JP2004364069A - Radio communication system, apparatus, and method, and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To save power consumption in a communication station to be operated as an access point in accordance with the operation state of a network. <P>SOLUTION: A receiving operation is stopped by utilizing a contention free period at the access point. Despite whether an apparatus connected to the access point utilizes the contention free period or not, the contention free period is made to be large during an idle time without performing packet communication, and a contention period is made to be small, so that the rate of time to be used for communication during an access control period is reduced. Consequently, the operation rate of the access point is reduced, and then, power consumption is saved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wireless communication system, such as a wireless LAN (Local Area Network), for mutually communicating between a plurality of wireless stations, a wireless communication apparatus, a wireless communication method, and a computer program. The present invention relates to a wireless communication system, a wireless communication device, a wireless communication method, and a computer program for performing data communication by competitive access or competitive access.
[0002]
More specifically, the present invention relates to a wireless communication system, a wireless communication device, a wireless communication method, and a computer program for reducing power consumption according to an operation state of a network, and particularly to a communication station operating as an access point. The present invention relates to a wireless communication system, a wireless communication device, a wireless communication method, and a computer program for reducing power consumption.
[0003]
[Prior art]
Conventionally, it has been common practice to make a wired LAN connection using an optical fiber, a coaxial cable, or a twisted pair cable. In this case, however, it is necessary to lay a line, making it difficult to easily construct a network. In addition, the cable routing becomes complicated. Further, even after the LAN is constructed, the moving range of the device is limited by the cable length, which is inconvenient.
[0004]
Therefore, a wireless LAN has been attracting attention as a system for releasing a user from a wired LAN wiring. According to the wireless LAN, most of the wired cable can be omitted in a work space such as an office, so that a communication terminal such as a personal computer (PC) can be relatively easily moved.
[0005]
In recent years, the demand for wireless LAN systems has been remarkably increased with the increase in speed and price. Particularly, recently, introduction of a personal area network (PAN) has been studied in order to establish a small-scale wireless network and perform information communication between a plurality of electronic devices existing around a person. For example, different wireless communication systems are specified using a frequency band that does not require a license of a regulatory agency, such as a 2.4 GHz band or a 5 GHz band.
[0006]
In order to configure a local area network using wireless technology, one device serving as a control station called an “access point” or “coordinator” is provided in the area, and under the overall control of this control station. In general, a method of forming a network is used.
[0007]
In a wireless network in which access points are arranged, when information is transmitted from a certain communication device, an access method for avoiding contention by polling, slot allocation, and the like, and a contention such as CSMA (Carrier Sense Multiple Access) are allowed to some extent. An access method is adopted. In the former access method for avoiding contention, by arranging access points, synchronous wireless communication in which communication devices in a wireless network synchronize with each other can be performed.
[0008]
One of the standard standards regarding wireless networks is IEEE (The Institute of Electrical and Electronics Engineers) 802.11 and IEEE 802.15.3. As for the IEEE802.11 standard, there are various wireless communication systems such as the IEEE802.11a standard and the IEEE802.11b standard, depending on the wireless communication system and the frequency band to be used.
[0009]
By the way, due to consideration for the global environment, there is a strong demand for reduction in power consumption of home electrical appliances. In particular, it is desired that the power consumption during the standby operation of the device be as close to zero as possible.
[0010]
In recent years, the construction of networks in homes has been progressing, but the reduction in power consumption of these devices has not been so advanced. Therefore, it is expected that a reduction in power consumption of devices such as ADSL (Asymmetrical Digital Subscriber Line) modems, routers, and wireless LANs will be strongly demanded in the future.
[0011]
As a general usage of the wireless LAN, it is configured by an access point and a plurality of wireless communication devices (described above). Further, the access point is connected to an ADSL modem or the like, which enables a computer in the home to access the external Internet.
[0012]
Regarding communication devices that operate as wireless communication devices, battery-powered devices are also conceivable. Therefore, reduction in power consumption has been studied, and some are described in standard specifications. On the other hand, a communication device that operates as an access point is generally used in such a manner that it always operates, and therefore, in reality, no consideration is given to reducing power consumption.
[0013]
Further, the low power mode defined by the wireless LAN is a method led by the wireless communication device, and is not suitable for an operation in which the access point reduces power consumption when the operation is free.
[0014]
[Problems to be solved by the invention]
An object of the present invention is to provide an excellent wireless communication system, a wireless communication device, a wireless communication method, and a computer program that can reduce power consumption according to the operation state of a network.
[0015]
A further object of the present invention is to provide an excellent wireless communication system, a wireless communication device, a wireless communication method, and a computer program that can reduce the power consumption of a communication station operating as an access point.
