WO2009113137A1

WO2009113137A1 - Wireless communication apparatus

Info

Publication number: WO2009113137A1
Application number: PCT/JP2008/003728
Authority: WO
Inventors: 佐藤　光
Original assignee: パナソニック株式会社
Priority date: 2008-03-14
Filing date: 2008-12-11
Publication date: 2009-09-17
Also published as: JP2009225043A

Abstract

A wireless communication apparatus wherein the number of retransmissions can be reduced and the power consumption can be reduced. The wireless communication apparatus (100) implements at least one of transmission output controls as follows: (1) in a case where no ACK is received for a current frame, raising, based on a degradation of communication environment state, a transmission output level at a fallback control time; (2) in a case where a determined communication environment state is an interference, raising a transmission output level established in advance at a retransmission time, while reducing the number of retransmissions; (3) in a case of raising a transmission output level for a retransmission, issuing a request for raising the transmission output level of an ACK from an access point of transmission destination; and (4) operating, based on a degradation of communication environment state, a reception switch (SW) (103) such that a received signal is supplied via a high-sensitivity mode amplifier (104).

Description

Wireless communication device

The present invention relates to a wireless communication apparatus that performs retransmission when an ACK is not received for a current frame, for example, a wireless terminal apparatus used in a wireless LAN (WLAN: Wireless Local Area Network).

In recent years, the number of cases where a wireless LAN is constructed in an office, a home, or the like in consideration of easiness of installation and economics of introduction cost is increasing. As a typical technique of wireless LAN, there is IEEE 802.11 standardized by IEEE (Institute of Electrical and Electronics Electronics). This standardized technology regulates the physical layer to the MAC (Medium Access Control) layer, which is the lower layer of the data link, in the OSI (Open System Interconnection) model. It can be replaced with the Ethernet, and the roaming function can be provided as an additional function because it is wireless.

Currently, 802.11b transmission speeds of 11 Mbps and 802.11a and 802.11g maximum transmission speeds of 54 Mbps have been established for wireless LAN, and corresponding products have come to the market. For this reason, low-cost wireless LANs have become widespread, the number of cases in which individual users construct wireless LANs has increased rapidly, and wireless LANs have rapidly spread. Now it is widely used not only for business purposes, but also as a personal home network.

Since wireless LAN uses the ISM (Industrial Science and Medicine) band, which is an unlicensed band, transmission errors are particularly frequent. Wireless LANs are susceptible to noise and interference even if narrowband transmission is performed. Therefore, the wireless LAN needs to consider radio waves from a microwave oven and other wireless transmission devices. Further, when a terminal enters a dead point due to multipath fading in addition to noise, frames cannot be transmitted.

In 802.11, retransmission of an acknowledgment (ACKnowledge 再送 Character) method is performed in order to deal with transmission errors. In the acknowledgment type retransmission, the receiving side needs to return ACK for all frames transmitted from the transmitting side. If all the steps that return ACK for all frames are successful, the operation is considered complete, otherwise all operations are considered failed. That is, if the data frame source does not receive an ACK, the frame is considered lost. If the source cannot receive an ACK, regardless of whether the data frame was lost during the initial transmission or the ACK was lost during transmission, the source retransmits the same data frame.

In a wireless LAN, while a given station is performing basic operations (the above described sequence) for one access point, communication is suppressed so that other stations do not interfere with the basic operations of the currently used station. And avoid collisions.

Detecting and correcting data frame transmission errors are performed at the station side that started the exchange of the basic frame, that is, at the transmitting station. Transmission errors must be detected at the sending station. For example, the transmitting station detects an error by not receiving an ACK from the receiving station. When the transmitting station detects an error, it retransmits the frame.

The transmitting station is provided with a retransmission counter for counting frame retransmission, and increments the retransmission counter by 1 each time a frame is retransmitted. The retransmission counter is provided for each frame or each fragment. The retransmission counter can be classified into two types, a short frame retransmission counter and a long frame counter.

