A TDMA wireless ad hoc network forked networking method

Abstract

The present invention relates to a TDMA wireless ad-hoc network forked networking method, which includes the following steps: S1: Each node on the main path transmits a branch beacon carrying information about the need to establish a branch; S2: Mobile stations that have not become relay nodes scan and receive the branch beacon and decide whether to apply to the node that sent the branch beacon to become the first node of the branch; S3: The node that sent the branch beacon receives the application beacons sent by each different mobile station to apply to become the first node of the branch, and selects the first node of the branch from these mobile stations; S4: The selected first node of the branch selects and broadcasts the service frequency. The advantages of the present invention are: Mobile stations that have not become relay nodes screen the nodes that need to generate branches, and the nodes that need to generate branches screen the mobile stations that apply to become relay nodes. The excellent quality of the first node of the branch is ensured through the two-way screening of the mobile stations and the nodes; the width of the coverage area of the ad-hoc network can be increased.

Description

Technical Field

[0001] The present invention relates to the field of wireless ad hoc networks, and in particular to a TDMA wireless ad hoc network forked networking method. Background Art

[0002] DMR / PDT is a widely used standard for digital professional wireless communication systems. Common DMR / PDT communication modes include conventional direct connection, conventional relay, and trunking communication. The first conventional direct connection mode only requires mobile station devices, such as walkie-talkies and / or vehicle-mounted radios, to directly perform service transmission, such as calls, between two or more mobile stations. Due to the straight-line propagation characteristics of wireless high-frequency radio frequency, the coverage area of this mode is extremely limited. The latter two modes require the establishment of a base station to forward services, which can expand the communication coverage area. To expand the communication coverage area, the base station antenna is erected at a higher position, such as on a mountain or a rooftop. However, in this case, the base station becomes a fixed base station. In some special occasions, such as the wild, caves / tunnels, basements, etc., there is often no base station signal or it is not easy to erect a base station. At this time, the ad hoc network technology can expand the communication distance through the networking between mobile stations under the condition of only using mobile station devices, and solve the problem of long-distance communication.

[0003] In areas without network coverage, a group of mobile terminals use several channels, and through competitive election, a relay mobile terminal is selected as a relay node to form a temporary service multi-hop network. Several relay mobile terminals can transmit services (such as voice) to a far place to form a service area with a larger coverage area.

[0004] The method of arranging relay nodes in a line is the simplest network mode, which can cover a long and narrow rectangular area. In actual use, there may be other shapes of areas to be covered, such as a square area with a large length and width. Summary of the Invention

[0005] The present invention mainly solves the problem that the traditional ad hoc network mode can only cover a long and narrow rectangular area, and provides a TDMA wireless ad hoc network forked networking method that enables the ad hoc network to fork and adjust the ad hoc network coverage area as needed.

[0006] The technical solution adopted by the present invention to solve its technical problems is a TDMA wireless ad hoc network forked networking method, including the following steps:

[0007] S1: Each node on the main path transmits a branch beacon carrying information about the need to establish a branch;

[0008] S2: Mobile stations that have not become relay nodes scan and receive the branch beacon and decide whether to apply to the node that sent the branch beacon to become the first node of the branch;

[0009] S3: The node that emits the branch beacon receives the application beacons sent by each different mobile station applying to become the branch head node, and selects the branch head node from these mobile stations.

[0010] S4: The selected branch head node selects and broadcasts the service frequency to be used by the branch.

[0011] The mobile stations that have not become relay nodes screen the nodes that need to generate branches, and the nodes that need to generate branches screen the mobile stations applying to become relay nodes. The excellent quality of the branch head node is ensured through the two-way screening of the mobile stations and the nodes.

[0012] As a preferred solution of the above solution, when the branch head node needs a secondary node, the following steps are executed:

[0013] S11: The branch head node transmits a branch beacon carrying information about the need for a secondary node.

[0014] S12: The mobile stations that have not become relay nodes scan and receive the branch beacon and decide whether to apply to the branch head node that emits the beacon to become a secondary node.

[0015] S13: The branch head node receives the application beacons sent by each different mobile station applying to become a secondary node, and selects the secondary node from these mobile stations.

[0016] S14: The branch head node informs the secondary node of the service frequency used by the branch.

