KR20120061316A - Adaptive Beam-based Communication System and Scheduling Method Thereof - Google Patents

Abstract

PURPOSE: An adaptive beam based communication system and scheduling method thereof are provided to increase the coverage and capacity of a communication system by minimizing interference between V2I(Vehicle to Infrastructure) communication and V2V(Vehicle to Vehicle) communication. CONSTITUTION: A resource request message for requesting V2V resources is received from a vehicle within a service area of infrastructure(S100). V2I resources for V2I communication is allocated(S300). The V2V resource is allocated to V2V communication link corresponds to the resource request message by using the V2I resources(S400). The resource allocation for a V2V communication link is determined by considering of interference between the V2V communication link and other V2I communication links.

Description

Adaptive Beam-based Communication System and Scheduling Method Thereof

The present invention relates to an adaptive beam-based communication system and a scheduling method thereof, and more particularly, to reuse the resources allocated for V2I communication for V2V communication to improve the use efficiency of resources and to prevent interference between V2I communication and V2V communication. The present invention relates to an adaptive beam-based communication system and a scheduling method thereof capable of maximizing the performance of an entire communication system by maximizing the capacity of the communication system.

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 case of the V2I communication system, since the infrastructure provides information through wireless communication using an omnidirectional antenna, it is impossible to allocate resources in consideration of the placement position and the moving speed of the vehicle. There is a problem that the lowering, waste of unnecessary resources in the absence of the vehicle.

Therefore, in order to solve this problem, an adaptive beam-based beam splitting system that maximizes the capacity of a communication system by preventing information from wasting unnecessary communication resources by providing information through an adaptive beam generated in consideration of a vehicle's arrangement position and a moving speed. The connection (BDMA, Beam Division Multiple Access) method is applied.

However, even in such a case, the V2I communication system is not only limited in connection time between the vehicle and the infrastructure because the relative speed between the infrastructure and the vehicle is large, but also a good Doppler effect due to the relative speed during the connection, so that the communication channel is in good condition. There is a problem that can not be.

On the other hand, in the case of the V2V communication system, since the relative speed between the vehicles is small, the connection time between the vehicles is long, there are many communication opportunities, and because the Doppler effect is smaller than that of the V2I communication, the state of the communication channel is relatively good. have.

However, even in such a V2V communication system, it is difficult to select an optimal route in multi-hop transmission using a relay terminal (vehicle) because the topology of the network changes rapidly due to the fast moving speed of the vehicle. There is a disadvantage that coordination between vehicles is not easy because there is no central node such as infrastructure.

In addition, in the case of the V2V communication system, since the vehicle broadcasts an emergency message to neighboring vehicles, there is a problem that communication is disconnected due to flooding of duplicate messages, and both the transmitting terminal and the receiving terminal are in a mobile state. There is a problem that it is difficult to apply the existing channel model (channel model).

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, It is to provide an adaptive beam-based communication system that can solve the problems of conventional V2I communication and V2V communication by applying 'V2V2I communication'.

In addition, another object of the present invention is to maximize the performance of the communication system by reducing the interference between the V2I communication and V2V communication while increasing the capacity of the communication system by sharing resources between the V2I communication and V2V communication in the communication system. It is to provide a scheduling method of an adaptive beam-based communication system.

In order to achieve the above object, the scheduling method of the adaptive beam-based communication system according to the present invention, in the scheduling method of the adaptive beam-based communication system using a beam split multiple access method, from the vehicle in the service area of the infrastructure A first step of receiving a resource request message for requesting a V2V resource which is a resource for inter-vehicle communication (hereinafter, 'V2V communication link'); A second step of allocating a V2I resource which is a resource for communication between the infrastructure and the vehicle (hereinafter, 'V2I communication link'); And a third step of allocating V2V resources to the corresponding V2V communication link corresponding to the resource request message by reusing the V2I resources allocated in the second step, wherein the V2V resources are allocated to the corresponding V2V communication link in the third step. Is assigned, the corresponding V2V communication is considered in consideration of interference generated between another V2I communication link (hereinafter, 'existing V2I communication link') or V2V communication link (hereinafter, 'existing V2V communication link'). It is characterized by determining whether to allocate resources for the link.

In the third step, when at least one of the source vehicle and the target vehicle of the corresponding V2V communication link belongs to the existing V2I communication link, V2V resources are not allocated to the corresponding V2V communication link.

Further, in the third step, a transmission power for satisfying a target signal-to-noise interference ratio (SINR) included in the resource request message of the corresponding V2V communication link is calculated, and the calculated transmission power belongs to a source belonging to the corresponding V2V communication link. If it is larger than the remaining transmission power of the vehicle, the corresponding V2V communication link may not be allocated a V2V resource.

In the third step, the signal-to-noise ratio (SNR) and the SINR of each of the existing V2I communication links are calculated, and when the difference between the calculated SNR and the SINR is larger than a set value in any one of the existing V2I communication links, The V2V communication link is not allocated to the V2V resource, but the SINR may include interference by the corresponding V2V communication link.

