JPH09321785A - Multi-access communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct a flexible mutli-access communication system by permitting the master station to dynamically assign lines to respective slave stations in accordance with line reserving information from the slave station. SOLUTION: The system is constituted by the one master station 11 and the plural slave stations 121 -123 . The master station successively transmits a transmission enabling signal including line assignment quantity information for indicating line assigning quantity to the plural slave stations 121 -123 through a broadcast line (down line) 45. The respective slave stations which receive the transmission enabling signal transmits data of quantity for the part of the designation by line assignment quantity information and line reserving information which designates the quantity of data desired to be transmitted next time through a multi-access-type line (up line) 46. The master stations calculates line assignment quantity sent to the respective slave stations based on the line reserving quantity information received from the slave stations, transmits the new transmission enabling signal including line assignment quantity information for indicating the calculated line assignment quantity and dynamically assign the lines to the respective slave stations in accordance with line reserving information from the slave stations.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-access communication system composed of one master station and a plurality of slave stations, and in particular, a MAN (Mertopolit) using a cable TV.
an area network) system, multiple downlinks (broadcast type) and uplinks (multi-access type)
And a multi-access control method in a communication system having

[0002]

As is well known, a lower layer of a standard protocol is defined as a communication function for efficiently performing transparent data transfer between two stations (nodes). As is well known, the lower layer is composed of four layers, but the lowermost layer is called a physical layer and the upper layer is called a data link layer.
The physical layer activates, maintains, deactivates the physical medium,
Performs electrical and mechanical control for bit transmission. That is, the physical layer provides a physical connection for bit transmission between adjacent stations (nodes). On the other hand, the data link layer performs data transmission between adjacent stations and controls transmission errors. That is, the data link layer provides a data link connection for reliable and transparent data transfer between adjacent stations.

As well known, the purpose of MAN is to provide a service in which data, voice, images, etc. are integrated in a geographically wide area. In general, MA
N is a LAN (Local Area Network) and a WAN (Wide A)
REA Network) and is considered to be a network capable of transmitting multimedia.

A multi-access communication system such as a MAN has one master station, a plurality of slave stations, and a broadcast line (downlink) for transmitting signals from the master station to all the slave stations.
And a multi-access line (uplink) for transmitting signals from all slave stations to the master station in a time division manner. Generally, in a communication system, when a transmission error occurs in data, an error correction function in the physical layer and
Transmission errors are corrected by the retransmission control function in the data link layer.

As is well known, there are two channel allocation methods in this type of multi-access communication system, a pre-assignment method and a demand assignment method. The pre-signment method is a method in which a channel is fixedly assigned to each slave station. On the other hand, the demand assignment method is a method of allocating each channel for each call. In other words, the demand assignment method can be said to be a method of changing the position of the slot. By the way, in the conventional multi-access communication system, whether the pre-assignment system or the demand assignment system is used, the slots for allocating channels are ATM (Asynchronous Tracing).
nsfer Mode) It has a fixed length like a cell. Therefore, the amount of data transmitted from each child station to the parent station on one channel is always constant.

Also, the conventional multi-access communication system does not have a retransmission or error correction function. Also,
When a plurality of uplink / downlink lines exist between a master station and a plurality of slave stations, any one uplink / downlink line is semi-fixedly assigned to each slave station.

The following are known as prior art related to the present invention. For example, JP-A-4-15674
Japanese Patent Laid-Open No. 0 (hereinafter referred to as Prior Art 1) prevents data collision by performing distributed processing of a function of scheduling the use order of transmission paths in advance and a function of performing data transmission based on the scheduling result. A "distributed scheduling / multi-access method" is disclosed in which the utilization efficiency of the main transmission line is improved and the burden on the interface unit is reduced. This prior art 1 discloses a main transmission line as a data transmission line for exchanging data between a data processing device and a plurality of terminals, as well as a data transmission line from each terminal and a sub-transmission line as a transmission line for transmitting a usage request. Related to a branch type local area network. In the prior art 1, a plurality of first type interfaces for controlling data transmission / reception between each terminal and the main transmission line and a use request of the main transmission line issued from each terminal are taken in, and the main transmission line It comprises a plurality of second type interfaces for scheduling the order of use. Each first type interface assembles packets for the terminal,
At the same time it plays the role of disassembling and controls the sending and receiving of packets. Each second type interface raises the use request of the main transmission line to the sub transmission line in a time division manner, and at the same time, takes in the use request issued from the other second type interface and uses each own transmission line. Make a table. When a packet is transmitted from each terminal, the packet has the address information of the terminal which can use the main transmission path next, so that the right to use the main transmission path is sequentially moved. This prevents data collision, improves the utilization rate of the main transmission line, and simplifies the circuit algorithm of the interface section.

Further, Japanese Laid-Open Patent Publication No. 6-284059 (hereinafter referred to as Prior Art 2) discloses a communication line between a slave station and a satellite access controller when line congestion occurs in a star access satellite communication network of a random access system. A "satellite communication line automatic switching system" is disclosed in which it is possible to switch to another line automatically and efficiently without disconnecting. In this prior art 2, a satellite access controller provided in a central satellite communication earth station that forms a star satellite communication network having satellites detects a congestion state of a satellite communication line, and when a congestion state is detected, a slave station A congestion state monitoring control module for switching the line to be used is provided, and the satellite access controller itself switches the satellite communication line without waiting for the determination by the satellite network controller. In this case, of the slave stations using that line,
Switch the line used by the slave station with high line frequency to another line with less traffic.

