Method, apparatus, and system for reducing power consumption in a mesh network

In a network of wireless communications apparatuses connected by a plurality of routes, a wireless communications apparatus includes a packet generating unit that generates a packet for each of the plurality of routes in the network; an operating unit that generates power consumption information for each of the routes, the power consumption information indicating power consumption for transmitting the packets; an attaching unit that attaches the power consumption information to the packets; and a transmit unit that transmits the packets to which the power consumption information is attached via the corresponding routes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to methods, apparatuses, and systems for reducing power consumption in a mesh network. The present invention also relates to a wireless communications program and a non-transitory recording media storing a wireless communications program.

2. Description of the Related Art

With the progress of wireless technologies, devices that have been connected using wires are increasingly connected wirelessly. For example, Ethernet networking technology according to the IEEE 802.3 standard has been the mainstream technology for local area networks (LAN). However, in recent years, wireless LAN connection technology according to the IEEE 802.11 standards has been adopted in increasing number of information communications devices. Wireless communications technologies, due to the high degree of freedom they offer, are expected to be used in realizing mesh networks that are dynamically configured.

Patent Documents 1 and 2 discuss route-search (“routing”) technologies for mesh networks. The technologies are discussed to be capable of minimizing the number of hops in a network. The technologies according to Patent Documents 1 and 2, however, do not take into consideration the power consumption by an entire network, and therefore do not attempt to overcome a problem of excessive power consumption in the network.Patent Document 1: JP 2007-74564APatent Document 2: JP 2008-219526A

SUMMARY OF THE INVENTION

The disadvantages of the prior art may be overcome by the present invention which, in one aspect, is a wireless communications apparatus in a network of a plurality of the wireless communications apparatuses connected by a plurality of routes. The apparatus includes a packet generating unit configured to generate a packet for each of the plurality of routes in the network; an operating unit configured to generate power consumption information for each of the routes, the power consumption information indicating power consumption for transmitting the packet; an attaching unit configured to attach the power consumption information to the corresponding packet; and a transmit unit configured to transmit the packets to which the power consumption information is attached via the corresponding routes.

In another aspect, the invention provides a wireless communications apparatus in a network of a plurality of the wireless communications apparatuses connected by a plurality of routes. The apparatus includes a receiving unit configured to receive a packet to which power consumption information is attached, the power consumption information indicating power consumption for transferring the packet in the network; an acquiring unit configured to acquire the power consumption information attached to the packet received by the receiving unit; and a decision unit configured to determine one of the plurality of routes that has the minimum power consumption by comparing the power consumption information acquired by the acquiring unit regarding one route with that of another route in the network.

In another aspect, the invention provides a network communications system having a transmitting wireless communications apparatus, a receiving wireless communications apparatus, and a plurality of interposed wireless communications apparatuses. The transmitting communications apparatus includes a packet generating unit configured to generate a packet for each of the plurality of routes in the network; an operating unit configured to generate power consumption information for each of the routes, the power consumption information indicating power consumption for transmitting the packet; an attaching unit configured to attach the power consumption information to the corresponding packet; and a transmit unit configured to transmit the packets to which the power consumption information is attached via the corresponding routes. The receiving wireless communications apparatus includes a receiving unit configured to receive a packet to which power consumption information is attached, the power consumption information indicating power consumption for transferring the packet in the network; an acquiring unit configured to acquire the power consumption information attached to the packet received by the receiving unit; and a decision unit configured to determine one of the plurality of routes that has the minimum power consumption by comparing the power consumption information acquired by the acquiring unit regarding one of the routes with that of another of the routes in the network.

In yet another aspect, the invention provides a communications method for a network having a transmitting wireless communications apparatus, a receiving wireless communications apparatus, and a plurality of interposed wireless communications apparatuses. The method includes generating a packet in the transmitting wireless communications apparatus for each of a plurality of routes of the network; generating power consumption information for each of the routes, the power consumption information indicating power consumption by the transmitting wireless communications apparatus for transmitting the packet; attaching the power consumption information to the corresponding packet; transmitting the packets to which the power consumption information is attached from the transmitting wireless communications apparatus via the corresponding routes; and receiving by the receiving wireless communications apparatus the packets transmitted in the transmitting step to which other power consumption information is attached. The other power consumption information indicates power consumed by transferring of the packet in the network. The method also includes acquiring the power consumption information attached to the received packets in the receiving wireless communications apparatus; and determining in the receiving wireless communications apparatus one of the plurality of routes in the network that has the minimum power consumption by comparing the power consumption information of one of the routes with that of another of the routes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1illustrates a mesh network including nodes1through5. The mesh network (which may be hereafter simply referred to as a “network”) may be used in a small-sized office. The nodes1through5correspond to wireless communications apparatuses. The “wireless communications apparatus” herein refers to an apparatus for transmitting and receiving information or data wirelessly. Examples of wireless communications technologies include wireless LAN according to the IEEE 802.11x standard, and a wireless communications protocol according to the IEEE 802.15.1 standard, such as Bluetooth and ZigBee (registered trademark).

