U.S. patent application number 12/441510 was filed with the patent office on 2009-10-29 for communication system, communication device, and data frame retransmission control method.
Invention is credited to Yasuhiro Nakamura, Toru Sahara, Nobuaki Takamatsu, Hironobu Tanigawa.
Application Number | 20090271680 12/441510 |
Document ID | / |
Family ID | 39183824 |
Filed Date | 2009-10-29 |
United States Patent
Application |
20090271680 |
Kind Code |
A1 |
Tanigawa; Hironobu ; et
al. |
October 29, 2009 |
COMMUNICATION SYSTEM, COMMUNICATION DEVICE, AND DATA FRAME
RETRANSMISSION CONTROL METHOD
Abstract
A mobile station device (12) includes a retransmission request
transmission timing identifying unit (40) which identifies, based
on a timing of reception of a data frame transmitted from a base
station device, a timing of transmission of a retransmission
request of the data frame to the base station device. The base
station device includes a retransmission data frame selecting unit
which selects, based on a timing of reception of the retransmission
request transmitted from the mobile station device (12), a data
frame to be retransmitted from among a plurality of data frames
transmitted to the mobile station device (12), and retransmits a
data frame selected by the retransmission data frame selecting unit
to the mobile station device (12).
Inventors: |
Tanigawa; Hironobu; (Tokyo,
JP) ; Nakamura; Yasuhiro; (Kanagawa, JP) ;
Takamatsu; Nobuaki; (Kanagawa, JP) ; Sahara;
Toru; (Kanagawa, JP) |
Correspondence
Address: |
MORRISON & FOERSTER LLP
12531 HIGH BLUFF DRIVE, SUITE 100
SAN DIEGO
CA
92130-2040
US
|
Family ID: |
39183824 |
Appl. No.: |
12/441510 |
Filed: |
September 13, 2007 |
PCT Filed: |
September 13, 2007 |
PCT NO: |
PCT/JP2007/067812 |
371 Date: |
June 5, 2009 |
Current U.S.
Class: |
714/748 ;
714/E11.113 |
Current CPC
Class: |
H04L 1/1854 20130101;
H04L 1/08 20130101 |
Class at
Publication: |
714/748 ;
714/E11.113 |
International
Class: |
H04L 1/18 20060101
H04L001/18; G06F 11/14 20060101 G06F011/14 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 15, 2006 |
JP |
2006-251772 |
Sep 15, 2006 |
JP |
2006-251773 |
Sep 15, 2006 |
JP |
2006-251774 |
Claims
1. A communication system having a transmitting device and a
receiving device which employ an automatic repeat request method of
a data frame, wherein the receiving device comprises retransmission
request transmission timing identifying means for identifying,
based on a timing of reception of a data frame transmitted from the
transmitting device, a timing of transmission of a retransmission
request of the data frame to the transmitting device, the
transmitting device comprises retransmission data frame selecting
means for selecting, based on a timing of reception of the
retransmission request transmitted from the receiving device, a
data frame to be retransmitted from among a plurality of data
frames transmitted to the receiving device, and retransmits the
data frame selected by the retransmission data frame selecting
means to the receiving device.
2. The communication system according to claim 1, wherein the
transmitting device further comprises transmitted data frame
storage means for storing at least some of the plurality of data
frames transmitted to the receiving device in a manner to allow
identification of a timing of transmission of each of the data
frames, and the retransmission data frame selecting means
identifies a timing of transmission of the data frame to be
retransmitted based on the timing of reception of the
retransmission request and selects the data frame to be
retransmitted from the transmitted data frame storage means based
on the identified timing.
3. The communication system according to claim 1, wherein the
communication system further employs a time division multiplex
communication system, and the timing is identified by a time slot
or a time frame according to time division multiplexing.
4. A receiving device which receives a data frame transmitted from
a transmitting device and which transmits, upon detection of an
error in the received data frame, a retransmission request of the
data frame to the transmitting device, the receiving device
comprising: retransmission request transmission timing identifying
means for identifying, based on a timing of reception of the data
frame, a timing of transmission of the retransmission request of
the data frame.
5. A transmitting device which transmits a data frame to a
receiving device and which retransmits, in response to a
retransmission request from the receiving device, a data frame
corresponding to the retransmission request, the transmitting
device comprising: retransmission data frame selecting means for
selecting, based on a timing of reception of the retransmission
request, a data frame to be retransmitted from among a plurality of
data frames transmitted to the receiving device, and retransmits a
data frame selected by the retransmission data frame selecting
means to the receiving device.
6. A data frame retransmission control method in a communication
system having a transmitting device and a receiving device, the
data frame retransmission control method comprising: a
retransmission request transmission timing identifying step of
identifying, based on a timing at which the receiving device
receives a data frame transmitted from the transmitting device, a
timing of transmission of a retransmission request of the data
frame to the transmitting device, and a retransmission data frame
selecting step of selecting, based on a timing at which the
transmitting device receives the retransmission request, a data
frame to be retransmitted from among a plurality of data frames
transmitted to the receiving device.
7. A communication device which communicates with another
communication device according to a time division duplex system and
which retransmits, in response to a retransmission request
transmitted from the other communication device, a data frame
corresponding to the retransmission request to the other
communication device, the communication device comprising: data
frame retransmission timing determining means for determining a
retransmission timing of the data frame based on a reception timing
of the retransmission request so that a timing difference between
the reception timing of the retransmission request and the
retransmission timing of the data frame corresponding to the
retransmission request is close to a reference required time
required from reception of a retransmission request to
retransmission of a data frame.
8. The communication device according to claim 7, further
comprising: timing difference information storage means for
storing, in correlation to information indicating a reception
timing of a retransmission request, timing difference information
indicating a timing difference which satisfies a condition related
to the reference required time, wherein the data frame
retransmission timing determining means reads timing difference
information from the timing difference information storage means in
correlation to the reception timing of the retransmission request
and determines the retransmission timing of the data frame based on
the reception timing of the retransmission request and the read
timing difference information.
9. A communication device which communicates with another
communication device according to a time division duplex system and
which retransmits, in response to a retransmission request
transmitted from the other communication device, a data frame
corresponding to the retransmission request to the other
communication device, the communication device comprising: data
frame retransmission timing determining means for determining a
retransmission timing of the data frame based on a processing
capability of the communication device so that a timing difference
between a reception timing of the retransmission request and the
retransmission timing of the data frame corresponding to the
retransmission request is close to a reference required time
required from reception of a retransmission request to
retransmission of a data frame.
10. The communication device according to claim 9, wherein the data
frame retransmission timing determining means determines the
retransmission timing of the data frame further based on the
reception timing of the retransmission request.
11. The communication device according to claim 10, further
comprising: timing difference information storage means for
storing, in correlation to information indicating a processing
capability of a communication device and information indicating a
reception timing of a retransmission request, timing difference
information indicating a timing difference which satisfies a
condition related to the reference required time, wherein the data
frame retransmission timing determining means reads the timing
difference information from the timing difference information
storage means in correlation to the processing capability of the
communication device and the reception timing of the retransmission
request and determines the retransmission timing based on the
reception timing of the retransmission request and the read timing
difference information.
12. The communication device according to claim 7, wherein the
reception timing is identified by a reception slot, and the
retransmission timing is identified by a transmission slot or a
transmission frame including the transmission slot.
13. A data frame retransmission method in which a data frame is
retransmitted in response to a retransmission request in a
communication according to a time division duplex system, the data
frame retransmission method comprising: a step of determining a
retransmission timing of the data frame based on a reception timing
of the retransmission request so that a timing difference between
the reception timing of the retransmission request and the
retransmission timing of the data frame corresponding to the
retransmission request is close to a reference required time
required from reception of a retransmission request to
retransmission of a data frame.
14. A data frame retransmission method in which a data frame is
retransmitted in response to a retransmission request in a
communication according to a time division duplex system, the data
frame retransmission method comprising: a step of determining a
retransmission timing of the data frame based on a processing
capability of the communication device so that a timing difference
between a reception timing of the retransmission request and the
retransmission timing of the data frame corresponding to the
retransmission request is close to a reference required time
required from reception of a retransmission request to
retransmission of a data frame.
15. The communication system according to claim 2, wherein the
communication system further employs a time division multiplex
communication system, and the timing is identified by a time slot
or a time frame according to time division multiplexing.
16. The communication device according to claim 8, wherein the
reception timing is identified by a reception slot, and the
retransmission timing is identified by a transmission slot or a
transmission frame including the transmission slot.
17. The communication device according to claim 9, wherein the
reception timing is identified by a reception slot, and the
retransmission timing is identified by a transmission slot or a
transmission frame including the transmission slot.
18. The communication device according to claim 10, wherein the
reception timing is identified by a reception slot, and the
retransmission timing is identified by a transmission slot or a
transmission frame including the transmission slot.
19. The communication device according to claim 11, wherein the
reception timing is identified by a reception slot, and the
retransmission timing is identified by a transmission slot or a
transmission frame including the transmission slot.
Description
TECHNICAL FIELD
[0001] The present invention relates to a communication system, a
communication device, and a data frame retransmission control
method.
BACKGROUND ART
[0002] In an ARQ (Automatic Repeat Request) method which is one of
error correction methods, when there is an error in a received data
frame, the receiving side transmits a retransmission request of the
data frame to the transmitting side. The transmitting side
identifies the data frame to be retransmitted based on the received
retransmission request, and retransmits the data frame to the
receiving side. The retransmission request includes a sequence
number (order number) for identifying the data frame to be
retransmitted, and the transmitting side identifies the requested
data frame based on the sequence number and retransmits the
requested data frame (for example, refer to Patent Document 1).
[0003] For improving the error correction efficiency in the ARQ
method, it is effective to reduce the number of retransmissions of
the data frame, reduce the time period from reception of the
retransmission request to retransmission of the data frame, etc. In
this regard, Patent Document 2 discloses a wireless transmitting
device to which a hybrid ARQ is applied wherein the number of
retransmissions of the data frame is reduced so that the system
throughput is improved.
[Patent Document 1] JP 10-117182 A
[Patent Document 2] JP 2004-253828 A
DISCLOSURE OF THE INVENTION
[0004] However, in the ARQ method of the related art as described
above, the data size of the retransmission request is enlarged
corresponding to the number of bits of the sequence number. In
particular, when communication data and other data are transmitted
along with the retransmission request, it is desired that the
number of bits assigned to the retransmission request be reduced so
that more number of bits can be assigned to the communication data
or the like.
