A High-Throughput Communication Method for a Large Propagation Delay Directional Ad Hoc Network

Abstract

The present invention discloses a high-throughput communication method for a large propagation delay ad hoc network. All nodes in the network are simultaneously in the receiving state or simultaneously in the transmitting state in the same time frame, and the receiving and transmitting states are alternately switched in adjacent time frames. Each node in the network simultaneously communicates with all other nodes in each time frame. At the same time, the frame length in the communication frame structure is selected as the frame length with the maximum sum of the effective transmission times between each node in the network. The communication timing sequence proposed by the present invention is combined with an approximately optimal communication frame length, that is, the frame length with the maximum sum of the effective transmission times between each node, which can significantly improve the network throughput.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless ad hoc network communication, and relates to a high-throughput communication method for a large propagation delay directional ad hoc network. Background Art

[0002] Unmanned aerial vehicles (UAVs) have the characteristics of high mobility, low cost, strong concealment, etc., and are widely used in modern military and civilian fields. At the same time, due to the relatively fast moving speed of UAVs, the network topology also changes at a high speed. Therefore, in order to achieve data intercommunication and planned cooperation among node devices in the UAV network, an energy-efficient networking technology is particularly important. The ad hoc network, with its characteristics of simple deployment, strong anti-destruction ability, and strong flexibility, is widely used to solve the networking problems in such scenarios. However, the distributed characteristics of the ad hoc network and the large propagation delay caused by the large network coverage also pose certain challenges to the dynamic allocation of network resources.

[0003] In the early research process of UAV ad hoc networks, researchers generally followed the typical access protocol IEEE 802.11 DCF in the ad hoc network field, and UAV nodes used an omnidirectional communication method to compete for and access the channel. In recent years, with the pursuit of node stealth performance in military data link systems, the directional narrow beam technology with long transmission distance, strong concealment performance, and high spatial reuse has been applied to UAV ad hoc networks. The use of narrow beams increases the effective transmission distance of the network, and correspondingly increases the maximum propagation delay between nodes in the network. Therefore, the research on the communication timing design of ad hoc networks under the conditions of large propagation delay and directional multi-beams is of great significance.

[0004] At present, a variety of advanced aviation data links already have the ability to build ad hoc networks between airborne platforms. Existing technical solutions in similar scenarios include High Integration Data Link (HIDL), Multifunction Advanced Data Link (MADL), Intra-Flight Data Link (IFDL), and General Tactical Data Link Link16, etc. Although researchers already have a preliminary understanding of the network characteristics under narrow beam conditions and have conducted some basic research, there is still a lack of specific timing scheme design for the specific conditions of large propagation delay and directional multi-beams.

[0005] Taking the general tactical data link Link16 as an example, in order to support data communication between a large number of different types of devices within the network, the Link16 system uses TDMA technology for time resource allocation. It divides the time axis into epochs, time frames, and time slots. Each member device in the system will be allocated several time slots within a time frame to transmit the intelligence information it perceives or the command and control commands from the upper layer. Other members then switch to the receiving state to receive broadcast information. Therefore, each network member will definitely conduct a data exchange with the network within a time frame. In addition, in order to address the problems brought about by large propagation delays, the Link16 system adds a certain guard interval to each transmission time slot to ensure that the signals in this time slot reach all member users before the signals in the next time slot arrive.

[0006] However, eliminating the impact of large propagation delays by setting a guard interval is, to a certain extent, an inefficient utilization of the system's time resources, thereby reducing the overall data throughput rate of the network. At the same time, for high-mobility platforms with directional multi-beam resources, this frame format design scheme in the Link16 data link where only one network member is in the receiving state in each time slot cannot fully utilize the approximately interference-free directional communication ability of the directional multi-beam. Therefore, for modern ad-hoc networks with an increasing demand for data rates, there is still a large room for improvement in the communication rate of existing data link schemes such as Link16 under the conditions of large propagation delays and directional multi-beams. Summary of the Invention

[0007] Aiming at the problem of low data throughput rate existing in the existing communication timing scheme for large propagation delay directional ad-hoc networks, the present invention provides a high-throughput communication method for large propagation delay directional ad-hoc networks to improve the network throughput.

[0008] A high-throughput communication method for large propagation delay directional ad-hoc networks, where all nodes in the network are simultaneously in the receiving state or simultaneously in the sending state within the same time frame, and the receiving and sending states are alternately switched within adjacent time frames. Each node in the network conducts data communication with all other nodes simultaneously within each time frame;

[0009] At the same time, the frame length in the communication frame structure is selected as the frame length with the maximum sum of the effective transmission times between each node in the network. The frame length with the maximum sum of the effective transmission times between each node is determined by searching in the following way:

[0010] First, set the minimum value, maximum value of the optional frame length, and the search step τ;

[0011] Second, starting from the minimum frame length, gradually increase the frame length with τ as the search step, and calculate the sum of the effective transmission times of all nodes in the network under each frame length until the frame length increases to the maximum value;

[0012] Finally, the frame length with the maximum sum of the effective transmission times between each node is used as the communication frame length.