Wireless LAN ensures reliability by retransmission. If the station that transmitted the frame does not receive the ACK from the access point or the receiving station, it determines that the frame transmission has failed. A failed transmission increments the retransmission counter by one. When the number of retransmissions reaches a predetermined upper limit value, the station gives up transmission of the frame and informs the upper layer of the protocol to that effect.

In Patent Document 1, when retransmission is performed, the transmission unit is switched to the high sensitivity mode when the transmission rate is changed, and the number of retransmissions is reduced by changing the transmission power of the transmission ACK at that time. A wireless communication device is described.

Patent Document 2 describes a data communication method that enables optimum communication according to a radio wave propagation environment and improves the throughput of the entire wireless communication system by enabling a transmission rate to be set for each wireless terminal. ing.

By the way, the wireless LAN can move each terminal that forms the wireless LAN within a communicable range as compared with the wired LAN that has been used before the introduction of the wireless LAN. The boundaries that indicate possible ranges are ambiguous. Since the boundary indicating the communicable range is ambiguous, when a plurality of wireless LANs exist adjacent to each other, the terminal exists in a range where the communicable ranges of the plurality of wireless LANs overlap. Sometimes. When these terminals receive respective radio waves in a wireless LAN adjacent to each other, radio wave interference problems may occur and throughput may be reduced.

The following interference avoidance method is adopted when radio wave interference is detected. Patent Document 3 discloses a technique for performing interference avoidance by changing a frequency channel when radio wave interference is detected. The radio wave interference avoidance method described in Patent Document 3 is based on a signal received by a wireless antenna when a plurality of frequency channels are selectively set and wirelessly connected to a device terminal in a wireless network system. The radio wave level of each channel is measured at a predetermined cycle, and the measured others are compared with a predetermined threshold value to determine whether each frequency channel is used or not used, and stored as usage frequency statistical data for each frequency channel. During the wireless communication with the device terminal, the frequency channel is changed based on the statistical data as necessary.

Further, when a communication error occurs, fallback control is performed to decrease the transmission rate and increase the transmission distance. However, if the transmission rate is lowered to the minimum rate due to fallback, the throughput will be significantly reduced. In Patent Document 4, when an error occurs due to the occurrence of interference, a reference throughput at the time of interference is set to be the throughput in order to avoid a significant decrease in throughput due to the fallback of the transmission rate to the minimum rate. The speed mode is controlled to ensure a certain level of throughput. Specifically, the presence / absence of interference from an interference device that operates in the same frequency band as the wireless communication device to receive and operates based on a standard different from the standard used for communication of the wireless communication device is determined wirelessly. When the communication device detects it, the wireless communication device sets the reference throughput when changing the speed mode as the interference throughput, thereby changing the speed mode.
JP 2000-49663 A JP 2003-51781 A JP 2005-333510 A Japanese Patent Laying-Open No. 2005-278052

Mobile terminals equipped with the above wireless LAN are becoming popular. In a portable terminal such as a cellular phone, low battery current consumption is important because battery life is directly linked to call time and standby time. However, if the current consumption during wireless LAN transmission is reduced, there is a problem that the transmission power is reduced and it is not possible to secure the communication distance.

For example, a conventional wireless communication apparatus is in a normal operation state when it transmits a frame and receives an ACK for each frame. However, if the ACK is not received due to the deterioration of the communication state, the transmitting STA (station) tries to retransmit. The STA on the transmitting side that has entered the re-transmission performs frame re-transmission for the preset number of times using the current transmission power and the same rate. Next, the STA on the transmitting side that has entered the retransmission enters a rate fallback state and lowers the data rate when the number of retransmissions of the frame expires. Due to this, the following problems can be considered.

(1) Regardless of the communication environment state, continuing transmission until the specified number of times has expired leads to an increase in power consumption.

(2) When the communication environment condition deteriorates due to interference waves or the like, retransmission occurs because ACK from the STA does not reach the AP (Access Point).

An object of the present invention is to provide a wireless communication apparatus that can reduce the number of retransmissions and reduce power consumption.

When no ACK is received for the current frame, the wireless communication apparatus of the present invention performs retransmission for a preset number of times at a predetermined transmission output level and transmission rate, and when the number of retransmissions for this frame expires, the transmission rate A communication environment determination unit that determines a communication environment state, and when no ACK is received for a current frame, the fallback based on the deterioration of the communication environment state A transmission output control means for increasing the transmission output level at the time of control is adopted.

