JPH0870292A - Low speed frequency hopping spread spectrum communication method - Google Patents

Abstract

PURPOSE: To allow each station to use each hopping frequency equally in average and to attain initial synchronization of hopping with simple control at a high speed. CONSTITUTION: On the occurrence of a communication request with a master station by a slave station 21 at a time t1, the slave station 21 sends data T×1 by a waiting frequency f1 at the time t1 to the master station and the master station sends data T×1 to the slave station 21 by using the frequency f1 similarly. On the occurrence of a communication request with the master station by a slave station 2n at a time t2, the slave station 2n sends data T×n to the master station by using a waiting frequency f2, and the master station sends the data T×n to the slave station 2n by using the waiting frequency f2 of the master station. Furthermore, on the occurrence of a communication request with the slave station 21 by the master station at a time t3, the master station sends data T×1 to the slave station 21 by using a waiting frequency f4, and the slave station 21 sends the data T×1 to the master station by using the frequency f4 similarly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low frequency frequency hopping spread spectrum communication method applied to a wireless LAN system or the like.

[0002]

2. Description of the Related Art A low-speed frequency hopping (low-speed FH) spread spectrum communication system is a system in which a carrier frequency operates at a switching speed lower than a bit speed of an information signal, and a plurality of bits are transmitted by one carrier.

Conventionally, as a communication method for such low-speed frequency hopping spread spectrum communication, a method is known in which the frequency is switched for each packet for communication. For example, in Japanese Unexamined Patent Publication No. 5-191378, in a low-speed frequency hopping system in which the frequency is switched for each packet, a number string indicating the sequence of hopping numbers of frequencies of one or more packets that are subsequently transmitted in the packet. It has been disclosed that the inclusion of the above facilitates hopping synchronization.

Further, in order to speed up the initial synchronization of hopping, it is necessary to fix the first hopping channel for each station, and when one communication is completed, the first hopping frequency is returned to the waiting state.

[0005]

In the low-speed frequency hopping spread spectrum communication system in which the frequency is switched for each packet for communication, when several packets are continuously transmitted, an FH sequence (a spread spectrum code for frequency hopping is used). However, if the communication is completed with one or a small number of packets, there will always be one or a small number of packets. Only hopping to frequency.

Therefore, in the low-frequency hopping spread spectrum communication system in which the frequency is switched for each packet for communication, the usage rate of a certain specific frequency is increased in each station. In particular, when the communication is continuously completed with one packet, only one frequency is used, and as a result, it becomes as if the communication is a narrow band rather than the spread spectrum by the frequency hopping.

For example, product sales registration is performed at a POS (point-of-sale information management) terminal, and the price of each product, the product name, and the product sales registration amount at each POS terminal are managed by the host computer. In a wireless POS system in which the POS terminal communicates using a low-frequency hopping spread spectrum communication method, each POS terminal makes an inquiry about the product to the host computer when each POS terminal performs sales registration of the product. The product name and price of the corresponding product are received as an inquiry response and sales registration processing is performed.

Such communication between the POS terminal and the host computer is called PLU (Price Look Up) communication. In this communication, since the data amount of one communication is as small as tens to hundreds of bytes, one packet is transmitted. Communication is completed just by sending. Therefore, if the initial hopping frequency is fixed for each station, there is a problem that each station uses only a specific frequency.

In order to avoid this problem, if the data is divided into a plurality of packets and sent out and hopping is performed many times in one communication, the wireless master station connected to the host computer side and the POS terminal side are connected. It takes time to synchronize with the connected wireless slave station, resulting in a problem that communication or response takes time. Further, when the data is divided into a plurality of packets and transmitted, it is necessary to newly add data for hopping synchronization or bit synchronization.

As a result, the transmission time required for one communication is increased. Therefore, if there are many stations communicating, the transmission time becomes long and the probability of collision increases. Then, if a collision occurs, retransmission is performed, which causes a problem that the communication time becomes longer.

As described above, when the data amount of one communication is small, there is a problem that the communication time becomes long in the system in which the first hopping frequency is fixed for each station.

For this reason, if the first hopping frequency is not fixed and is changed one after another, it is certainly possible to use each frequency equally on average in each station.
However, in a system in which a plurality of wireless slave stations are arranged in one wireless master station, the initial hopping frequencies of the communication partner and the local station are deviated, and it takes time for the initial synchronization of hopping and control is performed. A complicated problem occurs.

Therefore, the present invention is based on the P of the wireless POS system.
Even in communication such as LU communication in which transmission is completed in one packet, each hopping frequency can be used equally evenly in each station, and
Provided is a low-speed frequency hopping spread spectrum communication method capable of achieving initial hopping synchronization with simple control and at high speed.

[0014]

According to a first aspect of the present invention, a service area comprises one or a plurality of wireless zones, and the one or a plurality of wireless zones are connected to one wireless master station and one wireless master station.
When configuring low-speed frequency hopping spread spectrum communication between a wireless master station and a wireless slave station, all wireless stations in the wireless zone switch the standby frequency at a certain time interval and communicate with each other. Sometimes it is necessary to transmit and receive at the standby frequency.

The invention corresponding to claim 2 is the low-frequency frequency hopping spread spectrum communication method according to claim 1,
In the wireless zone, the wireless master station transmits a control signal indicating the standby frequency switching time to all the wireless slave stations at the standby frequency before switching.

The invention corresponding to claim 3 is the low frequency frequency hopping spread spectrum communication method according to claim 2,
When synchronization of the standby frequency between the wireless master station and the wireless slave station is not established, the wireless slave station continues to receive at one standby frequency, and when the control signal is received from the wireless master station, According to the received control signal, the standby frequency is synchronously acquired with the wireless master station to start communication.

The invention according to claim 4 is the low-frequency hopping spread spectrum communication method according to claim 1 or 2, when the standby frequency synchronization between the radio master station and the radio slave station is not established. , The wireless slave station is the wireless master station 1
The standby frequency is switched and the connection request signal is repeatedly transmitted according to the frequency hopping sequence at a time interval shorter than the dwell time of one standby frequency to recognize the standby frequency of the wireless master station and start communication.