The wireless communications apparatus at node1may be connected to, or implemented by, a personal computer (PC) of a user, such as an employee of an office. The wireless communications apparatus at node1is referred to as a transmitting wireless communications apparatus100. The wireless communications apparatus at node5may be connected to, or implemented by, an image forming apparatus. The wireless communications apparatus at node5is referred to as a receiving wireless communications apparatus200.

The wireless communications apparatuses at nodes2through4are referred to as interposed wireless communications apparatuses50. The interposed wireless communications apparatuses50may be used for relaying or transferring data such as a data packet. The interposed wireless communications apparatuses50may be connected to or implemented by devices or apparatuses (such as PCs) of other users, such as other office employees.

The transmitting wireless communications apparatus100(node1) transmits data such as image data generated on the user's PC to the receiving wireless communications apparatus200(node5) via nodes2through4. The receiving wireless communications apparatus200at node5may subject the image data to an image forming process. Hereafter, the term “node” and the term “wireless communications apparatus” may be used interchangeably.

The transmitting wireless communications apparatus100knows an address, such as an IP address, of the receiving wireless communications apparatus200. All of the nodes know the addresses of adjacent nodes. For example, node1knows the addresses of nodes2and3, and node2knows the address of node4, and so on. Further, the nodes know a transmission power required for transmitting data, such as a data packet, to adjacent nodes. For example, node1knows the transmission power required for transmitting a packet to nodes2and3, and node2knows the transmission power for transmitting a packet to node4.

Transmitting Wireless Communications Apparatus

FIG. 2is a functional block diagram of the transmitting wireless communications apparatus100. The transmitting wireless communications apparatus100includes a transceiver unit12, a RF unit14, a baseband modulating/demodulating unit16, a protocol control unit18, a RAM (random access memory)20, a CPU (central processing unit)22, and a ROM (read-only memory)24. The protocol control unit18, the RAM20, the CPU22, and the ROM24are connected via a bus50. The functional structure illustrated inFIG. 2is common to the interposed wireless communications apparatuses50at nodes2through4and the receiving wireless communications apparatus200(node5).

A wireless communications method according to an embodiment of the present invention includes a route-determining step and a real data transmit step. After a route is determined in the route-determining step, real data (such as image data) is transmitted in the real data transmit step.

In the route-determining step, the transmitting wireless communications apparatus100(node1) generates a routing packet and wirelessly transmits it. The routing packet is desired to be eventually received by the receiving wireless communications apparatus200(node5). The routing packet is generated for each route between node1and node5. In the network illustrated inFIG. 1, there are two routes between nodes1and5. One route connects nodes1and5via nodes2and4. The other route connects nodes1and5via nodes3and4. Thus, a routing packet A is generated for the one route and a routing packet B is generated for the other route by the transmitting wireless communications apparatus100.

Method of Generating a Routing Packet

FIG. 3is a flowchart of a routing packet generating process performed by node1.FIG. 4illustrates a format of a routing packet P generated by node1or by any of nodes2through4.FIG. 4also illustrates examples of data items contained in the routing packet P generated by nodes1(X),2(Y), and4(z).

The process ofFIG. 3is described with reference to a case where the transmitting wireless communications apparatus100generates the routing packet A for the route including nodes1,2,4, and5. First, a header/routing info generating unit132(seeFIG. 2) of the CPU22of the transmitting wireless communications apparatus100(node1) generates a MAC header62in the RAM20(step S2). The MAC header62generated at node1(“X”) ofFIG. 4includes the address of the next node (node2) and the address of the final node5(receiving wireless communications apparatus200). The “next node” may be an interposed wireless communications apparatus50or the receiving wireless communications apparatus200.

The header/routing info generating unit132of the CPU22then generates route information64in the RAM20. The route information64is then attached to the MAC header62. The route information64indicates a route from the node (node1) that initially transmitted the routing packet to the current node. For example, the route information64generated at node1(X) includes the address of node1. Then, a FCS generating unit87of the protocol control unit18calculates a FCS (frame check sequence)68(step S4).

