CN108012303B - Access congestion control method based on distributed networking - Google Patents
Access congestion control method based on distributed networking Download PDFInfo
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- H04W48/02—Access restriction performed under specific conditions
- H04W48/06—Access restriction performed under specific conditions based on traffic conditions
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Abstract
The invention discloses an access congestion control method based on distributed networking, which comprises the following steps: and (3) congestion control: the event triggers the MTC equipment to initiate an access request, and the MTC equipment enters a congestion control stage: firstly, starting a neighbor node discovery process and establishing communication connection with a neighbor node; after the communication is successfully established, determining the time slot and frequency of data transmission, storing the time slot and frequency, and completing networking and collection of data; base station access: the MTC equipment which collects the data sends a random access request to the base station until the access is successful. In the invention, the MTC devices can communicate autonomously, establish connection to realize transmission and aggregation of data, and then initiate a random access request to access the base station by the MTC devices with aggregated data; under the condition that the access resources of the base station are not additionally consumed, the number of MTC (machine type communication) equipment which directly communicate with the base station is greatly reduced, and instantaneous sudden access congestion caused by simultaneous network access of a large number of MTC equipment is relieved.
Description
Technical Field
The invention relates to the field of communication, in particular to an access congestion control method based on distributed networking.
Background
As 4G networks enter the commercial scale phase, the fifth generation mobile communication (5G) networks for the future have become a global research and development hotspot. Mobile internet and internet of things services will become the main driving force for the development of mobile communication networks.
As the most existing form of the internet of things, Machine-to-Machine communication (M2M) is different from traditional Human-to-Human communication (H2H), and refers to a generic name of a series of technologies or technology combinations for realizing autonomous data communication and information interaction between machines by using technologies such as automatic control and network communication without Human intervention or with very little intervention, and provides an effective way for various terminal devices to establish communication connection and transmit data in real time between systems, networks and remote entities; different M2M applications require different connection schemes, for which existing wireless cellular networks can provide connectivity for services requiring wide area coverage or mobility requirements; the 3GPP refers to M2M communication for data transmission through a cellular network as Machine Type Communication (MTC), i.e. mobile M2M communication, cellular M2M communication or cellular internet of things, which are well known in the academic world and the industry. MTC communication is rapidly becoming a vitality force changing the mobile communication market, and its application fields include important industries such as security monitoring, cargo tracking, intelligent payment, medical care, remote monitoring, consumer electronics, and the like, and are an indispensable important component of future communication systems.
In the future cellular internet of things, a mobile communication system which provides services for billions of users needs to additionally accommodate billions of devices. From the perspective of both the access network and the core network, the conventional network architecture and management control mode have been unable to meet the macro connection service requirement of the network. Therefore, how to greatly improve the access capability of the system becomes a problem to be solved urgently. Specifically, in the face of mass access requirements, the number and density of terminal users including H2H and M2M in a cellular network will increase rapidly, and the mere dependence on a Macro Base Station (MBS) for access will cause network congestion and overload, and cannot meet service requirements. By accessing a small base station with low power consumption or using other supplementary communication modes, the system access capability can be effectively improved, the network congestion can be reduced, the service quality can be improved, and the system energy efficiency can be improved.
Compared with H2H application, the probability of packet collision caused by random access overload in M2M application is increased greatly due to the large number of MTC devices needing to access a base station; random access overload caused by massive MTC equipment can cause the performance of a network system to be reduced to a great extent; when massive MTC equipment simultaneously initiates an access request to a base station, overload and signaling congestion of an access network are easily caused, and further, the access delay of the MTC equipment is increased, packet data packets are lost, and even service is interrupted. Moreover, more than 90% of MTC devices are based on low mobility and small amount of data services, according to the existing bearer technology, the scheme for establishing a bearer for each MTC device may cause a large amount of network bearer resources to be occupied by MTC type services, and the MTC devices frequently perform operations such as requesting, establishing connection, and deregistering, which may also cause the epc (evolved Packet core) network to generate a large amount of signaling overhead, so that the high bandwidth advantage of the sae system (Architecture evolution) network cannot be embodied.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides an access congestion control method based on distributed networking.A plurality of MTC (machine type communication) devices can communicate autonomously, establish connection to realize transmission and aggregation of data, and then initiate a random access request to access a base station by the MTC devices with the aggregated data; under the condition that the access resources of the base station are not additionally consumed, the number of MTC (machine type communication) equipment which directly communicate with the base station is greatly reduced, and instantaneous sudden access congestion caused by simultaneous network access of a large number of MTC equipment is relieved.
