Patent Document

The present application is based on Japanese priority application No. 2006-038663 filed Feb. 15, 2006, the entire contents of which are hereby incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a communication method, a communication system, and a communication apparatus and particularly to a communication method, a communication system, and a communication apparatus in a communication system having a base station for transmitting a beacon and a terminal for performing communication with the base station. 
     2. Description of the Related Art 
     In an electronic shelf label system, an electronic shelf label having rewritable display information is registered in a host computer and then attached to a product shelf. It is possible to rewrite the display information of the electronic shelf label from the host computer by accessing the electronic shelf label through an access point (refer to Patent Documents 1 to 5). 
     Such an electronic shelf label system employs a communication method such as IEEE 802.15.4 or the like, in which a beacon periodically transmitted by a coordinator is used as a standard and each node performs transmission and reception processing. In this communication method, when the coordinator is to transmit data to a certain node, an ID of the node is inserted into a beacon. 
     Each node that receives a beacon return a response when the ID included in the beacon corresponds to its own ID. When the ID included in the beacon does not correspond to its own ID, the node ends reception processing and enters a sleep mode. 
     Patent Document 1: Japanese Laid-Open Patent Application No. 2002-304673 
     Patent Document 2: Japanese Laid-Open Patent Application No. 2005-99888 
     Patent Document 3: Japanese Laid-Open Patent Application No. 2002-109177 
     Patent Document 4: Japanese Laid-Open Patent Application No. 2004-265196 
     Patent Document 5: Japanese Laid-Open Patent Application No. 9-138892 
     In a conventional communication method, in proportion as a period of time from beacon reception to sleep mode based on a judgment that the received beacon is not addressed to the node is reduced, lower power consumption is realized. However, when the number of nodes is increased and the number of bits of ID is increased, this poses problems in that power consumption is increased, for example. 
     SUMMARY OF THE INVENTION 
     It is a general object of the present invention to provide an improved and useful communication method, communication system, and communication apparatus in which the above-mentioned problems are eliminated. 
     A more specific object of the present invention is to provide a communication method, communication system, and communication apparatus that can realize low power consumption. 
     According to one aspect of the present invention, there is provided a communication method of a communication system having a base station for transmitting a beacon and a terminal for receiving the beacon transmitted from the base station and performing communication with the base station, the communication method including the steps of: transmitting the beacon by the base station, the beacon being made of a plurality of sub-beacons including an ID for identifying the terminal; and stopping processing for communication with the base station by the terminal when at least one of the plural sub-beacons has a portion that does not match an ID of the terminal. 
     According to another aspect of the present invention, in the communication method of a communication system, the terminal shifts an operation status of the terminal to a power saving status when at least one of the plural sub-beacons has a portion that does not match the ID of the terminal. 
     According to another aspect of the present invention, there is provided a communication system including: a base station for transmitting a beacon; and a terminal for receiving the beacon transmitted from the base station and performing communication with the base station, wherein the base station divides the beacon into a plurality of sub-beacons including an ID for identifying the terminal and transmits the plural sub-beacons, and the terminal stops processing for communication with the base station when at least one of the plural sub-beacons has a portion that does not match an ID of the terminal. 
     According to another aspect of the present invention, in the communication system, the terminal shifts an operation status of the terminal to a power saving status when at least one of the plural sub-beacons has a portion that does not match the ID of the terminal. 
     According to another aspect of the present invention, there is provided a communication apparatus for transmitting a beacon and receiving a response to the beacon from a terminal, the communication apparatus including: a communication unit transmitting the beacon and receiving the response from the terminal; and a process unit generating the beacon from a plurality of sub-beacons including an ID for identifying the terminal and transmitting the beacon from the communication unit. 
