Communication system and communication method

Abstract

To provide a communication system and a communication method that allow a plurality of FWA communication stations to share propagation conditions and to maintain good communication quality with each other.SOLUTION: A communication system and a communication method include a plurality of sets of fixed wireless access systems (FWA) each having a master station 1 and a slave station 2, and transmit and share information on propagation conditions in a specific FWA to another FWA using communication other than the FWA, and the master station 1 of the other FWA controls the movement of frequency channels or the increase or decrease of bandwidth based on the shared information on the propagation conditions of the FWA.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a communication system having a plurality of fixed wireless access systems, and more particularly to a communication system and a communication method for controlling communication in accordance with interference conditions among a plurality of communication devices. [Background technology]

[0002] [Prior Art] 2. Description of the Related Art Conventionally, there is a fixed wireless access (FWA) system in which wireless devices fixedly installed outdoors transmit and receive signals facing each other. Fixed wireless access systems (hereinafter referred to as FWA) are available in two types: the PP (Point-to-Point) method, which establishes a one-to-one wireless connection between stations, and the P-MP (Point-to-Multipoint) method, which establishes a one-to-many wireless connection.

[0003] The PP method consists of a master station that controls transmission and reception, and slave stations that are subordinate to the control of the master station.The master station first starts sending a signal, and the slave station receives the signal sent by the master station and performs synchronization processing to establish a connection.

[0004] Conventionally, the master station determines the modulation method and transmission power based on the quality of the received signal, notifies the slave station, and controls communication conditions such as the modulation method and transmission power according to the propagation conditions. In addition, in the PP method, communication is basically carried out only between opposing master and slave stations, and each FWA is independent, but if there is a master or slave station of another FWA nearby, changing the communication conditions may cause interference.

[0005] [Related Technology] Related prior art includes Japanese Patent Application Laid-Open No. 2013-34059 "Wireless communication system" (Patent Document 1), Japanese Patent Application Laid-Open No. 2005-198123 "Wireless communication system" (Patent Document 2), and Japanese Patent Application Laid-Open No. 2008-167500 "Transmission power control method and wireless access system" (Patent Document 3).

[0006] Patent document 1 describes a configuration in which, in a system in which transmission is performed using one of multiple antennas, a first transmission / reception device determines the timing for switching the transmission antenna based on the measurement results of the reception level and notifies a second transmission / reception device, and the second transmission / reception device performs processing in accordance with that timing, thereby preventing communication degradation immediately after switching.

[0007] Patent Document 2 describes a wireless communication system that performs efficient wireless transmission by switching modulation methods depending on wireless communication conditions. Patent document 3 also describes that in a wireless access system, a base station device measures the reception level from a subscriber base station and transmits the result to the subscriber base station, and the subscriber base station calculates the optimal transmission power and adjusts the transmission power. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-34059 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-198123 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-167500 Summary of the Invention [Problem to be solved by the invention]

[0009] However, in conventional communication systems, when there are multiple FWA master stations and slave stations in the vicinity, there is a problem that interference occurs due to control of communication conditions, which can degrade communication quality.

[0010] Incidentally, Patent Documents 1 to 3 do not describe a configuration for sharing information on propagation conditions between different FWA communication stations.

[0011] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a communication system and a communication method that, when multiple FWA communication stations are installed close to each other, can share propagation conditions between the FWA communication stations and maintain good communication quality. [Means for solving the problem]

[0012] The present invention, which aims to solve the problems of the above-mentioned conventional examples, is a communication system comprising a plurality of fixed wireless access systems, each having a master station that controls transmission and reception and a slave station that is subordinate to the control of the master station, and is characterized in that information on propagation conditions in communication of a specific fixed wireless access system is transmitted to and shared with other fixed wireless access systems using a separate communication method, and the master stations of the other fixed wireless access systems control the movement of frequency channels or the increase or decrease of bandwidth based on the shared information on propagation conditions.

[0013] Furthermore, in the above-mentioned communication system, the present invention is characterized in that the information on the propagation conditions indicates the degree of interference, and when the transmission environment in another fixed wireless access system deteriorates, the master station of the other fixed wireless access system controls the movement of frequency channels or the increase or decrease of bandwidth based on the information on the propagation conditions in the specific fixed wireless access system.

[0014] The present invention is also characterized in that it provides a communication system including a plurality of fixed wireless access systems, each having a master station that controls transmission and reception and a slave station that is subordinate to the control of the master station, and further includes a monitoring and control device that receives and stores information on propagation conditions in communication among the plurality of fixed wireless access systems using a separate communication method, and when one of the fixed wireless access systems controls shifting of frequency channels or increasing or decreasing of bandwidth, notifies the controlling fixed wireless access system whether or not the control is appropriate based on the propagation conditions of the fixed wireless access systems other than the controlling fixed wireless access system.

[0015] Furthermore, in the above communication system, the present invention is characterized in that the master station and slave stations of the plurality of fixed wireless access systems transmit the RACH at a timing that corresponds to a specific offset time relative to the 1PPS signal.

[0016] Furthermore, in the above-mentioned communication system, the present invention is characterized in that the specific offset time is a time obtained by adding a maximum transmission delay time in a plurality of fixed wireless access systems to the time of the DL subframe, and the master station and the slave station receive the RACH within a time obtained by adding the time required to transmit the RACH and twice the maximum transmission time from the timing of transmitting the RACH.

