JPH05160776A - The same information data transmission system in radio communication - Google Patents

Abstract

PURPOSE:To avoid a disadvantage of deterioration in the transmission efficiency of a reception station with excellent line quality due to the presence of a reception station with bad line quality by dividing object reception stations into plural groups and using a different communication channel from each group so as to send data. CONSTITUTION:A supervisor 11 of a transmission station 4 uses an ARQ12-1 to send data to all reception stations 3-4-6 at the start of data transmission. In parallel therewith, a line quality measurement section 10 measures the line quality for each reception station when a prescribed frame number is sent or till a prescribed time elapses. The supervisor 11 divides the reception stations 3-4-6 into plural groups based on the result of measurement of the line quality and a line quality threshold level, distributes the data to ARQ12-1-2 and implements data transmission continuously by using a communication channel different from each group. Then the interrupt of a multiple address communication line is informed to a reception station belonging to a group whose data transmission is finished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadcast data transmission system in wireless communication.

[0002]

2. Description of the Related Art Broadcast communication is one of communication services in a wireless communication system. FIG. 4 shows a broadcast data transmission method in satellite communication. In the figure, 1 is a communication satellite,
2 is an area where radio waves from the communication satellite 1 reach, 3-1 to 3-3-
3 is a receiving station for receiving broadcast data, 4 is a transmitting station, and 5 is a transmission frame.

In the broadcast communication, the transmitting station 4 transmits the transmission frame 5 only once, and a plurality of receiving stations 3-1 to 3-3 are used.
It has a feature that the same data can be transmitted to all of them simultaneously. However, if the line quality of the satellite line is poor, the data may be erroneous, so that it is necessary to apply the transmission method using ARQ in order to obtain higher transmission quality.

FIG. 5 shows that Selective-Repeat ARQ (S) is used when there is a receiving station with poor channel quality.
An example of broadcast data transmission when the R-ARQ) method is applied is shown. The SR-ARQ method is an ARQ method that requests retransmission of only frames in which an error is detected among frames received by a receiving station, and is a basic ARQ in one-to-one communication.
It has the best transmission efficiency among the methods.

That is, if the frame error rate is Pf and the buffer capacity at the receiving station is infinite, the transmission efficiency is 1-Pf. However, when applying ARQ to broadcast communication, the effective frame error rate varies depending on the number of receiving stations.

Now, assuming that there are R receiving stations and all the receiving stations have the same frame error rate Pf, the effective frame error rate Ps as seen from the transmitting station (any of the receiving stations among the R stations is seen). The error probability) is Ps = 1- (1-Pf) ^R.

This is because in broadcast communication, if the frame transmitted from the transmitting station is erroneous in at least one of all the receiving stations, the frame must be retransmitted.

[0008]

As described above, when ARQ is applied to broadcast communication, an increase in the number of receiving stations R and a deterioration in the frame error rate Pf of the receiving stations are factors that reduce the transmission efficiency. Furthermore, if even one station has a receiving station with an extremely poor error rate Pf, all the other receiving stations with good line quality will suffer from a decrease in transmission efficiency due to the influence of that one station.

In FIG. 5, although the receiving stations I and II have already correctly received the data having the transmission sequence numbers 1 to 5 of the data frame transmitted from the transmitting station, the receiving station III erroneously received them. Therefore, a new data frame cannot be received from the transmitting station, and data that has already been correctly received must be continuously received until the receiving station III correctly receives it.

As described above, the AR that has been conventionally used
When the Q method is applied to the broadcast communication, there arises a problem that a receiving station with poor line quality lowers the transmission efficiency of the receiving station with good line quality and binds the receiving station for a long time.

As described above, the conventional method has a problem in that if there is even one receiving station with poor line quality, the transmission efficiency of all other receiving stations is reduced. The present invention solves the above-mentioned drawbacks of the conventional method, and even if there is a receiving station with poor line quality, data transmission is terminated in a short time for a receiving station with good line quality, and it is meaningless. It is an object of the present invention to provide a broadcast data transmission method that does not perform long-term restraint.

