Transfer of a packet to a mobile communication terminal forming part of an adhoc network, through a core network

BACKGROUND OF THE INVENTION

1. Field of the Invention

0001The present invention relates to a mobile communication system which transfers, based on address information of a mobile communication terminal, a packet addressed to the mobile communication terminal which forms an adhoc network, through a core network.

0002The present invention also relates to a mobile communication terminal for use in the mobile communication system, and a method of operating a mobile communication system to transfer a packet to a mobile communication terminal forming part of an adhoc network through a core network.

2. Description of the Related Art

0003In <patcit id="pcit0001" dnum="US20040114553A1"><text>US 2004/0114553 A1</text></patcit> there is described an interconnecting mechanism between CDMA 2000 and WLAN. In more detail, the mechanism relates to interconnection and integrating of a WWAN and a WLAN to provide continuous packet data services to mobile users where each mobile access terminal is configured to support both air links with the WWAN and WLAN. The WWAN may be a CDMA 2000 system and the WLAN may be an IEEE 802.11 system.

0004In <patcit id="pcit0002" dnum="EP1345463A2"><text>EP-A-1 345 463 A2</text></patcit> there is described a mobile node, mobile communication system, and communication control program. In a first state, a link layer of a mobile host is connected to an access router and a default router is set to the access router such that data packets P1 and P2 reach the access router and are routed to a corresponding host. In a second and third state, data packets P3 to P8 are not transmitted but are buffered. When the mobile host switches the default router from the access router to an access router upon the reception of a router advertisement from the access router, processing moves to a 4^th state, and the buffered data packets P3 to P8 are transmitted. Since the link layer of the mobile host is connected to the access router and the default router is set to the access router, the data packets P3 to P8 reach the access router and are routed to the correspondent host.

0005<figref idref="f0001">Fig. 1</figref> is a diagram showing a whole configuration of a further mobile communication system. In the mobile communication system, based on address information of the mobile communication terminals MT#1 to MT3, a packet is addressed and transferred to mobile communication terminals MT#1 to MT#3 which form an adhoc network A, through a core network ON.

0006Conventionally, "Globalv6[1]" has been proposed as the mobile communication system described above.

0007In this mobile communication system, each of mobile communication terminals MT manages a home address HoA and a care-of address CoA of the terminal itself, as the address information.

0008In the mobile communication system, packets are configured to be sent to each of the mobile communication terminals MT based on the home address HoA and the care-of address CoA in communications through a core network.

0009In the mobile communication system, packets are configured to be transferred to each of the mobile communication terminals MT based on the home address HoA or the care-of address CoA in communications through an adhoc network.

0010To be more specific, each of the mobile communication terminals MT is configured to transfer packets to other mobile communication terminals MT, in accordance with a routing table which associates a "destination address" with a "next hop", in routing processing within the adhoc network.

0011In <figref idref="f0001">Fig. 1</figref>, a routing table stored in a mobile communication terminal MT#3 is shown as a representative of the mobile communication terminals MT within the adhoc network A. Here, both routing addresses before and after the mobile communication terminal MT has been moved are shown.

0012The care-of address CoA of each of the mobile communication terminals MT includes a prefix and a terminal number. The prefix is assigned by an access node AN connected to the adhoc network to which the mobile communication terminal MT belongs. The terminal number is unique within the adhoc network.

0013In <figref idref="f0001">Fig. 1</figref>, when the adhoc network A which is formed by the mobile communication terminals MT#1 to MT#3 is connected to an access node AN1, a care-of address of the mobile communication terminal MT#1 is "AN1prefix#1" including a prefix "AN1prefix" which is assigned by the access node AN1 and a terminal number "#1", a care-of address of the mobile communication terminal MT#2 is "AN1prefix#2" including the above described prefix "AN1prefix" and a terminal number "#2", and a care-of address of the mobile communication terminal MT#3 is "AN1prefix#3" including the above described prefix "AN1prefix" and a terminal number "#3",

0014However, in the aforementioned mobile communication system, there has been a problem in that, when a handoff occurs while the adhoc network A is formed by the mobile communication terminals MTs, or more specifically, when any one of the mobile communication terminals MT forming the adhoc network A moves, and a connection point between the adhoc network A and the core network CN accordingly is changed from the access node AN1 to another access node AN2, since a care-of address CoA of each of the mobile communication terminals MT is changed, a large amount of recalculation is required to be performed in each of the mobile communication terminals in order to reconstruct a routing table, irrespective of whether topology within the adhoc network A is changed or not.

