KR20130035903A - Methods of device to device communication - Google Patents

Abstract

PURPOSE: A direct communication method is provided to improve the performance of a wireless link in a selective wireless environment by transmitting a signal by mapping a PN(Pseudo-Noise) sequence to a plurality of sub-carrier waves. CONSTITUTION: A pager terminal generates a CID(Connection Identification) by inputting the ID of a terminal which wants to use a D2D(Device To Device) communication method through a hash function(S401). The pager terminal maps a specific PN sequence number with the generated CID(S403). The pager terminal determines whether the generated CID is occupied based on a PN sequence received from other terminals(S407). When the CID is not occupied, the pager terminal transmits a plurality of sub-carrier waves for a paging request related to the PN sequence corresponding to the sequence number(S411). [Reference numerals] (AA) Start; (BB) Yes; (CC) No; (DD) End; (S401) Generating a CID using a neighbor device ID as the input of a hash function; (S403) Mapping the generated CID with the sequence number of a specific sequence; (S405) Receiving a PN sequence broadcasted from other terminals in a CID broadcasting section; (S407) Is the CID occupied?; (S409) Standing by until a next paging section; (S411) Transmitting a sequence corresponding to the sequence number using a paging request resource; (S413) Receiving the PN sequence from the pager; (S415) Determining the effectiveness of the CID;

Description

Direct communication between devices {METHODS OF DEVICE TO DEVICE COMMUNICATION}

The present invention relates to a wireless communication system, and more particularly to a direct communication method between terminals.

In the point-to-multipoint wireless communication system, even when data is transmitted / received between adjacent terminals, the terminal should be transmitted from the base station and the base station to the counterpart terminal. The disadvantage is that the delay is large. As a technology for solving this problem, a device-to-device communication (D2D communication) technology has emerged.

That is, the direct communication between terminals refers to a communication method of directly transmitting and receiving data between two adjacent terminals without passing through a base station. That is, in direct communication between terminals, two terminals communicate with each other as a source and a destination of data.

1 is a conceptual diagram illustrating a concept of direct communication between terminals.

Referring to FIG. 1, a cellular communication network composed of a first base station 10 and a second base station 20 is configured. At this time, the terminal 1 (11) to the terminal 3 (13) belonging to the cell generated by the first base station 10 performs a communication through a normal access link through the first base station 10, the first base station ( Terminal 4 (14) and terminal 5 (15) belonging to 10) performs data transmission and reception between each other directly through the base station.

There may be various discussions regarding a user case in which such direct communication between terminals can be efficiently used. For example, the direct communication between terminals may be used for a local media server or the like that provides a large amount of material (eg, a program of a rock concert, information on a player) to visitors who attend a rock concert. In this case, each terminal is connected to the serving cell to perform the telephone call and the Internet access using a conventional cellular link, but the local media server operating as a counterpart of the direct communication between the terminals directly from the terminal to the large-capacity data described above. It can transmit and receive by communication method.

Meanwhile, referring back to FIG. 1, a direct communication link between terminals is not only possible between terminals having a same cell as a serving cell, but may also be established between terminals having different cells as a serving cell. For example, the terminal 3 (13) belonging to the first base station 10 may perform direct communication between the terminal and the terminal 6 (21) belonging to the second base station 20.

Due to the characteristics as described above, the direct communication technology between terminals is expected to become the underlying technology of the Internet of Things (IOT) or sensor network in the future.

On the other hand, for direct communication between terminals, a connection setup process between two terminals is required. Connection establishment for direct communication between terminals is a process in which each terminal acquires synchronization, a discovery process of notifying the existence of the neighboring terminal at the same time as notifying its existence to the neighboring terminal, and two neighboring terminals to perform direct communication. It includes a paging process for generating a connection ID (CID) between the two, and the process of transmitting and receiving traffic between the two devices.

In the process of establishing a connection for direct communication between terminals, a paging and a traffic transmission / reception process are conventionally performed by using a single-tone signaling method. That is, in the related art, a method of transmitting a signal using one subcarrier in a communication environment using orthogonal frequency division multiple access (OFDMA) and performing signaling using analog energy level detection has been used.

The single-tone signaling technique based on the reception power of a specific subcarrier measured by a receiving terminal has a disadvantage in that reception performance is degraded in a frequency selective channel environment because signaling is performed using only one specific subcarrier.

In addition, in the conventional method for establishing a connection for direct communication between terminals, one subcarrier is used in the signaling process and all subcarriers are used in the data transmission process, so that the reach distances of the signals are different from each other in the above two processes. The disadvantage is that you cannot expect the efficiency that can be achieved by allocation.

An object of the present invention for overcoming the above disadvantages relates to a direct communication method between terminals that can improve the performance and resource usage efficiency of the radio link.

Direct communication method between terminals according to an aspect of the present invention for achieving the above object of the present invention, generating a CID (Connection ID) for direct communication between terminals using the ID of a specific terminal, and the CID Selecting a sequence corresponding to the step and transmitting the selected sequence using a paging request resource consisting of a plurality of subcarriers.

In the generating of the CID, the CID may be generated as an output of a hash function by using an ID of the specific terminal as an input of a hash function.

The selecting of the sequence corresponding to the CID may select a sequence corresponding to the CID from a sequence set including a plurality of preset PN sequences.

In the direct communication method between the terminals, after selecting a sequence corresponding to the CID, receiving at least one sequence broadcast from other terminals and occupying the generated CID based on the received at least one sequence The method may further include determining whether or not. Here, in the step of transmitting the selected sequence by using a paging request resource composed of a plurality of subcarriers, if the generated CID is occupied by another terminal, after waiting until the next paging segment, the generated CID is the next paging segment. If not occupied, the selected sequence may be transmitted using a paging request resource.

