JPH06152503A - Mobile station position detecting method - Google Patents

Abstract

PURPOSE:To exactly control channel switching during communication or the like in a short time without using any special device or data base in a street microcell system by communicating intersection information from a base station to a mobile station. CONSTITUTION:A base station 12 stores the reception levels Lb-Ld of a radio wave from the base station 12 in the neighborhood of each intersection 19b-19d as a correction table. The base station 12 communicates the content of the table to the mobile station moving on a road 11a. In the mobile station, a control circuit 24 operates the level setting of a correction table corresponding level generating circuit 29 based on the table. The reception level detected by a reception level detecting circuit 25 is compared with the generation level of the generating circuit 29 by a level comparator circuit 31. When both levels are almost equal, it is communicated through the control circuit 24 to the base station 12. Thus, the base station 12 and the mobile station can recognize that the mobile station reaches the neighborhood of the intersection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile station position detecting method in a high quality and large capacity cellular mobile communication system which constitutes a service area along a road.

[0002]

2. Description of the Related Art In a conventional cellular mobile communication system having a small cell structure, the height of a base station antenna is higher than the height of surrounding buildings, and therefore radio waves from the base station propagate uniformly in all directions, so that the base station is covered. The service area is circular. Also,
In most cases, the mobile station cannot see through the base station because the mobile station is well below the surrounding building height. Therefore, the radio wave propagation characteristics can be uniformly treated as non-line-of-sight propagation characteristics within the service area. On the other hand, in a cellular mobile communication system (called a street microcell system) that aims to improve the frequency utilization rate by arranging small cells along the road and covering the service area with high density, the base station antenna height is around It is lower than the height of the building, and the radio wave propagation condition greatly differs depending on whether the base station and the mobile station are visible or not. For example,
It has been reported that the propagation loss increases by about 15 dB when an intersection turns from within the line-of-sight to outside the line-of-sight. IEICE Spring National Convention, B-
28).

FIG. 2A is a diagram for explaining a cell structure of the street microcell system. In this example, the road 11 is formed in a grid pattern and a base installed between adjacent intersections. Stations 12 are provided along the road 11 at appropriate intervals. The cell 13 of the base station 12 is elongated along the road 11. When viewed from the base station 12, the direction along the road 11 is in sight, whereas the direction that intersects with the road 11 after turning at the intersection of the road 11 is out of sight. When a base station is installed at an intersection, it can be seen in all four directions, but since radio waves fly too much, it is necessary to maintain a sufficient distance between stations to use the same frequency repeatedly. Compared with the case of installing a station, the frequency utilization rate is low and the system capacity is low.

FIG. 2B shows a situation in which the reception level at the mobile station changes depending on the relative position with respect to the base station. That is, when the roads 11b, 11c and 11d intersect the road 11a and the base station 12 is provided on the road 11a between the roads 11c and 11d, these roads 11a to 11
The mobile station reception level when the mobile station 14 moves is shown in d. The line 15 is the distance from the base station 12 along the road 11a, and the line 16 is the road 1 after turning the intersection of the road 11a.
The distances along 1b, 11c, and 11d are represented by the curve 17
Is each position within the line of sight from the base station 12, that is, the road 11a
The mobile station reception level at the curves 18b, 18c, 1
Reference numerals 8d indicate mobile station reception levels at the respective positions after turning the intersection, that is, on the roads 11b, 11c, and 11d.

When the mobile station 14 makes a turn at the intersection while communicating with the base station 12 on the road 11a, the reception level of the radio wave from the base station 12 is rapidly attenuated.
It is necessary to switch to the radio wave (communication channel) of the base station that covers 11c and 11d. When the mobile station takes the initiative in switching the communication channel, the following procedure is performed. (1) A mobile station that has detected that the reception level has dropped below a specified value monitors the radio waves from surrounding base stations, determines the base station that receives the highest reception level, and is currently performing communication. Then, the base station having the highest received level is requested to switch the channel. (2) The base station that has received this request notifies the control station (station controlling each base station) to that effect. The control station instructs the base station having the highest reception level to notify the idle communication channel. (3) Upon receiving the report of the idle communication channel, the control station causes the base station communicating with the mobile station to send a switching instruction signal to the idle communication channel to the mobile station. At the same time, the base station with the highest reception level is instructed to turn on the transceiver of the idle communication channel, and the wired communication path to the base station is received from the base station communicating with the mobile station. Switch to the line corresponding to the idle channel of the base station with the highest level. (4) The mobile station receiving the switching instruction signal switches to the instructed communication channel. This allows the mobile station to establish a communication channel with the base station having the highest reception level.

