JP4548723B2 - Network control method - Google Patents

Description

  The present invention relates to a mesh network in which a plurality of wireless nodes are distributed, and a pair of wireless nodes that terminate each wireless link is set to have a transmission period before or after the TDD boundary set in the TDD frame. The present invention relates to a network control method that is positioned exclusively in either the upper level or the lower level based on this and selects a frequency slot to be allocated to the radio link based on this positioning.

  In wireless networks where the link topology is mesh, adoption of the TDD (Time Division Duplex) method is being considered as a communication method that can effectively allocate communication resources even if the traffic volume between opposing nodes is asymmetric. Yes. The TDD method is an access method that realizes mutual communication by time-sharing a time axis with a constant period (time slot) in one frequency band (frequency slot) and assigning it to the uplink and downlink. Generally used in multiplexing systems such as (Time Division Multiple Access) and CDMA (Code Division Multiple Access).

  In such a TDD scheme, a frequency slot (FID) to be assigned to each radio channel is determined, and each line (ie, transmission period and reception period) is determined according to the uplink and downlink traffic volume for each opposed radio node. It is necessary to set the ratio of the number of time slots to be assigned to (hereinafter referred to as TDD ratio).

  Here, one control node on the mesh network grasps the traffic information and network topology of all nodes in the mesh network, determines the TDD ratio and FID for each link, and distributes them to all nodes. This is unrealistic in terms of increasing the load on the control node, the ability to follow instantaneously changing traffic volume, or the scalability of the network.

  Therefore, it is considered effective to use an autonomous distributed method in which each node determines its own TDD attribute and FID while obtaining neighboring information instead of central control by a specific control node. However, a radio communication system that employs the TDD scheme and uses a plurality of FIDs has the following technical problems.

  (1) In a mesh network, one node may have a plurality of radio links, and a plurality of antennas and radio stations are installed in each node. At this time, if the same FID is used for a plurality of links and the TDD ratio is different for each link, interference due to wraparound from an adjacent antenna of the same node may occur. Therefore, it is necessary to make the TDD ratio common between adjacent links using the same FID, and an optimum TDD ratio cannot be set for each link according to the traffic volume.

  (2) When updating the FID assigned to a radio link, if the pair of radio nodes sharing this radio link do not have a common knowledge about their TDD ratio and FID, each node will be different for the same link A FID will be assigned, and a trap will be generated, making communication impossible.

  In order to solve such a technical problem, the inventors of the present invention position, for each pair of wireless nodes, a node having the first half of each TDD frame as the transmission period and the second half as the reception period as “higher”. Conversely, a node whose transmission period is the second half of the TDD frame and reception period is the first half is positioned as “lower”, and for each radio link, one of the radio nodes positioned higher or lower than the radio link is a frequency slot. By allocating a wireless channel, a system in which a wireless channel can be allocated to each wireless link without any problems was invented and a patent application was filed (Patent Document 1).

  Furthermore, by allowing each node to terminate not only a wireless link that positions its own node at the higher level but also a wireless link that positions its own node as a lower level, the network is an odd number having a plurality of nodes as vertices. Even when a polygonal circuit is included, a system has been invented and a patent application has been filed (Patent Document 2).

  FIG. 8 is a diagram showing a configuration of a wireless network that adopts the above-described Patent Document 2 and in which each wireless node assigns FID to each link in an autonomous and distributed manner.

  A pair of nodes N that terminate each radio link L1 to Ln, one of which is positioned as "upper" and the other as "lower", regardless of whether it is higher or lower, only that one node, A frequency slot may be assigned to the radio link. For example, in the case of the wireless link L1, if one node N1 that terminates the wireless link L1 is positioned at the upper level (●), the other node N4 is positioned at the lower level (◯). Similarly, in the case of the radio link L2, one node N1 that terminates the radio link L2 is positioned higher, and the other node N2 is positioned lower.

  Here, nodes that are positioned higher than all of the wireless links that terminate at the own node, such as wireless nodes N1 and N7, are defined as “upper nodes”, and all of the wireless links that terminate at nodes N2 and N4, for example. Nodes that are positioned in the lower order are defined as “subordinate nodes”.