In addition, in the third step, the SINR of each of the existing V2V communication links is calculated, and when any of the existing V2V communication links is smaller than the target SINR of the calculated SINR, V2V resources are allocated to the corresponding V2V communication link. Although not assigned, the SINR may include interference by a corresponding V2V communication link.

In addition, the third step may be sequentially performed for all the corresponding V2V communication link when the corresponding V2V communication link is plural, and when the V2V resource is allocated to any one of the corresponding V2V communication links, The source vehicle does not allocate V2V resources to other corresponding V2V communication links that serve as target vehicles.

In addition, the allocated resource is a V2I downlink slot which is a resource for providing information to the vehicle by the infrastructure, and the third step is repeated for each V2I downlink slot included in the current frame.

The resource request message may further include information on the number of V2I downlink slots requested by each corresponding V2V communication link, and the remaining V2V communication links for the corresponding V2V communication links for which resource allocation is completed as many as the requested number of V2I downlink slots. The third step for the V2I downlink slot is not performed.

In order to achieve the above object, in the adaptive beam-based communication system according to the present invention, the communication between the infrastructure and the vehicle (hereinafter, 'V2I communication link') or the vehicle-to-vehicle communication (hereinafter, referred to as a beam splitting multiple access method). An adaptive beam-based communication system for performing a 'V2V communication link', wherein the vehicle transmits a resource request message requesting a V2V resource for allocating to a V2V communication link within a service area of the infrastructure; The infrastructure allocates V2I resources to the V2I communication link, and reuses the allocated V2I resources to allocate V2V resources to the corresponding V2V communication link corresponding to the resource request message received from the vehicle, while other V2I communication has already been allocated. Determining whether to allocate a resource to the corresponding V2V communication link in consideration of interference generated between the link (hereinafter, referred to as an existing V2I communication link) or a V2V communication link (hereinafter referred to as an existing V2V communication link). do.

The infrastructure may be configured to satisfy a target signal to noise interference ratio (SINR) included in the resource request message when at least one of the source vehicle and the target vehicle belongs to the existing V2I communication link. When the transmission power is larger than the remaining transmission power of the source vehicle belonging to the corresponding V2V communication link, the difference between the signal-to-noise ratio (SNR) and SINR of each of the existing V2I communication link is greater than the set value in any one of the existing V2I communication link. At least one of the cases in which the SINR of each of the existing V2V communication links is smaller than its target SINR is not allocated to any of the existing V2V communication links.

In addition, the infrastructure sequentially allocates V2V resources to all corresponding V2V communication links when the corresponding V2V communication links are plural, and when any one of the corresponding V2V communication links is allocated V2V resources, the corresponding one of the corresponding V2V communication links. The V2V resource is not allocated to another corresponding V2V communication link which is the source vehicle of the target vehicle.

In addition, the infrastructure is characterized by allocating a V2I downlink slot which is a resource for providing information to the vehicle requesting the V2V resource allocation.

As described in detail above, the adaptive beam-based communication system and the scheduling method according to the present invention overcome the limitations of the existing V2I communication and V2V communication because the V2I and V2V communication coexist in the service coverage of the infrastructure. As a result, coverage and capacity of a communication system can be increased.

In addition, the adaptive beam-based communication system and the scheduling method according to the present invention is a method of scheduling the V2V communication so that V2I communication and V2V communication share resources with each other while interference between each communication can be avoided. It has the advantage of maximizing performance and efficiency.

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;
2A and 2B illustrate different operation examples of V2V2I communication applied to the communication system of FIG. 1, respectively.
3A to 3C are diagrams illustrating interference scenarios that may occur between communication in a communication system according to an embodiment of the present invention shown in FIG.
4 is a view for explaining an interference model between each communication in a communication system according to an embodiment of the present invention;
5 is a conceptual diagram illustrating a scheduling method applied in a communication system according to an embodiment of the present invention; and
6A and 6B are flowcharts illustrating a scheduling 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.

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, and FIGS. 2A and 2B illustrate different operation examples of V2V2I communication applied to the communication system of FIG. 3A to 3C are diagrams illustrating interference scenarios that may occur between respective communications in the V2V2I communication scheme illustrated in FIG. 2B, respectively.

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.

On the other hand, the mixing method (BWAT) is a method that combines the advantages of the above-described beam width adaptation method (BWA) and the beam tracking method (BT) to simultaneously vary the width and direction of the beam in accordance with 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.

The communication system according to the present embodiment is based on the above-described BDMA scheme, but V2V2I simultaneously performs communication (ie, V2V communication) between the vehicles 20 together with V2I communication in the service coverage area of the infrastructure 10. It is configured in a communication method.

By such a configuration, the communication system according to the present embodiment can overcome the disadvantages of the conventional V2I communication and the V2V communication, as well as to expand the service coverage of the infrastructure 10 and increase the capacity of the communication system. .

In this case, the V2I communication and the V2V communication may be configured to operate using different resources as shown in FIG. 2A or to share the same resources as shown in FIG. 2B as needed.

