A network environment perception-based ad hoc network time-frequency resource management method

Abstract

The application relates to a network environment perception-based self-organizing network time-frequency resource management method and belongs to the technical field of wireless self-organizing network communication. The method is based on a RODD system, transmission and reception processing are separated, a corresponding time-hopping frequency-hopping pattern is designed according to the throughput requirement of a node in an early stage, the pattern is selected so that the spectrum resources in a current target network are discretized, the information quantity in each frequency point is kept relatively balanced, when a new node joins the network, network environment perception is performed, the influence of interference in the environment is removed, the duty cycle of each frequency point is measured, the throughput of the newly-added node is estimated, a time-hopping frequency-hopping pattern is selected from a library constructed in the early stage so that the information quantity in each frequency point is still kept relatively balanced, the resource distribution is relatively reasonable, the packet loss problem caused by resource allocation is reduced, and the communication of each node in the network is kept relatively stable.

Description

Technical Field

[0001] This invention relates to a time-frequency resource management method for ad hoc networks based on network environment awareness, belonging to the field of wireless ad hoc network communication technology. Background Technology

[0002] In ad hoc networks, multiple nodes typically interact with each other. To ensure that this interaction doesn't interfere with each other, resource allocation is necessary. Common methods for ad hoc networks involve processing time-domain and frequency-domain resources, such as FDD (Frequency Division Duplex), TDD (Time Division Duplex), and time-hopping frequency hopping. FDD systems separate uplink and downlink signals using different frequencies; this frequency isolation can be easily achieved through filters and up / down conversions to extract signals from different nodes. TDD systems separate the transmission and reception times of different nodes; this temporal separation allows for accurate acquisition of information from different nodes using the same time reference point. Time-hopping frequency hopping systems divide a single frame of data into many small pulses with different time intervals and carrier frequencies between them; collision recovery enables information exchange between different nodes.

[0003] (1) Time-hopping and frequency-hopping systems: In a time-hopping system, nodes control the transmission time of signals according to the time-hopping sequence, interpreting the smallest scale of the time hopping as a time slot. A time-hopping system can be considered a time-division system. In a frequency-hopping system, nodes control the carrier frequency of the transmitted signal according to the frequency-hopping sequence, enabling frequency hopping within a fixed frequency band. The receiver acquires and receives the transmitted signal according to the same frequency-hopping sequence. Time-hopping and frequency-hopping systems combine time hopping and frequency hopping, converting one-dimensional time-domain or frequency-domain resources into two-dimensional time-frequency resources, allowing for more efficient utilization of network resources. In a time-hopping and frequency-hopping system, the time-hopping and frequency-hopping pattern is initialized according to criteria, such as based on m-sequences, RS codes, Bent sequences, prime number sequence families, tooth sequences, etc. The construction of time-hopping and frequency-hopping patterns often only considers the autocorrelation characteristics of the pattern itself and the cross-correlation characteristics between different patterns. After generation, it generally remains fixed. For different network topologies and throughputs, there may be instances where the throughput of a single frequency point or multiple frequency points is excessively high, leading to a spectral resource skew towards certain frequency points.

[0004] Combining time-hopping frequency hopping with a RODD (Rapid On-off Division Duplex) system can realize a virtual full-duplex system. A single-frame signal is split into multiple short bursts, with the transmission interval between each burst controlled by a time-hopping sequence and the carrier frequency controlled by a frequency-hopping sequence. During the transmission burst, the received signal is erased; when no signal is transmitted, the received signal is monitored, and the original data frame is recovered from the collision-damped received signal through channel encoding and decoding. If the collision erasure rate exceeds the error correction capability of the channel encoding and decoding, packet errors and packet loss will occur.

[0005] (2) FDD-TDD hybrid system: FDD achieves non-interference between signals through frequency isolation, while TDD distinguishes signals between different nodes through transmission and reception time isolation. The FDD-TDD hybrid system combines these two aspects, allocating resources in a two-dimensional dimension of time and frequency. Only a single signal is transmitted at different times and frequencies. Its resource management can be divided into two categories:

[0006] Content-aware resource management employs a differentiated service strategy, allocating resources and service quality according to priority. When a high-priority user makes a service request, if the network load is heavy, the service quality will be reduced for lower-priority users or users with specific traffic volumes, while providing higher-priority users with better service quality and resource allocation. This type of resource management often provides different quality services based on user characteristics and content characteristics.

