Radio communication system using portable mobile terminal

A radio communication system comprises a transmitting antenna for transmitting radio signals. Each radio signal is transmitted via one of a plurality of beams of different maximum radiated directions. The system also comprises a transmitting section for adding to a radio signal, transmitted via an i-th beam among the plurality of beams, beam identification information that identifies on which i-th beam of said plurality of beams said radio signal is being transmitted. The system further comprises a receiving antenna for receiving the radio signals transmitted by the plurality of beams and a receiver for selectively receiving a signal transmitted by a specific beam according to a predetermined estimation standard. Alternatively, the system may comprise a first radio station and a second radio station. The first radio station may include a transmitting antenna for transmitting signals with beam identification numbers and a receiving antenna for receiving signals from other radio stations. The second radio station may include a receiving antenna capable of receiving signals transmitted by the first transmitting antenna and a receiver for selectively receiving a signal transmitted by a specific beam according to a predetermined estimation standard. The second radio station may also include a transmitting antenna that forms a wide-angle beam to transmit the specific beam.

BACKGROUND OF THE INVENTION 
The present invention relates to a radio communication system using a 
portable mobile terminal. More specifically, the invention relates to a 
radio communication system for realizing a high transmission rate and a 
large quantity of information. 
In recent years, with the development of mobile communication and the 
enhancement of the quantity of communication, it is expected that there 
will be a great demand for high-speed, large-capacity mobile radio 
communication systems using potable mobile terminals in the near future. 
FIG. 1 illustrates a conventional mobile radio communication system. In 
this figure, a base station 1 forms an omni-directional beam 11, which can 
covers a given area, by means of a transmitting antenna, so as to allow 
communication to be established wherever a mobile terminal lies in the 
coverage area. 
In addition, mobile terminals 2, 3 and 4 also form omni-divisional beams 
12, 13 and 14 by means of antennas, so as to allow communication to be 
established regardless of the direction of the base station from each of 
the terminals. 
With this construction, it is possible to realize a mobile communication 
system, which enable communication in any places. However, considering 
that information to be communicated will be large-capacity, high-capacity 
in the near future, it is desired to realize a radio communication link 
suitable for the high-speed, large-capacity information. 
In order to obtain a high-gain transmitting-receiving antenna suitable for 
such a communication system, it is required to sharpen an antenna beam 
pattern. In this case, the base station and the terminals must have the 
constructions for forming shaper beams as shown in FIG. 2. 
In FIG. 2, the base station 1 forms narrow beams 15, 16 and 17 which are 
capable of transmitting and receiving signals toward the terminals 2, 3 
and 4. On the other hand, the terminals 2, 3 and 4 forms narrow beams 6, 7 
and 8 which are capable of transmitting and receiving signals toward the 
base station 1. 
For example, in a case where different frequency bands are allotted to the 
respective beams 15, 16 and 17 formed by the base station 1, the beams 15, 
16 and 17 may be formed at the same time. 
Alternatively, in a case where communication is established in a 
time-division system, the beams 15, 16 and 17 formed by the base station 1 
may be switched every a predetermined period of time. In this way, it has 
been able to be technically practiced that the direction of a narrow beam 
is scanned by using a conventional phased array antenna. 
FIG. 3 illustrates an example of a high-gain beam scanning antenna in a 
conventional radio communication system. In this figure, antenna elements 
21, 22, 23 and 24 are connected to diplwxers or transmission-reception 
(TR) switches 25, 26, 27 and 28, respectively, so that the transmitting 
and receiving of a radio signal are separated. 
The signals received by the respective antenna elements are supplied to 
corresponding phase shifters 32 via amplitude-variable amplifiers 30, and 
the amplitude and phase of the signals are weighted so that radio waves in 
a predetermined direction are received. The signals outputted from the 
respective phase shifters 32 are supplied to a receiver 37 via a 
synthesizer circuit 34. 
With respect to transmission, the signals supplied from a transmitter 35 
are distributed by means of a distributing circuit 33, and then the 
amplitude and phase of the signals are weighted by means of 
amplitude-variable amplifiers 29. Then, the signals are transmitted to the 
respective antenna elements via the TR switches 25, 26, 27 and 28, so that 
the synthesized directivity of the respective antenna elements forms a 
beam in a predetermined direction. 
