U.S. patent application number 11/735637 was filed with the patent office on 2007-08-09 for radio reception apparatus and radio reception method.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. Invention is credited to Hideo Kasami, Tsuyoshi Kogawa.
Application Number | 20070184801 11/735637 |
Document ID | / |
Family ID | 34315595 |
Filed Date | 2007-08-09 |
United States Patent
Application |
20070184801 |
Kind Code |
A1 |
Kogawa; Tsuyoshi ; et
al. |
August 9, 2007 |
RADIO RECEPTION APPARATUS AND RADIO RECEPTION METHOD
Abstract
A radio reception apparatus is a radio reception apparatus for
demodulating a multicarrier signal modulated according to
multicarrier modulation. It includes a plurality of antenna
sections, each for receiving a multicarrier signal, a plurality of
carrier selection sections, each of the carrier selection sections
selecting at least one subcarrier signal for each of the antenna
sections out of the multicarrier signal received by each of the
antenna sections, an antenna selection section for selecting a
reception antenna section from among the antenna sections based on
the signal strengths of the subcarrier signals selected by the
carrier selection sections, and a demodulation section for
demodulating the multicarrier signal received by the antenna
section selected by the antenna selection section.
Inventors: |
Kogawa; Tsuyoshi; (Kanagawa,
JP) ; Kasami; Hideo; (Kanagawa, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
Tokyo
JP
|
Family ID: |
34315595 |
Appl. No.: |
11/735637 |
Filed: |
April 16, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10901202 |
Jul 29, 2004 |
7212793 |
|
|
11735637 |
Apr 16, 2007 |
|
|
|
Current U.S.
Class: |
455/277.1 ;
455/140; 455/226.1 |
Current CPC
Class: |
H04B 7/0802 20130101;
H04B 7/0602 20130101 |
Class at
Publication: |
455/277.1 ;
455/226.1; 455/140 |
International
Class: |
H04B 17/00 20060101
H04B017/00; H04B 1/06 20060101 H04B001/06; H04B 7/08 20060101
H04B007/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 2003 |
JP |
2003-202859 |
Jul 28, 2004 |
JP |
2004-220699 |
Claims
1. A method for receiving radio signals with a radio receiver
having a plurality of antennas, comprising: receiving multicarrier
signals which are modulated according to multicarrier modulation
using the antennas; selecting at least one subcarrier signal out of
the multicarrier signal received by each antenna; selecting a
reception antenna among the plurality of antennas based on signal
strengths of the subcarrier signals selected for each antenna;
demodulating the multicarrier signal received by the reception
antenna; measuring signal strength and distortion amounts of pilot
signals in the multicarrier signal being received by the reception
antenna; and correcting the multicarrier signal received by the
reception antenna using the measured signal strength and the
distortion amounts.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of and claims the benefit
of priority under 35 USC .sctn.120 from U.S. Ser. No. 10/901,202,
Jul. 29, 2004 and claims the benefit of priorities from both the
prior Japanese Application No. 2003-202859, filed on Jul. 29, 2003
and the prior Japanese Application No. 2004-220699, filed on Jul.
28, 2004; the entire contents of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a radio reception apparatus and in
particular to a radio reception apparatus for a multicarrier
signal.
[0004] 2. Description of the Related Art
[0005] Diversity reception has been used as a method for coping
with degradation of the communication quality caused by fading in
radio communications. A diversity reception apparatus in a related
art receives a multicarrier signal by a plurality of reception
means through a plurality of antennas. The diversity reception
apparatus finds received power for each of the multicarrier signals
received by the plurality of reception means, and selects one
antenna based on the received power. Further, the diversity
reception apparatus demodulates the multicarrier signal received
through the selected antenna. (Please see JP-A-2000-174726 (Kokai),
JP-A-2001-268050 (Kokai) and JP-A-2002-261727(Kokai))
[0006] The diversity reception apparatus in the related art selects
an antenna based on the signal strength of the whole multicarrier
signal. However, when an antenna is selected based on the received
power of the whole multicarrier signal, if a subcarrier signal of a
part of multicarrier signal has large distortion, the diversity
reception apparatus cannot select an antenna with good
communication quality.
SUMMARY OF THE INVENTION
[0007] It is an object of the invention to provide a radio
reception apparatus that can select an antenna with good
communication quality from among antennas if a multicarrier signal
has distortion.
[0008] According to one aspect of the invention, there is provided
a radio reception apparatus including: a plurality of antenna
sections, each of the antenna sections receiving a multicarrier
signal which is modulated according to multicarrier modulation and
demodulating the modulated multicarrier signal; a plurality of
carrier selection sections each of the carrier selection sections
selecting at least one subcarrier signal for each of the plurality
of antenna sections out of the multicarrier signal received by each
of the plurality of antenna sections; an antenna selection section
for selecting a reception antenna section from among the plurality
of antenna sections based on signal strengths of the subcarrier
signals selected by the plurality of carrier selection sections;
and
a demodulation section for demodulating the multicarrier signal
received by the antenna section selected by the antenna selection
section.
[0009] According to another aspect of the invention, there is
provided a radio reception method using a radio reception
apparatus, including: receiving a multicarrier signal modulated
according to multicarrier modulation through a plurality of antenna
sections; selecting at least one subcarrier signal for each of the
antenna sections out of the multicarrier signal received by each of
the antenna sections based on frequency; selecting a reception
antenna section from among the antenna sections based on the signal
strengths of the selected subcarrier; and demodulating the
multicarrier signal received by the selected reception antenna
section.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] These and other objects and advantages of the invention will
become more fully apparent from the following detailed description
taken with the accompanying drawings in which:
[0011] FIG. 1 is a block diagram of a diversity radio reception
apparatus 100 according to a first embodiment of the invention;
[0012] FIG. 2 is a schematic drawing to specifically show the
operation of the carrier selection sections 31 to 33 and the
antenna selection section 40 in the embodiment;
[0013] FIG. 3 is a flowchart to show the operation of the reception
apparatus 100;
[0014] FIG. 4 is a schematic drawing to show carrier selection
sections 31 to 33 of a reception apparatus 102 according to a third
embodiment of the invention.
[0015] FIGS. 5A, 5B, and 5C are schematic drawings showing carrier
selection sections of a reception apparatus according a fourth
embodiment of the invention;
[0016] FIGS. 6A, 6B, and 6C are schematic drawings showing carrier
selection sections of a reception apparatus according a fifth
embodiment of the invention;
[0017] FIGS. 7A, 7B, and 7C are schematic drawings showing carrier
selection sections of a reception apparatus according a sixth
embodiment of the invention;
[0018] FIGS. 8A, 8B, and 8C are schematic drawings showing carrier
selection sections of a reception apparatus according a seventh
embodiment of the invention;
[0019] FIGS. 9A, 9B, and 9C are schematic drawings showing carrier
selection sections of a reception apparatus according an eighth
embodiment of the invention;
[0020] FIG. 10 is a schematic drawing to show carrier selection
sections of a reception apparatus according a ninth embodiment of
the invention;
[0021] FIG. 11 is a block diagram to show a reception apparatus
according to a tenth embodiment of the invention;
[0022] FIG. 12 is a block diagram to show a demodulation section of
a reception apparatus according to an eleventh embodiment of the
invention;
[0023] FIG. 13 is a block diagram to show a demodulation section of
a reception apparatus according to a twelfth embodiment and a
thirteenth embodiment of the invention;
[0024] FIG. 14 is a block diagram to show a reception apparatus
according to one aspect of the invention;
[0025] FIG. 15 is a schematic diagram which shows a frequency
characteristic of a reception signal according to fourteenth
embodiment of the invention;
[0026] FIG. 16 is a flow chart to show an example of processing
operation of the radio reception apparatus as shown in FIG. 15;
[0027] FIG. 17 is a block diagram to show internal construction of
the radio reception apparatus according to the fifteenth
embodiment;
[0028] FIG. 18 is a block diagram to show an internal construction
of the radio reception apparatus according to the sixteenth
embodiment;
[0029] FIG. 19 is a flow chart to show one example of processing
operation of the radio reception apparatus as show in FIG. 18;
[0030] FIG. 20 shows a data construction of the packet. As show in
FIG. 20;
[0031] FIG. 21 is a block diagram to show a construction of the
radio reception apparatus according to the seventeenth
embodiment;
[0032] FIG. 22 represents a frequency characteristic of a data part
of a packet which was complied with IEEE802.11a;
[0033] FIG. 23 represents a frequency characteristic of a short
preamble, which is a part of a preamble part of the packet which
was complied with IEEE802.11a;
[0034] FIG. 24 is a block diagram to show the construction of the
radio reception apparatus according to the eighteenth
embodiment;
[0035] FIG. 25 is a flowchart to show an example of the processing
operation according to nineteenth embodiment;
[0036] FIG. 26 is flow chart to show an example of the processing
operation according to the twentieth embodiment;
[0037] FIG. 27 is a flow chart of the processing operation
according the radio reception apparatus according to the
twenty-first embodiment; and
[0038] FIG. 28 is an view to explain the general description
according the twenty-second embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0039] Referring now to the accompanying drawings, there are shown
embodiments of the invention. It is to be understood that the
invention is not limited to the embodiments thereof.