Here, the direct communication method between terminals may include receiving at least one sequence transmitted from at least one other terminal in a paging response period after transmitting the selected sequence using a paging request resource composed of a plurality of subcarriers; The method may further include measuring received power of a sequence corresponding to the generated CID among the at least one received sequence and determining that a paging response is received when the measured received power is equal to or greater than a preset threshold. Can be.

In addition, the direct-to-terminal direct communication method according to another aspect of the present invention for achieving the object of the present invention is a direct-to-terminal communication method performed in the transmitting terminal requesting a D2D communication connection, the sequence corresponding to the generated CID Transmitting a transmission request signal (RTS) by mapping to a transmission request resource composed of a plurality of subcarriers, and determining whether or not the transmission abandonment conditions are satisfied based on the transmission allowance signal (CTS) received from the receiving terminal; Transmitting a pilot signal when the condition is satisfied.

The determining of whether the abandonment condition is satisfied may include receiving a sequence mapped to a plurality of subcarriers as the transmission allowable signal, measuring channel quality considering all of the plurality of subcarriers, and measured channel quality. And when the threshold value is equal to or greater than the preset threshold value, determining that the transmission abandonment condition is satisfied. In the measuring of the channel quality, an effective SIR representing a signal to interference ratio (SIR) of each of the plurality of subcarriers may be measured.

In the transmitting of the pilot signal, the sequence corresponding to the CID may be transmitted as a pilot signal.

In addition, the direct-to-terminal communication method according to another aspect of the present invention for achieving the object of the present invention is a direct-to-terminal communication method performed in the receiving terminal is requested to connect the D2D communication, the transmission request signal (RTS) Determining whether the aeration condition is satisfied based on the received transmission request signal, and if the aeration condition is satisfied, mapping a sequence corresponding to the generated CID to a plurality of subcarriers to transmit a transmission permission signal ( CTS).

The determining of whether the reception abandonment condition is satisfied includes measuring channel quality considering all of a plurality of subcarriers constituting the received transmission request signal, and when the measured channel quality is equal to or greater than a preset threshold, It can be determined that the condition is satisfied.

In the measuring of the channel quality, an effective SIR representing a signal to interference ratio (SIR) of each of the plurality of subcarriers may be measured.

Here, in the direct communication method between terminals, after the step of transmitting the transmission allowable signal (CTS), the step of receiving a pilot signal and transmitting a channel quality indicator only when the received power of the received pilot signal is greater than or equal to a preset threshold value. It may further comprise the step.

According to the direct-to-terminal communication method as described above, the PN sequence is mapped to a plurality of subcarriers to transmit a signal in a paging process and a traffic transmission / reception process of establishing a D2D connection, thereby improving performance of a wireless link even in a channel-selective wireless environment. have.

In addition, in the traffic transmission and reception process, only when the transmitting and receiving abandonment conditions satisfy the transmitting and receiving abandonment conditions by using a valid SIR representing all channels, the transmitting and receiving terminals performing the D2D communication connection are satisfied. By performing distributed scheduling for transmitting a signal, interference with neighboring terminals can be prevented, thereby improving the use efficiency of radio resources.

1 is a conceptual diagram illustrating a concept of direct communication between terminals.
2 is a flowchart illustrating a connection establishment process for direct communication between terminals.
3 shows a structure of a frame used in a direct communication process between terminals.
4 is a flowchart illustrating a paging process in a method of direct communication between terminals according to an embodiment of the present invention.
5 is a conceptual diagram illustrating the paging process illustrated in FIG. 4.
6 is a conceptual diagram illustrating CID generation and PN sequence mapping during a paging process according to an embodiment of the present invention.
7 is a conceptual diagram illustrating a distributed resource allocation process in a traffic transmission and reception process according to an embodiment of the present invention.
8 is a conceptual diagram illustrating a reception abandonment condition in a traffic transmission / reception process according to an embodiment of the present invention.
9 is a conceptual diagram illustrating connection scheduling in a traffic transmission and reception process according to an embodiment of the present invention.
10 is a conceptual diagram illustrating SIR measurement for each subcarrier in a traffic transmission / reception process according to an embodiment of the present invention.
FIG. 11 is a conceptual diagram illustrating a measurement of a reception abandon condition using RTS in a process of transmitting / receiving traffic according to an embodiment of the present invention.
12 is a conceptual diagram illustrating a measurement of a transmission abandonment condition using a CTS in a traffic transmission / reception process according to an embodiment of the present invention.
13 is a flowchart illustrating a traffic transmission / reception procedure according to an embodiment of the present invention.
14 is a conceptual diagram illustrating a paging and connection scheduling process according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail.

It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be interpreted in an ideal or overly formal sense unless explicitly defined in the present application Do not.

The term 'terminal' used in the present application is a device, a mobile station (MS), a user equipment (UE), a user terminal (UT), a wireless terminal, an access terminal (AT), a terminal, a subscriber unit. (Subscriber Unit), Subscriber Station (SS), Wireless Device, Wireless Communication Device, Wireless Transmit / Receive Unit (WTRU), Mobile Node, Mobile or other terms. . Various embodiments of the terminal may be used in various applications such as cellular telephones, smart phones with wireless communication capabilities, personal digital assistants (PDAs) with wireless communication capabilities, wireless modems, portable computers with wireless communication capabilities, Devices, gaming devices with wireless communication capabilities, music storage and playback appliances with wireless communication capabilities, Internet appliances capable of wireless Internet access and browsing, as well as portable units or terminals incorporating combinations of such functions However, the present invention is not limited thereto.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, the same reference numerals are used for the same components in the drawings, and duplicate descriptions of the same components are omitted.

