DESCRIPTION
TECHNICAL FIELD
The present invention relates to a.
communications system for exchange of information (data)
between communications apparatuses by a multicarrier
transmission mode by a series of subcarriers, more
particularly relates to a communications apparatus
accommodated in that communications system.
BACKGROUND ART
A most preferred example of the above
communications system discussed in the present invention
is a mobile communications system. The following
explanation will be made by taking as an example this
mobile communications system. Accordingly, if according
to this example, the communications apparatus is a (i)
base station (or a higher base station controller
thereof) and/or a (ii) mobile station (including a mobile
terminal such as a PDA). Note that for convenience, in
the later explanation, the former (i) will be referred to
as the "base station" and the latter (ii) will be simply
referred to as the "terminal" in some cases. Note that,
as will be clear in the later explanation, the present
invention can be substantially equivalently applied to
not only the above base station, but also the above
terminal. It is not particularly necessary to
differentiate between the two.
In a mobile communications system, securing a
desired transmission rate for a user is a major issue in
providing it with service. On the other hand, usually the
used frequency band used by the mobile communications
system is fixed for each system. Therefore, even if
employing user multiplexing etc., the maximum
transmission rate thereof ends up being restricted. For

this reason, the method of flexibly changing the used
frequency band in accordance with the required
transmission rate is being studied.
Further, when considered by the mobile
communications system as a whole, the state of usage
differs for each used frequency band. Sometimes a band is
not used at all. For this reason, from the viewpoint of
the effective utilization of the frequency, it has been
studied to make the used frequency band variable.
Under this situation, technology of making the
used frequency band variable in an MC (Multi-Carrier)-
CDMA (Code Division Multiple Access) or OFDM (Orthogonal
Frequency Division Multiplex) or other multicarrier
transmission mobile communications system has been
proposed. For example, the methods disclosed in the
following four Patent Documents 1 to 4 are proposed.
Details thereof will be explained later with reference to
the drawings, but these may be summarized as follows:
1) A "multiple connection method and apparatus"
disclosed in Patent Document 1 is characterized by
dividing a series of subcarriers so as to freely assign
used frequency bands to users.
2) A "mobile station, base station, and mobile
communications network" disclosed in Patent Document 2
are characterized in that a subcarrier band dedicated to
transmission of control signals is set in the
communications network.
3) A "channel allocation method" disclosed in
Patent Document 3 is characterized by changing the number
of subcarriers in the series of subcarriers in accordance
with length of the communications distance between the
base station and the mobile station.
4) A "wireless transmission apparatus and
wireless communications method" disclosed in Patent
Document 4 is characterized by changing the bandwidth of
each subcarrier in the series of subcarriers to make the
bandwidth of the used frequency band variable.

[Patent Document 1] Japanese Patent Publication
(A) No. 9-205411
[Patent Document 2] Japanese Patent Publication (A)
No. 2003-264524
[Patent Document 3] Japanese Patent Publication (A)
No. 2004-21476
[Patent Document 4] Japanese Patent Publication (A)
No. 2002-330467
DISCLOSURE OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
The prior arts based on the above four Patent
Documents 1 to 4 involve the following problems:
1) In Patent Document 1 (Japanese Patent
Publication (A) No. 9-205411), information on the used
subcarrier is not transmitted, therefore the reception
side must receive all subcarriers and decode them. This
is inefficient.
2) In Patent Document 2 (Japanese Patent
Publication (A) No. 2003-264524), information on the used
subcarrier is transmitted, but it is necessary to
receive, demodulate, and decode a common control channel
for transmitting this subcarrier information.
Further, when multiplexing users, the
information needed by the user must be extracted from
data transmitted over the common control channel.
Further, information directed to each user is contained
in that common control channel, therefore the bandwidth
might become insufficient at a low transmission rate.
Furthermore, the common control channel is common to all
users, therefore changing the used subcarrier will end up
having an effect on all users. Accordingly, the
subcarrier of that common control channel cannot be
easily changed.
3) In Patent Document 3 (Japanese Patent
Publication (A) No. 2004-214746), the bandwidth of the
data channel is made variable, but the common control
channel still uses a fixed frequency band common to all

