NZ623748B2 - Simultaneous reporting of ack/nack and channel-state information using pucch format 3 resources - Google Patents
Simultaneous reporting of ack/nack and channel-state information using pucch format 3 resources Download PDFInfo
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
- H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
- H04L1/0026—Transmission of channel quality indication
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
- H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
- H04L1/0028—Formatting
- H04L1/003—Adaptive formatting arrangements particular to signalling, e.g. variable amount of bits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
- H04L1/1607—Details of the supervisory signal
- H04L1/1621—Group acknowledgement, i.e. the acknowledgement message defining a range of identifiers, e.g. of sequence numbers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
- H04L1/1607—Details of the supervisory signal
- H04L1/1671—Details of the supervisory signal the supervisory signal being transmitted together with control information
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
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- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
- H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
- H04L1/1829—Arrangements specially adapted for the receiver end
- H04L1/1861—Physical mapping arrangements
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0053—Allocation of signaling, i.e. of overhead other than pilot signals
- H04L5/0055—Physical resource allocation for ACK/NACK
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Abstract
new uplink control channel capability is introduced to enable a mobile terminal to simultaneously report multiple packet receipt status bits and channel-condition bits. In an example embodiment implemented in a mobile terminal the mobile terminal first determines that channel-state information and hybrid-ARQ ACK/NACK bits corresponding to a plurality of downlink subframes or a plurality of downlink carriers, or both, are scheduled for transmission in an uplink subframe. The mobile terminal then determines whether the number of the hybrid-ARQ ACK/NACK bits is less than or equal to a threshold number. If so, the mobile terminal transmits both the channel-state information and the hybrid-ARQ ACK/NACK bits in physical control channel resources of the first uplink subframe, on a single carrier; otherwise the CSI is dropped and the hybrid-ARQ ACK/NACK bits is sent. In some embodiments, the number of the hybrid-ARQ ACK/NACK bits considered in the previously summarized technique represents a number of ACK/NACK bits after ACK/NACK bundling. hybrid-ARQ ACK/NACK bits corresponding to a plurality of downlink subframes or a plurality of downlink carriers, or both, are scheduled for transmission in an uplink subframe. The mobile terminal then determines whether the number of the hybrid-ARQ ACK/NACK bits is less than or equal to a threshold number. If so, the mobile terminal transmits both the channel-state information and the hybrid-ARQ ACK/NACK bits in physical control channel resources of the first uplink subframe, on a single carrier; otherwise the CSI is dropped and the hybrid-ARQ ACK/NACK bits is sent. In some embodiments, the number of the hybrid-ARQ ACK/NACK bits considered in the previously summarized technique represents a number of ACK/NACK bits after ACK/NACK bundling.
Description
SIMULTANEOUS REPORTING OF ACK/NACK AND CHANNEL-STATE
INFORMATION USING PUCCH FORMAT 3 RESOURCES
RELATED APPLICATION
This application claims the benefit of U.S. Provisional Patent Application
61/542503, filed 3 October 2011.
TECHNICAL FIELD
The present invention relates generally to carrier aggregation in a mobile
communication system and, more particularly, to an efficient use of resources for the
physical uplink control channel in wireless systems using carrier aggregation.
BACKGROUND
Carrier aggregation is one of the new features recently developed by the
members of the 3rd-Generation Partnership Project (3GPP) for so-called Long Term
Evolution (LTE) systems, and is standardized as part of LTE Release 10, which is
also known as LTE-Advanced. An earlier version of the LTE standards, LTE Release
8, supports bandwidths up to 20 MHz. In LTE-Advanced, bandwidths up to 100 MHz
are supported. The very high data rates contemplated for LTE-Advanced will require
an expansion of the transmission bandwidth. In order to maintain backward
compatibility with LTE Release 8 mobile terminals, the available spectrum is divided
into Release 8 - compatible chunks called component carriers. Carrier aggregation
enables bandwidth expansion beyond the limits of LTE Release 8 systems by
allowing mobile terminals to transmit data over multiple component carriers, which
together can cover up to 100 MHz of spectrum. Importantly, the carrier aggregation
approach ensures compatibility with earlier Release 8 mobile terminals, while also
ensuring efficient use of a wide carrier by making it possible for legacy mobile
terminals to be scheduled in all parts of the wideband LTE-Advanced carrier.
The number of aggregated component carriers, as well as the bandwidth of
the individual component carrier, may be different for uplink (UL) and downlink (DL)
transmissions. A carrier configuration is referred to as “symmetric” when the number
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of component carriers in each of the downlink and the uplink are the same. In an
asymmetric configuration, on the other hand, the numbers of component carriers
differ between the downlink and uplink. The number of component carriers
configured for a geographic cell area may be different from the number of component
carriers seen by a given mobile terminal. A mobile terminal, for example, may
support more downlink component carriers than uplink component carriers, even
though the same number of uplink and downlink component carriers may be offered
by the network in a particular area.
LTE systems can operate in either Frequency-Division Duplex (FDD) mode or
Time-Division Duplex (TDD) mode. In FDD mode, downlink and uplink transmissions
take place in different, sufficiently separated, frequency bands. In TDD mode, on the
other hand, downlink and uplink transmission take place in different, non-overlapping
time slots. Thus, TDD can operate in unpaired spectrum, whereas FDD requires
paired spectrum. TDD mode also allows for different asymmetries in terms of the
amount of resources allocated for uplink and downlink transmission, respectively, by
means of different downlink/uplink configurations. These differing configurations
permit the shared frequency resources to be allocated to downlink and uplink use in
differing proportions. Accordingly, uplink and downlink resources can be allocated
asymmetrically for a given TDD carrier.
One consideration for carrier aggregation is how to transmit control signaling
from the mobile terminal on the uplink to the wireless network. Uplink control
signaling may include acknowledgement (ACK) and negative-acknowledgement
(NACK) signaling for hybrid automatic repeat request (Hybrid ARQ, or HARQ)
protocols, channel state information (CSI) and channel quality information (CQI)
reporting for downlink scheduling, and scheduling requests (SRs) indicating that the
mobile terminal needs uplink resources for uplink data transmissions. In the carrier
aggregation context, one solution would be to transmit the uplink control information
on multiple uplink component carriers associated with different downlink component
carriers. However, this option is likely to result in higher mobile terminal power
consumption and a dependency on specific mobile terminal capabilities. Accordingly,
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improved techniques are needed for managing the transmission of uplink control-
channel information in systems that employ carrier aggregation.
SUMMARY
Even with the several uplink control channel techniques and formats already
standardized by 3GPP, problems remain. For instance, an LTE mobile terminal
operating in TDD mode and configured with ACK/NACK multiplexing cannot
simultaneously report multiple ACK/NACK bits and a periodic CSI report. If such a
collision happens, the conventional approach is to simply drop the CSI report, and
transmit only the ACK/NACK bits. This behavior is independent of whether the
multiple ACK/NACK bits stem from multiple subframes or multiple aggregated cells.
Periodic CSI reports for multiple cells are handled in Release 10 with time-
shifted reporting times, to minimize collisions among CSI reports. To maintain
roughly the same CSI periodicity per cell, it is obvious that periodic CSI reports are
transmitted more frequently than in Release 8 systems. In each subframe without
PUSCH transmission where periodic CSI and multi-cell ACK/NACK collide, the
periodic CSI are dropped. Since CSI reports are required for link adaptation, reduced
CSI feedback degrades downlink performance. This is in particular a problem for
TDD, where only a minority of the available subframes may be uplink subframes.
Thus, without changes to current 3GPP specifications, collisions between
ACK/NACK transmissions and CSI reports will likely lead to dropped CSI reports.
The novel techniques described herein enable simultaneous transmission of multiple
ACK/NACK bits and CSI. With the use of these techniques, fewer CSI reports are
dropped, which improves link adaptation and increases throughput. More
particularly, in several embodiments of the present invention, these problems are
addressed by introducing a new uplink control channel capability that enables a
mobile terminal to simultaneously report to the radio network multiple packet receipt
status bits, (e.g., ACK/NACK bits) and channel-condition bits (e.g., CSI reports). In
some embodiments, this uplink control channel capability also supports sending
uplink scheduling requests from the UE in addition to transmitting multiple packet
receipt status bits and channel-condition bits. In several embodiments, if the mobile
6329952_3.doc
terminal does not have any channel-condition bits to report in a given subframe, it
may transmit ACK/NACK bits using an uplink control channel transmission mode that
does not allow such simultaneous transmission.
The present invention provides a method in a mobile terminal for simultaneous
reporting of channel-state information and hybrid-ARQ ACK/NACK information in
uplink subframes, the method comprising: determining that first channel-state
information and first hybrid-ARQ ACK/NACK bits corresponding to a plurality of
downlink subframes or a plurality of downlink carriers, or both, are scheduled for
transmission in a first uplink subframe; determining whether the number of the first
hybrid-ARQ ACK/NACK bits is less than or equal to a threshold number; and
transmitting both the first channel-state information and the first hybrid-ARQ
ACK/NACK bits in physical control channel resources of the first uplink subframe, on
a single carrier, in response to determining that the number of hybrid-ARQ
ACK/NACK bits to be transmitted in the first uplink subframe is less than or equal to
the threshold number; dropping the first channel state information and transmitting
the first hybrid-ARQ ACK/NACK bits in physical control channel resources of the first
uplink subframe, on a single carrier, in response to determining that the number of
hybrid-ARQ ACK/NACK bits to be transmitted in the first uplink subframe is not less
than or equal to the threshold number.
