u-blox SARA-R5 Series Application Development User Guide

All other values are to be interpreted as multiples of 1 minute.

Encoding of timer T3324
Bits 5 to 1 represent the binary coded timer value. Bits 6 to 8 define the timer value unit for the GPRS timer as follows:

• All other values are to be interpreted as multiples of 1 minute.

Example: “00000100” = 4 x 2 s = 8 s

Deep sleep state in out of service
The deep-sleep mode can be entered even in prolonged out-of-service conditions, provided that the host application has selected this optimization via the parameter of the +URATCONF AT command. In particular, after unsuccessful PLMN searches performed for seconds, the deep- sleep mode is entered for seconds, whose duration can be automatically increased at every cycle if configured with .

Example of usage of PSM

Persistent settings

other than +UPSV: 0 are required to enable the entrance into PSM deep-sleep mode.
AT&W| OK| Save +UPSV setting to the default profile, loaded at switch on.
AT+CEDRXS=0| OK| Disable eDRX.
AT+UPSMR=1| OK| Enable the +UUPSMR diagnostic URC.
AT+CSCON=1| OK| Enable +CSCON diagnostic URC.
AT+CPSMS=1,,,”10100010″

,”00000011″

| OK| Enable PSM with 6 s for T3324 and 120 s for T3412 (such small values can be used only for testing purposes!)
AT+CFUN=16| OK| [optional] If +UMNOPROF setting has been modified, a SW reset shall be triggered.

Volatile settings

negotiated PSM timer values. If issued in full functionality, the current status shall be queried via the +CEREG read command.
AT+CFUN=1| OK| [optional] If +CFUN: 0, turn on the modem, auto-cops feature will trigger registration. We assume PIN check is disabled when using PSM.

PSM in normal mode

,,”00100010″,”10111110″

| After successful LTE attach, location information is returned, together with the PSM timer values assigned by the NW (120 s for T3324, 1800 s for T3412 in the present case).
AT+CEREG?| +CEREG: 4,1,”1″,”0″,”1″,

7,,,”00100010″,”10111110 ”

OK

| Same information will be returned by querying the +CEREG AT command.
AT+UCPSMS?| +UCPSMS: 1,,,”00100010″,

“10111110”,1

| The NW assigned PSM timer values are returned also by the proprietary command +UCPSMS, whose last parameter indicates if the extended T3412 duration has been granted (1) or not (0), regardless of the timer effective duration.
 | +CSCON: 0| At expiry of inactivity time on the network side, the RRC connection is released by the eNodeB. Timer T3324 is set.
 | +UUPSMR: 1| T3324 elapses and the device can enter PSM deep-sleep mode.
AT| OK| If the UART interface is stimulated just after the URC is issued, the entrance in PSM deep-sleep mode will be postponed by +UPSV timeout. No temporal threshold can be provided, because the delay of saving information to NVM done at entrance in PSM depends on many factors. It is therefore assumed that the host application will use the AT interface on purpose to prevent the module from entering PSM.
Command| Response| Description
---|---|---
 | +UUPSMR: 0| At T3412 expiry (usually with 2 s tolerance) the module will exit PSM.
 | +CSCON: 1| At T3412 expiry, TAU is performed.
 | +CSCON: 0| At expiry of inactivity time on the NW side, the RRC connection is released by the eNodeB. Timer T3324 is set.
 | +UUPSMR: 1| T3324 elapses and the device can enter PSM deep-sleep.
 | +UUPSMR: 0| At early wakeup, the module will exit PSM.
ATD*99***1#| CONNECT| At exit from PSM, PPP mode shall be locally restored. IP address will be the same assigned during attach, and uplink data can be sent to the NW without the need to re-register.

eDRX
SARA-R5 series modules support the 3GPP Release 13 feature Extended Discontinuous Reception (eDRX). This feature allows power consumption reduction thanks to extended no-reception intervals (up to 2621.44 s in LTE Cat. M1 RAT) that separate shorter periods (called PTW – paging time windows, up to 20.48 s in LTE Cat. M1 RAT) in which the module can be paged by the eNodeB.

eDRX is often used standalone, as an alternative to PSM for applications that need more responsiveness from the module but still need to keep power consumption limited and can afford delaying the mobile terminated traffic for the eDRX cycle duration. In this case TAU keepalive procedures occur with the default periodicity of approximately 1 hour. eDRX can be also used in combination with PSM to avoid frequent TAU procedures. In this case, paging reception in the paging windows operates while the T3324 timer is running and therefore it is advisable to negotiate a T3324 timer duration longer than the eDRX cycle, otherwise eDRX will never be effective and reception of mobile terminated data or signaling will be postponed to the exit from PSM (see Figure 4).

