JPH1155266A - Radio communication system and communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow transmission in a priority order specific to terminal equipment without any collision even when transmission requests are simultaneously generated in plural terminals in a radio communication system. SOLUTION: In this radio communication system, plural terminals are provided with an interface 9 equipped with a transmitting and receiving part, a carrier sense part 11 for detecting the presence or absence of a carrier generated from another terminal on a communicating medium, a counter 10 for counting a waiting time from the reception of a data transmission instruction from a host part 3 during the detection of the presence by the carrier sense part 11 until the detection of the absence by the carrier sense part 11, a register 8 for indicating a priority order set for each of plural terminal, and a back-off generating part 7 for generating a back-off time from the waiting time and the priority order. Then, a CPU 4 controls data transmission from the host 3 through the MODEM interface 9 after the lapse of the back-off from the detection of absence by the carrier sensor part 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system in which a network is formed, and more particularly to an access control system for a communication system in which a network is formed not only by a wireless LAN or WAN but also by a wired transmission line on a transmission line using a communication medium. The present invention relates to a wireless communication system provided with the communication system.

[0002]

2. Description of the Related Art In recent wireless communication systems, the international standardization organization IEEE has established a wireless LAN system based on IEEE 802.11.
(Local Area Network) is being standardized, and standardization of a frame format, an access control method, power management, and the like is being studied in a physical layer and a MAC (Media Access Control) layer.

In this access control system using a wireless LAN, a modem of a wireless transmitting / receiving section, a carrier sensing section for monitoring a wireless carrier, and a terminal CPU for transmitting / receiving the modem are provided.
And a terminal device including a host computer connected by wire and a timer for measuring a back-off time for acquiring a transmission right. When a command for a transmission request is received from the host computer, the carrier sense unit detects an idle state of a predetermined control channel and communication channel, and when the carrier is input, a predetermined inter-frame space is set. The time from when a transmission request is received from the host computer to obtain the transmission right of each terminal device until the carrier becomes empty is set as the standby time, and the back-up time is set in accordance with this wait time. An off-time can be set, and transmission becomes possible when the back-off time has passed. This back-off time is set in order to avoid contention with other terminal devices, and there is a possibility that a high-priority frame from another terminal device may enter the inter-frame space of the carrier. It is possible to avoid a situation in which the terminal devices of the wireless LAN start transmitting at the same time when they become idle.

Conventionally, this type of wireless communication system is disclosed in, for example, Japanese Patent Application No. 7-189648 filed by the present applicant. The purpose of this application is to grant a transmission right to a terminal device in the order in which a transmission request is issued.

FIG. 6 is a block diagram showing an example of a conventional radio communication system. The hardware configuration shown in FIG. 6 includes a host interface (HOSTI / F) 3 having an input terminal 1 for inputting an input signal from the host side and an output terminal 2 for outputting an output signal to the host side, and a software OS and application programs. CPU (Central Processing Unit) 4 for executing the written processing, memory (MEM) 5 containing the software, timer (Timer) 6 for measuring time, and counter 10 for measuring standby time A back-off generation unit 19 that generates a back-off time based on the measured standby time; an output terminal 12 that outputs a transmission signal to another terminal; and an input terminal that inputs a reception signal from another terminal. A modem interface (MODEMI / F) 9 having a communication terminal 13 and a carrier receiving terminal 14 for inputting a carrier in an external wireless medium. A carrier sense (carrier detection section) 11.

[0006] The host interface 3 outputs an input signal from the host input through the input terminal 1 to the CPU 4, and outputs an output signal from the CPU 4 to the host through the output terminal 2.

The CPU 4 operates according to the OS and application programs of the software stored in the memory 5 and executes various processes. The software for processing executed by the CPU 4 is stored in the memory 5 in advance. The timer 6 counts a back-off timer for acquiring a transmission right when transmitting to another terminal device (not shown) of the wireless LAN system.

The modem interface 9 has a wireless transceiver unit, outputs a transmission signal from the CPU 4 to another terminal device through an output terminal 12, and sends a reception signal from another terminal device received through the input terminal 12 to the CPU 4. Output.

When a carrier signal indicating whether or not an external control channel and a communication channel are idle is input through a carrier receiving terminal 14, the carrier sense 11 converts the input signal of the carrier signal into a modem interface 9.
To the CPU 4 and the counter 10 through.

FIG. 7 is a flowchart showing the operation of the apparatus having the above-described configuration. The operation of one terminal device of this wireless LAN will be described with reference to FIGS.

When a transmission request is input from the host through the input terminal 1 and the host interface 3 (step S41 in FIG. 7), the CPU 4 performs a carrier signal through the carrier reception terminal 14 with the carrier sense 11 based on the software loaded from the memory 5. (Step S42 in FIG. 7).

When notified of the input of the carrier signal, the CPU 4 stops inputting the carrier signal, and then waits for a preset inter-frame space. Since there is a possibility that a high-priority frame different from the normal communication may be inserted between the inter-frame spaces, the CPU 4 confirms that there is no input of the carrier signal only during the inter-frame space, and then frees up the medium. Judge as the state. Hereinafter, this state is simply referred to as an empty state of the communication medium.

The CPU 4 performs the back-off timer setting process (step S40 in FIG. 7) with the hardware of the back-off generation unit 19 and the counter 10 in order to acquire the transmission right in the medium while determining the free state of the communication medium. The back-off time setting process (step S40 in FIG. 7) includes steps S43 to S47 in FIG.