The phase shifters 31 and 32 and the amplifiers 29 and 31 are controlled by 
a controller 36, so that radio waves in a predetermined direction are 
transmitted and received by comparing received signal levels and so forth. 
It is possible to perform the gain enhancement and the beam scanning 
according to the method as set forth above. However, considering that it 
is applied to an actual system, the construction, control and so forth of 
a radio transmitter-receiver are extremely complicated as described below. 
Since the base station 1 communicates with terminals serving as the other 
parties in communication, it is required to discriminate the directions of 
the respective terminals to turn beams to the optimum directions for the 
respective terminals. 
In addition, it must be assumed that the respective terminals move in 
mobile communication, so that it is required to cause the base station to 
independently follow the directions of all the terminals. 
For the reasons as set forth above, in a case where a phase array antenna 
is used, independent feed circuits are required for each of beams, so that 
the construction of the base station is complicated. For example, in a 
case where communications between the base station and a plurality of 
terminals are established, a plurality of feed circuits for setting the 
individual amplitude and phase weight are required. 
In addition, in a case where the direction of the beam (terminal) is 
switched by time base, a phase shifter and an amplifier must be switched 
at a high speed. In either cases, since a control system must be 
independently operated, the software therefor is complicated, and a great 
deal of labor is required in a processing system. 
As mentioned above, although it is required to enhance the gains of 
antennas of a base station and terminals in accordance with the increase 
of the speed and capacity of communication which will be required in 
future, there is a problem in that the construction and control of an 
antenna feed circuit are extremely complicated. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to eliminate the 
aforementioned problems and to provide a radio system in which a base 
station has a simple construction and which can be easily controlled. 
In order to accomplish the aforementioned and other objects, according to a 
first aspect of the present invention, a radio communication system 
comprises; a transmitting antenna for forming a plurality of beams of 
different maximum radiated directions, and for adding, to a signal 
transmitted by a beam of number i among the plurality of beams, a beam 
identification information being capable of discriminating that the signal 
is transmitted by the beam of number i, for transmitting the signal as a 
radio signal; a receiving antenna for receiving the radio signal 
transmitted from the transmitting antenna by the beam; and a receiver for 
selectively receiving a signal, which is transmitted from the transmitting 
antenna by a specific beam, on the basis of a predetermined estimation 
standard. 
The predetermined estimation standard may be a standard in which a signal 
of a beam of the maximum received-signal intensity transmitted from the 
transmitting antenna is selected. 
Alternatively, the predetermined estimation standard may be a standard in 
which a signal of a beam of the maximum signal-to-noise ratio (S-N ratio) 
transmitted from the transmitting antenna is selected. 
According to a second aspect of the present invention, a radio 
communication system comprises: a first radio station including a 
transmitting antenna for forming a plurality of beams of different maximum 
radiated directions and for adding, to a signal transmitted by a beam of 
number i among the plurality of beams, a beam identification information 
being capable of discriminating that the signal is transmitted by the beam 
of number i, and a receiving antenna for receiving radio signals, which 
are transmitted from other radio stations, by a wide-angle or 
omni-directional beam; and a second radio station including a receiving 
antenna which is capable of receiving the signal transmitted by the beam 
from the receiving antenna of the first radio station, a receiver for 
selectively receiving, on the basis of an estimation standard, a signal of 
a beam of number j among specific beams formed by the transmitting antenna 
of the first radio station, and a is transmitting antenna for forming a 
wide-angle or omni-directional beam to transmit the beam of number j 
selectively received among the beams transmitted from the transmitting 
antenna of the first radio station. 
The first radio station may receive a signal, to which information on the 
number j of the beam selectively received by the second radio station is 
added, and the signal to be transmitted to the second radio station may be 
transmitted using the beam of number j among the plurality of beams of 
different maximum radiated directions 
A frequency band of radio waves transmitted by the first radio station may 
be higher than a frequency band of received radio waves. 
By the above construction and function, the present invention has the 
following effects. 