     According to another aspect of the present invention, there is provided a communication apparatus for receiving a beacon made of a plurality of sub-beacons including an ID from a base station and returning a response to the base station, the communication apparatus including: a communication unit receiving the beacon from the base station and transmitting the response to the base station; and a process unit shifting an operation status of the communication apparatus to a power saving status when at least one of the plural sub-beacons has a portion that does not match the ID of the communication apparatus. 
     According to the present invention, a beacon made of plural sub-beacons including an ID for identifying a terminal is transmitted from a base station. And the terminal stops communication with the base station when at least one of the plural sub-beacons has a portion that does not match an ID of the terminal. In accordance with this, when a response request is not intended for the terminal, the terminal stops communication processing even when the beacon is being transmitted, so that it is possible to reduce power consumption without wasting unnecessary power. 
     Other objects, features and advantage of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a configuration diagram of an example of a system according to the present invention; 
         FIG. 2  is a block diagram of a relay device; 
         FIG. 3  is a block diagram of an electronic shelf label; 
         FIG. 4  is a process flow chart of a relay device; 
         FIG. 5  is a diagram illustrating a call operation by a relay device; 
         FIG. 6  is a diagram illustrating an operation of an example according to the present invention; and 
         FIG. 7  is a diagram showing a structure of a beacon in an example according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     [System Configuration] 
       FIG. 1  is a configuration diagram of an example of a system according to the present invention. 
     An electronic shelf label system  100  according to the example includes a management device  111 , a relay device  112 , and an electronic shelf label  113 . The electronic shelf label system  100  has the relay device  112  for relaying communication between the electronic shelf label  113  and the management device  111  managing the electronic shelf label  113  and manages the electronic shelf label  113  attached to a product shelf. 
     Examples of a radio communication method between the relay device  112  and the electronic shelf label  113  include IEEE 802.15.4 or the like, in which a beacon periodically transmitted by the relay device  112  is used as a standard and each electronic shelf label  113  performs transmission and reception processing. 
     [Relay Device] 
       FIG. 2  is a block diagram of the relay device  112 . 
     The relay device  112  includes a communication unit  141 , a process unit  142 , a storage unit  143 , a radio communication unit  144 , a power supply circuit  145 , and a battery  146 . 
     The communication unit  141  is connected to the management device  111  via a network such as LAN, WAN, a dedicated line, or the like. The communication unit  141  performs communication with the management device  111 . 
     The process unit  142  includes a microcomputer and the like and performs processing for relaying communication, for example, between the management device  111  and the electronic shelf label  113  based on a program installed on the storage unit  143 . 
     The storage unit  143  includes a rewritable non-volatile memory such as EEPROM, for example, ROM, RAM, and the like. In the storage unit  143 , information  131  on electronic shelf labels within a communication range is stored in addition to a communication control program. 
     The radio communication unit  144  performs radio communication with the electronic shelf label  113 . 
     The power supply circuit  145  is connected to an alternating-current power supply such as an external commercial power supply. The power supply circuit  145  converts the connected alternating-current power into a direct-current voltage and supplies the direct-current voltage as a driving voltage to the communication unit  141 , the process unit  142 , the storage unit  143 , and the radio communication unit  144 . 
     The battery  146  includes a Ni—Cd battery, a lithium ion battery, an electric double layer capacitor, or the like as a chargeable battery unit. The battery  146  is charged from the direct-current voltage generated in the power supply circuit  145  and supplies electric power for driving the communication unit  141 , the process unit  142 , the storage unit  143 , and the radio communication unit  144  for a certain period of time so as to execute an end program when alternating-current power is cut. 
     [Electronic Shelf Label] 
       FIG. 3  is a block diagram of the electronic shelf label  113 . 
     The electronic shelf label  113  includes a radio communication unit  151 , a process unit  152 , a storage unit  153 , a display device  154 , and a battery  155 . 
     The radio communication unit  151  performs radio communication with the relay device  112 . 
     The process unit  152  includes CPU, for example. The process unit  152  controls communication with the relay device  112  and also controls display of the display device  154  based on a program stored in the storage unit  153 . 