[0012]

According to the present invention, the above-mentioned problems are solved by the means described in the claims. That is, the present invention, in the wireless communication system,
From the start of data transmission, the transmitting station transmits data for all broadcast target receiving stations using the same communication channel until a predetermined number of frames have been transmitted or a predetermined time has elapsed, The line quality of each receiving station is measured, the receiving target stations are divided into a plurality of groups according to the measurement result of the line quality and a plurality of predetermined line quality threshold levels, and different communication channels are used for each group. Continue data transmission using
The broadcast target receiving station belonging to the group that has completed the data transmission is a broadcast data transmission system configured to release the communication connection with the transmission station when the data transmission is completed.

[0013]

According to the present invention, the transmitting station, at the start of data transmission, transmits data to all the receiving stations to be broadcast using the same channel. The transmitting station is transmitting data
The channel quality is measured for each receiving station to be broadcast until a predetermined number of frames are transmitted or a predetermined time elapses.

After that, the transmitting station determines, based on the measurement result of the line quality and the preset threshold levels of the plurality of line qualities, all the receiving stations to be broadcast to a plurality of groups for each receiving station having the same line quality. Then, data transmission is performed again using a different communication channel for each group.

Therefore, according to the method of the present invention, after the grouping, the receiving station with good line quality can perform efficient data transmission without being affected by the receiving station with bad line quality. In addition, since the group with good line quality completes data transmission before the group with poor line quality, unlike the method of simultaneously transmitting data to all receiving stations, the receiving stations belonging to the group that completed data transmission first Has an advantage that it can be released from the broadcast line at that point and can perform other communication.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a timing chart and signal configuration used in the broadcast data transmission system of the present invention. Note that this example shows the case where the number of receiving stations is three. In the figure, a indicates the signal transmission timing of the transmitting station, in which 5 is a transmission frame, 7 is a unique word, 8 is a control signal, and 9 is data.
Further, b, c and d in the same figure respectively show the response signal transmission timing of the receiving stations I, II and III, and these signals are transmitted in a time division manner so as not to collide.

The response frame 6 transmitted by the receiving station comprises a unique word 7, a control signal 8 and data 9. This signal is a response signal to the control signal from the transmitting station or A
It is used as a response signal for RQ. Further, FIG. 2 shows an example of the structure of the broadcast data transmission system and the transmitting station in the system of the present invention.

Note that this figure shows a case where three receiving stations using the same channel are divided into two groups by measuring the respective channel qualities, and different communication channels are assigned to each group. ing.
In the figure, 3-4 and 3-5 are receiving stations belonging to group 1, 3-6 are receiving stations belonging to group 2, 10 is a line quality measuring unit, 11 is a supervisor, 12-1 and 2 are ARQ, 13 Is a data source, and 14 is a transmitting antenna.

An example of the operation of the transmitting station 4 will be described below. At the start of data transmission, the transmitting station 4 receives all the receiving stations 3-4 ...
6, data transmission is performed using the same communication channel. After that, the channel quality for each receiving station is measured while transmitting data using the same channel until a predetermined number of frames are transmitted or until a predetermined time elapses.

That is, in the transmitting station 4, the supervisor 11 regards all the receiving stations 3-4 to 3-6 as a group 1 at the start of data transmission and performs data transmission using the ARQ (1) 12-1. The line quality measuring unit 10 measures the line quality for each receiving station. The concrete measuring method of the line quality is as follows.

In the present embodiment, as shown in FIG. 1, each receiving station responds to all transmission frames 5 sent from the transmitting station 4 to itself by a response signal (ACK or NAC).
K) is returned, so when the transmission of the X frame is completed after the data transmission is started in the transmitting station 4, or
By counting the number of ACKs returned from each receiving station by the time when a predetermined time has elapsed (here, for the sake of simplicity, it is assumed that the transmission of X frames has just completed at that time), It is possible to measure the frame error rate for each receiving station.

For example, assuming that the number of transmitted frames is X and the number of received ACKs is Y, the frame error rate Pf can be calculated by Pf = (1−Y) / X. At this time, it is considered that the response frame 6 transmitted by each receiving station does not cause an error because the frame length is very short.

The transmitting station 4 divides the receiving stations 3-4 to 6 into a plurality of groups based on the measurement result of the line quality, and uses the data 9 of the transmission frame 5 to divide the receiving stations 3-4 to 6 into groups. Notify the result.