Further, in Japanese Unexamined Patent Publication No. 4-362797 (hereinafter referred to as prior art 3), when the own temporary ID does not exist, a temporary number of the own station is set at a position of an empty area determined by generating a random number. A "contactless card multi-access system" is disclosed in which IDs are transmitted by avoiding collisions so that the master station and a plurality of slave stations can perform simultaneous communication in a time division manner. In the prior art 3, the master station transmits a read command in which the temporary ID of the slave station received is set in the corresponding area in a time division manner, and the slave station receives and checks this read command, and its own temporary ID does not exist. In this case, an empty area is determined based on a random number within the range of the number of areas notified by the read command, and the temporary ID of the own station is transmitted. ID from the parent station
When the slave station which received the command contactlessly sends the information of its own station to the master station when the temporary ID of its own station is set in the corresponding ID command, the master station receives the information of this slave station. Read. Therefore, a large number of communication can be performed simultaneously between the master station and a plurality of slave stations without collision in time division.

[0010]

By the way, the amount of data to be transmitted to the master station, which is generated in each slave station, is not always constant. In other words, the amount of data generated in each of the plurality of slave stations is different. However, in the conventional multi-access communication system, as described above, the amount of data transmitted from each slave station to the master station is always constant in one channel. Therefore, the conventional multi-access communication system has a problem that necessary data to be transmitted cannot be immediately transmitted from each slave station to the master station.

On the other hand, in the cable TV, there is a problem of uplink data transmission error caused by noise called ingress noise which is generated by overlapping noises generated from each slave station. Such noise has a long duration and frequently occurs for 1 to 2 hours, during which the quality of the line may be significantly deteriorated. In conventional multi-access communication systems,
When a data error occurs, it is dealt with by using the error correction function of the physical layer and the retransmission control function of the data link layer as described above. However, an error due to ingress noise generally occurs for several bytes in succession, and therefore it is often impossible to completely correct the error by the error correction function. Further, in the data link layer retransmission, Go-b is used.
Since the ackN type retransmission is performed, there is a problem that the amount of retransmitted data is large compared to erroneous data and the efficiency is low. In addition, since retransmission is not performed immediately, there is a problem that data delay increases.

Further, in the conventional multi-access communication system, since the line used by the slave station is semi-fixedly allocated, if the line quality is deteriorated due to ingress noise,
There is a problem that the slave station using the line and the communication quality during that time deteriorate.

Prior art 1 merely discloses the technical concept of a branch type local area network in which a plurality of terminals (slave stations) are connected to a transmission line, and only one master station is disclosed. The field of application is different from that of the present invention, which is a technique for multiple access to a plurality of slave stations. Prior art 2 discloses a technical idea of automatically switching a line used by a slave station having a high line usage frequency to another line with less traffic when a congestion state is detected. It does not disclose any technical idea of changing the length of the time slot according to the data generation amount. Prior art 3 only discloses a technique in which a master station and a plurality of slave stations can perform simultaneous communication in a time-division manner while avoiding collisions and transmitting the time slot according to the data generation amount of the slave station. It does not disclose the technical idea of changing the length of the. Furthermore, none of the prior arts 1 to 3 describes the retransmission method when the received data has an error.

Therefore, an object of the present invention is to provide a flexible multi-access communication system capable of immediately transmitting necessary data from each slave station to a master station.

Another object of the present invention is to provide a multi-access communication system capable of efficiently retransmitting with little delay when a data error occurs.

Still another object of the present invention is to provide a multi-access communication system capable of automatically switching the used line to another line when the quality of the used line deteriorates. .

[0017]

In order to solve the above problems, a multi-access communication system according to the present invention provides a master station, a plurality of slave stations, and signals from the master station to a plurality of slave stations. In a multi-access communication system consisting of a broadcast-type line for transmitting a signal and a multiple-access-type line for transmitting signals from multiple slave stations to the master station in a time division manner, the master station broadcasts to multiple slave stations. The transmission permission signal containing the line quota information indicating the line quota is sequentially transmitted through the type line, and each slave station that receives this transmission permission signal wants to transmit next time with the amount of data specified by the line quota information. The line reservation information that specifies the amount of data and the line reservation information are transmitted through the multi-access line, and the master station calculates the line allocation amount to each slave station based on the line reservation amount information received from the slave station. The allocated line quota Send a new transmission permission signal including a to line quota information, the multi-access communication system is obtained and allocates the line to dynamically each slave station according to channel reservation information from the slave station.

The multi-access communication system according to the present invention also introduces a function of correcting errors in the media access sublayer located between the data link layer and the physical layer. Therefore, in the present invention, the slave station is provided with means for generating an error detection code, and the master station is provided with means for detecting an error in the data received from the slave station. In addition, the master station has means for notifying the slave station of success / failure of reception based on the result of error detection, and the slave station has means for resending the previously sent data when the reception failure is notified.

Further, the master station has means for measuring the error frequency in each uplink, and when the error frequency of a certain line exceeds a predetermined threshold value, all the uplinks are used. It has means for transmitting a signal for instructing the slave station to switch the line. When the mobile station is instructed to switch the line, it specifies the uplink / downlink to use for the uplink / downlink.
It has a means to switch to the downlink.

Further, the master station has means for measuring the traffic of each uplink, and when the traffic of a certain line exceeds a preset threshold value, some slave stations using that uplink Has a means for transmitting a signal for instructing to switch the line.

[0021]

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

An operation procedure of the multi-access communication system according to the first embodiment of the present invention will be described with reference to FIG. In FIG. 1, the upper line shows the operation of the master station 11, and the lower three lines are the first to third slave stations 12 ₁ , 1.
The operations of 2 ₂ and 12 ₃ are shown. That is, in this example, there are 3 slave stations.
An example of a stand is shown. Time passes from right to left in the figure. Arrows from the top to the bottom indicate the parent station 11 to the first to third slave stations 12 ₁
Indicates a transmission permission signal to the 12 _3, the arrow from the bottom showing the transmission of signals to the master station 11 from the first to third slave stations 12 ₁ to 12 _3.

