KR20120061313A - Adaptive Beam based Communication System and Multi-hop Relay Transmission Method Thereof - Google Patents

Abstract

PURPOSE: An adaptive beam based communication system and multi-hop relay transmission method are provided to increase the capacity of a communication system by transmitting data to a target vehicle through a multi-hop transmission method. CONSTITUTION: Infrastructure schedules a target vehicle which transmits data. A communication state of the target vehicle is determined(S120). The target vehicle receives the data through a directing transmission method which directly transmits the data or a multi-hop transmission method according to determination results. The multi-hop transmission method transmits the data to a relay vehicle selected from other vehicles. The relay vehicle transmits the data to the target vehicle. The relay vehicle is existed within a service area of the infrastructure and is not scheduled.

Description

Adaptive Beam based Communication System and Multi-hop Relay Transmission Method Thereof}

The present invention relates to an adaptive beam-based communication system and a multi-hop relay transmission method, and more particularly, multi-hop transmission through a relay vehicle for a vehicle having a poor channel state with an infrastructure due to an obstacle or other vehicle nearby. Adaptive beam-based communication system and its multi-hop relay that can increase the channel capacity but maximize the overall performance and efficiency of the communication system by selecting the optimal relay vehicle and allocating its resources in consideration of interference with surrounding vehicles. It is to provide a transmission method.

Recently, the problem facing Telematics / ITS is to satisfy the requirements of the communication technology that can transmit and receive valid and appropriate information to the vehicle or the surrounding vehicle in urgent situation in order to improve the safety and traffic flow of the vehicle and the driver. To this end, various types of communication technologies have been developed and applied.

The representative among them is a V2I (Vehicle to infrastructure) communication system in which an infrastructure such as a roadside device provides various information and services to a vehicle by wireless communication, and information and services are transmitted and received through wireless communication between vehicles. V2V (Vehicle to Vehicle) communication system.

In the past, these communication systems use a wireless communication method using omni-directional antennas. However, in recent years, unnecessary communication resources are prevented by providing information through an adaptive beam generated in consideration of the placement position and the moving speed of a receiving vehicle. An adaptive beam-based beam division multiple access (BDMA) scheme is used to maximize the capacity of a communication system.

However, since the V2I communication system has a large relative speed between the infrastructure and the vehicle, the connection time between the vehicle and the infrastructure is not only very limited. Due to this, there is a problem that a vehicle in which a state of a communication channel is not good occurs.

In order to solve this problem, a method of using a multi-hop transmission method may be considered through a relay vehicle relaying between the infrastructure and the receiving vehicle. However, in this case, the relay may not be easily selected due to the high speed mobility of the vehicle. If the vehicle is incorrectly selected, there is a problem in that the capacity of the communication system is further reduced.

On the other hand, even in the case of the V2V communication system, the network topology changes rapidly due to the fast moving speed of the vehicle and there are no central nodes such as infrastructure. It is difficult to select an optimal route in multi-hop transmission.

In addition, in the case of the V2V communication system, since the vehicle broadcasts an emergency message to neighboring vehicles, the communication is not only disconnected due to flooding of duplicate messages, but also wastes resources for transmission of the same data. Another problem is that the capacity of the system is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is a communication scheme in which V2I communication and V2V communication coexist within a service coverage of an infrastructure in a BDMA adaptive beam-based communication system (hereinafter, In the case of the target vehicle in which the communication channel state with the infrastructure is not good by applying 'V2V2I communication'), the infrastructure is connected to the target vehicle by a multi-hop transmission method (using V2I communication and V2V communication) through a relay vehicle. An object of the present invention is to provide an adaptive beam-based communication system and a multi-hop relay transmission method capable of improving the capacity of a communication system by transmitting data.

In addition, another object of the present invention is to select the optimal relay vehicle and its transmission power in consideration of the interference between the infrastructure and other target vehicle performing V2I communication when transmitting data to the target vehicle using the relay vehicle as described above. An object of the present invention is to provide an adaptive beam-based communication system and a multi-hop relay transmission method capable of maximizing the capacity of a communication system.

In order to achieve the above object, the multi-hop relay transmission method of the adaptive beam-based communication system according to the present invention, the multi-hop relay transmission method of the adaptive beam-based communication system using a beam split multiple access method, the infrastructure is A first step of scheduling a target vehicle for transmitting data; and a direct transmission in which an infrastructure directly transmits data to the target vehicle according to the determination result and determines a communication state of the target vehicle, or among vehicles having different infrastructures. The purpose of the multi-hop transmission by transmitting data to the selected relay vehicle (hereinafter referred to as 'first transmission') and transmitting the data received by the selected relay vehicle to the target vehicle (hereinafter referred to as 'second transmission'). A second step of transmitting data to the vehicle, wherein the selected relay vehicle is within a service area of the infrastructure and the first Characterized in that the vehicle j is not scheduled in the step.

In addition, the second step may be performed by: C _i ^D , which is the channel capacity of the vehicle i, when the direct transmission is performed, and vehicle i, when the multi-hop transmission is performed through each of the vehicles j, for the vehicle i, the target vehicle to which data is to be transmitted. A second step of obtaining C _ij ^M , which is a channel capacity; A second step of obtaining a relay candidate vehicle in which C _ij ^M is greater than C _i ^{D in} the vehicle j; Obtaining C ^D , which is the capacity of the entire communication system when transmitting directly to the vehicle i, and C ^M, which is the capacity of the entire communication system when transmitting the multi-hop to the vehicle i, for each of the relay candidate vehicles; If there is a vehicle whose C ^M is greater than C ^D among the relay candidate vehicles, step 2-4 of selecting the relay candidate vehicle having the largest C ^M as the relay vehicle of the vehicle i may be included.

In addition, the remaining vehicle except for the vehicle i is composed of a first group to receive data by direct transmission and a second group to receive data by multi-hop transmission, wherein C _i ^D is the first group of the second group. C _i ^D1 obtained using SINR _i ^D1 including interference received by the vehicle i from direct transmission of the first group and first transmission of the second group in the first transmission step, and in the second transmission step of the second group. Vehicle i is the sum of C _i ^D2 obtained using SINR _i ^D2 including interference received from the first transmission of the first group and the second transmission of the second group, wherein C _ij ^M is the first transmission step of vehicle i; C _ij ^M1 obtained using SINR _ij ^M1 including interference received from the first group of the first group and the first group of the second group, and vehicle i directly transmits the first group and the second group in the second stage of transmission. is the SINR _ij ^M2, including receiving interference from the second transmission of the group And it characterized by a small value of C _ij ^M2 obtained.

In the case of obtaining C _ij ^M in step 2-1, after calculating SINR _ij ^M1 and C _ij ^M1 for vehicle j, the transmission power of the vehicle j when SINR _ij ^M1 is equal to SINR _ij ^M2 is calculated. If the calculated transmission power is less than or equal to the maximum transmission power of the preset vehicle j, the SINR _ij ^M2 and C _ij ^M2 are equal to SINR _ij ^M1 and C _ij ^M1 , respectively. Otherwise, the transmission power of the vehicle j is SINR _ij ^M2 and C _ij ^M2 at the maximum transmission power are obtained.

