Note: Descriptions are shown in the official language in which they were submitted.
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Description
APPARATUS AND METHOD FOR RETRANSMITTING
REQUEST IN WIRELESS RELAY COMMUNICATION SYSTEM
Technical Field
[1] The present invention relates generally to an apparatus and a method for
performing
an Automatic Retransmission reQuest (ARQ) in a wireless communication system,
and
more particularly, to an apparatus and a method for performing the ARQ in a
wireless
relay communication system.
Background Art
[2] A wireless communication system is subject to error in specific data
depending on a
channel condition of a radio resource. An error control and recovery method
largely
includes an ARQ scheme and a Frame Error Check (FEC) scheme. The ARQ scheme
requests the retransmission of the compromised data from a receiver to a
sender. The
FEC scheme corrects the error of the compromised data at the receiver.
[3] When the wireless communication system adopts the ARQ scheme, the receiver
checks whether an error occurs by decoding the received packet. When the
received
packet does not have an error, the receiver sends an acknowledgement (ACK)
signal to
the sender.
[4] When the received packet has an error, the receiver sends a Negative ACK
(NACK)
signal to the sender.
[5] Upon receiving the ACK signal from the receiver, the sender transmits a
new packet.
Upon receiving the NACK signal from the receiver, the sender retransmits the
packet
to the receiver.
[6] Recently, wireless communication systems have applied a relay scheme using
a relay
station to provide a better radio channel to a terminal in a cell boundary or
a shadow
area. In other words, the wireless relay communication system can provide the
better
radio channel between a base station and the terminal by relaying data between
the
base station and the terminal via the relay station. The wireless relay
communication
system therefore requires an ARQ method using the relay station.
Disclosure of Invention
Technical Solution
[7] The present invention has been made to address at least the above-
mentioned
problems and/or disadvantages and to provide at least the advantages described
below.
Accordingly, an aspect of the present invention is to provide an apparatus and
a
method for performing an ARQ in a wireless relay communication system.
181 Another aspect of the present invention is to provide an apparatus and a
method for
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performing an ARQ of an uplink signal in a wireless relay communication
system.
[9] The above aspects are achieved by providing a retransmission method of a
Base
Station (BS) in a wireless relay communication system. It is checked whether
an Ac-
knowledgement (ACK) message or a Negative ACK (NACK) message for data is
received from a Relay Station (RS), which receives the data from a Mobile
Station
(MS). Scheduling information for transmitting the data is transmitted to the
RS, when
the ACK message is received from the RS. An error of the data is checked, when
the
data is received from the RS. The RS is requested to retransmit the data, when
the data
has an error.
[10] According to one aspect of the present invention, a retransmission method
of an RS
in a wireless relay communication system is provided. Data is received from an
MS
using scheduling information for the MS to transmit data. An error of the
received data
is checked. An ACK message is transmitted to a BS when the data has no error.
The
data is forwarded to the BS using scheduling information, which is provided
from the
BS, for forwarding the data from the MS. The data is retransmitted to the BS,
when a
retransmission request signal is received from the BS.
[11] According to another aspect of the present invention, a retransmission
method of a
BS in a wireless relay communication system is provided. An error of the data
is
checked, when data is received from an MS. It is checked whether an ACK
message or
a NACK message is received with respect to data sent from the MS to an RS,
when the
data has an error. A node is determined for the data retransmission, when
receiving an
ACK message from the RS. The data retransmission to the RS is requested, when
the
RS is selected as the node for the retransmission.
[12] According to a further aspect of the present invention, a retransmission
method of an
RS in a wireless relay communication system is provided. Scheduling
information is
confirmed for an MS to send data. Data is received from the MS using the
scheduling
information. An error of the received data is checked. An ACK message is
transmitted
to a BS when the data has no error. The data is transmitted to the BS, when a
re-
transmission request signal is received from the BS.
[13] According to an additional aspect of the present invention, a
retransmission method
of a BS in a wireless relay communication system is provided. Scheduling
information
for an MS and an RS to send data is transmitted to the MS and the RS. It is
checked
whether data is received from the RS, which receives the data from the MS. An
error
of the data is checked, when receiving the data from the RS. Retransmission of
the data
to the RS is requested, when the data has an error.
[14] According to yet another aspect of the present invention, a
retransmission method of
an RS in a wireless relay communication system is provided. Data is received
from an
MS using scheduling information for the MS to send data. An error of the
received
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data is checked. The data is forwarded to the BS, when the data has no error.
The data
is retransmitted to the BS, when a retransmission request signal is received
from the
BS.
[15] According to a further aspect of the present invention, an RS of a
wireless relay com-
munication system is provided. The RS includes a checker for checking an error
of
data received from an MS, a data queue for storing error-free data, and a re-
transmission controller for controlling the data retransmission according to a
re-
transmission request of a BS. The RS also includes a data generator for
generating data
to be retransmitted to the BS using the data stored to the data queue under
control of
the retransmission controller, and a sender for transmitting the generated
data to the
BS.
Brief Description of the Drawings
[16] The above and other aspects, features and advantages of the present
invention will
become more apparent from the following detailed description when taken in con-
junction with the accompanying drawings, in which:
[17] FIG. 1 is a diagram illustrating a wireless relay communication system
according to
an embodiment of the present invention;
[18] FIG. 2 is a diagram illustrating an uplink signal retransmission method
in the
wireless relay communication system according to an embodiment of the present
invention;
[19] FIG. 3 is a diagram illustrating an uplink signal retransmission method
in the
wireless relay communication system according to another embodiment of the
present
invention;
[20] FIG. 4 is a flow diagram illustrating operations of a base station for
retransmitting the
uplink signal in the wireless relay communication system according to an
embodiment
of the present invention;
[21] FIG. 5 is a flow diagram illustrating operations of a relay station for
relaying the
uplink signal in the wireless relay communication system according to an
embodiment
of the present invention;
[22] FIG. 6 is a flow diagram illustrating operations of a mobile station for
relaying the
uplink signal in the wireless relay communication system according to an
embodiment
of the present invention;
[23] FIG. 7 is a diagram illustrating an uplink signal retransmission method
in the
wireless relay communication system according to yet another embodiment of the
present invention;
[24] FIG. 8 is a diagram illustrating an uplink signal retransmission method
in the
wireless relay communication system according to still another embodiment of
the
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present invention;
[25] FIG. 9 is a flow diagram illustrating operations of a base station for
retransmitting an
uplink signal in the wireless relay communication system according to another
em-
bodiment of the present invention;
[26] FIG. 10 is a flow diagram illustrating operations of a relay station for
relaying the
uplink signal in the wireless relay communication system according to another
em-
bodiment of the present invention;
[27] FIG. 11 is a diagram illustrating an uplink signal retransmission method
in the
wireless relay communication system according to a further embodiment of the
present
invention;
[28] FIG. 12 is a diagram illustrating an uplink signal retransmission method
in the
wireless relay communication system according to another embodiment of the
present
invention;
[29] FIG. 13 is a diagram illustrating an uplink signal retransmission method
in the
wireless relay communication system according to a further embodiment of the
present
invention;
[30] FIG. 14 is a flow diagram illustrating operations of a base station for
retransmitting
the uplink signal in the wireless relay communication system according to a
further
embodiment of the present invention;
[31] FIG. 15 is a flow diagram illustrating operations of a relay station for
relaying the
uplink signal in the wireless relay communication system according to a
further em-
bodiment of the present invention; and
[32] FIG. 16 is a diagram illustrating a structure of the relay station in the
wireless relay
communication system according to an embodiment of the present invention.