The invention corresponding to claim 5 is the low-frequency hopping spread spectrum communication method according to claim 3 or 4, wherein the wireless slave station performs communication with the wireless master station a preset number of times of retransmission. Regardless, if communication is not possible or the control signal from the wireless master station cannot be received a preset number of times, it is to recognize that the standby frequency synchronization with the wireless master station is not established.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a diagram showing a system configuration. One wireless master station 1 and n wireless slave stations 21 and 22.
, ~ 2n form one wireless zone.

The standard for the radio equipment of the radio station of the low power data communication system using the spread spectrum communication system of the 2.4 GHz band used in the wireless LAN etc. defines the spreading factor (spreading bandwidth, symbol rate of information signal). The ratio for equal frequencies) is defined to be 10 or more.

For example, if the symbol rate of the information signal is 1M
A hopping frequency of 10 is used in a system having bps, a spread bandwidth of 10 MHz, and a hopping frequency interval of 1 MHz. Therefore, the frequency hopping sequence (FH sequence) of this system is, for example, {1, 2, 4, 8, 5, 1
0, 9, 7, 3, 6}.

FIG. 2 is a time chart of the switching of the standby frequency and the communication between the parent and child stations. In the case of the communication in which the communication between the wireless master station 1 and each of the wireless slave stations 21 to 2n is completed in one packet. Is shown.

As shown in FIG. 2, each of the radio master station 1 and each of the radio slave stations 21 to 2n has a fixed frequency, that is, f at every T seconds, based on the FH sequence to which the standby frequency is assigned.
1, f2, f4, f8, ... f3, f6, f1, f2, ...
And the standby frequency is switched periodically.

Therefore, if the constant time T is the same for any standby frequency, any frequency is used as a standby frequency for T seconds in 10 × T seconds.

As a method of obtaining the timing for switching the frequency, the master station 1 and each of the slave stations 21 to 2n count their timers to find the switching time of the standby frequency, or the master station 1 and each slave station 21 to 2n. There is a method of exchanging data indicating timing information between 2n. In either method, the synchronizing circuit for hopping synchronization between the parent and child stations becomes very simple.

In FIG. 2, when a request for communication with the master station 1 is made at the slave station 21 at time t1, the slave station 21 sends the data Tx1 to the master station 1 at the standby frequency f1 at time t1. Then, as an ACK (response) to this, the master station 1 transmits the slave station 2
Similarly, the data Tx1 is transmitted at the frequency f1 with respect to 1.

When the slave station 2n issues a communication request with the master station 1 at time t2, the slave station 2n sends data Txn to the master station 1 at the standby frequency f2 at the start of transmission,
As an ACK (response) to this, the master station 1 transmits the data Txn to the slave station 2n by the standby frequency f2 when the master station 1 starts transmission.
Send with.

Furthermore, at the time t3 in the master station 1, the slave station 2
When a communication request to 1 occurs, the master station 1 transmits the data Tx1 to the slave station 21 at the standby frequency f4 at that time. As an ACK (response) to this, the slave station 21 transmits the data Tx1 to the master station 1 at the same frequency f4.

In this way, the master station 1 and each slave station 21 to 2n
Are waiting at the same frequency, the other station can instantly receive the transmission of its own station. Therefore, frequency synchronization for each communication is unnecessary, and transmission and response from the partner station can be speeded up.

There may be a case where the standby frequency switching timing occurs during the transmission of one packet. In that case, this packet is discarded and the frequency is switched, and then the packet is retransmitted or the standby frequency is set in advance. This can be dealt with by providing a transmission prohibited section before and after the frequency switching timing so that the switching timing does not occur during transmission.

A method may be considered in which the packet is transmitted without changing the frequency even if the frequency switching timing occurs during the transmission of the packet. However, in this case, the original frequency switching timing is deviated and the control is performed. Becomes complicated.

As described above, the master station 1 and each of the slave stations 21 to 2n in the wireless zone switch the standby frequency at a constant time interval T, and at the time of communication, transmission / reception is performed at the standby frequency at that time, whereby the wireless POS Inquiry response of product name and price in the system, that is, as in the case of PLU communication,
Even in a communication in which the amount of data in one communication is small and the transmission is completed by one or a small number of packets, the hopping frequency is equally used in the master station 1 and the slave stations 21 to 2n. can do.

The standby frequency switching interval T does not always have to be constant, and can be set to an arbitrary length.
Also, the switching interval T can be lengthened or shortened depending on the time zone, for example. However, the switching interval T
Is required to be longer than the transmission time of one packet. Therefore, if it is desired to transmit continuous data longer than the switching interval T, the data may be divided into packets shorter than the switching interval T and transmitted.

(Second Embodiment) The system configuration of this embodiment is the same as that shown in FIG. As shown in FIG. 3, the wireless master station 1 sends a control signal S indicating the switching time of the standby frequency to all the wireless slave stations 21 to 2n at each time t10, t1, t2, t3 at a fixed time interval T. , T4, the standby frequencies f6, f1, f2, f4, and f8 at that time are transmitted. The FH sequence is {1, 2 ,, as in the first embodiment.
4,8,5,10,9,7,3,6}.

The control signal can include time information at that time, timing information for switching the standby frequency, and the like.

Each of the slave stations 21 to 2n simultaneously receives the control signal S transmitted by the master station 1 and switches the standby frequency at a predetermined timing. For example, if the control signal is output from the master station 1 immediately before the switching timing, each slave station 21 to 2n immediately performs the standby frequency switching operation upon receiving the control signal, and the master station 1 also outputs the control signal. Immediately after transmission, the standby frequency of the own station is switched.

In this way, the radio master station 1 outputs the control signal S, and the radio slave stations 21 to 2n receive the control signal S to obtain the standby frequency switching timing. Therefore, it is possible to eliminate the shift in the standby frequency switching timing between the parent and child stations for a long time.

