U.S. patent application number 15/486927 was filed with the patent office on 2017-08-03 for methods and devices for reporting a downlink channel quality.
The applicant listed for this patent is Telefonaktiebolaget LM Ericsson (publ). Invention is credited to Marten Ericson, Bengt Lindoff, Stefan Parkvall, Mats Sagfors.
Application Number | 20170223565 15/486927 |
Document ID | / |
Family ID | 45688497 |
Filed Date | 2017-08-03 |
United States Patent
Application |
20170223565 |
Kind Code |
A1 |
Ericson; Marten ; et
al. |
August 3, 2017 |
METHODS AND DEVICES FOR REPORTING A DOWNLINK CHANNEL QUALITY
Abstract
Methods and devices for reporting a downlink channel quality are
provided. In one exemplary embodiment, a method is performed by a
user equipment for reporting channel quality in a communication
system that uses a first radio access technology (RAT) and a second
RAT. Further, the user equipment is operable to use the first and
second RATs. The method includes mapping a channel quality
indicator (CQI) associated with the second RAT that has a CQI
format of the second RAT to a CQI format of the first RAT. By doing
so, this method allows the user equipment to transmit on a channel
of the first RAT the CQI associated with the second RAT.
Inventors: |
Ericson; Marten; (Lulea,
SE) ; Lindoff; Bengt; (Bjarred, SE) ;
Parkvall; Stefan; (Bromma, SE) ; Sagfors; Mats;
(Kyrkslatt, FI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Telefonaktiebolaget LM Ericsson (publ) |
Stockholm |
|
SE |
|
|
Family ID: |
45688497 |
Appl. No.: |
15/486927 |
Filed: |
April 13, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14119254 |
Feb 10, 2014 |
9642026 |
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PCT/EP2012/052769 |
Feb 17, 2012 |
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15486927 |
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61494653 |
Jun 8, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 72/04 20130101;
H04W 24/08 20130101; H04B 17/309 20150115; H04W 88/06 20130101;
H04W 24/10 20130101 |
International
Class: |
H04W 24/10 20060101
H04W024/10; H04B 17/309 20060101 H04B017/309 |
Claims
1. A method performed by a user equipment for reporting channel
quality in a communication system, the communication system using a
first radio access technology (RAT) and a second RAT, comprising:
mapping a channel quality indicator (CQI) associated with the
second RAT that has a CQI format of the second RAT to a CQI format
of the first RAT so as to allow the user equipment to transmit the
CQI associated with the second RAT on a channel of the first RAT,
the user equipment being operable to use the first and second
RATs.
2. The method of claim 1, wherein the first RAT is associated with
a primary serving cell and the second RAT is associated with a
secondary serving cell.
3. The method of claim 1, further comprising: determining a channel
quality associated with the second RAT; and mapping the channel
quality associated with the second RAT to the CQI format of the
second RAT.
4. The method of claim 3, wherein said determining the channel
quality includes estimating the channel quality associated with the
second RAT.
5. The method of claim 1, further comprising: transmitting, on the
channel of the first RAT, the CQI associated with the second RAT
having the CQI format of the first RAT.
6. The method of claim 1, wherein said mapping includes adapting
the CQI format of the second RAT to the CQI format of the first
RAT.
7. The method of claim 1, comprising: mapping the channel quality
associated with the first RAT to the CQI format of the first RAT;
and transmitting, on the channel of the first RAT, the CQIs
associated with the first and second RATs.
8. The method of claim 7, wherein the CQIs associated with the
first and second RATs are time multiplexed on an uplink channel of
the first RAT.
9. The method of claim 1, wherein a number of CQI indices
associated with the second RAT is different from a number of CQI
indices associated with the first RAT.
10. The method of claim 1, further comprising: determining a
channel quality associated with the second RAT; determining a CQI
index associated with the second RAT based on the channel quality
associated with the second RAT; and wherein said mapping includes
quantizing the CQI index to a quantized CQI table associated with
the second RAT, with a number of indices of the CQI table
associated with the second RAT being no more than a number of
indices of a quantized CQI table associated with the first RAT.
11. The method of claim 1, wherein a number of CQI indices
associated with the second RAT is greater than a number of CQI
indices associated with the first RAT; and wherein said mapping is
based on an extended uplink transmission structure of the first RAT
that is configured for the larger number of CQI indices associated
with the second RAT.
12. The method of claim 11, wherein the extended uplink
transmission structure is associated with an increased code rate of
an error correcting code used for a CQI.
13. The method of claim 12, further comprising: increasing a
transmission power for a transmission of the CQI associated with
the second RAT having the CQI format of the first RAT to compensate
for an increased error probability due to the increased code
rate.
14. The method of claim 11, wherein said mapping based on the
extended uplink transmission structure is based on at least one of:
lowering a spreading factor; using multiple uplink resources; and
increasing a duration of a transmission of the CQI associated with
the second RAT having the CQI format of the first RAT by
transmitting a portion of CQI indices in one sub-frame and a
remaining portion of CQI indices in another sub-frame.
15. The method of claim 1, wherein a number of CQI indices of the
second RAT is equivalent to a number of CQI indices of the first
RAT; wherein said mapping includes using the CQI associated with
the second RAT having the CQI format of the second RAT as is.
