Triggers to initiate STATUS reporting include:
-
Polling from its peer AM RLC entity:
-
When a RLC data PDU with SN = x and the P field set to “1” is received from lower layer, the receiving side of an AM RLC entity shall:
-
if the PDU is to be discarded as specified in subclause 5.1.3.2.2; or
-
if x < VR(MS) or x >= VR(MR):
-
trigger a STATUS report;
-
else:
-
delay triggering the STATUS report until x < VR(MS) or x >= VR(MR).
NOTE 1:
This ensures that the RLC Status report is transmitted after HARQ reordering.
上面这段话中讲明P字段设为“1”的序列号SN< VR(MS) or SN>= VR(MR)时会触发状态报告，并说这是为了保证HARQ排序后传送状态报告。
小弟不明白的有两点：1、为什么要保证HARQ排序后传送状态报告？2、为什么x < VR(MS) or x >= VR(MR)时会触发状态报告。希望有高手指点。
时间: 2009-10-21 01:00
作者: luciferji
我理解是为了减少多余的RLC PDU重传。当VR(MS) <= X < VR(MR)时，PDU处于有效接受窗口内，这时即便有乱序或丢包也不急着STATUS report（从而触发RLC重传），因为MAC可能正在通过HARQ进行快速重传中。只有当HARQ已经无能为力了（reordering之后），才触发RCL重传。