U.S. patent application number 12/673712 was filed with the patent office on 2011-09-01 for data transmission method, data reception method, mobile terminal and radio communication system.
This patent application is currently assigned to NTT DOCOMO, INC.. Invention is credited to Masayuki Furusawa, Yousuke Iizuka, Yukihiko Okumura.
Application Number | 20110214032 12/673712 |
Document ID | / |
Family ID | 40378127 |
Filed Date | 2011-09-01 |
United States Patent
Application |
20110214032 |
Kind Code |
A2 |
Furusawa; Masayuki ; et
al. |
September 1, 2011 |
DATA TRANSMISSION METHOD, DATA RECEPTION METHOD, MOBILE TERMINAL
AND RADIO COMMUNICATION SYSTEM
Abstract
A data transmission method according to the present invention
includes the steps of: (A) adding a first CRC code to transmission
data; (B) dividing the transmission data to which the first CRC
code has been added into a plurality of encoded bit sequences; (C)
adding a second CRC code to at least one of the divided encoded bit
sequences; (D) performing error correction encoding processing on
the encoded bit sequences; and (E) transmitting the encoded bit
sequences on which the error correction encoding processing has
been performed.
Inventors: |
Furusawa; Masayuki;
(Chiyoda-ku, Tokyo, JP) ; Iizuka; Yousuke;
(Chiyoda-ku, Tokyo, JP) ; Okumura; Yukihiko;
(Chiyoda-ku, Tokyo, JP) |
Assignee: |
NTT DOCOMO, INC.
11-1, Nagatacho 2-chome, Chiyoda-ku
Tokyo
JP
100-6150
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20110060964 A1 |
March 10, 2011 |
|
|
Family ID: |
40378127 |
Appl. No.: |
12/673712 |
Filed: |
August 13, 2008 |
PCT Filed: |
August 13, 2008 |
PCT NO: |
PCTJP2008064521 |
371 Date: |
October 12, 2010 |
Current U.S.
Class: |
714/758;
714/E11.032 |
Current CPC
Class: |
H04L 1/0065 20130101;
H04L 1/0061 20130101; H04L 1/1607 20130101 |
Class at
Publication: |
714/758;
714/E11.032 |
International
Class: |
H03M 13/29 20060101
H03M013/29; G06F 11/10 20060101 G06F011/10 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 17, 2007 |
JP |
2007-213183 |
Claims
1. A data transmission method comprising the steps of: (A) adding a
first CRC code to transmission data; (B) dividing the transmission
data to which the first CRC code has been added into a plurality of
encoded bit sequences; (C) adding a second CRC code to at least one
of the divided encoded bit sequences; (D) performing error
correction encoding processing on the encoded bit sequences; and
(E) transmitting the encoded bit sequences on which the error
correction encoding processing has been performed.
2. The data transmission method according to claim 1, wherein in
the step (C), the divided encoded bit sequences are grouped into a
plurality of groups, and the second CRC code is added to any of the
encoded bit sequences in at least one of the plurality of
groups.
3. The data transmission method according to claim 2, wherein in
the step (C), the second CRC code is added to any of the encoded
bit sequences in each of the plurality of groups.
4. The data transmission method according to claim 2, wherein in
the step (C), the second CRC code is added to any of the encoded
bit sequences in a leading group among the plurality of groups.
5. The data transmission method according to claim 4, wherein in
the step (C), the second CRC code is added to a leading one of the
encoded bit sequences in the leading group among the plurality of
groups.
6. A data reception method comprising the steps of: dividing
received data into a plurality of encoded bit sequences, and
performing error correction decoding processing on the divided
encoded bit sequences; performing error detection processing, by
using the second CRC code added to one or more of the encoded bit
sequences on which the error correction decoding processing is
performed; transmitting a first retransmission request for a
specific encoded bit sequence, when an error is detected in the
specific encoded bit sequence; acquiring transmission data to which
a first CRC code has been added by connecting the plurality of
encoded bit sequences, when no error is detected in the plurality
of encoded bit sequences; performing error detection processing by
using the first CRC code; and transmitting a second retransmission
request for the transmission data, when an error is detected in the
transmission data.
