The above and/or other aspects of the present invention will be more apparent by describing certain embodiments of the present invention with reference to the accompanying drawings, in which:
Exemplary embodiments of the present invention will be described in greater detail with reference to the accompanying drawings.
In the description of the exemplary embodiments, same drawing reference numerals are used for the same elements even in different drawings. The matters defined in the description such as a detailed construction and elements are nothing but the ones provided to assist in a comprehensive understanding of the invention. Thus, it is apparent that the present invention can be carried out without those defined matters. Also, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.
According to the invention, a network topology enabling a relay transmission among sub-networks is established in a backbone network. In following embodiments, a method and process of embodying the network topology will be described. Then, a process of efficiently relay transmitting information among devices belonging to the respective sub-networks in accordance with the established network topology will be described.
In the embodiments of the present invention to be explained later, only a process of embodying a network topology among sub-master devices in the sub-networks will be described. However, it should be noted that the method of establishing the network topology can be applied to establish a network topology among plural devices in a sub-network having the plural devices.
The backbone network 1 comprises plural coordinator-based sub-networks in each of which sub-master devices 15, 25, 35, 45 are set as a coordinator. One of the plural sub-master devices 15, 25, 35, 45 included in the backbone network 1 is set as a super master device 45 for controlling communications of the backbone network 1. The super master device 45 controls a network topology formation among the plural sub-master devices 15, 25, 35 and communications among the sub-networks.
Herein, the super master device 45 is one of the sub-master devices 15, 25, 35, 45 and the sub-master devices 15, 25, 35, 45, including the super master device 45, may be formed as one of an appliance, a router, a wired/wireless bridge and a PNC (Piconet Coordinator). Each of the sub-master devices 15, 25, 35, 45 can carry out the communication in a wired or wireless manner. When carrying out the communication in a wired manner, a coaxial cable, an optical cable, a power line, a telephone line and the like can be used. In addition, each of devices belonging to the sub-networks can be connected to the sub-master devices 15, 25, 35, 45 of the corresponding sub-networks in a wired or wireless manner.
The super master device 45 transmits a beacon message, which is an ID request message for requesting an ID, to the first to third sub-master devices 15, 25, 35 included in the backbone network 1. At this time, the super master device 45 transmits the beacon message in a super frame unit as illustrated in
The super frame consists of a beacon area, a CAP (Contention Access Period) area and a CFP (Contention Free Period) area. The beacon area provides various information elements necessary for timing synchronization and operation of the sub-network. The data is carried in the CAP area depending on competition with the other sub-master devices, using a CSMA/CA (Carrier Sense Multiple Access/Collision Detect) technique having a back-off function. The CFP area comprises a MCTA (Management of Channel Time Allocation) and a plurality of CTAs (Channel Time Allocation). The CTA is allocated to the sub-master device having requested a channel time. In the MCTA, a relationship between each of the sub-master devices 15, 25, 35 and each CTA has been defined.
The first to third sub-master devices 15, 25, 35 having received the beacon message of the super frame, form transfer response messages to the super master device 45. Then, the super master device 45 assigns a master device ID (MASTER_DEV_ID) to the first to third master devices 15, 25, 35 in accordance with the response messages provided from the first to third master devices 15, 25, 35. The MASTER_DEV_ID is a MAC address, and is hierarchically assigned, depending on positions of the super master device 45 and each of the sub-master devices 15, 25, 35 on the network topology.
On the other hand, the super master device 45 measures connection qualities between the super master device 45 and each of the sub-master devices 15, 25, 35 using the response messages provided from the first to third master devices 15, 25, 35. At this time, a method of measuring a connection quality using the existing response signal based on IEEE 802.11 is used.
As shown, there is a target ER (Error Rate) level when the backbone network 1 is designed. The data rate is determined on the basis of SNR of each point at which the target ER and each BER curve meet. When each point of SNR is indicated as a, b, c and d, the data rate is set as follows.
SNR<a→data transmission is impossible
a<SNR<b→53.3 Mbps
b<SNR<c→110 Mbps
c<SNR<d 160 Mbps
SNR>d+320 Mbps
Accordingly, the connection quality is determined in accordance with the SNR. When the SNR is determined, it is determined that the data can be transmitted at certain speed.
