JP2012199860A - Portable terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology of reducing the impact on a packet signal to be notified from other terminal even when the packet signal is notified from a terminal which is required to reduce power consumption.SOLUTION: The portable terminal 18 is not mounting a reception function. A modulation unit 74 and an RF unit 72 notify a packet signal in a situation where communication is possible by the packet signal between terminals of other type mounting a carrier sense function and a demodulation function. The RF unit 72 sets the transmission power when informing the packet signal lower than the transmission power when a terminal of other type transmits the packet signal. A generation unit 82 generates the packet signal to be notified.

Description

  The present invention relates to communication technology, and more particularly to a terminal device that broadcasts a signal including predetermined information.

  Road-to-vehicle communication is being studied to prevent collisions at intersections. In the road-to-vehicle communication, information on the situation of the intersection is communicated between the roadside device and the vehicle-mounted device. Road-to-vehicle communication requires the installation of roadside equipment, which increases labor and cost. On the other hand, if it is the form which communicates information between vehicle-to-vehicle communication, ie, onboard equipment, installation of a roadside machine will become unnecessary. In that case, for example, the current position information is detected in real time by GPS (Global Positioning System), etc., and the position information is exchanged between the vehicle-mounted devices so that the own vehicle and the other vehicle enter the intersection respectively. (See, for example, Patent Document 1).

JP 2005-202913 A

  In a wireless LAN (Local Area Network) compliant with a standard such as IEEE 802.11, an access control function called CSMA / CA (Carrier Sense Multiple Access Collision Aviation) is used. Therefore, in the wireless LAN, the same wireless channel is shared by a plurality of terminal devices. In such CSMA / CA, a packet signal is transmitted after confirming that no other packet signal is transmitted by carrier sense. When applying a wireless LAN to inter-vehicle communication such as ITS (Intelligent Transport Systems), it is necessary to transmit information to terminal devices mounted on each of an unspecified number of vehicles. It is desirable that As a result, the terminal device detects the approach of another vehicle by receiving the broadcast signal, and notifies the driver of the approach by notifying the driver of the approach to the driver. To arouse.

  In addition to preventing collision accidents between vehicles, it is also desirable to prevent collision accidents between pedestrians and the like and vehicles. In order to cope with this, the terminal device is carried by a pedestrian in addition to being mounted on the vehicle. In order to prevent the pedestrian from colliding with the vehicle, the terminal device carried by the pedestrian notifies the in-vehicle terminal device of the existing position. On the other hand, since a terminal device carried by a pedestrian is driven by a battery, the amount of processing is required to be reduced as compared with an in-vehicle terminal device. For example, the approach of another vehicle is not notified to the pedestrian. Even when such a terminal device carried by a pedestrian broadcasts a packet signal, it is desirable that the influence on the packet signal broadcast from the vehicle-mounted terminal device is small.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a packet signal broadcast from another terminal device even when the packet signal is broadcast from a terminal device that requires low power consumption. It is to provide a technique for reducing the influence on the environment.

  In order to solve the above-described problem, a terminal device according to an aspect of the present invention is a terminal device that does not have a reception function, and is a packet between other types of terminal devices that have a carrier sense function and a demodulation function. In a situation where communication using signals is possible, a notification unit that notifies a packet signal and a generation unit that generates a packet signal to be notified by the notification unit are provided. An alerting | reporting part sets the transmission power at the time of alerting | reporting a packet signal lower than the transmission power at the time of a different kind of terminal device transmitting a packet signal.

  Another aspect of the present invention is also a terminal device. This device is a carrier that performs carrier sense in a terminal device that is not equipped with a demodulation function in a situation in which communication by a packet signal can be performed between other types of terminal devices that are equipped with a carrier sense function and a demodulation function. A sensing unit, a reporting unit that broadcasts a packet signal based on a result of carrier sensing in the carrier sensing unit, and a generation unit that generates a packet signal to be broadcasted by the reporting unit.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, even when a packet signal is broadcast from a terminal device that requires low power consumption, the influence on the packet signal broadcast from another terminal device can be reduced.

