JP5525833B2 - Transmission method of local watch system - Google Patents

Description

  The present invention relates to a transmission method of an area monitoring system suitable for use in watching an attending school child or the like by using an ad hoc network system.

  Recently, the number of incidents such as kidnapping by suspicious children has been increasing, and it has become an important issue how to ensure the safety of children. It has been requested.

  Conventionally, a local crime prevention system disclosed in Patent Document 1 is known as a system corresponding to such a request. The local security system includes a name tag with a wireless tag having a wireless tag storing a unique tag ID, a monitoring device arranged in a predetermined area, and a plurality of monitoring devices arranged with a child or a child as a confirmation target Constitutes a local security system that confirms the location of the person to be confirmed who has the name tag with the wireless tag by the management device connected via the network, and in particular, the wireless tag of the name tag with the wireless tag An ad hoc communication unit that performs ad hoc communication with a name tag with a wireless tag, and a power supply unit are further provided, and the monitoring device transmits a radio wave of a predetermined intensity to the surroundings, and receives a tag ID transmitted by the wireless tag in response thereto The wireless transmission / reception unit and a tag ID communication unit that notifies the management device via the network of the tag ID received at a predetermined timing. The tag ID acquisition unit that communicates with the predetermined monitoring device to acquire the tag ID, and compares the tag ID of the verification target person registered in the predetermined storage unit with the received tag ID, and the location of the verification target person The wireless tag of the name tag with the wireless tag is configured to communicate through one or more other wireless tags by ad hoc communication when communicating with the wireless transmission / reception unit of the monitoring device. Has been.

  By the way, in the conventional regional crime prevention system using such an ad hoc network system, carrier sense is usually executed when calling a child device, and the presence or absence of another carrier is confirmed. Then, when there is no other carrier, transmission is executed after a random waiting time generated by a random number, thereby avoiding the occurrence of collision between a plurality of waiting slave units. In this case, if the slave units are in a hidden relationship, the carriers of each other are not visible, and thus collisions are allowed. However, if the slave units are in an exposed relationship, the collision is not generated or is not generated. However, it is a negligible number of times.

  However, in the situation where the number of slave units increases, specifically, in the vicinity of a master unit installed near a school or kindergarten where the slave units gather, even if the slave units are exposed to each other, There is a tendency for collision between repeaters to increase, and this increase in collision leads to an increase in the number of discarded packets (packet loss rate), and further, the stability and reliability of the local crime prevention system. Therefore, the existing local crime prevention system has a limit in increasing the number of slave units, and there is a problem that the system operation cannot be performed flexibly and expandably.

  Therefore, in order to solve this problem, according to Patent Document 2, the present applicant already has a wireless communication unit provided with a wireless ID tag, and a plurality of slave devices each of which can be carried by a plurality of crime prevention subjects. A plurality of relay devices each having an ad hoc communication unit provided with a wireless ID tag and installed at a plurality of different predetermined locations in a predetermined region; at least one parent device having an ad hoc communication unit; A predetermined guard time in which a time length is set in advance based on the total number of slave units, particularly when no carrier is detected by executing carrier sense when a slave unit is called. After that, we proposed a transmission method for a local crime prevention system that performs packet transmission processing on the condition that a random waiting time generated by random numbers has passed.

JP 2007-042009 A JP 2009-104457 A

  However, the transmission method of the local crime prevention system disclosed in Patent Document 2 described above has the following points to be improved.

  First, since a guard time with a set time length is provided based on the total number of slave units that can be assumed, the number of slave units can be increased compared to the case where guard time is not provided, and the corresponding effect is achieved. Although it can be obtained, there is a limit to the number of slave units that can be increased. After all, if the number of slave units increases beyond the limit, it will allow an increase in collisions and further increase in the number of discarded packets. There was a difficulty that could not be handled.

