Interval link simultaneous frequency division concurrent transmission method in chain wireless multi-hop communication stream

Abstract

The invention relates to a method for simultaneous frequency-division concurrent transmission of interval links in a chain wireless multi-hop communication stream, which belongs to the field of wireless ad hoc networks and comprises the following steps: an omnidirectional antenna used by a node on a multi-hop path has m available frequencies; and on the multi-hop path, simultaneous and same-direction concurrent transmission is carried out by using different frequencies at intervals of # imgabs0 # wireless links of one hop. Aiming at the 1 / n descending trend characteristic of the multi-hop bandwidth formed by the wireless ad hoc network according to the link bandwidth and the hop count, a multi-hop transmission strategy is constructed to constrain the logarithmic descending trend of the multi-hop bandwidth according to the hop count, the optimal convergence ratio greater than 1 / n is formed, and the multi-hop bandwidth loss is reduced. Even if the hop count of the multi-hop relay system is increased, the multi-hop bandwidth is converged on a constant ratio of the multi-hop bandwidth to the link bandwidth. The method is high in compatibility with a traditional wireless ad hoc network, the protocol modification cost is low, the descending trend of the multi-hop bandwidth is restrained, and the effect is remarkable in application scenes such as mines and iron towers needing wireless relays as many as dozens of hops.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless ad hoc networks and relates to a method for simultaneous frequency division and concurrent transmission of interval links within a chain-like wireless multi-hop communication flow. Background Art

[0002] (1) Demand background

[0003] Mining environments are often characterized by long, narrow tunnels. The primary topology for mine wireless ad hoc networks is a chain-like wireless multi-hop network. End-to-end transmission in this network requires wireless nodes to relay data across multiple hops, hence the name multi-hop relay system or multi-hop path. A key performance metric for this network system is the wireless multi-hop head-to-end bandwidth (hereafter referred to as multi-hop bandwidth).

[0004] Typical wireless ad hoc networks, such as mesh technologies, operate using time-division duplex (TDD) technology and feature single-frequency omnidirectional transmission and reception, node equality, dynamic networking, and uniform link bandwidth. The head-to-end bandwidth of a mesh-based wireless multi-hop relay system generally decreases as the number of hops increases, ultimately converging to the link bandwidth (single-hop bandwidth) × 1 / n. Because the link bandwidth between hops is generally the same, this downward trend is referred to as the 1 / n trend. The characteristic of the 1 / n trend is that increasing the number of system hops inevitably leads to a loss of multi-hop bandwidth; the multi-hop bandwidth can never stably converge to a fixed ratio of the link bandwidth. If a fixed ratio exists in a system such that the multi-hop bandwidth no longer decreases mechanically with increasing hops, the system is said to have a convergence ratio (CR), represented by a fraction with a constant numerator of 1. If the multi-hop bandwidth convergence ratio of a multi-hop relay system is greater than 1 / n and is the largest of all convergence ratios, the system is said to have an optimal convergence ratio (OCR).

[0005] The optimal convergence ratio of multi-hop bandwidth in a multi-hop relay system built with mine wireless ad hoc networking technology is lower than that in a ground environment. The following describes the derivation process of the optimal convergence ratio of multi-hop bandwidth in two environments.

[0006] (2) Multi-hop bandwidth reduction mechanism of traditional ad hoc networks

[0007] The primary cause of multi-hop bandwidth loss is contention within shared channels caused by multi-hop relay systems to avoid co-channel interference between nodes. While the initial and final bandwidth of a multi-hop relay system inevitably decreases as the number of hops increases, the 1 / n decrease in multi-hop bandwidth is not always inevitable; it often depends on whether the path has an optimal convergence ratio. Any link on a multi-hop path has the potential to become a bottleneck link. The paper "Zhao Haitao. Estimation and Prediction of Available Bandwidth in Multi-hop Wireless Networks [D]. National University of Defense Technology, 2009" uses a systematic algorithm to quantify the degree of contention and identifies the bottleneck link as the first link to reach the maximum contention rank. Whether the multi-hop bandwidth has an optimal convergence ratio depends primarily on the length of the contention segment of the bottleneck link on the multi-hop path. The optimal convergence ratio is the reciprocal of the contention segment length. If the contention segment length equals the number of hops on the path, the optimal convergence ratio is 1 / n.

[0008] Another factor that determines the length of the contention segment is the node's carrier sensing distance, interference distance, communication distance, and whether the nodes on the path are evenly distributed. If the nodes are evenly distributed according to the communication distance, the ratio of the carrier sensing distance to the communication distance Δ S Indicates how many upstream or downstream adjacent nodes can be covered. S Directly determines the length of the competition segment. Under a uniformly distributed n-hop path, When the convergence ratio is 1 / n, the optimal convergence ratio for that path may be greater than 1 / n. Otherwise, the convergence ratio is directly equal to 1 / n, and the actual multi-hop bandwidth may be less than the link bandwidth multiplied by 1 / n. A convergence ratio of 1 / n generally means that the carrier sensing range of a node on the path covers all other nodes. The paper "Song An. Research on Performance Analysis Model and Available Bandwidth Estimation of Wireless Ad Hoc Networks [D]. National University of Defense Technology, 2011" uses the distance parameters of IEEE 802.11b to simulate multi-hop paths. In this ideal free space, the optimal convergence ratio for a relay system with more than 6 hops is 1 / 6, while the optimal convergence ratio for a relay system with no more than 6 hops is 1 / n. The following example illustrates this.

