CN114630434A - Contention sequencing admission method based on unknown number of nodes - Google Patents

Abstract

The invention discloses an admission method based on an unknown number of nodes competing for ordering, which mainly solves the problem that the prior art prolongs the admission time in the scenario of many subordinate nodes, and conflicts are prone to occur when each subordinate node sends an admission request. The scheme is: in a star-shaped access network composed of a central node and a number of slave nodes of unknown number, the central node forms a competition period according to the number of slave nodes currently requested to be admitted, and according to these The number of slave nodes dynamically adjusts the size of the contention period; each slave node randomly selects an admission period from the contention period, and randomly selects an uplink sounding frame timeslot among the multiple uplink sounding frame timeslots in the admission period to send an admission request; the central node presses The slave nodes are accepted in sequence. The invention reduces the receiving time, avoids the conflict when there are many slave nodes, improves the receiving efficiency, and can be used in the access network of various time division multiplexing/time division multiple access mechanisms to allocate channels.

Description

Competitive sorting and admission method based on unknown number of nodes

technical field

The invention belongs to the field of communication technology, and further relates to a competition ordering and admission method, which can be used in various access networks that use a time division multiplexing/time division multiple access mechanism to allocate channels, and quickly and efficiently performs a new power-on terminal node in the network. access.

Background technique

In an access network based on a shared medium, a star topology consisting of a central node and several slave nodes is often used. In this network structure, data communication can be performed directly between the central node and the subordinate nodes, and the communication between the subordinate nodes needs to be forwarded through the central node. After a new slave node is powered on and initialized or reset, the process of registering with the central node and joining the existing system is called node admission. Usually, normal data communication can only be carried out after the node acceptance is completed. In order to complete the node admission, the central node and the slave nodes usually need to exchange information many times. In this process, the channel is divided into multiple consecutive and non-overlapping admission periods in time, each admission period contains downlink sounding frame time slots and uplink sounding frame time slots, and the downlink sounding frame time slot is used for the central node The downlink sounding frame is generated and sent, and the uplink sounding frame time slot is used for the slave node to generate and send the uplink sounding frame. The uplink/downlink sounding frame mainly completes the channel training of the physical layer, and carries the uplink/downlink signaling frames of the medium access control layer that are exchanged between the central node and the slave node during the node admission process. The start time interval of two adjacent downlink sounding frames is an admission period.

In an existing access network system, each subordinate node usually adopts a contention-based method to obtain an admission opportunity. In this method, each admission period contains only one downlink sounding frame time slot and one uplink sounding frame time slot, each slave node backs off several admission periods randomly, and uses the unique uplink sounding frame time slot in the admission period to send the admission period. Requests, competition for admission opportunities. The slave node that has successfully sent the admission request can carry out the admission process with the central node. After the acceptance of the slave node is completed, the other slave nodes continue to repeat the above process, execute a random backoff algorithm, and compete for an acceptance opportunity. The disadvantage of this method is that when multiple slave nodes need to be admitted into the network at the same time, a large number of slave nodes compete for the admission opportunity in the unique uplink sounding frame time slot, so the admission request is prone to conflict; A slave node that can be accepted can be selected. After the slave node completes the admission process, the remaining slave nodes to be accepted need to compete for the admission opportunity again in the uplink sounding frame time slot in the subsequent acceptance period, so it takes a long time to complete the process. the entire acceptance process.