[0016]
Means and Action for Solving the Problems
The present invention has been made in view of the above problems, and a first aspect thereof is a wireless communication system that performs data communication by non-contention access or contention access within a predetermined access control period,
Set a non-contention period and a contention period within the access control period according to the frequency of packet exchange,
A wireless communication system characterized by the above.
[0017]
However, the term “system” as used herein refers to a logical collection of a plurality of devices (or functional modules that realize specific functions), and each device or functional module is in a single housing. It does not matter in particular.
[0018]
In the present invention, the access point stops the receiving operation using the non-contention period. Regardless of whether the device connected to the access point uses the non-contention period, access control is achieved by increasing the non-contention period and reducing the contention period when there is no time to communicate packets. Reduce the time rate used for communication during the period. As a result, the operation rate of the access point can be reduced, and the power consumption can be reduced.
[0019]
In the wireless network according to the present invention, a station operating as an access point or another station broadcasts a non-contention period and / or a contention period length in an access control period by using a beacon. Then, by stopping the operation using the non-contention period, low power consumption is realized.
[0020]
A station acting as an access point or other station may extend the non-contention period in response to reduced packet exchange during the contention period and may stop using the non-contention period. . In such a case, the non-contention period may be shortened in response to an increase in the exchange of packets during the contention period.
[0021]
Also, the station operating as an access point or other stations responds to the end of the packet exchange in the non-contention period and stops operation using the rest of the non-contention period to reduce power consumption. Can be realized.
[0022]
In the non-contention period, access control is performed by a polling method or a slot allocation method. For example, during the non-contention period, the access point may perform communication using polling, and after the transmission based on polling ends, may stop operation until the end of the non-contention period.
[0023]
Alternatively, in a non-contention period, a station operating as an access point or another station may make a fictitious slot reservation for a period during which operation is to be stopped, and stop operation during the reserved slot. Good.
[0024]
In the non-contention period, the terminal station can perform data communication avoiding contention based on polling or slot allocation by using a period in which the station operating as an access point does not stop operating.
[0025]
According to the present invention, when there is no communication device using the non-contention period in the wireless network, the operation of the wireless network is as follows.
[0026]
(1) In the normal mode, the non-contention period is eliminated and the contention period is maximized.
(2) When there is no packet exchange, the access point takes a long non-contention period and stops operating during the non-contention period (power save mode).
(3) In the power save mode, transmission from the wireless communication device is performed in a reduced contention period. In the power save state, the non-contention period is extended and the access point is stopped, and the contention period is shortened and used for communication.
(4) When communication starts using the reduced contention period, the access point transitions to the normal mode by eliminating the non-contention period.
[0027]
When there is a device that uses the non-contention period, the operation of the wireless network is as follows.
[0028]
(1) In the normal mode, communication is performed with a non-contention period provided as necessary.
(2) When the exchange of packets using the contention period stops, the access point takes a large non-contention period, and the access point stops operating during the non-contention period. At this time, if there is communication using polling, the access point stops until the end of the non-contention period after the transmission based on polling ends (power save mode).
(3) In the power save mode, transmission from the wireless communication device is performed in a reduced contention period.
(4) When communication starts using the reduced contention period, the access point shifts to the normal state by minimizing the non-contention period.
[0029]
In the normal mode, there is no difference from the operation of the conventional wireless LAN. In the power save mode, the operation rate can be reduced to 1% or less, and power consumption can be reduced. At this time, the non-contention period is made longer than necessary, but there is no need to perform communication, so that communication is not affected.
[0030]
Further, during the contention period, data transmission may be performed by the RTS / CTS method. In this case, other stations that have received the RTS signal or the CTS signal are prohibited from transmitting for a predetermined time.
[0031]
If the wireless communication device wants to reduce the operation rate during the contention period, it can transmit a fictitious RTS signal and stop the operation during the transmission prohibition period defined by the RTS signal.
[0032]
According to a second aspect of the present invention, there is provided a computer program described in a computer-readable format so as to execute, on a computer system, a wireless communication process for operating in a wireless communication environment in which terminals perform data communication. And
A communication state monitoring step of monitoring a communication state in the wireless communication environment,
An access control period setting step of setting a non-contention period for performing non-contention access and a contention period for performing contention access within a predetermined access control period in accordance with the monitored communication state;
An apparatus operation control step of setting an intermittent operation or a low power consumption operation state in the non-contention period,
A computer program characterized by comprising:
[0033]
The computer program according to the second aspect of the present invention defines a computer program described in a computer-readable format so as to realize a predetermined process on a computer system. In other words, by installing the computer program according to the second aspect of the present invention into a computer system, a cooperative action is exerted on the computer system, and the computer system operates as a wireless communication device. By activating a plurality of such wireless communication devices to construct a wireless network, it is possible to obtain the same operation and effect as those of the wireless communication system according to the first aspect of the present invention.