When no ACK is received for the current frame, the wireless communication apparatus of the present invention performs retransmission for a preset number of times at a predetermined transmission output level and transmission rate, and when the number of retransmissions for this frame expires, the transmission rate A communication environment determination unit for determining a communication environment state, and when the communication environment state determined by the communication environment determination unit is interference, the wireless communication device performs fallback control for reducing the communication environment state. And a transmission output control means for increasing the transmission output level.

When no ACK is received for the current frame, the wireless communication apparatus of the present invention performs retransmission for a preset number of times at a predetermined transmission output level and transmission rate, and when the number of retransmissions for this frame expires, the transmission rate A wireless communication device that performs fallback control for reducing the reception signal, an amplifying unit that increases reception sensitivity of a received signal, a switching unit that switches whether or not the received signal passes through the amplifying unit, and communication that determines a communication environment state An environment determining unit and a transmission output control unit that switches the switching unit so that a received signal passes through the amplification unit based on the deterioration of the communication environment state are employed.

According to the present invention, when the communication environment state is deteriorated, by increasing the transmission output level, the number of retransmissions can be reduced or the retransmission itself can be eliminated, and the power consumption can be reduced.

The figure which shows the structure of the radio | wireless communications system which concerns on one embodiment of this invention The block diagram which shows the structure of the radio | wireless communication apparatus which concerns on the said embodiment. The figure which shows the transmission / reception period between the radio | wireless communication apparatus which concerns on the said embodiment, and an access point. The figure explaining the relationship between the transmission side retransmission number and transmission power of the radio | wireless communication apparatus which concerns on the said embodiment. The figure explaining the transmission power control at the time of retransmission by the communication environment state of the radio | wireless communication apparatus which concerns on the said embodiment. The figure explaining the ACK control of the access point of the radio | wireless communication apparatus which concerns on the said embodiment Flow chart showing transmission output control of ACK accompanying reception sensitivity UP of the wireless communication apparatus according to the above embodiment The flowchart which shows the interference environment setting of the radio | wireless communication apparatus which concerns on the said embodiment

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

(Embodiment)
FIG. 1 is a diagram showing a configuration of a wireless communication system according to an embodiment of the present invention.

1, the wireless communication system includes a wireless communication device 100, an access point AP 200, and a network 300.

The wireless communication apparatus 100 is a station such as a PHS (Personal Handy-Phone System) / cell phone, PDA (Personal Digital Assistant) having a wireless LAN function, and performs wireless communication by connecting to the access point 200. The wireless communication device 100 receives a beacon from an access point 200 present in the vicinity, and acquires the network name of the access point 200, the communication speed of the communication device, the security strength, the communication channel, and the radio wave strength.

Note that the wireless communication device 100 may be a mobile terminal having a wireless LAN connection function, and is not limited to the mobile phone described above, and may be a mobile information terminal such as a PHS or PDA. Further, the form is not limited, such as a PCMCIA card or CF card type wireless LAN connection device. Further, the wireless communication is not limited to the wireless LAN, but may be Bluetooth (registered trademark), UWB (Ultra Wideband), or WiMAX. In addition, a wireless communication terminal that can move a place of use, such as an FWA (Fixed Wireless Access) terminal, is also included. A detailed configuration and function of the wireless communication device 100 will be described later with reference to FIG.

The access point 200 is a wireless LAN access point having a power save mode function, and connects the wireless communication apparatus 100 and the network 300 using the wireless LAN. The access point 200 relays communication between the wireless communication device 100 and a server (not shown). The access point 200 is used, for example, in a home having an Internet connection environment or a public wireless LAN service, and forms a wireless LAN usable area.

The network 300 includes the Internet or a dedicated line connecting the access point 200 and a server (not shown). The network 300 is a network composed of a mobile communication network, a public telephone network, a LAN, the Internet, and the like, and the type of network and the type of protocol such as a wired system or a wireless system are not particularly limited. In addition, as access lines of the network 300, FTTH (Fiber To The Home), HFC (Hybrid Fiber Coax: Optical Coaxial Cable), ADSL (Asymmetric Digital Subscriber Line) / VDSL (Very High Data Data Rate Digital Subscriber Line), etc. A capacity line is available.

