Communication systems and communication methods

Abstract

Provided is a communication system that adaptively implements optimal routing in a network that communication stations form by establishing links with each other. A routing control device 38 monitors traffic volumes of links 1-7 between communication stations comprising a satellite 30 and flying bodies 32, calculates a cost used for routing in the communication stations comprising the satellite 30 and the flying bodies 32, and performs routing on the basis of the cost. The cost calculation includes at least two of a process for calculating the degree of congestion of each of links 1-7, a process for calculating the delay time of each of links 1-7, and a process for calculating the degree of reliability of each of links 1-7. The cost is calculated by combining results obtained by weighting each of at least two factors obtained via the aforementioned processes.

Description

Technical Field

[0001] This disclosure relates to a communication system and a communication method, and particularly to a communication system and a communication method suitable for application to a network in which communication stations are connected to each other by links.

Background Art

[0002] In recent years, mobile communication systems have developed, and mobile services can be enjoyed in most of the areas on the ground. One of the requirements in the fifth or sixth generation mobile communication systems expected to be commercialized in the future is ultra-coverage. Ultra-coverage means expanding the service area to places where the laying cost of existing base stations is high, such as mountains, seas, and the air, or where it is difficult to lay base stations. In addition, strengthening the country against natural disasters is also required, and the emergence of a communication system that is resistant to ground disasters is desired.

[0003] To achieve the above, a non-terrestrial network (NTN) using satellites, unmanned aerial vehicles (UAVs), high altitude platform stations (HAPSs), drones, etc. has been in the spotlight. An example of an NTN composed of a HAPS network is shown in FIG. 1. The flying object 10 has a function of irradiating a beam to the ground to form a mobile service area 12. The ground terminal 14 existing in the mobile service area 12 connects to the HAPS flying object 10 and connects to the mobile network 16 via the flying object 10. The flying object 10 is equipped with a signal relay function, and the packet transmitted from the terminal 14 is sent to the Internet network 20 via the flying object 10, the ground base station 18, and the mobile network 16. Packets addressed to the terminal 14 from the Internet network 20 are also relayed in the same way.

[0004] In the future, a multi-layer satellite network consisting of multiple satellites and a HAPS network is conceivable. Figure 2 shows an example of NTN, which consists of geostationary orbit (GEO) satellites 22, low Earth orbit (LEO) satellites 24, and a HAPS network. The satellites 22, 24, and aircraft 10 belonging to each network are linked to each other to form a network. The satellites 22, 24, and aircraft 10 have routing capabilities, and traffic transmitted from terminal 14 is routed and sent to the internet network 20.

[0005] In the future multi-layer satellite network described above, traffic generated between terminal 14 and the internet network 20 will be routed using the GEO satellite network, each satellite 22, 24 within the LEO satellite network, or the aircraft 10 within the HAPS network as nodes. Multiple routing protocols exist, including protocols like RIP (Routing Information Protocol) that select the route with the smallest metric using the number of hops as a metric, and the OSPF (Open Shortest Path First) protocol that selects the route with the smallest cost using the bandwidth of the inter-node links as the path cost.

[0006] However, each network has different characteristics. These characteristics are shown in Table 1.

[0007] [Table 1]

[0008] For example, the propagation delays differ significantly because the altitudes at which the aircraft 10 and satellites 22 and 24 exist are all different. Since the GEO satellite 22 is located at an altitude of approximately 36,000 km, it takes about 120 ms for a signal transmitted from terminal 14 to reach satellite 22. On the other hand, since the aircraft 10 of the HAPS network is located at an altitude of approximately 20 km, the time it takes for a signal transmitted from terminal 14 to reach aircraft 10 is about 0.07 ms, resulting in low latency. Non-patent document 1 also proposes a protocol that uses the delay of the inter-node link as a cost. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] A Study on Efficient Routing in Hierarchical Satellite Networks, Yuta Tada, Daiki Nishiyama, Naoko Yoshimura, Yasushi Kato, Institute of Electronics, Information and Communication Engineers, IEICE Technical Journal, SAT2910-9, pp. 45-50, June 2010. [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] As described above, in NTN's network, in addition to significant differences in the distances between satellites 22 and 24 and aircraft 10, the communication equipment installed on each satellite 22, 24, and aircraft 10 may differ due to their respective onboard constraints (such as payload weight and power consumption). Therefore, the bandwidth of the inter-node links between satellites 22 and 24 and aircraft 10 may also differ. Consequently, NTN needs to select the optimal route by considering not just one factor, but multiple factors.

