Page 219 - From GMS to LTE

Universal Mobile Telecommunications System (UMTS) and High-Speed Packet Access (HSPA) 205

power‐consuming state for 1.5 minutes per hour in addition to the time it takes to com-
municate with the server, usually a few seconds per attempt. Further, typical networks
have a Cell‐FACH timer of 10–30 seconds. If the lower value is used for this example,
the mobile device will be in this state for an additional minute per hour. Together, the
mobile device will be in a heightened power‐consumption state for around 2.5 minutes
per hour. Over the course of a day, the total time amounts to a full hour, and as a conse-
quence this uses a significant part of a battery charge. Longer timeout values generate
an even less favorable result.
To reduce the power requirements of always‐on applications on mobile devices, a
number of solutions exist. In the past, some device manufacturers used proprietary
mechanisms to deactivate the air interface connection without waiting for the network
to take action when applications communicated only periodically with the network and
exchanged only a little data. As such proprietary functionality was not strictly in con-
formance with the standards, it was decided to properly standardize such ‘Fast
Dormancy’ functionality in 3GPP Release 8 [25]. The standardized feature enables
mobile devices to send a Signaling Connection Release Indication (SCRI) Request mes-
sage containing a new ‘Fast Dormancy’ value as release reason to the network to take
down the physical air interface connection to the network without waiting for the Cell‐
DCH and FACH timers to expire. The network can then set the mobile device into
Cell‐PCH or URA‐PCH state. As the feature is optional on the network side, the T323
parameter was added in the System Information Broadcast 1 (SIB1) message. If T323 is
present, the mobile knows that it can use the new mechanism. In practice, it can be
observed today that the new Release 8 Fast Dormancy feature was quickly adopted by
many network operators and significantly contributes to reducing the power consump-
tion of smartphones with many connected applications.

3.14 Automated Emergency Calls (eCall) from Vehicles

eCall is a functionality required by the European Union to be built into new cars from
April 2018. By combining a GPS receiver with a GSM and/or UMTS module, the idea
behind eCall is that a car can automatically make an emergency call after an accident
without manual intervention of the driver or a passenger who might be incapacitated.
In addition to setting up a speech call between the inside of the vehicle and a person at
an emergency response center, referred to in the specification as the Public Safety
Answering Point (PSAP), the eCall device can also send up to 140 bytes of information
such as location, travel direction, vehicle identification, etc. to the emergency center.
To set up the emergency call between the car, which the specification refers to as the
In‐Vehicle System (IVS), and the PSAP, the standard GSM/UMTS emergency voice call
setup procedure is used. Once the call is established, the data is sent inside the speech
channel (in‐band). While it might be strange from today’s point of view to send data
inside a speech channel, the advantage is that no additional equipment is required in the
circuit‐switched mobile and fixed networks between the car and the emergency
response center.
As sending bits as individual audible tones would far exceed the requirement of send-
ing an entire message within four seconds, a modulation scheme has been designed for
the data to pass through an AMR voice channel. Details are described in 3GPP TS