JP3484390B2 - Wireless packet priority control method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless LAN, and more particularly to a wireless packet priority control method that enables priority control by distinguishing packets within a best effort type range.

[0002]

2. Description of the Related Art Generally, IE is used as a wireless access method.
The access method in the wireless LAN system defined by the EE802 committee is typical.

This standard defines "IEEE802.11, Draft Standar".
d for Wireless LAN Medium AccessControl (MAC) and Ph
ysical Layer (PHY) Specification, P802.11D8.0,1 May 1
998 ”for more details.
The "E802.11 standard" will be described.

Regarding the access method of the MAC layer,
It is described in the "IEEE 802.11 standard".

Regarding the competitive access control, a CSMA / CA (Carrier) in which a wireless base station (AP) and a plurality of subordinate STAs (wireless stations) transmit data while carrying out carrier sensing so that packet collision does not occur. Se
DCF (Distributed Coordination Function distributed control procedure) using the nse Multiple Access Collision Avoidance method is used.

FIG. 5 shows a communication operation with respect to time in the DCF proposed in the "IEEE802.11 standard". In this figure, the horizontal axis indicates the passage of time, and for example, two wireless stations performing wireless packet communication (hereinafter referred to as STA
(Referred to as)), indicating the operation after the data transmission of STA1 is completed.

Here, in the "IEEE802.11 standard", I
FS (Inter Frame Space) is the time of carrier sense for the AP and STA to know the state of the wireless medium, and it is SIFS (Short IFS), PIFS (PCF) in ascending order of time, that is, in the order of priority of access. (Poi
nt Coordination Function (IFS), DIFS (Distr
ibutedIFS) and EIFS (ExtendedIFS) are defined. Note that the DIFS, which is the carrier sense time when transmitting the data packet signal, is related to the present invention.

Here, it is assumed that data is transmitted from STA1 to AP at time T, and AP and STA2 are in a transmission standby state.

First, the STA1 sends the data P1 to the AP and sends an ACK packet (Pa) in response to the reception of the data P1 to the AP.
After receiving from P, AP and STA2 wait until DIFS (TD) has elapsed.

A collision avoidance period (Contention Window: Tcw), which is a random time, is given to each of the AP and STA2. The collision avoidance period is obtained by multiplying the basic unit time by a random number, as will be described later.

In determining the collision avoidance period, as a general rule among all STAs including APs, APs and STAs having data packets to be transmitted are
Draw a random number with a uniform distribution of integers in a range. Then, the obtained random number value is multiplied by the basic unit time (slot time) of the collision avoidance period to obtain the collision avoidance period Tcw.

After the elapse of this period, if the wireless medium does not become busy, transmission is started. In FIG. 6, one slot time (one slot number) is shown as one frame. In this example, the AP is provided with a collision avoidance period of 4 frames × slot time, and the STA 2 has 7 frames × slot time. A collision avoidance period is given. The same applies to the drawings of the present invention described below. Collision avoidance period Tcw of given AP
Is shorter than STA2, so AP has priority,
After the collision avoidance period (4 slot time) has elapsed, data is transmitted from the AP to STA1. The transmission of STA2 at this time is postponed.

Further, after the ACK (Pa) transmission to the AP is completed and the DIFS (TD) period has further elapsed, this time ST
Since Tcw in the backoff of A2 is the shortest, S
TA2 becomes ready for data transmission. The above sequence ensures reliable packet transmission with few collisions in a race condition.

In the above-described random backoff, which is a waiting time after the DIFS has elapsed, the S that tries to perform transmission at the same time.
It is an operation for stochastically reducing collisions between TAs,
The waiting time in this backoff corresponds to the collision avoidance period.

A plurality of STs having data to be transmitted
Since A waits for different collision avoidance periods obtained by random numbers before transmitting data, it is possible to prevent simultaneous transmission, so that it is possible to prevent data packet collision.

FIG. 6 is a diagram for explaining another conventional method.

In the above-mentioned conventional technique, the collision avoidance period Tcw is randomly given regardless of the importance of data, but in this conventional example, the random number drawn by the STA having the data packet to be transmitted is uniform. By changing the range not according to the distribution but according to the priority of the packets to be transmitted, the length of the collision avoidance period Tcw is prioritized, and the priority control according to the priority of the data packet is performed. .

In this example, AP and two wireless stations (STA)
1, STA2) share the same frequency for communication,
After the STA1 completes the packet transmission, the AP has the packet data P1 for which the transmission is prioritized, and the STA2 has the data packet P2 for which the priority is lower than that of the AP. This data packet P
1 is assigned a slot time of 0 to 5, and the data packet P2 is assigned a slot time of 5 (fixed value) +0.
5, or 5-10 slot times are allocated. In this case, since the data packet P2 has a lower priority than P1, the 5-slot time is always a waiting time.