[0034]
Further objects, features, and advantages of the present invention will become apparent from more detailed descriptions based on embodiments of the present invention described below and the accompanying drawings.
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0036]
The communication propagation path assumed in the present invention is wireless, and a network is constructed between a plurality of communication stations using a transmission medium including a plurality of frequency channels. Further, the communication assumed in the present invention is store-and-forward type traffic, and information is transferred in packet units.
[0037]
In the embodiments of the present invention to be described later, it is assumed that a wireless network system for building a network under the control of an access point is constructed. The present invention can be similarly applied to a system that operates autonomously and performs ad hoc communication or the like in which information is transmitted asynchronously directly according to a scheme such as CSMA.
[0038]
FIG. 1 schematically shows a configuration of a wireless LAN system according to an embodiment of the present invention.
[0039]
Wireless LANs have been widely used because a network can be easily constructed at home without wiring. The illustrated wireless LAN includes an access point and a plurality of wireless communication devices. The access point is further connected to an ADSL modem or the like, which allows the computer to access the Internet.
[0040]
FIG. 2 schematically shows a functional configuration of a wireless communication device that can operate as an access point or a wireless communication device in a wireless communication environment according to the present invention. The wireless communication device 100 includes an interface 101, a data buffer 102, a central control unit 103, a wireless transmission unit 104, a timing control unit 105, an antenna 106, a wireless reception unit 107, a beacon generation unit 110, , A beacon analysis unit 111 and an information storage unit 112.
[0041]
The interface 101 exchanges various information with an external device (for example, a personal computer (not shown) or the like) connected to the wireless communication device 100.
[0042]
The data buffer 102 is used for temporarily storing data transmitted from a device connected via the interface 101 or received data before transmitting the data via the interface 101.
[0043]
The central control unit 103 centrally performs management of a series of information transmission and reception processing in the wireless communication device 100, access control of a transmission path, and control of low power consumption operation.
[0044]
In the present embodiment, the wireless communication device 100 performs non-contention using polling or slot allocation within an access control period defined by a beacon transmission interval in a wireless network in which an access point is located, or in an ad hoc network environment. It performs communication operations such as access and competitive access based on CSMA / CA. In the contention period, the communication quality can be maintained by adopting the RTS / CTS method. Further, in the non-contention period and the contention period, power consumption can be reduced by reducing the operation rate.
[0045]
The wireless transmission unit 104 performs modulation processing, for example, as a wireless LAN frame high-frequency signal in order to wirelessly transmit data or a beacon temporarily stored in the data buffer 102.
[0046]
The timing control unit 105 controls timing for transmitting and receiving a wireless LAN frame high-frequency signal. For example, it controls the already acquired reserved area, its own beacon transmission timing, the beacon reception timing from another communication device, and the like.
[0047]
The antenna 106 wirelessly transmits a signal to another wireless communication device, or collects a signal transmitted from another wireless communication device.
[0048]
Wireless receiving section 107 receives and processes information and signals such as beacons transmitted from another wireless communication apparatus at a predetermined time.
[0049]
The beacon generator 110 generates a beacon signal that is periodically exchanged with a nearby wireless communication device. However, in a wireless communication device that does not operate as an access point, generation of a beacon signal may not be necessary.
[0050]
The beacon analyzer 111 analyzes a beacon signal of another wireless communication device that has been able to receive, and grasps a wireless network configuration and its own data transmission / reception timing.
[0051]
The information storage unit 113 stores execution procedure commands such as a series of access control operations executed by the central control unit 103 and network configuration information obtained by beacon analysis.
[0052]
At the time of data transmission, a header, a CRC, and the like are added to the transmission data stored in the data buffer 102, and the wireless transmission unit 104 performs encoding and modulation processing. Then, a transmission signal is transmitted from the antenna. At the time of encoding, an error correction code is applied. Further, the signal is changed to a modulation signal such as BPSK, QPSK, or QAM by the modulation, and further converted and amplified to a desired carrier frequency. On the other hand, the received signal passes through an antenna and an antenna duplexer, is subjected to demodulation and decoding processing, is further subjected to a CRC check, and if there is no error, received data is output.
[0053]
FIG. 3 schematically shows a configuration of an access control period in a wireless communication environment according to the present invention.
[0054]
As shown in the figure, one access control period is defined by a beacon transmission interval transmitted from an access point or another communication terminal. In the illustrated example, the access control period includes a non-contention period (Content Free Period: CFP) and a contention period (Content Period: CP).
