JP5024379B2 - Inter-terminal communication control method, radio base station and radio terminal in radio communication system - Google Patents

Description

  The present invention relates to an inter-terminal communication control method, a radio base station and a radio terminal in a radio communication system. The present invention is preferably used for communication in, for example, Intelligent Transport Systems (ITS).

  In recent years, ITS has been developed with the aim of reducing traffic accidents. ITS is equipped with a radio base station (roadside machine) as a traffic light, and information on traffic lights (red or blue, etc.) at intersections and information on the presence or absence of a right turn car is installed on an approaching vehicle several meters ahead (hereinafter referred to as the ITS) There is also a form of road-to-vehicle communication that is transmitted to an in-vehicle device or a mobile station (for example, see Patent Documents 1 to 3 below). There is also a form of inter-vehicle communication in which vehicle-mounted devices located at a short distance communicate with each other to notify vehicle information such as the traveling direction and the traveling speed.

  In inter-vehicle communication provided as one form of ITS Advanced Safety Vehicle (ASV), a wireless terminal (hereinafter also referred to as an in-vehicle device) mounted on a vehicle communicates with a nearby in-vehicle device. By predicting the possibility of an accident in advance by exchanging information such as the position and speed of the own vehicle (hereinafter also referred to as “inter-terminal information” or “vehicle information”) between the vehicles, Applications that prevent it are being considered.

Such vehicle-to-vehicle communication includes, for example, a method in which vehicle-mounted devices autonomously secure radio resources and realize vehicle-to-vehicle communication, such as the Slotted Aloha method and the CSMA / CA method.
JP 2000-358265 A JP 2003-304188 A JP 2003-224505 A

  However, in a method in which the in-vehicle device autonomously secures radio resources, for example, the slot aloha method, radio interference occurs due to multiple vehicles securing the same radio resource at the same time, and vehicle information is normal in other in-vehicle devices. The phenomenon that cannot be received occurs. In the CSMA / CA system, radio interference occurs due to simultaneous transmission between a plurality of terminals caused by the fact that the other party's radio waves do not reach each other and the delay from the other party's radio wave detection to transmission. Occurs.

Furthermore, in the slot aloha system, there is a radio resource that no one selects, and in the CSMA / CA system, the radio resource cannot be effectively used due to a phenomenon in which transmission between in-vehicle devices is caused by a carrier sense backoff or the like. .
In the prior art, there is no problem when there are relatively few vehicles and available roads compared to the available radio resources, but in a congested environment, multiple in-vehicle devices transmit with the same radio resources. As a result of the frequent occurrence of interference, communication quality deteriorates and radio resources are wasted.

As a means for avoiding this, a method in which a radio base station (roadside machine) allocates radio resources to an in-vehicle device can be considered, but for an area controlled by a radio base station (hereinafter also simply referred to as “base station”), When the communication range of the in-vehicle device is small, the same radio resource must be assigned to a plurality of vehicles in the area from the viewpoint of effective use of resources.
In this case, it is sufficient if the same radio resource can be allocated to a vehicle that does not cause interference according to the position of the vehicle at each moment, but the processing load of the base station for the calculation and the terminal However, it is necessary to constantly transmit the position information to the base station, and there is a possibility that the radio resources required for this will become enormous, which is not realistic.

  Therefore, in reality, it is extremely difficult to avoid the occurrence of interference due to the use of the same radio resource by a plurality of neighboring vehicle-mounted devices. However, when the base station regularly assigns the same radio resource to the same vehicle-mounted device, it always interferes when those vehicle-mounted devices are in the vicinity. A phenomenon that does not reach the machine occurs.

Also, the in-vehicle device that is transmitting cannot receive at the same moment due to the wraparound of the radio wave transmitted by itself, and the in-vehicle device that transmits information at a certain moment switches from transmission to reception (or reception to transmission) Since it takes time, it cannot be received immediately (or immediately before). That is, depending on the time relationship between radio resources, there are situations in which communication is not possible.
In addition, since all of the technologies of Patent Documents 1 to 3 are technologies related to road-to-vehicle communication, there is no disclosure or suggestion regarding the existence of the above-described problems in vehicle-to-vehicle communication and means for solving the problems.

The present invention has been made in view of the above problems, and one of its purposes is to suppress the occurrence of radio wave interference in communication between wireless terminals.
Another object of the present invention is to improve the utilization efficiency of resources between wireless terminals.
Furthermore, it is an object of the present invention to effectively use resources between the radio base station and the radio terminal.

  In addition, the present invention is not limited to the above-described object, and is an operational effect derived from each configuration shown in the best mode for carrying out the invention described later, and has an operational effect that cannot be obtained by conventional techniques. Can be positioned as one of the purposes.

(1) As a first proposal, for example, a radio communication system comprising a radio base station and a plurality of radio terminals that perform inter-terminal communication with other radio terminals using resources allocated from the radio base station The wireless base station is a pattern related to the timing at which the wireless terminal uses the resource, and shows an initial used resource number and a used resource that is different for each time zone , indicating different time changes between successive time zones. holds a plurality of patterns defined by a shift amount for numbers, allocated and the use resource number and the shift amount to the wireless terminal end, the wireless terminal uses the resource number assigned by the radio base station seeking use resource numbers in the current time zone based on the shift amount and a row of communication between the terminal using the resources of the use resource number Cormorants, can be used-terminal communication control method in a radio communication system.
(2) As a second proposal, for example, a radio comprising a radio base station and a plurality of radio terminals that perform inter-terminal communication with other radio terminals using resources allocated from the radio base station. The wireless base station in the communication system, which is a pattern related to the timing at which the wireless terminal uses the resource, and shows an initial use resource number and each time period indicating different time changes between consecutive time periods A resource use pattern memory for holding a plurality of patterns defined by shift amounts for different use resource numbers, and resource use pattern assignment control means for assigning the use resource numbers and the shift amounts to the wireless terminals are provided. A radio base station in a radio communication system can be used.
(3) Further, as a third proposal, for example, a radio including a radio base station and a plurality of radio terminals that perform inter-terminal communication with other radio terminals using resources allocated from the radio base station. The wireless terminal in a communication system, which is a pattern related to timing of using the resource, and which uses the resource to receive any assignment of a plurality of patterns indicating different time changes between consecutive time zones from the wireless base station Pattern allocation receiving means, and inter-terminal communication control means for performing inter-terminal communication using the resource according to the pattern received by the resource usage pattern allocation receiving means, wherein the pattern is an initial use resource number And the shift amount for the used resource number that is different for each time period, and The allocation allocation receiving means includes a usage resource determining unit for obtaining a usage resource number in a current time zone based on a usage resource number and a shift amount allocated from the radio base station, and the inter-terminal communication control means includes: A radio terminal in a radio communication system that performs the inter-terminal communication using the resource of the use resource number obtained by the use resource determination unit can be used.

According to the present invention, at least one of the following effects or advantages can be obtained.
(1) Since the radio base station assigns to the radio terminal one of a plurality of patterns that are related to resource use timing of communication between terminals of the radio terminal and that shows different time changes between successive time zones, Compared with the case where the terminal autonomously acquires resources, the resource use timing of each wireless terminal in each time zone can be distributed (equalized), and the resource utilization efficiency is improved.

(2) Even if a plurality of wireless terminals use resources at the same timing in a certain time zone, the resource usage timing is shifted in the next time zone. It is possible to avoid a situation in which communication between terminals occurs continuously and becomes impossible for a long time.
(3) Furthermore, since the wireless terminal can autonomously determine the resource to be used if the pattern is assigned to the wireless terminal at least once, the resource allocation between the wireless base station and the wireless terminal can be determined. Utilization efficiency can be improved.

  (4) In addition, since the wireless terminal can autonomously detect competition of resources used for communication between terminals and request the wireless base station to reallocate (change) resources, It is possible to avoid a situation in which contention for used resources continuously occurs and communication between terminals becomes impossible for a long time.

