Abstract:
A command processing method for a radio LAN system composed of a plurality of terminals and at least one base apparatus is disclosed which prevents users of the terminals from suffering from confusion or conflict between them with regard to handling of a command issued from any of the terminals and from misunderstanding that the system has failed. When a channel changing command or a like command is issued from a terminal, the base apparatus determines whether or not the received command is a competitive command whose acceptance may result in the disturbance of reception of data of any other terminal. If the received command is a competitive command, then the base apparatus rejects the command and issues a notification of the rejection to the terminal which has issued the command. When a particular condition is satisfied such as when the priority of the terminal which has issued the command is higher than that of any other terminal receiving data, then the base apparatus may accept the command.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates generally to a command processing method for a radio LAN (Local Area Network) system, and a radio communication apparatus which composes a radio LAN system.  
           [0002]    In order to view an audio/video program, access the Internet, or perform various other desired functions with a computer it is conventionally necessary to maintain at least one hard-wired connection so that desired data may be transferred from any number of remote sites to the computer for processing, and then to an associated display device for display. It would therefore be beneficial to provide an improved device allowing for access to the above functions without maintaining such a hard-wired connection.  
         SUMMARY OF THE INVENTION  
         [0003]    Therefore, generally speaking, in accordance with the invention, an improved display terminal for a radio LAN system is provided.  
           [0004]    In accordance with the invention, it has been proposed to construct a radio LAN system from a plurality of apparatus and transmit and receive data between the apparatus in a limited area such as within a house or within a room. To this end, the IEEE (Institute of Electrical and Electronics Engineers) 802.11 standards prescribe a 2.4 GHz and 5 GHz radio frequency bands that can be used for such a radio LAN system.  
           [0005]    A radio LAN system of the type described includes, for example, a base apparatus and one or more terminals. The base apparatus includes a built-in tuner or a tuner connected thereto for receiving a broadcast and to which a telephone circuit or the like is connected. A terminal that communicates with the base apparatus by radio communication to send a command or other information to the base apparatus and receive information such as image data and audio data from the base apparatus to allow for the display of an image on a display section and the output sound from a speaker or an earphone is also provided. Thus, a user of such a radio LAN system can enjoy a ground wave TV (television) broadcast or a BS/CS (broadcasting satellite/communications satellite) digital broadcast, access the Internet, or enjoy telephone conversation using the display terminal regardless of the location of the user in a house or in a room.  
           [0006]    In particular, a radio LAN system can be configured as is shown in FIG. 1. The radio LAN system shown in FIG. 1 includes two terminals  30 A and  30 B each including an antenna  31 , a liquid crystal display (LCD) apparatus  32 , a speaker  33  and a microphone  34 . A base apparatus  10  is also shown, and includes an antenna  11  for radio communication with terminals  30 A and  30 B and a built-in TV tuner  13  connected to an antenna  12  for reception of a TV broadcast. A telephone circuit  1  is also connected to base unit  10 . In accordance with the radio LAN system of the invention, a user can use terminal  30 A in a first location while another user can use terminal  30 B in a second location to enjoy a TV broadcast, access the Internet or enjoy telephone conversation.  
           [0007]    In the radio LAN system in accordance with the invention including two terminals  30 A and  30 B, for example, when a TV broadcast is to be enjoyed by a user, if only one of the terminals is in use and receives the broadcast, then the user can freely change the channel. However, when both of terminals  30 A and  30 B are in use and receive the broadcast simultaneously, a problem arises with regard to channel selection.  
           [0008]    If the system is configured such that the channel to be received by the TV tuner  13  in base apparatus  10  is changed by base apparatus  10  each time a channel changing command is issued from one of the terminals, then each time a channel changing command is issued from any of the terminals, the broadcast channel to be received by the terminals  30 A and  30 B is changed for both terminals. As a result, confusion or conflict in channel selection occurs between the user of terminal  30 A and the user of terminal  30 B.  
