JPH1093661A - Retransmission control method - Google Patents

Abstract

An object of the present invention is to provide a retransmission control method capable of preventing unnecessary occurrence of a timeout until a reception response is received and performing efficient data transmission. Kind Code: A1 A predetermined response after transmitting data from one station (1) between two stations (1 and 2) mutually transmitting and receiving data via a bidirectional communication channel (3). When there is no response from the other station (2) within the waiting time,
In the retransmission control method for retransmitting data, one station (1) transmits data to the other station (2) on one logical channel of at least two types of logical channels multiplexed on the communication channel. Thereafter, when another logical channel is received from the other station (2) within the response waiting time measured by the timer 1d, the retransmission control unit 1b extends the response waiting time by a predetermined time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transmitting and receiving data between a portable information terminal (radio terminal) and an information providing station (radio base station) for providing information to the portable information terminal. It relates to a retransmission control method.

[0002]

2. Description of the Related Art When transmitting and receiving data between two stations, for example, as shown in FIG. 13, a sequence number and a parity for error detection are used in a unit of data (called a packet) on the transmitting station side. There is a method of adding bits for transmission.
The sequence number is used for the data to be passed to the receiver in the correct order.

The receiving side checks the packet for errors using parity bits for error detection, and if an error is detected, the transmitting side retransmits the packet in which the error was detected using the sequence number of the packet. A request is made, and the transmitting side retransmits the packet for which the packet retransmission was requested, thereby realizing error-free data transmission.

When such a retransmission control method is used, it is necessary that confirmation of packet delivery be sent from the receiving side to the transmitting side. Here, a case is considered in which the delivery confirmation is performed by sending the number of the packet expected to be received next.

[0005] Packets cannot have physically infinite sequence numbers. For this purpose, a sequence number is used by circulating a predetermined number. Then, for example, when four numbers 0, 1, 2, and 3 are used cyclically, if the sequence number "0"
Despite the fact that the delivery of the packet has not been confirmed,
If a packet with sequence number "3" is transmitted,
Whether the sequence number “0” included in the next acknowledgment is the retransmission request of the packet “0” sent because the first packet “0” did not reach successfully, or the next packet number “3” It is difficult to determine whether the packet is a transmission request for the packet “0”. As a result, the packet “3” cannot be transmitted until the delivery of the first packet “0” is confirmed. Then, if the delivery confirmation of the packet “0” does not return due to some failure, the delivery confirmation is waited forever, and the data transmission cannot be continued any more.

[0006] Therefore, in the retransmission control method, generally, when a predetermined time (response waiting time) has elapsed since the packet transmission on the data transmitting side,
Automatically resend packets. For this purpose, a timer for measuring the passage of time is provided. This timer is called a retransmission timer.

Here, in general packet transmission,
Retransmission processing when a timeout occurs will be described. As shown in FIG. 14, a packet A is transmitted from a transmitting side to a receiving side in a slot a, and the receiving side returns a response packet A 'for the packet A to the transmitting side using a slot a'. For example, if the selective retransmission control method is used, an acknowledgment to the packet A is normally received if the packet A is correctly received in the response packet A ', and if an error is detected in the packet A, A retransmission request for packet A is included. The transmitting side receiving this reception response inserts the next packet B into slot b if packet A 'is an acknowledgment, and inserts packet A into slot b if it is a retransmission request.

At this time, if the timeout period of the retransmission timer is set to two slot times, the response packet A 'may not arrive for some reason or an error may be detected in the response packet A' and the packet may be discarded. When this is done, the response to packet A will not arrive within two slot times, so the retransmission timer times out and packet A is automatically retransmitted in slot b.

In a mobile communication system, for example, as shown in FIG. 15, there is a communication system in which a user channel for transmitting user data and a control channel for transmitting control information are multiplexed on one physical channel.

[0010] In this method, a physical channel is divided at regular time intervals (hereinafter, a division is called a slot), and a user channel or a control channel is used for each slot. Make up another channel. At this time, the slot contains an identifier indicating whether the channel is a user channel or a control channel (FIG. 1).
5, the identifier of the user channel is shown as "u" and the identifier of the control channel is shown as "c").
Using this, a logical channel is multiplexed on a physical channel.

When the conventional retransmission control method as described above is applied to such a communication system and the timer is physically operated, the probability of occurrence of a timeout increases. This will be described with reference to FIG.

As shown in FIG. 14, a packet A is transmitted from a transmitting side to a receiving side in a slot a, and the receiving side returns a response packet A 'for the packet A to the transmitting side. Consider that you have to send

In general, since the occupation time of the physical channel is longer in the user channel than in the control channel,
When the user channel and the control channel are multiplexed, the control channel appears to interrupt the user channel as shown in FIG.

