JP6009993B2 - Base station apparatus and base station sleep control method - Google Patents

Description

  The present invention relates to a base station apparatus using a sleep mode and a base station sleep control method in a wireless communication system.

  In recent years, wireless local area networks (LANs) have become widespread in homes and offices, and wireless LAN functions are installed in many information devices and widely used as a means of Internet access. The specification of a wireless LAN that is generally used is standardized as IEEE (The Institute of Electrical and Electronics Engineers, Inc.) 802.11 standard.

  Generally, power saving is required for communication devices. Also in the IEEE 802.11 standard, as a power saving function of a wireless LAN terminal device (hereinafter referred to as “terminal”), operation of a power save mode based on switching between an active state and a sleep state is defined. An active terminal can perform all functions of transmission, reception, and listening. On the other hand, in a terminal in the sleep state, execution of some functions of transmission, reception, and listening is restricted by cutting off power supply to some circuits. In the sleep state, the power consumption of the terminal is smaller than in the active state.

  Hereinafter, the power save mode of the terminal will be described. The terminal uses a TIM (Traffic Indication Map) element on the beacon frame transmitted by the access point device to confirm whether data reception is necessary. When it is necessary to receive data, the terminal operates in an active state until all data reception is completed. When there is no need to receive data, the terminal is operated in an active state only when a beacon frame having a DTIM (Delivery Traffic Indication Message) count of 0 is received. The terminal achieves power saving by shifting to the sleep state at times other than when receiving a beacon frame in which the DTIM count is 0. The terminal can be a device driven by a battery, and power saving is more important in battery driving. For this reason, the power saving function of the terminal is defined by the IEEE 802.11 standard (for example, Non-Patent Document 1).

  On the other hand, the access point device is designed on the assumption that power is always supplied. Therefore, the IEEE 802.11 standard does not specify the power saving function of the access point device. NAV (Network Allocation Vector), which is a reservation signal that sets the channel reservation period of the used channel, is used as a power saving function of the access point device that is realized in accordance with the IEEE 802.11 standard without changing the function on the terminal side. A utilized power save mode has been proposed (for example, Non-Patent Document 2).

  Consider a case in which all TBTTs (Target Beacon Transmission Times) are DTIM counts and the terminal receives all beacon frames transmitted by the access point device. Since the power save mode in the terminal and the power save mode in the access point device operate in a beacon cycle, they can be applied simultaneously. In other words, in order to achieve both the power save mode in the terminal and the power save mode in the access point device, both modes need to operate in a beacon cycle.

IEEE Std 802.11TM-2007 Feng Zhang, et al, "Power saving Access Points for IEEE 802.11 Wireless Network Infrastructure", WCNC, 2004.

  FIG. 6 is a configuration example of the related art representing a model in which one access point apparatus 100 and one terminal 200 are wirelessly connected. Here, a one-to-one model is shown for convenience, but the following description also applies to a case where a one-to-many model is used by using two or more terminals.

  In FIG. 6, the access point device 100 is wirelessly connected to the terminal 2 in the infrastructure mode. The access point device 100 includes an antenna 101, a wireless communication processing unit 102, and a power management management unit 103. The wireless communication processing unit 102 communicates with the terminal 200 via the antenna 101. The power management management unit 103 monitors the communication status of the wireless communication processing unit 102 and restricts the operation of the wireless communication processing unit 102 to execute the sleep function when the wireless communication processing unit 102 does not need to be operated. .

  FIG. 7 is a diagram illustrating an example of frame transmission / reception when the sleep function is executed in the wireless communication processing unit 102. When the frame is not held in the transmission buffer at the time of TBTT 701 and the frame is not received from the terminal 200 within a certain time immediately before the TBTT 701, the access point apparatus 100 transmits the beacon frame 7101 through The terminal 200 is notified of the channel reservation period. The terminal 200 notified of the channel reservation period cannot transmit even if a data frame is generated in the channel reservation period. Therefore, the access point device 100 can operate in the sleep state during the channel reservation period.

  The TIM element of the beacon frame 7101 indicates that the access point device 100 does not hold a data frame addressed to the terminal 200 and a broadcast data frame. Therefore, terminal 200 operates in the sleep state until TBTT 702. Even if a data frame occurs in terminal 200 up to TBTT 702, terminal 200 does not transmit the generated data frame in the channel reservation period indicated by previous beacon frame 7101.