  By the way, if all of the closed circuits composed of a plurality of wireless nodes are even polygons, all the nodes can be defined as either upper nodes or lower nodes as shown in FIG. However, as shown in FIG. 8, when an odd polygonal cycle (for example, a triangle having nodes N1, N3, and N4 as vertices) is included, some nodes are forced to be positioned at both the upper and lower levels. The

  For example, the node N3 in FIG. 8 is positioned higher than the radio link L4, but is positioned lower than the other radio links L3, L5, and L6. Similarly, the node N5 is positioned higher than the radio link L8, but is positioned lower than the other radio links L7 and L9. Like the nodes N3 and N5, nodes positioned both higher and lower than the radio link terminated at the own node are the “upper node” and “lower node” (collectively, “pure anode”). In some cases, it is defined as “hybrid node”.

In the case of a pure anode, even if the same FID is used in adjacent links, problems such as interference do not occur as long as the TDD ratios match. On the other hand, in the hybrid node, the same FID as that used in the radio link that positions the own node “upper” cannot be used in the adjacent link that positions the own node “lower”. Therefore, in the hybrid node, as compared with the pure anode, there are more restrictions on the frequency slots that can be allocated, and the frequency utilization efficiency is inevitably lowered. In order to solve such a technical problem, the inventors of the present invention invented a system in which each node can switch the position of its own node with respect to each wireless link from one of the upper and lower ones to the other. (Japanese Patent Application No. 2002-70259).
JP 2002-345016 A JP 2003-339072 A JP 2004-304511 A

  In the above-mentioned Patent Document 3, the positioning of the upper and lower positions, the master node that performs the position switching actively, and the slave node that can only perform the positioning switching passively in response to an instruction from the master node. The relationship is fixed. For example, only the node positioned at the higher level can become the master node.

  An object of the present invention is to solve the above-described problems of the prior art and provide a network control method in which any of the nodes facing each other across a wireless link can be a master node regardless of the upper and lower positions. is there.

  In order to achieve the above-described object, the present invention is a mesh network in which a plurality of wireless nodes are distributed, and a pair of wireless nodes that terminate each wireless link are arranged before and after the TDD boundary set in the TDD frame. In the network system where the frequency slot to be allocated to the radio link is selected based on this positioning attribute based exclusively on the upper or lower level based on which is set as the transmission period, the TDD ratio is led The master to be set, the attribute of the slave in which the TDD ratio is passively set, the procedure for exclusively setting the pair of radio nodes, and the master node to which the master attribute is set is a predetermined link to the radio link A procedure for determining whether or not there is a frequency slot that satisfies the allocation condition, and when there is no frequency slot that satisfies the allocation condition, The star node determines whether a frequency slot that satisfies the allocation condition is newly generated by switching the master / slave attribute with the opposite node, and the frequency slot that satisfies the allocation condition by the attribute switching A procedure in which the master node and the slave node cooperate to perform the attribute switching, and a procedure in which a channel of a frequency slot that satisfies an allocation condition by the attribute switching is added to the radio link. It is characterized by including.

  According to the present invention, one of a pair of radio nodes facing each other is a master that leads the TDD ratio, and the other is a slave that passively sets the TDD ratio. Regardless of whether it is positioned in the lower level, the own node can be switched to the slave and the opposite node can be switched to the master. Therefore, if the network topology can increase the number of FIDs that can be split if the master / slave attribute is switched for some of the opposing nodes, the FID can be increased by executing the attribute switching.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a main part of a radio node according to the present invention, and all of “upper node”, “lower node”, and “hybrid node” have the same configuration.

  The wireless node N includes an outdoor wireless device 2 and an indoor wireless device 3. The outdoor wireless device 2 includes a plurality of outdoor wireless units (# 1 to # 4) 21. The indoor wireless device 3 includes a plurality of wireless channel units (# 1 to # 4) 33, a switch 31, a wireless channel manager (CHM) 32, and a network control device 34.

  The network control device 34 includes a topology information generator 34a and a default TDD plan generator 34b. The topology information generator 34a recognizes the topology configuration of the network and generates topology information. As will be described in detail later, the default TDD plan generation unit 34b obtains the standard positioning (upper or lower) of each node for each radio link based on the topology information, and uses this as the default TDD plan for the radio channel manager 32. To notify.

