Patent Publication Number: US-8989100-B2

Title: Wireless communication device and semiconductor device

Description:
TECHNICAL FIELD 
     The present invention relates to a wireless communication device, and a semiconductor device including a wireless communication circuit. 
     BACKGROUND ART 
     There has been studied a service that provides data including a variety of large-capacity contents using a high-definition image (including a moving image or a still image) or a sound to an end user through a wireless communication. In order to transmit large-volume data of several G (giga) bits at a high speed, there has been studied a wireless communication system that performs high-speed transmission of several Gbps with the use of a millimeter waveband including a 60 GHz band. 
     In the millimeter wave wireless communication system, a standardization work is conducted in an IEEE by, for example, IEEE 802.15.3c as a wireless PAN (personal area network), and by, for example, IEEE 802.11ad as a wireless LAN (local area network). 
     For example, in a single carrier transmission system using the millimeter waveband which has been studied in the IEEE802.11ad, a signal that has been subjected to PSK or QAM modulation is transmitted at 1.76 G symbols/sec. Data transmission at a super high speed where a time of one packet is short, that is, several μsec to several tens μsec, and a short inter-frame spacing is also short, that is, 3 μsec, is conducted. For that reason, an allowable latency for modulation and demodulation processing is short, and high speed arithmetic processing is required. 
     In a semiconductor circuit of an LSI that performs the high speed arithmetic processing, a size of transistors formed interiorly is increasingly miniaturized with an improvement of an operating frequency. However, there arises such a problem that the miniaturization causes an increase in leakage current. 
     A main cause of the leakage current is a quantum tunneling effect, which is generated by allowing electrons to pass through an insulator disposed between electric conductors located at a short distance. When a process rule of a digital semiconductor circuit requiring the high speed arithmetic operation becomes 100 nm or lower, more than half of a power consumed by the semiconductor circuit is consumed as the leakage current. 
     In the signal processing semiconductor circuit used in the millimeter wave wireless communication device that performs high speed transmission, for the purpose of reducing a power consumption, a power gating control that turns off a power supply of an unused circuit is an issue. 
     As a technique for reducing the power consumption in the wireless communication device, Patent Literatures 1 and 2 have been known. Patent Literature 1 discloses a technique in which when it is determined that an own device is not a destination at the time of receiving a header of an upper layer frame, a mode is shifted to a power saving mode on the basis of a length of the upper layer frame extracted from a header of a physical layer frame. Also, Patent Literature 2 discloses a technique in which a power supply is separate for each of arithmetic blocks in a semiconductor integrated circuit, and when input data effective in a buffer section of each arithmetic block could be prepared, a switch section that supplies a power to the arithmetic block is controlled, to thereby reduce a leakage current and realize a reduction in the power consumption. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Patent No. 3826893 
         Patent Literature 2: Japanese Patent No. 4551474 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     The above-mentioned related art mainly turns off the power supply to the circuit under the control. A rise time is required since the power supply turns on until a supply voltage is stabilized because of a load capacity connected to the power supply, and several μsec is required. In a conventional radio communication, because a packet length is decades of several hundreds μsec to several msec, and a short inter-frame spacing is also a decade of a dozen μsec, several μsec of the rise time of the power supply can be ignored. 
     However, in the millimeter wave wireless communication, the packet length is a dozen μsec, and the short inter-frame spacing is about 3 μsec, which are short. This makes it difficult to ignore several μsec of the rise time of the power supply, with difficulty to perform the on/off control of the power supply for each of packets. 
     The present invention has been made in view of the above circumstances, and an object of the present invention is to enable a reduction in the power consumption of a circuit that performs signal processing even in a millimeter wave wireless communication that performs a high speed transmission. 
     Solution to Problem 
     A wireless communication device according to the present invention includes: a transmitter that performs transmission processing in a wireless communication; a transmission power supply section that supplies a power to the transmitter; a transmission power controller that controls a power supply to the transmitter; a receiver that performs reception processing in a wireless communication; a reception power supply section that supplies a power to the receiver; and a reception power controller that controls a power supply to the receiver, wherein the transmission power controller turns on the power supply to the transmitter at a given time taking a power rise time into account before a start time of the transmission processing in the transmitter, and turns off the power supply to the transmitter when the transmission processing is finished, and the reception power controller turns on the power supply to the receiver at a given time taking a power rise time into account before a time at which an ACK is assumed to be arrival from a wireless communication device on a receiver side responsive to data transmitted from the transmitter, and turns off the power supply to the receiver when the reception processing of the ACK in the receiver is finished. 
     A wireless communication device according to the present invention includes: a receiver that performs reception processing in a wireless communication; a reception power supply section that supplies a power to the receiver; a reception power controller that controls a power supply to the receiver, a transmitter that performs transmission processing in a wireless communication; a transmission power supply section that supplies a power to the transmitter; and a transmission power controller that controls a power supply to the transmitter, wherein the reception power controller turns on the power supply to the receiver at a given timing, and turns off the power supply to the receiver when the reception processing of the data in the receiver is finished, and when the receiver has received data addressed to an own station without errors based on data received by the receiver, the transmission power controller turns on the power supply to the transmitter at a given time taking a power rise time into account before a start time of the transmission processing of an ACK to a wireless communication device on a transmitter side responsive to the received data, and turns off the power supply to the transmitter when the transmission processing of the ACK is finished. 
