A base station for a communication system comprising a plurality of cells, the base station being configured to support coverage enhancement and comprising: means for communicating signals, in a sequence of sub-frames, between the base station and a user equipment; and means for scrambling said signals transmitted for the user equipment in a cell, using a scrambling sequence, wherein: i) when the user equipment does not require coverage enhancement, said scrambling sequence is applied per sub-frame for a Physical Downlink Shared Channel, PDSCH, for one sub-frame, and the scrambling sequence is initialised, in each sub-frame, using the formula: c init = n RNTI ⋅ 2 14 + q ⋅ 2 13 + ⌊ n s / 2 ⌋ ⋅ 2 9 + N ID cell where c init is an initial scrambling code for a sub-frame; n RNTI is a temporary identifier associated with the user equipment connected to the cell; q is a codeword index; n s is a slot number; N ID cell is an identifier of the cell; and ii) when the user equipment is configured as a bandwidth limited user equipment that requires coverage enhancement, said scrambling sequence is applied per sub-frame for the PDSCH for a given block of sub-frames, wherein the block of sub-frames comprises ten sub-frames, and said scrambling sequence is initialised based on a parameter that changes from one block of sub-frames to the next block of sub-frames. means for communicating signals, in a sequence of sub-frames, between the base station and a user equipment; and means for scrambling said signals transmitted for the user equipment in a cell, using a scrambling sequence, wherein: i) when the user equipment does not require coverage enhancement, said scrambling sequence is applied per sub-frame for a Physical Downlink Shared Channel, PDSCH, for one sub-frame, and the scrambling sequence is initialised, in each sub-frame, using the formula: c init = n RNTI ⋅ 2 14 + q ⋅ 2 13 + ⌊ n s / 2 ⌋ ⋅ 2 9 + N ID cell where c init is an initial scrambling code for a sub-frame; n RNTI is a temporary identifier associated with the user equipment connected to the cell; q is a codeword index; n s is a slot number; N ID cell is an identifier of the cell; and ii) when the user equipment is configured as a bandwidth limited user equipment that requires coverage enhancement, said scrambling sequence is applied per sub-frame for the PDSCH for a given block of sub-frames, wherein the block of sub-frames comprises ten sub-frames, and said scrambling sequence is initialised based on a parameter that changes from one block of sub-frames to the next block of sub-frames. i) when the user equipment does not require coverage enhancement, said scrambling sequence is applied per sub-frame for a Physical Downlink Shared Channel, PDSCH, for one sub-frame, and the scrambling sequence is initialised, in each sub-frame, using the formula: c init = n RNTI ⋅ 2 14 + q ⋅ 2 13 + ⌊ n s / 2 ⌋ ⋅ 2 9 + N ID cell where c init is an initial scrambling code for a sub-frame; n RNTI is a temporary identifier associated with the user equipment connected to the cell; q is a codeword index; n s is a slot number; N ID cell is an identifier of the cell; and ii) when the user equipment is configured as a bandwidth limited user equipment that requires coverage enhancement, said scrambling sequence is applied per sub-frame for the PDSCH for a given block of sub-frames, wherein the block of sub-frames comprises ten sub-frames, and said scrambling sequence is initialised based on a parameter that changes from one block of sub-frames to the next block of sub-frames.