16. A user equipment for reporting channel quality in a
communication system, the communication system using a first radio
access technology (RAT) and a second RAT, the user equipment
comprising: one or more processing circuits configured to: map a
channel quality indicator (CQI) associated with the second RAT that
has a CQI format of the second RAT to a CQI format of the first RAT
so as to allow the user equipment to transmit the CQI associated
with the second RAT on a channel of the first RAT, the user
equipment being operable to use the first and second RATs.
17. The user equipment of claim 16, wherein the one or more
processing circuits are further configured to: determine a channel
quality associated with the second RAT; and map the channel quality
associated with the second RAT to the CQI format of the second RAT
to obtain the CQI associated with the second RAT.
18. The user equipment of claim 16, further comprising: a
transmitter configured to transmit, on the channel of the first
RAT, the CQI associated with the second RAT having the CQI format
of the first RAT.
19. A method performed by a network node of a communication system,
the communication system including a first radio access technology
(RAT) and a second RAT, the method comprising: mapping a channel
quality indicator (CQI) associated with the second RAT having a CQI
format of the second RAT that is mapped to a CQI format of the
first RAT to a channel quality associated with the second RAT so as
to allow the network node to receive the CQI associated with the
second RAT from a user equipment on a channel of the first RAT.
20. The method of claim 19, further comprising: determining that a
CQI received from the user equipment on the channel of the first
RAT is the CQI associated with the second RAT having the CQI format
of the second RAT that is mapped to the CQI format of the first
RAT.
21. The method of claim 19, further comprising: receiving, from the
user equipment on the channel of the first RAT, the CQI associated
with the second RAT having the CQI format of the second RAT that is
mapped to the CQI format of the first RAT.
22. A network node of a communication system, the communication
system including a first radio access technology (RAT) and a second
RAT, the network node comprising: one or more processing circuits
configured to: map a channel quality indicator (CQI) associated
with the second RAT having a CQI format of the second RAT that is
mapped to a CQI format of the first RAT to a channel quality
associated with the second RAT so as to allow the network node to
receive the CQI associated with the second RAT from a user
equipment on a channel of the first RAT.
23. The network node of claim 22, wherein the one or more
processing circuits are further configured to: determine that a CQI
received from the user equipment on the channel of the first RAT is
the CQI associated with the second RAT having the CQI format of the
second RAT that is mapped to the CQI format of the first RAT.
24. The network node of claim 22, further comprising: a receiver
configured to: receive, from the user equipment on the channel of
the first RAT, the CQI associated with the second RAT having the
CQI format of the second RAT that is mapped to the CQI format of
the first RAT.
Description
RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 14/119,254, filed Feb. 10, 2014, now U.S. Pat.
No. 9,642,026, issued May 5, 2017, which is the National Stage of
PCT/EP2012/052769, filed Feb. 17, 2012, which claims the benefit of
U.S. Provisional Patent Application 61/494,653, filed Jun. 8, 2011,
all of which the contents are hereby incorporated by reference as
if fully set forth below.
TECHNICAL FIELD
[0002] The technology disclosed herein relates generally to the
field of wireless communication systems, and in particular to
reporting of downlink channel quality within such wireless
communication systems.
BACKGROUND
[0003] Today, there are many radio and cellular access technologies
and standards such as GSM/GPRS, WCDMA/HSPA (Wideband Code Division
Multiple Access/High Speed Packet Access), CDMA (Code Division
Multiple Access)-based technologies, WiFi (Wireless Fidelity),
WiMAX (Worldwide Interoperability for Microwave Access) and
recently LTE (Long Term Evolution), to name a few. The technologies
and standards have been developed during the last few decades, and
it can be expected that the development will continue.
Specifications are developed in organizations like 3GPP, 3GPP2 and
IEEE. 3GPP is responsible for the development and maintenance of
GSM/GPRS, WCDMA/HSPA and LTE standards.
[0004] Various frequency bands are typically allocated and/or sold
by government organizations, such that an operator may "own"
certain bands for a particular use (i.e. the right to use the band
in a certain way). Regulations may specify that the owner, i.e. the
operator, should deploy a particular technology in a particular
frequency band. In some cases, the operator may be able to choose
what technology and standard to deploy in their spectrum provided
the choices fulfill certain criteria set up by e.g. the ITU
(International Telecommunications Union).
[0005] As a consequence of the fact that spectrum is a scarce
resource, an operator may have the rights to deploy a new cellular
access, such as LTE, in a limited spectrum of, say 20 MHz.
[0006] However, the fact that the operator may have an existing
customer base with existing terminals will prevent the operator
from deploying only one technology in the whole spectrum owned by
the operator. This could be the case e.g. for an operator that has
a large customer base with WCDMA/HSPA subscriptions using the
Universal Terrestrial Radio Access Network (UTRAN), and the
operator wants to deploy the most recent evolution, the Long Term
Evolution (LTE) of UTRAN, also called Evolved-UTRAN (E-UTRAN).
[0007] In this example, the operator may then have to divide the
available bands between HSPA and LTE. At initial deployment of LTE,
the operator may thus continue to use e.g. 10 MHz (corresponding to
two WCDMA carriers) with HSPA and reserve 10 MHz for initial LTE
deployment.
