Title: Transmission apparatus, reception apparatus and digital radio communication method
Abstract: Frame configuration determination section 101 judges a communication situation based on the transmission path information indicating the level of fluctuations of the transmission path due to fading and data transmission speed information indicating the transmission speed of the transmission data based on the level of the reception signal and determines the interval of inserting a known pilot symbol and the modulation system of a transmission digital signal. Quadrature baseband modulation section 102 modulates the transmission digital signal to a quadrature baseband signal according to the modulation system indicated from frame configuration determination section 101. Pilot symbol generation section 103 generates a pilot symbol known between the transmitting and receiving sides. Frame configuration section 104 inserts the known pilot symbol output from pilot symbol generation section 103 at the insertion interval instructed from frame configuration determination section 101 to configure a frame. This makes it possible to flexibly improve the data transmission efficiency and the quality of data at the same time.
Patent Number: 6,993,092 Issued on 01/31/2006 to Murakami, et al.
| Inventors:
|
Murakami; Yutaka (Yokohamai, JP);
Takabayashi; Shinichiro (Kawasaki, JP);
Orihashi; Masayuki (Ichikawa, JP);
Matsuoka; Akihiko (Yokohama, JP)
|
| Assignee:
|
Matsushita Electric Industrial Co., Ltd. (Osaka, JP)
|
| Appl. No.:
|
627070 |
| Filed:
|
July 27, 2000 |
Foreign Application Priority Data
| Jul 28, 1999[JP] | 11-213289 |
| Current U.S. Class: |
375/298; 375/261; 375/302 |
| Current Intern'l Class: |
H04L 27/36 (20060101); H04L 23/02 (20060101) |
| Field of Search: |
375/261,264,271,279,280,281,284,285,295,298,302,308,296,346,344,354,362
455/671.3,631,114.2,102,110
703/30
|
References Cited [Referenced By]
U.S. Patent Documents
| 4899367 | Feb., 1990 | Sampei.
| |
| 5596608 | Jan., 1997 | Sassa et al.
| |
| 5901185 | May., 1999 | Hassan.
| |
| 6490270 | Dec., 2002 | Krishnamoorthy et al.
| |
| Foreign Patent Documents |
| 1-196924 | Aug., 1989 | JP.
| |
| 7-250116 | Sep., 1995 | JP.
| |
| 01-065645 | Mar., 1998 | JP.
| |
| 10-247955 | Sep., 1998 | JP.
| |
| 11-197794 | Jul., 1999 | JP.
| |
Other References
English Language abstract of JP-1-196924.
Shinya Otsuki et al., "Performance Analysis of Adaptive Modulation Systems Using
Square-QAM", Technical Report of IEICE, RCS94-96, Sep. 1994, pp. 43-48.
English Language abstract of Shinya Otsuki et al., "Performance Analysis of Adaptive
Modulation Systems Using Square-QAM", Technical Report of IEICE, RCS94-96, Sep.
1994, pp. 43-48.
English Language Abstract of 7-250116, published Sep. 26, 1995.
English Language Abstract of 1-196924, published Aug. 9, 1989.
English Language Abstract of 10-247955, published Sep. 14, 1998.
English Language Abstract of 01-065645, published Mar. 6, 1998.
English Language Abstract of 11-197794, published Jul. 13, 1999.
Murakami, et al., A Study of Inserting QPSK Symbols into 16 QAM Streams, Lecture
Papers of The I Institute of Electronics, Information and Communication Engineers
(1998), Japan, The Institute of Electronics, Information and Communication Engineers,
Mar. 1998, Communication 1, B-5-69, p. 433, together with an English language Abstract thereof.
|
Primary Examiner: Deppe; Betsy L.
Attorney, Agent or Firm: Greenblum & Bernstein, P.L.C.
Claims
What is claimed is:
1. A transmission apparatus comprising:
a frame configuration determiner that determines a modulation system based on
a communication situation;
a first symbol generator that modulates a digital transmission signal according
to the modulation system determined by the frame configuration determiner to generate
a first symbol, the first symbol comprising a quadrature baseband signal;
a second symbol generator that generates a second symbol, the second symbol comprising
a pilot symbol; and
a third symbol generator that generates a third symbol to be inserted immediately
before and immediately after the second symbol, the third symbol being different
from the first symbol,
wherein, on a signal space diagram the third symbol generator arranges a signal
point of the third symbol on a virtual line that links an origin and a signal point
of the second symbol.
2. The transmission apparatus according to claim 1, wherein the pilot symbol
comprises a reference symbol.
3. The transmission apparatus according to claim 1, wherein the frame configuration
determiner determines an interval to insert the second symbol based on the communication situation.
4. The transmission apparatus according to claim 1, wherein the frame configuration
determiner initially determines the communication situation based on at least one
of transmission path information and data transmission speed information.
5. The transmission apparatus according to claim 1, wherein the frame configuration
determiner initially determines the communication situation based on at least a
quality of a received signal.
6. The transmission apparatus according to claim 1, wherein the second symbol
is used for estimating a frequency of the signal of the first symbol.
7. The transmission apparatus according to claim 1, wherein an amplitude of a
signal of the first symbol is smaller than an amplitude of a signal of the second symbol.
8. A digital radio communication method comprising:
determining a modulation system based on a communication situation;
modulating a digital transmission signal according to the determined modulation
system to generate a first symbol comprising a quadrature baseband signal;
generating a second symbol, the second symbol comprising a pilot symbol;
generating a third symbol to be inserted immediately before and after the second
symbol, the third symbol being different from the first symbol; and
arranging, on a signal space diagram, a signal point of the third symbol on a
virtual line that links an origin and a signal point of the second symbol.
9. The digital radio communication method according to claim 8, further comprising
determining an interval by which to insert the second symbol based on the communication situation.
10. The digital radio communication method according to claim 8, further comprising
determining the communication situation based on at least one of transmission path
information and data transmission speed information.
11. The digital radio communication method according to claim 8, further comprising
determining the communication situation based on at least a quality of a received signal.