Since this notification needs to guarantee sufficient reliability, it is continuously transmitted over a plurality of frames. In FIG. 2, receiving stations I and II (3-4, 3-5) are classified into group 1, and receiving station III (3-6) is classified into group 2. Upon receiving the notification of grouping, each of the receiving stations 3-4 to 6-6 replies that the grouping is recognized by using the control signal 8 of the response frame 6. After that, transmitting station 4
After receiving a response that all the receiving stations 3-4 to 5 have recognized the result of grouping, the data is transmitted using a different communication channel for each group.

The supervisor 11 adds the group number corresponding to the control signal 8 of the data frame to be transmitted to the receiving stations belonging to each group, and the corresponding ARQs 12-1 to 12-2.
Data is distributed to and data is transmitted. If the data transmission is completed in either group, the transmission station 4 uses the control signal 8 of the transmission frame 5 to notify the reception stations belonging to that group of the disconnection of the broadcast communication line.

FIG. 3 shows an example of broadcast data transmission in the system of the present invention. The figure shows a case where all the receiving stations are divided into two groups and data transmission is performed for each group by the SR-ARQ method. At the start of data transmission, data is transmitted to all receiving stations on the same channel.

During that time, the transmitting station measures the line quality of each receiving station. Here, the line quality from the transmission of the first transmission frame to the transmission of the eighth transmission frame is measured. Since the receiving stations I and II have correctly received all the frames, the frame error rate Pf is 0.
In the receiving station III, Pf is 1 because all the frames are incorrect.

Therefore, the transmitting station notifies all the receiving stations that the receiving stations I and II are divided into the group 1 and the receiving station III is divided into the group 2 to perform the data transmission using the different communication channels. After that, after confirming the response that the grouping notification is recognized from all the receiving stations, transmission is performed using a different channel for each group.

By doing so, the receiving stations I and II belonging to the group 1 with good line quality are the receiving stations with poor line quality.
Data is transmitted without being affected by III. Receiving station III belonging to group 2 repeats retransmission because the channel quality is poor, but since each group uses an independent communication channel, it does not affect receiving stations of other groups.

[0030]

As described above, in the present invention, at the start of data transmission, the transmitting station starts data transmission using the same channel for all receiving stations to be broadcast. After that, after transmitting a predetermined number of frames or after a predetermined time elapses, the transmitting station measures the line quality of each of all receiving stations to be broadcast.

When the line quality measurement is completed, the transmitting station divides each broadcast receiving target station into a plurality of groups according to a predetermined threshold level of the line quality, and transmits data using different communication channels for each group. To do. Therefore, in the method of the present invention, a receiving station with good line quality is not affected by a receiving station with bad line quality,
It becomes possible to perform efficient data transmission.

Further, since a group with good line quality completes data transmission before a group with poor line quality, unlike a system in which data transmission is performed simultaneously to all receiving stations, a group that has completed data transmission first The receiving station to which it belongs has the advantage that it can be released from the broadcast line at that point and can perform other communications.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a signal configuration used in a broadcast data transmission system of the present invention and a timing chart.

FIG. 2 is a diagram showing an example of a configuration of a broadcast data transmission system and a transmission station of the present invention.

FIG. 3 is a diagram showing an example of broadcast data transmission of the present invention.

FIG. 4 is a diagram showing a broadcast data transmission method in conventional satellite communication.

FIG. 5: Sel when there is a receiving station with poor transmission efficiency
It is a figure which shows the example of broadcast data transmission at the time of applying an active-RepeatARQ system.

[Explanation of symbols]

 1 Communication Satellite 2 Area where Radio Wave from Communication Satellite Reaches 3-1 to 3-6 Reception Station 4 Transmission Station 5 Transmission Frame 6 Response Frame 7 Unique Word 8 Control Signal 9 Data 10 Channel Quality Measurement Section 11 Supervisor 12-1 to 12 -3 ARQ 13 Data Source 14 Transmit Antenna

Claims (1)

[Claims] 1. A transmitting station performs data transmission using the same communication channel to all broadcast receiving stations until a predetermined number of frames have been transmitted or a predetermined time has elapsed from the start of data transmission. However, the channel quality for each receiving station targeted for broadcasting is measured, and the receiving stations targeted for broadcasting are divided into a plurality of groups according to the measurement result of the channel quality and a plurality of predetermined channel quality threshold levels, and each group is divided into groups. Data transmission is continued using different communication channels for each, and the broadcast target receiving station belonging to the group that has completed data transmission releases the communication connection with the transmitting station when the data transmission is completed. A broadcast data transmission method in wireless communication characterized by the following.