Abstract

An apparatus and method is provided for detecting when a mobile computer linked to a computer server over a wireless link is about to move out of the range of the LAN and for alerting the computer user before the communication link with the computer server becomes severely deteriorated. According to the apparatus and method, a predetermined number of data packets are periodically transmitted from the mobile computer to the computer server, and the number of data packets successfully transmitted is determined based on acknowledgments received from the computer server, preferably using a cyclical redundancy check (CRC) code in the transmitted packets. Based on the number of data packets successfully transmitted, a transmission error rate is computed. The error rate is compared to a threshold value and, if the threshold is exceeded, an indication is provided to the user that the communication quality is deteriorating. Parameters for controlling the number of predetermined packets, the time interval for repeating the transmissions, the method of indication, and the thresholds may be changed by the user to adapt to different requirements and environments. In a preferred embodiment, transmission of the predetermined number of data packets is inhibited if communication has been made with the computer server during a predetermined time interval, thereby improving efficiency. Additionally, a background error rate may be computed from which one or more threshold values are adjusted in order to adapt to noisy environments.