In addition, when the transmission power calculated in step 2-1 is less than or equal to the maximum transmission power of the preset vehicle j, the transmission power of the vehicle j is assigned as the calculated transmission power, otherwise the transmission power of the vehicle j Is assigned to the maximum transmission power.

In addition, in step 2-3, the C ^D and the C ^M are the sum of the channel capacity of the vehicle i and the channel capacity of the remaining target vehicle, respectively, and the target vehicle that is not determined whether it is direct transmission or multi-hop transmission among the remaining target vehicles. Is calculated by channel capacity in case of direct transmission.

In addition, when there is no relay candidate vehicle in step 2-2 or when there is no vehicle whose C ^M is greater than C ^D among the relay candidate vehicles in step 2-4, data is transmitted to the vehicle i by direct transmission. Characterized in that.

In order to achieve the above object, the adaptive beam-based communication system according to the present invention, in the adaptive beam-based communication system for performing communication between the infrastructure and the vehicle or vehicle-to-vehicle communication using a beam split multiple access method, The vehicle comprises at least one target vehicle in or out of or in the service area of the infrastructure and at least one relay vehicle in the service area of the infrastructure, the infrastructure transmitting data According to the communication state of the target vehicle scheduled to transmit data directly to the corresponding target vehicle or to the relay vehicle (hereinafter, 'first transmission') and the data corresponding to the object received by the relay vehicle Transmit to the vehicle (hereinafter referred to as 'second transmission'), but the infrastructure It is characterized in that the relay vehicle mobilized for multi-hop transmission is selected from among other vehicles not scheduled as the target vehicle for transmitting the data.

The infrastructure may further include a first channel capacity C _i ^D of the corresponding target vehicle when data is directly transmitted to the target vehicle and a second channel capacity of the target vehicle corresponding to multi-hop transmission through the relay vehicle. C _ij ^M ), respectively, and obtain a relay candidate vehicle in which the second channel capacity C _ij ^M is greater than the first channel capacity C _i ^{D among the} relay vehicles, and directly apply data to the corresponding target vehicle. Obtaining the first system capacity (C ^D ) of the entire communication system and the second system capacity (C ^M ) of the entire communication system for a multi-hop transmission to a relay candidate vehicle during transmission, and obtaining the relay candidate. If there is a vehicle having a second system capacity C ^M greater than the first system capacity C ^D among the vehicles, the relay candidate vehicle having the largest second system capacity C ^M is the relay vehicle of the corresponding target vehicle. To choose The.

In addition, the remaining target vehicle excluding the corresponding target vehicle comprises a first group receiving data by direct transmission and a second group receiving data by multi-hop transmission, and the infrastructure includes a first group of the second group. In the transmitting step, the third vehicle capacity C _i ^D1 is obtained in consideration of the interference received from the direct transmission of the first group and the first transmission of the second group, and the corresponding vehicle is obtained in the second transmission step of the second group. the purpose of the vehicle in consideration of the received interference from the second transmission of the direct transmission of the first group and the second group to obtain a fourth channel capacity (C _i ^D2), the third channel capacity (C _i ^D1) and the first to The sum of the four channel capacitances C _i ^D2 may be determined as the first channel capacitance C ^D.

In addition, the remaining target vehicle excluding the corresponding target vehicle comprises a first group receiving data by direct transmission and a second group receiving data by multi-hop transmission, and the infrastructure includes In the first transmission step, the fifth channel capacity C _ij ^M1 is obtained in consideration of interference received from the direct transmission of the first group and the first transmission of the second group, and the first channel is transmitted in the second transmission step of the corresponding vehicle. The sixth channel capacity C _ij ^M2 is obtained by considering interference received from the direct transmission of the group and the second transmission of the second group, and the fifth channel capacity C _ij ^M1 and the sixth channel capacity C _ij ^{M2 are obtained} . The smaller value is determined as the second channel capacity.

Further, the first system capacity and the second system capacity are respectively the sum of the channel capacity of the corresponding target vehicle and the channel capacity of the remaining scheduled vehicle except for the corresponding target vehicle, and the infrastructure is the remaining target vehicle. The target vehicle, which is not determined whether direct transmission or multi-hop transmission, is determined by channel capacity in the case of direct transmission.

In addition, the infrastructure transmits data by direct transmission to the corresponding target vehicle when there is no relay candidate vehicle or when there is no vehicle having a second system capacity larger than the first system capacity among the relay candidate vehicles. It is done.

As described in detail above, the multi-hop relay transmission method and the communication system using the adaptive beam-based communication system according to the present invention are compared with the infrastructure by comparing the channel capacity and the communication system capacity with and without using a relay vehicle. In the case of a target vehicle having a poor communication channel state, the infrastructure has an advantage of increasing the capacity of the communication system by transmitting data to the target vehicle in a multi-hop transmission method through a relay vehicle.

In addition, the multi-hop relay transmission method and a communication system using the same according to the present invention is optimal relay vehicle in consideration of the interference between the infrastructure and other target vehicle for V2I communication when transmitting data to the target vehicle using the relay vehicle By selecting the transmission power and its power, the capacity of the communication system can be increased to maximize the performance and efficiency of the communication system.

1 is a diagram illustrating a concept of a beam splitting multiple access technique applied to an adaptive beam based communication system according to the present invention;
2 and 2b are diagrams illustrating different applications in which a multi-hop relay transmission scheme is applied to a communication system according to an embodiment of the present invention, respectively.
3 illustrates an example of direct transmission and multi-hop relay transmission that can be made in a communication system according to an embodiment of the present invention;
4 is a view comparing resource usage of each transmission method shown in FIG. 3;
5 is a view showing a channel model of each communication in a communication system according to an embodiment of the present invention;
6 is a graph showing the antenna gain in dB units when θ _3dB = 70 ° in the channel model of FIG. 5;
7 illustrates a channel environment of multi-hop communication in a communication system according to an embodiment of the present invention;
8 is a diagram showing an interference model in the multi-hop communication shown in FIG.
9 is a flowchart illustrating a multi-hop relay transmission method applied in a communication system according to an embodiment of the present invention.

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

In the present embodiment, for convenience of description, a case in which a terminal constituting a communication system is a vehicle will be described as an example, but the present invention is not limited thereto, and the terminal may be applied to a portable communication terminal such as an iPad or a mobile phone.

First, in the beam splitting multiple access (BDMA) scheme applied in the communication system according to the present invention, an infrastructure (or base station) divides an antenna beam according to a location of a terminal (vehicle in this embodiment), thereby allowing terminals to be multiplexed. The beam splitting multiple access method is an adaptive beam having a beam pattern directed to a specific position through beam forming using a phased array antenna. Can be implemented by creating

In this case, each of the terminals is connected to multiple access by applying a conventional multiple access technology such as TDMA, FDMA, CDMA, OFDMA, etc. In this embodiment, it is configured to multiplex using the TDMA scheme as an example.

