Principles of mobile communication (2nd ed.)
Principles of mobile communication (2nd ed.)
OFDM and MC-CDMA for Broadband Multi-User Communications, WLANs and Broadcasting
OFDM and MC-CDMA for Broadband Multi-User Communications, WLANs and Broadcasting
Multi-Carrier and Spread Spectrum Systems
Multi-Carrier and Spread Spectrum Systems
FG-MC-CDMA System Performance in Multi-band Channels
CNSR '08 Proceedings of the Communication Networks and Services Research Conference
Optimum power control over fading channels
IEEE Transactions on Information Theory
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Transmit power allocation over multiple subcarriers is an effective way to improve system error probability performance and to save power in traditional multi-carrier systems. In this paper, we derive the optimum power allocation algorithm for multi-band MC-CDMA systems, where optimum is defined as minimal BER under the constraint of fixed transmitted power, assuming knowledge of power attenuation of different sub-bands. With a two-band MC-CDMA system and Rayleigh channel fading, we show that a BER performance improvement based on the optimum allocation can only be attained over a limited range of transmit power and a limited range of sub-band power attenuation difference values. This performance improvement is also modest compared with a uniform power allocation, which suggests that the uniform power allocation is near optimal for transmit power control under our assumptions. Two simple transmitted power control algorithms are provided, and the controlled transmit power for a two-band system is shown to be a linear function of the power attenuation difference between the two bands for a large range of these attenuation differences. The small non-linear range implies that in using a multi-band channel, any savings in total transmitted power can occur only when the power attenuation difference between the two bands is small.