Best Mode for Carrying Out the Invention
[33] Preferred embodiments of the present invention are described in detail
below with
reference to the accompanying drawings. It should be noted that the same or
similar
components are designated by the same or similar reference numerals although
used in
different drawings. Detailed descriptions of constructions or processes known
in the art
may be omitted to avoid obscuring the subject matter of the present invention.
[34] The present invention provides a technique for perfonning an ARQ of an
uplink in a
wireless relay communication system.
[35] Hereinafter, the wireless relay communication system employs an
Orthogonal
Frequency Division Multiple Access (OFDMA) by way of example. The present
invention is also applicable to other multiple access communication systems.
[36] To provide a relay service, the wireless communication system is
constructed as
shown in FIG. 1.
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[37] FIG. 1 depicts the wireless relay communication system according to an
embodiment
of the present invention.
[38] In the wireless communication system of FIG. 1, a Base Station (BS) 100
services a
Mobile Station (MS) 120 in its service coverage through a direct link.
[39] When the MS 120 travels in the outskirts (the cell boundary) of the
service coverage
of the BS 100 or in a shadow area, the BS 100 provides a high-speed data
channel to
the MS 120 using a relay link via a Relay Station (RS) 110.
[40] For instance, in a downlink, the MS 120 receives a control signal and low
speed data
through the direct link to the BS 100 because it belongs to the service
coverage of the
BS 100. The MS 120 receives high-speed data from the BS 100 via the RS 110.
[41] In an uplink, the BS 100 receives a control signal and a low speed data
channel from
the MS 120 through the direct link. The BS 100 receives high-speed data from
the MS
120 via the RS 110.
[42] As above, the BS, the RS, and the MS in the wireless relay communication
system
can communicate with each other.
[43] Namely, the MS can communicate with the BS through the direct link or
through the
relay link via the RS depending on the channel condition.
[44] If the MS and the BS communicate with each other through the direct link,
the RS
can listen to data transmitted from the MS to the BS. Hence, when error occurs
in the
data received at the BS, the BS can select a node for retransmitting the data.
For
example, the BS can request the retransmission of the data by checking data
reception
rates from the MS and the RS and selecting a node of the good data reception
rate.
[45] Now, a method for retransmitting an uplink signal in the wireless
communication
system is explained.
[46] When the RS retransmits uplink data errored at the BS, the wireless
communication
system operates as shown in FIG. 2 or FIG. 3.
[47] FIG. 2 illustrates the uplink signal retransmission method in the
wireless relay com-
munication system according to an embodiment of the present invention.
[48] In FIG. 2, the BS 200 transmits resource scheduling information for data
transmission of the MS 204 to the MS 204 in steps 211 and 213. For example,
the BS
200 transmits the scheduling information to the MS 204 via the RS 202 or to
the RS
202 and the MS 204 respectively.
[49] Alternatively, the BS 200 transmits the scheduling information directly
to the MS
204. The RS 202 can acquire the scheduling information of the MS 204 by
listening to
the scheduling information transmitted from the BS 200 to the MS 204. Herein,
the MS
204 indicates a terminal, which can receive the relay service via the RS 202.
[50] The RS 202 and the MS 204 confirm a time point of the data transmission
from the
MS 204 and the resource information using the scheduling information received
from
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the BS 200.
[51] Next, the MS 204 transmits data to the RS 202 according to the scheduling
in-
formation in step 215. If the MS 204 cannot recognize the RS 202, the MS 204
may
send the data to the BS 200. In this case, the RS 202 listens to and confirms
the data
transmitted from the MS 204 to the BS 200 according to the scheduling
information.
[52] The RS 202 checks for errors in the data received from the MS 204 in step
217. For
example, the RS 202 checks for errors in the data using a Cyclic Redundancy
Check
(CRC) code of the data.
[53] In doing so, the BS 200 can know the time point of the data transmission
from the
MS 204 to the RS 202 according to the scheduling information transmitted to
the MS
204. Accordingly, the BS 200 transmits scheduling information to the RS 202 so
that
the RS 202 forwards the data from the MS 204 to the BS 200, by taking into
account
the data transmission time of the MS 204 in step 219.
[54] When the data received from the MS 204 has no error, the RS 202 forwards
the data
to the BS 200 using the scheduling information received in step 219, in step
221. At
this time, the RS 202 transmits the data including an ACK message.
[55] The BS 200 checks for errors in the data received from the RS 202 in step
223. For
example, the BS 200 checks the data for errors using the CRC of the data.
[56] When the data received from the RS 202 has no error, the BS 200 sends an
ACK
message to the RS 202 or the MS 204 in step 225 or 227. For example, the BS
200
sends the ACK message to each of the RS 202 and the MS 204, or to the MS 204
via
the RS 202.
[57] Alternatively, the BS 200 can send the ACK message only to the MS 204. In
this
situation, the RS 202 confirms that there is no error in the data transmitted
to the BS
200 by listening to the ACK message transmitted from the BS 200 to the MS 204.
When the NACK message or the scheduling information for the data
retransmission is
not received from the BS 200 over a certain time, the RS 202 regards the data
transmitted to the BS 200 as having no errors.
[58] In this embodiment of the present invention, the BS 200, upon receiving
the error-
free data from the MS 204 via the RS 202, sends the ACK message to the RS 202
or
the MS 204. Alternatively, when receiving the data including the ACK message
from
the RS 202 as in step 221, the BS 200 sends the ACK message to the MS 204 re-
gardless of the error in the data received from the RS 202. When the data
received
from the RS 202 has no error, the BS 200 sends the ACK message to the RS 202
or
does not send the ACK message.
[59] FIG. 3 illustrates an uplink signal retransmission method in the wireless
relay com-
munication system according to another embodiment of the present invention.
Hereafter, it is assumed that the data transmitted from the MS 204 to the RS
202 and
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the data transmitted from the RS 202 to the BS 200 have error in FIG. 2.
[60] In FIG. 3, a BS 300 transmits resource scheduling information for data
transmission
of an MS 304, to the MS 304 in steps 311 and 313. For example, the BS 300
transmits
the scheduling information to each of an RS 302 and the MS 304, or to the MS
304 via
the RS 302.
[61] Alternatively, the BS 300 transmits the scheduling information only to
the MS 304.
The RS 302 can acquire the scheduling information of the MS 304 by listening
to the
scheduling information transmitted from the BS 300 to the MS 304. Herein, the
MS
304 indicates a terminal, which can receive the relay service through the RS
302.
[62] The RS 302 and the MS 304 confirm the time point of the data transmission
of the
MS 304 and the resource information using the scheduling information received
from
the BS 300.
[63] Next, the MS 304 transmits data to the RS 302 according to the scheduling
in-
formation in step 315. If the MS 304 cannot recognize the RS 302, the MS 304
may
transmit the data to the BS 300. In this case, the RS 302 listens to and
acquires the data
transmitted from the MS 304 to the BS 300 according to the scheduling
information.
[64] The RS 302 checks for errors in the data received from the MS 304 in step
317. For
example, the RS 302 checks for errors using the CRC of the data.
[65] The BS 300 can recognize the time information of the data transmission
from the MS
304 to the RS 302 according to the scheduling information received from the MS
304.
Hence, the BS 300 transmits scheduling information for the RS 302 to forward
the data
from the MS 304 to the BS 300, to the RS 302 by taking into account the time
point of
the data transmission of the MS 302 in step 319.
