JP6011081B2 - Wireless communication apparatus and priority control method - Google Patents

Description

  The present invention relates to a wireless communication apparatus and a priority control method.

  In recent years, with the development of wireless LAN (Wireless Local Area Network) technology and the expansion of access point installation bases, wireless LAN has various services ranging from email viewing and web browsing to video viewing and voice communication using VoIP. Has been used. In this way, services that are relatively unacceptable for data delay such as voice communication and require relatively real-time performance, on the other hand, background communication for server synchronization and alive monitoring that is automatically performed by the application, etc. Are mixed. That is, the QoS (Quality of Service) level required for each service or application is generally different.

  Therefore, there is an EDCA (Enhanced Distributed Channel Access) method for realizing QoS control in a wireless LAN. EDCA is an access control method that is defined by IEEE (American Institute of Electrical and Electronics Engineers) 802.11e and extends the CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) method, which is a standard access control method for wireless LANs.

  In EDCA, a transmission packet is stored in a transmission queue classified into four types of access categories (AC) according to the priority of transmission data. Then, by adjusting a fixed frame transmission interval (AIFS: Arbitration Inter Frame Space) set for each transmission queue and a back-off time of a random waiting time, data is transmitted earlier in a queue having a higher priority. Therefore, in a communication environment with a lot of high-priority data, the frequency of giving a transmission opportunity to the transmission queue of the low-priority access category is low, so that low-priority data may cause data to be discarded due to timeout Becomes higher. Therefore, there is a problem that communication becomes uncertain and unstable.

  Therefore, for the purpose of suppressing discarding of data due to timeout, communication having means for adjusting AIFS and backoff value of transmission data according to the elapsed time from transmission data transmission request occurrence or the number of retransmissions of transmission data A technique related to the apparatus is disclosed (for example, refer to “Cited document 1”).

  However, in the technique described in the cited document 1, the difference between the high-priority data waiting time is reduced by setting the AIFS and back-off value of the low-priority data short. Therefore, the waiting time of transmission queues having different priorities becomes 0 at the same time, and the possibility of occurrence of an internal collision in which a plurality of data is simultaneously output from the queue increases. For this reason, the load due to the internal collision processing increases, and the performance (for example, throughput) of the communication device decreases. Furthermore, if the data AIFS and the back-off value are set short, there is a high possibility that a plurality of communication devices to which this technology is applied will start transmission at the same time after the same waiting time has elapsed. For this reason, the packet collision rate in the radio wave space is increased, and the performance of the communication device is lowered.

  In addition, in the conventional EDCA technology, when an internal collision occurs, there is a high possibility that data in the transmission queue with low priority will not be given a transmission opportunity, and the number of retransmissions will be exceeded and the data will be discarded. Is not resolved.

  Therefore, the present invention has been made in view of the above problems, and the present invention relates to QoS control executed in a wireless communication apparatus, data that satisfies a certain standard different from the waiting time lapse according to priority. It is an object of the present invention to improve communication reliability and stability by giving a transmission opportunity preferentially.

  Therefore, in order to solve the above-described problem, the present invention provides a priority for transmitting data in which the difference between the priority response time defined shorter and the waiting time in which the transmission data has passed is smaller as the priority based on the attribute of the transmission data is higher. It has a control means.

  According to the present invention, regarding QoS control executed in a wireless communication device, a transmission opportunity is preferentially given to data that satisfies a certain standard different from the passage of waiting time according to priority, thereby enabling communication. Certainty and stability can be improved.

It is a figure which shows an example of a structure of the radio | wireless communications system in embodiment of this invention. It is a figure which shows an example of the process structure of the transmission data in an EDCA system, and an example of the data structure of a transmission queue. It is a figure which shows an example of the operation | movement outline | summary of the CSMA / CA control in an EDCA system. It is a figure which shows the setting value of the content window in an EDCA system. It is a figure which shows an example of the operation | movement outline | summary of the internal collision control in an EDCA system. It is a figure which shows an example of a function structure of the radio | wireless communication apparatus in embodiment of this invention. Set value of CW _min and CW _max for each AC in the embodiment of the present invention, and is a table showing an example of the retransmission limit number for each AC. It is a table showing the calculation results of the CW _i for each AC allowable ST number in the embodiment of the present invention. It is a flowchart figure which shows an example in embodiment of this invention. It is a figure which shows an example of operation | movement of the radio | wireless communication apparatus in Example 1 of this invention. It is a figure which shows an example of the initial state of the transmission queue buffer part in embodiment of this invention. It is a figure which shows an example of operation | movement of the radio | wireless communication apparatus in Example 2 of this invention. It is a figure which shows an example of operation | movement of the radio | wireless communication apparatus in Example 3 of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In the embodiment of the present invention, the data of the second layer (MAC frame) and the data of the third layer or higher of the OSI reference model are referred to as a packet.
[System configuration]
FIG. 1 is a diagram illustrating an example of a configuration of a wireless communication system 1 according to an embodiment of the present invention.

  The wireless communication system 1 includes a wireless communication device 10 and an access point 20. The wireless communication device 10 and the access point 20 are communicably connected via a wireless LAN 99 (Local Area Network).

  The wireless communication device 10 is a device having an information processing function, a communication function, and the like, and has a function of performing wireless communication based on the IEEE802.11b / a / g / n standard. Further, in the present embodiment, the wireless communication device 10 generates various data types (for example, background communication for synchronization with a server by voice, moving image, mail, and application), and transmits / receives the data. The wireless communication device 10 performs priority control according to the attributes of these various types of data by the EDCA method defined in IEEE802.11e. Examples of the wireless communication device 10 include a smartphone, a PC (Personal Computer), a tablet terminal, or a PDA (Personal Digital Assistance).

  The access point 20 periodically transmits beacons (channel (frequency range), ESSID, supported transmission speed, security method, time stamp, QoS, etc.) to the surroundings. When the wireless communication device 10 enters the beacon reach range, the probe request is made by receiving the beacon (the ESSID set in the own device is transmitted). Thereafter, wireless communication is enabled through authentication and association between the access point 20 and the wireless communication device 10.