STA1 AC for its own data transmission
After receiving K packets, AP, STA1 and STA2
Both go back to backoff after a lapse of DIFS (TD). At this time, in determining the collision avoidance period Tcw which is the backoff period, each of the STA and the AP draws a random number. The integer range in which this random number is distributed depends on the priority of the packet of data to be transmitted. Weighting is done.

Specifically, in the data packet P2
Has a lower priority than the data packet P1, the packet transmission waiting time is, for example, from "5" to "6".
Slot time is given. Then, the waiting slot time in the previous back-off control is "4", which is smaller than the slot time "5" which must be always waited. Therefore, the waiting slot time in this backoff becomes "6" again. , The waiting slot time in the previous back-off control is "3", which is the slot time that must be the waiting time.
It is smaller than 5 ". Therefore, the waiting slot time in this backoff becomes" 6 "again. Then," 4 "is obtained from 0 to 5 from the transmission of the data packet P1.
Then, the value "3" is obtained from 0 to 5 as the transmission waiting slot time of the data packet P1.

In the case of FIG. 6 as described above, the transmission priority is determined by referring to the header information or the like at the head of the data to be transmitted. Since the AP is trying to transmit a packet with a high priority, the random number distribution range is 0 to
5, STA2 is trying to transmit a packet with a low priority, so the random number distribution range is set to 5-10. In this way, the STA2, which is trying to transmit the data packet with the low priority, must wait at least in the backoff control for at least 5 slot times, so that the AP data packet must be the STA2.
Will be sent in advance.

As described above, by changing the distribution range of random numbers according to the priority order of data packets, priority control can be performed within the contention access control DCF period.

[0023]

As the priority control which is the subject of the present invention, a method using a priority class defined by the IEEE 802 committee is typical. This regulation is "IEEE P802.1D
Annex H, Design Consideration for Traffic Class Ex
pediting and Dynamic Multicast Filtering, P802.1D, 2
5 May 1998 ”in detail. Hereinafter, this standard is referred to as“ IEEE P802.1D standard ”.

Here, the priority class in the "IEEE P802.1D standard" is the class that requires "guaranteed guarantee" of service quality such as guarantee of maximum delay time or guarantee of bandwidth, and the guarantee is not necessary but the best. It is roughly divided into the "priority bestate" class (excellent effort type), which has a higher priority than the effort type. The priority control in the present invention is the latter type which performs control according to the priority order in the best effort type.

Here, D in the "IEEE 802.11 standard"
In CF, the "Contention Window" is set for the period required to enable conflict-free contention access control by multiplying the number of slots, which is the fixed length reference time, by the integer given by the generated random number. ing.

By the way, in order to perform the priority control in accordance with the priority order for the data packets having the priority order, in the radio access method in which the data transmission interval has a meaning, the priority is given to the setting of Tcw. Although ranking is required, the distributed control DCF based on CSMA / CA does not have this ranking because its main purpose is to give "fair access opportunities".

In other words, the length of the collision avoidance period Tcw is set by taking advantage of the randomness of the random numbers generated from the uniformly distributed integers by setting the slot time which is the reference time of backoff to a fixed time. Therefore, it is impossible to control the priority order of the packet as it is.

As a prioritized DCF-based priority control method as described above, a collision avoidance period T
There is a method to change the distributed integer range according to the priority of the data packet for the random number drawn when setting cw.

However, according to this method, even if there is no high-priority data packet, the low-priority data packet has a range prepared for the high-priority data packet after the completion of DIFS, for example, collision in FIG. The avoidance period of 5 slots must always wait. As a result, there is an unnecessary waiting time, and there is a problem in that frequency utilization efficiency is reduced.

Further, in the setting of the non-contention access period by the centralized control of the AP, priority control and the quality assurance of the communication are possible, whereas in the DCF which provides the contention access period by the distributed cooperative control, complete control is possible. Even if the priority control can be performed, it is difficult to guarantee the communication quality. Therefore, there is a problem that the features of the PCF and DCF control methods are not fully utilized.

Therefore, the present invention solves the problem that the priority control according to the priority order of data cannot be performed because the collision avoidance period Tcw is set based on a random random number, and has been proposed in the past. It is an object of the present invention to provide a wireless packet priority control method that further reflects the feature of “access fairness” that competitive access control does not have in priority control within a certain DCF period.

