Wireless communication system

Abstract

Each of a plurality of base stations (101, 102) measures the received radio wave strength from a plurality of mobile stations (201, 202). Each of the plurality of mobile stations (201, 202) measures the position of the mobile station and the received radio wave strength from the plurality of base stations (101, 102). A server (401) manages the received radio wave strength from the plurality of mobile stations (201, 202) measured by the plurality of base stations (101, 102), and the position of the plurality of mobile stations (201, 202) and the received radio wave strength from the plurality of base stations (101, 102) measured by the plurality of mobile stations (201, 202), in association with the measurement time. Communication between the plurality of base stations (101, 102) and the plurality of mobile stations (201, 202) is controlled on the basis of characteristics, for each time and location, of the strength of the radio waves transmitted and received between the plurality of base stations (101, 102) and the plurality of mobile stations (201, 202), the characteristics being obtained by statistically processing information stored in the server (401).

Description

wireless communication system

[0001] The present disclosure relates to wireless communication systems, and more particularly to wireless communication systems including communicators mounted on mobile objects.

[0002] As a wireless communication system including a communication device mounted on a moving object, for example, a wireless communication system for railways is known that includes a mobile station, which is a communication device mounted on a train, and a base station, which is a communication device placed on the ground along the train tracks (for example, Patent Document 1 listed below).

[0003] Japanese Patent Application Laid-Open No. 2017-136871

[0004] Wireless communication systems have the problem of being prone to unstable communications due to interference with other wireless communication systems. The degree of interference with other wireless communication systems varies not only depending on spatial location but also on time. In other words, even at the same location, the degree of interference changes over time.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to improve the stability of communication in a wireless communication system.

[0006] A wireless communication system according to the present disclosure includes a plurality of base stations, a plurality of mobile stations that move along the same route and perform wireless communication with the plurality of base stations, and a server capable of communicating with at least the plurality of base stations, wherein each of the plurality of base stations measures the received radio wave strength from the plurality of mobile stations, and each of the plurality of mobile stations measures its own location and the received radio wave strength from the plurality of base stations, and the server stores the received radio wave strengths from the plurality of mobile stations measured by the plurality of base stations, and the locations of the plurality of mobile stations and the received radio wave strengths from the plurality of base stations measured by the plurality of mobile stations, linked to the time of measurement, and communications between the plurality of base stations and the plurality of mobile stations are controlled in each of the base stations and the mobile stations based on the characteristics of the strength of radio waves transmitted and received between the plurality of base stations and the plurality of mobile stations, which are obtained by statistically processing information stored in the server.

[0007] According to the present disclosure, it is possible to improve the stability of communication in a wireless communication system.

[0008] The objects, features, aspects, and advantages of the present disclosure will become more apparent from the following detailed description and the accompanying drawings.

[0009] Fig. 1 is a configuration diagram of a wireless communication system according to embodiment 1. Fig. 2 is a diagram for explaining the operation of the wireless communication system according to embodiment 1. Fig. 3 is a diagram for explaining the operation of the wireless communication system according to embodiment 1. Fig. 4 is a configuration diagram of a wireless communication system according to embodiment 2.

[0010] <First Embodiment> Fig. 1 is a configuration diagram of a wireless communication system according to the first embodiment. As shown in Fig. 1, the wireless communication system includes a plurality of base stations including base stations 101 and 102, a plurality of mobile stations including mobile stations 201 and 202, a grandmaster 301 which is a time server, and a server 401 which is an information server. For the sake of simplicity, it is assumed here that the plurality of base stations are only two, base station 101 and base station 102, and the plurality of mobile stations are only two, mobile station 201 and mobile station 202. However, the wireless communication system may include three or more base stations and mobile stations, and the number of base stations does not have to be the same as the number of mobile stations.

[0011] The base stations 101 and 102 are connected by wire and can exchange data with each other. The base stations 101 and 102 are also connected by wire to the grand master 301 and perform time synchronization based on time information distributed from the grand master 301. This allows the base stations 101 and 102 to maintain accurate time information. The base stations 101 and 102 also have a function to measure the strength of radio waves received from the mobile stations 201 and 202.

