COMMUNICATION DEVICE, COMMUNICATION SYSTEM, AND CONTROL METHOD

Abstract

One aspect of the present invention is a communication device comprising: a sleep control unit that repeatedly executes an active mode and a sleep mode; a storage unit that stores link information required for linkup with an opposing device; and a communication control unit that, when a transition from the sleep mode to the active mode has occurred, communicates with the opposing device by using the link information stored in the storage unit.

Description

[Technical Field]

[0001] The present invention relates to a communication device, a communication system, and a control method. [Background technology]

[0002] It is known that the power consumed by user-side communication terminals (ONUs (Optical Network Units)) used in wired broadband services in Japan accounts for 60% of the power consumed by the entire network (see Non-Patent Document 1).

[0003] Against this background, to save power, communication devices such as ONUs are equipped with a sleep control function that repeatedly switches between active mode and sleep mode, as shown in Fig. 9. Even in sleep mode, the link with the other device is maintained by periodically switching to active mode for a short period of time, as shown in Fig. 10. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] https: / / journal.ntt.co.jp / backnumber2 / 1401 / files / jn201401027.pdf Summary of the Invention [Problem to be solved by the invention]

[0005] If the periodic short-term active mode execution during sleep mode operation is reduced in order to enhance the power saving effect, the link cannot be maintained in an established state, and a link down situation becomes unavoidable. In addition, there is a problem that the control signal communication to re-establish the link generates power consumption unrelated to the main signal communication.

[0006] In view of the above circumstances, an object of the present invention is to provide a technique for further reducing power consumption. [Means for solving the problem]

[0007] One aspect of the present invention is a communication device comprising: a sleep control unit that repeatedly executes active mode and sleep mode; a memory unit that stores link information necessary for linking up with a counterpart device; and a communication control unit that communicates with the counterpart device using the link information stored in the memory unit when transitioning from sleep mode to active mode.

[0008] One aspect of the present invention is a communication system including a first communication device, a second communication device connected to the first communication device, and multiple other communication devices connected to the second communication device, wherein the first communication device has a first memory unit that stores link information necessary for linking up with the second communication device, and the second communication device has a sleep control unit that repeatedly executes active mode and sleep mode, a second memory unit that stores link information necessary for linking up with the first communication device and link information necessary for linking up with each of the multiple other communication devices, and a communication control unit that communicates with the first communication device or the multiple other communication devices using the link information stored in the second memory unit when transitioning from sleep mode to active mode.

[0009] One aspect of the present invention is a control method for a communication device having a memory unit, which repeatedly executes active mode and sleep mode, stores link information required for linking up with a counterpart device in the memory unit, and communicates with the counterpart device using the link information stored in the memory unit when transitioning from sleep mode to active mode.

[0010] One aspect of the present invention is a control method for a communication system including a first communication device having a first memory unit, a second communication device connected to the first communication device and having a second memory unit, and a plurality of other communication devices connected to the second communication device, wherein the first communication device stores link information required for linking up with the second communication device in the first memory unit, and communicates with the second communication device using the link information stored in the first memory unit, and the second communication device repeatedly executes active mode and sleep mode, stores link information required for linking up with the first communication device and link information required for linking up with each of the plurality of other communication devices in the second memory unit, and when transitioning from sleep mode to active mode, communicates with the first communication device or the plurality of other communication devices using the link information stored in the second memory unit. [Effects of the Invention]