In order to perform communication without interruption, it is necessary to execute the above procedure accurately in a short time. In a conventional small cell configuration, the base station and the mobile station are almost invisible to each other, so when the mobile station detects a level drop and switches the channel during communication, even if it turns at the intersection, the There was no sudden change in the level, so it was not a big problem. However, in the street microcell system, the level deterioration is remarkable when the vehicle crosses an intersection. Therefore, for example, when the vehicle crosses an intersection during the operation of (1) above, the channel switching request does not reach the base station, or even if the request arrives. In the above operation (4), the instruction from the base station may not reach the mobile station.

As a method for grasping the position of the mobile station, a wideband signal is transmitted from the base station, the mobile station that receives this signal returns the signal and the distance from the base station is estimated from the round-trip time of the signal. It is possible to use a satellite or a distance measurement method using a satellite.However, these conventional methods require special equipment for measurement, and the distance measurement result and the map can be used to estimate the position of the intersection. We need a database to compare information and figure out intersections.

[0008]

As described above,
In the conventional small cell method, the radio wave propagation characteristics can be uniformly treated as non-line-of-sight propagation characteristics within the service area. Therefore, there is no abrupt level change even when turning an intersection, which is not a problem in system control. In the street microcell method, which aims to further improve the frequency utilization rate and to increase the system capacity compared to the small cell method, the radio wave propagation characteristics differ between line-of-sight and non-line-of-sight, causing abrupt level fluctuations at intersections. It is highly possible that control such as channel switching will fail in time and fail. If the mobile station fails to switch channels during communication, the mobile station issues a switching request and tries again and again, which puts pressure on system control and reduces the capacity that the system can handle. Furthermore, if channel switching fails, communication will be cut off, resulting in unacceptable quality for the user, making the system unusable. Further, in order to estimate the intersection by the conventional distance measuring method, a special device and a database are required, which is an unacceptable heavy burden on the system, especially on the portable device.

The present invention has been made in view of the above,
The purpose is to accurately control the channel switching during communication in a short time by detecting the intersection where a sudden level change occurs in advance, without using any special device or database in the street micro cell system. It is to provide a mobile station position detection method that enables the above.

[0010]

In order to achieve the above-mentioned object, the mobile station position detecting method of the present invention uses a street microcell system in which a service area is constructed along a road, The reception level of the radio wave from the base station near the intersection is measured in advance and stored in the base station as the intersection information of the base station, and this information is notified to the mobile station that communicates using the radio wave of the base station. However, when the reception level of the radio wave from the relevant base station to be used reaches the reception level that matches this information, the mobile station informs the base station to that effect to confirm that the mobile station has reached the intersection. Make the base station and the mobile station recognize each other.

[0011]

Since the mobile station position detecting method of the present invention is constructed in this way, in the street microcell system in which a service area is constructed along a road, the mobile station can grasp the reception level near the intersection in advance. , By detecting that the reception level from the base station has reached the level and knowing that it is approaching the intersection, the vicinity of the intersection, which is the core of the street microcell system, without using any special device or database It is possible to perform preparations and pre-processing for control such as channel switching during communication in advance, and therefore, it is possible to perform the control accurately in a short time. As a result, it is possible to truly realize the street microcell system, which has an increased system capacity as compared with the conventional small cell system, and it is possible to provide a high-quality, large-capacity cellular mobile communication system.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a diagram for explaining the creation of a calibration table used in one embodiment of the present invention, which is a road 11a.
The reception level corresponding to the distance 15 on the road 11a from the base station 12 provided in the above is shown by the curve 17, and the reception level decreases as the distance from the base station 12 increases. Intersections 19b, 19c of the road 11a and the roads 11b, 11c, 11d,
The reception levels at 19d are Lb, Lc, and L, respectively.
It has shown that it is d. Actually, the reception level at the intersection is also measured for the service area along the road 11a opposite to the intersections 19b and 19c of the base station 12.

FIG. 1B shows a circuit configuration of a mobile station used in an embodiment of the present invention. The mobile station receives the radio wave from the base station by the receiving antenna 21 and supplies it to the receiving circuit 22, converts it into an intermediate frequency signal by the receiving circuit 22, demodulates it by the demodulation circuit 23, and supplies it to the control circuit 24. A part of the output of the reception circuit 22 is supplied to the reception level detection circuit 25, and the level (strength) of the reception radio wave from the base station is detected. On the other hand, the modulation signal from the control circuit 24 is the modulation circuit 2
The intermediate frequency carrier wave is modulated by 6, and the modulated output is converted into a high frequency signal by the transmission amplifier circuit 27, and the power is amplified, and is transmitted from the transmission antenna 28 to the base station as a radio wave.

