JP2013250731A - Automatic meter-reading system, portable terminal and radio communication method for portable terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic meter-reading system for simplifying a communication procedure between a portable terminal and a radio terminal.SOLUTION: The automatic meter-reading system includes: a plurality of radio terminals; an automatic meter-reading server for transmitting a radio signal to the plurality of radio terminals, and for receiving and collecting the measurement data of a plurality of measurement units from the plurality of radio terminals; and a portable terminal capable of performing radio communication with the radio terminal. Between the automatic meter-reading server and the plurality of radio terminals and between the plurality of radio terminals and the portable terminal, radio communication is performed by applying time-division multiplex to downlink and uplink in a modulation system of performing spectral diffusion by diffusion code system. The radio terminal determines a radio power to be transmitted in the uplink on the basis of the radio power of the radio signal received in the downlink. The portable terminal detects the period of the downlink, and transmits the radio signal which has been subjected to the spectral diffusion by the same diffusion code system as that of the automatic meter-reading server to the radio terminal in the period of the downlink, and receives the radio signal from the radio terminal in the uplink.

Description

  The present invention relates to an automatic meter reading system, a portable terminal, and a wireless communication method for the portable terminal.

  2. Description of the Related Art Conventionally, a wireless meter reading system that performs meter reading by collecting measured values of an electric energy meter, a gas meter, a water meter, and the like by wireless communication is known. For example, Patent Document 1 describes a system that includes a handy terminal (portable terminal) and a wireless meter reading device, and collects meter reading data of a plurality of meters in the wireless meter reading device. The wireless meter reading device includes a wireless master device (wireless base station) and a plurality of wireless slave devices (wireless terminals). During operation of meter reading, the wireless master device communicates with each of the plurality of wireless slave devices. Wireless communication between them. Each of the plurality of wireless slave units is connected on a one-to-one basis corresponding to each of the plurality of meters.

JP 2010-271897 A

  The prior art has a problem that the communication procedure is complicated because the mobile terminal communicates with a plurality of wireless terminals through a communication procedure with the wireless base station.

The automatic meter-reading system according to claim 1 is connected to each of the measuring devices installed in each of the plurality of consumers, and a plurality of wireless terminals that respectively acquire measurement data of the measuring devices, and a predetermined wireless power An automatic meter-reading server that receives and collects weighing data of the plurality of measuring instruments from the plurality of wireless terminals by transmitting wireless signals to the plurality of wireless terminals; and a portable terminal capable of wireless communication with the wireless terminal; The wireless communication between the automatic meter-reading server and the plurality of wireless terminals, and between the plurality of wireless terminals and the mobile terminal is based on a modulation scheme in which spectrum is spread by a predetermined spreading code sequence, Wireless communication that time-division-multiplexes downlinks from the automatic meter-reading server to the plurality of wireless terminals and uplinks from the plurality of wireless terminals to the automatic meter-reading server. The end determines the radio power to be transmitted on the uplink based on the radio power of the radio signal received on the downlink, the mobile terminal detects the downlink period in the time division multiplexing, A radio signal spectrum-spread by the same spreading code sequence as that of the automatic meter-reading server is transmitted to the radio terminal during the downlink period, and a radio signal from the radio terminal is received via the uplink line.
The portable terminal according to claim 8 is connected to each of the measuring devices installed in each of the plurality of consumers, and a plurality of wireless terminals that respectively acquire measurement data of the measuring devices, and wireless with a predetermined wireless power An automatic meter reading server that receives and collects the weighing data of the plurality of measuring instruments from the plurality of wireless terminals by transmitting a signal to the plurality of wireless terminals, the automatic meter reading server and the plurality of wireless terminals; Between the automatic meter-reading server and the plurality of wireless terminals, and the mobile phone used in an automatic meter-reading system in which wireless communication is performed in a time-division multiplexed manner from the plurality of wireless terminals to the automatic meter-reading server. The terminal detects a downlink period in the time division multiplexing, and transmits a radio signal to the wireless terminal in the downlink period detected by the detection unit. And, characterized in that it comprises a communication unit that receives a radio signal from the radio terminal in the uplink.
A wireless communication method for a portable terminal according to claim 10 is connected to each of measuring instruments installed in each of a plurality of consumers, and a plurality of wireless terminals that respectively acquire measurement data of the measuring instrument, An automatic meter reading server that receives and collects weighing data of the plurality of measuring devices from the plurality of wireless terminals by transmitting wireless signals of wireless power to the plurality of wireless terminals; An automatic meter-reading system that performs time-division multiplexing of downlinks from the automatic meter-reading server to the plurality of wireless terminals and uplinks from the plurality of wireless terminals to the automatic meter-reading server In the wireless communication method of the portable terminal in, a detection step of detecting the downlink period in the time division multiplexing, and the downlink of the downlink detected in the detection step Sends said radio signal to the wireless terminal during, characterized in that it comprises a communication step of receiving a radio signal from the radio terminal in the uplink.

  ADVANTAGE OF THE INVENTION According to this invention, the communication procedure between a portable terminal and a radio | wireless terminal can be simplified.

It is a block diagram which shows the structure of the automatic meter-reading system which concerns on 1st Embodiment. 4 is a diagram schematically showing a sequence of wireless communication between a wireless base station 3 and a smart meter 4. FIG. FIG. 3 is a block diagram illustrating a configuration of a part related to wireless communication in the entire wireless base station 3. It is a block diagram which shows the structure of the part relevant to radio | wireless communication among the whole radio | wireless terminals 6 which the smart meter 4 has. It is a block diagram which shows the structure of the part relevant to radio | wireless communication among the whole HT7. It is a figure which shows typically the sequence of the radio | wireless communication with the wireless base station 3 and the smart meter 4, and the wireless communication with the smart meter 4 and HT7. It is a figure which shows typically the sequence of the radio | wireless communication with the wireless base station 3 and the smart meter 4, and the wireless communication with the smart meter 4 and HT7. It is a block diagram which shows the structure of the base station radio | wireless communication part 28 of the radio base station 3 which concerns on 3rd Embodiment. It is a block diagram which shows the structure of the HT radio | wireless communication part 45 of HT7 which concerns on 3rd Embodiment. It is a block diagram which shows the structure of the HT radio | wireless communication part 45 of HT7 which concerns on 4th Embodiment. It is a block diagram which shows the structure of the HT radio | wireless communication part 45 of HT7 which concerns on 5th Embodiment.