  FIG. 7 shows a case where data frames 8201 and 8202 addressed to the terminal 200 are held in the transmission buffer at the time of TBTT 702. In this case, the access point apparatus 100 notifies the terminal 200 that the data frames 8201 and 8202 addressed to the terminal 200 exist in the transmission buffer through the TIM element of the beacon frame 7102. The terminal 200 that has received the beacon frame 7102 transmits a PS_POLL frame 8101 to notify the access point apparatus 100 that the data frame 8201 can be received. The access point apparatus 100 that has received the PS_POLL frame 8101 transmits a data frame 8201 to the terminal 200. At this time, the access point apparatus 100 sets the MoreData field of the data frame 8201 to 1, and notifies the terminal 200 that there is a data frame 8202 to be continuously transmitted. The terminal 200 that has received the data frame 8201 returns an ACK (ACKnowledgement) frame 8301 and waits in an active state. The access point apparatus 100 that has received the ACK frame 8301 continuously transmits a data frame 8202 to the terminal 200. At that time, the access point apparatus 100 sets the MoreData field of the data frame 8202 to 0, and notifies the terminal 200 that there is no data frame to be continuously transmitted. The terminal 200 that has received the data frame 8202 returns an ACK frame 8302 and, since there is no data frame to be continuously received, shifts to a sleep state until TBTT 703. At this time, the access point device 100 cannot shift to the sleep state and operates in the active state even though there is no frame to communicate.

  Even if a data frame 8203 occurs in the access point device 100 before TBTT 703, it cannot be transmitted to the terminal 200. After TBTT 703, access point apparatus 100 transmits / receives data frame 8203 by the same method as described above. Even in this case, the access point apparatus 100 operates in an active state after transmission of the data frame 8203 even though there is no frame to be communicated. As described above, there is a problem that power consumption is wasted during a period of operation in the active state even though there is no frame to be communicated.

  In view of the above circumstances, an object of the present invention is to provide a base station apparatus and a sleep control method for a base station that improve the power saving efficiency of sleep control by aggregated transmission of data frames.

  One aspect of the present invention is a base station apparatus that communicates with a terminal station via a wireless channel while transitioning between an active state and a sleep state, a buffer memory that stores transmission planned data, and transmission of the transmission planned data Even if the data transmission time calculation unit for calculating the transmission time required for the transmission, the allowable delay time calculation unit for calculating the delay time allowed for each data frame of the scheduled transmission data, and the sleep state for a certain period, When the required transmission time is within the allowable delay time range for all the data frames, a transition processing unit that shifts to the sleep state for the certain period is provided.

  In the aspect of the invention, the data transmission time calculation unit calculates the required transmission time based on a transmission rate and a data amount of the transmission scheduled data.

  In the aspect of the invention, the allowable delay time calculation unit calculates a delay time allowed for each data frame based on an access category of the data frame.

  Further, according to one aspect of the present invention, in a sleep control method for a base station that communicates with a terminal station via a wireless channel while transitioning between an active state and a sleep state, the step of storing transmission schedule data and the transmission A step of calculating a transmission time required for transmission of the scheduled data, a step of calculating a delay time allowed for each data frame of the transmission planned data, and the transmission time even if the sleep state is shifted to a certain period Is within a range of allowable delay times for all the data frames, the method includes a step of shifting to a sleep state for the certain period.

  ADVANTAGE OF THE INVENTION According to this invention, the efficiency of the power saving of sleep control can be improved.

It is a functional block diagram which shows the structure of the access point apparatus by one Embodiment of this invention. It is a flowchart which shows the state switching operation | movement of an access point apparatus. It is a flowchart which shows the flow of a calculation process of allowable delay time. It is a figure which shows an example of the parameter preserve | saved at the information storage part. It is a figure which shows an example of the state switching operation | movement of an access point apparatus. It is a structural example of a prior art. It is a figure which shows an example of the state switching operation | movement in a prior art.

  A wireless LAN access point device (hereinafter referred to as “access point device”) according to an embodiment of the present invention will be described below with reference to the drawings. In the following description, as an embodiment of the present invention, a case where communication between an access point apparatus and a wireless LAN terminal (hereinafter referred to as “terminal”) is performed according to the IEEE 802.11 standard will be described.