In the embodiment of the present invention, in FIG. 1, the communication mode is an infrastructure mode connected via the access point 20, but the plurality of wireless communication devices 10 directly communicate one-on-one without the access point 20. It may be an ad hoc mode communication mode.
[Basic operation of EDCA method]
The EDCA method is used as a wireless LAN access control method in the embodiment of the present invention. Therefore, first, an outline of the basic operation of the EDCA method will be described.

FIG. 2 is a diagram illustrating an example of a processing outline of transmission data and an example of a data structure of a transmission queue in the EDCA scheme. The outline of EDCA operation is as follows. As shown in FIG. 2, in EDCA, when data is received from an upper layer, four access categories (AC: AC) are selected according to priority based on data attributes (for example, data types such as audio and video). Access Category) (hereinafter referred to as “AC”). The four ACs are AC_VO (Voice), AC_VI (Video), AC_BE (Best Effort), and AC_BK (Background) in descending order of priority. A transmission queue corresponding to each AC exists, and packets classified for each AC are stored in the corresponding queues. Next, when transmitting a packet, CSMA / CA is performed independently for each queue, and then data is transmitted through a wireless channel. Here, when the transmission timings of a plurality of queues overlap, AC data having a high priority is transmitted. The parameter related to the waiting time before transmission used in access control is set according to the priority of AC, and CSMA / CA is performed according to the parameter, thereby giving a statistical difference to the frequency of packet transmission. As a result, more transmission opportunities can be given to AC data with high priority. In the process of classifying the transmission data as AC, for example, the value of the TOS (Type Of Service) field (8 bits) of the IP header and the priority value of the VLAN tag defined by IEEE802.1Q are assigned to each AC. Is done. As shown in FIG. 1, for example, when the TOS of a packet “P_VO _{i + 1} ” before being distributed to each transmission queue is mapped to AC_VO in advance, “P_VO _{i + 1} ” is distributed to the AC_VO queue. .

  FIG. 3 is a diagram illustrating an example of an outline of CSMA / CA operation in the EDCA method. FIG. 3 illustrates packet transmission processing operations in the two transmission queues AC_VO and AC_BE. In EDCA, carrier sense is performed in order to confirm whether a wireless channel for transmitting a packet is in use. If the wireless channel is not in use, it waits until the AIFS and backoff time elapses, and during that time, if the use of the wireless channel is not detected by carrier sense, transmission is started. The AIFS and backoff time are set according to the priority of AC, and the shorter the AC, the higher the priority, and the longer the AC, the lower the priority. Here, the priority of AC_VO is set higher than AC_BE.

  AIFS is a fixed waiting time before packet transmission set for each AC, and is defined by the following formula in IEEE802.1e.

ここでSIFS（Short Inter Frame Space）及びSlot Time（スロットタイム）は物理層（PHY）により定義される定数である。Slot Time（スロットタイム：ST）（以下、「ST」という。）は、AIFSとバックオフ時間を規定する基本単位時間である。AIFSN（AIFS Number）はAC毎に設定されるAIFSを定義するパラメータであり、IEEE802.1eにおいてデフォルト値は図４に示されるように規定されており、優先度の高いACほど小さい値となっている。

Here, SIFS (Short Inter Frame Space) and Slot Time are constants defined by the physical layer (PHY). Slot Time (ST) (hereinafter referred to as “ST”) is a basic unit time that defines AIFS and backoff time. AIFSN (AIFS Number) is a parameter that defines AIFS set for each AC. IEEE802.1e defines the default value as shown in Fig. 4, and the higher the priority, the smaller the value. Yes.

  The back-off time is a random waiting time before packet transmission set for each AC. The back-off time at the i-th packet transmission is expressed by the following equation.

Random関数は[0, CW_i]の範囲の一様な分布関数から生成される乱数値である。つまりCW（コンテンションウィンドウ：Contention Window）（以下、「CW」という。）は、乱数値の取り得る範囲を規定し、CW_min（最小値）≦CW_i≦CW_max（最大値）（但し、i=1の場合、CW₁ = CW_min）の関係がある。CW_min及びCW_maxの設定値はAC毎に異なり、IEEE802.1eでは図４に示されるようにAC毎にデフォルトの変数が定義され、優先度の高いACほど値が小さくなるように設定される。なお、AC毎のCWを区別する場合、例えばキューAC_VOに対応するCWは、CW[AC_VO]のように表す。

The Random function is a random value generated from a uniform distribution function in the range [0, CW _i ]. In other words, CW (Contention Window) (hereinafter referred to as “CW”) defines the range of random values, CW _min (minimum value) ≦ CW _i ≦ CW _max (maximum value) (however, When i = 1, there is a relationship of CW ₁ = CW _min ). The setting values of CW _min and CW _max are different for each AC. In IEEE802.1e, default variables are defined for each AC as shown in FIG. 4, and the values are set so that the higher the priority, the smaller the value. . When distinguishing CW for each AC, for example, CW corresponding to the queue AC_VO is represented as CW [AC_VO].

  In IEEE 802.11, an upper limit number of retransmissions (Retry Limit) (hereinafter referred to as “the upper limit number of retransmissions”) is set for a packet to be transmitted. Packets that exceed the maximum number of retransmissions are discarded at the transmitting terminal. Here, CW at the time of the i-th packet transmission from the first transmission of the packet stored in the queue until the upper limit of retransmission is reached is expressed by the following equation.

但し、i=1の場合、CW₁ = CW_minである。また、CW_i≦CW_maxであるので、CW_iの値がCW _maxより大きい場合、CW_i = CW_maxである。

However, when i = 1, CW ₁ = CW _min . Further, since CW _i ≦ CW _max , when the value of CW _i is larger than CW _max , CW _i = CW _max .