[0032]

In order to achieve the above object, the present invention provides a wireless base station connected to a wired network and a plurality of wireless stations that are subordinate to the wireless base station and perform wireless packet communication. The wireless base station and the plurality of wireless stations use a common wireless channel, and at the time of communication, independently determine whether or not transmission is possible, avoid packet collisions, and transmit wireless packets. CSMA / C
A (Carrier Sense Multiple Access Collision Avoida
in a wireless packet priority control method for wireless packet communication that performs contention access control based on nce), the wireless base station and the wireless station are prioritized in best-effort type to perform transmission processing within a contention access control section. When a data packet including priority information indicating high or low is received, the priority information is acquired and stored, and a collision avoidance period consisting of a multiple of a basic unit time (slot time) is transmitted before data transmission by the contention access control. (Cont
There is provided a wireless packet priority control method for setting the slot time of a data packet having a higher priority information of the stored data packet when setting the (entition window).

According to such a wireless packet priority control method, by setting the slot time to a shorter time for the data having a higher priority, even if a larger random number is given to the data packet having a higher priority, the slot time is randomized. The probability of the collision avoidance period (Contention Window: Tcw) being shortened is high, and as a result, a data packet having a high priority is transmitted first.

[0034]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. First, the concept of the wireless packet priority control method according to the present invention will be described with reference to the flowchart shown in FIG. The communication of the present invention includes a wireless base station (AP) connected to a wired network and a wireless station (STA) that has a subordinate relationship with this AP and performs wireless packet communication. The AP and all STAs are
You are using a common wireless channel.

At this time, the wireless packets are transmitted by autonomously determining whether or not they can be transmitted and allowing packet collision.
Such as CSMA / CA (Carrier Sense Multiple Acc
essCollision Avoidance) -based contention access control and a period in which non-contention access control is performed by the AP polling are repeated in a fixed cycle, and the period and cycle are instructed by control information notified by the AP. Perform packet communication.

First, when the AP receives the data packet containing the priority information of the data arrived from the wired network side (step S1), it confirms the priority of the data packet (step S2). The data packet is inserted into the queue corresponding to the priority order confirmed here (step S3). Here, it is determined whether or not the data packet is for quality assurance (step S4). If the data packet is for quality assurance according to this determination (Yes), it is a quality assurance type (bandwidth guarantee / delay time guarantee). Assuming that there is (step S5), the wireless terminal ST by the central control PCF
It is transmitted to A (step S6).

On the other hand, if the packet is not a data packet for which quality assurance is requested (No), it is determined whether or not the packet should be transmitted preferentially over the best effort type (excellent effort type) (step S7).

In this determination, if the packet is not to be transmitted preferentially over the best effort type (No), it is recognized as the best effort type (step S8),
Random collision avoidance period (Contention Win
dow: Tcw) is given to each of AP and STA2. This collision avoidance period is a random value drawn from a certain range and the basic unit time (slot time) in the collision avoidance period.
To obtain the collision avoidance period Tcw.

After the DIFS (TD) period has elapsed, it is determined whether or not the radio frequency is unused (step S9). If the radio frequency is unused (Yes), the assigned collision avoidance period is determined. As soon as becomes zero (step S1
0), transmission is performed (step S11). If it is determined in step S7 that the packet should be transmitted with priority over the best effort type packet (Yes
s), that is, the excellent effort type is recognized (step S12).

In this excellent effort type, by setting the length of Tcw to be short as described in the embodiment to be described later, random collision is performed by the method of prioritizing in the backoff control period described later. The avoidance time is set to be high in probability (step S13).

Then, after the DIFS (TD) period has elapsed, it is judged whether or not the radio frequency is unused (step S14), and if the radio frequency is unused (Yes),
As soon as the assigned collision avoidance period becomes zero (step S
15), and transmission is performed (step S16). In particular,
When the AP receives a data packet containing priority information indicating the allowable transfer delay time of data arriving from the wired network side and the minimum required bandwidth, the AP receives the data packet having these priorities in the non-contention access control period. When the data packet is transmitted to the target terminal during a certain PCF period and a data packet including other priority information is received, the data packet is transmitted to the target terminal during the competitive access control period. Here, when the AP receives the data packet including the priority order information indicating the priority level in the best effort type in which the transmission process should be performed within the contention access control section, the AP acquires and stores the priority order information.

Further, according to the contention access control, a random number is subtracted if the wireless line is free before transmitting data,
When setting the collision avoidance period Tcw such as waiting for only that value, the length of the slot time is shortened in order from the class with the highest priority, thereby increasing the probability that the packet with the higher priority can be transmitted first.

Further, as a second method for prioritizing the setting of the collision avoidance period Tcw of the DCF control, a terminal which is trying to transmit a data packet having a low priority in the collision avoidance period Tcw setting of the competitive access control is When performing carrier sense in slot time units in backoff control, in addition to the originally allocated slot time,
Furthermore, an extra waiting time (waiting slot) in units of slot time is inserted N times every several slots.

As a result, the time during which the collision avoidance period Tcw of a terminal that is trying to transmit data having a low priority is zero is delayed, and as a result, the probability that a packet with a high priority can be transmitted first is increased.