Thus, the MAC header62and the route information64are generated by the header/routing info generating unit132of the CPU22, while the FCS68is generated by the FCS generating unit87of the protocol control unit18. At this point, the packet does not yet include power consumption information. Such a packet prior to the addition of power consumption information may be referred to as “non-power-consumption-information-attached packet”. Namely, the non-power-consumption-information-attached packet is generated by the header/routing info generating unit132of the CPU22and by the FCS generating unit87of the protocol control unit18. Thus, the header/routing info generating unit132and the FCS generating unit87may be collectively referred to as a “packet generating unit”. The packet generating unit generates the non-power-consumption-information-attached packets for the route including nodes1,2,4, and5and the route including nodes1,3,4, and5. The packet generating unit may be configured to generate non-power-consumption-information-attached packets for all of the routes.

Next, the CPU22sets a transmission power in a first register88of the protocol control unit18(step S6). The CPU22of all nodes may retain a table70in advance. In the table70, the adjacent nodes are associated with transmission power values for transmitting a packet to the adjacent nodes.FIG. 5illustrates an example of the table70, showing the transmission power required for transmitting a packet from the transmitting wireless communications apparatus100(node1) to the adjacent nodes2and3. For example, the transmission power required for transmitting a packet from node1to node2is −45 dBm. The transmission power required for transmitting a packet from node1to node3is −30 dBm.

Thus, when the routing packet A is generated by node1, the corresponding transmission power is −45 dBm. Therefore, the CPU22sets the information in the first register88of the protocol control unit18, indicating that the transmission power is −45 dBm (step S6). The protocol control unit18sends the transmission power information stored in the first register88to the RF unit14. The table70may be created by determining the transmission power for each node in accordance with the following equation:
E=αdr  (1)
where E is the transmission power, α is a constant, d is the distance (communications distance) between the nodes, and r is a constant of 2 to 4.

Next, an operating unit82of the protocol control unit18generates power consumption information for each route (step S8). The power consumption information indicates a value of power consumption involved in the transmission (or transfer) of the routing packet A to the adjacent node (node2in the present example). The power consumption information may be generated by various methods. In the following, two methods of generating the power consumption information from the transmission power information stored in the first register88are described.

In the first method, a converting unit822in the operating unit82and a table80are used. An example of the table80is illustrated inFIG. 6, in which transmission power information and power consumption information are associated with each other. For example, when the transmission power is −50 dBm, the corresponding power consumption is 120 mW. The table80may be generated and stored in the table storing unit84in advance. Because the transmission power for transmitting the packet from node1to node2is −45 dBm, the converting unit822converts the transmission power information (−45 dBm) to power consumption information indicating 130 mW by referring to the table80.

In the second method, a calculating unit824of the operating unit82calculates power consumption information from the transmission power information in the first register88in accordance with a predetermined calculation formula. The predetermined calculation formula may be experimentally determined from transmission power values and power consumption values corresponding to the transmission power values in advance. The calculation formula may be retained in the calculating unit82. The power consumption information may be generated by other methods.

By using the first method that utilizes the table80, calculation cost or processing load may be reduced. By using the second method involving a calculation formula, power consumption information corresponding to transmission power information that is not specified in the table80may be calculated. For example, the second method may enable the determination of an appropriate power consumption value when the exact transmission power, such as a value of −47 dBm, is not described in the table80.

The MAC header62and the route information64generated on the RAM20are transmitted to the protocol control unit18. In step S12(FIG. 3), the attaching unit86attaches the power consumption information70after the FCS68. Namely, the power consumption information70is included in the routing packet, thus obtaining the routing packet illustrated inFIG. 4. The routing packet A is then transmitted to a baseband modulating/demodulating unit16. The baseband modulating/demodulating unit16subjects the routing packet A to an OFDM (orthogonal frequency-division multiplexing) digital modulation process. After the OFDM process, the routing packet A is transmitted to node2by a transceiver unit12.

Flow of Routing Packet in a Network

FIG. 7is a flowchart of a process flow between the interposed wireless communications apparatuses50(nodes2through4) and the receiving wireless communications apparatus200(node5). A flow of the routing packet is illustrated inFIG. 8. The functional structure of the nodes2through5may be the same as illustrated inFIG. 2.

Node1transmits the routing packet A to node2(step S202ofFIG. 8). The transceiver unit12of node2receives the routing packet A (step S101ofFIG. 7). The transceiver unit12provides the received routing packet A to the RF unit14. The routing packet A is thereafter stored in the RAM20via the baseband modulating/demodulating unit16and the protocol control unit18.

The analyzing unit128of the CPU22analyzes the MAC header62contained in the routing packet A (step S102), and acquires the addresses of nodes2and5. Then, a destination determining unit126of the CPU22determines whether the address of the final node5corresponds to the address of the current node, i.e., node2(step S104). Because the address of the final node5does not correspond to the address of node2(NO in S104), the process advances to step S106.

In step S106, a rewriting unit130of the CPU12rewrites the MAC header62of the routing packet A stored in the RAM20. Specifically, the address of node2shown in the MAC header62of the packet (X) inFIG. 4is replaced with the address of the next node (node4), as shown in the MAC header62generated by node2(Y). As a result, the routing packet A is transmitted from node2to node4.