Further, control such as confirmation of synchronization and failure detection of the master station 1 can be performed using the control signal S output from the master station 1. If the timers of the slave stations 21 to 2n are reset by using the control signal S output from the master station 1, the timer error of the master station 1 will not be accumulated and the timer of the master station 1 will not be accumulated. There is also an advantage that the slave stations 21 to 2n operate on the basis of.

Even in this embodiment, as in the first embodiment, even in a communication in which the amount of data in one communication is small and the transmission is completed by one or a small number of packets, the master station 1 and each slave station 21 to 2n can use each hopping frequency equally on average.

In this embodiment, the timing for outputting the control signal S is set to a fixed time T interval immediately before the standby frequency switching time, but the timing is not limited to this, and it is sent at a 2T interval or a 3T interval, for example. Alternatively, regardless of the standby frequency switching interval T, it may be transmitted at a timing of once every several seconds, for example. In this case, each station 1, 21
When the control signal S is not received by counting the timer with .about.2n, the standby frequency switching timing is judged from the timer information of the own station to switch the frequency.

Further, if the standby frequency switching timing is determined from the timer information of the own station and the control signal S is received to obtain the standby frequency switching timing,
Even if an error occurs in the wireless section and the control signal S cannot be received normally, the slave stations 21 to 2n can switch the standby frequency at regular timing according to their own timer information.

When the control signal S is used to reset the timers of the slave stations, the error of the timers between the stations is not accumulated, and each slave station operates based on the timer of the master station. There is also.

Furthermore, it is possible to send the control signal S by an arbitrary time TC before the standby frequency switching timing. In this case, information of time TC is included in the control signal, and each slave station performs control to switch the standby frequency when time TC has elapsed after receiving the control signal S.
Similarly, the master station performs control to switch the standby frequency when time TC has elapsed after outputting the control signal S.

(Third Embodiment) FIG. 4 is a diagram showing a system configuration, in which m radio master stations 111 to 11m are connected to a line 10 and n radio stations are connected to the respective radio master stations 111 to 11m. The slave stations 1211 to 12n1, ... 12m1 to 12mn are arranged to form wireless zones 131 to 13n, respectively. The plurality of wireless zones 131 to 13n further form one service area.

Hopping synchronization, that is, the switching timing of the standby frequency is not synchronized between the wireless zones 131 to 13n, and the wireless zones are asynchronous. An FH sequence S ^k is assigned to each of the wireless zones 131 to 13n, for example, wireless zone 131: S ¹ = {1, 2, 3, 4, 5, 6,
7,8,9,10} wireless zone 13 ² : S ² = {6,1,7,2,8,3
9,4,10,5} radio zone 133: S ³ = {3,6,9,1,4,7,
10, 2, 5, 8} ... This code is an OCC code (One-Co).
When the sequence is called asynchronously, it is assumed that this sequence is repeated periodically.
It is a code with good characteristics, in which coincidence occurs at most twice within one cycle. The FH sequences such as OCC codes are described in the literature ("Spread spectrum communication system", written by Mitsuo Yokoyama, P433 to P453, Science and Technology Publishing Company).

Since the radio zones 131 to 13n are asynchronous, the standby frequency is successively changed in each radio zone based on the FH sequence assigned to its own radio zone as in the first embodiment.

In this embodiment, each of the wireless zones 131 ...
The communication system in 13n is the same as the communication system in the first embodiment, but the control signals S indicating the switching timing of the standby frequency are transmitted by the master stations 111 to 11m to all the slave stations 1211 to 12n1 in the wireless zone. , ... A communication method similar to that of the second embodiment, in which the data is transmitted to 12 m1 to 12 mn, may be adopted.

For the FH sequences assigned to the respective radio zones 131 to 13n, if a code having a good characteristic such as an OCC code that causes little difference between different sequences even if they are considered asynchronously is used, the radio zones between the radio zones can be used. The frequency coincidence at is stochastically small.

Therefore, F of the type corresponding to the number of wireless zones
If the H series is prepared and a contention method that transmits for the first time when a communication request is made, or a method that performs transmission after carrier sense is performed, it will be sufficient as a system even if the number of calls generated is large. Can be established. Note that the term "system is established" means that the transmission delay time due to collision detection or the like and the accompanying communication time delay are within the allowable range.

By adopting such a low-speed frequency hopping communication system, even when a service area is composed of a plurality of wireless zones 131 to 13n, each wireless station (master station and slave station) in each wireless zone 131 to 13n ) Can use each hopping frequency equally on average, so
Even in the wireless zone and the entire service area, each frequency is used uniformly.

Further, by using a code having a good characteristic that there is little collision between different sequences even in the asynchronous state, the frequency collision probability between the zones can be reduced even when the number of zones is large and the traffic is large. .

The FH sequence assigned to each of the radio zones 131 to 13n may be not only the OCC code but also other codes. For example, in the above-mentioned literature, in addition to OCC code, G. So
The FH sequence proposed by Lomon is also described.

When the number of zones or the number of slave stations is small or the traffic is small, the same F is applied to all zones.
It is also conceivable to allocate H series. If the same code is assigned to each radio zone, in the worst case, the frequencies used between the zones may always match. However, even in such a case, the system may be established due to the reason that the traffic is small. In such a case, there is no problem even if the same FH sequence is assigned to each zone.

(Fourth Embodiment) In the third embodiment, the system in which the service area is composed of a plurality of wireless zones 131 to 13n has been described in which the standby frequency is asynchronously switched between the zones. The present invention can be applied even when the zones are synchronized.

In FIG. 4, each of the radio master stations 111 to 11m can establish hopping synchronization with each other via the line 10.

At this time, for example, the same FH sequence {1, 2, 3, 4, 5, 6, 7,
8, 9, 10} to the wireless zone 131: {1, 2, 3, 4, 5, 6, 7,
8, 9, 10} wireless zone 132: {2, 3, 4, 5, 6, 7, 8,
9,10,1} wireless zone 133: {3,4,5,6,7,8,9,1
0,1,2} ... wireless zone 1310: {10,1,2,3,4,5,6,6
7, 8, 9}, the standby frequencies of the wireless zones 131 to 13n are switched in synchronization with each other as described above, and therefore the frequencies to be used do not match between the zones. However,
This corresponds to 10 zones, which is the same as the number of channels when there are 10 hopping channels.