The term ‘comprising’ as used in this specification and claims means
‘consisting at least in part of’. When interpreting statements in this specification and
claims which include the term ‘comprising’, other features besides the features
prefaced by this term in each statement can also be present. Related terms such as
‘comprise’ and ‘comprised’ are to be interpreted in similar manner.
The present invention further provides a method in a base station for
processing received reports of channel-state information and hybrid-ARQ ACK/NACK
information, the method comprising receiving a plurality of uplink subframes, each
uplink subframe comprising one or more physical control channel resources carrying
control channel information encoded by mobile terminals; for each of the physical
control channel resources, determining whether a number of expected hybrid-ARQ
ACK/NACK bits is less than or equal to a threshold number; and decoding both
6329952_3.doc
channel-state information and hybrid-ARQ ACK/NACK bits from each physical control
channel resource for which the number of expected hybrid-ARQ ACK/NACK bits is
less than or equal to the threshold number; decoding only hybrid-ARQ ACK/NACK
bits from each physical control channel resource for which the number of expected
hybrid-ARQ ACK/NACK bits is not less than or equal to the threshold number.
The present invention further provides a mobile terminal configured for
simultaneous reporting of channel-state information and hybrid-ARQ ACK/NACK
information in uplink subframes, the mobile terminal comprising a receiver circuit, a
transmitter circuit, and a processing circuit, wherein the processing circuit is adapted
to: determine that first channel-state information and first hybrid-ARQ ACK/NACK bits
corresponding to a plurality of downlink subframes or a plurality of downlink carriers,
or both, are scheduled for transmission in a first uplink subframe; determine whether
the number of the first hybrid-ARQ ACK/NACK bits is less than or equal to a
threshold number; and send both the first channel-state information and the first
hybrid-ARQ ACK/NACK bits to a base station, via the transmitter circuit, in physical
control channel resources of the first uplink subframe, on a single carrier, in response
to determining that the number of hybrid-ARQ ACK/NACK bits to be transmitted in
the first uplink subframe is less than or equal to the threshold number; drop the first
channel state information and send the first hybrid-ARQ ACK/NACK bits to the base
station, via the transmitter circuit, in physical control channel resources of the first
uplink subframe, on a single carrier, in response to determining that the number of
hybrid-ARQ ACK/NACK bits to be transmitted in the first uplink subframe is not less
than or equal to the threshold number.
The present invention still further provides a base station configured to
process received reports of channel-state information and hybrid-ARQ ACK/NACK
information, the base station comprising a transmitter circuit, a receiver circuit, and a
processing circuit, wherein the processing circuit is configured to: receive, via the
receiver circuit a plurality of uplink subframes, each uplink subframe comprising one
or more physical control channel resources carrying control channel information
encoded by mobile terminals; determine, for each of the physical control channel
resources, whether a number of expected hybrid-ARQ ACK/NACK bits is less than or
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equal to a threshold number; and decode both channel-state information and hybrid-
ARQ ACK/NACK bits from each physical control channel resource for which the
number of expected hybrid-ARQ ACK/NACK bits is less than or equal to the
threshold number; decode only hybrid-ARQ ACK/NACK bits from each physical
control channel resource for which the number of expected hybrid-ARQ ACK/NACK
bits is not less than or equal to the threshold number.
The processing circuit may comprise: an hybrid-ARQ processing unit adapted
to determine that the first channel-state information and the first hybrid-ARQ
ACK/NACK bits corresponding to the plurality of downlink carriers are scheduled for
transmission in the first uplink subframe, and to determine whether the number of the
first hybrid-ARQ ACK/NACK bits is less than or equal to the threshold number; and
an uplink control channel encoding unit adapted to send both the first channel-state
information and the first hybrid-ARQ ACK/NACK bits in physical control channel
resources of the first uplink subframe, on a single carrier, in response to determining
that the number of hybrid-ARQ ACK/NACK bits to be transmitted in the first uplink
subframe is less than or equal to the threshold number; and further adapted to drop
the first channel state information and send the first hybrid-ARQ ACK/NACK bits to
the base station, via the transmitter circuit, in physical control channel resources of
the first uplink subframe, on a single carrier, in response to determining that the
number of hybrid-ARQ ACK/NACK bits to be transmitted in the first uplink subframe
is not less than or equal to the threshold number.
There is disclosed herein a mobile terminal that first determines that channel-
state information and hybrid-ARQ ACK/NACK bits corresponding to a plurality of
downlink subframes or a plurality of downlink carriers, or both, are scheduled for
transmission in an uplink subframe. The mobile terminal then determines whether
the number of the hybrid-ARQ ACK/NACK bits is less than or equal to a threshold
number. If so, the mobile terminal transmits both the channel-state information and
the hybrid-ARQ ACK/NACK bits in physical control channel resources of the uplink
subframe, on a single carrier. In some embodiments, the number of the hybrid-ARQ
ACK/NACK bits considered in the previously summarized technique represents a
number of ACK/NACK bits after ACK/NACK bundling. In some embodiments, the
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threshold number depends on the number of channel-state information bits
scheduled for transmission in the uplink subframe.
In a variant of these techniques, the mobile terminal determines, for a different
uplink subframe, that second channel-state information and second hybrid-ARQ
ACK/NACK bits corresponding to a plurality of downlink subframes or a plurality of
downlink carriers, or both, are scheduled for transmission. The mobile terminal again
determines whether the number of the second hybrid-ARQ ACK/NACK bits is less
than or equal to the threshold number. In this case, the answer is no, so the mobile
terminal drops the second channel-state information and transmits the second hybrid-
ARQ ACK/NACK bits in physical control channel resources of the second uplink
subframe, on a single carrier, in response to determining that the number of hybrid-
ARQ ACK/NACK bits to be transmitted in the second uplink subframe is not less than
or equal to the threshold number.
In another variant, the mobile terminal determines, for a different uplink
subframe, that second channel-state information and a second hybrid-ARQ
ACK/NACK bits corresponding to a plurality of downlink subframes or a plurality of
downlink carriers, or both, are scheduled for transmission in a second uplink
subframe. The mobile terminal again determines whether the number of the second
hybrid-ARQ ACK/NACK bits is less than or equal to the threshold number. If not, the
mobile terminal bundles the second hybrid-ARQ ACK/NACK bits to produce a
number of bundled ACK/NACK bits that is less than or equal to the threshold number,
in response to determining that the number of hybrid-ARQ ACK/NACK bits to be
transmitted in the second uplink subframe is not less than or equal to the threshold
number, and transmits both the second channel-state information and the bundled
ACK/NACK bits in physical control channel resources of the second uplink subframe,
on a single carrier.
As discussed more fully below, the present techniques may be implemented in
a Long-Term Evolution (LTE) wireless system, in which case the hybrid-ARQ
ACK/NACK bits and the channel-state information are transmitted using a Physical
Uplink Control Channel (PUCCH) Format 3 resource. In some embodiments, the
mobile terminal encodes the hybrid-ARQ ACK/NACK bits using a first encoder and
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separately encodes the channel-state information bits using a second encoder, and
interleaves the encoded hybrid-ARQ ACK/NACK bits and the encoded channel-state
information bits before transmission.
Complementary techniques for receiving and processing information
transmitted according to the techniques described above are also disclosed in detail
below. In addition, mobile terminal apparatus and base station apparatus adapted to
carry out any of these techniques are disclosed. Of course, the present invention is
not limited to the above-summarized features and advantages. Indeed, those skilled
in the art will recognize additional features and advantages upon reading the
following detailed description, and upon viewing the accompanying drawings.
In the description in this specification reference may be made to subject matter
which is not within the scope of the appended claims. That subject matter should be
readily identifiable by a person skilled in the art and may assist in putting into practice
the invention as defined in the presently appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be described, by way of non-limiting example
only, with reference to the accompanying drawings, in which:
Figure 1 illustrates an example of a mobile communication system.
Figure 2 illustrates a grid of time-frequency resources for a mobile
communication system that uses OFDM.
Figure 3 illustrates the time-domain structure of an LTE signal.
Figure 4 illustrates the positioning of PUCCH resources in an uplink subframe
according to Release 8 standards for LTE.
Figure 5 illustrates the encoding and modulation of channel-status information
according to PUCCH Format 2.
Figure 6 illustrates several carriers aggregated to form an aggregated
bandwidth of 100 MHz.
Figures 7, 8, and 9 illustrate the coding of multiple ACK/NACK bits using
channel selection.
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Figure 10 illustrates the encoding and modulation of multiple ACK/NACK bits
according to PUCCH Format 3.
Figures 11, 12, 13 are process flow diagrams illustrating example methods for
simultaneous reporting of channel-state information and hybrid-ARQ ACK/NACK
information.
Figure 14 is a process flow diagram illustrating an example method for
receiving and decoding simultaneously reported channel-state information and
hybrid-ARQ ACK/NACK bits.
Figure 15 is a block diagram illustrating components of an example
communications node according to some embodiments of the invention.
Figure 16 illustrates functional components of an example mobile terminal.
DETAILED DESCRIPTION
Referring now to the drawings, Figure 1 illustrates an exemplary mobile
communication network 10 for providing wireless communication services to mobile
terminals 100. Three mobile terminals 100, which are referred to as “user
equipment” or “UE” in LTE terminology, are shown in Figure 1. The mobile terminals
100 may comprise, for example, cellular telephones, personal digital assistants,
smart phones, laptop computers, handheld computers, or other devices with wireless
communication capabilities. The mobile communication network 10 comprises a
plurality of geographic cell areas or sectors 12. Each geographic cell area or sector
12 is served by a base station 20, which is referred to in LTE as a NodeB or Evolved
NodeB (eNodeB). One base station 20 may provide service in multiple geographic
cell areas or sectors 12. The mobile terminals 100 receive signals from base station
20 on one or more downlink (DL) channels, and transmit signals to the base station
on one or more uplink (UL) channels.