[0008] However, such partitioning of the scarce spectrum to
different technologies has some undesired effects on performance:
[0009] There is a direct correlation between the peak-rate that can
be offered and the spectrum width that is used. Thus, limiting the
bandwidth of both HSPA and LTE to 10 MHz in the example above will
roughly limit the peak-rate offered to customers to a half. Thus,
assuming now, for the sake of illustration, that the technologies
can offer around 100 Mbps in 20 MHz, it will mean that the
peak-rate will now be limited to around 50 Mbps in each of the
technologies. [0010] Initially, it may happen that the HSPA
carriers are very loaded, while the LTE carriers in the example
only have a few users. Thus, there would be an imbalance between
allocation and usage resulting in undesired congestion on the HSPA
carriers. However, in order to offer a decent bit-rate on the LTE
carriers, it is still not possible to allocate e.g. only 5 MHz to
LTE customers, since then LTE would not provide competitive
performance in relation to HSPA.
[0011] There have been discussions to find a solution for
simultaneous use of multiple radio access technologies (LTE+HSPA
carrier aggregation), such that higher peak rates and load
balancing can be offered in heterogeneous deployments including at
least two radio-access technologies. Both LTE carrier aggregation
(CA) as well as HSPA carrier aggregation, i.e. carrier aggregation
within the same RAT, is defined in the Release 10 standard of the
3GPP specification. In fact HSPA CA is defined already in Release
9.
SUMMARY
[0012] Carrier aggregation (CA), wherein a combination or
aggregation of two independent carriers is made, is one way of
achieving increased resource utilization and spectrum efficiency.
For example, in LTE+HSPA carrier aggregation, each carrier is an
LTE carrier or a HSPA carrier. For such LTE+HS carrier aggregation
one possibility is that a mobile terminal, or a wireless device or
a user equipment (UE) is in connection to a primary serving cell on
a primary/first RAT (for instance HSPA) on a first carrier and a
secondary/second serving cell on a second RAT (for instance LTE) on
a second carrier, i.e. in a similar way as primary and secondary
cell are defined on intra RAT (such as for either LTE or HS)
carrier aggregation. It is possible that one of the RATs and
systems is considered as being the one in control of the UE, while
the carrier or carriers on the other system (or RAT) is considered
as a performance "booster", in the sense that such "secondary"
carriers are added to enhance the performance. For example,
UTRAN/HSPA could be the primary system/RAT, while E-UTRAN/LTE may
be the secondary system/RAT. In a possible configuration situation,
it could happen e.g. that a user equipment (UE) is first connected
to UTRAN/HSPA, and then later, the UE is configured to add carriers
on LTE/E-UTRAN. LTE is then a secondary RAT, i.e. the connection
control remains in UTRAN, even if some LTE carriers or cells are
added to "boost" the performance. Of course, it is also possible
with a configuration such that E-UTRAN/LTE acts as the primary
system/RAT, and UTRAN/HSPA is the secondary system/RAT.
[0013] In some scenarios one can expect that the carrier
aggregation only is made for carriers in the downlink (DL), and
hence a single RAT (typically corresponding to the primary RAT) is
used for the carriers in the uplink (UL). Carrier aggregation for
carriers in the downlink may be easier to implement, as there then
is no requirement for a UE to transmit on multiple carriers using
different radio access technologies on the UL. Simultaneous
transmission on several carriers can be rather complex, since a UE
may have a maximum output power that then needs to be distributed
on both carriers. An UE transmitting on multiple carriers may also
have to comply with various emission criteria, such as the SAR
(Specific Absorption Rate (SAR), which is a measure of the amount
of radio frequency (RF) energy absorbed by the body when using an
UE.
[0014] It may also be the case that carrier aggregation in the DL
is more urgent, in case the traffic load is biased towards downlink
data traffic (as opposed to uplink data traffic dominance).
[0015] However, introducing only carrier aggregation for carriers
in the DL would also introduce a new set of problems, since there
is some control information, or feedback information, related to
the downlink carriers, that needs to be transmitted on the uplink
carrier or carriers. Thus, if the UL carrier or carriers are
configured with only one RAT, hence there is no uplink carrier
configured with the other one of the radio access technologies.
There is currently no method for how to transmit the control
information associated with that other radio access technology.
[0016] In this case feedback information, like
acknowledgment/negative acknowledgment (ACK/NAK) signaling and
channel quality indicator (CQI) reports for the secondary RAT may
need to be reported using the primary RAT UL (assuming here, that
the secondary RAT is not configured with any UL).
[0017] HARQ ACK/NAK stands for Hybrid ARQ acknowledgements and
negative acknowledgements. HARQ with ACK/NACKs are implemented both
in HSPA and LTE, using binary feedback related to the successful or
non-successful reception of a related data unit (transport block).
This is known art, and HARQ and ACK/NAK will not be described in
further detail herein.
[0018] CQI stands for Channel Quality Indicator and is a quality
parameter describing the estimated quality of the downlink channel,
such that the downlink transmitter or network node (such as a Radio
Base Station, RBS) can decide e.g. what coding, modulation, power
or frequency to use in an upcoming transmission. The UE monitors
the downlink quality, and reports a CQI parameter to the network.
Both HSPA and LTE implements CQI, though there are differences in
the way CQI can be configured, and what information the report may
contain.