The purpose of the invention is realized by the following technical scheme: an access congestion control method based on distributed networking comprises the following steps:
and (3) congestion control: the event triggers the MTC equipment to initiate an access request, and the MTC equipment enters a congestion control stage: firstly, starting a neighbor node discovery process and establishing communication connection with a neighbor node; after the communication is successfully established, determining the time slot and frequency of data transmission, storing the time slot and frequency, and completing networking and collection of data; specifically, the congestion control step includes the substeps of: s01, when an event triggers a receiving request of the MTC equipment, the MTC equipment starts a radio frequency part after waiting for a period of random time; s02, the MTC equipment selects a fixed frequency point and monitors in a time period with a random length; s03, judging whether the MTC equipment receives invitation messages sent by other nodes within monitoring time; if yes, go to step S04; if not, go to step S05; s04, the MTC device serves as an invited node, communication connection is established with the inviting node, after communication is established successfully, time slots and frequency of data transmission are determined and stored, the inviting node enters a networking completion state, and the MTC device returns to the step S02 to continue monitoring; and S05, the MTC equipment is used as an invitation node, broadcasts an invitation message, establishes communication with the neighbor nodes responding to the invitation message, finishes data collection after all the neighbor nodes finish the access process, and enters a base station access step.
Base station access: the MTC equipment which collects the data sends a random access request to the base station until the access is successful.
Wherein the step S04 includes the following substeps: step one, the MTC equipment is used as an invited node, waits for a random length after receiving invitation messages sent by other nodes, broadcasts a response message, and waits for receiving a response message from the invited node; secondly, after the MTC equipment receives the reply message from the invitation node, the MTC equipment selects an unused frequency point and a communication time slot, sends a response message and establishes communication connection with the invitation node; and thirdly, the node is invited to enter a networking completion state, and the MTC equipment returns to the step S02 to continue monitoring.
Wherein the step S05 includes the following substeps: step one, the MTC equipment is used as an invitation node, broadcasts an invitation message and waits for receiving a response message from the invited node; secondly, judging whether the MTC equipment can receive a response message from an invited node or not within set time; if yes, entering a third step; if not, all the neighbor nodes are considered to have completed the access process, the data collection is completed, and the base station access step is directly entered; thirdly, the MTC equipment generates a reply message according to the time slot allocation condition, sends the reply message to the response node, and waits for receiving the response message of the response node; and fourthly, after receiving the response message of the response node, the MTC device establishes communication connection with the response node and returns to the step S02 to continue monitoring.
The invitation message comprises the ID of the invitation node and the number of the neighbor nodes which have already distributed channels.
The response message comprises an inviting node, an invited node address and a time slot allocation state of the invited node, wherein the time slot allocation state of the invited node is whether a time slot allocation schedule is empty or not.
The reply message comprises a designated invited node, a time node of the next frame of the reply message, and time slot allocation states of the inviting node and the invited node; in addition, the reply message further includes the following information: if the time slot allocation time tables of the inviting node and the invited node are not empty, the reply information also comprises the time slot allocation time table of the inviting node; if the time slot distribution time table of the inviting node is not empty and the time slot distribution time table of the invited node is empty, the response information comprises the distribution information of the channel; if the time slot allocation schedule of the inviting node is empty, the reply message has no other information.
The response message includes the following information: if the time slot allocation schedules of the inviting node and the invited node are both empty, the response message contains a channel specified by the invited node; if the time slot allocation schedule of the inviting node is not empty and the time slot allocation schedule of the invited node is empty, the response message does not contain information; if the time slot allocation schedule of the inviting node is empty and the time slot allocation time of the invited node is not empty, the response message contains a channel specified by the invited node; if the time slot allocation schedules of the inviting node and the invited node are not empty, the response message comprises a channel selected according to the time slot allocation schedule of the inviting node and the time slot allocation schedule of the invited node.
