KR101525977B1

KR101525977B1 - Method of resource allocation for Device-to Device communication based on distances in cellular system and apparatus thereof

Info

Publication number: KR101525977B1
Application number: KR1020140029050A
Authority: KR
Inventors: 신오순; 김현민; 강길모; 남종현
Original assignee: 숭실대학교산학협력단
Priority date: 2014-01-28
Filing date: 2014-03-12
Publication date: 2015-06-05

Abstract

The present invention relates to a method of allocating resources for D2D communications in a cellular system based on distance information, and to an apparatus thereof. According to the present invention, a method of allocating resources of each terminal by using a base station in a cellular system including a base station, a plurality of cellular terminals existing in a cell managed by the base station, and a plurality of D2D terminal pairs, comprising the steps of: searching for a cellular terminal located within a predetermined first radius from the base station from among the cellular terminals as a cellular terminal to be used for resource sharing; setting a priority for each of the searched cellular terminals as giving a higher priority to a cellular terminal which is more closely located to the base station; selecting at least one D2D terminal pair to be shared with a frequency resource which the cellular terminal has from among the D2D terminal pairs, and sequentially progressing the selection of the D2D terminal pairs from a cellular terminal having the highest priority; and allocating a frequency resource of a corresponding cellular terminal to the selected D2D terminal pairs and sharing the frequency resource. Accordingly, a base station is capable of collecting distance information between nodes in a cellular system for supporting direct communications between terminals and effectively allocating a frequency resource for D2D communications by using the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a distance information-based resource allocation method and apparatus for D2D communication in a cellular system,

[0001] The present invention relates to a distance information-based resource allocation method and apparatus for D2D communication in a cellular system, and more particularly, to a method and apparatus for allocating resources in a cellular system supporting D2D communication (D2D communication) The present invention relates to a distance information-based resource allocation method and apparatus for D2D communication in a cellular system in which a link can effectively share frequency resources with a D2D link.

In recent years, research and development and standardization of direct-to-terminal communication (device-to-device communication: D2D communication) in the cellular system are underway. Direct communication between terminals enables proximity-based new services by allowing terminals close to each other to communicate directly without going through an infrastructure of a base station and the like, and at the same time, it is a method for improving the frequency efficiency of a cellular system. To improve frequency efficiency, the D2D link needs to share existing cellular frequency resources with the cellular link. Therefore, mutual interference between the D2D link and the cellular link may occur, and a resource allocation technique capable of properly controlling the D2D link and the cellular link is needed.

D2D communication refers to a technology in which terminals close to each other in geographical proximity directly exchange information without going through an existing infrastructure such as a base station or an access point (AP). The D2D communication technology can be classified into the technology using the unlicensed band and the technology using the licensed band. Wi-Fi Direct, Bluetooth and ZigBee are examples of technologies that use the license-exempt band, and various products using the Wi-Fi Direct, Bluetooth, and ZigBee have already been commercialized. However, the license-exempt bandwidth is limited in terms of interference and service, so there is a limit to the guarantee of service quality, and the transmission range is also limited.

In order to overcome the limitations of license-exempt D2D communication technology, the need for D2D communication technology in cellular systems using licensed bands has emerged. In the cellular system, the terminals located close to each other can distribute the load of the base station by performing D2D communication. By transmitting the distance closer to the base station, the power consumption of the terminal can be reduced and the latency can be reduced. From the viewpoint of the whole system, the existing cellular terminal and the D2D terminal share the same frequency, and the frequency utilization efficiency is improved by spatially reusing the frequency.

Interest in cellular-based D2D communication technology began to be amplified with the launch of FlashLinQ, a proprietary D2D communication technology developed by Qualcomm in February 2011, at the Mobile Wireless Congress (MWC). In the IEEE 802.16, standardization of D2D technology for disaster communication has been underway since June 2009 under the name of GRIDMAN (Greater Reliability In Dis- tance Metropolitan Area Networks). Recently, standardization and technology development of D2D communication technology called LTE ProSe (Proximity-based Services) as one of the LTE-Advanced release 12 standard technologies in the 3rd Generation Partnership Project (3GPP), a mobile communication standardization group, is underway.

1 is a conceptual diagram of a general cellular based D2D communication procedure. Referring to FIG. 1, a base station, a cellular terminal, and terminals performing D2D communication exist in a cellular system. Cellular-based D2D communication procedures can be divided into three stages: terminal search, link generation, and data transmission. The main content to be dealt with in the present invention corresponds to the data transfer step.

The data transmission step is a step in which substantial communication is established after a link is established between terminals desiring D2D communication, and is the most important factor determining the performance of D2D communication. In order to transmit data through the D2D link, frequency resource allocation is required and it is necessary to share existing cellular resources in order to improve frequency utilization efficiency. Here, an interference problem occurs between the D2D link and the cellular link, but the interference can be controlled by the base station participating in the resource allocation of the D2D link as well as the cellular link.

Figure 2 illustrates an interference scenario when a D2D link shares cellular uplink resources within a cellular system. FIG. 2 shows a base station, a cellular terminal in a cell to which the base station manages, and a plurality of D2D terminal pairs in a cellular system. The D2D terminal pair is an example in which the D2D transmitting terminal and the D2D receiving terminal form a pair, and in the case of FIG. 2, there are two D2D terminal pairs (D2D Pair 1 and D2D Pair 2). 2, in the case where the D2D link shares the cellular uplink resources, the interference caused by the cellular link to the D2D link, the interference caused by the D2D link to the base station, and the interference caused by the D2D link mutual It can be seen that interference is additionally generated. If these three kinds of interference are not properly controlled, the D2D communication performance may be degraded or the performance of the cellular link sharing the same resources may be deteriorated. Therefore, the key to resource allocation for D2D links is to maximize spatial frequency reuse while maximizing frequency utilization efficiency while minimizing the impact of these three kinds of interference.