[0005] In addition, because a certain processing time (hereinafter
referred to as "reference required time") is required from the
reception of the retransmission request to the retransmission of
the data frame, it may become difficult to retransmit the data
frame using the transmission frame immediately following the frame
in which the retransmission request is received, particularly in a
communication according to a TDMA/TDD (Time Division Multiple
Access/Time Division Duplex) system. Because of this, in the ARQ of
the related art applied to the TDMA/TDD system, in order to secure
a sufficient time for the retransmission process of the data frame,
the data frame is uniformly retransmitted using the transmission
frame of two or more frames later than the frame in which the
retransmission request is received. As a result, there is a problem
in that a retransmission delay of greater than or equal to 1 TDMA
frame always occurs when there is an error in the data frame.
[0006] The present invention was conceived in view of the
above-described problem of the related art, and a first object is
to provide a communication system, a receiving device, a
transmitting device, and a data frame retransmission control method
which can achieve an automatic retransmission control of the data
frame without including the sequence number of the data frame in
the retransmission request.
[0007] A second object is to provide a communication device and a
data frame retransmission method which can preferably shorten the
time from the reception of the retransmission request to the
retransmission of the data frame.
[0008] In order to achieve the first object, a communication system
according to the present invention is a communication system having
a transmitting device and a receiving device which employ an
automatic repeat request method of a data frame, wherein the
receiving device includes retransmission request transmission
timing identifying means for identifying, based on a timing of
reception of a data frame transmitted from the transmitting device,
a timing of transmission of a retransmission request of the data
frame to the transmitting device, the transmitting device includes
retransmission data frame selecting means for selecting, based on a
timing of reception of the retransmission request transmitted from
the receiving device, a data frame to be retransmitted from among a
plurality of data frames transmitted to the receiving device, and
retransmits the data frame selected by the retransmission data
frame selecting means to the receiving device.
[0009] According to the present invention, the receiving device
identifies, based on a reception timing of a data frame
(transmission timing for the transmitting device), a response
timing (reception timing for the transmitting device) of the
retransmission request for the data frame. On the other hand, the
transmitting device identifies, based on the reception timing of
the retransmission request, the timing when the data frame
corresponding to the retransmission request was transmitted. In
other words, in this communication system, the receiving device and
the transmitting device share the timing difference (time interval)
between the transmission (reception) timing of the data frame and
the reception (transmission) timing of the retransmission request
for the data frame. Because of this configuration, even if the
sequence number of the data frame is omitted in the retransmission
request, the transmitting device can identify to which data frame
the received retransmission request corresponds.
[0010] The transmitting device may further include transmitted data
frame storage means for storing at least some of the plurality of
data frames transmitted to the receiving device in a manner to
allow identification of a timing of transmission of each of the
data frames, and the retransmission data frame selecting means may
identify a timing of transmission of the data frame to be
retransmitted based on the timing of reception of the
retransmission request and select the data frame to be
retransmitted from the transmitted data frame storage means based
on the identified timing.
[0011] The communication system may further employ a time division
multiplex communication system, and the timing may be identified by
a time slot or a time frame according to time division
multiplexing.
[0012] A receiving device according to the present invention is a
receiving device which receives a data frame transmitted from a
transmitting device and which transmits, upon detection of an error
in the received data frame, a retransmission request of the data
frame to the transmitting device, the receiving device including
retransmission request transmission timing identifying means for
identifying, based on a timing of reception of the data frame, a
timing of transmission of the retransmission request of the data
frame.
[0013] A transmitting device according to the present invention is
a transmitting device which transmits a data frame to a receiving
device and which retransmits, in response to a retransmission
request from the receiving device, a data frame corresponding to
the retransmission request, the transmitting device including
retransmission data frame selecting means for selecting, based on a
timing of reception of the retransmission request, a data frame to
be retransmitted from among a plurality of data frames transmitted
to the receiving device, and retransmits a data frame selected by
the retransmission data frame selecting means to the receiving
device.
[0014] A data frame retransmission control method according to the
present invention is a data frame retransmission control method in
a communication system having a transmitting device and a receiving
device, the data frame retransmission control method including a
retransmission request transmission timing identifying step of
identifying, based on a timing at which the receiving device
receives a data frame transmitted from the transmitting device, a
timing of transmission of a retransmission request of the data
frame to the transmitting device, and a retransmission data frame
selecting step of selecting, based on a timing at which the
transmitting device receives the retransmission request, a data
frame to be retransmitted from among a plurality of data frames
transmitted to the receiving device.
[0015] In order to achieve the second object, a communication
device according to the present invention is a communication device
which communicates with another communication device according to a
time division duplex system and which retransmits, in response to a
retransmission request transmitted from the other communication
device, a data frame corresponding to the retransmission request to
the other communication device, the communication device including
data frame retransmission timing determining means for determining
a retransmission timing of the data frame based on a reception
timing of the retransmission request so that a timing difference
between the reception timing of the retransmission request and the
retransmission timing of the data frame corresponding to the
retransmission request is close to a reference required time
required from reception of a retransmission request to
retransmission of a data frame.
[0016] According to the present invention, a retransmission timing
of a data frame is determined based on a reception timing of the
retransmission request so that the time from reception of the
retransmission request to the retransmission of the data frame is
close to a reference required time required for the retransmission
process of the data frame. Because of this configuration, it is
possible to preferably shorten the time from the reception of the
retransmission request to the retransmission of the data frame.
[0017] The communication device may further include timing
difference information storage means for storing, in correlation to
information indicating a reception timing of a retransmission
request, timing difference information indicating a timing
difference which satisfies a condition related to the reference
required time, wherein the data frame retransmission timing
determining means may read timing difference information from the
timing difference information storage means in correlation to the
reception timing of the retransmission request and determine the
retransmission timing of the data frame based on the reception
timing of the retransmission request and the read timing difference
information.
[0018] A communication device according to the present invention is
a communication device which communicates with another
communication device according to a time division duplex system and
which retransmits, in response to a retransmission request
transmitted from the other communication device, a data frame
corresponding to the retransmission request to the other
communication device, the communication device including data frame
retransmission timing determining means for determining a
retransmission timing of the data frame based on a processing
capability of the communication device so that a timing difference
between a reception timing of the retransmission request and the
retransmission timing of the data frame corresponding to the
retransmission request is close to a reference required time
required from reception of a retransmission request to
retransmission of a data frame.
[0019] According to the present invention, the retransmission
timing of the data frame is determined in consideration of the
processing capability of the communication device so that the time
from reception of the retransmission request to the retransmission
of the data frame is close to the reference required time required
for retransmission process of the data frame. Because of this
configuration, it is possible to preferably shorten the time from
the reception of the retransmission request to the retransmission
of the data frame.
[0020] The data frame retransmission timing determining means may
determine the retransmission timing of the data frame further based
on the reception timing of the retransmission request. With such a
configuration, it is possible to determine the retransmission
timing of the data frame further based on, in addition to the
processing capability of the communication device, the reception
timing of the retransmission request. Thus, it is possible to more
preferably shorten the time from the reception of the
retransmission request to the retransmission of the data frame.
[0021] The communication device may further include timing
difference information storage means for storing, in correlation to
information indicating a processing capability of a communication
device and information indicating a reception timing of a
retransmission request, timing difference information indicating a
timing difference which satisfies a condition related to the
reference required time, wherein the data frame retransmission
timing determining means may read the timing difference information
from the timing difference information storage means in correlation
to the processing capability of the communication device and the
reception timing of the retransmission request and determine the
retransmission timing based on the reception timing of the
retransmission request and the read timing difference
information.
[0022] The reception timing may be identified by a reception slot,
and the retransmission timing may be identified by a transmission
slot or a transmission frame including the transmission slot.
[0023] A data frame retransmission method according to the present
invention is a data frame retransmission method in which a data
frame is retransmitted in response to a retransmission request in a
communication according to a time division duplex system, the data
frame retransmission method including a step of determining a
retransmission timing of the data frame based on a reception timing
of the retransmission request so that a timing difference between
the reception timing of the retransmission request and the
retransmission timing of the data frame corresponding to the
retransmission request is close to a reference required time
required from reception of a retransmission request to
retransmission of a data frame.
[0024] A data frame retransmission method according to the present
invention is a data frame retransmission method in which a data
frame is retransmitted in response to a retransmission request in a
communication according to a time division duplex system, the data
frame retransmission method including a step of determining a
retransmission timing of the data frame based on a processing
capability of the communication device so that a timing difference
between a reception timing of the retransmission request and the
retransmission timing of the data frame corresponding to the
retransmission request is close to a reference required time
required from reception of a retransmission request to
retransmission of a data frame.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is an overall configuration diagram of a mobile
communication system according to a first embodiment of the present
invention.
[0026] FIG. 2 is a functional block diagram of a mobile station
device according to the first embodiment of the present
invention.
[0027] FIG. 3 is a functional block diagram of a base station
device according to the first embodiment of the present
invention.
[0028] FIG. 4 is a diagram showing an example of a time slot
structure according to TDMA/TDD and a subchannel structure
according to OFDMA.
[0029] FIG. 5 is a diagram showing an example of a PHY frame
structure in an uplink.
[0030] FIG. 6 is a diagram for explaining a transmission timing of
a retransmission request.
[0031] FIG. 7 is a flowchart showing a data frame transmission (and
retransmission) process in the base station device.
[0032] FIG. 8 is a flowchart showing an error correction process of
a received data frame in the mobile station device.
[0033] FIG. 9 is an overall configuration diagram of a mobile
communication system according to a second embodiment of the
present invention.
[0034] FIG. 10 is a functional block diagram of a mobile station
device according to the second embodiment of the present
invention.
[0035] FIG. 11 is a diagram showing an example of a timing
difference information storage unit.
[0036] FIG. 12 is a diagram showing an example of a time slot
structure according to TDMA/TDD and a subchannel structure
according to OFDMA.
[0037] FIG. 13 is a diagram for explaining a retransmission timing
of a data frame.
[0038] FIG. 14 is a flowchart showing a process for acquiring
timing difference information in the mobile station device.
[0039] FIG. 15 is a flowchart showing a data frame transmission
(and retransmission) process in the mobile station device.
[0040] FIG. 16 is an overall configuration diagram of a mobile
communication system according to a third embodiment of the present
invention.
[0041] FIG. 17 is a functional block diagram of a mobile station
device according to the third embodiment of the present
invention.
[0042] FIG. 18 is a diagram showing an example of a timing
difference information storage unit.