7. The data reception method according to claim 6, wherein the
second CRC code is added to any of the encoded bit sequences in at
least one of a plurality of groups.
8. The data reception method according to claim 7, wherein the
second CRC code is added to any of the encoded bit sequences in
each of the plurality of groups.
9. The data reception method according to claim 7, wherein the
second CRC code is added to any of the encoded bit sequences in a
leading group among the plurality of groups.
10. The data reception method according to claim 9, wherein the
second CRC code is added to a leading one of the encoded bit
sequences in the leading group among the plurality of groups.
11. A mobile terminal comprising: a first CRC adder unit configured
to add a first CRC code to transmission data; a divider unit
configured to divide the transmission data to which the first CRC
code has been added into a plurality of encoded bit sequences; a
second CRC adder unit configured to add a second CRC code to at
least one of the divided encoded bit sequences; an error correction
encoder unit configured to perform error correction encoding
processing on the encoded bit sequences; and a transmitter unit
configured to transmit the encoded bit sequences on which the error
correction encoding processing has been performed.
12. The mobile terminal according to claim 11, wherein the second
CRC adder unit is configured to group the divided encoded bit
sequences into a plurality of groups, and to add the second CRC
code to any of the encoded bit sequences in at least one of the
plurality of groups.
13. A radio communication system including a transmitter apparatus
and a receiver apparatus, wherein the transmitter apparatus
comprises: a first CRC adder unit configured to add a first CRC
code to transmission data; a divider unit configured to divide the
transmission data to which the first CRC code has been added into a
plurality of encoded bit sequences; a second CRC adder unit
configured to add a second CRC code to at least one of the divided
encoded bit sequences; an error correction encoder unit configured
to perform error correction encoding processing on the encoded bit
sequences; and a transmitter unit configured to transmit the
encoded bit sequences on which the error correction encoding
processing has been performed; and the receiver apparatus
comprised: an error correction decoder unit configured to divide
received data into a plurality of encoded bit sequences, and to
perform error correction decoding processing on the divided encoded
bit sequences; a second CRC checker unit configured to perform
error detection processing by using the second CRC code added to
one or more of the encoded bit sequences on which the error
correction decoding processing has been performed; a first
retransmission requester unit configured to transmit a first
retransmission request for a specific encoded bit sequence, when no
error is detected in the specific encoded bit sequence; a connector
unit configured to connect the plurality of encoded bit sequences,
when no error is detected in the plurality of encoded bit
sequences, and to acquire transmission data to which a first CRC
code has been added; a first CRC checker unit configured to perform
error detection processing by using the first CRC code; and a
second retransmission requester unit configured to transmit a
second retransmission request for the transmission data, when an
error is detected in the transmission data.
Description
TECHNICAL FIELD
[0001] The present invention relates to a data transmission method,
a data reception method, a mobile terminal and a radio
communication system.
BACKGROUND ART
[0002] In a digital radio communication system, transmission
quality (such as a bit error rate and throughput characteristics)
depends on a radio wave propagation environment such as fading and
shadowing, and transmission data transmitted by a transmitter
apparatus might be received as erroneous data by a receiver
apparatus.
[0003] In consideration of such circumstances, the digital radio
communication system uses an error control technique for allowing
the receiver apparatus to receive correct transmission data even in
a poor radio wave propagation environment.
[0004] The error control technique is a technique of reducing the
probability of bit error occurrences in the transmission data and
of realizing a radio communication system having higher
transmission quality even using the same received power.
[0005] Here, the error control technique can be roughly classified
into forward error correction (FEC) processing and automatic repeat
request (ARQ) processing.
[0006] Note that error correction encoding processing can be cited
as the FEC processing. Specifically, in the error correction
encoding processing, redundant bits are added to a bit sequence of
transmission data according to a certain rule, thereby allowing
restoration of bits erroneously received due to a radio wave
propagation environment.
[0007] A receiver apparatus adopting the ARQ processing is
configured to determine whether or not received data is correct and
to send a retransmission request back to the transmitting side when
an error is detected.