As a method of prioritizing the collision avoidance period Tcw of the DCF control, the random number generation range drawn by each STA when setting the collision avoidance period by the competitive access control is determined by the priority of the data packet. Random numbers to be assigned are determined from the respective integer ranges, leaving the overlapping parts of the ranges.

Furthermore, a collision avoidance period is obtained by multiplying the drawn random number by a slot time having a constant value regardless of the priority. Then, the terminal trying to transmit a data packet with a low priority always waits for the time of the value obtained by multiplying the minimum value in the distribution range of the drawn random numbers by the slot time in each backoff control, and during the collision avoidance period, STA stops data transmission from its own terminal by transmitting data and waits for the collision avoidance period of the next contention access control period beyond the time that must be always waited in each backoff control. By decreasing the number of slot times that have been waited for, the probability that a packet with a high priority can be transmitted first is increased.

When there is a data packet transmission request from the STA to the AP in the upstream direction, the STA transmits the priority of the packet to be transmitted to the AP as a contact packet before transmitting the priority data packet. Then, the AP that has received the contact packet determines the length of the basic time unit time of the collision avoidance period permitted for the STA,
The basic unit time is returned and the concatenated packet is transmitted to the STA.

When there is a data packet transmission request from the STA to the AP in the upstream direction, the STA transmits the priority of the packet to be transmitted to the AP as a contact packet before transmitting the priority data packet. Then, the AP that has received the contact packet determines the insertion interval of the waiting slot time in Tcw or the random number generation range that is permitted to the STA according to the priority of the packet, and returns the setting information of Tcw. , STA as a contact packet.

As described above, by setting the length of the slot time in the collision avoidance period Tcw and the integer range in which the random numbers are distributed according to the type of data to be transmitted, a "best effort" data packet is obtained. On the other hand, "excellent effort type" data packet priority control can be realized.

A first embodiment of a wireless packet priority control method according to the present invention will be described with reference to FIG.

The first embodiment is an access control system based on DCF in a wireless medium between an AP and a STA, and the length of Tcw in backoff control is set in advance according to the priority order of data. This is a method of performing priority control within the best effort type range by setting the unit time of one slot of the STA with a difference, making the best use of the feature of fairness of competitive access control.

In step S7 of the flowchart of FIG. 2 described above, when it is recognized as the excellent effort type, Tcw is prioritized. Here, the slot time is changed by making a difference in the basic unit time without changing the distribution range of the random numbers.

As shown in FIG. 1, a packet transmission with a high priority (for example, AP side) is given a slot time TA of a short period, and a packet transmission with a low priority (for example, AP).
The STA side) has a long slot time (TB × n:
(n = 0 to 10) is given to prioritize, shorten the collision avoidance period of the terminal which is trying to transmit a packet with a high priority, and increase the probability that it can be transmitted first.

Since a weighting method such as how much priority is given to a data packet having a high priority with respect to a data packet having a low priority is performed within the slot time width, the relationship between both slot times is as follows. It does not have to be an integral multiple. Therefore, it is possible to freely set the priority of the transmission probability according to the priority.

An example of the operation when the priority control is performed in the first embodiment will be described. In FIG. 1, the horizontal axis represents the time axis and the vertical axis represents the communication operation in each terminal.
When the data packet transmission from 1 to the AP and the ACK reception are completed, a packet including the priority order arrives at the AP from the wired network side, and there is a low-priority data packet waiting to be transmitted in STA2. It is an example regarding control.

It is assumed that one slot time for an AP having a high priority, which is a feature of this embodiment, is TA, and one slot time for the STA2 side having a low priority is TB.

First, after the STA1 receives an ACK packet which is a confirmation for the transmission to the AP, the AP and STA2 having the packet waiting to be transmitted have a predetermined period DI.
Enter the carrier sense of FS (TD).

During this DIFS period (TD), after confirming that the wireless medium is in a non-communication state, AP and STA2
Enter into the back-off control used for avoiding collision of data packet transmission. At this time, if the priority of the data packet that the AP is going to transmit is high, the slot time length TA given to the AP and ST
The relationship of the slot time length TB given to A2 is as follows: TA <TB (1) (TB = k × TA k: priority ratio of data packet transmission with different priorities). In the example shown in FIG. 1, k = 1.5 (2). In this relationship, random numbers are subtracted from the uniform distribution having the same integer range (0 to 10 in the example in FIG. 1), and the subtracted random numbers are multiplied by the respective slot times.

In the example shown in FIG. 1, the AP has "7",
“6” is assigned to STA2. But AP and S
Since the ratio of the packet priority order of TA2 is 1.5 times that of the above-mentioned formula (2), the collision avoidance period of AP is 7 slot time, and the collision avoidance period of STA2 is 6 slot time. The relationship of both Tcw observed is as follows: 7 × TA <6 × TB = 6 × 1.5 × TA (3) As a result, the AP having a higher priority performs data transmission (P1) before STA2. After the communication, the AP receives ACK (Pa) for its own transmission from STA1, and then carries out carrier sense for the DIFS period (TD).