     A semiconductor device according to the present invention includes a signal processor including: a transmitter that performs transmission processing in a wireless communication; a transmission power supply section that supplies a power to the transmitter; a transmission power controller that controls a power supply to the transmitter; a receiver that performs reception processing in a wireless communication; a reception power supply section that supplies a power to the receiver; and a reception power controller that controls a power supply to the receiver, wherein the transmission power controller turns on the power supply to the transmitter at a given time taking a power rise time into account before a start time of the transmission processing in the transmitter, and turns off the power supply to the transmitter when the transmission processing is finished, the reception power controller turns on the power supply to the receiver at a given time taking a power rise time into account before a time at which an ACK is assumed to be arrival from a wireless communication device on a receiver side responsive to data transmitted from the transmitter, and turns off the power supply to the receiver when the reception processing of the ACK in the receiver is finished, and a circuit including the signal processor is mounted on a semiconductor substrate. 
     A semiconductor device according to the present invention includes a signal processor including: a receiver that performs reception processing in a wireless communication; a reception power supply section that supplies a power to the receiver; a reception power controller that controls a power supply to the receiver; a transmitter that performs transmission processing in a wireless communication; a transmission power supply section that supplies a power to the transmitter; and a transmission power controller that controls a power supply to the transmitter; wherein the reception power controller turns on the power supply to the receiver at a given timing, and turns off the power supply to the receiver when the reception processing of the data in the receiver is finished, when the receiver has received data addressed to an own station without errors based on data received by the receiver, the transmission power controller turns on the power supply to the transmitter at a given time taking a power rise time into account before a start time of the transmission processing of an ACK to a wireless communication device on a transmitter side responsive to the received data, and turns off the power supply to the transmitter when the transmission processing of the ACK is finished, and a circuit including the signal processor is mounted on a semiconductor substrate. 
     With the above configuration, the on/off of the power supply to the transmitter and the receiver can be controlled at timing of the transmission data and the ACK to the transmission data. Accordingly, even in the millimeter wave wireless communication that performs the high speed transmission, the power consumption of the circuit that performs the signal processing can be reduced. 
     Advantageous Effects of Invention 
     According to the present invention, even in the millimeter wave wireless communication that performs the high speed transmission, the power consumption of the circuit that performs the signal processing can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration example of a wireless communication system according to an embodiment of the present invention. 
         FIG. 2  is a block diagram illustrating a configuration example of a wireless communication device according to the embodiment of the present invention. 
         FIG. 3  is a block diagram illustrating a configuration of a baseband processor according to the embodiment of the present invention. 
         FIG. 4  is a diagram illustrating a configuration of a MAC frame. 
         FIG. 5  is a diagram illustrating a configuration of an ACK frame. 
         FIG. 6  is a diagram illustrating a configuration of a block ACK frame. 
         FIG. 7  is a diagram illustrating a configuration of a PLCP frame in a mode for transmitting control information. 
         FIG. 8  is a diagram illustrating a configuration of the PLCP frame in a mode for transmitting data. 
         FIG. 9  is a diagram illustrating a configuration of a PHY frame. 
         FIG. 10  is a timing chart illustrating the operation when transmitting an ACK. 
         FIG. 11  is a timing chart illustrating the operation when a reception error occurs. 
         FIG. 12  is a timing chart illustrating the operation when a packet is not addressed to an own station. 
         FIG. 13  is a timing chart illustrating the operation when there is no request for immediate ACK transmission. 
         FIG. 14  is a timing chart illustrating the operation when controlling a power supply of the baseband processor. 
         FIG. 15  is a timing chart illustrating the operation of the power control when transmitting a data packet and receiving an ACK packet. 
         FIG. 16  is a timing chart illustrating the operation of the power control when the reception error occurs on a receiver side. 
         FIG. 17  is a timing chart illustrating the operation of the power control when there is no request for immediate ACK transmission. 
         FIG. 18  is a timing chart illustrating the operation of the power control when receiving the data packet and transmitting the ACK packet. 
         FIG. 19  is a timing chart illustrating the operation of the power control when an error is detected in a PHY header of the received data packet. 
         FIG. 20  is a timing chart illustrating the operation of the power control when the error is detected in an FCS field of the received data packet. 
         FIG. 21  is a timing chart illustrating the operation of the power control when there is no request for immediate ACK transmission. 
         FIG. 22  is a timing chart illustrating the operation of the power control when the received data packet has a short packet length. 
         FIG. 23  is a flowchart illustrating a procedure when transmitting the data packet and receiving the ACK packet in a wireless communication terminal according to this embodiment. 
         FIG. 24  is a flowchart illustrating a procedure when receiving the data packet and transmitting the ACK packet in the wireless communication terminal according to this embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the following embodiment, a configuration example of a wireless communication device and a semiconductor device which can be applied to a millimeter wave wireless communication system that performs a high speed transmission with the use of a millimeter waveband will be described as an example of a wireless communication device and a semiconductor device. 
       FIG. 1  is a diagram illustrating a configuration example of a wireless communication system according to an embodiment of the present invention. The wireless communication system includes a wireless communication terminal (STA 1 )  301  of a data transmission source, and a wireless communication terminal (STA 2 )  302  and a wireless communication terminal (STA 3 )  303 , which are data destinations. In this configuration, data is transmitted from the wireless communication terminal  301  to the wireless communication terminal  302  or  303 , or the wireless communication terminals  302  and  303 . 
     In each of the wireless communication terminals  302  and  303 , if data for the own station could be received without error, an ACK (acknowledgement) is returned to the wireless communication terminal  301  which is the transmission source. Individual addresses are allocated to the respective wireless communication terminals, and the transmission source and the destinations are discriminated on the basis of the allocated addresses. 
