JPH02166845A - Time slot reservation control system - Google Patents

Abstract

PURPOSE:To improve the using efficiency of a time slot by varying a reservation area and an information area within frame length according to the using frequency of the time slot. CONSTITUTION:Since the data of length '4' appears in a slave station A and the data of the length '3' appears in the slave station B by the start time of a first frame, both the slave stations A and B select first time slots between first and second time slots belonging to the reservation area, and transmit respective reserved packets. At a master station 11, collision is detected in a first time slot of a first frame by a collision detecting part 26, and thus, an ACK signal is generated by an ACK signal generating part 27, and in a reserved line distribution determining part 30, the number of the time slots belonging to the reservation area is increased from '2' to '4', and a reservation area distribution signal is generated. Such the ACK signal and a reservation distribution signal are informed to all the slave stations 12 by the start time of a third frame of a time series for every slave station 12 to transmit.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention provides a time slot system for reserving time slots when transmitting notes between a master station and a plurality of slave stations. Regarding reservation control method.

(Prior Art) FIG. 4 shows the structure of a frame of a line from a slave station to a master station in a reservation type TDMA time slot reservation control system based on the reservation Aloha system. In FIG. 4, the line from the slave station to the master station is divided into time slots 1 that are equally spaced in time, and frame 2 is composed of a fixed number of consecutive time slots (12 in FIG. 4). Each time slot within frame 2 belongs to either reserved area 3 or information area 4. Here, 5 indicates the boundary between the reserved area and the information area.

As a reservation type TDMA time slot reservation control system using the conventional reservation Aloha method, for example, see the document Shuji Tasaka 2.
Co-authored by Yutaka Ishibashi, “A Revelation Prot.
ocolfor 5atellite Packet
Corrmunication-A Performance
manceAnalysis and 5tabili
ty Con5ideration J (IEEE
Transactions, Volume C0M-32, No. 8, 92
0-927, August 1984).

The slave station that has generated data to be transmitted to the master station randomly selects one time slot 1 belonging to the reserved area in frame 2 after generation and growth, inserts a reservation packet into the relevant time slot 1, and sends the data to the master station. transmit to the station. When the reservation packet reaches the master station without colliding with reservation packets from other slave stations, the reservation packet is queued in the master station's queue, and the master station waits for the allocation of time slot 1 belonging to information area 4. This is performed for the slave stations that have reservation packets in the queue, and the slave stations assigned time slot 10 of information area 4 insert data into time slot 1 and transmit it to the master station. on the other hand,
When the slave station learns that the transmission of the reservation packet has failed, it randomly selects one time slot 1 belonging to the reservation area 3 of the next frame 2 and retransmits the reservation packet. At this time, the number of time slots 1 belonging to the reserved area 3 and the information area 4 within the frame 2 is equal within any frame 2. That is, the boundary 5 between the reserved area and the information area is fixed in all frames 2.

(Problem to be Solved by the Invention) However, in the conventional reservation type TDMA time slot reservation control method based on the reservation method, the boundary between the reserved area and the information area is fixed in all frames, so that the slave station As the frequency of data occurrence increases, collisions in the reserved area will occur more frequently, leaving the data line unnecessarily vacant, and as a result, the efficiency of using the line from the slave station to the master station will decrease. .

As a means to improve such a decrease in line usage efficiency, for example, as described in Japanese Patent Application Laid-Open No. 168435/1982, when the number of collisions on a reserved line exceeds a certain threshold, There is a method of dividing the time slots belonging to a reserved line into smaller pieces temporally, but if the time slots belonging to a reserved line are subdivided, highly accurate synchronization technology is required to synchronize the entire communication system. It ends up.

The present invention has been made in view of this point, and it prevents the information area from becoming unnecessarily vacant even if the frequency of data generation in the slave station increases without subdividing the slot. It is an object of the present invention to provide a time slot reservation control method that can improve the efficiency of time slot usage for stations.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an information area for transmitting packets within a frame composed of a plurality of time slots, and a time slot in this information area. In a slot reservation control method in which packets are transmitted between multiple slave stations and a master station by dividing them into reserved areas and sharing a transmission path configured by frames, the master station transmits packets between at least multiple slave stations. This system is characterized in that the ratio of the information area to the reserved area is varied depending on either the number of time slots reserved by the station or the number of 4-bit collisions within the reserved area.

(Function) The frames that make up the transmission path are divided into an information area and a reserved area, and multiple slave stations must ensure that the time slots in either area are not unused or overused. The ratio of the information area to the reserved area is varied depending on the number of reserved time slots and the number of packet collisions within the reserved area.