BRIEF SUMMARY OF THE INVENTION

0015The present invention has been made considering the problems, and its object is to provide a mobile communication system which makes a large amount of recalculation unnecessary in each of mobile communication terminals MT, even when a handoff occurs in a state where an adhoc network A is formed, and to provide a mobile communication terminal thereof.

0016A first aspect of the present invention is summarized as a mobile communication system having the features of claim 1, which transfers a packet to a mobile communication terminal forming an adhoc network, through a core network, based on address information of the mobile communication terminal. A care-of address of the address information of the mobile communication terminal includes common information which is changed when a connection point between the adhoc network and the core network is changed, and individual information which is maintained unchanged even when the connection point between the adhoc network and the core network is changed; and the packet is configured to be transferred based on the individual information in a communication within the adhoc network.

0017A second aspect of the present invention is summarized as a mobile communication terminal having the features of claim 2, which is capable of forming part of an adhoc network. The mobile communication terminal includes: an address information management unit configured to manage a care-of address of the address information including common information which is changed when a connection point between the adhoc network and a core network is changed, and individual information which is maintained unchanged even when the connection point between the adhoc network and the core network is changed; a core network communication unit configured to transfer a packet, based on the care-of address of the address information, in a communication through the core network; and an adhoc network communication unit configured to transfer a packet, based on the individual information, in a communication within the adhoc network.

0018A third aspect of the present invention is summarized as a method of operating a mobile communication system to transfer a packet to a mobile communication terminal forming a part of an adhoc network through a core network having the features of claim 3.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

0019<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Fig. 1</figref> is a diagram showing a whole configuration of a mobile communication system according to a related art.</li><li><figref idref="f0002">Fig. 2</figref> is a diagram showing a whole configuration of a mobile communication system according to a first embodiment of the present invention.</li><li><figref idref="f0003">Fig. 3</figref> is a functional block diagram of the mobile communication terminal according to the first embodiment of the present invention.</li><li><figref idref="f0003">Fig. 4</figref> is a functional block diagram of a mobility management router according to the first embodiment of the present invention.</li><li><figref idref="f0004">Fig. 5</figref> is a sequence diagram showing operations of the mobile communication system according to the first embodiment of the present invention.</li><li><figref idref="f0005">Fig. 6</figref> is a sequence diagram showing operations of the mobile communication system according to the first embodiment of the present invention.</li><li><figref idref="f0006">Fig. 7</figref> is a diagram showing a whole configuration of a mobile communication system according to a second embodiment of the present invention.</li><li><figref idref="f0007">Fig. 8</figref> is a sequence diagram showing operations of the mobile communication system according to the second embodiment of the present invention.</li></ul>

DETAILED DESCRIPTION OF THE INVENTION

(A Configuration of a Mobile Communication System according to a First Embodiment of the Invention)

0020A configuration of a mobile communication system according to a first embodiment of the invention will be described with reference to <figref idref="f0002 f0003">Figs. 2 to 4</figref>.

0021A mobile communication system according to this embodiment, as shown in <figref idref="f0002">Fig. 2</figref>, includes a core network CN, a plurality of access nodes AN1, AN2, and AN10, a mobility management router AGR, and home agents HA1 and HA2.

0022In the example shown in <figref idref="f0002">Fig. 2</figref>, an adhoc network A, which is formed by a plurality of mobile terminals MT#1 to MT#3, moves from the condition in which the adhoc network A is connected to the access node AN1 to the condition in which the adhoc network A is connected to the access node AN2.

0023In the mobile communication system according to this embodiment of the invention, as shown in <figref idref="f0002">Fig. 2</figref>, packets are addressed and transferred to each of the mobile communication terminals MT#1 to MT#3 which forms the adhoc network A, through the core network CN and based on address information (a care-of address CoA) of each of the mobile communication terminals MT#1 to MT#3.

0024Here, the care-of address CoA of each of the mobile communication terminals MT#1 to MT#3 includes common information and individual information.