For illustrative purposes, several embodiments of the present invention will be
described in the context of a Long-Term Evolution (LTE) system. Those skilled in the
art will appreciate, however, that several embodiments of the present invention may
be more generally applicable to other wireless communication systems, including, for
example, WiMax (IEEE 802.16) systems.
6329952_3.doc
LTE uses Orthogonal Frequency Division Multiplexing (OFDM) in the downlink
and Discrete Fourier Transform (DFT)-spread OFDM in the uplink. The basic LTE
downlink physical resource can be viewed as a time-frequency grid. Figure 2
illustrates a portion of the available spectrum of an exemplary OFDM time-frequency
grid 50 for LTE. Generally speaking, the time-frequency grid 50 is divided into one
millisecond subframes. Each subframe includes a number of OFDM symbols. For a
normal cyclic prefix (CP) length, suitable for use in situations where multipath
dispersion is not expected to be extremely severe, a subframe consists of fourteen
OFDM symbols. A subframe has only twelve OFDM symbols if an extended cyclic
prefix is used. In the frequency domain, the physical resources are divided into
adjacent subcarriers with a spacing of 15 kHz. The number of subcarriers varies
according to the allocated system bandwidth. The smallest element of the time-
frequency grid 50 is a resource element. A resource element consists of one OFDM
subcarrier during one OFDM symbol interval.
Resource elements are grouped into resource blocks, where each resource
block in turn consists of twelve OFDM subcarriers, within one of two equal-length
slots of a subframe. Figure 2 illustrates a resource block pair, comprising a total of
168 resource elements.
Downlink transmissions are dynamically scheduled, in that in each subframe
the base station transmits control information identifying the mobile terminals to
which data is transmitted and the resource blocks in which that data is transmitted,
for the current downlink subframe. This control signaling is typically transmitted in a
control region, which occupies the first one, two, three, or four OFDM symbols in
each subframe. A downlink system with a control region of three OFDM symbols is
illustrated in Figure 2. The dynamic scheduling information is communicated to the
UEs (“user equipment,” 3GPP terminology for a mobile station) via a Physical
Downlink Control Channel (PDCCH) transmitted in the control region. After
successful decoding of a PDCCH, the UE performs reception of traffic data from the
Physical Downlink Shared Channel (PDSCH) or transmission of traffic data on the
Physical Uplink Shared Channel (PUSCH), according to pre-determined timing
specified in the LTE specifications.
6329952_3.doc
As shown in Figure 3, LTE downlink transmissions are further organized into
radio frames of 10 milliseconds, in the time domain, each radio frame consisting of
ten subframes. Each subframe can further be divided into two slots of 0.5
milliseconds duration. Furthermore, resource allocations in LTE are often described
in terms of resource blocks, where a resource block corresponds to one slot (0.5 ms)
in the time domain and twelve contiguous subcarriers in the frequency domain.
Resource blocks are numbered in the frequency domain, starting with 0 from one end
of the system bandwidth.
For error control, LTE uses hybrid-ARQ (HARQ), where, after receiving
downlink data in a subframe, the mobile terminal attempts to decode it and reports to
the base station whether the decoding was successful (ACK) or not (NACK) via a
Physical Uplink Control Channel (PUCCH). In the event of an unsuccessful decoding
attempt, the base station (evolved NodeB, or eNodeB, in 3GPP terminology) can
retransmit the erroneous data. Similarly, the base station can indicate to the UE
whether the decoding of the PUSCH was successful (ACK) or not (NACK) via the
Physical Hybrid ARQ Indicator CHannel (PHICH).
In addition to the hybrid-ARQ ACK/NACK information transmitted from the
mobile terminal to the base station, uplink control signaling from the mobile terminal
to the base station also includes reports related to the downlink channel conditions,
referred to generally as channel-state information (CSI) or channel-quality information
(CQI). This CSI/CQI is used by the base station to assist in downlink resource
scheduling decisions. Because LTE systems rely on dynamic scheduling of both
downlink and uplink resources, uplink control-channel information also includes
scheduling requests, which the mobile terminal sends to indicate that it needs uplink
traffic-channel resources for uplink data transmissions.
When a UE has data to transmit on PUSCH, it multiplexes the uplink control
information with data on PUSCH. Thus, a UE only uses PUCCH for signaling this
uplink control information when it does not have any data to transmit on PUSCH.
Accordingly, if the mobile terminal has not been assigned an uplink resource for data
transmission, Layer 1/Layer 2 (L1/L2) control information, including channel-status
reports, hybrid-ARQ acknowledgments, and scheduling requests, is transmitted in
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uplink resources (resource blocks) specifically assigned for uplink L1/L2 control on
the Physical Uplink Control CHannel (PUCCH), which was first defined in Release 8
of the 3GPP specifications (LTE Rel-8).
As illustrated in Figure 4, these resources are located at the edges of the
uplink cell bandwidth that is available to the mobile terminal for use. Each physical
control channel resource is made up of a pair of resource blocks, where each
resource block in turn consists of twelve OFDM subcarriers, within one of the two
slots of the uplink subframe. In order to provide frequency diversity, the physical
control channel resources are frequency hopped on the slot boundary – thus, the first
resource block of the pair is at the lower part of the spectrum within the first slot of
the subframe while the second resource block of the pair is positioned at the upper
part of the spectrum during the second slot of the subframe (or vice-versa). If more
resources are needed for the uplink L1/L2 control signaling, such as in case of very
large overall transmission bandwidth supporting a large number of users, additional
resource blocks can be assigned, adjacent to the previously assigned resource
blocks.
The reasons for locating the PUCCH resources at the edges of the overall
available spectrum are two-fold. First, together with the frequency hopping described
above, this maximizes the frequency diversity experienced by the control signaling,
which can be encoded so that it is spread across both resource blocks. Second,
assigning uplink resources for the PUCCH at other positions within the spectrum, i.e.,
not at the edges, would fragment the uplink spectrum, making it difficult to assign
very wide transmission bandwidths to a single mobile terminal while still retaining the
single-carrier property of the uplink transmission.
When a UE has ACK/NACK to send in response to a downlink PDSCH
transmission, it determines which PUCCH resource to use from the PDCCH
transmission that assigned the PDSCH resources to the UE. More specifically, an
index to the PUCCH resource for the UE is derived from the number of the first
control channel element used to transmit the downlink resource assignment. When a
UE has a scheduling request or CQI to send, it uses a specific PUCCH resource that
has been pre-configured for the UE by higher layer signaling.
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Depending on the different types of information that PUCCH is to carry,
several different PUCCH formats may be used. The data-carrying capacity of a pair
of resource blocks during one subframe is more than is generally needed for the
short-term control signaling needs of one mobile terminal. Therefore, to efficiently
exploit the resources set aside for control signaling, multiple mobile terminals can
share the same physical control channel resource. This is done by assigning each of
several mobile terminals different orthogonal phase-rotations of a cell-specific,
length-12, frequency-domain sequence and/or different orthogonal time-domain
cover codes. By applying these frequency-domain rotations and/or time-domain
covering codes to the encoded control channel data, as many as 36 mobile terminals
can share a given physical control channel resource in some circumstances.
Several different encoding formats have been developed by 3GPP to encode
different quantities and types of uplink control channel data, within the constraints of
a single physical control channel resource. These several formats, known generally
as PUCCH Format 1, PUCCH Format 2, and PUCCH Format 3, are described in
detail at pages 226-242 of the text “4G LTE/LTE-Advanced for Mobile Broadband,”
by Erik Dahlman, Stefan Parkvall, and Johan Sköld (Academic Press, Oxford UK,
2011), and are summarized briefly below.
PUCCH formats 1, 1a, and 1b, which are used to transmit scheduling requests
and/or ACK/NACK, are based on cyclic shifts of a Zadoff-Chu sequence. A
modulated data symbol is multiplied with the cyclically Zadoff-Chu shifted sequence.
The cyclic shift varies from one symbol to another and from one slot to the next.
Although twelve different shifts are available, higher-layer signaling may configure
UEs in a given cell to use fewer than all of the shifts, to maintain orthogonality
between PUCCH transmissions in cells that exhibit high frequency selectivity. After
the modulated data symbol is multiplied with the Zadoff-Chu sequence, the result is
spread using an orthogonal spreading sequence. PUCCH formats 1, 1a, and 1b
carry three reference symbols per slot (when normal cyclic prefix is used), at SC-
FDMA symbol numbers 2, 3, and 4.
PUCCH Formats 1a and 1b refer to PUCCH transmissions that carry either
one or two hybrid-ARQ acknowledgements, respectively. A PUCCH Format 1
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transmission (carrying only a SR) is transmitted on a UE-specific physical control
channel resource (defined by a particular time-frequency resource, a cyclic-shift, and
an orthogonal spreading code) that has been pre-configured by RRC signaling.
Likewise, PUCCH Format 1a or 1b transmissions carrying only hybrid-ARQ
acknowledgements are transmitted on a different UE-specific physical control
channel resource. PUCCH Format 1a or 1b transmissions that are intended to carry
both ACK/NACK information and a scheduling request are transmitted on the
assigned SR resource for positive SR transmission, and are encoded with the
ACK/NACK information.