[0043] FIG. 19 is a diagram showing an example of a time slot
structure according to TDMA/TDD and a subchannel structure
according to OFDMA.
[0044] FIG. 20 is a diagram for explaining a retransmission timing
of a data frame.
[0045] FIG. 21 is a flowchart showing a process for acquiring
timing difference information in the mobile station device.
[0046] FIG. 22 is a flowchart showing a data frame transmission
(and retransmission) process in the mobile station device.
BEST MODE FOR CARRYING OUT THE INVENTION
[0047] Embodiments of the present invention will now be described
in detail with reference to the drawings.
First Embodiment
[0048] FIG. 1 is an overall configuration diagram of a mobile
communication system according to a first embodiment of the present
invention. As shown in FIG. 1, the mobile communication system 1
includes a base station device 10 and a plurality of mobile station
devices 12 (here, three mobile station devices).
[0049] Each of the mobile station devices 12 wirelessly
communicates with the base station device 10, and may be, for
example, a portable cellular phone, a personal digital assistant,
or a communication card. In this configuration, the mobile station
device 12 transmits and receives data to and from the base station
device 10 according to a TDD (Time Division Duplex) system and
executes a multiplex communication according to a TDMA (Time
Division Multiple Access) system and an OFDMA (Orthogonal Frequency
Division Multiple Access) system. In addition, the base station
device 10 includes an adaptive array antenna as will be described
below, and executes a multiplex communication with each of the
plurality of mobile station devices 12 at a same time slot and a
same carrier frequency according to an SDMA (Space Division
Multiple Access) system using the adaptive array antenna. In this
manner, a bidirectional communication with the plurality of mobile
station devices 12 is executed with a very high frequency usage
efficiency.
[0050] FIG. 4 is a diagram showing an example of a time slot
structure (1 TDMA frame) according to TDMA/TDD and a subchannel
structure according to OFDMA. As shown in FIG. 4, each of a
downlink (wireless transmission path from the base station device
10 to the mobile station device 12) and an uplink (wireless
transmission path from the mobile station device 12 to the base
station device 10) includes 4 time slots. Each time slot includes
28 subchannels, one of which is used as a control channel (CCH) and
the remaining 27 of which are used as traffic channels (TCH).
[0051] The base station device 10 assigns at least some of a total
of 108 subchannels (27 subchannels.times.4 slots) used as the
traffic channels to each of the mobile station devices 12 in each
of the downlink and the uplink. More specifically, as shown in FIG.
4, the base station device 10 assigns one anchor subchannel (ASCH)
and assigns one or a plurality of extra subchannels (ESCH) as
necessary, for each mobile station device 12.
[0052] The ASCH is a subchannel which is determined when a link is
established (at the start of communication) and notified to each of
the mobile station devices 12 using the CCH, and is used for
transmitting and receiving MAP information and other control
information. The MAP information is a bit sequence having a length
of 108 bits indicating one or a plurality of ESCH to be used in the
next TDMA frame (next uplink frame and downlink frame) after the
MAP information is received. More specifically, a bit corresponding
to ESCH to be assigned to the mobile station device 12 in the next
TDMA frame is indicated with "1" and bits corresponding to the
other subchannels (ASCH, ESCH to be assigned to other mobile
station devices 12, and idle subchannel) are indicated with "0".
The ESCH, on the other hand, is a subchannel which is determined
after the link is established and is identified by the MAP
information notified to the mobile station device 12 using the
ASCH, and is primarily used for transmission and reception of
communication data. As shown in FIG. 4, the ASCH and ESCH are
assigned to the same subchannel in the downlink slot and the uplink
slot having corresponding slot numbers (DL#1 and UL#1, DL#2 and
UL#2, . . . ).
[0053] FIG. 5 is a diagram showing an example of a PHY (Physical
Layer) frame structure in the uplink. Data of 1 PHY frame is
transmitted in 1 TDMA frame. More specifically, the data of 1 PHY
frame is distributed over SCH (Subchannel) payloads corresponding
to one ASCH and one or a plurality of ESCH in each TDMA frame and
is transmitted. As shown in FIG. 5, the PHY frame includes a PHY
header including ACKCH, RMAP, etc., and a plurality of PHY data
units including PHY payload, etc. In the present embodiment, a data
frame to be retransmitted indicates the PHY frame, and the
retransmission of the PHY frame is controlled using a hybrid ARQ
method.
[0054] In this configuration, the ACKCH (Acknowledge Channel) is a
region which stores ACK (Acknowledge) or NACK (Negative
Acknowledge) indicating presence or absence of error in the data
frame received in downlink. In particular, when the ACKCH stores
NACK, the ACKCH represents a retransmission request of a data
frame. A characteristic of the present embodiment is that ARQ is
achieved without including the sequence number of the data frame in
the retransmission request and that, as a result, the PHY header
size can be reduced.
[0055] The RMAP (Refuse MAP) is a region which stores RMAP
information having a same size as the MAP information. The RMAP
information is a bit sequence having a length of 108 bits
indicating the ESCH refusing the assignment from the base station
device 10 in the next TDMA frame. More specifically, the RMAP
information is a bit sequence having a length of 108 bits
indicating the ESCH refusing the assignment from the base station
device 10 in the next TDMA frame, and indicates a bit corresponding
to the ESCH refusing the assignment with "1" and the other bits
with "0".
[0056] Configurations and operations of the base station device 10
and the mobile station device 12 will now be described.
[0057] FIG. 2 is a functional block diagram of the mobile station
device 12. As shown in FIG. 2, the mobile station device 12
includes an antenna 20, a wireless communication unit 22, a signal
processor 24, a modulation/demodulation unit 26, a maximum ratio
combining unit 28, a receive buffer 30, an error correcting unit
32, an error detecting unit 34, and a retransmission request
transmission controller 36.
[0058] The wireless communication unit 22 includes a low noise
amplifier, a down-converter, and an up-converter. The wireless
communication unit 22 down-converts a wireless signal from the base
station device 10 received by the antenna 20 and outputs to the
signal processor 24. The wireless communication unit 22 also
up-converts a transmission signal which is input from the signal
processor 24 into a wireless signal, amplifies the wireless signal
to a transmission power level, and transmits from the antenna
20.
[0059] The signal processor 24 executes processes such as symbol
synchronization and removal of a guard interval (GI) signal on the
signal which is input from the wireless communication unit 22, to
acquire a baseband OFDM signal, and outputs to the
modulation/demodulation unit 26. The signal processor 24 also adds
a guard interval signal to a baseband OFDM signal which is input
from the modulation/demodulation unit 26 and outputs to the
wireless communication unit 22.
[0060] The modulation/demodulation unit 26 includes an A/D
converter, an FFT unit, and a channel estimation unit. The
modulation/demodulation unit 26 OFDM-demodulates the baseband OFDM
signal which is input from the signal processor 24 and outputs the
acquired received data frame (data corresponding to 1 downlink
frame) to the maximum ratio combining unit 28. More specifically,
after the modulation/demodulation unit 26 A/D-converts the baseband
OFDM signal, the modulation/demodulation unit 26 applies an FFT in
the FFT unit, to acquire subcarrier components of the OFDM symbol.
After the modulation/demodulation unit 26 applies a predetermined
channel estimation process or the like, the modulation/demodulation
unit 26 connects the subcarrier components corresponding to a
plurality of subchannels (one ASCH and one or a plurality of ESCH)
assigned by the base station device 10, to create a symbol
sequence. The modulation/demodulation unit 26 then outputs the
symbol sequence to the maximum ratio combining unit 28.
[0061] The modulation/demodulation unit 26 also includes a symbol
mapping unit, an IFFT unit, and a D/A converter. The
modulation/demodulation unit 26 OFDM-modulates a transmission data
which is input from an external connection device or data input
unit (not shown) and outputs the acquired baseband OFDM signal to
the signal processor 24. More specifically, the
modulation/demodulation unit 26 distributes the transmission data
over a plurality of PHY payloads, and adds a PHY header including
ACKCH which stores ACK or NACK which is input from the
retransmission request transmission controller 36 to a PHY data
unit acquired by combining the PHY payloads, to construct a
predetermined PHY frame. Then, the modulation/demodulation unit 26
divides the data corresponding to the PHY frame to SCH payloads
corresponding to a plurality of subchannels (one ASCH and one or a
plurality of ESCH) assigned by the base station device 10, to
create transmission data for each subchannel. During this process,
the data sequence including the ACKCH is assigned to the SCH
payload corresponding to the ASCH. Then, the
modulation/demodulation unit 26 converts the created transmission
data of each of the subchannels into a symbol sequence through a
symbol mapping and distributes the symbol sequence over subcarriers
of the subchannel. The modulation/demodulation unit 26 then applies
an IFFT in the IFFT unit and outputs the baseband OFDM signal
acquired through a D/A conversion to the signal processor 24.
[0062] The maximum ratio combining unit 28 maximum-ratio combines a
symbol sequence created from the received data frame which is input
from the modulation/demodulation unit 26 and a symbol sequence
created from past received data frame which is input from the
receive buffer 30, and is provided for improving an error
correction percentage of the received data in the error correcting
unit 32. The symbol sequence created from the past received data
frame is read from the receive buffer 30 based on the sequence
number of the received data frame which is input from the
modulation/demodulation unit 26.
[0063] The receive buffer 30 stores a symbol sequence which is
input from the maximum ratio combining unit 28 in correlation to
the sequence number of the received data frame. The symbol sequence
for which no error is detected by the error detecting unit 34 is
deleted from the receive buffer 30 at a predetermined timing.
[0064] The error correcting unit 32 applies an extraction of a bit
sequence and an error correction with a predetermined error
correction algorithm, on the symbol sequence which is input from
the maximum ratio combining unit 28. If an error is not corrected
in the error correcting unit 32, the error is detected by the error
detecting unit 34 which is at downstream of the error correcting
unit 32.
[0065] The error detecting unit 34 detects whether or not there is
a data error in the data after error correction which is input from
the error correcting unit 32. The error detecting unit 34 outputs,
as the received data, only the data for which no error is detected
to the external connection device (not shown). The data for which
an error is detected is set as a target of the retransmission
request, and the data is not output to the external connection
device until the correct data frame is retransmitted from the base
station device 10. A detection result by the error detecting unit
34 is output to the retransmission request transmission controller
36. As the method of detecting error, for example, CRC (Cyclic
Redundancy Check) is employed.
