This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2014-046831, filed Mar. 10, 2014, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to communication.
In a star network (for example, a wireless LAN (Local Area Network)), if a communication failure occurs in a master device (for example, an AP (Access Point)) corresponding to a hub, all communication processes in the network become impossible. When such communication failure occurs, one slave device (for example, an STA (STAtion)) selected in advance can serve as a new master device to reconstruct a new star network with the remaining slave devices. This technique may improve the reliability of a star network. However, when the technique is used, it is not always clearly defined how the previous master device should get involved in the new network.
Embodiments will be described below with reference to the accompanying drawings.
According to an embodiment, a communication apparatus includes a communicator, an acquisition unit and a controller. When an operation mode is a first mode, the communicator functions as a hub of a network to communicate with another communication apparatus in the network. When the operation mode is a second mode, the communicator communicates with another communication apparatus in the network without functioning as the hub of the network. The acquisition unit acquires communication quality information indicating a communication quality of each link in the network. When the operation mode of the communicator is the first mode, the controller decides based on the communication quality information whether to set the operation mode of the communicator to the second mode.
Note that the same or similar reference numerals denote the same or similar elements hereinafter and a repetitive description thereof will be basically omitted.
Although the following description assumes a star network topology, each embodiment is applicable to other types of network topologies. Furthermore, the following description assumes that a communication apparatus supports wireless communication. However, each embodiment may be applied to a communication apparatus that supports wired communication instead of wireless communication, or a communication apparatus that supports both wireless communication and wired communication.
As exemplified in
The acquisition unit 101 acquires, from the communicator 103, indices regarding the communication quality of each link in a network which the communication apparatus 100 joins, and saves the indices as communication quality information intact, or processes and saves the indices as communication quality information.
When, for example, the communication apparatus 100 performs wireless communication, the indices regarding the communication quality can include a reception power, a packet error rate, an SINR (Signal to Interference and Noise Ratio), a wireless communication connection state, and a TCP (Transmission Control Protocol) connection state.
The acquisition unit 101 may acquire and save the value of one of the indices as communication quality information intact, or may save the statistic (for example, the average) of the value of one of the acquired indices as communication quality information. Alternatively, the acquisition unit 101 may save the composite value (for example, the weighted sum) (or the statistic of the composite value) of the values of the plurality of acquired indices (or the statistics of the respective indices) as communication quality information. The acquisition unit 101 may integrate the pieces of communication quality information of a plurality of links, and save the integrated information. Note that practical examples of the communication quality information are not limited to them. The acquisition unit 101 outputs the communication quality information to the controller 102.
The acquisition unit 101 may also acquire preliminary master device information, and save the information. The preliminary master device information indicates at least whether another communication apparatus that can serve as a master device exists in the network which the communication apparatus 100 joins. For example, the preliminary master device information may be information indicating whether another communication apparatus that supports a master device mode (to be described later) exists in the network, or information indicating whether the corresponding communication apparatus supports the master device mode for each of the remaining communication apparatuses which join the network. The preliminary master device information may be fixed during the operation of the communication apparatus 100 or dynamically changed. The preliminary master device information may be acquired or created based on communication performed by the communicator 103, or saved in advance in a memory (not shown) storing setting information. The acquisition unit 101 may acquire the preliminary master device information from the communicator 103 or the memory.
The controller 102 receives the communication quality information from the acquisition unit 101. The controller 102 controls the operation mode of the communicator 103 based on the current operation mode of the communicator 103 and the communication quality information. More specifically, the controller 102 decides an appropriate operation mode. If the current operation mode of the communicator 103 is different from the appropriate operation mode, the controller 102 changes the operation mode of the communicator 103 to the appropriate operation mode. Note that the controller 102 may control the operation mode of the communicator 103 based on the preliminary master device information in addition to the current operation mode of the communicator 103 and the communication quality information. Control of the operation mode by the controller 102 will be described in detail later. When controlling the operation mode of the communicator 103, the controller 102 may reset the power supply of the communicator 103 or the memory connected to the communicator 103.