FIG. 1 is a diagram schematically showing a basic configuration and an operation concept of ITS as an example of a radio communication system according to the first embodiment of the present invention. It is a figure which shows a mode that the radio | wireless resource used for the vehicle-to-vehicle communication in ITS shown in FIG. It is a schematic diagram explaining the example of allocation of the resource usage pattern for the vehicle-to-vehicle communication of ITS shown in FIG. It is a schematic diagram explaining the time change of the resource usage pattern shown in FIG. It is a functional block diagram which shows the structure of the roadside machine (BS) in ITS shown in FIG. It is a functional block diagram which shows the structure of the vehicle equipment (MS) in ITS shown in FIG. It is a sequence diagram explaining the communication sequence of ITS shown in FIG. 6 is a flowchart for explaining resource usage pattern allocation processing in the BS shown in FIGS. 1 and 5. 6 is a flowchart for explaining resource use pattern release processing in the BS shown in FIGS. 1 and 5. FIG. 5 is a schematic diagram illustrating a state of communication collision avoidance between MSs by resource usage pattern allocation illustrated in FIGS. 3 and 4. It is a figure which shows typically the basic composition and operation | movement concept of ITS as an example of the radio | wireless communications system which concerns on 2nd Embodiment of this invention. It is a schematic diagram explaining the operation | movement outline | summary of ITS shown in FIG. It is a functional block diagram which shows the structure of the roadside machine (BS) in ITS shown in FIG. It is a functional block diagram which shows the structure of the vehicle equipment (MS) in ITS shown in FIG. It is a sequence diagram explaining the communication sequence of ITS shown in FIG. It is a flowchart explaining the resource allocation process in BS shown in FIG.11 and FIG.12. It is a flowchart explaining the resource release process in BS shown in FIG.11 and FIG.12. FIG. 12 is a sequence diagram illustrating resource change (reassignment) processing in ITS illustrated in FIG. 11. It is a flowchart explaining the resource change process in BS shown in FIG.11 and FIG.12. It is a flowchart explaining the period control message transmission process in BS shown in FIG.11 and FIG.12. It is a flowchart explaining the period control message reception process in MS shown in FIG.11 and FIG.12. It is a schematic diagram explaining the communication object area | region and communication non-object area | region in ITS shown in FIG. FIG. 12 is a sequence diagram illustrating an operation when controlling the timing of a resource change request in the ITS illustrated in FIG. 11. It is a flowchart explaining the information reception process between terminals in MS shown in FIG. It is a flowchart explaining the information transmission process between terminals in MS shown in FIG. It is a flowchart explaining the resource change request process in MS shown in FIG. It is a flowchart explaining the resource change process in MS shown in FIG.

Explanation of symbols

1,1A radio base station (BS (Base Station))
11 Resource usage pattern management database (DB)
11A Resource management database (DB)
111 In-area terminal management table 112 Allocated terminal number management table 12 Resource usage pattern management unit 12A Resource management unit 121 In-area terminal number memory 13, 13A Control message generation / interpretation unit 14, 14A Wireless communication control unit 15, 15A Antenna 16A Resource Change deterrence unit 2 (2-1, 2-2, 2-3), 2A (2A-1, 2A-2, 2A-3) Wireless terminal (vehicle equipment (MS: Mobile Station))
21, 21A, 28, 28A Antenna 22, 22A Inter-base station wireless communication control unit 23, 23A Inter-base station message control unit 24A Inter-terminal message processing unit 241 Memory 25, 25A Resource state management unit 251 Resource state management table 26A Format composition 27, 27A Inter-terminal wireless communication controller

Embodiments of the present invention will be described below with reference to the drawings. However, the embodiment described below is merely an example for helping understanding of the gist of the present invention, and there is no intention of excluding various modifications and technical applications that are not clearly shown in the embodiment described below. That is, modifications of the embodiments (combining examples) can be performed.
[1] First Embodiment FIG. 1 is a diagram schematically showing a basic configuration and an operation concept of an ITS as an example of a wireless communication system according to a first embodiment of the present invention. The ITS shown in FIG. 1 includes at least one radio base station (BS) 1 and at least one radio terminal that can communicate with the BS 1 in a communication area (hereinafter also referred to as a BS area) provided by the BS 1. (MS) 2, BS1 is installed as a roadside device, for example, on a traffic light on a road, and MS2 is installed as an on-vehicle device in a vehicle, for example.

  In the ITS, the MS 2 autonomously selects (secures) predetermined radio resources (time, frequency, code, etc.) for vehicle-to-vehicle communication outside the BS area, and vehicles with other MS 2 Inter-vehicle communication (ad hoc communication) is performed, and inter-vehicle communication with the BS 1 and other MS 2 can be performed using radio resources allocated from the BS 1 in the BS area.

  That is, the BS 1 centrally manages radio resources for communication with the MS 2 (road-to-vehicle communication) and communication between the MS 2 (vehicle-to-vehicle communication), and performs a process of assigning and releasing the radio resource to the MS 2. It has. In addition to this, the BS 1 in this example has a pattern (hereinafter also referred to as a radio resource usage pattern) regarding the timing (order) at which the MS 2 uses radio resources for each specific time zone, and information on the MS 2 to which the pattern is assigned. And information on the allocation status (blocking information) is stored.

Here, the radio resource usage pattern is such that a plurality of MSs 2 do not use the same radio resource continuously for each time zone, and the number of MSs assigned for each time zone is equal for each radio resource. Is defined as a combination of various radio resource usage patterns.
Therefore, BS1 assigns one of the radio resource usage patterns to MS2 in the BS area, so that MS2 selects a radio resource according to the assigned radio resource usage pattern and communicates with other neighboring MS2 (vehicles). Information broadcast), it is possible to suppress the occurrence of continuous communication collisions (radio wave interference) due to a plurality of MS2 continuously competing and using the same radio resource. Become.

For example, as shown in FIG. 2, a time slot (TS) that is divided by a time determined in accordance with the packet length of inter-vehicle communication, for a predetermined time zone (for example, the shortest transmission cycle of inter-vehicle communication) as a radio resource. (Hereinafter, it may be expressed as a phase), and each is numbered in order from the top.
Then, for example, as shown in FIG. 3, the radio resource usage pattern is defined by a combination of an initial TS (initial radio resource number) of the transmission cycle and a different shift amount in units of TS for each time zone. The same radio resource is not allocated between consecutive patterns in continuous time zones. Also, with respect to each pattern, the priority of assignment (assignment order indicated by circled numbers 1 to 20 in FIG. 3) is defined with priority given to those having a small shift amount. However, in FIG. 3, the initial TS numbers are assumed to be 0 to 4, and attention is paid to only four consecutive time zones.

  Thus, for example, as shown in FIG. 4, as the time zone elapses, the allocation order of the initial TS for each time zone is shifted by the shift amount in each time zone (in FIG. 4, the TS number increases in the right direction on the page). The allocation order of the initial TSs can be changed for each time zone. In FIG. 4, only three time zones out of the four time zones shown in FIG. 3 are illustrated.

  That is, if the state shown in FIG. 4A is the initial phase state, the shift amount for the first row from the bottom is 0 in the next time zone, as shown in FIG. 4B. The initial TS allocation order does not change regardless of the passage of time, and the shift amount for the second row from the bottom is 1, so the initial TS allocation order for the row (time zone) is TS for 1 TS. Shift from the previous time zone in the direction in which the number increases (the direction in which the priority of TS allocation with a larger TS number becomes higher), and the shift amount for the third row from the bottom is 2, so The allocation order of the initial TS shifts from the previous time zone in the direction in which the TS number increases by 2 TS.

  Thereafter, similarly, as shown in FIGS. 4 (3), (4), and (5), the allocation order of the initial TS for the first row from the bottom does not change because the shift amount is 0. The initial TS allocation order for the second row from the first is shifted by 1 TS, and the initial TS allocation order for the third row from the bottom is shifted by 2 TS, and the TS numbers are sequentially shifted in the direction of increasing time zone. I will do it. In FIG. 4, since it is assumed that the number of TSs per time zone is 5, the initial state is restored by five shifts (elapse of five time zones).

(BS configuration)
In order to realize the radio resource allocation as described above, the BS 1 of this example is configured as shown in FIG. 5, for example.
That is, the BS 1 includes a resource usage pattern management database (memory) 11, a resource usage pattern management unit 12, a control message generation / interpretation unit 13, a wireless communication control unit 14, and an antenna 15.

  Here, the resource usage pattern management database 11 (hereinafter also simply referred to as “management DB 11”) is the TS unit for each initial time zone (initial radio resource number) and time zone described with reference to FIGS. Are used to hold radio resource usage patterns (hereinafter also simply referred to as “patterns”) defined by combinations with different shift amounts. In FIG. 5, information for identifying MS2 for each initial TS in each time slot By holding a set (assignment information) of (block information such as a terminal ID) and blocking information indicating whether the initial TS is used / not used (whether or not assigned), which initial TS (that is, wireless) It is possible to manage to which MS 2 the resource usage pattern is assigned. The management DB 11 can be realized by a required memory (resource use pattern memory) such as a RAM.