2 is a flowchart illustrating a connection establishment process for direct communication between terminals. 3 shows the structure of a frame used in a direct communication process between terminals.

2 and 3, when power is applied to a terminal to perform D2D communication, the terminal acquires time synchronization (S201). In the D2D communication, it is assumed that all terminals have the same time reference. The terminal may use various means such as a GPS (Global Positioning System) or a synchronization signal transmitted by a base station of an existing cellular system for synchronization acquisition.

After acquiring synchronization, each terminal notifies its existence to neighboring terminals, and performs a discovery process of recognizing the existence of neighboring terminals (S203). Here, the terminal may notify its existence to neighboring terminals by broadcasting its ID using the discovery slot 310 and may recognize the existence of neighboring terminals by receiving the ID broadcasted from the neighboring terminals. Each terminal may obtain a list of IDs of neighboring terminals based on IDs of the respective terminals received from neighboring terminals in the discovery process.

When the discovery process is completed, the terminal may establish a connection with a specific neighboring terminal. The process of establishing a connection for D2D communication between two adjacent terminals is called a paging process (S205), and the paging slot 330 is used in the paging process. When the paging process is completed, a CID (Connection ID), which is an identifier for distinguishing a connection between two terminals wishing for D2D communication, is generated.

Thereafter, the two terminals perform a traffic transmission / reception process of occupying frequency and time resources and exchanging information with each other by using the occupied radio resources by using a distributed algorithm for avoiding collision and efficiently reusing radio resources (S207). . In the traffic transmission and reception process, the traffic slot 350 is used.

Meanwhile, the paging process S205 shown in FIG. 2 includes a CID broadcast, a paging request, and a paging response process, and the CID broadcast, paging request, and paging response are respectively shown in FIG. 3. The CID broadcast slot 331, paging request slot 332, and paging response slot 333 of the paging slot 330 shown in FIG.

In addition, the process of transmitting / receiving traffic (S207) illustrated in FIG. 2 includes a connection scheduling, a pilot, a channel quality indication (CQI), a data and an ACK process, and include connection scheduling, pilot transmission, CQI reception, The data and ACK process uses a connection scheduling slot 351, a pilot slot 352, a CQI slot 353, a data slot 354 and an ACK slot 355 of the traffic slot shown in FIG. 3, respectively. Here, the pilot transmission process and the CQI reception process are referred to as rate scheduling. The connection scheduling process again includes a request to send (RTS) transmission and a clear to send (CTS) reception.

Meanwhile, in the process of establishing a D2D communication connection, a single-tone signaling method is used in the connection scheduling process of paging (S205) and traffic transmission / reception (S207), and resources are allocated through the connection scheduling process. The terminal transmits information using all radio resources (for example, all subcarriers).

When single tone signaling is used, the receiving terminal measures power using one subcarrier during CID broadcasting, paging request, and paging response during paging. However, using a single tone signaling may cause performance degradation in a frequency selective channel environment because a channel applied to one particular subcarrier (or single-tone) may not represent the entire channel in a frequency selective channel environment.

In addition, in the conventional D2D communication connection setup process, since the RTS and CTS signals of the connection scheduling process use one subcarrier, abandonment and abandonment conditions of a corresponding UE may be incorrectly determined, which may cause a collision in the data transmission process. Can be.

In the direct-to-terminal communication method according to an embodiment of the present invention to improve the performance of the radio link by using a broadband transmission in the paging and connection scheduling process to solve the above problems, the use of radio resources Improve the efficiency.

4 is a flowchart illustrating a paging process in a method of direct communication between terminals according to an embodiment of the present invention.

When the discovery process is completed, the terminal acquires IDs of other terminals located around the terminal. Accordingly, the terminal may establish a connection for D2D communication using the ID of the neighboring terminal. Here, a unique identifier for indicating a D2D communication connection between two terminals is required, and this unique identifier is called a CID (Connection ID). Meanwhile, a terminal requesting paging among two terminals to be connected to D2D communication is called a pager, and a terminal responding to a paging request of the pager is called a pagee.

The pager terminal generates a CID by using an ID of a terminal to which D2D communication is connected as a input of a hash function from a list of neighbor terminals obtained through discovery (S401). Here, the generated CID means a result of the hash function.

Thereafter, the pager terminal maps a sequence number indicating a specific PN sequence, which is an element of a PN sequence set including a plurality of preset PN sequences, and the generated CID in one-to-one (S403). Here, the PN sequence means all kinds of sequences that can be separated by performing signal processing on the signal received by the receiving terminal.

Meanwhile, the pager terminal cannot immediately make a paging request using the generated CID after generating the CID by using the hash function, and first, check whether there is another terminal using the same CID as the generated CID. Should be.

Therefore, all the terminals that have already acquired the CID must broadcast to the other terminals using resources allocated for CID broadcasting purposes that they are using a specific CID.

The pager terminal transmits the PN sequence mapped to the CID in the CID broadcasting section using resources allocated for the CID broadcasting purpose, and receives a PN sequence corresponding to the CID of each terminal broadcasted from other terminals (S405).