Preferably, when there is only one invited node responding to the invitation message, the node is the answering node; when there is more than one invited node responding to the invitation message, the MTC device selects a node where the response first arrives or the strength of the response signal is the greatest from the invited nodes responding to the invitation message as the responding node.
The invention has the beneficial effects that: in the invention, MTC devices can communicate with each other in a distributed networking manner, connection is established to realize transmission and aggregation of data, and then the MTC devices with aggregated data initiate a random access request to access a base station; under the condition that the access resources of the base station are not additionally consumed, the number of MTC (machine type communication) equipment which directly communicate with the base station is greatly reduced, and instantaneous sudden access congestion caused by simultaneous network access of a large number of MTC equipment is relieved.
Drawings
FIG. 1 is a flow chart of a method of the present invention;
FIG. 2 is a schematic diagram of one embodiment of the present invention;
FIG. 3 is a node state transition diagram of the present invention;
fig. 4 is a schematic diagram comparing the delay theory of the conventional random access method and the access congestion control method in the present application;
fig. 5 is a schematic diagram comparing the simulation result of the average delay with the theoretical analysis.
Detailed Description
The technical solutions of the present invention are further described in detail below with reference to the accompanying drawings, but the scope of the present invention is not limited to the following.
As shown in fig. 1, an access congestion control method based on distributed networking includes the following steps:
and (3) congestion control: the event triggers the MTC equipment to initiate an access request, and the MTC equipment enters a congestion control stage: firstly, starting a neighbor node discovery process and establishing communication connection with a neighbor node; after the communication is successfully established, determining the time slot and frequency of data transmission, storing the time slot and frequency, and completing networking and collection of data; specifically, the congestion control step includes the substeps of: s01, when an event triggers a receiving request of the MTC equipment, the MTC equipment starts a radio frequency part after waiting for a period of random time; s02, the MTC equipment selects a fixed frequency point and monitors in a time period with a random length; s03, judging whether the MTC equipment receives invitation messages (Type1) sent by other nodes within the monitoring time; if yes, go to step S04; if not, go to step S05; s04, the MTC device serves as an invited node, communication connection is established with the inviting node, after communication is established successfully, time slots and frequency of data transmission are determined and stored, the inviting node enters a networking completion state, and the MTC device returns to the step S02 to continue monitoring; and S05, the MTC device serves as an invitation node, broadcasts an invitation message (Type1), establishes communication with the corresponding neighbor node, finishes data collection after all the neighbor nodes finish the access process, and enters a base station access step.
Base station access: the MTC equipment which collects the data sends a random access request to the base station until the access is successful.
Wherein the step S04 includes the following substeps: firstly, the MTC device serves as an invited node, waits for a random length after receiving an invitation message (Type1) sent by other nodes, broadcasts a response message (Type2), and waits for receiving a reply message (Type3) from the inviting node; secondly, after receiving a reply message (Type3) from the inviting node, the MTC device selects an unused frequency point and a communication time slot, sends a response message (Type4) and establishes communication connection with the inviting node; and thirdly, the node is invited to enter a networking completion state, and the MTC equipment returns to the step S02 to continue monitoring.
Wherein the step S05 includes the following substeps: firstly, the MTC device serves as an inviting node, broadcasts an inviting message (Type1), and waits for receiving a response message (Type2) from the invited node; secondly, judging whether the MTC equipment can receive a response message (Type2) from the invited node within a set time; if yes, entering a third step; if not, all the neighbor nodes are considered to have completed the access process, the data collection is completed, and the base station access step is directly entered; thirdly, the MTC device generates a reply message (Type3) to be sent to the answering node according to the time slot allocation condition, and waits for receiving the response message (Type4) of the answering node; fourthly, after receiving the response message (Type4) of the answering node, the MTC device establishes a communication connection with the answering node, and returns to step S02 to continue monitoring.
The invitation message (Type1) comprises the ID of the inviting node and the number of the neighbor nodes which have already allocated channels.
The response message (Type2) includes the inviting node, the invited node address and the time slot allocation status of the invited node, and the time slot allocation status of the invited node is whether the time slot allocation schedule is empty or not.