           [0009]    While terminals  30 A and  30 B receive the same broadcast channel X simultaneously, if a command for changing the channel to a channel Y is issued from terminal  30 A and another command for changing the channel to a channel Z is issued immediately or substantially simultaneously from terminal  30 B, then the channel is changed to channel Z (the second requested channel) on both of terminals  30 A and  30 B. Consequently, the user of the terminal  30 A who has requested the channel selection to channel Y may assume that the system has failed.  
           [0010]    In accordance with the invention, an improved command processing method and radio communication apparatus for a radio LAN system is provided composed of a plurality of terminals and at least one base apparatus which prevents users of the terminals from suffering confusion or conflict between them when issuing command from the terminals.  
           [0011]    According to an aspect of the present invention, there is provided a method for processing commands for a radio LAN system that includes a plurality of terminals and at least one base apparatus. In the system, commands issued from any of the terminals are received by the base apparatus. Information is transmitted from the base apparatus to the terminals by radio communication. The base apparatus first receives a command issued from any of the terminals. The base apparatus then determines whether or not the received command is a competitive command whose acceptance may result in the disturbance of any other terminal that is receiving information. If it is determined that the received command is a competitive command, the command is rejected. A notification of the rejection to the terminal which has transmitted the command is issued.  
           [0012]    The command processing method includes an alternative embodiment including the feature that a priority order among the terminals may be set. Thus, even if a received command is a competitive command, if the priority of the terminal which has transmitted the command is higher than that of any of the other terminals that is currently receiving information, then the base apparatus accepts the command and issues a notification of the acceptance of the command to the other terminal or terminals.  
           [0013]    In another alternative embodiment, a command processing method may be constructed such that, even if a competitive command is received, if a predetermined time or more has elapsed after implementation of a previous command regarding a process being currently executed by any other terminal, then the base apparatus accepts the command and issues a notification of the acceptance of the command to the other terminals that are a receiving state.  
           [0014]    In accordance with another alternative embodiment of the invention, a command processing method may be constructed such that, if a competitive command is received, then the base apparatus issues to the other terminals that are receiving information an inquiry whether the command may be accepted. If a reply from the other terminals accepts the command, the command is then accepted by the base unit.  
           [0015]    According to another aspect of the invention, a radio communication apparatus for a radio LAN system is provided that includes a plurality of terminals and at least one base apparatus. A command issued from any of the terminals is received by the base apparatus and information is transmitted from the base apparatus to the terminals by radio communication. The radio communication apparatus is located in the base apparatus. The radio communication apparatus comprises a receiver for receiving a command issued from any of the terminals, and a discriminator for determining, when a command issued from any of the terminals is received by the reception means, whether the command is a competitive command whose acceptance may result in disturbance of the reception of information by any other of the terminals. Based upon a result of the determination, it is determined whether or not the command should be accepted. Finally, when it is determined that acceptance of the command should be rejected, a notification of the rejection of the command is transmitted to the terminal which transmitted the command.  
           [0016]    In the command processing method and the radio communication apparatus in accordance with the invention, if a competitive command is issued from a terminal, it is generally not accepted by the base apparatus. Therefore no disturbance or conflict occurs among the users of the terminals in regard to handling of a command issued from one of the terminals. If the command is not accepted, then a notification of such a rejection is issued from the base apparatus to the terminal which originally transmitted the command. Therefore, if the command is not accepted, the user of the terminal which has issued the command does not think that the system has failed.  