[0040] A diversity radio reception apparatus according to each
embodiment of the invention selects a subcarrier signal from
multicarrier signals received through a plurality of antennas. The
radio reception apparatus selects an antenna based on the signal
strength of the subcarrier signal, and receives signals through the
selected antenna. Accordingly, the radio reception apparatus can
select the antenna with good communication quality. The diversity
radio reception apparatus can be used as a selection diversity
reception apparatus in OFDM (Orthogonal Frequency Division
Multiplexing) modulation of a radio LAN, etc
First Embodiment
[0041] FIG. 1 is a block diagram of a diversity radio reception
apparatus (simply, reception apparatus) 100 according to a first
embodiment of the invention. The reception apparatus 100 includes
antennas 11 to 13, signal conversion sections 21 to 23, carrier
selection sections 31 to 33, an antenna selection section 40, and a
demodulation section 50. Each of the antennas 11 to 13 receives the
multicarrier signal modulated according to multicarrier modulation
by the communicating party with the reception apparatus 100. In the
embodiment, the three antenna sections are provided, but two or
four or more antenna sections may be provided.
[0042] Each of the signal conversion sections 21 to 23 includes an
LNA (Low Noise Amplifier) for amplifying the multicarrier signal, a
D/C (Down Converter) section for converting the frequency of the
multicarrier signal into a base band, an A/D conversion section for
converting an analog signal into a digital signal, and an FFT (Fast
Fourier Transform) section for executing discrete Fourier transform
for each of the multicarrier signals. The multicarrier signal
passed through the signal conversion section 21 to 23 is made up of
a plurality of subcarrier signals different in frequency band.
[0043] The carrier selection sections 31 to 33 are connected to the
signal conversion sections 21 to 23 respectively for selecting a
specific subcarrier signal out of the multicarrier signal passed
through the signal conversion section 21 to 23 based on the
frequency.
[0044] As many signal conversion sections as and as many carrier
selection sections as the number of antenna sections are provided.
In the embodiment, three signal conversion sections 21 to 23 and
three carrier selection sections 31 to 33 are provided because the
number of antenna sections is three (11 to 13).
[0045] The antenna selection section 40 is connected to the carrier
selection sections 31 to 33 and obtains the subcarrier signals
selected by the carrier selection sections 31 to 33. The antenna
selection section 40 selects the reception antenna section based on
the signal strength of each of the subcarrier signals.
[0046] The demodulation section 50 demodulates the multicarrier
signal received through the antenna section selected by the antenna
selection section 40.
[0047] FIG. 2 is a schematic drawing to specifically show the
operation of the carrier selection sections 31 to 33 and the
antenna selection section 40 in the embodiment. The carrier
selection sections 31 to 33 and the antenna selection section 40
will be discussed in more detail with reference to FIG. 2.
[0048] The graph shown in the carrier selection section 31 in FIG.
2 is a graph to show the frequencies and the signal strength of the
multicarrier signal received through the antenna section 11. The
multicarrier signal is made up of a plurality of subcarrier signals
different in frequency band. Each subcarrier signal is indicated by
the dashed line in the graph. The carrier selection section 31
selects subcarrier signals SC.sub.1 and SC.sub.2 corresponding to
predetermined frequencies f.sub.1 and f.sub.2 from among the
subcarrier signals. Likewise, the carrier selection section 32 (33)
selects the subcarrier signals corresponding to the frequencies
f.sub.1 and f.sub.2 from among the subcarrier signals making up the
multicarrier signal received through the antenna section 12 (13).
The subcarrier signals selected by the carrier selection sections
31 to 33 are transmitted to the antenna selection section 40.
[0049] The antenna selection section 40 has a calculation section
42 and a signal strength comparison section 44. The calculation
section 42 calculates average signal strength AV.sub.1 of the
subcarrier signals SC.sub.1 and SC.sub.2 selected by the carrier
selection section 31, average signal strength AV.sub.2 of the
subcarrier signals selected by the carrier selection section 32,
and average signal strength AV.sub.3 of the subcarrier signals
selected by the carrier selection section 33.
[0050] The signal strength comparison section 44 compares the
average signal strengths AV.sub.1, AV.sub.2, and AV.sub.3 and
selects the antenna section corresponding to the maximum average
signal strength from among the antenna sections 11 to 13.
[0051] In the embodiment, each of the carrier selection sections 31
to 33 selects two subcarrier signals, but may select one or three
or more subcarrier signals.
[0052] FIG. 3 is a flowchart to show the operation of the reception
apparatus 100. To begin with, the antenna sections 11 to 13 receive
the multicarrier signal modulated according to multicarrier
modulation (S10). Next, the signal conversion sections 21 to 23
convert the multicarrier signals received from the antenna sections
11 to 13. Accordingly, the multicarrier signal is converted into a
signal made up of a plurality of subcarrier signals different in
frequency band (S20).
[0053] Each of the carrier selection sections 31 to 33 selects
specific subcarrier signals out of the multicarrier signal based on
the frequency (S30).
[0054] The antenna selection section 40 selects the antenna section
used to receive the multicarrier signal based on the signal
strengths of the subcarrier signals selected by the carrier
selection sections 31 to 33 (S40).
[0055] The demodulation section 50 demodulates the multicarrier
signal received through the antenna section selected by the antenna
selection section 40 (S50).
[0056] According to the embodiment, the antenna section can be
selected based on the signal strengths of specific subcarrier
signals on specific frequency band. Accordingly, the reception
apparatus 100 can select the subcarrier signals having a large
effect on demodulation, for example, and can conduct communications
using the antenna corresponding to the subcarrier signals having
the maximum average signal strength.
[0057] Generally, when large distortion is contained in the
multicarrier signal, the antenna with large received power of the
whole multicarrier signal is not necessarily the antenna with good
communication quality. According to the embodiment, the average
signal strength of the subcarrier signals having a large effect on
demodulation in the multicarrier signal can be calculated, so that
the reception apparatus 100 can reliably select the antenna section
with good communication quality from among the antenna sections 11
to 13.
Second Embodiment
[0058] A reception apparatus 101 according to a second embodiment
of the invention will be discussed with reference to FIGS. 1 and 2.
