JP2861653B2 - Random access communication method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is used for packet communication by wireless communication. The present invention relates to a random access communication system that can change the length of a slot depending on the length of a communication packet in random access communication using the slot Aloha system.

[0002]

2. Description of the Related Art In a conventional random access communication system of the slot ALOHA system, the line efficiency is only about 36% at maximum due to packet loss due to collision between packets.

In a system in which data packets of different lengths coexist, two types of slots are prepared, a long data packet is assigned to a long slot, a short data packet is assigned to a short slot, and a blank is sent in the slot. A system that avoids the deterioration of the line efficiency due to the above is adopted.

FIG. 3 is a block diagram showing the configuration of a conventional example. When transmission data is generated from the slave station, the packet division unit 2
At 01, when the packet length is longer than the slot length, the packet is divided according to the slot length. If the number of divisions is larger than the set value, the packet division unit 201 notifies the reservation requesting unit 203 of the number of divided packets. The reservation request unit 203 creates reservation data and inserts it into the transmission data in the transmission buffer 202. Transmission buffer 202
The data is modulated by the modulator 207 according to the timing generated by the slot timing generation circuit 206 and transmitted.

At the central station, the data demodulated by the demodulator 209 is removed from the reservation data by the reception buffer 211 and output as reception data. The reservation data is determined by the reservation receiving unit 212, and a slot that does not overlap with other slave stations is allocated as a reservation slot. The data of the reserved slot is combined with the timing data by the network control circuit 213,
Modulator 2 is inserted into transmission data in transmission buffer 214 and
Modulated at 10 and output.

In the slave station, a slot timing generation circuit 206 generates a transmission timing based on timing data among data demodulated by a demodulator 208. The reception data other than the timing data is output as the reception data after the reservation data is removed in the reception buffer 205. The reservation confirmation unit 204 confirms that the reservation permission information is addressed to the own station, notifies the reservation request unit 203, and notifies the transmission buffer 202 that the slot is assigned to the own station. As a result, the transmission buffer 202 sends out the reserved packets divided into continuous slots.

FIG. 5 is a line access diagram of the above-mentioned conventional system.

When a short packet having a length of one slot or less is transmitted, the packet is transmitted by random access to the latest slot which can be accessed randomly.

When transmitting a long packet, the packet is divided into a plurality of packets according to the slot length. If it is determined that there is a high possibility that a collision will occur when the data is transmitted in a large number and transmitted in a random system, the first packet is transmitted with reservation data added. The slave station receiving the reservation permission from the central station transmits the packet divided into the designated slot.

FIG. 4 is a block diagram showing the configuration of another example of the conventional example. In the network control circuit 311 of the central station, two timings of a long slot and a short slot are generated, inserted into transmission data in the transmission buffer 312, modulated by the modulator 309, and transmitted.

In the slave station, data obtained by removing timing information from the data demodulated by the demodulator 307 is output as received data. The timing information is sent to the slot timing generation circuit 304 to generate long and short slot timings.

When transmission data is generated, the packet length detector 301 compares the length of the packet with the length of the short slot. If the length is short, the packet is sent to the short packet transmission buffer 302. If the length is long, the packet is sent to the long packet transmission buffer 303. The short packet transmission buffer 302 modulates with the modulator 306 in accordance with the short slot timing from the slot timing generation circuit 304 and the long packet transmission buffer 303 with the long slot timing and outputs the modulated signal.

At the central station, the demodulator 308 demodulates and outputs the received data stored in the reception buffer 310.

FIG. 6 is a circuit access diagram of the conventional example shown in FIG. When transmitting a short packet, the packet is transmitted at the timing of the next short slot. When transmitting a long packet, the transmission is performed in accordance with the timing of the next long slot. At this time, the timing of the slot that does not match the packet length is ignored.

[0015]

In such a conventional slot ALOHA system, the length of the slot is determined. Therefore, the slot ALOHA system is used for a line in which data packets of various lengths are mixed and the length of the slot is increased. When matching with the packet, a blank is sent to many of the slots in the case of a short data packet, and there is a problem that the line efficiency is greatly deteriorated as compared with the theoretical value.

When the length of the slot is adjusted to the short data packet, the long data packet is divided according to the length of the slot, and overhead data is added to each of the divided packets. Therefore, if the division ratio is large, there is a problem that the ratio of the overhead to the data increases and the line efficiency becomes lower than the theoretical value.

Further, there is a method in which short slots and long slots are provided in the slots, and the line efficiency is allocated to each of the slots according to the length of the data packet to make the line efficiency close to the theoretical value. When the ratio is not close to the slot ratio, there is a problem that the line efficiency is not improved and the line is not suitable for a line in which the length of the data packet and the ratio of the long and short data packets are changed.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide a system in which the length of a slot is changed according to the length of a communication packet, and the line use efficiency can be improved.