           [0017]    Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification and the drawings  
           [0018]    The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combination(s) of elements and arrangement of parts that are adapted to effect such steps, all as exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is a schematic view showing an example of radio LAN system;  
         [0020]    [0020]FIG. 2 is a schematic view showing an example of a radio LAN system to which a command processing method according to an embodiment of the invention is applied;  
         [0021]    [0021]FIG. 3 is a block diagram showing an example of functional block configuration of a base apparatus of the radio LAN system of FIG. 2;  
         [0022]    [0022]FIG. 4 is a block diagram showing an example of functional block configuration of terminals of the radio LAN system of FIG. 2; and  
         [0023]    FIGS.  5  to  7  are flow charts illustrating different forms of a command processing method according to an embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]    [0024]FIG. 2 shows an example of radio LAN system to which a command processing method according to the present invention can be applied. Referring to FIG. 2, the radio LAN system shown includes a base apparatus  10  and two display terminals  30 A and  30 B.  
         [0025]    A telephone circuit  1  is connected to base apparatus  10 . Base apparatus  10  includes an antenna  11  for radio communication with display terminals  30 A and  30 B so that display terminals  30 A and  30 B are able to perform telephone communication as desired utilizing radio communication with base apparatus  10  (as will be described below) and access the Internet. Of course, any manner for accessing the Internet may be employed by display terminals  30 A and  30 B, as long as this method of access is properly connected to base unit  10 .  
         [0026]    Further, an antenna  12  for receiving a ground wave television broadcast and another antenna  14  for receiving a BS/CS digital broadcast are connected to the base apparatus  10 . A tuner  13  and a BS/CS tuner  15  are built into base apparatus  10  so that display terminals  30 A and  30 B can receive video and audio information of a ground wave television broadcast and a BS/CS digital through radio communication with base apparatus  10 . Of course, rather than an antenna, a cable feed wire or other transmission media for a television broadcast may be coupled with base apparatus  10 . In accordance with such a configuration, tuners  13  and  15  would be configured to allow a user to select from among various audio/video programs provided via the provided transmission media.  
         [0027]    Furthermore, a playback apparatus such as a DVD player may be connected as an external apparatus  50  so that the display terminals  30 A and  30 B can receive audio/video program information and so forth played back by external apparatus  50  through radio communication with base apparatus  10 . While a DVD player is shown, any appropriate playback device may be employed.  
         [0028]    A remote controller transmitter  29  such as a remote controller mouse or the like is connected to base apparatus  10 . An infrared remote control signal transmitted from remote controller transmitter  29  is received by a remote control signal reception section  51  provided on external apparatus  50  to control external apparatus  50 . Of course other control devices, such as a radio wave remote control, or hardwired controller may be provided for allowing control of external apparatus  50 .  
         [0029]    Display terminals  30 A and  30 B (collectively “display terminal  30 ”) will now be described. Display terminal  30  includes an antenna  31  for radio communication with base apparatus  10 , a liquid crystal display (LCD) apparatus  32  for displaying an image, a speaker  33  for outputting sound, and a microphone  34  for inputting sound. Display terminal  30  further includes a key selection and operation section  35  including a power supply key, an Internet key, an electronic mail key, a channel selection key, a sound volume adjustment key and the like.  
         [0030]    Further, a touch panel  36  is provided on a screen of LCD apparatus  32  so that, when a user touches touch panel  36  within a predetermined region, a control panel  37  is displayed on LCD apparatus  32 . A user can touch a key switch section of control panel  37  to control various functions of base apparatus  10 , such as requesting a channel change.  
         [0031]    Base apparatus  10  is functionally configured as shown in FIG. 3 while display terminal  30  is functionally configured as shown in FIG. 4, as will now be described.  
         [0032]    Referring next to FIG. 3, base apparatus  10  includes a key operation section  16  and a display section  17  which function as a user interface between the user and base apparatus  10 . Key operation section  16  is connected to a main control section  21  through an interface section  18 . Display section  17  is connected to main control section  21  through a display control section  19 . Remote controller transmitter  29  is connected to main control section  21  through an interface section  28 .  
