JP2020053830A - FDMA digital radio system - Google Patents

Abstract

To provide a technique which smoothly performs the handoff of a mobile station with an efficient use of frequency in a radio communication system of an FDMA method.SOLUTION: A radio communication system 1 is an FDMA digital radio system which includes a plurality of base stations 20, and a mobile station 30 communicating with the base stations 20. Each base station 20 uses a common control channel Cch to perform communication at each predetermined timing. The mobile station 30 stores a transmission frame number in a communication channel (super-frame), and based on a transmission frame number transmitted from a base station 20, determines the transmission timing of another base station 20 and measures the reception electric field of a signal transmitted from the other base station 20, so that the mobile station can perform automatic hand-off if the reception electric field level of a captured base station is deteriorated.SELECTED DRAWING: Figure 2

Description

  The present invention relates to FDMA digital wireless systems.

  ARIB STD T61 has proposed a standard as a digital mobile communication system for business use including public business use by the FDMA system. In this standard, for example, as shown in FIG. 1, a command console 114, a communication console 115, a management monitoring control console 113, a control server 112, a line control device 111, a base station 120, a mobile station 130 (on-vehicle radio, portable radio ) Is used as a communication means such as business communication.

  In the conventional FDMA system, one frequency for communication between a base station and a mobile station is required for each base station for a control channel and a plurality of frequencies for a communication channel. The example of FIG. 1 shows a communication system configuration in which three base stations 120 are assigned three communication channels. A total of 4n frequencies need to be allocated to the entire communication system for the control channel and the communication channel.

  In the case of such a frequency configuration, if the number of frequencies allocated to the range in which the user works is small, it is not possible to cover the entire business range. Therefore, various techniques for effectively utilizing a small number of frequencies have been proposed (for example, see Patent Document 1). Patent Literature 1 discloses a technique for sharing a control channel of one frequency and a communication channel of n frequencies.

JP 2015-192374 A

  According to the technology disclosed in Patent Literature 1, frequencies can be used more efficiently than in the past, but there is a demand for technology that further improves convenience. For example, there is a need for a technique for performing handoff of a mobile station smoothly while realizing efficient use of frequency.

  The present invention has been made in view of such circumstances, and has as its object to solve the above problems.

The present invention is an FDMA digital radio system including a plurality of base stations and a mobile station communicating with the base station, wherein the mobile station stores a transmission frame number in a communication channel of each of the base stations. And determining a transmission timing of another base station based on the transmission frame number transmitted from the base station, and measuring a reception electric field of a signal transmitted from the another base station.
The present invention is an FDMA digital wireless system including a plurality of base stations and a mobile station communicating with the base station, wherein the base station transmits a transmission frame number and a transmission frame number of each base station. The mobile station determines the transmission timing of another base station based on the received transmission frame number and the transmission frame number of each base station, and receives a signal transmitted from the other base station. Measure the electric field.
Further, each of the base stations may transmit the control channel by one signal.

  ADVANTAGE OF THE INVENTION According to this invention, in the radio | wireless communications system of FDMA system, the technique which implement | achieves the efficient use of a frequency, and can perform the handoff of a mobile station smoothly is realizable.

FIG. 1 is a diagram illustrating a schematic configuration of a wireless communication system according to a conventional technique. FIG. 1 is a diagram illustrating a schematic configuration of a wireless communication system according to an embodiment. FIG. 4 is a diagram illustrating an example of a frame configuration of a control channel and a communication channel according to the embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the present embodiment, a digital mobile communication system for business use, including public business use according to the SCPC / FDMA scheme, specified by the ARIB STD T61 standard will be described as an example.

  FIG. 2 shows a schematic configuration of the wireless communication system 1 according to the present embodiment. The wireless communication system 1 includes a center facility 10 as a higher-level device, a plurality of base stations 20, and a mobile station 30 that communicates with the base stations 20. The center equipment 10 and the base station 20 are connected by a predetermined network line 2.

  As the base station 20, base stations (1) 21 to (5) 25 are provided. Base station numbers 1 to 5 are set as identifiers in each of the base station (1) 21 to the base station (5) 25. The mobile station 30 includes, for example, a mobile station (1) 31, which is a portable wireless device, and a mobile station (2) 32, which is an in-vehicle wireless device.

  The center facility 10 includes a line control device 11, a control server 12, a management monitoring control console 13, a command console 14, and a communication console 15. The management monitoring control console 13 manages the operation of the entire system as a whole. The control server 12 is connected to the line control device 11 and centrally controls wireless communication with the mobile station 30 via the base station 20.