Then, the timer continues to operate for the slot time in which the control channel is in the slot, even though the user channel is stopped. Therefore, the timeout time is set to 2 slot times. Although the response packet A 'is to be returned in the next slot, it times out, and the packet A is retransmitted in the slot b.

That is, the retransmission timer is likely to time out in the user channel for the time that the control channel uses the physical channel. This unnecessarily increases the number of retransmissions, leading to a decrease in throughput. This tendency is considered to be more prominent as the timer has a smaller margin with respect to the round trip delay.

[0016]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and multiplexes at least two types of logical channels on one physical channel to communicate with each other between two stations. In such a communication system, after transmitting data to the other station on one logical channel of a plurality of logical channels, it is possible to prevent the occurrence of an unnecessary timeout before receiving a reception response regarding the data, An object of the present invention is to provide a retransmission control method capable of performing efficient data transmission.

[0017]

According to the retransmission control method of the present invention, data is transmitted from one station between two stations transmitting and receiving data to each other via a bidirectional communication channel. In the retransmission control method for retransmitting data when there is no response from the other station within the response waiting time, one of the stations has one of at least two types of logical channels multiplexed on the communication channel. After transmitting data to the other station, and when receiving a signal of another logical channel from the other station within the response waiting time, the response waiting time is extended by a predetermined time (specifically, By suspending the measurement of the response waiting time for a predetermined time, returning the measurement time of the response waiting time to a predetermined time, and adding a predetermined time to the response waiting time) To prevent generation of unnecessary timeouts for receiving the signal response in advance, it can be performed efficient data transmission.

Further, the retransmission control method according to the present invention transmits / receives data to / from each other via a bidirectional communication channel.
A retransmission control method for retransmitting data between two stations when there is no response from the other station within a predetermined response waiting time after transmitting data from one station, wherein one of the stations has the communication After transmitting data to the other station on one of at least two types of logical channels time-division multiplexed to the channel, counting the number of time slots on the communication channel assigned to the logical channel, By determining the response waiting time based on the count value and retransmitting the data, unnecessary time-out until a reception response is received can be prevented from occurring, and efficient data transmission can be performed.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 schematically shows an example of the simplest configuration of a communication system to which the retransmission control method of the present invention is applied, in which a first station 1 and a second station 2 Communication line 3 between
(Packet data) are mutually transmitted and received via the Internet.

In FIG. 1, since the first station 1 and the second station 2 have the same configuration, an example of the configuration of the first station 1 will be described. The first station 1 includes a transmission / reception circuit 1a as an interface for communicating with the second station 2 via the communication line 3, a retransmission control unit 1b, and a buffer memory for storing transmitted data or received data. 1c, a timer 1d for measuring a predetermined response waiting time after transmitting data to the partner station (second station 2).

In the communication line 3, for example, two types of logical channels (control channel and user channel) are multiplexed on the same physical channel (communication channel).
Communication between the first station 1 and the second station 2 is performed using a user channel.

The retransmission control section 1b performs retransmission for retransmitting data when there is no response from the other station (second station 2) within a predetermined response waiting time after transmitting data from the transmission / reception circuit 1a. It is responsible for control.

When data is transmitted from the transmission / reception circuit 1a, the timers 1d and 1e are started under the control of the retransmission control section 1b, and measure the response waiting time. Note that at least one timer is sufficient.

The retransmission control unit 1b receives the control channel transmitted from the other station (second station 2) multiplexed on the physical channel by the transmission / reception circuit 1a while the response waiting time is measured by the timer 1d. Then, control is performed to extend the response waiting time by operating the timer 1d.

The names of the components of the second station 2 are the same as those of the first station 1. Next, a retransmission processing operation (first operation) in the communication system of FIG. 1 will be described with reference to a flowchart shown in FIG.

When the transmission / reception circuit 1a of the first station 1 transmits a packet that requires confirmation of delivery by the timer to the second station 2, the timer 1d is activated and starts measuring a response waiting time. The retransmission control unit 1b checks the timeout of the response waiting time until a response packet is received from the second station 2 (Steps S1 and S2).

Here, as shown in FIG. 3, the first station 1
The packet A is transmitted from the (transmission side) to the second station 2 (reception side) in the slot a of the user channel, and the reception side transmits a response packet A 'to the packet A using the slot a' of the user channel. Shall be returned to The response waiting time is a time corresponding to one time slot, as shown in FIG.