[0017] The present invention also provides a communication method in a communication system including a plurality of fixed wireless access systems, each having a master station that controls transmission and reception and a slave station that is subordinate to the control of the master station, characterized in that a specific fixed wireless access system transmits and shares information on propagation conditions in communication of the specific fixed wireless access system to another fixed wireless access system using a different communication method, and the master station of the other fixed wireless access system controls movement of frequency channels or increase or decrease of bandwidth based on the shared information on propagation conditions. [Effects of the Invention]

[0018] According to the present invention, there is provided a communication system including a plurality of fixed wireless access systems, each having a master station that controls transmission and reception and a slave station that is subordinate to the control of the master station, in which information on the propagation conditions in communication of a specific fixed wireless access system is transmitted to and shared with other fixed wireless access systems using a different communication method, and the master stations of the other fixed wireless access systems control the movement of frequency channels or the increase or decrease of bandwidth based on the shared information on the propagation conditions. Therefore, the master station can monitor the propagation conditions of the other fixed wireless access systems and control the movement of frequency channels or the increase or decrease of bandwidth of its own system so as not to affect the propagation conditions of the other systems, and has the effect of realizing good communication quality while suppressing interference even when a plurality of fixed wireless access systems are installed close to each other.

[0019] Furthermore, according to the present invention, the information on the propagation conditions indicates the degree of interference, and when the transmission environment in another fixed wireless access system deteriorates, the master station of the other fixed wireless access system controls the shifting of the frequency channel or the increase / decrease of the bandwidth based on the information on the propagation conditions in the specific fixed wireless access system. Therefore, when the transmission environment deteriorates, the master station controls the shifting of the frequency channel or the increase / decrease of the bandwidth within a range that does not affect the propagation conditions in the other fixed wireless access system, thereby achieving the effect of maintaining good communication quality for both parties.

[0020] Furthermore, according to the present invention, there is provided a communication system including a plurality of sets of fixed wireless access systems, each having a master station that controls transmission and reception and a slave station that is subordinate to the control of the master station, and the communication system is equipped with a monitoring control device that receives and stores information on propagation conditions in communication between the plurality of fixed wireless access systems using a separate communication method, and when one of the fixed wireless access systems controls the movement of a frequency channel or the increase or decrease of bandwidth, notifies the controlling fixed wireless access system whether or not the control is appropriate based on the propagation conditions of the fixed wireless access systems other than the controlling fixed wireless access system. This has the effect of reducing the load on the master station by centrally monitoring the propagation conditions of the plurality of fixed wireless access systems.

[0021] Furthermore, according to the present invention, the master station and slave stations of a plurality of fixed wireless access systems are configured as the communication system in which the RACH is transmitted at a timing that corresponds to a specific offset time with respect to the 1PPS signal. This has the effect of shortening the time width of the RACH to improve frame utilization efficiency, and also enabling the receiving side to easily calculate the propagation delay from the reception timing of the RACH.

[0022] Furthermore, according to the present invention, the specific offset time is the time obtained by adding the maximum transmission delay time in a plurality of fixed wireless access systems to the time of the DL subframe, and the master station and the slave station receive the RACH within a time obtained by adding the time required to transmit the RACH and twice the maximum transmission time from the timing of transmitting the RACH, so that even if interference occurs, the RACH can be transmitted and received without any problems, and the time required for the RACH reception operation can be shortened.

[0023] Furthermore, according to the present invention, there is provided a communication method in a communication system including a plurality of fixed wireless access systems, each having a master station that controls transmission and reception and a slave station that is subordinate to the control of the master station, in which a specific fixed wireless access system transmits information on the propagation conditions in the communication of the specific fixed wireless access system to another fixed wireless access system using a different communication method, thereby sharing the information, and the master station of the other fixed wireless access system controls the movement of the frequency channel or the increase / decrease of the bandwidth based on the shared information on the propagation conditions. Therefore, the master station can monitor the propagation conditions of the other fixed wireless access systems and control the movement of the frequency channel or the increase / decrease of the bandwidth of its own system so as not to affect the propagation conditions of the other systems, and has the effect of realizing good communication quality while suppressing interference even when a plurality of fixed wireless access systems are installed closely to each other. [Brief explanation of the drawings]

[0024] [Figure 1] This is a schematic diagram of the FWA configuration. [Figure 2] FIG. 1 is a schematic explanatory diagram showing an example of FWA deployment in the present communication system. [Figure 3] FIG. 10 is a schematic configuration diagram of a second communication system. [Figure 4] FIG. 10 is a schematic explanatory diagram of a propagation status monitoring table. [Figure 5] 10 is a flowchart showing the processing of a monitoring control device in a second communication system. [Figure 6] 2 is an explanatory diagram showing a first frame configuration and transmission / reception timing in the present communication system. FIG. [Figure 7] FIG. 10 is an explanatory diagram showing a second frame configuration and transmission / reception timing in this system. DETAILED DESCRIPTION OF THE INVENTION

[0025] An embodiment of the present invention will be described with reference to the drawings. [Outline of the embodiment] A communication system according to an embodiment of the present invention (this communication system) includes multiple sets of fixed wireless access systems (FWAs) each having a master station and a slave station that is subordinate to the control of the master station. Information on the propagation conditions in a specific FWA is transmitted to and shared with other FWAs using communication other than the FWA. The master stations of the other FWAs control the movement of frequency channels or the increase or decrease of bandwidth based on the shared information on the propagation conditions of the FWAs. When the propagation conditions deteriorate due to rainfall or the like, the master station can control the movement of frequency channels or the expansion of bandwidth in its own system to the extent that it does not adversely affect the propagation conditions of other FWAs. Even if multiple FWAs are installed nearby, it is possible to maintain good communication quality while suppressing the effects of interference with each other.