The reply message (Type3) comprises the designated invited node, the time node of the next frame of the reply message, and the time slot allocation states of the inviting node and the invited node; further, the reply message (Type3) further includes the following information: if the time slot allocation time tables of the inviting node and the invited node are not empty, the reply information also comprises the time slot allocation time table of the inviting node; if the time slot distribution time table of the inviting node is not empty and the time slot distribution time table of the invited node is empty, the response information comprises the distribution information of the channel; if the slot allocation schedule of the inviting node is empty, the reply message (Type3) has no other information.
The response message (Type4) includes the following information: if the slot allocation schedules of both the inviting node and the invited node are empty, the response message (Type4) contains the channel specified by the invited node; if the slot allocation schedule of the inviting node is not empty and the slot allocation schedule of the invited node is empty, the response message (Type4) contains no information; if the slot allocation schedule of the inviting node is empty and the slot allocation time of the invited node is not empty, the response message (Type4) contains the channel specified by the invited node; if the slot allocation schedules of both the inviting node and the invited node are not empty, the response message (Type4) contains a channel selected according to the slot allocation schedule of the inviting node and the slot allocation schedule of the invited node.
In the embodiment of the application, when only one invited node responding to the invitation message exists, the node is the answering node; when there is more than one invited node responding to the invitation message, the MTC device selects a node where the response first arrives or the strength of the response signal is the greatest from the invited nodes responding to the invitation message as the responding node.
As shown in fig. 2, in one embodiment of the present application, it is assumed that the MTC device A, B, D needs to access a base station and transmit data to the base station; first, the devices A, B, D establish communication connections between the devices and perform data aggregation through a congestion control step. When the MTC equipment has data to transmit to the base station, the access process of the MTC equipment is triggered; first, the device turns on the radio frequency part in a random time period, and then listens for a random length of time on a fixed frequency point. In fig. 2, it is assumed that an MTC device B first opens a radio frequency for monitoring, and after the monitoring time of the MTC device B is over, the MTC device B has not received an invitation message Type1 of another node, so that the MTC device B actively sends out an invitation, that is, broadcasts an invitation message Type1, and at this time, neighbor nodes a and D of the MTC device B are still in a monitoring state, and therefore, both the MTC device a and the device D can receive a Type1 message sent by the MTC device B before the monitoring is over.
After receiving the Type1 message sent by the MTC device B, the devices A and D wait for a random period of time and then broadcast the response message Type 2; in fig. 2, device a selects a random time shorter than device D, and therefore device B first receives the Type2 message sent by device a. Here, the setting device B may select which device transmits the Type2 message, may select the responder that arrives first, or may select the responder having the highest received signal strength, as necessary.
Suppose that after device B receives the invitation response messages Type2 sent by A and D, the earliest responder A is selected and immediately sends a Type3 message to A; since the message is a broadcast message, the device D also receives the message, but the Type3 message includes the device information for establishing the communication connection with the device B, so the device D recognizes that it has failed to establish the communication connection with the device B, and then returns to the listening state.
Carrying channel allocation information of the device B in a Type3 message received by the device a, where the information includes a start time of a next frame of the device B; the device A obtains a time offset according to the Type3, finds out two common idle time periods as a time slot pair and allocates the two common idle time periods to a link between the device A and the device B; then, the device A selects a random frequency point, and sends the position information of the time slot pair and the selected frequency point to the device B through the Type 4; after the information is exchanged successfully, the time slot allocation and the frequency selection between the A and the B are completed, and the A and the B can be switched to the corresponding time slot and the corresponding frequency for data transmission, so that the data aggregation is completed.