Further, the rewriting unit130of node2updates the route information64by attaching the address of node2. As a result of the updating, the route information64indicates that the route is from node1to node2. For example, the route information64is updated from “address of node1” to “address of node1→address of node2”. Thereafter, the FCS generating unit87of the protocol control unit18generates the FCS68in step S108.

The power information acquiring unit122of the CPU22acquires the power consumption information70in the routing packet A stored in the RAM20. The power consumption information70is then stored in a second register90.

In step S110, as described above with reference to “Method of Generating a Routing Packet”, the CPU22sets transmission power information in the first register88of the protocol control unit18. The transmission power information indicates the amount of electric power required for wirelessly transmitting the routing packet A to the next node (node4). The operating unit82generates power consumption information based on the transmission power information stored in the first register88. The power consumption information may be generated by various methods, such as the above-described first or the second method. For example, the power consumption for wireless transmission of the packet from node2to node4may be 180 mW.

In step S112, an updating unit826of the operating unit82adds the power consumption value of 180 mW for wireless transmission from node2to node4to the power consumption value of 130 mW stored in the first register88. Then, the updating unit826updates the power consumption information70with the added result, i.e., a power consumption value of 310 mW. Thus, the operating unit82of node2(interposed wireless communications apparatus) generates the power consumption information by summing the power consumption value generated from the transmission power required for transmitting the routing packet from node1to node2, and the power consumption value generated from the transmission power required for transmitting the packet from node2to node4(another interposed wireless communications apparatus) or node5(receiving wireless communications apparatus200).

In step S114, the thus updated power consumption information70is attached after the FCS68by the attaching unit86, thus including the power consumption information70in the routing packet A. The routing packet A with the updated power consumption information is then processed by the baseband modulating/demodulating unit16, converted into a wireless signal by the RF unit14, and then transmitted to node4by the transceiver unit12(step S116and step S204).

The processes of steps S101through S116are also performed by node4. Node4sets a power consumption value of 150 mW corresponding to the transmission power that is set for the transmission of the packet from node4to node5. The wireless communications apparatus of node4changes the “Next node” information in the MAC header62from the address of node2to the address of node5, as illustrated inFIG. 4(z). Further, the route information64is updated from “address of node1→address of node2” with “address of node1→address of node2→address of node4”. Also, the power consumption information70is updated to 310+150=460 mW.

The routing packet A containing the information indicated by “z” inFIG. 4with the updated power consumption information and the like is transmitted to node5(receiving wireless communications apparatus200). Total power consumption for transmitting the packet from node1to node5is 460 mW. On the other hand, when the routing packet B is transmitted via the route of nodes1,3,4, and5, a total power consumption for transmitting the routing packet B is 400 mW.

Thus, the transceiver unit of an interposed wireless communications apparatus50transfers the routing packet to the next interposed wireless communications apparatus50or the receiving wireless communications apparatus200.

Receiving Wireless Communications Apparatus Route-Determining Step

A process performed by the receiving wireless communications apparatus200(node5) is described with reference to the flowchart ofFIG. 7. In step S101, the receiving wireless communications apparatus200receives the routing packets A and B from node4. The routing packets A and B are stored in the RAM20via the RF unit14, the baseband modulating/demodulating unit16, and the protocol control unit18. In step S102, the MAC header62of the routing packets A and B is analyzed by the analyzing unit128of the CPU22.

In step S104, the analyzing unit128of the CPU22determines whether the final node address in the MAC header62corresponds to the address of node5. Because the final node address in the MAC header62is the address of node5(YES in step S104), the process advances to step S118.

In step S118, the receiving wireless communications apparatus200stands by for a duration of time (step S118and step S208) in order to receive all of the routing packets for all routes. Thereafter, the power information acquiring unit122of the CPU22acquires the power consumption information for the routes (the route of nodes1,2,4, and5, and the route of nodes1,3,4, and5). Specifically, the power information acquiring unit122acquires the power consumption information (=460 mW) attached to the routing packet A and the power consumption information (=400 mW) attached to the routing packet B.

In step S120, the decision unit124determines the routing packet having the minimum power consumption by comparing the power consumption information acquired from the routing packets A and B by the power information acquiring unit122.

For example, the power consumption information attached to the routing packet A indicates 460 mW, while the power consumption information attached to the routing packet B indicates 400 mW. Thus, the decision unit124selects the routing packet B as the routing packet having the minimum power consumption. The decision unit124therefore determines that the route corresponding to the routing packet B (nodes1,3,4, and5) as the route via which a packet can be sent with the minimum power consumption (step S124). The route with the minimum power consumption is indicated by the route information contained in the routing packet B.