Here, if there is no communication, the AP and STA2 in which a packet waiting to be transmitted again enters the backoff control. At this time, the collision avoidance period of the STA2 is 3 slot time obtained by subtracting the elapsed 3 slot time from the 6 slot time. Further, since the priority of the AP data packet is high, the length of the slot time is set to TA, a new random number is drawn, for example, "4" is allocated, and the collision avoidance period becomes 4 slot time. I shall. As a result, the relationship between Tcw of both AP and STA2 becomes 4 × TA <3 × TB = 3 × 1.5 × TA (4) according to the equations (1) and (2), and again the AP Collision avoidance period is STA
It becomes shorter than 2, and the AP performs data transmission (P1) first.

Then, after carrying out carrier sensing in the DIFS period (TD), in the next back-off control,
The AP is requested to transmit a packet with a high priority for the third time, and the slot time length becomes TA. If the random number drawn by the AP in this backoff control is “5”, the relationship between AP and Tcw of STA2 is 5 × TA> 2 × TB = 2 × 1.5 × according to equations (1) and (2). TA ... (5), the collision avoidance period of the STA2 becomes shorter than that of the AP, and the data packet P2 can be transmitted.

As described above, in the priority control method according to the present embodiment, since the slot time in the collision avoidance period is set shorter from the higher priority order of data packets, the higher random number is assigned to the higher priority order of data packets. Is given, a random collision avoidance period (Contention Windo
The probability that w: Tcw) becomes short becomes high, and as a result, a data packet having a high priority can be transmitted first. This makes it possible to perform priority control without losing the features of competitive access control.

Next, a second embodiment of the wireless packet priority control method according to the present invention will be described with reference to FIG.

In the above-described first embodiment, the method of prioritizing packets by changing the slot avoidance period Tcw by changing the one-slot time without changing the distribution range of random numbers. In the embodiment, the method of digesting the given collision avoidance period Tcw is changed without changing the distribution range of random numbers and the one-slot time.

In the present embodiment, in the collision avoidance period Tcw setting, when a terminal which is trying to transmit a data packet having a low priority order confirms that the wireless medium is not used in the backoff control, This is a control method in which, in addition to the originally allocated slot time, a waiting slot time for waiting once every several slot times is inserted. As a result, the probability that a data packet with a high priority can be transmitted first is increased.

Therefore, in the step of subtracting the random number, the collision avoidance period Tcw is set randomly regardless of the priority level. However, the terminal trying to transmit a packet with a high priority level can quickly recover the collision avoidance period Tcw. Is faster than a packet with a lower priority, the waiting time until transmission is shorter, and as a result, a terminal that is trying to transmit a packet with a higher priority has a higher probability of transmitting first.

In this method, the priority of the data packet transmission probabilities having different priorities is set by the method of consuming the collision avoidance period in the backoff control, and can be performed without changing the slot time width and the random number generation range. In addition, the extra essential waiting time that occurs when a low priority packet is transmitted when a high priority packet is absent is not collected all together within a certain range, but is set to N times in a few slot times, so that the effect The feature is that it can be reduced.

In FIG. 3, the horizontal axis represents the time axis and the vertical axis represents the communication operation in each terminal. First, STA1 transmits a data packet to the AP, and the AC for the transmission is sent.
The reception of K (Pa) is completed. Then, a packet including the priority order arrives at the AP from the wired network side, and there is a data packet with a lower priority order to be transmitted to the STA2.

First, after a series of data transmission procedure from STA1 to AP is completed and DIFS (TD) has elapsed, the AP and STA2 operate in the same manner as in FIG. 1 described above until they enter the back-off control.

Then, one value is given from the random numbers of integers 0 to 10 to both the AP that is trying to send the data of high priority and the STA2 that is trying to send the data of low priority.

For example, one reference slot time consists of the same time regardless of the priority order, and in the case of FIG. 3,
It is assumed that AP is a 3-slot time by the random number "3" and STA2 is a 7-slot time by the random number "7". At this time, in the 7-slot time given to STA2, the waiting slot time is set once every two-slot time. Therefore, in actuality, the collision avoidance period Tcw becomes a time equivalent to 11 slot times.

While the AP and STA2 both reduce the collision avoidance period Tcw during the backoff control period, the priority ratio of the data packets existing in both AP and STA2 is set to 1.5. Therefore, an AP having a data packet with a high priority is
The collision avoidance period Tcw is consumed 1.5 times faster than in 2.