[0066] The retransmission request transmission controller 36
includes a data frame reception timing acquiring unit 38, a
retransmission request transmission timing identifying unit 40, and
a timing difference information storage unit 42, and creates ACK or
NACK based on the error detection result which is input from the
error detecting unit 34. The retransmission request transmission
controller 36 applies a control to transmit the created ACK or NACK
to the base station device 10 at a predetermined timing without
adding the sequence number of the data frame. More specifically,
the retransmission request transmission controller 36 creates ACK
when no error is detected in the error detecting unit 34 and
creates NACK when an error is detected. The retransmission request
transmission controller 36 outputs the created ACK or NACK to the
modulation/demodulation unit 26 so that the created ACK or NACK is
transmitted at a timing identified by the retransmission request
transmission timing identifying unit 40 to be described later.
[0067] The data frame reception timing acquiring unit 38 acquires a
reception timing of each received data frame acquired by the
modulation/demodulation unit 26. The reception timing may be
identified by the downlink slot or the downlink frame when the data
frame is received, and information on which of the downlink slot or
the downlink frame is to be used as the reception timing is shared
between each mobile station device 12 and the base station device
10 in advance.
[0068] The timing difference information storage unit 42 stores
timing difference information indicating a timing difference (time
interval) between the reception timing of the data frame and the
transmission timing of the retransmission request for the data
frame. The timing difference information may be time or may be the
number of TDMA slots or the number of TDMA frames, and is same
information as timing difference information stored in a timing
difference information storage unit 66 of the base station device
10. In other words, the timing difference between the reception
(transmission) timing of the data frame and the transmission
(reception) timing of the retransmission request for the data frame
is shared between each mobile station device 12 and the base
station device 10 in advance. The timing difference information may
be defined in the mobile communication system 1 in advance or may
be determined between each mobile station device 12 and the base
station device 10 at the start of the communication.
[0069] The retransmission request transmission timing identifying
unit 40 identifies a timing of transmission of the retransmission
request of the data frame based on the timing of reception of the
data frame which is transmitted from the base station device 10.
More specifically, the retransmission request transmission timing
identifying unit 40 identifies the transmission timing of the ACK
or the NACK for the data frame based on the reception timing of the
data frame acquired by the data frame reception timing acquiring
unit 38 and the timing difference information (information
indicating a timing difference between reception timing of the data
frame and the transmission timing of the retransmission request for
the data frame) stored in the timing difference information storage
unit 42. The transmission timing may be identified by the uplink
slot or the uplink frame in which the ACK or the NACK is
transmitted, and information on which of the uplink slot and the
uplink frame is used as the transmission timing is shared between
each mobile station device 12 and the base station device 10 in
advance.
[0070] FIG. 6 is a diagram for explaining a transmission timing of
the retransmission request identified by the retransmission request
transmission timing identifying unit 40. Here, a case will be
described in which the timing difference information stored in the
timing difference information storage unit 42 is "1 TDMA frame
(frame after next frame)" and the ASCH for transmitting data
including ACKCH is the first slot. As shown in FIG. 6, when the
data frame reception timing acquiring unit 38 acquires the downlink
frame in which the data frame for which an error is detected is
received, the retransmission request transmission timing
identifying unit 40 identifies the uplink slot (here, the first
slot) of the "frame after the next frame" of the downlink frame as
the transmission timing of the retransmission request (NACK) for
the data frame.
[0071] Next, FIG. 3 is a block diagram of the base station device
10. As shown in FIG. 3, the base station device 10 includes an
adaptive array antenna 50, a wireless communication unit 52, a
signal processor 54, a modulation/demodulation unit 56, a data
buffer 58, and a data frame retransmission controller 62.
[0072] The adaptive array antenna 50 is an array of a plurality of
antennas. The adaptive array antenna 50 receives a wireless signal
transmitted from the mobile station devices 12 at the antennas and
outputs the received signal to the reception unit 22. The adaptive
array antenna 50 also transmits a signal which is input from the
wireless communication unit 52 through the antennas. The reception
and transmission are switched in a time divisional manner.
[0073] The wireless communication unit 52 includes a low noise
amplifier, a down-converter, and an up-converter. The wireless
communication unit 52 down-converts the wireless signal received by
the adaptive array antenna 50 and outputs to the signal processor
24. The wireless communication unit 52 also up-converts the
transmission signal which is input from the signal processor 24
into a wireless signal, amplifies the wireless signal to a
transmission power level, and supplies to the adaptive array
antenna 50.
[0074] The signal processor 54 includes a space division multiplex
processor and a time division multiplex processor. The signal
processor 54 acquires a baseband OFDM signal from a signal which is
input from the wireless communication unit 52 and outputs to the
modulation/demodulation unit 56. In other words, because space
division multiple access (SDMA), time division multiple access
(TDMA), and orthogonal frequency division multiple access (OFDMA)
are applied to the signal which is input from the wireless
communication unit 52, the signal processor 54 applies a space
division process related to a weight control of the adaptive array
antenna 50 and time division process on the signal. Then, the
signal processor 54 executes processes such as a symbol
synchronization and removal of guard interval signal on the
separated signal, and acquires the baseband OFDM signal. The
baseband OFDM signal acquired in this manner is output to the
modulation/demodulation unit 56.
[0075] The signal processor 54 also adds the guard interval signal
to the baseband OFDM signal which is input from the
modulation/demodulation unit 56, creates a signal to which the time
division multiplex process and the space division multiplex process
related to the weight control of the adaptive array antenna 50 are
applied, and outputs to the wireless communication unit 52.
[0076] The modulation/demodulation unit 56 includes an A/D
converter, an FFT unit, a channel estimation unit, and a de-mapping
unit. The modulation/demodulation unit 56 OFDM-demodulates the
baseband OFDM signal which is input from the signal processor 54
and outputs the acquired received data frame (data corresponding to
1 uplink frame) from each mobile station device 12 to the data
buffer 58. The modulation/demodulation unit 56 also includes a
symbol mapping unit, an IFFT unit, and a D/A converter. The
modulation/demodulation unit 56 OFDM-modulates a transmission data
frame (data corresponding to 1 downlink frame) which is input from
the data buffer 58 (a transmission queue 60), and outputs the
acquired baseband OFDM signal to the signal processor 54. The
contents of the process in the modulation/demodulation unit 56 are
approximately common with the contents of the processes in the
modulation/demodulation unit 26 in the mobile station device 12,
and, thus, will not be described here in detail.
[0077] The data buffer 58 includes the transmission queue 60. The
data buffer 58 temporarily stores the received data frames from the
mobile station devices 12 which are input from the
modulation/demodulation unit 56 and sequentially outputs received
data which is acquired by connecting the received data frames to a
predetermined upper device (not shown). The data buffer 58 also
temporarily stores transmission data frames to each of the mobile
station devices 12 which are input from the upper device and the
data frame retransmission controller 62 and sequentially outputs to
the modulation/demodulation unit 56 through the transmission queue
60.
[0078] The transmission queue 60 holds the transmission data frames
in a list structure of a First In First Out (FIFO) method. The
transmission data frame or the retransmission data frame which is
input from the data frame retransmission controller 62 is added to
the transmission queue 60 in each TDMA frame. In addition, the
first data frame in the transmission queue 60 is extracted in each
TDMA frame and is output to the modulation/demodulation unit
56.
[0079] The data frame retransmission controller 62 includes a
retransmission request acquiring unit 64, a timing difference
information storage unit 66, a transmission-complete queue
(transmitted data frame storage unit) 68, and a retransmission data
frame selecting unit 70. The data frame retransmission controller
62 controls, in response to a retransmission request transmitted
from each mobile station device 12, retransmission of the data
frame corresponding to the retransmission request.
[0080] The retransmission request acquiring unit 64 acquires, in
each TDMA frame, the ACKCH of the PHY header shown in FIG. 5 from
the received data which is output from the data buffer 58, and
acquires a reception timing of the data frame including the ACKCH.
The reception timing may be identified by a downlink slot or a
downlink frame in which the retransmission request is received, and
information on which timing is used as the reception timing is
shared between the base station device 10 and each mobile station
device 12 in advance.
[0081] The timing difference information storage unit 66 stores
timing difference information indicating a timing difference
between the transmission timing of the data frame and the reception
timing of the retransmission request for the data frame. The timing
difference information may be time or the number of TDMA slots or
the number of TDMA frames, and is the same information as the
timing difference information stored in the timing difference
information storage unit 42 of the mobile station device 12. In
other words, the timing difference between the transmission
(reception) timing of the data frame and the reception
(transmission) timing of the retransmission request for the data
frame is shared between the base station device 10 and each mobile
station device 12 in advance. Because of this configuration, the
base station device 10 can identify the timing of transmission of
the data frame corresponding to the ACK or the NACK based on the
reception timing of the ACK or the NACK even though the sequence
number of the received data frame is not added to the ACK or the
NACK transmitted from the mobile station device 12. The timing
difference information may be defined in the mobile communication
system 1 in advance or may be determined between the base station
device 10 and each mobile station device 12 at the start of the
communication.
[0082] The transmission-complete queue 68 holds at least some of
the plurality of data frames transmitted to the mobile station
devices 12 in a list structure of a First In First Out (FIFO)
method, and functions as a transmitted data frame storage unit. The
first data frame in the transmission queue 60 is transmitted in
each TDMA frame, and with the transmission, the data frame is
extracted from the transmission queue 60 and added to the
transmission-complete queue 68. In the transmission-complete queue
68, an upper limit is set in the number of transmitted data frames
to be held and the transmission-complete queue 68 is configured to
allow identification of the timing of transmission of each of the
data frames.
[0083] More specifically, the transmission-complete queue 68 has a
size corresponding to the timing difference information
(information indicating a timing difference between the
transmission timing of a data frame and a reception timing of the
retransmission request for the data frame) stored in the timing
difference information storage unit 66. For example, when the
timing difference information is "1 TDMA frame", the
transmission-complete queue 68 has a size to allow holding of 2
TDMA frames acquired by adding 1 TDMA frame to the timing
difference information, that is, the transmission-complete queue 68
has a size to allow holding of a maximum of two transmitted data
frames. Similarly, when the timing difference information is 2 TDMA
frames, the transmission-complete queue 68 has a size to allow
holding of a maximum of three transmitted data frames. With this
configuration, the ACKCH acquired by the retransmission request
acquiring unit 64 in each TDMA frame would correspond to the first
data frame in the transmission-complete queue 68 at the timing of
reception of the ACKCH.