[0013] Further, assume that D ij represents the propagation delay between node i and node j in the network, and let K = D ij / T f , where T f represents the communication frame length. Then, the effective transmission time T e of the data packet sent by node i received by node j is calculated as follows:

[0014] Judge whether K is an integer. If it is an integer and odd, the effective transmission time T e = 1; if it is an integer and even, the effective transmission time T e = 0. Otherwise, judge whether the integer part A of K is odd or even. If A is odd, the effective transmission time T e = 1 - B; if A is even, the effective transmission time T e = B, where B is the value of the fractional part of K.

[0015] The communication timing collocation proposed by the present invention, that is, the frame length with the maximum sum of the effective transmission times between each node, can significantly improve the network throughput. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of a wireless ad hoc network;

[0017] Figure 2 is a relationship diagram of the communication frame length and the propagation delay in the ideal state;

[0018] Figure 3 is a schematic diagram for calculating the effective transmission time under normal conditions;

[0019] Figure 4 is a Monte Carlo comparison simulation diagram of the communication method proposed by the present invention and the existing Link16 data link system for ad hoc networks with different numbers of nodes. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments. The embodiments of the present invention are given for the purpose of illustration and description, and are not exhaustive or limited to the disclosed form. Many modifications and variations are obvious to those of ordinary skill in the art. The embodiments are selected and described to better illustrate the principles and practical applications of the present invention, and to enable those of ordinary skill in the art to understand the present invention and thus design various embodiments with various modifications suitable for specific purposes.

[0021] Example 1

[0022] Consider a Figure 1 large-scale wireless ad hoc network as shown, where the propagation delay of data frames between nodes with communication requirements may be relatively large and cannot be ignored compared to the data frame length; at the same time, each node device in the network has a phased array antenna that can simultaneously form multiple directional narrow beams, and it is assumed that the number of simultaneously operable directional narrow beams is greater than the number of nodes that need to communicate simultaneously. The multiple directional narrow beams enable each node to simultaneously communicate with multiple other nodes, including simultaneously sending data frames to multiple nodes or simultaneously receiving data frames from multiple nodes. Since the beam broadening angle is limited, it can be assumed that the communication between nodes is non-interfering, but each node can only operate in half-duplex mode, that is, it cannot simultaneously receive and send data.

[0023] To make full use of the directional beam resources of each node, it can be set that in each transmission state time frame, each node in the network simultaneously sends data packets to all other nodes, and in each reception state time frame, each node in the network simultaneously receives data packets sent by all other nodes.

[0024] In this embodiment, according to the characteristics of large propagation delay in the network, special designs are made for the network communication timing and the frame length in the communication frame structure. The communication timing is specifically that all nodes in the network are simultaneously in the reception state or simultaneously in the transmission state in the same time frame, and the transceiver states are alternately switched in adjacent time frames. Each node in the network simultaneously communicates with all other nodes in each time frame.

[0025] Figure 2 The relationship diagram between the communication frame length and the propagation delay in the ideal state is given under this communication timing. Node 1 sends a data packet in data frame 1, and the propagation delay between Node 1 and Node 2 is D 12 , when the propagation delay D 12 exactly equals the communication frame length Tf, Node 2 receives the data packet in data frame 2. When the propagation delay D 12 exactly equals 3 times the communication frame length Tf, Node 2 receives the data packet in data frame 4. From this, it can be deduced that when the propagation delay is an odd multiple of the communication frame length, it can be ensured that a data packet sent by a node in a certain transmission state time frame can definitely be received by the target node in a subsequent reception state time frame.

[0026] For a wireless ad hoc network, its communication frame length is fixed, but the propagation delays between different nodes are different and dynamically changing, and it cannot be guaranteed that the data packet transmissions between all nodes can achieve Figure 2The ideal effect shown. Therefore, from the perspective of the entire network, the maximization of the sum of the effective transmission times between various nodes in the network is considered. Although the nodes in the network are dynamic, for a multi-node network, due to more time delays, the transmission speeds of some nodes will be relatively large and those of some will be relatively small. Therefore, from the perspective of the entire network layer, the sum of the effective transmission times between various nodes is relatively stable.