The application can set the eDRX with +CEDRXS AT command and read the network assigned eDRX value using the +CEDRXRDP AT command.

• Enabling of eDRX might cause the delayed elapsing of internal module timers, whose timeout will be rounded to the next useful eDRX cycle.

Figure 4: paging reception in PTW with both PSM and eDRX enabled

• The following eDRX deep-sleep mode description applies to SARA-R5 “x1B” product versions.

Depending on the power saving settings (+UPSV), the SARA-R5 series modules can enter eDRX deep-sleep mode, where the module runs at negligeable current (for definitions and power consumption characterization, see the SARA-R5 series system integration manual [3]).

eDRX deep-sleep is the default enabled mode, but it can be disabled (unlike PSM deep-sleep) via the power saving mode version command, +UPSMVER (bit 3 of +UPSMVER to 0); if disabled, previously described eDRX mode is applied.
Like for the PSM deep-sleep case, if the module enters the eDRX deep-sleep mode, it will locally deactivate MUX and PPP and will not be responsive to AT commands; it will either wake up autonomously at next PTW time, or through an early wake-up triggered by the host application via the PWR_ON pin. The exit from eDRX deep-sleep mode is like a power-on, with the major difference that no LTE attach will be performed, and the previously activated EPS bearers and IP addresses will be locally restored: the module will reselect a cell of the PLMN that was registered and trigger data transmission or wait for paging in case of early wake-up or wake-up at eDRX cycle duration timeout respectively.
Enabling of PIN check is deprecated when using eDRX deep-sleep, because it will prevent the module from restoring the cellular connectivity until PIN is re-entered by the host application.

At eDRX deep-sleep mode entrance, any timer used in the module will be discarded (e.g. application timers). As an exception to this, the following throttling timers are saved and restored with the remaining value at deep- sleep exit: T3402, sever network failure (SNF, Verizon specific), T3346, T3396, and T3245 (if is configured in USIM). In addition to that, T3412 and T3324 timers are also stored and restored with the remaining value over deep- sleep cycle. Also, APN RATE CONTROL TIMER and T3448, if CIOT is enabled.

If the power saving mode is not active (i.e., if +UPSV: 0 and +CPSMS: 1) the module will not enter eDRX deep-sleep mode, but a standard eDRX state, whose power consumption is like +CFUN: 0 condition and the module is responsive on the AT interface. In this configuration the module will not be reachable either by mobile-terminated data and it will not receive any SMS.

Functional diagram of eDRX and PSM
For sake of clarity, Figure 5 illustrates the state transitions and the device activities during module operation with both PSM and eDRX active. Some configurable parameters are highlighted, among them the DRX cycle (2.56 s), the eDRX cycle (1024 s), T3324 and T3412 timers:

1. The device is in PSM deep-sleep mode; it has already registered at startup, negotiated PSM timers, and is now inactive, not responsive to AT commands, nor paging messages.
2. The device exits PSM at early wake-up triggered by the host application or by T3412 timeout.
3. The device re-connects to the network and sends and receives data or control packets.
4. The RRC connection is released by the network e.g., at the end of the TAU. The device enters the idle state and starts T3324 timer.
5. While T3324 timer is running, paging happens as per network configuration.
6. The device enters PSM after T3324 has elapsed. Operations continue as per point 1.

If after point 2. the device does not enter RRC connected state, the device will eventually re-enter PSM state as if it had not awakened from it after 6 s (fixed timer, per design).

• Starting with SARA-R5 “x1B” product versions, it is possible to have eDRX deep-sleep mode and PSM deep-sleep mode case together, if the eDRX deep-sleep is enabled. The UE is able to exercise deep-sleep due to eDRX when PSM is enabled and timers are aligned to support it.