[0023] The master station 11, the first to third slave station 12 ₁ to
To 12 ₃ sequentially transmits a transmission permission signal 13 _1, 13 _2, 13 ₃ added with ACK (information reception success). The _first to _third slave stations 12 _{1 to} 12 ₃ that have received the transmission permission signals 13 _{1 to} 13 ₃ receive the data D1 (1) 1 respectively.
4 ₁ , D 2 (1) 14 ₂ and D 3 (1) 14 ₃ are transmitted together with the next reservation amount information. The first to third slave stations 12 ₁ to
Data D1 (1) 14 _{1 to} D3 (1) 14 from 12 _3
The master station 11 which has received ₃ receives the data D1 (1) 14 _{1 to} D ₁
The presence or absence of a transmission error is checked by the error detection code added to 3 (1) 14 ₃ . In the illustrated example, the first slave station 12
Data D1 (1) 14 from the _first and third slave stations 12 _3
1 and D3 (1) 14 ₃ have no transmission error, and the data D2 (2) 14 ₂ from the _second slave station 12 ₂ has a transmission error.

The master station 11 includes the first slave station 12 ₁ and the third slave station 12 ₁ .
Against the child station 12 _3, and transmits the next transmission permission signal 15 ₁ and 15 ₃ by setting the ACK that means successful reception, for the second child station 12 _2, the reception failure The meaning NAK is set and the next transmission permission signal 15 ₂ is transmitted. Transmission permission signals 15 ₁ and 1 with ACK set
The first slave station 12 ₁ and the third slave station 12 which received 5 _3
3 is new data D1 (2) 16 ₁ and D3 (2)
16 ₂ is transmitted, but the second slave station 12 _{2 that} has received the transmission permission signal 15 ₂ with NAK set receives the previous data D 2
(1) Send 16 ₂ . The first to third slave stations 12 ₁ to
Data from 12 ₃ D1 (2) 16 ₁ , D2 (1) 16
₂ , the master station 11 receiving D3 (2) 16 ₃ receives the data D
1 (2) 16 ₁ , D2 (1) 16 ₂ , D3 (2) 16 ₃
The presence or absence of a transmission error is checked by the error detection code added to. In the illustrated example, data D1 (2) 16 ₁ and D2 from the _first slave station 12 ₁ and the second slave station 12 ₂
The case where there is no transmission error in (1) 16 ₂ and a transmission error occurs in the data D3 (2) 16 ₃ from the _third slave station 12 ₃ is shown.

The master station 11 includes a first slave station 12 ₁ and a second slave station 12 ₁ .
ACK indicating that the reception is successful is transmitted to the _second slave station 12 ₂ and the next transmission permission signals 17 ₁ and 17 ₂ are transmitted, but reception failure is transmitted to the third slave station 12 ₃ . The meaning NAK is set and the next transmission permission signal 17 ₃ is transmitted. Transmission permission signals 17 ₁ and 1 with ACK set
The first slave station 12 ₁ and the second slave station 12 which received 7 _2
2 is new data D1 (3) 18 ₁ and D2 (2)
18 ₂ is transmitted, and a transmission permission signal 17 in which NAK is set 17
₃ The third slave station 12 ₃ which has received the last data D3
(2) Send 18 ₃ .

FIG. 2 shows the structure of a downlink frame used in the multi-access communication system according to the first embodiment of the present invention. The downlink frame is composed of a plurality of slots. There are two slots, a control slot 20 for sending a transmission instruction signal and a data slot 21 for sending data.
There are types. The type of slot is designated in the control / data field 22 at the head of each slot. The control slot 20 is an address field 2 for designating the address of the slave station.
3, a command field 24 for setting ACK or NAK, and an allocation amount field 25 for specifying the amount of data permitted to be transmitted to the slave station. The data slot 21 includes a data field 27 that carries data.

FIG. 3 shows the structure of an upstream frame used in the multi-access communication system according to the first embodiment of the present invention. In the upstream frame, a plurality of burst signals 30 are time-division multiplexed. Each burst signal 30 includes a sync word field 31 that indicates a sync word for synchronization and an address field 32 that specifies a slave station address of a transmission source.
And the reserved amount field 3 that specifies the reserved amount for the next line
3, a data field 34 that carries data, and an error detection code field 35 that indicates an error detection code. The control information field 3 is composed of the synchronization word field 31, the address field 32, and the reserved amount field 33.
6 are configured.

FIG. 4 is a block diagram showing the system configuration of the multi-access communication system according to the first embodiment of the present invention. The illustrated multi-access communication system has one
It is composed of a master station 11 and _first to _third slave stations 12 _{1 to} 12 ₃ . The master station 11 includes a router 40, a master station access control device 41, and a slave station management device 42. The first slave station 12 ₁ is the first slave station access control device 4
3 ₁ and the first terminal 44 _1, and the second slave station 1
2 2 is composed of a second slave station access control device 43 ₂ and a second terminal 44 _2, and a third slave station 12 ₃ is a third slave station access control device 43 ₃ and a third terminal 44 ₃ . Composed of. The master station 11 transmits a signal to the _first to _third 12 _{1 to} 12 ₃ via the downlink 45 which is a broadcast type line,
The first to third 12 _{1 to} 12 ₃ transmit signals to the master station 11 through the up line 46 which is a multi-access type line.

FIG. 5 is a block diagram showing the configuration of the master station access control device 41 shown in FIG. The master station access control device 41 includes a transmission trigger generation means 51, a control slot generation means 52, a transmission buffer 53, and a multiplexing means 5.
4, reception trigger generation means 55, and reception buffer 56
And error detection means 57 and control information reception means 58.