In step S126, the protocol control unit8creates a route-determination packet indicating that the route has been selected. The route-determination packet is used for notifying the interposed wireless communications apparatuses in the selected route. In step S128, the transceiver unit2transmits the route-determination packet.

The route-determination packet is transferred back to node1via the selected route, i.e., via nodes4and3. Thus, the transceiver unit2of node4transfers the route-determination packet to node3(steps S212through S216).

Real Data Transmit Step

FIG. 9is a flowchart of a real data transmit process in which real data (such as image data) is transmitted by node1via the route determined by the above-described route-determining process. The flow ofFIG. 9is similar to the flow ofFIG. 3with the exception that steps S6, S8, and S12of the latter are omitted.

In step S902, the CPU22creates the MAC header62. Alternatively, the MAC header62created in the route-determining process and then stored in the RAM20may be used in this step. In step S904, the CPU22attaches real data (image data) to the MAC header and calculates a FCS (frame check sequence). In step S906, the FCS is attached to the real data, thus generating a real data packet. The packet is transmitted by the transceiver unit12.

In step S218, the transmitting wireless communications apparatus100(node1) transmits the real data packet to node3from which node1received the route-determination packet. In step S220, node3transmits the received real data packet to node4from which node3received the route-determination packet. In step S222, node4transmits the received real data packet to node5from which node4received the route-determination packet. In this way, node5(receiving wireless communications apparatus200) receives the image data from the transmitting wireless communications apparatus100(node1). In step S224, node5transmits an ACK signal to node4, indicating a safe reception of the real data packet. In step S226, node4transfers the ACK signal received from node5to node3from which node4received the real data packet. In step S228, node3transfers the ACK signal received from node4to node1that transmitted the real data packet. By receiving the ACK signal, node1recognizes that the real data packet has been safely received by node5.

Thus, in accordance the present embodiment, a route with the minimum power consumption can be determined from a plurality of routes, and the transmitting wireless communications apparatus100can transmit real data, such as image data, via the determined route. Thus, consumption of power required for transmitting real data can be minimized.

The operating unit82may convert transmission power information into power consumption information for the following reason. The transmission power information is determined by equation (1). Transmission power is not dependent on the type of the transceiver unit12of the interposed wireless communications apparatus. Transmission power may not be dependent on the type of an antenna of the interposed wireless communications apparatus.

On the other hand, power consumption is dependent on the type of the transceiver unit12of the interposed wireless communications apparatus. Thus, power consumption information can be appropriately determined by the operating unit82even if the type of the transmitting wireless communications apparatus is changed.

The power consumption information may be attached at the end of the routing packet as illustrated inFIG. 4for the following reason. In accordance with the present embodiment, all of the interposed wireless communications apparatuses50in the network are capable of processing the power consumption information. However, if one or more of the interposed wireless communications apparatuses are not capable of processing the power consumption information, and if the power consumption information is attached at a location other than at the end of the routing packet (such as next to the MAC header62), the power consumption information cannot be processed, resulting in an error in the one or more wireless communications apparatuses.

By attaching the power consumption information at the end of the routing packet, the interposed wireless communications apparatus50that is not capable of processing power consumption information can perform a process by deleting the power consumption information. Thus, no error is caused in the interposed wireless communications apparatuses50not capable of processing power consumption information in a network.

The packet generating unit (header/routing info generating unit132and FCS generating unit87inFIG. 2) of the transmitting wireless communications apparatus100generates routing packets Pm(1, . . . , m, . . . , M) for each of the M routes (in steps S2and S4inFIG. 3). Thus, the packet generating unit generates M packets.

After step S6(FIG. 3), the operating unit82of the transmitting wireless communications apparatus100generates power consumption information70mfor each of the M routes, indicating the amount of power consumed by transmitting the packet to the next wireless communications apparatus50. The routing packet Pm to which the power consumption information70mis attached is transmitted by the transceiver unit2.

Next, a process performed by the interposed wireless communications apparatus50mnm(node mnm) after steps S106, S108, and S110inFIG. 7is described. In step S112, a total of power consumed by the transmission of the routing packet Pm from node1to node mnmis stored in the second register90. Then, node mnmdetermines the power consumption for transmitting the routing packet Pm to the next node mnm+1. The thus determined power consumption is added by the updating unit826to the power consumption value stored in the second register, thereby updating the power consumption information70of the routing packet Pm. The subsequent process is similar to the process of steps S114and S116and is therefore not described herein.

Thus, when the packet is transmitted from node1to node Q via any one of the routes1, . . . , m, . . . , and M, each of the interposed wireless communications apparatuses successively adds a power consumption value. Namely, the updating unit826of each interposed wireless communications apparatus (seeFIG. 2) adds the value of power consumption by the previous transmission of the routing packet to the power consumption for transmitting the routing packet to the next interposed wireless communications apparatus or the receiving wireless communications apparatus.

