Enhanced PHICH with multibit ACK/NAK

摘要

In existing LTE (long term evolution) schemes eNodeBs (Enhanced basestations) use PHICH (Physical HARQ Indicator CHannel) to send ACK/NAK signals downlink to multiple UEs (user equipments). One bit for a UE has a four bit scrambling code associated with a RNTI (radio network temporary identifier) applied and is then repeated 3 times and mapped to 12 REs (resource elements). ACK/NAK bits for other UEs have orthogonal scrambling codes applied and several can be mapped to the same REs (See Figs. 1-4). The invention proposes collecting multiple ACK/NAKs into a bitmap for several UEs. Determining a CRC for the bitmap and then applying a scrambling code to the CRC. The multiple UEs can be configured with the same scrambling code, to determine if they are intended recipients of the ACK/NACK bitmap. If so they determine which bit applies to them based on earlier higher layer control configuration signalling.