[66] If the data received from the MS 304 has an error, the RS 302 sends a
NACK
message to the BS 300 using the scheduling information in step 321.
[67] Upon receiving the NACK message from the RS 302, the BS 300 sends a NACK
message to the MS 304 to request the retransmission in step 323.
[68] Next, the BS 300 transmits scheduling information for the MS 304 to
retransmit the
data, to the MS 304 in steps 325 and 327. For example, the BS 300 transmits
the
scheduling information to each of the RS 302 and the MS 304, or to the MS 304
via
the RS 302.
[69] Alternatively, the BS 300 can transmit the scheduling information only to
the MS
304. The RS 302 can listen to and acquire the scheduling information
transmitted from
the BS 300 to the MS 304.
[70] The RS 302 and the MS 304 confirm the time point and the resource
information of
the data retransmission of the MS 304 using the scheduling information
received from
the BS 300.
[71] Next, the MS 304 retransmits the data to the RS 302 according to the
scheduling in-
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formation in step 329. If the MS 304 cannot recognize the RS 302, the MS 304
can re-
transmit the data to the BS 300. In this case, the RS 302 listens to and
acquires the data
retransmitted from the MS 304 to the BS 300 according to the scheduling
information.
[72] The RS 302 checks for errors in the data retransmitted from the MS 304 in
step 331.
For example, the RS 302 checks for errors using the CRC of the data.
[73] The BS 300 can acquire the time point information of the data
retransmission from
the MS 304 to the RS 302 according to the scheduling information received from
the
MS 304. Thus, the BS 300 transmits scheduling information for the RS 302 to
forward
the retransmitted data from the MS 304 to the BS 300, to the RS 302 by taking
into
account the data retransmission time point of the MS 302 in step 333.
[74] When the data retransmitted from the MS 304 has no error, the RS 302
forwards the
retransmitted data from the MS 304 to the BS 300 using the scheduling
information
received in step 333, in step 335. In doing so, the RS 302 transmits the data
including
the ACK message.
[75] The BS 300 checks for errors in the data received from the RS 302 in step
337. For
example, the BS 300 checks for errors using the CRC of the data.
[76] When the data received from the RS 302 has an error, the BS 300 sends a
NACK
message and scheduling information for retransmitting the data to the RS 302
in steps
339 and 341. The BS 300 may transmit merely the scheduling information for the
data
retransmission to the RS 302.
[77] Receiving the NACK message from the BS 300, the RS 302 recognizes that
the data
transmitted to the BS 300 has an error. Accordingly, in step 343, the RS 302
re-
transmits the data to the BS 300 according to the scheduling information
received from
the BS 300 in step 341.
[78] In step 345, the BS 300 checks for errors in the data retransmitted from
the RS 302.
For example, the BS 300 checks the data error using the CRC of the data.
[79] When the data received from the RS 302 has no errors, the BS 300 sends an
ACK
message to the RS 302 or the MS 304 in step 347 or 349. For example, the BS
300
sends the ACK message to each of the RS 302 and the MS 304, or to the MS 304
via
the RS 302.
[80] Alternatively, the BS 300 can send the ACK message only to the MS 304.
The RS
302 confirms that there are no errors in the data transmitted to the BS 300 by
listening
to the ACK message sent from the BS 300 to the MS 304. When the NACK message
or the scheduling information for the data retransmission is not received from
the BS
300 for a certain time, the RS 302 regards the data transmitted to the BS 300
as having
no errors.
[81] In this embodiment of the present invention, the BS 300, upon receiving
the error-
free data from the MS 304 via the RS 302, sends the ACK message to the RS 302
or
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the MS 304. Alternatively, when receiving the data including the ACK message
from
the RS 302 as in step 335, the BS 300 sends the ACK message to the MS 304 re-
gardless of the error in the data received from the RS 302. In this case, when
the data
received from the RS 302 has no error, the BS 300 sends the ACK message to the
RS
302 or does not send the ACK message.
[82] In the following, operations of the BS, the RS, and the MS for the uplink
data re-
transmission of FIG. 2 or 3 are described.
[83] FIG. 4 illustrates the operations of the BS for retransmitting the uplink
signal in the
wireless relay communication system according to an embodiment of the present
invention. Herein, it is assumed that the BS sends the ACK message to the RS
or the
MS when the uplink data of the MS received via the RS has no errors.
[84] In step 401, the BS transmits the scheduling information for the RS and
the MS to
transmit the uplink data, to the RS and the MS. For example, the BS transmits
the
scheduling information of the MS to the RS and the MS respectively, or to the
MS via
the RS. Alternatively, the BS transmits the scheduling information only to the
MS. The
RS can acquire the scheduling information of the MS by listening to the
scheduling in-
formation transmitted from the BS to the MS.
[85] Also, the BS transmits the scheduling information for the RS to forward
the data
from the MS to the BS, to the RS. Herein, the BS transmits the scheduling
information
to the RS by considering the time point of the data transmission from the MS
to the
RS.
[86] In step 403, the BS checks whether the data including the ACK message is
received
from the RS according to the scheduling information for the RS to forward the
data
from the MS.
[87] When the NACK message, rather than the ACK message, is received according
to
the scheduling information, the BS sends the NACK message to request the data
re-
transmission to the MS in step 409.
[88] By contrast, when the data including the ACK message is received
according to the
scheduling information, the BS checks the data for errors in step 405. For
example, the
BS checks the data for errors using the CRC.
[89] When the data has an error, the BS transmits the scheduling information
for the data
retransmission to the RS in step 411. For example, after sending the NACK
message to
the RS, the BS transmits the scheduling information for the data
retransmission. Al-
ternatively, the BS can transmit merely the scheduling information for the
data re-
transmission to the RS.
[90] By contrast, when the data has no error, the BS sends the ACK message to
the RS or
the MS in step 407. For instance, the BS sends the ACK message to each of the
RS and
the MS, or to the MS via the RS. Alternatively, the BS can send the ACK
message
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only to the MS.
[91] Next, the BS finishes this process.
[92] As described above, when the data has an error, the BS performs the
retransmission
by requesting the data retransmission to the RS or the MS. The BS finishes the
re-
transmission process when a retransmission lifetime expires.
[93] FIG. 5 illustrates the operations of the RS for relaying the uplink
signal in the
wireless relay communication system according to an embodiment of the present
invention.
[94] In step 501, the RS checks the uplink scheduling information of the MS.
For
example, the RS receives the uplink scheduling information of the MS from the
BS.
Alternatively, the RS acquires the scheduling information by listening to the
uplink
scheduling information transmitted from the BS to the MS.
[95] In step 503, the RS checks whether data is received from the MS using the
scheduling information.
[96] When the data is not received from the MS for a certain time, the RS
returns to step
501 to confirm the uplink scheduling information of the MS.
[97] When receiving the data, the RS checks error of the data in step 505. For
example,
the RS checks the data error using the CRC.
[98] When the data has an error, the RS confirms the scheduling information
transmitted
from the BS so that the RS can forward the data from the MS, in step 513.
[99] In step 515, the RS sends the NACK message to the BS according to the
scheduling
information confirmed in step 513. Next, the RS goes to step 501 to confirm
the uplink
scheduling information of the MS.
[100] When the data has no errors in step 505, the RS confirms the scheduling
information
transmitted from the BS so that the RS forwards the data from the MS in step
507.
[101] In step 509, the RS forwards the data received from the MS to the BS
according to
the scheduling information. The data includes the ACK message.
[102] In step 511, the RS checks whether a retransmission request signal is
received from
the BS. Herein, the retransmission request signal includes the NACK message or
the
scheduling information for the retransmission.
