CN114007273A - Limited competition multiple access method and system in distributed frequency hopping network - Google Patents
Limited competition multiple access method and system in distributed frequency hopping network Download PDFInfo
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Abstract
The invention discloses a limited competition multiple access method and a system in a distributed frequency hopping network, which comprises the steps of selecting competition time slots according to the principle that the conflict probability is smaller than the conflict tolerance probability of service grouping, sequentially dequeuing a cache queue, and transmitting the service grouping; randomly selecting a sending moment in a time delay jitter window of a competition time slot, synthesizing a frequency hopping pattern, and carrying out phase delay on a sending signal of each node by using the synthesized frequency hopping pattern; realizing that a plurality of nodes compete to multiplex the same time slot; the receiving end carries out channel detection and carries out synchronization sequence matching and related peak detection according to the frequency hopping pattern synthesized by the current competition time slot; the random phase delay is added to the sending signal of each node, so that the signal reaching a receiving end has resolvability, the synchronous capture detection result is converted into the collision probability which is used as the indication of the channel competition multiplexing degree, the channel capacity of a competition channel is improved, and the channel multiplexing estimation has the characteristic index of reliable multiplexing.
Description
Technical Field
The invention relates to the technical field of wireless frequency hopping communication, in particular to a limited competition multiple access method and a limited competition multiple access system in a distributed frequency hopping network.
Background
In a joint tactical information system (JIDS), a Time Division Multiple Access (TDMA) access system is adopted to carry out channel resource division and centralized scheduling of time slot resources. To accommodate the dynamic grouping, flexible networking, and dynamic resource allocation requirements of joint operations, the JIDS system evolution has created a great need for packet-oriented dynamic scheduling techniques.
The packet scheduling technique is an important component of communication resource management, and when a plurality of users share communication resources, a reasonable packet scheduling mechanism is needed to determine a service order, effectively allocate network resources, effectively utilize idle time slot resources, and obtain statistical multiplexing gain.
The packet scheduling algorithm for the mobile wireless network considers the influence of the algorithm on the system performance, such as fairness, channel utilization rate, QoS and the like, and considers the influence of time-varying characteristics of a wireless channel, the limitation of bandwidth resources, the limitation of mobile power and the like, so as to reduce the complexity of algorithm implementation as much as possible. Typically, packet scheduling algorithms include round robin scheduling (RR), maximum carrier-to-interference ratio scheduling (max C/I), and proportional fair scheduling (PF).
The Round Robin (RR) algorithm assumes that all users have the same priority, and ensures that all users in the system are allocated the same number of resources with equal opportunity, so that the users occupy the radio resources in a certain order for communication. When the specific situation of a user wireless channel is not considered, the polling scheduling algorithm can ensure fairness, but the throughput is not high.
The maximum carrier-to-interference ratio scheduling algorithm (max C/I) preferentially allocates channel resources for the user with the best link conditions. The user with good wireless channel state transmits data preferentially, so that the probability of correct data transmission is increased, the number of times of error retransmission is reduced, and the throughput of the whole system is improved. The maximum carrier-to-interference ratio algorithm does not guarantee fairness for users.
Proportional fair scheduling (PF) makes a good compromise between system transmission efficiency and user Fairness. With the increase of the user rate, the priority of the user is reduced, so that the user with the original priority obtains more transmission opportunities.
The packet scheduling algorithms do not consider the multiplexing capability of the wireless channel, and cannot adaptively adjust the packet service scheduling request of the user according to the change of the channel capacity. In the JIDS evolution network technology, the traditional packet scheduling technology uses Time Division Multiple Access (TDMA) to divide the channel resource, and only 1 node occupies the channel resource in each time slot, which has the following problems:
1) the TDMA access mechanism allocates channel resources based on a completely conflict-free assumption, does not consider the multiplexing capability of a frequency hopping channel, and cannot fully utilize the channel resources;
2) the fixed time slot allocation mechanism of TDMA does not take into account the burst characteristics of mobile nodes and service packets, and cannot flexibly adjust the packet service scheduling request of a user according to the change of channel capacity.