         [0033]    A signal of a ground wave television broadcast selected and demodulated, and then converted into digital image data by tuner  13  from a data signal received by antenna  12 , and is then sent to a compression-decompression section  24 . A signal of a BS/CS digital broadcast is selected and separated into compressed image data and compressed audio data. The separated data are then decompressed by BS/CS tuner  15 , and are sent to compression-decompression section  24 . Telephone circuit  1  is connected to compression-decompression section  24  through a circuit interface section  25  and is also connected to a signal control section  23  through a modem section  26 .  
         [0034]    Furthermore, external apparatus  50  reproduces and outputs data to compression-decompression section  24 , via external input interface  52 .  
         [0035]    Compression-decompression section  24  compresses video data and audio data from TV tuner  13 , BS/CS tuner  15 , external input interface  52  and circuit interface section  25  in accordance with a predetermined compression system such as, for example, the MPEG (Moving Picture Experts Group) system. The compressed video data and audio data are forwarded to signal control section  23 .  
         [0036]    Further, compression-decompression section  24  decompresses compressed audio data transmitted thereto from display terminal  30 . This compressed audio data is received by a radio communication section  22  and then forwarded from radio communication section  22  to compression-decompression section  24  through signal control section  23 . The decompressed audio signal data is then forwarded to circuit interface section  25 .  
         [0037]    Radio communication section  22  modulates data forwarded from signal control section  23  in accordance with a predetermined modulation system such as, for example, the CCK (Complementary Code Keying) system or the OFDM (Orthogonal Frequency Division Multiplexing) system, for example. The modulated data is then converted into a high frequency signal in the 2.4 GHz band or the 5 GHz band. The high frequency signal is then transmitted from antenna  11  to display terminal  30 . Radio communication section  22  also converts a high frequency signal transmitted thereto from display terminal  30  and received by antenna  11  into an intermediate frequency signal, demodulates the intermediate frequency signal and forwards the demodulated data to signal control section  23 .  
         [0038]    Signal control section  23  arbitrates and selectively forwards video data and audio data compressed by compression-decompression section  24 , data received by modem section  26  and control data from main control section  21  to radio communication section  22 . Further, signal control section  23  selectively forwards data transmitted from display terminal  30  and received by radio communication section  22 . This received data is then forwarded from radio communication section  22  to signal control section  23 , and from signal control section  23  to main control section  21 , modem section  26  and compression-decompression section  24 .  
         [0039]    Main control section  21  controls the components of base apparatus  10 . Main control section  21  comprises, though not shown in FIG. 3, a CPU (Central Processing Unit), a ROM (Read Only Memory) in which programs to be executed by the CPU, fixed data and so forth are written, a RAM (Random Access Memory) which functions as a working area of the CPU and other necessary elements.  
         [0040]    Referring next to FIG. 4, display terminal  30  constructed in accordance with the invention includes a main control section  41  to which key operation section  35  is connected through an interface section  38 . Further, a coordinate detection section  39  is provided as an interface for touch panel  36  and detects coordinates of a touched position of touch panel  36 . The detected coordinate values are forwarded to main control section  41 .  
         [0041]    If touch panel  36  is touched in the predetermined region thereof, then main control section  41  controls a display control section  45  to display control panel  37  on LCD apparatus  32 . Then, if the key switch section of control panel  37  displayed on the LCD apparatus  32  is touched, main control section  41  produces control data in response to the touched position of the key switch section. Further, if key operation section  35  is operated, main control section  41  produces control data in response to the operated key. The control data produced by main control section  41  is forwarded to a signal control section  43 .  
         [0042]    In display terminal  30 , an audio signal from microphone  34  is amplified by an audio amplifier  48  and converted into digital audio data by an A/D (analog to digital) converter  49 . The audio data is compressed in accordance with a predetermined compression system by a compression-decompression section  44 . The compressed audio data is then forwarded to signal control section  43 .  
         [0043]    Signal control section  43  arbitrates and selectively forwards control data from main control section  41  and audio data compressed by compression-decompression section  44  to a radio communication section  42 . Further, signal control section  43  selectively forwards data transmitted from base apparatus  10  and received by radio communication section  42 . Control and other data that are previously received by modem section  26  of base apparatus  10  are forwarded to main control section  41 , while compressed video data and audio data are forwarded to compression-decompression section  44 .  