     The storage unit  153  includes a rewritable non-volatile storage device such as EEPROM, for example. In the storage unit  153 , a program executed in the process unit  152  is installed and shelf label IDs and product codes are stored. Some of the shelf label IDs and product codes are registered in advance and can be changed by the relay device  112 . 
     The display device  154  includes LCD, an EL panel, electronic paper, or the like. The display device  154  displays product names, product codes, prices and the like. 
     The battery  155  includes a small battery and supplies electric power for driving the radio communication unit  151 , the process unit  152 , the storage unit  153 , and the display device  154 . 
     [Operation] 
     First, a beacon transmission operation of the relay device  112  is described. 
       FIG. 4  is a process flow chart of the relay device  112 . 
     When a request for calling the electronic shelf label  113  is issued in step S 1 - 1 , the process unit  142  of the relay device  112  obtains an ID of a calling destination in step S 1 - 2 . Next, the process unit  142  generates a beacon based on the obtained ID of the calling destination in step S 1 - 3 . 
     The process unit  142  transmits the generated beacon from radio communication unit  144  in step S 1 - 4 . The process unit  142  transmits the beacon at predetermined times in step S 1 - 5  and ends the calling. 
       FIG. 5  is a diagram illustrating a call operation by the relay device  112 . 
     A call signal BCN for calling by the relay device  112  is made of plural beacons bcn  1  to bcn  5  as shown in  FIG. 5 . The plural beacons bcn  1  to bcn  5  are made of the same signal. Each of the plural beacons bcn  1  to bcn  5  is made of plural sub-beacons sbc  1  to sbc  6 . The ID of the calling destination is divided into plural sub-beacons sbc  1  to sbc  6 . 
     Next, a response operation in the electronic shelf label  113  is described. 
       FIG. 6  is a process flow chart of a response operation of the electronic shelf label  113 . 
     When the process unit  152  of the electronic shelf label  113  wakes up in step S 2 - 1 , namely, shifts to a normal operation status, first, the process unit  152  determines whether a beacon is received from the relay device  112  in step S 2 - 2 . 
     When a sub-beacon is received in step S 2 - 2 , the process unit  152  extracts a divided ID allocated to the received sub-beacon in step S 2 - 3 . 
     The process unit  152  determines whether the divided ID matches a corresponding portion of own ID stored in the storage unit  153  in step S 2 - 4 . When the divided ID does not match the corresponding portion of own ID in step S 2 - 4 , it is possible to determine that calling is not intended for the electronic shelf label  113 , so that the process unit  152  shifts an operation status to a sleep status so as to stop operations other than a necessary portion. 
     Further, when the divided ID matches the corresponding portion of own ID in step S 2 - 4 , the process unit  152  determines whether all sub beacons are received in step S 2 - 5 . When all sub beacons are yet to be received in step S 2 - 5 , the process returns to step S 2 - 2 , where the process unit  152  continues the reception of sub-beacons from the relay device  112 . 
     Further, when all sub-beacons are received in step S 2 - 5 , the process unit  152  transmits information as a response in accordance with calling from the relay device  112  in a predetermined communication slot in step S 2 - 6 . After the response is transmitted, the process unit  152  shifts the operation status to a sleep status in step S 2 - 7 . 
     In the following, a more specific example is considered based on a case where one beacon is divided into six sub-beacons as shown in  FIG. 5 . One beacon is capable of storing a 64-bit ID. One sub-beacon is capable of storing an ID obtained by dividing the 64-bit ID into an 8-bit ID. 
     The process unit  152  of the electronic shelf label  113  determines whether own ID is included upon each reception of sub-beacons. The relay device  112  repeatedly transmits the beacon made of six sub-beacons. In  FIG. 5 , the beacon is transmitted five times. 
     In this manner, since the same beacon is transmitted five times, it is possible to readily receive the beacon even when the electronic shelf label  113  has poor accuracy of wake-up timing. 
     Next, a method for determining matching/mismatching in the electronic shelf label  113  is described in detail. 
       FIG. 7  is a diagram showing a structure of a beacon in an example according to the present invention. 
     In the following, X indicates a bit column that is not received. { } indicates matching and [ ] indicates mismatching. 
     Description below is based on a case where a beacon as shown in  FIG. 7  is transmitted from the relay device  112  and the electronic shelf label  113  starts reception from a first sub-beacon sbc  2 . 
     The process unit  152  wakes up using a timer at a beacon transfer time. Thereafter, the process unit  152  receives the sub-beacon sbc  2  and compares it with eight sets of call ID information. As a result, two portions of call ID information are matched. 
     Identification number of the electronic shelf label  113 :
     1111101:{1100001}:1100111:1101001:1101101:011000   