As shown in FIG. 1, in the communication system according to the present invention, when the respective vehicles 20 exist at different angles from the infrastructure 10 such as a base station, the infrastructure 10 faces at different angles. The beam is transmitted to transmit data to several vehicles 20 at the same time.

At this time, the infrastructure 10 updates the beam in consideration of the speed and the direction (or the position) of the moving vehicle 20. As a method of updating the beam, as shown in FIG. (BWA, Beam Width Adaptation), a beam tracking method (BT, Beam Tracking) and a mixture of the two (BWAT, Beam Width Adaptation and Tracking) method of any one is used.

The beam width adaptation method (BWA) is a method of supporting the mobility of the vehicle 20 by varying the beam width according to the speed of the vehicle 20. When the speed of the vehicle 20 is fast, a wide beam width is allocated and the speed of the vehicle 20 is increased. When the slow speed is assigned, the narrow beam width can be allocated so that the communication service can be continuously supported even when the vehicle 20 is moved without knowing the exact position of the vehicle 20. Therefore, the feedback amount of the position and speed information of the vehicle 20 can be minimized. have.

In addition, the beam tracking method BT is a method of varying the direction of the beam according to the movement of the vehicle 20. The disadvantage of having to feed back the exact position information of the vehicle to the infrastructure 10 as the vehicle 20 moves. However, there is an advantage that the beam management is easy because the beam width is constant.

In addition, the mixing method BWAT combines the advantages of the above-described beam width adaptation method BWA and beam tracking method BT to simultaneously vary the width and direction of the beam according to the speed of the vehicle 20.

As described above, the communication system according to the present invention can easily and easily change the position, number, and beam width of beams according to the communication environment of the vehicle 20. Not only can it respond quickly, but it also has the advantage of maximizing the capacity of the communication system by improving the efficiency of use of communication resources.

2 and 2b are diagrams illustrating different application examples in which multi-hop relay transmission (hereinafter, referred to as 'multi-hop transmission') is applied to a communication system according to an embodiment of the present invention.

The communication system according to the present embodiment is based on the above-described BDMA scheme, but the communication between the vehicles (that is, the V2I communication) together with the communication between the infrastructure and the vehicle (that is, the V2I communication) within the service coverage area of the infrastructure 10. V2V communication) is also constituted by the V2V2I communication method.

In addition, the communication system, as described below, according to the channel state of the V2I communication, either the method of transmitting the data directly to the destination (destination) vehicle and the method of transmitting using a multi-hop transmission method through the relay vehicle In this case, V2I communication is performed between the infrastructure and the target vehicle or the relay vehicle, and V2V communication is performed between the relay vehicle and the target vehicle.

First, FIG. 2A illustrates a case in which the total capacity of the communication system is increased by applying a multi-hop transmission method to the communication system according to the present embodiment.

In the V2V2I communication system applied in the present embodiment, due to the high-speed mobility of the vehicle, the V2I channel, which is a communication channel between the infrastructure and the vehicle, is affected by a large Doppler effect. The more severe the lower the received signal strength of the vehicle may not satisfy the QoS of the vehicle.

However, in the case of the V2V channel, which is a communication channel between the vehicle and the vehicle, since the vehicles are moving in the same direction, the relative speed is smaller than that of the V2I channel, and thus the influence of the Doppler effect is relatively small.

As an example, attempting to transmit data to a relatively fast moving vehicle (eg, a passenger car) 20a at 70 km / h in a second lane (eg, a normal lane) in FIG. 2A may result in an infrastructure 10 and a vehicle 20a. The channels between) are highly influenced by the Doppler effect due to the high speed of the vehicle.

On the other hand, a relatively slow moving vehicle (such as a bus) 20b of 40 km / h in the first lane (for example, a bus-only lane) is located relatively close to the infrastructure 10 so that the vehicle 20b is located. Multi-hop transmission using as a relay enables transmission through a better channel because the relative speed is low and the signal attenuation effect due to path-loss is small.

As such, when the multi-hop transmission is performed using the relay vehicle 20b having a low relative speed, an effect of increasing the capacity of the communication system can be obtained.

However, in the process of selecting the relay vehicle 20b, if the vehicle having a distance from the infrastructure 10 is greater than the target vehicle 20a as the relay vehicle 20b, the path loss increases and the performance of the system decreases. Since there is a possibility, the method of selecting the optimum relay vehicle 20b in consideration of this is required.

Next, FIG. 2B is a diagram illustrating a case in which a service coverage area of an infrastructure is expanded by applying a multi-hop relay transmission method to a communication system according to the present embodiment.

In general, since the signal transmitted from the infrastructure decreases in strength as the distance from the infrastructure increases, there may be a shaded area where the signal reaches weakly in the coverage area of the infrastructure.

The shaded area appears mainly at the boundary portion of the infrastructure coverage area, and in the out of coverage area, the strength of the received signal is too weak to receive the signal properly.

In addition, in V2I communication, communication between the vehicle and the infrastructure can be performed only when the vehicle is within the coverage of the infrastructure. In general, since the speed of the vehicle is high, the time for the vehicle to stay within the coverage of the infrastructure is very limited, so that the V2I communication is properly performed. You won't lose.

In such cases, multi-hop transmission using a relay vehicle may have the effect of expanding the limited coverage area of the infrastructure, thereby increasing the time that the vehicle is connected to the infrastructure, thereby further increasing the vehicle and the infrastructure. Since a lot of data can be exchanged, it is possible to improve the performance of the communication system.

Figure 2b shows an example of increasing the coverage of the infrastructure by using a multi-hop relay transmission scheme as described above.

First, the vehicle 20a that tries to enter the coverage out of the coverage of the infrastructure 10 is connected to the infrastructure 10 by multi-hop transmission through the relay vehicle 20b in the coverage, and the infrastructure 10 The coverage area of the infrastructure 10 is extended to the vehicle 20a 'that exits the coverage of the antenna 10 by extending the connection with the infrastructure 10 by multi-hop transmission through the relay vehicle 20b' existing in the coverage. You can do it.

As described above, in order to expand the coverage area of the infrastructure 10 through the multi-hop reel transmission scheme, the relay vehicles 20b and 20b 'must exist near the coverage area of the infrastructure 10. As described above, a method for selecting appropriate relay vehicles 20b and 20b 'is required.

As described above, the communication system according to the present embodiment uses a multi-hop relay transmission method to increase the capacity of the adaptive beam-based V2V2I communication system, and the corresponding V2I communication using the relay vehicle to maximize the capacity of the communication system. The multi-hop relay transmission method is applied to select the optimal relay vehicle and allocate its resources in consideration of interference with other V2I communication.

Hereinafter, a multi-hop relay transmission method applied to the adaptive beam-based V2V2I communication system according to the present embodiment will be described in detail with reference to a specific example.