By making these regions variable, it is possible to improve the utilization efficiency of time slots within these regions.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of a satellite communication system showing an embodiment of the present invention. Still, FIG. 2 is a diagram showing one configuration of a master station according to the present invention. FIG. 3 is a diagram showing one configuration of a slave station according to the present invention. FIG. 4 is a diagram showing one structure of a frame. FIG. 5 is a diagram showing a packet structure from a slave station to a master station according to the present invention. Figure 6 shows
FIG. 3 is a diagram showing a packet structure from a master station to a slave station.

As shown in FIG. 1, in a satellite communication system implementing the present invention, a master station 11 and a plurality of slave stations 12 are connected to a communication satellite 13.
There are 7 systems for transmitting data via a line 14 called outbound, and communication from the master station to each slave station is carried out in a circular manner using a line 14 called outbound. That is, all the slave stations 12 can receive the signal from the master station 11. On the other hand, communication from each slave station to the master station is performed using a line 15 called inbound, but since each slave station 12 cannot know the status of other slave stations 12, it cannot be controlled by the master station 11. , and therefore only communicates.

In FIG. 2, the master station 11 has an antenna 21 that transmits and receives radio waves from the communication satellite 13, a receiver 22 that receives signals from each slave station 12, and a frame and time slot according to a synchronization signal included in the received signal. a synchronization unit 23 that synchronizes the received time slots; a switch 24 that identifies whether the received series of time slots belong to the reserved area or the information area; The receive data buffer 25, which stores packets sent in synchronization with time slots, determines whether or not a collision has occurred between the reservation packets synchronized with the time slots belonging to the reserved area. a collision detection unit 26 that detects a collision using a redundant signal for collision detection; and an ACK unit that generates an ACK signal for notifying each slave station of a retransmission request signal if a collision is detected and an acknowledgment signal if no collision is detected. The signal generating unit 27 and the collision detecting unit 26 extract the slave station number that transmitted the reservation packet and the reservation request signal from the reservation packets synchronized with the time slots belonging to the reservation area in which no collision was detected, and extract these. The queuing section 28 sequentially stores and forms a queue, and the time slot belonging to the reserved area of the currently received frame is monitored, and the output result of the collision detecting section 26 and the queuing section 28 a traffic estimation unit 29 that estimates the traffic of the inbound line 15 according to the length of the queue; and the number of time slots in which collisions are detected in the reserved area in the currently received frame is equal to or greater than a threshold; If the length of the queue is less than or equal to the threshold, the number of time slots belonging to the reserved area of the next frame is increased compared to the currently received frame, and if the length of the queue is greater than or equal to the threshold, Decrease the number of time slots belonging to the reserved area of the next frame from the currently received frame; otherwise, reduce the number of time slots belonging to the reserved area of the next frame from the currently received frame. Equally, identify the time slots that belong to the reserved area and the time slots that belong to the information area of the next frame, or determine the number of time slots for which collisions were detected in the reserved area of the currently received frame and the queue size. A reserved line that generates a signal for identifying the time slots belonging to the reserved area and the time slots belonging to the information area of the next frame according to a certain predetermined function whose length is a parameter, and for reporting such information to each slave station. According to the outputs regarding the information area from the allocation method determination unit 30 and the reservation line allocation determination unit 30, the reservation packets lined up at the head of the queue unit 28 are sequentially allocated to the time slots belonging to the information area. ACK Signal generation unit 27, reservation area allocation determination unit 30, information area request allocation unit 31, and timing signal generation unit 32
A signal synthesis section 33 synthesizes the respective outputs of and generates a signal for controlling all the slave stations 12 for each frame, and a signal synthesis section 33 that synthesizes the outputs of the signal synthesis section 33 for each frame to generate a signal for controlling all the slave stations 12. and a transmitting section 34 for transmitting data to.

Here, the signal transmitted from the master station 11 to each slave station 12 in a broadcast manner, that is, the output of the signal synthesis section 33, is a synchronization signal that is the output of the timing signal generation section 32, as shown in FIG. 41, an ACK signal 42 which is the output of the ACK signal generation unit 27, a reserved line allocation signal 43 which is output to the reserved line allocation determining unit 30, and a data line allocation signal 44 which is the output of the data line request allocation unit 31. It consists of