  The operation of CSMA / CA in EDCA is as shown in FIG. 3, for example, the waiting time of the queue AC_VO is 5ST which is the sum of AIFS = 2ST and backoff time = 3ST. On the other hand, the waiting time of the AC_BE queue is 10ST, which is the sum of AIFS = 3ST and backoff time = 7ST. Therefore, since the standby time of the queue AC_VO having a high priority with a short standby time until transmission elapses first, a transmission opportunity is given to P_VO1 first, and P_VO1 is output (dequeued) from the queue AC_VO. P_BE1 waits until P_VO1 is transmitted, and CSMA / CA is performed at that time.

FIG. 5 is a diagram illustrating an example of an outline of the operation of internal collision control when waiting times of a plurality of queues simultaneously become 0 in EDCA. In this case, the internal collision control described in IEEE802.11 gives a transmission opportunity to a packet in a queue having a high priority, and the packet is transmitted. On the other hand, for packets in a queue with low priority, “1” is added to the number of packet retransmissions, the backoff time is updated, and the packets are retransmitted. However, as described above, when the maximum number of retransmissions is exceeded, the packet is discarded.
[Function configuration]
FIG. 6 is a diagram illustrating an example of a functional configuration of the wireless communication device 10 according to the embodiment of the present invention.

  The wireless communication device 10 includes a CPU 11, a memory 12, a wireless LAN module 13, and the like.

  The memory 12 is a ROM that stores a wireless communication device program, a RAM that is used as a program load or a work area of the loaded program, and an NVRAM that stores various setting information of the wireless communication device 10. . Further, information such as the number of slot times for each AC and the upper limit number of retransmissions used for priority control of the present invention is stored.

  The transmission queue buffer unit 13 performs queuing and buffering of packets to be transmitted to the access point 20. The queue data structure of the transmission queue buffer unit 13 in the embodiment of the present invention is a data structure having four ACs of the EDCA method shown in FIG.

  The wireless LAN module 14 transmits and receives data by controlling the modulation method, transmission speed, frequency, and the like based on, for example, the IEEE802.11b / a / g / n standard. When data is received, the received radio wave is converted into a digital signal, and when data is transmitted, the data requested to be transmitted from the CPU 11 is modulated according to a communication standard and transmitted as a radio wave. The IP address of the wireless communication device 10 is given from a wireless LAN access point. The wireless LAN module 14 performs wireless communication using an ISM (Industry Science Medical) band of 2.4 GHz band or 5 GHz band according to the IEEE802.11b / a / g / n standard.

  The CPU 11 executes various functions by processing the wireless communication apparatus program loaded in the RAM of the memory 12. Programs executed by the CPU 11 include an input control unit 101, a priority control unit 102, a CSMA / CA transmission / reception control unit 103, an elapsed ST number recording unit 104, and the like. The priority control unit 102 includes an output packet determination unit 1021, a calculation unit 1022 including an allowable ST number calculation / setting unit 1023, a remaining ST number calculation unit 1024, and a backoff time update unit 1025.

  The input control means 101 stores the packet in one of the four AC queues of the priority based on the attributes of the packet to be transmitted (voice, video, still image, mail, etc.) and the transmission queue / buffer unit 13 mapped in advance. To do. The mapping is executed in association with, for example, the type set in the TOS of the IP header of the packet to be transmitted.

  The CSMA / CA transmission / reception control unit 103 controls the wireless LAN module 14 to transmit a packet determined as a transmission target by the priority control unit 102.

The priority control unit 102 determines that the output packet determination unit 1021 first determines the packet stored in one of the four AC queues of the transmission queue / buffer unit 13 based on a certain criterion calculated by the calculation unit 1022. Priority control is performed to determine a high priority packet to be transmitted. Note that the output packet determining means 1021, the allowable ST number calculating / setting means 1023, the remaining ST number calculating means 1024, and the backoff time updating means 1025, which are means for realizing the priority control means 102, are as follows. This will be described in the outline of control operation.
[Outline of operation of priority control of the present invention]
An outline of the priority control operation in the embodiment of the present invention will be described below.

  The priority control of the present invention is based on the following viewpoint. As described above with reference to FIG. 5, in the conventional EDCA technique, when an internal collision occurs, there is a high possibility that a packet in an AC queue with a low priority will not be given a transmission opportunity. It will be destroyed. Therefore, in the priority control of the present invention, a transmission opportunity is given preferentially to a packet that satisfies a certain standard different from the passage of AIFS and the back-off time so that an internal collision of the packet does not occur. Specific criteria will be described later.

  First, in priority control according to the embodiment of the present invention, a packet to be preferentially transmitted is determined based on the number of slot times of packets stored in each queue (hereinafter referred to as “ST number”). Here, as described above, the slot time (ST) is a basic unit time that defines the AIFS and the back-off time, and the AIFS and the back-off time are proportional to the ST. Therefore, AIFS = m × ST (m is a constant for each AC, AIFSN), and backoff time Backoff Time = CW × ST. The ST number is the number of slot times, and is m and CW.

  The priority control operation in the embodiment of the present invention is executed by the procedures (1) to (4).

(Procedure 1) Calculation of allowable ST number (performed by allowable ST number calculation / setting means 1023)
The allowable ST number is the ST number corresponding to the sum of the backoff times of each transmission when it is assumed that the packet has been transmitted up to the maximum number of retransmissions in the queue corresponding to each AC. The maximum number of retransmissions and the backoff time are values set according to the AC priority. Therefore, if the packet can be transmitted before the allowable ST number has elapsed, it can be said that the quality according to the priority (for example, service provision conditions required for voice service, background communication, etc.) can be satisfied. In principle, once the allowable ST number is calculated and stored in the memory 12, it is not changed unless the upper limit number of retransmissions and CW, which are parameters for determining the allowable ST number, are changed. A method for calculating the allowable ST number will be described later. Since the allowable ST number is a value set according to the priority as described above, the product of the allowable ST number and the ST is referred to as a priority correspondence time.

(Procedure 2) Recording of the elapsed ST number (executed by the elapsed ST number recording means 104)
The elapsed ST number is the ST number corresponding to the back-off time that has elapsed since the packet was input to each AC queue. That is, the total back-off time of packets for which no transmission opportunity was obtained. At this time, the back-off time is updated by the back-off time updating means 1025 for packets for which no transmission opportunity was obtained.