[0019]

According to the present invention, one central station is connected to a plurality of slave stations via a wireless communication path, and the central station and the slave stations temporarily wait for a transmission signal. In a random access communication system including a transmission buffer and a reception buffer for temporarily holding a reception signal, in each of the slave stations, a packet length detection unit that compares a packet length with a set length when transmission data occurs, A slot timing generation circuit that generates slot timing according to the timing information inserted by the central station, and when a packet length is longer than a set length by a detection output of the packet length detection unit,
A reservation requesting unit that forms <br/> operation the reservation request based on the slot length required for long packet transmission, detection output of the packet length detector
If the packet length is shorter than the set length by force
The transmission data is input at the timing of the slot.
If the packet length is longer than the set length,
A transmission buffer in which the reservation request is inserted into the transmission data
And § extracts the reservation request from the data transmitted from the central station, a reservation confirmation unit for notifying the request when was reservation request addressed to the own station in the reservation request part and the slot timing generating circuit A reservation receiving unit that receives a reservation request from the slave station and allocates and notifies a slot that does not overlap with another reservation to the central station, and generates the timing information and combines the transmission request with the reservation request from the reservation receiving unit. And a network control circuit for sending the data to the network.

When receiving the reservation request, the network control unit gives the requesting slave station a number of slots suitable for transmitting the remainder of the long packet, and accesses the slot from another slave station. It is desirable to include means for broadcasting information that prohibits the user from doing so.

[0021]

The slave station transmits a packet in synchronization with the next transmission slot when transmitting a short packet, and transmits a part of the packet and reservation request data to the central station when transmitting long packet data. When the central station receives the reservation request, it gives the requesting child station an appropriate number of slots to transmit the remainder of the long packet, and broadcasts information prohibiting other child stations from accessing the slot. I do. The slave station receiving the reservation permission transmits the long packet data using the designated slot as a long slot.

Thus, when packet data of different sizes is generated in a communication system using the slot Aloha system, the increase in transmission delay is suppressed as much as possible while avoiding the deterioration of line efficiency due to an extra header, and the use efficiency is reduced. Can be improved.

[0023]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment of the present invention.

In the embodiment of the present invention, one central station and a plurality of slave stations are connected via a wireless communication path, and the central station and the slave stations each have a transmission buffer 114 for temporarily suspending a transmission signal. 102 and reception buffers 111 and 105 for temporarily holding a reception signal, and modulators 110 and 1
07 and demodulators 109 and 108, and furthermore, as a feature of the present invention, a packet length detecting unit 101 that compares a packet length with a set length when transmission data occurs, A slot timing generating circuit 106 for generating slot timing according to the timing information inserted by the central station; and a slot necessary for packet transmission when the packet length is longer than a set length based on the detection output of the packet length detector. A reservation request unit 103 that creates a reservation request based on the length and inserts it into transmission data, and extracts a reservation request from the data transmitted from the central station, and reserves the request when it is a reservation request addressed to its own station. A request confirmation unit 104 and a reservation confirmation unit 104 for notifying the slot timing generation circuit 106; A reservation receiving unit 112 for receiving a reservation request from the slave station and allocating and notifying a slot that does not overlap with another reservation; and a network control circuit 113 for generating timing information and transmitting it to the transmission buffer 114 together with the reservation request from the reservation receiving unit 112. When receiving a reservation request, the network control unit 113 gives the requesting slave station a number of slots suitable for transmitting the remainder of the long packet, and sends the slot from another slave station. Means for broadcasting information that prohibits access to.

Next, the operation of the embodiment of the present invention configured as described above will be described.

When the transmission data is generated, the slave station compares the packet length in the packet length detection section 101 with the set length. If the packet length is shorter than the set length, the data is sent to the transmission buffer 102, and modulated and transmitted by the modulator 107 according to the slot timing.
The slot timing generating circuit 106 generates slot timing from a signal inserted into the data by the network control circuit 113 of the central station.

If the packet length is longer than the set length, the packet length detecting section 101 gives the slot length necessary for packet transmission to the reservation requesting section 103. The reservation request unit 103 creates reservation data and inserts it into transmission data in the transmission buffer 102.

The central station checks in the reception buffer 111 whether there is reserved data of the received data demodulated by the demodulator 109. If there is no reservation data, it is output as received data as it is. If there is reserved data, receive buffer 1
11 sends the reservation data to the reservation reception unit 112 except for the reservation data from the received data. The reservation receiving unit 112 allocates a slot that does not overlap with another reservation, and notifies the network control circuit 113 that there is a reserved slot. The network control circuit 113 combines the timing information and the reservation information and sends the combined information to the transmission buffer 114. The transmission buffer 114 inserts control data into transmission data, modulates the data with the modulator 110, and transmits the modulated data.

