R1-080947
`
`3GPP TSG RAN WG1 #52 Meeting
`Sorrento, Italy, February 11-15, 2008
`
`
`
`Nokia Siemens Networks, Nokia Corporation
`Source:
`Triggers for Power Headroom Reports in EUTRAN Uplink
`Title:
`Agenda item: 6.3.2
`Document for: Discussion/Decision
`
`1. Introduction
`This contribution is about Power Headroom (PH) reports for EUTRAN uplink. In RAN1 #51bis it was agreed that the
`PH report is transmitted in the same sub-frame that it refers to using L2/L3 signaling. The transmission format of PH
`reports is discussed in [5]. In this contribution we propose some triggering criteria for PH reporting which are based on
`a set of e-Node B configurable parameters. The proposed parameters can support both periodic and event-triggered PH
`reporting (but also a combination of the two).
`
`2. Power Headroom (PH) reports
`Information on the user power spectral density is important in order to perform correct radio resource management
`decisions at the eNode-B especially when allocating the transmission bandwidth and the modulation & coding scheme
`(MCS). Inaccurate knowledge of the power spectral density could e.g. cause the allocation of a too high transmission
`bandwidth (given the maximum UE power capabilities), thus resulting in a low SINR. Therefore information on the UE
`transmission power is conveyed from the UE to the eNode-B using PH reports. Knowing the corresponding PUSCH
`bandwidth the eNode-B can easily extract information on the UE power spectral density from PH reports.
`
`3. PH reports triggering criteria
`The PH is calculated at the UE as:
`
`where PMAX is the maximum UE Tx power and PPUSCH is the PUSCH transmission power in the corresponding TTI set
`according to the standardized power control formula in [1]:
`
`PH = 10⋅log10 (PMAX) - 10⋅log10 (PPUSCH),
`
`PPUSCH = min ( PMAX, 10 log10 M + P0 + α ⋅ PL + ∆MCS + f(∆i))
`
`We suggest the following reporting criteria for PH reports in LTE uplink.
`
`A PH report is triggered:
`
`1. After N closed loop PC corrections have been (correctly) received by the terminal.
`
`2. After the open loop PC component of the PSD is modified at the UE based on an updated path loss measurement;
`alternatively, a power headroom report can be triggered if the difference between the current and the latest path loss
`measurement is higher than a given threshold (X dB).
`
`3.
`
`If the power headroom is smaller than a specified threshold value, e.g. the UE Tx power comes close (<Y dB) to its
`maximum possible value PMAX.
`
`4.
`
`If the time elapsed from last transmission of a power headroom report is > P TTIs (periodic reporting).
`
`However, a PH report is NOT triggered:
`
`Petitioner's Exhibit 1007
`
`

`
`5.
`
`if the time elapsed from the last PH report is < K TTIs (this criteria is introduced to limit the signaling overhead)
`
`Notice that standardizing the proposed criteria would allow the implementation of a wide variety of power headroom
`reporting schemes by appositely tuning the parameters N, X, K, Y and P. Granularity and dynamic range of these
`parameters are FFS.
`
`Proposal: the power headroom reporting scheme proposed in this section is adopted in the EUTRAN standard.
`The parameters M, X, K, Y and P can be configured by the eNode-B using higher layer signaling (RRC).
`
`3. Signaling of PH reports
`In RAN2 several companies have agreed to transmit the power headroom reports using MAC control elements [3]. In
`[3] 1 byte is reserved for the transmission of a PH report. Therefore we propose to use 6 bits for signaling the PH report.
`6 bits are enough for a power control range from -30 dBm to 24 dBm with 1 dB granularity. However, such proposal is
`not meant to put any requirement on the measurement accuracy. Those requirements should be decided by RAN4. In
`case the power measurement accuracy is coarser than 1 dB, it should be considered to use less than 6 bits to signal PH
`reports. The transmission format of PH reports is discussed in [5].
`
`Proposal: a PH report is coded using 6 bits and transmitted using MAC control signaling [3] [5].
`
`4. Conclusions
`In this contribution we have addressed PH reports for EUTRAN uplink. Given the importance of PH headroom reports
`(especially in relation to the allocation of the uplink transmission bandwidth and MCS), we recommend RAN1 to reach
`an agreement on the following points:
`
`• The PH is calculated at the UE as:
`
`PH = 10⋅log10 (PMAX) - 10⋅log10 (PPUSCH),
`
`• where PMAX is the maximum UE Tx power and PPUSCH is the PUSCH transmission power in the corresponding TTI
`set according to the standardized power control formula in [1].
`
`• We propose to include into the EUTRAN standard the reporting rules and parameters described in Section 2.
`Notice that any of the reporting mechanisms can be deactivated by setting the corresponding parameter
`accordingly. The reporting parameters could be transmitted using the RRC protocol.
`
`• Power headroom reports are transmitted in the uplink using MAC control elements, but with the possibility to
`define separate reports for power headroom and buffer status reports [5]. 6 bits are used to transmit a power
`headroom report. Further details on the signaling of PH reports should be discussed in RAN2 [3] [5].
`
`4. References
`[1] R1-073224 - “Way Forward on Power Control of PUSCH” - CATT, Ericsson, et al. - 3GPP TSG RAN WG1,
`meeting #49-bis, Orlando, USA, 25-29 June, 2007.
`[2] R1-073209 - “Way Forward on Uplink Power Control of PUCCH” - CATT, Ericsson et al. - 3GPP TSG RAN
`WG1, meeting #49-bis, Orlando, USA, 25-29 June, 2007.
`[3] R2-074682, “Uplink Scheduling Information in E-UTRAN” - Ericsson, Nokia Corporation, Nokia Siemens
`Networks, NTT DoCoMo, Samsung - 3GPP TSG RAN WG2, meeting #60, Jeju, Korea, 5-9 November, 2007
`March, 2006.
`[4] R1-073209 - “Uplink Power Control for E-UTRA – Comments on Open Issues” - Ericsson - 3GPP TSG RAN
`WG1, meeting #50bis, Shanghai, China, 8-12 October, 2007.
`[5] R2-08xxxx - “LCID for Scheduling Information” – Nokia Corporation, Nokia Siemens Networks - 3GPP TSG
`RAN WG2, meeting #61, Sorrento, Italy, 11-15 February, 2008.
`
`Petitioner's Exhibit 1007