In accordance with the present embodiment, the transmitting wireless communications apparatus100, the receiving wireless communications apparatus200, and the interposed wireless communications apparatuses50include all of the functional units illustrated inFIG. 2. Alternatively, one or more of the nodes may not include all of the illustrated functional units as needed.

In accordance with an embodiment, the transmitting wireless communications apparatus100(node1) may be configured to broadcast the routing packet including the power consumption information. Transmission power used for calculating the power consumption information may be set between the transmitting wireless communications apparatus100and one of the interposed wireless communications apparatuses that can wirelessly communicate with the transmitting wireless communications apparatus100.

The interposed wireless communications apparatuses (nodes2and3) that received the routing packet via broadcasting may then broadcast the routing packet. When broadcasting the routing packet, the interposed wireless communications apparatuses (nodes2and3) each adds to the power consumption information in the routing packet a power consumption value calculated by using a transmission power value that is set between the interposed wireless communications apparatus (nodes2and3) and one of the other interposed wireless communications apparatuses that can wirelessly communicate with nodes2and3or the receiving wireless communications apparatus.

The interposed wireless communications apparatus (node4) that received the routing packet broadcast by the interposed wireless communications apparatuses (nodes2and3) broadcasts the routing packet. When broadcasting the routing packet, the interposed wireless communications apparatus (node4) adds to the power consumption information in the routing packet a power consumption value calculated by using a transmission power value set between the wireless communications apparatus (node4) and one of the other interposed wireless communications apparatuses that can wirelessly communicate with the wireless communications apparatus (node4) or the receiving wireless communications apparatus.

The receiving wireless communications apparatus200receives the routing packet broadcast by the interposed wireless communications apparatus (node4). The receiving wireless communications apparatus200determines a route based on the received routing packet. For example, the route may be determined based on the power consumption information in the routing packet, such that the power consumption can be minimized. The receiving wireless communications apparatus200then transmits a route-determination packet including the route information determined based on the routing packet. The route-determination packet is transferred between the interposed wireless communications apparatuses included in the route information and eventually received by the transmitting wireless communications apparatus100.

FIG. 11is a block diagram of a hardware structure of the transmitting wireless communications apparatus100, the receiving wireless communications apparatus200, or the wireless communications apparatus50according to the present embodiment. The structure includes a CPU22, a RAM20, a ROM24, a network I/F unit516, an input unit517, a display unit518, and an external storage I/F unit514.

The CPU22is an operating unit configured to control the various units of the apparatus or a computer and perform various data operations or processes. The CPU22may be configured to perform a process in accordance with a program stored in the RAM20. The CPU22may receive data from an input unit or a storage unit, operate or process the data, and then output resultant data to an output unit or the storage unit.

The RAM20is a storage unit in which an OS (operating system) or an application software program executed by the CPU22and various data may be saved or temporarily stored. The ROM24is another storage unit in which data related to the application software may be stored.

The network I/F unit516provides an interface for enabling communication with a network such as a LAN (Local Area Network) or a WAN (Wide Area Network) which may be set up using wired or wireless data transmission routes. Thus, the network I/F unit516enables communications with other wireless communications apparatuses or the like.

The input unit517and the display unit518may include an LCD (Liquid Crystal Display) having key switches (hardware keys) and a touch panel function. The touch panel function may include software keys for a graphical user interface (GUI). The input unit517and the display unit518may include a display/input unit configured to provide a user interface (UI) when a user utilizes a function of the wireless communications apparatus.

The external storage I/F unit514provides an interface with a recording medium515(such as a flash memory) which may be connected to the wireless communications apparatus via a data transmission route such as a USB (Universal Serial Bus) cable.

A program stored in the recording medium515may be installed in the wireless communications apparatus100,200, or50via the external storage I/F unit514, so that the installed program can be executed by the wireless communications apparatus, which may include a PC.

FIG. 12illustrates a mesh network including nodes1through5(wireless communications apparatuses). Initially, the route passing through nodes3and4may be determined by transmitting a routing packet and acquiring power consumption information contained in the route-determination packet. The route may be selected because the route has the least power consumption. However, one or more of the routes may be moved after such route determination. If the transmission of real data is continued using the selected route when a node has moved, power consumption may increase.

In the example ofFIG. 12, node3has been moved away from nodes1and4after the setting of the route. In this case, the transmission power as calculated in accordance with equation (1) may increase for transmitting the real data both from node1to node3and from node3to node4. As a result, power consumption increases. Thus, it is more preferable to select another route that requires lower power consumption than continue with the current route having the increased power consumption.

