JP3920425B2 - Wireless LAN system and battery saving method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wireless LAN system and a battery saving method, and more particularly to a wireless LAN system using a battery-driven terminal and a battery saving method thereof.
[0002]
[Prior art]
Conventionally, a wireless LAN system operating in time division duplex (TDD) has a configuration similar to that of a wired LAN system. When transmission data is generated, the transmission from the control station immediately sends it with a destination, and the terminal station constantly monitors the data that is flowing and checks whether the data is addressed to itself. The operation of performing reception only on was performed. In addition, since the generated data is processed in the order of generation in the control station, transmission is performed by first-in first-out.
[0003]
[Problems to be solved by the invention]
In recent years, with the spread of notebook PCs (Personal Computers), the usage form of wireless LAN has also changed from the use with fixed terminals to the use with portable terminals. However, since the portable terminal is basically driven by a battery, it is required to save the battery in order to improve the usage time. However, this is not considered in the conventional wireless LAN system.
[0004]
An object of the present invention is to provide a TDD operation wireless LAN system capable of improving the usage time of a mobile terminal and a battery saving method therefor.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides:
In a TDD operation wireless LAN system comprising at least one control station and a plurality of terminal stations,
To the control station
A terminal station state management table indicating whether the terminal station is in a battery saving mode or an operating mode;
Transmission data storage memory,
Battery save mode transition request signal receiving means from the terminal station,
Battery save transition permission signal sending means to the terminal station,
Wake Up instruction signal sending means,
The terminal station
Battery save mode transition request signal transmission means;
Battery save transition permission signal receiving means from the control station;
Wake Up instruction signal receiving means;
A wireless LAN system is provided.
[0006]
The present invention also provides:
In a battery saving method in a TDD operation wireless LAN system comprising at least one control station and a plurality of terminal stations,
The terminal station counts the time during which data is not continuously transmitted or received, and when the counted time exceeds a preset time A, sends a battery save mode transition request signal to the control station,
When the control station receives the battery save mode transition request signal, it stores in the built-in terminal station state management table that the terminal station is in the battery save mode, and sends a battery save transition permission signal to the terminal station. ,
When the terminal station receives the battery save transition permission signal, the terminal station shifts to a battery save mode,
When sending data to the terminal station in the battery save mode, the control station sends a wake-up instruction signal to the terminal station and receives a reception preparation completion signal from the terminal station. There is provided a battery saving method characterized by rewriting a description of a table during operation and transmitting data to the terminal station.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is a configuration diagram of a wireless lan system according to the present invention. Reference numeral 1 is a wireless control station, reference numeral 2 is a control unit, reference numeral 3 is a wired input / output unit, and reference numeral 4 is a wireless unit including a wireless transceiver. Reference numeral 5 denotes a transmission data storage memory for temporarily storing data to be transmitted to a wireless terminal station (hereinafter referred to as a terminal station), and reference numeral 6 denotes a terminal station state management table for managing the state of whether or not the terminal station is battery saving. Reference numeral 7 denotes a Wake Up counter that counts the retransmission time of a Wake Up signal for activating a terminal that is saving battery. Reference numeral 8 denotes a terminal station, reference numeral 9 denotes a control unit of the terminal station, reference numeral 10 denotes a radio unit composed of a transceiver, reference numeral 11 denotes an interface unit with a notebook PC, and reference numeral 12 denotes a time until shifting to battery saving. The reference numeral 13 is a permission waiting counter that counts the time for resending the battery saving transition permission signal, and the reference numeral 14 is a notebook PC. Although only one terminal station 8 is illustrated, it is assumed that there are a plurality of similar terminals.
[0008]
In FIG. 1, communication is performed between the control station and the terminal station by TDD operation. Since it is a TDD operation, the radio frequency is the same, but the time for transmitting radio waves from the control station to the terminal station (referred to as downlink) overlaps with the time for transmitting radio waves from the terminal station to the control station (referred to as uplink). In order to avoid this, transmission operations are performed alternately at different times. This time is called a frame, and a synchronization signal is included at the head of each frame. In the transmission of data from the control station to the terminal station, the address to the terminal station is transmitted in the first part of the downlink frame, and then the data is transmitted. All the terminal stations always receive the head part of the downstream frame and establish synchronization, and take in the subsequent data only when their own address is detected. To send data from the terminal station to the control station, an uplink frame is used. However, a collision occurs when a plurality of terminal stations use the same frame at the same time. Therefore, various collision prevention methods are considered. In the case of TDD operation, since the radio frequency transmitted by another terminal can be received, there is a method of receiving an uplink frame for a certain period of time and confirming that there is no transmission from the other terminal before transmitting its own radio wave. is there. The time for confirming that there is no transmission from another terminal for a certain period of time is made different for each terminal, or this time is randomly changed for each transmission to prevent collision. Here, it is assumed that any of the above existing collision prevention methods is adopted.