On the other hand, the super master device 45 does not assign the MASTER_DEV_ID if the sub-master device has the MASTER_DEV_ID already. Even when the super master device 45 has assigned the MASTER_DEV_ID, if the connection quality is lower than a predetermined level, i.e., SNR<a, as a measurement result of the connection quality with each of the sub-master devices 15, 25, 35, the assigned MASTER_DEV_ID is removed from the corresponding sub-master device.
Accordingly, as shown in
In this manner, when the first-order node master device is determined, the super master device 45 defines in what order the CTA will be allocated to the MCTA area of the CFA area of the super frame, with regard to the first and second sub-master devices 15, 25. Then, it allocates CTA to the CTA area, with regard to each of the first and second sub-master devices 15, 25, as defined in the MCTA.
In this manner, when the decision on the first-order node master devices 15, 25 and the allocation of CTA are completed, the first-order node master devices 15, 25 assign an ID to the other sub-master devices in the same manner as carried out at the super master device 45.
In other words, the first sub-master device 15 and the second sub-master device 25 determined as the first-order node master devices 15, 25 transmit an ID request message to the other master devices except its own self, respectively. In addition, since the super master device 45 is also the sub-master device, the first-order node master devices 15, 25 transmit the ID request message to the super master device 45, too.
First, the first sub-master device 15 transmits a beacon message, which is the ID request message, to the super master device 45 and the second and third master devices 25, 35. Then, the super master device 45 and the second and third master devices 25, 35 having received the beacon message transmit response messages to the first sub-master device 15.
When the first sub-master device 15 receives the response messages from the super master device 45 and the second and third master devices 25, 35, it determines whether the MASTER_DEV_ID is provided and the connection quality is higher than a predetermined level. First, the first sub-master device 15 assigns “000”, as a MASTER_DEV_ID, to the third sub-master device 35 having no MASTER_DEV_ID and sets the third sub-master device 35 as a second-order node master device. Then, the first sub-master device 15 sets the sub-master device having the connection quality higher than the predetermined level as a second-order node which is a lower node of the first sub-master device 15, and the super master device 45 and the second and third sub-master devices 25, 35 are set as the second-order node. Accordingly, a network topology as shown in
Then, the first sub-master device 15 allocates the CFA of the super master device 45 and the second and third master devices 25, 35, which are the second-order nodes, to the CFP area of the super frame thereof.
In this manner, when the construction of the network topology by the first sub-master device 15 is completed, it is checked whether a lower node master device is created to the first sub-master device 15. At this time, since the third sub-master device 35, which is the second-order node master device, is present, a process proceeds which establishes a network topology for the third sub-master device 35.
First, the third sub-master device 35 transmits a beacon message to the super master device 45 and the first and second sub-master devices 15, 25. Then, the super master device 45 and the first and second sub-master devices 15, 25 transmit response messages to the third sub-master device 35. The third sub-master device 35 determines the connection quality and whether or not the assignment of the MASTER_DEV_ID using the response messages. At this time, since the MASTER_DEV_ID has been already assigned to the first and second sub-master devices 15, 25, it is not necessary to assign the MASTER_DEV_ID at the third sub-master device 35. In addition, since the connection quality with the super master device 45 is lower than the predetermined level, a network topology as a lower node is established for the first and second sub-master devices 25 only. Accordingly, a network topology as shown in
Then, the third sub-master device 35 allocates the CTA to the CFP area of the super frame thereof, with regard to the first and second sub-master devices 15, 25
In this manner, when the network topology for the first and third sub-master devices 15, 35 is completed, a process of establishing a network topology for the second sub-master device 25 which is the first-order node master device is carried out.
The second sub-master device 25 transmits a beacon message to the super master device 45 and the first and third sub-master devices 15, 35 and receives a response messages from the super master device 45 and the first and third sub-master devices 15, 35. Likewise the first sub-master device 15, the second sub-master device determines whether the MASTER_DEV_ID is provided and the connection quality is higher than the predetermined level. At this time, since the super master device 45 and the first and third sub-master devices 15, 35 have the MASTER_DEV_ID already, the second sub-master device 25 does not assign a separate MASTER_DEV_ID. Then, the second sub-master device 25 sets the super master device 45 and the first and third sub-master devices 15, 35 determined to have the connection quality higher than the predetermined level, as a lower node of the second sub-master device 25.