users, so there is the same problem as that of Patent
Document 2.
4) In Patent Document 4 (Japanese Patent
Publication (A) No. 2002-330467), when considering the
use of user multiplexing, in order to suppress
interference due to the transmissions for many users, it
is necessary to further perform code multiplexing among
users. However, if the bandwidths of the subcarriers
become different among users, the orthogonality of codes
will be deteriorated and will end up becoming a cause of
interference.
In order to prevent this interference, where a
certain user changes the bandwidth of the subcarrier, the
other users must also change the bandwidths of the
subcarriers to match with that. As a result, the
bandwidths of the subcarriers are broadened due to the
user in a poor transmission situation, so the
transmission efficiency is lowered. Accordingly, there is
the inconvenience that changing the bandwidth of the
subcarrier sometimes will not be an effective means.
Accordingly, in consideration with the above
problems, an object of the present invention is to
provide a communications system (mobile communications
system) able to freely and easily extend, reduce, or
change the used frequency band of each user within the
overall frequency band allocated to the communications
system and preventing the above extension, reduction, or
change from having an effect on other users, more
particularly a communications apparatus (base station
and/or terminal) for this purpose.
DISCLOSURE OF THE INVENTION
According to the present invention, as will be
explained in detail later by using the drawings, a
specific frequency band is first set from among a
plurality of frequency bands obtaining by dividing the
overall frequency band allocated to the communications
system. Then, that specific frequency band is used to

transmit "used frequency band information" determining
which of the remaining frequency bands is to be used
between communications apparatuses from one
communications apparatus to another communications
apparatus. Further, that specific frequency band is set
as a "main band" in the above overall frequency band.
This main band transmits the above "used frequency band
information" plus "data information (user data)".
Further, among the above plurality of frequency bands, at
least one frequency band set from among the frequency
bands other than the above "main band" is defined as an
"extension band". This extension band is mainly used for
transmitting further data information and can deal with
an increase of amount of data. Accordingly, this
extension band is set according to need. However, the
above main band is always set at the time of
establishment of a wireless channel. In addition, this
main band transmits not only the above "used frequency
band information", but also the inherent "data
information" (user data) within a range permitted by the
transmission capacity. Further, this main band can
include also general "control information" (user control
information). Due to this, the above problems are solved.
BRIEF DESCRIPTION OF THE ACCOMPANYIN DRAWINGS
FIG. 1 is a view showing the basic
configuration of a communications apparatus (transmission
side) according to the present invention.
FIG. 2 is a view showing the basic configuration of
a communications apparatus (reception side) according to
the present invention.
FIG. 3 is a view showing a concrete example of a
communications apparatus (transmission side) 10 according
to the present invention.
FIG. 4 is a view showing a concrete example of a
communications apparatus (reception side) 20 according to
the present invention.
FIG. 5 is a view showing a modification of the

communications apparatus (transmission side) 10 according
to the present invention.
FIG. 6 is a view showing a modification of the
communications apparatus (reception side) 20 according to
the present invention.
FIG. 7 is a view showing another modification of the
communications apparatus (transmission side) 10 according
to the present invention.
FIG. 8 is a view showing another modification of the
communications apparatus (reception side) 20 according to
the present invention.
FIG. 9 is a view showing the pattern of frequency
division in a communications system.
FIG. 10 is a view showing a state of selecting one
"main band" and "extension band" each.
FIG. 11 is a view showing a first example of a mode
of allocation of main bands for a plurality of users.
FIG. 12 is a view showing a second example of a mode
of allocation of main bands for a plurality of users.
FIG. 13 is a flow chart showing an example of
dynamically changing the frequency band of a main band.
FIG. 14A and FIG. 14B are views showing an example
of the hardware configuration on the transmission side of
pilot signals.
FIG. 15A and FIG. 15B are views showing an example
of the hardware configuration on a return side of
response (CQI) information to a pilot signal.
FIG. 16 is a view showing a first example of
multiplexing of the pilot signals.
FIG. 17 is a view showing a second example of
multiplexing of the pilot signals.
FIG. 18 is a view showing an example of the dynamic
change of the main band for easy understanding.
FIG. 19 is a flow chart showing a first example of
introduction and allocation of an extension band.
FIG. 20 is a flow chart showing a second example of
introduction and allocation of an extension band.