The most common approach for resource allocation of a cellular link and a D2D link is to collect information on the channel status of each link as well as each link, and perform resource allocation based on the information. Although this method has the advantage of accurately measuring the influence of interference, the complexity and signaling overhead for measuring and collecting channel information increase, and the resource allocation algorithm is also undesirable in that it must solve complex optimization problems . Further, in the case of a time-varying channel that changes at high speed, it is difficult to obtain accurate channel information, so that deterioration in performance may be a serious problem.

Another method of measuring the influence of interference is to use distance information between the base station and the terminal, and between the terminal and the terminal. The distance information can be obtained from the position information estimated by the terminal equipped with the Global Positioning System (GPS) or by measuring the signal strength and the angle of arrival between the base station and the terminal. The distance information is relatively easy to obtain compared with the channel information, and is less sensitive to changes over time.

Another aspect not considered in conventional resource allocation techniques is the ability to share resources. For example, the resources of a cellular user located at the edge of a cell may be difficult to share a D2D link due to severe interference. Therefore, the resource allocation algorithm needs to be designed to preferentially share resources with low potential interference.

The technique of the background of the present invention is disclosed in Korean Patent Publication No. 2008-0028347 (published on Mar. 31, 2008).

The present invention relates to a distance information-based resource allocation method for D2D communication in a cellular system in which a cellular link can effectively share frequency resources with a D2D link using inter-node distance information collected by a base station in a cellular system, and Device. &Lt; / RTI >

The present invention provides a resource allocation method of each terminal using the base station in a cellular system including a base station and a plurality of cellular terminals and a plurality of D2D terminal pairs existing in a cell that the base station is in charge of, The method comprising the steps of: searching for a cellular terminal, which is located within a first radius set within a predetermined radius from the base station, to use for resource sharing; setting a priority for each of the searched cellular terminals, Selecting at least one D2D terminal pair to receive frequency resources of the cellular terminal from the plurality of D2D terminal pairs and selecting the D2D terminal pair from the higher priority cellular terminal For each of the selected D2D terminal pairs, It provides a resource allocation method in a cellular system by assigning frequency resources of the ruler terminal comprising the step of sharing frequency resources.

Here, the priority of the cellular terminal having a low transmission power may be higher.

Further, with respect to a cellular terminal of an arbitrary priority, when selecting the D2D terminal pair, the D2D terminal pair previously selected for the cellular terminal of the previous priority can be excluded and selected.

The selecting of the D2D terminal pair for the arbitrary priority cellular terminal may include setting a D2D terminal pair located outside the first radius among the plurality of D2D terminal pairs as a candidate group for sharing resources, And sequentially selecting D2D terminal pairs in descending order from the arbitrary priority cellular terminals among the D2D terminal pairs belonging to the candidate group.

The step of selecting the pair of D2D terminals for the cellular terminal of arbitrary priority may further comprise a step of selecting a pair of D2D terminals located outside the predetermined second radius from the cellular terminals of arbitrary priority among the plurality of D2D terminal pairs And selecting the D2D terminal pairs sequentially in descending order from the arbitrary priority cellular terminals among the D2D terminal pairs belonging to the candidate group.

The step of sequentially selecting the D2D terminal pairs includes: a step of preferentially selecting a D2D terminal pair which is at a greatest distance from the arbitrary priority cellular terminal among the D2D terminal pairs belonging to the candidate group, Selecting the D2D terminal pairs sequentially in the descending order of the D2D terminal pairs belonging to the D2D terminal pairs and selecting only the D2D terminal pairs that are separated from the previously selected D2D terminal pairs by more than the critical distance.

The step of sequentially selecting the D2D terminal pairs includes the steps of: examining a value of each SINR (Signal-to-Interference-plus-Noise Ratio) value of all the sequentially selected D2D terminal pairs, And finally selecting only a D2D terminal pair having a preset threshold value or more as a terminal pair for resource sharing.

Further, the SINR value

Can be defined by the following equation.

here,

A channel state between the D2D transmitting terminal and the D2D receiving terminal constituting the D2D terminal pair,

Th < / RTI > cellular terminal and the base station,

Is the distance between the D2D transmitting terminal and the D2D receiving terminal,

Is the transmission power of the D2D transmitting terminal,

Is the transmission power of the i-th cellular terminal,

Is the distance between the ith cellular terminal and the D2D receiving terminal,

Is the path loss coefficient,

Represents the power of the noise signal at the D2D receiving terminal.

The present invention also provides a resource allocation apparatus included in the base station in a cellular system including a base station and a plurality of cellular terminals and a plurality of D2D terminal pairs existing in a cell in which the base station manages, A cellular terminal searching for a cellular terminal located within a predetermined first radius from the base station, the cellular terminal using the cellular terminal for resource sharing; and setting a priority for each of the searched cellular terminals, Selecting at least one D2D terminal pair from among the plurality of D2D terminal pairs to share a frequency resource possessed by the cellular terminal, A D2D pair selection unit for sequentially selecting terminal pairs, And a resource allocation unit for allocating frequency resources of the corresponding cellular terminal to the selected D2D terminal pairs to share frequency resources.

According to the distance information-based resource allocation method and apparatus for D2D communication in a cellular system according to the present invention, in a cellular system supporting direct communication between terminals, a base station collects distance information between nodes, and uses D2D communication It is possible to allocate frequency resources efficiently. Therefore, the present invention can provide a resource allocation technique that enables the cellular link to effectively share frequency resources with the D2D link using the distance information between the nodes collected by the base station, and at the same time minimizes the influence of interference between the respective terminals .