First, for convenience of description, the following matters will be assumed for the communication system according to the present embodiment.

(Assumption about service environment of V2V2I communication system)

Assumption 1 The infrastructure assumes a base station (BS) used in an existing cellular network or a long-range broadband network (e.g., IEEE 802.16 standard).

Assumption 2 It is assumed that both the infrastructure and the vehicle are equipped with a BDMA antenna capable of adaptively forming a beam.

Assumption 3 It is assumed that all vehicles are equipped with an antenna on the rooftop and move at a constant speed.

(Assumption about service scenario of V2V2I communication system)

[Assumption 4] Assume that all vehicles are equipped with GPS and periodically transmit vehicle information messages including their location, speed, and direction to the infrastructure so that the infrastructure can know the location of the vehicle and estimate the channel status. do.

[Assumption 5] In V2V communication, it is assumed that channels between vehicles can be estimated because V2V slots periodically transmit and receive control messages.

FIG. 3 is a diagram illustrating an example of direct transmission and multi-hop relay transmission that can be made in a communication system according to an embodiment of the present invention. FIG. 4 is a view comparing resource usage of each transmission method shown in FIG. to be.

In the present embodiment, for convenience of description, a single cell V2V2I communication system in which one infrastructure exists and a plurality of vehicles exist within the coverage area of the infrastructure is considered.

In addition, the communication system operates in a TDMA scheme as an example, selects a target vehicle to provide a service through scheduling in an infrastructure at every time slot, and relay equipment and resources appropriate for the scheduled target vehicle. Selecting an allocation maximizes the capacity of the communication system.

As shown in FIG. 3, the multi-hop relay transmission method uses a two-hop relay transmission method using one relay vehicle 20b as an example.

In addition, in the present embodiment, when the infrastructure 10 transmits data through multi-hop communication, the relay vehicle 20b decodes a signal received from the infrastructure 10 and transmits the DF (decoded) to the destination vehicle 20a. As an example, it is assumed that the relay vehicle 20b can always decode the signal transmitted from the infrastructure 10 accurately.

In addition, hereinafter, direct transmission of data from the infrastructure 10 to the target vehicle 20a is referred to as 'direct transmission' and communication at that time is defined as 'direct V2I communication', and the relay vehicle 20b is used. In this case, the transmission process from the infrastructure 10 to the relay vehicle 20b and the transmission process from the relay vehicle 20b to the target vehicle 20a are referred to as 'first transmission' and 'second transmission', respectively. Communication is defined as 'multi-hop first communication' and 'multi-hop second communication', respectively.

In addition, since the BDMA-based V2V2I communication system applied in the present embodiment uses the TDMA method as an example as described above, when transmitting data in multi-hop transmission, one time slot is assigned to multi-hop first communication and multi-hop. The second communication is used separately.

That is, as shown in FIG. 4, when the infrastructure 10 directly transmits data to the target vehicle 20a without using the relay vehicle 20b (that is, direct V2I communication), one time slot is allocated. In contrast, when the infrastructure 10 uses the relay vehicle 20b to transmit data to the target vehicle 20a using multi-hop transmission, one time slot is allocated to the infrastructure 10 and the relay vehicle 20b. This will be used separately.

At this time, if the ratio of timeslots used by the infrastructure 10 to transmit to the relay vehicle 20b is α, the ratio of timeslots used by the relay vehicle 20b to transmit to the target vehicle 20a is 1-. α becomes.

The value of α is preferably set in consideration of the communication environment. In this embodiment, the amount of resources used by the infrastructure 10 and the relay vehicle 20b in multi-hop transmission using a value of α = 0.5 as an example. The amount of resources used is set equal (ie half of the timeslot resources used by the infrastructure for direct transmission).

In addition, among the vehicles existing in the coverage area of the infrastructure 10 in any timeslot t, there are a total of V target vehicles 20a scheduled by the infrastructure 10, and the set is V (t) = {1. , ..., V}.

On the other hand, in timeslot t, there are a total of R vehicles present in the coverage area of infrastructure 10 but not scheduled by the infrastructure, and the set is defined as R (t) = {1, ..., R}. Let's do it.

At this time, the set R (t) is a set of relay vehicle candidates that can be used as the relay vehicle 20b of the vehicle included in the set V (t), the vehicle included in the set V (t) and the set R (t) We use i and j as indices, respectively.

Meanwhile, the maximum number of beams that can be formed in the infrastructure 10 is not only limited by the number of antennas and transmission power of the infrastructure, but also when the number of beams formed by the infrastructure 10 is too large, the interference between the beams becomes severe. Therefore, the number of beams cannot be increased continuously.

Therefore, in this embodiment, the infrastructure 10 limits the number of beams that can be simultaneously formed in one time slot to B, and defines the maximum transmission power of the infrastructure 10 and the vehicle as P and P _v , respectively.

At this time, the transmission power of the beam formed in the vehicle scheduled to the time slot t by the infrastructure 10 is equally allocated to p (t). Therefore, when the maximum number of beams is formed in one time slot, each beam The transmission power p (t) = P / B for.

In addition, when the relay vehicle of the target vehicle is determined in the communication system according to the present embodiment, the relay vehicle 20b transmits the data received from the infrastructure through the multi-hop first communication to the target vehicle 20a through the multi-hop second communication. You must pass it.

In this case, the transmission power of the relay vehicle 20b is defined as p (t) = p _i ^j (t), where p _i ^j (t) is the transmission power of the relay vehicle j (20b) for the target vehicle i. it means.

Meanwhile, each target vehicle 20a included in the set V (t) may receive data from the infrastructure 10 directly through V2I communication according to channel conditions, and transmit multi-hop through the relay vehicle 20b. You can also receive services.

Therefore, if the target vehicle 20a receives data through the relay vehicle 20b, any target vehicle 20a among the plurality of target vehicles 20a receives a service through multi-hop transmission through some relay vehicle 20b. It should be shown.

For this purpose, in this embodiment, a relay usage indicator matrix A (t) = (a _{i, j} (t)) is defined (where A (t) has a size of V × R). In this case, if the vehicle j included in the set R (t) is assigned to the relay vehicle of the target vehicle i, a _{i, j} (t) has a value of 1, otherwise it has a value of 0.

The transmission power p _i ^j (t) and the relay use indication matrix a _{i, j} (t) of the relay vehicle 20b defined above must satisfy constraints as shown in Equations 1 to 3 below.

------------- [수식 1]

------------- [Equation 1]

------------- [수식 2]

------------- [Equation 2]

------------- [수식 3]

------------- [Equation 3]

Equation 1 is a constraint on transmission power used in the relay vehicle 20b. A vehicle j included in the R (t) not selected as the relay vehicle of the target vehicle i p _i ^j (t) will have a value of zero, if the vehicle j selected by the relay vehicle p _i ^j (t) is 0, It must be larger and smaller than the maximum transmit power P _v that can be used in the relay vehicle.

