JPS61147622A - Mobile communication system - Google Patents

Abstract

PURPOSE:To improve the ratio of a desired wave to a distrubing ratio to a land mobile station by providing an array antenna where a directivity within a vertical plane has two upper/lower main lobes in the horizontal direction and has no sensitivity in the horizontal direction to a base station to reduce fading to an aircraft. CONSTITUTION:The directivity characteristic in the vertical plane of a base station use array antenna 2 has two main lobes 31, 31' at the lower and upper side in the horizontal direction and has no sensitivity in the horizontal direction, the upper main lobe 31 is used for an aircraft telephone subscriber 4 for communication and the lower main lobe 31' is used for an automobile telephone subscriber 5. The depression angle of the main lobe 31' is set to have the maximum gain at slightly inner side from a radio zone peripheral part of the said radio base station 1. Thus, the communication between the base station 1 and the subscriber 4 reduces fading due to reflection on sea surface and the communication with the subscriber 5 is improved for the ratio of desired wave to disturbed wave.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a mobile communication system in which one base station can communicate with aircraft and land mobile stations.

Summary of the Invention The present invention provides two main types of vertical directivity characteristics of a base station antenna, upper and lower with respect to the horizontal direction, in a mobile communication system in which communication is performed between an aircraft, a land mobile station, and one base station. The upper main lobe is used for communication with aircraft, and the lower main lobe is used for communication with land mobile stations, so communication with aircraft is free from the effects of sea surface reflections, etc. By reducing the fading due to radio waves and improving the ratio of desired waves to interfering waves in communication with land stations, it is possible to effectively utilize frequencies.

BACKGROUND ART Conventionally, in a mobile communication system in which communication is carried out between one radio base station and land mobile stations such as aircraft and car telephones, as shown in FIG. Communication is carried out with an aircraft telephone subscriber 4 and a car telephone subscriber 5 so that the directivity characteristic 3 of the antenna 2 has a maximum gain in the horizontal direction. This is because if the directivity characteristic is set to 3', the communication radio waves with the aircraft telephone subscriber 4 will be weak.

Problems with the Prior Art: In the conventional method described above, the directivity of the directional characteristic 3 is maximum in the horizontal direction, so radio waves are propagated over long distances.

This is effective for mobile communication systems with large zone configurations, but for small base stations where other base stations repeatedly use the same frequency channel to communicate with mobile phone subscribers within their own zone. Mobile communication systems such as car telephone systems with zone configurations have the disadvantage of deteriorating the ratio of desired waves to interference waves.For example, if the am zone radius is 3 km and the height of the base station antenna 2 is 100 km If the angle of declination in the vertical plane is 3°, then the angle of depression when looking around the zone from the wireless base station l is 1.9°.

This is because the maximum gain direction of the directivity characteristic 3 is not within the own station zone, but rather the maximum gain occurs in other areas where the same frequency is repeatedly used.

Furthermore, communication with aircraft has the disadvantage that it is accompanied by fading due to reflections on the sea surface and the like.

In addition, in order to improve the ratio of desired waves to interference waves in a mobile communication system with a small zone configuration, beam tilting is performed as shown in directional characteristic 3' in Figure 5 to produce maximum gain at the periphery of the wireless zone. Although it is desirable to have such a directional characteristic, in that case, the communication radio waves with the aircraft telephone subscriber 4 become weak and communication becomes impossible.

OBJECTS OF THE INVENTION The purpose of the present invention is to solve the above-mentioned conventional drawbacks, and to reduce fading caused by the influence of sea surface reflections in communications with aircraft;
The purpose of communication with land mobile stations is to provide a mobile communication system that can improve the ratio of desired waves to interference waves and effectively utilize frequencies.

Composition of the Invention The mobile communication system of the present invention is a mobile communication system in which communication is performed between an aircraft, a land mobile station, and a base station through channels respectively allocated to the base station. It is equipped with an array antenna that has two main lobes on the upper and lower sides and has no sensitivity in the horizontal direction. Communication with aircraft uses the upper main lobe, and communication with land mobile stations uses the lower main lobe. It is characterized by using a robe.