In the first embodiment, the calculation section 42 calculates the
average signal strengths AV.sub.1, AV.sub.2, and AV.sub.3 of the
selected subcarrier signals, and the signal strength comparison
section 44 compares the average signal strengths AV.sub.1,
AV.sub.2, and AV.sub.3, thereby selecting the antenna section for
communications. The reception apparatus of the second embodiment
differs from the reception apparatus of the first embodiment in
that a calculation section 42 selects subcarrier signals MX.sub.1
to MX.sub.3 (not shown) having the largest signal strength for
carrier selection sections 31 to 33, that a signal strength
comparison section 44 compares the subcarrier signals MX.sub.1 to
MX.sub.3 and selects the subcarrier signal having the largest
signal strength from among the subcarrier signals, and that an
antenna selection section 40 selects the antenna section receiving
the subcarrier signal having the largest signal strength.
[0059] In the second embodiment, the subcarrier signal having the
maximum signal strength can be selected from among the subcarrier
signals except the subcarrier signals in the frequency band having
distortion in multicarrier signal. Accordingly, the reception
apparatus 101 can reliably select the antenna with good
communication quality.
Third Embodiment
[0060] FIG. 4 is a schematic drawing to show carrier selection
sections 31 to 33 of a reception apparatus 102 according to a third
embodiment of the invention. The carrier selection section 31 in
the embodiment selects pilot carrier signals PC.sub.1 and PC.sub.2
out of multicarrier signals received by an antenna section 11. The
carrier selection sections 32 and 33 select pilot carrier signals
out of multicarrier signals received by antenna sections 12 and 13.
Other components and the operation of the reception apparatus 102
are similar to those in the first or second embodiment replacing
the subcarrier signals with the pilot carrier signals.
[0061] Generally, if the pilot carrier signal is a subcarrier
signal used as the reference for correcting distortion. If the
signal length of the pilot carrier signal is small, the whole
multicarrier signal cannot accurately be corrected.
[0062] Therefore, the antenna section receiving the pilot carrier
signal having the maximum signal strength or the largest average
signal strength is selected from among the antenna sections 11 to
13, whereby the reception apparatus 102 can accurately correct the
whole multicarrier signal received through the selected antenna
section. Consequently, the reception apparatus 102 can conduct
good-quality communications. Further, the reception apparatus of
the third embodiment has similar advantages to those of the
reception apparatus of the first and second embodiments.
[0063] In the third embodiment, the number of pilot carrier signals
is two, but may be one or three or more.
Fourth Embodiment
[0064] FIG. 5A is a schematic drawing to show carrier selection
sections 31 to 33 of a reception apparatus 103 according to a
fourth embodiment of the invention. Each of the carrier selection
sections 31 to 33 in the embodiment has a threshold value
determination section 34 for determining a threshold value Th
concerning the signal strength of a pilot carrier signal. The
threshold value determination sections 34 of the carrier selection
sections 31 to 33 determine the same threshold value Th. The
carrier selection section 31 selects pilot carrier signals PC.sub.1
to PC.sub.3 exceeding the threshold value Th out of multicarrier
signal received by an antenna section 11. The carrier selection
sections 32 and 33 select pilot carrier signals exceeding the
threshold value Th out of multicarrier signals received by antenna
sections 12 and 13. Other components of the reception apparatus 103
are similar to those previously described with reference to FIG.
1.
[0065] Thus, in the embodiment, the pilot carrier signals each
including larger signal strength than the threshold value Th are
selected from among the pilot carrier signals in the multicarrier
signal. In the embodiment, only the pilot carrier signals exceeding
the threshold value Th are selected and thus the carrier selection
sections 31 to 33 may differ in the number of selected pilot
carrier signals.
[0066] The reception apparatus of the embodiment has similar
advantages to those of the reception apparatus of the third
embodiment. According to the fourth embodiment, the carrier
selection sections 31 to 33 exclude signals including the signal
strength lower than the threshold value Th, such as a pilot carrier
signal PC.sub.4. An antenna selection section 40 can select an
antenna section using the pilot carrier signal including the large
signal strength with small distortion among the pilot carrier
signals. Consequently, the reception apparatus 103 can select the
antenna with good communication quality. Particularly, it is
effective when a demodulation section uses only pilot carrier
signals including large signal strength for distortion
correction.
[0067] For example, FIGS. 5B and 5C provide graphs of multicarrier
signals received by the antenna sections 11 and 12. The carrier
selection section 31 selects pilot carrier signals PC.sub.2 and
PC.sub.3 out of multicarrier signal from the antenna section 11.
The carrier selection section 32 selects pilot carrier signals
PC.sub.5 to PC.sub.8 out of multicarrier signal from the antenna
section 12. The average signal strength of the pilot carrier
signals PC.sub.2 and PC.sub.3 is clearly larger than that of the
pilot carrier signals PC.sub.5 to PC.sub.8. Therefore, according to
the embodiment, the antenna selection section 40 reliably selects
the antenna section 11.
[0068] On the other hand, if the threshold value is not set, the
carrier selection section 31 selects not only the pilot carrier
signals PC.sub.2 and PC.sub.3, but also pilot carrier signals
PC.sub.1 and PC.sub.4. In this case, the average signal strength of
the pilot carrier signals PC.sub.1 to PC.sub.4 becomes smaller than
that of the pilot carrier signals PC.sub.2 and PC.sub.3. Therefore,
the difference between the average signal strength of the pilot
carrier signals PC.sub.1 to PC.sub.4 and that of the pilot carrier
signals PC.sub.5 to PC.sub.8 becomes smaller than that when the
threshold value is set. Therefore, for the antenna selection
section 40 to reliably select the antenna section 11, preferably
the threshold value of signal strength is provided in the carrier
selection section 31.
[0069] The embodiment is effective when good pilot carrier signals
including large signal strength and pilot carrier signals including
extremely small signal strength are mixed in the multicarrier
signal. Particularly, it produces effect when the demodulation
section uses only pilot carrier signals including large signal
strength for distortion correction.
Fifth Embodiment
[0070] FIG. 6A is a schematic drawing to show carrier selection
sections 31 to 33 of a reception apparatus 104 according to a fifth
embodiment of the invention. As shown in FIG. 6A, if it is obvious
that the signal strength of multicarrier signal is large or small
as a whole, threshold value determination sections 34 set threshold
value Th to zero. Accordingly, the carrier selection sections 31 to
33 select all pilot carrier signals in the multicarrier signal. An
antenna selection section 40 can select an antenna based on the
average signal strengths of all pilot carrier signals. For example,
FIGS. 9B and 9C provide graphs of multicarrier signals received by
antenna sections 11 and 12. As shown in FIGS. 6B and 6C, the
antenna selection section 40 calculates the average signal strength
of pilot carrier signals PC.sub.1 to PC.sub.4 and that of pilot
carrier signals PC.sub.5 to PC.sub.8. The antenna selection section
40 selects an antenna section 11 including large signal strength on
the whole based on the calculation result.
[0071] The reception apparatus of the embodiment has similar
advantages to those of the reception apparatus of the first
embodiment. Particularly, the embodiment is effective when the
distortion difference between the pilot carrier signals in the
multicarrier signal is comparatively small. That is, the embodiment
is effective when the signal strengths of the pilot carrier signals
are large or small on the whole.
Sixth Embodiment
[0072] FIGS. 7A to 7C are schematic drawings to show carrier
selection sections 31 to 33 of a reception apparatus 105 according
to a sixth embodiment of the invention. Each of the carrier
selection sections 31 to 33 in the embodiment has a minimum value
detection section 35. Other components of the reception apparatus
105 are similar to those previously described with reference to
FIG. 1.
[0073] The minimum value detection section 35 detects the pilot
carrier signal including the minimum signal strength among pilot
carrier signals. For example, in the carrier selection section 31,
the minimum value detection section 35 detects pilot carrier signal
PC.sub.4. The carrier selection section 31 selects the pilot
carrier signal PC.sub.4. Thus, in the embodiment, the pilot carrier
signal including the minimum signal strength is selected from among
the pilot carrier signals in multicarrier signal. The carrier
selection sections 32 and 33 also select the pilot carrier signal
including the minimum signal strength from among the pilot carrier
signals in multicarrier signal.
