JPH10322266A - Packet communication method - Google Patents

Abstract

(57) Abstract: The present invention relates to a packet communication method including a mobile unit in a wireless station, and includes a determination method for activating collision resolution control in mobile packet data communication when it is more appropriate, thereby improving communication efficiency. To provide a packet communication method that can achieve the above. A packet communication method for performing collision control for adjusting access timing or collision control for shifting access timing in any of a receiving station, another wireless station, and a station monitoring and controlling communication. Therefore, the quality deterioration factor is only when the error is detected consecutively at the head of the transmission data at the start of the communication or the reservation signal transmitted prior to the transmission of the transmission data at the start of the communication more than the threshold value. It is characterized in that collision is determined and collision control is activated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packet communication method for transmitting and receiving packet data via a wireless line.
In particular, the present invention relates to a packet communication method including a mobile station in a wireless station.

[0002]

2. Description of the Related Art In conventional collision control in packet communication using a wired line, since there is no error factor of transmission information supposed besides collision, a data head or a line transmitted prior to data transmission is not transmitted. If an error is detected in the reservation signal or the like, the probability of retransmission of the signal is unconditionally reduced, or a random number sequence used as a temporary ID is generated, and the signal retransmission is postponed to its own transmission order determined by the temporary ID. In general, a transition is made to a conflict resolution mode in which processing such as In this collision resolution mode, data is transmitted one by one according to a procedure for spreading the transmission timing of each data terminal.

[0003]

However, in radio communications, especially mobile communications, transmission error factors are not limited to collisions, but (a) interference waves arriving from surrounding radio base stations and radio cells, and (b) radio waves. The distance between the base station and the wireless terminal increases, and the reception level decreases, which is affected by noise generated in the wireless device. (C) The reception level decreases due to the presence of an obstacle, and the same result is generated. (D) A similar result is produced by the fact that the waves reflected on a building or the like overlap and the reception level is instantaneously reduced.

Therefore, when packet communication is to be performed on a wireless transmission path in accordance with a conventional wired packet transmission control method, when an error occurs in the reservation signal or the head of data due to various factors other than the above collision, Also transitions to the conflict resolution mode each time. In conflict resolution mode,
Since the transmission is delayed due to the control for shifting the transmission timing, it is not efficient to make the transition even when no collision occurs. Therefore, a packet transmission technique suitable for a mobile communication environment is required.

SUMMARY OF THE INVENTION An object of the present invention is to provide a packet communication method having a determination method for activating collision resolution control in wireless packet data communication, especially mobile packet data communication, when it is more appropriate, and improving communication efficiency. is there.

[0006]

According to the first aspect of the present invention, two or more wireless stations out of a plurality of wireless stations performing packet communication via a wireless line simultaneously access the wireless line. Collision control that adjusts the access timing or shifts the access timing at any of the receiving station, other wireless stations, and the station that monitors and controls communication to avoid reoccurrence or subsequent collision. In the packet communication method of performing collision control, the error is continuously detected more than the threshold number of times at the head of the transmission data at the start of communication or the reservation signal transmitted prior to the transmission of the transmission data at the start of communication. Only when detected, the quality degradation factor is determined to be a collision and activated.

That is, the head of transmission data at the start of communication,
Alternatively, if there is an error in the reservation signal transmitted prior to transmission of transmission data at the start of communication, instead of immediately shifting to the collision control mode, only when an error is detected consecutively more than the threshold value Then, it is determined that the quality deterioration factor is a collision, and the collision control is activated. Therefore, communication efficiency can be improved.