In step S2, when the timeout of the response waiting time is detected, the retransmission control unit 1b resets the timer 1d, extracts the previously transmitted packet from the buffer memory 1c, and retransmits the packet ( Step S7).

When the timeout has not been detected, the retransmission control unit 1b checks the received packet (step S3). If the packet has not been received, or if the packet is irrelevant even if it has been received, the timer is advanced without doing anything, and the process returns to the time-out check in step S2.

When a correct response packet is received, if the response packet is a normally received response packet, the flow advances to step S6 to stop the timer. When the response packet is an abnormal packet, the process proceeds to step S7, and the retransmission control unit 1b resets the timer 1d and retransmits the packet.

If the received packet is a control channel packet in step S3, the process proceeds to step S4, where the retransmission control unit 1b temporarily stops the progress of the timer 1d for, for example, one slot, and returns to step S2.

By doing so, unnecessary timeout can be prevented. Next, another retransmission processing operation (second operation) in the communication system of FIG. 1 will be described with reference to a flowchart shown in FIG. The same parts as those in FIG. 2 are denoted by the same reference numerals, and different parts will be described. That is, step S4 in FIG. 2 is replaced with step S10 in FIG.

If the received packet is a control packet in step S3, the process proceeds to step S10, where the retransmission control unit 1
b returns the time measured by the timer 1d by one slot, and returns to step S2.

By doing so, unnecessary timeout can be prevented. In the second operation,
The physical channel is divided into slots at equal intervals, and the data is made into packets of the same size according to the slot, but the packets are not made the same size, and there is no slot configuration, so that one physical channel has multiple logical channels. Even when multiplexing data, if the packet has a configuration in which the number of bits or bytes indicating the length of the packet is written, the length of the data on the time axis can be obtained from the number of bits or bytes. . Therefore, when the received packet is a packet of the control channel, an unnecessary timeout can be prevented by returning the time measured by the timer 1d by the time length of the packet.

Next, still another retransmission processing operation (third operation) in the communication system of FIG. 1 will be described with reference to a flowchart shown in FIG. The same parts as those in FIG. 2 are denoted by the same reference numerals, and different parts will be described. That is, step S4 in FIG. 2 is replaced with step S11 in FIG.

If the received packet is a control packet in step S3, the process proceeds to step S11, where the retransmission control unit 1
b adds the time for one slot to the response waiting time measured by the timer 1d (see FIG. 7), and returns to step S2.

By doing so, unnecessary timeout can be prevented. In the above description, the timer 1
Since d is operated in real time, it is effective to apply the method as described above, but the number of slots can be used as a method for setting the response waiting time of the timer 1d.

That is, as shown in FIG.
Using a counter 1g that counts the number of packets instead of
After sending a data packet related to a certain user channel and counting a packet other than a control packet to be received until a reception response from the partner station (second station 2) for the packet is returned, a reception response is returned. When the number of packets received up to this point exceeds a predetermined number, it is determined that a timeout has occurred and retransmission is performed.
By doing so, retransmission by timeout can be performed by a simple method of counting packets, rather than controlling the operation of a timer in real time.

If such a counter and a real-time timer for monitoring a relatively long time span are provided, a more reliable communication path can be provided in the event of a failure. Until now, it has been considered that data is transmitted when the data frame and the packet correspond one-to-one. Next, a retransmission control method when a data frame is divided into a plurality of packets and transmitted is described.

When a data frame is divided into a plurality of packets and transmitted, the receiving station (for example, the second station 2) receives the data frame when the timer operates on a real time basis. It is conceivable that the response waiting time measured by the transmitting station (for example, the first station 1) times out while the data frame is being received while the data frame is being received. It is clear that when a control channel interrupts a user channel, the probability increases.

Therefore, when the data frame is divided into a plurality of packets and transmitted from the transmitting side (for example, the first station 1), the retransmission control unit 1b on the transmitting side responds to the first packet of the data frame. When a reception response packet from the receiving side (for example, the second station 2) is detected, the timer 1d is temporarily stopped. Then, another timer 1e is operated to measure the time until the reception response packets corresponding to the packets from the beginning to the end of the data frame are received, and after the reception of all the reception response packets of these data frames is completed. The timer 1d is advanced at a time for the time measured by the timer 1e. By controlling the timers 1d and 1e in this way, when a desired data frame has arrived, the timer can be reset before the timer is advanced at one time. Timeout can be prevented. Here, as for the operation of another timer 1e, when the control frame is in the middle, the operation may be temporarily stopped or pulled back as described above.