[0009] 1. Conflict Types in Wireless Multi-Hop Flows

[0010] Without considering bidirectional operation, there are at least three types of conflicts in unidirectional transmission that will affect the efficiency of multi-hop path communication flow. Figure 1 Take a 6-hop path as an example. Typical IEEE802.11n network parameters with free space as the background are: the nodes are 200m apart, R CS Carrier sensing distance 550m, R TX Stable communication distance 250m, R I Interference distance is 350m. The ratio of the node's carrier sensing distance to the stable communication distance is Δ S=2.2, indicating that the node's carrier sensing range covers 2 nodes upstream and downstream; the ratio of interference distance to communication distance Δ I =1.4, indicating that the stable communication range and interference range of the node cover one node upstream and one node downstream. Figure 1 (a) shows the competition graph of a 6-hop path under three types of interference, which is broken down by interference type as follows.

[0011] The first type of interference is interference with the backoff process, such as Figure 1 As shown in Figure (b), after node D completes a transmission to node E, if it senses that nodes B, C, E, and F within its carrier sensing range are busy, D suspends the backoff process, freezing the backoff counter and extending the backoff time until the channel becomes idle before continuing the previous backoff process. This causes D to spend more time before its next transmission. This interference affects the sending node of the working link, mainly due to the mutual influence of adjacent links. This interference occurs both upstream and downstream of the working link.

[0012] The second type of interference is the synchronous collision of neighboring nodes, such as Figure 1 As shown in Figure (c), node D's carrier sensing range covers nodes E and F. Furthermore, node F's interference range covers E. When D transmits to E, i.e., when the fourth-hop link is operating, if F also transmits to D in the same timeslot, E cannot distinguish between D's and F's signals using the capture threshold, resulting in a synchronization collision. If E also transmits to F in the same timeslot, E simultaneously transmits and receives, and E does not acknowledge D, causing D to believe a collision has occurred. A synchronization collision results in packet loss or retransmission. This collision affects the receiving node of the operating link, primarily the downstream link affecting the upstream link, and is directional.

[0013] The third type of interference is asynchronous collision of hidden nodes, such as Figure 1 As shown in (d), if node F's transmission to G (the sixth hop) occurs earlier than node C's transmission to D (the third hop), and F's transmission has not yet completed when C begins, D will detect that the channel is busy. After C has completed transmitting a packet to D, D will not respond to C's transmission. C will then assume that a collision has occurred and that the packet has been lost, and will subsequently take actions such as retransmission. This collision affects the receiving node of the working link, primarily the downstream link affecting the upstream link, and is directional.

[0014] The multi-hop path has a chain topology. Any interruption of a single-hop link on the path will cause the multi-hop transmission to fail. Therefore, all three types of conflicts must be avoided to successfully complete a complete multi-hop intra-flow transmission process.

[0015] 2. Multi-hop bandwidth averaging calculation

[0016] Multi-hop bandwidth depends on the degree of contention within the multi-hop path and the optimal resource allocation strategy. The paper "Zhao Haitao. Estimation and Prediction of Available Bandwidth in Multi-hop Wireless Networks [D]. National University of Defense Technology, 2009" points out that in a multi-hop path, evenly distributing resources across all links results in links with poor channel gain having a much smaller bandwidth capacity than links with good channel gain, and the end-to-end bandwidth capacity is limited by the bottleneck link. This even resource allocation strategy limits the end-to-end bandwidth capacity. However, with optimal resource allocation, the bandwidth capacity of each link is essentially the same, thus maximizing the end-to-end bandwidth capacity. The document "K. Sanzgiri, ID Chakeres, E.M. Belding-Royer. Determining intra-flow contention along multihop paths in wireless networks [C]. Proceedings of First International Conference on Broadband Networks (BroadNets) 2004: 611-620" proposes an "average method" for approximate bandwidth estimation: the end-to-end available bandwidth is equal to the available bandwidth of the bottleneck link divided by the number of contentions; for multihop paths, the multihop bandwidth is equal to the link bandwidth divided by the number of hops.