The communicator 103 supports a plurality of operation modes including at least a master device mode and a slave device mode. If the operation mode of the communicator 103 is the master device mode, the communication apparatus 100 functions as the hub of the network which the communication apparatus 100 joins. On the other hand, if the operation mode of the communicator 103 is the slave device mode, the communication apparatus 100 does not function as the hub of the network which the communication apparatus 100 joins.
As described above, the controller 102 controls the operation mode of the communicator 103. The communicator 103 transmits/receives a signal on the network which the communication apparatus 100 joins. The signal transmitted/received by the communicator 103 may depend on its operation mode.
If, for example, the communication apparatus 100 performs wireless communication, the communicator 103 may include an RF (Radio Frequency) unit, a transmission processor, a reception processor, and a link management unit.
The RF unit performs analog signal processing. More specifically, the RF unit may include a general analog signal processing circuit in wireless communication, such as an LNA (Low Noise Amplifier), MIX (MIXer), VCO (Voltage Controlled Oscillator), or PA (Power Amplifier).
The transmission processor performs baseband digital signal processing corresponding to processing of transmitting a control packet and data packet. More specifically, the transmission processor may append a CRC (Cyclic Redundancy Check) code, and perform encryption, noise whitening, and error correction encoding (for example, FEC (Forward Error Correction)).
The reception processor performs baseband digital signal processing corresponding to processing of receiving a control packet and data packet. More specifically, the reception processor may perform correlation detection, error correction decoding, inverse noise whitening, decryption, and error detection.
The link management unit manages a wireless link. The operation of the link management unit may depend on the operation mode of the communicator 103.
Note that although not shown in
If the operation mode of the communicator 103 is the master device mode, the controller 102 may change the operation mode to the slave device mode under the condition that a change in communication quality information for a unit period satisfies a predetermined criterion. More specifically, if the communication qualities of a plurality of links degrade within a short period, it is appropriate to estimate that the communication failure has been caused by the communication apparatus 100 (master device) rather than the remaining communication apparatuses (slave devices). For example, if the total number of remaining communication apparatuses (slave devices) connected to the communication apparatus 100 (that is, the communicator 103) decreases by two or more for 1 sec, it is appropriate to estimate that the communication failure has been caused by the communication apparatus 100 (master device) rather than the remaining communication apparatuses (slave devices). Consequently, the controller 102 decides to set the operation mode of the communicator 103 to the slave device mode, and the communication apparatus 100 joins, as a slave device, a network reconstructed centered on a new master device.
For example, the controller 102 may operate, as shown in
Upon start of the operation shown in
In step S203, the controller 102 acquires current communication quality information N[1] from the acquisition unit 101. If the difference between the past communication quality information N[0] and the current communication quality information N[1] is equal to or smaller than the first predetermined value, the process advances to step S205; otherwise, the process advances to step S206 (step S204).
In step S205, the controller 102 decides to set the operation mode of the communicator 103 to the slave device mode. The controller 102 may immediately set the operation mode of the communicator 103 to the slave device mode, or further perform processing as exemplified in
Note that when setting the operation mode of the communicator 103 to the slave device mode, the controller 102 may reset the power supply of the communicator 103 or the memory connected to the communicator 103. When an abnormal operation or memory error occurs in the communicator 103, performing reset processing may improve the operation state of the communicator 103.
In step S206, the controller 102 substitutes the current communication quality information N[1] into the past communication quality information N[0]. Furthermore, the controller 102 stands by for the first period (step S207), and then the process returns to step S203.
That is, in the operation example shown in
Alternatively, the controller 102 may operate as exemplified in
Upon start of the operation shown in
In step S303, the controller 102 acquires a current connection count N[1] from the acquisition unit 101. If the difference between the past connection count N[0] and the current connection count N[1] is equal to or smaller than −2 (this predetermined value may be changed to −3 or less), the process advances to step S305; otherwise, the process advances to step S306 (step S304).