(First embodiment)
FIG. 1 is a block diagram showing a configuration of an automatic meter reading system according to the first embodiment. The automatic meter reading system 100 is an automatic meter reading system for the amount of electric power used by a specific electric power company, and automatically reads the electric energy of all households contracted with the electric power company. The automatic meter reading system 100 includes an automatic meter reading server 1 and a wireless base station 3 connected via an electric communication line 2, a smart meter 4 installed in each home, and a handy terminal used by a meter reader, maintenance staff, etc. 7.

  The automatic meter reading server 1 is connected to a radio base station 3 installed on a utility pole or the like via an IP network or a telecommunication line 2 which is a public line. The wireless base station 3 can perform wireless communication with a plurality of smart meters 4 installed in a plurality of homes. The automatic meter-reading server 1 collects the electric energy of each household from the smart meter 4 via the telecommunication line 2 and the wireless base station 3. Although only one radio base station 3 is illustrated in FIG. 1, there are actually a plurality of radio base stations 3 for one automatic meter reading server 1. In the present embodiment, the automatic meter-reading server 1 and the plurality of wireless base stations 3 are illustrated as separate devices, but it may be considered that these devices constitute an automatic meter-reading server as a whole. For example, the automatic meter reading server 1 may be configured to incorporate a plurality of wireless base stations 3.

  The smart meter 4 includes a wattmeter 5 and a wireless terminal 6. One wireless base station 3 is configured to perform wireless communication with, for example, several hundred or more smart meters 4, but FIG. 1 shows only three smart meters 4a, 4b, and 4c. Yes. The handy terminal (HT) 7 is a portable wireless communication device (portable terminal) used by a meter reader or maintenance personnel. The meter reader or maintenance staff performs meter reading or maintenance of a specific smart meter 4 by causing the HT 7 to perform wireless communication with the smart meter 4. Although only one HT 7 is illustrated in FIG. 1, a larger number of HT 7 may actually be included in the automatic meter reading system 100.

  FIG. 2 is a diagram schematically illustrating a wireless communication sequence between the wireless base station 3 and the smart meter 4. In the present invention, a communication path for transmitting data from the wireless base station 3 to the smart meter 4 is referred to as a downlink, and a communication path for transmitting data from the smart meter 4 to the wireless base station 3 is referred to as an uplink.

  The wireless base station 3 and the smart meter 4 according to the present embodiment perform time-division multiplexing wireless communication in which a downlink and an uplink are divided at regular intervals. That is, as shown in FIG. 2, bidirectional communication is realized by repeating a frame period T1 including a downlink period T2 in which downlink communication is performed and an uplink period T3 in which uplink communication is performed. . The radio base station 3 transmits the downlink signal 50 to each smart meter 4a, 4b, 4c in the downlink period T2, and receives the uplink signal 51a, 51b, 51c from each smart meter 4a, 4b, 4c in the uplink period T3. Each smart meter 4a, 4b, 4c receives the downlink signal 50 from the radio base station 3 in the downlink period T2, and transmits the uplink signals 51a, 51b, 51c to the radio base station 3 in the uplink period T3. In the present embodiment, the lengths of the frame period T1, the downlink period T2, and the uplink period T3 are determined in advance, and the radio base station 3, the smart meter 4, and the HT 7 operate based on those lengths in advance. I am going to do it. In addition, as shown in FIG. 2, the length of the down period T2 and the length of the up period T3 may differ. In the present embodiment, the upstream period T3 is longer than the downstream period T2.

  FIG. 3 is a block diagram illustrating a configuration of a part related to wireless communication in the entire wireless base station 3. The radio base station 3 includes a base station communication processing unit 29 including a CPU and its peripheral circuits, and a base station radio communication unit 28 connected to the base station communication processing unit 29. The base station communication processing unit 29 is connected to the automatic meter-reading server 1 via the telecommunication line 2, and communication between the automatic meter-reading server 1 and the smart meter 4 is converted to a protocol such as an Internet protocol or a wireless protocol. Mediate by doing

  Hereinafter, the transmission operation of the downlink signal 50 by the radio base station 3 will be described with reference to FIGS. 2 and 3. The base station communication processing unit 29 stores transmission data that needs to be transmitted on the downlink in the transmission buffer 21 of the base station wireless communication unit 28. The downlink transmission time control unit 27 of the base station radio communication unit 28 reads the time of the TDMA timer 19 and outputs a transmission start signal C to the transmission buffer 21 in accordance with the start time of the downlink period T2 of the frame period T1. The TDMA timer 19 is a timer that measures the uplink time width (uplink period T3) and the downlink time width (downlink period T2), and is used to determine the transmission timing of the radio signal. The transmission buffer 21 outputs transmission data stored therein to the code spreader 22 in response to the input of the transmission start signal C. The code spreader 22 spreads the input transmission data with a predetermined spreading code sequence and outputs the spread data to the modulator 23. The code spreader 22 uses an M sequence having high autocorrelation as a spreading code sequence. It is assumed that the spread code sequence used by the code spreader 22 is already known to the smart meter 4 and the HT 7. If the length of the spread code sequence is 128, for example, 1 bit of transmission data is spread to a length of 128 bits.

  The modulator 23 modulates digital data (spread transmission data) output from the code spreader 22 into an analog signal by BPSK (Binary Phase Shift Keying), and a predetermined frequency band (for example, 2.. 4 GHz, 920 MHz, etc.) and output to the transmission amplifier 24. The transmission amplifier 24 transmits the input analog signal from the antenna 13 with predetermined wireless power via the switch 14.

  As described above, a modulation scheme that directly spreads transmission data using a spreading code sequence is called a direct spread spectrum scheme (DSSS). As in the example described above, if the length of the spread code sequence is 128, the communication speed will be reduced to 1/128 compared to the case where the spread code sequence is not spread, but the sensitivity on the receiving side will be 128 times higher. The communication distance can be increased.