[103] Receiving the retransmission request signal from the BS, the RS confirms
the
scheduling information for the data retransmission in step 507. For example,
when
receiving the NACK message from the BS, the RS recognizes the error in the
data
transmitted to the BS and receives the scheduling information for the data re-
transmission from the BS. Alternatively, when receiving the scheduling
information
for the data retransmission from the BS, the RS recognizes the error in the
data
transmitted to the BS.
[104] Meanwhile, when no retransmission request signal is received from the BS
in step
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511, the RS finishes this process. For example, the RS finishes this process
when the
ACK message is received from the BS. Herein, the RS can confirm the ACK
message
by receiving the ACK message from the BS or listening to the ACK message
transmitted from the BS to the MS. Alternatively, when the retransmission
request
signal is not received from the BS for a certain time, the RS recognizes the
data
transmitted to the BS as having no errors and finishes this process.
[105] As above, the RS performs the data retransmission process according to
the re-
transmission request of the BS. In doing so, when the retransmission lifetime
expires,
the RS finishes the retransmission process.
[106] FIG. 6 illustrates the operations of the MS for relaying the uplink
signal in the
wireless relay communication system according to an embodiment of the present
invention.
[107] In step 601, the MS checks whether the scheduling information for
transmitting the
uplink data is received from the BS.
[108] Receiving the scheduling information, the MS transmits data to the BS or
the RS
according to the scheduling information in step 603. For example, when the MS
re-
cognizes the RS, it can transmit the data to the RS according to the
scheduling in-
formation. When not recognizing the RS, the MS transmits the data to the BS
according to the scheduling information.
[109] In step 605, the MS checks whether the ACK message is received from the
BS.
[110] When the NACK message, rather than the ACK message, is received or when
the
ACK message is not received over a certain time, the MS returns to step 601
and
checks whether the scheduling information for the data retransmission is
received from
the BS. By contrast, receiving the ACK message, the MS finishes this process.
[111] When the RS retransmits the uplink data erred at the BS, the wireless
communication
system operates as shown in FIG. 7 or FIG. 8.
[112] FIG. 7 illustrates an uplink signal retransmission method in the
wireless relay com-
munication system according to another embodiment of the present invention.
[113] A BS 700 transmits the resource scheduling information for an MS 704 to
send data,
to an RS 702 or the MS 704 in step 711 or 713. For example, the BS 700
transmits the
scheduling information to each of the RS 702 and the MS 704, or to the MS 704
via
the RS 702.
[114] Alternatively, the BS 700 can transmit the scheduling information only
to the MS
704. The RS 702 can acquire the scheduling information of the MS 704 by
listening to
the scheduling information transmitted from the BS 700 to the MS 704.
[115] The RS 702 and the MS 704 confirm the time point and the resource
information of
the data transmission of the MS 704 using the scheduling information received
from
the BS 700.
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[116] In step 715, the MS 704 transmits data to the RS 702 according to the
scheduling in-
formation. If the MS 704 cannot recognize the RS 702, it may transmit the data
to the
BS 700. The RS 702 listens to and acquires the data transmitted from the MS
704 to
the BS 700 according to the scheduling information.
[117] In step 717, the RS 702 checks for errors in the data received from the
MS 704. For
example, the RS 702 checks the data for errors using the CRC of the data.
[118] When the data received from the MS 704 has no errors, the RS 702 sends
the ACK
message to the BS 700 according to the scheduling information received from
the BS
700 for sending the ACK/NACK message in step 719. Herein, the BS 700 transmits
the scheduling information for sending the ACK/NACK message to the RS 702
according to the time point of the data transmission from the MS 704 to the RS
702.
[119] Upon receiving the ACK message from the RS 702, the BS 700 transmits the
scheduling information for the RS 702 to forward the data from the MS 704 to
the BS
700, to the RS 702 in step 721.
[120] In step 723, the RS 702 forwards the data from the MS 704 to the BS 700
using the
scheduling information.
[121] In step 725, the BS 700 checks for errors in the data received from the
RS 702. For
example, the BS 700 checks the data for errors using the CRC of the data.
[122] When the data received from the RS 702 has no errors, the BS 700 sends
the ACK
message to the RS 702 or the MS 704 in step 727 or 729. For example, the BS
700
sends the ACK message to each of the RS 702 and the MS 704, or to the MS 704
via
the RS 702.
[123] Alternatively, the BS 700 sends the ACK message only to the MS 704. The
RS 702
confirms no error in the data transmitted to the BS 700 by listening to the
ACK
message sent from the BS 700 the MS 704. Also, when the NACK message or the
scheduling information for the data retransmission is not received from the BS
700
over a certain time, the RS 702 regards as no error in the data transmitted to
the BS
700.
[124] In this embodiment of the present invention, the BS 700 sends the ACK
message to
the RS 702 or the MS 704 when the error-free data is received from the MS 704
via the
RS 702. Alternatively, when receiving the ACK message from the RS 702 as in
step
719, the BS 700 sends the ACK message to the MS 704. In this case, when the
data
received from the RS 702 has no error, the BS 700 sends the ACK message to the
RS
702 or does not send the ACK message at all.
[125] FIG. 8 illustrates an uplink signal retransmission method in the
wireless relay com-
munication system according to still another embodiment of the present
invention. It is
assumed that the data sent from the MS 704 to the RS 702 and the data sent
from the
RS 702 to the BS 700 have errors in FIG. 7.
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[126] In step 811 or 813, a BS 800 transmits the resource scheduling
information for an
MS 804 to send uplink data, to an RS 802 or the MS 804. For example, the BS
800
transmits the scheduling information to each of the RS 802 and the MS 804, or
to the
MS 804 via the RS 802.
[127] Alternatively, the BS 800 can transmit the scheduling information only
to the MS
804. The RS 802 can acquire the uplink scheduling information of the MS 804 by
listening to the scheduling information transmitted from the BS 800 to the MS
804.
[128] The RS 802 and the MS 804 confirm the time point of the data
transmission and the
resource information of the MS 804 using the scheduling information provided
from
the BS 800.
[129] In step 815, the MS 804 transmits data to the RS 802 according to the
scheduling in-
formation. If the MS 804 cannot recognize the RS 802, it may transmit the data
to the
BS 800. In this case, the RS 802 listens to and acquires the data transmitted
from the
MS 804 to the BS 800 according to the scheduling information.
[130] In step 817, the RS 802 checks for errors in the data received from the
MS 804. For
example, the RS 802 checks the data for errors using the CRC of the data.
[131] When the data received from the MS 802 has an error, the RS 802 sends
the NACK
message to the BS 800 according to the scheduling information provided from
the BS
800 for the ACK/NACK message transmission in step 819. Herein, the BS 800
transmits the scheduling information for the ACK/NACK message transmission to
the
RS 802 according to the time point of the data transmission from the MS 804 to
the RS
802.
[132] Upon receiving the NACK message from the RS 802, the BS 800 sends the
NACK
message to the MS 804 to request the retransmission in step 821.
[133] In step 823 or 825, the BS 800 transmits the scheduling information for
the data re-
transmission of the MS 804 to the RS 802 or the MS 804. For example, the BS
800
transmits the scheduling information to each of the RS 802 and the MS 804, or
to the
MS 804 via the RS 802.
[134] Alternatively, the BS 800 can transmit the scheduling information only
to the MS
804. The RS 802 can acquire the uplink scheduling information of the MS 804 by
listening to the scheduling information transmitted from the BS 800 to the MS
804.
