10 Iub/Iur aspects
25.2023GPP7.68 Mcps Time Division Duplex (TDD) optionOverall description: Stage 2Release 17TS
10.1 Impacts on Iub/Iur interfaces – general aspects
10.1.1 Timing advance and Rx Timing Deviation
The timing advance algorithm (in RRM, at the RNC) uses Rx Timing Deviation measurements made by the Node B and passed to the RNC in frame protocols. At 3.84 Mcps the resolution is 4 chips. The timing advance determined by RRM is signalled to the UE (RRC).
In addition, the Node B can be configured to take more accurate Rx Timing Deviation measurements of a UE, which are sent to the RNC as dedicated measurements. At 3.84 Mcps the resolution of these is 0.0625 chips. These accurate measurements can be used in location (they are passed to the location system using the PCAP protocol).
Strategy for 7.68 Mcps :
Timing advance & Rx Timing Deviation over FP
> 4 chip resolution
> same dynamic range as 3.84 Mcps (in secs)
Rx Timing Deviation, dedicated measurement
> 0.0625 chip resolution giving greater measurement accuracy
> same dynamic range as 3.84 Mcps (in secs)
10.1.2 Paging
For the 7.68Mcps option, the maximum number of paging indicators per paging block should be doubled to accommodate the greater number of users that may be supported by the 10 MHz carrier. To achieve this:
• the number of PICH blocks per paging block (NPICH) is extended from {2,4} to {2,4,8}
• the number of PCH blocks per paging block (NPCH) is extended from {1..8} to {1..16}.
Consequently, a unique value range for the PI-bitmap needs to be defined for 7.68 Mcps.
10.1.3 DSCH Power Control from the RNC
In 3.84 Mcps TDD, the PDSCH may be power controlled from the RNC by sending a transmit power level value in the DSCH DATA FRAME that carries DSCH transport blocks to the Node B. For 7.68 Mcps, the same method can be used and this has been agreed by RAN1. Since the transmit power level is expressed relative to the maximum transmit power, no changes are needed to accommodate 7.68Mcps.
10.2 Impacts on Iub/Iur control plane protocols
There are a number of changes to RNSAP, PCAP & NBAP protocols to incorporate:
– Use of SF 32: The signalling is extended to include support for SF32. The 7.68 Mcps cell will be configured to use SF 16 or 32 for PRACH and E-RUCCH rather than SF 8 and 16 as 3.84 Mcps
– Burst Types and Midambles: Signalling related to burst types is modified since burst type 2 at 7.68Mcps supports Kcell of 4 or 8.
– Number of physical channels: the SF32 change implies an increase in the number of physical channels that may be supported.
– Measurements: changes are introduced for Rx Timing Deviation and SFN-SFN measurements.
– Cell Synchronisation: this procedure is not supported.
10.3 Impacts on Iub/Iur user plane protocols
Specifications 25.425, 25.427 and 25.435 are modified to include 7.68Mcps operation in a similar fashion to 3.84 Mcps. Changes are also needed to accommodate the different rx timing deviation and timing advance signalling for 7.68Mcps compared to 3.84Mcps (see Section 10.1 above). The paging indicator bit-map is also revised (see Section 10.1 above).