JPH0447722A - Radio channel assignment control method in mobile communication - Google Patents

Abstract

PURPOSE:To improve the utilization factor of a frequency by providing 1st and 2nd antennas and selecting an antenna used for the communication with a mobile set in response to the quantity of a reception of a radio wave from the mobile set by both the antennas. CONSTITUTION:The system is provided with the 1st antenna 19 to be the 1st radio zone 23 of each base station as an object and with a 2nd antenna 28 to be the 2nd radio zone 24 as an object having a vertical planer directivity more downward than that of the 1st antenna 19, and an antenna used for the communication with a mobile set is selected depending on the quantity of a reception level of a radio wave from the mobile set by both antennas. That is, the beam tilt antenna 18 is used in common for the system and the reception level by this antenna is used for deciding the position of the mobile set. Thus, the position of the mobile set is accurately decided and when the distance between the base station and the mobile set is a prescribed distance or below, since a channel used repetitively at a zone closer than the usual state is assigned, the effect of reuse partition is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mobile communication channel allocation control method that can improve the geographical repetition efficiency of frequencies.

(Prior technology) In mobile communications, typified by car telephones, radio channels with the same frequency are allocated to radio zones that are separated by a certain distance, thereby repeating the frequency geographically and increasing the frequency utilization rate. It is common to improve

In land mobile communications, if the distance between the base station and the mobile device is r, the average reception level L (dB) of radio waves is L=-10.
It can be approximated as x a x log(r) + A. a has a value of about 3 or 4, and A is a constant determined by antenna gain and transmission power.

FIG. 3 is a diagram explaining frequency repetition, 1 and 2.
is the wireless zone that uses the same frequency, R is the zone radius,
D is the distance between repeating zones. The radio waves from 2 reach 1 and become interference waves in 1's zone. When the mobile device is at point 0, which is the edge of the zone, the radio waves in its own zone (called desired waves) are the lowest, and the interference wave level is the highest.

Even in this case, the distance is repeatedly determined so that the difference between the desired wave and the interference wave (referred to as D/U) can satisfy a certain value. 0
Average desired wave level L at the point. is LD=-10x a
x log (R) + A, and the average interference wave level LU is Lu = -10X a X log (D-R) +
Since A, the required value of the difference between the desired wave and the interference wave is G (d
B), then Lo-Lu=G], Ox a x l
ogf(DR)/R). From this, D(1+]
OG/1oll) ×R. That is, the distance between repeated zones is a constant value times the zone radius. This constant value is determined from the required level difference between the desired wave and the interference wave. From this, if we consider a virtual radius R'(R'<R) within the zone of radius R, then for the mobile station in the zone of Ro, D(1+10°/1oll)XR'
It becomes possible to repeat the frequency between the virtual zone of radius R and the distance D' determined by . D'= (R'/
R) X D, which is a smaller value than D. This is shown in Figure 4. 3 and 4 are virtual small wireless zones. In this way, we consider virtual small zones within the zone,
The process of repeating the use of frequencies at closer distances between small zones to increase frequency efficiency is called Leus partition. In the smart partition, the total of channels that are normally used repeatedly and channels that are used repeatedly between virtual small zones is allocated to each zone.

In Leus Participant, it has conventionally been determined whether a mobile device is in a virtual small zone based on the reception level at the base station. In other words, the radio waves from the mobile device are received by the base station and this is 110X a
If it is higher than X log (R') + A, it is determined that the distance to the base station is less than R° and a channel for small zone 3 is allocated, and if it is lower than -10X a X log (Ro) + A, the distance to the base station is determined. The channel was determined to be less than R° and was assigned a channel for the large zone 1.

(Problem to be solved by the invention) However, reception level - 10X a x log (R')
+A is the average reception level when the mobile device is in various locations; when the mobile device is used on an elevated road or next to a high-rise window of a building, it will be received at a higher level than the average reception level; When used on a narrow road or inside a building, the reception level will be lower than the average reception level. That is, it is not possible to accurately determine whether the mobile device is within the distance Ro from the base station based only on the reception level. If you mistakenly believe that you are farther than R° because the reception level is low even though you are within R゛ distance, you will not be able to use channels within R°, which have high frequency utilization efficiency. However, since the reception level is high, there is a drawback that if the error is within R, a large amount of interference will be caused to the interference zone.

SUMMARY OF THE INVENTION An object of the present invention is to provide a channel allocation control method that can accurately determine the distance between a mobile device and a base station, enhance the effect of Leus partition, and reduce interference.