  The radio channel manager 32 includes a first CPU that dynamically assigns the radio channel units 33 (# 1 to # 4) to the radio links L1 to L4 according to notification from the network control device 34, and the first CPU. And a second CPU for controlling. Each radio channel unit 33 establishes a TDD radio channel with the radio channel unit of the opposite node, and controls its TDD frame and TDD ratio. The switch 31 connects each radio channel unit 33 (# 1 to # 4) to each radio link L1 to L4 based on the assignment result.

  Next, the operation of each wireless node will be described in detail with reference to the flowchart. FIG. 2 is a flowchart showing the main operation of the wireless node. In step S1, the topology generation unit 34a of the network control device 34 recognizes the network topology. In step S2, a default TDD plan is generated based on the recognition result. The procedure for generating the default TDD plan will be briefly described below.

  If the network includes anything other than even polygonal cycles, a hybrid node is forced to occur. When traffic demand increases in a hybrid node, it is desirable to improve the use efficiency of FID by making it pure anodized. For this purpose, each node dynamically sets its own upper / lower attributes for each radio link. It is necessary to be able to switch.

  However, since the transmission efficiency decreases if the upper / lower attribute switching occurs frequently, it is necessary to minimize the occurrence even if the upper / lower attribute switching is allowed. It is desirable to always set the upper / lower attributes appropriately. Therefore, in the present embodiment, a “default TDD plan” that is determined only from network topology information without depending on traffic demand is defined.

  The “Default TDD Plan” gives a standard setting for the upper / lower attributes to all wireless nodes on the network, and does not fix the instantaneous instantaneous allocation. It also serves as a guide so that switching can be performed efficiently without unnecessary switching and even when switching occurs. Therefore, in the present embodiment, not only immediately after the start of operation, but also after switching some upper / lower attributes according to traffic fluctuations, when the traffic amount decreases, the default TDD plan is restored. Guiding principles work.

  The present inventors have devised an algorithm for creating a “default TDD plan” that can set the upper / lower attributes in all links so as not to generate hybrid nodes as much as possible for an arbitrary network topology. It is introduced in the “Research Results Report” for the Telecommunications Broadcasting Organization created in the process of research and development of broadband FWA. The contents are also explained in a patent application (Japanese Patent Laid-Open No. 2004-304511) filed earlier by the present applicant.

  In step S3, when the upper / lower attribute defined in the default TDD plan and the current upper / lower attribute of the own node are different, the upper / lower attribute of the own node is set to the upper and lower attributes in accordance with the default TDD plan. A “default TDD plan reflection process” for switching from the lower one to the other is executed. This “default TDD plan reflection process” is performed only in the master node of a pair of radio nodes facing each other across the radio link, and the slave node is passively switched in accordance with a request from the master node. Executed.

  FIG. 3 is a flowchart showing the procedure of the “default TDD plan reflection process”. In step S10, the current upper / lower attributes regarding the radio links L1, L2, L3, and L4 terminated at the own node are shown. Then, it is compared with the upper / lower attributes defined in the default TDD plan, and the presence / absence of a radio link that requires switching between the upper / lower attributes is determined. Here, all the radio links having attributes different from the upper / lower attributes defined in the default TDD plan are recognized as the switching target links. If there is a wireless link to be switched, the process proceeds to step S11.

  In step S11, the line quality of the switching target link is obtained. In this embodiment, CNR {C: carrier, N: noise, R: ratio, that is, C / N} is adopted as the line quality, and this is compared with the reference value CNRref. If CNR> CNRref, the process proceeds to step S12, and the radio link for switching the upper / lower attribute is selected. If there are a plurality of target links, one of them is selected at random.

  In step S13, it is determined whether or not the selected switching target link satisfies a predetermined switching condition. In this embodiment, it is switched that an adjacent link adjacent to the switching target link and having the same upper / lower attribute as the switching target link does not use the same FID as the FID used in the switching target link. It is set as a condition. If the same FID is used, interference occurs after switching of the upper / lower attributes, and therefore switching of the upper / lower attributes is stopped for the switching target link. On the other hand, if the same FID is not used, it is determined that the switching condition is satisfied, and the process proceeds to step S14.

  In step S14, the switching instruction and switching timing of the upper / lower attribute are notified to the opposite node. In step S15, the upper / lower attributes of the current switching target link are switched, and the upper / lower attributes of all radio channels included in the wireless link are switched from upper to lower or from lower to upper.