[0017] by Figure 2 For example, a multi-hop path with n+1 nodes forming a link number h=n hops is formed. Referring to the “average method”, the bandwidth set of each hop link in the multi-hop path unidirectional transmission is {B i},i∈[1,n], take any value of the set as B Δ , then each capacity value is equal to B Δ There exists a ratio k, forming a bandwidth ratio set {k i}, i∈[1,n]. When the head end sends a data frame, the cascade transmission is continued until the end end receives it, and then the head end sends the next data frame. It can be seen that within a fixed time period T, only one data frame of length D is transmitted from the head end to the end end. If D is to be maximized, the data frame length must be constant D=B i t i =B Δ k i t i ,i∈[1,n], then the time period Multi-hop bandwidth when the link bandwidth is unequal

[0018]

[0019] When the link bandwidths are all equal, the set {B i The value of} is always equal to B Δ , there is always ki =1, substitute into formula 1 to get the multi-hop bandwidth

[0020]

[0021] From formula 2, we know that the key factor that determines the size of the multi-hop bandwidth is the reciprocal of the number of hops n, so the trend of the multi-hop bandwidth decreasing with the increase of the number of hops is expressed as 1 / n. Δ The actual multi-hop rate S tps The ratio of is rounded down to

[0022]

[0023] When Δ H >1 / n, S tps >S equ , which means that as the number of hops increases, the multi-hop bandwidth does not decrease according to the 1 / n trend and can converge to S tps value, then put Δ H This is called the convergence ratio. If a multihop relay system has a convergence ratio, it proves that the system can constrain the 1 / n decrease in multihop bandwidth. Whether this convergence ratio can be achieved requires quantifying the degree of competition to prove whether the multihop relay system itself has a theoretical convergence ratio.

[0024] 3. Calculation of Convergence Ratio of Multi-Hop Bandwidth

[0025] Still using typical IEEE802.11n network parameters and Δ S =2.2, Δ I =1.4 Simulate a 10-hop path and superimpose three types of conflicts to form a link contention diagram as shown below Figure 3 As shown in the figure, when the first hop link is operational, the superposition of the three interference collisions indicates that the fifth hop does not compete with the first hop at all, allowing data frames to be sent simultaneously and in the same direction. The ideal multi-hop bandwidth converges to 1 / 4. However, this ideal calculation does not identify the bottleneck link with the highest contention, so a quantitative analysis of the contention level is necessary.

[0026] The concept of "rank" is used to represent the degree of contention experienced by a particular hop link. The rank of link i is Rank(i). The contention weight for backoff interference is set to 1.0, the contention weight for synchronous collisions is set to 1.1, and the contention weight for asynchronous collisions caused by hidden nodes is set to 1.5. When a hop link can simultaneously exert multiple interferences or collisions on link i, the one with the highest contention weight is taken as the final contention weight for the affected link. The rank of the multi-hop path from node i to node j is Rank(Gi,j) = max{Rank(i)}. This means that the link with the highest contention level on the multi-hop path is the bottleneck link. When a multi-hop path has multiple links with the highest rank, the transmission direction along the path is set to the link that first reaches the highest rank as the bottleneck link. The range formed by the upstream and downstream links that influence the bottleneck link is called the contention segment. When the number of hops in the multi-hop path continues to increase but the rank of the path no longer increases, the length of the bottleneck link's contention segment is equal to the number k of links (including the bottleneck link) downstream to upstream that influence the bottleneck link. The theoretical multi-hop bandwidth convergence ratio is also determined to be 1 / k. Table 1 shows the calculated link ranks for a 10-hop path. The maximum rank of the path is 5.7, and the third hop is the first to reach the maximum rank, making it the bottleneck link. The downstream links that conflict with the third hop include hops 4, 5, and 6, while the upstream links include hops 1 and 2. The contention segment for the third hop is the range from hop 6 to hop 1. The segment length is the number of links contained in it, which is 6 hops. Therefore, the theoretical multi-hop bandwidth convergence ratio for the 10-hop path is 1 / 6.

[0027] Table 1

[0028]

[0029]

[0030] Calculate the evenly distributed path Δ between 1 and 10 hops S = 2.2 when the competition rank and optimal convergence ratio are listed in Table 2.

[0031] Table 2

[0032] Link Number 3-hop path 4-hop path 5-hop path 6-hop path 7-hop path 8-hop path 9-hop path 10-hop path 1 2.2 3.7 3.7 3.7 3.7 3.7 3.7 3.7 2 2.1 3.2 4.7 4.7 4.7 4.7 4.7 4.7 3 2 3.1 4.2 5.7 5.7 5.7 5.7 5.7 4 / 2 3.1 4.2 5.7 5.7 5.7 5.7 5 / / 2 3.1 4.2 5.7 5.7 5.7 6 / / / 2 3.1 4.2 5.7 5.7 7 / / / / 2 3.1 4.2 5.7 8 / / / / / 2 3.1 4.2 9 / / / / / / 2 3.1 10 / / / / / / / 2 Optimal convergence ratio 1 / 3 1 / 4 1 / 5 1 / 6 1 / 6 1 / 6 1 / 6 1 / 6