That is, the counter 10 has the carrier sense 1
When the input of the carrier signal is notified from 1, the result is recorded while measuring and integrating the time until the communication medium becomes empty (step S 43 in FIG. 7). When the communication medium becomes free, the counter 10 stops measuring the time (step S44 in FIG. 7), and stores the measurement time from the transmission request from the host to the time when the communication medium becomes free (step S4 in FIG. 7).
5).

The counter 10 sends the stored standby time to the back-off generator 19, and the back-off generator 19 generates the back-off time based on the standby time from the counter 10 so that the back-off time becomes shorter as the standby time becomes longer. Then, the back-off timer is registered in the timer 6 (step S46 in FIG. 7).

For example, the back-off generation section 19 calculates [(the longest back-off time) − (standby time ×
α)] to generate the back-off time. In this equation, α is a coefficient set to increase as the standby time increases.

A back-off time is set in advance according to an assumed standby time, and the standby time and the back-off time are stored in an internal table or the like stored in a memory (not shown) in association with the back-off time. The generation unit 19 includes the counter 1
It is also possible to read out the corresponding back-off time by referring to an internal table or the like based on the standby time measured at 0.

When the CPU 4 determines that the medium is empty,
The processing of the back-off time is started, and the timer 6 measures the back-off time, that is, subtracts the back-off time (step S48 in FIG. 7).

When the back-off time reaches 0 without receiving another carrier signal during the measurement of the back-off time (step S49 in FIG. 7), the CPU 4 terminates the back-off process (step S51 in FIG. 7). Then, transmission starts through the modem interface 9 and the output terminal 12 (step S52 in FIG. 7). At this time, the CPU 4
Clear the waiting time stored in 0.

On the other hand, if another carrier signal is detected by the carrier sense 11 through the carrier receiving terminal 14 before the back-off time reaches 0, the CPU 4 interrupts the back-off process (step S50 in FIG. 7).

Thereafter, a back-off time setting process (FIG. 7)
Step S40) is the back-off generation unit 7 and the counter 1
0 hardware. That is, the counter 10
When the input of the carrier signal is notified from the carrier sense 11, the time until the communication medium becomes empty is added to the standby time stored therein (step S43 in FIG. 7). When the communication medium becomes empty, the counter 10 stops accumulating the standby time (step S44 in FIG. 7), and stores the accumulated time as the standby time (step S45 in FIG. 7).

The counter 10 sends the stored standby time to the back-off generator 19, and the back-off generator 7 sets the back-off time based on the standby time from the counter 10, and the back-off time becomes shorter as the standby time becomes longer. A back-off time is generated (step S46 in FIG. 7), and the back-off time is registered in the timer 6 (step S47 in FIG. 7).

When the CPU 4 determines that the communication medium is empty, the CPU 4 starts back-off processing and measures the back-off time by the timer 6, that is, subtracts the back-off time (step S48 in FIG. 7).

When the backoff time reaches 0 without receiving another carrier signal during the measurement of the backoff time (step S49 in FIG. 7), the CPU 4 ends the backoff processing (step S51 in FIG. 7). Then, transmission starts through the modem interface 9 and the output terminal 12 (step S52 in FIG. 7). At this time, the CPU 4
Clear the waiting time stored in 0.

If another carrier signal is detected by the carrier sense 11 through the carrier receiving terminal 14 before the back-off time reaches 0, the CPU 4 executes the above processing until the back-off timer reaches 0 and transmission starts. Is repeated.

FIG. 8 shows an example of the operation of a wireless LAN system composed of a plurality of terminal devices that perform the above processing operations. First, when a transmission request is input from each host in the order of the terminal D, the terminal B, and the terminal C while the terminal A is transmitting the frame f10, the transmission of the frame f10 by the terminal A is completed and the communication medium becomes available. In the state, the terminals B to D generate the back-off times b11 to b13 in accordance with the standby times t11 to t13 of the respective terminals until the predetermined inter-frame space.

The back-off times b11 to b13 are shorter as the standby times t11 to 13 (t12 <t11 <t13) are longer. In this case, since the standby time t13 of the terminal D to which the transmission request is first input from the host is the longest, the back-off time b13 of the terminal D is the shortest.
In FIG. 8, each of the back-off times b11 to b13 also includes a dotted line portion.

Similarly, the standby time t11 of the terminal B is changed to the terminal C
Therefore, the back-off time b11 of the terminal B becomes shorter than the back-off time b12 of the terminal C. Therefore, since the back-off time b13 generated by the terminal D is generated the shortest, the frame f1 from the terminal D is transmitted after the frame f10 from the terminal A is transmitted.
1 is transmitted.

When the frame f11 is transmitted from the terminal D, the standby times t14 and t15 of the terminals B and C are added to the previous standby time values t11 and t12. The standby time t16 of the terminal E to which the transmission request is input is reliably shorter than the standby times t11 + t14 and t12 + t15 of the terminals B and C.

Therefore, the back-off time b14 of the terminal B after the transmission of the frame f11 from the terminal D is
Are generated shorter than the back-off times b15 and b16 of the terminal B, the terminal f transmits the frame f11 and then the terminal B transmits the frame f12.

When the frame f12 is transmitted from the terminal B, the standby times t17 and t18 of the terminals C and E are added to the previous standby times t12 + t15 and t16, and therefore, after the frame f12 is transmitted from the terminal B. The back-off time b17 of the terminal C is the back-off time b18 of the terminal E.
Since the frame f13 is generated shorter, the frame f13 is transmitted from the terminal C after the frame f12 is transmitted from the terminal B.