Disclosure of Invention
Therefore, the present invention aims to provide a limited contention multiple access method and system in a distributed frequency hopping network, which can make signals reaching a receiving end have resolvability by adding a random phase delay to a transmission signal of each node, convert a synchronous acquisition detection result into a collision probability as an indication of channel contention multiplexing degree, improve channel capacity of a contention channel, and enable channel multiplexing estimation to have a reliable multiplexing characteristic index.
In order to achieve the above object, a method for limited contention multiple access in a distributed frequency hopping network according to the present invention includes the following steps:
s1, when the service packet arrives at the sending end of the node, the queue is cached according to the priority of the service packet;
s2, selecting competition time slots according to the principle that the conflict probability is smaller than the conflict tolerance probability of the service grouping, sequentially dequeuing the buffer queues and sending the service grouping;
s3, when the service packet is sent, randomly selecting a sending time in a time delay jitter window of a competition time slot, synthesizing a frequency hopping pattern, and carrying out phase delay on a sending signal of each node by using the synthesized frequency hopping pattern to realize that a plurality of nodes compete to multiplex the same time slot;
s4, when each competition time slot starts, the receiving end carries out channel detection, and carries out synchronization sequence matching and correlation peak detection according to the synthesized frequency hopping pattern of the current competition time slot;
and S5, capturing a plurality of correlation peaks with different phases in series in the detection window, carrying out correlation peak statistics, and evaluating the multiplexing state of each competition time slot according to the number of the statistical correlation peaks.
Further, it is preferable that the method further includes S6, and an average value is calculated for the channel multiplexing detection result of the current time slot.
Further, preferably, the specific calculation manner of calculating the average value of the channel multiplexing detection result of the current time slot is as follows: calculating an average estimation value according to the channel multiplexing detection result of the adjacent node by the following formula (9):
in the formula (I), the compound is shown in the specification,
is the probability of collision for the mth slot,
as a result of the channel multiplexing state detection for the mth slot of the neighboring node i,
and k is the total number of nodes.
Further, preferably, the specific calculation manner of calculating the average value of the channel multiplexing detection result of the current time slot is as follows: calculating a time domain average estimation value for the channel multiplexing detection result by using the following formula (10):
in the formula (I), the compound is shown in the specification,
is the probability of collision for the mth slot,
for the channel multiplexing state detection result for the mth slot in the jth frame period,
and H is the total number of frame periods.
Further, it is preferable that before transmitting the service packet, the method further includes configuring the capacity of the contention slot block according to the following steps:
s01, configuring the length T of the time delay jitter window for each competition time slotjitMaximum number of tolerated users NtolAnd a collision probability threshold value Pc_tol；
S02, establishing a functional relation of each parameter in S01 according to the probability that a plurality of users transmit no collision in the same time slot;
in the formula, ThFor synchronizing the pulse periods of frequency-hopping systems, TjitIs the delay jitter window length, NtolThe maximum number of tolerant users; pc_tolIs a collision probability threshold.
Further, preferably, in S2, when the buffered queues are sequentially dequeued for service packet transmission, the data packets in each queue follow a first-in first-out rule, and at least one scheduling method is adopted for different queues according to the difference of priority levels, where the scheduling method includes: strict priority service scheduling, round robin scheduling or weighted fair queuing scheduling, scheduling the dequeuing of traffic packets.
The invention also provides a limited competition multiple access system in the distributed frequency hopping network, which comprises a signal receiver, a signal transmitter, a channel multiplexing detection module and a competition time slot setting module;
the signal transmitter is used for transmitting signals;
the contention time slot setting module is used for carrying out queue caching according to the priority of the service packet when the service packet in the signal arrives; selecting competition time slots according to the principle that the conflict probability is smaller than the conflict tolerance probability of the service grouping, sequentially dequeuing the cached queues, and sending the service grouping; randomly selecting a sending moment in a time delay jitter window of a competition time slot, synthesizing a frequency hopping pattern, and adding random phase delay to a sending signal of each node by using the synthesized frequency hopping pattern; realizing that a plurality of nodes compete to multiplex the same sending time slot;
a signal receiver for receiving a signal; performing channel detection at the beginning of each contention slot, and performing synchronization sequence matching and correlation peak detection according to the synthesized hopping pattern of the current contention slot;
and the channel multiplexing detection module is used for capturing a plurality of correlation peaks with different phases in series in a detection window, carrying out correlation peak statistics, and evaluating the multiplexing state of each competition time slot according to the number of the statistical correlation peaks.