[0017] As a preferred solution of the above solution, when the secondary node needs a tertiary node, the following steps are executed:

[0018] S21: The secondary node transmits a branch beacon carrying information about the need for a tertiary node.

[0019] S22: The mobile stations that have not become relay nodes scan and receive the branch beacon and decide whether to apply to the secondary node that emits the beacon to become a tertiary node.

[0020] S23: The secondary node receives the application beacons sent by each different mobile station applying to become a tertiary node, and selects the tertiary node from these mobile stations.

[0021] S24: The secondary node informs the tertiary node of the service frequency used by the branch.

[0022] As a preferred solution of the above solution, after the mobile stations that have not become relay nodes receive the branch beacons from different nodes, they synchronize the time base and obtain the reachability parameters from themselves to each node that emits the branch beacon. The reachability parameters include field strength, distance, and signal-to-noise ratio.

[0023] As a preferred solution of the above solution, the mobile stations that have not become relay nodes also receive the application beacons of multiple mobile stations and obtain the reachability parameters from themselves to the mobile stations that send the application beacons.

[0024] As a preferred solution of the above solution, the mobile stations that have not become relay nodes select the nodes within a preset range of reachability parameters among the nodes that send branch beacons as candidate nodes. For each candidate node, it is judged whether the mobile stations within a certain distance range from itself send application beacons to the candidate node. If so, the candidate node is abandoned; if not, an application beacon is sent to the candidate node.

[0025] As a preferred solution of the above solution, when the nodes that send branch beacons select the first-level nodes, second-level nodes or third-level nodes for branching, they obtain the reachability parameters from themselves to the mobile stations that send application beacons to this node, and screen the mobile stations with reachability parameters within a preset range as the first-level nodes, second-level nodes or third-level nodes for branching.

[0026] As a preferred solution of the above solution, the service frequency of the first-level node for branching is different from the service frequency of the main path.

[0027] As a preferred solution of the above solution, the multi-frame format of the first-level node for branching is generated according to the odd / even access method of the upper-level node it follows, the multi-frame format of the second-level node is generated according to the odd / even access method of the first-level node for branching it follows, and the multi-frame format of the third-level node is generated according to the odd / even access method of the first-level node for branching it follows. The odd / even access method refers to: if the upper-level node uses the even access method, the first-level node for branching uses the odd access method, and the multi-frame format of the first-level node for branching is C0, C1, T0, X1, T2, X3, T4, X5, T6, X7, T8, X9, T10, X11, T12, X13, T14, X15, that is, when in standby, the service reception uses the frequencies and time slots specified by T0, T2, T4, T6, T8, T10, T12, T14, and the service transmission uses the frequencies and time slots specified by X1, X3, X5, X7, X9, X11, X13; if the upper-level node uses the odd access method, the first-level node for branching uses the even access method, and the multi-frame format of the first-level node for branching is C0, C1, X0, T1, X2, T3, X4, T5, X6, T7, X8, T9, X10, T11, X12, T13, X14, T15, that is, when in standby, the service reception uses the time slots of T1, T3, T5, T7, T9, T11, T13, and T15, and the service transmission uses the time slots of X2, X4, X6, X8, X10, X12, and X14. Among them, the Ti time slot uses the service frequency of the upper-level node, and the Xi time slot uses the service frequency selected by the first-level node for branching, where i = 0, 1,..., 15.

[0028] As a preferred solution of the above scheme, the odd / even access method of the upper-level node is determined by the following method: the group leader node of the main path sets the LIFE value, and the LIFE values of the remaining nodes in the main path decrease as the distance from the group leader node increases. When the LIFE value of a node is odd, the node uses the odd access method; otherwise, it uses the even access method.

[0029] The advantages of the present invention are as follows: The mobile stations that have not become relay nodes screen the nodes that need to generate branches, and the nodes that need to generate branches screen the mobile stations that apply to become relay nodes. The excellent quality of the branch head node is ensured through the two-way screening of the mobile stations and the nodes; the width of the self-organizing network coverage area can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic flow diagram of a TDMA wireless ad hoc network bifurcation networking method in Embodiment 1.