Thereafter, the pager terminal determines whether the generated CID is occupied based on the PN sequence received from the other terminals (S407). Here, when the received signal level of the PN sequence corresponding to the CID generated by the user among the PN sequences received from the other terminals in the CID broadcast period is higher than or equal to a preset reference level, the pager terminal has already generated the CID by another terminal. It is determined that it is occupied and unavailable, and waits until the next paging segment, and then performs step S405.

Alternatively, the pager terminal may have a received signal level of a PN sequence corresponding to a CID generated by itself among the PN sequences received from other terminals in a CID broadcast interval, or may be a PN corresponding to a CID generated by the pager terminal. If the sequence is not received, it is determined that the generated CID is not occupied, and the paging request for requesting the page for D2D communication connection is performed using the generated CID. Here, the pager terminal transmits the PN sequence corresponding to the sequence number using a plurality of subcarriers for the paging request (S411). Paging request interval can be used by a plurality of pagers at the same time, in the present invention, because the paging request is transmitted using a PN sequence, the page terminal by separating the paging request signals received from the plurality of terminals by using a correlation (correlation) characteristics You can determine if it is called.

On the other hand, the terminals located in the vicinity of the pager terminal to measure the received power of the PN sequence corresponding to its CID in the paging request interval to determine whether they are called from the other terminal, respectively, and the measured power is equal to or greater than a preset threshold value If it is determined that it is called.

The called terminal transmits a PN sequence corresponding to its CID by using subcarriers allocated to a paging response interval. Since the pager terminal and the page terminal use the same CID, the pager terminal and the page terminal use the same PN sequence.

Meanwhile, the pager terminal measures the reception power of the PN sequence corresponding to the CID generated by the pager terminal in the paging response period, and determines that the paging response is received when the pager terminal exceeds the preset threshold (S415). That is, when the pager terminal receives a paging response from the page terminal, the pager terminal determines that the CID generated by the pager terminal is usable, and uses it in a subsequent traffic transmission / reception process.

5 is a conceptual diagram illustrating the paging process illustrated in FIG. 4.

In FIG. 5, the pager terminal 510 performs D2D communication with the page terminal 520 in a network environment where the pager terminal 510, the page terminal 520, and the neighboring terminal 530 are located at a distance capable of D2D communication with each other. For example, a case of performing paging is illustrated.

The pager terminal 510 determines the page terminal 520 as a D2D communication target terminal from the ID list of neighbor terminals obtained after performing the discovery process, and uses the ID of the page terminal 520 as an input of a hash function. Generate #n In addition, the pager terminal 510 maps the generated CID # n with a sequence number and transmits a paging request signal using a PN sequence corresponding to the mapped sequence number.

Meanwhile, the pager terminal 510 receives a PN sequence broadcast using a plurality of subcarriers 531 from the neighboring terminal 530 in the CID broadcasting section and confirms that the CID # n generated by the pager terminal 510 is not occupied. Here, since the PN sequence received from the neighboring terminal 530 is a sequence mapped to CID # k, which is a CID value of the neighboring terminal 530, the pager terminal 510 is based on the PN sequence received from the neighboring terminal 530. The generated CID # n may be different from the CID # k generated by the neighboring terminal.

Thereafter, the pager terminal 510 maps the PN sequence corresponding to its CID # n to the plurality of subcarriers 511 allocated for the paging request and transmits the same.

The page terminal 520 receives a paging request signal including the PN sequence transmitted from the pager terminal 510 in the paging request period, and measures the reception power of the PN sequence corresponding to the page terminal 520. Here, when the page terminal 520 determines that the reception power of the PN sequence corresponding to its PN sequence is greater than or equal to a preset threshold, the PN corresponding to its CID # n in the plurality of subcarriers 521 for paging response Send the sequence by mapping it.

The pager terminal 510 receives a paging response signal in the paging response period and determines whether the received power of the PN sequence corresponding to its CID # n in the paging response signal is greater than or equal to a preset threshold. Here, when the received power of the PN sequence received by the pager terminal 510 is greater than or equal to a threshold value, CID # n is determined as a CID indicating a D2D communication connection between the pager terminal 510 and the page terminal 520.

6 is a conceptual diagram illustrating CID generation and PN sequence mapping during a paging process according to an embodiment of the present invention.

Referring to FIG. 6, the pager terminal 610 uses an ID N ₁ of a neighboring terminal (predetermined page terminal) that it wants to connect for D2D communication as an input of the hash function 611. Generate CID (n ₁ ) as the output. Thereafter, the pager terminal 610 selects a specific sequence number corresponding to the CID (n ₁ ) generated by the PN sequence set 613 composed of the PN sequences, thereby generating the CID (n ₁ ) of the PN sequence of the selected sequence number. Maps one-to-one with The pager terminal 610 maps the selected PN sequence to the plurality of subcarriers 631 constituting the paging request interval and transmits the mapped PN sequence.

Meanwhile, the pager terminal 620 uses the ID N ₂ of the neighboring terminal (predetermined page terminal) to be connected for D2D communication as an input of the hash function 621 and uses the CID () as an output value of the hash function 621. n ₂ ). Subsequently, the pager terminal 620 selects a specific PN sequence number corresponding to the CID (n ₂ ) generated by the PN sequence set 623 composed of the PN sequences, thereby generating the CID (n ₁ ) as the PN of the selected sequence number. Maps one-to-one with a sequence. Here, the PN sequence set 613 and the PN sequence set 623 may be composed of the same PN sequences, and each PN sequence included in each PN sequence set may have the same sequence number. The pager terminal 620 maps the selected PN sequence to a plurality of subcarriers 631 constituting the paging request interval and transmits the mapped PN sequence.