[0012] Mobile station 201 and mobile station 202 communicate wirelessly with base station 101 and base station 102. Mobile station 201 and mobile station 202 are mounted on mobile bodies and move along the same route. A railway radio communication system is a typical example of a radio communication system in which multiple mobile stations move along the same route.

[0013] Furthermore, mobile station 201 and mobile station 202 have a function for measuring their own position and a function for measuring the strength of radio waves received from base station 101 and base station 102. There are no restrictions on the method by which mobile station 201 and mobile station 202 measure their own position. For example, when mobile station 201 and mobile station 202 move along a fixed route, mobile station 201 and mobile station 202 may calculate their own travel distance from the number of rotations of the wheels of the moving body on which they are mounted, and identify their own position from their own travel distance.

[0014] Server 401 exchanges data with base station 101, base station 102, mobile station 201, and mobile station 202. Server 401 also includes a storage medium for saving data received from base station 101, base station 102, mobile station 201, and mobile station 202. Server 401 is connected to base station 101 and base station 102 via a network, and is connected to mobile station 201 and mobile station 202 via a public wireless network.

[0015] The operation of the wireless communication system according to the first embodiment will be described below.

[0016] Mobile station 201 measures its own location and transmits the measurement result, that is, location information of mobile station 201, together with other communication data, to base station 101 and base station 102. Mobile station 201 also measures the strength of the radio wave received from base station 101 and the strength of the radio wave received from base station 102. The strength of the radio wave received from base station 101 measured by mobile station 201 is stored as a log together with the location information of mobile station 201 in server 401 via the public wireless network.

[0017] The operation of mobile station 202 is basically the same as that of mobile station 201. That is, mobile station 202 measures its own location and transmits the measurement result, that is, location information of mobile station 202, together with other communication data, to base station 101 and base station 102. Mobile station 202 also measures the strength of the radio wave received from base station 101 and the strength of the radio wave received from base station 102. The strength of the radio wave received from base station 101 measured by mobile station 202 is stored as a log together with the location information of mobile station 202 in server 401 via the public wireless network.

[0018] The base station 101 receives communication data and location information transmitted from the mobile station 201 and the mobile station 202. The base station 101 also measures the received radio wave strength from the mobile station 201 and the received radio wave strength from the mobile station 202. The received radio wave strength from the mobile station 201 measured by the base station 101 is stored in the server 401 via the network, together with time information held by the base station 101 and location information of the mobile station 201 received from the mobile station 201, and these are linked and managed. The received radio wave strength from the mobile station 202 measured by the base station 101 is stored in the server 401 via the network, together with time information held by the base station 101 and location information of the mobile station 202 received from the mobile station 202, and these are linked and managed. The time information linked to the received radio wave strength corresponds to the time the received radio wave strength was measured, and the location information of the mobile station linked to the received radio wave strength corresponds to the location of the mobile station at the time the received radio wave strength was measured.

[0019] The operation of the base station 102 is basically the same as that of the base station 101. That is, the base station 102 receives communication data and location information transmitted from the mobile station 201 and the mobile station 202. The base station 101 also measures the received radio wave strength from the mobile station 201 and the received radio wave strength from the mobile station 202. The received radio wave strength from the mobile station 201 measured by the base station 102, together with time information held by the base station 102 and location information of the mobile station 201 received from the mobile station 201, is stored in the server 401 via the network, and is managed by being linked to each other. The received radio wave strength from the mobile station 202 measured by the base station 102, together with time information held by the base station 102 and location information of the mobile station 202 received from the mobile station 202, is stored in the server 401 via the network, and is managed by being linked to each other.

[0020] Here, since the mobile stations 201 and 202 move along the same route, the server 401 stores time-series data of the received radio wave intensity for each point on the route.

[0021] For example, assume that at time t1, mobile station 201 is located at point B and mobile station 202 is located at point C, as shown in Fig. 2, and that at subsequent time t2, mobile station 201 moves to point A and mobile station 202 moves to point B, as shown in Fig. 3. In this case, the received signal strength from base station 101 measured by mobile station 201 at time t1 is stored in server 401 as information on the received signal strength from base station 101 at point B at time t1. Furthermore, the received signal strength from base station 101 measured by mobile station 202 at time t2 is stored in server 401 as information on the received signal strength from base station 101 at point B at time t2. As a result, time-series data corresponding to times t1 and t2 for the received signal strength from base station 101 at point B is stored in server 401.