12. A transmission apparatus comprising:
a first symbol generator that modulates a digital transmission signal according
to a first predetermined modulation system to generate a first symbol, the first
symbol comprising a quadrature baseband signal;
a second symbol generator that generates a second symbol, the second symbol comprising
a known pilot symbol;
a third symbol generator that modulates the digital transmission signal according
to at least a second predetermined modulation system to generate a third symbol
to be inserted immediately before and immediately after the second symbol;
a frame configuration determiner that determines an interval of inserting the
second symbol based on a communication situation; and
a frame configurer that configures a frame by inserting the second symbol after
the first symbol at the insertion interval determined by the frame configuration determiner.
13. A transmission apparatus comprising:
a frame configuration determiner configured to determine a modulation system
based on a communication situation;
a first symbol generator configured to modulate a digital transmission signal
according to the modulation system determined by the frame configuration determiner
to generate a first symbol, the first symbol comprising a quadrature baseband signal;
a second symbol generator configured to generate a second symbol, the second
symbol being used for estimating a frequency of the signal of the first symbol; and
a third symbol generator configured to generate a third symbol to be inserted
immediately before and immediately after the second symbol;
wherein, a signal point of the first symbol is different from a signal point
of the second symbol, the signal point of the second symbol is different from a
signal point of the third symbol, and the signal point of the third symbol is different
from the signal point of the first symbol, and
wherein, on a signal space diagram, the third symbol generator arranges the signal
point of the third symbol on a virtual line that links an original and the signal
point of the second symbol.
14. The transmission apparatus according to claim 13, wherein an amplitude of
a signal of the first symbol is smaller than an amplitude of the signal of the
second symbol.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transmission apparatus, a reception apparatus
and a digital radio communication method for digital radio communications.
2. Description of the Related Art
As a conventional digital modulation system, a technology described in Unexamined
Japanese Patent Publication No. HEI 1-196924 is known. This is the technology whereby
the transmitting side configures a frame by inserting one known pilot symbol per
N data symbols and whereby the receiving side estimates a frequency offset and
amount of amplitude distortion by using the pilot symbol and removes these frequency
offset and amplitude distortion for demodulation.
Here, in the case of a radio communication, fluctuations in the transmission
path occur due to fading and in terrestrial mobile communication in particular,
fluctuations in the transmission path are not uniform. When fluctuations in the
transmission path are intense, pilot symbols must be inserted at shorter intervals
to prevent deterioration of the data demodulation error rate. On the contrary,
when fluctuations in the transmission path are gentle, inserting pilot symbols
at longer intervals does not severely deteriorate the data demodulation error rate.
On the other hand, when the level of a reception signal on the receiving side
is small, a modulation system used must be highly resistant to errors for information
symbol. On the contrary, when the level of a reception signal on the receiving
side is large, higher priority can be given to a modulation system of high transmission
efficiency for information symbol However, in the conventional digital modulation
system above, the pilot symbol insertion interval and the information symbol modulation
system are fixed. Therefore, when fluctuations in the transmission path are intense
or the level of the reception signal of the receiver is small, error resiliency
features during data demodulation reduces and the quality of data deteriorates.
On the other hand, when fluctuations in the transmission path are gentle or the
level of the reception signal on the receiving side is large, the data transmission
efficiency cannot be improved regardless of data quality.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a transmission apparatus,
a reception apparatus and a digital radio communication method that improve data
transmission efficiency and data quality.
The present invention attains the above object by changing the interval for inserting
known pilot symbol, binary phase (BPSK: Binary Phase Shift Keying) modulation symbol,
and quadrature phase (QPSK: Quadrature Phase Shift Keying) modulation symbol, and
by changing the modulation system of information symbol according to the communication
situation such as fluctuations in the transmission path and the level of a reception signal.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects and features of the invention will appear more fully
hereinafter from a consideration of the following description taken in connection
with the accompanying drawing wherein one example is illustrated by way of example,
in which;
FIG. 1 is a block diagram showing a configuration of a transmission apparatus
according to Embodiment 1 of the present invention;
FIG. 2 illustrates examples of a frame configuration of a signal transmitted
from the transmission apparatus of Embodiment 1 of the present invention;
FIG. 3 is a layout of signal points of 16QAM and known pilot symbol on an in-phase
I-quadrature Q plane;
FIG. 4 is a layout of signal points of 8PSK modulation and known pilot symbol
on an in-phase I-quadrature Q plane;
FIG. 5 is a block diagram showing a configuration of a reception apparatus according
to Embodiment 1 of the present invention;
FIG. 6 is a block diagram showing a configuration of a transmission apparatus
according to Embodiment 2 of the present invention;
FIG. 7 illustrates examples of a frame configuration of a signal transmitted
from the transmission apparatus of Embodiment 2 of the present invention;
FIG. 8 is a layout of signal points of 16QAM and BPSK modulation on an in-phase
I-quadrature Q plane;
FIG. 9 is a layout of signal points of 8PSK modulation and BPSK modulation on
an in-phase I-quadrature Q plane;
FIG. 10 is a block diagram showing a configuration of a reception apparatus
according to Embodiment 2 of the present invention;
FIG. 11 is a block diagram showing a configuration of a transmission apparatus
according to Embodiment 3 of the present invention;
FIG. 12 illustrates examples of a frame configuration of a signal transmitted
from the transmission apparatus of Embodiment 3 of the present invention;
FIG. 13 is a layout of signal points of 16QAM and QPSK modulation on an in-phase
I-quadrature Q plane;
FIG. 14 is a layout of signal points of 8PSK modulation and QPSK modulation
on an in-phase I-quadrature Q plane;
FIG. 15 is a block diagram showing a configuration of a reception apparatus
according to Embodiment 3 of the present invention;
FIG. 16 is a block diagram showing a configuration of a transmission apparatus
according to Embodiment 4 of the present invention;
FIG. 17 illustrates examples of a frame configuration of a signal transmitted
from the transmission apparatus of Embodiment 4 of the present invention;
FIG. 18 is a layout of signal points of BPSK modulation on an in-phase I-quadrature
Q plane;
FIG. 19 is a layout of signal points of QPSK modulation on an in-phase I-quadrature
Q plane;
FIG. 20 is a block diagram showing a configuration of a reception apparatus
according to Embodiment 4 of the present invention;
FIG. 21 is a block diagram showing a configuration of a transmission apparatus
according to Embodiment 5 of the present invention;
FIG. 22 illustrates examples of a frame configuration of a signal transmitted
from the transmission apparatus of the Embodiment 5 of the present invention;
FIG. 23 is a layout of signal points of 16QAM, known pilot symbol and symbols
before and after the pilot symbol on an in-phase I-quadrature Q plane;
FIG. 24 is a layout of signal points of 8PSK modulation, known pilot symbol
and symbols before and after the pilot symbol on an in-phase I-quadrature Q plane; and
FIG. 25 is a block diagram showing a configuration of a reception apparatus
according to Embodiment 5 of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference now to the attached drawings, embodiments of the present invention
will be explained in detail below.