  Secondly, since there is a fixed guard time regardless of the number of various scenes during use, that is, when the number of slave units is very large or small, the number of slave units is large. A good performance can be obtained from the viewpoint of avoiding the occurrence of collisions (when increased), but if the number of slave units is small, a delay time due to guard time may occur, etc. There was room for further improvement from the viewpoint of optimization.

  An object of the present invention is to provide a transmission method for an area monitoring system that solves such problems in the background art.

  In order to solve the above-described problems, the transmission method of the regional monitoring system 1 according to the present invention includes a wireless communication unit 2t provided with a wireless ID tag, and a plurality of monitoring target persons H can be carried by each. And the ad-hoc communication unit 4t, each having an ad hoc communication unit 3t provided with a wireless ID tag, and installed at a plurality of different predetermined locations in a predetermined area Ac. In the area monitoring system 1 including at least one base unit 4 having a server and a server computer 6 connected to the base unit 4, the local station information is repeatedly transmitted at regular time intervals when the handset 2 is called, Sometimes, when no other carrier is detected by performing carrier sense, a random waiting time (short random waiting time) generated by a random number from at least a predetermined time range (first time range) Ts When Tss is counted and packet Dp transmission processing is performed on the condition that the carrier is not detected continuously even after the elapse of this short random waiting time Tss, and another carrier is detected by executing carrier sense, A second carrier sense is executed after waiting for the set retransmission set time to elapse, and the number of executions reaches a preset switching condition number Nc, which is at least twice as long as the first time range Ts. The next carrier sense is executed on the condition that a random waiting time (long random waiting time) Tms generated by a random number from the time range Tm has passed, and a discard condition in which the number of occurrences of the long random waiting time is set in advance. The packet Dp is discarded on condition that the number Nr is reached.

  In this case, according to a preferred aspect of the invention, the first time range Ts can be set to a range of less than 0.5 [seconds]. The second time range Tm can be set to a range of 0.5 [seconds] or more. In addition, as area Ac, it is optimal to use at least to the school area.

  According to the transmission method of the area monitoring system 1 according to the present invention by such a method, the following remarkable effects are obtained.

  (1) When no other carrier is detected at the time of calling the handset 2, the short random waiting time Tss generated by a random number from at least the first time range Ts is counted, and even after the short random waiting time Tss has elapsed. The packet Dp is transmitted on the condition that the carrier is not detected continuously, and when another carrier is detected, it is generated by a random number from the second time range Tm that is at least twice longer than the first time range Ts. Since the next carrier sense is executed on the condition that the long random waiting time Tms has passed, the child is detected by the long random waiting time Tms before the collision between the slave units 2 is avoided by the short random waiting time Tss. The machines 2 can be dispersed on a relatively long time axis. As a result, it is possible to effectively reduce the number of the slave units 2 ... that are targets of collision avoidance due to the short random waiting time Tss. Therefore, even if the total number of the slave units 2 ... is significantly increased, In addition, the packet loss rate can be drastically reduced.

  (2) When the carrier is detected by executing the carrier sense, the carrier sense is executed again after the preset retransmission setting time has elapsed, and the number of times the carrier sense is executed again is the preset switching condition number Nc. Since the process to generate the long random waiting time Tms is executed on the condition that it reaches the time, the periodic notification is promptly performed without causing any transmission delay to all the slave units 2 in a situation where the number of slave units is relatively small. In the situation where the number of slave units has increased beyond the assumption, a long random waiting time Tms is automatically generated to avoid collision and reduce the packet loss rate. Optimization corresponding to the number of units can be realized.

  (3) Since the packet Dp is discarded on the condition that the number of occurrences of the long random waiting time Tms reaches the preset discard condition number Nr, the process for generating the long random waiting time Tms is performed. However, it is possible to stabilize the entire system.

  (4) According to a preferred embodiment, if the first time range Ts is set to a range of less than 0.5 [seconds] and the second time range Tm is set to a range of 0.5 [seconds] or more, A practically optimal system can be constructed as the regional monitoring system 1 used in the school area.

