Method and Apparatus for Non-adaptive Retransmission
Field of the Invention
Exemplary non-limiting embodiments of the present invention generally relate
to a wireless communication system, a method, an apparatus and a computer program,
and more particularly, to non-adaptive retransmission in the uplink.
Background of the Invention
3GPP long term evolution LTE technology aims to achieve higher data rate,
shorter delay, less cost, higher system capacity and improved coverage scope.
Multi-input multi-output MIMO technology is a crucial technology in enhancement of
frequency spectrum efficiency.
In the MIMO wireless communication system, a transmitter and a receiver both
use an antenna array, thereby providing rich space diversity and large communication
capacity. Space multiplexing is a common space-time modulating technology for
use in the MIMO communication system, wherein independent data streams are
transmitted through different transmitting antennas.
In the LTE-A, the uplink supports single user MIMO (SU-MIMO), i.e., the
uplink supports transmission of a plurality of antennas. This requires to provide a
plurality of uplink UL demodulation reference signals (DM-RS) for all the space
layers multiplexed together so that channel estimation can be carried out for each
layer at a receiving end. The reference signal RS, as commonly called "pilot signal",
is a known signal provided by a transmitting end to the receiving end for channel
estimation, synchronization or channel detection. Just as the technical term implies,
the uplink UL demodulation reference signal DM-RS is used as a reference for data
demodulation, whereby estimation is carried out with respect to the channel
parameters, such as the phase and the amplitude by using the UL DM-RS, and thereby
data transmitted on uplink can be demodulated correctly.
At the 3GPP RANI #57 meeting, the following DM-RS multiplexing principles
are agreed in respect of supporting the uplink space multiplexing.
- performing different cyclic shifts CSs for a pilot symbol serves as a main
multiplexing mechanism;
- multiplying different orthogonal cover codes OCCs between different time
slots of the same data frame serves a complementary multiplexing mechanism.
All the uplink DM-RSs have a reference signal sequence in the same form.
The uplink DM-RS sequences in the LTE system can be defined by a base sequence
plus cyclic shifts. Different amount of cyclic shifts is used for a base sequence, and
a plurality of reference signal sequences can be defined.
An optimal orthogonality can be provided between different reference signals
RSs by using the CS together with the OCC for DM-RS multiplexing, thereby
providing an optimal performance.
However, space multiplexing is extremely sensitive to bad conditions of the
channel. Hence, a hybrid automatic retransmission request HARQ mechanism is
used to ensure correctness of transmission. The HARQ can be classified into two
types, namely, adaptive retransmission and non-adaptive retransmission, depending
on whether data characteristics upon retransmission change. The data characteristics
comprise allocation of resource block, modulation mode, length of transmission block,
duration of transmission and so on.
The adaptive retransmission means that in each retransmission procedure, the
transmitting end can change partial transmission parameters according to actual
channel state information, so support from relevant control signaling is needed.
In the non-adaptive retransmission, these transmission parameters are already
known in advance to the receiving end, that is, the transmitting end and the receiving
end are informed before the initial transmission. Hence, the non-adaptive system
does not need the support of the corresponding control signaling.
Because of the complexity in the uplink, and interference from users in other
cells is uncertain, the base station cannot accurately estimate actual SINR value of
each user. Therefore, the 3GPP LTE system permits use of the non-adaptive HARQ
technology in the uplink.
In the current LTE-A standardization procedure, the non-adaptive HARQ
technology in the uplink is still under discussion and study. To date, there is not yet
provided a corresponding solution about how to configure the DM-RS(s) when
the user equipment UE carries out retransmission in the uplink.
Summary of the Invention
In view of the above, embodiments of the present invention provides a solution
about configuring the DM-RS(s) when the user equipment UE carries out
retransmission in the case that there is not an explicit signaling, i.e., in a
non-adaptive system.
According to an exemplary aspect of the present invention, there is provided a
method for use in non-adaptive retransmission, the method comprising: configuring
an uplink UL demodulation reference signal DM-RS for retransmission in response to
a retransmission request.
In a first embodiment, the demodulation reference signal DM-RS can be
configured to be the same as a demodulation reference signal for the initial
transmission.