In step S305, the controller 102 decides to set the operation mode of the communicator 103 to the slave device mode. At this time, the controller 102 may immediately set the operation mode of the communicator 103 to the slave device mode, or further perform processing as exemplified in
In step S306, the controller 102 substitutes the current connection count N[1] into the past connection count N[0]. Furthermore, the controller 102 stands by for 1 sec (step S307), and then the process returns to step S303.
That is, in the operation example shown in
Note that the controller 102 may operate, as exemplified in
Upon start of the operation shown in
In step S703, the controller 102 starts a timer. If the connection count decreases again with respect to the connection count determined in step S702 before the timer measures 1 sec, the process advances to step S706 (steps S704 and S705). On the other hand, if the connection count does not decrease again as compared with that determined in step S702 while the timer measures 1 sec, the process returns to step S702 (steps S704 and S705).
In step S706, the controller 102 decides to set the operation mode of the communicator 103 to the slave device mode. At this time, the controller 102 may immediately set the operation mode of the communicator 103 to the slave device mode, or further perform processing as exemplified in
That is, in the operation example shown in
According to the operation example shown in
In an example shown in
By using, as a trigger, the fact that it is impossible to receive a signal (for example, a beacon frame, an Alive message, or the like) expected to be transmitted by the communication apparatus 401 serving as a master device, each of the communication apparatuses 402, 403, and 404 detects a communication failure of the master device. Note that the communication apparatuses 402, 403, and 404 are designed to reconstruct a new network by causing one of the communication apparatuses 402, 403, and 404 to operate as a new master device in such case. In the example shown in
Since the communication apparatus 401 operates as a slave device instead of an isolated master device, it can be connected to the communication apparatus 403 serving as the current master device when the obstacle 405 disappears. That is, the communication apparatus 401 can join, as a slave device, the new network centered on the communication apparatus 403.
Note that a communication apparatus to serve as a new master device when a communication failure occurs in the current master device may be selected based on the suitability of each communication apparatus as a master device, which has been evaluated by various methods before the occurrence of the communication failure. For example, a communication apparatus to serve as a new master device may be selected based on the capability of each communication apparatus. Alternatively, a communication apparatus to serve as a new master device may be selected according to various standards such as a minimax standard based on the communication quality (for example, the reception power) of each link between communication apparatuses in the network.
Furthermore, the communication apparatus serving as the current master device may transfer the authority of the master device to the selected communication apparatus when it operates in the slave device mode.
In the example of
Upon receiving the master device designation notification, each of the communication apparatuses 502 and 503 cancels connection to the communication apparatus 501 serving as the master device. Furthermore, the communication apparatus 502 designated as a new master device by the master device designation notification changes its operation mode to the master device mode. On the other hand, the communication apparatus 503 which has not been designated as a new master device by the master device designation notification changes the connection destination to the communication apparatus 502 serving as the new master device. More specifically, the communication apparatus 503 is connected to the communication apparatus 502 at an appropriate timing. The communication apparatus 501 newly operating in the slave device mode is also connected to the communication apparatus 502 at an appropriate timing.
Note that in the example shown in
An operation of transferring the authority of the master device is not limited to the example shown in
When selecting a communication apparatus to serve as a new master device as described above, candidates each having the second or subsequent suitability as a master device may be selected together. By sharing information about the second and subsequent candidates among the communication apparatuses in the network, the authority of the master device is taken over in an appropriate order when a second or subsequent communication failure occurs.
Alternatively, the suitability of each communication apparatus as a master device may be continuously (for example, periodically) evaluated. With this operation, it is possible to appropriately update information of a communication apparatus to serve as a new master device even in an environment in which the communication quality readily changes. Furthermore, if continuous evaluation results in the presence of a communication apparatus having suitability higher than that of the current master device, the authority of the master device may be transferred to another slave device, or returned to the past master device, as exemplified in
In an example shown in
When the communication apparatus 604 starts operating as a new master device, a network is reconstructed centered on the communication apparatus 604. The communication apparatus 601 which has newly started operating as a slave device in addition to the communication apparatuses 602 and 603 is connected to the communication apparatus 604.