As shown in fig. 3, in the present invention, the states of the nodes can be mainly classified into the following six types: idle, monitoring, waiting for confirmation, completing networking, waiting for response and requesting to access the base station. In the idle state, the node is in a dormant state. This state is entered when there is no event trigger or when a certain communication process is finished. The listening state corresponds to steps S01 to S03, and when the MTC device has data to upload, the event of transmitting data triggers the node to enter the listening state. In the monitoring state, the node will open the radio frequency part in a random time period, and select a fixed frequency point to monitor a time of random length. If the node receives the invitation message sent by the neighbor node within the monitoring time, the node broadcasts a response message after waiting for a random time. If the invitation messages sent by other nodes are not received in the monitoring time, the nodes actively initiate the invitation messages. The wait for acknowledgement and networking complete state correspond to step S04 of the present application, and in the wait for acknowledgement state, since there may be a collision situation when waiting to receive Type3 message, that is, two or more neighbor nodes all send Type3 message, and the collision probability depends on the number of neighbor nodes. Therefore, only after the Type3 message is correctly received can the communication link between the pair of nodes be successfully established. Then the nodes of the two parties carry out subsequent data transmission according to the time slots and the frequency points agreed with each other. After the communication process is finished, the node receiving the data returns to a monitoring state, and the node sending the data enters a networking finishing state; the response waiting phase corresponds to step S05 of the present application, and if the node does not receive the invite message Type1 within the selected listening time, the node actively sends the invite message and waits for the response of the neighboring node. And if the response message is received within a certain time, establishing communication connection according to a normal communication flow and transmitting data. After receiving the data transmitted by the neighbor node, the system enters a monitoring state again to prepare for communicating with the next neighbor node. If the node does not receive the reply message of any neighbor node within a certain time, the node considers that the neighbor nodes all finish the access process, at the moment, the node enters a state of requesting to access the base station (corresponding to the base station access step), and actively initiates an access request to the base station to transmit the converged data.
In the node state transition diagram shown in fig. 3, the symbols represent the following meanings:
the state transition diagram shown in fig. 3 lists all possible state transition processes that may occur in the network, let PijIndicating a slave state S of a node in the networkiTransfer to SjBy state transition probability of Pij(t) represents PijAt the value of time t, using Si(t) indicates that time t is in state SiNumber of nodes, by the symbol Si→SjRepresents the node from SiState transition to SjAnd then:
Si→Sj：Sj(t+1)＝Si(t)×Pij(t)
specifically to each state of the migration process, the following results are obtained:
S1(t+1)＝S0(t)×P01(t)+S2(t)×P21(t)+S4(t)×P41(t)；
S2(t+1)＝S1(t)×P12(t)-S2(t)×P21(t)；
S3(t+1)＝S2(t)×P22(t)；
S4(t+1)＝S1(t)×P14(t)-S4(t)×P41(t)-S4(t)×P45(t)；
S5(t+1)＝S4(t)×P45(t)。
according to the method and the device, the MTC equipment does not need to be synchronized in the whole network, and only two pieces of communication MTC equipment need to be synchronized. Therefore, we cannot know exactly the time when each MTC device sends or receives a message, and only estimate an average value instead of the time when theoretical calculation is performed. Wherein, P21(t) and P23P in the expression (t) represents the probability that the MTC device may collide while waiting to receive the Type3 message. That is, there may be two or more neighbor nodes that reply to the Type3 message, but only one node can be selected for communication, and the collision probability depends on the number of neighbor nodes.
The main focus of the present invention is the average time delay of all MTC devices successfully accessing the base station, so we must know the number of MTC devices initiating access requests to the base station at each moment, i.e. S5The value of (t). Then obtaining S through the calculation formula5After (t), the average access delay can be obtained by calculating the result obtained by analyzing the delay in the random access process.
Consider that K MTC devices are deployed within an eNodeB coverage of radius R. The MTC equipment is uniformly distributed in the deployment range of the base station, the communication range of each MTC equipment is r, and the average time delay required by the MTC equipment to access the base station through the random access process is calculated. The deployment parameters are shown in the following table:
suppose that all MTC devices need to initiate I (I ═ 1, 2., I) random access requests to access the base station. KiIndicating the number of MTC initiating a random access request the ith time.
In the ith random access request process, the probability of collision of a certain MTC device is:
the average access delay of the MTC devices is:
in the embodiment of the present application, the delay of the congestion control method of the present application is analyzed and compared with the delay of the conventional random access method, and first, the following terms are described.
Channel listening delay: when the node turns on the radio frequency in a random time period, the node monitors the channel on a fixed frequency point for a random length of time. Here, the random length of time monitored is referred to as the channel monitoring delay, and the average value is represented by Tm.
Random waiting time delay: after receiving the Type1 message, the node waits for a random time, and then broadcasts a response message Type2, wherein the random time is a random waiting time delay, and the average value of the random waiting time delay is represented by Tw.
Transmission delay: the transmission delay is related to factors such as channel bandwidth, packet length and coding mechanism, including transmission of handshake messages and transmission of packets when establishing communication connection between devices, and its average value is denoted by Ts.