[0074] An antenna selection section 40 compares the pilot carrier
signals selected by the carrier selection sections 31 to 33 and
selects the antenna section including the maximum signal strength.
Accordingly, in the embodiment, the antenna section including large
signal strength can be selected.
[0075] The reception apparatus of the embodiment has similar
advantages to those of the reception apparatus of the first
embodiment. Particularly, the embodiment is effective when the
distortion difference between the pilot carrier signals in the
multicarrier signal is comparatively small. That is, the embodiment
is effective when the signal strengths of the pilot carrier signals
are large or small on the whole.
[0076] For example, FIGS. 7B and 7C provide graphs of multicarrier
signals received by antenna sections 11 and 12. Assume that the
pilot carrier signal including the minimum signal strength in the
multicarrier signal shown in FIG. 7B is PC.sub.4. Assume that the
pilot carrier signal including the minimum signal strength in the
multicarrier signal shown in FIG. 7C is PC.sub.5. The antenna
selection section 40 compares the pilot carrier signals PC.sub.4
and PC.sub.5. Further, the antenna selection section 40 selects the
antenna section 11 receiving the pilot carrier signals PC.sub.4
including comparatively large signal strength.
Seventh Embodiment
[0077] FIGS. 8A to 8C are schematic drawings to show carrier
selection sections 31 to 33 of a reception apparatus 106 according
to a seventh embodiment of the invention. Each of the carrier
selection sections 31 to 33 in the embodiment has a minimum value
detection section 35 and a minimum pilot carrier signal removal
section 36 (simply, removal section 36). Other components of the
reception apparatus 106 are similar to those previously described
with reference to FIG. 1.
[0078] The minimum value detection section 35 detects the pilot
carrier signal including the minimum signal strength among pilot
carrier signals. For example, in the carrier selection section 31,
the minimum value detection section 35 detects pilot carrier signal
PC.sub.4. The removal section 36 selects pilot carrier signals
PC.sub.1 to PC.sub.3 other than the pilot carrier signal PC.sub.4.
Thus, in the embodiment, signals other than the pilot carrier
signal including the minimum signal strength are selected from
among the pilot carrier signals in multicarrier signal. The carrier
selection sections 32 and 33 also select signals other than the
pilot carrier signal including the minimum signal strength from
among the pilot carrier signals in multicarrier signal.
[0079] In an antenna selection section 40, a calculation section 42
calculates average signal strengths AV.sub.1, AV.sub.2, and
AV.sub.3 of the pilot carrier signals selected by the carrier
selection sections 31 to 33. A signal strength comparison section
44 compares the average signal strengths AV.sub.1, AV.sub.2, and
AV.sub.3 and selects the antenna section including the maximum
average signal strength.
[0080] The reception apparatus of the embodiment has similar
advantages to those of the reception apparatus of the first
embodiment. Further, according to the embodiment, pilot carrier
signals other than the pilot carrier signal including the minimum
signal strength are selected, so that the reception apparatus 106
can reliably select the antenna with good communication quality.
Particularly, it is effective when a demodulation section uses only
pilot carrier signals including large signal strength for
distortion correction.
[0081] The embodiment is effective when good pilot carrier signals
including large signal strength and pilot carrier signals including
extremely small signal strength are mixed in the multicarrier
signal. The embodiment is effective when pilot carrier signals
including large distortion and pilot carrier signals including
small distortion are mixed in the multicarrier signal.
Particularly, it is effective when the demodulation section uses
only pilot carrier signals including large signal strength for
distortion correction.
Eighth Embodiment
[0082] FIG. 9A is a schematic drawing to show carrier selection
sections 31 to 33 of a reception apparatus 107 according to an
eighth embodiment of the invention. Each of the carrier selection
sections 31 to 33 in the embodiment has a minimum value detection
section 35, a removal section 36, and a minimum value detection
section 37. Other components of the reception apparatus 107 are
similar to those previously described with reference to FIG. 1.
[0083] The minimum value detection section 35 and the removal
section 36 are similar to the minimum value detection section 35
and the removal section 36 in the seventh embodiment. The minimum
value detection section 37 selects pilot carrier signal PC.sub.3
including the minimum signal strength from among pilot carrier
signals PC.sub.1 to PC.sub.3 selected by the removal section 36.
Thus, in the embodiment, the pilot carrier signal including the
second smallest signal strength is selected from among the pilot
carrier signals in multicarrier signal. The carrier selection
sections 32 and 33 also select the pilot carrier signal including
the second smallest signal strength from among the pilot carrier
signals in the multicarrier signal.
[0084] For example, FIGS. 9B and 9C provide graphs of multicarrier
signals received by antenna sections 11 and 12. In the carrier
selection section 31, the minimum value detection section 35
detects pilot carrier signal PC.sub.4. In the carrier selection
section 31, the removal section 36 selects the pilot carrier
signals PC.sub.1 to PC.sub.3. Further, in the carrier selection
section 31, the minimum value detection section 37 selects the
pilot carrier signal PC.sub.1.
[0085] On the other hand, in the carrier selection section 32, the
minimum value detection section 35 detects pilot carrier signal
PC.sub.8. In the carrier selection section 32, the removal section
36 selects pilot carrier signals PC.sub.5 to PC.sub.7. Further, in
the carrier selection section 32, the minimum value detection
section 37 selects the pilot carrier signal PC.sub.5.
[0086] An antenna selection section 40 compares the pilot carrier
signals PC.sub.1 and PC.sub.5. Accordingly, the antenna selection
section 40 can reliably select the antenna section 11.
[0087] The reception apparatus of the embodiment has similar
advantages to those of the reception apparatus of the first
embodiment. Further, the reception apparatus 107 according to the
embodiment can reliably select the antenna with good communication
quality if the signal strength of one pilot carrier signal is
extremely small and the signal strength of another pilot carrier
signal is large. Particularly, it is effective when a demodulation
section uses only pilot carrier signals including large signal
strength for distortion correction.
Ninth Embodiment
[0088] FIG. 10 is a schematic drawing to show carrier selection
sections 31 to 33 of a reception apparatus 108 according to a ninth
embodiment of the invention. The carrier selection section 31
selects a subcarrier signal SC.sub.mid between a pilot carrier
signal PC.sub.1 including the smallest frequency and a pilot
carrier signal PC.sub.4 including the largest frequency among
subcarrier signals. The carrier selection sections 32 and 33 also
select a subcarrier signal between a pilot carrier signal including
the smallest frequency and a pilot carrier signal including the
largest frequency among subcarrier signals. Other components of the
reception apparatus 108 are similar to those previously described
with reference to FIG. 1.
[0089] In an antenna selection section 40, a calculation section 42
calculates average signal strengths AV.sub.1 to AV.sub.3 of the
subcarrier signals SC.sub.mid for carrier selection sections 31 to
33. Further, a signal strength comparison section 44 compares the
average signal strengths AV.sub.1 to AV.sub.3 and the antenna
selection section 40 selects the antenna section receiving the
signal including the largest signal strength.
[0090] Usually, a subcarrier signal PC.sub.min including a smaller
frequency than the pilot carrier signal PC.sub.1 including the
smallest frequency and a subcarrier signal PC.sub.max including a
larger frequency than the pilot carrier signal PC.sub.4 including
the largest frequency do not have large effect on demodulation.
Therefore, the reception apparatus 108 can reliably select the
antenna with good communication quality by selecting the subcarrier
signal SC.sub.mid. Further, the reception apparatus of the
embodiment has similar advantages to those of the reception
apparatus of the first embodiment.