         [0044]    Radio communication section  42  modulates data forwarded from signal control section  43  in accordance with a predetermined modulation system, converts the modulated data into a high frequency signal in the 2.4 GHz band or the 5 GHz band and transmits the high frequency signal from antenna  31  to base apparatus  10 . Further, radio communication section  42  converts a high frequency signal transmitted from base apparatus  10  and received by antenna  31  into an intermediate frequency signal, demodulates the intermediate frequency signal and forwards the demodulated data to signal control section  43 .  
         [0045]    Compression-decompression section  44  decompresses compressed video data and audio data forwarded from signal control section  43 . The decompressed video data is displayed as an image on LCD apparatus  32  under the control of display control section  45 . The decompressed audio data is converted into an analog audio signal by a D/A (digital to analog) converter  46 , is amplified by an audio amplifier  47  and is output as sound from speaker  33 .  
         [0046]    Main control section  41  controls the components of display terminal  30  and includes, though not shown in FIG. 4, a CPU, a ROM, a RAM and so forth similarly to main control section  21  of base apparatus  10 .  
         [0047]    In order to receive a ground wave television broadcast or a BS/CS digital broadcast at display terminal  30  in the radio LAN system described above, video data and audio data from TV tuner  13  or BS/CS tuner  15  of base unit  10  from a selected channel are first compressed by compression-decompression section  24 . This compressed data is then transmitted by radio communication section  22  under the control of signal control section  23  to display terminal  30 . In display terminal  30 , the compressed video data and audio data are first received by radio communication section  42 . This received data is then forwarded to and decompressed by compression-decompression section  44  under the control of signal control section  43 . Consequently, an image is displayed on LCD apparatus  32  and sound is output from speaker  33 .  
         [0048]    If a user selects a channel of a TV or BS/CS broadcast using key operation section  35  or control panel  37 , a command indicating the desired channel is transmitted from main control section  41  of display terminal  30  to the base apparatus  10  by radio communication section  42  under the control of signal control section  43 .  
         [0049]    In base apparatus  10 , the transmitted command is received by radio communication section  22  and sent to main control section  21  under the control of signal control section  23 . Main control section  21  controls tuner  13  to select a channel in accordance with the received command.  
         [0050]    In order to view and hear data played back by external apparatus  50 , the user initiates a playback operation through key operation section  35  or control panel  37 . In response, a command is transmitted from terminal  30  to base apparatus  10  requesting playback of data by external apparatus  50 .  
         [0051]    External apparatus  50  is controlled in accordance with a command transmitted by remote controller  29 . Desired image and audio data are therefore played back by external apparatus  50 . Image and audio data output from external apparatus  50  are transmitted from base apparatus  10  to terminal  30  in a manner similar to that noted above. At terminal  30  an image is displayed on LCD  32  and sound is output from speaker  33  in accordance with the received image data and audio data, respectively.  
         [0052]    In order to access the Internet, a user operates key operation section  35  or control panel  37  to request connection to an ISP (Internet Service Provider). The request is transmitted from main control section  41  of display terminal  30  to base apparatus  10  by radio communication section  42  under the control of signal control section  43 .  
         [0053]    In base apparatus  10 , a request is received by radio communication section  22  and is forwarded to main control section  21  under the control of signal control section  23 . Consequently, modem section  26  and circuit interface section  25  are controlled in response to the request by main control section  21  to establish a connection to the ISP. Then, for example, data sent from the ISP to telephone circuit  1  in response to the access request to a certain homepage is sent to signal control section  23  through circuit interface section  25  and the modem section  26 . This data is in turn transmitted to display terminal  30  by radio communication section  22 .  
