JP2002368764A - Access control method in communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an access control method that efficiently utilizes a communication channel so as to enhance the response and the throughput of substations accommodated in a communication system. SOLUTION: A downlink frame generating/transferring portion 12 detects a free channel from a plurality of previously assigned uplink channels. The downlink frame generating/transferring portion 12 elects a substation 2 to which the free channel is to be assigned by referring to an address table 11 every time it detects a free channel. Then the downlink frame generating/transferring portion 12 sends out onto a downlink channel a downlink frame in which the substation address of the selected secondary station is set in an address slot corresponding to the free channel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an access control method, and more particularly, to an access control method in a communication system using a point-to-multipoint line configuration.

[0002]

2. Description of the Related Art In recent years, the integration of broadcasting and communication has progressed along with the deregulation of both, and two-way communication experiments using a cable television network or the like have been conducted. In a communication system using a point-to-multipoint line configuration such as a cable television system, a master station allocates communication channels to slave stations. The slave station communicates with the master station using the assigned communication channel. The polling method, which is one of the methods for allocating such a communication channel, is a method in which a master station inquires of a slave station whether or not there is a transmission message. However, conventionally, when a large number of slave stations are to be accommodated in a communication system, a problem has been pointed out that it takes a long time after a transmission message is generated in a certain slave station until the message is actually transmitted. Was.

In order to deal with such a problem and accommodate a large number of slave stations in a communication system, the following method is conceivable. In other words, the slave station is divided into several groups,
Assign a dedicated communication channel to each group. Then, the master station inquires of each group whether or not there is a transmission message.

[0004]

However, when the above-described method is applied, a certain group (hereinafter, referred to as a "first group") has many slave stations having a transmission message and another group (hereinafter referred to as a "first group"). Hereinafter, the "second group"
), There may be a situation where there are few slave stations having transmission messages. That is, a traffic difference occurs between the groups. Therefore, there is a problem that it takes a long time from when a transmission message is generated in a slave station belonging to the first group to when the transmission message is actually transmitted. Further, even when the traffic of the communication channel assigned to the first group falls into a congested state even though the communication channel assigned to the second group is not used, the first group Are unable to communicate until the communication channel allocated to the first group becomes free. Therefore, the response and the throughput of the slave stations belonging to the first group are equal to the second station.
In this case, there is a problem that the number of mobile stations significantly decreases as compared with the slave stations belonging to the group. That is, the above-described method causes a problem that the utilization rate of the communication channel (frequency, etc.) in the communication system is deteriorated.

[0005] Therefore, an object of the present invention is to provide an access control method capable of efficiently using a communication channel in a communication system and improving the response and throughput of a slave station accommodated in the communication system. That is.

[0006]

Means for Solving the Problems and Effects of the Invention In order to achieve this object, the following inventions have the means described below, and have the following effects.

A first invention is a method for controlling access from a slave station to the master station in a communication system in which the master station and a plurality of slave stations are capable of two-way communication. Can use a downlink channel to transmit a downlink signal, and each slave station can use a plurality of uplink channels to transmit an uplink signal. The master station detects a currently available uplink channel (hereinafter, referred to as an “empty channel”), selects a number of slave stations corresponding to the detected idle channel, and individually assigns the idle channels to the selected slave stations. A downlink signal for notifying the allocated and selected slave station of the vacant channel is created and transmitted to the downlink channel. In addition, the slave station determines whether an uplink channel is allocated to the own station based on a downlink signal input from the downlink channel.

In the first invention, the master station selects a slave station every time an idle channel is generated, and individually assigns the idle channel to the selected slave station. Therefore, even if a certain slave station performs communication using a certain uplink channel for a long time, the master station can allocate an uplink channel to another slave station if another free channel occurs. As a result, the uplink channel is always allocated to one of the slave stations, and the effect of the traffic of the uplink channel in a congested state is distributed to all slave stations, not to a specific slave station. Will be extended. Therefore, the response and throughput of all slave stations accommodated in the communication system are improved.

A second invention is a method for controlling access from a slave station to the master station in a communication system in which the master station and a plurality of slave stations are capable of two-way communication. Can use a downlink channel to transmit a downlink signal, and each slave station can use a plurality of uplink channels to transmit an uplink signal. The master station detects a currently vacant uplink channel (hereinafter referred to as an “empty channel”), creates a downlink signal for notifying the detected vacant channel to the slave station, and sends it to the downlink channel. Also,
The slave station uses the downlink signal input from the downlink channel to
It recognizes the upstream channel that is currently a free channel and sends an upstream signal to the free channel.

In the second invention, the master station immediately notifies the slave station of the information on the detected empty channel, thereby preventing traffic on the upstream channel from becoming congested. Moreover, since the slave station transmits an uplink signal using the idle channel detected by the master station, even if traffic of another uplink channel is congested, the effect is exerted on all slave stations. It will be distributed. Therefore, the response and throughput of all slave stations accommodated in the communication system are improved.

[0011]

FIG. 1 is a block diagram showing an overall configuration of a communication system to which an access control method according to a first embodiment of the present invention is applied. In FIG. 1, a master station 1 and eleven slave stations 2 (four in the figure) are connected to a communication system via a transmission line 3. The transmission path 3, and downlink channel for transmitting the downstream frame master station 1, and five uplink channels ch ₁ to CH ₅ for sending an uplink frame slave station 2 is set. Different frequency bands are assigned to the five uplink channels. That is, the present communication system uses the frequency division multiplexing method. The slave station 2 is given in advance slave station addresses (“a” to “k”) that do not overlap with each other. In the following description, the slave station 2 to which the slave station address “a” is given is referred to as a slave station 2a. The other slave stations 2 are similarly described as slave stations 2b to 2k.

FIG. 2 is a block diagram showing a configuration of master station 1 shown in FIG. In FIG. 2, the master station 1 is a memory unit 1
1, a downstream frame creation / transmission unit 12, and an upstream frame reception unit 13. The memory unit 11 stores an address table 111, a reception command 112, a collision detection command 113, a data error command 114, and a transmission enable command 115 in a predetermined address area. First, the address table 111 will be described.
In the present communication system, an order for allocating an empty channel (to be described later) to a slave station is predetermined. The address table 111 stores the order and the slave station address in association with each other. More specifically, as shown in FIG.
The slave station addresses “a” to “k” assigned to “−11” are stored in the address table 111. Note that the above-described four commands, the reception command 112, the collision detection command 113, the data error command 114, and the transmission enable command 115 will be clarified later, and thus description thereof will be omitted. Downstream frame creation / transmission unit 12
Creates a downlink frame and sends it to the downlink channel.
Note that the procedure for creating a downlink frame is described in FIGS.
11 and will be described later with reference to FIG.

FIG. 4 is a diagram showing the structure of a downlink frame. In FIG. 4, the downlink frame is configured with 16 slots (32 bits / slot) as one frame, and includes a header slot and five address slots AS.
And _{1 ~AS 5,} and a message slot. The header slot stores a preamble, a synchronization pattern (shown as “UW” (Unique Word) in FIG. 4), and the like. The synchronization pattern UW has a predetermined bit pattern and is used to establish various types of synchronization. Address slots AS _{1 to} AS ₅ respectively
One slave station address or one command is set. In the present communication system, the address slots AS ₁ to AS ₁
AS ₅ corresponds to the up channel ch ₁ ~ch _5. For example, setting the slave station address “a” in the address slot AS ₁ means that the master station 1 allocates the upstream channel ch ₁ to the slave station 2 a. A message from the master station 1 to the slave station 2 is stored in the message slot. This allows data to be transmitted from the master station 1 to the slave station 2, but has no relevance to the gist of the present invention, and a description of the message slot is omitted. Also, a preamble and synchronization pattern UW, the address slots AS ₁ ~AS ₅ and message slots, as shown in FIG. 4, are set to predetermined bit positions in the downstream frame.

FIG. 5 is a diagram showing a bit configuration of a slave station address and various commands. FIG. 5A shows the bit configuration of the slave station address. As described above, the slave station addresses “a” to “k” are given to the slave station 2 so as not to overlap each other. However, since many slave stations 2 are accommodated in an actual communication system, the actual address of each slave station is, as shown in FIG.
It is expressed in hexadecimal, with the first 1 bit being “0”,
The remaining 31 bits are used so as not to overlap each other. FIG. 5B shows a bit configuration of various commands. Each of these commands is
As shown in (b), it is represented by a 32-bit binary number, with the first 1 bit being “1” and the last 2 bits being “1” and “0”. The remaining 29 bits in each command have different bit patterns. That is, the reception command 112, the collision detection command 113, the data error command 114, and the transmission enable command 115 have different bit configurations.