  A radio signal (downlink signal 50) transmitted from the antenna 13 of the radio base station 3 includes a packet 31 that is data itself to be transmitted to the smart meter 4 and a packet 31 before the packet 31, as shown in a downlink period T2 in FIG. It is a series of signals obtained by modulating the added synchronization data 30. The synchronization data 30 is data known to the smart meter 4 and the HT 7 and is used for recognizing the downstream signal 50. The downlink transmission time control unit 27 of the base station radio communication unit 28 controls the transmission timing based on the time read from the TDMA timer 19 so that the downlink signal 50 is transmitted during the downlink period T2.

  FIG. 4 is a block diagram illustrating a configuration of a portion related to wireless communication in the entire wireless terminal 6 included in the smart meter 4. The wireless terminal 6 includes a terminal communication processing unit 44 including a CPU and its peripheral circuits, and a terminal wireless communication unit 43 connected to the terminal communication processing unit 44. The terminal communication processing unit 44 interprets the data received by the terminal wireless communication unit 43, reads the power amount from the wattmeter 5 as necessary, and transmits the read power amount data to the terminal wireless communication unit 43. I will let you.

  Hereinafter, the reception operation of the downlink signal 50 by the wireless terminal 6 will be described with reference to FIGS. 2 and 4. In the downlink period T2, the demodulator 15 of the wireless terminal 6 receives the downlink signal 50 transmitted from the wireless base station 3 via the antenna 13 and the switch 14 provided in the wireless terminal 6. The demodulator 15 demodulates the received downlink signal 50 into digital data (spread transmission data), and outputs it to the despreader 17 and the spread code synchronizer 16.

  The spreading code sequence of the downlink signal 50 transmitted from the radio base station 3 (spread code sequence used by the code spreader 22 of the base station radio communication unit 28) is known in each radio terminal 6, but the downlink signal 50 The arrival time is unknown. Therefore, the spread code synchronizer 16 detects the arrival of the downlink signal 50 by calculating the correlation value between the output data of the demodulator 15 and the above spread code sequence. Specifically, when the correlation value exceeds a predetermined threshold value, the synchronization data 30 included in the downstream signal 50 is captured. If the signal after spread spectrum is, for example, a signal that changes at 128 kHz intervals, the spread code synchronizer 16 calculates a correlation value about every 7.8 microseconds (1/128000 seconds), and the downstream signal 50 Determine the start time.

  The despreader 17 despreads the digital data output from the demodulator 15 at a cycle determined by the spread code synchronizer 16. For example, if the length of the spread code sequence is 128 and the signal after spread spectrum is a signal that changes at 128 kHz intervals, the output signal from the despreader 17 becomes a signal that changes at 1 kHz intervals. By this despreading process, the reception sensitivity can be increased by a factor corresponding to the length of the spread code sequence.

  The packet synchronizer 18 compares the data string output by the despreader 17 at 1 kHz intervals with the known synchronization data 30. If these two data match, it means that the downstream signal 50 has arrived. The packet synchronizer 18 detects the arrival time of the downlink signal 50 based on the coincidence of the two data, outputs the packet 31 following the synchronization data 30 to the terminal communication processing unit 44, and sets the TDMA timer 19 of the terminal radio communication unit 43. Correction is performed based on the arrival time of the downstream signal 50.

  The transmission operation of the uplink signals 51a, 51b, 51c by the radio terminal 6 is the same as that by the radio base station 3 except that the output of the radio signal is performed in the uplink period T3 instead of the downlink period T2. That is, the terminal communication processing unit 44 stores the transmission data in the transmission buffer 21 of the terminal wireless communication unit 43. The uplink transmission time control unit 20 of the terminal radio communication unit 43 reads the time of the TDMA timer 19 and outputs a transmission start signal C to the transmission buffer 21 in accordance with the start time of the uplink period T3 of the frame period T1. The transmission buffer 21 outputs transmission data to the code spreader 22 in response to the input of the transmission start signal C. Thereafter, radio signals (upstream signals 51a, 51b, 51c) based on the transmission data are transmitted from the antenna 13 via the code spreader 22, the modulator 23, the transmission amplifier 24, and the switch 14. Upstream signals 51a, 51b, and 51c are packets 35a, 35b, and 35c that are data themselves that are desired to be transmitted to the radio base station 3, respectively, and synchronization data 34a added before them, as shown in an upstream period T3 in FIG. , 34b, 34c are a series of signals.

  Incidentally, in the upstream period T3 shown in FIG. 2, three upstream signals 51a, 51b, 51c transmitted from the three smart meters 4a, 4b, 4c, respectively, are illustrated. Since each of these uplink signals 51a, 51b, 51c overlaps in time in the uplink period T3, the radio base station 3 receives a radio signal obtained by synthesizing these three signals. In this embodiment, the smart meters 4a, 4b, and 4c use different spreading code sequences, and all the spreading code sequences are known in the radio base station 3. By doing so, the wireless base station 3 can correctly receive the three upstream signals 51a, 51b, 51c transmitted by the smart meters 4a, 4b, 4c in the same upstream period T3. As described above, a technique for multiplexing lines by differentiating spreading code sequences used for transmitting radio signals in a plurality of smart meters 4a, 4b, 4c is known as so-called CDMA (Code Division Multiple Access). Therefore, explanation is omitted here.

  The reception operation of the uplink signals 51a, 51b, 51c by the radio base station 3 is performed by the radio terminal 6 except that the reception operation is performed in the uplink period T3 instead of the downlink period T2 and the TDMA timer 19 is not corrected. It is the same. That is, the demodulator 15 of the radio base station 3 receives the uplink signals 51a, 51b, 51c transmitted from the radio terminal 6 via the antenna 13 and the switch 14. The demodulator 15 demodulates the received upstream signals 51 a, 51 b, 51 c into digital data (spread transmission data) and outputs it to the despreader 17 and the spread code synchronizer 16. The spread code synchronizer 16 detects the arrival of the upstream signals 51a, 51b, 51c by calculating the correlation value between the output data of the demodulator 15 and the spread code sequence of each wireless terminal 6. The despreader 17 despreads the digital data output from the demodulator 15 at a cycle determined by the spread code synchronizer 16. The packet synchronizer 18 detects the arrival time of the synchronization data 34a, 34b, 34c, and outputs the packets 35a, 35b, 35c subsequent to the synchronization data 34a, 34b, 34c to the base station communication processing unit 29.

