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The high-speed downlink packet access (HSDPA) adopted in UMTS aims to support, integrated on the same carrier, voice on the dedicated channel (DCH) and high-speed data on the high-speed downlink shared channel (HS-DSCH). Taking account of some noticeable deficiencies in the system, the paper examines different signalling approaches for the HSDPA, based on a two-step signalling scheme. In this scheme, the downlink signalling control information associated with the HS-DSCH is carried by shared control channels (SCCH-HS). A high-speed indicator (HI) is provided by the dedicated physical channel (DPCH). We analyse the impact of using the uncoded HI on the power consumption and overall efficiency of the system. Based on that, we propose some channel coding schemes for protecting the HI and improving the deficiencies. In particular, we recommend a very similar code to the previous one for encoding the information of the transport format combination indicator (TFCI). This new coding scheme can provide protection for the HI with high error-control capacity and have good error performance for both Gaussian and fading channels.