[0008] Here, FIG. 1 shows configurations of a transmitter apparatus
10 and a receiver apparatus 30 in a radio communication system
using both ARQ processing and FEC processing.
[0009] As shown in FIG. 1, the transmitter apparatus 10 includes a
transmission data generator unit 11, a CRC adder unit 12, a divider
unit 13, an error correction encoder unit 14, an interleaver 15, a
modulator 16, and a transmission controller unit 17.
[0010] Meanwhile, the receiver apparatus 30 includes a demodulator
31, a deinterleaver 32, an error correction decoder unit 33, a
connector unit 34, a CRC checker unit 35, and a received data
acquirer unit 36.
[0011] As shown in FIG. 2, in the transmitter apparatus 10, the
transmission data generator unit 11 generates transmission data (a
bit sequence). In Step S1001, the CRC adder unit 12 performs error
detection encoding processing using a CRC (Cyclic Redundant Check)
code and thus adds the CRC code (a parity bit sequence) to the
transmission data (the bit sequence) in order to perform error
detection processing in ARQ processing.
[0012] In Step S1002, the divider unit 13 divides the transmission
data (the bit sequence) to which the CRC code (the parity bit
sequence) has been added into encoded bit sequences #1 to #9 in
units (bit size) for performing error correction encoding
processing.
[0013] In Step S1003, the error correction encoder unit 14 performs
the error correction encoding processing on the multiple encoded
bit sequences #1 to #9. As a result, encoded bit sequences #A1 to
#A9 to which redundant bits have been added are obtained.
[0014] In order to randomize errors occurring in a burst (burst
errors) in the radio communication system, in Step S1004, the
interleaver 15 performs interleaving for changing the order of the
bit sequences in the transmission data containing the encoded bit
sequences #A1 to #A9 according to a certain rule.
[0015] In Step S1005, the modulator 16 digitally modulates
transmission data X (containing the encoded bit sequences #A1 to
#A9) outputted from the interleaver 15, and then transmits the
transmission data to a radio section.
[0016] Meanwhile, in the receiver apparatus 30, as shown in FIG. 2,
the demodulator 31 converts a received signal into received data (a
bit sequence) by demodulating the received signal in Step
S2001.
[0017] In Step S2002, the deinterleaver 32 changes the order of the
bit sequences in the received data that is the output from the
demodulator 31 back to the original order of the bit sequences in
the transmission data X according to a rule opposite to that
adopted by the interleaver 15 in the transmitter apparatus 10.
[0018] In Step S2003, the error correction decoder unit 33 divides
the received data (the bit sequence) outputted from the
deinterleaver 32 into encoded bit sequences #A1 to #A9 in units
that are the same as for the error correction encoding processing
in the transmitter apparatus 10, and then performs error correction
decoding processing.
[0019] In Step S2004, the connector unit 34 connects multiple
encoded bit sequences #1 to #9 obtained by the error correction
decoding processing. In Step S2005, the CRC checker unit 35
performs error detection processing (i.e. CRC check) using the CRC
code added to the connected transmission data.
[0020] When no error is detected here, the receiver apparatus 30
transmits transmission acknowledgement information (ACK:
Acknowledgement) concerning the received data to the transmitter
apparatus 10. In response, the transmitter apparatus 10 transmits
transmission data to be transmitted next.
[0021] On the other hand, when an error is detected, the receiver
apparatus 30 transmits a retransmission request (NACK: Negative
ACK) to the transmitter apparatus 10. In response, the transmitter
apparatus 10 retransmits the same data as that previously
transmitted. [0022] Non-patent Document 1: "Digital Wireless
Transmission Technology" written by Seiichi Sampei, Pearson
Education
[0023] As described above, the ARQ processing is a technique useful
for achieving high transmission quality of the radio communication
system.
[0024] Nevertheless, in the case of real-time data transmission,
the receiver apparatus 30 receives all the transmission data (bit
sequences) transmitted by the transmitter apparatus 10, checks the
CRC code, and sends a retransmission request. For this reason,
there is a problem that transmission time is delayed depending on a
radio environment.