Further, the codes assigned to the respective zones are not necessarily the same, and other codes, such as G.G. Solomon and Eina
There is no problem even with the FH sequence for synchronization proposed by rsson.

Even when the zones are synchronized, the communication method described in the first or second embodiment is adopted as the communication method. As a result, each wireless master station 111 to 11m and each wireless slave station 1211 to 121n, ... 12m
1-12 mn is equal on average and each hopping frequency can be used. In addition, it is possible to construct a system in which the frequencies used in the zones do not match, or even if there is a match, the number is very small.

In this embodiment, each wireless master station 111-.
The line 11 is used for synchronization for 11 m, but the present invention is not limited to this, and a wireless section may be used.

(Embodiment 5) In this embodiment, the radio master station 1 described in the second embodiment sends a control signal S to each of the radio slave stations 21 to 2n.
In the method of transmitting the, the method of synchronizing the standby frequency when the standby frequency is not synchronized between the master station and the slave station will be described.

As shown in FIG. 5, the master station repeatedly transmits the control signal S at a certain time interval and switches the frequency from f1 to f10. Here, the F assigned to the master station and the slave station
The H sequence is represented by {f1, f2, f3, f4, f5, f6, f
7, f8, f9, f10}.

When the slave station waits at the frequency f1, it is time to receive the control signal S from the master station. According to the control signal S, the slave station can synchronize the standby frequency with the master station, and thereafter, the master station and the slave station can communicate with each other.

The control of the slave station will now be described. As shown in FIG. 6, the slave station which is out of synchronization is brought into the receiving state in ST1. The slave station is out of synchronization when the slave station is started up or when the standby frequency during communication is out of synchronization.

Subsequently, in ST2, it is judged whether or not the control signal S from the master station can be received, and if the control signal S can be received, the communication becomes possible. That is, according to the received control signal S, the standby frequency is synchronized with the master station, and the communication becomes possible.

By this method, if the control signal S is not disturbed, the master station switches the standby frequency at the maximum and the FH
The standby frequency can be synchronized between the parent station and the slave station within the time required to go around the sequence.

As described above, in order to synchronize the standby frequencies of the master station and the slave station, the slave station waits until it can receive the control signal S, so that the synchronization can be achieved by an extremely simple method.

(Sixth Embodiment) This embodiment will describe another method for synchronizing the standby frequency when the standby frequency synchronization between the master station and the slave station is not established.

That is, when the synchronization of the standby frequency between the master station and the slave station is not established, the slave station receives at one standby frequency and sends a connection request signal to a specific or all master stations. Transmit at a time interval that is less than half the frequency switching time of the master station, recognize the frequency used by the master station if there is a response signal,
When there is no response signal, retransmission of the connection request signal to a specific or all master stations is repeated until the response signal can be received, whereby the standby frequency of the master station is recognized and communication is started.

For example, as shown in FIG. 7, the slave station transmits the connection request signal RS to the master station at the frequency f1. The master station does not receive the connection request signal RS from the slave station unless the frequency f1 is used. Since the slave station has no response to the connection request signal RS, it recognizes that the master station does not use this frequency f1 as the standby frequency.

The slave station repeats the transmission of the connection request signal RS at a time interval of half the frequency switching time of the master station or less until it can receive the response signal AS from the master station.

When the master station switches the standby frequency from f10 to f1 after transmitting the control signal S after a lapse of time, the standby frequency of the master station coincides with the frequency f1 of the slave station. .

In this state, since the master station can receive the connection request signal RS from the slave station, the master station receives the connection request signal RS and transmits the response signal AS to the slave station. If the slave station can receive this response signal AS, it can communicate with the master station because it uses the same frequency as the master station.

The control of the slave station will now be described. As shown in FIG. 8, the slave station which is out of synchronization stands by in ST11 for the time of the transmission interval of the connection request signal RS. When the transmission time arrives, carrier sense is performed in ST12.
In this way, by performing carrier sense before transmission, it is possible to reduce interfering radio waves to other stations. That is, if carrier sense is present, a random time delay is performed in ST13, and then carrier sense in ST12 is performed again.

If there is no carrier sense, ST1
At 4, the connection request signal RS is transmitted. Then, after the end of the transmission, the receiving state is immediately set in ST15, and it is determined in ST16 whether the response signal AS is received from the master station. At this time, if the response signal AS is not received, the process returns to the control of ST11. Further, when the response signal AS can be received, the communication becomes possible.

If the master station to communicate with is determined, the master station to which the connection is requested can be limited by using the address of the master station determined as the destination address of the connection request signal RS. .

Further, in the case of a slave station that may communicate with any master station or a slave station that is not sure which master station can be connected, the connection request signal RS is transmitted by setting the destination address to the master station's global address. do it.

Further, by including the timer information of the master station in the response signal AS, the slave station receiving this response signal AS can match the timer of the slave station with the timer of the master station.

Further, when the destination of the connection request signal RS is the global address of the master station, the frequency information of a plurality of standby frequencies next to or after the control signal S is included, and the slave station receives the control signal. The standby frequency is switched based on the information of S. Also, upon receiving the response signal AS from the master station in response to the connection request signal RS from the slave station, the master station immediately transmits a packet containing the FH sequence information to the slave station.
As a result, the slave station can use the FH sequence received from the master station by itself.

Therefore, it becomes possible to communicate even if the wireless zone changes and the FH sequence changes.

As described above, in order to synchronize the standby frequencies of the master station and the slave station, the slave station transmits the response signal AS from the master station at a time interval of half or less of the frequency switching time of the master station. By repeating the transmission of the connection request signal RS until reception is possible, synchronization can be achieved by a relatively simple method, and moreover, synchronization can be achieved faster than simply waiting until the control signal S can be received.