(Means for Solving the Problems) A feature of the present invention for achieving the above object is that a plurality of base stations are provided in a service area corresponding to a first wireless zone,
A channel of the same frequency is assigned to a plurality of base stations that are separated by a first fixed distance or more, and a channel of the same frequency is assigned to a plurality of base stations that are separated by a second fixed distance that is shorter than the first distance. In a mobile communication system that further allocates a channel of the same frequency different from the above-mentioned frequency to target two wireless zones, each base station has a first antenna that targets the first wireless zone, and a channel that is perpendicular to the first antenna. a second antenna that has vertical in-plane directivity pointing downward from the in-plane directivity and targets a second wireless zone;
The present invention provides a method for controlling radio channel allocation in mobile communication in which an antenna to be used for communication with a mobile device is selected according to the magnitude relationship between reception levels of radio waves from the mobile device at both antennas.

(Function) The present invention uses a base station antenna to strongly receive radio waves from mobile devices near the base station, but weakly receive radio waves from mobile devices located at a relatively long distance from the base station, such as at the edge of a zone. A so-called beam tilt antenna is also used to transmit and receive normal repeating channels using the normal antenna, and transmit and receive using the beam tilt antenna for channels that repeat at closer distances between virtual small zones. If the radio waves from the mobile device are strongly received by the beam tilt antenna, or if the reception level of the beam tilt antenna is higher than the reception level of a normal antenna by a certain value, use the virtual small zone repetition channel. .

In the conventional technology, only one antenna was used and the position of the mobile device was estimated based only on the magnitude of the reception level at this antenna.However, in the present invention, a beam tilt antenna is also used to estimate the position of the mobile device based on the reception level at this antenna. The difference is that the level is used to determine the location of the mobile device.

(Embodiment) FIG. 1 is an example of the configuration of a base station device for explaining the present invention in detail, in which 5 to 9 are communication lines between a base station and a switching center (not shown), and IO is a A control device, 11 to 15 are wireless transceivers, 16 and 17 are antenna sharing devices, 18 is a beam tilt antenna, and 19 is a normal antenna.

FIG. 2 is a diagram for explaining the antenna directivity characteristics of a base station and the shape of a zone based on the antenna directivity characteristics, in which 22 is a base station;
0 is the directivity pattern of antenna 19, 23 is antenna 1
9 is a zone formed by the antenna 18, 21 is a directivity pattern of the antenna 18, and 24 is a zone formed by the antenna 18. Note that zone 23 corresponds to zone 1 in FIG. 4, and zone 24 corresponds to zone 3 in FIG. 4.

The transceivers 11 and 12 are connected to an antenna 18 by an antenna sharing device 16, and this antenna is a so-called beam tilt antenna having a directivity characteristic in a horizontal plane that is downward from the edge of the normal zone 1, as shown in 21.

Therefore, the range that the radio waves of the transceivers 11 and 12 can reach, that is, the zone radius, is smaller than 1 as shown in 3 in FIG. For example, Shinsho, co-supervised by Shinji, ``Fundamentals of Mobile Communications''
(Published by the Institute of Electronics and Communication Engineers, October 1, 1986) Details on pages 253 to 254.

The transceivers 13 to 15 are connected to an antenna 19 by an antenna sharing device 17, and since the antenna 19 is an antenna that has directivity in the horizontal direction and in the vertical plane as shown in 20, the radio waves can reach far and reach the zone. Figure 4 1
It is.

The method of directing the vertical directivity of the antenna 18 downward is as follows:
Mechanically tilting the antenna itself downward, or
When the antenna is composed of a vertical multi-stage array, there are methods such as adjusting the phase of feeding to each element so that the electrical composite directivity characteristics are directed downward.

Because the base station device is configured in this way, when the mobile station is within zone 3, the reception level at antenna 18 is stronger than a certain value, and when the mobile station is outside zone 3, 1, the antenna 18 cannot receive signals at a level above a certain value, but the antenna 19 can receive signals at a level above a certain value. Also, when the mobile device is in zone 3, it can be received at a strong level by antenna 19, but this level is lower than the reception level by antenna 18. This is because the area of zone 3 is close to the base station 22. When viewed from the antenna 19, whose directional characteristics are oriented in the horizontal direction, it is located at a considerable distance from the main beam direction, and the directivity is therefore considerably attenuated, whereas when viewed from the antenna 18, the directivity is downward. This is because the direction of the antenna 18 is closer to the main beam direction by the amount that it is facing, and therefore the amount of directivity attenuation is small.Conversely, outside zone 3, the reception level by the antenna 18 decreases rapidly as the distance from zone 3 increases. .The reason for this is antenna 1.
The directivity in the vertical plane of 8 points downward, and therefore, as the mobile device moves farther away from the edge of zone 3, in addition to the increase in attenuation due to distance, the attenuation due to deviation from the main beam direction of the antenna increases. This is due to the addition of an increase in