It is a figure which shows the structure of the communication system which concerns on the Example of this invention. It is a figure which shows the structure of the base station apparatus of FIG. FIGS. 3A to 3D are diagrams showing frame formats defined in the communication system of FIG. FIGS. 4A to 4B are diagrams illustrating the configuration of the subframes of FIGS. 3A to 3D. FIGS. 5A and 5B are diagrams showing a format of a MAC frame stored in a packet signal defined in the communication system of FIG. It is a figure which shows the structure of the vehicle-mounted terminal device mounted in the vehicle of FIG. It is a figure which shows the structure of the portable terminal device carried by the pedestrian of FIG. It is a figure which shows the structure of the OFDM signal in the communication system which concerns on the modification of this invention. It is a figure which shows the structure of the portable terminal device which concerns on another modification of this invention. It is a figure which shows operation | movement of the portable terminal device in FIG.

  Before describing the present invention in detail, an outline will be described. Embodiments of the present invention execute inter-vehicle communication between terminal devices mounted on a vehicle (hereinafter also referred to as “vehicle terminal device”), and from a base station device installed at an intersection or the like to a vehicle terminal device The present invention relates to a communication system that also executes road-to-vehicle communication. As the inter-vehicle communication, the in-vehicle terminal device broadcasts a packet signal storing information such as the speed and position of the vehicle (hereinafter referred to as “data”). Other in-vehicle terminal devices receive the packet signal and recognize the approach of the vehicle based on the data. The driver is alerted by notifying the driver of the approach of the vehicle. In order to reduce interference between vehicle-to-vehicle communication and road-to-vehicle communication, the base station apparatus repeatedly defines a frame including a plurality of subframes. The base station apparatus selects any of a plurality of subframes for road-to-vehicle communication, and broadcasts a packet signal in which control information and the like are stored during the period of the head portion of the selected subframe. The control information includes information related to a period for the base station apparatus to broadcast the packet signal (hereinafter referred to as “road vehicle transmission period”).

  The in-vehicle terminal device specifies a road and vehicle transmission period based on the control information, and transmits a packet signal in a period other than the road and vehicle transmission period. Thus, since the road-to-vehicle communication and the vehicle-to-vehicle communication are time-division multiplexed, the collision probability of packet signals between them is reduced. The inter-vehicle communication is performed by the CSMA method in a period for performing inter-vehicle communication other than the road-vehicle transmission period (hereinafter referred to as “vehicle transmission period”). Such terminal devices are also carried by pedestrians (hereinafter, terminal devices carried by pedestrians are referred to as “portable terminal devices”). The portable terminal device is battery-driven and requires low power consumption. Therefore, the portable terminal device only broadcasts a packet signal storing data, and does not notify the pedestrian of the approach of the vehicle. Even when such a portable terminal device broadcasts a packet signal, in order to reduce the influence on the packet signal broadcast from the in-vehicle terminal device, the communication system according to the present embodiment Execute the process. Hereinafter, even a portable terminal device is referred to as inter-vehicle communication and road-to-vehicle communication. Further, the in-vehicle terminal device and the portable terminal device may be referred to as “terminal device” without being distinguished, and the in-vehicle terminal device and the portable terminal device may be collectively referred to as “terminal device”.

  The portable terminal device does not have a packet signal reception function but has only a transmission function. Therefore, the portable terminal device cannot receive the packet signal from the base station device, and cannot grasp the road and vehicle transmission period and the vehicle and vehicle transmission period. Further, since carrier sense in CSMA is not executed, the portable terminal device can broadcast the packet signal under the situation where the packet signal is broadcast from another terminal device. Here, the transmission power in the portable terminal device is set to be smaller than the transmission power in the in-vehicle terminal device. For example, the former is set to be less than half of the latter, the former is set to 10 mW, and the latter is set to 100 mW. Since the transmission power in the portable terminal device is smaller than the transmission power in the in-vehicle terminal device, even when both packet signals collide, the influence on the packet signal from the in-vehicle terminal device is reduced.

