U.S. patent application number 11/715870 was filed with the patent office on 2007-07-05 for radio communication apparatus.
Invention is credited to Akinori Fujimura, Hiroaki Hirai, Yukimasa Nagai, Mari Otiai, Yosikatu Tajima.
Application Number | 20070155393 11/715870 |
Document ID | / |
Family ID | 33534730 |
Filed Date | 2007-07-05 |
United States Patent
Application |
20070155393 |
Kind Code |
A1 |
Hirai; Hiroaki ; et
al. |
July 5, 2007 |
Radio communication apparatus
Abstract
A reception processing unit measures reception states of input
reception signals of each of a plurality of channels, generates
local channel reception information, and applies a reception
processing to the input reception signals to generate decoded
signals. A media-access-control unit generates transmission frames
for each of the channels using transmission data. A transmission
processing unit generates radio signals including each of the
transmission frames. A channel-information processing unit
generates local feedback information, and inserts the local
feedback information generated into at least one of the radio
signals that are transmitted by the radio communication
apparatus.
Inventors: |
Hirai; Hiroaki; (Tokyo,
JP) ; Fujimura; Akinori; (Tokyo, JP) ; Nagai;
Yukimasa; (Tokyo, JP) ; Tajima; Yosikatu;
(Tokyo, JP) ; Otiai; Mari; (Tokyo, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
33534730 |
Appl. No.: |
11/715870 |
Filed: |
March 9, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10525069 |
Feb 18, 2005 |
7194240 |
|
|
PCT/JP04/08687 |
Jun 15, 2004 |
|
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11715870 |
Mar 9, 2007 |
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Current U.S.
Class: |
455/450 |
Current CPC
Class: |
H04W 24/00 20130101;
H04L 1/0016 20130101; H04L 1/0002 20130101; H04W 74/00
20130101 |
Class at
Publication: |
455/450 |
International
Class: |
H04Q 7/20 20060101
H04Q007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 18, 2003 |
JP |
2003-173725 |
Claims
1. A radio communication apparatus that is applied to a radio
communication system and communicates with another radio
communication apparatus in the radio communication system using one
available channel or a plurality of channels, the radio
communication apparatus comprising: a reception processing unit
that, when input reception signals of the channels of the radio
communication system is received, estimates local channel reception
information of each of the channels based the reception status, and
applies a reception processing to the input reception signals to
generate decoded signals; a media-access-control unit that, when
data is transmitted, generates transmission frames; and a
transmission processing unit that generates radio signal including
the transmission frames, wherein the radio communication apparatus
transmits the radio signals including the local feedback
information.
2. A radio communication apparatus that is applied to a radio
communication system and communicates with another radio
communication apparatus in the radio communication system using one
available channel or a plurality of channels, the radio
communication apparatus comprising: a reception processing unit
that, when input reception signals of the channels of the radio
communication system is received, estimates local channel reception
information of each of the channels based on the reception status,
and applies a reception processing to the input reception signals
to generate decoded signals; a media-access-control unit that, when
data is transmitted, generates local feedback information based on
the local channel reception information, further generates
transmission frames using transmission data; and a transmission
processing unit that generates radio signals including each of the
transmission frames that includes the local feedback information,
and transmits the radio signals generated.
3. A radio communication apparatus for communicating with another
radio communication apparatus, comprising: a reception processing
unit which receives an input reception signal from the other radio
communication apparatus, wherein the input reception signal
includes a transmission source feedback information that indicates
a reception status of the other radio communication apparatus; a
media-access-control unit which determines a transmission parameter
for a transmission frame based on the transmission source feedback
information, and a transmission processing unit which generates a
radio signal to be transmitted to the other communication apparatus
by modulating the transmission frame based on the transmission
parameter.
4. A radio communication method that is applied to a radio
communication apparatus communicating with another radio
communication apparatus in the radio communication system using one
available channel or a plurality of channels, the radio
communication method comprising the steps of: a reception
processing step for, when input reception signals of the channels
of the radio communication system is received, estimating local
channel reception information of each of the channels based on the
reception status, and applying a reception processing to the input
reception signals to generate decoded signals; a
media-access-control step for, when data is transmitted, generating
transmission frames; a transmission processing step for generating
radio signal including the transmission frames; and transmitting
the radio signals including the local feedback information.
5. A radio communication method that is applied to a radio
communication apparatus communicating with another radio
communication apparatus in the radio communication system using one
available channel or a plurality of channels, the radio
communication apparatus comprising the steps of: a reception
processing step for, when input reception signals of the channels
of the radio communication system is received, estimating local
channel reception information of each of the channels based on the
reception status, and applying a reception processing to the input
reception signals to generate decoded signals; a
media-access-control step for, when data is transmitted, generating
local feedback information based on the local channel reception
information, and further generating transmission frames using
transmission data; and a transmission processing step for
generating radio signal including each of the transmission frames
that includes the local feedback information, and transmitting the
radio signals generated.
6. A radio communication method for communicating with another
radio communication apparatus, comprising the steps of: a reception
processing step for receiving an input reception signal from the
other radio communication apparatus, wherein the input reception
signal includes a transmission source feedback information that
indicates a reception status of the other radio communication
apparatus; a media-access-control step for determining a
transmission parameter for a transmission frame based on the
transmission source feedback information; and a transmission
processing step for generating a radio signal to be transmitted to
the other communication apparatus by modulating the transmission
frame based on the transmission parameter.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional of co-pending application
Ser. No. 10/525,069 filed on Feb. 18, 2005, and for which priority
is claimed under 35 U.S.C. .sctn.120. Application Ser. No.
10/525,069 is the national phase of PCT International Application
No. PCT/JP2004/008687 filed on Jun. 15, 2004 under 35 U.S.C.
.sctn.371. This application further claims priority of Application
No. 2003/173725 filed in Japan on Jun. 18, 2003 under 35 U.S.C.
.sctn.119(a). The entire contents of all of the above-identified
applications are hereby incorporated by reference.
TECHNICAL FIELD
[0002] The present invention relates to a radio communication
apparatus that uses plural channels simultaneously to perform
mutual communication, and in particular to a radio communication
apparatus that notifies other radio communication apparatus of a
reception state of a channel to be used and selects an appropriate
communication system and communication speed.