[0055]
The non-contention period is a period in which it is basically guaranteed that no packet collision occurs, and access control is performed according to a method such as polling or slot allocation. In the case of the polling method, each wireless communication device transmits a packet in response to a polling packet transmitted by the access point.
[0056]
On the other hand, in the contention period, access control is performed on the basis of random access based on random access, based on a scheme such as CSMA / CA or Aloha, on the assumption that some degree of packet collision occurs. That is, each wireless communication device starts transmission after confirming that another wireless communication device is not transmitting by performing carrier sense, but this is not a mechanism that can guarantee 100% that no transmission is being performed.
[0057]
In wireless LANs, the latter, which is relatively simple access control, is widely used.
[0058]
The access point transmits a beacon periodically. When there is a non-contention period, a period following the beacon is a non-contention period, and information about the length of the period is notified by the beacon. When the non-contention period ends, the remaining period of the access control period, that is, the period until the next beacon becomes the contention period. The access point specifies the length of the non-contention period by using a beacon. If the communication of the non-contention period ends earlier than the scheduled time, the access point may notify the wireless communication device of the end using a CF_END packet. it can.
[0059]
Communication using non-contention periods is complicated. For this reason, most currently available wireless LANs have a function for coexistence of a non-contention period and a contention period, but do not have a function of communicating during the non-contention period. That is, only the communication using CSMA / CA is actually performed. In such a case, as shown in FIG. 4, all access control periods except the beacon transmission timing are contention periods.
[0060]
When random access is performed by the CSMA scheme, the communication device must be always in a reception state except during transmission, and power consumption of the wireless communication device becomes a problem. In the case of a station, it is possible to reduce power consumption by intermittent operation based on the beacon transmission timing. On the other hand, in the case of an access point, it must be constantly operated, and it is difficult to reduce power consumption.
[0061]
Therefore, in the present embodiment, the access point stops the receiving operation using the non-contention period. FIG. 5 shows a state in which the access point is stopped using the non-contention period when no device using the non-contention period exists. Regardless of whether the device connected to the access point uses the non-contention period, access control is achieved by increasing the non-contention period and reducing the contention period when there is no time to communicate packets. Reduce the time rate used for communication during the period. As a result, the operation rate of the access point can be reduced, and power consumption can be reduced.
[0062]
If there is no communication device using the non-contention period in the wireless network, the operation of the wireless network is as follows.
[0063]
(1) In the normal mode, the non-contention period is eliminated and the contention period is maximized.
(2) When the exchange of packets is lost, the access point increases the non-contention period and decreases the contention period. The operation is stopped during the non-contention period (power save mode).
(3) In the power save mode, transmission from the wireless communication device is performed in a reduced contention period. In the power save state, the non-contention period is extended, the access point is stopped, and the contention period is shortened and used for communication.
(4) When communication starts using the reduced contention period, the access point transitions to the normal mode by eliminating the non-contention period.
[0064]
In the normal mode, there is no difference from the operation of the conventional wireless LAN. In the power save mode, the operation rate can be reduced to 1% or less, and the power consumption can be reduced. Although the non-contention period is made longer than necessary, communication is not affected because communication is not required.
[0065]
On the other hand, when there is a device that uses the non-contention period, the operation of the wireless network is as follows. FIG. 6 shows a state where the access point is stopped using the non-contention period when there is a device using the non-contention period.
[0066]
(1) In the normal mode, communication is performed with a non-contention period provided as necessary (the same operation as a conventional wireless LAN).
(2) When the exchange of packets using the contention period stops, the access point increases the non-contention period and decreases the contention period. The access point stops operating during the non-contention period. At this time, if there is communication using polling, the access point stops until the end of the non-contention period after the transmission based on polling ends (power save mode).
(3) In the power save mode, transmission from the wireless communication device is performed in a reduced contention period.
(4) When communication starts using the reduced contention period, the access point shifts to the normal state by minimizing the non-contention period.
[0067]
FIG. 7 shows, in the form of a flowchart, an operation procedure of the wireless communication device when there is no device using the non-contention period.
[0068]
After the access point is started, it operates in the normal mode (step S1). Here, the non-contention period is set and the timer is reset. However, the timer measures the time from when communication is stopped.
[0069]
Next, it is determined whether or not communication is being performed (step S2). During the communication, no operation is performed except for initializing the timer (step S3).
[0070]
If communication has not been performed, the timer is updated (step S4), and it is checked whether the timer has timed out (step S5).
[0071]
If the timer has not timed out, there has not been much time since the communication was performed, so the flow returns to step S2 to continue the normal operation state.
[0072]
On the other hand, when the timer times out, the intermittent operation is set (step S6). Specifically, the non-contention period is set large, and the reception operation of the access point is stopped during the non-contention period.