In the slave station, the reservation information is extracted by the reception buffer 105 from the data demodulated by the demodulator 108 and sent to the reservation confirmation unit 104. When the reservation information is the reservation information addressed to the own station, the reservation confirmation unit 104 notifies the reservation request unit 103 that there is a response to the reservation and notifies the slot timing generation circuit 106 of the reserved slot. The slot timing generation circuit 106 generates a long slot timing for the reserved slot, and outputs a transmission timing signal to the transmission buffer 102. The transmission buffer 102 transmits a long packet to the long slot by being notified by the reservation confirmation unit 104 that the long slot is a transmittable slot.

FIG. 2 is a line access diagram in the embodiment of the present invention. When the slave station transmits short packet data,
It transmits to the central station by random access in synchronization with the next slot. Since random access is a collision system, it may not reach the central station in some cases. At that time, the slave station retransmits the same packet.

When transmitting long packet data, a part of the long packet data and reservation request data are transmitted to the next slot. Upon receiving the reservation request, the central station gives the requesting slave station an appropriate number of slots for transmitting the remainder of the long packet, and broadcasts information prohibiting other slave stations from accessing the slot. . By transmitting a long packet with the designated slot as a long slot, the slave station can transmit an extra header only twice when a reservation request is made and when a long slot is transmitted.

[0032]

As described above, according to the present invention, the length of a slot can be changed according to the length of a communication packet in a random access time division communication system using slot ALOHA. Further, it is possible to connect to a line of a random access system having a good response, and it is possible to increase the efficiency of the line when transmitting long data such as file transfer.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a line access diagram in the embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional example.

FIG. 4 is a block diagram showing the configuration of another example of the conventional example.

FIG. 5 is a line access diagram in a conventional example.

FIG. 6 is a line access diagram in the conventional example shown in FIG.

[Explanation of symbols]

101, 301 Packet length detection unit 102, 114, 202, 214, 312 Transmission buffer 103, 203 Reservation request unit 104, 204 Reservation confirmation unit 105, 111, 205, 211, 305, 310 Reception buffer 106, 206, 304 Slot timing Generation circuits 107, 110, 207, 210, 306, 309 Modulators 108, 109, 208, 209, 307, 308 Demodulators 112, 212 Reservation accepting units 113, 213, 311 Network control circuit 201 Packet dividing unit 302 Short packet transmission Buffer 303 Long packet transmission buffer

Continuation of the front page (56) References JP-A-6-77963 (JP, A) JP-A-5-260051 (JP, A) JP-A-5-235849 (JP, A) JP-A-5-136823 (JP) JP-A-4-354221 (JP, A) JP-A-2-94932 (JP, A) LEEE TRANSACTIONS ON COMMUNICATIONS Vol. COM-31 No. 10, Oct. 1983, Hyong W. Lee et al, "Combined Random / Reservation Access for Packet Switched Transmission Over a Satellite with On-Board Procesessing: PartI-Galmart. 1161-1171 IEICE Transactions B-IIII Vol. J75-B-II II No. 7, July 1992, Takehiko Kawazoe et al. "Aloha system with multiple slots to enable nonprocedural and efficient transmission of variable-length packet signals," pages. 433-497 (58) Fields surveyed (Int. Cl. ⁶ , DB name) H04L 12/28 H04B 7/26 INSPEC (DIALOG) JICST file (JOIS) WPI (DIALOG)

Claims (1)

(57) [Claims] 1. A central station and a plurality of slave stations are connected via a wireless communication path, and each of the central station and the slave stations temporarily suspends a transmission signal and a reception buffer for a reception signal. In the random access communication system provided with a reception buffer, a packet length detection unit that compares a packet length with a set length when transmission data occurs, at each of the slave stations, and a timing inserted by the central station. A slot timing generation circuit for generating slot timing according to the information; and when the packet length is longer than a set length based on a detection output of the packet length detection unit, a reservation request is generated based on a slot length necessary for transmitting a long packet. a reservation requesting unit that makes the packet length by the detection output of the packet length detector is set
If the length is shorter than the specified length,
The transmission data is input in the packet and the packet length is set.
If the length is longer than the specified length, the reservation request
A transmission buffer to be inserted into the data, and a reservation request extracted from the data transmitted from the central station, and when the reservation request is addressed to the own station, the request is transmitted to the reservation request unit and the slot timing generation circuit. A reservation receiving unit that receives a reservation request from the slave station and allocates and notifies a slot that does not overlap with other reservations; and a timing receiving unit that generates timing information from the reservation receiving unit. A network control circuit for sending to the transmission buffer together with a reservation request , wherein the network control unit receives a reservation request,
Slots of the number, suitable for sending the remaining length packets
To the requesting slave station, and from the other slave station to that slot.
A random access communication system comprising means for broadcasting information that prohibits access.