According to the first aspect of the present invention, it is possible to 
transmit high-gain radio waves in different directions by forming a 
plurality of beams of different maximum radiated directions in a 
transmitting antenna. In this case, beam identification information being 
capable of discriminating that a signal is transmitted by a beam of number 
i among the plurality of beams, is added to the signal transmitted by the 
beam of number i so that the transmitted respective beams can be 
discriminated (by receivers). The receiving antenna receives a signal by a 
beam from the transmitting antenna, and the receiver selectively receives 
a signal by a specific beam of the transmitting antenna, so that it is 
possible to receive a signal of the most preferred beam for the estimation 
standard. 
In addition, it is possible to select a signal of a beam of the maximum 
received-signal intensity from the transmitting antenna by selecting a 
received-signal intensity as the estimation standard. 
Moreover, it is possible to select a signal of a beam of the transmitting 
antenna, the beam having the maximum signal-to-noise ratio (S-N ratio) of 
the received signal, by selecting the S-N ratio as the estimation 
standard. 
According to the second aspect of the present invention, the transmitting 
antenna of the first radio station is capable of transmitting high-gain 
radio waves in different directions by forming a plurality of beams of 
different maximum radiated directions. In this case, beam identification 
information being capable of discriminating that a signal is transmitted 
by a beam of number i among the plurality of beams, is added to the signal 
transmitted by the beam of number i so that the transmitted respective 
beams can be discriminated (by the receivers). 
In addition, the receiving antenna of the first radio station is capable of 
receiving signal from a plurality of other radio signals by forming a 
wide-angle or omni-directional beam. The receiving antenna of the second 
radio station is capable of receiving the signals transmitted by the beams 
from the transmitting antenna of the first radio station, and the receiver 
thereof is capable of selectively receiving a beam of number i among 
signals of the transmitting antenna of the first radio station on the 
basis of the estimation standard. 
The transmitting antenna of the second radio station forms a wide-angle or 
omni-directional beam, and transmits a signal, to which information on the 
number j of the beam selectively received from the beam of the 
transmitting antenna of the first radio station is added. 
In addition, the first radio station is capable of receiving and 
discriminating a signal, to which the information on the number j of the 
beam selectively received by the second radio station is added, and of 
transmitting the signal to the second radio station using the most 
preferred beam of number j among the plurality of beams of different 
maximum radiated directions on the basis of the estimation standard. 
Moreover, a higher frequency band is used as the frequency band of the 
radio waves transmitted by the first radio station, and a lower frequency 
band is used as the frequency band of the received radio waves. 
According to the second preferred embodiment of the present invention, it 
is possible to select a beam of the best communication condition from a 
plurality of beams for communication. For example, in a case where a 
shielding lies on the way of transmitted radio wave, it is possible to 
hold a communication link by different beams arriving by reflection and 
diffraction. 
In addition, in a case where the communication link is deteriorated due to 
multipass and fading, it is also possible to hold a good communication 
link by changing the beam. The present invention has great advantageous 
effects particularly in a mobile communication in which the communication 
environment varies from hour to hour. 
Moreover, according to the second aspect of the present invention, it is 
possible to arrange for transmitting a great capacity of information from 
a base station to a terminal, using a simple system by operating a short 
period of time. Thereafter, since the information is transmitted all at 
once, It is possible to effectively use-communication capacity, link, 
frequency band and transmitting-receiving power.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the accompanying drawings, the preferred embodiments of a 
radio communication system, according to the present invention, will be 
described in detail. 
First of all, the first preferred embodiment of a radio communication 
system, according to the present invention, which is equipped with a 
transmitting antenna, a receiving antenna, a receiver, and transmitter 
will be described. 
FIG. 4 illustrates a system image of the first preferred embodiment of a 
radio communication system according to the present invention. In this 
figure, a base station 41 forms a plurality of beams (n beams) of 
different maximum radiated directions for establishing communication, and 
some of the beams reach a terminal 42. The beams radiated by the base 
station 41 have a narrow beam-width and a high gain. 
In addition, the respective beams may be formed at the same time or 
sequentially by the time-division system. The detailed structures of 
antennas will be described later. 
FIG. 5 illustrates a signal transmitted from each of the beams. This figure 
illustrates a time slot which is used for a time division multiple access 
(TDMA) communication system using a digital modulation. This is 
characterized in that a beam identification information being a beam 
number information is contained in a time slot. 