  (Procedure 3) The difference (number of remaining STs) between the allowable ST number and the elapsed ST number is calculated for each packet (executed by the remaining ST number calculating means 1024).

    The remaining ST number is the difference between the allowable ST number calculated in (Procedure 1) and the elapsed ST number recorded in (Procedure 2).

(Procedure 4) The packet with the smallest remaining ST number is determined as a transmission packet to be output first (executed by the output data determination means 1021)
In the conventional method, control is performed to give a transmission opportunity to a packet that has passed the AIFS and the back-off time at the time of transmitting one of the waiting packets stored in the four queues. Therefore, a packet transmission opportunity was not given to the AC queue with low priority. On the other hand, in the priority control of the present invention according to the procedures of (Procedure 1) to (Procedure 4), the standby time (AIFS and the AIFS and the standby time corresponding to the priority) is taken into consideration by considering the standby time that has elapsed since the packet is input to the queue. The probability that a transmission opportunity can be obtained also for packets for which the back-off time has not elapsed. Moreover, since the possibility of occurrence of an internal collision can be reduced, the processing load of the wireless communication device 10 can be reduced.
[Calculation of allowable ST number]
A method of calculating the allowable ST number calculated by the allowable ST number calculating / setting unit 1023 in the above (procedure 1) will be described.

From the equation (Equation 2), the maximum value that can be taken by the back-off time during the i-th packet transmission is CW _i × ST. Here, assuming that the upper limit number of retransmissions for packet transmission is n, the back-off time that elapses from the initial transmission to the upper limit number of retransmissions n times is:

と表される。

It is expressed.

  Hereinafter, a method for calculating the allowable ST number will be described using a specific example.

FIG. 7 shows a table showing an example of the set values of CW _min and CW _max for each of the four ACs and the upper limit number of retransmissions for each AC. Note that the setting values of CW for each AC are calculated values when CW _min = 15, AC_BE CW _max = 63, and AC_BK CW _max = 1023 in FIG.

The value of CW [AC_VO] _i when the packet is transmitted for the i-th time in the queue AC_VO is based on FIG. 7 and the above-described equation (Equation 3) and its conditions.
When i = 1, CW [AC_VO] ₁ = 3 (When i = 1, CW ₁ = CW _min )
When i = 2, CW [AC_VO] ₂ = 7 (From CW [AC_VO] ₁ × 2 + 1)
When i = 3, CW [AC_VO] ₃ = 7 (If CW [AC_VO] ₂ × 2 + 1 = 15> CW [AC_VO] max, CW [AC_VO] ₃ = CW [AC_VO] max)
If i = 4, CW [AC_VO] ₄ = 7
If i = 5, CW [AC_VO] ₅ = 7
It is calculated as follows. Since the upper limit number of retransmissions of the queue AC_VO is 4, there is no case where i = 6. Therefore, the maximum value of the back-off time that elapses from the first packet transmission to the upper limit number of retransmissions is “31ST” from Equation (Equation 4). Therefore, the ST number that is the number of slot times is “31”, and this value is the allowable ST number of the queue AC_VO. Calculating similarly for the other queues, CW _i and allowed ST number of each AC has a value as shown in FIG.
[Processing procedure]
FIG. 9 is a flowchart illustrating an example of a processing procedure of the wireless communication device 10 according to the embodiment of the present invention.

  First, the allowable ST number calculation / setting means 1023 calculates the allowable ST number corresponding to each AC queue, and sets the allowable ST number for each queue in the memory 12 (S1). The calculation result of the allowable ST number is, for example, a value shown in the table of FIG.

  Here, after the packet is dequeued, if the packet is transmitted and there is a packet waiting to be transmitted in another queue, the backoff time update unit 1025 backs off the packet waiting for transmission stored in the queue. The time is updated (S2). Note that the update operation of the back-off time is not executed during the first processing of this flowchart.

  The remaining ST number calculating means 1024 calculates the remaining ST number that is the difference between the allowable ST number and the elapsed ST number for each packet stored in each AC queue (S3).

  The output packet determining means 1021 compares the calculated remaining ST numbers of the respective packets, and determines a packet having the smallest remaining ST number from the queue as an output packet to be transmitted (S4).

  The output packet determining means 1021 determines whether or not there are a plurality of packets determined in step S4 (S5).

  When it is determined that there are a plurality of packets determined in step S4 (YES in S5), the output packet determination means 1021 compares the priority of each AC and determines the packet having the highest priority as an output packet to be taken out from the queue. (S6). The priorities are AC_VO, AC_VI, AC_BE, and AC_BK in descending order.

  On the other hand, when a plurality of packets determined in step S4 do not exist (NO in step S5), the packet determined in step S4 is determined as an output packet to be taken out from the queue.

  Subsequently, the CSMA / CA transmission / reception control means 103 transmits the output packet determined by the NO route in step S6 or step S5 by the CSMA method (S7).

  Thereafter, the elapsed ST recording means 104 records the elapsed ST number and notifies the backoff time means 1025 of the recording result (S8).

  After the transmission of the packet by the CSMA / CA transmission / reception control means 103, a transmission response from the transmission destination is received, and it is determined whether the transmission of the packet is successful (S9). In IEEE802.11, a procedure for confirming whether or not a packet has surely arrived at the destination is defined as an ACK procedure executed by the MAC sublayer. In the embodiment of the present invention, the access point 20 that has received a packet returns an ACK if the packet requires a ACK transmission. If the wireless communication apparatus 10 cannot receive this ACK, it is determined that packet transmission has failed.

  If the packet transmission is not successful (NO in S9), the CW value of the transmitted packet is updated (S11), and the process proceeds to step S2.

  On the other hand, if the transmission of the packet is successful (YES in S9), it is determined whether there is a packet waiting for transmission in the queue (S10).

  If there are no packets waiting to be transmitted in each queue (NO in S10), the process is completed.