FIG. 21 is a flow chart showing a third example of
introduction and allocation of an extension band.
FIG. 22 is a view showing an example of the dynamic
change of the extension band for easy understanding.
FIG. 23 is a flow chart showing an example of
changing both the main band and the extension band.
FIG. 24 is a flow chart showing an example of the
dynamic change of both the main band and the extension
band for easy understanding.
FIG. 25 is a view showing an example of the hardware
configuration on the return side of response (CQI)
information to a pilot signal.
FIG. 26 is a view showing a table for explaining
high efficiency transmission of the used frequency band
information.
FIG. 27 is a view showing an example of the dynamic
change of the extension band.
FIG. 28 is a view showing a first example of a band
extension pattern.
FIG. 29 is a view showing a second example of a band
extension pattern.
FIG. 30 is a view showing a third example of a band
extension pattern.
FIG. 31 is a view showing an example of the hardware
configuration of a communications apparatus (transmission
side) according to Embodiment 10.
FIG. 32 is a flow chart showing an example of the
operation in the apparatus of FIG. 31.
FIG. 33 is a view for explaining Embodiment 11.
FIG. 34 is a view showing the gist of the prior art
disclosed in Patent Document 1.
FIG. 35 is a view showing the gist of the prior art
disclosed in Patent Document 2.
FIG. 36 is a view showing the gist of the prior art
disclosed in Patent Document 3.
FIG. 37 is a view showing the gist of the prior art
disclosed in Patent Document 4.

BEST MODE FOR CARRYING OUT THE INVENTION
First of all, to speed the understanding of the
present invention, the prior arts (Patent Documents 1 to
4) explained above will be explained with reference to
the drawings.
FIG. 34 is a view showing the gist of the prior
art disclosed in Patent Document 1. The figure shows the
allocation of frequencies to for example seven users U1
to U7 (top part). The bottom parts shows details of the
allocation of a series of subcarrier to the users Ul and
U2. The abscissa is the frequency.
The present system is characterized by
consecutively arranging a plurality of carriers for the
frequency bands allocated at the transmission side,
dividing them into a plurality of subcarriers in
accordance with the users (Ul to U7), and consecutively
arranging these.
Specifically, for example, the overall
frequency band able to be used in one communications
system is set as 20 MHz, and 250 subcarriers are set
there. Accordingly, the bandwidth of each subcarrier
becomes 20 MHz/250 = 80 kHz. Then, these 250 subcarriers
are used while being dynamically allocated among the
plurality of users (U1 to U7).
At this time, for example, the subcarriers are
dynamically allocated, for example, 50 subcarriers are
allocated to a user A (U2) and 75 subcarriers are
allocated to another user B (Ul), to make the number of
subcarriers used variable.
Along with that, the used frequency band
becomes 50 x 80 kHz = 4 MHz for the user A and becomes 75
x 80 kHz = 6 MHz for the user B. That is, the used
frequency band is made variable for each user. In this
case, it is assumed that the allocated subcarriers are
consecutive on the frequency axis. Note that it is also
possible to further make the sizes of the divisions of
the frequency band variable.

FIG. 35 is a view showing the gist of the prior
art disclosed in Patent Document 2. The figure is a view
showing the state of allocation of the common control
channel and the data channel on the frequency axis.
In the present system, in a multicarrier CDMA
system, the subcarriers dedicated to the transmission of
the control signal and the subcarriers dedicated to the
transmission of data (data channel) are separately set.
The common control channel thereof is spread by a unique
spread code. Accordingly, when this common control
channel is received, it is sufficient to demodulate
specific subcarriers, so the amount of signal processing
thereof can be reduced.
FIG. 36 is a view showing the gist of the prior
art disclosed in Patent Document 3. The figure shows
making the frequency band of the data channel in FIG. 35
described above variable in accordance with a propagation
distance (communication distance with the base station).
Note that the transmission power is changed (large -
medium - small).
The present system is a system for realizing
variable speed communication by making the transmission
rate per subcarrier fixed and making the number of
subcarriers allocated to the user variable. When the
distance between the base station and the terminal is
short, the transmission power of each subcarrier is made
small and many subcarriers are allocated, while when that
distance is long, the transmission power of each
subcarrier is made large and a small number of
subcarriers are allocated.
Further, the number of subcarriers used for the
common control channel is made small, while a large
number of subcarriers are allocated with respect to the
data communications use channel (data channel). The two
are completely separately arranged along the frequency
axis. Note that the subcarriers dedicated to the common
control channel are used to notify the center subcarrier

