Abstract:
A wireless communication apparatus including: a plurality of transmitting/receiving sections which cooperate with each other to perform a wireless communication by the same communication method; a power supplying section which supplies power to the plurality of transmitting/receiving sections; and a switching section which switches between a mode in which only part of the plurality of transmitting/receiving sections is supplied with power from the power supplying section and the wireless communication is performed by the part of the plurality of transmitting/receiving sections and another mode depending on whether a prescribed condition is satisfied.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2004-380379, filed on Dec. 28, 2004; the entire contents of which are incorporated herein by reference.  
       BACKGROUND  
       [0002]     1. Field  
         [0003]     The present invention relates to a wireless communication apparatus and a wireless communication board.  
         [0004]     2. Description of the Related Art  
         [0005]     In recent years, to enable transmission and reception of a large amount of data such as video data, the transmission rate of wireless communications has been increased. For example, in the wireless LAN (local area network) technology, attention is now paid to the MIMO (multiple input multiple output) communication in which the communication capacity is increased by transmitting and receiving data using plural transmitting/receiving sections.  
         [0006]     In the MIMO communication, the power consumption is high because of the use of plural transmitting/receiving sections. Therefore, techniques for reducing the power consumption have been developed (e.g., JP-A-2004-129066) JP-A-2004-129066 proposes a technique in which the power consumption is reduced by sharing a frequency converting section among the transmitting/receiving sections. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a conceptual diagram showing the configuration of a communication system including a notebook PC according to an embodiment of the invention;  
         [0008]      FIG. 2  shows implementation examples of antennas and a Mini PCI card which performs a wireless communication in the notebook PC;  
         [0009]      FIG. 3  is a block diagram showing the configuration of the notebook PC;  
         [0010]      FIG. 4  shows an exemplary communication mode setting picture through which to set a communication mode in the notebook PC;  
         [0011]      FIG. 5  shows an exemplary setting picture through which to set a data size threshold value for communication mode switching in the notebook PC;  
         [0012]      FIG. 6  is a flowchart of a process that is executed by the notebook PC in determining a communication method;  
         [0013]      FIG. 7  shows an exemplary setting picture through which to set connection apparatus to enable determination of a communication method in a notebook PC according to a modification of the invention;  
         [0014]      FIG. 8  is a flowchart of a process that is executed by a notebook PC according to another modification of the invention in changing a communication method; and  
         [0015]      FIG. 9  is a block diagram showing the configuration of a notebook PC according to a further modification of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0016]     A wireless communication apparatus and a wireless communication board according to embodiments of the invention will be hereinafter described with reference to the drawings.  
         [0017]      FIG. 1  is a conceptual diagram showing the configuration of a communication system including a notebook PC as a wireless communication apparatus according to an embodiment of the invention. This communication system includes a notebook PC  10  and a communication apparatus  11  each of which has two antennas capable of wireless LAN transmission and reception. Each of the notebook PC  10  and the communication apparatus  11  transmits and receives data using the two antennas. The communication apparatus  11  may be any apparatus such as a TV receiver incorporating a TV tuner, a notebook PC, or a printer as long as it can perform wireless LAN transmission and reception.  
         [0018]      FIG. 2  shows an implementation example of the antennas and a Mini PCI card which performs a wireless communication. The notebook PC  10  includes a computer main body  21  and a display body  22  which are joined to each other rotatably via hinges  23 .  
         [0019]     The computer main body  21  is equipped with a computer board (not shown) incorporating a CPU, a memory, etc., and a Mini PCI card  24  (wireless communication board) incorporating a wireless communication module. The display body  22  is equipped with a display unit  25  and antennas  26  and  27 . The antennas  26  and  27  are disposed on the free-end side that is opposite to the hinges  23  so as to be spaced from each other in the right-left direction. The antennas  26  and  27  are connected to the Mini PCI card  24  incorporated in the computer main body  21  via respective coaxial cables  28  and  29 . While the notebook PC  23  is used, the display body  22  is opened relative to the computer main body  21  and hence the thus-arranged antennas  26  and  27  come to be located at such positions as to provide good radiation characteristics.  