In a second embodiment, the demodulation reference signal DM-RS can be
configured with respect to the transmission situation in retransmission according to
predetermined rules for the initial transmission, wherein the transmission situation in
the retransmission can be the number of layer(s) for retransmission.
Further, in the above second embodiment, cyclic shift indicator CSI in downlink
control information DCI is received, the cyclic shift indicator CSI indicates
configuration of the demodulation reference signal of the first layer for initial
transmission; configuration of demodulation reference signal of layer(s) for the
retransmission is derived with respect to the number of layer(s) for retransmission
according to the predetermined rules for the initial transmission, based on the received
cyclic shift indicator CSI.
Furthermore, configuring the demodulation reference signal DM-RS comprises
configuring the cyclic shift CS and the orthogonal cover code OCC of the DM-RS.
According to another exemplary aspect of the present invention, there is
provided an apparatus for use in non-adaptive retransmission, the apparatus
comprising: configuration means for configuring an uplink UL demodulation
reference signal DM-RS for retransmission in response to a retransmission request.
In a first embodiment, the configuration means can be used to configure the
demodulation reference signal DM-RS to be the same as a demodulation reference
signal for an initial transmission.
In a second embodiment, the configuration means can be used to configure the
demodulation reference signal DM-RS with respect to the transmission situation in
retransmission according to predetermined rules for the initial transmission, wherein
the transmission situation in the retransmission can be the number of layer(s) for
retransmission.
Furthermore, in the second embodiment, the apparatus further comprises:
receiving means for receiving cyclic shift indicator CSI in downlink control
information DCI, the cyclic shift indicator CSI indicating configuration of the
demodulation reference signal of the first layer for initial transmission; the
configuration means is further used to derive configuration of demodulation reference
signal of layer(s) for the retransmission with respect to the number of layer(s) for
retransmission according to the predetermined rules for the initial transmission, based
on the received cyclic shift indicator CSI.
Other aspects of the present invention can further comprise a computer program
product for implementing the above method and a storage medium for storing such
program.
Embodiments of the present invention provide the non-adaptive retransmission
system with a configuration solution of the uplink reference signal upon
retransmission without explicit signaling.
The first embodiment of the present invention is simple to implement without
needing standardization effort. The second embodiment of the present invention can
obtain a maximum RS separation between different layers. The second embodiment
needs standardization effort and has a little bit processing complexity for updating the
OCC and CS for retransmission. However, such cost is ignorable. Besides, a
mapping table of the optimized DM-RS configuration and the CSI is defined for the
MU-MIMO. When the mapping table is combined with the second embodiment, it
can be ensured that the same OCC is used for the two layers in the same UE, and
possibly different OCCs are allocated for two UEs in the MU-MIMO. This
increases the orthogonality of the DM-RSs, and is particularly adapted for
unequal bandwidth allocation of the MU-MIMO.
Brief Description of the Accompanying Drawings
The above-mentioned and other aspects of embodiments of the present invention
will be made clearer and apparent upon reading the following detailed description in
combination with the figures, wherein:
Fig. 1 illustrates an example of a wireless communication system environment in
which the present invention can be implemented;
Fig.2 shows an illustrative logic flowchart of a method according to an
embodiment of the present invention; and
Fig.3 illustrates an exemplary block diagram of an apparatus for implementing
the present invention according to an embodiment of the present invention.
In all of the above figures, the same reference numbers denote the same, like or
corresponding feature or function.
Detailed Description of the Preferred Embodiments
Specific embodiments of the present invention will be exemplarily described in
detail with reference to the figures.
Referring to Fig.l, the figure illustrates an example of a wireless communication
system environment 100 in which the present invention can be implemented. As
shown in Fig.l, the wireless communication system environment 100 can comprise a
base station BS 101 and a plurality of user equipment UE 102-1, 102-2 ...102-L,
wherein L is an integer greater than or equal to 1. The base station BS 101 has M
transmitting and receiving antennas, and each of user equipment UE102-1, 102-2, ...
102-L has N transmitting and receiving antennas, wherein M and N are both greater
than 1. In various embodiments, the base station BS 101 is also called eNB in LTE
and LTE-A systems. In the depictions in the following text, various embodiments
employ the base station eNB and user equipment UE for exemplary description.