The transmission trigger generating means 51 indicates the timing for generating the control slot 20 (FIG. 2). When the transmission trigger is input from the transmission trigger generation unit 51, the control slot generation unit 52 is based on the slave station address, the reservation amount, and the reception result input from the slave station management device 42 (FIG. 4). The control slot 20 shown in 2 is generated.
At this time, the slave station address is stored in the address field 23 of the control slot 20, the reserved amount is stored in the allocation amount field 25,
The reception result is set in the command field 24. Once a transmission trigger is generated, the transmission trigger generation means 51 generates a new transmission trigger at intervals corresponding to the allocated amount assigned to the slave station. The multiplexing means 54 outputs the control slot 20 (FIG. 2) when it is input, and the router 40 otherwise.
(FIG. 4) outputs the data written in the transmission buffer 53.

After transmitting the transmission instruction signal, the reception trigger generating means 55 starts a timer so as to generate a reception trigger after a time corresponding to the round-trip propagation delay time between the master station and the slave station. When the reception trigger is generated, the reception buffer 56 latches the burst signal 30 having the format shown in FIG. The error detection means 57 performs error detection based on the error detection code included in the received data, and sends the error detection result ed to the slave station management device 42 (FIG. 4). If there is no error, the data accumulated in the reception buffer 56 is sent to the router 40 (FIG. 4). Also,
When an error is detected, the data accumulated in the reception buffer 56 is discarded. The control information receiving means 58 holds the control information indicating the slave station address, the reservation amount, and the presence / absence of an error. This information information ci is sent to the slave station management device 42 (FIG. 4).

FIG. 6 is a block diagram showing the configuration of the slave station management device 42 shown in FIG. The slave station management device 42 includes a slave station table 61, a record reading means 62, and a record writing means 63.

The slave station table 61 stores a plurality of slave station records, and each slave station record is composed of slave station address, command, and allocation amount fields. The record reading means 62 reads the record of the slave station and uses the read record cr of the slave station as the master station access control device 41.
(Fig. 4) Further, the record reading means 62
When one record is read, the next record in the slave station table 61 is read the next time it is read. Further, after reading the last record, the record reading means 62 returns to the head of the slave station table 61 and reads the head record. The record writing means 63 receives the slave station address, the reception result, and the control information ci indicating the reserved amount from the master station access control device 41 (FIG. 4).
The slave station address is written in the address field of the record of the corresponding slave station in the slave station table 61, the reception result is written in the command field of this record, and the reservation amount is written in the allocation amount field of this record.

FIG. 7 is a block diagram showing the configuration of the slave station access control device 43 (subscripts are omitted) shown in FIG. The slave station access control device 43 includes a reception buffer 70, a control slot reception means 71, a transmission control means 72, a retransmission control means 73, a reservation amount calculation means 74, and a read pointer 75.
It comprises a previous read pointer 76, control information generation means 77, a transmission buffer 78, a write pointer 79, an error detection code generation means 80 and a multiplexing means 81.

The reception buffer 70 receives the data slots 21 shown in FIG. 2 and sequentially sends them to the terminal 44 (subscripts omitted). The control slot receiving means 71 receives the control slot 20 shown in FIG. 2, compares the slave station address of the address field 23 of the control slot 20 with the address of the self station, and when these addresses match, this control slot 20 Latch.

When NAK is set in the received command field 24 of the control slot 20, the retransmission control means 73 sets the value of the previous read pointer 76 in the read pointer 75 in advance. As a result, in the case of resending, the previously sent data is sent again.

The terminal 44 (FIG. 4) uses the write pointer 7
The data is written in the position in the transmission buffer 78 indicated by 9. Each time data is written to the transmit buffer 78, the value of the write pointer 79 is incremented to point to the next write position. The read pointer 75 points to the position of the data to be transmitted next to the data in the transmission buffer 78. The reservation amount calculation means 74 calculates the amount of data accumulated in the transmission buffer 78 from the value pointed by the read pointer 75 and the value pointed by the write pointer 79, and is set in the quota field 25 of the control slot 20 from this value. The value of the allocated amount is subtracted to obtain the reserved amount. The control information generating means 77 generates control information ci to be set in the control information field 36 of the burst signal 30 shown in FIG. 3 based on the address of the own station and the reserved amount, and inputs this to the multiplexing means 81. .

The transmission control means 72 uses the read pointer 7
The value of 5 is stored in the previous read pointer 76. The value previously stored in the read pointer 76 will be reloaded in the read pointer 75 when the next retransmission is instructed. After the control information ci is sent from the control information generation means 77, the transmission control means 72 sequentially inputs the data dt in the transmission buffer 78 pointed by the read pointer 75 to the multiplexing means 81. The value of the read pointer 75 is incremented by 1 each time one byte of data is sent.

The error detecting code generating means 80 is the multiplexing means 8
The error detection code ed is generated based on the control information ci and the data dt input to 1, and this is input to the multiplexing means 81. This error detection code ed is set in the error detection code field 35 of the burst signal 30 shown in FIG.

Next, a multi-access communication system according to a second embodiment of the present invention will be described with reference to the drawings. In the second embodiment, there are a plurality of broadcasting lines (downlinks) and a plurality of multi-access lines (uplinks). In the example shown, two broadcast lines (downlink)
And the case where there are two multi-access lines (uplink) will be described.

FIG. 8 is a sequence chart of the communication system according to the second embodiment of the present invention. When the error frequency of the signal received from the slave station becomes equal to or higher than a predetermined threshold value, the master station 11A sequentially transmits the line switching signal to all the slave stations using the line. The downlink and uplink identifiers to be transferred are set in the line switching signal. Upon receiving the line switching signal, the slave station switches the downlink and uplink to the line designated by the line identifier. Master station 11
A starts transmitting a transmission permission signal to these slave stations on the new line.

Example shown in FIG. 8, when the master station 11A and the first to third slave stations 12A ₁ ～12A ₃ are communicating using the line 1, the first to the master station 11A channel switching signal to the line 2 is transmitted to the third slave station 12A ₁ ~12A _3. In the line 2, the fourth to sixth slave stations 12A ₄ ,
Although 12A ₅ and 12A ₆ were communicating with the master station 11A, the _first to third slave stations 12A ₁ to 1A were connected to this line 2.
2A ₃ is newly added for communication.