[0007] Spectrum-aware resource management: Spectrum-aware resource management is often applied in wireless sensor networks and consists of two parts: spectrum sensing and spectrum allocation. Sensors detect the current spectrum usage through spectrum sensing and use idle spectrum or opportunistically licensed spectrum for information exchange. Spectrum allocation can be divided into static spectrum allocation and dynamic spectrum allocation. Static spectrum allocation allocates time-frequency resources to licensed users in a fixed manner, and even if a licensed user does not use the current time-frequency resources, they cannot be allocated to other users. Dynamic spectrum allocation dynamically allocates time-frequency resources based on graph coloring models, game theory models, Markov models, or deep learning-related algorithms, adaptively adjusting to the network environment.

[0008] Existing time-frequency resource management solutions have the following main shortcomings:

[0009] First, for systems combining time-hopping and frequency-hopping (RTD) with RODD, the randomly generated RDD patterns often only consider the autocorrelation characteristics of a single pattern and the cross-correlation characteristics between different RDD patterns. Due to its randomness, a single frequency point or multiple frequency points may occupy a large portion of the overall information. For virtual full-duplex systems, the erased signals are divided into two parts. One part is erased because the signal is transmitted simultaneously at the same frequency as the target node, and the power of the transmitted signal received by the node is much greater than the power of the target signal it is monitoring. In RODD systems, nodes need to erase the received signal when transmitting to separate the transmission and reception times. The other part is due to multiple nodes transmitting simultaneously at the same frequency. The target node receives signals from different nodes at the same frequency, and signal separation requires processing in the power domain, increasing signal processing complexity. To simplify processing, colliding signals are erased. If the signal volume within a single frequency point is too large, it will increase the probability of signal collisions, and the packet loss rate will also increase accordingly.

[0010] Second, FDD systems suffer from low spectrum utilization efficiency, failing to fully utilize spectrum resources. TDD systems experience high latency due to time slots, requiring waiting for the corresponding slot to arrive before signal transmission. For hybrid FDD-TDD systems, static resource allocation leads to both high latency and low spectrum utilization; dynamic resource allocation can optimize time-frequency resource utilization, but the use of distributed networks and deep learning increases computational complexity, making it unsuitable for current self-organizing networks. Summary of the Invention

[0011] The purpose of this invention is to overcome the aforementioned shortcomings of existing time-frequency resource management schemes and provide a network environment-aware ad hoc network time-frequency resource management method. This method is based on the RODD system, with transmission and reception processing separated. In the early stage, a corresponding time-hopping and frequency-hopping pattern is designed according to the throughput requirements of the nodes. The selected pattern discretizes the spectrum resources within the current target network, and the information content within each frequency point remains relatively balanced. When a new node joins the network, network environment awareness is performed to remove the influence of interference in the environment, the duty cycle of each frequency point is measured, the throughput of the newly added node is estimated, and a time-hopping and frequency-hopping pattern is selected from the previously constructed library to ensure that the information content within each frequency point remains relatively balanced, making the resource distribution relatively reasonable, reducing packet errors and loss caused by resource allocation, and ensuring that the communication between each node in the network remains relatively stable.

[0012] The above-mentioned objectives of the present invention are mainly achieved through the following technical solutions:

[0013] A method for managing time-frequency resources in ad hoc networks based on network environment awareness, comprising the following steps:

[0014] The first step is to initialize the time-hopping and frequency-hopping pattern of the central node, taking the node at the center of the expected network topology as the central node.

[0015] The second step is to construct time-hopping frequency hopping patterns suitable for other nodes in the expected network topology based on the time-hopping frequency hopping pattern of the central node after initialization in the first step, thus forming a time-hopping frequency hopping pattern library that includes the time-hopping frequency hopping pattern of the central node and the time-hopping frequency hopping patterns of other nodes.