In the LTE system, MIMO space multiplexing is usually realized by two
portions, namely, layer mapping and pre-coding. Basically, one layer corresponds to
one space multiplexing channel. The maximum number of layers is also called the
number of code streams, which is equal to the degree of freedom of the MEVIO
channel. The number of layers of MIMO is also called as the rank of an MIMO
system. As for a plurality of transmitting antenna ports, the rank is less than or equal
to the number of antennas. An MEVIO codeword will be respectively for channel
coding and modulation, and is converted into information block for transmission on a
single layer or multiple layers.
The MIMO technology is classified into singer user MEVIO SU-MIMO and
multi-user MIMO MU-MIMO. The SU-MIMO means that the eNB only serves one
user at a certain instant, and the user has a plurality of transmitting and receiving
antennas for space multiplexing. The MU-MIMO means that the eNB
simultaneously serves multiple users (also called a user group), each of which has a
plurality of transmitting and receiving antennas for space multiplexing.
Now referring to Fig.2, the figure shows an illustrative logic flowchart of a
method according to an embodiment of the present invention. The flow of Fig.2 will
be described in detail with reference the wireless communication system environment
100 as shown in Fig.l.
Fig.2 shows the base station eNB and an exemplary user equipment UE. As
shown in the figure, in step S201, at the user equipment UE, downlink control
information DCI is received from the base station eNB. As mentioned above, in
order to support SU-MIMO in the uplink in the LTE-A, there is a need to send to the
UE a plurality of cyclic shifts CSs and/or orthogonal cover codes OCCs for DM-RS
multiplexing. In the current LTE-A discussion, in the DCI format, a 3-bit field is
included so as to send a cyclic shift indicator CSI indicating the DM-RS configuration
for initial transmission. The 3-bit field corresponds to a cyclic shift CS index, which
is mapped to the DM-RS configuration for the first layer (marked as "layer-0).
As above stated, in the LTE Release 10, the cyclic shift CS separation serves as
a main multiplexing mechanism, and the orthogonal cover code OCC separation is
introduced between time slots to complement the orthogonality of the DM-RSs . The
configuration of the DM-RS comprises a cyclic shift CS value and an OCC value.
Therefore, the received cyclic shift indicator CSI is mapped to the cyclic shift CS
value ( ) and OCC value ( nocc 0 ) for the first layer (layer-0).
The above mapping relation can be directly expressed into a mapping table and
stored in the base station eNB and the user equipment UE. As such, the user
equipment UE can determine the DM-RS configuration indicated by the received CSI
by searching the mapping table. For example, Table 1 shows an exemplary mapping
table of the CSI and the DM-RS configuration for initial transmission according to an
embodiment of the present invention. Those skilled in the art can appreciate that the
mapping table in Table 1 is only exemplary and not limiting. Different mapping
tables can be constructed according to different needs and certain rules.
Table 1
Wherein when nocc = 0 , the corresponding OCC is [+1 +1]; when
occ = ' tne corresponding OCC is [+1 -1].
Then, in step S202, the user equipment UE derives the DM-RS
configurations of the remaining layers from the DM-RS configuration of the first
layer according to the rules defined for the initial transmission based on the received
CSI.
In the LTE-A, a CSI selection mode for the DM-RSs of respective space
layers for the initial transmission has already been determined. For example,
according to the following pre-determined rules, the DM-RS configurations of the
remaining space layers for initial transmission are derived from the DM-RS
configuration of the first layer for the initial transmission.
Regarding the CS of the kt ( k=0, 1,2,3 ) layer, it can be derived based
on a CS offset ( Ak ) and according to n MRS k = RS 0 + mod 12:
- as for two space layers, the CS offset ( Ak ) is respectively
0,6(k=0,l);
- as for four space layers, the CS offset ( Ak ) is respectively
0,6,3,9(k=0,l,2,3);
- as for three space layers, the CS offset ( Ak ) is to be further studied.
For example, it can be selected from {0,6,3} and {0,4,8} ( k=0,l,2 ) .
Regarding the OCC of kt ( k=0, 1,2,3 ) layer, it can be derived from the OCC
of the first layer (k=0):
- as for k=l, n ° 'k = n c o.