Here, description will be made again with reference to FIG. Uplink frame receiving sections 13 correspond to first to fifth uplink frame receiving sections 131 to 13 corresponding to the number of uplink channels.
5 (however, three are shown). The first to fifth uplink frame receiving units 131 to 135 are connected to the uplink channel c
For uplink frame that is transmitted to h ₁ to CH ₅ above, it executes the process described below. In addition, below
The processing of the first uplink frame receiving unit 131 will be described, and the second
The fifth to fifth uplink frame receiving units 132 to 135 execute the same processing as the first uplink frame 131, and thus the description thereof will be omitted. First, a first upstream frame receiving unit 131, using a comparator (not shown) included therein, after the uplink frame whether transmitted thereto an uplink channel ch ₁ above, the downlink frame is sent, Monitor only during a first predetermined time. Here, the first predetermined time is a time in consideration of a delay time or the like until the upstream frame reaches the master station from the slave station. Comparator compares the reference signal and the level of the received signal from the up channel ch _1. This reference signal has a predetermined constant level. The comparator outputs a first comparison output when detecting that the received signal level has changed from less than a certain level to more than a certain level. That is, the first comparison output is information indicating that the first uplink frame receiving unit 131 has detected the head of the uplink frame. Further, when the comparator does not detect the head of the uplink frame and detects that the level of the received signal is equal to or higher than the level of the reference signal when the first predetermined time has elapsed, the second comparator Is output, and at that time, when it is detected that the level of the received signal is lower than the level of the reference signal,
And outputting a third comparison output. The second comparison output is information for indicating that the uplink frame is continuously sent on the uplink channel ch _1. The third comparison output is information for indicating that uplink channel ch ₁ is empty channel. In this way, the first uplink frame receiving unit 131 monitors whether the uplink frame is sent onto the upstream channel ch _1. Further, when detecting the head of the upstream frame, the first upstream frame receiving unit 131 executes the detection of the synchronization pattern UW. The detection of the synchronization pattern UW is performed only for a second predetermined time from the time when the head of the upstream frame is detected. The second predetermined time is determined with reference to the distance from the head of the upstream frame to the bit position where the synchronization pattern UW is assumed to be stored. The first uplink frame receiving section 131 sets the synchronization pattern U during the second predetermined time.
When W is detected, the first reception information (UW detection) indicating that fact is output, and when it is not detected, the first reception information (UW non-detection) indicating that fact is output to the second reception information. Is output when a predetermined time has elapsed. When the first upstream frame receiving unit 131 determines that the upstream frame is continuously transmitted, the first upstream frame receiving unit 131 performs FCS (Fr
Run the ame the Check Sequence), each upstream frame data without errors up channel ch ₁ above, if it is determined that it has been correctly transmitted, and outputs the second reception information indicating that (normal). On the other hand, when the first uplink frame receiving section 131 determines that a data error has occurred in the uplink frame, it outputs second reception information (error) indicating the fact. The first upstream frame receiving unit 131 also extracts a message from the upstream frame, but does not relate to the gist of the present invention, and a description thereof will be omitted.

FIG. 6 is a block diagram showing a detailed configuration of the slave station 2 (see FIG. 1). In FIG. 6, the slave station 2 includes a command / address detection unit 21 and an upstream frame creation / transmission unit 22, and uses a vacant channel notified that the parent station 1 may transmit an upstream frame. And sends an upstream frame. Command / address detector 21
The operation of will be described later with reference to FIG.
Here, it is omitted. Here, an outline of the procedure when the upstream frame creation / transmission unit 22 creates an upstream frame will be described. The slave station 2 generates transmission data that is, for example, video data or audio data. The transmission data is stored in a buffer memory (not shown) provided in the slave station 2. The upstream frame creation / transmission unit 22 divides the transmission data in the buffer memory into 120 bits, and
An 8-bit FCS is added to the transmission data corresponding to the above-mentioned transmission data by adding an 8-bit header to the transmission data (see FIG. 7A).
An upstream frame is configured (see FIG. 7B).

In the communication system described above, the master station 1
Controls access from each slave station 2 using a downstream frame. Here, FIG. 8 is a flowchart showing an operation procedure when the frame creation / transmission unit 12 creates a downstream frame. The initial state, the uplink frame is not also sent to the uplink channel ch ₁ ~ch _5. In this situation, the first to fifth uplink frame receiving units 131 to 13
No. 5 outputs only the third comparison output because the detection of the synchronization pattern UW and the execution of FCS are not performed. Note that the first to first
The fifth upstream frame receiving units 131 to 135 transmit the comparison output and the like at a predetermined timing to the downstream frame generation / transmission unit 1.
Output to 2. The respective timings will not be described here because they will be clarified later. Hereinafter, a combination of the comparison output, the first reception information, and the second reception information is referred to as status information. Under such circumstances, the downlink frame creation / transmission unit 12 creates a first downlink frame. The downstream frame creation / transmission unit 12 includes a mode flag mode, counters C1, C2, and T, a slot pointer m, and an address pointer n (not shown), and stores the mode flag mode, and the counters C1, C2, and T, respectively. It is set to "0" and the address pointer n is set to "1" (FIG. 8; step S
1). Here, the mode flag mode is a flag for determining whether the downlink frame creation / transmission unit 12 proceeds to the contention mode (step S3 described later) or the polling mode (step S9 described later).
Takes a value of "0" or "1". Also, the counter C1
Is a counter for counting the number of uplink channels in which communication collision has occurred, and the counter C2 is a counter for counting the number of empty channels. Here, an empty channel refers to an uplink channel to which no uplink frame is transmitted (data communication is not performed). Further, the counter T is a counter for measuring a time section for counting the number of communication collisions and the number of free channels. The address pointer n indicates the order “n” in the address table 111, and specifies a slave station address to be set in the address slot AS. Therefore, in the present communication system, the address pointer n is
"1" to "11" are counted up by one. The slot pointer m will be described later where necessary. Next, the downstream frame creation / transmission unit 1
2 judges whether or not the mode flag mode indicates “0” (step S2), and when it indicates “0”, judges that it is better to create a downstream frame in the contention mode. Then, the process proceeds to step S3. On the other hand, when the mode flag mode does not indicate “0” (“1”), the downlink frame creation / transmission unit 12 determines that it is better to create a downlink frame in the polling mode, and will be described later. Proceed to step S9. At this time, as is clear from the above, the downstream frame creation / transmission unit 12 proceeds to step S3.

Here, the difference between the contention mode and the polling mode will be briefly described. The contention mode has a characteristic that a communication collision is more likely to occur than in the polling mode because the plurality of slave stations 2 can transmit an upstream frame to one free channel. However, the contention mode has the characteristic that the response is generally higher than in the polling mode because each slave station 2 freely sends an upstream frame to an empty channel. On the other hand, the polling mode has the characteristic that the response is lower than in the contention mode because one free channel is assigned to one slave station 2 regardless of whether or not transmission data is held. . But,
In principle, the polling mode has a property that communication collisions are less likely to occur than in the contention mode, since a plurality of slave stations 2 do not transmit an uplink frame on one uplink channel. However, when the number of vacant channels is relatively large, communication collision hardly occurs even if a downlink frame is created in the contention mode, and the response is considered to be high. Therefore, in an initial state where all uplink channels are empty channels, it is preferable that the mode flag mode is set to “0” and a downlink frame is created in the contention mode. On the other hand, if there are relatively few free channels,
It is considered that the response is higher in the polling mode in which communication collision is less likely to occur than in the contention mode.

Here, FIG. 9 is a flowchart showing step S3 shown in FIG.
It is a flowchart which shows the processing procedure of (contention mode) in detail. First, the downstream frame creation / transmission unit 1
2 sets the slot pointer m to "1" (FIG. 9;
Step S901). The slot pointer m is a pointer that specifies a slave station address or an address slot AS in which the above-described command is to be set. In the present communication system, since five address slots AS are set, the slot pointer m counts up from “1” to “5” by one. At this time, the downlink frame creation / transmission unit 12 includes the m-th uplink frame reception unit 13
The timing is controlled between the downstream frame generation / transmission unit 12 and the upstream frame reception unit 13 so that status information is input from m (this “m” also corresponds to the indication value of the slot pointer m). . At this time, since the slot pointer m indicates “1”, the status information output from the first uplink frame receiving unit 131 is input. Next, the downlink frame creation / transmission unit 12 checks whether the level of the received signal from the uplink channel designated by the slot pointer m (hereinafter referred to as “uplink channel ch _m ”) has changed from less than a certain level to more than a certain level. It is determined whether or not it is (step S902). When the status information includes the first comparison output, the downlink frame creation / transmission unit 12 determines that the level of the received signal has changed, and proceeds to step S908 described later.
If the comparison output is not included, it is determined that the level has not changed, and the process proceeds to step S903. At this time, as described above, the downlink frame creation / transmission unit 12
Has received the third comparison output from the first uplink frame receiving unit 131, the process proceeds to step S903. Next, the downlink frame creation / transmission unit 12 transmits the uplink channel c
level of the received signal from h _m determines whether less than a predetermined level (step S903). If the status information includes the second comparison output, the downlink frame creation / transmission unit 12 determines that the level of the received signal is equal to or higher than a certain level, and proceeds to step S912 described later. In the case where the comparison output of No. 3 is included, it is determined that the level is less than the certain level, and step S904
Proceed to. At this time, the downstream frame creation / transmission unit 12
Has received the third comparison output, so step S
Proceed to 904. Next, the downstream frame creation / transmission unit 12
Accesses the memory unit 11 and sends the transmission enable command 11
5 is taken out, the address slot AS designated by the slot pointer m (hereinafter referred to as “address slot A
S _m ) is set in the transmission permission command 115 (step S904). Thus, the master station 1 notifies the uplink channel ch _m is free channel to each slave station 2. At this time, since the slot pointer m indicates “1”, the transmission enable command 115 is set in the address slot AS ₁ . Next, the downstream frame creation / transmission unit 12 determines whether any command has been set for all address slots AS (step S90).
5). Upon determining that the command has been set in all the address slots AS, the downstream frame creation / transmission unit 12 determines
The process proceeds to step S907 described later. On the other hand, the downstream frame creating / sending unit 12 transmits all address slots AS
If it is determined that no command is set in step S
Proceed to 906. In the present communication system, since five address slots are set, the determination in step S905 is made based on whether or not the slot pointer m indicates “5”. At this time, since the slot pointer m indicates “1”, the downstream frame creation / transmission unit 1
2 proceeds to step S906. Next, the downlink frame creation / transmission unit 12 updates the slot pointer m to “m + 1” (Step S906), and then updates the next address slot AS.
In order to determine the command to be set to
Return to 2. At this time, the slot pointer m is updated from “1” to “2”. At this time,
The transmission unit 12 is controlled in timing so that status information is input from the m-th upstream frame receiving unit 13m, which is indicated by the updated value of the slot pointer m. At this time, the status information output from the second uplink frame receiving unit 132 is input. In the initial state, all uplink channels are empty channels. Therefore, after repeating the processing procedure shown in the order of steps S902 to S906 three times, the downlink frame creation / transmission unit 12 executes the processing procedure shown in the order of steps S902 to S905. As a result, the address slot AS ₂ ~AS _5, Send command 115 is set. Then, the downstream frame creation / transmission unit 12
If step S905 is executed when the slot pointer m indicates “5”, the process proceeds to step S907.
Next, the downlink frame creation / transmission unit 12 sets the preamble and the synchronization pattern UW in the header slot, and in some cases, sets the message in the message slot, and assembles the downlink frame (see FIG. 4). Is transmitted on the downlink channel (step S90).
7), the step S3 shown in FIG. 8 ends. The operation of the slave station 2 that receives this downstream frame will be described later.