PSM aware applications
Some embedded clients and features can alter the PSM timings; this holds in particular for LwM2M and security clients, which will temporarily postpone entrance into PSM deep-sleep mode until their sessions have been concluded. For more details on u-blox LwM2M objects and AT commands, see the LwM2M application note [9]. IP based applications (e.g., MQTT, USOCK, UDNS, UFTP, HTTP) instead have no control on PSM, and might be negatively impacted by entrance in PSM state if the host application is waiting for an answer from the network, which is delayed beyond the T3324 timer duration. If the AT commands are asynchronous, like +UMQTTC, the host application can enter AT commands until the final result code is received via URC. If the AT command is blocking, the UART interface can be polled on another virtual port or PSM can be temporary disabled via +CPSMS AT command.

Usage of UDP sockets instead of TCP ones can reduce the transactions duration and is more effective with respect to power consumption.

• Starting with SARA-R5 “x1B” product versions, the same applies also to the eDRX case, if the eDRX deep-sleep mode is enabled; it is possible to talk about eDRX-aware applications, by analogy.

Consider that in Coverage Enhancement mode the network may release the RRC connection later to accommodate the many retransmissions related to the CE mode currently selected by the UE. This can explain why PSM is sometimes entered with delay and can be confirmed by +CEINFO AT command.

Configuration of UE behavior for early wake-up from deepsleep mode

• This section applies to SARA-R5 “x1B” product versions only.

Early wake-up from deep-sleep mode (via PWR_ON pin) should be used when the HOST application needs to interact with the UE before the periodic interaction with the network (TAU for PSM, paging for eDRX). Two scenarios to be considered:

1. Interaction with UE with need to interact with SIM or protocol stack, and eventually with the network.
2. Interaction with UE without need to interact with SIM or protocol stack.

The UE can be configured to fit the two scenarios (in a power consumption perspective) via the power saving mode version AT command (+UPSMVER). In the former case, the required +UPSMVER configuration is with bit 4 set to 0; this is the default one (+UPSMVER: 8). At early wake-up from deep-sleep, if the device does not make any network interaction for the subsequent 6 s, it will re-enter the deep-sleep mode (if nothing else blocks the re-entering).

The SIM is fully accessible during the awake time, and there is no limitation on AT commands. If instead +UPSMVER configuration is with bit 4 set to 1, the SIM is not accessible, and protocol stack is kept in retention mode. This configuration is useful in case the interaction with the UE is limited to the application side (modem services are not requested); for instance, this includes:

• GNSS usage
• File system access
• GPIOs control

To be noticed that in this configuration every AT command requiring SIM status will return the “ERROR” final result code (since SIM status is not available); this is also the case for any AT command requiring protocol stack. In case interaction with SIM is required, the AT+CFUN=126 shall be issued, before. After AT+CFUN=16, the UE behavior is like the +UPSMVER: 8 configuration, that is deep-sleep mode is automatically re-entered after 6 s, if network is not required.

As soon as the engagement with the UE is completed (limited to the application services), and in case SIM or protocol stack access is not required (hence AT+CFUN=126 not issued), the UE can be put in deep-sleep mode again by means of +USLEEP AT command (if remaining TAU (or paging time) is enough). In this scenario, autonomous wake-up for serving next TAU (or paging) is guaranteed, unless the HOST triggers another early-wake-up via PWR_ON pin before, again.