If the result of continuously evaluating the suitability indicates that the suitability of the communication apparatus 601 exceeds that of the communication apparatus 604, the communication apparatus 604 returns the authority of the master device to the communication apparatus 601. When the communication apparatus 601 starts operating as a master device again, a network is reconstructed centered on the communication apparatus 601. The communication apparatus 604 which has started operating as a slave device again in addition to the communication apparatuses 602 and 603 is connected to the communication apparatus 601.
Even if the communication apparatus 100 operates as exemplified in
The operation shown in
In the operation example shown in
In an example shown in
By using, as a trigger, the fact that it is impossible to receive a signal expected to be transmitted by the communication apparatus 901 serving as the master device, each of the communication apparatuses 902, 903, and 904 detects a communication failure of the master device. Assume, however, that none of the communication apparatuses 902, 903, and 904 can serve as a master device for some reason. In this case, no master device exists and thus the network temporarily disappears.
If the network disappears, the communication apparatus 901 cannot be connected to a master device. Then, if this state is not resolved even when the third period elapses after the controller of the communication apparatus 901 starts a timer, the controller sets the operation mode of the communicator of the communication apparatus 901 to the master device mode.
By setting the operation mode of the communicator of the communication apparatus 901 to the master device mode, the communication apparatus 901 returns as a master device. As a result, a network is reconstructed centered on the communication apparatus 901. In the operation example shown in
As described above, after deciding the operation mode of the communicator 103 to the slave device mode, the controller 102 may immediately set the operation mode of the communicator 103 to the slave device mode, or further perform processing as exemplified in
An operation shown in
Alternatively, after deciding the operation mode of the communicator 103 to the slave device mode, the controller 102 may operate as exemplified in
An operation shown in
In the operation example shown in
In an example shown in
Upon receiving the master device designation notification, the communication apparatus 1204 starts operating as a master device. Note that as shown in
When the communication apparatus 1204 operates as a new master device, all the communication apparatuses 1201, 1202, 1203, and 1204 in the network can communicate with each other again by avoiding the obstacle 1205.
In the operation example shown in
The operation shown in
If it is determined in step S1302 that it is possible to set the operation mode of the communicator 103 to the slave device mode, the process advances to step S1304 (step S1303). On the other hand, if it is determined in step S1302 that it is impossible to set the operation mode of the communicator 103 to the slave device mode, the process of
In the operation example of
An operation shown in
Upon receiving the master device designation notification, each of the remaining communication apparatuses replies a response message to the master device designation notification. The response may indicate that the communication apparatus designated as a new master device in the master device designation notification can serve as a master device (OK) or indicate that the communication apparatus cannot serve as a master device (NG). For example, the response indicating “NG” may be replied when another communication apparatus exists outside the communication range of the designated communication apparatus in the network, when the designated communication apparatus does not support the master device mode, when the designated communication apparatus has no Internet connection capability, or when the designated communication apparatus lacks another function. Instead of the communication apparatus designated as a new master device, another communication apparatus having information about the designated communication apparatus may reply a response.
In step S1402, the communicator 103 receives the response to the master device designation notification, which has been transmitted in step S1401. If the response received in step S1402 indicates “OK”, the process advances to step S1404. On the other hand, if the response received in step S1402 does not indicate “OK”, the process of
In the operation example shown in
In an example shown in
The communication apparatus 1501 broadcasts a master device designation notification for designating the communication apparatus 1504 as a new master device. Since, however, the other communication apparatus 1502 exists outside the communication range of the communication apparatus 1504 in the network, the communication apparatus 1504 transmits a response indicating “NG” to the communication apparatus 1501. As a result, the communication apparatus 1501 continues operating as a master device. In the example of
When the obstacle 1505 disappears, the communication apparatuses 1502 and 1503 can be connected to the communication apparatus 1501 again. Consequently, the network centered on the communication apparatus 1501 recovers.