[0019] In case the UL carrier or carriers are configured with the
primary RAT only, the CQI reports for the secondary RAT need to be
transported using the primary RAT. This implies that, if CQI
reports related to the secondary RAT should be made available to
the network, they have to be transmitted to the network in by some
non-conventional means. No solution is known in the art and
therefore there is a need for method and apparatus solving this
problem.
[0020] Thus, there is a need to overcome the aforementioned
problems, to which the present disclosure provides solutions
through the embodiments described below.
[0021] An object of the invention is to overcome or at least
alleviate one or more of the above mentioned problems.
[0022] The object is, according to a first aspect of the invention,
achieved by a method in a user equipment for reporting a downlink
channel quality in a communication system comprising a first radio
access technology system and a second radio access technology
system. The user equipment is in connection with a primary serving
cell on the first radio access technology system and with a
secondary serving cell on the second radio access technology
system. The method comprises: determining channel quality for the
second radio access technology system using an indicator format of
the radio access technology of the second radio access technology
system; mapping an indicator of the channel quality having the
indicator format of the second radio access technology to an
indicator format used for channel quality indicators in the first
radio access technology system; and transmitting the indicator of
the channel quality for the second radio access technology system
to the communication system using the indicator format of the first
radio access technology on an uplink carrier of the first radio
access technology system.
[0023] The invention enables reporting of downlink channel quality
measured in a radio access technology for which there is no uplink
carrier configured.
[0024] In an embodiment, the mapping comprises adapting the
indicator format of the radio access technology of the second radio
access technology system to the indicator format used for channel
quality indicator in the first radio access technology system.
[0025] In an embodiment, the determining of channel quality
comprises estimating channel quality for the second radio access
technology system.
[0026] In an embodiment, the method comprises determining channel
quality for the first access technology system. Further, the
transmitting of the indicator of the channel quality for the second
radio access technology system comprises transmitting also an
indicator of the channel quality for the first radio access
technology system, wherein the indicator of channel quality for the
first radio access technology system and the indicator of the
channel quality for the second radio access technology system are
time multiplexed on an uplink channel of the first radio access
technology system.
[0027] In an embodiment, a number of channel quality indicator
indices for the second radio access technology system is larger
than a number of channel quality indicator indices for the first
radio access technology system. The determining of channel quality
comprises estimating a channel quality indicator index for the
second radio access technology system, resulting in a first channel
quality indicator index; and the mapping comprises quantizing the
first channel quality indicator index to a quantized channel
quality indicator table for the second radio access technology
system, having the same or less amount of indices as the first
radio access technology system.
[0028] In an embodiment, a number of channel quality indicator
indices for the second radio access technology system is larger
than a number of channel quality indicator indices for the first
radio access technology system. The mapping comprises using an
extended uplink transmission structure of the first radio access
technology system for handling the larger number of indices
required for the second radio access technology system.
[0029] In a variation of the above embodiment, using the extended
uplink transmission structure comprises increasing a code rate of
error correcting code used for a channel quality indicator.
[0030] In a variation of the above embodiment, the method further
comprises increasing the transmission power for compensating for an
increased error probability due to the increased code rate.
[0031] In another variation, using the extended uplink transmission
structure comprises one of: lowering a spreading factor, using
multiple uplink resources or increasing the duration of the
transmission, increasing the duration of the transmission by
transmitting some of a number of channel quality indicator indices
in one sub-frame and the remaining channel quality indicator
indices in another sub-frame.
[0032] In an embodiment, the number of channel quality indicator
indices of the second radio access technology system is equal to
the number of channel quality indicator indices of the first radio
access technology system, and the mapping comprises: using the
indicator of the channel quality having the indicator format of the
second radio access technology as is.
[0033] The object is, according to a second aspect of the
invention, achieved by a user equipment configured to operate in a
communication system comprising a first radio access technology
system and a second radio access technology system. The user
equipment is configured for connection with a primary serving cell
on the first radio access technology system and with a secondary
serving cell on the second radio access technology system. The user
equipment is configured to: determine channel quality for the
second radio access technology system by using an indicator format
of the radio access technology of the second radio access
technology system; map an indicator of channel quality having the
indicator format of the second radio access technology to an
indicator format used for channel quality indicators in the first
radio access technology system; and transmit the indicator of the
channel quality for the second radio access technology system to
the communication system by using the indicator format of the first
radio access technology on an uplink carrier of the first radio
access technology system.
[0034] In an embodiment, the user equipment is configured to map by
adapting the indicator format of the radio access technology of the
second radio access technology system to the indicator format used
for channel quality indicator in the first radio access technology
system.
[0035] In an embodiment, the user equipment is configured to
determine the channel quality by estimating channel quality for the
second radio access technology system.
[0036] In an embodiment, the user equipment is configured to
determine channel quality estimates for the first access technology
system; and wherein the user equipment is configured to transmit
the indicator of the channel quality for the second radio access
technology system by transmitting also an indicator of the channel
quality for the first radio access technology system, wherein the
indicator of channel quality for the first radio access technology
system and the indicator of the channel quality for the second
radio access technology system are time multiplexed on an uplink
channel for the first radio access technology system.