Embodiment 1
Embodiment 1 describes a digital radio communication method by which the
interval for inserting known pilot symbols and the modulation system of information
symbol are changed according to the communication situation.
FIG. 1 is a block diagram showing a configuration of a transmission apparatus
according to this embodiment. As shown in FIG. 1, the transmission apparatus according
to this embodiment mainly consists of frame configuration determination section
101, quadrature baseband modulation section 102, pilot symbol generation
section 103, frame configuration section 104, and LPFs (Low Pass
Filters) 105 and 106, transmission radio section 107 and transmission
antenna 108.
Frame configuration determination section 101 judges the communication
situation based on transmission path information that indicates the degree of fluctuations
of the transmission path due to fading and based on data transmission speed information
that indicates the transmission speed of transmission data based on the level of
a reception signal, and decides the interval for inserting known pilot symbols
and the modulation system of digital transmission signals. Then, frame configuration
determination section 101 outputs a signal indicating the determined modulation
system to quadrature baseband modulation section 102 and outputs a signal
indicating the determined interval for inserting known pilot symbol to frame configuration
section 104. By the way, details of the method of determining a frame configuration
by frame configuration determination section 101 will be described later.
Here, when the same frequency band is used for the uplink and the downlink,
the situation of fluctuations in the transmission path due to fading can be estimated
from a transition in the result of measuring the reception level of the modulated
signal transmitted from the communicating party on the unillustrated receiving
side of the communication apparatus in which the transmission apparatus shown in
FIG. 1 is mounted. Furthermore, the transmission apparatus shown in FIG. 1 can
recognize the situation of fluctuations in the transmission path due to fading,
as the reception apparatus of the communicating party of the transmission apparatus
shown in FIG. 1 measures the reception level of the modulated signal transmitted
from the communicating party and estimates the situation of fluctuations in the
transmission path due to fading based on the transition of the measurement result.
Then, when the same frequency band is used for the uplink and the downlink,
the transmission speed of the transmission data can be determined from a result
of measuring the reception level of the modulated signal transmitted from the communicating
party on the unillustrated receiving side, of the communication apparatus in which
the transmission apparatus shown in FIG. 1 is mounted. Furthermore, the transmission
apparatus shown in FIG. 1 can recognize the transmission speed of the transmission
data as the reception apparatus of the communicating party of the transmission
apparatus shown in FIG. 1 measures the reception level of the pilot symbol transmitted
from the communicating party and determines the transmission speed of the transmission
data based on the measurement result.
Quadrature baseband modulation section 102 modulates a digital
transmission signal to a quadrature baseband signal with the modulation system
indicated from frame configuration determination section 101 and outputs
the in-phase component and the quadrature component of the quadrature baseband
signal to frame configuration section 104.
Pilot symbol generation section 103 generates a known pilot symbol between
the transmitting side and the receiving side and outputs the in-phase component
and the quadrature component of the known pilot symbol to frame configuration section 104.
Frame configuration section 104 inserts known pilot symbols output from
pilot symbol generation section 103 into the output signal of quadrature
baseband modulation section 102 at the insertion interval instructed from
frame configuration determination section 101 and composes a frame.
LPF 105 lets pass only the portion corresponding to a predetermined frequency
bandwidth of the in-phase component output from frame configuration section 104.
LPF 106 lets pass only the portion corresponding to a predetermined frequency
bandwidth of the quadrature component output from frame configuration section 104.
Transmission radio section 107 transmits a radio frequency signal
as the electric wave from transmission antenna 108 after performing radio
processing on the output signals of LPF 105 and LPF 106.
Next, examples of the method of determining a frame configuration by frame
configuration determination section 101 of the transmission apparatus shown
in FIG. 1 above will be explained.
FIG. 2 illustrates examples of a frame configuration of a signal transmitted
from the transmission apparatus of this embodiment and shows a time-symbol relationship.
(201) is a frame configuration where the modulation system of information
symbol is 16-level quadrature amplitude modulation (16QAM: 16 Quadrature Amplitude
Modulation), with a known pilot symbol provided for every N symbols. (202)
is a frame configuration where the modulation system of information symbol is 16QAM,
with a known pilot symbol provided for every M symbols. (203) is a frame
configuration where the modulation system of information symbol is 8 phase (8PSK:
8 Phase Shift Keying) modulation, with a known pilot symbol provided for every
N symbols. (204) is a frame configuration where the modulation system of
information symbol is 8PSK modulation, with a known pilot symbol provided for every
M symbols. Suppose N<M at this time.
Frame configuration determination section 101 selects one of (201),
(202), (203) or (204) in FIG. 2 as the optimal frame configuration
based on the transmission path information and the request data transmission speed information.
For example, in the case of high-speed fading, frame configuration determination
section 101 sacrifices data transmission efficiency on the receiving side
and selects the frame configuration of either (201) or (203) in FIG.