       FIG. 2  is a block diagram illustrating a configuration example of a wireless communication device configuring each of the wireless communication terminals  301  and  302 . The wireless communication device includes an antenna  202  and a wireless processor  201 . The wireless processor  201  includes an RF section  203 , a baseband processor  101 , and a host processor  204 . The baseband processor  101  includes a receiver  102 , a transmitter  103 , and a MAC (media access control) controller  104 . 
     The RF section  203  up-converts an analog baseband signal output from the transmitter  103  into a radio frequency signal, and down-converts a radio frequency signal received by the antenna  202  into an analog baseband signal and inputs the converted signals to the receiver  102 . 
     The transmitter  103  performs a variety of processing including modulation processing on a received signal. The transmitter  103  and the receiver  102  process a PHY layer (physical layer) in a network. The MAC controller  104  processes a MAC layer (a part of a data link layer) in the network, and performs an access control in a wireless communication. 
     In the wireless communication terminal on the transmitter side, when the host processor  204  requests a data communication with another wireless communication terminal, the MAC controller  104  performs the access control in the wireless communication. When transmitting the data, the MAC controller  104  converts data to be transmitted and an access control header into a MAC frame, and inputs the frame to the transmitter  103 . 
     The transmitter  103  converts the input MAC frame into a PLCP (physical layer convergence protocol) frame in which a PHY (physical layer) header including a modulation system and a packet length is added to the input MAC frame. The transmitter  103  further adds, for example, a preamble to the PLCP, and converts the PLCP into a PHY frame as a signal necessary for demodulation. Then, the transmitter  103  modulates the PHY frame into an analog baseband signal, and inputs the analog baseband signal to the RF section  203 . 
     The RF section  203  up-converts the input analog baseband signal into a radio frequency signal, and transmits the radio frequency signal from the antenna  202 . 
     In the wireless communication terminal on the receiver side, the RF section  203  down-converts the radio communication signal received by the antenna  202  into an analog baseband signal, and inputs the analog baseband signal to the receiver  102 . 
     The receiver  102  performs synchronization processing on the preamble of the receive signal of the analog baseband signal, and demodulates the received frame. When the PHY header can be demodulated in success, the receiver  102  demodulates a payload portion according to the information on the modulation system and the packet length, and outputs a demodulation result to the MAC controller  104 . 
     The MAC controller  104  analyzes the MAC frame on the basis of the input demodulation result, performs the access control, and outputs the received data to the host processor  204 . 
       FIG. 3  is a block diagram illustrating a configuration of the baseband processor in the wireless communication terminal according to this embodiment. The baseband processor  101  is configured by a semiconductor integrated circuit of, for example, an LSI, and can be included within the wireless communication terminal as a semiconductor device including a wireless communication circuit. 
     The baseband processor  101  includes the receiver  102 , the transmitter  103 , and the MAC controller  104  as described above, and includes a reception power supply section  109 , a reception power controller  110 , a transmission power supply section  111 , and a transmission power controller  112 . The receiver  102  includes an AD converter (ADC)  105  and a demodulator  106 . The transmitter  103  includes a modulator  107  and a DA converter (DAC)  108 . 
     The power supplies of the receiver  102  and the transmitter  103  are independent from each other. The receiver  102  receives the power supply from the reception power supply section  109 , and the transmitter  103  receives the power supply from the transmission power supply section  111 . 
     When the MAC controller  104  receives a request for the wireless communication from the host processor  204 , the MAC controller  104  determines whether the radio communication is transmission or reception according to an access control protocol. If the wireless communication is reception, the MAC controller  104  requests the reception power controller  110  to turn on the power supply to the receiver  102 . On the other hand, if the wireless communication is transmission, the MAC controller  104  requests the transmission power controller  112  to turn on the power supply to the transmitter  103 . 
     The reception power controller  110  controls the reception power supply section  109  to supply a power to the receiver  102  in response to a power-on request from the MAC controller  104 , and puts the receiver  102  into a state where the wireless communication is enabled. Also, the transmission power controller  112  controls the transmission power supply section  111  to supply a power to the transmitter  103  in response to a power-on request from the MAC controller  104 , and puts the transmitter  103  into a state where the wireless communication is enabled. 
     In this embodiment, the power supplies to the transmitter  103  and the MAC controller  104  are separated from each other, and in order to turn on/off the power supply in the transmitter  103  and the receiver  102 , independently from each other, the power control is conducted in the transmission power supply section  111  and the reception power controller  110 . 
     At the time when the header included in the packet which is now being received can be demodulated, if it is predicted that the packet is transmitted immediately after the demodulation, the transmission power supply section  111  turns on the power supply to the transmitter  103  in advance, taking a power rise time into account. If it is predicted that the packet is received immediately after the transmission, from the header included in the packet which is now being received, the reception power controller  110  turns on the power supply to the receiver  102  in advance, taking the power rise time into account. In the prediction of the subsequent packet processing, MAC control information can be used. 
     The MAC control information includes at least one of a destination ID, presence or absence of an ACK request or a block ACK request, and presence or absence of a header error in the header information of the packet that is being transmitted or received. 
     The MAC controller  104  starts the wireless communication according to the access control protocol. When transmitting, the MAC controller  104  generates the MAC frame to be transmitted, and inputs the MAC frame to the transmitter  103 . The transmitter  103  modulates the input MAC frame into the PHY frame by the modulator  107 , and converts the PHY frame into an analog baseband signal by the DA converter  108 , and outputs the analog baseband signal. The modulator  107  has a function of a transmitter header processor that performs header processing on the data which is being transmitted to acquire the header information. 