As can be seen from the above, when receiving with a beam tilt antenna, it is possible to accurately determine whether or not the mobile device is within zone 3, and the reception level at the beam tilt antenna 18 and the antenna 19 which is not a beam tilt can be determined accurately. By comparing the reception levels at , it becomes possible to determine the location of the mobile device more accurately.

In a first embodiment of the invention, the antenna 18 from the mobile
If the reception level of radio waves at the mobile station is above a certain value, the antenna 18 and either the transceiver 11 or 12 connected to it are used to communicate with this mobile device, and the reception level at the antenna 18 reaches a certain value. If this is not the case, antenna 19 and one of transceivers 13 to 15 are used. Further, in the second embodiment, the reception level of radio waves from the mobile device is determined by the antenna 18.
Compare and 19, and if the reception level of 18 is higher than the reception level of month 9 by a certain value or more, the antenna] 8 and transmitter/receiver 11.
If the reception level of 18 becomes higher than the reception level of month 9 by a certain value or more, antenna 19 and any one of transceivers 13 to 15 are used.

The control device 10 performs controls such as determining the magnitude of the reception level of radio waves and selecting a transmitter/receiver to be used based on this result.

In the above description, the antenna 19 is a general antenna that is not a beam tilt antenna, but a beam tilt antenna can also be used for the antenna 19, and in this case, the tilt angle may be set to a value smaller than 18.

Further, although the case where the antennas 18 and 19 are installed at the same base station has been described, the effect is the same even if the antennas 18 and 19 are separated to such an extent that they can be considered to be almost the same location considering the size of the zone.

In other words, it is sufficient that the zones created by antennas installed apart from each other are approximately the same.

Although the antennas 18 and 19 have been described assuming the same gain, they do not necessarily need to have the same gain, as will be explained next. That is, although the zone created by the antenna 19 is wider than that of the antenna 18, the radio wave reception level of the mobile device is also lowered. Therefore, it is convenient to make the gain of the antenna 19 thicker than the gain of the antenna 18 (if this is done, the reception level of the mobile device using the antenna 19 can be increased). The virtual reception level obtained by adding the difference can be considered as the reception level at the antenna 18 in the explanation so far.

(Effects of the Invention) As explained above, the position of the mobile device can be accurately determined, and if the distance between the base station and the mobile device is less than a certain value, it can be repeatedly used in a zone that is closer than usual. Since it is possible to allocate channels that are already present, it is possible to enhance the effect of the Leus partition, and to suppress the increase in interference when the Leus partition is applied. In addition, since the vertical directivity of the beam tilt antenna is downward, the radiation level of radio waves to distant places can be kept low, and as a result, the repetition distance between virtual small zones can also be shortened. It is also possible to increase the frequency utilization rate.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams for explaining a configuration example of a base station device, antenna directivity characteristics, and zones for explaining the present invention in detail, and FIG. 3 is a diagram for explaining general frequency repetition. FIG. 4 is a diagram for explaining the Leus partition. 1.2...Wireless zone, 3.4...Virtual small wireless zone, 5-9...Communication line with switching center, 10...Control device, 11-15... Transmitter/receiver, 16, 1
7... Antenna sharing device, 18, 19... Antenna, 22... Base station,
20, 21... Directional characteristics in the vertical plane of the antenna, 23.
... Wireless zone, 24... Virtual small wireless zone.

Claims (1)

[Claims] A plurality of base stations are provided within a service area corresponding to a first wireless zone, and channels of the same frequency are assigned to the plurality of base stations that are separated by a first certain distance or more, and In a mobile communication system in which a channel of the same frequency different from the above frequency is further allocated to a plurality of base stations separated by a short second fixed distance for a second radio zone smaller than the first radio zone, each base The station includes a first antenna that targets a first wireless zone, and a second antenna that targets a second wireless zone and has vertical in-plane directivity that points downward from the vertical in-plane directivity of the first antenna. 2 antennas, and the antenna to be used for communication with the mobile device is selected according to the magnitude relationship between the reception levels of radio waves from the mobile device at both antennas. Channel allocation control method.