As shown in FIG. 6, although the plurality of subcarriers 631 constituting the paging request interval are resources used by a plurality of pager terminals at the same time, each page terminal knows a corresponding PN sequence number corresponding to its ID. By using the PN sequence number (or PN sequence) of its own, it is possible to determine whether or not to call itself by separating the received overlapped signals.

As described above, in a paging process for D2D communication according to an embodiment of the present invention, a PN sequence corresponding to a CID generated by each pager terminal is mapped to a plurality of subcarriers constituting a paging request interval and then transmitted. The performance degradation of the paging request caused by the frequency selective characteristic can be improved. In addition, the CID broadcast and paging response performance can be improved through the same method.

Hereinafter, a traffic transmission / reception process of the direct communication method between terminals according to an embodiment of the present invention will be described in more detail.

As described above, the traffic transmission and reception interval may include connection scheduling, pilot, CQI, data and ACK interval.

Connection scheduling is a process in which terminals occupy resources in a distributed manner without centralized control while maximizing spatial reuse efficiency of radio resources without causing interference with each other through RTS and CTS signal exchange.

The pilot and CQI intervals are rate scheduling intervals, and a transmission terminal that occupies radio resources in a distributed manner transmits a pilot signal through a connection scheduling process. The receiving terminal receiving the pilot signal measures the channel based on the pilot signal, and then transmits an adaptive modulation and coding (AMC) level (ie, CQI) to the transmitting terminal based on the measured channel. The transmitting terminal transmits data after performing adaptive modulation and coding using the received CQI, and the receiving terminal transmits an ACK to the transmitting terminal according to the received data.

What is important in the process of transmitting and receiving traffic for D2D communication as described above is to efficiently occupy and release resources in a distributed manner without centralized control.

7 is a conceptual diagram illustrating a distributed resource allocation process in a traffic transmission and reception process according to an embodiment of the present invention.

In FIG. 7, for example, the terminal A 710 and the terminal B 720 perform a D2D communication connection, and the terminal C 730 and the terminal D 740 perform a D2D communication connection.

In the D2D communication environment as illustrated in FIG. 7, the direct gain {| h _AB | between the terminal A 710 and the terminal B 720 and the terminal C 730 and the terminal D 740. ² , | h _CD | ² } and cross-link gain between the terminal A 710 and the terminal D 740 and the terminal C 730 and the terminal D 740 {| h _AD | ² , h _CB | ² } can be considered.

Here, when the cross link gain is sufficiently small, two links may be simultaneously configured on the same channel. Otherwise, no resource may be allocated to any one of the two links.

Therefore, if the cross link gain is not small enough, resources should be allocated to the higher priority links first, and other links with lower priorities do not cause significant interference to the higher priority links if resources are allocated. Only resources should be allocated.

In FIG. 7, it is assumed that the link between the terminal A 710 and the terminal B 720 (link AB) has a higher priority than the link between the terminal C 730 and the terminal D 740 (link CD). There is a need for a method capable of protecting the link AB by preventing the terminal C 730 of transmitting a random signal.

If the terminal C 730 transmits a signal, if the signal to interference ratio (SIR) affecting the terminal B 720 of the link AB may be known, the link AB having a higher priority may be protected.

Therefore, from the viewpoint of the terminal C 730, a rule such as Equation 1 for protecting the link AB having high priority is required, which is called a transmission abandonment condition.

는 미리 설정된 송신 SIR 기준값을 의미한다.In Equation 1, P _A means transmission power of the terminal A 710, P _C means the transmission power of the terminal C (730). In addition, | h _AB | ² indicates a channel gain between the terminal A 710 and the terminal B 720, and | h _CB | ² denotes a channel gain between the terminal C 730 and the terminal B 720.

Denotes a preset transmission SIR reference value.

보다 큰 경우 신호를 전송할 수 있다.That is, the terminal C 730 is the measured SIR is

If greater, the signal can be transmitted.

However, two links cannot be scheduled at the same time only according to the abandonment condition shown in Equation 1 according to the arrangement of the terminals.

8 is a conceptual diagram illustrating a reception abandonment condition in a traffic transmission / reception process according to an embodiment of the present invention.

As shown in FIG. 8, even when the link CD of the terminal C 830 and the terminal D 840 can sufficiently protect the link AB, the communication environment in which the terminal A 810 and the terminal D 840 are adjacent to each other. In this case, even though the terminal C 830 transmits a signal to the terminal D 840, the terminal D 840 normally receives a signal transmitted from the terminal C 830 due to the interference of the signal transmitted by the terminal A 810. Can not.

In such a case, if the terminal C 830 does not transmit, interference with the link EF between the terminal E 850 and the terminal F 860 is mitigated, thereby improving efficiency of the entire network. That is, if the terminal D 840 can identify the interference of the terminal A 810 and use it for scheduling, it may help to improve the efficiency of the network.

Therefore, in view of the terminal D 840, a condition such as Equation 2 is additionally required and this is called a reception abandonment condition.

는 미리 설정된 수신 SIR 기준값을 의미한다.In Equation 2, P _A means transmission power of the terminal A 810, P _C means the transmission power of the terminal C (830). In addition, | h _AD | ² means a channel gain between the terminal A 810 and the terminal D 840, and | h _CD | ² denotes a channel gain between the terminal C 830 and the terminal D 840.

Denotes a preset received SIR reference value.

보다 큰 경우 신호를 수신할 수 있다.
That is, the terminal C (830) is the measured SIR is

If greater, the signal can be received.

9 is a conceptual diagram illustrating connection scheduling in a traffic transmission and reception process according to an embodiment of the present invention.