  FIG. 1 shows a configuration of a communication system 100 according to an embodiment of the present invention. This corresponds to a case where one intersection is viewed from above. The communication system 100 includes a base station device 10, a first vehicle 12a, a second vehicle 12b, a third vehicle 12c, a fourth vehicle 12d, a fifth vehicle 12e, a sixth vehicle 12f, and a seventh vehicle 12g, collectively referred to as a vehicle 12. , An eighth vehicle 12h, a first pedestrian 16a and a second pedestrian 16b collectively referred to as a pedestrian 16. Each vehicle 12 is provided with an in-vehicle terminal device (not shown), and each pedestrian 16 carries a portable terminal device (not shown). The area 212 is formed around the base station apparatus 10, and the outside area 214 is formed outside the area 212.

  As shown in the drawing, the road that goes in the horizontal direction of the drawing, that is, the left and right direction, intersects the vertical direction of the drawing, that is, the road that goes in the up and down direction, at the central portion. Here, the upper side of the drawing corresponds to the direction “north”, the left side corresponds to the direction “west”, the lower side corresponds to the direction “south”, and the right side corresponds to the direction “east”. The intersection of the two roads is an “intersection”. The first vehicle 12a and the second vehicle 12b are traveling from left to right, and the third vehicle 12c and the fourth vehicle 12d are traveling from right to left. Further, the fifth vehicle 12e and the sixth vehicle 12f are traveling from the top to the bottom, and the seventh vehicle 12g and the eighth vehicle 12h are traveling from the bottom to the top.

  The base station device 10 controls communication between terminal devices. The base station device 10 repeatedly generates a frame including a plurality of subframes based on a signal received from a GPS satellite (not shown) and a frame formed by another base station device 10 (not shown). Here, the road vehicle transmission period can be set at the head of each subframe. The base station apparatus 10 selects a subframe in which the road and vehicle transmission period is not set by another base station apparatus 10 from among the plurality of subframes. The base station apparatus 10 sets a road and vehicle transmission period at the beginning of the selected subframe. The base station apparatus 10 notifies the packet signal in the set road and vehicle transmission period.

  The vehicle 12 is driven by an engine and is equipped with an in-vehicle terminal device. The in-vehicle terminal device generates a frame based on the control information included in the received packet signal. As a result, the frame generated in each of the plurality of in-vehicle terminal devices is synchronized with the frame generated in the base station device 10. Moreover, the vehicle-mounted terminal device notifies the packet signal by executing CSMA / CA during the vehicle transmission period. The in-vehicle terminal device stores, for example, information related to the location in the packet signal. The in-vehicle terminal device also stores control information in the packet signal. That is, the control information transmitted from the base station device 10 is transferred by the in-vehicle terminal device.

  On the other hand, an in-vehicle terminal device that cannot receive a packet signal from the base station device 10, that is, an in-vehicle terminal device that exists outside the area 214 executes the CSMA / CA regardless of the frame configuration, Inform. Furthermore, the in-vehicle terminal device receives a packet signal from another in-vehicle terminal device, thereby notifying the driver of the approach of the vehicle in which the other in-vehicle terminal device is mounted.

  The pedestrian 16 carries a portable terminal device. The portable terminal device has no reception function and has only a transmission function. The portable terminal device notifies the packet signal in which the position information is stored, similarly to the in-vehicle terminal device. However, such notification is performed regardless of the notification of the packet signal from the base station device or the notification of the packet signal from the in-vehicle terminal device. This can be said to be autonomously notified regardless of the frame configuration. In order to reduce the influence on this, the transmission power in the portable terminal device is set to be smaller than the transmission power of other devices.

  FIG. 2 shows the configuration of the base station apparatus 10. The base station apparatus 10 includes an antenna 20, an RF unit 22, a modem unit 24, a processing unit 26, a network communication unit 28, and a control unit 30. The processing unit 26 includes a frame definition unit 32, a selection unit 34, and a generation unit 36.

  The RF unit 22 receives a packet signal from a terminal device (not shown) or another base station device 10 by the antenna 20 as a reception process. The RF unit 22 performs frequency conversion on the received radio frequency packet signal to generate a baseband packet signal. Further, the RF unit 22 outputs a baseband packet signal to the modem unit 24. In general, baseband packet signals are formed by in-phase and quadrature components, so two signal lines should be shown, but here only one signal line is shown for clarity. Shall be shown. The RF unit 22 includes an LNA (Low Noise Amplifier), a mixer, an AGC, and an A / D conversion unit.