Further, preferably, the apparatus further includes a statistical filtering module, where the statistical filtering module is configured to calculate an average value for the channel multiplexing detection result of the current time slot.
Further, preferably, a specific calculation manner of calculating the average value of the channel multiplexing detection result of the current time slot is as follows: calculating an average estimation value according to the channel multiplexing detection result of the adjacent node by the following formula (9):
in the formula (I), the compound is shown in the specification,
is the probability of collision for the mth slot,
as a result of the channel multiplexing state detection for the mth slot of the neighboring node i,
and k is the total number of nodes.
Further, preferably, a specific calculation manner of calculating the average value of the channel multiplexing detection result of the current time slot is as follows: calculating a time domain average estimation value for the channel multiplexing detection result by using the following formula (10):
in the formula (I), the compound is shown in the specification,
is the probability of collision for the mth slot,
for the channel multiplexing state detection result of the m time slot in the j frame period of the node,
and H is the total number of frame periods.
Compared with the prior art, the limited competition multiple access method and the system in the distributed frequency hopping network at least have the following advantages:
1. according to the limited competition multiple access method and system in the distributed frequency hopping network, random phase delay is added to the sending signal, so that the signal reaching the receiving end has a phase distinguishing characteristic, a plurality of nodes are allowed to compete and multiplex the same sending time slot, and the channel capacity of a competition channel is greatly improved.
2. According to the limited competition multiple access method and system in the distributed frequency hopping network, the synchronous capture detection result is converted into the calculated conflict probability, and the conflict probability is used for indicating the channel competition reuse degree, so that the channel reuse estimation has the characteristic index of reliable reuse.
3. The limited competition multiple access method and the system in the distributed frequency hopping network also provide a competition time slot optimization target aiming at low time delay or high reliability service grouping, and the time slot can be optimized through a quick search algorithm to obtain a target competition time slot meeting the QoS requirement. By limiting the multiplexing degree of the competition time slot, the relatively reliable service packet transmission and the balanced use of the competition time slot resources are realized, and the resource utilization rate of the whole network is improved.
Drawings
FIG. 1 is a flow chart of a limited contention multiple access method in a distributed frequency hopping network according to the present invention;
FIG. 2 is a schematic diagram of limited contention multiple access for a limited contention multiple access system in a distributed frequency hopping network of the present invention;
fig. 3 is a process flow of contention-limited multiple access in an embodiment of the present invention.
Detailed Description
The invention is described in further detail below with reference to the figures and the detailed description.
In a limited contention multiple access method in a distributed frequency hopping network provided in an embodiment of an aspect of the present invention, before sending a service packet, the method further includes configuring a capacity of a contention slot block according to the following steps: s01, configuring the length T of the time delay jitter window for each competition time slotjitMaximum number of tolerated users NtolAnd a collision probability threshold value Pc_tol(ii) a S02, establishing a functional relation of each parameter in S01 according to a probability formula that a plurality of users transmit no collision in the same time slot;
in the formula, ThFor synchronizing the pulse periods of frequency-hopping systems, TjitIs the delay jitter window length, NtolThe maximum number of tolerant users; pc_tolIs a collision probability threshold.
As shown in fig. 1, when the traffic packet arrives at the transmitting end of the node, the queue buffering is performed according to the priority of the traffic packet S1. Specifically, when a service packet arrives, priority queuing is performed according to the priority of the service packet, and G parallel queues are enqueued for queue caching respectively for prioritized QoS service.