More specifically, using the line 1, the master station 11A goes to the first to third slave stations 12A ₁ to 12A ₃ ,
Sequentially NAK-added transmission permission signals 90 ₁ and 9
0 ₂ , 90 ₃ is transmitted. Transmission permission signals 90 _{1 to} 90 ₃
The first to third slave stations 12A ₁ ～12A ₃ which received the,
The previous data 91 ₁ , 91 ₂ , and 91 ₃ are transmitted to the master station 11A through the line 1 together with the next reservation amount information. The master station 11A that has received the data 91 ₁ to 91 ₃ from the first to third slave stations 12A ₁ ～12A _3, the data 90
Check for transmission errors by the error detection code has been added to _{1-90 3.} In the illustrated example, the transmission error in the data 91 ₁ and 91 ₃ of the first to third slave stations 12A ₁ ～12A ₃ has occurred, the frequency of errors becomes equal to or greater than a predetermined threshold value, the master station 11A, through line 1, to the first to third slave stations 12A ₁ ～12A _3, respectively, the switching circuit sets the line identifier indicating the channel 2 signal 9
Sending a 2 _1, 92 _2, 92 _3.

On the other hand, using the line 2, the master station 11A
AC to the _{fourth to} sixth slave stations 12A ₄ to 12A ₆ sequentially
Transmission permission signals 93 ₄ , 93 ₅ , 93 ₆ to which K is added are transmitted. 4 that has received the transmission permission signal 93 _{4-93 6}
To the slave station 12A ₄ ～12A ₆ of the sixth, respectively, through line 2, and transmits the data 94 _4, 94 _5, 94 ₆ with the next reservation amount information. The line switching signal 92 ₁ ~
After sending the 92 _3, the master station 11A, through line 2,
NA to the _{first to} third slave stations 12A ₁ to 12A ₃ in order.
The transmission permission signals 95 ₁ , 95 ₂ , 95 ₃ to which K is added are transmitted, and subsequently the _fourth to sixth slave stations 12A ₄ to 1
2A ₆ to the transmission permission signal 95 to which ACK is sequentially added
₄ , 95 ₅ and 95 ₆ are transmitted. Transmission permission signal 95 ₁ ~
95 ₆ first to receiving the sixth slave station 12A ₁ ～12A
₆ is the previous data 96 ₁ , 96 ₂ , 96 ₃ and data 96 ₄ , 9 to the master station 11A through the line 2 respectively.
6 _5, 96 ₆ to send along with the next time of the reservation amount of information.

FIG. 9 shows a format of a downlink frame used in the multi-access communication system according to the second embodiment of the present invention. The structure of the downlink frame is almost the same as that shown in FIG. The differences are as follows.
In the command field 24A of the control slot 20A,
In addition to ACK and NAK, a command indicating a line switching instruction is set. The control slot 20A further includes a line identifier field 28, and when the command set in the command field 24A is a line switching instruction, the line identifier field 28 is set with the identifier of the destination line.

FIG. 10 is a block diagram showing the configuration of the entire system of the multi-access communication system according to the second embodiment of the present invention. The illustrated multi-access communication system includes one master station 11A and first to sixth slave stations 12A ₁
12A ₆ (However, in the drawing, the first to third slave stations 12 ₁
~ 12 ₃ are shown, and the fourth to sixth slave stations 12 ₄ to 1 are shown.
4 ₆ are omitted). There are multiple pairs of downlinks and uplinks. Here, as an example, it is assumed that there are two uplinks / downlinks, such as a first uplink line 46 ₁ , a first downlink line 45 ₁ and a second uplink line 46 ₁ and a second downlink line 45 _2. To do.

The master station 11A comprises a router 40, first and second master station access control devices 41A ₁ and 41A ₂ and a slave station management device 42A. The first to third slave stations 12A ₁ ～12A _3, respectively, and first to third slave station access controller 43A ₁ ～43A ₃ first to third
The terminals 44 _{1 to} 44 ₃ are included.

FIG. 11 is a block diagram showing the configuration of the first master station access control device 41A ₁ shown in FIG.
The first master station access control device 41A ₁ has the same configuration as the master station access control device 41 shown in FIG. 5 except that it has an error frequency measuring means 59. The operation of the other means except the error frequency measuring means 59 is similar to that described with reference to FIG.

The error frequency measuring means 59 is the error detecting means 5
The result of the transmission error is obtained from 7. Error frequency measuring means 5
9 is receiving M (2 ≧ N) burst signals N (N ≧ 3) times.
When an error occurs ≦ M <N) times or more, a first line quality deterioration signal q indicating that the line is deteriorated in quality
Report d ₁ to the slave station management device 42A (FIG. 10).

The second master station access control device 41A
The configuration of No. _{2 is the same as} the configuration of the first master station access control device 41A ₁ , so its illustration is omitted.

FIG. 12 shows the slave station management device 4 shown in FIG.
It is a block diagram which shows the structure of 2A. Slave station management device 42
A is the first and second slave station tables 61 ₁ and 61
₂ , first and second record reading means 62 ₁ and 62 ₂ , first and second record writing means 63 ₁ and 63 _2, and first and second line switching instruction setting means 64 ₁ and 64 ₂ , a line state management table 65, and a record moving means 66.

Each of the first and second slave station tables 61 ₁ and 61 ₂ stores records of a plurality of slave stations, and each slave station record includes fields of a slave station address, a command, a quota, and a line identifier. Composed of. Line state management table 65, the first and second supplied from the first and second parent station access controller 41A ₁ and 41A ₂
It manages the availability of each line based on the line quality deterioration signals qd ₁ and qd ₂ .