  As a transmission process, the RF unit 22 performs frequency conversion on the baseband packet signal input from the modem unit 24 to generate a radio frequency packet signal. Further, the RF unit 22 transmits a radio frequency packet signal from the antenna 20 during the road-vehicle transmission period. The RF unit 22 also includes a PA (Power Amplifier), a mixer, and a D / A conversion unit.

  The modem unit 24 demodulates the baseband packet signal from the RF unit 22 as a reception process. Further, the modem unit 24 outputs the demodulated result to the processing unit 26. The modem unit 24 also modulates the data from the processing unit 26 as a transmission process. Further, the modem unit 24 outputs the modulated result to the RF unit 22 as a baseband packet signal. Here, since the communication system 100 corresponds to an OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, the modem unit 24 also performs FFT (Fast Fourier Transform) as reception processing and IFFT (Inverse Fast Forward) as transmission processing. Also execute.

  The frame defining unit 32 receives a signal from a GPS satellite (not shown), and acquires time information based on the received signal. In addition, since a well-known technique should just be used for acquisition of the information of time, description is abbreviate | omitted here. The frame defining unit 32 generates a plurality of frames based on the time information. For example, the frame defining unit 32 generates ten “100 msec” frames by dividing the “1 sec” period into ten on the basis of the timing indicated by the time information. By repeating such processing, the frame is defined to be repeated.

  The frame defining unit 32 may detect control information from the demodulation result and generate a frame based on the detected control information. Such processing corresponds to generating a frame synchronized with the timing of the frame formed by another base station apparatus 10. 3A to 3D show frame formats defined in the communication system 100. FIG. FIG. 3A shows the structure of the frame. The frame is formed of N subframes indicated as the first subframe to the Nth subframe. For example, when the frame length is 100 msec and N is 8, a subframe having a length of 12.5 msec is defined. The description of FIGS. 3B to 3D will be described later and returns to FIG.

  The selection part 34 selects the sub-frame which should set a road and vehicle transmission period among several sub-frames contained in the flame | frame. More specifically, the selection unit 34 receives a frame defined by the frame defining unit 32. The selection unit 34 inputs a demodulation result from another base station device 10 or a terminal device (not shown) via the RF unit 22 and the modem unit 24. The selection part 34 extracts the demodulation result from the other base station apparatus 10 among the input demodulation results. The selection unit 34 specifies the subframe that has not received the demodulation result by specifying the subframe that has received the demodulation result. This corresponds to specifying a subframe in which the road and vehicle transmission period is not set by another base station apparatus 10, that is, an unused subframe. When there are a plurality of unused subframes, the selection unit 34 selects one subframe at random. When there are no unused subframes, that is, when each of a plurality of subframes is used, the selection unit 34 acquires reception power corresponding to the demodulation result, and gives priority to subframes with low reception power. Select

  FIG. 3B shows a configuration of a frame generated by the first base station apparatus 10a. The first base station apparatus 10a sets a road and vehicle transmission period at the beginning of the first subframe. Moreover, the 1st base station apparatus 10a sets a vehicle transmission period following the road and vehicle transmission period in a 1st sub-frame. The vehicle transmission period is a period during which the in-vehicle terminal device can notify the packet signal. That is, in the road and vehicle transmission period which is the head period of the first subframe, the first base station device 10a can notify the packet signal, and in the vehicle, in the vehicle transmission period other than the road and vehicle transmission period, It is defined that the device can broadcast the packet signal. Furthermore, the first base station apparatus 10a sets only the vehicle transmission period from the second subframe to the Nth subframe.

  FIG. 3C shows a configuration of a frame generated by the second base station apparatus 10b. The second base station apparatus 10b sets a road and vehicle transmission period at the beginning of the second subframe. Also, the second base station apparatus 10b sets the vehicle transmission period from the first stage of the road and vehicle transmission period in the second subframe, from the first subframe and the third subframe to the Nth subframe. FIG. 3D shows a configuration of a frame generated by the third base station apparatus 10c. The third base station apparatus 10c sets a road and vehicle transmission period at the beginning of the third subframe. In addition, the third base station apparatus 10c sets the vehicle transmission period from the first stage of the road and vehicle transmission period in the third subframe, the first subframe, the second subframe, and the fourth subframe to the Nth subframe. As described above, the plurality of base station apparatuses 10 select different subframes, and set the road and vehicle transmission period at the head portion of the selected subframe. Returning to FIG. The selection unit 34 outputs the selected subframe number to the generation unit 36.

