Access Control Class (ACC) ramping is used to slowly make the cell
available to an increasing number of MS. This avoids overload at
startup time in cases where a lot of MS would discover the new
cell and try to connect to it all at once.
Ramping behaviour can be configured with new VTY commands:
[no] access-control-class-ramping
access-control-class-ramping-step-interval (<30-600>|dynamic)
access-control-class-ramping-step-size (<1-10>)
(The minimum and maximum values for these parameters are hard-coded,
but could be changed if they are found to be inadequate.)
The VTY command 'show bts' has been extended to display the
current ACC ramping configuration.
By default, ACC ramping is disabled.
When enabled, the default behaviour is to enable one ACC per
ramping step with a 'dynamic' step interval. This means the
ramping interval (time between steps) is scaled to the channel
load average of the BTS, i.e. the number of used vs. available
channels measured over a certain amount of time.
Below is an example of debug log output with ACC ramping enabled,
while many 'mobile' programs are concurrently trying to connect
to the network via an osmo-bts-virtual BTS. Initially, all ACCs
are barred, and then only one class is allowed. Then the current
BTS channel load average is consulted for scheduling the next
ramping step. While the channel load average is low, ramping
proceeds faster, and while it is is high, ramping proceeds slower:
(bts=0) ACC RAMP: barring Access Control Class 0
(bts=0) ACC RAMP: barring Access Control Class 1
(bts=0) ACC RAMP: barring Access Control Class 2
(bts=0) ACC RAMP: barring Access Control Class 3
(bts=0) ACC RAMP: barring Access Control Class 4
(bts=0) ACC RAMP: barring Access Control Class 5
(bts=0) ACC RAMP: barring Access Control Class 6
(bts=0) ACC RAMP: barring Access Control Class 7
(bts=0) ACC RAMP: barring Access Control Class 8
(bts=0) ACC RAMP: barring Access Control Class 9
(bts=0) ACC RAMP: allowing Access Control Class 0
(bts=0) ACC RAMP: step interval set to 30 seconds based on 0% channel load average
(bts=0) ACC RAMP: allowing Access Control Class 1
(bts=0) ACC RAMP: step interval set to 354 seconds based on 59% channel load average
(bts=0) ACC RAMP: allowing Access Control Class 2
(bts=0) ACC RAMP: step interval set to 30 seconds based on 0% channel load average
(bts=0) ACC RAMP: allowing Access Control Class 3
(bts=0) ACC RAMP: step interval set to 30 seconds based on 0% channel load average
Change-Id: I0a5ac3a08f992f326435944f17e0a9171911afb0
Related: OS#2591
Handover decision 2 will also store the last seen mr nr for neighbor cell
measurements and hence can tell whether a neighbor's measurement is outdated.
Change-Id: Ic1148364597f91b5a55666c80c758b61fa56f582
For unconnected BTS, the channel load would report a "bogus channel load
sample" every second (on RLL debug). Instead, skip unusable BTS.
This follows up on commit 6cee893a0f /
I57e38f6d6ba3b23cc6e1f9520b90261dbb1f1cec
'Make "waiting indicator" of IMMEDIATE ASSIGN REJECT dynamic.'
Change-Id: I627fe10e1f5c1f2f23745c906320871024b5c8c3
In addition to logging the current values of a BTS's channel load
average and T3122 override, maintain stat items for these values.
This allows for plotting these values over time, for instance.
These values show up in the VTY under 'show stats' like this:
base transceiver station:
Channel load average.: 25 %
T3122 IMMEDIATE ASSIGNMENT REJECT wait indicator.: 32 s
Change-Id: Icace0176e8b1d23d7c7b4816f7c67c65312844fa
Suggested-by: laforge
The IMMEDIATE ASSIGN REJECT message contains a wait indicator which
tells an MS requesting a channel to wait for a specified amount of
time before trying to request a channel again, i.e. the wait indicator
controls the T3122 timeout value in the MS.
Previously, the wait indicator was fixed to 10 seconds.
This is not sufficient if there are a lot of MS requesting channels
because the MS will retry too soon. Instead of using a fixed value,
maintain a dynamic wait indicator value based on average channel load.
The load (used vs. available channels on a BTS) is sampled once per
second, and once 8 samples have been collected we update a BTS-specific
T3122 wait indicator based on the measured load.
While the wait indicator could go up to 255 seconds, this initial
implementation keeps it in the range from 10 to 128 seconds.
Further experimentation and testing will show whether higher wait
indicator values are desirable, if the sampling rate needs to change,
or if the function mapping the load measurement to a wait indicator
value should change (currently we map the load average linearly into
the range [10, 128] inclusive).
Change-Id: I57e38f6d6ba3b23cc6e1f9520b90261dbb1f1cec
Related: OS#2592
This is needed for handover algorithm to balance free slots and to prevent
congestion of one cell, while other cells still have free capacities.
Change-Id: Ic8bee8a515ee8aa9a99af71756fe60b8dd8f868b
get_meas_rep_avg will return -EINVAL, if the required number of
measurements are not reached. There will be no handover possible until the
given number of measurements are available.
Change-Id: Ibc4410b4e162cdb6c070128d2c63946bb79d6d65
There still is a lot of dead code that we inherited from the NITB
days, let's remove more of it.
libtrau will be re-introduced as part of osmo-mgw later.
Change-Id: I8e0af56a158f25a4f1384d667c03eb20e72df5b8
* change return type to bool
* constify parameters
The nm_is_running(), trx_is_usable() and ts_is_usable() always return
boolean value and are always used as such anyway. The also do not change
their parameters.
Change-Id: I6a572fc78371c69f5308edbad0ebe15e143d0505
Previously we've used function so debug print always pointed to the same
place which is not very useful. Wrap it with macro so proper
file:line is printed. Also, make sure that we always change state only
through this wrapper and log only when the state has changed.
Change-Id: I21789f8021290965b61a54a2b23177ccbbfe8321
This is the first step in creating this repository from the legacy openbsc.git.
Like all other Osmocom repositories, keep the autoconf and automake files in
the repository root. openbsc.git has been the sole exception, which ends now.
Change-Id: I9c6f2a448d9cb1cc088cf1cf6918b69d7e69b4e7
Stefan Sperling
Harald Welte