Further, Equation 2 is a constraint that one target vehicle i can use a maximum of one relay vehicle, and two or more relay vehicles cannot be assigned to each target vehicle i.

In addition, Equation 3 is a constraint that one relay vehicle j must transmit data to at least one target vehicle, and each relay vehicle j cannot transmit data to two or more target vehicles at the same time.

5 is a view showing a channel model of each communication in the V2V2I multi-hop communication system according to the present embodiment, the infrastructure 10 and the target vehicle 20a, the infrastructure 10 and the relay vehicle 20b, the relay vehicle 20b ) And the channel gain between the target vehicle 20a is defined as h _i (t), h _j (t), and h _i ^j (t), respectively.

In this embodiment, the channel gain h _i (t) and h _j (t) between the infrastructure 10 and the vehicle (target vehicle 20a and relay vehicle 20b) are uplink feedback transmitted periodically from the vehicle. (uplink feedback) can be seen by the infrastructure 10, and h _i ^j (t), which is a channel between the target vehicle i 20a and the relay vehicle j 20b, can be estimated through periodic V2V communication. Is reported to the infrastructure (10).

Therefore, it is assumed that the infrastructure 10 knows both channel information between the infrastructure and the vehicle and channel information between the vehicle, and the three channel gains h (t) mentioned above are path-loss models. model and antenna mode are considered at the same time.

In general, the path loss model is expressed as Equation 4 below.

------------------ [수식 4]

------------------ [Equation 4]

는 경로손실지수(path-loss exponent)이고, 상기 K는 상수이다.In this case, l is the distance from the point where the signal is generated to the point to measure the path loss, l ₀ is the reference distance to the antenna far-field,

Is a path-loss exponent and K is a constant.

In addition, the antenna model in the BDMA transmission technology is expressed as Equation 5 below.

------------- [수식 5]

------------- [Equation 5]

At this time, θ is the beam width (beam-width), A _m is a maximum attenuation value, and G _A is to indicate the antenna gain, the maximum attenuation value A _m where the signal is angle, θ _3dB beam direction and the vehicle direction attenuated 3dB It can be represented by Equation 5-1 below.

On the other hand, the first term on the right side of [Equation 5] is a normalized value and the antenna gain G _A which compensates this value to its original value is expressed by Equation 5-2 below.

Therefore, the gain of the antenna model is determined according to the angle θ between the beam direction and the vehicle direction. FIG. 6 is a graph showing antenna gain in dB units when θ _3dB = 70 ° as an example.

----------------- [수식 5-1]

----------------- [Equation 5-1]

----------------- [수식 5-2]

----------------- [Equation 5-2]

FIG. 7 is a diagram showing a channel environment of multi-hop communication in the V2V2I multi-hop communication system according to the present embodiment, and FIG. 8 is a diagram showing an interference model in the multi-hop communication shown in FIG.

Since the communication system according to the present embodiment uses the BS of the existing cellular or long-distance broadband network as the infrastructure 10 as described above, the infrastructure 10 is installed at a higher position than the vehicles 20a and 20b. Away from the road.

Therefore, an obstacle such as a mountain, a building, a surrounding vehicle, or the like may exist between the infrastructure 10 and the target vehicle 20a, and the distance between the infrastructure 10 and the target vehicle 20a is too long to provide a non-line of sight. ) The environment may be formed, and there may be a vehicle having a bad channel situation.

On the other hand, the channel situation is relatively good because a line of sight (LOS) environment is formed between the vehicle and the vehicle, which is relatively close to each other and has little surrounding obstacles.

 In consideration of this, in the present embodiment, as shown in FIG. 7, the channel with the infrastructure 10 is assumed to be NLOS for the target vehicle 20a which is far from the infrastructure 10 or whose channel situation is poor due to surrounding obstacles. It was.

In particular, in the case of a passenger car, since the height of the vehicle is low and the position of the antenna is relatively low, the channel with the infrastructure 10 is more likely to be NLOS. Therefore, when the target vehicle 20a in the NLOS channel environment receives data directly from the infrastructure 10, the strength of the received signal in the target vehicle 20a is weakened.

On the other hand, in the case of a vehicle having a relatively close distance to the infrastructure 10 and having a high antenna position (for example, a bus or a truck), the infrastructure 10 and the LOS channel can be guaranteed. If the target vehicle 20a is close to the channel environment, the channel between the two vehicles may be guaranteed in the LOS environment.

Therefore, when the infrastructure 10 selects the vehicle in the LOS channel environment as the relay vehicle 20b and transmits data to the target vehicle 20a in the NLOS channel environment by multi-hop transmission, the multi-hop in the first communication and multi-hop Since propagation loss in the second communication can be reduced, the strength of the received signal of the target vehicle 20a can be increased.

However, even in this case, it is required to maximize the capacity of the communication system by selecting the optimal relay vehicle 20b and allocating resources in consideration of the interference between the multi-hop communication using the relay vehicle 20b and other V2I communication.

Hereinafter, an interference model that may be considered in the V2V2I multihop communication system according to the present embodiment will be described first, and then an optimal relay vehicle selection and its resource allocation method will be described in detail.

In the interference model considered in the communication system according to the present embodiment, when the infrastructure 10 directly transmits to the target vehicle 20a i as shown in FIG. 8, the direct V2I communication is applied to the other target vehicle 20a. Define the interference as I _i .

In addition, when the infrastructure 10 transmits data in the multi-hop transmission to the target vehicle 20a _i , the interference of the first transmission to the other target vehicle 20a is defined as I _i ¹ , and the second transmission is different. The interference on the target vehicle 20a is defined as I _i ² .

In this case, since the interferences can be obtained by modeling each interference channel using the above-described channel model, a detailed description thereof will be omitted.

In the BDMA-based V2V2I multi-hop relay communication system according to the present embodiment, when the target vehicles 20a scheduled by the infrastructure 10 are determined in one time slot, the infrastructure 10 simultaneously forms a plurality of beams to form the corresponding targets. Data is transmitted to the vehicles 20a, whereby the signal-to-noise interference ratio (SINR) of the received signal of each target vehicle 20a is reduced due to the interference generated between the beams, thereby reducing the capacity of the entire system. Can be.

Therefore, when determining whether to use the relay vehicle 20b, considering the interference between the communication between the infrastructure 10 and the target vehicle 20a, the communication between the infrastructure 10 and the target vehicle 20a can be obtained. There is a need for a method to maximize channel capacity.

To this end, in the present embodiment, the communication of the corresponding target vehicle 20a which performs multi-hop communication based on the interference model described above is the interference received from the communication of the other target vehicle 20a and the communication of the corresponding target vehicle 20a. The optimal relay vehicle 20b is selected in consideration of all the interference on the other target vehicle 20a. The method is largely composed of the following four steps.

1) Calculation of channel capacity when transmitting via direct V2I communication

2) Calculation of channel capacity during transmission through multihop communication

3) Calculate the set of available relay vehicle candidates

4) Optimal relay vehicle selection

That is, first, the channel capacity obtained when data is directly transmitted to the target vehicle 20a by the V2I communication in the infrastructure 10 and the channel obtained when the multi-hop is transmitted using the relay vehicle 20b. Calculate the dose.

