| 摘要 |
In a multiple access cellular communication system, a base station comprises a receiver able to receive access messages from users wishing to initiates calls. In the invention, a signal comprising at least one access message is received and a signal component processor determines a plurality of signal components 401-415 of the signal. The signal components arise from multipath propagation. Arrival times are determined for each of the components 401-415, preferably as relative time intervals relative to the beginning of a time slot or the arrival of a given component. A maximum delay interval 417, 419, relating to the time interval over which multipath propagation may spread a single access message, is determined and in response to the maximum delay interval 417, 419 and the arrival times, a determination is made of at least a minimum number of access messages in the signal. For example, fig. 4 shows that two maximum delay intervals 417, 419 are required to accommodate the arrival times of the components 401-415, indicating at least two access messages. The determination may involve further factors and component groupings. Demodulation resource appropriate for the determined number of access messages may then be allocated. Use in cellular systems, especially UMTS, to improve detection of initial access messages/preambles which collide or overlap, e.g. access messages having identical Walsh code signatures which interfere in RACH using slotted mode ALOHA protocol. |