BACKGROUND ART
[0003] In recent years, an increase in communication speed is
demanded in a radio communication apparatus as well. Therefore, in
a radio communication system, the increase in communication speed
is realized by increasing a transmission capacity using plural
channels.
[0004] In a conventional technology for realizing the increase in
communication speed using plural channels, plural channels are
allocated and secured in advance in a path between a specific
communication unit system and a specific terminal unit system, in
which a wide transmission band is required, to perform
communication on the plural channels (see, for example, Japanese
Application Laid-Open Publication No. 2002-135304).
[0005] However, in the case of radio communication, communication
state changes depending on environments like obstacles and weather
conditions (e.g., rainy weather). In addition, in the case of
mobile communication, a communication state always changes with
time due to movements. In the conventional technology, a technique
for selecting transmission systems and transmission speeds suitable
for communication states in performing communication on plural
channels is not disclosed. Therefore, there is a problem in that it
is impossible to select a transmission system and a transmission
speed suitable for a communication state in each channel.
[0006] For example, in the conventional technology, when a
modulation system with a high transmission speed is adopted,
although a transmission speed is increased, communication cannot be
performed in a place where a state of a transmission channel is bad
and retransmission requests increase, which results in decline in
throughput. In addition, when a modulation system in which
communication is possible even when a state of a transmission
channel is bad, a communication speed falls, and an advantage of
increasing a transmission capacity using plural channels is
reduced.
[0007] The present invention has been devised in view of the above,
and it is an object of the present invention to provide a radio
communication apparatus that can select transmission systems and
transmission speeds corresponding to respective channels in
performing mutual communication using plural channels.
DISCLOSURE OF THE INVENTION
[0008] To achieve the above object, a radio communication apparatus
according to one aspect of the present invention, which is applied
to a radio communication system and communicates with other radio
communication apparatus in the radio communication system using one
available channel or a plurality of channels, includes a reception
processing unit that, when input reception signals of the channels
of the radio communication system is received, measures reception
states of input reception signals of each of the channels,
generates local channel reception information of each of the
channels based on a result of the measurement, and applies a
reception processing to the input reception signals to generate
decoded signals; a media-access-control unit that, when data is
transmitted using two or more channels, generates transmission
frames for each of the channels using transmission data; a
transmission processing unit that generates radio signals including
each of the transmission frames; and a channel-information
processing unit that generates local feedback information based on
the local channel reception information, and inserts the local
feedback information generated into one of the radio signals or a
plurality of the radio signals. The radio communication apparatus
transmits the radio signals including the local feedback
information.
[0009] According to the present invention, a reception processing
unit generates local channel reception information based on
reception states of input reception signals of respective channels,
a channel-information processing unit generates local feedback
information based on the local channel reception information
generated by the reception processing unit, inserts the generated
local feedback information into radio signals, and transmits the
radio signals.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic diagram of a structure of a radio
communication system to which a radio communication apparatus
according to the present invention is applied;
[0011] FIG. 2 is a block diagram of a structure of transmission and
reception functions of a radio communication apparatus according to
a first embodiment of the present invention;
[0012] FIG. 3 is a block diagram of a structure of transmission and
reception functions of a radio communication apparatus according to
a second embodiment of the present invention;
[0013] FIG. 4 is a block diagram of a structure of transmission and
reception functions of a radio communication apparatus according to
a third embodiment of the present invention;
[0014] FIG. 5 is a block diagram of a structure of transmission and
reception functions of a radio communication apparatus according to
a fourth embodiment of the present invention;
[0015] FIG. 6 is a block diagram of a structure of transmission and
reception functions of a radio communication apparatus according to
a fifth embodiment of the present invention;
[0016] FIG. 7 is a flowchart for explaining a reception operation
of the radio communication apparatus according to the fifth
embodiment;
[0017] FIG. 8 is a flowchart for explaining a transmission
operation of the radio communication apparatus according to the
fifth embodiment;
[0018] FIG. 9 is a block diagram of a structure of transmission and
reception functions of a radio communication apparatus according to
a sixth embodiment of the present invention; and
[0019] FIG. 10 is a flowchart for explaining a transmission
operation of the radio communication apparatus according to the
sixth embodiment.
BEST MODE FOR CARRYING OUT THE INVENTION
[0020] Exemplary embodiments of a radio communication apparatus
according to the present invention will be explained in detail with
reference to the accompanying drawings.
[0021] FIG. 1 is a schematic diagram of a structure of a radio
communication system to which a radio communication apparatus
according to the present invention is applied. The radio
communication system, to which the radio communication apparatus in
the present invention is applied, includes plural (four in this
case; however, the number is irrelevant the number of channels and
the number of radio communication apparatuses in a radio
communication area) radio communication apparatuses 1 to 4 that
performs mutual communication via a radio area 5 that uses plural
(three in this case) channels. It is assumed that all the radio
communication apparatuses 1 to 4 have the same functions.
[0022] Note that the channels of this radio communication apparatus
indicate communication paths that are set for performing
communication at, for example, a frequency, time, a code, and a
space (multi input multi output (MIMO)).
[0023] A first embodiment of the present invention will be
explained using FIG. 2. FIG. 2 is a block diagram of a structure of
transmission and reception functions of a radio communication
apparatus 1 according to the first embodiment. The radio
communication apparatus 1 according to the first embodiment of the
present invention includes a reception processing unit 10 that has
plural (three in this case) reception channel processing units 110
to 130 corresponding to the number of channels usable by the
apparatus itself, a media access control (MAC) unit 20, a
channel-information processing unit 30, and a transmission
processing unit 40 that has plural (three in this case)
transmission channel processing units 410 to 430 corresponding to
the number of channels usable by the apparatus itself.
[0024] The reception channel processing unit 110 receives an input
reception signal of a channel corresponding to the reception
channel processing unit 110 and applies synchronization processing,
demodulation processing, and decoding processing to the input
reception signal. In addition, the reception channel processing
unit 110 measures reception levels of input reception signals in
the respective channels. Then, the reception channel processing
unit 110 generates local channel reception information based on the
measured reception levels or receive signal strength indication
(RSSI) and reception channel processing internal information that
is physical resources like a memory, a buffer, and a central
processing unit (CPU) and state resources of a control signal and
the inside of the memory according to processing of the channel
itself. The reception channel processing unit 110 judges whether
feedback information is included in the input reception signal. The
feedback information is information related to overall resources
like reception state information of the channel and states of the
memory, the CPU, and the buffer.