  The command console 14 is connected to the line control device 11 via the control server 12 and is a device that operates each function of the wireless communication system 1. The communication console 15 is connected to the line controller 11 and performs wireless communication with the mobile station 30 individually. The command console 14 and the communication console 15 may be provided in the same facility or may be provided in different facilities.

  The line control device 11 is further connected to a base station 20, which is under the control of the center facility 10, here, the base station (1) 21 to the base station (5) 25.

  The base station 20 communicates with the mobile station 30 using the same frequency configuration. Although details will be described later, the base station (1) 21 to the base station (5) 25 share one control channel Cch of the same frequency. However, since the control channel Cch of the same frequency is used, the transmission timing of each base station 20 has a time difference so as not to interfere. The mobile station 30 (here, the mobile station (1) 31, the mobile station (2) 32) transmits information indicating at which frame number the base station (1) 21 to the base station (5) 25 communicate with each other. It is stored in advance.

  In addition, the base station (1) 21 to the base station (5) 25 perform accurate synchronization by synchronizing transmission timing, for example, by receiving and using a GNSS signal (GPS signal). The downlink control channel Cch from the base station 20 to the mobile station 30 includes a code (identifier) for identifying the base station 20 and a frame number. For example, the base station number is set to the color code of the control channel Cch as the identification code.

  Further, three communication channels (S1ch to S3ch) are allocated to the base station (1) 21 to the base station (5) 25, respectively, and a free communication channel is selected to communicate with the mobile station 30. .

  That is, the frequency Freq_01 is assigned to the control channel Cch, and the frequencies Freq_02 to Freq_04 are assigned to the communication channels S1ch to S3ch, respectively, and they are synchronized.

  The communication operation between the base station 20 and the mobile station 30 will be described with reference to a frame configuration example of the control channel Cch and the communication channels S1ch to S3ch in FIG. Numbers (#) 1 and 2 indicate the frame structure of the control channel Cch of the base station (1) 21. Hereinafter, numbers (#) 3, 4, number (#) 5, 6, number (#) 7, 8, Numbers (#) 9 and 10 indicate the frame configurations of the control channels Cch of the base station (2) 22, the base station (3) 23, the base station (4) 24, and the base station (5) 25, respectively. In each control channel Cch, an odd number is a down signal and an even number is an up signal. The number (#) 11 indicates the frame configuration of the communication channels S1ch to S3ch.

  When there is no “call” from the mobile station 30, the base station 20 stops all communication channels S1ch to S3ch. When a “call” is made, the vacant communication channels S1ch to S3ch are activated in accordance with an instruction from the center equipment 10 (line control device 11) of the host device. The line control device 11 assigns a number corresponding to the control channel Cch to the communication channels S1ch to S3ch. In the example of FIG. 3, the communication channels S1ch to S3ch have a 50-frame configuration of 40 ms per frame from the beginning of even-numbered seconds to the end of odd-numbered seconds, and are assigned frame numbers of 0 to 49. A frame having a length of 40 ms is referred to as a “wireless frame” for convenience, and a set of wireless frames of frame numbers 0 to 49 is referred to as a “superframe”.

  The communication timing of each base station 20 is as follows. The base station (1) 21 transmits 10 frames (400 ms) from the beginning of the even number of seconds. Subsequently, the base station (2) 22 to the base station (5) 25 sequentially transmit 10 frames in the same manner. It takes a total of 2 seconds for all the base stations 20 to make one round of transmission. As described above, the base station (1) 21 to the base station (5) 25 are synchronized by the GPS signal.

  That is, the frame numbers 0 to 9 of the superframe correspond to the frame numbers 0 to 9 of the control channel Cch of the base station (1) 21. The frame numbers 10 to 19 of the superframe correspond to the frame numbers 0 to 9 of the control channel (Cch) of the base station (2) 22. The frame numbers 20 to 29 of the superframe correspond to the frame numbers 0 to 9 of the control channel (Cch) of the base station (3) 23. The frame numbers 30 to 39 of the superframe correspond to the frame numbers 0 to 9 of the control channel (Cch) of the base station (4) 24. The frame numbers 40 to 49 of the superframe correspond to the frame numbers 0 to 9 of the control channel (Cch) of the base station (5) 25.

  The mobile station 30 can convert the base station number of the color code of the control channel Cch and the frame number thereof into superframe numbers of the communication channels S1ch to S3ch. For example, if the base station number of the control channel Cch is “2” and the frame number is “3”, the frame number of the superframe is “13”.