[0011] Furthermore, the available bandwidth between nodes is not constant. In addition, network congestion changes as the amount of incoming traffic changes. Therefore, the network state can change moment by moment. And it is expected that the importance of each factor to be considered when routing will change depending on the network state. Moreover, since the importance of each factor may also depend on the operational policy of the network operator, it is necessary to perform routing processing with adaptive cost control.

[0012] This disclosure has been made in view of the above-mentioned issues, and its primary objective is to provide a communication system that adaptively performs optimal routing according to the network conditions.

[0013] Furthermore, a second objective of this disclosure is to provide a communication method for providing adaptively optimal routing according to the network conditions. [Means for solving the problem]

[0014] The first aspect is a communication system in which, in order to achieve the above objective, communication stations establish links with each other to form a network and transfer packets through the links, A process to monitor the traffic volume of links between communication stations, A cost calculation process for calculating the cost used for routing at the aforementioned communications station, The system is configured to perform a process that performs routing based on the aforementioned cost, The aforementioned cost calculation process is: A process to calculate the degree of congestion of each link based on the traffic volume of the links between the aforementioned communication stations; a process to calculate the delay time of each link based on at least one of the distance of the links between the aforementioned communication stations and the transfer processing delay; and a process to calculate the reliability of the links, at least two of the above. A process of applying a weight to each of the elements obtained in the two processes described above, It is desirable to include a process of calculating the cost by combining the results obtained by multiplying the aforementioned elements by the aforementioned weights.

[0015] Also, a second aspect is a communication method for communication stations to form a network by connecting links with each other and transfer packets through the links, a step of monitoring the traffic volume of the links between communication stations, a cost calculation step of calculating the cost used for routing in the communication station, a step of performing routing based on the cost, and includes the cost calculation step is a step of calculating the congestion degree of each link based on the traffic volume of the links between communication stations, a step of calculating the delay time of each link based on at least one of the distance and transfer processing delay of the links between communication stations, and a step of calculating the reliability of the link, and at least two steps of a step of multiplying weights to each of the elements obtained by the at least two processes, a step of combining the results obtained by multiplying the weights to the elements to calculate the cost, and it is desirable to include.

Effect of the Invention

[0016] According to the first and second aspects, it is possible to adaptively provide an optimal routing according to the state of the network. It can be.

Brief Description of the Drawings

[0017] [Figure 1] An example of a conventional NTN composed of a HAPS network is shown. [Figure 2] An example of a conventional NTN composed of GEO satellites, low-earth orbit satellites, and a HAPS network is shown. [Figure 3] A communication system according to Embodiment 1 of the present disclosure is shown. [Figure 4] A flowchart for explaining the main processing flow implemented by the routing control device shown in FIG. 3 is shown. [Figure 5]This is a diagram illustrating an example of the operation of the communication system according to Embodiment 1 of this disclosure. [Figure 6] Figure 5 shows the situation where the feeder link of the first aircraft 32-1 has been severed by heavy rain. [Figure 7] Figure 6 shows the situation where the feeder link of the second aircraft 32-2 was further severed by heavy rain. [Figure 8] Figure 7 shows the situation where the feeder link of the third aircraft 32-3 was further severed by heavy rain. [Figure 9] The network model assumed for evaluation through simulation is shown. [Figure 10] This figure shows the differences in characteristics, specifically normalized throughput and average E2E delay time, due to differences in weight w. [Modes for carrying out the invention]

[0018] Embodiment 1. [Configuration of Embodiment 1] Figure 3 shows the overall configuration of the communication system of Embodiment 1 of this disclosure. The communication system of this embodiment includes a GEO satellite 30 and an unmanned aerial vehicle 32, a ground base station 34, a mobile network 36, and a routing control device 38.