2 so as to insert known pilot symbols at shorter intervals to prevent deterioration
of the data demodulation error rate and maintain the quality of data. On the other
hand, in the case of low-speed fading, frame configuration determination section
101 selects the frame configuration of either (202) or (204)
in FIG. 2 so as to insert known pilot symbols at longer intervals to improve the
data transmission efficiency.
Also, when the level of the reception signal is large, frame configuration
determination section 101 gives priority to data transmission efficiency
on the receiving side and selects the frame configuration of either (201)
or (202) in FIG. 2 adopting 16QAM as the modulation system of information
symbol. On the other hand, when the level of the reception signal is small, frame
configuration determination section 101 gives priority to increasing error
resiliency features while sacrificing data transmission efficiency on the receiving
side, and selects the frame configuration of either (203) or (204)
in FIG. 2 that adopts 8PSK as the modulation system of information symbol.
FIG. 3 shows a signal point layout according to the 16QAM modulation system
on the in-phase I-quadrature Q plane and signal point layout of known pilot symbol.
Signal point 301 is the signal point of known pilot symbol and signal points
302 are the signal points of 16QAM modulation symbol. FIG. 4 shows a signal
point layout according to the 8PSK modulation system on the in-phase I-quadrature
Q plane and signal point layout of a known pilot symbol. Signal point 401
is the signal point of known pilot symbol and signal points 402 are the
signal points of 8PSK modulation symbol FIG. 5 is a block diagram showing a configuration
of the reception apparatus according to this embodiment. As shown in FIG. 5, the
reception apparatus according to this Embodiment mainly consists of reception antenna
501, reception radio section 502, transmission path distortion estimation
section 503 and detection section 504.
Reception radio section 502 receives the radio signal received by
reception antenna 501 as an input, performs predetermined radio processing
and outputs the in-phase component and the quadrature component of the reception
quadrature baseband signal.
Transmission path distortion estimation section 503 receives
the in-phase component and the quadrature component of the quadrature baseband
signal as inputs, extracts the signal of the known pilot symbol shown in FIG. 3
and FIG. 4 above, estimates the amount of transmission path distortion from the
reception condition of the known pilot symbol and outputs the amount of transmission
path distortion to detection section 504.
Detection section 504 receives the in-phase component and the quadrature
component of the quadrature baseband signal as inputs, detects information symbol
based on the amount of transmission path distortion and outputs a digital reception signal.
Thus, changing the interval for inserting known pilot symbols and the modulation
system of information symbol according to the communication situation such as fluctuations
in the transmission path and the level of the reception signal can improve both
the data transmission efficiency and the quality of data at the same time.
Here, this embodiment explains two intervals for inserting known pilot symbols,
but the present invention is not limited to this. Furthermore, this embodiment
explains two kinds of the modulation systems of information symbol, namely 16QAM
and the 8PSK modulation, but the present invention is not limited to these.
Furthermore, this embodiment only explains the frame configuration of
information symbol and known pilot symbol shown in FIG. 2, but since it is also
possible to consider a frame configuration in which signals such as symbol for
synchronization to adjust timing between the receiver and transmitter and symbol
for error correction on the receiver side are inserted, the present invention is
not limited to the frame configuration composed of only information symbol and
known pilot symbol.
Embodiment 2
Embodiment 2 describes a digital radio communication method by which the
interval for inserting BPSK modulation symbol and the modulation system of information
symbol other than the above BPSK modulation symbol are changed according to the
communication situation.
FIG. 6 is a block diagram showing a configuration of the transmission apparatus
according to this Embodiment. Here, in the transmission apparatus shown in FIG.
6, the components common to those in the transmission apparatus shown in FIG. 1
are assigned the same reference numerals as those in FIG. 1 and their explanations
will be omitted.
In the transmission apparatus in FIG. 6, frame configuration determination section
601 differs in the way of operation from the frame configuration determination
section 101 in FIG. 1. Also, when compared to FIG. 1, the transmission apparatus
in FIG. 6 adopts the configuration with BPSK symbol modulation section 602,
instead of pilot symbol generation section 103, added.
Frame configuration determination section 601 judges the communication
situation, determines the interval for inserting BPSK modulation symbols and the
modulation system of digital transmission signals, outputs a signal indicating
the determined modulation system to quadrature baseband modulation section 102
and outputs a signal indicating the determined interval for inserting BPSK modulation
symbols to quadrature baseband modulation section 102, BPSK symbol modulation
section 602 and frame configuration section 104.
BPSK symbol modulation section 602 performs BPSK-modulation on the digital
transmission signal at the timing indicated from frame configuration determination
section 601 and outputs the in-phase component and the quadrature component
of the BPSK modulation symbol to frame configuration section 104.
FIG. 7 illustrates examples of a frame configuration of a signal transmitted
from the transmission apparatus of this embodiment and shows a time-symbol relationship.
(701) is a frame configuration where the modulation system of information
symbol is 16QAM and the interval between BPSK modulation symbols is N symbols.
(702) is a frame configuration where the modulation system of information
symbol is 16QAM and the interval between BPSK modulation symbols is M symbols.
(703) is a frame configuration where the modulation system of information
symbol is 8PSK modulation and the interval between BPSK modulation symbols is N
symbols. (704) is a frame configuration where the modulation system of information
symbol is 8PSK modulation and the interval between BPSK modulation symbols is M
symbols. Suppose N<M at this time.
Frame configuration determination section 601 selects one of (701),
(702), (703) or (704) in FIG. 7 as the optimal frame configuration
based on the transmission path information and the request data transmission speed information.
For example, in the case of high-speed fading, frame configuration determination
section 601 sacrifices data transmission efficiency on the receiving side
and selects the frame configuration of either (701) or (703) in FIG.
7 so as to insert BPSK modulation symbols at shorter intervals to prevent deterioration
of the data demodulation error rate and maintain the quality of data. On the other
hand, in the case of low-speed fading, frame configuration determination section
601 selects the frame configuration of either (702) or (704)
in FIG. 7 so as to insert BPSK modulation symbols at longer intervals to improve
the data transmission efficiency.
