A spectral efficiency comparison of UMTS-FDD and 1xRTT cdma2000 for voice services

Third-generation (3G) cellular technologies are designed to carry more traffic than their second-generation (2G) predecessors. Spectral efficiency for voice services is compared between two competing technologies by simulation of their physical layer wireless transmission under IMT-2000 channel conditions. Assuming 25% of mobiles at 3 km/hr, 37.5% at 30 km/hr, and 37.5% at 100 km/hr, UMTS 12.2 kb/s AMR speech with spreading factor 128 is 0.78 dB more spectrally efficient than 8.6 kb/s 1xRTT RC4 (radio configuration 4) speech. UMTS 10.2 kb/s with spreading factor 128 is 0.6 dB more efficient, while UMTS 7.95 kb/s AMR speech with spreading factor 256 is 0.72 dB less efficient, than RC4. 1xRTT 8.6 kb/s RC3 speech is 0.98 dB more efficient than RC4. These calculations assume sufficient OVSF (orthogonal variable spreading factor)/Walsh codes exist in the system. Thus, efficiency is based on power utilization rather than code depletion.