The present invention relates to a method of producing a chip block for wireless transmission in a Direct Sequence Code Division Multiple Access (DS-CDMA) communication system. The method comprises spreading a symbol over at least one chip block (17). The method also comprises segmenting the chip block to form a first sub-block (a0) of the chip block. The method also comprises segmenting the chip block to form a second sub-block (a15) of the chip block. The method also comprises arranging a first sub-sequence (18) of chips furthest to a first end of the chip block in the first sub-block. The first sub-sequence is identical to a second sub-sequence (19) furthest to a second end of the chip block in the second sub-block. The method also comprises modifying at least one chip contained in the first sub-block and not being part of the first sub-sequence. The modifying is dependent on said first sub-sequence such that the symbol can be at least partially despread from the chip block.