[0011] The present invention makes it possible to further reduce power consumption. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram illustrating an example of a configuration of a communication system. [Figure 2A] FIG. 10 is a sequence diagram showing the flow of processing up to storing link information. [Figure 2B] 10 is a sequence diagram showing a process when a communication device 100A performing sleep control starts an active mode and performs communication. FIG. [Figure 2C] FIG. 10 is a sequence diagram showing a process when a communication device 100B that does not perform sleep control performs communication while a communication device 100A is in sleep mode. [Figure 3] FIG. 1 is a block diagram illustrating an example of a configuration of a communication system. [Figure 4] FIG. 10 is a sequence diagram showing a processing flow when performing link-up. [Figure 5] FIG. 1 is a block diagram illustrating an example of a configuration of a communication system. [Figure 6] FIG. 10 is a diagram for explaining an example of operation of a removable storage unit. [Figure 7] FIG. 10 is a diagram for explaining method A. [Figure 8] FIG. 10 is a diagram for explaining method B. [Figure 9] FIG. 1 is a diagram for explaining a conventional technique. [Figure 10] FIG. 1 is a diagram for explaining a conventional technique. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings. (First embodiment) FIG. 1 is a block diagram showing an example of the configuration of a communication system 10 according to a first embodiment. The communication system 10 is made up of communication devices 100A and 100B. The communication devices 100A and 100B are, for example, ONUs (Optical Network Units). In the first embodiment, the communication device 100A is an example of a communication device of the present invention. The communication device 100B is an example of a counterpart device. The communication devices 100A and 100B are connected by wire or wirelessly and perform bidirectional communication. In each of the embodiments described below, the communication devices are also connected by wire or wirelessly.

[0014] The communication device 100A has a sleep control function that repeatedly executes an active mode and a sleep mode, and consumes less power in the sleep mode than in the active mode.

[0015] The communication device 100A is composed of a control unit 110A, a communication interface 120A, and a storage unit 130A. The control unit 110A controls the entire communication device 100A. The control unit 110A includes a sleep control unit 111A and a communication control unit 112A. The sleep control unit 111A repeatedly switches between active mode and sleep mode. The communication control unit 112A controls overall communication with the other device. For example, when the communication control unit 112A transitions from sleep mode to active mode, it communicates with the other device (communication device 100B in this embodiment) using link information (described below) stored in the storage unit 130A.

[0016] The storage unit 130A stores link information required for linking up with the opposing device. Each storage unit described below, including the storage unit 130A, is configured with a non-volatile memory such as a flash memory. The storage unit 130A may be provided either non-detachably or detachably with respect to the communication device 100A. When the storage unit 130A is provided detachably, the storage unit 130A may be a USB (Universal Serial Bus) memory, a SIM (Subscriber Identity Module) dongle, or the like.

[0017] Furthermore, although each storage unit described below stores link information as described above, the method of storing link information is not limited to the method of storing link information obtained by negotiation between communication devices described below. Methods of storing link information include, for example, a method in which a field worker removes a storage unit from a communication device, stores the link information in the storage unit, and then re-installs the storage unit with the stored link information in the communication device, or a method in which the link information is stored in the storage unit remotely using a communication line.

[0018] The link information is a value acquired through negotiation between communication devices before the start of main signal communication, and is information necessary for link-up. Therefore, the link information is determined according to the communication protocol that controls communication with the opposite device.

[0019] In the first embodiment, communication with the communication devices 100A and 100B is controlled by TCP (Transmission Control Protocol) / IP (Internet Protocol). IP corresponds to Layer 3 in the OSI reference model. In this case, the storage unit 130A stores the IP address of the communication device 100A, the IP address of the communication device 100B, the MAC (Media Access Control) address of the communication device 100B, the communication mode, and the communication speed.

[0020] The communication device 100B is composed of a control unit 110B, a communication interface 120B, and a storage unit 130B. The control unit 110B controls the entire communication device 100B. The control unit 110B includes a communication control unit 112B. The communication control unit 112B controls overall communication with the communication device 100A. For example, when communicating with the communication device 100A, the communication control unit 112B communicates with the communication device 100A using link information stored in the storage unit 130B. The storage unit 130B stores link information necessary for linking up with an opposing device. The storage unit 130B may be provided either non-detachably or detachably with respect to the communication device 100B. When the storage unit 130A is provided detachably, the storage unit 130A may be a USB memory, a SIM dongle, or the like.