(Seventh Embodiment) Same FH as in the fifth embodiment
Another method for synchronizing the standby frequency between the parent and child stations using the sequence will be described.

As shown in FIG. 9, the slave station changes the frequencies f1, f2, f3, f4, ... In accordance with the FH sequence.
At this time, the slave station transmits the connection request signal RS while switching the standby frequency at intervals shorter than the residence time of one standby frequency in the master station.

If the master station uses the frequency f5, for example, even if the slave station transmits the connection request signal RS at a frequency other than the frequency f5, the master station does not receive the connection request signal RS. Then, the master station receives the connection request signal RS and transmits the response signal AS only when the slave station transmits the connection request signal RS at the frequency f5.

When the slave station receives the response signal AS, it recognizes that it is using the same frequency as that of the master station, and thereafter, communication with the master station becomes possible.

The control of the slave station will now be described. As shown in FIG. 10, the slave station which is out of synchronization sets the initial frequency and the FH sequence in ST21. Then, in ST22, the system waits for the time of the transmission interval of the connection request signal RS, and ST2
At 3, the counter a is set. This counter a is 1
It is a counter that counts the number of times that the connection request signal RS is transmitted at one frequency. Even if the master station and the slave station use the same frequency, the connection request signal RS is set in consideration that communication cannot be performed if there is interference. It can be retransmitted multiple times.

When the transmission time comes, carrier sense is performed in ST24. In this way, by performing carrier sense before transmission, it is possible to reduce interfering radio waves to other stations. That is, if carrier sense is present, a random time delay is performed in ST25, and then carrier sense in ST24 is performed again.

If there is no carrier sense, ST2
At 6, the connection request signal RS is transmitted. Then, after the end of the transmission, the receiving state is immediately set in ST27, and it is determined in ST28 whether or not the response signal AS is received from the master station. Then, when the response signal AS can be received, the communication becomes possible.

If the response signal AS cannot be received,
In ST29, the count value of the counter a is checked and the counter a
If is not the set number of times, the counter a is incremented in ST30, the process returns to ST24 to retransmit the connection request signal RS, and carrier sensing is performed again. Also,
If the count value of the counter a has reached the set number of times, S
At T31, the frequency is changed according to the FH sequence, and the operation returns to the operation of waiting for the transmission interval time of the connection request signal RS in ST22.

As described above, in order to synchronize the standby frequencies of the master station and the slave station, the slave station not only waits for the reception of the control signal but also transmits the connection request signal RS while changing the frequency. It is possible to shorten the time until the standby frequency is synchronized at the time of power-on or resynchronization.

Also, during the time when the master station stays at one standby frequency, the slave station transmits the connection request signal R at all standby frequencies.
If S can be transmitted, the time until the standby frequency is synchronized can be set to the time at which the master station stays at one frequency at the longest.

(Eighth Embodiment) This embodiment describes a method of synchronizing the standby frequency and starting communication with the master station when the slave station is a mobile slave station.

That is, when the slave station receives at one standby frequency and this slave station can receive the transmission contents of this master station in the communication between other slave stations and the corresponding master station, The connection request signal RS is transmitted to the master station, and if there is a response signal AS, communication is started, and if there is no response signal AS, the connection request signal RS is repeatedly transmitted to this master station until a response signal can be received. By receiving the response signal AS, the standby frequency of the master station is recognized and communication is started.

FIG. 11 is a plan view of one service area SA, and six wireless zones 211 to 216 are formed in this service area SA. In the figure, the shaded circles represent wireless master stations, the triangles represent wireless slave stations, and the pentagons represent wireless mobile slave stations.

The mobile slave station corresponds to, for example, a handy terminal or a mobile POS terminal in the POS system, and is a terminal that can freely move in the store and register the sale of goods from any place.

The mobile slave station 22 is, for example, in the wireless zone 211.
Since it is possible to move freely between the zones as if moving from the position indicated by the dotted line to the wireless zone 213, the corresponding master station cannot be specified. Further, even when the FH sequence is different for each zone, the FH sequence cannot be determined.

For this reason, the mobile slave station 22 performs the control shown in FIG. That is, at first, the mobile slave station 22 is in a state of not knowing which master station it can communicate with, and is out of synchronization.

In this state, first, the initial frequency is set in ST41, and then the receiving state is set at the set initial frequency in ST42. Then, in ST43, the system waits until there is a received signal.

When there is a received signal, it is determined at ST44 whether the received signal is from the master station. That is, even if the signal from the slave station is received, it is not known whether or not the master station can be communicated with. Therefore, when the signal from the slave station is received, the connection request signal is not transmitted. When the packet from the master station is received, the address of the master station is recognized from this packet.
As a result, the address of the master station transmitted by the slave station thereafter is determined.

When the address of the master station is determined, carrier sensing is performed in ST45. In this way, by performing carrier sense before transmission, it is possible to reduce interfering radio waves to other stations. If there is a carrier sense, ST46
Then, after a random time delay, the carrier sense in ST45 is performed again.

If there is no carrier sense, ST4
At 7, the connection request signal RS is transmitted. Then, after the end of the transmission, the receiving state is immediately set in ST48, and it is determined in ST49 whether the response signal AS is received from the master station. Then, when the response signal AS can be received, the communication becomes possible.

If the response signal AS cannot be received,
It returns to ST43 again and waits for signal reception from the master station.

In this way, the mobile slave station 22 judges the packet from the master station from the received signal, recognizes the address of the master station from this packet, determines the master station to which it should transmit, and then sends the connection request signal. Since communication is started by transmitting and synchronizing the standby frequency, even if the mobile slave station 22 freely moves between the zones, the mobile slave station can communicate with the corresponding master station. it can.