Therefore, in the case of the time chart shown in FIG. 8, the order in which transmission requests are generated, that is, terminals D, B, C,
The transmission right is acquired in the order of E, and the frames f11 to f14 are transmitted from the terminals D, B, C, and E, respectively.

FIG. 9 shows another example of the operation of the wireless LAN system including a plurality of terminal devices performing the above-described processing operations. First, when the transmission request is input from the respective hosts simultaneously to the terminal B and the terminal C during the transmission of the frame f20 by the terminal A, the back-off time b
21 and b22 are respectively generated.

The back-off times b21 and b22 are shorter as the standby times t21 and t22 (t21 = t22) are longer. In this case, the standby times t21 and t22 of the terminals B and C to which the transmission request is input from the host side are equal, so the back-off times b21 and b22 of the terminals B and C are equal.
Is also equal.

Therefore, frame f10 from terminal A
Is completed, the terminals B and C simultaneously acquire the transmission right, and the frames f21 and f2 from the terminals B and C are transmitted.
Since two are transmitted at the same time, a collision occurs.

Therefore, in the case of the time chart shown in FIG. 9, the back-off time is generated depending on the length of the standby time. And the frames f21 and f22 are transmitted simultaneously, so that a collision occurs.

On the other hand, a wired LA such as a bus type network
In the N system, the access method is generally CSMA /
CD (Carrier-Sence Multiple-Access with Collision
Detection) method is known. In the CSMA / CD system, a plurality of stations connected on a LAN monitor a carrier signal on a transmission line at the time of transmission, and when there is no signal, it is determined that the transmission line is empty (ready) and the transmission to the transmission line is performed. Start. However, due to the influence of propagation delay in the transmission path, a plurality of stations may check the vacancy of the transmission path at the same time and attempt transmission. In this case, a collision occurs on the transmission path and transmission fails. When a station that has attempted transmission detects a collision by monitoring the transmission path, it transmits a jam signal so that the collision is transmitted to all stations on the network. Each station that detects this jam signal waits for a random time called a back-off time and retransmits a retry. As described above, in the CSMA / CD system LAN, when a plurality of stations start transmission almost simultaneously and a collision occurs, a retry is performed after a lapse of the back-off time. Is significantly reduced. As a result, there is a high probability that the station having the shortest back-off time at the time of occurrence of the collision succeeds in retry. In the above method, all the stations are treated and operated on an equal basis. However, some stations may want to use the transmission line urgently, and even in this case, there is no guarantee that the retry will succeed because of the back-off time according to random signal generation, and other stations must wait while they are in use. In other words, if a collision occurs even if another station ends transmission, the retry is not successful and processing can be sent.

A method for solving this problem is disclosed in Japanese Patent Application Laid-Open No. 2-19041. According to this publication, an arbitrary station on a CSMA / CD system LAN is set to a privileged mode in which a transmission access right can be preferentially acquired. If the LAN transmission line is currently in use, a jam signal is sent to this transmission line, and transmission to the transmission line is started after waiting for a predetermined time shorter than the minimum back-off time. Also, the station in which the privilege mode is set transmits a jam signal even when a collision is detected, and waits for the predetermined time to retry.
In this way, the station set in the privileged mode sends a jam signal onto the transmission line even when the station is in use or in the event of a collision, stops sending the used station to the transmission line, and backs up other stations. Since transmission can be started after waiting for a shorter time than the off-time, transmission can be performed reliably without waiting for collision.

[0039]

In the access control method of the above-mentioned conventional wireless communication system, as shown in FIG. 9, the back-off time is set so that the longer the standby time, the shorter the back-off time. Since transmission is performed, transmission can be performed from a terminal device having a long waiting time.
Since the waiting time is equal and the back-off time is equal, if a transmission request is issued to a plurality of terminals at the same time, a plurality of terminals may acquire the transmission right at the same time and a collision may occur.

Further, even if a privileged mode is set for a specific terminal device in order to prevent occurrence of a collision on a CSMA / CD system LAN, there is no possibility that a plurality of stations will set the privileged mode. If the priority mode is set only for the station that can set the privileged mode, there is no equal balance with other stations, and more than one station can set the privileged mode. If you had
A transmission collision may occur between stations set in these privileged modes.

[0041]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems,
An object of the present invention is to provide a wireless communication / communication system capable of improving transmission efficiency without causing a collision even when transmission requests are simultaneously issued to a plurality of terminal devices.

[0042]

According to the present invention, there is provided a wireless communication system comprising a plurality of terminal devices connected to a host, wherein each of the terminal devices includes a transmission / reception unit. A modem interface, a carrier sense unit for detecting the presence or absence of a carrier transmitted from another terminal device on a communication medium, and the carrier sense unit after receiving a data transmission command from the host during detection of the presence of the carrier sense unit. A counter that counts a standby time until the detection of absence of a register, a register indicating a priority set for each of the plurality of terminal devices, and a back-off generation unit that generates a back-off time from the standby time and the priority. And a CPU for controlling the terminal device. To provide a wireless communication system, wherein after the lapse of the off-time from the modem interface to perform the control for sending data from the host.