A timing chart showing a communication state between a repeater and a slave when a long random waiting time is generated by a transmission method according to a preferred embodiment of the present invention, A timing chart showing a communication state between the repeater and the slave when not generating a long random waiting time in the transmission method; A flowchart showing a processing procedure of the transmission method; A flowchart showing some steps of the processing procedure according to the modified embodiment of the transmission method, System diagram showing the whole area monitoring system that implements the transmission method, External view showing the usage status of the slave unit and repeater used in the same area watch system, Electrical system diagram of slave unit and repeater used in the same area monitoring system, Data format diagram of the packet transmitted by the handset used in the same area monitoring system, Experimental data diagram showing the relationship between the number of slave units and the packet loss rate when using this transmission method, Experimental data diagram showing the relationship between the number of slave units and transmission delay time when using this transmission method,

  Next, preferred embodiments according to the present invention will be given and described in detail with reference to the drawings.

  First, in order to facilitate understanding of the transmission method according to the present embodiment, an overview of the entire area monitoring system 1 will be described with reference to FIGS.

  First, the overall system configuration (system system) in the regional monitoring system 1 will be described. FIG. 5 shows the entire system of the system 1. Ac is a predetermined area to which the area monitoring system 1 is applied. The example shows a school attendance area for elementary school students, and H ... indicates a child attending school along the school road R (a person to be watched). C ... is a school bag that the child H ... bears, and FIG. 6A shows the school bag C in an enlarged manner. As shown in FIG. 6A, a waterproof handset (terminal) 2 is attached to the side surface Cs of the school bag C. As shown in FIG. 6B, the slave unit 2 has a flat housing 12 formed in a rectangular shape, and an emergency button 13A, a function button 13B..., A speaker 14S, and a lamp are provided on the front panel of the housing 12. 14L. Further, an electric circuit 15 shown in FIG. 7A is accommodated in the housing 12. The electric circuit 15 of the handset 2 includes a handset processing unit 16 including a CPU, a memory 17 and a microcomputer function unit including a processing program (program memory) Ps, and also includes a battery 19. The slave unit processing unit 16 is connected to the emergency button 13A, the function button 13B..., The speaker 14S, and the lamp 14L, and the vibration sensor 20 and the wireless communication unit 2t provided with the wireless ID tag. Reference numeral 21 denotes a transmitting / receiving antenna.

  On the other hand, repeaters 3 are respectively installed at a plurality of different predetermined locations in the area (school area) Ac, that is, at a plurality of different locations in the middle of the school route R. The repeaters 3... Select a position of 4 to 5 [m] above the school road R. FIG. 6C shows a case where the lower part of the support stay 31 is fixed to the upper part of the pole Mp of the curve mirror M via the fixing brackets 30 and the relay unit 3 is attached to the upper end part of the support stay 31. FIG. 6C shows a case where the curved mirror M is used for installation, but it can also be installed using various public objects such as utility poles and street lamps. The repeater 3 includes a repeater box 32 having waterproofness. A solar cell 33 is disposed on the top surface of the repeater box 32 and a transmission / reception antenna 34 is disposed below the bottom surface. Further, the electric circuit 35 is accommodated in the relay box 32 as shown in FIG. The electrical circuit 35 of the relay unit 3 includes a relay unit processing unit 36 including a CPU, a memory 37, and a microcomputer function unit including a processing program (program memory) Psr, and a battery 39 connected to the relay unit processing unit 36. Prepare. The battery 39 and the solar cell 33 are connected to the semiconductor switch 40. In this case, the power supply unit of the repeater 3 is configured by a charge / discharge circuit that uses the functions of the solar cell 33, the battery 39, the semiconductor switch 40, and the repeater processing unit 36. Thereby, in this charging / discharging circuit, the voltage of the battery 39 is monitored, and when the voltage exceeds a certain voltage, the charging is stopped, and when the voltage falls below the minimum operating voltage, the repeater processing unit 36 is in standby. By shifting to the mode, overdischarge of the battery 39 is prevented. Furthermore, an ad hoc communication unit 3t provided with a wireless ID tag is connected to the relay processing unit 36. Reference numeral 41 denotes a GPS receiver.