The number of hopping frequencies used in the entire system, the number of FH sequences, the number of slave stations, the traffic in the wireless section, the time during which the master station stays in one frequency, and the allowance until the acquisition of the standby frequency are acquired. Depending on the usage conditions such as time, it is also possible to select and use a communication method that is satisfactory as a system from the above-mentioned fifth to eighth embodiments, or to use these embodiments in combination. You can also

(Ninth Embodiment) This embodiment describes two methods for controlling the slave station to recognize that the standby frequency of the master station is out of synchronization with the master station.

First Method If the standby frequency is out of synchronization during communication, communication cannot be performed at all. At this time, the slave station performs the control shown in FIG.

The slave station tries to communicate with the master station. And S
At T51, it is determined whether or not the communication is successful. If the communication is successful, the counter b is reset at ST52. This counter b is a counter that counts the number of retransmissions.

When communication is not possible, it is subsequently determined in ST53 whether the count value of the counter b is the set number of times.

If the count value of the counter b has not reached the set number of times, the counter b is incremented in ST54, the data is retransmitted in ST55, and the process returns to the judgment in ST51 of whether or not the communication is successful. If the count value of the counter b has reached the set number of times, it is recognized that the standby frequency is out of synchronization, that is, FH synchronization is lost.

That is, since there is a case where the transmission from the slave station cannot be communicated due to interference from other radio stations, the allowable number of retransmissions of the slave station is defined, the counter b counts the number of retransmissions, and the slave station FH is only when communication with the master station is not possible even though communication has been attempted the number of times allowed for retransmission.
I am trying to recognize out of synchronization.

As described above, when the slave station cannot communicate even after transmitting the specified number of times, it recognizes that the standby frequency between the master station and the slave station is out of synchronization, and therefore the resynchronization operation is performed to perform communication. Can return to the ready state.

Second Method When the standby frequency is out of synchronization, the control signal S from the master station cannot be received. At this time, the slave station is shown in FIG.
The control shown in is performed.

First, at ST61, the control signal S from the master station is sent.
When the control signal S is received, the counter c is reset in ST62, the timer T is reset in ST63, and the frequency is hopped in ST64. The counter c is a counter that counts the number of times the frequency is switched without receiving the control signal S, and the timer T is a timer that counts the frequency switching time.

When the control signal S cannot be received in ST61, it is continuously monitored whether or not the set time of the ST65 timer T has passed, and when the set time has passed, ST6
Hopping the frequency at 6. This allows the slave station to switch the frequency even if the slave station cannot receive the control signal S due to interference from other stations.

Then, in ST67, it is checked whether the set number of times of the timer c has been reached. If the set number of times has not been reached, the counter c is incremented in ST68, and if the set number of times has been reached, the standby frequency It is recognized as out of synchronization, that is, out of sync with FH.

In this way, the slave station recognizes that the standby frequency is out of synchronization when the frequency is switched without being able to receive the control signal S from the master station continuously for a predetermined number of times, and therefore the resynchronization operation is performed to perform communication. Can return to the ready state.

As described above, when the slave station recognizes that the standby frequency is out of synchronization by the first or second method,
The standby frequency is resynchronized by any of the methods of the fifth to eighth embodiments described above. In this way, communication with the master station becomes possible again.

Therefore, even if synchronization is lost between the parent and slave stations, it is possible to recognize the synchronization loss of the standby frequency and immediately return to the communicable state.

(Tenth Embodiment) In this embodiment, when the master station and the slave station are communicating with each other and the slave station recognizes that the standby frequency between the master and slave stations is out of synchronization, Attempts to receive the control signal S and the connection request signal RS while changing the frequency in order from the frequency of the frequency hopping sequence that is close in time from the time of recognizing that the frequency is out of synchronization, and wait for the standby between the parent and child stations. A control method for synchronizing frequencies and restarting communication will be described.

Considering the difference in the synchronization of the standby frequency between the parent station and the slave station caused by the difference in the timer between the master station and the slave station,
It is expected that the distance is closer in time than the frequency at which out-of-sync is recognized.

The control performed by the slave station for resynchronization is shown in FIG.
Is the same as. However, the order of changing the frequency in ST31 is different from that in FIG.

In the frequency hopping sequence shown in FIG. 15A, assuming that the standby frequency is out of synchronization at the position of frequency f3, this position is also close to frequency f2 at frequency f3. Therefore, the frequency at the shortest distance in time is f2. The frequency at the second closest distance is f4, and hereafter, f1, f5, f10, f
The order is 6, f9, f7, and f8. That is, in FIG.
The frequency switching order is as shown in (b).

Control for capturing synchronization of the standby frequency is performed until resynchronization can be performed according to the frequency switching order.

Also in this embodiment, even if the synchronization is lost between the parent station and the slave station, it is possible to recognize the loss of synchronization of the standby frequency and immediately return to the communicable state.

(Eleventh Embodiment) This embodiment is shown in FIG.
In the above configuration, although the wireless slave station attempts to receive the control signal S once or more for all frequencies of the frequency hopping sequence and transmits the connection request signal RS to the wireless master station, When the standby frequencies of are not synchronized, the frequencies are switched for all the frequencies used in the service area SA, and the control signals S are received from all the master stations and the master stations are transmitted to all the master stations at the respective frequencies. A control method for attempting to transmit the connection request signal RS and synchronizing the standby frequency between the parent and child stations to perform communication will be described.

In FIG. 11, wireless zones 211 to 21
The frequency hopping (FH) sequence of 3 is used in the wireless zone 21.
1 is {f1, f2, f3, f4, f5, f6, f7,
f8, f9, f10}, the wireless zone 212 is {f1
1, f12, f13, f14, f15, f16, f1
7, f18, f19, f20}, the wireless zone 213,
{F21, f22, f23, f24, f25, f26,
f1, f2, f3, f4}.

The slave station 23 is in a position where it can communicate with either of the master stations 251 and 252 of the zones 211 and 212.
First, communication is established with the master station 251 of the zone 211.

Communication can be performed if the standby frequency is synchronized with the frequency used in the FH sequence of zone 211 as in the fifth to seventh embodiments described above.

When the slave station 23 becomes unable to communicate due to a failure of the master station 251 of the zone 211, the out-of-sync state is recognized, and the processing of FIG. 16 is performed.