At this time, the infrastructure 10 is determined so that the transmission power of the relay vehicle 20b used is also determined when the channel capacity by the multi-hop communication is obtained.

When the channel capacity of the multihop transmission is higher as a result of the calculation, the infrastructure 10 transmits data to the corresponding target vehicle 20a by multihop transmission using the relay vehicle 20b. If not, send it directly to V2I communication.

In addition, when the infrastructure 10 transmits the multi-hop communication using the relay vehicle 20b, the infrastructure 10 selects a vehicle capable of achieving the highest channel capacity among the available relay vehicles 20b as the relay vehicle 20b. Done.

For a more detailed description of the present invention, a method of selecting an optimal relay vehicle 20b for the target vehicle 20a i will be described in detail for each step.

(Step 1) Calculation of Channel Capacity During Direct V2I Communication

In a first step, the infrastructure 10 calculates the channel capacity C _i ^D of the target vehicle 20a i when performing direct V2I communication with the target vehicle 20a i.

To this end, the infrastructure 10 first uses signal to intereference plus noise ratio considering the interference that the target vehicle 20a i receives from other target vehicles 20a using Equations 6 and 7 below. ) Is calculated by dividing the first transmission into the first transmission and the second transmission.

------------ [수식 6]

------------ [Equation 6]

------------ [수식 7]

------------ [Formula 7]

At this time, the interference that the target vehicle 20a i receives from the communication of the other target vehicle 20a l ( l∈ V (t) ) is when the infrastructure 10 transmits the VlI communication directly to the vehicle l and the relay vehicle 20b. Consider all the transmission when the multi-hop communication through the transmission, if the infrastructure 10 transmits directly to the target vehicle (20a) i to the V2I communication, and at the same time to the vehicle l to multi-hop communication and the first transmission of the vehicle l and This is because the interference received by the target vehicle 20a i from the second transmission is different.

That is, the total interference that the target vehicle 20a i receives in the first transmission is the interference received from the direct V2I communication of the other vehicle when the infrastructure 10 transmits the V2I communication directly to the other target vehicle 20a. 6] and the interference from the multi-hop first communication of the other vehicle when the infrastructure 10 transmits the multi-hop communication to the other target vehicle 20a (in [Equation 6] above). Sum of the second term of the denominator).

In addition, the total interference received by the target vehicle 20a i in the second transmission is the interference received from the direct V2I communication of the other vehicle when the infrastructure 10 transmits the V2I communication directly to the other target vehicle 20a. 7] and the interference from the multi-hop second communication of the other vehicle when the infrastructure 10 transmits the multi-hop communication to the other target vehicle 20a (in Equation 7 above). Sum of the second term of the denominator).

Accordingly, the channel capacities C _i ^D1 corresponding to the first transmission of the target vehicle 20a i using SINR _i ^D1 and SINR _i ^D2 of the target vehicle 20a i obtained in Equations 6 and 7 and The channel capacity C _i ^D2 corresponding to the second transmission may be calculated as shown in Equations 8 and 9 below (S100 and S110).

-------------- [수식 8]

-------------- [Equation 8]

-------------- [수식 9]

-------------- [Equation 9]

In addition, by using this, the channel capacity C _i ^D when the infrastructure 10 directly transmits to the target vehicle 20a i through V2I communication is the sum of the channel capacity of the first transmission and the second transmission as shown in Equation 10 below. It may be represented as (S120).

-------------------------- [수식 10]

-------------------------- [Formula 10]

(Step 2) Calculation of Channel Capacity for Multi-hop Transmission

In a second step, when the infrastructure 10 transmits data through multi-hop communication to the target vehicle 20a i through the relay vehicle 20b j, the channel capacity C _ij ^M of the target vehicle 20a i is transmitted. And simultaneously transmit power of the relay vehicle 20b.

The relay vehicle 20b that can be used when the infrastructure 10 performs multi-hop transmission to the target vehicle 20a i is one of the vehicles included in the set R (t), among which the target vehicle 20a i Vehicles having a distance greater than or equal to the critical distance (for example, D) have a large propagation loss in the multi-hop second communication due to the distance from the target vehicle 20a i. The propagation loss of communication can also be large.

Therefore, in the case of selecting the vehicles having a distance greater than or equal to the threshold distance from the target vehicle 20a as the relay vehicle 20b, there is no gain of multi-hop communication. 20A, only the vehicles whose distance from i is less than or equal to the threshold distance are selected to calculate the relay vehicle candidate set R _i (t) of the target vehicle 20a i (S130).

In this case, the threshold distance is preferably set in consideration of the communication environment and radio wave characteristics of the V2I communication and V2V communication of the communication system to which the present invention is applied.

Next, when the relay vehicle 20b j is selected using the following Equations 11 and 12, the SINR considering the interference that the target vehicle 20a i receives from the other target vehicles 20a is first. The calculation is divided into transmission and second transmission.

----------- [수식 11]

----------- [Equation 11]

------------ [수식 12]

------------ [Equation 12]

In this case, the interference received by the target vehicle 20a i from the communication of the other target vehicle 20a l may indicate when the infrastructure 10 transmits the vehicle l directly to the vehicle l through V2I communication and when the multi-hop is transmitted through the relay vehicle 20b. All must be considered.

That is, in the multi-hop first communication of the target vehicle 20a i, the total interference received by the relay vehicle 20b j is transmitted to the other target vehicle 20a when the infrastructure 10 directly transmits to the other target vehicle 20a. Interference received from direct V2I communication (the first term of the denominator in [Equation 11] above), and when the infrastructure 10 transmits the multi-hop transmission to the other target vehicle 20a through the multi-hop first of the other target vehicle It is the sum of the interference received from the communication (the second term of the denominator in [Equation 11] above).

In addition, in the multi-hop second communication of the target vehicle 20a i, the total interference received by the target vehicle 20a i is transmitted directly to the other target vehicle 20a when the infrastructure 10 directly transmits to the other target vehicle 20a. Interference received from the first term of the denominator in [Equation 12] above, and received from the multi-hop second communication of the other target vehicle when the infrastructure 10 transmits the multi-hop transmission to the other target vehicle 20a. Sum of the interference (second term of the denominator in Equation 12 above).

Accordingly, the channel capacities C _ij ¹ corresponding to the first transmission of the target vehicle 20a i using the SINR _ij ¹ and SINR _ij ² of the target vehicle 20a i obtained by the above Equations 11 and 12 The channel capacity C _ij ² corresponding to the second transmission may be calculated as shown in Equations 13 and 14 below (S150).

-------------- [수식 13]

-------------- [Equation 13]

------------- [수식 14]

------------- [Equation 14]

On the other hand, the channel capacity C _ij ^{M when} the infrastructure 10 transmits data to the target vehicle 20a through the relay vehicle 20b is a value when the infrastructure 10 transmits the data directly to the target vehicle 20a i. It is calculated differently from the channel capacity C _i ^D.