  On the other hand, a single parent device 4 having an ad hoc communication unit 4t is installed in an elementary school where the child H goes to school. Although the same main unit 4 as the relay unit 3 can be used, the power source unit can be changed to a DC power source device that can be connected to a commercial power source of AC 100 [V], for example. The base unit 4 is connected to the Internet (network) 5 via the gateway 51. On the other hand, a server computer 6 is installed in the monitoring center, and this server computer 6 is connected to the Internet 5. As a result, the server computer 6 and the parent device 4 can perform data transmission / reception via the Internet 5. Furthermore, the personal computer (personal computer) 52 or the cellular phone 53 possessed by the guardian and the server computer 6 are configured to be capable of bidirectional communication via the Internet 5.

  In this case, the wireless specifications of the slave units 2... And the relay units 3... Use specific low-power radio with the highest priority being independence from the power line, a long reach distance, and high connection capability due to diffraction. The example specific low power radio has a 429 [MHz] band and an output of 10 [mW]. Since this method has a weak point that the communication speed is not high (several kbps), the application used for the network is mainly character information. Further, in order to avoid wireless collision, the CSMA / CA with Ack method is adopted, and as a routing protocol suitable for the wireless communication system, the relay devices 3 periodically receive route information of the relay devices 3. An ad hoc network system using a proactive method for constructing a relay route of its own station is used. The CSMA / CA with Ack method is a method in which each wireless terminal transmits data after confirming that the communication path is continuously available for a certain time or more. Is determined by the arrival of an ACK signal from the receiving side. The proactive method is a method in which each wireless terminal confirms the state of the wireless network prior to communication and constructs a relay route. Furthermore, the ad hoc network system is an autonomous distributed network that does not require a fixed station such as a base station and performs data transmission flexibly to a destination station by hopping data between semi-fixed wireless terminals.

  Next, an outline of the operation of the area monitoring system 1 will be described. Now, it is assumed that an arbitrary child H carries the handset 2 and goes to elementary school. At this time, handset 2 senses vibration during walking with vibration sensor 20 and transmits (transmits) information of its own station in packets every 3 minutes. FIG. 8 shows the data format of the packet Dp transmitted by the handset 2. The information part Dpi in this data format includes the type of periodic notification or emergency notification, the unique ID of the handset 2, and the regular notification is performed in normal times. When each relay unit 3... Receives the periodic report, each received relay unit 3... Relays the packet with the received electric field strength to the base unit 4 in sequence. In this case, the relay route of each relay device 3... Is set in advance.

  And if the main | base station 4 receives a regular notification, the received regular information will be transmitted to the server computer 6 via the gateway 51 and the internet 5. The server computer 6 registers the position of the repeater 3 that received the strongest radio wave in the database as the position of the slave unit 2 (or based on the received electric field strength of the repeaters 3. Update. In this case, the position of the child device 2 may be an estimated position determined from the difference in the magnitude of the received electric field strength of the plurality of relay devices 3. On the other hand, the server computer 6 periodically grasps the position of the child device 2 based on the periodic notification of the child device 2 and monitors whether it is within the designated area of the child device 2 preset in the server computer 6. . At this time, when the user moves out of the designated area, the server computer 6 notifies the guardian (the personal computer 52, the mobile phone 53) and the related person by e-mail. On the other hand, in the case of an emergency call in which the emergency button 13A is pressed, the packet with the received electric field strength added is preferentially relayed to the base unit 4 and transmitted to the server computer 6 and immediately sent from the server computer 6 to the guardian. Emergency notification by e-mail is made to the personal computer 52 and the mobile phone 53 and related parties.

  Further, the guardian can access the server computer 6 from the personal computer 52 or the mobile phone 53 and check the location of the child H (child device 2). In this case, access to the server computer 6 requires input of an ID and a password. When the vibration sensor 20 does not sense vibration during walking, the periodic notification every 3 minutes is changed to the second periodic notification every 1 hour. As a result, communication traffic is reduced.