For this reason, when the AP transmits data and consumes 3 slot time, 1 slot time is added to 2 slot time in STA2. Therefore, the collision avoidance time set by the random number is actually used. Of this, only 2 slots are consumed, and the remaining part goes to the next back-off control, and the collision avoidance period Tcw is 5 slots (in practice, 3 waiting slots are included, so 8 slots are required). It corresponds to time).

Next, when the AP transmits the first data packet, and a data packet with a high priority arrives at the AP from the wired network side after the DIFS (TD) has elapsed, the AP again generates a random number. "6" is given by subtracting one value from the range 0-10, and the next collision avoidance time Tcw
Is 6 slot times. S for which the first transmission was postponed
Tcw of TA2 is 5 slot time, and as a result of comparing this with 6 slot time of AP, (6 × slot time / 1.5) <(5 × slot time) (6) Even in the off control, the collision avoidance period of the AP is shorter, and the AP is transmitted first.

When the AP transmits the second data packet, the STA2 consumes 6 slot time, and therefore the STA2 consumes 4 slot time and 1 slot time ( Actually, since one waiting slot time is included, it corresponds to two slot time).

Next, after a lapse of DIFS (TD), when a data packet having a higher priority than STA arrives at the AP from the wired network side, the AP subtracts a random number from the random number range 0-10. , Random value "3" is obtained.
As a result, the Tcw of the AP becomes 3 slot times.

By the way, in the third transmission, the value of Tcw of STA2 having a lower priority is one slot time (actually, it is two slot time including one waiting slot time), and AP and STA2 And Tcw is (3 × slot time / 1.5)> (1 × slot time) (7), and the data packet of STA2 is finally transmitted at the third time. In this transmission, 2 slot time is consumed, and the AP collision avoidance period becomes 1 slot time.

Further, in the fourth transmission, STA2
STA when there is a data packet to be sent to
2 is a random number value subtracted from the random number range 0-10
4 "is obtained, and Tcw of STA2 becomes 4 slot time (actually, it corresponds to 6 slot time because two waiting slot times are included).

According to the present embodiment as described above, since the waiting slot time is given once for every two slots in the collision avoidance period having the lower priority of the data packet, the data having the higher priority is given. Compared to packets, data packets with lower priority have the same random time value and the same slot time as Tcw, so the actual digestion time is 1.5 times longer. As a result, the probability of transmitting a data packet having a high priority first becomes high.

Next, a third embodiment of the wireless packet priority control method according to the present invention will be described with reference to FIG.

This embodiment is a method of weighting the distribution range of random numbers without changing the slot time and the method of consuming the collision avoidance period as in the first and second embodiments described above. By giving a priority to the transmission probability of the data packet by changing the generation range of, the collision avoidance is transmitted.

In this embodiment, the complete random number range is not divided according to the priority of the data, but a part where the ranges are overlapped with each other is created, so that the packet with a lower priority is already extracted from the random value first drawn. A short collision avoidance period may be assigned to the terminal that is trying to send.

Instead, in the conventional method, the collision avoidance period Tcw is shortened by the amount of waiting for the transmission, whereas in the present embodiment, the collision avoidance period Tcw is shortened to the terminal which is trying to transmit the data packet having the low priority. On the other hand, the collision avoidance period is fixed to the minimum value of the random number in the second and subsequent collision avoidance periods so that the collision avoidance period does not fall below the value obtained by multiplying the minimum value in the random number distribution range by the slot time. The method of adding the slot time to be used.

More specifically, as shown in FIG. 4, for example, the random number range distribution is such that, in the collision avoidance period Tcw setting, a terminal (for example, STA2) that wants to transmit a data packet having a low priority has 3 slots. When the time is fixed, the range of the given random number is set to 3 to 10, and the terminal (for example, AP) that is going to transmit the data packet having the higher priority sets the given random number range to 0 to 7. . This setting increases the probability that a terminal that is trying to send a data packet with a high priority will be able to send it first.

In FIG. 4, the STA1 finishes the data transmission and sends to the AP a high priority data packet, S
The operation up to the state where there is a data packet having a low priority in TA2 is the same as that in FIGS. 1 and 3 described above.

The operation for performing the priority control of this embodiment is performed by the AP which is trying to transmit a data packet having a high priority.
The random number range is set to 0 to 7, and the random number is subtracted from it.
In addition, the random number range of the STA2 which is trying to transmit the data packet of low priority is an integer from 3 to 10,
Subtract a random number. With such a setting, even if STA2 is given the minimum value, it takes 3 slot time, and in effect,
This is the same as the one in which the first three slots of the collision avoidance period are always fixed.

As described above, a fixed constant value is always taken on the data packet side having a low priority. Figure 4
At AP, “4” is given to the AP from the random number range, and ST
When "7" is given to A2 from the random number range, AP
Becomes 4 slot time, and STA2 becomes 7 slot time.