Description will be made again with reference to FIG. Next, when step S3 ends, the downstream frame creation / transmission unit 12 determines whether the counter C1 is equal to or greater than a first predetermined value (step S4). Here, the first predetermined value is a value for determining whether or not to update the mode flag mode from “0” to “1”. Is set to an appropriate value according to the specifications of the communication system. Hereinafter, the first
The description will be made assuming that the predetermined value of “3” is “3”. Step S4
In, when the counter C1 indicates a number equal to or more than the first predetermined value, the downlink frame creation / transmission unit 12 determines that it is better to create a downlink frame in the polling mode,
The process proceeds to step S5 described later. On the other hand, if the counter C1 indicates a number less than the first predetermined value, the downstream frame creation / transmission unit 12 determines that it is better to create a downstream frame in the contention mode, and proceeds to step S6.
At this time, since the indicated value “0” of the counter C1 is not equal to or more than the first predetermined value “3”, the downlink frame creation / transmission unit 12 proceeds to step S6. Next, create a downstream frame /
After updating the indicated value of the counter T to “T + 1” (step S6), the sending unit 12 determines whether the indicated value of the counter T has reached the third predetermined value (step S7). When determining that the indicated value of the counter T has reached the third predetermined value, the downstream frame creation / transmission unit 12 proceeds to step S8 described below, and determines that the indicated value has not reached the third predetermined value. Then, the process returns to step S2. Here, the third predetermined value is a numerical value for defining the end of the time section in which the downlink frame creation / transmission unit 12 measures the number of communication collisions and the number of free channels. That is, in this communication system,
The number of communication collisions or the number of free channels per time when the counter T counts from “0” to “third predetermined value” is measured. Hereinafter, the description will be made assuming that the third predetermined value is “3”. At this time, the downlink frame creation / transmission unit 12 updates the counter T from “0” to “1” (step S6), and then the indicated value of the counter T is not the third predetermined value “3”. (Step S7), returning to step S2.

Here, a part of the operation of the slave station 2 in the communication system will be described with reference to FIG. 10 which is a flowchart showing the operation procedure of the slave station 2. The command / address detection unit 21 provided in each slave station 2 has “0”,
A status flag S having a value of “1” or “2” is included. When the communication system is started, the status flag S is set to “0”.
Is set (step S101). Here, a certain child station 2
In the case where the status flag S indicates “0”,
This means that the slave station 2 does not hold data to be transmitted to the master station 1. If the status flag S indicates “1” in a certain slave station 2, the slave station 2 has data to be transmitted to the master station 1 and the data must be transmitted from the beginning. Means not to be. further,
When the status flag S indicates “2” in a certain slave station 2, it means that transmission data is being transmitted to the slave station 2 master station 1. Next, the command / address detection unit 21 determines whether or not the status flag S indicates “1” (step S102). If the status flag S indicates “1”, the process proceeds to step S106 described later. ,
If it indicates a value other than "1", the process proceeds to step S103. Next, each command / address detector 21 determines whether or not the status flag S indicates “2” (step S103). If the status flag S indicates “2”, the process proceeds to step S111 described later. Proceed to step S10 if it indicates a value other than “2” (that is, if it indicates “0”).
Proceed to 4. At present, the status flags S of all the slave stations 2
Indicates "0", so that all the command / address detection units 21 execute steps S102 and S103 and proceed to step S104. Next, each command / address detection unit 21 determines whether each slave station 2 has data to be transmitted to the master station 1 (step S10).
4). As described above, the slave station 2 generates transmission data and stores it in the buffer memory. The determination in step S104 is made by detecting whether transmission data is stored in the buffer memory. If no transmission data is stored in the buffer memory, each command / address detection unit 21 returns to step S102. That is,
The slave station 2 waits in a state where the state flag S is set to “0” until transmission data is generated. If the transmission data is stored in the buffer memory, the command / address detection unit 21 proceeds to step S105, and the status flag S
Is set to “1”, and the process returns to step S102. Thus, when transmission data is generated, each slave station 2 waits for a downstream frame to be transmitted with the status flag S set to “1”. The current down frame is received by the command / address detection units 21 of all the slave stations 2. At present, the status flag S of each slave station 2 is
Indicates “0” or “1”. However, only the operation of the slave station 2 whose status flag S indicates “1” will be described below. The command / address detection unit 21 determines that the status flag S indicates “1” at the time when the downlink frame is transmitted from the downlink channel (step S10).
2), proceed to step S106. Next, the command / address detection unit 21 determines whether or not the slave station address of the own station is set in any of the address slots AS (Step S106). However, the child station address is not set in the downstream frame created in the contention mode (see FIG. 8; step S3), as is clear from the above. Therefore, the command / address detection unit 2
1 proceeds to step S107. Step S106 will be described in detail later on where necessary. Next, the command / address detection unit 21 detects in the currently received downlink frame which address slot AS has the transmission enable command set (step S1).
07). The determination in step S107 is typically made as follows. Command / address detector 21
Stores the bit pattern of the transmission enable command in a register (not shown) or the like provided therein in advance. The command / address detection unit 21 compares whether or not this bit pattern matches the one set in the address slot AS ₁ of the downstream frame. If the bit pattern matches, the transmission enable command is set in the address slot AS _1. It is determined that it has been done. Then, the address slots AS _{2 to} AS
The same processing is performed for ₅ as well. Command / address detecting section 21, the Send command to the address slot AS _m is set, it recognizes that uplink channel ch _m corresponding to the slot AS _m is empty channel. Then, the command / address detection unit 21 proceeds to step S108 when the transmission enable command is set in any of the address slots AS. The address slot AS ₁ ~AS ₅ of this downstream frame, since the Send command is set, the command / address detecting section 21 proceeds to step S108. It should be noted that the command / address detection unit 21 checks all address slots A
If the transmission enable command is not set in S, it is determined that there is no available channel, and the process returns to step S102 to wait for a new downlink frame to be sent. Next, the command / address detecting section 21, from among the address slots AS the Send command set, select an address slot AS _m randomly (step S10
8), up channel ch corresponding to the slot AS _m
The upstream frame creation / transmission unit 22 is notified to transmit the upstream frame using _m (step S109). Thereafter, the command / address detection unit 21 determines in step S1
An address slot AS _m selected in 08, previously latched in the register (not shown) as a used channel information.
This used channel information is stored in step S111 described later.
Used in By the way, the upstream frame creation / transmission unit 2
FIG. 7 shows the state when the status flag S is set to “1”.
Are prepared in the uplink frame as (a), the sending this to the uplink channel ch _m that is notified by the command / address detecting portion 21. After step S109, the command / address detection unit 21 changes the status flag S from “1” to “2” (step S110), and the upstream frame creation / transmission unit 22 transmits the upstream frame to the master station 1. It is shown that it is in the middle of being. In order to give a specific description below, in response to the first downlink frame, the slave station 2a uplink channel ch _1, the slave station 2b is in the upstream channel ch _2, slave station 2c and the slave station 2d Doo is the uplink channel ch _5, it is assumed that the slave station 2f and the slave station 2j sends out an upstream frame to the uplink channel ch _4. Further, the uplink frame to the uplink channel ch ₅ shall not be sent. In this situation, since the communication collision on the up channel ch ₁ does not occur, the synchronization pattern UW in the uplink frame slave station 2a is sent is not destroyed. for that reason,
The first uplink frame receiving section 131 can detect the head of the uplink frame and the synchronization pattern UW, and outputs the first comparison output and the first reception information (UW detection) as status information. Further, the uplink channel ch _2, since in the same situation as the uplink channel ch _1, the second upstream frame receiving unit 132 outputs the same status information as the first uplink frame receiving unit 131. Further, since the communication collision on the up channel ch ₃ occurs, the synchronization pattern UW in the uplink frame slave station 2c and the slave stations 2d were respectively transmitted is destroyed. Therefore, the third upstream frame receiving unit 133 can detect the head of the upstream frame but cannot detect the synchronization pattern UW, and outputs the first comparison output and the first reception information (UW non-detection) as status information. I do. Also, the uplink channel ch ₄ is the uplink channel c
Since the similar situation as h _3, fourth upstream frame receiving unit 134 outputs the same status information as the third upstream frame receiving unit 133. A fifth upstream frame receiving unit 135, since the upstream channel ch ₅ is empty channel, and outputs only the third comparison output as the status information.