The point of the present invention is that signals transmitted by a 
plurality of beams transmitted by a base station contain information for 
identifying a beam, by which the signal is transmitted. The method for 
causing the beam identification information to be contained in a S signal 
should not be limited to the method by the beam number as shown in FIG. 5. 
For example, the respective beam number may be discriminated by changing 
the frequency band for each beam, or the relationship between carrier 
frequency and beam number information may be established. 
The terminal is designed to receive a signal transmitted from the base 
station and to identify a beam by which the signal is transmitted. For 
example, in a case where beam number information is contained in a time 
slot, is the terminal is designed to be capable of discriminating the beam 
number information, and in a case where the relationship between the beam 
number and the frequency is established, the terminal is designed to be 
capable of discriminating the beam number on the basis of the frequency of 
the received signal. 
Although the type of these designs depend upon how to cause beam number 
information to be contained in a signal, it is possible to identify the 
beam number using a conventional typical receiver regardless of the type 
of design. The receiver is designed to be capable of receiving signals 
from a plurality of beams among transmitted signals, and to select the 
most preferred signal from these signals on the basis of a predetermined 
estimation standard. 
The first preferred embodiment of a radio communication system according to 
the present invention, as described above, has the following advantageous 
effects. 
The base station is capable of forming a plurality of beams of different 
radiated directions, and the terminal (receiver) is capable of selecting 
the best conditioned beam among the plurality of beams to receive it. 
Therefore, it is possible to realize the optimum receiving environment 
(link). 
In the environment for mobile communication, in addition to the beam 
directly turned toward a terminal from a base station, the beams turned to 
the other directions also tend to reach the terminal due to reflection and 
diffraction of the beams and so forth. Therefore, even if waves do not 
directly reach the terminal due to a shielding such as a building, it is 
possible to prevent the communication link from being interrupted by 
receiving radio waves of the beams turned to the other directions, so as 
to be effectively used for mobile communication. 
This system is effectively used for anti-multipass and anti-fading in 
mobile communication. In the case of a conventional system wherein the 
link between a base station and a terminal is limited to a particular 
single beam from the base station, if the states of signal (intensity, 
sensitivity and signal-to-noise ratio (S-N ratio)) are deteriorated under 
the influence of multipass and fading, it is difficult to maintain a good 
communication link. 
However, according to the present invention, since different link states 
are realized by a plurality of beams of the base station, it is possible 
to select the optimum beam among the plurality of beams so as to always 
make the communication link good. 
As the estimation standard as set forth above, the following standards may 
be established: 
(1) a received signal of the maximum intensity (or power) is selected from 
the signals of the arrived beams, and is received; and 
(2) a received signal of the maximum signal-to-noise ratio (S-N ratio) is 
selected from the signals of the arrived beams, and is received. 
In a case where the aforementioned estimation standard (1) is used, a beam 
for transmitting radio waves serving as direct waves which directly reach 
the terminal from the base station tends to be selected, so that the 
direction of the selected beam tends to be coincident with the direction 
of the terminal, whereby the gain tends to be in a high state. Therefore, 
it is possible to select the most preferred link on the basis of this 
estimation standard. 
In a case where the aforementioned estimation standard (2) is used, it is 
effective when signals are turbulent under the influence of multipass 
and/or fading. For example, as the example shown in FIG. 6, in a case 
where the radio waves transmitted by beams 1 and 2 is able to be received 
and a direct wave and a delayed wave of beam 1 are simultaneously received 
to interfere with each other although the intensity of the received radio 
waves of the beam 1 is higher than that of the beam 2, it is effective to 
select and receive the radio waves from the beam 2 which has no 
interference although the received intensity is low. 
Thus, it is possible to select the optimum signal in view of environment 
special to mobile communication by using a signal-to-noise ratio (S-N 
ratio which may be referred to as SIN ratio since interference is 
contained in noises in this case) as the estimation standard. 