[0021] The storage unit 130B stores the IP address of the communication device 100B, the IP address of the communication device 100A, the MAC address of the communication device 100A, the communication mode, and the communication speed.

[0022] As described above, communication device 100B has a configuration in which the sleep control unit is removed from communication device 100A. In the following description, a configuration including a sleep control unit, similar to communication device 100A, will be referred to as configuration α. ​​A communication device with configuration α will alternate between active mode and sleep mode. Similar to communication device 100B, a configuration not including a sleep control unit will be referred to as configuration β. A communication device with configuration β will always operate in active mode.

[0023] 2A is a sequence diagram showing the process flow from the startup of the communication devices 100A and 100B to the storage of link information in the first embodiment. The communication devices 100A and 100B adjust the communication mode and communication speed (step S101). The communication device 100A transmits a DHCP Request to the communication device 100B (step S102). The communication device 100B receives the DHCP Request and notifies the communication device 100A of its IP address by a DHCP Ack (step S103). As a result, the communication device 100A sets the IP address of the communication device 100A.

[0024] The communication device 100A transmits an ARP Request to the communication device 100B (step S104). The communication device 100B receives the ARP Request and notifies the communication device 100A of the MAC address of the communication device 100B by sending an ARP Reply (step S105). The communication device 100A notifies the storage unit 130A of the link information obtained in the above steps (step S106), and the storage unit 130A stores the link information (step S107). Similarly, the communication device 100B notifies the storage unit 130B of the link information obtained in the above steps (step S108), and the storage unit 130B stores the link information (step S109).

[0025] 2B and 2C show the processing performed after the link information is stored in FIG. 2A. Specifically, FIG. 2B is a sequence diagram showing the processing when the communication device 100A performing sleep control starts active mode and performs communication. FIG. 2C shows the processing when the communication device 100B not performing sleep control performs communication while the communication device 100A is in sleep mode.

[0026] FIG.

[0027] 2B, communication devices 100A and 100B start up, and communication device 100A reads out link information stored in storage unit 130A (step S111). Communication device 100A uses the read out link information to transmit a signal to communication device 100B notifying the start of communication (step S112).

[0028] When communication device 100B receives the signal notifying the start of communication, it reads out the link information stored in storage unit 130B (step S113). This allows communication of the main signal. Thereafter, communication device 100A goes through sleep mode and enters active mode. At this time, communication device 100A reads out the link information stored in storage unit 130A (step S114). Communication device 100A uses the read link information to transmit a signal notifying the start of communication to communication device 100B (step S115). When communication device 100B receives the signal notifying the start of communication, it reads out the link information stored in storage unit 130B (step S116). This allows communication of the main signal.

[0029] Next, Fig. 2C will be described. In Fig. 2C, communication devices 100A and 100B start up, and communication device 100B reads out link information stored in storage unit 130B (step S121). Communication device 100B uses the read out link information to transmit a signal to communication device 100A notifying the start of communication (step S122).

[0030] When communication device 100A receives a signal notifying the start of communication, it reads out link information stored in storage unit 130A (step S123). This allows communication of the main signal. Thereafter, communication device 100A operates in sleep mode. While operating in sleep mode, communication device 100B reads out link information stored in storage unit 130B (step S124). Communication device 100B uses the read link information to transmit a signal notifying the start of communication to communication device 100A (step S125). When communication device 100A receives a signal notifying the start of communication, it enters active mode. Communication device 100A reads out link information stored in storage unit 130A (step S126). This allows communication of the main signal.

[0031] In this way, when the communication device 100 starts active mode, the communication devices 100A and 100B read the link information from the storage units 130A and 130B, respectively, and thus it is possible to skip processes such as DHCP, ARP, and auto-negotiation that are normally required before starting link-up. This enables link-up to be achieved faster than in conventional link-up processes. Note that, as shown in step S101, the communication mode and communication speed must be consistent between the communication devices 100A and 100B.