According to a second aspect of the present invention, among a plurality of wireless stations that perform packet communication via a wireless line, the recurrence and subsequent occurrence of a collision caused by simultaneous access of two or more wireless stations to the wireless line. In order to avoid this, in any of the receiving station, other wireless stations, and stations that monitor and control communication,
This is a packet communication method that performs collision control for adjusting access timing or collision control for shifting access timing, and the collision control is performed only when the transmission error rate of the radio line is equal to or higher than a threshold value. It is characterized by being activated when it is determined that

That is, when there is a transmission error in the radio channel, the mode is not immediately shifted to the collision control mode, but only when the transmission error rate of the radio channel is equal to or higher than the threshold value is determined that the factor of quality deterioration is collision. To activate the collision control. Therefore, communication efficiency can be improved. The invention according to claim 3 is
In order to avoid reoccurrence and subsequent collisions caused by simultaneous access of two or more wireless stations to the wireless line among a plurality of wireless stations performing packet communication via the wireless line, a receiving station and other wireless stations A packet communication method for performing a collision control for adjusting access timing or a collision control for shifting the access timing in any of the stations monitoring and controlling the communication, wherein the collision control is performed at a threshold value or more during communication. Only when an error is detected consecutively a number of times, the quality deterioration factor is determined to be a collision and activated.

That is, when an error occurs during communication, the mode is not immediately shifted to the collision control mode, but only when an error is detected continuously more than a threshold number is judged that the quality deterioration factor is a collision. Then, the collision control is started. Therefore, communication efficiency can be improved.

[0011]

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

FIG. 1 is a configuration diagram of a mobile packet communication system that performs a packet communication method according to an embodiment of the present invention. This embodiment corresponds to claims 1 to 3. In this mobile packet communication system, a plurality of wireless zones 1
At 0-1,..., 10-n, the wireless base station 1 and the plurality of mobile stations 2-1,..., 2-m are connected via one wireless line. The wireless base station 1 in each wireless zone is connected to the Internet 8 via the packet exchange 4.

The radio base station 1 constantly broadcasts downlink information in the format shown in FIG. 2, in the downlink information, a field 21 in which the identifier of the specific mobile station or all "0" is set, and information addressed to the specific mobile station corresponding to the identifier set in the field 21 or all "0" are set. Field 22 and a field 23 in which empty / busy line information is set.

The mobile stations 2-1,..., 2-m are empty / bu
If the line is free according to the line information of sy, the packet data is transmitted. Packet data of a plurality of mobile stations are packet-multiplexed on one wireless line and transmitted and received. There are various methods in which a mobile station accesses a radio line, such as reserving a slot and transmitting packet data. The collision control performed when packet data transmitted by two or more stations collides includes reception. Station, another mobile station or radio base station adjusts the timing of access, or
A method of shifting the access timing is adopted.

This embodiment is a system in which each mobile station communicates via a radio base station as shown in FIG.
In a system in which mobile stations directly communicate with each other, since each wireless station has a function equivalent to that of the base station in this embodiment, collision control in this case is performed by the receiving station or another mobile station. . As a function that triggers a transition to the collision resolution mode when transmitted packet data collides, the radio base station has an error detection function and a function of requesting retransmission of error information. Note that these functions are always provided because the mobile station also needs to perform data retransmission except at the time of collision.

The operation of the embodiment will be described below with reference to FIGS. FIG. 3 is an operation flowchart of collision control of the mobile station. In this embodiment, the mobile station first transmits a reservation signal to a wireless line prior to transmission (S1).
If normal, the radio base station transmits a permission signal when receiving the reservation signal. When the permission signal for the first reservation signal is not received (S2), the mobile station immediately transmits the second reservation signal without an interval (S3).
The reception of the permission signal is monitored (S4). If the permission signal is not received again after the reservation signal is retransmitted, the mode transits to the collision resolution mode (S5). The operation of the mobile station in the collision resolution mode will be described later.

When the permission signal for the first reservation signal is received (S2), or when the permission signal is received after retransmission of the reservation signal (S4), the permission signal for the own station is transmitted. (S6), and if it is a permission signal for the own station, transmission of packet data is started according to a normal procedure (S7). On the other hand, if the received permission signal is not directed to the own station, but is a permission signal for the reservation signal transmitted by another station, the mobile station determines that the other stations that transmitted the reservation signal at the same time transmit packet data thereafter. It transits to the transmission waiting mode (S8), monitors the downlink, and waits until it becomes an empty state (S9).

Next, FIG. 4 is an operation flowchart of collision control of the radio base station. The radio base station monitors whether there is a vacancy in the uplink radio channel used in the packet communication (S20), and if a vacant channel is detected (S2).
1) If the reception level is equal to or higher than a certain value (S22), it is determined that some signal has been received. When the identifier given to the signal is incorrect, the signal is recognized as an error in the reservation signal.