[0025] The reception channel processing units 120 and 130 have the
same function as the reception channel processing unit 110 and
apply the same processing as the reception channel processing unit
110 to channels corresponding to the reception channel processing
units 120 and 130, respectively.
[0026] At the time of a reception operation, the MAC unit 20
controls the reception channel processing units 110 to 130 serving
as physical communication media and applies processing like
protocol conversion and frame conversion to respective decoded
signals to generate reception frames. In addition, the MAC unit 20
judges whether feedback information is included in the respective
decoded signals.
[0027] At the time of a transmission operation, the MAC unit 20
applies the processing such as the protocol conversion and the
frame conversion to a transmission frame inputted from an upper
layer to generate transmission frames of respective channels. In
addition, the MAC unit 20 exchanges resource information with the
channel-information processing unit 30 and determines transmission
systems and transmission speeds for the respective channels based
on feedback information of the respective channels from a
transmission source that is inputted from the channel-information
processing unit 30.
[0028] The channel-information processing unit 30 mutually
exchanges resource information, which is the physical resources
such as the memory, the buffer, and the CPU and the state resources
of a control signal and the inside of the memory, with the MAC unit
20 to perform a reception operation and generates local feedback
information based on respective pieces of local channel reception
information inputted from the reception channel processing units
110 to 130 and the resource information. The local feedback
information may be all determined pieces of the local channel
reception information and the resource information or may be
information that is selected out of the local channel reception
information and the resource information and aggregated every
time.
[0029] In addition, the channel-information processing unit 30
judges whether the respective pieces of transmission source
feedback information inputted from the reception channel processing
units 110 to 130 or the MAC unit 20 have identical contents. As the
judgment, for example, when cyclic redundancy check (CRC) is used,
the channel-information processing unit 30 discards the pieces of
transmission source feedback information for which the CRC
indicates an error and adopts only the pieces of transmission
source feedback information for which the CRC is normal, or adopts
the pieces of transmission source feedback information that have
identical contents and are largest in number, or measures a
carrier/noise ratio (C/N) and a desired/undesired ratio (D/U) for
each channel and adopts the transmission source feedback
information of a channel having highest C/N and D/U, or synthesizes
weighting according to probability with respect to all pieces of
the information and adopts the respective pieces of transmission
source feedback information based on the weighting.
[0030] The channel-information processing unit 30 discards the
transmission source feedback information of a wrong channel as a
result of the judgment and extracts feedback information of
respective channels from the accurate transmission source feedback
information.
[0031] The transmission channel processing unit 410 selects a
transmission system and a transmission speed of a channel based on
transmission control information. Then, based on the selected
transmission system and transmission speed, the transmission
channel processing unit 410 applies encoding processing and
modulation processing to the transmission frame inputted from the
MAC unit 20 and the local feedback information inputted from the
channel-information processing unit 30 to generate a radio
signal.
[0032] The transmission channel processing units 420 and 430 have
the same function as the transmission channel processing unit 410
and apply the same processing as the transmission channel
processing unit 410 to channels corresponding to the transmission
channel processing units 420 and 430, respectively.
[0033] Next, operations of the radio communication apparatus will
be explained. First, a reception operation will be explained. The
reception channel processing units 110 to 130 receive input
reception signals in the corresponding channels, respectively,
apply demodulation processing and decoding processing to the input
reception signals, and output decoded signals to the MAC unit 20.
At the same time, the reception channel processing units 110 to 130
measure reception levels of the input reception signals in the
respective channels, and generate local channel reception
information based on the measured respective reception levels and
reception channel processing internal information. Then, the
reception channel processing units 110 to 130 output the generated
local channel reception information to the channel-information
processing unit 30. In addition, the reception channel processing
units 110 to 130 judge whether feedback information is included in
the input reception signals and, when feedback information is
included in the input reception signals, output the feedback
information in the input reception signals to the
channel-information processing unit 30 as transmission source
feedback information.
[0034] The MAC unit 20 applies the processing such as the protocol
conversion and the frame conversion to the decoded signals inputted
from the reception channel processing units 110 to 130,
respectively, generates reception frames, and outputs the reception
frames to the upper layer. In addition, the MAC unit 20 judges
whether feedback information is included in the respective decoded
signals and, when feedback information is included in the decoded
signals, outputs the feedback information in the decoded signals to
the channel-information processing unit 30 as transmission source
feedback information.
[0035] Next, a transmission operation will be explained. The
channel-information processing unit 30 generates local feedback
information based on the respective pieces of local channel
reception information inputted from the reception channel
processing units 110 to 130 and the resource information, copies
the generated local feedback information, and outputs the local
feedback information to the transmission channel processing units
410 to 430. At the same time, the channel-information processing
unit 30 extracts accurate transmission source feedback information
from the respective pieces of transmission source feedback
information inputted from the reception channel processing units
110 to 130 or the MAC unit 20 and outputs the extracted feedback
information of the respective channels to the MAC unit 20.
[0036] The MAC unit 20 applies the processing such as the protocol
conversion and the frame conversion to a transmission frame
inputted from the upper layer to generate transmission frames of
the respective channels. Then, the MAC unit 20 outputs the
generated respective transmission frames to the transmission
channel processing units 410 to 430. In addition, the MAC unit 20
exchanges the resource information with the channel-information
processing unit 30 and determines transmission systems and
transmission speeds of the respective channels based on the
feedback information of the respective channels from a transmission
source that is inputted from the channel-information processing
unit 30. Then, the MAC unit 20 outputs the transmission systems and
the transmission speeds determined for the respective channels to
the transmission channel processing units 410 to 430 as
transmission control information.
[0037] The transmission channel processing units 410 to 430 select
transmission systems and transmission speeds of the channels based
on the respective pieces of transmission control information
inputted from the MAC unit 20. Then, based on the selected
transmission systems and transmission speeds, the transmission
channel processing units 410 to 430 apply the encoding processing
and the modulation processing to the transmission frames inputted
from the MAC unit 20 and the local feedback information inputted
from the channel-information processing unit 30 to generate radio
signals. Then, the transmission channel processing units 410 to 430
output the generated radio signals.