Tenth Embodiment
[0091] FIG. 11 is a block diagram to show a reception apparatus 110
according to a tenth embodiment of the invention. The reception
apparatus 110 differs from the reception apparatus of the first
embodiment in that it further includes reception strength
measurement sections 61 to 63. The reception strength measurement
sections 61 to 63 measure the signal strengths of multicarrier
signals received through antenna sections 11 to 13. The reception
strength measurement sections 61 to 63 measure not only the signal
strengths of pilot carrier signals, but also the whole signal
strength.
[0092] An antenna selection section 40 selects an antenna section
based on the combination of the signal strengths of the pilot
carrier signals selected by carrier selection sections 31 to 33 and
the whole signal strengths measured by the reception strength
measurement sections 61 to 63. For example, the antenna selection
section 40 selects the antenna section with the largest sum
a*AV.sub.P+b*AV.sub.S where a*AV.sub.P is constant a multiplied by
average signal strength AV.sub.P of the pilot carrier signals
selected by the carrier selection sections 31 to 33 and b*AV.sub.S
is constant b multiplied by whole signal strength AV.sub.S measured
by the reception strength measurement sections 61 to 63. That is,
given weights are assigned and both the pilot carrier signal
strength and the whole signal strength are used to select the
antenna section.
[0093] The reception apparatus of the embodiment has similar
advantages to those of the reception apparatus of the first
embodiment. Further, in the tenth embodiment, not only the pilot
carrier signals, but also other subcarrier signals can be
considered for selecting the antenna section. Therefore, the
reception apparatus 110 can conduct high-quality
communications.
[0094] In the first to tenth embodiments, the antenna selection
section 40 selects the antenna section based on the signal
strengths of the subcarrier signals selected by the carrier
selection sections 31 to 33. However, the antenna selection section
40 may select the antenna section based on EVM (Error Vector
Magnitude) values of the subcarrier signals selected by the carrier
selection sections 31 to 33. In this case, the expression "signal
strength" in this specification may be replaced with "EVM
value."
Eleventh Embodiment
[0095] FIG. 12 is a block diagram to show a demodulation section 50
of a reception apparatus 120 according to an eleventh embodiment of
the invention. After an antenna selection section 40 selects an
antenna section, the demodulation section 50 demodulates the
multicarrier signal received through the selected antenna section.
Other components of the reception apparatus 120 may be similar to
those previously described with reference to FIG. 1. In FIGS. 12
and 13, a plurality of signals from a signal conversion section to
a distortion correction section 55 indicate flows of subcarrier
signals.
[0096] The demodulation section 50 has a strength measurement
section 51, a threshold value judgment section 52, a distortion
amount calculation section 53, a calculation section 54, and the
above-mentioned distortion correction section 55. The demodulation
section 50 receives a multicarrier signal from a signal conversion
section 21. The strength measurement section 51 measures the signal
strength of each pilot carrier signal in the multicarrier signal.
The threshold value judgment section 52 has a threshold value
concerning the signal strength and selects each pilot carrier
signal including the signal strength equal to or larger than the
threshold value.
[0097] The distortion amount calculation section 53 measures the
distortion amount of the pilot carrier signal selected by the
threshold value judgment section 52. Usually, the reception
apparatus 120 already knows the phase and frequency of the pilot
carrier signal when the signal is transmitted from the
communicating party, for example. Therefore, the distortion amount
calculation section 53 can calculate the phase difference between
the pilot carrier signal at the transmitting time and that at the
receiving time as the distortion amount.
[0098] The calculation section 54 calculates a distortion
correction value from the distortion amount provided by the
distortion amount calculation section 53. For example, if the
threshold value judgment section 52 selects a plurality of pilot
carrier signals, the calculation section 54 can calculate the
average value of a plurality of distortion amounts and adopt the
average value as the distortion correction value.
[0099] The distortion correction section 55 corrects each
subcarrier signal in accordance with the distortion correction
amount. For example, the distortion correction section 55 restores
the phase of each subcarrier signal by the phase difference
calculated by the calculation section 54. After the distortion of
each subcarrier signal is corrected, the multicarrier signal is
sent to a decoding section (not shown).
[0100] The pilot carrier signal including small signal strength
often is distorted largely. If such a pilot carrier signal is used
to make distortion correction, the demodulation section 50 cannot
precisely correct the subcarrier signal. Therefore, only pilot
carrier signals including the signal strength equal to or larger
than one threshold value as in the embodiment, whereby it is made
possible for the demodulation section 50 to precisely correct the
subcarrier signal. Consequently, the reception apparatus 120 can be
provided with high-quality reception characteristics.
[0101] The embodiment can be combined with any of the first to
tenth embodiments, so that the embodiment can also have the
advantages of any of the first to tenth embodiments. Particularly,
the embodiment and the fourth embodiment are used in combination,
the demodulation section 50 and the carrier selection sections 31
to 33 can use the common threshold value Th.
Twelfth Embodiment
[0102] FIG. 13 is a block diagram to show a demodulation section 50
of a reception apparatus 121 according to a twelfth embodiment of
the invention. The reception apparatus 121 differs from the
reception apparatus 120 of the eleventh embodiment in that a
calculation section 54 assigns a weight to the distortion amount
using the signal strength of each pilot carrier signal and then
calculates a distortion correction value.
[0103] The calculation section 54 acquires the signal strength of
each pilot carrier signal from a strength measurement section 51
and acquires the distortion amount of each pilot carrier signal
(for example, the phase difference) from a distortion amount
calculation section 53. The calculation section 54 assigns a weight
to the distortion amount based on the signal strength and then
calculates a distortion correction value. For example, the
calculation section 54 multiplies the ratio of the signal strengths
of pilot carrier signals by the distortion amount and further adds
the results together to find the distortion correction value.
[0104] Specifically, assume that the ratio of the signal strengths
of pilot carrier signals PC1, PC2, and PC3 is 0.5:0.2:0.3 and that
the phase differences between PC1 and PC2, between PC1 and PC3, and
between PC2 and PC3 are 10 degrees, 20 degrees, and 30 degrees
respectively. In this case, the calculation section 54 calculates
(0.5/1)*10+(0.2/1)*20+(0.3/1)*30. As a result, the calculation
section 54 adopts 18 degrees as the distortion correction
value.
[0105] Generally, the pilot carrier signal including small signal
strength often is distorted largely and thus the higher the signal
strength of the pilot carrier signal, the higher the reliability of
the distortion amount. Therefore, in the embodiment, a weight can
be assigned in response to the reliability of the pilot carrier
signal, so that the distortion amount of any other subcarrier
signal can be corrected precisely. Consequently, the reception
apparatus 121 can be provided with high-quality reception
characteristics.
Thirteenth Embodiment
[0106] A reception apparatus according to a thirteenth embodiment
of the invention will be discussed with reference to FIG. 13. In
the embodiment, a calculation section 54 acquires the signal
strength of each pilot carrier signal from a strength measurement
section 51 and acquires the distortion amount of each pilot carrier
signal (for example, the phase difference) from a distortion amount
calculation section 53.
[0107] Each pilot carrier signal can be represented by a vector
according to the signal strength and distortion amount of the pilot
carrier signal. The calculation section 54 combines the vectors
into one composite vector. Further, the calculation section 54
obtains the distortion correction value from the angle of the
composite vector.
[0108] In the embodiment, as in the twelfth embodiment, not only
the distortion amount of each pilot carrier signal, but also the
signal strength is considered for calculating the distortion
correction value. Therefore, the reception apparatus of the
embodiment has similar advantages to those of the reception
apparatus of the twelfth embodiment.
[0109] The twelfth and thirteenth embodiments may be combined with
the eleventh embodiment, so that the twelfth and thirteenth
embodiments can also obtain the advantages of the eleventh
embodiment.