  Next, a transmission method of the area monitoring system 1 according to the present embodiment will be described with reference to FIGS.

  First, the outline (principle) of the transmission method will be described. In the area monitoring system 1 according to the present embodiment, since each slave unit 2 ... performs regular notification every 3 minutes, it is necessary to avoid the occurrence of collision between the slave units 2 ... At the time of periodic notification (calling), carrier sense is executed to confirm the presence of other carriers. Then, when there is no other carrier and the line is free, a transmission is executed via a random waiting time (short random waiting time) Tss generated by a random number, and a collision between a plurality of waiting slave units 2... Is avoided. The short random waiting time Tss is generated from a predetermined time range (first time range) Ts. The first time range Ts is less than 0.5 [seconds], preferably 20 to 200 [ms], and more specifically, 37 times from 20 [ms] to 5 [ms] intervals. Set to range. Thereby, the subunit | mobile_unit 2 measures the short random waiting time Tss which generate | occur | produces with a random number from 20-200 [ms] (37 types), and does not detect a carrier continuously after progress of this short random waiting time Tss. The process of transmitting the packet Dp is performed under the above conditions.

  By the way, if such a short random waiting time Tss is set, the collision between the plurality of slave units 2 that are exposed to each other does not occur or the number of occurrences is negligible. When the number of units 2 increases, the collision between the sub units 2 and the relay unit 3 increases even if the sub units 2 are exposed to each other. In this case, normally, the carrier sense is repeated, and when the carrier sense reaches the preset number of discard conditions (for example, 7 times), the packet is discarded. Therefore, when the number of slave units 2 increases, the packet loss rate also increases due to an increase in collision.

  Therefore, in the transmission method according to the present embodiment, when another carrier is detected when carrier sense is executed at the time of periodic notification (calling) of the slave unit 2, a second random waiting time (long random) is detected. (Waiting time) The carrier sense is executed again on the condition that Tms has elapsed. In this case, the long random waiting time Tms is generated by a random number from the second time range Tm that is at least twice as long as the first time range Ts described above. The second time range Tm is 0.5 [seconds] or more, preferably 1 to 6 [seconds], more specifically, 6 [1] seconds to 1 [second] intervals. Set to range. Thereby, the subunit | mobile_unit 2 performs a carrier sense again on condition that the long random waiting time Tms which generate | occur | produces with a random number has passed from 1-6 [second] (six kinds).

  As described above, the first time range Ts is set to a range less than 0.5 [second] (range of 20 to 200 [ms]), and the second time range Tm is set to 0.5 [second] or more. If set to a range (range of 1 to 6 [seconds]), a practically optimal system can be constructed as the regional monitoring system 1 used for a school attending area or the like.

  1 and 2 show the state of each of the slave units 2 when the carrier sense is executed at the time of regular notification (calling) of the slave units 2... FIG. When such a transmission method is implemented, FIG. 2 shows a case where the transmission method is not used, that is, a case where the long random waiting time Tms is not provided. In any case, it is assumed that three slave units 2 collide with one repeater 3. In the figure, PT indicates a packet transmission period of the slave unit 2, PR indicates a packet reception period of the relay unit 3, AT indicates a packet transmission period of the relay unit 3, AR indicates a packet reception period of the slave unit 2, and tr Indicates the transmission request timing.

  As shown in FIG. 2, when the long random waiting time Tms is not provided, when the first slave unit 2 and the relay unit 3 are performing the periodic notification process, the other two slave units 2. Until the above-described periodic notification process of the first slave unit 2 and the relay unit 3 is completed, the self-periodic notification process cannot be performed and the transmission standby state is entered. In FIG. 2, Tw indicates a transmission waiting period. In this case, the other two slave units 2... Wait for the fixed retransmission set time to elapse and perform carrier sense again. However, the second slave unit 2... While the periodic notification process of the repeater 3 is being performed, the remaining (third) slave unit 2 cannot perform its own periodic report process and waits for transmission until the periodic report process is completed. Become. As a result, the third handset 2 has twice the number of carrier senses during this time. Therefore, when a large number of child devices 2 are concentrated, the number of times that the child devices 2 perform carrier sense again increases and the probability that the packet Dp is discarded increases.