         [0020]      FIG. 3  is a block diagram showing the configuration of the notebook PC  10 . The notebook PC  10  includes a CPU (central processing unit)  301 , a memory  303  which is connected to the CPU  301  via a bus  302 , an HDD (hard disk drive)  304 , the display unit  25 , a radio circuit  305  which is also connected to the bus  320  and controls a wireless communication, power amplifiers (hereinafter abbreviated as PAs)  306  and  307  for amplifying a transmission signal that is output from the radio circuit  305 , the antennas  26  and  27 , low-noise amplifiers (hereinafter abbreviated as LNAs)  308  and  309  for amplifying a reception signal that is received by the antennas  26  and  27 , switches  310  and  311  for switching between reception and transmission, a power circuit  314  for supplying power (originating from an external power source  312  or a battery  313 ) to the PAs  306  and  307 , a power control circuit  352  for switching between a MIMO communication mode and an existing communication mode (hereinafter referred to as “ordinary communication mode”) using a single-system transmitting/receiving section, and a switch  316  for switching between a state of supplying power to the PA  306  and a state of not supplying power to it. Among the above components, the radio circuit  305 , PAs  306  and  307 , LNAs  308  and  309 , and the switches  310  and  311  are incorporated in the Mini PCI card  24  shown in  FIG. 2 .  
         [0021]     The CPU  301 , which is a processor for controlling the entire operation of the notebook PC  10  in a unified manner, runs a program having a function of switching the communication mode in accordance with whether power is supplied from the external power source  312  or the battery  313 . The memory  303  is referred to while the above program is run. The HDD  304 , which is a high-capacity storage device, store data to be transmitted to the communication apparatus  11  and other information.  
         [0022]     Controlled by the CPU  301 , the radio circuit  305  sets a MAC (media access control) address, an IP (Internet protocol) address, etc., according to a communication protocol. Further, the radio circuit  305  performs communication controls of the MIMO communication mode and the ordinary communication mode using only a single-system transmitting/receiving section (the transmitting/receiving section includes a PA, an LNA, an antenna, and a switch) and communication controls of IEEE802.11a, IEEE802.11b, IEEE802.11g, etc.  
         [0023]     One end of the PA  306  is connected to the radio circuit  305  and the other end is connected to the antenna  26  via the switch  310 , and one end of the PA  307  is connected to the radio circuit  305  and the other end is connected to the antenna  27  via the switch  311 . The PAs  306  and  307  play a role of amplifying transmission signals to be transmitted from the antennas  26  and  27 , respectively, to a prescribed output power level (e.g., 15 dBm).  
         [0024]     One end of the LNA  308  is connected to the antenna  26  via the switch  310  and the other end is connected to the radio circuit  305 , and one end of the LNA  309  is connected to the antenna  27  via the switch  311  and the other end is connected to the radio circuit  305 . The LNAs  308  and  309  play a role of amplifying reception signals that are received by the antennas  26  and  27  and are to be output to the radio circuit  305 , respectively. Amplified reception signals have features of low noise and small distortion.  
         [0025]     The switches  310  and  311  are switches for switching between transmission and reception. Controlled by the radio circuit  305 , the switch  310  makes switching to the PA  306  side when data are to be transmitted from the antenna  26 , and makes switching to the LNA  308  side when data are to be received from the antenna  26 . Likewise, controlled by the radio circuit  305 , the switch  311  makes switching to the PA  307  side when data are to be transmitted from the antenna  27 , and makes switching to the LNA  309  side when data are to be received from the antenna  27 .  
         [0026]     Controlled by the CPU  301 , the power circuit  314  plays a role of switching the source of power to the external power source  312  or the battery  313 , converting the voltage to a proper value, and supplying power to the PAs  306  and  307 . The switch  316  is inserted in the path from the power circuit  314  to the PA  306 , which makes it possible to switch between a state of supplying power to the PA  306  and a state of not supplying power to it.  
