SARA-R42 - Application note
UBX-20050829 - R02
Network registration
Page 23 of 58
C1-Public
7.2.4
Radio Policy Manager
SARA-R4 series modules implement the Radio Policy Manager (RPM) feature according to GSMA
connection efficiency TS 34
. RPM aims to prevent cellular devices to aggressively try registration
or PDP context activation procedures in case of permanent failures (e.g. “invalid UE” or “EPS services
not allowed”), which are usually due to subscription restrictions, in addition to
standard 3GPP retry
algorithms. Since these aggressive behaviors can cause network overload and service outage, some
MNOs require to have RPM active by default: the RPM feature is enabled only on specific MNO profiles
(for more details, see appendix C of SARA-R4 series AT commands manual
), but they can be
enabled via AT commands on other MNOs requiring it.
7.2.4.1
Management of SW resets
In particular, RPM limits the number of user-initiated module resets per hour following a permanent
attach reject cause; the AT commands which are controlled and can provide an error result code are
the following:
AT
+CFUN=15
,
AT
+CFUN=16
,
AT
+CFUN=19
,
AT
+CFUN=1,1
and
AT
+CFUN=4,1
, and
AT
+CPWROFF
.
Eventually, RPM will again allow these commands and can even autonomously trigger a SW reset:
timers and maximum counters can be derived from the MNO SIM card (so they can be even OTA
updated) or are retrieved from the NVM (at most 1 module reset per hour is usually allowed per GSMA).
RPM counters are cleared after a successful registration.
7.2.4.2
Management of PDP context activations
RPM also limits the maximum number of successful PDP context activations on the same APN (e.g.
for Deutsche Telekom (DT) MNO the limit is 30), the maximum number of PDP context activations
requests per hour following a PDP context activation request ignored by the network (e.g. for DT it is
60), rejected with a “permanent” or a “temporary” reject cause (
e.g. for Deutsche Telekom they are 30
and 60 respectively).
If PDP context activation is blocked by RPM, the
AT+CGACT=1,<cid>
command will fail with an error
result code and the dial-up on a non-active <cid> will not be established.
Since the LTE attach usually implies a PDN connectivity activation, also LTE registration cycles
triggered, for example by
AT+CFUN=0/1
, are subjected to the same limitations (e.g. for Deutsche
Telekom maximum 30 attach/detach cycle per hours are allowed), however once the limit is exceeded
the module will not register to the network for the following hour and no specific error will appear.
7.3
+UMACQOSTMR timer configuration
The
+UMACQOSTMR
AT command allows configuration of a proprietary MAC layer timer that acts as an
additional mechanism that can be enabled to ensure LTE network local RRC release and return to idle
after prolonged RX and TX inactivity of the radio channel. It is referred to being an "additional back-up
mechanism", since the RRC procedure would normally handle the local RRC release. However, if there
is a rare instance that it does not release timely with a network, this mechanism provides added
reliability. An optimal and timely local RRC release is important to ensure the proper handling of any
potential inbound network pages.
For details on the dUMACQOSTMR settings, see the MNO profiles section in the appendix of
the SARA-R4 series AT commands manual
When using network simulators, to perform certain types of measurements there may be a need to
stay in local RRC connected state. See section
for details for guidance to disable the timer in
such situations.
