Patent Publication Number: US-2003235161-A1

Title: Communication control method and communication device

Description:
TECHNICAL FIELD  
       [0001] The present invention relates to a communication control method in a communications network wherein a control station controls asynchronous packet transmission of a terminal station in a polling system.  
       BACKGROUND ART  
       [0002] In a communications network composed of several terminal stations wherein communications are carried out mutually between individual terminal stations, one of them becomes a control station, the control station periodically transmits a synchronous packet to constitute a frame, and in the frame the individual terminal stations are controlled to transmit asynchronous packets by polling from the control station. At this time, the control station performs the polling to individual terminal stations usually in a fixed order or, when the polling priority is given to individual terminal stations, in an order based on that priority. In other words, the control station transmits polling packets to terminal stations in turn, and among the terminal stations that receives the polling packet, a terminal station having data to be transmitted can transmit it as asynchronous packets.  
       [0003] However, even when the control station performs polling to all terminal stations, individual terminal stations do not necessarily have transmittable data. Therefore, in order to give more opportunities of transmission to terminal stations which have data to be transmitted, a means of polling request is provided, which indicates from a terminal station to the control station that the terminal station has data to be transmitted, so that the control station transmits polling packets by priority to a terminal station that has made a polling request. This can shorten the waiting time for transmission of a terminal station, and further the control station can reduce the transmission of useless polling packets.  
       [0004] Meanwhile, among terminal stations of the communications network, terminal stations which are not in reception/transmission operation mode or have no transmittable data, are considered in a sleep mode under a restrictive operation state for a low power consumption.  
       [0005] A terminal station having sleep mode shifts from an ordinary operation mode to a sleep mode by notifying the control station of a sleep request. Even when the terminal station is in a sleep mode, it selectively receives synchronous packets the control station periodically transmits. Thus, when the control station has to release the sleep mode of the terminal station for some reason, it can make a sleep release request to the terminal station that is in the sleep mode by using this synchronous packet. When the terminal station that is in the sleep mode receives the sleep release request from the control station, it terminates the sleep mode and performs an ordinary operation.  
       [0006] In the communications network as described above, when one terminal station attempts to transmit an asynchronous packet to other terminal station, the source terminal station makes a polling request to the control station. Thereafter, when the source terminal station receives a polling packet for itself from the control station, it transmits, in response to that, an asynchronous packet to the destination terminal station.  
       [0007] However, when the destination terminal station is in a sleep mode, the asynchronous packet is not to be received at the destination terminal station even though being transmitted, resulting in the establishment of no communications. Therefore, the source terminal station, in this case, has to release the sleep mode of the destination terminal station in one way or another. In order to permit one terminal station to release a sleep mode of other terminal station, first, a means for judging whether the state of the destination terminal station is sleep mode or not, and further a means for calling on the control station to perform a sleep release of the destination terminal station are needed.  
       DISCLOSURE OF THE INVENTION  
       [0008] In order to solve the above problems, the present invention is featured in that: a station ID of a destination terminal station is included in a polling request message from a terminal station to a control station; the control station having received the polling request message confirms the operation state of the destination terminal station indicated by the station ID; polling is performed on a source terminal station having made the polling request only when the destination terminal station can perform communications; the control station makes a sleep release request to the destination terminal station when the control station confirms that the destination terminal station indicated by the station ID is in a sleep mode; and after confirming that the destination terminal station shifts to an active mode, the control station performs polling to the source terminal station having made the polling request when the destination terminal station can perform communications.  
       [0009] A communication control method according to the present invention in a wireless communications network having one control station and other terminal station(s), is featured in that: each station is identified by a uniquely assigned station ID; the terminal station is capable of receiving and transmitting an asynchronous packet; the control station controls the asynchronous packet transmission of the terminal station in a polling system; the terminal station has means for transmitting a polling request message to the control station; and the method comprises the step of including a station ID of a destination terminal station to which the terminal station attempts to transmit an asynchronous packet in the polling request message to be transmitted to the control station by the terminal station.  
