Communication method, base station and terminal apparatus

In order cope with a change of the transmitting capacity in a wireless telephone system. A number of transmission channels are set within the transmission frequency band prepared for each base station. When a communication is made between the terminal equipment and the base station through the transmission channels, at least a first transmission channel and a second transmission channel are set as the transmission channel depending on a class of information to be transmitted. The first transmission channel is set to have a fixed transmitting capacity and the second transmission channel is set so that the minimum transmitting capacity may be defined and the transmitting capacity greater than the minimum transmitting capacity may be set depending on the setting condition of the transmission channels within the transmission frequency band prepared.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method of communication which is 
applicable to a base station or a terminal equipment of, for example, the 
cellular wireless telephone system as well as to the base station and the 
terminal equipment to which the method of communication is applied. 
2. Description of the Related Art 
In a mobile communication such as a wireless telephone system, a plurality 
of base stations are arranged at regular intervals to make a service area 
and the multiple access which makes a plurality of mobile stations 
(terminal equipments or a subscriber) linked is performed in each base 
station. In this case, a predetermined transmission frequency band is 
allocated before hand to the respective base stations and a plurality of 
transmission channels are set or provided within the transmission 
frequency band. When a demand for communication is issued from any of the 
terminal equipments and so on, one of these transmission channels is 
allocated to that terminal equipment and the terminal equipment uses the 
allocated transmission channel to make the communication started via the 
base station. 
As the communication system in which the transmission channels are set in 
this manner, there are, for example, Frequency Division Multiple Access 
(FDMA), Time Division Multiple Access (TDMA) and Code Division Multiple 
Access (CDMA), etc. 
Describing briefly each of these systems, the communication system of FDMA 
is one in which a plurality of transmission channels are provided by 
dividing the transmission band prepared by a unit of frequency. The 
communication system of TDMA is one in which a transmission channel is 
divided by a predetermined time unit to form a plurality of time slots 
within a single transmission channel, each of the time slots being 
allocated to the terminal equipments to be linked. Therefore, it is 
possible to link the plurality of terminal equipment using the single 
transmission channel. The communication system of CDMA is one in which a 
specified code is allocated to each of the terminal equipments and a 
carrier having the same frequency is subjected to spectrum spread 
modulation by the code for transmitting it to the base station. The 
receiving side discriminates a signal transmitted from that terminal 
equipment using the same code which is synchronized. 
Incidentally, in the wireless telephone system, by whichever system the 
transmission channel may be provided, the transmitting capacity which can 
be transmitted by a single transmission channel is determined and so it is 
impossible to alter the transmitting capacity depending on a class of data 
to be transmitted. Generally, in case of the wireless telephone system, 
the transmitting capacity of one transmission channel is set to be such a 
capacity as is able to transmit audio data for communication by telephone. 
However, it is recently being put into practice to enable various data 
other than audio data to be transmitted by using a wireless terminal such 
as a portable telephone. If it is possible to transmit data of only a 
certain transmitting capacity on one transmission channel as described 
above, it will inconveniently take plenty of time to transmit a great deal 
of data for example. In order to overcome the inconvenience, it will be 
necessary to set a greater transmitting capacity as the transmitting 
capacity which one transmission channel can transmit. However, if the 
transmitting capacity of one channel is made greater, the wider frequency 
band width of one transmission channel will become necessary, so that the 
number of transmission channels which can be set within the transmission 
frequency band allocated to one base station will decrease. Moreover, when 
data of comparatively small amount such as audio data are transmitted, 
data amount transmitted through respective transmission channels becomes 
smaller than an amount which can be transmitted through that channel, 
which will result in an inconvenience that the transmission frequency band 
is not effectively utilized. 
SUMMARY OF THE INVENTION 
In view of such aspects, it is an object of the present invention to make 
it possible to cope with the change of the transmitting capacity, etc. in 
the wireless communication such as the wireless telephone system. 