FIG. 2 is a block diagram showing a configuration of radio communication apparatus 100 according to the embodiment of the present invention. The present embodiment is an example applied to a wireless communication apparatus in a wireless LAN.

In FIG. 2, a wireless communication device 100 includes an antenna 101, a transmission / reception switch (T / R SW) 102, a reception switch (SW) 103, a high sensitivity mode amplifier 104, a wireless reception unit 105, a demodulation unit 106, a modulation unit 107, a wireless communication device. A transmission unit 108, a network interface 109, a communication control unit 110, a communication environment determination unit 111, a retransmission number setting unit 112, a MAC unit 113, and a transmission power control unit 114 are configured.

The antenna 101 receives a signal of the wireless LAN communication method and outputs it to a transmission / reception switch (T / R SW) 102 through a filter (not shown). Further, the antenna 101 transmits a transmission signal of the wireless LAN communication method input from the transmission / reception switch (T / R SW) 102.

The transmission / reception switch (T / R SW) 102 switches the switch at the transmission timing and the reception timing. The transmission / reception SW 102 outputs the reception signal input from the antenna 101 to the wireless reception unit 105 via the reception switch (SW) 103 and outputs the transmission signal input from the wireless transmission unit 108 to the antenna 101.

The reception switch (SW) 103 switches whether or not the received signal passes through the high sensitivity mode amplifier 104 in accordance with an instruction from the MAC unit 113. The reception switch (SW) 103 switches to the <high sensitivity mode> so that the reception signal passes through the high sensitivity mode amplifier 104.

The high sensitivity mode amplifier 104 is an amplifier that increases the reception sensitivity of the received signal.

The radio reception unit 105 down-converts the reception signal input via the reception switch (SW) 103 from the radio frequency to the baseband frequency and outputs the down-converted signal to the demodulation unit 106.

The demodulation unit 106 demodulates the reception signal input from the wireless reception unit 105 and outputs it to the communication control unit 110 as reception data.

Modulation section 107 modulates transmission data to generate a transmission signal, and outputs the generated transmission signal to radio transmission section 108.

The radio transmission unit 108 up-converts the transmission signal input from the modulation unit 107 from the baseband frequency to the radio frequency, and outputs it to the transmission / reception SW 102.

The network interface 109 is an interface connected to the network 300.

The communication control unit 110 performs protocol processing at the MAC layer or higher and performs wireless LAN control of the entire apparatus including the network 300 connection function. When the ACK is not received for the current frame in cooperation with the MAC unit 113, the communication control unit 110 performs retransmission for the preset number of times at a predetermined transmission output level and transmission rate, and When the number of retransmissions expires, fallback control is performed to lower the transmission rate.

The communication environment determination unit 111 determines the communication environment state. In particular, the communication environment determination unit 111 determines communication quality deterioration due to radio wave interference due to interference waves, interference waves, and the like. In the present embodiment, the communication environment determination unit 111 determines that the SNR (Signal power to Noise power Ratio) of the current frame is equal to or less than a certain threshold, and determines the communication environment state in which there is interference due to a microwave oven or the like. To do. In addition to the SNR, the interference may be a noise floor value of a received packet, or a noise floor value at the time of Beacon acquisition. Further, the received packet may be an FCS (Frame CheckequSequence) error, a reception error other than the FCS error, or an S / N value.

The retransmission number setting unit 112 presets the number of retransmissions at the time of retransmission, the transmission output level, and the transmission rate. In accordance with an instruction from the MAC unit 113, the retransmission number setting unit 112 increases the transmission output level and reduces the number of retransmissions during fallback control or retransmission. The retransmission number setting unit 112 outputs the set transmission output level to the transmission power control unit 114 via the MAC unit 113.