       [0010] Further, a communication apparatus according to the present invention in a wireless communications network having one control station and other terminal stations, is featured in that: the control station controls asynchronous packet transmission of the terminal station in a polling system and accepts a polling request message from the terminal station; and the control station comprises polling request storage means for holding all the polling request messages indicating that polling packets are not yet transmitted, and communication reservation detection means for detecting whether a certain station ID is designated as any of destination terminal station IDs in the polling request message stored in the polling request storage means.  
       [0011] Furthermore, the present invention, in a wireless communications network having one control station and other terminal stations, is featured in that: the terminal station has two operation modes, that is active mode wherein ordinary operations are carried out and sleep mode wherein operations are limited, and further has means for making a sleep request to the control station; the control station that is the above mentioned communication apparatus, has means for making a response of sleep permission or sleep rejection to the sleep request from the terminal station; and the control station makes a response of sleep permission only when the station ID of the terminal station having made the sleep request is not detected by the communication reservation detection means.  
       [0012] Moreover, the present invention, in a wireless communications network having one control station and other terminal stations, is featured in that the control station has terminal station state storage means for storing active or sleep operation modes on all the terminal stations of the communications network.  
       [0013] Further, the present invention, in a wireless communications network having one control station and other terminal stations, is featured in that: the control station that receives a polling request message confirms operation mode of a terminal station indicated by a destination terminal station ID; and the control station judges that a terminal station having transmitted the polling request message can transmit a polling packet after confirming that the destination terminal station is not in a sleep mode.  
       [0014] Still further, the present invention, in a wireless communications network having one control station and other terminal stations, is featured in that: the control station that receives a polling request message transmits, when an operation mode of a terminal station indicated by a destination terminal station ID is sleep mode, a sleep release request to the terminal station being in a sleep mode; and the control station suspends the judgment for allowing a terminal station having transmitted the polling request to transmit a polling packet until confirming that the mode state of the destination terminal station shifts to an active mode upon reception of the sleep release request from the control station.  
       [0015] Furthermore, the present invention, in a wireless communications network having one control station and other terminal stations, is featured in that: the control station includes a station ID of a destination terminal station that is confirmed to be in an active mode in a polling packet to be transmitted to a terminal station having transmitted a polling request message.  
       [0016] This specification includes part or all of the contents as disclosed in the specification and/or drawings of Japanese Patent Application No. 2000-326741, which is a priority document of the present application. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0017]FIG. 1 is a schematic view of a communications network to which the present invention is applicable.  
     [0018]FIG. 2 is a block diagram of a frame on a wireless channel.  
     [0019]FIG. 3 is a block diagram of a frame start packet according to the present invention.  
     [0020]FIG. 4 is a block diagram of a terminal synchronous packet according to the present invention.  
     [0021]FIG. 5 is a block diagram of a control station according to the present invention.  
     [0022]FIG. 6 is a view illustrating a procedure for the case wherein the terminal station makes a sleep request.  
     [0023]FIG. 7 is a view illustrating a procedure for the case wherein the control station of the present invention receives the sleep request.  
     [0024]FIG. 8 is a view illustrating a procedure for the case wherein the control station performs a sleep release of the terminal station being in a sleep mode.  
     [0025]FIG. 9 is a view illustrating a procedure for the case wherein the terminal station being in a sleep mode receives the sleep release from the control station.  
     [0026]FIG. 10 is a view illustrating a procedure for the case wherein the terminal station transmits an asynchronous packet.  
     [0027]FIG. 11 is a view illustrating a procedure for the case wherein the control station receives a polling request from the terminal station.  
     [0028]FIG. 12 is a view illustrating a packet transmission procedure when an asynchronous packet recipient is in an active mode.  
     [0029]FIG. 13 is a view illustrating a packet transmission procedure when an asynchronous packet recipient is in a sleep mode. 