At this time, when the configuration as shown in Figure 2a does not cause interference between the V2I communication and V2V communication, there is a problem that the capacity of the communication system is reduced due to the resource use efficiency of the communication system due to the use of separate resources, In the case of 2b, the resource usage efficiency of the communication system is increased due to resource sharing (or reuse), but the capacity of the communication system is reduced due to the interference (I) between the V2I communication and the V2V communication.

In this embodiment, in order to improve the use efficiency of resources in a BDMA-based communication environment, a communication method in which V2I communication and V2V communication share the same resources is applied, but interference between each communication is maximized to maximize the capacity of the communication system. Scheduling method that can minimize the problem is applied.

To this end, the communication system according to the present embodiment will assume the following.

Assumption 1 The channel of V2I communication is basically assumed to be a line of sight (LOS), and V2V communication is to distinguish between LOS and non-line of sight (NLOS) according to the distance between the vehicles 20.

[Assumption 2] The channel of V2I communication and V2V communication shall consider a path loss model and an antenna model.

[Assumption 3] All vehicles 20 are equipped with GPS to know their location, speed and direction, and periodically report this to the infrastructure 10 so that the infrastructure 10 knows all the information of the vehicle 20. Assume that there is.

In this embodiment, the V2V communication is divided into a first communication for transmitting a message related to safety, emergency, and control (hereinafter referred to as a 'safety message') and a second communication for transmitting general data. In the service coverage area of (10), the first communication and the second communication are configured to use different resources.

Specifically, the V2V communication uses all the resources of the communication system because only V2V communication is performed for all the vehicles 20 outside the service coverage area of the infrastructure 10.

In this case, the V2V communication may be preferably implemented using the existing V2V communication protocol.

On the other hand, since the V2I communication and the V2V communication coexist in the service coverage area of the infrastructure 10 (that is, the V2V2I communication environment), the V2V communication uses different resources according to its type.

That is, when the V2V communication is the first communication, the V2V slot of the V2V subframe is used so that the safety message can be transmitted to the other vehicle 20 at any time. It consists of reusing slots in the frame.

In this case, since the uplink slot of the V2I subframe is used arbitrarily when the vehicle 20 forms an association with the infrastructure 10 or requests a service, the infrastructure 10 uses the V2I uplink transmission schedule. Since there is a problem that is difficult to predict, it is difficult to mitigate the interference between V2I communication and V2V communication when the V2I uplink slot is reused for V2V communication.

On the other hand, the V2I downlink slot is used by the infrastructure 10 to provide services to the vehicle 20, so that the infrastructure 10 can predict the V2I downlink transmission schedule. When reused for V2V communication, scheduling that minimizes interference with V2I communication is possible.

Therefore, in the present embodiment, when the V2V communication is the second communication, the V2I downlink slot that is not used can be reused to allocate resources for the V2V communication, thereby maximizing the capacity of the system and also mitigating interference with the V2I communication. It was made.

Hereinafter, the scheduling method of the communication system according to the present embodiment will be described in detail with reference to a specific example.

First, in the communication system according to the present embodiment, a total of M vehicles 20 exist in the service coverage area of the infrastructure 10, and the set of these vehicles 20 is M = {1, 2,... , M}.

In addition, one frame of the communication system includes N V2I downlink slots as an example, and the set of these downlink slots is N = {1, 2,... , N}.

In addition, the infrastructure 10 of the communication system may form a total of B V2I beams (the collection of these V2I beam resources is defined as B = {1, 2, ..., B}), and V2I communication. When allocating a resource, the infrastructure 10 allocates transmission power (hereinafter, referred to as p _i (n) ) to any vehicle i to form a V2I beam j (hereinafter, b _ij (n) ).

At this time, the transmission power allocated to the vehicle i by the infrastructure 10 when allocating the resources of the above-described V2I communication must satisfy two constraints as shown in Equations 1 and 2 below.

------------ [수식 1]

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

------------ [수식 2]

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

In this case, the first constraint according to [Equation 1] is that the transmission power p _i (n) allocated to each vehicle i by the infrastructure 10 is greater than 0 and less than the maximum transmission power P ⁱ _max of the infrastructure 10. Is that.

In addition, the second constraint according to Equation 2 is that the sum of the transmission power allocated by the infrastructure 10 to the vehicle 20 should be smaller than the maximum transmission power P ⁱ _max of the infrastructure 10.

On the other hand, the V2I beam j (ie, b _ij (n)) formed by the infrastructure 10 as the vehicle i when allocating the resources of the above-described V2I communication , as shown in [Equation 3] and [Equation 4] below The constraint must be satisfied.

------------ [수식 3]

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

------------ [수식 4]

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

In this case, the first constraint according to [Equation 3] is that each V2I beam should be assigned to only one vehicle 20 and the same V2I beam cannot be assigned to more than one vehicle 20, which will be described later. For convenience, the V2I beam allocated to the vehicle i will be defined as the V2I beam i.