FIG. 13illustrates an example in which a wireless communications apparatus in a selected route is replaced with another wireless communications apparatus. At the time of route setting, the selected route may include node3. The route may be determined by transmitting a routing packet and acquiring power consumption information contained in the route-determination packet. For example, the route via nodes3and4is selected because the route has the least power consumption. However, one or more of the interposed wireless communications apparatuses may become unable to communicate due to some failure. In such a case, the incapacitated node may be replaced with a node located nearby for transferring the real data. In the example ofFIG. 13, the route that has been originally set included node3. However, because node3became unable to communicate after the route setting, node6is used instead for transferring data from node1to node4, thus modifying the route. When transmission of the real data is continued with the modified route, power consumption may increase.

When node6is included in the route, the transmission power that is set for transmitting the real data as calculated in accordance with equation (1) may increase for transmitting the real data both from node1to node6and from node6to node4. When the transmission power thus increases, the power consumption also increases.

Thus, in accordance with the present embodiment, each wireless communications apparatus attaches power consumption information to the real data that is transmitted after the route setting when transmitting the real data. The receiving wireless communications apparatus200determines whether to request routing (route-determining process) by the transmitting wireless communications apparatus100based on the power consumption information contained in the received real data.

FIG. 14is a block diagram of the wireless communications apparatus according to the present embodiment. The wireless communications apparatus is similar to the apparatus ofFIG. 2with the exception that a power consumption determination unit134and a routing requesting unit136are additionally provided.

When the wireless communications apparatus is the receiving wireless communications apparatus200, the power consumption determination unit134determines whether routing should be performed based on the power consumption information contained in the real data packet received from an interposed wireless communications apparatus. For example, the power consumption determination unit134retains power consumption information (“reference power consumption”) when a route to be used is determined based on the routing packet. Upon reception of real data from the interposed wireless communications apparatus, the power consumption determination unit134determines whether the power consumption information contained in the real data is greater than the reference power consumption. The reference power consumption may include a margin so that routing (route-determining process) is not conducted too frequently. For example, when the amount of movement of the node is small, the power consumption may not be changed much from the reference power consumption. Similarly, when the wireless communications apparatus that is rendered incapable of performing communications is replaced with a nearby wireless communications apparatus for relaying data, the power consumption may not be changed much from the reference power consumption.

When the power consumption information value contained in the real data is greater than the reference power consumption, the power consumption determination unit134determines that routing should be conducted because the power consumption by the network as a whole can be expected to increase. The reference power consumption may include a margin, as mentioned above. On the other hand, when the power consumption value contained in the real data is equal to or less than the reference power consumption which may include a margin, the power consumption determination unit134may determine that routing should not be conducted because the power consumption of the network as a whole is not increased. Upon determining that routing should be conducted, the power consumption determination unit134instructs the routing requesting unit136to conduct the route-determination process.

The routing requesting unit136, upon reception of a routing instruction from the power consumption determination unit134, requests routing packets from the transmitting wireless communications apparatus100. For example, the routing requesting unit136is configured to transmit a packet for requesting the transmission of the routing packets.

Upon reception of the packet requesting the transmission of the routing packets from the receiving wireless communications apparatus200, the transmitting wireless communications apparatus100transmits the routing packets. Based on the routing packets, a route that would minimize power consumption is set.

FIG. 15is a flowchart of an operation of the transmitting wireless communications apparatus100according to the present embodiment. In step S1502, the header/routing info generating unit132of the CPU22generates the MAC header62on the RAM20. The MAC header62includes the address of the next node, as described above with reference toFIG. 4. The MAC header62may also include the address of the final node (receiving wireless communications apparatus200). The “next node” refers to one or more of the interposed wireless communications apparatuses capable of communicating with the current node that are included in the route that has been set, or the receiving wireless communications apparatus.

The header/routing info generating unit132of the CPU22generates real data66on the RAM20and adds the real data66to the MAC header62. Next, in step S1504, the FCS generating unit87of the protocol control unit18calculates the FCS68. In step S1504, the header/routing info generating unit132of the CPU22generates the MAC header62and the real data66. The FCS generating unit87of the protocol control unit18generates the FCS68.

In step S1506, the CPU22sets a transmission power value in the first register88of the protocol control unit18. The protocol control unit18then notifies the RF unit14of the transmission power value stored in the first register88. In step S1508, the operating unit82of the protocol control unit18generates power consumption information to be attached to the real data66that is to be relayed to the next node. The operating unit82may generate the power consumption information by the above-described first and/or the second method.