Furthermore, when the level of the reception signal is large, frame
configuration determination section 601 gives priority to data transmission
efficiency on the receiving side and selects the frame configuration of either
(701) or (702) in the FIG. 7 that adopts adopting 16QAM as the modulation
system of information symbol. On the other hand, when the level of the reception
signal is small, frame configuration determination section 601 gives priority
to increasing error resiliency features while sacrificing data transmission efficiency
on the receiving side and selects the frame configuration of either (703)
or (704) in FIG. 7 adopting 8PSK as the modulation system of information symbol.
FIG. 8 shows a signal point layout according to the 16QAM modulation system
on the in-phase I-quadrature Q plane and signal point layout of BPSK modulation
symbol. Signal points 801 are the signal points of BPSK modulation symbol
and signal points 802 are the signal points of 16QAM modulation symbol.
FIG. 9 shows a signal point layout according to the 8PSK modulation system on the
in-phase I-quadrature Q plane and signal point layout of BPSK modulation symbol.
Signal points 901 are the signal points of BPSK modulation symbol and signal
points 902 are the signal points of 8PSK modulation symbol FIG. 10 is a
block diagram showing a configuration of the reception apparatus according to this
Embodiment. In the reception apparatus shown in FIG. 10, the components common
to the reception apparatus shown in FIG. 5 are assigned the same reference numerals
as those in FIG. 5 and their explanations will be omitted.
In the reception apparatus in FIG. 10, transmission path distortion estimation
section 1001 differs in the way of operation from transmission path distortion
estimation section 503 in FIG. 5 and detection section 1002 differs
in the way of operation from detection section 504 in FIG. 5.
Transmission path distortion estimation section 1001 receives
the in-phase component and the quadrature component of the quadrature baseband
signal as inputs, extracts the signals of the BPSK modulation symbol shown in FIG.
8 and FIG. 9 above, estimates the amount of transmission path distortion from the
reception condition of the BPSK modulation symbol and outputs the amount of transmission
path distortion to detection section 1002.
Detection section 1002 receives the in-phase component and the quadrature
component of the quadrature baseband signal as inputs, detects information symbol
and BPSK modulation symbol based on the amount of transmission path distortion
and outputs a digital reception signal.
Thus, in this embodiment, by sending information with BPSK modulation symbols
inserted therein, instead of known pilot symbols, it is possible to improve the
transmission speed compared with Embodiment 1.
Here, this embodiment describes two intervals for inserting BPSK modulation
symbols but the present invention is not limited to these. Also, this embodiment
describes two modulation systems of information symbol, namely 16QAM and 8PSK modulation,
but the present invention is not limited to these.
Furthermore, this embodiment describes the frame configuration of only
information symbol and BPSK modulation symbol shown in FIG. 7 but the present invention
is not limited to this frame configuration.
Embodiment 3
Embodiment 3 describes a digital radio communication method by which the
interval for inserting QPSK modulation symbols and the modulation system of information
symbol other than the above QPSK modulation symbols are changed according to the
communication situation.
FIG. 11 is a block diagram showing a configuration of the transmission apparatus
according to this Embodiment. In the transmission apparatus shown in FIG. 11, the
components common to those in the transmission apparatus shown in FIG. 1 are assigned
the same reference numerals as those in FIG. 1 and their explanations will be omitted.
In the transmission apparatus in FIG. 11, frame configuration determination section
1101 differs in the way of operation from the frame configuration determination
section 101 in FIG. 1. Also, when compared to FIG. 1, the transmission apparatus
in FIG. 11 adopts a configuration having QPSK symbol modulation section 1102
instead of pilot symbol generation section 103.
Frame configuration determination section 1101 judges the communication
situation, determines the interval for inserting QPSK modulation symbols and the
modulation system of digital transmission signals, outputs a signal indicating
the determined modulation system to quadrature baseband modulation section 102
and outputs a signal indicating the determined interval for inserting QPSK modulation
symbols to quadrature baseband modulation section 102, QPSK symbol modulation
section 1102 and frame configuration section 104.
QPSK symbol modulation section 1102 performs QPSK-modulation on a digital
transmission signal at the timing indicated from frame configuration determination
section 1101 and outputs the in-phase component and the quadrature component
of the QPSK modulation symbol to frame configuration section 104.
FIG. 12 illustrates examples of a frame configuration of a signal transmitted
from the transmission apparatus of this embodiment and shows a time-symbol relationship.
(1201) is a frame configuration where the modulation system of information
symbol is 16QAM and the interval between QPSK modulation symbols is N symbols.
(1202) is a frame configuration where the modulation system of information
symbol is 16QAM and the interval between QPSK modulation symbols is M symbols.
(1203) is a frame configuration where the modulation system of information
symbol is 8PSK modulation and the interval between QPSK modulation symbols is N
symbols. (1204) is a frame configuration where the modulation system of
information symbol is 8PSK modulation and the interval between QPSK modulation
symbols is M symbols. Suppose N<M at this time.
Frame configuration determination section 1101 selects one of (1201),
(1202), (1203) or (1204) in FIG. 12 as the optimal frame configuration
based on the transmission path information and the request data transmission speed information.
For example, in the case of high-speed fading, frame configuration determination
section 1101 sacrifices data transmission efficiency on the receiving side
and selects the frame configuration of either (1201) or (1203) in
FIG. 12 so as to insert QPSK modulation symbols at shorter intervals to prevent
deterioration of the data demodulation error rate and maintain the quality of data.
On the other hand, in the case of low-speed fading, frame configuration determination
section 1101 selects the frame configuration of either (1202) or
(1204) in FIG. 12 so as to insert QPSK modulation symbols at longer intervals
to improve the data transmission efficiency.