DISCLOSURE OF THE INVENTION
[0025] The present invention has been made in the light of the
above problem. It is an object of the present invention to provide
a data transmission method, a data reception method, a mobile
terminal and a radio communication system, by which a delay time
required by a receiver apparatus to detect an error and to return
ACK/NACK to a transmitter apparatus can be reduced as much as
possible for more real-time data transmission.
[0026] A first aspect of the present invention is summarized as a
data transmission method including the steps of: (A) adding a first
CRC code to transmission data; (B) dividing the transmission data
to which the first CRC code has been added into a plurality of
encoded bit sequences; (C) adding a second CRC code to at least one
of the divided encoded bit sequences; (D) performing error
correction encoding processing on the encoded bit sequences; and
(E) transmitting the encoded bit sequences on which the error
correction encoding processing has been performed.
[0027] In the first aspect, in the step (C), the divided encoded
bit sequences can be grouped into a plurality of groups, and the
second CRC code can be added to any of the encoded bit sequences in
at least one of the plurality of groups.
[0028] In the first aspect, in the step (C), the second CRC code
can be added to any of the encoded bit sequences in each of the
plurality of groups.
[0029] In the first aspect, in the step (C), the second CRC code
can be added to any of the encoded bit sequences in a leading group
among the plurality of groups.
[0030] In the first aspect, in the step (C), the second CRC code
can be added to a leading one of the encoded bit sequences in the
leading group among the plurality of groups.
[0031] A second aspect of the present invention is summarized as a
data reception method including the steps of: dividing received
data into a plurality of encoded bit sequences, and performing
error correction decoding processing on the divided encoded bit
sequences; performing error detection processing, by using the
second CRC code added to one or more of the encoded bit sequences
on which the error correction decoding processing is performed;
transmitting a first retransmission request for a specific encoded
bit sequence, when an error is detected in the specific encoded bit
sequence; acquiring transmission data to which a first CRC code has
been added by connecting the plurality of encoded bit sequences,
when no error is detected in the plurality of encoded bit
sequences; performing error detection processing by using the first
CRC code; and transmitting a second retransmission request for the
transmission data, when an error is detected in the transmission
data.
[0032] In the second aspect, the second CRC code can be added to
any of the encoded bit sequences in at least one of a plurality of
groups.
[0033] In the second aspect, the second CRC code can be added to
any of the encoded bit sequences in each of the plurality of
groups.
[0034] In the second aspect, the second CRC code can be added to
any of the encoded bit sequences in a leading group among the
plurality of groups.
[0035] In the second aspect, the second CRC code can be added to a
leading one of the encoded bit sequences in the leading group among
the plurality of groups.
[0036] A third aspect of the present invention is summarized as a
mobile terminal including: a first CRC adder unit configured to add
a first CRC code to transmission data; a divider unit configured to
divide the transmission data to which the first CRC code has been
added into a plurality of encoded bit sequences; a second CRC adder
unit configured to add a second CRC code to at least one of the
divided encoded bit sequences; an error correction encoder unit
configured to perform error correction encoding processing on the
encoded bit sequences; and a transmitter unit configured to
transmit the encoded bit sequences on which the error correction
encoding processing has been performed.
[0037] In the third aspect, the second CRC adder unit can be
configured to group the divided encoded bit sequences into a
plurality of groups, and to add the second CRC code to any of the
encoded bit sequences in at least one of the plurality of
groups.