The MAC unit 113 generates a transmission frame when the wireless communication device 100 performs transmission, and processes the transmission frame when the wireless communication device 100 performs reception. The MAC unit 113 performs the following transmission output control in addition to the basic function of access control in the wireless section. Note that the transmission output control in the present embodiment is transmission output control at the time of retransmission, and is used in the same meaning as the transmission power control at the time of retransmission.

(1) When the ACK is not received for the current frame, the MAC unit 113 increases the transmission output level during the fallback control based on the deterioration of the communication environment state. (2) Also, when the determined communication environment state is interference, the MAC unit 113 increases the transmission output level set in advance at the time of retransmission. When the transmission output level is increased, it is preferable to reduce the number of retransmissions. (3) The MAC unit 113 switches the reception switch (SW) 103 so that the received signal passes through the high sensitivity mode amplifier 104 based on the deterioration of the communication environment state. The transmission output controls (1) to (3) may be used alone or in combination.

In the present embodiment, the MAC unit 113 is configured to have the transmission output control functions (1) to (3) described above. However, the MAC unit 113 is not limited thereto, and the MAC unit 113 is a basic function of media access control (MAC). However, the transmission output control function of (1) to (2) may be executed by the communication control unit 110 or newly provided by the transmission output control unit. Each control unit including the communication control unit 110 is configured by a CPU or the like, and the execution unit is for convenience regardless of which function unit is responsible.

The transmission power control unit 114 controls the transmission power of the wireless transmission unit 108 to transmit at the set transmission output level.

In wireless LAN communication at home, it is necessary to secure a station capable of simultaneous communication by connecting a plurality of stations to one access point.

Hereinafter, the transmission power control operation of the wireless communication apparatus 100 configured as described above will be described.

FIG. 3 is a diagram showing a transmission / reception cycle between the station (wireless communication apparatus 100) and the access point 200. In FIG. 3, on the transmission side, data is transmitted at a maximum transmission rate of 54 Mbps by a wireless LAN. On the receiving side, after data transmission, ACK is returned after a short interframe space (SIFS: Short Inter-Frame space) elapses, and a standby for a certain idle time called DCF interframe space (DIFS: DCF Inter-Frame Space) is waited. Start. It is an access waiting period for other stations from the start of data transmission to the end of the DIFS section. When the DIFS section ends, a contention window (contention window), which is a channel that is transmitted between the stations without being scheduled between the stations, is obtained.

This embodiment is characterized by performing transmission power control as described in [1]-[3] below.

[1] Transmission power control at the time of retransmission When an ACK is not received for a current frame due to degradation of communication quality, a transmission output level is increased when the data rate after retransmission is decreased for the current frame. .

[2] Transmission power control at the time of retransmission according to the communication environment state The transmission power is varied by judging the communication environment state when the communication quality is deteriorated.

Communication quality degradation is caused by interference. In this embodiment, when the reception sensitivity is equal to or less than a certain threshold value from the SNR of the current frame, it is determined that the interference is caused by an indoor microwave oven or the like. In this case, the transmission output is set to Maxpower.

[3] ACK transmission power control (1) ACK control of access point The transmission power of ACK on the access point side is increased according to the communication environment state.

(2) Transmission output control of ACK accompanying UP of reception sensitivity Communication is performed without performing retransmission by switching to high sensitivity mode by SW based on determination of communication environment state. In addition, transmission power control is performed for an ACK from the station after reception in the high sensitivity mode.

First, [1] Transmission power control during retransmission will be described.

4A and 4B are diagrams for explaining the relationship between the number of retransmissions on the transmission side and transmission power, FIG. 4A shows a conventional example, and FIG. 4B shows transmission power control according to the embodiment.

As shown in FIG. 4A, in the conventional example, the transmission output of the transmitting station is constant regardless of the data transmission speed and the number of retransmissions.

On the other hand, in the present embodiment, as shown in FIG. 4B, when the transmission side station (wireless communication apparatus 100) reaches the predetermined number of retransmissions when ACK is not received, the transmission output Raise the level. Although not shown in FIG. 4B, at the time of retransmission, a rate fallback state is entered to lower the data rate. The transmission output level is raised when the data rate after this retransmission is lowered. In this control, the MAC unit 113 sets based on the number of retransmissions of the retransmission number setting unit 112 and the communication environment state of the communication environment determination unit 111, and instructs the transmission power control unit 114. The MAC unit 113 issues an instruction to increase the transmission output level when the number of retransmissions reaches a predetermined number, or when entering the rate fallback state and lowering the data rate. The transmission power control unit 114 controls the wireless transmission unit 108 to increase the transmission output level.