[0016] The third step is to select a time-hopping frequency hopping pattern from the time-hopping frequency hopping pattern library obtained in the second step based on the expected network topology and the network throughput of adjacent nodes, so that the throughput distribution at each frequency point remains relatively balanced.

[0017] The fourth step is to use the short-time fast Fourier transform to obtain the signal power at each frequency point at different times, remove the influence of interference signals in the network environment, and calculate the duty cycle of the received signal at each frequency point in the current environment.

[0018] Fifth, when a new node joins the topology network, based on the duty cycle of the received signal in each frequency point under the current environment obtained in the fourth step, and considering the impact of its joining the network on adjacent nodes, a time-hopping frequency hopping pattern is selected from the time-hopping frequency hopping library obtained in the second step so that the throughput of the newly joined node and its adjacent nodes remains relatively balanced in each frequency point.

[0019] In the time-hopping frequency-hopping pattern, a single frame of data contains N pulses, and the length of a single pulse is denoted as L. pulse Its duty cycle is DC, and the length of a single frame of data is The transmission time of a single frame of data is divided into N intervals, and the length of each interval is... The lengths of individual pulses all fall within a certain interval, and the time-jump sequence of pulse n is denoted as t. n This represents the starting position of pulse n in the corresponding interval, with a range of... The time-jump pattern of node a is denoted as T. a ={t1,t2,...,t N Let M be the number of usable frequency points, and F be the frequency point library. lib ={f lib_1 ,f lib_2 ,...,f lib_M The frequency hopping sequence of pulse n is denoted as f. n ∈F lib The frequency hopping pattern of node a is denoted as F. a ={f1,f2,...,f N The time-hopping frequency hopping sequence of pulse n is denoted as h. n ={t n ,f nThe time-hopping frequency-hopping pattern of node a is denoted as H. a ={h1,h2,...,h N};

[0020] In the first step, when initializing the time-hopping and frequency-hopping pattern of the central node, the time-hopping sequence of each node is fixed, which is... Keep the interval between each pulse the same. If the number of pulses N is less than or equal to the number of frequency points M, the carrier frequency of each pulse is randomly selected from the frequency point library without repetition. If the number of pulses N is greater than the number of frequency points M, the frequency point library is repeatedly traversed.

[0021] In the second step, the method for constructing the first layer of the time-hopping frequency-hopping pattern library is as follows: the number of the center node is recorded as 1, the frequency-hopping pattern is subjected to cyclic cross-correlation calculation, and the maximum number of points with the same frequency during the cyclic process is recorded as P. max traverse and search for P max =2 patterns, the set XCORR2 initially contains only F1, assume the frequency hopping pattern of node a satisfies P max =2, add to set XCORR2, and we get XCORR2 = XCORR2∪{F a After the first traversal is completed, the frequency hopping patterns in XCORR2 are cross-correlated, and the result P cross-correlated with the first pattern is... max Patterns ≤2 are added to the second-order set XCORR. 21 Let L2 = |XCORR2| be the number of elements in the set XCORR2. Count the frequency hopping patterns in the L2 sets, sorting them from largest to smallest. The pattern with the highest frequency is denoted as Threshold. Find the frequency hopping pattern whose frequency R ≥ Threshold. If no Threshold+1 pattern appears, all patterns appear in their respective secondary sets XCORR2. 2i In the middle, decrease the Threshold value and continue searching; if Threshold+1 patterns all appear in their respective second-order sets XCORR, 2i In this process, select the Threshold+1 frequency hopping patterns to form the first layer of frequency hopping patterns. The corresponding hopping time patterns are randomly generated to ensure that the relative positions between different pulses are different.

[0022] Using the patterns in the upper layer as the original library, find the cyclic cross-correlation result P with them. max Patterns with a value less than or equal to the number of each layer minus one are used to construct the next layer pattern library.