  Returning to FIG. 2, in step S <b> 4, the number of requested channels notified from the network control device 34 is determined. The network controller 34 periodically or irregularly calculates the appropriate number of channels for each of the radio links L1, L2, L3, and L4 whose one end is terminated at its own node based on the network topology and traffic volume. The result is notified to the radio channel manager 32 as the requested channel number Lreq (Lreq (1) to Lreq (4)).

  In step S5, the notified request channel number Lreq is compared with the current radio channel number Lref, and for a radio link of Lreq> Lref, the process proceeds to step S6. In step S6, “pre-processing for channel addition” is executed, the FID assigned to the radio channel to be added is determined, and further, switching between higher / lower attributes is executed as necessary.

FIG. 4 is a flowchart showing the procedure of “channel addition preprocessing”. In step S31, among the unassigned FIDs that are not assigned to any radio channel, there is an FID that satisfies the assignment condition. Is determined. In the present embodiment, the following three are set as allocation conditions.
(1) Condition 1: It is not assigned to another radio link having a different upper / lower attribute.
(2) Condition 2: Satisfy predetermined line quality continuously for a certain period
(3) Condition 3: A FID in which links that are not adjacent to each other (that is, links terminated at different nodes) must have the same TDD ratio cannot be selected.

  FIG. 5 is a diagram for explaining the condition 3. When a radio link L1 having an FID of f1 is established between the nodes N1 and N2, and the radio link L2 adjacent thereto is f1, the link L1, The TDD ratio of L2 is set to be the same to avoid mutual interference. In this state, when a channel is added to another radio link L3 terminated at the node N2, if the FID is set to f1, the TDD ratio between the two is avoided in order to avoid interference between the link L3 and the link L1. Must be matched, and this also affects the link L2, so the links L3 and L2 must match the TDD ratio even though they are not adjacent to each other.

  Similarly, since the radio links L2 and L3 are not adjacent to each other, it is not necessary to match the TDD ratio even if both use the same FID (eg, f1). However, when a channel is added to the radio link L1 in such a state, if the FID is set to f1, the radio links L2 and L3 adjacent to the radio link L1 have their TDD ratios compared to that of the radio link L1. In the end, the links L3 and L2 must match the TDD ratio even though they are not adjacent to each other.

  In this way, if control for matching the TDD ratio across a plurality of nodes is performed, the process for exchanging TDD ratio information between the plurality of links in order to match the TDD ratio becomes complicated. In the present embodiment, in order to avoid such a situation, it is not possible to select an FID such that links that are not adjacent to each other (links L2 and L3 in FIG. 5) must have the same TDD ratio. Condition 3 is satisfied. If there is an FID that satisfies these allocation conditions, the process proceeds to step S32, and one of them is selected.

In step S33, it is determined whether or not the selected FID is the same as the FID assigned to the adjacent link. If it is the same FID, the process proceeds to step S34 to determine whether or not the same FID allocation condition is satisfied. That is, if network synchronization is not established, even if the TDD ratio is matched, interference is caused and channel down is caused. In addition, since the function that controls the FID and TDD ratio in units of channels is the node that is the master in that link, the node that terminates multiple links that should have the same TDD ratio is the “master” in that link. Need to be. Therefore, in the present embodiment, the following two are set as the same FID allocation condition.
(1) Condition 1: Network synchronization is established between adjacent links
(2) Condition 2: The node that terminates the link is the master of the link.

  If the same FID allocation condition is not satisfied, the FID is removed from the unallocated FID in step S35 and the process returns to step S31, and the above-described procedure is repeated. If the same FID allocation condition is satisfied, the process proceeds to step S36, and the selected FID is notified to the channel addition processing function.

  On the other hand, if it is determined in step S31 that there is no FID satisfying the allocation condition, the process proceeds to step 37, and any one of the unallocated FIDs is arbitrarily selected. In step S38, it is determined whether or not the FID can satisfy the allocation condition if the upper / lower attribute is switched. In step S39, even if the upper / lower attribute of the link to which the radio channel is to be added is switched, it is determined whether all the FIDs currently used in the existing radio channel can satisfy the allocation condition. Proceed to step S40. In step S40, the upper / lower attribute of the radio link to which the radio channel is added is switched.