Then, when the AP transmits the first data and the data packet with the higher priority arrives at the AP again from the wired network side, the random number range 0 to 7 is again provided in the collision avoidance period of the AP. A random number is subtracted from among these, and, for example, "3" is given.

Also, the S postponed in the first transmission
In the collision avoidance period Tcw, TA2 is consumed for 4 slot time, and has 3 slot time remaining. However, of these 4 slot times, 3 slot times are the periods that must be waited for in the backoff control, so
It does not count as slot time spent. Therefore, the number of slots consumed in the previous backoff control is
It becomes 1 slot time, and the remaining 3 slot time is
It is carried over as the time that must be waited.

In the second transmission, the collision avoidance period Tcw in STA2 is 6 slot time obtained by adding 3 slot time which must be waited to 3 slot time which has not been exhausted in the first transmission. Also,
In the AP, a random number is subtracted from the random number range 0 to 7, and “3” is given, for example. As a result, even in the transmission of the second data packet, the collision avoidance period Tcw of the AP becomes shorter than the collision avoidance period Tcw in STA2, and A
P is transmitted preferentially.

When a second data packet is transmitted and a data packet with a high priority level arrives at the AP again after a lapse of DIFS (TD), the AP selects from the random number range 0 to 7. Subtract a random number, "7"
Is given, the collision avoidance period Tcw of the AP becomes 7 slot times.

The collision avoidance period Tcw of STA2 is
In the second back-off control, the 3 slot time is exhausted, and the 3 slot time is the remaining time. However, the collision avoidance period Tcw of STA2 this time is always the waiting time of 3 slot time and the remaining time. It becomes 6 slot time which is obtained by adding 3 slot time.

Therefore, since the collision avoidance period Tcw of the AP is 7 slot times and the collision avoidance period Tcw of STA2 is 6 slot times, the STA2 is shorter and data can be transmitted.

As described above, according to the priority control method of the third embodiment, during the collision avoidance period Tcw given to a terminal which is going to transmit a data packet having a lower priority of the data packet, the leading side is previously set. By setting a fixed wait slot time that always becomes a wait time and adding a slot time that has not been exhausted last time excluding the wait slot time, the probability that a data packet with a high priority will be transmitted first becomes higher. Is the way to do so.

In the above description, in the first to third embodiments, the case where a data packet having a high priority is mainly transmitted from the AP to the STA has been described. AP to STA
The AP can centrally manage the setting of the priority order of the data. The setting of the priority order of the data generated in each STA can be controlled as a system by performing the procedure described below.

First, in order to implement each priority control method described in FIGS. 1, 3, and 4, all STAs are APs.
Before sending a data packet, it is necessary to notify the priority of the data packet and to obtain permission from the AP to send the data packet at the priority.

STA1 and S in FIGS. 1, 3, and 4
Prior to transmitting the data packet, the TA 2 transmits to the AP, as a contact packet, priority order information considered necessary for transmitting the data packet.

First, the AP, which has received the contact packet containing the priority order information from the STA1 and STA2, considers the overall traffic and the priority level requested by the STA, and determines the priority order to be granted to the STA1 and STA2. It is decided and this is sent to each STA as a return contact packet.

Then, STA1 and STA2 are
In the priority control method of the first embodiment shown in FIG. 1, according to the priority information of the contact packet from P, the length of the slot time is changed to the priority control method of the second embodiment shown in FIG. In the priority control method of the third embodiment shown in FIG. 4, the slot time consumption method is to perform priority control by weighting the random number generation range.

By setting the priorities by the communication packet between the AP and the STA in advance of the execution of the priority control, each STA does not arbitrarily obtain a high priority and perform the data transmission. The system can be controlled.

As described above, in the priority control method of the present invention, the higher the priority of the data packet, the higher the probability that the length of Tcw will become shorter, and as a result, the probability of transmitting the data packet having the higher priority first. It takes advantage of the fact that This makes it possible to perform priority control without losing the features of competitive access control.

[0102]

As described above in detail, according to the present invention, not all data packets are treated similarly as the best effort type, but priority control is performed by prioritizing, so that "from the best effort type". Allows preferential packet transmission. Therefore, it is possible to provide a wireless packet priority control method capable of flexibly responding to a user who wants to receive preferential service rather than the best-effort type, without requiring quality assurance.

[Brief description of drawings]

FIG. 1 is a first diagram of a wireless packet priority control method according to the present invention.
It is a figure for explaining the embodiment of.

FIG. 2 is a flowchart for explaining the concept of a wireless packet priority control method of the present invention.

FIG. 3 is a second diagram related to the wireless packet priority control method of the present invention.
It is a figure for explaining the embodiment of.

FIG. 4 is a third embodiment of the wireless packet priority control method of the present invention.
It is a figure for explaining the embodiment of.

FIG. 5 is a diagram for explaining a conventional competitive access control DCF.