[0026] Furthermore, when this communication system uses a Random Access Channel (RACH) to transmit and receive signals for measuring propagation conditions (interference conditions, interference levels), the transmission timing of the RACH is set to a specific offset time from the beginning of the frame, so that the transmission timing of the RACH is synchronized among all radio devices in the system, thereby improving frame utilization efficiency. A communication method according to an embodiment of the present invention is a communication method in this communication system.

[0027] [FWA schematic configuration: Figure 1] First, the schematic configuration of the FWA constituting this communication system will be explained using Fig. 1. Fig. 1 is a schematic configuration diagram of the FWA. Note that the FWA shown in Fig. 1 has a configuration common to first to third embodiments described later. 1 shows a PP FWA in which two radio devices are arranged facing each other: a master station 1 and a slave station 2. The master station 1 and the slave station 2 are sometimes referred to as communication stations or radio devices.

[0028] The master station 1 controls transmission and reception, and the slave station 2 operates under the control of the master station 1. In particular, the master station 1 of this communication system monitors the propagation conditions, such as interference received by its own device, shares the propagation conditions with other FWAs, and controls the increase / decrease of bandwidth and the movement of frequency channels based on the results. For example, the received field strength is measured and the value is used as information representing the propagation conditions. Sharing of propagation conditions and the associated control will be described later.

[0029] The master station 1 includes a transmission baseband signal processing unit 101, an RF (Radio Frequency) unit 102, an antenna 103, a reception baseband signal processing unit 104, a GNSS (Global Navigation Satellite System) receiver 105, and a control unit 106.

[0030] The transmission baseband signal processing unit 101 performs error correction coding and modulation on information to be transmitted in a DL (Down Link) subframe. The RF unit 102 performs processes such as frequency conversion from baseband to radio frequency band, frequency conversion from radio frequency band to baseband, and signal amplification. The antenna 103 is a highly directional parabolic antenna that radiates DL radio signals into space and captures UL (Up Link) radio signals from space.

[0031] The reception baseband signal processing unit 104 demodulates the signal received via UL and performs error correction decoding. The GNSS receiver 105 receives signals from GNSS satellites, extracts and outputs 1 PPS (Pulse Per Second) signals. In addition to controlling the DL transmission timing and UL reception timing, the control unit 106 of the master station 1 of this communication system shares propagation conditions with other FWA communication stations, and controls the bandwidth and frequency channel movement of its own system (its own FWA) based on the results.

[0032] The slave station 2 includes the same parts as the master station 1, namely, a transmission baseband signal processing unit 201, an RF unit 202, an antenna 203, a reception baseband signal processing unit 204, and a GNSS receiver 205, and further includes a control unit 206 and a synchronization unit 207. The synchronization unit 207 performs synchronization processing to synchronize the operation of the slave station 2 with the DL signal received from the master station 1 . The control unit 206 controls the timing of transmission and reception and monitors the propagation conditions in the device itself, just like the control unit 106 in the master station 1. However, regarding the movement of bandwidth and frequency channel, it operates according to instructions from the master station 1.

[0033] Furthermore, although not shown in the figure, the master station 1 and the slave station 2 of this communication system are provided with components necessary for communication, such as a signal processing unit and a radio unit that perform signal processing for a communication different from FWA (for example, a wireless LAN (Local Area Network)) in order to communicate with other FWA communication stations as will be described later.

[0034] [FWA operation: Figure 1] Next, the basic operation of FWA will be explained using Figure 1. First, the transmitting baseband signal processing unit 101 of the master station 1 places a synchronization preamble at the beginning of the DL subframe, and then performs error correction coding and modulation on the control information and user information to be transmitted in the DL subframe and places the result immediately after the preamble.

[0035] On the other hand, the GNSS receiver 105 outputs a 1-second periodic 1PPS signal, which serves as the reference timing, to the control unit 106, and the control unit 106 synchronizes a transmission timing control signal for the DL subframe with the 1PPS signal and outputs it to the transmission baseband signal processing unit 101, so that the DL subframe is synchronized with the 1PPS signal and output to the RF unit 102.

[0036] Similarly, the control unit 106 synchronizes the reception timing control signal of the UL subframe with the 1PPS signal and outputs it to the reception baseband signal processing unit 104 . Thereafter, the DL subframe is frequency-converted from the baseband to the radio frequency band in the RF unit 102, amplified, and then output as a radio wave from the antenna 103.

[0037] Then, in slave station 2, antenna 203 receives the DL subframe, and RF unit 202 converts the frequency from the radio frequency band to the baseband. At this point, synchronization has not been established between slave station 2 and master station 1, so synchronization unit 207 detects the synchronization preamble placed at the beginning of the DL subframe, and if it detects the preamble, notifies control unit 206 of the reception timing.

[0038] Since the control unit 206 also receives a 1PPS signal from the GNSS receiver 205, the control unit 206 calculates a propagation delay time t from the reception timing of the preamble and the 1PPS signal, and outputs a reception timing control signal for the DL subframe that is delayed by t from the reference timing to the reception baseband signal processing unit 204, and also outputs a transmission timing control signal for the UL subframe that is advanced by t from the reference timing to the transmission baseband signal processing unit 201. In practice, the synchronization establishment process is performed by also referring to control information such as ID included in the DL subframe, but details are omitted here.

