KR20070103439A - Radio device and interference avoiding method by transmission power control - Google Patents

Abstract

In reception, a propagation attenuation calculating section (5) of a radio device calculates the attenuation value of propagation from a source radio device to the radio device from the reception power and the transmission radiation power information included in a reception PLCP frame, a transmission power control section (6) calculates an optimal transmission power at each transmission rate from the propagation attenuation value and the minimum required reception power and records the optimal transmission power in an optimal transmission power table, with a radio device identifier for identifying the source radio device associated with each transmission rate. In transmission, a transmission power control section (6) selects the optimal transmission power for transmission to a destination radio device according to the optimal transmission power table, the radio identifier of the destination radio device, and the transmission rate, performs transmission power control of transmission, on the selected optimal transmission power, of a transmission PLCP frame including the optimal transmission power as transmission radiation power information, and detects whether or not there is any value smaller than the selected optimal transmission power among the optimal transmission power for the lowest transmission rates of radio devices different from the transmission destination radio devices recorded in the optimal transmission power table.

Description

Interference avoidance method by wireless device and transmit power control {RADIO DEVICE AND INTERFERENCE AVOIDING METHOD BY TRANSMISSION POWER CONTROL}

TECHNICAL FIELD The present invention relates to a wireless device applied to a wireless network system, and more particularly, to a wireless device in which each wireless device in the system avoids radio interference by performing power control in an independent (open loop) manner.

At present, as a device for constructing a home / office target high-speed wireless network system, products complying with the IEEE 802.11b, IEEE 802.11a, and IEEE 802.11g standards, which are standardized in the wireless LAN standardization standard IEEE 802.11 of the United States, are on the market. . In these wireless LAN standards, it is assumed that communication is performed under an ideal radio wave environment without interference, and the situation where an access point (AP) is provided at a high density as today is not sufficiently considered. IEEE 802.11h specifies a closed loop method of acquiring transmit power (EIRP) and received power in the Request & Response format, but it is control during association and actively interferes with interference. It is not a workaround.

Patent documents 1 to 3 are conventional techniques related to radio wave interference avoidance in a wireless network system. Patent Literature 1 discloses that the radio communication apparatus determines the transmission output and the communication speed from the information included in the signal from the radio control apparatus and the received electric field strength, and determines the possible transmission power and communication speed based on the state of the radio communication apparatus. Therefore, communication based on the indicated transmission output or communication speed and possible transmission output or communication speed is disclosed. That is, in the radio communication system of this patent document 1, a transmission power control method of performing interference control to a radio communication device by adding transmission power and interference information in a transmission frame using a radio control device in a communication service provider facility, and radio A closed loop type method of defining a transmission power range from the remaining battery capacity of the communication device itself and changing the communication speed in order to communicate within the range is disclosed.

Patent Document 2 discloses that when the measurement of the received power of a desired wave signal from a counter station is greatly wrong, or when the level of the received signal suddenly decreases, a sudden increase in the transmission power is prevented, and a large interference is made to other users. In order to prevent this from being applied, when the measurement of the received power of the desired wave signal from the other station is greatly wrong, or when the level of the received signal is suddenly reduced, the increase of the transmission power is suppressed so as to be large for other users. In order to prevent the interference, the base station estimates the amount of interference with other users from the desired wave signal-to-interference power ratio (SIR) obtained from the received radio waves from the mobile station, and changes the transmission power that is changed in the control cycle of the transmission power control. Has a function of determining the maximum change amount, and the base station An open loop method of controlling interference by giving a large change amount indication is disclosed.

Patent Document 3 describes a reception CNR (carrier to noise ratio) estimated by equalization error power obtained from a signal transmitted from a transmission / reception apparatus of a partner, and transmission power information included in a transmission signal from the transmission / reception apparatus of a partner. From the calculated channel attenuation and the transmission modulation scheme, the transmission level having the lowest power value that satisfies the reception required CNR at the other side of the modulation scheme used in the local station is determined, and the determined transmission level is determined. Disclosed is an invention in which a transmission signal is generated by inserting a transmission signal into a control information symbol of a radio frame, adjusting the transmission level of the generated transmission signal to a transmission level determined first, and transmitting the same.

Patent Document 1: Japanese Patent Laid-Open No. 2000-217144

Patent Document 2: Japanese Patent Application Laid-Open No. 11-145899

Patent Document 3: Japanese Patent Application Laid-Open No. 2004-72666

The conventional techniques described in the above Patent Documents 1 to 3 take into account wireless of the subscriber system, such as using a time division duplex (TDD) for access control, and the base station manages frame synchronization, base station receiving terminal, and subscriber station to perform multiplexing. We are planning.

However, in a wireless network system in which access control using a Carrie Sense Multiple Access (CSMA) scheme such as a wireless local area network (LAN) system is used, each wireless terminal independently executes carrier sense to avoid packet collision. . For this reason, when the interference avoidance method according to the prior art is used for the AP and the terminal of the wireless LAN system, the AP and the terminal in communication can adaptively change the transmission power, so that the RSSI (Received) enables carrier sense until the transmission power is changed. The waiting terminal received by the Siglal Strength Indicator may not be able to perform a carrier sense after changing the transmission power of the AP and the communicating terminal, thereby becoming a pseudo hidden terminal. There was a problem that the AP could not manage.

In each of the above conventional techniques, the amount of interference is measured by the base station, and the transmission power is controlled for the terminal. However, in the CSMA method used by the wireless LAN system or the like, when each terminal enforces transmission power limitation, the terminal received by RSSI capable of carrier sensing until the transmission power is changed, the carrier sense is changed after the transmission power is changed. It may not be possible to become a pseudo hidden terminal. At this time, there is a problem that the AP cannot estimate pseudo hidden terminals generated by the transmission power limitation of each terminal and perform control in consideration of the amount of interference.

In addition, in each of the above conventional techniques, adaptive modulation control is used to insert transmission power into a TDD frame or transmission information to calculate propagation attenuation from the difference between transmission power and reception power, and to control transmission power based on the calculation result. . However, under low environmental conditions, there is a problem that information of transmission power cannot be acquired unless the user waits for a modulation scheme that enables adaptive modulation control to be received.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and in a wireless network system using access control by the CSMA method, a radio apparatus that independently calculates the amount of radio wave attenuation and controls transmission power based on the calculated amount of radio wave attenuation to avoid interference. And an interference avoiding method by transmission power control.

