Scheduling retransmissions for contention-based access

摘要

A base station supports a contention-based channel and a schedule-based channel. If too many mobile terminals simultaneously transmit on the contention-based channel, the base station schedules retransmissions to those terminals on the schedule-based channel. Supporting this, a terminal transmits a user transmission on the contention-based channel that includes both a data transmission and a reference signal. The terminal derives this reference signal by selecting one of a plurality of cyclic shifts (CSs). Correspondingly, the base station receives the user transmission and can determine the selected CS even if it is unable to demodulate the data transmission. The base station then determines a retransmission identifier (RTI) mapped to that CS, according to a mapping between CSs and RTIs, and sends scheduling information for any needed retransmission to the terminal by addressing that information to the RTI. Meanwhile, the terminal knows this mapping and monitors for scheduling information addressed to that RTI.

主权项

1. A method in a base station for managing multiple user access to a communication link, the method comprising:
receiving from a mobile terminal a user transmission on a contention-based channel of the communication link, the user transmission including a data transmission and a reference signal, the reference signal being derived from a base sequence that is shifted according to a cyclic shift selected by the mobile terminal; determining the cyclic shift selected by the mobile terminal, by detecting the reference signal included in the user transmission; determining which of a plurality of retransmission identifiers is mapped to that cyclic shift according to a defined mapping between cyclic shifts and retransmission identifiers; and upon failing to demodulate the data transmission included in the user transmission:
scheduling a retransmission of the user transmission on a schedule-based channel of the communication link; andsending scheduling information for the scheduled retransmission to the mobile terminal, by addressing the scheduling information to the determined retransmission identifier.