U.S. patent application number 13/994322 was filed with the patent office on 2013-10-10 for transmitting uplink control information.
The applicant listed for this patent is Shafi Bashar, Xiaogang Chen, Jong-Kae Fwu, Apostolos Papathanassiou, Hooman Shirani-Mehr. Invention is credited to Shafi Bashar, Xiaogang Chen, Jong-Kae Fwu, Apostolos Papathanassiou, Hooman Shirani-Mehr.
Application Number | 20130265975 13/994322 |
Document ID | / |
Family ID | 47437330 |
Filed Date | 2013-10-10 |
United States Patent
Application |
20130265975 |
Kind Code |
A1 |
Shirani-Mehr; Hooman ; et
al. |
October 10, 2013 |
Transmitting Uplink Control Information
Abstract
In accordance with some embodiments, uplink control information,
including a channel quality index, may be transmitted using at
least two layers. As a result, more information can be provided for
use in situations, such as those involving carrier aggregation,
where information for a large number of component carriers must all
be provided on one primary component carrier.
Inventors: |
Shirani-Mehr; Hooman;
(Portland, OR) ; Bashar; Shafi; (Santa Clara,
CA) ; Fwu; Jong-Kae; (Sunnyvale, CA) ; Chen;
Xiaogang; (Beijing, CN) ; Papathanassiou;
Apostolos; (San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Shirani-Mehr; Hooman
Bashar; Shafi
Fwu; Jong-Kae
Chen; Xiaogang
Papathanassiou; Apostolos |
Portland
Santa Clara
Sunnyvale
Beijing
San Jose |
OR
CA
CA
CA |
US
US
US
CN
US |
|
|
Family ID: |
47437330 |
Appl. No.: |
13/994322 |
Filed: |
December 30, 2011 |
PCT Filed: |
December 30, 2011 |
PCT NO: |
PCT/US11/68001 |
371 Date: |
June 14, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61504054 |
Jul 1, 2011 |
|
|
|
Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04W 4/70 20180201; H04L
27/34 20130101; H04W 76/28 20180201; H04W 24/00 20130101; H04L 5/14
20130101; H04W 72/02 20130101; H04L 1/0038 20130101; H04W 52/0258
20130101; H04W 72/04 20130101; H04L 1/0025 20130101; Y02D 30/70
20200801; H04W 52/325 20130101; H04W 72/082 20130101; H04L 1/0045
20130101; H04B 15/00 20130101; H04W 52/244 20130101; H04W 52/0212
20130101; H04L 5/0037 20130101; H04W 52/242 20130101; H04W 24/08
20130101; H04W 52/0251 20130101; H04L 27/362 20130101; H04W 72/1215
20130101; H04W 72/1278 20130101; H04W 72/0446 20130101; H04L 1/0041
20130101; H04W 76/19 20180201; H04W 84/042 20130101; H04W 88/06
20130101; H04W 52/143 20130101; H04L 1/06 20130101; H04W 8/02
20130101; H04B 7/0697 20130101; H04W 72/042 20130101; H04W 52/0209
20130101 |
Class at
Publication: |
370/329 |
International
Class: |
H04W 72/04 20060101
H04W072/04 |
Claims
1. A method comprising: aperiodically providing channel quality
information; and using a physical uplink shared channel having at
least two layers to provide said information.
2. The method of claim 1 including providing channel quality
information using two layers with two
modulation-coding-schemes.
3. The method of claim 1 including using at least two
codewords.
4. The method of claim 3 including using link adaptation.
5. The method of claim 3 including using layer shifting.
6. The method of claim 3 including using at least two layers with
two modulation-coding-schemes.
7. The method of claim 1 including sending the same codeword over
two different layers.
8. A non-transitory computer readable medium storing instructions
to enable a processor to: aperiodically provide channel quality
information; and send said information over a physical uplink
shared channel having at least two layers.
9. The medium of claim 8 further storing instructions to provide
channel quality information using two layers with two
modulation-coding-schemes.
10. The medium of claim 8 further storing instructions to use at
least two codewords.
11. The medium of claim 10 further storing instructions to use link
adaptation.
12. The medium of claim 10 further storing instructions to use
layer shifting.
13. The medium of claim 10 further storing instructions to use at
least two layers with two modulation-coding-schemes.