MEANS TO SOLVE THE PROBLEM In order to solve the above-mentioned subject, and to achieve an objective, this invention is a wireless device applied to the wireless communication system which performs access control by a CSMA system, Comprising: According to the received power and the transmission radiation power information contained in a received frame, A propagation attenuation calculation unit that calculates an amount of propagation attenuation from the source radio apparatus of the reception frame to the own apparatus; The optimum transmission power is calculated, and the calculated optimal transmission power is registered in the optimum transmission power table in correspondence with the wireless device identifier for identifying the transmission source wireless device and each transmission rate, and the optimal transmission power table and transmission destination at the time of transmission. The radio identifier and transmission rate of the wireless device and thus the transmission target Selects an optimal transmission power to the local wireless device, performs transmission power control for transmitting a transmission frame including the selected optimal transmission power as transmission radiation power information at the selected optimal transmission power, and adds to the optimal transmission power table. And a transmission power control unit for detecting whether there is a value smaller than the selected optimal transmission power among the optimum transmission powers of the lowest transmission rates of the wireless devices different from the registered transmission destinations, and by the transmission power control unit, the optimum transmission power. If it is detected that there is a value smaller than the selected optimal transmission power among the optimal transmission powers of the lowest transmission rate of the wireless device different from the transmission destination registered in the power table, the predetermined hidden terminal avoidance control process is executed. .

Effects of the Invention

The radio apparatus according to the present invention calculates the amount of propagation attenuation from the source radio apparatus to the own apparatus according to the received power and the transmission radiation power information included in the reception frame, and according to the calculated amount of propagation attenuation and the minimum required power for each transmission rate. The optimum transmission power at each transmission rate is calculated and stored in association with the wireless device identifier for identifying the transmission source wireless device and each transmission rate. At the time of transmission, the optimum transmission power is selected according to the radio identifier and transmission rate of the transmission destination wireless device, and the transmission frame including the selected optimal transmission power as transmission radiation power information is transmitted at the selected optimal transmission power, If the value is smaller than the selected optimal transmission power among the optimum transmission powers of the lowest transmission rates of the other wireless devices, the predetermined hidden terminal avoidance control process is executed. Accordingly, each wireless device can independently select an optimal transmission power without deploying a device that collectively executes power control in the system, and for a hidden terminal similarly generated by the selected optimal transmission power. This has the effect that the avoidance control can be performed independently.

1 is a diagram showing a configuration of Embodiment 1 of a wireless device according to the present invention;

FIG. 2 is a diagram showing an example of the configuration of a PLCP frame including transmission radiated power values created by the frame combining unit shown in FIG. 1; FIG.

FIG. 3 is a diagram showing an example of the configuration of a PLCP frame including a transmission radiated power value created by the frame combining unit shown in FIG. 1; FIG.

4 is a diagram showing the configuration of a wireless LAN system according to the first embodiment using the wireless device according to the present invention;

5 is a flowchart for explaining a power control procedure of Embodiment 1 of a wireless device according to the present invention;

6 is a diagram showing the configuration of a wireless LAN system according to a second embodiment using a wireless device according to the present invention;

7 is a flowchart for explaining an interference avoidance procedure of Embodiment 2 of the radio apparatus according to the present invention;

8 is a diagram showing the configuration of a wireless LAN system according to a third embodiment of a wireless device according to the present invention;

9 is a flowchart for explaining a communication sequence after interference control according to the third embodiment of the wireless device according to the present invention;

10 is a diagram illustrating an example of a configuration of a TRQ frame;

11 is a diagram illustrating an example of a configuration of a TRQ frame;

12 is a diagram showing the configuration of a wireless LAN system according to a fourth embodiment of a wireless device according to the present invention;

Fig. 13 is a flowchart for explaining a communication sequence following the interference control procedure of Embodiment 4 of the wireless device according to the present invention.

Explanation of symbols for the main parts of the drawings

1: aerial 2: RF unit

3: demodulation part 4: frame separation part

5 radio wave attenuation calculation unit 6 transmission power control unit

7 modulator 8 frame synthesizer

10, 20, 22, 30, 33: AP 24, 35: BBS (1)

25, 36: BBS (2)

11, 12, 13, 21, 23, 31, 32, 34: STA

50, 60: PLCP preamble field

51, 61: PLCP header field

52, 62: transmit power information field

53, 63: data field 511: Rate unit

512: Reservation section 513: Length section

514, 523: Parity part 515, 524: Tail part

521: TX Power unit 522: Duration unit

611 frame control unit

EMBODIMENT OF THE INVENTION Hereinafter, the Example of the interference avoidance method by the wireless device and transmission power control which concerns on this invention is described in detail based on drawing. In addition, this invention is not limited by this Example.

<Example 1>

A first embodiment of the present invention will be described with reference to FIGS. 1 to 5. 1 is a diagram showing the configuration of Embodiment 1 of a wireless device according to the present invention. The radio apparatus comprises an aerial 1, an RF unit 2, a demodulator 3, a frame separator 4, a radio wave attenuation calculation unit 5, a transmission power control unit 6, a modulator 7 and a frame. The synthesis section 8 is provided.

The aerial line 1 converts an electromagnetic wave signal into an electrical signal and outputs it to the RF unit 2, and also converts the electrical signal into an electromagnetic signal. The RF unit 2 amplifies an electric signal input from the aerial line 1, outputs a baseband signal obtained by frequency converting the amplified electric signal to the demodulator 3, and also needs information for calculating a received power value. Is output to the propagation attenuation calculation unit 5 as first received power information. In addition, the RF unit 2 frequency-converts the electric signal input from the modulator 7 based on the power control information and outputs it to the aerial line 1.

The demodulation section 3 performs a predetermined demodulation process on the baseband signal input from the RF section 2 to generate a reception frame, and outputs the generated reception frame to the frame separation section 4. The demodulation section 3 also outputs the information necessary for the calculation of the received power value obtained by the demodulation process to the radio wave attenuation calculation section 5 as the second received power information.