Fourteenth Embodiment
[0110] A pilot carrier signal including a frequency near a
frequency of the pilot carrier signal is selected in the fourteenth
embodiment. FIG. 15 is a block diagram to show radio reception
apparatus according to the fourteenth embodiment. Plural antenna
sections 11 to 13, plural signal conversion section 21 to 23,
plural carrier selection sections 31 to 33, antenna selection
section 40, and demodulation section 50 are provided with the radio
reception apparatus as shown in FIG. 15. each of the antenna
sections 11 to 13 receives multi-carrier signal which transmitted
from the transmitter (not shown).
[0111] The numbers of signal conversion sections 21 to 23 and the
carrier selection sections 31 to 33 are as same as that of the
antenna sections 11 to 13 in accordance with the antenna sections.
Three antenna sections, three signal conversion sections, and three
carrier selection sections are provided with FIG. 15 as an example,
but the number is not limited.
[0112] Each of the carrier selection sections 31 to 33 selects at
least one sub carrier signal having frequencies each of which is
respectively near the plural pilot sub carriers among multi-carrier
signals which pass the corresponding signal conversion section. The
demodulation section 50 demodulates the multi carrier signal which
is received at the antenna section selected in the antenna
section.
[0113] The carrier selection sections 31 to 33 selects a sub
carrier signal in accordance with a characteristic graph as shown
in FIG. 15. a signal waveform of the multi-carrier signals are
shown in the graph in which a horizontal axis shows a frequency,
and a vertical axis shows a signal strength. As shown in the graph,
the multi-carrier signals have plural sub carrier signals which
have different frequency bans from one another. Plural known pilot
carrier signals are provided with the multi-carrier signals.
(Frequency f1, f2 in the graph)
[0114] The carrier selection sections 31 to 33 selects four sub
carrier signals f1-fa, f1+fa, f2-fa, and f2+fa which are nearest
from the pilot carrier signals corresponding to f1 and f2.
[0115] The sub carrier signals selected in the carrier selection
sections 31 to 33 are transmitted to the antenna selection section
40.
[0116] The antenna selection section 40 has calculation section 42
and signal strength comparison section 44. the calculation section
42 calculates AV1 which is an signal strength average among sub
carrier signals SC1, SC2, SC3, and SC4 which are selected by the
carrier selection section 31, AV2 which is a signal strength
average of the sub carrier signals selected by the carrier
selection section 32, and AV3 which is a signal strength average of
the sub carrier signals selected by the carrier selection section
33, respectively.
[0117] The signal strength comparison section 44 compares the
signals strength averages AV1, AV2, and AV3 and selects antenna
section which has a maximum signal strength average among antenna
sections 11 to 13.
[0118] According to the fourteenth embodiment, the carrier
selection sections 31 to 33 select four sub carrier signals, but
may select no more than three sub carrier signals or no fewer than
five sub carrier signals. Accordingly, the above described example,
each of sub carrier signals which are nearest from the pilot
carrier signal at both sides thereof are selected, but plural sub
carrier signals at both sides which are nearest from the pilot
carrier signal may be selected, and the sub carrier signal which
are nearest from the pilot carrier signal at one side thereof may
be selected. In addition, a number of pilot carrier signals which
are included in the multi-carrier signal is not limited in two.
Further, the sub carrier signals having a frequency except for a
frequency which is nearest from the frequency of the pilot carrier
signal may be selected.
[0119] FIG. 16 is a flow chart to show an example of processing
operation of the radio reception apparatus as shown in FIG. 15.
First, the antenna sections 11 to 13 receives multi carrier signals
modulated by multi carrier modulation method. (Step 60) Then, each
of the signal conversion sections 21 to 23 converts the multi
carrier signals received from the antenna sections 11 to 13. Thus,
the multi carrier signals are converted into a signal in which sub
carrier signals have a different frequency with one another. (Step
62)
[0120] Next, the carrier selection sections 31 to 33 respectively
select plural sub carrier signals which have a nearest frequency
from the frequency of the pilot carrier signal. (Step 64)
[0121] The antenna section 40 selects an antenna section which
receives the multi carrier signal on the basis of the signal
strength of the sub carrier signals selected by the carrier
selection sections 31 to 33. the demodulation section 50
demodulates the multi carrier signals received by the antenna
section selected by the antenna section 40. (Step 68)
[0122] The demodulation section 50 does not perform the
demodulation until the antenna selection section 40 selects the
antenna. The demodulation section 50 receives a signal indicating
that the antenna selection section 40 selects the antenna. After
the demodulation section 50 receives the signal, the demodulation
section 50 performs the demodulation. Thus, power consumption of
the demodulation section 50 can be decreased. The demodulation
section 50 does not demodulate a signal having a less communication
quality by mistake.
[0123] According to the fourteenth embodiment, the antenna section
can be selected on the basis of a signal strength of a certain sub
carrier signal in a predetermined frequency band. In particular, it
can be more effective in case that the pilot carrier signals are
not inadvertently transmitted when the carrier is selected and that
the antenna section selects a pilot carrier signal having large
signal strength thereof which have much effect on the demodulation.
In the fourteenth embodiment, even if the pilot carrier signals are
not received, sub carrier signals which are near from the pilot
carrier signal are selected. The sub carrier signals near from the
pilot carrier signal has a high mutual relation with the pilot
carrier signal with respect to a signal strength, so that the
antenna section having high communication quality can be selected
as well as in case the antenna section is selected on the basis of
the pilot carrier signal.
Fifteenth Embodiment
[0124] In the fifteenth embodiment, the construction of the antenna
selection section 40 is different from that of the fourteenth
embodiment.
[0125] FIG. 17 is a block diagram to show internal construction of
the radio reception apparatus according to the fifteenth
embodiment. The radio reception apparatus has a same construction
of the apparatus as shown in FIG. 15 other than the internal
construction of the antenna selection section 40. The antenna
selection section 40 as shown in FIG. 17 includes pilot adjacent
carrier extraction section 35 and reception level comparison
section 36. The pilot adjacent carrier extraction section 35, in
each antenna section, selects sub carrier signal having a minimum
reception strength among sub carrier signals which include a
nearest frequency from the frequency of the pilot carrier signal.
The reception level comparison section 36 includes selects an
antenna section which is corresponding to the sub carrier signal
having a maximum signal reception strength among the sub carrier
signals extracted from the pilot adjacent carrier extraction
section 35.
[0126] The pilot adjacent carrier extraction section 35 selects a
sub carrier signal having a minimum signal reception strength since
the smaller the signal reception strength is, the more effective
the noise is. The reception level comparison section 36 selects the
corresponding antenna section by extracting the sub carrier signal
having a maximum signal reception strength among the sub carrier
signals susceptible from the effectiveness of the noise.
[0127] Thus, in the fifteenth embodiment, the sub carrier signal
having a small signal reception strength is selected and compared
in stead of average of the sub carrier signal reception strength,
so that the effectiveness of the noise is not receptive.
Sixteenth Embodiment
[0128] In the sixteenth embodiment, all carrier selection sections
share signal conversion section and carrier selection section.
[0129] FIG. 18 is a block diagram to show an internal construction
of the radio reception apparatus according to the sixteenth
embodiment. The radio reception as shown in FIG. 18 includes plural
antenna sections 11 to 13, a signal conversion section 21 shared by
each antenna section, and a demodulation section 50.
[0130] The signal conversion part 21 includes LNA (Low Noise
Amplifier) which amplifies a multi-carrier signal, a D/C (Down
Converter) part which frequency-converts frequency of a
multi-carrier signal into a base band, an A/D conversion part which
converts an analog signal into a digital signal, and a FFT (Fast
Fourier Transfer) part which carries out discrete Fourier
conversion to each of multi-carrier signals. A multi-carrier
signal, which passed through the signal conversion part 21, has a
plurality of sub carrier signals with different frequency bands
each other.