At present, the downstream frame creation / transmission unit 12
Returning to step S2 shown in FIG. 8, the mode flag m
mode indicates “0”, so that the step
Proceed to step S3. The downstream frame creation / transmission unit 12
The second predetermined time has passed since the
Immediately after the time
Is controlled. Here, the second predetermined time is also
Delay until upstream frame reaches slave station 1 from slave station 2
This is a time considering the time, etc., but at the first predetermined time described above.
Different from between. Next, the downstream frame creation / transmission unit 12
Sets the slot pointer m to “1” (FIG. 9;
Step S901), from the first uplink frame receiving unit 131
Address slot AS based on the status information of₁ 
The command to be set this time is determined. Next,
The frame creation / transmission unit 12 outputs the first comparison output at this time.
Since it has been received, step S902 is executed, and
Proceed to step S908. Next, create / transmit downlink frame
The unit 12 includes an uplink channel ch_m Same from upstream frame
It is determined whether the initial pattern UW has been detected (step
S908). The determination in step S908 is the first
Is performed on the basis of the received information. Specifically,
The frame creation / transmission unit 12 receives the first reception information (UW undetected).
Out), the m-th upstream frame receiving unit
13m determined that synchronization pattern UW could not be detected
Then, the process proceeds to step S910 described later. On the other hand,
The frame creation / transmission unit 12 receives the first reception information (UW detection
Out), the m-th upstream frame receiving unit
13m determines that the synchronization pattern UW has been detected, and
Proceed to step S909. At the moment, the creation of downstream frames /
The sending unit 12 sends the first upstream frame receiving unit 131
1 received information (UW detection),
Proceed to step S909. Next, a downstream frame creation / transmission unit
12 accesses the memory unit 11 and receives the received command 1
12 is taken out, the command 112 is
Lot AS_m(Step S909). to this
Therefore, the master station 1 transmits the uplink channel ch _m Slave station using
Notify 2 that uplink frame is received correctly
Can be At present, the address slot AS₁ 
Command 112 is set in the
Is notified that the game is being received correctly. Then, below
The frame creation / transmission unit 12 is “1” at the moment.
Update the indicated value of the slot pointer m to “2” (step
(Steps S905 and S906), and returns to step S902.
Then, the downstream frame creation / transmission unit 12 transmits the second upstream
Based on status information from frame receiving unit 132
And address slot AS_Two Command to set this time
To determine. This status information is based on the first
Has the same content as that from the frame receiving unit 131
From step S9, the downlink frame creation / transmission unit 12 performs step S9.
02 → S908 → S909 → S905 → S906
(The above) is executed. As a result,
Slot Slot AS_Two Is also set to receive command 112
(Step S909) The indicated value of the slot pointer m is
"2" is updated to "3" (step S906).
After that, the downstream frame creation / transmission unit 12 performs step S
Returning to 902, the third uplink frame receiving unit 133
Address slot AS based on status information_Three To
Determine the command to be set this time. Down frame creation
/ Sending unit 12 receives the first comparison output at this time
Therefore, after executing step S902, the first reception
Since the communication information (UW non-detection) has been received,
After executing step S908, the process proceeds to step S910. next,
The downstream frame creation / transmission unit 12 accesses the memory unit 11
Fetches the collision detection command 113 to
Slot AS_m (Step S910). this
In response, the master station 1_m Child using
Notify station 2 that the uplink frame has not been received correctly.
And prompts the slave station 2 to perform retransmission control (described later).
You. At present, the address slot AS_Three Collision detection
Command 113 is set, whereby the slave stations 2c and 2c are set.
This prompts d to perform retransmission control. Next, the downstream frame
The generation / transmission unit 12 is configured to transmit_m Communication collision on
Since it is determined that the error has occurred, the counter C1 is set to “C1 +
"1" (step S911). At the moment,
The indicated value of the counter C1 is updated from “0” to “1”.
Next, the downstream frame creation / transmission unit 12
Update the indicated value of the slot pointer m of “3” to “4”.
Newly (Steps S905 and S906), Step S9
Return to 02. Then, the downstream frame creation / transmission unit 12
Is the status from the fourth uplink frame receiving unit 134
Based on the information, the address slot AS_Four Set this time
Determine the command to be performed. This status information is
Same as that from the third uplink frame receiving unit 133
Therefore, the downstream frame creation / transmission unit 12
Step S902 → S908 → S910 → S911 → S
Execute the processing (described above) shown in the order of 905 → S906
I do. As a result, this time, the address slot AS_Four Opposition
The collision detection command 113 is set (step S91).
0), the indicated value of the counter C1 is updated from “1” to “2”
(Step S911), and further, the slot pointer
The indicated value of m is updated from “4” to “5” (step
S905, S906). After that, downlink frame creation / transmission
Returning to step S902, the output unit 12 returns to the fifth upstream frame.
Based on the status information from the
Dress slot AS_Five Command to set this time
I do. This status information is used for creating / transmitting downlink frames.
The unit 12 referred to when creating the previous downlink frame
Of the same as those from the upstream frame receiving unit 131 etc.
The downstream frame creation / transmission unit 12
Are steps S902 → S903 → S904 → S905
(The above) are executed. as a result,
This time, the address slot AS_Five Has a send available command 11
5 is set (step S904). Down frame
The generating / sending unit 12 determines that the slot pointer m is
Since “5” is indicated (step S905), the synchronization
Turn UW, etc. in the header slot, etc.
Frame and place this downstream frame on the downstream channel.
(Step S907). In this way,
The frame creation / transmission unit 12 performs the processing in step S3 shown in FIG.
After that, the process proceeds to step S4. In addition, under the second
The operation of each slave station 2 that receives a frame will be described later.
State. Next, the downstream frame creation / transmission unit 12
At this point, the indicated value of the counter C1 is “2”,
Since the value “2” is less than the first predetermined value “3” (step
Step S4), the value of the counter T is changed from “1” to “2”.
After the update (step S6), the indicated value "2"
Since it is not the predetermined value “3” (step S7),
Return to step S2.

Here, the operation of the slave station 2 shown in FIG. 6 will be described with reference to FIG. 10 again. At present, there is a slave station 2 in the communication system that is waiting with the status flag S set to “0”, “1”, or “2”. The current down frame is also received by the command / address detection units 21 of all the slave stations 2. However, the operation of the slave station 2 in which the status flag S indicates “0” or “1” has already been described, and therefore, the operation in the case where the status flag S indicates “2” will be described below. . When the status flag S indicates “2”, the command / address detection unit 21 determines in steps S102 and S1
03, and then proceeds to step S111. Then, whether the command / address detecting section 21, the slave station address of the received command 112 or own address slot AS _m uplink frame creation / transmission section 22 corresponds to the upstream channel ch _m currently in use is set Is determined (step S111). In addition, this down frame is
Since the slave station address is created in the contention mode, the slave station address is not set in the address slot AS. Therefore, only the description regarding the reception command 112 will be given here. The determination in step S111 is performed as follows. First, the command / address detection unit 2
1 is used channel information currently latched (described above)
After extracting a command from the address slot AS _m specified by
It is determined whether the bit pattern matches the bit pattern of the received command 112 stored in advance therein. If the two do not match, the command / address detection unit 21 determines that the reception command 112 has not been set, clears the used channel information from the register, and proceeds to step S115 described later. The command / address detection unit 21
If they match, it is determined that the reception command 112 has been set, and the process proceeds to step S112 without clearing the used channel information. Next, the command / address detection unit 21 notifies the upstream frame creation / transmission unit 22 to continue data transmission (Step S112). After transmitting the upstream frame as shown in FIG. 7A, the upstream frame generation / transmission unit 22 generates an upstream frame as shown in FIG. 7B and transmits the same using the same upstream channel. ing. When receiving the above notification from the command / address detection unit 21, the upstream frame creation / transmission unit 22 continues transmission of the upstream frame without interruption. Next, the command / address detection unit 21 determines whether or not the upstream frame creation / transmission unit 22 has completed data transmission (Step S113). The determination in step S113 can be easily made by checking whether the buffer memory is empty. When determining that the data transmission has been completed, the command / address detection unit 21 sets the status flag S to “0” (step S114), and waits for generation of new transmission data. On the other hand, the command / address detection unit 21
Determines that the data transmission has not been completed, and returns to step S102 with the status flag S set to “2”. On the other hand, if the command / address detection unit 21 determines that the reception command 112 is not set in step S111, it determines that the upstream frame transmitted by the upstream frame creation / transmission unit 22 is not correctly received by the master station 1. I do. That is, the command / address detection unit 21 determines that the upstream frame creation / transmission unit 22 is performing useless data communication, and notifies the upstream frame creation / transmission unit 22 to interrupt the data transmission (step S115). In this case, the uplink frame generating / sending unit 22, as described above, is sending the uplink frame created by using an uplink channel ch _m, in response to the interruption notification, interrupts the transmission of uplink frames Then, useless data communication is interrupted. Thus, in the present communication system, the slave station 2 does not use the uplink channel for a long time for useless data communication. As a result, it is possible to improve the utilization rate of the uplink channel. Thereafter, the command / address detection unit 21 sets the status flag S to "1" (step S105), and returns to step S102. As described above, when the status flag S is set to “1”, the command / address detection unit 21 executes the above-described step S109 in response to the next downlink frame. That is,
The slave station 2 executes retransmission control when the upstream frame transmitted by the slave station 2 is not correctly received by the master station 1.
Here, at present, the slave stations 2a, 2b, 2c, 2d, 2
f and 2j execute step S111. In the current down frame, a reception command 112 is placed in the address slots AS ₁ and AS ₂ , and a collision detection command 11 is placed in the address slots AS ₃ and AS _4.
3 further, the Send command 115 is set in the address slot AS _5. Therefore, only the upstream frame creation / transmission units 22 of the slave stations 2a and 2b receive the continuation notification from the respective command / address detection units 21 (step S112). Here, the buffer memory of the slave station 2a and 2b, when a not yet empty, the uplink frame generating / sending unit 22 of the slave station 2a and 2b, the uplink channel ch ₁ and ch uplink frame
Keep sending out on ₂ . Incidentally, the uplink frame sent from the slave station 2a is on the uplink channel ch _1, and shall not cause data errors. However, the uplink frame sent from the slave station 2b shall cause data error on the uplink channel ch _2. In addition, the upstream frame creation / transmission units 22 of the slave stations 2c, 2d, 2f, and 2j receive the interruption notification from the respective command / address detection units 21 (Step S115), and thus interrupt the transmission of the upstream frame. Therefore, uplink channel ch ₃ and ch ₄ become free channel. Further, the slave stations 2e and 2g are:
In response to the current down frame, steps S102, S
Run the 106～S110, and has sent an uplink frame to the uplink channel ch _5. Therefore, communication collision occurs on the uplink channel ch _5. In such a situation,
The first uplink frame receiver 131 receives the second comparison output and the second reception information (normal), the second uplink frame receiver 132 receives the second comparison output and the second reception information (error), Each of the third uplink frame receiving unit 133 and the fourth uplink frame receiving unit 134 outputs only the third comparison output, and further, the fifth uplink frame receiving unit 135 outputs
The first comparison output and the second reception information (UW non-detection) are output as status information.