[0019] The GEO satellite 30 and the unmanned aerial vehicle 32 function as communication stations that form service areas on the ground, as part of the GEO satellite network and the HAPS network, respectively. The GEO satellite 30 and the unmanned aerial vehicle 32 are also equipped with link communication equipment and routing functions for relaying signals. These connect to each other via links to form a network, relaying transmitted and received signals between connected terminals 40 and the mobile network 36 located within the service area. Furthermore, the GEO satellite 30 and the unmanned aerial vehicle 32 are equipped with the ability to observe the amount of traffic flowing through the links.

[0020] The ground base station 34 transmits and receives signals between the satellite 30 and the unmanned aerial vehicle 32 and the ground mobile network 36. The mobile network 36 manages the terminal 40 and controls the transmission and reception sessions. It also forwards packets between the terminal 40 and the internet network 42.

[0021] The routing control device 38 calculates the cost of each link according to the network connectivity status and the network operator's operational policy, and notifies the satellite 30 and the aircraft 32. The routing control device 38 also has the function of collecting information from the satellite 30 and the aircraft 32 for cost calculation, collecting information on link speed and the amount of traffic flowing. It also has the function of collecting feeder link connectivity information from the ground base station 34, that is, connectivity information for the radio link between the ground base station and the space station (GEO satellite 30 and unmanned aircraft 32). Furthermore, it has link connectivity information and position information for the satellite 30 and the aircraft 32 to which the links are connected, and calculates the propagation delay of the links for the satellite 30 and the aircraft 32.

[0022] [Processing flow in Embodiment 1] Figure 4 shows a flowchart of the main processes performed by the routing control device 38. First, information on congestion, including link speed and the average amount of traffic per unit time flowing through the link, is collected from the satellite 30 and the aircraft 32 (step 100).

[0023] Next, information regarding the feasibility of feeder link connectivity is collected from each of the ground base stations 34 (step 102).

[0024] Subsequently, link connection information for satellite 30 and aircraft 32 is obtained, and propagation delay for each link is calculated from their positions (step 104). Specifically, the propagation delay time is calculated by dividing the distance to satellite 30 and aircraft 32 by the speed of light.

[0025] Subsequently, weights are calculated from the feeder link connectivity status information (step 106). Furthermore, the cost of each link is calculated based on the link speed and traffic volume collected from satellite 30 and aircraft 32, the propagation delay calculated based on the respective positions of satellite 30 and aircraft 32, and the weights calculated in step 106 (step 108). The formula (1) for calculating the cost S of each link is shown below.

[0026]

number

[0027] Here, w is the weight, Br is the reference value of the link speed [bit / s], R is the link speed [bit / s], T is the average amount of traffic per unit time flowing through the link [bit / s], D is the link propagation delay time [s], and Bd is the reference value of the delay time [s]. The first term on the right-hand side is the available bandwidth reserve, in other words, the cost related to congestion, and the second term on the right-hand side is the cost related to delay time.

[0028] After calculating the cost of each link, the satellite 30 and the aircraft 32 are each notified of the cost of each link (step 110). The satellite 30 and the aircraft 32 then perform traffic routing based on the notified costs.

[0029] [Example of operation of Embodiment 1] Next, an example of operation of Embodiment 1 will be described. Here, we assume a network as shown in Figure 5. The GEO satellite network consists of one GEO satellite 30. The HAPS network is assumed to be a network of four aircraft 32-1 to 32-4. Hereafter, when it is necessary to distinguish between the four aircraft, a subscript such as "32-1" will be added, and when it is not necessary to distinguish between them, the subscript will be omitted and they will simply be referred to as "32". The same applies to the other elements.