[0027] Therefore, the present invention proposes an approximately optimal frame structure, in which the communication frame length does not strictly satisfy the odd multiple constraint condition with the propagation delay, but maximizes the sum of the effective transmission times between various nodes in the network. Since the transceiver states of the communication frame structure are fixed, the non-odd multiple relationship will result in only a part of the time within each time frame being the effective transmission time, as shown in Figure 3 shown.

[0028] In this embodiment, the frame length that maximizes the sum of the effective transmission times between various nodes is determined by searching in the following manner:

[0029] 1. Set the minimum value and maximum value of the optional frame length, and the search step size τ;

[0030] 2. Starting from the minimum value of the frame length, gradually increase the frame length with τ as the search step size, and calculate the sum of the effective transmission times of all nodes in the network under each frame length until the frame length increases to the maximum value;

[0031] 3. Use the frame length that maximizes the sum of the effective transmission times between various nodes as the communication frame length.

[0032] Assume D ij represents the propagation delay between node i and node j in the network, and record K = D ij / T f , where T f represents the communication frame length. Then the effective transmission time T e of the data packet sent by node i received by node j is calculated in the following manner:

[0033] Judge whether K is an integer. If it is an integer and odd, the effective transmission time T e = 1. If it is an integer and even, the effective transmission time T e = 0. Otherwise, judge whether the integer part A of K is odd or even. If A is odd, the effective transmission time T e = 1 - B. If A is even, the effective transmission time T e = B, where B is the numerical value of the fractional part of K.

[0034] Next, refer to Figure 3Analyze the above calculation method. Node 1 sends data packets to other nodes in data frame 1; when the propagation delay from node 1 to node 2 is between 2 and 3 times the frame length, A = 2 is an even number, and the latter part of the data packet falls into data frame 4 (the receiving frame), that is, Figure 3 the T in e = B; when the propagation delay from node 1 to node 2 is between 3 and 4 times the frame length, A = 3 is an odd number, and the former part of the data packet falls into data frame 4 (the receiving frame), that is, Figure 3 the T in e = 1 - B.

[0035] Through the above approximate optimal communication frame length search algorithm, this embodiment gives a method for selecting a communication frame length that can achieve better throughput in general. Although there is a certain throughput loss compared with Figure 2 the ideal state shown, it can work for any structure network, so it has strong robustness.

[0036] Perform Monte Carlo simulation on the communication method proposed by the present invention for ad hoc networks with different numbers of nodes, and at the same time compare the Monte Carlo simulation results of the existing Link16 data link system, as Figure 4 shown. From Figure 4 it can be seen that although the approximate optimal communication frame length obtained by the communication timing matching approximate optimal communication frame length search algorithm proposed by the present invention has a certain performance loss compared with the optimal frame length, it has a significant improvement compared with the timing scheme in the existing Link16 data link system. At the same time, different from the linear growth relationship between the network throughput and the number of nodes in the Link16 data link system, the communication method proposed by the present invention can achieve a square - level growth of the network throughput as the number of nodes increases.

[0037] Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art and related fields without creative work shall fall within the protection scope of the present invention.

Claims

1. A high-throughput communication method for a large propagation delay directional ad-hoc network, characterized in that, All nodes in the network are in the receiving state or the transmitting state simultaneously in the same time frame, and the receiving and transmitting states are alternately switched in adjacent time frames. Each node in the network communicates with all other nodes simultaneously within each time frame; Meanwhile, the frame length in the communication frame structure is selected as the frame length with the largest sum of effective transmission times between all nodes in the network. The frame length with the largest sum of effective transmission times between all nodes is determined by searching in the following way: First, set the minimum value and maximum value of the frame length, as well as the search step size τ; Second, starting from the minimum value of the frame length, gradually increase the frame length with τ as the search step size, and calculate the sum of the effective transmission times of all nodes in the network under each frame length until the frame length increases to the maximum value; Finally, use the frame length with the largest sum of effective transmission times between all nodes as the communication frame length.

2. The high-throughput communication method for a large propagation delay directional ad hoc network according to claim 1, characterized in that, Hypothesis D ij Denote the propagation delay between node \(i\) and node \(j\) in the network as \(D\). Let \(K = D\) ij / T f , where \(T\) f denotes the communication frame length. Then the effective transmission time \(T\) of the data packet sent by node \(i\) and received by node \(j\) is calculated as follows: e ​ Judge whether K is an integer. If it is an integer and odd, the effective transmission time T e = 1. If it is an integer and even, the effective transmission time T e = 0. Otherwise, judge whether the integer part A of K is odd or even. If A is odd, the effective transmission time T e = 1 - B. If A is even, the effective transmission time T e = B, where B is the value of the fractional part of K.

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