[0084] Because of this, when the NACK is stored in the ACKCH
acquired by the retransmission request acquiring unit 64, the first
data frame is extracted from the transmission-complete queue 68 as
the retransmission data frame and is added to the transmission
queue 60. When, on the other hand, the ACK is stored in the ACKCH,
the first data frame does not need to be retransmitted and is
deleted.
[0085] In this configuration, the transmission-complete queue 68 is
used as the transmitted data frame storage unit, but the
transmitted data frame storage unit does not need to have the queue
structure, and it is sufficient that the transmitted data frame
storage unit stores at least some of the plurality of data frames
transmitted to the mobile station devices 12 in a manner to allow
identification of the timing of transmission of each of the data
frames. For example, it is possible to store the transmitted data
frame in correlation to an identification number of the TDMA frame
in which the data frame was transmitted.
[0086] The retransmission data frame selecting unit 70 selects,
based on a reception timing of the retransmission request
transmitted from a mobile station device 12, a data frame to be
retransmitted from among the plurality of data frames transmitted
to the mobile station device 12. More specifically, based on the
timing of reception of the ACKCH from the mobile station device 12
acquired by the retransmission request acquiring unit 64 and the
timing difference information (information indicating the timing
difference between the transmission timing of the data frame and
the reception timing of the retransmission request for the data
frame) stored in the timing difference information storage unit 66,
the retransmission data frame selecting unit 70 identifies the
transmission timing of the data frame corresponding to the ACKCH.
Based on the identified transmission timing, the retransmission
data frame selecting unit 70 selects, from among the plurality of
data frames transmitted in the past to the mobile station device
12, the data frame transmitted at the identified timing from the
transmission-complete queue 68.
[0087] As described above, in the present embodiment, because the
transmission-complete queue 68 has a size corresponding to the
timing difference information stored in the timing difference
information storage unit 66, the ACKCH acquired in each TDMA frame
by the retransmission request acquiring unit 64 corresponds to the
first data frame in the transmission-complete queue 68 at the
timing of reception of the ACKCH. Because of this configuration,
when the NACK is stored in the ACKCH, the retransmission data frame
selecting unit 70 selects (extracts) the first data frame as the
retransmission data frame from the transmission-complete queue 68
and adds to the transmission queue 60. When, on the other hand, the
ACK is stored in the ACKCH, the retransmission data frame selecting
unit 70 deletes the first data frame for which no retransmission is
required from the transmission-complete queue 68.
[0088] Next, an operation of the base station device 10 will be
described. FIG. 7 is a flowchart showing a data frame transmission
(and retransmission) process in the base station device 10.
[0089] As shown in FIG. 7, first, in a downlink frame, a data frame
including a transmission packet received from an upper device is
stored in the data buffer 58 (S100). The data frame is added to the
transmission queue 60 (S102). Then, the first data frame is
extracted from the transmission queue 60 and is converted to a
transmission signal, and the transmission signal is transmitted to
the mobile station device 12 (S104). The transmitted data frame is
added to the transmission-complete queue 68 (S106).
[0090] Then, in an uplink frame, received data from the mobile
station device 12 is acquired. The retransmission request acquiring
unit 64 acquires the ACKCH from the PHY header in the received data
and determines whether the value stored in the ACKCH is ACK or NACK
(S108). When the value is ACK, the retransmission data frame
selecting unit 70 deletes the first data frame from the
transmission-complete queue 68 (S110). Then, it is determined
whether or not the data transmission is completed (S112), and, if
the transmission is not completed, the processes from S102 are
executed in the next downlink frame.
[0091] When, on the other hand, it is determined in S108 that the
value stored in the ACKCH is NACK, the retransmission data frame
selecting unit 70 extracts the first data frame from the
transmission-complete queue 68 as a retransmission data frame
(S114) and adds to the transmission queue 60 (S116). Then, the
processes from S104 are executed in the next downlink frame.
[0092] Next, the operation of the mobile station device 12 will be
described. FIG. 8 is a flowchart showing an error correction
process of the received data frame in the mobile station device
12.
[0093] First, in a downlink frame, a data frame is received from
the base station device 10 (S200). Then, the maximum ratio
combining unit 28 maximum-ratio combines the symbol sequence
created from the received data frame which is input from the
modulation/demodulation unit 26 and the symbol sequence which is
read from the receive buffer 30 based on the sequence number of the
received data frame (S202). The combined symbol sequence is stored
in the receive buffer 30 in correlation to the sequence number of
the received data frame (S204). The combined symbol sequence is
converted to a bit sequence in the error correcting unit 32 and an
error correction is applied (S206).
[0094] Next, the error detecting unit 34 determines whether or not
there is a data error in the data after error correction which is
input from the error correcting unit 32 (S208) and outputs the
detection result to the retransmission request transmission
controller 36. When no data error is detected, the retransmission
request transmission timing identifying unit 40 identifies a
transmission timing of the ACK for the received data frame based on
the reception timing of the received data frame acquired by the
data frame reception timing acquiring unit 38 and the timing
difference information stored in the timing difference information
storage unit 42 (S210). The retransmission request transmission
controller 36 then outputs the ACK to the modulation/demodulation
unit 26 such that the ACK is transmitted at a timing identified in
S210 (for example, the uplink frame after the next uplink frame).
The ACK which is input to the modulation unit 26 is stored in the
ACKCH of the PHY header without the sequence number of the data
frame and is transmitted (S212). Then, the retransmission request
transmission controller 36 deletes the received data frame
corresponding to the ACK from the receive buffer 30 (S214).
[0095] When, on the other hand, a data error is detected in S208,
the retransmission request transmission timing identifying unit 40
identifies the transmission timing of the NACK for the received
data frame based on the reception timing of the received data frame
acquired by the data frame reception timing acquiring unit 38 and
the timing difference information stored in the timing difference
information storage unit 42 (S216). The retransmission request
transmission controller 36 outputs the NACK to the
modulation/demodulation unit 26 such that the NACK is transmitted
at the timing identified in S216 (for example, the uplink frame
following the next uplink frame). The NACK which is input to the
modulation unit 26 is stored in the ACKCH of the PHY header without
the sequence number of the data frame and is transmitted
(S218).
[0096] According to the above-described embodiment, because the
base station device 10 and the mobile station device 12 share the
timing difference (time interval) between the transmission
(reception) timing of the data frame and the reception
(transmission) timing of the retransmission request for the data
frame, even when the sequence number of the data frame is omitted
in the retransmission request, the base station device 10 can
identify to which data frame the received retransmission request
corresponds. Because of this configuration, the size of the PHY
header section can be reduced and the size of the PHY body section
can be expanded.
[0097] The present invention is not limited to the above-described
embodiment and various modified embodiments can be employed. For
example, in the above description, the present invention is applied
to a mobile communication system which uses SDMA, TDMA, and OFDMA
in combination, but the present invention can also be applied to a
general communication system having a transmitting device and a
receiving device and which applies an automatic repeat request
method of data frame.
[0098] In addition, in the above-described embodiment, a
configuration is described in which the mobile station device 12
requests retransmission of the data frame and the base station
device 10 retransmits the data frame in response to the request,
but the present invention can also be applied to a configuration in
which the roles of the mobile station device 12 and the base
station device 10 are exchanged or to a configuration in which each
of the mobile station device 12 and the base station device 10 has
the functions of the retransmission request and the data frame
retransmission.
Second Embodiment
[0099] FIG. 9 is an overall configuration diagram of a mobile
communication system according to a second embodiment of the
present invention. As shown in FIG. 9, a mobile communication
system 1001 includes a base station device 1010 and a plurality of
mobile station devices 1012 (here, three mobile station
devices).
[0100] Each of the mobile station devices 1012 wirelessly
communicates with the base station device 1010, and may be, for
example, a portable cellular phone, a personal digital assistant,
or a communication card. In this configuration, the mobile station
device 1012 transmits and receives data to and from the base
station device 1010 according to a TDD system and executes a
multiplex communication according to a TDMA system and an OFDMA
system. The base station device 1010 includes an adaptive array
antenna as will be described below, and executes a multiplex
communication with each of the plurality of mobile station devices
1012 at a same time slot and a same carrier frequency according to
a space division multiple access (SDMA) using the adaptive array
antenna. With such a configuration, a bidirectional communication
with the plurality of mobile station devices 1012 is realized with
a very high frequency usage efficiency.
[0101] FIG. 12 is a diagram showing an example of a time slot
structure (1 TDMA frame) according to TDMA/TDD and a subchannel
structure according to OFDMA. As shown in FIG. 12, each of a
downlink (wireless transmission path from the base station device
1010 to the mobile station device 1012) and an uplink (wireless
transmission path from the mobile station device 1012 to the base
station device 1010) includes 4 time slots. Each time slot includes
28 subchannels, one of which is used as a control channel (CCH) and
the remaining 27 of which are used as traffic channels (TCH).
[0102] The base station device 1010 assigns at least some of a
total of 108 subchannels (27 subchannels.times.4 slots) used as the
traffic channels to each of the mobile station devices 1012 in each
of the downlink and the uplink. More specifically, as shown in FIG.
12, the base station device 1010 assigns one anchor subchannel
(ASCH) and assigns one or a plurality of extra subchannels (ESCH)
as necessary, for each mobile station device 1012.
[0103] The ASCH is a subchannel which is determined when a link is
established (at the start of communication) and notified to each of
the mobile station devices 1012 using the CCH, and is primarily
used for transmitting and receiving control information such as MAP
information and ACK information. The MAP information is a bit
sequence having a length of 108 bits indicating one or a plurality
of ESCH to be used in the next TDMA frame (next uplink frame and
downlink frame) after the MAP information is received. More
specifically, a bit corresponding to ESCH to be assigned to the
mobile station device 1012 in the next TDMA frame is indicated with
"1" and bits corresponding to the other subchannels (ASCH, ESCH to
be assigned to the other mobile station devices 1012, and idle
subchannel) are indicated with "0". The ACK information stores a
sequence number of the data frame received in the uplink and ACK
(Acknowledge) or NACK (Negative Acknowledge) indicating presence or
absence of an error in the data frame. In particular, when the ACK
information stores NACK, the ACK information represents a
retransmission request of the data frame.
[0104] The ESCH, on the other hand, is a subchannel which is
determined after the link is established and is identified by the
MAP information notified to the mobile station device 12 using the
ASCH, and is primarily used for transmission and reception of
communication data. As shown in FIG. 12, the ASCH and the ESCH are
assigned to the same subchannel in the downlink slot and the uplink
slot having corresponding slot numbers (DL#1 and UP#1, DL#2 and
UL#2, . . . ).