number of the subcarriers allocated for the data channel
and the number of used subcarriers from the base station
to the mobile station.
FIG. 37 is a view showing the gist of the prior
art disclosed in Patent Document 4. The figure shows that
the bandwidth of each subcarrier is made variable in
accordance with whether or not the propagation
environment is good.
The present system changes the bandwidth of
each subcarrier while making a total number of
subcarriers constant in accordance with the condition of
the propagation environment in wireless transmission. For
example, when the propagation condition becomes poor, the
band of each subcarrier is made wider. Due to this, the
transmission can be carried out without changing the
total subcarriers, therefore the transmission rate can be
maintained constant without regard to the propagation
environment.
The present invention solves the already
explained problems of the prior arts (Patent Documents 1
to 4) explained with reference to FIG. 34 to FIG. 37
explained above. This will be explained in detail below
with reference to the drawings.
FIG. 1 is a view showing the basic
configuration of a communications apparatus (transmission
side) according to the present invention, and
FIG. 2 is a view showing the basic configuration of
a communications apparatus (reception side) according to
the present invention.
In FIG. 1, reference numeral 10 indicates the
communications apparatus (transmission side), and in FIG.
2, reference numeral 20 indicates the communications
apparatus (reception side). These are accommodated in the
same communications system (mobile communications
system). Note that as already explained, the
communications apparatus 10 may be a base station and the
communications apparatus 20 may be a terminal, or vice

versa. The present invention can be applied to both
cases, but for easier understanding, in the following
explanation, the communications apparatus 10 on the
transmission side will be assumed as the base station,
and the communications apparatus 20 on the reception side
will be assumed as a terminal unless otherwise indicated.
First, referring to FIG. 1, the selection
function in particular of a used frequency band
selecting/setting unit 15 is used to select the used
frequency band to be used with the other communications
apparatus 20. The "used frequency band information" If
(frequency) according to this selection is input to a
transmission data generation unit 11 where transmission
data Dt (transmission) combined integrally with
transmission data (user data) Du (user) to be transmitted
to the communications apparatus 20 is generated.
Accordingly, the transmission data Dt includes the
transmission data Du and the used frequency band
information If, but in actuality further includes also
other "communication control information" let (control).
This information let is the information concerning a used
modulation scheme for example QAM and information etc.
concerning a one time transmission data amount of the
transmission data Du.
The above transmission data Dt is modulated in
a predetermined way at a modulation unit 12, then input
to the next multicarrier transmission sender unit 13.
This sender unit 13 is supplied with a band set
instruction signal Sb (band) instructing processing for
transmission at the above selected used frequency band by
the setting function of the above used frequency band
selecting/setting unit 15. The sender unit 13 performs
the processing for signal transmission by multicarrier
transmission at the frequency band based on this signal
Sb.
Further, a wireless unit 14 converts the
frequency conversion of the transmission data signal St

from the above sender unit 13 and transmits this from the
next antenna AT toward another communications apparatus
(terminal) 20.
On the other hand, referring to FIG. 2, the
wireless signal from the above antenna AT (FIG. 1) is
received at the antenna AT (FIG. 2) and further converted
in frequency by a wireless unit 21 to be a received data
signal Sr which is then input to a multicarrier
transmission receiver unit 22. This receiver unit 22
processes the received data signal Sr for signal
reception according to the multicarrier transmission,
then the next demodulation unit 23 demodulates the signal
after the signal reception processing.
The demodulated received data Dr is decoded at
a received data decoding unit 24 and separated to the
original transmission data Du and the previously set used
frequency band information If explained before. Further,
the above communication control information let is also
separated from that data Dr. Note that the units to be
controlled according to this information let are not
directly related to the gist of the present invention, so
explanations are omitted.
As explained above, the original used frequency
band information If obtained by separation from the
received data Dr is input to a used frequency band
setting unit 25. The setting unit 25 receives this
information If and reproduces the above band set
instruction signal Sb. This signal Sb is supplied to the
above multicarrier transmission receiver unit 22, then
this receiver unit 22 performs processing for signal
reception according to the multicarrier transmission by
using the frequency band selected on the transmission
side. Note that the previously determined frequency band
may be selected in the initial stage of establishment of
the wireless channel.
In the present invention, the transmission side
(10) and the reception side (20) can use the same used