[0038] A fourth aspect of the present invention is summarized as a
radio communication system including a transmitter apparatus and a
receiver apparatus, wherein the transmitter apparatus includes: a
first CRC adder unit configured to add a first CRC code to
transmission data; a divider unit configured to divide the
transmission data to which the first CRC code has been added into a
plurality of encoded bit sequences; a second CRC adder unit
configured to add a second CRC code to at least one of the divided
encoded bit sequences; an error correction encoder unit configured
to perform error correction encoding processing on the encoded bit
sequences; and a transmitter unit configured to transmit the
encoded bit sequences on which the error correction encoding
processing has been performed; and the receiver apparatus
comprised: an error correction decoder unit configured to divide
received data into a plurality of encoded bit sequences, and to
perform error correction decoding processing on the divided encoded
bit sequences; a second CRC checker unit configured to perform
error detection processing by using the second CRC code added to
one or more of the encoded bit sequences on which the error
correction decoding processing has been performed; a first
retransmission requester unit configured to transmit a first
retransmission request for a specific encoded bit sequence, when no
error is detected in the specific encoded bit sequence; a connector
unit configured to connect the plurality of encoded bit sequences,
when no error is detected in the plurality of encoded bit
sequences, and to acquire transmission data to which a first CRC
code has been added; a first CRC checker unit configured to perform
error detection processing by using the first CRC code; and a
second retransmission requester unit configured to transmit a
second retransmission request for the transmission data, when an
error is detected in the transmission data.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 is a functional block diagram of a transmitter
apparatus and a receiver apparatus that are conventional.
[0040] FIG. 2 is a diagram showing operations of the conventional
transmitter apparatus and receiver apparatus.
[0041] FIG. 3 is a functional block diagram of a transmitter
apparatus and a receiver apparatus according to a first embodiment
of the present invention.
[0042] FIG. 4 is a diagram showing operations of the transmitter
apparatus and receiver apparatus according to the first embodiment
of the present invention.
[0043] FIG. 5 is a diagram showing operations of a transmitter
apparatus and a receiver apparatus according to a second embodiment
of the present invention.
[0044] FIG. 6 is a diagram showing operations of a transmitter
apparatus and a receiver apparatus according to a third embodiment
of the present invention.
BEST MODES FOR CARRYING OUT THE INVENTION
First Embodiment of the Invention
[0045] With reference to FIGS. 3 and 4, a radio communication
system according to a first embodiment of the present invention
will be described. The radio communication system according to this
embodiment is a system which exhibits a significant effect
particularly when a temporal variation in a radio path is small
relative to a total data transmission time.
[0046] In this embodiment, an example where a mobile terminal is
used as a transmitter apparatus 10 will be described. However, it
is obvious that the present invention is not limited to such an
example.
[0047] As shown in FIG. 3, the transmitter apparatus 10 according
to this embodiment includes a transmission data generator unit 11,
a first CRC adder unit 21, a divider unit 13, a second CRC adder
unit 22, an error correction encoder unit 14, an interleaver 15, a
modulator 16, and a transmission controller unit 17.
[0048] The transmission data generator unit 11 is configured to
generate transmission data (a bit sequence) in response to a user
operation.
[0049] The first CRC adder 21 unit is configured to perform error
detection encoding processing by using a CRC code for the
transmission data (the bit sequence) generated by the transmission
data generator unit 11. Specifically, the first CRC adder unit 21
is configured to add a first CRC code (a parity bit sequence) to
the transmission data (the bit sequence) generated by the
transmission data generator unit 11.
[0050] The divider unit 13 is configured to divide the transmission
data (the bit sequence) to which the first CRC code (the parity bit
sequence) has been added into multiple encoded bit sequences in
units (bit size) for performing error correction encoding
processing.
[0051] Here, the divider unit 13 may previously divide an encoded
bit sequence to which a second CRC code is to be added (e.g., a
leading encoded bit sequence in a leading group to be described
later) so that the encoded bit sequence is reduced by a bit amount
of the CRC code.
[0052] The second CRC adder unit 22 is configured to add the second
CRC code (the parity bit sequence) to at least one of the encoded
bit sequences divided by the divider unit 13.
[0053] To be more specific, the second CRC adder unit 22 may be
configured to divide the encoded bit sequences divided by the
divider unit 13 into groups (G1 to G3 in examples shown in FIGS. 4
to 6), and to add the second CRC code to one of the encoded bit
sequences in at least one of the multiple groups (G1 to G3 in the
examples shown in FIGS. 4 to 6).
[0054] Here, the number of encoded bit sequences in each of the
groups, the number of groups or the like may be fixed or variable
as long as the number is are shared as information between the
transmitter apparatus 10 and a receiver apparatus 30.