[0009]
FIG. 4 shows a control flow when the terminal station 8 shifts to the battery saving mode. Hereinafter, description will be made with reference to FIGS. 1 and 4. First, the control unit 9 of the terminal station 8 sets the battery save counter 12 and the permission waiting counter 13 to 0 (STEP 16), and waits for the reception timing of the downstream frame (NO loop in STEP 17). When the reception timing is reached (YES in STEP 17), it is determined whether or not there is data for itself by checking whether or not there is its own address (STEP 18). If there is data for itself (YES in STEP 18), reception processing is performed (STEP 20), the battery save counter 12 is set to 0 (STEP 21), and the next reception timing is awaited (STEP 17). If there is no data for itself (NO in STEP 18), it is determined whether the value of the battery save counter 12 is equal to or greater than a preset value A (STEP 19). If the value of the battery save counter 12 is smaller than A (NO in STEP 19), 1 is added to the value of the battery save counter 12 (STEP 22), and the next reception timing is awaited (STEP 17). If there is no downlink data in this way, 1 is added to the battery save counter 12 at each reception timing. That is, the time is counted with the period of the reception timing as a unit. If the reception timing is every downstream frame, the time is counted by the number of frames.
[0010]
When the value of the battery save counter 12 becomes A or more (YES in STEP 19), the control unit 9 sends a battery save transition request signal from the wireless unit 10 to the control station 1 (STEP 23), and the battery save transition from the control station 1 occurs. Wait for a permission signal (STEP 24). If a battery save transition permission signal is received (YES in STEP 24), the battery save mode is entered (STEP 25). When the battery saving mode is entered, the terminal station 8 minimizes power consumption and reduces battery consumption. Normally, power is supplied only to the circuit for receiving only the Wake Up signal that requests to exit the battery save mode from the control station 1, and the rest is stopped or the operation speed is reduced to reduce power consumption. It will be. For example, if the Wake Up signal is to periodically receive and detect a part of the downstream frame from which the Wake Up signal will be transmitted, a periodic timer circuit, a periodic signal receiving circuit, a Wake Up signal for that purpose Power is supplied only to the startup circuit for Wake Up during reception, and the power of other circuits is turned off.
[0011]
In FIG. 4, if the battery save transition permission signal does not come (NO in STEP 24), it is checked whether the value of the permission waiting counter 13 is equal to or greater than the preset value B (STEP 27). If it is smaller (NO in STEP 27), 1 is added to the value of the permission waiting counter 13 (STEP 26), and it is waited for a battery save transition permission signal at the next reception timing (STEP 24). If the value of the permission waiting counter becomes B or more, the value of the permission waiting counter 13 is set to 0 (STEP 28), and a battery save mode shift request signal is sent again to the control station 1 (STEP 23). Increasing the parameter B that determines the time for retransmitting the battery save transition permission signal reduces the traffic on the uplink frames of other terminals, but it takes time to shift to the battery save mode.
[0012]
On the other hand, the control station 1 that has received the battery save mode transition request signal confirms that there is no data to be transmitted to the terminal station 8 in the transmission data storage memory 5 and changes the status of the terminal station 8 in the terminal station status management table 6. While the battery is being saved, a battery save transition permission signal is transmitted from the wireless unit 4 in a downstream frame.
In this way, since the terminal station is requested to shift to the battery save mode and the transition is performed by the permission of the control station, the state of the terminal station can be managed by the control station without error. FIG. 2 shows the configuration of the terminal station state management table 6. Further, by setting the setting value A for comparing the value of the battery save counter and the setting value B for comparing the value of the permission waiting counter, it is possible to set an optimum value for the wireless LAN system.
[0013]
Next, a case where the terminal station 8 shifts from the battery save mode to the operation mode will be described. The transition to the operation mode occurs when the terminal station 8 transmits data and receives data. FIG. 5 is a control flow when the terminal station 8 transmits data. When the terminal station 8 is in the battery save mode, the notebook PC 14 is also in the battery save mode. The notebook PC 14 shifts to the battery saving mode because the notebook PC 14 does not have an input / output operation, and may shift to the battery saving mode independently (a normal notebook PC has such a function. The battery save mode transition signal may be received from the control unit 9 via the interface unit 11. In any case, when the notebook PC 14 shifts from the battery saving mode to the operation mode by keyboard input or the like on the notebook PC 14 and transmission data is generated, the interface unit 11 is activated (YES in STEP 31). When the interface unit 31 is activated, the control unit 9 turns on the power of the transmission / reception circuit (STEP 32), and shifts from the battery save mode to the operation mode. The control unit 9 monitors the uplink frame for communication with the control station 1 and waits for the transmission timing (NO loop of STEP 33), and transmits the transmission data when the transmission timing is reached (YES in STEP 33) ( STEP 34), normal communication processing is performed (STEP 35). The control station 1 that has received the transmission data from the terminal station 8 rewrites the state of the terminal station 8 in the terminal station state management table from battery saving to operation.