[0032] In the prior art, it was necessary to operate in active mode to maintain a link even when not transmitting a main signal. However, in the first embodiment, such operation in active mode solely for maintaining a link is not necessary. This makes it possible to further reduce power consumption. Also, it becomes possible to establish a link quickly.

[0033] (Second embodiment) In the second embodiment, when communicating with a plurality of counterpart devices, the storage unit stores link information for each of the plurality of counterpart devices. FIG. 3 is a diagram showing an example of the configuration of a communication system 1010 to which the second embodiment can be applied. The communication system 1010 is made up of a communication device 1100A, a communication device 1100B, a communication device 1100C, a communication device 1100D, and a communication device 1100E. The communication device 1100A is connected to the communication device 1100B. The communication device 1100B is connected to the communication devices 1100C, 1100D, and 1100E.

[0034] 3, a communication device 1100A is a communication device of configuration β, and communication devices 1100B, 1100C, 1100D, and 1100E are communication devices of configuration α.

[0035] The communication device 1100A includes a storage unit 1130A. The communication device 1100B includes a storage unit 1130B. The communication device 1100C includes a storage unit 1130C. The communication device 1100D includes a storage unit 1130D. The communication device 1100E includes a storage unit 1130E. The storage unit 1130A may be provided in a non-removable manner with respect to the communication device 1100A, or may be provided in a detachable manner. If the storage unit 1130A is provided in a detachable manner, the storage unit 1130A may be a USB memory, a SIM dongle, or the like. The storage unit 1130B may be provided in a non-removable manner with respect to the communication device 1100B, or may be provided in a detachable manner. If the storage unit 1130B is provided in a detachable manner, the storage unit 1130B may be a USB memory, a SIM dongle, or the like. The storage unit 1130C may be provided non-removably with respect to the communication device 1100C, or may be provided detachably. If the storage unit 1130C is provided detachably, the storage unit 1130C may be a USB memory, a SIM dongle, or the like. The storage unit 1130D may be provided non-removably with respect to the communication device 1100D, or may be provided detachably. If the storage unit 1130D is provided detachably, the storage unit 1130D may be a USB memory, a SIM dongle, or the like. The storage unit 1130E may be provided non-removably with respect to the communication device 1100E, or may be provided detachably. If the storage unit 1130E is provided detachably, the storage unit 1130E may be a USB memory, a SIM dongle, or the like.

[0036] 3, A to E are written in parentheses in each storage unit. A in parentheses indicates link information A for communicating with communication device 1100A. B in parentheses indicates link information B for communicating with communication device 1100B. C in parentheses indicates link information C for communicating with communication device 1100C. D in parentheses indicates link information D for communicating with communication device 1100D. E in parentheses indicates link information E for communicating with communication device 1100E.

[0037] Storage unit 1130A stores link information B. Storage unit 1130B stores link information A, C, D, and E. Storage unit 1130C stores link information B. Storage unit 1130D stores link information B. Storage unit 1130E stores link information B.

[0038] As shown in storage unit 1130B of communication device 1100B, when communicating with multiple counterpart devices, link information is stored for each of the multiple counterpart devices. This allows each communication device to quickly establish a link. Furthermore, communication devices 1100B, 11100C, 1100D, and 1100E, which are communication devices of configuration α, can further reduce power consumption.

[0039] Furthermore, when the communication system 1010 of the second embodiment performs communication control using TCP / IP, it is possible to prevent flooding due to the absence of data in the MAC address table and unnecessary active operations resulting from this. As a counterexample of a case where no MAC address is recorded, for example, when data is sent from communication device 1100C to communication device 1100A, if communication device 1100B does not store the MAC address of communication device 1100A, communication device 1100B will transmit the data to all connected communication devices. This may cause communication devices 1100D and 1100E to initiate unnecessary active operations.