1 is a conceptual diagram of a general cellular based D2D communication procedure.
Figure 2 illustrates an interference scenario when a D2D link shares cellular uplink resources within a cellular system.
3 is a configuration diagram of a cellular system model according to an embodiment of the present invention.
4 is a configuration diagram of a resource allocation apparatus according to an embodiment of the present invention.
5 is a flowchart of a resource allocation method using FIG.
FIG. 6 illustrates an example of a resource allocation map of an uplink traffic channel obtained through resource allocation of a cellular link in an embodiment of the present invention.
7 and 8 are conceptual diagrams for forming a D2D terminal pair candidate group for sharing resources with a cellular terminal in the first and second embodiments of the present invention.
FIG. 9 shows a resource allocation procedure according to the first embodiment shown in FIG.
FIG. 10 shows the number of D2D pairs sharing the same resources as the cellular user when the resource allocation technique according to the second embodiment of the present invention is applied.
FIG. 11 shows an improvement in throughput of a system in which resources are shared between a cellular terminal and a D2D pair when the SINR _TH is fixed to 15 in the second embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

The present invention relates to a distance information-based resource allocation method and apparatus for D2D communication in a cellular system, and in a cellular system supporting direct communication between terminals (D2D communication; Device-to-Device) And provides a method for efficiently allocating frequency resources for D2D communication. Therefore, the present invention can provide a resource allocation technique that enables the cellular link to effectively share frequency resources with the D2D link using the distance information between the nodes collected by the base station, and at the same time minimizes the influence of interference between the respective terminals. By using the resource allocation method of the present invention, it is possible to assign the same resource as the resource allocated to the cellular link to a single or multiple D2D links while controlling the influence of interference.

Generally, the first consideration in allocating frequency resources in a cellular system is the ordering of resource allocation for a cellular link by a cellular terminal and a D2D link by a D2D pair (hereinafter, D2D terminal pair). The method of resource allocation is classified into a method in which a base station first allocates resources to a cellular link and then allocates resources to a D2D link, and conversely allocates resources to a D2D link and then allocates resources to a cellular link. This will be determined according to the service priority of the cellular terminal and the D2D terminal pair.

The following embodiments of the present invention consider a method of assigning resources to a D2D link after first allocating resources to a cellular link when the cellular terminal has priority. To this end, a method for efficiently selecting a D2D link in which a frequency resource allocated to a cellular link is shared with a certain D2D link in a cellular system, but interference of interference due to frequency sharing can be minimized is provided.

3 is a configuration diagram of a cellular system model according to an embodiment of the present invention. The cellular system considered in the embodiment of the present invention includes a base station (BS), a plurality of cellular UEs (CUEs) and a plurality of D2D terminals (BSs) D2D Pair).

That is, the system to be a reference in this embodiment corresponds to a system in which N cellular terminals (CUE) and M D2D terminal pairs (D2D Pair) coexist in a cell managed by one base station (BS). Here, the D2D terminal pair means a configuration in which a D2D transmitting terminal (D2D-Tx) and a D2D receiving terminal (D2D-Rx) existing within a predetermined distance form a pair with each other.

The cellular terminal CUE performs uplink transmission to the base station BS and the D2D transmitting terminal D2D-Tx constituting the D2D terminal pair directly transmits data to the D2D receiving terminal D2D-Rx. In this embodiment, the D2D terminal pair can transmit data using uplink resources of the cellular terminal.

In the embodiment of the present invention, it is assumed that the transmission power of the cellular terminal (CUE) is set such that the received signal-to-noise ratio (SNR) at the base station (BS) satisfies a certain value. According to this, the cellular terminal (CUE) will have higher transmission power as far as it is located away from the base station (BS). It is also assumed that the transmission power of the D2D transmitting terminal D2D-Tx is set such that the SNR at the receiving terminal D2D-Rx satisfies a certain value.

It is assumed that the channel between each node undergoes path loss due to distance and independent Rayleigh fading. The BS assumes that it knows the location of all UEs in the cell and performs resource allocation based on this information. Herein, the node includes a base station, a cellular terminal, a D2D transmitting terminal, and a D2D receiving terminal constituting a cellular system.

In the following embodiments of the present invention, the base station performs resource allocation in the direction of maximizing the frequency efficiency while minimizing the influence of the interference between the D2D link and the cellular link based on the inter-node distance information. The entity that performs resource allocation is a base station (BS), and the resource allocation device described below is included in the base station.

FIG. 4 is a configuration diagram of a resource allocation apparatus according to an embodiment of the present invention, and FIG. 5 is a flowchart of a resource allocation method using FIG. 4 and 5, a resource allocation apparatus 100 according to an exemplary embodiment of the present invention includes a required resource amount collection unit 110, a distance information collection unit 120, a resource allocation unit 130, A priority setting unit 150, and a D2D pair selection unit 160.

First, the required resource amount collection unit 110 collects a resource amount requested by each of the D2D terminal 300 and the cellular terminal 200 (S510), and compares the collected total resource amount with the available resource amount available in the base station (S520).

If the amount of collected resources is smaller than the amount of available resources, there is no need to share resources among the nodes because the amount of frequency resources to be allocated is sufficient. Therefore, at this time, the resource allocator 130 allocates the orthogonal frequency resources to the cellular link and the D2D link without interfering with each other (S530).

Conversely, if the amount of resources required is more than the amount of available resources, the resources must be shared. To do this, the base station collects the inter-node distance information and performs resource allocation for the cellular link first.

That is, the focus of this embodiment corresponds to a case where the amount of required resources is larger than the amount of available resources, and when the collected required amount of resources is larger than the available amount of resources, there is a need to share resources among the links. In this case, allocating resources for cellular links first, then allocating resources for D2D links, and sharing resources previously allocated to cellular links with arbitrary D2D links.

In other words, if the resources are allocated to the cellular link and the remaining resources are sufficient, the remaining resources will be allocated to the D2D link, so that the interference problem will not occur. However, if you allocate resources to a cellular link and there are not enough remaining resources, inevitably the D2D link should share the resources already allocated to the cellular link.

That is, in the embodiment of the present invention, among the resources already allocated to the cellular link, the priority of the resources to be reassigned to the D2D link is determined, and resources are allocated to the D2D link in that order. Also, in this embodiment, for the D2D link resource allocation, the influence of mutual interference is predicted based on the inter-node distance information, and resource allocation is performed within the allowable interference range.

If it is determined in step S520 that the requested resource amount is larger than the available resource amount, the base station first collects the inter-node distance information, and then performs resource allocation for the cellular link based on the acquired distance information.