[0014]
Next, data reception during battery saving will be described. FIG. 6 shows the control flow. The terminal station 8 in the battery save mode exits from the battery save mode by receiving the Wake Up signal from the control station. Therefore, during battery saving, only when the Wake Up signal is sent. Now, if the control station 1 sends out the Wake Up signal included in the synchronization signal of the downstream frame, the terminal station 8 first receives the synchronization signal (STEP 40), and then receives the Wake Up signal addressed to itself. If there is a Wake Up signal addressed to itself (YES in STEP 41), the power of the transmission circuit of the radio unit 10 is turned on (STEP 42), and the transmission timing of the upstream frame comes Wait for (NO in STEP43). When the transmission timing is reached (YES in STEP 43), a reception preparation completion signal is sent to the control station 1 (STEP 44), and normal communication processing is started (STEP 45).
[0015]
Next, the case of sending data from the control station 1 to the terminal station 8 will be described using the control flow of FIG. Transmission data to the terminal station is stored in the transmission data storage memory 5 of FIG. The storage method is a configuration in which transmission data to the terminal station is divided into packet units that can be transmitted within one frame, a destination address of the terminal station is given to each divided packet data, and the packet data is indexed from the destination address. Store. When transmission data is input from the wired input / output unit 3 or the wireless unit 4 (YES in STEP 50), the control unit 2 knows the destination address of the terminal station as shown in FIG. The data is stored in packet units (STEP 51). The reason for storing in this way is to enable transmission by the destination address regardless of the order of the stored data. As shown in the diagram on the right side of FIG. 3, the destination address of the terminal station and the data transmitted to the terminal station can be indexed by pointer connection using a pointer (not shown) added to the destination address. To do. Next, the control unit 2 confirms the state of the terminal station that is the destination of the data to be transmitted in the terminal station state management table 6 (STEP 52). If the state of the terminal station is in operation (YES in STEP 53), data is extracted by pointer connection from the destination address, and data is transmitted after waiting for the downstream frame timing (STEP 59). If the destination terminal station is in the battery saving state (NO in STEP 53), the value of the Wake Up counter 7 is set to 0, a Wake Up signal is sent to the corresponding terminal station (STEP 54), and at the next reception timing. It is checked whether a reception preparation completion signal is received from the terminal station (STEP 55). If a reception preparation completion signal is received from the terminal station (YES in STEP 55), the state of the corresponding terminal station in the terminal station state management table 6 is rewritten from battery saving to operation (STEP 58), and data is transmitted (STEP 59). . If the reception preparation completion signal is not received at the reception timing (NO in STEP 55), it is determined whether the value of the wake up counter 7 is equal to or larger than a preset value C (STEP 56). If (NO in STEP 56), 1 is added to the value of the Wake Up counter 7 (STEP 57), and it is waited for a reception preparation completion signal to be received at the next reception timing (STEP 55). If the value of the wake up counter 7 is equal to or larger than the preset value C (YES in STEP 56), the value of the wake up counter 7 is set to 0 and the wake up signal is transmitted again (STEP 54). .
[0016]
The preset value C is also variable so that it can be matched to the system operation mode, like the above-described counter setting values A and B. While sending the Wake Up signal and waiting for the reception completion signal to be received, by sending data to other terminal stations, it is possible to effectively use downlink frames and send data to other terminals. Time can be shortened. FIG. 8 is an explanatory diagram of the transmission procedure of the present invention. Conventionally, it has been common to use first in first out as a method of transmitting data in the data storage memory. That is, if there is data for the terminal station A in the transmission data storage memory 5, the terminal station state management table 6 is seen to find that the terminal station A has battery saving data. As shown in the “transmission procedure”, first, a Wake Up signal is transmitted to the terminal station A and waits until a reception preparation completion signal is received. Even if transmission data to the terminal station B is generated in the meantime, since it is performed on a first-in first-out principle, it waits for a reception preparation completion signal. When the reception preparation completion signal is received, the data portion 1 and the data portion 2 which are data to the terminal station A are transmitted in the order stored in the transmission data storage memory 5, and then the state of the terminal station B is set to the terminal Since it is detected in the station state management table 6 and is in operation, the data part 3 is transmitted without transmitting a Wake Up signal. In this method, the downstream frame is not used while waiting for the reception ready signal to be received after the Wake Up signal is transmitted.