[0039] After synchronization is established, the DL subframe is frequency-converted from the radio frequency band to the baseband in the RF unit 202, and then demodulated and error-corrected and decoded in the received baseband signal processing unit 204. Furthermore, the transmission baseband signal processing unit 201 performs error correction coding and modulation on the control information and user information to be transmitted in the UL subframe to form the UL subframe, and outputs it to the RF unit 202 at a timing that is advanced by t from the reference timing, as will be described later. The transmission and reception timing will be described in detail using FIG. 6. The UL subframe is then frequency converted from baseband to radio frequency band and amplified in RF section 202, and then output as radio waves from antenna 203.

[0040] After synchronization is established, the master station 1 receives the UL subframe at the antenna 103. However, the slave station 2 adjusts the transmission timing of the UL subframe to match the reception timing of the UL subframe at the master station 1. Therefore, the frequency conversion from the radio frequency band to baseband in the RF unit 102 and the demodulation and error correction decoding in the reception baseband signal processing unit 104 can be performed in accordance with the fixed timing generated by the control unit 106 in synchronization with 1 PPS.

[0041] In this way, by adjusting the transmission and reception timing of the slave station 2 so as to absorb the propagation delay time between the master station 1 and the slave station 2, synchronization is achieved in the FWA system composed of the master station 1, which serves as the reference for the transmission and reception timing, and the slave station 200, which is subordinate to the transmission and reception timing of the master station 1.

[0042] [Example of FWA deployment in this communication system: Figure 2] This communication system is equipped with multiple FWAs as shown in Figure 1. An example of the arrangement of FWAs in this communication system will be explained using Figure 2. Figure 2 is a schematic explanatory diagram showing an example of the arrangement of FWAs in this communication system. FIG. 2 shows an example in which three FWAs are arranged in close proximity, with the first FWA comprising a master station (1) (first master station) 1a and a slave station (1) (first slave station) 2a, the second FWA comprising a master station (2) (second master station) 1b and a slave station (2) (second slave station) 2b, and the third FWA comprising a master station (3) (third master station) 1c and a slave station (3) (third slave station) 2c. When there is no need to distinguish between the master stations 1a, 1b, and 1c, they may be referred to as master station 1. When there is no need to distinguish between the slave stations 2a, 2b, and 2c, they may be referred to as slave station 2.

[0043] FIG. 2 also shows the propagation delay time between the master station 1 and the slave station 2 in each FWA. The propagation delay time between the master station (1) 1a and the slave station (1) 2a in the first FWA and the propagation delay time between the master station (2) 1b and the slave station (2) 2b in the second FWA is T, and the propagation delay time between the master station (3) 1c and the slave station (3) 2c in the third FWA is 0.25T.

[0044] The first FWA master station (1) 1a, the second FWA slave station (2) 2b, and the third FWA master station (3) 1c are installed close to each other, for example, on the roof of the same building. As described above, in FWA, when the propagation conditions deteriorate due to rainfall or the like, the master station 1 performs control to expand the bandwidth used for communication or move the frequency channel. However, when multiple FWAs are placed close to each other as shown in FIG. 2, the control may cause interference, deteriorating the propagation conditions of other FWAs.

[0045] Therefore, in this communication system, each radio device monitors the propagation conditions in the FWA, and radio devices located nearby are connected via communication other than FWA (for example, short-range communication such as wireless LAN) to send and receive information about each other's propagation conditions.Furthermore, radio devices performing short-range communication notify the opposing FWA station of the propagation conditions received via short-range communication, thereby allowing multiple FWA devices to share each other's propagation conditions and use them to control the movement of bandwidth and frequency channels. In the example of Figure 2, a master station 1a, a slave station 2b, and a master station 1c are located close to each other, and they communicate over short distances via wireless LAN to transmit and receive information about the propagation conditions. The information about the propagation conditions indicates the level (degree) of interference.

[0046] [First embodiment] A communication system (first communication system) according to a first embodiment will be described with reference to Figures 1 and 2. In the first communication system, the master station 1 of each FWA autonomously controls bandwidth and the like by referring to the propagation conditions of other FWAs that it has acquired.

[0047] The operation of the first communication system will now be described. Each wireless device (master station 1, slave station 2) shown in Figure 2 measures (monitors) the received field strength from the FWA received signal and stores it as propagation status information (propagation status value). Furthermore, each wireless device transmits information about its own propagation status to the opposite FWA station and stores the propagation status information received from the opposite station.

[0048] In the example of FIG. 2, the master station (1) 1a transmits information on the propagation conditions of the master station (1) 1a and the slave station (1) 2a of the first FWA to the slave station (2) 2b and the master station (3) 1c arranged nearby via wireless LAN. Similarly, the slave station (2) 2b transmits information on the propagation conditions of the master station (2) 1b and the slave station (2) 2b of the second FWA to the master station (1) 1a and the master station (3) 1c, and the master station (3) 1c transmits information on the propagation conditions of the master station (3) 1c and the slave station (3) 2c of the third FWA.

[0049] As a result, the master station (1) 1a, slave station (2) 2b, and master station (3) 1c, which are located close to each other, receive and share information about the propagation conditions of each wireless device in the other FWAs. In addition, the slave station (2) 2b transmits the received information on the propagation status of the other FWA to the opposing master station (2) 1b using the FWA, and the master station (2) 1b also shares the information on the propagation status of the other FWA.

[0050] Furthermore, the master station (1) 1a and the master station (3) 1c may also transmit information on the propagation conditions to the opposing slave station (1) 2a and slave station (3) 2c, respectively, so that all of the radio devices constituting the three adjacent sets of FWAs can share the FWA propagation conditions with each other.