The patent document with the domestic application number of 201310165257 discloses a "multi-channel-based parallel node admission method". The steps of node acceptance in the method are as follows: (1) divide the access channel, divide the downlink channel into Q downlink access channels in frequency, carry N downlink MAC layer signaling frames, and divide the uplink channel in time into Q uplink access channels carry the Q uplink MAC layer signaling frames; (2) build a bidirectional signaling frame channel, and correspond one-to-one with the Q downlink MAC layer signaling frame channels and the Q uplink MAC layer signaling frame channels , constitute Q parallel two-way signaling frame channels; (3) The slave node selects the signaling frame channel, and each slave node randomly selects an idle two-way signaling frame channel from the Q two-way signaling frame channels, and performs the node admission process. . This method can simultaneously accept slave nodes on multiple parallel bidirectional signaling frame channels, which shortens the acceptance time to a certain extent. However, this method still has two shortcomings: When the number of busy two-way signaling frame channels is large, the number of idle two-way signaling frame channels each slave node can select when sending an admission request is small, which is prone to contention and conflict, resulting in a low acceptance success rate of the node. Second, when using this method for node admission, it is necessary to configure N sets of receivers at the central node of the network to complete the admission of slave nodes on different signaling frame channels, and the implementation of the method is too complicated.

A domestic patent document with the application number of 201910173511 discloses a "node admission method based on competition ranking". The steps of node admission in the method are: (1) dividing the admission period, dividing the channel into multiple continuous and non-overlapping time periods in time, and each time period as an admission period; (2) dividing the M Consecutive admission periods form a contention period. The central node announces that each subordinate node can randomly select an admission period to send an admission request within the contention period. The value range of M is greater than or equal to 1 and less than or equal to the subordinate nodes in the access network. (3) The slave node sends an admission request, each slave node randomly selects an admission period in the advertised contention period, and randomly selects a time slot from the Q uplink sounding frame time slots in the admission period to send the admission request ; (4) The central node decides the admission order of the subordinate nodes and announces them, (5) The nodes that successfully request start to receive in sequence. The method changes the contention period of the slave node from Q uplink sounding frame time slots in one admission period to M*Q uplink sounding frame time slots in M admission periods. This method reduces the number of contention conflicts and shortens the admission period. However, since the contention period M is taken as a fixed value, the contention period cannot be changed in real time according to the actual number of subordinate nodes requested to be admitted; when there are many subordinate nodes requesting admission and the contention period is small, the number of conflicts and the number of competitions are high. Promotion, or when the competition period is large, will lead to waste of the competition period, which will lead to poor acceptance.

SUMMARY OF THE INVENTION

The purpose of the present invention is to propose a competitive sorting and admission method based on an unknown number of nodes in view of the above-mentioned shortcomings of the prior art, so that the network center node can change the duration of the contention period in real time according to the number of slave nodes requested to be admitted, and reduce the admission delay. , improve the acceptance efficiency.

In order to achieve the above purpose, the technical idea of the present invention is that in a star-shaped access network composed of a central node and an unknown number of slave nodes, in order to achieve the minimum average admission delay, the number of nodes admitted by the central node according to the current request will be continuous. The multiple acceptance periods of the node form a contention period; each slave node randomly selects an acceptance period from the contention period, and randomly selects an uplink sounding frame timeslot among the Q uplink sounding frame timeslots in the acceptance period to send an admission request; the center The nodes accept each slave node in sequence; the duration of the first and second contention periods is selected as a fixed value, after that, the total number of nodes is estimated according to the number of successfully admitted nodes in the first two contention periods, and rely on the estimation The value selects the duration of the subsequent contention period. The specific implementation is as follows:

(1) Divide the channel into multiple continuous and non-overlapping time periods in time, and use each time period as an admission period;

(2) Planning time slots for different purposes:

(2a) The start time of each admission period is taken as the start time of the downlink sounding frame time slot, and the central node uses the downlink sounding frame time slot to send the downlink physical layer sounding frame carrying the downlink medium access control MAC layer signaling frame frame;

(2b) Divide the remaining part Q of each admission period into equal parts, and take the starting point of each division as the start time of each uplink sounding frame time slot. The slave node uses the uplink sounding frame time slot to send the bearer uplink medium access Control the uplink physical layer detection frame of the MAC layer signaling frame;

(3) The slave node adjusts the received power gain and determines the downlink physical layer channel parameters:

(3a) The central node continuously sends downlink detection frames in the downlink detection frame time slot, and each slave node detects the signal strength of the continuously received downlink detection frames;

(3b) The slave node records the detected signal strength of the downlink sounding frame, and uses the gain adjustment method to adjust the gain of the received power of the slave node;

(3c) The slave node determines the channel parameters of the downlink physical layer by using the channel parameter estimation method;

(4) Choose the length of the competition period

(4a) M admission periods are formed into a competition period, and the duration of the first and second competition periods, that is, M, is selected as a fixed value;

(4b) The central node estimates the number N of slave nodes waiting to be accepted in the current competition period according to the number of nodes successfully accepted in the previous two competition periods, and N is an integer between [0, 64], that is, in each competition period, the uplink The time slot of the sounding frame is M*Q, and the approximate value P of the probability of successful admission by n nodes is obtained through simulation;

(4c) Find the best N that satisfies the establishment of max(P _n1 *P _n2 ), where n1 and n2 are the number of slave nodes successfully admitted in the first two competition periods, and both are non-negative integers, and N is the current The number of slave nodes waiting to be accepted during the competition period;

(4d) Selecting the duration of the competition period according to N determines the value of M;

(5) The central node sends a downlink detection frame, and the slave node sends an acceptance request:

(5a) During the contention period, the central node sends a downlink sounding frame in the downlink sounding frame time slot, and informs each subordinate node to randomly select an admission period from the competition period;

(5b) Each slave node receives the downlink sounding frame, and randomly selects an uplink sounding frame time slot from the Q uplink sounding frame time slots in the selected admission period, and sends an admission request;

(6) According to the sequence of receiving the admission request, the central node first fills the downlink medium access control MAC layer signaling frame with the slave node ID that can be accepted; then encapsulates the downlink medium access control MAC layer signaling frame Enter the downlink detection frame, broadcast and send the downlink detection frame in the downlink detection frame time slot, and announce the node acceptance sequence to each slave node;

(7) The slave node judges whether the ID of its own node exists in the downlink medium access control MAC layer signaling frame:

If so, execute (8);

Otherwise, wait for the end of the admission process of all the slave nodes notified in the downlink medium access control MAC layer signaling frame and return to (4);

(8) The central node accepts each slave node in sequence:

(8a) The central node sends an acceptance response to each slave node in sequence in the downlink sounding frame time slot, and adjusts the uplink transmit power gain of the slave node;

(8b) The slave node sends the uplink sounding frame in Q uplink sounding frame time slots in the admission period;

(8c) The central node determines the uplink channel parameters by using the training sequence signal in the uplink sounding frame, and accepts the slave node into the current network.

Compared with the prior art, the present invention has the following advantages:

In the present invention, the total number of slave nodes is estimated according to the existing nodes with successful acceptance, and the duration of each competition period is dynamically adjusted in real time according to the estimated value, so that the selection of the competition period can be more in line with the number of nodes currently requested to be admitted, thereby avoiding the need for Due to the inappropriate selection of the competition period, the admission time is prolonged, and the total admission delay is reduced.

Description of drawings

Fig. 1 is the realization flow chart of the present invention;

FIG. 2 is a structural diagram of an acceptance period in the present invention.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

In this embodiment, the star-shaped access network consists of a central node and 28 slave nodes, and 24 newly powered-on slave nodes N ₁ , N ₂ . . . N ₂₄ will be added to the star-shaped access network.

1, the implementation steps of this embodiment are as follows:

Step 1, divide the acceptance period.

The channel is divided into multiple continuous and non-overlapping time periods in time, and each time period is regarded as an admission period, and the time length of the admission period is set by the user as a fixed length or an indefinite length according to requirements.

In this embodiment, the time length of the acceptance period is fixed, which is set to 65536uS.

Step 2, planning time slots for different purposes.