[0031] Figure 2 A schematic structural diagram of a superframe in Embodiment 1. DETAILED DESCRIPTION OF THE INVENTION

[0032] The technical solutions of the present invention will be further described below through embodiments in conjunction with the accompanying drawings.

[0033] Embodiment 1:

[0034] A TDMA wireless ad hoc network bifurcation networking method in this embodiment, as Figure 1 shown, includes the following steps:

[0035] S1: Each node in the main path transmits a branch beacon carrying information about the branch to be established. Each node randomly selects one of the C0 time slot and the C1 time slot on the predetermined multi-frame or transmits a beacon signal in the service time slot allowed for beacon transmission. The C0 time slot and the C1 time slot are the beacon transmission and reception time slots in the multi-frame. There are 5 single-frequency points set for the transmission frequency in the main path, which are f0, f1, f2, f3, and f4 respectively. Among them, f0 is called the C frequency, and f1, f2, f3, and f4 are called the T frequencies. As Figure 2As shown, there are 2 time slots in 1 TDMA frame, and each time slot is 30 ms. The 2 time slots of 1 TDMA frame at frequency f0 are respectively denoted as C0 and C1; the 2 time slots of 1 TDMA frame at frequency f1 are respectively denoted as T0 and T1; the 2 time slots of 1 TDMA frame at frequency f2 are respectively denoted as T2 and T3; the 2 time slots of 1 TDMA frame at frequency f3 are respectively denoted as T4 and T5; the 2 time slots of 1 TDMA frame at frequency f4 are respectively denoted as T6 and T7. In the following time slot order: C0, C1, T0, T1, T2, T3, T4, T5, T6, T7, T0, T1, T2, T3, T4, T5, T6, T7 are arranged together to form 1 multiframe. In a multiframe, each time slot is denoted as C0, C1, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15 in the above time order, where T8, T9, T10, T11, T12, T13, T14, T15 are the repetitions of the time slot channels of T0, T1, T2, T3, T4, T5, T6, T7. 16 multiframes are arranged together to form 1 superframe. In 1 superframe, the multiframe numbers are arranged as MF0, MF1, MF2, MF3, …, MF15. Each node randomly selects one of the C0 time slot and the C1 time slot on the predetermined multiframe or transmits a beacon signaling in the service time slot allowed to transmit beacons. The C0 time slot and the C1 time slot are the beacon transmission and reception time slots in the multiframe;

[0036] S2: The mobile stations that have not become relay nodes scan and receive the branch beacons and decide whether to apply to the node that sent the branch beacon to become the first node of the branch. The mobile stations receive the branch beacons by continuously scanning the f0 frequency band. After receiving the branch beacons from different nodes, they synchronize the time base and obtain the reachability parameters from themselves to each node that sent the branch beacon. The reachability parameters include field strength, distance, and signal-to-noise ratio. At the same time, the mobile stations also receive the application beacons of multiple other mobile stations and obtain the reachability parameters from themselves to the mobile stations that sent the application beacons. After completing the above work, the mobile stations select the nodes with reachability parameters within the preset range among the nodes that sent the branch beacons as alternative nodes. For each alternative node, it is judged whether the mobile stations within a certain distance from itself send application beacons to the alternative node. If so, the alternative node is abandoned; if not, an application beacon is sent to the alternative node. The screening of alternative nodes is specifically to set the field strength threshold range and the signal-to-noise ratio threshold, screen out the nodes with field strength within the field strength threshold range and signal-to-noise ratio greater than the signal-to-noise ratio threshold, and at the same time set the weight as a according to the position of the field strength of each node within the field strength threshold range. The node with the field strength as the middle value of the field strength threshold range has the largest weight, and the node with the field strength as the edge of the field strength threshold range has the smallest weight. Then calculate the quotient of the distance and the field strength of the screened nodes and record it as b. Sort in descending order according to the value of a*b to finally determine the ranking of alternative nodes. After completing the ranking of alternative nodes, it is judged in order whether there are other mobile stations within a certain distance from itself that send application beacons to the alternative node. If so, it is abandoned; if not, an application is made.