[0033] Analysis shows that when Δ S = 2.2, the multi-hop bandwidth of the path with more than 6 hops has a convergence ratio of 1 / 6. Only when the number of nodes covered by the carrier sensing range is greater than 2, or even when all nodes are within each other's carrier sensing range, will the multi-hop bandwidth convergence ratio be reduced from 1 / 6 to 1 / n. SWhen rank ≥ 4, the maximum rank of a 10-hop path reaches 9.7. The fifth hop becomes a bottleneck link, and its contention segment length is 10 hops. At this point, the multihop bandwidth convergence ratio of 1 / 10 is equivalent to a 1 / n downward trend. Therefore, paths with 6 or fewer hops inevitably decline at a 1 / n downward trend, making it impossible to constrain their multihop bandwidth convergence. Only when the multihop bandwidth of paths with more than 6 hops has a convergence ratio can it be possible to constrain the downward trend of multihop bandwidth.

[0034] Therefore, the optimal convergence ratio of the multi-hop path depends on the contention segment length, and the segment length depends on Δ S and Δ I The parameters further depend on the spacing distance of node deployment and the wireless transmission loss characteristics.

[0035] (3) Declining trend of multi-hop bandwidth in mine environment self-organizing networks

[0036] The radio transmission in mine tunnels has fast attenuation and large loss, and its boundary characteristics lead to Δ S Generally greater than 3. In reality, there is no wireless coverage planning in mines. The deployment of wireless multi-hop nodes often adopts the equidistant method + corner deployment. This results in the carrier sensing coverage range of the sending node of the bottleneck link of the n-hop path deployed in the straight tunnel of the mine being particularly far away. In this case, the Δ S Almost equal to the skip path The following examples illustrate this.

[0037] The signal attenuation boundary effect in mines causes a logarithmic relationship between wireless transmission loss and transmission distance. To facilitate calculation and verification, the 5.4GHz wireless transmission loss data in mines is taken as an example, and the wireless transmission loss curves of four scenarios, namely, fully mechanized mining face, corner, auxiliary transport tunnel, and excavation tunnel, are logarithmically fitted. Referring to the IEEE 802.11n standard, it is assumed that the signal strength in the carrier sensing range is ≥-80dBm, the signal strength in the interference range is ≥-73dBm (capture threshold 3dB), and the signal strength in the communication range is ≥-70dBm. The fitting curve is used to calculate the coverage distance of the three ranges, and the Δ S ≈3, Δ I ≈1.4. The ground space is generally taken as Δ S ≈2.2, Δ I ≈1.78, or Δ S ≈2.2, Δ I ≈1.41, we know that the mine Δ S Greater than free space. Therefore, practically speaking, to ensure sufficient maximum bandwidth for a single-hop link, it's essential to choose a single-hop where the two nodes are within a stable communication distance. Following this pattern, a multi-hop path with an intermediate node's carrier sensing coverage covers three upstream and downstream nodes, and its interference range covers one upstream and downstream node.

[0038] According to the mine Δ Sand Δ I The link competition graph of the 10-hop path in the mine tunnel is as follows: Figure 4 The calculated ranks of each link are shown in Table 3. The fourth hop link reaches the maximum rank first. There are eight links that conflict with the fourth hop, so the multi-hop bandwidth of this path converges to 1 / 8. It can be seen that the optimal convergence ratio of multi-hop bandwidth in the mine environment is smaller than that in the free space environment. Summary of the Invention

[0039] In light of this, the present invention aims to provide a method for concurrent transmission of chain-like wireless multi-hop communication flows with frequency division within interval links, targeting multi-hop relay systems composed of typical single-frequency omnidirectional radiating nodes, such as mesh wireless ad hoc networks. Using passive multi-frequency antennas, the method stipulates that both the sender and receiver operate at different frequencies in each time slot. The sending node transmits data at different frequencies in different time slots, while the receiving node demodulates only the signal at the agreed frequency in each time slot. This method increases the number of shared channels at the hardware configuration level. Theoretically, during multi-hop transmission, nodes in the same communication flow direction no longer compete for access to the shared channel, thereby avoiding the constraints of intra-flow contention, significantly reducing contention time for the sending and receiving nodes, and increasing their transmission operating time. Under the conditions of uniform node distribution and spacing within the communication distance, the optimal convergence ratio of the multi-hop bandwidth for a mesh-based path with n ≥ 6 hops is 1 / 6. The method created by the present invention, based on a passive multi-frequency omnidirectional antenna with m frequencies, achieves an optimal convergence ratio of 1 / 2 for the multi-hop bandwidth of paths with n ≥ m and m ≥ 3 hops. Under the conditions of uneven node distribution and overlapping carrier sensing ranges, the optimal convergence ratio of the multi-hop bandwidth of the mesh with n≥6 hops is 1 / n. The method created by the present invention is based on the condition of m-frequency omnidirectional antennas, and the optimal convergence ratio is always greater than 1 / n.