The frame separator 4 separates the control information or data included in the received data frame demodulated by the demodulator 3, and outputs the separated data to the host apparatus (not shown) as the received data. The frame separation unit 4 also outputs the transmission radiation power information (the value obtained by adding transmission power, antenna characteristics, system loss, etc.) included in the control information to the radio wave attenuation calculation unit 5.

The propagation attenuation calculator 5 receives the first received power information input from the RF unit 2, the second received power information input from the demodulator 3, and the transmission radiated power information input from the frame separator 4. The radio wave attenuation amount from the plurality of transmitting radio stations to the own station is calculated. The propagation attenuation calculation unit 5 outputs the calculated propagation attenuation amount to the transmission power control unit 6 as propagation attenuation information.

The transmission power control section 6 calculates the optimum transmission power at each transmission rate by using the amount of propagation attenuation of each radio apparatus input from the radio wave attenuation calculation section 5 and the minimum required reception power predetermined for each transmission rate. The optimum transmission power at each calculated transmission rate is registered in the optimum transmission power table in association with the wireless device identifier for identifying each wireless device and each transmission rate. The transmission power control unit 6 selects the optimum transmission power based on the optimum transmission power table when the device transmits a data frame to the transmission destination wireless device, and uses the selected optimal transmission power as the power control information as the RF control unit 2. ), And transmits the radiated power information to the frame synthesizing section 8.

The frame synthesizing section 8 creates a transmission data frame according to the transmission data input from the host apparatus, the transmission radiation power information input from the transmission power control section 6, and outputs the transmission data frame to the modulation section 7. The modulator 7 performs a predetermined modulation process on the transmission PLCP frame input from the frame combiner 8, modulates it into an electric signal of a baseband, and outputs the modulated signal to the RF unit 2.

FIG. 2 shows a PLCP frame as a transmission data frame containing transmission radiation power information generated by the frame synthesis section 8. The Physical Layer Convergence Protocol (PLCP) frame has a PLCP preamble field 50, a PLCP header field 51, a transmission power information field 52, and a data field 53.

In the PLCP preamble field 50, information used for reception synchronization processing is set. The PLCP header field 51 includes a 4-bit Rate unit 511, a 1-bit Reservation unit 512, a 12-bit Length unit 513, a 1-bit Parity unit 514, and a 6-bit Tail unit ( 515).

The rate unit 511 sets the transmission rate of the PLCP frame. The reservation unit 512 is set to a value indicating whether the transmission power information field 52 is included in the PLCP frame, and here the transmission power information field 52 is set by setting "1" in the reservation unit 512. Indicates that it is a PLCP frame. In the length part 513, the length of the data field 53 is set. The parity unit 514 is set with a code used for error detection during demodulation processing. The tail portion 515 is set with a value indicating the end of the PLCP header field 51.

The transmission power information field 52 is composed of a 6-bit TXPower unit 521, an 11-bit Duration unit 522, a 1-bit Parity unit 523, and a 6-bit Tail unit 524.

TX radiation unit 521 is set to transmit radiated power information. In the duration section 522, transmission period information is set. The parity unit 523 is set with a code used for error detection during demodulation processing. The tail portion 524 is set to the last value in the transmission power information field 52. In the data field 53, data to be transmitted input from the host apparatus is set.

In FIG. 2, the PLCP header field 51 and the transmission power information field 52 have a length of one symbol, which is a unit of modulation used in the Orthogonal Frequency Division Multiplexing (OFDM) scheme, and the transmission rate of the PLCP frame. Regardless, it is transmitted at the lowest transmission rate (here 6 Mbps). In other words, since the PCLP header field 51 and the transmission power information field 52 including the transmission radiated power information and the transmission period information are transmitted at the lowest transmission rate, the PCLP header field 51 and the transmission power information field 52 are random even in an environmental condition with low Carrie to Noise Ratio (CNR). Regardless of whether or not the reception of the data field 53 transmitted at the transmission rate is successful, it is possible to receive the transmission radiation power information and the transmission period information set in the transmission power information field 52.

In the PLCP frame shown in FIG. 2, the transmission power information field 52 is provided between the PLCP header field 51 and the data field 53. However, as shown in FIG. It is good also as a structure provided with the transmission power information field 52. FIG.

In addition, although the OFDM scheme is taken as an example of the modulation scheme, the modulation scheme is not limited thereto, but the transmission power information field 52 is transmitted at a transmission rate that can be received at a CNR lower than the CNR of the transmission rate of the data field 53. As long as it is a system, a modulation system such as a single carrier may be used.

Next, the operation of the wireless device at the time of reception will be described. The aerial line 1 converts an electromagnetic wave signal including a PLCP frame into an electrical signal and outputs the electrical signal to the RF unit 2. The RF unit 2 amplifies the input electric signal and outputs a baseband signal obtained by frequency converting the amplified electric signal to the demodulator 3. The RF unit 2 also outputs, to the radio wave attenuation calculator 5, information necessary for calculating the received power value as the first received power information.

The demodulator 3 demodulates the baseband signal converted by the RF unit 2 to generate a reception frame, and generates the received frame (here, the PLCP frame shown in FIG. 2) by the frame separation unit 4. Output to The demodulation section 3 also outputs, to the radio wave attenuation calculation section 5, second received power information necessary for the calculation of the received power value obtained by the demodulation process.

The frame separator 4 separates the PLCP header field 51, the transmit power information field 52, and the data field 53 of the PLCP frame input from the demodulator 3. At this time, the frame separator 4 determines whether or not the transmission power information field 52 is included, based on the value of the reservation unit 512 of the PLCP header field 51. The frame separation unit 4 outputs the transmission radiation power information set in the TXPower unit 52 of the transmission power information field 52 to the radio wave attenuation calculation unit 5, and the data set in the data field 53. Is output to the host device as received data.

The propagation attenuation calculator 5 calculates the received power value using the first received power information input from the RF unit 2 and the second received power information input from the demodulator 3. The propagation attenuation calculation unit 5 calculates the propagation attenuation amount TrATT [dB] between the transmitting station and the local station by using the calculated received power value and the transmission radiation power information input from the frame separation unit 4. Calculate accordingly.