     Call ID information # 5 :
     XXXXXXX:{1100001}:XXXXXXX:XXXXXXX:XXXXXXX:XXXXXX   

     Call ID information # 7 :
     XXXXXXX:{1100001}:XXXXXXX:XXXXXXX:XXXXXXX:XXXXXX   

     The process unit  152  receives the sub-beacon sbc  3  and compares it with two sets of call ID information # 5  and # 7 . As a result, one portion of call ID information is matched. 
     Identification number of the electronic shelf label  113 :
     1111101:{1100001}:1100111:1101001:1101101:011000   

     Call ID information # 5 :
     XXXXXXX:{1100001}:{1100111}:XXXXXXX:XXXXXXX:XXXXXX   

     Call ID information # 7 :
     XXXXXXX:{1100001}:[1100001]:XXXXXXX:XXXXXXX:XXXXXX   

     The process unit  152  receives the sub-beacon sbc  4  and compares it with one set of call ID information # 5 . As a result, no portion is matched. 
     Identification number of the electronic shelf label  113 :
     1111101:{1100001}:1100111:1101001:1101101:011000   

     Call ID information # 5 :
     XXXXXXX:{1100001}:{110011}:[1100001]:XXXXXXX:XXXXXX   

     In this case, the process unit  152  determines that the calling is not intended for the electronic shelf label  113  and sets the timer such that the process unit  152  wakes up at the next beacon transfer time, and then the process unit  152  enters a sleep status. 
     Next, a case where the electronic shelf label  113  starts reception from the sub-beacon sbc  3  is described. 
     The process unit  152  wakes up at the beacon transfer time. Thereafter, the process unit  152  receives the sub-beacon sbc  3  and compares it with eight sets of call ID information. As a result, one portion of call ID information is matched. 
     Identification number of the electronic shelf label  113 :
     0000000:0000000:0000000:0000000:0000000:000000   

     Call ID information # 1 :
     XXXXXXX:XXXXXXX:{0000000}:XXXXXXX:XXXXXXX:XXXXXX   

     The process unit  152  receives the sub-beacon sbc  4  and compares it with one set of call ID information # 1 . As a result, the portion is matched. 
     Identification number of the electronic shelf label  113 :
     0000000:0000000:0000000:0000000:0000000:000000   

     Call ID information # 1 :
     XXXXXXX:XXXXXXX:{0000000}:{0000000}: XXXXXXX:XXXXXX   

     The process unit  152  receives the sub-beacon sbc  5  and compares it with one set of call ID information # 1 . As a result, the portion is matched. 
     Identification number of the electronic shelf label  113 :
     0000000:0000000:0000000:0000000:0000000:000000   

     Call ID information # 1 :
     XXXXXXX:XXXXXXX:{0000000}:{0000000}:{0000000}:XXXXXX   

     The process unit  152  receives the sub-beacon sbc  6  and compares it with one set of call ID information # 1 . As a result, the portion is matched. 
     Identification number of the electronic shelf label  113 :
     0000000:0000000:0000000:0000000:0000000:000000   

     Call ID information # 1 :
     XXXXXXX:XXXXXXX:{0000000}:{0000000}:{0000000}:{000000}   

     The process unit  152  receives the sub-beacon sbc  1  and compares it with one set of call ID information # 1 . As a result, the portion is matched. 
     Identification number of the electronic shelf label  113 :
     0000000:0000000:0000000:0000000:0000000:000000   

     Call ID information # 1 :
     {0000000}:XXXXXXX:{0000000}:{0000000}:{0000000}:{000000}   

     The process unit  152  receives the sub-beacon sbc  2  and compares it with one set of call ID information # 1 . As a result, the portion is matched. 
     Identification number of the electronic shelf label  113 :
     0000000:0000000:0000000:0000000:0000000:000000   

     Call ID information # 1 :
     {0000000}:{0000000}:{0000000}:{0000000}:{0000000}:{000000}   

     In accordance with this, the process unit  152  receives six different sub-beacons and the identification number of the shelf label is included, so that the process unit  152  determines that the electronic shelf label  113  is called. 
     The ID of the electronic shelf label  113  is stored in the call ID information # 1 , so that communication with a base station is performed in a communication slot in a frame following the beacon. Thus, the process unit  152  enters a sleep status until the next communication slot time. 
     The process unit  152  of the electronic shelf label  113  wakes up at the communication slot time and performs communication with the relay device  112 . When the communication with the relay device  112  is ended, the process unit  152  of the electronic shelf label  113  enters a sleep status until the next beacon transfer time. 
     [Effects] 
     According to the present example, the beacon is transmitted as plural sub-beacons, so that it is not necessary to receive all beacons when the electronic shelf label is not called. Accordingly, it is possible to reduce a time for checking radio waves, namely, a length of time in which a communication circuit is switched on for reception, thereby realizing low power consumption. 
     Further, since the same beacon is repeatedly transmitted, it is possible to readily receive the beacon even when the electronic shelf label has poor accuracy of wake-up timing. Accordingly, it is possible to use an inexpensive element as a timer for waking-up in synchronization with the beacon and to manufacture the electronic shelf label  113  in an inexpensive manner. 
     According to the present example, the electronic shelf label  113  is capable of reducing an unnecessary reception period, so that it is possible to realize low power consumption. 
     The present invention is not limited to the specifically disclosed embodiment, and variations and modifications may be made without departing from the scope of the present invention.

Technology Category: 4