`
`3GPP TSG RAN WG1 Meeting #50bis
`Shanghai, China, October 8-12, 2007
`
`Source:
`Title:
`Agenda Item:
`Document for:
`
`
`Panasonic
`Ack/Nack repetition and Implicit Resource Allocation for PUCCH
`6.2.4 Uplink Control Channel
`Discussion and Decision
`
`R1-074408
`
`Introduction
`1.
`The ACK/NACK signal over PUCCH is code-spread by 12-length CAZAC sequence in one SC-FDMA symbol,
`and then block-wise spreading is applied. At the Kobe meeting, the following baseline of implicit ACK/NACK
`resource allocation was agreed.
`“For non-persistent scheduling the ACK/NACK resource is linked to the index of the control channel used for
`scheduling.”
`In [1], we proposed to clarify that “index of control channel” is “index of control channel elements”.
`[2] shows without the repetition of ACK/NACK, the achievable cell radius is up to 1.2-1.8 km when the
`penetration loss of 20 dB and the required BER of 10-4 are assumed under the various ACK/NACK load and
`propagation channel model conditions. Therefore, we think the repetition of ACK/NACK is necessary. One of
`design for a repeated uplink ACK/NACK channel for PUCCH was discussed in [3]. In this design, to allow the
`coexistence of the different UEs with different repetition factors, each subframe has its own repetition factor. In
`other words, the DL data for the UEs which require uplink ACK/NACK repetition shall be sent in the subframe
`where uplink ACK/NACK repetition is allowed. Hence, there is a restriction that the scheduler shall take into
`account the repetition factor of each UE when it allocates DL data into the subframes.
`In this contribution, we propose the implicit mapping methodologies which achieve
`a) less restriction for the scheduler when allocating DL data and
`b) the reduced usage of the ACK/NACK resources for repetition.
`2.
`Implicit resource allocation with uplink ACK/NACK repetition
`The uplink ACK/NACK repetition is required to only UEs who have difficult condition like cell edge. Given that
`the CCE aggregation sizes of DL grants for such UEs would be large in order to obtain low coding rate of
`PDCCH, the required resources for repeated ACK/NACK per subframe are much less than those of non-repeated
`ACK/NACK.
`For example, we think following would be reasonable assumption;
`- For the UE whose uplink Ack/Nack repetition factor is 2, the DL grant is sent by 4 or more CCE aggregation.
`- For the UE whose uplink Ack/Nack repetition factor is 3, the DL grant is sent by 8 CCE aggregation.
`The maximum required dynamic uplink ACK/NACK signals per subframe is equal to the maximum number of
`CCEs per subframe(k). Therefore, k resources shall be reserved for 1st ACK/NACK transmission per subframe.
`However, the maximum numbers of the dynamic ACK/NACK signals which require the 2nd and 3rd ACK/NACK
`repetition per subframe are k/4 and k/8 or less, respectively. This property can utilize to reduce the number of
`reserved ACK/NACK resources.
`Figure 1 shows an example of the implicit resource mapping table which supports uplink ACK/NACK
`repetitions. As shown in this figure, the ACK/NACK resources for 1st transmission, 2nd transmission and 3rd
`transmission are separately prepared. The reserved ACK/NACK resources for 2nd and 3rd transmissions are much
`less than those for 1st transmission.
`In the following, the 1st ACK/NACK is transmitted x subframes after receiving PDCCH and PDSCH in non-
`repetition case. Followings are the operations of each UE with different repetition factors.
`1)
`If the repetition factor is “1”, the uplink ACK/NACK signal is not repeated. The UE sends the ACK/NACK
`signal using the resource, within the “1st transmission” group of PUCCHs at x subframes later, linked to the
`index of CCE which carries DL grant.
`If the repetition factor is “2”, the uplink ACK/NACK signal is repeated two times. The UE sends the 1st
`ACK/NACK signal using the resource within the “1st transmission” group of PUCCHs at x subframes later,
`
`2)
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`Samsung Exhibit 1016, Page 1
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`

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`linked to e.g. the first index of CCEs which carry the DL grant. At the next subframe, the UE sends the 2nd
`ACK/NACK signal using the resource within the “2nd transmission” group, linked to e.g. the smallest “4*n”
`index of CCEs which carry the DL grant. For example, if the DL grant is sent by CCE#1 to CCE#4, the 1st
`ACK/NACK is transmitted via the resource linked to CCE#1 within the “1st transmission” group of
`PUCCHs at x subframes later. The 2nd ACK/NACK is transmitted via the resource linked to CCE#4 within
`the “2nd transmission” group of PUCCHs at x+1 subframes later.
`If the repetition factor is “3”, the uplink ACK/NACK signal is repeated three times. The UE sends the 1st
`ACK/NACK signal using the resource within the “1st transmission” group of PUCCHs at x subframes later,
`linked to e.g. the first index of CCEs which carry the DL grant. The next subframe, the UE sends the 2nd
`ACK/NACK signal using the resource, within the “2nd transmission” group of PUCCHs, linked to e.g. the
`smallest “4*n” index of CCEs which carry the DL grant. (“n” is the integer value) At x+2 subframes later,
`the UE will send the 3rd ACK/NACK signal using the resource, within the “3rd transmission” group of
`PUCCHs, linked to the indices of CCEs which carry the DL grant. For instance, if the DL grant is sent by
`CCE#4 to CCE#11, the 1st ACK/NACK will be transmitted via the resource linked to CCE#4 within the “1st
`transmission” group of PUCCHs at x subframes later. Then the 2nd ACK/NACK will be transmitted via the
`resource linked to CCE#4 within the “2nd transmission” group of PUCCHs at x+1 subframes later and the
`3rd ACK/NACK will be transmitted via the resource linked to CCE#8 within the “3rd transmission” group of
`PUCCHs at x+2 subframes later.
`
`
`
`Orthogonal Cover
`
`index (0 to 2)
`
`Orthogonal Cover
`
`index (0 to 2)
`
`
`
`3)
`
`
`
`Figure 1 Implicit resource allocation with ACK/NACK repetition
`
`
`The merit of having such a rule is to allow the less restriction for the scheduler of eNB and to reduce the number
`of reserved ACK/NACK resources for repetitions. There is no restriction on the subframe where repetition is
`transmitted. The restriction for scheduler is “not to allocate the DL grants/data for the same cell edge UEs which
`require the uplink ACK/NACK repetitions in the consecutive subframes to avoid multiple ACK/NACK
`transmission from the same UE in the same subframe”.
`
`3. Conclusion
`In this contribution, we propose to allow the repetitions of uplink ACK/NACK signals for the robustness and the
`repetition factors for non-persistently scheduled UEs shall be linked to the CCE aggregation sizes of PDCCHs
`used for the DL grants.
`The resources for repetitions of uplink ACK/NACK is separately prepared like in Figure 1 in order to simplify
`the scheduler and to reduce the required resources for the repetitions. The relation with CCE aggregation should
`be taken into account.
`
`References
`[1] R1-074410, Panasonic, “Clarification of Implicit Resource Allocation of Uplink ACK/NACK Signal”
`[2] R1-070101, NTT DoCoMo, et al, “Repetition of ACK/NACK in E-UTRA Uplink”
`[3] R1-073261, Qualcomm Europe, “Support of ACK Repetition for E-UTRA Uplink”
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`Samsung Exhibit 1016, Page 2
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