On the other hand, if it is determined in step S38 that the allocation condition is not satisfied even if the upper / lower attribute is switched, or if the upper / lower attribute is switched in step S39, the FID being used in the existing radio channel is If it is determined that the allocation condition cannot be satisfied, the process proceeds to step S41. In step S41, it is determined whether or not there is another unassigned FID. If there is, the process returns to step S37 and the above processes are repeated for the other FIDs. If there is no other unassigned FID, the process proceeds to step S42. If the master / slave attribute is switched, the presence / absence of an FID that satisfies the assignment condition is determined based on the following two conditions.
(1) Condition 1: FID that satisfies the allocation condition only by switching the master / slave attribute.
(2) Condition 2: FID that satisfies the allocation condition by switching the upper / lower attribute and switching the master / slave attribute.

  If there is an FID that satisfies any of the above conditions, the process proceeds to step S43, and a master / slave attribute switching process described later is executed.

  FIG. 6 is a diagram schematically showing how FIDs that can be allocated increase by switching the master / slave attribute. Here, the maximum number of channels that can be established for each radio link is four, which is secured in advance. A case where there are six frequency slots f1 to f6 will be described as an example.

  As shown in FIG. 4A, here, for the radio link L1, the node N1 is the slave S, the node N2 is the master, and the radio link L2 adjacent thereto is the node N1 is the master and the node N3 is the slave. Consider a case in which the FIDs f1, f2, and f3 have been assigned to the wireless link L1, and the FIDs f4, f5, and f6 have been assigned to the wireless link L2.

  Here, when there is a channel addition request for the link L1, there are three FIDs f4, f5, and f6 that are not assigned to the link L1, but these FIDs have already been assigned to the adjacent link L2. And for link L1, node N1 is a slave and cannot control the TDD ratio etc. of each channel, so the FID already assigned to link L2 cannot be assigned to link L1, and therefore a channel is added to link L1. Can not.

However, as shown in Figure (b), if the nodes N1 and N2 switch the master / slave attribute and the node N1 becomes the master, the node N1 controls the TDD ratio etc. for all channels of the links L1 and L2. Node N1 adds a channel that uses f4 assigned to link L2 to link L1, and if the TDD ratio matches the channel that uses f4 in link L2, the FID is added to link L1. f4 channels can be added.

  Returning to FIG. 2, when the FID to be assigned to the channel to be added is determined as described above, in step S7, negotiation with the opposite node regarding the TDD ratio and frame synchronization is performed, and then the radio channel is added at a predetermined timing. Is done.

Next, the master / slave attribute switching procedure will be described with reference to the sequence diagram of FIG. Here, the description starts from a state in which the attributes of a pair of nodes A and B facing each other are a master and a slave, respectively.
(1) Procedure 1: In the master node A, a master switching request is notified from the first CPU of the radio channel manager 32 to the second CPU. This master switching request is transmitted to the opposite node B via the radio channel unit 33 and the switch 31 and the outdoor radio apparatus 3, and is notified from the second CPU of the radio channel manager 32 to the first CPU. The radio channel manager 32 of the node B determines whether or not the attribute of the own node can be switched from the slave to the master.
(2) Procedure 2: In Node B, if the master / slave attribute switching causes the FID being used on the existing radio channel to fail to satisfy the allocation condition, a master switching response (NAK) is sent to Node A. I will reply.
(3) Procedure 3: In Node B, if there is no FID that is being used on the existing radio channel that cannot satisfy the allocation conditions due to the switching of the master / slave attribute, a master switching response (NAK) is sent to Node A. I will reply.
(4) Procedure 4: In the node A, when the first CPU of the radio channel manager 32 receives the master switching response (ACK), the node A issues a TDD ratio fixing request for changing the TDD ratio to a fixed value (for example, 6: 6). Notify 2 CPUs.
(5) Procedure 5: The second CPU of the node A returns a TDD ratio fixed response (ACK) in response to the TDD ratio fixed request.
(6) Procedure 6: In the node A, the first CPU of the radio channel manager 32 notifies the second CPU of a slave switching request in response to the TDD ratio fixed response (ACK). The second CPU requests the wireless channel unit for slave setting.
(7) Procedure 7: In the second CPU of node A, the attribute identifier of the control channel is changed from master (M) to slave (S), and the TDD ratio is set to a fixed value.
(8) Procedure 8: The second CPU of the node B detects that the attribute identifier is changed from the master (M) to the slave (S) in the control channel of the received signal, and requests the radio channel unit to perform master setting. Further, in the second CPU, the attribute identifier of the control channel of the transmission signal is changed from the slave (S) to the master (M).
(9) Procedure 9: In the node B, the master switching notification is output from the second CPU to the first CPU, and the attribute is switched from the slave to the master. The second CPU of the node A detects that the attribute identifier is changed from the slave (S) to the master (M) in the control channel of the received signal, and outputs a slave switching response (ACK) to the first CPU.
(10) Procedure 10: At node B, the attribute is set as the master, and at node A, the attribute is set as the slave. Thereafter, communication is performed at a TDD ratio that is dynamically set by the node B according to the traffic amount and the like.