[0022] Furthermore, the received radio wave strength from mobile station 201 measured by base station 101 at time t1 is stored in server 401 as information on the received radio wave strength at base station 101 of radio waves transmitted from point B at time t1. Furthermore, the received radio wave strength from mobile station 202 measured by base station 101 at time t2 is stored in server 401 as information on the received radio wave strength at base station 101 of radio waves transmitted from point B at time t2. As a result, time-series data corresponding to time t1 and time t2 for the received radio wave strength at base station 101 of radio waves transmitted from point B is stored in server 401.

[0023] The received radio wave strength from the base station 101 measured by the mobile station 201 is stored in the server 401 together with the location information of the mobile station 201, and at the time of storage in the server 401, it is not linked to time information synchronized with the grand master 301. However, the time corresponding to the location information of the mobile station 201 can be regarded as the time when the base station 101 received the same location information of the mobile station 201. Therefore, the time corresponding to the location information of the mobile station 201 can be determined from the time information linked to the location information of the mobile station 201 stored in the server 401 by the base station 101. Therefore, the received radio wave strength from the base station 101 measured by the mobile station 201 can be linked to the time information afterwards in the server 401. The same applies to the received radio wave strength from the base station 102 measured by the mobile station 201, and the received radio wave strength from the base station 101 or the base station 102 measured by the mobile station 202.

[0024] By repeatedly performing the operations described in Figures 2 and 3 at each point on the route, time-series data on the received radio wave strength from base station 101 and base station 102 at each point on the route of mobile station 201 and mobile station 202, as well as the received radio wave strength at base station 101 and base station 102 of radio waves transmitted from each position on the route, is accumulated in server 401.

[0025] Server 401 stores information such as time, location of mobile station 201, radio wave strength from base station 101 to mobile station 201 (i.e., radio wave strength received from base station 101 at mobile station 201), radio wave strength from base station 102 to mobile station 201 (i.e., radio wave strength received from base station 102 at mobile station 201), location of mobile station 202, radio wave strength from base station 101 to mobile station 202 (i.e., radio wave strength received from base station 101 at mobile station 202), and radio wave strength from base station 102 to mobile station (i.e., radio wave strength received from base station 102 at mobile station 202). Server 401 performs statistical processing on the stored information to extract characteristics of the strength of radio waves transmitted and received between base stations 101 and 102 and mobile stations 201 and 201.

[0026] For example, focusing on information related to the mobile station 201, by averaging data of radio wave strength from the base station 101 to the mobile station 201 over multiple days for each combination of time and the location of the mobile station 201, it is possible to extract the characteristics of the radio wave strength from the base station 101 to the mobile station 201 for each combination of time and the location of the mobile station 201. By similar processing, it is also possible to extract the characteristics of the radio wave strength from the base station 102 to the mobile station 201 for each combination of time and the location of the mobile station 201, the characteristics of the radio wave strength from the base station 101 to the mobile station 202 for each combination of time and the location of the mobile station 202, and the characteristics of the radio wave strength from the base station 102 to the mobile station 202 for each combination of time and the location of the mobile station 202.

[0027] Communications between the base stations 101 and 102 and the mobile stations 201 and 201 are controlled based on the characteristics of radio wave strength extracted by the server 401, for example, information on the locations and times when the radio wave strength becomes weak (or strong).

[0028] For example, if the radio wave strength characteristics at time tn are that the radio wave strength from base station 101 to point α is weaker and that from base station 102 to point α is stronger, then when transmitting communication data to a mobile station located at point α (mobile station 201 or mobile station 202) at time tn, the transmission is made from base station 102. This allows the mobile station located at point α to receive the communication data with strong radio wave strength.

[0029] For example, if the radio wave strength at time tm is characterized by weak radio wave strength from base station 101 to point β and weak radio wave strength from base station 102 to point β, then when transmitting communication data to a mobile station (mobile station 201 or mobile station 202) located at point β at time tm, base station 101 or base station 102 will increase its transmission power and transmit the data, allowing the mobile station located at point β to receive the communication data with strong radio wave strength.

