JPH02199931A - Data transmission system - Google Patents

Abstract

PURPOSE:To improve a data arrival rate by sharing one and same communication channel dividing each communication equipment into groups each composed of one or plural communication equipments and presetting an inherent standby time different from each group at every group. CONSTITUTION:Radio equipments M1-M3 of plural mobile stations S1-S3 and a radio equipment M0 of a base station S0 make radio communication through one and same channel. When other mobile station S2 starts the transmission at a time while the mobile station S1 makes data transmission with a high line hit rate, the base station S0 cannot receive both the data simultaneously. Thus, a processing circuit 2 in the mobile station S1 starts the retransmission of the data from a time when the data transmission is finished and a limit time of a timer T3 elapses. Moreover, the processing circuit 2 of the mobile station S2 starts the retransmission of the data in a standby time by the limit time of the timer T3 after the data transmission is finished.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a data transmission system between communication devices that is suitably used in the transportation industry such as the delivery industry.

Problems to be Solved by the Prior Art and the Invention In the delivery business, the same communication line is shared by a plurality of communication devices, and each communication device constitutes a single base station and a plurality of mobile stations. A data transmission system is used in which, for example, a customer name, that is, a dealer's name, a receiving number, or a slip number, etc. are sent and received between a base station and a mobile station.

In typical prior art, a mobile station desiring to transmit data is configured to begin transmitting data when the request for transmission occurs. Therefore, when data is being transmitted between another mobile station and a base station, the transmission operation is interrupted, and the data being transmitted or the data that has started transmission are destroyed.

In order to eliminate such problems and achieve reliable data transmission, the mobile station transmits the following information as shown in Figure 6 (1).
When data is transmitted between times t1 and t2 and the base station reliably receives this data as shown in FIG. 6(2), the base station returns an acknowledgment signal between times t3 and t4, The mobile station is configured to repeatedly retransmit data until this confirmation signal is received.

However, in such a configuration, when the retransmission timings are the same, as shown in FIG. 7(1), the mobile station starts transmitting data at time t1L, and this transmission ends at time t12. A time t earlier than
13, when another mobile station starts transmitting data as shown in FIG. 7(2), data collides as described above and retransmission is performed.

However, this retransmission also ends at the transmission end time t12 of each mobile station.
At time t15., a predetermined period W1 has elapsed since time t14. Each starts from t16, and from time t15 to tlT when one mobile station is retransmitting as shown in FIG. 7(1).
In the meantime, as shown in FIG. 7(2), the other mobile station starts retransmission, and data collision occurs again.

If the retransmission interval W1 is the same, such data collisions will be repeated, and as shown in FIG. 7 (3), the base station will not be able to receive data, and the data arrival rate will decrease. Resulting in.

In order to solve the above-mentioned problems, it is possible to add a separate circuit and set the retransmission interval W1 for each mobile station, or to set the retransmission interval W1 by software.
A configuration is used in which the value is set to 1. However, in a configuration in which 11 additional circuits are added, the cost increases, and in a software configuration, there is no software compatibility between mobile stations with configurations with different retransmission intervals, making it difficult to use common software. The problem is that it can't be done.

On the other hand, in other conventional techniques, the timing at which each mobile station starts transmitting data is controlled by so-called polling. That is, the base station sequentially calls a plurality of mobile stations and allows only the called mobile station to transmit data, thus preventing data collisions.

However, in this method, a call is made even to a mobile station that does not have data to be transmitted, which may result in a long waiting time for a mobile station that wishes to transmit data.

Furthermore, a call is made to a mobile station that does not need to transmit data, and the mobile station has to respond to the call, which reduces the efficiency of using the communication line.

An object of the present invention is to provide a data transmission method that can improve the reception rate during data retransmission without using a complicated configuration.

Means for Solving the Problems The present invention provides a system in which the same communication line is shared by a plurality of communication devices,
In a data transmission method between communication devices, when data transmitted from a communication device is received, the communication device that received the data returns a confirmation signal, for each group of one or more communication devices. By setting unique wait times that are different from each other, the transmitting communication device
This data transmission method is characterized in that, after transmitting data, if the confirmation signal is not returned from the receiving communication device, the data is retransmitted after the waiting time has elapsed.

Function According to the present invention, a plurality of communication devices share the same communication line, and when data is transmitted from one of the communication devices, the communication device that has received the data returns a confirmation signal. Each communication device is divided into groups of one or more communication devices. Each group has its own unique waiting time set in advance.

A communication device that performs transmission starts transmitting data when a transmission request occurs, and for example, collides with data transmitted from another communication device, thereby causing data to be transmitted from the communication device receiving the data. If the confirmation signal is not returned, the data is retransmitted after the waiting time has elapsed.