14. The medium of claim 8 further storing instructions to send the
same codeword over two different layers.
15. A mobile station comprising: a processor to aperiodically
provide channel quality information; and a wireless transceiver to
send the information over a physical uplink shared channel having
at least two layers.
16. The station of claim 15 said processor to provide channel
quality information using two layers with two modulation coding
schemes.
17. The station of claim 15 said processor to use at least two
codewords.
18. The station of claim 17 said processor to use link
adaptation.
19. The station of claim 17 said processor to use layer
shifting.
20. The station of claim 17 said processor to use at least two
layers with two modulation coding schemes.
21. The station of claim 15 said processor to send the same
codeword over two different layers.
22. The station of claim 15 wherein said station is a user
equipment.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to provisional application
Ser. No. 61/504,054, filed on Jul. 1, 2011.
BACKGROUND
[0002] This relates generally to cellular communications and,
particularly, to techniques for signaling information about the
nature of a channel between two wirelessly connected devices.
[0003] In order to initiate radio communications between two
devices, one device needs to tell the other device about the
channel conditions between the two devices. Then the transmitting
device knows how to send the transmission because the transmitting
device has information about the nature of the channel between the
two devices.
[0004] One way such information may be exchanged is for a first
device, called the base station or eNodeB, to trigger the
transmission of channel information from another device, called the
user equipment or a mobile station. In such case, the eNodeB sends
a pilot (reference) signal to the user equipment and user equipment
uses this signal to measure the channel. This channel information
is sent to the eNodeB by user equipment through physical uplink
shared channel (PUSCH) when the transmission is triggered by the
eNodeB. The need for triggering is specific to aperiodic
arrangements and is not typically used in periodic arrangements
wherein the user equipment periodically advises the eNodeB of the
channel conditions.
[0005] As system complexity increases, the amount of information
that must be transmitted on the uplink channel in aperiodic
triggering situations is increasing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a flow chart for one embodiment of the present
invention;
[0007] FIG. 2 is a schematic depiction of one embodiment of the
present invention;
[0008] FIG. 3 is a depiction of layer shifting according to one
embodiment;
[0009] FIG. 4 is a system depiction for one embodiment; and
[0010] FIGS. 5A-5E are schematic depictions of different ways for
uplink channel information transmission between two radio devices
in accordance with some embodiments of the present invention.
DETAILED DESCRIPTION
[0011] Uplink control information may include channel quality
information (CQI) transmitted from a mobile station to a base
station. In the case of some wireless technologies, such as the
Long Term Evolution (LTE), the mobile station is generally known as
the user equipment (UE) and the base station is generally known as
the eNodeB (eNB).
[0012] When the transmission of information from the user equipment
to the eNodeB is aperiodic, the transmission of the information may
be triggered by a signal sent from the eNodeB to the user
equipment. Uplink information is information that is sent from the
user equipment to the eNodeB and downlink information is
information sent from the eNodeB to the user equipment.
[0013] In some embodiments, once properly triggered, user equipment
can send a substantial amount of information over the uplink
channel. There are many reasons why the amount of information may
become substantial. These will be discussed hereinafter. What will
be discussed initially is to enumerate the ways in which more
information may be provided on the uplink channel.
[0014] In some embodiments, the uplink channel may be segmented
into one or more layers. Each layer may carry the same or different
codewords. Thus, in one embodiment, two separate layers may provide
one codeword (CW), as shown in FIG. 5A. In another embodiment, the
two uplink layers can provide two different codewords, codeword
(CW) one and codeword (CW) two, as shown in FIG. 5B. In the case of
FIG. 5B, although two different codewords are used, the same
modulation coding scheme (MCS) is used for each layer. The
modulation coding scheme indicates the type of modulation, among
other things, that may be used in subsequent transmissions. The
type of modulation is, to some degree, a function of the channel
quality because, for higher order modulation schemes, better
channel quality is generally needed. Still another option, shown in
FIG. 5C, is that two different layers are used for the uplink
control information (UCI), with each layer having a different
codeword. But, in this case, instead of being stuck with just one
MCS, the user equipment can specify one of two MCSs. Still another
option, shown in FIG. 5D, is to use an uplink layer one (UL1) and
an uplink layer two (UL2), each with a different codeword, codeword
one (CW1) or codeword two (CW2), each with one MCS, but using layer
shifting.