Then, the second sub-master device 25 allocates the CTA to the super frame, with respect to the super master device 45 and the first and third sub-master devices 15, 35.
Accordingly, as shown in
In this manner, when the network topology for the super master device 45 and each of the sub-master devices 15, 25, 35 is established, a process proceeds which collects information about each of the routes constituting the network topology at the super master device 45. The information about each route includes the super frame structures of the super master device 45 and the first to third sub-master devices 15, 25, 35.
First, the channel information is collected from the leftmost route. The information collection is carried out from the lowest node to the upper mode. Accordingly, the information is provided from the super master device 45, which is the lowest node (No. 1 in the table) of the leftmost route, to the first sub-master device 15 that is the first-order node master device. The super master device 45 broadcasts the MASTER_DEV_ID thereof and the connection quality of the channel.
Then, the first sub-master device 15, which is the upper node, receives the information from the super master device 45, and, as shown in No. 2 of the table, the second sub-master device 25 broadcasts the MASTER_DEV_ID thereof and the connection quality of the channel. Accordingly, the first sub-master device 15 receives the information from the second sub-master device 25.
Then, as shown in No. 3 of the table, the first sub-master device 15 broadcasts the MASTER_DEV_ID thereof and the connection quality of the channel, and the third sub-master device 35 receives the information from the first sub-master device 15. Likewise, as shown in No. 4 of the table, the second sub-master device 25 broadcasts the MASTER_DEV_ID thereof and the connection quality of the channel, and the third sub-master device 35 receives the broadcasted information. Then, as shown in No. 5 of the table, the third sub-master device 35 broadcasts the information, which is received from the first and second sub-master devices 15, 25 through the processes of Nos. 3 and 4 in the table. At this time, the third sub-master device broadcasts the MASTER_DEV_ID thereof, the MASTER_DEV_ID of the first and second sub-master devices 15, 25, which are the lower nodes thereof, and the connection quality of the channel.
In this manner, when the information is collected from each of the sub-master devices 15, 25, 35 connected to the first sub-master device 15, among the first-order node master devices, the first sub-master device 15, as shown in No. 6 of the table, broadcasts the collected information, the MASTER_DEV_ID thereof, the MASTER_DEV_ID of the first and second sub-master devices 15, 25, which are the lower nodes thereof, and the connection quality of the channel. Then, the super master device 45 receives the information from the first sub-master device 15.
On the other hand, the information collection from the second sub-master device 25 that is another first-order node master device is also carried out through the same process.
First, as shown in No. 7 of the table, the super master device 45 broadcasts the super MASTER_DEV_ID thereof and the connection quality of the channel. Then, the second sub-master device 25 receives the information from the super master device 45.
Likewise, as shown in Nos. 8 and 9 of the table, the first and third sub-master devices 15, 35 broadcast the MASTER_DEV_ID thereof and the connection quality of the channel. Then, the second sub-master device 25 receives the information from the first and third sub-master devices 15, 35.
Then, the second sub-master device 25 broadcasts the collected information, the MASTER_DEV_ID thereof, the MASTER_DEV_ID of the super master device 45 and the second and third sub-master devices that are the lower nodes thereof, and the connection quality of the channel. Then, the super master device 45 receives the information from the second sub-master device 25.
In this manner, when the information is received from each of the sub-master devices 15, 25, 35 constituting each route of the network topology, the super master device 35 has the information including the structure of the network topology as shown in
In order to establish a network topology, initialization for construction of each sub-network, setting of the sub-master devices of each sub-network, initialization of the backbone network 1, and setting of the super master device 45 are first performed.
When such operations are completed, the super master device 45 transmits a beacon message to each of the sub-master devices 15, 25, 35 (S505). Then, each of the sub-master devices 15, 25, 35 transmits a response message to the super master device 45 (S510). When each of the sub-master devices 15, 25, 35 having transmitted the response messages has the MASTER_DEV_ID (S515-Y), the super master device 45 determines that the network topology has been completed (S565).