  The generation unit 36 sets a road and vehicle transmission period in the subframe of the subframe number received from the selection unit 34, and generates an RSU packet signal to be notified in the road and vehicle transmission period. In the following description, the RSU packet signal and the packet signal are used without distinction. FIGS. 4A to 4B show subframe configurations. FIG. 4A shows a subframe in which a road and vehicle transmission period is set. As illustrated, one subframe is configured in the order of a road and vehicle transmission period and a vehicle and vehicle transmission period. FIG. 4B shows the arrangement of packet signals during the road and vehicle transmission period. As illustrated, a plurality of RSU packet signals are arranged in the road and vehicle transmission period. Here, the front and rear packet signals are separated by SIFS (Short Interframe Space).

  Here, the configuration of the RSU packet signal will be described. FIGS. 5A and 5B show the formats of MAC frames stored in packet signals defined in the communication system 100. FIG. FIG. 5A shows the format of the MAC frame. In the MAC frame, “MAC header”, “LLC header”, “message header”, “data payload”, and “FCS” are arranged in order from the top. Information included in the data payload will be described later. FIG. 5B is a diagram illustrating a configuration of a message header generated by the generation unit 36. The message header includes a basic part.

  The basic part includes “protocol version”, “transmission node type”, “number of reuses”, “TSF timer”, and “RSU transmission period length”. The protocol version indicates the version of the corresponding protocol. The transmission node type indicates the transmission source of the packet signal including the MAC frame. For example, “0” indicates a terminal device, and “1” indicates the base station device 10. When distinguishing between the in-vehicle terminal device and the portable terminal device, the transmission node type is indicated by 2 bits. When the selection unit 34 extracts a demodulation result from another base station device 10 from among the input demodulation results, the selection unit 34 uses the value of the transmission node type. The reuse count indicates an index of validity when the message header is transferred by the terminal device, and the TSF timer indicates the transmission time. The RSU transmission period length indicates the length of the road and vehicle transmission period, and can be said to be information relating to the road and vehicle transmission period. Returning to FIG.

  The network communication unit 28 is connected to a network 202 (not shown). The network communication unit 28 receives traffic jam information from the network 202. The generation unit 36 acquires the traffic jam information from the network communication unit 28 and stores it in the data payload, thereby generating the RSU packet signal described above. The control unit 30 controls processing of the entire base station apparatus 10.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it can be realized by a program loaded in the memory, but here it is realized by their cooperation. Draw functional blocks. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  FIG. 6 shows a configuration of the in-vehicle terminal device 14 mounted on the vehicle 12. The in-vehicle terminal device 14 includes an antenna 40, an RF unit 42, a modem unit 44, a processing unit 46, and a control unit 48. The processing unit 46 includes a timing specifying unit 50, a transfer determining unit 56, an acquiring unit 58, a notification unit 60, and a generating unit 62. The timing specifying unit 50 includes an extracting unit 52 and a carrier sense unit 54. The antenna 40, the RF unit 42, and the modem unit 44 perform the same processing as the antenna 20, the RF unit 22, and the modem unit 24 in FIG. Therefore, here, the difference will be mainly described.

  The modem unit 44 and the processing unit 46 receive packet signals from other terminal devices (not shown) and the base station device 10. As described above, the modem unit 44 and the processing unit 46 receive the packet signal from the base station apparatus 10 during the road and vehicle transmission period. As described above, the modem unit 44 and the processing unit 46 receive packet signals from other in-vehicle terminal devices 14 during the vehicle transmission period. Furthermore, although details will be described later, the modem unit 44 and the processing unit 46 receive a packet signal from a portable terminal device (not shown) regardless of the road and vehicle transmission period and the vehicle and vehicle transmission period.