[0038] In this way, according to the first embodiment, the
reception channel processing units 110 to 130 generate local
channel reception information based on reception states of
respective input reception signals, and the channel-information
processing unit 30 generates local feedback information based on
the local channel reception information generated by the reception
channel processing units 110 to 130 and the resource information
and inserts the generated local feedback information into a radio
signal to be transmitted on a channel used for transmission. Thus,
it is possible to notify other radio communication apparatus of
states of respective channels such that the other radio
communication apparatus can select transmission systems and
transmission speeds suitable for the states of the respective
channels.
[0039] In addition, the MAC unit 20 determines transmission systems
and transmission speeds of the respective channels based on
respective pieces of local feedback information inserted by the
other radio communication apparatus (transmission source feedback
information of the apparatus itself). This makes it possible to
select transmission systems and transmission speeds of the
respective channels, and retransmission requests can be controlled
to improve throughput and reduce communication delays.
[0040] Moreover, since local feedback information is inserted into
all channels to be used, it is possible to learn feedback
information of the respective channels if one channel among plural
channels can be received.
[0041] A second embodiment of the present invention will be
explained using FIG. 3. According to the first embodiment, local
feedback information is inserted into all channels. According to
the second embodiment, channels into which local feedback
information is inserted are limited, whereby a radio band necessary
for notifying the local feedback information of other radio
communication apparatus is reduced to realize an increase in a
radio capacity.
[0042] FIG. 3 is a block diagram of a structure of transmission and
reception functions of a radio communication apparatus according to
the second embodiment. In the radio communication apparatus 1
according to the second embodiment, a selector 50 is added to the
radio communication apparatus 1 according to the first embodiment
shown in FIG. 2. Components having the same functions as those
according to the first embodiment will be denoted by the identical
reference numerals, and a redundant explanation will be
omitted.
[0043] The selector 50 determines a channel, on which local
feedback information generated by the channel-information
processing unit 30 is transmitted, based on respective pieces of
local channel reception information inputted from the reception
channel processing units 110 to 130. The local channel reception
information is information such as the C/U and the D/U. The
selector 50 judges communication states of respective channels from
these pieces of local channel reception information and selects a
channel having a best communication state. In other words, from the
local channel reception information of the respective channels, the
selector 50 judges which channel should be used to transmit local
feedback information such that the local feedback information can
be notified to other radio communication apparatus at a high
probability. Note that a selection method is not limited to this
and, for example, a specific number of specific channels may be
used without using channel information.
[0044] Next, operations of the radio communication apparatus
according to the second embodiment of the present invention will be
explained. First, a reception operation will be explained. The
reception channel processing units 110 to 130 receive input
reception signals in the corresponding channels, respectively,
apply the demodulation processing and the decoding processing to
the input reception signals, and output decoded signals to the MAC
unit 20. At the same time, the reception channel processing units
110 to 130 generate local channel reception information based on
reception levels of respective channels and reception channel
processing internal information. Then, the reception channel
processing units 110 to 130 output the generated local channel
reception information to the channel-information processing unit 30
and the selector 50. In addition, when feedback information is
included in the input reception signals, the reception channel
processing units 110 to 130 output the feedback information in the
input reception signals to the channel-information processing unit
30 as transmission source feedback information.
[0045] The MAC unit 20 applies the processing such as the protocol
conversion and the frame conversion to the decoded signals inputted
from the reception channel processing units 110 to 130,
respectively, generates reception frames, and outputs the reception
frames to the upper layer. In addition, the MAC unit 20 judges
whether feedback information is included in the respective decoded
signals and, when feedback information is included in the decoded
signals, outputs the feedback information in the decoded signals to
the channel-information processing unit 30 as transmission source
feedback information.
[0046] Next, a transmission operation will be explained. The
channel-information processing unit 30 generates local feedback
information based on the respective pieces of local channel
reception information inputted from the reception channel
processing units 110 to 130 and resource information and outputs
the generated local feedback information to the selector 50. In
addition, the channel-information processing unit 30 outputs
feedback information of the respective channels for the
transmission source feedback information, which is inputted from
the reception channel processing units 110 to 130 or the MAC unit
20, to the MAC unit 20.
[0047] The MAC unit 20 applies the processing such as the protocol
conversion and the frame conversion to a transmission frame
inputted from the upper layer to generate transmission frames of
the respective channels. Then, the MAC unit 20 outputs the
generated respective transmission frames to the transmission
channel processing units 410 to 430. In addition, the MAC unit 20
exchanges the resource information with the channel-information
processing unit 30 and determines transmission systems and
transmission speeds of the respective channels based on the
feedback information of the respective channels from a transmission
source that is inputted from the channel-information processing
unit 30. Then, the MAC unit 20 outputs the transmission systems and
the transmission speeds determined for the respective channels to
the transmission channel processing units 410 to 430 as
transmission control information.
[0048] The selector 50 determines a channel, on which the local
feedback information generated by the channel-information
processing unit 30 is transmitted, based on the respective pieces
of local channel reception information inputted from the reception
channel processing units 110 to 130. Then, the selector 50 outputs
the local feedback information to a transmission channel processing
unit corresponding to the determined channel.
[0049] The transmission channel processing units 410 to 430 select
transmission systems and transmission speeds of the channels based
on the respective pieces of transmission control information
inputted from the MAC unit 20. Then, based on the selected
transmission systems and transmission speeds, the transmission
channel processing units 410 to 430 apply the encoding processing
and the modulation processing to the transmission frames inputted
from the MAC unit 20 to generate radio signals. In that case, when
the local feedback information is inputted from the selector 50,
the transmission channel processing units 410 to 430 apply the
encoding processing and the modulation processing to the
transmission frames and the local feedback information to generate
radio signals. Then, the transmission channel processing units 410
to 430 output the generated radio signals.
[0050] In this way, according to the second embodiment, the
selector 50 determines a channel, on which local feedback
information generated by the channel-information processing unit 30
is transmitted, based on the respective pieces of local channel
reception information inputted from the reception channel
processing units 110 to 130 to limit channels into which the local
feedback information is inserted. Thus, it is possible to reduce
radio bands in which the local feedback information is notified to
other radio communication apparatus and realize an increase in a
radio capacity.
[0051] Note that, although the selector 50 is independently
provided according to the second embodiment, the function of the
selector 50 may be included in the channel-information processing
unit 30.