Further, in the above wireless communication system, the back-off generation section may calculate back-off time = [(the longest back-off time)
− (Standby time × α) + (priority order × β)] (where α and β indicate coefficients, and the longest backoff time is a predetermined time.) It is characterized by doing.

Further, in a wireless communication system composed of a plurality of terminal devices, a first input terminal for inputting an input signal from the host and a first output terminal for outputting an output signal to the host are provided. A first host interface, connected to the first host interface,
The first CP that executes the process written in the software
U, a first memory connected to the first CPU and containing software, a first timer connected to the first CPU for measuring time, the first timer A first modem interface connected to a CPU for outputting a transmission signal to another terminal, a second modem terminal having a second input terminal for receiving a reception signal from the other terminal, Connected to one modem interface,
A first carrier sensing unit having a first carrier receiving terminal for inputting a carrier in an external wireless medium, and a terminal connected to the first timer, the longer the standby time waiting for transmission and the longer the terminal A first back-off generation unit that generates a shorter back-off time as the device-specific priority is higher, and a first register that is connected to the first back-off generation unit and holds the priority, A first hardware configuration that is connected to a first back-off generation unit and the first carrier sense unit and includes a first counter for measuring the standby time; and And a plurality of terminal devices having software for control.

Further, in a wireless communication system composed of a plurality of terminal devices, a first input terminal for inputting an input signal from the host and a first output terminal for outputting an output signal to the host are provided. Connected to one host interface and the first host interface,
The first CP that executes the process written in the software
U, a first ROM (Read Only Memory) connected to the first CPU and containing software, and a first ROM (Read Only Memory) connected to the first CPU for setting the priority order unique to the terminal device. A first RAM (random access memory) held therein, a timer 6 connected to the first CPU for measuring time, and a timer connected to the first CPU for other terminals A second output terminal for outputting a transmission signal of the second terminal and a second output terminal for receiving a reception signal from the other terminal.
A first modem interface having an input terminal, a first carrier sense unit connected to the first modem interface and having a first carrier receiving terminal for inputting a carrier in an external wireless medium, A first back-off generation unit connected to the first timer, and configured to generate a shorter back-off time as the waiting time for waiting for transmission is longer and the terminal device-specific priority is higher, and A hardware configuration that is connected to one back-off generation unit and the first carrier sense unit and includes a first counter for measuring the standby time; and a control unit for controlling the first hardware configuration. And software.

In a communication system including a host and a plurality of terminal devices connected to the host, the terminal device includes an interface having a transmission / reception unit for transmitting / receiving data to / from another terminal device, and a communication transmission / reception unit. A data sensing unit for detecting the presence / absence of data from another terminal device on the road; and a data transmission unit from receiving a data transmission command from the host during the detection of the presence of the data sensing unit until detecting the absence of the data sensing unit. A counter for counting a standby time, a register indicating a priority set for each of the plurality of terminal devices, a back-off generation unit for generating a back-off time from the standby time and the priority, and controlling the terminal device And a CPU that performs the back-off time after the detection of the absence of the data sense unit. And performing control of transmitting the data from the host from the interface.

More specifically, with reference to FIG. 1, the wireless communication system of the present invention uses the back-off time by means for holding the standby time and the priority order unique to the terminal device (8 in FIG. 1). A hardware configuration including back-off generating means (7 in FIG. 1) for generating a longer standby time and a shorter priority as the priority is higher, based on the held priority unique to the terminal device; It comprises a plurality of terminal devices provided with means for controlling the configuration.

The back-off time is generated based on the standby time and the terminal-specific priority held by the register for holding the terminal-specific priority, so that the standby time becomes shorter as the standby time becomes longer and the priority becomes higher. Generated by the back-off generation unit. Thereby, even when transmission requests are issued to a plurality of terminals at the same time, collision does not occur and transmission efficiency can be improved.

[0049]

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

[First Embodiment] FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention. In the figure, the terminal device according to the first embodiment of the present invention is provided with a register 8 for holding a terminal-specific priority, and otherwise has the same configuration as the conventional terminal device described in FIG. Therefore, the same components are denoted by the same reference numerals, and redundant description will be omitted.

The operation of the same components is almost the same as the operation of the conventional terminal device. Since the operation of the back-off generation unit 7 is different from the operation of the conventional terminal device, the back-off generation unit 7 is denoted by a different symbol from the conventional terminal device. The register 8 stores data corresponding to a numerical value that sets a different priority for each of a plurality of terminal devices in the wireless communication LAN, and includes a shift register and a memory.

FIG. 2 is a flowchart showing the operation of the first embodiment of the present invention. The access control to the communication medium according to the first embodiment of the present invention will be described with reference to FIGS.

When a data transmission request is input from the host through the input terminal 1 and the host interface 3 (step S1 in FIG. 2), the CPU 4 operates based on an OS (Operating System) of software loaded from the memory 5 and an application program. The carrier sense 11 controls the carrier signal to be detected through the carrier receiving terminal 14 to determine whether the carrier signal exists in the communication medium of the control channel or the communication channel predetermined in the wireless communication system. (Step S2 in FIG. 2).

When notified of the input of the carrier signal, the CPU 4 waits until the input of the carrier signal disappears, and the input of the carrier disappears, and then waits until a preset inter-frame space. Since there is a possibility that a high-priority frame different from normal communication may enter between the inter-frame spaces, the CPU 4 confirms that there is no input of a carrier signal only during the inter-frame space, and then performs communication communication for the first time. Is determined to be empty. Hereinafter, this state is simply referred to as a “medium empty state”.

