a base station receives an uplink data packet from a user equipment based on a synchronous hybrid automatic repeat request protocol , and transmits a first information element and a second information element in parallel to the user equipment . the first information element indicates whether to perform a retransmission of the uplink data packet , and the second information element indicates modulation and coding scheme for the retransmission . the base station receives the retransmission from the user equipment according to the modulation and coding scheme . the first information element is for example an ack / nack feedback message .