As shown in FIG. 9, the connection scheduling section 910 includes an RTS section 911 and a CTS section 913. The pager terminal maps a sequence designed to allow the page terminal to measure the SIR for each subcarrier and then transmits the mapping to the subcarriers allocated to the RTS resource. To this end, the pager terminal may use various sequences such as PN and Cyclic shifted Zadoff-Chu. Hereinafter, the Cyclic shifted ZC (Zadoff-Chu) sequence will be described.

The CID generated by the transmitting terminal (or pager terminal) and the specific sequence are mapped one-to-one. Sequence division is made by sequence number, and the sequence used by the transmission / reception terminal pair is the same. In addition, the priority of the link may be set according to the sequence number. In the embodiment of the present invention, the lower the sequence number, the higher the link priority.

 If the length of the cyclic shift is longer than the channel impulse response, even if a plurality of transmitting terminals transmit the same ZC sequence of different cyclic shifts using the same RTS resource, Since the channel estimation is possible for each terminal and for each subcarrier, the receiving terminal can measure the SIR for each transmitting terminal and subcarrier.

개의 송신 단말이 같은 자원을 이용하여 사이클릭 시프트가 다른 동일 ZC 시퀀스를 전송하고 수신 단말은 OFDM 심볼을 구성하는 전체 부반송파가 경험한 채널을 송신 단말별로 분리하여 정확하게 측정할 수 있다. 이와 같은 경우 연결 스케줄링에 참여하는 CID 수가 수가

보다 클 경우 문제가 발생된다. 그러나 동시에 연결 및 스케쥴링에 참여하는 CID의 수가

보다 클 확률은 매우 작다.For example, if the length of the OFDM symbol T _p, the maximum impulse response length of the channel in an OFDMA assuming that T _CS

Two transmitting terminals transmit the same ZC sequence having different cyclic shifts using the same resource, and the receiving terminal can accurately measure the channel experienced by all subcarriers constituting the OFDM symbol by separating the transmitting terminals. In this case, the number of CIDs participating in connection scheduling

If it is larger, a problem occurs. However, the number of CIDs participating in the connection and scheduling at the same time

The probability of greater than is very small.

의 값이 원하는 값보다 작을 경우 베이스(base)가 다른 ZC 시퀀스를 추가적으로 사용할 수 있다.if

If the value of is smaller than the desired value, the base can additionally use another ZC sequence.

Through the above-described method, since the receiving terminal can measure a channel for each transmitting terminal and each subcarrier, the receiving terminal can measure the SIR for each subcarrier.

10 is a conceptual diagram illustrating SIR measurement for each subcarrier in a traffic transmission / reception process according to an embodiment of the present invention.

Referring to FIG. 10, when four UEs G, H, I, and J (1010, 1020, 1030, and 1040) transmit ZC sequences having different cyclic shifts using subcarriers allocated to an RTS interval, reception is performed. The terminal K 1050 may measure the channel by separating the transmission terminal and the subcarrier. For example, the SIR of the i th subcarrier in the D2D communication link including the terminal J 1040 and the terminal K 1050 may be obtained by using Equation 3 below.

However, the SIR for any one subcarrier calculated through Equation 3 cannot represent the SIR of the entire broadband channel composed of a plurality of subcarriers. Accordingly, there is a need for a method for obtaining an SIR that can represent a channel composed of a plurality of subcarriers in a frequency selective environment. Hereinafter, a representative SIR of a channel composed of a plurality of subcarriers is referred to as an effective SIR (SIR _eff ).

Methods of obtaining effective SIR (SIR _eff ) include quasi-static method, Convex method, Shannon method, and Exponential Effective SIR Mapping (EESM) method. The effective SIR is a function value of each subcarrier SIR as an input, and can be expressed as shown in Equation 4.

In Equation 4, SIR _i represents the SIR of the i th subcarrier among the N subcarriers.

In the embodiment of the present invention, both the above-described aeration abandonment condition and the aforesaid abandonment condition use the effective SIR measured by Equation 4.

The effective SIR is an SIR representing all subcarriers constituting a channel that transmits data, not the SIR of any one subcarrier, so that an accurate SIR can be provided in a frequency selective channel environment, thereby determining transmission abandonment conditions and reception abandonment conditions. To ensure reliability. In addition, in an embodiment of the present invention, since the sequence number assumes the priority, each terminal can identify a link having a higher priority than itself.

Hereinafter, a distributed scheduling process in a direct communication method between terminals according to an embodiment of the present invention will be described in detail.

FIG. 11 is a conceptual diagram illustrating a measurement of a reception abandon condition using RTS in a process of transmitting / receiving traffic according to an embodiment of the present invention. 12 is a conceptual diagram for explaining measurement of abandonment conditions using CTS in a traffic transmission / reception process according to an embodiment of the present invention.

11 and 12, in an environment in which terminal A 1110 and terminal B 1120 form a link AB, and terminal C 1130 and terminal D 1140 form a link CD, the receiving terminal D In operation 1140, a reception abandonment condition is tested using an RTS signal (ie, a sequence transmitted using an RTS resource) transmitted by the terminal A 1110 having a higher priority than itself.

When the receiving terminal D 1140 determines that the reception is impossible due to the interference caused by the link AB having a higher priority than itself as a result of testing the abandonment condition, the receiving terminal D 1140 abandons the CTS transmission, waits for the next traffic slot, and then waits for the next traffic slot. Do the same in. Here, the RTS signals transmitted from the terminal A 1110 and the terminal C 1130 are transmitted at a direct power level to support the reception terminal D 1140 to measure a reception abandonment condition.