         [0027]     Controller by the CPU  301 , the power control circuit  315  switches the communication mode to the MIMO communication mode or the ordinary communication mode. More specifically, the power control circuit  315  switches between opening and closing of the switch  316  and thereby switches between the state that power is supplied from the power circuit  314  to the PA  306  and the state that power is not. Further, the power control circuit  315  switches the communication mode to the MIMO communication mode or the ordinary wireless LAN communication mode by sending a control signal to the radio circuit  305 .  
         [0028]     Next, a description will be made of a process for determining a communication method. A user makes communication-mode-related settings in advance.  FIG. 4  shows an exemplary communication mode setting picture through which the user is to set a communication mode. Using the setting picture of  FIG. 4 , the user can select one of the ordinary communication mode (button  41 ), the MIMO communication mode (button  42 ), and automatic switching between them (button  43 ).  
         [0029]     When the button  43  is selected (i.e., automatic switching), it is possible to set, using check boxes  44  and  45 , an item in accordance with which the communication mode should be switched. When the check box  44  is checked, the switching between the MIMO communication mode and the ordinary communication mode is made in accordance with the source of power. More specifically, when the source of power of the notebook PC  10  is the battery  313 , the ordinary communication mode is employed for power saving.  
         [0030]     When the check box  45  is checked, switching between the switching between the MIMO communication mode and the ordinary communication mode is made in accordance with the data size. A threshold value for the switching is set by the user.  FIG. 5  shows a setting picture through which to set a threshold value for the switching between the switching between the MIMO communication mode and the ordinary communication mode. In the setting picture of  FIG. 5 , the user inputs an arbitrary number to the box. Switching is made to the MIMO communication mode when the file size is larger than or equal to the thus-input setting number (in the example of  FIG. 5 , 500 kB), and to the ordinary communication mode when the file size is smaller than that. Settings that have been made through the setting pictures of  FIGS. 4 and 5  are stored in the memory  303 .  
         [0031]     A communication method is determined in accordance with settings made by the user through the setting pictures of  FIGS. 4 and 5 .  FIG. 6  is a flowchart of a process that is executed by the notebook PC  10  in determining a communication method of a communication to be performed with the communication apparatus  11 .  
         [0032]     First, the CPU  301  refers to a communication mode setting of a user that is stored in the memory  303  (step  401 ). If the user has made a setting that only the ordinary communication mode should be employed (“ordinary communication mode” at step  401 ), the CPU  301  causes the power control circuit  315  to open the switch  316  and thereby interrupts the supply of power from the power circuit  314  to the PA 306  (step  402 ). Further, the CPU  301  sends the radio circuit  305  a control signal to the effect that a communication should be performed in the ordinary communication mode (step  403 ).  
         [0033]     When the user has made a setting that only the MIMO communication mode should be employed (“MIMO communication mode” at step  401 ), the CPU  301  causes the power control circuit  315  to close the switch  316  and thereby permits the supply of power from the power circuit  315  to the PA 307  (step  404 ). Further, the CPU  301  sends the radio circuit  305  a control signal to the effect that a communication should be performed in the MIMO communication mode (step  405 ).  
         [0034]     When the user has made a setting that automatic switching should be made between the MIMO communication mode and the ordinary communication mode (“automatic switching” at step  401 ), the CPU  301  judges, by referring to the corresponding user setting stored in the memory  303 , whether or not the user has made a setting that the communication mode should be switched in accordance with the source of power (step  406 ). More specifically, the CPU  301  judges whether or not the user checked the check box  44  after selecting the button  43  in the setting picture of  FIG. 4 .  
         [0035]     When the user has made a setting that the communication mode should be switched in accordance with the source of power (“yes” at step  406 ), the CPU  301  judges whether the power circuit  314  is being supplied with power from the external power source  312  or the battery  313  (step  407 ). When the power circuit  314  is being supplied with power from the battery  313  (“no” at step  407 ), the CPU  301  judges that the power consumption should be reduced and hence effects a communication in the ordinary communication mode which is featured by a low power consumption (steps  402  and  403 ).  