0025The common information is designed to be changed, when a connection point (the access node AN) between the adhoc network A and the core network CN is changed.

0026The individual information, on the other hand, is designed not to be changed, even when the connection point (the access node AN) between the adhoc network A and the core network CN is changed.

0027The common information is designed to be associated with the access node AN1 or AN2 to which the adhoc network A is connected.

0028The individual information, on the other hand, is designed not to be associated with the access node AN1 or AN2 to which the adhoc network A is connected.

0029Specifically, when the adhoc network A is connected to the access node AN1, the care-of address CoA of the mobile communication terminal MT#1 is "AN1prefix(1) (common information) + #1 (individual information)".

0030When the adhoc network A is connected to the access node AN2, the care-of address CoA of the mobile communication terminal MT#1 is "AN2prefix(1) (common information) + #1 (individual information)".

0031As mentioned above, the common information (AN1prefix(1) or AN2prefix(1)) is designed to be changed, depending on whether the adhoc network A is connected to the access node AN1, or to the access node AN2.

0032Specifically, the access node AN is configured to assign CoP (Care-of-Prefix) to the adhoc network A, based on broadcast information (Agent Advertisement) .

0033Each of the mobile communication terminals, which forms the adhoc network A, is configured to manage the assigned CoP as common information.

0034As shown in <figref idref="f0002">Fig. 2</figref>, packets sent from a mobile communication terminal MT#10 are addressed and transferred, through the home agent HA1 or HA2, and a mobility management router AGR, to any one of the mobile communication terminals MT#1 to MT#3 within the adhoc network A.

0035For example, packets sent from the mobile communication terminal MT#10 and addressed to the mobile communication terminal MT#1 (a home address HoA of the mobile communication terminal MT#1 is included as a destination address) are transferred to the home agent HA1 of the mobile communication terminal MT#1.

0036The home agent HA1 is configured to refer to a routing table by using the home address HoA of the mobile communication terminal MT#1 (a destination address), and to transfer the packets addressed to the mobile communication terminal MT#1, to the mobility management router AGR.

0037The mobility management router AGR is configured to set a care-of address CoA of the mobile communication terminal MT#1 as a destination address of the packets addressed to the mobile communication terminal MT#1.

0038Next, the mobility management router AGR is configured to transfer the packets addressed to the mobile communication terminal MT#1, through the access node AN1 or AN2, to the mobile communication terminal MT#1 which forms the adhoc network A.

0039Here, with reference to <figref idref="f0003">Fig. 3</figref>, a configuration of a mobile communication terminal MT according to this embodiment will be described.

0040As shown in <figref idref="f0003">Fig. 3</figref>, the mobile communication terminal MT includes an address information management unit 11, a core network communication unit 12, an adhoc network communication unit 13, and a routing table management unit 14.

0041The mobile communication terminal MT according to this embodiment is configured to be capable of forming the adhoc network A, by directly communicating with another mobile communication terminal.

0042The address information management unit 11 is configured to manage a care-of address (address information) CoA of the mobile communication terminal MT itself which includes the common information and the individual information.

0043In the example shown in <figref idref="f0003">Fig. 3</figref>, the address information management unit 11 is configured to manage "AN2prefix(1) (common information) + #1 (individual information)" as a care-of address.

0044In this case, the mobile communication terminal MT is assumed to be connected to the access node AN2. In other words, the adhoc network A formed by the mobile communication terminals MT is assumed to be connected to the access node AN2.

0045The core network communication unit 12 is configured to transfer packets based on the care-of address (address information) CoA of each of the communication terminals MT, in communications through the core network CN.

0046For example, the core network communication unit 12 is configured to receive a packet whose destination address is "AN2prefix(1) (common information) + #1 (individual information) ", and which is received through the core network CN, as one which is addressed to itself.

0047Furthermore, the core network communication unit 12 is configured to send update information (Binding Update) to the mobility management router AGR, when detecting that the adhoc network A has moved, specifically, when the access node to which the adhoc network A is connected has been changed.

0048The update information is to notify that the care-of address CoA of the mobile communication terminal MT itself has been changed.

0049It should be noted that, since the individual information is still maintained unchanged even in this case, it is sufficient that the update information sent to the mobility management router AGR is designed to include identification information of the mobile communication terminal MT (for example, a home address of the mobile communication terminal MT) and the common information obtained after the care-of address CoA of the mobile communication terminal MT has been changed.