[0040] In order to achieve the above object, the present invention provides the following technical solutions:

[0041] A method for concurrent transmission of chain-like wireless multi-hop communication streams with interval links simultaneously divided by frequency, comprising: an omnidirectional antenna used by a node on a multi-hop path has m available frequencies; wireless links, using different frequencies to transmit in the same direction simultaneously.

[0042] Furthermore, n+1 nodes form an n-hop path, using A i Represents one of the nodes, node subscript n≥1 and is a positive integer; the omnidirectional antenna has m available frequencies, represented by F j Indicates one of the frequencies, the frequency subscript m≥1 and is a positive integer, m≤n, Indicates that the quotient of m divided by 2 is rounded up; Represents one of the data frames, the superscript t is the time slot number of the origination, t≥1 and is a positive integer, and the subscript i is the number of the originating link. It indicates that the current link uses a certain frequency to transmit a data frame originating from link i in time slot t; the optimal convergence ratio of the multi-hop bandwidth achieved by this transmission method is 1 / 2.

[0043] Furthermore, the omnidirectional antenna is a multi-frequency antenna having m available frequency points, and the isolation between the available frequency points is sufficient; assuming that the time slot for the node to transmit and receive on the multi-hop path is t, the node switches to a different frequency each time it completes a time slot t; adjacent links on the multi-hop path operate at different frequencies in the same time slot, with the same link bandwidth and modulation order.

[0044] Furthermore, there are two frequency selection strategies for each hop link:

[0045] Strategy I: A certain hop link uses only one fixed frequency in all time slots;

[0046] Strategy II: A certain hop link switches frequency in different time slots according to the agreement.

[0047] Furthermore, if the 1st hop link and the 2m+1th hop link are not within each other's carrier sensing range, the frequency can be reused; if the carrier sensing covers all nodes, the frequency cannot be reused.

[0048] Furthermore, when applied to wireless protocols, the method senses the node distribution topology, estimates the transmission distance, and estimates the available multi-hop bandwidth to select a transmission strategy. The optimal multi-hop bandwidth convergence ratios for the following three chain-like distributions are listed for estimating the upper limit of the multi-hop bandwidth.

[0049] (1) Ideal chain distribution: The links between the 1st hop and the 2m+1th hop, the 2nd hop and the 2m+2th hop, and even the 2mth hop and the 4m+1th hop are not within each other's carrier sensing range. In this case, Δ S <2m+1, all nodes in the entire multi-hop path can perform simultaneous frequency division transmission with no hops;

[0050] (2) The most competitive chain distribution: From the first hop to the nth hop, the links are all within each other's carrier sensing coverage. At this time, Δ S =n, the entire path can only use m frequencies at the same time;

[0051] (3) Chain distribution of frequency reuse segments requiring guard intervals: There is mutual carrier sensing coverage between the first hop and the m+1th hop link, and the downstream segment needs to avoid contention with the upstream segment. The wireless link between the last node of the upstream segment and the first node of the appropriate downstream segment is called the guard interval GI, Δ S<2m-1+GI, when the number of frequencies is less than the threshold, a chain distribution with a guard interval is required. When the number of frequencies exceeds the threshold, the same chain distribution as the most competitive one is used.

[0052] Furthermore, for the ideal chain distribution, there are two chain distributions based on the relationship between the number of frequencies and the number of hops:

[0053] ① For multi-hop bandwidths with n≥2m≥6 hops, there is an optimal convergence ratio of 1 / 2;

[0054] ② There is an optimal convergence ratio of 1 / 2 for the multi-hop bandwidth of 2m≥n≥3 hop paths.

[0055] Furthermore, for the most competitive chain distribution, there are two chain distributions based on the relationship between the number of frequencies and the number of hops:

[0056] ① There is an optimal convergence ratio for the multi-hop bandwidth of n≥2m≥6 hop paths

[0057] ② There is an optimal convergence ratio of 1 / 2 for the multi-hop bandwidth of 2m≥n≥3 hop paths.

[0058] Furthermore, for the chain distribution case where the frequency reuse segment requires a guard interval, if:

[0059] ① When the protection interval GI≤n+1-2m hops and n≥2m-1, there is an optimal convergence ratio

[0060] ② When 2m≥n≥3, there is no need for a protection interval.

[0061] The beneficial effects of the present invention are:

[0062] The method of the present invention significantly reduces the level of intra-stream contention during multi-hop transmission in traditional wireless ad hoc networks by adjusting the passive antenna configuration of wireless ad hoc network nodes and reconstructing the transmission strategy. This method changes the loss pattern of the multi-hop bandwidth of traditional multi-hop relay systems, which decreases by 1 / n of the number of hops, reversing this logarithmic downward trend. This allows the loss of multi-hop bandwidth to converge to a constant ratio, rather than decreasing as the number of hops n increases. Mathematically speaking, this means that when the denominator of the convergence ratio is less than n, the convergence ratio is greater than 1 / n. The method of the present invention ensures that the optimal convergence ratio for paths greater than 6 hops is greater than 1 / n in all cases.