[0030] In the example shown in Figure 5, the speed (bandwidth) of each link, the altitude of the GEO satellite 30 and the aircraft 32, and the distance between the aircraft are assumed to be the same as those shown in Table 1 above. Note that any difference in distance between the GEO satellite 30 and each aircraft 32 due to the position of the aircraft 32 is ignored, and the distance between the GEO satellite 30 and each aircraft 32 is assumed to be uniform.

[0031] Each aircraft 32 and satellite 30 is equipped with one ground base station 34, which is connected to a mobile network 36 via a feeder link. Each aircraft 32 also forms a coverage area 44 on the ground surface using its beam. Terminals 40 within the coverage area 44 connect to the aircraft 32 and communicate with the internet network 42 via the GEO satellite network, HAPS network, and mobile network 36.

[0032] The routing control device 38 has information on the altitude of the GEO satellite 30 and the aircraft 32, as well as the distance between the aircraft. The routing control device 38 also periodically collects information on the link speed and average traffic volume of each link, as well as information on the connection status of the feeder links, from the GEO satellite 30 and the aircraft 32. Because the feeder links in the HAPS network use high frequency bands, they are susceptible to rain attenuation, and the links are more likely to be disconnected when there is heavy rain around the ground base station 34.

[0033] Traffic generated by terminal 40-1 located in the coverage area 44-1 of the first aircraft 32-1 is sent to the internet network 42 via the mobile network 36 through the feeder link of the first aircraft 32-1.

[0034] Figure 6 shows the state in which the feeder link of the first aircraft 32-1 is severed by heavy rain. In this case, the routing control device 38 first calculates the propagation delay of each link from the altitude of the GEO satellite 30 and the aircraft 32, and the distance between the aircraft. Table 2 shows examples of the calculated propagation delay, as well as the link speed and traffic amount of each link collected from the GEO satellite 30 and the aircraft 32.

[0035] [Table 2]

[0036] The routing control device 38 then calculates the cost of each link. The reference value for link speed is set to 1 Gbits / s, and the reference value for delay time is set to 100 ms. In addition, the value of weight w is usually set to 0.5. The calculated link capacity utilization and cost are shown in Table 3. The calculated cost is transmitted to the GEO satellite 30 and the aircraft 32.

[0037] [Table 3]

[0038] The first aircraft 32-1 selects the route for traffic generated in coverage area 44-1 based on the cost of each transmitted link. Specifically, it compares the costs of Link 1 and Link 5, which are available to the first aircraft 32-1, and selects the one with the smaller cost. In this case, since Link 5 has a lower cost, the traffic is transferred to Link 5. The traffic transferred via Link 5 is then forwarded to the mobile network via the feeder link of the second aircraft 32-2.

[0039] Figure 7 shows the feeder link of the second aircraft 32-2 severed by heavy rain. Table 4 shows the propagation delay calculated under these conditions, as well as the link speed and traffic volume of each link collected from the GEO satellite 30 and aircraft 32.

[0040] [Table 4]

[0041] Furthermore, the calculated link capacity utilization rate and cost are shown in Table 5.

[0042] [Table 5]

[0043] In a comparison of Link 1 and Link 5, which can be used by the first aircraft 32-1, Link 5 is less expensive. Therefore, the traffic of the first aircraft 32-1 is transferred to Link 5. Next, in a comparison of Link 2 and Link 6, which can be used by the second aircraft 32-2, Link 6 is less expensive. Therefore, the traffic of the second aircraft 32-2 is transferred to Link 6. The traffic transferred via Link 6 is then transferred to the mobile network 36 via the feeder link of the third aircraft 32-3.

[0044] Figure 8 further shows the feeder link of the third aircraft 32-3 being severed by heavy rain. The routing control device 38 changes the value of weight w used in cost calculation from the normal value of 0.5 to 0.8 because the number of severed feeder links has increased. This reduces the weight of the cost related to delay and relatively increases the weight of the cost related to link speed. Table 6 shows the propagation delay calculated under these conditions, as well as the link speed and traffic amount for each link collected from the GEO satellite 30 and aircraft 32.