Here, TXPow [dB]: transmit radiated power information, RXPow [dBm]: receive power value. The radio wave attenuation calculation unit 5 outputs the radio wave attenuation amount TrATT [dB] calculated by the equation (1) to the transmission power control unit 6 as radio wave attenuation information.

The transmission power control section 6 uses the following propagation rate TrATT [dB] input from the propagation attenuation calculating section 5 and the minimum required reception power RXPow_min predetermined for each transmission rate, using each of the following transmission rates. The optimal transmission power TXPow_min [dBm] in is calculated. The minimum required received power RXPow_min [dBm] at this time is uniquely determined by the characteristics of the demodulator 3, and this value is assumed to be previously obtained from known or broadcast data such as a beacon.

The transmission power control section 6 stores the calculated optimum transmission power for each transmission rate in the optimum transmission power table in association with the wireless device. Specifically, the transmission power control section 6 stores the optimum transmission power with the corresponding wireless device for each transmission rate in correspondence with the wireless device identifier for identifying the transmission source wireless device of the received PLCP frame. The data set in the data field of the PLCP frame is generally an IP packet or a MAC frame. The IP packet or MAC frame contains the MAC address of the source radio. The frame separation unit 4 extracts the MAC address set in the data field 53 and notifies the transmission power control unit 6, and the transmission power control unit 6 notifies the MAC address notified from the frame separation unit 4. Is used as the wireless device identifier. The wireless device identifier is not limited to the MAC address but may be a unique ID or the like as long as the wireless device can be identified.

Next, the operation of the wireless device at the time of transmission will be described. When the transmission event occurs, the transmission data is input to the frame synthesizing section 8. In addition, the transmission power control section 6 selects a transmission rate to the transmission destination wireless device, and notifies the frame synthesis section 8 of the selected transmission rate. The transmission power control section 6 searches the optimum transmission power table using the radio key identifier identifying the transmission destination wireless device and the selected transmission rate as a search key, and selects the optimum transmission power TXPow_min when transmitting the PLCP frame. The transmission power control unit 6 outputs the selected optimal transmission power TXPow_min to the RF unit 2 as power control information, and generates transmission radiation power information including antenna characteristics, system loss, etc., to the optimal transmission power TXPow_min. It outputs to the frame composition part 8.

The frame synthesizing section 8 creates a PLCP frame using the transmission radiant power information and transmission rate input from the transmission power control section 6 and the transmission data input from the host apparatus. Specifically, the frame synthesizing section 8 sets information used for reception synchronization processing in the PLCP preamble field 50, sets a transmission rate notified from the transmission power control section 6 in the rate section 511, Set "1" which means to include the transmission power information field in the reservation unit 512, set the number of bytes of transmission data in the Length unit 513, the Rate unit 511 in the Parity unit 514, The code used for error detection created from the information set in the reservation unit 512 and the length unit 513 is set, a value indicating the end of the PLCP header field 51 is set in the tail unit 515, and the TXPower unit ( The transmission radiation power information notified from the transmission power control section 6 in the 521, the transmission period information in the Duration section 522, and generated from the information set in the TXPower section 521 and the Duration section 512. A code used for error detection is set, and in the tail unit 524, the transmission power information field 5 A value indicating the end of 2) is set, and the received data is set in the data field 53. The frame synthesizing section 8 outputs the created PLCP frame to the modulating section 7.

The modulator 7 modulates the PLCP frame input from the frame combiner 8 into an electric signal of a base band and outputs the modulated PLCP frame to the RF unit 2. The RF unit 2 frequency-converts the baseband electric signal input from the modulator 7 into a signal having the optimum transmit power TXPow_min instructed by the transmit power control unit 6, and also emits an electromagnetic wave signal by the aerial line 1. Transmit to and transmit.

Next, when the wireless device shown in FIG. 1 is applied to the AP (Access Point: 10) and STA (Stations 11 to 13) shown in FIG. 4, the AP 10 and the STA 11 perform opposite communication. Power control will be described with reference to FIG. 5.

First, a transmission event from the AP 10 to the STA 11 occurs (step S1). The transmission power control unit 6 of the AP 10 notifies the RF control unit 2 of the initial value of the transmission power with the transmission power, and generates the transmission radiation power information from the transmission power of the initial value to synthesize the frame. The unit 8 is notified (step S2). The frame synthesizing unit 8 of the AP 10 sets the transmitted transmit power information (in this case, an initial value) to TXPower 521 to create a PLCP frame, and the created PLCP frame is passed through the modulation unit 7. Output to RF unit 2. The RF unit 2 of the AP 10 transmits a PLCP frame to the STA 11 at the transmission power corresponding to the power control information (in this case, the initial value) instructed by the transmission power control unit 6 (wireless transmission). do.

The RF unit 2 of the STA 11 converts an electrical signal including a PLCP frame received through the aerial 1 into a baseband signal, outputs the signal to the demodulator 3, and calculates a received power value RXPow. The first received power information necessary for is output to the propagation attenuation calculation unit 5. The demodulator 3 of the STA 11 performs demodulation on the baseband signal, generates a received PLCP frame, and outputs the received PLCP frame to the frame separator 4. In addition, the demodulation section 3 of the STA 11 outputs, to the radio wave attenuation calculation section 5, second received power information necessary for calculating the received power value obtained by the demodulation process.

The frame separation unit 4 of the STA 11 outputs the transmission radiation power information TXPow set in the TXPower unit 521 in the received PLCP frame to the radio wave attenuation calculation unit 5. In addition, when "1" is not set in the reserved portion of the PLCP header, that is, when the transmission power information field 52 is not included in the PLCP frame, and the transmission radiation power information is not notified from the AP 10, the frame The separating section 4 reports the effect to the radio wave attenuation calculating section 5.