     In this example, the MAC frame to be transmitted is also input to the reception power controller  110 . The reception power controller  110  determines a timing at which the MAC frame is to be received subsequently, on the basis of the control information of the MAC frame which is now being transmitted. In order to stably supply the power to the receiver  102  at the timing to be received, the reception power controller  110  instructs the reception power supply section  109  to control the power-on at an offset timing advanced by the power rise time of about several μsec. 
     When the MAC controller  104  determines that the transmission of the present PHY frame has been finished, and the power supply to the transmitter  103  can be turned off, the MAC controller  104  requests the transmission power controller  112  to turn off the power supply to the transmitter  103 . The transmission power controller  112  controls the transmission power supply section  111 , and stops the power supply to the transmitter  103  in response to a power-off request from the MAC controller  104 . 
     When receiving, the AD converter  105  converts the analog baseband signal input to the baseband processor  101  into a digital signal, and the demodulator  106  demodulates the PHY frame. The demodulator  106  has a function of a receiver header processor that performs header processing on the data which is being demodulated to acquire the header information. The demodulated payload, that is, MAC frame is input to the MAC controller  104 . The MAC controller  104  performs the reception processing according to the access control protocol. 
     When there is an ACK request to the presently received MAC frame, there is a need to transmit the ACK frame. The MAC controller  104  determines whether the ACK frame is transmitted or not, according to the access control protocol, and when transmitting, the MAC controller  104  generates the ACK frame to conduct transmitting operation. 
     In this example, the received MAC frame is also input to the transmission power controller  112 . The transmission power controller  112  determines a timing at which the MAC frame is to be transmitted subsequently, on the basis of the control information of the PHY header and the MAC frame which are now being received. In order to stably supply the power to the transmitter  103  at the timing to be transmitted, the transmission power controller  112  instructs the transmission power supply section  111  to control the power-on at an offset timing advanced by the power rise time of about several μsec. 
     When the MAC controller  104  determines that the reception of the present PHY frame has been finished, and the power supply to the receiver  102  can be turned off, the MAC controller  104  requests the reception power controller  110  to turn off the power supply to the receiver  102 . The reception power controller  110  controls the reception power supply section  109 , and stops the power supply to the receiver  102  in response to a power-off request from the MAC controller  104 . 
       FIG. 4  is a diagram illustrating a configuration of the MAC frame. A MAC frame  401  includes a MAC header  402 , a frame body  411  that stores data therein, and an FCS (frame check sequence) field  412  for detecting an error. The FCS field  412  is arranged on a trailing side of the frame body  411 , and used as an error detection field. 
     The MAC header  402  includes a variety of control fields, and has a frame control (frame control) field  403  indicative of a frame type, a duration (duration) field  404  indicative of an occupation time of the frame, a destination address field  405 , and a transmission source address field  406 . 
     Also, the MAC header  402  includes a BSSID (basic service set identifier) field  407 , a sequence control field  408 , an address field  409 , and a QoS (quality of service) control field  410  indicative of the ACK request. 
     The QoS control field  410  stores, as information (QoS control ACK policy) indicative of the type of the ACK request, any one of “00”: immediate ACK transmission compliant with IEEE 802.11, “10”: no ACK transmission, and “11”: block ACK transmission therein. “01” is reserved information for future extension. 
     If the address of the destination address field  405  is addressed to the own station, the radio communication terminal on the receiver side transmits the ACK to the address of the transmission source address field  406  according to the ACK request of the QoS control field  410 . 
     The immediate ACK transmission is an ACK request for transmitting the ACK frame immediately after 3 μsec which is a short inter-frame spacing (SIFS: short inter frame spacing) after receiving the packet. The block ACK transmission is an ACK request for transmitting the ACKs for a plurality of packets that has been received in the past in block. 
     The block ACK transmission is further classified into the immediate block ACK for transmitting the plurality of ACKs in block immediately, and a delay ACK for not currently transmitting the ACKs but transmitting the ACKs the subsequent packets in block. 
       FIG. 5  is a diagram illustrating a configuration of the ACK frame. An ACK frame  501  is a shortest packet having a frame control field  502  indicative of the ACK, and a destination address field  504  as main information. Also, the ACK frame  501  includes a duration field  503  and an FCS  505 . 
       FIG. 6  is a diagram illustrating a configuration of the block ACK frame. A block ACK frame  601  includes a frame control field  602  indicative of the block ACK, a block ACK control field  606  indicative of the type of the block ACK, and a block ACK information field  607  which is ACK information of a plurality of frames that has been received in the past. Also, the block ACK frame  601  includes a duration field  603 , a destination address field  604 , a transmission source address field  605 , and an FCS  608 . The block ACK control field  606  stores, as information (block ACK control BA ACK policy) indicative of the type of the block ACK, any one of “0”: immediate ACK transmission (normal ACK), and “1”: no ACK transmission (delay ACK) therein. 
     The MAC frame generated by the MAC controller  104  is modulated to the PLCP frame in the modulator  107  of the transmitter  103 . The PLCP frame includes the MAC frame added with the PHY header. The PHY header stores a parameter used for modulation therein, and includes an MCS (modulation and coding scheme) indicative of the modulation and a coding scheme of an error correction. 
       FIG. 7  is a diagram illustrating a PLCP frame including a control PHY header in a mode for transmitting the control information. A control PHY header  702  of a PLCP frame  701  includes a scrambler initial value (scrambler init) field  704  indicative of an initial value (scrambler system information) for bit scrambler, a length (length) field  705  represented by a byte length of the overall frame, a packet information field  706 , and an HCS (header check sequence) field  707  that detects an error of the header. 
     Also, the control PHY header  702  includes a reserved (reserved) field  703  for future extension. In the mode for transmitting the control information, because one kind of modulation system is provided, the MCS field is omitted in the control PHY header  702 . 