[0045] [Table 6]

[0046] Furthermore, the calculated link capacity utilization rate and cost are shown in Table 7.

[0047] [Table 7]

[0048] Comparing Link 1 and Link 5 available to the first aircraft 32-1, Link 5 is less expensive. Therefore, the traffic from the first aircraft 32-1 is routed to Link 5. Next, comparing Link 2 and Link 6 for the second aircraft 32-2, Link 2 is less expensive. Therefore, the traffic from the second aircraft 32-2 is routed to Link 2. For the third aircraft 32-3, based on a comparison of Link 3 and Link 7, the traffic is routed to Link 7, which is less expensive. This routing means that some of the traffic generated in the HAPS network will be routed to the GEO satellite network.

[0049] Thus, in the communication system of this embodiment, if the number of disconnections in the feeder links of the HAPS network increases and traffic on the HAPS network becomes congested, the weight can be changed to divert the traffic to the GEO satellite network. As a result, this system allows traffic to be efficiently routed to the internet network 42 even when the number of disconnections increases.

[0050] [Modified example of Embodiment 1] In this embodiment, the routing control device 38 calculates the cost of each link and notifies each satellite 30 and aircraft 32 of the results, but this disclosure is not limited to this. The routing control device 38 may notify the satellites 30 and aircraft 32 of necessary information such as the propagation delay of each link and the status of the feeder link, and the satellites 30 and aircraft 32 may calculate the cost, notify each other within the network, and perform routing autonomously.

[0051] In this embodiment, link speed and link capacity utilization were used as indicators of congestion, but this disclosure is not limited thereto. For example, the utilization rate of a buffer that temporarily stores received traffic in a routing function may be used as an indicator of congestion.

[0052] In this embodiment, only propagation delay time based on the distance between satellites or aircraft was used as the link delay time, but this disclosure is not limited thereto. The link delay time may also include transmission waiting time due to traffic congestion in the routing function of satellite 30 or aircraft 32, and the time required for transmission and reception processing.

[0053] In this embodiment, we assumed GEO satellites and HAPS networks whose positions hardly change, but similar processing is possible with LEO satellites as long as positional information can be obtained. For example, if the routing control device 38 can acquire orbital information of LEO satellites, it can recognize the distance between satellites and aircraft and calculate the propagation delay.

[0054] In this embodiment, information was collected from satellite 30 and aircraft 32, and routing between the satellite and aircraft was controlled. However, it is not limited to this, and it is also possible to perform routing processing including the feeder link by similarly calculating the congestion level and propagation delay of the feeder link.

[0055] Furthermore, while this example assumes a non-terrestrial network consisting of satellites and HAPS, it is not limited to these and can be applied to networks consisting of node stations equipped with communication devices, regardless of whether they are wireless or wired.

[0056] Furthermore, in the embodiment 1 described above, the weight w is changed according to the number of disconnections of the feeder links in the HAPS network, but this disclosure is not limited thereto. The weight w may be changed according to the network connectivity status, for example, the weight w may be changed according to the disconnection rate.

[0057] Embodiment 2. As described above, in Embodiment 1, control was performed to change the weight w according to the number of disconnections in the feeder links of the HAPS network and to route traffic to the GEO satellite network. This is because traffic congestion within the HAPS network is predicted. Similarly, the amount of traffic circulating within the HAPS network is directly monitored, and the weight w is adaptively controlled when the total amount of congestion increases. Alternatively, the total amount of packets congested within the communication device is monitored, and the weight w is adaptively controlled when that amount increases. This makes it possible to perform the same processing as in Embodiment 1.

[0058] Embodiment 3. In the above-described embodiment 1, the weight w was changed according to the number of disconnected feeder links in the HAPS network, but the method for controlling the weight w is not limited to this. In this embodiment, the weight w is controlled based on the operational policy of the network operator.

