Context-Aware Applications - Guide to Cloud Computing for Business and Technology Managers - page 518

TABLE 23.3
Accuracy and TIFF for Several Location Techniques

Technique Network Impact Terminal Impact Accuracy TTFF

Cell ID None None 250 m-20 km <1 s

Signal strength None None 100 m-10 km <1 s

TOA/TDOA Medium Low/medium 40-150 m <1 s

AOA/DOA High None 50-150 m <1 s

Fingerprint High None 50-150 m Seconds

GPS Low Very high 3-50 m Seconds

Hybrid systems Depends on the

techniques hybridized

Depends on the
techniques
hybridized

3-100 m Seconds

Ultrawide baud Dedicated infrastructure Very high 10-50 cm <1 s

carefully designed interfaces and/or detailed knowledge of cus-
tomer profiles, needs, and preferences. So, given existing technical
limitations such as device capabilities and access speeds combined
with human limitations such as reduced consideration sets and the
need for speed and convenience, in order for LBSs to succeed, they
will need to deliver relevant, targeted, and timely information to
consumers at the time and place of their choice.

Also, from a database perspective, LBSs raise critical challenges
such as spatial and temporal query processing because the contin-
uous movement of users or objects leads to the need for fast and
frequent or continuous updates to the databases. Some of the most
important database research challenges brought to the surface by
LBS are the following:

i. Support for nonstandard-dimension hierarchies : In LBS, the
geographical area may be divided into multidimensional
regions following the pattern of network coverage. Until
now, geographical area representation models used by data
warehouses were in the form of completely balanced trees
(strict hierarchies), which cannot capture irregularities like
those that frequently occur in mobile networks (e.g., the same
region covered by more than one base station).

ii. Support for imprecision and varying precision : Varying precision
means that the location of the same user may be pinpointed
with different accuracies depending on the positioning tech-
nology used while he or she is roaming from network to net-
work. Imprecision means that the location data for the trace of
a specific user may be incomplete (e.g., a user may have gone
out of the network coverage or may have switched off the
device for some time). So, varying precision and imprecision