FIG. 1 is a functional block diagram showing a configuration of an access point device 1 according to an embodiment of the present invention. In FIG. 1, an access point device 1 is wirelessly connected to a terminal 2 in an infrastructure mode.
The access point device 1 includes an antenna 11, a wireless communication processing unit 12, a power management management unit 13 (transition processing unit), a frame transmission time calculation unit 14 (data transmission time calculation unit), an allowable delay time calculation unit 15, and information storage. A portion 16 is provided. The wireless communication processing unit 12 performs various communication processes with the terminal 2 via the antenna 11. The wireless communication processing unit 12 includes a buffer 12a (buffer memory) for temporarily storing transmission data. The power management management unit 13 performs power management of the wireless communication processing unit 12. This power management includes switching processing between the active state and the sleep state. The frame transmission time calculation unit 14 executes a frame transmission time calculation process in response to an instruction from the power management management unit 13 and transmits the calculation result to the power management management unit 13. The allowable delay time calculation unit 15 executes an allowable delay time calculation process in response to an instruction from the power management management unit 13 and transmits the calculation result to the power management management unit 13. The information storage unit 16 stores various types of information described later.

FIG. 2 is a flowchart showing the switching procedure of the active state / sleep state in the access point device 1. Details of the switching procedure will be described with reference to the flowchart of FIG.
The flow in FIG. 2 starts with the timing of TBTT _AP- T _Awake as a trigger. The TBTT _AP is the TBTT of the access point device 1. T _Awake is a time determined so as to be always in an active state for the purpose of reliably receiving a new terminal belonging signal and a data frame held in the buffer 12a addressed to the terminal 2. When T _Awake is set to a small value, the power saving effect is increased.

The power management manager 13 determines whether or not the wireless communication processor 12 is in a sleep state (S1).
When the wireless communication processing unit 12 is in the sleep state (S1-Yes), the power management management unit 13 shifts the wireless communication processing unit 12 to the active state and changes the state to be able to receive the frame (S2). The process proceeds to S3. On the other hand, when the wireless communication processing unit 12 is in the active state (S1-No), the power management management unit 13 proceeds to the process of S3 while keeping the wireless communication processing unit 12 in the active state.
Next, the wireless communication processing unit 12 performs transmission / reception freely in the time until TBTT _AP , and the power management management unit 13 performs the time T _Awake from the timing of TBTT _AP- T _{Awake to} the timing of TBTT _AP. Then, it is determined whether or not the wireless communication processing unit 12 has received a data frame from the terminal 2 (S3).

数式（１）において、ＢＩはＴＢＴＴとＴＢＴＴとの間隔を示すビーコンインターバル、Ｂはビーコンの送信に要する時間である。Ｔ_{Ｒｅｓｅｒｖｅ}とＴ_{Ａｗａｋｅ}との値によって、スリープ効率が定まる。前述の通り、Ｔ_{Ａｗａｋｅ}の時間内は、無線通信処理部１２は必ずアクティブ状態となる。 When the wireless communication processing unit 12 receives a data frame from the terminal 2 during the time T _Awake (S3-Yes), the wireless communication processing unit 12 sets a beacon without setting a channel reservation period at the timing of TBTT _AP. (S9), and the power management management unit 13 maintains the active state of the wireless communication processing unit 12 until the next TBTT _AP (S10).
On the other hand, when the wireless communication processing unit 12 does not receive the data frame from the terminal 2 during the time T _Awake , the power management management unit 13 stores the data in the transmission buffer 12a of the wireless communication processing unit 12 at the timing of TBTT _AP. It is determined whether there is a data frame addressed to the terminal 2 (S4).
In the determination of S4, when there is no data frame addressed to the terminal 2 in the transmission buffer 12a of the wireless communication processing unit 12 (S4-No), the wireless communication processing unit 12 sets the channel reservation period T _RESERVE at the timing of TBTT _AP. The beacon is set and transmitted (S11), and the power management manager 13 shifts the wireless communication processor 12 to the sleep state (S12). The value of T _RESERVE can be expressed by the following mathematical formula (1).