In addition, the second constraint according to [Equation 4] means that the number of V2I beams that can be formed by the infrastructure 10 to the maximum should be B or less.

Next, an interference scenario of V2I communication and V2V communication considered in the present embodiment will be described with reference to FIGS. 3A to 3C.

3A illustrates a scenario in which V2I communication interferes with V2V communication. When V2I communication is performed with a vehicle 20a located in a direction in which a V2I beam is formed or a vehicle 20b located near a vehicle in V2I communication, the V2I communication is performed. A diagram showing a situation in which interference is caused in the V2V communication.

Also, FIG. 3B relates to a scenario in which V2V communication interferes with V2I communication. In case of performing V2V communication with the vehicle 20c in V2I communication as shown in (Case 1) and the direction in which the V2V beam is formed as shown in (Case 2) FIG. 2 is a diagram illustrating a situation in which the V2V communication interferes with the V2I communication when the vehicle 20d in the V2I communication exists.

In addition, FIG. 3C relates to a scenario in which interference between V2V communication is performed, and a vehicle 20e located in a direction in which another V2V beam is formed, such as (Case 1), or a vehicle 20f in V2V communication, such as (Case 2), is different. In the case of V2V communication, a diagram showing a situation in which V2V communication interferes with each other.

As described above, in the communication system according to the present embodiment, which is a V2V2I communication environment in which V2I communication and V2V communication coexist, the above-mentioned three interference scenarios exist between the V2I communication and V2V communication, and these interferences eventually result in V2I communication and V2V. Since the capacity of the communication is reduced to reduce the overall performance of the communication system, a communication scheduling method for minimizing the communication is required.

To this end, FIG. 4 illustrates an interference model of V2I communication and V2V communication in the communication system according to the present embodiment, and when it is expanded, an interference model between V2V communication can be easily represented.

That is, in FIG. 4, the infrastructure forms V2I beam k to vehicle k to perform V2I communication, and at the same time, vehicle i forms V2V beams (i, j) to vehicle j to perform V2V communication.

At this time, the V2I communication signal from the infrastructure to the vehicle k is indicated by a solid blue line, and the V2V communication signal from vehicle i to the vehicle j is indicated by a dotted blue line.

In addition, the V2I communication interference from the infrastructure to the vehicle j is indicated by a solid red line, and the V2V communication interference from the vehicle i to the vehicle k is indicated by a red dotted line.

Meanwhile, the channel model of the V2I communication is defined as g _j ^{θ (k)} (n) and θ (k) is defined as an angle between the direction of the vehicle j and the direction of the V2I beam k in the infrastructure.

Therefore, the interference channel of the V2I communication from the infrastructure to the vehicle j is defined as g _j ^{θ (k)} (n) and the channel of the V2I communication signal from the infrastructure to the vehicle k is g _k ^{θ (k) = 0} (n) . In this case, the infrastructure satisfies θ (k) = 0 because it forms a V2I beam in the direction of the vehicle k.

In addition, the channel model of the V2V communication is defined as h _ik ^{φ (i, j)} (n) and φ (i, j) is the angle between the direction of the vehicle k and the direction of the V2V beam (i, j) in the vehicle i. Is defined as

Accordingly, the channel of interference that V2V communication from vehicle i to vehicle j affects vehicle k is defined as h _ik ^{φ (i, j)} (n) and the channel of the V2V communication signal from vehicle i to vehicle j is h _ij ^{φ (i, j) = 0} (n) , where the vehicle i forms a V2V beam in the direction of the vehicle j, thereby satisfying φ (i, j) = 0 .

In this embodiment, since the channels of the V2I communication and the V2V communication consider both the path loss model and the antenna model, in the case of the V2I communication, the distance between the infrastructure and the vehicle and the angle θ (k) between the V2I beam and the vehicle are determined later. The channel gain can be obtained by applying the equations of the conventional path loss model and the antenna model.

Similarly, in the case of V2V communication, the channel gain can be obtained if the distance between the source vehicle and the destination vehicle and the angle ? (I, j) between the V2V beam and the destination vehicle are determined.

The general path loss model is expressed as in [Equation 5-1] below.

--------------------- [수식 5-1]

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

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 5-2 below.

------------ [수식 5-2]

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

Where θ is the angle between the beam direction and the vehicle direction, θ _3dB is the beam-width at which the signal is attenuated by 3dB, A _m is the maximum attenuation value, and G _A is the antenna gain.

Therefore, the gain of the antenna model is determined according to the angle θ between the beam direction and the vehicle direction, where θ = θ (k) and θ = φ (i, j) are satisfied for V2I communication and V2V communication, respectively. .

Next, a scheduling method applied to minimize interference between V2I communication and V2V communication in the communication system according to the present embodiment configured as described above will be described.

5 is a conceptual diagram illustrating a scheduling method applied in a communication system according to the present embodiment, and FIGS. 6A and 6B are flowcharts illustrating a scheduling method applied in a communication system according to an embodiment of the present invention.