[0015] A problem may arise in that each of the layers may have
different transmission conditions and, as a result, data in one
layer may be more likely to be compromised than information on the
other layers. Thus, a given codeword may be split up and shifted
between layers so that a single codeword is broken up and pieces of
the codeword may go on one layer and pieces of the same codeword
may go on another layer. At the same time, the second codeword may
be shifted in the same way. Thus, as shown in FIG. 5D, a first
codeword, CW1, may be partially sent on one layer and partially
sent on another layer, while the second codeword is split between
the two layers as well.
[0016] One benefit of layer shifting is that, hopefully, enough
information from each codeword gets through, even if it is only the
portion that goes on the better quality stream, so that the
necessary information is received by the eNodeB.
[0017] Still another option, shown in FIG. 5E, is to have two
uplink layers, two different codewords, and each layer selecting
between one of two available MCSs. One way this may be done is to
use the I_MCS signaling for a second transport block to signal two
MCSs simultaneously.
[0018] The I_MCS provides indices 0 through 31, which are mapped to
different modulation coding and signaling schemes. In some cases, a
particular index, such as I_MCS=29 may be used for signaling in
connection with uplink control information. Thus, by using two
transport blocks, more information may be provided, including the
provision of different MCSs for each stream. This allows for a
combination of streams experiencing different transmission
conditions.
[0019] Thus, referring to FIG. 1, in some embodiments, a sequence
10 may be implemented in software, firmware, and/or hardware. In
software and firmware embodiments, the sequence may be implemented
by computer executed instructions stored in a non-transitory
computer readable medium, such as an optical, magnetic, or
semiconductor memory. The sequence is generally implemented on the
user equipment side of the transaction.
[0020] The sequence begins by generating the codewords at block 12.
Then the codewords are scrambled, as indicated in block 14. Next,
each codeword is modulation mapped, as indicated in block 16. Each
codeword is pre-coded at block 18. Then resource element mapping is
done in block 20, followed by signal generation in block 22.
[0021] Generally, multiple-input/multiple-output (MIMO)
transmission and receiving schemes are used. MIMO is a wireless
technology that uses multiple transmitters and receivers to
transfer more data at the same time. It takes advantage of a radio
wave phenomenon called multipath, wherein transmitted information
bounces off of walls, ceilings, and other objects, reaching the
receiving antenna multiple times via different angles and at
slightly different times. MIMO technology leverages multipath
behavior by using multiple smart transmitters and receivers with an
added spatial dimension to increase performance and range. Multiple
antennas send and receive multiple spatial streams at the same
time, allowing antennas to transmit and receive simultaneously.
MIMO enables antennas to combine data streams arriving from
different paths and at different times to effectively increase
receiver signal-capturing power.
[0022] Aperiodic CQI-only transmission on PUSCH is generally
signaled by the eNodeB using downlink control information (DCI)
format 0 or 4 via a combination of I_MCS=29, which is a reserved
modulation coding scheme, and a small number of allocated physical
resource blocks (PRBs) for transmitting quality information.
Generally, the number of physical resource blocks must be less than
or equal to 4 for this purpose. The quality information may be the
so-called channel quality index (CQI), which is a number indicating
the quality of channel to the transmitter provided by a receiver.
In general, the channel quality index is supplemented by a
so-called pre-coding matrix indicator (PMI) to form what is called
the channel state information (CSI). Of course, other ways of
providing the channel quality information may also be
contemplated.
[0023] More than one component carrier may be assigned in schemes
that use carrier aggregation. Since service providers do not always
have available a wide band for transmission, they sometimes
aggregate narrower bands together to provide a given quality of
wireless service. Each port may be one component carrier and, by
combining the plurality of component carriers, carrier aggregation
of two to five carriers may be accomplished to form a wider
transmission band. However, generally, all the quality information
is provided on only one of those component carriers, called the
primary component carrier. This means that a large amount of
quality feedback information must be provided on one component
carrier due to the larger number of carriers and the larger maximum
number of primary resource blocks supported by carrier aggregation.
Specifically, up to 20 primary resource blocks may be used and all
the quality information for all those resource blocks is provided
on the primary component carrier.