In Equation (1), BI is a beacon interval indicating an interval between TBTT and TBTT, and B is a time required for transmitting a beacon. The sleep efficiency is determined by the values of T _Reserve and T _Awake . As described above, the wireless communication processing unit 12 is always in an active state during the time of T _Awake .

数式（２）において、Ｔ_{ＤＡＴＡ，ｉ}は、フレーム番号ｉのデータフレームの送信に要する時間であり、Ｔ_{ＡＣＫ，ｉ}は、フレーム番号ｉのデータフレームに対するＡＣＫフレームの送信に要する時間である。これらは、端末２との通信に用いている変調レート及びフレームサイズに基づいて算出する。また、ＤＩＦＳ(Distributed Inter Frame Space)、ＣＷｍｉｎ、Ｓｌｏｔ＿ｔｉｍｅ、ＳＩＦＳ(Short Inter Frame Space)は、ＩＥＥＥ８０２．１１規格で定められている値である。
フレーム送信時間算出部１４は、算出した時間Ｔをパワーマネジメント管理部１３に送信して、フレーム送信時間の算出処理を完了する。 On the other hand, when the data frame addressed to the terminal 2 exists in the transmission buffer 12a of the wireless communication processing unit 12 in the determination of S4 (S4-Yes), the frame transmission time calculation unit 14 is based on the instruction of the power management management unit 13. Performs a frame transmission time calculation process (S5).
Here, the frame transmission time calculation process will be described. The frame transmission time calculation process is triggered by the notification from the power management management unit 13. The frame transmission time calculation unit 14 that has received the notification from the power management management unit 13 calculates the time T required to transmit all the data frames stored in the buffer 12a by the following mathematical formula (2).

In Equation (2), T _{DATA, i} is the time required for transmitting the data frame with frame number i, and T _{ACK, i} is the time required for transmitting the ACK frame for the data frame with frame number i. These are calculated based on the modulation rate and frame size used for communication with the terminal 2. Further, DIFS (Distributed Inter Frame Space), CWmin, Slot_time, and SIFS (Short Inter Frame Space) are values defined in the IEEE 802.11 standard.
The frame transmission time calculation unit 14 transmits the calculated time T to the power management management unit 13 to complete the frame transmission time calculation process.

数式（３）において、ＢＩはＴＢＴＴとＴＢＴＴとの間隔を示すビーコンインターバル、Ｔ_{Ｂｅａｃｏｎ}はビーコンフレームの送信に要する時間を示している。
バッファ１２ａに保持している全てのデータフレームを次のビーコン送信時迄に送信不可能な場合（Ｓ６−Ｙｅｓ）、無線通信処理部１２は、ＴＢＴＴ_ＡＰのタイミングで、チャネル予約期間を設定せずにビーコンを送信し（Ｓ９）、パワーマネジメント管理部１３は、次のＴＢＴＴ_ＡＰまで無線通信処理部１２のアクティブ状態を維持させる（Ｓ１０）。この場合、アクティブ状態を維持するため、バッファ１２ａに保存されたデータフレームを送信することができる。つまり、ビーコンインターバルの間に全て送信できない量のデータフレームをバッファ１２ａに保持しているため、データフレームをビーコンインターバル内に集約して送信することができる。 Returning to FIG. 2, the power management management unit 13 determines whether or not the data frame held in the buffer 12 a can be transmitted by the next beacon transmission depending on whether or not the following mathematical formula (3) is satisfied. Determine (S6).

In Equation (3), BI represents a beacon interval indicating an interval between TBTT and TBTT, and T _Beacon represents a time required for transmitting a beacon frame.
If all the data frames held in the buffer 12a cannot be transmitted by the time of the next beacon transmission (S6-Yes), the wireless communication processing unit 12 does not set the channel reservation period at the timing of TBTT _AP. (S9), the power management management unit 13 maintains the active state of the wireless communication processing unit 12 until the next TBTT _AP (S10). In this case, in order to maintain the active state, the data frame stored in the buffer 12a can be transmitted. That is, since an amount of data frames that cannot be transmitted during the beacon interval is held in the buffer 12a, the data frames can be aggregated and transmitted within the beacon interval.