UICC suspend resume

• Starting with SARA-R5 “01B” product versions, the UICC suspend/resume feature is supported, for both PSM and eDRX.
• It is used to store the internal status of the UICC so that the power supply to the UICC can be switched off, and to subsequently restore the UICC status. This mechanism allows, in a new card session, restoration of certain states saved at the suspension of a previous card session. The final goal is to save power consumption.
• It is implemented according to 3GPP TS 31.102 [13].
• The UICC SUSPEND and RESUME APDUs are defined in ETSI TS 102.221 [14].
• For PSM, if supported by the UICC, UICC suspend is performed during PSM entering phase, regardless of the +UPSV configuration (it is triggered even if deep-sleep mode cannot be entered).
• For eDRX, if supported by the UICC, UICC SUSPEND is only executed if eDRX deep-sleep mode is enabled (+UPSMVER bit 3 to 1), eDRX cycle time is higher than threshold (327.68 s), and +UPSV: 1 mode is set.
• The only difference between the PSM and eDRX procedures is an additional check for eDRX bit, read from EF AD (see 3GPP TS 31.102 [13]).
• When the UICC receives the SUSPEND command, it stores the complete UICC status to a non-volatile memory. The UICC status includes all data that are required to resume later the UICC in the exact same condition, so that it is equivalent as if the power supply was never removed.
• The UICC SUSPEND command also provides the minimum and maximum suspend time. The module uses the same minimum and maximum suspend time, calculated according to the remaining PSM or eDRX cycle time (in order to be ready for next TAU or paging).
• Upon reception of the response indicating the successful execution of the SUSPEND UICC command, the terminal deactivates the UICC.
• The UICC resume is performed during the PSM or eDRX leaving procedure; UICC RESUME APDU is the first sent, after UICC re-activation.

1. ☞ The UICC Suspend/Resume mechanism allows entering PSM or eDRX even if the PIN is enabled.
2. ☞ If UICC Suspend fails, the UICC deactivation is then executed (UICC Resume is clearly not performed at PSM or eDRX leaving, but a full USIM re-initialization is done, instead)
3. ☞ UICC Resume is performed without re-initializing the USIM application and without performing verification of the SIM; this saves energy (SIM verification is done using a token provided in the response to the UICC SUSPEND APDU).
4. ☞ If eDRX deep-sleep mode is enabled and only blocked by a deep-sleep client (like GNSS), the execution of UICC Suspend provides some power saving in comparison to the “legacy” eDRX thanks to the UICC deactivation (UICC power is removed).
5. ☞ The execution of UICC Suspend command might take a significant amount of time (depending on the UICC). To be noticed that there is not a way to disable the UICC SUSPEND command, if the UICC supports it.

Example of usage of eDRX

Persistent settings

other than +UPSV: 0 are required to enable the entrance into PSM deep-sleep mode.
AT&W| OK| Save +UPSV setting to the default profile, loaded at switch on.
AT+CPSMS=0| OK| Disable PSM.
AT+UPSMR=1| OK| Enable the +UUPSMR diagnostic URC.
AT+CSCON=1| OK| Enable +CSCON diagnostic URC.
AT+CEDRXRDP| +CEDRXRDP: 0,””,””,”” OK| Verify that eDRX is disabled.
AT+CEDRXS=1,4,”1010″| OK| Enable eDRX with access technology E-UTRAN (WB-S1 mode) and with an eDRX cycle length of 327.68 seconds.
AT+CFUN=16| OK| [optional] If +UMNOPROF setting has been modified, a SW reset shall be triggered.

Volatile settings

feature will trigger registration.

eDRX in normal mode

0″,”0001″

| The network assigned eDRX timer values are returned via the

+CEDRXRDP AT command. The same URC is also returned in case the parameter of +CEDRXS AT command is set to 2. ssigned paging time window is “0001” (2.5 s in LTE Cat M1 RAT).

 | +CSCON: 0| At expiry of inactivity time on the network side, the RRC connection is released by the eNodeB; eDRX cycle starts with the paging window.
 | +UUPSMR: 1| At paging time window completion, device can enter eDRX deep- sleep mode (SARA-R5 “01B” product versions modules only).
AT| OK| If the UART interface is stimulated just after the URC is issued, the entrance in eDRX deep-sleep mode will be postponed by +UPSV timeout. No temporal threshold can be provided, because the delay of saving information to NVM done at entrance in eDRX depends on many factors. It is therefore assumed that the host application will use the AT interface on purpose to prevent the module from entering eDRX deep-sleep mode.
 | +UUPSMR: 0| Before eDRX cycle length expiry the module will boot-up (if deep-sleep mode was entered), and it will be ready to receive the programmed paging event. The URC notifies that the protocol stack is reactivated, and the module is ready to handle the reception of paging.
 | +UUPSMR: 1| At paging time window completion, the device can re-enter the eDRX deep-sleep mode, if nothing is preventing it.
 | +UUPSMR: 0| In case of early wake-up from deep-sleep mode, the module will re-activate the protocol stack, without forcing any network operation.
ATD*99***1#| CONNECT| At exit from eDRX deep-sleep mode, PPP mode shall be locally restored. IP address will be the same assigned during attach, and uplink data can be sent to the network without the need to re-register.