On the other hand, if packets waiting to be transmitted remain in each queue (YES in S10), the processes after step S2 are repeated.
[Operation procedure]
<Example 1>
FIG. 10 is a diagram illustrating an example of a basic operation of the wireless communication device 10 according to the first embodiment of the present invention.

  In addition, the numerical value in FIG. 10 is a slot time number (ST number).

(initial state)
FIG. 11A is a diagram illustrating an initial state of packets stored in the transmission queue buffer unit 13 according to the first embodiment of the present invention. In FIG. 11A, packets P_VO1, P_VO2, and P_VO3 are stored in the queue AV_VO, and a packet P_VI1 is stored in the queue AC_VI.

  In the first embodiment of the present invention, the allowable ST number calculation / setting unit 1023 sets the allowable ST number of the queue AC_VO to “31” and sets the allowable ST number of the queue AC_VI to “31” as illustrated in FIG. Set to “67”. That is, in the initial state of FIG. 10 in which the waiting time for transmission has not elapsed, the remaining ST number calculating means 1024 sets the remaining ST, which is the difference between the allowed ST number and the elapsed ST number of the packets P_VO1 to P_VO3 to “31”. The remaining ST number of the packet P_VI1 is calculated as “67”.

As shown in FIG. 10, the ST number of AIFS [VO1 ₀ ] of P_VO1 in the initial state is “2”, the ST number of the initial backoff time [VO1 ₀ ] is “3”, and AIFS [VI1 of P_VI1 _The number of STs of [ ₀ ] is “3”, and the number of STs of the initial back-off time [VI1 ₀ ] is “7”. Note that the AIFS and backoff time of P_VO2 and P_VO3 are the same as P_VO1.

(State 1)
(A) Output packet determination and transmission The output packet determination means 1021 compares the remaining ST number “31” of P_VO1 with the remaining ST number “67” of P_VI1, and outputs P_VO1 having the smallest remaining ST number from the queue. The packet is determined, and the memory address of the packet to be transmitted is notified to the CSMA / CA transceiver 103. Next, the CSMA / CA transmission / reception unit 103 transmits the packet P_VO1 by the CSMA / CA method.

(B) Calculation and update of remaining ST number
At the time when P_VO1 is transmitted, the back-off time of P_VO1 is “3ST”. Therefore, the elapsed ST number recording unit 104 records the elapsed ST number as “3”. The remaining ST number “64”, which is the difference between the allowable ST number “67” of P_VI1 calculated by the remaining ST number calculating means 1024 and the elapsed ST number “3”, is the remaining ST number of P_VI1 in (state 2). .

(C) Update backoff time
The ST number of the back-off time of P_VI1 that has elapsed until P_VO1 is transmitted is (the ST number “2” of AIFS [VO ₀ ] ”+ (the ST number“ 3 ”of the back-off time [VO ₀ ])) − ( The ST number “3”) of AIFS [VI ₀ ] is calculated as “2”. Here, the back-off time update unit 1025 calculates the back-off time of P_VI1 in (state 2). The difference “5” between the ST number “7” of the initial backoff time [VI ₀ ] of P_VI1 and the ST number “2” of the backoff time of P_VI1 that has elapsed until P_VO1 is transmitted is (state 2). ) Is the backoff time of P_VI1.

(State 2)
(A) Determination and transmission of output packet
After transmission of P_VO1, P_VO2 is waiting to be transmitted in queue AC_VO. The output packet determining means 1021 compares the remaining ST number “31” of P_VO2 with the remaining ST number “64” of P_VI1, determines the P_VO2 having the smallest remaining ST number as an output packet to be taken out from the queue, and transmits / receives CSMA / CA The memory address of the packet to be transmitted is notified to the unit 103. Next, the CSMA / CA transmission / reception unit 103 transmits the packet P_VO2 by the CSMA / CA method.

(B) Calculation and update of remaining ST number
At the time when P_VO2 is transmitted, the back-off time of P_VO2 is “3ST”. Therefore, the elapsed ST number recording unit 104 records the elapsed ST number as “3”. The remaining ST number “61”, which is the difference between the allowable ST number “64” of P_VI1 calculated by the remaining ST number calculating means 1024 and the elapsed ST number “3”, is the remaining ST number of P_VI1 in (state 3). .

(C) Update backoff time
The ST number of the back-off time of P_VI1 that passed until P_VO2 was transmitted is (the ST number “2” of AIFS [VO ₀ ] ”+ (the ST number“ 3 ”of the back-off time [VO ₀ ]) − ( The ST number “3”) of AIFS [VI ₀ ] is calculated as “2”. Here, the back-off time updating unit 1025 calculates the back-off time of P_VI1 in (State 3). The difference “3” between the ST number “5” of the back-off time [VI] of P_VI1 in (state 2) and the ST number “2” of the back-off time of P_VI1 elapsed until P_VO1 is transmitted is ( This is the back-off time of P_VI1 in state 3).

(State 3)
(A) Determination and transmission of output packet
After transmission of P_VO2, P_VO3 is waiting to be transmitted in queue AC_VO. The output packet determination means 1021 compares the remaining ST number “31” of P_VO2 with the remaining ST number “61” of P_VI1, determines the smallest remaining ST number P_VO3 as an output packet to be taken out from the queue, and performs CSMA / CA transmission / reception The memory address of the packet to be transmitted is notified to the unit 103. Next, the CSMA / CA transmission / reception unit 103 transmits the packet P_VO3 by the CSMA / CA method.

(B) Calculation and update of remaining ST number
At the time when P_VO3 is transmitted, the back-off time of P_VO3 is “3ST”. Therefore, the elapsed ST number recording unit 104 records the elapsed ST number as “3”. The remaining ST number “58”, which is the difference between the allowable ST number “61” of P_VI1 calculated by the remaining ST number calculating means 1024 and the elapsed ST number “3”, is the remaining ST number of P_VI1 in (state 4). .