[0037] S3: The nodes that send branch beacons receive the application beacons sent by each different mobile station to apply to become the first node of the branch, and select the first node of the branch among these mobile stations. When the nodes that send branch beacons select the first node of the branch, they obtain the reachability parameters from themselves to each mobile station that sent the application beacon to this node, and screen out the mobile stations with reachability parameters within the preset range as the first node of the branch FGR. The screening is specifically to set the field strength threshold range and the signal-to-noise ratio threshold, screen out the mobile stations with field strength within the field strength threshold range and signal-to-noise ratio greater than the signal-to-noise ratio threshold, and at the same time set the weight as a1 according to the position of the field strength of each mobile station within the field strength threshold range. The mobile station with the field strength as the middle value of the field strength threshold range has the largest weight, and the mobile station with the field strength as the edge of the field strength threshold range has the smallest weight. Then calculate the quotient of the distance and the field strength of the screened mobile stations and record it as b1, and select the mobile station with the largest a1*b1 as the first node of the branch.

[0038] S4: The selected branch head node selects and broadcasts the service frequency. The service frequency of the branch head node FGR is different from that of the main path. In the branch, frequency points f0 and f5 are used. Therefore, the superframe format in the branch is different from that in the main path. In the branch, f0 is called the C frequency, and f5 is called the X frequency. There are 2 time slots in 1 TDMA frame, and each time slot is 30 ms. The 2 time slots of 1 TDMA frame at frequency point f0 are respectively denoted as C0 and C1; the 2 time slots of 1 TDMA frame at frequency point f5 are respectively denoted as X0 and X1. According to time, the following time slot sequence: C0, C1, X0, X1, X0, X1, X0, X1, X0, X1, X0, X1, X0, X1, X0, X1, X0, X1 are arranged together to form 1 multiframe. In a multiframe, each time slot is denoted as C0, C1, X0, X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12, X13, X14, X15 according to the serial number. Among them, X2, X3 and X4, X5 and X6, X7 and X8, X9 and X10, X11 and X12, X13 and X14, X15 are respectively the time slots of X0, X1 frequencies. 16 multiframes are arranged together to form 1 superframe, and this superframe is the branch superframe. The multiframe format of the branch head node FRG is generated according to the parity access method of its following upper-level node. If the upper-level node is the even access method, then the branch head node is the odd access method. The multiframe format of the branch head node is C0, C1, T0, X1, T2, X3, T4, X5, T6, X7, T8, X9, T10, X11, T12, X13, T14, X15, that is, when in standby, the service reception uses the frequencies and time slots specified by T0, T2, T4, T6, T8, T10, T12, T14, and the service transmission uses the frequencies and time slots specified by X1, X3, X5, X7, X9, X11, X13; if the upper-level node is the odd access method, then the branch head node is the even access method. The multiframe format of the branch head node is C0, C1, X0, T1, X2, T3, X4, T5, X6, T7, X8, T9, X10, T11, X12, T13, X14, T15, that is, when in standby, the service reception uses the time slots of T1, T3, T5, T7, T9, T11, T13 and T15, and the service transmission uses the time slots of X2, X4, X6, X8, X10, X12 and X14. Among them, the Ti time slot uses the service frequency of the upper-level node, and the Xi time slot uses the service frequency selected by the branch head node, that is, f5, i = 0, 1,..., 15. The parity access method of the upper-level node is determined by the following method. The group leader node of the main path sets the LIFE value, and the LIFE values of the remaining nodes in the main path decrease as the distance from the group leader node increases. When the LIFE value of a node is odd, then the node is the odd access method, otherwise it is the even access method.

[0039] When the branch head node FGR requires a secondary node FSGR, the following steps are executed:

[0040] S11: The branch head node FGR transmits a branch beacon carrying information about the required secondary node;

[0041] S12: Mobile stations that have not become relay nodes scan and receive the branch beacon and decide whether to apply to the sending branch head node to become a secondary node FSGR;

[0042] S13: The branch head node FGR receives application beacons sent by various different mobile stations to become secondary nodes and selects a secondary node FSGR from these mobile stations;