According to a first aspect of the present invention, a cellular system is 
one having a subscriber and a base station, a communication resource 
allocation method, and includes a class information transmitting step at 
the subscriber for transmitting class information about communicated 
information from the subscriber to the base station, a class information 
receiving step at the base station for receiving the transmitted class 
information from the subscriber, and a resource allocating step at the 
base station for calculating the number of communication resources which 
is able to be allocated for new communication tasks based on received 
class information by the class information receiving step and on a 
resource utilizing situation at the time. 
According to a second aspect of the present invention, a base station 
apparatus of a cellular system includes a class information receiving 
means for receiving class information transmitted from a subscriber, a 
resource allocating means for calculating the number of communication 
resources which is able to be allocated for new communication tasks based 
on received class information by the class information receiving means and 
on a resource utilizing situation at the time, and a transmitting means 
for transmitting an output signal of the resource allocating means to the 
subscriber. 
According to a third aspect of the present invention, a subscriber 
apparatus of a cellular system includes a transmitting means for 
transmitting class information about communicating information to a base 
station, a receiving means for receiving information from the base 
station. The transmitting means and the receiving means communicate within 
allocated communication resource by the base station.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An embodiment according to the present invention will be described below 
with reference to the accompanying drawings. 
In the embodiment, the present invention is applied to the cellular 
wireless telephone system in which the base stations are arranged at 
regular intervals to establish a communication area. Firstly, a 
configuration of the terminal equipment used for the wireless telephone 
system is shown in FIG. 1. Describing first the configuration of its 
receiving system, an antenna 11 is connected to a receiver 13 through an 
antenna sharing unit 12 and an output frequency signal of a frequency 
synthesizer 14 made of a PLL circuit or the like is supplied to the 
receiver 13. Here, a received signal supplied from the antenna 11 to the 
receiver 13 is mixed with the output frequency signal of the frequency 
synthesizer 14 for converting the received signal of a predetermined 
frequency into an intermediate frequency signal. In this case, the output 
frequency of the frequency synthesizer 14 is determined under the control 
of the control unit 22 which is a system controller for controlling a 
communicating operation of the terminal equipment. 
The received signal converted into the intermediate signal is supplied to a 
demodulator 15 where a demodulation processing is performed under a 
prescribed communication standard to make received data in a symbolic 
sequence. The demodulated received data in the symbolic sequence are 
supplied to a data processor 16 for extracting necessary data which are 
supplied to respective corresponding signal processors. 
For instance, concerning audio data contained in the received data, they 
are supplied to an audio processor 17 and converted into an analogue audio 
signal by audio processing in the audio processor 17 for driving a speaker 
18 connected thereto. Concerning facsimile data contained in the received 
data, they are supplied to a facsimile processor 24 and are made into data 
for supplying to a facsimile equipment(not shown) in the facsimile 
processor 24. Also, concerning electronic mail data contained in the 
received data, they are supplied to an electronic mail processor 25 and 
are made into data for supplying to an electronic mail receiver (a 
personal computer or an electronic portable terminal, etc. not shown) in 
the electronic mail processor 25. Again, concerning control data contained 
in the received data, they are supplied to the control unit 22 where a 
corresponding control of communication is performed. In addition, the 
class of these received data is distinguished by control data, etc. 
contained in the received data. 
Next, describing a transmitting system of the terminal equipment, for 
example concerning audio data, an audio signal picked up by a microphone 
19 connected to the audio processor 17 is made into digital audio data for 
transmission in the audio processor 17 and the audio data is supplied to 
the data processor 16 which arranges them in a predetermined position of 
the symbolic sequence for transmission. In other positions of the symbolic 
sequence for transmission, a predetermined synchronous pattern and control 
data supplied by the control unit 22 or the like are arranged. 
And then, the transmitting data in the symbolic sequence output by the data 
processor 16 is supplied to a modulator 20 which performs a modulation 
processing for transmission, and the modulated signal is supplied to a 
transmitter 21 which mixes it with the frequency signal output by the 
frequency synthesizer 14 and frequency converts into a predetermined 
transmitting frequency. The transmitting signal of the transmitting 
frequency is supplied to the antenna 11 through the antenna sharing unit 
12 for wireless transmission. 