To this end, the distance information collecting unit 120 collects distance information between nodes (S540). The distance information between nodes includes the concept of the distance between the base station and the terminal, and the distance between the terminal and the terminal. The distance information between the nodes can be obtained by measuring the signal strength, the angle of arrival, and the like.

Then, the resource allocation unit 130 first performs resource allocation for each of the cellular terminals 200 (S550). In step S550, frequency bands orthogonal to each other can be allocated to each of the N cellular terminals 200. [

FIG. 6 illustrates an example of a resource allocation map of an uplink traffic channel obtained through resource allocation of a cellular link in an embodiment of the present invention. FIG. 6 shows an example in which frequency resources orthogonal to each other are allocated to eight cellular terminals.

6 (a) shows an uplink resource allocation map of the cellular terminal. RBi (i-th RB) denotes an RB (Resource Block) allocated to the cellular UE i (i-th UE).

6 (b) shows the transmission power of each cellular UE (CUE). In this embodiment, since the transmission power of the cellular terminal is set to have a constant SNR with respect to the base station in the cell to which the base station is controlled, the cellular terminal adjacent to the base station has a lower transmission power. In the example of FIG. 6 (b), it can be seen that the cellular UE 2 is closest to the base station among all the cellular terminals. The size of the transmission power of each of the cellular terminals is used to determine the priority of the subsequent resource allocation, and a detailed description thereof will be described later.

After completing the frequency resource allocation to all the cellular terminals through S550, the frequency resource allocated to the cellular terminal is allocated to at least one D2D terminal pair among the plurality of D2D terminal pairs (resource sharing) .

Referring to FIG. 5, resource allocation for the D2D terminal pair is largely divided into two steps (a first step and a second step). The two steps are briefly described as follows.

First, a first step is to set a priority order of frequency resources to be shared among the frequency resources pre-allocated to each of the cellular terminals in step S550 (refer to S560 to S570 in FIG. 5).

To this end, the cellular terminal search unit 140 searches for a cellular terminal located within a certain distance (eg, a predetermined radius R ₁ ) from the base station among all the cellular terminals within the cell (S 560). Thereafter, the priority setting unit 150 sets a priority order for the searched cellular terminal in descending order of the distance from the base station (in order of smaller transmission power) (S570).

Generally, because of the power control of the uplink, the transmission power of the UE located in the inner region of the cell controlled by the base station is relatively small and becomes larger toward the boundary of the cell. Accordingly, the transmission power of the terminal closer to the base station is smaller, and the transmission power of the terminal farther is higher.

Here, since a terminal having a low transmission power has a relatively small influence of interference with a peripheral terminal, the terminal of the present invention shares a resource to be used by a cellular terminal having a low transmission power among a plurality of cellular terminals.

This is because it is generally preferable that the smaller the interference of the cellular link on the D2D link is, the easier it is to share with the D2D link, and the more the cellular link resources that generate the least interference are shared first.

That is, the interference generated in the cellular link will be in proportion to the transmission power of the corresponding cellular terminal, and it is advantageous that the interference is shared from the frequency resource to be used by the cellular terminal with low transmission power. However, in the present embodiment, due to the high transmission power in the case of a cellular terminal having a certain radius (R ₁ ) from the base station, the probability of interference with neighboring terminals is very high in the case of resource sharing.

Meanwhile, in order to set the priority as described above, the base station must know the transmission power of each terminal. In general, a base station can easily estimate information on the transmission power of each UE from feedback information for power control of a cellular terminal or channel quality indicator (CQI) feedback information.

6 (b) shows the transmission power of each cellular terminal and the priority set based on the transmission power. Assuming that the transmission power of the cellular terminal is in the order of UE2 <UE5 <UE3 <UE8 <UE7 <UE1 <UE6 <UE4 as shown in FIG. 6B, priority of each frequency resource is given by parentheses (RB2, RB5, RB3, RB8, RB7, RB1, RB6, and RB4), as shown in FIG. That is, RB2, which is a frequency resource allocated to UE2, has the highest priority (rank 1). Of course, if there is an empty RB, the RB will have the highest priority.

In the next step, allocating resources to the D2D link sequentially in accordance with the priority set in advance, resource allocation for the D2D link is sequentially performed starting from a high-priority frequency resource (S580 to 690 in Fig. 5 Reference).

To this end, the D2D pair selection unit 160 sequentially selects D2D terminal pairs for resource sharing from the higher priority cellular terminals (S580). Then, the resource allocator 130 allocates frequency resources of the corresponding cellular terminal to the selected D2D terminal pair (S590).

Of course, in step S590, the resource allocation refers to a concept of sharing frequency resources pre-allocated to the cellular link to at least one D2D link. It is obvious that for a cellular terminal of an arbitrary priority, when selecting a D2D terminal pair, the D2D terminal pair previously selected for the cellular terminal of the previous priority is excluded and selected.

Meanwhile, in the second step (S580 to S590), when allocating the pre-allocated resources to the at least one D2D terminal pair in the cellular terminal, the base station uses the distance information between the nodes so that the allowable interference does not exceed To perform resource allocation. The present invention is divided into two embodiments according to which distance information is used, which will be described later.

The processes of the first step (S560 to S570) and the second step (S580 to S590) are summarized as follows. In step S560, the BS searches for a cellular terminal within a first radius (R ₁ ) centered around a base station (BS) among the N cellular terminals to be used for resource sharing in operation S560. For example, the cellular terminal search unit 140 searches for a cellular terminal whose received signal strength is within 20 dB (R ₁ radius), which is a signal intensity according to distance based on a base station.

Then, the priority setting unit 150 sets a priority order for each of the cellular terminals searched within the first radius R ₁ , in order of a distance close to the base station BS (S570).

That is, the cellular terminal located closest to the base station (BS) is ranked first. Here, as described above, since the transmission power is low in a cellular terminal located close to the base station (BS), the interference with peripheral terminals is small. Therefore, the embodiment of the present invention allows sharing of resources to be used by terminals with low transmission power.