On the other hand, as shown in FIG. 12, when the terminal B 1120 satisfies the reception abandonment condition because the effective SIR is sufficiently high, the reception terminal B 1120 uses inverse echo power using subcarriers allocated to the CTS region. By transmitting the sequence with power, the terminal A 1110 having the same CID transmits a response (CTS) to the RTS, and supports the transmission abandonment condition for the transmitting terminal C 1130 having a low priority. In this case, the receiving terminal B 1120 uses a ZC sequence having the same cyclic shift as the transmitting terminal A 1110 having the same CID.

That is, the terminal B 1120 is the reverse power of the direct power transmitted from the terminal A 1110 K / P _A | h _AB | Transmitting power of ² (where K is a constant value), the lower priority terminal C 1130 transmits K | h _BC | ² / P _A | h _AB | Will receive ^two powers. Here, since K and P _C are values known to the terminal C 1130, the terminal C 1130 may measure the transmission abandonment condition.

The terminal C 1130 does not perform any further procedure for allocating resources unless the effective SIR that is a condition for giving up a transmission is high enough.

As described above, the transmission abandonment condition and the reception abandonment condition allow a terminal having higher priority than itself to realize distributed resource allocation which enables the recycling of radio resources due to spatial separation without causing communication interference due to interference. .

If both the abandonment condition and the abandonment condition are satisfied, the transmitting terminal (pager terminal) and the receiving terminal (page terminal) may use resources in the current traffic slot.

13 is a flowchart illustrating a traffic transmission / reception procedure according to an embodiment of the present invention.

Referring to FIG. 13, the transmitting terminal 1310 transmits an RTS signal to the receiving terminal 1320 (S1301), and the receiving terminal 1320 receives the abandon condition based on the RTS signal transmitted from the transmitting terminal 1310. To judge. When the reception terminal 1320 satisfies the reception abandonment condition, the reception terminal 1320 transmits the CTS signal to the transmission terminal 1310 (S1303), and the transmission terminal 1310 based on the CTS signal received from the reception terminal 1320. To judge.

When the transmitting terminal 1310 satisfies the abandonment condition, the receiving terminal 1320 transmits a pilot signal to determine the AMC by measuring the channel (S1305), and receives a CQI from the receiving terminal 1320 (S1307). In step S1309, data is transmitted. Here, even if the transmitting terminal 1310 occupies a data slot once, the resource cannot be continuously used in the next data slot, and if it is necessary to use the data slot, the same procedure is repeated for each data slot.

The receiving terminal 1320 transmits an ACK to the transmitting terminal 1310 according to the data received from the transmitting terminal 1310, and the transmitting terminal 1310 receives the ACK signal transmitted from the receiving terminal 1320 (S1311). ).

Meanwhile, in the traffic transmission / reception procedure illustrated in FIG. 13, the reception terminal 1320 may measure a reception power of a pilot signal transmitted by the transmission terminal 1310 to know a result of a test for abandonment condition of the transmission terminal 1310. That is, the receiving terminal 1320 continues the following procedure when the received power of the received pilot signal is greater than or equal to a predefined value, and does not transmit the CQI when the received power of the pilot signal is smaller than the predefined value. Can be.

In this case, when a PN sequence mapped to a CID in a one-to-one manner is used as a pilot signal, the reception terminal 1320 can more accurately measure the pilot signal using a correlation function. Infer test results more accurately.

14 is a conceptual diagram illustrating a paging and connection scheduling process according to an embodiment of the present invention.

First, the paging process 1410 includes a CID broadcast 1411, a paging request 1412, and a paging response 1413, and all of the CID broadcast 1411, paging request 1412, and paging response 1413 processes. Using a plurality of subcarriers, a plurality of sequences may be mapped to the same resource consisting of a plurality of subcarriers and transmitted simultaneously. Therefore, a plurality of terminals can use the same resource at the same time.

In detail, the transmitting terminal generates a CID by using an ID of a receiving terminal for establishing a D2D connection as an input of a hash function, and selects a PN sequence mapped one-to-one to the generated CID. Meanwhile, all terminals using the CID must transmit the PN sequence corresponding to the CID being used by using the CID broadcast resource.

The transmitting terminal receives the PN sequence transmitted from another terminal in the CID broadcast 1411 section, and determines whether to occupy the CID generated by the transmitting terminal based on the received PN sequence.

When the CID generated by the transmitting terminal is not occupied, the transmitting terminal transmits the PN sequence using a paging request resource composed of a plurality of subcarriers. Here, since the paging request period 1412 can be used by the CDMA method, multiple transmitting terminals can use the same paging request period at the same time.

The receiving terminal checks whether it is called during the paging request 1412 period, and if it is determined that the calling terminal is called, transmits the same PN sequence to the transmitting terminal using the paging response resource, and the transmitting terminal is the receiving terminal. Receives the PN sequence transmitted from the paging response interval 1413.

Traffic transmission and reception 1420 includes connection scheduling 1421, pilot 1422, CQI 1423, data 1424, and ACK 1425.

The connection scheduling process 1421 includes an RTS 1441-1 and a CTS 1421-2. In the RTS1421-1 process, a sequence corresponding to a CID is mapped and transmitted to an RTS section including a plurality of subcarriers. Here, since the ZC sequence to which the cyclic shift is applied is very easy for channel estimation, even when a plurality of terminals simultaneously transmit different cyclic shifted identical ZC sequences in the RTS interval, the receiving terminal selects a channel for each subcarrier and for each transmitting terminal. Can be measured separately.

