Patent ID: 9705642
Date: 2017-07-11
CPC Classifications: H04L,H04W

Claim:
1. A method for performing a hybrid automatic repeat request (HARQ) by a user equipment (UE) to which a plurality of serving cells based on Time Division Duplex (TDD) has been allocated, the method comprising: receiving an uplink (UL) grant for a first subframe of a second serving cell through a first serving cell; transmitting UL data in the first subframe based on the UL grant; and performing a non-adaptive retransmission for the UL data in a second subframe of the second serving cell if a not-acknowledgement (NACK) for the UL data is received through a physical HARQ indicator channel (PHICH) in a subframe i of the first serving cell, wherein the first serving cell and the second serving cell use different uplink-downlink (UL-DL) configurations, and each of the UL-DL configurations is information on which each subframe within a TDD frame is configured as a UL subframe, a DL subframe or a special subframe, wherein if a PHICH resource corresponding to the UL data is not present in the subframe i, the non-adaptive retransmission is not allowed in the second subframe of the second serving cell, and wherein if a UL grant for the second subframe is received through a physical downlink control channel (PDCCH) in the subframe i, the UE performs a retransmission according to the UL grant for the second subframe.