The propagation attenuation calculator 5 of the STA 11 calculates the received power value RXPow using the first received power information input from the RF unit 2 and the second received power information input from the demodulator 3. do. The propagation attenuation calculation unit 5 of the STA 11 calculates the difference between the calculated received power value RXPow and the transmitted radiated power information TXPow input from the frame separation unit 4 according to Equation (1). And the propagation attenuation amount TrATT between the STA 11 and the corresponding STA 11. The radio wave attenuation calculation unit 5 notifies the transmission power control unit 6 of the calculated radio wave attenuation amount TrATT (step S3). In addition, when the radio wave attenuation calculation unit 5 receives a report from the AP 10 that the transmission radiation power information is not notified, the radio wave attenuation calculation unit 5 does not perform the calculation and reports the notification to the transmission power control unit 6.

The transmission power control unit 6 of the STA 11 uses the radio wave attenuation amount TrATT between the AP 10 acquired from the radio wave attenuation calculation unit 5 and the corresponding STA 11, and the minimum required received power RXPow_min predetermined for each transmission rate. The optimum transmission power TXPow_min at each transmission rate is calculated according to Equation (2) above, and the optimal transmission power TXPow_min is calculated according to the wireless device identifier of the AP 10 and the respective transmission rates. It registers to a table (step S4). In addition, when the transmission power control unit 6 receives a report from the AP 10 that the transmission radiation power information is not notified from the radio wave attenuation calculation unit 5, the transmission source radio apparatus transmits power according to the first embodiment. It registers that it is a wireless device which does not control, and performs the conventional communication using a normal frame.

Next, it is assumed that a transmission event from the STA 11 to the AP 10 has occurred (step S5). The transmission power control unit 6 of the STA 11 selects a transmission rate to the AP 10 and notifies the frame synthesis unit 8. The transmission power control section 6 selects the optimum transmission power TXPow_min when transmitting the PLCP frame by searching the optimum transmission power table by using the wireless device identifier of the AP 10 and the selected transmission rate as the search key. The transmission power control unit 6 notifies the RF unit 2 of the selected optimal transmission power TXPow_min as power control information, generates transmission radiation power information from the selected optimal transmission power TXPow_min, and notifies the frame synthesis unit 8. (Step S6).

The frame synthesizing section 8 of the STA 11 sets the transmitted transmit power information to the TXPower section 521 of the transmission power information field 52 to create a transmission PLCP frame, and modulates the created PLCP frame. ) Is output to the RF unit 2 of the STA (11). The RF unit 2 of the STA 11 transmits (wireless transmission) the PLCP frame to the AP 10 at the transmission power corresponding to the power control information notified from the transmission power control unit 6.

The RF unit 2 of the AP 10 converts an electrical signal including a PLCP frame received through the aerial 1 into a baseband signal, outputs the signal to the demodulator 3, and calculates a received power value RXPow. The first received power information necessary for is output to the propagation attenuation calculation unit 5. The demodulator 3 of the AP 10 performs demodulation on the baseband signal, generates a received PLCP frame, and outputs it to the frame separator 4.

The frame separation unit 4 of the AP 10 outputs the transmission radiation power information TXPow set in the TXPower unit 521 in the received PLCP frame to the radio wave attenuation calculation unit 5. In addition, when "1" is not set in the reserved portion of the PLCP header, that is, when the transmission power information is not reported from the STA 11 because the transmission power information field 52 is not included in the PLCP frame. The frame separation unit 4 reports the effect to the radio wave attenuation calculation unit 5.

The propagation attenuation calculator 5 of the AP 10 calculates the received power value RXPow using the first received power information input from the RF unit 2 and the second received power information input from the demodulator 3. do. The propagation attenuation calculation unit 5 of the AP 10 obtains the difference between the calculated received power value RXPow and the transmission radiated power information TXPow input from the frame separation unit 4 according to the above formula (1), and the AP 10 And the propagation attenuation amount TrATT between the STA 11 and the corresponding STA 11. The radio wave attenuation calculation unit 5 notifies the transmission power control unit 6 of the calculated radio wave attenuation amount TrATT (step S7). In addition, when the propagation attenuation calculation unit 5 receives a report from the STA 11 that the transmission radiation power information is not notified, the radio wave attenuation calculation unit 5 does not perform the calculation and reports the notification to the transmission power control unit 6.

The transmission power control section 6 of the AP 10 determines the radio wave attenuation amount TrATT between the AP 10 acquired from the radio wave attenuation calculation section 5 and the corresponding STA 11, and the minimum required received power RXPow_min predetermined for each transmission rate. Calculate the optimized optimal transmission power TXPow_min at each transmission rate using Equation (2) above, and use the calculated optimal transmission power TXPow_min to correspond to the wireless device identifier of the STA 11 and each transmission rate for optimal transmission. It registers to a power table (step S8).

When the transmission power control unit 6 of the AP 10 receives a PLCP frame including a transmission power information field from the STAs 12 and 13 before executing the opposite communication with the STA 11, the STA 12, The optimum transmission power TXPow_min for each transmission rate for 13) is registered in the optimum transmission power table. The transmission power control unit 6 compares the optimum transmission power TXPow_min for the STA 11 and the optimum transmission power of the lowest transmission rate for the STAs 12 and 13 calculated according to the above formula (2), and thus the STA 11 It is determined whether or not there is a hidden terminal that occurs similarly by changing the optimal transmit power TXPow_min for. If there is a pseudo hidden terminal (the optimal transmission power TXPow_min of the lowest transmission rate of the STA 12 and / or the STA 13 is smaller than the optimal transmission power TXPow_min for the STA 11), the transmission power control unit ( 6) performs a hidden terminal avoidance control process by using a general transmission request / reception ready completion (RTS / CTS: Request To Send / Clear To Send) (step S9). In addition, the use of RTS at this time is not determined by the conventional RTS threshold. In addition, since control frames such as RTS / CTS should be transmitted to all wireless devices as much as possible, they are transmitted without being limited by the optimum transmission power value. When the transmission power control section 6 receives a report from the radio wave attenuation calculation section 5 that the transmission radiation power information section is not included in the PLCP frame, the counterpart device does not perform transmission power control according to the first embodiment. It registers as a wireless device which does not, and performs conventional communication using a normal frame. This communication is executed between the AP 10 and the STA 11.