  The resource usage pattern management unit (resource usage pattern allocation control means) 12 has a function of allocating and releasing a radio resource (usage pattern) to the MS 2 based on the information of the management DB 11. When entering the area of BS1, any one of the patterns in the management DB 11 is assigned to the SM2.

  More specifically, for example, the resource usage pattern management unit 12 assigns a pattern having the highest priority among usage patterns (initial TS) indicating that the blockage information is not used, and information (terminal information) of the MS 2 Is stored in the management DB 11 and the blocking information is set to “allocated”, and when the MS 2 leaves the base station area, the allocation information of the pattern assigned to the leaving MS 2 is released. In this case, if there is an MS 2 to which a pattern having a lower priority than the released pattern is assigned to the MS 2 in the base station area, the released pattern is reassigned to the MS 2. May be.

The control message generation / interpretation unit 13 generates a downlink control message addressed to the MS 2 (such as a radio resource allocation message that notifies pattern allocation information, a message that notifies the release of the allocation), and an uplink control message from the MS 2 And a function of interpreting the contents of (such as a message requesting radio resource allocation or release).
The wireless communication control unit 14 includes at least a transmission / reception function that performs reception processing of a signal received from the MS 2 via the antenna 15 and transmission processing of a signal addressed to the MS 2 to be transmitted from the antenna 15. The reception process includes processes such as low noise amplification, frequency conversion (down-conversion), AD conversion, demodulation, and decoding of the signal received by the antenna 15, and the transmission process includes encoding of transmission information, Processing such as modulation, DA conversion, frequency conversion (up-conversion), and high output amplification is included.

In addition, in the transmission process, the MS 2 can periodically recognize that the MS 2 is located in the BS area, the current time zone, the time zone boundary, and each resource (time slot) location. A process of transmitting a synchronization signal and necessary information (may be broadcast) is also included.
Further, when the MS 2 leaves the BS area, the reception radio wave strength may be weak, or a communication impossible state may occur due to abnormal termination of the mobile terminal. Therefore, a radio resource release request is transmitted from the MS 2 in the transmission process and the reception process. Since there is no guarantee, it is preferable to include a process of periodically performing a life check (keep alive) from BS1 to MS2.

(MS configuration)
On the other hand, as shown in FIG. 6, for example, the MS 2 in this example includes antennas 21 and 28, an inter-base station radio communication control unit 22, an inter-base station message control unit 23, a resource state management unit 25, and an inter-terminal unit. A wireless communication control unit 27 is provided.
Here, the antenna 21 is an antenna used for communication with the BS 1, and the antenna 28 is an antenna used for communication with another MS 2. These antennas 21 and 28 may be shared.

  The inter-base station communication control unit 22 controls radio communication with the BS 1 and performs reception processing of signals received from the antenna 21 from the BS 1 and transmission processing of signals addressed to the BS 1 to be transmitted from the antenna 21. It has at least a transmission / reception function. The reception process includes processes such as low-noise amplification, frequency conversion (down-conversion), AD conversion, demodulation, and decoding of the signal received by the antenna 21. The transmission process includes transmission information encoding, Processing such as modulation, DA conversion, frequency conversion (up-conversion), and high output amplification is included.

The inter-base station message control unit 23 generates an uplink control message (such as a radio resource allocation / release request message) to be transmitted to BS1, and transmits a downlink control message (such as a radio resource allocation message or a radio resource release notification message) received from BS1. It has at least a function of performing interpretation and the like.
The resource state management unit 25 manages radio resources for communication with BS1 (road-to-vehicle communication) and radio resources for communication with other MS2 (vehicle-to-vehicle communication) allocated from BS1. Thus, at least a function for performing road-to-vehicle communication and vehicle-to-vehicle communication according to the assignment is provided. In this example, the function as resource use pattern assignment accepting means for accepting any assignment of the pattern from BS1 is achieved. .

  However, in this example, instead of receiving the pattern itself, it is used for each time zone (transmission cycle) based on radio resource allocation information (resource number, shift amount, and number of resources) notified from BS1. A radio resource (resource number) to be calculated can be calculated (determined) by a predetermined calculation. That is, the resource state management unit 25 also has a function as a used resource determination unit that obtains a used resource number in the current time zone (transmission cycle) based on the resource number assigned from the BS 1 and the shift amount. Details thereof will be described later.

  The inter-terminal radio communication control unit 27 performs inter-vehicle communication so as to perform communication (transmission of vehicle information) with another MS 2 using the radio resource of the resource number (TS number) calculated by the resource state management unit 25. It controls, and has at least a transmission / reception function for performing a reception process of a signal received from the other MS 2 from the other MS 2 and a transmission process of a signal addressed to the other MS 2 to be transmitted from the antenna 28.

Here, the reception process includes processes such as low noise amplification, frequency conversion (down-conversion), AD conversion, demodulation, and decoding of the signal received by the antenna 28, and the transmission process includes transmission information Processing such as encoding, modulation, DA conversion, frequency conversion (up-conversion), and high output amplification is included.
(Description of operation)
Hereinafter, the operation of the ITS configured as described above will be described in detail with reference to FIGS. 7 is a sequence diagram for explaining a communication sequence between BS1 and MS2, FIG. 8 is a flowchart for explaining resource usage pattern allocation processing at BS1, and FIG. 9 is for explaining resource usage pattern release processing at BS1. A flowchart and FIG. 10 are schematic diagrams showing a state of avoiding a communication collision between the MSs 2 by the pattern assignment.

First, as shown in FIG. 7, when the MS 2 enters the BS area (or when the MS 2 located in the BS area is powered on) and can receive a signal from the BS 1, the MS 2 Requests radio resource allocation (step S1). The request includes terminal information such as a terminal ID.
When BS1 receives the allocation request, the resource usage pattern management unit 12 executes resource usage pattern allocation processing (step S2).

That is, as shown in FIG. 8, when the allocation request is received by the control message generation / interpretation unit 13 via the antenna 15 and the radio communication control unit 14 of the BS 1 (step S2-1), a control message generation is performed. / Interpretation unit 13 extracts terminal information (terminal ID) included in the received allocation request and notifies resource usage pattern management unit 12 (step S2-2).
Then, the resource usage pattern management unit 12 (hereinafter also simply referred to as “management unit 12”) has an entry in the management DB 11 whose block information is “in use” and whose terminal information matches the extracted terminal ID. (I.e., an allocation request from the MS 2 that has allocated radio resources in the past) is searched and checked (steps S2-3 and S2-4).

As a result, if there is a corresponding entry (Y route in step S2-4), the management unit 12 sets the blockage information of the entry to “in use” and sets the initial radio resource (initial TS) and the shift amount. Extracted from the management DB 11 (step S2-5).
On the other hand, if there is no corresponding entry (N route in step S2-4), that is, if it is an allocation request from the MS 2 that performs radio resource allocation for the first time, the management unit 12 indicates that the blocking information is “unused” in the management DB 11. A certain entry is searched in descending order of priority (step S2-6), and it is checked whether or not an “unused” entry exists (step S2-7).

  As a result, if there is an “unused” entry (Y route in step S2-7), the management unit 12 sets the blockage information of the entry to “in use” and an initial radio resource (initial TS). And the shift amount are extracted from the management DB 11 (step S2-8). If there is no “unused” entry (N route in step S2-7), the management unit 12 ends the process or causes the control message generation / interpretation unit 13 to generate a control message for error notification. Then, the wireless communication control unit 14 causes the allocation request source MS2 to transmit (step S2-12).

  Thereafter, the management unit 12 calculates a resource number (TS number) to be allocated based on the initial TS and the shift amount extracted in step S2-5 or S2-8 (step S2-9). More specifically, for example, “resource number = [initial radio resource + (current time zone−time zone of initial phase state) × shift amount] mod (number of resources per time zone)” can be calculated. Note that z = x mod y represents that z is a remainder obtained by dividing x by y (the same applies hereinafter).