Furthermore, when the level of the reception signal is large, frame
configuration determination section 1101 gives priority to data transmission
efficiency on the receiving side and selects the frame configuration of either
(1201) or (1202) in FIG. 12 that adopts 16QAM as the modulation system
of information symbol. On the other hand, when the level of the reception signal
is small, frame configuration determination section 1101 gives priority
to increasing error resiliency features while sacrificing data transmission efficiency
on the receiving side and selects the frame configuration of either (1203)
or (1204) in FIG. 12 that adopts 8PSK as the modulation system of information symbol.
FIG. 13 shows a signal point layout according to the 16QAM modulation system
on the in-phase I-quadrature Q plane and signal point layout of QPSK modulation
symbol. Signal points 1301 are the signal points of QPSK modulation symbol
and signal points 1302 are the signal points of 16QAM modulation symbol.
FIG. 14 shows a signal point layout according to the 8PSK modulation system on
the in-phase I-quadrature Q plane and signal point layout of QPSK modulation symbol.
Signal points 1401 are the signal points of QPSK modulation symbol and signal
points 1402 are the signal points of 8PSK modulation symbol.
FIG. 15 is a block diagram showing a configuration of the reception apparatus
according to this embodiment. In the reception apparatus shown in FIG. 15, the
components common to the reception apparatus shown in FIG. 5 are assigned the same
reference numerals as those in FIG. 5 and their explanations will be omitted.
In the reception apparatus in FIG. 15, transmission path distortion estimation
section 1501 differs in the way of operation from transmission path distortion
estimation section 503 in FIG. 5 and detection section 1502 differs
in the way of operation from detection section 504 in FIG. 5.
Transmission path distortion estimation section 1501 receives
the in-phase component and the quadrature component of the quadrature baseband
signal as inputs, extracts the signals of the QPSK modulation symbol shown in FIG.
13 and FIG. 14 above, estimates the amount of transmission path distortion from
the reception condition of the QPSK modulation symbol and outputs the amount of
transmission path distortion to detection section 1502.
Detection section 1502 receives the in-phase component and the quadrature
component of the quadrature baseband signal as inputs, detects information symbol
and QPSK modulation symbols based on the amount of transmission path distortion
and outputs a digital reception signal.
Thus, in this embodiment, by sending information with QPSK modulation symbols
inserted therein instead of known pilot symbols, it is possible to improve the
transmission speed compared with Embodiment 1 and Embodiment 2.
Here, this embodiment describes two intervals of inserting QPSK modulation
symbols but the present invention is not limited to these. Also, this embodiment
describes two modulation systems of information symbol, namely 16QAM and 8PSK modulation,
but the present invention is not limited to these.
Furthermore, this embodiment describes the frame configuration of only
information symbol and QPSK modulation symbol as shown in FIG. 12, but the present
invention is not limited to this frame configuration.
Embodiment 4
Embodiment 4 describes a digital radio communication method by which the
modulation system of information symbol is changed according to the communication
situation and when the modulation system of information symbol has a level of 8
or higher, known pilot symbols are inserted at insertion intervals subject to change
according to the communication situation.
FIG. 16 is a block diagram showing a configuration of the transmission apparatus
according to this Embodiment. In the transmission apparatus shown in FIG. 16, the
components common to those in the transmission apparatus shown in FIG. 1 are assigned
the same reference numerals as those in FIG. 1 and their explanations will be omitted.
In the transmission apparatus in FIG. 16, frame configuration determination section
1601 differs in the way of operation from the frame configuration determination
section 101 in FIG. 1.
Frame configuration determination section 1601 determines the modulation
system of digital transmission signals based on the communication situation and
outputs a signal indicating the determined modulation system to quadrature baseband
modulation section 102. Also, when the determined modulation system uses
8 or more-levels, frame configuration determination section 1601 determines
the interval of inserting a pilot symbol based on the communication situation and
outputs a signal indicating the determined interval of inserting the pilot symbol
to frame configuration section 104. Also, when the level of the determined
modulation system is less than 8, frame configuration determination section 1601
outputs a signal giving an instruction to stop generating pilot symbols to pilot
symbol generation section 103.
Pilot symbol generation section 103 generates known pilot symbol between
the transmitting side and the receiving side and outputs the in-phase component
and the quadrature component of the known pilot symbol to frame configuration section
104. However, when instructed to stop generating pilot symbols from frame
configuration determination section 1601, pilot symbol generation section
103 stops operation.
FIG. 17 illustrates examples of a frame configuration of a signal transmitted
from the transmission apparatus of this embodiment and shows a time-symbol relationship.
(1701) is a frame configuration where the modulation system of information
symbol is BPSK. (1702) is a frame configuration where the modulation system
of information symbol is QPSK.
The ranking of the frame configurations shown in FIG. 2 and FIG. 17 in descending
order of resistance to fading speed is (1701), (1702), (203),
(201), (204) and (202) Furthermore, the ranking in descending
order of error resiliency features is (1701), (1702), (203),
(204), (201) and (202). On the other hand, the ranking in
descending order of data transmission efficiency on the receiving side is (202),
(201), (204), (203), (1702) and (1701).
Frame configuration determination section 1601 selects one of (201),
(202), (203) or (204) in FIG. 2 or (1701) or (1702)
in FIG. 17 above as the optimal frame configuration based on the transmission path
information and the request data transmission speed information.
FIG. 18 shows a signal point layout according to the BPSK modulation method
on the in-phase I-quadrature Q plane and signal points 1801 are the signal
points of BPSK symbol.
FIG. 19 shows a signal point layout according to the QPSK modulation method
on the in-phase I-quadrature Q plane and signal points 1901 are the signal
points of QPSK symbol.
FIG. 20 is a block diagram showing a configuration of the reception apparatus
according to this embodiment. In the reception apparatus shown in FIG. 20, the
components common to those in the reception apparatus shown in FIG. 5 are assigned
the same reference numerals as those in FIG. 5 and their explanations will be omitted.
In the reception apparatus in FIG. 20, transmission path distortion estimation
section 2001 differs in the way of operation from transmission path estimation
section 503 in FIG. 5 and detection section 2002 differs in the way
of operation from detection section 504 in FIG. 5.