[0052] A third embodiment of the present invention will be
explained using FIG. 4. FIG. 4 is a block diagram of a structure of
transmission and reception functions of a radio communication
apparatus according to the third embodiment. In the radio
communication apparatus 1 according to the third embodiment, a MAC
unit 20a is provided instead of the MAC unit 20 of the radio
communication apparatus 1 according to the first embodiment shown
in FIG. 1, and a channel processing control unit 60
(channel-information processing unit described in patent claims) is
provided instead of the channel-information processing unit 30.
[0053] The MAC unit 20a applies the processing such as the protocol
conversion and the frame conversion to decoded signals inputted
from the reception channel processing units 110 to 130,
respectively, generates reception frames, and outputs the reception
frames to an upper layer. At the same time, the MAC unit 20a
outputs address information (transmission source addresses) in the
respective reception frames to the channel processing control unit
60. In addition, the MAC unit 20a applies the processing such as
the protocol conversion and the frame conversion to a transmission
frame inputted from the upper layer to generate transmission frames
of the respective channels.
[0054] The channel processing control unit 60 belongs to a physical
layer and performs timing control and feedback processing control
for the reception processing unit 10 and the transmission
processing unit 40 belonging to the same physical layer. The
channel processing control unit 60 identifies a transmission source
address of other radio communication apparatus from the respective
pieces of address information or input reception signals of the
respective channels and creates a local feedback table in which
transmission source addresses and respective pieces of channel
reception information are associated with each other. More
specifically, the channel processing control unit 60 generates a
local feedback table in which transmission source addresses and the
respective pieces of local cannel reception information of the
reception channel processing units 110 to 130 are associated with
each other. In addition, the channel processing control unit 60
determines transmission systems and transmission speeds of the
respective channels based on the respective pieces of transmission
source feedback information inputted from the reception channel
processing units 110 to 130. Then, the channel processing control
unit 60 registers the determined transmission systems and
transmission speeds in the local feedback table for the respective
channels in association with the transmission source addresses.
Note that it is also possible that transmission source feedback
information is registered in association with transmission source
addresses in the local feedback table, and a transmission system
and a transmission speed are determined at the time of transmission
based on this transmission source feedback information.
[0055] Next, operations of the radio communication apparatus
according to the third embodiment of the present invention will be
explained. First, a reception operation will be explained. The
reception channel processing units 110 to 130 receive input
reception signals in the corresponding channels, respectively,
apply the synchronization processing, the demodulation processing,
and the decoding processing to the input reception signals, and
output decoded signals to the MAC unit 20a. At the same time, the
reception channel processing units 110 to 130 generate local
channel reception information based on reception levels of the
respective channels and reception channel processing internal
information. Then, the reception channel processing units 110 to
130 output the generated local channel reception information to the
channel processing control unit 60. In addition, the reception
channel processing units 110 to 130 judge whether feedback
information is included in the input reception signals and, when
feedback information is included in the input reception signals,
output the feedback information in the input reception signals to
the channel-information processing unit 30 as transmission source
feedback information.
[0056] The MAC unit 20a applies the processing such as the protocol
conversion and the frame conversion to the decoded signals inputted
from the reception channel processing units 110 to 130,
respectively, generates reception frames, and outputs the reception
frames to the upper layer. In addition, the MAC unit 20a outputs
transmission source addresses in the respective reception frames to
the channel processing control unit 60.
[0057] The channel processing control unit 60 identifies a
transmission source address of other radio communication apparatus
from the respective transmission source addresses inputted from the
MAC unit 20a or the input reception signals of the respective
channels and creates a local feedback table in which the
transmission source addresses and respective pieces of local
channel reception information are associated with each other.
[0058] Next, a transmission operation will be explained. The MAC
unit 20a applies the processing such as the protocol conversion and
the frame conversion to a transmission frame inputted from the
upper layer to generate transmission frames of the respective
channels. Then, the MAC unit 20a outputs the generated respective
transmission frames to the transmission channel processing units
410 to 430. In addition, the MAC unit 20a outputs destination
addresses in the respective transmission frames to the channel
processing control unit 60.
[0059] The channel processing control unit 60 searches through the
local feedback table with the destination addresses as keywords and
determines local feedback information, transmission systems, and
transmission speeds of the respective channels. When data is
transmitted to the transmission source addresses at the time when
the local feedback information table is generated, it is sufficient
to search through the local feedback table with the destination
addresses of the transmission frames generated by the MAC unit 20a
as keywords. The channel processing control unit 60 outputs the
local feedback information, the transmission systems, and the
transmission speeds, which are determined for the respective
channels, to the corresponding channel transmission channel
processing unit 410 to 440, respectively.
[0060] The transmission channel processing units 410 to 430 select
transmission systems and transmission speeds of the channels based
on the respective transmission systems and transmission speeds
inputted from the channel processing control unit 60. Then, based
on the selected transmission systems and transmission speeds, the
transmission channel processing units 410 to 430 apply the encoding
processing and the modulation processing to the transmission frame
inputted from the MAC unit 20a and the local feedback information
inputted from the channel processing control unit 60 to generate
radio signals. Then, the transmission channel processing units 410
to 430 output the generated radio signals.
[0061] In this way, according to the third embodiment, the MAC unit
20a notifies the channel processing control unit 60 of the
transmission source addresses and the destination addresses, the
channel processing control unit 60 generates a local feedback table
associating the transmission source addresses and local feedback
information, and at the time of transmission, the channel
processing control unit 60 generates local feedback information
based on the local feedback table and determines transmission
systems and transmission speeds of the respective channels. Thus,
it is possible to perform processing with the processing closed in
a physical layer and to cope with system change of a MAC layer or
higher layers easily.
[0062] In addition, since it is possible to perform processing with
the processing closed in a physical layer, for example, in the case
of a system returning response frames in response to transmission
frames, it is possible to insert local feedback information into
part of the response frames. The local feedback information is
notified to other radio communication apparatus in shortest time,
which makes it possible to perform high-speed feedback processing
even when a fluctuation state in a transmission channel is intense
and deterioration of radio signals in the respective channels is
severe.
[0063] A fourth embodiment of the present invention will be
explained using FIG. 5. FIG. 5 is a block diagram of a structure of
transmission and reception functions of the radio communication
apparatus 1 according to the fourth embodiment. In the radio
communication apparatus 1 according to the fourth embodiment, the
channel-information processing unit 30 of the radio communication
apparatus 1 according to the first embodiment shown in FIG. 2 is
removed, and a MAC unit 20b is provided instead of the MAC unit 20.