In the above-described various operation examples, a description has been given by assuming the default operation mode of the communication apparatus according to the embodiment is the master device mode. However, the default operation mode of the communication apparatus may be the slave device mode. If, for example, the default operation mode of the communication apparatus 100 is the slave device mode, the communication apparatus 100 may operate as exemplified in
Upon start of the operation shown in
If, for example, a plurality of communication apparatuses according to this embodiment operate as shown in
In the operation example shown in
The timer measures the fifth period shorter than the fourth period. When the timer measures the fifth period, the controller 102 determines whether the communication apparatus 100 is connected to the master device. If the communication apparatus 100 is connected to the master device, the process ends; otherwise, the controller 102 increments or decrements the counter. If the count value satisfies a predetermined criterion, the controller 102 sets the operation mode of the communicator 103 to the master device mode; otherwise, the controller 102 restarts the timer. The predetermined criterion may indicate that the count value coincides with a value representing that the timer repeatedly measures the fifth period a predetermined number of times (for example, a quotient obtained by dividing the fourth period by the fifth period).
When a communication failure estimated to be caused by the communication apparatus according to the embodiment is detected based on the communication quality information while the communication apparatus operates as a master device, the remaining communication apparatuses reconstruct a network. However, if a plurality of master devices simultaneously appear at the time of reconstruction of a network, the network may be dissolved, resulting in too many small-scale networks. In this case, it is desirable to reconstruct a network on an expected scale by consolidating the small-scale networks. More specifically, when the communication apparatus 100 operates as exemplified in
An operation shown in
The first reference value is set to about half the expected connection count of the network. The expected connection count of the network may be derived by subtracting 1 from the total number of communication apparatuses which joined the network before occurrence of a communication failure, or set in advance by the acquisition unit 101 or the like. Note that if the first reference value is too large, not only a small-scale network but also a relatively large-scale network is dissolved, and the number of communication apparatuses which cannot temporarily communicate is unnecessarily increased, resulting in inefficient processing. On the other hand, if the first reference value is too small, the small-scale networks are difficult to be dissolved, resulting in inefficient processing.
In step S1704, the controller 102 decides to set the operation mode of the communicator 103 to the slave device mode. The controller 102 may immediately set the operation mode of the communicator 103 to the slave device mode, or further perform processing as exemplified in
In the operation example shown in
In an example shown in
In the example shown in
When the obstacle 1806 disappears, the communication apparatuses 1804 and 1805 can be connected to the communication apparatus 1801. The two networks respectively centered on the communication apparatuses 1801 and 1804 are finally consolidated into a network centered on communication apparatus 1801.
As described above, if the operation mode of the communicator is the master device mode, the communication apparatus according to the first embodiment changes the operation mode to the slave device mode under the condition that a change in communication quality information for a unit period satisfies a predetermined criterion. That is, when a communication failure estimated to be caused by the communication apparatus occurs, the communication apparatus can promote reconstruction of a new network, and automatically join the reconstructed network as a slave device. This communication apparatus can, therefore, improve the reliability (especially, fault tolerance) of the network.
In the above-described first embodiment, the communicator for performing communication and the acquisition unit and controller for controlling the communicator are arranged in the same apparatus. The acquisition unit and controller, however, may be arranged in an apparatus different from that including the communicator.
As exemplified in
In
In the communication system exemplified in
As described above, in the communication system according to the second embodiment, the acquisition unit and controller which are the same as or similar to those included in the communication apparatus according to the above-described first embodiment are arranged in the communication control apparatus which is independent of the communication apparatus. Therefore, the communication system can improve the reliability (especially, fault tolerance) of the network, similarly to the communication apparatus according to the first embodiment.
The communication apparatus according to the first embodiment and the communication system according to the second embodiment are applicable to an energy management apparatus such as a smart meter.
