Project Number:
Wireless World Initiative New Radio – WINNER+
Project Title:
Document Type:
I (Internal)
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Document Title:
Questions for clarification to 3GPP
Source Activity:
WP3
Editor:
Johan Nyström
Authors:
Johan Nyström
Status / Issue:
Draft / 0.1
Date Last changes:
06.03.16
File:
Template for WINNER+ documents.doc
Abstract:
Keywords:
Document History:
20.05.2008
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Table of Contents
1.
Introduction ............................................................................................ 3
2.
Handover ................................................................................................ 3
2.1
2.2
2.3
Winner+ observations ............................................................................................................. 3
Winner+ analysis .................................................................................................................... 3
Questions for clarifications to 3GPP ....................................................................................... 4
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1. Introduction
The Winner+ evaluation group is in the process of evaluation the 3GPP proposal ITU-R WP5D document
IMT-ADV/8 (technically identical to Japan contribution described in IMT-ADV/6 and TDD part identical
to proposal in IMT-ADV/9 by China).
In the process, in order to understand the proposal we have a few questions for clarification to 3GPP.
Winner+ has the understanding that the latency budget Table for handover latency is exemplified by the
FDD RIT although it is not explicitly stated.
Our calculations for the TDD RIT suggest small increments in delay due to the inherent slot structure in
TDD compared to what is shown in the self-evaluation.
Compared to the overall latencies, the margin to the IMT-Advanced requirements and the fact that other
latency components are based on estimations of implementation dependent factors like processing time
could be potentially be substantially improved (at a cost), the overall impact seem to be negligible.
However, for the sake of correctness and in order to help Winner+ understanding the proposal (and
possible assist other Evaluation Groups as well) we have some questions for clarification and kindly
request feedback from 3GPP.
2. Handover
2.1 Winner+ observations
The handover procedure is described in TR 36.912 (submitted by proponent) in section 16.5.
Table 16.5-1 describes the components in the latency budget. The component 2 is called
“Average delay due to RACH scheduling period (1ms periodicity)”.
The 1 ms periodicity characteristic seems to indicate that the Table 16.5-1 exemplifies a latency budget
for the FDD RIT but not the TDD RIT. For FDD RIT, each UL slot (of 1 ms) can be configured for a
RACH opportunity, hence there is at most a 1 ms wait for such RACH scheduling, or on the average 0.5
ms assuming uniform start of waiting time in that slot. Thus, the values in the Table seem appropriate for
the FDD RIT.
Due to the time slot structure of TDD RIT it seems that the average must be slightly larger, since for TDD
RIT not all slots can be allocated for UL.
2.2 Winner+ analysis
The TDD RIT slot structure can be configured according to Figure 1 below, with 2 DL slots, 2 SP slots
and 6 UL slots per 10 ms frame according to the pattern: <DL,SP,UL,UL,UL,DL,SP,UL,UL,UL>.
We assume that RACH can be scheduled in each UL slot, but not in the DL or SP slots. Hence the waiting
time for the next RACH opportunity depends in which slot the waiting is initiated.
At most, a 3 ms wait is necessary. This happens when it is initiated just in the beginning of the last UL
slot. If the wait is instead initiated just at the very end of the same slot the wait is just 2 ms. On the
average for this slot, the waiting time value is 2.5 ms.
With a similar reasoning for each slot, and then averaging over the 10 equally probable slots, the overall
average waiting time can be calculated to 1.1 ms.
Figure 1 indicates with dotted arrows, the average waiting time given waiting initiation in a certain slot.
These conditional average waiting times are 0.5, 1.5 or 2,5 ms depending on which slot we condition
upon.
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TDD
DL
SP
UL
UL
UL
DL
SP
UL
UL
UL
On average 2/10 * 2.5 + 2/10*1.5 + 6/10*0.5 = 1.1 ms
Figure 1: TDD slot structure and waiting times.
Thus, assuming the same values for the other components in the latency table, the average latency would
increase by 0.6 ms to 11.1 ms.
2.3 Questions for clarifications to 3GPP
Q1: Is the Winner+ assumption that the Table exemplifies the latency budget for the FDD RIT and not the
TDD RIT correct?
Q2: Is the Winner+ reasoning and analysis for the TDD RIT example correct?
Q3: Are there any changes in calculation for the other components in the Table 16.5-1 for the TDD RIT
example?
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