At present, the downstream frame creation / transmission unit 12
Returning to step S2 shown in FIG. 8, the mode flag m
Since mode indicates “0”, the process proceeds to step S3 as in the previous case. Next, the downstream frame creation / transmission unit 12
Sets the slot pointer m to "1" (FIG. 9; step S901), and based on the status information from the first uplink frame receiving unit 131, the address slot AS ₁
The command to be set this time is determined. Since the downlink frame creation / transmission unit 12 has received the second comparison output at this time, the downstream frame creation / transmission unit 12 executes steps S902 and S903 and proceeds to step S912. Next, a downlink frame generating / sending unit 12 determines whether the data error in the uplink frame of the uplink channel ch _m is occurring (step S912). The downstream frame creation / transmission unit 12
If the second reception information (error) has been received, it is determined that the data error has occurred, and the process proceeds to step S913 described later. If the second reception information (normal) has been received, the data error has occurred. Is determined not to have occurred, and the process proceeds to step S909. At present, the downstream frame creation / delivery portion 12, since the received second reception information (normal), the process proceeds to step S909 described above, sets the received command 112 into the address slot AS _1. Next, the downlink frame creation / transmission unit 12 updates the indicated value of the slot pointer m, which is currently "1", to "2" (steps S905, S906), and proceeds to step S9.
Return to 02. Then, the downstream frame creation / transmission unit 12
Based on the status information from the second upstream frame receiving unit 132, determines a command to be set this time into the address slot AS _2. Next, since the downlink frame creation / transmission unit 12 has received the second comparison output at this time, it executes steps S902 and S903, and
Proceed to step S912. Downlink frame creation / transmission unit 1
2, since the received second reception information (error), after executing step S912 described above, accesses the memory unit 11 retrieves the data error command 114 is set in the address slot AS _m (Step S
913). This also allows the master station 1 to transmit the uplink channel c
the slave station 2 in use h _m, it is possible to notify that no correctly received the uplink frame, and to encourage retransmission control the child station 2. At present, the data error command 113 into the address slot AS ₂ is set, which makes it possible to prompt the retransmission control in the slave station 2b. Next, the downstream frame creation / transmission unit 12 outputs “2” at this time.
Is updated to "3" (steps S905 and S906), and the process returns to step S902. Then, the downstream frame creation / transmission unit 12 performs the third
Based on the status information from the uplink frame receiver 133, determines the command to be set this time into the address slot AS _3. Thereafter, the downstream frame creation / transmission unit 12
It is sequential to receive status information from the third to fifth upstream frame receiving unit 133 to 135, based on the respective, successively determining the command to be set in the address slot AS ₃ ~AS _5. However, the operations performed by the downlink frame creation / transmission unit 12 in each case have already been described. Therefore, the description of the operation in each case is omitted. Incidentally, the address slots AS ₃ and AS ₄ are set Send command 115 (step S904). Further, the address slot AS ₅ is set collision detection command 113 (step S910), the indicated value of the further counter C1 is "2"
Is updated to "3" (step S911). The downstream frame creation / transmission unit 12 sends the address slots AS ₁ to
When determining the command to set the AS _5, it sends assembles the downstream frame (step S907), step S
3 (see FIG. 8), and the process proceeds to step S4.
The operation of each slave station 2 that receives the third downstream frame will be described later. Next, create a downstream frame /
The sending unit 12 performs step S4 described above. At this time, the indicated value of the counter C1 is “3”, and this indicated value “3” is the same as the first predetermined value “3” (step S4). Proceeding to S5, the mode flag mode is updated to "1", and the counters C1 and T are each updated to "0" (step S5). Here, in step S4, while the counter T counts the third predetermined value from “0” in step S4, the communication collision on the uplink channel occurs more than the first predetermined value. It is determined that it is not suitable for creating a downlink frame in the contention mode (FIG. 8; step S3). By changing the mode flag mode to “1”, the next time a downstream frame is created in the polling mode (FIG. 8; step S9). Also, counter C
1 prepares to update the instruction value to “0” so that the next time a downlink frame is created in the contention mode, the number of times of communication collision can be newly counted. Further, the counter T updates the indicated value to “0”, thereby defining the beginning of a time section for measuring the number of available channels. Next, the downstream frame creation / transmission unit 12 updates the indicated value of the counter T, which is currently “0”, to “1” (Step S
6) Since the indicated value "1" is not the third predetermined value "3" (step S7), the process returns to step S2.

Here, the operation of the slave station 2 shown in FIG.
The description will be made again with reference to FIG. Clear from the above
Thus, at present, in the communication system, the status flag S
Waits with the set to "0", "1" or "2".
There is a slave station 2 which is located. Regarding the operation of these slave stations 2,
As described above, each explanation is omitted.
Abbreviate. The following describes the collision detection command 113 and data
Error command 114 to execute retransmission control.
The operation of the slave station 2 urged by the user will be described. Repeat upstream frame
The command / address detection unit 21 of the slave station 2 to be sent
As described above, the status flag S is set to “1” and the process waits.
When the downstream frame is transmitted,
(Steps S102 to S106 to S110)
By doing so, retransmission control is executed in the slave station 2. This
Here, the buffer memory provided inside the slave station 2a is the third buffer memory.
Empty when the first downstream frame is received
Then, the command / address detection unit 21 of the slave station 2a
Sets the status flag S to "0" (step S11).
3) Wait for new transmission data to be generated. That
Therefore, the uplink channel ch₁ Becomes an empty channel. Ma
The upstream frame creation / transmission unit 22 of the slave station 2b
Address slot AS of downstream frame of_Two Data
Command 114 is set, and the command / add
Since the interruption notification is received from the
S115), the transmission of the upstream frame is interrupted. That
Channel_Two Becomes an empty channel. Also,
The slave stations 2c, 2d, 2f and 2j execute retransmission control
You. As described above, transmission is possible in the third downlink frame
Command 115 is set in the address slot.
AS_Three And AS_Four It is. At this time, only the slave station 2j
Is the upstream channel ch_Three Sends an upstream frame to the slave station
2c, 2d and 2f are uplink channels ch_Four Go up
Suppose a frame is sent. In addition, the slave stations 2e and 2g
The upstream frame creating / sending unit 22 outputs the current downstream frame.
Address slot AS_Five Has a collision detection command 113
Is set, and each command / address is detected.
Since the interruption notification is received from the unit 21 (step S11)
5) The transmission of the upstream frame is interrupted. Therefore, going up
Channel ch _Five Becomes an empty channel. This situation
Now, the first uplink frame receiving unit 131 and the second uplink frame
Frame receiving section 132 and fifth upstream frame receiving section 1
35 outputs only the third comparison output as status information.
Power. The third uplink frame receiving unit 132 performs the first ratio
Compare output and first received information (UW detection) status
Output as information. Fourth upstream frame receiving section 134
Is the first comparison output and the first reception information (UW undetected).
Out) is output as status information.