[0040] 4 is a sequence diagram showing the flow of processing from startup to link-up of the communication devices 100A, 100B, 100C, 100D, and 100E in the second embodiment. In FIG. 4, the series of processing from step S101 to step S105 shown in FIG. 2 is referred to as the link-up processing.

[0041] In FIG. 4, when communication devices 1100A and 1100B perform link-up processing (step S201), communication device 1100A stores link information B in storage unit 1130A (step S202), and communication device 1100B stores link information A in storage unit 1130B (step S203).

[0042] When communication devices 1100B and 1100C perform link-up processing (step S204), communication device 1100B stores link information C in storage unit 1130B (step S205), and communication device 1100C stores link information B in storage unit 1130C (step S206).

[0043] When communication devices 1100B and 1100D perform link-up processing (step S207), communication device 1100B stores link information D in storage unit 1130B (step S208), and communication device 1100D stores link information B in storage unit 1130D (step S209).

[0044] When communication devices 1100B and 1100E perform link-up processing (step S210), communication device 1100B stores link information E in storage unit 1130B (step S211), and communication device 1100E stores link information B in storage unit 1130E (step S212).

[0045] As described above, according to the second embodiment, even when there are multiple opposing devices, the communication devices 1100B, 1100C, 1100D, and 1100E of the configuration α can further reduce power consumption and can establish a link at high speed.

[0046] (Third embodiment) The third embodiment is an embodiment in which link information is determined for each of a plurality of counterpart devices according to the layer to be controlled for communication. Fig. 5 is a diagram showing an example of the configuration of a communication system 2010 to which the third embodiment can be applied. The communication system 2010 is made up of a communication device 2100A, a communication device 2100B, a communication device 2100C, a communication device 2100D, and a communication device 2100E. The communication device 2100A is connected to the communication device 2100B. The communication device 2100B is connected to the communication device 2100C. The communication device 2100C is connected to the communication device 2100D. The communication device 2100D is connected to the communication device 1100E.

[0047] 5, communication devices 2100A, 2100B, 2100C, and 2100D are communication devices of configuration β, and communication device 2100E is a communication device of configuration α.

[0048] The communication device 2100A includes a storage unit 2130A. The communication device 2100B includes a storage unit 2130B. The communication device 2100D includes a storage unit 2130D. The communication device 2100E includes a storage unit 2130E. The storage unit 2130A may be provided in a non-removable manner with respect to the communication device 2100A, or may be provided in a detachable manner. If the storage unit 2130A is provided in a detachable manner, the storage unit 2130A may be a USB memory, a SIM dongle, or the like. The storage unit 2130B may be provided in a non-removable manner with respect to the communication device 2100B, or may be provided in a detachable manner. If the storage unit 2130B is provided in a detachable manner, the storage unit 2130B may be a USB memory, a SIM dongle, or the like. The storage unit 2130D may be provided non-removably with respect to the communication device 2100D, or may be provided detachably. If the storage unit 2130D is provided detachably, the storage unit 2130D may be a USB memory, a SIM dongle, or the like. The storage unit 2130E may be provided non-removably with respect to the communication device 2100E, or may be provided detachably. If the storage unit 2130E is provided detachably, the storage unit 2130E may be a USB memory, a SIM dongle, or the like.

[0049] 5, each storage unit has B, D, and E written in parentheses. B in parentheses indicates link information B for communicating with communication device 2100B. D in parentheses indicates link information D for communicating with communication device 2100D. E in parentheses indicates link information E for communicating with communication device 2100E.

[0050] In Figure 5, solid and dashed arrows indicate connections between different layers. Specifically, solid connections indicate that the layer that is the target of communication control is a lower layer, while dashed connections indicate that the layer that is the target of communication control is a higher layer.

[0051] Therefore, in the communication system 2010, the communication device 2100A and the communication device 2100B communicate at a lower layer and an upper layer. The communication device 2100B and the communication device 2100C communicate at a lower layer. On the other hand, the communication device 2100B and the communication device 2100E communicate at an upper layer. The communication device 2100C and the communication device 2100D communicate at a lower layer. The communication device 2100D and the communication device 2100E communicate at a lower layer.