0050Still furthermore, the core network communication unit 12 is configured to receive broadcast information which is sent from the access node AN.

0051The broadcast information includes CoP. The CoP has been assigned to the adhoc network A, by the access node to which the adhoc network A is connected.

0052The adhoc network communication unit 13 is configured to transfer packets, based on the individual information, in communications within the adhoc network A.

0053Specifically, the adhoc network communication unit 13 is configured to refer to a routing table which is managed by the routing table management unit 14 , and to transfer the packets.

0054Further, the adhoc network communication unit 13 is configured to receive a packet whose destination address is "#1 (individual information)", as a packet addressed to itself, within the adhoc network A.

0055The adhoc network communication 13 does not use the common information in communications within the adhoc network A. Therefore, even when the adhoc network A moves and the common information is accordingly changed, it is possible to continue communications within the adhoc network A without performing, for example, update of a routing table which manages a care-of address of another communication terminal.

0056Specifically, as shown in <figref idref="f0002">Fig. 2</figref>, when the adhoc network A has moved and the common information has been accordingly changed (for example, AN1prefix(1) to AN2prefix(1)), the routing table is not be changed even after the adhoc network A has moved.

0057The adhoc network communication unit 13 is configured to perform processing concerning communications within the adhoc network such as those to join the adhoc network A,and to leave the adhoc network A.

0058The routing table management unit 14 is configured to manage a routing table within the adhoc network A.

0059The routing table is designed to associate a "destination address" with a "next hop". In the "destination address", the individual information of an addressed mobile communication terminal is set. In the "next hop" , the individual information of a mobile communication terminal to which the packet is to be transferred is set.

0060<figref idref="f0002">Fig. 2</figref> shows, as a representative of the mobile communication terminals MT within the adhoc network A, routing tables stored in the mobile communication terminal MT#3 (routing tables for both before and after the mobile communication terminal MT#3 has been moved).

0061Here, with reference to <figref idref="f0003">Fig. 4</figref>, a configuration of the mobility management router AGR will be described.

0062As shown in <figref idref="f0003">Fig. 4</figref>, the mobility management router AGR includes an address information management unit 21, an update information receiving unit 22, and a routing processing unit 23.

0063The address information management unit 21 is configured to manage the home address HoA and the care-of address CoA of all of the mobile communication terminals MT which are capable of communicating through the core network CN.

0064Specifically, the address information management unit 21 is configured to associate the home address HoA of each of the mobile communication terminals MT (which may be replaced with an identification information of each of the mobile communication terminals MT) with the care-of address CoA of each of the mobile communication terminals MT, and to store both of the addresses.

0065In the example shown in <figref idref="f0003">Fig. 4</figref>, the address information management unit 21 is configured to manage a care-of address CoA of the mobile communication terminal MT#1, a care-of address of the mobile communication terminal MT#2, and the like.

0066The care-of address CoA of the mobile communication terminal MT#1 includes "the common information - AN2prefix(1)" and "the individual information = #1", whereas the care-of address CoA of the mobile communication terminal MT#2 includes "the common information = AN2prefix(1)" and "the individual information = #2".

0067Furthermore, the address information management unit 21 is configured to change the care-of address of the mobile communication terminal MT, by changing the common information which constructs the care-of address CoA of the mobile communication terminal MT that is managed by the address information management unit 21, based on the update information which is sent from each of the mobile communication terminals MT.

0068The update information receiving unit 22 is configured to receive various kinds of information such as registration information which includes a care-of address sent from a mobile communication terminal MT which has initiated to join the adhoc network A, and the update information sent from any of mobile communication terminals MT.

0069The routing processing unit 23 is configured to refer to the address information management unit 21, and to transfer packets to a mobile communication terminal MT in the adhoc network A, through the core network.

0070In the example shown in <figref idref="f0003">Fig. 4</figref>, the routing processing unit 23 is configured to receive packets which are sent from a mobile communication terminal MT#10 through an access node AN10, and to transfer the packets to the mobile communication terminal MT#1 through the access node AN2.

(Operations of the Mobile Communication System according to this Embodiment)

0071Operations of the mobile communication system according to this embodiment will be described with reference to <figref idref="f0004">Figs. 5</figref> and <figref idref="f0005">6</figref>.