[0030] In this way, the communication between base station 101 and base station 102 and mobile station 201 and mobile station 201 is controlled based on the time- and location-specific characteristics of radio wave strength at each point on the mobile station's route, thereby improving the stability of communication.

[0031] [Modification] In the first embodiment, an example was shown in which mobile station 201 and mobile station 202 have the function of measuring their own positions and the function of measuring the strength of radio waves received from base station 101 and base station 102. However, mobile station 201 and mobile station 202 may also have the function of measuring the atmospheric pressure at their own positions and the function of measuring the humidity at their own positions. In this case, the atmospheric pressure information and humidity information measured by mobile station 201 and mobile station 202 are stored in server 401 together with the information on the strength of radio waves received and the position information, and are taken into consideration when extracting the characteristics of radio wave strength at each location and at each time.

[0032] For example, in an environment with low atmospheric pressure and high humidity, it is more likely to rain, which weakens the radio wave strength. Therefore, by further subdividing the characteristics of the radio wave strength at each location and time into combinations of atmospheric pressure and humidity, it is possible to obtain more accurate characteristics of the radio wave strength, further improving the stability of communication.

[0033] <Embodiment 2> Fig. 4 is a configuration diagram of a wireless communication system according to embodiment 2. The configuration of the wireless communication system according to embodiment 2 is the same as that of embodiment 1 (Fig. 1) except that the communication paths (public wireless network) between mobile station 201 and server 401 and between mobile station 202 and server 401 are omitted.

[0034] In the first embodiment, information on received radio wave strength from base station 101 and base station 102 measured by mobile station 201 and mobile station 202 is stored in server 401 together with location information via a public wireless network. In contrast, in the second embodiment, information on received radio wave strength and location information from base station 101 and base station 102 measured by mobile station 201 and mobile station 202 is not transmitted to server 401, but is stored within mobile station 201 or mobile station 202 that measured it. The information on received radio wave strength and location information stored in mobile station 201 and mobile station 202 is retrieved using a storage medium at a specific point on the route and transferred to server 401. Since other points are the same as those in the first embodiment, description thereof will be omitted here.

[0035] The wireless communication system according to the second embodiment can also improve the stability of communication, as in the case of the first embodiment. Furthermore, the wireless communication system according to the second embodiment is configured to transfer information on received radio wave intensity and location information measured by the mobile stations 201 and 202 to the server 401 without passing through a public wireless network, thereby improving the confidentiality of the information.

[0036] It is possible to freely combine the embodiments, and to modify or omit the embodiments as appropriate.

[0037] The above description is illustrative in all respects, and it is understood that countless variations not illustrated can be envisioned.

[0038] 101, 102 base stations, 201, 202 mobile stations, 301 grand master, 401 server.

Claims

1. A wireless communication system comprising: a plurality of base stations; a plurality of mobile stations that travel the same route and communicate wirelessly with the plurality of base stations; and a server capable of communicating with at least the plurality of base stations, wherein each of the plurality of base stations measures the strength of radio waves received from the plurality of mobile stations; each of the plurality of mobile stations measures its own location and the strength of radio waves received from the plurality of base stations; the server stores the strength of radio waves received from the plurality of mobile stations measured by the plurality of base stations, and the positions of the plurality of mobile stations and the strength of radio waves received from the plurality of base stations measured by the plurality of mobile stations, linked to the time of measurement; and communications between the plurality of base stations and the plurality of mobile stations are controlled by the base stations and the mobile stations, respectively, based on characteristics of the strength of radio waves transmitted and received between the plurality of base stations and the plurality of mobile stations for each time and for each location, which are obtained by statistically processing information stored in the server.

2. The wireless communication system according to claim 1, wherein each of the plurality of mobile stations further measures the atmospheric pressure and humidity at its own location, and the server further stores the atmospheric pressure and humidity measured by the plurality of base stations in association with the time of measurement.

3. A wireless communication system according to claim 1 or claim 2, wherein the information measured by the plurality of mobile stations is transmitted to the server via a public wireless network.

4. A wireless communication system according to claim 1 or 2, wherein the information measured by the plurality of mobile stations is stored within the plurality of mobile stations.

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