  Note that the packets 35a, 35b, and 35c carried by the upstream signals 51a, 51b, and 51c include destination data indicating the destination of the packet. This is data indicating to which of the plurality of radio base stations 3 and HT7 the packet transmitted from the smart meter 4 is transmitted. When the base station communication processing unit 29 (and the HT communication processing unit 46 described later) receives the packets 35a, 35b, and 35c, the base station communication processing unit 29 first confirms the destination data of the received packet, and the packet is transmitted to itself. It is determined whether it is a thing. If the packet is not sent to itself, the packet is simply ignored.

  Next, transmission power control (TPC) by the smart meter 4 will be described with reference to FIGS. The wireless terminal 6 according to the present embodiment performs TPC in order for the wireless base station 3 to receive the signals with the minimum interference between the plurality of uplink signals 51a, 51b, 51c transmitted from the plurality of smart meters 4. The intensity detector 25 of the radio terminal 6 receives the radio signal (downlink signal 50) transmitted by the radio base station 3 in the downlink period T2 via the antenna 13 and the switch 14, and detects the reception intensity. If the transmission power of the radio base station 3 is determined in advance, the radio signal attenuation amount between the radio base station 3 and the radio terminal 6 can be measured from the reception intensity detected by the intensity detector.

It is known that the reception power of each signal should be equal in order to receive with the minimum interference between the plurality of upstream signals 51a, 51b, 51c. This is because, for a received signal from one wireless terminal 6, a received signal from another wireless terminal 6 is noise, and this relationship is the same for any wireless terminal 6. Therefore, in the transmission power control unit 26, the transmission power of the radio base station 3 and the target value of the reception power from the radio terminal 6 in the radio base station 3 are determined in advance, and the reception intensity detected by the intensity detector 25. From the above, it is possible to calculate the transmission power command value A necessary for the uplink signals 51a, 51b, 51c to reach the radio base station 3 with the target value. For example, the transmission power of the radio base station 3 is 10 dBm, the target value of the reception power of the radio signal from the radio terminal 6 in the radio base station 3 is −100 dBm, and the reception intensity detected by the intensity detector 25 is −70 dBm. In some cases, the transmission power command value A can be obtained from the following calculation.
A = −100 dBm − (− 70 dBm−10 dBm) = − 20 dBm

  The transmission power control unit 26 calculates the transmission power command value A as described above, and gives the transmission power command value A to the transmission amplifier 24. The transmission amplifier 24 amplifies the signal output from the modulator 23 to the transmission power command value A (−20 dBm in the above example) in the uplink period T3 and transmits the amplified signal to the radio base station 3. In this way, by performing TPC, even if a plurality of upstream signals 51a, 51b, 51c are received at the same time in the upstream period T3, these signals can be received correctly. In this embodiment, the uplink and downlink are time-division multiplexed. Therefore, the same communication frequency can be used for the uplink and downlink, and there is no influence of radio attenuation that varies depending on the frequency.

  The maximum transmission power is determined by the communication frequency used. When the maximum transmission power of the wireless terminal 6 is set to 10 dBm, for example, when the attenuation amount exceeds 110 dB, the uplink signal transmitted from the wireless terminal 6 is received by the wireless base station 3 at the reception intensity target− It will be less than 100 dBm. Since the reception power of the uplink signal transmitted from the other wireless terminal 6 is −100 dBm, the wireless signal transmitted from the wireless terminal 6 that receives attenuation exceeding 110 dB causes a communication error more than the other wireless terminal 6. Probability increases. In the DSSS system, this problem can be avoided by lengthening the spreading code sequence (increasing the spreading factor).

  For example, when the attenuation amount is less than 110 dB, the spreading code sequence length is set to 128, and when the attenuation amount is 110 dB or more, the spreading code sequence length is made larger than 128 accordingly to compensate for the strength reduction. For example, if the diffusion rate is doubled, the S / N ratio is improved by 10 × Log 2 = 3 dB. Therefore, when the attenuation is 113 dB, the reception power at the radio base station 3 is −113 dBm, which is 3 dB lower than the target value, but the spreading code sequence length may be increased from 128 to 256.

  FIG. 5 is a block diagram showing a configuration of a part related to wireless communication in the entire HT 7. The HT 7 includes an HT communication processing unit 46 including a CPU and its peripheral circuits, and an HT wireless communication unit 45 connected to the HT communication processing unit 46. The HT communication processing unit 46 transmits control data from the HT wireless communication unit 45 to a specific smart meter 4 in accordance with an operation performed on an operation member (not shown) (for example, a button or a switch), Data received by the HT wireless communication unit 45 from the smart meter 4 is displayed on a display unit (not shown) (for example, a liquid crystal display unit).

  FIG. 6 is a diagram schematically showing a sequence of wireless communication between the wireless base station 3 and the smart meter 4 and wireless communication between the smart meter 4 and the HT 7. Hereinafter, the communication operation between the HT 7 and the smart meter 4 (wireless terminal 6) according to the present embodiment will be described with reference to FIGS. The HT radio communication unit 45 of the HT 7 transmits the radio signal transmitted from the radio base station 3 to the antenna 13, the switch 14, the demodulator 15, the spreading code, similarly to the reception operation of the terminal radio communication unit 43 of the radio terminal 6. Received via the synchronizer 16, despreader 17, and packet synchronizer 18, the time of the TDMA timer 19 is corrected. Since the above reception operation is the same as the reception operation in the wireless terminal 6 described above, description thereof is omitted.

  The HT 7 of the present embodiment does not (cannot) transmit a radio signal at the start of communication (downlink period T2a in the frame period T1a in FIG. 6). This is because the start time of the frame period T1a (start time of the downlink period T2a) is not known. The HT wireless communication unit 45 performs the above-described reception operation during this period, and captures the downlink signal 52 transmitted from the radio base station 3, thereby obtaining the start time of the next frame period T1b (start time of the next downlink period T2b). ). Specifically, the downlink transmission time control unit 27 reads the time of the TDMA timer 19 corrected by the packet synchronizer 18, and determines the start time of the downlink period T2b in the next frame period T1b. Then, in the subsequent downlink period T2b, the wireless signal (downstream signal 54) is transmitted to the wireless terminal 6.