[0105] FIG. 10 is a functional block diagram of the mobile station
device 1012. As shown in FIG. 10, the mobile station device 1012
includes an antenna 1020, a wireless communication unit 1022, a
signal processor 1024, a modulation/demodulation unit 1026, a data
buffer 1028, an external I/F unit 1032, a data input unit 1034, a
data frame retransmission controller 1036, and a storage unit
1046.
[0106] The wireless communication unit 1022 includes a low noise
amplifier, a down-converter, and an up-converter. The wireless
communication unit 1022 down-converts a wireless signal from the
base station device 1010 received by the antenna 1020 and outputs
to the signal processor 1024. The wireless communication unit 1022
also up-converts a transmission signal which is input from the
signal processor 1024 into a wireless signal, amplifies the
wireless signal to a transmission power level, and transmits from
the antenna 1020.
[0107] The signal processor 1024 applies processes such as symbol
synchronization and removal of a guard interval (GI) signal on the
signal which is input from the wireless communication unit 1022, to
acquire a baseband OFDM signal, and outputs to the
modulation/demodulation unit 1026. The signal processor 1024 also
adds a guard interval signal to a baseband OFDM signal which is
input from the modulation/demodulation unit 1026 and outputs to the
wireless communication unit 1022.
[0108] The modulation/demodulation unit 1026 includes an A/D
converter, an FFT unit, a channel estimation unit, and a de-mapping
unit. The modulation/demodulation unit 1026 OFDM-demodulates the
baseband OFDM signal which is input from the signal processor 1024
and outputs the acquired received data frame to the data buffer
1028. More specifically, the modulation/demodulation unit 1026
applies an A/D conversion on the baseband OFDM signal and then
applies an FFT in the FFT unit, to acquire subcarrier components of
the OFDM symbol. Then, after the modulation/demodulation unit 1026
applies a predetermined channel estimation process or the like, the
modulation/demodulation unit 1026 connects the subcarrier
components corresponding to a plurality of subchannels (one ASCH
and one or a plurality of ESCH) assigned by the base station device
1010 referring to the assignment status of subchannels stored in a
channel information storage unit 1048, to create a symbol sequence.
The modulation/demodulation unit 1026 outputs the received data
frame acquired by decoding the symbol sequence to the data buffer
1028.
[0109] The modulation/demodulation unit 1026 also includes a symbol
mapping unit, an IFFT unit, and a D/A converter. The
modulation/demodulation unit 1026 OFDM-modulates a transmission
data frame which is input from the data buffer 1028 (transmission
queue 1030) and outputs the acquired baseband OFDM signal to the
signal processor 1024. More specifically, the
modulation/demodulation unit 1026 divides the transmission data
frame referring to the assignment status of subchannels stored in
the channel information storage unit 1048, and creates transmission
data corresponding to each of the plurality of subchannels (one
ASCH and one or a plurality of ESCH) assigned by the base station
device 1010. Then, the modulation/demodulation unit 1026 converts
the created transmission data of each of the subchannels into a
symbol sequence through a symbol mapping, and distributes the
symbol sequence over the subcarriers of the subchannel. The
modulation/demodulation unit 1026 then applies an IFFT in the IFFT
unit and outputs the baseband OFDM signal acquired through a D/A
conversion to the signal processor 1024.
[0110] The data buffer 1028 includes the transmission queue 1030.
The data buffer 1028 temporarily stores the received data frames
from the base station device 1010 which are input from the
modulation/demodulation unit 1026 and sequentially outputs received
data which is acquired by connecting the received data frames to an
upper device (not shown) through the predetermined external I/F
unit 1032. The data buffer 1028 also temporarily stores
transmission data frames to each of the mobile station devices 1012
which are input from the upper device through the external I/F unit
1032 and data which is input from the data input unit 1034 such as
a numerical pad, creates a transmission data frame based on these
transmission data, and sequentially outputs to the
modulation/demodulation unit 1026 through the transmission queue
1030.
[0111] The transmission queue 1030 holds the transmission data
frame in a list structure of a First In First Out (FIFO) method.
The transmission data frame or the retransmission data frame which
is input from the data frame retransmission controller 1036 is
added to the transmission queue 1030 in each TDMA frame. The first
data frame in the transmission queue 1030 is extracted in each TDMA
frame and is output to the modulation/demodulation unit 1026.
[0112] The storage unit 1046 includes a memory, and also includes
the channel information storage unit 1048 and a timing difference
information storage unit 1050.
[0113] The channel information storage unit 1048 stores the
subchannels (one ASCH and one or a plurality of ESCH) assigned by
the base station device 1010. Because the ASCH is the subchannel
for transmitting the ACK information, the slot position of the ASCH
represents the reception timing (reception slot) of the ACK
information.
[0114] The timing difference information storage unit 1050 stores,
in correlation to information indicating a reception timing of a
NACK, timing difference information indicating a timing difference
which satisfies a condition related to a reference required time.
Here, the reference required time is the minimum time which is
required for a process from the reception of the NACK to the
retransmission of the data frame (hereinafter referred to as data
frame retransmission process), and is set, for example, with
reference to the mobile station device 1012 having the slowest
process executing speed (the lowest processing capability). The
timing difference which satisfies a condition related to the
reference required time is a timing difference between the
reception timing of the NACK and the retransmission timing of the
data frame corresponding to the NACK, and is a timing difference
which is greater than or equal to the reference required time and
which is as close to the reference required time as possible. The
reception timing of the NACK may be identified by the reception
slot of the NACK, and the retransmission timing of the data frame
may be identified by the transmission slot of the retransmission
data frame or the transmission frame including the transmission
slot.
[0115] FIG. 11 is a diagram showing an example of the timing
difference information storage unit 1050. As shown in FIG. 11, the
timing difference information storage unit 1050 stores timing
difference information (timing 1, timing 2) in correlation to the
slot position of the ASCH (subchannel for transmitting the ACK
information). This shows the correspondence relationship between
the slot position of the ASCH indicating the reception slot of the
NACK and the transmission frame indicating the timing of the
retransmission of the data frame corresponding to the NACK, and the
transmission frame is set such that the reference required time
required for the data frame retransmission process in the mobile
station device 1012 is secured and is minimized. In other words,
the information shown in the timing difference information storage
unit 1050 shown in FIG. 11 indicates, for each slot position of
ASCH indicating the reception slot of the NACK, an optimum
transmission frame which secures the reference required time and
minimizes the data frame retransmission process time. Because of
this, for example, when the NACK is received in the "first slot"
(when the slot position of ASCH is the "first slot"), if the data
frame is retransmitted in the next frame of the reception slot
(timing 1), the data frame retransmission process time is
minimized.
[0116] The data frame retransmission controller 1036 includes a
retransmission request acquiring unit 1038, a data frame
retransmission timing determining unit 1040, a
transmission-complete buffer 1042, and a retransmission data frame
selecting unit 1044. The data frame retransmission controller 1036
controls, in response to a retransmission request transmitted from
the base station device 1010, retransmission of the data frame
corresponding to the retransmission request.
[0117] The retransmission request acquiring unit 1038 acquires the
ACK information in each TDMA frame from the received data which is
output from the data buffer 1028 and acquires the reception timing
(reception slot) of the ACK information.
[0118] The data frame retransmission timing determining unit 1040
determines, based on the reception timing of the NACK, the
retransmission timing (transmission slot or transmission frame) of
the data frame corresponding to the NACK so that the timing
difference between the reception timing of the NACK and the
retransmission timing of the data frame corresponding to the NACK
is close to the reference required time required for the data frame
retransmission process.
[0119] FIG. 13 is a diagram for explaining a retransmission timing
of the data frame identified by the data frame retransmission
timing determining unit 1040. As shown in FIG. 13(a), when the slot
position of the ASCH indicating the reception slot of the NACK is
the first slot, the data frame retransmission timing determining
unit 1040 determines the next transmission frame of the NACK
reception slot as the data frame retransmission timing. This
determination is based on design and experimental results that all
mobile station devices 1012 can complete the retransmission process
of the data frame within time period of approximately 3 slots from
the NACK reception slot to the next transmission frame. In this
case, the data frame retransmission process time can be shortened
by at least 1 TDMA frame compared to the related art. When, on the
other hand, the slot position of the ASCH (NACK reception slot) is
the fourth slot as shown in FIG. 13(b), the data frame
retransmission timing determining unit 1040 determines a
transmission frame following the next transmission frame of the
NACK reception slot as the data frame retransmission timing. This
determination is based on design and experimental results that it
is difficult for all mobile station devices 1012 to complete the
data frame retransmission process within a time period from the
NACK reception slot to the next transmission frame (about 0
slot).
[0120] The data frame retransmission timing determining unit 1040
may read the timing difference information from the timing
difference information storage unit 1050 in correlation to the slot
position of the ASCH indicating the reception slot of the NACK and
determine a retransmission timing (transmission frame) of the data
frame corresponding to the NACK based on the reception slot of the
NACK and the read timing difference information.
[0121] The transmission-complete buffer 1042 temporarily stores at
least some of the plurality of data frames transmitted to the base
station device 1010 in correlation to the sequence number of each
of the data frames. The first data frame in the transmission queue
1030 is transmitted in each TDMA frame, and, with the transmission,
the data frame is extracted from the transmission queue 1030 and
stored in the transmission-complete buffer 1042.
[0122] The retransmission data frame selecting unit 1044 selects,
when the NACK is stored in the ACK information acquired by the
retransmission request acquiring unit 1038, a data frame to be
retransmitted from the transmission-complete buffer 1042 based on
the sequence number of the data frame stored in the ACK
information, and adds the data frame to the transmission queue
1030. On the other hand, when the ACK is stored in the ACK
information, the retransmission data frame selecting unit 1044
deletes the data frame corresponding to the sequence number of the
data frame stored in the ACK information from the
transmission-complete buffer 1042.
[0123] An operation of the mobile station device 1012 will now be
described.
[0124] FIG. 14 is a flowchart showing a process of acquiring the
timing difference information at the start of the communication. As
shown in FIG. 14, when the communication is started, the channel
information storage unit 1048 stores one ASCH and one or a
plurality of ESCH assigned by the base station device 1010. Then,
the data frame retransmission timing determining unit 1040 acquires
the slot position of the ASCH from the channel information storage
unit 1048 (S1100). In addition, the data frame retransmission
timing determining unit 1040 acquires the timing difference
information from the timing difference information storage unit
1050 in correlation to the acquired slot position of the ASCH
(S1102).