As shown in
The measurement unit 2005 obtains measurement data by measuring at least one physical quantity with respect to at least one kind of energy based on sensing data from a sensor or sensing device (not shown). For example, the measurement unit 2005 may measure the power consumption, generated power amount, or accumulated power amount for electricity, or measure a flow rate for water or gas.
The energy management unit 2004 manages the above-described measurement data. More specifically, the energy management unit 2004 manages the measurement data based on the logical or physical network arrangement among a plurality of energy management apparatuses.
The logical network arrangement indicates the relationship between the plurality of energy management apparatuses for hierarchically managing the measurement data. A given energy management apparatus may be able to directly communicate with an energy management apparatus positioned at an upper level in the logical network arrangement, or need to communicate with the energy management apparatus via one or more other energy management apparatuses. On the other hand, the physical network arrangement indicates the relationship (for example, master device—slave device) between the plurality of energy management apparatuses for exchanging the measurement data.
For example, the energy management unit 2004 may request the controller 2002 to externally transmit the measurement data. Upon receiving the request to transmit the measurement data from the energy management unit 2004, the controller 2002 requests the communicator 2003 to transmit the measurement data. Note that the controller 2002 adjusts the transmission timing in accordance with the state of the network. More specifically, the controller 2002 may temporarily buffer, in a memory (not shown), the measurement data which has been requested to be transmitted before a network is constructed. Then, the controller 2002 may request the communicator 2003 to transmit the measurement data buffered in the memory after the network is constructed. For example, “before the network is constructed” corresponds to a period during which the connection count of the energy management apparatus 2000 is equal to or smaller than a predetermined number (for example, the above-described expected connection count) when the operation mode of the communicator 2003 is the master device mode, and a period during which the energy management apparatus 2000 is not connected to a master device when the operation mode of the communicator 2003 is the slave device mode.
The controller 2002 may predict the probability (that is, the communication occurrence probability) that the energy management unit 2004 requests to transmit the measurement data. While the probability is equal to or lower than a threshold, the controller 2002 may sense the communication quality of each link in the network, or reconstruct a network (that is, the controller 2002 may change the operation mode of the communicator 2003). This operation can reduce the influence of sensing of the communication quality and reconstruction of the network on the measurement data traffic.
Furthermore, the controller 2002 may perform evaluation so that an energy management apparatus with a larger measurement data traffic amount has higher suitability as a master device when selecting an energy management apparatus to serve as a new master device. For example, the controller 2002 may acquire the type of measurement data managed by the energy management unit of each energy management apparatus, a measurement frequency by the measurement unit of each energy management apparatus, and the like by communication, and estimate in advance the measurement data traffic amount in each energy management apparatus based on the acquired data. Since an energy management apparatus whose measurement data traffic amount is large corresponds to a hub in a logical network with a high probability, it is possible to improve the efficiency of the traffic in the network by causing the energy management apparatus to function as a hub in a physical network as well as the logical network (that is, by making the physical network arrangement more similar to the logical network arrangement).
As described above, the energy management apparatus according to the third embodiment includes the acquisition unit and controller which are the same as or similar to those included in the communication apparatus according to the above-described first embodiment, respectively. Therefore, the energy management apparatus can improve the reliability (especially, fault tolerance) of the network, similarly to the communication apparatus according to the first embodiment and the communication system according to the second embodiment.
At least a part of the processing in the above-described embodiments can be implemented using a general-purpose computer as basic hardware. A program implementing the processing in each of the above-described embodiments may be stored in a computer readable storage medium for provision. The program is stored in the storage medium as a file in an installable or executable format. The storage medium is a magnetic disk, an optical disc (CD-ROM, CD-R, DVD, or the like), a magnetooptic disc (MO or the like), a semiconductor memory, or the like. That is, the storage medium may be in any format provided that a program can be stored in the storage medium and that a computer can read the program from the storage medium. Furthermore, the program implementing the processing in each of the above-described embodiments may be stored on a computer (server) connected to a network such as the Internet so as to be downloaded into a computer (client) via the network.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Number | Date | Country | Kind |
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2014-046831 | Mar 2014 | JP | national |