3GPP TSG RAN WG1 Meeting #61bis
`Dresden, Germany
`28 June – 2 July, 2010
`
`Source:
`Ericsson, ST-Ericsson
`Title:
`PUCCH Design for CA
`Agenda Item:
`6.2.4.1
`Document for:
`Discussion and decision
`
`
`
`R1-103506
`
`1 Introduction
`At RAN WG1 #61 meeting it has been decided to conclude on the PUCCH design for carrier aggregation
`[1]. In this contribution we present our view on the PUCCH design. In addition to isolated HARQ
`feedback transmission we also present our view how to transmit HARQ feedback together with scheduling
`request and also consider the case of PUCCH being transmitted in subframes configured for sounding
`reference signals.
`
`2 Discussion
`2.1 PUCCH Transmission
`2.1.1 Carrier Aggregation HARQ Feedback Transmission Scheme
`We propose to use the transmission scheme presented in [2] and shown in Figure 1 for the transmission of
`HARQ feedback bits due to carrier aggregation. The multiple HARQ feedback bits are encoded by the
`(32, O) RM code with circular buffer rate matching [5] into 48 coded bits, where O=n with spatial
`bundling and O=2n without spatial bundling. The number n denotes the number of configured component
`carriers. It is worthwhile to mention that this is encoder is already used in Rel-8/9. The coded bits are
`scrambled with cell-specific and possible DFTS-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 are
`converted into 12 QPSK symbols, DFT precoded, spread across five DFTS-OFDM symbols and
`transmitted within one resource blocks (bandwidth) and five DFTS-OFDM symbols (time). The spreading
`sequence is UE specific and enables multiplexing of up to five users within the same resource blocks. The
`used spreading sequences are DFT sequences of length five. Frequency hopping is applied at slot
`boundaries to achieve frequency diversity.
`For the reference signals cyclic shifted CAZAC sequences, e.g. the computer optimized sequences in [7]
`can be used.
`Proposal 1: Carrier aggregation PUCCH is based on DFTS-OFDM transmission.
`In [6] we present simulation results of the proposed transmission scheme and compare it even with other
`currently discussed proposals.
`
`Ericsson Exhibit 1019
`Page 1
`ERICSSON v. ETRI
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`ACK/NACKACK/NACK
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`FECFEC
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`Scrambl.Scrambl.
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`Bit  SymBit  SymBit  Sym
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`Bit  SymBit  SymBit  Sym
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`Bit  SymBit  SymBit  Sym
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`Bit  SymBit  SymBit  Sym
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`Bit  SymBit  SymBit  Sym
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`oc0oc0oc0oc0
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`DFTDFTDFT
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`oc1oc1oc1oc1
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`oc2oc2oc2oc2
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`RSRSRS
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`oc4oc4oc4oc4
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`DFTDFTDFT
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`RSRSRS
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`Symb. 6
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`Symb. 5
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`Symb. 4
`Symb. 4
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`Symb. 3
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`Symb. 2
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`Symb. 1
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`Symb. 0
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`Figure 1: Block diagram to feed back HARQ feedback bits due to carrier aggregation. In the first slot
`(shown here) the first 24 coded bits are transmitted, in the second slot (not shown) the remaining 24 coded
`bits.
`
`If a terminal – even if configured with multiple component carriers – only receives a DL assignment for
`the PCC the terminal should transmit the HARQ feedback using Rel-8/9 PUCCH. Since a PCC
`assignment is scheduled with PDCCH on the DL PCC there will be according to Rel-8/9 rules a
`corresponding PUCCH resource reserved on the UL PCC.
`If only an assignment for a single SCC is received no such resource is reserved on the UL PCC. HARQ
`feedback should therefore be transmitted using the carrier aggregation PUCCH. Typically a terminal is not
`scheduled only on an SCC since in this case the scheduler would preferable schedule a terminal on the
`PCC and de-activated not used SCC.
`HARQ feedback for assignments received on multiple component carriers is fed back using the proposed
`DFTS-OFDM structure.
`Proposal 2: Independent of the number of configured and activated DL component carriers a
`terminal uses Rel-8/9 PUCCH format and resources if it only receives a DL PCC assignment.
`Proposal 3: Carrier aggregation PUCCH is used to feed back HARQ feedback from an assignment
`received on a single SCC. Carrier aggregation PUCCH is used to feed back HARQ feedback from
`assignments received on multiple component carriers.