[0023] In the third step, the method for selecting the time-hopping frequency-hopping pattern is as follows: the amount of data transmitted by node a per unit time is denoted as Traffic. aAssume the first-layer library contains R1 patterns. If R1 ≥ 28, only the patterns from the first layer are needed; if R1 < 28, the patterns from the first and second layers are combined; if R1 + R2 ≥ 28, the patterns from the first and second layers are selected as the library; if this still doesn't satisfy the condition, patterns from lower layers are added sequentially, and the comparisons are repeated until a basic library is selected for node selection. To effectively utilize the patterns, the pattern selected by a node only needs to be different from those of its two adjacent layers. The proportion of the pattern selected by node a at frequency m is denoted as Duty. am Taking node 1 as an example, the sum of its traffic and that of its neighboring nodes at frequency point 1 is as shown in equation (1):

[0024]

[0025] The mean and variance of the flow distribution at each frequency point of node 1 are shown in equations (2) and (3):

[0026]

[0027]

[0028] The sum of the variances of all nodes in the topology is given by equation (4):

[0029]

[0030] Iterate through the database to select time-hopping frequency-hopping patterns, choosing those that result in Traffic_Var sum The smallest set serves as the initial time-hopping frequency-hopping pattern for the static topology;

[0031] In the fifth step, the method for selecting the time-hopping and frequency-hopping pattern of the newly added node is as follows: find the neighboring nodes of the newly added node, measure the duty cycle of the signals received by the newly added node and its neighboring nodes at each frequency point, that is, the amount of information received per unit time. The amount of information received by node a at frequency point m is denoted as Traffic_Detect. am The total throughput of node a at frequency m is given by equation (6):

[0032] Traffic_Sum am =Traffic_Detect am +Traffic a Duty am (6)

[0033] The mean and variance of the flow distribution at each frequency point of node a are shown in equations (7) and (8):

[0034]

[0035]

[0036] Traverse the patterns in the library and select the pattern that minimizes the sum of the variances of the flow distributions of the newly added node and its neighboring nodes.

[0037] The advantages of this invention compared to the prior art are:

[0038] (1) This invention implements a virtual full-duplex network based on the RODD system, which has a small transmission delay for single-frame data and good utilization efficiency of time and frequency resources. At the whole frame level, data transmission and reception are full-duplex, which simplifies the upper layer design, improves throughput, and makes network communication more stable and efficient.

[0039] (2) When selecting the time-hopping frequency hopping pattern, this invention performs different processing based on the initial static network topology and the subsequent dynamic changes in the network, which can effectively address different design requirements in the network. The design of equalizing the frequency distribution based on network throughput also makes resource allocation more efficient and reduces packet errors and loss caused by excessive collision ratio.

[0040] (3) Under the condition of good cross-correlation characteristics of time-hopping and frequency-hopping patterns, this invention strives to maintain a relatively balanced throughput across frequency points in both the initial static network planning and the dynamic network changes caused by the addition of new nodes. In the virtual full-duplex system, it reduces the erasure ratio caused by collisions, thereby reducing the packet loss ratio caused by uneven resource allocation. Specifically, it consists of three parts:

[0041] 1. Construction of a Time-Hopping and Frequency-Hopping Pattern Library: This library enables a single pulse sequence to hop time within a fixed interval, avoiding interference with pulse sequences in other intervals. The cross-correlation characteristics of the time-hopping and frequency-hopping patterns are simplified to the cross-correlation characteristics of the frequency-hopping patterns. The time-hopping sequences help reduce the collision rate of the time-hopping and frequency-hopping patterns, ensuring that the relative positions of different pulses are distinct. Dividing the patterns into different levels according to their cross-correlation characteristics facilitates more efficient use of spectrum resources and achieves better communication quality even with a small number of nodes.

[0042] 2. Network Environment Awareness: Network environment awareness is based on STFT. Noise power is estimated from the previous noise environment, multiplied by a corresponding coefficient to obtain a threshold, and compared with the threshold to determine whether it is a signal. Simultaneously, based on signal characteristics, if a single-frequency continuous signal or a broadband signal is found, the signal is erased, and the duty cycle is obtained using the area ratio.