First, in ST71, slave station connection processing is performed.
This process is the same as the fifth to eighth embodiments described above or the tenth embodiment.
Any of the control methods of the above embodiments may be used.

Subsequently, in ST72, it is checked whether or not communication is possible, and if communication is possible, the communication becomes possible.
It communicates with the master station 251 of the zone 211. However, communication is not possible unless the master station 251 of the zone 211 is operating.

If the slave station 23 cannot communicate with the master station despite the resynchronization operation, the zone 21 1
It is determined whether the operation of synchronizing the frequency used in step n has been repeated for n cycles, and if n cycles have not been repeated, ST
The control for switching the frequency is performed at 74, and the slave station connection processing at ST71 is performed again.

The frequency used in the zone 211 is n
If communication with the master station is not possible even after repeating the cycle, control for enabling connection to any master station is performed in ST75, and slave station connection processing is performed in ST76. This process is a process in which the frequencies to be used are all frequencies used in the service area SA, and the destination of the connection request signal RS is used as the global address of the master station to attempt to connect to any master station.

Since the frequencies used in the zones 211 and 212 are all different, it is necessary to try the slave station connection processing at all frequencies in the service area.

If the frequencies used by the slave station 23 and the zone 212 do not match, communication is disabled at ST77, the frequency is switched at ST78, and the process returns to ST76 to perform slave station connection processing again. In addition, the slave station 23 and the zone 212
If the frequencies used by are coincident with each other, it is determined in ST77 that communication is possible, and communication is possible.

Also, when the mobile station 22 moves to zone 213 after performing communication in zone 211, FIG.
The connection process similar to 6 is performed.

Also in this embodiment, even if the synchronization is lost between the parent and slave stations, it is possible to recognize the synchronization loss of the standby frequency and immediately return to the communicable state.

(Twelfth Embodiment) In the twelfth embodiment, even though the slave station attempts to receive the control signal S and transmit the connection request signal RS once or more for all usable frequencies, the slave station When the standby frequency between the stations is not synchronized, the receiving operation is performed at the initial setting frequency, and the standby frequency between the parent and slave stations is synchronized according to the control signal S only when the control signal S from the parent station is received. A control method for starting the take communication will be described.

In FIG. 11, the slave station 24 in the wireless zone 211 can communicate with the master station 251 by synchronizing the standby frequency. Base station 25 of wireless zone 211
When 1 becomes unable to communicate due to a failure etc., the slave station 24
Similar to the slave station 23 of the first embodiment, the control based on FIG. 16 is performed. However, unlike the slave station 23, the slave station 24 is not in a position where it can communicate with a master station in another zone, so that the slave station 24 does not enter the communicable state.

The slave station 24 uses ST71 and ST shown in FIG.
After performing the processes of 72, ST73, ST74, and ST75, the process of FIG. 17 is performed.

In this process, first, in ST81, a slave station connection process is performed. Then, in ST82, it is determined whether or not communication is possible.

When the master station 251 of the zone 211 is not operating, communication is not possible, and it is determined in ST83 whether the slave station connection processing is performed n times at all frequencies, and the slave station connection processing is performed n times. If not, the control for switching the frequency is performed in ST84, and the slave station connection processing in ST81 is performed again.

If communication with the master station is not possible even though the slave station connection processing has been performed n times at all frequencies, the reception state at the initial frequency is set in ST85, and the operation waits. Then, when the master station 251 of the zone 211 returns, the master station 251 transmits the control signal S.
At T86, the control signal S from the master station 251 is received, and the communication becomes possible.

In this way, if the slave station 24 finds that it cannot communicate with any of the master stations, it stops transmitting the connection request signal RS and enters the reception state at the initial frequency. This makes it possible to reduce interference with other stations.

(Thirteenth Embodiment) In this embodiment, when the power is turned off in the slave station, the frequency hopping sequence used last is stored, and the initial frequency hopping sequence is stored when the power is turned on again. Instead of using the stored frequency hopping sequence.

As described in the eleventh embodiment, it is assumed that the slave station 23, which is supposed to communicate with the master station 251 of the zone 211 in the initial setting, is communicating with the master station 252 of the zone 212.

If it is necessary to turn off the power at this time, the power off operation process shown in FIG. 18 is performed. First, S
The last used FH sequence and frequency are stored at T91. Then, in ST92, the power is turned off.

Then, when the power is turned on again in ST93, it is checked in ST94 whether or not the last used frequency is stored, and if so, in ST95 the last used frequency and FH are stored. After setting the sequence, in ST96, the slave station connection process is performed in an attempt to communicate with the master station 252 of the zone 212. If the last used frequency is not stored, the initial frequency and the FH sequence are set in ST97, and the slave station connection process of ST96 is attempted to communicate with the master station 251 of zone 211.

As a result, even if the slave station and mobile slave station communicating over two or more zones are powered off once, when the power is turned on again in the same zone, the master station of this zone is promptly turned on. And the standby frequency can be synchronized.

In this embodiment, both the last used frequency and the FH sequence are stored when the power is turned off, but the present invention is not limited to this. Either the last used frequency or the FH sequence is stored. It may be stored.

[0151]

As described above, according to the present invention, even in communication such as PLU communication of a wireless POS system in which transmission is completed in one packet, each station uses each hopping frequency equally on average. Moreover, the initial synchronization of hopping can be achieved with simple control and at high speed.

Further, according to the present invention, the radio master station outputs the control signal for switching the standby frequency, and the radio slave station obtains the standby frequency switching timing based on the control signal.
It is possible to eliminate the deviation of the standby frequency switching timing between the parent and child stations for a long time.

Further, according to the present invention, even when a service area is constituted by a plurality of wireless zones, each master station and each slave station use each hopping frequency equally on average, and accordingly, the wireless zones are used. Also, each frequency can be used even when viewed in the entire service area. Also, when the master stations are synchronized, it is possible to eliminate or minimize the frequency match between the wireless zones, and use a code with good characteristics with little collision between different sequences even when they are asynchronous. By doing so, it is possible to reduce the frequency collision probability between zones even when the number of zones is large and the traffic is heavy.