 In the communication system according to the present embodiment as shown in Figs. 5 and 6A, scheduling of a three-step process is performed to minimize interference between V2I communication and V2V communication.

First, the vehicle 20 connected to the infrastructure 10 in an arbitrary communication frame (that is, (t-1) frame) in the first step transmits a "V2V resource request message" requesting resources for V2V communication. A V2V communication resource is requested by transmitting to (10), wherein the "V2V resource request message" includes information of a source and a target vehicle (s, d) (hereinafter referred to as V2V communication link (s, d)). Includes the number of V2I slots, the target signal-to-integration plus noise ratio (SINR) of the V2V communication link (s, d).

At this time, when the infrastructure 10 receives the “V2V resource request message” from the vehicle 20 (S100), the request for the corresponding V2V communication link (s, d) is included in the set R of the V2V resource request (S100). S200), expressed as a formula is as shown in Equation 6 below.

---------------------------- [수식 6]

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

When the first step is completed, the infrastructure 10 performs a second step (S300) for allocating the resources of the V2I communication first in the next frame (that is, the t frame), the resource allocation of the V2I communication is one frame It is performed in units of (frames) and each frame is configured to include N V2I downlink slots.

Accordingly, the infrastructure 10 allocates resources of V2I communication for each downlink slot at the beginning of every frame.

When the second step is completed, the infrastructure 10 performs a third step (S400) of allocating resources of the V2V communication based on the determined resource allocation of the V2I communication.

Likewise, the resource allocation of the V2V communication is performed in units of one frame, and the infrastructure 10 allocates resources of the V2V communication by reusing each V2I downlink slot at the beginning of each frame, wherein V2I communication and V2V communication are performed. By scheduling the V2V communication as described below to minimize the interference, it is possible to maximize the capacity of the communication system according to the present embodiment, which is a V2V2I communication environment.

Next, the scheduling method of the V2V communication applied in the present embodiment in order to minimize the interference between the V2I communication and the V2V communication will be described in detail with reference to FIG. 6B.

The scheduling method of V2V communication, which will be described later, is performed every frame, and when the resource allocation of the V2I communication is determined for each V2I downlink slot, V2V communication is sequentially performed in order from the first V2I downlink slot to the Nth V2I downlink slot. Allocate resources.

Hereinafter, for convenience of description, the V2V communication scheduling method will be described by distinguishing each step.

(Step 3-1: Initialization step)

First, when the resource allocation for the V2I communication is completed through the second step, the infrastructure 10 performs an initialization step of setting the following parameters to initial values (S410).

1) n = 1 : Set the index (n) of the V2I downlink slot to 1

2) P _i = P ^V _max , for i = 1,2,... , M : Initialize the remaining transmission power of each vehicle to the maximum transmission power of the vehicle ( P ^V _max )

3) p _ij (n) = 0, for ∀ (i, j) ∈ R : Initializes the power allocated to all V2V communication links (i, j) included in the V2V resource request set R to 0

4) S (n) = Ø : Initializes the set S (n) of the scheduled V2V communication link to empty because there is no scheduled V2V communication link by allocating V2V communication resources.

(Step 3-2: Formation Set V Formation of Set R)

In the V2V communication link, the closer the distance between the source vehicle and the target vehicle is, the smaller the transmission power is.

Accordingly, the infrastructure 10 forms an alignment set V by arranging the distances between the vehicle i and the vehicle j in a close order with respect to all V2V communication links (i, j) included in the V2V resource request set R (S410). .

In this case, the method of aligning the V2V resource request set R may consider not only the distance between the vehicles 20 as in this embodiment, but also other factors that interfere with the surrounding communication, such as the QoS of the vehicle 20 as necessary. have.

(Step 3-3: removing the vehicle in V2I communication from the alignment set V)

In the V2V2I communication environment applied in the present embodiment, as described in (Case 1) of the inter-communication interference scenario of FIG. 3B, when the V2V beam is formed in the vehicle 20c in V2I communication, the V2V communication is performed in V2I communication. 20c) is a big interference.

In addition, the vehicle in V2I communication cannot form a V2V beam at the same time to perform V2V communication, and thus the vehicle in V2I communication cannot be a source vehicle or a target vehicle of V2V communication.

Therefore, as shown in Equation 7 below, the set I (n) of the vehicle in V2I communication is calculated in the V2I downlink slot n.

------------ [수식 7]

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

When the V2I beam j is allocated to each vehicle i in Equation 7, since b _ij (n) = 1 is satisfied, the set I (n) of vehicles in V2I communication can be obtained.

Further, as described above, since the vehicle 20 in V2I communication cannot be a source vehicle or a target vehicle of other V2V communication, V2V communication is simultaneously performed for each vehicle i in communication with V2I included in the set I (n) . Calculate the set T _i of this impossible V2V communication link as shown in Equation 8 below.

------------ [수식 8]

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

As shown in Equation 9 below, by removing the set T _i from the alignment set V , the vehicle in V2I communication is removed from the alignment set V (S420).