Then, the base station BS selects at least one D2D terminal pair from among the plurality of D2D terminal pairs to which frequency resources of the cellular terminal are to be shared, and sequentially selects the D2D terminal pair from the higher priority cellular terminal (S580).

To this end, the cellular terminal search unit 140 selects a D2D terminal pair to receive resources of the cellular terminal corresponding to the first rank, and then selects the D2D terminal pair sequentially . However, the D2D terminal pairs previously selected for the cellular terminal of the previous rank are excluded from the selectable objects at the time of selecting the D2D terminal pair for the next priority.

In step S590, the resource allocator 130 allocates the frequency resources of the corresponding cellular terminal to the selected D2D terminal pair corresponding to the corresponding cellular terminal in step S580.

In the second step S580 to S590, the resource allocation for the D2D link is performed according to the priority order after the priorities of the resources to be shared are determined. In the present embodiment, resources are shared according to the location of the cellular terminal The D2D link is determined. In addition, in selecting a D2D link, interference between D2D links and a different D2D link must be considered along with the interference on the cellular link. That is, it is preferable in terms of frequency efficiency of the overall system that the maximum number of D2D links share the same resource while limiting the interference of the D2D link to the cellular link.

In the present embodiment, a method of using the first radius R ₁ centered on the base station BS (first embodiment) and a method of using the first radius R ₁ centered on the base station (BS) in the second step of selecting a D ₂ D pair to share resources with the cellular terminal (Second embodiment) using a second radius (R ₂ ) centered at the center of the substrate 200.

That is, the above-described second step is divided into the following two embodiments according to the method of performing the above-mentioned steps. Hereinafter, Figs. 7 and 8 will be described separately for the first embodiment and the second embodiment of the present invention.

FIGS. 7 and 8 are conceptual diagrams for forming a D2D fair candidate group for sharing resources with the cellular terminal in the first and second embodiments of the present invention, respectively. In the above two embodiments, the first step of setting the priority order (S560 to S570) may use the above-described method in common. Alternatively, the D2D terminal pair to share the resource may be selected, Steps S580 to S590 use the method of another embodiment, which is distinguished from each other as follows. A brief explanation of the method is as follows.

First, in the case of the first embodiment of FIG. 7, in step S580, the D2D pair selector 160 selects a D2D terminal pair with respect to a cellular terminal having an arbitrary priority, R ₁ ) is set as a candidate group to share a resource (a. A candidate set process using R ₁ ). Then, the D2D terminal pairs are sequentially selected from the D2D terminal pairs belonging to the candidate group in descending order of distance from the cellular terminals of the arbitrary priority (b. Sequential selection process according to distances).

Otherwise, in the case of the second embodiment of FIG. 8, the D2D pair selection unit 160 selects a D2D terminal pair for a cellular terminal of an arbitrary priority in step S580, The D2D terminal pair located outside the predetermined second radius R ₂ from the priority cellular terminal is set as a candidate group to share the resource (a candidate set process using R ₂ ). Then, the D2D terminal pairs are sequentially selected from the D2D terminal pairs belonging to the candidate group in descending order of distance from the cellular terminals of the arbitrary priority (b. Sequential selection process according to distances).

In the first and second embodiments, the a process for setting the candidate group of the D2D terminal pair to share the resources is different, but the following principle is used in the process b for sequentially selecting the D2D terminal pairs .

First, among the D2D terminal pairs belonging to the candidate group set in the process a, the D2D terminal pairs located at the greatest distance from the arbitrary priority cellular terminal are preferentially selected first. Then, the D2D terminal pair D2D terminal pair to the next by a distance in order from belonging to the candidates sequentially secondary, but more selected third, etc., prior to pre-selected D2D terminal pair to the threshold distance (D _TH) over Select only for dropped D2D terminal pairs.

For example, if the second distance D2D terminal pair in distance order is less than the first distance D2D terminal pair (the first selected D2D terminal pair) is less than the threshold distance, the second far D2D terminal pair is not selected . The reason for using this threshold distance condition is to prevent data interference between D2D pairs that are close to each other when sharing the same frequency resources.

Hereinafter, each embodiment will be described in more detail. First, a first embodiment of the present invention will be described in detail with reference to FIG.

The first embodiment of FIG. 7 shows a case where a first priority (CUEn) of a cellular terminal closest to a base station (BS) among cellular terminals (CUE4, CUEn) within a first radius (R ₁ ) (S560 to S570; first step). Here, 'CUE4' will be the second priority.

Then, among the entire D2D terminal pairs in the cell, only the D2D terminal pair outside the first radius R ₁ is selected as a candidate group to share resources (S580). Accordingly, when D2D-Tx is within the radius R ₁ as in 'D2D pair 1', it is excluded as a candidate group.

In order to limit the interference of the D2D link on the cellular link, this process is performed by configuring only the D2D terminal pairs located at a certain distance (R ₁ ) around the base station (BS), which is a common receiver of the cellular link, . In this manner, the D2D terminal pair to which resources of the cellular terminal are to be shared must be spaced a certain distance from the corresponding cellular terminal, and interference between the terminals may be excluded when resources are shared.

Thereafter, among the D2D terminal pairs belonging to the candidate group out of the first radius (R ₁ ), the D2D terminal pairs that are the farthest from the cellular terminal 'CUEn' are selected in order from the D2D terminal pairs, Select.

That is, the D2D terminal pair (D2D Pair M) which is the farthest from the cellular terminal 'CUEn' among the D2D terminal pairs outside the first radius R ₁ is firstly selected. Thereafter, the D2D terminal pair (D2D Pair 2, D2D Pair m), which is the next farther, is additionally selected as the second and third terminals. However, the D2D terminal pair that is selected later so as not to cause mutual interference between the D2D terminal pairs is selected to be away from the already selected D2D terminal pair by a distance greater than the threshold distance (D _TH ). In this embodiment, it is assumed that the sequentially selected D2D terminal pairs D2D Pair M, D2D Pair 2, and D2D Pair m satisfy a mutual critical distance or more.