[0052] The storage unit 2130A stores link information E. The storage unit 2130B stores link information E. The storage unit 2130D stores link information E. The storage unit 2130E stores link information B and D. By storing information in this manner, the communication device 1100E of configuration α can further reduce power consumption even when communicating with an opposing device that controls communication on a different layer. It also becomes possible to link up quickly.

[0053] When communication system 2010 performs communication control using TCP / IP, storage unit 2130A stores the IP address of communication device 2100E. Storage unit 2130B stores the IP address and MAC address of communication device 2100E. Storage unit 2130D stores the MAC address, communication speed, and communication mode of communication device 2100E. Storage unit 2130E stores the IP address of communication device 2100A, the IP address of communication device 2100B, the MAC address of communication device 2100B, the MAC address of communication device 2100D, the communication speed of communication device 2100D, and the communication mode of communication device 2100D. This enables high-speed link-up. Note that communication device 2100C does not require a storage unit because adjacent communication devices 2100B and 2100D always operate in active mode and link disconnection does not occur. In the third embodiment, the link information corresponding to the upper layer is an IP address, and the link information corresponding to the lower layer is a MAC address.

[0054] (Example of using a removable memory unit) Here, the configuration of the first embodiment will be described as an example. As described above, in the first embodiment, as shown in Fig. 6, the storage unit 130A stores link information B. The storage unit 130B stores link information A. Here, if the communication device 100A fails but the storage unit 130A does not fail, the storage unit 130A is removed from the communication device 100A.

[0055] When the communication device 100A is replaced with the communication device 100a, the storage unit 130A can be reused by setting the storage unit 130A in the communication device 100a. Therefore, compared to when the storage device is non-removable, the replacement work is less laborious and the number of times data is written to the storage unit can be reduced. Note that, since the communication device 100A is replaced with the communication device 100a, it is necessary to update the link information in the storage unit 130B of the communication device 100B. There are no particular limitations on the method for updating the link information in the storage unit 130B, but since the storage unit 130B can also be removed, the options for update methods increase. For example, the storage unit 130B can be updated by another terminal. In this case, power consumption in the communication system 10 can be reduced.

[0056] The method of storing link information is not limited to the method of storing link information obtained by negotiation between communication devices as shown in Fig. 2A. Methods of storing link information include, for example, Method A, in which a field worker removes the storage unit from the communication device, stores the link information in the storage unit, and then resets the storage unit with the stored link information in the communication device, and Method B, in which the link information is stored in the storage unit remotely using a communication line.

[0057] Method A will be described with reference to Fig. 7. As shown in Fig. 7, the worker removes storage unit 3130A provided in communication device 3100A, sets storage unit 3130A in worker terminal 4000 such as a PC, and writes link information to storage unit 3130A by the worker's operation. Thereafter, the worker removes storage unit 3130A from worker terminal 4000 and sets it back in communication device 3100A. This allows the link information to be stored in the storage device.

[0058] Method B will be described with reference to FIG. 8. As shown in FIG. 8, communication device 3100A and communication device 3100B are capable of communicating with each other. Furthermore, worker terminal 4000 and communication device 3100B are capable of communicating with each other. In this configuration, link information is transmitted from worker terminal 400 to communication device 3100B. Link information to be stored in communication device 3100A and link information to be stored in communication device 3100B are transmitted from worker terminal 400. Communication device 3100B stores the link information in storage unit 3130B provided in communication device 3100B, and transmits the link information to communication device 3100A. Communication device 3100A stores the link information in storage unit 3130A provided in communication device 3100A. This allows the link information to be stored in a storage device.