    
    
     BEST MODE FOR CARRYING OUT THE PRESENT INVENTION  
     [0030] The present invention will be described when it is applied to a communications network which wirelessly implements equivalent functions of the IEEE 1394 interface.  
     [0031]FIG. 1 is an embodiment of a communications network, to which the present invention is applied. There exist a plurality of wireless terminal stations  10 ,  11 ,  12 , and  13 , each of which is identified by a station ID. Among them the terminal station  10  works as a control station, and the other terminal stations have a sleep mode. The control station  10  manages frame timing, communication band, and operation modes of individual terminal stations, and controls polling operations over a wireless channel. When the terminal station  13  is in a sleep mode, the control station  10  and the terminal stations  11  and  12  can mutually communicate with each other through a wireless channel, but the terminal station  13  only receives in a fixed cycle a frame start packet transmitted by the control station  10 .  
     [0032]FIG. 2 shows a frame configuration existing over a wireless channel. The frame is time-divided into a management area  200  and a data area  201 . In the management area  200 , a frame start packet  202  that the control station  10  transmits to all the terminal stations  11 ,  12 , and  13  for each frame cycle, and terminal synchronous packets  203 ,  204 , and  205  that the terminal stations  11 ,  12 , and  13  transmit based on the information of the frame start packet are structured. The data area  201  is divided into isochronous slots  206 ,  207 , and  208  pertaining to a band reserved for isochronous packet transmission, and an asynchronous slot  209  for the remaining band. The isochronous slots  206 ,  207 , and  208  are bands reserved for use in transmitting mainly stream data, through which isochronous packets are transmitted. The asynchronous slot  209  is a band to perform communications by polling control. It is used to transmit polling packets  210 ,  211 ,  212 , and  213  whereby the control station  10  performs polling to the terminal stations  11 ,  12 , and  13 , and asynchronous packets  214  and  215  whereby the control station and the terminal stations  11 ,  12 , and  13  can transmit arbitrary data.  
     [0033]FIG. 3 shows the contents of the frame start packet  202 , which contains frame basic information  301 , a plurality of terminal station information pieces  302 ,  303 , and  304 , and data area information  305 . Further, each of the terminal station information pieces  302 ,  303 , and  304  has a station ID  306 , a terminal synchronous packet transmission instruction  307 , and a terminal synchronous state  308 . In the terminal station information pieces  302 ,  303 , and  304 , when a terminal station indicated by a station ID  306  operates in an active mode, the terminal synchronous packet transmission instruction  307  is set to ON, and also “transmission” is indicated in the terminal synchronous state  308 . When the terminal station indicated by the station ID  306  is in a sleep mode, the terminal synchronous packet transmission instruction  307  is set to OFF, and also “suspension” is indicated in the terminal synchronous state  308 . In the data area information  305 , the length of the data area  201  followed by the management area  200 , start positions of individual isochronous slots  206 ,  207 , and  208 , and the asynchronous slot  209  are indicated. The terminal stations  11 ,  12 , and  13  which have received the frame start packet  202 , if terminal station information pieces  302 ,  303 , and  304  containing the indication of their own station ID  306  are provided, refer to them. When the terminal synchronous frame transmission instruction  307  is established, the terminal stations transmit the terminal synchronous packets  203 ,  204 , and  205  to the management area  200  at a predetermined timing.  
     [0034]FIG. 4 shows the contents of the terminal synchronous packets  203 ,  204 , and  205 , which contain a sleep request  401 , a polling request  402 , a destination terminal station ID  403 , terminal station ability information  404 , and reception quality  405 . When the terminal stations  11 ,  12 , and  13  make the shift to the sleep mode, the sleep request  401  is set to ON and the transmission is carried out. Also, when the terminal stations  11 ,  12 , and  13  make a polling request to the control station  10 , the polling request  402  is set to ON and further the terminal synchronous packets  203 ,  204 , and  205  provided with the destination terminal station ID  403  are transmitted.  