PUCCH Format 1/1a/1b transmissions carry only one or two bits of information
(plus scheduling requests, depending on the physical control channel resource used
for the transmission). Because channel-state information reports require more than
two bits of data per subframe, PUCCH Format 2/2a/2b is used for these
transmissions. As illustrated in Figure 5, in PUCCH formats 2, 2a, and 2b, the
channel-status reports are first block-coded, and then the block-coded bits for
transmission are scrambled and QPSK modulated. (Figure 5 illustrates coding for a
subframe using a normal cyclic prefix, with seven symbols per slot. Slots using
extended cyclic prefix have only one reference-signal symbol per slot, instead of
two.) The resulting ten QPSK symbols are then multiplied with a cyclically shifted
Zadoff-Chu type sequence, a length-12 phase-rotated sequence, where again the
cyclic shift varies between symbols and slots. Five of the symbols are processed and
transmitted in the first slot, i.e., the slot appearing on the left-hand side of Figure 5,
while the remaining five symbols are transmitted in the second slot. PUCCH formats
2, 2a, and 2b carry two reference symbols per slot, located on SC-FDMA symbol
numbers 1 and 5.
For UEs operating in accordance with LTE Release 8 or LTE Release 9 (i.e.,
without carrier aggregation), it is possible to configure the UE in a mode where it
reports ACK/NACK bits and CSI bits simultaneously. If the UE is using normal cyclic
prefix, one or two ACK/NACK bits are modulated onto a QPSK symbol on the second
reference signal (RS) resource element in each slot of the PUCCH format 2. If one
ACK/NACK bit is modulated on the second RS in each slot, the PUCCH format used
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by the UE is referred to as PUCCH Format 2a. If two ACK/NACK bits are modulated
on the second RS in each slot the PUCCH format used by the UE is referred to as
PUCCH Format 2b. If the UE is configured with extended cyclic prefix, one or two
ACK/NACK bits are jointly coded with channel-state information (CSI) feedback and
transmitted together within PUCCH format 2.
As with PUCCH Format 1 transmissions, a pair of resource blocks allocated to
PUCCH can carry multiple PUCCH Format 2 transmissions from several UEs, with
the separate transmissions separated by the cyclic shifting. As with PUCCH Format
1, each unique PUCCH Format 2 resource can be represented by an index from
which the phase rotation and other quantities necessary are derived. The PUCCH
format 2 resources are semi-statically configured. It should be noted that a pair of
resource blocks can either be configured to support a mix of PUCCH formats 2/2a/2b
and 1/1a/1b, or to support formats 2/2a/2b exclusively.
3GPP’s Release 10 of the LTE standards (LTE Release 10) has been
published and provides support for bandwidths larger than 20 MHz, through the use
of carrier aggregation. One important requirement placed on the development of LTE
Release 10 specifications was to assure backwards compatibility with LTE Release
8. The need for spectrum compatibility dictated that an LTE Release 10 carrier that
is wider than 20 MHz should appear as a number of distinct, smaller bandwidth, LTE
carriers to an LTE Release 8 mobile terminal. Each of these distinct carriers can be
referred to as a component carrier.
For early LTE Release 10 system deployments in particular, it can be
expected that there will be a relatively small number of LTE Release 10-capable
mobile terminals, compared to many “legacy” mobile terminals that conform to earlier
releases of the LTE specifications. Therefore, it is necessary to ensure the efficient
use of wide carriers for legacy mobile terminals as well as Release 10 mobile
terminals, i.e., that it is possible to implement carriers where legacy mobile terminals
can be scheduled in all parts of the wideband LTE Release 10 carrier.
One straightforward way to obtain this is by means of a technique called
carrier aggregation. With carrier aggregation, an LTE Release 10 mobile terminal
can receive multiple component carriers, where each component carrier has (or at
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least may have) the same structure as a Release 8 carrier. The basic concept of
carrier aggregation is illustrated in Figure 6, which illustrates the aggregation of five
-MHz component carriers to yield an aggregated bandwidth of 100 MHz.
The number of aggregated component carriers as well as the bandwidth for
each individual component carrier may be different for uplink and downlink. In a
symmetric configuration, the number of component carriers in downlink and uplink is
the same, whereas the numbers of uplink and downlink carriers differ in an
asymmetric configuration.
During initial access, an LTE Release 10 mobile terminal behaves similarly to
an LTE Release 8 mobile terminal, requesting and obtaining access to a single
carrier for the uplink and downlink. Upon successful connection to the network a
mobile terminal may – depending on its own capabilities and the network – be
configured with additional component carriers in the uplink (UL) and downlink (DL).
Even if a mobile terminal is configured with additional component carriers, it
need not necessarily monitor all of them, all of the time. This is because LTE
Release 10 supports activation of component carriers, as distinct from configuration.
The mobile terminal monitors for PDCCH and PDSCH only component carriers that
are both configured and activated. Since activation is based on Medium Access
Control (MAC) control elements – which are faster than RRC signaling – the
activation/de-activation process can dynamically follow the number of component
carriers that is required to fulfill the current data rate needs. All but one component
carrier – the downlink Primary component carrier (DL PCC) – can be deactivated at
any given time.
Scheduling of a component carrier is done using the PDCCH or ePDCCH
(extended PDCCH), via downlink assignments. Control information on the PDCCH
or ePDCCH is formatted as a Downlink Control Information (DCI) message. In
Release 8, where a mobile terminal only operates with one downlink and one uplink
component carrier, the association between downlink assignment, uplink grants, and
the corresponding downlink and uplink component carriers is very clear. In Release
10, however, two modes of carrier aggregation need to be distinguished. The first
mode is very similar to the operation of multiple Release 8 mobile terminals, in that a
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downlink assignment or uplink grant contained in a DCI message transmitted on a
component carrier applies either to the downlink component carrier itself or to a
uniquely associated uplink component carrier. (This association may be either via
cell-specific or UE-specific linking.) A second mode of operation augments a DCI
message with a Carrier Indicator Field (CIF). A DCI containing a downlink
assignment with CIF applies to the specific downlink component carrier indicated by
the CIF, while a DCI containing an uplink grant with CIF applies to the indicated
uplink component carrier.
DCI messages for downlink assignments contain, among other things,
resource block assignment, modulation and coding scheme related parameters, and
HARQ redundancy version indicators. In addition to those parameters that relate to
the actual downlink transmission, most DCI formats for downlink assignments also
contain a bit field for Transmit Power Control (TPC) commands. These TPC
commands are used to control the uplink power control behavior of the corresponding
PUCCH that is used to transmit the HARQ feedback.
Transmission of PUCCH in a carrier aggregation scenario (called “CA
PUCCH” hereinafter) creates several issues. In particular, multiple hybrid-ARQ
acknowledgement bits need to be fed back in the event of simultaneous transmission
on multiple component carriers. Furthermore, from the perspective of the UE, both
symmetric and asymmetric uplink/downlink component carrier configurations are
supported. For some configurations, one may consider the possibility to transmit
uplink control information on multiple PUCCH, or on multiple uplink component
carriers. However, this option is likely to result in higher UE power consumption and
a dependency on specific UE capabilities. It may also create implementation issues
due to inter-modulation products, and would lead to generally higher complexity for
implementation and testing.
Therefore, the transmission of PUCCH should have limited dependency on the
uplink/downlink component carrier configuration. Thus, all uplink control information
for a UE is transmitted on a single uplink component carrier, according to the 3GPP
Release 10 specifications. A semi-statically configured and UE-specific uplink
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primary component carrier, which is frequently referred to as the “anchor carrier,” is
exclusively used for PUCCH.
UEs operating in accordance with LTE Release 8 or LTE Release 9 (i.e.,
without carrier aggregation) are configured with only a single downlink component
carrier and uplink component carrier. The time-frequency resource location of the
first Control Channel Element (CCE) used to transmit PDCCH for a particular
downlink assignment determines the dynamic ACK/NACK resource for Release 8
PUCCH. No PUCCH collisions can occur, since all PDCCH for a given subframe are
transmitted using a different first CCE.
In a cell-asymmetric carrier aggregation scenario (or perhaps also for other
reasons), multiple downlink component carriers may be cell-specifically linked to the
same uplink component carrier. Mobile terminals configured with the same uplink
component carrier but with different downlink component carriers (with any of the
downlink component carrier that are cell-specifically linked with the uplink component
carrier) share the same uplink PCC but may have different aggregations of
secondary component carriers, in either the uplink or downlink. In this case, mobile
terminals receiving their downlink assignments from different downlink component
carriers will transmit their HARQ feedback on the same uplink component carrier. It
is up to the scheduling process at the base station (in LTE, the evolved Node B, or
eNB) to ensure that no PUCCH collisions occur.
When a mobile terminal is configured with multiple downlink component
carriers it makes sense to use the Release 8 approach when possible. Each PDCCH
transmitted on the downlink primary component carrier has, according to Release 8
specifications, a PUCCH resource reserved on the uplink primary component carrier.
Thus, when a mobile terminal is configured with multiple downlink component carriers
but receives a downlink assignment for only the downlink primary component carrier,
it should still use the PUCCH resource on the uplink primary component carrier as
specified in Release 8.
An alternative would be to specify the use of a “carrier aggregation PUCCH,”
or “CA PUCCH,” which enables feedback of HARQ bits corresponding to the number
of configured component carriers, for use whenever the mobile terminal is configured
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with multiple downlink carriers, regardless of whether a particular assignment is only
for the downlink primary component carrier. Since configuration is a rather slow
process and a mobile terminal may be configured with multiple component carriers
often – even though only the downlink primary component carrier is active and used
– this would lead to a very inefficient usage of carrier aggregation PUCCH resources.
Upon reception of downlink assignments on a single secondary component
carrier or upon reception of multiple downlink assignments, a special carrier
aggregation PUCCH should be used. While in the latter case it is obvious to use CA
PUCCH – since only CA PUCCH supports feedback of HARQ bits of multiple
component carriers – it is less clear that CA PUCCH should also be used in the first
case. First, a downlink secondary component carrier assignment alone is not typical.