[0073]
After that, it is checked whether the communication has been started. Then, if started, the process returns to step S1 to set the normal state. If the communication has not been started, the process proceeds to the next step S7.
[0074]
In the wireless LAN, whether or not a series of communications has been completed is determined by using a timer timeout in the above operation flow.
[0075]
Even when there is an apparatus that uses the non-contention period, the operation procedure is almost the same as that shown in FIG. However, in step S1, the normal mode is set (there is no non-contention period), but the normal mode is set (only necessary non-contention period is secured).
[0076]
In the above-described embodiment of the present invention, the description has been made assuming a system using the polling method for the non-contention period and the CSMA method for the contention period. However, the gist of the present invention is not limited to this. For example, as a method of the non-contention period, a slot allocation method generally used in a TDMA (Time Division Multiple Access) method is adopted, and as a method of the contention period, an Aloha method is adopted. Therefore, the present invention can be widely applied.
[0077]
Since the wireless communication device has a function necessary for coexisting a non-contention period and a contention period, it is possible to realize low power consumption of the access point according to the present invention only for the access point. According to the present invention, it is possible to reduce the power consumption of a wireless communication device that operates as a station, but this requires the wireless communication device to cope with this.
[0078]
As described above, the access control period in the wireless network is defined by the beacon transmission interval. Hereinafter, a case will be described in which the access control period has a frame structure and is divided into a slot allocation period and a random access period.
[0079]
FIG. 8 shows how a frame is divided into a non-contention period by slot allocation and a random access period.
[0080]
During a non-contention period due to slot allocation, a slot used by each wireless communication device is reserved in advance and data transmission is performed. The slot allocation period usually increases or decreases according to the total number of reserved slots.
[0081]
In the illustrated example, the random access period is after the slot allocation period. In the random access period, communication without reservation is performed by a method such as CSMA / CA.
[0082]
FIG. 9 shows an example in which the random access period is shortened and the power consumption of the access point is reduced by arranging dummy slots in the non-contention period.
[0083]
Here, the dummy slot means a fictitious slot for which slot reservation is made but communication is not actually performed. The access point makes a slot reservation for a period during which operation is to be stopped, and stops operation during that period. When there is no (or few) stations performing random access, the random access period can be shortened and the slot allocation period can be extended by that amount. That is, the access point leaves a minimum random access period in which communication can be performed, and reserves the remaining period as a dummy slot, so that power consumption can be extremely reduced.
[0084]
FIG. 10 shows an access control period in which transmission is performed by slot assignment. In the example shown in the figure, two regular slots are allocated during the non-contention period, and dummy slots are allocated during the remaining non-contention period.
[0085]
During the period of the dummy slot, the operation of the access point is stopped, and power consumption is reduced. The slot allocated for communication can be stopped as long as the access point does not involve transmission / reception (operation is described in the example shown in the figure). Also, during the random access period, the access point must operate.
[0086]
FIG. 11 shows, in the form of a flowchart, a processing procedure for realizing low power consumption of the wireless communication device by assigning dummy slots.
[0087]
After the access point is activated, it first operates in the normal mode (step S11). Here, there is no dummy slot, and the timer is reset. The timer measures the time from when communication is stopped.
[0088]
Next, it is determined whether communication is being performed (step S12). During the communication, no operation is performed except for initializing the timer (step S13).
[0089]
If the communication has not been performed, the timer is updated (step S14), and it is checked whether the timer has timed out (step S15).
[0090]
If the timer has not timed out, it has not passed much time since the communication was performed, so the flow returns to step S12 to continue the normal communication operation state.
[0091]
On the other hand, if the timer has timed out, an intermittent operation setting is performed (step S16). Specifically, the dummy slot period is set large, and the reception operation of the access point is stopped during that period.
[0092]
Thereafter, it is determined whether or not the communication has been started (step S17). Then, when the communication is started, the process returns to step S11 to set the normal state. If the communication has not been started, the process stands by until the communication is started.
[0093]
In this specification, a low power consumption operation of an access point by dummy slot allocation is described using a system having an access point, but the gist of the present invention is not limited to this. For example, the present invention can be applied to a system in which all wireless communication devices emit a beacon. For example, when transmission and reception are not performed, a predetermined period following the beacon is reserved and operation is stopped, thereby reducing power consumption. Reduction can be realized.
[0094]
In each of the embodiments of the present invention described above, the access control period includes the non-contention period and the contention period, and the access point or another terminal performs the low power consumption operation using the non-contention period. However, a wireless LAN often has only a contention period during which access control is relatively easy. Therefore, an embodiment in which an access point or another terminal performs a low power consumption operation using a contention period will be described below.