The first line switching instruction setting means 64 ₁ is
When the first channel quality deterioration signal qd ₁ is input from the first master station access control device 41A ₁ , the first slave station table 6
1 line switch sets the instruction to all slave stations record commands registered in _1, to set the identifier of the destination line to the line identifier field. In the case of this example, since there is only line 2 other than line 1, an identifier indicating line 2 is set in the line identifier field. However, for example, when there are three uplink / downlink lines and there are lines 2 and 3 other than line 1, line 2 is indicated in the line identifier field of half the slave station records of the first slave station table 61 _1. A line identifier indicating the line 3 is set in the line identifier field of the remaining half of the slave station records.

The operation of the second line switching instruction setting means 64 ₂ is also the same as that of the first line switching instruction setting means 64 ₁ , so its explanation is omitted.

When the command field of the record read from the first slave station table 61 ₁ is set to the line switching instruction, the first record reading means 62 ₁ uses this as the first master station access control device 41A. _{At the same time} , the record moving means 66 is instructed to move the record. Other operations are similar to those of the record reading means 62 described with reference to FIG. The operation of the second record reading means 62 ₂ is similar to the operation of the first record reading means 62 ₁ , and therefore its explanation is omitted. First
And second record writing means 63 ₁ and 63 ₂
The operation of is similar to that of the record writing means 63 described with reference to FIG.

When the record moving means 66 is instructed to move the record, the record moving means 66 moves the record to the end of the slave station table for the line corresponding to the line identifier of the record. As a result, the master station access control device of the destination line continues to transmit the control slot to this slave station.

FIG. 13 is a block diagram showing the configuration of the slave station access control device 43A (subscripts are omitted) shown in FIG. The slave station access control device 43A has the same configuration as the slave station access control device 43 shown in FIG. 7 except that it has a line switching control means 82, a reception line selection means 83, and a transmission line selection means 84. Only the parts different from the slave station access control device 43 will be described below.

The line switching means 82 analyzes the command set in the command field 24A in the control slot 20A (FIG. 9) received by the control slot receiving means 71, and when this command indicates the line switching instruction,
The reception line selection means 83 and the transmission line selection means 84 are instructed to switch the lines, and the line identifier set in the line identifier field 28 in the control slot 20A is sent to the reception line selection means 83 and the transmission line selection means 84. To do. When receiving the line switching instruction from the line switching unit 82, the receiving line selecting unit 83 switches the currently used downlink line to the line designated by the line identifier. Similarly, when the transmission line selection means 84 receives a line switching instruction from the line switching means 82, it switches the currently used uplink to the line designated by the line identifier. As a result, the slave station restarts communication with the master station 11A on the new line.

Next, a multi-access communication system according to a third embodiment of the present invention will be described with reference to the drawings. In the third embodiment as well, as in the second embodiment, there are a plurality of broadcast-type lines (downlinks) and a plurality of multi-access-type lines (uplinks). In the illustrated example, a case will be described where there are two broadcast-type lines (downlinks) and two multi-access-type lines (uplinks).

FIG. 14 is a sequence chart of a multi-access communication system according to the third embodiment of the present invention. When the communication volume of a certain line exceeds a predetermined threshold value, the master station 11B transmits a line switching signal to a part of the slave stations that use that line. Upon receiving the line switching signal, the slave station switches the downlink and uplink to the line designated by the line identifier. The master station starts transmitting a transmission permission signal to these slave stations on the new line.

In the example shown in FIG. 14, when the master station 11B and the first to third slave stations 12A _{1 to} 12A ₃ are communicating using the line 1, the communication amount of the line 1 is reduced. Since the threshold value is exceeded, the master station 11B instructs the first slave station 12A ₁ to switch to the line 2. In the line 2, the fourth to sixth slave stations 12A ₄ , 12A ₅ and 12A ₆ are the master stations 11B.
However, the first slave station 12A ₁ is newly added to the line 2 and the communication is continued.

In detail, using the line 1, the master station
11B is a first to third slave station 12A₁~ 12A_ThreeWhat,
Transmission permission signal 110 to which ACK is sequentially added₁, 11
0_Two , 110_ThreeTo send. Transmission permission signal 110₁~ 1
10_ThreeFirst to third slave stations 12A that received the₁~ 12A
_ThreeTo the master station 11B via line 1 respectively.
111₁, 111_Two, 111_ThreeTogether with the next reservation amount information
Send to First to third slave stations 12A₁~ 12A_ThreeOr
Data 111₁~ 111_Three11B that received the
Checks if the traffic on line 1 exceeds the threshold
You. In the example shown, the traffic on line 1 exceeds the threshold
Therefore, the master station 11A is connected to the first slave station through the line 1.
12A₁Line switching with line identifier indicating line 2 to
Signal 92₁To send.

On the other hand, using the line 2, the master station 11B
AC to the _{fourth to} sixth slave stations 12A ₄ to 12A ₆ sequentially
Transmission permission signals 93 ₄ , 93 ₅ , 93 ₆ to which K is added are transmitted. 4 that has received the transmission permission signal 93 _{4-93 6}
To the slave station 12A ₄ ～12A ₆ of the sixth, respectively, through line 2, data 94 ₄ to the master station 11B, 94 _5, 94
Send with ₆ and next reservation amount information. After transmitting the line switching signal 92 ₁ , the master station 11B sends the first slave station 12A ₁ and the fourth to sixth slave stations 1 through the line 2.
The transmission permission signals 95 ₁ , 95 ₄ , 95 ₅ , 95 ₆ to which ACK is added are sequentially transmitted to 2A _{4 to} 12A ₆ . Transmission permission signal 95 _1, 95 ₄ to 95 ₆ to the first slave station 12A ₁ and 4 that received the sixth slave station 12A ₄ ～12A
_6, respectively, through line 2, and transmits the data 96 _1, 96 _4, 96 _5, 96 ₆ with the next reservation amount information to the master station 11B.