[0059] In the event of a disaster, when traffic volume increases, the GEO satellite network will be actively used to accommodate as much traffic as possible. In this case, the value of weight w in cost calculation formula (1) will be increased to increase the impact of congestion and decrease the impact of delay time. This will increase the amount of traffic transferred to the GEO satellite network.

[0060] Conversely, if the increase in latency due to routing through the GEO satellite network is undesirable, the value of weight w in cost calculation formula (1) is reduced to decrease the impact of congestion and increase the impact of latency. This reduces traffic transfer to the GEO satellite network, enabling low-latency communication.

[0061] In this embodiment, the function of controlling the weight w based on the operational policy can be realized by having the network operator manually set the weight w and having the communication system detect that setting. Alternatively, events occurring within the network may be stored in memory in advance for each situation where it is necessary to switch the operational policy, such as the occurrence of a disaster or a situation where delay avoidance is required. In this case, the communication system may be made to detect these events occurring within the network and automatically switch the weight w.

[0062] Embodiment 4. In the above-described embodiment 1, no distinction was made between traffic types, but such distinctions may be made. For example, traffic such as voice, which requires real-time performance, is required to have a low latency. Such traffic may be distinguished from other traffic, and routing control may be performed for each type of traffic. Information about the application type, or QoS (Quality of Service) information corresponding to the application type, is stored in the traffic packet, and routing is performed for each traffic type by acquiring this information in the routing function of the satellite or aircraft.

[0063] The routing control device 38 calculates costs for each type of traffic. Specifically, in equation (1), the weight is controlled for each type of traffic. Table 8 shows the variable range of the weight w for each type of traffic.

[0064] [Table 8]

[0065] For traffic requiring small delays, such as voice traffic, traffic transfer to the GEO satellite network is undesirable, so a variable range is set to limit the weight value. On the other hand, for traffic where relatively large delays are acceptable, such as SNS traffic, a variable range is set to limit the weight value to actively transfer traffic to the GEO satellite network.

[0066] Embodiment 5. In Embodiment 1 described above, cost was calculated using measures of congestion and delay for each link. In this embodiment, cost is calculated by combining the reliability of each link. For example, when a high frequency is used in a feeder link, the impact of weather on radio waves becomes greater, and power attenuation of radio waves due to rainfall, etc., becomes greater. Therefore, in bad weather, the link is more likely to be disconnected, and the reliability of the link decreases. Thus, the reliability of the link is added to the cost calculation.

[0067]

number

[0068] However, w1, w2, and w3 are set so that w1 + w2 + w3 = 1. Here, C is the reliability of the link; for feeder links, it should be higher in good weather and lower in bad weather. As a network operator's operational policy, the value of w3 is usually set high to avoid using feeder links with low reliability as much as possible. If the traffic in the network increases and becomes congested, the value of w3 is lowered, and even feeder links with low reliability are actively used to handle the traffic in the network.

[0069] As explained above, the communication system described in this disclosure enables adaptive cost calculation in routing. Therefore, adaptive routing is possible in response to congestion due to increased traffic and changes in operational policies by network operators.

[0070] The following shows the evaluation based on simulation. Figure 9 shows the network model. Table 9 shows the evaluation parameters.

[0071] [Table 9]

[0072] As shown in Figure 9, nine HAPS were arranged in a grid, connected vertically and horizontally with links, and evaluated using a network topology in which one central HAPS was connected to a GEO satellite by a link. A traffic volume of 0.1 to 1 Gbit / s was randomly generated in each HAPS, and routing to ground base stations was performed based on the cost calculation in equation (1). Assuming that rain areas were randomly generated and the feeder links of the HAPS were randomly interrupted, the normalized throughput (with the case without rain areas set to 1) and average E2E delay time averaged across all HAPS were evaluated. E2E delay time is considered to be only the link propagation time. As the size of the rain area increases, the number of feeder link interruptions also increases.