[0095]
In a communication environment where random access is performed, the RTS / CTS method is known as a means for avoiding collision and improving communication quality. That is, in this case, before transmitting the net information, the transmission source communication device transmits an RTS (Request to Send: transmission request), and if the reception destination communication device can receive the RTS and receive data, As a response, CTS (Clear to Send: reception preparation completed) is returned. Then, data transmission is performed after a connection is established between the devices by information exchange of RTS / CTS.
[0096]
FIG. 12 shows an example of a data transmission / reception sequence based on RTS / CTS. The example shown in the figure is a sequence when data transmission is performed from the source wireless communication device # 1 to the destination wireless communication device # 2.
[0097]
First, prior to transmitting data from the wireless communication device # 1 to the wireless communication device # 2, the wireless communication device # 1 detects that the transmission path is idle, and then transmits a predetermined preamble signal P (131). Transmit the RTS signal (132).
[0098]
Here, in the RTS signal, CTS and subsequent data, time information necessary for transmitting ACK are described, and the peripheral wireless communication device that has been able to receive the RTS signal stops transmitting the signal during that period. Performs a collision avoidance operation. In the illustrated example, the wireless communication device # 0 receives the RTS signal of the wireless communication device # 1, and performs an operation of setting a time (transmission standby period) for which transmission from the wireless communication device # 1 is to be suppressed based on the reception time information. .
[0099]
Further, if the wireless communication device # 2 can receive the RTS signal and can receive data thereafter, it returns a predetermined preamble signal P (133) and a CTS signal (134).
[0100]
The CTS signal describes time information up to the end of data reception, and the peripheral wireless communication devices that have been able to receive the CTS signal stop signal transmission during that period to perform a collision avoidance operation. In the illustrated example, when the wireless communication device # 3 receives the CTS signal of the wireless communication device # 2, the wireless communication device # 3 performs an operation of setting a time during which transmission from itself is to be suppressed (transmission standby period) based on the reception time information. .
[0101]
Then, the wireless communication device # 1 that has been able to receive the CTS signal performs transmission processing of the predetermined preamble signal P (135) and data Data (136) for the time described by the CTS signal, and In 2, the data Data (136) is simultaneously received.
[0102]
At this time, the wireless communication device # 0 knows from the header information Head (not shown) of the data Data (136) that the data communication from the wireless communication device # 1 will be performed. Control may be performed such that transmission to communication device # 1 is not performed.
[0103]
In addition, if ACK information is not returned as to whether or not data reception has been performed properly, the time information indicated by the RTS is a length necessary to transmit CTS and data.
[0104]
The original purpose of RTS-CTS is that the transmitting wireless communication device transmits an RTS signal to urge the surroundings of the transmitting wireless communication device to prohibit transmission, and the receiving wireless communication device returns a CTS signal to receive the signal. This is to reduce collision by urging the surroundings of the wireless communication device to prohibit transmission.
[0105]
On the other hand, in the present embodiment, by transmitting a dummy RTS signal, data transmission is not performed from a surrounding wireless communication device, that is, by securing a period in which the wireless communication device does not need to perform a reception operation, an operation is performed. Achieving a reduced rate.
[0106]
FIG. 13 shows an example in which the operation rate is reduced by transmitting a dummy RTS signal.
[0107]
As shown in the figure, the wireless communication device may stop the reception operation by transmitting an RTS signal to the dummy RTS for the fictitious (non-existent) wireless communication device and prompting the surrounding wireless communication devices to prohibit transmission. it can.
[0108]
A time interval is set between the operation suspension periods (RTS and the subsequent transmission period) so that another wireless communication device can start transmission. When transmission by another wireless communication device is performed, transmission of the dummy RTS signal is stopped to avoid a decrease in throughput. When communication is not performed, a dummy RTS signal is transmitted to save power.
[0109]
FIG. 14 shows, in the form of a flowchart, a processing procedure for realizing low power consumption of the wireless communication device by transmitting the dummy RTS signal.
[0110]
After the access point is activated, it first operates in the normal mode (step S21). Here, there is no dummy RTS signal, and the timer is reset. The timer measures the time from when communication is stopped.
[0111]
Next, it is determined whether or not communication is being performed (step S22). During the communication, no operation is performed except for initializing the timer (step S23).
[0112]
If the communication has not been performed, the timer is updated (step S24), and it is checked whether the timer has timed out (step S25).
[0113]
If the timer has not timed out, it has not passed much time since the communication was performed, so the flow returns to step S22 to continue the normal operation state.