Next, [2] Transmission power control at the time of retransmission according to the communication environment state will be described.

5A and 5B are diagrams for explaining transmission power control at the time of retransmission according to the communication environment state, FIG. 5A shows the relationship between the number of retransmissions on the transmission side due to fading and the transmission power, and FIG. 5B shows retransmission on the transmission side due to interference. The relationship between the number and transmission power is shown respectively.

As shown in FIGS. 5A and 5B, the transmitting station (wireless communication apparatus 100) performs data retransmission when the communication environment state deteriorates and ACK is not received. The communication environment determination unit 111 determines the communication environment by comparing the SNR of the current frame with a threshold value, and outputs the determination result to the MAC unit 113. If the MAC unit 113 determines that the deterioration of the communication environment state is fading, the MAC unit 113 continues to transmit retransmission at a constant transmission output level until the prescribed number of times expires. Note that after a predetermined number of retransmissions, the transmission rate is lowered to 48 Mbps by fallback control.

On the other hand, as indicated by the arrow in FIG. 5B, when the MAC unit 113 determines that the deterioration of the communication environment state is interference, the MAC output level is increased and the retransmission is reduced from the specified number of times. That is, when interference occurs, while increasing the transmission output level to increase the transmission possibility, the number of retransmissions is reduced to reduce the power consumption.

When the communication environment state deteriorates, if it is an interference wave or the like, the ACK from the station does not reach the access point 200, so retransmission occurs. In this case, the ACK from the station often does not reach the access point 200 even after the set number of retransmissions. Since the generation of interference wave itself cannot be prevented, a mode in which frame retransmission is performed uniformly for a predetermined number of times only increases power consumption. Therefore, when interference occurs, the transmission output level is raised to determine whether transmission is possible at an early stage. The retransmission is aborted when the number of retransmissions is smaller than the number of retransmissions previously set. Note that after this number of retransmissions, the transmission rate is lowered to 48 Mbps by fallback control.

Next, [3] ACK transmission power control will be described.

6A and 6B are diagrams for explaining ACK control of an access point. In the figure, AP indicates an access point 200, and STA indicates a station (wireless communication apparatus 100). Further, ◯ indicates transmission OK between the AP and STA, and X indicates transmission NG between the AP and STA.

As shown in FIG. 6A, when the communication environment is good, data transmission from the AP is received on the STA side, and ACK from the STA is received on the AP side. Then, data transmission from the STA is received on the AP side, and ACK from the AP is received on the STA side. This is repeated thereafter.

As shown in FIG. 6B, when communication degradation due to interference occurs, the AP cannot receive data from the STA. For this reason, the AP does not transmit ACK to the STA. In this embodiment, in this case, the transmission output level is increased and data is retransmitted for the first time. Specifically, the MAC unit 113 issues an instruction to increase the transmission output level to the transmission power control unit 114, and the transmission power control unit 114 controls the wireless transmission unit 108 to increase the transmission output level.

The AP receives the first retransmission data from the STA transmitted at a higher transmission output level. Since the first retransmission data is transmitted with the transmission output level increased, the AP can receive the data even if the communication environment state deteriorates due to interference. When the STA increases the transmission output level, it sends a request to the AP to increase the AP's ACK transmission output level. In response to the request to increase the transmission output level, the AP increases the transmission output level of ACK and transmits ACK. The STA can receive the ACK from the AP even if the communication environment state deteriorates due to interference because the ACK is transmitted with the transmission output level increased.

FIG. 7 is a flowchart showing transmission output control of ACK accompanying reception sensitivity increase, and is executed by the MAC unit 113. In the figure, S is each step of the flow.