FIG. 6 is a diagram for explaining prioritized control using a conventionally proposed DCF control.

[Description of Codes] Ts ... SIFS TD ... DIFS Tcw ... Collision avoidance period (Contention Window: Tcw) P1 ... Priority data packet P2 ... Non-priority data packet AP ... Base stations STA1, STA2 ... Wireless terminal TA ... Slot time (priority packet Slot time for transmitting terminal) TB ... Slot time (slot time for non-priority packet transmitting terminal)

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masahiro Morikura 2-3-1, Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) References Japanese Patent Laid-Open No. 11-55266 (JP, A) Special Features Kaihei 10-84307 (JP, A) JP 10-98474 (JP, A) JP 2000-253017 (JP, A) JP 2000-244523 (JP, A) JP 2001-53745 (JP, A) ) JP-A-7-336365 (JP, A) JP-A-11-239140 (JP, A) JP-A-10-84343 (JP, A) JP-A-9-135254 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H04L 12/28 H04L 29/08

Claims (7)

(57) [Claims] 1. A wireless base station connected to a wired network, and a plurality of wireless stations that are subordinate to the wireless base station and perform wireless packet communication. The wireless base station and the multiple wireless stations. CSMA / which uses a common wireless channel, determines whether to transmit each other autonomously during communication, avoids packet collision, and transmits wireless packets.
CA (Carrier Sense Multiple Access Collision Avoi
A wireless packet priority control method in wireless packet communication that performs competitive access control based on dance), wherein the wireless base station and the wireless station are prioritized in a best-effort type to perform transmission processing within a competitive access control section. When a data packet including priority information indicating the level of is received and stored, the priority information is stored together with the collision avoidance period consisting of a multiple of a basic unit time (slot time) before data transmission by the contention access control. (Co
(ntention Window) setting, the wireless packet priority control method is characterized in that the slot time is set shorter for a data packet having higher priority information of the stored data packet. 2. The wireless packet priority control method according to claim 1, wherein the collision avoidance period is set shorter for a data packet having a higher priority in the stored priority information of the data packet, The slot time for the high priority data packet is set shorter than the slot time for the low priority data packet, and a time obtained by multiplying the random number value obtained by using the random number is set as the collision avoidance period. A characteristic wireless packet priority control method. 3. The wireless packet priority control method according to claim 1, wherein the collision avoidance period is set to be shorter for a data packet having a higher priority in the stored priority information of the data packet. The collision avoidance period for the highest priority data packet is the time obtained by multiplying the predetermined slot time by a value obtained by using a random number.For other priority data packets, the random number is set for the predetermined slot time. The time obtained by multiplying the time obtained by multiplying by the random value obtained by using 1 (N: an integer) slot time is set as the collision avoidance period, and the higher the priority of the data packet, the higher the priority. A wireless packet priority control method comprising increasing the value of N. 4. The wireless packet priority control method according to claim 1, wherein the collision avoidance period is set shorter for a data packet having a higher priority in the stored priority information of the data packet. The minimum and maximum values of the random numbers that generate numerical values are set to be smaller for higher priority data packets, and the collision avoidance period for data packets is obtained by using the random numbers in a predetermined slot time. The value is multiplied by the value, and the collision avoidance period spent by the highest priority data packet is subtracted from the collision avoidance time during the first backoff control of data packets other than the highest priority data packet. The time obtained by adding the time obtained by multiplying the small value of the random number by a predetermined slot time to the time is set as the collision avoidance time in the next backoff control. Wireless packet priority control method characterized by repeating this until transmitting the data packets. 5. The wireless packet priority control method according to claim 2, wherein when the data packet is transmitted from the wireless station to the wireless base station, the wireless station is configured to perform data transmission before the contention access control. , The priority information of the data packet to be transmitted is transmitted to the radio base station by a contact packet, and the radio base station which has received the contact packet assigns a corresponding slot time to the radio base station based on the priority information of the data packet. A wireless packet priority control method characterized by notifying a station by a contact packet. 6. The wireless packet priority control method according to claim 3, wherein, when the data packet is transmitted from the wireless station to the wireless base station, the wireless station is configured to perform data transmission before the contention access control. , The priority information of the data packet to be transmitted is transmitted to the radio base station by a contact packet, and the radio base station which has received the contact packet sets the value of N to the radio value based on the priority information of the data packet. A wireless packet priority control method characterized by notifying a station by a contact packet. 7. The wireless packet priority control method according to claim 4, wherein, when the data packet is transmitted from the wireless station to the wireless base station, the wireless station is configured to perform data transmission before the contention access control. , The priority information of the data packet to be transmitted is transmitted to the wireless base station by a contact packet, and the wireless base station which has received the contact packet determines the minimum value of the random number value based on the priority information of the data packet. A wireless packet priority control method, which notifies the maximum value to the wireless station by a contact packet.