Components having the same functions as those according to the
first embodiment will be denoted by the identical reference
numerals, and a redundant explanation will be omitted.
[0064] At the time of a reception operation, the MAC unit 20b
extracts feedback information included in decoded signals inputted
from the reception channel processing units 110 to 130,
respectively. Then, the MAC unit 20b creates a local feedback
information table in which local channel reception information of
the respective channels and the extracted feedback information are
associated with the transmission source addresses. In addition, the
MAC unit 20b applies the processing such as the protocol conversion
and the frame conversion to the decoded signals inputted from the
reception channel processing units 110 to 130, respectively,
generates reception frames, and output the reception frames to the
upper layer.
[0065] At the time of a transmission operation, the MAC unit 20b
applies the processing such as the protocol conversion and the
frame conversion to a transmission frame inputted from the upper
layer to generate transmission frames of the respective channels.
In that case, the MAC unit 20b inserts local feedback information
into the respective transmission frames based on the local feedback
information table and determines transmission systems and
transmission speeds of the respective channels.
[0066] Next, operations of the radio communication apparatus
according to the fourth embodiment of the present invention will be
explained. First, a reception operation will be explained. The
reception channel processing units 110 to 130 receive input
reception signals in the corresponding channels, respectively, and
apply the synchronization processing, the demodulation processing,
and the decoding processing to the input reception signals to
generate decoded signals. At the same time, the reception channel
processing units 110 to 130 measure reception levels of the input
reception signals in the respective channels, and generate local
channel reception information based on the measured respective
reception levels and reception channel processing internal
information. The reception channel processing units 110 to 130
output the respective decoded signals and the local channel
reception information to the MAC unit 20b.
[0067] The MAC unit 20b extracts feedback information from the
decoded signals inputted from the reception channel processing
units 110 to 130, respectively. Then, the MAC unit 20b generates a
local feedback information table in which the local channel
reception information for the respective channels and the extracted
feedback information are associated with transmission source
addresses. In addition, the MAC unit 20b applies the processing
such as the protocol conversion and the frame conversion to the
decoded signals, from which the feedback information is extracted,
generates reception frames, and outputs the reception frames to the
upper layer.
[0068] Next, a transmission operation will be explained. The MAC
unit 20b applies the processing such as the protocol conversion and
the frame conversion to a transmission frame inputted from the
upper layer to generate transmission frames of the respective
channels. In generating the transmission frames of the respective
channels, the MAC unit 20b searches through the local feedback
information table with destination addresses as keywords and
extracts local channel reception information of the respective
channels. Then, the MAC unit 20b generates local feedback
information based on the local channel reception information
corresponding to the respective channels and inserts the generated
local feedback information into predetermined places of the
transmission frames of the respective channels. In addition, the
MAC unit 20b searches through the local feedback information table
with the destination addresses as keywords and extracts feedback
information of the respective channels corresponding to the
destination addresses. Then, the MAC unit 20b determines
transmission systems and transmission speeds based on the feedback
information corresponding to the respective channels and outputs
the determined transmission systems and transmission speeds to the
transmission channel processing units 410 to 430 as transmission
speed information.
[0069] The transmission channel processing units 410 to 430 select
transmission systems and transmission speeds of the channels based
on the respective pieces of transmission control information
inputted from the MAC unit 20b. Then, based on the selected
transmission systems and transmission speeds, the transmission
channel processing units 410 to 430 apply the encoding processing
and the modulation processing to the transmission frames inputted
from the MAC unit 20 and the local feedback information inputted
from the channel-information processing unit 30 to generate radio
signals. Then, the transmission channel processing units 410 to 430
output the generated radio signals.
[0070] In this way, according to the fourth embodiment, the MAC
unit 20b generates the local feedback information table in which
the local channel reception information for the respective channels
and the extracted feedback information are associated with the
transmission source addresses and inserts the local feedback
information into appropriate places in the transmission frames.
Thus, it is possible to notify other radio communication apparatus
of the local feedback information without having means for
inserting the local feedback information anew and to reduce decline
in efficiency of the radio communication apparatus.
[0071] In addition, since it is possible to notify local feedback
information with a structure closed in a MAC layer and determine
transmission systems and transmission speeds, it is possible to
apply the radio communication apparatus to a system in a different
physical layer that uses plural channels.
[0072] Moreover, since it is possible to perform processing with
the processing closed in a MAC layer, for example, in the case of a
system returning response frames in response to transmission
frames, it is possible to insert local feedback information into
part of the response frames, reduce radio bands in which the local
feedback information is notified to other radio communication
apparatus, and realize an increase in a radio capacity. The local
feedback information is notified to the other radio communication
apparatus in shortest time, which makes it possible to perform
high-speed feedback processing even when a fluctuation state in a
transmission channel is intense and deterioration of radio signals
in the respective channels is severe.
[0073] Note that the transmission frames into which the local
feedback information is inserted may be all transmission frames of
the respective channels, or channels on which the local feedback
information is transmitted may be determined based on the
respective pieces of local channel reception information.
[0074] A fifth embodiment of the present invention will be
explained using FIGS. 6 to 8. FIG. 6 is a block diagram of a
structure of transmission and reception functions of the radio
communication apparatus 1 according to the fifth embodiment. The
radio communication apparatus 1 according to the fifth embodiment
includes a MAC unit 20c instead of the MAC unit 20b of the radio
communication apparatus 1 according to the fourth embodiment shown
in FIG. 5.
[0075] At the time of reception, the MAC unit 20c extracts
transmission source addresses from decoded signals inputted from
the reception channel processing units 110 to 130, respectively,
and creates a local feedback information table in which the
extracted transmission source addresses and local channel reception
information notified from the reception channel processing units
110 to 130 are associated with each other. In addition, when the
respective decoded signals are feedback frames for notifying other
radio communication apparatus of local feedback information, the
MAC unit 20c extracts transmission source addresses in the feedback
frames and creates a transmission source feedback information table
in which transmission feedback information for the respective
channels in the feedback frames and the extracted transmission
source addresses are associated with each other. When the decoded
signals are normal frames, the MAC unit 20c applies the processing
such as the protocol conversion and the frame conversion to the
decoded signals, generates reception frames, and outputs the
reception frames to an upper layer.