[0037] In an embodiment, a number of channel quality indicator
indices for the second radio access technology system is larger
than a number of channel quality indicator indices for the first
radio access technology system. The user equipment is configured to
determine the channel quality by estimating a channel quality
indicator index for the second radio access technology system,
resulting in a first channel quality indicator index; and wherein
user equipment is configured to map by quantizing the first channel
quality indicator index to a quantized channel quality indicator
table for the second radio access technology system, having the
same or less amount of indices as the first radio access technology
system.
[0038] In an embodiment, a number of channel quality indicator
indices for the second radio access technology system is larger
than a number of channel quality indicator indices for the first
radio access technology system. The user equipment is configured to
map by using an extended uplink transmission structure of the first
radio access technology system for handling the larger number of
indices required for the second radio access technology system.
[0039] In a variation of the above embodiment, the user equipment
is configured to use the extended uplink transmission structure by
increasing a code rate of error correcting code used for a channel
quality indicator.
[0040] In a variation of the above embodiment, the user equipment
further being configured to increase the transmission power for
compensating for an increased error probability due to the
increased code rate.
[0041] In another variation, the user equipment is configured to
use the extended uplink transmission structure by: lowering a
spreading factor, using multiple uplink resources or increasing the
duration of the transmission, or increasing the duration of the
transmission by transmitting some of the channel quality indicator
indices in one sub-frame and the remaining channel quality
indicator indices in another sub-frame.
[0042] In an embodiment, the number of channel quality indicator
indices of the second radio access technology system is equal to
the number of channel quality indicator indices of the first radio
access technology system. The user equipment is configured to map
by using the indicator of the channel quality having the indicator
format of the second radio access technology as is.
[0043] The object is, according to a third aspect of the invention,
achieved by a method in a network node of a communication system
comprising a first radio access technology system and a second
radio access technology system. A user equipment is in connection
with a primary serving cell on the first radio access technology
system and with a secondary serving cell on the second radio access
technology system. The method comprises receiving a report of
channel quality from the user equipment, in which report an
indicator of the channel quality having the indicator format of the
second radio access technology is mapped to an indicator format
used for channel quality indicators in the first radio access
technology system, and determining whether the report of channel
quality relates to the first radio access technology system or to
the second radio access technology system.
[0044] In an embodiment, the method further comprises making, for a
report of channel quality relating to the second radio access
technology system, a mapping of the channel quality indicator of
the second radio access technology system for determining the
channel quality indicator for the second radio access technology
system.
[0045] In an embodiment, the mapping is an inverse mapping.
[0046] In an embodiment, the determining whether the report of
channel quality relates to the first radio access technology system
or to the second radio access technology system is based on timing,
code and/or frequency allocation.
[0047] The object is, according to a fourth aspect of the
invention, achieved by a network of a communication system
comprising a first radio access technology system and a second
radio access technology system. A user equipment is in connection
with a primary serving cell on the first radio access technology
system and with a secondary serving cell on the second radio access
technology system. The network node is configured to receive a
report of channel quality from the user equipment, in which report
an indicator of the channel quality having the indicator format of
the second radio access technology is mapped to an indicator format
used for channel quality indicators in the first radio access
technology system; and determine whether the report of channel
quality relates to the first radio access technology system or to
the second radio access technology system.
[0048] In an embodiment, the network node is further configured to
make, for a report of channel quality relating to the second radio
access technology system, an mapping of the channel quality
indicator of the second radio access technology system for
determining the channel quality indicator for the second radio
access technology system.
[0049] In an embodiment, the mapping is an inverse mapping.
[0050] In an embodiment, the network node is configured to
determine whether the report of channel quality relates to the
first radio access technology system or to the second radio access
technology system based on timing, code and/or frequency
allocation.
[0051] Further features and advantages of the invention will become
clear upon reading the following description and the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0052] FIG. 1 exemplifies aggregation with a primary system and
secondary system.
[0053] FIG. 2 is a flowchart of methods implemented in a mobile
terminal, wireless device or a user equipment.
[0054] FIG. 3 illustrates quantization of CQI index.
[0055] FIG. 4 illustrates time multiplexing of CQI reports.
[0056] FIG. 5 illustrates schematically an environment, and in
particular a communication system, in which embodiments of the
invention may be implemented.
[0057] FIG. 6 illustrates schematically a user equipment suitable
for implementing embodiments of the methods.
[0058] FIG. 7 illustrates a user equipment comprising functional
blocks or means for implementing the methods.
[0059] FIG. 8 illustrates an exemplifying base station comprising
functional blocks or means for implementing embodiments of the
methods.
[0060] FIG. 9 is a flowchart of a method implemented in a network
node.
DETAILED DESCRIPTION
[0061] In the following description, for purposes of explanation
and not any limitation, specific details are set forth such as
particular architectures, interfaces, techniques, etc. in order to
provide a thorough understanding. In other instances, detailed
descriptions of well-known devices, circuits, and methods are
omitted so as not to obscure the description with unnecessary
detail. Same reference numerals refer to same or similar elements
throughout the description.
[0062] In this disclosure, the primary focus is on the
HSPA-evolution built on the WCDMA radio access also called UTRAN,
and LTE, which is based on OFDM and SC-FDMA, also recognized as the
Long Term Evolution of UTRAN, or E-UTRAN. Detailed UTRAN radio
access specifications are described in the 25-series of 3GPP
specifications, while E-UTRAN specifications are found in the
36-series. LTE was introduced in 3GPP Release 8, but the
development and future evolution of both HSPA and LTE continues in
parallel in Release 9, 10 and so on.