  Then, the management unit 12 notifies the control message generation / interpretation unit 13 of the calculated resource number, the shift amount, and the number of resources, and the control message generation / interpretation unit 13 that has received the notification is notified. Then, a control message (radio resource allocation message) addressed to the allocation request source MS2 is generated (step S2-10) and transferred to the radio communication control unit 14. The radio communication control unit 14 transmits the radio resource allocation message from the antenna 15 (step S2-11, step S3 in FIG. 7).

When the allocation request source MS2 (resource state management unit 25) receives the radio resource allocation message from BS1, as shown in FIG. 7, each information of resource number, shift amount and number of resources included in the message is received. Based on the above, the radio resource (resource number) to be used this time is calculated (determined) by the following equation (1) or (2) (steps S4 and S6).
(1) Current resource number = [resource number at previous transmission + (current time zone−time zone at previous transmission) × shift amount] mod number of resources (2) current resource number = [when allocation request is received Resource number + (current time zone−time zone when receiving the allocation request) × shift amount] mod number of resources If a signal indicating the boundary of the time zone can be received from BS 1, the current time is calculated by the following equation (3). The resource number of the band can also be calculated.

(3) Resource number of current time zone = (resource number of previous time zone + shift amount) mod number of resources And MS2 communicates with other MS2 using TS of the calculated resource number (transmission of vehicle information) (Steps S5 and S7). Here, the resource number calculated by each MS2 changes from time to time (transmission cycle) so that the collision (contention) of the used TS does not continuously occur as seen from the BS1 side. Since the pattern to be (shifted) corresponds to a pattern that is changed and assigned for each MS2, it is possible to avoid the occurrence of continuous collisions of used TS.

For example, as shown in FIG. 10, assuming that the shift amount allocated to MS 2-1 by the allocation process is 0 and the shift amount allocated to MS 2-2 is 1, MS 2-1 has the same radio resource. The MS 2-2 continues to use (TS), and the radio resource (TS) to be used is shifted by 1 TS every fixed time (transmission period).
Therefore, at a certain point in time (transmission cycle) (2), MS2-1 and MS2-2 use the same radio resource, and the vehicle information of each other does not reach the other party, and the vehicle information is also interfered with surrounding MS2-3 due to interference. Even if a situation that does not reach occurs, at the next time point (transmission cycle) (3), each MS 2-1 and 2-2 will use different radio resources, so the vehicle information of each other will reach the other party, It will reach the surrounding MS2-3. That is, it is possible to avoid a state in which vehicle information does not reach continuously.

  Next, when the MS 2 to which radio resources are allocated as described above leaves the BS area, the MS 2 generates a radio resource release request message addressed to the BS 1 by the inter-base station message control unit 23 and transmits it to the BS 1 ( Step S8 in FIG. When BS1 receives this radio resource release request message, BS1 performs a resource use pattern release process (step S9 in FIG. 7).

That is, for example, as shown in FIG. 9, when the release request message is received by the control message generation / interpretation unit 13 via the antenna 15 of the BS 1 and the wireless communication control unit 14 (step S9-1), the control message is generated. The message generation / interpretation unit 13 extracts terminal information (terminal ID) included in the received release request and notifies the management unit 12 (step S9-2).
Then, the management unit 12 searches the management DB 11 for an entry having terminal information that matches the extracted terminal ID (steps S9-3 and S9-4). If there is an entry (step S9- 4), after setting the blockage information of the entry to “unused” (step S9-5), the control message generation / interpretation unit 13 is requested to generate a control message (radio resource release notification message). .

If there is no entry whose terminal information matches the extracted terminal ID in the management DB 11 (N route in step S9-4), the management unit 12 does not update the management DB 11 and generates a control message / The interpreter 13 is requested to generate a control message (radio resource release notification message).
The control message generation / interpretation unit 13 that has received the request generates a radio resource release notification message addressed to the MS 2 that is the transmission source of the release request message, transmits the message to the MS 2, and indicates that the release of the radio resource has been completed. Notification is made (step S9-6, step S10 in FIG. 7).

  As described above, according to the present embodiment, the BS 1 has a plurality of resource usage patterns related to the timing (cycle) at which the MS 2 uses radio resources for inter-vehicle communication in advance, and any one of the patterns is stored in the BS. Since it is assigned to the MS 2 in the area, it is possible to easily equalize the usage status of individual radio resources in each time period as compared with the case where each MS 2 autonomously acquires resources. Use efficiency improves.

  Here, the pattern is set to a pattern that shows different time changes between successive time zones, in other words, a pattern that excludes the use pattern of radio resources that are the same radio resource or simultaneous transmission / reception. Since the setting is made, it is possible to avoid the occurrence of continuous interference between the MSs 2 and the long-term continuous communication disabled state due to simultaneous transmission and reception.

In particular, since the pattern setting is performed based on the initial resource (TS) number and the shift amount of the resource (TS) number that is different for each time zone, the pattern of the used TS varies with time. It is possible to reliably avoid the occurrence of communication collisions continuously by the MS 2 using the same radio resource with simple control.
Further, since MS2 can autonomously obtain a resource to be used based on the initial resource number and the shift amount, BS1 determines the initial resource number and shift amount for MS2, For example, it is sufficient to notify (assign) only once when entering the BS area. Therefore, the utilization efficiency of radio resources between BS1 and MS2 is also improved. However, when there is a margin in road-to-vehicle communication resources, more information may be transmitted to the MS 2.

In the above-described embodiments, time-divided time slots are associated as radio resources, but frequency division, code division, or division in both the frequency direction and the time direction are performed, and different resource numbers are assigned individually. Also good.
Further, in the above-described embodiment, the resource number (logical number) and the time slot position (physical resource) are fixedly allocated, but in order not to be adjacent in time between consecutive time zones, You may change the correspondence of a time slot position and a radio | wireless resource number for every time slot | zone.

[2] Second Embodiment FIG. 11 is a diagram schematically showing a basic configuration and an operation concept of ITS as an example of a wireless communication system according to a second embodiment of the present invention. The ITS shown in FIG. 11 includes at least one radio base station (BS) 1A and at least one radio terminal (MS) 2A that can communicate with the BS 1A in a communication area (BS area) provided by the BS 1A. Also in this example, BS1A is installed as a roadside device, for example, on a traffic light on a road, and MS2A is installed as an onboard device in a vehicle, for example.

  In the ITS of this example, for example, as schematically illustrated in FIG. 12, when interference is detected for each radio resource in reception by the MS 2A (2A-3) (1), the MS 2A-3 Using inter-vehicle communication, MS2A-1 and 2A-2 are notified of the interfered radio resource (2), so that one MS2A-1 causes the radio resource in use to interfere with another MS2A-2 Triggered by this, the BS 1A is requested to reallocate radio resources (3), and the BS 1A is reassigned radio resources (4).

In order to realize such an operation, the BS 1A of this example is configured as shown in FIG. 13, for example, and the MS 2A is configured as shown in FIG.
(BS configuration)
That is, the BS 1A includes a resource management database (DB) 11A, a resource management unit 12A, a control message generation / interpretation unit 13A, a wireless communication control unit 14A, an antenna 15, and a resource change suppression unit 16A. Is done.

  Here, the resource management DB (memory) 11A, for each radio resource (TS) divided in the same manner as in FIG. 2, information about the MS 2A to which radio resources are allocated in the BS area [terminal information such as terminal ID and the number of units] (MS number)] is stored and managed. In this example, as shown in FIG. 13, data (terminal management table 111 in the area) in which terminal information (terminal ID) and use (allocation) resource numbers are associated, radio resource numbers, and MSs in the BS area. By storing data in which numbers are associated (assigned terminal number management table 112), area terminal management and assigned terminal number management can be performed.

  The resource management unit 12A cooperates with the resource management DB 11A (hereinafter, also simply referred to as “management DB 11A”) to perform road-to-vehicle communication with the MS 2 in the BS area and between the vehicles of the MS 2 in the BS area. A function for managing each radio resource for communication and performing allocation and release processing of each radio resource for road-to-vehicle communication and inter-vehicle communication, and when a radio resource reassignment request is received from the MS 2A through the radio communication control unit 14A And at least a function (resource reassignment control means) for reallocating (changing) radio resources. Note that the resource management unit 12A manages the number of MSs in the BS area where radio resources are allocated in the in-area terminal number memory 121, and performs the reassignment as long as the number of MSs does not exceed a predetermined threshold. carry out.