The resource allocation unit 130 allocates frequency resources of the corresponding cellular terminal 'CUEn' to the selected D2D terminal pairs (D2D Pair M, D2D Pair m, and D2D Pair 2) to share mutual frequencies S590).

Of course, in the next-ranked cellular terminal, the process of resource sharing may be performed in the same manner as the above-described method, but D2D terminal pairs that have not been selected in the first priority cellular terminal may be performed.

Next, a second embodiment of the present invention will be described in detail with reference to FIG.

The second embodiment of FIG. 8 shows a case where the 'CUEn', which is the cellular terminal closest to the base station (BS) among the cellular terminals (CUE4 and CUEn) within the first radius (R ₁ ) (S560 to S570; first step). Here, 'CUE4' will be the second priority. This first step is the same as in the first embodiment of FIG.

Then, among the entire D2D terminal pairs in the cell, only the D2D terminal pairs (D2D pair 2, D2D pair m) outside the second radius (R ₂ ) centered on the "CUEn" (S580). This is because the interference probability between the cellular terminal and the D2D terminal pair increases when the cellular terminal 'CUEn' shares frequency resources with the D2D terminal pair within the second radius R ₂ .

For example, D2D terminal pairs having a received signal strength of 15 dB (radius R ₂ ) from the cellular terminal 'CUEn' are selected as candidates. Accordingly, the D2D terminal pairs (D2D Pair 1, D2D Pair M) within the second radius R ₂ are excluded from the candidate group.

Thereafter, the D2D terminal pairs that are the farthest from the cellular terminal 'CUEn' among the D2D terminal pairs belonging to the candidate group out of the second radius R ₂ are sequentially selected, Select.

That is, the D2D terminal pair (D2D pair 2) which is the farthest from the cellular terminal 'CUEn' is first selected among the D2D terminal pairs outside the first radius R ₁ . Then, the D2D terminal pairs are sequentially selected in the second, third, and so on for the D2D terminal pairs that are farther next.

As a result, the D2D terminal pair (D2D Pair m), which is the next longest distance, is additionally selected in a second order. At this time, 'D2D pair m' should be separated from the previously selected 'D2D pair 2' by a distance D _TH or more.

That is, also in the case of the second embodiment, the plurality of D2D terminal pairs (primary, secondary, tertiary, etc.) selected for one cellular terminal must be separated by a mutual threshold distance D _TH or more. Therefore, when selecting the first, second, third, and so on, the D2D terminal pairs should be selected so that the distance between adjacent D2D terminal pairs satisfies a predetermined distance (D _TH ) or more.

Thereafter, the first priority cellular terminal 'CUEn' shares frequency resources with the selected D2D terminal pairs (D2D pair m, D2D pair 2) (S590). That is, the selected D2D terminal pairs can receive resources of the cellular terminal 'CUEn'.

Of course, the second priority cellular terminal, which is the next priority, will perform the resource sharing process in the same manner as described above. If D2D terminal pairs that have not been selected in the first priority cellular terminal are performed do.

On the other hand, in the first and second embodiments described above, all D2D terminal pairs selected for one cellular terminal (ex, CUEn) need to be selected at a time when the SINR value according to the channel information is equal to or greater than the threshold value (SINR _TH ) May be possible. Herein, SINR denotes a signal-to-interference-plus-noise ratio.

That is, in the case of the embodiment of the present invention, the D2D pair selection unit 160 sequentially selects all D2D terminal pairs (eg, In the second embodiment, each SINR (Signal-to-Interference-plus-Noise Ratio) value is checked for D2D pair m and D2D pair 2). Then, only the D2D terminal pair having the SINR value equal to or greater than the preset threshold value can be finally selected as a terminal pair for resource sharing.

That is, in the case of both the first and second embodiments of the present invention, at the time of selecting the D2D terminal pair, the D2D terminal pair in which the SINR value of the D2D terminal pair for the cellular terminal is SINR _TH or more is finally selected May also be used. This is a method for finally selecting only the D2D terminal pairs in which the SINR value satisfies a predetermined value or more among the selected D2D terminal pairs. Of course, this is not necessarily required in the first and second embodiments, and can be selectively used depending on the situation.

The SINR is a concept including noise in the D2D terminal pair and interference from the cellular terminal, and the SINR value

Can be defined by the following equation (1).

here,

Th < / RTI > cellular terminal and the base station,

Is the transmission power of the D2D transmitting terminal,

Is the transmission power of the i-th cellular terminal,

Is the path loss coefficient,

Represents the power of the noise signal at the D2D receiving terminal.

That is, Equation (1) is expressed by the signal-to-interference and noise ratio in D2D-Rx of the corresponding D2D terminal pair, assuming that the i-th cellular terminal shares resources with the corresponding D2D terminal pair.

In the first and second embodiments of the present invention as described above, the detailed procedure for sharing the specific resource already allocated to the cellular terminal to the D2D terminal pair can be briefly summarized as follows.

First, a D2D terminal pair, which can share resources with a cellular terminal, is sequentially selected based on distance information between each node, and a D2D terminal pair to share resources based on channel information (see SINR) of selected D2D terminal pairs Finally, choose. If the channel information is further considered, the overhead of channel information acquisition for D2D resource allocation can be reduced.

The summary information of the detailed procedure according to this embodiment is as follows.

Course ①. The D2D terminal pair outside the R ₁ (the first embodiment) or the R ₂ (the second embodiment) is identified from the cellular terminal to form the D2D candidate group.

Course ②. And sequentially selects from the D2D terminal pairs that are far from the cellular terminal. Here, to select the most far from D2D terminal pair from the cellular terminal, and holding the distance from the cellular terminal, but then select a long D2D terminal pairs in sequence, off already selected D2D terminal pair and all over D _TH the D2D terminal pair And if not, the corresponding D2D terminal pair is not selected. This process (2) is performed sequentially for all D2D terminal pairs in the candidate group.

