Power-Adjusted Random Access to a Wireless Channel

The operation of widely-deployed random access to wireless networks is based on limited information on the result of each access attempt. When making a random access attempt, users usually do not know the exact amount of transmit power to make it successful. Also, upon failure of a transmission attempt, a user cannot tell whether the failure was caused by collision with other simultaneously-transmitting users or by his use of insufficient transmit power. To handle lack of information on the cause of failure, we propose an innovative Cause-of-Failure (CoF) resolution which increases the transmit power after a given number of consecutive unsuccessful access attempts when the probability that a given failure is caused by collision becomes sufficiently low. To exploit the thus-achieved transmit power for the next random access attempt, we also determine the Cause-of-Success (CoS) based on the number of consecutive successful attempts, i.e., whether to decrease or maintain the present transmit power probabilistically. This way, users can adjust their transmit power for random access, which we call Auto Power Fallback (APF). We evaluate APF by modeling analysis and numerical computation based on the slotted Aloha, showing that APF makes significant energy-savings for uplink random accesses while achieving good performance.