Furthermore, concerning a facsimile signal supplied from an unshown 
facsimile equipment (or a computer equipment to which a modem for 
facsimile communication is connected, etc.) to the facsimile processor 24, 
the facsimile processor makes the signal into facsimile data for 
transmission and supplies the facsimile data to the data processor 16 
which performs the same transmission processing as that in the aforesaid 
case of audio data. Moreover, concerning electronic mail data supplied 
from an unshown electronic mail transmitting/receiving equipment to the 
electronic mail processor 25, the electronic mail processor makes it into 
electronic mail data to the data processor 16 which performs the same 
transmission processing as that in the case of audio data. 
In addition, various keys 23 are connected to the control unit 22 and 
operations of sending or receiving are performed by means of the keys 23. 
Furthermore, the terminal equipment according to the present embodiment is 
capable of performing simultaneously the communication processing of a 
plurality of transmission channels and the transmission channel is set 
under the control of the control unit 22. As to the processing which sets 
simultaneously the plurality of transmission channels, it will be 
described later. As to the facsimile processor 24 and the electronic mail 
processor 25, when they do not perform the transmission processing of 
corresponding data, the operation of these processors is stopped, whereas, 
when they perform the transmission processing of corresponding data, they 
are activated under the control of the control unit 22 and then execute a 
corresponding application program for processing. 
In the present embodiment, the facsimile processor 24 and the electronic 
mail processor 25 comprise a memory means for storing the received data 
and the transmitting data and transferring these data to the facsimile 
equipment or the computer equipment connected thereto after once storing 
the data received from the base station side. On the other hand, they 
transmit to the base station side the data which are transferred from the 
facsimile equipment or the computer equipment and stored after the 
transmission channel has been set. Alternatively, the terminal equipment 
itself may comprise a function corresponding to the facsimile equipment or 
the computer equipment. 
Next, referring to FIG. 2, a configuration of the base station which makes 
communication with the terminal equipment will be described. A basic 
configuration for the communicating processing of the base station is the 
same as that of the terminal equipment, but a configuration for making 
communication simultaneously with a plurality of the terminal equipments 
is different. Particularly, antennas 51, 52 of two systems are connected 
to a combine/separate circuit 53 which separates received signals into a 
signal of each transmission channel, etc. and for separating the received 
signal from each terminal equipment into signals of plural systems of a 
single or a predetermined number of terminal equipment(s). The separate 
received signal of the respective systems is supplied to respective 
different communicating units 54a, 54b, . . . 54n (where n is an arbitrary 
number) each of which performs a reception processing, a demodulating 
processing and a transmission processing for sending the received data 
demodulated to an exclusive line 57 connected to a communication control 
station for generally controlling the base stations, thus causing the 
processed signal to be sent via the combine/separate circuit 56 to the 
exclusive line 57. 
Also, a signal transmitted from the side of the exclusive line 57 to the 
base station is separated by the combine/separate circuit 56 into signals 
of plural systems and the separated signals of each system are supplied to 
the respective different communicating units 54a, 54b, . . . 54n which 
perform the reception processing from the exclusive line 57 and then 
perform the modulation processing and the transmission processing for 
transmitting them to the terminal equipment, thus making them to be 
supplied to either of the antennas 51 and 52 via the combine/separate 
circuit 53 for wireless transmission. 
In addition, the transmission processing and the reception processing in 
each of the communicating units 54a to 54n of the base station are 
performed under the control of a control unit 55, and necessary addition 
or distinction, etc. of control data is also performed under the control 
of the control unit 55. Further, when call demand data are transmitted 
from the terminal equipment to the base station of the present embodiment, 
data indicating a class of data to be transmitted are added. Concerning 
the class of data, at least audio data for communication by telephone or 
data other than the audio data for communication by telephone (facsimile 
data, electronic mail data, etc.) are differentiated. 
Next, a state of communication when a communication is made between the 
above terminal equipment and the base station will be described. In the 
present embodiment, the transmitting capacity when a communication is made 
between the terminal equipment and the base station can be set adaptively. 