         [0054]    In display terminal  30 , the data is received by the radio communication section  42  and sent to main control section  41  under the control of signal control section  43 . Main control section  41  processes the data to produce display data. This display data is then forwarded to display control section  45  so that the retrieved homepage is displayed on the LCD apparatus  32 . Of course, access to the Internet may be performed employing any other type of provided ISP connection, including but not limited to cable transmissions, satellite transmissions, DSL transmissions, or any other information data transmission medium.  
         [0055]    In order to perform the function of allowing for a telephone conversation, a transmission audio signal from microphone  34  of display terminal  30  is converted into digital audio data by A/D converter  49  and compressed by compression-decompression section  44 . Then, the compressed audio data is transmitted to base apparatus  10  by radio communication section  42  under the control of the signal control section  43 .  
         [0056]    In base apparatus  10 , the compressed audio data is received by radio communication section  22 . This received data is in turn forwarded to and decompressed by compression-decompression section  24  under the control of signal control section  23 . Then, the decompressed transmission audio signal is forwarded to telephone circuit  1  through circuit interface section  25 .  
         [0057]    Meanwhile, a received audio signal transmitted over telephone circuit  1  is sent through circuit interface section  25  to compression-decompression section  24  where it is compressed. The compressed audio data is transmitted to display terminal  30  by radio communication section  22  under the control of signal control section  23 .  
         [0058]    In display terminal  30 , the compressed audio data is received by radio communication section  42 . This received audio data is forwarded to and decompressed by compression-decompression section  44  under the control of signal control section  43 . Then, the decompressed audio data is converted into an analog audio signal by D/A converter  46  and output as a voice from speaker  33 .  
         [0059]    Different forms of command processing methods according to the invention will now be described. A command issued from the terminal  30 A or  30 B is processed by the base apparatus  10  in the radio LAN system described hereinabove.  
         [0060]    According to the command processing method of the present invention, if a command issued from terminal  30 A or  30 B is a competitive command, then the base apparatus  10  does not accept the command. A competitive command is one that would disturb the reception of information by another terminal from the base apparatus. For example, if a channel selection command is issued from terminal  30 A while the power supply to terminal  30 B is off and terminal  30 B is not in receiving information, then the command is not a competitive command. On the other hand, if a channel changing command is issued from terminal  30 A while terminals  30 A and  30 B are receiving the same channel from the base apparatus, then the command is a competitive command.  
         [0061]    In the command processing method of the invention, when a command is a competitive command and therefore is not accepted, base apparatus  10  issues a notification to the terminal from which the command has been transmitted indicating that the command could not be accepted. In the terminal receiving the notification, a message such as “This command cannot be accepted.” is displayed on LCD  32  or is output from speaker  33  under the control of main control section  41 .  
         [0062]    Identification information (ID) for identification of the terminal which transmits a command is added to the command transmitted from terminal  30 A or  30 B to base apparatus  10 . Also, ID for identification of the terminal of the destination of a response to command is added to a notification transmitted from base apparatus  10  to terminal  30 A or  30 B.  
         [0063]    Several detailed examples of the command processing method according to the present invention will now be described.  
         [0064]    Referring next to FIG. 5, a priority order is determined between terminals  30 A and  30 B. In other words, priority is given to one of terminals  30 A and  30 B.  
         [0065]    However, the priority need not necessarily be given permanently to one of the terminals. For example, priority may be given to terminal  30 A or  30 B depending upon a current time. Thus, priority may be given to terminal  30 A from 6:00 a.m. to 6:00 p.m. but to terminal  30 B from 6:00 p.m. to 6:00 a.m. Priority may also be determined based upon the day of the week such that priority is given to terminal  30 A from Monday to Friday but to terminal  30 B on Saturday and Sunday. The desired priority order is set by the user in main control section  21  of base apparatus  10  through key operation section  16  of base apparatus  10 .  