The eNodeB scheduler should strive to schedule a single downlink component carrier
assignment on the downlink primary component carrier and try to de-activate
secondary component carriers if only a single downlink carrier is needed. Another
issue is that the PDCCH for a downlink secondary component carrier assignment is
transmitted on the secondary component carrier (assuming CIF is not configured)
and, hence there is no automatically reserved Rel-8 PUCCH resource on the uplink
primary component carrier. Using the Rel-8 PUCCH even for stand-alone downlink
secondary component carrier assignments would require reserving Rel-8 resources
on the uplink primary component carrier for any downlink component carrier that is
configured for any mobile terminal that uses this uplink primary component carrier.
Since stand-alone secondary component carrier assignments are atypical, this would
lead to an unnecessary over-provisioning of Rel-8 PUCCH resources on uplink
primary component carrier.
It should be noted that a possible error case that may occur with CA PUCCH
arises when the eNodeB schedules a mobile terminal on multiple downlink
component carriers, including the primary component carrier. If the mobile terminal
misses all but the downlink primary component carrier assignment, it will use Rel-8
PUCCH instead of CA PUCCH. To detect this error case the eNodeB has to monitor
both the Rel-8 PUCCH and the CA PUCCH in the event that assignments for multiple
downlink component carriers have been sent.
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The number of HARQ feedback bits that a mobile terminal has to provide
depends on the number of downlink assignments actually received by the mobile
terminal. In a first case, the mobile terminal could adopt a particular CA PUCCH
format according to the number of received assignments and provide feedback
accordingly. However, one or more PDCCHs carrying downlink assignments can
get lost. Adopting a CA PUCCH format according to the number of received
downlink assignments is therefore ambiguous, and would require the testing of many
different hypotheses at the eNodeB.
Alternatively, the PUCCH format could be set by the carrier activation
message. A working group in 3GPP has decided that activation and de-activation of
component carriers is done with Medium Access Control (MAC) layer control element
and that per-component-carrier activation and de-activation is supported. MAC
signaling, and especially the HARQ feedback signaling indicating whether the
activation command has been received successfully, is error prone. Furthermore,
this approach requires testing of multiple hypotheses at the eNodeB.
Accordingly, basing the CA PUCCH format on the number of configured
component carrier seems therefore the safest choice. Configuration of component
carrier is based on Radio Resource Control (RRC) signaling. After successful
reception and application of a new configuration, a confirmation message is sent
back, making RRC signaling very safe.
As noted earlier, feedback of ARQ ACK/NACK information for two or more
component carriers may require the transmission of more than two bits, which is the
most that can be handled by PUCCH Format 1. Accordingly, PUCCH for carrier
aggregation scenarios requires additional techniques or formats. Two approaches
were specified in LTE Release 10 specifications. First, PUCCH Format 1 may be
used in combination with a technique called resource selection or channel selection.
However, this is not an efficient solution for more than four bits. Accordingly, another
format, PUCCH Format 3, has been developed to enable the possibility of
transmitting more than four ACK/NACK bits in an efficient way.
The first of these two approaches is often simply called channel selection.
The basic principle behind this approach is that the UE is assigned a set of up to four
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different PUCCH format 1a/1b resources. The UE then selects one of the resources
according to the ACK/NACK sequence the UE should transmit. Thus, the selection
of a particular one of the resources serves to communicate up to two bits of
information. On one of the assigned resources the UE then transmits a QPSK or
BPSK symbol value, encoding the remaining one or two bits of information. The
eNodeB detects which resource the UE uses as well as the QPSK or BPSK value
transmitted on the used resource and combines this information to decode a HARQ
response for downlink cells associated with the transmitting UE.
The use of channel selection to code ACK (A), NACK (N) and DTX (D) for
multiple component carriers is shown in Figure 7, Figure 8, and Figure 9, which apply
to LTE FDD systems. A similar type of mapping, but including a bundling approach,
is done for TDD in the event that the UE is configured with channel selection.
In Figure 7, two ACK/NACK messages are transmitted and two PUCCH
resources are configured. In each resource, a BPSK modulated symbol can be
transmitted, as shown in the figure, hence in total one out of four different signals can
be transmitted. If PUCCH resource 1 is selected, then one of the BPSK constellation
points indicates an ACK for primary cell codeword 0 (indicated as PCell CW0 in the
figures) and a NACK for secondary cell codeword 0 (Scell CW0), or ACK and DTX
respectively. This is shown as A/N and A/D in Figure 7. The other constellation
point in this PUCCH resource 1 indicates NACK and NACK (or NACK and DTX) for
the primary cell and secondary cell respectively. Thus, a BPSK symbol transmitted in
PUCCH resource 1 indicates either ACK/NACK or ACK/DTX for the primary cell and
secondary cell, respectively, for a first value of the BPSK symbol, and NACK/NACK
or NACK/DTX for the primary cell and secondary cell, respectively, for the other value
of the BPSK symbol. If PUCCH resource 2 is selected for transmission, on the other
hand, then the first value of the BPSK symbol indicate A/A (ACK/ACK) for the primary
and secondary cells, respectively, while the second value indicates N/A (NACK/ACK)
or D/A (DTX/ACK) for the primary and secondary cells.
For example, if the mobile terminal wants to report an ACK for the primary and
a NACK for the secondary cell, then PUCCH resource 1 is selected and the BPSK
constellation point corresponding to A/N is transmitted. Note that since this
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constellation point also indicates A/D, there is no difference from the eNB perspective
whether the mobile terminal reports a NACK or DTX for the transmission on the
secondary cell. In Figure 8 and 9, this principle is extended to 3 and 4 ACK/NACK
bits, respectively. Thus, three PUCCH resources are configured to send 3
ACK/NACK bits, as shown in Figure 8, while four PUCCH resources are configured
to send 4 ACK/NACK bits, as shown in Figure 9. QPSK modulation is used in both
cases; thus a symbol transmitted in a given one of the 3 or four PUCCH resources
can indicate one of up to four different combinations of ACK/NACK bits.
A second approach, which is more efficient when more than four bits of
information need to be transmitted, is called PUCCH Format 3 and is based on
Discrete Fourier Transform (DFT)-spread OFDM. Figure 10 shows a block diagram
of that design, for a single slot. The same processing is applied to the second slot of
the uplink frame. The multiple ACK/NACK bits are encoded, using a forward-error
correction (FEC) code, to form 48 coded bits. The coded bits are then scrambled,
using cell-specific (and possibly DFT-spread OFDM symbol dependent) sequences.
24 bits are transmitted within the first slot and the other 24 bits are transmitted within
the second slot. The 24 bits per slot are then mapped into 12 QPSK symbols, as
indicated by the blocks labeled “QPSK mapping” in Figure 10, which appear in five of
the OFDM symbols of the slot (symbols 0, 2, 3, 4, and 6). The sequence of symbols
in each of these five symbols in the slot is spread with OFDM-symbol-specific
orthogonal cover codes, indicated by OC0, OC1, OC2, OC3, and OC4 in Figure 10,
and cyclically shifted, prior to DFT-precoding. The DFT-precoded symbols are
converted to OFDM symbols (using an Inverse Fast-Fourier Transform, or IFFT) and
transmitted within one resource block (the bandwidth resource) and five DFT-spread
OFDM symbols (the time resource). The spreading sequence or orthogonal cover
code (OC) is UE-specific and enables multiplexing of up to five users within the same
resource blocks.
For the reference signals (RS), cyclic-shifted constant-amplitude zero-
autocorrelation (CAZAC) sequences can be used. For example, the computer
optimized sequences in 3GPP TS 36.211, “Physical Channels and Modulation,” can
be used.
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Even with the several PUCCH formats already standardized by 3GPP,
problems remain. For instance, an LTE mobile terminal operating in TDD mode and
configured with ACK/NACK multiplexing cannot simultaneously report multiple
ACK/NACK bits and a periodic CSI report. If such a collision happens, the
conventional approach is to simply drop the CSI report, and transmit only the
ACK/NACK bits. This behavior is independent of whether the multiple ACK/NACK
bits stem from multiple subframes or multiple aggregated cells.
Periodic CSI reports for multiple cells are handled in Release 10 with time-
shifted reporting times, to minimize collisions among CSI reports. To maintain
roughly the same CSI periodicity per cell, it is obvious that periodic CSI reports are
transmitted more frequently than in Release 8 systems. In each subframe without
PUSCH transmission where periodic CSI and multi-cell ACK/NACK collide, the
periodic CSI are dropped. Since CSI reports are required for link adaptation, reduced
CSI feedback degrades downlink performance. This is in particular a problem for
TDD, where only a minority of the available subframes may be uplink subframes.
In several embodiments of the present invention, these problems are
addressed by introducing a new uplink control channel capability that enables a
mobile terminal to simultaneously report to the radio network multiple packet receipt
status bits, (e.g., ACK/NACK bits) and channel-condition bits (e.g., CSI reports). In
some embodiments, this uplink control channel capability also supports sending
uplink scheduling requests from the UE in addition to transmitting multiple packet
receipt status bits and channel-condition bits. In several embodiments, if the mobile
terminal does not have any channel-condition bits to report in a given subframe, it
may transmit ACK/NACK bits using an uplink control channel transmission mode that
does not allow such simultaneous transmission.