- as for k=2,3, °cc -k = 1 ~ °cc -° .
In this way, the DM-RS configurations of respective space layers for initial
transmission can be derived according to these predetermined rules.
Thereafter, in step S203, the user equipment UE carries out data
transmission according to the configured DM-RSs, for example, transmission on
the physical uplink sharing channel (PUSCH). This is initial transmission of
data.
After the base eNB receives the initially transmitted data, the data can be
demodulated. For example, by using the known DM-RS configurations, the
base station eNB can carry out channel estimation of the uplink channel so as to
determine properties of parameters such as phase and amplitude of the channel.
Therefore, the received data can be correctly demodulated.
By means of various encoding and modulating modes, the base station eNB
can determine whether the data is received correctly. Correspondingly, in the
step S204, the user equipment UE receives a feedback signal ACK/NACK from
the base station eNB. If the feedback signal is NACK, it means that the data of
the space layers is not received correctly, and the user equipment UE must
retransmit the data.
For example, a HARQ indicator channel (PHICH) is defined in the LTE to carry
response information, and indicate whether the base station eNB receives correctly the
data transmitted by the user equipment UE on the physical uplink sharing channel
PUSCH.
In the current LTE system, the above steps S201-S204 are all defined
explicitly. However, regarding the non-adaptive retransmission in the uplink,
there is not yet provided a specific solution about how to configure the DM-RSs
of the respective space layers to be retransmitted when the user equipment carries
out retransmission.
For non-adaptive retransmission, there is no explicit signaling to inform
what kind of DM-RS configurations should be utilized by the user equipment UE,
so the user equipment UE does not know how to configure specifically. Besides,
upon HARQ retransmission, the number of layers to be retransmitted might be
varied for example when one codeword is received correctly while other
codewords are not received correctly. The embodiments of the present
invention take the above factors into account and provide several solutions for
the user equipment UE to configure the DM-RS s upon retransmission.
According to embodiments of the present invention, in step S205, the user
equipment UE configures the DM-RS for retransmission in response to the
feedback signal NACK received from the base station eNB, i.e., in response to a
retransmission request received from the base station eNB.
In a first embodiment of the present invention, configuring the DM-RS for
retransmission can comprise configuring it to be the same as the DM-RS for
initial transmission. The first embodiment of the present invention will be
illustrated in detail with an example.
For the sake of brevity, first the SU-MIMO system is taken into
consideration. Assume the number of layers for the user equipment UE space
multiplexing is 3, i.e., the rank of the MIMO is 3, the cyclic shift indicator CSI
received from the base station eNB is 000. According to the mapping table as
shown in Table 1, the DM-RS configuration of the first layer (Layer-0) for the
initial transmission can be determined as below:
Then the user equipment UE can derive the DM-RS configurations of the
remaining two layers (Layer- 1, Layer-2) according to the DM-RS configuration
of Layer-0 and the above-mentioned rules defined for the initial transmission,
with results thereof as shown in Table 2-1.
Table 2-1: DM-RS Configurations for Initial Transmission
The user equipment UE carries out data transmission according to the DM-RS
configurations in Table 2-1. Assume that the base station eNB correctly receives the
codeword on the Layer-0, whereas the codewords on Layer- 1 and Layer-2 are not
received correctly, the base station eNB returns a response message to the user
equipment UE to indicate the codewords on Layer- 1 and Layer-2 need to be
retransmitted.
At this time, responsive to the retransmission request, the user equipment UE
can configure the DM-RSs for retransmission to be the same as the DM-RSs for initial
transmission, as shown in Table 2-2.
Table 2-2: DM-RS Configurations for Retransmission
It is noted that in Table 2-2, since the number of layers for retransmission is
changed to 2, the identifications thereof become Layer-0 and Layer- 1 accordingly, but
the DM-RS configurations thereof are the same as the DM-RS configurations of
Layer-1 and Layer-2 (namely, layers for retransmission) upon initial transmission.
Obviously, the first embodiment can be readily implemented without need of
standardization effort. However, the disadvantage thereof is also obvious, e.g., since
the change of the number of layers (the number of layers is decreased) upon
retransmission is not taken into account, sometimes the maximum RS separation
cannot be achieved between the layers for retransmission. For instance, in above
Table 2-2, the RS separation between two layers is 3.
