JPH03291027A - Reception level detection method in mobile communication - Google Patents

Abstract

PURPOSE:To implement zone discrimination and zone transit accurately and quickly by utilizing the difference from a fluctuation characteristic depending on zone constitution and mobile speed so as to switch a detection time length of a reception level thereby detecting the level. CONSTITUTION:A reception level of a radio wave from a base station received by a receiver 1 is detected by a level detection circuit 2. An instantaneous value detection circuit 4 in a portable equipment level processing circuit 3 in a portable equipment receives a level signal from the circuit 2 to apply level sampling. An arithmetic processing circuit 5 applies averaging processing to the sampled output according to a mode switching control signal from a level detection control section 8 and uses the result as level information to the portable equipment control section. When the portable equipment is mounted on a vehicle and the portable equipment transits from an area of a small zone to an area of a minimum zone, the level averaging time at the detection of the reception level is decreased to detect the level and when the portable equipment is mounted on the vehicle and the portable equipment transits from an area of a minimum zone to an area of a small zone, the level averaging time at the detection of the reception level is increased to detect the level through the changeover of the level detection mode.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is applicable to a mobile station in a cellular mobile communication system in which a service area is configured by a combination of zones of different sizes, such as a small zone configuration and a very small zone configuration. (portable device,
The present invention relates to a level determination method when an on-vehicle device (on-vehicle device, on-vehicle portable device) detects the reception level and detects the zone where the device is located or the zone to which it is communicating.

(Prior art) Conventionally, in cellular mobile communication systems where a service area is configured by a combination of zones of different sizes, such as a small zone configuration or a very small zone configuration, reception levels are detected and the location zone and the destination zone where communication is being transferred are determined by detecting the reception level. When determining the level, a method is used in which level detection is performed while the length of the level averaging time during reception level detection remains constant regardless of the size of the zone.

(Problem to be Solved by the Invention) Figure 2 shows the minimum zone configuration, the small zone configuration, and the attenuation of radio waves from the base station that is the transmission point in each zone configuration, and therefore the fluctuation status of the reception level of the mobile station. It is something. The characteristic of radio waves attenuating with distance r from the transmission point (distance characteristic) is L=α+βlog(r)...(1
), and since dL/dr = 1/r, the closer to the transmission point the larger the change in attenuation with respect to a change in distance, and the farther away the change is, the more gradual the change in attenuation becomes. If the required reception level to ensure the required communication quality around the zone is the same for the small zone configuration and the very small zone configuration, then
In the case of a small zone configuration, it is necessary to increase the transmission output as the zone radius is larger than that in a very small zone configuration. However, the amount of attenuation of radio waves from the transmission point is determined only by the distance from the transmission point, regardless of the transmission output, so as shown in Figure 2, when moving at the same speed, the area around the minimum zone
The fluctuation in the reception level at B is larger than the fluctuation at the vicinity B of the small zone. Furthermore, the moving speed of the mobile station = dr
/dt, then from (1) dL/dt=(dL/dr
)・(dr/dt)”s v/r, it can be seen that the faster the moving speed, the larger the fluctuation at point A will be compared to point B. Note that the instantaneous value of the reception level is It fluctuates violently in proportion to the moving speed of the mobile station, which is called Rayleigh fading, and the median value of this instantaneous fluctuation fluctuates slowly over a short period of time where the topography, buildings, etc. around the mobile station change. This is called median variation.

Furthermore, the median value of this short-term median value fluctuation has a distance characteristic expressed by equation (1) when viewed over a long distance, and is also called a long-term median value fluctuation. Conventional level detection uses a received level detection method in which the detection time is constant, even though the tendency of fluctuation of the long-term median value of the received level varies greatly depending on the zone configuration. FIG. 3 is a diagram showing the relationship between the reception level fluctuation characteristics when the portable device is used in a car and when it is carried by a person. In the case of a portable device mounted on a vehicle, as shown in C, it is a diagram showing the relationship with the fluctuation characteristics of the reception level. In the case of a portable device installed in a car, C.
As shown in , the instantaneous value of the reception level is, for example, reception frequency 9
When the frequency is 00MHz and the vehicle speed is 50km/H, it fluctuates at a maximum of 40Hz. Furthermore, the long-term median value also decreases rapidly as the distance from the transmission point increases. On the other hand, when a person carries it, the instantaneous value is a receiving frequency of 900 MHz and a walking speed of 6 k, as shown in D.
m/H, the maximum value is 511Z, which fluctuates more gently than when mounted on a vehicle. Similarly, the long-term median value also decreases very slowly. As described above, the level fluctuations differ greatly between when the portable device is mounted in a car and when it is carried around. There is no problem when limiting the size of the zone or how to use the mobile device, such as when communicating using an in-vehicle device in a small zone configuration or when a person carries a mobile device in a very small zone configuration, When configuring a service area by combining a minimum zone configuration with a minimum zone configuration, the problem is that detection errors become large and correct level judgment cannot be made unless there is a distinction between whether the portable device is installed in the car or carried. was there. The present invention aims to improve the above drawbacks.