2.1) The start time of each admission period is taken as the start time of the downlink sounding frame time slot, and the central node uses the downlink sounding frame time slot to send the downlink physical layer sounding frame carrying the downlink medium access control MAC layer signaling frame. ;

2.2) Divide the rest of each admission period into 8 equal parts, and take the starting point of each equal division as the start time of each uplink sounding frame time slot, and the slave node uses the uplink sounding frame time slot to send the bearer uplink medium access control. The uplink physical layer sounding frame of the MAC layer signaling frame.

FIG. 2 is an admission period of an embodiment of the present invention, which includes one downlink sounding frame time slot and eight uplink sounding frame time slots.

Step 3, the slave node adjusts the received power gain and determines the downlink physical layer channel parameters.

3.1) The central node continues to send downlink detection frames in the downlink detection frame time slot, and each slave node detects and records the signals of the continuously received downlink detection frames;

3.2) The slave node adjusts the gain of its received power:

(3.2a) Set the initial received power gain of the slave node to the maximum value;

(3.2b) When receiving a downlink sounding frame signal with an error check or not receiving a downlink sounding frame signal within a specified time, reduce its receive power gain and continue to detect the received downlink sounding frame signal;

(3.2c) Repeat (3.2b) until the slave node can receive the correct downlink signaling frame signal, and the received power gain at this time is the best;

3.3) The slave node uses the channel parameter estimation method to determine the channel parameters of the downlink physical layer, that is, the header is extracted from the received correct downlink sounding frame signal, and the frame synchronization signal and the frequency synchronization signal can be obtained by analyzing and calculating the preamble sequence in the header.

Step 4, select the duration of the competition period.

4.1) The M admission periods are formed into a competition period, and the duration of the first and second competition periods, that is, M, is selected as a fixed value;

4.2) The central node estimates the number N of slave nodes waiting to be accepted in the current competition period according to the number of nodes successfully accepted in the previous two competition periods. In each contention period, the uplink sounding frame time slot is M*Q, and the approximate value P of the probability of successful admission by n nodes is obtained through simulation. The simulation process is as follows;

(4.2a) During the contention period, there are M*Q uplink sounding frame time slots, and there are N slave nodes waiting to send admission requests, and N is an integer between [0, 64];

(4.2b) Each slave node is independent of each other and randomly selects an uplink sounding frame time slot within the contention period to send an admission request;

(4.2c) At the end of the contention period, count the number of uplink sounding frame time slots for which there is only one admission request in the contention period, that is, the number n of nodes successfully admitted in this contention period, where n is a non-negative integer;

(4.3d) Repeat (4.2b)-(4.2c) several times, and count the number of occurrences of successfully admitted n slave nodes, we can get that when the contention period is M acceptance cycles, N slave nodes waiting to be admitted are successfully accepted n probability approximations P, where the more repetitions, the more accurate P;

4.3) Find the best N that satisfies the establishment of max(P _n1 *P _n2 ), where n1 and n2 are the number of slave nodes successfully accepted in the first two competition periods, and both are non-negative integers, and N is the current competition The number of slave nodes waiting to be accepted;

4.4) Select the duration of the competition period according to N, that is, determine the value of M according to the following rules;

When 1≤N≤11, M=1; when 12≤N≤19, M=2;

When 20≤N≤27, M=3; when 28≤N≤35, M=4;

When 36≤N≤43, M=5; when 44≤N≤51, M=6;

When 52≤N≤59, M=7; when 60≤N≤64, M=8.

In this example, the first and second competition periods are selected as one admission period, that is, M=1; the central node estimates the number of slave nodes waiting to be admitted in the current competition period according to the number of nodes successfully admitted in the previous two competition periods. Assuming that the first successful admission of node n ₁ =2, and the second successful admission of node n ₂ =1, the simulation obtains the probability of successful admission of n ₁ and n ₂ nodes when the number of uplink sounding frame timeslots is 1*8 The approximate values P _n1 and P _n2 are screened according to max(P _n1 *P _n2 ), and the number of slave nodes waiting to be admitted in the current competition period is estimated to be N=19; the rule for selecting the length of the competition period according to N takes M=2, that is, the competition period 2 admission cycles.