[0024] Due to the limited number of primary resource blocks used
for quality transmissions, it is desirable to increase the capacity
for the CSI transmission, typically using physical uplink shared
channel (PUSCH). (It should be noted that there is no particular
reason why, in other embodiments, physical uplink control channel
(PUCCH) could not be used, or some other comparable uplink physical
channel.)
[0025] Thus, generally, when download control information is in
format 0 or format 4, it causes the triggering of the transmission
of the uplink control information described herein.
[0026] Currently, for a download control information format 0, the
CQI-only transmission on PUSCH is triggered in one of two cases. In
the first case, if the channel quality index request field is one
bit and the channel quality index request field is one with the
I_MSC=29 and the number of primary resource blocks being less than
or equal to four, then the triggering will occur.
[0027] In the other situation for downlink control information
format 0, if, instead, the channel quality index request field is
two bits, then the transmission will be triggered in the following
circumstances. If the channel quality index request field is 01,
10, or 11, and if a single downlink component carrier is reported
with I_MCS=29 and the number of primary resource blocks is less
than or equal to four, then the transmission will be triggered.
However, if there are multiple downlink component carriers
reported, then it is permissible if I_MCS=29 and the number of
primary resource blocks is less than or equal to 20.
[0028] On the other hand, for the download control information
format 4, the CQI-only transmission on PUSCH is triggered under the
following circumstances. First the downlink control information
format must indicate that only one transport block is enabled.
Then, if the channel quality index request field is one bit, then
the channel quality index request field must be one and for the
enabled transport block, I_MCS must equal 29 and the number of
programmable resource blocks must be equal to or less than four.
However, if the channel quality index request field is two bits,
then the channel quality request field must be 01, 10, or 11. Then,
if a single downlink component carrier is reported for the enabled
transport block I_MCS must be 29 and the number of programmable
resource blocks must be less than or equal to four. However, if
multiple downlink component carriers are reported, then, for the
enabled transport block, I_MCS must be 29 and the number of
programmable resource blocks must be less than or equal to 20.
[0029] In the situation shown in FIG. 5A where one codeword is
mapped to two layers, the initial data transmission contains two
codewords. This mapping is already available for data transmission
and is used when the initial data transmission contains two
codewords and data retransmission of a codeword mapped to two
layers.
[0030] In some embodiments, the modulation scheme for the uplink
control information may be limited to QPSK. However, other
modulations, such as 16 QAM, may also be used in some
embodiments.
[0031] In the embodiments shown in FIGS. 5B and 5C, the channel
state information bits are first segmented and then encoded into
two codewords. Each codeword is then independently mapped to one
layer. In one option for supporting different common modulation
schemes for the two codewords, the two codewords use the same MCS,
such as QPSK. Thus, in some embodiments, QPSK or some other
modulation scheme may be used for both layers. In such case, link
adaption is not supported. In link adaptation, the modulation
scheme can be changed on the fly based on then current channel
conditions. In some embodiments, other modulations may be used in
addition to QPSK, such as 16 QAM.
[0032] As another example of using two codewords and two layers
with one MCS, two codewords supporting link adaption may be used,
as indicated in FIG. 5C. This involves changing the MCS, for
example, changing between QPSK and 16 QAM as one example, without
explicit signaling. The modulation scheme can be derived based on
the two MCSs used in rank 2 uplink data transmission on PUSCH,
which is known to both the user equipment and the eNodeB and by
applying the same rule predefined for both the user equipment and
the eNodeB. This rule can be to choose the lowest order of
modulation of the two MCSs, as a conservative example, or, for
example, by some kind of averaging where one modulation scheme is
chosen when the two MCSs are two particular modulation schemes.
[0033] Transmitting the channel state information on PUSCH with
rank higher than one may only be helpful when the uplink channel
condition is good enough to support ranks higher than one for both
data and the channel state information itself.
[0034] Of course, the examples of FIGS. 5B and 5C may sometimes be
sub-optimal, such as, for example, when the modulation scheme is
conservatively selected to be QPSK. Consequently, although
transmission is more robust, good channel conditions cannot be
exploited if capacity cannot be increased. In the embodiment of
FIG. 5C, the modulation scheme can be of higher order than QPSK,
but as the two codewords experience different channels, they will
have different error probabilities and the performance of the
system may depend on the performance of the codeword that
experiences the worst channel.