[0073] Figure 10 shows the characteristics for w=0.5, w=1, and w=0, where the two scales are equally weighted. When w=1, the delay time of each link is not considered, making it easier to select GEO satellite links. While the throughput reduction is minimized because traffic is offloaded to GEO satellites, the average E2E delay time is the largest. When w=0, GEO satellites with large delay times are not selected, resulting in the largest throughput reduction. On the other hand, w=0.5 corresponds to a rain area of ​​15,000 km. 2 Below this value, it is possible to achieve both improved throughput and reduced end-to-end latency, making it the optimal value. (Rain area: 15,000 km) 2 In the above cases (six or more feeder links are disconnected), set w according to the operational policy. For example, if throughput improvement is prioritized over delay time, setting w to a large value is considered an effective control method. [Explanation of Symbols]

[0074] 30 GEO satellites 32 (32-1~32-4) Flying Object 34 Ground base stations 36 Mobile Networks 38 Routing control device 40 (40-1~40-4) terminals 42 Internet Network 44 (44-1~44-6) Coverage Area

Claims

1. A communication system in which communication stations establish links with each other to form a network and transfer packets through these links, A process to monitor the traffic volume of links between communication stations, A cost calculation process for calculating the cost used for routing at the aforementioned communications station, The system is configured to perform a process that performs routing based on the aforementioned cost, The aforementioned cost calculation process is: A process to calculate the degree of congestion of each link based on the traffic volume of the links between the aforementioned communication stations; a process to calculate the delay time of each link based on at least one of the distance of the links between the aforementioned communication stations and the transfer processing delay; and a process to calculate the reliability of the links, at least two of the above. A process for monitoring the connection status of the aforementioned network, A process to set the distribution of weights to be multiplied by each of the elements obtained in the above two processes, based on the network connection status, A process of multiplying each of the elements obtained in the above two processes by the weight, A process of calculating the cost by combining the results obtained by multiplying the aforementioned elements by the aforementioned weights, A communication system that includes this.

2. The network connectivity status includes the percentage of link disconnections. The communication system according to claim 1, wherein the weight is set based on the cutting ratio.

3. A policy detection process for detecting operational policies to be applied to the aforementioned network, A process to set the weight based on the aforementioned operational policy, A communication system according to claim 1 or 2, configured to perform the following:

4. The network is provided with a memory that stores events occurring in the network, corresponding to each of the multiple operational policies to be applied to the network. The communication system according to claim 3, wherein the policy detection process includes a process of detecting an operational policy corresponding to an event stored in the memory as an operational policy to be applied to the network when such event occurs.

5. A process for monitoring at least one of the total traffic volume circulating within the network and the total packet volume accumulating at the communication station, A process for calculating the weight based on at least one of the total traffic volume and the total packet retention volume, A communication system according to any one of claims 1 to 4, configured to perform the following:

6. A process for identifying at least one of the QoS and application type of traffic flowing through the aforementioned network, The system is configured to perform a process of calculating the weight based on at least one of the QoS and application type, The communication system according to any one of claims 1 to 5, wherein the routing process is performed for each traffic.

7. A communication method for which communication stations establish links with each other to form a network and transfer packets through the links, The steps include monitoring the traffic volume of the links between communication stations, A cost calculation step for calculating the cost used for routing at the aforementioned communication station, The step includes, The aforementioned cost calculation step is: The steps include: calculating the degree of congestion of each link based on the traffic volume of the links between the aforementioned communication stations; calculating the delay time of each link based on at least one of the distance between the links and the transfer processing delay; and calculating the reliability of the links, at least two of these steps. The steps include monitoring the connection status of the aforementioned network, A step of setting the distribution of weights to be multiplied by each of the elements obtained in the above two steps, based on the network connection status, A step of multiplying each of the elements obtained in the above two steps by the weight, The steps include: calculating the cost by combining the results obtained by multiplying the aforementioned elements by the aforementioned weights; A communication method that includes this.

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