In one non-limiting example embodiment, a situation may arise where the total
number of transmitted packet-receipt status bits and channel-condition bits that can
be reported with satisfactory performance is limited. The combined reporting in this
embodiment is only enabled up to a certain number of packet-receipt status bits. For
example, if the number of packet-receipt status bits to be transmitted is less than or
equal to a predetermined number (i.e., a threshold), then packet-receipt status bits
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and channel-condition bits are reported simultaneously over the uplink control
channel. On the other hand, if the number of packet-receipt status bits to be
transmitted exceeds that number, then the channel-condition bits may be dropped,
i.e., discarded, and only the transmitted packet receipt status bits are transmitted.
In another non-limiting example embodiment, if the mobile terminal applies
partial “bundling” of the packet-receipt status bits, then the number of transmitted
packet-receipt status bits corresponds to the number of bits after bundling. If
channel-condition bits are scheduled for reporting and the number of available
packet-receipt status bits is larger than a predetermined number, then the packet
receipt status-bits are bundled to produce that number of bits or fewer, which are
then transmitted together with the channel-condition bits.
In the discussion that follows, specific details of particular embodiments of the
present invention are set forth for purposes of explanation and not limitation. It will
be appreciated by those skilled in the art that other embodiments may be employed
apart from these specific details. Furthermore, in some instances detailed
descriptions of well-known methods, nodes, interfaces, circuits, and devices are
omitted so as not obscure the description with unnecessary detail. Those skilled in
the art will appreciate that the functions described may be implemented in one or in
several nodes. Some or all of the functions described may be implemented using
hardware circuitry, such as analog and/or discrete logic gates interconnected to
perform a specialized function, ASICs, PLAs, etc. Likewise, some or all of the
functions may be implemented using software programs and data in conjunction with
one or more digital microprocessors or general purpose computers. Where nodes
that communicate using the air interface are described, it will be appreciated that
those nodes also have suitable radio communications circuitry. Moreover, the
technology can additionally be considered to be embodied entirely within any form of
computer-readable memory, including non-transitory embodiments such as solid-
state memory, magnetic disk, or optical disk containing an appropriate set of
computer instructions that would cause a processor to carry out the techniques
described herein.
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Hardware implementations may include or encompass, without limitation,
digital signal processor (DSP) hardware, a reduced instruction set processor,
hardware (e.g., digital or analog) circuitry including but not limited to application
specific integrated circuit(s) (ASIC) and/or field programmable gate array(s)
(FPGA(s)), and (where appropriate) state machines capable of performing such
functions.
In terms of computer implementation, a computer is generally understood to
comprise one or more processors or one or more controllers, and the terms
computer, processor, and controller may be employed interchangeably. When
provided by a computer, processor, or controller, the functions may be provided by a
single dedicated computer or processor or controller, by a single shared computer or
processor or controller, or by a plurality of individual computers or processors or
controllers, some of which may be shared or distributed. Moreover, the term
“processor” or “controller” also refers to other hardware capable of performing such
functions and/or executing software, such as the example hardware recited above.
In the following descriptions of non-limiting examples of the present invention,
a mobile terminal operating according to the LTE specifications for TDD is assumed,
but the described techniques and technology may be applied more generally.
A mobile terminal is configured to report multiple ACK/NACK feedback bits
using an uplink control channel, e.g., PUCCH, and an encoding format that enables
simultaneous transmission of multiple ACK/NACK bits and CSI bits. This
simultaneous transmission of multiple ACK/NACK bits and CSI bits may include
configuration of new PUCCH resources, but not necessarily. One example of a
PUCCH mode that could be used for this transmission is the PUCCH mode
described in a co-pending U.S. patent application, filed on the same date as the
present application and entitled “Simultaneous transmission of AN and CSI using
PUCCH Format 3 resources,” the entire contents of which are incorporated herein by
reference. A mobile terminal feeds back multiple ACK/NACK bits if it has to report
ACK/NACK bits for multiple subframes and/or for multiple cells. Configuration of the
mobile terminal may be performed for example using RRC signaling.
6329952_3.doc
Figure 11 is a process flow diagram that shows example procedures for a
mobile terminal in accordance with a first, non-limiting example embodiment. As
shown at block 1110, the operation of the UE may depend on whether the UE has
been configured, e.g., by RRC signaling, to utilize a PUCCH mode that supports
simultaneous transmission of ACK/NACK bits and CSI. If not, operation proceeds as
illustrated at blocks 1120, 1130, and 1140. The UE first determines whether
ACK/NACK bits and a CSI report are both scheduled for transmission in a given
subframe, as shown at block 1120. In either case, as shown at blocks 1130 and
1140, the ACK/NACK bits are transmitted, using a PUCCH mode that does not
support simultaneous transmission of ACK/NACK bits. If a CSI report is scheduled,
however, this involves dropping, i.e., discarding, the CSI report and transmitting only
the ACK/NACK bits as shown at block 1140.
On the other hand, if the UE is configured to support a PUCCH mode that
supports simultaneous transmission of CSI reports and ACK/NACK bits, the mobile
terminal also determines whether ACK/NACK bits and a CSI report are both
scheduled for transmission in a given subframe, as shown at block 1150, and may
still use a configured PUCCH mode that does not allow simultaneous CSI
transmission, as shown at blocks 1160, if the mobile terminal has no CSI bits to
report. But if a mobile terminal has ACK/NACK bits and CSI bits to report in the
uplink, then the mobile terminal may use a configured PUCCH mode that enables
simultaneous transmission of multiple ACK/NACK bits and CSI bits. This PUCCH
mode may even support a scheduling request transmission in addition to transmitting
multiple ACK/NACK bits and CSI bits.
The process flow illustrated in Figure 11 reflects the fact that it may be
desirable to also take into account a situation where the total number of ACK/NACK
and CSI bits that can be reported with satisfactory performance may be limited. In
that case, combined reporting is enabled only up to a certain number of ACK/NACK
bits. Thus, as shown at block 1170, the UE determines whether the number of
ACK/NACK bits to be transmitted is less than or equal to a threshold value, L. If so,
then ACK/NACK bits and CSI bits are reported simultaneously, using the new
PUCCH mode, as shown at block 1180. If the number of ACK/NACK bits exceeds L,
6329952_3.doc
on the other hand, then the CSI bits may be dropped and the ACK/NACK bits
transmitted, as shown at block 1190, using a configured PUCCH mode that does not
supporting simultaneous CSI transmissions. The number L may be any suitable
integer, but one non-limiting example is L=10. If the UE applies partial bundling, then
the number of ACK/NACK bits to be transmitted and compared to L is the number of
bits after bundling.
A flow chart in accordance with a second non-limiting example embodiment
that includes bundling is shown in Figure 12. Most of the flow chart is identical to that
of Figure 11. However, if multiple ACK/NACK bits and a CSI report are scheduled for
transmission, and if the number of ACK/NACK bits for transmission is greater than L,
then the mobile terminal determines whether ACK/NACK bundling is configured, as
shown at block 1210. If so, then the ACK/NACK bits are bundled to produce L or
fewer bits, as shown at block 1220. These bundled ACK/NACK bits are then
transmitted together with CSI bits. If not, the CSI bits are dropped, and the
ACK/NACK bits transmitted using a PUCCH mode that does not support
simultaneous ACK/NACK and CSI transmission, as shown at block 1230.
Figure 13 is another process flow diagram that illustrates, more generally, a
method for simultaneous reporting of channel-state information and hybrid-ARQ
ACK/NACK information, suitable for implementation by a mobile terminal. Of course,
the illustrated method should be understood within the context of mobile terminal
processing in general, and in the context of forming and transmitting uplink control
channel information, more particularly. The pictured method may be carried out as
part of the processing carried out by a mobile terminal for each uplink subframe, for
example.
As shown at block 1310, the method begins with determining whether
channel-state information and hybrid-ARQ ACK/NACK bits corresponding to a
plurality of downlink subframes or a plurality of downlink carriers, or both, are
scheduled for transmission in a given uplink subframe. If not, then conventional
techniques for transmitting only ACK/NACK bits may be used, as shown at block
1340. On the other hand, if there is a “collision” between a periodic CSI report and
ACK/NACK bits, the method continues with an evaluation of whether the number of
6329952_3.doc
the first hybrid-ARQ ACK/NACK bits is less than or equal to a threshold number, as
shown at block 1320. If not, conventional techniques for transmitting only
ACK/NACK bits may be used, in some embodiments. If there are no more than a
threshold number of ACK/NACK bits to transmit, however, the channel-state
information and the hybrid-ARQ ACK/NACK bits are transmitted, as shown at block
1330, using physical control channel resources of the first uplink subframe.
In some embodiments, where ACK/NACK bundling is employed, the number
of hybrid-ARQ ACK/NACK bits, which is compared to the threshold number,
represents the number of ACK/NACK bits after ACK/NACK bundling. Further, in
some embodiments the threshold number may vary, depending on the number of
channel-state information bits scheduled for transmission. For embodiments where
the threshold number is static, a suitable number might be 10, for example.
Several variants of the technique illustrated in Figure 13 are possible. For
example, as suggested by the flow diagram of Figure 12, if the number of ACK/NACK
bits scheduled for transmission is greater than the threshold, the number of bits may
be reduced to a suitable number, e.g., by employing bundling. The bundled
ACK/NACK bits may then be transmitted along with channel-state information bits,
using a control channel format that supports both.
Any of a number of techniques for encoding the channel-state information and
the hybrid-ARQ ACK/NACK bits can be used. In one embodiment, the hybrid-ARQ
ACK/NACK bits are encoded with a first encoder and the channel-state information
bits are encoded using a second encoder. The encoded and hybrid-ARQ ACK/NACK
bits and the encoded channel-state information bits are interleaved before
transmission. This approach allows the degree of error protection to be allocated
between the hybrid-ARQ ACK/NACK bits and the channel-state information.