Here, referring again to FIG.
The operation of the frame creation / transmission unit 12 will be described. At the moment, below
The frame creation / transmission unit 12 returns to step S2
And the mode flag mode does not indicate “0”.
To step S9. Mode flag mode
If “1” is indicated, the downstream frame creation / transmission unit 1
2 means that communication collision occurs on relatively many uplink channels.
The polling mode, and
Judge that it is better to create a program. Here, FIG.
Step S9 (polling mode) shown in FIG.
It is a flowchart which shows an order in detail. First, the downfall
The frame creation / transmission unit 12 sets the slot pointer m to “1”.
(FIG. 11; step S1101), and the first uplink
Based on status information from frame receiving unit 131
And address slot AS₁ To be set this time
Address or command. Next, the downstream frame
The generation / transmission unit 12 performs the same processing as in step S902 (see FIG. 9).
Step S1102 is executed. Down frame creation
/ Sending unit 12 determines that the status information includes the first comparison output.
If not, the process proceeds to S1110 to be described later, and the status information
Does not include the first comparison output, step S1103
Proceed to. At this time, the downstream frame creation / reception unit 12
Has received the third comparison output, so step S
Proceed to 1103. Next, the downstream frame creation / transmission unit 12
Is the same as step S903 (see FIG. 9).
1103 is executed, and the status information indicates the second comparison output.
If it does, the process proceeds to step S1112 described later,
If the status information includes the third comparison output, step S1
Proceed to 104. At present, downlink frame creation / transmission unit
12, step S1104, as is clear from the above.
Proceed to. As described above, the m-th uplink frame receiving unit 1
3m outputs the third comparison output, the uplink channel c
h_m Is an empty channel. Therefore, the downstream frame
The creating / sending unit 12 counts the number of empty channels.
The counter C2 is updated to “C2 + 1” (Step S1
104). At present, the indicated value of the counter C2 is "0"
Is updated to "1". Next, create / transmit downlink frame
The output unit 12 accesses the memory unit 11 and stores the address
The order represented by the indicated value of int n
The slave station address is stored in the address table 111 (see FIG. 3).
), The slave station address is
Lot AS_m Is set (step S1105). this
As a result, the master station 1 has an idle channel for a single slave station 2.
Upstream channel ch_m Can be assigned. Now
At this point, the value indicated by the address pointer n is “1”.
And the address slot AS₁ Has a slave station address "a"
Is set. Next, the downstream frame creation / transmission unit 12
The slave station addresses with the last order (hereinafter simply referred to as
Address) as the address slot AS_m 
It is determined whether or not is set (step S1106).
The downstream frame creation / transmission unit 12 outputs the last slave station address.
When it is determined that is set, step S111 described later is performed.
Proceed to 4 and determine that the last slave station address has not been set
Then, the process proceeds to step S1107. This communication system
Since 11 slave stations 2 are accommodated, step S1106
Is determined that the address pointer n indicates “11”.
It depends on whether or not. Next, create / transmit downlink frame
The unit 12 indicates that the address pointer n indicates “1” at this time.
The slave station address from the address table 111.
Address pointer n so that
Is updated to "n + 1" (step S110).
7). At present, the indicated value of the address pointer n is
"1" is updated to "2". Next, the downstream frame
The generating / sending unit 12 outputs the slot
The instruction value of the counter m is updated to “2” (step S110)
8, S1109), and returns to step S1102. Soshi
Thus, the downstream frame creation / transmission unit 12 transmits the second upstream frame.
Based on the status information from the
Dress slot AS _Two Command to set this time or
Determine the slave station address. This status information is
Same as that from the first uplink frame receiving unit 131
Therefore, the downstream frame creation / transmission unit 12
Processing shown in the order of steps S1102 to S1109
(Described above). As a result, the count value of the counter C2
Is updated from “1” to “2” (step S110)
4), this time address slot AS_TwoIs the slave station address
“B” is set (step S1105), and the address
The indicated value of the n is updated from “2” to “3” (step
(Step S1107), and the indicated value of the slot pointer m
Is updated from “2” to “3” (step S110)
9). After that, the downstream frame creation / transmission unit 12
Returning to step S1102, the third uplink frame receiving unit 13
Address slot based on status information from
AS_Three The command to be set this time is determined. Downfall
The frame creation / transmission unit 12 outputs the first comparison output at this time.
Since it has been received, step S1102 has been executed.
Thereafter, step S908 similar to step S908 (see FIG. 9) is performed.
Execute 1110. Downlink frame creation / reception unit 12
Receives the first reception information (UW detection) at this time
Therefore, the process proceeds to step S1111 (step S1
110), as in step S909 (see FIG. 9).
And address slot AS_m Receive command 112
(Step S1111). This step 11
11, the address slot AS_m Slave station previously set to
An address may be set. At this time, Addresses
Lot AS_Three Is set to the reception command 112. Next
At this time, the downstream frame creation / transmission unit 12
Update the indicated value of the slot pointer m to "4"
(Steps S1108 and S1109), Step S11
Return to 02. Then, the downstream frame creation / transmission unit 12
Is the status from the fourth uplink frame receiving unit 134
Based on the information, the address slot AS _Four Set this time
Determine the command or slave address to be sent. Downfall
The frame creation / transmission unit 12 outputs the first comparison output at this time.
Since it has been received, step S1102 has been executed.
Later, the first reception information (UW non-detection) has been received.
Then, the process proceeds to step S1105 (step S111).
0). Next, the downstream frame creation / transmission unit 12
Is specified by the address pointer n indicating "3"
The slave station address "c" to be assigned to the address slot AS_FourTo
It is set (step S1105). After that,
The indicated value of the n is updated from “3” to “4” (step
Step S1107), the slot showing “4” at the moment
The pointer pointer m is updated to “5” (step
S1108, S1109). And create a downstream frame
/ The sending unit 12 returns to step S1102 and
Based on the status information from the frame receiving unit 135
And address slot AS_Five Command to set this time
Or determine the slave station address. This status information
Is transmitted from the first uplink frame receiving unit 131 described above.
Has the same content as Therefore, create a downstream frame
/ Sending unit 12 performs the order of steps S1102 to S1108
The process described above (described above) is executed. As a result, cow
The count value of the counter C2 is updated from “2” to “3” (step
S1104), address slot AS _Five The child station a
The dress “d” is set (step S1105), and the
The pointer pointer n is updated from "4" to "5".
(Step S1107). After that, create a downstream frame
/ The sending unit 12 sets the value indicated by the slot pointer m to “5”.
(Step S1108), step S111
Proceed to 3. Next, the downstream frame creation / transmission unit 12
Step S111 similar to step S907 (see FIG. 9)
3 to assemble the downstream frame (see Fig. 4)
To the channel. Finish step S9 shown in FIG.
I do. The slave station 2 receiving the fourth downstream frame
The operation of will be described later.

The description will be continued with reference to FIG. Next, when step S9 ends, the downstream frame creation / transmission unit 12 determines whether the counter C2 is equal to or greater than a second predetermined value (step S10). Here, the second predetermined value is a value for determining whether or not to update the mode flag mode from “1” to “0”, and is the same as the first predetermined value (described above). Is set to an appropriate value according to the specification of. Hereinafter, description will be made assuming that the second predetermined value is “4”. In step S10, if the counter C2 indicates a number greater than or equal to the second predetermined value, the downlink frame creation / transmission unit 12 determines that it is better to create a downlink frame in the contention mode, and proceeds to step S10. Proceed to S11. On the other hand, if the counter C2 indicates a number less than the second predetermined value, the downstream frame creation / transmission unit 12 determines that it is better to create the downstream frame in the polling mode,
Proceed to step S6. At this time, the indicated value of the counter C2 is "3", and since the indicated value is not equal to or more than the second predetermined value "4", the downstream frame creation / transmission unit 12 proceeds to step S6. Next, the indicated value of the counter T is updated from "1" to "2" (step S6). Since the indicated value "2" is not the third predetermined value "3" (step S7), Return to S2.

FIG. 10 shows the response operation of the slave station 2 to the downstream frame created in the polling mode.
This will be described with reference to FIG. Note that the response of the slave station 2 in which the status flag S indicates “0” and “2” is the same in the case of the contention mode and the case of the polling mode. Only the response of the slave station 2 in which S indicates “1” will be described. As described above, in one slave station 2, the command /
When the status flag S included in the address detecting unit 21 indicates "1", the slave station 2 has data to be transmitted to the master station 1, and the data must be transmitted from the head. Means that. The command / address detection unit 21 of the slave station 2 in which the status flag S indicates “1”, when the downstream frame is transmitted, returns to step S
After executing step 102, it is determined whether or not the slave station address of the own station is set in any of the address slots AS (step S106). The determination in step S106 is typically made as follows. The command / address detection unit 21 stores the bit pattern of the slave station address of the own station in advance in a register (not shown) provided therein. The command / address detection unit 21 determines that the bit pattern is the address slot AS of the downstream frame.
It determines whether it is set to _{1 ~AS 5.} When the slave station address of the own station is set in any of the address slots AS _m , the command / address detection unit 21 determines that the uplink channel ch _m corresponding to the slot AS _m has been assigned by the master station 1. Recognize, step S1
Go to 09. Note that the command / address detection unit 21
If the slave station addresses of the own station are not set in all the address slots AS, it is determined that the uplink channel _m has not been allocated this time, and the process proceeds to step S107. However, in the polling mode, the transmission enable command 115 is not set in the address slot AS. Therefore, the command / address detection unit 12 determines in step S10
2 and waits for a new downstream frame to be sent. The command / address detection unit 21 determines in step S1
When the process proceeds to step S09, the upstream frame generation / transmission unit 22 is notified to transmit the upstream frame using the upstream channel ch _m corresponding to the address slot AS _m in which the local station address of the own station has been detected (step S109). Then, the command / address detecting section 21, the address slot AS _m assigned in step S106, keep latched in the register (not shown) as a used channel information. This used channel information is used in step S111 as described above. Subsequent operations of the slave station 2 are the same in the contention mode and the polling mode, and a description thereof will be omitted. Here, the command / address detection units 21 of the slave stations 2a and 2b set the status flag S to “0” at the time of receiving the current down frame, and the transmission data is stored in the buffer memory. If not, steps S102 to S104 are executed, and the process returns to step S102. Therefore, slave station 2
uplink frame generating / sending unit 22 of a and 2b, does not send an uplink frame to the uplink channel ch ₁ and ch _2, up channel ch ₁ and ch ₂ is a free channel. Here, the slave station 2b interrupts the transmission of the upstream frame in response to the previous (third) downstream frame, but for convenience of description of the present communication system, as described above, the slave station 2b It is assumed that it is in the above state. The command / address detection unit 21 of the slave station 2j
Sets the status flag to “2” at the time of receiving the current downlink frame. Uplink frame generating / sending unit 22 of the slave station 2j is the address slot AS ₃ of this downstream frame is set with a reception command 112, the receive continuation notice from the command / address detecting section 21 (Step S112) continues to sends an uplink frame on an uplink channel ch _3. Note that this upstream frame, it is assumed that data errors on the uplink channel ch ₃ does not occur. Also, the command / address detection units 21 of the slave stations 2c and 2d set the status flag S to "1" at the time of receiving the current down frame, and thus execute steps S106, S109 and S110. The address slots AS ₄ and A _{4 of the} frame
From S _5, detects the slave station address "c" and "d". Therefore, the upstream frame creation / sending unit 22 of the slave station 2c and 2d, as is clear from the above, and sends the upstream frame to the uplink channel ch ₄ and ch _5. However, on the uplink channel ch ₅ shall be sent the uplink frame incorrectly other slave station 2g. In such a situation,
The first uplink frame receiving section 131 and the second uplink frame receiving section 132 output only the third comparison output as status information. Third upstream frame receiving section 132
Outputs the first comparison output and the second reception information (normal) as status information. The fourth uplink frame receiving unit 134 outputs the first comparison output and the first reception information (U
W detection). Further, the fifth uplink frame receiving section 135 outputs the first comparison output and the first reception information (UW
(Not detected) is output as status information.