[0125] FIG. 15 is a flowchart showing the data frame transmission
(and retransmission) in the mobile station device 1012. As shown in
FIG. 15, first, in an uplink frame, a data frame including a
transmission packet received from an upper device is stored in the
data buffer 1028 (S1200). Then, the data frame is added to the
transmission queue 1030 (S1202). Next, the first data frame is
extracted from the transmission queue 1030, the data frame is
converted to a transmission signal, and the transmission signal is
transmitted to the base station device 1010 (S1204). The
transmitted data frame is stored in the transmission-complete
buffer 1042 in correlation to its sequence number (S1206).
[0126] Then, in a downlink frame, the received data from the base
station device 1010 is acquired. The retransmission request
acquiring unit 1038 acquires the ACK information from the received
data and determines whether the value stored in the ACK information
is ACK or NACK (S1208). When the value is ACK, the retransmission
data frame selecting unit 1044 deletes, based on the sequence
number of the data frame stored in the ACK information, the
corresponding data frame from the transmission-complete buffer 1042
(S1210). It is then determined whether or not the data transmission
is completed (S1212), and, if the transmission is not completed,
the processes from S1202 are executed in the next uplink frame.
[0127] When, on the other hand, the value stored in the ACK
information is NACK in S1208, the data frame retransmission timing
determining unit 1040 determines the transmission frame of the data
frame corresponding to the NACK based on the reception slot of the
NACK acquired by the retransmission request acquiring unit 1038 and
the timing difference information acquired in S1102 (S1214). Then,
the retransmission data frame selecting unit 1044 selects a data
frame to be retransmitted from the transmission-complete buffer
1042 based on the sequence number of the data frame stored in the
ACK information (S1216), and adds the data frame to the
transmission queue 1030 so that the data frame is transmitted in
the transmission frame determined in S1214 (S1218). Then, in the
next uplink frame, the processes from S1204 are executed.
[0128] According to the above-described embodiment, the
retransmission timing (transmission frame) of the data frame
corresponding to the NACK is determined based on the reception
timing (reception slot) of the NACK so that the time from the
reception of the NACK to the retransmission of the data frame
corresponding to the NACK is close to the reference required time
required for the data frame retransmission process. Because of this
configuration, it is possible to preferably shorten the time from
the reception of the NACK to the retransmission of the data
frame.
[0129] The present invention is not limited to the above-described
embodiment and various modified embodiments may be employed. For
example, in the above description, the present invention is applied
to the mobile station device in a mobile communication system which
uses SDMA, TDMA/TDD, and OFDMA in combination, but the present
invention can be applied to a general communication device which
employs a TDMA/TDD and an automatic repeat request method of data
frame.
[0130] In addition, in the above-described embodiment, a
configuration is described in which the mobile station device 1012
retransmits a data frame in response to a data frame retransmission
request from the base station device 1010, but the present
invention can be applied to a configuration in which the roles of
the mobile station device 1012 and the base station device 1010 are
exchanged or to a configuration in which each of the mobile station
device 1012 and the base station device 1010 has the functions of
the retransmission request and the data frame retransmission.
Third Embodiment
[0131] FIG. 16 is an overall configuration diagram of a mobile
communication system according to a third embodiment of the present
invention. As shown in FIG. 16, a mobile communication system 2001
includes a base station device 2010 and a plurality of mobile
station devices 2012 (here, three mobile station devices).
[0132] Each of the mobile station devices 2012 wirelessly
communicates with the base station device 2010, and may be, for
example, a portable cellular phone, a personal digital assistant,
or a communication card. In this configuration, the mobile station
device 2012 transmits and receives data to and from the base
station device 2010 according to a TDD system and executes a
multiplex communication according to a TDMA system and an OFDMA
system. The base station device 2010 includes an adaptive array
antenna as will be described below, and executes a multiplex
communication with each of the plurality of mobile station devices
2012 at a same time slot and a same carrier frequency according to
a space division multiple access system (SDMA) using the adaptive
array antenna. With such a configuration, a bidirectional
communication with the plurality of mobile station devices 2012 is
achieved with a very high frequency usage efficiency.
[0133] FIG. 19 is a diagram showing an example of a time slot
structure (1 TDMA frame) according to TDMA/TDD and a subchannel
structure according to OFDMA. As shown in FIG. 19, each of a
downlink (wireless transmission path from the base station device
2010 to the mobile station device 2012) and an uplink (wireless
transmission path from the mobile station device 2012 to the base
station device 2010) includes 4 time slots. Each time slot includes
28 subchannels, one of which is used as a control channel (CCH) and
the remaining 27 of which are used as traffic channels (TCH).
[0134] The base station device 2010 assigns at least some of a
total of 108 subchannels (27 subchannels.times.4 slots) used as the
traffic channels to each of the mobile station devices 2012 in each
of the downlink and the uplink. More specifically, as shown in FIG.
19, the base station device 2010 assigns one anchor subchannel
(ASCH) and assigns one or a plurality of extra subchannels (ESCH)
as necessary, for each mobile station device 2012.
[0135] The ASCH is a subchannel which is determined when a link is
established (at the start of communication) and notified to each of
the mobile station devices 2012 using the CCH, and is primarily
used for transmission and reception of control information such as
MAP information and ACK information. The MAP information is a bit
sequence having a length of 108 bits indicating one or a plurality
of ESCH to be used in the next TDMA frame (next uplink frame and
downlink frame) after the MAP information is received. More
specifically, a bit corresponding to ESCH to be assigned to the
mobile station device 2012 in the next TDMA frame is indicated with
"1", and bits corresponding to the other subchannels (ASCH, ESCH to
be assigned to other mobile station devices 2012, and idle
subchannel) are indicated with "0". The ACK information stores a
sequence number of the data frame received in the uplink and ACK
(Acknowledge) or NACK (Negative Acknowledge) indicating presence or
absence of an error in the data frame. In particular, when the ACK
information stores NACK, the ACK information represents a
retransmission request of the data frame.
[0136] The ESCH, on the other hand, is a subchannel which is
determined after the link is established and is identified by the
MAP information notified to the mobile station device 12 using the
ASCH, and is primarily used for transmission and reception of
communication data. As shown in FIG. 19, the ASCH and the ESCH are
assigned in the same subchannels in the downlink slot and uplink
slot having corresponding slot numbers (DL#1 and UL#1, DK#2 and
UL#2, . . . ).
[0137] FIG. 17 is a functional block diagram of the mobile station
device 2012. As shown in FIG. 17, the mobile station device 2012
includes an antenna 2020, a wireless communication unit 2022, a
signal processor 2024, a modulation/demodulation unit 2026, a data
buffer 2028, an external I/F unit 2032, a data input unit 2034, a
data frame retransmission controller 2036, and a storage unit
2046.
[0138] The wireless communication unit 2022 includes a low noise
amplifier, a down-converter, and an up-converter. The wireless
communication unit 2022 down-converts a wireless signal from the
base station device 2010 received by the antenna 2020 and outputs
to the signal processor 2024. The wireless communication unit 2022
also up-converts a transmission signal which is input from the
signal processor 2024 into a wireless signal, amplifies the
wireless signal to a transmission power level, and transmits from
the antenna 2020.
[0139] The signal processor 2024 applies processes such as symbol
synchronization and removal of a guard interval (GI) signal on the
signal which is input from the wireless communication unit 2022, to
acquire a baseband OFDM signal, and outputs to the
modulation/demodulation unit 2026. In addition, the signal
processor 2024 adds a guard interval signal to a baseband OFDM
signal which is input from the modulation/demodulation unit 2026
and outputs to the wireless communication unit 2022.
[0140] The modulation/demodulation unit 2026 includes an A/D
converter, an FFT unit, a channel estimation unit, and a de-mapping
unit. The modulation/demodulation unit 2026 OFDM-demodulates the
baseband OFDM signal which is input from the signal processor 2024
and outputs the acquired received data frame to the data buffer
2028. More specifically, after the modulation/demodulation unit
2026 A/D-converts the baseband OFDM signal, the
modulation/demodulation unit 2026 applies an FFT in the FFT unit,
to acquire the subcarrier components of the OFDM symbol. Then,
after the modulation/demodulation unit 2026 applies a predetermined
channel estimation process or the like, the modulation/demodulation
unit 2026 connects the subcarrier components corresponding to a
plurality of subchannels (one ASCH and one or a plurality of ESCH)
assigned by the base station device 2010 referring to the
assignment status of subchannels stored in a channel information
storage unit 2050, to create a symbol sequence. The
modulation/demodulation unit 2026 outputs the received data frame
acquired by decoding the symbol sequence to the data buffer
2028.
[0141] The modulation/demodulation unit 2026 also includes a symbol
mapping unit, an IFFT unit, and a D/A converter. The
modulation/demodulation unit 2026 OFDM-modulates a transmission
data frame which is input from the data buffer 2028 (transmission
queue 2030) and outputs the acquired baseband OFDM signal to the
signal processor 2024. More specifically, the
modulation/demodulation unit 2026 divides the transmission data
frame referring to the assignment status of subchannels stored in
the channel information storage unit 2050, and creates transmission
data corresponding to each of the plurality of subchannels (one
ASCH and one or a plurality of ESCH) assigned by the base station
device 2010. Then, the modulation/demodulation unit 2026 converts
the created transmission data of each of the subchannels into a
symbol sequence through a symbol mapping, and distributes the
symbol sequence over the subcarriers of the subchannel. The
modulation/demodulation unit 2026 applies an IFFT in the IFFT unit,
and outputs the baseband OFDM signal acquired through a D/A
conversion to the signal processor 2024.
[0142] The data buffer 2028 includes the transmission queue 2030.
The data buffer 2028 temporarily stores the received data frames
from the base station device 2010 which are input from the
modulation/demodulation unit 2026 and sequentially outputs the
received data acquired by connecting the received data frames to an
upper device (not shown) through the predetermined external I/F
unit 2032. In addition, the data buffer 2028 temporarily stores
transmission data frames to each of the mobile station devices 2012
which are input from the upper device through the external I/F unit
2032 and the data which is input from the data input unit 2034 such
as a numerical pad, creates a transmission data frame based on
these transmission data, and sequentially outputs to the
modulation/demodulation unit 2026 through the transmission queue
2030.
[0143] The transmission queue 2030 holds the transmission data
frame in a list structure of a First In First Out (FIFO) method.