  On the other hand, when the long random waiting time Tms is provided as in the transmission method according to the present embodiment shown in FIG. 1, the first slave unit 2 and the relay unit 3 are performing periodic notification processing. In the other two slave units 2..., A long random waiting time Tms generated by random numbers is set from 1 to 6 [seconds] which is the second time range Tm, and each slave unit 2 is relatively long. Distributed on the time axis. Therefore, in each of the slave units 2..., Even if another carrier sense occurs once, the probability that it will be more than that will be greatly reduced. That is, even when the total number of slave units 2... Is greatly increased, the occurrence of collision and the packet loss rate can be drastically reduced.

  FIG. 9 shows experimental data on the relationship of the packet loss rate [%] to the number of slave units. Graph data Qnr has no long random waiting time Tms, and graph data Qni has a long random waiting time Tms. Each is shown. If the long random waiting time Tms is not provided as in the graph data Qnr, the packet loss rate is 0 or close to 0 if the number of slave units does not reach 240, but the number of slave units is When it exceeds 240 [units], the packet loss rate [%] increases rapidly, and when it exceeds 250 units, the network is in a failed state. On the other hand, when the long random waiting time Tms is provided as in the graph data Qni, the packet loss rate is a value close to 0 or 0 even if the number of slave units exceeds 240 and further reaches 350. It becomes. In FIG. 9, the scale of the number of slave units is up to 350. However, when the long random waiting time Tms is provided, the packet loss rate is close to 0 until about 750 units.

  FIG. 10 shows experimental data on the relationship of the maximum transmission delay time [seconds] of the child devices 2 to the number of child devices. When the graph data Qrr does not have the long random waiting time Tms, the graph data Qri has the long random waiting time. The case where Tms is provided is shown respectively. When the long random waiting time Tms is not provided as in the graph data Qrr, the maximum transmission delay time is a certain minimum delay time on the system if the number of slave units does not reach 240. When the number of slave units exceeds 240, the maximum transmission delay time increases abruptly, which means a network failure state. On the other hand, when the long random waiting time Tms is provided as in the graph data Qri, the maximum transmission delay time gradually increases in response to the increase in the number of slave units after the number of slave units exceeds 150. . With 350 units, the maximum transmission delay time is about 120 [seconds]. However, since the transmission interval of the regular notification is set to an interval of 3 [minutes] in the example, even if the maximum transmission delay time of about 120 [seconds] occurs, the periodic notification is not hindered.

  As described above, according to the transmission method of the area monitoring system 1 according to the present embodiment, when no other carrier is detected at the time of calling the handset 2, short random numbers generated by random numbers from at least the first time range Ts. When the waiting time Tss is measured and the transmission process of the packet Dp is performed on the condition that the carrier is not detected continuously even after the elapse of the short random waiting time Tss, and another carrier is detected, the first time range Since the next carrier sense is executed on the condition that the long random waiting time Tms generated by the random number has passed from the second time range Tm that is at least twice longer than Ts, the slave unit 2 is used by the short random waiting time Tss. ... Can be dispersed on a relatively long time axis by the long random waiting time Tms before avoiding a collision between them. As a result, it is possible to effectively reduce the number of the slave units 2 ... that are targets of collision avoidance due to the short random waiting time Tss. Therefore, even if the total number of the slave units 2 ... is significantly increased, In addition, the packet loss rate can be drastically reduced.

  Next, a specific processing procedure related to the transmission method of the slave unit 2 will be described according to the flowchart shown in FIG.