As described above, in Embodiment 1, each wireless device in the wireless network system independently receives a PLCP frame including a transmission power information field, thereby calculating the amount of propagation attenuation between the transmitting and receiving devices, and calculating the optimum transmission power for each transmission rate. Since the PLCP frame is transmitted using the optimal transmission power at the time of transmission, the power consumption of the wireless device can be suppressed and further interference can be prevented.

In the first embodiment, since the wireless device that receives the PLCP frame that does not include the transmission power information field is registered as a wireless device that does not perform transmission power control, the conventional wireless device is included in the system. Communication can also be performed.

In the first embodiment, the optimum transmission power selected at the time of transmission is compared with the optimal transmission power of the lowest transmission rate of the radio apparatus different from the transmission destination radio apparatus, and the lowest transmission rate of the radio apparatus different from the transmission destination radio apparatus is compared. If the value is smaller than the optimal transmission power selected from among the optimal transmission powers, the RTS / CTS is applied. Thus, a pseudo hidden terminal by transmission power control can be avoided.

Further, in the first embodiment, since the PLCP header field 51 and the transmission power information field 52 are transmitted at the lowest transmission rate, the transmission radiation power information is reliably transmitted even from an interference wireless device whose communication quality is not guaranteed. The optimal transmission power can be calculated by receiving.

In the first embodiment, the communication between the AP and the STA has been described. However, the present invention does not particularly limit the type of the wireless device, and may be communication with the AP, the AP, the STA, and the STA.

In the first embodiment, the wireless LAN system has been described as an example, but the present invention is not limited to the wireless LAN system, and the access method may be TDMA or polling control.

In addition, the optimum transmission power may be determined from statistical processing such as an average value through repeated communication, or may be shared by transmitting the optimal transmission power value to another wireless device.

In the case of communicating with the same radio apparatus, the radio wave attenuation amount may be calculated only once at the start of communication, and the calculation of the subsequent radio wave attenuation amount may be omitted.

<Example 2>

Next, Example 2 of this invention is demonstrated using FIG. 6 and FIG. 6 shows the configuration of a wireless LAN system according to the second embodiment. In FIG. 6, the radio devices 20 to 23 have an internal configuration shown in FIG. 1. Of the wireless devices 20 to 23, the wireless devices 20 and 22 are APs, and the wireless devices 21 and 23 are STAs. The first basic service set (hereinafter referred to as BSS 1) 24 includes an AP 20 and an STA 21. The second basic service set (hereinafter referred to as BSS 2) 25 includes an AP 22 and a STA 23. In the communication between the same BSSs (communication in the AP 20 and the STA 21, the AP 22 and the STA 23), the transmission power is optimized in the same procedure as in the first embodiment. Is omitted.

Unintentional radio interference occurs because the distance between the STAs 21 and the AP 22, which are different BSSs, is within a range of electromagnetic waves. A procedure for avoiding such interference occurring between different BSSs will be described with reference to FIG. 7.

FIG. 7 illustrates an interference avoidance procedure of the STA 21 belonging to the BSS 1 and 24 and the AP 22 belonging to the BSS 2 and 25. First, in the AP 22 of the BSS 2, it is assumed that a communication event has occurred for the STA 23 of the BSS 2 (step S11). In response to this communication event, the transmission power control section 6 of the AP 22 carries out the transmission power value of the initial value (or optimized for the STA 23) as the transmission radiation power information in the same manner as in the first embodiment. The PLCP frame is transmitted to the STA 23 at the transmission power of the initial value or the transmission power optimized for the STA 23 (step S12).

In the STA 21 of the BSS 1 and 24 that has received a PLCP frame capable of demodulating only the PLCP frame or the PLCP header field 51 and the transmission power information field 52 of another BSS, the radio attenuation calculation unit 5 In this case, the propagation attenuation amount TrATT of the AP (in this case, the AP 22) and the STA 21 that transmitted this PLCP frame is calculated according to the above formula (1) (step S13). The propagation attenuation calculation unit 5 of the STA 21 notifies the transmission power control unit 6 of the STA 21 of the calculated propagation attenuation amount TrATT.

The transmission power control unit 6 of the STA 21 of the BSS (1) 24 does not impart interference to the AP 22 using the notified propagation attenuation amount TrATT (does not exceed the carrier sense threshold by the CSMA method). The maximum transmission power value is calculated (step S14).

Next, it is assumed that a communication event for the AP 20 has occurred from the STA 21 which is the same BSS (step S15). The transmission power control unit 6 of the STA 21 selects the optimum transmission power within the range of the maximum transmission power value calculated in step S14, that is, the maximum transmission power value that does not interfere with the AP 22 belonging to another BSS. To notify the RF unit 2 (step S16). At this time, in the case where the maximum transmission power value is exceeded at the current transmission rate, it is controlled so as to satisfy the maximum transmission power value by lowering the transmission rate. That is, the maximum transmission power value is compared with the optimum transmission power TXPow_min for each transmission rate for the AP 20 registered in the optimum transmission power table, and the transmission rate of the optimum transmission power TXPow_min which is equal to or less than the maximum transmission power value is determined. Choose. If the maximum transmission power value cannot be satisfied even by the control for lowering the transmission rate, the control for reducing the communication opportunity of the STA 21 (specifically, an increase in the number of CW (Contention Window: transmission waiting period)) Is carried out. In addition, when transmitting the control frame by the RTS / CTS, the limitation of the maximum transmission power value is not executed because of its importance.

In the same manner as in Embodiment 1, the transmission power control unit 6 of the STA 11 calculates the transmission radiation power information using the selected optimal transmission power, and selects the selected PLCP frame including the calculated transmission radiation power information. The transmission power is transmitted (wireless transmission) to the AP 20.

As described above, in the second embodiment, when the own device receives a PLCP frame that is an interference frame which is not a target while receiving, the amount of propagation attenuation is calculated using the transmission radiation power information included in the received PLCP frame, The radio apparatus independently calculates a maximum transmission power value that avoids interference of its own apparatus with respect to the source radio apparatus of the frame, and selects an optimal transmission power equal to or less than the maximum transmission power value calculated at the time of transmission. As a result, interference with the interference frame transmission source can be suppressed. As a result, even when a user randomly installs an AP or STA in a home or office, it is possible to avoid falling into an inaccessible state due to an improvement in throughput or interference from another BSS, and thus a wireless device that does not require a license. It is possible to secure a communication path even in the case of high density, and as a result, it is possible to improve the frequency utilization efficiency without installing a control radio.