In the above procedure, when an error is detected in the reservation signal received twice consecutively (S24), it is determined that a collision has occurred, and the mode transits to the collision resolution mode (S25). That is, the mobile station under its control is notified of the transition to the collision resolution mode. On the other hand, each mobile station generates a random number sequence to be used as the temporary ID, waits for the wireless base station to receive the transmission permission for the temporary ID, and receives the transmission permission for the temporary ID. Send data only when. Thereby, the radio base station can cause each mobile station to perform data transmission avoiding collision.

The algorithm of the collision control is known as a block stack algorithm (for example, BSTsybakov, “Survey of USSR Contribution”).
toRandom Multiple-Access Communication, ”IEEE Tra
nsactions on InformationTheory, vol.IT-31, No.2, Marc
h 1985).

On the other hand, if the received signal can be recognized as a reservation signal (S23), and if the reservation signal can be correctly received a second time with only one error (S24), a permission signal is transmitted to the corresponding mobile station. Then, data transmission in the normal mode is started (S26). After the start of the data transmission, the radio base station determines whether the communication quality deterioration factor is a collision or an interference based on the frame error rate and the reception level (see S23 in FIG. 4). As a measure, switching between wireless links within the same wireless base station and switching between wireless links between adjacent wireless base stations are appropriately activated.

In the collision control described above, the reservation signal is targeted. However, in the system not using the reservation signal, the head of the transmission data can be selected as a judgment target. Also, packet collision occurs during communication. Therefore, the transmission error rate of the wireless line is monitored, and only when the transmission error rate is equal to or higher than the threshold value, it is determined that the quality deterioration factor is a collision and the collision control is activated. Alternatively, the error occurrence status of the line being communicated is monitored, and only when an error is detected continuously for a number of times equal to or greater than the threshold value, the quality deterioration factor is determined to be a collision, and collision control is activated. Is also good. Further, the number of times of determining a collision is not limited to two times, and can be appropriately determined according to the quality of the transmission path, traffic, and the like.

As described above, in this embodiment, even if an error is detected at the head of the reservation signal or the transmission data due to an error other than collision such as interference, the system immediately shifts to the collision resolution mode as in the prior art. Rather than making a transition, the mobile station is given an opportunity to transmit the reservation signal or the beginning of the transmission data several times (n times), and if an error is detected n consecutive times, or if an error is detected. A method of transitioning to the collision resolution mode is adopted only when detection is performed continuously for m or more times (m <n). As a result, transition when no collision occurs can be prevented, and communication efficiency can be improved.

Next, the transmission delay between the conventional system which transits to the collision resolution mode with one error and the system of this embodiment which transits to the collision resolution mode with two errors will be compared and examined. The number of mobile stations under the control of the radio base station is n, the collision probability is P (n), the frame error rate of the radio line in use is α, the time width of the time slot is t, the number of packets per mobile station. Let the incidence be λ.

(A) A transition to the conflict resolution mode with one error. The transmission delay in this case is given by equation (1). {P (n) + α} × (１ ／) × n × t (1) The probability that the first signal is incorrect is (collision probability) + (frame error rate). The expected value of the control delay when the determination is made and the mode transits to the collision resolution mode is based on the fact that the transmission permission is given to each of the mobile stations and the order of the transmission is determined and the time is reached.

(B) Transition to collision resolution mode due to two errors. This transmission delay is given by equation (2). {P (n) + α ² } × (1/2) × (n + 1) × t (2) This is obtained in the same manner as Expression (1). That is, the probability of the first signal being erroneous twice consecutively is (collision probability) + (frame error rate) ² . The fact that one slot is spent for determining the cause of the error is taken into consideration. The collision probability P (n) is obtained by approximating the Poisson distribution as follows: P (n) = 1−exp (−nλt) −nλt × exp (−nλt) (3) However, as a special case, P (1) = 0.