[0114]
On the other hand, when the timer times out, the intermittent operation is set (step S26). Specifically, a dummy RTS signal in which a transmission inhibition period of a surrounding station is set is transmitted, and the reception operation of the access point is stopped during that period.
[0115]
Thereafter, it is determined whether or not the communication has been started (step S27). Then, when the communication is started, the process returns to step S21 to set the normal state. If the communication has not been started, the process stands by until the communication is started.
[0116]
In a wireless communication system based on the RTS / CTS method, a station other than the communication partner receiving the RTS signal or the CTS signal confirms that the station is not related to the data transmission and reception, and is designated by the RTS signal or the CTS signal. The operation is stopped only for a period of time, thereby saving power.
[0117]
[Supplement]
The present invention has been described in detail with reference to the specific embodiments. However, it is obvious that those skilled in the art can modify or substitute the embodiment without departing from the scope of the present invention. That is, the present invention has been disclosed by way of example, and the contents described in this specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims described at the beginning should be considered.
[0118]
【The invention's effect】
As described above in detail, according to the present invention, there are provided an excellent wireless communication system, a wireless communication device, a wireless communication method, and a computer program, which can reduce power consumption according to an operation state of a network. be able to.
[0119]
Further, according to the present invention, it is possible to provide an excellent wireless communication system, a wireless communication apparatus, a wireless communication method, and a computer program that can reduce power consumption of a communication station operating as an access point. .
[0120]
According to the present invention, regardless of whether or not a device connected to the access point uses the non-contention period, the access point takes a large non-contention period when it is not busy communicating a packet, By reducing, the time rate used for communication can be reduced, so that the operation rate of the access point can be reduced.
[0121]
Further, according to the present invention, the function of the wireless communication device is not changed. Low power consumption can be realized by simple function modification of the access point.
[0122]
Further, according to the present invention, low power consumption of an access point can be realized without causing inconvenience in the operation of an existing wireless LAN.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a configuration of a wireless LAN system according to an embodiment of the present invention.
FIG. 2 is a diagram schematically illustrating a functional configuration of a wireless communication device that can operate as an access point or a wireless communication device in a wireless communication environment according to the present invention.
FIG. 3 is a diagram schematically showing a configuration of an access control period in a wireless communication environment according to the present invention.
FIG. 4 is a diagram showing a state in which a function of performing communication during a non-contention period is not implemented, and all access control periods except a beacon transmission timing are contention periods.
FIG. 5 is a diagram illustrating a state where an access point stops a receiving operation using a non-contention period when there is no device using the non-contention period.
FIG. 6 is a diagram illustrating a state in which an access point stops a reception operation using a non-contention period when a device using a non-contention period exists.
FIG. 7 is a flowchart showing an operation procedure of the wireless communication device when there is no device using a non-contention period.
FIG. 8 is a diagram showing a frame structure divided into a slot allocation period and a random access period.
FIG. 9 is a diagram showing an example in which power consumption of an access point is reduced by arranging dummy slots in a non-contention period.
FIG. 10 is a diagram showing an access control period during which transmission is performed by slot assignment.
FIG. 11 is a flowchart showing a processing procedure for realizing low power consumption of the wireless communication device by assigning a dummy slot.
FIG. 12 is a diagram showing an example of a data transmission / reception sequence based on RTS / CTS.
FIG. 13 is a diagram illustrating an example in which the operation rate is reduced by transmitting a dummy RTS signal.
FIG. 14 is a flowchart showing a processing procedure for realizing low power consumption of the wireless communication device by transmitting a dummy RTS signal.
[Explanation of symbols]
100 wireless communication device
101 ... Interface
102 Data buffer
103: Central control unit
104: Wireless transmission unit
105 timing control unit
106 ... antenna
107 ... Wireless receiver
110: Beacon generator
111: Beacon analysis unit
112 Information storage unit

Claims (27)

A wireless communication system performing data communication by non-contention access or contention access within a predetermined access control period,
Set a non-contention period and a contention period within the access control period according to the frequency of packet exchange,
A wireless communication system, comprising: The station operating as an access point or another station notifies the beacon of a contention-free period and / or the length of the contention period in the access control period, and stops operation using the contention-free period.
The wireless communication system according to claim 1, wherein: The station or other station operating as an access point expands the non-contention period in response to reduced packet exchange during the contention period and stops operating using the non-contention period.
The wireless communication system according to claim 2, wherein: Shorten non-contention periods in response to increased packet traffic during contention periods;
The wireless communication system according to claim 3, wherein: The station operating as an access point or another station stops using the remainder of the non-contention period in response to the end of the packet exchange in the non-contention period,
The wireless communication system according to claim 2, wherein: In the non-contention period, the access point performs communication using polling, and stops operating until the end of the non-contention period after transmission based on polling is completed.