On the other hand, in the present embodiment, as shown in the “transmission procedure of the present invention” at the lower right of FIG. 8, first, a Wake Up signal is sent to the terminal station A and waits until a reception preparation completion signal is received. If transmission data to the terminal station B is generated in the meantime, the state of the terminal station B is immediately detected by the terminal station state management table 6, and the data section 3 is immediately sent to the terminal station B when it is in operation. Next, when the reception preparation completion signal is received, the data part 1 and the data part 2 are transmitted to the terminal station A. By performing such a transmission procedure, it is possible to effectively use the time until the Wake Up signal is transmitted and the reception preparation completion signal is received.
[0017]
【The invention's effect】
As described above in detail, using the present invention has the following effects.
(1) The battery saving operation can be introduced into the wireless LAN system of TDD operation, and the usage time of the wireless terminal station including the notebook PC is improved.
(2) Since the shift to the battery save mode is requested from the terminal station and is performed after the control station permits, the state of the terminal station can be managed by the control station without error.
(3) By making the retransmission interval of each signal variable, a value suitable for the system can be set, and a flexible wireless LAN system is possible.
(4) Since the control station transmits a wake up signal and transmits transmission data to another terminal while waiting for reception completion signal reception, the data transmission time is shortened. As a result, the user convenience is significantly improved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration example of a wireless LAN system of the present invention.
FIG. 2 is a configuration diagram of a terminal station state management table.
FIG. 3 is a configuration diagram of a transmission data storage memory.
FIG. 4 is a control flow of transition to battery saving in the terminal station.
FIG. 5 is a data transmission control flow from the battery saving mode of the terminal station.
FIG. 6 is a data reception control flow from the battery saving mode of the terminal station.
FIG. 7 is a data transmission control flow of the control station.
FIG. 8 is an explanatory diagram of a transmission procedure in a control station.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Radio control station 2 Control station control part 3 Wired input / output part 4 Control station radio part 5 Transmission data storage memory 6 Terminal station state management table 7 Wake Up counter 8 Terminal station 9 Terminal station control part 10 Terminal station Wireless unit 11 Interface unit with notebook PC 12 Battery save counter 13 Waiting permission counter 14 Notebook PC

Claims (4)

In a TDD operation wireless LAN system comprising at least one control station and a plurality of terminal stations,
To the control station
A terminal station state management table indicating whether the terminal station is in a battery saving mode or an operating mode;
Transmission data storage memory,
Battery save mode transition request signal receiving means from the terminal station,
Battery save transition permission signal sending means to the terminal station,
Wake Up instruction signal sending means,
The terminal station
Battery save mode transition request signal transmission means;
Battery save transition permission signal receiving means from the control station;
Wake Up instruction signal receiving means;
A wireless LAN system comprising: The wireless LAN system according to claim 1,
The transmission data storage memory of the control station divides and stores transmission data to the terminal station in units of packets that can be transmitted within one frame, and a pointer indicating the storage address of the data for each divided packet data Store the destination address indicating the terminal station address of the destination of the data as index data,
A battery-saving wireless LAN system characterized in that data can be transmitted to a terminal station that can transmit data at any time. In a battery saving method in a TDD operation wireless LAN system comprising at least one control station and a plurality of terminal stations,
The terminal station counts the time during which data is not continuously transmitted or received, and when the counted time exceeds a preset time A, sends a battery save mode transition request signal to the control station,
When the control station receives the battery save mode transition request signal, it stores in the built-in terminal station state management table that the terminal station is in the battery save mode, and sends a battery save transition permission signal to the terminal station. ,
When the terminal station receives the battery save transition permission signal, the terminal station shifts to a battery save mode,
In the control station, when sending data to the terminal station in battery save mode,
When a Wake Up instruction signal is transmitted to the terminal station and a reception preparation completion signal is received from the terminal station, the state management table description of the terminal station is rewritten during operation, and data is transmitted to the terminal station. A battery saving method. The battery saving method according to claim 3,
The time until the terminal station stops transmitting or receiving data and sends the battery save mode transition request signal,
When the terminal station sends the battery save mode transition request signal to the control station and cannot receive the battery save transition transition signal from the control station, the terminal station again sends the battery save mode transition request signal to the control station. Time,
When the control station sends the Wake Up instruction signal to the terminal station and cannot receive the reception preparation completion signal from the terminal station, the time until the Wake Up instruction signal is again sent to the terminal station,
A battery saving method characterized in that at least one of the above can be variably set.

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