Because faulty ACK/NACK data can cause unnecessary re-transmissions, it may be
advantageous to provide more robust error protection to the hybrid-ARQ ACK/NACK
bits, for example.
Figure 14 is a process flow illustrating a corresponding technique for handling
uplink control channel that has been generated and transmitted according to the
methods described above. The method illustrated in Figure 14 might be
6329952_3.doc
implemented in a base station, for example, such as an LTE eNodeB. For a given
subframe the method begins, as shown at block 1410, with the receiving of an uplink
subframe that carries control channel information in one or several physical control
channel resources. As shown at block 1420, the base station determines whether a
number of expected hybrid-ARQ ACK/NACK bits is less than or equal to a threshold
number. If so, the base station decodes both channel-state information and hybrid-
ARQ ACK/NACK bits from each physical control channel resource for which the
number of expected hybrid-ARQ ACK/NACK bits is less than or equal to the
threshold number, as shown at block 1430. Otherwise, the base station uses
conventional techniques to decode only ACK/NACK bits from the physical control
channel resource, as shown at block 1440.
In some cases, the threshold number varies, depending on a number of
expected channel-state information bits. In some embodiments, where ACK/NACK
bundling is used, the decoding of the control channel information yields bundled
hybrid-ARQ ACK/NACK bits, in which case the method further includes unbundling
the bundled hybrid-ARQ ACK/NACK bits. In some systems, it may be the case that
not all mobile terminals are configured for simultaneous reporting of channel-state
information and hybrid-ARQ ACK/NACK information, even where they support the
feature. Accordingly, the process pictured in Figure 11 may be preceded, in some
instances, by a determination that the mobile terminal of interest has been
configured, via Radio Resource Control signaling, for simultaneous reporting
according to the techniques described herein.
The functions in the flowcharts of Figures 11-13 may be implemented using
electronic data processing circuitry provided in the mobile terminal. Likewise, the
functions in the flowchart of Figure 14 may be implemented using electronic data
processing circuitry provided in a base station. Each mobile terminal and base
station, of course, also includes suitable radio circuitry for receiving and transmitting
radio signals formatted in accordance with known formats and protocols, e.g., LTE
formats and protocols.
Figure 15 illustrates features of an example communications node 1500
according to several embodiments of the present invention. Although the detailed
6329952_3.doc
configuration, as well as features such as physical size, power requirements, etc., will
vary, the general characteristics of the elements of communications node 1500 are
common to both a wireless base station and a mobile terminal. Further, both may be
adapted to carry out one or several of the techniques described above for encoding
and transmitting ACK/NACK bits and channel-state information or decoding such
information from a received signal.
Communications node 1500 comprises a transceiver 1520 for communicating
with mobile terminals (in the case of a base station) or with one or more base stations
(in the case of a mobile terminal) as well as a processing circuit 1510 for processing
the signals transmitted and received by the transceiver 1520. Transceiver 1520
includes a transmitter 1525 coupled to one or more transmit antennas 1528 and
receiver 1530 coupled to one or more receive antennas 1533. The same antenna(s)
1528 and 1533 may be used for both transmission and reception. Receiver 1530 and
transmitter 1525 use known radio processing and signal processing components and
techniques, typically according to a particular telecommunications standard such as
the 3GPP standards for LTE and/or LTE-Advanced. Because the various details and
engineering tradeoffs associated with the design and implementation of such circuitry
are well known and are unnecessary to a full understanding of the invention,
additional details are not shown here.
Processing circuit 1510 comprises one or more processors 1540 coupled to
one or more memory devices 1550 that make up a data storage memory 1555 and a
program storage memory 1560. Processor 1540, identified as CPU 1540 in Figure
, may be a microprocessor, microcontroller, or digital signal processor, in some
embodiments. More generally, processing circuit 1510 may comprise a
processor/firmware combination, or specialized digital hardware, or a combination
thereof. Memory 1550 may comprise one or several types of memory such as read-
only memory (ROM), random-access memory, cache memory, flash memory
devices, optical storage devices, etc. Again, because the various details and
engineering tradeoffs associated with the design of baseband processing circuitry for
mobile devices and wireless base stations are well known and are unnecessary to a
full understanding of the invention, additional details are not shown here.
6329952_3.doc
Typical functions of the processing circuit 1510 include modulation and coding
of transmitted signals and the demodulation and decoding of received signals. In
several embodiments of the present invention, processing circuit 1510 is adapted,
using suitable program code stored in program storage memory 1560, for example,
to carry out one of the techniques described above encoding and transmitting
ACK/NACK bits and channel-state information or decoding such information from a
received signal. Of course, it will be appreciated that not all of the steps of these
techniques are necessarily performed in a single microprocessor or even in a single
module.
Figure 16 illustrates several functional elements of a mobile terminal 1600,
adapted to carry out some of the techniques discussed in detail above. Mobile
terminal 1600 includes a processing circuit 1610 configured to receive data from a
base station, via receiver circuit 1615, and to construct a series of uplink subframes
for transmission by transmitter circuit 1620. In several embodiments, processing
circuit 1610, which may be constructed in the manner described for the processing
circuits 1510 of Figure 15, includes a hybrid-ARQ processing unit 1640, which is
adapted to determine that first channel-state information (from channel-state
measurement unit 1650) and first hybrid-ARQ ACK/NACK bits corresponding to a
plurality of downlink subframes or a plurality of downlink carriers, or both, are
scheduled for transmission in a first uplink subframe, and to determine whether the
number of the first hybrid-ARQ ACK/NACK bits is less than or equal to a threshold
number. Processing circuit 1610 further includes a channel state measurement unit
1650, which produces channel-state information (CSI) bits based on observations of
the radio channel, and an uplink control channel encoding unit 1630, which is
adapted to send both the first channel-state information and the first hybrid-ARQ
ACK/NACK bits in physical control channel resources of the first uplink subframe, on
a single carrier, in response to determining that the number of hybrid-ARQ
ACK/NACK bits to be transmitted in the first uplink subframe is less than or equal to
the threshold number. Of course, all of the variants of the techniques described
above are equally applicable to mobile terminal 1600 as well.
6329952_3.doc
Without changes to current 3GPP specifications, collisions between
ACK/NACK transmissions and CSI reports will likely lead to dropped CSI reports.
The novel techniques described herein enable simultaneous transmission of multiple
ACK/NACK bits and CSI. With the use of these techniques, fewer CSI reports are
dropped, which improves link adaptation and increases throughput.
It will be appreciated by the person of skill in the art that various modifications
may be made to the above described embodiments without departing from the scope
of the present invention. For example, it will be readily appreciated that although the
above embodiments are described with reference to parts of a 3GPP network, an
embodiment of the present invention will also be applicable to like networks, such as
a successor of the 3GPP network, having like functional components. Therefore, in
particular, the terms 3GPP and associated or related terms used in the above
description and in the enclosed drawings and any appended claims now or in the
future are to be interpreted accordingly.
Examples of several embodiments of the present invention have been
described in detail above, with reference to the attached illustrations of specific
embodiments. Because it is not possible, of course, to describe every conceivable
combination of components or techniques, those skilled in the art will appreciate that
the present invention can be implemented in other ways than those specifically set
forth herein, without departing from essential characteristics of the invention. The
present embodiments are thus to be considered in all respects as illustrative and not
restrictive.
6329952_3.doc
Claims (28)
1. A method in a mobile terminal for simultaneous reporting of channel-state 5 information and hybrid-ARQ ACK/NACK information in uplink subframes, the method comprising: determining that first channel-state information and first hybrid-ARQ ACK/NACK bits corresponding to a plurality of downlink subframes or a plurality of downlink carriers, or both, are scheduled for transmission in 10 a first uplink subframe; determining whether the number of the first hybrid-ARQ ACK/NACK bits is less than or equal to a threshold number; transmitting both the first channel-state information and the first hybrid-ARQ ACK/NACK bits in physical control channel resources of the first uplink 15 subframe, on a single carrier, in response to determining that the number of hybrid-ARQ ACK/NACK bits to be transmitted in the first uplink subframe is less than or equal to the threshold number; and dropping the first channel state information and transmitting the first hybrid- ARQ ACK/NACK bits in physical control channel resources of the first 20 uplink subframe, on a single carrier, in response to determining that the number of hybrid-ARQ ACK/NACK bits to be transmitted in the first uplink subframe is not less than or equal to the threshold number.
2. The method of claim 1, wherein the number of the first hybrid-ARQ ACK/NACK 25 bits represents a number of ACK/NACK bits after ACK/NACK bundling.
3. The method of claim 1 or 2, wherein the threshold number depends on the number of first channel-state information bits scheduled for transmission in the first uplink subframe. 6329952_3.doc
4. The method of claim 1, further comprising: determining that second channel-state information and a second hybrid-ARQ ACK/NACK bits corresponding to a plurality of downlink carriers are scheduled for transmission in a second uplink subframe; 5 determining whether the number of the second hybrid-ARQ ACK/NACK bits is less than or equal to the threshold number; bundling the second hybrid-ARQ ACK/NACK bits to produce a number of bundled ACK/NACK bits that is less than or equal to the threshold number, in response to determining that the number of hybrid-ARQ 10 ACK/NACK bits to be transmitted in the second uplink subframe is not less than or equal to the threshold number; and transmitting both the second channel-state information and the bundled ACK/NACK bits in physical control channel resources of the second uplink subframe, on a single carrier.
5. The method of any one of claims 1 to 4, wherein the threshold number is 10.
6. The method of any one of claims 1 to 5, wherein the first hybrid-ARQ ACK/NACK bits and the first channel-state information are transmitted using a Physical Uplink 20 Control Channel (PUCCH) format 3 resource in a Long-Term Evolution (LTE) wireless system.