     The PLCP frame  701  includes a MAC header  708 , a frame body  709 , and an FCS  710  as the MAC frame, after the control PHY header  702 . 
       FIG. 8  is a diagram illustrating the PLCP frame including the SC PHY header in the mode for transmitting the data. An SC PHY header  802  of a PLCP frame  801  includes a scrambler initial value field  803 , an MCS field  804 , a length (length) field  805 , a packet information field  806 , and an HCS field  807 . In the mode for transmitting the data, because a transmission rate is variable, the MCS field  804  for designating the MCS to be used is provided in the SC PHY header  802 . 
     The PLCP frame  801  includes a MAC header  808 , a frame body  809 , and an FCS  810  as the MAC frame after the SC PHY header  802 . 
     The PLCP frame having any one of the above configurations is divided on a block unit on the basis of the coding scheme designated by the MCS of the PHY header, and subjected to error correcting coding by the modulator  107  of the transmitter  103 , and thereafter converted into a digital modulation signal on the basis of the modulation system designated by the MCS. In the modulator  107 , the preamble necessary for the reception processing is added, and modulated to the PHY frame. The PHY frame is output by the transmitter  103 , and converted into the radio frequency signal and transmitted by the RF section  203 . 
       FIG. 9  is a diagram illustrating a configuration of the PHY frame. A PHY frame  901  includes a preamble  902 , and a PLCP frame  903 . The preamble  902  includes an STF (short training field) field  904 , and a CEF (channel estimation field) field  905 . The PLCP frame  903  includes a PHY header  906 , and a plurality of FEC (forward error correction) block fields (FECBLK)  907 . The PHY frame  901  includes a sub-field  908  after the PLCP frame  903 . 
       FIG. 10  is a timing chart illustrating the operation when transmitting the ACK. The wireless communication terminal  301  (STA 1 ) transmits a data packet  1001  for the wireless communication terminal  302  (STA 2 ), and the wireless communication terminal  302  (STA 2 ) receives the data packet  1001 . The wireless communication terminal  302  (STA 2 ) determines the success or failure of reception, and the type of ACK according to the information on the MAC frame of the data packet  1001 . In this example, when the packet addressed to the own station can be received without error, and the immediate ACK transmission is required, the wireless communication terminal  302  (STA 2 ) transmits an ACK packet  1003  for the wireless communication terminal  301  (STA 1 ) after the wireless communication terminal  302  finishes the reception processing, and the short inter-frame spacing (SIFS, 3 μsec)  1002  elapses. 
     When the conditions of the above immediate ACK transmission are not satisfied, the wireless communication terminal  302  (STA 2 ) executes the following operation.  FIG. 11  is a timing chart illustrating the operation when a reception error occurs. The wireless communication terminal  302  (STA 2 ) does not transmit the ACK when the reception error occurs while a data packet  1101  is being demodulated. That is, an ACK packet  1103  is not transmitted after the reception processing has been finished, and a short inter-frame spacing  1102  has elapsed. 
       FIG. 12  is a timing chart illustrating the operation when the packet is not addressed to an own station. When the destination address field  405  of the MAC header in a data packet  1201  does not match an own station address, the wireless communication terminal  302  (STA 2 ) does not transmit the ACK. That is, after the reception processing has been finished, and a short inter-frame spacing  1202  has elapsed, an ACK packet  1203  is not transmitted. 
       FIG. 13  is a timing chart illustrating the operation when there is no request for immediate ACK transmission. When the QoS control field  410  of the MAC header in a data packet  1301  is no ACK request for immediate ACK transmission, the wireless communication terminal  302  (STA 2 ) does not immediately transmit the ACK. That is, after the reception processing has been finished, and a short inter-frame spacing  1302  has elapsed, an ACK packet  1303  is not transmitted. 
       FIG. 14  is a timing chart illustrating the operation when controlling the power supply of the baseband processor  101 .  FIG. 14  schematically illustrates a waveform of a rising of the supply voltage under the power control. 
     When a power control signal  1402  output by the reception power supply section  109  or the transmission power controller  112  is high level (hereinafter referred to as “H”), the corresponding reception power supply section  109  or transmission power supply section  111  supplies the power to the receiver  102  or the transmitter  103 . 
     When the power control signal  1402  is H, the supply voltage to be applied to the circuit of the receiver  102  or the transmitter  103  needs a rise time until the voltage is stabilized due to a load capacity of the circuit. In a subsequent operation time when the supply voltage is stabilized, the circuit to which the power is supplied operates. In order to process a data packet  1401 , there is a need to offset the power control signal  1402  the rise time ago to set the power control signal  1402  to H in advance. 
       FIG. 15  is a timing chart illustrating the operation of the power control when transmitting the data packet and receiving the ACK packet. Also,  FIG. 23  is a flowchart illustrating a procedure when transmitting the data packet and receiving the ACK packet in the wireless communication terminal according to this embodiment. 
     Prior to the transmission of a data packet  1501 , the transmission power controller  112  sets a transmission power control signal  1502  to H, and supplies the power to the transmitter  103  to start the transmitter  103  (Step S 101 ). Then, the transmitter  103  determines a transmission start to start the transmission processing (Step S 102 ), and acquires a packet length of the data packet  1501  (Step S 103 ). Then, the transmitter  103  determines whether the ACK request responsive to the transmission of the data packet  1501  is a request for immediate ACK transmission, or not (Step S 104 ), and if the ACK request is the request for immediate ACK transmission, the transmitter  103  sets up a receiver start timer (Step S 105 ). 