[0043] 3. Time-Hopping Frequency Hopping Pattern Selection: Time-hopping frequency hopping pattern selection is divided into two cases: under the initial static topology and under the condition of new nodes joining the network later. Under the static topology, the pattern is selected to minimize the variance of the throughput distribution of a single node across all frequencies. Considering the impact on the entire network, the optimal solution is found through a traversal. Under the condition of new nodes joining the network later, the throughput of the new node and its neighboring nodes is obtained through network environment awareness. Considering the nodes within the network under the condition of the new node's first hop, the time-hopping frequency hopping pattern is selected to minimize the variance of the throughput distribution of the nodes within the network across all frequencies. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the method flow of the present invention;

[0045] Figure 2 This is a schematic diagram of the time-hopping frequency-hopping pattern;

[0046] Figure 3 This is a schematic diagram of the cyclic cross-correlation process;

[0047] Figure 4 This is a diagram of the network topology;

[0048] Figure 5 This is a waterfall image;

[0049] Figure 6 The network topology diagram after the addition of the new node. Detailed Implementation

[0050] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0051] Example

[0052] The flowchart of this invention is as follows Figure 1 As shown below, the specific implementation scheme of the present invention will be described in detail according to the process, which is mainly divided into two parts: static network planning and dynamic network changes. Static network planning constructs a static time-hop frequency hopping pattern allocation based on the previously known network topology and node throughput, ensuring that the amount of information exchanged between each node and its neighboring nodes is relatively evenly distributed across all frequency points. Dynamic network changes handle the situation of new nodes joining the current network. Based on network environment awareness, it monitors the amount of information received by the newly joined node and its neighboring nodes from various frequency points. Knowing the estimated throughput of the current node, a pattern is selected from the time-hop frequency hopping pattern library to ensure that the distribution of information across all frequency points remains relatively balanced.

[0053] (1) Static network planning:

[0054] 1. Initialize the time-hopping and frequency-hopping pattern of the central node;

[0055] When building the network in the early stage, the node in the relatively central position of the expected topology is selected as the central node, and its time hopping frequency hopping pattern is initialized.

[0056] A schematic diagram of time-hopping frequency hopping patterns is shown below. Figure 2 As shown, assume that a single frame of data contains N pulses, and the length of a single pulse is denoted as L. pulse Its duty cycle is DC, and the length of a single frame of data is The transmission time of a single frame of data is divided into N intervals, and the length of each interval is... The length of each individual pulse falls within a certain interval. The time-jump sequence of pulse n is denoted as t. n It represents the starting position of pulse n in interval n, with a range of... The time-jump pattern of node a is denoted as T. a ={t1,t2,...,t N Assume the number of available frequency points is M, and the frequency point library is denoted as F. lib ={f lib_1 ,f lib_2 ,...,f lib_M The frequency hopping sequence of pulse n is denoted as f. n ∈F lib The frequency hopping pattern of node a is denoted as F. a ={f1,f2,...,f N The time-hopping frequency hopping sequence of pulse n is denoted as h. n ={t n ,f n The time-hopping frequency-hopping pattern of node a is denoted as H. a ={h1,h2,...,h N}

[0057] During the initialization of the central node pattern, the jump sequence of each node is fixed, which is... Keep the interval between each pulse the same. If the number of pulses N is less than or equal to the number of frequency points M, the carrier frequency of each pulse is randomly selected from the frequency point library without repetition. If the number of pulses N is greater than the number of frequency points M, the frequency point library is repeatedly traversed.

[0058] 2. Construct a time-hopping and frequency-hopping pattern library:

[0059] The pattern is divided into multiple layers based on cross-correlation properties through traversal.