  Note that the transmission processing by the HT wireless communication unit 45 of HT7 and the reception processing from the smart meters 4a, 4b, and 4c are the same as those by the base station wireless communication unit 28 of the wireless base station 3, and thus description thereof is omitted. . It is the same as that of the radio base station 3 in that the destination data included in the received packet is confirmed, and the packet is ignored when the packet is not transmitted to itself.

  The HT wireless communication unit 45 uses the same spreading code sequence as the spreading code sequence used by the radio base station 3. By making the spread code sequences the same in this way, each smart meter 4a, 4b, 4c only needs to perform synchronization detection processing for only one spread code sequence, and the configuration of the wireless terminal 6 can be simplified.

  In the downlink period T2b, the wireless base station 3 and HT7 transmit downlink signals 53 and 54 in time overlap, so that the smart meters 4a, 4b and 4c receive these two downlink signals 53 and 54 simultaneously. I can't. However, since the HT7 carried by a meter reader, maintenance personnel, etc. often communicates with a specific smart meter 4 that is the subject of meter reading or maintenance at a short distance of about several meters, the reception intensity of the downstream signal 54 from the HT 7 Is considered to be higher than the downlink signal 53 from the radio base station 3. Therefore, even if the reception function unit of the terminal wireless communication unit 43 of the wireless terminal 6 is made two systems so that both of the downstream signals 53 and 54 can be received, it is difficult to receive the downstream signal 53 from the wireless base station 3. There is no problem that the two downstream signals 53 and 54 cannot be received at the same time.

  In the downlink period T2b of FIG. 6, the HT7 transmits at the same timing as the downlink signal 53 from the radio base station 3 by the operation as described above. There is no problem in the reception processing by the smart meters 4a, 4b, 4c even if the timings of both are slightly shifted. For example, after the downlink signal 53 is transmitted from the radio base station 3, the downlink signal 54 is transmitted from the HT7. In the case (when the two downstream signals 53 and 54 do not overlap in time), the TPC described above becomes unstable in the smart meters 4a, 4b, and 4c. That is, the radio terminal 6 detects the downlink reception intensity and controls the transmission power. However, if both the radio base station 3 and the HT 7 exist independently for a certain period of time, the reception intensity differs. May fluctuate.

  For example, in FIG. 6, the downlink periods T2a and T2b are set to have a length required for transmitting one downlink signal 52, 53, and 54. It is also possible to do. Further, if the packet 31 has a variable length, the relative length with respect to the downlink periods T2a and T2b may be different for each of the downlink periods T2a and T2b.

  In order to cope with such a TPC problem, the HT 7 of the present embodiment has the downstream signal 54 over the entire downstream period T2b even if the length of the downstream signal 54 is shorter than the downstream periods T2a and T2b. Send. That is, the HT 7 extends the downlink signal 54 that can actually complete transmission in a shorter time to the entire area of the downlink period T2b by, for example, padding the packet 31 with an invalid value or the like.

The automatic meter reading system according to the first embodiment described above provides the following operational effects.
(1) The automatic meter reading system 100 includes a plurality of wireless terminals 6, a wireless base station 3, an automatic meter reading server 1, and an HT 7. The plurality of wireless terminals 6 are connected to each of the wattmeters 5 installed in each of the plurality of consumers, and acquire measurement data of the wattmeters 5 respectively. The automatic meter-reading server 1 receives and collects the measurement data of the plurality of wattmeters 5 from the plurality of wireless terminals 6 by transmitting wireless signals of predetermined wireless power to the plurality of wireless terminals 6 via the wireless base station 3. To do. The HT 7 is a portable terminal capable of wireless communication with each wireless terminal 6. In this automatic meter reading system 100, a wireless communication between the wireless base station 3 and the plurality of wireless terminals 6 and between the plurality of wireless terminals 6 and the HT 7 is performed by a modulation method that spreads spectrum using a predetermined spreading code sequence. The wireless communication is time-division multiplexed on the downlink from the wireless base station 3 to the plurality of wireless terminals 6 and the uplink from the plurality of wireless terminals 6 to the wireless base station 3. Further, the plurality of wireless terminals 6 determine the wireless power to be transmitted on the uplink based on the wireless power received on the downlink. Then, the HT 7 detects a downlink period T2 in time division multiplexing, and transmits a radio signal spectrum-spread by the same spreading code sequence as that of the radio base station 3 to the radio terminal 6 in the downlink period T2. The wireless signal from the wireless terminal 6 is received. Since it did in this way, the communication procedure between a portable terminal and a radio | wireless terminal can be simplified.

(2) The HT 7 detects the downlink period T2 in the time division multiplexing by the TDMA timer 19 that measures the uplink time width and the downlink time width, and receives the radio signal received from the radio base station 3 on the downlink. The TDMA timer is corrected from the reception time. Since it did in this way, in the some radio | wireless terminal 6, the transmission signal from the radio base station 3 and the transmission signal from HT7 can be received with the same communication procedure and communication equipment, The structure of the radio | wireless terminal 6 is possible. Can be simplified.

(3) Each of the plurality of wireless terminals 6 performs wireless communication with the wireless base station 3 and the HT 7 using a spreading code sequence different from that of the other wireless terminals 6. Since it did in this way, the radio | wireless base station 3 and HT7 can each receive correctly the several upstream signal 51a, 51b, 51c transmitted from the some smart meter 4a, 4b, 4c in the same uplink period T3, respectively. it can.

(4) In a radio communication between the radio base station 3 and the plurality of radio terminals 6 and between the plurality of radio terminals 6 and the HT 7, a modulation scheme that performs spectrum spread by a predetermined spreading code sequence is used. did. Since it did in this way, the transmission control by the side of the radio | wireless terminal 6 in order to avoid the interference between the transmission signals from each radio | wireless terminal 6 in an uplink (for example, confirming that other radio | wireless terminals 6 are not in a transmission state ( Carrier sense), CSMA transmitted by itself if it is not in a transmission state, transmission control using a frame obtained by further time-dividing an uplink, and the like are not required, and the communication procedure is simplified.