     [0035]FIG. 5 shows a configuration of a communication device, according to the present invention, which operates as the control station  10 . The communication device comprises a packet reception section  501 , a packet transmission section  502 , a polling list  503  as a polling request storage means, a station ID detection circuit  504  as an ID detection means, registered terminal station information  505  as a means for storing terminal station states, and a sleep mode management section  506  as a means for making a response regarding sleep permission or sleep rejection to the sleep request from the terminal station. The packet reception section  501 , when receiving the terminal synchronous packets  203 ,  204 , and  205  having polling requests  402  set in ON, generates a transmitter terminal station ID and destination terminal station ID of the polling request as a pair of polling request information pieces. Subsequently, the packet reception unit  501  confirms the operation mode of the terminal station indicated by the destination terminal station ID in accordance with the registered terminal station information  505 . When the terminal station is in an active mode, the polling request message is stored in the polling list  503  as clear-to-send. When the terminal station is in a sleep mode, the message is stored as pending.  
     [0036] When the sleep request  401  of the received terminal synchronous packet  205  is set to ON or the terminal synchronous packet  205  indicating that the terminal station  13  makes a shift from a sleep mode to an active mode is received, the ID of that terminal station is notified to the sleep mode management section  506 . The sleep mode management section  506  refers to the polling request messages stored as pending in the polling list  503  and instructs the packet transmission section  502  to release the sleep mode of the terminal station that is a recipient of the polling request message and in a sleep mode. Further, the sleep mode management section searches, by the station ID the detection circuit  504 , destination terminal station IDs of the polling list  503  for an ID of terminal station that has made a sleep request. When the terminal station ID is not detected, the operation mode of the terminal station corresponding to the terminal station ID in the registered terminal station information  505  is stored as in a sleep mode. When the terminal station ID is detected, the sleep request is neglected. Furthermore, the sleep mode management section  506  searches, by the station ID detection circuit  504 , the destination terminal station IDs in the polling list  503  for the station ID of the terminal station  13  that is released from the sleep mode. When the detected polling request is pending, that polling request is changed to clear-to-send. While transmitting the frame start packet  202 , the packet transmission section  502  generates and transmits the terminal station information pieces  302 ,  303 , and  304  in accordance with the content of the registered terminal station information  505  and the instruction of the sleep mode management section  506 . Also, in the asynchronous slot  209  region of the frame, the packet transmission section  502  refers to clear-to-send polling request messages of the polling list  503 , and generates and transmits the polling packets  210 ,  211 ,  212 , and  213 , each containing a destination terminal station ID corresponding to a terminal station indicated by the transmitter terminal station ID. Then, the processed polling request message is deleted from the polling list  503 .  
     [0037]FIG. 6 shows a sleep request procedure wherein a terminal station makes a shift from an active mode to a sleep mode. When the terminal station  11  shifting to a sleep mode transmits the terminal synchronous packet  203  from itself, it transmits the packet with the sleep request  401  set in ON (S 601 ). Thereafter, when the terminal station  11  monitors the frame start packet  202  from the control station  10  (S 602 ), and detects that the terminal synchronous state  308  in the terminal station information  302  of itself is set in the suspension state (S 603 ), the control station  10  is assumed to accept the sleep request and then the terminal station  11  makes a shift to a sleep mode.  
     [0038]FIG. 7 shows a procedure undertaken by the control station  10  in response to the sleep request of FIG. 6. The control station  10  searches the destination terminal station IDs of the polling pending memory for a station ID of the terminal station  11  that has transmitted the sleep request  401  (S 701 ). When it is not detected, the sleep request is accepted and it is stored in the registered terminal station information that the terminal station  11  that has made the sleep request is in a sleep mode (S 702 ). By this, the terminal synchronous packet transmission instruction  307  of the terminal station information  302  corresponding to the terminal station  11  is set to OFF and the terminal synchronous state  308  is set in the suspension state in subsequent frame start packet  202 . When being detected, the sleep request is neglected (S 703 ).  