Transmission path distortion estimation section 2001 receives
the in-phase component and the quadrature component of the quadrature baseband
signal as inputs, estimates the amount of transmission path distortion from the
reception condition of the BPSK modulation symbol shown in FIG. 18 or the QPSK
modulation symbol shown in FIG. 19 and outputs the amount of transmission path
distortion to detection section 2002.
Detection section 2002 receives the in-phase component and the quadrature
component of the quadrature baseband signal as inputs, detects information symbols
based on the amount of transmission path distortion and outputs a digital reception signal.
In this way, by changing the modulation system of information symbol according
to the communication situation such as fluctuations in the transmission path and
the level of the reception signal and by inserting known pilot symbols when the
information symbol modulation system is a multi-level modulation system with a
level of 8 or higher, and changing the interval for inserting the above known pilot
symbols according to the communication situation, it is possible to improve both
the data transmission efficiency and the quality of data at the same time.
Here, in this embodiment, the transmission apparatus in FIG. 16 can also have
a configuration having BPSK symbol modulation section 602 shown in FIG.
6 instead of pilot symbol generation section 103.
In this case, frame configuration determination section 1601 determines
the modulation system of the digital transmission signal based on the communication
situation. For example, frame configuration determination section 1601 selects
one of (701), (702) (703) or (704) in FIG. 7 above
or (1701) or (1702) in FIG. 17 as the optimal frame configuration.
Then, frame configuration determination section 1601 outputs the signals
indicating the determined modulation system to quadrature baseband modulation section
102. Also, when the determined modulation system has a level of 8 or higher,
frame configuration determination section 1601 determines the interval for
inserting BPSK modulation symbols based on the communication situation and outputs
a signal indicating the determined interval for inserting the BPSK modulation symbols
to BPSK symbol modulation section 602 and frame configuration section 104.
Furthermore, when the level of the determined modulation system is less than 8,
frame configuration determination section 1601 outputs a signal giving an
instruction to stop generating for BPSK modulation symbols to BPSK symbol modulation
section 602.
BPSK symbol modulation section 602 performs BPSK-modulation on a digital
transmission signal at the timing indicated from frame configuration determination
section 1601 and outputs the in-phase component and the quadrature component
of the BPSK modulation symbol to frame configuration section 104. However,
when instructed to stop generating BPSK modulation symbols from frame configuration
determination section 1601, BPSK symbol modulation section 602 stops operation.
Transmission path distortion estimation section 2001 receives
the in-phase component and the quadrature component of the quadrature baseband
signal as inputs, estimates the amount of transmission path distortion from the
reception condition of the BPSK modulation symbol shown in FIG. 8 and FIG. 9 above,
the BPSK modulation symbol shown in FIG. 18 or the QPSK modulation symbol shown
in FIG. 19 and outputs the amount of transmission path distortion to detection
section 2002.
Furthermore, in this embodiment, the transmission apparatus in FIG.
16. can also have a configuration having QPSK symbol modulation section 1102
shown in FIG. 11 instead of pilot symbol generation section 103.
In this case, frame configuration determination section 1601 determines
the modulation system of the digital transmission signal based on the communication
situation. For example, frame configuration determination section 1601 selects
one of (1201), (1202), (1203) or (1204) in FIG. 12
above or (1701) or (1702) in FIG. 17 as the optimal frame configuration.
Then, frame configuration determination section 1601 outputs a signal
indicating the determined modulation system to quadrature baseband modulation section
102. Also, when the determined modulation system uses 8 or more-levels,
frame configuration determination section 1601 determines the interval for
inserting QPSK modulation symbols based on the communication situation and outputs
a signal indicating the determined interval for inserting the QPSK symbols to QPSK
symbol modulation section 1102 and frame configuration section 104.
Also, when the level of the determined modulation system is less than 8, frame
configuration determination section 1601 outputs a signal giving an instruction
to stop generating QPSK modulation symbols to QPSK symbol modulation section 1102.
QPSK symbol modulation section 1102 performs QPSK-modulation on a digital
transmission signal at the timing indicated from frame configuration determination
section 1601 and outputs the in-phase component and the quadrature component
of the QPSK modulation symbol to frame configuration section 104. However,
when instructed to stop generating QPSK modulation symbols from frame configuration
determination section 1601, QPSK symbol modulation section 1102 stops operation.
Transmission path distortion estimation section 2001 receives
the in-phase component and the quadrature component of the quadrature baseband
signal as inputs, estimates the amount of transmission path distortion from the
reception condition of the QPSK modulation symbol shown in FIG. 13 or FIG. 14 and
the BPSK modulation symbol shown in FIG. 18 or the QPSK modulation symbol shown
in FIG. 19 and outputs the amount of transmission path distortion to detection
section 2002.
Here, this embodiment explains two intervals for inserting known pilot symbols,
but the present invention is not limited to these. Also, this embodiment explains
two modulation systems that have a level of 8 or higher for information symbol,
namely 16QAM and the 8PSK modulation, but the present invention is not limited
to these.
Furthermore, this embodiment describes the frame configurations in FIG.
2, FIG. 7, FIG. 12 and FIG. 17 but the present invention is not limited to these
frame configurations.
Furthermore, the BPSK modulation method and the QPSK modulation method
of the modulation system of information symbols of the present invention are not
limited to the signal point layouts shown in FIG. 18 and FIG. 19 but π/2
shift BPSK modulation or π/4 shift QPSK modulation can also be used.
Embodiment 5
Embodiment 5 describes a digital radio communication method by which the
interval of inserting a known pilot symbol, the number of signal points with one
symbol immediately before and immediately after a known pilot symbol (hereinafter
referred to as "symbols before and after the pilot symbol") and signal point layout
and the modulation system of information symbol other than those symbols are changed.
FIG. 21 is a block diagram showing a configuration of the transmission apparatus
according to this embodiment. In the transmission apparatus shown in FIG. 21, the
components common to those in the transmission apparatus shown in FIG. 1 are assigned
the same reference numerals as those shown in FIG. 1 and their explanations will
be omitted.