----------------------------- [수식 9]

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

(Step 3-4: Step to consider interference received by V2V communication link)

When the step 3-3 is completed, the infrastructure 10 considers interference received from the V2I communication and other V2V communication that is already scheduled for the V2V communication link included in the set V obtained in the step 3-3. Perform

)을 만족하는 전송파워 p ^* _ij 를 아래의 [수식 10]을 이용하여 계산한다(S430).To this end, the infrastructure 10 first determines the target SINR of the V2V communication link (i, j) that has made a V2V resource request.

) To be calculated using [Expression 10] below the transmit power p _ij ^* is satisfied (S430).

---- [수식 10]

---- [Formula 10]

In Equation 10, the numerator on the left side is the received signal strength of the V2V communication link (i, j), and the first term of the denominator is noise ( W : channel bandwidth, N ₀ : power spectral density of noise), and the second term is Interference from V2I communication, the third term represents interference from V2V communication already scheduled.

)은 V2V 통신링크 (i,j)가 V2I 통신과 다른 V2V 통신으로부터 받을 간섭을 고려해서 목표 SINR에 마진을 두어 전송파워가 할당되도록 하기 위한 것이다.In addition, the right side is expressed as the sum of the target SINR of the V2V communication link (i, j) and the SINR margin of the V2V communication link, wherein the SINR margin of the V2V communication link (

In order to allow the transmission power to be allocated by margining the target SINR in consideration of the interference that the V2V communication link (i, j) may receive from the V2V communication and other V2V communication.

The SINR margin is a value that can be set in consideration of a communication environment. In the present embodiment, the SINR margin is considered, but in an ideal case, the SINR margin may be performed without considering the SINR margin. Therefore, in the present invention, the transmission power includes both cases of considering and not considering SINR margin.

In this case, the infrastructure 10 may determine that the remaining transmission power P _i of the source vehicle i of the corresponding V2V communication link (i, j) is greater than or equal to the transmission power ( p ^* _ij ) obtained from Equation 10 (i.e., If the remaining transmission power of the source vehicle i of the V2V communication link (i, j) can satisfy the target SINR, steps 3-5 to be described later are performed, otherwise (that is, p ^* _ij > P). _{If i} ), the corresponding V2V communication link is not scheduled, and steps 3-4 are performed on the V2V communication link of the next order (S440).

(Step 3-5: considering the interference that the V2V communication link has on the V2I communication link)

When the third step 4-4 is completed, the infrastructure 10 performs the step of considering the interference that the corresponding V2V communication link to the V2I communication link.

)을 아래의 [수식 11]을 이용하여 계산한다.To this end, first, the infrastructure 10 performs signal to noise ratio (SNR) when the vehicle k (hereinafter, referred to as 'V2I communication link k') in V2I communication does not receive interference from V2V communication.

) Is calculated using Equation 11 below.

------------------- [수식 11]

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

At this time, the numerator on the right side is the received signal strength of the V2I communication link k, and the denominator is noise.

) 을 아래의 [수식 12]를 이용하여 계산한다(S450).Next, the infrastructure 10 may determine SINR in the case where the V2I communication link k receives interference from the V2V communication.

) Is calculated using Equation 12 below (S450).

----- [수식 12]

----- [Equation 12]

At this time, the right side of the numerator is the received signal strength of the V2I communication link k, the first term of the denominator is noise, the second term is the interference from the V2V communication links that are already scheduled with V2V communication resources, and the third term is the corresponding term. Interference received when the V2V communication link (i, j) is additionally scheduled.

)가 V2I 통신링크의 SINR 마진(

)보다 이하인 경우이면 해당 V2V 통신링크 (i,j)를 추가적으로 스케줄링했을 때 V2I 통신링크가 받는 간섭이 작다고 판단하여 후술하는 제3-6단계를 수행한다.In this case, the infrastructure 10 determines the difference between the SNR and SINR of all V2I communication links k included in the aforementioned set I (n) (

) Is the SINR margin of the V2I communication link

If it is less than or equal to), when the corresponding V2V communication link (i, j) is additionally scheduled, it is determined that the interference received by the V2I communication link is small, and steps 3-6 to be described later are performed.

)보다 큰 간섭을 받게 되면(즉,

) 해당 V2V 통신링크는 스케줄링하지 않고 다음 순서의 V2V 통신링크에 대하여 상기 제3-4단계를 수행한다(S460).On the other hand, when any one of the V2I communication links included in the set I (n) further schedules the corresponding V2V communication link (i, j), the SINR margin (

If you receive greater interference than (i.e.,

In step S460, the V2V communication link is not scheduled, and the V2V communication link is performed in the following order (S460).

In this case, the SINR margin of the V2I communication link is preferably set in consideration of the communication environment as in the SINR margin of the V2V communication link.

(Step 3-6: Step of considering the interference that the V2V communication link gives to other V2V communication link)

When the third step 3-5 is completed, the infrastructure 10 performs the step of considering the interference that the corresponding V2V communication link to another V2V communication link.