[0035] For example, consider the case where the channel conditions
for the first codeword are not good enough and can only support
transmission with QPSK, while the second codeword sees good channel
conditions which support 64 QAM transmission. In the embodiment of
FIG. 5B, both codewords use QPSK, which is pessimistic for
transmitting the second codeword. Similarly, in the option in FIG.
5C, 16 QAM may be used as the average of QPSK and 64 QAM for
codewords and, consequently, error probability for this codeword
may be high.
[0036] Thus, in the embodiment of FIG. 5D, two codewords and two
layers are used with layer shifting. Layer shifting is shown in
FIG. 3 where the first layer (layer 1) and the second layer (layer
2) are provided to the layer shifter 29 that produces two output
layers by mixing up the four depicted modulation symbols of each
codeword. Specifically, the first and third symbols from layer 2
are interleaved with the second and fourth symbols of layer 1, and
so on, in this example. Other shifting techniques may also be
used.
[0037] Thus, as shown in FIG. 2, the first codeword, CW1, and the
second codeword, CW2, are subjected to parallel scrambling at
scrambling stages 24. The scrambling randomly changes the bit
order. Then the two codewords are subjected to parallel modulation
mapping in modulation mappers 26. The modulation mappers 26 map
bits to modulation symbols, such as those associated with 16 QAM.
Next, layer mapping at 28 is done to both codewords simultaneously.
Then the output from the layer mapping is provided to the layer
shifter 30 that changes the bit sequences already described.
Thereafter, the two shifted layers are provided to separate
parallel transform pre-coders 32. Next, pre-coding is done at 34
and then each layer is separately resource element mapped at
resource element mappers 36. The resource element mappers 36
determine how primary resource blocks are allocated to each user.
Finally, signal generation occurs at 38, pursuant to SC-FDMA. Then
each signal is transmitted to the appropriate antenna port in an
MIMO system.
[0038] One benefit of layer shifting is to provide additional
diversity between the two codewords. The benefit is clear when you
consider the previous example. When the layer shifter is applied,
some symbols of both codewords will experience the better channel
and this will help the system to increase the probability of
correct decoding. Therefore, this scheme may have better
performance, in some embodiments.
[0039] Finally, as indicated in FIG. 5E, two codewords with two
layers and two MCSs may be used. Different modulation schemes may
be used for different codewords. For example, by using I_MCS for a
second transport block to signal two MCSs simultaneously, different
modulations can be considered and signaled. Thus, in some
embodiments, good channel conditions may be more fully
exploited.
[0040] The computer system 130, shown in FIG. 4, may include a hard
drive 134 and a removable medium 136, coupled by a bus 104 to a
chipset core logic 110. The computer system may be any computer
system, including a smart mobile device, such as a smart phone,
tablet, or a mobile Internet device. A keyboard and mouse 120, or
other conventional components, may be coupled to the chipset core
logic via bus 108. The core logic may couple to the graphics
processor 112, via a bus 105, and the applications processor 100 in
one embodiment. The graphics processor 112 may also be coupled by a
bus 106 to a frame buffer 114. The frame buffer 114 may be coupled
by a bus 107 to a display screen 118, such as a liquid crystal
display (LCD) touch screen. In one embodiment, a graphics processor
112 may be a multi-threaded, multi-core parallel processor using
single instruction multiple data (SIMD) architecture.
[0041] The chipset logic 110 may include a non-volatile memory port
to couple the main memory 132. Also coupled to the logic 110 may be
multiple antennas 121, 122 to implement multiple input multiple
output (MIMO) in one embodiment. Speakers 124 may also be coupled
through logic 110.
[0042] References throughout this specification to "one embodiment"
or "an embodiment" mean that a particular feature, structure, or
characteristic described in connection with the embodiment is
included in at least one implementation encompassed within the
present invention. Thus, appearances of the phrase "one embodiment"
or "in an embodiment" are not necessarily referring to the same
embodiment. Furthermore, the particular features, structures, or
characteristics may be instituted in other suitable forms other
than the particular embodiment illustrated and all such forms may
be encompassed within the claims of the present application.
[0043] While the present invention has been described with respect
to a limited number of embodiments, those skilled in the art will
appreciate numerous modifications and variations therefrom. It is
intended that the appended claims cover all such modifications and
variations as fall within the true spirit and scope of this present
invention.
* * * * *