0072First, with reference to <figref idref="f0004">Fig. 5</figref>, operations in the mobile communication system according to this embodiment will be described, in a case where the mobile communication terminal MT#3 initiates communications. The mobile communication terminal MT#3 is within the adhoc network A which is dependent on the Proactive routing protocol.

0073In step S1001, the access node AN1 periodically sends the common information (AN1prefix(1)) and the broadcast information containing an address of the mobility management router AGR.

0074In step S1002, when the mobile communication terminal MT#3 is going to communicate with a communication terminal existing out of the adhoc network A, the mobile communication terminal MT#3 generates a care-of address CoA of the mobile communication terminal MT#3 itself, based on the received broadcast information.

0075In step S1003, the mobile communication terminal MT#3 sends registration information which includes the care-of address CoA of the mobile communication terminal MT#3 itself and a home address HoA of the mobile communication terminal MT#3 itself, to the mobility management router AGR and a home agent HA.

0076In step S1004, the mobility management router AGR, in response to the registration information sent from the mobile communication terminal MT#3, initiates to manage the care-of address CoA and the home address HoA of the mobile communication terminal MT#3.

0077In step S1005, the home agent HA, in response to the registration information sent from the mobile communication terminal MT#3, initiates to manage an address of the mobility management router AGR, as the care-of address CoA of the mobile communication terminal MT#3.

0078Secondly, with reference to <figref idref="f0005">Fig. 6</figref>, change operations of the care-of address CoA will be described, in a case where the adhoc network A has moved, in the mobile communication system according to this embodiment.

0079Here, it is assumed that the mobile communication terminals MT#1 to MT#3 form the adhoc network A, and communicate with each other.

0080In step S1101, an access node AN2 to which the mobile communication terminals MT#1 to MT#3 have moved, sends common information (AN2prefix(1)) and broadcast information to all of the mobile communication terminals MT#1 to MT#3 within the adhoc network A. The common information here is assigned to the adhoc network A. The broadcast information contains an address of the mobility management router AGR.

0081In steps S1102a to S1102c, the mobile communication terminals MT#1 to MT#3 change the common information (AN1prefix(1)) of the mobile communication terminals MT#1 to MT#3 to another common information (AN2prefix(1)) included in the broadcast information which has been received from the access node AN2. The common information (AN1prefix(1)) here is managed by the mobile communication terminals themselves.

0082In step S1103, the mobile communication terminals MT#1 to MT#3 send the update information including the changed common information (AN2prefix(1)), to the mobility management router AGR.

0083In step 1104, the mobility management router AGR changes the common information (AN1prefix(1)) to another common information (AN2prefix(1)). The common information (AN1prefix(1)) constructs the care-of address CoA of the mobile communication terminals MT#1 to MT#3 within the adhoc network A. The common information (AN2prefix(1) is included in the update information which has been received from the mobile communication terminals MT#1 to MT#3. As a result, a handoff processing of the mobile communication terminals MT#1 to MT#3 will be completed.

0084Incidentally, the present invention is also applicable to a case where the Reactive routing protocol is performed.

(Operations and Effects of the Mobile Communication System according to this Embodiment)

0085According to this embodiment, the adhoc network communication unit 13 of the mobile communication terminal MT performs routing processing within the adhoc network A, based on the individual information which is maintained unchanged even when the adhoc network A has moved.

0086Therefore, when a handoff occurs in a state where the adhoc network A is formed, although the care-of addresses CoA of all of the mobile communication terminals MT are accordingly changed, a large amount of recalculation for routing within the adhoc network A is not necessary.

0087Also, according to this embodiment, only routing processing based on the individual information which will not be changed even when the adhoc network has moved, operates.

0088Therefore, even when a handoff occurs in a state where the adhoc network is formed, a large amount of recalculation is not necessary in each of the mobile communication terminals.

(A Mobile Communication System according to a Second Embodiment of the Present Invention)

0089With reference to <figref idref="f0006">Figs. 7</figref> and <figref idref="f0007">8</figref>, a mobile communication system according to a second embodiment of the present invention will be described.

0090Hereinafter, the mobile communication system according to this embodiment will be described, mainly by describing differences thereof from the mobile communication system according to the aforementioned first embodiment.