For this reason, in a second embodiment according to the present invention, the
the DM-RS for retransmission is reconfigured with respect to the change of the
transmission situation in retransmission according to the predetermined rules for the
initial transmission, wherein change of the transmission situation in retransmission
can be for example change of the number of layers for retransmission. The second
embodiment according to the present invention is illustrated in detail by way of
example as below.
Similarly, the SU-MIMO system is taken into account first. Still assume that
the number of layers for the user equipment UE space multiplexing is 3, the
cyclic shift indicator CSI received from the base station eNB is 000. According
to the mapping table as shown in Table 1 and rules defined for initial
transmission, the DM-RS configurations of the layers for the initial transmission
can be determined, as shown in Table 3-1 below.
Table 3-1 DM-RS Configurations for Initial Transmission
The user equipment UE carries out data transmission according to the DM-RS
configurations in Table 3-1. Similarly, assume that the codewords on Layer-1 and
Layer-2 need to be retransmitted.
At this time, responsive to the retransmission request, the user equipment UE
can configure the DM-RSs for retransmission with respect to the layers for
retransmission according to the predetermined rules for initial transmission. As far
as the example is concerned, the number of layers for retransmission is 2. Hence,
referring to the above-mentioned derivation rules: as for two space layers, the CS
offset ( Ak ) is respectively 0,6(k=0,l), the configurations as shown in Table 3-2
can be obtained.
Table 3-2 DM-RS Configurations for Retransmission
It is noted that in Table 3-2, since the number of layers for retransmission is 2,
the identifications thereof become Layer-0 and Layer-1 accordingly, and the DM-RS
configurations thereof are derived from the initially received CSI according to the
predetermined rules for initial transmission with respect to the number of layers for
retransmission, which is 2.
Compared with the first embodiment, since the second embodiment reconfigures
the DM-RS for retransmission according to the rules for initial transmission by taking
into account the change of number of layers upon retransmission (e.g., the number of
layers is decreased), a maximum RS separation between different layers can be
obtained. For example, in the above Table 3-2, the RS separation between two
layers is 6. The disadvantage of the second embodiment lies in the need of
standardization effort and a little bit processing complexity for updating the OCC and
CS for retransmission. However, such cost is ignorable.
Returning to Fig.2, in step S205, the user equipment UE, responsive to the
retransmission request of the base station eNB, configures the DM-RS for
retransmission according to any one embodiment of the present invention.
Thereafter, in step S206, the user equipment UE can use the configured DM-RS to
retransmit the data.
After the base station eNB receives the retransmitted data, the DM-RS
configuration for retransmission can be used to estimate the uplink channel so as to
demodulate the data. Similarly, the data retransmitted for the first time might
partially or totally be received incorrectly, and needs to be retransmitted again. At
this time, as in the step S204, the base station eNB sends the feedback signal NACK
to the user equipment UE to request retransmission. Step S205, S206, and S204 are
repeated until all the data are already received correctly or the number of times of
retransmission or transmission duration reaches a predetermined threshold value.
Two exemplary embodiments of the present invention are described above in
combination with the SU-MIMO system. Then embodiments of the present invention
will be described hereunder in view of the MU-MIMO system.
In the MU-MIMO system, the base station eNB simultaneously serves a
plurality of users (also called a user group), each of which has a plurality of
transmitting and receiving antennas for space multiplexing.
As for the uplink MU-MIMO, the same OCC should be applied to different
layers of the same user equipment UE, whereby it is possible that different OCCs are
used for different user equipments UEs. Table 4-1 shows an example of DM-RS
configurations in view of MU-MIMO, wherein there are two space layers.
Table 4-1 DM-RS Configurations in View of MU-MIMO
As a contrast, Table 4-2 shows an example of DM-RS configurations in view of
SU-MIMO, wherein there are also two space layers.
Table 4-2 DM-RS Configurations in View of SU-MIMO
To this end, there is a need to optimize the mapping table of the DM-RS
configuration and CSI so as to ensure that the same OCC is used for the two layers of
the same UE when the CSI is selected according to the predetermined rules.