     In the wireless communication terminal on the transmitter side, as illustrated in  FIG. 15 , the terminal must provide for the reception of the ACK packet  1504  with the short inter-frame spacing (SIFS) after the transmission of an ACK packet  1504  has been finished. For that reason, the reception power controller  110  offsets a reception power control signal  1503  the power rise time before a time at which the ACK packet is assumed to be arrival from the wireless communication device on the receiver side to set the reception power control signal  1503  to H in advance. 
     The time at which the ACK packet is assumed to be arrival can be calculated on the basis of the packet length of the data packet  1501 . In the transmitter  103 , the packet length can be calculated on the basis of the byte length and the MCS set for the PHY header when transmitting the data packet  1501 . As a result, the packet length is acquired in Step S 103 . Then, the reception power controller  110  calculates a timing at which the reception power control signal  1503  is set to H by (packet length+SIFS−power rise time). The calculated timing is set for the receiver start timer in Step S 105 . 
     The reception power controller  110  completes the timing of the receiver start timer, and determines whether the timing reaches the receiver start timing, or not (Step S 106 ). If the timing reaches the receiver start timing, the reception power controller  110  sets the reception power control signal  1503  to H, and supplies the power to the receiver  102  to start the receiver  102  (Step S 107 ). As a result, the receiving operation can be conducted immediately when receiving the ACK packet  1504 . 
     Thereafter, the transmission power controller  112  determines the transmission completion (Step S 108 ), and if the transmission processing of the data packet  1501  has been completed, the transmission power controller  112  sets the transmission power control signal  1502  to low level (hereinafter referred to as “L”), and stops the power supply to the transmitter  103  to turn off the circuit operation (Step S 109 ). If there is no request for immediate ACK transmission in the determination in Step S 104 , the transmission power controller  112  skips Steps S 105  to S 107 , and determines the transmission completion of Step S 108 . 
     Subsequently, the reception power controller  110  determines whether the ACK request responsive to the transmission of the data packet  1501  is a request for immediate ACK transmission, or not (Step S 110 ). If the ACK request is the request for immediate ACK transmission, the reception power controller  110  determines whether the reception processing of the ACK packet  1504  has been completed in the receiver  102 , or not (Step S 111 ). 
     In this example, if the reception processing of the ACK packet  1504  has been completed, the reception power controller  110  sets the reception power control signal  1503  to L, and stops the power supply to the receiver  102  to turn off the circuit operation (Step S 113 ). In the power-off of the receiver  102 , a termination time of the ACK packet is given a margin with the inclusion of a latency, for example, taking a delay into account because of the wireless transmission, to set a longer operation time. 
     Also, if the reception processing of the ACK packet  1504  has not been completed, the reception power controller  110  determines whether the timer that times a given period has timed out, or not, (Step S 112 ). In this situation, if the timer has timed out, the reception power controller  110  sets the reception power control signal  1503  to L, and stops the power supply to the receiver  102  to turn off the circuit operation (Step S 113 ). 
     If there is no request for immediate ACK transmission in the determination in Step S 110 , this processing is finished as it is. 
     As illustrated in  FIG. 15 , when the ACK packet  1504  has been received, after the reception processing has been finished, the reception power controller  110  can set the reception power control signal  1503  to L, and stop the power supply to the receiver  102 . 
       FIG. 16  is a timing chart illustrating the operation of the power control when the reception error occurs on a receiver side. In the wireless communication terminal on the transmitter side, the transmission power controller  112  sets a transmission power control signal  1602  to H, turns on the power supply to the transmitter  103 , and transmits a data packet  1601 . In the wireless communication terminal on the receiver side, if a reception error of the data packet  1601  occurs, because an ACK packet  1604  is not transmitted, the reception power controller  110  sets a reception power control signal  1603  to L after timing out the given period, and turns off the power supply to the receiver  102 . 
       FIG. 17  is a timing chart illustrating the operation of the power control when there is no request for immediate ACK transmission. In the wireless communication terminal on the transmitter side, the transmission power controller  112  sets a transmission power control signal  1702  to H, turns on the power supply to the transmitter  103 , and transmits a data packet  1701 . 
     When transmitting the data packet  1701 , if there is no request for immediate ACK transmission in the QoS control field  410  of the MAC header (no in Steps S 104  and S 110 ), the reception power controller for the ACK reception becomes unnecessary. The reception power controller  110  keeps the L level of a reception power controller  1703 , and maintains the power-off of the receiver  102 . Then, the reception power controller  110  may conduct the operation to set the reception power controller  1703  to H for conducting the subsequent communication operation, for example, a reception standby. 
       FIG. 18  is a timing chart illustrating the operation of the power control when receiving the data packet and transmitting the ACK packet. Also,  FIG. 24  is a flowchart illustrating a procedure when receiving the data packet and transmitting the ACK packet in the wireless communication terminal according to this embodiment. 
     Prior to the transmission of a data packet  1801 , the reception power controller  110  sets a reception power control signal  1802  to H, and supplies the power to the receiver  102  to start the receiver  102  (Step S 201 ). As a result, the wireless communication terminal comes to a reception standby state. Then, when the data packet  1801  is arrival, the receiver  102  determines a reception start to start the reception processing (Step S 202 ). 
     Subsequently, the receiver  102  determines whether there has been an error (header error) in the demodulation of the header of the received data packet  1801 , or not (Step S 203 ). If there is no error in the header, the receiver  102  acquires the packet length, and determines whether the packet length is a short packet length of a given value or lower, or not (Step S 204 ). The receiver  102  can calculate the packet length on the basis of the byte length and the MCS which are set for the PHY header of the received data packet  1801 . 