Therefore, when data is transmitted from multiple communication devices at the same time and the data cannot be completely transmitted, and the data is retransmitted, the timing to start retransmission depends on the group to which the communication device belongs. In contrast, a communication device that performs reception in this manner can reliably receive data at the time of retransmission, and can improve the call reception rate.

Embodiment FIG. 1 is a system diagram of a wireless communication system for a delivery business using a data transmission system according to an embodiment of the present invention. The multiple vehicles that collect and deliver packages are equipped with radio devices M1 to M1, which are communication devices.
M3 is installed and constitutes mobile stations 81 to S3, respectively. Further, a central processing unit U is connected to the radio device MO of the single base station SO.

The radios M1 to M3 of the plurality of mobile stations 81 to S3 and the radio 1f of the base station SO! MO refers to the wireless devices M1 to M3 of mobile stations 81 to S3 that perform wireless communication on the same channel, that is, the same frequency band, each of which is assigned a unique number corresponding to, for example, a vehicle number. Radio M
1 to M3 and the wireless device MO of the base station SO use this unique number to identify the communication partner station and transmit data.

The data transmitted from the base station SO includes the customer name, that is, the name of the dealer, the reception number, that is, the slip number, the reception time, and the address of the dealer. Furthermore, the mobile stations M1 to M3 transmit data indicating, for example, the end of collection and delivery services. When the transmission of such data is completed and the communication partner station has reliably received this data, it returns a confirmation signal.

FIG. 2 is a block diagram showing the electrical configuration of radio devices M1 to M3 of mobile stations 81 to S3. When data to be transmitted is input from the keyboard 11, reading sensor 12, etc.
This input data is led out from the input/output circuit 1 to the processing circuit 2 together with the car number data set in the car number setting means 13 realized by a dip switch or the like.

The processing circuit 2 determines whether a carrier wave is detected within the same communication channel, that is, whether another mobile station is communicating, based on the line busy signal derived from the transmitting/receiving unit 3. Also, based on the count results of built-in timers T1 to T3, which will be described later, input data from the input/output circuit 1 is derived to the modem 4 as transmission data. Transmission data modulated by the modem 4 is transmitted from the transmitting/receiving section 3 via the antenna 5.

The processing circuit 2 is also provided with a random access memory (hereinafter referred to as rRAMJ) 6, and this RAM 6 stores unsent data that could not be transmitted out of the input data from the aforementioned input/output circuit 1. Transmitted data is temporarily stored. A data management area is provided in the RAM 6, and the presence or absence of the unsent data is stored in this data management area. The processing circuit 2 searches this data management area, and if there is untransmitted data, retransmits the data as described later.

The timer T1 measures a predetermined unit time, and the processing circuit 2 calculates and obtains the ratio of the period during which the line busy signal is derived, ie, the line busy rate, within this unit time. As described above, the timer T2 starts clocking when data is transmitted from the processing circuit 2 via the modem 4 and the transmitting/receiving section 3, and the data is transmitted from the transmitting/receiving section 3 via the modem 4. Then, the time W3 until the confirmation signal is received is measured.

The timer T3 is a time limit timer, and the time limit W2 is set corresponding to the vehicle number data inputted through the input/output circuit 1 as described above, and the timer T3 starts the timing operation when the data transmission is completed. If the confirmation signal is not received even after a predetermined time W4 has elapsed by the clock time W3 of the timer T2, the processing circuit 2 retransmits the data at the time when the time limit W2 has elapsed. W2 differs depending on each mobile station 81 to S3, and for example, mobile station SL,
In S3, the unit time WO is set as the time limit W21, and in the mobile station S2, a time twice the unit time Wo is set as the time limit W22.

FIGS. 3 and 4 are timing charts for explaining data transmission operations of the radios M1 to M3 of the mobile stations 81 to S3 configured as described above. When the busy rate of the line is low and the communication line is idle, as shown in Fig. 3 (
As shown in 1), when data is transmitted from a mobile station, for example, Sl, between times t21 and t22, the base station SO reliably receives it and transmits data between times t23 and t22.
A confirmation signal is sent back within 24 seconds. In the mobile station S1 that transmitted the data, the timer T2 starts clocking from time t22 when the data transmission ends, and the timer T2 receives this confirmation signal within the predetermined time W4. Then, the data transmission is deemed to have been completed and the operation is terminated.

On the other hand, the busy rate of the line is high, and
As shown in the figure, time t3 between time t31 and time t32 when a mobile station consisting of, for example, Sl is transmitting data.
3, when another mobile station, for example S2, starts transmitting, data collides at the base station SO from time t33 to time t32, making it impossible to receive data from both.

Therefore, since the confirmation signal is not returned even after the clock time W3 of the timer T2 has passed the predetermined time W4, the processing circuit 2 in the mobile station Sl starts the timer T3 from the time t32 when the data transmission ends. Data retransmission starts from time t34 when the time limit W21 has elapsed.