[0063] Briefly, a basic concept of the present invention is to
provide a solution to the earlier mentioned problems. Embodiments
for mapping CQI for a secondary RAT on a primary RAT uplink are
described.
[0064] In a first embodiment, where the CQI indices for the
secondary RAT is different than the number of CQI indices for the
primary RAT a Quantized CQI index for the secondary RAT is
determined and then transmitted using the same transmission
structure (coding, modulation, etc.) as for the primary RAT.
[0065] In another embodiment, an extended CQI transmission
structure is introduced in the primary RAT for enabling possibility
to transmit CQI for the secondary RAT.
[0066] In addition, methods for multiplexing CQI reports from the
primary and secondary RATs on a same uplink are provided. These
methods can be used in combination with the two embodiments
above.
[0067] Regarding the carrier aggregation set-up, examples of which
were given earlier, various possible future scenarios apply, and
should not be seen as limiting the applicability of embodiments of
the present invention. In FIG. 1, for the sake of illustration, one
possible solution is outlined where HSPA is acting as the first or
primary system and RAT 2 and LTE is the second or secondary system
and RAT 3. In such a situation, it is possible that e.g. mobility
is controlled by the primary system and RAT, as further described
below. A communication system 1 or communication network thus
comprises the primary radio access technology system 2 and the
secondary radio access technology system 3. Further, a user
equipment 4 or wireless device receives on at least one downlink
carrier on the first radio access technology system 2 and on at
least one downlink carrier on the second radio access technology
system 3. In the FIG. 1, the communication system 1 is illustrated
to comprise also a core network 5, associated with the primary RAT
2.
[0068] It is noted that the present invention is not limited to
these exemplary technologies, but embodiments of the invention are
equally applicable to any combination of accesses, as will be
further explained below. For example, the RATs may comprise LTE and
WLAN or HSPA and WLAN or any other radio access technologies.
[0069] FIG. 2 shows a flow chart of a basic principle of the
invention. The user equipment (UE) 4 or terminal is in connection
with a primary serving cell on a primary RAT 2, or differently
stated in connection with a network node serving a primary cell
using a primary RAT 2. The UE 4 is also in connection with a
secondary serving cell on a secondary RAT 3, or differently stated
in connection with a network node serving a secondary cell using a
secondary RAT 3. Furthermore only the primary serving cell and
primary RAT 2 is configured for the UL carrier or carriers.
Therefore CQI reports (from the UE to the network node on the UL)
for the secondary RAT 3, are, in accordance with embodiments of the
invention, signaled via UL carrier or carriers on the primary RAT
2. The user equipment 4 does, on regular basis, CQI estimates for
the primary RAT 2 (step 100) and secondary RAT 3 (step 110),
according to known principles for respective RAT 2, 3. The
regularity may be according to information received by higher layer
signaling from the network node. For instance, pilot symbols are
used for estimating a received Signal-to-Interference ratio (SIR)
and then the SIR is mapped to a CQI index corresponding to possible
modulation and coding scheme possible to support under the current
radio characteristics. The CQI index for the primary RAT 2 can be
fed back using the already present transmission structures in the
primary RAT uplink. Then, in step 120, the CQI index for the
secondary RAT 3, determined using secondary RAT 3 principles, is
mapped to a CQI format used for CQI reports for the primary RAT 2
Different embodiments are described below. Then, in step 130, the
CQI reports for the primary and secondary RAT 2, 3 are transmitted
to the network node, conveniently in a time multiplexed fashion,
although frequency or code multiplexing (or combinations of the
three multiplexing schemes) could be used. The network node then
reacts accordingly.
[0070] FIG. 3 illustrates quantization of CQI index for the
secondary RAT 3 to fit CQI format of the primary RAT 2. In
particular, FIG. 3 shows an embodiment of the mapping in case the
number of CQI indices for the secondary RAT 3 is larger than the
number of CQI indices for the primary RAT 2. For instance, LTE has
15 different CQI indices, while HSPA has 31 different CQI indices.
In this case, the different indicator formats or CQI formats imply
that the format for reporting CQI of the secondary RAT has more
bits available for reporting CQI compared to the number of bits
available in the CQI format used in the primary RAT.
[0071] In this case, the CQI index for the secondary RAT 3 (in this
example being HSPA) is estimated according to prior art techniques,
giving a certain CQI index (0 to 30). This CQI index is then
quantized to a quantized CQI (QCQI) index table for the secondary
RAT 3, having the same (or less) amount of CQI indices as the
primary RAT 2. For example, the quantized CQI index could include
the even indices, and the mapping is made according to
QCQI=div(CQI,2), where two consecutive CQIs are mapped onto one
QCQI. It is noted that other mapping functions may also be applied.
Next the quantized CQI values are mapped to CQI values for the
primary RAT 2 (in the example value 0-7), and then mapped to CQI
formats used by the primary RAT 2. If the number of indices for the
secondary RAT 3 is less than or equal to the number of indices
supported by the feedback transmission structure for the primary
RAT 2, there is no need for quantization and the sRAT (secondary
RAT) CQI index can be transmitted on the uplink "as is".