S2, selecting competition time slots according to the principle that the conflict probability is smaller than the conflict tolerance probability of the service grouping, sequentially dequeuing the cached queues and sending the service grouping;
further, preferably, in S2, when the buffered queues are sequentially dequeued for service packet transmission, the data packets in each queue follow a first-in first-out rule, and for different queues, the service scheduling at the transmitting end may select a queue scheduling method such as strict priority Service (SP), Round Robin (RR), Weighted Fair Queuing (WFQ), or the like, to transmit the service packets according to different application scenarios.
In S2, when selecting the contention slot, the contention slot meeting the QoS requirement is preferred according to the principle that the collision probability is smaller than the collision tolerance probability of the service packet, so that the real-time requirement can be met when the access latency is the lowest; or when the collision probability is minimized, the high reliability requirement is met.
And is
（3）
In the formula (I), the compound is shown in the specification,
is the minimum value of the time delay difference between the mth time slot and the current time slot.
A minimum value; and M is the total number of the contention slots.
The collision tolerance probability for the current traffic. The collision tolerance probability of general traffic varies depending on the traffic type, for example, 90% of the collision tolerance probability of image type data, 95% of the collision tolerance probability of sound type data, and the like.
S3, when sending the service packet, randomly selecting the sending time in the time delay jitter window of the competition time slot, synthesizing the frequency hopping pattern, and adding random phase delay to the sending signal of each node by using the synthesized frequency hopping pattern; and realizing that a plurality of nodes compete to multiplex the same transmission time slot.
Random phase delay is added to a transmission signal of each node, so that a signal reaching a receiving end has a phase-distinguishable characteristic. The mixed signal of the phase-shifted channel multiple access multiplexing can be expressed as:
in the formula (I), the compound is shown in the specification,p i is the signal power of the ith transmitting node,f ni for the frequencies of the frequency hopping frequency table,d i for the purpose of error-coding the data signal,
in order to be a function of the modulation,
a frequency hopping frequency variation gradient; h is the number of the frequency hopping synchronous subnets, and t is the current hopping moment;T h is a hop period; and N is a hop period coefficient of random delay.Δt i The value range of the random delay of the ith sending node is more than or equal to 0Δt i ≤NT h Stepped by one hop period Th。
According to the random sequence autocorrelation principle, the cyclic collision probability of different phases of the same frequency hopping pattern is extremely low, and the collision probability of any two phase-shifting channels can be reduced to the minimum.
Wherein, represents a conjugate convolution,
is a correlation function of any two paths of pseudo-random sequences,
and
for two phase shifted sequences of the same hopping pattern,
is the correlation peak of the frequency hopping sequence,
is a pseudo-random sequence when no phase shift is generated.
Due to the autocorrelation characteristic of the hopping sequence, the hopping pattern has a steep correlation peak, and the synchronous hopping pattern reaching the receiving end has distinguishable phase delay outside a limited number of hopping periods, so that the receiving end can capture the multipath hopping signal at a large rate.
According to the autocorrelation characteristic of the frequency hopping sequence, as long as the overlapping windows of the grouped pulse signals of the two sending ends at the receiving end are larger than the pulse period, the two groups of frequency hopping patterns can be orthogonal, and collision-free transmission is realized on a propagation path.
At a given collision probability threshold Pc_tolUnder the condition (2), the node capacity accommodated by a single time slot is represented by formula (7):
the above equation illustrates that at a given pulse period T of a synchronous frequency hopping systemhUnder the condition, the user capacity n of the multiple access multiplexing of the phase shift channel and the conflict probability threshold value Pc_tolLength of delay jitter windowT jit The correlation is respectively in a logarithmic positive correlation and a positive correlation.
Using a transmission window random jitter scheme, when the delay jitter window lengthT jit Pulse period T far greater than frequency hoppinghThe contention channel can be in the sense of tolerating a certain collision probability (P)c< 10%), accommodating a larger number of users (n > 10).
