The Use of COFDM for MMDS

Propagation aspects are inspected for the MMDS range from 2 to 60 GHz. The differences between the free air propagation and the delivering via cable are shown, too. Deutsche Telekom has tested different kinds of digital modulation in a difficult environment. The single-carrier QAM was compared with the multi-carrier QAM (COFDM). These measurements were carried out at frequencies of about 2.6 GHz in the capital of Germany, Berlin. For a valid statistic statement the number of measurements is not yet sufficient. But the difference between both kinds of modulation is so large that a general judgement can already be derived. It was shown that for equal transmitting conditions the number of successful receiving points for COFDM is approximately ten times so frequent than the number of positive input situations for single-carrier QAM. The methodology of measurements is described. Recorded receiving spectra are shown. Further general advantages are named for COFDM. A preview is given for MMDS applications.