[0060] The central node is numbered 1, and the frequency hopping pattern is cyclically cross-correlated as follows: Figure 3 As shown, the frequency points within the boxes are the same. The maximum number of points with the same frequency during the loop is denoted as P. max traverse and search for P max =2 patterns, the set XCORR2 initially contains only F1, assume the frequency hopping pattern of node a satisfies Pmax =2, add to set XCORR2, and we get XCORR2 = XCORR2∪{F a After the first traversal is complete, the frequency hopping patterns in XCORR2 are cross-correlated, and the result P cross-correlated with the first pattern is... max Patterns ≤2 are added to the second-order set XCORR. 21 Let L2 = |XCORR2| be the number of elements in the set XCORR2. Count the frequency hopping patterns in the L2 sets, sorting them from largest to smallest. The pattern with the highest frequency is denoted as Threshold. Find the frequency hopping pattern whose frequency R ≥ Threshold. If no Threshold+1 pattern appears, all patterns appear in their respective secondary sets XCORR2. 2i In the middle, decrease the Threshold value and continue searching; if Threshold+1 patterns all appear in their respective second-order sets XCORR, 2i In this process, the Threshold+1 frequency hopping patterns are selected to form the first layer of frequency hopping patterns. The corresponding time hopping patterns are randomly generated to ensure that the relative positions between different pulses are different.

[0061] Similarly, using the patterns in the upper layer as the original library, we search for the cyclic cross-correlation result P with them. max Patterns with a value less than or equal to the number of each layer minus one are used to construct the next layer pattern library.

[0062] 3. Preliminary Static Network Planning

[0063] Given the initial static network topology and the throughput of each node, the network is divided into multiple layers based on the number of hops from the central node. The network topology diagram is shown below. Figure 4 As shown.

[0064] The amount of data emitted by node a per unit time is denoted as Traffic. a ,by Figure 4 Taking the network topology as an example, this paper introduces the selection of time-hopping and frequency-hopping patterns in the early stage. Figure 4 There are 15 nodes in total, excluding the central node, leaving 14 nodes. To ensure flexibility in selecting time-hopping patterns, at least twice the number of nodes needs to be provided with a pattern selection space, i.e., 28 patterns. Assuming the first-layer library contains R1 patterns, if R1 ≥ 28, only the first-layer patterns are needed; if R1 < 28, the first and second-layer patterns are combined; if R1 + R2 ≥ 28, the first and second-layer patterns are selected as the library; if this still doesn't meet the requirements, patterns from lower layers are added sequentially, and the comparisons are repeated until a basic library is selected for node selection. To effectively utilize patterns, the pattern selected by a node only needs to be different from those of its two adjacent nodes. The proportion of the pattern selected by node a at frequency m is denoted as Duty.am Taking node 1 as an example, the sum of its traffic and that of its neighboring nodes at frequency point 1 is as shown in equation (1):

[0065]

[0066] The mean and variance of the flow distribution at each frequency point of node 1 are shown in equations (2) and (3):

[0067]

[0068]

[0069] The sum of the variances of all nodes in the topology is given by equation (4):

[0070]

[0071] Iterate through the database to select time-hopping frequency-hopping patterns, choosing those that result in Traffic_Var sum The smallest set is used as the initial time-hopping frequency-hopping pattern for the static topology.

[0072] (2) Network dynamic changes

[0073] 1. Network environment awareness

[0074] Network environment perception is based on short-time Fourier transform. The noise power is obtained by averaging the accumulated noise power under pure noise conditions in the early stage, and then multiplied by a threshold coefficient to obtain the signal threshold value, as shown in equation (5):

[0075]

[0076] In equation (5), T ratio The threshold coefficient, To obtain the average noise value.

[0077] The signal power at each frequency point at different times is obtained using STFT (Short Time Fourier Transform), and the resulting waterfall plot is shown below. Figure 5 As shown.

[0078] Figure 5 The waterfall plot is obtained after STFT calculation. The vertical axis represents frequency, the horizontal axis represents time, and the color represents signal strength, increasing from blue to yellow. The yellow area within the middle box indicates the presence of pulse signals that jump between different frequencies and times. Interference in the channel environment is considered in two types: short-duration broadband interference, characterized by continuous high-strength signals over a large bandwidth; and long-duration interference within a fixed frequency band, characterized by prolonged strong signals within a fixed frequency band. The effects of both types of interference need to be removed. When performing network environment sensing, if the signal strength exceeds a threshold T...threshold If the signal is within a certain threshold, it is considered a signal; if it is less than a threshold, it is considered noise. If a strong signal appears within the bandwidth, it is classified as Type I interference, and the signal in the corresponding area is removed. If a continuous strong signal appears within a single frequency band, it is classified as Type II interference, and the signal in the corresponding area is removed. Finally, the proportion of the area classified as a signal within the signal bandwidth of the corresponding frequency point to the total area is calculated to obtain the duty cycle.