7. The method of any one of claims 1 to 6, further comprising, before transmitting both the first channel-state information and the first hybrid-ARQ ACK/NACK bits: 25 encoding the hybrid-ARQ ACK/NACK bits using a first encoder and separately encoding the channel-state information bits using a second encoder; interleaving the encoded hybrid-ARQ ACK/NACK bits and the encoded channel-state information bits. 6329952_3.doc
8. A method in a base station for processing received reports of channel-state information and hybrid-ARQ ACK/NACK information, the method comprising: receiving a plurality of uplink subframes, each uplink subframe comprising one or more physical control channel resources carrying control channel 5 information encoded by mobile terminals; for each of the physical control channel resources, determining whether a number of expected hybrid-ARQ ACK/NACK bits is less than or equal to a threshold number; decoding both channel-state information and hybrid-ARQ ACK/NACK bits from 10 each physical control channel resource for which the number of expected hybrid-ARQ ACK/NACK bits is less than or equal to the threshold number; and decoding only hybrid-ARQ ACK/NACK bits from each physical control channel resource for which the number of expected hybrid-ARQ ACK/NACK bits 15 is not less than or equal to the threshold number.
9. The method of claim 8, wherein the threshold number depends on a number of expected channel-state information bits. 20
10. The method of claim 8, further comprising: decoding both channel-state information and bundled hybrid-ARQ ACK/NACK bits from each physical control channel resource for which the number of expected hybrid-ARQ ACK/NACK bits is not less than or equal to the threshold number; and 25 unbundling the bundled hybrid-ARQ ACK/NACK bits.
11. The method of any one of claims 8 to 10, wherein the threshold number is 10. 6329952_3.doc
12. The method of any one of claims 8 to 11, wherein decoding both channel-state information and hybrid-ARQ ACK/NACK bits comprises: de-interleaving encoded bits from the physical control channel resource, to obtain encoded hybrid-ARQ ACK/NACK bits and separate encoded 5 channel-state information bits; and decoding the hybrid-ARQ ACK/NACK bits using a first decoder and separately decoding the channel-state information bits using a second decoder.
13. The method of any one of claims 1 to 12, further comprising first determining that 10 the mobile terminal has been configured, via Radio Resource Control signaling, for simultaneous reporting of channel-state information and hybrid-ARQ ACK/NACK information.
14. A mobile terminal configured for simultaneous reporting of channel-state 15 information and hybrid-ARQ ACK/NACK information in uplink subframes, the mobile terminal comprising a receiver circuit, a transmitter circuit, and a processing circuit, wherein the processing circuit is adapted to: determine that first channel-state information and first hybrid-ARQ ACK/NACK bits corresponding to a plurality of downlink subframes or a plurality of 20 downlink carriers, or both, are scheduled for transmission in a first uplink subframe; determine whether the number of the first hybrid-ARQ ACK/NACK bits is less than or equal to a threshold number; send both the first channel-state information and the first hybrid-ARQ 25 ACK/NACK bits to a base station, via the transmitter circuit, in physical control channel resources of the first uplink subframe, on a single carrier, in response to determining that the number of hybrid-ARQ ACK/NACK bits to be transmitted in the first uplink subframe is less than or equal to the threshold number; and 30 drop the first channel state information and send the first hybrid-ARQ ACK/NACK bits to the base station, via the transmitter circuit, in 6329952_3.doc physical control channel resources of the first uplink subframe, on a single carrier, in response to determining that the number of hybrid- ARQ ACK/NACK bits to be transmitted in the first uplink subframe is not less than or equal to the threshold number.
15. The mobile terminal of claim 14, wherein the number of the first hybrid-ARQ ACK/NACK bits represents a number of ACK/NACK bits after ACK/NACK bundling.
16. The mobile terminal of claim 14, wherein the processing circuit is further adapted 10 to: determine that second channel-state information and a second hybrid-ARQ ACK/NACK bits corresponding to a plurality of downlink subframes or a plurality of downlink carriers are scheduled for transmission in a second uplink subframe; 15 determine whether the number of the second hybrid-ARQ ACK/NACK bits is less than or equal to the threshold number; bundle the second hybrid-ARQ ACK/NACK bits to produce a number of bundled ACK/NACK bits that is less than or equal to the threshold number, in response to determining that the number of hybrid-ARQ 20 ACK/NACK bits to be transmitted in the second uplink subframe is not less than or equal to the threshold number; and send both the second channel-state information and the bundled ACK/NACK bits to the base station, via the transmitter, in physical control channel resources of the second uplink subframe, on a single carrier.
17. The mobile terminal of any one of claims 14 to 16, wherein the threshold number is 10.
18. The mobile terminal of any one of claims 14 to 17, wherein the first hybrid-ARQ 30 ACK/NACK bits and the first channel-state information are sent using a Physical 6329952_3.doc Uplink Control Channel (PUCCH) format 3 resource in a Long-Term Evolution (LTE) wireless system.
19. The mobile terminal of any one of claims 14 to 18, wherein the processing circuit 5 is further adapted to, before sending both the first channel-state information and the first hybrid-ARQ ACK/NACK bits to the base station: encode the hybrid-ARQ ACK/NACK bits using a first encoder and separately encoding the channel-state information bits using a second encoder; 10 interleave the encoded hybrid-ARQ ACK/NACK bits and the encoded channel- state information bits.
20. A base station configured to process received reports of channel-state information and hybrid-ARQ ACK/NACK information, the base station comprising a 15 transmitter circuit, a receiver circuit, and a processing circuit, wherein the processing circuit is configured to: receive, via the receiver circuit a plurality of uplink subframes, each uplink subframe comprising one or more physical control channel resources carrying control channel information encoded by mobile terminals; 20 determine, for each of the physical control channel resources, whether a number of expected hybrid-ARQ ACK/NACK bits is less than or equal to a threshold number; decode both channel-state information and hybrid-ARQ ACK/NACK bits from each physical control channel resource for which the number of 25 expected hybrid-ARQ ACK/NACK bits is less than or equal to the threshold number; and decode only hybrid-ARQ ACK/NACK bits from each physical control channel resource for which the number of expected hybrid-ARQ ACK/NACK bits is not less than or equal to the threshold number. 6329952_3.doc
21. The base station of claim 20, wherein the processing circuit is further adapted to: decode both channel-state information and bundled hybrid-ARQ ACK/NACK bits from each physical control channel resource for which the number of expected hybrid-ARQ ACK/NACK bits is not less than or equal to the 5 threshold number; and unbundle the bundled hybrid-ARQ ACK/NACK bits.
22. The base station of any one of claims 20 to 21, wherein the threshold number is
23. The base station of any one of claims 20 to 22, wherein the processing circuit is adapted to decode both channel-state information and hybrid-ARQ ACK/NACK bits de-interleaving encoded bits from the physical control channel resource, to 15 obtain encoded hybrid-ARQ ACK/NACK bits and separate encoded channel-state information bits; and decoding the hybrid-ARQ ACK/NACK bits using a first decoder and separately decoding the channel-state information bits using a second decoder. 20
24. The mobile terminal of claim 14, wherein the processing circuit comprises: an hybrid-ARQ processing unit adapted to determine that the first channel- state information and the first hybrid-ARQ ACK/NACK bits corresponding to the plurality of downlink carriers are scheduled for transmission in the first uplink subframe, and to determine whether the 25 number of the first hybrid-ARQ ACK/NACK bits is less than or equal to the threshold number; and an uplink control channel encoding unit adapted to send both the first channel- state information and the first hybrid-ARQ ACK/NACK bits in physical control channel resources of the first uplink subframe, on a single 30 carrier, in response to determining that the number of hybrid-ARQ ACK/NACK bits to be transmitted in the first uplink subframe is less 6329952_3.doc than or equal to the threshold number; and further adapted to drop the first channel state information and send the first hybrid-ARQ ACK/NACK bits to the base station, via the transmitter circuit, in physical control channel resources of the first uplink subframe, on a 5 single carrier, in response to determining that the number of hybrid- ARQ ACK/NACK bits to be transmitted in the first uplink subframe is not less than or equal to the threshold number.
25. A method in a mobile terminal for simultaneous reporting of channel-state 10 information and hybrid-ARQ ACK/NACK information in uplink subframes, the method being substantially as hereinbefore described with reference to the accompanying drawings.
26. A method in a base station for processing received reports of channel-state 15 information and hybrid-ARQ ACK/NACK information, the method being substantially as hereinbefore described with reference to the accompanying drawings.
27. A mobile terminal configured for simultaneous reporting of channel-state information and hybrid-ARQ ACK/NACK information in uplink subframes, the mobile 20 terminal comprising a receiver circuit, a transmitter circuit, and a processing circuit, the mobile terminal being substantially as hereinbefore described with reference to the accompanying drawings.
28. A base station configured to process received reports of channel-state 25 information and hybrid-ARQ ACK/NACK information, the base station comprising a transmitter circuit, a receiver circuit, and a processing circuit, the base station being substantially as hereinbefore described with reference to the accompanying drawings. 6329952_3.doc
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US201161542503P | 2011-10-03 | 2011-10-03 | |
US61/542,503 | 2011-10-03 | ||
PCT/SE2012/050152 WO2013051983A1 (en) | 2011-10-03 | 2012-02-14 | Simultaneous reporting of ack/nack and channel-state information using pucch format 3 resources |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ623748A NZ623748A (en) | 2016-03-31 |
NZ623748B2 true NZ623748B2 (en) | 2016-07-01 |
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