[135] The RS 802 and the MS 804 confirm the time point of the data
retransmission and
the resource information of the MS 804 using the scheduling information
provided
from the BS 800.
[136] In step 827, the MS 804 retransmits the data to the RS 802 according to
the
scheduling information. If the MS 804 cannot recognize the RS 802, it can
retransmit
the data to the BS 800. In this situation, the RS 802 listens to and acquires
the data re-
transmitted from the MS 804 to the BS 800 according to the scheduling
information.
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[137] In step 829, the RS 802 checks for errors in the data retransmitted from
the MS 804.
For example, the RS 802 checks the data for errors using the CRC of the data.
[138] When the data retransmitted from the MS 804 has no errors, the RS 802
sends the
ACK message to the BS 800 according to the scheduling information, which is
provided from the BS 800, for the ACK/NACK message transmission in step 831.
Herein, the BS 800 transmits the scheduling information for the ACK/NACK
message
transmission to the RS 802 according to the time point of the data sent from
the MS
804 to the RS 802.
[139] Upon receiving the ACK message from the RS 802, the BS 800 transmits the
scheduling information for the RS 802 to forward the data from the MS 804 to
the BS
800, to the RS 802 in step 833.
[140] In step 835, the RS 802 forwards the data retransmitted from the MS 804
to the BS
800 according to the scheduling information.
[141] In step 837, the BS 800 checks for errors in the data retransmitted from
the RS 802.
For example, the BS 800 checks the data for errors using the CRC of the data.
[142] When the data received from the RS 802 has an error, the BS 800 sends
the NACK
message and the scheduling information for the data retransmission of the RS
802 to
the RS 802 in steps 839 and 841. Herein, the BS 800 can transmit only the
scheduling
information to the RS 802.
[143] Upon receiving the NACK message, the RS 802 recognizes the error in the
data
transmitted to the BS 800 and checks the scheduling information for the data
re-
transmission from the BS 800. Next, the RS 802 retransmits the data to the BS
800
according to the scheduling information in step 843.
[144] In step 845, the BS 800 checks for errors in the data retransmitted from
the RS 802.
For instance, the BS 800 checks the data for errors using the CRC of the data.
[145] When the data retransmitted from the RS 802 has no errors, the BS 800
sends the
ACK message to the RS 802 or the MS 804 in step 847 or 849. For example, the
BS
800 sends the ACK message to each of the RS 802 and the MS 804, or to the MS
804
via the RS 802.
[146] Alternatively, the BS 800 can send the ACK message only to the MS 804.
The RS
802 confirms that there are no errors in the data sent to the BS 800 by
listening to the
ACK message sent from the 800 to the MS 804. Also, when the NACK message or
the
scheduling information for the data retransmission is not received from the BS
800
over a certain time, the RS 802 regards as no error in the data sent to the BS
800.
[147] In this embodiment of the present invention, receiving the error-free
data from the
MS 804 via the RS 802, the BS 800 sends the ACK message to the RS 802 or the
MS
804. Alternatively, when receiving the ACK message from the RS 802 as in step
831,
the BS 800 sends the ACK message to the MS 804. In this case, when the data
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received from the RS 802 has no errors, the BS 800 sends the ACK message to
the RS
802 or does not send the ACK message at all.
[148] Now, the operations of the BS and the RS for the uplink data
retransmission of FIG.
7 or 8 are illustrated.
[149] FIG. 9 illustrates the operations of the BS for retransmitting an uplink
signal in the
wireless relay communication system according to another embodiment of the
present
invention. It is assumed that the BS sends the ACK message to the RS or the MS
when
the uplink data received from the MS via the RS has no error.
[150] In step 901, the BS transmits the resource scheduling information for
the MS to send
the uplink data, to the RS and the MS. For instance, the BS transmits the
scheduling in-
formation of the MS to each of the RS and the MS, or to the MS via the RS. Al-
ternatively, the BS transmits the scheduling information only to the MS. In
this case,
the RS can acquire the scheduling information of the MS by listening to the
scheduling
information sent from the BS to the MS.
[151] Also, the BS transmits the scheduling information for the RS to send the
ACK/
NACK message, to the RS. The BS transmits the scheduling information for the
uplink
data transmission to the RS according to the time point of the data
transmission from
the MS to the RS.
[152] Next, the BS checks whether the ACK message is received from the RS in
step 903.
[153] Upon receiving the NACK message rather than the ACK message, the BS
sends the
NACK message to the MS to request the data retransmission in step 913.
[154] By contrast, upon receiving the ACK message, the BS transmits the
scheduling in-
formation for the RS to forward the data from the MS, to the RS in step 905.
[155] In step 907, the BS receives the data from the RS.
[156] In step 909, the BS checks the data for errors. For example, the BS
checks the data
for errors using the CRC.
[157] When the data has an error, the BS sends the NACK message to request the
data re-
transmission in step 915. Next, the BS goes to step 905 and transmits the
scheduling
information for the RS to retransmit the data.
[158] When the data is free from error, the BS sends the ACK message to the RS
or the MS
in step 911. For instance, the BS sends the ACK message to each of the RS and
the
MS, or to the MS via the RS. Alternatively, the BS can send the ACK message
only to
the MS. Next, the BS finishes this process.
[159] As such, when the data has an error, the BS performs the retransmission
process by
requesting the data retransmission to the RS or the MS. When the
retransmission
lifetime expires, the BS finishes the retransmission process.
[160] FIG. 10 illustrates the operations of the RS for relaying the uplink
signal in the
wireless relay communication system according to another embodiment of the
present
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invention.
[161] In step 1001, the RS confirms the uplink scheduling information of the
MS. For
instance, the RS receives the uplink scheduling information of the MS from the
BS.
Alternatively, the RS acquires the scheduling information by listening to the
uplink
scheduling information sent from the BS to the MS.
[162] In step 1003, the RS checks whether data is received from the MS
according to the
scheduling information.
[163] When the data is not received over a certain time, the RS goes back to
step 1001 and
confirms the uplink scheduling information of the MS.
[164] By contrast, when receiving the data from the MS according to the
scheduling in-
formation, the RS checks for errors in the data received from the MS in step
1005. For
example, the RS checks for errors in the data using the CRC.
[165] When the data has an error, the RS sends the NACK message to the BS
according to
the scheduling information for the ACK/NACK message transmission, which is
provided from the BS, in step 1015. Next, the RS returns to step 1001 and
confirms the
scheduling information for the data retransmission of the MS.
[166] When the data has no errors in step 1005, the RS sends the ACK message
to the BS
according to the scheduling information for the ACK/NACK message transmission
in
step 1007.
[167] In step 1009, the RS receives from the BS and confirms the scheduling
information
for the uplink data transmission.
[168] In step 1011, the RS forwards the data received from the MS to the BS
according to
the scheduling information.
[169] In step 1013, the RS checks whether the retransmission request signal is
received
from the BS. Herein, the retransmission request signal includes the NACK
message.
[170] When receiving the retransmission request signal from the BS, the RS
goes back to
step 1009 to receive from the BS and confirm the scheduling information for
the data
retransmission. For example, the RS, upon receiving the NACK message from the
BS,
recognizes the error in the data sent to the BS and receives the scheduling
information
for the data retransmission from the BS.
[171] By contrast, when not receiving the retransmission request signal from
the BS, the
RS finishes this process. For example, the RS finishes this process when
receiving the
ACK message from the BS. The RS may receive the ACK message from the BS or
listen to the ACK message sent from the BS to the MS. Alternatively, when the
re-
transmission request signal is not received from the BS over a certain time,
the RS
regards the data sent to the BS as having no errors and thus finishes this
process.