When the first embodiment according to the present invention is used, for
example, by referring to the DM-RS configurations for retransmission as shown in
Table 2-2, it can be seen that the two layers Layer-0 and Layer-1 for retransmission
employ different OCCs so that orthogonality between UEs cannot be ensured.
When the second embodiment according to the present invention is employed,
by referring to the DM-RS configurations for retransmission as shown in Table 3-2, it
can be seen that the two layers Layer-0 and Layer- 1 for retransmission employ the
same OCC so that orthogonality between two UEs can be ensured.
The two embodiments are both based on the mapping table of the DM-RS
configuration and CSI shown in the above Table 1. In the first embodiment, since
the DM-RS configurations in the initial transmission is maintained, the selecting
range of DM-RS configurations is very large, which makes it hard to design a suitable
mapping table to optimize for MU-MIMO to ensure that different OCCs are employed
between paired users of the MU-MIMO.
It can be seen from the mapping table of Table 1 that the mapping table is
designed such that the same OCC is maintained between the two layers with a nDMRS
separation as 6. Therefore, the DM-RS configurations for two-layer transmission
are limited: there are only four pairs in total, namely, (0,6), (3,9), (4,10) and
(2,8).
As such, in the second embodiment, use of such optimized mapping table
can ensure the same OCC is used for the two layers in the same UE, and thereby
make it possible to configure different OCCs for two UEs in the MU-MIMO.
This increases the orthogonality of the DM-RS s, and is particularly adapted for
unequal bandwidth allocation of the MU-MIMO.
It is known from the above depictions that the OCC and CS configurations
for retransmission need to be taken into account carefully to ensure the maximum
RS separation for retransmission. When the RS orthogonality between the
paired users in the MU-MIMO is considered, preferably the second embodiment
is selected to ensure the maximum RS separation and simplify the design of the
mapping table.
Fig.3 illustrates an exemplary block diagram of an apparatus for implementing
the present invention according to an embodiment of the present invention.
As shown in Fig.3, the apparatus 300 can be located in the user equipment UE
and comprise receiving means 301, configuration means 302 and transmitting means
303.
The receiving means 301 can be used to receive various information transmitted
by the base station eNB, for example, the cyclic shift indicator CSI in the downlink
control information DCI format 0, and response information ACK/NACK for the data.
The cyclic shift indicator CSI indicates the DM-RS configuration of the first layer for
the initial transmission.
As for the initial transmission, the configuration means 302 can derive the
DM-RS configurations of the remaining layers for the initial transmission in response
to the cyclic shift indicator CSI received by the receiving means 301 according to the
predetermined rules for initial transmission.
As for the HARQ retransmission, the configuration means 302 can configure an
uplink UL demodulation reference signal DM-RS for retransmission in response to
the retransmission request (NACK) received by the receiving means 301.
In the first embodiment according to the present invention, the configuration
means 301 can configure the demodulation reference signal DM-RS for
retransmission to be the same as the DM-RS for initial transmission.
In the second embodiment according to the present invention, the configuration
means 301 can derive the DM-RS configurations of the respective layers for
retransmission with respect to the number of layers for retransmission according to
the predetermined rules for the initial transmission.
These DM-RS configurations can comprise cyclic shifts CSs and orthogonal
cover codes OCCs of DM-RSs.
The transmitting means 303 can transmit or retransmit the data according to the
configuration of the configuration means 302.
Those skilled in the art may readily appreciate that the steps of the above
various methods may be performed by a programming computer. In this text,
some embodiments are intended to cover program storage devices, for example, a
digital data storage medium that may be machine or computer-readable and
programmed with a machine-executable or computer-executable instruction
program, wherein these instructions perform part or all of the steps of the above
methods. The program storage medium, for example, may be a digital storage, a
magnetic storage medium (such as magnetic diskette or magnetic tape), hard
driver, or optical readable digital data storage medium. The embodiments are also
intended to cover a computer programmed to execute steps of the above method.
It should be noted that in order to make the present invention more
comprehensible, the above description omits some more specific technical details
which are known to the skilled in the art and may be essential to implement the
present invention.