[0131] The carrier selection section 31 is connected to output of
the FFT section 27 of the signal conversion section 21. The carrier
selection section 31 includes the pilot adjacent carrier extraction
section 35 and signal reception strength comparison section 36. The
pilot adjacent carrier extraction section 35 selects at least one
signal among the sub carrier signals which has a nearest frequency
from each frequency of plural pilot sub carrier signals among multi
carrier signals input from the FFT section 27. The signal reception
strength comparison section 36 selects and output a sub carrier
having a minimum signal reception strength among the sub carriers
extracted from the pilot adjacent carrier extraction section 35 to
the antenna selection section 40.
[0132] The antenna selection section 40 includes storage section 45
in which an information of the sub carrier selected by the carrier
selection section 31 is stored and reception level comparison
section between antenna 46 which can determine which antenna is
selected by performing a comparison on the basis of the stored
information in the storage section 45.
[0133] First, the antenna selection section 40 selects an antenna
section 11. The signal conversion section 21 converts a signal
received in the antenna section 11. The carrier selection section
31 selects a sub carrier having a minimum signal reception level
among sub carriers which has nearest frequency from that of each of
the plural pilot sub carrier. The storage section 45 of the antenna
selection section 40 stores the information.
[0134] Next, the antenna selection section 40 selects the antenna
section 12, performs same processing as the antenna section 11, and
stores the information in the storage section 45 of the antenna
selection section 40.
[0135] Then, the antenna selection section 40 selects the antenna
section 13, performs same processing as the antenna section 12, and
stores the information in the storage section 45 of the antenna
selection section 40.
[0136] The reception level comparison section between antenna 46
selects an antenna which having a maximum signal reception level of
the sub carrier selected on the basis of the information stored in
the storage section of the antenna selection section 40.
[0137] FIG. 19 is a flow chart to show one example of processing
operation of the radio reception apparatus as show in FIG. 18.
First, the antenna selection section 40 selects on of the antenna
sections. (Step S71) Next, the selected antenna section receives a
multi-carrier signal. (Step S72) Next, the signal conversion
section 21 converts a received multi-carrier signal into a signal
which includes sub carrier signals having different frequency with
one another. (Step S73) Next, the carrier selection section 31
selects a certain sub carrier signal, and selects a sub carrier on
the basis of a signal strength of the extracted sub carrier signal.
(Step S74) Then, the information of the sub carrier signal selected
by the carrier selection section 31 is stored in the storage
section 45 of the antenna selection section. (Step S75)
[0138] Next, whether or not all antenna sections complete a
processing is determined (Step 76), one of the antenna sections is
selected and Step S71 to S76 are repeated, if the antenna section
does not complete the above-processing.
[0139] Then, the reception level comparison section between
antennas 46 selects antenna section when all antenna sections
complete the processing. (Step S78)
The multi-carrier signal received in the antenna section selected
by the antenna selection section 40 is transmitted to the
demodulation section 50, and the demodulation processing is
performed. (Step S79)
[0140] The radio reception apparatus of FIG. 18 has only one pair
of the signal conversion section 21 and the carrier selection
section 31, so that the apparatus selects the antenna sections in
turn, performs the processing in the signal conversion section 21
and the carrier selection section 31, and stores the information of
the sub carrier signal corresponding to each antenna section in the
storage section 45. When the multi-carrier signal is transmitted in
a form of the packet, the processing as show in FIG. 19 may be
performed at the step that the preamble section of the packet is
received before receiving the data section of the packet.
[0141] FIG. 20 shows a data construction of the packet. As show in
FIG. 20, each packet has a preamble section 15 and a data section
16. each of the preamble section 15 and the data section 16 is
configured by the multi-carrier signal, so that in the embodiment,
the processing as show in FIG. 19 is performed by the preamble
section of the packet. When the antenna section is selected by the
data section 16, it is a risk that gain control and correction of
the transmission channel have inappropriate values. Thus, in the
embodiment, unit the data section 16 of the packet is received, the
selection of the antenna section, the correction of the
transmission channel, and correction of the transmission channel
after D/C section are performed by using the preamble section of
the packet.
[0142] Thus, in the sixteenth embodiment, all antenna sections
share one pair of the signal conversion section 21 and the carrier
selection section 31, so that it is not necessary to provide the
signal conversion section 21 and the carrier selection section 31
with each antenna section, the internal construction of the radio
reception apparatus becomes simple. Thus, it is possible to
decrease the electric power consumption and to make the apparatus
miniaturization. Further, the appropriate antenna section is
selected by the processing as show in FIG. 19, so that an antenna
section having a high communication quality may be certainly
selected. Further more, the antenna section is selected on the
basis of the preamble section of the received packet, so that
timely processing of the received data (Real Time Processing) can
be performed.
Seventeenth Embodiment
[0143] In the seventeenth embodiment, a processing in the carrier
selection section 31 is accelerated.
[0144] FIG. 21 is a block diagram to show a construction of the
radio reception apparatus according to the seventeenth embodiment.
The radio reception apparatus as show in FIG. 21 have a different
internal construction of the carrier selection section from that of
the apparatus as show in FIG. 18.
[0145] In FIG. 21, the carrier selection section 31 in the radio
reception apparatus has FFT section 37 other than FFT section 27
within the signal conversion section 21. output signal of A/D
section within the signal conversion section 21 is input into the
FFT section 37. the reason of the FFT 37 section is as follow:
[0146] It is necessary to perform the selection of the antenna
section, a gain control of the signal received by the antenna
section, and the correction of the transmission channel after D/C
section in the radio reception apparatus of FIG. 21. when the
antenna is changed in the data section 16 of the packet, the gain
control and the correction of the transmission channel are
performed
[0147] FIG. 22 represents a frequency characteristic of a data part
of a packet which was complied with IEEE802.11a. A horizontal axis
corresponds to frequency, and a vertical axis represent a signal
level. It is composed of 52 pieces of sub y carriers from +26 up to
-26, except for 0. Sub carriers of -21, -7, +7, +21 are pilot
carriers. On one hand, Fig. represents a frequency characteristic
of a short preamble, which is a part of a preamble part of the
packet which was complied with IEEE802.11a. A horizontal axis
corresponds to frequency, and a vertical axis represents a signal
level. Unlike the data part, it is composed of 12 pieces of sub
carriers of +24, +20, +16, +12, +8, +4, -4, -8, -12, -16, -20, -24,
and there exists no sub carrier with a frequency component which is
comparable to a pilot carrier of the data part.
[0148] In this connection, in order to select a sub carrier with
high correlation with a pilot sub carrier, selected is a sub
carrier which is of the nearest frequency to each of a plurality of
pilot sub carriers. That is, selected are sub carriers of -20, -8,
+8, +20.
[0149] In addition, by utilizing a characteristic of a
configuration of a short preamble of Fig., electric power
measurement of each sub carrier is possible with shorter time than
usual. Usually, i.e., in a configuration of a data part, there is a
necessity to carry out Fourier conversion with time of Tk=1/fk,
inverse number of fundamental frequency fk of a sub carrier in
which sub carrier number is of the nearest to 0, rather than
orthogonality of OFDM, and to measure reception strength. However,
in the configuration of Fig., since fundamental frequency is 4*fk,
4 times, and further, only a frequency component of its constant
number multiple exists, it is possible to carry out Fourier
conversion and measurement of reception strength with time of
Tk/4=1/(4*fk). That is, it is possible to measure signal strength
with time of 1/4 multiple.
[0150] In this embodiment, even in case that a pilot carrier does
not exist in a preamble part, in packet communication, it is
possible to select a carrier with a high correlation with a pilot
carrier, and on the basis of signal strength of that carrier, to
carry out antenna selection. By this, the communication apparatus
101 can surely select an antenna with good communication
quality.
