In this paper channel estimation techniques for a mobile fourth generation coherent orthogonal frequency division multiplexing (OFDM) system are proposed. Coherent detection dictates that a per-subband estimate of the frequency response of the channel is generated for each OFDM symbol. This is achieved by inserting pilot symbols amongst the data symbols in the OFDM modulation grid. With suitable interpolation, the channel estimate at all intermediate symbols can be generated. A number of channel estimation methods with different pilot patterns and interpolation methods are examined for a range of UTRA specified channel environments. Each environment is shown to have an optimal pilot scheme, power level, pattern and density and the paper proposes the use of adaptive pilot processing.