The reason for this is that in the case of multi-hop transmission, a communication link having a smaller value among the channel capacities of the first transmission and the second transmission becomes a bottleneck, and the end-to-end channel capacity is multihop-based. This is because it is the minimum value of the two channel capacities of the one communication and the multi-hop second communication.

Therefore, the channel capacity C _ij ^M when the infrastructure 10 transmits data in multi-hop to the target vehicle 20a i can be calculated using Equation 15 below (S200).

----------------- [수식 15]

----------------- [Equation 15]

In the present embodiment, in performing the second step, SINR ( SINR _ij ¹ ) for the first transmission of the target vehicle 20a is first calculated (S150), and then the second transmission of the target vehicle 20a i is performed. SINR ( SINR _ij ² ) for SINR _ij ¹ = The transmission power of the relay vehicle 20b j is determined by making SINR _ij ² satisfied (S160).

Because, as described above, due to the bottleneck of the channel capacity ( C _ij ¹⁾ for the first transmission and the channel capacity ( C _ij ² ) for the second transmission generated in the multi-hop transmission for the first and second transmission This is because the total channel capacity C _ij ^M is largest when the channel capacity is the same.

In this case, when the determined transmission power of the relay vehicle 20b j is greater than the maximum transmission power P _v of the vehicle, the transmission power of the relay vehicle 20b j is set to P _v to set the SINR _ij ² and C _ij ^2. Calculate (S170, S190).

On the other hand, when the determined transmission power of the relay vehicle 20b j is not greater than P _v , the determined transmission power is allocated to the relay vehicle 20b j, and SINR _ij ² and C _ij ² are calculated first, SINR _ij ^1. And C _ij ² (S170, S180).

This means that even if the channel capacity of the multi-hop second communication becomes larger than the channel capacity of the multi-hop first communication using more transmission power in the relay vehicle 20b j (that is, C _ij ¹ <C _ij ² ), The channel capacity of the terminal-to-terminal multi-hop communication is to prevent unnecessary waste of resources because the channel capacity of the terminal-to-terminal multi-hop communication is limited to the channel capacity of the multi-hop first communication having a smaller channel capacity.

In addition, when the relay vehicle 20b j uses a large amount of transmission power in the multi-hop second communication, the interference to other vehicles is increased by that much, thereby preventing the capacity of the entire communication system from being lowered.

Therefore, in the present embodiment, it is possible to prevent unnecessary waste of transmission power of the relay vehicle 20b through the resource allocation as described above, and to minimize the interference to other vehicles, thereby preventing capacity degradation of the communication system. The performance of the communication system can be maximized.

(Step 3) Available Relay Vehicle Candidate Calculation

When the second step is completed, the infrastructure 10 transmits the channel capacity C _ij ^M when the multi-hop is transmitted to the target vehicle 20a i through the relay vehicle 20b j. 20a) If it is larger than the channel capacity C _i ^D when transmitting data by direct transmission to _i , the relay vehicle 20b j is R _i ^A (t, which is a set of available relay vehicle candidates of the target vehicle 20a i). ) To be included (S210 to S230).

Meanwhile, the above-described second and third steps are sequentially and repeatedly performed for all relay vehicle candidates belonging to the set R _i (t) (S240 and S250).

(Step 4) Optimal Relay Vehicle Selection

Upon completion of the third step, the infrastructure 10 is R _i ^A (t) which is a set of available relay vehicle candidates of the target vehicle 20a i. In order to select the optimal relay vehicle 20b among the first, the system capacity C ^D at the time of direct transmission to the target vehicle 20a i is calculated as follows (S270).

That is, the channel capacity of the target vehicle 20a i is C _i ^D determined in the first step, and the channel capacity of the other target vehicle 20a is multicast whether the infrastructure 10 transmits the transmission directly to the target vehicle 20a. Calculate depending on whether you are sending in hop transmission.

If the infrastructure 10 has not yet decided whether to transmit to the target vehicle by direct transmission or multi-hop transmission, the channel capacity of the target vehicle is calculated when the transmission is performed by direct transmission.

Therefore, once the channel capacity for all the target vehicles is obtained, the system capacity C ^D is calculated as the sum of these.

At this time, when the set R _i ^A (t) of the usable relay vehicle candidates of the target vehicle 20a i obtained in the third step is an empty set, the infrastructure 10 does not perform the next step any further and the target vehicle 20a does not perform the next step. i) is transmitted directly to i, in which case the system capacity becomes C ^D (S260, S300).

Next, the infrastructure 10 transmits the system capacity C ^M for each relay candidate vehicle j belonging to the set R _i ^A (t) through the relay vehicle 20b to the target vehicle 20a i through multi-hop transmission. To calculate (S270).

In this case, the channel capacity of the target vehicle 20a i is C _ij ^M determined in the second step and the channel capacity of the other target vehicle is transmitted by the infrastructure 10 to the target vehicle by direct transmission or multi-hop transmission. So calculate.

If the infrastructure 10 has not yet decided whether to transmit to another target vehicle by direct transmission or multi-hop transmission, the channel capacity of the corresponding target vehicle calculates the channel capacity when the direct transmission is transmitted.

Therefore, once the channel capacities of all the target vehicles are obtained, the system capacity C ^M is calculated as the sum of these.

Next, the infrastructure 10 selects a vehicle that achieves the largest system capacity C ^M among the candidates of the relay vehicle 20b as an optimal relay vehicle 20b for the target vehicle 20a i, and the corresponding relay vehicle 20b. ) And assigns the transmission power determined in the second step (S280, S290).

On the other hand, if C ^M > C ^D is not satisfied for all relay vehicle candidates included in the set R _i ^A (t), the infrastructure 10 transmits the data by direct transmission to the target vehicle 20a i. (S280, S300).

10: infrastructure 20a: destination vehicle
20b: relay vehicle

Claims (13)