However, when the sub-master device having no MASTER_DEV_ID exists among the respective sub-master devices 15, 25, 35 having transmitted the response messages (S515-N), the super master device 45 assigns the MASTER_DEV_ID to those of the sub-master devices 15, 25, 35 (S520) having no MASTER_DEV_ID. Then, the super master device determines the connection quality, based on the response messages provided from each of the sub-master devices 15, 25, 35. When the connection quality to any of the sub-master devices is lower than the predetermined level, i.e., SNR<a (S525-N), the super master device 45 removes the MASTER_DEV_ID of the corresponding sub-master device (S530).
Then, the first-order node master device, to which the MASTER_DEV_ID has been assigned from the super master device 45, transmits the beacon message to the sub-master devices except its own self, i.e., to the super master device 45 and the other sub-master devices in the backbone network 1 (S535). When the response messages are received from the super master device 45 and the other sub-master devices in the backbone network 1 (S540), the first-order node master device determines whether the MASTER_DEV_ID is provided (S545) and assigns the MASTER_DEV_ID to the other sub-master devices having no MASTER_DEV_ID (S550). Then, the first-order node master device determines whether the connection quality is satisfied (i.e., SNR is less than a (SNR<a)) (S555), and removes the MASTER_DEV_ID of the sub-master device not satisfying the connection quality (S560).
In this manner, a second-order node master device, to which the MASTER_DEV_ID has been assigned from the first-order node master device, assigns the MASTER_DEV_ID to a third-order node master device through the same process as the first-order node device. These processes are continued until the MASTER_DEV_ID is assigned to all the sub-master devices in the backbone network 1.
When the MASTER_DEV_ID is assigned to all the sub-master devices in the backbone network 1, it is determined that the network topology establishment has been completed (S565). Then, the information including the connection quality of each channel from the super master device 45 and each of the sub-master devices 15, 25, 35 included in the respective routes constituting the network topology is transferred to the upper node from the lower node (S570), and finally transferred to the super master device 45 (S575).
The super master device 45 stores the construct of the network topology and the connection quality information about each channel (S580), and allocates the CTA to the super frame, with regard to the sub-master devices 15, 25, 35
First, the information transfer from the PDA 21 of the second sub-network 20 to the second sub-master device 25 that is the master device of the second sub-network 20 is requested, and then to the notebook 41 of the fourth sub-network 40 (S605). Then, the second sub-master device 25 requests the super master device 45 to allocate a route and time for the information transfer to the notebook 41 of the fourth sub-network 40 (S610).
The super master device 45 having received the request extracts a possible route from the pre-stored network topology (S615). At this time, according to the network topology shown in
When the route is extracted, the super master device 45 compares the connection qualities of the respective routes (S620). Since the super master device 45 has the information about the connection qualities of respective channels, it should calculate the connection quality of the whole route when the plurality of channels are connected. At this time, the super master device 45 compares the connection qualities among the routes, using Equation (1).
Here, A, B and C are channels of the respective routes, B and C are channels constituting one route, and A is a single route. When satisfying the equation 1, the super master device 45 transfers the information to the route passing through B and C, rather than A route. If three channels constitute the route, it may be possible to compare the connection qualities among the routes, using Equation (2).
Here, B, C and D are channels constituting one route, and A is a single route.
The super master device 45 compares the connection qualities among the respective routes with the equations 1 and 2 and selects a route having the highest connection quality when communicating among the sub-networks (S625). Then, the super master device 45 transfers the information about the corresponding route and time allocated, to the second sub-master device 25 (S630). The second sub-master device 25 allocates the route and time to the PDA 21 and controls the information to be transferred through the corresponding route and time (S635).
In this manner, according to the method of establishing a network topology of the backbone network 1, it is possible to set a network topology enabling the communication to be carried out among the respective sub-networks included in the backbone network 1. In addition, when carrying out the communication among the respective sub-networks, the information is transferred through the route having the highest connection quality, so that the reliability of the communication can be secured.
As described above, according to the invention, it is possible to set a network topology enabling the communication to be carried out among the respective sub-networks included in the backbone network. In addition, when carrying out the communication among the respective sub-networks, the information is transferred through the route having the highest connection quality, so that the reliability of the communication can be secured.
The foregoing exemplary embodiments are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. Also, the description of the embodiments of the present invention is intended to be illustrative, and not to limit the scope of the claims, and many alternatives, modifications, and variations will be apparent to those skilled in the art.
Number | Date | Country | Kind |
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10-2006-0051042 | Jun 2006 | KR | national |