)을 아래의 [수식 13]을 이용하여 계산한다(S470). To this end, when the infrastructure 10 additionally schedules the corresponding V2V communication link (i, j), the SINR (s) of another previously scheduled V2V communication link (s, d) (

) Is calculated using Equation 13 below (S470).

---- [수식 13]

---- [Equation 13]

In this case, the right-side numerator is the received signal strength of the other scheduled V2V communication link (s, d), the first term of the denominator is noise, the second term is interference from the V2I communication, and the third term is the V2V communication link. (s, d) Interference from other V2V communication links scheduled by allocating V2V communication resources except for itself, and the fourth term represents interference received when additionally scheduling the corresponding V2V communication link (i, j).

Also, in the third term of the denominator S _{(s, d)} is = S (n) of a set of V2V communication links except for V2V communications link (s, d) from the V2V set S (n) of the communication link scheduling the existing _{S (s, d)} - ₍ s, d) .

) 이하의 간섭을 받는 경우이면(즉,

) 목표 SINR(

)을 만족할 수 있다.In this case, when the corresponding V2V communication link (i, j) is additionally scheduled, the previously scheduled V2V communication link (s, d) becomes the SINR margin of the V2V communication link (

) If you are receiving interference below

) Target SINR (

) Can be satisfied.

)에는 목표 SINR을 만족할 수 없다. On the other hand, when the V2V communication link (i, j) is additionally scheduled when the V2V communication link (s, d) scheduled based on the interference is greater than the SINR margin of the V2V communication link (i.e.,

) Cannot satisfy the target SINR.

Accordingly, the infrastructure 10 performs steps 3-7 described below when all V2V communication links (s, d) included in the previously scheduled V2V communication link set S (n) satisfy the target SINR, If any one of the V2V communication links (s, d) included in the set S (n) does not satisfy the target SINR, the corresponding V2V communication link is not scheduled and the third to fourth V2V communication links are performed in the following order. To perform the step (S480).

(Step 3-7: Scheduling and variable update of V2V communication link)

When the step 3-6 is completed, the infrastructure 10 determines that interference with V2I communication and other V2V communication can be avoided even if the corresponding V2V communication link is additionally scheduled, and then schedules the corresponding V2V communication link as follows. The step of updating is performed (S490).

1) S (n) = S (n) ∪ (i, j) : Scheduling the corresponding V2V communication link (i, j) to V2I downlink slot n

2) p _ij (n) = p ^* _ij : Allocate transmit power p ^* _ij that satisfies the target SINR of the corresponding V2V communication link (i, j).

3) P _i = Pi-p ^* _ij : Update the remaining transmission power of the source vehicle of the corresponding V2V communication link (i, j)

4) N _{(i, j)} = N _{(i, j)} -1 : Reduce the number of V2I downlink slots requested by the corresponding V2V communication link (i, j).

5) V = V- (i, j) : Remove the scheduled V2V communication link (i, j) from set V

(Steps 3-8: removing other V2V communication links that cannot be scheduled simultaneously with the V2V communication link)

When the steps 3-7 are completed, the infrastructure 10 may not be scheduled at the same time as the corresponding V2V communication link (i, j) scheduled in steps 3-7 among the V2V communication links included in the set V. Follow the steps to remove the link.

Since the vehicle included in the communication system according to the present embodiment communicates in a half-duplex, data cannot be simultaneously transmitted and received.

Accordingly, the infrastructure is set to the set T _ij of another V2V communication link in which the source vehicle of the corresponding V2V communication link (i, j) scheduled in the above steps 3-7 among the communication links belonging to the set V becomes the target vehicle. 14], the set T _ij is removed from the set V (ie, V = V − T _ij ) (S500).

---------------- [수식 14]

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

(Step 3-9: updating the V2V resource request set R)

When the steps 3-8 have been completed, the infrastructure 10 has allocated all of the requested number of V2I downlink slots by the corresponding V2V communication link (i, j) (that is, N _{(i, j)} = 0 ). Removing the corresponding V2V communication link (i, j) from the V2V resource request set R (ie, R = R- (i, j) ) is performed (S510, S515).

(Step 3-10: updating the V2I downlink slot index n)

When the step 3-9 is completed, the infrastructure determines whether there is a V2V communication link that can still be scheduled in the set V (ie, if V ? Step -4 is performed, otherwise, in step 3-1, after increasing the V2I downlink slot index (that is, n = n + 1 ), the remaining steps are repeated (S520 and S530).

At this time, if the current V2I downlink slot is the last slot of the frame (that is, n = N ), the infrastructure 10 terminates V2V communication scheduling in the frame (S540).

According to the above-described configuration and scheduling method, the communication system according to the present embodiment is a method of scheduling the V2V communication so that V2I communication and V2V communication share resources with each other while interference between each communication can be avoided. The advantage is that the system's performance and efficiency can be maximized.