On the other hand, in FIG. 3, the slave station 12 has an antenna 51 that transmits and receives radio waves from the communication satellite 13, a receiver 52 that receives signals from the master station 11, and a synchronization signal 41 that extracts the synchronization signal 41 included in the received signal. , a synchronization unit 53 that synchronizes frames and time slots, and extracts an ACK signal 42 included in the received signal, and if the ACK signal 42 is an acknowledgment signal, discards the reservation packet corresponding to the ACK signal 42, or If the ACK signal 42 is a retransmission request signal, an ACK signal detection unit 54 generates a command to retransmit the reservation packet corresponding to the ACK signal, extracts the reservation area allocation signal 43 included in the received signal, and extracts the reservation area allocation signal 43 contained in the received signal, a reserved area allocation detection unit 55 that outputs a signal identifying whether each time slot 1 belongs to a reserved area or an information area; and an information area allocation signal 44 included in the received signal. A data line allocation detection unit 56 outputs a signal that extracts the number of the slave station 12 assigned to each time slot belonging to the information area of the next frame, and detects the length of the data to be transmitted to the master station 12. A data length detection unit 57 detects the length of the data, and divides the data into packets with a length that can be synchronized to one time slot of the inbound line 15, stores this, and sequentially discards packets transmitted in the time slots belonging to the information area. A transmission data buffer 58 that transmits a signal representing a request for allocation of a time slot belonging to the information area prior to packet transmission, and a redundant buffer for collision detection that allows the collision detection unit 26 of the master station 11 to detect a collision of reservation packets. This signal generates a reservation packet to be transmitted to the master station 11 in synchronization with the time slot node belonging to the reservation area, and the master station transmits an AC signal to the reservation packet.
A reservation signal generation unit 59 stores the K signal 42 until it becomes an acknowledgment signal, and a reservation area allocation detection unit 55 determines whether each time slot in the frame belongs to a reservation area or not. The reservation signal generation unit 59 identifies whether the reservation belongs to the area and has not received an acknowledgment signal from the master station 11.
If the time slot is stored in the reserved area of the next frame, one time slot belonging to the reserved area of the next frame is selected at random, and the reserved packet stored in the reservation signal generation unit 59 is synchronized with the related time slot. If there is a time slot/node assigned to the own station among the time slots belonging to the information area allocation detection section 56, transmission is performed to sequentially synchronize the data stored in the transmission data node 58 with the relevant time slot. The transmitting unit 61 includes a timing switch 60 and a transmitting unit 61 that transmits packets synchronized to each time slot by the transmitting timing switch 60 to the inbound line 15 via the transmitting/receiving device 51.

Here, as shown in FIG. 5(a), a reservation packet that is synchronized with a time slot belonging to a reserved area includes a synchronization signal 70, a slave station number 71 indicating the address of its own station, and a time slot belonging to the information area. It is composed of a reservation request signal 72 representing the number of time slot allocation requests, and a collision detection redundant signal 73 for enabling the master station 11 to detect collisions of reservation packets.

On the other hand, a packet synchronized to a time slot belonging to the information area is composed of a synchronization signal 70, a slave station number 71, and a data signal 74, as shown in FIG. 5(b).

Next, an example of the operation of the nokkerato transmission according to the present invention will be explained using FIG. In FIG. 7, 80 indicates each slave station 12.
81 represents a time sequence transmitted by the master station 11, and 81 represents a time sequence received by the master station 11. Still, each frame is composed of 6 time slots, and each frame has 6 time slots as an initial state.
The second to second time slots belong to the reserved area, the third to sixth time slots belong to the information area, and the queue section 2 of the master station 11
The length of the queue of No. 8 is assumed to be zero, the threshold value regarding the number of collision slots in the reservation area allocation determining unit 30 is assumed to be 1, and the threshold value regarding the queue is assumed to be 2.

By the first frame start time, data of length 4 is generated in slave station A and data of length 3 is generated in slave station B, so slave stations A and B are connected to the first and Among the second time slots, both the first time slots are selected and each reservation packet is transmitted. The master station detects a collision in the first time slot of the first frame in the collision detection unit 26, generates an ACK signal 42 in pAcKAc raw signal generation, and in the reservation line allocation determination unit 30 detects the collision in the time slot that caused the collision. Since the number exceeds the threshold value, the number of time slots belonging to the reserved area is increased from 2 to 4, and a reserved area allocation signal 43 is generated. The ACK signal 42 and reservation allocation signal 43 are transmitted to each slave station 1.
All slave stations are notified by the start time of the third frame of the time sequence 80 transmitted by No. 2.

On the other hand, by the second frame start time, data of length 5 is generated in slave station C, and slave station C
and selects the second time slot among the second time slots and transmits the reservation packet. Since the master station 11 did not detect a collision in the second frame, it adds 5 to the queue in the queue unit 28 in response to the reservation request signal 72 from the slave station C.