  When the demodulation result from the modem unit 44 is a packet signal from the base station apparatus 10 (not shown), the extraction unit 52 specifies the timing of the subframe in which the road-vehicle transmission period is arranged. In that case, the extraction part 52 estimates that it exists in the area 212 of FIG. The extraction unit 52 generates a frame based on the timing of the subframe and the content of the message header of the packet signal, specifically, the content of the RSU transmission period length. Note that the generation of the frame only needs to be performed in the same manner as the frame defining unit 32 described above, and thus the description thereof is omitted here. As a result, the extraction unit 52 generates a frame synchronized with the frame formed in the base station device 10.

  On the other hand, when the extraction unit 52 has not received the RSU packet signal, the extraction unit 52 estimates that the extraction unit 52 exists outside the area 214 in FIG. When it is estimated that the extraction unit 52 exists in the area 212, the extraction unit 52 selects a vehicle transmission period. When it is estimated that the extraction unit 52 exists outside the area 214, the extraction unit 52 selects a timing unrelated to the frame configuration. When the vehicle transmission period is selected, the extraction unit 52 outputs information on the frame and subframe timing and the vehicle transmission period to the carrier sense unit 54. When the extraction unit 52 selects a timing unrelated to the frame configuration, the extraction unit 52 instructs the carrier sense unit 54 to execute carrier sense.

  The carrier sense unit 54 receives information regarding the timing of the frames and subframes and the vehicle transmission period from the extraction unit 52. The carrier sense unit 54 measures the interference power by executing carrier sense during the vehicle transmission period. Moreover, the carrier sense part 54 determines the transmission timing in a vehicle transmission period based on interference power. More specifically, the carrier sense unit 54 stores a predetermined threshold value in advance, and compares the interference power with the threshold value. If the interference power is smaller than the threshold value, the carrier sense unit 54 determines the transmission timing. When the carrier sense unit 54 is instructed by the extraction unit 52 to execute carrier sense, the carrier sense unit 54 determines the transmission timing by executing CSMA without considering the frame configuration. The carrier sense unit 54 notifies the generation unit 62 of the determined transmission timing.

  The acquisition unit 58 includes a GPS receiver, a gyro sensor, a vehicle speed sensor, and the like (not shown). Based on data supplied from the GPS receiver, the presence position, the traveling direction, the moving speed, and the like (hereinafter referred to as “position”). (Collectively referred to as “information”). The existence position is indicated by latitude and longitude. Since a known technique may be used for these acquisitions, description thereof is omitted here. The acquisition unit 58 outputs the position information to the generation unit 62.

  The transfer determination unit 56 controls the transfer of the message header. The transfer determination unit 56 extracts a message header from the packet signal. When the packet signal is transmitted directly from the base station device 10, the number of reuses is set to “0”, but when the packet signal is transmitted from another in-vehicle terminal device 14, The number of reuses is set to a value of “1 or more”. The transfer determination unit 56 selects a message header to be transferred from the extracted message header. Here, for example, the message header with the smallest number of reuses is selected. In addition, the transfer determination unit 56 may generate a new message header by combining the contents included in the plurality of message headers. The transfer determination unit 56 outputs the message header to be selected to the generation unit 62. At that time, the transfer determination unit 56 increases the reuse count by “1”.

  The generation unit 62 receives position information from the acquisition unit 58 and receives a message header from the transfer determination unit 56. The generation unit 62 stores the position information in the data payload using the MAC frame shown in FIGS. The generation unit 62 generates a packet signal including a MAC frame, and broadcasts the generated packet signal via the modem unit 44, the RF unit 42, and the antenna 40 at the transmission timing determined by the carrier sense unit 54. Send. This corresponds to inter-vehicle communication. The transmission timing is included in the vehicle transmission period.

  The notification unit 60 acquires the packet signal from the base station device 10 (not shown) and the packet signal from the other in-vehicle terminal device 14 (not shown) via the extraction unit 52. As a process for the acquired packet signal, the notification unit 60 notifies the driver of the approach of another vehicle 12 or a pedestrian 16 (not shown) via a monitor or speaker according to the content of the data stored in the packet signal. To do. Furthermore, the notification unit 60 notifies the driver of traffic jam information and the like via a monitor and a speaker.

  FIG. 7 shows a configuration of the portable terminal device 18 carried by the pedestrian 16. The portable terminal device 18 includes an antenna 70, an RF unit 72, a modulation unit 74, a processing unit 76, and a control unit 78. The processing unit 76 includes an acquisition unit 80 and a generation unit 82. The acquisition unit 80 acquires position information in the same manner as the acquisition unit 58 of FIG. The acquisition unit 80 outputs the position information to the generation unit 82.

