Multilevel Selection Keyboard with Huffman Encoding for Individuals with Upper Limb Disabilities

This study evaluated the performance of three keyboard layouts: T9, hierarchical character selection, and Huffman encoding-based systems. Five participants were tasked with typing six sentences, including three pangrams and three simple sentences, all in the national language to minimize language-related difficulties. The total time taken to type each sentence was recorded for analysis. The results indicate a clear hierarchy in performance, with the T9 keyboard consistently outperforming the other two layouts. The T9 keyboard proved to be the most efficient, showing significantly shorter typing times compared to the hierarchical character selection and Huffman encoding-based keyboards. Although the hierarchical keyboard was specifically designed for individuals with upper limb disabilities, it performed less effectively due to its limited number of buttons, which led to slower typing speeds. Despite these limitations, the proposed hierarchical system shows promise as an intermediate solution, offering better performance than the multilevel selection method, though it still requires further refinement to reach the efficiency level of the T9 keyboard. These findings highlight the trade-off between accessibility and performance, emphasizing the importance of continued development to optimize the proposed system for users with disabilities while maintaining competitive typing efficiency.