As a result, the length of the queue in the queue unit 28 becomes equal to or greater than the threshold value, so the number of time slots belonging to the reserved area is reduced from 2 to 1, and the reserved area allocation signal 43 is generated.
The information area allocation requesting unit 31 allocates the first 5 slots in the queue of the queue unit 28, that is, the slave station C, to the second to sixth time slots belonging to the information area, thereby allocating the information area. A signal 44 is generated. The ACK signal 42, reserved area signal 43, and information area allocation signal 44 are transmitted to each slave station 12.
All slave stations are notified by the start time of the fourth frame of the time sequence 80 transmitted by.

By the start time of the third frame, slave stations A and B, which have learned of the collision of the reserved packets transmitted in the first frame, simultaneously know that the first to fourth time slots belong to the reserved area in the third frame. , selects the first time slot and the fourth time slot of the third frame, respectively, and retransmits the reservation packet. Since the master station 11 receives the two reservation packets without collision, the master station 11 transfers the reservation packet 4 to the queue section 28 based on the reservation request signal 72 from the slave station A received in the first time slot.
In addition, 3 is added to the queue section 2 in response to the reservation request signal 72 from slave station B received in the fourth time slot.
Add to queue for 8. As a result, the length of the queue in the queue section 28 becomes 7, which is equal to or greater than the threshold value, so the number of time slots belonging to the reserved area is reduced from 4 to 1, the reserved area allocation signal 43 is generated, and the information area Allocation request section 31
, for the second to sixth time slots belonging to the information area, the first 51 queues of the queue section 28, that is,
The slave station A is assigned to the 2nd to 5th time slots, and the 6th time slot is
The slave station B is assigned to the time slot and an information area assignment signal 44 is generated. The ACK signal 42, reservation allocation signal 43, and information area allocation signal 44 are reported to all the slave stations by the start time of the fifth frame of the time sequence 80 transmitted by each slave station 12.

The subsequent frame 2 proceeds in a similar manner.

In the above embodiment, the reservation packet from the slave station 12 is shown as an example in the configuration shown in FIG. Data signal 74 in the reservation packet as shown in the figure.
It is also possible to adopt a configuration in which .

〔Effect of the invention〕

As described in detail above, according to the present invention, the master station determines at least one of the number of packet collisions in the reserved area and the number of time slots in the information area reserved using the reserved area. The ratio between the reserved area and the information area is determined accordingly. That is, the reserved area and the information area can be varied within the frame length depending on the frequency of use of the time slot.

Therefore, time slot utilization efficiency is improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a satellite communication system implementing the present invention, FIG. 2 is a block diagram of a master station according to the present invention, and FIG.
FIG. 4 is a configuration diagram of a slave station according to the present invention. FIG. 4 is a diagram showing a frame configuration. FIG. 5 is a diagram showing a packet configuration from a slave station to a master station according to the present invention. FIG. FIG. 7 is a diagram showing a packet structure sent to a slave station, FIG. 7 is a diagram showing an operation example according to the present invention, and FIG. 8 is a diagram showing a packet structure sent from a slave station to a master station according to the present invention. DESCRIPTION OF SYMBOLS 11... Master station, 12... Slave station, 13... Communication satellite, 14... Inbound line, 15... Outbound line, 21... Antenna, 22... Receiving section, 2
3...Synchronization section, 24...Switch, 25...Reception data buffer, 26...Collision detection section, 27...A
CK signal generation unit, 28... Queue unit, 29... Traffic estimation unit, 30... Reservation area allocation determination unit, 31.
... Information area request allocation unit, 32... Timing signal generation unit, 33... Signal synthesis unit, 34... Transmission unit, 51
. . . Antenna, 52 . . . Receiving unit, 53 .・・・
Data length detection unit, 58... Transmission data buffer, 59
. . . Reservation signal generation section, 60 . . . Transmission timing switch, 61 . . . Transmission section. Agent Patent Attorney Noriyuki Chika Yudo Mitsuru Matsuyama Figure 1 Figure 1

Claims (1)

[Claims] A frame made up of multiple time slots is divided into an information area for transmitting packets and a reservation area for reserving the time slots in this information area, and the transmission path made up of the frames is shared. In the slot reservation control method for transmitting the packets between a slave station and a master station, the master station transmits at least the number of time slots reserved by the plurality of slave stations or the number of packet collisions within the reserved area. A time slot reservation control method characterized in that the ratio between the information area and the reserved area is varied depending on either one of them.