In the case of the aforementioned estimation standard (2), a 
carrier-to-noise ratio (C-N ratio) may be substituted for the 
signal-to-noise ratio. There is an advantage in that the C-N ratio is 
easily measured. If other ratios are used as the estimation standard, the 
advantageous effects of the present invention are the same. For example, a 
new estimation standard may be established by combining the aforementioned 
two standards. 
Alternatively, error correction function for use in communication by 
digital modulation may be utilized to judge the quality of signals of each 
beams on the basis of the quantity of error correction performed for the 
signals, so as to select the best conditioned signal. 
Then, an antenna which is one element of the radio system will be 
described. The function of an antenna of the base station in the radio 
system of the present invention is that a plurality of narrow beams of a 
high gain and different maximum radiated directions are formed at the same 
time or by the time-division system. The structure of the antenna having 
such a function will be described below. 
FIG. 7 illustrates an example of a transmitting antenna which forms a 
plurality of beams by changing-over of a switch. Antennas 43, 44, 45 and 
46 have beams in which the maximum radiated directions are different from 
each other. The signals transmitted from a transmitter 48 are changed over 
by means of a switch 47. The changing-over of the switch is performed by 
means of a control unit 49, and the beam to be transmitted in synchronism 
with a transmitted signal is able to be switched in a time domain. 
FIG. 8 illustrates an example of a transmitting antenna which forms a 
plurality of beams by means of a phased array antenna. In this case, it is 
possible to turn the beams to desired directions by applying a given 
excited weight (amplitude and phase) to a plurality of antenna elements 
51, 52, 53 and 54. Since the beam pattern is synthesized by the plurality 
of antenna elements, it is possible to realize a radiation directivity 
having a sharp beam and a high gain. 
The excited weight is set by amplitude-variable amplifiers 55 and phase 
shifters 56 which are connected to the respective antenna elements. The 
amplifiers 55 are provided for setting the excited weight, and may be 
gain-variable amplifiers. Alternatively, the amplifiers 55 may be the 
combination of an amplifier and a variable attenuator. 
The phase shifters 56 are provided for setting the excited phase, and may 
use systems of a line switching type, a loaded line type and so forth 
regardless of the type of system. The output transmitted from a 
transmitter 58 is distributed toward the respective antenna elements by 
means of a distributor 57, and the excited weight is set by the amplifiers 
55 and the phase shifters 56 as set forth above. 
The direction of beam is switched by the time-division system, and is 
controlled by means of a control unit 59. The control unit 59 identities 
the beam to which the signal outputted from the transmitter belongs, and 
sets the gains (amplitudes) of the respective amplifiers and phase 
shifters and the quantities of phases so as to form the beam. 
FIG. 9 illustrates an example of an antenna which is capable of forming a 
plurality of beams at the same time. In this figure, the antenna comprises 
a plurality of antenna elements 61, 62, 63 and 64, to which amplifiers 65 
are connected, respectively, for amplifying and transmitting the signals 
transmitted to the respective antenna elements. In this example, a signal 
from a transmitter 68 is first divided into signals for each beams, to be 
transmitted to feed circuits 67 corresponding to the respective beams. The 
signals transmitted from the transmitter are able to be discriminated for 
each beam in the frequency domain, the time domain or the other means, and 
the respective signals discriminated for each beams contain information 
which is capable of identifying beam numbers to be used. The feed circuits 
67 set excited weights for the antenna elements 61, 62, 63 and 64 so as to 
realize radiation directivities corresponding to the respective beams. In 
order to set the excited weights, with respect to amplitude, a distributor 
is provided in each of the feed circuits and its distributed ratio is set 
at a give value, and with respect to phase, a phase shifter is provided in 
each of the feed circuits and its passing phase quantity is set at a given 
value. 
Since the distributed ratio and the phase quantity are constant for each 
beam, the distributor and the phase shifter in the feed circuit may have a 
simple construction in which the distributed ratio and the phase quantity 
are constant, not variable. The signals, whose excited weights are set, 
are collected for each antenna element by means of synthesizers (or 
distributors) 66 to be transmitted from the respective antenna elements. 
In this example of an antenna, there is an advantage in that a plurality 
of beams are commonly used at the same time. In addition, since it is not 
required to vary (switch) the excited weight, it is possible to simplify a 
component forming an antenna at a low cost. 