[0079] 2. Pattern Selection

[0080] When a new node joins the network, based on network environment awareness, the signal duty cycle of each frequency point in the current environment is measured. The impact of its joining the network on adjacent nodes is considered. The pattern selection ensures that the throughput of the newly joined node and its adjacent nodes remains relatively balanced across all frequency points. Figure 6 For the network topology graph after the addition of the new node, Figure 6 The topology is used as an example to explain the pattern selection process in detail.

[0081] First, find the neighboring nodes of the newly added node. Figure 6 The nodes are 7 and 15. The duty cycle of the signals received by the newly added node and its neighboring nodes at each frequency point is measured, i.e., the amount of information received per unit time. The amount of information received by node a at frequency point m is denoted as Traffic_Detect. am The total throughput of node a at frequency m is given by equation (6):

[0082] Traffic_Sum am =Traffic_Detect am +Traffic a Duty am (6)

[0083] The mean and variance of the flow distribution at each frequency point of node a are shown in equations (7) and (8):

[0084]

[0085]

[0086] Traverse the patterns in the library and select the pattern that minimizes the sum of the variances of the flow distributions of the newly added node and its neighboring nodes.

[0087] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for managing time-frequency resources in ad hoc networks based on network environment awareness, characterized in that... The steps of this method include: The first step is to initialize the time-hopping and frequency-hopping pattern of the central node, taking the node at the center of the expected network topology as the central node. The second step is to construct time-hopping frequency hopping patterns suitable for other nodes in the expected network topology based on the time-hopping frequency hopping pattern of the central node after initialization in the first step, thus forming a time-hopping frequency hopping pattern library that includes the time-hopping frequency hopping pattern of the central node and the time-hopping frequency hopping patterns of other nodes. The third step is to select a time-hopping frequency hopping pattern from the time-hopping frequency hopping pattern library obtained in the second step based on the expected network topology and the network throughput of adjacent nodes, so that the throughput distribution at each frequency point remains relatively balanced. The fourth step is to calculate the signal power at each frequency point at different times, remove interference signals in the network environment based on the calculated signal power, and calculate the duty cycle of the received signal at each frequency point after removing interference signals in the current environment. Fifth, when a new node joins the topology network, based on the duty cycle of the received signal in each frequency point under the current environment obtained in the fourth step, a time-hopping frequency-hopping pattern is selected from the time-hopping frequency-hopping pattern library obtained in the second step so that the throughput of the newly joined node and the nodes adjacent to the newly joined node remains relatively balanced in each frequency point.

2. The method for managing time-frequency resources in ad hoc networks based on network environment awareness according to claim 1, characterized in that: In the time-hopping frequency-hopping pattern, it is assumed that a single frame of data contains There are 1 pulse, and the length of a single pulse is denoted as . Its duty cycle is The length of a single frame of data is Divide the transmission time of a single frame of data into There are n intervals, each with a length of n. The length of each individual pulse falls within a certain range. The time-skip sequence is denoted as It represents a pulse. At the starting position of the corresponding interval, the range is ,node The jump pattern is recorded as Let the number of usable frequency points be... The frequency point library is recorded as ,pulse The frequency hopping sequence is denoted as ,node The frequency hopping pattern is denoted as ,pulse The time-hopping frequency hopping sequence is denoted as ,node The time-hopping frequency-hopping pattern is denoted as .

3. The method for managing ad hoc network time-frequency resources based on network environment awareness according to claim 2, characterized in that: In the first step, when initializing the time-hopping and frequency-hopping pattern of the central node, the time-hopping sequence of each node is fixed, which is... Keep the interval between each pulse the same, if the number of pulses Less than or equal to the number of frequency points The carrier frequency of each pulse is randomly selected from a frequency point library, with no repetition; if the number of pulses... Greater than the number of frequency points Repeatedly traverse the frequency point library.