S4, when each competition time slot starts, the receiving end carries out channel detection, and carries out synchronization sequence matching and correlation peak detection according to the synthesized frequency hopping pattern of the current competition time slot;
in this embodiment, the synchronization sequence matching process includes the following methods:
acquiring a group of synchronous sequences synchronously received under the frequency hopping pattern according to the frequency hopping pattern of the current competition time slot; since a random phase delay is added to the synthesized hopping pattern, the set of synchronization sequences is composed of a plurality of signals arranged in order of phase delay.
In the system, when receiving signals in a competition time slot, a synchronous parallel receiving mode is adopted for receiving the multi-path signals, but asynchronous serial detection is carried out on the received signals, wherein the asynchronous serial detection means that the arrival time of the multi-path signals has a sequence, and the related peak detection can detect a plurality of signals arriving at different times in sequence and count the number of the related peaks. Therefore, before asynchronous detection, signal extraction and timing are performed on multiple paths of signals in a synchronous sequence which is received synchronously according to different time delays, synchronous sequence matching of the multiple paths of received signals is completed, and asynchronous detection is performed on the matched synchronous sequence.
The relationship between the synchronization sequence and the synchronization timing of the received signal is established according to the following equation (11)
Where s (T) is a known synchronization sequence, r (T) is a baseband received signal, τ is a sliding time delay of the received signal, and TwIs the maximum detection window of tau and,
is the corresponding sliding time delay at the maximum correlation peak and is used for representing the timing synchronization value of the received signal.
The number of the correlation peaks represents the number of paths that the signal arrives successively, represents the superposition of the signal paths of the multipath signal and the multiple access multiplexing signal, and can be used for representing the multiplexing state of the time slot, so that the multiplexing state of each competition time slot can be evaluated by adopting a method for counting the number of the correlation peaks.
And S5, capturing a plurality of correlation peaks with different phases in series in the detection window, carrying out correlation peak statistics, and evaluating the multiplexing state of each competition time slot according to the number of the statistical correlation peaks. The channel multiplexing state adopts the collision probability P of any time slotcMeans that the collision probability of any time slot and the number N of related peakscorThe relationship of (a) to (b) is as follows:
number of correlation peaks NcorThe number of the users is large, which means that the number of the users of the competitive multiplexing of the channel is large, and the collision probability of the competitive multiplexing is relatively high; the small number of the correlation peaks indicates that the competitive multiplexing degree of the channel is low and the collision probability is low.
Further, it is preferable that the method further includes S6, and an average value is calculated for the channel multiplexing detection result of the current time slot.
In one embodiment, the specific calculation manner of calculating the average value of the channel multiplexing detection result of the current time slot is as follows: calculating an average estimation value according to the channel multiplexing detection result of the adjacent node by the following formula (9):
in the formula (I), the compound is shown in the specification,
is the probability of collision for the mth slot,
as a result of the channel multiplexing state detection for the mth slot of the neighboring node i,
and k is the total number of nodes.
In another embodiment, the specific calculation method for calculating the average value of the channel multiplexing detection result of the current time slot is as follows: calculating a time domain average estimation value for the channel multiplexing detection result by using the following formula (10):
in the formula (I), the compound is shown in the specification,
is the probability of collision for the mth slot,
for the channel multiplexing state detection result of the m time slot in the j frame period of the node,
and H is the total number of frame periods.
As shown in fig. 2, the present invention further provides a limited contention multiple access system in a distributed frequency hopping network, which is used for implementing the above access method, and includes a signal receiver, a signal transmitter, a channel multiplexing detection module, and a contention slot setting module;
a contention slot setting module; the method comprises the steps of configuring competition time slots of a line, wherein when service packets such as data or images in signals arrive, queue buffering is carried out according to the priority of the service packets; as shown in fig. 2, the priority 0 queue, the priority 1 queue … … and the queue buffer of the priority G queue are respectively performed according to the priority; in the figure, a plurality of competition time slots such as a competition time slot 1, a competition time slot 2 … … and a competition time slot M are set, after a queue buffers, the time slots are competed according to the principle that the conflict probability is smaller than the conflict tolerance probability of service grouping, and the buffered queue is sequentially dequeued for service grouping transmission; randomly selecting a sending moment in a time delay jitter window of a competition time slot, synthesizing a frequency hopping pattern, and adding random phase delay to a sending signal of each node by using the synthesized frequency hopping pattern; realizing that a plurality of nodes compete to multiplex the same sending time slot;
the signal transmitter is used for transmitting signals;
the signal receiver is used for receiving signals, performing channel detection when each competition time slot starts, and performing synchronization sequence matching and correlation peak detection according to the frequency hopping pattern synthesized by the current competition time slot;
and the channel multiplexing detection module is used for capturing a plurality of correlation peaks with different phases in series in a detection window, performing correlation peak statistics, and evaluating the multiplexing state of each competition time slot according to the number of the counted correlation peaks, for example, in the figure, by performing statistics on the correlation peaks, sequentially evaluating the user number statistics of the competition time slot 1, the user number statistics of the competition time slot 2, and the user number statistics of the competition time slot 3 … … for the user number statistics of the competition time slot M.