[172] As above, the RS performs the data retransmission process according to
the re-
transmission request of the BS. In doing so, when the retransmission lifetime
expires,
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the RS finishes the retransmission process.
[173] Now, descriptions provide how the wireless communication system
selectively
receives the retransmitted data from the RS or the MS when the BS of the
wireless
communication system receives data directly from the MS without the RS as
shown in
FIG. 11 or 12.
[174] FIG. 11 illustrates an uplink signal retransmission method in the
wireless relay com-
munication system according to another embodiment of the present invention.
[175] In step 1113, a BS 1100 transmits resource scheduling information for an
MS 1104
to send uplink data, to the MS 1104. An RS 1102 can acquire the uplink
scheduling in-
formation of the MS 1104 by listening to the scheduling information sent from
the BS
1100 to the MS 1104.
[176] Alternatively, the BS 1100 transmits monitoring information including an
ID of the
MS 1104 to the RS 1102 so that the RS 1102 can confirm the uplink data
received
from the MS 1104 in step 1111.
[177] In doing so, the RS 1102 confirms time point of the data transmission
and resource
information of the MS 1104 from the scheduling information or the monitoring
in-
formation received from the BS 1100.
[178] In step 1115, the MS 1104 transmits data to the BS 1100 according to the
scheduling
information. The RS 1102 listens to and confirms the data sent from the MS
1104 to
the BS 1100 according to the scheduling information or the monitoring
information.
[179] The RS 1102 checks for errors in the listened data. When the data has no
errors, the
RS 1102 temporarily stores the data and sends an ACK message to the BS 1100.
By
contrast, when the listened data has an error, the RS 1102 sends a NACK
message to
the BS 1100. At this time, the RS 1102 sends the ACK message or the NACK
message
to the BS 1100 according to the scheduling information, which is provided from
the
BS 1100, for sending the ACK/NACK message.
[180] In step 1117, the BS 1100 checks for errors in the data received from
the MS 1104.
For example, the BS 1100 checks the data for errors using the CRC of the data.
[181] When the data from the MS 1104 has no errors, the BS 1100 sends an ACK
message
to the RS 1102 or the MS 1104 in step 1119 or 1121. For instance, the BS 1100
sends
the ACK message to each of the RS 1102 and the MS 1104, or to the MS 1104 via
the
RS 1102.
[182] Alternatively, the BS 1100 can send the ACK message only to the MS 1104.
The RS
1102 confirms there are no errors in the data sent to the BS 1100 by listening
to the
ACK message transmitted from the BS 1100 to the MS 1104.
[183] When the NACK message or the scheduling information for the data
retransmission
is not received from the BS 110 over a certain time, the RS 1102 regards the
data sent
to the BS 1100 as having no errors.
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[184] FIG. 12 illustrates an uplink signal retransmission method in the
wireless relay com-
munication system according to another embodiment of the present invention. It
is
assumed that the data sent from the MS 1104 to the RS 1102 and the data sent
from the
RS 1102 to the BS 1100 in FIG. 11 have errors.
[185] In step 1213, a BS 1200 transmits the resource scheduling information
for an MS
1204 to send uplink data, to the MS 1204. An RS 1202 can acquire the uplink
scheduling information of the MS 1204 by listening to the scheduling
information sent
from the BS 1200 to the MS 1204, which communicates with the RS 1202.
[186] Alternatively, the BS 1200 transmits monitoring information including
the ID of the
MS 1204 to the RS 1202 so that the RS 1202 can confirm the uplink data sent
from the
MS 1204 in step 1211.
[187] In this case, the RS 1202 confirms time point of the data transmission
and resource
information of the MS 1204 from the scheduling information or the monitoring
in-
formation.
[188] In step 1215, the MS 1204 transmits data to the BS 1200 according to the
scheduling
information. The RS 1202 listens to and acquires the data sent from the MS
1204 to the
BS 1200 according to the scheduling information or the monitoring information.
[189] In steps 1217 and 1219, the BS 1200 and the RS 1202 check for errors in
the data
received from the MS 1204. When the data received from the MS 1204 has no
errors,
the RS 1202 temporarily stores the data and sends an ACK message to the BS
1200.
When the data received from the MS 1204 has an error, the RS 1202 sends a NACK
message to the BS 1200. Herein, the RS 1202 sends the ACK or NACK message to
the
BS 1200 according to the scheduling information, which is provided from the BS
1200, for the ACK/NACK transmission.
[190] Provided that the data received at the RS 1202 has an error, the RS 1202
sends the
NACK message to the BS 1200 in step 1221.
[191] Provided that the data received at the BS 1200 has an error, the BS 1200
checks the
ACK/NACK message received from the RS 1202. In doing so, when receiving the
NACK message from the RS 1202, the BS 1200 sends a NACK message to the MS
1204 to request the data retransmission in step 1223.
[192] In step 1227, the BS 1200 transmits resource scheduling information for
the MS
1204 to retransmit the uplink data, to the MS 1204. The RS 1202 can acquire
the
uplink scheduling information of the MS 1204 by listening to the scheduling in-
formation sent from the BS 1200 to the MS 1204, which communicates with the RS
1202.
[193] If the BS 1200 transmits the monitoring information to the RS 1202 in
step 1225, the
RS 1202 can confirm the time point and the resource of the data retransmission
from
the MS 1204 according to the monitoring information.
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[194] In step 1229, the MS 1204, upon confirming the scheduling information
from the BS
1200, retransmits the data to the BS 1200 according to the scheduling
information. The
RS 1202 listens to and acquires the data sent from the MS 1204 to the BS 1200
according to the scheduling information or the monitoring information.
[195] In steps 1231 and 1233, the BS 1200 and the RS 1202 check for errors in
the data
received from the MS 1204. When the data has no errors, the RS 1202
temporarily
stores the data and sends an ACK message to the BS 1200. When the data has an
error,
the RS 1202 sends a NACK message to the BS 1200. The RS 1202 sends the ACK or
NACK message to the BS 1200 according to the scheduling information, which is
provided from the BS 1200, for the ACK/NACK message transmission.
[196] Provided that the data received at the RS 1202 is free from errors, the
RS 1202 sends
an ACK message to the BS 1200 in step 1235.
[197] When the data received at the BS 1200 has an error, the BS 1200 checks
whether the
ACK or NACK message is received from the RS 1202.
[198] When receiving the ACK message from the RS 1202, the BS 1200 determines
a node
for retransmitting the data among the RS 1202 and the MS 1204. For example,
the BS
1200 determines the node for retransmitting the data by taking into account
channel in-
formation of the RS 1202 and channel information of the MS 1204.
[199] When the RS 1202 is selected as the node for retransmitting the data,
the BS 1200
transmits scheduling information for the RS 1202 to send the listened data
from the
MS 1204, to the RS 1202 in step 1237.
[200] In step 1239, the RS 1202 sends the data listened from the MS 1204 to
the BS 1200
using the scheduling information.
[201] In step 1241, the BS 1200 checks for errors in the data retransmitted
from the RS
1202. For example, the BS 1200 checks the data error using the CRC of the
data.
[202] When the data has an error, the BS 1200 transmits a NACK message and
scheduling
information for the RS 1202 to retransmit the data, to the RS 1202 in steps
1243 and
1245. The BS 1200 can transmit merely the scheduling information to the RS
1202.