0091As shown in <figref idref="f0006">Fig. 7</figref>, the mobile communication system according to the second embodiment differs from the mobile communication system according to the aforementioned first embodiment in including a mobile node MN which manages an adhoc network A.

0092The mobile node MN functions as an interface between the mobile communication terminals MT within the adhoc network A and an access node AN.

0093According to the second embodiment, the common information is an address of the mobile node MN which is assigned by the access node AN to which the mobile node MN is connected.

0094The individual information is an address of the mobile communication terminal MT assigned by the mobile node MN which manages the adhoc network A.

0095Specifically, when the adhoc network A is connected to the access node AN1, the address information (care-of address CoA) of the mobile communication terminal MT#1 is "AN1prefixMN (common information) + MNprefix#1 (individual information)".

0096When the adhoc network A is connected to the access node AN2, the address information (care-of address CoA) is "AN2prefixMN (common information) + MNprefix#1 (individual information)",

0097Likewise, when the adhoc network A is connected to the access node AN1, the address information (care-of address CoA) of the mobile communication terminal MT#2 is "AN1prefixMN (common information) + MNprefix#2 (individual information)".

0098When the adhoc network A is connected to the access node AN2, the address information (care-of address CoA) of the mobile communication terminal MT#2 is "AN2prefixMN (common information) + MNprefix#2(individual information) ".

0099Also, when the mobile node MN detects that the adhoc network A has moved, as the representative of all the mobile communication terminals MT#1 to MT#3 within the adhoc network A, the mobile node MN is configured to notify the mobility management router AGR of the update information concerning the care-of address CoA of all of the mobile communication terminals MT#1 to MT#3 within the adhoc network A.

0100Incidentally, in the mobile communication system according to the second embodiment, a representative mobile communication terminal (for example, the mobile communication terminal MT#1) within the adhoc network A may be configured to function as the mobile node MN.

0101With reference to <figref idref="f0007">Fig. 8</figref>, change operations of the care-of address will be described as follows, in a case where the adhoc network A has moved, with regard to the mobile communication system in the second embodiment.

0102Here, it is assumed that the mobile communication terminals MT#1 to MT#3 form the adhoc network A, and communicate with each other.

0103In step S1301, an access node AN2 to which the adhoc network A has moved sends the broadcast information including the common information (AN2prefixMN) which is assigned to a mobile node MN, to the mobile node MN which manages the adhoc network A.

0104In step S1302, the mobile node MN changes the common information (AN1prefixMN) which constructs the care-of address of the mobile communication terminal MT within the adhoc network A, to another common information (AN2prefixMN) included in the broadcast information which has been received from the access node AN2.

0105Next, the mobile node MN sends the broadcast information including the changed common information (AN2prefixMN), to all the mobile communication terminals MN#1 to MN#3 within the adhoc network A.

0106In steps S1303a to S1303c, the mobile communication terminals MT#1 to MT#3 change the common information (AN1prefixMN) which is managed by and belongs to each mobile communication terminal itself, to another common information (AN2prefixMN) included in the broadcast information which has been received from the mobile node MN.

0107Here, the mobile communication terminals MT#1 to MT#3 are configured not to send the update information concerning the care-of address CoA, to the mobility management router AGR.

0108In step S1304, the mobile node MN sends, to the mobility management router AGR, the update information for notifying that the adhoc network A has moved, specifically, the care-of addresses of the mobile communication terminals MT#1 to MT#3 within the adhoc network A have been changed (AN1prefixMN to AN2prefixMN).

0109In step S1305, the mobility management router AGR changes the common information (AN1prefixMN) which constructs the care-of address CoA of the mobile communication terminals MT#1 to MT#3 within the adhoc network A, to another common information (AN2prefixMN) included in the update information which has been received from the mobile communication terminals MT#1 to MT#3.

0110As a result, a handoff processing of the mobile communication terminals MT#1 to MT#3 within the adhoc network A will be completed.

0111As mentioned above, according to the invention, a mobile communication system and a mobile communication terminal can be provided which do not require a large amount of recalculations in each of the mobile communication terminals MT, even if a handoff occurs in a state that the adhoc network A is formed.

0112Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and the representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the scope of the general inventive concept as defined by the appended claims and their equivalents.