When this flow starts due to the start of retransmission or a change in transmission rate, in step S1, the MAC unit 113 determines whether the interference wave is an interference wave based on the communication environment state detection result from the communication environment determination unit 111. The process proceeds to step S2, and if it is an interference wave, the process proceeds to step S4.

In step S2, the MAC unit 113 determines whether or not fading is based on the communication environment state detection result from the communication environment determining unit 111. If fading, the process proceeds to step S3, and if not fading, the process proceeds to step S4.

In step S3, the MAC unit 113 sets the station to <normal reception mode>.

If it is an interference wave in step S1 or not fading in step S2, the MAC unit 113 switches to the high sensitivity mode in step S4 to increase the reception sensitivity of the station when the station is receiving. Specifically, the MAC unit 113 outputs a switching signal to the reception switch (SW) 103 in the <high sensitivity mode>, and the reception switch (SW) 103 sets the transmission destination of the reception signal by the switching signal in the high sensitivity mode. Switch to the amplifier 104 side. High sensitivity mode amplifier 104 amplifies the received signal and outputs the amplified signal to radio receiving section 105. As described above, when an interference wave is detected in the determination of the communication environment state of the communication environment determination unit 111, the retransmission is performed by shifting to the <high sensitivity mode> and switching the reception switch (SW) 103 to the high sensitivity mode amplifier 104 side. Try to communicate without doing. The number of AP retransmissions can be reduced.

In step S5, the MAC unit 113 determines whether or not reception is possible in the <high sensitivity mode>. If reception is possible in <high sensitivity mode>, the MAC unit 113 raises the transmission output level of the ACK of the station and ends this flow in step S6. This is to make the ACK for the AP less susceptible to interference waves.

If reception is not possible in the <high sensitivity mode> in step S5, the MAC unit 113 retransmits the station at the maximum transmission output level for the number of times set for each rate in step S7. This is to make it less susceptible to interference waves.

FIG. 8 is a flowchart showing interference environment setting. This flow sets the number of retransmissions and the transmission output level in the interference environment at the time of interference determination. The set number of retransmissions and transmission output level are used in ACK transmission output control of FIG.

In step S11, the MAC unit 113 determines whether or not the SNR for each packet is equal to or less than the threshold based on the communication environment state detection result from the communication environment determination unit 111. If the SNR for each packet is less than or equal to the threshold value, the MAC unit 113 determines in step S12 that the interference is caused by a microwave oven or the like, sets the interference environment retransmission count and the transmission output level to Maxpower, and ends this flow. Specifically, the MAC unit 113 sets the interference environment retransmission count and transmission output level to Maxpower for the retransmission count setting unit 112.

If the SNR for each packet is greater than the threshold value in step S11, the MAC unit 113 determines in step S13 that interference has not occurred, sets the number of retransmissions for each application, and ends this flow. Specifically, the MAC unit 113 sets the number of retransmissions for each application in the retransmission number setting unit 112.

As described above, according to the present embodiment, radio communication apparatus 100 (1) when ACK is not received for the current frame, the transmission output during fallback control based on the degradation of the communication environment state (2) When the determined communication environment state is interference, increase the transmission output level preset at the time of retransmission and reduce the number of retransmissions, and (3) increase the transmission output level and retransmit , Issue a request to increase the transmission output level of ACK from the destination access point, (4) receive switch (SW) so that the received signal passes through the high sensitivity mode amplifier 104 based on the deterioration of the communication environment state Since at least one of transmission output control is performed to switch 103, by varying the transmission power according to the communication environment state In a situation where the communication environment state is deteriorated, it is possible to avoid a situation where unnecessarily repeated retransmission of the prescribed number of retransmissions, it is possible to reduce power consumption.

That is, according to the above (1) transmission output control, by increasing the transmission output level at the time of fallback control, fallback control can be supported from the viewpoint of increasing transmission power, and the effectiveness of fallback control can be enhanced. . Until the fallback control, the transmission output level is the same as the specified transmission output level, so the power consumption during this period does not increase.

Further, according to the above (2) transmission output control, when interference or the like occurs at the time of retransmission before shifting to fallback control, transmission may not always be possible even if the retransmission is performed a prescribed number of times. In view of the fact that there is no transmission, the transmission output level is raised once to confirm whether transmission is possible, and the number of retransmissions is reduced accordingly. As a result, it is possible to prevent an increase in power consumption caused by continuing to transmit retransmission until the specified number of times has expired.