(C) Update backoff time
The ST number of the back-off time of P_VI1 that has elapsed until P_VO3 is transmitted is (the ST number “2” of AIFS [VO ₀ ] ”+ (the ST number“ 3 ”of the back-off time [VO ₀ ])) − ( The ST number “3”) of AIFS [VI ₀ ] is calculated as “2”. Here, the back-off time updating unit 1025 calculates the back-off time of P_VI1 in (state 4). The difference “1” between the ST number “3” of the back-off time [VI] of P_VI1 in (state 3) and the ST number “2” of the back-off time of P_VI1 elapsed until P_VO1 is transmitted is ( This is the back-off time of P_VI1 in state 4).

(State 4)
Here, the operation when P_VO3 transmitted in (state 3) fails to be transmitted and is retransmitted will be described. Since the transmission of P_VO3 has failed, in the initial state (state 4), the CW and backoff time of P_VO3 are updated. The CW of P_VO3 at this time is “7” when calculated based on the above-described equation (Equation 3). Therefore, the back-off time of P_VO3 is updated to “7ST”. Since the ST number of P_VO3 in (State 3) has passed “3”, the remaining ST number “3”, which is the difference between the allowable ST number “31” of P_VO3 in (State 3) and the elapsed ST number “3” “28” is the remaining ST number of P_VO3 in (state 4).

(A) Output packet determination and transmission Output packet determination means 1021 compares the remaining ST number “28” of P_VO3 with the remaining ST number “58” of P_VI1, and outputs P_VO3 having the smallest remaining ST number from the queue. The packet is determined, and the memory address of the packet to be transmitted is notified to the CSMA / CA transceiver 103. In this case, since the remaining ST number of P_VI1 is larger than P_VO3, even if the waiting time of P_VI1 elapses before the packet P_VO3 (even if the waiting time becomes 0), P_VI1 is not output. Next, the CSMA / CA transmission / reception unit 103 transmits the packet P_VO3 by the CSMA / CA method.

(B) Calculation and update of remaining ST number
At the time when P_VO3 is transmitted, the back-off time of P_VO3 is “7ST”. Therefore, the elapsed ST number recording unit 104 records the elapsed ST number as “7”. The remaining ST number “51”, which is the difference between the allowable ST number “58” of P_VI1 calculated by the remaining ST number calculation means 1024 and the elapsed ST number “7”, is the remaining ST number of P_VI1 in (state 5). .

(C) Update backoff time
The ST number of the back-off time of P_VI1 that has passed until P_VO3 is transmitted is (the ST number “2” of AIFS [VO ₀ ]) + (the ST number “7” of the back-off time [VO]) − (AIFS It is calculated as “6” by the ST number “3” of [VI ₀ ]. Here, the back-off time update unit 1025 calculates the back-off time of P_VI1 in (State 5). The difference between the ST number “1” of the back-off time [VI] of P_VI1 in (state 4) and the ST number “6” of the back-off time of P_VI1 that has elapsed until P_VO1 is transmitted is “−5” < Since it is 0, the back-off time of P_VI1 in (state 5) is not updated.

(State 5)
(A) Determination and transmission of output packet Since there is no packet waiting for transmission in the transmission queue except for P_VO3, the output packet determination means 1021 determines P_VO3 with the smallest remaining ST number as an output packet to be taken out from the queue, The memory address of the packet to be transmitted is notified to the CSMA / CA transceiver 103. Next, the CSMA / CA transmission / reception unit 103 transmits the packet P_VO3 by the CSMA / CA method.

<Example 2>
FIG. 12 is a diagram illustrating an example of the operation of the wireless communication device 10 according to the second embodiment of the present invention. In the second embodiment, a state in which a transmission opportunity is given to a packet having a lower priority than the prior art by the priority control of the present invention will be described. In addition, the numerical value of FIG. 12 is a slot time number (ST number).

(initial state)
FIG. 11B is a diagram illustrating an initial state of a packet stored in the transmission queue buffer unit 13 according to the second embodiment of the present invention. In FIG. 11B, packets P_VO1, P_VO2, P_VO3... P_VOi are stored in the queue AV_VO, and a packet P_BK1 is stored in the queue AC_BK.

  In the second embodiment of the present invention, the allowable ST number calculation / setting unit 1023 sets the allowable ST number of the queue AC_VO to “31” and sets the allowable ST number of the queue AC_BK to “31” as illustrated in FIG. Set to 3048 ". That is, in the initial state of FIG. 12 in which the standby time for transmission has not elapsed, the remaining ST number calculating means 1024 sets the remaining ST, which is the difference between the allowable ST number and the elapsed ST number of the packet P_VOi, to “31”, The number of remaining STs of the packet P_BK1 is calculated as “3048”.

As shown in FIG. 12, the ST number of AIFS [VOi ₀ ] of P_VOi in the initial state is “2”, the ST number of initial backoff time [VOi ₀ ] is “3”, and AIFS [BK1 of P_BK1 ₀ ] is “7”, and the initial backoff time [VI1 ₀ ] is “15”.

(State 1 ')
(A) Output packet determination and transmission Output packet determination means 1021 compares the remaining ST number “31” of P_VO1 with the remaining ST number “3048” of P_BK1, and outputs P_VO1 having the smallest remaining ST number from the queue. The packet is determined, and the memory address of the packet to be transmitted is notified to the CSMA / CA transceiver 103. Next, the CSMA / CA transmission / reception unit 103 transmits the packet P_VO1 by the CSMA / CA method.

(B) Calculation and update of remaining ST number
At the time when P_VO1 is transmitted, the back-off time of P_VO1 is “3ST”. Therefore, the elapsed ST number recording unit 104 records the elapsed ST number as “3”. The remaining ST number “3045”, which is the difference between the allowable ST number “3048” of P_BK1 calculated by the remaining ST number calculating means 1024 and the elapsed ST number “3”, is the remaining ST number of P_BK1 in (state 2 ′) Become.

(C) Update backoff time
The ST number of the backoff time of P_BK1 that has elapsed until P_VO1 is transmitted is (the ST number “2” of AIFS [VO ₀ ] ”+ (the ST number“ 3 ”of the backoff time [VO ₀ ])) − ( Since “−2” <0 according to the ST number “7” of AIFS [BK ₀ ], the back-off time update unit 1025 does not update the back-off time of P_BK1 in (state 2 ′) (state 2 The backoff time of P_BK1 in ') is "15".