[0051] For example, if the second FWA is unable to ensure sufficient transmission speed due to deterioration in wireless communication quality caused by rain attenuation or the like, the master station (2) 1b performs control such as widening the bandwidth of its own FWA or moving the frequency channel to compensate for the decrease in throughput caused by rain. The following describes the case where the bandwidth is widened as an example. At this time, the master station (2) 1b of the second FWA controls the bandwidth while monitoring information on the propagation conditions of the other shared FWAs.

[0052] Specifically, when the master station (2) 1b widens the bandwidth in the second FWA, if there is no change in the information on the propagation status of the other FWAs received from the slave station 2b, it determines that interference is not occurring and widens the bandwidth further, or if it detects that the information on the propagation status of one of the radio devices of the other FWAs has become lower than a predetermined value, it determines that the other FWAs are being affected and controls to narrow the bandwidth of the second FWA that was once widened.

[0053] In this way, in the first communication system, each master station 1 can autonomously determine an appropriate bandwidth and channel while monitoring the propagation conditions of other FWAs, and can perform good communication while suppressing deterioration of the propagation conditions due to interference across multiple FWAs.

[0054] [Second embodiment] Next, a communication system according to a second embodiment (second communication system) will be described. The second communication system is configured to include a monitoring control device, which centrally monitors the values ​​of the propagation conditions of multiple FWAs and notifies the master station of each FWA of the propagation conditions of the other FWAs.

[0055] [Schematic configuration of the second communication system: Figure 3] The configuration of the second communication system will be explained using Fig. 3. Fig. 3 is a schematic configuration diagram of the second communication system. Note that the second communication system is also applied to the three FWAs shown in Fig. 2, and each FWA has the arrangement shown in Fig. 2. As shown in FIG. 3, the second communication system includes a master station (1) 1a, a master station (2) 1b, a master station (3) 1c, a slave station (1) 2a, a slave station (2) 2b, a slave station (3) 2c, a monitoring control device 3, and a network 4.

[0056] Each master station 1 and the monitoring control device 3 are connected via a network 4 by wire or wirelessly (LAN, wireless LAN). The monitoring and control device 3 is a computer basically equipped with a control unit, a storage unit, and an interface unit.

[0057] In the second communication system, unlike the first communication system in which closely located radio devices communicate with each other to share propagation conditions, each master station 1 reports information about the propagation conditions to the monitoring and control device 3, which then monitors the propagation conditions of all radio devices in the system. Furthermore, the monitor and control device 3 notifies the master station 1 that controlled the bandwidth and frequency channels whether or not the control had an adverse effect on the propagation conditions of other FWAs.

[0058] The master station 1 in the second communication system stores information on the propagation conditions of its own FWA (information on the propagation conditions of the master station 1 and the opposing slave station 2) and transmits this information to the monitoring control device 3. Furthermore, when the propagation conditions of the FWA deteriorate, the master station 1 controls the expansion of the bandwidth and the movement of the frequency channel, and transmits the bandwidth and frequency channel of the FWA to the monitoring control device 3. The transmission of the propagation condition information, bandwidth, and frequency channel to the monitoring control device 3 is, for example, periodic or when control is performed. The monitoring control device 3 stores the information on the propagation conditions, bandwidths, and frequency channels received from each master station 1 in a propagation condition monitoring table provided in the storage unit.

[0059] [Propagation status monitoring table: Figure 4] Here, the propagation condition monitoring table of the monitor control device 3 will be explained using Fig. 4. Fig. 4 is a schematic explanatory diagram of the propagation condition monitoring table. As shown in FIG. 4, the propagation status monitoring table stores, for each FWA, the values ​​of the propagation status of master 1 and slave 2 (values ​​of received field strength), the value of the frequency channel used for communication of the FWA, and the value of the bandwidth.

[0060] [Operation of the second communication system] The operation of the second communication system will now be described. When a bandwidth or frequency channel is controlled in any of the master stations 1, the monitoring and control device 3 determines whether the propagation condition values ​​in other FWA radio devices have deteriorated below the reference value, and feeds back the result to the controlling master station 1.

[0061] For example, if the propagation status values ​​of other FWAs have not deteriorated, the monitoring control device 3 notifies the master station 1 that performed the control that the current control has not adversely affected the other FWAs ("OK"), and if interference has occurred and the propagation status values ​​of other FWAs have deteriorated, the monitoring control device 3 notifies the master station 1 that this has occurred ("NG").

[0062] Upon receiving the NG notification, the master station 1 performs control in the opposite direction, such as returning the expanded bandwidth to half the original size if the bandwidth was expanded, or returning the frequency channel to the original frequency before the change.

[0063] As a result, in the second communication system, the monitoring control device 3 can perform comprehensive control based on the propagation conditions of all FWAs to prevent control such as excessive expansion of bandwidth, and can suppress deterioration of the propagation conditions due to interference throughout the system, thereby enabling good communication.

[0064] [Monitoring and control device processing: Figure 5] The processing of the monitor control device 3 in the second communication system will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the processing of the monitor control device in the second communication system. 5, when the monitoring control device 3 receives information about the propagation conditions from the master station 1 (S11), it stores the information in the propagation conditions monitoring table (S12). Then, when the monitoring control device 3 receives the frequency channel and bandwidth (S13), it compares them with the values ​​stored in the propagation conditions monitoring table to determine whether they have changed (S14). If they have not changed (No), the process returns to step S11.