Release Assistance Indication (RAI)

This section is not applicable to ‘00B’ product version.

The module can enter low power mode states like DRX, eDRX and PSM only in idle mode. Once the RRC connection has been established, only the network can release it: the module cannot force an RRC connection release other than detaching using e.g., AT+CFUN=0 command. If there is no transmission for the duration of the so called “inactivity timer”, the base station will send an RRC Connection Release message to the module. The inactivity timer can range from 5 s to 10, 20 or even 60 s depending on the current RAT and the coverage extension level/mode.

First introduced in 3GPP Release 13 for Non Access Stratum (NAS) for data over the Control Plane (CP) and Release14 for Access Stratum (AS) over the User Plane (UP), the Release Assistance feature allows the module to request the network to release the RRC connection as soon as it receives the RAI flag. SARA-R5 supports the two modes for the Release Assistance feature: Access Stratum (AS) RAI, that can be relied on when data is sent over the User Plane (e.g. in Cat M1), and Non Access Stratum (NAS) RAI, that can be used when data is sent over the Control Plane (e.g. in NB-IoT). Support of AS RAI by the eNB is optional, while NAS RAI is basically part of the 3GPP protocol when using the Control Plane.

The user can send data either over the UP or over the CP, depending on the current RAT and optionally on the +CCIOTOPT configuration:

• If data is sent over the UP, only the AS RAI can be set when the uplink buffers (BO – Buffer Occupancy) have been emptied and will be reset after first usage.
• If data is sent over the CP, both the NAS and the AS RAI flags can be used and then reset after first usage.

SARA-R5 series supports usage of the RAI flag with the following AT commands:

• +USOSTF: sends UDP data (both over the UP and the CP) with flags.
• +UCOAPC: CoAP Non-CONF messages (can exploit NAS RAI only).
• +CSODCP: Non-IP Data when Non-IP PDP type has been activated.
• +UDCONF=89: allows setting at runtime the RAI flag for once shot or permanently. In case of AS RAI, the trigger of the RAI flag with this AT command is immediately effective as soon as BO reaches 0; in case of NAS RAI, it shall be followed by an IP packet including the flag, which can be sent by the host application (depending on setting it is the last packet or the last but one packet of the data session) or by a proprietary command (e.g. +UTGSINK or + USOSTF).

For SARA-R5 “01B” product version and previous ones there is no URC or AT command to know if the network supports RAI feature. The application can monitor +CSCON URCs and in case the RAI feature is supported by network, it should expect to get +CSCON: 0 URC soon after the last packet is sent (or the next-to-last one).

Example of usage of RAI

Data session with internal sockets

connection state.
AT+UPSDA=0,3| OK

+UUPSDA: 0,”10.18.88.94″

| Activate an internal data context.
AT+USOCR=17| +USOCR: 0 OK| Create an UDP socket.
AT+USOST=0,”18.196.19.141″,7,5,”

H2j3j”

| +USOST: 0,5 OK| Send data to an echo server.
---|---|---
 | +CSCON: 1| The module is in connected status.
 | +UUSORD: 0,5| Data received from echo server.
AT+UDCONF=89,1| OK| Enable one shot RAI flag; the UE will immediately send AS RAI by setting buffer status report (BSR) to 0 when buffer occupancy (BO) reaches 0 bytes.
AT+USOST=0,”18.196.19.141″,7,5,”

22j3j”

| +USOST: 0,5 OK| In NB-IoT (check in the +COPS information text response to the read command) this triggers an uplink packet to convey NAS RAI flag.
 | +CSCON: 1| The module is in connected status.
 | +CSCON: 0| The module goes immediately in idle status (RRC connection has been released).