The processing for adaptively setting the transmission capacity when the 
TDMA system (time division multiple access) is applied as a communication 
system between the terminal equipment and the base station will be 
described. In case of TDMA-TDD (time division duplex) system, the 
transmitting frequency is equal to the receiving frequency and as a 
transmission signal which is transmitted using the same frequency a burst 
signal for a predetermined unit time (e.g. several hundred .mu.sec or so) 
is used, the burst signal being intermittently transmitted and received 
between the terminal equipment and the base station. 
The burst signal of one unit corresponds to a signal of one slot period, 
and, for examples an eight slots period defines one frame as shown in FIG. 
3, this one frame being repeated. When one frame is defined by the eight 
slots period, for example, the first half of four slots of one frame is 
used for transmitting from the base station and the second half of four 
slots is used for receiving at the base station. Here, the first half of 
the four slots period forming the transmitting slots period are given slot 
numbers as slot T1, T2, T3 and T4 and the second half of the four slots 
period forming the receiving slots period are given slot numbers as slot 
R1, R2, R3 and R4. 
When the audio data (audio data for communication by telephone which are 
processed by the audio processor 17 in the terminal equipment) are 
transmitted, the bidirectional communication is performed using the slots 
T1, R1 as shown in FIG. 4A between one terminal equipment and the base 
station. Also, between another terminal equipment and the base station, 
the bidirectional communication is performed using the slots T2, R2. 
Concerning also slots T3, R3 and slots T4, R4, the communications with 
respective other terminal equipments is performed. Accordingly, when the 
audio data for communication by telephone is transmitted, theoretical four 
transmission channels are set using one transmission frequency band and so 
it is possible to simultaneously communicate with up to four terminal 
equipments. 
Furthermore, the terminal equipment according to the present embodiment is 
able to transmit and receive the data other than the audio data. In that 
case, the base station will estimate the transmitting capacity for data to 
be transmitted and determine the number of slots allocated to a 
communication between one terminal equipment and the base station. 
Particularly, in case of data that will require almost the same 
transmitting capacity as that of the case where the audio data are 
transmitted, the transmission channel which uses one transmitting slot and 
one receiving slot in one frame will be set, as shown in FIG. 4A. 
Moreover, in case of data which require the transmitting capacity about 
twice that of the case where the audio data are transmitted, the 
transmission channel which uses two transmitting slots and two receiving 
slots (here, T1, T2 and R1, R2 are used) in one frame for one terminal 
equipment will be set, as shown in FIG. 4B. Furthermore, in case of data 
which require the transmitting capacity about three times that of the case 
where the audio data are transmitted, the transmission channel which uses 
three transmitting slots and three receiving slots (here, T1, T2, T3 and 
R1, R2, R3 are used) in one frame for one terminal equipment will be set, 
as shown in FIG. 4C. In addition, in case of data which require the 
transmitting capacity about four times that of the case where the audio 
data are transmitted, the transmission channel which uses all transmitting 
slots and all receiving slots in one frame for one terminal equipment will 
be set. However, the slot allocation is not limited to the continuous slot 
allocation as shown in FIGS. 4B, 4C, but may be such allocation that 
separate slots (e.g. transmitting slot T1 and T3) are simultaneously 
employed. 
In the present embodiment, when data other than such audio data are to be 
transmitted, the setting of the number of slots to be used is performed by 
estimating a vacant channel condition within the transmission frequency 
band allocated to the present base station. Particularly, if there are 
sufficient vacant channels (i.e. slots unused for communication) within 
the transmission frequency band allocated to the present base station, 
such a channel allocation is performed that the simultaneous use of plural 
slots as shown in FIGS. 4B, 4C is allowed. Conversely, if it is estimated 
that there are few vacant channels, even though a transmission start 
demand of data other than the audio data may be issued, only an allocation 
of a transmission channel with the minimum capacity (i.e. the allocation 
of one transmitting slot and one receiving slot in one frame, as shown in 
FIG. 4A) is performed, and data transmission takes place at a low 
transmission rate with the minimum transmitting capacity. With the data 
transmission at the low transmission rate, it will take some time to 
complete the data transmission, whereas by providing memories to store the 
transmitted data in both the transmitting side and the receiving side, it 
will be possible to cope with the change of the transmission rate. 