  Note that, according to the standard, the radio frame serving as the uplink transmission enable / disable signal of the control channel Cch has a start timing offset by 60 ms after the downlink radio frame, and an end timing offset by 60 ms before the need for a partial echo response. , 7 frames.

  Processing when the power of the mobile station 30 is turned on will be described. When the power is turned on, the mobile station 30 measures the received electric field of the control channel Cch transmitted from each base station 20 for 2 seconds (that is, the time required until all the base stations 20 transmit a signal once).

  The mobile station 30 determines the base station 20 with reference to the color code included in the control channel Cch, and compares the received electric fields of the respective base stations 20. The mobile station 30 synchronously acquires the base station 20 having the highest reception electric field. That is, synchronization acquisition starts at the timing when the selected base station 20 transmits. When the synchronization is successfully acquired, the broadcast information is received, the location is registered, and the acquisition of the base station is completed. If synchronization acquisition has failed or location registration has failed, the mobile station 30 selects the base station 20 having the next highest reception electric field and performs the synchronization acquisition processing as described above.

  When the mobile station 30 transmits, it transmits at the communication timing of the acquisition base station. However, since the transmission of the control channel Cch of the mobile station 30 needs to receive the partial echo for arrival confirmation as described above, the transmission is performed up to three frames before the capture base stops. In the example of FIG. 3, since the base station 20 transmits 10 frames, the mobile station transmits the 0th to 6th frames.

  Next, a handoff process when the level is reduced during communication will be described. The mobile station 30 determines the communication timing of the base station 20 other than the acquisition base station based on the frame number of the communication channel of the acquisition base station and the previously stored frame number with which each base station 20 communicates. The reception electric field of each base station 20 is measured at the timing.

  For example, when measuring the reception electric field of the base station (3) 23, the mobile station 30 measures the reception electric field of the control channel Cch corresponding to the frame numbers 20 and 21 of the communication channel (that is, the superframe). The handoff procedure after the level measurement is the same as before, but the base station 20 to be handed off may be determined by measuring the reception electric field for all base stations 20 other than the acquisition base station, or the reception level higher than a predetermined value may be determined. When the electric field is received, the handoff may be performed to the corresponding base station 20.

  As described above, in the configuration in which the control channel Cch is commonly used between the base stations 20, when the level of the reception electric field is reduced and the handoff becomes necessary, the mobile station 30 automatically searches for the base station 20 of the handoff destination. Handoff is possible.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of the components, and that such modifications are also within the scope of the present invention.

  For example, in the above-described embodiment, the mobile station 30 previously stores information on the transmission timing of each base station 20 (that is, which frame number of the superframe is used for communication). However, the base station 20 may put information on the neighboring base stations (such as the total number of base stations and the number of frames per base station 20) on the control channel Cch to be transmitted. In this case, the mobile station 30 does not need to store the transmission timing of the base station 20, and can determine the transmission timing of the base station 20 from the information transmitted from the base station 20. Therefore, even in the case of handoff, the mobile station 30 determines the transmission timing of another base station 20 other than the acquisition base station based on the information received from the base station 20, and determines the signal transmitted from the other base station 20. Can be measured.

  Further, in the above-described embodiment, the frequency of the control channel Cch shared by the base station 20 is only one (one channel), but may be a plurality of frequencies. When the communication area of the wireless communication system 1 is large and the number of base stations 20 is large, different control channels Cch are set for the base stations 20 that do not cover the same area. Can be realized.

REFERENCE SIGNS LIST 1 wireless communication system 2 network line 10 center equipment 11 line control device 12 control server 13 management and monitoring control console 14 command console 15 communication console 20 base stations 21 to 25 base station (1) to base station (5)
30 mobile station 31, 32 mobile station (1), mobile station (2)

Claims (3)

An FDMA digital wireless system comprising a plurality of base stations and a mobile station communicating with the base station,
The mobile station stores a transmission frame number in a communication channel of each of the base stations, and determines a transmission timing of another base station based on the transmission frame number transmitted from the base station, An FDMA digital wireless system for measuring a reception electric field of a signal transmitted from another base station. An FDMA digital wireless system comprising a plurality of base stations and a mobile station communicating with the base station,
The base station transmits a transmission frame number and a transmission frame number of each base station,
The mobile station determines the transmission timing of another base station based on the received transmission frame number and the transmission frame number of each base station, and determines the reception electric field of a signal transmitted from the other base station. An FDMA digital wireless system characterized by measuring.   The FDMA digital radio system according to claim 1 or 2, wherein each of the base stations transmits a control channel by one signal.

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