On the forward link capacity of a cdma2000-1X system with transmit diversity

The capacity gain expected from next generation CDMA (IS-2000) voice networks over current (IS-95) networks is attributed to fast forward power control and transmit diversity. We compare the forward link capacity of IS-2000 to IS-95 for 9600 bps voice traffic. Three transmit diversity schemes are considered: orthogonal transmit diversity (OTD), phase sweeping transmit diversity (PSTD), and space-time spreading (STS). The study indicates that IS-2000 radio configuration 4 (RC4) with STS will maximize capacity over IS-95. This gain is 5.5 dB when averaged over the two IMT-2000 pedestrian channel models; and 1.5 dB when averaged over the two IMT-2000 vehicular models. Due to lower rate convolutional coding, RC3 users will require lower forward link power than RC4 users. However, the fewer Walsh codes in RC3 will likely lower RC3 Erlang capacity below RC4 Erlang capacity at typical system blocking levels (1-5%)