Performance of direct-sequence spread spectrum multi-h CPM in indoor mobile radio systems

The increasing number of users of mobile communication systems and the corresponding need for increased capacity show the importance of using a modulation scheme both power and spectrally efficient. In this paper, multi-h continuous-phase modulation (CPM) is combined with a direct-sequence spread spectrum system and its performance is assessed in several indoor environments (line-of-sight (LOS), non-LOS and factories). This study is performed for two different multi-h codes considering a coherent receiver structure which is optimum for AWGN. Results show that multi-h CPM can achieve a good performance when used in indoor environments for relatively high bit rates but specially for factories the use of diversity techniques, further coding or interleaving will be needed to achieve a given BER for realistic values of E_b/N_o