In addition, according to the above (3) transmission output control, by receiving an ACK whose transmission output level has been raised from the access point of the transmission destination, the possibility of ACK reception from the access point is increased, and retransmission is made faster. By ending, an increase in power consumption can be prevented.

In addition, according to the above (4) transmission output control, when the communication environment state is deteriorated, the reception sensitivity is increased, thereby increasing the possibility of not performing retransmission, and communication without performing retransmission. By doing so, an increase in power consumption can be prevented.

The above description is an illustration of a preferred embodiment of the present invention, and the scope of the present invention is not limited to this. For example, although a specific interference source such as a microwave oven that does not belong to the wireless communication system has been described, any interference source may be used, and all interference devices that affect inside and outside the wireless LAN system can be applied.

In the present embodiment, when the communication environment determination unit 111 detects interference, the MAC unit 113 sets the transmission output level and the number of retransmissions, but this may be performed by the communication control unit 110. . In any case, an increase in power consumption at the time of retransmission can be effectively prevented when affected by an interference wave from an interference source such as a microwave oven.

Further, the transmission output control (1) to (4) described above may be used alone or in combination.

In the above embodiment, the names wireless communication device and transmission output control are used. However, this is for convenience of explanation, and it is needless to say that the mobile terminal, wireless communication device, transmission power control, and the like may be used. In particular, the transmission output control may be retransmission transmission power control.

Further, the type, number, connection method, and the like of each circuit unit constituting the wireless communication device are not limited to the above-described embodiments.

The wireless communication device described above can also be realized by a program for causing the transmission output control method of the wireless communication device to function. This program is stored in a computer-readable recording medium.

The disclosure of the specification, drawings and abstract contained in the Japanese application of Japanese Patent Application No. 2008-066584 filed on March 14, 2008 is incorporated herein by reference.

The wireless communication apparatus according to the present invention has an effect of reducing power consumption by transmission output control at the time of retransmission, and in particular, a wireless communication system that connects a station such as a mobile phone to a wireless network via an access point. Effective for communication devices.

Claims

If an ACK (acknowledgement) is not received for the current frame, a retransmission is performed for a preset number of times at a predetermined transmission output level and transmission rate, and fallback is performed to lower the transmission rate when the number of retransmissions for this frame expires. A wireless communication device that performs control,
A communication environment determining means for determining a communication environment state;
If ACK is not received for the current frame, transmission output control means for increasing the transmission output level during the fallback control based on the degradation of the communication environment state;
A wireless communication device comprising:
When no ACK is received for the current frame, a radio that performs retransmission for a preset number of times at a predetermined transmission output level and transmission rate, and performs fallback control to lower the transmission rate when the number of retransmissions of this frame expires A communication device,
A communication environment determining means for determining a communication environment state;
When the communication environment state determined by the communication environment determination unit is interference, a transmission output control unit that increases a transmission output level set in advance at the time of retransmission;
A wireless communication device comprising:
When no ACK is received for the current frame, a radio that performs retransmission for a preset number of times at a predetermined transmission power level and transmission rate, and performs fallback control to lower the transmission rate when the number of retransmissions of this frame expires A communication device,
Amplifying means for increasing the reception sensitivity of the received signal;
Switching means for switching whether or not the received signal passes through the amplification means; and
A communication environment determining means for determining a communication environment state;
A transmission output control means for switching the switching means so that a received signal passes through the amplification means based on the deterioration of the communication environment state;
A wireless communication device comprising:
The radio communication apparatus according to claim 2, wherein the transmission output control means reduces the number of retransmissions set in advance at the time of retransmission when increasing the transmission output level.
The radio communication apparatus according to claim 1, wherein the transmission output control means issues a request to increase the transmission output level of ACK from a destination access point when the transmission output level is increased and retransmitted.
The wireless communication apparatus according to claim 3, wherein the transmission output control means executes retransmission when ACK is not received after the switching means is switched.