(Means for Solving the Problems) A feature of the present invention is that in a mobile communication system that configures a service area by combining zones with different zone radii,
The mobile station is notified through a control channel, etc. that each zone that touches zones with different radii has different zone radii, and based on this information, the mobile station, in-vehicle device and in-vehicle portable device, When moving from a zone with a large zone radius to a zone with a small radius, shorten the level averaging time when detecting the received level, and vice versa, switch the level detection mode to set it longer. In the case of a mobile station and a portable device carried by a person, the reception level detection method in mobile communication is such that the reception level is detected by keeping the level averaging time long regardless of the transition between zones of different sizes. .

(Function) Highly accurate level judgment is achieved by switching the reception level detection mode and performing level detection, taking into account the above fluctuation characteristics of the reception level, especially the differences in fluctuation characteristics depending on the zone configuration and mobile station moving speed. It is something to do. In other words, in a mobile communication system that configures a service area by combining a very small zone configuration and a small zone configuration, the base station of the zone belonging to each zone configuration at the boundary between the small zone configuration area and the very small zone configuration area The mobile station is notified through a control channel etc. that it is an area boundary, and the mobile station learns of the change in zone configuration based on this information, and the mobile station (on-vehicle device) installed in the vehicle changes from an area with a small zone configuration to a very small zone configuration. When moving to the area of When a person carries a portable device and communicates while moving or stopped, and when a person carries a portable device and communicates while driving, it is determined by detecting the speed of fluctuation in the reception level. If the portable device moves from an area with a small zone configuration to an area with a very small zone configuration, shorten the level averaging time when detecting the reception level, and in the opposite case, set it longer. Level detection is performed by switching the level detection mode, and when carried, the level detection is performed in a level detection mode that sets a long level averaging time during reception level detection regardless of changes in the zone configuration.

(Embodiment) FIG. 1 is a diagram showing a configuration example for realizing the level determination method of the present invention. The level detection circuit 2 detects the reception level of the radio waves from the base station received by the receiver 1. In a portable device, the instantaneous value detection circuit in the portable device level processing circuit 3 receives the level signal from the level detection circuit and performs level sampling. The sampled output is averaged by the arithmetic processing circuit 5 in accordance with the mode switching control signal from the level detection control section 8, and is used as level information for the portable device control section. If there is a change in the zone configuration, a level detection section 8 generates a mode switching control signal in response to mode information from the portable device control section. In addition, the fluctuation speed detection circuit 7 which obtained the instantaneous value output from the level detection circuit detects the single interval median value in an interval that can follow the short interval median value fluctuation based on the short interval median value detected by the arithmetic processing circuit. A constant level corresponding to the level is generated by the reference value generating circuit 6, and the number of instantaneous value fluctuations that cross this level reference value is counted to detect the fluctuation speed of the instantaneous fluctuation. The detected fluctuation speed is used by the level output control section 8 to determine whether the portable device is being used in a vehicle or being carried.

On the other hand, in the on-vehicle device, as shown in FIG. 3B, 12 level detection control sections perform mode switching control based on mode information from the on-vehicle device control section regarding changes in zone configuration. In other words, the level signal from the level detection circuit is
0 instantaneous value detection circuits are sampled, and 11 arithmetic processing circuits perform averaging processing in accordance with mode switching control signals from 12 level detection control units, and provide level information to the on-vehicle device control unit.

In the above description, an on-vehicle device is a mobile station whose moving speed corresponds to the speed of a car (for example, 10 km/h or more), and a portable device is a mobile station whose moving speed is slower than this.

(Effects of the Invention) As explained above, the present invention provides characteristics of received level fluctuations,
In particular, we decided to perform level detection by switching the reception level detection time length, taking advantage of the difference in fluctuation characteristics depending on the zone configuration and moving speed. As a result, mobile stations (in-vehicle devices, portable devices) can accurately and quickly perform zone determination and zone transition in service areas that combine zones of different sizes, such as a micro zone configuration and a small zone configuration. Efficient system operation becomes possible.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a configuration diagram for realizing the level determination method of the embodiment, and Fig. 2 shows the minimal zone configuration and small zone configuration, and the relationship between the distance from the transmission point and the reception level in each zone configuration. FIG. 3 is a diagram illustrating the relationship between reception level fluctuation characteristics when the portable device is used in a car and when it is carried. A... Level fluctuations around the minimum zone, B...
Level fluctuations around the small zone, C... Fluctuations in the reception level of a portable device mounted on the vehicle, D... Fluctuations in the reception level of a portable device carried by a person, 1... Receiver, 2.・Level detection circuit,
3... Level processing circuit for portable device, 4... Instantaneous value detection circuit, 5... Arithmetic processing circuit, 6...
... Reference value generation circuit, 7... Fluctuation speed detection circuit, 8.
...Level detection control unit, 9...Level processing circuit for onboard equipment, 10...Instantaneous value detection circuit b, 11...Arithmetic processing circuit, 12...Level detection control unit.

Claims (1)

[Claims] In a mobile communication system in which a service area is configured by combining zones with different zone radii, a control channel or the like is used to inform a mobile station that each zone adjacent to a zone with a different radius is a boundary with a different zone radius. Based on this information, the mobile stations (in-vehicle units and in-vehicle portable units) adjust the level averaging time when detecting the received level when moving from a zone with a large zone radius to a zone with a small radius. Level detection is performed by switching the level detection mode to shorten the length and vice versa, and in the case of a mobile station and a portable device carried by a person, transition between zones of different sizes. 1. A reception level detection method in mobile communication, characterized in that reception level detection is performed while keeping the level averaging time long regardless of the current level.