  On the other hand, when all the data frames held in the buffer 12a can be transmitted before the next beacon transmission (S6-No), based on the instruction of the power management management unit 13, the allowable delay time calculation unit 15 An allowable delay time calculation process is executed (S7).

Here, the flow of the calculation process of the allowable delay time will be described in detail with reference to FIG. The calculation process of the allowable delay time is triggered by the notification from the power management management unit 13 (S13).
As an initial value, 1 is substituted into i (S14). i is an identifier of a data frame held in the buffer 12a. Next, it is determined whether i exceeds N (S15). N indicates the number of data frames held in the buffer 12a.
When i is larger than N (S15-No), that is, when all held data frames are referred to, the allowable delay time calculation unit 15 ends the calculation process of the allowable delay time (S16), and the allowable delay The power management manager 13 is notified of the end of the time calculation process.
On the other hand, if i is N or less (S15-Yes), BI is added to T _{Delay, i} corresponding to data frame i (S17), and the delay time in the case of transmitting data frame i in the next TBTT is estimated.

Ｔ_{ＭａｘＤｅｌａｙ，ＢＫ}は、アクセスカテゴリＢＫにおいて許容できる遅延時間を定義した値であり、要求されるサービススペックによって定めることができる。
データフレームｉのアクセスカテゴリＡＣ_ｉがＢＥ（ベスト・エフォート用）の場合、下記の数式（５）を充足するか否かによって、スリープ制御によって遅延を許容できるか否かの判定を行う（Ｓ２０）。

Ｔ_{ＭａｘＤｅｌａｙ，ＢＥ}は、アクセスカテゴリＢＥにおいて許容できる遅延時間を定義した値であり、要求されるサービススペックによって定めることができる。
データフレームｉのアクセスカテゴリＡＣ_ｉがＶＩ（ビデオ伝送用）の場合、下記の数式（６）を充足するか否かによって、スリープ制御によって遅延を許容できるか否かの判定を行う（Ｓ２１）。

Ｔ_{ＭａｘＤｅｌａｙ，ＶＩ}は、アクセスカテゴリＶＩにおいて許容できる遅延時間を定義した値であり、要求されるサービススペックによって定めることができる。
データフレームｉのアクセスカテゴリＡＣ_ｉがＶＯ（音声用）の場合、下記の数式（７）を充足するか否かによって、スリープ制御によって遅延を許容できるか否かの判定を行う（Ｓ２２）。

Ｔ_{ＭａｘＤｅｌａｙ，ＶＯ}は、アクセスカテゴリＶＯにおいて許容できる遅延時間を定義した値であり、要求されるサービススペックによって定めることができる。 Next, with reference to the access category ACi data frame i, the access category AC _i, branches the next step (S18). The classification of the access category AC _i follows the provisions of the IEEE 802.11 standard.
If the access category AC _i of the data frame i is BK (for background traffic), depending on whether satisfies the formula (4) below, to determine whether or not an acceptable delay by sleep control (S19 ).

T _{MaxDelay, BK} is a value defining a delay time allowable in the access category BK, and can be determined by a required service specification.
If the access category AC _i of the data frame i is BE (for best effort), depending on whether satisfies Equation (5) below, to determine whether or not an acceptable delay by sleep control (S20) .

T _{MaxDelay, BE} is a value that defines an allowable delay time in the access category BE, and can be determined by a required service specification.
If the access category AC _i of the data frame i is VI (for video transmission), depending on whether satisfies Equation (6) below, to determine whether or not an acceptable delay by sleep control (S21).

T _{MaxDelay, VI} is a value that defines an allowable delay time in the access category VI, and can be determined by a required service specification.
If the access category AC _i of the data frame i is VO (for voice), depending on whether satisfies Equation (7) below, to determine whether or not an acceptable delay by sleep control (S22).

T _{MaxDelay, VO} is a value defining a delay time allowable in the access category VO, and can be determined by a required service specification.

When the prescribed relational expression is satisfied in S19 to S22, that is, when the delay of the data frame i can be tolerated, it is determined whether or not the data frame i is a priority frame for other reasons (S23). The priority frame for other reasons is a frame that should be prioritized for reasons other than the access category, such as the data frame i being a broadcast frame. When the data frame i is not a priority frame for other reasons (S23-No), the value of Flag _i indicating whether or not the delay of the data frame i is allowed is set to 0 (S24).
On the other hand, if the data frame i is a priority frame for other reasons (S23-Yes), and if the prescribed relational expression is not satisfied in S19 to S22, the value of Flag _i indicating whether or not the delay of the data frame i is allowed Is set to 1 (S25).
Then, the identifier i is advanced to the next data frame (S26), and each processing after S15 is repeated.

