Some of the
characteristics of computing in the mobile environment include
·
High communication latency
·
Intermittent wireless connectivity
·
Limited battery life
·
Changing client location.
·
Latency is caused by the processes unique to
the wireless medium, such as coding data for wireless transfer, and tracking
and filtering wireless signals at the receiver.
·
Battery life
is directly related to battery size, and indirectly related to the mobile
device’s capabilities.
·
Intermittent connectivity (Types)
i.
Intentional
Intentional disconnections occur by user intent, e.g., during the
takeoff of an airplane, or when the mobile device is powered down.
ii.
Unintentional.
Unintentional
disconnections happen in areas wireless signals cannot reach, e.g., elevator
shafts or subway tunnels.
·
To compensate for high latencies and
unreliable connectivity, clients cache replicas of important, frequently
accessed data, and work offline, if necessary.
·
Besides increasing data
availability and response time, caching can also reduce client power consumption
by eliminating the need to make energy-consuming wireless data transmissions
for each data access.
·
On the other hand, the server may not be able
to reach a client. A client may be unreachable because it is dozing—in an
energy-conserving state in which many subsystems are shut down—or because it is
out of range of a base station.
·
In either case, neither client nor server can
reach the other, and modifications must be made to the architecture in order to
compensate for this case.