     [0039]FIG. 8 is a sleep release procedure of the terminal station  13  by the control station  10 . The control station  10  transmits, when sleep release of the terminal station  13  being in a sleep mode is required, the frame start packet  202  wherein the terminal synchronous state  308  of terminal station information  304  of the terminal station to be sleep-released is set in the suspension state and the terminal synchronous packet transmission instruction  307  is set to ON (S 801 ). This setting is kept until the terminal synchronous packet  205  from the terminal station  13  to be sleep-released is received (S 802 ). When the terminal synchronous packet  205  of interest is received, the sleep release of the terminal station  13  is judged to be completed and the state of the terminal station is stored as an active mode in the registered terminal station information  505  (S 803 ).  
     [0040]FIG. 9 shows a procedure for receiving the sleep release at the side of the terminal station  13  in contrast to FIG. 8. When the terminal station  13  being in a sleep mode detects that the terminal synchronous packet transmission instruction  307  is set to ON in the terminal station information  304  of itself in the received frame start packet  202  (S 901 ), the terminal station  13  makes a shift from a sleep mode to an active mode and starts the transmission of the terminal synchronous packet  205  (S 902 ).  
     [0041]FIG. 10 shows a transmission procedure of the asynchronous packet  215  by the terminal station  12 . When the terminal station  12  has to transmit the asynchronous packet  215 , in the terminal synchronous packet  204  to be transmitted from itself, the terminal ID  403  of a destination terminal station and the polling request  402  ON are set up, and then the transmission is carried out (S 1001 ). Thereafter, the terminal station  12  waits for reception of the polling packet  211  for itself from the terminal station  10 , of the asynchronous slot  209  (S 1002 ). Upon the reception, the asynchronous packet  215  is transmitted to the destination terminal station (S 1003 ). When the polling packet in the asynchronous slot  209  is not received (S 1002 ), the polling request is repeated at a time of transmitting a subsequent terminal synchronous packet.  
     [0042]FIG. 11 shows a polling procedure by the control station  10  in contrast to FIG. 10. In the case where the control station receives the terminal synchronous packet  204  from the terminal station  12  (S 1101 ) and the polling request  402  is set to ON (S 1102 ), the station ID of the terminal station  12  having made the polling request and a destination terminal station ID are stored as polling request information in the polling pending memory (S 1103 ), and then the registered terminal station information  505  is searched to determine whether the recipient terminal ID is stored as in a sleep mode (S 1104 ). When the destination terminal station is in a sleep mode, the control station  10  makes a sleep release (S 1105 ). This sleep release is, in fact, carried out in accordance with the procedure shown in FIG. 8. When the destination terminal station is not in a sleep mode or the sleep release is completed, polling request information is added to the polling list  503  (S 1106 ) and deleted from the polling pending memory (S 1107 ). The control station  10  sequentially transmits polling packets in the asynchronous slot  209  region in accordance with polling request information stored in the polling list  503  (S 1108 ).  
     [0043]FIG. 12 shows a packet transmission procedure over a wireless channel in the case where there are a control station  10 , terminal stations (ID:  1 ) and (ID:  2 ), and the terminal station (ID:  1 ) transmits asynchronous packets  214  and  215  to the terminal station (ID:  2 ). At this time, it is stored in the registered terminal station information  505  of the control station  10  that the terminal station (ID:  2 ) is in an active mode. The terminal station (ID:  1 ) sets the polling request  402  in ON and “ID : 2 ” as a destination terminal station in the terminal synchronous packet  1201  to be transmitted from itself, and then transmits the packet. When the control station receives the terminal synchronous packet  1201 , it confirms the state of the destination terminal station (ID:  2 ) by referring to the registered terminal station information  505  because the polling request  402  is ON. Then, the terminal station is in an active mode, and thus it is judged that communication is possible and the polling request information is stored as clear-to-send in the polling list  503 . Later, the control station  10  refers to the polling list  503  in the asynchronous slot  209  region in the frame, and in accordance with the polling request information  402  of the clear-to-send terminal synchronous packet  1201 , the control station transmits a polling packet  1202  wherein the destination terminal station ID : 2  is set to the terminal station (ID : 1 ). Immediately after the terminal station (ID:  1 ) receives the polling packet  1202 , it transmits the asynchronous packet  1203  to the terminal station (ID:  2 ).  