frequency band by the above-explained band set
instruction signal Sb. Further, based on that signal Sb,
that used frequency band can be simultaneously extended,
reduced, or changed at both of the transmission side (10)
and the reception side (20). Thus, the object of the
present invention explained before can be achieved.
The basic configuration of the present
invention explained above will be explained a little more
concretely in comparison with the above prior arts.
In the present invention, the frequency band
usable in the communications system as a whole is divided
into a plurality of bands. For example, when the used
frequency band of the communications system as a whole is
set as 20 MHz, it is divided into four bands of 5 MHz
each. One band 5 MHz is used to transmit the information
of the control channel for transmitting the used
frequency band information and the transmission channel
(data channel) for transmitting the transmission data.
According to the present invention, as
explained before, the frequency band for transmitting at
least the control channel is defined as the "main band"
and a further extended frequency band is defined as an
"extension band". For example, when considering this in
an OFDM communications system, 100 subcarriers are
included in one band 5 MHz, the bandwidth of each
subcarrier is 50 kHz, and the information of the control
channel and the data channel are transmitted by using the
series of these 100 subcarriers. The two information may
be multiplexed by time division multiplexing, frequency
division multiplexing, or code division multiplexing.
As explained above, unlike Patent Document 3
(Japanese Patent Publication (A) No. 2004-214746), the
information of the "main band" is received and decoded to
learn the used frequency band (or number of used
frequency bands), therefore, the used frequency band can
be easily extended, reduced, and changed. Further, due to
this, unlike Patent Document 1 (Japanese Patent

Publication (A) No. 9-205411) and Patent Document 3
(Japanese Patent Publication No. 2004-214746), the
configuration of the reception unit is simplified.
Further, if making the number of subcarriers
per frequency band constant, the number of subcarriers
will change with a ratio of a whole number along with a
change of the number of used frequency bands.
Accordingly, when compared with Patent Document 3
(Japanese Patent Publication (A) No. 2004-214746) in
which the subcarriers dynamically change, the
configuration of the reception unit is simplified.
Further, by designating the used frequency band
from the base station to the terminals in advance, the
extension band described above can be easily changed and
added to and even the main band can be changed.
Further, if making the bandwidth of each
subcarrier fixed as explained above, the used frequency
band can be changed without influencing other users as in
Patent Document 4 (Japanese Patent Publication (A) No.
2002-330467). Various embodiments according to the
present invention will be explained below.
[Embodiment 1: Setting of used frequency band]
First, describing some characteristic features
disclosed in the present Embodiment 1, these are as
follows. The principal points of these characteristic
features are as already described and reside in the
following three points (i) to (iii):
(i) A specific frequency band from among a
plurality of frequency bands formed by dividing the
overall frequency band allocated to a communications
system is set, and that specific frequency band is used
to transmit "used frequency band information" If
determining which remaining frequency band is to be used
between communications apparatuses (10, 20), (ii) that
specific frequency band is set as a "main band" in the
overall frequency band, and that main band transmits, in
addition to the used frequency band information If, data