Course ③. The channel information between the selected D2D terminal pairs is acquired and the SINR is calculated using the channel information.

Course ④. The D2D terminal pair corresponding to the SINR _TH SINR _TH is finally selected as the D2D terminal pair to share the frequency resource.

In the above process (1), the second radius (R ₂ ) may be determined according to the transmission power of the cellular terminal. In this embodiment, it is assumed that the transmission power of the cellular terminal is set such that the SNR at the base station satisfies a certain value. Therefore, the transmission power of the cellular terminal located far from the base station will be larger. Accordingly, the transmission power increases as the cellular terminal is located outside the cell, and the second radius (R ₂ ) increases as the transmission power increases, so that the number of selectable D2D terminal pairs will be relatively reduced.

As described above, by extending the present invention, channel information between D2D terminal pairs is obtained for the D2D terminal pairs selected based on the distance information as described above, and the SINR is calculated using the channel information, and the D2D terminal Pair to be finally selected. Of course, when it is difficult to obtain channel information between the pair of D2D terminals, the above steps (3) and (4) may be omitted.

FIG. 9 shows a resource allocation procedure according to the first embodiment shown in FIG. The blocks in the left part of FIG. 9 indicate the resource allocation procedure according to the first embodiment described above, and therefore, detailed description thereof will be omitted. Blocks in the right part are allocated as frequency resources for at least one D2D link when the arbitrary frequency resources are empty. Also, if multiple D2D links share the same frequency resources, then each D2D link shall satisfy the critical distance.

Hereinafter, simulation results using the second embodiment of the present invention will be described. One cell is assumed and the cell radius is normalized to one. The parameter settings used in the simulation are summarized in Table 1 below.

parameter Set Cell radius 1.0 Cellular User Location Uniform distribution (R ₁ = 0.3) in a circle with a radius of 0.3 or less centered on a base station Number and location of D2D pairs 30 are uniformly distributed in the base station area, and the distance between the D2D transmitting terminal and the D2D receiving terminal is set to be within 0.1 Transmit power of cellular user Set the receive SNR to 20dB at the base station D2D transmit power Set the SNR at the D2D receiving terminal to be 20dB The radius of region 2 (R ₂ ) Set the receive SNR of the cellular user signal to be 15dB at the area 2 edge (periphery)

FIG. 10 shows the number of D2D terminal pairs (D2D pairs) sharing the same resources as the cellular users when the resource allocation technique according to the second embodiment of the present invention is applied.

Each axis represents the threshold distance (D _TH ; D2D _TH ) between the D2D terminal pairs, the threshold of the SINR (SINR _TH ), and the number of D2D terminal pairs selected for the cellular link. 10 is a graph showing the average number of D2D terminal pairs sharing the same resources with the cellular user according to the change of SINR _TH , which is a threshold of D _TH and SINR, which are distance thresholds.

As the D _TH increases, the number of D2D terminal pairs increases and decreases from a certain point. If the D _TH is too small, the number of D2D terminal pairs selected in the process 2 is large, but the influence of interference between the D2D terminal pairs becomes large. On the other hand, if D _TH is too large, the number of D 2 D pairs selected in the above process (2) becomes small and the influence of interference decreases, but the efficiency of resource sharing will decrease. Thus, it can be seen that there is an optimal D _TH value.

In addition, when the SINR _TH increases, the number of D2D pairs selected in the above steps (3) and (4) tends to decrease.

FIG. 11 shows an improvement in throughput of a system in which resources are shared between a cellular terminal and a D2D pair when the SINR _TH is fixed to 15 in the second embodiment of the present invention. This figure 11 shows that a significant yield gain can be achieved through D2D communication with little effect on the yield of the cellular user.

In FIG. 11, the green graph at the bottom shows the yield of the cellular link, the red graph thereon shows the yield of the D2D link, and the blue graph shows the sum of the two preceding values. More specifically, it can be seen that the green graph is substantially independent of D _TH as the yield between the cellular terminal and the base station. The red graph corresponds to the sum of the performance of the D2D terminal pairs sharing resources with the cellular terminal. The fact that the D _TH is small means that the distance between the pair of D 2 D terminals is close to each other, so that the probability of interference increases, so that the performance is degraded. In addition, if D _TH is too large, the distance between D2D terminal pairs is long, so that the probability of interference is reduced, but the number of selected D2D terminal pairs becomes small, thereby degrading performance.

Therefore, according to the result of FIG. 11, it can be seen that there is an optimal D _TH interval with a high number of D2D terminal pairs to be selected and a high transmission efficiency. In Fig. 11, the optimum D _TH corresponds to about 0.35 point. In this case, the maximum throughput of the D2D communication is about 5 times that of the cellular user.

According to the embodiment of the present invention as described above, a D2D user in a cellular based D2D communication provides a resource allocation technique for sharing and sharing the same resources as a cellular user. The resource allocation algorithm firstly selects D2D terminal pairs capable of sharing resources with the cellular user based on the distance information of the terminals, and determines the final D2D terminal pairs based on the channel information between the selected D2D terminal terminals Method can be used. Using the technique according to the present embodiment, it was verified through a simulation that a significant amount of throughput gain due to D2D communication can be obtained without substantially affecting the throughput of a cellular user. In addition, it was confirmed that the optimum value of the distance threshold (D _TH ) exists when selecting on the initial D2D terminal.