(State 2 ')
(A) Determination and transmission of output packet
After transmission of P_VO1, P_VO2 is waiting to be transmitted in queue AC_VO. The output packet determination means 1021 compares the remaining ST number “31” of P_VO2 with the remaining ST number “3045” of P_BK1, determines the smallest remaining ST number P_VO2 as an output packet to be taken out from the queue, and transmits / receives CSMA / CA The memory address of the packet to be transmitted is notified to the unit 103. Next, the CSMA / CA transmission / reception unit 103 transmits the packet P_VO1 by the CSMA / CA method.

(B) Calculation and update of remaining ST number
At the time when P_VO2 is transmitted, the back-off time of P_VO2 is “3ST”. Therefore, the elapsed ST number recording unit 104 records the elapsed ST number as “3”. The remaining ST number “3042”, which is the difference between the allowable ST number “3045” of P_BK1 calculated by the remaining ST number calculating means 1024 and the elapsed ST number “3”, is the remaining ST number of P_BK1 in the next transition state Become.

(C) Update backoff time
The ST number of the backoff time of P_BK1 that passed until P_VO2 was transmitted is (the ST number “2” of AIFS [VO ₀ ] ”+ (the ST number“ 3 ”of the backoff time [VO ₀ ])) − ( According to AIFS [BK ₀ ] ST number “7”), “−2” <0. Therefore, the back-off time updating unit 1025 does not update the back-off time of P_BK1 in the next transition state, and the back-off time of P_BK1 in the next transition state is “15”.

(State i)
When the packet transmission process is repeated as described above, the remaining allowable ST number of P_BK1 becomes 30 when P_VOi is transmitted (when i = 1007).

(A) Determination and transmission of output packet
After transmission of P_VOi-1, P_VOi is waiting to be transmitted in queue AC_VO. The output packet determining means 1021 compares the remaining ST number “31” of P_VOi with the remaining ST number “30” of P_BK1, determines the P_BK1 having the smallest remaining ST number as an output packet to be taken out from the queue, and transmits / receives CSMA / CA The memory address of the packet to be transmitted is notified to the unit 103. In this case, since the remaining ST number of P_VOi is larger than P_BK1, P_VOi is not output even if the standby time of P_VOi elapses before P_BK1 (even if the standby time becomes 0). Next, the CSMA / CA transmission / reception unit 103 transmits the packet P_BK1 by the CSMA / CA method.

(B) Calculation and update of remaining ST number
At the time when P_BK1 is transmitted, the backoff time of P_BK1 is “15ST”. Therefore, the elapsed ST number recording unit 104 records the elapsed ST number as “15”. The remaining ST number “16”, which is the difference between the allowed ST number “31” of P_VOi calculated by the remaining ST number calculating means 1024 and the elapsed ST number “15”, is the remaining P_BK1 remaining in the next transition (state i + 1). ST number.

(C) Update backoff time
The ST number of the P_VOi time elapsed until P_BK1 is transmitted is (AIFS [BK ₀ ] ST number “7”) + (backoff time [BK ₀ ] ST number “15”) − (AIFS [ The ST number “2”) of VO ₀ ] becomes “20”, which is longer than the ST number “3” of the back-off time [VOi] of P_VOi. Therefore, the back-off time [VOi] of P_VOi is not updated in the next transition (state i + 1).

(State i + 1)
Since there is no packet waiting for transmission in the transmission queue except for P_VOi, the output packet determining means 1021 determines the smallest remaining ST number P_VOi as an output packet to be extracted from the queue, and sends it to the CSMA / CA transceiver 103. Notify the memory address of the packet. Next, the CSMA / CA transmission / reception unit 103 transmits the packet P_VOi by the CSMA / CA method.

  As described above, the ST number of the back-off time elapsed until the packet P_BK1 is transmitted is the difference “3018” between the allowable ST number [BK]: “3048” and the remaining ST number [BK]: “30”. is there. That is, in the embodiment of the present invention, the back-off time actually elapsed until P_BK1 is transmitted is “3018ST”, which is shorter than the total value “3048ST” of the maximum back-off time in the queue AC_BK. For this reason, packets stored in the queue AC_BK, which is an AC with low priority, can be transmitted earlier, and in this case, the service provision conditions required for P_BK (background communication) can be satisfied.

<Example 3>
FIG. 13 is a diagram illustrating an example of the operation of the wireless communication device 10 according to the third embodiment of the present invention. In the third embodiment, an operation when the number of remaining STs of packets existing in each AC queue is the smallest and the same value will be described. In addition, the numerical value of FIG. 12 is a slot time number (ST number).

(initial state)
FIG. 11C is a diagram illustrating an initial state of a packet stored in the transmission queue / buffer unit 13 according to the third embodiment of the present invention. In FIG. 11C, a packet P_VO1 is stored in the queue AV_VO, P_VI1 is stored in the queue AC_VI, and P_BK1 is stored in the queue AC_BK.

  In the initial state of the third embodiment of the present invention, as shown in FIG. 13, the remaining ST number calculating means 1024 sets the remaining ST number of the queue AC_VO to “31”, the remaining ST number of the queue AC_VI to “28”, The number of remaining STs in the queue AC_BK is calculated as “28”.

Further, as shown in FIG. 13, the ST number of AIFS [VO ₀ ] of P_VO1 in the initial state is “2”, and the ST number of initial backoff time [VO ₀ ] is “3”. The ST number of AIFS [VI ₀ ] of P_VI1 is “3”, and the ST number of the initial backoff time [VI ₀ ] is “3”. The ST number of AIFS [BK ₀ ] of P_BK1 is “7”, and the ST number of the initial back-off time [VI ₀ ] is “15”.