Also, when an interference frame that does not target the own device is received and the interference frequency (the number of interferences) is low, the target of the wireless device (the maximum of the own device) that performs the interference avoidance is regarded as a wireless device having a low communication amount. The transmission power value).

In addition, even if an interference frame that does not target the own device is not received for a certain period of time, it may be regarded as a radio station having a small amount of communication and may be excluded from the target of the wireless device that performs interference avoidance.

In the second embodiment, the wireless LAN system has been described as an example. However, the present invention is not limited to the wireless LAN system. The access method may be TDMA or polling control.

Further, for example, by providing a field indicating the priority of the wireless device itself in the transmission frame, a wireless device may be provided which gives priority to the wireless devices and preferentially avoids interference.

In addition, the wireless device to which the method of Embodiment 2 is applied can be applied to any other wireless device, not just an AP or STA. In addition, if the reachability of the frame is important to satisfy the QoS control by providing priority for each queue, it may be allowed to temporarily exceed the maximum transmission power value.

<Example 3>

Next, Example 3 of this invention is demonstrated using FIGS. 8-10. 8 shows the configuration of a wireless LAN system according to the third embodiment. In FIG. 8, the radio devices 30 to 34 have an internal configuration shown in FIG. Of the wireless devices 30 to 34, the wireless devices 30 and 33 are APs, and the wireless devices 31, 32, and 34 are STAs. The BSS (1) 35 is configured to include the AP 30, the STA 31, and the STA 32. The BSS (2) 36 is configured to include the AP 33 and the STA (34). As in the second embodiment, interference occurs between different BSSs between the STA 31 and the AP 33. In Embodiment 3, since the order by which the STA 31 avoids interference with respect to the AP 33 is the same as that of Embodiment 2, the description thereof is omitted.

9, the communication sequence after interference control in the STA 31 will be described. First, in the STA 31, in order to communicate with the AP 30, a control frame called TRQ (Transmission request) for making a transmission request (see FIG. 10) is set as the maximum transmission power value or control frame transmission power setting value. The broadcast transmission is performed without any transmission power limitation (step S21). In addition, the TRQ frame does not determine the application by the frame length like the RTS threshold, but the application refers to the amount of propagation attenuation, where it is possible to determine that a temporary hidden terminal is generated by the transmission power control of the TRQ frame. use.

The TRQ frame has a PLCP preamble field 60, a PLCP header field 61, a transmission power information field 62, and a data field 63 as shown in FIG. 10. The preamble field 60, the PLCP header field 61 and the transmission power information field 62 are the PLCP preamble field 50, the PLCP header field 51 and the transmission power information field of the PLCP frame shown in FIG. Since it is the same as (52), the description is omitted here.

The data field 63 includes a 16-bit frame control (TRQ) section 631, a 16-bit Duration section 632, a 48-bit receiver address section 633, a 48-bit transmitter address section 634, and 32-bit. Has a FCS section 635, a 6-bit Tail section 636, and a padding bit section 637, and information indicating that the TRQ frame is set in the frame control section 631, and transmission in the Duration section 632. Period information is set, the MAC address assigned to the receiver is set in the receiver address section 633, the MAC address assigned to the transmitter is set in the transmitter address section 634, and the error correction is used in the FCS section 635. A sign is set, a value indicating the end of valid information in the data field 63 is set in the tail part 636, and a value for adjusting the length of the data field 63 is set in the padding bit part 637. .

The STA 32 that receives the TRQ frame has a predetermined SIFS (Short InterFrame Space) period from the TRQ reception, and then uses the transmission period information set in the Duration section 632 of the TRQ frame received from the STA 31. NAV (transmission stop period: Network Allocation Vector) is set for the period until the STA 31 completes reception (step S22). On the other hand, the STA 31 has a SIFS period after transmitting the TRQ frame, and then with the limited transmission power indicated by the transmission power control unit 6 of the STA 31, that is, with the limited transmission power obtained by the method of the second embodiment, The data frame is transmitted to the AP 30 (step S23). The AP 30 returns the ACK to the STA 31 after leaving the SIFS period from the completion of the data frame reception (step S24).

As described above, in the third embodiment, although the SAT 31 whose transmission power is limited by the interference avoidance control can acquire the communication state of the STA 32, the newly generated hidden from the STA 32 to the STA 31 is generated. In the situation where the carrier sense becomes impossible from the STA 32 to the STA 31, the terminal is partially hidden by transmitting a control frame called a TRQ frame at a set value of maximum power or control frame transmission power. The problem can be avoided with less overload. That is, compared with the case of transmitting the RTS, the overload can be suppressed and the throughput can be improved.

In the third embodiment, the wireless LAN system is described as an example. However, the present invention is not limited to the wireless LAN system. In the present invention, the wireless device may be any wireless device other than the AP or STA.

In the third embodiment, communication is performed between the TRQ frame and the data frame with the SIFS interposed therebetween. However, as shown in FIG. 11, the TRQ unit and the data are not interposed between the TRQ frame and the data frame. Additional consecutive frames may be transmitted.

<Example 4>

Next, Example 4 of this invention is described using FIG. 12 and FIG. 10 shows the configuration of a wireless LAN system according to the fourth embodiment. APs 40 to 43 as wireless devices have the internal configuration shown in Fig. 1, and each of the APs 40 to 43 is included in a separate BSS. Among them, the AP 40 is called a newly established wireless device. In Embodiment 4, since the order in which the AP 40 avoids interference with respect to the APs 41 to 43 is the same as in Embodiment 2, the description thereof is omitted.

A communication sequence following the interference control procedure in the AP 40 will be described with reference to FIG. 13. In step S31, the AP 40 receives the PLCP frame from the AP 41 on the channel CH1, and interference occurs in the AP 40.