Returning to FIG. 2, after the calculation process of the allowable delay time is completed, the power management management unit 13 checks all the data frames and determines whether the value of Flag _i is 0 (S8).
If the value of Flagi is 0 in all data frames (S8-Yes), that is, if the delay time due to transmission after the next TBTT _AP is allowed in all data frames i, the wireless communication processing unit 12 At the timing of TBTT _AP , a channel reservation period T _RESERVE is set and a beacon is transmitted (S11), and the power management management unit 13 shifts the wireless communication processing unit 12 to a sleep state (S12).

On the other hand, if there is even one data frame with a Flag _i value of 1 (S8-No), the wireless communication processing unit 12 transmits a beacon without setting a channel reservation period at the timing of TBTT _AP. (S9) The power management management unit 13 maintains the active state of the wireless communication processing unit 12 until the next TBTT _AP (S10). In this case, since there is a frame whose delay cannot be allowed until the next TBTT, the sleep state is not shifted after the beacon frame is transmitted.

A priority order of data frames to be transmitted when the beacon frame is in an active state after transmission will be described. As for the data frame existing in the buffer 12a, the data frame whose Flag _i value is 1 is transmitted most preferentially. That is, transmission is performed preferentially from a data frame whose delay time has already increased. Next, for a data frame with a Flag _i value of 0, the difference between the allowable delay time (eg, T _{MaxDelay, BK in} the case of the access category _BK ) and the expected delay time (T _{Delay, i} ) is small. Sent preferentially from the frame.

  The parameters indicating the characteristics of each data frame used in the above description are managed by the information storage unit 16. FIG. 4 is a diagram illustrating an example of parameters. Information managed by the information storage unit 16 can be referred to and modified from the power management management unit 13, the frame transmission time calculation unit 14, and the allowable delay time calculation unit 15.

  An example of the frame transmission / reception operation by the access point device 1 will be described with reference to FIG. When the frame is not held in the buffer 12a at the time of the TBTT 101 and no frame is received from the terminal 2 at a certain time immediately before the TBTT 101, the access point apparatus 1 transmits a beacon frame 1101 to transmit a channel reservation period. To the terminal 2. The terminal 2 notified of the channel reservation period cannot transmit the data frame even if a data frame occurs in the channel reservation period. Therefore, the access point device 1 can operate in the channel reservation period in the sleep state.

  The TIM element of the beacon frame 1101 indicates that the access point device 1 does not hold a data frame addressed to the terminal 2 and a broadcast data frame. Therefore, the terminal 2 can operate in the sleep state until the TBTT 102. Even if a data frame occurs in the terminal 2 before the TBTT 102, the data frame is not transmitted in the channel reservation period indicated by the previous beacon frame 1101.

  As an example, assume that data frames 2201 and 2202 addressed to the terminal 2 are held in the buffer 12a at the time of TBTT102. In this example, all transmissions of the data frames 2201 and 2202 are expected to be completed by the TBTT 103, and the delay time of each of the data frames 2201 and 2202 is allowed. In this case, the access point apparatus 1 does not notify the terminal 2 using the TIM element even though the data frame to be transmitted to the terminal 2 is held. Instead, it notifies the terminal 2 of the channel reservation period and shifts to the sleep state.