[0065] If there is a change in the process S14 (Yes), the monitor control device 3 updates the values ​​of the propagation condition monitor table with the received bandwidth and frequency channel and stores them (S15). The case where the bandwidth or frequency channel is changed means that control is performed in the master station 1 that is the source of transmission.

[0066] Then, the monitoring control device 3 checks the propagation status of other FWAs (S16), determines whether any have dropped below the reference value (S17), and if there are no drops (No), notifies the master station 1, which is the control source (the sender of process S13), of "OK" to inform that the control is appropriate (S18), and returns to process S11.

[0067] Also, if any of the propagation conditions values ​​has dropped below the reference value in process S17, the monitoring control device 3 notifies the controlling master station 1 of "NG" indicating that the control is inappropriate (S19), and returns to process S11. In this manner, the processing of the monitoring control device 3 of the second communication system is carried out.

[0068] Note that instead of notifying the control source master station 1 whether the bandwidth or frequency channel control is appropriate, the monitoring control device 3 may notify the control source master station 1 of information on the propagation conditions of other FWAs, and the control source master station 1 may control the bandwidth or frequency channels based on the information on the propagation conditions of other FWAs, similar to the first communication system.

[0069] Also, the monitoring and control device 3 may be configured to be operated by any master station 1 in the system (for example, master station (1) 1a). In this case, the master station (2) 1b and master station (3) 1c of the other FWAs report information on the propagation status of their own FWAs, bandwidth, and frequency channel to the master station (1) 1a that performs monitoring and control.

[0070] In the second communication system, the monitoring and control device 3 centrally monitors the propagation conditions of the FWAs within the system, and when the master station 1 of any FWA controls the bandwidth or frequency channel, it checks the propagation conditions of the other FWAs and notifies the controlling master station 1 whether the control is appropriate or not, thereby reducing the processing load of the master station 1.

[0071] [Measurement of propagation conditions using RACH] In order to measure propagation conditions that reflect interference levels and the like, there is a method of transmitting and receiving signals for measuring propagation conditions using a random access channel (RACH) that allows all stations to transmit and receive simultaneously. When applying RACH to a time division duplex (TDD) system that alternates between transmission and reception on the same frequency channel, as in the FWA of this communication system, timing synchronization must be performed using GNSS to align the RACH timing at all stations.

[0072] [First frame structure and transmission / reception timing: Figure 6] Next, an example of a frame structure and transmission / reception timing in this communication system will be described with reference to Fig. 6. Fig. 6 is an explanatory diagram showing a first frame structure and transmission / reception timing in this communication system. FIG. 6 shows the transmission and reception timing in the communication system shown in FIG. 2, and is applicable to both the first and second communication systems described above.

[0073] As shown in Figure 2, the propagation delay time between the master station (1) 1a and slave station (1) 2a of the first FWA, and the propagation delay time between the master station (2) 1b and slave station (2) 2b of the second FWA is T, and the propagation delay time between the master station (3) 1c and slave station (3) 2c of the third FWA is 0.25T. In other words, the maximum propagation delay time excluding interference in the communication system of Figure 2 is T.

[0074] First, the frame structure and operation timing of the master station 1 will be described. As shown in Figure 6, in master station (1) 1a, master station (2) 1b, and master station (3) 1c, a DL subframe is placed in which a DL (Down Link) signal is transmitted in synchronization with the 1PPS signal output by the GNSS receiver 105, followed by a guard time (G) to prevent the DL signal and the UL (Up Link) signal from overlapping each other. Since each FWA is synchronized with the 1PPS signal, the frame start timings of the master station (1) 1a, the master station (2) 1b, and the master station (3) 1c are synchronized.

[0075] In this communication system, the time width of the guard time is set to 2T, and if the round-trip propagation delay time is 2T or less, that is, if the one-way propagation delay time is T or less, the DL signal and the UL signal will not overlap, preventing interference between the DL signal and the UL signal.

[0076] Then, following guard time, T RA RACH with a time width of +3T is placed. RA is a transmission section in the RACH, and when a signal is transmitted in the RACH, the time width T RA Transmit during the interval. Finally, a UL subframe for receiving a UL signal is placed to form a frame.

[0077] Next, the frame structure and operation timing of the slave station 2 will be described. The slave station (1) 2a and the slave station (2) 2b receive the DL subframe (DL subframe (received)) delayed by the propagation delay T from the 1PPS signal output by the GNSS receiver 205. Next, the RACH and UL subframes (transmission) are arranged ahead of the end of the frame by the propagation delay T so as to match the reception timing of the RACH and UL subframes at the opposing master station (1) 1a and master station (2) 1b.

[0078] As a result, in slave station (1) 2a and slave station (2) 2b, the first half of the guard time is shortened by T due to the delay time (T) from the 1PPS signal to the DL subframe (reception), and the second half of the guard time is shortened by T due to the advance time (T) of the UL subframe (transmission), making it appear as if the guard time has disappeared.

[0079] Furthermore, the slave station (3) 2c receives the DL subframe with a delay of 0.25T, which is the propagation delay from the master station (3) 1c, relative to the 1PPS signal. Following this, the RACH and UL subframes are arranged ahead of the end of the frame by a propagation delay of 0.25T so as to match the reception timing of the RACH and UL subframes in the opposing master station (3) 1c. Therefore, the first half of the guard time is shortened by 0.25T by the DL subframe (reception), and the second half of the guard time is shortened by 0.25T by the RACH, so that the remaining guard time appears to have a time width of 1.5T.