[0055] For example, three encoded bit sequences may be set as one
group. Alternatively, the number of groups may be set to 5 and the
respective groups may be set to have the same number of encoded bit
sequences. In this case, if there is a fraction, the number of
encoded bit sequences may be controlled using the number of encoded
bit sequences in the last group.
[0056] Moreover, in order to increase the possibility of
acquisition of the first group, the number of encoded bit sequences
only in the first group may be reduced. Alternatively, measures may
be taken according to a movement speed in such a manner that the
number of encoded bit sequences in each group is reduced when the
movement speed is high and that the number of encoded bit sequences
in each group is increased when the movement speed is low.
[0057] In this embodiment, as shown in FIG. 4, the second CRC adder
unit 22 is configured to add the second CRC code to only a leading
encoded bit sequence #A1 in the leading group G1 among the multiple
groups G1 to G3.
[0058] The error correction encoder unit 14 is configured to
perform error correction encoding processing for the encoded bit
sequences outputted from the second CRC adder unit 22, and to
output encoded bit sequences #A1 to #A9 to which redundant bits
have been added.
[0059] The interleaver 15 is configured to perform interleaving
processing for changing the order of bit sequences in transmission
data X according to a certain rule, the transmission data X
containing the encoded bit sequences #A1 to #A9 outputted from the
error correction encoder unit 14.
[0060] The modulator 16 is configured to modulate the transmission
data X containing the encoded bit sequences on which the error
correction encoding processing and interleaving processing have
been performed, and to transmit the transmission data through an
antenna.
[0061] The transmission controller unit 17 is configured to
instruct the transmission data generator unit 11 to retransmit data
of encoded bit sequences specified by a first retransmission
request (NACK) from the receiver apparatus 30, upon receipt of the
retransmission request.
[0062] Moreover, the transmission controller unit 17 is configured
to instruct the transmission data generator unit 11 to retransmit
transmission data specified by a second retransmission request
(NACK) from the receiver apparatus 30, upon receipt of the
retransmission request.
[0063] Furthermore, the transmission controller unit 17 is
configured to instruct the transmission data generator unit 11 to
transmit transmission data to be transmitted next, upon receipt of
transmission acknowledgement information (ACK) from the receiver
apparatus 30.
[0064] The receiver apparatus 30 according to this embodiment
includes a demodulator 31, a deinterleaver 32, an error correction
decoder unit 33, a second CRC checker unit 41, a connector unit 34,
a first CRC checker unit 42, and a received data acquirer unit
36.
[0065] The demodulator 31 is configured to demodulate a signal
received through the antenna, and to acquire and output received
data (a bit sequence).
[0066] The deinterleaver 32 is configured to perform deinterleaving
processing for the received data outputted from the demodulator 31
according to a rule opposite to that adopted by the interleaver 15
described above.
[0067] The error correction decoder unit 33 is configured to divide
the received data on which the deinterleaving processing has been
performed into multiple encoded bit sequences (#A1 to #A9 in the
examples shown in FIGS. 4 to 6), and to perform error correction
decoding processing for the divided encoded bit sequences (#A1 to
#A9 in the examples shown in FIGS. 4 to 6).
[0068] The second CRC checker unit 41 is configured to perform
error detection processing (i.e., checking processing of the second
CRC code) using the second CRC code added to one or more of the
encoded bit sequences on which the error correction decoding
processing has been performed.
[0069] Here, as described above, the second CRC code is added to
one of encoded bit sequences (#1 to #9 in the examples shown in
FIGS. 4 to 6) in at least one of the multiple groups (G1 to G3 in
the examples shown in FIGS. 4 to 6).
[0070] In this embodiment, as shown in FIG. 4, the second CRC code
is added to only the leading encoded bit sequence #1 in the leading
group G1 among the multiple groups G1 to G3.
[0071] The connector unit 34 is configured to connect the multiple
encoded bit sequences (#1 to #9 in the examples shown in FIGS. 4 to
6) described above, when no error is detected in the multiple
encoded bit sequences, and to acquire transmission data to which
the first CRC code has been added.