  At the time of TBTT 103, the data frames 2201, 2202, 2203 addressed to the terminal 2 are held in the buffer 12a. In this example, all transmissions of the data frames 2201, 2202, 2203 are expected to be completed by the TBTT 104, but the delay time of each of the data frames 2201, 2202 is not allowed. In this case, the access point apparatus 1 notifies that the data frames 2201, 2202, 2203 addressed to the terminal 2 exist in the buffer 12a through the TIM element of the beacon frame 103. The terminal 2 that has received the beacon frame 1103 transmits a PS_POLL frame 2101 to notify the access point device 1 that the data frame can be received. The access point device 1 that has received the PS_POLL frame 2101 transmits a data frame 2201 to the terminal 2. At that time, the access point apparatus 1 sets the MoreData field of the data frame 2201 to 1, and notifies the terminal 2 that there is a data frame 2202 to be continuously transmitted. The terminal 2 that has received the data frame 2201 returns an ACK frame 2301 and waits in an active state. The access point device 1 that has received the ACK frame 2301 transmits a data frame 2202 continuously. Similarly, the access point device 1 receives an ACK frame 2302 from the terminal 2. The access point apparatus 1 that has received the ACK frame 2302 continuously transmits a data frame 2203. At that time, the access point device 1 sets the MoreData field of the data frame 2203 to 0, and notifies the terminal 2 that there is no data frame to be continuously transmitted. The terminal 2 that has received the data frame 2203 returns an ACK frame 2303 and shifts to the sleep state until the TBTT 104 since there is no data frame to be continuously received.

  According to the access point device 1 described above, the efficiency of power saving in sleep control can be increased by collecting data frames. By consolidating data frames, it is possible to reduce the percentage of time that is active despite no frame transmission / reception and to reduce the power consumption of the access point device.

  In the above description, the case where the wireless communication between the access point apparatus 1 and the terminal 2 is performed according to the IEEE802.11 standard is shown. However, the wireless communication standard between the access point apparatus 1 and the terminal 2 is IEEE802. It is not limited to the .11 standard.

  1 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed to perform communication processing. Also good. The “computer system” here includes an OS (Operating System) and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible disk, a magneto-optical disk, a portable medium such as a ROM (Read Only Memory) and a CD-ROM, and a hard disk incorporated in a computer system. Say. Furthermore, “computer-readable recording medium” refers to a fixed volatile memory such as a volatile memory inside a computer system serving as a server or client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. Including those holding time programs.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, what is called a difference file (difference program) may be sufficient.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes a design that does not depart from the gist of the present invention. Needless to say, the above-described embodiment and a plurality of modifications can be combined within a range in which the contents do not conflict with each other. Further, in the above-described embodiments and modifications, the structure of each part has been specifically described, but the structure and the like can be changed in various ways within a range that satisfies the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Access point apparatus, 2 ... Terminal, 11 ... Antenna, 12 ... Wireless communication processing part, 12a ... Buffer (buffer memory), 13 ... Power management management part (transition processing part), 14 ... Frame transmission time calculation part (data Transmission time calculation unit), 15 ... allowable delay time calculation unit 16 ... information storage unit

Claims (4)

In a base station device that communicates with a terminal station via a wireless channel while transitioning between an active state and a sleep state,
A buffer memory for storing transmission-scheduled data; a wireless communication processing unit for performing various communication processes with the terminal station ;
A data transmission time calculation unit for calculating a transmission time required for transmission of the transmission planned data;
An allowable delay time calculation unit for calculating a delay time allowed for each data frame of the transmission-scheduled data;
If the required transmission time is within the allowable delay time range for all the data frames even after shifting to the sleep state for a certain period, a beacon in which a channel reservation period is set is transmitted to the wireless communication processing unit. after the base station device and a said wireless communication processing unit migration processing unit Ru is shifted to the period of time the sleep state. The data transmission time calculator is
The base station apparatus of Claim 1 which calculates the said transmission required time based on the transmission rate and data amount of the said transmission plan data.   The base station apparatus according to claim 1 or 2, wherein the allowable delay time calculation unit calculates an allowable delay time for each data frame based on an access category of the data frame. In a sleep control method of a base station that communicates with a terminal station via a wireless channel while transitioning between an active state and a sleep state,
A buffer memory included in a wireless communication processing unit that performs various types of communication processing with the terminal station , accumulates transmission schedule data;
A data transmission time calculating unit calculating a transmission time required for transmitting the transmission-scheduled data;
An allowable delay time calculating unit calculating an allowable delay time for each data frame of the transmission-scheduled data; and
If the time required for transmission falls within the allowable delay time range for all the data frames even after shifting to the sleep state for a certain period , the transition processing unit transmits the beacon in which the channel reservation period is set to the wireless after transmitted to the communication processing unit, the sleep control method of a base station and a step of the wireless communication processing unit Ru is shifted to the period of time sleeping.

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