     If the received data packet  1801  is not the short packet length, the receiver  102  determines whether the destination address field  405  of the MAC header matches the own station address, or not, that is, whether the destination address field  405  is the packet for the own station, or not (Step S 205 ). If the destination address field  405  is the packet for the own station, the receiver  102  determines whether the ACK request responsive to the data packet  1801  is the request for immediate ACK transmission, or not (Step S 206 ). If the ACK request is the request for immediate ACK transmission, the receiver  102  sets the transmitter start timer (Step S 207 ). 
     In the wireless communication terminal on the receiver side, as illustrated in  FIG. 18 , the terminal must provide for the transmission of an ACK packet  1804  with the short inter-frame spacing (SIFS) after the reception of the data packet  1801  has been finished. However, if the ACK transmission start is determined according to whether there is an error in the FCS field  412  added at the end of the MAC frame, or not, the power rise time is not obtained, and the ACK transmission processing is not on time. 
     For that reason, in this embodiment, at the time when it is determined that the destination address field  405  is the packet for the own station with the user of the destination address field  405  of the MAC header which enables the determination at an early stage of the reception processing, the transmission power controller  112  sets a transmission power control signal  1803  to H. For example, in the millimeter wave wireless communication system, the PHY header can be demodulated to about 3 μsec, and the MAC header can be demodulated to about 4 μsec, from the reception start of the data frame. 
     It is desirable to further adjust the timing at which the transmission power control signal  1803  is set to H on the basis of the packet length of the received data packet  1801 . The receiver  102  acquires the packet length on the basis of the byte length and the MCS which are set in the PHY header of the data packet  1801  in Step S 204 , and calculates the timing at which the transmission power control signal  1803  is set to H according to the packet length. The receiver  102  sets the calculated timing for the transmitter start timer in Step S 207 . 
     The transmission power controller  112  completes the timing of the transmitter start timer, and determines whether the timing reaches the transmitter start timing, or not (Step S 208 ). If the timing reaches the transmitter start timing, the transmission power controller  112  sets the transmission power control signal  1803  to H, and supplies the power to the transmitter  103  to start the transmitter  103  (Step S 209 ). As a result, the transmitting operation can be conducted immediately when transmitting the ACK packet  1804 . 
     Thereafter, the reception power controller  110  determines the reception completion (Step S 210 ), and if the reception processing of the data packet  1801  has been completed, the reception power controller  110  sets the reception power control signal  1802  to low, and stops the power supply to the receiver  102  to turn off the circuit operation (Step S 211 ). In the power-off of the receiver  102 , a termination time of the data packet is given a margin for example, taking a delay into account because of the wireless transmission, to set a longer operation time. 
     If there is the header error in the determination in Step S 203 , if there is no packet for the own station in the determination in Step S 205 , and if there is no request for immediate ACK transmission in the determination in Step S 206 , the subsequent steps are skipped to determine the reception completion in Step S 210 . 
     Subsequently, the transmission power controller  112  determines whether the ACK request responsive to the data packet  1801  is the request for immediate ACK transmission, or not (Step S 212 ). If the ACK request is the request for immediate ACK transmission, the transmitter  103  determines whether the transmission processing of the ACK packet  1804  has been completed, or not (Step S 213 ). When the reception processing in the receiver  102  is completed, no error is detected in the FCS field  412  added at the end of the MAC frame, and the immediate ACK transmission is requested by the MAC head, the transmitter  103  transmits the ACK packet  1804 . 
     If the transmission processing of the ACK packet  1804  has been completed, the transmission power controller  112  sets the transmission power control signal  1803  to L, and stops the power supply to the transmitter  103  to turn off the circuit operation (Step S 214 ). 
     If there is no request for immediate ACK transmission in the determination in Step S 212 , this processing is finished as it is. 
     As illustrated in  FIG. 18 , when the data packet  1801  can be received without error, and the request for immediate ACK transmission is made, the transmission power control signal  1803  is set to H early at the time of demodulating the MAC header to start the transmitter  103 . As a result, the reception processing of the data packet  1801  is finished, and the ACK packet  1804  can be transmitted immediately after the short inter-frame spacing (SIFS) has elapsed. 
     Also, after the reception processing has been finished, the reception power control signal  1802  can be set to L to turn off the power supply to the receiver  102 . After the transmission processing of the ACK packet  1804  has been finished, the transmission power control signal  1803  can be set to L to turn off the power supply to the transmitter  103 . 
     In  FIG. 18 , the reception power control signal  1802  is set to L after the transmission processing of the ACK packet  1804  has been finished, and a given time has elapsed. Alternatively, the reception power control signal  1802  may be set to L immediately after the transmission processing of the ACK packet  1804  has been finished. 
       FIG. 19  is a timing chart illustrating the operation of the power control when an error is detected in the PHY header of the received data packet. The wireless communication terminal on the receiver side sets a reception power control signal  1902  to H to turn on the power supply to the receiver  102  by the reception power controller  110 , and receives a data packet  1901 . 
     In the reception processing, if an error is detected in the HCS field  807  of the PHY header (yes in Step S 203 ), since the ACK packet is not transmitted, the transmission power controller  112  keeps the L level of the transmission power control signal, and maintains the power-off of the transmitter  103 . 
       FIG. 20  is a timing chart illustrating the operation of the power control when the error is detected in the FCS field of the received data packet. The wireless communication terminal on the receiver side sets a reception power control signal  2002  to H to turn on the power supply to the receiver  102 , and receives a data packet  2001  by the reception power controller  110 . 