[0072] Another embodiment, with extended CQI format for the primary
RAT 2 for supporting CQI indices for the secondary RAT 3, is
described next. The basic approach is to extend the uplink
transmission structure such that it can handle the larger number of
indices (bits) required for feedback of the CQI from the secondary
RAT 3. Several possibilities exist. For example, the code rate of
the error correcting code used for the feedback messages can be
increased, resulting in a larger payload capability. To compensate
for the increased error probability due to an increased code rate,
the transmission power can be increased. Another possibility is to
lower the spreading factor (in case of HSPA uplink), to use
multiple uplink resources (multiple channelization codes in case of
HSPA, multiple "resources" as defined in 36.211 in case of LTE) or
to increase the duration of the transmission (e.g. to transmit some
of the bits in one subframe and the remaining bits in another
subframe).
[0073] FIG. 4 illustrates time multiplexing of CQI reports for the
primary RAT 2 and the secondary RAT 3 onto a CQI format for the
primary RAT 2. In particular, FIG. 4 shows a method for time
multiplexing the CQI reports from both the primary and the
secondary RAT 2, 3 on the CQI indicator format for the primary RAT
2. The FIG. 4 shows a time multiplexed fashion, where every second
CQI report is allocated to the different RATs, respectively. A
particular example: Primary/secondary RAT is reported every 10 ms,
and hence the user equipment needs to transmit a CQI report every 5
ms. It is noted that also other time multiplexing principles may be
used. For instance, the primary RAT 2 could be more frequently
reported than the secondary RAT 3 or vice versa. The rate could be
configured independently for respective RAT. This may be
advantageous since different RATs typically have different
transmission time interval (TTI) lengths, performance requirements
or scheduling constraints (e. g. number of modulation and coding
schemes) used. Alternatively, the rate could be event-triggered,
based for instance on the SIR value, although such event-triggered
solution would require larger modifications to existing HSPA and
LTE structures.
[0074] Other multiplexing schemes are also conceivable, allowing at
least partially simultaneous transmission of CQI reports from the
two RATs 2, 3. For example, multiple uplink resources, one for the
CQI from the primary RAT 2 and one for the CQI from the secondary
RAT 3, could be used simultaneously using different resources in
frequency and/or code domain. If the uplink carriers are using HSPA
(also denoted "a HSPA uplink" herein), code multiplexing can be
achieved by assigning different channelization codes and/or IQ
(in-phase and quadrature-phase) branches to the CQIs from the
primary and secondary RAT 2, 3. The spreading factor and channel
code rates could in this case be chosen freely for the two CQI
reports depending on their respective payload size. If the uplink
carriers are using LTE (also denoted "an LTE uplink" herein),
different "PUCCH resources" (Physical Uplink Control Channel) as
defined in 3GPP TS 36.211 (a resource is in principle a combination
of a frequency region and a spreading code) could be used. The CQI
reports for the two RATs 2, 3 could also be multiplexed into a
single bit stream, which in turn is coded and transmitted.
[0075] The above disclosure on CQI reporting focus on so-called
periodic CQI reports, i.e. the network node, such as a base station
or NodeB/eNodeB, configures periodic reporting instants. Periodic
reporting is supported in both HSPA and LTE. However, LTE also
supports aperiodic CQI reports, where the network node on a need
basis can request the user equipment to transmit a CQI report. The
resources upon which an aperiodic report is transmitted is given by
the network node as part of the CQI reporting request. The
structure for an aperiodic report in LTE supports (more or less)
arbitrary payload sizes and can therefore support CQI reports for
multiple RATs. The CQI request transmitted in the downlink could
also be extended with information for which combinations of RATs
CQI reports are requested (e.g. LTE only, HSPA only or both).
[0076] The invention also encompasses network node embodiments.
Briefly, a network node, such as a base station or NodeB/eNodeB,
receives the CQI report and determines, for instance by the timing,
code or frequency allocation whether the CQI is related to the
primary or secondary RAT 2, 3. In case of secondary RAT 3, the
inverse mapping (according to described above) is made to determine
the CQI index for the secondary RAT 3.
[0077] In the description above it has been assumed a full LTE-HSPA
carrier aggregation system, i.e. where the user equipment is
capable of simultaneous decoding of a first and a second RAT 2, 3.
The present invention is however also applicable to the case when
the user equipment is only capable to decode one RAT but CQI
measurements are also needed on a second RAT. This scenario happens
for example in the case fast load balancing is used. In fast load
balancing, the user equipment needs to monitor another RAT and
report CQI in order for the network to do fast IRAT HO (inter-RAT
handover) for optimized spectrum utilization.
[0078] In an aspect thus, the invention encompasses a method 90 in
a user equipment 4 for reporting a downlink channel quality in a
communication system 1. The communication system 1 comprises a
first radio access technology system 2, e.g. HSPA, and a second
radio access technology system 3, e.g. LTE. The user equipment 4 is
in connection with a network node serving a primary cell using the
first radio access technology system 2. The user equipment 4 is
further in connection the network node (or another network node)
serving a secondary serving cell and using the second radio access
technology system 3. The method 90 comprises determining 110 the
channel quality for the second radio access technology system 3.