The CPU 4 performs the back-off time setting process (step S0 in FIG. 2) of the back-off generation unit 7, the register 8, and the counter 10 in order to acquire the transmission right in the communication medium while determining the free state of the medium. Perform in hardware. Back-off time setting process (step S in FIG. 2)
0) is composed of steps S3 to S8 in FIG.

That is, when the input of the carrier signal is notified from the carrier sense 11, the counter 10 records the time until the communication medium becomes empty (step S3 in FIG. 2). The counter 10 stops the time measurement when the communication medium becomes free (FIG. 2).
In step S4), a predetermined inter-frame space time is added to the measured time up to that time, and the result is stored as a standby time (step S5 in FIG. 2). Since the inter-frame space time is the same in other terminal devices, the measurement time up to that time may be stored as the standby time.

Next, the counter 10 sends the stored standby time to the back-off generation unit 7, and the back-off generation unit 7 reads the priority from the register 8 (Step S2 in FIG. 2).
6). The back-off generation unit 7 generates a back-off time based on the standby time from the counter 10 and the priority from the register 8 so that the back-off time becomes shorter as the standby time becomes longer and the priority becomes higher (step S7 in FIG. 2). ), And registers the back-off time in the timer 6 (step S in FIG. 2).
8).

For example, the back-off generation unit 7 generates the back-off time according to the following equation: [(the longest time of the back-off time)-(standby time × α) + (priority order × β)] (1) . In this equation, α is a coefficient set so that the back-off time becomes longer as the standby time becomes longer.
Is a coefficient set such that the higher the priority order, the smaller the back-off time.

The back-off time is set in advance according to the assumed standby time and priority, and the standby time and the priority are associated with the back-off time in an internal table or the like stored in a memory (not shown) or the like. The back-off generation unit 7 reads out the corresponding back-off time by referring to the internal table or the like based on the standby time measured by the counter 10 and the priority stored in the register 8. Is also possible.

Here, the method of assigning the priority order of each terminal device is such that the frequency of use of each terminal device in the wireless communication system,
It may be determined by the importance of the terminal device, the frequency of sending data from the host computer connected to the terminal device, the importance of the data, the type of operating system or the type of application of the terminal device, and the like. do not do. However, it is preferable that this priority does not have the same level of priority, and there is no terminal device having the same priority among a plurality of terminal devices. It should be noted that when the transmission efficiency of the communication medium in the wireless communication system is small as a whole or when the risk of collision is small, it is apparent that the same priority may be specified.

Next, when the CPU 4 determines that the medium is empty, it starts processing the back-off time after a predetermined inter-frame space time has elapsed, and measures the back-off time by the timer 6, that is, the back-off time. The time is subtracted (step S9 in FIG. 2).

When the back-off time reaches 0 without receiving another carrier signal during the measurement of the back-off time (step S10 in FIG. 2), the CPU 4 ends the processing of the back-off time (step S12 in FIG. 2). ), Transmission of transmission data requested by the host via the modem interface 9 and the output terminal 12 is started (step S in FIG. 2).
13). At this time, the transmission data requested by the host for transmission may be stored in the memory 5 in advance, and the transmission data in the memory 5 may be transmitted when the back-off time becomes zero. At this time, the CPU 4 clears the standby time stored in the counter 10.

On the other hand, if another carrier signal is detected by the carrier sense 11 through the carrier receiving terminal 14 before the back-off time reaches 0, the CPU 4 interrupts the processing of the back-off time (step S11 in FIG. 2).

Thereafter, back-off time setting processing (FIG. 2)
Step S0) is performed by hardware of the back-off generation unit 7, the register 8, and the counter 10. That is, when the counter 10 is notified of the input of the carrier signal from the carrier sense 11, the counter 10 adds the time until the communication medium becomes empty to the waiting time stored therein (step S2 in FIG. 2).
3). When the medium becomes empty, the counter 10 stops accumulating the standby time (step S4 in FIG. 2) and stores the accumulated time as the standby time (step S4 in FIG. 2).
5).

The counter 10 sends the stored standby time to the back-off generator 7, and the back-off generator 7 reads the priority from the register 8 (step S6 in FIG. 2). The backoff generation unit 7 generates the backoff time based on the standby time from the counter 10 and the priority from the register 8 so that the backoff time becomes shorter as the standby time becomes longer and the priority becomes higher (step S7 in FIG. 2). The back-off timer is registered in the timer 6 (step S8 in FIG. 2).

When the CPU 4 determines that the medium is empty,
The back-off process is started, and the back-off time is counted by the timer 6, that is, the back-off time is subtracted (step S9 in FIG. 2).

When the back-off time reaches 0 without receiving another carrier signal during the measurement of the back-off time (step S10 in FIG. 2), the CPU 4 ends the processing of the back-off time (step S12 in FIG. 2). ), Transmission starts via the modem interface 9 and the output terminal 12 (step S13 in FIG. 2). At this time, the CPU 4 clears the standby time stored in the counter 10.

If another carrier signal is detected by the carrier sense 11 through the carrier receiving terminal 14 before the back-off time reaches 0, the CPU 4 executes the above processing until the back-off timer reaches 0 and transmission starts. Is repeated.

FIG. 3 is a timing chart showing the operation of the wireless LAN system composed of a plurality of terminal devices for performing the processing operation of the first embodiment as described above. Terminal B is given a higher priority than terminal C.