In a multi-hop relay transmission method of an adaptive beam-based communication system using a beam split multiple access method,
A first step of scheduling an object vehicle to which the infrastructure transmits data; and
The communication state of the target vehicle is determined, and the infrastructure directly transmits the data to the target vehicle according to the determination result, or the data is transmitted to a relay vehicle selected from vehicles having different infrastructures (hereinafter, 'first transmission'). And a second step of transmitting data to the target vehicle by any one of multi-hop transmissions of the data received by the selected relay vehicle to the target vehicle (hereinafter, 'second transmission'),
And the selected relay vehicle is a vehicle j within a service area of the infrastructure and not scheduled in the first step. The method of claim 1,
The second step comprises:
For vehicle i, the target vehicle to which data is to be transmitted, C _i ^D which is the channel capacity of the vehicle i in the direct transmission and C _ij ^M which is the channel capacity of the vehicle i in the multi-hop transmission through the respective vehicles j are obtained. Step 2-1;
A second step of obtaining a relay candidate vehicle in which C _ij ^M is greater than C _i ^{D in} the vehicle j;
Obtaining C ^D , which is the capacity of the entire communication system when transmitting directly to the vehicle i, and C ^M, which is the capacity of the entire communication system when transmitting the multi-hop to the vehicle i, for each of the relay candidate vehicles;
An adaptive beam comprising: selecting a relay candidate vehicle having the largest C ^M as the relay vehicle of the vehicle i when there is a vehicle whose C ^M is larger than C ^D among the relay candidate vehicles; Multi-hop relay transmission method of communication system based. The method of claim 2,
The remaining vehicle except for the vehicle i is composed of a first group receiving data by direct transmission and a second group receiving data by multi-hop transmission,
The C _i ^D is C _i ^D1 obtained using SINR _i ^D1 including interference received by the vehicle i from direct transmission of a first group and first transmission of a second group in a first transmission step of a second group; Is the sum of C _i ^D2 obtained using SINR _i ^D2 including interference received from the direct transmission of the first group and the second transmission of the second group in the second transmission step of the second group,
C _ij ^M is C _ij ^M1 obtained using SINR _ij ^M1 including interference received by vehicle i from direct transmission of the first group and first transmission of the second group in the first transmission step, and vehicle i is The multi-hop relay of the adaptive beam-based communication system, characterized in that the smaller of the C _ij ^M2 obtained using the SINR _ij ^M2 including the interference from the first group of direct transmission and the second group of the second transmission in the second transmission step Transmission method. The method of claim 3,
In the case of obtaining C _ij ^M in step 2-1, after calculating SINR _ij ^M1 and C _ij ^M1 for vehicle j, the transmission power of the vehicle j when SINR _ij ^M1 is equal to SINR _ij ^M2 is calculated. If the calculated transmission power is equal to or less than the maximum transmission power of the preset vehicle j, the SINR _ij ^M2 and C _ij ^M2 are equal to SINR _ij ^M1 and C _ij ^M1 , respectively. Otherwise, the transmission power of the vehicle j is the maximum. A method of multi-hop relay transmission in an adaptive beam based communication system characterized by obtaining SINR _ij ^M2 and C _ij ^M2 at the time of transmission power. The method of claim 4, wherein
If the transmission power calculated in step 2-1 is less than or equal to the maximum transmission power of the preset vehicle j, the transmission power of the vehicle j is allocated as the calculated transmission power, and otherwise, the transmission power of the vehicle j is assigned. Multi-hop relay transmission method of the adaptive beam-based communication system, characterized in that the allocation to the maximum transmission power. The method of claim 2,
In step 2-3, the C ^D and the C ^M are respectively the sum of the channel capacity of the vehicle i and the channel capacity of the remaining target vehicle,
The target vehicle, which is not determined whether direct transmission or multi-hop transmission among the remaining target vehicles, is calculated as channel capacity in case of direct transmission. The method according to any one of claims 2 to 6,
In the case where there is no relay candidate vehicle in step 2-2 or when there is no vehicle whose C ^M is greater than C ^D among the relay candidate vehicles in step 2-4, transmitting data to the vehicle i by direct transmission. Multi-hop relay transmission method of the adaptive beam-based communication system characterized in that. In the adaptive beam-based communication system for performing the communication between the infrastructure and the vehicle or the inter-vehicle communication using a beam split multiple access method,
The vehicle comprises at least one target vehicle in or out of or in the service area of the infrastructure and at least one relay vehicle in the service area of the infrastructure,
The infrastructure directly transmits data to the corresponding target vehicle or transmits the data to the relay vehicle according to the communication state of the target vehicle scheduled to transmit data (hereinafter, referred to as 'first transmission') and is received by the relay vehicle. Transmit the data to the corresponding target vehicle (hereinafter referred to as 'second transmission'),
The infrastructure is an adaptive beam-based communication system, characterized in that for selecting the relay vehicle mobilized for multi-hop transmission among other vehicles that are not scheduled as the target vehicle for transmitting the data. The method of claim 8,
The infrastructure may include the first channel capacity C _i ^D of the corresponding target vehicle when data is directly transmitted to the target vehicle, and the second channel capacity C _ij of the target vehicle corresponding to multi-hop transmission through the relay vehicle. ^M ) is obtained, and a relay candidate vehicle is obtained which is a vehicle having a second channel capacity C _ij ^M greater than the first channel capacity C _i ^{D among the} relay vehicles, and when data is directly transmitted to the corresponding target vehicle. Obtaining the first system capacity (C ^D ) of the entire communication system and the second system capacity (C ^M ) of the entire communication system for the relay candidate vehicle in multi-hop transmission of data to the corresponding target vehicle, and among the relay candidate vehicles a second system capacity (C ^M) is the first system capacity when there is a large vehicle than (C ^D) and the second system capacity (C ^M) to select the relay vehicle of the target vehicle which corresponds to the largest relay candidate vehicle Characterized by An adaptive beam-based communication systems. 10. The method of claim 9,
The remaining vehicle except for the corresponding target vehicle comprises a first group receiving data by direct transmission and a second group receiving data by multi-hop transmission,
The infrastructure obtains a third channel capacity (C _i ^D1 ) in consideration of interference received from the direct transmission of the first group and the first transmission of the second group in the first transmission step of the second group. In the second transmission step of the two groups, the fourth vehicle capacity C _i ^D2 is obtained by considering the interference received from the direct transmission of the first group and the second transmission of the second group, and the third channel. An adaptive beam based communication system, characterized in that the sum of the capacity (C _i ^D1 ) and the fourth channel capacity (C _i ^D2 ) is determined as the first channel capacity (C ^D ). 10. The method of claim 9,
The remaining vehicle except for the corresponding target vehicle comprises a first group receiving data by direct transmission and a second group receiving data by multi-hop transmission,
The infrastructure obtains the fifth channel capacity C _ij ^M1 in consideration of interference received from the first transmission of the first group and the first transmission of the second group in the first transmission step of the corresponding vehicle, and the corresponding object In the second transmission step of the vehicle, the sixth channel capacity C _ij ^M2 is obtained by considering the interference received from the first transmission of the first group and the second transmission of the second group, and the fifth channel capacity C _ij ^M1 and The adaptive beam-based communication system, characterized in that the smaller of the sixth channel capacity (C _ij ^M2 ) is determined as the second channel capacity. 10. The method of claim 9,
The first system capacity and the second system capacity are each the sum of the channel capacity of the corresponding target vehicle and the channel capacity of the other scheduled scheduled vehicle except for the corresponding target vehicle,
The infrastructure determines an adaptive beam-based communication system for the destination vehicle that is not determined whether the direct transmission or multi-hop transmission of the remaining target vehicle is the direct transmission. 10. The method of claim 9,
The infrastructure transmits data by direct transmission to the corresponding target vehicle when there is no relay candidate vehicle or when there is no vehicle having a second system capacity larger than the first system capacity among the relay candidate vehicles. Adaptive Beam Based Communication System.

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