In the examples of FIGS. 8 and 9, both of the amplitude and phase have been 
set for setting the excited weight. However, in order to form beams of 
different radiated directions, the weight of only amplitude (when the 
radiation directivities of the antenna elements are different and so 
forth) or only phase may be varied. 
FIG. 10 illustrates an example of an antenna which is capable of forming a 
plurality of beams at the same time, similar to FIG. 9. In this figure, 
the antenna comprises a plurality of antenna elements 71, 72, 73 and 74, 
to which amplifiers 75 are connected, respectively, for amplifying and 
transmitting the signals supplied to the respective antennas. In this 
example, a signal transmitted from a transmitter 78 is first divided into 
signals of the respective beams, which are inputted to a Butler matrix 
circuit 76, respectively. 
In the Butler matrix circuit 76, an input signal is distributed by a hybrid 
coupler 77 so as to appear at output ports thereof at given phase 
differences, and the output port is connected to the antenna elements to 
form beams having a synthesized-directivity different from radiated 
directions. In this example of an antenna, there is an advantage in that a 
plurality of beams are able to be commonly used at the same time, similar 
to the example of FIG. 9, and it is possible to simply a component forming 
an antenna at a low cost. The same operation can be realized by a 
directional coupler in place of the Butler matrix system. 
Furthermore, the antenna of the terminal (receiver) in the first preferred 
embodiment may use any systems. With respect to the directivity thereof, 
if it is capable of receiving radio waves from a base station (the 
directivity gain toward the base station is greater than a certain value, 
for example, a wide-angle directivity), it is possible to obtain the 
advantageous effects of the present invention. Naturally, it is possible 
to realize a better communication state by enhancing the gain of the 
receiving antenna. 
As a method for enhancing the gain of the receiving antenna, for example, 
it is possible to use a beam scanning antenna which turns a beam toward a 
base station or a radio-waves arrival direction (for example, a phased 
array antenna), and an adaptive antenna which suppresses jamming waves by 
forming the directivity. 
Referring to the figures, the second preferred embodiment of a radio system 
according to the present invention will be described below. 
FIGS. 11 and 12 illustrate the second preferred embodiment of a radio 
system according to the present invention. FIG. 11 illustrates the 
propagation of radio waves transmitted from a base station 81 (first radio 
station) and received by a terminal 82 (second radio station), and FIG. 12 
illustrates the propagation of radio waves transmitted from the terminal 
82 and received by the base station 81. 
The base station 81 forms a plurality of beams (n beams) of different 
maximum radiated directions to transmit the beams. Among these beams, a 
number of beams reach the terminal 82. The beams radiated from the base 
station 81 have a narrow beam and a high gain. The respective beams may be 
formed at the same time or by the time-division system. The constructions 
of the antennas thereof are the same as those of FIGS. 7 through 10 in the 
first preferred embodiment. The signals transmitted from the respective 
beams of the base station 81 is also the same as that of FIG. 5. 
The feature of this preferred embodiment is that the signals transmitted by 
the plurality of beams transmitted by the base station contain information 
being capable of identifying a beam by which the signal is transmitted. In 
addition to the case of FIG. 5, the respective beam numbers may be 
identified by changing the frequency band for each beam, or the 
relationship between the carrier frequency and the beam number information 
may be established. In the terminal 82, the signals transmitted from the 
base station are received by an antenna of a wide-angle directivity, and 
it is designed to identify a beam by which the signal is transmitted. 
Although this design depends upon how to cause information on beam number 
to be contained in the signal, it is possible to identify the beam number 
using a conventional typical receiver regardless of the design. The 
receiver is designed to be capable of receiving signals from a plurality 
of beams among the transmitted signals, and of selecting the optimum 
signal from these signals on the basis of a predetermined estimation 
standard. 
The predetermined estimation standard may be the same as that in the first 
preferred embodiment of a radio communication system according to the 
present invention. 
FIG. 12 illustrates the state in which the radio-wave signal transmitted 
from the terminal 82 is received by the base station 81. In this case, 
both of the transmitting antenna of the terminal and the receiving antenna 
of the base station have a wide-angle directivity. 