[0072] The first CRC checker unit 42 is configured to perform error
detection processing using the first CRC code added to the
transmission data described above. In other words, the first CRC
checker unit 42 is configured to check the first CRC code.
[0073] Note that the first CRC checker 42 is configured to transmit
a first retransmission request for a specific encoded bit sequence
in the error detection processing by the first CRC checker unit 42
to the transmitter apparatus 10, upon detection of an error in the
specific encoded bit sequence.
[0074] Moreover, the first CRC checker unit 42 is configured to
transmit a second retransmission request for a specific
transmission data in the error detection processing by the first
CRC checker 42 to the transmitter apparatus 10, upon detection of
an error in the specific transmission data.
[0075] The received data acquirer unit 36 is configured to acquire
the transmission data from the first CRC checker unit 42, and to
transfer the acquired transmission data to necessary functions in
the receiver apparatus 30.
[0076] With reference to FIG. 4, a description is given below of
operations of the radio communication system according to this
embodiment.
[0077] As shown in FIG. 4, in the transmitter apparatus 10, the
transmission data generator unit 11 generates transmission data (a
bit sequence). In Step S101, the first CRC adder unit 21 performs
error detection encoding processing using a CRC (Cyclic Redundant
Check) code and thus adds a first CRC code (a parity bit sequence)
to the transmission data (the bit sequence), in order to perform
error detection processing in ARQ processing.
[0078] In Step S102, the divider unit 13 divides the transmission
data (the bit sequence) to which the first CRC code (the parity bit
sequence) has been added into encoded bit sequences #1 to #9 in
units (bit size) for performing error correction encoding
processing.
[0079] In Step S103, the second CRC adder unit 22 selects the
leading encoded bit sequence #1 from among the divided multiple
encoded bit sequences #1 to #9, calculates a CRC code, and adds the
CRC code to the encoded bit sequence #1.
[0080] This is because, when a temporal variation in a radio path
is small relative to a data transmission time, errors are
considered to occur in almost all of the encoded bit sequences #1
to #9 rather than occurring in only one of the encoded bit
sequences.
[0081] In Step S104, the error correction encoder unit 14 performs
error correction encoding processing on the multiple encoded bit
sequences #1 to #9. As a result, encoded bit sequences #A1 to #A9
to which redundant bits have been added are obtained.
[0082] In Step S105, the interleaver 15 performs interleaving for
changing the order of the bit sequences in the transmission data
containing the encoded bit sequences #A1 to #A9 according to a
certain rule.
[0083] In Step S106, the modulator 16 digitally modulates
transmission data X (containing the encoded bit sequences #A1 to
#A9) outputted from the interleaver 15, and then transmits the
transmission data to a radio section.
[0084] Meanwhile, in the receiver apparatus 30, as shown in FIG. 4,
the demodulator 31 converts a received signal into received data (a
bit sequence) by demodulating the received signal in Step S201.
[0085] In Step S202, the deinterleaver 32 changes the order of the
bit sequences in the received data that is the output from the
demodulator 31 back to the original order of the bit sequences in
the transmission data X according to a rule opposite to that
adopted by the interleaver 15 in the transmitter apparatus 10.
[0086] In Step S203, the error correction decoder unit 33 divides
the received data (the bit sequences) outputted from the
deinterleaver 32 into encoded bit sequences #A1 to #A9 in units
that are the same as for the error correction encoding processing
in the transmitter apparatus 10, and then performs error correction
decoding processing.
[0087] In Step S204, when the error correction decoder unit 33
completes the error correction decoding processing for the leading
encoded bit sequence #1, the second CRC checker unit 41 immediately
performs error detection processing by determining whether or not
the CRC code added to the encoded bit sequence #1 is correct.
[0088] When an error is detected based on the result of the
determination on whether or not the CRC code is correct for the
leading encoded bit sequence #1, a first retransmission request
(NACK) is sent back to the transmitter apparatus 10.
[0089] When no error is detected based on the result of the
determination on whether or not the CRC code is correct for the
leading encoded bit sequence #1, the error correction decoder unit
33 keeps on performing decoding processing on all the other encoded
bit sequences #2 to #8.