The difference between the equations (1) and (2) is α × (1/2) × n × t−α ² × (1/2) × (n + 1) × t−P (n) × (1/2) × t (4) Therefore, when P (n) is small and α × n is large, it can be said that the method in the case of transition to the collision resolution mode with two errors (b) is excellent.

However, if the packet occurrence rate per mobile station increases and the collision probability increases, collision control using the method (b) may be disadvantageous. A fixed threshold is provided, the packet occurrence rate per mobile station is monitored, and when the occurrence rate exceeds the threshold, collision control is performed by the method of (a). When the occurrence rate is less than the threshold, (b) The collision control is performed by the method described above. Thereby, communication efficiency can be improved.

FIG. 5 shows that 0.001 / 1 / mobile station is used.
FIG. 9 is a diagram showing a comparison between the conventional method (a) and the method (b) of the present embodiment when a packet is generated at a normalized occurrence rate called a slot. The evaluation is performed using the transmission delay as a measure. This is because the delay caused by two reasons, that is, retransmission of error information and transition to the collision resolution mode and adjustment of signal reproduction timing, is the most direct cause of deterioration in the serviceability of packet communication. , Based on the idea.

From FIG. 5, it can be understood that when the frame error rate is deteriorated, the characteristics of the conventional system in which a collision is determined by one error become worse. In addition, when the number of mobile stations (packet terminals) increases, the effect of the method of this embodiment, in which transmission timing is spread, appears remarkably. This is because the effect of increasing the collision probability is due to the increase in delay associated with collision resolution (this is based on the spread of transmission timing).
This is because the method of this embodiment has a more strict condition that a collision is determined as a condition for transition to the collision resolution mode, so that the method of this embodiment is more advantageous.

[0031]

As described above, according to the first to third aspects of the present invention, the condition for transition to the collision control is determined by setting the error rate of the data head, the reserved signal and the like, the number of continuous errors, and the like. Can be separated from interference as a factor of quality degradation, so it is possible to distinguish between factors that have a low probability of a continuous data error other than a collision and those that routinely have a continuous data error It is possible to prevent the transition to collision control when no collision occurs,
Communication efficiency can be improved by reducing transmission delay.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a mobile packet communication system that implements a packet communication method according to an embodiment of the present invention.

FIG. 2 shows a format of downlink information.

FIG. 3 is an operation flowchart of collision control of a mobile station.

FIG. 4 is an operation flowchart of collision control of the wireless base station.

FIG. 5 is a characteristic comparison diagram between the conventional system and the system of this embodiment.

[Explanation of symbols]

 1 wireless base station 2-1 to 2-m mobile station 4 packet switching station 8 internet 10-1 to 10-n wireless zone

Claims (3)

[Claims] 1. A receiving station for avoiding reoccurrence and subsequent collisions caused by simultaneous access of two or more wireless stations among a plurality of wireless stations performing packet communication via a wireless line. , Another radio station, in any of the stations monitoring and controlling the communication, collision control to adjust the access timing, or a packet communication method to perform collision control to shift the access timing, wherein the collision control is The quality deterioration factor is a collision only when errors are detected consecutively at the beginning of the transmission data at the start of communication or in the reservation signal transmitted prior to transmission of the transmission data at the start of communication more than the threshold. A packet communication method characterized by being activated upon determination of 2. A receiving station for avoiding reoccurrence or reoccurrence of collision caused by simultaneous access of two or more wireless stations among a plurality of wireless stations performing packet communication via a wireless line. , Another radio station, in any of the stations monitoring and controlling the communication, collision control to adjust the access timing, or a packet communication method to perform collision control to shift the access timing, wherein the collision control is A packet communication method characterized in that a quality deterioration factor is determined to be a collision and activated only when a transmission error rate of a wireless line is equal to or greater than a threshold value. 3. A receiving station for avoiding reoccurrence and subsequent collisions caused by simultaneous access of two or more wireless stations among a plurality of wireless stations performing packet communication via a wireless line. , Another radio station, in any of the stations monitoring and controlling the communication, collision control to adjust the access timing, or a packet communication method to perform collision control to shift the access timing, wherein the collision control is A packet communication method characterized in that a quality deterioration factor is determined to be a collision and activated only when an error is detected continuously more than a threshold during communication.