Further, in such a channel allocation, after the transmission of data other 
than the audio data has been started, the number of slots to be used may 
be changed depending on the estimation of the vacant channels by the 
control unit of the base station. For example, it is conceivable that, 
after the communication has been started under the minimum slot allocation 
of one transmitting slot and one receiving slot in one frame, if the 
control unit 55 of the base station estimates that the vacant channels 
increase and room is made in links, channel allocation data for increasing 
the number of slots to be allocated are transmitted to the terminal 
equipment under communication in order to increase the number of slots to 
be allocated in the middle of communication for increasing the 
transmitting capacity. 
Conversely, when the communication has been started under the allocation of 
plural transmitting slots and plural receiving slots in one frame, if the 
control unit 55 of the base station estimates that the vacant channels 
decrease, the channel allocation data for decreasing the number of slots 
to be allocated may be transmitted to the terminal equipment under 
communication in order to decrease the number of slots to be allocated in 
the middle of communication for decreasing the transmitting capacity. 
Moreover, when a transmit demand of the transmission of data other than the 
audio data is issued from the terminal equipment, etc. to the base 
station, if the control unit 55 of the base station estimates that there 
are few vacant channels, the channel allocation for that transmit demand 
may not be performed, and when the vacant channels (the number of vacant 
slots) increases over a predetermined value, the channel allocation for 
that transmit demand may be performed. 
Furthermore, in the aforesaid embodiment, the same number of slots are 
allocated for both an up link from the terminal equipment to the base 
station and a down link from the base station to the terminal equipment, 
whereas when the slot allocation is performed for the transmission of data 
other than the audio data, plural slots may be allocated only to the link 
in the direction of data transmission. 
Having described the TDMA-TDD system in which the same transmitting 
frequency is used for both the up link from the terminal equipment to the 
base station and the down link from the base station to the terminal 
equipment, the above slot allocation is of course applicable to a case 
where data are transmitted in such a frame structure that the slots are 
arranged in the up link and the down link respectively using transmitting 
frequencies different between the up link and the down link. 
Having described so far the embodiment in which the present invention is 
applied to TDMA system, the present invention's processing is of course 
applicable to other communication systems. By way of another example, a 
case where the present invention is applied to a system in which a 
multicarrier signal is transmitted will be described below. 
When performing the transmission of the multicarrier signal, a plurality of 
subcarriers are arranged at intervals of a predetermined frequency within 
one transmission frequency band required for the communication between the 
base station and the terminal equipment, and information are dispersed to 
the respective subcarriers to modulate them for data transmission. For 
example, as a modulation processing in the base station or the terminal 
equipment (In case of the terminal equipment, it corresponds to the 
modulation processing in the modulator 20. In case of the base station, it 
corresponds to the modulation processing included in each communicating 
unit 54a to 54n), a processing of a configuration shown in FIG. 5 will be 
performed. 
Thus, the transmitting data in the symbolic sequence are supplied to a 
convolution encoder 61 where they are encoded into convolution encoded 
data which are supplied to an interleave buffer 62. The buffer 62 performs 
an interleave processing which rearranges the data arrangement in a unit 
of a predetermined length and the interleaved data is made into a 
transmitting signal which is DQPSK modulated by a DQPSK modulator 63. The 
modulated transmitting signal is supplied to an inverse fast Fourier 
transform circuit (IFFT circuit) 64 where the fast Fourier transform 
processing is performed, the transform processing being such that data 
arranged on the frequency axis are transformed into the multicarrier 
signal arranged on the time axis. 
