E-HICH – DCH HARQ Acknowledgement Indicator Channel
The E-HICH is a downlink channel. As its name suggests, it carries an uplink E-DCH HARQ -ACK (Hybrid-ARQ Acknowledgement) indicator, which is transmitted using 3 or 12 consecutive slots. The 3 and 12 slot duration is used for UE which E-DCH TTI is set to respectively 2 ms and 10 ms. This channel uses the concept of signatures, in a similar way to the AICH (Acquisition Indicator Channel).
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