First, while terminal A is transmitting frame f0,
When a transmission request is input to each of the terminals B and C from the respective hosts at the same time, the terminals B and C have the same standby time (t1).
= T2) occurs, and the back-off times b1 and b2 are respectively generated.

The back-off times b1 and b2 are shorter as the standby times t1 and t2 (t1 = t2) are longer and the priority is higher. In this case, the standby times t1 and t2 of the terminals B and C to which the transmission request is input from the host side.
Are equal, but since the priority of terminal B is higher than the priority of terminal C, the back-off time b1 of terminal B is shorter than the back-off time b2 of terminal C as a result of the calculation of equation (1). In FIG. 3, the back-off time b2 includes a dotted line portion.

Therefore, after the transmission of the frame f0 from the terminal A, the terminal B preferentially acquires the transmission right, and the frame f1 from the terminal B is transmitted. Terminal C is Terminal B
After waiting for transmission of the frame f1, the transmission right is acquired after the newly added waiting time (t2 + t3) and the back-off time b3 generated by the priority of the terminal C, and the frame f3 is transmitted.

Therefore, according to the first embodiment of the present invention, the back-off time is generated based on the standby time and the priority order. C does not acquire the transmission right at the same time, and the transmission right is acquired in the order of terminals B and C,
The frames f1 and f2 are transmitted from the terminals B and C, and no collision occurs.

In the above embodiment, the case of transmission by this terminal device has been described. However, when data is transmitted from another terminal device, the data is input to the input terminal 3 of the corresponding terminal device and transmitted to the modem. Received on interface 9,
The data is output from the host interface 3 to the output terminal 2 via the CPU 4 and sent to the host computer.

[Second Embodiment] FIG. 4 is a block diagram showing a configuration of a second embodiment of the present invention. In the figure, one terminal device of the wireless LAN system according to the second embodiment of the present invention has a ROM (read only memory) 16 containing software instead of the memory 5.
And a RAM (random /
The configuration is the same as that of the conventional terminal device shown in FIG. 6 except that an access memory (access memory) 17 is provided. The same components are denoted by the same reference numerals, and redundant description will be omitted.

The operation of the same component is almost the same as that of the conventional terminal device except for a part. In addition, CP
The U15 and the back-off generation unit 18 are different from the operation of the conventional terminal device, and thus are denoted by different reference numerals from the conventional terminal device.

FIG. 5 is a flowchart showing the operation of the second embodiment of the present invention. The configuration of the terminal device according to the second embodiment of the present invention and access control to a communication medium will be described with reference to FIGS.

First, when a transmission data transmission request is input from the host through the input terminal 1 and the host interface 3 (step S21 in FIG. 5), the CPU 15 returns to the RO.
Based on the software loaded from M16, the carrier sense 11 is controlled to detect a carrier signal through the carrier receiving terminal 14 (step S22 in FIG. 5).

When the input of the carrier signal of the communication medium is notified from the carrier sense 11, the CPU 15 loses the input of the carrier signal and thereafter waits for a preset inter-frame space.

The CPU 15 executes the back-off timer setting process (step S20 in FIG. 5) based on the software loaded from the ROM 16 in order to acquire the transmission right in the medium while judging the free state of the medium.
Do with. Back-off time setting process (step S2 in FIG. 5)
0) is composed of steps S23 to S28 in FIG.

That is, the counter 10 has the carrier sense 1
When the input of the carrier signal is notified from No. 1, the time until the communication medium becomes empty is recorded (step S23 in FIG. 5). When the communication medium becomes available, the counter 10 stops measuring time (step S24 in FIG. 5), and stores the measured time up to that time as a standby time (step S25 in FIG. 5).

The counter 10 sends the stored standby time to the back-off generation unit 18, and the back-off generation unit 18
The priority order is read from the RAM 17 via U4 (FIG. 5)
Step S26). The back-off generation unit 18 has a counter 1
Based on the waiting time from 0 and the priority from RAM 17,
The back-off time is calculated in accordance with the above equation (1) or the following equation (2), for example, so that the back-off time becomes longer as the standby time becomes longer and the priority becomes higher. 5 step S27), and registers the back-off time in the timer 6 (step S28 in FIG. 5).

The generation of the back-off time by the back-off generation unit 18 is performed in the same manner as described above. [(The longest back-off time) − (standby time × α) + (priority order × β)] (2) Or the back-off time is set in advance according to the standby time and the priority, and an internal table or the like that stores the standby time, the priority, and the back-off time in association with each other is performed. In this equation, α is a coefficient set so that the back-off time becomes longer as the standby time becomes longer, and β is a coefficient set so that the back-off time becomes smaller as the priority order becomes higher.

When the CPU 15 determines that the medium is empty, it starts a back-off process and counts the back-off time by the timer 6, that is, subtracts the back-off time (step S29 in FIG. 5).

When the back-off time reaches 0 without receiving another carrier signal during the measurement of the back-off time (step S30 in FIG. 5), the CPU 15 ends the back-off process (step S32 in FIG. 5). Then, transmission starts through the modem interface 9 and the output terminal 12 (step S33 in FIG. 5). At this time, the CPU 15 clears the standby time stored in the counter 10.

On the other hand, the CPU 15 determines that the back-off time is 0.
Before the other carrier signal arrives at the carrier receiving terminal 14
If the detection is performed by the carrier sense 11, the back-off process is interrupted (step S31 in FIG. 5).

