Apparatus and method for reducing message collisions between mobile stations accessing base stations in CDMA cellular communication devices at the same time

摘要

Conflicts between messages sent simultaneously by multiple spread-spectrum transmitters are reduced by transmission distribution across the available resources of the receiver. The transmitter may be a mobile station and the receiver may be a base station in a CDMA cellular telephone system. Each mobile station distributes transmissions using one or more randomization methods. In the first randomization, the mobile station delays the transmission by the number of chips of the PN code to spread the transmitted signal. The hash function generates a number from an identification number specifically associated with the mobile station. In the second randomization, the mobile station randomly selects a PN code. In the third randomization, the mobile station inserts any delay between successive message transmissions or probes if it does not receive a response after a preset timeout period. The predetermined number of transmissions is called the probe sequence. In the fourth randomization, the mobile station inserts a relatively long random delay between successive probe sequences if it does not receive a response from any probe in the sequence. The noise level is reduced by minimizing the transmission power. The mobile stations each increment the power of the continuous probe in the probe sequence. The first probe of each probe sequence is transmitted at a preset level.