The wireless communication system according to claim 5, wherein: In the non-contention period, a station operating as an access point or another station makes a fictitious slot reservation for a period during which it wants to stop operation, and stops operation during the reserved slot.
The wireless communication system according to claim 5, wherein: In the non-contention period, data communication is performed using a period in which the station operating as an access point does not stop operating.
The wireless communication system according to claim 2, wherein: In the contention period, data transmission is performed by the RTS / CTS method, and other stations that have received the RTS signal or the CTS signal are prohibited from transmitting for a predetermined time.
The wireless communication system according to claim 1, wherein: In the contention period, the station whose operation is to be stopped transmits an imaginary RTS signal, and stops the operation in the transmission prohibition period defined by the RTS signal.
The wireless communication system according to claim 9, wherein: A wireless communication device that operates in a wireless communication environment in which terminals perform data communication,
Communication state monitoring means for monitoring a communication state in the wireless communication environment,
Access control period setting means for setting a non-contention period for performing non-contention access and a contention period for performing contention access within a predetermined access control period according to the monitored communication state;
Device operation control means for setting an intermittent operation or a low power consumption operation state in the non-contention period,
A wireless communication device comprising: It further comprises means for reporting the length of the non-contention period and / or the contention period in the access control period by a beacon,
The wireless communication device according to claim 11, wherein: The access control period setting means extends a non-contention period in response to a decrease in exchange of packets during the contention period,
The wireless communication device according to claim 11, wherein: The access control period setting means shortens the non-contention period in response to an increase in the exchange of packets during the contention period,
The wireless communication device according to claim 13, wherein: The device operation control means, in response to the end of the packet exchange in the non-contention period, sets the intermittent operation or low power consumption operation using the rest of the non-contention period,
The wireless communication device according to claim 11, wherein: During the non-contention period, communication using polling is performed,
The device operation control means sets an intermittent operation or a low power consumption operation until the end of the non-contention period after transmission based on polling is completed,
The wireless communication device according to claim 15, wherein: During the non-contention period, communication based on slot assignment is performed,
The device operation control means performs a fictitious slot reservation for a period of time during which operation is to be stopped, and stops operation during the period of the reserved slot.
The wireless communication device according to claim 15, wherein: What is claimed is: 1. A wireless communication device that performs data transmission by an RTS / CTS method,
Transmitting an imaginary RTS signal and stopping operation during a transmission prohibition period defined by the RTS signal;
A wireless communication device characterized by the above-mentioned. A wireless communication method for operating in a wireless communication environment in which terminals perform data communication,
A communication state monitoring step of monitoring a communication state in the wireless communication environment,
An access control period setting step of setting a non-contention period for performing non-contention access and a contention period for performing contention access within a predetermined access control period in accordance with the monitored communication state;
An apparatus operation control step of setting an intermittent operation or a low power consumption operation state in the non-contention period,
A wireless communication method comprising: The method further includes a step of notifying the length of the non-contention period and / or the contention period in the access control period by using a beacon.
The wireless communication method according to claim 19, wherein: In the access control period setting step, extending a non-contention period in response to a decrease in the exchange of packets in the contention period,
The wireless communication method according to claim 19, wherein: In the access control period setting step, the non-contention period is shortened in response to an increase in the exchange of packets during the contention period.
The wireless communication method according to claim 21, wherein: In the device operation control step, in response to the end of the packet exchange in the non-contention period, set the intermittent operation or low power consumption operation using the rest of the non-contention period,
The wireless communication method according to claim 19, wherein: During the non-contention period, communication using polling is performed,
In the device operation control step, after the transmission based on polling is completed, set an intermittent operation or a low power consumption operation until the end of the non-contention period,
The wireless communication method according to claim 23, wherein: During the non-contention period, communication based on slot assignment is performed,
In the device operation control step, a fictitious slot reservation is performed for a period for which the operation is to be stopped, and operation during the reserved slot is stopped.
The wireless communication method according to claim 23, wherein: A wireless communication method for performing data transmission by an RTS / CTS method,
Transmitting an imaginary RTS signal and stopping operation during a transmission prohibition period defined by the RTS signal;
A wireless communication method, comprising: A computer program written in a computer-readable format so as to execute a wireless communication process on a computer system for operating in a wireless communication environment in which terminals perform data communication,
A communication state monitoring step of monitoring a communication state in the wireless communication environment,
An access control period setting step of setting a non-contention period for performing non-contention access and a contention period for performing contention access within a predetermined access control period in accordance with the monitored communication state;
An apparatus operation control step of setting an intermittent operation or a low power consumption operation state in the non-contention period,
A computer program comprising:

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