For the purpose of the present invention, a calibration table corresponding level generating circuit 29 is provided, and a calibration table showing each intensity (level) of the radio wave from the base station at each intersection of the road on which the mobile station is moving is provided. The values are stored in the control circuit 24, and the control circuit 24 sequentially reads each value of the calibration table, causes the calibration table corresponding level generating circuit 29 to generate a level corresponding to the value, and receives the level detecting circuit 25.
And the level comparison circuit 31 compares the received level from the control circuit 24 and the comparison result is supplied to the control circuit 24.

When the base station 12 is installed on the road 11a in constructing the system, the road 11 from the base station 12 is
The level of the transmitted wave on a is measured at each intersection 19 using the mobile station.
b, 19c, and 19d, and the result is detected at each level Lb, near the intersections 19b, 19c, and 19d.
A calibration table is created as Lc and Ld and stored in the base station 12. Even if the mobile station bends from the road 11a, the intersection 19b close to the base station 12 which has a margin of reception level, the intersection with the road 11a outside the service area covered by the base station 12, etc. are omitted from the calibration table. The table can be simplified.

The base station 12 notifies the content of the calibration table to the mobile station which communicates using the radio wave of the base station 12, for example, while waiting in the cell of the base station 12 or when communication is started. The mobile station having received the notification stores the calibration table in the control circuit 24, and the control circuit 24 reads the calibration table and sets the level of the calibration table corresponding level generation circuit 29. The mobile station detects the reception level of the radio wave from the base station 12 used during communication by the reception level detection circuit 25, and compares the detected level and the generation level of the calibration table corresponding level generation circuit 29 with the level comparison circuit 31. If the reception levels reach so that they substantially agree with each other, the control circuit 24 reports the fact to the base station 12 as a control signal. As a result, the base station 12 and the mobile station mutually recognize that the mobile station has reached the vicinity of the intersection.

The control signal indicating that the vehicle has reached the intersection is the mobile station number, and the level generating circuit 29 at that time.
It includes the number of intersections that correspond to the level that was generated from. When the base station 12 receives this control signal, the intersection number included in the control signal is, for example, the intersection 19
If it indicates c, the base station 12c whose service area is the road 11c intersecting the road 11a at the intersection 19c
(Not shown), a switching instruction to a free communication channel is issued through the control station, information of the free communication channel is received from the base station 12c from the base station 12c through the control station, and the free communication channel information is received. Notify the mobile station. When the mobile station bends at the intersection 19c and approaches a level where the reception level is not suitable for communication, the mobile station switches to the communication channel of the previously received free communication channel information and immediately enters communication via the base station 12c, that is, the previous base station. It is possible to communicate continuously with the communication via 12.

When a predetermined time has passed after the mobile station transmitted the control signal to the base station 12 and the vehicle passed the intersection 19c without turning, the control circuit 24 uses the calibration table to advance the mobile station. Next intersection 19 in direction
The value Ld for d is read out, and the level corresponding to this is generated from the calibration table corresponding level generating circuit 29.
Also, the fact is notified to the base station 12. Upon receiving this, the base station 12 notifies the base station 12c via the control station that the free communication channel instructed to switch back to the free communication channel.

The level comparison in the level comparison circuit 31 detects that both inputs are substantially coincident with each other, so that when the mobile station approaches the intersection from the base station 12 side, it approaches from the side far from the base station 12. In any case, it can be detected.

[0020]

As described above, according to the present invention,
The base station and mobile station grasp the reception level near the intersection in advance and detect whether or not the level is almost reached to know that they are approaching the intersection. Compared to the method of estimating, without using any special device or database, it is possible to prepare in advance for the control such as channel switching during communication in the vicinity of the intersection, which is the backbone of the street microcell method, and preprocessing, therefore, The control can be accurately performed in a short time. As a result, it is possible to truly realize the street microcell method that aims to increase the system capacity compared to the conventional small cell method, and to achieve high quality,
A large capacity cellular mobile communication system can be provided.

[Brief description of drawings]

1A is a diagram for explaining the creation of a calibration table that associates an intersection with a reception level, and FIG. 1B is a block diagram showing an example of a mobile station used in the present invention.

FIG. 2A is a diagram showing an example of a cell configuration of a street microcell system, and B is a diagram showing a situation in which the reception level of a mobile station in the street microcell system changes depending on the distance from a base station.

Claims (1)

[Claims] 1. A method for detecting the position of a mobile station of a cellular mobile communication system which constitutes a service area along a road, the radio wave from the base station near each intersection in the service area covered by the base station in advance. The reception level is measured and stored in the relevant base station as the intersection information of the relevant base station, and this intersection information is notified to the mobile station that communicates using the radio wave of the relevant base station. When the reception level of the radio wave from the base station reaches a reception level that almost matches the notified intersection information, this is detected, and the fact that the mobile station has reached the vicinity of the intersection is reported to the base station. A mobile station position detecting method characterized in that the base station and the mobile station mutually recognize each other.