And then, the multicarrier signal output by the FFT circuit 64 is supplied 
to a window multiplier circuit 65 where every signal of a predetermined 
unit length is multiplied by window multiplier data, and the data 
multiplied by the window multiplier data are converted into an analogue 
signal in a digital/analogue converter 66. The analogue signal is supplied 
to the transmitter 21 (see FIG. 1) where it is frequency converted for 
transmitting with a predetermined frequency band. 
Next, as a demodulation processing in the terminal equipment or the base 
station which receives the multicarrier signal processed and transmitted 
in this manner. In case of the terminal equipment it corresponds to the 
demodulation processing in the demodulator 15. In case of the base 
station, it corresponds to the demodulation processing contained in each 
communicating unit 54a to 54n), a processing is shown in FIG. 6. 
Thus, the signal received and converted into the intermediate signal is 
supplied to an analogue/digital converter 71 where it is sampled by a 
predetermined sampling frequency, and the sampled data are supplied to an 
inverse window multiplier circuit 72 where every signal of a predetermined 
unit length is multiplied by inverse window multiplier data (data inverse 
to the window multiplier data when transmitting) for restoring the 
original data. The restored data are supplied to the fast Fourier 
transform circuit (FFT circuit) 73 which performs the fast Fourier 
transform processing for transforming the multicarrier signal arranged in 
time series into data of each of sub-carriers. The transformed signal is 
then supplied to a DQPSK demodulator 74 for demodulation processing and 
the demodulated signal is supplied to a deinterleave buffer 75 which 
performs a deinterleave processing for restoring the original arrangement. 
The data of the original arrangement which are interleave processed are 
supplied to a Viterbi decoder 76 which performs a decode processing of the 
convolution encoded data for providing received data of the symbolic 
sequence. 
The foregoing encoding and decoding are not restricted to the convolution 
coding and the Viterbi decoding. It will be sufficient to prepare an 
encoder for taking a large distance between the transmitting symbolic 
sequences for the encoding, and a decoder which performs the maximum 
likelihood sequence estimation on the bases of the receiving symbol for 
the decoding. Thus, the know Turbo code or the like can be employed. 
Next, a processing for simultaneously transmitting data of plural classes 
in the case where the multicarrier signal thus processed is transmitted 
will be described with reference to FIGS. 7A, 7B. Firstly, as shown in 
FIG. 7A, one transmission frequency band F.sub.A having a predetermined 
frequency band width (e.g. 150 kH.sub.z width) is established, and in a 
center of that frequency band ten subcarrier signals f.sub.1, f.sub.2, . . 
. f.sub.10 are arranged at intervals of a predetermined frequency (e.g. 
12.5 kH.sub.z interval) for transmitting the respective subcarriers 
modulated by the data. In this regard, for example, data such as the audio 
data are dispersed and modulate these ten subcarrier signals f.sub.i to 
f.sub.10 for transmission, and the audio data are bidirectionally 
transmitted between the terminal equipments linked via the base station, 
thus enabling a data transmission such as a communication through the 
voice to be performed. Further, in FIGS. 7A, 7B, f.sub.c denotes a central 
frequency. 
A transmitting condition shown in 7A corresponds to the case where the 
audio data for communication by telephone are transmitted as well as the 
case where the minimum channel allocation is performed when data other 
than the audio data are transmitted. When data other than the audio data 
are transmitted, if there is room for vacant channels of the transmission 
channel allocated to the base station, two or more transmission frequency 
bands will be allocated. For example, as shown in FIG. 7B, when a 
transmission frequency band of 2F.sub.A twice that in the case of FIG. 7A 
is allocated using the transmission frequency band for two channels, 
twenty subcarrier signals f.sub.1, f.sub.2 . . . , f.sub.20 are arranged 
so that data may be dispersed and modulated by the respective subcarrier 
signals for transmission, thereby ensuring the transmitting capacity twice 
that in the case where the audio data are transmitted. Although not shown, 
it will be possible to allocate three or more times the transmission 
frequency band. 
The allocation of the transmission frequency band when the multicarrier 
signal is transmitted may be performed under the control of the control 
unit 55 in the base station by the same processing as that in the case 
where the slot allocation is performed according to the aforesaid TDMA 
system. 