         [0066]    In the first example in accordance with the invention, main control section  21  of base apparatus  10  executes a command processing routine  60  as illustrated in FIG. 5. In accordance with command processing routine  60 , even if a received command is a competitive command, if the terminal which has issued the command has priority, then the command is accepted and a notification of the acceptance of the command is sent to the other receiving terminals.  
         [0067]    In particular, referring to FIG. 5, a command is received by base apparatus  10  from one of the terminals. At step  61  it is determined whether the command is a competitive command. If it is determined that the command is not a competitive command, then processing advances from step  61  to step  62 , in which main control section  21  of base apparatus  10  accepts the command. Accordingly, if no other terminal is receiving information, then the user of the terminal can change the channel freely irrespective of whether or not the user has the priority.  
         [0068]    However, if it is determined in step  61  that the received command is a competitive command, then the processing advances from step  61  to step  63 . At step  63  main control section  21  determines whether the terminal that has issued the command has priority. If it is determined that the terminal issuing the command does not have the priority, then processing advances from step  63  to step  64 . At step  64  main control section  21  of base apparatus  10  rejects the command and issues a notification of the rejection of the command request to the terminal that issued the command. Accordingly, if a channel changing command is issued from terminal  30 A while terminals  30 A and  30 B are simultaneously receiving the same channel, if terminal  30 A does not have priority, then the channel changing command from terminal  30 A is not accepted.  
         [0069]    If it is determined in step  63  that the terminal that issued the command has priority, then processing advances from step  63  to step  65 . At step  65  main control section  21  of base apparatus  10  accepts the command and notifies the other terminal of this acceptance. Thereafter, processing advances to step S 66 , in which base apparatus  10  performs the process requested in the command. Accordingly, if a channel changing command is issued from the terminal  30 A while the terminals  30 A and  30 B are simultaneously receiving the same channel, then if terminal  30 A has priority, the channel changing command from the terminal  30 A is accepted. Because terminal  30 B is notified in advance that the channel will be changed, the user of terminal  30 B is aware of the change.  
         [0070]    Where the priority is given to terminal  30 A or  30 B depending upon time or day of the week as described above, it is therefore determined in step  63  whether or not the terminal which has issued the command has priority at the present time or day of the week. Where the priority is given to the terminal  30 A or  30 B depending upon time or day of the week as described above, control by terminal  30 A and terminal  30 B can be adjusted appropriately.  
         [0071]    Referring next to FIG. 6, main control section  21  of base apparatus  10  executes such a command processing routine  70 . In accordance with processing routine  70  if a received command is a competitive command, and the desired command is issued after a predetermined time or more after a beginning of a process being currently executed by the other terminal, then the command is accepted and the other terminal is notified. Preferably, the predetermined time represents around one to two hours.  
         [0072]    In particular, when base apparatus  10  receives a command from one of the terminals, at step  71 , main control section  21  first determines whether the command is a competitive command. If it is determined that the command is not a competitive command, then processing advances from step  71  to step  72 . At step  72 , main control section  21  of base apparatus  10  accepts the command. Then, processing further advances to step  73 , in which main control section  21  resets a timer to update time measurement. Accordingly, when only one terminal is in a receiving state, the user of the terminal can change the channel freely. Each time the channel is changed, the timer is reset.  
         [0073]    If it is determined at in step  71  that the command is a competitive command, then processing advances from step  71  to step  74 . At step  74  main control section  21  of base apparatus  10  determines from the timer whether or not a predetermined time or more has elapsed after the acceptance of a prior command initiating the process being currently executed by the other terminal. If the predetermined time or more has not elapsed, then processing advances from step  74  to step  75 . At step  75  main control section  21  of base apparatus  10  rejects the requested command and notifies the terminal which has issued the command of the rejection. Accordingly, when a terminal is receiving a certain channel, if the user of another terminal tries to select a channel different from the channel being received by the first terminal, if at least a predetermined time period has not elapsed after the acceptance of a preceding command that selected the certain channel the channel selection command from the other terminal is not accepted.  
