formation. 12 http://www.pure.com/. Making Telecoms Work However, while this optimised the receiver power budget, it saved less power than might seem immediately apparent (the baseband processor still had to work pretty hard) and there had to be careful (and fast) synchronisation with the continuous and scattered pilots modulated on to the OFDM signal. Extended receiver power down was, however, a well-understood technique and had been used in paging systems for at least 30 years, SO it should have been possible to make this work satisfactorily. The time slicing also allowed for neighbour measurements and mobile initiated handover in multifrequency networks. This would have allowed a high-density DVB H network to be overlaid onto an existing cellular network. There were, however, some practical issues when implementing a DVB H receiver in to a cellular handset. Producing a DVB H front end capable of accessing low band VHF, UHF (and L band) was challenging in terms of antenna design resulted typically in negative antenna gain of the order of between 5 and 10 dBi. Equally problematic was the issue of GSM (or equivalent cellular) transmit power and wideband noise from the TX PA desensitising the DVB H receiver. This implied either a careful choice of DVB H channel allocation and/or some carefully designed (and potentially expensive and lossy) filtering. There were various ways in which DVB H receiver sensitivity could have been improved, for example by using antenna diversity or additional time diversity (using the optional MPE FEC encoder) but this would not have overcome the problem of locally generated interference within the handset. Diversity gains within present handset form factors would also have been marginal. The other problem was that people didn't want to watch TV on their handsets, particularly if they had to pay for it and the battery went flat. Additionally there was scant incentive for operators to bear the cost of delivering content which they did not own and with no associated revenue stream. ISDBT 