[0059] The control unit in each embodiment may be configured using a processor such as a CPU (Central Processing Unit) and a memory. In this case, the control unit functions as a control unit when the processor executes a program. Note that all or part of the functions of the control unit may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The program may be recorded on a computer-readable recording medium. Examples of computer-readable recording media include portable media such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, and a semiconductor storage device (e.g., an SSD: Solid State Drive), as well as storage devices such as a hard disk or semiconductor storage device built into a computer system. The program may be transmitted via a telecommunications line.

[0060] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention. [Industrial Applicability]

[0061] The present invention is applicable to communication devices that require link information to establish a link. [Explanation of symbols]

[0062] 10, 1010, 2010 Communication Systems 100, 100a, 100A, 100B, 100C, 100D, 100E, 1100A, 1100B, 1100C, 1100D, 1100E, 2100A, 2100B, 2100C, 2100D, 2100E Communication equipment 110A, 110B control section 111A Sleep control unit 112A, 112B communication control unit 120A, 120B communication interface 130A, 130B, 1130A, 1130B, 1130C, 1130D, 1130E, 2130A, 2130B, 2130D, 2130E Storage

Claims

1. a sleep control unit that repeatedly executes an active mode and a sleep mode; a storage unit that stores link information indicating values ​​acquired through negotiation between communication devices, the link information being determined according to a communication protocol that controls communication with the opposite device and that is necessary for linking up with the opposite device; a communication control unit that communicates with the opposing device using the link information stored in the storage unit when the device transitions from a sleep mode to an active mode; A communication device comprising:

2. A sleep control unit that repeatedly executes an active mode and a sleep mode; a storage unit that stores link information necessary for linking up with an opposing device; a communication control unit that communicates with the opposing device using the link information stored in the storage unit when the device transitions from a sleep mode to an active mode; Equipped with When communicating with a plurality of the opposite devices, the storage unit stores the link information for each of the plurality of opposite devices; The link information is determined for each of the plurality of opposite devices according to a layer to be controlled in communication. Communication equipment.

3. 3. The communication device according to claim 1, wherein the storage unit is detachably provided.

4. A communication system including a first communication device, a second communication device connected to the first communication device, and a plurality of other communication devices connected to the second communication device, The first communication device a first storage unit that stores link information necessary for linking up with the second communication device; the second communication device, a sleep control unit that repeatedly executes an active mode and a sleep mode; a second storage unit that stores link information necessary for linking up with the first communication device and link information necessary for linking up with each of the plurality of other communication devices; a communication control unit that communicates with the first communication device or the plurality of other communication devices using the link information stored in the second storage unit when the communication device transitions from a sleep mode to an active mode; Equipped with the second storage unit stores the link information for each of the first communication device and the plurality of other communication devices; the link information is determined for each of the first communication device and the plurality of other communication devices according to a layer to be controlled in communication; Communication system.

5. A control method for a communication device including a storage unit, Repeatedly cycles through active and sleep modes, storing link information necessary for linking up with the opposing device in the storage unit; When the device transitions from a sleep mode to an active mode, the device communicates with the other device using the link information stored in the storage unit; When communicating with a plurality of the opposite devices, the link information is stored in the storage unit for each of the plurality of opposite devices; The link information is determined for each of the plurality of opposite devices according to a layer to be controlled in communication. Control method.

6. A control method for a communication system including a first communication device having a first storage unit, a second communication device connected to the first communication device and having a second storage unit, and a plurality of other communication devices connected to the second communication device, In the first communication device, storing link information required for linking up with the second communication device in the first storage unit; communicating with the second communication device using the link information stored in the first storage unit; In the second communication device, Repeatedly cycles through active and sleep modes, storing link information required for linking up with the first communication device and link information required for linking up with each of the plurality of other communication devices in the second storage unit; When the communication device transitions from a sleep mode to an active mode, the communication device communicates with the first communication device or the plurality of other communication devices using the link information stored in the second storage unit; storing the link information for each of the first communication device and the plurality of other communication devices in the second storage unit; the link information is determined for each of the first communication device and the plurality of other communication devices according to a layer to be controlled in communication; Control method.

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