     If the timing reaches the transmitter start timing during the reception processing, the wireless communication terminal sets a transmission power control signal  2003  to H, and turns on the power supply to the transmitter  103  in advance, taking the power rise time into account. If an error is detected in the FCS field  412  of the received data packet  2001 , since the ACK packet is not transmitted, the transmission power controller  112  sets the transmission power control signal  2003  to L at the time of detecting the error, and can turn off the power supply to the transmitter  103 . 
       FIG. 21  is a timing chart illustrating the operation of the power control when there is no request for immediate ACK transmission. The wireless communication terminal on the receiver side sets a reception power control signal  2102  to H to turn on the power supply to the receiver  102 , and receives a data packet  2101  by the reception power controller  110 . 
     If there is no request for immediate ACK transmission in the QoS control field  410  of the MAC header in the received data packet  2101  (no in Steps S 206  and S 212 ), the transmission power controller for the ACK transmission becomes unnecessary. The transmission power controller  112  keeps the L level of the transmission power control signal, and maintains the power-off of the transmitter  103 . 
       FIG. 22  is a timing chart illustrating the operation of the power control when the received data packet has a short packet length. The wireless communication terminal on the receiver side sets a reception power control signal  2202  to H to turn on the power supply to the receiver  102 , and receives a data packet  2201  by the reception power controller  110 . 
     If it is determined from the PHY header of the received data packet  2201  that the packet length (length) is shorter than a given value (yes in Step S 204 ), the transmission power controller  112  may set a transmission power control signal  2203  to H at the time of determining the short packet length, and may turn on the power supply to the transmitter  103 . The transmission power controller  112  can conduct the transmission power control to also deal with the reception of the data packet  2201  having the short packet length, and can transmit an ACK packet  2204  immediately after the reception processing has been finished, and the short inter-frame spacing has elapsed. 
     As has been described above, in this embodiment, because the power supplies of the transmitter and the receiver are separated from each other and controlled, the power supplies can turns on/off in the transmitter and the receiver, independently from each other. At the time when the header included in the packet which is now being received could be demodulated, if it is predicted that the packet is transmitted immediately after the demodulation, the power supply to the transmitter turns on in advance, taking the power rise time into account. If it is predicted that the packet is received immediately after the transmission, from the header included in the packet which is now being received, the power supply to the receiver turns on in advance, taking the power rise time into account. 
     As a result, even in the millimeter wave wireless communication that executes the high-speed packet transmission, the power on/off of the transmitter and the receiver can be controlled at the timing of the data packet to be transmitted and the ACK packet responsive to the data packet to be transmitted. Accordingly, a time when the power supply to the transmitter and the receiver is off is provided for each of the packets under the power control, the leakage current can be reduced, and the power consumption can be reduced. 
     Hence, this embodiment is applied to a semiconductor device of a semiconductor integrated circuit that processes the baseband signal in the wireless communication device. As a result, the power saving of the device can be conducted, and the leakage current can be reduced. In particular, this embodiment is applied to the wireless communication device including a mobile communication device requiring the low power consumption in the wireless communication system requiring the high speed signal processing and the low latency, thereby obtaining the large advantages. 
     According to the present invention, modifications and applications by an ordinary skilled person on the basis of the disclosure of the present specification and known techniques without departing from the subject matter and scope of the present invention are also intended by the present invention, and included in a scope to be protected. Also, the respective components in the above embodiments may be arbitrarily combined together without departing from the subject matter of the present invention. 
     In the above respective embodiments, an example in which the present invention is configured by a hardware has been described. Alternatively, the present invention can be realized by a software. 
     Also, the respective functional blocks used in the description of the respective embodiments are realized as an LSI that is typically an integrated circuit. Each of those functional blocks may be configured by one chip, or a part or all of those functional blocks may be integrated into one chip. In this example, the chip is called the LSI, but may be called IC, system LSI, super LSI, or ultra LSI due to a difference in integration. 
     Also, a technique of the integrated circuit is not limited to the LSI, but may be realized by a dedicated circuit or a general-purpose processor. There may be used an FPGA (field programmable gate array) that is programmable after manufacturing an LSI, or a reconfigurable processor that can reconfigure the connection or setting of a circuit cell within the LSI. 
     Also, the calculations of the respective functional blocks can be conducted by using, for example, a DSP or a CPU. Further, the processing steps of the respective functions can be recorded in a recording medium as a program, and executed. 
     Further, if a technology for integration circuit which is substituted for the LSI appears due to the development of the semiconductor technology or another technology derived therefrom, the functional blocks may be integrated by that technology. A biotechnology may be applied. 
     The present application is based on Japanese Patent Application No. 2011-075833 filed on Mar. 30, 2011, the contents of which are incorporated herein by reference. 
     INDUSTRIAL APPLICABILITY 
     The present invention has an advantage that the power consumption of the circuit that performs the signal processing can be reduced in the millimeter wave wireless communication that performs the high speed transmission. For example, the present invention is useful as the wireless communication device applied to the wireless communication system requiring the high speed signal processing and the low latency, and the semiconductor device including the wireless communication circuit, and can be widely applied to the general wireless communication devices including a mobile communication device requiring the low power consumption. 
     REFERENCE SIGNS LIST 
     
         
         
           
               101 : Baseband processor 
               102 : Receiver 
               103 : Transmitter 
               104 : MAC controller 
               105 : AD converter 
               106 : Demodulator 
               107 : Modulator 
               108 : DA converter 
               109 : Reception power supply section 
               110 : Reception power controller 
               111 : Transmission power supply section 
               112 : Transmission power controller 
               201 : Wireless processor 
               202 : Antenna 
               203 : RF section 
               204 : Host processor 
               301 ,  302 ,  303 : Wireless communication terminal