Thereafter, the back-off time setting process (FIG. 5)
Step S20) is performed by the back-off generation unit 18 based on the software loaded from the ROM 16. That is, when the counter 10 is notified of the input of the carrier signal from the carrier sense 11, the counter 10 adds the time until the medium becomes empty to the standby time stored therein (step S2 in FIG. 5).
3).

When the medium becomes empty, the counter 10
The integration of the standby time is stopped (step S24 in FIG. 5), and the integrated time is stored as the standby time (step S25 in FIG. 5).

The counter 10 sends the stored standby time to the back-off generator 18, and the back-off generator 17
The priority order is read from the RAM 17 via U15 (step S26 in FIG. 5). The back-off generation unit 18 generates the back-off time based on the standby time from the counter 10 and the priority from the RAM 17 such that the back-off time becomes shorter as the standby time becomes longer and the priority becomes higher (step S in FIG. 5).
27), the back-off timer is registered in the timer 6 (step S28 in FIG. 5).

When the CPU 15 determines that the medium is empty, it starts back-off processing and counts the back-off time by the timer 6, that is, subtracts the back-off time (step S29 in FIG. 5).

When the back-off time reaches 0 without receiving another carrier signal during the measurement of the back-off time (step S30 in FIG. 5), the CPU 15 ends the back-off process (step S32 in FIG. 5). Then, transmission starts through the modem interface 9 and the output terminal 12 (step S33 in FIG. 5). At this time, the CPU 15 clears the standby time stored in the counter 10.

If another carrier signal is detected by the carrier sense 11 through the carrier receiving terminal 14 before the back-off time reaches 0, the CPU 15 executes the above processing until the back-off timer reaches 0 and transmission starts. Is repeated.

Note that the operation of the wireless LAN system including a plurality of terminal devices performing the processing operation of the second embodiment of the present invention is performed in the same manner as the time chart shown in FIG.

Therefore, in the second embodiment of the present invention, the back-off time is generated based on the standby time and the priority order. C does not acquire the transmission right at the same time, and the transmission right is acquired in the order of terminals B and C,
The frames f1 and f2 are transmitted from the terminals B and C, and no collision occurs.

[Third Embodiment] In the first and second embodiments, the wireless LAN system has been described. However, in a local area network system such as a bus type network, in addition to the CSMA / CD method, By providing the terminal devices with the above-described priorities and simultaneously setting a back-off time in the event of a collision, it is possible to minimize collisions on the transmission line, thereby minimizing wireless communication. The present invention is not limited to this, but can be applied to a wide range of communication LANs.

In the present embodiment, of the configuration shown in FIG. 1, an interface connected to a wired transmission path is used instead of the modem interface 9 and data transmission on the transmission path is connected instead of the carrier sense 11 to the transmission path. The CPU 4 also controls the interface and the data sense, with the data sense detecting the presence or absence. Also, the interface of another terminal device is connected to the transmission path, and when there is a data transmission request from each host computer, the CPU of each terminal device responds to the data transmission request and places it on the transmission path. It is determined whether or not data can be transmitted, and the data transmission request is responded.

With such a configuration, when the data sense detects the presence or absence of data from another terminal device on the transmission path, and the data sense detects the presence of data, and there is a data transmission request from the host computer, The time from the time of the data transmission request to the time when the data sense detects the absence of data is defined as the standby time, and the back-off generation unit 7 determines the back-off time = [ (The longest time of the back-off time) − (the standby time × α) + (priority order × β)] (3) (However, the longest time of the back-off time is a predetermined time. The coefficient is set so that the back-off time becomes longer as the time becomes longer, and the coefficient β is set so that the back-off time becomes smaller as the priority order becomes higher. )) To generate the back-off time. Using this back-off time, the count-down of the back-off time starts when data from another terminal device on the transmission line is lost, and when the back-off time is lost, data from the host device is transmitted from the terminal device. The transmission data corresponding to the transmission request is transmitted.

Even when there are a plurality of terminal devices having the same standby time, as in the first and second embodiments, the back-off times have different priorities, so the back-off times are different times, and the Collisions can be avoided. Further, in the above equation (3), the back-off time of a plurality of terminal devices may be the same based on the standby time and the priority. However, the probability of occurrence in this case is extremely small, and there is almost no problem in an actual communication system. In this case, the back-off time becomes the same and data collision occurs once on the transmission line. When the collision is detected by data sense and the retransmission is performed, the backoff time is calculated by emphasizing the value of the coefficient α or the coefficient β of the above-mentioned equation (3), and retransmission is performed using the backoff time. Data collision does not occur again. If this execution is programmed in the program software stored in the memory 5, it can operate effectively without adding any hardware.

[0099]

As described above, according to the radio communication system of the present invention, the back-off time of a specific terminal device is set so that the back-off time becomes shorter as the standby time becomes longer and the priority becomes higher. In order to generate, that is, the waiting time is the same for a plurality of terminals that have issued a transmission request at the same time, but because the priority order is different, the generated back-off time is different, so the transmission request has been issued to a plurality of terminals at the same time Even in this case, there is an effect that transmission efficiency can be improved without occurrence of transmission collision.

By applying the present invention to a communication system connected by wire, even if a transmission request is issued to a plurality of terminals at the same time, a plurality of terminals simultaneously acquire the transmission right and cause a collision. Can be avoided and transmission efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a flowchart showing an operation of the first exemplary embodiment of the present invention.