  Now, it is assumed that an arbitrary slave unit 2 is in a standby state (step S1). Since the handset 2 makes a periodic notification every 3 [minutes], when 3 [minutes] have elapsed since the previous periodic notification and the call time has come, carrier sense is executed (steps S2 and S3). When no other carrier is detected by executing carrier sense, it is determined that the line is idle, and a guard time (for example, 230 [ms]) is counted (steps S4 and S5). This guard time is set to an optimum time length (fixed length) in consideration of the total number of slave units 2. It is not always necessary to provide the guard time. Further, even if other carriers are not detected by executing carrier sense, carrier sense is continuously executed thereafter, and the presence / absence of other carriers is monitored (step S7). On the other hand, if the guard time has elapsed, a short random waiting time Tss is generated using a random number, and the generated short random waiting time Tss is counted (step S6). As described above, 37 types of short random waiting time Tss with 5 [ms] intervals in the range of 20 to 200 [ms] are prepared.

  If no other carrier is detected continuously after the elapse of the short random waiting time Tss, the handset 2 transmits (transmits) the packet Dp (TEXT signal) shown in FIG. 8 (step S8). Accordingly, since one or a plurality of relay devices 3 installed nearby receive the packet Dp, the received relay devices 3 transmit an acknowledgment packet (ACK signal). Therefore, the subunit | mobile_unit 2 can receive this confirmation response packet (step S9). If the handset 2 receives the confirmation response packet, the periodic notification ends normally, so the handset 2 returns to the standby state again (step S10).

  On the other hand, when another carrier is detected in step S4, since the line is in use, the handset 2 generates a long random waiting time Tms using a random number, and measures the generated long random waiting time Tms. (Step S11). As described above, the long random waiting time Tms is generated by a random number from 1 to 6 [seconds] which is the second time range Tm. Thereby, in the subunit | mobile_unit 2, after long random waiting time Tms progress, a carrier sense is performed again (step S12). Thus, if the long random waiting time Tms is provided, since the subunit | mobile_unit 2 is disperse | distributed on a comparatively long time axis, the probability that another carrier will not be detected by a second carrier sense becomes high. If another carrier is not detected by the second carrier sense, the handset 2 determines that the line is in an idle state, and executes the normal transmission process related to the periodic notification described above (steps S13, S4˜). S10).

  On the other hand, when another carrier is detected in step S12, since the line is in use, the handset 2 generates a second random waiting time Tms again with a random number, and the generated long random waiting time. While measuring Tms, the slave unit 2 performs carrier sense again after the elapse of this long random waiting time Tms (steps S13, S14, S11...). When the number of occurrences of the long random waiting time Tms again reaches the preset discard condition number Nr (for example, 7 times), the handset 2 discards the packet Dp and shifts to a standby state (step S14). , S15, S10). As described above, when the packet Dp is discarded on condition that the number of occurrences of the long random waiting time Tms reaches the preset number of discarding conditions Nr, processing for generating the long random waiting time Tms is performed. Even in this case, the entire system can be stabilized.

  On the other hand, FIG. 4 shows a transmission method according to the modified embodiment. The embodiment shown in the flowchart in FIG. 3 is a basic embodiment in which a long random waiting time Tms is generated from the beginning. In the case of the transmission method according to the modified embodiment shown in FIG. Without generating the waiting time Tms, when the number of slave units 2 increases during use, the mode is switched to the second mode in which the long random waiting time Tms is automatically generated. Therefore, the flowchart of the transmission method according to the modified embodiment is a flowchart in which step SE related to the switching process is added between step S4 and step S10 in the flowchart of FIG. FIG. 4 shows specific processing steps of step SE.

  Hereinafter, the processing procedure of step SE will be described with reference to FIG. In FIG. 4, the same steps as those in FIG. 3 are denoted by the same reference numerals, and the configuration is clarified. If the handset 2 does not detect another carrier in step S4, it is determined that the line is idle, and a guard time (for example, 230 [ms]) is counted (steps S4 and S5). When the guard time has elapsed, a short random waiting time Tss is generated by a random number, and a process related to a regular periodic notification for measuring the generated short random waiting time Tss is executed. Further, when another carrier is detected in step S4, a process related to a regular periodic report for performing carrier sense again is executed after the elapse of a preset retransmission setting time (fixed) (steps S4 and SE1). , SE2, S3 ...).