[0043] S14: The branch head node informs the secondary node FSGR of the service frequency used by the branch. The standby multi-frame format of the mobile station that has become an FSGR node changes according to the parity access method of the FGR node it follows. If the followed FGR node uses the even access method, the access method of the FSGR is odd access, and its multi-frame format is C0, C1, X0, X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12, X13, X14, X15, that is, during standby, service reception uses the frequencies and time slots specified by X0, X2, X4, X6, X8, X10, X12, X14, and service transmission uses the frequencies and time slots specified by X1, X3, X5, X7, X9, X11, X13. If the followed FGR node uses the odd access method, the access method of the FSGR is even access, and its multi-frame format is C0, C1, X0, X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12, X13, X14, X15, that is, during standby, service reception uses the frequencies and time slots specified by X1, X3, X5, X7, X9, X11, X13, X15, and service transmission uses the frequencies and time slots specified by X2, X4, X6, X8, X10, X12, X14.

[0044] When the secondary node FSGR requires a tertiary node FSR, the following steps are executed:

[0045] S21: The secondary node FSGR transmits a branch beacon carrying information about the required tertiary node FSR;

[0046] S22: Mobile stations that have not become relay nodes scan and receive the branch beacon and decide whether to apply to the sending secondary node FSGR to become a tertiary node FSR;

[0047] S23: The secondary node FSGR receives application beacons sent by various different mobile stations to become tertiary nodes FSR and selects a tertiary node FSR from these mobile stations;

[0048] S24: The secondary node FSGR notifies the tertiary node FSR of the service frequency used by the branch. The standby multiframe format of the mobile station that has become an FSR node changes according to the parity access method of the FSGR node it follows. If the followed FSGR node uses the even access method, the access method of the FSR is odd access, and its multiframe format is C0, C1, X0, X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12, X13, X14, X15. That is, during standby, service reception uses the frequencies and time slots specified by X0, X2, X4, X6, X8, X10, X12, X14, and service transmission uses the frequencies and time slots specified by X1, X3, X5, X7, X9, X11, X13. If the followed FSGR node uses the odd access method, the access method of the FSR is even access, and its multiframe format is C0, C1, X0, X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12, X13, X14, X15. That is, during standby, service reception uses the frequencies and time slots specified by X1, X3, X5, X7, X9, X11, X13, X15, and service transmission uses the frequencies and time slots specified by X2, X4, X6, X8, X10, X12, X14.

[0049] In steps S12 and S22, the mobile station uses the same method as in step S2 to determine whether to apply to become a secondary node FSGR and a tertiary node FSR; in steps S13 and S23, the branch head node FGR and the secondary node FSGR use the same method as in step S3 to select the secondary node FSGR and the tertiary node FSR.

[0050] By repeating steps S1 - S3, multiple mobile stations can be selected by the nodes on the main path to become branch head nodes FGR to form multiple branches. There can only be one secondary node FSGR in each branch on the main path.

[0051] Branches can be nested, that is, one or more standard branches can be generated on the three nodes of a standard branch path: FGR, FSGR, FSR. FGR, FSGR, FSR can transmit a beacon carrying the information "branch required" in the C0 or C1 time slot of the predetermined beacon transmission multiframe, and this beacon will also be transmitted at other times when it is allowed to transmit a beacon.

[0052] When there is already a branch FGR - FSGR - FSR on the main path, when steps S11 - S14 or steps S21 - S24 are executed again, a secondary branch of the branch FGR - FSGR - FSR can be formed, and the secondary branch uses a different X frequency from the branch FGR - FSGR - FSR.

[0053] As a variation of the branch structure, another FSR node can be connected under the FSR node, using the X frequency of this branch. It is even possible to continuously connect FSR nodes in sequence, but the entire branch must use a set of five X frequencies.

[0054] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar means for substitution, without departing from the spirit of the present invention or exceeding the scope defined by the appended claims.