This can be done in different ways, for example using pilot symbols
for estimating a received SIR, as described earlier.
[0079] The method 90 further comprises mapping 120 an indicator of
the channel quality to an indicator format used for channel quality
indicator reports for the first radio access technology system 2.
It is noted that this feature encompasses different alternatives.
In particular, the first RAT 2 may use a certain format for
reporting the channel quality (e.g. received SIR). The second RAT 3
may typically use another format for reporting a channel quality,
but could use the same format for reporting a channel quality as
the first RAT 2 uses. That is, the format used by a particular RAT,
as e.g. defined in a specification relating to this particular RAT,
may be the same or may differ for the different RATs. The method 90
encompasses both alternatives. Thus, the indicator of the channel
quality for the second RAT 3 may be different than or be the same
as the indicator of the channel quality for the first RAT 2.
[0080] The method 90 further comprises transmitting 130 the
indicator of the channel quality for the second radio access
technology system 3 to the communication system 1 using an uplink
carrier of the first radio access technology system 2.
[0081] Example Implementations
[0082] Although the described solutions may be implemented in any
appropriate type of telecommunication system supporting any
suitable communication standards and using any suitable components,
particular embodiments of the described solutions may be
implemented in an LTE network, such as that illustrated in FIG.
5.
[0083] As shown in FIG. 5, the example communication system 1 may
include one or more instances of user equipment 4 and one or more
network nodes or base stations 6 capable of communicating with
these UEs 4, along with any additional elements suitable to support
communication between UEs 4 or between a UE 4 and another
communication device (such as a landline telephone). Although the
illustrated UEs 4 may represent communication devices that include
any suitable combination of hardware and/or software, these UEs 4
may, in particular embodiments, represent devices such as the
example UE illustrated in greater detail by FIGS. 6 and 7.
Similarly, although the illustrated base stations 6 may represent
network nodes that include any suitable combination of hardware
and/or software, these base stations 6 may, in particular
embodiments, represent devices such as the example base station 6
illustrated in greater detail by FIG. 8.
[0084] As shown in FIG. 6, the example UE 4 includes a processing
circuitry or processor 408, a memory 411, a transceiver (TRX) 409,
and an antenna 410. In particular embodiments, some or all of the
functionality described above as being provided by mobile
communication devices or other forms of UEs 4 may be provided by
the UE processor executing instructions stored on a computer
readable medium, such as the memory 411 shown in FIG. 6.
Alternative embodiments of the UE 4 may include additional
components beyond those shown in FIG. 6 that may be responsible for
providing certain aspects of the UE's functionality, including any
of the functionality described above and/or any functionality
necessary to support the solution described above.
[0085] FIG. 7 shows a block diagram over a UE 4 operating according
to the presented disclosure. The UE 4 comprises a transceiver unit
(TRX) 47 responsible for translating the radio signal to a baseband
signal (and vice versa), a ND and D/A unit 45 responsible to
transforming a analog(digital) signal to a digital(analog) signal.
The UE 4 also comprises demodulators and decoders 41, 42 for
respective supported RAT and the UE 4 is capable to operate these
demodulators and decoders simultaneously. The UE 4 further
comprises timing determination units 40, 43 capable of determining
the DL timing for respective RAT, and a control unit 408 that is
responsible for mapping the HARQ feedback response for the
secondary RAT 3 to correct UL sub frame of the primary RAT 2
according to the embodiments described. Also blocks including
coders and modulators 44 for the at least the primary RAT 2 is
included in the UE 4.
[0086] As shown in FIG. 8, the example network node or base station
6 includes processing circuitry 601 or processor, a memory 603, a
transceiver 602, and an antenna 605. In particular embodiments,
same or all of the functionality described above as being provided
by a mobile base station, a base station controller, a node B, an
enhanced node B, and/or any other type of mobile communications
node may be provided by the base station processor 601 executing
instructions stored on a computer-readable medium, such as the
memory 603 shown in FIG. 8. Alternative embodiments of the base
station 6 may include additional components responsible for
providing additional functionality, including any of the
functionality identified above and/or any functionality necessary
to support the solution described above.
[0087] In particular, and with reference to FIG. 9, the network
node or base station 6 may be configured to perform a method 200
comprising receiving 210 a report of channel quality from the user
equipment 4. In the report a channel quality indicator of the
second radio access technology system 3 is mapped to an indicator
format used for channel quality indicator reports for the first
radio access technology system 2.
[0088] The method 200 further comprises determining 220 whether the
report of channel quality relates to the first radio access
technology system 2 or to the second radio access technology system
3. If the report relates to the second radio access technology
system 3, the network node 6 may e.g. transmit a report further to
a node e.g. handling channel allocation for the second radio access
technology system 3.
[0089] In an embodiment (not shown in the FIG. 9), the method 200
further comprises making, for a report of channel quality relating
to the second radio access technology system 3, a mapping of the
channel quality indicator of the second radio access technology
system 3 for determining the channel quality indicator for the
second radio access technology system 3. The mapping could for
example be an inverse mapping.
[0090] In an embodiment, the determining whether the report of
channel quality relates to the first radio access technology system
2 or to the second radio access technology system 3 is based on
timing, code and/or frequency allocation.
* * * * *