FIG. 3 is a time chart of a wireless LAN system including a plurality of terminal devices performing the processing operation of the first or second embodiment of the present invention.

FIG. 4 is a block diagram of a second embodiment of the present invention.

FIG. 5 is a flowchart showing the operation of the second embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a conventional example.

FIG. 7 is a flowchart showing the operation of the conventional example.

FIG. 8 is a time chart of a wireless LAN system including a plurality of terminal devices performing a processing operation of a conventional example.

FIG. 9 is a time chart of a wireless LAN system including a plurality of terminal devices performing a processing operation according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input terminal 2 Output terminal 3 Host interface 4, 15 CPU 5 Memory 6 Timer 7, 18, 19 Back-off generation part 8 Register 9 Modem interface 10 Counter 11 Carrier sense 12 Input terminal 13 Output terminal 14 Carrier receiving terminal 16 ROM 17 RAM

Claims (8)

[Claims] 1. A wireless communication system comprising a plurality of terminal devices each connected to a host, the terminal device comprising: a modem interface having a transmission / reception unit; and a carrier transmitted from another terminal device on a communication medium. A carrier sensing unit that detects the presence or absence of the carrier sensing unit; a counter that counts a standby time from receiving a data transmission command from the host during detection of the presence of the carrier sensing unit to detecting the absence of the carrier sensing unit; A register indicating a priority set for each terminal device, a back-off generation unit that generates a back-off time from the standby time and the priority, and a CPU that controls the terminal device,
A wireless communication system, wherein the CPU performs control of transmitting data from the host from the modem interface after the back-off time elapses from the detection of the absence of the carrier sense unit. 2. The wireless communication system according to claim 1, wherein the back-off generation unit generates a back-off time = [(the longest back-off time).
− (Standby time × α) + (priority order × β)] (where α and β indicate coefficients, and the longest backoff time is a predetermined time.) A wireless communication system, comprising: 3. The wireless communication system according to claim 1, wherein the back-off generation unit is configured to perform an operation according to an internal table stored in a memory indicating a relationship between the standby time, the priority, and the back-off time. A wireless communication system, wherein a back-off time is generated from the standby time and the priority. 4. A wireless communication system comprising a plurality of terminal devices, comprising a first input terminal for inputting an input signal from a host and a first output terminal for outputting an output signal to the host. A first host interface, a first CPU connected to the first host interface to execute processing written in software, and a software embedded in the first CPU connected to the first CPU A first memory, a first timer connected to the first CPU to measure time; a second timer connected to the first CPU to output a transmission signal to another terminal An output terminal, a first modem interface having a second input terminal for inputting a reception signal from the other terminal; and a first modem interface connected to the first A first carrier sensing unit having a first carrier receiving terminal for inputting a carrier, and connected to the first timer, the longer the waiting time for waiting for transmission, and the higher the priority unique to the terminal device. A first backoff generation unit that generates a shorter backoff time as the height is higher, a first register that is connected to the first backoff generation unit, and holds the priority, and the first backoff generation Unit and a first hardware configuration that is connected to the first carrier sense unit and includes a first counter for measuring the standby time, and software for controlling the first hardware configuration. ,
A wireless communication system comprising a plurality of terminal devices having the following. 5. A wireless communication system comprising a plurality of terminal devices, comprising: a first input terminal for inputting an input signal from a host, and a first output terminal for outputting an output signal to the host. A first CPU that is connected to the first host interface and executes processing written in software; and a first CPU that is connected to the first CPU and includes software. A first ROM (read only memory), a first RAM (random access memory) connected to the first CPU and holding a priority order unique to the terminal device, A timer 6 connected to the CPU for measuring time; a second output terminal connected to the first CPU for outputting a transmission signal to another terminal; and the other terminal. A first modem interface having a second input terminal for inputting a received signal from a first modem interface; and a first carrier receiving terminal connected to the first modem interface for inputting a carrier in an external wireless medium. A first carrier sense unit, connected to the first timer, the longer the standby time waiting for transmission, and the shorter the terminal device-specific priority, the shorter the back-off time, A hardware configuration including a back-off generation unit, a first counter connected to the first back-off generation unit and the first carrier sense unit, and configured to measure the standby time; Software for controlling one hardware configuration,
A wireless communication system comprising: 6. A communication system comprising a host and a plurality of terminal devices connected to the host, wherein each of the terminal devices includes an interface having a transmission / reception unit for transmitting / receiving data to / from another terminal device; A data sensing unit for detecting the presence / absence of data from another terminal device on the road; and a data transmission unit from receiving a data transmission command from the host during the detection of the presence of the data sensing unit until detecting the absence of the data sensing unit. A counter for counting the waiting time,
A register indicating a priority set for each of the plurality of terminal devices, a back-off generation unit configured to generate a back-off time from the standby time and the priority, and a CPU controlling the terminal device. A communication system, wherein the CPU performs control to transmit data from the host from the interface after the back-off time elapses from the detection of the absence of the data sense unit. 7. The communication system according to claim 6, wherein the back-off generation unit calculates a back-off time = [(the longest back-off time).
− (Standby time × α) + (priority order × β)] (where α and β indicate coefficients, and the longest backoff time is a predetermined time.) A communication system, comprising: 8. The communication system according to claim 6, wherein the back-off generation unit is configured to perform the processing according to an internal table stored in a memory that indicates a relationship among the standby time, the priority, and the back-off time. A communication system, wherein a back-off time is generated from a standby time and the priority.