[0063] (1) Optimal situation

[0064] When the nodes of a multi-hop path are distributed ideally and evenly, the nodes are formed by the Mesh and evenly distributed. SThe optimal convergence ratio of the multi-hop bandwidth of the n≥6-hop path is 1 / 6. The method created by the present invention makes the optimal convergence ratio of the multi-hop bandwidth of the n≥2m≥6-hop path be 1 / 2.

[0065] (2) Worst case

[0066] When the multi-hop path from the 1st hop to the nth hop links are in each other's coverage, then Δ S =n. The optimal convergence ratio of the multi-hop bandwidth of n≥6 hop paths formed by Mesh is 1 / n. The method created by the present invention makes the optimal convergence ratio of the multi-hop bandwidth of n≥2m≥6 hop paths be

[0067] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0069] Figure 1 Schematic diagram of intra-flow competition in a multi-hop path;

[0070] Figure 2 Schematic diagram of calculating multi-hop bandwidth using the average method;

[0071] Figure 3 Schematic diagram of link contention for a typical 10-hop path

[0072] Figure 4 The link competition graph for the 10-hop path of the mine;

[0073] Figure 5 Schematic diagram of intra-stream hopping and simultaneous frequency division transmission according to the present invention;

[0074] Figure 6 This is a schematic diagram of an ideal chain distribution with a relatively small number of frequencies according to the present invention;

[0075] Figure 7 This is a schematic diagram of an ideal chain distribution with a large number of frequencies according to the present invention;

[0076] Figure 8 This is a schematic diagram of the most competitive chain distribution with a small number of frequencies of the present invention;

[0077] Figure 9 This is a schematic diagram of the most competitive chain distribution with a large number of frequencies of the present invention;

[0078] Figure 10 This is a schematic diagram of the most intense chain distribution with a small number of frequencies according to the present invention. DETAILED DESCRIPTION

[0079] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0080] It should be noted that the illustrations provided in the following embodiments are merely schematic illustrations of the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.

[0081] In the following description, numerous details are discussed to provide a more thorough explanation of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the embodiments of the present invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring the embodiments of the present invention.

[0082] Example 1:

[0083] The key to increasing multi-hop bandwidth and limiting its downward trend is how many links within a flow can operate simultaneously without interfering with each other. Time-division duplexing (TDD) requires avoiding co-channel interference, so wireless ad hoc networks must incorporate a mechanism for competing for access to shared channels. However, intra-flow competition inevitably leads to a decrease in multi-hop bandwidth. Changing intra-flow competition can only be achieved through modifications to the wireless protocol and hardware configuration. Modifying only the conflict handling mechanisms at the MAC layer of the wireless ad hoc network protocol can reduce intra-flow competition, but it also limits the flexibility of the system's dynamic networking. Significant changes to the system's hardware configuration would also alter the low-power, compact structure of the wireless ad hoc network.

[0084] This invention addresses the 1 / n decreasing trend in multi-hop bandwidth in wireless ad hoc networks and constructs a novel multi-hop transmission strategy that constrains the logarithmic decrease in multi-hop bandwidth based on the number of hops, resulting in an optimal convergence ratio greater than 1 / n and reducing bandwidth loss from the beginning to the end of the multi-hop path. Even as the number of hops in the multi-hop relay system increases, the multi-hop bandwidth ultimately converges to a constant ratio of the link bandwidth, such as 1 / 2, 1 / 3, or 1 / 6, where the denominator is not equal to n.

[0085] The proposed method relies on multi-frequency antennas. Because they are passive antennas, hardware configuration modifications are relatively minor, and using multi-frequency antennas does not affect the normal operation of traditional wireless ad hoc networks. The proposed method is highly compatible with traditional wireless ad hoc networks and requires relatively little protocol modification.

[0086] The present invention provides a method for simultaneous frequency division and concurrent transmission of an interval link within a chain-like wireless multi-hop communication flow. The omnidirectional antenna used by the nodes on the multi-hop path has m available frequencies. Wireless links, using different frequencies to transmit in the same direction at the same time. Figure 5 As shown, suppose that n+1 nodes form an n-hop path, and A i Represents one of the nodes, node subscript n≥1 and is a positive integer; the omnidirectional antenna has m available frequencies, represented by F j Indicates one of the frequencies, the frequency subscript m≥1 and is a positive integer, m≤n, Indicates that the quotient of m divided by 2 is rounded up; Represents one of the data frames, the superscript t is the time slot number of the origination, t≥1 and is a positive integer, and the subscript i is the number of the originating link. Indicates that the current link uses a certain frequency to transmit a data frame originating from link i in time slot t; the optimal convergence ratio of the multi-hop bandwidth achieved by this transmission method is 1 / 2. Figure 5 shown.