Eighteenth Embodiment
[0151] The eighteenth embodiment is a modification of the
embodiment of FIG. 17. The internal construction of the carrier
selection section 31 is different from that of the carrier
selection section as show in FIG. 21.
[0152] FIG. 24 is a block diagram to show the construction of the
radio reception apparatus according to the eighteenth embodiment.
The carrier selection section 31 in the apparatus of FIG. 24 has a
mutual relation calculating section 38 and a reception level
comparison section 36. The mutual relation calculating section 38
calculates a mutual relation degree with a frequency of the sub
carrier signal included in the multi-carrier signal. A frequency of
the pilot carrier signal is unknown, so that the sub carrier signal
having a frequency which is nearest from the frequency of the pilot
carrier signal is extracted by calculating the mutual relation
degree with a frequency which is nearest from the frequency of the
pilot carrier signal.
[0153] Thus, in the eighteenth embodiment, the subcarrier signal
having a frequency which is nearest from the frequency of the pilot
carrier signal can be extracted without FFT section and pilot
adjacent carrier extraction section within the carrier selection
section 31, so that the internal construction of the carrier
selection section 31 makes simple, and the miniaturization of the
apparatus and the decrease of the electric power consumption can be
achieved.
Nineteenth Embodiment
[0154] In the embodiments of FIGS. 16 and 17, the selection of the
antenna section is performed on the basis of the preamble section
15 of the packet as an example. However, according algorithm of the
signal conversion section 21 and the demodulation section 50, there
is an unimportant pilot carrier signal. For example, in
IEEE802.11a, the pilot carrier signal is mainly used for frequency
correction and phase correction, but all four pilot sub carrier
signals are always necessary. Thus, there is algorithm such that
the pilot carrier having a low reliability and a predetermined
value smaller than a threshold value with respect to the signal
reception strength of the pilot carrier is not used for the
frequency correction and phase correction, that is, it is not
important to use the pilot carrier having a small signal reception
strength in this case for the demodulation.
[0155] According to the nineteenth embodiment, the internal
construction of the radio reception apparatus is same as that of
the apparatus of FIG. 21, so that the explanation is omitted.
[0156] FIG. 25 is a flowchart to show an example of the processing
operation according to nineteenth embodiment. The processing is as
same as that of FIG. 19 from Step S81 to step S83. Next, The sub
carrier signal having a minimum value of the signal reception
strength is selected among the sub carrier signals except for sub
carrier signal having a value of the signal reception strength
lower than the threshold value. (Step S84) Then, the processing
from step S85 to step S87 are performed as same as that from step
S75 to step S77 as shown in FIG. 19.
[0157] Next, the antenna selection section 40 an antenna section
which has a maximum signal reception strength among the sub carrier
signals stored in the storage section 45. (Step S88)
[0158] Thus, in the nineteenth embodiment, the sub carrier signals
are narrow by previously setting the threshold value, so that the
processing of the carrier selection section 31 is accelerated by
previously getting out of the unnecessary sub carrier signals.
Twentieth Embodiment
[0159] The twentieth embodiment is a modification of the embodiment
of FIG. 19. whether or not the antenna section is selected is
determined by a number of the sub carrier signals having a value
over the threshold value.
[0160] FIG. 26 is flow chart to show an example of the processing
operation according to the twentieth embodiment. The processing
from step S91 to step S97 is perform as same as that from step S81
to step S87 as shown in FIG. 25. Next, the antenna selection
section 40 compares a number of the sub carrier signals selected by
the carrier selection section 31 and selects an antenna which has a
largest number of the sub carrier signals over the threshold value.
(Step S98)
[0161] In the processing of Step S98, in case that plural antenna
sections are applicable, the sub carrier signal which has a maximum
signal strength value is selected by comparing a signal strength of
the sub carrier signal having a minimum value among the plural
antenna sections with one another.
[0162] Further, in Step S98, the antenna section which has maximum
average signal strength of the sub carrier signal selected by the
carrier selection section 31 may be selected.
[0163] Thus, according to twentieth embodiment, in case that the
algorism such that the pilot carrier having a low reliability and a
predetermined value smaller than a threshold value with respect to
the signal reception strength of the pilot carrier is not used for
the frequency correction and phase correction is used, more pilot
carrier signals can be used for the frequency correction and the
phase correction. In addition, in case that plural antenna sections
having a maximum number of selected sub carrier signals, among the
plural antenna sections, more reliable antenna section can be
selected on the basis of the signal strength of the sub carrier
signals selected by the carrier selection section 31. Thus, the
communication quality is improved.
Twenty-First Embodiment
[0164] According to the twenty-first embodiment, sub carrier
signals included in multi-carrier signals are weighted in
accordance with frequency differences between frequencies of the
pilot carrier signals and frequencies of the sub carrier
signals.
[0165] FIG. 27 is a flow chart of the processing operation
according the radio reception apparatus according to the
twenty-first embodiment. The processing from step S101 to step S103
is as same as that of FIG. 19. Next, with respect to each sub
carrier signal, a weighted coefficient is set in accordance with
the frequency difference. (Step S104) a relation between the
frequencies and the weighted coefficient may be previously
prepared. The smaller frequency differences between the pilot
carrier signal and sub carrier signal are, the larger weighted
coefficient is set.
[0166] Next, the weighted signal reception strength is calculated
by multiplying the signal reception strength with the set weighted
coefficient. (Step S105) Next, the processing from step S106 to
step S108 is as same as that from step S75 to step S77 as shown in
FIG. 19.
[0167] Next, the antenna selection section 40 selects an antenna
section which has a sub carrier signal having a maximum signal
reception strength on the basis of the calculation result of the
signal reception strength by the step S105. (Step S109)
[0168] Thus, according to the twenty-first embodiment, since the
sub carrier signal is weighted in accordance with the frequency
differences between the pilot carrier signal and the sub carrier
signal, the sub carrier signal near the frequency of the pilot
carrier signal can be preferentially selected.
Twenty-Second Embodiment
[0169] According to the twenty-second embodiment, the processing is
performed in each group which holds plural subcarrier signals
together as one group.
[0170] FIG. 28 is an view to explain the general description
according the twenty-second embodiment. In the twenty-second
embodiment, all sub carrier signals is divided into first sub
carrier group 55 in which the sub carrier signals are near the
frequency of the pilot carrier signal and second sub carrier group
56 in which the subcarrier signals is far from the frequency of the
pilot carrier signal.
[0171] Each carrier selection section 31 selects at least one sub
carrier signal from the first sub carrier group 55, and selects at
least one sub carrier signal from the second sub carrier group 56.
The antenna selection section 40 selects an antenna section on the
basis of the signal reception strength of the sub carrier signals
which selected from both sub carrier groups 55, 56.
[0172] For example, the carrier selection section 31 respectively
selects a sub carrier signal having a minimum signal reception
strength from the sub carrier signal groups. Thus, the two selected
sub carrier signals is differently weighted, and calculates the
weighted signal reception strength.
[0173] The antenna selection section 40 selects an antenna which is
corresponding to the sub carrier signal having the weighted maximum
signal reception strength.
[0174] Alternatively, the carrier selection section 31 selects a
sub carrier signal having a minimum signal reception strength from
the first sub carrier group 55, and selects all sub carrier signals
of the second sub carrier group 56. the signal reception strength
of the sub carrier signal selected by the first sub carrier group
55 and the average signal reception strength of all sub carrier
signals of the sub carrier group 56 are respectively weighted, and
thus are combined. In this case, the antenna selection section 40
selects an antenna section which has a sub carrier signal having a
maximum signal reception strength calculated by the carrier
selection section 31.
[0175] Thus, according to the twenty-second embodiment, the sub
carrier signals are divided into plural groups. The signal
reception strength are weighted and corrected in each group, so
that the antenna section can be selected in a short time compared
with the case that a weighted operation is performed in each sub
carrier signal.
* * * * *