This is the consequence of setting the RAI flag.

 | +CSCON: 1| The module is in connected status.
 | +UUSORD: 0,5| Data received from echo server.
 | +CSCON: 0| The module goes in idle status as per network timer (RRC connection has been released).
AT+UDCONF=89,2| OK| Enable one shot RAI flag; (CP CIoT only) NAS RAI flag 2 will be sent in the next NAS packet containing IP or non-IP data, indicating that the following packet will be the last but-one in the data session and that a downlink packet is expected.
AT+USOST=0,”18.196.19.141″,7,5,”

72j3j”

| +USOST: 0,5 OK|
 | +CSCON: 1| The module is in connected status.
 | +UUSORD: 0,5| Data received from echo server.
 | +CSCON: 0| The module goes immediately in idle status (RRC connection has been released).

This is the consequence of setting the RAI flag.

Data session with dialup (i.e. single UART with multiplexer)
In the following example one AT interface is reserved for dial-up (PPP) and another AT interface is used to issue AT commands and monitor URCs.

nable C C  diagnostic  C to better follow the module’s

connection state.

 |  | Application is sending UDP packets on PPP.
AT+UDCONF=89,1| OK| Enable one shot RAI flag.
 |  | Application sends last UDP packet.
+CSCON: 0|  | The +CSCON URC is received immediately and RRC connection is released.

CE Mode A and B

• CE (Coverage Enhancement) Mode A and B is a standard 3GPP feature, introduced starting from R.13, as specified in 3GPP TS 36.211, 3GPP TS 36.213 and 3GPP TS 36.331.
• The Coverage Enhancement determines the number of times downlink and uplink messages can be repeated to reach devices in poor coverage and the number of repetitions is predefined by the network.
• The main difference between the two modes is that Mode A allows only moderate coverage enhancement whereas Mode B supports very deep coverage. CE Mode A is a mandatory feature for Cat.M1, while Mode B is an optional feature.
• From application point of view, this is a tradeoff for deep coverage (up to 20dB) with more power consumption in case of large repetitions configured.
• The main reason for disabling CE Mode B would be for saving power; in addition to the increased number of repetitions used for DL or if the UL link was poorer, there could also be a lot more time spent searching for weaker cells in poor coverage areas, this might result in the module trying to attach to much weaker cells.
• Be aware that CE Mode B feature must be supported at network level too.
• In AT commands manual [2], in the Appendix related to MNO profiles, it is possible to retrieve the information for each MNO profile if the CE Mode B is enabled or disabled by default for each RAT.

Example of use of CE Mode B
Reading and setting CE Mode B

(1) or disabled (0): the third parameter reports the info.
AT+UDCONF=91,7,1| OK| Enable CE mode B feature (the change is immediately effective and stored in NVM).
AT+UDCONF=91,7,0| OK| Disable CE mode B feature.
AT+CFUN=1| OK| Set the module in full mode.

Monitoring module status

Retrieve and interpret diagnostic information

• It is recommended to track the module status in the host application. Such diagnostic information allows to detect specific scenarios and implement proper handling and countermeasures in the host application.
• The module status can be returned by AT command responses and unsolicited result codes (URCs). Depending on the host application architecture, URCs, periodic polling, or both, can be used. URCs provide the most updated information and, in some cases, diagnostic information which is not available via polling. For AT commands that enable URCs, they might also return the same information when polled, as indicated below.
• Some commands store the setting of the URC reporting in NVM, so they are referred to as persistent settings.
• Some AT commands provide a choice on how to handle the URCs when the AT interface is busy; for all other AT commands, URC is issued at the return into command mode, as explained in SARA-R5 series AT command manual [2], in the “URCs presentation deferring” section.
• URCs and AT command responses are presented with their generic syntax because parameters names are quite explanatory; for precise meaning see the SARA-R5 series AT command manual [2].

Diagnostic information via URCs

TStatus>][,,]]]

| Enable registration status URC for non- EPS services (e.g. SMS) and reject cause in case of unavailability of such services.| Yes
AT+CEREG=5| +CEREG: [,[],[],[<Ac

T>][,[],[

][,[,[]]]]]

| Enable registration status URC for EPS services, reject cause in case of unavailability of such services and PSM related timers if granted by the NW.| Yes
AT+UCELLINFO=2,| +UCELLINFO: ,,,