It is a block diagram of the radio | wireless communications system mounted in each radio | wireless node. It is the flowchart which showed operation | movement of each radio | wireless node. It is a flowchart of a default TDD plan reflection process. It is a flowchart of a channel addition pre-processing. It is a figure for demonstrating allocation conditions. It is the figure which showed typically a mode that the FID which can be allocated increases by switching a master / slave attribute. It is the sequence diagram which showed the switching procedure of the master / slave attribute. It is the figure which showed typically the structure of the network containing the circuit of an odd-numbered polygon. It is the figure which showed typically the structure of the network containing only the closed circuit of an even polygon.

Explanation of symbols

  2 ... Outdoor wireless device, 3 ... Indoor wireless device, 31 ... Switch, 32 ... Wireless channel manager, 33 ... Wireless channel unit, 34 ... Network control device

Claims (5)

In a mesh network in which multiple wireless nodes are distributed, a pair of wireless nodes that terminate each wireless link is based on whether the transmission period is before or after the TDD boundary set in the TDD frame. In the network system in which the frequency slot to be allocated to the radio link is selected based on the positioning attribute,
A procedure for setting the TDD ratio as a master, each attribute of a slave whose TDD ratio is passively set, and a procedure for exclusively setting the pair of wireless nodes;
A procedure for determining whether or not there is a frequency slot satisfying a predetermined allocation condition for the radio link by the master node set with the master attribute;
When there is no frequency slot that satisfies the allocation condition to the radio link, the master node sets the allocation condition to the radio link if the opposite node connected by the radio link sets the TDD ratio in a leading manner. A procedure for determining whether a satisfactory frequency slot can be added ; and
A procedure in which the master node and the slave node cooperate to perform the attribute switching when a frequency slot that satisfies the allocation condition can be added if the opposite node sets the TDD ratio in a leading manner ;
A step in which a new master node adds a channel of a frequency slot in which the TDD ratio is set so as to satisfy the allocation condition to the radio link after successfully switching the master / slave attribute. Network control method. The procedure in which the master node and the slave node cooperate to perform attribute switching,
The master node transmits a master / slave attribute switching request to the slave node;
A procedure in which the slave node determines whether or not the attribute of the own node can be switched from the slave to the master in response to the master / slave attribute switching request, and returns a switching permission to the master node if switching is possible. When,
In response to the switching permission, the master node switches its master / slave attribute to the slave, and changes the attribute identifier to the slave in the control channel of the transmission signal;
The slave node detects that the attribute identifier of the control channel of the received signal is switched to the slave, switches its master / slave attribute to the master, and changes the attribute identifier of the control channel of the transmission signal to the master. The network control method according to claim 1, further comprising:   The network control method according to claim 2, wherein the master node sets a TDD ratio to a fixed ratio in the control channel in response to the switching permission.   The master node returns its master / slave attribute to the master if the master / slave attribute of the opposite node does not switch to the master even if a predetermined time elapses after switching its master / slave attribute to the slave. The network control method according to claim 2, wherein: When there is no frequency slot that satisfies the allocation condition, the master node newly sets a frequency slot that satisfies the allocation condition by switching the master / slave attribute with the opposite node and switching the upper / lower attribute. A procedure for determining whether or not it occurs,
The method further comprising: a step in which the master node and the slave node cooperate to perform the attribute switching when a frequency slot that satisfies the allocation condition is generated by the attribute switching. 5. The network control method according to any one of 4.

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