  The generation unit 82 receives position information from the acquisition unit 80. The generation unit 82 generates a packet signal in which position information is stored. Here, since the portable terminal device 18 does not have a reception function unlike the in-vehicle terminal device 14, the generation unit 82 does not include a message header transfer portion. The generation unit 82 outputs the generated packet signal to the modulation unit 74. The modulation unit 74 executes only transmission processing, that is, modulation processing, of the modem unit 44 of FIG. The modulation unit 74 outputs the modulated packet signal to the RF unit 72.

  The RF unit 72 executes only transmission processing in the RF unit 42 of FIG. That is, the RF unit 72 notifies the packet signal received from the modulation unit 74 from the antenna 70. Here, the transmission power when notifying the packet signal from the RF unit 72 is set lower than the transmission power when the vehicle-mounted terminal device 14 (not shown) transmits the packet signal. For example, the former is defined to be ½ or less of the latter. Moreover, the former may be prescribed | regulated to 10 mW or less, and the latter may be prescribed | regulated to 100 mW or less.

  Here, the processing unit 76, the modulation unit 74, and the RF unit 72 notify the packet signal at a predetermined period, for example, 100 msec. At that time, carrier sense is not executed. In other words, the processing unit 76, the modulation unit 74, and the RF unit 72 are configured so that the packet signals can be communicated with each other in a situation in which communication by the packet signal can be performed between the in-vehicle terminal device 14 in which the carrier sense function and the demodulation function are mounted. Regardless of, the packet signal is broadcast.

  Next, a modified example of the present invention will be described. The modification of this invention is related with the portable terminal device which is not equipped with a receiving function like an Example. The portable terminal device according to the modified example also aims to reduce the influence on the packet signal broadcast-transmitted from the base station device or the in-vehicle terminal device, as in the embodiment. In the communication system according to the modified example, only a portable terminal device uses some of the subcarriers. On the other hand, the remaining subcarriers are used by the base station device and the in-vehicle terminal device. That is, frequency division multiplexing is performed between the subcarrier used by the portable terminal device and the subcarrier used by the base station device and the in-vehicle terminal device.

  FIG. 8 shows a configuration of the OFDM signal in the communication system 100 according to the modification of the present invention. As shown, the frequency is shown on the horizontal axis. Here, the center subcarrier is used for the portable terminal device, and this is indicated as “portable subcarrier”. In addition, surrounding subcarriers are used for in-vehicle terminal devices and base station devices, which are referred to as “in-vehicle subcarriers”. Since the data amount of the packet signal notified from the portable terminal device is smaller than the data amount of the packet signal notified from the in-vehicle terminal device and the base station device, the number of portable subcarriers is the number of in-vehicle subcarriers It is defined to be less than the number of. Although the subcarrier is defined in this way, the communication system 100, the base station apparatus 10, the in-vehicle terminal apparatus 14, and the portable terminal apparatus 18 according to the modification are the same as those in FIGS. 1, 2, 6, and 7. Of the type. Here, the description is omitted.

  Next, another modification of the present invention will be described. Another modification of the present invention relates to a portable terminal device that does not have a reception function, as in the embodiment. Conventional portable terminal devices are not equipped with a reception function. On the other hand, in the portable terminal device according to another modification, the carrier sense function is mounted out of the reception functions, but the demodulation function is not mounted. Therefore, the portable terminal device cannot grasp the contents of the packet signal broadcast from the base station device, and cannot grasp the frame configuration. However, since the portable terminal device performs carrier sense, the collision probability of packet signals is reduced. A communication system 100, a base station apparatus 10, and an in-vehicle terminal apparatus 14 according to another modification are the same types as those in FIGS. Here, the difference will be mainly described.

  FIG. 9 shows a configuration of a portable terminal device 18 according to another modification of the present invention. The portable terminal device 18 includes a carrier sense unit 84 as compared with the portable terminal device 18 of FIG. The carrier sense unit 84 performs carrier sense similarly to the carrier sense unit 54 of FIG. In addition, since the portable terminal device 18 is not equipped with a demodulation function, the contents of the packet signal from the base station device 10 (not shown) cannot be acquired. Therefore, the carrier sense unit 84 performs carrier sense regardless of the frame configuration. That is, carrier sense is executed in a situation where communication by a packet signal can be performed between the in-vehicle terminal devices 14. Here, an outline of CSMA operation by carrier sense will be described.