In the technical scheme of the invention, the transmission quantity of the data packets between the devices is less, and queuing delay and backoff delay cannot occur. To simplify the calculation, we will make a further assumption that propagation delays and data processing delays are ignored.
The time delay of the congestion control method mainly comprises two parts, including the time delay of a congestion control stage and the time delay of a random access (base station access) process. First, we analyze the delay of the congestion control phase, taking the embodiment shown in fig. 2 as an example:
initially, the device A, B, D is in an idle state, and when there is data to be transmitted, an access procedure is triggered. In fig. 2, device B first turns on the radio frequency to listen for a random length of time Tm. After the monitoring is finished, B does not receive the invitation message Type1 sent by other nodes, and then actively sends out an invitation and broadcasts an invitation message Type 1. At this point, devices a and D will receive the Type1 message sent by device B. When devices a and D receive the Type1 message, they wait for a random time Tw and then broadcast their response message Type 2.
When B receives the invitation response message Type2, it will immediately send Type3 message to A. Since it is a broadcast message, device D also receives the message at this time. When the device D recognizes that the communication connection between the device D and the device B fails to be established, the device D returns to the monitoring state. Device a will get a time offset according to Type3 to find two common idle time periods as a timeslot pair to allocate to the link between a and B. Then, the device a selects a random frequency point, and sends the position information of the time slot pair and the selected frequency point to the device B through Type 4. After the information is successfully exchanged, the time slot allocation and the frequency selection between A and B are completed, and the corresponding time slot and frequency can be switched to for data transmission. The average delay of the message transmission after the four-way handshake is 4 × Ts。
As can be seen from the above working flows, the average time delay for a certain MTC device to complete a data aggregation process at the congestion control stage is:
D1＝Tm+Tw+4×Ts
for the device with the communication connection failure, after recognizing the communication connection failure and returning to the listening state, the device may be considered to restart the congestion control phase. Its latency must include the time from the start of triggering the access procedure to the last entry into the listening state, which is included in the congestion control phase part.
Next, we analyze the time delay of the second phase random access (base station access) process part. When the data aggregation node does not need to communicate with the neighbor node, the congestion control phase is ended, and the node initiates an access request to the base station. Therefore, only the number K of MTC devices initiating random access requests simultaneously in the coverage range of the base station at the moment i needs to be knowniNamely:
in order to verify the effectiveness of the access congestion control method, the delay theory comparison is performed between the existing random access method and the access congestion control method adopted in the present application, and the obtained result is shown in fig. 4. It can be seen that when a large amount of MTC devices are directly accessed to a base station by the existing random access method, a huge access delay is experienced, and the size of the delay increases exponentially with the increase of the number of MTC devices. For some low latency services, such a result is unacceptable. Before the random access begins, the access congestion control method is adopted to carry out congestion control firstly and then carry out random access to the base station, so that the access time delay of the MTC equipment can be greatly reduced.
After theoretical calculation results of the two access methods are obtained, the traditional random access and the congestion control method are simulated; the concerned performance index is the average access time delay required by the MTC equipment to successfully access the base station; the simulation parameters are shown in the following table:
the average time delay obtained by simulation is compared with the theoretical calculation result, and the obtained result is shown in fig. 5. The simulation result value of the congestion control method is higher than the theoretical calculation result, because the distribution density of the MTC equipment in the coverage area of the base station is considered to be equal in the theoretical calculation, and the position of the MTC equipment is randomly generated in the actual simulation process, so that the obtained result has certain errors. Generally speaking, the congestion control is performed before the random access, so that the access delay of the MTC equipment can be effectively reduced.
In summary, in the present invention, MTC devices may communicate with each other in a distributed networking manner, establish a connection to implement transmission and aggregation of data, and then initiate a random access request to access a base station by the MTC devices with aggregated data; under the condition that the access resources of the base station are not additionally consumed, the number of MTC (machine type communication) equipment which directly communicate with the base station is greatly reduced, and instantaneous sudden access congestion caused by simultaneous network access of a large number of MTC equipment is relieved.