  The resource change inhibition unit 16A is in a state where the number of MSs in the BS area managed by the resource management unit 12A is equal to or greater than a predetermined threshold (S) and resource change (reassignment) is not possible because there are few or no free resources ( A function that suppresses transmission of useless resource change requests from the MS 2A in a situation where the number of collisions of vehicle-to-vehicle communication increases and the vehicle-to-vehicle communication environment may be deteriorated instead of resource change. It is.

  The control message generation / interpretation unit 13A generates a downlink control message (a radio resource assignment message, a radio resource change notification message, a radio resource release notification message, etc.) addressed to the MS 2A in the BS area, and from the MS 2A in the BS area. It has at least a function of interpreting the contents of uplink control messages (radio resource allocation request message, radio resource change request message, radio resource release request message, etc.).

The wireless communication control unit 14A controls communication with the MS 2 in the BS area. The radio communication control unit 14A receives a signal received from the MS 2A via the antenna 15A, and transmits a signal addressed to the MS 2A to be transmitted from the antenna 15A. It has at least a transmission / reception function for performing processing.
Also in this example, the reception process includes processes such as low noise amplification, frequency conversion (down-conversion), AD conversion, demodulation, and decoding of the signal received by the antenna 15A, and the transmission process includes transmission Processing such as information encoding, modulation, DA conversion, frequency conversion (up-conversion), and high-power amplification is included. Further, in the transmission / reception processing by the wireless communication control unit 14A, as in the first embodiment, processing for periodically transmitting a synchronization signal and necessary information (may be broadcast), periodic life check (keep alive) ) Includes a process of transmitting and receiving a signal.

(MS configuration)
On the other hand, the MS 2A shown in FIG. 14 includes, for example, antennas 21A and 28A, an inter-base station radio communication control unit 22A, an inter-base station message control unit 23A, an inter-terminal message processing unit 24A, and a resource state management unit 25A. The format combining unit 26A and the inter-terminal wireless communication control unit 27A are configured.

Here, the antenna 21A is an antenna used for communication with the BS 1A, and the antenna 28A is an antenna used for communication with the other MS 2A. Also in this example, these antennas 21A and 28A may be shared.
The inter-base station communication control unit 22A controls wireless communication with the BS 1A, and performs a reception process of the signal from the BS 1A received by the antenna 21A and a transmission process of a signal addressed to the BS 1A to be transmitted from the antenna 21A. It has at least a transmission / reception function.

Also in this example, the reception process includes processes such as low noise amplification, frequency conversion (down-conversion), AD conversion, demodulation, and decoding of the signal received by the antenna 21A, and the transmission process includes transmission Processing such as information encoding, modulation, DA conversion, frequency conversion (up-conversion), and high-power amplification is included.
The inter-base station message control unit 23A generates an uplink control message (radio resource allocation / release request message, radio resource change request message, etc.) to be transmitted to the BS 1A, and a downlink control message (radio resource allocation / release notification message received from the BS 1A). , A radio resource change notification message, etc.).

The resource state management unit 25A manages radio resources for communication (road-to-vehicle communication) with BS 1A and radio resources for communication with other MS 2A (vehicle-to-vehicle communication) assigned by BS 1A. Thus, at least a function of performing road-to-vehicle communication and vehicle-to-vehicle communication according to the assignment is provided. In this example, the following functions are also provided.
(A) Function for managing the reception status (not received / good / bad) of each TS other than the radio resource (TS) used to transmit the vehicle information of the own MS 2A by the resource status management table 251 (b) the table A function (resource contention detection means) for determining (detecting) whether or not a plurality of surrounding MSs 2A are using the same radio resource (the presence or absence of contention) based on 251
(C) Function of creating interference information (reception status information) indicating the presence or absence of interference for each TS based on the determination result. The reception status of each TS is determined by, for example, the inter-terminal radio communication control unit 27A The received radio wave intensity and the noise state can be detected and identified based on the detection result.

The inter-terminal message processing unit 24A includes at least a function of performing transmission / reception processing of a message (vehicle information) in inter-vehicle communication with another MS 2A. In this example, the inter-terminal message processing unit 24A also includes the following functions. .
(A) From the vehicle information received from the other MS 2A (position, speed information, etc. of the MS 2A), the other MS 2A to which the own vehicle information should be transmitted (that is, the communication target) is determined, and the MS 2A's own use TS From the other MS 2A indicating that the reception status of the self-used TS is bad, the interference information is aggregated from the resource state management unit 25A (resource state management table 251) and the number of MSs subject to inter-vehicle communication is used as a parameter. (B) When the information received from the other MS 2A is given information notifying that interference has occurred in the resource used by the own MS 2A, or When the ratio exceeds a predetermined threshold, the BS 1A is requested to reassign (change) the TS (the radio resource is sent to the inter-base station message control unit 23A). Function to request generation and transmission of change request message (resource reallocation request means)
The format synthesizing unit 26A adds the interference information of each TS created by the resource state management unit 25A to the transmission information (vehicle information) addressed to the other MS 2A and transmits the vehicle from the inter-terminal message processing unit 24A. It has a function of combining information and the interference information from the resource state management unit 25A as a transmission signal of a predetermined format.

  The inter-terminal radio communication control unit 27A performs communication (transmission of vehicle information) with the other MS 2A using the radio resource of the resource number (TS number) assigned from the BS 1A and managed by the resource state management unit 25A. Controls vehicle-to-vehicle communication, and has at least a transmission / reception function for performing reception processing of signals from other MS 2A received by antenna 28A and transmission processing of signals destined for other MS 2A to be transmitted from antenna 28A. .

Here, the reception process includes processes such as low noise amplification, frequency conversion (down-conversion), AD conversion, demodulation, and decoding of the signal received by the antenna 28A, and the transmission process includes transmission information Processing such as encoding, modulation, DA conversion, frequency conversion (up-conversion), and high output amplification is included.
(Description of operation)
Hereinafter, the operation of the ITS of the present embodiment configured as described above will be described in detail.

First, as shown in FIG. 15, when the MS 2A enters the BS area (or when the MS 2A located in the BS area is powered on) and can receive a signal from the BS 1A, the MS 2A Requests allocation of radio resources (step S11). The request includes terminal information such as a terminal ID.
When the BS 1A receives the allocation request, the resource management unit 12A executes resource allocation processing (step S12).

That is, as shown in FIG. 16, when the allocation request is received by the control message generation / interpretation unit 13A via the antenna 15A of the BS 1A and the wireless communication control unit 14A (step S12-1), a control message generation is performed. / Interpretation unit 13A extracts terminal information (terminal ID) included in the received allocation request and notifies the resource management unit 12A (step S12-2).
The resource management unit 12A determines whether there is an entry whose terminal information matches the extracted terminal ID in the in-area terminal management table 111 of the resource management DB 11A (that is, allocation from the MS 2A that performed radio resource allocation in the past). Whether it is a request) or not (steps S12-3, S12-4).

  As a result, if there is no matching entry (N route in step S12-4), the resource management unit 12A selects the entry with the smallest number of allocated terminals in the allocated terminal number management table 112 of the resource management DB 11 (step S12- 6) Add 1 to the number of allocated terminals of the selected entry, and determine the resource number of the radio resource to which the resource number of the selected entry is assigned (step S12-7).

Then, the resource management unit 12A registers (records) the terminal ID and the used resource number in the in-area terminal management table 111 (step S12-8), and adds 1 to the number of terminals in the area in the in-area terminal number memory 121. (Step S12-9).
Thereafter, the resource management unit 12A notifies the control message generation / interpretation unit 13A of the resource number determined in step S12-7, and the control message generation / interpretation unit 13A controls the control message (radio resource allocation) including the resource number. Message) (step S12-10), and is transmitted from the antenna 15A to the allocation request source MS2A via the wireless communication control unit 14A (step S12-11, step S13 in FIG. 15).

  In step S12-4, if there is a matching entry (Y route in step S12-4), the resource management unit 12A determines the resource number of the radio resource to which the used resource number of the entry is assigned (step S12-4). S12-5), the resource number is notified to the allocation request source MS2A by a radio resource allocation message (steps S12-10, S12-11).

  Each MS 2A in the BS area performs inter-vehicle communication with other MS 2A using the radio resource allocated from BS 1A as described above. That is, each MS 2A transmits (broadcasts) vehicle information such as the position and speed information of its own MS 2A to other neighboring MS 2A using the TS allocated from BS 1 in the BS area. Further, the vehicle information from the other MS 2A is received in the TS other than the TS assigned to the own MS 2A.