(5) The HT 7 transmits the downstream signal 54 over the entire downstream period T2b. Since it did in this way, destabilization of TPC can be suppressed. Compared with other methods for suppressing TPC instability, such as a method of further time-dividing the downlink and transmitting a signal from the radio base station 3 and a signal from the HT 7 in a plurality of frames, The communication procedure can be simplified.

(6) The plurality of wireless terminals 6 determine the wireless power to be transmitted on the uplink based on the wireless power received on the downlink. Since it did in this way, even if it receives the transmission signal from many radio | wireless terminals 6 in the radio base station 3, radio | wireless communication with the specific radio | wireless terminal 6 does not become unstable.

(7) The HT 7 transmits a radio signal spectrum-spread by the same spreading code sequence as the radio base station 3 to the radio terminal 6 in the downlink period T2. Since this is done, each of the plurality of radio terminals 6 can receive the transmission signal from the radio base station 3 and the transmission signal from the HT 7 as long as only one spreading code sequence is stored. The configuration of the wireless terminal 6 can be simplified.

(Second Embodiment)
Hereinafter, the automatic meter reading system according to the second embodiment of the present invention will be described while referring to differences from the first embodiment. In the automatic meter reading system of this embodiment, each wireless terminal 6 transmits a wireless signal to the wireless base station 3 and the HT 7 using the same spread code sequence. However, the transmission timing is shifted by a time determined at random every transmission.

  FIG. 7 is a diagram schematically showing a sequence of wireless communication between the wireless base station 3 and the smart meter 4 and wireless communication between the smart meter 4 and the HT 7. The upstream signals 51a, 51b, 51c transmitted from the smart meters 4a, 4b, 4c are transmitted delayed from the start times of the upstream periods T3a, T3b by random times, respectively. In this way, by shifting the transmission start time within the periods of the uplink periods T3a and T3b, the radio base station 3 can correctly receive a plurality of uplink signals 51a, 51b, and 51c that overlap in time. This is an application of a technique that separates a direct wave directly propagating between a transmission point and a reception point and a plurality of multiple reflected waves that arrive after delay due to multiple reflection at a building or the like. Since this is a well-known technique as a reception method, further explanation is omitted.

The automatic meter reading system according to the second embodiment described above provides the following operational effects.
(1) The plurality of radio terminals 6 perform radio communication with the radio base station 3 and the HT 7 using the same spreading code sequence, and change the radio signal transmission start times in the uplink periods T3a and T3b each time. To do. Since it did in this way, the radio | wireless base station 3 and HT7 can each receive correctly the several upstream signal 51a, 51b, 51c transmitted from the some smart meter 4a, 4b, 4c in the same uplink period T3, respectively. it can. In addition, the radio base station 3 and HT7 do not need to handle a large number of spreading code sequences, and the configuration of the radio base station 3 and HT7 can be simplified.

(Third embodiment)
Hereinafter, the automatic meter reading system according to the third embodiment of the present invention will be described while referring to differences from the first embodiment. In the automatic meter reading system according to the present embodiment, the radio base station 3 and the HT 7 do not include the TDMA timer 19 and determine the transmission timing of the radio signal by a method different from that of the first embodiment.

  FIG. 8 is a block diagram illustrating a configuration of the base station radio communication unit 28 of the radio base station 3 according to the third embodiment. The difference from the configuration of the base station radio communication unit 28 according to the first embodiment shown in FIG. 3 is that a satellite signal receiver 40 is provided instead of the TDMA timer 19. The satellite signal receiver 40 receives a GPS signal transmitted from an artificial satellite constituting a so-called GPS (Global Positioning System). This GPS signal includes time information from the atomic clock mounted on the artificial satellite, and the time of the timer built in the satellite signal receiver 40 is synchronized with the time of the above atomic clock with high accuracy. Can do.

  FIG. 9 is a block diagram illustrating a configuration of the HT wireless communication unit 45 of the HT 7 according to the third embodiment. The difference from the configuration of the HT wireless communication unit 45 according to the first embodiment shown in FIG. 5 is that a satellite signal receiver 40 is provided in place of the TDMA timer 19 as in the base station wireless communication unit 28 described above. It is a point. Also in the HT wireless communication unit 45, the time of the timer built in the satellite signal receiver 40 is synchronized with the time of the above-described atomic clock with high accuracy. That is, the time of the timer built in the satellite signal receiver 40 of the radio base station 3 and the time of the timer built in the satellite signal receiver 40 of the HT 7 are synchronized with high accuracy. Thus, for example, if the frame period T1 is 2 seconds, the downlink period T2 is 1 second, and the uplink period T3 is 1 second, the start timing of the downlink period T2 is synchronized between the radio base station 3 and HT7. Can do. That is, the downlink transmission time control unit 27 reads the time from the timer in the satellite signal receiver 40 and controls the start timing of the downlink period T2.

  The signal received by the satellite signal receiver 40 only needs to be a signal whose time can be synchronized, and is not limited to a signal from a satellite constituting the GPS. For example, it may be a signal from an artificial satellite constituting another satellite positioning system, or may be a signal from an artificial satellite used for satellite broadcasting or the like. Further, it may be a so-called standard frequency radio wave broadcast from a base station installed on the ground.

The automatic meter reading system according to the third embodiment described above provides the following operational effects.
(1) The HT 7 detects a downlink period in time division multiplexing by a satellite signal receiver 40 that receives a signal transmitted from an artificial satellite and detects a current time. Since this is done, it is not necessary to receive the downlink signal 52 from the radio base station 3 and detect the downlink periods T2a and T2b, and the downlink periods T2a and T2b can be accurately recognized. Therefore, the HT 7 can communicate with a specific wireless terminal 6 without using a complicated communication procedure.

(Fourth embodiment)
Hereinafter, the automatic meter reading system according to the fourth embodiment of the present invention will be described while referring to differences from the first embodiment. In the automatic meter reading system of the present embodiment, the HT 7 determines the strength of the transmission power by measuring the strength of the radio signal from the radio base station 3.