At present, the downstream frame creation / transmission unit 12
Returning to step S2 shown in FIG.
Since the mode flag mode indicates “1”, the
Similarly, the process proceeds to step S9. Next, create a downstream frame /
The sending unit 12 sets the slot pointer m to “1”.
(FIG. 11; step S1101). Here, from above
As is apparent, from the first uplink frame receiving unit 131
Status information of the second uplink frame receiving unit 132
These means that the downstream frame creation / transmission unit 12
The first upstream frame referenced when creating the downstream frame
The contents are the same as those from the system receiving unit 131 and the like. That
Therefore, the downstream frame creation / transmission unit 12 performs step S1
The processing (described above) shown in the order of 102 to S1109 is
Execute repeatedly. As a result, the counter C2 becomes "5".
(Step S1104), and the address
Lot AS₁ And AS_Two Has the slave station address "e" and
And “f” are set (step S1105), and the address is set.
The pointer n indicates "7" (step S11).
07), and the slot pointer m indicates “3”
(Step S1109). Then the downstream frame
The creation / transmission unit 12 returns to step S1102, and
Based on the status information from the upstream frame
Address slot AS_Three Frame to set this time
Command or slave station address. Down frame creation
/ Sending unit 12 receives the second comparison output at this time
Therefore, steps S1102 and S1103 are executed.
After that, the same steps as in step S912 (see FIG. 9) are performed.
Step S1112 is executed. Downlink frame creation / reception unit
12 is a case where the second reception information (error) is being received.
In this case, the process proceeds to step S1105, and the second
If the information (normal) has been received, step S1111
Proceed to. The downstream frame creation / transmission unit 12
2 received information (normal)
Slot AS_m Is set to receive command 112 (step
Step S1111). At present, the address slot AS
_Three Is set to the reception command 112. Next,
The frame creation / transmission unit 12 outputs the slot “3” at the moment.
The pointer pointer m is updated to “4” (step S
1108, S1109), and returns to step S1102.
Then, the downstream frame creation / transmission unit 12 outputs the fourth upstream
Based on status information from frame receiving unit 134
And address slot AS _Four Command to set this time
Or determine the slave station address. This status information
Indicates that the downstream frame generation / transmission unit 12
Third upstream frame receiving unit 1 referred to when creating a system
Since the content is the same as that from 33,
The frame creation / transmission unit 12 determines in step S1102 → S
1110 → S1111 → S1108 → S1109
(The above) is executed. As a result,
Slot Slot AS_Four Contains the reception command 112 (or slave station)
Address “c”) is set (step S1111),
Further, the slot pointer m indicates "5".
(Step S1109). Then, create a downstream frame /
The sending unit 12 returns to step S1102 and performs the fifth uplink
Based on status information from frame receiving unit 135
And address slot AS_Five Command to set this time
Or determine the slave station address. Downlink frame creation / transmission
The output unit 12 is currently receiving the first comparison output.
Therefore, after executing step S1102, the first reception
Since information (UW non-detection) has been received, step S
Go to 1110, address slot AS_Five Child station address
Is set (step S1111). Then, below
The frame creation / transmission unit 12 is “7” at the moment.
After updating the indicated value of the address pointer n to “8” (the
(Step S1107) The slot pointer m indicates “5”.
(Step S1108), the downlink frame
Assembled and transmitted (step S1113). Like this
Thus, the downstream frame creation / transmission unit 12 performs the steps shown in FIG.
Step S9 ends, and the process proceeds to step S10. Then go down
At this time, the frame creation / transmission unit 12
2 is greater than or equal to the second predetermined value “4”
(Step S10), the process proceeds to step S11. Downfall
The frame creation / transmission unit 12 sets the mode flag mode
Update to "0" and further increase counters C2 and T
Each is updated to "0" (step S10). Down frame
In step S10, the system creation / transmission unit 12
While T is counting the third predetermined value from “0”,
That there are more channels than the second predetermined value.
Recognizes the current upstream channel status and
(FIG. 8; step S9) to create a downstream frame
Judge that it is not suitable. Mode flag mode
By being updated to "0", the contention
Frame is created in the download mode (FIG. 8; step S3)
Will be done. Further, the counter C2 outputs the indicated value.
By updating to "0", the next polling mode
Number of empty channels when downlink frames are created in
Prepare for a new count. In addition, cow
By updating the indicated value to “0”, the communication
Time interval for measuring the number of
Specify the beginning. Next, a downstream frame creation / transmission unit
12 indicates the indicated value of the counter T which is currently “0”.
After updating to "1" (step S6), the designated value
Since “1” is not the third predetermined value “3” (step
Step S7), and return to step S2.

As described above, according to the communication system according to the first embodiment, the downlink frame creation / transmission unit 1
2 generates a downstream frame in a contention mode when the upstream channel is not congested, and generates a downstream frame in a polling mode when the upstream channel is congested. Thereby, the slave station accommodated in the communication system can always obtain high throughput and response regardless of whether the uplink channel is congested or not.

In step S7 (see FIG. 8),
When the indicated value of the counter T reaches a third predetermined value,
Step S8 is executed. In step S8, the downstream frame creation / transmission unit 12 updates the counters C1, C2, and T to “0”. This step S8
Means that communication collision has not occurred more than the first predetermined number on the uplink channel while the counter T has counted from the "0" to the third predetermined value, or the number of empty channels has exceeded the second predetermined number. This is a step necessary to measure the number of communication collisions or the number of free channels again because the number of has not occurred. The polling mode (FIG. 9; step S)
When 9) is repeatedly executed, the designated value of the address pointer n eventually becomes “11”. At this time, the downstream frame creation / transmission unit 12 updates the indicated value of the address pointer n to “1” (FIG. 11; step S1114).

Next, a communication system to which the access control method according to the second embodiment of the present invention is applied will be described. The second embodiment is different from the first embodiment only in that only the polling mode (see FIG. 11) is executed.
The transmitting unit 12 does not need to determine whether to create a downlink frame in the polling mode or create a downlink frame in the contention mode, and thus does not execute step S1104). Other configurations of the communication system and the like are the same as those in the first embodiment, and the same reference numerals are used for corresponding parts. Here, FIG. 12 is a diagram showing the transition of the state of the slave station address set in the address slot AS of the downstream frame and the communication state of the upstream channel when the access control method according to the second embodiment is applied. It is. The downlink frame creation / transmission unit 12 sets the indicated value of the slot pointer m to “1” (Step S1101). In this embodiment, the value indicated by the address pointer n is also updated to “1” in step S1101. Subsequent processing is clear from the first embodiment, and a description thereof will be omitted. When the communication system is in the initial state, since no uplink frame has been transmitted on any uplink channel, the downlink frame creation / transmission unit 12 executes step S1102 → S
After repeating the processing procedure shown in the order of 1103 → S1105 to S1109 four times, step S1102 → S1
Steps 103 → S1105 to S1108 → S1113 are executed, and the same operation as described above is executed in each step. Therefore, the indicated values of the slot pointer m and the address pointer n are “1” → “2” → “3” →
Transition is made from “4” to “5”. Then, step S110
In 8, if the instruction value m is “5”, the downlink frame creation / transmission unit 12 ends the creation of the first downlink frame and transmits the downlink frame to the downlink channel (step S1113). Therefore, when the indicated values of the slot pointer m and the address pointer n are “1”, the downstream frame creation / transmission unit 12 extracts the slave station addresses “a” assigned with the order “1” from the address table 111 (see FIG. 3 see), the child station address "a" is set in the address slot AS _1. Similarly, the downstream frame creation / transmission unit 12 assigns the slave station address “b” to the address slot AS ₂ , the slave station address “c” to the address slot AS ₃ , and the slave station address “d” to the address slot AS _4. to further set the slave station address "e" into the address slot AS ₅ (FIG. 12, reference AS ₁ ~AS ₅ of the first downlink frame). As a result, the downstream frame creation / delivery portion 12, so that the allocating the uplink channel ch ₁ to CH ₅ to slave station 2a to 2e. In addition, master station 1
Has transmitted the first downstream frame, the indicated value n of the address pointer is “6”.

Next, the operation of each slave station 2 for the first downlink frame is the same as that described in the first embodiment, and a description thereof will be omitted. The first
In response to the rotating first downstream frame, the slave station 2a~2e is the uplink channel ch ₁ to CH _5, and sends their upstream frames (see Fig. 12, up channel ch ₁ ~ch _5).

The downstream frame generation / transmission unit 12 generates a second downstream frame after a second predetermined time has passed since the transmission of the first downstream frame. At this time, the upstream frame from the slave station 2a to 2e, and is sent to the uplink channel ch ₁ ~ch _5. Further, the upstream frame from the upstream channel ch ₁ to CH ₃ shall not cause communication collisions. However, the upstream frame from the upstream channel ch ₄ and ch ₅ is the uplink channel ch
_It is assumed that a communication collision occurs due to, for example, an incorrect transmission of an uplink frame by a slave station to which channel ₄ or channel ₅ is not assigned. The downstream frame creation / transmission unit 12 performs the first
Of As it is clear by referring to the description of embodiments, in the second downlink frame, the address slots AS ₁ ~
Slave station address "a" to the "c" is set again to AS _3, sets the address slots AS ₄ and AS ₅ slave station address "f" to and "g". After completing the creation of the second downlink frame, the downlink frame creation / transmission unit 12 sends the downlink frame to the downlink channel (FIG. 1).
2, reference AS ₁ ~AS ₅ of the second downlink frame).
By the second downlink frame, slave stations 2f and 2g
Is newly assigned an uplink channel.