[0087] In this method, the omnidirectional antenna should be a multi-frequency antenna with m available frequencies (resonance points). The available frequencies must have sufficient isolation, typically ≥ 80 MHz. The time slot for a node's transmission and reception on a multi-hop path is t. After each time slot t, the node switches to a different frequency. Adjacent links on a multi-hop path operate at different frequencies within the same time slot, with the same link bandwidth and modulation order.

[0088] In this method, as long as the frequencies used between different links in the same time slot are different and have a certain degree of isolation, it complies with this method. In actual implementation, there are two frequency selection strategies for each hop link. Strategy I: A certain hop link only uses one fixed frequency in all time slots; for example, the first hop link can only use the F1 frequency for each operation in different time slots. Strategy II: A certain hop link switches frequencies in different time slots according to agreement; for example, the first hop link can use the F1 frequency in the t1 time slot, the F3 frequency in the t3 time slot, the F2 frequency in the t4 time slot, and the F1 frequency again in the t6 time slot. Which strategy to choose depends on the actual wireless coverage planning and the transmission distance that is expected to be achieved between nodes, which is not discussed in this invention.

[0089] Example 2:

[0090] In this method, considering that antennas cannot achieve infinite frequency points, frequencies can only be reused after a 2m-hop link. If the first-hop link and the 2m+1-hop link are not within each other's carrier sensing range, they can be reused; if the carrier sensing covers all nodes, reuse is not possible. When applied to wireless protocols, this method requires sensing the node distribution topology, estimating the transmission distance, and estimating the available multi-hop bandwidth to select a transmission strategy. Therefore, the optimal multi-hop bandwidth convergence ratio for each of the following three chain distribution scenarios is listed, which can be used to estimate the upper limit of the multi-hop bandwidth.

[0091] (1) Ideal chain distribution

[0092] The node distribution of this multi-hop path is ideal. The links between the 1st hop and the 2m+1th hop, the 2nd hop and the 2m+2th hop, and even the 2mth hop and the 4m+1th hop are not within each other's carrier sensing range. S <2m+1. All nodes along the multi-hop path can perform simultaneous frequency-divided transmission with every other hop. Two chain-like distributions exist, depending on the relationship between the number of frequencies and the number of hops.

[0093] (1) For multi-hop bandwidths with n≥2m≥6 hops, there exists an optimal convergence ratio of 1 / 2. Figure 6 As shown, if there are m=3 frequencies for antennas, strategy II requires that 3 frequencies be used simultaneously in each time slot when there are n=13 hops, and all frequencies are reused at least once. times, some frequencies are used simultaneously times, the same time slot can have a maximum of The jump links work simultaneously.

[0094] (2) In the multi-hop bandwidth of 2m≥n≥3 hop paths, there is an optimal convergence ratio of 1 / 2. Figure 7 As shown, assuming that there are m=3 frequency usage strategies for the antenna, when there are n=3 hop paths, only two frequencies need to be used at the same time.

[0095] (2) Chain distribution with the most intense competition

[0096] This multi-hop path is in the carrier sensing coverage of each other from the first hop to the nth hop. S = n. In this case, only m frequencies can be used simultaneously on the entire path. There are two chain distribution scenarios based on the relationship between the number of frequencies and the number of hops.

[0097] (1) There is an optimal convergence ratio for the multi-hop bandwidth of n ≥ 2m ≥ 6 hop paths It can be seen that like Figure 8 As shown in the figure, assuming that there are m=3 frequency strategies in the antenna when there are n=13 hops, only 3 frequencies can be used simultaneously on the entire path in each time slot. At this time, the optimal convergence ratio of multi-hop bandwidth is

[0098] (2) In the multi-hop bandwidth of 2m≥n≥3 hop paths, there is an optimal convergence ratio of 1 / 2. Figure 9 As shown, assuming that there are m=3 frequencies for the antenna, strategy II only needs to use 3 frequencies at the same time when there are n=6 hops.

[0099] (3) Chain distribution of guard intervals required in frequency reuse segments

[0100] In this multi-hop link, there is mutual carrier sensing coverage between the first hop and the m+1th hop link. The downstream segment needs to avoid contention with the upstream segment. Therefore, the wireless link between the last node of the upstream segment and the first node of the appropriate downstream segment is called the guard interval GI. The length unit of GI is hop. In reality, the physical length corresponding to GI is greater than the carrier sensing distance, so Δ S <2m-1+GI. A chain-like distribution requires a guard interval only when the number of frequencies is small. When the number of frequencies is large, it is the same as the chain-like distribution with the most intense competition.

[0101] (1) When the guard interval GI ≤ n+1-2m hops and n ≥ 2m-1, there is an optimal convergence ratio It can be seen that like Figure 10 As shown, assuming that there are m=2 frequencies for the antenna, strategy II uses a path with n=13 hops, and a guard interval GI=3 hops. The path must reuse two frequencies in the same time slot, and the optimal convergence ratio is 1 / 3.

[0102] (2) When 2m≥n≥3, there is no need for a guard interval. The distribution is as follows: Figure 10 .