[203] Receiving the NACK message, the RS 1202 recognizes the error in the data
sent to
the BS 1200 and retransmits the data to the BS 1200 according to the
scheduling in-
formation in step 1247.
[204] In step 1249, the BS 1200 checks for errors in the data retransmitted
from the RS
1202. For example, the BS 1200 checks the data error using the CRC of the
data.
[205] When the data has no errors, the BS 1200 sends an ACK message to the RS
1202 or
the MS 1204 in step 1251 or 1253. For instance, the BS 1200 sends the ACK
message
to each of the RS 1202 and the MS 1204, or to the MS 1204 via the RS 1202.
[206] Alternatively, the BS 1200 can send the ACK message only to the MS 1204.
The RS
102 listens to the ACK message sent from the BS 1200 to the MS 1204 and
confirms
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that there are no errors in the data transmitted to the BS 1200. When the NACK
message or the scheduling information for the data retransmission is not
received from
the BS 1200 over a certain time, the RS 1202 regards the data transmitted to
the BS
1200 as having no errors.
[207] In this embodiment of the present invention, when receiving the error-
free uplink
data of the MS 1204 via the RS 1202, the BS 1200 sends the ACK message to the
RS
1202 or the MS 1204. Alternatively, when receiving the ACK message from the RS
1202 as in step 1235, the BS 1200 sends the ACK message to the MS 1204. In
this
case, when the data received from the RS 1202 has no error, the BS 1200 sends
the
ACK message to the RS 1202 or does not send the ACK message at all.
[208] When the BS selects the MS as the node for requesting the retransmission
of the data,
the wireless communication system performs the retransmission process as shown
in
FIG. 13.
[209] FIG. 13 illustrates an uplink signal retransmission method in the
wireless relay com-
munication system according to another embodiment of the present invention.
[210] A BS 1300 transmits resource scheduling information for an MS 1304 to
send uplink
data, to the MS 1304 in step 1313. An RS 1302 can acquire the uplink
scheduling in-
formation of the MS 1304 by listening to the scheduling information sent from
the BS
1300 to the MS 1304.
[211] Alternatively, the BS 1300 transmits monitoring information including an
ID of the
MS 1304 to the RS 1302 so that the RS 1302 can confirm the uplink data
transmitted
from the MS 1304 in step 1311.
[212] The RS 1302 confirms time point and resource information of the data
transmission
of the MS 1304 from the scheduling information or the monitoring information.
[213] In step 1315, after confirming the scheduling information, the MS 1304
transmits
data to the BS 1300 according to the scheduling information. The RS 1302
listens to
and confirms the data sent from the MS 1304 to the BS 1300 according to the
scheduling information or the monitoring information.
[214] In steps 1317 and 1319, the BS 1300 and the RS 1302 check for errors in
the data
received from the MS 1304. When the data has no errors, the RS 1302
temporarily
stores the data and sends an ACK message to the BS 1300. When the data has an
error,
the RS 1302 sends a NACK message to the BS 1300. The RS 1302 sends the ACK or
NACK message to the BS 1300 according to the scheduling information, which is
provided from the BS 1300, for the ACK/NACK message transmission.
[215] Provided that the data received at the RS 1302 has no errors, the RS
1302 sends an
ACK message to the BS 1300 in step 1321.
[216] Provided that the data received at the BS 1300 has an error, the BS 1300
selects a
node for requesting the data retransmission (e.g., RS 1302 or MS 1304). For
example,
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the BS 1300 selects the node for requesting the data retransmission by
checking the
channel conditions of the RS 1302 and the MS 1304.
[217] Provided that the MS 1304 is the node for retransmitting the data to the
BS 1300, the
BS 1300 sends the NACK message to the MS 1304 to request the data
retransmission
even when the ACK message is received from the RS 1302 in step 1323.
[218] In step 1325, the BS 1300 transmits resource scheduling information for
the MS
1304 to retransmit the uplink data, to the MS 1304.
[219] After confirming the scheduling information, the MS 1304 retransmits the
data to the
BS 1300 according to the scheduling information in step 1327.
[220] In step 1329, the BS 1300 checks for errors in the data received from
the MS 1304.
For example, the BS 1300 checks the data for errors using the CRC of the data.
[221] When the data has no errors, the BS 1300 sends an ACK message to the RS
1302 or
the MS 1304 in step 1331 or 1333. For instance, the BS 1300 sends the ACK
message
to each of the RS 1302 and the MS 1304.
[222] The BS 1300 can send the ACK message only to the MS 1304. The RS 1302
confirms that there are no errors in the data sent to the BS 1300 by listening
to the
ACK message sent from the BS 1300 to the MS 1304. When the NACK message or
the scheduling information for the data retransmission is not received from
the BS
1300 over a certain time, the BS 1302 regards the data sent to the BS 1300 as
having
no errors.
[223] Now, the operations of the BS and the RS for performing the uplink data
re-
transmission of FIG. 11, 12, or 13 are explained.
[224] FIG. 14 illustrates the operations of the BS for retransmitting the
uplink signal in the
wireless relay communication system according to further embodiment of the
present
invention.
[225] In step 1401, the BS transmits the scheduling information for the MS to
send the
uplink data, to the MS. The BS also transmits the monitoring information
including the
ID information of the MS to the RS to confirm the uplink data of the MS. If
the RS
listens to the scheduling information sent from the BS to the MS, the BS needs
not to
transmit the monitoring information to the RS.
[226] In step 1403, the BS receives the data from the MS.
[227] In step 1405, the BS checks for errors in the data. For example, the BS
checks the
data for errors using the CRC.
[228] When the data has no errors, the BS goes to step 1419 and sends the ACK
message to
the RS and the MS. The BS can send the ACK message to each of the RS and the
MS,
or only to the MS.
[229] By contrast, when the data has an error, the BS checks whether the ACK
message is
received from the RS in step 1407.
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[230] When receiving the NACK message from the RS, the BS sends the NACK
message
to request the data retransmission to the MS in step 1421.
[231] When receiving the ACK message from the RS, the BS determines the node
(e.g., RS
or MS) for the data retransmission request in step 1409. Herein, the BS
determines the
node for the data retransmission request by taking into account the channel
conditions
of the RS and the MS.
[232] In step 1411, the BS checks whether the RS is selected as the node for
the re-
transmission request.
[233] When the MS is selected as the retransmission request node, the BS goes
to step
1421 and sends the NACK message indicative of the data error to the MS.
[234] Next, the BS returns to step 1401 and transmits the scheduling
information for the
uplink data retransmission of the MS, to the MS.
[235] By contrast, when the RS is selected as the retransmission request node,
the BS
transmits the scheduling information for the RS to forward the data listened
from the
MS, to the RS in step 1413.
[236] In step 1415, the BS receives the data from the RS.
[237] In step 1417, the BS checks for errors in the data. For example, the BS
checks the
data error using the CRC.
[238] When the data has an error, the BS goes back to step 1413 and transmits
the
scheduling information for the data retransmission to the RS. Alternatively,
the BS
transmits the NACK message indicative of the data error to the RS, which is
not
shown. Next, the BS returns to step 1413 and transmits the scheduling
information to
the RS.
[239] When the data is free from errors, the BS sends the ACK message to the
RS or the
MS in step 1419. The BS can send the ACK message to each of the RS and the MS,
or
only to the MS. Next, the BS finishes this process.
[240] As mentioned above, when the data has an error, the BS performs the
retransmission
process by requesting the data retransmission to the RS or the MS. When the re-
transmission lifetime expires, the BS finishes the retransmission process.