         [0036]     When the power circuit  314  is being supplied with power from the external power source  312  (“yes” at step  407 ) or the user has not made a setting that the communication mode should be switched in accordance with the source of power (“no” at step  406 ), the CPU  301  judges, by referring to the memory  303 , whether or not the user has made a setting that the communication mode should be switched in accordance with the data size (step  408 ). More specifically, the CPU  301  judges whether or not the user checked the check box  45  after selecting the button  43  in the setting picture of  FIG. 4 .  
         [0037]     When the user has made a setting that the communication mode should be switched in accordance with the data size (“yes” at step  408 ), the CPU  301  judges whether or not the data size of a file to be transmitted or received is larger than or equal to a threshold value that was set by the user in the setting picture of  FIG. 5  (step  409 ). The threshold value that was set by the user is stored in the memory  303 . When the data size is smaller than the threshold value (“no” at step  409 ), the CPU  301  judges that a high-capacity communication is not necessary and hence effects a communication in the ordinary communication mode (steps  402  and  403 ).  
         [0038]     When the data size of the file to be transmitted or received is larger than or equal to the threshold value (“yes” at step  409 ) or the user has not made a setting that the communication mode should be switched in accordance with the data size (“no” at step  408 ), the CPU  301  effects a communication in the MIMO communication mode (steps  404  and  405 ).  
         [0039]     After judging whether a communication should be performed in the MIMO communication mode or the ordinary communication mode (step  403  or  405 ), the CPU  301  determines a frequency to be used in the communication. More specifically, the CPU  301  checks the frequency of occurrence of radio interference events in the 2.4 GHz band (step  410 ). The frequency of occurrence of radio interference events can be judged by, for example, checking the number of nearby clients who are performing communications in the 2.4 GHz band. If, for example, the number of nearby clients who are performing communications in the 2.4 GHz band is larger than or equal to a prescribed number, the CPU  301  judges that the frequency of occurrence of radio interference events is high (“no” at step  410 ) and effects a communication in the 5 GHz band (IEEE802.11a; step  411 ).  
         [0040]     If judging that the frequency of occurrence of radio interference events is low (“yes” at step  410 ), the CPU  301  effects a communication in the 2.4 GHz band (IEEE802.11g; step  412 ).  
         [0041]     After determining a communication method in the above-described manner, the notebook PC  10  communicates with the communication apparatus  11  by the thus-determined communication method.  
         [0042]     As described above, in this embodiment, whether to reduce the power consumption is judged on the basis of a user&#39;s direct setting of a communication mode or whether power is supplied from the external power source  312  or the battery  313 . On the basis of a result of this judgment, the ordinary communication mode in which only the single-system transmitting/receiving section (i.e., the PA  307 , antenna  27 , and LNA  309 ) is used or the MIMO communication mode in which plural antennas are used and hence a high-capacity communication is possible is selected. This makes it possible to reduce the power consumption in accordance with the situation. In particular, a MIMO communication can be avoided during a battery drive, which enables long-time use of the battery  313 .  
         [0043]     In this embodiment, selection between a MIMO communication and an ordinary communication can be made in accordance with a user&#39;s communication mode setting. In the case of automatic switching, a setting can be made as to whether this switching should be made in accordance with the source of power or the data size. As a result, whether the power consumption should be reduced or a method for attaining a large communication capacity should be sought can be determined according to an intention of a user.  
         [0044]     In this embodiment, the communication mode to be employed is switched in accordance with the data size of a file to be communicated. In general, the load on the CPU  301  is heavy when a high-capacity communication such as a MIMO communication is performed. In contrast, according to the embodiment, the CPU  301  can be prevented from bearing an unduly heavy load because a high-capacity communication is not performed when the data size is small as exemplified by a case of text data.  
         [0045]     In this embodiment, the frequency band used is determined in accordance with the radio interference status, which makes it possible to avoid being subjected to undue radio interference.  