Here, each MS 2A monitors the information reception status from the other MS 2A in each TS by the resource status management unit 25A, determines whether a plurality of neighboring MS 2A use the same TS, and interference information for each TS. (Resource state management table 251) is created.
And each MS2A gives the interference information for every TS to the said vehicle information, when transmitting own vehicle information by each function of message processing part 24A between terminals, resource state management part 25A, and format composition part 26A. The other MS2A is transmitted (broadcast) (steps S14 to S16, S17 to S19).

As a result, each MS 2A can recognize the occurrence status of collision (interference) for each TS, and, as will be described later with reference to FIGS. ) Reassignment (provisional change) can be requested, and it is possible to avoid the occurrence of continuous collision in inter-vehicle communication.
Next, when the MS 2A to which radio resources are allocated as described above leaves the BS area, the MS 2A generates a radio resource release request message addressed to the BS 1A by the inter-base station message control unit 23A and transmits it to the BS 1A ( Step S20 in FIG. When BS1A receives this radio resource release request message, BS1A performs resource release processing (step S21 in FIG. 15).

  That is, for example, as shown in FIG. 17, when the release request message is received by the control message generation / interpretation unit 13A via the antenna 15A of the BS 1A and the wireless communication control unit 14A (step S21-1), control is performed. The message generation / interpretation unit 13A extracts terminal information (terminal ID) included in the received release request and notifies the resource management unit 12A (step S21-2).

  Then, the resource management unit 12A searches the in-area terminal management table 111 of the resource management DB 11A for whether there is an entry whose terminal information matches the extracted terminal ID (steps S21-3, S21-4). If it exists (Y route in step S21-4), the used resource number of the entry is determined as the resource number to be released (step S21-5).

  Then, the resource management unit 12A subtracts 1 from the number of allocated terminals corresponding to the determined resource number in the allocated terminal number management table 112 (step S21-6), and calculates the number of terminals in the area in the in-area terminal number memory 121. 1 is subtracted (step S21-7). Further, the control message generation / interpretation unit 13A is requested to generate a control message (radio resource release notification message).

  When there is no entry whose terminal information matches the extracted terminal ID in the in-area terminal management table 111 of the resource management DB 11A (N route in step S21-4), the resource management unit 12A uses the resource management DB 11A ( The control message generation / interpretation unit 13A is requested to generate a control message (radio resource release notification message) without updating the tables 111, 112) and the in-area terminal number memory 121.

Then, the control message generation / interpretation unit 14A that has received the request generates a radio resource release notification message addressed to the release request source MS 2A, transmits the message to the MS 2A, and notifies that the release of the radio resource has been completed (step). S21-8, step S22 in FIG. 15).
Note that the resource management unit 12 </ b> A is configured so that when the number of terminals in the area for each resource is unbalanced as a result of the update of the allocated terminal number management table 112 associated with the resource release processing, the unbalance is resolved. Resource reallocation may be performed.

(Radio resource reallocation (change) processing)
Next, referring to FIG. 18 and FIG. 19, the MS 2A autonomously detects the occurrence of a vehicle-to-vehicle communication collision based on the interference information and requests the BS 1A to reallocate (change) radio resources. It will be described in detail. However, here, the description will be given focusing on three MS2A (2A-1, 2A-2, 2A-3).

  As shown in FIG. 18, it is assumed that MS2A-1 and MS2A-2 in the BS area perform transmission using the same radio resource (TS) x (x represents a resource number) at a certain time (steps). S31). In this case, the other MS 2A-3 in the vicinity can detect the occurrence of interference of the radio resource x from the reception state of each TS by the resource state management unit 25A (step S32).

When the occurrence of interference is detected, the MS2A-3 adds the interference information to the vehicle information transmitted (broadcast) by the MS2A-3 by the inter-terminal message processing unit 24A, so that the surrounding MS2A-1, 2A- 2 (steps S33 and S34).
Each of the MSs 2A-1 and 2A-2 receives the interference information together with the vehicle information at the inter-terminal message processing unit 24A, so that a collision occurs in the use TS and the transmission information (vehicle information) interferes. If it is recognized, the inter-base station message control unit 23A generates a resource change request (radio resource reallocation request message) and transmits it to the BS 1A (steps S35, S36, S37, S38). Note that terminal information such as a terminal ID is added to the message.

  When the BS 1A receives the resource change request, the BS 1A performs resource change processing (step S39). That is, as shown in FIG. 19, when the BS 1A receives the resource change request (step S39-1), the resource management unit 12A refers to the in-area terminal number memory 121 and allocates radio resources within the BS area. It is checked whether the number of completed MSs is equal to or greater than a predetermined threshold S (step S39-2).

  As a result, if the number of radio resources allocated in the BS area is less than the threshold value S (N route in step S39-2), the resource management unit 12A uses the terminal information ( (Terminal ID) is extracted (step S39-3), and it is searched whether or not an entry matching the terminal ID exists in the in-area terminal management table 111 of the resource management DB 11 (steps S39-4 and S39-5).

  If there is a matching entry (Y route in step S39-5), the resource management unit 12A sets the “used resource number” of the entry as “old resource number” (step S39-6) and the number of allocated terminals. In the management table 112, the resource number of the entry with the smallest number of allocated terminals (number of terminals in the area) is set as “new resource number” (step S39-7), and “allocated terminal number” of “old resource number” is decremented by 1. At the same time, 1 is added to the “number of allocated terminals” of the “new resource number” (step S39-8).

  Then, the resource management unit 12A notifies the control message generation / interpretation unit 13A of the “new resource number”, and the control message generation / interpretation unit 13A generates a change resource notification message including the “new resource number”. (Step S39-9), the resource change request source MS2A-1 (or MS2A-2) is transmitted (Step S39-10, Step S40 in FIG. 18).

  When the number of MSs to which radio resources are allocated in the BS area in step S39-2 is greater than or equal to the threshold S (Y route in step S39-2), and in step S39-5 In any case where the entry that matches the terminal ID of the received message does not exist in the in-area terminal management table 111 (N route in step S39-5), the resource management unit 12A ends the processing (the resource change request is Not accepted). At this time, a resource change request rejection notice may be transmitted to the resource change request source.

As described above, the BS 1A that has received the resource change request, when the number of MSs in the BS area is equal to or less than a predetermined number S, uses the resource (TS) with the smallest number of assigned MSs as the MS 2A that issued the resource change request. Reassign resources to any of them as necessary, and update the number of assigned MSs for each resource.
Next, as shown in FIG. 18, the MS 2A-1 that has received the change resource notification message uses the radio resource of the “new resource number” specified by the message to perform subsequent vehicle-to-vehicle communication. (Steps S40, S41, S42). As a result, the radio resources used differ between MS2A-1 and MS2A-2, so the collision is resolved (step S43). Thereafter, each MS 2A gives the reception status information (interference information) for each radio resource (TS) to the transmission information (vehicle information) of its own MS 2A and notifies the surrounding MS 2A to notify each other of the presence or absence of TS interference. Vehicle-to-vehicle communication is carried out while making it possible to detect (steps S44, S45).

  By the way, in the BS 1A, when the number of MSs to which radio resources are allocated in the BS area (the number of terminals in the area in the terminal number memory 121 in the area) is equal to or greater than the threshold value S, the BS 1A uses the function of the resource change inhibiting unit 16A to To suppress transmission of a resource change request (control message) from. This is because, as described above, there is no available resource or there are few resources, so the resource cannot be changed (if the resource change is implemented, the number of vehicle-to-vehicle communication collisions may increase and the vehicle-to-vehicle communication environment may deteriorate. This is to prevent transmission of useless resource change requests from the MS 2A in the (status).

That is, for example, as shown in FIG. 20, when the cycle control message transmission timer (not shown) expires (step S51), the resource change inhibiting unit 16A receives from the resource managing unit 12A the number of terminals in the area in the area terminal number memory 121. To check whether the number of terminals in the area is equal to or greater than the threshold S (step S52).
As a result, if the number of terminals in the area is equal to or greater than the threshold value S (Y route in step S52), the resource change inhibiting unit 16A sets the inhibition state of the control message (resource change request message) to “inhibited” ( If the number of terminals in the area is less than the threshold value S (N route of step S52), the control message suppression state is set to “normal state” (step S54).