The propagation attenuation calculation unit 5 of the AP 40 calculates the propagation attenuation amount TrATT of the AP (in this case, the AP 41) and the AP 40 which transmitted this PLCP frame according to the above formula (1). The propagation attenuation calculation unit 5 of the AP 40 outputs the calculated propagation attenuation amount TrATT to the transmission power control unit 6 of the AP 40 (step S32).

The transmission power control unit 6 of the AP 40 calculates a maximum transmission power value that does not impart interference to the AP 41 (step S33).

Similarly, in steps S34 to S36, the maximum transmission power that receives the PLCP frame from the AP 42 on the channel CH2 for the AP 42 and does not give interference to the AP 42 as described above. Calculate the value. Similarly, in steps S37 to S39, the maximum transmit power value is calculated for the AP 43, without causing interference to the AP 43, instead of the channel CH3.

After a certain time has elapsed, the transmission power control unit 6 compares the maximum transmission power values of the channels CH1 to CH3 in step S40, and selects the channel having the largest maximum transmission power value. Then, the transmission power control unit 6 of the AP 40 notifies the modulation unit 7 of the AP 40 by using the control channel.

As described above, in the fourth embodiment, since the maximum transmission power value is set as the evaluation value, and the channel to be used by the new wireless device is independently selected, the frequency resource can be efficiently utilized.

In the fourth embodiment, the wireless LAN system has been described as an example. However, the present invention is not limited to the wireless LAN system, and the access method may be TDMA or bowling control.

In the fourth embodiment, the AP is described as an example, but the type of the communication device is not limited.

As mentioned above, the interference avoidance method by the radio apparatus and transmission power control which concerns on this invention is useful for a digital radio communication system, and is especially suitable for the wireless LAN system which is IP packet radio communication.

Claims (8)

A wireless device applied to a wireless communication system that performs access control by a CSMA method, A propagation attenuation calculation unit that calculates an amount of propagation attenuation from the source radio apparatus of the reception frame to the own apparatus based on the reception power and transmission radiation power information included in the reception frame; Calculating the optimum transmission power at each transmission rate based on the amount of propagation attenuation calculated by the propagation attenuation calculation unit and the minimum required reception power determined for each transmission rate, and identifying the calculated source transmission apparatus with the calculated optimal transmission power. It is registered in the optimum transmission power table in correspondence with the wireless device identifier and each transmission rate, and at the time of transmission, the optimum transmission to the transmission destination wireless device based on the optimum transmission power table and the wireless identifier and transmission rate of the transmission destination wireless device. Selecting power, performing transmission power control for transmitting a transmission frame including the selected optimal transmission power as transmission radiation power information at the selected optimal transmission power, and different from the transmission destinations registered in the optimal transmission power table. Before optimal transmission of the lowest transmission rate of the wireless device A transmission power controller for detecting whether a value smaller than the selected optimum transmission power in the Provided with If the transmission power control unit detects that there is a value less than the selected optimal transmission power among the optimal transmission powers of the lowest transmission rate of the wireless device different from the transmission destination registered in the optimal transmission power table, a predetermined hidden To perform hidden terminal avoidance control processing Wireless device characterized in that. The method of claim 1, The predetermined hidden terminal avoidance control process is a process based on a transmission request frame and a reception ready frame. The method of claim 1, The predetermined hidden terminal avoidance control process is a process of transmitting a TRQ frame by broadcast, or after receiving a TRQ frame, a predetermined period is set, and then a transmission stop period is set using the transmission period information set in the TRQ frame. A wireless device comprising a processing to provide. The method of claim 1, The transmission power control section performs the transmission power control only when transmitting a data frame containing user data, and when transmitting a control frame by the predetermined hidden terminal avoidance control process, the transmission power control unit is larger than the transmission power of the data frame. Wireless device characterized by selecting a transmit power. The method of claim 1, When the transmission power control unit receives a PLCP frame from a wireless device belonging to another wireless network system, the transmission power control unit calculates a maximum transmission power value that does not interfere with the source wireless device of the received PLCP frame. When the optimal transmission power to the transmission destination wireless device selected based on the transmission power table and the radio identifier and transmission rate of the transmission destination wireless device exceeds the maximum transmission power value, the optimum transmission power becomes less than or equal to the maximum transmission power value. And selecting an optimal transmission power of the transmission rate. The method of claim 1, When the reception frame from the source radio apparatus is a frame including the transmission radiation power information, the transmission power control is performed using the transmission radiation power information, and the frame including the transmission radiation power information is transmitted. And when the transmission radiation power information is not included in the reception frame from the source radio apparatus, communication is performed by a normal frame. The method of claim 1, And the transmission power control section registers a channel in which the reception frame from the source radio apparatus is received in the optimal transmission power table, and selects a channel having the largest optimal transmission power at the time of transmission. An interference avoidance method by transmission power control applied to a wireless communication system which performs access control by a CSMA method, A propagation attenuation calculation step of calculating an amount of propagation attenuation from the source radio apparatus of the reception frame to the own apparatus based on the reception power and transmission radiation power information included in the reception frame; A radio which calculates an optimum transmission power at each transmission rate based on the amount of propagation attenuation calculated by the propagation attenuation calculation unit and the minimum required power determined for each transmission rate, and identifies the transmission source wireless device with the calculated optimal transmission power. It is registered in the optimum transmission power table in correspondence with the device identifier and each transmission rate, and at the time of transmission, optimal transmission to the transmission destination wireless device based on the optimum transmission power table and the wireless identifier and transmission rate of the transmission destination wireless device. Selecting power, performing transmission power control for transmitting a transmission frame including the selected optimal transmission power as transmission radiation power information at the selected optimal transmission power, and different from the transmission destinations registered in the optimal transmission power table. Optimal transmit power at the lowest transmission rate of the wireless device A transmission power control step of detecting whether there is a value smaller than the selected optimal transmission power during the operation; When the transmission power control unit detects that there is a value smaller than the selected optimal transmission power among the optimal transmission powers of the lowest transmission rate of the wireless device different from the transmission destination registered in the optimal transmission power table, a predetermined hidden terminal Hidden terminal avoidance control step of performing avoidance control Method for avoiding interference by transmission power control, characterized in that it comprises a.

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