         [0046]     In this embodiment, a communication mode is determined in accordance with a user&#39;s communication mode setting, a source of power, and a data size. However, the invention is not limited to such a case. For example, a communication mode may be determined in accordance with a type of the communication apparatus  11 .  FIG. 7  shows a setting picture through which to set connection apparatus  11 . The setting picture of  FIG. 7  makes it possible to set apparatus types (in the example of  FIG. 7 , a TV receiver, a notebook PC, and a printer) of connection apparatus  11 , their MAC addresses, and communication modes to be used (the MIMO communication mode for the TV receiver and the printer and the ordinary communication mode for the notebook PC). If the notebook PC  10  is configured so as to be able to determine a communication mode in accordance with a type of a connection apparatus  11  on the basis settings thus made by a user, the MIMO communication mode can be employed forcibly for a communication with a TV receiver or the like which is high in realtimeness.  
         [0047]     Another modification is as follows. While a MIMO communication is performed with driving by the battery  313 , the power circuit  314  and the CPU  301  check, always or regularly, the remaining life of the battery  313 . When the remaining life of the battery  313  has become shorter than a prescribed value (e.g., a half of the original life), switching is made automatically to the ordinary communication mode.  
         [0048]      FIG. 8  is a flowchart of a process in which the communication mode is switched in accordance with the remaining battery life. It is assumed that at the start of this process the notebook PC  10  is operating on power that is supplied from the battery  313  and is performing a MIMO communication with the communication apparatus  11 . During the MIMO communication, the power circuit  314  and the CPU  301  monitor the remaining life of the battery  313  (step  801 ). When the remaining life is longer than or equal to a prescribed value (e.g., a half of the original life; “no” at step  801 ), the MIMO communication is continued. When the remaining life is shorter than the prescribed value (“yes” at step  801 ), switching is made to the ordinary communication mode (step  802 ). In this case, a frequency band to be used is determined in the same manner as at steps  410 - 412  in  FIG. 6 . More specifically, the CPU  301  checks the frequency of occurrence of radio interference events in the 2.4 GHz band (step  803 ). If the frequency of occurrence of radio interference events is high (“no” at step  803 ), the CPU  301  effects a communication in the 5 GHz band (IEEE802.11a; step  804 ). If the frequency of occurrence of radio interference events is low (“yes” at step  803 ), the CPU  301  effects a communication in the 2.4 GHz band (IEEE802.11g; step  805 ).  
         [0049]     With the above process, a MIMO communication can be performed in the case where, for example, the driving by the battery  313  can continue only for a short time. Where the battery  313  can be used for a long time, the time during which the battery  313  is usable can be elongated by switching to the ordinary communication mode halfway which is featured by a low power consumption. This modification may be such that a user is allowed to set, in terms of a remaining life (percentage), when to switch from the MIMO communication mode to the ordinary communication mode.  
         [0050]     Although in the above embodiment the two systems of transmitting/receiving sections are provided, more systems of transmitting/receiving sections may be provided. In this case, a control can be performed in many stages. For example, where three systems of transmitting/receiving sections are provided, the number of systems used can be determined in accordance with a power consumption and a necessary communication capacity by performing a control in three stages (a single system, two systems, and three systems).  
         [0051]     Although in the above embodiment the Mini PCI card  24  incorporates the radio circuit  305 , the PAs  306  and  307 , the LNAs  308  and  309 , and the switches  310  and  311 , the invention is not limited to such a configuration. For example, as shown in  FIG. 9 , the Mini PCI card  24  may incorporates the radio circuit  305 , the PAs  306  and  307 , the LNAs  308  and  309 , the switches  310  and  311 , the power control circuit  315 , and the switch  316 . Whereas in the former configuration the Mini PCI card  24  can be increased in general versatility, in the latter configuration the notebook PC  10  (excluding the Mini PCI card  24 ) can be increased in general versatility. Even in the configuration of  FIG. 9 , the process relating to the determination of a communication method and other features are the same as in the configuration of  FIG. 3  and hence will not be described.