The MAC header62and the real data66generated on the RAM20are transmitted to the protocol control unit18. In step S1510, the attaching unit86attaches the power consumption information70after the FCS68. Namely, the power consumption information70is included in the real data packet, which is then transmitted to the baseband modulating/demodulating unit16. The baseband modulating/demodulating unit16subjects the real data packet to an OFDM (orthogonal frequency-division multiplexing digital modulation) process. Thereafter, the routing packet A is transmitted by the transceiver unit12in step S1512.

FIG. 16is a flowchart of an operation of the interposed wireless communications apparatus50and the transmitting wireless communications apparatus100. In step S1602, the interposed wireless communications apparatus50receives the real data packet from the transmitting wireless communications apparatus100via the transceiver unit12. The real data packet is then fed to the RF unit14. The real data packet is then stored in the RAM20via the baseband modulating/demodulating unit16and the protocol control unit18.

In step S1604, the analyzing unit128of the CPU22analyzes the MAC header62contained in the real data packet. In step S1606, the destination determining unit126of the CPU22determines whether the address of the final node corresponds to the address of the interposed wireless communications apparatus50.

If the address of the final node does not correspond to the address of the interposed wireless communications apparatus50(NO in step S1606), the power information acquiring unit122of the CPU22acquires the power consumption information70in the real data packet stored in the RAM20, and stores the power consumption information70in the second register90.

In step S1610, the CPU22sets a transmission power value in the first register88within the protocol control unit18. The transmission power value is the electric power required for wirelessly transmitting the real data packet to the next node. The operating unit82generates power consumption information based on the transmission power information stored in the first register88. The power consumption information may be generated by the above-described first or second method.

The updating unit826of the operating unit82adds the power consumption value generated by the operating unit82to the power consumption value stored in the second register90. The updating unit826then updates the power consumption information70with the calculated value of power consumption (step S1612). In other words, the operating unit82of the interposed wireless communications apparatus generates the power consumption information by adding the power consumption value generated from the transmission power required for transmitting the real data packet from the transmitting wireless communications apparatus100to the interposed wireless communications apparatus, to the power consumption value generated from the transmission power required for transmission of the real data packet from the interposed wireless communications apparatus to the next interposed wireless communications apparatus or the receiving wireless communications apparatus.

In step S1614, the attaching unit86attaches the updated power consumption information70after the FCS68. Namely, the power consumption information70is included in the real data packet. The real data packet to which the updated power consumption information is attached is processed by the baseband modulating/demodulating unit16, converted into a wireless signal by the RF unit14, and then transmitted by the transceiver unit12(step S1616).

If it is determined in step S1606that the address of the final node corresponds to the address of the intermediate wireless communications apparatus (YES in step S1606), the power consumption determination unit134of the CPU22determines whether the power consumption value contained in the real data packet is increased over the power consumption value at the time of initial route setting (step S1608). If the power consumption value contained in the real data packet is increased over the power consumption value at the time of initial route setting (YES in step S1618), the power consumption determination unit134determines that a routing request should be made. Specifically, the power consumption determination unit134instructs the routing requesting unit136to send a routing request to the transmitting wireless communications apparatus100. Upon reception of the routing request instruction from the power consumption determination unit134, the routing requesting unit136of the CPU22transmits a routing requesting packet to the transmitting wireless communications apparatus100.

On the other hand, if it is determined in step S1618that the power consumption value contained in the real data packet is not more than the power consumption at the time of initial route setting (NO in step S1618), the process returns to step S1602because the power consumption has not increased and there is no need for additional routing.

In accordance with the present embodiment, the value of the reference power consumption may be set by a user. In this way, it can be determined whether routing should be conducted in accordance with user requests. For example, when it is desired to reduce power consumption even if routing is conducted very frequently, the reference power consumption value may be set to a low value. Conversely, when it is desired to reduce the time required for routing even if power consumption is increased somewhat, the reference power consumption value may be set to a high value. Thus, the reference power consumption value can be set to an appropriate value depending on the environment in which the wireless communications apparatus is used, so that an appropriate route can be selected.

In accordance with the present embodiment, the wireless communications apparatus may include a display unit for displaying power consumption information. The display unit allows the user to monitor power consumption, thereby facilitating the management of the network. For example, the number of the wireless communications apparatuses in a network can be increased or decreased depending on the amount of power consumption.

The wireless communications apparatus may also include a notifying unit for issuing a notification when it is determined that a routing is to be conducted. Further, the wireless communications apparatus may include a routing initiating unit for initiating the routing process. For example, in response to the notification that a routing is to be conducted, a user may or may not instruct the routing initiating unit to initiate a routing.

Although this invention has been described in detail with reference to certain embodiments, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.

The present application is based on Japanese Priority Applications No. 2009-262237 filed Nov. 17, 2009 and No. 2010-138332 filed Jun. 17, 2010, the entire contents of which are hereby incorporated by reference.