After transmitting the line switching signal 92 ₁ ,
The master station 11B sequentially transmits the transmission permission signal 112 to the second and third slave stations 12A ₂ and 12A ₃ through the line 1.
₂ and 112 ₃ are transmitted. Transmission permission signal 112 ₂ , 11
Second and third slave stations 12A ₂ and 1 that received 2 ₃
2A ₃ respectively transmits the data 113 ₂ and 113 ₃ to the master station 11B through the line 1 together with the next reservation amount information. Since the traffic on line 1 does not exceed the threshold,
The master station 11B sequentially transmits the transmission permission signal 114 to the second and third slave stations 12A ₂ and 12A ₃ through the line 1.
₂ and 114 ₃ are transmitted. Transmission permission signals 114 ₂ and 11
Second and third slave stations 12A ₂ and 1 that received 4 ₃
2A ₃ transmits the data 115 ₂ and 115 ₃ to the master station 11B through the line 1 together with the next reservation amount information.

The master station 11B, which has received the data 96 ₆ from the sixth slave station 12A ₆ through the line 2,
The transmission permission signal 97 ₁ with ACK added is transmitted to the first slave station 12A ₁ . The _first to receive the transmission permission signal 97 1
The slave station 12A ₁ of 2 transmits the data 98 ₁ to the master station 11B through the line 2 together with the next reservation amount information.

Referring to FIG. 15, the multi-access communication system according to the third embodiment of the present invention includes a master station 11
It has the same configuration as that shown in FIG. 10 except that the configuration of B is different from that of the master station 11A shown in FIG. 10 as described later.

That is, the master station 11B uses the first and second
The master station access control device and the slave station management device of FIG.
It is changed from those of the master station 11A shown in FIG. Therefore, reference numerals 41B ₁ and 41B ₂ and 42B are assigned to the first and second master station access control devices and slave station management devices, respectively.

FIG. 16 is a block diagram showing the configuration of the first master station access control device 41B ₁ shown in FIG.
The first master station access control device 41B ₁ has the same configuration as the _first master station access control device 41A ₁ shown in FIG. 11 except that it has the line utilization rate measuring means 60. Below, only the part different from the first master station access control device 41A ₁ will be explained.

The line utilization rate measuring means 60 monitors the total amount of data from the slave station within a fixed time, and when the value exceeds a certain threshold value, the first overflow signal is sent to the slave station management device 42B. sends of ₁ .

The second master station access control device 41B
The configuration of No. _{2 is the same as} the configuration of the first master station access control device 41B ₁ , so its illustration is omitted.

FIG. 17 shows the slave station management device 4 shown in FIG.
It is a block diagram which shows the structure of 2B. Slave station management device 42
In B, the first and second line switching instruction setting means are shown in FIG.
12 except that it is different from that shown in FIG.
It has the same configuration as the slave station management device 42A shown in FIG. Therefore, reference numerals 64A ₁ and 64A ₂ are attached to the first and second line switching instruction setting means. Only the differences will be described below.

The first line switching instruction setting means 64 ₁ is
When the first overflow signal of ¹ is input from the first master station access control device 41A ₁ , of all slave stations registered in the first slave station table 61 ₁ (that is, using the line 1) , A line switching instruction is set in a command of a record of some slave stations based on a predetermined ratio, and an identifier of a destination line is set in a line identifier field. The operation of the second line switching instruction setting means 64A ₂ is similar to the operation of the first line switching instruction setting means 64A ₁ and therefore its explanation is omitted.

It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0074]

As is apparent from the above description, in the present invention, the master station sequentially transmits the transmission permission signal including the channel quota information indicating the channel quota to the plurality of slave stations through the broadcast line. , Each slave station receiving the transmission permission signal transmits the amount of data designated by the line quota information and the line reservation information designating the amount of data to be transmitted next time through the multi-access type line, and the master station , Calculates the line quota to each slave station based on the line reservation amount information received from the slave station, and transmits a new transmission permission signal including the line quota information indicating the calculated line quota, A line is dynamically allocated to each slave station according to the line reservation information from the station, so that each slave station can immediately transmit the necessary data to the master station, which is a flexible multi-access communication system. Can be built.

Further, in the present invention, when there is no error in the data received from the slave station, the master station adds the information of successful reception to the transmission permission signal to be transmitted to the slave station, and transmits it to the slave station. If there is an error in the received data, the transmission permission signal to be transmitted to the slave station is sent with the reception failure information added.When the slave station receives the transmission permission signal with the reception success information added, When the data for the transmitted data is discarded, new data is transmitted, and when the transmission permission signal with the reception failure information is received, the data specified by the line allocation information is included from all the data including the previously transmitted data. Since the data is transmitted, if the received data has an error, it can be efficiently retransmitted with a small delay.

Further, according to the present invention, when there are a plurality of broadcasting type lines and a plurality of multi access type lines between the master station and a plurality of slave stations, the master station has each multi access type line. Record the frequency of error in data reception for each line, and if the frequency of error in reception of a particular multi-access line exceeds a preset threshold, use that particular multi-access line. Sends a line change instruction signal to instruct the change of the broadcast / multi-access line to be used, or the master station constantly records the traffic on each multi-access line. However, if the communication volume in the specific multi-access type line exceeds a predetermined threshold value, for some of the slave stations using the specific multi-access type line,
Since the slave station that has transmitted the line change instruction signal and received the line change instruction signal has switched the broadcast / multi-access line to be used to the broadcast / multi-access line instructed by the line change instruction signal, Another advantage is that the line can be switched automatically when the quality of the line deteriorates.

[Brief description of drawings]

FIG. 1 is a sequence chart for explaining an operation procedure of a multi-access communication system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a format of a downlink frame used in the multi-access communication system according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a format of an upstream frame used in the multi-access communication system according to the first, second and third embodiments of the present invention.