Embodiments of the Invention Next, one embodiment of the present invention will be described in detail with reference to one drawing.

FIG. 1 is a conceptual diagram showing one embodiment of the present invention. That is, the vertical plane directivity characteristic of the base station antenna 2 has two main lobes 31 and 31' on the upper and lower sides in the horizontal direction, and the upper main lobe 31 is used to connect the aircraft telephone subscriber 4. and the lower main lobe 31' is used to communicate with the mobile phone subscriber 5. Main lobe 31'
The angle of depression is set so that the maximum gain is achieved slightly inside the periphery of the radio zone of the radio base station I.

FIG. 2 is a diagram showing the arrangement of the base station antenna 2 of this embodiment, in which all eight antenna elements A1 to A8 are arranged vertically so that the element spacing is one wavelength λ. Antenna element A! ~A8 is fed in-phase, and eight similar antenna elements AI'~A8' are fed in reverse phase, and arranged in upper and lower two stages so that the center spacing S between the two element groups is 8λ. There is. Each antenna element is composed of, for example, a dipole antenna.

FIG. 3 is a diagram showing the directivity characteristics in the vertical plane of the base station antenna 2, where the horizontal axis shows the elevation angle or depression angle with respect to the horizontal direction, and the vertical axis shows the directivity characteristics, that is, the horizontal direction. It has a main lobe of maximum gain in the direction of 2°5° above.

On the wood flow side, communication between the radio base station 1 and the aircraft telephone subscriber 4 uses the upper main lobe 31t, and communication with the car telephone subscriber 5 uses the lower main lobe 31'. Therefore, for example, the height of the base station antenna 2 is
00m, the altitude of the aircraft is 10Km, and the radius of the radio zone is 3Km. Since the maximum gain direction for the aircraft is +2.5 degrees, the maximum gain for the aircraft at the position of approximately 230 is given. , can cover the target zone. In addition, scattered waves caused by radio waves from an aircraft being distorted in the horizontal direction by buildings on the ground, etc. are reduced by the antenna directivity characteristics, so fading is alleviated.

On the other hand, the angle of the main lobe 3F with respect to the horizontal direction is -2,5
°, the direction of maximum gain is directed slightly inside the periphery of the wireless zone.

Figure 4 shows II! It is a diagram showing the relationship between the distance from the 1-line base station 1 and the reception level on the ground, where the curve a shown by a solid line shows the characteristics of this embodiment, and the curve shown by a broken line shows the conventional characteristics. That is, in this embodiment, the reception level is higher than the conventional one within the zone within the third layer, and the reception level is lower than the conventional one outside the zone beyond the third layer. Moreover, the degree of level reduction increases as the distance increases.For example, if the ratio of the desired signal to the interfering signal is required to be 20 dB or more, conventionally, unless the area is more than 20 layers away, the same frequency However, in this example, it is possible to shorten the length of the eel to approximately 9 mm.

Effects of the Invention As described above, the present invention has the effect of reducing fading for aircraft and improving the ratio of desired waves to interference waves for land mobile stations. This has the effect of improving frequency usage efficiency.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing one embodiment of the present invention, FIG. 2 is a diagram showing an example of the array of base station antennas of the above embodiment, and FIG.
The figure shows the directivity characteristics in the vertical plane of the base station antenna, FIG. 4 shows the relationship between the distance from the base station and the ground reception level in the above embodiment and the conventional example, and FIG. FIG. 2 is a conceptual diagram showing an example of a communication method. In the figure, 1: wireless base station, 22: base station antenna,
3.3': Directional characteristics of conventional example, 4: Aircraft telephone subscriber,
5: Car phone subscriber, 31°31': Main lobe.

Claims (1)

[Claims] In a mobile communication system in which communication is performed between an aircraft or a land mobile station and a base station through channels respectively allocated, the base station has two main vertical directivity characteristics, one above and the other below the horizontal direction. Equipped with an array antenna that has lobes and is not sensitive in the horizontal direction, communication with aircraft is performed using the upper main lobe, and communication with land mobile stations is performed using the lower main lobe. mobile communication system.