`2.1.2 Carrier Aggregation HARQ Feedback Transmission together with
`Scheduling Request
`Transmission of HARQ feedback due to carrier aggregation together with scheduling request on the
`carrier aggregation PUCCH is achieved by joint coding of HARQ feedback bits and the scheduling
`request bit. If the HARQ feedback is already 10 bits this increases the payload to 11 bits. However, the
`RM code from [5] already supports payload sizes up to 11 bits. Contribution [6] shows simulation results
`of this joint HARQ feedback and scheduling request transmission scheme.
`
`Ericsson Exhibit 1019
`Page 2
`ERICSSON v. ETRI
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`

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`Proposal 4: HARQ feedback due to carrier aggregation and scheduling request are jointly encoded
`and transmitted using carrier aggregation PUCCH.
`Scheduling request together with Rel-8/9 PUCCH ACK/NACK (the terminal only received a PCC
`assignment) is transmitted according to Rel-8/9 rules.
`2.1.3 Carrier Aggregation HARQ Feedback Transmission in same
`Subframe as SRS
`In subframes that are configured for SRS transmissions the last OFDM symbol needs to be punctured.
`This needs even to be done by terminals that do not transmit SRS in such a subframe to avoid collisions
`with SRS transmissions from other terminals.
`This can be easily achieved by the proposed carrier aggregation PUCCH with minor modifications, see
`Figure 2. Nothing changes for the first slot (i.e. Figure 1 is still valid) but in the second slot the last DFTS-
`OFDM symbol is punctured.
`The multiplexing capacity is reduced from five to four users since the orthogonal cover applied to the
`second slot is only four elements long. DFT sequences of length four are used as orthogonal cover
`sequences.
`Simulation results are presented in [6].
`Proposal 5: HARQ feedback due to carrier aggregation transmitted in subframes configured for
`SRS uses DFTS-OFDM where the last DFTS-OFDM symbol in the second slot is punctured.
`An ACK/NACK transmission on the Rel-8/9 PUCCH (the terminal only received a PCC assignment) is
`done according to Rel-8/9 rules.
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`ACK/NACK
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`FEC
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`Scrambl.
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`Bit  SymBit  Sym
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`Bit  SymBit  Sym
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`Bit  SymBit  Sym
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`Bit  SymBit  Sym
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`oc0oc0oc0
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`oc1oc1oc1
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`oc2oc2oc2
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`0
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`Symb. 6
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`RSRS
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`IFFTIFFT
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`Symb. 5
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`DFTDFT
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`IFFTIFFT
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`Symb. 4
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`Symb. 3
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`Symb. 2
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`RSRS
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`Symb. 1
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`DFTDFT
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`Symb. 0
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`Figure 2: Block diagram of the transmission scheme to be used in subframes that are configured for SRS
`transmissions. Above figure shows the block diagram for the second slot.
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`
`Ericsson Exhibit 1019
`Page 3
`ERICSSON v. ETRI
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`

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`2.1.4 Carrier Aggregation HARQ Feedback Transmission together with
`Scheduling Request in same Subframe as SRS
`The same transmission scheme outlined in Section 2.1.3 is also used here. As described in Section 2.1.2
`HARQ feedback information and scheduling request are jointly encoded. A numerical analysis of the
`proposed scheme is presented in [6].
`Proposal 6: HARQ feedback due to carrier aggregation transmitted in subframes configured for
`SRS uses DFTS-OFDM where the last DFTS-OFDM symbol in the second slot is punctured. HARQ
`feedback bits and scheduling request are jointly encoded.
`2.1.5 Carrier Aggregation HARQ Feedback Transmission together with CQI
`Already in Rel-8/9 a terminal can be configured to drop the periodic CQI report if its transmission
`instance coincides with an ACK/NACK transmission on PUCCH. We propose that a Rel-10 terminal
`always drops the periodic CQI report if the report should be sent on carrier aggregation PUCCH together
`with carrier aggregation HARQ feedback bits.
`Proposal 7: Simultaneous transmission of periodic CQI report and HARQ feedback bits due to
`carrier aggregation is not supported; in such cases the periodic CQI report is dropped.
`If a terminal uses Rel-8/9 PUCCH for its HARQ feedback transmission (the terminal only received a PCC
`assignment) the multiplexing of CQI and HARQ feedback is done according to Rel-8/9 rules.