4. The method for managing time-frequency resources in ad hoc networks based on network environment awareness according to claim 2, characterized in that: In the second step, the constructed time-hopping frequency-hopping pattern library is divided into multiple layers. The construction method of the first layer is as follows: the number of the center node is recorded as 1, and cyclic cross-correlation calculation is performed on the frequency-hopping pattern. The maximum number of points with the same frequency during the cyclic process is recorded as . traverse and search patterns, collection Initially only contains Assuming node The frequency hopping pattern satisfies Add to set ,get After the first traversal is completed, Cross-correlation is performed on the frequency hopping patterns in the data, where the result of cross-correlation with the first pattern is... Add the pattern to the secondary set , The number of elements in a set is denoted as ,look The frequency hopping patterns in each set are sorted in descending order of frequency occurrence, with the highest frequency recorded as _____. Find the number of occurrences The frequency hopping pattern, if it does not appear Each pattern appears in its respective secondary set. In the middle, If the value decreases, continue searching; if it appears Each pattern appears in its respective secondary set. In the middle, this A frequency hopping pattern is selected to form the first layer of frequency hopping patterns. The corresponding hopping time pattern is randomly generated to ensure that the relative positions between different pulses are different. Using the patterns in the upper layer as the original library, find the results of their cyclic cross-correlation. Patterns with a value less than or equal to the number of each layer minus one are used to construct the next layer pattern library.

5. The method for managing time-frequency resources in ad hoc networks based on network environment awareness according to claim 2, characterized in that: In the third step, the method for selecting the time-hopping frequency-hopping pattern is as follows: Node The amount of data transmitted per unit time is denoted as Assume there are 100 nodes in the network. , with nodes The number of adjacent nodes is denoted as ,node The set of adjacent node indices is denoted as , No. The number of time-hopping frequency-hopping patterns in the layer's time-hopping frequency-hopping pattern library is denoted as ,like If only the pattern of the first layer is needed; if Then combine the patterns from the first and second layers; if The first and second layer patterns are selected as the library; if this is still not sufficient, the lower layer libraries are added sequentially, and the comparisons are repeated until a basic time-hopping and frequency-hopping pattern library is selected for node selection. To effectively utilize the patterns, the pattern selected by a node only needs to be different from the patterns of its two adjacent layers. The selected pattern at the frequency point The percentage is recorded as ,node With neighboring nodes at frequency points The total flow is as shown in equation (1): (1) node The mean and variance of the flow distribution at each frequency point are shown in equations (2) and (3): (2) (3) The sum of the variances of all nodes in the topology is given by equation (4): (4) Iterate through the library to select time-hopping frequency-hopping patterns, and choose the ones that make... The smallest set is used as the initial time-hopping frequency-hopping pattern for the static topology.

6. The method for managing time-frequency resources in ad hoc networks based on network environment awareness according to claim 1, characterized in that: In the fourth step, the signal power at each frequency point at different times is obtained using the short-time fast Fourier transform.

7. The method for managing time-frequency resources in ad hoc networks based on network environment awareness according to claim 2, characterized in that: In the fifth step, the method for selecting the time-hopping and frequency-hopping pattern of the newly added node is as follows: find the neighboring nodes of the newly added node b, and measure the duty cycle of the signals received by the newly added node b and its neighboring nodes at each frequency point, that is, the amount of information received per unit time. The amount of information received by node b at frequency point m is denoted as... Node b and its neighboring nodes at frequency points The total flow is as shown in equation (6): (6) node The amount of data transmitted per unit time is denoted as ; node The selected pattern at the frequency point The percentage is recorded as ; The mean and variance of the flow distribution at each frequency point of node b are shown in equations (7) and (8): (7) (8) Traverse the patterns in the library and select the pattern that minimizes the sum of the variances of the flow distributions of the newly added node and its neighboring nodes.

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