Step 5, the central node sends a downlink detection frame, and the slave node sends an admission request.

5.1) During the contention period, the central node sends a downlink sounding frame in the downlink sounding frame time slot, and announces that each slave node can randomly select an acceptance period from the competition period;

5.2) Each slave node receives the downlink sounding frame, and randomly selects an uplink sounding frame time slot from the 8 uplink sounding frame time slots in the selected admission period, and sends an admission request;

During the first competition period:

The slave node 5 randomly selects the third uplink sounding frame time slot from the 8 uplink sounding frame time slots to send the admission request;

The slave node 2 randomly selects the 5th uplink sounding frame time slot from the 8 uplink sounding frame time slots to send the admission request;

The rest of the slave nodes randomly select the 6th uplink sounding frame time slot from the 8 uplink sounding frame time slots to send the admission request;

During the 2nd competition period:

The slave node 9 randomly selects the third uplink sounding frame time slot from the 8 uplink sounding frame time slots to send the admission request;

The remaining 21 slave nodes that are not successfully accepted randomly select the 5th uplink sounding frame time slot from the 8 uplink sounding frame time slots to send the admission request;

During the 3rd competition period:

The slave node 10 randomly selects the 4th uplink sounding frame time slot from the 8 uplink sounding frame time slots of the first admission period in the contention period to send the admission request;

The slave node 19 randomly selects the first uplink sounding frame time slot from the 8 uplink sounding frame time slots of the first admission period in the contention period to send the admission request;

The slave node 17 randomly selects the second uplink sounding frame time slot from the eight uplink sounding frame time slots of the second admission period in the contention period to send the admission request;

The slave node 21 randomly selects the 8th uplink sounding frame time slot from the 8 uplink sounding frame time slots of the first admission period in the contention period to send the admission request;

The slave node 23 randomly selects the second uplink sounding frame time slot from the 8 uplink sounding frame time slots of the first admission period in the contention period to send the admission request;

The remaining slave nodes that are not successfully accepted randomly select the 4th uplink sounding frame time slot from the 8 uplink sounding frame time slots in the second admission period in the contention period to send the admission request;

After each competition, the contention period duration is determined according to step 4, and step 5 is repeated until the acceptance of all slave nodes is completed.

Step 6, the central node decides the admission sequence of each slave node and announces it.

The central node fills in the ID of the slave node that can be accepted in the downlink medium access control MAC layer signaling frame according to the sequence of receiving the admission request, and broadcasts the signaling frame in the downlink detection frame time slot, to each slave node. Node advertisement node admission order:

The central node receives the admission request sent by the subordinate node 5 in the third uplink detection frame time slot, so the central node fills the downlink medium access control MAC layer signaling frame from the node ID of the subordinate node 5;

The central node receives the admission request sent by the subordinate node 2 in the fifth uplink detection frame time slot, so the central node fills in the downlink medium access control MAC layer signaling frame from the node ID of the subordinate node 2, and places it in the subordinate node 5 After the node ID of ;

Since the admission requests of the other slave nodes all collide in the 6th uplink detection frame time slot, the central node does not receive the uplink detection frame in the 6th uplink detection frame time slot, and the central node does nothing;

The central node announces to each subordinate node through broadcasting that the subordinate node 2 and the subordinate node 5 can be admitted, and the admission is performed in the order of the subordinate node 5 and the subordinate node 2 .

Step 7, the slave node judges whether the ID of its own node exists in the downlink medium access control MAC layer signaling frame:

If yes, go to step 8;

Otherwise, wait for the end of the admission process of all the slave nodes notified in the downlink medium access control MAC layer signaling frame, and then return to step 4.