  Then, the resource change suppression unit 16A notifies the control message generation / interpretation unit 13A of the suppression state (“inhibited” or “normal state”), and the control message generation / interpretation unit 13A displays the notified suppression state. A control message (period control message) for notifying (broadcasting) to the MS 2A in the BS area is generated and transmitted to the BS area (step S55). With this transmission, the cycle control message transmission timer is restarted (step S56), and thereafter, the above-described processing is repeated every time the timer expires.

  On the other hand, when the MS 2A (inter-base station message control unit 23A) receives the periodic control message (step S111), for example, as shown in FIG. 21, the suppression state set in the message is “normal state” or “ It is checked whether it is “suppressed” (step S112). If it is “normal state” (N route in step S112), a resource change request can be transmitted (step S113). If it is “suppressed” (step S112) (Y route of S112), the resource change request becomes incapable of transmission (step S114). The inhibition state is managed by, for example, a memory (not shown) of the inter-base station message control unit 23A of the MS 2A.

In other words, the BS 1A in this example periodically checks the radio resource allocation status (number of terminals in the area) and controls whether or not the control message (resource change request) can be transmitted from the MS 2A according to the allocation status. It can be done.
Incidentally, in the example described above with reference to FIG. 18, the MS 2A makes a resource change request to the BS 1 in response to reception of interference information from another MS 2A (interference occurrence notification). The transmission timing may be changed (controlled) as appropriate.

For example, the resource change is performed according to the number of times the MS 2A has received a notification of interference occurrence from another MS 2A for the radio resource used for vehicle-to-vehicle communication (transmission) or the ratio of the number of times with the number of MSs subject to vehicle-to-vehicle communication as a parameter. It is also possible to control the transmission of requests.
If such control is performed, it is possible to suppress a request for useless resource change to the BS 1A, and thus it is possible to improve the utilization efficiency of each resource for road-to-vehicle communication and vehicle-to-vehicle communication. .

Note that “MS for vehicle-to-vehicle communication” means, for example, as schematically shown in FIG. 22, when focusing on MS2A waiting for a right turn at an intersection, other MS2A located in an area where there is a possibility of collision within the intersection Or other MS 2A located in an area where there is a possibility of rear-end collision.
Hereinafter, the transmission timing control of the resource change request in the MS 2 will be described in detail.

First, as shown in FIG. 23, a certain MS 2A in the BS area (hereinafter referred to as “target MS 2A”) receives a resource (TS) x (x is a resource number) allocated from the BS 1A by the inter-terminal message processing unit 24A. Terminal-to-terminal information (vehicle information) is transmitted using (representation) (step S61).
More specifically, for example, as shown in FIG. 25, the focused MS 2A starts the inter-terminal information transmission process by the inter-terminal message processing unit 24A when the timing (transmission cycle) of the resource (TS) allocated from the BS 1A is reached. (Step S101), transmission information (vehicle information) is generated (Step S102).

  The transmission information is transferred to the format synthesizing unit 26A, and the format synthesizing unit 26A gives the reception status information of each resource in the resource status management table 251 (step S103). At that time, the resource state management unit 25A resets all the contents of the resource state management table 251 (sets to not received) (step S104), and the inter-terminal message processing unit 24A performs the information (the parameter m, the resource of the memory 241). The reception state failure notification count r) for x is reset (m = 0, r = 0) (step S105).

Then, the transmission information to which the reception status information is added is transmitted from the antenna 28A to the other MS 2A in the surroundings through the inter-terminal wireless communication control unit 27A (step S106).
On the other hand, as shown in FIG. 23, the focused MS 2A receives the interference information (reception state information) from the other MS 2A in the vicinity together with the inter-terminal information of the other MS 2A (steps S62, S64, S65, S67, S68). Note that the focused MS 2A (inter-terminal message processing unit 24A) resets the information in the memory 241 (the parameter m and the reception state failure notification number r for the resource x) every time the inter-terminal information is transmitted.

Here, interference information from the other MS2A that is not subject to inter-vehicle communication is also received (steps S64 and S67), but the focused MS2A (inter-terminal message processing unit 24A) is subject to inter-vehicle communication (hereinafter simply referred to as “communication subject”). The information (m, y) in the memory 241 is updated only when the inter-terminal information of the other MS 2A is received.
That is, every time the inter-terminal message processing unit 24A receives inter-terminal information (reception status information) from the other MS 2A to be communicated, the parameter m is incremented by 1, and the reception status information indicates “bad”. The reception status defect notification count (hereinafter also simply referred to as “defect notification count”) y is incremented by 1 for each piece of information. Note that when reception state information from another non-communication target MS 2A is received, the parameter m is not updated, and when the reception state information is information indicating “good”, the failure notification number y is updated. Not.

Then, the inter-terminal message processing unit 24A updates the information in the memory 241 every time receiving the reception status information from the other MS 2A to be communicated as described above, and then, based on the information in the memory 241, the resource for the BS 1A It is determined whether or not a change request is made (steps S63, S66, and S69).
The detailed operation of the focused MS 2A will be described with reference to the flowchart shown in FIG. 24. When the focused MS 2A first receives an inter-terminal radio wave (step S81), the inter-terminal radio communication control unit 27A receives the received radio wave. It is checked whether the inter-terminal information received by (1) has been normally received (whether it has been correctly demodulated and decoded) (step S82).

  If it has been normally received (Y route in step S82), the resource state management unit 25A sets the state of the corresponding resource number (TS number of the received TS) in the resource state management table 251 to “good” ( If not received normally (step S83), the status of the corresponding resource number is set to "bad" (step S84).

When the inter-terminal information can be normally received, the focused MS 2A further checks in the inter-terminal message processing unit 24A whether the receiving inter-terminal information is information from the other MS 2A to be communicated. (Step S85).
As a result, if it is information from the other MS 2A to be communicated (Y route of step S85), the inter-terminal message processing unit 24A adds (increases) the parameter of the memory 241 by 1 (step S86), It is checked whether or not the reception status information is information indicating “defective” (step S87), and if it is information indicating “defective” (Y route in step S87), 1 is added to the number y of defective notifications in the memory 241. (Step S88).

  Next, the inter-terminal message processing unit 24A determines that the parameter m in the memory 241 is equal to or larger than the minimum value that can be taken, and the value of the number of failure notifications y / the parameter m is a predetermined threshold (change request probability lower limit) α. It is determined whether or not (step S89), and if the condition is satisfied (Y route of step S89), the resource change request process is started (step S90), and the resource change request message is sent to the inter-base station message control unit 23A. Request generation.

  As shown in FIG. 26, the inter-base station message control unit 23A confirms the current suppression state (“normal state” or “inhibiting”) (step S121), and if it is “normal state” As long as a resource change request message is generated, the message is transmitted to the BS 1A (from the N route in step S121 to steps S122 and S123, and step S71 in FIG. 23).

In BS1A, when the resource change request is received, the process as described above with reference to FIG. 19 (steps S39-1 to S39-10) is performed (step S72 in FIG. 23), and if the resource change is completed, The changed resource number is transmitted to the target MS 2A of the resource change request source by the changed resource notification message (step S73 in FIG. 23).
As shown in FIG. 27, the focused MS 2A receives the change resource notification message (step S131), and the inter-terminal message processing unit 24A sets the resource number used for inter-vehicle communication (transmission) to the notified resource number. Setting is made (step S132, step S74 in FIG. 23), and vehicle-to-vehicle communication is performed using the radio resource (TS) of the resource number (step S91 in FIG. 24).

  As described above, according to the present embodiment, each MS 2A should transmit its own vehicle information based on reception information (vehicle information such as position and speed) of inter-vehicle communication from other MS 2A (communication target) The other MS 2A is discriminated, and interference information related to the resource (TS) used for transmission to the MS 2A is aggregated. When the information indicating the interference exceeds a certain ratio, the resource change to the BS 1A (Reassignment) is requested, and the BS 1A changes (reassigns) the assigned resource according to the request, so that it is possible to avoid the occurrence of continuous vehicle-vehicle communication collisions.