[0080] Next, a method of transmitting and receiving a signal for measuring propagation conditions using the RACH will be described with reference to FIG. As shown in Figure 6, the earliest timing among all six stations is T RA The slave stations (1) 2a and (2) 2b transmit signals in this section. RA The timing of this section overlaps with the guard times of other stations.

[0081] The guard time is provided to prevent the DL signal and the UL signal from overlapping with each other, and processing for receiving the RACH may be performed during this period, allowing transmission and reception via the RACH without any problems.

[0082] On the other hand, of all six stations, the ones that transmit signals from the beginning of the RACH at the latest timing are master station (1) 1a, master station (2) 1b, and master station (3) 1c, and the section from the end of the RACH of these three stations to T (RACH reception section) overlaps with the UL subframe (transmission) of slave station 2 of another FWA.

[0083] In the communication system shown in Figure 2, the farthest distance is between slave station (1) 2a and master station (2) 1b. When the FWA is operating without interference, no transmission or reception takes place between these stations. However, when considering the propagation delay time when interference occurs, the propagation delay time is 2T.

[0084] If the time width of the RACH is short, when interference occurs between FWAs, for example, the RACH transmitted from the slave station (1) 2a overlaps with the UL subframe (reception) of the master station (2) 1b, causing problems in receiving the UL signal. Therefore, to transmit and receive data on the RACH without any problems, the time width of the RACH should be set to T RA Just make it +3T.

[0085] [Frame utilization efficiency] As described above, in the first frame configuration and transmission / reception timing shown in FIG. 6, in order to enable transmission / reception of RACH up to a propagation delay of 2T, taking into consideration interference, the time width of RACH is set to T RA +3T is necessary, and the proportion of guard time and RACH in the frame increases, which reduces the utilization efficiency of the frame.

[0086] [RACH transmission timing] In the first frame configuration and transmission / reception timing, as shown in FIG. 6, the timing at which a station transmits a signal on the RACH (T RASince the timing of the RACH is different, the receiving side must widen the interval in which it searches for the received signal, and furthermore, it is not possible to directly calculate the propagation delay time from the reception timing of the RACH.

[0087] Therefore, in this system, the second frame structure and transmission / reception timing can be applied. As will be described later, the second frame configuration and transmission / reception timing include a guard time function in the RACH, and the RACH transmission timing of all stations is made the same.

[0088] [Second frame structure and transmission / reception timing: Figure 7] The second frame structure and transmission / reception timing will be described with reference to Fig. 7. Fig. 7 is an explanatory diagram showing the second frame structure and transmission / reception timing in this system. Note that Figure 7 shows the transmission and reception timing in the communication system shown in Figure 2. In the absence of interference, the maximum propagation time is T because transmissions other than those within each FWA are not taken into consideration. In the presence of interference, there is a possibility of reception between different FWAs, so the maximum propagation delay time is 2T between the slave station (1) 2a and the master station (2) 1b.

[0089] As shown in Figure 7, in the second frame configuration, the guard time function is included in the RACH, and the time width of the entire RACH is set to a maximum of T RA It is +4T. In the first frame configuration shown in Figure 6, the combined time span of the guard time and RACH is T RA +5T, and by using the second frame structure, the time width can be reduced by 1T, which can be used for DL ​​subframes and UL subframes, improving frame utilization efficiency.

[0090] RACH to T RA By setting it to +4T, the RACH signal transmitted from the slave station (1) 2a is received within the RACH of the master station (2) 1b, and does not affect the reception of the UL subframe.

[0091] Within the RACH, the time width corresponding to the guard time is 2T (twice the maximum propagation delay time among multiple FWAs), which is the same as the guard time in the first frame configuration, but this time width apparently increases or decreases. For example, in the slave station (1) 2a and the slave station (2) 2b, as explained in FIG. 6, 2T corresponding to the guard time is lost, and the time width of the RACH becomes the shortest, and the time length of the RACH becomes T RA It's +2T.

[0092] In addition, in the slave station (3) 2c, the beginning of the DL subframe (reception) is delayed by 0.25T relative to the 1PPS signal, and the UL subframe (transmission) is advanced by 0.25T from the end of the frame, so the time corresponding to the guard time is reduced by 0.5T, and the time length of the RACH is T RA It will be +3.5T.

[0093] When the RACH is the shortest, as in the case of slave station (1) 2a and slave station (2) 2b, the RACH of the communication station always overlaps with the RACH of the other master station 1 and slave station 2. Therefore, all communication stations that transmit signals on the RACH transmit at the beginning of this section, and the time width of the section where the RACHs always overlap is set to T RA If +2T is set, even if interference occurs, transmission and reception are possible on the RACH up to a propagation delay time of 2T. In addition, each communication station must have a T RA Reception processing only needs to be performed in the +2T section.

[0094] The transmission timing of the RACH is offset by DL subframe length+T from the reference timing (timing of the beginning of the frame of master station 1) defined by 1PPS. Only one station transmits on the RACH of a particular frame, but regardless of which station transmits, the transmission occurs at the same timing in each frame (a timing offset of DL subframe length + T from the reference timing).

[0095] Specifically, as shown in FIG. 7, master station (1) 1a, master station (2) 1b, and master station (3) 1c transmit RACHs with an offset that includes the DL subframe and the time width T after the DL subframe. In addition, in the slave station (1) 2a and the slave station (2) 2b, the offset is the sum of the time width T before the DL subframe and the DL subframe. In the slave station (3) 2c, the offset is the sum of the time width 0.25T before the DL subframe, the time width of the DL subframe, and the time width of 0.75T after the DL subframe.