According to the present invention, it is possible to appropriately select a single or plural D2D links sharing a corresponding resource with a cellular link to increase the frequency reuse rate, and it is possible to reduce interference caused by a cellular link to a D2D link, , The interference between the D2D links can be effectively controlled. In addition, frequency resources can be shared by selecting an optimal D2D group having a small interference influence on the basis of the cellular terminal.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

100: resource allocation unit 110: required resource amount collection unit
120: distance information collecting unit 130: resource allocation unit
140: Cellular terminal search unit 150: Priority setting unit
160: D2D pair selection unit 200: Cellular terminal
300: D2D terminal pair

Claims

A resource allocation method of each terminal using the base station in a cellular system including a base station and a plurality of cellular terminals and a plurality of D2D terminal pairs existing in a cell controlled by the base station,
Searching for a cellular terminal located within a predetermined first radius from the base station among the plurality of cellular terminals to use for a resource sharing;
Setting a priority for each of the searched cellular terminals, and setting a higher priority for a closer distance to the base station;
Selecting at least one D2D terminal pair to receive frequency resources of the cellular terminal from the plurality of D2D terminal pairs and sequentially selecting the D2D terminal pair from the higher priority cellular terminal; And
And allocating frequency resources of the corresponding cellular terminal to the selected D2D terminal pair to share frequency resources.

The method according to claim 1,
A method of allocating resources in a cellular system having a higher priority for a cellular terminal having a lower transmission power.

The method according to claim 1,
For a cellular terminal of an arbitrary priority,
Upon selection of the D2D terminal pair,
And excluding the previously selected D2D terminal pair with respect to the prior-ranked cellular terminal.

The method of claim 3,
For the cellular terminal of the arbitrary priority,
Wherein selecting the D2D terminal pair comprises:
Setting a D2D terminal pair located outside the first radius among the plurality of D2D terminal pairs as a candidate group to share resources; And
And sequentially selecting D2D terminal pairs in descending order from the arbitrary priority cellular terminal among the D2D terminal pairs belonging to the candidate group.

The method of claim 3,
For the cellular terminal of the arbitrary priority,
Wherein selecting the D2D terminal pair comprises:
Setting a D2D terminal pair located outside a predetermined second radius from the arbitrary priority cellular terminal among the plurality of D2D terminal pairs as a candidate group to share resources; And
And sequentially selecting D2D terminal pairs in descending order from the arbitrary priority cellular terminal among the D2D terminal pairs belonging to the candidate group.

Claim 6 has been abandoned due to the setting registration fee.

The method according to claim 4 or 5,
The step of sequentially selecting the D2D terminal pairs comprises:
Preferentially selecting a D2D terminal pair that is the farthest from the arbitrary priority cellular terminal among the D2D terminal pairs belonging to the candidate group; And
Selecting a D2D terminal pair sequentially in a descending order from among the D2D terminal pairs belonging to the candidate group, and selecting only a D2D terminal pair that is not less than a threshold distance from the previously selected D2D terminal pair, A method of resource allocation in a system.

Claim 7 has been abandoned due to the setting registration fee.

The method of claim 6,
The step of sequentially selecting the D2D terminal pairs comprises:
Checking each SINR (Signal-to-Interference-plus-Noise Ratio) value of all the sequentially selected D2D terminal pairs; And
And finally selecting only a D2D terminal pair having the SINR value equal to or greater than a predetermined threshold value as a terminal pair for resource sharing.

Claim 8 has been abandoned due to the setting registration fee.

The method of claim 7,
The SINR value

Is a resource allocation method in a cellular system defined by the following equation:

here,

Th < / RTI > cellular terminal and the base station,

Is the transmission power of the D2D transmitting terminal,

Is the transmission power of the i-th cellular terminal,

Is the path loss coefficient,

Represents the power of the noise signal at the D2D receiving terminal.

A resource allocation apparatus included in a base station in a cellular system including a plurality of cellular terminals and a plurality of D2D terminal pairs existing in a cell in which the base station manages,
A cellular terminal search unit for searching, among the plurality of cellular terminals, a cellular terminal located within a predetermined first radius from the base station, for use in resource sharing;
A priority setting unit configured to set a priority for each of the searched cellular terminals, and to set a higher priority for a closer distance to the base station;
A D2D pair selection unit for selecting at least one D2D terminal pair to receive frequency resources of the cellular terminal from among the plurality of D2D terminal pairs and sequentially selecting the D2D terminal pair from the cellular terminal having a higher priority, ; And
And a resource allocation unit for allocating frequency resources of the corresponding cellular terminal to the selected D2D terminal pair to share frequency resources.

The method of claim 9,
A resource allocation apparatus in a cellular system having a higher priority as a cellular terminal having a lower transmission power.

The method of claim 9,
The D2D-
And selects a D2D terminal pair previously selected for a cellular terminal of a previous priority in selecting a D2D terminal pair for a cellular terminal of an arbitrary priority.

The method of claim 11,
For the cellular terminal of the arbitrary priority,
The D2D-
Setting a D2D terminal pair located outside the first radius among the plurality of D2D terminal pairs as a candidate group for sharing resources,
And sequentially selects D2D terminal pairs in descending order from the arbitrary priority cellular terminals among the D2D terminal pairs belonging to the candidate group.

The method of claim 11,
For the cellular terminal of the arbitrary priority,
The D2D-
Setting a D2D terminal pair located outside a predetermined second radius from the arbitrary priority cellular terminal among the plurality of D2D terminal pairs as a candidate group for sharing resources,
And sequentially selects D2D terminal pairs in descending order from the arbitrary priority cellular terminals among the D2D terminal pairs belonging to the candidate group.

Claim 14 has been abandoned due to the setting registration fee.

The method according to claim 12 or 13,
The D2D-
Upon sequentially selecting the D2D terminal pairs,
The D2D terminal pair located at the farthest distance from the arbitrary priority cellular terminal among the D2D terminal pairs belonging to the candidate group is preferentially selected,
The D2D terminal pairs are sequentially selected in descending order from the D2D terminal pairs belonging to the candidate group, and the resources in the cellular system to be selected only for the D2D terminal pairs that are distant from the previously selected D2D terminal pairs Allocation device.

Claim 15 is abandoned in the setting registration fee payment.

15. The method of claim 14,
The D2D-
(SINR) value for all the D2D terminal pairs selected in the sequential manner, and only the D2D terminal pair having the SINR value equal to or greater than the preset threshold value is used as a terminal pair for resource sharing A device for resource allocation in a final selected cellular system.

Claim 16 has been abandoned due to the setting registration fee.

16. The method of claim 15,
The SINR value