  FIG. 10 is a block diagram illustrating a configuration of the HT wireless communication unit 45 of the HT 7 according to the fourth embodiment. The difference from the configuration of the HT wireless communication unit 45 according to the first embodiment shown in FIG. 5 is that a downlink strength detector 47 to which signals received via the antenna 13 and the switch 14 are input, and a downlink An uplink power control unit 48 connected to the intensity detector 47 is provided.

  The downlink strength detector 47 detects the reception strength of the downlink signal 52 transmitted from the radio base station 3 in the downlink period T2a. When a meter reader, maintenance personnel, etc. perform meter reading and maintenance using the HT 7, it is expected that they will be near the wireless terminal 6 to be metered and maintained with the HT 7. Accordingly, the reception strength of the downlink signal 52 detected by the downlink strength detector 47 of the HT 7 and the reception strength of the downlink signal 52 received by the wireless terminal 6 subject to meter reading / maintenance are considered to be substantially the same value. It's okay. Therefore, if the received power from the radio base station 3 detected in the HT 7 is, for example, −70 dBm, the radio terminal 6 transmits the downlink signal 54 from the HT 7 with a transmission power larger by about 10 dB than the radio terminal 6. The downstream signal 54 from the HT 7 can be received without receiving interference from the downstream signal 53 from the mobile station. As described above, the uplink power control unit 48 gives the transmission amplifier 24 the transmission power command value A having a value larger than the reception intensity detected by the downlink intensity detector 47 by a predetermined amount.

  Assuming that the maximum transmission power of HT7 is 10 dBm, the downlink signal 54 from HT7 is always transmitted at 10 dBm unless the transmission power is adjusted as described above. On the other hand, when the transmission power is adjusted as described above and the downstream signal 54 is transmitted at −60 dBm, the difference is 70 dB. The downlink signal 54 transmitted from the HT 7 is a noise source that interferes with communication for other wireless terminals 6 that are not subject to meter reading / maintenance, but the downlink signal 54 (noise) received from these other wireless terminals 6 is received from the HT 7. The received intensity of the source is also reduced by 70 dB. Accordingly, in these other wireless terminals 6, the probability of disturbing the downlink signal 53 from the wireless base station 3 is reduced.

The automatic meter reading system according to the fourth embodiment described above provides the following operational effects.
(1) The HT 7 detects the reception intensity of the radio signal received from the radio base station 3, and transmits the radio signal to the radio terminal 6 with a radio power larger than the reception intensity by a predetermined amount or more. Since it did in this way, the influence which the signal from the wireless base station 3 and the signal from HT7 interfere on a downlink can be suppressed.

(Fifth embodiment)
Hereinafter, the automatic meter reading system according to the fifth embodiment of the present invention will be described while referring to differences from the first embodiment. In the automatic meter-reading system of this embodiment, HT7 has the structure which can switch two different types of antennas.

  FIG. 11 is a block diagram illustrating a configuration of the HT wireless communication unit 45 of the HT 7 according to the fifth embodiment. The difference from the configuration of the HT wireless communication unit 45 according to the first embodiment shown in FIG. 5 is that the directional antenna 13a and the omnidirectional antenna 13b connected to the antenna changeover switch 49 are used instead of the antenna 13. It is a point that has.

  The HT 7 of the present embodiment is configured such that a meter reader, maintenance staff, etc. using the HT 7 can switch an antenna used for transmission / reception of a radio signal by operating an operation member (not shown) of the HT 7. When an antenna switching command is input to the HT 7 by the operation member, the HT communication processing unit 46 switches the antenna switching switch 49 according to the input. Specifically, when the HT 7 communicates only with a specific smart meter 4 (for example, smart meter 4 subject to meter reading / maintenance), the directional antenna 13a and the switch 14 are connected by the antenna changeover switch 49, and wireless A directional antenna 13a is used for transmitting and receiving signals. A meter reader, maintenance personnel, and the like can reduce the influence of the HT 7 on the other smart meters 4 by communicating with the directional antenna 13a of the HT 7 toward the smart meter 4 to be communicated. In addition, when communicating with a number of neighboring smart meters 4 simultaneously using HT7, the omnidirectional antenna 13b and the switch 14 are connected by the antenna changeover switch 49, and the omnidirectional antenna 13b is used for transmitting and receiving radio signals. It should be used.

The automatic meter reading system according to the fifth embodiment described above provides the following operational effects.
(1) The HT 7 includes a directional antenna 13a and an omnidirectional antenna 13b, and an antenna used for wireless communication with the wireless terminal 6 can be switched to one of the directional antenna 13a and the omnidirectional antenna 13b. Since it did in this way, the influence which HT7 has on the other radio | wireless terminal 6 which is not the object of radio | wireless communication can be reduced.

  The following modifications are also within the scope of the present invention, and one or a plurality of modifications can be combined with the above-described embodiment.

(Modification 1)
The length of the frame period T1 may not be fixed to a predetermined length. For example, the length of the uplink period T2 and the downlink period T3 can be varied by including information related to the length of the frame period T1 in the downlink signal 50 from the radio base station 3.

(Modification 2)
In each of the above-described embodiments, the system for measuring the amount of power measured by the wattmeter has been described, but the present invention is not limited to such an embodiment. For example, the present invention can be applied to an automatic meter reading system for gas or water.

(Modification 3)
The wireless terminal 6 may be built in a measuring instrument such as the wattmeter 5 or may be connected to the measuring instrument by wire or the like. Moreover, these may be integrally stored in the same housing | casing, and may be stored in a different housing | casing.

(Modification 4)
The configurations of the uplink signal and the downlink signal are not limited to those shown in FIGS. For example, components other than the synchronization data and the packet may be included.

  As long as the characteristics of the present invention are not impaired, the present invention is not limited to the above-described embodiments, and other forms conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention. .