In the embodiment of the present invention, the slave node 5 queries the ID of its own node from the received downlink medium access control MAC layer signaling frame, and learns that its own admission request has been sent successfully, and it is the first one waiting to be admitted. slave node;

The slave node 2 queries the ID of its own node from the received downlink medium access control MAC layer signaling frame, and learns that its own admission request has been sent successfully, and it is the second slave node waiting to be accepted;

The other slave nodes do not query the ID of their own node from the received downlink medium access control MAC layer signaling frame, and learn that the sending of their own admission request fails. The remaining subordinate nodes wait for the end of the admission process of all subordinate nodes notified in the downlink medium access control MAC layer signaling frame, and then return to step 5 .

Step 8, the central node accepts each slave node in sequence.

8.1) The central node sends an acceptance response to each slave node in turn in the downlink sounding frame time slot, and adjusts the uplink transmit power gain of the slave node by the same method as in step 3.2);

8.2) The slave node sends uplink sounding frames simultaneously in 8 uplink sounding frame time slots in the admission period;

8.3) The central node uses the training sequence signal in the uplink sounding frame to participate in the same method as step 3.3) to determine the uplink channel parameters, and admits the slave node to the current network.

In the embodiment of the present invention, the central node accepts two subordinate nodes into the star access network in the order of subordinate node 5 and subordinate node 2, and then subordinate node 2 and subordinate node 5 can perform normal data communication with other nodes in the network. communication.

The above description is only a specific example of the present invention, and does not constitute any limitation to the present invention. Obviously, for those skilled in the art, after understanding the content and principles of the present invention, they may not deviate from the principles and structures of the present invention. Under certain circumstances, various corrections and changes in form and details are made, but these corrections and changes based on the idea of the present invention are still within the protection scope of the claims of the present invention.

Claims (6)

1. An admission method based on an unknown number of node competition ordering is characterized by comprising the following steps:

(1) dividing a channel into a plurality of continuous time periods which are not overlapped with each other in time, and taking each time period as an admission period;

(2) planning time slots for different purposes:

(2a) the initial time of each admission period is used as the initial time of a downlink detection frame time slot, and the central node transmits a downlink physical layer detection frame for bearing a downlink medium access control MAC layer signaling frame by using the downlink detection frame time slot;

(2b) equally dividing the rest part Q of each admission period, taking the starting point of each equal division as the starting moment of each uplink detection frame time slot, and sending an uplink physical layer detection frame for bearing an uplink medium access control MAC layer signaling frame by the slave node by using the uplink detection frame time slot;

(3) the slave node adjusts the receiving power gain and determines the parameters of the downlink physical layer channel:

(3a) the central node continuously sends downlink detection frames in downlink detection frame time slots, and each slave node detects the continuously received downlink detection frames;

(3b) the slave node records the detected downlink detection frame and adjusts the gain of the receiving power by using a gain adjustment method;

(3c) the subordinate node determines the channel parameters of a downlink physical layer by using a channel parameter estimation method;

(4) selecting a duration of a contention period

(4a) Forming a competition period by the M admission periods, and selecting the duration of the first competition period and the second competition period, namely M, as a fixed value;

(4b) the central node estimates the number N of subordinate nodes waiting to be admitted in the current competition period according to the number of successfully admitted nodes in the previous two competition periods, wherein N is an integer between [0 and 64], namely in each competition period, the time slot of an uplink detection frame is M x Q, and a probability approximate value P of the successful admission of the N nodes is obtained through simulation;

(4c) find out to satisfy max (P)_n1*P_n2) The best N is established, wherein N1 and N2 are the numbers of slave nodes successfully admitted in the previous two competition periods respectively and are non-negative integers, and N is the number of slave nodes waiting to be admitted in the current competition period;

(4d) selecting the duration of the competition period according to N to determine the value M;

(5) the central node sends a downlink detection frame, and the subordinate nodes send admission requests:

(5a) in a competition period, a central node sends a downlink detection frame in a downlink detection frame time slot and informs each subordinate node to randomly select an admission period from the competition period;