`2.2 PUCCH Resources
`Depending on the number of actually received DL assignments the terminal has to provide the
`corresponding number of HARQ feedback bits. In a first case the terminal could adopt the carrier
`aggregation PUCCH format and resources according to the number of received assignments and provide
`feedback accordingly. However, PDCCH with DL assignments may be missed. Adopting carrier
`aggregation PUCCH format and resources according to received DL assignments is therefore ambiguous
`and would require testing of many different hypotheses at eNB. Due to a mismatch of resources that are
`used by the terminal and expected by the eNB even PUCCH collisions may occur if the same PUCCH
`resources are (correctly) used by another terminal.
`Alternatively the PUCCH format and resources could be set/included in the activation message. RAN2
`decided that activation/de-activation is done with MAC control elements and per-CC activation/de-
`activation is supported [3]. MAC signalling together with the HARQ feedback signalling indicating if the
`activation command has been received successfully is error prone and also this approach has the same
`drawbacks as mentioned above.
`Basing the carrier aggregation PUCCH format on the number of configured CCs seems therefore the
`safest choice. Configuration of component carriers is based on RRC signalling and therefore reliable.
`Drawback of RRC signalling is the relatively slow speed and the carrier aggregation PUCCH format
`cannot track the number of actually scheduled component carriers.
`The carrier aggregation PUCCH format is designed to provide two HARQ feedback bits per configured
`component carrier if spatial bundling is not applied and one HARQ feedback bit if spatial bundling is
`applied. Not needed HARQ feedback bits (e.g. not scheduled/received assignments for component
`carriers) are set to NACK. The drawback of this proposal seems at a first glance that unnecessarily many
`bits are transmitted if not all configured component carriers are actually scheduled. However, we show in
`[4] that eNB receiver can compensate for this loss if it utilizes scheduling knowledge during carrier
`aggregation PUCCH decoding.
`Proposal 8: The Carrier Aggregation PUCCH resources and format are semi-statically configured.
`
`Ericsson Exhibit 1019
`Page 4
`ERICSSON v. ETRI
`
`

`

`
`
`3 Conclusion
`In this contribution we presented our view on the transmission scheme for carrier aggregation PUCCH.
`PUCCH transmission schemes for
` Carrier aggregation HARQ feedback bits
` Carrier aggregation HARQ feedback bits together with scheduling request
` Carrier aggregation HARQ feedback bits in subframes configured for SRS, and
` Carrier aggregation HARQ feedback bits together with scheduling request in subframes
`configured for SRS
`are presented. We make the following recommendations:
`Proposal 1: Carrier aggregation PUCCH is based on DFTS-OFDM transmission.
`Proposal 2: Independent of the number of configured and activated DL component carriers a
`terminal uses Rel-8/9 PUCCH format and resources if it only receives a DL PCC assignment.
`Proposal 3: Carrier aggregation PUCCH is used to feed back HARQ feedback from an assignment
`received on a single SCC. Carrier aggregation PUCCH is used to feed back HARQ feedback from
`assignments received on multiple component carriers.
`Proposal 4: HARQ feedback due to carrier aggregation and scheduling request are jointly encoded
`and transmitted using carrier aggregation PUCCH.
`Proposal 5: HARQ feedback due to carrier aggregation transmitted in subframes configured for
`SRS uses DFTS-OFDM where the last DFTS-OFDM symbol in the second slot is punctured.
`Proposal 6: HARQ feedback due to carrier aggregation transmitted in subframes configured for
`SRS uses DFTS-OFDM where the last DFTS-OFDM symbol in the second slot is punctured. HARQ
`feedback bits and scheduling request are jointly encoded.
`Proposal 7: Simultaneous transmission of periodic CQI report and HARQ feedback bits due to
`carrier aggregation is not supported; in such cases the periodic CQI report is dropped.
`Proposal 8: The Carrier Aggregation PUCCH resources and format are semi-statically configured.
`
`References
`[1] Chairman notes 3GPP TSG RAN WG1 #61
`[2] R1-102611, “PUCCH Design for Carrier Aggregation”, Ericsson, ST-Ericsson
`[3] Chairman notes 3GPP TSG RAN WG2 #69
`[4] R1-103508, “On ACK/NACK codebook performance for carrier aggregation” , Ericsson, ST-Ericsson
`[5] 3GPP TS 36.212, “Multiplexing and channel coding”
`[6] R1-103507, “Evaluation of PUCCH proposals for carrier aggregation”, Ericsson, ST-Ericsson
`[7] 3GPP TS 36.211, “Physical channels and modulation”
`
`
`Ericsson Exhibit 1019
`Page 5
`ERICSSON v. ETRI
`
`