Blind joint detection is performed at the MS end points receiving a CDMA signal transmitted by the serving Base Station which makes exceptions to the Default Midamble Association (DMA) indication, and over-rules the default scheme in a pre-defined way signalling it in advance to the served MSs. In a first case the BS allocates less midambles to the assigned codes with respect to the broadcast DMA indication, declaring that the midamble assigned to a pool of orthogonal channelisation codes is the one defined for the first common root of these codes; on the other hand the MS assumes that all the channelisation codes which can be associated to a midamble meeting the above over-rule are also transmitted. In a second case the BS allocates different Spreading Factor (SF) values in a given time slot, declaring the maximum distance on the binary code tree admitted between SF values on the same time slot; on the other hand the MS assumes that the CDMA sequences are transmitted with the channelisation codes resulting from the lowest possible SF value and the broadcast DMA indication.