Further, preferably, the apparatus further includes a statistical filtering module, where the statistical filtering module is configured to calculate an average value for the channel multiplexing detection result of the current time slot.
In one embodiment, the specific calculation method for calculating the average value of the current timeslot channel multiplexing detection result is as follows: calculating an average estimation value according to the channel multiplexing detection result of the adjacent node by the following formula (9):
in the formula (I), the compound is shown in the specification,
is the probability of collision for the mth slot,
as a result of the channel multiplexing state detection for the mth slot of the neighboring node i,
and k is the total number of nodes.
In another embodiment, the specific calculation method for calculating the average value of the current timeslot channel multiplexing detection result is as follows: calculating a time domain average estimation value for the channel multiplexing detection result by using the following formula (10):
in the formula (I), the compound is shown in the specification,
is the probability of collision for the mth slot,
for the channel multiplexing state detection result of the m time slot in the j frame period of the node,
and H is the total number of frame periods.
As shown in fig. 3, in a specific embodiment of the present invention, when starting implementation, first, a contention time slot block is allocated to a communication link, and parameters such as the maximum number of tolerant users of each contention time slot are set, for a node sending end, whether a service packet arrives is detected, when the service packet arrives, priority queuing is performed according to the priority of the service packet, and if the service packet does not arrive, waiting is continued (the process only needs to wait, not shown in the figure); after queuing, performing service scheduling and queue query, checking whether the queue is empty, if not, performing service packet dequeuing, and if the queue is empty, returning to the previous step to continue to perform queue query; when dequeuing the service packet, preferably selecting the competition time slot meeting the requirement according to the principle that the collision probability is smaller than the collision tolerance probability of the service packet, and when the preferred time slot arrives, dequeuing the service.
And for the node receiving end, after receiving the signal, carrying out channel detection, checking whether a channel detection window is finished, if so, carrying out competition time slot multiplexing state statistics, calculating an average value of statistical results, and accurately evaluating the multiplexing state of competition time slots. If not, it only needs to wait for the completion of channel detection, so the process is not shown in the figure, and after the completion, the contention slot multiplexing status statistics is performed.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (10)
1. A limited competition multiple access method in a distributed frequency hopping network is characterized by comprising the following steps:
s1, when the service packet arrives at the sending end of the node, the queue is cached according to the priority of the service packet;
s2, selecting competition time slots according to the principle that the conflict probability is smaller than the conflict tolerance probability of the service grouping, sequentially dequeuing the buffer queues and sending the service grouping;
s3, when the service packet is sent, randomly selecting a sending time in a time delay jitter window of a competition time slot, synthesizing a frequency hopping pattern, and carrying out phase delay on a sending signal of each node by using the synthesized frequency hopping pattern to realize that a plurality of nodes compete to multiplex the same time slot;
s4, when each competition time slot starts, the receiving end carries out channel detection, and carries out synchronization sequence matching and correlation peak detection according to the synthesized frequency hopping pattern of the current competition time slot;
and S5, capturing a plurality of correlation peaks with different phases in series in the detection window, carrying out correlation peak statistics, and evaluating the multiplexing state of each competition time slot according to the number of the statistical correlation peaks.