Further, according to the present invention, in order to synchronize the standby frequencies of the wireless master station and the wireless slave station, the wireless slave station waits until it can receive the control signal from the wireless master station. You can synchronize in a very simple way.

Further, according to the present invention, in order to synchronize the standby frequencies of the wireless master station and the wireless slave station, the wireless slave station not only waits until it can receive the control signal from the wireless master station, By transmitting the connection request signal while changing the time, it is possible to shorten the time until the standby frequency is synchronized when the power is turned on or at the time of resynchronization.

Further, according to the present invention, when the wireless slave station cannot communicate even after transmitting the specified number of times, it recognizes that the standby frequency between the parent and slave stations is out of synchronization, and therefore the resynchronization operation is performed. You can go back to the state where you can communicate immediately. In addition, the wireless slave station recognizes that the standby frequency is out of synchronization even when the frequency is switched without receiving the control signal from the wireless master station continuously for the specified number of times, so even when there is no communication between the parent and slave stations, the standby It is possible to judge whether or not the frequencies are synchronized. As a result, it is possible to create a state in which the parent and child stations can always communicate with each other.

[Brief description of drawings]

FIG. 1 is a system configuration diagram in one wireless zone.

FIG. 2 is a time chart showing the switching timing of the standby frequency and the communication timing between the parent station and the slave station in the first embodiment of the present invention.

FIG. 3 is a time chart showing an output timing of a control signal transmitted from a wireless master station to each wireless slave station and a switching timing of a standby frequency in a second embodiment of the present invention.

FIG. 4 is a system configuration diagram in which a service area includes a plurality of zones.

FIG. 5 is a time chart showing a timing at which a wireless slave station waits for reception of a control signal from a wireless master station in order to synchronize a standby frequency between the master and slave stations in the fifth embodiment of the present invention.

FIG. 6 is a flowchart showing a control signal reception process of a wireless slave station in the fifth embodiment.

FIG. 7 is a time chart showing the timing at which a wireless slave station transmits a connection request signal to a wireless master station in order to synchronize the standby frequency between the parent and slave stations in the sixth embodiment of the present invention.

FIG. 8 is a flowchart showing a process of transmitting a connection request signal and receiving a response signal of a wireless slave station according to the sixth embodiment.

FIG. 9 is a time chart showing the timing at which the wireless slave station transmits a connection request signal to the wireless master station while changing the frequency in order to synchronize the standby frequency between the parent and slave stations in the seventh embodiment of the present invention.

FIG. 10 is a flowchart showing a process of transmitting a connection request signal and receiving a response signal of a wireless slave station according to the seventh embodiment.

FIG. 11 is a diagram showing an arrangement relationship between zones and wireless stations according to an eighth embodiment of the present invention.

FIG. 12: The wireless slave station knows the frequency to be used from the communication content of the wireless master station and transmits a connection request signal to the wireless master station in order to synchronize the standby frequency between the parent and slave stations in the eighth embodiment. The flowchart which shows the process which tries.

FIG. 13 is a first diagram for recognizing out-of-synchronization of the standby frequency when the wireless slave station cannot communicate in the ninth embodiment of the present invention.
6 is a flowchart showing the processing of FIG.

FIG. 14 is a flowchart showing a second process of recognizing out-of-synchronization of the standby frequency when the wireless slave station is unable to communicate in the ninth embodiment.

FIG. 15 is a diagram showing a frequency switching sequence at the time of resynchronization of the standby frequency of the wireless slave station according to the tenth embodiment of the present invention.

FIG. 16 is a flowchart showing resynchronization processing of a standby frequency of a wireless slave station according to an eleventh embodiment of the present invention.

FIG. 17 is a flowchart showing a process in which a wireless slave station receives a control signal and restarts communication in a twelfth embodiment of the present invention.

FIG. 18 is a flowchart showing the processing when the wireless slave station turns off and then on again in the thirteenth embodiment of the present invention.

[Explanation of symbols]

 1,111 to 11m ... Wireless master stations 21 to 2n, 1211 to 12mn ... Wireless slave stations 131 to 13n ... Wireless zone

Claims (5)

[Claims] 1. A service area is composed of one or a plurality of wireless zones, and the one or a plurality of wireless zones is constituted by one wireless master station and one or more wireless slave stations, and the wireless master station and the wireless slave stations. When performing low-frequency hopping spread spectrum communication between stations, all stations in the wireless zone switch the standby frequency at a certain time interval, and during communication, transmission and reception are performed at the standby frequency. Spread communication method. 2. The wireless master station within the wireless zone transmits a control signal indicating a standby frequency switching time to all wireless slave stations at the standby frequency before switching. 1. The low frequency frequency hopping spread spectrum communication method according to 1. 3. The wireless slave station continues to receive at one standby frequency when the standby frequency synchronization between the wireless master station and the wireless slave station is not established, and a control signal is transmitted from the wireless master station. 3. The low-speed frequency hopping spread spectrum communication method according to claim 2, characterized in that, upon reception of the control signal, the standby frequency is synchronously acquired with the radio master station according to the received control signal to start communication. . 4. The wireless slave station is shorter than a dwell time of one standby frequency in the wireless master station when synchronization of the standby frequency between the wireless master station and the wireless slave station is not established. 2. The standby frequency switching and the connection request signal transmission are repeated at time intervals in accordance with the frequency hopping sequence to recognize the standby frequency of the radio master station and start communication.
Alternatively, the low-frequency frequency hopping spread spectrum communication method according to item 2. 5. The low-frequency hopping spread spectrum communication method according to claim 3, wherein the wireless slave station was unable to communicate with the wireless master station despite performing a predetermined number of retransmissions set in advance. When the control signal from the radio master station cannot be received a preset number of times, it is recognized that synchronization of the standby frequency with the radio master station is not established. Spread spectrum communication method.