[0076] At the time of transmission, when transmission frames are
feedback frames, the MAC unit 20c generates local feedback
information based on a local channel reception information table
and inserts the generated local feedback information into the
feedback frames. The MAC unit 20c determines transmission systems
and transmission speeds of the respective channels based on the
transmission source feedback information table.
[0077] Next, operations of the radio communication apparatus 1
according to the fifth embodiment of the present invention will be
explained with reference to flowcharts in FIGS. 7 and 8. First, a
reception operation will be explained with reference to the
flowchart in FIG. 7. The reception channel processing units 110 to
130 receive input information of channels corresponding to the
reception channel processing units 110 and 130, respectively, and
apply the synchronization processing, the demodulation processing,
and the decoding processing to the input information to generate
decoded signals. At the same time, the reception channel processing
units 110 and 130 measure reception levels of input reception
signals of the respective channels and generate local channel
reception information based on the measured respective reception
levels and reception channel processing internal information (steps
S100 and S110). The reception channel processing units 110 to 130
output the respective decoded signals and the local channel
reception information to the MAC unit 20c.
[0078] The MAC unit 20c extracts transmission source addresses from
the decoded signals inputted from the reception channel processing
units 110 to 130, respectively (step S120). Then, the MAC unit 20c
creates a local feedback information table in which the extracted
transmission source addresses and the respective pieces local
channel reception information notified from the reception channel
processing units 110 to 130 are associated with each other (step
S130).
[0079] The MAC unit 20c judges whether the respective decoded
signals are feedback frames for notifying other radio communication
apparatus of local feedback information (step S140). When the
respective decoded signals are feedback frames, the MAC unit 20c
performs predetermined feedback frame processing such as extraction
of transmission source feedback information from the decoded
signals (step S150). Then, the MAC unit 20c creates a transmission
source feedback information table in which the extracted
transmission source feedback information and transmission source
addresses extracted from the decoded signals are associated with
each other (step S160).
[0080] When the respective decoded signals are normal frames, the
MAC unit 20c performs normal frame processing of applying the
processing such as the protocol conversion and the frame conversion
to the respective decoded signals, generating reception frames, and
outputting the reception frames to the upper layer (step S170).
[0081] Next, a transmission processing will be explained with
reference to the flowchart in FIG. 8. The MAC unit 20c extracts a
destination address from a transmission frame inputted from the
upper layer (step S200). Then, the MAC unit 20c judges whether the
transmission frame is a feedback frame (step S210). When the
transmission frame is a feedback frame, the MAC unit 20c searches
through the local feedback information table with the extracted
destination address as a keyword and extracts local channel
reception information of the respective channels. Then, the MAC
unit 20c generates local feedback information from the extracted
local channel reception information of the respective channels
(step S220). Then, the MAC unit 20c inserts the generated local
feedback information into the feedback frame to generate a feedback
frame (step S230).
[0082] The MAC unit 20c searches through the transmission source
feedback information table with the extracted destination address
as a keyword and extracts transmission source feedback information
of the respective channels corresponding to the destination
address. Then, the MAC unit 20c determines transmission systems and
transmission speeds based on the feedback information corresponding
to the respective channels and outputs the determined transmission
systems and transmission speeds to the transmission channel
processing units 410 to 430 as transmission speed information (step
S240).
[0083] The transmission channel processing units 310 to 430 select
transmission systems and transmission speeds of the channels based
on respective pieces of transmission control information inputted
from the MAC unit 20c. Then, the transmission channel processing
units 310 to 340 apply the encoding processing and the modulation
processing to the transmission frames inputted from the MAC unit
20c based on the selected transmission systems and transmission
speeds to generate radio signals. Then, the transmission channel
processing units 310 to 340 output the generated radio signals
(step S250).
[0084] When the transmission frames are normal frames, the MAC unit
20c performs normal frame processing of applying the processing
such as the protocol conversion and the frame conversion to the
transmission frames and generating transmission frames of the
respective channels (step S260). In addition, the MAC unit 20c
searches through the transmission source feedback information table
with the extracted destination address as a keyword and extracts
transmission source feedback information of the respective channels
corresponding to the destination address. Then, the MAC unit 20c
determines transmission systems and transmission speeds based on
feedback information corresponding to the respective channels and
outputs the determined transmission systems and transmission speeds
to the transmission channel processing units 410 to 430 as
transmission speed information (step S240).
[0085] The transmission channel processing units 410 to 430 select
transmission systems and transmission speeds of the channels based
on the respective pieces of transmission control information
inputted from the MAC unit 20c. Then, based on the selected
transmission systems and transmission speeds, the transmission
channel processing units 410 to 430 apply the encoding processing
and the modulation processing to the transmission frames inputted
from the MAC unit 20c to generate radio signals. Then, the
transmission channel processing units 410 to 430 output the
generated radio signals (step S250).
[0086] In this way, according to the fifth embodiment, since a
dedicated frame for transmitting local feedback information is
provided, it is possible to notify other radio communication
apparatus of feedback information of respective channels without
requiring a change with respect to an existing system and with
simplified control and processing. It is possible to select
transmission systems and transmission speeds suitable for the
respective channels.
[0087] Note that, when the dedicated frame for transmitting local
feedback information is transmitted periodically, it is necessary
to transmit the dedicated frame at a short period with respect to
fluctuation in a transmission channel. Therefore, throughput
declines. In addition, when the local feedback information cannot
be transmitted, reliability of the local feedback information may
decline to cause a communication error. In such a case, it is
sufficient that the reception channel processing units 110 to 130
detect fluctuation in the transmission channel, and the MAC unit
20c judges the fluctuation in the transmission channel to determine
a transmission interval of the dedicated frame for transmitting the
local feedback information.
Sixth Embodiment
[0088] A sixth embodiment of the present invention will be
explained using FIGS. 9 and 10. FIG. 9 is a block diagram of a
structure of transmission and reception functions of a radio
communication apparatus according to the sixth embodiment. The
radio communication apparatus 1 according to the sixth embodiment
includes a MAC unit 20d instead of the MAC unit 20c according to
the fifth embodiment shown in FIG. 6. Components having the same
functions as those according to the fifth embodiment will be
denoted by the identical reference numerals, and a redundant
explanation will be omitted.
[0089] At the time of a reception operation, the MAC unit 20d has a
function of also registering a creation time of day in creating a
local feedback information table and a transmission source feedback
information table in addition to the same function as at the time
of the reception operation of the MAC unit 20c of the fifth
embodiment.