2. The method for contention-limited multiple access in a distributed frequency hopping network according to claim 1, further comprising S6, calculating an average value for the channel multiplexing detection result of the current time slot.
3. The method according to claim 2, wherein the specific calculation manner for calculating the average value of the channel multiplexing detection results of the current time slot is as follows: calculating an average estimation value according to the channel multiplexing detection result of the adjacent node by the following formula (9):
in the formula (I), the compound is shown in the specification,
is the probability of collision for the mth slot,
as a result of the channel multiplexing state detection for the mth slot of the neighboring node i,
and k is the total number of nodes.
4. The method according to claim 2, wherein the specific calculation manner for calculating the average value of the channel multiplexing detection results of the current time slot is as follows: calculating a time domain average estimation value for the channel multiplexing detection result by using the following formula (10):
in the formula (I), the compound is shown in the specification,
is the probability of collision for the mth slot,
for the channel multiplexing state detection result for the mth slot in the jth frame period,
and H is the total number of frame periods.
5. The method of claim 2, further comprising configuring the capacity of the contention slot block before transmitting the traffic packet according to the following steps:
s01, configuring the length T of the time delay jitter window for each competition time slotjitMaximum number of tolerated users NtolAnd a collision probability threshold value Pc_tol；
S02, establishing a functional relation of each parameter in S01 according to the probability that a plurality of users transmit no collision in the same time slot;
in the formula, ThFor synchronizing the pulse periods of frequency-hopping systems, TjitIs the delay jitter window length, NtolThe maximum number of tolerant users; pc_tolIs a collision probability threshold.
6. The method of claim 2, wherein when the buffered queues are sequentially dequeued for service packet transmission in S2, the data packets in each queue follow a first-in first-out rule, and at least one scheduling method is adopted for different queues according to the difference of priority levels, the scheduling method includes: strict priority service scheduling, round robin scheduling or weighted fair queuing scheduling, scheduling the dequeuing of traffic packets.
7. A limited competition multiple access system in a distributed frequency hopping network is characterized by comprising a signal receiver, a signal transmitter, a channel multiplexing detection module and a competition time slot setting module;
the signal transmitter is used for transmitting signals;
the contention time slot setting module is used for carrying out queue caching according to the priority of the service packet when the service packet in the signal arrives; selecting competition time slots according to the principle that the conflict probability is smaller than the conflict tolerance probability of the service grouping, sequentially dequeuing the cached queues, and sending the service grouping; randomly selecting a sending moment in a time delay jitter window of a competition time slot, synthesizing a frequency hopping pattern, and adding random phase delay to a sending signal of each node by using the synthesized frequency hopping pattern; realizing that a plurality of nodes compete to multiplex the same sending time slot;
a signal receiver for receiving a signal; performing channel detection at the beginning of each contention slot, and performing synchronization sequence matching and correlation peak detection according to the synthesized hopping pattern of the current contention slot;
and the channel multiplexing detection module is used for capturing a plurality of correlation peaks with different phases in series in a detection window, carrying out correlation peak statistics, and evaluating the multiplexing state of each competition time slot according to the number of the statistical correlation peaks.
8. The system of claim 7, further comprising a statistical filter module, configured to calculate an average value of the channel multiplexing detection result of the current timeslot.
9. The system of claim 8, wherein the specific calculation manner for calculating the average value of the channel multiplexing detection results of the current time slot is as follows: calculating an average estimation value according to the channel multiplexing detection result of the adjacent node by the following formula (9):
in the formula (I), the compound is shown in the specification,
is the probability of collision for the mth slot,
as a result of the channel multiplexing state detection for the mth slot of the neighboring node i,
and k is the total number of nodes.
10. The system of claim 8, wherein the specific calculation manner for calculating the average value of the channel multiplexing detection results of the current time slot is as follows: calculating a time domain average estimation value for the channel multiplexing detection result by using the following formula (10):
in the formula (I), the compound is shown in the specification,
is the probability of collision for the mth slot,
for the channel multiplexing state detection result of the m time slot in the j frame period of the node,
and H is the total number of frame periods.
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