information Du, and (iii) among the above-explained
plurality of frequency bands, at least one frequency band
set from among the frequency bands other than above "main
band" is defined as an "extension band", and that
extension band mainly transmits further data information
(Du) .
Next, some principal points further disclosed
in the present Embodiment 1 reside in the following four
points (iv) to (vii):
(iv) The above "main band" is set fixedly at
the time of the establishment of the wireless channel
between the communications apparatuses (10, 20),
(v) when there are a plurality of communications
apparatuses (20), "main bands" are individually set for
the above plurality of frequency bands and, at the same
time, main bands are individually assigned corresponding
to these plurality of communications apparatuses (20),
(vi) two or more communications apparatuses (20) can
simultaneously use the same "main band" by time division
multiplexing and/or code division multiplexing, and
(vii) further, the number of extension bands is
changed in accordance with the predetermined transmission
rate of the data information (Du).
FIG. 3 is a view showing a concrete example of
the communications apparatus (transmission side) 10
according to the present invention, and
FIG. 4 is a view showing a concrete example of the
communications apparatus (reception side) 20 according to
the present invention. Note that, same components will be
indicated by same reference numerals or symbols
throughout all of the figures. Further, the concrete
examples shown in FIG. 3 and FIG. 4 are not only applied
to the present Embodiment 1, but also commonly applied to
the other Embodiments 2 to 10 explained later.
Referring to the communications apparatus
(transmission side) 10 first, the parts corresponding to
the components 11 to 15 and Du, Dt, St, and Sb shown in

FIG. 1 are shown assigned these reference numerals or
symbols 11 to 15 and Du, Dt, St, and Sb.
The transmission data generation unit 11 is
configured by a data block preparation unit 31, an
encoding unit 32, a transmission data amount calculation
unit 33, an encoding unit 34, and a multiplexing unit
(Mux) 35 according to the example of the present figure.
Based on the used frequency band information If
from the above used frequency band selecting/setting unit
15, the transmission data amount calculation unit 33
first calculates a transmission data length, then the
data block preparation unit 31 prepares data blocks for
each transmission data length. Further, the encoding unit
32 encodes the transmission data by using that
transmission data length.
The above used frequency band information If is
encoded together with the communications control
information let indicating the used modulation scheme
etc. at the encoding unit 34. Note that the encoding
units 32 and 34 may encode Du and If all together as one
encoding unit.
The encoded outputs from the two encoding units
32 and 34 are multiplexed at the multiplexing unit (Mux)
35 and become the already explained transmission data Dt.
This data Dt is further modulated at the modulation unit
12 as explained before. As the method of this
multiplexing, there are frequency division multiplexing
separating subcarriers and using the same, time division
multiplexing (by using for example a frame format shown
in FIG. 16), code division multiplexing etc. Further, as
the modulation scheme by the modulation unit 12, there
are QPSK, 16QAM, 64QAM, etc.
E-0060] - Next, when looking at the multicarrier
transmission sender unit 13, in the example shown in the
present figure, this is configured by components 36, 37,
38, 39, and 40. Note that this is shown as an example
based on communications according to OFDM. Another

example based on communications according to MC-CDMA is
shown in FIG. 7 (FIG. 8).
The demultiplexing unit (DeMux) 36
demultiplexes this into the information belonging to the
"main band" and the information belonging to the
"extension bands". The information belonging to the "main
band" is converted to a parallel signal at a
serial/parallel converter (S/P) 37, then a time-frequency
transform is applied to the parallel signal at an Inverse
Fast Fourier Transform unit (IFFT) 38. The parallel
signal transformed into frequency is converted to a
serial signal again at a parallel/serial converter (P/S)
39. Further, a guard interval (GI) insertion unit 40
inserts a guard interval GI into the serial signal for
preventing inter-symbol interference.
The thus obtained transmission data signal St
is input to the wireless unit 14. This wireless unit 14
is, according to the example of the present figure,
configured by a general mixer 41, a local oscillator 42,
and a power amplifier 44 (a D/A converter, a filter, etc.
are omitted) and transmits the transmission data signal
St from the antenna At. In this case, an adder unit 43 is
provided in the middle.
The adder unit 43 applies the same processing
as the processing for the "main band" by the above-
explained components 37, 38, 39, 40, 41, and 42 with
respect to the information belonging to the above
"extension bands" demultiplexed at the demultiplexing
unit (DeMux) 36 as explained before by the components
37', 38', 39', 40', 41', and 42', obtains the
transmission data signal St on the "extension band" side,
and combines the same together with the already explained
transmission data signal St on the "main band" side.
f