섭신호가 존재하지 않는 경우 소스/릴레이 경로의 평균 채널 품질과 간섭신호의 평균 채널 품질간의 비를 뜻하며, 테일러 시리즈 근사화는

의 조건에 의해 이루어진다.
here

Denotes the ratio between the average channel quality of the source / relay path and the average channel quality of the interference signal when no interference is present, and the Taylor series approximation is

Is made by the conditions of.

As described above, a probability density function of channel power, in which performance deterioration occurs due to a plurality of interference signals, may be made into Rayleigh distribution by Equation 3 or Equation 4. Therefore, even in the analysis of the relay network environment in which a large number of interference signals exist, the analysis method used in the relay network without the interference signal can be used as it is.

On the other hand, while the preferred embodiment of the present invention has been shown and described, the present invention is not limited to the specific embodiments described above, in the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims Various modifications are possible by those skilled in the art, and these modifications should not be understood individually from the technical spirit or the prospect of the present invention.

For example, in the above-described embodiment of the present invention, a method of determining a transmission path based on an uplink has been described. However, it is obvious that the same method of selecting or determining the transmission path proposed in the above-described embodiment of the present invention can be applied to the downlink. In the case of applying the embodiment of the present invention to the downlink, only the subject that determines or selects a transmission path is changed to the base station, not the mobile terminal.

In addition, in the above-described embodiment of the present invention, data transmission through one indirect transmission path can be selected as necessary, but only one indirect transmission path is not necessarily selected for data transmission. That is, a plurality of indirect transmission paths may be selected as necessary. In order to implement only a plurality of indirect transmission paths, the source node needs to select a desired number of indirect transmission paths among all indirect transmission paths in consideration of path quality.

Claims (10)

delete An apparatus for selecting a data transmission path at a source node constituting a relay network,
Transmission paths for measuring indirect transmission path qualities corresponding to a plurality of indirect transmission paths indirectly connecting a destination node via a plurality of relay nodes and direct transmission path quality corresponding to a direct transmission path directly connecting the destination node. A quality measuring unit,
Selecting the best indirect transmission path quality among the indirect transmission path qualities measured by the transmission path quality measuring unit, comparing the selected indirect transmission path quality with the measured direct transmission path quality, and according to the comparison result. A transmission path selector for selecting an indirect transmission path having a direct transmission path or the direct transmission path and the best indirect transmission path quality;
A transmission unit for transmitting data to the destination node through a transmission path selected by the transmission path selection unit,
Each of the plurality of indirect transmission paths includes a first path connecting the source node and the relay node and a second path connecting the relay node and the destination node,
The transmission path quality measuring unit measures any one of a signal-to-interference signal and a noise ratio in the first path and a signal-to-noise ratio in the second path in each of the plurality of indirect transmission paths as indirect transmission path quality. Data transmission path selector. The method of claim 2, wherein the transmission path quality measuring unit,
The indirect transmission path qualities are measured in consideration of the strength of interference signals differently generated for each of the plurality of indirect transmission paths, and the direct transmission path quality is considered in consideration of the strength of the interference signal generated for the direct transmission path. Device for selecting a data transmission path, characterized in that for measuring. The method of claim 3, wherein the transmission path quality measuring unit,
And measuring the indirect transmission path qualities and the direct transmission path qualities using an approximation of a probability density function corresponding to a path where performance degradation occurs due to an interference signal. The method of claim 2, wherein the transmission path selection unit,
The indirect transmission path quality is selected by selecting a smaller value of the signal-to-interference signal and noise ratio in the first path and the signal-to-noise ratio in the second path measured in each of the plurality of indirect transmission paths. And selecting the best indirect transmission path quality among the selected indirect transmission path quality corresponding to each. delete In the method for selecting a data transmission path in the source node constituting the relay network,
Transmission paths for measuring indirect transmission path qualities corresponding to a plurality of indirect transmission paths indirectly connecting a destination node via a plurality of relay nodes and direct transmission path quality corresponding to a direct transmission path directly connecting the destination node. Quality measurement process,
An indirect transmission path quality selection process of selecting the best indirect transmission path quality among the measured indirect transmission path qualities;
The selected indirect transmission path quality is compared with the measured direct transmission path quality, and according to the comparison result, the indirect transmission path having the direct transmission path or the direct transmission path and the best indirect transmission path quality to the destination node. A transmission path selection process of selecting a transmission path for transmitting data,
Each of the plurality of indirect transmission paths includes a first path connecting the source node and the relay node and a second path connecting the relay node and the destination node,
The transmission path quality measuring process is a process of measuring any one of a signal-to-interference signal and a noise ratio in a first path and a signal-to-noise ratio in a second path in each of the plurality of indirect transmission paths. A data transmission path selection method characterized by the above-mentioned. The method of claim 7, wherein the transmission path quality measurement process,
The indirect transmission path qualities are measured in consideration of the strength of interference signals differently generated for each of the plurality of indirect transmission paths, and the direct transmission path quality is considered in consideration of the strength of the interference signal generated for the direct transmission path. Data transmission path selection method characterized in that the process of measuring. The method of claim 8, wherein the transmission path quality measurement process,
And measuring the indirect transmission path qualities and the direct transmission path qualities using an approximation of a probability density function corresponding to a path where performance degradation occurs due to an interference signal. The method of claim 7, wherein the transmission path selection process,
Selecting, as the indirect transmission path quality, a smaller value of the signal-to-interference signal and noise ratio in the first path and the signal-to-noise ratio in the second path measured in each of the plurality of indirect transmission paths;
And selecting the best indirect transmission path quality among the selected indirect transmission path quality corresponding to each of the plurality of indirect transmission paths.

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