In the transmission apparatus in FIG. 21, frame configuration determination section
2101 differs in the way of operation from frame configuration determination
section 101 in FIG. 1. Furthermore, the transmission apparatus in FIG. 21
adopts a configuration with symbols-before-and-after-pilot modulation section 2102
added compared to FIG. 1.
Frame configuration determination section 2101 determines the interval
for inserting known pilot symbols and the modulation system of digital transmission
signals based on the communication situation. In this case, frame configuration
determination section 2101 applies different modulation systems to the symbols
before and after the pilot symbol, and to other information symbols.
Then, frame configuration determination section 2101 outputs a signal
indicating the modulation system of the symbols before and after the pilot symbol
to symbols-before-and-after-pilot modulation section 2102, outputs a signal
indicating the modulation system of other information symbols to quadrature baseband
modulation section 102 and outputs a signal indicating the determined interval
for inserting known pilot symbols to symbols-before-and-after-pilot modulation
section 2102 and frame configuration section 104.
Symbols-before-and-after-pilot modulation section
2102 modulates a digital transmission signal by a predetermined modulation
system at the timing indicated from frame configuration determination section 2101
and outputs the in-phase component and the quadrature component of the symbols
before and after the pilot symbol to frame configuration section 104.
FIG. 22 illustrates examples of a frame configuration of a signal transmitted
from the transmission apparatus of this embodiment and shows a time-symbol relationship.
(2201) is a frame configuration where the modulation system of information
symbol is 16QAM and the interval between known pilot symbols is N symbols. (2202)
is a frame configuration where the modulation system of information symbol is 16QAM
and the interval between known pilot symbols is M symbols. (2203) is a frame
configuration where the modulation system of information symbol is 8PSK modulation
and the interval between known pilot symbols is N symbols. (2204) is a frame
configuration where the modulation system of information symbols is 8PSK modulation
and the interval between known pilot symbols is M symbols. Suppose N<M at
this time.
Signal point 2211 is 1 symbol immediately before the known pilot symbol
when the information symbol modulation system is 16QAM, and signal point 2212
is 1 symbol immediately after the known pilot symbol when the information symbol
modulation system is 16QAM. Signal point 2213 is 1 symbol immediately before
the known pilot symbol when the information symbol modulation system is 8PSK modulation,
and signal point 2214 is 1 symbol immediately after the known pilot symbol
when the information symbol modulation system is 8PSK modulation.
Frame configuration determination section 2101 selects one of (2201),
(2202), (2203) or (2204) in FIG. 22 as the optimal frame configuration
based on the transmission path information and the request data transmission speed information.
For example, in the case of high-speed fading, frame configuration determination
section 2101 sacrifices data transmission efficiency on the receiving side
and selects the frame configuration of either (2201) or (2203) in
FIG. 22 so as to insert known pilot symbols at shorter intervals to prevent deterioration
of the data demodulation error rate and maintain the quality of data. On the other
hand, in the case of low-speed fading, frame configuration determination section
2101 selects the frame configuration of either (2202) or (2204)
in FIG. 22 so as to insert known pilot symbols at longer intervals to improve the
data transmission efficiency.
Furthermore, when the level of the reception signal is large, frame
configuration determination section 2101 gives priority to data transmission
efficiency on the receiving side and selects the frame configuration of either
(2201) or (2202) in FIG. 22 that adopts 16QAM as the modulation system
of information symbol. On the other hand, when the level of the reception signal
is small, frame configuration determination section 2101 gives priority
to increasing error resiliency features while sacrificing data transmission efficiency
on the receiving side and selects the frame configuration of either (2203)
or (2204) in FIG. 22 that adopts 8PSK as the modulation system of information symbol.
FIG. 23 shows a signal point layout according to the 16QAM modulation method
on the in-phase I-quadrature Q plane and a signal point layout according to a known
pilot symbol and a signal point layout of symbols before and after the pilot symbol.
Signal point 2301 is the signal point of known pilot symbol, signal points
2302 are the signal points of 16QAM modulation symbol and signal points
2303 are the signal points of symbols before and after the pilot symbol.
FIG. 24 shows a signal point layout according to the 8PSK modulation system
on the in-phase I-quadrature Q plane, a signal point layout of known pilot symbol
and a signal point layout of symbols before and after the pilot symbol. Signal
points 2401, 2401-A and 2401-B are the signal points of 8PSK
modulation symbol, 2401-A is the signal point of the known pilot symbol,
2401-A and 2401-B are the signal points of symbols before and after
the pilot symbol and straight line 2402 is the straight line formed by linking
the signal point of the known pilot symbol and the origin on the in-phase I-quadrature
Q plane.
FIG. 25 is a block diagram showing a configuration of the reception apparatus
according to this embodiment. In the reception apparatus shown in FIG. 25, the
components common to those in the reception apparatus shown in FIG. 5 are assigned
the same reference numerals as those shown in FIG. 5 and their explanations will
be omitted.
In the reception apparatus in FIG. 25, transmission path estimation section 2501
differs in the way of operation from transmission path estimation section 503
and detection section 2502 differs in the way of operation from detection
section 504 in FIG. 5.
Transmission path distortion estimation section 2501 receives
the in-phase component and the quadrature component of the quadrature baseband
signal as inputs, extracts the signal of the known pilot symbol shown in FIG. 23
and FIG. 24 above, estimates the amount of transmission path distortion from the
reception condition of the known pilot symbol and outputs the amount of transmission
path distortion to detection section 2502.
Detection section 2502 receives the in-phase component and the quadrature
component of the quadrature baseband signal as inputs, detects information symbol
including symbols before and after the pilot symbol based on the amount of transmission
path distortion and outputs a digital reception signal.
Thus, changing the interval for inserting known pilot symbols and the modulation
system of information symbol according to the communication situation such as fluctuations
in the transmission path and the level of the reception signal can improve both
the data transmission efficiency and the quality of data at the same time.
Furthermore, as shown in FIG. 23 and FIG. 24, by arranging