[0090] In Step S205, when the error correction decoder unit 33
completes the decoding processing for all the encoded bit sequences
#1 to #9, the connector unit 34 reproduces the transmission data to
which the first CRC code has been added by connecting all the
encoded bit sequences #1 to #9.
[0091] In Step S206, the first CRC checker unit 42 again performs
error detection processing using the first CRC code, when the
transmission data described above is reproduced.
[0092] The first CRC checker unit 42 sends transmission
acknowledgement information (ACK) or a second retransmission
request (NACK) back to the transmitter apparatus 10, based on the
result of the error detection processing.
[0093] With the radio communication system according to this
embodiment, the receiver apparatus 30 is allowed to send back a
first retransmission request (NACK) without receiving all the
encoded bit sequences constituting the transmission data. Thus, the
radio communication system can reduce a delay time compared with
the conventional radio communication system.
Second Embodiment of the Invention
[0094] With reference to FIGS. 3 and 5, a radio communication
system according to a second embodiment of the present invention
will be described. The radio communication system according to this
embodiment will be described below mainly about a difference from
the radio communication system according to the first embodiment
described above.
[0095] In this embodiment, as shown in FIG. 5, the second CRC adder
unit 22 in the transmitter apparatus 10 is configured to add second
CRC codes to leading encoded bit sequences #1, #4 and #7 in the
respective groups G1 to G3.
[0096] The operation shown in FIG. 5 is the same as that shown in
FIG. 4 except for the point that the second CRC codes are added to
the leading encoded bit sequences #1, #4 and #7 in the respective
groups G1 to G3. Thus, a description for the operation shown in
FIG. 5 is omitted here.
Third Embodiment of the Invention
[0097] With reference to FIGS. 3 and 6, a radio communication
system according to a third embodiment of the present invention
will be described. The radio communication system according to this
embodiment will be described below mainly about a difference from
the radio communication systems according to the first and second
embodiments described above.
[0098] In this embodiment, as shown in FIG. 6, the second CRC adder
unit 22 in the transmitter apparatus 10 is configured to add second
CRC codes to encoded bit sequences #1, #5 and #9 in the respective
groups G1 to G3.
[0099] Specifically, in this embodiment, the second CRC adder unit
22 in the transmitter apparatus 10 is configured to add second CRC
codes to predetermined encoded bit sequences among the encoded bit
sequences #1 to #9 in the respective groups, the predetermined
encoded bit sequences being selected according to a rule prescribed
between the transmitter apparatus 10 and the receiver apparatus
30.
[0100] Note that the second CRC adder unit 22 in the transmitter
apparatus 10 may be configured not to add a second CRC code to an
encoded bit sequence in a specific group.
[0101] The operation shown in FIG. 6 is the same as that shown in
FIG. 4 except for the point that the second CRC codes are added to
the predetermined encoded bit sequences #1, #5 and #9 among the
encoded bit sequences #1 to #9 in the respective groups, the
predetermined encoded bit sequences being selected according to the
rule prescribed between the transmitter apparatus 10 and the
receiver apparatus 30. Thus, a description for the operation shown
in FIG. 6 is omitted here.
[0102] The present invention has been described above in detail
with regard to the embodiments. It is apparent to those skilled in
the art that the present invention is not limited to the
embodiments described herein. The present invention can be
implemented as modified and altered embodiments without departing
from the spirit and scope of the present invention defined in the
description of the claims. Therefore, the disclosure herein merely
aims at exemplary explanation, and is not intended to limit the
present invention in any way
[0103] The content of Japanese Patent Application No. 2007-213183
(filed on Aug. 17, 2007) is incorporated herein by reference in its
entirety.
INDUSTRIAL APPLICABILITY
[0104] Thus, a data transmission method, a data reception method, a
mobile terminal and a radio communication system according to the
present invention are useful, because a delay time required by a
receiver apparatus to detect an error and to return ACK/NACK to a
transmitter apparatus can be reduced as much as possible for more
real-time data transmission.
* * * * *