As shown in FIG. 8, it is possible to use counters 1g and 1h for counting the number of packets, instead of the timer for measuring the actual time. That is, when the transmitting side (for example, the first station 1) detects the reception response packet corresponding to the first packet of the data frame, the counting of the number of packets by the counter 1g is temporarily stopped, and the counting by the other counter 1h is stopped. Counting the number of received response packets from the beginning to the end of the data frame, and counting the number of packets counted by the counter 1h after receiving all the received response packets related to the data frame.
The count value of the counter 1g is advanced at a time. In this way, the same effect as described above can be realized by counting the number of packets.

If it is predicted that the control channel interrupt method is uniform in advance, the response waiting time (timer setting value) set in the timer is set to be longer by the frequency of use of the control channel. Is considered to be an effective way to prevent timeout.

Further, it is considered that a method of determining the response waiting time every moment from the interrupt frequency of the control channel a predetermined time in the past is also effective as a method of preventing timeout.

In the above embodiment, a case has been described where a packet is transmitted from the first station 1 to the second station 2, but the packet is transmitted from the second station 2 to the first station 1. Is transmitted in the same manner as described above. (Second Embodiment) The retransmission control method described in the first embodiment is very effective in a communication system having a configuration as shown in FIG. 9, for example. Therefore, as a second embodiment, an application example of the retransmission control method of the present invention will be described.

The communication system shown in FIG.
This is a communication system for performing communication between a wireless terminal 11 and wireless terminals 11 via wireless communication paths 12 and 13. For data transmission from the wireless base station 10 to the wireless terminal 11, the downlink wireless communication path 13
The data transmission from the wireless terminal 11 to the wireless base station 10 is performed via the uplink wireless communication path 12,
The wireless communication path 13 is a communication system with an asymmetric transmission rate capable of transmitting data at a higher transmission rate than the wireless communication path 12.

Mainly, information data is provided from the wireless base station 10 to the wireless terminal 11 via the wireless communication path 13, and the reception response is transmitted via the wireless communication path 12 to the wireless terminal 1.
1 to the wireless base station 10.

In a communication system in which the transmission speed is asymmetric as shown in FIG. 9, information transmission from the radio base station 10 to the radio terminal 11 is desired to be performed as efficiently as possible. However, the conventional retransmission control method, that is, the method of setting the response waiting time is not efficient. This will be described with reference to FIG.

As shown in FIG. 10, information data is transmitted from the radio base station 10 to downlink data packets 61a, 61b,
61c, and transmitted using the wireless communication path 13, and the response to each data packet is placed on the uplink data packets 62a, 62b, 63c,.
2 is transmitted from the wireless terminal 11.

In FIG. 10, the horizontal axis represents time. Since the transmission speed of the wireless communication path 13 is higher than the transmission rate of the wireless communication path 12, a packet containing bits of the same degree is a downlink data packet. However, because the transmission speed is high,
Seems short in time. For this reason, for example, when the uplink data packet 62b is used for the control channel, measurement of a timer for measuring a predetermined response waiting time for the time length (unnecessary time) of the uplink data packet 62b is performed. It is added to the value.

The time length of the uplink data packet 62b is such that the larger the ratio between the transmission speeds of the uplink and downlink wireless communication paths 12 and 13 is, the more downlink data packets are transmitted to the transmitting side (radio base station 10). Equivalent to a minute. Therefore, in the method of determining the timeout by counting the number of packets, the timeout tends to occur when one uplink data packet is used for the control channel.

The case where the retransmission control method of the present invention is applied to the communication system in which the uplink and downlink wireless transmission paths are asymmetric as shown in FIG. 9 will be described below. FIG. 11 shows a radio base station 10 in the communication system as shown in FIG.
An example of the configuration will be described.

The radio base station 10 includes a transmission / reception circuit 10a as an interface for communicating with another radio base station or a database or the like connected via a predetermined network, a radio terminal 11 and an antenna 10b,
A wireless transmission / reception circuit 10c as an interface for communicating with each other via the wireless communication lines 12 and 13, a retransmission control unit 10d, a buffer memory 10e for storing transmitted data, and transmitting data to the wireless terminal 11;
Timer 1 for measuring a predetermined response waiting time (real time measurement, measurement based on the time length of a packet)
0f.

When data is transmitted from the transmission / reception circuit 1a, the timer 10f is started under the control of the retransmission control unit 1b, and measures a response waiting time. FIG. 12 shows a configuration example of the wireless terminal 11 of the communication system as shown in FIG.

The wireless terminal 11 communicates with the wireless base station 10 via the wireless communication lines 12 and 13 and the antenna 11a. It comprises a buffer memory 11c for temporarily storing packet data from the base station 10 and assembling them in a predetermined order, and a control unit 11d for controlling the operation of these units.

