Services and Security for Handset

Given the range of mobile device capability in today’s market, there are many types
of service that may be available to the user. Some of these services depend on handset
capability; others rely on the services supported by the network.
Until recently, many services relied on proprietary techniques in the handset
or network, which means that services are often limited to just a certain handset
model or are only available with a particular mobile operator. The process of defining
services by organizations such as 3GPP has led to the standardization of many
services, or the development of standard environments where services can be developed,
deployed, and executed.

Described below are some of the services that can be seen on handsets that
are available today. All of these services have benefited from the process of
standardization.

Support for Location Technologies
There are a number of techniques for providing location information for handsets.
Some of these require involvement of the handset in the location process; others use
data that is already collected by the handset during normal modes and operation
and do not place additional processing requirements on the handset.
The least accurate location technique uses either Timing Advance (TA) in GSM
or Cell Identity (Cell ID) in UMTS. When a mobile connects to the network (in
dedicated mode), the TA or Cell ID is known and can be reported to a location
server and used to deliver some form of location service to the user. More accurate
location information can be obtained using a triangulation process, wherein the
handset measures information from multiple base stations and uses this, along with
data obtained from the network, to calculate the true time differences of the signals
it has received.

In GSM, this technique is known as Observed Time Difference of Arrival
(OTDOA). In UMTS, the equivalent process is Enhanced-Observed
Time Difference (E-OTD). In both cases, the handset measures the time difference
of signals between base stations; it also receives information about the real-time difference
(either sent by broadcast messages or to one specific mobile) and it calculates
from these a geometric time difference. This geometric time difference is the result
of location and can be reported to the network to deliver location services. This
calculation requires some additional processing in the handset.

The final location mechanism is potentially the most accurate, and involves integrating
a GPS receiver in the handset. When required, the handset
can take GPS measurements and report these to the location servers in the network.
To speed the satellite acquisition process, the network can broadcast assistance
data, which tells handsets in a particular area which satellites are visible. GPS-based
location has the largest impact on the mobile because of the GPS receiver and the
processing that is required to resolve position information. It is possible to combine
location techniques; thus, for example, when GPS fails to give a fix because the
handset is inside a building, the location information could be obtained from the
time-difference techniques.


Mobile TV Reception
The multimedia capabilities of handsets have raised the possibility of delivering
television to mobile or handheld devices, and indeed a number of services have
been launched that allow users to download short video clips and even video ringtones
onto their phones.

However, these services are using the bearers or channels in the 2.5G or 3G
network, which in many cases may not have the bandwidth or the format to support
high-quality video transmission. There is also an impact on all other services.
Because video has a relatively high bandwidth, it will limit the capacity for all the
other services delivered by the network.

A possible solution is the use of a technology known as Digital Video Broadcast-
Handheld (DVB-H). DVB-H is a derivative of the main DVB Terrestrial (DVBT)
format, which includes a number of features targeted at delivering content to
mobile devices.

To minimize power consumption in a DVB-H receiver, the information sent
to the handheld device is time-sliced. That is, it is delivered in concentrated bursts
so the receiver is not switched on all the time. This reduces power consumption by
up to 95 percent compared to DVB-T. In addition, the DVB-H standard includes
a number of features aimed at supporting user mobility, such as seamless handovers
between DVB transmitters. The signal format is able to accommodate users moving
at several hundred kilometers per hour.