diff options
| author | Neels Hofmeyr <neels@hofmeyr.de> | 2021-01-09 18:25:36 +0100 |
|---|---|---|
| committer | neels <nhofmeyr@sysmocom.de> | 2021-01-14 06:24:57 +0000 |
| commit | 8e830dd136877a65ed294bee3693a1b2463c059f (patch) | |
| tree | f5fd1101f4ed7548f73084e3972e640a627854ef /doc/manuals | |
| parent | 55a015dddf7fa1467b2b9b9def0174990a514490 (diff) | |
hodec2: to balance congestion, use overload percent
For balancing load across congested cells and across congested TCH/*
kinds, instead of comparing the number of lchans above the configured
congestion threshold, compare the percent of lchans of overload.
In short, using a percentage prevents cells with less min-free-slots to
fill up 100% while neighbor cells still may have several free lchans
available.
An obvious example of why this is desirable is illustrated by
test_balance_congestion_by_percentage.ho_vty:
Cell A has min-free-slots 2, and has all slots occupied.
Cell B has min-free-slots 4, and has 2 slots remaining free.
If we count congested lchans as in current master: cell A has a
congestion count of 2: two more lchans in use than "allowed". If we move
one lchan over to cell B, it ends up with a congestion count of 3, which
is worse than 2. So when counting lchans, we decide that cell A should
remain full.
Instead, when comparing percentage of remaining lchans, we would see
that cell A is loaded 100% above congestion (2 of 2 remaining lchans in
use), but when moving one lchan to cell B, that would only be 75% loaded
above its treshold (3 of 4 remaining lchans in use). So a percentage
comparison would cause a handover to cell B.
Related: SYS#5259
Change-Id: I55234c6c99eb02ceee52be0d7388bea14304930f
Diffstat (limited to 'doc/manuals')
| -rw-r--r-- | doc/manuals/chapters/handover.adoc | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/doc/manuals/chapters/handover.adoc b/doc/manuals/chapters/handover.adoc index 4de744b9e..56e9aea46 100644 --- a/doc/manuals/chapters/handover.adoc +++ b/doc/manuals/chapters/handover.adoc @@ -511,9 +511,11 @@ periodical congestion check attempts to distribute MS to less loaded neighbor cells. Every time, the one MS that will suffer the least RXLEV loss while still reducing congestion will be instructed to move first. -If a cell and its neighbors are all loaded past their `min-free-slots` -settings, the algorithmic aim is equal load: a load-based handover will never -cause the target cell to be more congested than the source cell. +If a cell and its neighbors are all loaded past their `min-free-slots` settings, +the algorithmic aim is to improve the percentage of load above the +`min-free-slots` setting: a load-based handover always requires the target cell +to have a lower load percentage after handover than the source cell had before +handover. The min-free-slots setting is a tradeoff between immediate voice service availability and optimal reception levels. A sane choice could be: |