The control unit 11d receives the result of monitoring the quality of the packet data from the radio base station 10 received via the radio transmission / reception circuit 11b as a reception response via the radio transmission / reception circuit 11b and the radio communication path 12. It also has a function of transmitting to the wireless base station 10.

Now, an example of the retransmission processing of the communication system having such a configuration will be briefly described with reference to the flowchart of FIG. Note that the description of FIG. 4 is almost the same when the first station 1 is the wireless base station 10 and the second station 2 is the wireless terminal 11, and in this embodiment, the received packet is If so, step S10
The retransmission control unit 10d returns the time measured by the timer 10f by the time length of the uplink data packet, and returns to step S2. Thus, unnecessary timeout can be prevented beforehand, and the system throughput increases.

[0058]

As described above, according to the retransmission control method of the present invention, it is possible to prevent the occurrence of an unnecessary time-out until a reception response is received, thereby enabling efficient data transmission.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a configuration example of a communication system according to a first embodiment of the present invention.

FIG. 2 is a flowchart for explaining a retransmission processing operation (first operation) of the communication system of FIG. 1;

FIG. 3 is a view for explaining the principle of the retransmission processing operation shown in FIG. 2;

FIG. 4 is a flowchart for explaining a retransmission processing operation (second operation) of the communication system of FIG. 1;

FIG. 5 is a view for explaining the principle of the retransmission processing operation shown in FIG. 4;

FIG. 6 is a flowchart for explaining a retransmission processing operation (third operation) of the communication system of FIG. 1;

FIG. 7 is a view for explaining the principle of the retransmission processing operation shown in FIG. 6;

FIG. 8 is a diagram schematically illustrating another configuration example of a communication system.

FIG. 9 is a diagram schematically illustrating a configuration example of a communication system according to a second embodiment of the present invention.

FIG. 10 is a diagram for explaining a problem when a conventional retransmission control method is applied to the communication system of FIG. 9;

FIG. 11 is a diagram schematically illustrating a configuration example of a wireless base station in FIG. 9;

FIG. 12 is a diagram schematically showing a configuration example of the wireless terminal in FIG. 9;

FIG. 13 is a diagram illustrating an example of a packet transmission method.

FIG. 14 is a diagram for explaining a conventional retransmission control method.

FIG. 15 is a diagram for explaining a communication method for multiplexing a user channel for transmitting user data and a control channel for transmitting control information on one physical channel.

FIG. 16 is a diagram for explaining a problem of a conventional retransmission control method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st station, 1a ... Transmission / reception circuit, 1b ... Retransmission control part,
1c: buffer memory, 1d, 1e: timer, 1g, 1
h ... counter, 2g, 2h ... counter, 2 ... second station,
2a transmission / reception circuit, 2b retransmission control unit, 2c buffer memory, 2d, 2e timer, 3 communication line, 10 wireless base station, 11 wireless terminal, 12 wireless communication path (low speed), 13 wireless Communication path (high speed).

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Mutsuri Serizawa 1 Tokoba, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa

Claims (5)

[Claims] 1. A communication between two stations that transmit and receive data to and from each other via a bidirectional communication channel, and a response from the other station within a predetermined response waiting time after transmitting data from one of the stations. In the retransmission control method for retransmitting data, when one station transmits data to the other station on one logical channel of at least two types of logical channels multiplexed on the communication channel, A retransmission control method characterized in that when a signal of another logical channel is received from the other station within the response waiting time, the response waiting time is extended by a predetermined time. 2. The method according to claim 1, wherein when a signal of another logical channel is received from the other station within the response waiting time, the measurement of the response waiting time is stopped for a predetermined time. Retransmission control method. 3. The system according to claim 1, wherein when a signal of another logical channel is received from the other station within the response waiting time, the measurement time of the response waiting time is returned by a predetermined time. Retransmission control method. 4. The retransmission according to claim 1, wherein when a signal of another logical channel is received from the other station within the response waiting time, a predetermined time is added to the response waiting time. Control method. 5. Between two stations transmitting and receiving data to and from each other via a bidirectional communication channel, a response is transmitted from the other station within a predetermined response waiting time after transmitting data from one station. In the retransmission control method for retransmitting data, when one station transmits data to the other station on one logical channel of at least two types of logical channels time-division multiplexed on the communication channel, A retransmission control method comprising: counting the number of time slots on a communication channel assigned to the logical channel; determining the response waiting time based on the counted value; and retransmitting the data.