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for concurrent transmission of chain-like wireless multi-hop communication flows with simultaneous frequency division and interval links within the flow, characterized by: include: The omnidirectional antennas used by nodes on the multi-hop path have m available frequencies; Each hop on a multi-hop path wireless links, using different frequencies to transmit in the same direction simultaneously.

2. The method for concurrent transmission of chain-like wireless multi-hop communication flows with interval links within the flow according to claim 1, characterized in that: An n-hop path is formed by n+1 nodes, using A i Represents one of the nodes, node subscript n≥1 and is a positive integer; the omnidirectional antenna has m available frequencies, represented by F j Indicates one of the frequencies, the frequency subscript m≥1 and is a positive integer, m≤n, Indicates that the quotient of m divided by 2 is rounded up; Represents one of the data frames, the superscript t is the time slot number of the origination, t≥1 and is a positive integer, and the subscript i is the number of the originating link. It indicates that the current link uses a certain frequency to transmit a data frame originating from link i in time slot t; the optimal convergence ratio of the multi-hop bandwidth achieved by this transmission method is 1 / 2.

3. The method for concurrent transmission of chain-like wireless multi-hop communication flows with interval links within the flow according to claim 2, characterized in that: The omnidirectional antenna is a multi-frequency antenna with m available frequency points, and the isolation between the available frequency points is sufficient. The time slot of the node's transmission and reception on the multi-hop path is t. After each time slot t, the node switches to a different frequency. Adjacent links on the multi-hop path operate at different frequencies in the same time slot, with the same link bandwidth and modulation order.

4. The method for concurrent transmission of chain-like wireless multi-hop communication flows with interval links within the flow, according to claim 3, characterized in that: There are two frequency selection strategies for each hop link: Strategy I: A certain hop link uses only one fixed frequency in all time slots; Strategy II: A certain hop link switches frequency in different time slots according to the agreement.

5. The method for concurrent transmission of chain-like wireless multi-hop communication flows with interval links within the flow, according to claim 4, characterized in that: If the 1st hop link and the 2m+1th hop link are not within each other's carrier sensing range, the frequency can be reused; if the carrier sensing covers all nodes, the frequency cannot be reused.

6. The method for concurrent transmission of chain-like wireless multi-hop communication flows with interval links within the flow, according to claim 5, characterized in that: When applied to wireless protocols, it senses the node distribution topology, estimates the transmission distance, and estimates the available multi-hop bandwidth to select the transmission strategy to use; The optimal multi-hop bandwidth convergence ratios for the following three chain distributions are listed respectively to estimate the upper limit of the multi-hop bandwidth. (1) Ideal chain distribution: The links between the 1st hop and the 2m+1th hop, the 2nd hop and the 2m+2th hop, and even the 2mth hop and the 4m+1th hop are not within each other's carrier sensing range. In this case, Δ S <2m+1, all nodes in the entire multi-hop path can perform simultaneous frequency division transmission with no hops; (2) The most competitive chain distribution: From the first hop to the nth hop, the links are all within each other's carrier sensing coverage. At this time, Δ S =n, the entire path can only use m frequencies at the same time; (3) Chain distribution of frequency reuse segments requiring guard intervals: There is mutual carrier sensing coverage between the first hop and the m+1th hop link, and the downstream segment needs to avoid contention with the upstream segment. The wireless link between the last node of the upstream segment and the first node of the appropriate downstream segment is called the guard interval GI, Δ S <2m-1+GI, when the number of frequencies is less than the threshold, a chain distribution with a guard interval is required. When the number of frequencies exceeds the threshold, the same chain distribution as the most competitive one is used.

7. The method for concurrent transmission of chain-like wireless multi-hop communication flows with interval links within the flow according to claim 6, characterized in that: For the ideal chain distribution, there are two chain distributions based on the relationship between the number of frequencies and the number of hops: ① For multi-hop bandwidths with n≥2m≥6 hops, there is an optimal convergence ratio of 1 / 2; ② There is an optimal convergence ratio of 1 / 2 for the multi-hop bandwidth of 2m≥n≥3 hop paths.

8. The method for concurrent transmission of chain-like wireless multi-hop communication flows with interval links within the flow, according to claim 6, characterized in that: For the most competitive chain distribution, there are two chain distributions based on the relationship between the number of frequencies and the number of hops: ① There is an optimal convergence ratio for the multi-hop bandwidth of n≥2m≥6 hop paths ② There is an optimal convergence ratio of 1 / 2 for the multi-hop bandwidth of 2m≥n≥3 hop paths.

9. The method for concurrent transmission of chain-like wireless multi-hop communication flows with interval links within the flow, according to claim 6, characterized in that: For the chain distribution of frequency reuse segments requiring guard intervals, if: ① When the protection interval GI≤n+1-2m hops and n≥2m-1, there is an optimal convergence ratio ② When 2m≥n≥3, there is no need for a protection interval.

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