[241] FIG. 15 illustrates the operations of the RS for relaying the uplink
signal in the
wireless relay communication system according to another embodiment of the
present
invention.
[242] In step 1501, the RS confirms the uplink scheduling information of the
MS. For
instance, the RS acquires the scheduling information by listening to the
uplink
scheduling information sent from the BS to the MS communicating with the RS.
Al-
ternatively, the RS confirms the scheduling information for the uplink data
transmission of the MS based on the monitoring information provided from the
BS.
[243] In step 1503, the RS checks whether the data is received from the MS
using the
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scheduling information.
[244] When no data is received over a certain time, the RS goes back to step
1501 and
confirms the uplink scheduling information of the MS.
[245] Upon receiving the data, the RS checks for errors in the data in step
1505. For
example, the RS checks the data for errors using the CRC.
[246] When the data has an error, the RS sends the NACK message to the BS
according to
the scheduling information, which is provided from the BS, for the ACK/NACK
message transmission in step 1515. Next, the RS goes to step 1501 and confirms
the
uplink scheduling information of the MS.
[247] By contrast, when the data is free from errors in step 1505, the RS
sends the ACK
message to the BS according to the scheduling information for the ACK/NACK
message transmission in step 1507.
[248] In step 1509, the RS checks whether the scheduling information for the
uplink data
transmission is received from the BS.
[249] When receiving the scheduling information, the RS transmits the data to
the BS
according to the scheduling information in step 1511.
[250] In step 1513, the RS checks whether the ACK message is received from the
BS.
[251] When the NACK message, rather than the ACK message, is received, the RS
goes
back to step 1509 and checks whether the scheduling information for the data
re-
transmission is received from the BS.
[252] When the ACK message is received, the RS finishes this process. For
instance, the
RS can receive the ACK message from the BS or listen to the ACK message sent
from
the BS to the MS communicating with the RS. Alternatively, when no
retransmission
request signal is received from the BS over a certain time, the RS regards the
data
transmitted to the BS as having no error and accordingly finishes this
process.
[253] As described above, the RS performs the data retransmission process
according to the
retransmission request of the BS. When the retransmission lifetime expires,
the RS
finishes the retransmission process.
[254] Now, the structures of the BS, the RS, and the MS for performing the
data re-
transmission in the wireless communication system are explained. Herein, since
the
BS, the RS, and the MS have the same structure, only the structure of the RS
is il-
lustrated based on FIG. 16 and the descriptions on the BS and the MS shall be
omitted.
[255] FIG. 16 is the block diagram of the RS in the wireless relay
communication system
according to an embodiment of the present invention. While it is assumed that
a sender
1600 and a receiver 1620 use different antennas, they may use a singe antenna.
[256] The RS of FIG. 16 includes the sender 1600, the receiver 1620, an ARQ
controller
1640, an ARQ state part 1650, an ARQ timer 1660, and a channel estimator 1670.
The
sender 1600 and the receiver 1620 share the ARQ controller 1640, the ARQ state
part
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1650, the ARQ timer 1660, and the channel estimator 1670.
[257] The sender 1600 includes a data generator 1601, a channel encoder 1603,
a CRC
generator 1605, a modulator 1607, an Inverse Fast Fourier Transform (IFFT)
operator
1609, and a Radio Frequency (RF) processor 1611.
[258] The data generator 1601 gathers data stored to a data queue 1613 and a
control
message generated at a message generator 1617 in a Service Data Unit (SDU)
generator 1615 and generates one data for the physical layer transmission.
Herein, the
message generator 1617 generates an ACK control message when the data received
through the receiver 1620 is free from errors. By contrast, when the data has
an error,
the message generator 1617 generates an NACK message.
[259] The channel encoder 1603 encodes the data provided from the data
generator 1601 at
a corresponding modulation level (e.g., Modulation and Coding Scheme (MCS)
level).
The CRC generator 1605 generates and adds the CRC to the data output from the
channel encoder 1603.
[260] The modulator 1607 modulates the data output from the CRC generator 1605
at the
corresponding modulation level (e.g., MCS level).
[261] The IFFT operator 1609 converts the frequency-domain data output from
the
modulator 1607 to a time-domain signal through the IFFT process.
[262] The RF operator 1611 up-converts the baseband signal output from the
IFFT operator
1609 to an RF signal and outputs the RF signal to the BS or the MS over an
antenna.
[263] The receiver 1620 includes an RF processor 1621, an FFT operator 1623, a
de-
modulator 1625, a CRC remover 1627, a channel decoder 1629, and a data
processor
1631.
[264] The RF processor 1621 down-converts the RF signal received from the BS
or the MS
over an antenna to a baseband signal.
[265] The FFT operator 1623 converts the time-domain signal output from the RF
processor 1621 to a frequency-domain signal through the FFT process.
[266] The demodulator 1625 demodulates the signal output from the FFT operator
1623 at
the corresponding modulation level. The demodulator 1625 outputs the
demodulated
signal to the CRC remover 1627 and the channel estimator 1670.
[267] The CRC remover 1627 detennines whether error occurs in the signal by
checking
the CRC of the signal output from the demodulator 1625. The CRC remover 1627
removes the CRC from the signal output from the demodulator 1625.
[268] The channel decoder 1629 decodes the error-free signal output from the
CRC
remover 1627 at the corresponding modulation level.
[269] An SDU processor 1635 of the data processor 1631 separates the data and
the control
message from the physical layer signal output from the channel decoder 1629.
The
SDU processor 1635 provides the data to a second data queue 1637 to store it,
and
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provides the control message to a message processor 1633 to decode it. Herein,
the
first data queue 1613 and the second data queue 1627 may be the same data
queue.
When the NACK control message is received from the BS, the message processor
1633 informs the ARQ controller 1640 of the NACK control message reception.
[270] The ARQ state part 1650 manages the ARQ condition with respect to the re-
transmitted data. The ARQ timer 1660 manages the retransmission lifetime of
the RS.
[271] The ARQ controller 1640 controls the overall ARQ operation of the RS in
as-
sociation with the ARQ state part 1650 and the ARQ timer 1660. The ARQ
controller
1640 controls the retransmission while communicating with the data generator
1601,
the channel encoder 1603, and the CRC generator 1605 of the sender 1600. For
example, upon receiving the retransmission request from the BS through the
receiver
1620, the ARQ controller 1640 controls to encode the data received from the MS
and
stored to the data queue 1613 according to the channel condition, to insert
the CRC,
and to retransmit the data to the BS.
[272] Also, the ARQ controller 1640 controls the retransmission while
communicating
with the data processor 1631, the channel decoder 1629, and the CRC remover
1627 of
the receiver 1620. For example, when the data has an error at the CRC remover
1627,
the ARQ controller 1640 controls the message generator 1617 to generate the
NACK
control message to be sent to the BS.
[273] When receiving the lifetime expire message from the ARQ timer 1660 in
the process
of the retransmission, the ARQ controller 1640 finishes the retransmission
process.
[274] While the wireless communication system provides the relay service using
the single
RS by way of example, a multihop relay wireless communication system can
perform
substantially the same operations.
[275] As set forth above, the wireless relay communication system carries out
the ARQ for
the uplink signal using the RS. Therefore, the RS can retransmit the error-
free data to
the BS and the BS can enhance the data reliability.
[276] While the invention has been shown and described with reference to
certain preferred
embodiments thereof, it will be understood by those skilled in the art that
various
changes in fonn and details may be made therein without departing from the
spirit and
scope of the invention as defined by the appended claims and their
equivalents.
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