Also in the second embodiment described above, as in the first embodiment, as a radio resource for inter-vehicle communication, in addition to the time division time slot, frequency division, code division, or division in both the frequency direction and the time direction is performed. Resources may be allocated. Further, the correspondence relationship between the time slot position and the radio resource number may be changed for each time zone so as not to be adjacent in time between consecutive time zones. That is, it is possible to combine the first embodiment and the second embodiment.
Regarding the above embodiments, the following additional notes are disclosed.
[3] Appendix
(Appendix 1)
In a radio communication system comprising a radio base station and a plurality of radio terminals that perform inter-terminal communication with other radio terminals using resources allocated from the radio base station,
The radio base station is
The wireless terminal is a pattern related to the timing of using the resource, and has a plurality of patterns indicating different time changes between successive time zones,
Assign any of the patterns to any of the wireless terminals;
The wireless terminal is
An inter-terminal communication control method in a radio communication system, wherein the inter-terminal communication is performed using the resource in accordance with the pattern assigned by the radio base station.
(Appendix 2)
The pattern is defined by an initial use resource number and a shift amount for a use resource number that is different for each time period,
The radio base station is
Assigning the used resource number and the shift amount to the wireless terminal;
The wireless terminal is
Based on the used resource number and shift amount allocated from the radio base station, find the used resource number in the current time zone,
The inter-terminal communication control method in the wireless communication system according to appendix 1, wherein the inter-terminal communication is performed using the resource of the used resource number.
(Appendix 3)
The radio base station is
The terminal-to-terminal communication control method in the wireless communication system according to appendix 2, wherein the used resource number and the shift amount are assigned in order from the smallest shift amount.
(Appendix 4)
In a radio communication system comprising a radio base station and a plurality of radio terminals that perform inter-terminal communication with other radio terminals using resources allocated from the radio base station,
The wireless terminal is
Detecting contention of the resource among a plurality of other wireless terminals based on the reception status of signals transmitted by other wireless terminals;
Notifying one of the other wireless terminals of the detection of the conflict,
The wireless terminal that has received the notification
Request the radio base station to reallocate the resource;
The radio base station is
An inter-terminal communication control method in a radio communication system, wherein the resource is reassigned to any of the plurality of other radio terminals upon receiving the request.
(Appendix 5)
The wireless terminal that has received the notification
The inter-terminal communication control method in the radio communication system according to appendix 4, wherein the reassignment request timing for the radio base station is controlled according to the number of received notifications.
(Appendix 6)
The radio base station is
6. The terminal in the wireless communication system according to appendix 4 or 5, wherein the reassignment is not performed when the number of wireless terminals to which the resource has been allocated is a predetermined number or more at the time of receiving the request. Inter-communication control method.
(Appendix 7)
The radio base station is
The reassignment request is prohibited to the notified wireless terminal when the number of wireless terminals to which the resource has been allocated is a predetermined number or more when the request is received. The communication control method between terminals in the radio | wireless communications system of any one of 4-6.
(Appendix 8)
The radio base station in a radio communication system comprising a radio base station and a plurality of radio terminals that perform inter-terminal communication with other radio terminals using resources allocated from the radio base station,
A resource usage pattern memory that holds a plurality of patterns that are related to the timing at which the wireless terminal uses the resource and that shows different time changes between successive time zones;
Resource usage pattern allocation control means for allocating any of the patterns to any of the wireless terminals;
A radio base station in a radio communication system, characterized by comprising:
(Appendix 9)
The pattern is defined by an initial use resource number and a shift amount for a use resource number that is different for each time period,
The resource usage pattern allocation control means includes:
Assigning the used resource number and the shift amount to the wireless terminal;
The radio base station in the radio communication system according to appendix 8, wherein
(Appendix 10)
The resource usage pattern allocation control means includes:
The radio base station in the radio communication system according to appendix 9, wherein the used resource number and the shift amount are assigned in order from the smallest shift amount.
(Appendix 11)
The wireless terminal in a wireless communication system comprising a wireless base station and a plurality of wireless terminals performing inter-terminal communication with other wireless terminals using resources allocated from the wireless base station,
A resource usage pattern allocation receiving means for receiving, from the radio base station, an allocation of any of a plurality of patterns which are patterns related to the timing of using the resources and exhibit different temporal changes between successive time zones;
Inter-terminal communication control means for performing inter-terminal communication using the resource according to the pattern received by the resource use pattern allocation receiving means;
A wireless terminal in a wireless communication system, characterized by comprising:
(Appendix 12)
The pattern is defined by an initial use resource number and a shift amount for a use resource number that is different for each time period,
The resource usage pattern allocation receiving means
A use resource determining unit for obtaining a use resource number in a current time zone based on a use resource number and a shift amount allocated from the radio base station;
The inter-terminal communication control means includes
The inter-terminal communication is performed using the resource of the used resource number obtained by the used resource determining unit.
12. A wireless terminal in a wireless communication system according to appendix 11, wherein
(Appendix 13)
The wireless terminal in a wireless communication system comprising a wireless base station and a plurality of wireless terminals performing inter-terminal communication with other wireless terminals using resources allocated from the wireless base station,
Resource contention detection means for detecting contention of the resources among a plurality of other wireless terminals based on the reception status of signals transmitted by other wireless terminals;
Notification means for notifying one of a plurality of other wireless terminals of the detection of the contention by the resource contention detection means;
A wireless terminal in a wireless communication system, characterized by comprising:
(Appendix 14)
The wireless terminal in a wireless communication system comprising a wireless base station and a plurality of wireless terminals performing inter-terminal communication with other wireless terminals using resources allocated from the wireless base station,
Receiving means for receiving notification from the other wireless terminal that the resource contention for the own wireless terminal has been detected in the other wireless terminal;
When the notification is received by the receiving means, resource reassignment requesting means for requesting the radio base station to reallocate the resources;
A wireless terminal in a wireless communication system, characterized by comprising:
(Appendix 15)
The radio base station in a radio communication system comprising a radio base station and a plurality of radio terminals that perform inter-terminal communication with other radio terminals using resources allocated from the radio base station,
Receiving means for receiving a resource reassignment request transmitted by the second wireless terminal notified from the first wireless terminal that the resource conflict for the second wireless terminal is detected in the first wireless terminal When,
When the resource reassignment request is received by the receiving means, resource reassignment control means for reassigning the resource to the second wireless terminal;
A radio base station in a radio communication system, characterized by comprising:

  As described above in detail, according to the present invention, it is possible to avoid a situation in which contention for resources used by a plurality of wireless terminals continuously occurs and communication between terminals becomes impossible for a long time. It is considered extremely useful in the field of wireless communication technology.

Claims (3)

In a radio communication system comprising a radio base station and a plurality of radio terminals that perform inter-terminal communication with other radio terminals using resources allocated from the radio base station,
The radio base station is
A pattern related to the timing at which the wireless terminal uses the resource, and is defined by an initial use resource number and a shift amount for a use resource number that is different for each time period , indicating different time changes between consecutive time periods. Possess multiple patterns
Allocation and the shift amount and the use resource number to the radio terminal end,
The wireless terminal is
A use resource number in a current time zone is obtained based on a use resource number and a shift amount allocated from the radio base station, and the inter-terminal communication is performed using the resource of the use resource number. A communication control method between terminals in a wireless communication system . The radio base station in a radio communication system comprising a radio base station and a plurality of radio terminals that perform inter-terminal communication with other radio terminals using resources allocated from the radio base station,
A pattern related to the timing at which the wireless terminal uses the resource, and is defined by an initial use resource number and a shift amount for a use resource number that is different for each time period , indicating different time changes between consecutive time periods. a resource usage pattern memory that holds a plurality of patterns,
And resource usage pattern allocation control means for allocating said shift amount and the use resource number to the radio terminal end,
A radio base station in a radio communication system, characterized by comprising: The wireless terminal in a wireless communication system comprising a wireless base station and a plurality of wireless terminals performing inter-terminal communication with other wireless terminals using resources allocated from the wireless base station,
A resource usage pattern allocation receiving means for receiving, from the radio base station, an allocation of any of a plurality of patterns which are patterns related to the timing of using the resources and exhibit different temporal changes between successive time zones;
Inter-terminal communication control means for performing inter-terminal communication using the resource according to the pattern received by the resource use pattern allocation receiving means;
The equipped,
The pattern is defined by an initial use resource number and a shift amount for a use resource number that is different for each time period,
The resource usage pattern allocation receiving means
A use resource determining unit for obtaining a use resource number in a current time zone based on a use resource number and a shift amount allocated from the radio base station;
The inter-terminal communication control means includes
The inter-terminal communication is performed using the resource of the used resource number obtained by the used resource determining unit.
A wireless terminal in a wireless communication system .

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