[0090] At the time of a transmission operation, the MAC unit 20d
applies the processing such as the protocol conversion and the
frame conversion to a transmission frame inputted from an upper
layer to generate transmission frames of respective channels. In
that case, the MAC unit 20d inserts local feedback information into
the respective transmission frames based on the local feedback
information table and, at the same time, determines transmission
systems and transmission speeds of the respective channels.
[0091] Operations of the radio communication apparatus 1 according
to the sixth embodiment of the present invention will be explained
with reference to a flowchart in FIG. 10. First, a reception
operation will be explained. The reception channel processing units
110 to 130 receive input information of channels corresponding to
the reception channel processing units 110 to 130, respectively,
and apply the synchronization processing, the demodulation
processing, and the decoding processing to the input information to
generate decoded signals. At the same time, the reception channel
processing units 110 to 130 measure reception levels of input
reception signals of the respective channels, and generate local
channel reception information based on the measured respective
reception levels and reception channel processing internal
information. The reception channel processing units 110 to 130
output the respective decoded signals and the local channel
reception information to the MAC unit 20d.
[0092] The MAC unit 20d extracts transmission source addresses from
the decoded signals inputted from the reception channel processing
units 110 to 130, respectively. Then, the reception channel
processing units 110 to 130 create a local feedback information
table in which the extracted transmission source addresses, the
respective pieces of local channel reception information notified
from the reception channel processing units 110 to 130, and present
times of day are associated to one another.
[0093] The MAC unit 20d judges whether feedback information is
included in the respective decoded signals and, when feedback
information is included in the respective decoded signals, extracts
the feedback information in the decoded signals. The MAC unit 20d
creates a transmission source feedback information table in which
the transmission source feedback information extracted from the
decoded signals, the extracted transmission source addresses, and
present times of day are associated to one another.
[0094] The MAC unit 20d applies the processing such as the protocol
conversion and the frame conversion to the respective decoded
signals, generates reception frames, and outputs the reception
frames to an upper layer.
[0095] Next, a transmission operation will be explained with
reference to the flowchart in FIG. 10. The MAC unit 20d extracts a
destination address from a transmission frame inputted from the
upper layer (step S300).
[0096] The MAC unit 20d searches through the local feedback
information table with the extracted destination address as a
keyword and extracts local channel reception information of the
respective channels and creation times of day of the local channel
reception information (step S310). The MAC unit 20d calculates a
difference between the extracted creation times of day and the
present time of day. Then, the MAC unit 20d judges whether a
calculation result is within a reference value decided in advance
(step S320). When the calculation result is within the reference
value decided in advance, the MAC unit 20d inserts the local
feedback information into predetermined places of the transmission
frames from the extracted local channel reception information of
the respective channels (step S330). When the calculation result
exceeds the reference value decided in advance, the MAC unit 20d
judges that the local cannel reception information of the
respective channels is different from present states of the
respective channels because time has passed since the local channel
reception information was created and does not insert the feedback
information in the transmission frames. The MAC unit 20d applies
the processing such as the protocol conversion and the frame
conversion to the transmission frames to generate transmission
frames of the respective channels. Then, the MAC unit 20d outputs
the generated respective transmission frames to the transmission
channel processing units 410 to 430.
[0097] The MAC unit 20d searches through the transmission source
feedback information table with the extracted destination address
as a keyword and extracts transmission source feedback information
of the respective channels and creation times of day of the
transmission source feedback information (step S340). The MAC unit
20d calculates a difference between the extracted creation times of
day and the present time of day. Then, the MAC unit 20d judges
whether a calculation result is within a reference value decided in
advance (step S350). When the calculation result is within the
reference value decided in advance, the MAC unit 20d determines
transmission systems and transmission speeds of the respective
channels based on the extracted transmission source feedback
information (step S360). When the calculation result exceeds the
reference value decided in advance, the MAC unit 20d judges that
the local channel reception information of the respective channels
is different from present states of the respective channels because
time has passed since the local channel reception information was
created and determines to use transmission systems and transmission
speeds decided in advance (step S370). The MAC unit 20d notifies
the transmission channel processing units 410 to 430 of the
determined transmission systems and transmission speeds.
[0098] The transmission channel processing units 410 to 430 select
transmission systems and transmission speeds of the channels based
on the respective pieces of transmission control information
inputted from the MAC unit 20d. Then, based on the selected
transmission systems and transmission speeds, the transmission
channel processing units 410 to 430 apply the encoding processing
and the modulation processing to the transmission frames inputted
from the MAC unit 20d to generate radio signals. Then, the
transmission channel processing units 410 to 430 output the
generated radio signals (step S380).
[0099] In this way, according to the sixth embodiment, in creating
a local cannel reception information table and a transmission
source feedback information table, creation times of day of the
tables are registered, and the creation times of day and a present
time of day are compared to judge reliability concerning whether
the local channel reception information and the transmission source
feedback information are used. Thus, it is possible to use
information suitable for temporal fluctuation in a state of a
transmission channel and to reduce a wasteful communication
fee.
[0100] Note that, according to the sixth embodiment, the case in
which the local feedback information is inserted into transmission
frames is explained as an example. However, it is needless to
mention that it is possible to apply the case to the first to the
fifth embodiments by creating a local feedback information table in
which transmission addresses, respective pieces of local channel
reception information, and present times of day are associated to
one another and a transmission source feedback information table in
which transmission source feedback information, extracted
transmission source addresses, and present times of day are
associated to one another.
[0101] As explained above, in the radio communication apparatus
according to the present invention, a reception processing unit
generates local channel reception information based on reception
states of input reception signals of respective channels, a
channel-information processing unit generates local feedback
information based on the local channel reception information
generated by the reception processing unit, inserts the generated
local feedback information into radio signals, and transmits the
radio signals. Thus, it is possible to notify other radio
communication apparatus of states of the respective channels, and
the other radio communication apparatus can select transmission
systems and transmission speeds suitable for the states of the
respective channels.
INDUSTRIAL APPLICABILITY
[0102] As described above, the radio communication apparatus
according to the present invention is useful for a communication
system that performs mutual communication using plural channels
simultaneously and, in particular, suitable for a communication
system in which a communication state is likely to change due to
obstacles, weather conditions, and the like.
* * * * *