FIG. 4 is a block diagram showing an overall configuration of a multi-access communication system according to the first embodiment of the present invention.

5 is a block diagram showing a functional configuration of a master station access control device used in the multi-access communication system shown in FIG.

6 is a block diagram showing a functional configuration of a slave station management device used in the multi-access communication system shown in FIG.

7 is a block diagram showing a functional configuration of a slave station access control device used in the multi-access communication system shown in FIG.

FIG. 8 is a sequence chart for explaining an operation procedure of the multi-access communication system according to the second embodiment of the present invention.

FIG. 9 is a diagram showing a format of a downlink frame used in the multi-access communication system according to the second and third embodiments of the present invention.

FIG. 10 is a block diagram showing an overall configuration of a multi-access communication system according to a second embodiment of the present invention.

11 is a block diagram showing a functional configuration of a first master station access control device used in the multi-access communication system shown in FIG.

12 is a block diagram showing a functional configuration of a slave station management device used in the multi-access communication system shown in FIG.

FIG. 13 is a block diagram showing a functional configuration of a slave station access control device used in the multi-access communication system according to second and third embodiments of the present invention.

FIG. 14 is a sequence chart for explaining an operation procedure of the multi-access communication system according to the third embodiment of the present invention.

FIG. 15 is a block diagram showing an overall configuration of a multi-access communication system according to a third embodiment of the present invention.

16 is a block diagram showing a functional configuration of a first master station access control device used in the multi-access communication system shown in FIG.

17 is a block diagram showing a functional configuration of a slave station management device used in the multi-access communication system shown in FIG.

[Explanation of symbols]

11, 11A, 11B Master station 12 _{1 to} 12 ₃ , 12A _{1 to} 12A ₆ Slave station 40 Router 41, 41A ₁ , 41A ₂ , 41B ₁ , 41B ₂ Master station access control device 42, 42A, 42B Slave station management device 43 ₁ to 43 ₃ , 43A _{1 to} 43A ₃ slave station access control device 44 _{1 to} 44 ₃ terminal 45, 45 ₁ , 45 ₂ downlink (broadcast type line) 46, 46 ₁ , 46 ₂ uplink (multi-access type line) 51 transmission trigger generation means 52 control slot generation means 53 transmission buffer 54 multiplexing means 55 reception trigger generation means 56 reception buffer 57 error detection means 58 control information reception means 59 error frequency measurement means 60 line utilization rate measurement means 61, 61 ₁ , 61 ₂ slave station table 62 _1, 62 ₂ record reading means 63 _1, 63 ₂ record writing means 64 ₁ 64 _2, 64A _1, 64A _2-line switching instruction setting means 65 line status management table 66 records the moving means 70 receive buffer 71 control slots receiving unit 72 transmits the control means 73 the retransmission control unit 74 reservation amount calculating means 75 reads the pointer 76 last read pointer 77 Control Information Generation Means 78 Transmission Buffer 79 Write Pointer 80 Error Detection Code Generation Means 81 Multiplexing Means 82 Line Switching Control Means 83 Reception Line Selection Means 84 Transmission Line Selection Means

Claims (7)

[Claims] 1. A master station, a plurality of slave stations, a broadcast line for transmitting a signal from the master station to the slave stations, and a slave station from the slave stations to the master station. In a multi-access communication system including a multiple access type line that transmits signals in a time division manner, the master station includes line quota amount information indicating a line quota amount to the plurality of slave stations through the broadcast type line. Each slave station that sequentially transmits the transmission permission signal and receives the transmission permission signal transmits the amount of data specified by the line allocation amount information and the line reservation information that specifies the amount of data to be transmitted next time to the multi-channel. Transmitting through an access type line, the master station calculates a line allocation amount to each slave station based on the line reservation amount information received from the slave station, and a line allocation amount indicating the calculated line allocation amount. New transmission permission including information A multi-access communication system, which transmits a valid signal and dynamically allocates a line to each slave station according to the line reservation information from the slave station. 2. The master station adds information of successful reception to the transmission permission signal to be transmitted to the slave station when the data received from the slave station has no error, and transmits the same. 2. The multi-access communication system according to claim 1, wherein when there is an error in the received data, information of reception failure is added to the transmission permission signal to be transmitted to the slave station, and the signal is transmitted. 3. When the slave station receives the transmission permission signal to which the information of successful reception is added, the data of the previously transmitted data is discarded and new data is transmitted, and information of reception failure is added. The multi-access communication system according to claim 2, wherein when the transmitted transmission permission signal is received, the data designated by the line allocation information is transmitted from all the data including the previously transmitted data. . 4. A plurality of broadcast-type lines and a plurality of multi-access type lines are present between the master station and the plurality of slave stations, and the master station has data for each multi-access type line. The frequency of the reception error of is recorded for each line, and when the frequency of the reception error of the specific multi-access line exceeds a preset threshold, the specific multi-access line is used. 2. The multi-access communication system according to claim 1, wherein a line change instruction signal for instructing a change of the broadcast / multi-access line to be used is transmitted to all the slave stations. 5. The slave station receiving the line change instruction signal switches the broadcast / multi-access line to be used to the broadcast type / multi-access line instructed by the line change instruction signal. The multi-access communication system according to claim 4. 6. A plurality of broadcast type lines and a plurality of multi-access type lines are provided between the master station and the plurality of slave stations, and the master station has respective multi-access type lines. Always records the amount of communication in, and when the amount of communication in a specific multi-access line exceeds a predetermined threshold, some of the slave stations using the specific multi-access line are The multi-access communication system according to claim 1, wherein a line change instruction signal is transmitted to the multi-access communication system. 7. The slave station receiving the line change instruction signal switches the broadcast / multi-access line to be used to the broadcast type / multi-access line instructed by the line change instruction signal. The multi-access communication system according to claim 6.