     [0044]FIG. 13 shows a communication procedure wherein the terminal station (ID:  1 ) transmits the asynchronous packets  214  and  215  to the terminal station (ID:  3 ), when there are a control station  10 , a terminal station (ID:  1 ), and a terminal station (ID:  3 ) and the terminal station (ID:  3 ) is in a sleep mode. At this time, it is stored in the registered terminal station information  505  of the control station  10  that the terminal station (ID:  3 ) is in a sleep mode. The terminal station (ID:  1 ) sets the polling request  402  to the ON state and ID:  3  as a destination terminal station in a terminal synchronous packet  1301  to be transmitted by itself, and then transmits the terminal synchronous packet. When the control station  10  receives the terminal synchronous packet  1301  from the terminal station (ID:  1 ), the control station confirms the state of the terminal station (ID:  3 ) as a recipient by referring to the registered terminal station information  505  since the polling request  402  is set to ON. Then, when it judges the terminal station to be in a sleep mode, it stores the polling request information in the polling list  503  as pending. Subsequently, in order to perform sleep release of the terminal station (ID:  3 ), the frame start packet  1302  is transmitted, containing terminal station information corresponding to the terminal station (ID:  3 ), which has that the terminal synchronous state  308  is set in the suspension state and the terminal synchronous packet transmission instruction  307  is set to ON. When the terminal station (ID:  3 ) in a sleep mode receives the frame start packet  1302  and the terminal synchronous packet transmission instruction  307  is set to ON in the terminal station information for itself, the terminal station shifts to an active mode and transmits the terminal synchronous packet  1303 . The control station judges that the terminal station (ID:  3 ) has shifted to an active mode when it receives the terminal synchronous packet  1303 . Then, the control station changes the mode of the terminal station (ID:  3 ) in the registered terminal station information  505  into active mode and stores it, thereby judging that the terminal station (ID:  3 ) can perform communications. The polling request information of the terminal synchronous packet  1301  in the polling list  503  is changed from pending to clear-to-send. Later, the control station refers to the polling list  503  in the asynchronous slot region of the frame, and transmits to the terminal station (ID:  1 ) the polling packet  1304  wherein ID:  3  is set as a destination terminal station in accordance with the polling request information of the clear-to-send terminal synchronous packet  1301 . Immediately after receiving the polling packet  1304 , the terminal station (ID:  1 ) transmits the asynchronous packet  1305  for the terminal station (ID:  3 ).  
     [0045] According to the present invention, a terminal station that attempts to transmit an asynchronous packet includes a destination terminal station ID in a polling request to a control station, thereby enabling the control station to control the operation mode of the destination terminal station if necessary. Thus, it is not necessary for the terminal station at the polling request side to judge the operation mode of the destination terminal station, and the transmission processing of an asynchronous packet can be always carried out by an identical procedure, thereby making the processing of the terminal station simple.  
     [0046] Further, the present invention can automatically prevent the transmission of an asynchronous packet for a terminal station in a sleep mode.  
     [0047] Industrial Applicability  
     [0048] The present invention, in the case where one terminal station attempts to transmit an asynchronous packet to other terminal station, can provide a communication control method that enables the source terminal station to perform communications, even when the destination terminal station is in a sleep mode, without the necessity of any special processing.