In this paper we present a usability measure adapted to mobile services, which is based on the well-known theoretical framework defined in the ISO 9241-11 standard. This measure is then applied to a representative set of services of the Telefónica’s portfolio for residential customers. The user tests that we present were carried out by a total of 327 people. Additionally, we describe the detailed application of the methodology to a particular service and present the results of all the experiments that were carried out with the different services. These results show highly significant differences in the three usability measures considered (effectiveness, efficiency and satisfaction), though all of them have the same trend. The worst performers in all cases were the WAP and i-mode user interfaces (UI), while the best performers were the SMS and web based UIs closely followed by the voice UI. Finally, we also analyse the results and present our conclusions.

One of the greatest challenges in the design of speech recognition based interfaces is about the navigation through the different service hierarchies and structures. On the one hand, the interactions based on human machine dialogues force a high level of hierarchical structuring of services, and on the other hand, it is necessary to wait for the last phases of the user interface development to obtain a global vision of the dialogue problems by means of user trials. To tackle these problems, Telefónica Móviles España has carried out several projects with the final aim to define a corporate methodology based on rapid prototyping of the user interfaces, so that designers could integrate the process of design of voice interfaces with emulations of the navigation through the flow charts. This was also the starting point for a specific software product (MEDUSA) which addresses the needs of rapid prototyping of these user interfaces from the earliest stages of the design and analysis phases.

Third generation (3G) services boost mobile multimodal interaction offering users richer communication alternatives for accessing different applications and information services. These 3G services provide more interaction alternatives as well as active learning possibilities than previous technologies but, at the same time, these facts increase the complexity of user interfaces. Therefore, usability in multimodal interfaces has become a key factor in the service design process. In this paper we present the work done to evaluate the usability of automatic video services based on avatars with real potential users of a video-voice mail service. We describe the methodology, the tests carried out and the results and conclusions of the study. This study addresses UMTS/3G problems like the interface model, the voice-image synchronization and the user attention and memory. All the user tests have been carried out using a mobile device to take into account the constraints imposed by the screen size and the presentation and interaction limitations of a current mobile phone.