Those skilled in the art should understand these embodiments are
exemplary and non-limiting. Different technical features appearing in different
embodiments may be combined to achieve advantageous effects. Those skilled in
the art should understand and implement other variations of the embodiments as
depicted here based on the study on the drawings, specification, and claims. In
these claims, the term "comprising" does not exclude other means or steps; the
indefinite article "a/ an" does not exclude plurality. Any reference signs in claims
all shall not be understood as limiting the protection scope. Functions of a
plurality of portions occurring in claims can be performed by individual
hardware or software module. Appearance of some technical features in
different dependent claims does not mean that these technical features cannot be
combined to achieve advantageous effects.
Therefore, embodiments are selected and described in order to better
construe principles of the present invention and actual application thereof and
enable those having ordinary skill in the art to appreciate that all modifications
and alterations without departure from the essence of the present invention fall
within the protection scope of the present invention as defined by the appended
claims.
WHATIS CLAIMED IS:
1. A method for use in non-adaptive retransmission, the method comprising:
configuring an uplink UL demodulation reference signal DM-RS for
retransmission in response to a retransmission request.
2. The method according to claim 1, wherein said configuring comprises:
configuring the demodulation reference signal DM-RS to be the same as a
demodulation reference signal for an initial transmission.
3. The method according to claim 1, wherein said configuring comprises:
configuring the demodulation reference signal DM-RS with respect to a transmission
situation in retransmission according to predetermined rules for the initial
transmission.
4. The method according to claim 3, wherein the transmission situation in the
retransmission comprises the number of layers for retransmission.
5. The method according to claim 2 or 3, further comprising:
receiving a cyclic shift indicator CSI in downlink control information DCI, the
cyclic shift indicator CSI indicating the configuration of the demodulation reference
signal of the first layer for initial transmission; and
deriving the configuration of demodulation reference signal of remaining layer(s)
for the initial transmission according to the predetermined rules for the initial
transmission based on the received cyclic shift indicator CSI.
6. The method according to claim 4, further comprising:
receiving a cyclic shift indicator CSI in a downlink control information DCI, the
cyclic shift indicator CSI indicating the configuration of the demodulation reference
signal of the first layer for initial transmission;
wherein said configuring further comprises:
deriving the configuration of demodulation reference signal of layer(s) for the
retransmission with respect to the number of layer(s) for retransmission according to
the predetermined rules for the initial transmission, based on the received cyclic shift
indicator CSI.
7. The method according to any one of claims 1-6, wherein said configuring
comprises: configuring a cyclic shift CS and an orthogonal cover code OCC of the
demodulation reference signal DM-RS.
8.An apparatus for use in non-adaptive retransmission, comprising:
configuration means for configuring an uplink UL demodulation reference
signal DM-RS for retransmission in response to a retransmission request.
9. The apparatus according to claim 8, wherein the configuration means is used
to configure the demodulation reference signal DM-RS to be the same as a
demodulation reference signal for an initial transmission.
10. The apparatus according to claim 8, wherein the configuration means is used
to configure the demodulation reference signal DM-RS with respect to the
transmission situation in retransmission according to predetermined rules for the
initial transmission.
11. The apparatus according to claim 10, wherein the transmission situation in
the retransmission comprises the number of layers for retransmission.
12. The apparatus according to claim 9 or 10, further comprising:
receiving means for receiving a cyclic shift indicator CSI in downlink control
information DCI, the cyclic shift indicator CSI indicating configuration of the
demodulation reference signal of the first layer for initial transmission; and
the configuration means is further used to derive the configuration of
demodulation reference signal of remaining layer(s) for the initial transmission
according to the predetermined rules for the initial transmission, based on the received
cyclic shift indicator CSI.
13. The apparatus according to claim 11, further comprising:
receiving means for receiving a cyclic shift indicator CSI in downlink control
information DCI, the cyclic shift indicator CSI indicating the configuration of the
demodulation reference signal of the first layer for initial transmission;
wherein said configuration means is further used to:
derive the configuration of demodulation reference signal of layer(s) for the
retransmission with respect to the number of layer(s) for retransmission according to
the predetermined rules for the initial transmission, based on the received cyclic shift
indicator CSI.
14. The apparatus according to any one of claims 8-13, wherein said
configuration means is used to configure a cyclic shift CS and an orthogonal cover
code OCC of the demodulation reference signal DM-RS .