DESCRIPTION OF SYMBOLS 1 ... Automatic meter-reading server, 2 ... Electric communication line, 3 ... Wireless base station 4, 4a, 4b, 4c ... Smart meter, 5 ... Wattmeter, 6 ... Wireless terminal, 7 ... Handy terminal, 13 ... Antenna, 13a ... Directional antenna, 13b ... Omnidirectional antenna, 14 ... Switch, 15 ... Demodulator, 16 ... Spreading code synchronizer, 17 ... Despreader, 18 ... Packet synchronizer, 19 ... TDMA timer, 20 ... Uplink transmission time Control unit, 21 ... transmission buffer, 22 ... code spreader, 23 ... modulator, 24 ... transmission amplifier, 25 ... intensity detector, 26 ... transmission power control unit, 27 ... downlink transmission time control unit, 28 ... base station Wireless communication unit, 29 ... Base station communication processing unit, 40 ... Satellite signal receiver, 43 ... Terminal wireless communication unit, 44 ... Terminal communication processing unit, 45 ... HT wireless communication unit, 46 ... HT communication processing unit, 47 ... Downlink Line strength Can, 48 ... uplink power control unit, 49 ... antenna switch, 100 ... automatic meter reading system

Claims (11)

A plurality of wireless terminals connected to each of the measuring instruments installed in each of the plurality of consumers and respectively acquiring the weighing data of the measuring instruments;
An automatic meter reading server that receives and collects weighing data of the plurality of measuring instruments from the plurality of wireless terminals by transmitting wireless signals of predetermined wireless power to the plurality of wireless terminals;
A portable terminal capable of wireless communication with the wireless terminal;
Wireless communication between the automatic meter reading server and the plurality of wireless terminals, and between the plurality of wireless terminals and the mobile terminal, the automatic meter reading server according to a modulation method in which spectrum is spread by a predetermined spreading code sequence Wireless communication that time-division-multiplexes downlinks from the plurality of wireless terminals and uplinks from the plurality of wireless terminals to the automatic meter reading server,
The plurality of radio terminals determine radio power to be transmitted on the uplink based on radio power of radio signals received on the downlink,
The portable terminal detects a period of the downlink in the time division multiplexing, and transmits a radio signal spectrum-spread by the same spreading code sequence as the automatic meter reading server to the wireless terminal during the downlink period; An automatic meter reading system characterized by receiving a radio signal from the radio terminal on the uplink. The automatic meter reading system according to claim 1,
The said portable terminal detects the reception intensity | strength of the radio signal received from the said automatic meter-reading server, and transmits a radio signal to the said radio | wireless terminal with the radio | wireless power larger than the said reception intensity | strength more than predetermined amount, The automatic meter-reading system characterized by the above-mentioned. The automatic meter reading system according to claim 2,
The mobile terminal detects a period of the downlink in the time division multiplexing by a timer that measures the time width of the uplink and the time width of the downlink, and a radio received from the automatic meter reading server on the downlink An automatic meter reading system, wherein the timing of the measurement by the timer is corrected from a signal reception time. The automatic meter reading system according to claim 2,
An automatic meter-reading system, wherein the portable terminal detects a period of the downlink in the time division multiplexing by a satellite signal receiver that receives a signal transmitted from an artificial satellite and detects a current time. In the automatic meter-reading system as described in any one of Claims 1-4,
The portable terminal includes a directional antenna and an omnidirectional antenna, and an antenna used for wireless communication with the wireless terminal can be switched to one of the directional antenna and the omnidirectional antenna. Automatic meter reading system. In the automatic meter-reading system as described in any one of Claims 1-4,
The plurality of wireless terminals perform wireless communication with the automatic meter-reading server and the portable terminal using the spreading code sequence different from other wireless terminals. In the automatic meter-reading system as described in any one of Claims 1-4,
The plurality of radio terminals perform radio communication with the automatic meter-reading server and the mobile terminal using the same spreading code sequence, and change the radio signal transmission start time every time in the uplink period. Automatic meter reading system characterized by A plurality of wireless terminals connected to each of the measuring devices installed in each of the plurality of consumers, respectively, for obtaining the weighing data of the measuring devices, and transmitting a wireless signal of a predetermined wireless power to the plurality of wireless terminals An automatic meter-reading server that receives and collects the weighing data of the plurality of measuring devices from the plurality of wireless terminals, and the automatic meter-reading server between the automatic meter-reading server and the plurality of wireless terminals In a portable terminal used in an automatic meter reading system in which wireless communication is performed in a time-division-multiplex manner with downlinks to a plurality of wireless terminals and uplinks from the plurality of wireless terminals to the automatic meter-reading server,
A detection unit for detecting a period of the downlink in the time division multiplexing;
A communication unit that transmits a radio signal to the radio terminal during the downlink period detected by the detection unit and receives a radio signal from the radio terminal on the uplink;
A portable terminal comprising: The mobile terminal according to claim 8, wherein
Between the automatic meter-reading server and the plurality of wireless terminals, modulation-type wireless communication is performed in which a spectrum is spread by a predetermined spreading code sequence,
The mobile terminal transmits a radio signal spectrum-spread by the same spread code sequence as the automatic meter reading server to the radio terminal. A plurality of wireless terminals connected to each of the measuring devices installed in each of the plurality of consumers, respectively, for obtaining the weighing data of the measuring devices, and transmitting a wireless signal of a predetermined wireless power to the plurality of wireless terminals An automatic meter-reading server that receives and collects the weighing data of the plurality of measuring devices from the plurality of wireless terminals, and the automatic meter-reading server between the automatic meter-reading server and the plurality of wireless terminals In a wireless communication method for a portable terminal in an automatic meter reading system in which wireless communication is performed in a time-division multiplexed manner with downlinks to a plurality of wireless terminals and uplinks from the plurality of wireless terminals to the automatic meter reading server,
A detection step of detecting a period of the downlink in the time division multiplexing;
A communication step of transmitting a radio signal to the radio terminal during the downlink period detected in the detection step, and receiving a radio signal from the radio terminal on the uplink;
A wireless communication method for a mobile terminal, comprising: The wireless communication method for a mobile terminal according to claim 10,
Between the automatic meter-reading server and the plurality of wireless terminals, modulation-type wireless communication is performed in which a spectrum is spread by a predetermined spreading code sequence,
In the communication step, a radio signal spread spectrum using the same spread code sequence as the automatic meter reading server is transmitted to the radio terminal.

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