  On the other hand, the slave unit 2 monitors the number of executions of carrier sense again, and generates a long random waiting time Tms at this point if the number of executions reaches a preset switching condition number Nc (for example, 2 times). The mode is switched to the second mode (steps S4, SE1, SE3, S10...). In other words, the process for generating the long random waiting time Tms is executed on condition that the number of times carrier sense is executed again reaches the switching condition number Nc.

  As described above, at first, the transmission process related to the periodic notification is executed in the first mode in which the long random waiting time Tms is not provided, and the number of times of performing the carrier sense again reaches the switching condition number Nc. If the mode is switched to the second mode that generates the long random waiting time Tms, a periodic report can be made promptly without any transmission delay in all the slave units 2 in a situation where the number of slave units is relatively small. In the situation where the number of slave units has increased beyond the assumption, a long random waiting time Tms is automatically generated to avoid collisions and reduce the packet loss rate. There is an advantage that optimization corresponding to can be realized.

  Although the preferred embodiment (modified embodiment) has been described in detail above, the present invention is not limited to such an embodiment, and the present invention is not limited to such a configuration, shape, technique, quantity, numerical value, and the like. Any change, addition, or deletion can be made without departing from the scope of the above. For example, the case where the first time range Ts is set to a range of less than 0.5 [seconds] and the second time range Tm is set to a range of 0.5 [seconds] or more is shown. Can be arbitrarily set according to the installation environment, use environment, etc. of the area monitoring system 1 to be implemented. Moreover, although the case where the main | base station 4 and the server computer 6 were connected via the internet was shown, you may connect by other networks 5, such as LAN, and you may connect by a simple connection line.

  The area monitoring system according to the present invention can be used for various area monitoring systems as local infrastructure, such as a commuting area exemplified as an area, the safety of an elderly person living alone, a bus location, and the like.

  1: Regional monitoring system, 2 ...: Slave unit, 2t ...: Wireless communication unit, 3 ...: Relay unit, 3t ...: Ad hoc communication unit, 4: Master unit, 4t ...: Ad hoc communication unit, 6: Server computer, H ...: Person to watch, Ac: Predetermined area, Tss: Short random waiting time, Tms: Long random waiting time, Dp: Packet

Claims (4)

  A plurality of slave units each having a wireless communication unit provided with a wireless ID tag and capable of being carried by a plurality of persons to be watched, and an ad hoc communication unit provided with a wireless ID tag, and having a plurality within a predetermined area In a transmission method of an area monitoring system comprising a plurality of relay devices installed at different predetermined locations, at least one parent device having an ad hoc communication unit, and a server computer connected to the parent device, Randomly generated by random numbers from at least a predetermined time range (first time range) when the local station information is repeatedly transmitted at a fixed time interval when a call is made and no other carrier is detected by executing carrier sense. Packets are transmitted on the condition that the waiting time (short random waiting time) is measured and no carrier is detected after the short random waiting time has elapsed. On the other hand, when another carrier is detected by executing the carrier sense, the carrier sense is executed again after the preset retransmission setting time elapses, and the number of execution times reaches the preset number of switching conditions. As a condition, the next carrier sense is executed on the condition that a random waiting time (long random waiting time) generated by a random number from a second time range that is at least twice longer than the first time range has passed, Further, the transmission method of the regional monitoring system, wherein the packet is discarded on condition that the number of occurrences of the long random waiting time reaches a preset number of discard conditions.   2. The transmission method for an area monitoring system according to claim 1, wherein the first time range is set to a range of less than 0.5 [seconds].   3. The transmission method for an area monitoring system according to claim 1, wherein the second time range is set to a range of 0.5 [seconds] or more.   4. The transmission method for an area monitoring system according to claim 1, wherein the area is applied to at least a school area.

Images