(State 1 ")
(A) Determination and transmission of output packet The output packet determination means 1021 compares the remaining ST number “31” of P_VO1 with the remaining ST number “28” of P_VI1 and the remaining ST number “28” of P_BK1. The ST number of packets is determined as an output packet to be extracted from the queue. Here, since the remaining ST numbers of P_VI1 and P_BK1 are the smallest and the same value, the output packet determining means 1021 determines P_VI1 stored in the queue AC_VI, which is an AC having a higher priority, as an output packet to be taken out from the queue. To do. Next, the output packet determining unit 1021 notifies the CSMA / CA transmitting / receiving unit 103 of the memory address of the packet to be transmitted. Next, the CSMA / CA transmission / reception unit 103 transmits the packet P_VI1 by the CSMA / CA method.

(B) Calculation and update of remaining ST number
At the time when P_VI1 is transmitted, the back-off time of P_VI1 is “3ST”. Therefore, the elapsed ST number recording unit 104 records the elapsed ST number as “3”. The remaining ST number of P_VO1 is P_VO1 when the remaining ST number “28”, which is the difference between the allowable ST number “31” in (state 1 ″) and the elapsed ST number “3”, makes the next transition (state 2 ″). The number of remaining STs of P_BK1 at the next transition (state 2 ″) is “25”, as in the case of calculating the number of remaining STs of P_VO1.

(C) Update backoff time
The ST number of the time of P_VO1 elapsed until P_VI1 is transmitted is (AIFS [VI ₀ ] ST number “3”) + (Backoff time [VI ₀ ] ST number “3”) − (AIFS [ The ST number “2”) of VO ₀ ] becomes “4”, which is longer than the ST number “3” of the back-off time [VOi] of P_VOi. Therefore, the backoff time [VO] of P_VO1 is not updated at the next transition (state 2 ″), and the backoff time of P_VO1 at the next transition state is “3”.

On the other hand, the ST number of the back-off time of P_BK1 that has elapsed until P_VI1 is transmitted is (AIFS [VI ₀ ] ST number “3”) + (ST number “3” of back-off time [VI ₀ ]) − (− 1) <0 according to (ST number “7” of AIFS [BK ₀ ]). Therefore, the back-off time update unit 1025 does not update the back-off time of P_BK1 in the next transition (state 2 ″), and the back-off time of P_BK1 in the next transition state becomes “15”.

(State 2 ")
(A) Determination and transmission of output packet Output packet determination means 1021 compares the remaining ST number “28” of P_VO1 with the remaining ST number “25” of P_BK1, and outputs P_BK1 having the smallest remaining ST number from the queue. The packet is determined, and the memory address of the packet to be transmitted is notified to the CSMA / CA transceiver 103. In this case, since the remaining ST number of P_VO1 is larger than P_BK1, P_VO1 is not output even if the standby time of P_VO1 elapses before P_BK1 (even if the standby time becomes 0). Next, the CSMA / CA transmission / reception unit 103 transmits the packet P_BK1 by the CSMA / CA method.

As described above, the priority control of the present invention proposes a new method that does not exist in the conventional priority control method, and is for data that satisfies a certain standard different from the passage of the waiting time according to the priority. By giving transmission opportunities preferentially, it is possible to improve the reliability and stability of communication. Further, by applying the priority control of the present invention, it is possible to reduce the probability of occurrence of internal packet collisions, increase the opportunity to transmit packets with particularly low priority, and reduce the processing load on the device.
[Modification]
In the embodiment of the present invention, the priority control method of the present invention is applied to the priority control of the EDCA method, but may be applied to other QoS control.

  In the embodiment of the present invention, the priority control method according to the present invention is applied to a wireless LAN (IEEE802.11x), but may be applied to QoS control in a wired LAN.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications are possible within the scope of the gist of the present invention described in the claims. Can be changed.

DESCRIPTION OF SYMBOLS 1 Wireless communication system 10 Wireless communication apparatus 13 Transmission queue buffer part 101 Input control means 102 Priority control means 103 CSMA / CA transmission / reception control means 104 Elapsed ST number recording means 1021 Output packet determination means 1022 Calculation means 1023 Calculation and setting of allowable ST number Means 1024 Remaining ST number calculation means 1025 Backoff time update means

JP 2006-135441 A

Claims (10)

Have a priority control means for transmitting a small difference data between the elapsed waiting time priority higher short-defined priorities corresponding time and the transmission data based on the attribute of the transmission data,
The priority corresponding time is a wireless communication apparatus corresponding to the sum of back-off times when the transmission data is transmitted up to the maximum number of retransmissions set for each priority . The wireless communication apparatus according to claim 1, wherein the total sum of the back-off times is set so as to satisfy a service provision condition corresponding to the priority. It said priority control means, when a plurality of data difference between the waiting time and the elapsed and between the priority pair latency time are equivalent is present, the wireless of claim 1 or 2, wherein transmitting the high the priority data Communication device.   The wireless communication apparatus according to claim 1, wherein the priority control unit is applied to an EDCA method. 5. The backoff time according to claim 1, wherein the backoff time is based on a product of a contention window value defining a random range and a slot time that is a minimum unit time constituting the backoff time. Wireless communication device. The back-off time is determined by the contention window value CWi, the slot time ST, and the number of retransmissions n.

The wireless communication apparatus according to claim 5, defined as: A priority control method executed in a wireless communication device,
The priority based on the attribute of the transmission data is higher as a priority control means for transmitting data having a smaller difference between the priority response time defined shorter and the waiting time for which the transmission data has passed,
The priority control method corresponds to a priority control method , wherein the priority response time corresponds to a total sum of backoff times when the transmission data is transmitted up to the maximum number of retransmissions set for each priority. The priority control method according to claim 7, wherein the total sum of the back-off times is set so as to satisfy a service provision condition corresponding to the priority. A priority control program executed in a wireless communication device,
The priority based on the attribute of the transmission data is higher as a priority control means for transmitting data having a smaller difference between the priority response time defined shorter and the waiting time for which the transmission data has passed,
The priority control program corresponds to a priority control program corresponding to the sum of back-off times when the transmission data is transmitted up to the retransmission upper limit number set for each priority. The priority control program according to claim 9, wherein the total back-off time is set so as to satisfy a service provision condition corresponding to the priority.

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