Diversity techniques in indoor mobile radio with DS-CDMA multi-h CPM

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). The study is performed for two different multi-h codes considering a coherent receiver structure which is optimum for AWGN. Improvements in the performance are obtained with the use of diversity in the receiver. Two different types of diversity are considered, selection diversity and a post-detection diversity scheme implemented by means of two Viterbi receivers. Results show that CDMA 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 is needed to achieve a given BER for realistic values of E_b/N₀