FIG. 13 is a flowchart illustrating a communication method in the second 
preferred embodiment of a radio communication system, according to the 
present invention, which is shown in FIGS. 11 and 12. The operations in 
the respective steps will be described below. 
At step S1, in the base station, signals containing beam number information 
on all of n beams are carried on signals to be transmitted, and the 
signals are transmitted from the base station. 
Then, the operations at steps S2 through S4 are performed on the terminal 
side. First, at step S2, one beam or more among n beams are received. This 
receiving is performed by a receiving antenna of a wide-angle beam. Then, 
at step S3 the best beam number is selected from the beam (beam number) 
received by the terminal in a predetermined estimation standard, and the 
selected beam number is assumed to be j. This selection may be performed 
by a processor, such as a CPU, or a comparator for merely comparing gains 
and so forth. Thereafter, at step S4, the selected beam number j is 
transmitted from the terminal toward the base station. This transmission 
is performed by a transmitting antenna of a wide-angle beam. 
Then, at step S5, the base station receives the beam number j transmitted 
from the terminal. This receiving is performed by a receiving antenna of a 
wide-angle beam. 
Then, at step S6, the base station transmits "information", which the 
terminal desires to be transmitted, using a beam of number j among a 
plurality of beams formed by the transmitting antenna. The term 
"information" herein is information, such as image, picture, voice and 
other data, which is requested by the terminal. 
Then, the operation returns the terminal side again, and at step S7, the 
terminal receives the signal transmitted from the beam of number j the 
base station, and obtains the required information. 
According to the system construction and control method as mentioned above, 
in addition to the advantageous effects of the first preferred embodiment, 
it is expected that the second preferred embodiment has the following 
advantageous effects. 
First of all, the "information" finally requested by the terminal has a 
large volume of information such as picture, image and data. According to 
the conventional method, in order to this information without any errors, 
it is required to accurately enhance the gain of an antenna and control 
the direction of a beam so as to form a good communication link, so that 
the processing therefor and the construction of a radio 
transmitter-receiver are complicated. 
However, according to the present invention, there is an advantage in that 
it is possible to form a communication link by a short period of time 
using a simple radio system, since only beam information is exchanged at 
the stage prior to the formation of a good communication link and since 
the antenna to be used has a wide-angle, simple structure. 
There is also an advantage in that it is possible to effectively use 
communication links, frequency bands and output power on the transmitting 
side, by quickly transmitting and receiving information to be requested by 
the terminal after realizing the good communication link. 
To put the aforementioned advantageous effects in other words, there is a 
great advantageous effect in order to increase the number of terminals 
(the number of users) joined in this communication system. 
Moreover, it is convenient to perform the exchange of information at a 
large capacity and at a high speed. 
In a communication service for offering various information on demand from 
a terminal, although the information capacity from the terminal to a base 
station is small, the information capacity from the base station to the 
terminal is great. If the present invention is applied to such a radio 
communication system, there is an extremely great advantageous effect. 
According to the present invention, the same effect can be obtained if the 
following changes are done. 
First of all, dB the receiving antennas of FIGS. 11 and 12 (the receiving 
antenna of the terminal 82 in FIG. 11, and the receiving antenna of the 
base station 81 in FIG. 12), a high-gain antenna, such as a phased array 
antenna and an adaptive antenna, which is capable of accurately forming 
beams In the arrival direction of radio waves, may be used. In particular, 
it is possible to transmit information at a larger capacity and at a 
higher speed by enhancing the gain of the receiving antenna of the 
terminal at the stage (step 57) at which the information is finally 
received from the base station. 
While the plurality of beams transmitted from the base station have had 
different maximum radiated directions in the aforementioned preferred 
embodiments, some of the plurality of beams may have the same maximum 
radiated direction. In this case, since the condition for causing 
interference such as multipass and fading is varied by changing the 
transmitting frequency of the beam radiated in the same direction, the 
probability that the communication link can be maintained by any one of 
the frequencies. 
While the information on the beam number has been arranged at the head (or 
a part) of a time slot in FIG. 5, it may be arranged at any places in the 
frame. In particular, it is possible to effectively use the frame by 
independently providing a slot (in which the respective beam numbers are 
transmitted by the respective beams) for transmitting only the beam 
number.