Next, the operation of each slave station 2 for the first downlink frame is the same as that described in the first embodiment, and a description thereof will be omitted. The second
In response to the second downstream frame, the slave stations 2a, 2b, 2f
And 2g is the up channel ch _1, ch _2, ch ₄ and ch _5, but sends their upstream frame, the slave station 2
c does not send an uplink frame to the uplink channel ch ₃ (see FIG. 12, the uplink channel ch ₁ ~ch _5).

The downstream frame generating / transmitting section 12 generates a third downstream frame after a second predetermined time has passed since the transmission of the second downstream frame. At this time, the uplink frame is composed of uplink channels ch ₁ , ch ₂ , c
It is sent to h ₄ and ch _5. Also, it is assumed that the uplink frames from the uplink channels ch ₁ , ch ₂ , ch ₄ and ch ₅ do not cause an error and do not cause a communication collision. As apparent from the description of the first embodiment, the downstream frame creation / transmission unit 12 sets the address slots AS ₁ and A ₁ in the third downstream frame.
The slave station address “a” is assigned to S ₂ , AS ₄ and AS ₅ ,
“B”, “f” and “g” (or the reception command 11
2) Set again, to set the slave station address "h" in the address slot AS _3. Downstream frame creation / transmission unit 12
Transmits the downlink frame to the downlink channel after completing the creation of the third downlink frame (FIG. 12, third
See AS ₁ ~AS ₅ times eyes of the downstream frame). By the third downlink frame, the child station 2h is newly assigned an uplink channel.

As described above, the downstream frame creation / transmission unit 12 has the following effects even when only the polling mode is executed. Down frame creation /
Each time the sending unit 12 detects a free channel, it sends the slave station 2 in accordance with the order set in the address table 111.
To the uplink channel. As a result, it is possible to prevent only a specific uplink channel from being in a congestion state. Further, the downstream frame generation / transmission unit 12 detects useless data communication based on the status information from the upstream frame reception unit 13. The downlink frame creation / transmission unit 12 releases the allocation of the uplink channel to the slave station 2 performing the useless data communication, and renews the uplink channel used for the useless data communication according to the above-described order. Assigned to slave station 2. That is, the downlink frame creation / transmission unit 12 prevents the response and throughput of the slave station 2 from being reduced due to useless data communication. Thereby, the uplink channel is used efficiently. This effect also applies to the polling mode in the first embodiment described above.

In the first and second embodiments described above, the table shown in FIG. 3 is used as the address table 111. The priority is defined in the address table 111 shown in FIG. 3 in that the slave station 2a is assigned the uplink channel first and the slave station 2k is assigned the latest uplink channel. However, each slave station 2 has a rate of once every 11 times,
The use of the uplink channel is permitted. But,
When the table shown in FIG. 13 is applied, the slave station 2a is permitted to use the uplink channel once every six times, unlike the other slave stations 2. Accordingly, for example, when the slave station 2a generates an uplink frame more frequently than the other slave stations 2, the response and throughput of the slave station 2a can be increased.

Next, a communication system to which the access control method according to the third embodiment of the present invention is applied will be described. This communication system has the same configuration as that of the communication system shown in FIG. 1, and thus the description thereof is omitted. However, the following points are different from the communication system shown in FIG. 1.

The slave stations 2 connected to the transmission path 3 are divided into a plurality of predetermined groups. In the present embodiment, as an example, eleven slave stations 2 are divided into two groups (a first group and a second group).
a to 2e belong to the first group, and the slave stations 2f to 2k belong to the second group.
It belongs to a group. Further, in the first group, assigned uplink channel ch ₁ to CH _3, second
The group is allocated uplink channels ch ₄ and ch _5. Therefore, the master station 1 has, for example, an address table as shown in FIG. In FIG.
The address table stores, for each group, a slave station address assigned with an order in which uplink channels are assigned to slave stations. That is, in the first group, slave station addresses “a” to “e” are added to the first order “1” to “5” (hereinafter, this is referred to as a first table), and in the second group, , The slave station addresses “f” to “k” are assigned to the second order “1” to “6” (hereinafter, this is referred to as “second table”).

The downstream frame creation / transmission unit 12 of the master station 1 includes an address pointer n for each group. Therefore, in the present embodiment, two first and second
Contains the address pointer n ₁ and n _2. The first address pointer n ₁ counts up from “1” to “5” by one based on an instruction from the downstream frame creation / transmission unit 12, and the indicated value of the _first address pointer n ₁ is , The first order described above. The second address pointer n ₂ counts up from “1” to “6” by one based on an instruction from the downstream frame creation / transmission unit 12. Indicated value of the second address pointer n ₂ illustrates a second order described above.

Also, the downstream frame creation / transmission unit is provided with the configuration shown in FIG.
The downlink frame is created based on the flowchart shown in FIG. Flowchart shown in FIG. 15, the one shown in FIG. 11 has two cascaded aspect was to detect a free channel from upstream channel ch ₁ to CH _3, a first order of the idle channel, the above-described Is assigned to the slave stations 2a to 2e belonging to the first group (step S1).
21), then, detects a free channel which is not used from the uplink channel ch ₄ and ch _5, the idle channel, based on the second order is assigned to the slave station 2f~2k belonging to the second group (step S122). Therefore, the downstream frame creation / transmission unit 12 sets the slave station address extracted from the above-described first table in the downstream frame address slots AS _{1 to} AS ₃ ,
Up channel ch ₁ to CH in any one of the slave stations 2a~2e
Assign ₃ . Further, the address slots AS ₄ and AS ₅ of the downstream frame, sets the slave station address retrieved from the second table described above, allocating the uplink channel ch ₄ or ch ₃ to one of the slave stations 2F～2k.

Various information such as computer data and voice data are communicated between the master station 1 and the slave station 2. However, in general, the amount of audio data is determined to some extent, but the amount of computer data varies. Moreover, audio data often does not make sense as audio data unless a response or throughput is guaranteed. Therefore, in a communication system in which the slave station 2 that performs the communication of the audio data and the slave station 2 that performs the communication of the computer data that does not need to guarantee the response and the throughput are mixed, the communication of the audio data is performed. The response and throughput of the slave station 2 may not be guaranteed. Therefore, in the second embodiment, the slave stations 2 connected to the master station 1 are grouped according to the attribute of the information held by the slave station 2. In addition, each uplink channel is assigned so as not to overlap for each group. When detecting the free channel, the master station 1 selects the slave station 2 from the group to which the detected free channel is assigned. Therefore, for example, if the slave stations that perform the communication of the audio data are grouped, the slave stations belonging to the group can secure the periodicity in which the uplink channel is allocated. Can be guaranteed.

In the third embodiment, the response and throughput of a specific slave station 2 may be increased by applying the address table shown in FIG. 13 described in the second embodiment. In addition, the above-described reception command 112
May be set in the address slot.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of a communication system to which an access control method according to a first embodiment of the present invention is applied.

FIG. 2 is a block diagram showing a detailed configuration of a master station 1 shown in FIG.

FIG. 3 is a diagram illustrating an example of an address table 111 illustrated in FIG. 2;

4 is a diagram showing a configuration of a downstream frame transmitted by a master station 1 shown in FIG.

5 is a diagram showing bit configurations of a slave station address and various commands set in the address slot shown in FIG. 4;

FIG. 6 is a block diagram showing a detailed configuration of a slave station 2 shown in FIG.

FIG. 7 is a diagram illustrating an example of a configuration of an uplink frame transmitted by a slave station illustrated in FIG. 6;

8 is a flowchart showing an operation procedure of the master station 1 shown in FIG.

FIG. 9 is a flowchart showing a detailed operation procedure of step S3 shown in FIG. 8;

10 is a flowchart showing an operation procedure of the slave station 2 shown in FIG.

FIG. 11 is a flowchart showing a detailed operation procedure of step S9 shown in FIG. 8;

FIG. 12 is a diagram showing a transition of a state of a slave station address set in an address slot of a downlink frame and a communication state of an uplink channel when the access control method according to the second embodiment of the present invention is applied. .

FIG. 13 is a diagram showing another example of the address table 111 shown in FIG.

FIG. 14 is a diagram illustrating an example of an address table in a communication system to which an access control method according to a third embodiment of the present invention is applied.

FIG. 15 is a flowchart showing an operation procedure when a downlink frame creation / transmission unit 12 creates a downlink frame in a communication system to which an access control method according to a third embodiment of the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Master station 11 ... Memory part 12 ... Downlink frame creation / transmission part 13 ... Uplink frame reception part 2 ... Child station 21 ... Command / address detection part 22 ... Uplink frame creation / transmission part

Claims (2)

[Claims] 1. A method for controlling access from a slave station to the master station in a communication system in which the master station and a plurality of slave stations are capable of two-way communication, wherein the master station includes a downlink. A downlink channel can be used to transmit a signal, each of the slave stations can use a plurality of uplink channels to transmit an uplink signal, and the master station can use a currently available uplink channel (hereinafter, referred to as an uplink channel). , "Free channel"
), Selects a number of slave stations corresponding to the detected vacant channels, individually assigns the vacant channels to the selected slave stations, and notifies the vacant channels assigned to the selected slave stations. An access control method comprising: generating a downlink signal for transmission to the downlink channel; and transmitting the downlink signal to the downlink channel, wherein the slave station determines whether an uplink channel is allocated to the own station based on the downlink signal input from the downlink channel. 2. A method for controlling access from a slave station to the master station in a communication system in which the master station and a plurality of slave stations are capable of two-way communication, the master station comprising: A downlink channel can be used to transmit a signal, each of the slave stations can use a plurality of uplink channels to transmit an uplink signal, , "Free channel"
) Is detected, and a downlink signal for notifying the detected idle channel to the slave station is created and transmitted to the downlink channel. The slave station receives the currently available channel by the downlink signal input from the downlink channel. An access control method for recognizing an uplink channel and transmitting the uplink signal to the empty channel.