Furthermore, since the confirmation signal is not received as described above, the processing circuit 2 of the mobile station S2 receives the confirmation signal at the time t3 when the data transmission ends.
5, waits for the time limit W22 of timer T3 and returns to time t.
Data retransmission starts from 36. At this time t36, data transmission from the mobile station S1 is completed and the base station SO
From the time t when the return of the confirmation signal from the mobile station 811\ is completed.
37 or later, data can be reliably transmitted in this way without the occurrence of data collisions as described above.

FIG. 5 is a flowchart for explaining the above-mentioned transmission operation. In step n1, when the transmission switch of the keyboard 11 is operated or data to be transmitted is inputted by the reading sensor 12, etc., and a data transmission request is generated, the process moves to step n2, and the processing circuit 2
Based on the line busy signal from the mobile station, it is determined whether the communication line is not in use by another mobile station, and if so, that is, when the communication line is in use, this step n2 is returned green and the communication When the line becomes free, the process moves to step n3.

In step n3, the input data is delivered to the modem 4 as transmission data, and data transmission is started. When data transmission ends in step n4.

In step n5, the time limit W21 (=WO
) or W22 (=2WO> is set in the timer T3, and the timer T3 starts clocking operation.

In step n6, it is determined whether or not the confirmation signal has been received. If so, the operation is ended, and if not, the process moves to steps after step n7 and data is retransmitted.

In step n7, it is determined whether the vehicle number set as described above is an even number, and if not, that is, if it is an odd number and corresponds to the mobile station S1 in FIGS. 3 and 4 described above. , it is determined whether or not the timer T3 has elapsed the unit time WO. If not, this step n8 is repeated. When the unit time WO has elapsed, the timer T3 is reset in step n9 and the process returns to step n2, where the data is stored. Perform retransmission.

When the vehicle number is an even number in step n7, that is, when it corresponds to the mobile station S2 in FIGS. It is determined whether or not time has elapsed. If not, this step nlo is repeated, and when the waiting time 2WO has elapsed, the process returns from step rm9 to step n2 to retransmit the data.

In this way, in the data transmission system according to the present invention, data retransmission is started when the standby time based on the vehicle number unique to each mobile station 81 to S3 has elapsed, so that data can be transmitted over a single communication line. Even if the data is retransmitted, the base station SO can reliably receive the retransmitted data, and with a relatively simple configuration, the data reception rate at the time of retransmission can be increased. In addition, since each mobile station 81 to S3 starts data transmission by making an arbitrary call when transmitting data for the first time, there is no need to wait for a long time before starting data transmission as in the above-mentioned polling method. Transmission can be started as soon as a request occurs, and line usage efficiency can be improved.

Note that in the above embodiment, the mobile stations 81 to S3 are divided into two groups with even or odd vehicle numbers;
As another embodiment of the present invention, when the number of mobile stations is large, the mobile station may be divided into three or more groups, and when it is the main mobile station, the mobile station may belong to multiple groups. You may also do so.

Effects of the Invention As described above, according to the present invention, a plurality of communication devices share the same communication line, each communication device is divided into groups each consisting of one or more communication devices, and each group has mutual communication. Since different unique waiting times are set in advance for each device, and data is retransmitted after the waiting time has elapsed, when data is retransmitted, the retransmission start timing is determined by the group to which the communication device belongs. It depends.

Therefore, a communication device that performs reception can reliably receive data upon retransmission, and thus can improve the data arrival rate without using a complicated configuration.

Furthermore, since each communication device starts the first transmission of data by making an arbitrary call, it is not necessary to wait for a long time before starting data transmission, unlike the polling method, and it is possible to improve the usage efficiency of the communication line.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a wireless communication system using a data transmission system according to an embodiment of the present invention, FIG. 2 is a block diagram showing the electrical configuration of radio devices M1 to M3 of mobile stations 81 to S3, and FIG.
4 and 4 are timing charts for explaining the data transmission operation, FIG. 5 is a flowchart for explaining the operation shown in FIGS. 3 and 4, and FIG. 6 and 7I21 are for the prior art. 5 is a timing chart for explaining a data transmission operation. DESCRIPTION OF SYMBOLS 1... Input/output circuit, 2... Processing circuit, 3... Transmission/reception section, 4... Modem, 6... RAM, MO~M3・
...Radio equipment, SO...Base station, 81-S3...Mobile station, U...Central processing unit

Claims (1)

[Claims] The same communication line is shared by a plurality of communication devices, and when data transmitted from a certain communication device is received, the communication device that received the data returns a confirmation signal. In a data transmission method between communication devices, a unique waiting time is set for each group of one or more communication devices, and the transmitting communication device
A data transmission system characterized in that, after transmitting data, if the confirmation signal is not returned from the receiving communication device, the data is retransmitted after the waiting time has elapsed.