The transmission data frame or the retransmission data frame which
is input from the data frame retransmission controller 2036 is
added to the transmission queue 2030 in each TDMA frame. The first
data frame in the transmission queue 2030 is extracted in each TDMA
frame and output to the modulation/demodulation unit 2026.
[0144] The storage unit 2046 includes a memory, and also includes a
processing capability storage unit 2048, the channel information
storage unit 2050, and a timing difference information storage unit
2052.
[0145] The processing capability storage unit 2048 stores
information indicating the processing capability of the mobile
station device 2012 (for example, level 1). In general, a device
with a higher processing capability can complete each process in
shorter time.
[0146] The channel information storage unit 2050 stores the
subchannels (one ASCH and one or a plurality of ESCH) assigned by
the base station device 2010. Because the ASCH is a subchannel for
transmitting the ACK information, the slot position of the ASCH
indicates the reception timing (reception slot) of the ACK
information.
[0147] The timing difference information storage unit 2052 stores,
in correlation to information indicating the processing capability
of the mobile station device 2012 and information indicating a
reception timing of a NACK, timing difference information
indicating a timing difference which satisfies a condition related
to a reference required time. Here, the reference required time is
the minimum time required for the process from the reception of the
NACK to the retransmission of the data frame (hereinafter referred
to as data frame retransmission process) and varies according to
the process executing speed of the mobile station device 2012. In
other words, the reference required time is shorter for a mobile
station device 2012 having a higher processing capability and is
longer for a mobile station device 2012 having a lower processing
capability. The timing difference which satisfies a condition
related to the reference required time is a timing difference
between the reception timing of the NACK and the retransmission
timing of the data frame corresponding to the NACK, and is a timing
difference which is greater than or equal to the reference required
time and which is as close to the reference required time as
possible. The reception timing of the NACK may be identified by the
reception slot of the NACK, and the retransmission timing of the
data frame may be identified by the transmission slot of the
retransmission data frame or the transmission frame including the
transmission slot.
[0148] FIG. 18 is a diagram showing an example of the timing
difference information storage unit 2052. As shown in FIG. 18, the
timing difference information storage unit 2052 stores timing
difference information (timing 1, timing 2) in correlation to
information indicating the processing capability of the mobile
station device 2012 (level 0, level 1, . . . ) and the slot
position of the ASCH (subchannel for transmitting the ACK
information). This indicates a correspondence relationship between
the slot position of the ASCH indicating the reception slot of the
NACK and the transmission frame indicating the timing of the
retransmission of the data frame corresponding to the NACK, and the
transmission frame is set so that the reference required time
required for the data frame retransmission process in the mobile
station device 2012 is secured and minimized. Because the reference
required time varies according to the processing capability
indicating the process executing speed of the mobile station device
2012 as described above, FIG. 18 shows a plurality of the
correspondence relationships (in this configuration, five
correspondence relationships) for each processing capability of the
mobile station device 2012. In other words, the information
indicated in the timing difference information storage unit 2052
shown in FIG. 18 indicates, for each slot position of ASCH
indicating the reception slot of the NACK, an optimum transmission
frame which secures the reference required time corresponding to
the processing capability of the mobile station device 2012 and
minimizes the data frame retransmission process time. Because of
this, for example, when the processing capability of the mobile
station device 2012 is "level 1" and the NACK is received in the
"third slot" (when the slot position of the ASCH is the "third
slot"), the data frame retransmission process time is shortened by
the maximum amount if the data frame is retransmitted in the next
frame of the reception slot (timing 1).
[0149] The data frame retransmission controller 2036 includes a
retransmission request acquiring unit 2038, a data frame
retransmission timing determining unit 2040, a
transmission-complete buffer 2042, and a retransmission data frame
selecting unit 2044. The data frame retransmission controller 2036
controls, in response to a retransmission request transmitted from
the base station device 2010, retransmission of the data frame
corresponding to the retransmission request.
[0150] The retransmission request acquiring unit 2038 acquires the
ACK information in each TDMA frame from the received data which is
output from the data buffer 2028 and acquires the reception timing
(reception slot) of the ACK information.
[0151] The data frame retransmission timing determining unit 2040
determines the retransmission timing (transmission slot or
transmission frame) of the data frame corresponding to the NACK
based on the processing capability of the mobile station device
2012 so that the timing difference between the reception timing of
the NACK and the retransmission timing of the data frame
corresponding to the NACK is close to the reference required time
required for the data frame retransmission process.
[0152] FIG. 20 is a diagram for explaining a retransmission timing
of the data frame identified by the data frame retransmission
timing determining unit 2040. FIG. 20 shows a case where the slot
position of the ASCH indicating the reception slot of the NACK is
the first slot. As shown in FIG. 20(a), when the processing
capability (process executing speed) of the mobile station device
2012 is high, the data frame retransmission timing determining unit
2040 determines the next transmission frame of the NACK reception
slot as the data frame retransmission timing. This determination is
based on design and experimental results that a mobile station
device 2012 having a high processing capability can complete the
retransmission process of the data frame within time period of
approximately 3 slots from the NACK reception slot to the next
transmission frame. In this case, the data frame retransmission
process time can be shortened by at least 1 TDMA frame compared to
the related art. When, on the other hand, the processing capability
(process executing speed) of the mobile station device 2012 is low
as shown in FIG. 20(b), the data frame retransmission timing
determining unit 2040 determines a transmission frame following the
next transmission frame of the NACK reception slot as the data
frame retransmission timing. This determination is based on design
and experimental results that, with the mobile station device 2012
having a low processing capability, although it is difficult to
complete the data frame retransmission process in the time from the
NACK reception slot to the next transmission frame (approximately 0
slot), the data frame retransmission process can be completed if
there is time until the transmission frame following the next
transmission frame. The data frame retransmission timing
determining unit 2040 may determine the retransmission frame of the
data frame further based on the reception timing (reception slot)
of the NACK.
[0153] Alternatively, the data frame retransmission timing
determining unit 2040 may read the timing difference information
from the timing difference information storage unit 2052 in
correlation to the processing capability of the mobile station
device 2012 and the slot position of the ASCH indicating the
reception slot of the NACK and determine the retransmission timing
(transmission frame) of the data frame corresponding to the NACK
based on the reception slot of the NACK and the read timing
difference information.
[0154] The transmission-complete buffer 2042 temporarily stores at
least some of the plurality of data frames transmitted to the base
station device 2010, in correlation to the sequence number of each
of the data frames. The first data frame in the transmission queue
2030 is transmitted in each TDMA frame, and, with the transmission,
the data frame is extracted from the transmission queue 2030 and
stored in the transmission-complete buffer 2042.
[0155] The retransmission data frame selecting unit 2044 selects,
when the NACK is stored in the ACK information acquired by the
retransmission request acquiring unit 2038, a data frame to be
retransmitted from the transmission-complete buffer 2042 based on
the sequence number of the data frame stored in the ACK
information, and adds to the transmission queue 2030. When the ACK
is stored in the ACK information, the retransmission data frame
selecting unit 2044 deletes the data frame corresponding to the
sequence number of the data frame stored in the ACK information
from the transmission-complete buffer 2042.
[0156] An operation of the mobile station device 2012 will now be
described.
[0157] FIG. 21 is a flowchart showing a process for acquiring the
timing difference information at the start of the communication. As
shown in FIG. 21, when the communication is started, the channel
information storage unit 2050 stores one ASCH and one or a
plurality of ESCH assigned by the base station device 2010. Then,
the data frame retransmission timing determining unit 2040 acquires
the processing capability of the mobile station device 2012 from
the processing capability storage unit 2048 (S2100). The data frame
retransmission timing determining unit 2040 also acquires the slot
position of the ASCH from the channel information storage unit 2050
(S2102). The data frame retransmission timing determining unit 2040
acquires the timing difference information from the timing
difference information storage unit 2052 in correlation to the
acquired processing capability of the mobile station device 2012
and the slot position of the ASCH (S2104).
[0158] FIG. 22 is a flowchart showing a data frame transmission
(and retransmission) in the mobile station device 2012. As shown in
FIG. 22, first, in an uplink frame, a data frame including a
transmission packet received from an upper device is stored in the
data buffer 2028 (S2200). Then, the data frame is added to the
transmission queue 2030 (S2202). Next, the first data frame is
extracted from the transmission queue 2030, converted to a
transmission signal, and transmitted to the base station device
2010 (S2204). The transmitted data frame is stored in the
transmission-complete buffer 2042 in correlation to its sequence
number (S2206).
[0159] Next, in a downlink frame, the received data from the base
station device 2010 is acquired. The retransmission request
acquiring unit 2038 acquires the ACK information from the received
data and determines whether the value stored in the ACK information
is ACK or NACK (S2208). When the value is ACK, the retransmission
data frame selecting unit 2044 deletes, based on the sequence
number of the data frame stored in the ACK information, the
corresponding data frame from the transmission-complete buffer 2042
(S2210). It is then determined whether or not the data transmission
is completed (S2212), and, if the transmission is not completed,
the processes from S2202 are executed in the next uplink frame.
[0160] When, on the other hand, the value stored in the ACK
information is NACK in S2208, the data frame retransmission timing
determining unit 2040 determines the transmission frame of the data
frame corresponding to the NACK based on the reception slot of the
NACK acquired by the retransmission request acquiring unit 2038 and
the timing difference information acquired in S2104 (S2214). Then,
the retransmission data frame selecting unit 2044 selects a data
frame to be retransmitted from the transmission-complete buffer
2042 based on the sequence number of the data frame stored in the
ACK information (S2216), and adds to the transmission queue 2030 so
that the data frame is transmitted in the transmission frame
determined in S2214 (S2218). At the next uplink frame, the
processes from S2204 are executed.
[0161] According to the above-described embodiment, the
retransmission timing (transmission frame) of the data frame
corresponding to the NACK is determined in consideration of the
processing capability of the mobile station device 2012 so that the
time from the reception of the NACK to the retransmission of the
data frame corresponding to the NACK is close to the reference
required time required for the retransmission process of the data
frame. Because of this configuration, it is possible to preferably
shorten the time from the reception of the NACK to the
retransmission of the data frame.
[0162] The present invention is not limited to the above-described
embodiment, and various modified embodiments may be employed. For
example, in the above description, the present invention is applied
to the mobile station device in a mobile communication system which
uses SDMA, TDMA/TDD, and OFDMA in combination, but the present
invention can be applied to a general communication device which
employs a TDMA/TDD and an automatic repeat request method of data
frame.
* * * * *