On the other hand, when the reception terminal satisfies the abandonment condition shown in Equation 2, the receiving terminal transmits a cyclic shifted ZC sequence corresponding to its CID by using the resources of the CTS 1421-2.

The transmitting terminal can measure the cyclic shifted ZC transmitted by the receiving terminal using the CTS 1421-2 section by dividing a channel for each subcarrier and each terminal, and using the equation 4 for the SIR values measured for each subcarrier. To calculate an effective SIR and determine whether to perform the next step.

If it is determined that the calculated effective SIR value satisfies the abandonment condition, the transmitting terminal transmits a pilot signal in the pilot section 1422.

Thereafter, when the transmitting terminal receives the CQI 1423 from the receiving terminal in response to the pilot signal, the transmitting terminal transmits data 1424 and receives the ACK 1425 signal in response to the data transmission from the receiving terminal.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. It will be possible.

10: first base station 11: terminal 1
12: terminal 2 13: terminal 3
14: terminal 4 15: terminal 5
20: second base station 21: terminal 6
310: discovery slot 330: paging slot
331: CID broadcast 332: Paging request
333: Paging Response 350: Traffic Slot
351 connection scheduling 352 pilot
353: CQI 354: data
355: ACK 510: pager terminal
520: page terminal 530: adjacent terminal
610: pager terminal 620: pager terminal
710: terminal A 720: terminal B
730: terminal C 740: terminal D
810: terminal A 820: terminal B
830: terminal C 840: terminal D
850: terminal E 860: terminal F
910: connection scheduling 911: RTS
913: CTS 1010: terminal G
1020: terminal H 1030: terminal I
1040: terminal J 1050: terminal K
1110: terminal A 1120: terminal B
1130: terminal C 1140: terminal D
1310: transmitting terminal 1320: receiving terminal
1410: paging slot 1411: CID broadcast
1412: Paging Request 1413: Paging Response
1420: traffic slot 1421: connection scheduling
1421-1: RTS 1421-2: CTS
1422: Pilot 1423: CQI
1424: data 1425: ACK

Claims (14)

Generating a connection ID (CID) for direct communication between terminals using an ID of a specific terminal;
Selecting a sequence corresponding to the CID; And
And transmitting the selected sequence using a paging request resource composed of a plurality of subcarriers. The method according to claim 1,
The generating of the CID may include generating the CID as an output of a hash function by using an ID of the specific terminal as an input of a hash function. The method according to claim 1,
The selecting of the sequence corresponding to the CID may include selecting a sequence corresponding to the CID from a sequence set including a plurality of preset PN (Pseudo Noise) sequences. The method according to claim 1,
The direct communication method between terminals may include receiving at least one sequence broadcast from other terminals after selecting a sequence corresponding to the CID; And
And determining whether the generated CID is occupied based on the received at least one sequence. The method of claim 4,
Transmitting the selected sequence using a paging request resource composed of a plurality of subcarriers,
If the generated CID is occupied by another terminal, wait until the next paging segment, and if the generated CID is not occupied in the next paging segment, the selected sequence is transmitted using a paging request resource. Direct communication method. The method according to claim 1,
In the direct communication method between terminals, the selected sequence is transmitted by using a paging request resource composed of a plurality of subcarriers.
Receiving at least one sequence transmitted from at least one other terminal in a paging response interval;
Measuring reception power of a sequence corresponding to the generated CID among the at least one received sequence; And
And determining that a paging response has been received when the measured received power is equal to or greater than a preset threshold. In the direct communication method between terminals performed in the transmitting terminal requesting a D2D communication connection,
Mapping a sequence corresponding to the generated CID to a transmission request resource composed of a plurality of subcarriers and transmitting a transmission request signal (RTS);
Determining whether a condition for giving up a transmission is satisfied based on a transmission allowed signal (CTS) received from a receiving terminal; And
A direct communication method between terminals comprising transmitting a pilot signal when a condition for abandoning transmission is satisfied. The method of claim 7,
The determining of whether the transmission abandonment condition is satisfied may include receiving a sequence mapped to a plurality of subcarriers as the transmission permission signal;
Measuring channel quality considering all of the plurality of subcarriers; And
And determining that the transmission abandonment condition is satisfied when the measured channel quality is equal to or greater than a preset threshold. The method according to claim 8,
Measuring the channel quality
And measuring an effective SIR representing an SIR (Signal to Interference Ratio) of each of the plurality of subcarriers. The method of claim 7,
The transmitting of the pilot signal may include transmitting a sequence corresponding to the CID as a pilot signal. In the direct communication method between the terminals performed in the receiving terminal is requested to connect the D2D communication,
Receiving a transmission request signal (RTS);
Determining whether an abandonment condition is satisfied based on the received transmission request signal; And
And transmitting a transmission allowance signal (CTS) by mapping a sequence corresponding to the generated CID to a plurality of subcarriers when the reception abandonment condition is satisfied. The method of claim 11,
Determining whether the reception abandonment condition is satisfied
Measuring channel quality considering all of a plurality of subcarriers constituting the received transmission request signal; And
And determining that the reception abandonment condition is satisfied when the measured channel quality is equal to or greater than a preset threshold. The method of claim 12,
Measuring the channel quality
And measuring an effective SIR representing an SIR (Signal to Interference Ratio) of each of the plurality of subcarriers. The method of claim 11,
In the direct communication method between the terminals, after transmitting the transmission permission signal (CTS),
Receiving a pilot signal; And
And transmitting the channel quality indicator only when the received power of the received pilot signal is greater than or equal to a preset threshold.

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