Claims

1. A TDMA wireless ad hoc network forked networking method, characterized in that: It includes the following steps: S01: Each node on the main path transmits a branch beacon carrying information about the branch to be established; S02: The mobile stations that have not become relay nodes scan and receive the branch beacons and decide whether to apply to the node that sent the branch beacon to become the first node of the branch. After receiving the branch beacons from different nodes, they synchronize the time base and obtain the reachability parameters from themselves to each node that sent the branch beacon. At the same time, the mobile stations that have not become relay nodes also receive the application beacons from multiple other mobile stations and obtain the reachability parameters from themselves to the mobile stations that sent the application beacons. The mobile stations that have not become relay nodes select the nodes with reachability parameters within the preset range among the nodes that sent the branch beacons as candidate nodes. For each candidate node, the mobile stations that have not become relay nodes judge whether the mobile stations within their predetermined distance range send application beacons to the candidate node. If so, they abandon the candidate node; if not, they send application beacons to the candidate node; S03: The node that sent the branch beacon receives the application beacons sent by each different mobile station to apply to become the first node of the branch, and selects the first node of the branch from these mobile stations based on the reachability parameters from itself to each mobile station that sent the application beacon; S04: The selected first node of the branch selects and broadcasts the service frequency to be used by the branch; the service frequency of the first node of the branch is different from the service frequency of the main path.

2. The TDMA wireless ad hoc network forked networking method according to claim 1, characterized in that: when When the first node of the branch needs a second-level node, the following steps are executed: S11: The first node of the branch transmits a branch beacon carrying information about the need for a second-level node; S12: The mobile stations that have not become relay nodes scan and receive the branch beacon and decide whether to apply to the first node of the branch that sent the branch beacon to become a second-level node; S13: The first node of the branch receives the application beacons sent by each different mobile station to apply to become a second-level node, and selects a second-level node from these mobile stations; S14: The first node of the branch informs the second-level node of the service frequency used by the branch.

3. A TDMA wireless ad-hoc network forked networking method according to claim 2, characterized in that: When the second-level node needs a third-level node, the following steps are executed: S21: The second-level node transmits a branch beacon carrying information about the need for a third-level node; S22: The mobile stations that have not become relay nodes scan and receive the branch beacon and decide whether to apply to the second-level node that sent the branch beacon to become a third-level node; S23: The second-level node receives the application beacons sent by each different mobile station to apply to become a third-level node, and selects a third-level node from these mobile stations; S24: The second-level node informs the third-level node of the service frequency used by the branch.

4. A TDMA wireless ad hoc network forked networking method according to claim 3, characterized in that: The reachability parameters include field strength, distance, and signal-to-noise ratio.

5. A TDMA wireless ad hoc network forked networking method according to claim 1, characterized in that: When the node that sent the branch beacon selects the first node, second-level node, or third-level node of the branch, it obtains the reachability parameters from itself to each mobile station that sent the application beacon to this node, and screens the mobile stations with reachability parameters within the preset range as the first node, second-level node, or third-level node of the branch.

6. A TDMA wireless ad-hoc network forked networking method according to claim 1, characterized in that: The multiple-frame format of the said branch head node is generated according to the even / odd access method of the superior node it follows. The multiple-frame format of the secondary node is generated according to the even / odd access method of the branch head node it follows. The multiple-frame format of the tertiary node is generated according to the even / odd access method of the branch head node it follows. The even / odd access method means that: if the superior node uses the even access method, then the branch head node uses the odd access method, and the multiple-frame format of the branch head node is C0, C1, T0, X1, T2, X3, T4, X5, T6, X7, T8, X9, T10, X11, T12, X13, T14, X15, that is, when in standby, service reception uses the frequencies and time slots specified by T0, T2, T4, T6, T8, T10, T12, T14, and service transmission uses the frequencies and time slots specified by X1, X3, X5, X7, X9, X11, X13; if the superior node uses the odd access method, then the branch head node uses the even access method, and the multiple-frame format of the branch head node is C0, C1, X0, T1, X2, T3, X4, T5, X6, T7, X8, T9, X10, T11, X12, T13, X14, T15, that is, when in standby, service reception uses the time slots T1, T3, T5, T7, T9, T11, T13, and T15, and service transmission uses the time slots X2, X4, X6, X8, X10, X12, and X14. Among them, the Ti time slot uses the service frequency of the superior node, and the Xi time slot uses the service frequency selected by the branch head node, where i = 0, 1, …, 15.

7. A TDMA wireless ad hoc network forked networking method according to claim 6, characterized in that: The even / odd access method of the said superior node is determined by the following method. The group leader node of the main path sets the LIFE value, and the LIFE values of the remaining nodes in the main path decrease as the distance from the group leader node increases. When the LIFE value of a node is odd, then this node uses the odd access method, and vice versa for the even access method.

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