10: infrastructure 20: vehicles

Claims (12)

A scheduling method of an adaptive beam based communication system using a beam split multiple access method,
A first step of receiving a resource request message for requesting a V2V resource which is a resource for inter-vehicle communication (hereinafter, 'V2V communication link') from a vehicle in the service area of the infrastructure;
A second step of allocating a V2I resource which is a resource for communication between the infrastructure and the vehicle (hereinafter, 'V2I communication link'); And
And a third step of allocating V2V resources to a corresponding V2V communication link corresponding to the resource request message by reusing the V2I resources allocated in the second step.
In the third step, when the V2V resource is allocated to the corresponding V2V communication link, another V2I communication link (hereinafter, referred to as an existing V2I communication link) or a V2V communication link (hereinafter, referred to as an existing V2V communication link) that has already been allocated resources. And determining resource allocation for the corresponding V2V communication link in consideration of interference generated between and. The method of claim 1,
In the third step, if at least one of the source vehicle or the target vehicle of the corresponding V2V communication link belongs to the existing V2I communication link, the adaptive beam-based communication characterized in that the V2V communication link is not allocated to the corresponding V2V communication link. Scheduling method of the system. The method of claim 2,
In step 3, a transmission power for satisfying a target signal-to-noise interference ratio (SINR) included in the resource request message of the corresponding V2V communication link is calculated, and the calculated transmission power corresponds to that of a source vehicle belonging to the corresponding V2V communication link. If the transmission power is greater than the remaining transmission power scheduling method of the adaptive beam-based communication system, characterized in that the V2V resources are not allocated to the corresponding V2V communication link. The method of claim 3,
In step 3, the signal-to-noise ratio (SNR) and the SINR of each of the existing V2I communication links are calculated, and when the difference between the calculated SNR and the SINR is larger than a set value in any one of the existing V2I communication links, the corresponding V2V. Do not allocate V2V resources to the communication link.
The SINR includes the interference by the corresponding V2V communication link scheduling method of the adaptive beam-based communication system. The method of claim 4, wherein
In step 3, the SINR of each of the existing V2V communication links is calculated, and if any of the existing V2V communication links is smaller than its target SINR, the V2V resource is not allocated to the corresponding V2V communication link. No,
The SINR includes the interference by the corresponding V2V communication link scheduling method of the adaptive beam-based communication system. The method of claim 5,
The third step may be performed sequentially for all corresponding V2V communication links when the corresponding V2V communication links are plural, and when a V2V resource is allocated to any one of the corresponding V2V communication links, the source vehicle of the one of the corresponding V2V communication links. A scheduling method of an adaptive beam-based communication system, characterized in that no V2V resource is allocated to another corresponding V2V communication link which becomes the target vehicle. The method according to any one of claims 1 to 6,
The allocated resource is a V2I downlink slot that is a resource for the infrastructure to provide information to the vehicle,
The third step is repeated for each V2I downlink slot included in the current frame scheduling method of the adaptive beam-based communication system. The method of claim 7, wherein
The resource request message further includes information about the number of V2I downlink slots requested by each corresponding V2V communication link,
And the third step for the remaining V2I downlink slots is not performed for the corresponding V2V communication link for which resource allocation is completed as many as the requested number of V2I downlink slots. In an adaptive beam-based communication system that performs a communication between an infrastructure and a vehicle (hereinafter, 'V2I communication link') or an inter-vehicle communication (hereinafter, 'V2V communication link') using a beam split multiple access method,
The vehicle sends a resource request message requesting a V2V resource for allocating to a V2V communication link in the service area of the infrastructure;
The infrastructure allocates V2I resources to the V2I communication link, and reuses the allocated V2I resources to allocate V2V resources to the corresponding V2V communication link corresponding to the resource request message received from the vehicle, while other V2I communication has already been allocated. Determining whether to allocate a resource to the corresponding V2V communication link in consideration of interference generated between the link (hereinafter, referred to as an existing V2I communication link) or a V2V communication link (hereinafter referred to as an existing V2V communication link). Adaptive beam based communication system. 10. The method of claim 9,
The infrastructure transmits power for satisfying a target signal-to-noise interference ratio (SINR) included in the resource request message when at least one of the source vehicle and the target vehicle belongs to the existing V2I communication link. Is greater than the remaining transmission power of the source vehicle belonging to the corresponding V2V communication link, when any one of the existing V2I communication link is greater than the set value, the difference between the signal-to-noise ratio (SNR) and SINR of each of the existing V2I communication link, Adaptive beam-based communication, characterized in that any one of the existing V2V communication link SINR of each existing V2V communication link is smaller than its target SINR does not allocate resources to the corresponding V2V communication link system. 10. The method of claim 9,
The infrastructure may sequentially allocate V2V resources to all corresponding V2V communication links when there are a plurality of corresponding V2V communication links, and when V2V resources are allocated to any one of the corresponding V2V communication links, the source of any one of the corresponding V2V communication links. Adaptive beam-based communication system characterized in that the vehicle does not allocate the V2V resources for the other corresponding V2V communication link that is the target vehicle. 10. The method of claim 9,
The infrastructure allocates a V2I downlink slot which is a resource for providing information to the vehicle requesting the V2V resource allocation.

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