1. INTRODUCTION
Complex computer systems are finding their way into
everyday life, and with a much broader customer base. This
has made usability more critical. As a result, companies are
seeing the benefits of designing and developing their
products with user oriented methods instead of technology
oriented methods, and are endeavoring to understand both
user and product, by investigating the interactions between
them.
Mobile devices and their applications provide significant
advantages to their users, in terms of portability, location
awareness, and accessibility. Lower price points and
improvements in the hardware and software capabilities of
smartphones in particular, the so-called “handhelds,” have
led to tremendous expansion of the mobile and related
markets. This has led to huge numbers of mobile
applications (“apps”) being developed over the past few
years.
This vast and increasing number of mobile apps in the
marketplace has challenged developers to develop apps of
superior quality in order to compete [1]. There are many
aspects to the quality of mobile apps, an important one
being usability. Furthermore, the architecture of these
applications must take into account a number of design
constraints, such as limited resources, connectivity issues,
data entry models, and the varying display resolutions of
mobile devices.
The usability of mobile devices and their apps differs
from other computer systems, because their characteristics
are different. The software needs of handhelds, such as
PDAs and mobile phones, affect the development process of
mobile apps, as these are embedded in the phones during
manufacturing or installed by customers from various
mobile software distribution platforms, such as Apple’s App
Store and Google’s Android Market. Users tend to choose
mobile apps that are easy to learn, take less time to complete
a particular task, and appear to be more user-friendly
because they are less computer-oriented.
In the past, the usability of software systems was
evaluated subjectively and the process was not well defined.
Researchers would select the aspects of usability to evaluate
and measure what they considered important. At the same
time, usability measurement and analysis methods and
methodologies were being developed. Lab experiments,
field studies, and hands-on measurement are some of
methodologies most often applied by researchers
[2][3][4][5].
Every usability evaluation method has its advantages and
disadvantages. Some are difficult to apply, and others are
dependent on the measurers’ opinions or instruments. In
addition to these challenges, mobile devices and
applications change very quickly, and updated methods of
usability evaluation and measurement are required on an
ongoing basis.
This paper presents an analysis of previous studies by
considering: 1) up-to-date mobile technologies; 2) the
challenges to defining mobile usability questionnaires; and
3) an inventory of measures for mobile usability
measurement.
This paper is structured as follows. Section 2 presents
some of the generic definitions of usability, as well as
specific definitions of mobile usability. Section 3 presents
the methodologies for evaluating mobile usability. Section 4
presents observations on the evaluation studies surveyed.
Finally, section 5 presents a summary and a discussion on
further work.