[0096] Here, T is a value determined by system design, so that in this system, the transmission timing can be uniquely determined. This eliminates the need for a long search on the RACH receiving side, and furthermore, since the RACH transmission timing is known, the propagation delay can be easily calculated from the RACH reception timing.

[0097] In the second frame configuration and transmission / reception timing, the maximum time width of the RACH is set to T RA +2T plus 2T for guard time, T RA +4T. This makes it possible to prevent the transmission signal of the RACH from overlapping with the DL subframe or UL subframe up to the propagation delay T between the opposing master station 1 and slave station 2.

[0098] Furthermore, even if interference occurs, in this example, the maximum propagation delay time is 2T between the slave station (1) 2a and the master station (2) 1b, and the time width from the transmission timing of the RACH of the master station (2) 1b to the end of the RACH is T RA Since it is +3T, there is no problem in transmitting and receiving the RACH.

[0099] [Effects of the embodiment] According to the first communication system, there are provided a plurality of sets of fixed wireless access systems (FWA) each having a master station 1 and a slave station 2 that is subordinate to the control of the master station 1, and information on the propagation conditions in a specific FWA is transmitted to and shared with other FWAs using communication other than the FWA, and the master station 1 of the other FWA controls the movement of frequency channels or the increase or decrease of bandwidth based on the shared information on the propagation conditions of the FWAs, and when the propagation conditions deteriorate due to rainfall or the like, the master station 1 can control the movement of frequency channels or the expansion of bandwidth in its own system to the extent that it does not adversely affect the propagation conditions of the other FWAs, and even if multiple FWAs are installed nearby, there is an effect that it is possible to maintain good communication quality while suppressing the effects of interference with each other.

[0100] Furthermore, according to the second communication system, the monitoring and control device 3 intensively monitors the propagation conditions of the FWAs within the system, and when the master station 1 of any FWA controls the bandwidth or frequency channel, it checks the propagation conditions of the other FWAs and notifies the controlling master station 1 whether the control is appropriate or not, which has the effect of reducing the processing load of each master station 1.

[0101] Furthermore, according to this communication system, the second frame structure and transmission / reception timing provide the RACH with a guard time function, and all master stations 1 and slave stations 2 in the system transmit the RACH at a timing that is a specific offset time relative to the 1PPS signal. This shortens the time width of the RACH, lengthens the time allocated to the DL subframe and the UL subframe, improves frame utilization efficiency, and also enables the receiving side to easily calculate the propagation delay from the reception timing of the RACH. [Industrial Applicability]

[0102] The present invention is suitable for a communication system and a communication method in which, when multiple FWA communication stations are installed close to each other, the propagation conditions can be shared between the FWA communication stations, thereby maintaining good communication quality among them. [Explanation of symbols]

[0103] REFERENCE SIGNS LIST 1...master station, 2...slave station, 3...monitoring and control device, 4...network, 101...transmission baseband signal processing section, 102, 202...RF section, 103, 203...antenna, 104, 204...reception baseband signal processing section, 105, 205...GNSS receiver, 106, 206...control section, 207...synchronization section

Claims

1. A communication system comprising a plurality of fixed wireless access systems each having a master station that controls transmission and reception and a slave station that is subordinate to the control of the master station, A communication system characterized in that information on propagation conditions in communication of a specific fixed wireless access system is transmitted to and shared with other fixed wireless access systems using a separate communication method, and the master station of the other fixed wireless access system controls the movement of frequency channels or the increase or decrease of bandwidth based on the shared propagation condition information.

2. 2. The communication system according to claim 1, wherein the information on the propagation conditions indicates a degree of interference, and when a transmission environment in the other fixed wireless access system deteriorates, a master station of the other fixed wireless access system controls movement of a frequency channel or increase or decrease of a bandwidth based on the information on the propagation conditions in the specific fixed wireless access system.

3. A communication system comprising a plurality of fixed wireless access systems each having a master station that controls transmission and reception and a slave station that is subordinate to the control of the master station, a monitoring and control device that receives and stores information on propagation conditions in communications among the plurality of fixed wireless access systems using another communication method, and, when one of the fixed wireless access systems performs control of shifting of frequency channels or increasing or decreasing of bandwidth, notifies the controlling fixed wireless access system whether the control is appropriate or not, based on the propagation conditions of the fixed wireless access systems other than the controlling fixed wireless access system.

4. 4. The communication system according to claim 1, wherein the master station and the slave station of the plurality of fixed wireless access systems transmit the RACH at a timing that corresponds to a specific offset time with respect to one PPS signal.

5. the specific offset time is a time obtained by adding a maximum transmission delay time in the plurality of fixed wireless access systems to a DL subframe time, 5. The communication system according to claim 4, wherein the master station and the slave station receive the RACH within a time obtained by adding, from the timing of transmission of the RACH, the time required to transmit the RACH and twice the maximum transmission time.

6. A communication method in a communication system including a plurality of fixed wireless access systems each having a master station that controls transmission and reception and a slave station that is subordinate to the control of the master station, comprising: A communication method characterized in that a specific fixed wireless access system transmits information on propagation conditions in communication of the fixed wireless access system to another fixed wireless access system using a different communication method, and shares the information, and the master station of the other fixed wireless access system controls the movement of frequency channels or the increase or decrease of bandwidth based on the shared propagation condition information.

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