In addition, when the multicarrier signal is transmitted, the frequency 
interval of the multicarrier signal within one transmission frequency band 
may be narrowed for increasing the number of the subcarrier signal being 
arranged rather than increasing the transmission frequency band for 
increasing the transmitting capacity. For example, when the audio data for 
communication by telephone are transmitted, the ten subcarrier signals may 
be arranged within one transmission frequency band at intervals of 12.5 
kH.sub.z, and when other data are transmitted and the transmitting 
capacity is desired to be greater, the twenty subcarrier signals may be 
arranged within one transmission frequency band at intervals of 6.25 
kH.sub.z. 
Having described the embodiment in which the video data for facsimile and 
the data for electronic mail as the data other than the audio data are 
transmitted, the present invention is of course applicable also to a case 
where other classes of data are transmitted. Moreover, it is also 
applicable to a communication to which a transmission system other than 
TDMA system and the multicarrier system is applied, particularly to a 
processing for simultaneously setting a plurality of logical transmission 
channels in that communication. For example, in case of CDMA system, when 
the transmitting capacity is to be increased, if data to be transmitted 
are caused to be dispersed by using a plurality of spread code and at the 
same time the plurality of logical transmission channels are set for 
transmission, it will be possible to deal with it. Furthermore, a 
destination of each application is not restricted to one place and it may 
be possible to communicate with different destinations. 
According to the present invention, by enabling at least a first 
transmission channel and a second transmission channel to be set as the 
transmission channel depending on a class of information to be 
transmitted, setting the first transmission channel to have a fixed 
transmitting capacity, and setting the second transmission channel so that 
the minimum transmitting capacity may be determined and a transmission 
capacity greater than the minimum transmitting capacity may be set 
depending on the setting condition of the transmission channels within the 
transmission frequency band prepared, concerning data for which the 
transmitting capacity is fixed such as the audio data, if the first 
channel is set for transmission, the efficient transmission without a 
waste of transmitting capacity can be performed, and at the same time, 
when a great deal of data are to be transmitted, it is sufficient to use 
the second channel and to set the transmitting capacity greater, thereby 
allowing a communication in which the prepared transmission frequency band 
is effectively utilized to be made. 
In this case, the second transmission channel is set so that the 
transmitting capacity may be made variable depending on a change of the 
setting condition of the transmission channel within the transmission 
frequency band prepared, thereby causing an appropriate transmitting 
capacity to be set depending on the vacant channel condition, etc at that 
time, which in turn results in a communication in which the transmission 
frequency band is more effectively utilized. 
Furthermore, when making the transmitting capacity variable, by setting the 
transmitting capacity of the second transmission channel so that the 
transmitting capacity may be limited to a minimum when there are few 
vacant channels within the transmission frequency band prepared, it is 
possible to secure necessary channels in the wireless telephone system or 
the like. 
Moreover, in the aforesaid case, by setting the second channel only when 
there are vacant channels more than the predetermined value within the 
transmission frequency band prepared, only when there is room for links, 
the channel whose transmitting capacity is adaptively set will be 
prepared, whereas when the links are crowded only the transmission channel 
of fixed capacity will be set for making the transmission frequency band 
to be effectively unitized. 
In addition, in the above case, by making information transmitted through 
the first channel to be audio information and making information 
transmitted through the second channel to be information other than the 
audio, information such as the audio communication by telephone requiring 
the real-time nature are satisfactorily transmitted through the 
transmission channel of fixed transmitting capacity, and at the same time, 
concerning the data for electronic mail or the data for the computer whose 
data amount is uncertain, when there is room for the links, it is possible 
to transmit them fast through the transmission channel of greater 
capacity, thus enabling the appropriate transmission depending on the 
class of respective information to be performed. 
Having described preferred embodiments of the present invention with 
reference to the accompanying drawings, it is to be understood that the 
present invention is not limited to the above-mentioned embodiments and 
that various changes and modifications can be effected therein by one 
skilled in the art without departing from the spirit or scope of the 
present invention as defined in the appended claims.