         [0074]    If base apparatus  10  determines in step  74  that at least a predetermined time has elapsed, then processing advances from step  74  to step  76 . At step  76  main control section  21  of base apparatus  10  notifies the other terminal currently receiving data that the newly requested command will be accepted. Then, processing advances to step  77 , in which main control section  21  of base apparatus  10  performs a process requested by the command. Further, in a step  78 , main control section  21  resets the timer to update the time measurement. Accordingly, in the case described above, if a fixed predetermined time or more has elapsed after the acceptance of a preceding command initiating a present activity from one terminal, then channel selection command received from another terminal is accepted. The user of the one terminal is therefore notified in advance that the channel will be changed.  
         [0075]    Referring next to FIG. 7, main control section  21  of base apparatus  10  executes a command processing routine  80 . In accordance with this embodiment of the invention, even if a competitive command is received, if the user of the other terminal which is receiving data consents to acceptance of the command, then the command is accepted.  
         [0076]    In command processing routine  80 , base apparatus  10  first determines in step  81  whether or not a received command is a competitive command. If the command is not a competitive command, then processing advances from step  81  to step  82 . At step  82 , main control section  21  of base apparatus  10  accepts the command.  
         [0077]    If it is determined in step  81  that the command is a competitive command, then processing advances from step  81  to step  83 . At step  83  main control section  21  of base apparatus  10  issues to the other terminal currently receiving data an inquiry whether or not the command may be accepted. The inquiry is performed by transmitting control data from base apparatus  10  to the other terminal and displaying a message such as “May the channel be changed?” on the LCD  32 , or outputting from speaker  33  on the other terminal an audio version of the question.  
         [0078]    In response to the inquiry, the user of the other terminal operates key operation section  35  or control panel  37  to issue a reply representing whether or not the command may be accepted. Reply data is transmitted from the other terminal to the base apparatus  10 .  
         [0079]    After the inquiry in step  83 , processing advances to step  84 . At step  84  main control section  21  of base apparatus  10  determines whether or not the received reply accepts the command. If the reply objects to the acceptance of the command, then processing advances from step  84  to step  85 . At step  85  main control section  21  of base apparatus  10  rejects the command and notifies the terminal that issued the command of the rejection.  
         [0080]    If the reply consents to the acceptance of the command, then processing advances from step  84  to step  86 . At step  86  main control section  21  of the base apparatus  10  accepts the command and implements the requested action.  
         [0081]    While the radio LAN system described hereinabove includes the single base apparatus  10  and the two terminals  30 A and  30 B, the present invention can be applied also to a radio LAN system which includes a single base apparatus and three or more terminals.  
         [0082]    In this instance, where a priority order is set among the terminals as in the first example described hereinabove, it is possible to give priority permanently to one or more of the terminals, to permanently give different order numbers to the terminals, to give priority to one or more of the terminals depending upon the time or day of the week, or to give different priority order numbers to the terminals.  
         [0083]    In this case with three or more terminals, base apparatus  10  determines, at step  63  of command processing routine  60  of FIG. 5, whether or not the priority of the terminal which has issued a command is higher than the priority of the other terminal or terminals that are currently receiving data. If the priority is not higher or is equal, then the command is not accepted. If the priority is higher, then the command is accepted.  
         [0084]    Further, where the command is accepted when the user of the other terminal consents to acceptance of the command, if a plurality of other terminals are also receiving data, then the base apparatus  10  accepts the command, in step  84  of the command processing routine  80  of FIG. 7, only when the command is accepted by a majority of the plurality of terminals currently receiving data including the terminal which has issued the command. If the command is accepted, base apparatus  10  issues to those terminals that objected to the command a notification that the command will be accepted.  
         [0085]    Further, the present invention can be applied also to a radio LAN system which is composed of a plurality of base apparatus and a plurality of terminals.  
         [0086]    It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, because certain changes may be made in carrying out the above method and in the construction(s) set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.  
         [0087]    It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.