  FIG. 10 shows the operation of the portable terminal device 18. The horizontal axis shows time. Busy indicates that a signal from another device is being received. After the busy state ends, a wait is made during DIFS (DCF IFS). Further, after the DIFS is completed, the process waits during the contention window. During this time, if no signal is received, a packet signal is transmitted. Here, the contention window is composed of a plurality of slots. The size of one slot is 13 μsec. The number of slots is determined by random numbers from 0 to N. The length of the packet signal notified from the portable terminal device 18 is shorter than the length of the packet signal notified from the in-vehicle terminal device 14.

  Therefore, if the contention window period is the same between the two, the former has a longer waiting time for the packet signal length than the latter. In order to cope with this, the range of random numbers that can be set for carrier sense by the carrier sense unit 84 is set to be narrower than the range of random numbers that can be set by the in-vehicle terminal device 14 for carrier sense. . For example, the range of random numbers that can be set for carrier sense by the carrier sense unit 84 is determined by 0 to N / 2. This corresponds to the range of the waiting time that can be set by the in-vehicle terminal device 14 being shorter than the range of the waiting time that can be set by the portable terminal device 18.

  According to the embodiment of the present invention, since the transmission power of the packet signal notified from the portable terminal device is set smaller than the transmission power of the packet signal notified from the base station device or the in-vehicle terminal device, the latter Can be reduced. In addition, since the influence is reduced, the reception function can be omitted. In addition, since the reception function is not installed, power consumption can be reduced. In addition, since the transmission power is set small, the power consumption can be reduced. Further, since the power consumption is reduced, the driving time can be lengthened. Further, since the usable subcarriers are separated for each apparatus, the influence of interference can be reduced. Moreover, since only some subcarriers are used, power consumption can be reduced. Moreover, since carrier sense is performed, the influence of interference can be reduced. Further, since the waiting time range is narrow, it is easy to transmit the packet signal with a small waiting time. In addition, since the packet signal can be easily transmitted with a small waiting time, the location can be notified immediately.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  DESCRIPTION OF SYMBOLS 10 Base station apparatus, 12 Vehicle, 14 In-vehicle terminal device, 16 Pedestrian, 18 Portable terminal device, 20 Antenna, 22 RF unit, 24 Modulation / demodulation unit, 26 Processing unit, 28 Network communication unit, 30 Control unit, 32 Frame Definition unit, 34 selection unit, 36 generation unit, 40 antenna, 42 RF unit, 44 modulation / demodulation unit, 46 processing unit, 48 control unit, 50 timing identification unit, 52 extraction unit, 54 carrier sense unit, 56 transfer determination unit, 58 Acquisition unit, 60 notification unit, 62 generation unit, 70 antenna, 72 RF unit, 74 modulation unit, 76 processing unit, 78 control unit, 80 acquisition unit, 82 generation unit, 84 carrier sense unit, 100 communication system.

Claims (3)

A terminal device having no receiving function,
In a situation where communication by a packet signal can be performed between other types of terminal devices equipped with a carrier sense function and a demodulation function, a notification unit that notifies the packet signal;
A generating unit that generates a packet signal to be notified in the notification unit,
The said notification part sets the transmission power at the time of alert | reporting a packet signal lower than the transmission power at the time of another type of terminal device transmitting a packet signal, The terminal device characterized by the above-mentioned. In a terminal device that does not have a demodulation function,
A carrier sense unit that performs carrier sense under a situation in which communication by a packet signal can be performed between other types of terminal devices equipped with a carrier sense function and a demodulation function;
Based on the result of carrier sense in the carrier sense unit, a notification unit for reporting a packet signal;
A generator for generating a packet signal to be notified in the notification unit;
A terminal device comprising:   3. The waiting time range that can be set for carrier sensing by the carrier sense unit is narrower than the waiting time range that can be set for carrier sensing by other types of terminal devices. Terminal equipment.

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