Claims (5)
1. An access congestion control method based on distributed networking is characterized in that: the method comprises the following steps:
and (3) congestion control: the event triggers the MTC equipment to initiate an access request, and the MTC equipment enters a congestion control stage: firstly, starting a neighbor node discovery process and establishing communication connection with a neighbor node; after the communication is successfully established, determining the time slot and frequency of data transmission, storing the time slot and frequency, and completing networking and collection of data;
base station access: the MTC equipment which collects the data initiates a random access request to the base station until the access is successful;
the congestion control step comprises the sub-steps of:
s01, when an event triggers a receiving request of the MTC equipment, the MTC equipment starts a radio frequency part after waiting for a period of random time;
s02, the MTC equipment selects a fixed frequency point and monitors in a time period with a random length;
s03, judging whether the MTC equipment receives invitation messages sent by other nodes within monitoring time; if yes, go to step S04; if not, go to step S05;
s04, the MTC device serves as an invited node, communication connection is established with the inviting node, after communication is established successfully, time slots and frequency of data transmission are determined and stored, the inviting node enters a networking completion state, and the MTC device returns to the step S02 to continue monitoring;
s05, the MTC device serves as an invitation node, broadcasts an invitation message, establishes communication with a neighbor node responding to the invitation message, finishes data collection after all neighbor nodes finish an access process, and enters a base station access step;
the step S04 includes the following sub-steps:
step one, the MTC equipment is used as an invited node, waits for a random length after receiving invitation messages sent by other nodes, broadcasts a response message, and waits for receiving a response message from the invited node;
secondly, after the MTC equipment receives the reply message from the invitation node, the MTC equipment selects an unused frequency point and a pair of communication time slots, sends a response message and establishes communication connection with the invitation node;
thirdly, inviting the node to enter a networking completion state, and returning the MTC equipment to the step S02 to continue monitoring;
the step S05 includes the following sub-steps:
step one, the MTC equipment is used as an invitation node, broadcasts an invitation message and waits for receiving a response message from the invited node;
secondly, judging whether the MTC equipment can receive a response message from an invited node or not within set time; if yes, entering a third step; if not, all the neighbor nodes are considered to have completed the access process, the data collection is completed, and the base station access step is directly entered;
thirdly, the MTC equipment generates a reply message according to the time slot allocation condition, sends the reply message to the response node, and waits for receiving the response message of the response node;
fourthly, after receiving the response message of the response node, the MTC device establishes communication connection with the response node and returns to the step S02 to continue monitoring;
when only one invited node responding to the invitation message exists, the node is the answering node; when there is more than one invited node responding to the invitation message, the MTC device selects a node where the response first arrives or the strength of the response signal is the greatest from the invited nodes responding to the invitation message as the responding node.
2. The access congestion control method based on distributed networking according to claim 1, wherein: the invitation message comprises the ID of the invitation node and the number of the neighbor nodes which have already distributed channels.
3. The access congestion control method based on distributed networking according to claim 1, wherein: the response message comprises an inviting node, an invited node address and a time slot allocation state of the invited node, wherein the time slot allocation state of the invited node is whether a time slot allocation schedule is empty or not.
4. The access congestion control method based on distributed networking according to claim 1, wherein: the reply message comprises a designated invited node, a time node of the next frame of the reply message, and time slot allocation states of the inviting node and the invited node; in addition, the reply message further includes the following information:
if the time slot allocation time tables of the inviting node and the invited node are not empty, the reply information also comprises the time slot allocation time table of the inviting node;
if the time slot distribution time table of the inviting node is not empty and the time slot distribution time table of the invited node is empty, the response information comprises the distribution information of the channel;
if the time slot allocation schedule of the inviting node is empty, the reply message has no other information.
5. The access congestion control method based on distributed networking according to claim 1, wherein: the response message includes the following information:
if the time slot allocation schedules of the inviting node and the invited node are both empty, the response message contains a channel specified by the invited node;
if the time slot allocation schedule of the inviting node is not empty and the time slot allocation schedule of the invited node is empty, the response message does not contain information;
if the time slot allocation schedule of the inviting node is empty and the time slot allocation time of the invited node is not empty, the response message contains a channel specified by the invited node;
if the time slot allocation schedules of the inviting node and the invited node are not empty, the response message comprises a channel selected according to the time slot allocation schedule of the inviting node and the time slot allocation schedule of the invited node.
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