(5b) each slave node receives the downlink detection frame, randomly selects an uplink detection frame time slot from Q uplink detection frame time slots in the selected admission period, and sends an admission request;

(6) according to the sequence of receiving the admission request, the central node firstly fills the slave node ID which can be admitted in the downlink media access control MAC layer signaling frame; then, a downlink medium access control MAC layer signaling frame is encapsulated into a downlink detection frame, the downlink detection frame is broadcast and sent in a downlink detection frame time slot, and a node admission sequence is announced to each subordinate node;

(7) the slave node judges whether the downlink media access control MAC layer signaling frame has the ID of the node:

if yes, executing (8);

otherwise, the process returns to the step (4) after the admission process of all the subordinate nodes notified in the signaling frame of the downlink media access control MAC layer is finished;

(8) the central node sequentially receives all the subordinate nodes in sequence:

(8a) the central node sequentially sends admission responses to all the slave nodes in a downlink detection frame time slot, and adjusts the uplink sending power gain of the slave nodes;

(8b) the slave node sends uplink detection frames in Q uplink detection frame time slots in an admission period;

(8c) and the central node determines the uplink channel parameters by using the training sequence signals in the uplink detection frame and admits the slave nodes to the current network.

2. The method according to claim 1, wherein the admission period in (1) has a time length set by a user to a fixed length or an unfixed length according to a requirement.

3. The method of claim 1, wherein the slave node in (3b) adjusts the gain of its received power by using a gain adjustment method, which is implemented as follows:

(3b1) setting an initial received power gain of the slave node to a maximum value;

(3b2) when a downlink detection frame signal with a check error is received or a downlink detection frame signal is not received within a specified time, reducing the receiving power gain of the downlink detection frame signal and continuously detecting the received downlink detection frame signal;

(3b3) and repeating (3b2) until the slave node receives the downlink signaling frame signal which is checked to be correct, wherein the receiving power gain is optimal.

4. The method of claim 1, wherein the slave node in (3c) determines the channel parameters of the downlink physical layer by using a channel parameter estimation method, which is implemented as follows:

(3c1) extracting a header of the received correct downlink detection frame signal to obtain a leader sequence;

(3c2) analyzing the preamble sequence to obtain the physical layer channel parameters, including: frame synchronization signal, frequency synchronization signal.

5. The method according to claim 1, wherein in (4b), the probability approximation P of successful admission of the n slave nodes is obtained through simulation, and the simulation process is as follows:

(4b1) there are M × Q uplink sounding frame time slots in the contention period, there are N slave nodes waiting for sending admission requests, and N is an integer between [0 and 64 ];

(4b2) each slave node is mutually independent and randomly selects an uplink detection frame time slot in a competition period to send an admission request;

(4b3) when the competition period is ended, counting the number of uplink detection frame time slots with only one admission request in the competition period, namely the number n of successfully admitted nodes in the competition period, wherein n is a non-negative integer;

(4b4) repeating (4b2) and (4b3) for a plurality of times, and counting the times of occurrence of successfully admitting N slave nodes, so as to obtain an approximate probability value P of successfully admitting N slave nodes waiting for admission when the contention period is M admission periods, wherein the more the repetition times, the more accurate P is.

6. The method according to claim 1, wherein the selecting of the contention period duration (M) in (4d) according to N is performed according to the following rule:

when N is more than or equal to 1 and less than or equal to 11, M is 1; when N is more than or equal to 12 and less than or equal to 19, M is 2;

when N is more than or equal to 20 and less than or equal to 27, M is 3; when N is more than or equal to 28 and less than or equal to 35, M is 4;

when N is more than or equal to 36 and less than or equal to 43, M is 5; when N is more than or equal to 44 and less than or equal to 51, M is 6;

when N is more than or equal to 52 and less than or equal to 59, M is 7; when N is more than or equal to 60 and less than or equal to 64, M is 8.

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